CN219559260U - SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas - Google Patents
SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas Download PDFInfo
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- CN219559260U CN219559260U CN202320820374.2U CN202320820374U CN219559260U CN 219559260 U CN219559260 U CN 219559260U CN 202320820374 U CN202320820374 U CN 202320820374U CN 219559260 U CN219559260 U CN 219559260U
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Abstract
The utility model provides an SCR denitration system for hood-type annealing furnaces or heating annealing furnace flue gas, which comprises an air inlet pipe, a mixer, an SCR reactor, a flue gas heater and a premixer, wherein the air inlet pipe is connected with the inlet end of the mixer, the air inlet pipe is also connected with the flue gas heater through a return pipe, and a pyrolysis return fan is arranged on the return pipe; the outlet end of the mixer is connected with the SCR reactor through a first connecting pipe, the outlet end of the flue gas heater is connected with the inlet end of the pre-mixer through a second connecting pipe, and the outlet end of the pre-mixer is connected with the mixer. According to the SCR denitration system for the hood-type annealing furnace or the heating annealing furnace flue gas, provided by the utility model, part of flue gas is heated to raise the temperature to prepare ammonia by urea pyrolysis, and the high-temperature flue gas is utilized to adjust the temperature of flue gas at the inlet of the SCR reactor, so that the integration of ammonia preparation by urea pyrolysis and flue gas temperature adjustment is realized, and the operation cost of flue gas denitration and the investment cost of equipment are reduced.
Description
Technical Field
The utility model relates to the technical field of SCR denitration, in particular to an SCR denitration system for hood-type annealing furnaces or heating annealing furnace smoke.
Background
The hood-type annealing furnace and the heating annealing furnace in the steel industry can discharge a large amount of industrial flue gas in the production process, the main pollutants in the flue gas are nitrogen oxides, and the concentration of the nitrogen oxides is 300-1000mg/Nm 3 In the range, the national and local emission standards are exceeded. Nitrogen oxides are the main pollutants of photochemical smog and acid rain, and severely pollute the atmosphere. With the increasing of the national environmental protection treatment force, the emission standard is becoming stricter, and the treatment of the nitrogen oxide waste gas emitted by the hood-type annealing furnace and the heating annealing furnace is not slow.
The hood-type annealing furnace and the heating annealing furnace have high flue gas flow (30000-80000 Nm) 3 And/h), the flue gas temperature is lower (120-220 ℃) and the oxygen content (10-18%) is high. The denitration of the waste gas of the nitrogen oxides by adopting an alkaline washing process has the efficiency lower than 70 percent, can not realize the standard emission, and has a large amount of vapor evaporation due to higher flue gas temperature, and a white dragon is arranged on a chimney; the ozone oxidation process is adopted for denitration, the power consumption of an ozone generator is high, steam evaporation is also caused, and a chimney has the phenomenon of white dragon.
