A method for preparing aluminatc cement from secondary aluminum dross with low carbon

Abstract

A method for low-carbon preparation of aluminate cement from secondary alumina ash belongs to the field of solid waste resource utilization. Secondary alumina ash is mixed with quicklime, using alumina from the secondary alumina ash as the aluminum source and quicklime as the calcium source. After the mixture is ignited with an igniter, the oxidation reaction of aluminum nitride, aluminum carbide, and metallic aluminum in the secondary alumina ash serves as the heat source, and fluoride and chloride salts in the secondary alumina ash act as co-oxidants. The mixture is calcined in an oxidizing atmosphere to synthesize calcium aluminate, thus achieving low-carbon preparation of aluminate cement from secondary alumina ash. This invention utilizes secondary alumina ash to prepare aluminate cement, fully leveraging the aluminum resource characteristics of secondary alumina ash; it uses oxygen to oxidize aluminum nitride, aluminum carbide, and metallic aluminum in the secondary alumina ash, avoiding the generation of dangerous gases such as ammonia, methane, and hydrogen from the hydrolysis of aluminum nitride, aluminum carbide, and metallic aluminum; and it uses the oxidation reaction of aluminum nitride, aluminum carbide, and metallic aluminum as the heat source, with fluoride and chloride salts acting as co-oxidants, eliminating the need for an external heat source during the calcination process. This invention has the advantages of a short process, low carbon footprint, and ease of industrialization.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization, and specifically relates to a method for preparing aluminate cement from secondary aluminum ash in a low-carbon manner. Background Technology

[0002] Secondary aluminum ash is a solid waste generated after aluminum extraction from molten aluminum slag. With the development of the aluminum industry, the amount of secondary aluminum ash has increased rapidly (over 2.2 million tons were produced in my country in 2022). Secondary aluminum ash contains a large amount of alumina (40-60 wt.%), aluminum nitride (20-40 wt.%), salt refining agents (sodium, potassium, chloride, and fluoride salts totaling 10-20 wt.%), and small amounts of aluminum carbide and metallic aluminum. Landfill disposal easily leads to ammonia pollution from aluminum nitride hydrolysis and salt refining agent pollution. Therefore, the disposal of secondary aluminum ash urgently needs to be addressed.

[0003] Currently, there are two methods for treating secondary aluminum ash: wet and pyrometallurgical processes. Wet processing mainly involves the following steps: first, water washing and evaporation to remove salt and hydrolysis to remove aluminum nitride; then, acid / alkali leaching to extract aluminum from the secondary aluminum ash; finally, the leachate is processed through precipitation and calcination to produce activated alumina. Pyrometallurgical processing mainly produces building materials and refractory materials. It involves the following steps: first, water washing and evaporation to remove salt and hydrolysis to remove aluminum nitride; then, the desalinated and denitrified secondary aluminum ash is uniformly mixed with other raw materials; finally, it is sintered or melted to produce building materials and refractory materials.

[0004] Chinese invention patent (CN106830030B) discloses a method for safely and efficiently producing granular alumina using aluminum ash. By adjusting the Bayer process, the method utilizes the aluminum element in the aluminum ash to produce granular alumina, while also reusing ammonia and hydrogen produced during the process. However, the recovered ammonia has a high impurity content, making its utilization difficult.

[0005] Chinese invention patent (CN108516688A) discloses a method for producing spinel microcrystalline glass using aluminum ash as the main raw material. The product has a compressive strength of 400-500 MPa and a flexural strength of 70-90 MPa. However, the production process consumes a lot of energy and has a high cost.

[0006] Chinese invention patent (CN112958584A) discloses a method for reducing heavy metals in hazardous solid waste using secondary aluminum ash slag and utilizing the slag. The method utilizes secondary aluminum ash to reduce heavy metals in hazardous solid waste using aluminum nitride, and the slag is used in building materials. However, the secondary aluminum ash processing capacity is low, and the production process consumes a lot of energy.

