Development of oxy-fuel IGCC system with CO₂ recirculation for CO₂ capture

CO₂ emission control is significant issue as a countermeasure for a global warming problem. Utility companies are required to reduce CO ₂ emission from thermal power stations and make various efforts to improve thermal efficiency and to utilize carbon neutral fuels such as biomass fuels. CCS (CO₂ capture and storage) technology is regarded as one method to reduce CO₂ emission, but CCS required great decrease of thermal efficiency. As amount of fossil fuel on the globe is so restricted, it is important to keep high thermal efficiency as high as possible, in order to utilize valuable fossil fuel effectively. This project plans to develop innovative gasification technology with CO₂ capture, which can keep thermal efficiency as high as state of the art IGCC plant, namely more than 40%. This is to gasify coal with mixed gas of O₂ and recycled CO ₂ flue gas, just like oxy-fuel combustion system. We expect following two merits. First merit is to simplify the system. As the CO₂ concentration in exhaust gas is almost 100%, this system doesn't require CO ₂ separation unit. So no steam is required to bleed from steam cycle in order to maintain absorber for CO₂, therefore thermal efficiency is kept high even after capturing CO₂. We expect another merit in this system. Generally speaking, CO₂ gas works as gasifying agent for coal, so high CO₂ concentration improves gasification performance of gasifier. This paper is to report the status of the project executed by CRIEPI.