Application of Secondary Aluminum Ash Safe Calcination System, Method and Calcined Product

Abstract

The present invention discloses a safe calcination system and method for secondary aluminum ash and the application of the calcined product, relating to the technical field of harmless treatment and resource utilization of aluminum ash, and solving the problems of kiln blocking and temperature out-of-control after the spontaneous combustion of aluminum ash during the calcination of secondary aluminum ash in the prior art. The safe calcination system of the present invention includes a first-stage rotary kiln provided with an aluminum ash and slag inlet, and a second-stage incinerator connected to the first-stage rotary kiln for heating and burning the aluminum ash. The second-stage incinerator is provided with a self-preheating recovery system. The method of the present invention includes: feeding the secondary aluminum ash into the first-stage rotary kiln for heating; then sending it to the second-stage incinerator, heating it first under an oxygen-deficient state at the front end, and then burning it at a high temperature under an oxygen-rich state at the rear end; the burned material is sent to the external heating jacket of the first-stage rotary kiln to provide heat for heating the material in the first-stage rotary kiln. The present invention creatively realizes the safe calcination of secondary aluminum ash with little or no addition of anti-caking agent. The obtained product has a high content of α-Al2O3, low energy consumption, and is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of harmless treatment and resource utilization of aluminum ash, and specifically relates to a safe calcination system and method for secondary aluminum ash and the application of calcined products. Background Art

[0002] Aluminum ash is divided into primary aluminum ash and secondary aluminum ash. Primary aluminum ash is a kind of dross that is insoluble in molten aluminum during the production of primary aluminum by electrolyzing alumina. After aluminum recovery from primary aluminum ash, it becomes secondary aluminum ash. The main components of secondary aluminum ash are alumina, aluminum nitride, aluminum carbide, a small amount of metallic aluminum, and a certain amount of salts and silicon dioxide.

[0003] Secondary aluminum ash is an important solid waste in the aluminum smelting industry and is produced in large quantities. Since the nitrogen oxides contained in aluminum ash are very unstable and prone to chemical reactions, forming flammable and harmful irritating gases such as ammonia and methane, causing air and groundwater pollution, aluminum ash is defined as hazardous waste in the national hazardous waste catalog.

[0004] In the prior art, the treatment methods for secondary aluminum ash mainly include wet treatment and dry calcination. The traditional wet treatment method has the disadvantages of low treatment efficiency, large environmental pollution, and high cost, resulting in potential safety hazards during the long-term storage of aluminum ash. Dry calcination is considered an effective method for treating secondary aluminum ash. However, during the production process, when using a traditional rotary kiln for calcination, the combustion of secondary aluminum ash is uncontrollable and prone to caking, and finally there are safety problems such as furnace explosion, furnace blockage, and even burning of the pulse bag filter. To solve the problems of furnace blockage and explosion, the prior art adds a large amount of substances such as calcium carbide and bauxite. Although this method can solve the problem of caking in the secondary aluminum ash calcination furnace, it leads to a significant decrease in the ability to effectively treat secondary aluminum ash, and the value-added of the calcined product is greatly reduced due to the low content of Al 2 O 3 content.

[0005] Therefore, providing a treatment method for secondary aluminum ash that is efficient, safe, and has a high Al 2 O 3 content has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a safe calcination system for secondary aluminum ash, which can solve the problems of kiln blockage and temperature out-of-control in the pyrometallurgical treatment process of secondary aluminum ash without adding or adding a small amount of auxiliary agents.

[0007] Another purpose of the present invention is to provide a method for safely calcining secondary aluminum ash using the above system.

[0008] The third purpose of the present invention is to provide α-Al obtained by the method for safely calcining secondary aluminum ash as described above2 O 3 Application of the product.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A secondary aluminum ash safe calcination system provided by the present invention includes a first-stage rotary kiln provided with an aluminum ash slag inlet, and a second-stage incineration kiln connected from the first-stage rotary kiln for heating and burning the aluminum ash. The second-stage incineration kiln is provided with a self-preheating recovery system.

[0011] In some embodiments of the present invention, the first-stage rotary kiln is a double-layer indirect heating rotary kiln. The material outlet of the second-stage incineration kiln is connected to the outer heating jacket of the double-layer indirect heating of the first-stage rotary kiln through a sealed pipeline, and the aluminum ash combustion material at the material outlet of the second-stage incineration kiln enters the outer heating jacket of the double-layer indirect heating of the first-stage rotary kiln through the sealed pipeline.

