Integrated Gasification Combined Cycle

An Integrated Gasification Combined Cycle, or IGCC, is a power plant using synthetic gas (syngas). This gas is often used to power a gas turbine generator whose waste heat is passed to a steam turbine system (Combined cycle gas turbine).

Description

An Integrated Gasification Combined Cycle, or IGCC, is a technology that turns coal into gas - synthesis gas (syngas). It then removes impurities from the coal gas before it is combusted. This results in lower emissions of sulfur dioxide, particulates and mercury. It also results in improved efficiency compared to conventional pulverized coal. Because coal is the most abundant energy source for America and many other countries, the environmental benefits of this technology could be strategically important.POV-statement|date=September 2008 Below is a schematic flow diagram of an IGCC plant:

The gasification process can produce syngas from high-sulfur coal, heavy petroleum residues and biomass.

The plant is called "integrated" because its syngas is produced in a gasification unit in the plant which has been optimized for the plant's combined cycle. In this example the syngas produced is used as fuel in a gas turbine which produces electrical power. To improve the overall process efficiency heat is recovered from both the gasification process and also the gas turbine exhaust in 'Waste Heat Boilers' producing steam. This steam is then used in steam turbines to produce additional electrical power.

There are currently (2007) only two IGCC plants generating power in the U.S.Fact|date=September 2008; however, several new IGCC plants are expected to come online in the U.S. in the 2012-2020 time frame. The [http://www.fossil.energy.gov/programs/powersystems/cleancoal/ DOE Clean Coal] Demonstration Project helped construct 3 IGCC plants: Wabash River Power Station in West Terre Haute, Indiana, Polk Power Station in Tampa, Florida (online 1996), and Pinon Pine in Reno, Nevada. In the Reno demonstration project, researchers found that then-current IGCC technology would not work more than 300 feet (100m) above sea level [Source: Joe Lucas, Executive Director of Americans for Balanced Energy Choices, as interviewed on NPR's Science Friday, Friday May 12, 2006] ] . The plant failed. [ [http://www.osti.gov/bridge/servlets/purl/805670-S8pCpG/native/805670.pdf Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI ] ]

The first generation of IGCC plants polluted less than contemporary coal-based technology, but also polluted water: For example, the Wabash River Plant was out of compliance with its water permit during 1998–2001. [ cite web
url= http://www.osti.gov/bridge/servlets/purl/787567-a64JvB/native/787567.pdf
title= Wabash River Coal Gasification Repowering Project Final Technical Report
accessdate= 2008-06-30
author= Wabash River Energy Ltd.
year= 2000
month= August
format= PDF
work= Work performed under Cooperative Agreement DE-FC21-92MC29310
publisher= The U.S. Department of Energy / Office of Fossil Energy / National Energy Technology Laboratory / Morgantown, West Virginia
quote= As a result, process waste water arising from use of the currentfeedstock, remains out of permit compliance due to elevated levels of arsenic, selenium and cyanide. To rectify these concerns, plant personnel have been working on several potential equipment modifications and treatment alternatives to bring the discharge back into compliance. Wabash River is currently obligated to resolve this issue by September of 2001. [p. ES-6] Elevated levels of selenium, cyanide and arsenic in the waste water have caused the process waste water to be out of permit compliance. Daily maximum values, though not indicated in the table above, were routinely exceeded for selenium and cyanide, and only occasionally for arsenic. [p. 6-14, Table 6.1L] ] because it emitted arsenic, selenium and cyanide. The Wabash River Generating Station is now wholly owned and operated by the Wabash River Power Association.

IGCC is now touted as "capture ready" and could potentially capture and store carbon dioxide. (See FutureGen)

Cost and reliability

The main problem for IGCC is its extremely high capital cost, upwards of $3,593/kW [Excelsior's Mesaba Project] . Official US government figures give more optimistic estimates [http://www.eia.doe.gov/oiaf/aeo/assumption/pdf/electricity.pdf#page=3] of $1491/kw installed capacity (2005 dollars) v $1290 for a conventional clean coal facility, but in light of current applications, these cost estimates have been demonstrated to be incorrect.

