CHALLENGES TO INCREASED USE OF COAL COMBUSTION PRODUCTS IN CHINA

CHALLENGES TO INCREASED USE OF COAL COMBUSTION PRODUCTS IN CHINA
ISRN-LIU-IEI-TEK-A—10/00853—SE
CHALLENGES TO INCREASED USE OF COAL
COMBUSTION PRODUCTS IN CHINA
Jiabin Fu
Spring 2010
Master’s Program: Energy and Environmental Engineering
Department of Management and Engineering
Abstract
Electricity accounts for much of the primary energy used in China, and more than
three-quarter of the total electricity is generated by coal combustion. Coal burning
combined with flue gas cleaning system generates large quantity of coal combustion
products (CCPs), which has caused significant environmental and economic burden to
the economy, ecology and society. Of great importance are thus different applications
which contribute to the increased use of CCPs. This thesis looks at an overview of
CCPs production and utilization all around the world and investigates current CCPs
applications as well as potential technically sound and economically justified
technologies. Results of this thesis show that CCPs utilization rate in different
countries varies widely from 13% to 97%. Worldwide, a significant proportion of
CCPs from the main producers, e.g. China, the United States and India, is still being
disposed off, resulting in a low-level of overall utilization of these products. It is
evident that the amount of CCPs produced substantially exceeds consumptions
because of various existing obstacles and limitations. In order to formulate effective
approaches, identifying challenges to increased use of CCPs is of great weight. The aim
of this thesis is to analyze current and potential utilizations of CCPs and more
specifically address factors that inhibit or promote the use of CCPs from coal-fired
power plants in China.
Savings of natural resources, energy, emissions of pollutants, GHG emissions and
useful land were found as the major incentives for CCPs utilization. In China, a ban of
solid clay bricks was also found to be a very powerful measure to stimulate the
development of other by-product based wall materials while saving useful land and
protecting the environment. However, this strong support from the government has
not been fully implemented, which seriously hampered CCPs uses. Results presented
in this thesis also show that high transportation cost of low unit-value CCPs,
competition from available natural materials and spatial variation in supply-demand
poses three of the most important barriers to the increased use of CCPs in China.
Industrial organizations with assistances from the government have shown to be of
fundamental importance for formulating approaches to take in overcoming the
barriers.
This thesis emphasized that transforming laboratory- and pilot-scale technologies into
commercial productivity is of the highest priority for increased use of CCPs. A
conceptual model of CCPs Eco-Industry Park (EIP) as a potential effective solution
was proposed. Mutual economic and environmental benefits can be achieved through
the collaboration between different industries in the CCPs EIP. And other feasible
recommendations of initiatives from both the government and industries were also
discussed.
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Acknowledgment
First of all, I would like to extend my sincere gratitude to my supervisor, Dr. Joakim
Krook, for his instructive advice and continuous support in this master’s thesis. He
showed me different ways to map out a research strategy, identify research questions
and the need to be persistent to accomplish objectives. Without his encouragement
and constant guidance, I could not have finished this thesis. He has always been so
patient to talk my ideas, to proofread, and make comments to help me think through
my research problems. My sincere thanks are also given to Pro. Mats Eklund from
whose lectures of Eco-Industry I benefited greatly. I would especially like to express
my great appreciation to Swedish people who provide me a good opportunity to learn
advanced knowledge in energy and environmental engineering.
Special thanks should go to my former colleagues, Wenyong Li and Yincan Meng,
who provided me with valuable data and information, and helped me to carry out
questionnaire survey in several power plants. I am also deeply indebted to my best
friend, Lijun Huang, who has been a great helpful and encouragement, and provided
me great assistance to complete interviews with different companies. I would also like
to express my appreciation to all the managers who agreed to be interviewed. Sincere
thanks to my friend, Songmei Dong, for her valuable suggestions and hours of
commenting on the draft.
Finally, I owe great thanks to my beloved parents for unconditional support and
encouragement to purse my ideals and interests, even when the pursuits went beyond
boundaries of language and country.
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Table of Contents
1 Introduction ................................................................................................................. 1
1.1 Aim and research questions ................................................................................. 2
1.2 Scope and delimitations ....................................................................................... 2
2 Methods....................................................................................................................... 5
2.1 Research process and methodology ..................................................................... 5
2.2 Research design ................................................................................................... 6
3 Coal combustion products........................................................................................... 9
3.1 Composition of CCPs .......................................................................................... 9
3.2 Properties of fly ash ........................................................................................... 11
3.3 Properties of bottom ash/ boiler slag ................................................................. 13
3.4 Properties of FGD materials .............................................................................. 14
4 CCPs utilization ........................................................................................................ 17
4.1 Worldwide utilization of CCPs .......................................................................... 17
4.2 CCPs utilization in China................................................................................... 19
4.3 CCPs use applications ........................................................................................ 22
5 Driving forces for the use of CCPs ........................................................................... 27
5.1 Environmental incentives................................................................................... 28
5.2 Economic incentives .......................................................................................... 29
5.3 Legislations ........................................................................................................ 30
6 Barriers to the increased use of CCPs in China ........................................................ 33
6.1 Technical barriers ............................................................................................... 35
6.2 Economic barriers .............................................................................................. 38
6.3 Marketing barriers .............................................................................................. 39
6.4 Regulatory barriers............................................................................................. 40
6.5 Public perception and attitude barriers .............................................................. 41
7 Discussion ................................................................................................................. 43
7.1 CCPs Eco-Industry Park .................................................................................... 44
7.2 Recommendations for industry initiatives ......................................................... 46
7.3 Recommendations for government initiatives ................................................... 47
7.4 Actors’ role in overcoming the barriers to increased use of CCPs..................... 48
8 Conclusions ............................................................................................................... 51
References .................................................................................................................... 53
Appendix ...................................................................................................................... 59
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List of Figures
Figure 1 Framework for research process and methodology. The figure is inspired by
Haes & Grembergen (2008). .......................................................................................... 5
Figure 2 Selection, analysis and statement of research questions ................................. 6
Figure 3 Schematic diagram of coal combustion products (CCPs) generation ............. 9
Figure 4 Typical compositions of CCPs in Europe (EU15) in 2007; total production 61
million tonne (ECOBA, 2009) ..................................................................................... 10
Figure 5 Utilization and disposal of CCPs in Europe (EU15); total amount 61 million
tonnes (based on ECOBA, 2009) ................................................................................. 18
Figure 6 U.S.A CCPs utilization and disposal in 2008; total amount 136.1 million
tonnes (based on ACAA, 2009) ................................................................................... 18
Figure 7 Fly ash production and utilization trend from 1979 to 2000 in China (Wang
& Wu, 2004)................................................................................................................. 20
Figure 8 China fly ash utilization and disposal in 1997; total production 106 million
tonnes (based on Wang & Wu, 2004) .......................................................................... 21
Figure 9 Possible use pattern of fly ash based on the properties of fly ash (reproduced
from Wang & Wu, 2006).............................................................................................. 23
Figure 10 Schematic plant view of flue gas desulfurization using coal ash (Kikuchi,
1999). ........................................................................................................................... 26
Figure 11 Identified incentives from the perspective of CCPs producers ................... 27
Figure 12 Identified incentives from the perspective of CCPs users ........................... 28
Figure 13 Identified barriers from the perspective of CCPs producers ....................... 33
Figure 14 Identified barriers from the perspective of CCPs users ............................... 34
Figure 15 Overview of identified barriers ................................................................... 43
Figure 16 Conceptual CCPs Eco-Industrial Park......................................................... 45
List of Tables
Table 1 List of companies consulted in the study .......................................................... 7
Table 2 Normal range of chemical composition for fly ash produced from different
coal types (-wt %) (TFHRC, 2010).............................................................................. 11
Table 3 Typical composition of fly ash in China (Gu, 2004) ....................................... 12
Table 4 Overview of coal combustion products production and use in different
countries ....................................................................................................................... 17
Table 5 Profitably utilization rate of CCPs in Europe (EU15) and USA..................... 19
Table 6 Potential fly ash high value added applications (based on TIFAC, 2009 and
Wang & Wu, 2004) ...................................................................................................... 24
Table 7 National Standard of the People’s Republic of China: Fly Ash used for cement
and concrete (GB1596-1991, 1991)............................................................................. 35
Table 8 Actors' role in overcoming barriers to CCPs uses ........................................... 48
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Acronyms
ACAA
ADAA
ASTM
CCPs
CFB
CGOSC
CIRCA
ECOBA
EERC
EIP
ESP
FBC
FF
FGD
GB
GHG
HVFAC
JCOAL
LOI
NCASL
R&D
SDA
TFHRC
TIFAC
TPY
USEPA
VAT
American Coal Ash Association
Ash Development Association of Australia
American Society for Testing Materials
Coal Combustion Products
Circulating Fluidized-Bed
China’s General Office of the State Council
Association of Canadian Industries Recycling Coal Ash
European Coal Combustion Products Association
US Energy and Environmental Research Center
Eco-Industry Park
Electrostatic Precipitator
Fluidized Bed Combustion
Fabric Filter
Flue Gas Desulphurization
National Standard of the People’s Republic of China
Green House Gas
High Volume Fly Ash Concrete
Japan Coal Energy Center
Loss of Ignition
US National Council for Air and Stream Improvement
Research and development
Spray Dryer Absorption
US Turner-Fairbank Highway Research Center
Technology Information, Forecasting and Assessment Council
Tonne per Year
US Environmental Protection Agency
Value-Added Tax
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1 Introduction
Coal is and continues to be one of the most important primary energy sources for
countries all over the world. The worldwide coal reserves are estimated to be 8 × 1012
tonnes with annual consumption of 5 × 109 tonnes (CIRCA, 2010), among which the
majority is consumed by electric power utilities. Coal combustion products (CCPs)
are the byproducts generated during the combustion of coal, combined with pollution
control technologies, for the purpose of electricity generation. The estimates of
current worldwide annual production of coal combustion products range from 500
million tonnes (Berg & Feuerborn, 2001) to 600 million tonnes (Ahmaruzzaman,
2010) with fly ash shared 75-80% (Ahmaruzzaman, 2010) of the total CCPs produced.
Based on the statistics and forecasts the worldwide CCPs production has been
increased steadily over the years and will keep on rise over the next decade.
China has abundant coal reserves and coal will remain the dominating energy source
to produce power and steam for the industries in a long run. In 2003, the total power
generation capacity in China has reached 391 GW of which coal constituting about 70%
(Mukherjee et al., 2008). It is estimated that about 1.1 billion tonnes coal is consumed
by the power industries and over 200 million tonnes of fly ash are produced annually
in China (Liu, 2009), which makes the country the largest CCPs producer in the world.
It is anticipated that this figure will gradually increase in the years to come. The
amount of cumulated fly ash by far was about 2.2 billion tonnes, which have covered
300 square kilometer of useful land in China (Mukherjee et al., 2008), and this
volume is expected to be 3 billion tonnes by 2020 (Liu, 2009). These large amounts
of by-products, which were unable to be recovered for beneficial uses, have become
real industrial wastes and pollutants. CCPs as industrial by-products, if inadequately
disposed, can produce severe water and air pollution which is likely to cause serious
human health risks. In China, CCPs with the gangue and calcium carbide slag has
been listed as the top three industrial wastes (Wei, 2009).
The majority of the total CCPs produced worldwide are currently disposed of, which
has caused significant environmental and economic burden to the ecology and society.
Of great importance are thus different applications which promote the use of CCPs.
From the worldwide perspective, growing concern for increased landfill cost and
shortage of natural resources has led to the development of a number of CCPs
recovery technologies such as fly ash cement, concrete addition, structure fill, mining
backfill, etc. Manz (1997) reported that worldwide the major use of fly ash is in
cement and concrete industries, which exceeds any other single application. There are
several environmental and economic benefits connected with the use of CCPs as
saving of natural resources, saving of energy, saving of emissions of pollutants,
saving of GHG emissions and saving of useful land (ACAA, 2008). However, the
demand for fly ash in the cement and construction industries is limited by various
factors in terms of fly ash quality, market development, location affects, season
problems (Kikuchi, 1999), etc. In many cases, the market for utilization of fly ash in
construction industries is close to being saturated. Regardless of the positive uses, it is
obviously that more CCPs are being produced than the current applications can
consume (Iyer & Scott, 2001). More laboratory researches and industrialization
practices, therefore, need to be conducted in order to find other technically viable and
economically justified applications and to promote the efficient utilization of CCPs as
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well as decrease the impacts on the environment and economy. Several commercial
testing have been attempted in the past, however, often with little success. It has been
shown that these attempts failed to commercialization, not for technical reasons, but
mainly for economic reasons.
There exist a number of barriers to the increased use of large quantities of CCPs. The
principle obstacles are those issues with regard to materials characterization, market
abilities, standards, specifications, policies, regulations, demonstration, public
perceptions, etc. Hitch (2005) argued that a prerequisite for formulating approaches to
take in overcoming the barriers to CCPs uses is the full range of identification of
those barriers. Identifying the barriers to, and driving forces for increased use of CCPs
is of fundamental importance for going extra miles on the way of CCPs utilization.
1.1 Aim and research questions
To meet the challenges of increased use of CCPs and formulate effective approaches,
it is of great importance to identify the incentives and obstacles to CCPs utilization.
The aim of this thesis is to analyze present and potential use of CCPs and more
specifically address factors that inhibit or promote the utilization of CCPs from coalfired power plants in China.
In order to make real and steady progress in the face of those challenges, three
research questions are formulated and examined based on the aim of the thesis. The
research questions are:
1. What are the current and potential utilization of CCPs in China and other
developed countries? What are the possible environmental impacts and health
risks from coal combustion products?
2. What are the benefits derived from CCPs recovery and the obstacles to the
increased use of CCPs in China? What are the most important challenges to the
use of CCPs?
3. What kinds of policies, regulations and recommendations can be applied to
strengthen the management of CCPs utilization and increase the use of CCPs in
China?
1.2 Scope and delimitations
This thesis highlights the utilization of coal combustion products generated from coalfired power plants in China, especially the obstacles that inhibit the use of CCPs both
from a scientific point of view and a societal point of view. Although coal combustion
products consist of many different materials, which contain fly ash, boiler slag,
bottom ash and flue gas desulphurization (FGD) products, the vast majority of CCPs
are fly ash and FGD products. Fly ash clearly accounts for the largest share of CCPs
usage. For this reason, how to use fly ash in an optimal and viable way is the key
issue for the increased use of CCPs. In China, from the perspective of commercial
utilization, generally, bottom ash and boiler slag are embodied in the category of fly
ash (Wang & Wu, 2004). The focus of this thesis, therefore, will be on barriers to, and
driving forces for the utilization of fly ash and a lesser degree on FGD materials
utilization.