[0007] Chinese invention patent (CN108863123B) discloses a process for preparing aluminate cement by replacing part of high-alumina bauxite with aluminum ash. The process uses limestone, high-alumina bauxite, and aluminum ash as raw materials, and obtains aluminate cement after calcination at 1380-1440℃ for 25-35 minutes. However, the weight ratio of aluminum ash is only 1-5.5%, and the calcination process requires a continuous external heat source.

[0008] Chinese invention patent (CN112811835B) discloses a method for preparing aluminate cement, using red mud, limestone, aluminum ash, and industrial alumina as raw materials, and calcining them at 900-1150℃ for 2-3 hours to obtain aluminate cement. However, the weight ratio of aluminum ash is only 2-3.5%, and the calcination process requires a continuous external heat source.

[0009] Chinese invention patent (CN114477827B) discloses a method for producing cement accelerators through the comprehensive treatment of secondary aluminum ash. The method uses secondary aluminum ash, calcium source, and alkaline additives as raw materials, and obtains cement accelerators after calcination at 950-1200℃ for 1-4 hours. However, the calcination process consumes a large amount of natural gas, resulting in high energy consumption.

[0010] Chinese invention patent (CN111170750A) discloses a method for manufacturing refractory materials by harmlessly treating secondary aluminum ash. The method involves grinding the secondary aluminum ash until 80% of the particle size passes through a 74 μm sieve, then calcining it in an oxidizing atmosphere at 1150-1550℃ for 0.5-4 hours. This converts the metallic aluminum, aluminum nitride, and aluminum carbide in the secondary aluminum ash into alumina, while fluoride and chloride salts volatilize, yielding calcined oxides. These calcined oxides, alone or mixed with additives, are then smelted by electric arc to produce alumina-magnesia refractory materials. However, the calcination process requires a continuous external heat source, resulting in high energy consumption. Furthermore, the exothermic oxidation of metallic aluminum, aluminum nitride, and aluminum carbide is not effectively utilized during the secondary smelting process after calcination of the secondary aluminum ash, which is then combined with magnesium raw materials.

[0011] In summary, existing secondary aluminum ash disposal technologies suffer from problems such as long processes, high energy consumption, and high costs. There is an urgent need for short-process, low-energy-consumption, and low-cost disposal technologies for secondary aluminum ash to achieve green and low-carbon resource utilization of secondary aluminum ash. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing aluminate cement from secondary alumina ash using low carbon content. The method involves mixing secondary alumina ash with quicklime, using alumina from the secondary alumina ash as the aluminum source and quicklime as the calcium source. After ignition with an igniter, the mixture utilizes the oxidation reaction of aluminum nitride, aluminum carbide, and metallic aluminum from the secondary alumina ash as the heat source, and fluoride and chloride salts from the secondary alumina ash as oxidizing agents. The mixture undergoes self-heating calcination in an oxidizing atmosphere to synthesize calcium aluminate, thus achieving the low-carbon preparation of aluminate cement from secondary alumina ash. This completely solves the problem of secondary alumina ash disposal.

[0013] The present invention adopts the following technical solution:

[0014] A method for preparing aluminate cement from secondary aluminum ash using low carbon content, characterized in that the secondary aluminum ash comprises: 40-60 wt.% alumina, 20-40 wt.% aluminum nitride, 10-20 wt.% sodium salts, potassium salts, chloride salts, and fluoride salts, and 5-10% aluminum carbide and metallic aluminum. The secondary aluminum ash is mixed with quicklime, using alumina in the secondary aluminum ash as the aluminum source and quicklime as the calcium source. After the mixture is ignited by an igniter, the oxidation reaction of aluminum nitride, aluminum carbide, and metallic aluminum in the secondary aluminum ash serves as the heat source, and the fluoride and chloride salts in the secondary aluminum ash act as oxidizing agents. The mixture is then calcined in an oxidizing atmosphere to synthesize calcium aluminate, thereby achieving the low-carbon preparation of aluminate cement from secondary aluminum ash.

[0015] Furthermore, the igniter includes hot aluminum slag, charcoal, and heavy oil; the oxidizing atmosphere includes air and pure oxygen.

[0016] Furthermore, the raw material mass ratio is: 60-80 parts secondary aluminum ash, 20-40 parts quicklime, and 2-12 parts igniter.

