Method for preparing aluminum alloy by taking aluminum ash as raw material through vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen removal

Abstract

The invention relates to a method for preparing an aluminum alloy by taking aluminum ash as a raw material through vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen removal, and belongs to the technical fields of environmental protection, resource recovery and aluminum alloy preparation. Uniformly mixing aluminum ash and carbon black, and tabletting to obtain a pressed blank; vacuumizing the pressed blank at the temperature of 800-1300 DEG C, then introducing CH4-N2 mixed gas, keeping the temperature for 0.5-3 hours, and stopping introducing the CH4-N2 mixed gas to obtain an intermediate product mixture; the vacuum degree is kept unchanged, the temperature is increased to 1350-1680 DEG C, then N2 is introduced, heat preservation is conducted for 0.5-2 h, N2 introduction is stopped, and a mixture of AlN and Fe, Si and C is obtained; and the AlN and the Fe, Si and C mixture are subjected to vacuum C and N removal, and the Al-Si-Fe alloy is obtained. According to the method, the aluminum alloy is prepared by taking the solid waste as the raw material through vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen removal, so that resource recycling is realized.

Description

Technical Field

[0001] The invention relates to a method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen treatment using aluminum ash as raw material, belonging to the technical field of environmental protection, resource recovery and aluminum alloy preparation. Background Art

[0002] Aluminum ash is a solid waste containing a large amount of harmful elements in the aluminum smelting process. With the development of society, China has become the second largest industrial country, making the scale of aluminum production larger and showing an upward trend. This also results in a huge output of aluminum ash and abundant sources. At present, aluminum ash is mostly treated by stockpiling and landfilling. Such treatment methods not only cause a large amount of valuable elements in aluminum ash to be wasted, but also cause environmental pollution. Aluminum ash mainly comes from three aspects. First, in the electrolytic production process, a certain amount of aluminum ash is generated in the entire electrolytic aluminum process, and 30 to 50 kg of aluminum ash can be generated for every ton of aluminum produced; secondly, in the consumption process, a certain amount of aluminum ash will also be generated in related operations such as aluminum ingot casting, processing and molding, and the amount of aluminum ash generated by the processing of 1 ton of aluminum is about 30 to 40 kg; finally, the recycling of scrap aluminum can also produce aluminum ash, and the recovery rate is not high in the process of reprocessing scrap aluminum into aluminum products. Therefore, a certain amount of aluminum ash will still be generated, so that 1 ton of scrap aluminum can produce 150 to 250 kg of aluminum ash.

[0003] At present, aluminum ash is mainly treated by landfill. This treatment method not only wastes valuable elements in aluminum ash, but also pollutes the environment. Therefore, the exploration of aluminum ash treatment methods has been favored by many researchers. The current aluminum ash treatment methods are mainly divided into two categories, namely pyrometallurgical treatment and wet treatment. Most wet treatments use aluminum ash as raw materials to prepare alumina. Shahien et al. used acid leaching, pH adjustment, precipitation, solid-liquid separation, pH adjustment, reprecipitation, reseparation, and roasting to prepare alumina. This process requires multiple pH adjustment and solid-liquid separation operations, which is complicated and consumes a lot of reagents, which is not conducive to reducing costs in large-scale applications. The pyrometallurgical treatment process is divided into three types according to the different products. One is the extraction process of metallic aluminum, the second is the resource utilization of aluminum ash to synthesize composite materials, and the third is the process of preparing alumina. Yoshimura et al. proposed a method of using aluminum ash as a refractory material to replace aggregate casting. Tian Lin et al. also used alkaline smelting method and leached the smelting product. Through reading and understanding the above and related literature, it is analyzed that the pyrometallurgical treatment method has shortcomings: aluminum ash is used as an auxiliary material in the study, and the leaching product of water immersion belongs to the second category of solid waste. The aluminum ash has not been treated in an ideal way in terms of quantity.

[0004] Aluminum is a silvery-white metal and the most abundant metal in the earth's crust. It has good thermal and electrical conductivity. At room temperature, the thermal conductivity of aluminum is 1.5 times that of copper, and the electrical conductivity of aluminum wire is 60% of that of copper wire. Aluminum also has good ductility and can be drawn into aluminum wire, aluminum plate and aluminum foil. According to its purity, it is divided into "pure aluminum" and "refined aluminum". In industry, aluminum with no artificial alloying elements and a purity of at least 99.0% is usually called pure aluminum, and the purity of high-purity aluminum is usually 99.8% to 99.95%. The purity of refined aluminum is at least 99.95%. Because aluminum has the outstanding advantages described above and can form high-quality aluminum-based light alloys with many metals, aluminum is widely used in modern industrial technology, mainly in construction, transportation, engineering, cables, packaging and other fields. Aluminum is mainly used in two forms: pure aluminum and aluminum alloys.

