SIMATIC PCS7系统在聚氯乙烯生产中的应用研究

发布时间：2018-03-29 21:30

  本文选题：过程控制　切入点：PCS7系统　出处：《东华大学》2017年硕士论文

【摘要】：聚氯乙烯(PVC)因其在大分子中引入氯原子,使其在耐燃、透明、耐折和力学性能等方面均超过了聚乙烯,是世界五大通用热塑树脂之一。聚氯乙烯的生产具有很强的连续控制性,因此需要操作和调节的变量也很多,同时根据聚氯乙烯生产的工艺需求,现场的执行机构会拥有复杂的控制逻辑结构。考虑到聚氯乙烯的生产也会涉及到氯气这样有毒有害气体的配比和传输,所以控制系统本身就要具有很高的稳定性和灵敏性。温度的变化是影响聚合度的关键因素,如果温度不能很好的在生产工艺温度曲线的范围内进行控制,那么得到的产品就会出现质量问题。因此本课题的重点和难点是:如何建立一个关于温度的数学模型;找到一个合适的算法对关于温度的数学模型进行仿真及优化,并且证明该算法对温度达到了理想的控制需求。本论文的主要工作有:首先,对聚氯乙烯的生产环节进行简单的介绍,为建立聚合温度的数学模型做了铺垫;其次,根据其在聚合反应阶段的热量变化,使用机理建模构建温度变化的数学模型,该传递函数将会用于对聚合温度的控制;第三、采用基于免疫粒子群算法的PID参数整定的方法来控制循环水阀的开度,从而控制聚合温度在允许的范围内进行波动。通过MATLAB对传递函数进行仿真后发现,采用免疫粒子群算法的系统动态性能指标要比整定之前的系统性能指标优异。同时将该方法投入实际运行后发现,聚合温度可以维持在最佳温度的±0.2℃之内;第四、对于精细化工行业的控制,从硬件和软件设计的两个方面入手。在硬件设计方面,在控制柜中采用了高度的冗余来保证系统的稳定性。在软件设计方面,通过上位机和下位机的设计,使软件部分能够很好地和硬件部分相融合。由于硬件和软件实行了高度冗余设计,所以当PCS7控制系统应用于聚氯乙烯生产的控制过程后,系统的运行稳定性比之前有了明显的提升,在系统发生故障或者维护设备时可以使用备用的控制器、现场总线以及服务器等,让生产过程实现了不停炉操作;第五、在对聚合反应阶段的控制方案实施的过程中,通过使用强大的WINCC人机界面,可以很好的了解生产情况,并且可以通过操作员面板对生产环节进行相应的干预。通过对聚合反应阶段的控制方案的介绍,具体的了解了PCS7控制系统在聚氯乙烯生产中的应用。同时也对生产的各个控制环节,利用程序进行了说明,并且利用了WINCC的图形监控界面对生产进行监控。论文使用PCS7控制系统和免疫粒子群算法对聚氯乙烯的生产进行控制,在投入实际生产后,聚氯乙烯的年产量比之前提升了近一倍,系统的故障率也降低到了0.4/万炉,对冷却水的使用率降低了20%,生产整体的反应时间比原来减少的24%,经济效益和产品的质量取得了显著的提高。
[Abstract]:Polyvinyl chloride (PVC) is one of the five universal thermoplastic resins in the world because of its introduction of chlorine atoms in macromolecules, which makes it superior to polyethylene in the aspects of flame resistance, transparency, folding resistance and mechanical properties. The production of PVC has strong continuous control. So there are a lot of variables that need to be operated and adjusted, and at the same time, according to the process requirements of PVC production, The field executive will have a complex control logic structure. Considering that the production of PVC also involves the proportion and transport of toxic and harmful gases such as chlorine, Therefore, the control system itself should have high stability and sensitivity. The change of temperature is the key factor affecting the degree of polymerization. If the temperature is not well controlled within the temperature curve of the production process, So the focus and difficulty of this subject are: how to build a mathematical model about temperature; find a suitable algorithm to simulate and optimize the mathematical model of temperature. The main work of this paper is as follows: firstly, the production of PVC is simply introduced, and the mathematical model of polymerization temperature is established. According to the heat change during the polymerization stage, the mathematical model of temperature change is built by using the mechanism. The transfer function will be used to control the polymerization temperature. The PID parameter tuning method based on immune particle swarm optimization algorithm is used to control the opening of circulating water valve, thus controlling the polymerization temperature to fluctuate within the allowable range. The transfer function is simulated by MATLAB. The dynamic performance index of the system using immune particle swarm optimization algorithm is better than the system performance index before tuning. After putting the method into practice, it is found that the polymerization temperature can be kept within 卤0.2 鈩，

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