CN-117771930-B - Static mixer and SCR flue gas denitration ammonia spraying mixing system

CN117771930BCN 117771930 BCN117771930 BCN 117771930BCN-117771930-B

Abstract

The invention discloses a static mixer and an SCR flue gas denitration ammonia spraying mixing system, wherein the static mixer is arranged in a flue and comprises a plurality of static mixing components, grooves and a second ash discharging pipe, the static mixing components comprise a reducing section, a flow guiding section and at least one turbulent flow section, the reducing section is of a hollow tubular structure, the opening area of the upper end face of the hollow tubular structure is smaller than that of the lower end face of the hollow tubular structure, the flow guiding section is positioned above the reducing section, the at least one turbulent flow section is of a concave hollow structure, the upper end face of the concave hollow structure is open, the flow guiding section is positioned at the lower part or the inside of the reducing section, the bottom of the turbulent flow section is communicated with the first ash discharging pipe, and the first ash discharging pipe is used for discharging dust in the turbulent flow section out of the flue. The invention can improve the mixing uniformity of ammonia and flue gas and simultaneously realize the removal of dust in the flue gas, thereby slowing down the structural blockage of an ammonia nozzle, a catalyst bed pore channel, rear-end equipment and the like in the flue gas denitration technology, further reducing the ammonia escape and effectively overcoming a series of problems caused by the ammonia escape.

Inventors

JIN PING
LI LEI
LI XIN
Han tianzhu
GUO MINGYUAN

Assignees

中国石油化工股份有限公司
中石化（大连）石油化工研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20220929

Claims (10)

1. A static mixer is characterized by comprising one or more layers of static mixing assemblies arranged in a flue, wherein each static mixing assembly comprises a reducing section, a flow guiding section, at least one turbulence section, a first ash discharging pipe and a groove, the reducing section is of a hollow tubular structure with an upper end face smaller than an opening area of a lower end face, the flow guiding section is arranged above the reducing section and is of an inverted concave structure and used for guiding smoke leaving the reducing section to collide with smoke leaving the static mixing assembly adjacently, the at least one turbulence section is of a concave hollow structure with an upper end face open and is arranged at the lower part or the inside of the reducing section, the bottom of the turbulence section is communicated with a first ash discharging pipe, the first ash discharging pipe is used for discharging dust in the turbulence section out of the flue, the groove is formed by sealing connection between two adjacent static mixing assemblies, the second ash discharging pipe is communicated with the groove through an ash discharging hole and is used for discharging dust in the groove, the lower end face of the flow guiding section is lower than the upper end face of the reducing section and is used for guiding oblique downward flow, and the turbulence section is of one or more hemispherical, semi-hemispherical, inverted spherical, four-conical or four-inverted conical structures.
2. The static mixer of claim 1, wherein a gap is formed between two adjacent static mixing components and is used as an ash discharge channel, an ash collecting groove is connected to the lower part of the ash discharge channel, the ash collecting groove is connected with the diameter-reduced section in a sealing manner and is used for collecting falling dust, and a third ash discharge pipe is communicated with the ash collecting groove and is used for discharging dust in the ash collecting groove.
3. The static mixer of claim 1, wherein the lower part of the static mixing assembly is provided with an inclined tube, and the first ash discharge tube and the second ash discharge tube are communicated with the inclined tube, and the dust is discharged out of the flue through the inclined tube.
4. The static mixer of claim 2, wherein the cross-sectional area of the dust collection trough is greater than the cross-sectional area of the dust discharge passage.
5. The static mixer according to claim 2, wherein the lower part of the static mixing assembly is provided with a chute, and the third ash discharge pipe is communicated with the chute, and the dust is discharged out of the flue through the chute.
6. The static mixer of claim 1, wherein a wind deflector is disposed above the recess.
7. The static mixer of claim 6, wherein the wind deflector is a straight or curved plate connected to the reduced diameter section and inclined downward.
8. A flue gas denitration ammonia spraying mixing system is characterized by sequentially comprising an ammonia spraying assembly, a static mixer and a static mixing assembly, wherein the ammonia spraying assembly comprises an ammonia gas nozzle, an ammonia spraying branch pipe and an ammonia spraying main pipe, the ammonia gas nozzle is connected with the ammonia spraying main pipe through the ammonia spraying branch pipe, and the static mixer is characterized in that the static mixing assembly in the static mixer is arranged corresponding to the ammonia gas nozzle.
9. The flue gas denitration ammonia injection mixing system as set forth in claim 8, wherein each static mixing assembly corresponds to the same number of ammonia gas nozzles.
10. The flue gas denitration ammonia injection mixing system as set forth in claim 8, wherein the ammonia gas nozzles are in one-to-one correspondence with the flow guiding sections of the static mixing assembly and are located right below the flow disturbing sections.

