通过对当前轻烃回收装置研究发现，原料气组分变富导致处理量下降，冷箱超过设计负荷17.69%，C₃回收率下降2.64%，通过分析确定冷箱成为了装置操作的短板，提出了采用丙烷制冷系统降低脱乙烷塔顶气温度的优化对策，并计算确定单套装置的丙烷制冷系统负荷为3 000 kW。优化后冷箱负荷和膨胀机负荷降低，有利于设备的稳定运行，同时C₃组分回收率达到设计值，液化气和稳定轻烃产品分别增加8.01%和4.91%，优化后的经济效益十分明显。

It is found through researching the current light hydrocarbons recovery unit that the enrichment of feed gas components results in a decrease in the handling capacity and a decrease of 2.64% in the C₃ recovery rate,and causes the load of cold box to go beyond the design load by 17.69%.Through analysis,it is confirmed that cold box becomes the bottleneck of the unit.An optimized method to drop the temperature of gas from de-ethane tower top is proposed by using propane refrigeration system,and the cold load of the propane refrigeration system for a single unit of load is determined as 3 000 kW.After optimization,the loads of both cold box and expander decrease,which is beneficial to the stable operation of the equipment,making C₃ recovery rate reach the design value,and increasing the yields of liquefied gas and stable light hydrocarbons by 8.01% and 4.91%,respectively.Economic efficiency is improved obviously.