Linde Technology 1 2004 En17 10192

Linde Technology 1 2004 En17 10192
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Reports on Science and Technology
Linde Technology
Biotechnology Plants
Forklift Ergonomics
Cracking with Oxygen
Economic Ammonia
LNG for Land and Sea
Flexible Solutions for
Wastewater Treatment
11:33 Uhr
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Reports on Science and Technology
Linde Technology
Dear Readers,
What are the processes involved in the modern concept development,
design and construction of biotechnology plants – a rapidly growing
industry, in which the time-to-market factor has extreme priority?
Has the science of ergonomics already reached its limits in the design
of forklift trucks? What are the options of chemical plant operators
to respond to the ever-increasing economic challenges they face?
These and other topical questions which are subject to the often
conflicting influences of technology and economics are investigated in
the newest issue of Linde Technology. The issue provides an overview
of the wide spectrum of active research, which Linde considers to
be just as important as the market-oriented further development of
existing technical solutions. We hope to have put together another
interesting mix of topics for a stimulating and enjoyable read and
look forward to your feedback.
Stefan Metz
Head of Technical Press
Linde AG
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Cover Photograph
Innovative plant technology
on the western coast of
Norway. At this natural gas
separation plant in Kolisnes we
produce the environmentally
friendly fuel LPG (Liquified
Petroleum Gas).
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New Design Approach for Biotechnology Projects
Front-End Engineering for Pharmaceutical Plants
Marc Reifferscheid and Dr. Karin Bronnenmeier
Biotechnology Plant for Insulin Production
Planning and Construction of Complete Pharmaceutical Plants
Jens-Peter Mendelsohn
Swivel Seat Improves Ergonomics
How a Swivel Seat Affects the Ergonomics of Reverse Driving
in Counterbalanced Forklifts
Dr. Frank Schröder und Dr. Thomas Seitz
Lantus Aventis: Tank station at the
insulin plant in the Höchst Industrial Park
near Frankfurt.
Cracking with Oxygen
Approaches to Economic Solutions for Refineries
Dr. Michael Heisel, Dr. Christer Morén, Prof. Dr. Alexander Reichhold,
Andreas Krause und Antonio J. Berlanga-González
The Location Makes the Difference
Economic Production of Ammonia
Dr. Paul Kummann
Offshore Plants for LNG Production
The Benefits of Cold Deep-Water for LNG FPSOs in Tropical Seas
Eginhard Berger, Manfred Boelt und Bjørn Sparby
LNG Travels Through China
Linde Series 392 forklift with swivel seat.
Using Available Resources Creatively
Upgrading Industrial Wastewater Treatment Plants
Dr. Manfred Morper
Oxygen is used in one of Spain’s largest
refineries, near Gibraltar.
LNG Baseload Plant in Remote North-West of China
Max Bräutigam
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Marc Reifferscheid and Dr. Karin Bronnenmeier
Front-End Engineering for Pharmaceutical Plants
New Design Approach for
Biotechnology Projects
“Products come from technologies”. This sentence from the
2003 Biotechnology Report by Ernst & Young characterizes
the current status of “red” (medically oriented)
biotechnology in Germany and throughout the world.
Biopharmaceuticals have already surpassed the classical
chemically-synthesized active pharmaceutical ingredients
[APIs] as newly approved medications. The Front-End
Engineering Approach for Biotech Projects from Linde-KCA
takes this development into account
According to a new study by Frost & Sullivan, biopharmaceuticals, medications produced using biotechnological
processes, reached sales of 41.3 billion dollars in 2002.
That amounts to about 10% of worldwide pharmaceutical
sales. It is noteworthy that a significant portion of these
sales (about 6 billion dollars) is from medications based
on EPO [erythropoietin], which have gained the top rank
in the “hit list” of the most-often-sold medications. EPO,
the hormone erythropoietin, is used to treat anemia. It
is one of the best-known biotech products for the public.
The potential for biopharmaceuticals becomes even more
apparent from a glance at the product development
portfolios of the pharmaceutical and biotech companies.
This class of APIs has been dominant there for some
time, with the result that biopharmaceuticals surpassed
the classical chemically-synthesized APIs as approved
medications for the first time in 2002.
Construction of production plants has to keep up
with this development, and must not become the limiting factor for introducing new drugs to the market. “Time
to Market” is a critical factor for the commercial success
of innovative biopharmaceuticals. The consequence for
the plant designer is that the engineering activities for
biotech projects must – in contrast with conventional
plant construction projects – usually start while the
client’s product and process development are still going
on, so that they suffer from particularly great uncertainties. The engineering conversion of the client’s particular
production process is extremely complex, and must
comply with strict regulatory requirements. Because of
that, the plant designer must have a thorough understanding of the process, coupled with biotechnological
knowledge, to lead interdisciplinary cooperation between
engineers and scientists. That is best accomplished by
teams into which the client’s experts are integrated.
Linde-KCA’s Front-End Engineering Approach was
developed specifically to make reliable evaluation of
status, risks, costs and schedule possible in the early
phase of biotechnological high-tech projects with the
goal of fast-track realization. That can minimize risks and
optimize the schedule for planning and construction of
plants. The result is reliability of plans and decisions for
both the client and for the plant designer. The need for
front-end engineering services has been identified both
on the route from the laboratory to biopharmaceutical
production in biotech companies, as well as in
established pharmaceutical companies. This has been
confirmed in reference projects.
Front-End Engineering
Figure 1 presents a survey of the major services of
front-end engineering by Linde-KCA: After getting the
existing process and project information from the client
at the beginning of the project, a technology concept is
generated and then a block layout is developed. The
technology concept together with the block layout make
up the basis for an early estimate of the capital investment. In parallel with those activities, a process risk
analysis can be carried out in close cooperation with the
pharmaceutical company. The results of this analysis flow
back into the process development. Development of a
preliminary project schedule completes the documentation of the front-end study.
Depending on the size and complexity of the project,
such a study can be completed within three to six weeks.
This gives the pharmaceutical company early information
about costs, process and project status, and the schedule
for the project. The documentation also makes up a
reliable basis for the subsequent project phases, i. e. for
the conceptual and basic design.
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Generation of the Technology
Know-how concentrated in the plant design company is
a prerequisite for the fast and efficient generation of a
technology concept, shown in Figure 2. To assure quick
availability of the information required, this know-how
is assembled in a library of plant unit models, e.g.
for bioreactors or for centrifuges. This library contains
functional descriptions as well as information about
interfaces, procurement times, and costs of the various
units. It makes up the basis for generating a technology
concept. Project-specific plant units are defined on the
basis of the process information from the pharmaceutical
manufacturer. With the help of identification parameters
for each plant unit, such as the working volume of a
bioreactor, a plant unit model can be selected from the
library and adapted to the specific project. In this way,
the entire process is described with project-specific
plant units. This serves as the basis for developing the
block layout and the cost estimate.
Additional Services
for Transatlantic
Technology Transfer
Client’s Process & Project Information
Technology Concept
Review & Block Layout
Investment Cost
Process Risk Analysis
for Scale up
Preliminary Project Schedule
Conceptual Design
Basic Design
Figure 1: Linde-KCA’s Front-End Engineering Approach.
Linde-KCA‘s Sources
of Know-how
Library of Plant Unit Models
(Functional Descriptions, Interfaces, Delivery Times & Costs)
Linde-KCA Tools
Block Layout Development
A block layout brings together the preliminary space
requirements for all the engineering disciplines such
as process, process infrastructure, HVAC (heating,
ventilation, air conditioning), electrical engineering and
automation. Figure 3 shows the Linde-KCA concept
for development of a block layout.
Specific tools such as a layout-typical library for
plant units and a layout planning handbook have been
developed to assure an efficient design approach. A
layout-typical for a plant unit shows the arrangement of
the equipment and all the other space requirements
for the unit, such as those for handling and logistics, in
a plan view and side view.
Every project-specific plant unit is assigned a layouttypical from the library, and is adapted to the specific
project. At the same time, a functional program and an
initial layout arrangement are worked out on the basis of
the layout planning handbook. With this information,
the layout-typicals can be assembled into a block layout.
Estimation of the
Capital Investment
The total investment cost [TIC] can be estimated from the
technology concept and the block layout by making use
of benchmarking factors (Figure 4). The hardware costs
for package units and other equipment are determined
from the project-specific plant units. The hardware costs
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Conversion into Unit
Process Information
from the Client
Project-specific Plant Units
for Block Layout
and Cost Estimation
Figure 2: Generation of the technology concept.
Linde-KCA Tools
Linde-KCA Activities
Plant Units
Assignment / Adaptation
Layout-typical Library
for Plant Units
Functional Program
Layout Arrangement
Linde-KCA Layout
Planning Handbook
Block Layout
Figure 3: Block layout development.
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Project-specific Plant Units
Block Layout
Project Scope
for HVAC
Project Scope
for Cleanrooms
Project Scope
for Buildings
Bulk and
Constriction Factors
Total Technology Costs
Eng. Factor for
Eng.Factor for
Eng. Factor for
Costs of
Package Units
Eng. Factor for
Package Units
Eng. Factor for
Eng. Factor
for PCS
Engineering Costs
for Technology
Engineering Costs for
Eng. Costs for
for the process control system are determined likewise,
with the complexity taken into consideration. The complete technology costs are obtained by adding the bulk
and construction costs, estimated using benchmarking
factors. The engineering costs can also be determined by
using specific benchmarking factors for package units,
equipment and process control systems.
The block layout also serves as the basis for the
facility costs. It is used to determine the scope of the
project for HVAC, cleanrooms and buildings. Then the
hardware costs can be determined from the HVAC
volume factors and from the area factors for cleanrooms
and buildings. The engineering costs for the facility are
also determined by means of benchmarking factors.
As a rule, this route for an early estimate of the total
investment cost allows an accuracy of ± 30%.
Total Investment Cost ± 30%
Figure 4: Estimation of total investment cost using benchmarking factors.
Process Risk Analysis
Check requirements of the Linde standard against the client‘s process status
Process steps
Cell Separation
Cell Disintegration
Risk Analysis
Product Isolation
High Resolution
To be done
Process Risk Analysis
■ Review of development reports and
process documentation
■ Verification of the scale-up requirements
■ Review design data
■ Establishment of the qualification requirements
Test Program
Process Development
Figure 5: Process risk analysis
No. Description
Conceptual Design
Basic Design
Extended Basic Design
Detailed Design
10 Installation
11 Mechanical Completion
12 IQ
13 Start-up / OQ
14 Handover
Figure 6: Preliminary project schedule
Critical process steps and critical scale-up steps must be
identified at an early stage for the plant design to be
reliable. To accomplish that, an analysis of the developmental results and of the process documentation is
carried out with experienced biotechnologists and bioprocess engineers. That includes a comparison of target
and actual design data for the plant and an initial determination of the principal requirements for qualification.
In this way, it is possible to determine which stages of
the process have attained the status required for starting
conceptual design, and which require deeper analysis.
For the latter case, shown in orange in Figure 5, the
measures necessary to reduce risk and to make sure
of the scale-up are derived. They are documented
in the form of a test program for process development,
synchronized with the requirements for further plant
Close interaction with the pharmaceutical manufacturer’s experts is critical for the process risk analysis
described. Only close cooperation can assure feedback of
results to process development and assure that the test
program is translated into action. This is the responsibility
of the client.
Preliminary Project Schedule
The last step of a front-end study is working out a preliminary project schedule. Figure 6 shows an example of
such a schedule with reduced project time, under the
boundary conditions of a fast-track project for a small
plant with modular design. The major project phases and
their durations are stated, from conceptual design and
basic design to start-up and qualification. The finished
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front-end study forms a reliable basis for the fastest and
technically best performance of the next project phases;
the conceptual and basic design.
Linde-KCA’s Phased Approach for Pharma & Biotech Projects versus Client’s Project Status
Prozess &
Basic Data
Handling &
International Technology Transfer
Demands of the global market, cost advantages and
regulatory aspects have become decisive criteria for the
selection of a production site for pharmaceutical and
biotechnical companies, too. As a result, new production
plants are often built far from the centers of excelllence
for research and development and for engineering. This
requires international technology transfer, which often
has a transatlantic dimension because of the leading
position of the USA in medically oriented biotechnology,
with all its consequences for the internal resources of
the companies affected.
Linde-KCA supports such technology transfer
projects with know-how from front-end engineering,
with particular in European plant design and construction,
and with particular knowledge about authority
Linde Technology I 1/ 2004
Building &
Status of Delivered Documents: Basic Data
Conceptual Design and
Basic Design
Client Specialists and Linde-KCA Key Team Evaluate Project Status
Requirements Concerning Completion of the Concept Design
Status of Documents: Conceptual Design
Basic Design
Focus: Process
Figure 7: Conceptual design and basic design
Mature Biotech &
Pharamceutical Companies
The conceptual design should be strictly coordinated
over all engineering disciplines simultaneously from the
very beginning. That achieves high reliability for the
technology, building size, and cost estimate, and assures
the fastest possible development of all the necessary
planning documents. To comply with those requirements,
Linde-KCA has developed a phase model for pharmaceutical and biotechnical projects which predefines the
work and document flow for each discipline and for the
interfaces among the disciplines (Figure 7).
At the beginning of the conceptual design, a core
team, together with the experts from the pharmaceutical manufacturer, checks the documents provided
and evaluates the status of the project for the various
engineering disciplines. This provides an early focus
on the planning jobs that are critical for completing the
conceptual design.
The conceptual design, worked out iteratively,
should include all the relevant documents for the major
disciplines, a detailed project schedule and a cost
estimate that serves as a basis for management decision
on the investment. The conceptual design makes up the
reliable base for beginning the basic design. In the latter
planning phase, the phase model is also applied as well
as engineering tools tailored for the application to assure
error-free know-how transfer from the conceptual design
and to allow the fastest and best development of the
basic design.
Preferred Regions
LINDE Technology-Transfer
Technology Transfer
Site Evaluation
Figure 8: International
technology transfer
Financing Models
engineering and commercial aspects for future production sites in Europe (Figure 8).
Front-end engineering, with analysis of the project
and process status, risk, costs and schedules is of particular importance in technology transfer projects. The status
analysis of a project, and especially of the process
development, must also be performed at the site of the
process development, as must the additional required
development missions that are identified. However,
on-site analysis at the selected site of the investment
is preferred for costs and scheduling due to the decisive
influence of regional factors and requirements.
Complete and well-founded technology transfer
documentation is the best basis for successful execution
of the project at the selected site utilizing the proven
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engineering and contracting service spectrum from
conceptual design to start-up and qualification. Success of
the project can be assured by additional support in the
search for potential financing and by cooperation in site
The Authors
Marc Reifferscheid
Increased requirements on the pharmaceutical and
biotechnological industries in past years have fundamentally changed the demands for pharmaceutical plant
design and construction. Linde-KCA has developed
know-how in front-end engineering and in international
technology transfer to support early-phase decisions
about investments, to minimize design risks, and to
optimize the overall project schedule. This involves the
following points in particular:
■ Experience in assembling integrated project
teams involving pharmaceutical companies
and Linde-KCA, as well as on-site planning
■ Established methods for early and accurate
estimation of capital investment
■ Established capabilities and methods for
process risk analysis
■ Tools for tailored adaptation of the work
flow to a specific project
■ International experience with highly varied
■ Knowledge of the relevant laws and
regulations of quite different countries
These capabilities and experiences facilitate very close
cooperation with the experts from the pharmaceutical
company in the earliest possible phase of the project.
The objective is to offer capabilities tailored to the
specific project and thus to assure the fastest and best
planning and execution of high-tech projects.
Dipl.-Ing. Marc Reifferscheid has
studied bioprocessing technology
and has since 1999 been a
Senior Process Engineer at LindeKCA-Dresden GmbH. In this
position, he has been involved in planning and building of numerous pharmaceutical plants in Germany,
Denmark and Hungary. Before joining Linde-KCA, he
worked at the Instituto Superior Técnico, Lisbon,
Portugal from 1997 to 1998 and, in 1996, at TIBRAS
Titânio do Brasil in Camacarí, Brazil.
Dr. Karin Bronnenmeier
Dr. rer. nat. habil. Karin Bronnenmeier has been Senior Process
Biologist at Linde-KCA-Dresden
GmbH since 2001. She works
there in business development
for pharmaceutical plants emphasizing biotechnology.
Before joining Linde-KCA, Ms. Bronnenmeier was
active in fundamental biotechnology research as
Research Group Leader for molecular enzymology
at the Technical University, Munich, where she
qualified as a lecturer.
Biotechnology is continuing to develop at break-neck
speed. Biopharmaceuticals have already overtaken the
conventional chemically synthesized medications in
new medical approvals. Construction of production
plants must keep up with this development, and must
not become the limiting factor in the introduction of
innovative medications to the market. With the FrontEnd Engineering approach of Linde-KCA we now have
a concept that assures the fastest and best planning and
execution of high-tech projects in biotechnology.
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Jens-Peter Mendelsohn
Planning and Construction of Complete Pharmaceutical Plants
Biotechnology Plant for
Insulin Production
About 800,000 people in Germany alone must use insulin every
day to control their blood sugar level. Because of the speedy
progress of genetic technology in the past 30 years, it has become
possible to make almost unlimited amounts of human insulin and
insulin analogs with consistently high quality using genetically
modified microorganisms. The most modern biotechnological
production plants are needed to meet the demand for innovative
analogs, such as glargin insulin.
Planning and construction of pharmaceutical plants is
a relatively young field of business for Linde Plant
Construction, located in Dresden at Linde-KCA (LKCA).
Even so, LKCA has, over the past ten years, established
itself as a leading bidder in the design, planning and
construction of pharmaceutical and biotechnological
plants. The latest reports are among others which confirm
that: the Bayer AG pharmaceutical pilot plant in
Elberfeld, which started up in October 2000, and the
new F. Hoffmann-La Roche AG “Kilolabor” in Basel, are
both plants for synthesis of innovative pharmaceuticals.
LKCA obtained its first contract, as general planner
for construction of a new biotechnology plant, in April,
2000. The plant, for Aventis Pharma, Frankfurt, is to
produce glargin insulin, a genetically engineered insulin
derivative with depot action. LKCA turned the plant
over to Aventis only 29 months later, after successful
completion of the start-up activities, for continuation of
special performance tests by Aventis, and for the
beginning of Validation (Figures 1 and 2).