[0012] In some embodiments of the present invention, the aluminum ash slag inlet is provided with a screw feeder or a bucket elevator for conveying the aluminum ash slag material into the first-stage rotary kiln.

[0013] In some embodiments of the present invention, a material transfer bucket elevator is provided between the second-stage incineration kiln and the first-stage rotary kiln for transferring the processed aluminum ash slag in the bucket elevator into the second-stage incineration kiln.

[0014] In some embodiments of the present invention, the self-preheating recovery system includes an integrated furnace tail box provided at the tail of the second-stage incineration kiln, and a furnace front pipeline connected from the integrated furnace tail box. The furnace front pipeline is connected to the front end of the second-stage incineration kiln to convey the hot air after the spontaneous combustion of the aluminum ash at the rear end of the second-stage incineration kiln to the front end of the second-stage incineration kiln.

[0015] In some embodiments of the present invention, it further includes a tail gas treatment device connected through pipelines from the first-stage rotary kiln and the second-stage incineration kiln. A cyclone dust collector, a bag filter, and a denitration and desulfurization machine are sequentially distributed in the tail gas treatment device along the tail gas flow direction. The tail gas treatment device is provided with a preheated exhaust port.

[0016] In some embodiments of the present invention, a furnace head platform is provided at the heads of the first-stage rotary kiln and the second-stage incineration kiln. The furnace head platform is provided with an integrated furnace head box. The tail gas treatment device is installed on the furnace head platform. A furnace tail platform is provided at the tails of the first-stage rotary kiln and the second-stage incineration kiln.

[0017] A method for safely calcining secondary aluminum ash using the above secondary aluminum ash safe calcination treatment system provided by the present invention includes the following steps:

[0018] Step 1. Feed the secondary aluminum ash without adding or adding a very small amount of anti-caking agent into the first-stage rotary kiln for heating. Preferably, the furnace temperature is 400 - 600 °C, and the material residence time is 40 - 180 min;

[0019] Step 2. Feed the heated material in a rotary kiln to the secondary incinerator. The furnace temperature of the secondary incinerator is controlled in sections. The material is first heated under an oxygen-deficient state at the front end and then subjected to high-temperature incineration under an oxygen-rich state at the rear end. Preferably, the temperature at the front end is 700-1000 °C, and the residence time of the material is 30-90 min. Preferably, the temperature at the rear end is 1200 °C-1600 °C, and the residence time of the material is 30-120 min. Preferably, pure oxygen is introduced during the high-temperature incineration at the rear end to ensure full combustion of the aluminum ash.

[0020] Step 3. Feed the material after high-temperature incineration into the external heating jacket of the primary rotary kiln to provide heat for heating the material in the primary rotary kiln. Through heat exchange, the temperature of the material drops. After being discharged from the safe calcination treatment system and cooled, a harmless high-content α-Al 2 O 3 product is obtained.

[0021] In some embodiments of the present invention, the mass fraction of aluminum in the secondary aluminum ash is less than 20 wt%.

[0022] Preferably, the particle size of the secondary aluminum ash is 120-180 mesh.

[0023] Preferably, the dosage of the anti-caking agent is 0-5 wt% of the mass of the secondary aluminum ash.

[0024] The technical idea of the present invention is that the secondary aluminum ash is either not added with or added with a very small amount of anti-caking agent. First, the secondary aluminum ash is heated under an oxygen-deficient state and at a temperature lower than the melting point of aluminum to remove impurities such as moisture in the secondary aluminum ash. Then it enters the secondary incinerator. At the front end of the secondary incinerator, the temperature of the material is raised above the melting point of aluminum under an oxygen-deficient state, and then it enters the rear end of the secondary incinerator and is rapidly incinerated under an oxygen-rich state. The secondary aluminum ash is first heated at a temperature lower than the melting point of aluminum. While removing some impurities, it will not cause the secondary aluminum ash to liquefy, resulting in caking or explosion. Secondly, the aluminum ash is first heated in the oxygen-deficient section at the front end of the secondary kiln to raise the temperature, and there will be no overflow of molten aluminum and combustion of aluminum, which is beneficial to temperature control. Finally, the aluminum is rapidly oxidized and incinerated in the oxygen-rich section, and there will be no caking or explosion. The present invention does not add or adds a very small amount of anti-caking agent, and the obtained product α-Al 2 O 3 is of high quality and can be used as a production material for tiles or refractory bricks.

