IGCC Precombustion CO_2 Capture Using K_2CO_3 Solvent and Utilizing the Intercooling Heat Recovered From CO_2 Compressors for CO_2 Regeneration

摘要

CO_2 capture (CC) using hot K_2CO_3 solvent in integrated gasification combined cycle (IGCC) plant is a promising technology for CO_2 emission reduction. Based on pilot scale trials, an innovative IGCC system with CC using hot K_2CO_3 solvent is proposed, in which the intercooling heat between CO_2 compressors is recovered for CO_2 regeneration (IGCC + CC + HR). Thermodynamic performance and exergy and energy utilization diagram (EUD) analysis are presented. Results show that recovery of the intercooling heat between CO_2 compressors reduces the steam extraction requirement from turbines for CO_2 regeneration by around 18% and enhances the efficiency of IGCC with CO_2 capture (IGCC + CC) plant by 0.3-0.7 percentage points. With 90% CC, the efficiency of the IGCC + CC + HR plant is around 35.4% which is higher than IGCC + CC plant using Selexol technology. Compared to IGCC, the energy penalty for CC in IGCC + CC + HR plant is mainly caused by the exergy losses in CO_2 separation (45.2%), water gas shift (WGS) (28.5%), combined cycle (20.7%) and CO_2 compression units (5.6%). EUD analysis shows that the IGCC + CC + HR plant realizes good match of the energy levels between the intercooling heat and the recovered steam for CO_2 regeneration, thereby obviously reducing the exergy losses in CO_2 compression and separation units and improving the plant efficiency. The results presented in this paper confirm the sources causing the energy penalty for CC in IGCC power plant and the new IGCC + CC + HR system helps to reduce the energy penalty for CC in IGCC power plant based on solvent technologies.