隔板塔(DWC)多定态解的净物质流分析

Analysis of Net Material Flow among Multiple Steady State Solutions in DWC

与传统精馏分离工艺相比,完全热耦合精馏技术(隔板塔)有更多的操作变量(即自由度),这些操作变量在实现优化设计的同时,也会引起多定态现象。采用单组分净物质流,针对隔板塔在三组分分离过程中存在多定态解的现象进行分析,通过等效热耦合四塔模型,研究其多解现象。在不同定态解的条件下,计算并分析隔板塔内部的净物质流。结果表明,多个定态解对应的塔内部组分净物质流之间存在差异。

Compared with the conventional distillation process, the fully thermally coupled distillation technology such as dividing wall column has more manipulated variables or degrees of freedom and can be used to optimize design parameters. These redundant manipulated variables can also result in multiple steady states （MSS）. MSS is a special phenomenon occurring in the dividing wall column. That is, there exist two or more pairs of internal coupled flow rate to satisfy the specified product purifications under the same conditions as the total feed flow rate, component fraction, thermodynamic condition and so on. In order to have a better understanding on MSS occurring in the dividing wall column, the analyses of the net material flows of one simple component and four-section model are given in this paper and the differences among these multiple steady state solutions for three-component distillation dividing wall column are analyzed. In the first section, based on the simulation software like Aspen Plus and mapping software like Origin, benzene-toluene-xylene system is used to explore the MSS phenomenon. In the second section, the differences of net material flow between multiple steady state solutions are analyzed. Results show that MSS phenomenon indeed exists, which matches the published literatures very well. Besides, the results of net material flow also illustrate that there exist obvious differences among these multiple steady state solutions, which can provide a useful method to choose the optimum values from these candidates. Hence, MSS is a common case existing among the fully thermally coupled distillation process and the analysis of net material flow can bring a useful way to explain and select the best values among these multiple candidate solutions.