Denitration system of annealing furnace
By installing a straight pipe section and a swirl sheet at the entrance of the SCR reactor of the cold rolling annealing furnace, combined with the design of a three-layer catalyst, the problem of excessive nitrogen oxide emissions and ammonia escape in SCR denitrification technology was solved, and an efficient and stable Denitrification effect.
Patent Information
- Application Number
- CN202420044948.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-09
- Publication Date
- 2025-01-21
- Estimated Expiration
- 2034-01-09
AI Technical Summary
When cold-rolled annealing furnace adopts SCR denitrification technology, it is difficult to effectively reduce nitrogen oxide emissions, and there is a problem of ammonia escape exceeding the standard, which affects the compliance of environmental protection emission standards.
Install a straight pipe section at the inlet of the SCR reactor and install a swirl plate in the straight pipe section to ensure that nitrogen oxides and ammonia are fully mixed. At the same time, three layers of catalysts are set up, including the first, second and third layers of catalysts to ensure stable catalyst performance and control of ammonia escape.
By fully mixing nitrogen oxides and ammonia, the denitrification efficiency of the annealing furnace is improved, the nitrogen oxide emissions are controlled to less than 15mg/m3@8%O2, and the ammonia escape is less than 2.5mg/m3@8%O2, achieving environmental protection emission standard requirements.
Smart Images
Figure CN222368772U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of denitration in the steel industry, in particular to an annealing furnace denitration system. Background Art
[0002] The heating method of cold rolling annealing furnace is mainly radiant tube heating. Due to the limitation of the combustion space of the radiant tube, the commonly used measures to reduce nitrogen oxides cannot be effectively implemented, so the nitrogen oxide emissions of the radiant tube burner are generally greater than 100mg / m 3 @8%O 2 , @8%O 2 :The base oxygen content is 8%. As environmental protection standards are becoming more stringent year by year, some regions require nitrogen oxide emissions to be less than 15mg / m 3 @8%O 2 It is very difficult to reduce nitrogen oxides from the source and achieve standard emissions. In recent years, end-of-pipe treatment using SCR denitrification technology has gradually emerged.
[0003] SCR denitration technology is used in cold rolling annealing furnaces to reduce nitrogen oxide emissions. Since the environmental emission standards for cold rolling annealing furnaces are very strict, nitrogen oxide emissions are generally required to be less than 15mg / m 3 @8%O 2 There are higher requirements for ammonia injection control, ammonia nitrogen mixing, catalyst layout, etc., and improvements are urgently needed. Utility Model Content
[0004] The present application provides an annealing furnace denitration system, which solves the technical problem of the control difficulty in reducing nitrogen oxide emissions when the SCR denitration technology is used in the cold rolling annealing furnace.
[0005] The present application provides an annealing furnace denitrification system, which includes an SCR reactor. The annealing furnace denitrification system includes a straight pipe section installed at the inlet of the SCR reactor. The diameter of the straight pipe section is the same as the inlet diameter of the SCR reactor. The length of the straight pipe section is 7-13 times the diameter of the pipe. The annealing furnace denitrification system includes a swirl plate, which is fixedly installed in the straight pipe section. The swirl plate is used to transform the passing gas into a swirl state.
[0006] In some embodiments, the length of the straight pipe segment is 10 times the pipe diameter.
[0007] In some embodiments, the annealing furnace denitrification system includes at least two swirl blades, and the at least two swirl blades are installed in the straight pipe section at intervals from each other.
[0008] In some embodiments, the swirl vane is located near the inlet of the SCR reactor.
[0009] In some embodiments, there is a swirl vane installed at the end of the straight pipe section.
[0010] In some embodiments, a first layer of catalyst and a second layer of catalyst are provided in the SCR reactor, and the catalyst amounts of the first layer of catalyst and the second layer of catalyst are arranged according to theoretical requirements, so that the initial catalyst amount of the SCR reactor is configured at twice the theoretical requirement.
[0011] In some embodiments, the SCR reactor is further provided with an installation position for a third layer catalyst, which serves as a spare installation position. When the catalyst performance decreases and ammonia slip occurs, a new catalyst is installed in the third layer catalyst.
[0012] In some embodiments, when the performance of the catalyst decreases and ammonia slip occurs, the third layer of catalyst is newly installed with the same amount of catalyst as that of the first layer of catalyst.
[0013] In some embodiments, when the annealing furnace denitration system is in operation, the oxygen content in the flue gas of the cold rolling annealing furnace is controlled below 15%.
