COAL-FIRED GENERATION: Proven and Developing Technologies

COAL-FIRED GENERATION: Proven and Developing Technologies
Proven and Developing Technologies
Brenda Buchan
Christi Cao
Office of Market Monitoring and Strategic Analysis
Florida Public Service Commission
December 2004
Proven and Developing Technologies
The topic of coal-fired generation is appearing more frequently in the media and
particularly within energy publications. This is a change from the past decade when most of the
energy industry’s attention was on natural gas and the inexpensive, clean, and efficient combined
cycle electric generators that burn natural gas. The returning interest to coal-fired generation is
based on several factors, including:
z U.S. Department of Energy (DOE) funding of new technologies to burn coal more
z High prices for natural gas as compared to coal,
z Increase in demand worldwide for natural gas,
z Large supply of coal in the United States, and
z Government instability in some countries providing natural gas and oil resources.
With these events occurring simultaneously, it is not surprising that the energy industry in the
United States is once again taking a close look at coal-fired power plants.
In this paper we discuss various technologies that have been developed over the past
couple of decades to produce coal-fired energy with fewer air emissions and the clean coal
technologies that are under development. We also examine counter-balancing issues behind
coal-fired generation. Economic drivers motivating utilities and governments to invest in coal
must be balanced with the environmental concerns associated with coal-burning emissions. We
also discuss the investment in and use of clean coal technologies in Florida.
The DOE defines Clean Coal Technology (CCT) in general terms as, “technology that
when implemented improves the environmental performance and efficiency as compared to the
current state-of-the-art in coal-fired power plants.”1 CCT describes a new generation of energy
processes that sharply reduce air emissions and other pollutants compared to older coal-burning
systems. CCT also involves developing ways to reduce greenhouse gas emissions from coal
plants by boosting the efficiency at which they convert coal to electricity or other energy forms.
Once a technology has been proven, it is no longer classified as a CCT, and is considered to be a
best available control technology (BACT) or best available retrofit technology (BART), which is
to be used commercially.
NARUC Web site. <>
Coal Technologies
CCT research has led to new coal-fired generation systems as well as new technologies
that can be used to update existing coal-fired generation plants to reduce emissions. The primary
focus of the United States’ clean coal efforts is to develop innovative designs that can be used to
retrofit the roughly 320,000 megawatts of existing base load coal-fired generating capacity in the
United States. The nation relies on this generating capacity for over 50 percent of its electricity.
Most advances in coal technologies have occurred in two main areas:
z pollution control systems to reduce sulfur dioxide (SO2) and nitrogen oxide (NOx)
emissions; and
z super-clean, more efficient advanced power generation systems for new coal-based
power plants.
Pollution Control Systems
The most common post-combustion SO2 control technology is flue gas desulfurization,
also known as scrubbing. Modifications to boilers or particulate emission control devices are not
necessary with flue gas desulfurization technology, making this technology particularly useful on
existing boilers. The process entails removing sulfur from flue gas with the use of a sorbent,
usually lime or limestone. Scrubbers can remove up to 90 percent of the SO2 emitted at a typical
power plant. Another way to control SO2 is through dry sorbent injection (DSI). In this
technology, a reactive calcium- or sodium-based sorbent is injected into the upper part of the
furnace to react directly with the SO2 in the flue gas. Controlling SO2 can also be accomplished
by converting it into sulfuric acid, or SO3, by passing the flue gas over a catalyst bed.
Controlling NOx emissions can be accomplished by using many different technologies.
NOx reduction technologies that modify combustion include low-NOx burners (which are on
about 75 percent of coal-based power plants and can remove 37 to 68 percent of NOx emissions),
overfire air, reburning (which can reduce NOx emissions by 50 to 67 percent), and flue gas
recirculation. Post-combustion technologies that reduce NOx include selective catalytic
reduction (which can reduce NOx emissions by 80 to 90 percent or more and is on order or under
construction on 30 percent of U.S. coal-fired generators), selective noncatalytic reduction (which
can reduce NOx emissions by 30 to 50 percent), and hybrid processes that combine the previous
two technologies.
Advanced Power Generation Systems
There are three major areas of technology that are considered to be advanced electric
power generators. Fluidized-bed combustion, integrated gasification combined cycle (IGCC),
and advanced combustion/heat engines are technologies that have high thermal efficiency, low
pollutant emissions, reduced carbon dioxide (CO2) emissions, few solid waste problems, and
enhanced economics.2 Fluidized-bed combustion allows for greater than 90 percent SO2
removal and reduces the amount of thermal NOx formed because plants operate at a much lower
temperature than conventional boilers. A circulating fluidized-bed combustion plant reduces
Topical Report Number 18: Environmental Benefits of Clean Coal Technologies. U.S. Department of Energy.
April 2001. <>
most of the pollutants inside the furnace as the coal burns. Crushed limestone, when added to
the coal as it enters the combustor, captures 90 percent of sulfur pollutants. Fluidized-bed
combustion allows for a “slow burn” that reduces the formation of NOx. IGCC systems involve
the gasification of coal, cleaning the gas, and combusting it in a gas turbine generator to produce
electricity. Residual heat in the exhaust gas from the gas turbine is recovered in a heat recovery
boiler as steam. Additional electricity can be produced using the steam in a steam turbine
generator. IGCC systems are among the cleanest and most efficient of the emerging coal
technologies. Advanced combustion/heat engines include slagging combustors and coal-fired
diesel engines. Slagging combustors are designed to remove coal ash as molten slag in the
combustor rather than the furnace. Coal-fired diesel engines use either coal-oil or coal-water
slurry fuel to drive an electric generation system.3
Coal Technology Categories
According to the National Mining Association (NMA), coal technologies can be
categorized into three groups:
z Combustion involves “combining coal with other substances in the boiler to improve
efficiency and remove impurities.” During basic fluidized-bed combustion, for
example, limestone or dolomite is added during combustion to reduce SO2.
z Post-combustion technologies use scrubbers, chemical cleaning or precipitators to
remove sulfur and other impurities from emissions. Flue gas desulfurization is an
example of this technology category and uses scrubbers.
z Conversion uses heat and pressure to convert coal into a gas or liquid that can be
further refined and used cleanly. IGCC is an example of conversion coal technology.
Federal Coal Research
The federal government has been very active in clean coal technology research over the
past few decades. The DOE’s Clean Coal Technology Program (CCTP) began in 1986.
Research focused on commercializing processes that reduced SO2 and NOx emissions, and that
were more efficient than conventional pulverized coal boilers. From 1986 through 1993 the
government and industry selected, funded and conducted 38 technology demonstrations.
According to the DOE, clean coal technology research over the past twenty years resulted in
more than 20 new, lower-cost, more efficient and environmentally compatible technologies for
electric utilities and other industries. Some of the demonstrations, such as JEA’s Large-Scale
Circulating Fluidized-Bed Combustion Demonstration Project in Florida (which will be
discussed more later in the paper), are still ongoing. A significant feature of the CCTP is that the
DOE and participant companies share the costs of each demonstration, with the DOE funding up
to half of the project costs in some cases. This funding assistance provides a valuable incentive
to a company to participate in a demonstration project.
