CN115354170A - Method for preparing magnesium metal by using aluminum ash as reducing agent - Google Patents

Abstract

The invention belongs to the technical field of metal smelting. The invention provides a method for preparing metal magnesium by using aluminum ash as a reducing agent, which comprises the following steps: calcining and crushing magnesite in sequence to obtain caustic magnesite particles; mixing and grinding aluminum ash and caustic magnesite particles to obtain a mixture, and carrying out reduction reaction on the mixture to obtain magnesium vapor and reduced furnace slag; cooling the magnesium vapor to obtain the metal magnesium. The method adopts the aluminum ash as a reducing agent, reduces the treatment cost of the aluminum ash, changes the aluminum ash into a valuable industrial raw material, and is applied to the high-magnesium smelting process to realize the resource utilization of the solid waste aluminum ash; compared with the traditional silicothermic method, the cost of the reducing agent is reduced by more than 40 percent; the reduction period is shortened to be within 3 hours from 10-12 hours of the traditional silicothermic method, the smelting temperature is obviously lower than that of the conventional magnesium smelting process, the energy consumption is greatly reduced, the production efficiency is improved, and the problem that the reducing slag can not be treated is solved.

Description

A method for preparing magnesium metal with aluminum ash as reducing agent

technical field

The invention relates to the technical field of metal smelting, in particular to a method for preparing metallic magnesium by using aluminum ash as a reducing agent.

Background technique

Magnesium has attracted much attention as a strategic resource since its discovery. At the same time, magnesium, as a new type of structural material, is playing an increasingly important role in the fields of aerospace, military industry, and transportation lightweight. The application fields and markets of magnesium and magnesium products will have wider and faster development; with the continuous expansion of magnesium applications, its demand is also increasing.

At present, the main production process of primary magnesium in the world is silicothermal method, commonly known as Pidgeon method, and more than 95% of primary magnesium in my country is produced by Pidgeon method. The Pidgeon method mainly uses dolomite as raw material, ferrosilicon as reducing agent, and fluorite as mineralizing agent. After crushing, mixing, pelletizing and other processes, metal magnesium is obtained under high temperature and high vacuum conditions. However, the silicothermal method has problems such as long production cycle (10-12 hours), high cost of reducing agent (ferrosilicon 6000-8000 yuan/ton), difficulty in using reducing slag, low production efficiency, and high carbon emissions. Can not meet the requirements of sustainable development. The prior art discloses a new type of magnesium smelting process, which completes the calcination and reduction process of raw materials in one step, improves the utilization rate of raw materials, and reduces the cost, but the problems of high cost of ferrosilicon and difficult handling of reduced slag have not been solved. The prior art proposes a process for carbothermally reducing magnesium with a vacuum induction furnace. Although the cost of raw materials is reduced, the carbon monoxide generated during the reaction is prone to reverse reaction with the produced magnesium, and the produced magnesium powder is prone to explosion, which is difficult to produce. applied to actual production. Invention patent CN 110512094 A discloses a process for clean and continuous reduction of metal magnesium. The process has high thermal efficiency, low power consumption, fast heating speed and strong controllability. However, the process uses aluminum powder as the reducing agent, and the cost is relatively high , not suitable for industrial production.

All aluminum production and aluminum alloy smelting processes in the aluminum industry will produce aluminum ash and aluminum slag by-products, which are hazardous solid waste. Invention patent CN 112442598 A discloses a method for recycling aluminum ash, but the process of the invention is complicated, the actual operation is difficult, and it is not suitable for large-scale production. The invention patent of Beijing University of Science and Technology CN 113089028 A discloses a method for producing aluminum alloys using recycled aluminum alloy ash as a raw material. This method can recycle aluminum alloy recycled ash and reduce the production cost of aluminum alloys. Electrolysis process, high energy consumption. The above process method only recycles the elements in the aluminum ash, and does not take into account the comprehensive utilization of metal aluminum contained in the aluminum ash.

Therefore, it is of great significance to improve the existing magnesium smelting process by converting aluminum ash into usable resources, and to establish a new green magnesium smelting process with low energy consumption, low carbon emission, and no waste residue.

