CO2 enhanced in-situ oxy-coal gasification based carbon-neutral conventional power generating systems

• CO2 as a gasifying medium to UCG (underground coal gasification).
• Estimation of thermal efficiency of CO2 based UCG with conventional power systems.
• Evaluation of the effect of UCG operating pressure on net thermal efficiency of IGCC system.

UCG (Underground coal gasification) is an economic and a viable in-situ clean coal technology in exploiting deep underground coal resources. Sustaining a combustion front in the in-situ gasification of high ash coal is difficult if steam acts as a gasifying medium. In addition, the use of superheated steam causes the transportation problem for deep coal seam. Conversely, these problems could be avoided if CO2 is used as the gasifying medium. In order to implement a CCS ready system in existing plants, the present study investigates the feasibility of integration of CO2/O2 gasification of in-situ coal with conventional power generating systems such as steam turbine and combined cycle power plants performing in a CO2/O2 mode of combustion. The effect of operating pressure and the ratio of CO2/O2 input to an UCG system on the net thermal efficiency of the IGCC system are evaluated. A detailed energy analysis of the CO2 enhanced IUGCC (UCG integrated with the combined cycle) shows a high net thermal efficiency of 41% with CCS (carbon capture and storage) at the UCG operating pressure of 27 bar. IUGST (Integration of low pressure UCG with a steam turbine cycle) system shows a net thermal efficiency of 27% with CCS.