A continuous denitrogenation system for secondary aluminum dross
By combining a premixer and a continuous denitrification reactor, the problems of long reaction time and low efficiency in the secondary aluminum ash denitrification process of existing technologies are solved, achieving efficient and low-cost secondary aluminum ash denitrification treatment and reducing wastewater generation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SICHUAN KERUI ENVIRONMENTAL PROTECTION TECH CO LTD
- Filing Date
- 2025-06-27
- Publication Date
- 2026-05-29
AI Technical Summary
Existing wet denitrification technologies have long reaction times, low efficiency, and large wastewater production, while pyrometallurgical treatments are energy-intensive and pose a risk of flue gas pollution, making it difficult to achieve efficient and low-cost secondary aluminum ash denitrification.
By combining a premixer and a continuous denitrification reactor, the secondary aluminum ash and auxiliary materials are continuously mixed and reacted. The exothermic reaction is used to reduce energy consumption, and the denitrification efficiency is improved and wastewater generation is reduced through the continuous flow reactor.
Shorten reaction time, improve denitrification efficiency, reduce wastewater generation, and achieve efficient and low-cost secondary aluminum ash denitrification treatment.
Smart Images
Figure CN224294251U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of chemical equipment technology, specifically, it is a secondary aluminum ash continuous denitrification system. Background Technology
[0002] A large amount of aluminum dross is generated during the production of electrolytic aluminum, aluminum products, and recycled aluminum. The aluminum dross produced from primary aluminum production is called primary aluminum ash, while the portion of primary aluminum ash unsuitable for recycling, as well as the aluminum dross generated during recycling, is called secondary aluminum ash, with an aluminum content of 1-20%. Each ton of electrolytic aluminum produces 5-10 kg of secondary aluminum ash. Secondary aluminum ash contains substances such as Al₂O₃, AlN, AlC, Al, SiO₂, CaF₂, and NaCl, and may also contain other components such as NaAlO₂. Therefore, secondary aluminum ash reacts readily with water or in humid air to generate toxic, harmful, explosive, and foul-smelling gases, such as ammonia, methane, and hydrogen. Proper disposal is necessary; otherwise, it will cause serious environmental pollution. Industrially, secondary aluminum ash is generally treated by leaching the aluminum with acid or auxiliary materials, and then used to prepare polyaluminum chloride, aluminum sulfate, sodium aluminate, etc.; or by sintering to produce microcrystalline glass, calcium aluminate, sintered materials, building materials, etc.
[0003] The primary consideration for aluminum ash treatment should be its harmless disposal, i.e., denitrification. Aluminum ash denitrification mainly employs pyrometallurgical and wet methods. Pyrometallurgical denitrification offers higher efficiency and more thorough treatment. However, it is extremely energy-intensive, poses a risk of secondary flue gas pollution, requires high equipment investment, and has limitations in further comprehensive resource utilization. Wet denitrification consumes less energy, eliminates the risk of high-temperature flue gas pollutant pollution, has relatively lower investment costs, allows for selective recovery of valuable components, and is easily industrialized. However, wet denitrification technologies for aluminum ash generally have low denitrification rates and long reaction times. Even with improved denitrification rates under auxiliary material conditions, additional methods such as stirring and high temperatures are required, resulting in high water consumption and complex, costly wastewater treatment. Therefore, a new type of aluminum ash denitrification technology is urgently needed.
