Development of High-efficiency Oxy-fuel IGCC System

CO2 emission control is a significant issue as a countermeasure for a global warming problem. Carbon dioxide capture and storage technology is regarded as one of the methods of reducing CO2 emission, but it leads to a drop in a thermal efficiency. It is important to maintain thermal efficiency as high as possible for an efficient use of limited fossil fuel resources. CRIEPI started a joint project with Kyushu university to develop “High-efficiency oxy-fuel IGCC”, a high thermal efficiency integrated coal gasification combined cycle power generating system with CO2 capture, which can keep its efficiency more than 40% (HHV). This system gasifies coal with mixed gas of O2 and recirculated exhaust gas mainly composed by CO2, just as oxy-fuel combustion boiler. This paper is to introduce latest achievements done by CRIEPI on this project by quoting latest papers. In order to clarify the effect of CO2 enrichment on coal gasification reaction, coal gasification experiments were executed using pressurized entrained flow coal gasifier whose fuel capacity is 3TPD. And in order to evaluate characteristics of O2- CO2 gasifier by numerical simulation, pressurized drop tube experiments were performed to obtain reaction data necessary for constructing high precision reaction model for numerical simulation code. The data clarified difference between O2 gasification and CO2 gasification on soot behaviour. When we start this project, this system had a problem to be solved. That is carbon deposition on the surface of hot gas clean-up sorbent, installed to improve thermal efficiency. As CO concentration of syngas is so high that carbon particles are supposed to deposit on desulfurization sorbent. But fundamental experiments showed an appropriate countermeasure for carbon deposition, whose impact on thermal efficiency is quite small. Now it is time for us to summarize achievements and propose the next steps toward realization of this system.