Therefore, the current SCR denitration technology is mostly adopted for flue gas, the SCR denitration purification efficiency is high, the emission reaching the standard can be ensured, but the denitration reaction temperature of the medium-temperature denitration catalyst is more than 300 ℃, so that the flue gas is necessarily heated to 300 ℃ and the temperature is 50000Nm 3 The natural gas consumption of the SCR denitration system with the smoke amount per hour is about 150m < 3 >/h, so that the natural gas energy consumption of the medium-temperature SCR denitration is high. In recent years, with the technical progress of SCR denitration catalysts, the technology of low-temperature denitration catalysts has become very mature, and the denitration efficiency of the low-temperature denitration catalysts can reach 80% at 160 ℃. The flue gas temperature of the hood-type annealing furnace and the heating annealing furnace is 120-220 ℃, more than 50% of the flue gas temperature is 180-220 ℃, about 30% of the flue gas temperature is 160-180 ℃, and only 20%The time is between 120 and 160 ℃. The temperature of the catalyst is very close to the temperature window of the low-temperature SCR denitration, so that the low-temperature SCR denitration is selected as the optimal process, and the proper reaction temperature of the low-temperature SCR denitration process is about 180 ℃. In addition, ammonia gas or ammonia water solution or urea solution is required to be injected into the flue gas in the SCR reaction. Ammonia is vaporized from liquid ammonia, the liquid ammonia is dangerous chemical, the fire hazard is class B, the construction of a liquid ammonia station is required to have a safety distance requirement, the ammonia water also belongs to dangerous chemical, and the transportation and the storage of the ammonia water have strict requirements. The urea solution is a nontoxic and harmless chemical, is easy to transport and store, and does not need special safety measures, so that most iron and steel enterprises select 30-50% of urea solution as a reducing agent. The method for preparing ammonia from urea mainly adopts a pyrolysis method, namely, 35-50% of urea solution is directly atomized and sprayed into high-temperature flue gas, and urea is pyrolyzed into NH 3 And CO 2 。
The existing ammonia production process of urea by pyrolysis in flue gas SCR denitration process mainly uses hot air as a heat source to rapidly decompose urea aqueous solution with concentration at 400-650 ℃ to prepare ammonia, wherein the hot air generally adopts primary air heated by an air preheater, namely hot primary air, and the temperature of the hot primary air at the outlet of a conventional air preheater is generally about 300 ℃ and is far lower than the air temperature required by urea pyrolysis. The conventional technology generally sets an electric heating system in front of the pyrolysis furnace to increase the temperature of the hot primary air, but the method can generate larger electricity consumption, and the hot primary air passing through the air preheater is provided with smoke dust, so that the electric heater can be blocked to cause faults in operation, and the method has the advantages of high energy consumption, high operation cost and poor stability. Therefore, the whole SCR denitration cost is high, and the SCR denitration system is complex. In addition, before SCR denitration, when the flue gas temperature of the hood-type annealing furnace and the heating annealing furnace is lower than the reaction temperature of the lowest denitration device, the activity of the catalyst is poor, the ammonia escape rate is high, the denitration efficiency is low, and the NOx emission cannot meet the environmental protection requirement. Therefore, measures are needed to increase the temperature of the flue gas at the denitration inlet so as to meet the use requirements.
Disclosure of Invention
The utility model aims at the defects of the prior art and provides an SCR denitration system for hood-type annealing furnaces or heating annealing furnace smoke.
The utility model adopts the following technical scheme for solving the technical problems:
the SCR denitration system for the hood-type annealing furnace or the heating annealing furnace flue gas comprises an air inlet pipe, a mixer, an SCR reactor, a flue gas heater and a premixer, wherein the air inlet pipe is connected with the inlet end of the mixer, the air inlet pipe is also connected with the flue gas heater through a return pipe, and a pyrolysis return fan is arranged on the return pipe; the outlet end of the mixer is connected with the SCR reactor through a first connecting pipe, the outlet end of the flue gas heater is connected with the inlet end of the pre-mixer through a second connecting pipe, and the outlet end of the pre-mixer is connected with the mixer.
Further, the interior of the mixer is provided with an ammonia injection grid and a plurality of first cyclone mixing plates from left to right in sequence.
Further, a gas burner is arranged in the smoke heater, one end of the gas burner penetrates through one side of the smoke heater and stretches into the smoke heater, and the other end of the gas burner is located on the outer side of the smoke heater.
Further, one end of the gas burner, which is positioned outside the flue gas heater, is connected with a gas pipeline.
Further, a control valve is arranged on the gas pipeline.
Further, an atomization spray gun and a plurality of second cyclone mixing plates are sequentially arranged in the premixer from left to right, one end of the atomization spray gun penetrates through one side of the premixer and stretches into the premixer, and the other end of the atomization spray gun is located on the outer side of the premixer.
Further, one end of the atomizing spray gun, which is positioned outside the premixer, is respectively connected with a compressed air pipe and a water inlet pipe.
Further, a first temperature transmitter is arranged on the first connecting pipe and used for detecting the inlet temperature of the SCR reactor, and the first temperature transmitter and the pyrolysis reflux fan are in interlocking control.
Further, a second temperature transmitter is arranged on the second connecting pipe and used for detecting the outlet temperature of the flue gas heater, and the second temperature transmitter and the control valve are in interlocking control.