[0025] The application of the α-Al 2 O 3 product obtained by the method for safely calcining secondary aluminum ash provided by the present invention as a production material for tiles or refractory bricks.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The design of the present invention is scientific and the concept is ingenious. The present invention creatively realizes the safe calcination of secondary aluminum ash with little or no addition of anti-caking agent, and the obtained product has a high content of α-Al 2 O 3 , low energy consumption and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of the safe calcination system for secondary aluminum ash of the present invention;

[0029] Figure 2 is Figure 1 the sectional view taken along line A-A in

[0030] Figure 3 is a schematic diagram of the furnace head platform of the present invention;

[0031] Attached Figure 4 is a thermogravimetric curve of secondary aluminum ash;

[0032] Attached Figure 5 is a DSC curve of secondary aluminum ash;

[0033] Figure 6 is a graph of the removal rate of harmful elements in secondary aluminum ash at different temperatures in air;

[0034] Attached Figure 7 is a graph of secondary aluminum ash calcined at different parts in the calcination system of the present invention.

[0035] Among them, the names corresponding to the reference numerals are:

[0036] 1. Aluminum ash and slag inlet; 2. First-stage rotary kiln; 3. Second-stage incineration kiln; 4. Integrated furnace tail box; 5. Front furnace pipeline; 6. Tail gas treatment device; 7. Preheating smoke exhaust port; 8. Furnace tail platform; 9. Furnace head platform; 10. Integrated furnace head box; 11. Foundation platform. SPECIFIC EMBODIMENTS

[0037] The present invention will be further described below in conjunction with the drawings and embodiments. The implementation manners of the present invention include but are not limited to the following embodiments.

[0038] Embodiment 1

[0039] As attached Figure 1-3As shown in the figure, this embodiment discloses a safe calcination system for secondary aluminum ash of the present invention, which includes a first-stage rotary kiln 2 provided with an aluminum ash slag inlet 1, a second-stage incineration kiln 3 connected to the first-stage rotary kiln 2 for heating and burning the aluminum ash, an exhaust gas treatment device 6 connected to the first-stage rotary kiln 2 and the second-stage incineration kiln 3 through pipelines, a furnace head platform 9 provided at the heads of the first-stage rotary kiln 2 and the second-stage incineration kiln 3, and a furnace tail platform 8 provided at the tails of the first-stage rotary kiln 2 and the second-stage incineration kiln 3; the second-stage incineration kiln 3 is provided with a self-preheating recovery system, an integrated furnace head box 10 is provided on the furnace head platform 9, and the exhaust gas treatment device 6 is installed on the furnace head platform 9.

[0040] The first-stage rotary kiln 2 is a double-layer indirectly heated rotary kiln, and there are lifters inside the kiln body; the material outlet of the second-stage incineration kiln 3 is connected to the outer heating jacket of the double-layer indirect heating of the first-stage rotary kiln 2 through a sealed pipeline, and the aluminum ash combustion material at the material outlet of the second-stage incineration kiln 3 enters the outer heating jacket of the double-layer indirect heating of the first-stage rotary kiln 2 through a sealed pipeline. The second-stage incineration kiln is fixedly supported on the ground by several foundation platforms 11.

[0041] The aluminum ash slag inlet 1 is provided with a screw feeder or a bucket elevator for conveying aluminum ash slag materials into the first-stage rotary kiln 2. A material transfer bucket elevator is provided between the second-stage incineration kiln 3 and the first-stage rotary kiln 2 for transferring the treated aluminum ash slag in the bucket elevator into the second-stage incineration kiln 3.

[0042] The self-preheating recovery system includes an integrated furnace tail box 4 provided at the tail of the second-stage incineration kiln 3, and a furnace front pipeline 5 connected to the integrated furnace tail box 4. The furnace front pipeline 5 is connected to the front end of the second-stage incineration kiln 3 to convey the hot air after the spontaneous combustion of aluminum ash at the rear end of the second-stage incineration kiln 3 to the front end of the second-stage incineration kiln 3.

