特殊精馏分离乙酸乙酯-乙腈共沸物系的优化与控制

发布时间：2018-04-18 17:09

本文选题：共沸物分离 + 萃取精馏　；参考：《青岛科技大学》2017年硕士论文

【摘要】：乙酸乙酯和乙腈是化工工业和制药工业中用途广泛的化工原料和良好的有机溶剂。本文利用特殊精馏法对乙酸乙酯-乙腈共沸物系进行分离。利用化工流程软件Aspen Plus及Aspen Dynamics对该物系的工艺流程分别进行优化设计及动态控制研究。最终实现该物系分离的严格经济优化及稳健的动态控制。首先提出常规双塔萃取精馏分离法对乙酸乙酯-乙腈共沸物系进行分离,以最低年度总费用TAC(Total Annual Cost)为目标函数,设计并优化工艺流程,获得最佳工艺流程参数,进而开始动态控制的研究。首先提出了固定回流比的基本控制结构,对其进行流量和组成的扰动,扰动结果存在乙腈产品纯度波动过大,再沸器热负荷的响应速度较慢等问题,进而提出改进的回流量与进料量(R/Fn)及再沸器热负荷与进料量(QR/Fn)比例控制的动态控制方案,该方案在对产品纯度控制方面有明显优势,最终实现了动态的稳健控制。由于常规双塔萃取精馏工艺能耗较高,而隔壁塔的节能优势明显,所以将其引入萃取精馏中,探究该物系分离的萃取精馏隔壁塔的稳态工艺流程及其动态控制。首先建立热力学等价双塔段模型的萃取精馏隔壁塔的分离方案,对其进行工艺优化,与常规萃取精馏流程比较,其TAC减少约19.7%。但由于热力学等价双塔段模型的分离方案存在气相分配比不易调节的缺陷,不易对其进行更灵活的动态控制研究,因此在热力学等价双塔段模型的基础上建立了热力学等价三塔段模型的萃取精馏隔壁塔分离方案。在稳态模拟优化基础上对其进行动态控制研究,首先建立带有气相分配比的控制结构,进行流量和组成扰动。结果显示乙酸乙酯和乙腈产品纯度较低,所以在此基础上进一步改进,固定回流比改为带有回流量和采出量(R/Vn)前馈比例控制,添加组成控制器CC2,与气相分配比构成串级,进行扰动,结果显示两产品纯度偏差减小,但仍达不到分离要求。对其进一步改进,在温度控制器基础上,添加QR/F比例控制,最终控制结构对进料流量和组成的扰动都能实现稳健处理。本文对乙酸乙酯-乙腈共沸物系分离的稳态及动态控制研究将对采用特殊精馏法分离二元共沸物系的实际工业设计及生产控制提供一定的理论依据。
[Abstract]:Ethyl acetate and acetonitrile are widely used chemical raw materials and good organic solvents in chemical and pharmaceutical industries.The azeotrope system of ethyl acetate and acetonitrile was separated by special distillation method.The optimization design and dynamic control of the process were studied by using the chemical process software Aspen Plus and Aspen Dynamics respectively.Finally, strict economic optimization and robust dynamic control are realized.Firstly, the conventional two-tower extraction distillation separation method was proposed to separate ethyl acetate and acetonitrile azeotrope system. The minimum annual total cost TAC(Total Annual cost was used as the objective function to design and optimize the process flow and obtain the best technological process parameters.And then start the research of dynamic control.Firstly, the basic control structure of fixed reflux ratio is put forward, and the flow rate and composition are disturbed. The result of disturbance is that the purity of acetonitrile product fluctuates too much, the response speed of reboiler heat load is slow, and so on.Furthermore, an improved dynamic control scheme for reflow volume and feed volume (R / Fn) and reboiler heat load / feed ratio control is proposed. The scheme has obvious advantages in product purity control, and finally realizes dynamic robust control.Due to the high energy consumption of the conventional two-tower extractive distillation process and the obvious energy-saving advantage of the next-wall column, the steady state process and its dynamic control of the adjoining column of the separated extractive distillation column are explored.In this paper, the separation scheme of extraction distillation next door column with thermodynamic equivalent two-column model is established, and the process is optimized. Compared with the conventional extractive distillation process, the TAC is reduced by about 19.7.However, because the separation scheme of thermodynamic equivalent two-tower model is not easy to adjust the gas-phase distribution ratio, it is not easy to carry out a more flexible dynamic control study.On the basis of the thermodynamic equivalent two-column model, the separation scheme of the extraction distillation next-wall column for the thermodynamic equivalent three-column model is established.On the basis of steady state simulation optimization, the dynamic control is studied. Firstly, a control structure with gas phase distribution ratio is established, and the flow rate and composition disturbance are carried out.The results show that the purity of ethyl acetate and acetonitrile products is low, so the fixed reflux ratio is changed to feed forward ratio control with reflux and yield R / V _ n, and the composition controller CC2 is added to form cascade with gas phase distribution ratio.The results show that the purity deviation of the two products is reduced, but the separation requirements are still not met.On the basis of temperature controller and adding QR/F proportional control, the control structure can deal with the disturbance of feed flow and composition.In this paper, the steady state and dynamic control of the separation of ethyl acetate and acetonitrile azeotrope system will provide a certain theoretical basis for the practical industrial design and production control of separation of binary azeotrope system by special distillation method.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ028.31

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