Method for efficiently preparing superfine aluminum oxide from waste aluminum material

Abstract

The invention discloses a method for efficiently preparing superfine aluminum oxide from a waste aluminum material. The method comprises the steps of high-temperature chlorination, cooling oxidation, multi-stage condensation, vaporization, gasification, crystallization and the like. According to the method, heat released by reaction of gas-phase AlCl and oxygen is removed in time through heat exchange in the oxidation reaction process, a large amount of sintering of the product can be effectively avoided, and the obtained aluminum oxide product is fine in granularity and narrow in distribution. According to the method, the waste aluminum material is used as an aluminum source, AlCl3 is used as a chlorinating agent, oxygen is used as an oxygen source, the superfine aluminum oxide powder is prepared through high-temperature chlorination-cooling oxidation, and compared with an aluminum / aluminum chloride direct oxidation method, the process is easier to adjust and control, the operability is higher, and the product quality is better. In addition, AlCl3 is consumed as a chlorinating agent in a chlorination reaction link, is equivalently regenerated as a byproduct in an oxidation reaction link, and can be recycled in a system, so that the production cost is effectively reduced. Chlorination reaction gas is preheated by using heat released by oxidation reaction, so that the heat efficiency of the whole process system is effectively improved.

Description

Technical Field

[0001] The invention relates to the fields of chemical industry and metallurgy, and in particular to a method for efficiently preparing ultrafine alumina from waste aluminum. Background Art

[0002] High-purity ultrafine alumina powder has the characteristics of high wear resistance, high temperature corrosion resistance, high resistivity and high thermal conductivity, and is widely used in mechanical industry, refractory materials, electronics industry, petrochemical industry, aerospace and other fields.

[0003] At present, the preparation methods of ultrafine alumina powder mainly include liquid phase method, solid phase method and gas phase method. The liquid phase method is to select one or more soluble aluminum salts and precipitants, generate precipitation, and then dehydrate and decompose to prepare alumina powder, including hydrothermal synthesis method, sol-gel method, microemulsion method, organic alcohol salt hydrolysis method and chemical coprecipitation method. Among them, the chemical coprecipitation method has become the main method for industrial production of ultrafine alumina powder by liquid phase method due to its simple equipment, high yield, and large-scale production. However, the chemical coprecipitation method is more complicated to operate and has many steps, and the obtained product particle size is larger and unevenly distributed. The solid phase method includes mechanical ball milling method, solid phase reaction method, ammonium aluminum sulfate thermal decomposition method and amorphous crystallization method. The solid phase method is simple and easy to operate, has a large output and a short production cycle, but the product purity is low, and there are also problems such as wide product particle size distribution and uneven distribution, which makes it difficult to apply in high-end fields. The gas phase method refers to the aluminum source being heated by electric arc, laser, plasma, etc. to become gas, and then reacting in an oxidizing atmosphere to generate aluminum oxide powder, including laser-induced vapor deposition, plasma vapor synthesis, and chemical vapor deposition. Compared with the liquid phase method and the solid phase method, the advantages of the gas phase method are simple operation, easy control of reaction conditions, and high product purity. The most commonly used gas phase method is the chemical vapor deposition method, that is, the gas phase aluminum chloride reacts with water vapor to generate ultrafine aluminum oxide and hydrogen chloride, but there are problems such as easy product agglomeration, easy equipment corrosion, and difficulty in product collection, which makes it difficult to apply on a large scale.

[0004] Therefore, in response to the current problems in the preparation of ultrafine alumina powder, the key to achieving efficient and low-cost large-scale production of ultrafine alumina powder is to optimize the reaction path, strengthen the reaction process, improve reaction efficiency and product purity, and effectively control product particle size and distribution through process and technological innovation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method for efficiently preparing ultrafine alumina from waste aluminum.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for efficiently preparing ultrafine alumina from waste aluminum materials comprises the following steps:

[0008] S1. High temperature chlorination: using a mixture of gaseous AlCl3 and argon to chlorinate the waste aluminum at high temperature to obtain a mixture of gaseous AlCl3 and argon. The temperature of the high temperature chlorination is 1050-1250°C.

