The Research And Application Of Advanced Measurement And Control Technology For Ball Mill Of Coal-fired Power Plants

Coal-fired power plants are both electricity producers and electricity users and consumers.Coal mill as raw coal processing equipment,its operation quality will directly affect the burning efficiency of boilers in thermal power plants.Although the tube ball mill coal-pulverized storage system is widely used in coal-fired power plants,its energy consumption is up to about 20%of the auxiliary power of whole power plant.The tube ball mill coal-pulverized storage system is a multivariable coupled time-varying complex system.Conventional single-variable decentralized 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 advanced measurement and control technology which is suitable for the ball mill coal pulverized systems,and take it into automatic control and optimal operation effectively.This paper reviews the advanced measurement and control methods and application research situation of the power plant ball mill storage pulverized coal system,and then research and application of advanced measurement and control technology was carried out for ball mill coal pulverized systems of the coal-fired power Plants.According to practical operation circumstances of the existing measurement and control systems of the tube ball mill coal-pulverized storage system in No.2 generating unit of Zhangqiu power plant,this paper integrates expert intelligent control with decoupling control and conventional control techniques,and proposes a hybrid hierarchical control scheme with a direct control layer and a supervisory-optimization layer,and convenient to be applied to industrial application.The tuning method for controllers and decoupler of the direct control layer is proposed in this paper.Simulation results demonstrate the good performance of the proposed direct control layer normal working condition control scheme using the tuning method for the controllers and decoupler.As for the design of supervisory-optimization layer in the hierarchical control scheme,the expert control rules and set-point optimization method based on steady-state gains of the tube ball mill coal-pulverized storage system are designed.In this paper,after analyzing the disadvantages of current measurement technology for the coal load inside the ball mill or fill level of the ball mill,the vibration signal of ball mill bearing is used to express the coal load inside the ball mill and the corresponding measurement instrument is developed and introduced.The proposed hierarchical control scheme is successfully applied to measurement and control systems of the tube ball mill coal-pulverized storage system in No.2 generating unit of Zhangqiu power plant.Considering the tube ball mill coal-pulverized storage system characteristics and control requirements,hardware configuration,control strategy design,software realization,and engineering implement are carried out in sequence.The software packages for set-point optimization,process supervisory,and direct process control are all developed.Application in industry field shows that the proposed hierarchical control scheme can not only make dynamic responses better,improve the adaptation for varying work condition,and get better control performance,but also decrease electricity consumption for coal pulverizing,and energy conservation can be achieved.Finally,the author summarizes all the works which have been done in the thesis,and some possible future research directions and improvements for the proposed hierarchical control scheme in the thesis are provided.