Research On Temperature Control System Of Shale Distillation Column

Economic and social development needs energy to provide power, but the exploitation of oil resources can only be maintained for 40 years. On the other hand, the world has abundant shale reserves. Therefore shale has become very important replaceable energy in the 21st century. Extraction of shale oil requires distillation process and distillation process is one of the largest energy consumption units. Energy consumption accounts for about one-third of the total chemical energy consumption.This thesis is on the background of shale oil refinery distillation process.In order to get a pure overhead product and bottom product of distillation column and reduce energy consumption in the same time, the temperature of the distillation column should be controlled rapidly and precisely. First, we analyze the principle of binary distillation process accoding to the technology of distillation. After fully understand the technology of distillation column, top back flow and botton back flow are selected as a manipulated variables, feed quantity as uncontrollable input, temperature of bottom back flow and top back flow as the controlled objects. Then model the controlled plants, using traditional PID cascade control to control the object in matlab by simulation. After simulation, we can conclude that the traditional control method has several deficiencies, such as poor dynamic performance, poor ability of major loop anti-disturbance, coupling between the top loop and botton loop. Then use feedfoward decoupling control method to control the object by simulation. The result is good when model is precise. However, the decoupling is failed when model mismatch and overall system performance is poor in the same time, which can not meet the technical requirements. Prodictive control is introduced to replace cascade control because of the shortcomings in the traditional control method. New method use cascade control made of predictive control and PID control. Predictive control use dynamic matrix control arithmetic. The characteristic of model prediction and rolling optimization in predictive control increase the ability of major loop anti-disturbance and inhibition of coupling. The characteristic of feedback correction improves the robustness of system, which can be used to deal with the inevitable mismatch problem in chemical process model. Multivariable predictive control has good performance in major loop anti-disturbance, but it still have poor dynamic performance as well as poor anti-disturbance of feed quantity because of the uncontrollable input. Finally, a multivariable predictive control with feedforward is designed to reduce the influence of the uncontrollable input.Multivariable predictive control improves the dynamic performance, enhances the ability of inhibiting the feed quantity disturbance according to the simulation. Multivariable predictive control has better robustness than traditional control method according to simulation of model mismatch 10% and 30%. Therefore, multivariable predictive control with feedforward is a control method suitable for oil shale distillation process.