[0043] In the exhaust gas treatment device 6, a cyclone dust collector, a bag filter, and a denitration and desulfurization machine are sequentially distributed along the tail gas flow direction. The exhaust gas treatment device 6 is provided with a preheating smoke outlet 7.

[0044] Embodiment 2

[0045] This embodiment discloses a method for safely calcining secondary aluminum ash using the system of Embodiment 1. The secondary aluminum ash used in this embodiment is Weiqiao aluminum ash.

[0046] The secondary aluminum ash with a particle size of 120 - 180 mesh is mixed with an anti-caking agent and then sent to the safe calcination treatment system for secondary aluminum ash for calcination. The dosage of the anti-caking agent is 5wt% of the mass of the secondary aluminum ash.

[0047] The specific steps are as follows:

[0048] The secondary aluminum ash and the anti-caking mixed material are fed into a first-stage rotary kiln for heating, the temperature of the furnace is controlled at 400 - 450 °C, and the residence time of the mixed material is 180 min; the heated mixed material is turned back in the first-stage rotary kiln and then sent to the second-stage incineration kiln through a bucket elevator. The gas generated in the first-stage rotary kiln enters the tail gas treatment device for dust removal, denitrification and desulfurization.

[0049] The furnace temperature of the second-stage incineration kiln is controlled in sections. The mixed material is first heated at 700 - 750 °C under anoxic conditions at the front end, and the residence time of the material is 90 min; then it is incinerated at high temperature at the back end; pure oxygen is introduced during the high-temperature incineration at the back end to ensure complete combustion of the aluminum ash; the temperature at the back end is controlled at 1550 - 1600 °C, and the residence time of the mixed material is 30 min. The heat energy for the high-temperature incineration at the back end comes from the spontaneous combustion of the aluminum ash, and the heat for the front-end heating comes from the hot air of the high-temperature incineration at the back end.

[0050] The mixed material after high-temperature incineration is sent to the external heating jacket of the first-stage rotary kiln to provide heat for heating the mixed material in the first-stage rotary kiln; through heat exchange, the temperature of the mixed material drops. After being discharged from the safe calcination treatment system and cooled, harmless high-content α-Al 2 O 3 products are obtained.

[0051] In this embodiment, the chemical composition content before and after the calcination of the secondary aluminum ash is shown in the following table:

[0052] Table 1

[0053] Chemical composition Content before treatment (mass%) Content after treatment (mass%) Removal rate F 0.8731 —— 100％ <![CDATA[Sodium 2 O]]> 2.0142 2.85 MgO 8.8284 7.89 10.60％ <![CDATA[Al 2 O 3 > 71.1325 82.04 <![CDATA[SiO 2 > 7.0539 0.53 92.50％ <![CDATA[K 2 O]]> 0.2171 0.12 45％ CaO 3.0505 3.07 0 <![CDATA[Fe 2 O 3 > 1.3236 0.77 42％

[0054] It can be seen from the above table that after the secondary aluminum ash is calcined, the harmful substance F is completely removed, and the content of alumina is significantly increased.

[0055] The appearance diagrams of the secondary aluminum ash after calcination at different parts in different calcination systems are as shown in the appendix Figure 7 shown. During the calcination of this embodiment, there are no phenomena such as kiln blocking and temperature runaway, and the safety performance is high.

[0056] Example 3

[0057] Compared with Example 2, this embodiment has different temperatures and times for heating, temperature raising and incineration, and the other conditions are the same. Specifically:

[0058] In step 1, when heating, the furnace temperature is controlled at 550 - 600 °C, and the residence time of the mixed material is 40 min;

[0059] In step 2, the material is first heated at 950 - 1000 °C at the front end, and the residence time of the material is 30 min; then it is incinerated at high temperature at the back end; the temperature at the back end is 1200 - 1250 °C, and the residence time of the material is 120 min.

[0060] It was found that in the product obtained in this example, harmful substance F was completely removed, and the content of alumina was significantly increased; moreover, during the calcination in this example, there were no phenomena of kiln blocking and temperature runaway, and the safety performance was high.

[0061] Example 4

[0062] Compared with Example 2, no anti-caking agent was added in this example, and the other conditions were the same. It was found that in the product obtained in this example, harmful substance F was completely removed, and the content of alumina was significantly increased; moreover, during the calcination in this example, there were no phenomena of kiln blocking and temperature runaway, and the safety performance was high.

