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{{Original research|date=December 2022}}
<span lang="id" dir="ltr">An</span> '''integrated gasification combined cycle''' ('''IGCC''') is a technology using a high pressure gasifier to turn [[coal]] and other carbon based fuels into pressurized gas—synthesis gas ([[syngas]]). It can then remove impurities from the syngas prior to the [[electricity generation]] cycle. Some of these pollutants, such as sulfur, can be turned into re-usable byproducts through the [[Claus process]]. This results in lower emissions of [[sulfur dioxide]], particulates, [[mercury (element)|mercury]], and in some cases [[carbon dioxide]]. With additional process equipment, a [[water-gas shift reaction]] can increase gasification efficiency and reduce [[carbon monoxide]] emissions by converting it to carbon dioxide. The resulting carbon dioxide from the shift reaction can be separated, compressed, and stored through [[Carbon sequestration|sequestration]]. Excess heat from the primary combustion and syngas fired generation is then passed to a [[steam cycle]], similar to a [[combined cycle gas turbine]]. This process results in improved thermodynamic efficiency, compared to conventional [[pulverized coal]] combustion.
==Significance==
Coal can be found in abundance in the USA and many other countries and its price has remained relatively constant in recent years. Of the traditional hydrocarbon fuels - [[oil]], [[coal]], and [[natural gas]] - coal is used as a feedstock for 40% of global electricity generation. Fossil fuel consumption and its contribution to large-scale {{CO2}} emissions is becoming a pressing issue because of the adverse [[
==Operations==
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In this example the syngas produced is used as fuel in a gas turbine which produces electrical power. In a normal combined cycle, so-called "waste heat" from the gas turbine exhaust is used in a [[Heat Recovery Steam Generator]] (HRSG) to make steam for the steam turbine cycle. An IGCC plant improves the overall process efficiency by adding the higher-temperature steam produced by the gasification process to the steam turbine cycle. This steam is then used in steam turbines to produce additional electrical power.
IGCC plants are advantageous in comparison to conventional coal power plants due to their high [[thermal efficiency]], low non-carbon greenhouse gas emissions, and capability to process low grade coal. The disadvantages include higher capital and maintenance costs, and the amount of {{CO2}} released without pre-combustion capture.<ref name="Padurean2011">{{cite journal|last1=Padurean|first1=Anamaria|title=Pre-combustion carbon dioxide capture by gas–liquid absorption for Integrated Gasification Combined Cycle power plants|journal=International Journal of Greenhouse Gas Control|date=5 July 2011|volume=7|page=1|url=https://www.researchgate.net/publication/271560078|access-date=28 April 2016|doi=10.1016/j.ijggc.2011.12.007}}</ref>
==Process overview==
* The solid coal is gasified to produce syngas, or synthetic gas. Syngas is synthesized by gasifying coal in a closed pressurized reactor with a shortage of oxygen. The shortage of oxygen ensures that coal is broken down by the heat and pressure as opposed to burning completely. The chemical reaction between coal and oxygen produces a product that is a mixture of carbon and hydrogen, or syngas. C<sub>x</sub>H<sub>y</sub> + (x/2)O<sub>2</sub> → (x)CO
* The heat from the production of syngas is used to produce steam from cooling water which is then used for [[steam turbine]] electricity production.
