Simultaneous desulfurization and denitrification method using aqueous ammonia

Abstract

The invention relates to a method for simultaneously removing sulfur oxides and nitrogen oxides in flue gas by using aqueous ammonia. According to the method, the (NH4)2SO3, which is obtained from a desulfurization reaction for absorbing SO2 by aqueous ammonia, is used as an absorption solution for a denitrification reaction; and the (NH4)2SO3 has reducibility for reducing NOx in the flue gas to N2 to achieve the denitrification purpose. The method provided by the invention comprises the following steps that: the flue gas firstly enters into a denitrification spraying layer of a contraction segment in a venturi tower and is subjected to a downstream contact reaction with a circulating liquid from an oxidation pond on the tower bottom, an aqueous ammonia spraying layer is arranged at the throat part of the venturi tower to carry out the desulfurization reaction, the concentration of the (NH4)2SO3 is instantly increased due to the desulfurization reaction, the denitrification reaction is further carried out, the liquid after reaction and the flue gas transversely enter into the middle lower part of a cylindrical tower along the lower part of the venturi tower, the liquid flows downwards to the bottom of the cylindrical tower, the flue gas moves upwards after passing through a tower plate and is countercurrent contact with the circulating liquid to further generate a desulfurization reaction and a denitrification reaction, fine liquid drops and aerosol of the purified flue gas are captured when the purified flue gas passes through the water spraying layer and a folded plate type defroster, the purified flue gas is then directly exhausted from a direct exhaust chimney connected to the tower top, and simultaneously, a by-product of the system is ammonium sulfate, which is a raw material of an agricultural nitrogenous fertilizer or a compound fertilizer.

Description

technical field [0001] The invention relates to a method for removing SO in flue gas with ammonia water 2 , NOx method, belonging to the technical field of flue gas purification. Background technique [0002] SOx and NOx are the main sources of air pollutants, which have caused great harm to the environment. With the increasingly stringent national environmental protection regulations, combined with the existing flue gas treatment technology, the development of a flue gas desulfurization and denitrification process with reliable operation and low investment and operation costs is in line with my country's national conditions and has a good application prospect. [0003] At present, the flue gas desulfurization process is relatively mature, among which the wet process occupies the largest market share, the process is simple, the desulfurization effect is good, and there are many absorbents that can be used; but most of the flue gas denitrification processes currently use sel...

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Problems solved by technology

[0003] At present, the flue gas desulfurization process is relatively mature, among which the wet process occupies the largest market share, the process is simple, the desulfurization effect is good, and there are many absorbents that can be used; but most of the flue gas denitrification processes currently use selective catalytic reduction method (SCR), which uses ammonia as a reducing agent to reduce NOx to N under the action of a catalyst 2 , the process system and equipment are relatively complicated, the catalyst depends on imports, and the price is very expensive

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