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Gasification technology has been in use for over 100 years from the "town gas" operations in the late 19th and early 20th centuries. The arrival of electricity displaced these first commercial gasification plants and the technology laid dormant until German scientists employed gasification to produce oil during WWII. In the early 1950s, gasification was revived for use in refineries to dispose of low value refinery byproducts for the production of hydrogen. It was also used in areas of the world to produce various chemical feed stocks. In the early 1970s, research was initiated on using solid fuel as the primary feedstock in the gasification process. By the late 1980s, gasification technology was then integrated with a combined cycle power plant to produce a high efficiency low-emission coal fueled power plant. As natural gas prices were rising in the 1970s, Shell, Texaco, and Dow Chemical each initiated research projects to develop solid fuel gasification technology to replace natural gas. These efforts culminated in building demonstration coal gasification projects in the early 1980s. Eastman Chemical Company built the first commercial scale coal gasification plant in 1984 at their Knoxville, Tennessee plant using syngas as a feedstock replacement for natural gas. This plant uses the Texaco gasification technology and has been in successful continuous operation for over 22 years. In the early 1990s, government supported efforts were initiated in the United States and Europe to build commercial coal gasification IGCC projects. Dow technology was applied at the Wabash, Indiana plant and Texaco technology at the Tampa, Florida Plant. Shell technology was utilized at the Buggenum plant in Europe. These projects were demonstration plants used to advance the technology and establish coal gasification as a viable, clean electric power generating option. Each project successfully expanded the knowledge base, and demonstrated the potential of the technology, and provided invaluable lessons for the commercialization of solid fuel gasification.
Wabash, Indiana Plant
Tampa, Florida Plant Three large scale IGCC projects fueled with liquid refinery wastes were built in Italy using Texaco technology in the late 1990s. These projects totaled 1,300 MW, and were successfully financed with over $3 billion of long-term, non-recourse financing. In the early 2000s, two petroleum coke fueled gasification projects were built in the United States, at Motiva and Coffeyville, with Texaco technology. The Negishi, Japan 342 MW IGCC plant was completed in 2003. This facility is fueled by refinery waste oils and uses the Texaco gasifier, Shell gas clean-up technology, and selective catalytic reduction NOx controls.
Negishi, Japan Siemens recently entered the gasification industry with its acquisition of Sustec Group's technology and engineering in May 2006. The company has been involved in power generation activities since the late 1920's. Siemens produces gas and steam turbines, generators, and electrical controls; now the company is taking this considerable experience to branch into cleaner energy solutions such as solar and wind power, fuel cells, and clean coal technologies including IGCC. The Sustec Group GSP gasification technology can use a wide range of fuel including biomass, coals, and petroleum coke. Siemens and Sustec already have several contracts for coal gasification projects in China. Siemens also plans to build a 1000 MW IGCC plant at the Spreetal, Saxony location to use and develop its newly acquired technology as quickly as possible. This plant is expected to begin commercial production in 2009. The term "gasification" refers to the process of converting carbon based feedstocks to synthetic gas, called "syngas." Gasification can use a wide range of fuels including coal, petroleum coke, biomass, oil refinery bottoms (waste oil), digester sludge, and virtually anything that contains carbon and can be fed into a gasification chamber. The high temperature (1,600 degrees C) melts the inert material and then flows to the bottom of the gasification vessel where it is cooled into a glass-like non-leachable inert slag. This slag is used primarily as aggregate in road gravel or concrete applications. The syngas contains small amounts of particulates, and various other elements that are not captured as slag including sulfur. These materials must be removed before the syngas is used. In electric power applications, where the syngas fuels a gas turbine, it has to be cleaned up to low contaminate levels. If particulates, sulfur, heavy metals, or any other pollutants are in the syngas, they can damage the gas turbine or the accompanying selective catalytic reduction system. Gasification Process Chart (.pdf) The emission limits in an IGCC power plant versus a solid fueled facility are significantly lower than any other technology. Sulfur scrubbing is in excess of 98 percent, with 99.9 percent scrubbing levels reached in certain