[0063] Test Example 1

[0064] This test example discloses the investigation of the calcination temperature of secondary aluminum ash. In this test example, the aluminum ash of a certain enterprise was used for calcination.

[0065] The composition analysis of secondary aluminum ash before and after calcination was carried out. The secondary aluminum ash before calcination contained 43.96 wt.% of aluminum element, and the main phases were alumina, followed by aluminum nitride, magnesium aluminate spinel, metallic aluminum and β-alumina; the impurity phases containing fluorine were mainly calcium fluoride, magnesium fluoride, potassium fluoride and sodium fluoride; the phases containing chlorine were mainly potassium chloride and sodium chloride, and the others were quartz, etc. The particle size of the aluminum ash was distributed between 0.25 μm and 632.456 μm, the angle of repose was 43°, and the fluidity was lower than that of industrial alumina.

[0066] Table 2 Chemical composition analysis results of secondary aluminum ash

[0067] Elemental composition Al Mg Si K Na Ca Content / wt.% 42.86 5.34 1.65 2.36 1.94 1.63 Elemental composition Cl F Fe Ti Mn AlN* Content / wt.% 1.47 2.86 1.08 0.11 0.38 20.13％

[0068] Table 3 Main phase composition and relative content of secondary aluminum ash

[0069] Mineral name Content, wt.% Mineral name Content, wt.% Aluminum oxide 37.69 Calcium fluoride 0.21 Aluminum nitride 20.13 Magnesium fluoride 3.36 Magnesium spinel 8.88 Potassium fluoride 4.02 Metallic aluminum 6.68 Sodium fluoride 3.38 β-aluminum oxide 4.35 Grossular 3.38 Potassium chloride 3.46 Others 0.45 Sodium chloride 4.01 Total 100.00

[0070] 1. The secondary aluminum ash was heated to 1400 °C at a heating rate of 10 °C / min respectively, and its thermogravimetric analysis was carried out to draw the thermogravimetric curve and DSC curve, as shown in the appendix Figure 4 and 5 as shown.

[0071] The results showed that: between 600 - 800 °C, the secondary aluminum ash showed the first endothermic peak, mainly due to the oxidation of aluminum nitride to alumina. In addition, the heat flow curve (DSC curve) in the region of 600 - 800 °C showed an obvious downward trend, and the oxidation of aluminum nitride mainly originated from this temperature region, and external heat energy should be provided. After 1100 °C, the secondary aluminum ash was basically in a weight loss state, and at this time, most of the aluminum nitride had been oxidized, mainly in the form of salt volatilization.

[0072] During the calcination process, aluminum nitride may react with oxygen in the air as follows:

[0073] 4AlN + 3O 2 = 2Al 2 O 3 + 2N 2 (1)

[0074] 4AlN + 7O 2 = 2Al 2 O 3 + 4NO 2 (2)

[0075] 2AlN + 4O 2 = Al 2 O 3 + N 2 O 5 (3)

[0076] 4AlN + 5O 2 = 2Al 2 O 3 + 4NO (4)

[0077] 2AlN + 2O 2 = Al 2 O 3 + N 2 O (5)

[0078] 2. Calcination denitrification and desalination experiment

[0079] The secondary aluminum ash was calcined in air for 0.5 h under different temperature conditions, and the results are shown in the following table: When calcined at 1000 °C for 0.5 h, the oxidation rate of aluminum nitride reaches over 96%, the chlorine removal rate exceeds 90%, the fluorine removal rate exceeds 50%, and the removal rates of potassium and sodium reach 40%. Pure oxygen is more conducive to denitrification and desalination.

[0080] Table 4 Oxidation rate of aluminum nitride in aluminum ash at different calcination temperatures

[0081]

[0082]

[0083] The toxicity leaching experiment was carried out on the above air denitrification products, and the results are as shown in the appendix Figure 6 The concentrations of F and Cl in the leaching solution of the product calcined at 1000 °C for 0.5 h are 6.79 mg / L and 3.59 mg / L respectively, which proves that the denitrified aluminum ash product at this time no longer belongs to hazardous waste. At this time, the main phases in the ash are alumina and part of magnesium aluminate spinel, and other impurities are mainly in the form of CaF 2 and glass phase.

[0084] Therefore, in the present invention, the temperature of high-temperature incineration is set at 1200°C - 1600°C.

