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DOE - Fossil Energy Techline - Issued on: October 19, 1999 Bechtel Project Rids CO2 From Coal Gas Streams By Converting It To 'Ice'Could Help "Cool" Concerns Over Global WarmingCan cooling the hot gases of tomorrow's power plants provide a way to reduce global warming? The Department of Energy has awarded a contract to Bechtel National Inc., San Francisco, CA, to study a process that removes carbon dioxide, a greenhouse gas, from the gas streams of future energy plants by converting it to "ice" - or more correctly, into an ice-like hydrate. Hydrates are solid structures in which ice forms a crystalline latticework around molecules of entrapped gases. Methane hydrates - where methane, or natural gas, molecules are encased in the ice crystals - are known to exist naturally in Arctic regions or beneath the ocean. Now, the Energy Department wants to study whether the same hydrate-forming phenomenon that exists in Nature can be used in future power plants to separate carbon dioxide from the gases produced by a coal gasifier. The department is providing Bechtel $9 million for a 64-month research project. Bechtel will team with the Los Alamos National Laboratory, IPSI LLC, and SIMTECHE, the California company (Half Moon Bay, CA) which originally developed the innovative process. The department will also provide $5.3 million to Los Alamos for the laboratory's role in the project. The process is intended to be integrated with future coal gasification systems. Many technology experts predict that coal gasifiers -- rather than traditional coal combustors -- will form the core of advanced, 21st century, super-clean power plants. In a coal gasifier, coal is converted into a gaseous mixture of carbon monoxide and hydrogen. The carbon monoxide can be converted into carbon dioxide, or CO2, by a process called a "shift" reaction. To start the CO2 separation process, water would first be "nucleated" using high-pressure CO2 to form clusters of molecules ready to grab onto additional CO2. The nucleated water would be injected into the mainstream of coal-derived gas. CO2 hydrates would form in the water slurry at near-freezing temperatures and high pressures. Hydrogen gas, now separated from the ice-like CO2 hydrates, would continue to pass through the system. In a purified form, it could be combusted in a turbine or used in a fuel cell to generate electricity, or perhaps used as a chemical building block to make liquid fuels and chemicals. The hydrate slurry would then be pumped to another vessel where it would be heated or the pressure lowered to release the CO2. The concentrated stream of CO2 could potentially be sequestered if necessary, and the nucleated water would be regenerated for reuse. The Energy Department is studying ways to store CO2 in geologic formations or deep beneath the oceans or possibly convert it into an environmentally benign form. Prior tests project 86% separation efficiency from a 500-MW coal-fueled plant with 99.8% hydrogen recovery from the hydrate slurry/gas separation. The CO2 scrubbing technology could be a key "enabling" system for the Energy Department's Vision 21 energy plant of the future. Vision 21 is a DOE concept in which a fleet of highly efficient, fuel-flexible power plants would produce electricity along with a slate of energy products -- such as clean liquids for transportation fuels, chemicals and feedstocks -- in response to regional energy markets. The plants would emit virtually no air pollutants, and combined with carbon sequestration, would have greatly reduced or no emissions of carbon dioxide. The Federal Energy Technology Center, a major DOE field organization, will manage the project. Phase 1 of the project will determine the process' feasibility through R&D and testing. If successful, Phase 2, consisting of 22 months of additional laboratory tests, would begin. An optional 15-month Phase 3 would call for laboratory and "slipstream unit" tests to provide detailed design and operating data. The final phase would relocate the "slipstream unit" to an existing coal gasification-based power plant for final evaluation. Assessments and economic comparisons will be made throughout the project. Bechtel is a major engineering and consulting firm known for providing high-quality services for large, complex programs. IPSI, a subsidiary of Bechtel also based in the San Francisco area, brings extensive technical background information related to hydrate formation. LANL offers experience in building and testing a hydrothermal pilot plant for mixed waste destruction. Except for Phase 4, all experimental work will be conducted at the Los Alamos National Laboratory. The Federal Energy Technology Center is the major research arm of the U.S. Department of Energy's Office of Fossil Energy. - End of TechLine - For more information, contact: Technical contact: |