2018 Volume 60 Issue 194 Pages 242-248
The mitigation of greenhouse gas emission from thermal power plants is strongly required towards 2050. CCUS (Carbon dioxide Capture, Utilization and Storage) is one of the promising technologies for drastic reduction of greenhouse gas from thermal power plant. However, capturing carbon dioxide from flue gas requires huge energy and it causes the reduction of thermal efficiency. Recently, the new concept of carbon dioxide capturing thermal power generation system with keeping high efficiency, named “oxy-fuel IGCC system” was proposed and has been developed. This system injected CO2 into a coal gasifier to purify CO2 concentration in flue gas. This paper firstly introduces the outline of coal gasification and chemical reaction model used for numerical simulation. A coal gasifier is one of the most important utilities in oxy-fuel IGCC system as well as the conventional IGCC system. The results of numerical simulation in a coal gasifier under oxy-fuel IGCC system are also introduced. Gaseous temperature in the combustor decreases when N2 is just replaced with CO2, while gaseous temperature recovers with increasing O2 concentration. The CO concentration increases with replacing N2 with CO2, while the H2 concentration decreases. This is due to the fact that rich CO2 concentration promotes the reverse reaction of the water gas shift reaction. Although gaseous temperature drastically decreases by replacing N2 with CO2, the performance of coal gasifier, such as carbon conversion efficiency does not decrease very much and it increases with increasing O2 concentration. Therefore, the advantage of oxy-fuel IGCC system was clearly showed by the numerical simulation. Finally, the expectations of “K-computer” and advanced numerical simulation technology are mentioned.
