甜苷液浓缩逆流三效蒸发器控制方法的研究

发布时间：2018-05-20 20:50

本文选题：三效蒸发器 + 一效二次蒸汽流量　；参考：《广西师范大学》2017年硕士论文

【摘要】：在食品、制药及化工等工业生产中,以生蒸汽为热源的蒸发器被广泛应用于原料液的浓缩工艺中。早期这种蒸发器通常为能耗较高、效率较低的单效蒸发器。近年能耗低、效率高的多效蒸发器逐渐替代了单效蒸发器,最为常见的是三效蒸发器。早期的三效蒸发器多为手动控制使得其在生产过程中的能耗及效率不甚理想,为了提高三效蒸发器工作状态的稳定性,降低能耗、提高效率,研究三效蒸发器的自动控制方法具有重要意义。本文是受广西师范大学环资学院植物成分提取实验室的委托,对该实验室原有的设备一手动控制的三效蒸发器所设计的技术改造方案,该设备主要用于罗汉果甜苷提取液的浓缩工艺中。针对该浓缩对象浓度较高时粘性大、流动性差的特点,确定改造后的蒸发器工作方式为逆流三效自循环方式,并根据其工艺流程设计一套自动控制系统,以求改造完成后能达到降低能耗、提高效率、操作便利的目的。控制系统以PLC为控制核心,以安装有MCGS工控软件的PC和触摸屏为上位机构建。PC用作过程监控,触摸屏用于现场控制,具有自动控制模式和手动控制模式。对蒸发器的控制主要有以下几个部分,生蒸汽压力的控制、各效分离室及原料罐液位的控制、蒸发室真空度的控制、成品液浓度的控制、一效二次蒸汽流量的控制等。其中一效二次蒸汽流量的控制相关变量较多,简单的PID控制已无法满足控制要求,在本文中采用前馈模糊PID算法实现一效二次蒸汽流量的控制。关键参数的控制,在编写相关PLC的控制程序前依据所确定的控制策略进行Matlab仿真,确认其合理性后,再通过编写PLC应用程序予以实现。控制系统设计完成后,在我院工控实验室进行了现场应用前的模拟调试,并对模拟调试中暴露的问题进行了改进。模拟调试的结果表明控制系统对传感器信号采集正常,控制动作稳定可靠,监控界面工作正常。文中对所采用的改造方案及三效逆流蒸发器的工艺流程作了介绍,给出了技术改造所需器件的选型,控制系统原理图,对所编写的PLC关键程序、PC机实时监控界面的功能及组态方法和触摸屏界面的控制功能作了介绍,并重点对一效二次蒸汽流量的控制策略的原理方法、Matlab仿真以及控制程序的编写作了重点阐述。
[Abstract]:In the industrial production of food, pharmacy and chemical industry, the evaporator with steam as the heat source is widely used in the concentration process of raw liquid. The early evaporators were usually single-effect evaporators with high energy consumption and low efficiency. In recent years, the multi-effect evaporator with low energy consumption and high efficiency has gradually replaced the single-effect evaporator, the most common of which is the three-effect evaporator. In order to improve the stability of the three-effect evaporator, reduce the energy consumption and improve the efficiency, the early three-effect evaporator is mostly controlled by hand, which makes the energy consumption and efficiency of the evaporator in the production process not ideal, so as to improve the stability of the three-effect evaporator. It is of great significance to study the automatic control method of three-effect evaporator. This paper is commissioned by the Plant composition extraction Laboratory of Huanzi College, Guangxi normal University, to design a technical transformation scheme for the original equipment of the laboratory, a manual controlled three-effect evaporator. The equipment is mainly used in the concentration process of the extract of the glucoside of Siraitia grosvenori. In view of the characteristics of viscosity and poor fluidity when the concentration of the condensed object is high, it is determined that the working mode of the revamped evaporator is the reverse flow three-effect self-circulation mode, and a set of automatic control system is designed according to its technological process. In order to achieve the purpose of reducing energy consumption, improving efficiency and convenient operation after the revamping. The control system uses PLC as the control core, PC with MCGS industrial control software and touch screen as the upper mechanism for process monitoring. The touch screen is used for field control, with automatic control mode and manual control mode. The control of evaporator mainly includes the following parts: the control of steam generating pressure, the control of liquid level in each separation chamber and feedstock tank, the control of vacuum degree in evaporation chamber, the control of the concentration of finished product liquid, the control of primary and secondary steam flow rate, etc. There are many variables related to the control of primary and secondary steam flow, and the simple PID control can no longer meet the control requirements. In this paper, the feedforward fuzzy PID algorithm is used to realize the control of primary and secondary steam flow. For the control of key parameters, the Matlab simulation is carried out according to the determined control strategy before writing the control program of the related PLC, and then realized by writing the PLC application program after confirming its reasonableness. After the design of the control system was completed, the simulation debugging was carried out in the industrial control laboratory of our hospital before application, and the problems exposed in the simulation debugging were improved. The results of simulation and debugging show that the control system can collect the sensor signal normally, the control action is stable and reliable, and the monitoring interface works normally. In this paper, the retrofit scheme and the process flow of the three-effect countercurrent evaporator are introduced, and the selection of the device and the schematic diagram of the control system are given. The functions and configuration methods of the PC real-time monitoring interface and the control function of the touch screen interface are introduced. The principle and method of the control strategy of primary and secondary steam flow are emphasized. The Matlab simulation and the programming of the control program are emphasized.
【学位授予单位】：广西师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP273

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