[0004] In the prior art, Chinese patent CN222343781U discloses a secondary aluminum ash denitrification treatment device, including a grinding device, a slurry pipeline, a gas-liquid separator, and a gas collection pipeline. The grinding device is used to grind the slurry formed by mixing secondary aluminum ash and water. The slurry pipeline is used to transport the ground slurry and the gas generated by the hydrolysis reaction of secondary aluminum ash and water. The gas-liquid separator is installed on the slurry pipeline to separate the gas generated by the hydrolysis reaction of secondary aluminum ash and water. The gas collection pipeline is connected to the gas-liquid separator to collect the gas generated by the hydrolysis reaction of secondary aluminum ash and water. By removing the coating layer on the surface of aluminum nitride particles through grinding, the hydrolysis reaction can proceed continuously and efficiently. The particle size of the slurry gradually becomes smaller during the grinding process, which is more conducive to the rapid progress of the hydrolysis reaction. The gas is collected in time to the gas collection pipeline, so that the reaction can proceed in the forward direction, which greatly improves the decomposition rate of aluminum nitride in secondary aluminum ash and shortens the reaction time. However, the patent still has problems with low reaction efficiency, such as long reaction time (the reaction time for slurry grinding requires 6 to 12 hours) and low heating efficiency (the heater is placed in the slurry pipeline instead of the cylinder of the continuous ball mill, which easily leads to uneven temperature inside the slurry pipeline, and serious heat loss and increased energy consumption when heating the slurry pipeline). Utility Model Content
[0005] The purpose of this invention is to provide a continuous denitrification system for secondary aluminum ash. By combining a premixer and a continuous denitrification reactor, it balances the high efficiency of secondary aluminum ash denitrification with the continuity of production. This effectively shortens the reaction time, increases the denitrification capacity of secondary aluminum ash, and reduces wastewater generation during wet denitrification by controlling the amount of initiator used. It effectively solves the problems of low denitrification efficiency, long production cycle, and large wastewater production in existing wet denitrification processes.
[0006] This utility model is achieved through the following technical solution: a secondary aluminum ash continuous denitrification system, including a premixer and a continuous denitrification reactor. The inlet of the premixer is connected to the secondary aluminum ash silo and the auxiliary material silo respectively. The continuous denitrification reactor is provided with a feed inlet, a denitrified aluminum ash outlet and a gas phase outlet. The feed inlet is connected to the outlet of the premixer and the initiating material pipe respectively. The denitrified aluminum ash outlet is connected to the leaching kettle. The gas phase outlet is connected to the dust removal device. The ash collection outlet of the dust removal device is connected to the secondary aluminum ash silo.
[0007] The continuous denitrification reactor includes a reactor shell, a drive shaft, and a drive motor. The reactor shell is fitted onto the drive shaft, which is equipped with blades. The end of the drive shaft is connected to the drive motor. The feed inlet, the denitrified aluminum ash outlet, and the gas phase outlet are respectively connected to the reactor shell.
[0008] The blades are helical blades, and together with the drive shaft, they form a helical mixer.
[0009] The outlets of the secondary aluminum ash silo and the auxiliary material silo are respectively equipped with metering devices.
[0010] The premixer is a pipeline premixer.
[0011] The exhaust gas outlet of the dust removal device is connected to the exhaust gas absorption system.
[0012] Compared with the prior art, this utility model has the following advantages and beneficial effects:
[0013] (1) This utility model adopts a continuously set premixer (pipeline premixer) and a continuous denitrification reactor. The equipment structure is simple and can realize continuous processing. The secondary aluminum ash and auxiliary materials are mixed in the pipeline premixer in sequence and then sent into the continuous denitrification reactor. After a series of chemical reactions, the processed product can be continuously discharged, avoiding the use of traditional intermittent denitrification method, shortening the reaction time and improving the denitrification efficiency.
[0014] (2) This utility model adopts a continuous denitrification reactor, which is designed as a continuous flow reaction mode, and can maintain stable reaction conditions. Due to continuous operation, the processing efficiency is high and it can quickly process a large amount of secondary aluminum ash.
[0015] (3) In this invention, secondary aluminum ash and auxiliary materials are premixed in a premixer to ensure that the reactants are fully mixed and improve the reaction efficiency. When the initiator material is added after the secondary aluminum ash and auxiliary materials are mixed, the exothermic reaction during the denitrification reaction can be used to reduce the energy consumption during the reaction. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of this utility model.
[0017] Figure 2 This is a schematic diagram of the continuous denitrification reactor of this utility model.
