Denitration spraying ammonia automation control method and system

Abstract

The invention discloses a denitration spraying ammonia automation control method which is applied to a coal-fired boiler SCR system. The method comprises the following steps of acquiring a total air volume of a boiler and an entrance nitric oxide content of the system, and multiplying the total air volume of the boiler by the entrance nitric oxide content of the system so as to obtain a total nitric oxide content in a flue gas; according to the nitric oxide content, using a predetermined basic spraying ammonia amount feedforward function to obtain a basic spraying ammonia amount; according to an entrance nitric oxide content set value of the system, acquiring a correction coefficient of the predetermined basic spraying ammonia amount, multiplying the correction coefficient by the basic spraying ammonia amount so as to obtain a target spraying ammonia amount, and taking the target spraying ammonia amount as a denitration spraying ammonia amount. By using the method, a theoretical spraying ammonia amount can match an actual-needed spraying ammonia amount; a probability of excess emission of nitric oxide and an environmental protection risk brought by the excess emission can be reduced; and negative effects and economic losses brought by excessive spraying ammonia are decreased.

Description

technical field [0001] The invention relates to the technical field of automatic control, in particular to an automatic control method and system for denitrification and ammonia spraying. Background technique [0002] The logic of the denitrification and ammonia injection automatic control method used in the prior art is to use the product of the flue gas flow rate and the nitrogen oxide content at the SCR inlet to obtain the flow rate of nitrogen oxides in the flue gas, and then use the theoretical calculation formula to obtain the corresponding nitrogen oxide flow rate. The theoretical ammonia injection amount is used as the feed-forward to control the ammonia injection regulating valve to control the ammonia injection amount. In order to precisely control the nitrogen oxide content at the SCR outlet near the target value, a PID closed-loop control strategy is added to correct the theoretical ammonia injection amount, so that the nitrogen oxide at the SCR outlet is control...

AI Technical Summary

Problems solved by technology

[0004] First of all, because there is often a large error in the measurement of the flue gas flow rate, this causes a large deviation between the calculation result of the theoretical ammonia injection amount and the actual required ammonia injection amount, and the measurement of the ammonia gas flow rate is sometimes not very accurate. The calculated amount of ammonia injection is not ideal in practical application;

[0005] Secondly, when the coal mill is started and stopped under different loads of the boiler, the nitrogen oxide content in the flue gas will fluctuate greatly, and there is a large delay in the process of measuring the nitrogen oxide content of the SCR outlet by the analytical instrument

When the measuring instrument shows that the nitrogen oxide content is normal, the actual nitrogen oxide content in the flue gas has begun to change greatly. When the measuring instrument detects this change and then controls the amount of ammonia injection, it is too late, or it will cause The content of nitrogen oxides in the flue gas emission process exceeds the assessment value of the environmental protection department, resulting in environmental fines, or because of excessive injection of ammonia gas, resulting in waste, and because of the large amount of NH4HSO4 generated, the air preheater is blocked and the heat transfer of the air preheater is reduced. efficiency

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