Energy, exergy, economic, and environmental compromising performance of dual-stage evaporation-ammonia hybrid compression–absorption refrigeration system for the cooling supply of keto-benzene dewaxing process

Abstract

Absorption refrigeration systems driven by low-temperature waste heat is one way to achieve “carbon neutrality”. Meanwhile, the keto-benzene dewaxing equipment needs cooling capacity of 5 MW which refrigeration temperature of –10 °C and –25 °C. This paper researches the feasibility of DSE-AHCARS (Dual-stage Evaporation-Ammonia Hybrid Compression-Absorption Refrigeration System) replacing the vapor compression refrigeration system for keto-benzene dewaxing process based on 4E (Energy, Exergy, Economic, and Environmental) analysis. At the primary and secondary stage evaporation temperature of 0 and –23 °C, COP reaches the maximum value of 0.85. However, COP-Electricity reaches the minimum value of 8.1. When the secondary stage refrigeration temperature is –23 °C, CO2 emission increases from 1150 t·a–1 to 3600 t·a–1, and Life Cycle Climate Performance increases from 3.29×104 tons to 7.7×104 tons with the primary stage refrigeration temperature is –15 °C to 0 °C. As well as matching three parameters to ensure the 4E compromising performance by the multi-objective optimization. To guarantee the Life Cycle Climate Performance is less than 5.5×104 tons, the payback period is less than 2 yr, and COP is greater than 0.6 at the optimal operation ranges that refrigeration temperature difference between primary stage and secondary stage is within 20 °C. The power of DSE-AHCARS was reduced by 77% compared with the vapor compression refrigeration system. Therefore, the DSE-AHCARS can reduce CO2 emissions by about 6250 t·a–1 and save 1.2×105 tons of CO2 in the Life Cycle Climate Performance term. This result shows that the DSE-AHCARS can completely replace the vapor compression refrigeration system.