From ammonium bicarbonate fertilizer production process to power plant CO2 capture

摘要

Ammonia-based CO2 capture technology has attracted wide research interest. Substantial work has been reported that includes theoretical evaluation, laboratory tests, pilot plant tests and economic analysis. Alstom and PowerSpan have conducted a few MW level demonstration tests. However, three inherent hurdles with this potential CO2 capture technology have not been fully solved yet: ammonium bicarbonate solid formation in the absorption tower which may plug the tower packing, high ammonia vapor pressure that results in ammonia slip into the cleaned flue gas, and low CO2 absorption rate resulting in large absorption equipment. Industrial ammonium bicarbonate fertilizer production processes are proven technology and have been optimized both technologically and economically for decades. This technology is also based on the chemistry and physics of the NH3–CO2–H2O system. In the ammonia synthesis plant, CO2 in shifted gas from the syngas obtained by gasification of coal is absorbed into partly carbonated aqueous ammonia in a liquid bubbling column to produce ammonium bicarbonate solid as fertilizer. Using this process, ammonium bicarbonate has been sustainably produced with low ammonia slip into the shifted gas after the CO2 was captured. In this report, the ammonium bicarbonate fertilizer production process is described and analyzed. The advantageous aspects of the fertilizer production technology are compared with the current widely studied ammonia-based CO2 capture technology for power plant applications. Insights into the modifications required for the flue gas CO2 capture application are discussed. New designs of ammonia-based CO2 capture processes are presented.