Compared with the prior art, the utility model has the following technical advantages:
according to the SCR denitration system for the hood-type annealing furnace or the heating annealing furnace flue gas, a small part of flue gas (accounting for 5-15% of total flue gas amount) is heated to 500-550 ℃, so that urea is fully pyrolyzed, and the high-temperature flue gas is sprayed and mixed into flue gas to be purified through the ammonia spraying grid, so that the purpose of heating the flue gas temperature entering the SCR reactor is achieved, the inlet flue gas temperature of the SCR reactor is controlled to be about 160-260 ℃, and the stable and reasonable SCR reaction temperature is ensured.
The SCR denitration system for the flue gas of the hood-type annealing furnace or the heating annealing furnace provided by the utility model is characterized in that the flue gas is respectively introduced into a mixer (most flue gas) and a heater (less flue gas), and firstly, the flue gas is used as a heat source for preparing ammonia by pyrolysis of urea; secondly, the flue gas is used as a heat source for heating flue gas at the inlet of the SCR reactor; thirdly, the ammonia gas can be diluted and can be uniformly distributed into the purified flue gas through the ammonia spraying grid.
According to the SCR denitration system for the hood-type annealing furnace or the heating annealing furnace flue gas, provided by the utility model, part of flue gas is heated to raise the temperature to prepare ammonia by urea pyrolysis, and the high-temperature flue gas is utilized to adjust the temperature of flue gas at the inlet of the SCR reactor, so that the integration of ammonia preparation by urea pyrolysis and flue gas temperature adjustment is realized, and the operation cost of flue gas denitration and the investment cost of equipment are reduced.
Drawings
FIG. 1 is a schematic diagram of the structure of an SCR denitration system for hood-type annealing furnaces or heating annealing furnace fumes of the utility model;
wherein the reference numerals are as follows:
a mixer 1; 1-1 parts of ammonia spraying grids; 1-2 a swirl mixing plate; an SCR reactor 2; an air intake pipe 3; a flue gas heater 4; a premixer 5; a swirl mixing plate 5-1; an atomizing spray gun 6; a gas burner 7; a first temperature transmitter 8; a control valve 9; a second temperature transmitter 10; a first connection pipe 11; a second connection pipe 12; a gas line 13; a compressed air pipe 14; a water inlet pipe 15; a return pipe 16; pyrolysis reflux fan 17.
Detailed Description
The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
In the description of the present utility model, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model will be understood in specific cases by those of ordinary skill in the art.
Example 1
Referring to fig. 1, the embodiment provides an SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas, which comprises an air inlet pipe 3, a mixer 1, an SCR reactor 2, a flue gas heater 4 and a premixer 5, wherein the air inlet pipe 3 is connected with the inlet end of the mixer 1, the outlet end of the mixer 1 is connected with the SCR reactor 2 through a first connecting pipe 11, the outlet end of the flue gas heater 4 is connected with the inlet end of the premixer 5 through a second connecting pipe 12, and the outlet end of the premixer 5 is connected with the mixer 1.
In this embodiment, the mixer 1 is sequentially provided with an ammonia spraying grid 1-1 and a plurality of first cyclone mixing plates 1-2 from left to right, the high-temperature gas which is primarily mixed with ammonia through the premixer 5 is sprayed into the flue gas to be purified through the ammonia spraying grid, and is fully mixed under the cyclone mixing effect of the first cyclone mixing plates 1-2, firstly, the temperature of the flue gas entering the SCR reactor 2 is increased to about 180 ℃, and the ammonia is uniformly mixed into the flue gas.
In this embodiment, a gas burner 7 is installed in the flue gas heater 4, one end of the gas burner 7 penetrates through one side of the flue gas heater 4 and extends into the flue gas heater 4, and the other end of the gas burner is located at the outer side of the flue gas heater 4.
