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在醋酸脱水共沸精馏系统中,水相回流不仅能调节物料平衡,而且能控制塔顶出料中的醋酸浓度。在醋酸脱水系统设计和控制的研究中,水相回流往往给定一个固定的流量,很少被用作控制变量,水相回流与精馏塔的进料变化及出料组成的关系未见报道。本文利用Aspen Plus流程模拟软件模拟计算精对苯二甲酸(PTA)装置溶剂脱水共沸精馏系统。利用三元相图分析醋酸-水-醋酸正丁酯(HAC-H_2O-NBA)体系中,进料组成变化与水相回流和酯相回流之间的关系。在稳态模型的基础上模拟分析进料中水含量和杂质对二甲苯(PX)对水相回流的影响,结果与相图分析一致。研究结果表明:对于某一特定的出料要求,当进料水含量高于69%时,水相回流可以降低为零,如果此时进料组成发生变化,只要调节酯相回流即可保证精馏塔的分离要求,而当进料水含量低于69%时,水相回流需要进行调节以保证塔顶采出水中醋酸含量合格;不能让杂质PX在塔内累积过多,以免因水相回流大量增加而使塔的能耗增加。本文的研究很容易扩展到其它具有特定出料要求的醋酸脱水共沸精馏系统中,研究结果将为实际生产过程中精馏塔出料组成和能耗的控制提供参考。
In acetic acid dehydration azeotropic distillation system, the aqueous reflux can not only adjust the material balance, but also control the concentration of acetic acid in the overhead discharge. In the study of the design and control of acetic acid dehydration system, the aqueous reflux usually gives a fixed flow rate and is seldom used as the control variable. The relationship between the reflux of aqueous phase and the rectification tower feed composition and discharge composition has not been reported . In this paper, Aspen Plus process simulation software was used to simulate the solvent dehydration azeotropic distillation system of PTA plant. The ternary phase diagram was used to analyze the relationship between the change of feed composition and the reflux of water phase and ester phase in acetic acid-water-n-butyl acetate (HAC-H_2O-NBA) system. Based on the steady-state model, the influence of water content and impurity p-xylene (PX) on the aqueous reflux was simulated and analyzed. The results are consistent with the phase diagram analysis. The results show that when the feed water content is higher than 69%, the reflux of the aqueous phase can be reduced to zero for a given discharge requirement. If the feed composition changes at this time, the ester phase reflux can be adjusted to ensure the fine Distillation tower distillation requirements, and when the feed water content of less than 69%, the water phase reflux needs to be adjusted to ensure that the acetic acid content of the tower produced water qualified; can not allow impurities in the tower too much accumulation of accumulation in order to avoid the water phase A large increase in backflow increases the energy consumption of the tower. The research in this paper can be easily extended to other acetic acid dehydration azeotropic distillation systems with specific discharge requirements. The results of this study will provide reference for the control of discharge composition and energy consumption of the rectification column in the actual production process.