In the 1960s, the U.S. Government initiated studies to determine if coal was feasible as a gas turbine fuel. In these tests, coal was pulverized and mixed with various liquids prior to being fired in a gas turbine combustor. The result of these tests was that gas turbines are not capable of directly combusting pulverized or slurried coal for electrical production.
Following up on the results of the tests in the 1960s, the U.S. Government sponsored studies which evaluated the potential for firing synthesis gas (syngas) produced via coal gasification in gas turbines. These studies, done in the 1970s, led directly to the first successful demonstration of the basic integrated gasification combined cycle (IGCC) concept at a commercial scale, the Cool Water Project, part of DOE's Clean Coal Technology (CCT) Program. The Cool Water Project was conducted in Southern California, and was a five-year R&D project running from 1984 through 1989. Texaco gasifier technology (now owned by GE) was used to produce syngas to feed a GE-7E gas turbine based combined cycle. A net power generation capacity of 96 MWe was achieved using bituminous coal as a fuel and 99.5% pure oxygen as the oxidant. The lessons learned in the Cool Water Project provided a sound basis for the advancement of IGCC design. Throughout the 1990s several commercial IGCC plants were put into operation as IGCC technology matured.
Described below are four operational, commercial-scale, coal9 IGCC plants, two in the U.S. and two in Europe. Each has been operational for well over a decade, experiencing similar availabilities (around 80%) and similar operational issues, including the fouling of heat exchangers.
Recent major IGCC projects recently begun or nearing commercial operation in the United States include the following two facilities:
Duke Energy Edwardsport IGCC Project1
In June of 2008, Duke Energy broke ground on a new IGCC plant in Edwardsport, Indiana. The project, which began commercial operations in June 2013, will be using 1.7-1.9 million tons of coal per year to generate 618 MW of base-load electricity. It is based on the GE Energy "Reference Plant" design2; main units consist of two GE gasifiers in parallel, two GE 7FB combustion turbines in parallel (232 MWe each), and one GE steam turbine (320 MWe). The IGCC plant replaces a now demolished 160 MW coal-fired power plant at the site. The new IGCC plant is cleaner than the old plant while providing more power; SOx, NOx, and particulate emissions are well under new source limits as illustrated3:
In addition, activated carbon beds for mercury removal will be utilized, and no thermal discharge will occur to the adjacent White River. In reference to CO2 emissions, there is potential for carbon capture and geologic sequestration in the context of the Edwardsport IGCC project. Space has been reserved at the site for CO2 capture equipment. Also, Duke has initiated a front-end engineering and design study for carbon capture and filed a $121 million request with Indiana Utility Regulatory Commission for detailed characterization of deep saline aquifers, depleted oil or gas fields, and enhanced oil recovery. Schlumberger Carbon Services is to begin site assessment for deep saline sequestration near the plant. Total installed costs for the project are estimated at $3.55 billion4.
Kemper County IGCC Project
Southern Company Services/Mississippi Power started construction on a new IGCC plant located in Kemper County, Mississippi in December of 2010. Start of commercial operations for the plant is scheduled for 2017, in which the plant will convert 12,000 tons of local Mississippi low-rank coal per day (large reserves of 4 billion tons of mineable lignite are located near the plant) to produce 582 MW (net) of electricity. The new plant will utilize KBR's TRIG™ gasifier technology, suitable for utilization of the local lignite resources; two of the gasifiers will operate in air-blown mode at the Kemper County plant.
TRIG™ and related systems for gasification of low-rank coal had been developed by KBR and Southern Company in conjunction with DOE at the Power Systems Development Facility (PSDF) in Wilsonville, Alabama, which comprised an engineering-scale demonstration of TRIG™ and associated critical subsystems. This provided the engineering and operational basis for the full-scale plant now being constructed in Kemper County.
The plant will capture and sequester 65% of the CO2 it produces through enhanced oil recovery. Emissions controls will remove over 99% SO2 and P25, at least 90% mercury, and limit NOx emissions to less than 0.07 lb/million Btu.
The Kemper County IGCC project costs have been recently revised to approximately $7.1 billion. Mississippi Power has received a $270 million grant from the Department of Energy and $412 million in investment tax credits approved by the IRS through the National Energy Policy Act of 2005 and the Energy Improvement and Extension Act of 20085.
