Desulfurization system pH value control system and method based on predictive control

Abstract

The invention discloses a desulfurization system pH value control system and method based on predictive control in the technical field of wet flue gas desulfurization, and the method comprises the steps of obtaining a PH set value, and processing the PH set value based on a generalized predictive control model with disturbance control; performing rolling optimization based on a processing result; and performing feedback correction on the PH set value based on an optimization result. The generalized predictive control model with disturbance suppression is adopted to replace a PID regulator of a traditional cascade control main regulation loop, compared with a traditional cascade control strategy, the control effect is better, and for the set tracking performance, the regulation time and overshoot of the advanced pH control strategy are obviously better than those of the traditional cascade control strategy; in the aspect of anti-disturbance performance, the advanced control callback time is shorter, the anti-disturbance capability is higher, the control quality of the wet desulphurization pH value can be obviously improved based on the generalized predictive control with disturbance suppression, and the method plays an important role in stable and economical operation of wet desulphurization.

Description

technical field [0001] The invention relates to a system and method for controlling the pH value of a desulfurization system based on predictive control, and belongs to the technical field of wet flue gas desulfurization. Background technique [0002] Because the wet desulfurization process is mature and has high desulfurization efficiency, it has become the most widely used desulfurization technology for thermal power units. However, in the actual operation of wet desulfurization, there are problems such as high energy consumption and material consumption of the desulfurization system, large fluctuations in SO2 concentration, and serious instantaneous exceeding of the standard. The reason is that the desulfurization system has the characteristics of non-linearity, large inertia, and large lag, and the poor reliability of the measurement and equipment of the desulfurization system makes it difficult to ensure that the desulfurization system maintains optimal conditions. For...

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Problems solved by technology

The most critical core subsystem in the desulfurization system is the control of the pH value of the absorption tower slurry. If the pH value is too high, it will cause fouling and blockage of the demister and the absorption tower, and at the same time reduce the quality of desulfurization by-products and increase the consumption of limestone. If the pH value is too low, the desulfurization efficiency of the desulfurization system will be reduced. In addition, large fluctuations in pH value will cause large fluctuations in SO2 concentration, which is not conducive to the precise control of SO2 concentration. Therefore, accurate control of pH value becomes the key to the stable operation of the desulfurization system. one of the factors

[0003] Traditional pH value control methods mainly include two methods: one is the most common cascade control system, the main loop is controlled by SO2 concentration, and the inner loop is controlled by limestone slurry flow; the other is the most basic single closed-loop PID control, which only uses a single loop Realizing the closed-loop control of pH cannot avoid the nonlinear problem of limestone slurry flow adjustment

The above two conventional control strategies have the problem of poor automatic control effect and weak anti-disturbance ability in the actual operation process, and even cannot be put into automatic operation

After the thermal power unit is put into AGC, there are problems such as frequent load changes and large changes, resulting in large changes in the flue gas flow rate, making the wet desulfurization system unable to track the flue gas flow change, resulting in lagging automatic pH value control and large fluctuations

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