Advanced Control On Papermaking Alkali Recovery Process

Alkali recovery is an effective way dealing with the black-liquor in pulp mill. Black-liquor evaporation and combustion in, alkali recovery are complicated industrial processes. They have characteristics such as strong coupling, non-linearity, large time delay, parameter examining difficulty, etc. And people require more effective control system for the processes'. Custom control technique can't satisfy industry produce requirement. The purpose of developing advanced control technique is to solve the control problem in complex industry processes that custom control technique can't control well. Now we have many achievements on papermaking process control, also some advanced control techniques have been used in papermaking process and get good economic benefits. Research of control technique for alkali recovery process is not very much. How to use advanced control technique on alkali recovery process is the key point of this paper. Rough set theory is a newly developed mathematical tool for dealing with uncertain knowledge. It can be combined with other theories and has great effects.The main contents of this thesis are as follows:In the first two chapters, basic concepts of rough set theory and latest achievements of rough set theory and its applications are introduced, as well as methods that combine rough set theory with other theories on artificial intelligence.Chapter 3 introduces black-liquor evaporation and combustion process in alkali recovery. Models used in alkali recovery control are summarized and an overview of the alkali recovery control are given. The problems in alkali recovery control research and its development trend are discussed too.Black-liquor evaporation process is a process with strong coupling and big time delay. In chapter 4, based on the analysis of shortage in custom decoupling control technique. Neural network decoupling algorithm for black-liquor evaporation is presented. Simulation results show the effectiveness of the algorithm. Based on the integration of rough set and neural networks, a rough neural network based onpredictive model control strategy for alkali recovery boiler control is developed.The framework of alkali recovery dedicated control system is introduced in chapter 5, including system hardware frame and software design and basic functions of system.Finally, a conclusion of our work and the future research directions on alkali recovery control are given.