Characteristics of Coal Gasified Fuel Oxy-Combustion in H₂O/CO₂

(Effect of Exhaust Recirculation on Exhaust Gas Composition)

Abstract

A gas turbine for high-efficiency oxy-fuel IGCC system corresponds to a semi-closed type gas turbine. Exhaust gas from the gas turbine is recirculated, and a part of it is used as a diluent for the combustors. Therefore, it is necessary to examine the effect of the exhaust recirculation on the diluent composition (purity of captured CO₂) and the effect of the diluent composition on combustion characteristics. In this study, the atmospheric pressure combustion tests assumed exhaust recirculation with a small diffusion burner have been carried out. Under overall stoichiometric condition (equivalent ratio φ < 1), the effect of O₂ concentration in diluent on combustion characteristics and residual O₂ concentration has been experimentally examined. As the results, the combustion efficiency improved with the increase of the O₂ concentration in diluent, and it was confirmed the residual O₂ concentration is decided by equivalent ratio and is saturated to a constant value with the increase of the circulating number.