Integration of a Coal-Fired Power Plant with an Ammonia-Based CO_2 Capture Process in Three Operation Modes

摘要

The techno-economic performance of a coal fired power plant integrated with postcombustion capture is affected by not only the capture system but also the way the power plant is operated. The existing integration studies typically use amines as the CO2 capture absorbent. However, amines will degrade in the capture process and produce harmful substances. Ammonia is a robust, low-cost alternative solvent for reducing CO2 emissions from coal-fired power plants. On the basis of a 660 MW coal-fired power plant, this study analyzes the performance of the integration of coal-fired power plant with an ammonia based CO2 capture process in three operation modes which include (1) reduction of power plant output compared to the original power station without CO2 capture and 85% CO2 capture efficiency, (2) the same power output as the original power station without CO2 capture and the same CO2 capture rate as in (1), and (3) the same power output as the original power station without CO2 capture and 85% CO2 capture efficiency. In each of three operation modes, we also analyzed the effect of stream extraction with and without auxiliary equipment energy consumptions in the CO2 capture process on the energy performance of the power plant. Results show that operation mode 2 exerts the least energy penalty on the power plant, but captures less CO2. On the premise of capturing as much CO2 as possible, operation mode 3 is the optimal operating mode, but the boiler and high-pressure cylinder require modification. Operation mode 3 is used as an example to analyze the effect of the solvent regeneration heat duty and temperature on the performance of the power plant. A decrease in heat duty is found to increase the system thermal efficiency and reduce the coal consumption rate and energy penalty. Lowering regeneration temperature while keeping the heat duty unchanged will improve the thermal efficiency of the system and reduce the coal consumption rate and energy penalty.