气相法聚乙烯装置排放气回收系统的改造总结

REFORM SUMMARY ON RECOVERY SYSTEM FOR THE EXHAUST GAS FROM THE POLYETHYLENE PLANT WITH GAS PHASE PROCESS

针对基于双膨胀自深冷分离技术下的2~#HDPE装置排放气回收系统冷量富余以及LLDPE装置排放气回收系统冷量不足的问题,通过能量集成技术,从2~#HDPE装置冷箱引出一股低温冷流体到LLDPE装置冷箱进行换热,使LLDPE装置冷箱出口气体温度降至-120℃,实现了氮气和乙烯的分离回用;同时,2~#HDPE装置通过排放气与气相、液相产品的换热,实现了冷量的梯级利用和低聚物的分离回用。改造后的运行结果表明:2018年多回收了乙烯、丁烯、戊烷,并且节约了氮气、电量、蒸汽,经济效益显著。

Aimed at the problem of excess cooling capacity on the recovery system for exhaust gas in the 2#HDPE plant with double expansion and self-cryogenic separation technology but insufficient cooling capacity existing in the LLDPE plant,adopting energy integration technology,a low temperature cold fluid was introduced from cold box of the 2#HDPE plant to that of the LLDPE plant for heat exchange.The outlet gas temperature of the LLDPE cold box was lowered to-120℃,and the separation and recovery of nitrogen and ethylene was realized.At the same time,cascade utilization of the cooling capacity,separation and recovery of the oligomers were realized in the 2#HDPE plant by the heat transfer between the effluent gas and the gas&liquid phase products.The operation results of the plants showed that more ethylene,butylene and pentane was recoverd,Consumption of the nitrogen,electricity and steam was saved in 2018,and obvious economic profit was obtained.