Abstract: Different models for a polytropic compression process were analyzed by using Aspen Plus, with the multi-stage compression process of an actual cracking gas plant taken as background. According to the principle of thermodynamics, exergy analysis were conducted for the compression process of raw cracking gas under conditions of adiabatic, isothermal and multi-stage compression. The results showed that during the compression process, exergy increased as pressure increased, while the corresponding total exergy droped in the inter-stage cooling process. The compression exergy efficiency increased as the number of stages increased, and flattened gradually. The analysis for the practical five-stage compression process showed the exergy increase was 2 350 kW, and the exergy efficiency was 62.67%, potential for exergy recovery was 476 kW.

Key words: simulation, cracking gas, Multi-stage compression, thermodynamic, Exergy analysis