A denitration device for flue gas of a chain grate rotary kiln
By performing SCR denitrification treatment on the preheated flue gas and forming a sealed air curtain in the chain grate rotary kiln system, the problem of ultra-low NOx emissions in the chain grate rotary kiln system has been solved, achieving efficient NOx control and energy-saving and environmental protection effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- FUJIAN LONGKING DSDN ENGINEERING CO LTD
- Filing Date
- 2025-07-15
- Publication Date
- 2026-07-14
AI Technical Summary
Existing technologies struggle to achieve ultra-low NOx emissions in pellet production, especially in chain grate rotary kiln systems, where traditional methods suffer from high energy consumption and insufficient denitrification efficiency.
SCR denitrification is performed on the flue gas that is drawn into the preheating stage near the preheating stage 2. A high-temperature regenerating fan is used to form a sealed air curtain to prevent untreated flue gas from leaking out. At the same time, an SNCR spray gun is set between the annular cooling stage 2 and the preheating stage 1 for pretreatment.
It effectively prevents untreated flue gas from entering the first preheating stage, thus achieving ultra-low NOx emissions, reducing operating costs and improving denitrification efficiency.
Smart Images
Figure CN224485488U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the technical field of rotary kilns for pelletizing ore, and specifically relates to a denitrification device for flue gas from a chain grate rotary kiln. Background Technology
[0002] The NOx (nitrogen oxides) concentration in the exhaust gas emitted from the main ventilation system of pellet production reaches 250–500 mg / nm. 3 Furthermore, the oxygen content is as high as 17-19%, and the latest ultra-low emission standards require NOx emission concentrations to be ≤50 mg / nm. 3 Furthermore, the emission concentration must be converted to a baseline oxygen content of 18%, and the actual denitrification efficiency must reach over 85%. Among traditional flue gas denitrification methods, SNCR denitrification efficiency is generally between 20% and 40%, and activated carbon denitrification efficiency is generally between 30% and 60%, both of which are difficult to meet ultra-low emission requirements. However, the SCR process can achieve a denitrification efficiency of 85% to 95%, making it the preferred process method.
[0003] Currently, the treatment of flue gas from pellet mines mostly adopts a process route of adding desulfurization and dust removal + SCR denitrification device to the main exhaust system. Since the catalytic reaction temperature range of SCR denitrification process is 260℃~400℃, while the temperature of flue gas from the main exhaust system of pellet mines is between 150℃ and 180℃, a flue gas heating system must be equipped, resulting in high operating costs and energy waste.
[0004] CN112755756A discloses an embedded SCR+SNCR flue gas denitrification device for a rotary kiln of a chain grate machine. By installing an SNCR denitrification system in the preheating stage and an SCR denitrification device between the multi-tube dust collector and the regenerating fan, it shows some effectiveness in treating NOx in the flue gas from the chain grate machine used for pelletizing ore, achieving ultra-low emissions when NOx concentrations are not high. However, because the chain grate bed is movable, and the different drying and preheating stages are separated only by partition walls, there is a 100-200mm gap between the lower part of the partition wall and the material layer. Furthermore, most chain grate machine partition walls are masonry structures that are easily broken and leaky. High-NOx flue gas from the preheating stage can easily pass through these gaps and leaks, directly entering the preheating and drying stages. This results in NOx being emitted directly into the chimney without passing through the denitrification device, leading to excessive NOx emissions. In addition, this patent does not address the NOx generated in the annular cooling stage. Therefore, this patent is only applicable to projects with less stringent NOx emission standards and cannot meet the more stringent ultra-low emission standards. Utility Model Content
[0005] The purpose of this utility model is to provide a denitrification device for flue gas from a chain grate rotary kiln. By combining the flue gas from the first preheating stage near the second preheating stage with the flue gas generated in the second preheating stage for SCR denitrification treatment, the device effectively prevents the flue gas from the second preheating stage that has not undergone denitrification treatment from being directly discharged.
[0006] The technical solution of this utility model is as follows:
[0007] A chain grate rotary kiln flue gas denitrification device for drying and roasting pellets includes an SNCR spray gun, a multi-tube dust collector, an SCR denitrification reactor, a high-temperature regenerating fan, a desulfurization and dust removal device, and a chain grate machine, a rotary kiln and an annular cooler connected in sequence.
[0008] Along the direction of pellet passage, the chain grate machine includes a drying section 1, a drying section 2, a preheating section 1, and a preheating section 2 connected in sequence; wherein, the inner wall of the preheating section 2 is equipped with SNCR spray guns for denitrification treatment of the flue gas in the preheating section 2.