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Efforts were made to compile the up to date total CCPs production and consumption
data in China. However, for details of multiple applications of CCPs only the year of
1997 data were available. There is no specific institution or organization taking charge
of CCPs production and utilization statistics in China. Various versions of CCPs
statistics can be found, however, some of them often differ widely from each other.
The reliability of some statistics of CCPs production and utilization is still open to
question.
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2 Methods
The research will be carried out mainly based on data collection, literature survey,
interviews and questionnaires. Literature for this project was sourced from the internet,
library, company reports and other available information. CCPs producers, users and
general public were involved in a method of interview and questionnaire investigation.
An approach to problem-finding and problem-solving has been mapped out as follows.
2.1 Research process and methodology
The research strategy was based on multiple research methods: literature survey, topdown approach, concept of industrial ecology, previous-case study, questionnaire and
interviews. The combination of research methods enables a deep insight into the
utilization of CCPs as well as its challenges (Haes & Grembergen, 2008). Each step of
research process applied different research method individually or multiply, as shown
in Figure 1.
Defining research questions
Exploring the research domain
Formulating reaseach objectives
Giving an overview of worldwide and
domestic CCPs production and
utilization
Identifying incentives and barriers to
the increased use of CCPs
Formulating effective solutions
Conclutions
Based on:
- Literature survey
Based on:
- Literature survey
- Top-down approach
- Previous-case study
Based on:
- Questionnaire survey
- Interviews
- Literature survey
Based on:
- Interviews
- Concept of Industrial
Ecology
- Literature survey
Figure 1 Framework for research process and methodology. The figure is inspired by Haes
& Grembergen (2008).
The research process started with exploring the experimental documents and
identifying the research questions through a detailed literature review in the field of
CCPs utilization. The focus was on finding an initial structure of research process and
formulating research objectives (Haes & Grembergen, 2008). After having formulated
the objectives, properties of CCPs’ different components, worldwide production and
utilization of CCPs were investigated by means of literature survey and studying
previous CCPs utilization cases. A top-down approach, which is known as the
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breaking down of a system to gain more details about its sub-systems, was also used
for analyzing worldwide CCPs uses. In a top-down approach an overview of CCPs
production and utilization all around the world was first formulated. And then
multiple patterns of CCPs use applications in subsystems – different countries – were
specified. The utilization of CCPs in China was further refined in a greater detail. In
identifying barriers to, and driving forces for the increased use of CCPs, a method of
questionnaires and interviews with CCPs producers, CCPs users and general public
was conducted. The following research step was aimed at analyzing the CCPs
application challenges from the stand points of different actors involved, and then
indicating potential improvements and effective solutions in combing with a concept
of industrial ecology.
2.2 Research design
A research process of problem-finding is first carried out. A method of questionnaire
is designed for the purpose of identifying incentives and barriers to CCPs use from the
perspective of different actors involved in CCPs production and utilization.
2.2.1 Identification of research questions
Problem identification is the first and important step in designing and conducting a
research. Inspired by IDRC (2010), selection, analysis and statement of research
questions were structured in Figure 2.
Disposal of CCPs
CCPs
Production & Utilization
Definition
Worlwide
Environmental
impacts
Components
Domestic
Health risks
Properties
RQ1: What are CCPs? What are worldwide
and domestic production and utilization of
CCPs? What are the environmental impacts
from CCPs disposal?
Incentives & Barriers
Uses of CCPs
Current
Potential
Economic
Solutions
Technical
Government
Environmental
Regulatory
Industries
Marketing
Legislation
Attitude
RQ3: What kinds of effective solutions can be formulated
by the government and industries to overcome the barriers?
Figure 2 Selection, analysis and statement of research questions
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RQ2: What are the barriers
to, and driving forces for
utilization of CCPs? What
are the most important
challenges to the increased
use of CCPs?
The first question mainly concerns the current and potential utilization of CCPs in
China and other developed countries. The second one concerns obstacles to, and
driving forces for the increases use of CCPs. The third question regards the initiatives
from the government and industries to strengthen and promote CCPs uses. The focus
of this thesis will be on the obstacles of utilization of CCPs and the potential
approaches that minimize or overcome the barriers to the increased use of CCPs in
China.
2.2.2 Identification of barriers
Based on a study of CCPs utilization barriers identification, which was conducted by
US Energy and Environmental Research Center (EERC) in 1999, the barriers to the
utilization of CCPs in China were similarly classified into following distinct
categories: technical, economic, marketing, regulatory, public perception and attitude.
A method of questionnaire and interview investigation in combining with literature
survey was embodied in this thesis to examine general barriers existing in China’s
CCPs industries.
2.2.3 Interview and questionnaire design
A research method of questionnaire and structured telephone interview was used for
investigating the present production and utilization of CCPs in some coal-fired power
plants and CCPs users. In China, cement and concrete industries play significant roles
in the development of CCPs uses because the majority of the recovered fly ash was
currently used in construction material manufacturing and civil engineering
applications. For this reason, as important actors of CCPs utilization, a cement plant, a
construction company and a gypsum manufacturing plant have also been involved in
the interviews.
Table 1 List of companies consulted in the study
Company
Type
Position of interviewee
Method
Baotou No.2 Thermal
Power Plant
CCPs Producer
Environmental manager
Questionnaire
Ningxia Jinyuyuan
Thermal Power Plant
CCPs Producer
Environmental manager
Questionnaire and
telephone interview
FAW Thermal Power
Plant
CCPs Producer
Environmental manager
Questionnaire
Taizhou Power Plant
CCPs Producer
Environmental manager
Questionnaire
CCPs user
Sales manager
Telephone interview
and Questionnaire
Potential CCPs
user
Structural engineer
Telephone interview
CCPs user
Sales manager
Telephone interview
Anhui Runji Cement
Plant
Zhejiang Jiangong
Real Estate
Development Group
Co., Ltd.
HSLB Gypsum board
Manufacturing Plant
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The respondents from power plants and other companies were asked to indicate which
barriers to, and driving forces for increased use of CCPs are most relevant to their
companies and provide input regarding the importance of incentives and barriers
identified. The rank of different barriers and drivers for utilization of CCPs was
designed based on a three grade scale where 3 points corresponding to very important,
2 points for moderate and 1 point if the respondent considered the identified factors
are weak drivers/barriers. And the results derived from the questionnaires and
structured interviews were normalized to avoid biases. For details see AppendixQuestionnaire. The results were translated from Chinese to English and presented in
this thesis. The questionnaires were sent out via emails to the respondents and
designed to be answered by environmental managers or people in charge of waste
handling issues in the power plants. As such people are familiar with the processes of
the power plants’ waste handling systems and destabilizing factors that influence the
output quality of CCPs. Furthermore, they are the ones who are often in charge of
directly contact with the users of the CCPs, which implies that more feedback
information from the users could be grasped by these people.
Structured telephone interviews were carried out with the managers from technical
and sales department of CCPs use companies. In addition to asking questions about
obstacles and driving forces, the interviews also included questions about the
respondents’ view of whether there exist weaknesses in the management of CCPs at
their companies and related improving measures which had not been undertaken.
Questions such as what is the cost for CCPs materials and transportation, whether
there is a need for investments on additional facilities, and what kind of preference
and support could be obtained from the government to promote the use of CCPs were
also asked.
2.2.4 Validity and reliability of research method
The validity and reliability of the scientific method are of great importance
(Shuttleworth, 2008). An investigation of questionnaire and structured telephone
interview carried out among different actors involved in the CCPs production and
utilization is an effective and reliable method to identify incentives and barriers from
the economic, environmental and societal perspectives. However, an experiment that
uses human judgment, to some extent, is likely to come under question (Shuttleworth,
2008). When drawing conclusions from the questionnaires and in-depth interviews the
respondent’s answers may include a degree of bias; and personal opinions, for
example, may affect the respondent’s answers to some questions (Thollander, 2008).
To make the results derived from the interviews and questionnaire valid enough and
minimize biases, a wide range of sample groups including the government, CCPs
producers, CCPs users and the general public, should be involved. Furthermore, it
must be kept in mind that the number of companies interviewed is limited and they
are mainly located in some specific areas. Data or information collected from the
interviews and questionnaires, to some extent, may not be very representative from
the perspective of the whole country.
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3 Coal combustion products
The definition for solid materials generated from coal combustion processes has been
evolved from the first used term "coal combustion wastes" to "coal combustion
byproducts" and lately to the term "coal combustion products" (Kalyoncu, 2001).
From the transition of working definition for CCPs, it is evident that the CCPs from
coal combustion power plants has been gaining wide public concern and its
environmental and commercial value has also been emphasized due to current interest
in "low-carbon economy" and "sustainable development".
3.1 Composition of CCPs
Coal Combustion Products (CCPs) are the solid, inorganic minerals that remain after
coal is burned to generated electricity in power plants. The major solid residues
included in CCPs are fly ash, bottom ash, boiler slag and FGD materials.
Ash Collector
Coal
Boiler
Bottom Ash/
Boiler Slag
FGD
Scrubber
Stack
Fly Ash
FGD
Materials
Figure 3 Schematic diagram of coal combustion products (CCPs) generation
Fly ash is produced from the burning of fine grinded coal in a pulverized coal
combustion boiler. It is collected from the coal-fired power plant exhaust gases
primarily by electrostatic precipitators (ESP), or fabric filters (FF) and secondary
FGD scrubbers. Fly ash is a fine and powdery material, which is composed mainly of
non-combustible inorganic materials, such as spherical glassy particles, and some
carbon due to incomplete combustion of coal.
Bottom ash is a heavier, coarser and granular material removed from the dry-bottom
boiler which is the most common boiler type. When pulverized coal is burned in such
type of boiler, about 80% leaves as fly ash and 20% remains as bottom ash which is
too large to be carried in the flue gases (The Fly Ash Resource Center, 2010).
Boiler slag is the molten bottom ash drawn from the base of slag-type boiler or
cyclone boiler and discharged into a water pit where it is quenched and removed. The
proportion of bottom ash generated in these kinds of boilers is higher than that of
pulverized coal boilers. The resulting boiler slag is made up of coarse, hard, black,
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dense, glassy particles. The boiler slag accounts for a mere fraction, only about 2.5%,
of the total amount of CCPs produced from coal-fired power plants (Kalyoncu, 2001).
Flue gas desulphurization material is a product of a process used for the purpose of
removing SO2 from a coal-fired boiler exhausted gas. Generally, FGD material
consists of fluidized bed combustion (FBC) ash, spray dryer absorption (SDA)
products and FGD gypsum. In the European Union of the EU15, the total production
of CCPs was 61 Mt in 2007, with fly ash accounts for a major component about 69%
of CCPs produced, followed by FGD material which represents about 18% by weight
(ECOBA, 2009). Figure 4 shows the typical proportions of different constituents of
CCPs produced for 2007 in Europe (EU15).
FBC Ash
1,5%
SDA Product
0,7%
Boiler Slag
2,4%
Fly Ash
68,5%
Bottom Ash
9,3%
FGD Gypsum
17,6%
Figure 4 Typical compositions of CCPs in Europe (EU15) in 2007; total production 61
million tonne (ECOBA, 2009)
In China, the ash content of electricity coal, which ranges from 15% - 30%, is
relatively higher than that in other countries (Chen P. , 2007). Consequently, the
amount of fly ash contained in CCPs produced from coal-fired power plants accounts
for a much higher percentage than normal. Based on the country’s energy structure
and economic foundation, it is foreseeable that the framework of primary energy
source dominated by coal is hard to be changed in the next five decades. The
production of FGD materials, therefore, will be rising rapidly along with the
increasing intension on SO2 emission control in China. It is estimated that 8.5 million
tonnes of FGD gypsum will be produced in 2010, while the use rate is hard to reach
30% (Tian et al., 2006). Increasing the use of fly ash and FGD materials to the
greatest extent, therefore, plays a significant role towards the increased use of CCPs.
The distinct chemical and physical properties of CCPs’ different constituents allow
each of them well-suited for particular applications (Kalyoncu, 2001). As these
distinct properties of different components are likely to influence the opportunities for
CCPs uses, an understanding of characterization of CCPs in terms of physical,
mineral, surface chemistry and reactivity, therefore, is of great importance (González
et al., 2009). What follows fly ash and FGD materials are mainly discussed.
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3.2 Properties of fly ash
Fly ash is an artificial volcanic ash, i.e. a siliceous or siliceous and aluminous material,
which has slight or non self-cementing properties. Such materials with pozzolanic
properties will react with calcium hydroxide in the presence of water at ambient
temperature to produce calcium silicate hydrates (cementitious compounds). The
pozzolanic properties of fly ash, including its lime binding capacity allows it to
replace Portland cement in concrete products or to be used as raw material for cement
clinker (Ahmaruzzaman, 2010). The chemical and physical properties of fly ash vary
considerably depending upon the properties of coal, powder preparation equipments,
furnace types, ash collection methods, flue gas emission control measures and etc,
which influence, to a great extend, the development of various fly ash applications.
3.2.1 Chemical properties
The chemical properties of fly ash, which is nearly identical to volcanic ash, are
influenced significantly by the source of coal and the techniques used for storage,
preparing and combustion (TFHRC, 2010). Coal consists of inorganic and organic
substances. Organic matter is made up of volatile and fixed carbon; mainly consists of
carbon, hydrogen and oxygen. Fly ash is the residue generated from the combustion
of inorganic matters, which is composed principally of silica, alumina and iron oxide,
with smaller percentage of calcium oxide, sulphur oxide, magnesium oxide, unburned
carbon and other compounds (TFHRC, 2010; Gu, 2004). Table 2 compares the
normal range of the chemical constituents for fly ash generated from burning different
ranks of coals.
Table 2 Normal range of chemical composition for fly ash produced from different coal
types (-wt %) (TFHRC, 2010)
Component
Bituminous
Sub-bituminous
Lignite
SiO2
20-60
40-60
15-45
Al2O3
5-35
20-30
10-25
Fe2O3
10-40
4-10
4-15
CaO
1-12
5-30
15-40
MgO
0-5
1-6
3-10
SO3
0-4
0-2
0-6
Na2O
0-4
0-2
0-4
K 2O
0-3
0-4
0-4
LOI1
0-15
0-3
0-5
As shown in Table 3, typical fly ash in China is composed primarily silica, alumina
and iron oxide, which accounts for about 85% of the total amount of fly ash. The
relatively low calcium oxide content makes fly ash presenting non self-cementing in
nature (Gu, 2004). Properties of other constituents are not over the standards of
1
Loss of Ignition.
