Characteristics and economic evaluation of a power plant applying oxy-fuel combustion to increase power output and decrease CO_2 emission

摘要

This paper evaluates power generation characteristics, economics, and CO_2 reduction effects of a proposed CO_2-capturing repowering system that utilizes low pressure steam (LPS) to increase generated power and to capture generated CO_2 based on the oxy-fuel combustion method. A case study was adopted wherein LPS from a combined cycle power generation system (CCPS) is used. It is estimated that the proposed system can generate 2.03 times greater power compared to a conventional steam turbine power generation system (the reference system) using the same LPS, with an exergy efficiency of 54.2%, taking into account O_2 production power and captured CO_2 liquefaction power. The proposed system is estimated to be economically feasible (the depreciation year is estimated to be 4.78 years; BCR 2.50; and IRR 23.0%), and will economically outperform the reference system if CO_2 emission credit higher than 30 $/(t - CO_2) is applied for the captured CO_2. The effects of retrofitting the proposed system into the CCPS are estimated as follows: the net generated power can be increased by 27.9% and the CO_2 emission amount can be reduced by 21.8% with a 2.41% degradation of the net power generation efficiency, from 56.2% to 53.8%.