The Research On Temperature And Pressure Technology Accurately Control For Supercritical Fluid Extraction Process

In the process of CO2 supercritical extraction, the temperature and pressure are the most important control parameters, subtle changes in temperature and pressure in the vicinity of the critical point of CO2, will make significant change in the ability of the raw to be dissolved in the CO2, then affecting the extraction rate.Therefore high control precision of temperature and pressure is demanded in the process of supercritical CO2 extraction.And the temperature and pressure can be influenced by a variety of disturbance in the extraction process,some can be measured, while some cannot, and there are some coupling problems between the temperature and pressure, so there will be difficulties in controlling the temperature and pressure with high precision in the supercritical extraction process. So it is of great significance to study on the decoupling control of temperature and pressure in the CO2 supercritical extraction process in order to improve extraction efficiency and quality and extracted a lot of meaning.Based on the comprehensive analysis of the mechanism of extraction process, the mathematical model is established,with which multivariable reasoning control method is proposed to control the temperature and pressure within the extraction process of extraction kettle. The simulation results show that: the method can decouple the temperature and pressure in the extraction process. between the track and to fully compensate completely unmeasurable value Disturbance disturbance, and to control the process with a certain ability to adapt to the uncertainty for provide increased CO2 supercritical extraction rate and quality extraction theoretical basis, the main contents of this article is completed based on the above objectives are as follows:1、The main control parameters for temperature and pressure extraction autoclave extraction process, using the mechanism of modeling and experimental combination, the energy conservation principle, a mathematical model of extraction kettle temperature and heating time between the kettle and the extract mathematical model and pressure between the motor speed; for the coupled problem of temperature and pressure within the extraction process between the extraction kettle, PR status using a mathematical method mathematical model and temperature and pressure between the motor speed and the heating time between model. Finally, comparing the measured value and the calculated value of the error model to analyze the accuracy of the mathematical model built for the precise control of CO2 in the supercritical extraction process extraction reactor temperature and pressure provides a theoretical basis.2 、 Based on the supercritical CO2 extraction extraction kettle temperature and pressure on the established model for temperature and pressure nonlinear, strong coupling and interference unpredictable, it proposed inference control method uses multiple variables, and the theory this method can not only analyze the decoupling extraction process between temperature and pressure, but also can realize fully compensated fully tracked and unmeasurable setpoint disturbance disturbance. Term problems ahead for the actual control process specification V controller, the design method V specification controller and verify its rationality. Finally, in order to better highlight the control method used in this paper the advantages associated model under the same conditions of temperature and pressure extraction kettle established within the simulation analysis,compared with PID control method and multivariate inference control methods control effect, come to control the effectiveness and feasibility of the proposed.3 、 CO2 supercritical extraction process temperature and pressure control system hardware and software part of the design, control system uses two layers: the upper layer to monitor, select MCGS configuration software to create a user platform for extraction after selecting the next crew PLC programmable logic controller to control the core, the temperature and the pressure inside the autoclave was extracted by the load cell measurement and temperature measurement element; kettle trend parameters controlled by real-time monitoring and alarm system, the formation of human-machine interface after measuring the actual input to the controller after conversion, the output control data to the device and the thermostat regulator after multivariate inference algorithm operation, so as to achieve precise control of temperature and pressure within the extraction vessel.