SNCR and SCR combined denitration device and process

Abstract

The invention discloses an SNCR and SCR combined denitration device for CFB boilers. The device consists of a cyclone separator, a tail part flue, a coal economizer and an air preheater, which are connected in sequence, wherein a first layer of spray gun is arranged in a pipeline which is used for connecting the cyclone separator and the tail part flue; a second layer of spray gun is arranged in the tail part flue; a catalyst device is arranged in a pipeline between the coal economizer and the air preheater. The process comprises the following steps: the NOx-containing smoke comes out from a boiler furnace, passes through the cyclone separator and is sprayed into a urea solution or ammonium hydroxide through the first layer of spray gun to carry out SNCR denitration reaction; the smoke generated after the reaction is sprayed into a urea solution or ammonium hydroxide at the second layer of spray gun to become ammonia gas; the ammonia gas enters into the coal economizer and passes through the catalyst device which carries out SCR; the smoke after the reaction treatment enters the air preheater. The SNCR and SCR combined denitrification device for CFB boilers has the advantages that the denitration efficiency is up to 70-90%, the NOx is discharged up to the standard, the final ammonia escape is less than 3 ppm, the generation of ammonium bisulfate is less than SCR, the blocking or corrosion probability is lower than SCR, and the generated pressure loss and catalyst change cost are relatively low.

Description

technical field [0001] The invention relates to a combined SNCR and SCR denitrification device and process for a CFB boiler. Background technique [0002] Usually CFB boiler denitrification adopts selective catalytic reduction denitrification technology (SCR) or selective non-catalytic reduction denitrification technology (SNCR). [0003] Selective catalytic reduction denitrification technology (SCR) refers to the reduction agent (NH3, urea) in the presence of catalyst and oxygen in a lower temperature range (280 ~ 420 ° C) under the action of two or three layers of catalyst , selectively react with NOx to form N 2 and H 2 O to reduce NOx emissions technology. The advantage is that the denitrification rate can be greater than 80%, the amount of ammonia escape is small, and the NH 3 The consumption is relatively optimized. [0004] Selective non-catalytic reduction denitrification technology (SNCR) does not use a catalyst, and the reducing agent is the same as SCR, also ...

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Problems solved by technology

[0007] The purpose of the present invention is to provide a combined SNCR and SCR denitrification device and process for CFB boilers, which can effectively solve the problems of complex design and high ammonia consumption of SNCR or SCR denitrification for existing CFB boilers

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