In September 2008, a milestone was reached in the development of a coal gasification power plant. A pilot plant, making extensive use of resources from Mitsubishi Heavy Industries, proved its high reliability by achieving 2,000 hours of continuous operation from June 2008, during the three summer months when electricity demand normally peaks. The technology involved in the power plant is called ?½gIntegrated Gasification Combined Cycle?½h (IGCC), and is a new coal-fired power generation method with several advantages. Yuichiro Kitagawa,Manager, Boiler Engineering Department, Power Systems HQ

Combined cycle power plants have been around for several years. How is the IGCC plant different? A combined cycle power plant is a high-efficiency electric power generation system using relatively clean, but increasingly expensive oil or natural gas. Coal, which is used in the IGCC system, on the other hand, costs less to purchase and supply is stable.       In an IGCC system, a coal gasifier and a gas clean-up system are installed in the fuel section. These systems create cleaned synthesis gas that is supplied to a gas turbine, enabling coal to be burned as a gas the way natural gas is burned in a combined cycle plant.

		What are the advantages of IGCC?
The chief advantage is that by burning coal in a combined cycle plant, one attains higher efficiency than a conventional pulverized coal-fired steam power plant. There are also other advantages as follows: 1. High thermal efficiency In addition to IGCC having higher efficiency than a conventional pulverized coal-fired steam power plant, as mentioned above, the air-blown gasifier undergoing operational testing in the IGCC system is characterized by high transmission end efficiency, because it consumes less power than oxygen-blown gasifiers. Therefore, the net thermal efficiency of commercial IGCC plants using 1,500?½?½C class gas turbines would be about 20% higher compared with conventional pulverized coal-fired plants. 2. High environmental performance Emissions of CO2, nitrogen oxides (NOX), sulfur oxides (SOX) and dust are sharply reduced due to the high thermal efficiency. 3. Flexible coal sourcing IGCC can burn low-grade coal, which is unsuitable for burning in conventional pulverized coal-fired boilers due to lower ash fusion temperatures and higher moisture content. This means that coal can be much more flexibly sourced. 4. Better coal ash disposal Coal ash, which occupies half the volume of fly ash from conventional pulverized coal-fired plants, is discharged in the form of glass-like slag and therefore causes no leaching of trace elements into groundwater.

		How did the IGCC plant come about?
In Japan, the development of original air-blown IGCC technology has been advanced as a national project since 1986. 11 Japanese corporations, including nine regional utilities and other organizations, are conducting joint research on IGCC systems.       This association operated a 200 ton/day (equivalent to 25 MW) pilot plant from 1991 to 1996 to improve the reliability and performance of an air-blown IGCC system. This was then followed by feasibility studies and trial design studies for a larger 250 MW demonstration plant in Iwaki City, Fukushima Prefecture. Clean Coal Power R&D, established in 2001 to undertake operational testing, began construction in 2004, and has been conducting actual operational testing since 2007.       MHI provided a set of essential systems together with civil engineering and construction, including the plant?½fs gasifier, desulfurization system, gas turbine and steam turbine, and heat-recovery steam generator.       The continuous operation of the 250 MW plant achieved in 2008 is a huge step towards commercialization of a next-generation power plant that is both clean and highly efficient, even though it relies on a natural resource conventionally seen as an “environmental burden”?½\coal.

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