A new integration scheme for CO2 capture in low-rank coal fired power plants with energy savings

Abstract

Integration of CO2 capture process into a fossil fuel fired power plant leads to an unavoidable efficiency loss. Thus, optimization of the integration scheme is of great necessity to reduce the efficiency loss. This study proposes a new integration scheme for a low-rank coal (LRC) fired power plant with CO2 capture system of solid amine-based sorbents, specifically including a steam cycle, a CO2 capture system and a LRC pre-drying process. By suitable system integration, the low-quality heat in the CO2 capture system could be used to replace the high-quality waste heat of flue gas for LRC pre-drying, thus achieving great energy savings. Compared to the conventional integration scheme, the thermal and exergy analyses show that the new integration scheme efficiently recovers the low-quality heat in the CO2 capture system to generate more power output and the corresponding efficiency loss is reduced by 2.66%. Economic analysis shows that the economic benefits from the new integration scheme outweigh the disadvantages of the investment increase, and the cost of electricity (COE) and the cost of CO2 avoided (COA) are reduced by 5.95 $/MWh and 8.32 $/tCO2.