Optimization of energy requirements for CO2 post-combustion capture process through advanced thermal integration

Abstract

The energy optimization modeling work described here was performed to determine efficiency improvements that could be achieved for existing coal-fired power plants to retrofit a partial CO2 capture from the post-combustion flue gas for carbon sequestration through thermal integration. The work presented includes optimization of the mono-ethanol amine (MEA)-based post-combustion CO2 capture to reduce energy requirements that could be achieved at existing power plants by thermal integration of the steam turbine cycle, boiler, CO2 compression train and post-combustion CO2 capture process to offset efficiency and capacity losses that would be incurred by retrofit or implementation of post-combustion CO2 capture. Partial CO2 capture, involving treatment of less than 100% of the flue gas leaving the plant and modular design of the CO2 scrubbing system, was also investigated. Thermal integration of the steam turbine cycle with boiler and CO2 compression train improved cycle and plant performance and offset, in part, the negative effects of post-combustion CO2 capture. The best-analyzed integration options improved gross power output by 5% and net unit efficiency by 1.57%, relative to the conventional MEA process. Operating with 40% CO2 capture increased gross power output by 11.6–14% (depending on the MEA thermal integration option), relative to the conventional MEA integration and 90% CO2 capture. The improvement in net unit performance is larger compared to the improvement in turbine cycle performance because of the CO2 compression work, which is also reduced by partial CO2 capture.