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We provide Coal
Liquefaction - also known as "coal to liquid" project development services as well as Coal-Gasification,
Clean Coal Technologies, Coal
Liquefaction, and Integrated
Gasification Combined Cycle project development. Unlike most
companies, we are equipment supplier/vendor neutral. This
means we help our clients select the best equipment for their specific
application. This approach provides our customers with superior
performance, decreased operating expenses and increased return on
Cleaner, Greener Power & Energy Solutions project
development services are one of our specialties. These projects are Kyoto
Protocol compliant and generate clean energy and significantly fewer
greenhouse gas emissions. Unlike most companies, we are equipment
supplier/vendor neutral. This means we help our clients select the best
equipment for their specific application. This approach provides our
customers with superior performance, decreased operating expenses and
increased return on investment.
Energy Technologies provides
project development services that generate clean energy and significantly
reduce greenhouse gas emissions and
carbon dioxide emissions.
Included in this are our
products and services which includes; Clean
Coal Technologies, Renewable
Energy Technologies, Waste to Energy,
Waste to Watts and Waste
Heat Recovery solutions. Other project development
technologies include; Anaerobic Digester,
Anaerobic Lagoon, Biogas
Recovery, BioMethane, Biomass
Gasification, and Landfill Gas To
Energy, project development services.
services provided by Cogeneration Technologies includes the following
power and energy project development services:
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Funding & Financing Options; including Equity Investment, Debt
Financing, Lease and Municipal Lease
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more information: call us at: 832-758-0027
are Renewable Energy
Technologies specialists and develop clean power and energy projects
that will generate a "Renewable
Energy Credit," Carbon
Dioxide Credits and Emission
Reduction Credits. Some of our products and services solutions
and technologies include; Absorption
Chillers, Adsorption Chillers, Automated
Demand Response, Biodiesel
Refineries, Biofuel Refineries, Biomass
Gasification, BioMethane, Canola
Biodiesel, Coconut Biodiesel, Cogeneration,
Concentrating Solar Power, Demand
Response Programs, Demand Side
Conservation Measures, Energy
Master Planning, Engine Driven
Chillers, Geothermal Heatpumps,
Groundsource Heatpumps, Solar
CHP, Solar Cogeneration, Rapeseed
Biodiesel, Solar Electric Heat
Pumps, Solar Electric Power
Systems, Solar Heating and
Cooling, Solar Trigeneration, Soy
Biodiesel, Trigeneration, and Watersource
What is Coal Liquefaction?
Coal liquefaction is the conversion of coal to produce synthetic fuels.
To convert coal to synthetic fuels, a process has been developed that
requires the coal to be in contact with a hydrogen environment at high
temperatures and pressures.
The major objective of coal liquefaction is to produce synthetic oil to
supplement the natural sources of petroleum. Liquid and solid products
from coal can be used for fueling transportation vehicles, providing fuels
for power generation, and yielding raw materials for chemicals.
Coal-liquefaction plants will be expensive, but their products
should be very competitive when world oil production declines.
Integrated Gasification Combined Cycle (IGCC)
Integrated Gasification Combined Cycle (IGCC) is
rapidly emerging as one of the most promising technologies in
power generation that utilizes low-quality solid and liquid fuels and is
able to meet the most stringent emissions requirements.
IGCC systems are extremely clean, and are much more efficient than
traditional coal-fired systems. IGCC uses a combined cycle format with a gas turbine driven by the combusted syngas from the gasifier, while the exhaust gases are heat exchanged with water/steam to generate superheated steam to drive a steam turbine.
Using IGCC, typically 60-70% of the power comes from the gas turbine with
IGCC, compared with about 20% using PFBC. The result is an integrated gasification combined-cycle configuration that provides ultra-low pollution levels and high system efficiencies.
The President's Clean Coal Power Initiative
his campaign for the Presidency, George W. Bush pledged to commit $2
billion over 10 years to advance clean coal technology - a pledge he
has subsequently carried out in the National Energy Policy and in
budget requests to Congress.
coal technology" describes a new generation of energy processes that
sharply reduce air emissions and other pollutants compared to older
coal-burning systems. In the late 1980s and early 1990s, the U.S.