[0017] Furthermore, the principle of fluoride and chloride salts as oxidizing agents is that they react with the aluminum oxide protective layer on the surface of aluminum nitride, aluminum carbide, and metallic aluminum to generate aluminum fluoride and aluminum chloride, which then corrode the protective layer.

[0018] The method for preparing aluminate cement from secondary aluminate ash using low carbon content, as described above, includes the following specific preparation steps:

[0019] S1. Mixing: Mix the secondary aluminum ash and quicklime evenly to obtain a mixture;

[0020] S2, Ignition: The mixture is ignited by an igniter, and the aluminum nitride, aluminum carbide and metallic aluminum in the secondary aluminum ash undergo an oxidation reaction;

[0021] S3. Calcination: Using oxidation reaction as a heat source, the mixture is calcined for 1.0-3.0 h. The original alumina in the secondary aluminum and the newly generated alumina react with the calcium oxide in the quicklime to produce calcium aluminate, thus obtaining high-temperature aluminate clinker.

[0022] S4. Cooling: The high-temperature aluminate clinker is naturally cooled and transformed into aluminate clinker;

[0023] S5. Ball milling and sieving: The aluminate clinker is ball-milled and sieved to obtain aluminate cement.

[0024] The principle of this invention is as follows:

[0025] (1) The oxidation reactions of aluminum nitride, aluminum carbide, and metallic aluminum are used as heat sources. The oxidation reactions of aluminum nitride, aluminum carbide, and metallic aluminum are all exothermic reactions, and the reaction equations are shown in equations (1)-(3). The enthalpy changes of the reactions are as follows:Figure 2 As shown, the enthalpy changes of aluminum nitride, aluminum carbide, and metallic aluminum are approximately -250, -515, and -400 kcal, respectively. The contents of aluminum nitride, aluminum carbide, and metallic aluminum in the secondary aluminum ash are approximately 20 wt.%, 5 wt.%, and 3 wt.%, respectively. 100 kg of secondary aluminum ash can release approximately 112,000 kcal of heat through oxidation. The specific heat capacities of alumina and calcium oxide are 0.205 and 0.059 kcal / kg℃, respectively. Assuming that the specific heat capacity of secondary aluminum ash is the same as that of alumina, and the specific heat capacity of quicklime is the same as that of calcium oxide, then the heat released by 100 kg of secondary aluminum ash can theoretically heat itself to over 5000℃. Even with an equal mass of quicklime, the mixture can be heated to over 3500℃. Therefore, the self-heating production of aluminate cement using secondary aluminum ash is theoretically feasible.

[0026] 2AlN + 1.5O2(g) → Al2O3 + N2(g) (1)

[0027] 1 / 2Al4C3 + 3O2(g) → Al2O3 + 3 / 2CO2(g) (2)

[0028] 2Al + 1.5O2(g) → Al2O3 (3)

[0029] (2) The chloride and fluoride salts in the secondary aluminum ash promote the oxidation of aluminum nitride, aluminum carbide, and metallic aluminum. After the aluminum nitride, aluminum carbide, and metallic aluminum are oxidized, an aluminum oxide protective layer is formed on the surface, which prevents the aluminum nitride, aluminum carbide, and metallic aluminum from contacting oxygen, thereby inhibiting the oxidation reaction. The chloride and fluoride salts can react with the aluminum oxide protective layer to generate aluminum chloride and aluminum fluoride, as shown in equations (4) and (5). This corrodes the aluminum oxide protective layer, allowing the aluminum nitride, aluminum carbide, and metallic aluminum to fully contact oxygen and promote oxidation.

[0030] 2Al2O3 + 3NaCl → 3NaAlO2 + AlCl3(g) (4)

[0031] 2Al2O3 + 3NaF → 3NaAlO2 + AlF3(g) (5)

[0032] (3) Utilizing the aluminum resource characteristics of secondary aluminum ash as an aluminum source to prepare aluminate cement in low carbon with quicklime. The aluminum in secondary aluminum ash exists in the forms of aluminum oxide, aluminum nitride, aluminum carbide and metallic aluminum. During the calcination process, the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum occurs first. The exothermic oxidation reaction causes the newly generated aluminum oxide to combine with calcium oxide to synthesize calcium aluminate. The excess heat causes the original aluminum oxide in the secondary aluminum ash to combine with calcium oxide to synthesize calcium aluminate. The coupling of multiple reactions ultimately realizes the low carbon preparation of aluminate cement from secondary aluminum ash.

