Washington, DC — Changes in operating conditions coupled with changes in commercially manufactured catalysts can produce both power generation increases and significant cost savings at Integrated Gasification Combined Cycle (IGCC) power plants, according to new research from a U.S. Department of Energy (DOE)-sponsored project.
Results from the project at DOE’s National Carbon Capture Center (NCCC) could ultimately lead to lower-cost carbon-capture technologies and help provide affordable, reliable, and clean energy from our nation’s domestic coal resources. Carbon capture, utilization and storage (CCUS) technologies are viewed by experts as an important option in helping reduce atmospheric carbon dioxide (CO2) emission linked to potential global climate change.
Advanced power plants using IGCC technology convert coal into a synthesis gas, or "syngas," which can then be combusted to produce electricity. The syngas contains combustible hydrogen and carbon monoxide (CO), along with water, nitrogen, and CO2, a greenhouse gas.
To capture CO2 and prevent its release into the atmosphere, the syngas is "shifted" in a chemical process called the water-gas shift (WGS) reaction. The reaction converts CO into CO2 in the presence of a catalyst and steam and produces additional hydrogen for combustion. A large amount of steam ensures maximum conversion of CO and inhibits side reactions, but it also reduces the overall efficiency of the IGCC plant. The amount of steam is quantified by the steam-to-CO ratio of the gas fed to the WGS reactor.
Testing a variety of commercially available WGS catalysts, NCCC researchers were able to significantly reduce the steam-to-CO ratio while still achieving high CO conversion without side reactions. A reduction in the ratio translates into increased net power output and a smaller increase in the cost of electricity associated with carbon capture. Specifically, the 1.0 reduction in steam-to-CO ratio that was achieved corresponds to a 40-megawatt increase in power generation in a 500-megawatt IGCC plant. This could result in cost savings of more than $275 million over a plant’s estimated 30-year lifespan at current IGCC power costs of about $33 per megawatt-hour.
NCCC researchers are providing the test results to manufacturers to assist them in specifying future WGS systems for IGCC plants that incorporate carbon capture. The researchers are also planning further tests with other commercially available, newly formulated WGS catalysts. In addition, the findings are being implemented at a commercial IGCC plant now under construction in Kemper County, Miss. The plant will showcase a transport gasifier technology developed at the NCCC.
Located in Wilsonville, Ala., the NCCC is a state-of-the-art test facility dedicated to the advancement of clean coal technology. The Office of Fossil Energy’s National Energy Technology Laboratory, in cooperation with Southern Company Services, established the NCCC to bolster national efforts to develop cost-effective technologies to capture the CO2 produced by fossil-fueled power plants and help secure the nation’s energy future.