Department of Energy conducted a joint program with industry and State
agencies to demonstrate the best of these new technologies at scales large
enough for companies to make commercial decisions. More than 20 of the
technologies tested in the original program achieved commercial success.
early program, however, was focused on the environmental challenges of the
time - primarily concerns over the impact of acid rain on forests and
watersheds. In the 21st century, additional environmental concerns have
emerged - 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.
coal likely to remain one of the nation's lowest-cost electric power
suppliers for the foreseeable future, President Bush has pledged a new
commitment to even more advanced clean coal technologies. As the President
said in presenting his National Energy Policy to the American public on
May 17, 2001
, "More than half of the electricity generated in
today comes from coal. If we weren't blessed with this natural resource,
we would face even greater [energy] shortages and higher prices today.
Yet, coal presents an environmental challenge. So our plan funds research
into new, clean coal technologies."
on the successes of the original program, the new clean coal initiative
encompasses a broad spectrum of research and large-scale projects that
target today's most pressing environmental challenges.
the demonstration portion of the program, the Clean Coal Power Initiative,
is providing government co-financing for new coal technologies that can
help utilities meet the President's Clear Skies Initiative to cut sulfur,
nitrogen and mercury pollutants from power plants by nearly 70 percent by
the year 2018. Also, some of the early projects are showing ways to reduce
greenhouse gases from coal plants by boosting the efficiency at which they
convert coal to electricity or other energy forms.
gasification offers one of the most versatile and cleanest ways to convert
the energy content of coal into electricity, hydrogen, and other energy
first pioneering coal gasification electric power plants are now operating
commercially in the United States and in other nations, and many experts
predict that coal gasification will be at the heart of the future
generations of clean coal technology plants for several decades into the
future. For example, at the core of the U.S. Department of Energy's FutureGen
power plant of the future will be an advanced coal gasifier.
than burning coal directly, gasification breaks down coal - or virtually
any carbon-based feedstock - into its basic chemical constituents. In a
modern gasifier, coal is typically exposed to hot steam and carefully
controlled amounts of air or oxygen under high temperatures and pressures.
Under these conditions, carbon molecules in coal break apart, setting into
motion chemical reactions that typically produce a mixture of carbon
monoxide, hydrogen and other gaseous compounds.
in fact, may be one of the best ways to produce clean-burning hydrogen for
tomorrow's automobiles and power-generating fuel cells. Hydrogen and other
coal gases can also be used to fuel power-generating turbines or as the
chemical "building blocks" for a wide range of commercial
Energy Department's Office of Fossil Energy is working on coal gasifier
advances that enhance efficiency, environmental performance, and
reliability as well as expand the gasifier's flexibility to process a
variety of feedstocks (including biomass and municipal/industrial waste).
environmental benefits stem from the capability to cleanse as much as 99
percent of the pollutant-forming impurities from coal-derived gases.
Sulfur in coal, for example, emerges as hydrogen sulfide and can be
captured by processes used today in the chemical industry. In some
methods, the sulfur can be extracted in a form that can be sold
commercially. Likewise, nitrogen typically exits as ammonia and can be
scrubbed from the coal gas by processes that produce fertilizers or other
Office of Fossil Energy is also exploring advanced syngas cleaning and
conditioning processes that are even more effective in eliminating
emissions from coal gasifiers. Multi-contaminant control processes are
being developed that reduce pollutants to parts-per-billion levels and are
effective in cleaning mercury and other trace metals in addition to other
gasification may offer a further environmental advantage in addressing
concerns over the atmospheric buildup of greenhouse gases, such as carbon
dioxide.. If oxygen is used in a coal gasifier instead of air, carbon
dioxide is emitted as a concentrated gas stream. In this form, it can be
captured more easily and at lower costs for ultimate disposition in
various sequestration approaches. (By contrast, when coal burns or is
reacted in air, 80 percent of which is nitrogen, the resulting carbon
dioxide is much more diluted and more costly to separate from the much
larger mass of gases flowing from the combustor or gasifier.)