The following section discusses four federal coal technology programs. The first two
focus on pollution control, the third deals with advanced power generation systems, and the
fourth is comprised of projects that fit into either category -- pollution control systems or
advanced power generation systems.
Recent Federal Programs
Clean Coal Power Initiative (CCPI)
The new Clean Coal Power Initiative (CCPI) is an industry/government partnership that
is intended to build on the successes of the CCTP by perfecting technologies to reduce mercury
and carbon dioxide emissions and increase fuel efficiencies. Future coal research is expected to
focus on developing coal-based hydrogen fuels, that when coupled with sequestration will allow
for the use of coal with zero emissions.4
On January 15, 2003, the DOE announced the first eight projects selected for the initial
phase of the CCPI. The eight projects were expected to be awarded approximately $317 million
by the DOE. Projects focused on reductions in mercury, SO2 and NOx, on increasing efficiency
and reducing greenhouse gas emissions, and on using coal waste. Two of the projects have been
withdrawn by participants since the announcement.
Of the six remaining projects in the initial phase of the CCPI, one is focused on
complying with the Clear Skies Initiative, three are expected to reduce greenhouse gasses, and
two are aimed at reducing air pollution through advanced gasification and combustion systems
designed to extract the energy potential of waste coal piles as a new fuel source.5 An example of
this type project is the $25.6 million Great River Energy Project, which will test the Lignite Fuel
Enhancement System. The DOE announced in June 2004 the testing of the system, “a new
process that could dramatically reduce air emissions from certain coal-based power plants while
boosting overall generating capacity.” The site for the project will be Great River Energy’s Coal
Creek Station in Underwood, North Dakota. The project’s new technology will use waste heat to
dry nearly a quarter of the moisture in the high-moisture lignite coal before it enters the power
plant boiler. Researchers expect that drying the lignite first will result in greater plant efficiency
and lower emissions of SO2, mercury, CO2, NOx, and particulates.6 Following successful
demonstration of the prototype, Great River Energy will perform full-scale, long-term
operational testing needed for full power operation of one of the 546 MW units at Coal Creek
On October 22, 2004, the DOE awarded a new $235 million grant to a consortium
consisting of Southern Power Company, Orlando Utilities Commission and KBR, a subsidiary of
Halliburton. The federal money, awarded under the CCPI, covers approximately 40 percent of
the $557 million project, which is to be built at the Stanton power plant in Orlando, Florida
operated by the Orlando Utilities Commission. The Consortium will build a 285-megawatt
gasified coal power plant featuring a technology developed by the Southern Company called
“transport gasifier.” This technology is unique among coal gasification concepts in that it is
cost-effective when burning low-rank coal and coal with high moisture or ash content. The
transport gasifier is capable of both air- and oxygen-blown operation. This flexibility would
Sequestration is a family of methods for capturing and permanently isolating gasses that otherwise could contribute
to global climate change, during the burning of coal based fuel.
DOE NETL Techline. Secretary of Energy Announces First Projects to Meet President’s Commitment to New
Clean Coal Technologies. January 15, 2003.
DOE Techline. More Electricity, Lower Emissions from Lignite Plants Are Goals of New Clean Coal Project.
June 25, 2004. <>
allow it to readily adapt to other applications beyond power generation, including chemical
production and possible future carbon dioxide reduction requirements. According to the DOE,
this flexibility supports its goal of fostering the development and demonstration of a zeroemissions coal plant that can also provide feedstock chemicals. Teamed with carbon
sequestration technology, this plant could allow continued, long-term use of coal to generate
FutureGen is another project currently being developed by DOE. FutureGen is an
initiative to build the world’s first integrated sequestration and hydrogen production research
power plant. The $1 billion dollar project is intended to create the world’s first zero-emissions
fossil fuel plant. The DOE envisions the plant to produce 275 MW of electricity output at an
undetermined site in the U.S.7 When operational, the prototype will be the cleanest fossil fuel
fired power plant in the world. While the U.S. is taking the lead on this project, other countries
will be invited to participate in the demonstration project through the Carbon Sequestration
Leadership Forum.
The prototype plant will establish the technical and economic feasibility of producing
electricity and hydrogen from coal, while capturing and sequestering the CO2 generated in the
process. The initiative will be a government/industry partnership to pursue an innovative
“showcase” project focused on the design, construction and operation of a technically cuttingedge power plant that is intended to eliminate environmental concerns associated with coal
utilization. The project will use coal gasification technology integrated with combined cycle
electricity generation and the sequestration of carbon dioxide emissions. It will be supported by
the ongoing coal research program, which will also be the principal source of technology for the
The project will require 10 years to complete and will be led by an industrial consortium
representing the coal and power industries, with the project results being shared among all the
participants, and industry as a whole. Numerous states are currently competing for this project
and the industrial consortium has until the end of 2004 to choose the location.
Hybrid Technologies
The DOE is also researching advanced combustion technology that involves new types of
hybrid technologies. Hybrid technologies are typically coal-based systems that combine coal
combustion and coal gasification into a highly efficient, environmentally clean power generating
technology. In a hybrid system, coal is partially gasified in a pressurized gasifier. This produces
a fuel gas that can be combusted in a gas turbine. Left behind in the gasifier is a combustible
char that can be burned in a fluidized bed combustor or advanced high temperature furnace to
produce steam to drive a steam-turbine power cycle and to heat combustion air for the gas
turbine. Heat from the gas turbine exhaust also can be recovered to produce steam for the steam
DOE Office of Fossil Energy Web site. FutureGen International Prospectus. June 14, 2004.
Hybrid technologies are central to the DOE’s Vision 21 Program, which is currently
under development. The concept envisions a virtually pollution-free energy plant. The Vision
21 plant would produce multiple products, perhaps electricity in combination with liquid fuels
and chemicals or hydrogen or industrial process heat. It would not be restricted to a single fuel
type, instead, it would process a wide variety of fuels such as coal, natural gas, biomass,
petroleum coke (from oil refineries), and municipal waste. It would generate electricity at
unprecedented efficiencies, and coupled with carbon sequestration technologies, it would emit
few, if any, greenhouse gases into the atmosphere. Vision 21 builds on a portfolio of
technologies already being developed, including low-polluting combustion, gasification, high
efficiency furnaces and heat exchangers, advanced gas turbines, fuel cells, and fuel synthesis,
and adds other critical technologies and system integration techniques.
2001 Power Plant Improvement Initiative Example
In October 2001, the DOE announced the selection of eight new projects using clean coal
technologies to improve the reliability and environmental performance of coal-fired generation
plants. Two of the projects have since been withdrawn by their industrial sponsors. The projects
were funded under the Power Plant Improvement Initiative (PPII), which was approved by
Congress in response to a series of blackouts and brownouts that occurred in 1999 and 2000.