Contents of the invention

The purpose of the present invention is to provide a method for preparing magnesium metal using aluminum ash as a reducing agent in view of the deficiencies of the prior art, to recycle industrial solid waste aluminum ash, and to apply it as a reducing agent in the magnesium smelting process , in order to solve the problems of high cost of reducing agent, high reduction reaction temperature, long production cycle, high energy consumption and difficult treatment of reducing slag existing in the existing magnesium smelting process.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a method for preparing metallic magnesium with aluminum ash as a reducing agent, comprising the following steps:

1) sequentially calcining and crushing the magnesite to obtain caustic magnesite particles;

2) After mixing aluminum ash and caustic magnesite particles and grinding them to obtain a mixture, the mixture is subjected to a reduction reaction to obtain magnesium vapor and reduced slag;

3) The magnesium vapor is cooled to obtain metallic magnesium.

Preferably, the calcining temperature in step 1) is 1100-1300° C., the calcining time is 40-80 min, and the particle size of the caustic magnesite particles is ≤150 μm.

Preferably, in step 2), the mass ratio of aluminum ash to caustic magnesite particles is 1-3:1.

Preferably, in step 2), aluminum ash, caustic magnesite particles and quicklime are mixed; the mass ratio of quicklime to aluminum ash is 1˜2:1.

Preferably, in the aluminum ash in step 2), the mass fraction of aluminum is ≥15%; the particle size of the mixture is ≤150 μm.

Preferably, in step 2), the mixture is press-molded to obtain balls and then reduction reaction is performed, the mass of each ball is 4-6g, and the pressure of the press-molding is 80-120 MPa.

Preferably, the reduction reaction temperature in step 2) is 950-1250° C., the reduction reaction time is 50-180 minutes, and the heating rate to the reduction reaction temperature is 3-7° C./min.

Preferably, the reduction reaction is carried out under normal pressure, an inert atmosphere or in a vacuum state; when the reduction reaction is carried out in a vacuum state, the degree of vacuum is 5 to 15 Pa, and the temperature of the reduction reaction is 950 to 1050 ° C; when the reduction reaction When carried out under normal pressure and inert atmosphere, the temperature of the reduction reaction is 1150-1250°C.

Preferably, the cooling in step 3) is condensation or crystallization.

The beneficial effects of the present invention include the following points:

1) The present invention uses aluminum ash as a reducing agent, reduces the processing cost of aluminum ash, turns aluminum ash into a valuable industrial raw material, and realizes the resource utilization of solid waste aluminum ash in the application of high-magnesium smelting process, which has great significance Economic value and environmental significance.

2) Compared with the traditional silicon thermal method, the reducing agent cost is reduced by more than 40%, the reduction period is shortened from 10 to 12 hours in the traditional silicon thermal method to within 3 hours, and the smelting temperature is significantly lower than the conventional magnesium smelting process, which is extremely It greatly reduces energy consumption, improves production efficiency, and solves the problem that the reduction slag cannot be processed.

3) The method of the present invention not only reduces the smelting cost, but also reduces the processing cost of aluminum ash, which is a green production process; the reduced slag is calcium aluminate or Al ₂ O ₃ with high industrial value, which can be recycled; The method of the invention can be directly applied to the original Pidgeon method production equipment without changing the equipment, and has universal applicability.

Detailed ways

The invention provides a method for preparing metallic magnesium with aluminum ash as a reducing agent, comprising the following steps:

1) sequentially calcining and crushing the magnesite to obtain caustic magnesite particles;

2) After mixing aluminum ash and caustic magnesite particles and grinding them to obtain a mixture, the mixture is subjected to a reduction reaction to obtain magnesium vapor and reduced slag;

3) The magnesium vapor is cooled to obtain metallic magnesium.

In the present invention, the calcining temperature in step 1) is preferably 1100-1300°C, more preferably 1150-1250°C, more preferably 1200°C; the calcining time is preferably 40-80min, more preferably 45-75min, more preferably It is preferably 50-70 min; the particle size of the caustic magnesite particles is preferably ≤150 μm, more preferably ≤130 μm, more preferably ≤120 μm.

In the present invention, the main component of caustic magnesite is MgO.

In step 2) of the present invention, the mass ratio of aluminum ash to caustic magnesite particles is preferably 1-3:1, more preferably 1.5-2.5:1, more preferably 2:1.

In the present invention, the aluminum ash is a reducing agent, and the aluminum ash is preferably the waste slag produced in the smelting process of electrolytic aluminum, aluminum and aluminum alloy; the aluminum ash is preferably pretreated before mixing, and the pretreatment preferably includes drying treatment, harmful gas deal with.