A stand-alone plant
on the ‘green-field’
The plant is an independent complex consisting of
four buildings among which the production and auxiliary
operations are distributed on the basis of their requirements for classified cleanrooms and for areas and
processes with explosion protection. All the subplants
are supplied through a central connecting road. The road
serves the flow of both personnel and materials. It
also connects the central main building to the offices,
conference rooms, laboratories and the real heart of the
plant, the central control room. There are also
storage tanks as well as the entire infrastructure with
lines from the plant to medium supply and disposal at
the Höchst Industrial Park (Figures 2 and 5). The plant
produces about 1,700 kg of glargin insulin every year.
The total investment is around 200 million euro. Because
its amino acid sequence has been altered by genetic
engineering, this insulin derivative has depot action
for 24 hours in the body. Glargin insulin was developed
independently by Aventis, which was the client for
this project. The product is made in the subplants for
fermentation, processing, purification and end-product
treatment. The production complex also includes supply
and disposal installations (propanol distillation plant,
auxiliary material preparation, wastewater disposal, tank
storage and a warehouse for packaged goods).
Figure 1: Lantus
Aventis at the Höchst
Industrial Park.
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Production in five steps
The plant for producing biosynthetic glargin insulin is
organized into these five processing sections:
■ Fermentation
■ Processing 1
■ Processing 2
■ Purification, and
■ End product treatment.
The steps in the process for producing glargin insulin
differ from those for producing rapid-acting insulins
essentially in purification and end product treatment.
The fermentation and processing stages use similar
production technology.
In the fermentation stage genetically modified
Escherichia coli bacteria are cultured and grown in
successive fermenters with increasing capacities. They
are stimulated to produce a fusion protein by adding
an inducer. When the fusion protein has been formed,
the bacteria are killed with a disinfectant. This part of
the process – culture and killing of genetically modified
bacteria – is covered by the Genetic Technology Act,
and is the genetic engineering part of the process.
After killing, the bacterial suspension is concentrated
by centrifugation during processing, and then disintegrated.
After disintegration, the specific heavier fusion protein is
separated from the other cell components by continuous
centrifugation, washed twice with water, and isolated.
The “folding” of the molecule, in which the fusion protein
folds into a “native spatial structure” takes place in
the next step of the process. That is accomplished by
dissolving the fusion protein in an aqueous urea
solution in the presence of cysteine. Byproducts are then
precipitated by a shift in the pH and separated by
In the subsequent purification process, the
glargin insulin is freed of urea and inorganic salts by
adsorption-desorption steps and simultaneously
concentrated. The desorption is done with an aqueous
solution of propanol. The crude intermediate product is
then purified chromatographically in two process steps.
Then it is crystallized at high purity, filtered off by
suction, and stored temporarily as moist crystals.
The high-purity glargin insulin crystals are dissolved
again, crystallized and freeze-dried to get larger
homogeneous batches. The end product treatment is
done in Class C cleanroom conditions because there
are limits for the bacterial counts and endotoxins
(“pyrogens”) in the dried material. The plant, which only
produces the solid pharmaceutical, not the finished
medicinal product, had to be approved not only under
the Genetic Technology Act but also under the Federal
Environmental Protection Act.
Figure 2: View of the
tank storage, with
the propanol distillation plant and the
fermentation buildings (right).
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Diabetes mellitus
Diabetes mellitus is one of the most
common and significant metabolic
diseases in humans. It can be caused
by malfunction of the pancreas,
which produces too little insulin, or
by insulin resistance of the body cells.
The result is that the concentration
of sugar in the blood is no longer
normal and must be corrected by
medications. Although the pancreas
of a healthy person produces 2 mg
of insulin a day, a diabetic must get
about 1.5 mg of insulin per day
externally. In Germany alone, about
800,000 people must take insulin
daily to adjust their blood sugar
According to an estimate by the
World Health Organization (WHO)
there are at least 120 million
diabetics in the world today, including undiagnosed cases. More than
Exacting production process
All the steps of the process use deionized and purified
water. Its microbiological and physical-chemical quality
are monitored routinely (“Purified water”). Ozone is
removed from the water with UV light before it reaches
the points where it is used. The consumers are supplied
with process water through a ring piping system.
“Pyrogen-free purified water” produced by ultrafiltration
is used In the last steps of the process (purification and
end product treatment).
In addition, all the raw materials and auxiliary
materials (solvents, acids, bases, salts, buffers, etc.) are
of pharmaceutical quality or meet internal plant
specifications, and are checked regularly. The solvent,
propanol, is distilled after use and returned to the
process. The nitrogen used for inerting is purified through
a HEPA (high-efficiency particulate air) filter before use
to prevent contamination by particles.
As a rule, all the stages of the process are carried
out in closed tanks with solid pipe connections. Manual
handling of the product is reduced to a minimum. The
material used for the tanks and connecting pipes are
corrosion-resistant stainless steel with defined surface
roughness (internally electropolished for critical process
steps). This assures good and complete cleaning. These
cleaning processes have a critical part in the planning of
pharmaceutical plants to assure the required sterility and
constant product quality. They are generally established
by the client in the corresponding specifications.
Linde Technology I 1/ 2004
8 million patients are being treated
with insulin in the industrialized
countries alone. The worldwide
insulin consumption is around five
to six tons per year. It is predictable,
too, that this requirement will
increase substantially in the future,
in view of the worldwide increase
in population and changing social
Process monitoring
and documentation
The heart of the glargin insulin production plant is a
high-capacity process control system, which processes
about 18,000 items of input and output information
and monitors and controls the entire process.
All quality-related instruments were calibrated when
they were put into service. This calibration is repeated
regularly at appropriately established intervals. In-process
samples of the intermediate products are also tested in
the laboratory to make sure that their quality meets
specifications (Figure 4).
All the process and analytical data, either from
routine operations or from deviations, are stored in the
process control system or in the laboratory information
management system (LIMS). Then the specific process
data are supplemented with the general operating
data and printed out either in partial lot records or a full
lot record, along with the operational data.
Conceptual design –
the key to success
This project began with a process which Aventis
developed and tested at pilot plant level, which had
to be converted to a full-scale plant. Utilization of the
structure of a similar project for insulin production,
which had already been accomplished, was a significant
boundary condition. In this phase, the plant designers
were expected to apply their experience and know-how
to work out the technological problem and to participate
actively in the design process, especially with respect
to process optimization, scaling up and the defined
production concept.
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Figure 3: The 3D
design model and the
structural plan of the
plant for producing a
genetically engineered
insulin derivative
with depot action.
Tank Storage
Main Building
Laboratory and Administration
Connecting Structure – Central Supply Route
High Purification
Purification and End Product
The major emphasis in planning is that of making sure
that the product is produced under reproducible
conditions (with respect to product quality and
validation). LKCA set up a team of 12 employees
specifically for the project. They worked together with
the Aventis project team for three months following
April 2000, under a preliminary contract, to develop the
initial plant concept.
In this planning phase, it was important to bring
the process technology into harmony with these
■ building architecture
■ cleanroom classification and HVAC
(heating, ventilation, air conditioning)
■ logistics and storage
■ information technology and process control
■ functional descriptions as the basis for
the formulating operation
■ product quality and GMP (Good Manufacturing
Practice) concepts.
Plant-oriented design planning was established,
starting from the basic data determined and specifications of process-oriented design principles (Figure 3):
Warehouse and Supply
■ functional layout
■ building concept
■ master plans for beginning-to-end quality
assurance, from design to start-up
■ plant design, connected to the existing
This process was essential so that the documents
needed for the construction contract and for the Federal
Environmental Protection Act contract could be produced
as quickly as possible on an assured design basis and
submitted to the authorities responsible.
The conceptual design produced in that manner
was based on:
■ Layout studies of critical plant areas
(e. g., recrystallization) with respect to
structure, GMP requirements, material
handling, cleaning, and serviceability
■ layout designs for medium supply and
disposal, electrical engineering, measurement,
and control technology, as well as HVAC
■ logistical concepts with respect to material,
personnel and product flow.
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Figure 4: Quality
monitoring by
offline-testing in the
analytical laboratory
in the main building.
Insulin glargin (Lantus®)
Glargin insulin is a peptide hormone
analog of insulin, produced by
genetic engineering. Like human
insulin (NPH insulin), it controls the
blood sugar balance in humans,
but has a long-term action profile.
Because of that, a diabetic needs
only one insulin injection per day.
That is a definite improvement from
the patient’s viewpoint. This makes
glargin insulin a product that is
tailor-made for diabetics. Together
with the classical human insulin
Serum insulin
(with a relatively fast action profile),
it rounds out the patient’s requirement. The active pharmaceutical
agent, glargin insulin (solid, nonsterile) is dissolved in the finished
medicinal production and supplemental materials are added. The
product is filled into cylindrical
ampules, and marketed under the
tradename Lantus®. Glargin insulin,
like human insulin, is a protein
molecule, which reduces the blood
sugar content to the normal value of
about 70 to 120 mg/100 ml.
In current treatment of diabetes,
human insulins play an important
role in the basal supply of insulin for
the body. NPH insulins exhibit a
distinct maximum action after about
4 to 7 hours, and have an effective
duration of about 12 to 16 hours. In
contrast, glargin insulin does not
have any distinct maximum activity,
instead having a constant flat action
profile over 24 hours.
Previous NPH insulin
The difference in the action profile between glargin insulin and NPH insulin.
Linde Technology I 1/ 2004
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Seite 14
Figure 5: View to the
southeast of the complete Aventis Lantus
plant at the Höchst
Industrial Park, with the
central office building in
the foreground.
Successful plant start-up
Aventis received approval for construction promptly in
December 2000, so that the groundwork could be
started in January 2001. Laying of the cornerstone was
celebrated jointly on 4 April 2001. Then it was possible
to complete the rough construction work, an important
project milestone, in August 2001. The mechanical
preparation was done building-by-building, oriented to
the course of the process, until August 2002. After
finishing the assembly, we could then begin the start-up
in the same sequence.
The plant is distinguished by a high degree of
complexity. It is a large-scale computer-controlled plant.
Just one single person at the control room computer
screen could manage it. It does require about 6,500
control points (connections to the process control
system). The start-up of the entire process control system
ran smoothly. By February 2002 the technology was
available to start operations of the individual sections
of the plant.
The total investment is about 200 million euro. The
centerpiece of the glargin insulin production plant is a
high-capacity process control system, with which about
18,000 pieces of input and output information are
processed, and which monitors and controls the entire
course of the process.
The Author
Jens-Peter Mendelsohn
Jens-Peter Mendelsohn, a graduate engineer, has been manager
of the Development Department
in the area of Pharmaceutical
Plants since 2003. He started at
Linde in 1980, as manager of plant design, and,
after 1987, he coordinated use of CAD technology
for pharmaceutical plants. Since 1990 he has been
responsible for the Central Engineering Technology
Department. From 1995 to 2002 he directed various
major projects, including the construction of the
new Aventis insulin plant.
Within ten years, Linde-KCA-Dresden GmbH has
established itself as a leading bidder in the area of
pharmaceutical plants. In just 29 months, under a
contract with Aventis, Linde built a plant to produce
genetically engineered insulin (glargin insulin). The
plant produces bout 1,700 kg of glargin insulin annually.
Linde Technology I 1/ 2004
14:43 Uhr
Seite 15
Dr. Frank Schröder, Dr. Thomas Seitz and Jörg Hudelmaier
How a Swivel Seat Affects the Ergonomics of Reverse Driving in Counterbalanced Forklifts
Swivel Seat Improves Ergonomics
Frequent reverse driving places a significant strain on the
operators of counterbalanced forklifts. A joint study conducted
by Linde AG in Germany and the Institute of Ergonomics at the
Technical University of Munich shows how the ergonomics of
forklifts with double-pedal control can be improved by the use
of swivel seats.
When moving bulky loads or traveling down an incline,
a forklift operator is often forced to drive in reverse for
relatively long stretches. This comes in addition to other
common instances when driving in reverse is required,
such as loading and unloading goods. The position that
the operator is forced to assume is uncomfortable when
held for longer periods of time and his field of vision is
also greatly restricted during these maneuvers.
Surveys have found that, depending on specific
circumstances, forklift operators spend between 6%
and 73% of their time driving in reverse with counterbalanced forklifts. Out of 162 cases studied, an average
of one third of the total driving time was spent going in
reverse [2]. Medical studies have documented increased
muscle tension as rates of reverse driving increased.
Drivers with approximately ten years of experience or
more under such conditions also had an increased rate
of back-related complaints [3].
Several design-based solutions already exist for
improving the posture of forklift drivers when driving in
reverse. For example, the field of vision to the rear
can be increased using various rear-view mirror
arrangements; however, as in street traffic, a look to the
rear at the beginning of each turning operation remains
Swivel seats
Another solution is the driver’s seat on the Linde 336
series of electric forklifts, which turns 45° on the
“Panorama” version. On this model, when the driver
needs to go in reverse, he rotates the seat, including the
Linde Load Control (LLC) control lever (located on the
arm supports attached to the chair), 45° to the right. An
additional set of pedals is available in this swiveled
position for driving and braking. The steering wheel
remains fixed in place for both seat positions, where it
continues to meet ergonomic requirements in the
swiveled position as well.
The proven benefits of the “Panorama” solution are
accompanied by high design costs. In addition, the
increased space required by this concept for the second
set of pedals and the seat’s wide turning range is not
practical for more compact vehicles and current forklifts
powered by internal combustion engines.
Figure 1: Linde forklift series 392 H25D and
swivel seat for Linde forklift series 392 with
a rotational range of 17° to the right.
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Seite 16
For this reason, a second variant of the swivel seat
was designed that could forgo an additional set of pedals
(Figure 1). The driver uses the fixed-position pedals
even when the seat is turned. A maximum angle of 17°
proved to be most suitable for the swivel seat, providing
the best compromise between the ability to comfortably
reach the pedals, an improved rear field of vision and
compatibility with available special equipment. The
angle also reduces the amount of static twisting to which
a driver’s spinal column is subjected.
The swivel seat’s point of rotation was chosen so
that the distance between the edge of the seat and the
reverse driving pedal remains nearly constant both in the
non-swiveled and in the swiveled position. To rotate the
seat, the driver activates a lever (conveniently integrated
into the front area of the arm support) that disengages
the seat’s position lock and permits the seat to turn.
The ergonomics of different variants of the swivel
seat were studied jointly by Linde AG and the Institute of
Ergonomics at the Technical University of Munich. Driving
tests and three-dimensional human models provided detailed information on the positions assumed by individual
joints in the human body. Some of the results from this
study are described below.
Vehicle variants and the test course
In driving trials, three vehicle-mounted video cameras
were used to observe the test subjects (who had
different body and waist sizes) while they performed
their driving tasks. In addition, the drivers were
questioned as to their impressions after each test drive,
and the drivers’ individual seat adjustments were noted
in order to statistically record how drivers used the
available turning range.
Lifting mast control
Driving control
Type of seat
FS 392
(“joystick”+arm support)
Standard seat
(“joystick”+arm support)
Swivel seat (17°)
(“joystick”+arm support)
with direction of
travel switch
Swivel seat (17°)
Standard seat
FS 392
FS 392
FS 351
Mechanical actuation
of control valve,
no arm support
The investigators compared three different versions
of the forklift series (FS) 39X. Compared to their predecessor (FS 351), the FS 39X vehicles offer numerous
improvements to ergonomics and operator comfort in
addition to a standard electronic lift-mast controller that
takes the form of a “joystick” integrated into the right
arm support. This arrangement reduces the actuation
forces and paths required by the driver while simultaneously improving the sensitivity of the controls [4].
The test vehicles differed in their control pedal
arrangements and in the types of driver’s seats (standard
fixed seat or swivel seat that can be turned to the
right to make reverse driving easier). For comparison
purposes, the driving maneuvers were also performed
with a forklift from the earlier BR 351 series.
From the driver’s perspective, it is characteristic of a
hydrostatic drive that the vehicle’s driving and braking
functions are controlled using a single pedal. The driver
accelerates the vehicle both forward and backward up to
its maximum speed by altering the position of the pedal.
Unlike with other vehicles, there is no need to switch the
foot between drive and brake pedals; hydrostatic braking
is activated simply by the driver removing his foot from
the pedal.
Linde combustion engine forklifts come with Linde’s
double-pedal system as standard equipment: there is
one pedal each for forward and reverse driving, with
the two pedals mechanically linked to one another.
The driver uses the right foot to accelerate and brake
in forward driving while the left foot controls these
functions when driving in reverse. As a result, the driver’s
feet can rest continuously on the pedals and he can very
quickly change driving directions. If desired by the
customer, these forklifts can also be delivered in a
single-pedal version with a supplementary directional
switch in the arm support.
During the driving trials described here, both pedal
variations were tested in order to assess their suitability
for use with the swivel seat. The driving task consisted of
transporting a load on a defined course. In addition to a
straight section to be covered in forward and reverse,
the course also consisted of two right-angle curves, and
at the end of the course, the driver had to operate the
vehicle’s lifting hydraulics.
The straight section was narrow enough that the
drivers could only go straight ahead or in reverse. In
order to bring about comparable head positions, a pylon
placed directly behind the vehicle was used as a visible
target on this section of the course. Video recordings
were taken of this section. Stills from the video recordings were used to create three-dimensional assessments
of the drivers’ postures when traveling forward and in
Table 1: Vehicle designs for ergonomic comparisons
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Seite 17
The test drivers and the
human model
The group of test drivers consisted of 13 persons with
different body sizes and waist circumferences in order to
cover typical segments of the population. All test subjects
were measured digitally using still images. The “human
model” (RAMSIS) for each test driver was individually
adapted to the anthropometrical data obtained from
these images. As a result, each of the human models
corresponds, in all dimensions, to the extremities of the
respective test driver and can be displayed and moved
three-dimensionally on a computer with the aid of
PCMAN software [6]. In doing so, all joints can be rotated
according to their actual physiology.
In connection with the tests, the human models
were adjusted three-dimensionally to conform to the
actual driver positions recorded on video. During this
adjustment, all of the models’ joints were adapted
translationally and rotationally to the various camera
perspectives so that every position assumed by the driver
(during reverse driving, for example) could be recreated
(Figure 2). In this manner, it was possible to spatially
measure the driver’s positions while he was driving
without impairing his normal range of motion with
measurement devices attached to his body.
Using measurement functions, it was then possible
to use PCMAN to evaluate the angular positions of each
human joint depicted in the human model and compare
these to known comfort angles and critical angles for that
joint. The body positions calculated in this manner for all
of the test drivers were stored in a database of positions.
