A novel technology could reduce the cost of carbon capture at integrated gasification combined-cycle power plants, the U.S. Department of Energy reported May 9. The results of DOE-sponsored research could translate into higher net power output and limit increases in electricity costs. The research was conducted at the National Carbon Capture Center in Wilsonville, Ala.
IGCC plants convert coal into a synthesis gas that can be burned to generate electricity. The syngas contains combustible hydrogen and CO along with water, nitrogen and CO2. Carbon capture can help reduce atmospheric CO2 emissions linked to climate change.
To capture CO2 and prevent its release, the syngas can be "shifted" in a chemical process called the water-gas shift reaction, or WGS. The reaction converts CO into CO2 in the presence of a catalyst and steam, the DOE said, and produces more hydrogen for combustion. The amount of steam is quantified by the steam-to-CO ratio of the gas fed into a WGS reactor. A large amount of steam ensures maximum conversion of the CO and inhibits side reactions, but reduces the overall efficiency of the IGCC plant.
Testing a variety of commercially available WGS catalysts, researchers were able to significantly reduce the steam-to-CO ratio while still achieving high CO conversion without side reactions. According to the DOE, "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." These results could create savings of more than $275 million over the estimated 30-year life of a plant based on current IGCC power costs of about $33/MWh, the DOE said.
The NCCC is providing the test results to manufacturers to help in specifying future WGS systems for IGCC plants designed to incorporate carbon capture. Researchers also plan further tests with other commercially available, newly formulated WGS catalysts. In addition, the test results are already being implemented at the 582-MW Plant Ratcliffe IGCC project under construction in Kemper County, Miss., which will showcase a transport gasifier technology developed at the NCCC.
The NCCC, a state-of-the-art test facility dedicated to advancing clean coal technology, was established by the DOE's National Energy Technology Laboratory in cooperation with Southern Co. subsidiary Southern Co. Services Inc.
On April 25, the International Energy Agency reported that IGCC offers greater efficiency and reduction in CO2 emissions than other clean energy options. Due to high costs, however, few IGCC plants are being built or planned, the IEA said.
On March 15, the Mississippi Supreme Court overturned a June 2010 order by the Mississippi Public Service Commission granting Mississippi Power Co. a certificate to construct and operate the controversial Ratcliffe IGCC plant.
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(Originally published May 14, 2012, in SNL Coal Report.)