基于重组分占优的热泵隔壁塔最佳拓扑结构

Optimum topological configuration for a vapor recompressed dividing wall column with a predominance of heavy-components

在隔壁塔(DWC)分离重组分占优宽沸点三元物系的过程中,重组分的分离产生的大量高温过热蒸汽可以被蒸汽再压缩热泵(VRHP)加以利用,进而形成不同的热泵隔壁塔(VRHP-DWC)拓扑结构。根据DWC的稳态运行特征,提出VRHP-DWC的最佳拓扑结构,包括两个VRHP:第一个VRHP用来压缩过热蒸汽并将其潜在热量释放至预分离塔的再沸器或公共再沸器;另一个VRHP用来压缩由第一个VRHP产生的高温冷凝液体和塔底产品流预热后的塔顶蒸汽,并将其潜在热量释放至预分离塔的再沸器或公共再沸器。用苯/甲苯/邻二甲苯和正戊烷/正己烷/正庚烷两组物系验证了所提出结构的经济性能,结果表明,对于隔板在中部的DWC(DWC with a middle partition,DWCM),两个例子的年度总成本(TAC)分别下降了17.22%和7.11%;而当隔板位于顶部(DWC with a top partition,DWCT)和底部(DWC with a bottom partition,DWCB)时,TAC也都有不同程度的降低。此外,还讨论了不同隔板位置对DWC性能的影响,对于两个例子而言,DWCT显示出的性能最差,而DWCM与DWCB在稳态与动态上的性能表现各有优劣。VRHP-DWC最佳拓扑结构的预先确定可以大大降低化工过程开发阶段的复杂性和乏味性,并对过程中强化技术的应用具有重要意义。

In the separation of ternary mixtures with a predominance of heavy-components and a wide-boiling point range using a dividing-wall distillation column(DWC),a certain amount of excess heat always exists during the stripping of the heavy-component from the intermediate-and light-components.This can be employed to develop a vapor recompression heat pump(VRHP)-assisted DWC(VRHP-DWC).In the light of the steady-state operating characteristics of the DWC,the optimum topological configuration of the VRHP-DWC is found to involve two VRHPs.One compresses the excess heat and releases its latent heat to the reboiler or the reboiler of the pre-fractionator.The other compresses the overhead vapor stream pre-heated with the condensed liquid from the first VRHP and the bottom product stream and releases its latent heat to the reboiler or the reboiler of the pre-fractionator.The separations of ternary mixtures of benzene,toluene,and o-xylene and of n-pentane,n-hexane,and n-heptane are examined to determine the optimum economic performance.The results showed that for a DWC with a middle partition(DWCM),the total annual cost for the two ternary mixtures decreased by 17.2%and 7.1%,respectively.The TAC also decreased to varying degrees when the partition was at the top(DWCT)or bottom(DWCB).The origins of the differences between VRHP-DWCs with a dividing-wall in different positions are discussed.Predetermination of the optimum topological configuration of the VRHP-DWC can considerably lower the complications and tediousness involved in process development,which is of great significance in terms of application of this process intensification technology.