Method and system for removing nitrogen oxides from low-temperature flue gas

Abstract

The invention relates to a method for removing nitrogen oxides from low-temperature flue gas, which comprises the following steps of: S1, preparing at least two reactors containing a catalyst and urealoaded on the catalyst, and dividing the reactors into a reaction group and a to-be-reacted group.S2, introducing low-temperature flue gas into the reaction group for denitration reaction; introducing the low-temperature flue gas into the reaction group for denitration reactionwhen urea in the reaction group is consumed to a preset value, and supplementing the urea in the reaction group.S3, introducing the low-temperature flue gas into the to-be-reacted group for denitration reactionwhen urea in the to-be-reacted group is consumed to a preset value, and supplementing the urea in the to-be-reacted group; and S4, alternately introducing the low-temperature flue gas into the reaction group and the to-be-reacted group according to the mode so as to achieve the continuous denitration of the low-temperature flue gas.The invention also provides a system for removing nitrogen oxides from low-temperature flue gas according to the method.The removal of nitrogen oxides in low-temperature flue gas is achieved, the problem of ammonia escape is avoided, and meanwhile, the continuous denitration of low-temperature flue gas and the repeated use of the catalyst are ensured.

Description

technical field [0001] The invention belongs to the technical field of environmental protection and flue gas purification, and in particular relates to a method and system for removing nitrogen oxides from low-temperature flue gas. Background technique [0002] As one of the main pollutants in the atmosphere, nitrogen oxides NO X Emissions mainly come from stationary sources such as thermal power stations and steel mills, and mobile sources such as motor vehicle exhaust. The emission of nitrogen oxides will cause acid rain, ozone depletion, photochemical pollution and human respiratory diseases, seriously endangering the environment and human health. NO X The main component of nitrogen oxides is nitric oxide. Among many nitrogen oxide removal technologies, selective catalytic reduction SCR is widely used in industry due to its high denitrification efficiency, and it is mainly used for the reduction of selective catalytic reduction. Ammonia NH 3 and urea. [0003] NH 3 ...

AI Technical Summary

Problems solved by technology

[0003] NH 3 -The development of SCR denitrification technology has been relatively mature, and its reaction temperature window is 300-450°C. Due to the low exhaust temperature of flue gas, it is necessary to reheat the flue gas to realize NH 3 -SCR denitrification, complex process, high energy consumption, and the use of ammonia as a reducing agent will also lead to ammonia escape, consuming raw materials

In the urea-SCR denitrification technology, the reducing agent urea is injected into the flue gas in the form of a solution, and the urea is decomposed into ammonia at a higher temperature, and its essence is still NH 3 -SCR denitrification technology, and the amount of ammonia gas decomposed into urea solution is difficult to control, which will further lead to the escape of ammonia gas

[0004] In summary, if the above traditional SCR technology is used to denitrify low-temperature flue gas, it is necessary to heat the low-temperature flue gas to the working temperature of denitrification first, which is a complex process and consumes a lot of energy; moreover, the problem of ammonia escape in traditional SCR denitrification technology cannot be solved. avoid

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