Method for efficient utilization of aluminum dross

Abstract

The application discloses a kind of aluminum ash efficient utilization method, after being finely ground, preheating, microwave heating oxidation denitrification is added to fluidized bed under the assistance of large particle wave-absorbing material, aluminum, aluminum nitride in aluminum ash is converted into alumina, nitrogen, after heat exchange, fluoride, chlorides and other salts are removed by microwave vacuum distillation to denitrification residue, after screening, wave-absorbing material is recycled to microwave flow chlorination deoxidation, alumina, silicon oxide and magnesium oxide in aluminum ash are converted into aluminum chloride, silicon chloride and magnesium chloride, and magnesium chloride enters tailings, and aluminum chloride and silicon chloride are recovered by multistage condensation, respectively, unreacted chlorine and carbon monoxide are recycled by multistage separation.The application uses microwave heating, without balling, oxidation denitrification, distillation desalination and chlorination deoxidation reaction rate is fast, efficiency is high, raw material is widely used, system energy utilization rate is high, can realize large-scale clean and efficient utilization of aluminum ash, with good economic benefit and social benefit.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly production technology, specifically to a method for the efficient utilization of aluminum ash. Background Technology

[0002] Aluminum ash is an industrial byproduct generated during the production of electrolytic aluminum, cast aluminum, and waste aluminum recycling. my country's aluminum industry produces more than 3 million tons of aluminum ash annually. Because aluminum ash contains harmful substances such as aluminum nitride, soluble fluoride salts, and chloride salts, it is listed in the "National Hazardous Waste List". The harmless treatment and high-value utilization of aluminum ash are of great significance to the green and high-quality development of the aluminum industry.

[0003] The harmless treatment of aluminum ash mainly involves denitrification and desalination. The most common denitrification method is to calcine the aluminum ash at high temperature in air to convert aluminum nitride into nitrogen and alumina. However, during the oxidative calcination process, a dense alumina film easily forms on the surface of the aluminum nitride particles, hindering the further denitrification reaction and resulting in low denitrification efficiency. Chinese patent application CN112744850A discloses a method for the comprehensive utilization of secondary aluminum ash resources. First, secondary aluminum ash and sodium alkali are used to form pellets of 30-200mm using a binder. Then, these pellets are placed in a high-temperature kiln for calcination. The sodium alkali is used to oxidize aluminum nitride to convert the resulting alumina into sodium aluminate, thereby alleviating the barrier effect of the formed alumina film and enhancing the denitrification reaction. Although this method uses alkali sintering to improve denitrification efficiency, the amount of alkali added is large, resulting in high production costs. Furthermore, the large pellet diameter leads to uneven heating, high solid-phase reaction temperature, long reaction time, and high energy consumption. Chinese patent application CN110902706A discloses a method for preparing polyaluminum chloride from aluminum ash. First, aluminum ash and coke are formed into 5-20 mm pellets using a binder. Then, these pellets are calcined in chlorine gas at 700-1100℃ in a moving bed, converting aluminum nitride into nitrogen and aluminum chloride. While this method can denitrify aluminum nitride and obtain high-value-added aluminum chloride, the use of large-particle pellets in the chlorination calcination process leads to uneven heating and high diffusion resistance for the generated aluminum chloride and nitrogen, resulting in a slow reaction rate, low efficiency, and high energy consumption. Chinese patent application CN112850762A discloses a method for preparing aluminum chloride from aluminum ash pellets via chlorination-oxygen pressure conversion and utilizing all components. First, aluminum ash and coke are mixed uniformly in a certain proportion to form pellets. Then, these pellets are calcined in chlorine gas at 1000℃ in a moving bed, yielding nitrogen and high-value-added products such as aluminum chloride, silicon chloride, and magnesium chloride. Although this scheme can harmlessly treat aluminum ash and realize the high-value utilization of elements such as aluminum, silicon, and magnesium, it also suffers from problems such as slow reaction rate, low efficiency, and high energy consumption due to the use of pellet chlorination, which results in large gas phase diffusion resistance.

[0004] Therefore, given the current limitations of efficient aluminum ash utilization in existing technologies, the key to achieving large-scale, efficient, and clean utilization of aluminum ash lies in strengthening denitrification, desalination, and the high-value utilization of elements such as aluminum and silicon through process and technological innovation, thereby improving reaction efficiency and reducing process energy consumption. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention aims to provide a method for the efficient utilization of aluminum ash.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for the efficient utilization of aluminum ash includes the following steps:

[0008] S1. Grinding process: Grind aluminum ash into fine powder to obtain fine ash;

[0009] S2, Preheating process: The fine ash obtained in step S1 is preheated with hot nitrogen-rich air to obtain hot fine ash and cold nitrogen-rich air.

