Method for efficiently preparing aluminum nitride from aluminum ash

Abstract

The application discloses a method for efficiently preparing aluminum nitride from aluminum ash, and steps are as follows: the aluminum ash is finely ground and preheated, and then fluidized chlorination denitrification is carried out under the assistance of large particles, so that aluminum and aluminum nitride in the aluminum ash are converted into aluminum chloride and nitrogen; the aluminum chloride is recovered through condensation, gasified, preheated, and then reacted with magnesium nitride to generate a mixture of aluminum nitride and magnesium chloride; the mixture is crystallized and purified to obtain high-purity aluminum nitride; the by-produced magnesium chloride is electrolyzed to generate magnesium and chlorine gas; the chlorine gas is recycled for denitrification of the aluminum ash; and the magnesium is reacted with nitrogen to generate magnesium nitride and is recycled for the nitration of the aluminum chloride. The application does not need to make balls and mix carbon, the chlorination denitrification temperature is low and the efficiency is high, the aluminum nitride is prepared by nitration of the aluminum chloride with the magnesium nitride, the product is easy to separate and purify, the by-product magnesium chloride can provide magnesium and chlorine gas for the system through electrolysis, the recycling utilization rate is high, the energy utilization rate of the system is high, the harmless treatment of the aluminum ash and the large-scale efficient preparation of the aluminum nitride can be realized, and the application has good economic and social benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical non-ferrous metallurgy environmental protection, and particularly relates to a method for efficiently preparing aluminum nitride from aluminum dross. BACKGROUND

[0002] Aluminum dross is an industrial by-product generated in the process of electrolytic aluminum production, cast aluminum production and waste aluminum recycling. More than 3 million tons of aluminum dross are produced in the aluminum industry in China every year. Because aluminum dross contains harmful substances such as aluminum nitride, soluble fluoride salt and chloride salt, it is listed in the National Hazardous Waste List. Harmless treatment and high-value utilization of aluminum dross are of great significance to the green and high-quality development of the aluminum industry.

[0003] The main harmless treatment of aluminum dross is denitrogenation and desalination. The most commonly used denitrogenation method is to convert aluminum nitride into nitrogen and alumina by high-temperature calcination of aluminum dross in air. However, a dense alumina film is easily formed on the surface of aluminum nitride particles during oxidation calcination, which hinders the further progress of the denitrogenation reaction, resulting in low denitrogenation efficiency. Chinese Patent Application CN112744850A discloses a method for comprehensive utilization of secondary aluminum dross. First, secondary aluminum dross and sodium base are made into 30-200mm pellets with a binder, and then the pellets are calcined in a high-temperature kiln. The generated alumina is converted into sodium aluminate by oxidation of aluminum nitride with sodium base, thereby alleviating the blocking effect of the generated alumina film and strengthening the denitrogenation reaction. Although the use of alkali sintering can improve the denitrogenation efficiency, the amount of alkali added is large, the production cost is high, and the pellets are large in diameter, uneven in heating, high in solid-phase reaction temperature, long in reaction time and high in energy consumption. Chinese Patent Application CN110902706A discloses a method for preparing polyaluminum chloride from aluminum dross. First, aluminum dross and coke are made into 5-20mm pellets with a binder, and then the pellets are calcined in a moving bed at 700-1100℃ in chlorine gas to convert aluminum nitride into nitrogen and aluminum chloride. Although this method can denitrogenate aluminum nitride and obtain aluminum chloride with high added value, the raw material used for chlorination calcination is large-diameter pellets, which are uneven in heating, and the diffusion resistance of the generated aluminum chloride and nitrogen is large, resulting in slow reaction rate, low efficiency and high energy consumption. Chinese Patent Application CN112850762A discloses a method for preparing aluminum chloride and full-component utilization by aluminum dross pellet chlorination-oxygen pressure conversion. First, aluminum dross and coke are mixed uniformly at a certain ratio to form pellets, and then the pellets are calcined in a moving bed at 1000℃ in chlorine gas to obtain nitrogen, aluminum chloride, silicon chloride, magnesium chloride and other products with high added value. Although this method can harmlessly treat aluminum dross and realize high-value utilization of aluminum, silicon and magnesium, it still has the problems of slow reaction rate, low efficiency and high energy consumption due to the large gas-phase diffusion resistance.

