大型聚氯乙烯装置反应温度的新型控制研究

发布时间：2018-05-19 11:20

本文选题：聚氯乙烯 + 聚合温度　；参考：《北京化工大学》2016年硕士论文

【摘要】：聚氯乙烯(polyvinyl chloride, PVC)在各个行业都被广泛的应用,在国民经济中发挥着重要的作用,而决定PVC产品质量的关键因素之一就是聚合装置的反应温度。PVC聚合反应属于间歇的放热反应,呈现出较强的非线性和大时滞特性,而PVC的生产对温度有着非常严格的控制要求。目前,PVC生产过程中的聚合反应温度通常采用PID控制,但传统的PID控制器无法达到理想的控制效果,容易造成反应温度的调节时间长,超调大,波动幅度大等问题,严重影响着产品的质量。针对实际工业过程,本文研究了大型聚氯乙烯反应温度的新型控制方法,主要工作如下：(1)根据聚氯乙烯生产工艺过程,基于聚合反应机理,分析了聚合反应各个阶段的工艺过程及影响反应温度控制的因素,并总结了整个反应温度被控对象的控制难点。从聚合反应的动力学方程和能量物料平衡方程出发,推导出反应温度和其夹套水温的函数关系方程式。通过最小二乘法辨识出系统的传递函数,转化为状态空间形式,并且对辨识出的模型进行在线修正和离线验证,证实模型的准确性和有效性,为控制器的设计奠定基础。(2)根据聚合装置反应温度的不同动态特性,针对升温段和恒温段分别设计了最小协方差约束控制器(Minimum Variance Covariance Constrained Control, MVC3)。在预先给定被控对象的输入方差和输出方差的基础上,对被控对象的综合性能指标进行最小化,利用线性矩阵不等式进行求解出最优的反馈控制律。然后采用单增限界的控制器切换算法对这两个阶段的控制器进行无扰切换,并运用到实际工业过程中,应用结果证实了所研究方法的可行性和有效性。(3)针对聚合反应釜存在较大的外界干扰,研究了采用线性变参数模型(Linear parameter varying, LPV)进行建模和控制。所研究方法是以外界的变量作为调度变量,描述被控对象在沿着调度参数变化的全部轨迹对应的全局动态特性。通过线性分式变换的方法设计控制器,这样就能够把系统的不确定单独剥离出来进行考虑,用线性矩阵不等式求解控制器。这样设计出的控制器在调度参数的变化轨迹内都能够很好的满足当前的控制要求。(4)针对实际工业中难以一一直接判定控制器性能优劣的实际情况,利用被控闭环系统的灵敏度函数和互补灵敏度函数判定原理,用C#语言开发了控制系统性能评价和参数优化软件,并给出了该软件的使用方法。
[Abstract]:Polyvinyl chloride (PVC) is widely used in various industries and plays an important role in the national economy. One of the key factors determining the quality of PVC products is that the reaction temperature of the polymerization plant belongs to the intermittent exothermic reaction. PVC has strong nonlinear and large time delay characteristics, and the production of PVC has very strict temperature control requirements. At present, the polymerization reaction temperature of PID is usually controlled by PID, but the traditional PID controller can not achieve the ideal control effect, which can easily lead to the problems of long adjusting time, overshoot and large fluctuation of reaction temperature. The quality of the product is seriously affected. According to the actual industrial process, a new control method of reaction temperature of large PVC is studied in this paper. The main work is as follows: (1) according to the production process of PVC, based on the polymerization mechanism, The process of polymerization and the factors influencing the reaction temperature were analyzed, and the difficulties of controlling the reaction temperature were summarized. Based on the kinetic equation of polymerization and the equation of energy and material balance, the functional equation of reaction temperature and jacket water temperature is derived. The transfer function of the system is identified by the least square method, which is transformed into the form of state space, and the model is corrected on line and verified off-line, which proves the accuracy and validity of the model. According to the different dynamic characteristics of the reaction temperature of the polymerization device, the minimum covariance constrained controller is designed for the heating stage and the constant temperature stage, respectively. On the basis of the input variance and output variance of the controlled plant given in advance, the comprehensive performance index of the plant is minimized, and the optimal feedback control law is obtained by using linear matrix inequality (LMI). Then the controller switching algorithm with single increasing limit is used to switch the controller in these two stages without disturbance, and it is applied to the actual industrial process. The application results show the feasibility and effectiveness of the proposed method. Aiming at the large external interference in the polymerization reactor, the linear variable parameter model linear parameter varying, LPV) is used to model and control the polymerization reactor. The method is to use external variables as scheduling variables to describe the global dynamic characteristics of the controlled object along the whole trajectory of the scheduling parameters. The controller is designed by the method of linear fractional transformation, so that the uncertainty of the system can be taken into account separately, and the controller can be solved by linear matrix inequality (LMI). The controller designed in this way can meet the current control requirements very well within the changing trajectory of scheduling parameters) in view of the actual situation that it is difficult to directly judge the performance of the controller one by one in the actual industry. Based on the principle of sensitivity function and complementary sensitivity function of the controlled closed-loop system, the performance evaluation and parameter optimization software of the control system is developed with C # language, and the application method of the software is given.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ325.3;TP273

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