Coal fired power plants provide roughly half of the power generated in the United States each year. Since these plants will inevitably keep operating, amine scrubbing to capture CO2 from the plants could be the most effective way to reduce emissions. A technique patented in the 1930’s and currently the most common method for removing sulfur from flue gas at power plants, amine scrubbing has seen technological improvements in the last decade amounting to a cost reduction from $77 to $52/ton of CO2 removed (Rochelle, 2009). Strong legislation in the form of a cap-and-trade system, or a carbon tax could provide the necessary incentives for the first major amine scrubbing project. — Jake Bauch
Rochelle, Gary T., 2009. Amine Scrubbing for CO2 Capture. Science. 325, 1652-1654
Gary Rochelle of the Department of Chemical Engineering at University of Texas at Austin looked at ways that current process and solvent improvements could reduce costs of amine scrubbing. His basis for the economics of amine scrubbing was a 2007 study by the U.S. Department of Energy that showed cost reductions from 2001 to 2006. The process of amine scrubbing is as follows: CO2 is absorbed at a high temperature into an amine solution, water vapor is used to strip the amine from the CO2, the water in the vapor is condensed leaving pure CO2, and then the CO2 is compressed to between 100 and 150 bar for transportation and storage. Costs can be divided into power used (half is steam to heat the vapor and half to compress the CO2), capital costs, and operating and maintenance cost. Improvements in the process such as stripping at multiple pressures could reduce power used but would increase capital costs. Solvents with higher rates of absorption, or greater capacity can reduce power costs.
The theoretical minimum amount of energy used in amine scrubbing is 12% of the power plant capacity. With the improvements in solvents and process, the amount used could get down to 20%. Amine scrubbing technology can be added on to existing plants, and can be shut off during times of peak electricity demand. If the energy demanded is replaced with gas fired power, there will be a projected 74% decrease in CO2 emissions.