gains are another benefit of coal gasification. In a typical coal
combustion plant, heat from burning coal is used to boil water, making
steam that drives a steam turbine-generator. Only a third of the energy
value of coal is actually converted into electricity by most combustion
plants, the rest is lost as waste heat.
coal gasification power plant, however, typically gets dual duty from the
gases it produces. First, the coal gases, cleaned of their impurities, are
fired in a gas turbine - much like natural gas - to generate one source of
electricity. The hot exhaust of the gas turbine is then used to generate
steam for a more conventional steam turbine-generator. This dual source of
electric power, called a "combined cycle," converts much more of
coal's inherent energy value into useable electricity. The fuel efficiency
of a coal gasification power plant can be boosted to 50 percent or more.
concepts that incorporate a fuel cell or fuel cell-gas turbine hybrid
could achieve even higher efficiencies, perhaps in the 60 percent range,
or nearly twice today's typical coal combustion plants. And if any of the
remaining waste heat can be channeled into process steam or heat, perhaps
for nearby factories or district heating plants, the overall fuel use
efficiency of future gasification plants could reach 70 to 80 percent.
efficiencies translate into more economical electric power and potential
savings for ratepayers. A more efficient plant also uses less fuel to
generate power, meaning that less carbon dioxide is produced. In fact,
coal gasification power processes under development by the Energy
Department could cut the formation of carbon dioxide by 40 percent or more
compared to today's conventional coal-burning plant.
capability to produce electricity, hydrogen, chemicals, or various
combinations while virtually eliminating air pollutants and potentially
greenhouse gas emissions makes coal gasification one of the most promising
technologies for the energy plants of tomorrow.
is our most abundant fossil fuel. The
has more coal than the rest of the world has oil. There is still enough
coal underground in this country to provide energy for the next 200 to 300
coal is not a perfect fuel.
inside coal are traces of impurities like sulfur and nitrogen. When coal
burns, these impurities are released into the air.
floating in the air, these substances can combine with water vapor (for
example, in clouds) and form droplets that fall to earth as weak forms of
sulfuric and nitric acid scientists call it "acid rain."
are also tiny specks of minerals including common dirt mixed in
coal. These tiny particles don't burn and make up the ash left behind in a
coal combustor. Some of the tiny particles also get caught up in the
swirling combustion gases and, along with water vapor, form the smoke that
comes out of a coal plant's smokestack. Some of these particles are so
small that 30 of them laid side-by-side would barely equal the width of a
coal like all fossil fuels is formed out of carbon. All living things -
even people - are made up of carbon. (Remember - coal started out as
living plants.) But when coal burns, its carbon combines with oxygen in
the air and forms carbon dioxide. Carbon dioxide is a colorless, odorless
gas, but in the atmosphere, it is one of several gases that can trap the
earth's heat. Many scientists believe this is causing the earth's
temperature to rise, and this warming could be altering the earth's
climate (read more about the "greenhouse effect").
like coal is a dirty fuel to burn. Many years ago, it was. But things have
changed. Especially in the last 20 years, scientists have developed ways
to capture the pollutants trapped in coal before the impurities can escape
into the atmosphere. Today, we have technology that can filter out 99
percent of the tiny particles and remove more than 95 percent of the acid
rain pollutants in coal.
also have new technologies that cut back on the release of carbon dioxide
by burning coal more efficiently.
of these technologies belong to a family of energy systems called
"clean coal technologies." Since the mid-1980s, the U.S.
Government has invested more than $2 billion in developing and testing
these processes in power plants and factories around the country. Private
companies and State governments have been part of this program. In fact,
they have contributed more than $4 billion to these projects.
do you make coal cleaner?
there are several ways.
sulfur, for example. Sulfur is a yellowish substance that exists in tiny
amounts in coal. In some coals found in
and other eastern states, sulfur makes up from 3 to 10 percent of the
weight of coal.
some coals found in
and other western states (as well as some places in the East), the sulfur
can be only 1/100ths (or less than 1 percent) of the weight of the coal.
