Research On Distributed Predictive Control Of Multi-component Rare Earth Extraction Process Based On Ladder Correlation

Rare earths are called"industrial vitamins"and are widely used in new energy,new materials,energy conservation and environmental protection,aerospace,electronic information and other fields,and are important non-renewable strategic resources.China is a country with large rare earth resources,and its reserves and output rank first in the world.However,due to the unreasonable structure of my country’s rare earth industry and the backward separation and smelting technology,the domestic rare earth industry presents a small,scattered and chaotic development pattern.In order to ensure the healthy development of my country’s rare earth industry,the State Council has promulgated the"Several Opinions of the State Council on Promoting the Sustainable and Healthy Development of the Rare Earth Industry"^[2]with the aim of"promoting integration,controlling the total amount,restricting import and export,and promoting utilization",so to make the industrial structure of my country’s rare earth industry.Significant progress has been made in adjustment.With the integration and development of a new generation of information technology and manufacturing technology,and the in-depth integration of production,education and research,my country’s manufacturing industry has begun to shift from"Made in China"to"China Smart Manufacturing",and the economy has shifted from a high-speed development stage to a high-quality development stage.Under the premise of rare earth production and cost indicators,it is of great significance to increase the content of hard-extracted and easy-extracted rare earth elements.However,Hard-extracted and easy-extracted component of rare earth elements are difficult to continuously on-line,And there are strong coupling,nonlinearity,time lag between solvent,liquid,acid,It is difficult to use a more accurate mathematical model to describe their relationship,The relationship changes with the influence of boundary conditions such as the degree of saponification of the extractant,the composition of the material and concentration of the detergent,So it is difficult to use the existing control method to control the production process of Hard-extracted and easy-extracted component of rare earth elements.Most rare earth companies still use the"off-line analysis,experience control,and manual adjustment"dosing operation mode,resulting in low production efficiency,high resource consumption,unstable product yield and quality,and it has been difficult to meet the requirements of green intelligent manufacturing.Aiming at the difficulty of controlling the content of multi-component rare earth elements,this paper takes the P507-HCL extraction separation La Ce/Pr Nd light rare earth extraction production process as the specific research object,and has completed the following research work.（1）For the extraction and separation process of multi-component rare earths,the cascade extraction theory is used to model the mechanism.Firstly,the two-component step-by-step extraction dynamic model was combined with the extraction equilibrium separation coefficient of the"cascade extraction theory",and the nonlinear characteristics of the extraction process were described by the material balance equation.A nonlinear dynamic model for multicomponent extraction is proposed,which takes the concentration of each component of rare earth elements in each stage of water phase and organic phase as the state quantity,extractant,feed liquid,detergent as input variables,and the content of difficult-to-extract and easy-to-extract rare earth elements as the output.Secondly,considering the production structure of the multi-component rare earth extraction process,the difficult-to-extract output of the extraction sub-process of the previous level is used as the feed liquid input of the sub-process of extraction production of the next level.Ladder relational structure distributed model is proposed,which equals the production process of multi-component extraction as multiple two-component extraction production processes,so the nonlinear dynamic model of multi-component extraction can be decomposed into multiple two-component extraction dynamics models.Then,the Jacobian linearization was performed near the equilibrium point,and the linear model of the content of the multi-component elements was established.Finally,the simulation results showed that the established dynamic model could simulate the dynamic characteristics of the multi-component rare earth extraction process.（2）According to the principle of predictive control,the distributed predictive control method of drug dose composed of non-linear predictive model,feedback correction,drug dose optimization and other units is studied.First,establish a non-linear prediction model for the content of rare earth element components based on the rare earth extraction process model established in content（1）,and predict the component content at the next moment according to the mining conditions,drug dosage,and historical component content distribution;Then this paper combine the component content detected in real time to feedback and correct the predicted component content to overcome the mismatch of the prediction model.The component content deviation has been obtain by the difference between the corrected component content and the target component content;Finally,the optimization objective function and its constraints are established,and the quadratic programming method is used to solve the dosage of the drug to achieve tracking control of the target component content of rare earth elements to meet the requirements of rare earth extraction production indicators.Hard-extracted and easy-extracted components are obtained by using the step correlation DMPC algorithm for the above simple linear model.When the concentration of the material liquid or the yield changes due to changes in working conditions,The content of hard-to-extract and easy-to-extract rare earth elements will change with the increase（decrease）of the input extractant flow rate and detergent flow rate,and the production target can still be reached.