Process and Integration Optimization of Post-Combustion CO2 Capture System in a Coal Power Plant

Post-combustion CO2 capture (PCC) is commonly believed to be one of the major strategic means to reduce the CO2 emission in coal power plant. However, the operation of PCC system will cause substantial increase of operation cost due to the energy consumption for regeneration of the capture solvent. The optimal integration schemes of large-scale PCC system with thermal power plant are studied in this work, based on a feasibility study of 1 million tpa PCC system conducted for a thermal power plant in northeast China. A power plant model coupled with PCC system is setup by Thermoflow STEAM PRO. Based on the model, various steam extraction options and their impact on the steam turbine performance are studied, the impact of large-scale PCC operation on power plant performance under various boiler loads (100%, 75%, 60%) is investigated, and the impact of PCC operation on heating supply during winter is studied. An environmental assessment is also conducted by investigating the impact of PCC operation on the emission of CO2 and pollutants such as SO2, NOx and dust. In addition, process optimization is conducted by APSEN Plus simulation to reduce the steam consumption of reboiler. The impacts of mechanical vapor recompression (MVR) system on the regeneration duty of stripper is studied. The application of MVR can reduce the regeneration duty from 3.85 to 3.1 GJ/ tCO2 if the flash pressure is 100 kPa. The impact of flash pressure of MVR system on the regeneration duty and electricity consumption is also studied. It found that the regeneration duty decreases with increasing flash pressure, however the electricity consumption increase with flash pressure dramatically. The optimal flash pressure is between 50~100 kPa.