Research On Decoupling Of Wiped Scraping Membrane Molecular Distillation

Molecular distillation is a new separation technology with great development prospect.It has a wide development prospect in precision chemical industry,petrochemical industry,daily chemical industry,food industry,pharmaceutical industry,plastic manufacturing and other practical production fields.Generally,the optimization of molecular distillation equipment only takes the optimization control method on each process parameter,and usually ignores the coupling relationship within the evaporator.However,scraping film molecular distillation is a strong coupling system,and the optimization of process parameters alone can not completely eliminate the interaction between various process variables in the system,which in the actual production process has an impact on the control design It is very difficult to prepare,which makes the molecular distillation system unable to achieve the desired control effect.Through the analysis of the experimental data in the early stage,temperature and vacuum are the most critical factors affecting the molecular distillation system,and the coupling relationship between them is very strong,so it is necessary to take the necessary decoupling control strategy.Therefore,it is very important to study the decoupling controller for the temperature and vacuum degree of molecular distillation system in the actual production optimization process.Based on the MDS-80-?molecular distillation equipment,this paper mainly studies the coupling characteristics of the molecular distillation system by analyzing the previous experimental data:First of all,according to the characteristics of the data changes in the early stage,the fitting curve of temperature and vacuum degree in the molecular distillation system is made.According to the obtained fitting curve,the coupling relationship model of the molecular distillation system is established by the way of system identification combined with the characteristics of the step response curve of the second-order underdamped system,and the relative gain matrix of the system model is calculated by the indirect method The analysis of the relative gain matrix shows that the system has a serious coupling relationship,and it needs to take necessary decoupling control strategy.Secondly,according to the coupling relationship model of molecular distillation system,the corresponding decoupling compensation controller is designed by decoupling compensation control matrix and inverse decoupling compensation control.Among them,diagonal matrix decoupling compensator,unit decoupling compensator and feed-forward decoupling compensator are designed respectively by using the algorithm of decouplingcompensation control matrix,and compared with the inverse decoupling compensation controller,it is concluded that the inverse decoupling compensation controller is the most suitable method in the actual operation of molecular distillation system and the design of optimal controller.According to the model of molecular distillation system after decoupling compensation,the expected dynamic method is adopted,and the expected dynamic equation coefficient is reflected in the controller parameters through the actual system demand design.The Tornambe controller is designed to decouple the molecular distillation system,and compared with the traditional PID controller.The simulation is carried out with MATLAB software,and the simulation curve is analyzed It is concluded that the Tornambe controller designed by the expected dynamic method has better performance index and better robustness.Finally,according to the actual situation of MDS-80-? molecular distillation equipment,the DCS control system of molecular distillation equipment is designed by using the distributed control method,which makes it more convenient and intuitive for operators to conduct actual experiments and production operations on the molecular distillation system through the interactive interface,and realize the automatic transformation and upgrading of the molecular distillation system.