Development of Oxy-Fuel IGCC System With CO₂ Recirculation for CO₂ Capture: Experimental Examination on Effect of Gasification Reaction Promotion by CO₂ Enriched Using Bench Scale Gasifier Facility

To cope with global warming problem, utility companies are required to reduce CO₂ emission from pulverized coal fired power plants. Japanese utility companies are advancing various measures to improve plant thermal efficiency and to promote utilization of biomass as a fuel. In Europe and America, CO₂ capture and storage (CCS) technology is regarded as one effective approach, and various demonstration projects are planned all over the world. However, the introduction of conventional CO₂ capture system to power station causes a decrease in the plant thermal efficiency and an increase in the power generating cost. In this reason, it is necessary to develop a new power generating system with high thermal efficiency. Therefore, Central Research Institute of Electric Power Industry (CRIEPI) proposed an innovative integrated coal gasification combined cycle power generating system (IGCC) with CO₂ capture whose plant thermal efficiency is very high, and is working on the research and development of the new system. This is a system to combine a new oxygen-CO₂ blown coal gasifier in that captured CO₂ is used with the closed gas turbine in which coal gas from the gasifier is burned with the gas mixed oxygen and recycled exhaust CO₂. The system has the following features. The gasification performances improve greatly. The processes of concentrating and separating CO₂ are unnecessary. It is estimated that the carbon conversion efficiency (CCE) and the cold gas efficiency (CGE) in oxygen-CO₂ blown gasifier improve more than conventional oxygen blown gasifiers by the effect of the gasification reaction promotion of CO₂ by gasifying coal with oxygen and CO₂. As a result, the gasifier and the char recycling system can make to compact, and the equipment cost can be reduced. This paper reports on examination of CO₂ promotion effect on the gasification performances by gasification test using a bench scale gasifier facility.