Study Of Online Optimal Control In Annealing Process And Evaluation And Diagnosis Of Annealing Performance For High Performance Hydrogen Bell-type Annealers

Accelerating technical innovation is an effective way to realize the sustainable development in the steel industry of China. The model calculation and control technology has become one of the difficult problems which restricted the self-transformation and expansion of the bell annealers. In order to improve the online control performance and control level, the online annealing control and regulation technique of high performance hydrogen bell-type annealers has been investigated in this study.The research work on the annealing technology of the bell annealers (including offline prediction of annealing craft systems, online optimization of annealing process and evaluation and diagnosis of annealing process) at home and abroad have been summarized, analyzed and evaluated systematically. The several parts in the research work are as follows:The modeling researches on the radial equivalent thermal conductivity, the convective heat transfer coefficient, the radiation heat transfer coefficient, flow characteristic of work base and heat transfer of heating chamber have been carried out based on the analysis of the heat transfer process, and a suit of heat transfer mathematical models for the bell annealers has been established. Combining with the analysis of the annealing craft process, the simulation system for the calculation of the coil's temperature has been developed. Basing on the heat transfer mathematical models and the simulation system, the temperature fields of coils during annealing process have been calculated. At the same time, the annealing craft systems have been predicted. The practical applications shows that the relative error of the temperature between the prediction results and the actual results were in the arrange of±5% in heating period, and±7% in annealing period, which were all in the acceptable range of the industrial process.For some unforeseen events taking place during the annealing cycle, such as, the fluctuation of the fuel nature, the change of the equipment performance, the equipment failure and the man-made fault, etc, online annealing curve is always deflected away from the offline optimized curve. And thus, in order to increase the efficiency of work base and ensure the annealed qualitative properties, a suit of online self-adapting control approach has been developed. The approach based on the online tracking of the coil's cold-spot temperature consists of two critical parts including self-adapting optimization method and self-learning updating method. Firstly, the self-adapting optimization approach consists of two parts including "annealing process reappearance" and "annealing process optimization". Secondly, the self-learning updating approach, based on the equipment performance and variations in the technology, is designed to improve the accuracy of the optimization results. The results obtained from the proposed approach are in agreement with the test values, such as the deviation of the temperature for the hot-spot and cold-spot are within 10℃, and the mechanical properties meet the specified product quality standard.In order to gain the real-time annealing performance and control level, the influence between annealing craft and annealing performance of strip steel has been analyzed. By adopting the process capability index (CPK) and process performance index (PPK), the system for online evaluation and diagnosis of annealing process has been developed. The practical applications in periodic production have been carried out. The results showed that the fault could be diagnosed by the proposed approach based on the evaluation results of the annealing process performance. And the fault diagnosis messages were agree with the field detection results basically.Finally, the core software platform for bell annealers including the annealing craft system offline prediction platform, the annealing craft system online self-adapting optimization platform and the online annealing evaluation and diagnosis platform was developed based on the research of the annealing approaches. The application results in the field showed that the action effects were remarkable and the economic benefits were great.