The projects focused on lower cost technologies for reducing pollutants, improving the
performance and reliability of power plants, and the problem of waste handling from coalburning plants.8
One example of a project funded through the DOE’s PPII is at the Birchwood Power
Facility in King George, VA (to see information about the other five selected projects, see
appendix A). The project is testing a new recycling technology that would turn its coal
combustion ash into a lightweight aggregate that can be used to make a variety of construction
materials from masonry blocks to concrete to asphalt paving material. In the past, Mirant has
had to pay to annually dump 100,000 tons of ash in the municipal landfill. This project pursues
new types of recycling technology for coal-burning power plants. The ash is produced as a byproduct of the power plant’s “spray dryer” scrubber system. Scrubbers are used on many coalfired power plants in the U.S. to reduce sulfur pollutants, but currently less than 20 percent of the
28 million tons of residue produced annually by these scrubbers is reused and most of that is
from wet scrubbers. The Universal Aggregates process is designed to recycle the by-products
from either wet or dry scrubbers, thereby lowering the costs of waste disposal while reducing the
environmental drawbacks of landfilling. The Birchwood Power Facility project will be the final
step to verify that the aggregate manufacturing process and equipment is ready for future
commercial use. According to DOE projections, the plant began operations in January 2004 and
the project will be complete in February 2005.9
DOE Office of Fossil Energy Web site. The 2001 Power Plant Improvement Initiative. August 15, 2003.
Power Plant Improvement Initiative 2003 Fact Sheet.
As previously mentioned, the United States has a contradictory relationship with coal.
On one hand the price and availability of coal is attractive in motivating utilities and
governments to investment in coal. On the other hand, the environmental concerns associated
with coal-burning emissions are expensive in terms of health impact and clean up. The current
economics of building coal-fired generators, including the cost of the fuel source coal versus
natural gas, the length of time to build the generator, and the cost components of construction
merits discussion.
According to a recent trade journal interest in new U.S. coal plants is strong, with five
new plants under construction and progress on proposed plants being reported every week10. In
addition, there are 94 coal-fired electric power plants currently in the planning stages in 36
states11. However, the same article says that experts in the energy industry predict that no more
than half of these proposed plants will be built.
A Balanced Fuel Mix
According to Standard & Poor’s, the current interest in coal is not because the nation
needs additional capacity, in fact the U.S. has a generating capacity surplus that is beyond the 15
to 17 percent capacity reserve margin desired by most utilities12. Instead, the interest in coal is
caused by the desire to have a more balanced generation fuel mix. Most of the generation plants
being built are natural gas fired and, given the increase in demand for natural gas in the
international market, this has resulted in an overall increase in the cost of electricity and created
price volatility. In contrast, U.S. coal prices have remained stable and inexpensive relative to
natural gas prices. Considered the Saudi Arabia of coal, U.S. coal reserves are estimated by the
U.S. Geological Survey to be at 230 billion tons, which would last 230 years at the current
consumption rates.
The principal market for coal is the electricity generation sector, accounting for
approximately 90 percent of domestic sales. Although coal has been and continues to be the
primary fuel for electricity generation in the U.S., electricity producers are increasingly turning
to natural gas as the fuel source for new generating capacity. The U.S. electricity producers have
turned to natural gas because the combined cycle natural gas burning generators can be built
quickly and emission levels are relatively low. In contrast, recent efforts to improve air
emissions require many older coal-fired plants to be retrofitted with scrubbers and low NOx
burner technology and/or switch to lower sulfur coals to allow them to remain in operation and to
maintain their position in the dispatch order.
The Cost of Coal
Historically, the price differential between coal and natural gas has been critical to
determining whether new coal projects are built. According to Standard and Poor’s, in the past
four years the cost of natural gas has roughly tripled from $2 per one million British thermal
Energy Daily. King Coal Comes Roaring Back. By George Lobsenz. April 26, 2004.
Christian Science Monitor. America’s New Coal Rush. By Mark Clayton. March 2, 2004.
Standard and Poor’s. King Coal on the Comeback Trail. By Swami Venkataraman and Nancy Hwang. February
26, 2004.
units (mmbtu) of heat generated to over $6 mmbtu. By contrast, coal costs less than $2 mmbtu.
Standard and Poor’s studies have shown that when natural gas prices stay above $3.50 mmbtu,
coal plants are a competitive alternative to natural gas fired plants. The index price of natural
gas at Henry Hub (South Louisiana which supplies Florida) for October 26, 2004, according to
Platts Gas Daily was $7.76 mmbtu. If natural gas prices above $3.50 mmbtu is the threshold for
deciding to build coal burning power plants, a natural gas price of $7.76 mmbtu would provide a
strong incentive to build coal-fired generation plants.
Standard and Poor’s expects that any new coal plants will be built by either regulated
utilities, public power entities, or cooperatives. The key motivators for them are: (1) the need to
acquire a long-term, reliable, low-cost source of base load generation, and (2) the returns being
assured by the inclusion of the plant in the rate base. Coal plants are attractive because they have
low variable costs of production, meaning that the fuel needed to power the plant (coal) is
inexpensive and readily available. However, because coal plants take approximately two years
to permit and 36 to 42 months for construction, building coal plants is not attractive to merchant
companies that wish to enter the market rapidly.
According to a recent news article, construction costs for building a state of the art coalfired power plant are expected to be about $1,200 to $1,400 per kW, compared with $1,000 per
kW to build a conventional coal fired power plant13. In contrast, a highly efficient natural gas
combined-cycle plant can be built for $500 per kW. Thus, while coal is currently cheaper than
natural gas and is much more plentiful in the U.S, when utilities are considering whether to build
new generation those considerations must be weighed against the higher cost and construction
time of building a coal-fired generator.
One of the draw-backs to investing in coal-fired power plants is the risk of new and more
stringent laws on carbon dioxide and mercury emissions, requiring additional capital investment.
In many states, the environmental issues inherent in building a coal fired plant are as important a
consideration in deciding to build as is the economic advantage to using coal over natural gas.
When Clean Air Laws are being changed, the risks associated with building coal-fired power
plants are greater because the capital expenditures needed to meet the new environmental
standards are unknown. Once new Clean Air Laws are passed and the environmental standards
are known, the risk of installing new technology coal fired power plants will decrease.
Environmental concerns associated with coal-fired generators and the steps the U.S. has
taken to reduce hazardous air emissions are significant issues when deciding what type of
generating plant to build. The motivation for the energy industry to develop clean use of coal is
the environmental challenge presented by coal-fired power plants, a primary concern being the
impact of acid rain on forests and watersheds. Additional concerns are the potential health
impacts of trace emissions of mercury, the effects of microscopic particles on people with
respiratory problems, and the potential global climate-altering impact of greenhouse gases.
Chemical & Engineering News. Getting to Clean Coal. By Jeff Johnson. C&EN Washington. February 23, 2004.