* The syngas must go through a pre-combustion separation process to remove CO<sub>2</sub> and other impurities to produce a more purified fuel. Three steps are necessary for the separation of impurities:<ref>{{cite journal|last1=Stephens|first1=Jennie C.|title=Coupling CO<sub>2</sub> Capture and Storage with Coal Gasification: Defining "Sequestration-Ready" IGCC|journal=Energy Technology Innovation Project, Harvard University|date=May 2, 2005|url=https://www.netl.doe.gov/publications/proceedings/05/carbon-seq/Tech%20Session%20Paper%20144.pdf|access-date=1 May 2016}}</ref>
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==Benefits and drawbacks==
A major drawback of using coal as a fuel source is the emission of carbon dioxide and pollutants, including sulfur dioxide, nitrogen oxide, mercury, and particulates. Almost all coal-fired power plants use pulverized coal combustion, which grinds the coal to increase the surface area, burns it to make steam, and runs the steam through a turbine to generate electricity. Pulverized coal plants can only capture carbon dioxide after combustion when it is diluted and harder to separate. In comparison, gasification in IGCC allows for separation and capture of the concentrated and pressurized carbon dioxide before combustion. Syngas cleanup includes filters to remove bulk particulates, scrubbing to remove fine particulates, and solid adsorbents for mercury removal. Additionally, hydrogen gas is used as fuel, which produces no pollutants under combustion.<ref>{{cite web|title=Syngas Composition for IGCC|url=http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition-igcc|website=National Energy Technology Laboratory|publisher=US Department of Energy|access-date=30 April 2016|archive-date=22 May 2022|archive-url=https://web.archive.org/web/20220522055652/http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition-igcc|url-status=dead}}</ref>
IGCC also consumes less water than traditional pulverized coal plants. In a pulverized coal plant, coal is burned to produce steam, which is then used to create electricity using a steam turbine. Then steam exhaust must then be condensed with cooling water, and water is lost by evaporation. In IGCC, water consumption is reduced by combustion in a gas turbine, which uses the generated heat to expand air and drive the turbine. Steam is only used to capture the heat from the combustion turbine exhaust for use in a secondary steam turbine. Currently, the major drawback is the high capital cost compared to other forms of power production.
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==Cost and reliability==
A key issue in implementing IGCC is its high capital cost, which prevents it from competing with other power plant technologies. Currently, ordinary pulverized coal plants are the lowest cost power plant option. The advantage of IGCC comes from the ease of retrofitting existing power plants that could offset the high [[capital cost]]. In a 2007 model, IGCC with CCS is the lowest-cost system in all cases. This model compared estimations of [[levelized cost of electricity]], showing IGCC with CCS to cost 71.9 $US2005/MWh, pulverized coal with CCS to cost 88 $US2005/MWh, and natural gas combined cycle with CCS to cost 80.6 $US2005/MWh. The levelized cost of electricity was noticeably sensitive to the price of natural gas and the inclusion of carbon storage and transport costs.<ref>{{cite journal|last1=Rubin|first1=Edward|title=Cost and performance of fossil fuel power plants with CO2 capture and storage|journal=Energy Policy|date=26 April 2007|volume=35|issue=9|pages=4444–4454|doi=10.1016/j.enpol.2007.03.009|url=https://www.cmu.edu/epp/iecm/IECM_Publications/2007b%20Rubin%20et%20al,%20Energy%20Policy%20(Mar).pdf|access-date=5 May 2016|archive-url=https://web.archive.org/web/20100525004823/http://www.cmu.edu/epp/iecm/IECM_Publications/2007b%20Rubin%20et%20al,%20Energy%20Policy%20(Mar).pdf|archive-date=2010-05-25|url-status=dead}}</ref>
The potential benefit of retrofitting has so far, not offset the cost of IGCC with carbon capture technology. A 2013 report by the U.S. Energy Information Administration demonstrates that the overnight cost of IGCC with CCS has increased 19% since 2010. Amongst the three power plant types, pulverized coal with CCS has an overnight capital cost of $5,227 (2012 dollars)/kW, IGCC with CCS has an overnight capital cost of $6,599 (2012 dollars)/kW, and natural gas combined cycle with CCS has an overnight capital cost of $2,095 (2012 dollars)/kW. Pulverized coal and [[NGCC]] costs did not change significantly since 2010. The report further relates that the 19% increase in IGCC cost is due to recent information from IGCC projects that have gone over budget and cost more than expected.<ref>{{cite web|title=Updated Capital Cost Estimates for Utility Scale Electricity Generating Plants|url=http://www.eia.gov/forecasts/capitalcost/#6|website=U.S. Energy Information Administration|publisher=U.S. Energy Information Administration|access-date=5 May 2016}}</ref>
Recent testimony in regulatory proceedings show the cost of IGCC to be twice that predicted by Goddell, from $96 to 104/
Wabash River was down repeatedly for long stretches due to gasifier problems. 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.