In step 2) of the present invention, it is preferred to mix aluminum ash, caustic magnesite particles and quicklime; the mass ratio of quicklime to aluminum ash is preferably 1-2:1, more preferably 1.2-1.8:1, more preferably It is 1.4～1.6:1.

In the present invention, the mass fraction of aluminum in the aluminum ash in step 2) is preferably ≥ 15%, more preferably ≥ 20%, more preferably ≥ 25%; the particle size of the mixture is preferably ≤ 150 μm, more preferably ≤ 130 μm, more preferably Preferably ≤ 120 μm.

In the present invention, the mixture in step 2) is preferably press-molded to obtain balls and then subjected to a reduction reaction. The mass of each ball is preferably 4-6g, more preferably 4.5-5.5g, and more preferably 5g; The pressure of press molding is preferably 80-120 MPa, more preferably 90-110 MPa, more preferably 100 MPa.

In the present invention, the temperature of the reduction reaction in step 2) is preferably 950-1250°C, more preferably 1000-1200°C, more preferably 1050-1150°C; the time of the reduction reaction is preferably 50-180min, more preferably 60 min ~150min, more preferably 80~140min; the heating rate to the reduction reaction temperature is preferably 3~7°C/min, more preferably 4~6°C/min, more preferably 5°C/min.

In the present invention, the reduction reaction is preferably carried out at normal pressure, under an inert atmosphere or in a vacuum state; when the reduction reaction is carried out in a vacuum state, the degree of vacuum is preferably 5-15Pa, more preferably 8-12Pa, more preferably 10Pa; the temperature of the reduction reaction is preferably 950-1050°C, more preferably 970-1030°C, more preferably 1000-1010°C; when the reduction reaction is carried out under normal pressure and inert atmosphere, the temperature of the reduction reaction is preferably 1150°C ~1250°C, more preferably 1170~1220°C, more preferably 1180~1200°C.

In the present invention, the temperature of the reduction reaction preferably changes with the change of the pressure; the time of the reduction reaction is greatly affected by the amount of material charged.

In the present invention, the cooling in step 3) is preferably condensation or crystallization.

In the present invention, the magnesium vapor is condensed to obtain liquid magnesium, the magnesium vapor is crystallized to obtain solid crystalline magnesium, and metallic magnesium is collected in the form of liquid magnesium or crystalline magnesium; the condensation is carried out in a condenser, and the liquid magnesium is refined or directly formed , to obtain magnesium ingots; the crystallization is carried out in a crystallizer, and the form of crystallized magnesium is affected by the degree of vacuum.

In step 2) of the present invention, when the raw materials are aluminum ash and caustic magnesite particles, the reduced slag is aluminum oxide; when the raw materials are aluminum ash, caustic magnesite particles and quicklime, the reduced slag is calcium aluminate; The reduced slag is recycled after cooling.

The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be interpreted as limiting the protection scope of the present invention.

Example 1

The magnesite with uniform particle size is calcined in a muffle furnace, the calcination temperature is 1200°C, and the calcination time is 60 minutes. After the calcination is completed, it is crushed with a crusher to obtain caustic magnesite particles with a particle size of less than 150 μm. Using the aluminum ash produced in the electrolytic aluminum process (in the aluminum ash, the mass fraction of metal aluminum is 25%) as the reducing agent, the aluminum ash and caustic magnesite particles with a mass ratio of 2:1 are mixed and ground to obtain the particle size Homogeneous mixture less than 150μm.

The mixture was placed in a briquetting mold, and pressed at 100 MPa to form 5 g/balls. Put the pellets in the reduction furnace, evacuate and maintain a pressure of 10Pa, raise the temperature to 1000°C at a rate of 5°C/min, and keep it at 1000°C for 60 minutes to obtain magnesium vapor and reduction slag, and the magnesium vapor is crystallized in the magnesium crystallizer , to obtain crystalline magnesium.

The crystalline magnesium in this embodiment has high purity, the recovery rate of metal magnesium is above 87%, and the main component of the reduced slag is Al ₂ O ₃ .

