SNCR-SCR combined denitration system and method based on ammonia nitrogen molar ratio detection and regulation

Abstract

The invention belongs to the technical field of controlling atmospheric pollutants exhausted by coal-fired boilers, and particularly relates to an SNCR-SCR combined denitration system and method based on ammonia nitrogen molar ratio detection and regulation. The system comprises an ammonia-containing storage tank, an air preheater, an SNCR reaction zone, an SCR reaction zone, a first detection system, a second detection system, a third detection system and a control system, wherein the SNCR reaction zone is arranged in a boiler furnace, the SCR reaction zone is arranged in a boiler flue, and the first detection system, the second detection system and the third detection system are connected with the control system. The combined denitration system can achieve full-load denitration operation, is high in denitration efficiency and solves the problem of corrosion and deposition of ammonium bisulfate in follow-up equipment.

Description

technical field [0001] The invention belongs to the technical field of controlling air pollutants discharged from coal-fired boilers, and in particular relates to an SNCR-SCR combined denitrification system and method based on ammonia nitrogen molar ratio detection and regulation. Background technique [0002] In order to meet the NOx emission standards of GB13223-2011 "Emission Standards of Air Pollutants for Thermal Power Plants", coal-fired units of thermal power plants, especially to meet the "ultra-clean" emission requirements of coal-fired units proposed by the National Development and Reform Energy 2014 (2093), the coal-fired units Coal units must be equipped with a denitrification system to meet the emission requirements of flue gas nitrogen oxides. In the denitrification process, selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), and SNCR+SCR combined technology are widely used denitrification technologies. [0003] SCR process uses NH ...

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Problems solved by technology

[0003] SCR process uses NH 3 etc. as the reducing agent, on the action line of the catalyst, the NO in the flue gas x Revert to N 2 , the denitrification rate can reach more than 90%, which is the most mature denitrification technology with the highest denitrification efficiency. Under low-load operation conditions for a long time, at this time, the temperature of the flue gas at the inlet of the SCR reactor is lower than the operating temperature of the catalyst, and the denitrification system stops injecting ammonia, which affects the normal operation of the denitrification system of the thermal power plant and affects the flue gas NO. x Emissions and denitrification power price compensation for power plants cannot meet the recent National Energy Administration's full-load denitrification requirements for power plants; 2) SO in flue gas 2 Under the action of SCR catalyst, it is converted into SO 3 , react with excess escaped ammonia to generate ammonium bisulfate ABS, a by-product of denitrification, which leads to new problems such as corrosion and blockage of air preheater and subsequent equipment, and bag dust bag sticking. Many domestic units have different degrees of air preheater pressure. Increased difference, low operating current of electrostatic precipitator, significant increase in pressure difference of bag filter, tearing of flue, etc.; 3) The catalyst is easily poisoned, and the operation and maintenance costs are high

However, there are still problems in this patent that the amount of ammonia escape is difficult to be reasonably, timely, accurately and continuously controlled, and the problem of equipment blockage and corrosion caused by ammonium bisulfate

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