11
engineering applications. However, the loss of ignition varies widely and the average
value is relatively high than normal, which poses a potential barrier to CCPs used in
concrete applications.
Table 3 Typical composition of fly ash in China (Gu, 2004)
Component
SiO2
Al2O3
Fe2O3
CaO
MgO
SO3
Na2O
K 2O
LOI
Average
50.6
27.2
7.0
2.8
1.2
0.3
0.5
1.3
8.2
Range
33.959.7
16.535.4
1.515.4
0.84.0
0.71.9
0-1.1
0.21.1
0.72.9
1.223.5
The chemical make-up of fly ash draws wide concern from power plants and end
users. Loss of ignition (LOI) is generally used by power plants for indicating whether
the coal is combusted completely. As fly ash is becoming a useful engineering
material, LOI, which is a measurement of the amount of unburned carbon remaining
in fly ash, can be used as an indicator of suitability for use as a cement replacement in
concrete. Fly ash with high carbon content will influence the quality of concrete when
using this material as a cement replacement. As a result, LOI is considered as one of
the most significant chemical properties of fly ash (TFHRC, 2010). And the chemical
composition of fly ash has been widely accepted as a mainly standard for quality
classification and grading of fly ash by CCPs marketers and engineering departments
(Gu, 2004).
According to the American Society for Testing Materials (ASTM), two categories of
fly ash are recognized. The ash containing more than 70 mass percent SiO2 + Al2O3 +
Fe2O3 are defined as class F, while class C requires a SiO2+ Al2O3 +Fe2O3 content at
least 50 mass percent (ASTM C618, 2005). In general, Class C fly ash contains higher
CaO than Class F fly ash. In China, there is no specific accepted standard for
classification of fly ash, but briefly sort into high-calcium and low-calcium fly ash,
which are similar to ASTM Class C and Class F fly ash respectively (Gu, 2004). The
high-calcium Class C fly ash is normally produced from the burning of low-rank coals
(lignite or sub-bituminous coals) and have cementitious properties (self-hardening
when reacted with water) (Ahmaruzzaman, 2010). While, the low-calcium Class F fly
ash is commonly produced from the burning of higher-rank coals (bituminous coals or
anthracites) that are pozzolanic in nature (hardening when reacted with Ca(OH)2 and
water) (ASTM C618, 2005).
3.2.2 Physical properties
Fly ash consists of fine, powdery particles that are generally largely spherical in shape,
either solid or hollow, and mostly glassy (amorphous) in nature. Because of the
different constituents and contents of fly ash, the color can vary widely from tan to
gray to black, depending on the amount of unburned carbon in the ash (TFHRC,
2010). Generally, the variation of fly ash properties and the composition of fly ash can
be identified and reflected briefly based on the changes of ash colour (Shen & Wu,
2004). The particle size distribution of coal fly ash collected generally ranges from
0.5-300µm, which is close to the variation range of cement particle size, but majority
of the fly ash particles are smaller than those in cement (Shen & Wu, 2004). The
fineness of fly ash particles is considered as one of the most important parameters that
12
influence the fly ash quality for applications in cement and concrete industries. Based
on National Standard of the People’s Republic of China Fly Ash used for cement and
concrete GB1596-1991, the percentage of material passing the 45µm (No. 325) sieve
is applied as an indicator for fly ash fineness. In China, coal ash captured from
particles collection systems seldom fulfills the GB standard of fly ash used in
reinforced concrete without further classifying and grading treatment. Shen and Wu
(2004) has pointed out that large fluctuation in fly ash physical properties makes the
use of CCPs more difficult. The specific gravity of fly ash usually ranges from 2.1 to
3.0, while its specific surface area may vary from 170 to 1000 m2/kg (ASTM C204,
1994). Molten minerals such as clay, quartz, and feldspar, solidify in the flue gas,
giving approximately 60% of the fly ash particles a spherical shape (TFHRC, 2010).
The particular cementitious properties of fly ash with its unique spherical shape,
particle size distribution, and alkalinity offer CCPs additional value for a variety of
beneficial use options (NCASI, 2003). As fly ash is a mixture compounded by various
particles with different properties, it is of great importance to understand clearly about
the particle components and contents in the ash in order to develop and explore the
use of CCPs in broader range.
3.3 Properties of bottom ash/ boiler slag
Coal bottom ash and boiler slag are the heavier and coarser coal combustion byproducts that are collected from the bottom of furnaces. The type of bottom ash and
boiler slag produced depends on the type of boiler furnace (dry-bottom boiler, wetbottom boiler and cyclone furnace) used to burn the coal (TFHRC, 2010).
When coal is burned in a most common dry-bottom boiler, 20% remains in the
furnace as bottom ash and 80% leaves as fly ash. Bottom ash is gray to brown, coarsegrained, granular, incombustible material that is collected in a water-filled hopper at
the bottom of the furnace (The Fly Ash Resource Center, 2010). Bottom ash is
predominantly sand-sized particles, usually with 50 to 90 percent passing a 4.75 mm
(No. 4) sieve and a top size usually ranging from 19 mm to 38.1 mm (TFHRC, 2010).
Boiler slag is vitrified bottom ash generated from a wet-bottom boiler. The bottom ash
in wet-bottom boiler is kept in a molten state and tapped off as a liquid which is
cooled by quenching water contained in the ash hopper in wet-bottom furnace. In this
type of furnace, the molten slag is fractured instantly, and thus the resulting product is
often a coarse, hard, black, angular, and glassy material (NCASI, 2003). Boiler slag is
essentially a coarse to medium sand, predominately single sized with 90-100 percent
passing a 4.75 mm (No. 4) sieve (TFHRC, 2010).
The particular particle size of bottom ash and boiler slag and the durability of boiler
slag are considered as the primary and additional value of these materials. These
advantages of the particle size of bottom ash and boiler slag and the durability of the
slag are taken by various lucrative applications such as fine aggregate in asphalt
paving, structure fill and etc (NCASI, 2003).
13
3.4 Properties of FGD materials
FGD material is a product of a process typically used for reducing SO2 emissions
from the exhaust gas system of a coal-fired boiler, which mainly contains three
categories of products: fluidized bed combustion (FBC) ash, spray dryer absorption
(SDA) products and FGD gypsum (ECOBA, 2010). The physical nature of these
materials varies from a wet sludge to a dry powdered material depending on the
process.
FBC ash is produced in fluidized bed combustion boilers which introduce ground
limestone (or lime) into the combustion furnace that burns the finely pulverized coal
at temperatures of 800 to 900°C (ECOBA, 2010) to minimize the emission of
pollutants such as SO2 and NOx from the exhaust gas. Because of the incomplete
combustion of coal, this process intends to result in "weaker fuel mineral
decomposition", "lower novel mineral formation intensity" and a significant increase
in the LOI of fly ash, which makes the ash unsuitable for cement and concrete
applications (Kalyoncu, 2001). The FBC ash chemical composition is directly
influenced by coal characteristics resulting from the chemical composition of
inorganic fraction of coal, the sulfur content of coal and the SO2 removal rate
(Lecuyer, Gueraud, & Bursi, 2001). Depending on coal sulfur content and the sorbent
reactivity for desulphurization, FBC ashes may rich in lime and sulphur and this
chemical composition of FBC ash usually results in a high alkaline and high content
of SiO2+Al2O3+Fe2O3 (Lecuyer, Gueraud, & Bursi, 2001). In this case, FBC ash does
not meet the ASTM C618 and GB1596-1991 requirements for conventional civil
engineering and concrete applications.
SDA product is a fine grained material resulting from dry flue gas desulphurization
with quick lime or slaked lime acting as the react reagent. The dry material from dry
scrubbers or reactors that is captured in an ESP or FF mainly consists of fly ash,
CaSO3 and Ca(OH)2, with some impurities such as CaSO4, CaCO3 and CaCl2.
Although fly ash accounts for about 50% of the SDA product, the chemical and
physical properties of SDA product have become very different from normal fly ash
because of the introduced De-SOx end products (Xu Q. , 2003). The chemical activity
of SDA product has been significant impacted by higher content of sulphur and lower
content of SiO2+Al2O3+Fe2O3 compared with normal fly ash. The beneficial use of
SDA product in construction materials and civil engineering applications is, therefore,
restricted and limited significantly by its relatively inactive properties (Cui et al.,
2008).
FGD gypsum is natural gypsum like solid residue generated from the wet
desulphurization of flue gas from coal-fired power plants. It is estimated that the wet
limestone (or lime) FGD system accounts about 80% of all of the FGD systems which
have been extensively installed in coal-fired power plants (Wang & Wu, 2004).
Because the wet FGD systems are designed to introduce primarily lime or limestone
as reagent sorbent and generally combined with fly ash removal facilities, the
obtained end product is usually a mixture of gypsum, calcium sulfite (CaSO3), fly ash,
and un-reacted lime or limestone (TFHRC, 2010). FGD gypsum is generally
characteristic of yellowy color and consists of small, fine particles with 10% - 15%
moisture content. The wet product from limestone based reagent wet scrubbing
processes is predominantly calcium sulfite. Generally, calcium sulfite is converted to
14
calcium sulfate (CaSO4) by forced oxidation and the moisture and other impurities in
FGD gypsum are reduced by appropriate measures, such as vacuum dewatering and
physical processing, to satisfy the requirements for industrial applications (Kalyoncu,
2001). The primary value of FGD gypsum is the higher calcium sulfate content
renders it suitable for a variety of beneficial use applications in the construction and
agricultural industry (NCASI, 2003). Calcium sulfate, once it has been dewatered, is a
material similar as natural gypsum, can be used in wallboard manufacturing and in
place of gypsum for the production of cement. The impurities, such as CaSO3 and
carbon, contained in the FGD gypsum tends to have negative impacts on applications
in cement manufacturing; while for gypsum board production, the detrimental
impurities are those water soluble organic or inorganic substances, such as potassium,
sodium, iron, magnesium and etc (Wang & Wu, 2004).
15
4 CCPs utilization
The utilization of CCPs began with Roman times; some 2000 years ago - long before
the invention of Portland cement - the Romans used volcanic ash in the construction
of aqueducts and coliseums that are still standing today (Kalyoncu, 2001; NCASI,
2003). The history of CCPs in China began from the late Ming Dynasty - about 400
years ago - with the use of lime and volcanic ash mixed concrete in hydraulic
engineering (Shen & Wu, 2004). The first research on applying fly ash to concrete
was reported by America scientist R. E. Davis in 1935 (Kalyoncu, 2001; Shen & Wu,
2004). One of the milestones of large scale CCPs applications is the project carried by
the U.S. Bureau of Reclamation who used more than 100,000 tonnes of fly ash in the
construction of the Hungry Horse Dam in Montana from 1948 to 1953 (Kalyoncu,
2001; Shen & Wu, 2004; Chang & Xu, 2007). The patterns of CCPs utilization and
corresponding use rate vary due to the differences of individual countries in terms of
economic and technology level of development.
4.1 Worldwide utilization of CCPs
Berg and Feuerborn reported in 2001 that about 500 million tonnes of CCPs were
generated worldwide. However, only mere fraction of the total CCPs produced was
beneficially used. The untreated disposal of such vast sum of products can have
significant economic and environmental problems. The current utilization of CCPs on
worldwide basis varied widely from a minimum of 13% to a maximum of 97% as
showing in Table 4. While the world average utilization rate of CCPs is still keeping
low.
Table 4 Overview of coal combustion products production and use in different countries
Country/
Region
USA
CCPs
Production
(Mt)
136.1
2
CCPs
Utilization
(Mt)
60.6
Utilization
Rate
Year
References
44.5%
2008
(ACAA, 2009)
China
120.0
69.6
58.0%
2000
(Wang & Wu, 2004)
India
90.0
11.7
13.0%
2000
(Kalyoncu, 2001)
EU15
61.2
55.4
89.3%
2007
(ECOBA, 2009)
Australia
14.6
4.6
31.0%
2008
(ADAA, 2009)
Japan
11.0
10.7
97.2%
2006
(JCOAL, 2010)
Canada
6.8
2.3
33.0%
2004
(CIRCA, 2005)
Based on the statistics issued by European Coal Combustion Products Association
(ECOBA) in 2009, the overall CCP production for 2007 in the European Union of the
EU 15 was about 61 Mt with a utilization rate of 89.3% as shown in Figure 5. About
52.7% of the CCPs produced were used in construction industries (concrete, cement,
2
This figure includes only the production of coal ash based on the data available. With new
figures also on FGD products the total amount of CCPs produced in China will be much
higher.
17
gypsum panel, etc.) and civil engineering (road base, embankment, flowable fill, etc.)
and 36.5% were used in restoration of open cast mines with 2.5% were temporary
stockpiled for future use and 8.3% were disposed of. ECOBA member countries are
Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, the Netherlands,
Poland, Portugal, Romania, Russia, Spain and the United Kingdom. In the larger EU
of 27 member states the total production in 2007 is estimated to be about 100 million
tonnes (ECOBA, 2010). That is to say ECOBA members account for over 60% of
CCP production in Europe.
Disposal
8,3%
Temporary
stockpile
2,5%
Construction
industries and
Civil
engineering
52,7%
Mining
Restoration
36,5%
Figure 5 Utilization and disposal of CCPs in Europe (EU15); total amount 61 million
tonnes (based on ECOBA, 2009)
Below Figure 6 shows the CCPs applications and related distribution rate for 2008 in
the United States. The America Coal Ash Association (ACAA) reported in 2009 that
the overall CCP production for 2008 is estimated at 136.1 million tons, while 60.6
million tons, which represents a 44.5% of total CCPs generation, are beneficially used
compared with about 89.3% use in the EU15. As in Europe (EU15), the United States
used CCPs in a number of applications, with construction industries and civil
engineering leading the way at 32.1%, followed by mining applications with 7.7%
and other applications with 4.7%. The remained 75.5 million tons were still being
stockpiled or disposed in landfills and/or lagoons, which accounts up to 55.5% of total
CCPs produced (ACAA, 2009).
Construction
industries and
Civil
engineering
32,1%
Mining
Applications
7,7%
Disposal
55,5%
Miscellaneous/
Other
4,8%
Figure 6 U.S.A CCPs utilization and disposal in 2008; total amount 136.1 million tonnes
(based on ACAA, 2009)
18
Table 5 summarizes profitably utilization rate of different components of CCPs in the
EU15 and the United States. Over 20 million tonnes of the 42 million tonnes of fly
ash produced in the EU15 was beneficially used (47% use rate) with a slightly smaller
fraction (44%) of bottom ash, 88% of boiler slag, and 81% of synthetic gypsum
produced found beneficial uses. As in the EU15, the United States has almost same
profitably utilization rate of fly ash (40%), bottom ash (44%) and boiler slag (83%).