Example 2

The magnesite with uniform particle size is calcined in a muffle furnace, the calcination temperature is 1200°C, and the calcination time is 60 minutes. After the calcination is completed, it is crushed with a crusher to obtain caustic magnesite particles with a particle size of less than 150 μm. Using the aluminum ash produced in the electrolytic aluminum process (in the aluminum ash, the mass fraction of metal aluminum is 25%) as the reducing agent, the aluminum ash and caustic magnesite particles with a mass ratio of 2:1 are mixed and ground to obtain the particle size Homogeneous mixture less than 150μm.

The mixture was placed in a briquetting mold, and pressed at 100 MPa to form 5 g/balls. Put the material ball in the reduction furnace, feed argon to maintain normal pressure, raise the temperature to 1200°C at a rate of 5°C/min, and keep it at 1200°C for 60 minutes to obtain magnesium vapor and reduction slag, and the magnesium vapor is crystallized in the magnesium crystallizer , to obtain crystalline magnesium.

The crystalline magnesium in this embodiment has high purity, the recovery rate of metal magnesium is above 81%, and the main component of the reduced slag is Al ₂ O ₃ .

Example 3

The magnesite with uniform particle size is calcined in a muffle furnace, the calcination temperature is 1200°C, and the calcination time is 60 minutes. After the calcination is completed, it is crushed with a crusher to obtain caustic magnesite particles with a particle size of less than 150 μm. Using the aluminum ash produced in the electrolytic aluminum process (in the aluminum ash, the mass fraction of metal aluminum is 25%) as the reducing agent, the aluminum ash, caustic magnesite particles, and quicklime with a mass ratio of 2:1:2 are mixed and ground , to obtain a uniform mixture with a particle size of less than 150 μm.

The mixture was placed in a briquetting mold, and pressed at 100 MPa to form 5 g/balls. Put the pellets in the reduction furnace, evacuate and maintain a pressure of 10Pa, raise the temperature to 1000°C at a rate of 5°C/min, and keep it at 1000°C for 180min to obtain magnesium vapor and reduction slag, and the magnesium vapor is crystallized in the magnesium crystallizer , to obtain crystalline magnesium.

The crystalline magnesium in this embodiment has high purity, the recovery rate of metal magnesium is above 91%, and the main component of the reduction slag is calcium aluminate.

Example 4

The magnesite with uniform particle size is calcined in a muffle furnace, the calcination temperature is 1200°C, and the calcination time is 60 minutes. After the calcination is completed, it is crushed with a crusher to obtain caustic magnesite particles with a particle size of less than 150 μm. Using the aluminum ash produced in the electrolytic aluminum process (in the aluminum ash, the mass fraction of metal aluminum is 25%) as the reducing agent, the aluminum ash, caustic magnesite particles, and quicklime with a mass ratio of 2:1:2 are mixed and ground , to obtain a uniform mixture with a particle size of less than 150 μm.

The mixture was placed in a briquetting mold, and pressed at 100 MPa to form 5 g/balls. Put the material ball in the reduction furnace, feed argon to maintain normal pressure, raise the temperature to 1200°C at a rate of 5°C/min, and keep it at 1200°C for 180min to obtain magnesium vapor and reduction slag, and the magnesium vapor is crystallized in the magnesium crystallizer , to obtain crystalline magnesium.

The crystalline magnesium in this embodiment has high purity, the recovery rate of metallic magnesium is above 85%, and the main component of the reduced slag is calcium aluminate.

Example 5

The magnesite with uniform particle size is calcined in a muffle furnace, the calcination temperature is 1120°C, and the calcination time is 70 minutes. After the calcination is completed, it is crushed with a crusher to obtain caustic magnesite particles with a particle size of less than 135 μm. The aluminum ash produced in the aluminum alloy smelting process (in the aluminum ash, the mass fraction of metal aluminum is 18%) is used as the reducing agent, and the aluminum ash is used after drying treatment, and the aluminum ash and caustic magnesite with a mass ratio of 1.7:1 are used The ore particles are mixed and then ground to obtain a uniform mixture with a particle size of less than 135 μm.

Put the mixture in the reduction furnace, evacuate and maintain a pressure of 7Pa, raise the temperature to 980°C at a rate of 4°C/min, and keep it at 980°C for 100min to obtain magnesium vapor and reduced slag, and the magnesium vapor is condensed in the condenser to liquid magnesium.

