The Applied Research Of Predictive Control In Molecular Distillation Production Process

Molecular distillation is a high-tech and can be separated objects are suitable for use in the separation of the liquid material where it exceeded the boiling point difference between the conventional separation rely on the principle of separation of substances, in10-2～10-4mmHg vacuum to separate the absolute material non-equilibrium distillation process, in this condition the evaporator and the condenser is less than the distance between the object to be distilled light oil component of the mean motion from the process, it can be called the Short-Pathdistillation-short-path distillation. The overall objective of this thesis is based on the lowest energy consumption index constraints, optimization of process parameters, building heat (steam temperature and pressure), the relationship between the degree of vacuum and thin materials boiling point and its mathematical model, integrated multi-effect theory, the heat pump technology and low temperature evaporation process to achieve the upgrading of the distillation unit. Through the integration of innovation and engineering, formed in the field of distillation has to promote the significance of energy-saving technology research.This paper first describes the research background and significance, molecular distillation technology and predictive control methods are reviewed, molecular distillation of the state of development at home and abroad, the technical characteristics and device type, and wiped film molecular distillation, for example detailed analysis of the basic principles of molecular distillation technology, the technical parameters of film molecular distillation and process, based on mass and heat transfer theory, the study established a heat source (steam temperature and pressure), the vacuum degree and the boiling point of the relationship between the mathematical model of thin material.In addition, this paper gives a detailed analysis of the predictive control theory, focuses on the study of the predictive control method in the generalized predictive control algorithm, combined with PLC practice construct PLC predictive controller, gives a specific design steps. At the same time, selection of wiped film molecular distiller film temperature as the research object, determine the model of the optimization objective function, predictive value as the system output is compared with the set-point value, the error and error change rate prediction value, into the predictive controller implementation. The use of Matlab for the system simulation, simulation results:the steady-state error control in+0.2degrees, each100s temperature not exceeding0.01degrees Celsius, the maintenance of homeostasis of the time reached more than30minutes. Further evidence of the predictive controller design, the successful implementation of film temperature effective smooth control.On the basis of this, combined with the actual production process of molecular distillation, to the experimental obtained parameters as the basis, the success of research and development of multi effect evaporation process based on low energy consumption and low temperature distillation unit DCS energy saving control system. The system adopts the distributed control technology, can be divided into centralized monitoring level, process control level and field basic level three hierarchy, choose" three-dimensional force control configuration software for monitoring system", SIEMENS S7-300series PLC as lower machine control system, HMI is the scene of the touch screen, can realize temperature, vacuum degree and scraping film speed automatic adjustment, levels of scraped film speed0-150rpm, evaporation temperature20-250DEG C, the vacuum degree of1-101Kpa can be respectively adjusted continuously. Finally, taking Fructus Schisandrae oil purification experiment further proof, the system to achieve a better correlation function, and achieve the satisfactory control effect.The whole system is based on the vacuum low temperature evaporation energy saving technology research and development, so the design is completed the system energy saving effect is remarkable, the actual operation of equipment power consumption is about13Kw/h, evaporation consumption ratio is less than1:5, with the traditional distillation device, per hour to save electric energy7.8Kw, equivalent to annual coal saving25tons of.