[0009] Several air boxes are installed at the bottom of the preheating section. The flue gas in the preheating section is drawn out of the preheating section through the air boxes. The flue gas drawn out by the air box adjacent to the preheating section merges with the flue gas in the preheating section and enters the multi-tube dust collector, SCR denitrification reactor and high-temperature regenerating fan arranged in sequence. Then, at least part of it enters the drying section. The flue gas drawn out by the remaining air boxes is treated by the desulfurization and dust removal device and then discharged from the chain grate rotary kiln flue gas denitrification device.
[0010] In some preferred embodiments, the upper parts of the first preheating stage and the second preheating stage are separated by a partition wall;
[0011] The denitrification device for rotary kiln flue gas of the chain grate machine also includes a circulating air box. The circulating air box is set along the partition wall and connected to the high-temperature regenerating fan through the circulating flue. The flue gas that has not entered the second drying stage after being treated by the high-temperature regenerating fan enters the circulating air box through the circulating flue and is blown downward to form a sealed air curtain.
[0012] In some preferred embodiments, the wind speed of the sealed air curtain is 15–20 m / s.
[0013] In some preferred embodiments, the circulating air box is located below the partition wall or at the lower end of the side of the partition wall.
[0014] In some preferred embodiments, along the direction of pellet passage, the annular cooler includes an annular cooling section 1, an annular cooling section 2, an annular cooling section 3, and an annular cooling section 4 connected in sequence. The flue gas generated in the annular cooling section 2 enters the preheating section 1 through a flue. An SNCR spray gun is also installed on the flue between the annular cooling section 2 and the preheating section 1.
[0015] In some preferred embodiments, the SNCR spray gun is used to spray a reducing agent, which is a urea or ammonia solution.
[0016] In some preferred embodiments, an ammonia injection grid is provided at the inlet of the SCR denitrification reactor and a denitrification catalyst is provided inside the SCR denitrification reactor.
[0017] In some preferred embodiments, the temperature of the flue gas discharged from the second annular cooling stage is 800–900°C;
[0018] The rotary kiln feeds flue gas at 900-1100℃ into the second preheating stage, where the flue gas preheats the pellets and then cools them down to 400-450℃.
[0019] This utility model has at least the following beneficial effects:
[0020] (1) This utility model effectively prevents the flue gas in the preheating section that has not been denitrified from being merged into the flue gas in the preheating section and discharged without denitrification treatment by combining the flue gas in the preheating section near the preheating section with the flue gas generated in the preheating section.
[0021] (2) In some preferred embodiments, the flue gas treated by the high-temperature regenerating fan is partially injected from top to bottom into the space between the first and second preheating stages through a circulating flue. This flue gas forms a "wind wall" between the first and second preheating stages, preventing the flue gas in the second preheating stage that has not undergone denitrification treatment from entering the first preheating stage.
[0022] (3) In some preferred embodiments, an SNCR spray gun is installed on the flue between the second cooling stage and the first preheating stage to further reduce NOx in the exhaust gas. Attached Figure Description
[0023] Figure 1 A schematic diagram of the structure of the chain grate rotary kiln flue gas denitrification device provided in Example 1;
[0024] Figure 2 for Figure 1 Enlarged view of section A;
[0025] Figure 3 for Figure 1 Left view of the section at point B-B', bellows omitted;
[0026] Figure 4 for Figure 3 A schematic diagram of the structure of the medium-circulation air box.
[0027] The reference numerals in the diagram are as follows: 1-Chain grate machine; 11-Drying section 1; 12-Drying section 2; 13-Preheating section 1; 131-Blowbox; 14-Preheating section 2; 15-Circulating blowbox; 16-Partition wall between preheating section 1 and preheating section 2; 2-Rotary kiln; 3-Annular cooler; 31-Annular cooler section 1; 32-Annular cooler section 2; 33-Annular cooler section 3; 34-Annular cooler section 4; 4-SNCR spray gun; 5-Multi-tube dust collector; 6-SCR denitrification reactor; 7-High temperature regenerating fan; 8-Desulfurization and dust removal device. Detailed Implementation
[0028] The technical solution of this utility model will be further explained and described below through specific embodiments.
[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are preferred embodiments of the present utility model and should not be considered as excluding other embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model. The present utility model improves upon the existing chain grate rotary kiln; for parts that are not improved, if not mentioned in the application documents, the existing structure is assumed to be used.
[0030] Unless otherwise expressly defined, in the claims, description and accompanying drawings of this utility model, the use of directional terms such as "top", "bottom", "inner", "outer", "upper", "lower", "front", "rear" to indicate orientation or positional relationship is based on the orientation and positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific protection scope of this utility model.