The database contains the driver’s position in the form
of 29 joint angles as well as the coordinates of the hip
reference point for each time point evaluated during the
test. Using these data as a foundation, conclusions can
be drawn as to the comfort of a given body position and
the accessibility of operational elements, as well as lineof-sight analyses.
Influence of the arm supports
The technical literature describes numerous requirements for seated workstations [e.g., 5]. Under different
conditions, an arm support is seen as mandatory in
the following situations:
■ When the task is fulfilled primarily in a sitting position
with one's back against the backrest.
■ During precision fine-motor work when the elbows
or the lower arm need support independent of the
working surface.
■ When working in dynamic systems (ground, air,
and water vehicles), the arm supports can contribute
to minimizing the translational and/or rotational
accelerations affecting the body.
Linde Technology I 1/ 2004
From an ergonomic perspective, an arm support design
must meet the following criteria:
■ If there is no variable height adjustment, the height (h)
between the supporting surface of the
arm support and the sitting reference point must
be 180 mm < h < 230 mm.
■ The width of the supporting surface may not be less
than 50 mm.
■ Arm supports that are coupled to angle-adjustable
backrests must be designed so that they can be
brought into a horizontal position independent of the
angle assumed by the backrest.
■ Arm supports should be padded in order to minimize
the surface pressure, especially in the elbow area.
These points show that it is reasonable, from an
ergonomic standpoint, to expect significantly improved
sitting comfort and a reduction of muscle fatigue using
an arm support in forklifts. The arm supports used on
Linde forklifts meet these requirements.
Figure 2: Adapting the human model to the actual
position during reverse driving.
There are two typical positions associated with
driving in reverse. The majority of the test drivers
generally retain the arm position used during forward
driving and turn themselves using only the pelvis and
the spinal cord. However, in about 10% of the driving
instances, it was observed that the driver reaches with
the right arm behind the B-pillar, using his arm as a
supporting lever.
It was also revealed that in vehicles without an arm
support, about one third of the test drivers moved their
right hand significantly away from the normal position
during reverse driving. In other words, they released
their grip on the hydraulics control lever. With only
one exception, however, drivers operating an FS 392
(equipped with an arm support) kept their arm on the
arm support so that the right hand always remained in
the immediate area of the operational controls.
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Seite 18
FS 351
FS 392 standard seat
FS 392 swivel seat,
FS 392 swivel seat,
Figure 3: Average positions of all drivers during reverse driving.
Rotation of
neck joints and head
■ Relief of the spinal column
Rotation of the
spinal column
Pelvis rotation on the seat
Figure 4: Spinal column rotation in
the individual spinal column joints
of the human model, average values of all drivers.
Seat swiveling range
FS 392
standard seat, double-pedal
Under practical conditions, this hand position
represents an increased level of safety because the
driver has faster access to the operating lever in critical
situations. Furthermore, the arm support significantly
relieves the arm and shoulder muscles, which contributes
to a noticeable stress reduction for the driver both when
driving forward and in reverse.
Body position when
driving in reverse
When the angular data of each body joint (available in
the position database described above) are averaged
individually, the result is an “average position” of all
drivers for each vehicle in a given driving situation.
RAMSIS was used to convert these positions into a visual
FS 392
swivel seat, double-pedal
Rotational angle [°]
FS 392
swivel seat, single-pedal
depiction from which the influence of the various vehicle
designs can be inferred. Figure 3 shows the average
positions during reverse driving. The positional data also
permit conclusions regarding the stress placed on
individual regions of the body while driving a forklift.
The rotation of the spinal column is of special interest.
Figure 4 shows the spinal column joints that were incorporated into the model.
Of these, the ribcage (7) should be perceived as
rigid, while the neck and head joints (8 and 9) exhibit
high degrees of movement and are subject to major
positional changes depending on the line of sight. A
rotation of the pelvis (1) means that the driver is rotating
with his entire body relative to the seat surface. In other
words, the person is changing his position in space.
Therefore, the rotational angles in the spinal column area
between the lumbar sacrum (2) and the lower cervical
vertebrae (7) are definitive for the analysis of the sitting
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Seite 19
Seat swiveling
Rotation of the
spinal column
(2 through 7)
Rotation of the lower
lumbar spinal column
region (2 through 4)
Total rotation between
the driver’s head and the
vehicle (1 through 9)
FS 392 standard seat,
FS 392 swiveling seat,
21° (-32%)
12° (-37%)
130° (+5%)
FS 392 swiveling seat,
23° (-26%)
20° (+5%)
129° (+4%)
Percentage values indicate changes relative to standard seat
Table 2: Total rotation between head and vehicle, average values of all drivers
Seat/pedal type
Driver model
Angle of line
of sight [°]
Field of vision [°]
Change relative
to standard seat [°]
Standard seat,
left pedal depressed
Very tall, corpulent
Very short, corpulent
57 - 177
56 - 176
54 - 174
Swiveling seat 17°,
left pedal depressed
Very tall, corpulent
Very short, corpulent
63 - 183
64 - 184
66 - 186
Swiveling seat 17°,
pedal (right) depressed
Very tall, corpulent
Very short, corpulent
54 - 174
56 - 176
49 - 169
Table 3: Line-of-sight angle for various body models
position. When a person drives a vehicle, the joints in
this area are exerted primarily in a static posture, which
causes the muscles to tire rapidly.
From an ergonomic point of view, small rotational
angles in the joints are better than large ones. In addition,
rotating the pelvis on the seat so that the driver sits at a
slight angle to the driving direction is better than rotating
the joints of the spinal column relative to one another.
The forces and therefore the individual strain increase
very disproportionately as the body approaches its
physiological limits of movement. The result is that the
driver fatigues significantly faster when assuming larger
angles of rotation. In addition to other physiological and
biomechanical effects such as fatigue, agitation, pain,
etc., the strain of muscle groups, in particular, contributes
to perceived discomfort. It is also important to note
that as a person ages the maximum possible rotation of
the person’s joints decreases greatly. Therefore, reducing
joint rotation is beneficial, especially for older people.
Linde Technology I 1/ 2004
The lower section of the lumbar spinal column
(depicted in the model as joints 2 through 4) is especially
important for assessing posture. This area is well known
as the starting point for common lower back pain [1]. As
described above, it was possible to use the drivers’ body
postures (measured during the driving tests) to obtain a
realistic driver posture during reverse driving in the form
of a human model and depict this through the use of the
RAMSIS software. By altering the body proportions in
RAMSIS, it was also possible to reach conclusions about
the probable sitting positions and resulting fields of
vision for people with extreme body proportions that
were not represented in the group of test drivers. For
these advanced position analyses, two extreme body
types (corpulent and very tall or corpulent and very
short) were used in addition to an average body type.
11:46 Uhr
Physiological Limits
Seite 20
Hip joint (A)
Knee joint (B)
Ankle (C)
Figure 5: Critical rotations of the leg joints,
physiological limiting angles.
Reverse driving, standard seat, double-pedal
Reverse driving, swivel seat, double-pedal
Rotation around the X-axis [°]
Reverse driving, swivel seat, single-pedal
Forward driving
Hip joint
Knee joint
Ankle joint
Figure 6: Rotation of the right leg during reverse driving (“average man”).
The disadvantages of
single-pedal control
The results of the analyses indicated that when operators
drive in reverse with a non-swiveling seat, they turn in
the seat by an average of 22°. In addition, they rotate
themselves approximately 102° around the spinal column
and the head joint. With a non-swiveling seat, the total
rotation of the head relative to the vehicle averages
124°. These results are shown in Figure 4 and table 2.
The rotational angles in the individual joints show
how the swivel seat, when combined with the doublepedal control, relieves the spinal column by approximately
one third in the region between the lumbar sacrum (2)
and the rigid ribcage (7). When compared to a standard
seat, a seat that rotates 17° can reduce the rotational
burden by more than one third (37%), especially in the
important lower lumbar spinal column region (joints 2
through 4). On double-pedal vehicles, the extra angle of
rotation increases the total rotation of the driver’s head
relative to the vehicle’s longitudinal axis to 130°, thereby
increasing the field of vision. In this vehicle variant, the
pelvis is rotated a distance relative to the seat surface
that is similar on average to a standard seat, which does
not place a burden on the spinal column.
In contrast, on a vehicle with a swivel seat and
single-pedal control, the driver is able to rotate his pelvis
considerably less (compared to the other vehicle
variants) relative to the seat because he must use his
right foot to operate the pedal, which on this vehicle
variation is located on the right, when driving in reverse.
The driver must compensate for this lack of pelvic
rotation by rotating the lower lumbar region of his spinal
column in a manner similar to that encountered with a
standard seat. Thus the tested combination of a swivel
seat and single-pedal control did not prove to help
relieve this area of the back, which is associated with
lower back pain.
In fact, reduced rotational strains were recorded
with the single-pedal vehicle only in the upper section
between the upper lumbar vertebra and the ribcage
(4 through 7), an area where the spinal column rotates
almost not at all. Instead, a greater rotation of the head
in the region of the cervical vertebrae is observed, which
resulted in the highest recorded values in a comparison
of the vehicle variants. The recorded values range up to
the physiological limits of these joints. Consequently, a
vehicle equipped with single-pedal control provides the
driver only incomplete relief with regard to rotation of
the spinal column. The relief that is provided is distributed
unevenly along the back, the cervical vertebrae reach
the limits of their flexibility and there is no improvement
in the lower section of the lumbar spinal column.
When driving in reverse, it is not only the torso
that rotates, but also the area of the hips and legs. The
advanced positional analysis evaluated leg rotations in
the hip joint, knee joint, and ankle joint for typical
body proportions. The rotations of the joints shown in
Figure 5 were used as the critical measure of discomfort
because these joints move closer than the others to
their physiological limits of flexibility.
Due to the location of the seat’s point of rotation
relative to the vehicle frame, the left leg has nearly a
constant distance from the pedal during the swiveling
motion, so that the most clearly noticeable angular
changes appear on the right side of the body.
Compared to forward driving with double-pedal
control, only small differences to the ergonomically
favorable leg position appear with the standard seat and
the swivel seat with double pedals, Figure 6. With
double-pedal equipment, the driver uses his left foot for
both acceleration and braking when driving in reverse.
On a single-pedal vehicle, however, the driver must
stretch the right side of his body to a great degree in
order to operate the pedal, which is located on the right.
This results in a rotation (particularly in the right hip
joint) compromising the driver’s comfort in the length of
time. Therefore, with regard to the position of the
legs, the combination of a swivel seat and double-pedal
control produces the best sitting comfort
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Seite 21
Standard seat
Left eye
Increased field
of vision
Right eye
Reduced rotation
of the spinal column
Adjustable range of
the swivel seat
Swivel seat
Left eye
Right eye
Figure 8: Overlay of the reverse position on the 392 forklift
series, comparison between rotated and non-rotated sitting
Figure 7: The average man’s fields of vision when
driving in reverse, unmoving eyes, comparison between
the standard seat and the swivel seat, both with doublepedal control.
Visibility to the rear
Besides to the driver’s posture, the combination of seat
and pedal arrangement also affects the driver’s line of
vision. In addition to RAMSIS, the analysis functions from
pro/ ENGINEER were used to analyze the visibility. In
these tests, the RAMSIS model was configured with
various lines of sight, for example: in the direction of the
driving path behind the vehicle or in the direction of a
possible obstacle behind the vehicle at a medium height.
The line of sight was different from the driving task for
the test drivers, for whom a fixed visual target was
provided during reverse driving. Therefore, while the test
drivers’ visual target was constant and they had to adjust
their body positions accordingly, the RAMSIS simulation
calculation described here assumes a uniform strain on
the body’s joints and compares the resulting lines of
sight for the different vehicles. As a result, the calculated
lines of sight are different from the measured head
positions of the test driver group, depicted above.
Figure 7 shows an example of the lines of sight of
both eyes for the “average man” body stature as
determined by the RAMSIS visual analysis; the rotation of
the eyes is not reflected in this depiction (“fixed gaze”).
The fields of view visually depict the increased vision
to the rear that is achieved by the swivel seat in combination with double-pedal control.
To evaluate the actual vision in the vehicle, it is
necessary to also take into account the rotational range
of the eyes. Eyes typically have a horizontal range of
movement from –60° to +60°. Assuming typical body
Linde Technology I 1/ 2004
rotation with a standard seat, the driver has a field of
vision of approximately 180° to the direction of travel, so
that the driver can just discern objects that are located in
a straight line behind the vehicle. In contrast, the swivel
seat increases this field of vision (as already determined
in the examinations of body position) into the region to
the rear and diagonally to the left while simultaneously
reducing the rotation of the upper body.
In order to reach quantitative conclusions in addition
to this qualitative evaluation, pro/ENGINEER was used to
calculate the angle of the line of sight with respect to the
vehicle median level for the calculated body positions. As
shown in table 3, equipping a vehicle with a swivel seat
and double-pedal control increases the field of vision
to the rear, depending on the size of the driver, by +6° to
+12° compared to a fixed seat. As a result, the field of
vision includes much more than 180° for drivers of all
sizes. However, a swivel seat combined with single-pedal
control does not result in improved vision during reverse
driving due to the need for the driver to stretch the right
half of his body. The total rotation of the spinal column
is also reduced only slightly (see table 2). This becomes
even more apparent for drivers with extreme body
measurements (corpulent and very tall or corpulent and
very short; in other words: in both cases with relatively
short leg lengths). In these cases, the need to operate
the driving pedal with the right foot on vehicles
equipped in this manner even leads to a slight limitation
of the field of vision (up to –5°, see table 3) when driving
in reverse. In summary, it can be shown that vehicles
equipped with a swivel seat and the Linde double-pedal
control also represent the best variant ergonomically as
regards the resulting field of vision.
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Seite 22
As depicted in Figure 8, assuming the same general
conditions, the swivel seat with an adjustment
range of 17° offers the following advantages over a
non-swiveling seat:
■ The operating elements swiveling together with the
arm support (a necessary prerequisite for a swivelseat vehicle) increase the driver’s comfort by reducing
muscle fatigue during both forward and reverse driving.
■ Compared to a non-swiveling seat, the sitting comfort
increases significantly, which can be demonstrated
with approximately one-third (double-pedal) or onequarter (single-pedal) reductions in strain, measured
as the spinal column’s decreased angle of rotation.
■ On vehicles with double-pedal control, in which the
right foot does not perform any driving or braking
function in reverse, but can instead be positioned as
desired, the vast majority of the relief occurs in the
lower section of the lumbar spinal column (relevant
for lower back pain), which must be rotated by 7° less.
■ In addition, on vehicles with double-pedal control the
swivel seat also improves visibility during reverse
driving for drivers of all sizes compared to the standard seat, resulting in improved safety.
Linde AG and the Institute of Ergonomics at the Technical
University of Munich worked together to assess the
ergonomic design of the new 39X series of Linde forklifts
with various levels of equipment. The analysis focused
primarily on the seated workstation with a newly
designed swivel seat, which permits the operator to
rotate his body to the right in order to relieve strain
when driving in reverse. The data obtained during
measured driving stretches with various drivers served
as the basis for a CAD-supported analysis of the sitting
workstation with regard to the importance of arm
supports and body position and the driver’s field of vision
when driving in reverse. The results demonstrate that the
swivel seat, especially when combined with the Linde
double-pedal control, considerably reduces torso and
head rotation. In addition, this vehicle configuration
permits the driver’s legs to assume a more comfortable
position and improves the driver’s sight conditions during
reverse driving.
[1]: Drug Commission of the German Medical Association
(publisher): Kreuzschmerzen, AVP-Sonderheft
Therapieempfehlungen, 2nd edition, Cologne, 2000
The Authors
Dr. Frank Schröder
Before joining Linde AG, Dr. Frank Schröder was a scientist
in the Department of Automotive Engineering at Darmstadt University of Technology (Germany). In Darmstadt,
he led studies on driver behavior, emissions and fuel
consumption for various types of motorized vehicles. He
has been employed since 1999 in the forklift development department of
Linde AG where he contributes to the development process by conducting
vehicle trials. In 2001, Dr. Schröder took over responsibility for the product
acceptance department in the development of industrial trucks; since that
time, he has concentrated on balancing vehicle functions with customer
needs, compliance with conformity regulations, and questions regarding
the ergonomics of forklifts.
Dr. Thomas Seitz
Dr. Thomas Seitz is a certified physicist and a scientist
at the Institute of Ergonomics at Technical University
of Munich where he focuses on the development of
the RAMSIS PC-supported human model in various
applications. His has researched automotive design,
the ergonomics of work stations (including medical work stations),
and the modeling of people as operators of technical systems.
[2]: Gebhardt, H.; Müller, B.H.; Meissner, K.: Komplexe
Arbeitssysteme – Herausforderung für Analyse
und Gestaltung. In: Bericht zum 46. Arbeitswissenschaftlichen Kongress der Gesellschaft für
Arbeitswissenschaft, GfA-Press, Dortmund, 2000
[3]: Meissner, K.; Gebhardt, H.; Küpper, T.: Belastungen
von Gabelstaplerfahrern. In: Die BG 10/1998, 1998
[4]: Roth, J.: Verbesserte Flurförderzeug-Funktionen
durch elektrische Verarbeitung der Bedienvorgänge.
In: VDI reports 1590, Düsseldorf, 2001
[5]: Schmidtke, H. (publisher): Ergonomie, 3rd edition,
C. Hanser Verlag, Munich, Vienna, 1993
[6]: Seitz, T.: PCMAN – Ein Messsystem nicht nur zur
Analyse von Fahrerarbeitsplätzen in Gabelstaplern.
In: REFA-Nachrichten issue 6/2002, Darmstadt, 2002
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Seite 23
Dr. Michael Heisel, Dr. Christer Morén, Prof. Dr. Alexander Reichhold, Andreas Krause, and Antonio J. Berlanga-González
Approaches to Economic Solutions for Refineries
Cracking with Oxygen
Refineries are confronted with a major challenge due to
the worldwide, increasing demand for high quality fuels,
such as diesel and kerosene, and shrinking markets
for heating oil and heavy fuel oil. Consequently, it is an
important goal to increase the production of middle
distillates and simultaneously reduce the fraction of lower
value residues. In terms of technology, chemistry and
economics, the admixture of residue oils from atmospheric or vacuum distillation to the crude oil used in FCC
(Fluid Catalytic Cracking) plants is a suitable measure.