The liquid magnesium in this embodiment has high purity, the recovery rate of metal magnesium is above 92%, and the main component of the reduced slag is Al ₂ O ₃ .

Example 6

The magnesite with uniform particle size is calcined in a muffle furnace, the calcination temperature is 1250°C, and the calcination time is 50 minutes. After the calcination is completed, it is crushed with a crusher to obtain caustic magnesite particles with a particle size of less than 125 μm. The aluminum ash produced in the aluminum smelting process (in the aluminum ash, the mass fraction of metal aluminum is 22%) is used as the reducing agent, and the aluminum ash is used after drying treatment. The magnesium ore particles and quicklime are mixed and then ground to obtain a uniform mixture with a particle size of less than 125 μm.

The mixture was placed in a briquetting mold, and pressed at 110 MPa to form 5.5 g/balls. Put the material ball in the reduction furnace, feed argon to maintain normal pressure, raise the temperature to 1170°C at a rate of 6°C/min, and keep it at 1170°C for 140 minutes to obtain magnesium vapor and reduction slag, and the magnesium vapor is crystallized in the magnesium crystallizer , to obtain crystalline magnesium.

The crystalline magnesium in this embodiment has high purity, the recovery rate of metal magnesium is above 90%, and the main component of the reduction slag is calcium aluminate.

The present invention uses aluminum ash as a reducing agent, reduces the processing cost of aluminum ash, turns aluminum ash into a valuable industrial raw material, and applies it to the high-magnesium smelting process to realize resource utilization of solid waste aluminum ash; the method of the present invention Compared with the traditional silicon thermal method, the cost of the reducing agent is reduced by more than 40%, the reduction period is shortened from 10 to 12 hours of the traditional silicon thermal method to less than 3 hours, and the smelting temperature is significantly lower than the conventional magnesium smelting process, which greatly reduces energy consumption , improve the production efficiency, and solve the problem that the reducing slag cannot be processed; the method of the invention can be directly applied to the original Pidgeon method production equipment without changing the equipment, and has universal applicability.

The above is only a preferred embodiment of the present invention, and it should be pointed out that for those of ordinary skill in the art, some improvements and modifications can also be made without departing from the principles of the present invention. It should be regarded as the protection scope of the present invention.

Claims (9)

1. a method for preparing magnesium metal with aluminum ash as reducing agent, is characterized in that, comprises the steps: 1) sequentially calcining and crushing the magnesite to obtain caustic magnesite particles; 2) After mixing aluminum ash and caustic magnesite particles and grinding them to obtain a mixture, the mixture is subjected to a reduction reaction to obtain magnesium vapor and reduced slag; 3) The magnesium vapor is cooled to obtain metallic magnesium. 2. The method according to claim 1, characterized in that in step 1), the calcining temperature is 1100-1300° C., the calcining time is 40-80 min, and the particle size of the caustic magnesite particles is ≤150 μm. 3. The method according to claim 1, characterized in that, in step 2), the mass ratio of aluminum ash and caustic magnesite particles is 1-3:1. 4. The method according to claim 1, characterized in that, in step 2), aluminum ash, caustic magnesite particles and quicklime are mixed; the mass ratio of quicklime and aluminum ash is 1-2:1. 5. The method according to claim 3 or 4, characterized in that, in the aluminum ash in step 2), the mass fraction of aluminum is ≥ 15%; the particle size of the mixture is ≤ 150 μm. 6. The method according to claim 3 or 4, characterized in that, in step 2) the mixture is press-molded to obtain balls and then the reduction reaction is carried out, the mass of each ball is 4-6g, and the press-molded The pressure is 80 ~ 120MPa. 7. The method according to claim 1 or 4, characterized in that the temperature of the reduction reaction in step 2) is 950 to 1250° C., the time of the reduction reaction is 50 to 180 min, and the heating rate to the reduction reaction temperature is 3～7℃/min. 8. The method according to claim 7, characterized in that the reduction reaction is carried out under normal pressure, an inert atmosphere or in a vacuum state; when the reduction reaction is carried out in a vacuum state, the degree of vacuum is 5 to 15 Pa, and the reduction The reaction temperature is 950-1050°C; when the reduction reaction is carried out under normal pressure and inert atmosphere, the reduction reaction temperature is 1150-1250°C. 9. The method according to claim 8, characterized in that the cooling in step 3) is condensation or crystallization.