Outdated per megawatt-hour cost of an IGCC plant vs. a pulverized coal plant coming online in 2010 would be $56 vs $52, and it is claimed that IGCC becomes even more attractive when you include the costs of carbon capture and sequestration, IGCC becoming $79 per megawatt-hour vs. $95 per megawatt-hour for pulverized coal. [ Goodell, Jeff. "Big Coal." pg. 214. New York, Houghton Mifflin. 2006] Recent testimony in regulatory proceedings show the cost of IGCC to be twice that predicted by Goddell, from $96 to 104/MWhr. [ Testimony of Dr. Elion Amit, Minnesota Dept. of Commerce.] [http://www.mncoalgasplant.com/puc/05-1993%20pub%20rebuttal.pdf.] That's before addition of capital intensive and efficiency sucking carbon capture and sequestration (sequestration is not available or probable on commercial level) -- capture at a 30% rate is expected to have a $50/MWhr additional cost. Id.

Wabash River was down repeatedly for long stretches due to gasifier problems, and the gasifier problems have not been remedied -- subsequent projects, such as Excelsior's Mesaba Project, have a third gasifier and train built in. However, the past year has seen Wabash River running reliably, with availability comparable to or better than other technologies.

General Electric is currently designing an IGCC model plant that should introduce greater reliability. GE's model features advanced turbines optimized for the coal syngas. Eastman's industrial gasification plant in Kingsport, TN uses a GE Energy solid-fed gasifier. Eastman, a fortune 500 company, built the facility in 1983 without any state or federal subsidies and turns a profit. [ Goodell, Jeff. "Big Coal." New York, Houghton Mifflin. 2006] [ [http://www.eastman.com/ Eastman - Eastman Chemical Company - Home Page ] ]

There are several refinery-based IGCC plants in Europe that have demonstrated good availability (90-95%) after initial shakedown periods. Several factors help this performance:

# None of these facilities use advanced technology ("F" type) gas turbines.
# All refinery-based plants use refinery residues, rather than coal, as the feedstock. This eliminates coal handling and coal preparation equipment and its problems. Also, there is a much lower level of ash produced in the gasifier, which reduces cleanup and downtime in its gas cooling and cleaning stages.
# These non-utility plants have recognized the need to treat the gasification system as an up-front chemical processing plant, and have reorganized their operating staff accordingly.

Another IGCC success story has been the 250 MW Buggenum plant in The Netherlands. It also has good availability. This coal-based IGCC plant currently uses about 30% biomass as a supplemental feedstock. The owner, NUON, is paid an incentive fee by the government to use the biomass. NUON is contructing a 1300 MW IGCC plant in the Netherlands. The Nuon Magnum IGCC power plant wil commissioned in 2011. MItsubishi Heavy Industrie has been awarded to construct the power plant. http://www.nuon.com/about-nuon/Innovative-projects/magnum.jsp

A new generation of IGCC-based coal-fired power plants has been proposed, although none is yet under construction. Projects are being developed by AEP, Duke Energy, and Southern Company in the US, and in Europe, by Centrica (UK), E.ON and RWE (both Germany) and NUON (Netherlands). In Minnesota, the state's Dept. of Commerce analysis found IGCC to have the highest cost, with an emissions profile not significantly better than pulverized coal. In Delaware, the Delmarva and state consultant analysis had essentially the same results.

The high cost of IGCC is the biggest obstacle to its integration in the power market; however, most energy executives recognize that carbon regulation is coming soon. Bills requiring carbon reduction are being proposed again both the House and the Senate, and with the Democratic majority it seems likely that with the next President there will be a greater push for carbon regulation. The Supreme Court decision requiring the EPA to regulate carbon (Commonwealth of Massachusetts et al. v. Environmental Protection Agency et al.) [ [http://supreme.lp.findlaw.com/supreme_court/docket/2006/november/05-1120-massachusetts-v-environmental-protection-agency.html Massachusetts, et al. v. Environmental Protection Agency, 05-1120 - FindLaw US Supreme Court Center ] ] also speaks to the likelihood of future carbon regulations coming sooner, rather than later. With carbon capture, the cost of electricity from an IGCC plant would increase approximately 30%. For a natural gas CC, the increase is approximately 33%. For a pulverized coal plant, the increase is approximately 68%. This potential for less expensive carbon capture makes IGCC an attractive choice for keeping low cost coal an available fuel source in a carbon constrained world.