[0009] S2, cooling oxidation: the mixed gas of gaseous AlCl3 and argon obtained in step S1 is input into the oxidation reaction system, and oxygen is input into the oxidation reaction system to oxidize the gaseous AlCl3 therein by using oxygen; after the oxidation reaction is completed, a mixed gas of oxygen, argon and gaseous AlCl3 and amorphous aluminum oxide are finally obtained, and the mixed gas of oxygen, argon and gaseous AlCl3 is sent to the multi-stage condensation process of step S3, and the amorphous aluminum oxide is sent to the crystallization process of step S6;

[0010] At the same time, another mixed gas of argon and gaseous AlCl3 is used to exchange heat with the oxidation reaction system to absorb the heat generated in the oxidation reaction to obtain a mixed gas of high-temperature gaseous AlCl3 and argon. The mixed gas of high-temperature gaseous AlCl3 and argon is fed into the high-temperature chlorination process of step S1 for high-temperature chlorination of the waste aluminum material;

[0011] S3, multi-stage condensation: the mixed gas of oxygen, argon and gaseous AlCl3 obtained in step S2 is subjected to primary condensation at -182°C to 170°C to obtain solid AlCl3, and the remaining mixed gas of oxygen and argon is subjected to secondary condensation at -185°C to -184°C to separate liquid oxygen and argon; the liquid oxygen is fed to the vaporization process of step S4, and the argon and solid AlCl3 are fed to the vaporization process of step S5;

[0012] S4, vaporization: vaporize the liquid oxygen obtained in step S3 at room temperature, and the obtained oxygen is sent to the cooling oxidation process in step S2;

[0013] S5, gasification: using room temperature argon and the argon separated in step S3 as carrier gas, the solid phase AlCl3 obtained in step S3 is gasified to obtain a mixed gas of argon and gaseous phase AlCl3, and the mixed gas of argon and gaseous phase AlCl3 is sent to the cooling oxidation process of step S2 for heat exchange with the oxidation reaction system;

[0014] S6, crystallization: crystallize the amorphous aluminum oxide obtained in step S2 to obtain an aluminum oxide product.

[0015] Furthermore, in step S1, the scrap aluminum material is one or a combination of scrap aluminum and scrap aluminum alloy, the main element contained in the scrap aluminum and scrap aluminum alloy is aluminum, and the other elements contained are one or a combination of manganese, zinc, silicon and copper.

[0016] Furthermore, in step S2, the temperature of the oxidation reaction is 670-800°C; the oxidation reaction system adopts a fluidized bed reactor, and the fluidized bed reactor is provided with a bed material, and the bed material is alumina with a particle size of 0.5-2mm; the fluidized bed reactor is provided with an indirect heat exchange device for heat exchange with a mixed gas of argon and gaseous AlCl3.

[0017] Furthermore, in step S5, the gasification temperature is ≥ 190°C.

[0018] Furthermore, in step S1, indirect heating by burning external fuel is used to provide sufficient temperature and heat to the high-temperature gaseous AlCl3 and argon mixed gas. During the high-temperature chlorination process, the temperature of the high-temperature chlorination is controlled and maintained by controlling the addition amount of scrap aluminum and the introduction amount of the high-temperature gaseous AlCl3 and argon mixed gas.

[0019] Furthermore, in step S2, the temperature conditions required for the oxidation reaction are provided by the heat brought by the mixed gas of gaseous AlCl and argon. During the oxidation reaction, the oxidation temperature is controlled and maintained by controlling the feeding amount of the bed material alumina, the introduction amount of the mixed gas of gaseous AlCl and argon, and the heat exchange amount.