Still, it is important that most of this sulfur be removed before it goes
up a power plant's smokestack.
Although coal is primarily a mixture of carbon (black) and hydrogen
(red) atoms, sulfur atoms (yellow) are also trapped in coal,
primarily in two forms. In one form, the sulfur is a separate
particle often linked with iron (green) with no connection to the
carbon atoms, as in the center of the drawing. In the second form,
sulfur is chemically bound to the carbon atoms, such as in the upper
way is to clean the coal before it arrives at the power plant. One of the
ways this is done is by simply crushing the coal into small chunks and
washing it. Some of the sulfur that exists in tiny specks in coal (called
"pyritic sulfur " because it is combined with iron to form iron
pyrite, otherwise known as "fool's gold) can be washed out of the
coal in this manner. Typically, in one washing process, the coal chunks
are fed into a large water-filled tank. The coal floats to the surface
while the sulfur impurities sink. There are facilities around the country
called "coal preparation plants" that clean coal this way.
all of coal's sulfur can be removed like this, however. Some of the sulfur
in coal is actually chemically connected to coal's carbon molecules
instead of existing as separate particles. This type of sulfur is called
"organic sulfur," and washing won't remove it. Several process
have been tested to mix the coal with chemicals that break the sulfur away
from the coal molecules, but most of these processes have proven too
expensive. Scientists are still working to reduce the cost of these
chemical cleaning processes.
modern power plants and all plants built after 1978 are required
to have special devices installed that clean the sulfur from the coal's
combustion gases before the gases go up the smokestack. The technical name
for these devices is "flue gas desulfurization units," but most
people just call them "scrubbers" because they
"scrub" the sulfur out of the smoke released by coal-burning
do scrubbers work?
scrubbers rely on a very common substance found in nature called
"limestone." We literally have mountains of limestone throughout
this country. When crushed and processed, limestone can be made into a
white powder. Limestone can be made to absorb sulfur gases under the right
conditions much like a sponge absorbs water.
most scrubbers, limestone (or another similar material called lime) is
mixed with water and sprayed into the coal combustion gases (called
"flue gases"). The limestone captures the sulfur and
"pulls" it out of the gases. The limestone and sulfur combine
with each other to form either a wet paste (it looks like toothpaste!), or
in some newer scrubbers, a dry powder. In either case, the sulfur is
trapped and prevented from escaping into the air.
Clean Coal Technology Program tested several new types of scrubbers that
proved to be more effective, lower cost, and more reliable than older
scrubbers. The program also tested other types of devices that sprayed
limestone inside the tubing (or "ductwork') of a power plant to
absorb sulfur pollutants.
what about nitrogen pollutants? That's another part of the Clean Coal
the Nitrogen Oxides (NOx) Out of Coal
Nitrogen Oxides Form
is mostly nitrogen molecules (green in the above diagram) and oxygen
molecules (purple). When heated hot enough (around 3000 degrees F),
the molecules break apart and oxygen atoms link with the nitrogen
atoms to form NOx, an air pollutant.
is the most common part of the air we breathe. In fact, about 80% of the
air is nitrogen. Normally, nitrogen atoms float around joined to each
other like chemical couples. But when air is heated in a coal boiler's
flame, for example these nitrogen atoms break apart and join with
oxygen. This forms "nitrogen oxides" or, as it is sometimes
called, "NOx" (rhymes with "socks"). Nitrogen oxides
can also be
formed from the atoms of nitrogen that are trapped inside coal.
air, NOx is a pollutant. It can cause smog, the brown haze you sometimes
see around big cities. It is also one of the pollutants that forms
"acid rain." And it can help form something called "groundlevel
ozone," another type of pollutant that can make the air dingy.
can be produced by any fuel that burns hot enough. Automobiles, for
example, produce NOx when they burn gasoline. But a lot of NOx comes from
coal-burning power plants, so the Clean Coal Technology Program developed
new ways to reduce this pollutant.