Coal burning power plants produce more airborne mercury and greenhouse gases than
any other single fuel source. Coal-fired power plants are responsible for 60 percent of U.S. SO2
emissions, 33 percent of U.S. mercury emissions, 25 percent of U.S. NOx emissions, and more
than 33 percent of the nation’s CO2 air emissions14. The two pollutants that generate that largest
volume of pollution are SO2 and NOx. SO2 is one of six air pollutants identified by the federal
Clean Air Act. The largest emitters of SO2 are coal-based electricity generators. The U.S.
concern with damage caused by acid rain prompted the inclusion of SO2 as a major pollutant.
NOx is commonly known as urban smog and is a precursor to the formation of ozone. Cars,
other transportation vehicles and coal-based power plants are the primary emitters of NOx.
Environmental Changes
The U.S. Legislature began addressing the concerns of coal-fired pollution in 1970. The
original 1970 Clean Air Act established national standards to limit levels of such air pollutants
as SO2, NOx, carbon monoxide, ozone, lead, and particulate matter.15 The Act, and its
amendments in 1977, set into motion both public and private sector efforts to develop new
environmental control technologies, including new flue gas desulfurization units (scrubbers) that
remove sulfur from the exhaust gases of coal-fired power plants. Federal research projects
helped improve the reliability of the early scrubbers and the DOE’s Clean Coal Technology
Program (CCTP) in the 1980’s demonstrated new, lower cost and more effective scrubber
The 1990 Clean Air Act Amendments contained sweeping revisions to the original Act
requiring further reductions in power plant emissions, especially sulfur- and nitrogen-based
pollutants that can contribute to acid rain. The amendments put into place a new market-based
“cap-and-trade” system that required power plants either to reduce emissions or acquire
allowances from others to achieve compliance. To meet the more stringent NOx standards, many
power plants turned to new low-NOx burners that had been pioneered in the CCTP.
In 2002, the Clear Skies Initiative (Clear Skies) was proposed by DOE to reduce three
pollutants emitted from coal-fired power plants. While the U.S. Congress has not amended the
Clean Air Act to include Clear Skies, the DOE is encouraging utilities to pursue these goals.
z SO2 emissions would be cut by 73 percent, from current emissions of 11 million tons to a
cap of 4.5 million tons in 2010, and 3 million tons in 2018.
z NOx emissions would be reduced by 67 percent from current emissions of 5 million tons
to a cap of 2.1 million tons in 2008, and to 1.7 million tons in 2018, and
z Mercury emissions – never before regulated as a power plant pollutant – would be cut by
69 percent, from current emissions of 48 tons to a cap of 26 tons in 2010 and 15 tons in
The Clear Skies proposal encourages the use of new and cleaner pollution control
technologies that the U.S. EPA believes will reduce compliance costs. The intent is to deliver
DOE Office of Fossil Energy Web site. <>
guaranteed emissions reductions of SO2, NOx, and mercury at a fraction of the costs. Also, by
setting specific dates in the future to meet the Ambient Air Quality Standards (AAQS), it
provides certainty for industry, regulators, and consumers. AAQS are U.S. Environment
Protection Agency (EPA) restrictions that limit the concentration of an air pollutant that may be
allowed to exist in the atmosphere for any specific period of time. Some standards are
established with substantial safety margins to protect the public’s health, whereas, other
standards are intended to protect property, plant and animal life, visibility and atmosphere
clarity. Florida Department of Environmental Protection (FDEP) states that the purpose of air
quality analysis is to develop plans to ensure maintenance of acceptable levels of air quality in
the face of population or industrial growth and to develop local and statewide strategies for
controlling emissions.
One of the major objectives of the Clear Skies proposal is to clean up older coal burning
facilities. According to Neville Holt, a technical fellow with the EPRI, most of the coal-fired
power plants operating today were built 30 to 50 years ago. Having been paid off long ago, the
utilities’ costs to generate electricity and to operate these older coal-fired plants are low. The
plants are frequently considered must-run units by load serving entities and are heavily relied
upon to provide a low cost baseload of energy. These older coal-fired plants produce over 320
gigawatts of electricity, yet less than a third of the power produced (100 gigawatts) by these units
have scrubbers to clean up their emissions.
The Clear Skies proposal would require older coal-fired generators to either be retrofitted
or retired by 201816. The U.S. EPA estimates that at least 54 units at 30 different coal plants
nationwide would be designated as uneconomic and retired at that time. With the strengthening
of the AAQS, the U.S. EPA estimates that by 2020, there will be 300 gigawatts of coal-fired
units and 81 percent (243 gigawatts) will have one or more of the following: selective catalytic
reduction (SCR) for NOx reductions, flue gas desulfurization (scrubbers) for SO2 reduction, and
activated carbon injection (ACI) for mercury reduction. Thus by 2020, the U.S. EPA estimates
that the United States will have less coal-fired generation than it does today and the vast majority
of the remaining coal-fired generation will incorporate technologies to reduce the amount of
toxic emissions.
Coal Use in Florida
The 2004 Regional Load & Resource Plan produced by the Florida Reliability
Coordinating Council (FRCC), states that 30 percent of the net energy generated in Florida was
produced from coal-fired generation. The following table illustrates that the percent of coal-fired
energy produced in Florida is projected to decline over time as more natural gas fired generators
are built. The FRCC estimates that in the year 2013, the amount of coal-fired generation in
peninsula Florida will decline to 26 percent. In contrast, over that same period of time the FRCC
estimates that the amount of energy generated by natural gas fired power plants will increase
from 26 percent in 2003 to 52 percent in 2013. Florida will become more dependent upon
natural gas for fuel and the price for energy in Florida will be more closely tied to the price of
EPA Web site. July 2003. <>
natural gas. As mentioned earlier, the price of coal has been relatively stable over the past
decade whereas the price for natural gas has been more volatile.
as of January 1, 2004
Reported by Florida Reliability Coordinating Council
Energy Sources
Firm Inter-region
Residual (oil #6)
Distillate (oil #2)
Natural Gas
Non Utility Generated
(such as waste burners)
Net Energy for Load
There are 27 coal-fired generators in Florida located in 10 counties. The two oldest inuse coal-fired generators are Scholz Units 1 & 2, located in Jackson County. They are owned by
Gulf Power Company and were built in 1953. The newest coal-fired generator was built in 2002
by JEA and is located in Duval County. Another new coal-fired generator is in the planning
stages in Alachua County and will be built by Gainesville Regional Utilities. Included as
Appendix B is a listing of existing coal-fired generation facilities in Florida.
Clean Coal Technology Projects in Florida
Six of the 38 DOE CCTP demonstration projects were to be conducted in Florida.
Southern Company Services was involved in two projects, TECO participated in one
demonstration, JEA is still conducting a fluidized-bed project demonstration in Jacksonville, and
two pressurized circulating fluidized-bed projects to be conducted by the City of Lakeland were
terminated in June 2003.
