A Study of CO2 Capture in Advanced IGCC Systems by Ammonia Scrubbing

Abstract

This paper deals with post-combustion CO2 capture by aqueous ammonia in air-blown gasification-based combined cycles and follows previous authors’ investigations of CO2 capture by MEA scrubbing. Based on the calculations, CO2 capture seems to be more penalizing when realized by chilled ammonia instead of MEA. As a matter of fact, chilling down to 7°C both the exhaust gas and the ammonia solution results in significant power consumption of chillers, which is only partly balanced by the lower consumption for CO2 compression and lower steam extraction from the bottoming cycle compared to the MEA case. Cases with cooled instead of chilled ammonia are investigated as well. In particular, raising the process temperature up to 20°C seems to be an interesting solution, since temperature control in the absorber can be realized by passing the aqueous ammonia solution through an heat exchanger, using ambient-temperature water as refrigerant medium and removing the chillers from the system.