A novel combined system for LNG cold energy utilization to capture carbon dioxide in the flue gas from the magnesite processing industry

Abstract

A novel system which include a new concept called cascade nested organic Rankine cycle (ORC) was proposed based on LNG (liquified natural gas) cryogenic exergy utilization. The flue gas from the magnesite processing industry and LNG was used as heat source and heat sink for ORC respectively. Meanwhile CO2 in the flue gas was captured by LNG. The mixed working fluid, regenerator and LNG regasification pressure play a key role in the system. Furthermore, the generating power capacity, the exergy efficiency, the CO2 capture quantity and the cold energy utilization efficiency were calculated as criteria to evaluate the system performance. The results indicate that the selection of suitable mixed working fluid and the installation of regenerator can improve the system performance effectively. Under the given condition, the exergy efficiency of the integrated system, the efficiency of LNG cold energy utilization, the output power of the integrated system and the amount of CO2 capture reaches to 56.9%, 20.81%, 22.59 kWh/tLNG and 0.29tCO2/tLNG respectively. Moreover, as the LNG gasification pressure increases, the exergy efficiency and cold energy utilization efficiency increases, while the CO2 capture quantity and power generation decreases.