[0014] In some embodiments, the annealing furnace denitration system adds a water seal tank at the exhaust port of the ammonia water tank.
[0015] The beneficial effects of the present application are as follows: an annealing furnace denitrification system is provided. On the basis of the existing SCR denitrification technology, a straight pipe section is installed at the inlet of the SCR reactor. The diameter of the straight pipe section is the same as the inlet diameter of the SCR reactor, and the length of the straight pipe section is limited to 7-13 times the diameter of the pipe, so that nitrogen oxides and ammonia are fully mixed in the straight pipe section before entering the reactor; and the system has a swirl plate fixedly installed in the straight pipe section, and the swirl plate is used to transform the passing gas into a swirl state, so that the nitrogen oxides and ammonia are further fully mixed, thereby improving the denitrification efficiency of the annealing furnace and providing a reliable technical solution for the denitrification of cold rolling annealing furnaces. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model.
[0017] Figure 1 A schematic diagram of an annealing furnace denitration system provided in this application;
[0018] Figure 2 This is a schematic diagram of the swirl blade in the system provided in this application.
[0019] Figure markings: 100-reactor, 200-straight pipe section, 300-swirl blade. DETAILED DESCRIPTION
[0020] The main difficulties in using SCR denitrification technology to reduce nitrogen oxide emissions in cold rolling annealing furnaces are as follows:
[0021] 1. The environmental emission standards for cold rolling annealing furnaces are very strict, generally less than 15 mg / m 3 @8%O 2 , and the ammonia escape is required to be less than 2.5mg / m 3 @8%O 2 Therefore, there are higher requirements for ammonia injection control, ammonia nitrogen mixing, catalyst layout, etc.
[0022] 2. The oxygen content in the flue gas of the cold rolling annealing furnace is relatively high. The measured nitrogen oxide concentration after denitrification is about 5 mg / m 3 , the instrument detection accuracy is required to be high, and the instrument zero drift will affect the detection and control accuracy.
[0023] 3. The exhaust port of the ammonia tank is directly connected to the flue. When filling ammonia, volatile ammonia gas is discharged into the flue, which will cause control disorders and excessive ammonia escape.
[0024] Based on the above problems, this embodiment discloses an annealing furnace denitration system. Based on the existing SCR denitration technology, the existing SCR denitration system includes an SCR reactor 100. SCR refers to selective catalytic reduction. This system includes a straight pipe section 200. Please refer to Figure 1 The straight pipe section 200 is installed at the inlet of the SCR reactor 100, and the nitrogen oxides and ammonia pass through the straight pipe section 200 before being input into the reactor 100. The diameter of the straight pipe section 200 is defined to be the same as the inlet diameter of the SCR reactor 100, and the length of the straight pipe section 200 is 7-13 times the diameter of the pipe. This allows the nitrogen oxides and ammonia to be fully mixed in the straight pipe section 200 before entering the reactor 100.
[0025] Also, please refer to Figure 1 The system further includes a swirl sheet 300, which is fixedly installed in the straight pipe section 200. The swirl sheet 300 is used to transform the passing gas into a swirl state. The swirl sheet 300 transforms the passing gas into a swirl state, so that the nitrogen oxides and ammonia are further fully mixed, thereby improving the denitration efficiency of the annealing furnace and providing a reliable technical solution for the denitration of the cold rolling annealing furnace.
[0026] In some embodiments, a first layer of catalyst and a second layer of catalyst are provided in the SCR reactor 100, and the catalyst amounts of the first layer of catalyst and the second layer of catalyst are arranged according to the theoretical demand, so that the initial catalyst amount of the SCR reactor 100 is configured at twice the theoretical demand.
[0027] In some embodiments, the SCR reactor 100 is further provided with an installation position for a third layer catalyst, and the third layer catalyst is used as a spare installation position. When the catalyst performance decreases and ammonia slip occurs, a new catalyst is installed on the third layer catalyst. The same amount of catalyst as the first layer catalyst can be selected to be installed on the third layer catalyst.
[0028] When the catalyst performance continues to decline and ammonia slip occurs again, the first layer of catalyst is updated.
[0029] As described above, by arranging three layers of catalyst in the reactor 100, the three layers of catalyst are used for two purposes and one as a backup, ensuring that ammonia slip does not exceed the standard, improving the denitrification efficiency of the annealing furnace, and fundamentally solving the control problem of low nitrogen oxides and zero ammonia slip.
[0030] In some embodiments, the length of the straight pipe section 200 is 10 times the pipe diameter, which ensures that the nitrogen oxides and ammonia are fully mixed in actual use.