Almost all of the FBC ash produced from the EU15 and the United States was not
used in value-added applications and the utilization rate of SDA products in the
United States is only 17% compared with that of the EU15 (61%).
Table 5 Profitably utilization rate of CCPs in Europe (EU15) and USA3
Country/Region
FA
BA
BS
FBC
SDA
FGD
Year
References
EU15
47%
44%
88%
15%
61%
81%
2007
(ECOBA, 2009)
USA
40%
44%
83%
2.3%
17%
60%
2008
(ACAA, 2009)
FA = fly ash; BA = bottom ash; BS = boiler slag; FBC = fluidized bed combustion residues;
SDA = spray dryer absorption product; FGD = flue gas desulphurization gypsum
Among the other individual countries investigated, India used only 11.7 million
tonnes (13%) of 90 million tonnes fly ash produced in 1999, the remainder was
disposed of. Approximately 14.6 million tonnes of CCPs were produced within
Australia, and some 4.6 million tonnes (or 31%) of CCPs have been effectively
utilized in various applications. Whereas, Canada generated 6.8 million tonnes CCPs
in 2004, of which about 33% (2.3 million tonnes) was used. In Japan, the total
generated coal ash was 11 million tonnes in 2006, among which 10.6 million tonnes
was effectively used, equivalent to 97.2% use rate of the total production. The high
disposal cost of CCPs in Japan ($100.00 per metric ton) (Kalyoncu, 2001) and
scarcity in natural resources makes alternative uses economically viable.
4.2 CCPs utilization in China
The use of CCPs in China has become an increasing concern in recent years due to
increasing costs of landfill space and current interest in sustainable development.
China is the biggest coal output country all around the world and coal is and will be
the main driver for economic development. In response to the growth in coal and
electricity demand, the amount of CCPs produced in China continues to increase. The
total fly ash produced from coal-fired power plants was increased from 37.7 Mt
(million tonnes) in 1985 to 120 Mt in 2000 with an average annual production of 55
Mt (Wang & Wu, 2004). It is estimated that about 1.1 billion tonnes coal is consumed
by the power industries and over 200 million tonnes of fly ash are produced during
2006 in China (Liu, 2009), which makes the country the largest CCPs producer in the
world. The predicted amounts of fly ash in 2010 and 2020 will be 320 - 380 Mt and
570 - 610 Mt, respectively (Cao et al., 2008).
Utilization of CCPs has attracted much attention from the government over the years.
3
Restoration and mining applications are not counted as beneficial uses in the statistics.
19
Fly ash has been used as a mineral admixture material in concrete and grout for
construction applications, especially for dam constructions, from the early 1950s in
China (Wang & Wu, 2004). While only few amounts of total generated fly ash were
beneficially utilized at that time. Along with the increasing pace of the economic
development, coupled with great demand from the construction industries, making the
pattern of fly ash applications more diverse. Since 1970s, several advanced
production lines have been imported to produce novel wall materials, such as fly ash
blocks, wall board and fly ash fused ceramics. However, for a variety of reasons these
technologies have not been widely spread across the country, which had led to a lower
utilization rate of fly ash, only 14% in 1980 (Wang & Wu, 2004). Until 1990s, the
government promulgated series preference policies and incentive measures to develop
other high volume applications, such as road base pavement, structural fill, backfill
and agriculture fertilizer, outside cement and concrete industries. Simultaneously,
researches on high levels applications have also been listed in the government
research and development agenda, which had CCPs utilization to be promoted to a
quite new stage.
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Production
Utilization
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Fly ash production and utilization (Mt)
The domestic fly ash production and utilization trend from 1979 to 2000 is presented
in Figure 7. From late 1970s, the utilization rate has been hanging around at 20% for
many years, however, with the increased interested in the value of CCPs and the
reinforced policies the use rate grew rapidly in recent years and this figure reached up
to 58% in 2000 (Wang & Wu, 2004). It is anticipated that this rate continues to grow
for the years to come.
Data years
Figure 7 Fly ash production and utilization trend from 1979 to 2000 in China (Wang & Wu,
2004)
Presently, in China, fly ash is used extensively in construction, road-building, backfill,
agriculture applications and mineral extraction, among which the first three
applications share more than 90% of the total recovered fly ash. The distribution of
20
different applications of fly ash is summarized in Figure 8. More than 56.8% of total
fly ash produced in 1997 was disposed of. Use in construction industries and civil
engineering tops the list of leading fly ash applications with about 32.8%, followed by
restoration (6.7%) and agriculture (1.8%) (Wang & Wu, 2004).
Construction
industries and
Civil engineering
32,8%
Disposal 56,8%
Restoration 6,7%
Agriculture 1,8%
Others 1,9%
Figure 8 China fly ash utilization and disposal in 1997; total production 106 million tonnes
(based on Wang & Wu, 2004)
A number of fly ash utilization projects have been carried out from 1960s in China.
However, the current development level of fly ash utilization in China is still lower
than that of in developed countries. Because of the unbalanced development levels of
region economy, the utilization rate varies widely from a minimum of 10% to a
maximum of 100% (Chang & Xu, 2007). Moreover, most of the fly ash generated
from coal-fired power plants was used for low value added applications such as road
pavement and mine restoration. Only 5% of the total fly ash produced was used in
novel construction materials manufactures (Chang & Xu, 2007). Nevertheless, China
has scored substantial achievements on fly ash treatment and utilization in recent
years. A massive amount of fly ash based concrete has been used in the Great Three
Gorges dam project known as the largest hydroelectric project in the world. The total
amount of concrete used is estimated about 27 million m3 and fly ash as an admixture
to the normal concrete accounts for about 50 percent (Chang & Xu, 2007). In some
developed areas, Shanghai, Nanjing and Nantong of Jiangsu Province and Nanchang
of Jiangxi Province, the utilization rate of produced fly ash was 100% in the past five
years and used extensively in geotechnical engineering of road construction and
wallboard materials (Cao et al., 2008).
While the situation in some less developed areas is not so optimistic, substantial
amount of CCPs is currently unable to be used in gainful applications, but only to be
land filled or stockpiled on site. Most of the fly ash produced in China’s Western
areas is stockpiling in open fields without any treatment, which has produced serious
environmental contaminations. A significant proportion of electricity produced from
power plants in these economic underdeveloped areas is being sent to the developed
coastal regions of East China; however, the produced fly ash as a combustion byproduct is difficult to find beneficial use applications because of the market
limitations, such as relatively high cost of transportation and lack of local market
21
demand of CCPs. It can be predicted that this situation is getting much worse by
increasing production of electricity and expansion of power plants in these areas.
4.3 CCPs use applications
Growing concern for increased landfill costs, shortage of natural resources, negative
impacts to the environment and threaten to public health has led to significant interest
in developing other CCPs recovery technologies. Because of the substantial amounts
of CCPs generated, the focus has primarily been on high volume utilization
applications, generally in the engineering and construction areas. Such current CCPs
utilization efforts have so far met with much success in many countries. However,
despite the large scale and positive uses, the amount of CCPs produced clearly far
exceeds consumptions currently (Iyer & Scott, 2001), which leads to continued efforts
are still needed to achieve high levels utilization of CCPs.
4.3.1 Current CCPs applications
Among the most common applications of CCPs is the substitution of fly ash for
Portland cement in concrete or the use of fly ash as a mineral additive in concrete and
as a raw feed for cement clinker (ACAA, 2008; ECOBA, 2009), because of the
advantages in particular geotechnical properties, e.g. specific gravity, permeability,
internal angular friction, and consolidation characteristics (Ahmaruzzaman, 2010).
Coal ash can be considered as the world’s fifth largest raw material resource with its
large amount and particular cementitious properties (Ahmaruzzaman, 2010). As Manz
(1997) writes: "worldwide the major use of coal ash is in concrete, which exceeds any
other single application…The state of the art is well established with respect to coal
ash as a cement raw material, for use in blended cement and as a partial replacement
for cement" (Manz, 1997). Using fly ash concrete can improve the performance of
concrete and quality of construction while saving cement and concrete cost. Fly ash
has a successful history of use in concrete around the world for over 50 years (Cao et
al., 2008). In the United States of America about 16 million tonnes (ACAA, 2009) fly
ash, and in Europe of the EU15 more than 14 million tonnes (ECOBA, 2009) fly ash
are used annually in cement and concrete industries.
And the second most common use of CCPs is the replacement of FGD gypsum for
natural gypsum, which is a hydrated form of calcium sulfate, in wallboard (ACAA,
2008; USEPA, 2010). The FGD gypsum utilization progress is better in developed
countries and most of FGD gypsum produced are extensively used in construction
material industries. Apart from wallboard manufacturing, there exist other
applications such as gypsum grout, gypsum powder, cement retarder, etc. The primary
value of FGD material is its chemical composition (NCASI, 2003) , which makes
FGD gypsum that is rich in calcium sulfate content well-suited for replacing the
natural gypsum in cement retarder as well as wallboard. In China, the total amount of
cement produced in 2000 has reached to 300 million tonnes and the requirement of
natural gypsum as cement retarder was 12 million tonnes based on the calculations in
accordance with retarder agent makes up 4% of cement; and the production of natural
gypsum in 2000 was 13.7 million tonnes, it can be seen that approximately 88% of
natural gypsum produced was used in cement industries (Wang & Wu, 2004). Using
FGD gypsum as cement retarder agent, therefore, possesses a large market potential.
By proper treatment, the quality of FGD gypsum can superior to natural gypsum
22
making FGD gypsum in replacement of natural gypsum as cement retarder agent
more feasible.
In addition to the cementitious properties, the unique spherical shape, particle size
distribution, and alkalinity of fly ash provide value for a variety of beneficial use
options (NCASI, 2003). These processes and applications include, but are not limited
to mining restoration, embankments, pavement, underground void filling, lightweight
aggregate, brick and ceramic, cenospheres, mineral filler, soil modification and waste
stabilization. Wang and Wu (2005) showed the possible multiple fly ash utilization
patterns in different sectors based on the natural advantages of this resource (Figure 9).
Roller Compacted
Concrete for
Roads and Dams
Construction of
Road Base
Controlled
Low Strength
Material
Waste
Stabilization
Cement Replacement in
Ready Mix Concrete
Land Reclamation
Fly Ash
Resource
Fillers for Asphalts,
Plastic, Paper
Size Range
Backfill for
excavations,
mine fill, trenches,
retaining walls
Abundant
Reserves
Pozzolanic
Nature
Abrasives for scouring
powders, polishes
Chemical
Composition
Agricultural uses
Ceramic raw material
for Bricks,
Glass, Refractory
Recovery of
Magnetite,
Raw material Source of
Cenospheres,
Silica, Alumina,
for cement
Carbon
Iron
Figure 9 Possible use pattern of fly ash based on the properties of fly ash (reproduced from
Wang & Wu, 2006)
4.3.2 Potential CCPs applications
Currently, CCPs are mainly used in civil construction industries and these
applications have scored substantial achievements, however, such efforts are not
adequate for increased use of CCPs as is obvious from the low level of utilization, e.g.
low utilization rate and low value added (Kikuchi, 1999). Moreover, in many cases
the markets for CCPs as an ingredient in cementitious and other construction process
are close to saturation (Iyer & Scott, 2001). As a consequence, alternative uses of
CCPs other than the conventional cement and construction industry are, therefore,
needed to be developed and industrialized. Efforts have been directed to
developments of other commercially viable products, which may yield high value
addition to its manufacturers (TIFAC, 2009) and help to save other dwindling
23
resources (Iyer & Scott, 2001). Potential high value added fly ash applications listed
as shown below in Table 6.
Table 6 Potential fly ash high value added applications (based on TIFAC, 2009 and Wang
& Wu, 2004)
Category
High value-added applications
Mineral extraction
Alumina
Magnetite
Iron
Carbon
Cenospheres
Other miner and trace items
Enhanced Pozzolana cement
Oil Well Cement
Decorative glass
Ceramic Fibers
Glazed floor and wall tiles
Ash alloys
Synthetic marble
High ware resistance ceramic tile
Reflective material
Ultra light hollow sphere for arid zone
Continuous casting mould powder
Domestic cleaning powder
Synthetic wood
Mineral fillers
Distemper
Plastic fillers
Fire Bricks
Fire abatement applications
Glass Ceramics
Foam insulation products
Anti-corrosion coating
Mineral Wool
FGD Adsorbent
Synthetic Zeolites
Activated Cenospheres
Cultivation
Potassium silicate fertilizer
Construction and engineering
Filler
Protective material
Waste treatment material
Agriculture
Fly ash is a mixture which is mainly constituted by hollow glass beads, solid glass
beads, iron-rich glass beads, porous spherical carbon grains, fragmental carbon grains
and other spongy substances (Wang & Wu, 2004). The components, density and
shape are quite different in different particles, thus the utilization and value of those
particles are also distinct. Through a certain physical or chemical processing, various
microspheres can be selected and obtained from the ash. These kinds of high value
added products consume lower volume of fly ash than that of construction, back fill
and road pavement applications. However, they have the potential in generating
considerable sales revenues for power plants and manufacturers, which helps to
prompt the development of different high level CCPs technologies.
24
A conceptual commercial scale design and financial estimate for a plant to recover
high value added products from fly ash using a direct acid leaching process, with the
rate of return exceeding 20% of the investment, was developed by the US Department
of Energy during 1983-1984 (Golden & Wilder, 1985). It was estimated that by
processing 1180 000 tons/year (TPY) of fly ash, 158 000 TPY of alumina, 102 000
TPY of ferric oxide, 46 000 TPY of gypsum, 81 000 TPY of alkali sulfate salts and
866 000 TPY of spent fly ash would be obtained. An excess cogeneration of 1940
MWh of energy from a commercial scale plant was also included.
The main component of fly ash are SiO2 (40–65 wt %) and Al2O3 (25–40 wt %), with
small quantities of Fe2O3, Mg, Ca, P, and Ti (Kikuchi, 1999). Fly ash therefore can be
considered to be an aluminum silicate compound containing some impurities, which
enables its use for the synthesis of zeolite (Kikuchi, 1999) and alum (Park et al., 2004).
