焦化分馏塔上部取热流程比较

Comparison processes of heat removal from fractionators overhead of delayed coking units

以一套5.60 Mt/a延迟焦化装置为例,用ASPEN PLUS和HTRI软件对分馏塔顶循取热流程(流程1)、分馏塔顶冷回流取热流程(流程2)进行了模拟计算及流程分析,对产品指标、分馏塔顶结盐、投资及能耗等方面进行了比较。结果表明:两种流程均可以达到相同的分离要求,对原油换后温度没有影响;流程2分馏塔顶蒸汽分压低、温度高,有利于减少NH4Cl溶液产生,防结盐弹性大,但在线洗盐操作不易控制且污油量大;对于低温热无法再利用的装置,流程2比流程1投资多136×104RMB$,电负荷减少29 kW;对于低温热可回收的装置,推荐流程1。

In a case study of a 5.6 MM TPY delayed coking unit,the two process schemes of fractionator upper pumparound heat removal process（Process Ⅰ） and fractionator overhead cold reflux heat removal process（Process Ⅱ） are simulated and compared by using softwsares ASPEN PLUS and HTRI in respect of product yields,overhead salt deposition,facilities investment and energy consumption.The results demonstrate that： the two processes have the same separation efficiency,there is no impact on the temperature of feedstock to heater;Process II has a lower fractionator overhead steam partial pressure and a higher overhead temperature,which helps to reduce NH4Cl solution and has a greater anti-salt deposition feasibility,but it is not easy to control the online salt washing operation and amount of slop oil is large;When the low-temperature heat can＇t be reutilized,Process II requires 1.36 MM Yuan RMB more facility investment than Process Ⅰ but has saved 29 kW electricity.Therefore,Process I is recommended when low-temperature heat can be reutilized.