Energy, exergy, economic, and environmental analysis of an integrated system of high-temperature heat pump and gas separation unit

A novel integrated system consisting of a high-temperature heat pump providing 120–130 °C heat and a gas separation unit was developed to recover the industrial waste heat and replace the low-pressure steam used in traditional refinery process. An energy, exergy, economic, and environmental analysis was carried out to evaluate the performance of such integrated system according to its operational data of the project.

Energy and exergy analyses provide an insight into the quantity and quality of the energy conversion of the integrated system. The results show that the coefficient, which evaluates the performance of the system in a stable operation mode, are 8.05 and 4.45 in the presence and absence of the waste heat recovery mechanism, respectively.

The total exergy efficiency decreases from 34.57% to 33.03% in the ambient temperature range of −10–40 °C. When an electricity price of 0.109 $/kW·h and a steam price of 22.361 $/t are considered, the annual net profit of the integrated system measures a minimum of 187.4*103 $/year and 169.8*103 $/year, the payback period measures a maximum of 2.21 years and 2 years, with and without considering the penalty cost induced by emission reductions.

Assuming a 8000 h/year operating time, the reduction of CO2, SO2, and NOx emissions reaches 3348 t, 101 t, and 50 t, respectively. These results indicate that the integrated system operates with a high performance and provides significant economic and environmental benefits.