碱减量废水残渣甲酯化反应与精制研究

发布时间：2018-01-04 10:16

本文关键词：碱减量废水残渣甲酯化反应与精制研究　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：碱减量处理是改善涤纶织物性能的重要工序,生产过程中会产生大量高浓度碱性有机废水,称之为碱减量废水,其主要成分为对苯二甲酸盐。现有废水处理方法主要是通过酸析的方式结晶析出对苯二甲酸(TA),以降低废水的COD,然后达标排放。过滤得到的TA粗品称之为碱减量废水残渣,目前主要作为低端聚酯原料、烟花添加剂、燃料等,多作为固废利用考虑,并未得到高值化的利用。本论文提出一种新颖的残渣高值转化方法,即以碱减量废水残渣为原料,通过甲酯化反应制备得到对苯二甲酸二甲酯(DMT),论文对这一工艺的反应过程和产品精制过程进行了系统的实验与计算机模拟研究,确定了甲酯化反应动力学、热力学、减压精馏条件、单元条件与流程结果。残渣的定量分析给出,其中的对苯二甲酸湿基含量达到87.79%,并含有水分,无机盐及可溶性有机物。甲酯化实验与模拟表明,宜采用两步酯化工艺,两步酯化反应均对温度敏感,二级酯化反应动力学模型能够很好的模拟反应过程中各组分浓度变化。通过自主设计的减压精馏塔对精馏的真空度和回流比两个因素进行的考察表明,最佳真空度为8-10kPa,最佳回流比为2,在此精馏条件下,塔顶所得DMT纯度可以达到99.3%以上。通过实验和DSC测定了 DMT、间苯二甲酸二甲酯(DMI)和邻苯二甲酸二甲酯(DMP)的二元固液相平衡数据,提出低共熔型物系的固液相平衡模型。结果显示DMT/DMI和DMT/DMP为低共熔型物系而DMI/DMP为固体溶液型物系。DMT/DMI和DMT/DMP的低共熔温度分别为63.8℃和-2℃。DMT/DMI的低共熔组成是质量分数为12.8%的DMT和87.2%的DMI。DMT/DMP的低共熔组成是质量分数为7%的DMT和93%的DMP。在此基础上得到三个二元体系的固液平衡相图并以此为基础提出针对三种异构体的溶剂结晶结合降膜结晶的混合结晶方案。最后,通过Aspen Plus软件对碱减量废水残渣甲酯化制备DMT的工艺进行全流程的模拟与设计,工艺包括一级酯化、二级反应精馏、甲醇回收、DMT精制和热量回用五个部分,完成了各单元物料与能量衡算,最终得到通过碱减量废水残渣甲酯化制备DMT的新工艺概念流程。
[Abstract]:Alkali treatment is an important process to improve the performance of polyester fabric, the production process will produce a large number of high concentration of alkaline organic wastewater, called alkali reduction wastewater, the main component of terephthalic acid salt. The existing wastewater treatment method is mainly through the analysis of the precipitated crystalline acid of two formic acid (TA), in order to reduce waste water COD, then discharge. The crude TA filtering called alkali reduction wastewater residue, mainly as a low-end polyester raw material, fuel additives, fireworks, as solid waste utilization has not been considered, high value of utilization. This paper presents a novel method of high conversion value of the residue in alkali residue reduction wastewater as raw material, through esterification reaction of terephthalic acid methyl ester was prepared by two (DMT), simulation experiment and computer system based on the process of the reaction process and product refining process were determined. The esterification reaction kinetics, thermodynamics, distillation conditions, conditions and results are given. The flow unit analysis of residue quantitative, the wet terephthalic acid content reached 87.79%, and contain water, inorganic salt and soluble organic matter. The experiment and simulation show that the methyl esterification process should be adopted, the two step, the two step reaction of esterification temperature sensitive, two Esterification Kinetics model can simulate the reaction process were very good in concentration. Through the vacuum distillation tower to independently design distillation vacuum and reflux ratio of two factors for the study showed that the optimum vacuum degree is 8-10kPa, the optimum reflux ratio is 2, the distillation conditions, the top of the tower the purity of DMT can reach more than 99.3%. DMT was determined by experiment and DSC, benzene two formic acid two methyl ester (DMI) and the adjacent benzene two formic acid two methyl ester (DMP) of two yuan of solid-liquid phase equilibrium data were put forward Phase equilibrium melting type solid - liquid model. The results showed that DMT/DMI and DMT/DMP eutectic type system and DMI/DMP system for solid solution type.DMT/DMI and DMT/DMP eutectic temperature were -2 and 63.8 DEG C C.DMT/DMI eutectic composition is the mass fraction of 12.8% DMT and 87.2% DMI.DMT/ DMP the eutectic composition is the mass fraction of 7% DMT and 93% DMP. on the basis of the three two yuan system of solid-liquid equilibrium phase diagram as the basis for the three isomers of solvent crystallization with falling film crystallization crystallization hybrid scheme. Finally, the preparation of DMT residue alkali reduction wastewater by methyl esterification Aspen Plus software for simulation and design of the whole process, including a process of esterification, two reactive distillation, methanol recovery, with five parts back to DMT refining and heat, to complete the unit material and energy balance, finally obtained by alkali reduction A new process concept process for the preparation of DMT in the residue of waste water residue.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X791;TQ245.24

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