[0085] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system, Characterized in that, The secondary aluminum ash safe calcination system includes a first-stage rotary kiln (2) provided with an aluminum ash slag inlet (1), and a second-stage incineration kiln (3) connected from the first-stage rotary kiln (2) for heating and burning the aluminum ash. The second-stage incineration kiln (3) is provided with a self-preheating recovery system; The first-stage rotary kiln (2) is a double-layer indirect heating rotary kiln. The material outlet of the second-stage incineration kiln (3) is connected to the outer heating jacket of the double-layer indirect heating of the first-stage rotary kiln (2) through a sealed pipeline, and the aluminum ash combustion material at the material outlet of the second-stage incineration kiln (3) enters the outer heating jacket of the double-layer indirect heating of the first-stage rotary kiln (2) through the sealed pipeline; The method includes the following steps: Step 1. Feed the secondary aluminum ash without adding or adding a very small amount of anti-caking agent into the first-stage rotary kiln for heating; Step 2. Send the material heated in the first-stage rotary kiln to the second-stage incineration kiln. The furnace temperature of the second-stage incineration kiln is controlled in sections. The material is first heated in an oxygen-deficient state at the front end and then burned at a high temperature in an oxygen-rich state at the rear end; Step 3. Feed the material after high-temperature incineration into the external heating jacket of the first rotary kiln to provide heat for heating the material in the first rotary kiln; through heat exchange, the temperature of the material drops. After being discharged from the safe calcination system and cooled, a harmless high-content α-Al 2 O 3 product is obtained.

2. The method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system according to claim 1, Characterized in that, The aluminum ash slag inlet (1) is provided with a screw feeder or a bucket elevator for transporting the aluminum ash slag material into the first-stage rotary kiln (2).

3. The method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system according to claim 1, Characterized in that, A material transfer bucket elevator is provided between the second-stage incineration kiln (3) and the first-stage rotary kiln (2) for transferring the treated aluminum ash slag in the bucket elevator into the second-stage incineration kiln (3).

4. The method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system according to claim 1, Characterized in that, The self-preheating recovery system includes an integrated furnace tail box (4) provided at the tail of the second-stage incineration kiln (3), and a furnace front pipeline (5) connected from the integrated furnace tail box (4). The furnace front pipeline (5) is connected to the front end of the second-stage incineration kiln (3) to convey the hot air after the self-ignition of the aluminum ash at the rear end of the second-stage incineration kiln (3) to the front end of the second-stage incineration kiln (3).

5. The method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system according to claim 1, Characterized in that, It also includes a tail gas treatment device (6) connected through pipelines from the first-stage rotary kiln (2) and the second-stage incineration kiln (3). A cyclone dust collector, a bag dust collector, and a denitration and desulfurization machine are sequentially distributed in the tail gas treatment device (6) along the direction of the tail gas flow. The tail gas treatment device (6) is provided with a preheating smoke exhaust port (7).

6. The method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system according to claim 5, Characterized in that, The heads of the first-stage rotary kiln (2) and the second-stage incineration kiln (3) are provided with a furnace head platform (9), the furnace head platform (9) is provided with an integrated furnace head box (10), and the tails of the first-stage rotary kiln (2) and the second-stage incineration kiln (3) are provided with a furnace tail platform (8).

7. The method for safely calcining secondary aluminum ash in a secondary aluminum ash safe calcination system according to any one of claims 1-6, Characterized in that, In step 1, the furnace temperature is 400-600°C and the material residence time is 40-180min; In step 2, the front-end temperature is 700-1000°C, and the material residence time is 30-90min; the rear-end temperature is 1200°C-1600°C, and the material residence time is 30-120min.

8. The method for safely calcining secondary aluminum ash by the secondary aluminum ash safe calcination system according to claim 7, It is characterized in that The mass fraction of elemental aluminum in the secondary aluminum ash is less than 20wt%.

9. The method for safely calcining secondary aluminum ash by the secondary aluminum ash safe calcination system according to claim 7, It is characterized in that The particle size of secondary aluminum ash is 120-180 mesh.

10. The method for safely calcining secondary aluminum ash by the secondary aluminum ash safe calcination system according to claim 7, It is characterized in that The dosage of anti-caking agent is 0-5wt% of the secondary aluminum ash mass.

11. Use of the α-Al 2 O 3 product prepared by the method according to any one of claims 1 to 10 as a production material for tiles or refractory bricks.

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