The two Southern Company projects that were both hosted by Gulf Power Company
(Gulf) focused on the reduction of NOx emissions. One of the projects was in Pensacola and the
other in Lynn Haven. The Pensacola project was located at Gulf’s Plant Crist, Unit No. 5. The
objective of the Pensacola project was to evaluate the performance of commercially available
selective catalytic reduction (SCR) catalysts when applied to coal-fired utility boilers, while
removing NOx. The SCR technology consists of injecting ammonia into boiler flue gas and
passing it through a catalyst bed where the NOx and ammonia react to form nitrogen and water
vapor.17 The Lynn Haven project took place at the Plant Lansing Smith, Unit No. 2. The project
was expected to demonstrate NOx reduction capabilities when using a technology called LowNOx Concentric Firing System.18 These two projects are finished and classified by the DOE as
commercial successes.
From September 1996 through September 2001, TECO conducted a demonstration of a
250 MW advanced IGCC system at Polk Power Station Unit No. 1. During the five-year
demonstration period, TECO was able to reduce emissions of SO2, NOx, and particulate matter to
lower levels than compared to conventional coal-fired plants. The project was the largest of its
kind and was initiated after a similar 100 MW IGCC program was conducted in the early 1980s.
The project continues to operate commercially and has been the recipient of many awards.
Along with successes, the project also exposed some problems, such as refractory liner life, with
the IGCC technology.19 Most of the issues were resolved during the demonstration and the
lessons learned should benefit future IGCC projects.
JEA currently is the operator of a 297 MW gross atmospheric circulating fluidized-bed
combustor demonstration project. In addition to the demonstration using JEA’s Northside Unit 2
plant, JEA also decided to repower its Northside Unit 1 using circulating fluidized-bed
technology, bringing the total capacity to nearly 600 MW. According to the DOE, the
demonstration’s objective is “to verify expectations of the technology’s economic,
environmental, and technical performance; to provide potential users with the data necessary for
evaluating a large-scale atmospheric circulating fluidized-bed as a commercial alternative; to
accomplish greater than 90 percent SO2 removal; and to reduce NOx emissions by 60 percent
when compared to conventional technology.” The project was originally sited in York,
Pennsylvania, but was moved to Jacksonville after the original participants terminated activities
in September 1996. As a result of a commitment to the Jacksonville community, JEA has added
several features to the plants to reduce emissions even more than the circulating fluidized-bed
technology alone would allow. One such voluntary addition is a polishing scrubber which helps
control sulfur and mercury emissions. The polishing scrubber applies a lime slurry to absorb
SO2. JEA was the first company in the U.S. to use a polishing scrubber on a commercial-scale
circulating fluidized-bed boiler.20 The circulating fluidized-bed boiler provides approximately
90 percent SO2 capture via limestone injection, with the remaining capture from the semi-dry
polishing scrubber via injection of lime. The combination results in SO2 capture above 98
percent.21 The Northside power station is one of the cleanest burning coal plants in the world.
Two demonstration test burns were conducted by JEA in January 2004 and emissions at various
Clean Coal Technology Demonstration Program 2003 Fact Sheet.
Clean Coal Technology Demonstration Program 2003 Fact Sheet.
Clean Coal Technology Demonstration Program 2003 Fact Sheet.
Coal Cleans Up in Jacksonville. Public Power Magazine. May-June 2004 issue.
The JEA CFB Demonstration Project: An Update.
load levels were all well below permitted values.22 In addition to reducing emissions, the
circulating fluidized-bed technology has allowed the JEA plants to be 2.5 times more efficient.23
Two pressurized circulating fluidized-bed combustor projects were selected for Lakeland
Electric’s McIntosh Power Station, Unit No. 4. In April 1998, the Lakeland City Council
approved a plan that included both projects, but according to the DOE, technical and economic
issues could not be resolved and the projects were later terminated. According to an article by
the Natural Resources Defense Council, the City of Lakeland abandoned the projects after the
price ballooned from $300 million to $450 million.
The projects selected for the Power Plant Improvement Initiative (PPII) included two
projects to be conducted by TECO. One project at the Big Bend Power Station in Apollo Beach
was to use computer controlled soot blowing technology to clean internal boiler surfaces,
allowing for improved plant performance. This project is tentatively scheduled to be completed,
and a final report issued, in March 2005.24 The second TECO project was to demonstrate a laser
system that measures the water pattern of the brick liner inside a coal gasifier at the Polk Power
Station.25 According to TECO, the project has not been active for about a year because the
additional accuracy offered was not justified by the costs associated with the technology. One
critical cost of concern to TECO is that in order to use the technology, the plant must be cooled
to a temperature that keeps it out of service for a longer period of time than TECO would like.
Current Coal-Fired Generation Plant Proposals
Gainesville Regional Utilities (GRU) has been engaged in a community outreach effort
regarding future electric needs since September 2003. GRU in December 2003, issued a
preliminary Integrated Resource Plan (IRP) proposing alternatives to meet Gainesville’s electric
needs through 2022. The IRP presented options that included building a new coal-fired plant and
retrofitting the existing Deerhaven 2 coal-fired plant to reduce NOx and SO2 emissions. The
Gainesville city commission in March 2004, dismissed two of the options presented in the IRP
and ordered GRU to continue researching the option that entails a 220 MW coal-fired circulating
fluidized-bed unit. This option includes plans to retrofit Deerhaven 2.
As mentioned earlier, the DOE announced on October 21, 2004 that it had awarded a
$235 million grant to Southern Company and the Orlando Utilities Commission (OUC) to build a
285 MW plant that will demonstrate IGCC technology. The project will be built at OUC’s
Stanton plant in Orlando and commercial operation of the facility is scheduled to begin in early
2010.26 The grant was awarded as part of the 2002 Clean Coal Power Initiative and will fund
approximately 40 percent of the $557 million project.
DOE Office of Fossil Energy, Clean Coal Today Newsletter. Spring 2004 issue.
DOE Office of Fossil Energy Techline. Clean Coal Power Now Serving Customers in Jacksonville, FL. October
14, 2002. <>
Power Plant Improvement Initiative 2003 Fact Sheet.
DOE Office of Fossil Energy Techline. Abraham Announces Projects to Bolster Electricity Supply from Coal
Plants. October 16, 2001. <>
DOE Taps Southern, Florida Muni For Clean Coal Project. The Energy Daily, ED Volume 32, Number 203.
October 22, 2004.
Florida’s Environmental Picture
Florida has an air quality monitoring program that measures six pollutants. Those
pollutants are: carbon monoxide (CO), lead, nitrogen dioxide (NO2), ozone (O3), particulate
matter (10 microns or less in diameter (PM10) and 2.5 microns or less in diameter (PM2.5)), and
SO2. Ambient air data is collected by 221 monitors in 34 counties throughout the state.
According to the FDEP’s Air Monitoring Report 2002, an essential component of air
quality management in the State of Florida is the identification of areas where the AAQS are
being violated.27 If a violation is determined, then plans are developed to reduce pollution
concentration levels to allow the areas or entire state to be in attainment with the standards.
Areas that meet all AAQS are designated by the U.S. EPA as attainment areas. Also, areas that
face anticipated population or industrial growth require the FDEP to develop plans to ensure
attainment/maintenance of the AAQS.
