聚氯乙烯精馏系统优化与节能减排的研究

发布时间：2018-04-28 07:59

  本文选题：聚氯乙烯 + 精馏　； 参考：《北京化工大学》2015年硕士论文

【摘要】：聚氯乙烯(PVC)是我国国民经济中不可或缺的重要原材料,由氯乙烯单体(VCM)聚合而成。目前我国PVC分离提纯过程普遍存在分离效率低、产品纯度差、能耗高、操作控制不稳定、高附加值釜液未有效回收。对于以上关键技术难题,本文从工艺流程、能量集成、过程控制三个方面着手,利用计算机模拟技术对年产40万吨PVC的精馏系统进行模拟分析、能量集成优化以及动态控制,得到最优的工艺参数、换热网络和控制方案,达到节能减排的目标。根据热力学一致性检验结果,验证了氯乙烯(VCM)-二氯乙烷(EDC)体系汽液相平衡(VLE)数据的可靠性。对NRTL、WILSON、UNIQUAC热力学模型的交互作用参数拟合回归,通过比较发现NRTL模型的模拟数据与实验数据的平均相对偏差最小。同时用回归后各个模型的计算数值与工程采集值对比,验证了NRTL模型可以准确的模拟VCM-EDC体系。对低沸塔(TQ201)、高沸塔(TQ202)和高沸物回收塔(TQ203)进行模拟优化。通过单因素灵敏度和正交试验的分析得到TQ201、TQ202塔的最佳工艺参数,包括操作压力、进料状态、进料位置、回流比及馏出比。结果表明TQ201塔回流比由5.0降为3.6,节能28.0%；TQ201塔回流比由1.0降为0.6,节能40.0%。VCM产品纯度达到99.999%,低沸点杂质含量小于1 ppm,高沸点杂质含量小于3 ppm。同时,冷却介质由32℃循环水替代5℃冷冻水,节省了电耗。两塔共节约操作费用3472.1万元／年。TQ203塔采用恒回流比式间歇精馏,通过分析塔顶、塔釜及储罐成分随时间的动态变化,产品收益、操作费用和经济效益的影响因素,得到最佳塔板数、回流比和操作周期。最终得到质量分数大于99.9%的氯乙烯、质量分数大于99.0%的二氯乙烯和二氯乙烷,年经济效益为735.3万元,同时环境效益显著。对于PVC精馏工段能耗较高、余热利用不充分的问题,建立公用工程用量最低和换热器数目最少两个目标函数,通过分析△Tmin与设备费、操作费和年度总成本目标的关系,求得最佳的△Tmin,利用夹点技术获得冷、热物流夹点位置和最小公用工程用量。方案一公用工程用量最低,投资回收期为6个月；方案二最大化利用现有设备,投资回收期为4个月,对于实际工厂改造更为适宜。对于PVC精馏工段操作控制不稳定的问题,从产品纯度、操作稳定及节能环保的角度确定适用于PVC精馏系统的最佳控制方案。通过分析动态数学模型,确定控制变量,对TQ201塔提出三种控制方案；对TQ202塔提出两种控制方案；对TQ203塔提出各组分采出的控制条件。对比不同控制方案下精馏塔在受到扰动后的动态响应,结果表明TQ201塔更适用于回流量与馏出量比值恒定的控制,TQ202塔宜选择回流量与进料量比值恒定的操作。
[Abstract]:Polyvinyl chloride (PVC) is an indispensable raw material in our national economy, which is polymerized by vinyl chloride monomer (VCM). At present, the separation and purification process of PVC in China is generally characterized by low separation efficiency, poor product purity, high energy consumption, unstable operation control and inefficient recovery of high value-added kettle liquid. For the above key technical problems, this paper starts from three aspects of technological process, energy integration and process control, and makes use of computer simulation technology to simulate and analyze the distillation system with an annual output of 400000 tons PVC, and optimize the energy integration and dynamic control. The optimal process parameters, heat exchange network and control scheme are obtained to achieve the goal of energy saving and emission reduction. Based on the results of thermodynamic consistency test, the reliability of the Vapor-liquid equilibrium VLEs data of vinyl chloride (VCM) -dichloroethane (EDCC) system was verified. By fitting the interaction parameters of NRTL WILSONNU UNIQUAC thermodynamic model, it is found that the average relative deviation between the simulated data and experimental data of NRTL model is the smallest. At the same time, the calculation value of each model after regression is compared with the data collected in engineering, which verifies that the NRTL model can accurately simulate the VCM-EDC system. The low boiling tower TQ201, high boiling tower TQ202 and high boiling recovery tower TQ203) were simulated and optimized. Through the analysis of single factor sensitivity and orthogonal test, the optimum process parameters of TQ201 TQ202 tower were obtained, including operating pressure, feed state, feed position, reflux ratio and distillation ratio. The results show that the reflux ratio of TQ201 column is decreased from 5.0 to 3.6, the reflux ratio of energy-saving TQ201 tower is reduced from 1.0 to 0.6, the purity of energy-saving 40.0%.VCM product is 99.999, the impurity content of low boiling point is less than 1 ppm, and the impurity content of high boiling point is less than 3 ppm. At the same time, the cooling medium is replaced by 32 鈩，

本文编号：1814440