Description

Static mixer and SCR flue gas denitration ammonia spraying mixing system Technical Field The invention relates to the technical field of flue gas denitration, in particular to a static mixer and an SCR flue gas denitration ammonia spraying mixing system. Background Among the flue gas denitration methods, the most widely used industry and the most mature technology are Selective Catalytic Reduction (SCR) denitration technologies. The principle of the SCR denitration technology is that ammonia serving as a reducing agent is sprayed into flue gas at 280-420 ℃ through an ammonia spraying mixing system, ammonia and the flue gas are uniformly mixed through a static mixer, and nitrogen oxides (NO x) in the flue gas are reduced into non-toxic and pollution-free nitrogen and water through ammonia (NH 3) under the action of an SCR denitration catalyst, so that the purpose of removing NO x from mixed gas is achieved. The ammonia spraying and mixing system for denitration of coal-fired flue gas (GB/T34339-2017) is defined as a system for spraying ammonia diluted by air in an inlet flue of an SCR reactor and uniformly mixing the ammonia with flue gas. GB/T34339-2017 divides the ammonia spraying mixing system into an ammonia spraying grid (AIG) and an ammonia spraying static mixer, wherein the ammonia spraying static mixer is defined by using a certain fixed part, and a device for fully mixing ammonia and flue gas is achieved by changing the flowing state of the ammonia and the flue gas, so that higher NH 3/NOx mixing efficiency is obtained. Typical static mixers for ammonia injection have vortex, swirl, longitudinal vortex, V-shape and other structural forms. The ammonia spraying mixing system is generally arranged in front of the dust remover, dust content in flue gas is high, nozzle blockage is easy to occur, a large amount of dust enters the SCR catalyst bed through the ammonia spraying mixing system, and partial blockage of pore channels of the catalyst bed is easy to occur. In recent years, the utilization hours of coal-fired units, heating furnaces, incinerators, waste heat boilers and the like are continuously reduced under the influence of factors such as economic acceleration and slowing, environmental protection pressure increase, epidemic situation prevention and control and the like, part of the coal-fired units, the heating furnaces, the incinerators, the waste heat boilers and the like are in low-load operation for a long time, the smoke quantity is reduced, the ammonia spraying quantity is reduced, and at the moment, the nozzles are easier to block. The ammonia spraying amount of the blocked ammonia gas nozzles is very low or even zero, the ammonia spraying amount of other unblocked ammonia gas nozzles is increased, the ammonia nitrogen molar ratio difference in the cross section of the same flue is caused to be larger, the distribution uniformity of the ammonia nitrogen molar ratio of the catalyst inlet of the SCR reactor is caused to be poor, the NOx reaction in the area with insufficient ammonia spraying amount is reduced in denitration efficiency when the ammonia gas passes through the SCR denitration catalyst bed layer, and the ammonia gas which does not participate in denitration reaction in the area with excessive ammonia spraying enters the flue gas to form ammonia escape. A large amount of dust in the flue gas enters the following SCR catalyst bed through the ammonia spraying mixing system, catalyst poisoning and partial bed pore channel blockage are easy to cause, the dust with larger particle size is easy to abrade the catalyst bed, the wall surface of the catalyst pore channel is thinned, the service life of the catalyst is reduced, the long-period operation of the device is influenced, meanwhile, the denitration efficiency is reduced, the ammonia utilization rate is reduced, and ammonia can escape. The escaped ammonia of the SCR denitration system can react with SO 3 in the flue gas to generate Ammonium Bisulfate (ABS), SO that equipment such as a downstream air preheater or an economizer is seriously blocked or leaked, the safe and economic operation of a boiler/device is threatened, if a wet desulfurization device is arranged downstream, the problems of unqualified gypsum products (limestone/lime-gypsum method) or exceeding ammonia nitrogen in desulfurization wastewater (sodium-alkali desulfurization) and the like are caused, and secondary pollution is caused after the escaped ammonia is discharged into the atmosphere. Disclosure of Invention The invention aims to provide a static mixer and an SCR flue gas denitration ammonia spraying mixing system, and the static mixer can improve the mixing uniformity of ammonia and flue gas and simultaneously realize the removal of dust in the flue gas, so that the structure blockage of an ammonia nozzle, a catalyst bed pore channel, rear-end equipment and the like in the flue gas denitration technology is relieved, the ammonia escape is further reduced,