Control method for multi-point sampling and accurate ammonia spraying

Abstract

The invention discloses a control method for multi-point sampling and accurate ammonia spraying. The method comprises the following steps: dividing the section of a flue into a plurality of subareas,arranging a sampling point and an ammonia spraying control valve in each subarea, and controlling the opening of the corresponding ammonia spraying control valve by a system according to the nitrogenoxide concentration of the sampling point. The control method is reasonable and ingenious in design, on the basis of electromagnetic valve coordination work of pre-sampling, sampling, reverse blowingand the like, the problem of measurement lag can be solved and the reliability and economy of the system can be improved by the multi-point measuring system, the system carries out precise calculationaccording to measurement data, the opening degree of an ammonia injection control valve is controlled, precise ammonia injection is achieved, and finally energy conservation and emission reduction are achieved.

Description

technical field [0001] The invention relates to a control method for multi-point sampling and accurate ammonia injection, in particular to an ammonia injection control method for flue gas denitrification in coal-fired boilers. Background technique [0002] Nitrogen oxides contained in flue gas emissions from coal-fired boilers are an important part of air pollution. To control the nitrogen oxides (NOx) x ) content is the focus of my country's environmental protection regulations. Selective catalytic reduction (SCR) is currently the mainstream technology for flue gas denitrification: spray ammonia on the raw flue gas, reduce it to nitrogen through a catalyst and discharge it into the air, and detect nitrogen oxides through the flue gas detection system (CEMS) , to achieve the purpose of controlling the amount of ammonia injection. But for coal-fired power plants, excessive injection of ammonia will not improve the denitrification efficiency, but will interact with SO in the...

AI Technical Summary

Problems solved by technology

But for coal-fired power plants, excessive injection of ammonia will not improve the denitrification efficiency, but will interact with SO in the flue gas 3 The reaction produces ammonium bisulfate. Ammonium bisulfate is a highly viscous liquid substance in a certain temperature range. Especially under low-temperature and low-load operation conditions, it absorbs dust in the flue gas to form compacted ammonium salts, which may cause air preheater blockage in severe cases.

If the ammonia injection is reduced, the NH in the flue gas 3 Insufficient, NO X Can not be restored, resulting in NO in the chimney outlet X Exceeding the standard, resulting in environmental assessment

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