Reducing the efficiency penalty of carbon dioxide capture and compression process in a natural gas combined cycle power plant by process modification and liquefied natural gas cold energy integration

Abstract

Natural gas power plants integrated with a carbon capture process, have recently attracted a lot of attention due to their capability of synergizing with renewable technologies and decarbonization of the power industry. The natural gas plant is fueled by liquefied natural gas at extremely low temperatures and is subsequently regasified. During regasification, a substantial amount of cold energy is available which is conventionally wasted. Furthermore, the integration of the carbon capture process poses a significant energy penalty on the system. This study, therefore, investigated the optimal utilization of the cold energy of the liquefied natural gas and the configuration of the post-combustion carbon dioxide capture process for the natural gas plant. Firstly, the carbon dioxide capture process was modified to reduce its thermal energy requirement. Secondly, the application of liquefied natural gas as a heat sink for the organic Rankine cycle was investigated. Subsequently, an alternative application of liquefied natural gas cold energy in the carbon dioxide compression process was evaluated. The results show that the modified carbon dioxide capture process reduces the thermal energy requirement by 12.8% and improves the efficiency of the power plant by 0.6%. The optimized organic Rankine cycle generates 4.9 MW electrical power using cold energy. In comparison, the intensified compression process integrated with liquefied natural gas regasification reduces the compression power by 7.15 MW, outperforming the application of liquefied natural gas in power generation. Thus, the optimal utilization of liquefied natural gas cold energy is in the carbon dioxide compression process as it improves the net efficiency and reduces the footprint of the liquefied natural gas cold energy utilization process. The modified carbon dioxide capture process and intensified carbon dioxide compression process using liquefied natural gas cold energy can enhance power generation by 13 MW and reduce the efficiency penalty from 6.1% to 4.8%.