Research On Modeling Optimization And Fault Diagnosis Of Refining Process Based On Bond Graph Theory

With the improvement of people's living standards,consumers not only on the demand for tissue paper growing demand,but also on the quality requirements are getting higher and higher.At the same time as for tissue paper,there is the saying of "three-point papermaking and seven-point beating." In order to meet the huge market demand and to conform to the development mode of low-carbon economy,On the premise of ensuring the quality of the pulp,how to improve the pulping output and reduce the energy consumption is an urgent problem for enterprises to solve.When the refining system fails,Not only the quality of refining will be directly affected,but also lead to serious accidents such as knife grinder and so on.Therefore,the diagnosis of refining system is also an important research topic.With the support of Key Technology Innovation Team Project of Shaanxi Province(2014KCT-15),this paper takes DCS of pulp mill process in a paper mill in Hebei Province as research object,and focuses on the multi-objective optimization of the refining process,the design and implementation of the control system and the fault diagnosis.The main content of the thesis can be summarized in the following four aspects.(1)The establishment and Simulation of the bond graph model of the refining systemThrough the analysis of the actual refining system,Based on bond graph theory,from the new perspective of energy transfer,this paper analyzes the nature of the main motor,spindle and dynamic setting disk of the refiner,and the causality between each element and its components,and the establishment of the refining system bond graph model is derived the state equation of the system.The simulation and analysis of the bonding diagram model of the grinding system in the 20-sim simulation software have been simulated and analyzed,which lays the foundation for the subsequent optimization of the grinding process and the research on fault diagnosis of the pulping machine.(2)Establishment and solution of multi-objective optimization model for grinding processAccording to the refining process,the mathematical model of the refining process was set up,with the aim of refining quality,refining output and refining energy consumption,And the ant colony optimization algorithm which is easy to be programmed and has good portability is proposed to solve the model.Aiming at the shortcomings of the basic ant colony algorithm such as premature convergence and so on,this paper improves the basic ant colony algorithm,The improved ant colony algorithm is used to solve the multi-objective function in MATLAB,and the optimal production process parameters are obtained.(3)Fault diagnosis and simulation verification of grinding system based on fault treeBased on the bond graph model of the refining system,the causality diagram of the refining system was deduced and the fault tree model of the refining system was established.According to each fault state in the fault tree model and forward reasoning combined with time causality diagram,all causes that may lead to fault are generated.Finally,the system parameters are monitored before and after the fault by simulation,the simulation results are consistent with the fault inference results.This proves the feasibility and correctness of the fault diagnosis method proposed in this paper.(4)Design and implementation of grinding process control systemThe cascade control scheme of constant beating degree is given,the order of the refiner start,stop and interlock protection program are designed.And taking S7-400 PLC as the core,the DCS of the refining process was completed on the PCS7 software development platform to realize the control of the pulp production line.The final use of OPC technology to achieve the exchange between MATLAB and WinCC variables,the optimized process parameters applied to the actual pulp production process,and achieved good refining control.In summary,based on the simulation analysis of the bond diagram of the refining system,a multi-objective mathematical model of the refining process is established,then an ant colony optimization algorithm is used to solve the multiobjective mathematical model,and the optimal production process parameters of refining process is obtained,which achieves the production goal of high quality,high yield and low energy consumption.Based on the bond graph model of the refining system,the fault diagnosis of the refiner is completed.The practical application results show that the optimized refining concentration,feed rate and refining power obtained by this method can not only obtain stable beating degree in the DCS of refining process,but also increase the slurry output by 5.9%,and the energy consumption per ton pulp is reduced by 2.3%,and a good control effect is received.