Additional Examples of IGCC Projects
Among the many gasification projects in place worldwide, a few additional IGCC plants are particularly noteworthy:
In April of 2012, China Huaneng Group, together with Peabody Energy of St. Louis, Missouri, demonstrated the successful startup of an IGCC plant located in Tianjin City, Bohai Rim, China. During official operation, the plant will convert 2,000 tons of coal per day to 250 MW of electricity. The IGCC plant, using Chinese HCERI gasification technology, is the first phase of the GreenGen Project; the second phase currently underway involves a smaller pilot plant that will send a clean stream of hydrogen through fuel cells and turbines to produce electricity, with carbon dioxide being captured for industrial use. The third phase, scheduled for 2015–20, will be a 400 MW power plant with full-scale carbon capture and storage in underground rock layers (over 80% of produced CO2 captured and stored). Ultimately, with all phases, power production from the GreenGen Project will total about 650 MW6.
Nakoso, Japan IGCC Demonstration
Construction began on this pulverized coal IGCC demonstration plant in August 2004. The plant, which uses Mitsubishi Heavy Industries' (MHI's) two-stage entrained-flow, pressurized, air-blown gasifiers, is located at the Nakoso Power Station in Iwaki City, Fukushima, Japan. Clean Coal Power Research and Development (R&D) Corporation, Ltd. began development in 2001, with the goal of proving an IGCC design for commercial use on a wide variety of coals that Japan imports. The plant came online in late 2007, and has been operating since that time, consuming 1,700 TPD coal and producing 250 MWe gross.
The project uses cyclone and porous filters to remove and recycle char back to the combustor. MHI lists the system's carbon conversion efficiency at 99.8%. The syngas is cleaned of sulfur and other trace contaminants by a commercial MDEA and COS unit. The sulfur is further processed into a saleable byproduct: high-grade gypsum.
During the years of plant operation, operability, continuity of operation, environmental performance, load variation/change, durability, reliability, and maintainability have been evaluated/proven. Economic evaluation continues, along with interest in assessing carbon capture and storage in plant context. The facility was damaged by the March 2011 tsunami but recovered fully by the end of that year7. The demonstration project was finished in March 2013, and the Nakoso IGCC plant is now operated commercially by Joban Joint Power Company as a high efficiency power generating station.
Vresova, Czech Republic IGCC
In 1996, a former town gas plant in Vresova, Czech Republic, was reconfigured to use IGCC technology. The plant gasifies approximately 2,000 tons per day (tpd) of local lignite coal in 26 Lurgi-design fixed-bed gasifiers. The synthesis gas (syngas) is then fired in two 200 MWe combined-cycle power blocks (which use GE turbines) for a total power output of approximately 400 MW (Gasification Technology Council, 2008).
Syngas is cleaned, in part, by a Rectisol process unit. Acid gases from the Rectisol unit are used to produce sulfuric acid in a wet sulfuric acid (WSA) plant, added in 1993. Beyond electricity, the plant produces liquid byproducts like coal tar, phenol concentrate and liquid ammonia. Recently, a Siemens liquids gasifier was added to enable additional syngas production from these liquid byproducts, especially the coal tars. Economically this makes sense as the price of electricity is still higher than the value of the liquids. Additionally, gasifying the liquids allows for more syngas to be produced to counter the declining quality of coal from the local Sokolov mine8.
Finally, most of the foregoing examples and other IGCC facilities are examined in the following linked report, containing useful information and analysis:
2. Edwardsport IGCC - Moving Forward, Gasification Technologies Conference - (October 4-7, 2009)
3. Zeus Syngas Refining Report Vol. VIII, No. 21, 11/19/2012
5. Jeff Tollefson, Richard Van Noorden (2012). "Slow progress to cleaner coal". Nature (Nature Publishing Group) 484: 151-152. doi:10.1038/484151a
7. Benchmarking Biomass Gasification Technologies for Fuels, Chemicals and Hydrogen Production, Jared Ciferno and John Marano, National Energy Technology Laboratory, June 2002.
8. Wabash River and Tampa Electric plants originally used coal feedstock, but in more recent years Wabash River is gasifying petroleum coke (petcoke), and Tampa often includes petcoke in the feed mix.