[0004] Therefore, in view of the current situation that aluminum ash cannot be efficiently utilized by current process technology, through process and technical innovation, the denitrification and desalination process is strengthened, the reaction efficiency is improved, the process energy consumption is reduced, and the aluminum resources in the aluminum ash are utilized to prepare high value-added products, which is the key to realize large-scale efficient clean and high-value utilization of aluminum ash. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a method for efficiently preparing aluminum nitride from aluminum ash.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for efficiently preparing aluminum nitride from aluminum ash, comprising the following steps:

[0008] S1, grinding: grinding the aluminum ash into fine powder to obtain fine ash;

[0009] S2, preheating I: preheating the fine ash obtained in step S1 to obtain hot fine ash;

[0010] S3, chlorination: using high-temperature chlorine gas to chlorinate and denitrate the hot fine ash obtained in step S2 to obtain high-temperature chlorination flue gas and hot chlorination residue; the high-temperature chlorination flue gas is sent to the preheating I process of step S2 for heat exchange preheating of the fine ash, and the low-temperature chlorination flue gas after heat exchange is sent to the condensation recovery process of step S7;

[0011] S4, heat exchange cooling: using normal temperature chlorine gas to cool the hot chlorination residue obtained in step S3 by heat exchange to obtain cold chlorination residue and hot chlorine gas, and the hot chlorine gas is sent to the combustion preheating I process of step S5;

[0012] S5, combustion preheating I: heating the hot chlorine gas obtained in step S4 by combustion of air and fuel to obtain high-temperature chlorine gas and combustion tail gas I, and the high-temperature chlorine gas is sent to the chlorination process of step S3;

[0013] S6, water washing and drying: using deionized water to wash and dry the cold chlorination residue obtained in step S4 to obtain washing liquid and tail residue;

[0014] S7, condensation recovery: condensing the low-temperature chlorination flue gas obtained after heat exchange preheating of the fine ash to obtain chlorine gas, nitrogen gas and solid phase chlorinated aluminum, and the chlorine gas and nitrogen gas are sent to the separation process of step S8;

[0015] S8, separation: separating the chlorine gas and nitrogen gas obtained in step S7 to obtain circulating chlorine gas I and circulating nitrogen gas, and the circulating chlorine gas I is sent to the heat exchange cooling process of step S4 for heat exchange cooling of the hot chlorination residue, and the circulating nitrogen gas is sent to the nitriding II process of step S15;

[0016] S9, gasification: gasifying the solid phase chlorinated aluminum obtained in step S7 to obtain gas phase chlorinated aluminum;

[0017] S10, combustion preheating II: heating the gaseous aluminum chloride obtained in S9 by combustion of air and fuel to obtain high-temperature aluminum chloride and combustion tail gas II;

[0018] S11, preheating II: preheating the magnesium nitride to obtain hot magnesium nitride, and the hot magnesium nitride is sent to the nitriding I process of step S12;

[0019] S12, nitriding I: using the high-temperature aluminum chloride obtained in step S10 and the hot magnesium nitride obtained in step S11 to carry out a nitriding reaction to obtain a nitride and high-temperature nitriding flue gas, and the high-temperature nitriding flue gas is sent to the heat exchange preheating II process of step S11 to heat exchange and preheat the magnesium nitride;

[0020] S13, crystallization: crystallizing the nitride obtained in step S12 to obtain aluminum nitride and magnesium chloride;

[0021] S14, electrolysis: electrolyzing the magnesium chloride obtained in step S13 to obtain magnesium and recycled chlorine gas II, and the recycled chlorine gas II is sent to the heat exchange cooling process of step S4 to heat exchange and cool the hot chlorination residue;

[0022] S15, nitriding II: using nitrogen and the recycled nitrogen gas obtained in step S8 to nitride the magnesium obtained in step S14 to obtain recycled nitriding magnesium, and the recycled nitriding magnesium is sent to the heat exchange preheating II process of step S12 to carry out a nitriding reaction with the high-temperature aluminum chloride.