FDEP’s Air Monitoring Report 2002 states that all areas of Florida are now attainment
areas. Florida is one of only two states east of the Mississippi River, and the only highly
urbanized state, that currently meets all AAQS. Orange County (Orlando), Duval County
(Jacksonville), the Tampa Bay area including Hillsborough and Pinellas Counties and Southeast
Florida including Dade, Broward and Palm Beach Counties, continue to be classified by the
FDEP as attainment/maintenance areas for the pollutant ozone and Tampa is a maintenance area
for lead. Specifically looking at NOx, all monitors in Florida reported annual concentrations of
less than 35 percent of the standard. As reported:
z Nitrogen dioxide levels have never threatened the standard in Florida. The importance of
monitoring nitrogen dioxide is in helping to understand its influence in the formation of
ozone and fine particles.
z Sulfur dioxide - the annual average in Florida at all monitors indicated concentrations at
or below 35 percent of the standard.
z Ozone levels in 2002 were exceptionally low. There were only three exceedances of the
standard in Florida in 2002. Broward, Orange, and Escambia Counties each had one such
z Inhalable particulate concentrations (PM10 or smaller) were usually less than the
standard. PM10 is more harmful to humans than the larger particles of dust or pollen
because it is able to enter the lungs.
Even though Florida meets all U.S. EPA AAQS, and despite the efforts of Florida’s
utilities to implement the best available control technology to reduce air emissions, Florida’s
coal-burning utilities release a significant amount of emissions into the air. A May 6, 2004, St.
Petersburg Times article titled, “Power Plant Called One of Worst,” stated that Progress
Energy’s coal-burning power plant at Crystal River is one of the worst-polluting plants in the
nation, according to a report released by an environmental group. The report, called America’s
Dirtiest Power Plants, evaluated power plants on three emissions: sulfur dioxide, carbon dioxide,
and mercury. Crystal River was named on all three lists of the 50 worst offenders. The rankings
placed the Crystal River plant in the top 5 percent of pollution-producers among 1,000 plants
FDEP Division of Air Resource Management. <>
nationwide. Crystal River is one of the largest coal-burning plants in Florida and in the U.S.,
burning 6-million tons of coal and producing 16.1 billion kilowatt hours of electricity last year
for Progress Energy’s 1.5-million Florida customers.
It appears contradictory that Florida meets all U.S. EPA air standards, yet, at the same
time releases some of the highest levels of emissions compared to other states in the United
States. For NOx emissions, Florida ranked third highest in the nation; for CO2 emissions, Florida
ranked fifth highest; and for SO2 emissions, Florida ranked ninth highest in the nation as reported
by the U.S. Public Interest Research Groups using the U.S. EPA, National Air Quality and
Emission Trends Report data28. This contradiction can be explained by the geography of Florida.
Because Florida is a peninsula it has the advantage of cross winds from the Gulf of Mexico and
the Atlantic Ocean blowing across the state and cleansing the air. Thus, while power plants in
Florida may release tons of emissions into the atmosphere, the emissions do not remain
stationary over the land.
Generally, the older power plants in Florida are the ones that release the most emissions
because they predate the current U.S. EPA and FDEP’s clean air requirements. Utilities have not
been required to retrofit older plants because they were initially built with the BACT at the time
and the older plants have not been materially changed in a manner that would increase air
emissions. In general, it is difficult to retrofit older power plants because of urbanization, lack of
physical space, obsolescence, and it is expensive. With the U.S. EPA’s Clear Skies proposal,
even those coal-fired generation facilities that had previously been grandfathered would have to
meet the new AAQS by 2018. With that in mind, Florida’s utilities have taken steps to phase
out or retrofit their older coal-fired generators. For example, in 2003, TECO shut down its six
Gannon coal-fired units. TECO used the steam turbine portions of four Gannon units to
construct a natural gas combined cycle facility at the same site which has been renamed Bayside.
Also, for the past four years TECO has invested over $300,000 a year on cleaning up its Big
Bend coal-fired units to address acid rain concerns. Gulf Power Company has also addressed
acid rain concerns by investing approximately $2,000,000 a year for the past four years in
retrofitting its Crist coal-fired generation units. The two sites discussed are among the oldest
coal fired generation facilities dating to the 1950’s and 1960’s.
Clean coal technology research has been a goal of the federal government and the electric
industry in recent years. DOE-sponsored research programs produced many technologies that
have been proven effective and are now available commercially. These technologies are
reducing emissions of pollutants, including NOx, SO2, and particulate matter. Some of the coal
technologies are used to retrofit existing coal-fired plants and others are advanced power
generation systems for new coal-fired plants. Building on past successes, current clean coal
technology research is expected to produce technologies that reduce emissions of NOx, SO2,
mercury, and greenhouse gases. Current projects will also focus on using coal waste and
producing the world’s first zero-emissions fossil fuel plant.
U.S. PIRG. October 2003. <>
Coal-fired power plants are a stabilizing component of Florida’s and the nation’s energy
generation fleet. Coal, as a fuel source, is plentiful in the U.S. and its price has been stable for
the past decade. Coal-fired generation helps balance out the higher prices of natural gas fired
generation. In a state, such as Florida, that has a large percentage of retirees living on a fixed
income, it is very important to protect them from large fluctuations in energy prices. Thus,
investing in coal-fired generation may help stabilize the prices of energy and those products and
services that rely on energy.
Proof that utility companies are considering the economic and environmental benefits of
new coal technologies is the announcement by American Electric Power (AEP) in October 2004
that it would build at least one commercial-scale ICGG power plant “with an eye toward
developing an economical means of meeting potential greenhouse gas limits.”29 The
announcement marked the first time a U.S. power producer publicly pledged to build an IGCC
plant. The announcement came in response to a report by a three-member panel comprised of
AEP board members who were asked to assess the utility’s strategy for reducing its emissions of
SO2, NOx, mercury and CO2. “While technology risks, performance uncertainties and capital
costs remain formidable at this early stage in IGCC’s development, AEP also recognizes sizable
operational, policy and economic benefits that this technology potentially could deliver as the
next generation of power generation assets,” said the panel. “Weighing these costs and benefits,
the company has committed to emerging as a leader and first-mover in advancing IGCC into the
mainstream of power generation.” The location and size of the facility have not been announced.
An industry publication reported that the announcement could be a breakthrough for the
emerging clean-coal technology.30
Florida’s utilities are pursuing investment in both the best available control technologies
as well as in clean coal technologies. They are also undertaking steps to retrofit older plants with
technology to reduce air emissions and in a number of cases, replacing older coal facilities with
plants using newer coal technology. The utilities are attempting to replace their grandfathered
coal-fired generation with newer, cleaner generation now to address future EPA air emission
standards and the health concerns in their communities.
In Industry First, AEP Commits To Clean Coal Plant. By George Lobsenz. The Energy Daily, ED Volume 32,
Number 168. September 1, 2004.
