Modeling And Control Of Multiple-Effect Evaporation In A Sugar Mill

Multiple-effect evaporation plays a very important refinery project and economic role in sugar mill. The main goal is keeping the brix of the last evaporation stable. However, the automation degree of most sugar mill’s evaporation section in China is not very perfect, with the brix detected off-line every two hours and manually controlled by the adjustment of operation workers, so that the detection and the control of the brix is severely lag and frequently changed, leading the output of system could not to be desirable and influencing subsequent production. Therefore, modeling and control of cane multiple-effect evaporation are significant for the whole sugar mill.In order to solve the accuracy and stability of the brix of the fifth evaporation, taking Nanning Lingli sugar mill as the studying case, on the basis of the principles of heat and mass balance, with characteristics of sucrose material, considering the boiling point rise caused by concentration effect and the temperature loss caused by pipe resistance, the dynamic knowledge model of the multiple-effect evaporation in a sugar mill is established with collected data. Taking MATLAB as working platform, by building Simulink modules, the simulation results shows that the error between the model output and the actual output is inter±2.5%, so the model can describe the multiple-evaporation properly.Basing on particle swarm optimization algorithm, treating the sugar flow of the first evaporation and the brix of the fifth evaporation respectively as the input and the output, a PID controller for the built model is designed. The simulation results show that the error between the model output and the actual output is inter±0.15%, and the controller is simple and effective, the good stability of which makes the system having strong robustness and the anti-interference ability.