SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) combined denitration method and SNCR and SCR combined denitration device for flue gas of coal-fired boiler

Abstract

The invention relates to an SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) combined denitration method and an SNCR and SCR combined denitration device for flue gas of a coal-fired boiler. The SNCR and SCR combined denitration method includes adding reducing agents which are ammonia-containing solution into a temperature window at the temperature ranging from 800 DEG C to 1050 DEG C of a hearth, enabling partial ammonia to be subjected to SNCR reaction with NOX in flue gas and allowing rest escaping ammonia to flow to a flue with flue gas to carry out heat exchange and cooling; and adding to replenish reducing agent to a temperature zone at the temperature ranging from 500 DEG C to 650 DEG C of the flue at an outlet of the boiler, dissolving ammonia, and enabling the ammonia to be subjected to SCR reaction with NOX at the temperature ranging from 300 DEG C to 420 DEG C in the presence of V2O5 and WO3 to remove the NOX remained in the flue gas. The V2O5 and the WO3 are active substances of catalysts, the molar weight of NH3 in the total amount of the added ammonia-containing solution is 1.45-1.6 times of that of NOx in the original flue gas, the ammonia-containing solution containing the NH3 with the molar weight of 1.1-1.2 times of that of the NOx in the original flue gas is added into the temperature window at the temperature ranging from 800 DEG C to 1050 DEG C in the hearth of the boiler, and the rest ammonia-containing solution is added into the temperature zone at the temperature ranging from 500 DEG C to 650 DEG C of the flue of the outlet of the boiler. By the method, the amount of the reducing agents added into an SNCR reaction section and the amount of escaping ammonia can be reduced, the total NH3 of the reducing agents added into the flue gas at the temperature ranging from 500 DEG C to 650 DEG C participates in the SCR reaction, the total consumption of the reducing agents is reduced, and the denitration efficiency is improved.

Description

technical field [0001] The invention relates to a coal-fired boiler flue gas SNCR and SCR combined denitrification method and a denitrification method and a device thereof, which are mainly used in coal-fired power stations, and belongs to the field of flue gas purification. [0002] Background technique [0003] The flue gas produced by coal combustion contains a large amount of nitrogen oxides (NO X ), including N 2 O, NO, NO 2 ,N 2 o 3 ,N 2 o 4 and N 2 o 5 , Nitrogen oxides are extremely harmful and are one of the main pollutants that cause greenhouse effect, acid rain and ozone layer damage. In my country's energy structure, the proportion of coal is as high as about 70%, and flue gas has a great impact on the environment. In recent years, my country's environmental protection regulations have imposed stricter restrictions on nitrogen oxide emission standards, and require NO X Emissions reduced to 100mg / Nm 3 the following. [0004] At present, the more mature...

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Problems solved by technology

[0006] The purpose of the present invention is to provide a coal-fired boiler flue gas SNCR and SCR joint denitrification method, which uses the appropriate temperature range at the boiler tail to accurately measure the NH3 molar concentration entering the SCR reactor area, and overcomes the existing SNCR and SCR combined denitrification process. The defect that the amount of reducing agent entering the SCR reactor in the back stage cannot be measured can reduce the excessive injection of reducing agent in the SNCR stage and improve reaction stability and denitrification efficiency

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