直接换热常规流程的改进及分析

Improvement and analysis of DHX conventional process

针对直接换热(DHX)常规流程重接触塔塔底凝液直接进脱乙烷塔塔顶造成重接触塔塔顶回流重烃含量多、冷凝吸收效果差、丙烷回收率低的缺陷。通过增设脱乙烷塔塔顶回流罐得到两种改进流程:(1)改进流程Ⅰ,脱乙烷塔塔顶回流罐分离液相作重接触塔和脱乙烷塔塔顶回流;(2)改进流程Ⅱ,脱乙烷塔塔顶回流罐分离气相冷却后作重接触塔塔顶回流,分离液相作脱乙烷塔塔顶回流。并针对不同的原料气压力及气质贫富,对两种改进流程进行调整,分别得到适用于中压凝析气、低压油田伴生气和高压凝析气丙烷回收的DHX改进流程。并通过HYSYS软件对3种流程进行模拟对比分析,结果表明改进流程Ⅰ对于中压和高压凝析气丙烷回收率均很高(>99%),但对于油田伴生气改进效果不明显,并且改进流程Ⅰ对高压凝析气进行丙烷回收时能耗较高。而改进流程Ⅱ在不同原料气气质工况下均表现出很高的回收率(>99%),且能耗较低,是一种回收率高、适应范围广、节能高效的丙烷回收流程。因此可得结论:改进流程Ⅱ是3种流程中的最佳丙烷回收流程,但改进流程Ⅰ在某些特殊条件下也是一种值得参考的流程。

For the defects of DHX conventional process that DHX column bottoms condensate directly flowing into the deethanizer column overhead caused more heavy hydrocarbon in the DHX column overhead reflux,resulting in the poor effect of absorption and condensate,and low propane recovery.This paper summarized two improved processes by adding deethanizer column overhead reflux drum:①improved processⅠ:the separated liquid by deethanizer column top reflux tank serving as DHX column and deethanizer column top reflux;and②improved processⅡ:the separated gas bydeethanizer column top reflux tank was cooled and then served as DHX column top reflux,and the separated liquid by deethanizer column top reflux tank served as deethanizer column top reflux.Adjusting the two improved process for different feed gas pressure,rich or lean gas and respectively obtained processes applying to medium pressure condensate gas,low pressure oil-associated gas and high pressure condensate gas.By using HYSYS software to simulate and analyze the three processes,the results showed that the improved processⅠhad high propane recovery(>99%)in medium and high pressure condensate gas,but the improved effect for low pressure oil-associated gas was relatively unsatisfactory.Furthermore,the improved processⅠhad more energy consumption for high pressure condensate gas.The improved processⅡindicated the high propane recovery(>99%)at different feed gas pressure and low energy consumption,and was an efficient process with high propane recovery,wide range of adaptation and low energy consumption.Thus,the improved processⅡwas the best process of the three processes,but the improved processⅠcould be a referable process under certain special conditions.