[0033] The beneficial effects of this invention are as follows:

[0034] (1) Existing secondary aluminum ash treatment technologies mainly include wet and pyrometallurgical methods. The wet method uses water to desalinate aluminum nitride salts and washes the salts, generating secondary pollution such as ammonia and saline wastewater, as shown in formulas (6) and (7). The pyrometallurgical method uses high-temperature oxidation of aluminum nitride into alumina, nitrogen, and volatile salts, as shown in formulas (8) and (9). However, the heat of oxidation of aluminum nitride is not fully utilized. This invention uses the oxidation reaction of aluminum nitride as a heat source and salt as a co-oxidant, which solves the pollution problems of salt and aluminum nitride and realizes the high-value utilization of secondary aluminum ash.

[0035] AlN + 3H2O → Al(OH)3 + NH3(g) (6)

[0036] NaCl + H2O → NaCl(aq) (7)

[0037] 2AlN + 3 / 2O2 → Al2O3 + N2(g) (8)

[0038] NaCl + Heat → NaCl(g) (9)

[0039] (2) This invention utilizes the aluminum resource characteristics of secondary aluminum ash and the exothermic oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum to compound quicklime, thus producing aluminate cement without the need for an external heat source. The calcination process first involves the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum. The exothermic oxidation reaction causes the newly generated alumina to combine with calcium oxide to synthesize calcium aluminate. The excess heat causes the original alumina in the secondary aluminum ash to combine with calcium oxide to synthesize calcium aluminate. The coupling of multiple reactions ultimately achieves the green and low-carbon preparation of aluminate cement from secondary aluminum ash.

[0040] (3) This invention utilizes chloride and fluoride salts in secondary aluminum ash to promote the oxidation of aluminum nitride, aluminum carbide, and metallic aluminum. After oxidation, aluminum nitride, aluminum carbide, and metallic aluminum form an aluminum oxide protective layer on their surface, preventing them from contacting oxygen and inhibiting the oxidation reaction. Chloride and fluoride salts can react with the aluminum oxide protective layer to generate aluminum chloride and aluminum fluoride gases, which corrode the aluminum oxide protective layer and promote oxidation. Attached Figure Description

[0041] Figure 1 The diagram shown is a process flow chart of the present invention.

[0042] Figure 2 The figure shows the enthalpy changes of the oxidation reactions of aluminum nitride, aluminum carbide, and metallic aluminum. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0045] Example 1

[0046] 60 parts of secondary aluminum ash and 40 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 12 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.0 h to realize the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0047] Example 2

[0048] 61 parts of secondary aluminum ash and 39 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 12 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.1 h to realize the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining high-temperature aluminate clinker; the high-temperature aluminate clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0049] Example 3

[0050] 62 parts of secondary aluminum ash and 38 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 11 parts of heavy oil were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.2 h to realize the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0051] Example 4

[0052] 63 parts of secondary aluminum ash and 37 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 11 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.3 h to achieve the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0053] Example 5

[0054] 64 parts of secondary aluminum ash and 36 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 10 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.4 h to realize the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0055] Example 6

[0056] 65 parts of secondary aluminum ash and 35 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 10 parts of heavy oil were added to ignite the mixture; the mixture was calcined for 1.5 h using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source to achieve the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0057] Example 7

[0058] 66 parts of secondary aluminum ash and 34 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 9 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.6 h to achieve the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0059] Example 8

[0060] 67 parts of secondary aluminum ash and 33 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 9 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.7 h to realize the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0061] Example 9

[0062] 68 parts of secondary aluminum ash and 32 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 8 parts of heavy oil were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.8 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0063] Example 10

[0064] 69 parts of secondary aluminum ash and 31 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 8 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 1.9 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0065] Example 11

[0066] 70 parts of secondary aluminum ash and 30 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 7 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.0 h to realize the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0067] Example 12

