Method for calculating NOx measurement value of denitration inlet under purging condition by system error method

Abstract

The invention relates to a method for calculating a NOx measurement value of a denitration inlet under a purging working condition by a system error method. According to the method, the NOx measurement value of the denitration inlet under the purging working condition is calculated by calculating a system error between the NOx measurement values of the denitration inlets on the two sides of a boiler. The method comprises: taking the A side as an example, under a normal working condition, outputting an A side denitration inlet NOx concentration measurement value; and under the A-side purging working condition, correcting the NOx concentration measurement value of the B-side denitration inlet by using a system error, and replacing the NOx concentration measurement value of the A-side denitration inlet with the corrected NOx concentration measurement value of the B-side denitration inlet for outputting. By means of the method, it can be guaranteed that the automatic denitration process is not interrupted in the denitration inlet NOx concentration measuring instrument purging process; in addition, undisturbed switching of NOx concentration signals of a denitration inlet at the purging moment can be achieved, and the possibility of excessive ammonia spraying or NOx emission exceeding the standard is reduced.

Description

technical field [0001] The invention relates to a method for estimating the measured value of NOx at a denitrification inlet under a purging working condition by a systematic error method, and belongs to the technical field of NOx concentration measurement in thermal power plants. Background technique [0002] The vast majority of denitrification systems in most thermal power plants adopt the SCR ammonia injection denitrification mode. A set of SCR denitration systems are designed on the left and right sides of each boiler in a thermal power plant. The ammonia injection volume of the SCR denitration system is mainly determined according to the NOx concentration at the inlet of the SCR denitration reactor; secondly, according to the deviation of the NOx concentration at the outlet of the SCR denitration reactor Make minor adjustments. [0003] The NOx concentration measurement method at the SCR denitrification inlet is flue gas extraction measurement. That is to say, a smal...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is: when the unit loads and decreases, it is easy to cause excessive ammonia injection or the NOx concentration on the chimney side seriously exceeds the standard

The disadvantage of this method is that it ignores that the NOx concentration values ​​at the left and right sides of the SCR denitrification are not equal, and sometimes the difference is relatively large; during the switching process, there are large deviations and new alternative signals, which automatically bring large disturbances without symptoms to the denitrification. Such as excessive ammonia injection or under-injection ammonia, and induce blockage of air preheater

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