[0018] Among them, 1—premixer, 2—continuous denitrification reactor, 3—secondary aluminum ash silo, 4—auxiliary material silo, 5—feed inlet, 6—denitrified aluminum ash outlet, 7—gas phase outlet, 8—initiator material pipe, 9—dust removal device, 10—reactor shell, 11—drive shaft, 12—drive motor, 13—paddle, 13-2—feed paddle, 13-2—mixing paddle, 13-3—discharge paddle, 14—metering device, 15—initiator material silo, 16—controller, 17—extraction vessel. Detailed Implementation
[0019] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.
[0020] Example:
[0021] This embodiment is a secondary aluminum ash continuous denitrification system, such as Figure 1 The structure includes the following equipment: secondary aluminum ash silo 3, auxiliary material silo 4, premixer 1, continuous denitrification reactor 2, initiator material silo 15, leaching kettle 17, and dust removal device 9. It enables continuous and efficient treatment of secondary aluminum ash. The process flow is as follows: After the secondary aluminum ash and auxiliary materials are mixed evenly in the pipeline premixer, they are continuously added to the continuous denitrification reactor 2 along with the initiator for mixing and reaction. During the reaction, gas and liquid are separated. The gas phase is sent to the dust removal device 9, and the liquid phase is sent to the leaching kettle 17. Industrial acid or auxiliary material liquid is continuously added to the leaching kettle 17 for treatment.
[0022] Furthermore, the specific structure of this embodiment can be summarized as follows: The bottom of the secondary aluminum ash silo 3 and the bottom of the auxiliary material silo 4 are respectively provided with discharge ports, which are respectively connected to the inlet of the premixer 1 (such as a pipeline premixer) through pipes. A metering device 14 (such as a rotor scale system) is installed at the discharge port to achieve quantitative feeding of secondary aluminum ash and auxiliary materials. The continuous denitrification reactor 2 is provided with an inlet 5, a denitrified aluminum ash outlet 6, and a gas phase outlet 7. The inlet 5 is connected to the outlet of the pipeline premixer and the initiating material pipe 8, which is connected to the initiating material silo 15. The denitrified aluminum ash outlet 6 is connected to the leaching kettle 17. The gas phase outlet 7 is connected to the dust removal device 9, and the ash collection outlet of the dust removal device 9 is connected to the secondary aluminum ash silo 3. The tail gas outlet of this device is connected to the tail gas absorption system.
[0023] Figure 2 This is a schematic diagram of the structure of the continuous denitrification reactor 2. Figure 2 As shown, the continuous denitrification reactor 2 includes a reactor shell 10, a drive shaft 11, a drive motor 12, and a controller 16. The reactor shell 10 is sleeved on the drive shaft 11, and the drive shaft 11 is provided with blades 13, which are helical blades. The drive shaft 11 can be configured as one or more sets. The two ends of the drive shaft 11 pass through the two ends of the reactor shell 10 respectively. The ends of multiple sets of drive shafts 11 are driven by belts or sprockets. At least one end of the drive shaft 11 is connected to the drive motor 12.
[0024] In a specific implementation case, the helical blades of paddle 13 can adopt a tightly meshing design, utilizing the mutual scraping of the two screws (drive shafts) to prevent material retention, reduce the risk of adhesion, and possess self-cleaning characteristics. Furthermore, to achieve efficient reaction and continuous material conveying, a stepped design strategy can be adopted for paddle 13: In the conveying stage, feed paddle 13-1 is set with a blade angle of 60°, ensuring high conveying efficiency, stable pressure establishment, and smooth feeding; in the mixing reaction stage, mixing paddle 13-2 is set with a blade angle of 30–45°, exhibiting high shear and strong dispersibility, increasing the uniformity of reactants within the reactor; in the discharge stage, discharge paddle 13-3 is set with a blade angle of 90°, characterized by gentle mixing and high conveying capacity.
[0025] During production, the drive motor 12 can be controlled by the controller 16 according to process requirements. After the drive motor 12 is started, it drives the drive shaft 11 to rotate. The drive shaft 11 and the blade 13 form a spiral mixer in the reactor shell 10 to realize the mixing reaction of secondary aluminum ash, auxiliary materials and initiator. It can realize continuous feeding and continuous discharge of reaction materials. The liquid phase material obtained from the reaction (mainly aluminum hydroxide and aluminum oxide) is continuously sent to the leaching kettle 17 from the denitrified aluminum ash outlet 6. The gas phase material (mainly ammonia, hydrogen, water vapor and a small amount of escaped aluminum ash dust) is sent to the dust removal device 9 from the gas phase outlet 7.