In this embodiment, one end of the gas burner 7 located at the outer side of the flue gas heater 4 is connected with a gas pipeline 13, where the heating mode of the flue gas heater 4 may adopt a gas heating mode or an electric heating mode, the gas heating mode adopts an air-fuel ratio mode to automatically adjust the operation power of the gas burner, if electric heating mode adopts electric heating mode, the electric heater adopts a silicon controlled rectifier to automatically adjust the operation power of the electric heater, and the outlet flue gas temperature of the flue gas heater is controlled to be 500-550 ℃ by automatically adjusting the operation power of the gas heating mode or the electric heating mode.
In this embodiment, an atomization spray gun 6 and a plurality of second rotational flow mixing plates 5-1 are sequentially arranged inside the premixer 5 from left to right, one end of the atomization spray gun 6 penetrates through one side of the premixer 5 and stretches into the premixer 5, the other end of the atomization spray gun is located outside the premixer 5, urea solution or ammonia water is sprayed into the premixer 5 through the atomization spray gun 6 under the atomization effect of compressed air, and the urea solution is rapidly pyrolyzed into ammonia and carbon dioxide in high-temperature flue gas.
In this embodiment, one end of the atomizing spray gun 6 located outside the premixer 5 is connected with a compressed air pipe 14 and a water inlet pipe 15, the compressed air pipe 14 is used for introducing compressed air, and the water inlet pipe 15 is used for introducing urea solution or ammonia water.
As a preferred example, the first connection pipe 11 is provided with a first temperature transmitter 8 for detecting the inlet temperature of the SCR reactor 2; the first temperature transmitter 8 and the pyrolysis reflux fan 17 are in interlocking control, a control cabinet can be connected, the control cabinet sets a preset value to be reached, and the running rotation speed of the pyrolysis reflux fan 17 is automatically adjusted through the temperature signal of the first temperature transmitter 8, so that the temperature of flue gas at the inlet of the SCR reactor 2 is controlled between 160 ℃ and 260 ℃, and is preferably 180 ℃.
As a preferred example, the second connecting pipe 12 is provided with a second temperature transmitter 10 for detecting the outlet temperature of the flue gas heater 4, and the gas pipeline 13 is provided with a control valve 9; the second temperature transmitter 10 and the control valve 9 are in interlocking control, a control cabinet can be connected, the control cabinet sets a preset value to be achieved, the control valve 9 on the gas pipeline 13 is automatically adjusted through a temperature signal of the second temperature transmitter 10, and the temperature of the flue gas at the outlet of the flue gas heater 4 is ensured to be stable at 500-550 ℃.
The working process of the SCR denitration urea pyrolysis ammonia production system provided by the utility model is as follows:
the method comprises the steps that most of flue gas discharged by a hood-type annealing furnace or a heating annealing furnace enters an inlet of a mixer 1, a small part of flue gas (accounting for 5-15% of total flue gas) is conveyed by a pyrolysis reflux fan 17 on a return pipe 16 to enter a heater 4 for heating, then the flue gas is heated to 500-550 ℃ by the heater 4 and enters a premixer 5, meanwhile, urea solution is sprayed into the premixer 5 through an atomization spray gun 6 under the atomization effect of compressed air, the urea solution is rapidly pyrolyzed into ammonia and carbon dioxide in high-temperature flue gas, the ammonia and the flue gas are primarily mixed under the mixing effect of a second cyclone mixing plate 5-1, the high-temperature flue gas containing the ammonia after mixing enters the mixer 1 through a pipeline, the flue gas to be purified and the high-temperature flue gas sprayed into the mixer 1-1 are fully mixed under the cyclone mixing effect of a plurality of stages of first cyclone mixing plates 1-2, and then enters an SCR reactor 2 through a first connecting pipe 11 for performing a low-temperature SCR denitration reaction; and the operation rotating speed of the pyrolysis reflux fan 17 is automatically adjusted by the temperature signal of the first temperature transmitter 8 on the first connecting pipe 11, so that the temperature of the flue gas at the inlet of the SCR reactor 2 is controlled between 160 ℃ and 260 ℃, preferably 180 ℃.
