Exergy and exergoeconomic evaluation of gas separation process

Exergy and exergoeconomic analyses for product recovery and separation systems of natural gas plant as well as the refrigeration system required for the plant are carried out. The exergetic and exergoeconomic costs of all process and utility streams are calculated through a systematic method of assigning exergetic cost relations to the streams. The results indicate that the exergetic efficiencies of the Debutanizer, Depropoanizer, and De-ethanizer columns are the lowest. Distillation columns have 64% of the total exergy loss, which is the maximum value of the system components. In the second place, heat exchangers have 15% of the exergy loss. Next there are compressors and expanders which have 13% and 6% of the exergy loss, respectively. It should be noted that the expander is replaced by a choke valve for energy-saving purposes. On the other hand, the results of the exergoeconomic analysis show that the percentage increases in the unit thermoeconomiccosts of the compression and the Demethanizer sections are the highest. This study demonstrates that the exergoeconomic analysis, whose results present cost-based information suggesting potential locations for the process improvement, can provide more information in comparison to the exergy analysis.