[0020] Furthermore, in step S6, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention can effectively avoid the large-scale sintering of the product by timely removing the heat released by the reaction of gas phase AlCl and oxygen by heat exchange during the oxidation reaction, and the obtained alumina powder has a fine particle size and a narrow distribution;

[0023] 2. The present invention uses waste aluminum as an aluminum source, AlCl3 as a chlorinating agent, and oxygen as an oxygen source to prepare ultrafine alumina powder through high-temperature chlorination-cooling oxidation. Compared with the aluminum-oxygen direct oxidation method and the gas-phase aluminum chloride-water vapor chemical vapor precipitation method, the process is easier to adjust and control, has stronger operability, better product quality, and no harmful by-products are generated;

[0024] 3. The present invention uses a fluidized bed with an alumina bed material to carry out the oxidation reaction of gas-phase AlCl and oxygen. The gas-solid fluidized bed has a fast mass transfer and heat transfer rate, which can effectively remove the heat generated by the reaction. At the same time, the alumina bed material can provide nucleation sites and matrix for the oxidation reaction, promote the occurrence of the oxidation reaction, and the obtained product is easy to collect and has high purity;

[0025] 4. In the present invention, AlCl3 is consumed as a chlorinating agent in the chlorination reaction link, and is regenerated in equal amounts as a by-product in the oxidation reaction link, and can be recycled in the system, effectively reducing production costs;

[0026] 5. The present invention utilizes the heat released by the oxidation reaction to preheat the chlorination reaction gas, effectively improving the thermal efficiency of the overall process system;

[0027] 6. The present invention can efficiently convert aluminum resources in waste aluminum materials into high-value-added aluminum oxide, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a method flow chart of each embodiment of the present invention;

[0029] Figure 2 This is an electron microscope scanning image of the aluminum oxide solid product obtained by the method of Example 1 of the present invention;

[0030] Figure 3 This is an electron microscope scanning image of the aluminum oxide solid product obtained by the method of Example 2 of the present invention;

[0031] Figure 4 This is an electron microscope scanning image of the aluminum oxide solid product obtained by the method of Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0033] Example 1

[0034] This embodiment provides a method for efficiently preparing ultrafine alumina from waste aluminum materials, such as Figure 1 As shown, the following steps are included:

[0035] S1. High-temperature chlorination: high-temperature chlorination of waste aluminum material by using a mixed gas of high-temperature gaseous AlCl3 and argon. The waste aluminum material is waste aluminum. The main element contained in the waste aluminum is aluminum, and it also contains other elements such as manganese, zinc, silicon, and copper. The mixed gas of gaseous AlCl3 and argon is obtained. The temperature of high-temperature chlorination is 1050° C. When the heat of the mixed gas of high-temperature gaseous AlCl3 and argon is insufficient, sufficient temperature and heat are provided for the mixed gas of gaseous AlCl3 and argon by indirect heating through combustion of external fuel. In the process of high-temperature chlorination, the chlorination temperature is controlled and maintained by controlling the feeding amount of the waste aluminum material and the introduction amount of the mixed gas of high-temperature gaseous AlCl3 and argon.

[0036] S2, cooling oxidation: The mixed gas of gaseous AlCl3 and argon obtained in step S1 is input into the oxidation reaction system, and oxygen is input into the oxidation reaction system, and the gaseous AlCl3 therein is oxidized by oxygen, and the oxidation temperature is 670°C. After the oxidation reaction is completed, a mixed gas of oxygen, argon and gaseous AlCl3 and amorphous aluminum oxide are finally obtained. The mixed gas of oxygen, argon and gaseous AlCl3 is sent to the multi-stage condensation process of step S3, and the amorphous aluminum oxide is sent to the crystallization process of step S6.

