超临界萃取釜溶剂输送流量补偿控制技术

发布时间：2018-05-05 04:14

本文选题：超临界萃取 + 流量补偿　；参考：《长春工业大学》2015年硕士论文

【摘要】：超临界萃取技术起源于七十年代末,是一种物质分离精制的新技术,它与传统的萃取方式相比有萃取率高,无残留,可以根据沸点高低的顺序把成分先后萃取出来等优点。还可以萃取很多具有特殊化学特性的物质,是一种绿色环保的萃取手段。本文以HA221-40-11型超临界萃取装置为研究对象,萃取釜内的压力和温度决定着萃取过程是否处于超临界状态,因而萃取压力和温度的动静态性能指标直接决定着萃取率的高低,所以有必要精确的控制萃取压力。在注入二氧化碳时,增压泵全速运转,会造成压力的超调,由于本实验设备的超调是不可逆的,所以我们需要引入流量控制,使萃取压力性能指标时刻处于最优状态,为此有必要引入流量控制内环。通过分析其特点以及工艺控制流程特点,总结并研究了影响超临界萃取剂输送流量补偿控制的诸多因素：温度,压力,进料量,流量,泵产生的多余热量等等。这些参数都具有非线性和时变性等特点,为了达到提高萃取率的目的,对流量补偿控制系统提出了更高的要求。根据控制要求,制定了温度、压力、流量的控制方案,重点研究了流量补偿控制系统,对萃取剂补偿系统控制对象建立数学模型,根据萃取剂流量补偿的控制要求,应用内模控制理论设计了前馈—IMC控制器,利用MATLAB/SIMULINK对前馈—工MC控制器进行仿真验证。接着分别对前馈—工MC控制器和IMC控制器进行仿真,对比二者的仿真曲线,证明了前馈—IMC控制器可以提高控制精度,提高萃取率。其次,本文应用改造后的超临界萃取设备进行萃取实验,在同样的实验条件下,将得到的实验数据与之前未经改造的设备萃取实验的数据进行对比,结果表明,经改造后的实验设备的萃取率有了较大的提高,验证了超临界萃取流量补偿控制系统的控制效果。最后,设计了基于PLC的萃取釜溶剂输送流量补偿控制系统,上位机由研华工控机以及触摸屏组成,下位机由西门子S7-300系列,执行单元以及传感器组成,利用组态软件MCGS完成上位机触摸屏和PLC的监控组态的设计,实现了监控流量、温度、转速、压力等控制和参数设置、证书信息添加、查询,打印等功能。研究结果表明,该超临界萃取釜溶剂输送流量补偿控制系统具有萃取率高、能耗低、控制精度高等特点,达到了设计要求,为萃取釜溶剂流量的精确控制和补偿提供了一种有效的方法。
[Abstract]:Supercritical extraction (SFE), which originated in the late 1970s, is a new technique for separation and purification of substances. Compared with the traditional extraction method, it has the advantages of high extraction rate and no residue, and it can be extracted successively according to the order of boiling point. It can also extract many substances with special chemical properties. It is a green extraction method. In this paper, HA221-40-11 supercritical extraction device is used as the research object. The pressure and temperature in the autoclave determine whether the extraction process is in the supercritical state or not, so the dynamic and dynamic performance indexes of the extraction pressure and temperature directly determine the extraction rate. Therefore, it is necessary to accurately control the extraction pressure. When carbon dioxide is injected, the pressure overshoot will be caused by the full speed operation of the booster pump. Since the overshoot of the experimental equipment is irreversible, we need to introduce flow control to make the extraction pressure performance index in the optimal state at all times. Therefore, it is necessary to introduce the inner loop of flow control. Based on the analysis of its characteristics and the characteristics of the process control process, the factors affecting the flow compensation control of supercritical extractant transportation are summarized and studied, such as temperature, pressure, feed volume, flow rate, excess heat produced by pump, and so on. These parameters are nonlinear and time-varying. In order to improve the extraction rate, a higher demand is put forward for the flow compensation control system. According to the control requirements, the control scheme of temperature, pressure and flow rate is formulated. The flow compensation control system is studied emphatically. The mathematical model of the control object of the extractant compensation system is established, and according to the control requirements of the extractant flow compensation, The feedforward-IMC controller is designed by using the theory of internal model control. The simulation of the feedforward MC controller is carried out by using MATLAB/SIMULINK. Then the feedforward MC controller and IMC controller are simulated, and the simulation curves are compared. It is proved that the feedforward controller can improve the control precision and the extraction rate. Secondly, the experiment was carried out by using the modified supercritical extraction equipment. Under the same experimental conditions, the obtained experimental data were compared with those of the previous unmodified equipment. The results show that, After modification, the extraction rate of the experimental equipment has been greatly improved, which verifies the control effect of the supercritical extraction flow compensation control system. Finally, a solvent conveying flow compensation control system based on PLC is designed. The upper computer is composed of the industrial control computer and touch screen, and the lower computer is composed of Siemens S7-300 series, executive unit and sensor. The configuration software MCGS is used to design the monitoring configuration of the upper computer touch screen and PLC. The functions of monitoring flow, temperature, speed, pressure and parameter setting, certificate information adding, query, printing and so on are realized. The research results show that the system has the characteristics of high extraction rate, low energy consumption and high control precision, and meets the design requirements. It provides an effective method for accurate control and compensation of solvent flow in extractor.
【学位授予单位】：长春工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ028.32;TP273

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