The zeolite has an ability to exchange one cation for another, known as “cation
exchange capacity” or CEC (Liu, 2009). Synthetic zeolite is, therefore, accepted
wildly as a drying agent, deodorant, freshness-holding agent, water-softening agent,
soil conditioner, fertilizer additive, and feed additive (Kikuchi, 1999). The synthesis
of artificial zeolite from coal ash on a semi-industrial scale has been conducted.
Kikuchi (1999) has pointed out that natural zeolite is not widely distributed but is
localized in certain regions of the world, which means synthetic zeolite will be in a
highly competitive position outside of the natural ore field. It is anticipated that the
zeolite converted from coal ash has a big potential for commercialization in terms of
quality, localization of natural zeolite mines, and commercial price (Kikuchi, 1999).
As alumina is widely used as high performance raw material for many applications
and fly ash primary consists of fine inorganic particles SiO2 and Al2O3, the synthesis
of Al2O3 powder from the ash, is of great commercial interest (Park et al., 2004). The
process applying coal fly ash for alumina powder synthesis and using spent fly ash as
raw material for cement production was shown to be technically viable, and this
technology has been semi-industrialized successfully in Poland (Wang & Wu, 2004).
China has also obtained a number of achievements in this field. However, the research
on alumina synthesized from fly ash is still of laboratory-scale. Experiences from the
semi-industrialized project in Poland showed that the quality of alumina produced
from fly ash based on a limestone-sintering process is far superior to that of other
conventional alumina extraction processes, which makes the commercial price of fly
ash alumina several times higher than that of conventional one (Wang & Wu, 2004).
Along with the development of alumina synthesis technology, it is foreseeable that the
alumina extracted from fly ash may have a big market potential.
Coal fly ash can also be used to produce a cheap and environmentally-friendly
absorbent for dry-type flue gas desulphurization and this process has been
successfully commercialized (Wang & Wu, 2006) (refer to Figure 10). The adsorbent
used in dry-type FGD processes are high reactivity pellets produced from fly ash and
slaked lime spent absorbent (could be FGD gypsum). These pellets have favorably
large pore volume making it possible to achieve a high De-SOx efficiency (Kikuchi,
1999). This process, to a certain extent, is superior to other traditional FGD processes,
e.g. Dry-type, Semi-dry and Wet-type FGD. Because the adsorbent is made of
recycled waste materials and no drainage and gas re-heater are required. Wet FGD
can achieve high De-SOx efficiency and is easy for operation. However, it has
drawbacks such as a large consumption of water and the need for waste water
25
treatment. Although dry-type and semi-dry FGD do not have drainage, in order to
obtain a same high DeSOx efficiency as wet-type FGD, a larger amount of adsorbent
are needed because a higher molar ratio of calcium to sulfur is required, compared
with wet-type FGD (Kikuchi, 1999).
Figure 10 Schematic plant view of flue gas desulfurization using coal ash (Kikuchi, 1999).
Some industrial plants using active-treated fly ash as FGD absorbent have achieved
DeSOx efficiencies of over 90%, such as the Ebetsu power station (50 000 Nm3/h) and
the Tomtoh Atsuma power station (644 000 Nm3/h) under a high molar ratio of
calcium to sulfur (1.0–1.2) (Kikuchi, 1999). As Kikuchi (1999) writes: During
operation, there is no need for wastewater treatment or gas reheating, and so this
process is considered to be an ideal choice for controlling the emission of sulfur
dioxide and an environmentally-friendly method for reuse of coal ash…but this FGD
process has not yet spread worldwide (Kikuchi, 1999). This technology of activating
coal ash as FGD adsorbent with double benefits of environmental and economic
should be widely spread in China, where there exits a large demand of FGD
adsorbents to increase the reduction of SO2 emissions. Although the FGD process
using coal ash as adsorbent has been industrialized and achieved a good success in
some developed countries, few researches in this field have been done in China
(Chang & Xu, 2007).
A number of researches on high value added applications, such as waste water
treatment, anti-corrosion materials, glass ceramics and reflective materials, have also
been carried out in China (Wang & Wu, 2004). Several researches have achieved
abundant accomplishment. However, a number of projects on high value added fly
ash applications reported work to date are still of laboratory- or pilot- scale, even
some of the technologies have been commercialized in other developed countries for
many years. Thus, further development work in this area is needed.
26
5 Driving forces for the use of CCPs
CCPs from coal combustion power plants have been gaining wide public concern and
its environmental and commercial value has also been highlighted under the
worldwide background of "low-carbon economy" and "sustainable
sustainable development".
development
Based on the normalized results derived from questionnaires and interviews, different
kinds of incentives and corresponding degree of importance have been identified from
the stand point of both CCPs producers and users,
users, as shown in Figure 11 and 12. The
preference policies, such as tax exemption, "green" subsidies and low interest loan,
made by the government
nt were identified by the power plants as policy drivers for
CCPs use. Investment savings from reduced maintenance and operation cost, financial
rewards from the sales of CCPs and land saving were also considered as main
economic incentives. Reduction of environmental
environmental impacts, such as air pollution, water
contamination and GHG emission, were regarded as driving forces
force for CCPs
utilization.
Preference policies
Investment savings
Reducing Env impacts
Financial rewards
Land saving
0
Ningxia TPP
20
40
60
FAW TPP
80
Baotou TPP
100
120
140
160
Taizhou PP
Figure 11 Identified incentives from the perspective of CCPs producers
The four power plants
ts interviewed as CCPs producers considered land saving is the
most important driving force followed by the incentive of environmental impacts
reduction. Using CCPs helps to save disposal cost while releasing useful land
occupied by CCPs stockpiling. For this
this reason, all of the consulted power plants input
the highest grade on the category of land saving. The power plants also considered
reducing impacts on the environment as important driver for utilization of CCPs.
Investment on storage facilities and maintenance
maintenance or operation costs could also be
reduced by using CCPs. As the amount of revenues provided by the sale of CCPs and
subsidy from the government are insignificant in relation to the profits generated from
the sale of electricity, therefore, financial
financial rewards and preference policies were likely
to be considered less important.
27
Preference policies
Reducing Env impacts
Financial rewards
Land saving
0
Runji Cement
20
40
Jiangong Construction
60
80
100
120
HSLB Gypsum Board
Figure 12 Identified incentives from the perspective of CCPs users
While from the point view of CCPs users, economic factors were considered as the
overriding incentive for using CCPs. Fly ash as the principle component of CCPs,
generally costs less than other available raw materials for cement and concrete
industries. It helps to reduce the cost of raw materials while maintaining or improving
the quality of end products. Policy supports and subsidies provided by the government
also play a significant role in increasing use of CCPs in those companies. Land saving
was not a significant factor that promotes the use of CCPs in those CCPs users.
The identified driving
riving forces for the use of CCPs were briefly grouped into three
categories: environmental incentives, economic incentives and legislations.
5.1 Environmental incentives
Reduction of environmental
environment impacts plays a significant role in promoting use of CCPs.
Water contamination and air pollution from the disposed and stockpiled CCPs will be
prevented by CCPs utilization.
5.1.1 Water pollution prevention
A greater proportion of CCPs produced in China is still disposed of in landfills and
impoundments or stockpiled for future use,
use which has caused significant burden to the
environment. As those substantial amounts of CCPs are sometimes disposed on
unlined landfills,, water from rainfall can potentially dissolve elements in the CCPs
and then mix with surrounding water system.
system Coal fly ash, bottom ash, and boiler slag
are primarily aluminum and silica and FGD materials composition is dominated
d
by
calcium and sulfur, while all CCPs contain metals in trace amounts (Murarka et al.,
1992). A potential surface
ace and ground water contamination can be caused by the
leaching of dissolved toxic elements and heavy metals such as lead, mercury,
cadmium, copper and zinc in fly ash if inadequately deposited (Polie et al., 2006).
Hung et al. (2009) indicated that Pb leaching
le
from large scale fly ash landfills may
induce serious human health risks.
Murarka (2003) reported that the increasing use of low NOx emission combustion
technologies at coal-fired
fired power plant is expected to result in elevated concentrations
28
of ammonium in coal ash. The ammonium leached from landfills is likely to convert
to nitrate that could migrate in groundwater and resulting in water pollution thereby.
5.1.2 Air pollution prevention
Fly ash is a fine and powdery material, the particle size distribution of coal fly ash
collected generally ranges from 0.5-300 µm. The toxic trace elements are generally
concentrated in the fine particles with a grain diameter of 2 µm, which can be inhaled
and retented in human bronchus, is likely to pose significant human health risks (Tang
et al., 2004). For the dry stockpile fields, the dust escaped from fly ash would
aggravate the air quality on a regional basis. The residents in the vicinity of power
plants, where dry stockpile fields are constructed, will under high risk of exposure
into harmful fugitive dust in air.
5.1.3 GHG emissions reduction
The pozzolanic properties of coal fly ash make it suitable for replacing a portion of
the Portland cement used in making concrete. Portland cement manufacture accounts
for about 80% of green house gas (GHG) emissions embodied in concrete (Flower &
Sanjayan, 2007). The average CO2 emission is approximately 0.8 kg/kg cement (Josa
et al., 2004), using 1 tonne of fly ash in cement results in about 0.8 tonne reduction of
CO2 emission. Using CCPs in place of virgin materials by reducing the energyintensive mining operations and mining energy use needed to generate virgin
materials can also lead to reduction in GHG emissions.
5.2 Economic incentives
Various economic benefits can be obtained from reduced quantities of disposed CCPs
and increased use of those products. Using CCPs helps to reduce disposal cost and
save natural resources while releasing useful land.
5.2.1 Land saving
Land saving was identified as the most important driving forces by the power plants
interviewed. The disposal of CCPs will result in a significant cost to the power plants
and utilizing companies in terms of operation, maintenance, transportation and on-site
storage investment. On the other hand, high disposal cost of CCPs makes alternative
uses economically viable (Kalyoncu, 2001). In China, the amount of cumulated fly
ash has reached to about 2.2 billion tonnes. Based on the current CCPs annual amount
of production, the requirements for ash-sluicing water and land for storage will be
increased to about 10 billion tonnes and 300 square kilometers, respectively (Wang &
Wu, 2004).
China is scarce in water resource and land per capita, such significant amount of
water and land requirement for CCPs disposal will cause huge economic burden to the
country. Power plants located in urban areas, especially for those in prosperous
coastal regions, may no longer have adequate on-site storage space, which
necessitates the CCPs produced to be transported to remote areas for disposal. The
cost for disposal will increase dramatically due to the long distance for transportation.
Some China’s lager power plants, e.g. Tuhe Power Plant, Shijingshan Power Plant
29
and Jianbi Power Plants, have to invest more than 100 million ¥ each on the
construction of on-site storage silos or stockpile fields (Wang & Wu, 2004).
5.2.2 Natural resources conservation
Fly ash can typically replace between 15 to 30 percent of the cement in concrete with
even higher percentages used for mass concrete placements (USEPA, 2010). CCPs,
therefore, have a big potential for natural resources and energy conservation. Proper
use of CCPs in construction applications makes good economic sense.
The interviewed CCPs use companies considered economic factors as the overriding
incentive for using CCPs. Fly ash as the principle component of CCPs has been
widely applied as cement replacement in concrete industries in China. It generally
costs less than other available raw materials and helps to reduce the cost of raw
materials while maintaining or improving the quality of end products. Fly ash
concrete is technically superior to conventional concrete. Combining fly ash with
Portland cement mixtures can produce for higher performance and longer-lasting
buildings than conventional constructions (ACAA, 2008). Economic gains are
significant from both technical and sustainability perspectives, as well as from
aesthetic point of view (ACAA, 2008).
Moreover, FGD synthetic gypsum material has a potential for replacing about 10% of
total wall bricks consumed currently by the construction industries in China, which is
likely to help saving about 2.5 million tonnes of standard coal annually (Wang & Wu,
2004). CCPs are often considered as more cost-effective materials, they are less costly
than the materials they replace. Economic benefits from CCPs utilization can include
reduced costs from landfill disposal, increased revenue from the sale of CCPs as well
as savings from using CCPs in place of other, more costly materials (USEPA, 2010).
5.3 Legislations
Tightened regulations on landfill of CCPs and strong policy support provided by the
government are also of great importance for promoting CCPs uses.
5.3.1 Heightened regulations for landfill
The heightened regulations are making the disposal of CCPs an undesirable option.
When the CCPs disposal locations are filled, new land and facilities must be found for
storage. The extensive environmental impact evaluations and regulatory hurdles make
obtaining the required permits and authorizations for those new disposal facilities
increasingly difficult (Hall & Livingston, 2002).
5.3.2 Ban of solid clay bricks
In 2005, China’s General Office of the State Council (CGOSC) promulgated "Advices
to further speed up wall materials innovation and to promote building energy
efficiency." China’s wall construction material market is currently dominated by solid
clay bricks, which consumed more than 1 billion m3 clay resources, equivalent to 330
square kilometer useful land, and 70 million tonnes standard coal annually (CGOSC,
2005). This advice aims to speed up moves to ban the use of solid clay bricks in all
30
construction industries and promote the utilization of "green" wall materials, which is
a significant control means to protect limited land resources and the environment.
Studies show that using other new building materials, e.g. fly ash based construction
products, instead of solid clay bricks can save 47 percent of the energy in producing
wall materials and 30 to 50 percent of the heating energy of dwellings (Xinhua, 2004).
The production and use of solid clay bricks in all municipalities, large and mid-sized
cities in coastal areas, and cities in provinces where capita farmland is scarce have to
be banned from 2000 (Xinhua, 2004). And the ban of using solid clay bricks in
construction has to be mandatory implemented in all municipalities by the end of
2010 (CGOSC, 2005). The government also imposes mineral resource tax and reimposes 17% value-added tax (VAT) on solid clay brick manufacturers, which makes
the solid clay brick manufacturers less competitive in the construction material
markets (Chen E. , 2008). Under this regulation background, moving to use CCPs
based construction materials in place of traditional solid clay bricks will be
accelerated dramatically in China.
5.3.3 Preferential policies for CCPs applications
Besides the regulations on the ban of solid clay bricks, China Central Government and
local authorities also unveiled fresh policies for encouraging the use of CCPs in
different applications, which was also acknowledged by the interviewed CCPs users
as important incentives. Representatives of Baotou No.2 thermal power plant, Inner
Mongolia, and Jinyuyuan thermal power plant, Ningxia Province, stated that when
using CCPs as raw materials to produce other industry products, the company or
personnel will receive a tax exemption of 0.5 ¥/tonne of CCPs (BTTPP, 2010) and the
industry enterprises also have the right for 5-year income tax exemption from the
business began (JYYTPP, 2010).