[0005] Aluminum alloys are widely used in transportation, building materials, medical equipment and other industries due to their excellent physical properties. As the market demand for aluminum alloys increases, the output of aluminum alloys is also gradually increasing. At present, the preparation of aluminum alloys is to add an appropriate amount of required metal elements to aluminum materials, and the raw materials are mainly aluminum.

[0006] To sum up, on the one hand, my country has a large reserve of aluminum ash and has not found an ideal treatment method. A large amount of aluminum ash is still treated by landfill and stockpiling, and the problem of aluminum ash treatment needs to be solved urgently; on the other hand, the market demand for aluminum alloys is getting higher and higher.

[0007] The patent application number is 2019108567605, which discloses a method for comprehensive utilization of secondary aluminum ash resources. The invention desalts the secondary aluminum ash through high-temperature treatment, and the salt in the secondary aluminum ash is volatilized. The volatilized flue gas is cooled by high-pressure air and the salt is recovered; the secondary aluminum ash is mixed after high-temperature treatment and desalination, and a carbonizing agent is added to mix evenly, and an aluminum nitride product is obtained through high-temperature reaction. In this invention, the salt in the secondary aluminum ash is volatilized through high-temperature treatment, but impurities such as silicon and iron still exist in the desalted mixture, so that the purity of the generated aluminum nitride is impure, which affects the comprehensive recovery efficiency of aluminum. Summary of the invention

[0008] In view of the problems and shortcomings of the above-mentioned prior art, the present invention provides a method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen treatment using aluminum ash as raw material. The present invention not only effectively prepares aluminum alloy, but also saves production costs, realizes resource recycling, and efficiently recovers aluminum resources.

[0009] The present invention is achieved through the following technical solutions.

[0010] A method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen treatment using aluminum ash as raw material, the steps comprising:

[0011] Step 1, mixing aluminum ash and carbon black uniformly and pressing into tablets to obtain green compacts;

[0012] Step 2: The green compact is evacuated at a temperature of 800-1300°C, and then a CH4-N2 mixed gas is introduced, and the temperature is kept for 0.5-3h, and the introduction of the CH4-N2 mixed gas is stopped to obtain an intermediate product mixture; the reaction principle is:

[0013] Al2O3(s)+CH4(g)+N2(g)→2AlN(s)+2H2O(g)+CO(g)+intermediate products in aluminum ash;

[0014] Iron and silicon compounds in aluminum ash + carbon + CH4(g) → elemental iron, elemental silicon or iron-silicon mixture;

[0015] Step 3: Keep the vacuum constant, raise the temperature to 1350℃-1680℃, then introduce N2, continue deep nitridation, keep warm for 0.5-2h, stop introducing N2, and obtain a mixture of AlN and Fe, Si, and C; the principle is:

[0016] Intermediate product + N2 → AlN(s);

[0017] Step 4: vacuum-degassing the mixture of AlN and Fe, Si and C to obtain Al-Si-Fe alloy.

[0018] In the step 1, the mass ratio of aluminum ash to carbon black is 1:3-4.

[0019] The vacuum pressure in step 2 is 1-5000 Pa.

[0020] In the step 2, the flow rate of the CH4-N2 mixed gas is 0.1-0.2 L / min, and the flow rate ratio of CH4 to N2 in the CH4-N2 mixed gas is 0.07-0.1:0.01-0.05.

[0021] In step 3, the flow rate of N2 gas is 0.5-1 L / min.

[0022] In the fourth step, the vacuum removal of C and N is as follows: the mixture of AlN and Fe, Si and C is heated to 1000-1400°C and the vacuum degree is 10 -3 ~1Pa, and the insulation time is controlled at 0.5~2h.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention uses solid waste as raw material, and prepares aluminum alloy through vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation, thereby realizing resource recycling.

[0025] 2. The present invention makes full use of the aluminum, silicon and iron elements in the aluminum ash, effectively prepares the aluminum alloy after processing, and efficiently recycles the aluminum resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process of the present invention;

[0027] Figure 2 The XRD pattern of the mixture of AlN and Fe, Si and C prepared in step 3 of Example 1 of the present invention;

[0028] Figure 3 is the XRD pattern of the aluminum-silicon-iron alloy prepared in step 4 of Example 1 of the present invention;

[0029] In the present invention, the abscissa of all XRD graphs is twice the incident angle of the X-ray, and the ordinate is the intensity after diffraction. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Example 1

[0032] like Figure 1 As shown, a method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation of aluminum ash (Al2O3 accounts for 29.57wt%, Fe2O3 accounts for 4.87wt%, SiO2 accounts for 11.06wt%) as raw material, the steps of which include:

