Research And Application Of Ball Mill Pulverizing System Based On Fuzzy Control

At present, the ball mill pulverizing system is widely used in flue gas desulfurization technology of power plants in China. It is a typical nonlinear, multi-variable and time-varying system. Those control variables and controlled variables have serious coupling. They have characteristics of pure delay and great inertia, so it's hard to establish mathematical model, and the model changes slowly with time. Single-loop PID control systems which are widely used in China can not be put into operation. Although they are narrowly put into use, it is also difficult to achieve satisfactory control effects. Milling systems are difficult to operate economically and safely. They have problems of low efficiency and high energy consumption. Therefore, research on control methods of pulverizing system and transformation of existing mill control systems have become a hot topic of industrial process control field.This paper analyzes and studies the working principle and object characteristics of the ball mill pulverizing system detailedly. It can be obtained that the ball mill pulverizing system is a typical three input three output system. Its input variables are the quantity of given stuff, the quantity of hot wind and the quantity of recycle wind. Its output variables are exit temperature, entrance negative press and burthen of the mill. From control requirements of various controlled variables, this paper takes different control methods. The exit temperature subsystem uses the two-dimensional fuzzy controller, the entrance negative pressure subsystem uses the fuzzy + PI controller, and the burthen subsystem uses the double fuzzy controller. Thus, in the case of the keeping exit temperature and entrance negative pressure stable, the burthen of the mill reaches the required value, and the pulverizing system always works at the point of greatest efforts. It will greatly increase the milling efficiency and reduce the pulverizing energy consumption.In this paper, the control arithmetic of fuzzy controllers is realized by the computer. The program contains two parts. The one is used for computer to compute rogatory table offline; the other is used for PLC to compute according variables (error and error change) online, to dispose them in fuzzy algorithm, and to look up the rogatory table to control output.In the part of control scheme realization, this paper chooses Modicon Quantum programmable logical controller (PLC). The lower controller uses Concept 2.6 programmable language to design the function block program of the mill and its related devices. The upper computer uses iFIX4.0 configuration software to design the monitoring screen of technology flow.This control scheme has been applied in the limestone pulverizing system of some power plant in Shuo Zhou city of Shan Xi province and the system operates well. By the analysis of system operating results, it proves that the control scheme is correct and feasible. Thus, it provides a new control mentality and a new control strategy for research and application of pulverizing system, and it has certain theoretical and practical meanings.