31
6 Barriers to the increased use of CCPs in China
The use of CCPs in China has steadily increased in recent years however only a
portion of the products
cts were beneficially used. Obviously, there is quite a bit room to
grow the CCPs market, the CCPs industry
indust has to step up the effort to find additional
beneficial uses or increase the amount used in the present applications (Hitch, 2005).
It is predictable that new problems will emerge in endlessly during the practice
progress of CCPs applications (Wei, 2009). Examining and minimizing the barriers to
CCPs use is of great importance in the quest for increased use of CCPs.
CCPs Based on the
normalized results derived from questionnaires and interviews, various
variou barriers have
been identified from the different point view of CCPs producers and users, as shown
in Figure 13 and 14. The identified principle barriers to CCPs uses are those issues
related to materials characterization, market abilities, standards, specifications,
spe
policies, regulations, demonstration and public perceptions.
Hard to use FGD materials
Weakness in using techniques
High cost for transportation
Market limitation
Inconsistent qualities of CCPs
0
Ningxia TPP
20
40
FAW TPP
60
Baotou TPP
80
100
120
140
Taizhou PP
Figure 13 Identified barriers from the perspective of CCPs producers
Difficulties in using FGD materials were identified by the power plants as one of the
t
most important challenges to the increased use of CCPs. The utilization of FBC ash
and SDA products was largely restricted to the special characteristics of high-calcium,
high
high-sulphur, and high-carbon
carbon content;
content; because these materials do not meet the
standards
ndards of coal ash applications in cement and concrete, making them unsuitable for
replacement of cement in concrete. The power plants have to dispose of these
products as real industrial wastes. Outdated facilities and techniques in using CCPs
were considered
ered as factors
factor that are likely to result in low quality of end products,
making the expansion of CCPs market more difficult.
The representatives from power plants have also pointed out that high transportation
cost for low unit-value
value of CCPs poses a significant
significant barrier to the sales of CCPs. Some
of the power plants
ts are located in remote areas and tends to increase the unit
transportation cost significantly, making the produced CCPs less competitive in
relation to other local available materials. Market limitation is another vital factor
which inhibited the use of CCPs. The interviewed power plants are mainly located in
northern China,, where demand of CCPs from construction industries is limited to a
33
great extend by season problems, they are usually unable to find outlet with the
incremental CCPs produced during wintertime. The interviewees also pointed out that
the qualities of CCPs are also influenced by several factors, such as source of coal,
coal handling system and combustion techniques. The inconsistent
nt qualities of CCPs
are likely to hinder the expansion of CCPs in various applications.
Changes in processes or facilities
Competition from other materials
Lack of specifications and standards
Weakness in using techniques
High cost for transportation
Market limitation
Variation in CCPs price
Inconsistent qualities of CCPs
0
Runji Cement
10
20
Jiangong Construction
30
40
50
60
70
HSLB Gypsum Board
Figure 14 Identified barriers from the perspective of CCPs users
While from the point view of CCPs users interviewed, competition from other
oth
materials and high cost for transportation pose two of the most important barriers
b
to
the use of CCPs. The market ability of CCPs is influenced significantly by the
competition from local available resources, such as natural gypsum and minerals,
especially
lly from solid clay bricks. The market price of CCPs varied greatly depending
on the grade of materials, season problems and transportation cost. Because of the
undersupply of CCPs in some areas and increased transportation cost, the price tends
to be increased
eased dramatically, which makes the CCPs based end products less
competitive. And unbalanced supply-demand
supply
of CCPs in some areas was also
indentified as a factor that limits the development of CCPs market.
There are also some quality problems in relation to the CCPs end products because of
the outmoded production capacity,
capacity, which is likely to influence the sales of those
products. The general public concerned that they may be exposed to a high risk of
failed projects if the quality of CCPs materials is unguaranteed.
ung
The interviewed
representative from cement plant pointed out that investment in additional fly ash
storage facilities is also likely to impede the increased use of CCPs in their company.
company
And the construction company interviewed as a potential CCPs
CCPs user was not willing
to take unnecessary risks in using CCPs because of the inconsistent qualities of CCPs
and lack of perfect technical specifications and standards.
standards When using CCPs in many
potential applications, there are usually few technical standards
standards available to allow
34
their uses, which is likely to impede CCPs uses.
6.1 Technical barriers
The technical barriers included issues related to CCPs production, specifications and
standards, product commercialization, and user-related factors.
6.1.1 Lower rate of high-grade fly ash
In China, the rate of fly ash which can be used directly in the cement industries is not
high and the number of power plants that can produce high-grade (Class I) fly ash is
even small (Cong, 2009). The chemical and physical properties of fly ash vary
considerably depending upon the sources of coal, powder preparation equipments,
furnace types, ash collection methods as well as types of ash discharge system.
Consequence upon the various coal sources and different types of coal mills, the
pulverized coal tend to be coarse and can not be combusted completely in the furnace,
which lead to a great amount of coarse particles and unburned carbon remaining in the
ash. The fineness and loss of ignition (LOI) of fly ash are defined as two key
indicators by GB standard for the direct utilization of fly ash in cement industries
(Huang H. , 2010). The coarse and high-carbon content fly ash, which is over GB
standard, therefore, is unable to be used in cement industries.
Table 7 National Standard of the People’s Republic of China: Fly Ash used for cement and
concrete (GB1596-1991, 1991)
No.
Indicator
I
Class
II
III
12
20
45
95
105
115
2
Fineness (amount retained on 0.045mm
sieve, %) ≤
Water requirement ratio, % ≤
3
LOI, % ≤
5
8
15
4
Moisture, % ≤
1
1
N.A.
5
SO3, % ≤
3
3
3
1
Approximately 95% of fly ash produced from coal-fired power plants in China is
Class III or off-grade fly ash (Wang et al., 2004). The viability of fly ash quality and
the scarcity of high-grade fly ash have been wildly acknowledged by the international
cement industries as barriers to the development of fly ash cement (Shen & Wu,
2004). Moreover, high efficiency dust collectors have been installed successively in
the large scale power plants in China since 1980s; however, many of those plants are
still using wet sluicing system to transform fly ash, or even mixed with bottom ash, to
storage impoundments (Cong, 2009). Large amount of high-grade fly ash was also
flushed into the impoundments, which has quelled the activities of the fly ash making
it difficult to be used.
6.1.2 Difficulties in using FGD materials
Difficulties in using FGD materials have been identified by the interviewed power
plants as an important challenge to increased use of CCPs. The utilization of FBC ash
and SDA products was largely restricted to the special characteristics of those FGD
35
materials, such as high-calcium, high-sulphur, and high-carbon content. In China,
coal-fired power plants must comply with the acid rain provisions and reduce SO2 and
NOx emissions. Until clean coal technologies emerged, the flue gas scrubber was the
only commercial technology capable of achieving the SO2 reduction (Manz, 1998).
The conventional FGD processes, wet-type and dry-type, both remove only SO2;
neither reduces NOx emissions. In complying with the current China’s emission
regulations, emission control systems for both SO2 and NOx have to be installed in the
coal-fired power plants, which have led to the widespread use of low-NOx burning
technologies combined with the SO2 removing processes.
The low-NOx burning technologies have been extensively applied by most coal-fired
power plants in China into circulating fluidized-bed (CFB) coal combustion system
for power and steam generation (Wang & Wu, 2004). Within a CFB boiler, coal is
burned at 800 to 900°C (ECOBA, 2010), while limestone is added in the boiler to
minimize the emission of SO2 and NOx from the exhaust gas. Spray dryer absorption
(SDA) products resulting from dry FGD scrubbers or reactors take quick lime or
slaked lime as an FGD adsorbent to reduce the SO2 emission before it goes into the
atmosphere. These NOx and SO2 emission control technologies impair complete coal
combustion (Manz, 1998) and produce high-carbon, high-calcium, and high-sulphur
fly ash (ECOBA, 2010), which is unsuitable for using in cement industries. GB15961991 (refer to Table 7) requires Class I fly ash used for cement and concrete the LOI
and SO3 must be lower than 5% and 3%, respectively. Fly ash carbons and un-reacted
FGD sorbent are left in the ash after the incomplete combustion of coal in the furnace,
rendering the ash above specification for GB1596-1991 applications for cement and
concrete. The stability of concrete products will be affected by higher LOI and
calcium oxide remained in the fly ash. This kind of coal ash has lower biding ability
with other components in the concrete, which impacts the setting process, causes high
alkalinity (Huang H., 2010), air entrainment problems, and reduces the material’s
strength and durability, especially during freeze-thaw conditions (Manz, 1998). Manz
(1998) also indicated that the increasing use of NOx control technologies at power
plants is also expected to result in increased concentration of ammonium in coal ash.
Consequently, this kind of CCPs will become a real industry waste (Wei, 2009). It is
evident that fly ash marketability at those specific coal-fired units was reduced due to
the introduction of NOx and SO2 reduction systems.
Moreover, along with the development of clean coal technologies, changing from
high-sulfur coal into low-sulfur coal may require the addition of SO3 to the flue gas to
facilitate particle collecting efficiency of ESP systems. The addition of SO3 may
impact the properties of the fly ash, making it less suitable for use in cement
replacement applications (EERC, 1999).
6.1.3 Engineering specifications and standards barriers
Before a new material is able to be used in manufacturing or engineering applications,
specifications and standards of materials and products should be well established by
industrial institutions to ensure this kind of new material meet with the specific
requirements. While CCPs utilization standards are not developed very well in many
industries, making many companies or contractors are reluctant to consider using
CCPs in their projects when a standard material has been shown to meet project
requirements. In addition, when using CCPs in many potential applications, there are
36
usually few technical standards available to allow their uses, which is likely to present
a huge obstacle for their industrialization.
Even current CCPs utilizations standards also need to be further perfected and
improved. There exist imperfections in current specification of using fly ash as
cement replacement in concrete. Li Y. (2010) has pointed out that when applying fly
ash Class I into concrete there is only one specification available, which specifies a
same substitution rate of cement in concrete no matter what kind of project and
location, or whether there are some special technical requirements. In addition, a test
of compressive strength after 28 days standard curing is generally applied as
acceptance criteria for fly ash concrete products (Li Y. , 2010). However, because less
cement is used in the fly ash concrete, which renders the setting time of the concrete
extended, and the initial strength of fly ash concrete is lower compared with the later
strength. The fly ash concrete may, therefore, unable to pass the compressive strength
test after 28d standard curing, which has limited the amount of admixture-grade fly
ash in concrete.
EERC (1999) has argued that "various ashes that pass ASTM C618 may perform quite
differently: one may be sulfate-resistant while another is not, or one may be a good
water reducer or unaffected by alkali expansion while others do not share these
properties." This argument is also applicable in China’s national standards for fly ash
as cement replacement in concrete (GB1596-1991). As has already pointed out by
EERC (1999), the fly ash classification system should take these performance factors
into account and engineering properties should also be specified. The Class I, Class II
and Class III distinction in GB1596-1991 is inadequate.
6.1.4 Changes in manufacturing processes or facilities
Changes in manufacturing processes or facilities may be required for CCPs to be used
in cement and concrete industries, gypsum wallboard manufacturing, and other
applications (EERC, 1999). Based on the interview with the representative of Anhui
Runji Cement Plant, it was told that additional storage facilities, tank trucks and
necessary technical transformations are required for applying fly ash into cement
industries (Huang H. , 2010). Because of the relatively high cost of such additional
facilities, making the fly ash application may not be advantageous or economically
feasible for small operators who may intend to use CCPs as raw materials in their
production processes. The changes in normal manufacturing processes may raise the
cost of the end products and limit the use of CCPs, such as longer curing times and
increased operation procedures for fly ash concrete bricks or other preformed concrete
products. As EERC writes: "A necessary incentive to implement changes in
procedures must include an equal- or higher-quality end product at an equal or lower
cost" (EERC, 1999). Numerous small cement industries are, therefore, not likely to
invest on additional facilities and modify their production processes because of the
comparatively low profits (Huang H. , 2010).
6.1.5 Lack of practical experiences
The scarcity of practical experiences and skilled analysts is a big bottleneck for the
increased use of fly ash in construction material industries (Wei, 2009). In China,
more than 70 million tonnes fly ash is generated annually, of which 25% is applied
37
into construction material industries (Wang & Wu, 2004). As mentioned above, the
physical and chemical character of CCPs is very individual and varies widely in terms
of different coal sources and operation conditions. In construction material industries,
there is no universal process formulation which can match all types of fly ash.
Consequence upon the variety of fly ash characters, the formulation of raw materials
in production lines will be adjusted accordingly after technical analysis. Therefore, a
technical analyst plays a significant role in producing high performance fly ash end
products. The end product quality will not be guaranteed and the cost of products
would be very high, even the whole production lines will break down, without an
appropriate formulation of ingredients (Wei, 2009).
6.2 Economic barriers
Economic barriers to increased CCPs utilization are widely accepted as the most
important elements among all other factors that affecting by-product use (EERC,
1999). Once the economic incentives for CCPs uses are in place, the necessary
resources needed to overcome other barriers will be available (EERC, 1999).
6.2.1 Large variation in CCPs price
The market price of CCPs varied greatly depending on the material (fly ash or FGD
gypsum), the grade of fly ash, season and transportation cost. Representatives of two
power plants interviewed indicated that the average price of untreated original fly ash
from their power plants is about 15 Yuan per tonne, without transportation cost. After
further classification, the price of high grade fly ash Class I and Class II will be much
higher than that of original ash. The transportation cost is of great importance in
influencing the market price of fly ash. For those cement industries that near the
interviewed power plants, the transportation cost takes equal weight to the material
cost of original fly ash. For longer distance transportation, fly ash price will be
increased dramatically, which makes CCPs less competitive.
The price of fly ash is also impacted by season factors, power load and construction
work periods. Larger amount of CCPs is emitted in the winter months when power
plants are operating at full load. However, the fly ash produced in winter time is very
difficult to be used because of lower demands from local construction industries
(BTTPP, 2010). There may be no market available for CCPs in this case, especially in
North China. On the other hand, the construction industry often needs most of the fly
ash during the other seasons especially in the summer. The price of fly ash tends to be
higher than usual accordingly. The primary barrier for marketers is economics.
Therefore, there must be a profit available when marketing CCPs as a particular
commodity (EERC, 1999).