[0023] Further, in step S1, the particle size of the fine ash is <1 μm.

[0024] Further, in step S3, the chlorination denitriding temperature is 400-600℃, and the time is 0.1-1h; the chlorination denitriding reactor is a fluidized bed reactor, and inert oxides are provided in the fluidized bed reactor to assist fluidization and heat storage, the inert oxides are one or a combination of spherical aluminum oxide particles and spherical zirconium oxide particles, and the particle size of the inert oxides is 0.5-3mm.

[0025] Further, in step S7, the condensation temperature is 20-170℃.

[0026] Further, in step S12, the particle size of the hot magnesium nitride is <1 μm, the nitriding reaction temperature is 450-650℃, the nitriding reaction time is 0.1-1h, and the nitriding reaction reactor is a fluidized bed reactor, and inert oxides are provided in the fluidized bed reactor to assist fluidization and heat storage, the inert oxides are one or a combination of spherical aluminum oxide particles and spherical zirconium oxide particles, and the particle size of the inert oxides is 0.5-3mm.

[0027] Further, in steps S2 and S11, the preheating is performed by indirect heat exchange.

[0028] Further, in step S15, the nitriding temperature is 400-600 DEG C, and the nitriding time is 0.1-1h.

[0029] Further, in step S13, the crystallization temperature is 1500-1700 DEG C, and the crystallization time is 0.5-2h.

[0030] The present application has the following advantages:

[0031] 1. The present application does not need balling, and the fine grinding and activation can significantly improve the chlorination reaction activity of aluminum ash, reduce the reaction temperature, save energy consumption, directly chlorinate aluminum and aluminum nitride in aluminum ash with chlorine, does not need to be carbon, is simple to operate, does not contain carbon dioxide in tail gas, is green and environmental protection, and the excess chlorine is easy to separate and recycle;

[0032] 2. The present application uses a fluidized bed provided with inert large particle oxides to perform the chlorination denitrification of fine aluminum ash and the nitriding reaction of fine magnesium nitride and chlorinated aluminum, the inert large particle oxides can inhibit fine particle agglomeration, break bubbles, and strengthen the mass and heat transfer between gas and solid phases, and also can play a heat storage role, effectively improving the reaction efficiency and system operation stability;

[0033] 3. The present application prepares aluminum nitride by the reaction of aluminum chloride and magnesium nitride, compared with the carbon thermal reduction nitriding method of aluminum oxide, the reaction temperature is significantly reduced, and the reaction product is easy to separate and purify, and the product purity is high;

[0034] 4. The present application uses magnesium nitride as the nitrogen source for preparing aluminum nitride, the byproduct magnesium chloride is easy to separate, and can produce magnesium and chlorine through electrolysis, and is recycled in the system, effectively saving the cost;

[0035] 5. The present application has high waste heat recovery rate, effectively improving the overall process system heat efficiency;

[0036] 6. The present application not only can realize the harmless treatment of aluminum ash, but also can efficiently convert the aluminum resource in the aluminum ash into high value-added aluminum nitride, and the economic benefit and social benefit are remarkable. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The method flowchart of the embodiments of the present application. DETAILED DESCRIPTION

[0038] The present application will be further described below with reference to the drawings, and it should be noted that the present embodiment is based on the technical solution, and gives detailed implementation mode and specific operation process, but the protection scope of the present application is not limited to the present embodiment.

[0039] Example 1

[0040] This embodiment provides a method for efficiently preparing aluminum nitride from aluminum ash, such as... Figure 1 As shown, it includes the following steps:

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

[0042] S2, Preheating I: Preheat the fine ash obtained in step S1 to obtain hot fine ash.