[0026] In one possible implementation example, such as for alkaline extraction, sodium hydroxide solution can be used. During the operation, sodium hydroxide solution is continuously added to the extraction vessel 17, and the reaction proceeds (Al₂O₃ + 2OH⁻). — +3H₂O→2 [Al(OH)₄] - and Al(OH)3+OH — -[A1(OH)4] - Sodium aluminate is obtained after extraction, which can be sold directly or further purified or hydrolyzed. For acid extraction, industrial hydrochloric acid or sulfuric acid can be used. During operation, industrial hydrochloric acid or sulfuric acid is continuously added to the extraction vessel 17, and the reaction proceeds (Al(OH)3 + 3H+). + →Al 3+ +3H₂O and Al₂O₃ + 6H₂O + →2Al 3+ After reacting with 3H2O, aluminum sulfate or aluminum chloride is obtained. Aluminum sulfate can be further concentrated into solid aluminum sulfate or sold directly as liquid aluminum sulfate; aluminum chloride can be further reacted to prepare polyaluminum chloride.
[0027] In one possible implementation, the dust removal device 9 can be a bag filter. The ammonia, hydrogen, water vapor and a small amount of escaped aluminum dust generated by the continuous denitrification reactor 2 are sent to the bag filter via an absorption fan. After the dust is collected by the bag filter, the collected aluminum dust is returned to the secondary aluminum dust silo 3 through the dust collection outlet for further recycling. The exhaust gas after dust removal is connected to the exhaust gas absorption system through the exhaust gas outlet. In the exhaust gas absorption system, 20-25% dilute sulfuric acid can be used to absorb the exhaust gas. The ammonium sulfate solution produced after absorption is cooled and crystallized by circulating water, centrifuged and dehydrated, and then sold. The mother liquor produced after crystallization and dehydration is returned to the dilute sulfuric acid preparation tank for preparing the dilute sulfuric acid used in the exhaust gas absorption system.
[0028] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.
Claims
1. A secondary aluminum ash continuous denitrification system, characterized in that: It includes a premixer (1) and a continuous denitrification reactor (2). The inlet of the premixer (1) is connected to the secondary aluminum ash silo (3) and the auxiliary material silo (4) respectively. The continuous denitrification reactor (2) is provided with a feed inlet (5), a denitrified aluminum ash outlet (6) and a gas phase outlet (7). The feed inlet (5) is connected to the outlet of the premixer (1) and the initiation material pipe (8) respectively. The denitrified aluminum ash outlet (6) is connected to the leaching kettle (17). The gas phase outlet (7) is connected to the dust removal device (9). The ash collection outlet of the dust removal device (9) is connected to the secondary aluminum ash silo (3).
2. The secondary aluminum ash continuous denitrification system according to claim 1, characterized in that: The continuous denitrification reactor (2) includes a reactor shell (10), a drive shaft (11) and a drive motor (12). The reactor shell (10) is fitted onto the drive shaft (11), and the drive shaft (11) is provided with blades (13). The end of the drive shaft (11) is connected to the drive motor (12). The feed inlet (5), the denitrified aluminum ash outlet (6) and the gas phase outlet (7) are respectively connected to the reactor shell (10).
3. The secondary aluminum ash continuous denitrification system according to claim 2, characterized in that: The blade (13) is a helical blade and together with the drive shaft (11) forms a helical mixer.
4. The secondary aluminum ash continuous denitrification system according to claim 1, characterized in that: The outlets of the secondary aluminum ash silo (3) and the auxiliary material silo (4) are respectively equipped with metering devices (14).
5. The secondary aluminum ash continuous denitrification system according to claim 1, characterized in that: The premixer (1) is a pipeline premixer.
6. The secondary aluminum ash continuous denitrification system according to claim 1, characterized in that: The exhaust outlet of the dust removal device (9) is connected to the exhaust gas absorption system.