6.2.2 Competition from other materials
The economics of CCPs utilization are influenced by the cost and availability of
competing materials. The best example is traditional wall materials, such as solid clay
brick with its lower price and easy availability has been widely used in China for
thousands of years. Fly ash based wall materials can not pose competition with solid
clay bricks from the economic point of view. Without explicitly forbidden of solid
clay bricks, the development of other novel wall materials will be seriously hindered
38
(Wei, 2009). Another example is FGD gypsum, which can be used for replacing the
natural gypsum in wallboard. As has already pointed by EERC (1999), a necessary
incentive to market CCPs must include an equal- or higher-quality raw material at an
equal or lower cost. As China has substantial natural gypsum reserves, FGD gypsum
produced from power plants in mine sections does not have so many advantages in
quality and price compared with natural gypsum, which makes the CCPs users
preference for natural gypsum rather than taking FGD gypsum as their raw materials
for wallboard production. As EERC writes: "Cost savings and end product quality
were of key importance to most industries, and anything that would improve or at
least maintain product quality while maintaining or reducing the cost would be
favorably considered" (EERC, 1999).
One more example is high value added CCPs application, extraction of alumina from
fly ash. Wang & Wu (2004) argued that when producing one tonne of alumina from
fly ash, an additional consumption of 11 tonnes of limestone, 100 kg of sodium
carbonate, 450 kWh of electricity and 1.6 tonne of coal is required compared to
conventional alumina extraction from bauxite. And the current reserves of bauxite in
China is abundant, therefore, from the standpoint of economics, the process of
extracting alumina from fly ash is unable to compete with conventional process.
Many other concepts of high value added fly ash application, such as recovery of
magnetic material from fly ash (Groppo & Honaker, 2009), have been attempted at
the commercial scale numerous times in the past, however most of the attempts were
unsuccessful, not for technical reasons, but for economic reasons.
6.3 Marketing barriers
Spatial variation in supply-demand of high grade fly ash and high transportation cost
for low unit-value CCPs are likely to impede the expansion of CCPs market.
6.3.1 Unbalanced development of CCPs market
China Flying Ash Website CEO Wei (2009) has pointed out that the development of
use of CCPs in China’s different regions is extremely unbalanced. There are not so
many coal-fired power plants in southern China, therefore, the demand of CCPs
exceeds the supply, which makes the utilization of CCPs in this area is relatively
successful. Fly ash is widely used as cement replacement and raw material for
concrete products in the south region. However, in northern China where coal-fired
power plants are centralized and CCPs produced have been excessively accumulated.
The power plants in this area have to spend huge sums of money to establish CCPs
storage silos or stockpile fields. Consequently, large amount of high quality CCPs is
accumulated in the north area without any profitable applications, while the short
supply of CCPs in southern China has left a broad market gap in this area (Wei, 2009).
6.3.2 Market limitation
Market limitation is another crucial factor that impedes promoting CCPs utilization.
China’s economy has developed rapidly over the years, however, the rate of economic
growth is quiet different between China’s and eastern area. The western area is an
economically backward area where building material industries are not developed
very well and the needs of such materials in this area are relatively less. In the western
39
interior area, such as Inner Mongolia, Shanxi, Yunnan, and Guizhou, the majority of
CCPs produced from power plants are being directly disposed of as industry wastes
(Li L. , 2008).
In addition, this economically underdeveloped region is usually remote from large
economically developed cities and villages located in China’s eastern region where
CCPs is widely used in construction applications. Based on Wei’s (2009) research, for
low value added fly ash applications, when a demand of building materials exceeds
the range of 50 kilometers in distance the cost of fly ash end products will be much
higher than market price because of the additional transportation cost. There will be
no market demand for CCPs and the use of CCPs will lose its meaning if the haul
distance exceeds the limitation.
Fly ash application in road-building has been made a great contribution to the
increased use of CCPs in China since 1990s, which has led to the use rate of fly ash
increased dramatically from 10% in 1980 to 42% in 1997 (Cong, 2009). However,
currently the number of road-building projects near the power plants is decreasing in
some areas, and the markets for CCPs used in these projects are close to saturation
(Cong, 2009). On the part of a power plant or an area which is near the plant or within
the area, after a road-building project has been done the demand for CCPs produced
from this area will be declined rapidly.
6.4 Regulatory barriers
The widespread use of CCPs in construction material manufacturing is likely to be
inhibited, to a great extent, by poor execution of regulations and weak market
supervision.
6.4.1 Poor execution of regulations
The ban of solid clay bricks is a great boost to the development of CCPs based
construction materials. However, the power of execution of this regulation is very
weak. Motivated by the economic benefits, a number of manufacturers are still
producing solid clay bricks instead of completely closing down the production lines.
Solid bricks are still used widely in many areas, even in provincial capitals where
solid bricks should be radically restricted (Wei, 2009). And the development of CCPs
based construction materials is significantly inhibited by the halfway implementation
of solid clay bricks ban, dealt a blow to the confidence of novel construction material
market.
6.4.2 Weakness in market supervision
Along with the fly ash changes from a waste to a resource, imperfect regulatory
system for CCPs utilization management has led to illegal marketers had a chance to
hoard high quality fly ash for speculation and monopolization of the market (Wei,
2009). The local market price of admixture-grade fly ash will be increased
extraordinarily because of the monopoly of marketing; CCPs producers are, therefore,
concerned that they may be exposed to a high financial risk if their end products
become markedly less competitive because of the high cost of raw materials. Market
monopoly becomes a strong deterrent to those novel construction material producers
40
who are willing to use CCPs.
6.5 Public perception and attitude barriers
Many barriers of CCPs use are from the definition of CCPs as industry wastes and the
general public lack of familiarity and negative perception on CCPs.
6.5.1 Lack of familiarity with CCPs
A number of leaders of government and managers of companies are generally
unfamiliar with CCPs utilization technologies and policies. Many incentive policies
can not be executed very well. Because of the ignorance towards CCPs utilization
policies and unfamiliarity with the potential applications for CCPs materials, the
government authorities and company managers are frequently described as a key
barrier to increased utilization of CCPs (Cong, 2009). It was widely indicated that
many industries has missed opportunities to enjoy the incentive policies to develop
CCPs use applications, which is responsible for the slow commercialization of CCPs
in those industries. Lack of adequate understandings on the advantages of fly ash
based construction materials among the general public and end users is also
influencing the expansion of CCPs market (Ahmaruzzaman, 2010).
6.5.2 Unwillingness to change
As Hitch (2005) writes: "Humans are hesitant to change as it is often uncomfortable.
A definition for change is to ‘undergo a loss or modification’. Sometimes it is very
hard emotionally for human to undergo that loss, or modification, without knowing
what will be put in its place. Acceptance of the unknown may be difficult for some
people. Often moving into the unknown creates risks and some people may not be
willing to take them. The higher the risk, the more difficult the decision to change
becomes" (Hitch, 2005). In many cases, CCPs is regarded as a certain new material,
private companies and engineers are lack of willingness to change or experiment with
this material in their projects. The representative from construction company
interviewed stated that there is no specific engineering standard available in the
company for using CCPs products and using of an unproven material in replacing
older and more established material is considered as an unnecessary risk (Huang L. ,
2010). CCPs industries are generally concerned that they may be exposed to a high
risk of failed projects if the quality of CCPs materials is unguaranteed and the
products later found to cause environmental contamination or engineering structures
damage (EERC, 1999).
6.5.3 Negative perception on CCPs utilization
The perception of CCPs as waste is of itself a barrier to increased use of CCPs (EERC,
1999) and CCPs utilization is hindered where it is regarded as a waste rather than a
product. CCPs are generally mistaken for hazardous wastes because of inadequate
engineering and environmental information available for the public. Recognition of
the nonhazardous properties of these materials is not accepted widely. Users and the
general public lack of familiarity and negative perceptions are likely to hamper the
use of CCPs (EERC, 1999). It is also important to note that lower quality of some
CCPs end products often contribute to the negative perception on CCPs. In China, the
size of construction material manufactures, which use CCPs as raw materials for
41
production, is generally small and often equipped with laggard production lines (Wei,
2009). Some illegal manufacturers even use untreated off-grade fly ash or FBC ash
for construction materials production to reap fabulous profits. It is evident that the
quality of end products produced from these individual workshops is often not
guaranteed, which is likely to lead to failed CCPs demonstration projects and the end
users and general public will lose confidence to CCPs utilization.
42
7 Discussion
Though the government has unveiled multiple preference policies to encourage the
use of CCPs in different applications and other incentives have also helped to promote
the rate of utilization, the demand for CCPs is limited by various factors associated
with characterization, market ability, location, transportation, seasons, etc. Identifying
the barriers to the increased use of CCPs is of fundamental importance to formulate
effective approaches to take in overcoming those obstacles. Based on the results from
the literature survey, questionnaires and interviews, an overview of identified barriers
in terms of different actors involved in CCPs utilization is shown in below (Figure 15).
CCPs Producers
CCPs Users
- Lower rate of high-grade fly ash
- Inconsistent qualities of CCPs
- Difficulties in using FGD
materials
- Market ability
- High cost for transportation
- Unbalanced development of CCPs
market
- Lack of available technical
standards and specifications
- Changes in manufacturing processes
or facilities
- Lack of practical experiences
- Weakness in using techniques
- Large variation in fly ash prices
- Competition from other materials
- High transportation cost
CCPs
Use
Government
General Public
- Poor execution of regulations in
banning solid clay bricks
- Weakness in market supervision
- Insufficient R&D funds
- Lack of familiarity with CCPs
- Unwillingness to change
- Negative perception on CCPs
utilization
Figure 15 Overview of identified barriers
Various barriers are identified from the perspective of different actors, such as
producers, users, the government and general public. High transportation cost of low
unit-value CCPs, competition from available natural materials and spatial variation in
supply-demand of CCPs are recognized as the most critical challenges to the
increased use of CCPs. High transportation cost tends to increase the CCPs price
dramatically, which makes it less competitive in relation to other available materials.
For this reason, some potential CCPs users will prefer to select other materials, rather
than taking CCPs as feed stocks, for their products. The economics of CCPs
utilization are greatly influenced by the cost and availability of competing materials.
As a result, fly ash based novel wall materials would be unable to compete with
traditional solid clay bricks on price. Without explicitly banning of solid clay bricks,
the development of using CCPs in construction materials will be seriously hindered.
43
Spatial variation in level of economic development and power plants distribution has
caused unbalanced supply-demand of CCPs. The utilization of CCPs in the most
developed economic areas of southern China is relatively successful, and often the
demand exceeds supply in this region. While in western and northern China, large
amount of CCPs is still being accumulated without any profitable applications
because of the oversupply of CCPs in markets. Although a large number of researches
have been conducted and some pilot-scale plants have also been built, many of the
projects failed to be commercialized because of the insufficient R&D funds and lower
priority of support from the government. Industries have also responded to the
interviews that standards and specification of CCPs utilization are comparatively
imperfect that have yet to be fully developed to satisfy the demands of practical
applications.
Judging from the nationwide situation, it is obviously that more CCPs are being
produced than the current applications can consume. There is quite a bit room to grow
the current CCPs market in China. The government regulators and CCPs industries
have to step up the effort to strengthen the management of CCPs utilization and find
potential applications that is likely to minimize or overcome the barriers. The
government authorities and industrial association are promising to be the great
enablers for the increased use of CCPs. Following are action recommendations for
industrial organizations and the government with regard to eliminating obstacles on
increased use of CCPs.
7.1 CCPs Eco-Industry Park
The concept of industrial ecology "requires that an industrial system be viewed not in
isolation from its surrounding systems, but in concert with them. It is a system view in
which one seeks to optimize the total materials cycle, from virgin materials, to
finished material, to component, to product, to obsolete product, and to ultimate
disposal. Factors to be optimized include resources, energy, and capital" (Graedel &
Allenby, 1995). As an element of industrial ecology, industrial symbiosis engages
traditionally separate entities in a collective approach to competitive advantage
involving share of resources and physical exchange of materials (Chertow, 2000). A
conceptual CCPs Eco-Industry Park (EIP) derived from the idea of industry symbiosis
could be realized to optimize and maximize the use of CCPs (refer to Figure 16).
Power plant that produces CCPs plays a key role, or "anchor tenant", in this CCPs EIP.
CCPs generated from the power plants are used as feed stocks for various applications
and the produced electricity is supplied to those plants as primary energy source. FGD
gypsum is applied as a raw material by gypsum board manufacturer for producing
gypsum board which is widely used in construction projects. Fly ash serves as a
valuable resource for several applications. Various high value added products, such as
alumina, carbon, magnetite and cenospheres, are extracted from fly ash and FBC ash
in an integrated mineral extraction plant. And the spent fly ash from the process is
used for cement production. Various industries take alumina extracted from the ash as
a valuable engineering raw material. Magnetite recovered is used as dense medium
for coal cleaning by which high rank of coal is obtained for further clean burning in
the power plant. The Selected carbon is used as fuel for combustion and as activated
absorbent agent for power plant waste water treatment. Cenospheres extracted from
the ash is used as fillers in building painting and coating. Fly ash is also synthesized
44
in a zeolite synthesis plant as effective absorbent for waste water treatment. FGD
adsorption agent, which is applied to reduce the SO2 emission from exhausted flue gas,
is synthesized from fly ash. Large quantity of off-grade fly ash is firstly classified and
grinded; the refined high-grade fly ash is used as raw material for producing high
performance cement and the remainder coarse ash is used as an aggregate in concrete.
Collaboration between different industries for mutual economic and environmental
benefits, known as a "win-win situation", can be achieved through the closing of
material and energy flows in EIP (Eklund, 2009).
FGD
Adsorbtion
Agent Synthesis
Gypsum
Board
Manufacture
Zeolite
Synthesis
Fly ash
Zeolite
Fly ash
Coal-fired
Power Plants
Waste water
Waste Water
Treatment Plant
Gypsum board
FGD Gypsum
Fly ash
FGD Adsorbent
Off-grade Fly Ash
Classification &
Grinding Plant
Coarse ash
FGD Gypsum
Fly ash
FBC ash
High-grade coal
High-grade ash
Electricity
Activated carbon
Electricity
Carbon fuel
Coal
Cleaning
Concrete
Products
Integrated Mineral
Extraction Process
Construction
Industries
Cement
Plant
Magnetite
Cement
Dense medium
Carbon
Cement
Alumina
Alumina
Spent ash
Mineral fillers
Alumina
Industries
Concrete
Industries
Cenospheres
Figure 16 Conceptual CCPs Eco-Industrial Park
45
Coating
Painting
Factory
Some marketing and economic barriers could be overcome through collaboration
between the different actors within the CCPs EIP. As one of the most important
economic barriers, high cost of transportation of low unit-value CCPs can be
minimized by the geographic proximity of synergistic industries in the CCPs EIP.
