Method for accurately controlling temperature and pressure of supercritical extraction process

Abstract

The invention discloses a method for accurately controlling the temperature and pressure of a supercritical extraction process. By aiming at the characteristics of non-linearity, strong coupling and interference nonmeasurability of temperature and pressure as well as high requirement on temperature and pressure control accuracy in a carbon dioxide supercritical extraction process, the method is characterized on the basis of deeply analyzing an extraction process mechanism, a partial mathematic model of the extraction process is established; based on the model, a multivariable inference control method is adopted to control the temperature and pressure in an extraction kettle in the extraction process. The method is capable of not only realizing decoupling between the temperature and pressure of the extraction process, but also realizing full tracking under set value disturbance and full compensation under nonmeasurable disturbance, improving the temperature and pressure control accuracy and substance extraction ratio of the extraction process and improving economic benefits.

Description

technical field [0001] The invention relates to a carbon dioxide supercritical extraction production process, in particular to a precise control method for the temperature and pressure of the supercritical extraction process. Background technique [0002] As a fluid medium with a wide range of green and environmental sources, supercritical carbon dioxide is widely used in the research and application of supercritical fluid extraction technology. The critical pressure of pure carbon dioxide is 7.38Mpa, and the critical temperature is 31.06°C. Carbon dioxide in a state above the critical pressure and critical temperature is called supercritical carbon dioxide. Supercritical carbon dioxide extraction depends on the dissolving ability of supercritical carbon dioxide fluid to solute, the solubility of solute in carbon dioxide fluid is related to the density of supercritical carbon dioxide, and the density of supercritical carbon dioxide depends on its temperature and pressure. ...

AI Technical Summary

Problems solved by technology

[0003]In the production process of carbon dioxide supercritical extraction, temperature and pressure are the most important control parameters. The influence of temperature on the dissolving capacity of supercritical fluid is complicated. The volatility of the extracted substance increases with temperature, which increases the concentration of the extracted substance in the supercritical gas phase, thereby increasing the extraction amount; but on the other hand, as the temperature rises, the density of the supercritical fluid decreases, so that the chemical composition Solubility decreased

When the control system is in the closed-loop working state, it is necessary to insert a test signal in the control process, but this method will cause disturbance, and the PID controller will produce overshoot due to the influence of disturbance

However, in the supercritical extraction process of carbon dioxide, there are various measurable and unmeasurable interferences, and there are certain coupling and mutual interference problems between temperature and pressure; Influence; part of the carbon dioxide is not in the supercritical state, which reduces the amount of solvent and reduces the extraction rate. These problems need to be solved

Images