Shift reactors and physical absorption for low-CO2 emission IGCCs

Integrated gasification combined cycles (IGCC) exhibit conditions particula rly favourable to the sequestration of CO2. The concept pursued in this pap er is the generation of syngas low in carbon, where most of the heating val ue of the coal fuel is carried by hydrogen. Catalytic shift reactors conver t most of the CO in the syngas into CO2, which is subsequently removed by p hysical absorption and then compressed to make it suitable for transport an d permanent storage. Energy balances, performance, and cost of electricity are evaluated for two plants based on a Texaco gasifier and a large, heavy- duty gas turbine giving an overall IGCC power output between 350 and 400 MW . In one plant, the raw syngas exiting the gasifier is cooled in a high-tem perature, radiative cooler; in the other it is quenched by the injection of liquid water With respect to ''conventional'' Texaco IGCCs, the reduction of specific CO2 emissions by 90 percent reduces LHV efficiency from 5 to 7 percentage points and increases the cost of electricity of about 40 percent . These penalties can be reduced by accepting lower reductions of CO2 emiss ions. Compared to the semiclosed cycle considered by other authors, where C O2 is the main component of the gas turbine working fluid the plants analyz ed here exhibit higher efficiency over the whole range of specific CO2 emis sions.