The low-temperature SCR denitration technology refers to that under the catalysis of a low-temperature denitration catalyst, nitrogen oxides and ammonia in the flue gas are converted into nontoxic and harmless nitrogen (N) 2 ) And water (H) 2 O), the temperature section of SCR denitration is 180-220 ℃.
In summary, according to the SCR denitration system for hood-type annealing furnaces or heating annealing furnace flue gas, provided by the utility model, part of flue gas is heated to raise the temperature to prepare ammonia by urea pyrolysis, and the high-temperature flue gas is used for adjusting the temperature of flue gas at the inlet of the SCR reactor, so that the integration of ammonia preparation by urea pyrolysis and flue gas temperature adjustment is realized, and the operation cost of flue gas denitration and the investment cost of equipment are reduced.
The foregoing description is only illustrative of the preferred embodiments of the present utility model and is not to be construed as limiting the scope of the utility model, and it will be appreciated by those skilled in the art that equivalent substitutions and obvious variations may be made using the description and illustrations of the present utility model, and are intended to be included within the scope of the present utility model.
Claims (9)
1. The SCR denitration system for the hood-type annealing furnace or the heating annealing furnace flue gas is characterized by comprising an air inlet pipe (3), a mixer (1), an SCR reactor (2), a flue gas heater (4) and a premixer (5), wherein the air inlet pipe (3) is connected with the inlet end of the mixer (1), the air inlet pipe (3) is also connected with the flue gas heater (4) through a return pipe (16), and a pyrolysis return fan (17) is arranged on the return pipe (16); the outlet end of the mixer (1) is connected with the SCR reactor (2) through a first connecting pipe (11), the outlet end of the flue gas heater (4) is connected with the inlet end of the pre-mixer (5) through a second connecting pipe (12), and the outlet end of the pre-mixer (5) is connected with the mixer (1).
2. SCR denitration system for hood-type annealing furnace or heating annealing furnace fumes according to claim 1, characterized in that the interior of the mixer (1) is provided with an ammonia injection grid (1-1) and a plurality of first swirl mixing plates (1-2) in sequence from left to right.
3. The SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas according to claim 1, wherein a gas burner (7) is installed in the flue gas heater (4), one end of the gas burner (7) penetrates through one side of the flue gas heater (4) and stretches into the flue gas heater (4), and the other end is located outside the flue gas heater (4).
4. SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas according to claim 3, characterized in that one end of the gas burner (7) located outside the flue gas heater (4) is connected with a gas line (13).
5. SCR denitration system for hood-type annealing furnace or heating annealing furnace fumes according to claim 4, characterized in that the gas line (13) is provided with a control valve (9).
6. SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas according to claim 1, characterized in that the inside of the pre-mixer (5) is provided with an atomizing spray gun (6) and a plurality of second swirl mixing plates (5-1) in sequence from left to right, one end of the atomizing spray gun (6) penetrates one side of the pre-mixer (5) to extend into the pre-mixer (5), and the other end is located outside the pre-mixer (5).
7. SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas according to claim 6, characterized in that one end of the atomizing spray gun (6) located outside the pre-mixer (5) is connected with a compressed air pipe (14) and a water inlet pipe (15) respectively.
8. SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas according to claim 1, characterized in that the first connecting pipe (11) is provided with a first temperature transmitter (8) for detecting the inlet temperature of the SCR reactor (2), the first temperature transmitter (8) and the pyrolysis reflux fan (17) are controlled in an interlocking way.
9. SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas according to claim 5, characterized in that a second temperature transmitter (10) is arranged on the second connecting pipe (12) for detecting the outlet temperature of the flue gas heater (4), and the second temperature transmitter (10) and the control valve (9) are controlled in an interlocking way.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320820374.2U CN219559260U (en) | 2023-04-13 | 2023-04-13 | SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202320820374.2U CN219559260U (en) | 2023-04-13 | 2023-04-13 | SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas |
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| CN219559260U true CN219559260U (en) | 2023-08-22 |
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| CN202320820374.2U Active CN219559260U (en) | 2023-04-13 | 2023-04-13 | SCR denitration system for hood-type annealing furnace or heating annealing furnace flue gas |
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