the best ways to reduce nitrogen oxides is to prevent it from forming in the first
place. Scientists have found ways to burn coal (and other fuels) in
burners where there is more fuel than air in the hottest combustion
chambers. Under these conditions, most of the oxygen in air combines with
the fuel, rather than with the nitrogen. The burning mixture is then sent
into a second combustion chamber where a similar process is repeated until
all the fuel is burned.
concept is called "staged combustion" because coal is burned in
stages. A new family of coal burners called "low-NOx burners"
has been developed using this way of burning coal. These burners can
reduce the amount of nitrogen oxides released into the air by more than half. Today,
because of research and the Clean Coal Technology Program, more than half
of all the large coal-burning boilers in the
will be using these types of burners. By the year 2000, more than 3 out of
every four boilers will have been outfitted with these new clean coal
is also a family of new technologies that work like "scubbers"
by cleaning NOx from the flue gases (the smoke) of coal burners. Some of
these devices use special chemicals called "catalysts" that
break apart the NOx into non-polluting gases. Although these devices are
more expensive than "low-NOx burners," they can remove up to 90
percent of NOx pollutants.
the future, there may be an even cleaner way to burn coal in a power
plant. Or maybe, there may be a way that doesn't burn the coal at all.
Bed Boilers, a Bed for Burning Coal?
a wet, chilly day in
in 1979 when a few scientists and engineers joined with government and
college officials on the campus of
to celebrate the completion of one of the world's most advanced coal
a small coal burner by today's standards, but large enough to provide heat
and steam for much of the university campus. But the new boiler built
beside the campus tennis courts was unlike most other boilers in the
Fluidized Bed Boiler
a fluidized bed boiler, upward blowing jets of air suspend burning
coal, allowing it to mix with limestone that absorbs sulfur
called a "fluidized bed boiler." In a typical coal boiler, coal
would be crushed into very fine particles, blown into the boiler, and
ignited to form a long, lazy flame. Or in other types of boilers, the
burning coal would rest on grates. But in a "fluidized bed
boiler," crushed coal particles float inside the boiler, suspended on
upward-blowing jets of air. The red-hot mass of floating coal called
the "bed" would bubble and tumble around like boiling lava
inside a volcano. Scientists call this being "fluidized." That's
how the name "fluidized bed boiler" came about.
does a "fluidized bed
boiler" burn coal cleaner?
are two major reasons. One, the tumbling action allows limestone to be
mixed in with the coal. Remember limestone from a couple of pages ago?
Limestone is a sulfur sponge it absorbs sulfur pollutants. As coal
burns in a fluidized bed boiler, it releases sulfur. But just as rapidly,
the limestone tumbling around beside the coal captures the sulfur. A
chemical reaction occurs, and the sulfur gases are changed into a dry
powder that can be removed from the boiler. (This dry powder called calcium
sulfate can be processed into the wallboard we use for building
walls inside our houses.)
second reason a fluidized bed boiler
burns cleaner is that it burns
"cooler." Now, cooler in this sense is still pretty hot
about 1400 degrees F. But older coal boilers operate at temperatures
nearly twice that (almost 3000 degrees F). Remember NOx from the page
back)? NOx forms when a fuel burns hot enough to break apart nitrogen
molecules in the air and cause the nitrogen atoms to join with oxygen
atoms. But 1400 degrees isn't hot enough for that to happen, so very
little NOx forms in a fluidized bed boiler.
result is that a fluidized bed boiler
can burn very dirty coal and remove
90% or more of the sulfur and nitrogen pollutants while the coal is
burning. Fluidized bed boilers can also burn just about anything else
wood, ground-up railroad ties, even soggy coffee grounds.
fluidized bed boilers are operating or being built that are 10 to 20 times
larger than the small unit built almost 20 years ago at Georgetown
University. There are more than 300 of these boilers around this country
and the world. The Clean Coal Technology Program helped test these boilers
and most recently, in
Ohio Power Company built this advanced pressurized
fluidized bed boiler near the town of
, OH, as part of a joint project with
the U.S. Department of Energy.
