Exergy analysis of air separation unit products

Air separation unit (ASU) is the largest energy consume plant, about 15%-20% consumption of overall energy in steel industry. Therefore, improving the operating efficiency of ASU is an effective way to achieve energy saving and emission reduction. The detail exergy calculation is presented in this study and the product exergy analysis of an actual 40000 Nm3/h ASU in Tangshan Tangsteel gases Co., Ltd. is evaluated using the developed exergy calculation program. The results show that: the molar exergy contained in oxygen is the largest among all gaseous products, liquid argon contains the largest molar exergy among all liquid products, and liquid products get larger exergy value than the gaseous. In a same environmental condition with a same air feed mass flow, the process would be more efficient by improving liquid production in the rated load operation of the expander.