[0043] S3. Chlorination: High-temperature chlorine gas is used to chlorinate and denitrify the hot fine ash obtained in step S2, resulting in high-temperature chlorinated flue gas and hot chlorinated slag. The high-temperature chlorinated flue gas is sent to the preheating step I of step S2 for heat exchange and preheating of the fine ash. After heat exchange, the low-temperature chlorinated flue gas is sent to the condensation and recovery step S7. In the chlorination and denitrification process, the temperature is 400℃ and the time is 1h. The reactor is a fluidized bed reactor, which contains spherical zirconium oxide particles with a particle size of 3mm for auxiliary fluidization and heat storage.

[0044] S4. Heat exchange and cooling: The hot chlorinated slag obtained in step S3 is cooled by heat exchange using room temperature chlorine gas to obtain cold chlorinated slag and hot chlorine gas. The hot chlorine gas is sent to the combustion preheating step I in step S5.

[0045] S5. Combustion preheating I: The hot chlorine gas obtained in step S4 is heated by the combustion of air and fuel to obtain high-temperature chlorine gas and combustion tail gas I. The high-temperature chlorine gas is sent to the chlorination process in step S3.

[0046] S6. Washing and drying: The cold chlorination residue obtained in step S4 is washed and dried with deionized water to obtain washing liquid and tailings.

[0047] S7. Condensation and recovery: The low-temperature chlorinated flue gas obtained after heat exchange and preheating of fine ash is condensed at a temperature of 20°C to obtain chlorine, nitrogen and solid aluminum chloride. The chlorine and nitrogen are sent to the separation process in step S8.

[0048] S8. Separation: Separate the chlorine and nitrogen obtained in step S7 to obtain circulating chlorine I and circulating nitrogen. Circulating chlorine I is sent to the heat exchange and cooling process in step S4 to cool the hot chlorinated slag. Circulating nitrogen is sent to the nitriding II process in step S15.

[0049] S9. Gasification: The solid aluminum chloride obtained in step S7 is gasified to obtain gaseous aluminum chloride;

[0050] S10, Combustion Preheating II: The gaseous aluminum chloride obtained in S9 is heated by the combustion of air and fuel to obtain high-temperature aluminum chloride and combustion exhaust gas II;

[0051] S11, preheating II: the magnesium nitride is preheated to obtain hot magnesium nitride, and the hot magnesium nitride is sent to the nitriding I process of step S12; the particle size of the hot magnesium nitride is <1 μm.

[0052] S12, nitriding I: the high-temperature aluminum chloride obtained in step S10 is used for nitriding reaction with the hot magnesium nitride obtained in step S11 to obtain nitride and high-temperature nitriding flue gas, and the high-temperature nitriding flue gas is sent to the heat exchange preheating II process of step S11 to be used for heat exchange preheating of the magnesium nitride; wherein the nitriding reaction temperature is 450 ℃, the nitriding reaction time is 1 h, and the nitriding reaction reactor is a fluidized bed reactor, and the fluidized bed reactor is provided with spherical aluminum oxide particles with a particle size of 0.5 mm to assist fluidization and heat storage.

[0053] S13, crystallization: the nitride obtained in step S12 is crystallized and purified at a crystallization temperature of 1500 ℃ for 2 h to obtain aluminum nitride and magnesium chloride;

[0054] S14, electrolysis: the magnesium chloride obtained in step S13 is electrolyzed to obtain magnesium and recycled chlorine gas II, and the recycled chlorine gas II is sent to the heat exchange cooling process of step S4 to be used for heat exchange cooling of the hot chlorination slag;

[0055] S15, nitriding II: the magnesium obtained in step S14 is nitrided by using nitrogen and the recycled nitrogen gas obtained in step S8 at a nitriding temperature of 400 ℃ for 1 h to obtain recycled nitriding magnesium, and the recycled nitriding magnesium is sent to the heat exchange preheating II process of step S12 to be used for nitriding reaction with the high-temperature aluminum chloride.

