Abstract
A chemical process usually needs to combust fossil fuels to provide the energy required for production, then a large number of low temperature waste heat is discharged to the environment. Recovery of such waste heat plays an important role in saving primary energy and protecting the environment. There are many waste heat recovery technologies, among which heat pump and power cycles are widely used. In order to make a proper choice of the utilization mode for the low temperature waste heat, the simulation models of mechanical heat pump, steam turbine and Organic Rankine Cycle are established in this paper. Calculations are made under different waste steam temperatures (100 °C to 150 °C) and different heat pump temperature lifts (10 °C, 15 °C, 30 °C). Exergy efficiency is used as the index to compare the energy performance of the three waste heat recovery cycles. The results show that the exergy efficiency of the mechanical heat pump is always higher than 0.9, while that of the Organic Rankine Cycle and steam turbine is between 0.3 and 0.5. The exergy efficiency of the mechanical heat pump is always highest under any working conditions. Based on energy performance, the mechanical heat pump is always a better choice than a power cycle in low-temperature waste heat recovery. Besides, the energy performance of the Organic Rankine Cycle is better than that of the steam turbine. This article compares these two waste heat recovery technologies with completely different working principles, and can provide a reference for factories to choose a suitable waste heat recovery technology.