[0037] In this embodiment, the oxidation reaction system is a fluidized bed reactor, and a bed material is provided in the fluidized bed reactor, and the bed material is aluminum oxide with a particle size of 0.5 mm, and an indirect heat exchange device is provided in the fluidized bed reactor. During the oxidation reaction, another mixed gas of argon and gaseous AlCl3 is introduced into the indirect heat exchange device, and heat is exchanged with the oxidation reaction system to absorb the heat generated in the oxidation reaction to obtain a high-temperature mixed gas of gaseous AlCl3 and argon. The high-temperature mixed gas of gaseous AlCl3 and argon is sent to the high-temperature chlorination process of step S1 for high-temperature chlorination of the waste aluminum material, so that the heat generated by the oxidation reaction can be fully utilized.

[0038] The temperature conditions required for the oxidation reaction are provided by the heat brought by the mixed gas of gaseous AlCl and argon. During the oxidation reaction, the oxidation temperature is controlled and maintained by controlling the feeding amount of the bed material alumina, the introduction amount of the mixed gas of gaseous AlCl and argon, and the heat exchange amount in the indirect heat exchange device.

[0039] S3, multi-stage condensation: the mixed gas of oxygen, argon and gaseous AlCl3 obtained in step S2 is subjected to primary condensation at -182°C to obtain solid AlCl3, and the remaining mixed gas of oxygen and argon is subjected to secondary condensation at -185°C to separate liquid oxygen and argon; the liquid oxygen is fed to the vaporization process of step S4, and the argon and solid AlCl3 are fed to the vaporization process of step S5;

[0040] S4, vaporization: vaporize the liquid oxygen obtained in step S3 at room temperature, and the obtained oxygen is sent to the cooling oxidation process in step S2;

[0041] S5, gasification: using room temperature argon and the argon separated in step S3 as carrier gas, the solid phase AlCl3 obtained in step S3 is gasified at 190°C to obtain a mixed gas of argon and gaseous phase AlCl3, which is fed into the cooling oxidation process of step S2 for heat exchange with the oxidation reaction system;

[0042] S6, crystallization: the amorphous aluminum oxide obtained in step S2 is crystallized at 1300°C for 5 hours to obtain an aluminum oxide product. The shape of the aluminum oxide product is as follows: Figure 2 As shown. Figure 2 It can be seen that the alumina solid product obtained in this embodiment has a narrow particle size distribution, and the average particle size is about 0.4 μm.

[0043] Example 2

[0044] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the waste aluminum material is waste aluminum alloy, the main element contained in the waste aluminum alloy is aluminum, and other elements such as manganese, zinc, silicon, and copper are contained, and the temperature of the chlorination reaction is 1250°C; in step S2, the temperature of the oxidation reaction is 750°C, the particle size of the alumina bed material is 2 mm, and the morphology of the obtained alumina solid product is as follows: Figure 3 As shown; in step S3, the primary condensation temperature is 170°C to obtain circulating solid phase AlCl3, and the secondary condensation temperature is -184°C; in step S5, the vaporization temperature is 260°C; in step S6, the crystallization temperature is 1400°C and the crystallization time is 3h. Figure 3 It can be seen that the alumina solid product obtained in this embodiment has a narrow particle size distribution and an average particle size of about 0.7 μm.

[0045] Example 3

[0046] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the waste aluminum material includes waste aluminum alloy and waste aluminum, the main element contained is aluminum, and contains other elements such as manganese, zinc, silicon, copper, etc., and the temperature of the chlorination reaction is 1100°C; in step S2, the temperature of the oxidation reaction is 800°C, the particle size of the alumina bed material is 1mm, and the morphology of the obtained alumina solid product is as follows: Figure 4 As shown; in step S3, the primary condensation temperature is 0°C, and the secondary condensation temperature is -184.5°C; in step S5, the vaporization temperature is 200°C; in step S6, the crystallization temperature is 1500°C, and the crystallization time is 0.5h. Figure 4 It can be seen that the alumina solid product obtained in this embodiment has a narrow particle size distribution, and the average particle size is about 1.1 μm.