circumstances. Particulates from the combustion of syngas, both PM10 and PM2.5, are almost non-existent. The primary particulate emissions are from the handling of bulk materials and the movement of people on the plant site. Virtually no metals or hazardous air products are emitted and instead are captured as inert slag or as small amounts of inert fly ash. Equipment vendors guarantee 90 percent mercury scrubbing efficiency and in practice virtually 100 percent is actually recovered. NOx emissions are also dramatically lower than those produced from a standard coal fired power plant. In a standard coal plant, limits of 25 ppm are common whereas a gasification power plant can meet limits of 15 ppm without scrubbing and can be reduced to below 5 ppm. A gasification plant integrated with a combined cycle electricity power plant comprise an IGCC facility. The total plant consists of four operating components: an air separation unit ("ASU"), a gasification plant, a gas clean-up system, and a combined cycle power plant. The ASU separates air into its component parts and sends the gasifier a stream of pure oxygen. The gasification plant then produces the syngas from a variety of fuels. Syngas is then piped through environmental control processes where pollutants and particulates are easily removed and this is called the "gas clean-up" phase of gasification. Afterwards, syngas can be cleanly burned in a combined cycle gas turbine. Combined cycle technology is composed of gas turbines, steam turbines, and their supporting infrastructure. The component parts of an IGCC plant are well established with thousands of ASUs, gas clean-up systems, and combined cycle power plants operational today. Approximately 360 gasifiers are operating in the world today. It is the integration of these well established technologies that has been the focus of extensive research over the last 20 years. There are now over 10 IGCC plants operating in the world with one to two years' operating experience. The integration of the gasification plant with a combined cycle power plant is the most efficient method currently available to convert solid fuel into electricity. An IGCC plant needs 10 to 20 percent less fuel than a large scale standard coal fired power plant and up to 35 percent less than a small scale industrial coal fired power plant. IGCC plants use about 30 percent less water than a coal fired power plant. Gas turbines do not require cooling, which greatly reduces the amount of water required. There are also no unusual smells or noise levels. IGCC plants are considerably smaller in physical size and footprint than a standard coal fired power plant. The buildings are much smaller, with the outside facilities consisting of mostly vessels and pipes. The gas turbine exhaust stack is the tallest structure and depending on the local terrain and dispersion modeling is typically 250 to 280 feet tall, as much as half the size of a standard coal fired power plant. Finally, IGCC plants have minimal need for landfills. The ash in the feedstock is recovered as marketable slag, or if there is a local cement market, some can be captured as salable ash. The sulfur is captured as elemental sulfur and sold to the fertilizer industry for agricultural use. The mercury is captured, encased in steel drums and sent to regulated hazardous material processing facilities for permanent disposal. No lime scrubbers are required. This lack of waste products greatly reduces the burden on the local landfill and reduces the impacts from trucks hauling such materials offsite. IGCC plants have an additional advantage not available through traditional combustion technology. IGCC plants can be designed to capture CO2 and make it available for disposal. These "greenhouse" gasses are rapidly becoming a concern for their potential impact on global warming. In a coal or gas fired power plant, CO2 can only be removed after combustion which is not economically feasible. However, CO2 may be removed before the syngas is fed to the gas turbines in IGCC plants. This is currently being done at gasification plants operating in refineries that remove CO2 to get pure hydrogen. The next frontier for power generation technology will be to use gasification to produce hydrogen as the sole power plant fuel and capture CO2 for disposal in deep underground reservoirs. If fuel cell technology becomes commercially viable, it may be possible to use the hydrogen from an IGCC facility in fuel cells and have pure water as the only emission. This is the vision of PowerGen, a zero-emission coal fueled power plant funded by the DOE , and it is the next step in the development of gasification based power plants. The movement to control CO2 emissions in the United States is rapidly gaining support. Without carbon control, IGCC is currently cost competitive with standard PC technology, and with carbon control IGCC becomes by far the least cost option. For more information about IGCC, go to www.gasification.org
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