The Research And Application Of Advanced Control And Optimization For Ball Mill Storage Coal-pulverized System

Ball mill coal pulverized system is a multivariable coupled nonlinear time-varying system which is extensively applied in coal fired power plants. Conventional single-variable controller based on linear system theories cannot meet the control requirements. It is difficult to keep the pulverized system in safe condition and in low energy consumption in the same time. So it is of very important theoretical significance and practical value to study multivariable advanced control methods which are suitable for the ball mill coal pulverized systems, and take it into automatic control and optimal operation effectively. This paper reviews the advanced control methods and application research situation of the power plant ball mill storage pulverized coal system, and then studies the application research of the multivariable advanced control methods for ball mill coal pulverized systems.Chapter 1 is the introduction of the paper. Firstly, it describes the background and the significance of the research, and then reviews the situation and development of advanced control methods for the power plant ball mill storage pulverized coal system at present. Lastly, it puts forward the primary work based on the problems existing at practical controls of ball mill coal pulverized system.Chapter 2 studies the multivariable system decoupling control method for the ball mill storage pulverized coal system. First, this paper analyses the work theory and operation character of ball milling. The ball mill coal pulverized system is a multi-input and multi-output system. The controlled variables of ball mill are the negative pressure in the input, the temperature in the output and the difference pressure of the ball mill. The control means are to adjust the recycling air gate, the hot air gate and the coal feed quality. Then, we make the coupling analysis and give the loop matching method of multivariable system. Loop matching should not only consult relative gain array (RGA), but also have to consider the technology and control requirement of practical process to choose more appropriate input and output matching. Based on the model of the power plant, we make the system design and simulation of it. From the simulation results, we can see that the feed forward compensation decoupling control can realize the completely decoupling for controlled object.Chapter 3 proposes a control method that combined multivariable decoupling control and steady-state optimization. This method is simple and liable to apply. In direct control layer, to simplify the controller design, a 3×3 system can be decomposed into a two-input two-output (TITO) system and a single loop by constructing the two matrices A and B. The direct control layer is to keep the system running in a stable. The task of the optimization layer is to select optimal values of set-points for the lower control layer, optimizing a defined objective function of economic nature. When the ball mill coal pulverizing system is operated at about its maximal capacity of the coal stock level, the electric power consumption of pulverizing a ton of coal will be reduced to a minimum. Therefore, increasing the coal feed rate to the tube mill, i.e., increasing the feeder speed, can increase the flow rate of pulverized coal and then reduce electric energy consumption. Simulation results demonstrate the good performance of the proposed control scheme.Chapter 4 introduces the project realizes. According to the idea of designing, the overall structure of the Optimizing Control System is designed. In this system, PLC is chosen to be the lower machine, and the designing plan of hardware of this system is illustrated particularly. The configuration of sensors, converters and computer is introduced. Furthermore, the software designing and the realization of the system are illustrated precisely and meticulously. Using configuration software-King View 6.53 to realize the communication between the lower machine and the host machine, and provides the complete picture of coal pulverizing system. Operation staff may set running target value, if real-time value deviated from the target can propose alarm to remind staff to correct the deviations, which could improve operating efficiency of coal pulverizing system.At last, the author summarizes all the works which have been done in the thesis, and look forward further explorations and research questions in the next work.The research development result indicated: This system fuses the configuration software and the optimized algorithm, enhances automation level and management level of coal pulverizing system, save the energy, improve the work condition. The system will bring the obvious economic efficiency and the social efficiency.