Energy Flow of Advanced IGCC With CO2 Capture Option

Abstract

Conventional IGCC (integrated gasification combined cycle) employs a cascaded energy flow with a high efficiency, yet it is difficult to achieve over 50% HHV (higher heating value). The current study proposes an alternative model of exergy recuperated Advanced IGCC (A-IGCC) to achieve higher plant efficiency by applying an autothermal reaction in the gasifier. This requires an additional heat supply from the gas turbine exhaust and the steam extracted from the steam turbine. System and performance analyses were studied on base IGCC and A-IGCC cases incorporating the heat (exergy) recuperation concept with an air-blown twin circulating fluidized bed gasifier for the gasification of sub-bituminous coal, both with and without the post combustion carbon dioxide (CO2) capture option. A-IGCC could deliver sufficient energy in the gasifier to the gas turbine without losing heat as resulted in IGCC. Chemical absorption methods using monoethanolamine (MEA) and methyldiethanolamine (MDEA) were selected as a CO2 absorbent. A-IGCC demonstrated a significantly higher system efficiency (51%) than IGCC (43%) without CO2 separation, provided the gas purification was at high temperature. The thermal efficiency penalty by CO2 capture was −8% using MDEA (56% absorption) and −11% using MEA (90% absorption).