[0031] Example 1
[0032] This embodiment provides a chain grate rotary kiln flue gas denitrification device for drying roasted pellets and treating the generated flue gas. It includes two sets of SNCR spray guns 4, a multi-tube dust collector 5, an SCR denitrification reactor 6, a high-temperature regenerating fan 7, a desulfurization and dust removal device 8, a circulating air box 15, and a chain grate machine 1, a rotary kiln 2, and an annular cooler 3 connected in sequence.
[0033] Along the direction of the pellet passing through, the chain grate machine 1 includes a drying section 11, a drying section 2 12, a preheating section 13, and a preheating section 2 14 connected in sequence; the ring cooler 3 includes a ring cooler section 1 31, a ring cooler section 2 32, a ring cooler section 33, and a ring cooler section 4 34 connected in sequence.
[0034] The first drying stage 11 uses forced air drying, and its bottom is connected to the third annular cooling stage 33. The flue gas generated in the third annular cooling stage 33 performs the first dehydration and drying of the pellets from bottom to top. After that, the flue gas in the first drying stage 11 enters the second drying stage 12.
[0035] The second drying section 12 adopts the exhaust drying mode. Its top is connected to the bottom of the second preheating section 14 through the flue. The flue gas in the second preheating section 14 enters the second drying section 12 from top to bottom and performs a second dehydration and drying of the pellets. The flue gas extracted from the bottom of the second preheating section 14 enters the desulfurization and dust removal device 8 through the flue. After desulfurization and dust removal treatment, it is discharged from the chain grate rotary kiln flue gas denitrification device.
[0036] The preheating section 13 adopts the exhaust preheating mode. Its top is connected to the annular cooling section 32 through the flue. The flue gas of the annular cooling section 32 enters the preheating section 13 from top to bottom and preheats and oxidizes the pellets. Most of the flue gas extracted from the bottom of the preheating section 13 enters the desulfurization and dust removal device 8 through the flue. After desulfurization and dust removal treatment, it is discharged from the chain grate rotary kiln flue gas denitrification device.
[0037] Because the flue gas temperature generated in the second stage of the annular cooling system (32) is between 800 and 900°C, NO will be produced under such a high-temperature environment. x Therefore, in this embodiment, an SNCR spray gun 4 is installed on the flue between the annular cooling stage 32 and the preheating stage 13. The SNCR spray gun 4 reduces NOx to N2 by spraying an ammonia-based reducing agent into the flue, thus avoiding the problem of direct emission of nitrogen oxides generated by the annular cooling stage 32 without denitrification treatment in traditional devices. In this embodiment, the reducing agent is an ammonia solution.
[0038] The second preheating stage 14 adopts a draft preheating mode. The flue gas generated by the first annular cooling stage 31 assists in the combustion of the rotary kiln 2. The flue gas generated by the rotary kiln 2 at 900-1100℃ is introduced into the second preheating stage 14 to preheat and oxidize the pellets. NO will be generated under such high temperature conditions. x Therefore, in this embodiment, an SNCR spray gun 4 is installed at the top of the preheating stage 14. The SNCR spray gun 4 reduces NOx to N2 by spraying an ammonia-based reducing agent into the preheating stage 14 chamber. Since the flue gas temperature of the preheating stage 14 is exactly the reaction temperature of the SNCR reaction, the reaction can be carried out without additional heating, which is more energy-saving and environmentally friendly.
[0039] The gas extracted from the bottom of the preheating stage 14 passes sequentially through the multi-tube dust collector 5, the SCR denitrification reactor 6, and the high-temperature regenerating fan 7 before mostly entering the drying stage 12. Because the different sections of the chain grate machine 1 are separated only by partition walls, there is a 100-200mm gap between the lower part of the partition wall and the material layer. Furthermore, since most of the partition walls of the chain grate machine 1 are masonry structures, they are prone to breakage and air leakage. Figure 3 As shown in this embodiment, a partition wall 16 is provided at the lower end of its side along the space between the first preheating section 13 and the second preheating section 14. Figure 4 The circulating air box 15 shown has a circulating flue leading out from the flue between the high-temperature regenerating fan 7 and the second drying section 12, which is connected to the circulating air box 15. Part of the flue gas treated by the high-temperature regenerating fan 7 enters the circulating air box 15 through the circulating flue and is swept from top to bottom by the circulating air. The wind speed at the outlet of the circulating air box 15 is 15-20 m / s. This flue gas forms a "sealed air curtain" between the first preheating section 13 and the second preheating section 14, preventing the flue gas in the second preheating section 14 that has not undergone denitrification treatment from entering the first preheating section 13.
