异丁烷脱氢制异丁烯装置脱异丁烷塔工艺及设备优化模拟研究

Simulation study on optimization of process and equipment for DIB tower in dehydrogenation of isobutane to isobutene plant

异丁烷脱氢制异丁烯装置原料进入反应器前需经过脱异丁烷塔,将原料中的正丁烷分离出去。该塔原工艺设计塔顶异丁烷中正丁烷的质量分数小于2%。为了提高原料利用率和异丁烯产品纯度,需要将塔顶异丁烷中正丁烷的质量分数降至1%以下。利用Aspen Plus流程模拟软件对目标工艺和设备进行模拟计算,在不改变回流比的条件下,进料位置由当前的第15块板下移至第21块板,塔顶正丁烷的质量分数由1.75%降至1.73%;进料位置优化后,当回流比大于3.4时,塔顶正丁烷的质量分数小于1%。但当增大回流比后,塔内气液负荷增大,全塔蒸汽消耗亦增大;模拟计算得到新的分离要求条件下最小理论板数为25,最小回流比为2.74,论证了将塔内件由塔板更换为高效规整填料的可行性。在适当提高回流比的条件下,脱异丁烷塔可满足新的分离要求。

Before into the reactor,N-butane was separated from the raw material in DIB column for the process of dehydrogenation of isobutane to isobutene.In DIB column,the content of n-butane,which was in the overhead distillate,was less than 2%(wt) according to previous process design.In order to increase the raw material utilization and the purity of isobutene,the content of n-butane in the overhead distillate was needed to reduce to less than 1%(wt).Aspen Plus was used to simulate the optimization of process and equipment.The simulation results showed that when the feed stage moved down to 21 th stage from 15 th stage,the content of n-butane in the overhead distillate was reduced to 1.73%(wt) from 1.75%(wt) at the same reflux ratio.After optimization of feed stage,when reflux ratio was more than 3.4,the content of n-butane in the overhead distillate was less than 1%.But after increasing reflux ratio,liquid and vapor load in the column increased and steam consumption became greater too.The minimum number of theoretical plate was 25 and the minimum reflux ratio was 2.74 at new separation condition.The feasibility of changing column internals into structured packings was discussed.After packed with high efficiency structured packings,new separation demand was satisfied when the reflux ratio was slightly increased.