Refineries are facing a number of major challenges these
days, some new and some older, in part enforced ones:
■ Refinery operators have to comply with the new
“clean fuels” regulations, while
■ the pressure persists to improve economy and
margins, and
■ the demand for refinery products is shifting, e.g.
towards more diesel and kerosene in Europe, while
the demand for heating oil and heavy fuel oil is
The remaining refineries are being operated at
higher load. Essentially that means less spare capacity is
available to respond flexibly to shifting markets. The
example of shifting diesel demand versus gasoline shows
that there are substantial changes in the offing (Figure 4).
Compounding the problem is the economic situation
of the refineries. In the period 1993 through 1999,
the return on capital employed (ROCE) of the refining
operation was typically a low 4 to 6%. The easiest
solution to this economic pinch is the operation of
the refineries at a higher load as shown in Figure 3
illustrating US and German refineries.
Obviously, there are limits to this option. Once
the max. operational capacity is reached, the load can
be increased only by making changes in the existing
equipment. This often involves major investment.
However, for a few processes, solutions are available
which allow the refiners to expand capacity substantially
at a low cost. The most economic of these processes
is the FCC, in which oxygen enrichment can be used to
increase throughput by approx. 15% and conversion by
up to 3% with only a small investment of capital.
The economic pressure resulted in a reduction of the
number of refineries in Western Europe at slightly
increased capacity (see Figure 2). Both the capacity and
the number of refineries decreased in the US (Figure 3).
Figure 1: FCC plant in a
refinery at Ingolstadt
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Seite 24
No. of refineries
Capacity [million t/a]
Figure 2: Development of the refining industry in Western Europe.
Capacity [mio t/a]
no. refineries
Utilization (%)
Changes in US Refinieries
Capacity and utilization in German Refineries
Figure 5 shows a schematic diagram of an FCC plant. In
the oxygen enrichment process, oxygen O2 (blue arrow)
is admixed to the air for regenerating the catalyst.
More than 30 FCC plants throughout the world apply
oxygen in the regeneration process so that this
technology can be considered “mature”. Experience has
shown that the conversion to oxygen enrichment is
not associated with any undue problems.
The hardware required for conversion is straightforward and simple (Figure 6): Oxygen from a liquid
oxygen tank, a dedicated on-site air separation unit or
from a pipeline is metered via a control unit into the air
duct leading to the FCC regeneration. Preferably, O2 is
added downstream of the air blower in order for this unit
to need no approval for operation with oxygen.
The piping of the air duct is usually made of carbon
steel and does not need to be changed for adding
oxygen. However, certain restrictions apply in other
areas, such as maximum allowable gas velocities in
elbows. For safety it is advisable to have a block-andbleed installation during the shut-down of the oxygen
addition to ensure that there are no undetected
creeping gas flows from the FCC back to the O2 source.
Figure 3: Development in the number, capacity and load in US refineries,
and capacity and load in German refineries.
Testing at Vienna University
of Technology
Diesel versus Gasoline
Ratio Diesel/Gasoline consumptions
for Oxygen Enrichment
Figure 4: Diesel versus Gasoline consumption by geographical region.
Utilization (%)
Capycity [million t/a]
Hardware Needs
The technology of oxygen enrichment in FCC plants
is straightforward and not spectacular. But since all
reactions in an FCC riser are limited by kinetics, the
results are difficult to calculate. Therefore, a test program
was developed in cooperation with the Institute of
Chemical Engineering, Fuel and Environmental Technology of Vienna University of Technology to quantify the
effects of oxygen enrichment on throughput, conversion,
and product composition in an FCC pilot plant.
The feeds to the FCC pilot plant were to be varied:
not only the typical vacuum gas oil, but also atmospheric
and vacuum residue was to be admixed. Since these
feeds accelerate the heavy metal poisoning of the
catalyst, the accumulation of heavy metals was measured
also. The same equilibrium catalyst from an FCC plant in
a nearby refinery was applied in all tests. The composition
of the catalyst and especially the load of heavy metals
was analyzed before and after the experiments.
The oxygen concentrations in the regenerator
fluidization gas was varied. In each test run, the composition of the cracking products and the conversion were
analyzed and the composition of the off-gas from the
regenerator was measured. The feed load of the system
was varied between 100 and 135%. The temperature
in the riser and regenerator was kept as constant as
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Seite 25
Figure 5: Schematic diagram of a Fluid Catalytic Cracker (FCC) plant.
FCC reactor
Steam boiler
Cycle oil
Figure 6: Process principle of oxygen enrichment for FCC regeneration.
Result: Enhanced Catalyst Activity
The experiments showed that oxygen enrichment
resulted in improved regeneration of the FCC catalyst
leading to higher catalyst activity. As shown in Figure 7,
oxygen enrichment facilitated an increase in plant load at
constant conversion by approx. 10% (dotted blue line).
Alternatively, it was possible to increase the conversion
at a constant load by approximately 2 to 3% (continuous
red line). When the increase in catalyst capacity was
used to increase the conversion, less residue was
generated: as shown in Figure 8 3.5 to 5 % by weight
less residue was generated with oxygen enrichment as
compared to air alone. This can help the refinery to
reduce the low value residues to produce more gasoline
and middle distillates.
Linde Technology I 1/ 2004
The tests showed that oxygen enrichment in FCC
units allows the refinery operator to:
■ Increase the FCC capacity at constant conversion, or
■ Increase conversion at constant throughput
■ Utilize the improved conversion to admix heavier
residues, such as atmospheric residue
■ Get more flexibility in the choice of feedstocks
■ Process heavier feedstocks, and
■ Reduce the quantity of residues produced
by the FCC unit.
Seite 26
Increase of Load
Conversion [weight %]
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Conversion 27 Vol.-% O2
Increase of coversion
Conversion 21 Vol.-% O2
Feed Amount [%]
Figure 7: Increased conversion and capacity with oxygen enrichment
in FCC regeneration.
Conversion [weight %]
Residue at 21 Vol.- % O2
Residue at 27 Vol.- % O2
Feed amount [l/h]
Figure 8: Reduced production of residues with oxygen enrichment
in FCC regeneration.
This test plant also allows to process feed oils from
customers applying their equilibrium catalyst to predict the
effects of oxygen enrichment. However, the small-scale
pilot plant generates trends only, rather than numbers
that can be applied directly to large-size units.
Operating results of the
CEPSA Refinery
The CEPSA FCC in San Roque (Spain) is a UOP side-by-side
design with complete combustion of CO in the regenerator. The original design capacity of 4,200 m3/d has since
been increased to an actual capacity of 6,000 m3/d.
Since the existing air blower was not designed for this
increased demand it was decided to employ oxygen
CEPSA’s experience at the San Roque refinery was
that oxygen enrichment increases the flexibility of the
FCC with regard to varying feedstocks. This allows to
increase conversion, or alternatively to increase throughput at constant conversion.
This was of particular interest to CEPSA since the
feedstock for the FCC plant changed daily. Because
the feed changed on a day-to-day basis, the decision
concerning the use of oxygen was also made daily on
the basis of the production demand. The highest oxygen
concentration used at the CEPSA plant was 22.4 vol %.
The resulting potential was exploited in three ways:
■ the unit was able to cope with rapid changes
in feed composition;
■ conversion could be increased for a given feed;
■ as another option, throughput could be increased
at constant conversion.
A frequently asked question is whether oxygen enrichment does not raise the temperature in the regenerator
beyond tolerable levels. A simple heat balance showed
that oxygen enrichment resulted only in a negligible
reduction in heat sink capacity due to the reduced
amount of nitrogen. The main heat sink is the catalyst
whose heat capacity is not changed by the addition of
oxygen. Accordingly, there is basically no correlation
between regenerator temperature and oxygen concentration of the regenerator air feed. In contrast, the coke
burn-off from the catalyst has a much more significant
impact on the regenerator temperature. The operating
results of the CEPSA FCC at San Roque can be summarized
as follows:
■ increasing the oxygen content by 1% resulted in an
increase in regenerator capacity of 6%.
■ increasing the oxygen content by 1% increased the
regenerator temperature by less than 2 ºC. Coke
burn-off, rather than O2, defines the temperature rise.
■ Normal operating conditions were easily
obtained with enriched air.
■ Oxygen increases the ability to handle
high coke formation.
■ This, in turn, allows the refiner to treat heavier feeds,
especially by adding residues to the feed.
■ Oxygen enrichment allows to increase conversion
and/or throughput capacity of the FCC.
■ Oxygen reduces the formation of residues in the FCC.
Costs of Oxygen Enrichment
The modification of an FCC unit for oxygen enrichment
requires relatively small investments, typically of the
order of 100 000 to 300 000 US$. An oxygen source must
also be provided, though often a simple liquid oxygen
tank is sufficient. The costs of this depend primarily on
the tank size, i.e. ultimately on oxygen needs and size
of the FCC. The length of the O2 duct between O2 source
and FCC also contributes to the costs.
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Seite 27
Before tests
First test run
Second test run
After tests
Riser temperature
Feed temperature
Additional feed due to
oxygen enrichment [t/d]
Additional feed
[% of original load]
Table 1: Test conditions (CEPSA refinery)
* Conditions changed for the test, while the other conditions were kept constant.
Before tests
First test run
Second test run
After tests
Energy savings [€/d]
Daily turn-over [€/d]
Net profit due to oxygen enrichment
during test [€/d]*
Calculated annual net profit
due to oxygen [€/a]*
* For calculation of the net profit the cost of oxygen
has been deducted from the gross profit
Table 2: Economic evaluation of the tests (CEPSA refinery)
If large amounts of O2, i.e. in excess of 1 000 m3/h,
are consumed continuously, an air separation unit may
become economically feasible. Many industrial gas
suppliers offer lease options for such units or over-thefence delivery sparing the refiner the investment.
Economic Results of the
CEPSA refinery
Two test runs with oxygen enrichment were carried
out at the San Roque refinery within a short period of
time keeping the quality of the feed consistent. Oxygen
enrichment was tested at two different levels. The main
test parameters are listed in Table 1.
In the first test run, the temperature of the feed
oil was kept constant at 235°C. Oxygen was added to
the regenerator air. The feed inlet was raised until the
output of the wet gas compressor became limiting. The
temperature of the riser was allowed to increase. After
seven hours, samples were taken and then the second
test run was initiated.
In the second run, the oxygen concentration was
increased to 22.4%, the feed preheat was lowered
by 11°C to 224°C, and the riser temperature was kept
Linde Technology I 1/ 2004
almost constant except for an increase by 1°C. The feed
amount was increased until the wet gas compressor
capacity again became limiting. After four hours, samples
were taken and the addition of oxygen was discontinued.
As planned, the quality of the feed was basically
constant during the tests. Only the aniline point increased
by 2.2°C. The 90% distillation end point for gasoline
was 158°C before the tests, 156°C during the first test
run, 157°C during the second test run, and 162°C after
the tests. The octane indices were not measured.
The economic data shown in Table 2 were obtained in
the analysis. CEPSA drew the following conclusions from
these test runs:
■ The use of oxygen is profitable.
■ It allows to use HCO (heavy cycle oil) as
a normal feed component.
■ The limitation posed by the air blower capacity
can be eliminated.
Subsequently, the oxygen enrichment test installation
was converted to a permanent supply and the FCC was
successfully operated in this mode for several years.
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Seite 28
Economy of Oxygen enrichment in FCC, “gasoline” FCC
% op. cost O2
at 110% load
% op. cost O2
at 100% load
1.75 %
1.77 %
15.33 %
16.24 %
61.25 %
61.99 %
12.01 %
11.13 %
9.68 %
8.87 %
- 2.18 %
- 2.19 %
Feed oil
94.39 %
95.03 %
1.89 %
1.90 %
5.23 %
5.26 %
Cost of oxygen
0.67 %
0.00 %
105.93 %
100.00 %
Decanted Oil
Net profit
Figure 9: Comparison of operating cost air operation versus oxygen enriched operation.
Economic Results of a Refinery
in Brazil
A refinery operator in Brazil permitted the use of his
proprietary valuation numbers to calculate the effects of
oxygen enrichment. This operation was a fairly typical
case in that the production of gasoline was the primary
goal of this FCC. All other products are less valuable,
though the value of LPG comes very close to that of
gasoline. The data included the change in conversion and
ensuing change in product spectrum that resulted from
the increased load and oxygen enrichment. Based on this
these data, we calculated the respective turn-over using
this refineries’ internal rating numbers. The results for
oxygen enrichment to 22.9% are summarized in Figure 9.
Oxygen enrichment increases the capacity of the
plant. Due to the influence of oxygen there is a slight
shift in product composition in favor of LCO/Diesel and
decanted oil. This was paralleled by a shift in costs and
revenues. Altogether, the refinery increased its profits
by 5.93% by oxygen enrichment as compared to the
operation with air.
However, this these data is are dependent on the
oxygen price. Oxygen enrichment necessitates a relatively
small investment only, but increases operating costs,
which is equivalent to low fixed costs, but high variable
costs. Consequently, this option becomes less attractive
with increasing oxygen prices. The O2 price is very
site-specific and different between individual FCCs. By
comparison, the installation of a new air blower is
associated with higher investment costs that need to be
depreciated over several years. This is equivalent to high
fixed costs, but low variable costs.
Economic Results of
the HOLBORN Refinery
Various refiners confirmed that the payback of the
oxygen enrichment installation in their FCCs also was on
the order of a few weeks only. A more detailed insight
was granted by HOLBORN refinery in Hamburg. HOLBORN
is especially interesting because they use their FCC
primarily to produce middle distillates rather than
gasoline. Therefore, the FCC is operated at a low cat/oil
ratio of less than 5 and the riser operating temperature
is a mild 500°C.
HOLBORN has two main incentives to consider oxygen
1. The air blower of the regenerator often reaches its
limits leading to an insufficient amount of air being
available to burn-off all the coke on the catalyst. This
limits flexibility in the choice of feed oils with higher
ConCarbon content.
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Seite 29
Figure 10: The Spanish
mineral oil company,
CEPSA, operates one
of the largest refineries
in Spain near the Rock
of Gibraltar.
2. As the FCC riser is operated for middle distillates at low
severity it generates barely enough coke to keep the
temperature of the system up. Oxygen enrichment can
improve this situation by burning more coke off the
catalyst and at the same time reducing the amount of
inert nitrogen needing to be heated up without use.
decision on whether or not to convert to permanent
oxygen use. A test installation requires:
■ An O2 dosing station, a so-called FLOWTRAIN®
■ A trailer tank for supply of liquid O2
■ Piping or pressure hoses connecting the O2 tank and
the FCC unit.
We calculated the profit for the HOLBORN case based on
the internal valuation numbers using the procedure
described above. The result evidenced an increase of the
net profit by approx. 10% with oxygen accounting for
only 0.22% of the combined feed cost.
Comparing the gasoline-FCC in Brazil and the
HOLBORN middle distillate-FCC, substantial differences in
the effects of oxygen addition are apparent. These
differences are due to the difference in cracking severity:
more severe cracking in the gasoline-FCC is associated
with more extensive coke formation and an ensuing
higher air demand for regeneration. The much higher air
demand in the gasoline-FCC reduces the economic effect
of a given amount of oxygen added.
FLOWTRAINS® and liquid oxygen supply tanks can be
leased from Linde. Only the installation of the piping
between tank and FCC is associated with investment
costs, though often pressure hoses can be used
for connecting tank and FCC. These hoses can also be
obtained on a rental basis.
The subsequent test runs usually take between
4 and 6 weeks depending on whether or not the effects
of strongly varying compositions of feedstocks and/or the
addition of residue oil is to be tested. Usually, oxygen is
added in the test runs to the predetermined level.
Alternatively, the oxygen content of the regenerator air
can be slowly increased while monitoring the temperatures in the plant. The oxygen flow can be interrupted at
any time without difficulties. However, since it takes the
equilibrium catalyst several hours to adjust to the new
conditions it is not advisable to interrupt the tests. The
interruption of oxygen addition does not adversely affect
plant safety.
Equipment Needs for Test Runs
Typically, refinery operators want to see the effects of
oxygen enrichment first hand and, therefore, tests are
desired. The test runs usually require only little investment.
The majority of the equipment required for the tests is
available for rent. The tests generate reliable data for the
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Seite 30
Switching to Permanent Use
The rented FLOWTRAIN® can be converted from a lease
to a buy option. Often, a tailor-made device may better
serve the purpose at hand. For the supply of oxygen,
either a tank installation, an on-site air separator or overthe-fence deliveries from a pipeline may be considered.
Which of these supply options is best suited depends
on the amount of oxygen required, the fraction of time
in the supply is needed, and the range of fluctuation
The control of the FLOWTRAIN® has to be integrated
into the FCC unit’s control system including safety
interlocks, etc. While alarms may be adequate during
the test period, an automatic switch-off may be required
in the permanent installation. The details have to be
discussed for each case and adapted to the refinery’s
overall control and safety system.
Safety of Oxygen
The FCC unit is guarded by FLOWTRAINS® against unplanned admission of O2 by a number of safety installations.
1. Surplus oxygen: The FLOWTRAIN”contains a high alarm
in the flow controller which reacts when the target
value for oxygen is exceeded by 0.2 % (v/v). This
alarm allows the operator to re-adjust the oxygen
content by appropriate means. If the oxygen content
continues to rise there is a high-high alarm plus safety
switch at 0.35 % (v/v) of excess oxygen and the
O2 flow is stopped completely.
2. Failure of oxygen injection: A failure of the oxygen
supply is irrelevant for plant safety, means that coke
accumulates on the catalyst over time leading to
reversible deactivation of the catalyst. If the oxygen
supply cannot be re-established within 1/2 hour,
the amount of feed oil must be adapted to operating
conditions with air only.
3. Failure of instrument air: upon failure of the
instrument air, the block-and-bleed valves automatically switch into safe position, i.e. the block
valves are closed and the bleed valve is opened.
4. Low temperature switch for oxygen: If the oxygen
temperature drops below –5°C (23°F) an alarm rings.
This type of failure can happen when feeding the plant
from an liquid oxygen tank. If the temperature drops
below –20°C (-2°F), the oxygen flow is stopped to
ensure that no liquid oxygen enters the air duct of the
regenerator where it might cause thermal stress. This
measure also effectively prevents the instrument air
in any of the actuators from freezing.
Safety controls and switches of the DCS system of the
FCC: If the FCC is switched off by the DCS of the refinery,
the air flow is switched off also. Since the oxygen flow is
coupled to the air flow, switching off the air necessarily
also switches off the O2. That means that the O2 control
is indirectly connected to the safety switches of the FCC.
Oxygen enrichment in FCCs is a mature technology applied in more than 30 units world-wide. The procedure is
safe to use, yields high returns, and is associated with
only small investments. To quantify its effects, a test program was carried out at Vienna University of Technology,
in which the chemical and physical effects of oxygen
enrichment in a small-scale FCC plant were measured.
