Meitan xuebao (Oct 2023)
Energy consumption analysis and new process of CO2 compression liquefaction based on exergy analysis
Abstract
Among various carbon dioxide capture technologies, the organic amine absorption is the most widely used and reliable choice today. The combination of liquefied natural gas cold energy with carbon dioxide compression and liquefaction process can not only solve the problem of liquefied natural gas cold energy utilization but also obtain the low temperature required for liquefied carbon dioxide directly, which can reduce energy consumption. A new process of carbon dioxide compression and liquefaction by applying liquefied natural gas cold energy to chemical absorption capture is proposed, using organic amine to absorb the high concentration carbon dioxide feed gas captured, and using Aspen Hysys software to simulate the process flow with Peng-Robison equation of state. Firstly, the system performance of the conventional compression process and the pumping compression process were investigated. It was found that the system unit energy consumption could be reduced from 931.65 kJ/kg gas source to 892.61 kJ/kg gas source under the pumping process, the system exergy efficiency increased from 63.28% to 63.67%, and the water consumption decreased from 3.84 kg gas source to 3.01 kg gas source. On this basis, the pumping process was optimized and five optimized processes were proposed according to the different ways of heat exchange series connection. Under the optimal optimized process, the system unit energy consumption was 892.61 kJ/kg gas source, the system exergy efficiency increased from 63.67% to 64.10%, and the water consumption decreased from 3.01 kg gas source to 2.44 kg gas source. Finally, the system sensitivity analysis of interstage cooling temperature and heat transfer medium flow rate was conducted for the optimal optimized process. The results showed that the lower the interstage cooling temperature, the lower the system energy consumption and the greater the exergy efficiency. The lowest unit energy consumption was 879.5 kJ/kg gas source at 10 ℃, and the maximum system exergy efficiency was 65.5%. The effect of heat transfer mass flow rate on the system energy consumption was not obvious, but the system exergy efficiency increased with the increase of heat transfer mass flow rate. The effect of liquefied natural gas mass flow rate on the system exergy efficiency was greater, and the system exergy efficiency was 68.91% when the water mass flow rate was 8000 kg/h and the liquefied natural gas mass flow rate was 1000 kg/h.
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