Selective catalytic reduction (SCR) denitrification ammonia-spraying optimization method and system based on advanced measuring instrument and advanced control algorithm

Abstract

The invention discloses a selective catalytic reduction (SCR) denitrification ammonia-spraying optimization method and system based on an advanced measuring instrument and an advanced control algorithm. The method comprises steps as follows: (1) an inlet nitric oxide concentration model is established on the basis of operating data of a coal-fired thermal power generating unit combustion system; apredicted value of the inlet nitric oxide concentration is obtained by the aid of the model and the currently acquired operating data; (2) an ammonia spraying amount feed-forward signal under the current operating condition is calculated according to the predicted value and is sent to an SCR denitrification system; (3) a measured value of the outlet nitric oxide concentration of the coal-fired thermal power generating unit combustion system is deviated from a set value of the outlet nitric oxide concentration and then is input into a self-adaptive PID controller, an ammonia spraying amount feedback control signal is obtained by the self-adaptive PID controller on the basis of the deviation and an ammonia escape measured value and is sent to the SCR denitrification system; (4) the SCR denitrification system controls the ammonia spraying amount of an SCR denitrification reactor according to the ammonia spraying amount feed-forward signal and the ammonia spraying amount feedback controlsignal. The system is high in response rate and short in transformation period.

Description

technical field [0001] The invention belongs to the technical field of thermal power outages, and relates to an SCR (Selective Catalytic Reduction) denitrification intelligent ammonia injection optimization method and system, in particular to an SCR denitrification ammonia injection optimization method and system combining advanced measuring instruments and advanced control algorithms. 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 conce...

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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

[0009] 5. The measurement of the ammonia escape instrument is inaccurate and cannot reflect the change of ammonia escape

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