[0031] In some embodiments, the annealing furnace denitration system includes at least two swirl plates 300 , and the at least two swirl plates 300 are installed in the straight pipe section 200 at intervals from each other. Figure 1 The solution of simultaneously setting two swirl blades 300 is shown in the figure, which further improves the beneficial mixing effect of the swirl.
[0032] In some embodiments, see Figure 1 The swirl plate 300 is installed near the inlet of the SCR reactor 100. The nitrogen oxides and ammonia are first mixed by the straight pipe section 200, and then mixed several times by the swirl plate 300 to ensure that the nitrogen oxides and ammonia are fully mixed.
[0033] In some embodiments, see Figure 1 There is a swirl plate 300 installed at the pipe end of the straight pipe section 200, specifically at the pipe end of the straight pipe section 200 close to the inlet of the SCR reactor 100.
[0034] In the prior art, the oxygen content in the flue gas of the cold rolling annealing furnace is above 20%, and it needs to be converted to the reference oxygen content of 8% during measurement. Since the instrument zero drift will affect the detection and control accuracy, the error of the instrument zero drift will become too large after the oxygen content is converted to 8%, affecting the accuracy of the measurement results. In this system, when the annealing furnace denitrification system is running, the oxygen content in the flue gas of the cold rolling annealing furnace is controlled below 15%, thereby reducing the negative impact of the instrument zero drift and ensuring the accuracy of the measurement results.
[0035] In view of the prior art that the exhaust port of the ammonia tank is directly connected to the flue, volatile ammonia is discharged into the flue when filling with ammonia, which will lead to control disorder and excessive ammonia escape. In some embodiments, the system adds a water seal tank at the exhaust port of the ammonia tank, and the volatile ammonia is absorbed by water before being discharged into the flue, thereby solving the above problems.
[0036] The above system adopts the straight pipe section 200, swirl sheet 300, three-layer catalyst, flue gas oxygen content controlled below 15%, and water seal tank design. After being put into use, nitrogen oxides are stably controlled to less than 15mg / m 3 @8%O 2 , and ammonia escape is stable at less than 2.5mg / m 3 @8%O 2 , achieving efficient and stable denitrification.
[0037] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.
[0038] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.
Claims
1. An annealing furnace denitrification system, characterized in that: The annealing furnace denitration system includes an SCR reactor, and the annealing furnace denitration system includes a straight pipe section installed at the inlet of the SCR reactor, the diameter of the straight pipe section is the same as the inlet diameter of the SCR reactor, and the length of the straight pipe section is 7-13 times the pipe diameter; The annealing furnace denitration system comprises a swirl plate, which is fixedly installed in the straight pipe section and is used to transform the passing gas into a swirl state.
2. The annealing furnace denitration system according to claim 1, characterized in that: The length of the straight pipe section is 10 times the pipe diameter.
3. The annealing furnace denitration system according to claim 1, characterized in that: The annealing furnace denitration system comprises at least two swirl plates, and at least two swirl plates are installed in the straight pipe section at intervals from each other.
4. The annealing furnace denitration system according to claim 3, characterized in that: The swirl plate is close to the inlet of the SCR reactor.
5. The annealing furnace denitration system according to claim 4, characterized in that: There is a swirl plate installed at the pipe end of the straight pipe section.
6. The annealing furnace denitration system according to claim 1, characterized in that: The SCR reactor is provided with a first layer of catalyst and a second layer of catalyst, and the catalyst amounts of the first layer of catalyst and the second layer of catalyst are arranged according to theoretical demand, so that the initial catalyst amount of the SCR reactor is configured at twice the theoretical demand.
7. The annealing furnace denitration system according to claim 6, characterized in that: The SCR reactor is also provided with an installation position for a third layer of catalyst, and the third layer of catalyst is used as a spare installation position. When the catalyst performance decreases and ammonia slip occurs, a new catalyst is installed on the third layer of catalyst.
8. The annealing furnace denitration system according to claim 7, characterized in that: When the performance of the catalyst decreases and ammonia slip occurs, the third layer of catalyst is newly installed with the same amount of catalyst as that of the first layer of catalyst.
9. The annealing furnace denitration system according to any one of claims 1 to 8, characterized in that: When the annealing furnace denitration system is in operation, the oxygen content in the flue gas of the cold rolling annealing furnace is controlled below 15%.
10. The annealing furnace denitration system according to any one of claims 1 to 8, characterized in that: The annealing furnace denitration system adds a water seal tank at the exhaust port of the ammonia water tank.