[0047] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for efficiently preparing ultrafine alumina from waste aluminum, characterized in that: The following steps are involved: S1. High temperature chlorination: using a mixture of gaseous AlCl3 and argon to chlorinate the waste aluminum at high temperature to obtain a mixture of gaseous AlCl3 and argon. The temperature of the high temperature chlorination is 1050-1250°C. S2, cooling oxidation: the mixed gas of gaseous AlCl3 and argon obtained in step S1 is input into the oxidation reaction system, and oxygen is input into the oxidation reaction system to oxidize the gaseous AlCl3 therein by using oxygen; after the oxidation reaction is completed, a mixed gas of oxygen, argon and gaseous AlCl3 and amorphous aluminum oxide are finally obtained, and the mixed gas of oxygen, argon and gaseous AlCl3 is sent to the multi-stage condensation process of step S3, and the amorphous aluminum oxide is sent to the crystallization process of step S6; At the same time, another mixed gas of argon and gaseous AlCl3 is used to exchange heat with the oxidation reaction system to absorb the heat generated in the oxidation reaction to obtain a mixed gas of high-temperature gaseous AlCl3 and argon. The mixed gas of high-temperature gaseous AlCl3 and argon is fed into the high-temperature chlorination process of step S1 for high-temperature chlorination of the waste aluminum material; S3, multi-stage condensation: the mixed gas of oxygen, argon and gaseous AlCl3 obtained in step S2 is subjected to primary condensation at -182°C to 170°C to obtain solid AlCl3, and the remaining mixed gas of oxygen and argon is subjected to secondary condensation at -185°C to -184°C to separate liquid oxygen and argon; the liquid oxygen is fed to the vaporization process of step S4, and the argon and solid AlCl3 are fed to the vaporization process of step S5; S4, vaporization: vaporize the liquid oxygen obtained in step S3 at room temperature, and the obtained oxygen is sent to the cooling oxidation process in step S2; S5, gasification: using room temperature argon and the argon separated in step S3 as carrier gas, the solid phase AlCl3 obtained in step S3 is gasified to obtain a mixed gas of argon and gaseous phase AlCl3, and the mixed gas of argon and gaseous phase AlCl3 is sent to the cooling oxidation process of step S2 for heat exchange with the oxidation reaction system; S6, crystallization: crystallize the amorphous aluminum oxide obtained in step S2 to obtain an aluminum oxide product.

2. The method according to claim 1, characterized in that In step S1, the scrap aluminum material is one or a combination of scrap aluminum and scrap aluminum alloy. The main element contained in the scrap aluminum and scrap aluminum alloy is aluminum, and the other elements contained are one or a combination of manganese, zinc, silicon and copper.

3. The method according to claim 1, characterized in that In step S2, the temperature of the oxidation reaction is 670-800°C; the oxidation reaction system adopts a fluidized bed reactor, and the fluidized bed reactor is provided with a bed material, which is alumina with a particle size of 0.5-2mm; the fluidized bed reactor is provided with an indirect heat exchange device for heat exchange with a mixed gas of argon and gaseous AlCl3.

4. The method according to claim 1, characterized in that: In step S5, the gasification temperature is ≥190°C.

5. The method according to claim 1, characterized in that In step S1, indirect heating by burning external fuel is used to provide sufficient temperature and heat to the high-temperature gaseous AlCl3 and argon mixed gas. During the high-temperature chlorination process, the temperature of the high-temperature chlorination is controlled and maintained by controlling the addition amount of scrap aluminum and the introduction amount of the high-temperature gaseous AlCl3 and argon mixed gas.

6. The method according to claim 1 or 3, characterized in that: In step S2, the temperature conditions required for the oxidation reaction are provided by the heat brought by the mixed gas of gaseous AlCl and argon. During the oxidation reaction, the oxidation temperature is controlled and maintained by controlling the feeding amount of the bed material alumina, the introduction amount of the mixed gas of gaseous AlCl and argon, and the heat exchange amount.

7. The method according to claim 1, characterized in that In step S6, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

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