Research On Temperature Control System Of Distillation Column Based On IMC Decoupling

The Distillation column is the most important element of oil recovery system in ATP shale oil refining, which directly effects the quality of products. Due to the complexity of internal mechanism and high control requirement so that researching on the automatic control of distillation column has always been a hotspot and realistic.In this thesis, the background is the shale oil refining production line in shale oil refining factory and the study object is the oil shale distillation column temperature control system. Through researching and analyzing the process of the system, this thesis selects the outlet temperature from top and bottom in distillation column as the controlled variable, which are non-linear, strong-coupling, large inertia, lag and uncertainty controlled object. It’s hard to build a precise mathematical model, therefore the thesis builds a approximate mathematical model. Then through analysis and simulink on the two loop of cascade control system, the thesis found the coupling problem is very serious. Focus on the coupling problem, using the relative gain matrix method to quantitative analysis the system coupling degree, this thesis determines the necessity of decoupling. And then designing a feedforward decoupling device, after the simulink of feedforward decoupling control system, the coupling problem is solved. But when model mismatch, the control effect is not ideal. In view of how to improve the system control performance when model mismatching, the thesis adopts the internal model decoupling control scheme without depending on the accurate model to conquer model mismatch. And when designing the IMC controller, the thesis adopts GA method to approximate model for avoiding multiple calculation. Through simulink we found the dynamic, stability, robustness and convenience of internal model control system are superior to the traditional feedforward decoupling control system. Finally, the internal model decoupling controller is made two improvements:one is making the filter has the function of the fuzzy self-tuning parameters without manual adjustment to achieve good control performance; the other one is considering the internal model decoupling controller can be implemented in DCS system, the internal model controller is converted to the form of the PID controller structure.All in all, the internal model decoupling controller provides a convenient, efficient, advanced, enforceable decoupling control method for temperature control of distillation column system.