[0068] 71 parts of secondary aluminum ash and 29 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 7 parts of heavy oil were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.1 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0069] Example 13

[0070] 72 parts of secondary aluminum ash and 28 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 6 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.2 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0071] Example 14

[0072] 73 parts of secondary aluminum ash and 27 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 6 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.3 h to achieve the reaction of aluminum oxide and calcium oxide to produce calcium aluminate, thus obtaining high-temperature aluminate clinker; the high-temperature aluminate clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0073] Example 15

[0074] 74 parts of secondary aluminum ash and 26 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 5 parts of heavy oil were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.4 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0075] Example 16

[0076] 75 parts of secondary aluminum ash and 25 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 5 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.5 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0077] Example 17

[0078] 76 parts of secondary aluminum ash and 24 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 4 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.6 h to achieve the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0079] Example 18

[0080] 77 parts of secondary aluminum ash and 23 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 4 parts of heavy oil were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.7 h to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0081] Example 19

[0082] 78 parts of secondary aluminum ash and 22 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 3 parts of hot aluminum slag were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.8 h to achieve the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0083] Example 20

[0084] 79 parts of secondary aluminum ash and 21 parts of quicklime were mixed evenly to obtain a mixture; pure oxygen was introduced and 3 parts of charcoal were added to ignite the mixture; using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source, the mixture was calcined for 2.9 h to achieve the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

[0085] Example 21

[0086] 80 parts of secondary aluminum ash and 20 parts of quicklime were mixed evenly to obtain a mixture; air was introduced and 2 parts of heavy oil were added to ignite the mixture; the mixture was calcined for 3.0 h using the oxidation reaction of aluminum nitride, aluminum carbide and metallic aluminum as a heat source to realize the reaction of alumina and calcium oxide to produce calcium aluminate, thus obtaining aluminate high-temperature clinker; the aluminate high-temperature clinker was naturally cooled, ball-milled and sieved to obtain aluminate cement.

Claims

1. A method for preparing aluminate cement from secondary aluminate ash using low carbon content, characterized in that, The secondary aluminum ash comprises: 40-60 wt.% aluminum oxide, 20-40 wt.% aluminum nitride, 10-20 wt.% sodium salts, potassium salts, chloride salts, and fluoride salts, and 5-10% aluminum carbide and metallic aluminum. The secondary aluminum ash is mixed with quicklime, using the aluminum oxide in the secondary aluminum ash as the aluminum source and the quicklime as the calcium source. After the mixture is ignited by an igniter, the oxidation reaction of aluminum nitride, aluminum carbide, and metallic aluminum in the secondary aluminum ash serves as the heat source, and the fluoride and chloride salts in the secondary aluminum ash act as oxidizing agents. The mixture is then calcined in an oxidizing atmosphere to synthesize calcium aluminate, thereby achieving the low-carbon preparation of aluminate cement from secondary aluminum ash. The raw material mass ratio is: 60-80 parts secondary aluminum ash, 20-40 parts quicklime, and 2-12 parts igniter.

2. The method for preparing aluminate cement from secondary aluminate ash using low carbon as described in claim 1, characterized in that, The ignition source is hot aluminum slag, charcoal, or heavy oil; the oxidizing atmosphere is air or pure oxygen.

3. The method for preparing aluminate cement from secondary aluminate ash using low carbon as described in claim 1, characterized in that, The specific preparation steps are as follows: S1. Mixing: Mix the secondary aluminum ash and quicklime evenly to obtain a mixture; S2, Ignition: The mixture is ignited by an igniter, and the aluminum nitride, aluminum carbide and metallic aluminum in the secondary aluminum ash undergo an oxidation reaction; S3. Calcination: Using oxidation reaction as a heat source, the mixture is calcined for 1.0-3.0 h. The original alumina in the secondary alumina and the newly generated alumina react with the calcium oxide in the quicklime to produce calcium aluminate, thus obtaining high-temperature aluminate clinker. S4. Cooling: The high-temperature aluminate clinker is naturally cooled and transformed into aluminate clinker; S5. Ball milling and sieving: The aluminate clinker is ball-milled and sieved to obtain aluminate cement.

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