DOE - Fossil Energy Techline - Issued on: February 18, 1997
Fourth Clean Coal Plant to Win Powerplant Award Sets Record Operation for Coal Gasifier
Operators at the Wabash River Coal Gasification Power Plant in West Terre Haute, IN, have followed the plant's selection as Power magazine's 1996 Powerplant of the Year with the longest operating run of the gasifier to date.
In their September/October 1996 issue, Power magazine editors named the Indiana project as one of five power plant award winners for 1996 -- the fourth time since 1991 that a Department of Energy-sponsored Clean Coal Technology project has been cited for the prestigious award.
Beginning on December 10, 1996, and running through January 14, 1997, the Wabash project set a record of more than 500 hours of coal operation. This run represented the longest operating campaign of the gasifier to date. In addition, a new monthly record was set in December as the plant operated on coal for 372 hours.
Power magazine described the Wabash River project as demonstrating "a technology to bridge the millennium...being proven under the rigors of commercial service. An order-of-magnitude improvement in coal-fired plant performance comes with a step-change in complexity." The Powerplant Awards are given annually to recognize "leadership in the application of fresh ideas and new technology and equipment to minimize environmental impact and maximize efficiency."
As one of 40 government/industry funded projects in the Clean Coal Technology Program, the Wabash River project repowered the oldest of six pulverized coal units using a "next-generation" coal gasifier, an advanced gas turbine and a heat-recovery steam generator. Since it began operating in December 1995, the project has completed a year of its three-year commercial-scale demonstration phase with demonstration of full design syngas production and record low sulfur emissions in more than 1,250 hours on syngas in combined cycle mode.
The 265-megawatt Wabash River commercial-scale demonstration unit is a joint venture between Destec Energy, Inc. and PSI Energy, Inc. The project, selected by the U.S. Department of Energy in the fourth round of the Clean Coal Technology Program, is located at PSI Energy's Wabash River Generating Station, Unit 1, in West Terre Haute, Indiana.
Prior to Wabash River's 1996 award three other Clean Coal Technology Program projects received the Powerplant Award. In 1991 the award went to American Electric Power's Tidd Pressurized Fluidized-Bed Combustion Project. In 1993 the Pure Air on the Lake, L.P., Advanced Flue Gas Desulfurization Demonstration Project won the Powerplant Award and in 1994 it was presented to Southern Company Services, Inc.'s Innovative Applications of Technology for the CT-121 Flue Gas Desulfurization Process.
At the most recent Power magazine awards ceremony, the Wabash River project was joined by Virginia Power's North Anna nuclear plant, Florida Power & Light Co.'s Martin station, Interpower/Ahlcon Partners LP Colver power project, and Associated Electric Cooperative Inc.'s Thomas Hill/New Madrid stations as 1996 award winners.
The Wabash River facility is the largest single-train coal gasification unit in the world, and the first to operate an advanced gas turbine firing gasified coal. It is also the first to include high-temperature dry particulate removal at full commercial scale with no provision for bypass.
Advanced features of the gasifier include a particulate recycle loop, a high-pressure boiler to cool raw syngas, a slag fines recycle loop to enhance efficiency and byproduct slag quality, and fuel-gas moisturization to reduce the quantity of steam injected into the gas turbine to control NOx emissions.
"What also makes this a century turning technology," Power magazine said, "is that it takes a quantum leap towards exploiting coal for more than its energy content. Here, a raw material is converted into several marketable products steam, electricity, sulfur, and slag. Present-day economics do not necessarily value these capabilities, but with environmental pressures escalating, though not necessarily continuously, valuation may be different in the future."
Although only one-third of the way through its demonstration phase the Wabash River project achieved strategic performance goals very early in its initial operations. The operators first gasified coal at the plant on August 17, 1995 during the pre-operation setup phase of the technology demonstration -- even before the December 1995 official operation startup.
Within four months of that December startup the gasification plant had run for over 100 hours at or above design capacity. The first year has also shown total SO2 emissions at below 0.1 lb/million Btu. This is well below the Clean Air Act requirement of 1.2 Ib/million Btu. NOx emissions limitations -- 65 ppm on oil and 25 ppm on coal gas -- were also met during the first year of demonstration.
In order to achieve these goals the Wabash River system begins with ground coal, slurried with water, and gasified in a pressurized, two-stage (slagging first stage and nonslagging entrained-flow second stage), oxygen-blown, gasifier. The product gas is cooled through heat exchangers and passed through a conventional cold gas cleanup system which removes particulates, ammonia, and sulfur.
The clean, medium-Btu gas is then reheated and burned in an advanced 192 megawatt gas turbine. Hot exhaust from the gas turbine is passed through a heat recovery steam generator to produce high-pressure steam. High pressure steam is also produced from the gasification plant and superheated in the heat recovery steam generator. The combined high-pressure steam flow is supplied to an existing 104 megawatt steam turbine.
The demonstration unit is designed to use 2,544 tons/day of high-sulfur (2.3-5.9 percent sulfur), Illinois Basin bituminous coal. The design heat rate for the repowered unit is 9,034 Btu/kWh (approximately 38% efficiency).
During the first year of the demonstration, one of the most significant problems identified was in the gasification plant's particulate removal system. Further testing and modifications of filters are under way to correct the problem.
Once this technology has been demonstrated it will be available to serve a U. S. market of more than 95,000 megawatt of existing coal-fired utility boilers that reached more than 30 years of age in 1996, as well as plants in foreign markets. Many of these plants are without air pollution controls and are candidates for repowering with integrated gasification combined-cycle technology. Repowering these plants with IGCC systems will improve plant efficiencies and reduce SO2, NOx, and CO2 emissions.
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