Novel control strategy for injecting ammonia into boiler feed water for power plant

Abstract

The invention relates to the field of power plants, in particular to a novel control strategy for injecting ammonia into boiler feed water for a power plant. Conventional deviation adjustment is changed into the mode with adjustment according to the demands as priority and deviation correction as aiding, on the one hand, the overadjustment and excessive adjustment phenomena of conventional PID adjustment to a large lag adjustment object are avoided, and on the other hand, timeliness of adjustment is greatly improved; the frequency of a dosing metering pump of the novel control strategy can beimmediately changed through changing of the unit load or changing of a set value, the situation that adjusting is conducted when a feedback value and the set value have deviations is avoided, and thestability of the feed water ratio conductivity of the boiler is ensured.

Description

technical field [0001] The invention relates to the field of power plants, in particular to a novel control strategy for adding ammonia to boiler feed water in a power plant. Background technique [0002] In the power plant boiler feed water system, the PH value of the feed water or condensed water is generally increased by adding ammonia to neutralize the free carbon dioxide in the feed water, so as to reduce the corrosion of the boiler feed water system pipes and boiler heating surface pipes caused by the low pH value , but an excessively high pH value will cause corrosion to the copper system, so the ammonia addition control must be kept stable in the water supply system. [0003] At present, the ammonia addition workshop of power plant boilers and the online chemical instrument measurement workshop of the water supply system are generally arranged at a relatively long distance from the dosing point. The detected pH value is compared with the standard pH value to obtain t...

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Problems solved by technology

[0002] In the power plant boiler feed water system, the PH value of the feed water or condensed water is generally increased by adding ammonia to neutralize the free carbon dioxide in the feed water, so as to reduce the corrosion of the boiler feed water system pipes and boiler heating surface pipes caused by the low pH value , but an excessively high pH value will cause corrosion to the copper system, so the ammonia addition control must be kept stable in the water supply system

[0003] At present, the ammonia addition workshop of power plant boilers and the online chemical instrument measurement workshop of the water supply system are generally arranged at a relatively long distance from the dosing point. The detected pH value is compared with the standard pH value to obtain the deviation, from the metering pump to the dosing point. The length of the dosing pipeline at the dosing point is more than 100 meters, and the sampling pipeline of the chemical instrument is also more than 100 meters long. As a result, the process from changing the dosing amount to detecting the change in the pH of the water supply takes nearly 30 minutes

The conventional PID control strategy is adjusted on demand, and it is impossible to correct the lag of up to 30 minutes, resulting in too high a dosing overshoot and cannot be automatically put into operation. The operator manually controls the dosing and needs to adjust it every 20 minutes on average. Once, the work intensity is high and the adjustment effect is not ideal

According to the research situation, even if the distance of the dosing pipeline is shortened, the conventional PID control will still have periodic divergence, and the automatic manual adjustment has to be released every 3 to 4 hours after the automatic activation.

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