The main effect of oxygen enrichment is that
throughput and/or conversion can be increased, while
residue is reduced. These features enable a refiner
to respond flexibly to fluctuations in throughput,
feed composition, and market trends. Heavier feeds,
especially residues, can be treated such that only a
smaller amount of residues needs to be marketed.
Oxygen enrichment can contribute to the production
of more middle distillate.
The economic impact was calculated on the basis of
data from three commercial refinery FCCs. The payback
time of oxygen enrichment proved to be on the order of
a few weeks and no more than several months. The
profits were up to 25% higher as compared to the
air-blown FCC operation. Therefore, the application of
oxygen enrichment can be expected to increase as the
refineries are forced to further improve their economic
New regulations for “clean fuels” and changes in demand
are some of the major challenges faced by refineries.
An efficient response to this situation is the increase of the
use of residues in the FCC in order to enhance the
production of middle distillate and reduce the fraction of
lower-value residues. To quantify the effects of this
procedure, test runs with a small-scale FCC unit have been
performed at Vienna University of Technology. The
additional capacity required for the use of more residues
was supplied by oxygen enrichment in the FCC. The test
results were evaluated with regard to their economic
impact on a number of refineries.
Linde Technology I 1/ 2004
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Seite 31
[1] L. Cabra, “Refinery Challenges in the Current Decade”,
ERTC 6th Annual Meeting, Madrid, Nov. 2001
[2] 1999 Annual Report of the Mineralölwirtschaftsverband (Petroleum Economic Union) [registered
association], Hamburg, 1999, pp. 48.
[3] Oil & Gas Journal, Worldwide Refining Survey,
issues 1996, 1999, 2000, 2001
[4] T.E. Swaty et al., “What are the options to meet
Tier II sulfur requirements?”,
Hydrocarbon Processing, Feb 2001, p 62 ff
[5] Hydrocarbon Processing, Jan 2002, p 21
[6] R. Sadeghbeigi, “Fluid Catalytic Cracking Handbook”,
Gulf Publishing, Houston, Texas, 1995.
[7] D. Farshid et al., “Hydroprocessing Solutions
to Euro Diesel Specifications”,
Petroleum Technology Quarterly,
Winter 1999/2000, pages 29 ff.
The Authors
Dr. Michael Heisel
Dr. Michael Heisel is Project Manager of
Linde Gas and Engineering Germany. He is
responsible for the area of gas applications
in refineries and, in particular, for new
applications for process intensification. In his
previous position with Linde Engineering and Contracting, several
of his projects inventions received international awards. He
has published various papers and owns patents that have been
applied in process plants. Michael Heisel received his Doctorate
from the Technical University of Munich.
Dr. Christer Morén
Dr. Christer Morén is a member of Linde Gas
and Engineering’s working group on
refineries and petrochemistry. He joined the
AGA group, now owned by Linde, in 1976
being responsible at its affiliate, Tudor AB,
for improved battery systems. He has held various positions with
AGA AB and AGA Gas AB since 1981 in the following areas:
process technology, cryo-technology, the food and health industries, welding and cutting technology, and acquisition. He majored
in process technology at the Royal Institute of Technology in
Stockholm and is a member of ACS and AIChe.
Prof. Dr. Alexander Reichhold
Prof. Dipl.-Ing. Dr. techn. Alexander Reichhold
received his Doctorate in Process Technology
from the Vienna University of Technology.
He currently holds a position as an Assistant
Professor at the same university’s Institute of
Process Technology and is the director of the research group,
“Refinery Technology & Fluidized Bed Systems.” Alexander Reichhold
is a member of the board of the Austrian Society for Petroleum
Andreas Krause
Alexander Krause is a process engineer with
HOLBORN Europe Refinery GmbH where he is
responsible for the FCC Department. He looks
back on more than 13 years of experience
with process control applications and petrochemical plant technologies. He majored in Process Technology at
Hamburg (Germany) and then worked for seven years as a process
Control Engineer for Shell Chemie Köln. His area of expertise
includes processes, technical support, and process analysis. He
designs and calculates the technical components and equipment
for the improvement of the plant.
Antonio J. Berlanga-González
Dipl-Ing. Antonio J. Berlanga-González graduated from
the University of Málagá. Since joining CEPSA, he has
accumulated more than 30 years of experience in petrochemistry. He has held a position in the FCC Process and
Operations Department since 1982.
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Seite 32
Dr. Paul Kummann
Economic Production of Ammonia
The Location Makes the Difference
Ammonia is a base product of the chemical industry.
A variety of feedstocks is used to make the production
of ammonia economical. While natural gas is preferred
as a starting product in countries with natural gas
resources, countries depending on imports use cheap
refinery residues.
Despite large price fluctuations (between 90 and 250
USD/t), the average price for ammonia has essentially
remained unchanged over the past 20 years. This is also
evident from the historical price trends in the Caribbean
and Middle East, as the major export regions, and NorthWest Europe as a typical import region. The average
FOB prices derived from these charts are 146 and 145
USD/t for the Caribbean and Middle East respectively,
as compared to a CIF N.W. Europe of 169 USD/t.
Wellhead-sited locations with low NG prices are
typical export regions for ammonia. The price difference
to major import regions, like Europe, India and East Asia,
is mainly due to transport costs. Since the costs of shipment from the Middle East to Shanghai are in the range
of 40 USD/t, market-sited average ammonia cost CIF
East Asia (excluding import duties) of approx. 190 USD/t
have to be expected for coastal areas in East Asia, and
even higher prices further inland, when further transshipment and/or import taxes have to be considered.
Based on this background it can be investigated,
under which conditions new projects become economical.
Including a satisfactory internal rate of return (IRR)
export plants in wellhead-sited regions must not exceed
ammonia production costs of approx. 145 USD/t. At
market-sited locations at some distance from the coast,
even ammonia production costs of up to 250 USD/t may
be tolerated, in particular if this production is protected
by distant transport and/or import duties.
Three feedstocks, one product
Ammonia, a compound containing hydrogen and oxygen,
can be produced by a number of different process technologies. The characteristic feature of these technologies
is how the hydrogen is obtained from the feedstock.
The sequence of process steps is basically the same and
Figure 1: Heavy oil gasification-based ammonia plant in Jilin
(China) with a capacity of 1,000 t/day.
Generation of synthesis gas
Heat recovery and CO conversion
Purification of synthesis gas
Ammonia synthesis
Steam/driver system
This article analyses in more detail three different plant
concepts, which make use of either natural gas, refinery
residues or raw hydrogen.
■ Steam reforming of natural gas or naphtha
according to the Linde Ammonia Concept (LAC™).
■ Partial Oxidation of refinery residues by
Texaco high pressure gasification
■ Ammonia synthesis from raw hydrogen and nitrogen
Most ammonia plants use light hydrocarbons, especially
natural gas, as a feedstock. The high hydrogen content of
methane and the high purity of NG favor this use, since
relatively little energy is required for the generation and
purification of synthesis gas as compared to other
feedstocks. With only small additional investment costs,
natural gas-based ammonia plants can be operated
continuously, temporarily or partly with naphtha or other
light hydrocarbon feed streams. The supplementary
costs are in the range of a few percent and include
additional costs for the vaporization and pre-reforming
of naphtha.
The Linde Ammonia Concept (LAC™) is a process
for the production of ammonia from natural gas. This
concept involves the process steps illustrated in Figure 2.
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Another feedstock basis for the production of ammonia
are refinery residues, such as vacuum residue, visbreaker
tar or asphalt. The driving force behind the use of these
heavy and sulfurous feeds is their general availability at
moderate cost in regions where NG or naphtha are not
available in sufficient quantity and at an attractive cost.
The production of synthesis gas from heavy hydrocarbons is based on partial oxidation of these types of
feedstocks with oxygen. Further design features of
ammonia plants of this type are high operating pressures
during synthesis gas generation, Rectisol wash, nitrogen
wash, and ammonia synthesis in the absence of
inert components. A typical plant is represented by the
process description of Figure 3.
Ammonia plants with much lower investment
costs can be designed if raw hydrogen and nitrogen are
available. A hydrogen surplus may be available for
instance from a refinery, methanol plant or ethylene plant.
Provided the available quantity is sufficient, hydrogen
can be converted to ammonia following the production
scheme shown in Figure 4.
In this process scheme, the hydrogen can be purified
either by pressure swing adsorption (PSA) or by a
liquid nitrogen wash. PSA is advantageous if the raw gas
pressure is below 50 bar. At higher pressure, though,
depending on the composition of the gas, the liquid
nitrogen wash may be more beneficial due to its high
hydrogen recovery rate above 99 %.
Long-term profitability
The economic evaluation of the three basic plant
concepts is to take into consideration the investment
costs, operating costs, and profit expectations. The
investments costs of a new facility include the price of
the turn-key process plant and additional project costs
of the buyer. The turn-key price for a process plant is
determined on the basis of the required technology
and plant capacity. Buyer's additional costs for project
development, approval, and in house works are added
as lump sums. This type of cost may differ significantly
from one project to another, depending on available
infrastructure and plant integration with existing
facilities. For the purpose of this investigation, buyer's
additional project costs were rated to be 30% of the
turn-key price for the process plant and added.
A common commercial evaluation method was used
to compare the ammonia production costs of the three
different technologies. Firstly, the annual net cash flow
(NCF) was determined for the construction period and
15 subsequent years of plant service. The net cash
flow is obtained by subtracting investment and operating
costs from revenues. Applying a market-typical
interest rate (cut-off rate), the NCF values are then
Linde Technology I 1/ 2004
1. Natural gas desulfurization
2. Feedstock preheating
3. Reformer
4. Reformed gas cooler
5. CO conversion in isothermal reactor
6. Heat recovery
7. Hydrogen purification by PSA
8. Fuel gas recycling
9. Fuel gas heat recovery
10. Nitrogen production by air separation
11. Syngas compression
12. Heat exchanger
13. Ammonia synthesis
14. Steam production
15. Ammonia separation
16. Cooling with refrigerant
17. Steam/driver system
18. Condensate system
19. Refrigeration unit
Figure 2: Flow diagram of the Linde Ammonia Concept (LACTM).
Figure 3: Block diagram showing the production of ammonia from residue oil.
1. Drier station
2-4. Heat exchanger and gas cooling
5. Nitrogen wash
7. Cold box
10. Nitrogen production by air separation
11. Syngas compression
12. Heat exchanger
13. Ammonia synthesis
14. Steam production
15. Ammonia separation
16. Cooling with refrigerant
19. Refrigeration unit
Figure 4: Schematic diagram showing the production of ammonia from raw hydro-
14:44 Uhr
Seite 34
Figure 5: Linde LAC™ Ammonia plant in Vadodara (Spain)
with a capacity of 1,350 t/day.
converted into a series of discounted cash flows (DCF),
such that the sum of DCF values corresponds to the net
present value (NPV) of the plant after a certain period
of operation.
Finally, the NPV after 18 years is set equal to zero
(0) and the required max. interest rate is determined.
This interest rate is the internal rate of return (IRR)
and has to cover all interest and risks. The ammonia
production cost determined with this procedure correspond to the desired product prices leading to a desired
IRR of 20% and a net present value of the plant of zero
after 18 years (construction period plus service period).
The plant operating costs are an influential element
in the calculation of the annual net cash flows. Common
parameters were taken into account in the calculation of
the operating costs at fixed rates (static method). The
calculation includes as fixed costs constant feedstock
prices (0.7/1.7/3.0 USD/MMBTU, million British thermal
units = approx. 293 kWh), maintenance and insurance
costs (2% each per year), cooling water prices (0.04
USD/m3), and personnel costs according to European
standards (40,000 USD/year). The plants were
assumed to be operated for 8,000 hours per year and a
construction period of 30 months was assumed.
Three prices for one product
taking the capital requirements and operating conditions
of the plant into consideration. In a first approximation,
the result obtained is also valid for naphtha as the
feedstock and for steam reformer-based technologies
offered by other contractors.
Obviously, the ammonia production costs depend
mainly on the feedstock cost and plant capacity.
Analyzing historical price trends since 1993, it is evident
that, at a NG price of 0.7 USD/MMBTU, new plants
with capacities of 1,350 t/day and above are an attractive
investment in export regions where the average
ammonia price is 145 USD/t.
The operation of market-side ammonia plants
remote from gas wells and closer to consumers can
tolerate higher gas prices and/or smaller capacities and
still be economical. To give an example, a NG-based
ammonia plant with a capacity of 600 t/d serving
a phosphate complex some distance from the ocean
and waterways is an attractive investment. In this case,
the acceptable NG price level depends on the transport
surcharges of imported ammonia.
On the other hand, it is also evident from Figure 6a
why ammonia producers in market regions with excellent
transport infrastructure, e.g. near rivers and canals
in Central Europe, face severe competition by imported
material. NG prices in Central Europe are too high to
support the construction of new ammonia plants. The
price of ammonia in certain market regions is mainly
determined by the cost of imported material. As a result,
only large and fully depreciated ammonia plants can be
operated economically in Europe.
Refinery residues are advantageous in that they
are available at moderate cost in industrial regions
throughout the world. Depending on the capacity, type of
crude oil, and process configuration of the respective
refinery, the surplus of residue is frequently sufficient to
serve as the feedstock for one (1) ammonia plant.
A typical residue price of 60 USD/t corresponds to
approx. 1.6 USD/MMBTU was used as a fixed value in this
evaluation. Compared to the NG price at the wellhead
this may still seem high. However, for the comparison to
be valid it must be related to NG prices of 3.5 – 4.5
USD/MMBTU in the markets at the end of a NG pipeline
or LNG supply chain.
For example, only small amounts of NG are available
in countries like China and India. Consequently, the
ammonia and urea production in Asia is largely based
on refinery residues, or even on coal. The construction of
oil-based plants in regions with a high fertilizer demand
provides the additional advantage that the regional
transport infrastructure is not burdened by these transportation loads. This may explain why many ammonia/urea projects using refinery residues were built in
Asia. Many of these projects were also supported by soft
loans from countries like Japan, Germany and Italy in
The costs of ammonia production from NG under these
conditions are illustrated in Figure 6a. The production
costs listed therein were evaluated for the LAC™ process,
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Seite 35
order to promote a certain degree of self-sufficiency.
According to Figure 6b, production costs of 240 - 285
USD/t are obtained for partial oxidation (POX)-based
ammonia plants with capacities of 1,000 – 1,350 t/d.
Since approx. 0.8 t of residues are required to produce 1 t of ammonia, the product price contains approx.
45 USD/t of feedstock costs. This explains the strong
dependence of the production cost on the capital costs
required for the generation and purification of synthesis
gas from a chemically less optimal feedstock.
Any economic analysis has to take into account that
many plants of this type were built at lower cost than
today's costs of a turn-key plant. Plant costs increased
moderately, while the market prices of ammonia
remained fairly constant. Some partial oxidation plants
have been in operation for more than 15 years and are
essentially paid off. In several plants, the plant capacity
was enlarged or the customers integrated additional
CO-based downstream production facilities, e.g. for acetic
acid, toluene diisocyanate (TDI), and methanol, to
further improve plant efficiency.
Subject to the condition that the raw hydrogen is
available from other sources, the investment costs of
ammonia production can be significantly lower. This is
because an investment in syngas generation is not
required under these conditions. The resulting costs of
ammonia production from raw hydrogen are illustrated
in Figure 6c as a function of plant size and hydrogen cost.
For the production of 600 t/d ammonia, approx.
50,000 Nm3/h hydrogen are required. For stoichiometric
reasons, this amount of hydrogen may in principle be
available as purge gas from older methanol plants
lacking an auto-thermal reformer. If this hydrogen is used
as fuel gas, its value is basically only 0.7 USD/MMBTU,
resulting in attractive ammonia production costs.
However, more realistically one has to assume
that rather less hydrogen is available as free capacity.
Considering, for example, a market region with average
ammonia prices of 200 to 250 USD/t, the surplus
hydrogen (e.g. 25,000 Nm3/h) is supplied to an external
ammonia synthesis loop of 300 t/d. The associated
investment is attractive for hydrogen costs of up to
approx. 3 USD/MMBTU (LHV).
The LAC™ process provides for the production of
several by-products aside from ammonia. For example,
in an LAC™ plant hydrogen and nitrogen are available as
pure intermediate products prior to their processing into
synthesis gas. Consequently, these two by-products
can be exported for other applications without a need
for additional equipment and changes in the process
configuration. The production of these by-products is
associated with an attractive economy of scale resulting
from the often larger scale of ammonia production.
Further products, such as CO2 (from conversion),
oxygen and argon can be produced after some
Ammonia production cost [USD/t]
● NG Cost: 3.0 USD/MMBTU
● NG Cost: 1.7 USD/MMBTU
● NG Cost: 0.7 USD/MMBTU
Plant capacity [t/day]
Figure 6a: Ammonia production costs as a function of plant size and natural gas prices.
Ammonia production cost [USD/t]
● Oil Feed 1.6 USD/GJ
Plant capacity [t/day]
Figure 6b: Costs of ammonia production from residue oil.
Integrated Facilities
Further opportunities to enhance the economic efficiency
result if ammonia production is integrated into existing
facilities rather than newly erected on the green field.
These opportunities, though, largely depend on the
individual circumstances of the project and are difficult
to present in the form of charts and diagrams. Generally,
improvement in economic efficiency is due to the
utilization of suitable by-products and cost savings from
integration into existing facilities.
Linde Technology I 1/ 2004
Ammonia production cost [USD/t]
● H2: 3.0 $/MMBTU
● H2: 1.7 $/MMBTU
● H2: 0.7 $/MMBTU
Plant capacity [t/day]
Figure 6c: Costs of ammonia production from raw hydrogen.
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Seite 36
equipment is added, however, with no substantial
increase in the feedstock and operating costs. For
example, the reboiler duty to separate CO2 by a gas
scrubber can be covered by cool down of process gas.
The production of oxygen or argon requires additional
columns in the air separation cold box, but no increase
in air compression.
Basically, other side products, such as CO and
methanol, can also be added, but their production
increases the feedstock needs and requires additional
equipment. In this case, the co-production of other
products can only make use of a larger economy of scale.
In view of these facts it is not surprising that most of
the LAC™ plants contracted so far produce side products.