[0056] Example 2

[0057] The method flow of the embodiment is basically the same as that of example 1, and the difference lies in that in step S3, the chlorination denitriding temperature is 600 ℃, the chlorination denitriding time is 0.1 h, and the fluidized bed reactor of the chlorination reaction is provided with spherical zirconium oxide particles with a particle size of 0.5 mm; in step S7, the condensation temperature is 170 ℃; in step S12, the nitriding reaction temperature is 650 ℃, the nitriding reaction time is 0.1 h, and the fluidized bed reactor of the nitriding reaction is provided with spherical aluminum oxide particles with a particle size of 3 mm; in step S13, the crystallization temperature is 1700 ℃, and the crystallization time is 0.5 h; and in step S15, the nitriding temperature is 600 ℃, and the nitriding time is 0.1 h.

[0058] Example 3

[0059] The method flow of the embodiment is basically the same as that of Embodiment 1, except that in step S3, the chlorination denitrogenation temperature is 500℃, the chlorination denitrogenation time is 0.5h, and the fluidized bed reactor for the chlorination reaction is provided with spherical alumina particles with a particle size of 0.5mm; in step S7, the condensation temperature is 100℃; in step S12, the nitridation reaction temperature is 550℃, the nitridation reaction time is 0.4h, and the fluidized bed reactor for the nitridation reaction is provided with spherical zirconia particles with a particle size of 3mm; in step S13, the crystallization temperature is 1600℃, and the crystallization time is 0.9h; and in step S15, the nitridation temperature is 500℃, and the nitridation time is 0.6h.

[0060] Embodiment 4

[0061] The method flow of the embodiment is basically the same as that of Embodiment 1, except that in step S3, the chlorination denitrogenation temperature is 530℃, the chlorination denitrogenation time is 0.4h, and the fluidized bed reactor for the chlorination reaction is provided with spherical alumina particles with a particle size of 3mm; in step S7, the condensation temperature is 80℃; in step S12, the nitridation reaction temperature is 480℃, the nitridation reaction time is 0.7h, and the fluidized bed reactor for the nitridation reaction is provided with spherical zirconia particles with a particle size of 0.5mm; in step S13, the crystallization temperature is 1580℃, and the crystallization time is 1.1h; and in step S15, the nitridation temperature is 530℃, and the nitridation time is 0.5h.

[0062] Embodiment 5

[0063] The method flow of the embodiment is basically the same as that of Embodiment 1, except that in step S3, the chlorination denitrogenation temperature is 450℃, the chlorination denitrogenation time is 0.8h, and the fluidized bed reactor for the chlorination reaction is provided with spherical alumina particles with a particle size of 1.5mm; in step S7, the condensation temperature is 70℃; in step S12, the nitridation reaction temperature is 580℃, the nitridation reaction time is 0.3h, and the fluidized bed reactor for the nitridation reaction is provided with spherical zirconia particles with a particle size of 1.5mm; in step S13, the crystallization temperature is 1550℃, and the crystallization time is 1.6h; and in step S15, the nitridation temperature is 570℃, and the nitridation time is 0.3h.

[0064] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all these changes and modifications shall be included in the protection scope of the claims of the present application.

