Exhaust circulation into dry gas desulfurization process to prevent carbon deposition in an Oxy-fuel IGCC power generation

•Power plant with semi-closed gas turbine and O2–CO2 coal gasifier was studied.•We adopt dry gas sulfur removal process to establish the system.•The exhaust gas circulation remarkably prevented carbon deposition.•Efficiency loss for exhaust gas circulation is quite small.•Appropriate operating condition of sulfur removal process is revealed.

Semi-closed cycle operation of gas turbine fueled by oxygen–CO2 blown coal gasification provides efficient power generation with CO2 separation feature by excluding pre-combustion type CO2 capture that usually brings large efficiency loss. The plant efficiency at transmission end is estimated as 44% at lower heating value (LHV) providing compressed CO2 with concentration of 93 vol%. This power generation system will solve the contradiction between economical resource utilization and reduction of CO2 emission from coal-fired power plant. The system requires appropriate sulfur reduction process to protect gas turbine from corrosion and environment from sulfur emission. We adopt dry gas sulfur removal process to establish the system where apprehension about the detrimental carbon deposition from coal gas. The effect of circulation of a portion of exhaust gas to the process on the retardation of carbon deposition was examined at various gas compositions. The circulation remarkably prevented carbon deposition in the sulfur removal sorbent. The impact of the circulation on the thermal efficiency is smaller than the other auxiliary power consumption. Thus, the circulation is appropriate operation for the power generation.