System modeling of exergy recuperated IGCC system with pre- and post-combustion CO2 capture

Abstract

This paper describes a novel advanced integrated gasification combined cycle (A-IGCC) for heat integration technology with carbon dioxide (CO2) capture. The feature of this system is an exergy recuperation in which the exhaust heat from the gas turbine and the steam are used as gasifying agents, providing higher cold gas efficiency. A-IGCC can achieve higher plant thermal efficiency with much less energy/exergy loss compared to a conventional IGCC. Two CO2 capture options, (i) pre-combustion by a mixture of dimethyl ethers of polyethylene glycol (DEPG) and (ii) post-combustion by monoethanolamine (MEA), were assessed to compare the total plant performance and necessary technologies for future implementation. A-IGCC maintained a higher plant performance than IGCC, delivering sufficient energy in the gasifier for the autothermal reaction. A higher efficiency was obtained in IGCC with pre-combustion capture, with a thermal efficiency of 33.2% compared to 43% without capture. In A-IGCC, however, the higher efficiency was obtained with post-combustion capture, with a thermal efficiency of 38.5% compared to 50.6% without capture. Adding a CO2 removal unit with 81 mol% CO2 absorption imposed the plant efficiency loss of 9.9–15.2%. The surplus heat at lower temperature was left unused when pre-combustion capture was used for the A-IGCC plant model, which resulted in a large reduction in plant efficiency.