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# 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, which was commissioned in 1994 and closed in 2013,<ref>{{Cite web|url=https://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/nuon|title=nuon {{!}} netl.doe.gov|website=www.netl.doe.gov|language=en-US|access-date=2018-01-12}}</ref> had good availability. This coal-based IGCC plant was originally designed to use up to 30% biomass as a supplemental feedstock. The owner, NUON, was paid an incentive fee by the government to use the biomass. NUON has constructed a 1,311 MW IGCC plant in the Netherlands, comprising three 437 MW CCGT units. The Nuon Magnum IGCC power plant was commissioned in 2011, and was officially opened in June 2013. Mitsubishi Heavy Industries has been awarded to construct the power plant.<ref>[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 [[American Electric Power|AEP]], [[Duke Energy]], and [[Southern Company]] in the US, and in Europe by [[Kedzierzyn Zero-Emission Plant|ZAK/PKE]], [[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.)[20] 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 33%. For a natural gas CC, the increase is approximately 46%. For a pulverized coal plant, the increase is approximately 57%.<ref>{{cite journal|last1=Rubin|first1=Edward|title=Cost and performance of fossil fuel power plants with CO2 capture and storage|journal=Energy Policy|date=26 April 2007|volume=34|issue=9|pages=4444–4454|url=https://www.cmu.edu/epp/iecm/IECM_Publications/2007b%20Rubin%20et%20al,%20Energy%20Policy%20(Mar).pdf|access-date=5 May 2016|doi=10.1016/j.enpol.2007.03.009|archive-url=https://web.archive.org/web/20100525004823/http://www.cmu.edu/epp/iecm/IECM_Publications/2007b%20Rubin%20et%20al,%20Energy%20Policy%20(Mar).pdf|archive-date=2010-05-25|url-status=dead}}</ref> 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. However, the industry needs a lot more experience to reduce the risk premium. IGCC with CCS requires some sort of mandate, higher carbon market price, or regulatory framework to properly incentivize the industry.<ref>{{cite web|title=Costs and Challenges of CCS|url=http://www.fossiltransition.org/pages/costs_and_challenges/136.php|website=Clear Air Task Force|access-date=5 May 2016|archive-date=28 June 2016|archive-url=https://web.archive.org/web/20160628174404/http://www.fossiltransition.org/pages/costs_and_challenges/136.php|url-status=dead}}</ref>
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 250 MW demo plant in Nakoso. 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)
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As a reference for powerplant efficiency:
* With Frame E gas turbine, 30bar quench gas cooling, Cold Temperature Gas Cleaning and 2 level HRSC it is possible to achieve around 38% [[Energy efficiency (physics)|energy efficiency]].
* With Frame F gas turbine, 60 bar quench gasifier, Cold Temperature Gas Cleaning and 3 level+RH HRSC it is possible to achieve around 45% energy efficiency.
* Latest development of Frame G gas turbines, ASU air integration, High temperature desulfurization may shift up performance even further.<ref>Analisi Termodinamica di cicli Igcc avanzati, G.Lozza P.Chiesa, Politecnico di Milano, ati2000 conference proceedings</ref>
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==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 CO<sub>2</sub> 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 [[emission intensity|carbon-intensive]] coal generation";<ref>{{cite web |url=http://www.marketwire.com/mw/rel_us_print.jsp?id=776699 |title=Archived copy |website=www.marketwire.com |access-date=17 January 2022 |archive-url=https://web.archive.org/web/20190831204856/http://www.marketwire.com/mw/rel_us_print.jsp?id=776699 |archive-date=31 August 2019 |url-status=dead}}</ref> U.S. Senator [[Hillary Clinton]] from New York has proposed that this full risk disclosure be required of all publicly traded power companies nationwide.<ref>[http://www.hillaryclinton.com/files/pdf/poweringamericasfuture.pdf
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, he claimed (no source attributed). "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."<ref>[http://publicutilities.utah.gov/news/cleanenergysummitreidopposescoal.pdf
One of the most efficient ways to treat the H<sub>2</sub>S gas from an IGCC plant is by converting it into sulphuric acid in a wet gas sulphuric acid process [[Wet sulfuric acid process|WSA process]]. However, the majority of the H<sub>2</sub>S treating plants utilize the modified Claus process, as the sulphur market infrastructure and the transportation costs of sulphuric acid versus sulphur are in favour of sulphur production.
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