[0010] S3, Microwave oxidation denitrification process: The hot fine ash obtained in step S2 is mixed with ceramic-based microwave absorbing material, hot air is introduced, and the hot fine ash obtained in step S2 is oxidized and denitrified under microwave heating to obtain hot nitrogen-rich air and denitrification slag. The hot nitrogen-rich air is used for the preheating process of step S2.

[0011] S4. Heat exchange and cooling process: The denitrification slag obtained in step S3 is cooled by heat exchange using room temperature air to obtain cooled slag and hot air. The hot air is used in the microwave oxidation denitrification process of step S3.

[0012] S5. Microwave vacuum distillation process: The cooled residue obtained in step S4 is vacuum distilled under microwave heating to volatilize and separate the low-melting-point salts, and obtain gaseous fluorides, gaseous chlorides and desalination residue.

[0013] S6. Screening process: The desalination residue obtained in step S5 is screened to obtain ceramic-based microwave absorbing material and fine material. The ceramic-based microwave absorbing material is returned to the microwave oxidation denitrification process in step S3.

[0014] S7. High-energy ball milling process: The carbon-based microwave absorbing material and the fine material obtained in step S6 are thoroughly mixed by high-energy ball milling to obtain a mixture.

[0015] S8. Microwave chlorination deoxygenation process: The mixture obtained in step S7 is subjected to chlorination deoxygenation under microwave heating using chlorine and carbon monoxide to obtain tailings and mixed gas, wherein the mixed gas contains gaseous aluminum chloride, gaseous silicon chloride, carbon dioxide, and unreacted carbon monoxide and chlorine.

[0016] S9. Washing and drying process: The tailings obtained in step S8 are first washed with water to remove soluble salts, and then dried and dehydrated to obtain washing liquid and carbon-based microwave absorbing material. The carbon-based microwave absorbing material is returned to the high-energy ball milling process in step S7.

[0017] S10, First-stage heat exchange and condensation process: The mixed gas obtained in step S8 is subjected to first-stage heat exchange and condensation using room temperature chlorine and carbon monoxide to obtain a mixed gas phase and solid phase aluminum chloride product containing gaseous silicon chloride, carbon dioxide, carbon monoxide and chlorine. The hot chlorine and hot carbon monoxide after heat exchange are used in the microwave chlorination and deoxygenation process of step S8.

[0018] S11, Secondary heat exchange and condensation process: The mixed gas phase obtained in step S10 is subjected to secondary heat exchange and condensation to obtain a mixed gas phase and liquid phase silicon chloride product containing gaseous carbon dioxide, carbon monoxide and chlorine.

[0019] S12, Primary separation process: The mixed gas phase obtained in step S11 is subjected to primary separation to convert chlorine gas into liquid phase, resulting in a mixed gas phase containing carbon dioxide and carbon monoxide, as well as liquid chlorine.

[0020] S13, Gasification process: The liquid chlorine obtained in step S12 is vaporized to obtain chlorine gas, which is then returned to the microwave chlorination and deoxygenation process in step S8.

[0021] S14, Secondary separation process: The mixed gas phase of carbon dioxide and carbon monoxide obtained in step S12 is subjected to secondary separation to obtain gaseous carbon monoxide and solid carbon dioxide. The gaseous carbon monoxide is returned to the microwave chlorination deoxygenation process in step S8.

[0022] Furthermore, in step S1, the particle size of the fine ash is <1μm.

[0023] Furthermore, in step S3, the reaction temperature for oxidative denitrification is 500-700℃, the reaction time is 0.1-0.5h, the reactor used is a fluidized bed reactor, and the ceramic-based microwave absorbing material is SiC particles with a particle size of 0.5-5mm.

[0024] Furthermore, in step S5, the vacuum distillation is performed at a vacuum level of 5-50 Pa, a temperature of 600-800 °C, and a time of 0.5-1 h.

[0025] Furthermore, in step S7, the carbon-based microwave absorbing material is one or a combination of graphite, carbon black, carbon fiber, and graphene; the particle size of the mixture is <1μm.

[0026] Furthermore, in step S8, the chlorination deoxygenation temperature is 500-700℃, the time is 0.5-1h, and the reactor used is a fluidized bed reactor.

[0027] Furthermore, in step S10, the temperature of the mixed gas phase after primary heat exchange condensation is 70°C to 170°C.