In Japan, electric power companies, in conjunction with Mitsubishi Heavy Industries has been operating a 200 t/d IGCC pilot plant since the early '90s. In September 2007 they started up a 250mw demo plant in Nakaso. It runs on air-blown (not oxygen) dry feed coal only. It burns PRB coal with an unburned carbon content ratio of < 0.1% and no detected leaching of trace elements. It employs not only "F" type turbines but "G" type as well. (see gasification.org link below)

"Next generation IGCC plants with CO2 capture technology will be expected to have higher thermal efficiency and to hold the cost down because of simplified systems compared to conventional IGCC. The main feature is that instead of using oxygen and nitrogen to gasify coal, they use oxygen and CO2. The main advantage is that it is possible to improve the performance of cold gas efficiency and to reduce the unburned carbon (char).

With a 1300 degrees C class gas turbine it is possible to achieve 42% net thermal efficiency, rising to 45% with a 1500 degree class gas turbine, with CO2 capture. In case of conventional IGCC systems, it is only possible to achieve just over 30% efficiency with a 1300 degree gas turbine.

The CO2 extracted from gas turbine exhaust gas is utilized in this system. Using a closed gas turbine system capable of capturing the CO2 by direct compression and liquefication obviates the need for a separation and capture system." [ Inumaru,Jun - senior research scientist, Central Research Institute of Electric Power Industry (CRIEPI)(Japan) G8 Energy Ministerial Meeting Symposium, Nikkei Weekly.

Recent Emerging IGCC Emission Controversy

In 2007, the New York State Attorney General's office demanded full disclosure of "financial risks from greenhouse gases" to the shareholders of electric power companies proposing the development of IGCC coal-fired power plants. “Any one of the several new or likely regulatory initiatives for CO₂ emissions from power plants - including state carbon controls, EPA's regulations under the Clean Air Act, or the enactment of federal global warming legislation - would add a significant cost to carbon-intensive coal generation” [http://www.marketwire.com/mw/rel_us_print.jsp?id=776699] ); U.S. Senator Hillary Clinton from New York, a 2008 Presidential Candidate, has proposed that this full risk disclosure be required of all publicly-traded power companies nationwide. [http://www.hillaryclinton.com/files/pdf/poweringamericasfuture.pdf] This honest disclosure has begun to reduce investor interest in all types of existing-technology coal-fired power plant development, including IGCC.

Senator Harry Reid (Majority Leader of the 2007/2008 U.S. Senate) told the 2007 Clean Energy Summit that he will do everything he can to stop construction of proposed new IGCC coal-fired electric power plants in Nevada. Reid wants Nevada utility companies to invest in solar energy, wind energy and geothermal energy instead of coal technologies. Reid stated that global warming is a reality, and just one proposed coal-fired plant would contribute to it by burning seven million tons of coal a year. The long-term healthcare costs would be far too high. "I'm going to do everything I can to stop these plants," he said. "There is no clean coal technology. There is cleaner coal technology, but there is no clean coal technology.” [http://publicutilities.utah.gov/news/cleanenergysummitreidopposescoal.pdf]

References

External links

* [http://www.powergeneration.siemens.com/en/press/pg200303017e/index.cfm Hunstown: Ireland's most efficient power plant] @ Siemens Power Generation website
* [http://www.westgov.org/wieb/electric/Transmission%20Protocol/SSG-WI/pnw_5pp_02.pdf Natural Gas Combined-cycle Gas Turbine Power Plants] Northwest Power Planning Council, New Resource Characterization for the Fifth Power Plan, August 2002
* [http://www.ingenia.org.uk/ingenia/articles.aspx?index=244&print=true Combined cycle solar power]