聚乙烯醇聚合工段和回收工段精馏工艺模拟与优化

发布时间：2018-12-08 13:49

【摘要】：聚乙烯醇是一种重要的高分子化工原料,被广泛应用于多个领域。聚乙烯醇聚合工序中大量的醋酸乙烯单体未参与聚合。醇解过程中,聚醋酸乙烯醇解产生大量醇解废液,其中主要组成为醋酸甲酯和甲醇。这些都是重要的化工原料,一般通过精馏工艺分离回收再利用。因此,聚乙烯醇聚合工段和回收工段精馏工艺进行深入研究有助于优化工艺过程,提高经济效益。Aspen Plus流程模拟软件是辅助工艺研究的重要工具。本文在熟悉国内某公司10万吨/年聚乙烯醇聚合工段和回收工段精馏工艺的基础上,利用Aspen Plus对其进行流程模拟。根据物系特点分析,聚乙烯醇聚合工段精馏工艺中聚合一塔、聚合二塔和聚合三塔采用NRTL模型,聚合四塔和聚合五塔采用WILSON模型。聚乙烯醇回收工段精馏工艺中回收一塔、回收二塔、回收三塔、回收四塔、回收五塔和回收七塔采用NRTL模型,回收六塔采用NRTL-HOC模型。根据所选的热力学模型,对聚乙烯醇聚合工段和回收工段精馏工艺进行单塔以及全流程的模拟计算,对比实际值,验证模型的可靠性。在聚乙烯醇聚合工段和回收工段精馏工艺流程模拟的基础上,利用Aspen Plus灵敏度分析工具分析理论板数、回流比、塔顶馏出率和进料位置等工艺参数对各塔分离指标的影响,获得较优的工艺参数。通过优化后工艺参数,调整流程模拟,得到回收的醋酸乙烯产品质量分数达到99.86%,整个聚合工段精馏装置再沸器热负荷降低8.02%,工艺用水减少12.1%。回收的乙醛质量分数为98.34%,回收的甲醇质量分数为99.94%,回收二塔采出的甲醇蒸气质量分数为99.92%,用于分解的醋酸甲酯质量分数为92.58%,用于回收醋酸的水溶液中醋酸质量分数为56.13%,回收工段精馏装置再沸器热负荷降低4.8%。结果表明,通过优化工艺参数,达到了节能降耗的目的。
[Abstract]:Polyvinyl alcohol (PVA) is an important polymeric chemical raw material, which is widely used in many fields. A large number of vinyl acetate monomers were not involved in the polymerization of polyvinyl alcohol. In the process of alcoholysis, polyvinyl acetate alcoholysis produces a large amount of alcoholysis waste liquid, mainly composed of methyl acetate and methanol. These are important chemical raw materials, which are generally separated and reused by distillation process. Therefore, the further study on the distillation process of polyvinyl alcohol polymerization section and recovery section is helpful to optimize the process, and the. Aspen Plus process simulation software is an important tool to assist the process research. On the basis of familiar with the distillation process of 100000 t / a polyvinyl alcohol polymerization section and recovery section in a domestic company, the Aspen Plus was used to simulate the process. According to the characteristics of the polymerization system, the polymerization of polyvinyl alcohol in the distillation process was carried out in the first column, the second column and the third tower were modeled by NRTL, and the four towers and the five towers were modeled by WILSON. In the distillation process of polyvinyl alcohol recovery section, one tower is recovered, two towers are recovered, three towers are recovered, four towers are recovered, five towers and seven towers are recovered by NRTL model, and the NRTL-HOC model is used for six towers. According to the selected thermodynamic model, the distillation process of polyvinyl alcohol polymerization section and recovery section were simulated and calculated in a single column and the whole process, and the reliability of the model was verified by comparing the actual values. Based on the simulation of the distillation process of polyvinyl alcohol polymerization section and recovery section, the effects of theoretical plate number, reflux ratio, tower top distillation rate and feed position on the separation index of each column were analyzed by Aspen Plus sensitivity analysis tool. The optimum process parameters were obtained. By optimizing the process parameters and adjusting the process simulation, the recovered vinyl acetate product mass fraction reached 99.86, the heat load of the reboiler of the whole polymerization section distillation unit was reduced by 8.02 and the process water consumption was decreased by 12.1. The recovered mass fraction of acetaldehyde was 98.34, the recovered mass fraction of methanol was 99.94, the mass fraction of methanol vapor recovered from the second tower was 99.92, and the mass fraction of methyl acetate for decomposition was 92.58. The mass fraction of acetic acid in the aqueous solution for recovery of acetic acid is 56.13 and the heat load of the reboiler of the recovery distillation unit is reduced by 4.8%. The results show that the energy saving and consumption reduction can be achieved by optimizing the process parameters.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ316

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