Appendix A: Power Plant Improvement Initiative Projects31
The DOE announced the selection of eight project proposals for the PPII on September 28, 2001.
Details about the Birchwood Power Facility project were reported in the body of this document.
Of the remaining seven projects, two were withdrawn by their industrial sponsors. The other
projects selected were:
z Arthur D. Little Inc. proposed to outfit a boiler at the Orion Power Company’s Avon
Lake Power Plant near Cleveland, OH, with a hybrid pollution control system to
reduce nitrogen oxides. The system will integrate three exiting NOx reduction
technologies (natural gas reburning, selective non-catalytic reduction, and selective
catalytic reduction), which will lower the cost of reducing NOx.
z CONSOL Energy Inc. proposed to demonstrate a multi-pollutant control system at the
AES Greenridge Power Plant near Dresden, NY, to reduce NOx, SO2, mercury, acidic
gases, and fine particles from smaller coal plants for less money than it costs to
control NOx and SO2 separately. Innovations CONSOL planned to install at the plant
included a catalytic NOx reduction technology that works inside the plant’s ductwork,
a low-NOx combustion technology that burns coal mixed with biomass, and a flue gas
scrubber that is less complex and nearly half the cost of conventional systems.
z Otter Tail Power Company proposed to install a technology designed to capture up to
99.9999% of the fly ash particles emitted from a coal boiler. The demonstration will
take place at the Big Stone Power Plant in South Dakota and will integrate a fabric
filter system with an electrostatic precipitator in a single unit.
z Sunflower Electric Power Corporation proposed to install at it’s power plant in
Garden City, KS, ultra-low-NOx burners with other combustion controls to
demonstrate a pollution control concept that has never been attempted in power plants
that burn western subbituminous coals.
z Tampa Electric Company proposed to apply a neural network system to determine
when and how best to dislodge soot that can build up inside a boiler and degrade
performance. The demonstration will take place at the Big Bend Power Station in
Apollo Beach, FL. Computer controlled sootblowing technology, as opposed to
manually activated sootblower, will permit the cleaning of internal boiler surfaces
with improved power plant performance.
DOE Office of Fossil Energy Web site. The 2001 Power Plant Improvement Initiative. August 15, 2003.
Big Bend Unit 1
Big Bend Unit 2
Big Bend Unit 3
Big Bend Unit 4
Crist Unit 4
Crist Unit 5
Crist Unit 6
Crist Unit 7
Crystal River Unit 1
Crystal River Unit 2
Crystal River Unit 4
Crystal River Unit 5
Lansing Smith Unit 1
Lansing Smith Unit 2
McIntosh (342/342)
Unit 3
Northside Unit 1
Northside Unit 2
Polk Unit 1
St. Johns River
(628/640) Unit 1
St. Johns River
(628/640) Unit 2
Scholz Unit 1
Scholz Unit 2
Plant Name
Tampa Electric Company
Tampa Electric Company
Tampa Electric Company
Tampa Electric Company
Gulf Power Company
Gulf Power Company
Gulf Power Company
Gulf Power Company
Progress Energy Florida
Progress Energy Florida
Progress Energy Florida
Progress Energy Florida
Gainesville Regional Utilities
Gulf Power Company
Gulf Power Company
City of Lakeland
Orlando Utilities Commission
Tampa Electric Company
Florida Power & Light
Florida Power & Light
Gulf Power Company
Gulf Power Company
Gross Capability –
Net Capability - MW
FRCC Form 1.0 as of January 1, 2003
Appendix B:
Plant Name
Seminole Unit 1
Seminole Unit 2
Stanton (440/443)
Unit 1
Stanton (446/446)
Unit 2
Seminole Electric Cooperative
Seminole Electric Cooperative
Florida Municipal Power
Kissimmee Utility Authority
Orlando Utilities Commission
FL Municipal Power Agency
Orlando Utilities Commission
Gross Capability –
Net Capability - MW
FRCC Form 1.0 as of January 1, 2003
Appendix B:
U.S. Department of Energy, Energy Information Administration, Coal News and Markets, April 4, 2004.
U.S. Department of Energy, Energy Information Administration, Edward J. Flynn, Impact of
Technological Change and Productivity on the Coal Market, 2000.
U.S. Department of Energy, Office of Fossil Energy, New Recycling Technology to be Tested at Virginia
Coal-Fired Power Plant,
U.S. Department of Energy, Office of Fossil Energy, Clean Coal Power Now Serving Customers in
Jacksonville, Florida,
Environmental Media Services, The Dirty Folly of “Clean Coal” by the Natural Resources Defense
Council, May 8, 2001,
Green Scissors Cutting Wasteful and Environmentally Harmful Spending, Dirty Pork in Green Clothing
“Clean Coal” Programs,
Florida Reliability Coordinating Council, 2003 Regional Load & Resource Plan, July 2003
U.S. PIRG Reports, Lethal Legacy: A Comprehensive Look at American’s Dirtiest Power Plants, October
Gainesville Regional Utilities, Alternatives For Meeting Gainesville’s Electrical Requirements Through
2022: Base Studies and Preliminary Findings, December 2003
Florida Department for Environmental Protection, (July 24, 2003) “Florida Achieves Milestone in Clean
Acid Rain: Rainfall that occurs when atmospheric water vapor combines with oxides of sulfur
and nitrogen to form sulfuric or nitric acid. Natural rainfall is slightly acidic due to the presence
of carbon dioxide in the atmosphere, which forms a mild carbonic acid. If rainfall becomes too
acidic, it may cause environmental damage.
Ambient Air Quality Standards: Standards, authorized by the 1970 Clean Air Act, that
establish level of pollutants that can be present in the air without endangering public health and
welfare. These standards set maximum levels allowed in a three-hour period and a 24-hour
period, and mandate average levels that must be met in a year. An area with air quality superior
to the standards for a particular pollutant is classified as an “attainment” area.
Best Available Control Technology (BACT): A pollutant emissions limitation based in the
maximum degree of reduction possible, taking into account energy, environmental, and
economic impacts and other costs. BACT requirements are intended to ensure that the pollution
control systems incorporated into the design of a proposed facility reflect the latest in pollution
control technologies used in a particular industry, while taking into account existing and future
air quality in the vicinity of the facility.
Best Available Retrofit Technology (BART): A regulatory requirement for utilities to use the
best technology available in bringing existing generation equipment into compliance with current
environmental regulations. BART applies to technology that is added to existing facilities.
Boiler: A device for generating steam for power, processing, or heating purposes or for
producing hot water for heating purposes or hot water supply. Heat from an external combustion
source is transmitted to a fluid contained within the tubes in a boiler shell, a close vessel in
which water is converted to pressurized steam. This fluid is delivered to an end-use at a desired
pressure, temperature, and quality.
Catalyst: A substance that changes the speed of a chemical reaction without itself changing.
Char: A porous, solid, nearly pure carbon residue resulting from the incomplete combustion of
organic material. If produced from coal, it is called coke; if produced from wood or bone, it is
called charcoal.