Claims

1. A method for efficient production of aluminum nitride from aluminum dross, characterized by: The method comprises the following steps: S1, grinding: grinding aluminum ash into fine powder to obtain fine ash; S2, preheating I: preheating the fine ash obtained in step S1 to obtain hot fine ash; S3, chlorination: using high-temperature chlorine to chlorinate and denitrogenate the hot fine ash obtained in step S2 to obtain high-temperature chlorination flue gas and hot chlorination residue; the high-temperature chlorination flue gas is sent to the preheating I process of step S2 to heat and preheat the fine ash, and the low-temperature chlorination flue gas after heat exchange is sent to the condensation recovery process of step S7; the chlorination and denitrogenation temperature is 400-600℃, and the time is 0.1-1h; the chlorination and denitrogenation reactor is a fluidized bed reactor, and inert oxides are arranged in the fluidized bed reactor to assist fluidization and heat storage; the inert oxides are one or a combination of spherical aluminum oxide particles and spherical zirconium oxide particles, and the particle size of the inert oxides is 0.5-3mm; S4, heat exchange cooling: using normal temperature chlorine to heat exchange and cool the hot chlorination residue obtained in step S3 to obtain cold chlorination residue and hot chlorine, and the hot chlorine is sent to the combustion preheating I process of step S5; S5, combustion preheating I: heating the hot chlorine obtained in step S4 by combustion of air and fuel to obtain high-temperature chlorine and combustion tail gas I, and the high-temperature chlorine is sent to the chlorination process of step S3; S6, water washing and drying: using deionized water to wash and dry the cold chlorination residue obtained in step S4 to obtain washing liquid and tail residue; S7, condensation recovery: condensing the low-temperature chlorination flue gas obtained after heat exchange preheating of the fine ash to obtain chlorine, nitrogen and solid phase chlorinated aluminum, and the chlorine and nitrogen are sent to the separation process of step S8; S8, separation: separating the chlorine and nitrogen obtained in step S7 to obtain circulating chlorine I and circulating nitrogen, and the circulating chlorine I is sent to the heat exchange cooling process of step S4 to heat and cool the hot chlorination residue, and the circulating nitrogen is sent to the nitriding II process of step S15; S9, gasification: gasifying the solid phase chlorinated aluminum obtained in step S7 to obtain gas phase chlorinated aluminum; S10, combustion preheating II: heating the gas phase chlorinated aluminum obtained in S9 by combustion of air and fuel to obtain high-temperature chlorinated aluminum and combustion tail gas II; S11, preheating II: preheating the magnesium nitride to obtain hot magnesium nitride, and the hot magnesium nitride is sent to the nitriding I process of step S12; S12, nitriding I: using the high-temperature chlorinated aluminum obtained in step S10 and the hot magnesium nitride obtained in step S11 to carry out nitriding reaction to obtain nitride and high-temperature nitriding flue gas, and the high-temperature nitriding flue gas is sent to the heat exchange preheating II process of step S11 to heat and preheat the magnesium nitride; the particle size of the hot magnesium nitride is <1μm, the nitriding reaction temperature is 450-650℃, the nitriding reaction time is 0.1-1h, and the nitriding reaction reactor is a fluidized bed reactor, and inert oxides are arranged in the fluidized bed reactor to assist fluidization and heat storage; the inert oxides are one or a combination of spherical aluminum oxide particles and spherical zirconium oxide particles, and the particle size of the inert oxides is 0.5-3mm; S13, crystallization: crystallizing and purifying the nitride obtained in step S12 to obtain aluminum nitride and magnesium chloride; S14, electrolysis: electrolyzing the magnesium chloride obtained in step S13 to obtain magnesium and recycled chlorine II, the recycled chlorine II being sent to the heat exchange and cooling process in step S4 to be used for heat exchange and cooling of the hot chlorination residue; S15, nitriding II: nitriding the magnesium obtained in step S14 by using nitrogen and the recycled nitrogen obtained in step S8 to obtain recycled nitriding magnesium, the recycled nitriding magnesium being sent to the heat exchange and preheating II process in step S12 to react with the high-temperature aluminum chloride.

2. The method of claim 1, wherein, In step S1, the particle size of the fine ash is <1 μm.

3. The method of claim 1, wherein, In step S7, the condensing temperature is 20-170 ℃.

4. The method of claim 1, wherein, In steps S2 and S11, the preheating is performed by using indirect heat exchange.

5. The method of claim 1, wherein, In step S15, the nitriding temperature is 400-600 ℃, and the nitriding time is 0.1-1 h.

6. The method of claim 1, wherein, In step S13, the crystallization temperature is 1500-1700 ℃, and the crystallization time is 0.5-2 h.

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