(Click on photo for larger
type of fluidized bed boiler makes a major improvement in the basic
system. It encases the entire boiler inside a large pressure vessel, much
like the pressure cooker used in homes for canning fruits and vegetables
except the ones used in power plants are the size of a small house!
Burning coal in a "pressurized fluidized bed boiler" produces a
high-pressure stream of combustion gases that can spin a gas turbine to
make electricity, then boil water for a steam turbine two sources of
electricity from the same fuel!
"pressurized fluidized bed boiler" is a more efficient way to
burn coal. In fact, future boilers using this system will be able to
generate 50% more electricity from coal than a regular power plant from
the same amount of coal. That's like getting 3 units of power when you
used to get only 2.
it uses less fuel to produce the same amount of power, a more efficient
"pressurized fluidized bed boiler" will reduce the amount of
carbon dioxide (a greenhouse gas) released from coal-burning power plants.
fluidized bed boilers" are one of the newest ways to burn coal
cleanly. But there is another new way that doesn't actually burn the coal
think of coal as a solid black rock. Think of it as a mass of atoms. Most
of the atoms are carbon. A few are hydrogen. And there are some others,
like sulfur and nitrogen, mixed in. Chemists can take this mass of atoms,
break it apart, and make new substances like gas!
of the most advanced - and cleanest - coal power plants in the world
is Tampa Electric's Polk Power Station in
. Rather than burning coal, it turns
coal into a gas that can be cleaned of almost all pollutants.
you break apart the atoms of coal? You may think it would take a
sledgehammer, but actually all it takes is water and heat. Heat coal hot
enough inside a big metal vessel, blast it with steam (the water), and it
breaks apart. Into what?
carbon atoms join with oxygen that is in the air (or pure oxygen can be
injected into the vessel). The hydrogen atoms join with each other. The
result is a mixture of carbon monoxide and hydrogen a gas.
what do you do with the gas?
can burn it and uses the hot combustion gases to spin a gas turbine to
generate electricity. The exhaust gases coming out of the gas turbine are
hot enough to boil water to make steam that can spin another type of
turbine to generate even more electricity. But why go to all the trouble
to turn the coal into gas if all you are going to do is burn it?
major reason is that the impurities in coal like sulfur, nitrogen and
many other trace elements can be almost entirely filtered out when
coal is changed into a gas (a process called gasification). In
fact, scientists have ways to remove 99.9% of the sulfur and small dirt
particles from the coal gas. Gasifying coal is one of the best ways to
clean pollutants out of coal.
reason is that the coal gases carbon monoxide and hydrogen don't
have to be burned. They can also be used as valuable chemicals. Scientists
have developed chemical reactions that turn carbon monoxide and hydrogen
into everything from liquid fuels for cars and trucks to plastic
West Terre Haute
, there are power plants generating electricity by gasifying coal, rather
than burning it. At a plant in
, coal gas is being used to make plastic for photographic film and to make
methanol (a fuel that can be burned in automobile engines).
gasification could be one of the most promising ways to use coal in the
future to generate electricity and other valuable products. Yet, it is
only one of an entirely new family of energy processes called "Clean
Coal Technologies" technologies that can make fossil fuels future
is Fluidized Bed Combustion?
beds suspend solid fuels on upward-blowing jets of air during the
combustion process. The result is a turbulent mixing of gas and solids.
The tumbling action, much like a bubbling fluid, provides more effective
chemical reactions and heat transfer. Fluidized
bed combustion evolved from efforts to find a combustion process able
to control pollutant emissions without external emission controls (such as
scrubbers). The technology burns fuel at temperatures of 1,400 to 1,700
degrees F, well below the threshold where nitrogen oxides form (at
approximately 2,500 degrees F, the nitrogen and oxygen atoms in the
combustion air combine to form nitrogen oxide pollutants).
The mixing action of the fluidized bed results brings the flue gases into
contact with a sulfur-absorbing chemical, such as limestone or dolomite.