[0040] Several air boxes 131 are installed at the bottom of the preheating stage 13. The flue gas in the preheating stage 13, as well as the flue gas forming a sealed air curtain, is drawn out of the preheating stage 13 through the air boxes 131. In order to further control the possible air leakage between the preheating stage 2 14 and the preheating stage 13, in this embodiment, the flue gas drawn by a set of air boxes 131 adjacent to the preheating stage 13 and the preheating stage 2 14 is merged with the flue gas of the preheating stage 2 14 and then processed by the subsequent multi-tube dust collector 5, SCR denitrification reactor 6 and high-temperature regenerating fan 7. The flue gas drawn by the remaining air boxes 131 is treated by the desulfurization and dust removal device 8 and then discharged from the chain grate rotary kiln flue gas denitrification device. The flue gas in the preheating stage 2 14 preheats the pellets and then cools them to 400-450°C. After merging with the flue gas in the preheating stage 13, the temperature drops to about 350-400°C, which is exactly the reaction temperature of the SCR denitrification reaction.
[0041] The SCR denitrification reactor 6 has a selective catalyst inside its chamber and an ammonia injection grid at its inlet, which can spray ammonia-based reducing agent into the chamber. For example, the catalyst used in this embodiment is V2O5 / TiO2.
[0042] Tests showed that the NO content in the flue gas discharged from the rotary kiln flue gas denitrification device of the chain grate machine was [data missing]. x The lowest concentration that can be achieved is 15 mg / Nm 3 Emission targets.
[0043] The above description is only a preferred embodiment of the present utility model, and therefore cannot be used to limit the scope of the present utility model. All equivalent changes and modifications made in accordance with the scope of the present utility model patent and the contents of the specification should still fall within the scope of the present utility model.
Claims
1. A chain grate rotary kiln flue gas denitrification device for drying and roasting pellets, characterized in that, It includes SNCR spray gun, multi-tube dust collector, SCR denitrification reactor, high-temperature regenerating fan, desulfurization and dust removal device, and a chain grate machine, rotary kiln and annular cooler connected in sequence. Along the direction of pellet passage, the chain grate machine includes a drying section 1, a drying section 2, a preheating section 1, and a preheating section 2 connected in sequence; wherein, the inner wall of the preheating section 2 is provided with an SNCR spray gun for denitrification treatment of the flue gas in the preheating section 2; The bottom of the preheating section is equipped with several air boxes, through which the flue gas in the preheating section is drawn out. The flue gas drawn by the air box adjacent to the preheating section merges with the flue gas in the preheating section and enters the multi-tube dust collector, the SCR denitrification reactor and the high-temperature regenerating fan arranged in sequence, and then at least part of it enters the drying section. The remaining flue gas drawn by the air box is treated by the desulfurization and dust removal device and then discharged from the chain grate rotary kiln flue gas denitrification device.
2. The denitrification device for rotary kiln flue gas using a chain grate machine as described in claim 1, characterized in that, The upper parts of the first preheating section and the second preheating section are separated by a partition wall; The denitrification device for the rotary kiln of the chain grate machine also includes a circulating air box. The circulating air box is arranged along the partition wall and is connected to the high-temperature regenerating fan through a circulating flue. The flue gas that has not entered the second drying stage after being treated by the high-temperature regenerating fan enters the circulating air box through the circulating flue and is blown downward to form a sealed air curtain.
3. The chain grate rotary kiln flue gas denitrification device as described in claim 2, characterized in that, The wind speed of the sealed air curtain is 15~20m / s.
4. The denitrification device for rotary kiln flue gas using a chain grate machine as described in claim 2, characterized in that, The circulating air box is located below the partition wall or at the lower end of the side of the partition wall.
5. The chain grate rotary kiln flue gas denitrification device as described in any one of claims 1 to 4, characterized in that, Along the direction of the pellet ore passage, the annular cooler includes annular cooler section one, annular cooler section two, annular cooler section three and annular cooler section four connected in sequence. The flue gas generated by the annular cooler section two enters the preheating section one through the flue. The SNCR spray gun is also installed on the flue between the annular cooler section two and the preheating section one.
6. The denitrification device for rotary kiln flue gas as described in claim 1, characterized in that, The SNCR spray gun is used to spray a reducing agent, which is a urea or ammonia solution.
7. The denitrification device for rotary kiln flue gas as described in claim 1, characterized in that, The SCR denitrification reactor is equipped with an ammonia injection grid at its inlet and a denitrification catalyst is installed inside the SCR denitrification reactor.
8. The denitrification device for rotary kiln flue gas of the chain grate machine as described in claim 5, characterized in that, The temperature of the flue gas discharged from the second annular cooling stage is 800~900℃; The rotary kiln inputs flue gas at 900~1100℃ into the second preheating stage, where the flue gas preheats the pellets and then cools them down to 400~450℃.