[0028] Furthermore, in step S11, the temperature of the mixed gas phase after the secondary heat exchange condensation is 20°C to 50°C.

[0029] Furthermore, in step S12, the temperature of the primary separation is -70°C to -40°C.

[0030] Furthermore, in step S14, the temperature of the secondary separation is from -190°C to -80°C.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. This invention eliminates the need for pelletizing. It uses air to directly heat finely ground aluminum ash into a fluidized state for oxidation and denitrification with the assistance of large-particle microwave absorbing material. This results in a large gas-solid contact area, a fast reaction rate, and effectively avoids the blocking effect of aluminum oxide generated during the oxidation of aluminum nitride, thus achieving high denitrification efficiency.

[0033] 2. In this invention, aluminum ash denitrification and desalination material is mixed evenly with carbon-based high-temperature resistant microwave absorbing material by high-energy ball milling, and then directly subjected to microwave low-temperature fluidized bed chlorination and deoxidation. The gas-solid phase mass and heat transfer rate is fast, the reaction efficiency is high, and energy consumption is effectively reduced.

[0034] 3. In this invention, the oxidation denitrification, distillation desalination and chlorination deoxidation of aluminum ash are all carried out by microwave heating, which has a fast heating rate and uniform heating. At the same time, the materials used are all finely ground and uniformly mixed fine powders with high reactivity, low reaction temperature, low gas phase diffusion resistance and high gas-solid reaction conversion rate.

[0035] 4. Both the ceramic-based high-temperature resistant microwave absorbing material and the carbon-based high-temperature resistant microwave absorbing material used in this invention can be recycled in the system, effectively saving costs;

[0036] 5. This invention has a high waste heat recovery and utilization rate, which effectively improves the thermal efficiency of the overall process system. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the methods of various embodiments of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0039] Example 1

[0040] This embodiment provides a method for the efficient utilization of aluminum ash, such as... Figure 1 As shown, it includes the following steps:

[0041] S1. Grinding process: Grind aluminum ash into fine powder to obtain fine ash with a particle size of less than 1μm;

[0042] S2, Preheating process: The fine ash obtained in step S1 is preheated with hot nitrogen-rich air to obtain hot fine ash and cold nitrogen-rich air.

[0043] S3. Microwave Oxidation Denitrification Process: The hot fine ash obtained in step S2 is mixed with the ceramic-based microwave absorbing material, and hot air is introduced. Under microwave heating, the hot fine ash obtained in step S2 is oxidized and denitrified to obtain hot nitrogen-rich air and denitrified slag. The hot nitrogen-rich air is used for the preheating process of step S2. The reaction temperature of the oxidation denitrification is 500℃, the reaction time is 0.5h, the reactor used is a fluidized bed reactor, and the ceramic-based microwave absorbing material is SiC particles with a particle size of 0.5mm.

[0044] S4. Heat exchange and cooling process: The denitrification slag obtained in step S3 is cooled by heat exchange using room temperature air to obtain cooled slag and hot air. The hot air is used in the microwave oxidation denitrification process of step S3.

[0045] S5. Microwave vacuum distillation process: The cooled residue obtained in step S4 is vacuum distilled under microwave heating. The vacuum degree is 50 Pa, the distillation temperature is 600 ℃, and the distillation time is 1 h, so that the low melting point salts are volatilized and separated to obtain gaseous fluorides, gaseous chlorides and desalted residue.

[0046] S6. Screening process: The desalination residue obtained in step S5 is screened to obtain ceramic-based microwave absorbing material and fine material. The ceramic-based microwave absorbing material is returned to the microwave oxidation denitrification process in step S3.

[0047] S7. High-energy ball milling process: The carbon-based microwave absorbing material and the fine material obtained in step S6 are thoroughly mixed using a high-energy ball mill to obtain a mixture with a particle size of less than 1 μm; the carbon-based microwave absorbing material is one or a combination of graphite, carbon black, carbon fiber, and graphene.

[0048] S8. Microwave chlorination deoxygenation process: In a fluidized bed reactor, the mixture obtained in step S7 is subjected to chlorination deoxygenation under microwave heating using chlorine and carbon monoxide. The chlorination deoxygenation temperature is 500℃ and the time is 1h, resulting in tailings and mixed gas. The mixed gas contains gaseous aluminum chloride, gaseous silicon chloride, carbon dioxide, and unreacted carbon monoxide and chlorine.

