Optimization method and optimization system of SCR denitrification intelligent ammonia injection based on soft measurement and predictive control

Abstract

The invention discloses an optimization method and an optimization system of SCR denitrification intelligent ammonia injection based on soft measurement and predictive control. The method comprises the following steps: firstly, establishing an entrance nitrogen oxide concentration model based on operation data; then utilizing the model and currently-collected operation data to obtain a predicted value; secondly, calculating the ammonia injection amount at the current operation condition as a feedforward signal according to an entrance nitrogen oxide concentration predicted value and transmitting the feedforward signal of the ammonia injection amount to an SCR denitrification system; thirdly, measuring a measured value of exit nitrogen oxide concentration of a coal-fired generation unit combustion system, making deviation between the measured value and an entrance nitrogen oxide concentration set value and inputting a difference value into a prediction controller, obtaining a feedback control signal of the ammonia injection amount based on the deviation and transmitting the feedback control signal to the SCR denitrification system by a prediction controller; fourthly, controlling the ammonia injection amount of an SCR denitrification reactor according to the feedforward signal of the ammonia injection amount and the feedback control signal of the ammonia injection amount by theSCR denitrification system. The system disclosed by the invention has the advantages of higher response rate, lower investment, short transformation period and the like.

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 SCR (selective catalytic reduction) denitrification intelligent ammonia injection optimization method and system based on soft measurement and predictive control. 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 gas × t...

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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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