Application of organic Rankine cycle in integration of thermal power plant with post-combustion CO2 capture and compression

Abstract

Post-combustion CO2 capture process is the most mature technology to mitigate CO2 emissions from the large-scales emission points. However, integrating the power plant with this process leads to significant thermal efficiency penalty due to steam extraction for solvent regeneration, power consumption by CO2 compression unit and other auxiliary equipment. In the current work, the detailed models of the 350 MWe thermal power plant, MEA-based CO2 capture and compression process were developed in Aspen HYSYS v8.3. Different configurations of integration process were investigated to achieve lower energy penalty. The power plant net thermal efficiency is 40.55% based on lower heating value and is reduced to 31.26% due to integration with CO2 capture and compression process. The net efficiency of the best studied configuration is 33.4%. CO2 compression intercoolers, steam cooler before reboiler and flue gas cooler are three low-temperature heat sources located in the integrated system were identified for utilizing by organic Rankine cycle (ORC). Three ORCs were used to recover these waste heats and can generate 17.38 MWe extra power that increase net thermal efficiency to 35.45%. The results show that efficiency drop is reduced significantly by utilizing ORCs in integration of thermal power plant with CO2 capture and compression.