More than 95 percent of the sulfur pollutants in coal can be captured
inside the boiler by the sorbent.
(PFBC) builds on earlier work in atmospheric fluidized-bed combustion
technology. Atmospheric fluidized bed combustion is crossing over the
commercial threshold, with most boiler manufacturers currently offering
fluidized bed boilers as a standard package. This success is largely due
to the Clean Coal Technology Program and the Energy Department's Fossil
Energy and industry partners R&D.
The popularity of Fluidized
is due largely to the technology's fuel flexibility - almost any
combustible material, from coal to municipal waste, can be burned - and
the capability of meeting sulfur dioxide and nitrogen oxide emission
standards without the need for expensive add-on controls.
The Clean Coal Technology Program
led to the initial market entry of 1st generation pressurized fluidized
bed technology, with an estimated 1000 megawatts of capacity installed
worldwide. These systems pressurize the fluidized bed to generate
sufficient flue gas energy to drive a gas turbine and operate it in a
The 1st generation pressurized fluidized bed combustor uses a
"bubbling-bed" technology (The joint Energy Department-American
Electric Power Clean Coal Technology
project at the Tidd Plant in Ohio used bubbling bed technology). A
relatively stationary fluidized bed is established in the boiler using low
air velocities to fluidize the material, and a heat exchanger (boiler tube
bundle) immersed in the bed to generate steam. Cyclone separators are used
to remove particulate matter from the flue gas prior to entering a gas
turbine, which is designed to accept a moderate amount of particulate
matter (i.e., "ruggedized").
A 2nd generation pressurized fluidized bed combustor uses
"circulating fluidized-bed" technology and a number of
efficiency enhancement measures. Circulating fluidized-bed technology has
the potential to improve operational characteristics by using higher air
flows to entrain and move the bed material, and recirculating nearly all
the bed material with adjacent high-volume, hot cyclone separators. The
relatively clean flue gas goes on to the heat exchanger. This approach
theoretically simplifies feed design, extends the contact between sorbent
and flue gas, reduces likelihood of heat exchanger tube erosion, and
improves SO2 capture and combustion efficiency.
A major efficiency enhancing measure for 2nd generation pressurized
fluidized bed combustor is the integration of a coal gasifier (carbonizer)
to produce a fuel gas. This fuel gas is combusted in a topping combustor
and adds to the combustor's flue gas energy entering the gas turbine,
which is the more efficient portion of the combined cycle. The topping
combustor must exhibit flame stability in combusting low-Btu gas and low-NOx
emission characteristics. To take maximum advantage of the increasingly
efficient commercial gas turbines, the high-energy gas leaving the topping
combustor must be nearly free of particulate matter and alkali/sulfur
content. Also, releases to the environment from the pressurized fluid bed
combustion system must be essentially free of mercury, a soon-to-be
regulated hazardous air pollutant.
To reduce cost and carbon dioxide emissions, new sorbents are being
evaluated. Sorbent utilization has a major influence on operating costs,
and carbon dioxide emissions streams can result in the production and use
of alkali-based sorbents.
Efforts are ongoing at the Power Systems Development Facility (PSDF) in
Wilsonville, Alabama to ensure critical components and subsystems are
ready for demonstration of 2nd generation pressurized fluidized bed
combustion. The PSDF is operated by Southern Company Services under DOE
contract to conduct cooperative R&D with industry.
Tests conducted at the PSDF in 1998 verified that a newly developed
multi-annular swirl burner (MASB) provided the needed flame stability and
low-NOx performance characteristics. Tests of promising new hot gas filter
components and systems are continuing at the PSDF. Advances made to date
in this critical technology area include the development of clay-bonded
silicon carbide candle filters and the associated filter vessel. Efforts
are currently focused on improved candle filter materials for enhanced
durability under extreme temperatures and corrosive environment. New
ceramics and ceramic-metallic composites are showing promise. Those
passing laboratory screening tests will undergo testing at the PSDF.
Some of the above information from the Department of Energy
website with permission