2012 Volume 91 Issue 2 Pages 134-137
A CO-rich gasified coal fuel, derived from an oxygen-CO2 blown gasifier, is burnt with oxygen under stoichiometric conditions in a closed cycle gas turbine for the highly-efficient, oxy-fuel IGCC (integrated coal gasification combined cycle) power generation system with CO2 capture. Stoichiometric combustion is diluted with the recycled gas turbine exhaust and adjusted for given temperatures. Since some of the exhaust is used to feed coal into the gasifier, it is necessary to minimize not only CO and H2 of unburned fuel constituents but also residual O2, not consumed in the gas turbine combustion process. In this study, reaction characteristics of reactant gases in the combustor and exhaust have been clarified through numerical analysis based on reaction kinetics. As a result, it was clarified that since fuel oxidation is inhibited due to reasons of exhaust-recirculation and stoichiometric combustion, combustion efficiency was estimated to be lower than those in the cases of the developed H2/O2, LNG/O2 fired closed-cycle gas turbines and a conventional LNG fired-gas turbine. Meanwhile, unburned constituents in exhausts were slowed to oxidize in an HRSG, and exhaust gases reached equilibrium. However, reaction heat in HRSG couldn't devote enough energy for combined cycle thermal efficiency, making advanced combustion technology necessary for achieving highly-efficient oxy-fuel IGCC.