CCPs storage can be optimized to offer maximum capacity with minimum footprint to
allow different users to purchase and stockpile of sufficient CCPs over seasons when
they are least expensive to when they are most in demand (Smith, 2005). The high
fluctuation of fly ash price can also be inhibited by accurate forecasting of seasonal
demand and integration of ash marketing with appropriate coal procurement and
handling functions within the CCPs EIP (Smith, 2005).
As has already mentioned numerous attempts of extracting high value minerals from
CCPs were failed to be commercialized not for technical reasons, but for economic
reasons. One recovery process may not be economically feasible for each of mineral
product individually (Groppo & Honaker, 2009). For this reason, Groppo and
Honaker (2009) from the University of Kentucky have proposed a process that
recovers several products, such as magnetite, aggregate material, carbon fuel,
pozzolan for cement replacement, cenospheres and mineral-grade filler,
simultaneously has been shown to be economically justified and technically viable.
Using spent fly ash from the alumina synthesis process as raw material for cement
production is also shown to be technically viable (Wang & Wu, 2004). This integrated
mineral extraction process can play a significant important role in realizing the
conceptual CCPs EIP. A number of practices on zeolite synthesized from fly ash have
been attempted and this process is anticipated to have a large potential to be
industrialized. The process produces FGD adsorption agent from fly ash has already
been successfully commercialized in Japan (Kikuchi, 1999). However, researches on
this area have not been given as much attention in China.
7.2 Recommendations for industry initiatives
To satisfy practical application of CCPs in different domains, completing standards
and specification need to be further developed. Some potential CCPs users are not
willing to take unnecessary risks in using CCPs because of the lack of perfect
technical standards. Continuing development of current standards and specification of
fly ash used for cement and concrete should be expedited by industrial organizations
and universities collaborative technology-based researches (EERC, 1999). Additional
engineering specifications are needed for high-volume and high value-added fly ash
applications. Industrial standards institute should also shine light on changes in fly ash
classifications and wider ranges on LOI, moisture, alkali, and fineness to promote the
use of fly ash in broader areas.
In many cases, the market for fly ash used in cement and concrete applications is
tending to be saturated based on current replacing rate. For this reason, developing
high volume fly ash concrete technology (HVFAC) and increasing the amount of
CCPs used in the present cement and concrete applications is likely to be a foremost
measure for increased use of CCPs. Among the most common applications of CCPs is
the substitution of fly ash for Portland cement in concrete or the use of fly ash as a
mineral additive in concrete (ACAA, 2008). In 1997, about 46 million tonnes fly ash
was beneficially used in China, of which 27.6% was used in concrete industries.
However, the use of fly ash in cement and concrete is limited by the maximum
46
blended rate, normally is about 30% (Wang & Wu, 2004). If the replacement rate
could be increased to technically viable level of 50%, which means larger amount of
fly ash can be utilized beneficially in concrete industries.
As has been shown, many barriers to increased use of CCPs are from the general
public and end users who may have negative perception on CCPs. For this reason,
public education on benefits and methods of CCPs utilization is of significant
importance. Industry association with assistances from the government should support
for publicizing annual survey of CCP production, utilization, and GHG reductions by
using CCPs. Educational programs can be implemented with engineering and science
departments at universities, government’s propaganda and communication media.
Action on promoting the education on the value of life-cycle analysis of CCPs
applications can be initiated through the collaboration with private owners and groups
(EERC, 1999). The government should sponsor high-volume and high value added
CCPs utilization commercial-scale demonstration projects and valuate the viability
and environmental acceptability of these applications. The demonstration project can
shine light on road-building, bridge, dam, and industrial symbiosis networks.
The quality problems in relation to CCPs end products have also led to some negative
perceptions on CCPs. The end users and general public are generally concerned that
they may be exposed to a high risk of failed projects if the quality of CCPs materials
is unguaranteed. To improve the quality of CCPs products, actions that can be taken
by CCPs industries include enhancement of quality control, operator training and
laboratory analysis, modification of equipments and operating methods, and
investment in advanced facilities. CCPs industry association should increase research
and data assessment to track engineering and environmental performance of CCPs
projects and report the value of CCPs uses versus virgin materials. Quality control
department should enhance source certification of CCPs, development and
standardization of sampling and analysis protocol, and support for development of
other quality control instruments (EERC, 1999).
7.3 Recommendations for government initiatives
Governmental incentives should be targeted to achieve technical innovation and to
extend CCPs applications in other areas, e.g. high-value added fly ash applications,
outside of the cement and concrete industries. Monetary incentives such as funding
preferences should be offered by the government to encourage the research and
development of such high-tech applications and to promote the transformation from
patent technologies into commercial productivity. A number of researches on high
value added applications, such as waste water treatment, anti-corrosion materials,
glass ceramics and reflective materials, have been carried out in China (Wang & Wu,
2004). Several researches have achieved abundant accomplishment. However,
because of the lack of research funds and strong support from the government, a
number of projects reported work to date are still of laboratory- scale or failed to
commercialization. Making policies to encourage the innovative CCPs use
technologies and streamlining approval for CCPs beneficially utilization projects are
required for the government.
Policy and economic incentives, including tax exemption, "green" subsidies,
regulatory preferences and low interest loan, should be offered by the government to
47
prompt the use of CCPs that are long-term interest of the public (EERC, 1999).
Eliminating regulatory barriers are also required for industries improvements that
increase the commercial viability of CCPs. And those preferential policies should be
well-established as long-range policies instead of annually policy determination. For
government bidding construction projects, contractors or companies that use CCPs
with enhanced quality and durability shall have the priority to receive bid preferences
from the government. Newly built or rebuilt or extended coal-fired power plants
without any ancillary CCPs utilization projects simultaneously operated should not
get approval from the government. Monetary incentives for creating optimized
logistical solutions to increased CCPs beneficial use should also be provided.
The widespread use of novel "green" wall materials, such as fly ash hollow blocks
and aerated concrete, can be realized only when the ban of using solid clay bricks is
mandatory implemented. For this reason, the government should strengthen the
execution of regulations to speed up moves to ban the production and utilization of
solid clay bricks in all municipalities, especially cities in coastal areas where capita
farmland is scarce.
7.4 Actors’ role in overcoming the barriers to increased use of CCPs
Various barriers were identified from the perspectives of different actors involved in
CCPs production and utilization. Corresponding solutions can be formulated by the
initiatives from the government and industries. Actors’ role in overcoming and
minimizing the barriers to increased use of CCPs is summarized in Table 8 as shown
in below.
Table 8 Actors' role in overcoming barriers to CCPs uses
Barriers
Solutions
Actors
Lower rate of high-grade fly
ash
Developing ash handling
system
CCPs producer
Inconsistent qualities of
CCPs
Applying classification and
grinding technology
CCPs producer
Difficulties in using FGD
materials
Developing mineral extraction
process
CCPs Eco-Industry Park, high
volume fly ash concrete
technology
Market limitation
High cost for transportation
CCPs Eco-Industry Park
Spatial variation in supplydemand
CCPs Eco-Industry Park
Lack of perfect technical
standards
Lack of practical experiences
Weakness in using
techniques
Developing CCPs use technical
standards and specification
Employee training and
education
Applying advanced
technologies, enhancing end
products quality control
48
CCPs user
Government, CCPs
producer and CCPs user
Government, CCPs
producer and CCPs user
Government, CCPs
producer and CCPs user
Government and industrial
institutes
CCPs user
CCPs user
Competition from other
materials
Strengthening execution of
solid clay bricks, providing
monetary incentives and policy
support
Government
Large variation in high grade
fly ash price
Tightening market supervision
Government
Insufficient R&D funds
Providing sufficient funds
Government
Unwillingness to change and
negative perception on CCPs
Public education
Government, general
public
Lack of familiarity with
CCPs
Demonstration projects
CCPs users
49
8 Conclusions
Coal burning combined with flue gas cleaning system generates large quantity of coal
combustion products, which has caused significant environmental and economic
burden to the economy, ecology and society. Growing concern for scarce in useful
land, shortage of natural sources and negative impacts to the environment has led to
significant interests in utilization of CCPs. China as the world’s largest CCPs
producer, influenced greatly by the increased environmental and economic burden
resulting from the disposed and stockpiled CCPs.
Incentives
Savings of natural resources, energy, emissions of pollutants, GHG emissions and
useful land were found as the major incentives for CCPs utilization. Increased use of
CCPs, which can be an environmental and economic palliative, is of significant
importance for achieving sustainable development.
Utilization of CCPs
The value of CCPs has been well established by researches and industrialized
practices carried out all over the world. As valuable engineering materials, these
products have led to the emerging of considerable utilization technologies for the
purpose of saving costs while protecting the environment. Because of the substantial
amounts of CCPs generated - most of which is fly ash - the focus of CCPs utilization
has primarily been on high volume applications, generally as pozzolan cement
replacement in civil engineering and construction areas. Such efforts have so far met
with much success in China as well as other developed countries. CCPs utilization
rate in different countries varies widely from 13% to 97%. The utilization rate of
CCPs in the Europe Union of EU 15 has reached to a high level of 89% in 2007, and
Japan used almost all of the coal ash (97%) produced in 2006. In China, from the late
1970s, the utilization rate has been hanging around at 20% for many years. Along
with the increasing interested in the value of CCPs and the reinforced policies, the use
rate grew rapidly and reached up to 58% in 2000. Worldwide, a significant proportion
of CCPs from the main producers, e.g. China, the United States and India, however, is
still being disposed off, resulting in a low-level of overall utilization of these coal
combustion products. Current efforts to increase use of CCPs are not adequate as is
obvious from the low level of utilization, e.g. low use rate and low value added. In
many cases, the markets for CCPs as an ingredient in cementitious applications are
tending to be saturated. Therefore, alternatives for CCPs utilization, such as mineral
extraction, zeolite synthesis, fly ash FGD absorbent, etc., other than traditional cement
and construction applications are needed to be developed and industrialized. Some of
those high-value added applications have been commercialized in other developed
countries while few relevant researches have been done in China. Further work in
developing alternative applications of CCPs is urgently needed.
Barriers to increased use of CCPs
The role of policy makers in China over the past years has added more weight to the
issue of promoting CCPs utilization. However, despite the large-scale and positive
uses, more CCPs are being produced than the current applications can consume
because of numerous limitations and various barriers existed in CCPs industries and
domestic markets. Identification of barriers to CCPs uses is one of the foremost steps
in developing CCPs utilization. Economic barriers to increased use of CCPs are
51
widely accepted as the most important elements among all other factors that affecting
CCPs uses. The high cost of transportation of low unit-value CCPs, competition from
available natural materials and spatial variation in supply-demand poses three of the
most important barriers to the increased use of CCPs in China. CCPs markets in
northern areas and economic backward regions are limited, to a large degree, by high
transportation cost and oversupply of fly ash especially in winter months. On the other
hand, the short supply of fly ash in southern area and the most economic developed
costal regions has led to an unreasonable high CCPs price, which is also likely to
encourage illegal speculations and inhibit the spread of different CCPs applications.
More regulatory measures from the government are required for stabilizing the CCPs
market. A ban of solid clay bricks was also found to be a very powerful measure to
stimulate the development of other by-product based wall materials while saving
useful land and protecting the environment. However, this strong policy support from
the government has not been well executed, which seriously limited new initiatives
and market potential.
Corresponding solutions
There should be a greater emphasis on eliminating and overcoming those barriers to
the increased use of CCPs. Industrial organizations with assistances from the
government have shown to be of fundamental importance for formulating approaches
to take in overcoming the barriers. A conceptual model of CCPs Eco-Industry Park
was proposed as a potential effective solution. Some marketing and economic barriers,
such as transportation cost and unbalanced supply-demand, could be overcome
through share of information and resources between different actors. Mutual
economic and environmental benefits can be achieved through the collaboration
between different industries in the CCPs EIP. It has been shown that a number of high
value-added CCPs commercial applications have been attempted for several times,
but few of them succeed mainly due to economic reasons. An integrated process in
CCPs EIP for simultaneously extracting different high value materials from CCPs was
shown to be one of the potential feasible options. The ban of solid clay bricks as
another large propellant for increasing CCPs use in China aims at encouraging the use
of novel construction materials produced from industrial by-products. However, the
widespread use of those novel construction materials can be realized only when the
ban of using solid clay bricks is mandatory executed. For this reason, strengthened
execution of regulations to speed up moves to ban the production and utilization of
solid clay bricks is urgently needed. The government should enhance the power of
execution and provide additional economic funds and preferences to encourage the
development of novel CCPs based construction materials in place of solid clay bricks.
In conclusion, there is a need for concerted effort to promote the "technically sound",
"environmentally safe", and "economically justified" utilization of CCPs. A number of
researches and projects on high levels utilization of CCPs have been carried out in
China, however, the majority of which have not yet been commercialized. It should be
emphasized that transforming such laboratory- or pilot-scale technologies into
industrial productivity is of the highest priority for increased use of CCPs.
52
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58
Appendix
Questionnaire for CCPs production and utilization
1. Name of Power Plant:
MW
2. Capacity of the Power Plant:
tonnes
3. Annual CCPs production:
4. Applications of CCPs:
Identified (mark: ×)
Concrete / Concrete Products / Grout
□
Structural Fills / Embankments
□
Mining Applications
□
Gypsum Panel Products
□
Blended Cement/ Raw Feed for Clinker
□
Waste Stabilization/Solidification
□
Burning-free Bricks
□
Road Base/Sub-base
□
Soil Modification/Stabilization
□
Aggregate
□
Grinding / Sorting
□
Agriculture
□
Mineral extraction
□
Miscellaneous / Other (if any)
□
5. CCPs qualities:
(e.g. comply with which industrial standards)
6. CCPs price:
¥/tonne
7. Transport charge for CCPs:
¥/tonne
8. Driving forces for CCPs utilization:
Identify
Landfill space release
□
□
Financial rewards
□
□
Reduction of hazardous exposure to flying ash
□
□
Ground water contaminant prevention
□
□
Investment savings
□
□
Other driving forces (if any)
Rank*
□
59
* Identified (×); Rank (High-3; Medium-2; Low-1)
9. Barriers to CCPs utilization:
Identify
Unstable qualities of CCPs
□
□
Low added-value
□
□
Market limitation
□
□
High transportation charge
□
□
Business fraud
□
□
Weakness in utilization technologies
□
□
Imperfect legal system for CCPs commercial utilization
□
□
Imperfect standard system for CCPs industrial application
□
□
Other barriers (if any)
Rank*
□
* Identified (×); Rank (High-3; Medium-2; Low-1)
10. Is there any preference policy applied to the use of CCPs?
60
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