Novel cryogenic argon recovery from the air separation unit integrated with LNG regasification and CO_2 transcritical power cycle

摘要

Two novel air separation units at cryogenic temperature were proposed to reach high purity nitrogen, oxygen, and argon. The first process refers to a three-column cryogenic air separation plant without using an external refrigeration system. An integrated process including cryogenic air separation, combined-cycle power plants (e.g., transcritical CO2 cycle and gas turbine), and LNG regasification was presented and analyzed as the second process to produce liquid oxygen and vaporize LNG without using external refrigeration source. Results of the first proposed process demonstrate that the specific energy consumption of high purity nitrogen, oxygen, and argon reduces to 18.7%, 13%, and 12% respectively when compared with the conventional processes. Specific energy consumptions and exergy efficiency for the second plant improved by nearly 33% and 16% in comparison with the first process. Also, the gas turbine and CO2 power cycle efficiencies were almost 35% and 45% in the second process. Exergy analysis on both systems demonstrated that expansion valve V-2 (99.42%), high-pressure distillation columns (99.41%), and argon recovery section (98.34%) have the lowest irreversibility and highest exergy efficiency. Meanwhile, the highest exergy destructions in the first and second proposed plants belong to the low-pressure distillation tower of the first process and the combustion chamber of the second process with around 3400 kW and 24,000 kW respectively.