Research On Quality Control Of Pellet Drying And Preheating Process Based On Cascade Control

With the continuous development of iron and steel industry, pellets have become an indispensable part of the blast furnace burden. The grate-kiln production system has been widely used by the iron and steel enterprises due to the advantage on technology. In the process of pellet production, drying and preheating is a key step to improve the strength of pellets and it is also an important factor in determining the quality of pellets. However, the process of drying and preheating process is complex and process parameters are coupled. It's difficult to establish the precise mathematical model to determine the quality of pellets. The economic benefits of enterprises are affected by the quality of pellets directly. So it's a current topic concerned by the enterprises to study on the quality control of the preheated pellets.At first, the production process of grate-kiln was analyzed, and the factors affecting the quality of preheated pellets were found out combined with mechanism. Process parameters in the process of drying and preheating on the quality of the preheated pellets were analyzed in detail. The detection of pellet quality was mostly offline and it was unable to adjust production process parameters according to the pellet quality in time. So the quality prediction model of preheated pellet was established with the GA-BP neural network. According to the relationship between advanced control and basic automation, the quality control system was designed for preheated pellets. Combining with the drying and preheating process of pellets, the cascade control system that takes compressive strength as the parameter of primary-loop and process parameters as the parameters of minor-loops was designed. According to the object characteristics in the loops, the quality controller based on Case-Based Reasoning and the controllers of process parameters based on PID control strategy were designed. The results of simulation experiments showed that the control strategy for quality of preheated pellets was feasible and there was high reference value for guiding the production process of pellets.