[0049] S9. Washing and drying process: The tailings obtained in step S8 are first washed with water to remove soluble salts, and then dried and dehydrated to obtain washing liquid and carbon-based microwave absorbing material. The carbon-based microwave absorbing material is returned to the high-energy ball milling process in step S7.

[0050] S10, First-stage heat exchange and condensation process: The mixed gas obtained in step S8 is subjected to first-stage heat exchange and condensation using room temperature chlorine and carbon monoxide to obtain a mixed gas phase and solid aluminum chloride product containing gaseous silicon chloride, carbon dioxide, carbon monoxide and chlorine. The hot chlorine and hot carbon monoxide after heat exchange are used in the microwave chlorination and deoxygenation process in step S8. The temperature of the mixed gas phase after first-stage heat exchange and condensation is 70°C.

[0051] S11, Secondary heat exchange and condensation process: The mixed gas phase obtained in step S10 is subjected to secondary heat exchange and condensation to obtain a mixed gas phase containing gaseous carbon dioxide, carbon monoxide and chlorine and a liquid silicon chloride product. The temperature of the mixed gas phase after secondary heat exchange and condensation is 20°C.

[0052] S12, Primary separation process: The mixed gas phase obtained in step S11 is subjected to primary separation to convert chlorine gas into liquid phase, resulting in a mixed gas phase containing carbon dioxide and carbon monoxide as well as liquid chlorine. The primary separation temperature is -40℃.

[0053] S13, Gasification process: The liquid chlorine obtained in step S12 is vaporized to obtain chlorine gas, which is then returned to the microwave chlorination and deoxygenation process in step S8.

[0054] S14. The mixed gas phase of carbon dioxide and carbon monoxide obtained in step S12 is subjected to secondary separation to obtain gas phase carbon monoxide and solid phase carbon dioxide. The gas phase carbon monoxide is returned to the microwave chlorination deoxygenation process in step S8. The secondary separation temperature is -80℃.

[0055] Example 2

[0056] The method flow of this embodiment is basically the same as that of Embodiment 1, except that: in step S3, the oxidation temperature is 700℃, the oxidation time is 0.1h, and the particle size of SiC particles is 5mm; in step S5, the vacuum degree is 5Pa, the distillation temperature is 800℃, and the distillation time is 0.5h; in step S8, the chlorination deoxygenation temperature is 700℃, and the chlorination deoxygenation time is 0.5h; in step S10, the temperature of the mixed gas phase after the first-stage heat exchange condensation is 170℃; in step S11, the temperature of the mixed gas phase after the second-stage heat exchange condensation is 50℃; in step S12, the temperature of the first-stage separation is -70℃; and in step S14, the temperature of the second-stage separation is -190℃.

[0057] Example 3

[0058] The method flow of this embodiment is basically the same as that of Embodiment 1, except that: in step S3, the oxidation temperature is 600℃, the oxidation time is 0.3h, and the particle size of SiC particles is 3mm; in step S5, the vacuum degree is 30Pa, the distillation temperature is 700℃, and the distillation time is 0.7h; in step S8, the chlorination temperature is 600℃, and the chlorination time is 0.7h; in step S10, the temperature of the mixed gas phase after the first-stage heat exchange and condensation is 100℃; in step S11, the temperature of the mixed gas phase after the second-stage heat exchange and condensation is 40℃; in step S12, the first-stage separation temperature is -50℃; and in step S14, the second-stage separation temperature is -130℃.

[0059] Example 4

[0060] The method flow of this embodiment is basically the same as that of Embodiment 1, except that: in step S3, the oxidation temperature is 660℃, the oxidation time is 0.2h, and the particle size of SiC particles is 2mm; in step S5, the vacuum degree is 25Pa, the distillation temperature is 730℃, and the distillation time is 0.6h; in step S8, the chlorination deoxygenation temperature is 550℃, and the chlorination deoxygenation time is 0.8h; in step S10, the temperature of the mixed gas phase after the first-stage heat exchange condensation is 150℃; in step S11, the temperature of the mixed gas phase after the second-stage heat exchange condensation is 45℃; in step S12, the first-stage separation temperature is -60℃; and in step S14, the second-stage separation temperature is -150℃.

