SCR (selective catalytic reduction) denitration intelligent ammonia spraying optimization method and system based on soft measurement and model adaptation

Abstract

The invention discloses an SCR (selective catalytic reduction) denitration intelligent ammonia spraying optimization method and system based on soft measurement and model adaptation. The method comprises steps as follows: 1), an inlet nitrogen oxide concentration model is established on the basis of operation data of a coal-fired power unit combustion system, and a predicted value of inlet nitrogen oxide concentration is obtained by adopting the model and the currently collected operation data; 2), ammonia spraying amount under the current operation condition is calculated according to the predicted value and is taken as a feedforward signal to be sent to an SCR denitration system; 3), deviation of a measured value of outlet nitrogen oxide concentration and a set value of the outlet nitrogen oxide concentration is obtained and input into an adaptive PID controller, an ammonia spraying feedback control signal is obtained and sent to the SCR denitration system, and the adaptive PID controller adjusts PID parameters under the current condition with an adaptive PID control algorithm; 4), the SCR denitration system controls the ammonia spraying amount of an SCR denitration reactor according to the ammonia spraying amount feedforward signal and the ammonia spraying feedback control signal.

Description

technical field [0001] The invention belongs to the technical field of denitrification in coal-fired thermal power plants, and in particular relates to an intelligent ammonia injection optimization method and system for SCR (Selective Catalytic Reduction) denitrification based on soft measurement and model self-adaptation. Background technique [0002] At present, in order to achieve ultra-low emissions of nitrogen oxides, most coal-fired thermal power plants have installed SCR denitrification devices, using the CEMS system (flue gas online monitoring system) to collect the concentration of nitrogen oxides at the inlet and outlet, and then perform PID (proportion- Integral-derivative) feedback control. [0003] PID feedback control such as figure 1 As shown, the calculated value of the ammonia flow rate is (the measured value of the concentration of nitrogen oxides at the inlet - the measured value of the concentration of nitrogen oxides at the outlet) × the amount of flue ...

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Problems solved by technology

[0005] 1. The concentration of nitrogen oxides at the inlet and outlet is measured by the CEMS system. The sampling pipeline of the CEMS system is relatively long, resulting in a large pure delay in measurement, and the measured value has a delay of 2-3 minutes;

[0006] 2. The existing CEMS system uses single-point sampling measurement, so the measurement data cannot represent the average concentration of the entire cross-section;

[0007] 3. PID control is adopted, and the PID parameters will not change after the initial setting. Therefore, when the operating conditions of the unit load change, the denitrification system is not adjusted in time, and excessive emissions are prone to occur;

[0008] 4. In order to ensure discharge standards, the operator of the power plant set the PID parameter setting value very low, resulting in excessive ammonia injection, large overshoot of the control system, and low system response rate

It not only wastes reducing agent, but also increases the risk of subsequent equipment blockage

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