Research On Solar Aided Coal-fired Power Plant And CO₂ Capture System Performance

Post-combustion CO2 capture based on MEA solution is one of the main ways to reduce the greenhouse effect. However, this method can consume lots of turbine extractions, resulting in a serious decline in the efficiency of coal-fired units system. Introducing the solar heat into the system can compensate for this energy penalty to some extent. This paper presents two solar aided coal-fired power plant and CO2 capture system integration programs. One is using the solar heat to replace the first high-pressure extraction of turbine, and the replaced high-pressure extraction can reture to the turbine continue working, it can compensate for part of energy penalty. The other is using the solar heat to provide the heat demand of MEA regeneration. In addition, the coal-fired power plant with CO2 capture system is chosen as a reference system to do comparative analysis.In this paper,the models of two kinds of solar aided coal-fired power plant and CO2 capture system and the reference system are built based on Aspen Plus and Ebsilon Professional software. Then the thermal performance evaluation indexes (thermal efficiency, coal consumption rate, solar to electricity conversion efficiency) and economic performance evaluation indexes (power generation costs, CO2 avoidance costs) of three systems are calculated. In addition, this paper calculated the exergy efficiency of each device in three systems based on exergy analysis theory. The reason of the devices with low exergy efficiency are analyzed and the improvement methods are proposed.The results show:(1) Total system power fell 160.50 MW after taking measures of CO2 capture system to coal-fired power plant. Adopting scheme one can compensate for 57.17MW while adopting scheme two can compensate for 39MW. (2) The output of scheme one is higher than 18.17MW to scheme two, solar to electricity conversion efficiency is higher than 10.82%, coal consumption rate is lower than 6.19 g/kWh, COE is lower than 0.47$/MWh, CO2 avoidance costs is lower than 0.7$/tCO2 and thermal efficiency is lower than 0.57%. In total, scheme one is better than scheme two. (3) The exergy efficiency of solar collector field and boiler is low. And the exergy efficiency of boiler in scheme one is higher than that in scheme two and reference system. The exergy efficiency of solar collector field in scheme one is higher than that in scheme two.