The Modeling And Control Of Thermal Process For The Plate Solid-solution Furnace With High Temperature

Based on plate roller hearth furnace with high temperature, the key technologies and problems in thermal process control have been studied systematically. On the basis of models and theories established in this paper, the softwares of "basic automation control system for plate roller hearth furnace with high temperature" and "heating process optimization system for plate roller hearth furnace with high temperature" have been developed, and then the automation control system has been constructed successfully. The automatic operation and precise control for furnace have been realized by the system developed. The main contents and results are as follows:(1) The strategy of pulse duration time fixed combined with blanking time fixed was put forward and then a new pulse combustion timing control model was established. The application results show that the established model’s parameters can be set optimally compared with the integral method, and its computation is small compared with the furnace imported.In this paper, the composition and principle of pulse combustion were studied systematically. By the analysis of timing control for pulse combustion modeling, three kinds of timing control models were established with proportional method. They were pulse duration time fixed, blanking time fixed and pulse cycle time fixed. The factors affecting the furnace temperature deviation in timing control model were determined by mathematical analysis. The three models were analyzed, and then a new composite pulse combustion timing control model was put forward, which inherited the merits of pulse duration time fixed and pulse blanking time fixed. The new model developed has been successfully applied in solid-solution furnace and it appears a better quality of temperature control and heating effects. The precision of furnace temperature is not more than3℃and the absolute temperature deviation of the same plate and various plates are both not more than8℃. (2) In order to make the calculation result of furnace temperature closing to the actual value, a furnace temperature model considering influence for each zone was put forward. In addition, a heating model for the furnace adopted pulse combustion was established and then the problem that plate temperature calculated accurately was solved.Based on the study of furnace heat exchange, characteristics of plate heat exchanger were determined, and a calculation model of comprehensive heat flux was established with total heat exchange factor method. Using measured datas and heating parameters, a total heat exchange factor of furnace was determined by the back-calculation method of heat transfer theory. On the basis of above studies, a heating mathematical model for RAL furnace was established and it was composed of furnace temperature calculation model, plate thermal conductivity model, furnace heat transfer model and plate temperature tracking model for the whole furnace. As the application results proven, the heating model is accurate and reliable. Furthermore, it can truly reflect the plate temperature during heating process.(3) The grey asynchronous particle swarm optimization strategy was put forward and heating procedure optimization for steady-state process was realized. The dynamic heating process was optimized by setting of furnace temperature and plate speed. Consequently, the problem has been solved that plate temperature and holding time couldn’t meet requirements.It is multidimensional for optimization objectives of steady-state heating process in the solid-solution furnace. In order to solve this problem, the strategy of grey relational analysis (GRA) algorithm combined with asynchronous particle swarm optimization (APSO) algorithm was proposed and a GRA-APSO heating optimization model was established. With this model, a new way to solving heating optimization problems is provided and solving performances of heating process optimization problems is improved. In addition, compensation strategies in heating process of RAL’s roller hearth furnace were established, considering the setting optimization of furnace temperature and plate speed. The strategies established have been applied for the production line. The application results show that the strategies are effective to guarantee plates’tapping temperature hits.(4) Whereas furnace roller water-cooled mechanism was unknown and it could cause the furnace temperature couldn’t be heated to requirement temperature, convection about furnace roller water-cooled was studied and then a model on roller cooling was established. This model can solve the key problem through its calculation. A simulation study was put forward using the model and then a cooling principle about furnace roller was provided.In this paper, a single-phase-flow state in roller’s cooling process was systematically studied. With correlations formulas of Dittus-Boelter and Sieder-Tate tube forced convection test, a convection heat transfer coefficient model was established. Then, a furnace roller cooling computational model was constructed. Compared simulation results with actual datas, the model of furnace roller cooling was proposed that it could correctly reflect roller’s cooling process. With the furnace roller cooling model, the effects of the cooling water flow rate and inlet temperature on the critical interface temperature of furnace roller, cooling water temperature and energy consumption were studied. The roller cooling studies provide a theoretical basis for realizing rollers cooling optimization of furnace.(5) The basic automation and process automation control systems were developed. The application results show that the systems have solved the problem of automatic continuous production, and one-button operation for the large-scale high-temperature solid-solution furnace has been realized.An automatic heating function of basic automatic system was designed and it mainly consisted of start/shutdown furnace, plate micro-location tracking, plate production sequence tracking, furnace temperature control and furnace pressure control. On the basis of automatic heating, a heating process control system was constructed. The system developed was composed of tracking&scheduling module, hold temperature control module, heating procedure setting&optimization module, discharging results prediction module, parameters self-learning module and data communication and processing module.The thermal process models and control systems developed have been applied successfully in plate roller hearth furnaces with high temperature in Baosteel and JISCO. The production has been satisfied and a remarkable benefit has been achieved.