醋酸乙烯—甲醇萃取精馏过程的计算机模拟优化与控制研究

发布时间：2018-04-05 03:03

  本文选题：醋酸乙烯　切入点：甲醇　出处：《北京化工大学》2016年硕士论文

【摘要】：目前我国聚乙烯醇(PVA)生产企业在生产过程中会产生大量的醋酸乙烯(VAc)和甲醇(MeOH)的共沸物,而在分离提纯过程中普遍存在产品纯度不高、萃取剂用量大、能耗高、设备投资费用大、过程控制不稳定等技术难题。本文从工艺流程、能量节约、过程控制、经济效益四个方面着手,利用计算机模拟技术对年产10万吨PVA中用水作为萃取剂萃取精馏分离醋酸乙烯-甲醇共沸体系的过程进行模拟计算、经济优化及动态控制,分别采用连续萃取精馏、间歇萃取精馏和隔壁萃取精馏三种工艺流程,通过对比获得最佳工艺流程和最优的工艺参数及控制方案,达到节能增效的目标。通过热力学一致性检验,验证了实验所得醋酸乙烯-甲醇共沸体系汽液相平衡(VLE)数据的可靠性。对Wilson、NRTL、UNIQUAC热力学模型的二元交互作用参数拟合回归,通过对比实验与回归的数据偏差和图像吻合度,得到UNIQUAC模型的效果最好。同时用回归后各个模型的计算数值与实际生产数据进行对比,验证了UNIQUAC模型可以准确的用于醋酸乙烯-甲醇-水体系的萃取精馏模拟研究。对原有双塔连续萃取精馏进行模拟优化,通过灵敏度分析及经济优化,得到萃取精馏塔49块塔板(理论板),萃取剂进料流量17800 kg/h,温度76℃,塔顶采出量18477 kg/h,萃取剂进料位置第2块塔板,物料进料位置第18块塔板,回流比0.27；溶剂回收塔32块塔板,塔顶采出量12626 kg/h,物料进料位置第22块,回流比1.08；醋酸乙烯产品纯度从90%提高到93.5%,甲醇产品纯度从95%提高到99.9%；连续萃取精馏工艺的“全年总费用”(TAC)为2370万元/a。对于设备投资费用大和过程控制不稳定,采用恒定回流比的间歇萃取精馏工艺,得到间歇萃取精馏塔16块塔板,萃取剂进料流量24673 kg/h,温度100℃,萃取剂进料位置第5块塔板,回流比10,间歇萃取精馏操作时间1.75 h；间歇萃取精馏工艺的TAC为8363万元/a。对于能耗高,采取热耦合精馏原理的隔壁萃取精馏工艺,得到隔壁萃取精馏塔主塔51块塔板,萃取剂进料流量17800 kg/h,温度75℃,塔顶采出量18477 kg/h,萃取剂进料位置第2块塔板,物料进料位置第18块塔板,侧线汽相采出位置第43块塔板,侧线汽相采出量16325 kg/h,回流比0.22；侧线精馏塔30块塔板,塔顶采出量12874 kg/h,回流比1.0；隔壁萃取精馏工艺的TAC为2037万元/a。从经济角度分析,隔壁萃取精馏过程比连续萃取精馏过程固定成本投资节省约9.99%,能耗成本投资节省约14.19%,TAC减少了14.06%,隔壁萃取精馏工艺具有很大的经济优势。从动态控制角度分析,对于连续萃取精馏过程双温度控制结构更加有效,对于隔壁萃取精馏过程R/F恒定的控制结构更有效,二者对于进料流量扰动和进料组成扰动都能产生较好的控制效果。综合比较,隔壁萃取精馏过程更加适合该体系的分离。
[Abstract]:At present, a large number of azeotropic compounds of vinyl acetate (VAC) and methanol (MeOH) will be produced in the production process of polyvinyl alcohol (PVA) production enterprises in China. However, in the process of separation and purification, the purity of the product is not high, the amount of extractant is large, and the energy consumption is high.Equipment investment costs, process control instability and other technical problems.This paper starts from four aspects: technological process, energy saving, process control and economic benefits.The process of separation of vinyl acetate and methanol azeotropic system with water used as extractant in PVA with annual output of 100000 tons was simulated and calculated by computer simulation technology.By comparing the three processes of batch extractive distillation and adjoining extractive distillation, the optimal technological process, the optimal technological parameters and the control scheme are obtained to achieve the goal of saving energy and increasing efficiency.The reliability of the VLEE data of the azeotropic system of vinyl acetate and methanol was verified by the thermodynamic consistency test.The fitting regression of binary interaction parameters of Wilsonian NRTLUAC UNIQUAC thermodynamic model is carried out. By comparing the data deviation and image coincidence between the experiment and the regression, the best result of UNIQUAC model is obtained.At the same time, the calculated values of each model after regression were compared with the actual production data, which verified that UNIQUAC model could be used to simulate the extractive distillation of vinyl acetate methanol-water system accurately.Through sensitivity analysis and economic optimization, 49 trays of extraction distillation column (theoretical plate, feed rate of extractant 17800 kg / h, temperature 76 鈩，

本文编号：1712883