IGCC Technology: A Promising – and Complex – Solution
by Steven Edwards, Senior Vice President and Managing Director
Americas Region
and Rich Chapman, Vice President, Consulting Engineering Services
Strategic Projects
Black & Veatch Corporation
By 2010, the United States will need new base-load generation. Given the
lengthy planning, permitting and construction process for new generation
facilities, utilities are making their fuel-source evaluations now. Volatility
of natural gas supply and price is forcing companies to consider all alternatives,
including nuclear, renewables and coal. Environmental concerns are exerting
additional pressure on traditional coal plants, driving interest in newer,
cleaner technologies.
Black & Veatch expects that coal will continue to play a significant
role in meeting the country's energy needs for power generation,
even for transportation fuel synthesis. The coal-fueled power generation
plants being planned today will provide cleaner, more efficient and more
reliable power from an energy source that is plentiful in the United States.
Technologies for cleaner, more efficient coal plants are currently available,
including advanced pulverized coal, circulating fluidized bed and integrated
gasification combined cycle (IGCC) technologies, making coal a sensible
choice for present and future energy-producing strategies. IGCC has recently
become of particular interest because of its potential for providing significant
environmental benefits.
With their combination of high efficiency, low emissions and potential
to utilize a variety of fuel types, the gasification technologies associated
with IGCC have merited significant capital and engineering investment
from energy industry leaders such as ConocoPhillips, GE and Shell. However,
IGCC adds a level of complexity to power generation that demands a broad-based
and in-depth evaluation.
Performance Considerations
IGCC utilizes two steps to efficiently convert coal to electricity.
• In the first step, coal is converted by gasification into a synthetic
gas ("syngas"). Heat from the gasifier is captured as steam
for use in power generation. This first step is rounded out with gas treating,
which scrubs pollutants and particulates from the syngas in preparation
for the power-generation step.
• In the second step, clean syngas is burned in a combustion turbine
to generate electricity. Waste heat from the combustion turbine is recovered
and used to generate steam, which feeds a steam turbine generator for
additional electrical generation.
The "I" in IGCC comes from three primary areas of integration:
air extraction from the combustion turbine, steam generation and utilization
of nitrogen. Auxiliary electrical consumption within the plant is partially
optimized by extracting compressed air from the combustion turbine for
use in the plant's air-separation processes. Various waste-heat
streams are used to raise steam for power generation and required process
heating within the plant. Nitrogen produced in the course of generating
oxygen required by the gasifier is used to minimize nitrogen oxide (NOx)
emissions from the combustion turbine, which also increases the power
output. This integration contributes to the efficiency of IGCC.
As compared to conventional coal-fueled generation, the IGCC process requires
less water and produces less waste, much of which is produced in a form
that is more environmentally benign than ash. Reduced emissions are another
key benefit of IGCC. Gasification produces raw syngas, which is then treated
to remove contaminants. The clean syngas is fed into the combustion turbine,
producing emissions approaching those from natural gas combustion.
Connection to Coal and Other Feedstocks
What does this mean for coal? Coal is the most plentiful fossil fuel on
Earth. In the United States, it accounts for more than 90 percent of recoverable
fossil fuel reserves. It has been estimated that at current rates of recovery
and use, America's coal reserves would last about 200 years. Thanks
to the potential of clean-coal technologies, such as advanced pulverized
coal and circulating fluidized bed units as well as IGCC, it is possible
to utilize coal more effectively while significantly reducing emissions
and greenhouse gases.
In addition to coal, other feedstocks can be gasified in IGCC systems,
depending on the type of gasifier used. This is an important point and
has implications for the continuing development and commercial potential
of IGCC. Potential fuels include petroleum coke, heavy fuel-oil, biomass
and municipal sludge. All of the major gasification technologies can gasify
solid feedstocks, though some use solids-water slurry to fuel the gasifier.
Some can also use liquid feedstocks. In general, gasifiers can be designed
to handle a large variety of feedstocks. Low-quality "opportunity
fuels" that have high sulfur and metals content, such as petroleum
coke, are also well-suited for gasification because the process allows
superior environmental performance for these fuels.
Existing Facilities
Four commercial-sized, coal-fueled IGCC plants are currently in operation:
two in Europe and two in the United States.
