乙烯装置甲烷-丙烯二元混合制冷系统有效能分析

Exergy analysis of methane-propylene binary refrigeration system of ethylene plant

针对300 kt/a乙烯装置甲烷-丙烯二元制冷系统的能耗及有效能进行优化与分析,目前尚无针对乙烯装置甲烷-丙烯二元制冷系统的相关文献与研究。本文采用Aspen Plus软件对乙烯装置甲烷-丙烯二元制冷系统建立流程模型,通过调整二元冷剂中甲烷与丙烯的含量来寻找最优冷剂比,使得系统能耗最低,并对此时系统中冷剂压缩、换热、节流阀节流降压及冷剂混合4个过程进行有效能分析。计算得出二元冷剂中甲烷含量为17.0%(mol),一段压缩机进口流量为68 000 kg/hr时,压缩机总功耗最低为4466 kW,有效能损失为1944 kW,换热系统、节流阀节流降压及不同的冷剂混合有效能损失分别为1125 kW、242kW、1.7 kW,总有效能损失为3312.7 kW。甲烷-丙烯二元混合制冷系统的有效能损失主要发生在压缩过程和冷剂换热中,分别占有效能损失的58.7%、34.0%,所以这2个部分是节能降耗的重点。

The power consumption and exergy of methane-propylene binary refrigeration system based on a 300 kt/a ethylene plant were analyzed and optimized.There is no paper about the methane-propylene binary refrigeration system currently.The Aspen Plus was used to establish the process model of methane-propylene binary refrigeration system.The optimized component proportion which made refrigeration system to get low power consumption was found by adjusting the component proportion of methane-propylene.Then the exergy of compressors, heat exchangers,expansion valves and the process of fluids mixing were obtained.The results indicate that the lowest total compressors consumption and exergy loss are 4 466 kW and 1 944 kW,when the mole percentage of methane is 17.0%and mass flow of the first compressor stage is 68 000 kg/hr.The exergy loss of heat exchangers,throttling valves and the process of fluids mixing are 1 125 kW,242 kW and 1.7 kW,respectively.The total exergy loss of refrigeration system is 3 312.7 kW.The exergy loss of the compressors and heat exchangers are respectively 58.7%and 34.0%of the total refrigeration system exergy loss,which are the big part of the refrigeration system exergy loss.Thus,it is very important to save energy consumption in the compressors and heat exchangers.