[0033] Step 1: Mix aluminum ash and carbon black evenly and press them into sheets to obtain a green sheet (sheet length and width are 25×35 mm), wherein the mass ratio of aluminum ash to carbon black is 1:3.25;

[0034] Step 2: The compact is vacuumed to 300Pa and at a temperature of 1250°C, and then a CH4-N2 mixed gas is introduced, and the temperature is kept for 2.5 hours, and the introduction of the CH4-N2 mixed gas is stopped (the flow rate of the CH4-N2 mixed gas is 0.2L / min, and the flow ratio of CH4 and N2 in the CH4-N2 mixed gas is 0.1:0.05), to obtain an intermediate product mixture; the reaction principle is:

[0035] Al2O3(s)+CH4(g)+N2(g)→2AlN(s)+2H2O(g)+CO(g)+intermediate products in aluminum ash;

[0036] Iron and silicon compounds in aluminum ash + carbon + CH4(g) → elemental iron, elemental silicon or iron-silicon mixture;

[0037] Step 3: Keep the vacuum constant, raise the temperature to 1550°C, then introduce N2 (N2 gas flow rate is 0.5L / min), continue deep nitridation, keep warm for 1h, stop introducing N2, and obtain a mixture of AlN and Fe, Si, and C; the principle is:

[0038] Intermediate product + N2 → AlN(s);

[0039] Step 4: vacuum decarbonize the mixture of AlN and Fe, Si, and C at 1150°C and a vacuum degree of 9×10 -3 Pa and the holding time are controlled at 1h to obtain Al-Si-Fe alloy.

[0040] The XRD pattern of the mixture of AlN and Fe, Si, and C in step 3 of this embodiment is as follows Figure 2 As shown, from Figure 2 It can be seen from the figure that the mixture of AlN and Fe, Si, and C is mainly composed of AlN, C, and FeSi phases. The XRD pattern of the Al-Si-Fe alloy prepared in this embodiment is shown in FIG. Figure 3 shown.

[0041] The Al-Si-Fe alloy prepared in this embodiment has a Si content of 5.32 wt %, a Fe content of 5.23 wt %, and the rest is Al.

[0042] Comparative Example 1

[0043] Compared with Example 1, this comparative example only lacks the step 2 process, and the rest is exactly the same as Example 1. Without the processing process of step 2, only Al alloy doped with iron oxide and silicon oxide can be obtained in the end, and Al-Si-Fe alloy cannot be obtained.

[0044] Example 2

[0045] like Figure 1 As shown, the method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash (Al2O3 accounts for 29.57wt%, Fe2O3 accounts for 4.87wt%, SiO2 accounts for 11.06wt%) as raw materials comprises the following steps:

[0046] Step 1: Mix aluminum ash and carbon black evenly and press into sheets to obtain green sheets (sheet length and width are 25×35 mm), wherein the mass ratio of aluminum ash to carbon black is 1:3;

[0047] Step 2: The compact is vacuumed to 500Pa and at a temperature of 800°C, and then a CH4-N2 mixed gas is introduced, and the temperature is kept for 0.5h, and the introduction of the CH4-N2 mixed gas is stopped (the flow rate of the CH4-N2 mixed gas is 0.15L / min, and the flow ratio of CH4 and N2 in the CH4-N2 mixed gas is 0.05:0.01), to obtain an intermediate product mixture; the reaction principle is:

[0048] Al2O3(s)+CH4(g)+N2(g)→2AlN(s)+2H2O(g)+CO(g)+intermediate products in aluminum ash;

[0049] Iron and silicon compounds in aluminum ash + carbon + CH4(g) → elemental iron, elemental silicon or iron-silicon mixture;

[0050] Step 3: Keep the vacuum constant, raise the temperature to 1600°C, then introduce N2 (N2 gas flow rate is 1L / min), continue deep nitridation, keep warm for 0.5h, stop introducing N2, and obtain a mixture of AlN and Fe, Si, and C; the principle is:

[0051] Intermediate product + N2 → AlN(s);

[0052] Step 4: vacuum-degassing the mixture of AlN and Fe, Si and C at 1000° C., vacuum degree 0.2 Pa and holding time of 2 h to obtain Al-Si-Fe alloy.