The first such plant started up in 1993 in Buggenum, Netherlands, with
an electrical output of 250 megawatts (MW). A similar plant in Puertollano,
Spain, uses a mixture of coal and petroleum coke. Its output is 320 MW.
In the United States, Polk Power Station in Polk County, Florida, operates
a gasifier that originally used only coal, but now uses a blend of coal
and petroleum coke. The station's output is 250 MW. The Wabash River
plant in Terre Haute, Indiana, also uses both coal and petroleum coke,
with an output of 262 MW.
Barriers to Using IGCC
Aside from the efficiency and emissions advantages of IGCC, there are
barriers keeping IGCC from becoming widely implemented:
Cost. Capital and non-fuel operating costs for IGCC are currently higher
than conventional PC and CFB plants with present-day emissions controls.
As future air emissions standards increase the cost of air quality controls
for conventional coal technologies, the cost gap will likely be reduced.
The development of larger and more efficient advanced combustion turbines
as well as other technology advances, such as in air separation processes,
are also expected to narrow the cost gap. Regardless, the capital cost
is a barrier for current generation planning.
Consistency. Reliability has been another challenge. IGCC availability
has not yet been demonstrated to be comparable to that of top-performing
pulverized coal units. Low availablity was a demonstrated problem during
the first few years of operation at the four commercial coal-fueled IGCC
plants. Solids-related problems, such as erosion, plugging, unstable flows,
syngas cooler leaks and gasifier maintenance, have caused significant
downtime for existing IGCC power generation plants. They have also encountered
combustion turbine problems related to syngas combustion and startup air
extraction. It is worth noting, however, that plant modifications and
operations and maintenance alterations have resulted in significantly
improved performance and reliability.
Complexity. Relatively few plants have been built recently as IGCC technology
continues to be developed and refined. Often, the uncertainty of an emerging
technology such as IGCC serves as a roadblock to implementation unless
significant incentives, such as tax credits and loan guarantees, are available
to mitigate an owner's financial risk.
Additionally, capable engineering, procurement and construction (EPC)
contractors are becoming resource-constrained due to robust energy markets
in the United States. Compounding this issue, few companies have strong
in-house gasification expertise. As a result, there is a limited pool
of qualified contractors willing to execute these complex projects under
EPC contract conditions.
Another barrier regarding IGCC exists between integration and operational
simplicity. The more highly integrated a system, the more complex it is
to operate. From the perspective of a traditional utility, the operational
requirements of an IGCC plant present additional operating complexities.
A Promising Future
The U.S. Department of Energy (DOE) has committed to a 10-year, $2 billion
clean-coal research initiative, and IGCC is central to the nation's
pursuit of clean-coal technologies. Commercial projects using opportunity
fuels and DOE-supported, coal-fed projects will yield operational and
technological advances during this next phase of developments, and those
improvements will help coal-fueled IGCC become more competitive as a technology
of choice.
Coal gasification and IGCC are commercial technologies that offer strong
efficiency, high environmental performance and fuel flexibility, providing
fuel price control options for plant operators. Coal gasification is a
technology that can be applied to more than just electricity generation.
It also has demonstrated applications in coal-to-liquids and synthetic
natural gas production, which have the potential to provide domestic fuel
supplies. It is reasonable to think that current activity in coal gasification
and IGCC will enable the technology to become a widely applied alternative
for coal-fueled power generation and a key piece in the long-term energy
solutions for the United States.
Steven Edwards is senior vice president and Americas regional director
for Black & Veatch. He is responsible for all aspects of the region's
operations and performance, including planning, policy and financial results.
Mr. Edwards has been associated with projects for electric utilities throughout
his career. His extensive background encompasses domestic and international
engineering, procurement and construction (EPC) projects as well as executive
business unit level administrative duties.
Rich Chapman is a Black & Veatch vice president and project director.
Mr. Chapman is responsible for services associated with clean coal technologies
projects, including gasification technologies. He has provided project
management and engineering services on numerous steam plants, combustion
turbine, gasification/IGCC and retrofit projects, both in EPC and traditional
engineering roles, and is involved with several technology assessments,
design studies and continuing consultation assignments for clients considering
gasification and IGCC technologies.
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