Research On Application For Theory Of Large-Scale Systems In Iron&Steel Metallurgical Reheating Process

This thesis has been carried out based on the reheating furnace of some steel mill. The reheating furnace is a very important equipment of the steel mill. The reheating furnace should provide qualified billets gratifying the request of the rolling process. A great deal of research work has been done to reduce the energy consumption of the reheating furnace. It is important to execute the effective control of the reheating furnace in today's increasing competition in the steel metallurgy.The characteristic of the combustion, such as, the great inertia, the nonlinearity, the long time delay, makes us very difficult to control the reheating furnace. So it is difficult to establish an accurate model by simple method. As to large-scale systems, the control and optimization problems can be solved using the conventional hierarchical optimization theory if the objective functions are separable. The object has a large number of variables, and its interaction is complex. Each of its subsystems is related with each other. Therefore, the problem can be calculated by decomposition coordination algorithm. It will make a positive drive on study and application if we apply theory of large-scale systems on the reheating furnace.The author's contribution has been addressed in detail logically in this paper in the manner of the reheating furnace's large-scale systems control. Also, the author's design strategy and creativity has been given in this paper. Specifically, it includes:①Theory of large-scale systems has been introduced by the principle of decomposition coordination of large-scale systems, namely interaction-prediction principle and interaction-balance principle. Then the math model of the reheating furnace according to the basic steps of large-scale systems modeling has been established;②The furnace model has been established by mechanical analyzing, and the cubic form has been advanced to describe the temperature distributing, then three methods of steel temperature estimating have been discussed by analyzing difficulties, algorithm's astringency, real time character, model's self-adaptability and so on;③According to the characteristic of furnace temperature distributing corresponds with the billet temperature uniquely, a new method that the furnace temperature distributing can be conversely reasoned by optimizing the billet temperature curve has been advanced. the objective function and restrictions in the model has been analyzed by giving attention to more things to billet's quality and saving energy, and the temperature setting of the furnace is made to accord with the aim of producing process better;④On the base of decentralized control, every disturbs'influence has been analyzed, and the hierarchical control has been advanced by taking the furnace temperature and air/fuel ratio as associated variables to enhance model's self-adaptability and control's real time character;⑤Theory of large-scale systems and intelligent control has been combined, and a new road has been explored to solve correlative complex system'control.Based on the deep analysis of the reheating furnace's large-scale systems characteristic, the temperature distributing form has been improved, and the converse illation method has been advanced, especially the combinative exertion of theory of large-scale systems and intelligent control can be for reference to the academy and project.