Further opportunities for the improvement of the
economic efficiency are provided by integrating the plant
into existing facilities: e.g. the LAC™ plant in Daqing
(China) does not need to have it's own nitrogen production facility. Instead, the customer owns an oxygen plant
which was built to feed an oxygen blown secondary
reformer in his methanol plant. Consequently, nitrogen
was available on site and a nitrogen plant accounting for
additional investment costs of approx. 15% of the total
cost of the ammonia plant was dispensable. Moreover,
the ammonia can be exported making use of the existing
storage tanks and loading facilities. H2 and CO2 are
exported for other applications.
The LAC™ process typically includes a turbo generator for conversion of the steam surplus into plant power.
In Phosphate Hill and Moura (Australia) steam
surplus or the need for downstream facilities is balanced
by the LAC™ plant. Moreover, the involved nitrogen
plants produce the instrument air and plant nitrogen as
well as power for other consumers.
In the major industrial complex in Vadodara, India,
hydrogen, carbon dioxide, oxygen and argon are
produced as by-products. The storage and distribution of
ammonia and the supply of utilities were integrated
with other facilities of the complex.
The price of ammonia increases with the distance of a
consumer from the NG well-heads. This is because large
natural gas-based ammonia plants located in regions
such as the Middle East and Caribbean determine the
worldwide price structure.
However, at some distance from the major export
markets medium sized NG-based ammonia plants can also be an attractive investment, in particular if such plants
serve a downstream consumer, such as a phosphate
complex or ammonium nitrate plant. Refinery residues
may be an alternative feed stock, if NG is not available
in sufficient quantity and at an attractive cost. As bottom
of the barrel product, refinery residues are available at
moderate cost in refineries throughout the world and can
be processed.
The economic efficiency of such partial oxidationbased ammonia plants is influenced mainly by plant
capacity, integration with existing refinery facilities,
and the co-production of by-products. In countries such
as China and India, ammonia plants utilizing refinery
residues as feedstock provide for a certain degree of self
sufficiency in the production of ammonia and urea.
The location of the plant is a crucial factor for the design
of new ammonia production facilities. The economic
efficiency depends mainly on the availability of the
feedstocks and the local ammonia demand. Especially in
the proximity of oil-producing countries, natural gas is
the preferred source for the production of hydrogen and
ensuing synthesis of ammonia. In contrast, oil refinery
residues are often more economical in oil-import regions,
such as the countries in Europe. In countries, such as
China and India, the close proximity of ammonia and
fertilizer plants reduces the burden on the local traffic
infrastructure and is therefore subsidized by the
governments. In addition, synergy effects with existing
facilities can be utilized to save on investment and
operating costs.
The Author
Dr. Paul Kummann
Dr. Paul Kummann was awarded
a doctorate in Physical Chemistry
by the University of Münster
(Germany). He taught Technical
Chemistry at the Institute Algerienne des Petrol
(Boumerdes, Algeria) and joined Linde in 1981
as a process engineer for natural gas plants.
From 1989 he directed the Linde branch in Beijing
(China) before focusing his attention on various
marketing tasks at Linde between 1993 and 1998.
He currently is Senior Project Engineer for Synthesis
Gas Facilities.
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Eginhard Berger, Manfred Boelt and Bjørn Sparby
The Benefits of Cold Deep-Water for LNG FPSOs in Tropical Seas
Offshore Plants for LNG Production
Major natural gas fields situated approx. 100 kilometers
off the coast of Nigeria are waiting to be developed.
Linde’s advanced floating production, storage, and
offloading technology for liquefied natural gas offers
an innovative solution for the commercial exploitation
of these deposits.
Extensive preliminary work has been performed as part
of the development of the natural gas fields off the shore
of Nigeria. The benefits of the floating LNG-FPSO concept
(LNG = liquefied natural gas; FPSO = floating production,
storage, and offloading) convinced the shareholders to
further pursue this concept. As the next step, exploration
wells will be drilled in order to demonstrate the resources
available for exploitation. These efforts follow the lead of
the Snøhvit project with 4.3 MTPA (million tonnes per
annum) LNG production capacity which is currently under
construction. Its execution includes the following steps:
■ Design and installation of the process plant on a barge
■ Yard construction of the barge
■ Yard construction of the process units
■ Integration and hook-up of barge and process
units in a yard
■ Ocean transportation of the integrated process barge
Deep-sea LNG-FPSO
Water depth: 1,000 m
Air temperature: 28°C
Water temperature at a
depth of 1,000 m: 5°C
Shallow-water LNG-GBS
Water depth: 23 m
Air temperature: 35°C
Water temperature: 28°C
approx. 100 km
NG Deposits
These steps are in principle the same as required for LNG
FPSOs, although the Snøhvit LNG process barge will eventually be grounded and integrated into a more or less
conventional land-based LNG complex. Therefore, the
Snøhvit LNG project can be considered as a first reference
towards marinization of LNG baseload plants.
Based on this experience, Linde has developed the
topside process and utility facilities for two offshore
LNG concepts:
■ An LNG FPSO (floating production storage and
offloading) on a barge in deep-waters
■ A fixed LNG-GBS-plant in shallow-waters near the
shore (GBS = gravity base structure = gravity platform
grounded on the sea floor, usually made of concrete)
Design Conditions Deep-water
A floating LNG plant concept in benign waters approx.
100 km offshore the West African coast had to be
designed on the basis of the following main parameters:
Ambient conditions:
■ Air temperature:
28 °C
■ Seawater temperature: 5 °C (at a depth of 1000 m)
The process plant had to be designed to meet the
following requirements:
■ The quality of the produced LNG, LPG (Liquefied
Petroleum Gas) and gasoline must be suitable for
international trade
■ No permanent flaring is permitted
■ International rules and regulations must be
applied, e.g. API (American Petroleum Institute)
and DNV (Det Norske Veritas).
The plant had to be designed to handle feed streams
from 3 fields with typical compositions. The pressure was
120 bar at plant inlet at a temperature of 28°C. The
compositions of these three feed streams turned out to
be ideally suited to LNG production, since there is only a
very small fraction of nitrogen and the acid gas (CO2)
content is comparatively low. H2S is not present. Any
nitrogen would need to be removed, because nitrogen
Figure 1: Alternative LNG concepts for the development of natural gas
resources off the coast of Nigeria.
Linde Technology I 1/ 2004
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Seite 38
Design Conditions Shallow-water
The task was to design a fixed LNG plant on a GBS in
23 m water depth for the same feed gas compositions
as in the LNG FPSO case. However, the location in
shallow-water, relatively close to the shore, but remote
from the production wells, required the following design
parameter changes:
■ Design air temperature
■ Seawater temperature
Figure 2:
The Statoil-Linde
MFC® Process.
In addition, the gas pressure of one feed gas stream
drops in the sub-sea pipeline to 60 bar by the time it
reaches the plant on the GBS.
Streams to be heated
Streams to be cooled
Process Selection
Several processes are available for the large-scale
liquefaction of natural gas:
■ SFMR process (Single Flow Mixed Refrigerant)
■ CC process (Classical Cascade)
■ C3/MR process (Propane Pre-cooled
Mixed Refrigerant)
■ DMR process (Dual Mixed Refrigerant)
■ MFC® process (Mixed Fluid Cascade)
■ Nitrogen Expander Process
Figure 3: Typical Cooling Curves in the MFC® Process.
has no calorific value and excessive amounts of nitrogen
fail to meet gas sales specifications. H2S, had it been
present in addition to nitrogen, also needs to be removed,
because this component would also freeze at low
temperatures and plug the heat exchangers. The removal
of these components would have been associated with
considerable investment costs and power requirements.
Both the high feed gas pressure of 120 bar and the low
cooling water temperature turned out to be extremely
beneficial for the process design.
The requirements on these processes are as follows:
■ Safety and reliability
■ Low weight and low area requirement
■ Low investment and operating costs
■ Low emissions
■ Large capacities in a single process train
to obtain the economy of scale due to the
lower specific investment costs
At first glance, the safety criterion is met best by a
nitrogen expander process. An inert gas, nitrogen is safer
than all other processes, since these use hydrocarbons
as refrigerants.
These are flammable in case of a leakage. However,
the power requirement of the nitrogen process exceeds
drastically the power requirement of all other processes.
For a given LNG production capacity this means that the
prime movers (mostly gas turbines), the compressors and
the cooling system, as well as all support systems have
to be increased, which counterbalances the safety benefit
to some extent and increases the investment costs to an
unfavorable level.
Linde and Statoil jointly investigated the features of
all these processes in detail and concluded that the
existing requirements are best met by the potentials of
the MFC® Process (please refer to “The Snøhvit Project”,
in Linde Technology 1/03).
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Seite 39
Figure 4: GE LM 6000 Power Output and Heat Rate.
The MFC® Process is a proprietary process jointly
developed and owned by the Statoil-Linde LNG Technology
Alliance. The flow scheme is illustrated in Figure 1.
The excellent efficiency of the MFC® Process is
evidenced by an analysis of the cooling curve. Natural
gas is usually liquefied at pressures above 40 bar in order
to reach acceptable levels of compressor shaft power
requirements. The typical cooling curve (heat over
temperature) is S shaped as shown in Figure 2 and
can be subdivided into the 3 sections:
■ Pre-cooling
■ Liquefaction
■ Sub-cooling
The craftsmanship of the process designer is to match
this cooling curve with refrigerant cycles as closely as
possible, i.e. with minimum temperature differences at
any enthalpy (heat) point. Linde “Optisim” software is a
powerful tool to achieve optimized results taking into
account relevant constraints like avoiding temperature
overlapping (integrated pinch analysis) and compressor
efficiencies, etc.
Therefore, the MFC® Process was applied to the deep
and shallow-water offshore LNG concepts. The cooling
curve indicates that the cycle compressor shaft power
requirements depend on the inlet temperature of the
natural gas and the refrigerant cycles after cooling by the
available cooling water. The effects of the cold deep
sea water (5°C) and the warm shallow-water (28°C) as
cooling water as well as the reduced feed gas pressure
on the total refrigerant cycle compressor shaft power is
shown below for an LNG production capacity of 5.1 MTPA:
■ LNG FPSO deep-water case (cooling water at 5°C):
132 MW
■ LNG GBS Shallow-water Case: (cooling water at 28°C):
176 MW
Linde Technology I 1/ 2004
Prime Mover Selection and LNG
Production Capacity
The cycle compressors can be driven by
■ Steam turbines
■ Gas turbines
■ Electric motors
■ Combinations of the above drivers
The compressors of the first LNG baseload plants were
driven by steam turbines which was advantageous in
that any required capacity was available. However, the
lower efficiency, large size of the equipment, and the
extensive cooling system caused the investors to decide
in favor of a direct gas turbine drive.
The gas turbines, however, are the most sensitive
equipment of an LNG plant. Redundancy is required in
order to obtain acceptable plant availability. Therefore, it
is proposed to use an incremental number of highly
efficient General Electric LM 6000 gas turbines to drive
electric generators with at least one gas turbine/
generator set as back-up. The cycle compressors are
driven by electric motors, operating on the plant’s power
distribution system.
This all-electric drive scheme is now being used at
the Snøhvit LNG project (see Linde Technology 1/03).
It is considered to be the most advanced system and
provides the highest degree of availability for single train
installations. The concept is expected to be adapted
to further LNG plant projects both for land-based and for
offshore installations. This concept increases the
availability of the plant and thus the sales revenues
considerably as compared to direct drive by gas turbines.
An additional benefit is the decoupling of the train
capacity from the size of the existing gas turbines.
11:59 Uhr
Seite 40
Figure 5: The MFC® Process with All-electric Drive and Waste Heat Recovery for Hot Oil Heating.
Directly driving compressors by gas turbines leads to
limitations since gas turbines are commercially available
only at incremental capacities.
The best option of a gas turbine both for onshore
and offshore installations is the aero-derivative GE LM
6000 gas turbine made by Nuovo Pignone. It’s characteristic features are its low weight and high efficiency.
All gas turbines are dependent on the outside air
temperature, which is admitted and compressed and
then used for fuel gas combustion. The dependence
of the gas turbine power output and the heat rate is
indicated in the diagram in Figure 4.
As is evident from the diagram, the output of the
LM 6000 gas turbine is approx. 46 MW at 10°C, compared
to only approx. 33 MW at 35°C. Therefore, it is proposed
to cool the air intake of the gas turbine with the 5°C
cooling water available in the deep-water case. This
air-cooling is performed in so-called quench coolers with
a secondary demineralized water cycle, which is
re-cooled counter-currently to the seawater. The cold
seawater with its constant cooling temperature provides
for very low fluctuations of turbine power output and
consequently for stable production rates. This quench
cooling corresponds to the state of the art in air separation plants operating under similar climatic conditions,
where relatively cold cooling water (as compared to the
ambient air) is available.
The exhaust gas of the gas turbines is best used for
hot oil heating in a waste heat recovery unit. A hot oil
cycle is normally used for process heating mainly in the
dehydration and acid gas removal units.
The stated gas turbine output figures represent
gross values. The net power that can be distributed to
the electric consumers in an LNG plant is calculated
by subtracting the losses due to air intake cooling
(deep-water LNG-FPSO), aging, waste heat recovery, and
generators. The net gas turbine output for the two cases
investigated are as follows:
■ Deep-water LNG-FPSO:
40.7 MW
■ Shallow-water LNG-GBS:
30.5 MW
Multiple installations of these gas turbines are necessary
to meet the power requirements of large LNG plants
with production rates between 4 and 6 MTPA, which are
currently envisaged for several baseload LNG projects.
A capacity of 5.1 MTPA was chosen for the two cases for
comparison reasons. The following number of GE LM
6000 gas turbines is required in each case:
Deep-water LNG-FPSO: 4 +1 spare GE LM6000
Shallow-water LNG-GBS: 7 +1 spare GE LM6000
The spare unit is needed as a back-up to improve the
plant availability, since the gas turbines require regular
down time for maintenance. The combination of the
MFC® Process and the all-electric drive system, waste
heat recovery, and hot oil cycle for the deep-water LNG
FPSO is illustrated in Figure 5.
Power Requirements and
Plant Efficiencies
The all-electric drive concept with waste heat recovery
presented above provides for excellent utilization of the
fuel gas in excess of 70%. In addition, the all-electric
drive configuration allows the compressor power loads
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Seite 41
Figure 7: CAD Model of a
Shallow-Water LNG-GBS
(Gravity Base Structure)
for 5.1 MTPA.
for the three refrigerant cycles to be adjusted freely such
that the cooling curve can be optimally matched. As a
consequence of this lowest possible total compressor
shaft power requirement, the plant becomes highly
efficient. This can be expressed as conversion factor or as
internal consumption (hydrocarbon products / feed, or
fuel gas / feed, all expressed in gross calorific values).
In the two cases investigated here, these parameters are
as follows:
All products (LNG, LPG, and condensate) and
process and utility consumers are taken into account
in the above figures.
Selection of Heat Exchangers
Linde is in the unique position to fabricate the two types
of cryogenic heat exchangers conventionally used in LNG
baseload plants: the plate fin and the spiral wound heat
exchangers. Each of these heat exchanger types has
specific benefits and disadvantages. Among other things,
the single plate fin heat exchanger core has a relatively
competitive cost. However, large LNG plants need to have
multiple, parallel plate fin heat exchanger installations,
such that this advantage is counterbalanced to some
degree by the complex interconnecting piping. The spiral
Linde Technology I 1/ 2004
wound heat exchangers show extreme resistance to the
thermal stress encountered in the low temperature
sections during start-up or maloperation. A detailed
comparison showed that each heat exchanger type has
specific merits at the proper place. Therefore, it was
decided to use the plate fin heat exchanger for the
pre-cooling section and the spiral wound heat exchanger
for the liquefaction section and the sub-cooling section.
The Cold Box
In most of the large LNG baseload plants, the cryogenic
heat exchangers have individual insulation, which applies
to both plate fin and spiral wound heat exchangers. This
insulation mainly consists of polyurethane foam or of
foam glass. However, an alternative insulation method
was selected for the Snøhvit LNG project and in offshore
LNG concepts: the cold box. Cold boxes are usually
installed in cryogenic processes such as air separation
and LNG peakshaving plants. It consists of a box of
normal carbon steel plates enclosing the cryogenic
equipment and piping. The void space is filled with the
powdered mineral, Perlite, as the insulation material.
The benefits of this type of cold box are evident:
■ The cryogenic process equipment and piping is all
welded together and laid out as tight as possible
resulting in minimized material and thermal losses
and maximal safety.
■ The cold box is mechanically completed in workshops
under optimized conditions
■ The cold box provides external mechanical protection
during transportation and in the plant itself
■ Apart from the “all welded” principle of the cold box
interior, which is considered as the safest installation
mode, the cold box enables detection of possible
leakages by control of a nitrogen purge stream in the
Perlite-insulated space.
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Seite 42
Figure 6: CAD Model
of a Deep-Water
LNG-FPSO for 5.1 MTPA.
■ Fire resistance requirements can be met efficiently
with a cold box. This is relevant for the compact
Snøhvit plant layout as well as in general for offshore
LNG plant concepts.
The process and equipment configurations shown above
have been used to design concepts for the floating
deep-water case platform and the fixed shallow-water
LNG-GBS. The respective CAD models are shown in
Figures 6 and 7. All process and utility facilities are
installed on the topsides.
Deep Water LNG FPSO
Shallow Water LNG GBS
Area requirement
11700 m2
12 700 m2
35 000 t
38 000 t
Fuel gas consumption
13.4 x 106 GJ/a
18.0 x 13.4 106 GJ/a
CO2 emissions
1.02 Mill t/a
1.37 Mill t/a
Compressor shaft power
Number of gas turbines
4 + 1 spare
7 + 1 spare
Cooling water
26 000 t/h
36 000 t/h
Investment cost
100 %
120 %
Table 1: Comparison of deep-water-LNG-FPSO versus shallow-water-LNG-GBS
Overall Comparison of
Deep-water LNG FPSO and
Shallow-water LNG GBS
The design conditions are obviously favoring the
deep-water LNG FPSO concept in many respects, and
penalize the shallow-water LNG GBS concept. The
higher refrigerant cycle shaft power requirement and
the lower power output of the gas turbines in the
LNG GBS case impact the following items:
■ More gas turbines are required
■ Larger compressors are required
■ More cooling water is required
■ More piping, structural steel, instrumentation,
electrical works, construction etc.
■ Higher capital and operating expenditures
■ More fuel gas required
■ Higher emissions
The benefits of the deep-water LNG-FPSO concept as
compared to the shallow-water LNG-GBS are summarized
in Table 1. The deep-water concept is beneficial according
to all criteria shown in the table and ultimately results in
lower investment and operating costs. Moreover, the
submarine pipelines between the wells and the plant are
substantially shorter than in the shallow-water concept,
in which they increase the overall costs substantially.