[0053] Example 3

[0054] like Figure 1 As shown, the method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash (Al2O3 accounts for 29.57wt%, Fe2O3 accounts for 4.87wt%, SiO2 accounts for 11.06wt%) as raw materials comprises the following steps:

[0055] Step 1: Mix aluminum ash and carbon black evenly and press into sheets to obtain green sheets (sheet length and width are 25×35 mm), wherein the mass ratio of aluminum ash to carbon black is 1:4;

[0056] Step 2: The green compact is vacuumed to 400Pa and at a temperature of 1300°C, and then a CH4-N2 mixed gas is introduced, and the temperature is kept for 3 hours, and the introduction of the CH4-N2 mixed gas is stopped (the flow rate of the CH4-N2 mixed gas is 0.15L / min, and the flow ratio of CH4 and N2 in the CH4-N2 mixed gas is 0.07:0.01), to obtain an intermediate product mixture; the reaction principle is:

[0057] Al2O3(s)+CH4(g)+N2(g)→2AlN(s)+2H2O(g)+CO(g)+intermediate products in aluminum ash;

[0058] Iron and silicon compounds in aluminum ash + carbon + CH4(g) → elemental iron, elemental silicon or iron-silicon mixture;

[0059] Step 3: Keep the vacuum constant, raise the temperature to 1480°C, then introduce N2 (N2 gas flow rate is 0.8L / min), continue deep nitridation, keep warm for 2h, stop introducing N2, and obtain a mixture of AlN and Fe, Si, and C; the principle is:

[0060] Intermediate product + N2 → AlN(s);

[0061] Step 4: vacuum-degassing the mixture of AlN and Fe, Si and C at 1400° C., vacuum degree 1 Pa and holding time of 1 h to obtain Al-Si-Fe alloy.

[0062] Example 4

[0063] like Figure 1 As shown, the method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash (Al2O3 accounts for 29.57wt%, Fe2O3 accounts for 4.87wt%, SiO2 accounts for 11.06wt%) as raw materials comprises the following steps:

[0064] Step 1: Mix aluminum ash and carbon black evenly and press into sheets to obtain green sheets (sheet length and width are 25×35 mm), wherein the mass ratio of aluminum ash to carbon black is 1:4;

[0065] Step 2: The green compact is vacuumed to 700Pa and at a temperature of 1100°C, and then a CH4-N2 mixed gas is introduced, and the temperature is kept for 2 hours, and the introduction of the CH4-N2 mixed gas is stopped (the flow rate of the CH4-N2 mixed gas is 0.2L / min, and the flow ratio of CH4 and N2 in the CH4-N2 mixed gas is 0.08:0.05), to obtain an intermediate product mixture; the reaction principle is:

[0066] Al2O3(s)+CH4(g)+N2(g)→2AlN(s)+2H2O(g)+CO(g)+intermediate products in aluminum ash;

[0067] Iron and silicon compounds in aluminum ash + carbon + CH4(g) → elemental iron, elemental silicon or iron-silicon mixture;

[0068] Step 3: Keep the vacuum constant, raise the temperature to 1680°C, then introduce N2 (N2 gas flow rate is 0.5L / min), continue deep nitridation, keep warm for 1h, stop introducing N2, and obtain a mixture of AlN and Fe, Si, and C; the principle is:

[0069] Intermediate product + N2 → AlN(s);

[0070] Step 4: vacuum-degassing the mixture of AlN and Fe, Si and C at 1200° C., vacuum degree 1 Pa and holding time of 1 h to obtain Al-Si-Fe alloy.

[0071] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen treatment using aluminum ash as raw material, It is characterized by the steps include: Step 1, mixing aluminum ash and carbon black uniformly and pressing into tablets to obtain green compacts; Step 2: The compact is evacuated at a temperature of 800-1300°C and then CH 4 -N 2 Mixed gas, keep warm for 0.5-3h, stop introducing CH 4 -N 2 Mixing the gases to obtain an intermediate product mixture; Step 3: Keep the vacuum constant, raise the temperature to 1350℃-1680℃, and then introduce N 2 , keep warm for 0.5-2h, stop introducing N 2 , obtaining a mixture of AlN and Fe, Si, and C; Step 4: vacuum-degassing the mixture of AlN and Fe, Si and C to obtain Al-Si-Fe alloy.

2. The method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash as raw material according to claim 1, Features: In the step 1, the mass ratio of aluminum ash to carbon black is 1:3-4.

3. The method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash as raw material according to claim 1, Features: The vacuum pressure in step 2 is 1-5000 Pa.

4. The method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash as raw material according to claim 1, Features: In step 2, CH 4 -N 2 The mixed gas flow rate is 0.1~0.2L / min, CH 4 -N 2 CH in mixed gas 4 and N 2 The flow ratio is 0.07~0.1:0.01~0.

05.

5. The method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogen treatment using aluminum ash as raw material according to claim 1, Features: In step 3, N 2 The gas flow rate is 0.5~1L / min.

6. The method for preparing aluminum alloy by vacuum carbon thermal reduction nitridation and vacuum decarburization and nitrogenation using aluminum ash as raw material according to claim 1, Features: In the fourth step, the vacuum removal of C and N is as follows: the mixture of AlN and Fe, Si and C is heated to 1000-1400°C and the vacuum degree is 10 -3 ~1Pa, and the insulation time is controlled at 0.5~2h.

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