关键词: 碳捕集, CO₂液化, 低温废热, 吸收式制冷, 优化设计

Abstract: CO₂ liquefaction is a crucial procedure for carbon capture,utilization and storage (CCUS). The conventional cryogenic technique,running with the temperature lower than -20℃ and to prevent water from freezing,requires a complicated dehydration unit and consumes numerous mechanical power for refrigeration,and consequently the total running cost for CCUS is increased greatly. In this instance,a novel liquefaction technique based on LiBr absorption refrigeration system using flue gas waste heat was proposed in this research. The LiBr absorption refrigeration system driven by flue gas waste heat was used for generating the cold source at about 4℃. At the same time,the liquefaction temperature is increased to about 7℃ via upgrading the pressure of crude CO₂,so that it can be well matched with the refrigeration condition. Moreover,the increase in liquefaction temperature can avoid the holdback relating to water freezing and CO₂ hydration,and it is beneficial that the complicated dehydration unit is no longer demanded. Afterwards,process simulation and optimization was carried with ASPEN Plus. The simulation results revealed that the novel liquefaction technique can reduce the ecific power consumption to 123.7kW·h/tCO₂,and the energy saving degree is about 23.9% compared to the conventional technique. For a 200kt/a liquefaction plant,it is expected that this new-type technique can save electricity 7.70×10⁶ kW·h and running cost 2.25 million CNY per year. On the whole,the novel liquefaction technique behaves excellent in energy saving and economic benefit.

Key words: carbon capture, CO₂ liquefaction, low-grade heat, LiBr refrigeration, optimal design