The disadvantages of the LNG-GBS concept apply equally
to a land-based installation near the shore.
In general, both concepts are characterized in that,
unlike onshore installations, there is no need for harbor
facilities and complex cooling water systems, which may
be associated with substantial costs in some coastal areas
with shallow waters, in which a deep-water channel
must be maintained for access of large LNG tankers.
Some other beneficial aspects of offshore LNG
concepts are attracting increasing attention: they involve
no land use and the facility cannot be seen from the
shore and does not give rise to concerns because of its
environmental impact.
Linde Technology I 1/ 2004
11:59 Uhr
Seite 43
The design of the deep-water LNG-FPSO off the African
shore features the highly efficient MFC® Process, cooling
with cold deep seawater (5°C), and gas turbine air intake
cooling. This enables the installation of LNG baseload
projects offshore in tropical regions under conditions that
are usually encountered only in northern regions like
Norway or Alaska. The positive impact on the economic
viability of such an LNG baseload project is enormous.
■ Eginhard Berger, Wolfgang Förg, Roy Scott Heiersted,
Pentti Paurola: The Snøhvit Project, Linde Technology,
■ Roy Scott Heiersted, Statoil: Snøhvit LNG
ProjectConcept Selection for Hammerfest LNG Plant,
GASTECH 2002, Qatar, Oktober 13-16, 2002
■ W Förg, W Bach, R Stockmann, Linde and
R S Heiersted, P Paurola, A O Fredheim, Statoil:
A New LNG Baseload Process and Manufacturing
of the Main Heat Exchangers. LNG 12 Conference,
Perth, May 1998.
The development of natural gas fields off the coast of
Nigeria is being continued in 2004. The specific benefits
of the floating LNG-FPSO concept convinced the shareholders of these deposits to further pursue this concept
following the example of the Snøhvit project which is
under construction. This paper focuses mainly on the
advantages of deep-water LNG-FPSO concepts due to the
availability of cold cooling water, whereas installations
based on GBS plants are forced to utilize relatively warm
surface water for process cooling.
Linde Technology I 1/ 2004
The Authors
Eginhard Berger
Eginhard Berger graduated in
mechanical engineering at the
Technical University, Munich. He
worked in the aerospace industry
before joining the Linde AG,
Engineering Division, Höllriegelskreuth, Munich,
in 1969. He was first involved in computerizing
the physical properties of natural gas components. As a project and sales manager he was
later decisively involved with the LNG projects
at Snøhvit (Norway) and Xinjiang (China). In
addition, Eginhard Berger functions as project
manager for the development of offshore-LNG
plants. He is, among other things, a member
of the European Technical Committee for the
standardization of LNG plants.
Manfred Boelt
Manfred Boelt studied technical
physics in Munich and joined Linde
in 1980. He started with process
engineering and was engaged in
the design of plants for the treatment, separation and purification of hydrogen as
well as natural gas. From the beginning, he
participated in the development of natural gas
separation plants and natural gas liquefaction
plants. He has a wide experience in natural gas
plant designs and holds several international
patents in this field.
Bjørn Sparby
Bjørn K. Sparby, Project Manager,
INT GEX Africa, Statoil, has spent
more than 28 years in the upstream
oil and gas business. He holds a BS
and MS degree from the University
of Wyoming in petroleum engineering. Most of
his career has been in Stavanger, Norway, with
various technical and commercial responsibilities
for domestic and international activities. He has
been in charge of developing Statoil’s floating
LNG concept since 1990.
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Seite 44
Max Bräutigam
LNG Baseload Plant in Remote North-West of China
LNG Travels Through China
The first large-scale LNG baseload plant in China is being
erected in Shan Shan in Xinjiang province. The nominal
production capacity of the facility is approx. 430,000 metric
tons per year. The liquid natural gas produced by the plant
will be transported over several thousand kilometers
to consumers at the East Coast of China. The technical and
logistic challenges of the construction of the plant are
enormous and the climatic conditions extreme: temperature differences of 70 °C between winter and summer
are common.
In March 2002, the decision was made to build an LNG
(Liquefied Natural Gas) baseload plant in Shan Shan in
Xinjiang province in the North-West of China. This LNG
baseload plant will be the first large-scale baseload
plant in China, and it will be associated with far-reaching
changes in the development of China´s natural gas
industry. Natural gas consists mainly of methane whose
volume is reduced by the factor 1:600 during liquefaction. The temperature of the liquid is -162°C at atmospheric pressure. The facilities comprise units for gas
processing and liquefaction, intermediate storage, and
unloading of the LNG into tank wagons and road tankers.
The LNG will be transported overland across several
thousand kilometers to satellite stations in the East Coast
Provinces of China, where the LNG is re-vaporized and
distributed via local gas grids to industrial and household
New Era in Natural Gas Supply
in China
This LNG plant commences a new era of meeting the
demand for natural gas in China, which continued to rise
even during the recent economic crisis in China. The
introduction of this type of LNG plant combined with the
respective transport infrastructure is the basis for dynamic
opening and development of the natural gas markets.
The natural gas processed in the LNG plant consists mainly
of methane (> 90%), which is a very clean fuel since it
consists only of carbon (one carbon atom) and hydrogen
(four hydrogen atoms). It is evident that natural gas will
play an increasingly important role in the primary energy
mix, since it has a low environmental impact in terms of
emission levels. The Shan Shan LNG plant is a valuable
contribution to increase the wealth of the country similar
to the commercialization of natural gas and LNG in other
This LNG scheme is unique in the world with regard
to plant type as well as plant and transport capacity. The
market is comparatively small and, therefore, a pipeline
would not be economical. The method applied in the
facility will have a positive impact on the way of energy
consumption and on the development of the market
for clean natural gas. Therefore, the project has attracted
wide national and international attention. It can be
considered as an incentive for the commercialization of
remote gas resources with similar market conditions
worldwide and particularly in China. Some data of the
LNG plant in Shan Shan:
■ The production capacity of the plant shall be the LNG
equivalent of 1,500,000 m3(n)/d with an expected
on-stream time of 330 days per year. This amounts to
approx. 430,000 MTY.
■ LNG production capacity the Shan Shan LNG plant will
be approx. 3 times larger than that of the largest
existing peakshaving plants, and only one-third of
that of existing small baseload plants.
■ The storage capacity will be 30,000 m3 of LNG
(equivalent to approx. 18 million Nm3 natural gas)
corresponding to the amount liquefied in 12 days.
■ The capacity of the LNG shipping and distribution
system is designed for loading 100 trucks / train
transport containers within the 16 working hours
per day of the unit. The ratio of trucks to movable
containers is approx. 30:70.
■ The specification of product LNG contains no special
requirements, with the exception of the nitrogen
content being limited to 1 mol% max.
■ The feed gas operating pressure can range from
approx. 0.6 MPaG to 1.1 MPaG. The feed gas
operating temperature can range from -15°C to 40°C.
■ Composition of the feed gas: nitrogen = 4 mol%,
methane = 81 mol%, ethane = 10 mol%,
propane = 4 mol%, butane = 1 mol%.
■ In addition, CO2 and traces of H2S and sulfur are
present in the feed gas.
■ The ambient conditions at the site are unusual for
LNG plants: The average ambient temperature is
37.1 °C in the hottest month; the extreme ground
temperature varies between approx. 75 °C in the
hottest and -15.6 °C in the coldest month.
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Seite 45
Figure 1: The LNG is
transported from Shan
Shan to Shanghai where
it is locally distributed.
The process plant for the LNG production has been
optimized with regard to power requirement, equipment
cost and the inclusion of a maximal amount of engineering works and supplies from China. The main plant units
include feed gas compression, acid gas removal, drying,
liquefaction, storage, loading and utility facilities. The
compressor-driving concept and the power supply from
the grid were designed taking into account the relatively
high specific cost of electric power and high cost of the
feed or fuel gas. The main process of the Shan Shan LNG
plant is illustrated in the diagram in (Figure 2).
Natural gas treatment
The pressure of the natural gas (feed gas) entering the
plant is too low for the liquefaction process to be
efficient. Therefore, the natural gas is compressed in
3 compressor stages after removal of solid and liquid
particles in a separator. Air coolers provide for intermediate and after-cooling during the compression steps.
After compression, the feed gas is routed to the CO2
wash unit for removal of CO2. A MEA (monoethanolamine)
chemical wash process using an aqueous MEA solution
as the solvent was selected for the removal of CO2
from the natural gas. The feed gas enters the MEA wash
column and flows from bottom to top through valve
trays. The lean amine flows in the opposite direction,
forms a very weak bond to the alkali, and thus extracts
the carbon dioxide. The clean gas exits the wash
tower with its CO2 content being 50 ppm (v) water
saturated. The loaded amine solution from the CO2 wash
column is regenerated in a strip column, which requires
hot oil heating and air cooling in order to separate
the CO2 from the loaded amine. The purified amine is
returned to the wash column. The sweet feed gas exiting
from the CO2 wash column is then routed to the drier
Linde Technology I 1/ 2004
The drier station is a 2-bed adsorber station with a
cycle time of approx. 8 hours The natural gas flows downwards in the first adsorber bed. The water contained
in the natural gas is adsorbed by the adsorbent and
reduced to a level , at which no freezing can occur in the
downstream liquefaction section. During this period, the
second adsorber bed is heated and then cooled by the
regeneration gas stream. The regeneration gas is heated
by hot oil and cooled by ambient air, and then guided
to a regeneration gas knockout drum, where the water is
removed. The operation of the two vessels is switched
periodically (Figure 3).
Natural Gas Liquefaction
The liquefaction process (Figure 4) uses a closed mixed
refrigerant cycle utilizing nitrogen, ethylene, propane,
and pentane as its components.
Once the H2O and CO2 are removed, the natural gas
is routed to the cold part (cold box) of the process, which
contains three spiral wound heat exchangers, which are
integrated in one shell (“rocket”), and several separation
vessels. The natural gas is first cooled in the feed gas
pre-cooler, potential off-spec heavy hydrocarbons are
removed in a feed gas heavy hydrocarbon separator. The
gas is then condensed in a feed gas liquefier and the
liquefied natural gas (LNG) is then sub-cooled in a feed
gas sub-cooler. The LNG from the bottom heat exchanger
is guided to the storage tank where it is relaxed to
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Seite 46
atmospheric pressure. The gas fraction thus produced is
then returned to the heat exchanger for feed gas cooling
and subsequently used as fuel gas in the gas turbine.
The cooling energy required for liquefaction is mainly
provided by a closed refrigerant cycle.
This cycle provides cold temperatures by JouleThomson expansion at 3 different pressure and temperature levels.
A special feature of the cryogenic section of the
process plant is the spiral wound heat exchanger
designed and manufactured by Linde. It is characterized
by its operative robustness in the natural gas pre-cooling,
liquefaction and sub-cooling process, in which the
refrigerant cycle and product streams attain temperatures
down to -160°C.
Refrigerant System
Figure 2: Block diagram of the Shan Shan LNG plant showing the process units.
Figure 3: Natural gas (NG) treatment process.
The refrigerant gas stream is withdrawn from the shell
side of the pre-cooling section of the cryogenic spiral
wound heat exchanger set. The refrigerant is slightly
super-heated above its dew point. before its is compressed in the 3-stage cycle compressor and after-cooled
in an air inter-cooler, in which it is not only cooled but
also condensed to some extent. The liquid formed in the
after-cooler is removed in the cycle compressor discharge
drum. The liquid collected in the discharge drum is
routed to the pre-cooling section of the cryogenic
heat exchanger, in which it is sub-cooled, expanded in a
Joule-Thomson expansion valve, and then used to
pre-cool the natural gas.
The cycle gas from the discharge drum is cooled in
the pre-cooling section to the same temperature,
condensed to some extent, and fed to the refrigerant
separator. The liquid collected in this separator is subcooled in the cryogenic heat exchanger liquefier section
to a temperature that is sufficiently low for the liquid to
be as a refrigerant in the liquefier section after expansion
in a Joule-Thomson expansion valve. The vapor from the
refrigerant separator is condensed in the liquefier
section and sub-cooled in the cryogenic heat exchanger
sub-cooling section to a sufficiently low temperature and
provides the final cold for the natural gas sub-cooling
after expansion in a Joule-Thomson expansion valve.
After expansion to the lower pressure, the cycle gas
streams are warmed up in the common shell side of
the cryogenic spiral wound heat exchangers and returned
jointly to the suction side of the 1st stage of the cycle
Figure 4: Natural gas liquefaction process.
Linde Technology I 1/ 2004
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Seite 47
Figure 5:
The LNG plant (top) with the process
units (under construction) and the
LNG storage tank (bottom).
Compressor Driver Configuration
A gas turbine is used as the prime driver for the cycle
compressor. The compressed boil-off, flash, and displacement gas from the LNG storage tank is used first as
regeneration gas and then as fuel gas for the gas turbine.
Special challenges for the design of the gas turbine
as the main compressor driver and for the design of the
air coolers are provided by the climatic conditions at the
Shan Shan site with high fluctuations of the air temperatures during summer, winter, day and night times. The
conventional refrigerant for cooling, cooling water, is not
available in Shan Shan. Therefore, ambient air has to be
used as the cooling medium. The feed gas compressor is
driven by an electric motor powered by the local grid.
LNG Storage and Loading System
The LNG is transported from the liquefaction unit to the
storage tank via the tank filling line (Figure 6). Either
the bottom or the top filling connection can be used to
fill the tank. If large differences in LNG density are
encountered, top filling will be selected. The storage tank
is equipped with measurement instruments for filling
level, pressure, and temperature. The protection system
of the tank is connected via the safety control system to
the distributed control system. The temperature and the
density of the LNG in the tank are measured throughout
the height of the tank to monitor the risk of a possible
roll-over in the tank. The tank is equipped with a control
valve relief to the flare, safety valves to the atmosphere,
and vacuum breakers for under-pressure protection of the
The tank will be filled continuously during operation
of the liquefaction system at a filling rate of approx.
111 m3/h. During 16 hours per day a discontinuous
send-out operation to the truck and container filling is
scheduled. For send-out operation, two submerged
in-tank pumps with a nominal capacity of 320 m3/h
will be installed, which is sufficient to cover the send-out
The filling time of one container or one truck is
estimated to approx. 1.2 hours including connection /
disconnection time. The filling system consists of 6
loading stations for containers and 3 loading stations
for trucks.
Linde Technology I 1/ 2004
All of the flash, boil-off, and displacement gas from the
LNG storage tank is compressed, cooled by ambient air,
and used as regeneration gas in the drier section before
it is guided to the gas turbine to serve as fuel gas.
In order to enhance plant efficiency, the waste heat
from the exhaust stack of the gas turbine is recovered
by using it to heat hot oil at two different temperature
levels, which covers the heating requirements of the
process plant. The hot oil is heated to approx. 260°C to
supply the heat for regeneration gas heating, operation
of the CO2 wash unit and start-up in the winter. The
system is heat-traced.
The LNG plant is equipped with two flare headers: a
warm gas flare header and a cold gas and liquid flare
header including a blow-down vessel for the separation
of cold liquid and vapor. The plant is designed for non–
flaring during normal operation.
Make-up for the refrigerant system is required
mainly due to cycle gas losses via the gas seals of the
refrigerant cycle compressor. The quantities for the
individual components are adjusted as required according
to the compositions as measured and the temperatures
in the cold part. The nitrogen is stored as liquid nitrogen
and vaporized, heated to near ambient temperature,
and fed to a compressor suction drum when needed.
Commercial ethylene is stored in gas bottles at high
pressure. Commercial propane and pentane are stored in
separate tanks and fed to the refrigerant cycle suction
drum when needed.
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Seite 48
Figure 6: LNG storage tank and loading system.
In March 2002, Xinjiang Guanghui Industry and
Commerce Group Co. Ltd. awarded a contract for the
erection of a LNG baseload plant in Shan Shan in Xinjiang
Province in China. This is an important step towards a
more extensive utilization of the gas from the remote
Xinjiang region of China. The facilities include units for
gas processing and liquefaction, intermediate storage,
and unloading of the LNG into containers and into
road tankers. The LNG is then transported over several
thousand kilometers to satellite stations located in some
of the East Coast Provinces of China, where the LNG is
re-vaporized and distributed in the gaseous state via
short pipelines to industrial and household consumers.
The LNG production rate of the Shan Shan LNG plant
will be 1 500 000 m3(n)/day, which is equivalent to
approx. 430,000 metric tons per year. This contribution
focuses on the challenges that have to be faced during
the construction of the new LNG baseload plant in China.
The Author
Figure 7: CAD model of the Shan Shan LNG plant.
Max Bräutigam
Make-up water for the closed cooling water cycle for
machinery cooling and demineralized water for use as
make-up water in the MEA in the CO2 wash unit will be
obtained from sources outside the plant.
is a graduate of Munich University
of Science. He joined Linde Engineering several decades ago and
gained extensive experience in
cryogenic process engineering and
the mechanical design of components. He is now
a Senior Gas Plant Sales Manager and involved in
several projects.
Project Execution
The plant is currently under construction and the
majority of the work on the LNG storage tank has been
completed. The construction work on the site was
completed early in 2004. The commissioning is imminent. The final layout of the plant is shown in the CAD
model in Figure 7. The model shows the compressor
house, the pipe rack and air coolers, and the cryogenic
spiral wound heat exchanger set included in a steel
structure. The equipment and piping was arranged in
compliance with all applicable safety regulations and
aiming for the shortest possible pipeline length. The
plant covers approx. 60 m x 130 m. The height of the
cryogenic heat exchanger is approx. 43 m.
Linde Technology I 1/ 2004
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Seite 49
Industrial gas plants installed directly at the
customer’s site are used throughout the world.
This synthetic gas plant supplies Celanese AG
at its Oberhausen, Germany location.
Linde Technology I 1/ 2004
14:46 Uhr
Seite 50
Dr. Manfred Morper
Upgrading Industrial Wastewater Treatment Plants
Using Available Resources Creatively
Industrial wastewater treatment plants, once designed and
built, must be adjusted to comply with changing requirements more frequently than municipal effluent treatment
plants. Such upgrades are a good opportunity to reassess
the resources available on the site. Frequently this can help
to find a technically and economically more advantageous
solution than a mere repetition of what already exists.
in order to develop a solution with maximum benefit
from synergies. Creative use of all available resources on
a site can greatly ease the situation.