Clean Air Act: A specific national law passed in 1963, and amended several times since, giving
the U.S. government powers to limit air pollution. The term “Clean Air Act” also is applied
loosely to the Air Quality Act of 1967.
Coal: a fossil fuel made up of carbon, hydrogen, oxygen, nitrogen and sulfur. Formed from the
remains of trees and plants alive millions of years ago, various types (anthracite, bituminous,
lignite, and steam coal) are used as a fuel to generate electricity.
Flue Gas: A mixture of gases resulting from combustion and other reactions in a combustion
device. The gas is routed through a chimney or stack into the outdoor air.
Flue Gas Desulfurization (FGD): The process of removing sulfur oxides from power plant
exhaust gases. This is done with flue gas desulfurization devices, commonly called scrubbers.
Typically, a flue gas desulfurization system can remove 90 percent or more of the sulfur oxides.
In an FGD system, the flue gas produced by coal combustion is sprayed with a slurry of water
and an alkaline agent – a lime or limestone. The sulfur oxides react with the slurry, forming
calcium sulfite and/or calcium sulfate. This is removed as wet sludge. Scrubbers are classified
by the type of chemical absorbent used and the waste produced; the process is “throwaway” if
the waste has little or no market value and “regenerative” if it can be reused or marketed for
some other purpose. A salable product from a “regenerative” system could include gypsum,
elemental sulfur, or sulfuric acid.
Flue Gas Recirculation: Technology, in which part of the flue gas is recirculated to the furnace,
that can be used to modify conditions in the combustion zone (lowering the temperature and
reducing the oxygen concentration) to reduce NOx formation. Another use for flue gas
recirculation is as a carrier to inject fuel into a reburn zone to increase penetration and mixing.
Fluidized Bed Combustion (FBC): A method of controlling emissions during the combustion
process. There are two basic types – atmospheric and pressurized. In atmospheric fluidized bed
combustion (AFBC), crushed coal is fed into a bed of inert ash mixed with limestone or
dolomite. The bed is fluidized, or held in suspension, by an injection of air through the bottom,
which causes the mixture to agitate, much like boiling water. As the coal burns, the sulfur
released reacts with the limestone or dolomite to form dry calcium sulfate. This solid waste is
periodically removed. In pressurized fluidized bed combustion (PFBC), combustion occurs in a
similar fashion, but the furnace is maintained at a higher pressure. This compresses the flue
gases, allowing a significant reduction in furnace size compared to AFBC. The hot, pressurized
gases are used to power a gas turbine, and waste heat from the process is used to produce steam
to drive a steam turbine. This is called a combined cycle unit.
Greenhouse Gases: The gases include water vapor, carbon dioxide, methane, ozone, nitrous
oxides, fluorocarbons, and particulates among others. They trap heat in the earth’s biosphere and
affect global heat balances that affect weather and climate.
Lignite: a usually brownish black coal intermediate between peat and bituminous coal;
especially: one in which the texture of the original wood is distinct – called also brown coal.
Low-NOx Burner: Technology that is designed to control the mixing of fuel and air to achieve
what amounts to staged combustion. This results in a lower maximum flame temperature and a
reduced oxygen concentration during some phases of combustion. This results in both lower
thermal NOx and lower fuel NOx production.
Mercury: mercury is a naturally occurring element that is present throughout the environment.
It becomes a toxic air pollutant when released into the air, water and soil by human activity.
Reactive, inorganic mercury is emitted to the atmosphere primarily from coal-burning power
plants and incinerators that combust mercury-containing wastes.
Natural Gas: a combustible, gaseous mixture of simple hydrocarbon compounds, usually found
in deep underground reservoirs formed by porous rock. Natural gas can be found by itself or in
association with crude oil. Gas also can be manufactured. Manufactured gas can be obtained
from distillation of coal, thermal decomposition of oil or by the reaction of steam passing
through a bed of heated coal.
Nitrogen Oxides (NOx): compounds of nitrogen and oxygen. They are products of automobile
exhaust and may be produced by the burning of fossil fuels. They are a contributor to the
formation of smog.
Overfire Air: Air that is injected into the furnace above the normal combustion zone. Overfire
air is generally used in conjunction with operating the burners at a lower than normal air-to-fuel
ratio, which reduces NOx formation. The overfire air completes the combustion at a lower
temperature. Overfire air is frequently used in conjunction with low-NOx burners.
Particulates, Particulate Matter: discrete particles in a condensed form. Particulate matter
emitted from coal combustion is primarily a mixture of carbon, silica, calcium and iron oxide,
also smoke and soot may be emitted.
Precipitators (Electrostatic Precipitator): A device for collecting particulate material from
waste gases, such as those released by coal burning power stations. The main principle of
operation is based on the fact that particulates, moving through a region of high electrostatic
potential, tend to become charged and then are attracted to an oppositely charged electrode
where they can be collected and removed.
Reburning: Technology where part of the boiler fuel input is added in a separate reburn zone.
In this zone, the fuel-rich reducing conditions lead to the reduction of NOx formed in the normal
combustion zone. Overfire air is injected above the reburn zone to complete combustion. Thus,
with reburn there are three zones in the furnace: 1) a combustion zone with an approximately
normal air-to-fuel ratio; 2) a reburn zone, where added fuel results in a fuel-rich condition; and
3) a burnout zone, where overfire air leads to completion of combustion. Coal, oil, or gas can be
used as the reburn fuel.
Retrofit: The process of modifying or updating existing equipment to incorporate advantageous
changes or to include current technologies used in newer equipment.
Scrubber: an apparatus for removing impurities especially from gases.
Selective Catalytic Reduction: In this technology, a catalyst vessel is installed downstream of
the furnace. Ammonia is injected into the flue gas before it passes over the fixed-bed catalyst.
The catalyst promotes a reaction between the ammonia and NOx to form nitrogen and water
Selective Noncatalytic Reduction: In this technology, a reducing agent, typically ammonia or
urea, is injected into the furnace above the combustion zone, where it reacts with NOx.
Sequestration: Sequestration is a family of methods for capturing and permanently isolating
gasses that otherwise could contribute to global climate change, during the burning of coal based
Slag: A residue produced by the combustion of coal. Slag is the fused or vitrified matter that
accumulates in the bottom of a boiler. It is removed periodically and disposed of according to
environmental regulations.
Sludge: Any mixture of solids and liquids resulting in a thick liquid. One example of sludge is
the end product of flue gas desulfurization, which is a mixture of water, limestone and calcium
sulfite or sulfate.
Smog: a fog made heavier and darker by smoke and chemical fumes; also: a photochemical haze
caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and
oxides of nitrogen from automobile exhaust.
Sorbent: a substance that takes up and holds by either adsorption or absorption.
Sulfur Dioxide (SO2): a heavy pungent toxic gas SO2 that is easily condensed to a colorless
liquid, is used especially in making sulfuric acid, in bleaching, as a preservative, and as a
refrigerant, and is a major air pollutant especially in industrial areas.
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