Research Of Wiped Film Evaporation Process Modeling And Control Technology

Wiped film molecular distillation device is the third generation of molecular distillation equipment, totally dependent on the designer’s experience and the large number of repeating tests on the structural design, and structure parameter setting has no corresponding theoretical basis for support. In addition, the practical application in order to determine the optimum experimental conditions of a material also requires the operator to do many experiments to determine the experimental conditions relatively ideal. This resulted in the wiped film molecular distiller for optimal state requires a lot of financial and material resources waste in design and application. In order to solve these problems, the key is to establish the mathematical model of wiped film molecular distiller, and numerical calculation using this model provides an important reference for the design and control of application of wiped film molecular distiller.This paper studies the wiped film molecular distiller roller type of wiper operation structure characteristics, the use of fluid mechanics and molecular distillation process of feed quantity, concentration, viscosity, diameter and other factors. First set up the roller mass balance between the class n, and through the iterative model of mass transfer the overall, and through iterative overall mass transfer model. Again uses the actual experimental parameters into the mass transfer model for numerical calculation, compared with the actual experimental results to determine the reliability of the model and the relative error range of the model is about 1.5%～2.5%. The numerical simulation was carried out by using the model, by adjusting the parameter of the model, in order to determine the influence of each parameter on molecular distillation process. According to the influence of various parameters on molecular distillation process, adjust the experiment parameters for the better separation effect of molecular distillation.Through the model simulation found in wiped film molecular distillation process separation effect is very sensitive to the film scraper motor speed, especially at low speed, speed fluctuation is very small changes occurred in distillate concentration has changed greatly. In order to improve the stability of film wiper speed motor, control of the brushless DC motor adopts double closed loop, the inner loop adopts current discharge loop control and outer loop using ADRC, the wiper speed film motor in the load changes can still maintain a relatively steady speed.In order to improve the control precision and the separation of wiped film molecular distiller’s rate, and easy to record data, improve the automation control level, using SIMATIC S7-300 series programmable controller to build distributed control system, using STEP7 and Kingview for distributed control system hardware and software configuration, and realize the data exchange between MATLAB/Simulink and PLC using OPC technology, which makes the numerical control the output of ADRC can realize the control of wiped film of the brushless DC motor by PLC.