Existing facilities and resources
Just like municipal effluent treatment plants, industrial
wastewater treatment plants are designed and built for
certain flows and pollution loads. Any increase or change
of production is likely to increase both flow and load
and may even substantially change wastewater quality.
In addition, changing effluent regulations in the context
of environmental legislation may require higher degrees
of purification or the removal of additional pollutants.
It is therefore not uncommon that an existing effluent
treatment plant, although technically in good shape, no
longer serves its purpose.
Those in charge of managing the challenge will
often prefer to tear the plant down and substitute it by a
more suitable one. However, this is only rarely feasible
for many reasons. Typically, there is not enough space
available on the premises and ongoing production
will not allow longer periods of interrupted operation.
The budget allocated for the measures to be taken is
hardly ever generous enough for comfortable redundancies. Last but not least, demolition and scrapping of
tanks, pipes and electro-mechanical equipment is always
also a destruction of capital, i.e. an increase of investment costs.
Mainly due to lack of better knowledge, production
sites are not particularly inclined to share utilities with
the local effluent treatment plant, apart from such
commodities as electricity and service water. Conversely,
central waste water treatment plants at larger production
sites with numerous contributors do not readily accept
what they regard as odd sub-streams, bound to disturb
the steady function of the wastewater treatment plant.
Instead, costly pre-treatment on the spot is a typical
requirement, particularly if the discharger is not also the
operator of the wastewater treatment plant.
The necessity to upgrade an existing industrial
effluent treatment plant should be an opportunity to
check the suitability of available resources of a site
In addition to the bulk utilities normally supplied centrally,
e.g. electricity, potable and cooling water, steam and
heat, data processing and communications services, there
are other, less obvious, resources worth evaluating for
creative upgrading solutions for wastewater treatment
■ Civil structures, particularly tanks and reactors,
the capacities of which can be increased or the
functions of which can be changed.
■ Gaseous (e.g. oxygen, carbon dioxide), liquid
(e.g. acids and bases, organic solvents) and solid
(e.g. lime, alum) bulk chemicals, either produced
on site or purchased for production purposes, can
be supplied to and shared by all the users.
■ By-products of wastewater treatment can be used
as low-cost utilities.
Most major industrial wastewater treatment plants
use biological treatment methods supported, where
necessary, by physico-chemical process stages. The
examples described in the following therefore also
focus on biological systems.
Alternative uses for existing tanks
Tanks used for wastewater treatment are either designed
on the basis of hydraulic (e.g. buffer and equalization
tanks, sedimentation tanks) or kinetic (e.g. aeration
basins, digesters, chemical reactors) parameters. Once
built, their volumes are fixed. For those of hydraulic
design, increased flows or change of function generally
results in a certain decrease in performance. This is
acceptable, if it can be compensated by improved performance on the part of the associated facilities of the
treatment chain.
Linde Technology I 1/ 2004
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Seite 51
If, on the other hand, space is scarce and upgrading
cannot be done without erection of new tankage, a
change of function of existing tanks may be of advantage. This has been demonstrated for a pulp and viscose
mill in India [1]. The existing treatment plant, consisting
of two square tanks for equalization and neutralization,
two circular primary clarifiers and an aerated lagoon
(the biological stage) did not perform according to expectations and requirements. The lagoon was identified as
the weak spot and had to be replaced by an efficient
state-of-the-art bioreactor. Due to the lagoon’s large
footprint, very little firm ground was left on the factory
site for building new facilities. Although an oxygen
aerated bioreactor of the LINDOX® type, known to have
low space requirements, could be placed there, all other
elements of the treatment chain had to be created from
the existing tankage.
For this purpose, one of the two equalization tanks
was converted into five parallel primary clarifiers by constructing separation walls. Thus the two original primary
clarifiers became available as secondary clarifiers for the
new LINDOX® reactor. Figures 1 and 2 show the site plan
of the plant before and after upgrading.
Figure 1: Existing wastewater treatment plant at a pulp
and viscose mill in India.
Performance improvement
of aeration tanks
The activated sludge process is by far the most widespread method of biological wastewater treatment. The
limiting design parameters (sludge age, sludge loading)
are derived from the ratio of the daily pollution load to
the quantity of active biomass in the bioreactor, also
known as the F/M (food to micro-organism) ratio.
The quantity of biomass is the product of the biomass
concentration (MLSS) and the reactor volume.
An overloaded plant can be defined as not having
enough biomass for a given pollution load. Obviously,
the required ratio must be established by increasing the
biomass quantity. This can be done either by increasing
the reactor volume, which means construction of new
tankage, or by increasing the biomass concentration,
which means no, or at least less, new tankage.
The LINPOR® system, which can be applied for
almost all kinds of common aeration tanks, substantially
increases the biomass concentration without requiring
major modifications to existing tankage. The effect is
achieved by filling a certain quantity of highly porous
plastic sponge cubes into the aeration tank, which serve
as mobile carriers for the active biomass. Just like large
biomass flocs they follow the hydraulic regime of an
aeration tank. Contrary to conventional biomass flocs,
they are retained in the aeration tanks by specially
designed screens and thus do not contribute to the solids
load of secondary clarifiers.
Linde Technology I 1/ 2004
Figure 2: Extended wastewater treatment plant at the pulp and
viscose mill showing changes of use for existing tanks.
As all LINPOR® systems derive from the conventional
activated sludge process, proven and readily available
equipment for this established technology can be kept.
LINPOR® is therefore particularly suitable for upgrading
existing activated sludge plants.
One of the numerous examples is the wastewater
treatment plant of a waste paper processing mill in South
Korea, where the overload situation of the existing plant
was caused both by a production increase and poor
sludge settling characteristics (bulking sludge). Space
shortage demanded that performance be improved
essentially by the appropriate modification of the existing facilities. The existing aeration tank was therefore
converted into a LINPOR®-C reactor by the installation of
effluent screens and an air-lift pump to distribute and
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Seite 52
Figure 3: Aeration tank of
a paper mill in South
Korea, converted to the
LINPOR®-C process
regenerate the carrier material and by replacing the
surface aerators with a fine bubble aeration system,
using standard membrane diffusers. In order to
accommodate the full flow and load, a smaller new
LINPOR®-C reactor and an additional secondary clarifier
were erected on a narrow stretch of land next to the
existing facilities. Figure 3 shows the aeration tank
which was converted into the LINPOR®-C reactor.
Change of function of existing
aeration tanks
Over the years, effluent quality requirements have
become more and more stringent in most industrialized
countries. Treatment plants, once designed for compliance with effluent limits for organic materials (BOD/COD)
and SS now also have to eliminate additional pollutants
such as N- and P-nutrients.
TKN (ammonium and organic nitrogen) is biologically removed by nitrification and denitrification, which,
chemically speaking, is oxidation to nitrate followed by
reduction to the gaseous molecular nitrogen. Due to the
slow growth rate of nitrifying bacteria, nitrification is the
rate-limiting step. In order to provide favorable growth
conditions for nitrifying bacteria, the respective aeration
tank must be designed with a high sludge age or a low
F/M ratio, which once again means a larger quantity of
biomass than that needed for carbonaceous removal
For municipal and comparatively polluted industrial
effluents, this biomass increase can be comfortably
achieved by converting aeration tanks into LINPOR®-CN
reactors for simultaneous carbonaceous and nitrogen
removal [2]. However, for industrial effluents with both
high organic and TKN pollution, the requirement of a low
F/M ratio would result in extremely large aeration
volumes. This can be avoided by separating carbonaceous
removal and nitrification in a two-stage plant. If the
organic load is removed in a first aeration tank with a
comparatively high load, the requirement of a low F/M
ratio for nitrification at the second stage is achieved in a
comparatively small reactor volume.
Unfortunately, nitrifying bacteria on their own do not
readily form from settling sludge flocs, but they do attach
easily to carrier surfaces. The LINPOR®-N process, where
all the biomass is fixed on the mobile carrier material,
again takes advantage of this fact. At a major coke works
in Germany, total N effluent limits could be achieved by
converting the existing activated sludge plant, once
designed for carbonaceous removal, into a two-stage
facility [3]. The new first stage consisting of an aerobic
and an anoxic section both the organic load is removed
and the nitrate, generated in the second stage and
recycled to the first stage, is denitrified. The second stage
is the aeration tank of the existing plant, now converted
into a LINPOR®-N reactor. Even the existing sedimentation
tank is integrated into the treatment chain for the polishing stage. Figure 4 shows an aerial view of this plant.
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Seite 53
Figure 4: Two-stage
treatment plant for
wastewater from a
coking plant in
Germany, showing
the use of an existing
aeration tank (circular
tank left on the
top) as a nitrification
reactor according
to the LINPOR®-N
Sharing of on-site utilities
The upgraded coke oven effluent treatment plant
described above is also a good example of how existing
resources of a site can be of advantage for wastewater
treatment. The new first stage uses pure oxygen instead
of air for the aeration tank. Oxygen is produced in large
quantities for the associated steel works. By diverting
the comparatively minor quantity needed for effluent
treatment, a host of technical and economical
advantages are achieved:
■ Neither compressors nor large numbers
of aerators are needed
■ Energy expenditure for oxygen
dissolution is low
■ The aeration volume is considerably smaller
than with air aeration
■ Foaming is no longer a problem
■ Adjustment to load variations is easy
■ No odor or corrosion problems from
stripping effects occur
For the elimination of recalcitrant organic substances, contained in particular sub-streams or in biologically pre-treated effluents, chemical oxidation by ozone is
a potential solution. As ozone has to be produced on site
from oxygen anyway, the use of oxygen for the biological
treatment of the bulk wastewater is reasonable in order
to avoid wasting oxygen. A covered LINDOX® reactor will
also decompose non-reacted ozone without the
costs associated with a chemical decomposer. The block
diagram in Figure 5 shows the dual use of oxygen for
both production and wastewater treatment.
Other options for reducing investment and operation
costs by the sharing of operational utilities in production
and the treatment of wastewater include lime cycles [4],
carbon dioxide from oxidation processes for neutralization or the use of organic solvents – even spent ones – as
carbon sources for denitrification.
For any industry bound to produce and use oxygen
(or nitrogen) for its genuine production, using oxygen for
wastewater treatment is logical. Potential candidates
include steel works, pulp mills and major chemical and
petrochemical factories. The availability of oxygen also
facilitates other treatment options.
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Seite 54
neutralized with mineral acid and chemically oxidized
with air or oxygen under pressure or oxidants such as
A suitably designed and operated closed oxygen
aerated LINDOX® reactor does not require such costly
pre-treatment. Due to its low exhaust gas flow, almost
all of the carbon dioxide produced remains available for
Figure 5: The use of oxygen integrated into the
production process for wastewater treatment
Using treatment by-products
as low-cost utilities
Substances thought to be particularly toxic for microorganisms in wastewater treatment plants are generally
eliminated by physico-chemical pre-treatment prior to
biological treatment of the respective effluents. This is
costly and often not necessary, if a suitably designed and
operated biological wastewater treatment plant is used.
Carbon dioxide for neutralization
In aerobic wastewater treatment plants, the organic
pollution load is partly converted into biomass (surplus
sludge) and partly oxidized, as shown by the following
CxHyOz + ( x+ y/4 – z/2) O2 ➔ x CO2 + y/2 H2O
In conventional air-aerated plants the carbon dioxide
produced is mostly stripped off, i.e. driven off, with the
waste air and lost.
In petrochemical plants and refineries spent caustic is a
very common wastewater, resulting from scrubbing acidic
components (e.g. H2S, SO2) from gaseous products with
NaOH. Central biological wastewater treatment plants
generally do not accept untreated spent caustic because
of the toxic effect of high pH and the content of reduced
sulfur compounds. Traditionally, spent caustic is therefore
CO2 + NaOH ➔ NaHCO3
Normally, the amount of carbon dioxide produced
exceeds the stoichiometric demands for spent caustic
neutralization. Indeed, carbon dioxide consumption by
NaOH neutralization improves the oxygen utilization rate,
i.e. the economics of biological wastewater treatment,
as lowering the partial pressure of carbon dioxide
increases the partial pressure of oxygen in the gas phase
and thus reduces the waste gas flow needed to maintain
a set level of the latter.
Reduced sulfur compounds at sub-toxic levels are
readily oxidized biochemically in aeration tanks as
shown by the following equations, provided that the
oxygen concentration is maintained high enough to allow
maximum reaction rates and to prevent subsequent
reduction of sulphates by sulphate-reducing bacteria.
S2- + 2 O2 ➔ SO422 SO32- + O2 ➔ 2 SO42In order to avoid the toxic effects of alkaline pH and
respective concentrations of sulphur species, it is necessary
to dose the spent caustic not into the bulk influent but
into the different compartments of the biological reactor
at controlled pH. This is shown in the diagram of Figure
6. An integrated spent caustic treatment of this type has
been in continuous operation at a major petrochemical
site in France for 25 years [5] [6].
Nitrate for sulfide oxidation
Nitrate in industrial wastewaters, although sometimes
due to nitric acid application for production purposes, is
mainly due to TKN nitrification and therefore a wastewater treatment by-product. In order to comply with
respective effluent quality requirements, it is biologically
removed by denitrification, using either raw wastewater
organics or external carbon sources, e.g. methanol, as
reducing agents. But nitrate can also be regarded as an
oxidant for suitable pollutants, such as reduced sulfur
compounds, which are found in many industrial effluents.
There are autotrophic bacteria that can oxidize
sulphide by denitrification of nitrate, as shown by the
following equation:
5 S2-+ 8 H+ + 8 NO3- ➔ 4 N2 + 5 SO42- + 4 H2O
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Seite 55
Waste Gas
Spent caustic (NaOH, Na2S, Na2So3)
Returned Sludge
Figure 6: Treating non-pretreated spent caustic in the oxygen-aerated
activated sludge plant of a petrochemical works in France
This reaction is used at a refinery in Germany as the first
of three biological treatment stages [7] as shown in
Figure 7. A recycle stream, taken from the clarifier
effluent of the second nitrifying stage is fed into the
denitrifying sulphide oxidizer, which is a combined mixing and settling tank. This flow pattern provides favorable growth conditions for the autotrophic denitrifying
bacteria, separate from the heterotrophic denitrifiers in
the second stage.
Surplus sludge for heavy
metal removal
Aerobic and anaerobic surplus sludge from biomass
growth is an unavoidable by-product of biological
wastewater treatment. It is primarily a waste product,
the disposal of which contributes to the overall costs of
wastewater treatment.
However, the physico-chemical properties and the
metabolism of viable anaerobic sludge, as obtained from
anaerobic digestion of primary and secondary sludges,
make it a unique biosorbent for the removal of heavy
metals [8]. Functional groups of bacterial cell walls act as
chelating agents, while metabolites such as CO2 and H2S
form insoluble metal precipitates
The METEX® process, using an anaerobic sludge bed
with an upward flow pattern, has been in operation at
various industries with metal bearing wastewaters for
more than a decade without it ever being necessary to
change the sludge beds
Linde Technology I 1/ 2004
Figure 7: Use of biochemically generated nitrate for sulphide oxidation
in the treatment of wastewater at a refinery in Germany
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Seite 56
There are several aspects to the upgrading of industrial
wastewater treatment plants. Primarily, it refers to the
measures to be taken in order to make an existing facility
cope with flow and/or load changes or changing (i.e.
generally more stringent) effluent quality requirements.
Other aspects are the improvement of a plant’s performance and the economics involved.
A thorough check of all available resources of a site
can help to find a technically and economically more
advantageous solution than a mere repetition of what
already exists. The capacities or functions of existing
tanks can be increased or changed by application of
advanced process technologies. Utilities can be shared
with other users. Even metabolites of biochemical
reactions occurring with wastewater treatment can
be used as low or no cost utilities. The potential is
certainly larger than the few examples given. However,
higher degrees of integration mean higher levels of
interdependence, and therefore more mutual responsibility and less forgiving attitudes on a site. Hence
efficient monitoring and control, highly qualified and
communicative personnel and an overall management
capable of enforcement are indispensable requirements
for maximum synergistic benefits.
The extension and conversion of effluent treatment
plants on industrial sites is a job that recurs regularly in
plant engineering and construction. The cost in time
and money can be minimized by the innovative use of
existing structures. The construction of new facilities is
avoided. Making skilful use of resources and shared
utilities leads to an improvement in working procedures
and a saving in running costs. Conversely, products from
effluent treatment can also be reused as utilities.
Numerous projects around the world are already profiting
from creative measures like these.
[1] M. Morper, gwf Water Wastewater, No. 14/1999,
pp 22 – 25, ISSN 0016-3651 B 5399
[2] M. Morper, Wat. Sci. Tech. Vol. 29, No. 12/ 1994,
pp 167 – 176
[3] M. Morper, A. Jell, Linde Reports on Science
and Technology, No. 62/2000, pp 20 – 26,
ISSN 0942 – 5268
[4] M. Morper, Chemical Engineering, Volume 106,
No. 8/1999, pp 66 – 70, ISSN 0009-2640
[5] C. Granger, Verdeil, Eaux de Rhone –
Méditerranée – Corse, troisième trimestre 1981
[6] M.Morper, personal information on site Feb. 2003
[7] H.A. Joel, Th. Jenke, Erdöl Erdgas Kohle,
Volume 110, No. 4/ 1994, pp 171 – 173
[8] T. Pümpel, K.M. Paknikar, Advances in
Applied Microbiology, Vol. 48/2001,
Academic Press, San Diego, p 135 – 171
The Author
Dr. Manfred Morper
Dr. rer. nat. Manfred Morper studied
chemistry at the Technical University
of Munich and was awarded his Ph.D.
in that subject. Afterwards he worked
at the Bavarian Regional Water
Management Authority on the
subject of industrial wastewater treatment plants,
before coming to Linde in 1980. Here he worked
in R&D until 1986. In 1987 he was appointed
Head of Department with responsibility for the
project planning, marketing and construction of
waste-water treatment plants within the Plant
Construction division. Since 1994 he has headed
the Environmental Technology Department
of Linde-KCA-Dresden GmbH on the company’s
Höllriegelskreuth site in Munich. Manfred Morper
has written over 50 articles for technical magazines
and papers for international conferences on
wastewater treatment.
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Reports on Science and Technology
Linde Technology
Biotechnology Plants
Linde AG, Wiesbaden
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Forklift Ergonomics
Cracking with Oxygen
Economic Ammonia
LNG for Land and Sea
Flexible Solutions for
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P.O. Box 4020, D-65030 Wiesbaden
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