Abstract:

An expander is used to recover the energy released during the expansion of working fluid. In actual operation, the composition of working fluid may change continuously, so operating parameters must be adjusted in real time to achieve optimal energy recovery. This paper, based on an actual engineering case of working fluid lightening (i.e., an increase in the mole fraction of H₂ and a decrease in that of C₂H₄), employs an Aspen Hysys model to systematically analyze the factors affecting expander performance. The results indicate that when the working fluid lightens, relying solely on speed adjustment yields only limited improvements in energy recovery, whereas adjusting the mass flow rate can significantly enhance recovery efficiency. Additionally, using a two-stage series configuration can effectively prevent the impeller from operating at supersonic speeds, thereby improving both system stability and energy recovery performance.

Key words: expander, energy recovery, working fluid lightening