[0061] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A method for the efficient utilization of aluminum ash, characterized in that, Includes the following steps: S1. Grinding process: Grind aluminum ash into fine powder to obtain fine ash; S2, Preheating process: The fine ash obtained in step S1 is preheated with hot nitrogen-rich air to obtain hot fine ash and cold nitrogen-rich air. S3, Microwave oxidation denitrification process: The hot fine ash obtained in step S2 is mixed with ceramic-based microwave absorbing material, hot air is introduced, and the hot fine ash obtained in step S2 is oxidized and denitrified under microwave heating to obtain hot nitrogen-rich air and denitrification slag. The hot nitrogen-rich air is used for the preheating process of step S2. S4. Heat exchange and cooling process: The denitrification slag obtained in step S3 is cooled by heat exchange using room temperature air to obtain cooled slag and hot air. The hot air is used in the microwave oxidation denitrification process of step S3. S5. Microwave vacuum distillation process: The cooled residue obtained in step S4 is vacuum distilled under microwave heating to volatilize and separate the low-melting-point salts, and obtain gaseous fluorides, gaseous chlorides and desalination residue. S6. Screening process: The desalination residue obtained in step S5 is screened to obtain ceramic-based microwave absorbing material and fine material. The ceramic-based microwave absorbing material is returned to the microwave oxidation denitrification process in step S3. S7. High-energy ball milling process: The carbon-based microwave absorbing material and the fine material obtained in step S6 are thoroughly mixed by high-energy ball milling to obtain a mixture. S8. Microwave chlorination deoxygenation process: The mixture obtained in step S7 is subjected to chlorination deoxygenation under microwave heating using chlorine and carbon monoxide to obtain tailings and mixed gas, wherein the mixed gas contains gaseous aluminum chloride, gaseous silicon chloride, carbon dioxide, and unreacted carbon monoxide and chlorine. S9. Washing and drying process: The tailings obtained in step S8 are first washed with water to remove soluble salts, and then dried and dehydrated to obtain washing liquid and carbon-based microwave absorbing material. The carbon-based microwave absorbing material is returned to the high-energy ball milling process in step S7. S10, First-stage heat exchange and condensation process: The mixed gas obtained in step S8 is subjected to first-stage heat exchange and condensation using room temperature chlorine and carbon monoxide to obtain a mixed gas phase and solid phase aluminum chloride product containing gaseous silicon chloride, carbon dioxide, carbon monoxide and chlorine. The hot chlorine and hot carbon monoxide after heat exchange are used in the microwave chlorination and deoxygenation process of step S8. S11, Secondary heat exchange and condensation process: The mixed gas phase obtained in step S10 is subjected to secondary heat exchange and condensation to obtain a mixed gas phase and liquid phase silicon chloride product containing gaseous carbon dioxide, carbon monoxide and chlorine. S12, Primary separation process: The mixed gas phase obtained in step S11 is subjected to primary separation to convert chlorine gas into liquid phase, resulting in a mixed gas phase containing carbon dioxide and carbon monoxide, as well as liquid chlorine. S13, Gasification process: The liquid chlorine obtained in step S12 is vaporized to obtain chlorine gas, which is then returned to the microwave chlorination and deoxygenation process in step S8. S14, Secondary separation process: The mixed gas phase of carbon dioxide and carbon monoxide obtained in step S12 is subjected to secondary separation to obtain gaseous carbon monoxide and solid carbon dioxide. The gaseous carbon monoxide is returned to the microwave chlorination deoxygenation process in step S8.

2. The method according to claim 1, characterized in that, In step S1, the particle size of the fine ash is <1μm.

3. The method according to claim 1, characterized in that, In step S3, the reaction temperature for oxidative denitrification is 500-700℃, the reaction time is 0.1-0.5h, the reactor used is a fluidized bed reactor, and the ceramic-based microwave absorbing material is SiC particles with a particle size of 0.5-5mm.

4. The method according to claim 1, characterized in that, In step S5, the vacuum distillation is performed at a vacuum level of 5-50 Pa, a temperature of 600-800 °C, and a time of 0.5-1 h.

5. The method according to claim 1, characterized in that, In step S7, the carbon-based microwave absorbing material is one or a combination of graphite, carbon black, and carbon fiber; the particle size of the mixture is <1μm.

6. The method according to claim 1, characterized in that, In step S8, the chlorination deoxygenation temperature is 500-700℃, the time is 0.5-1h, and the reactor used is a fluidized bed reactor.

7. The method according to claim 1, characterized in that, In step S10, the temperature of the mixed gas phase after primary heat exchange and condensation is 70°C to 170°C.

8. The method according to claim 1, characterized in that, In step S11, the temperature of the mixed gas phase after the secondary heat exchange condensation is 20°C to 50°C.

9. The method according to claim 1, characterized in that, In step S12, the temperature of the primary separation is -70°C to -40°C.

10. The method according to claim 1, characterized in that, In step S14, the temperature of the secondary separation is -190°C to -80°C.

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