Method and device for spraying reducing agent used for selective catalytic reduction (SCR) of NOx

Abstract

The invention discloses a method and a device for spraying a reducing agent used for selective catalytic reduction (SCR) of NOx and belongs to the field of SCR of NOx. The method comprises the following steps of self-extracting out a small amount of flue gas in an area having a temperature of 500 to 900 DEG C in a boiler by a pressure difference, wherein the small amount of the extracted flue gas is used as urealysis flue gas, spraying a urea solution to the flue gas so that the urea solution is decomposed into ammonia and the ammonia is mixed with the flue gas, feeding back the mixed gas to a reactor for SCR of NOx, and carrying out denitration. The device comprises a denitration reducing agent channel of which one end is communicated with the area having a temperature of 500 to 900 DEG C in the boiler and the other end is communicated with an inlet flue gas channel of the reactor for SCR of NOx. The denitration reducing agent channel comprises a urealysis pipe, an ammonia / flue gas mixed gas pipe and an ammonia injection pipe, wherein the urealysis pipe, the ammonia / flue gas mixed gas pipe and the ammonia injection pipe are communicated orderly. The urealysis pipe is provided with a urea solution spray gun. The method and the device for spraying a reducing agent used for SCR of NOx have the advantages of low investment and operation costs, low energy consumption, high safety, high reliability and complete urealysis.

Description

technical field [0001] The invention belongs to the field of boiler SCR denitrification. Background technique [0002] Selective Catalytic Reduction of NO x , SCR denitrification process for short) The reducing agent mainly has three forms: liquid ammonia, ammonia water, and urea. Liquid ammonia is widely used in the SCR denitrification process due to its simple process system and low investment and operating costs. However, liquid ammonia is a high-risk reduction product, and its transportation and storage requirements are demanding and are increasingly restricted by policies and regulations. , which is extremely inconvenient; similarly, ammonia water is also limited in application due to its transportation, storage problems and high investment and operation costs; as an SCR denitrification reducing agent with lower safety requirements - urea has the same denitrification performance as liquid ammonia and is green Fertilizers are not restricted by dangerous policies and re...

AI Technical Summary

Problems solved by technology

The disadvantages of this method are: the technical difficulty of transporting molten urea, high material requirements, difficulty in atomization, poor safety and reliability, continuous decomposition of ammonia-containing mixed gas into ammonia requires a catalyst, and high investment and operating costs

This method has disadvantages: use urea powder, and introduce the flue gas of only 280-410 ℃ in the downstream flue of the SCR reactor to heat the urea powder to decompose it into ammonia gas, the decomposition of urea is incomplete, the yield of ammonia gas is low, and the associated intermediate The by-products are high, the utilization rate of urea is low, and the consumption is large; the extraction of flue gas requires energy consumption; spraying urea powder into the upstream flue of the reactor for denitrification will also bring new problems: urea powder treatment Difficult, difficult to control the injection volume, and the pipes and nozzles are easy to block, poor safety and reliability

At the same time, due to the need to introduce hot steam to consume additional energy, the investment and operating costs are relatively high, and the energy consumption of the entire denitrification device is also relatively large.

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