CN110669926B

CN110669926B - Magnesium smelting method

Info

Publication number: CN110669926B
Application number: CN201911118877.XA
Authority: CN
Inventors: 车玉思; 宋建勋; 买耕鹏; 何季麟
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2019-11-15
Filing date: 2019-11-15
Publication date: 2021-05-25
Anticipated expiration: 2039-11-15
Also published as: CN110669926A

Abstract

The embodiment of the application discloses a magnesium smelting method, which comprises the following steps: (1) mixing a magnesium-containing raw material, a reducing agent, a mineralizer and a pore-forming agent according to a certain proportion to obtain a raw material mixture; (2) pressing and forming the raw material mixture under the pressure of 50-300 MPa to obtain raw material pellets; (3) carrying out heat treatment on the raw material pellets at the temperature of not higher than 1000 ℃, and preserving heat for a certain time to obtain porous pellets; (4) the porous pellets are subjected to chemical reaction at the temperature of more than 1100 ℃ to generate magnesium vapor; (5) and the magnesium vapor enters a low-temperature area to be condensed to obtain the crystallized magnesium. The magnesium smelting method disclosed by the embodiment of the application effectively improves the diffusion rate of magnesium vapor in the pellet, shortens the time for the chemical reaction to reach the balance, improves the chemical reaction rate and the magnesium reduction efficiency, shortens the reduction period, reduces the energy consumption, improves the production efficiency and reduces the production cost.

Description

Magnesium smelting method

Technical Field

The application belongs to the technical field of metal smelting, and particularly relates to a magnesium smelting method.

Background

At present, 85 percent of raw magnesium in the world is produced in China, and raw magnesium smelting in China mainly depends on the Pidgeon method for production. Pidgeon process belongs to silicothermic process, using 75 ferrosilicon as reducing agent, dolomite as raw material and fluorite as mineralizing agent to produce magnesium metal, and its reduction tank is horizontally placed. The process comprises the steps of firstly, crushing, mixing, grinding and pressing smelted raw materials (calcined dolomite, ferrosilicon, fluorite and the like) into material balls, then adding the material balls into a reduction tank, heating the material balls from the outside of the reduction tank, and transferring heat to the material balls along the wall of the tank. Meanwhile, a vacuum pump is used for vacuumizing the reduction tank, so that material balls in the tank are subjected to reduction reaction under the conditions of high temperature and vacuum, generated magnesium steam is condensed into crude magnesium in a crystallizer, and the crude magnesium is refined and cast into commercial magnesium. The reduction process in the reduction tank is carried out under the vacuum condition, heat is transferred to the material balls from the wall of the reduction tank and then transferred among the material balls, and when the temperature of the material balls reaches the reaction temperature, the raw materials start to carry out chemical reaction to generate magnesium vapor. But the generated magnesium vapor has larger escape resistance from the interior of the material ball, and the chemical process is slowed down, so that the reduction efficiency is influenced, the reduction period of the smelting process is long (generally 10-12 hours), and the production efficiency is low.

Disclosure of Invention

In order to solve at least one of the above-mentioned technical problems of the prior art, an embodiment of the present application discloses a magnesium smelting method, which includes:

(1) mixing a magnesium-containing raw material, a reducing agent, a mineralizer and a pore-forming agent according to a certain proportion to obtain a raw material mixture;

(2) pressing and forming the raw material mixture under the pressure of 50-300 MPa to obtain raw material pellets;

(3) carrying out heat treatment on the raw material pellets at the temperature of not higher than 1000 ℃, and preserving heat for a certain time to obtain porous pellets;

(4) the porous pellets are subjected to chemical reaction at the temperature of more than 1100 ℃ to generate magnesium vapor;

(5) and the magnesium vapor enters a low-temperature area for condensation to obtain the crystallized magnesium.

Further, some embodiments disclose the magnesium smelting process wherein the magnesium-containing feedstock comprises one or a combination of dolomite, magnesite, calcined dolomite or magnesium oxide.

In some embodiments, the reducing agent comprises a silicon-containing reducing agent, wherein the amount of silicon-containing reducing agent to magnesium-containing raw material is based on a molar ratio M_Si:M_2MgOThe silicon-containing reducing agent is determined to be 1.0-1.5, and specifically comprises one or a combination of more of ferrosilicon, silicon-aluminum alloy and silicon-aluminum-iron alloy.

In some embodiments disclosed herein, the reducing agent comprises a carbonaceous reducing agent, wherein the amount of carbonaceous reducing agent to magnesium-containing feedstock is in accordance with a molar ratio M_C:M_MgOThe carbon-containing reducing agent is determined to be 1.0-4.5, and specifically comprises calcium carbide and a carbonaceous reducing agent.

Some embodiments disclose a magnesium smelting method, wherein the reducing agent comprises calcium or calcium alloy, and the amount of the calcium or calcium alloy and the magnesium-containing raw material is based on the molar ratio M_Ca:M_MgDetermined as 1.1-1.5.

Some embodiments disclose a magnesium smelting method, wherein the pore-forming agent has a pyrolysis temperature not higher than 1000 ℃, and the pore-forming agent specifically comprises one or more of inorganic ammonium salt, carbonate, chloride salt, plant debris, rice hull, starch, urea, polypropylene carbonate, dextrin and sucrose.

Further, some embodiments disclose the magnesium smelting method, wherein the volume content of the pore-forming agent is not more than 50%, and the particle size of the pore-forming agent is less than 3 mm.

Some examples disclose magnesium smelting processes in which the heat treatment of the raw material pellets is performed under vacuum conditions, or under air, argon, nitrogen atmosphere, or a mixture of atmospheres.

Some examples disclose magnesium smelting processes in which the chemical reaction of the porous pellets is carried out under vacuum conditions, or in a stream of argon gas.

In some embodiments, the magnesium smelting method is disclosed, wherein the content of the mineralizer is set to be 1-5%.

The magnesium smelting method disclosed by the embodiment of the application effectively improves the diffusion rate of magnesium vapor in the raw material pellets, shortens the time for the chemical reaction to reach the balance, improves the chemical reaction rate and the magnesium reduction efficiency, shortens the smelting period, reduces the energy consumption, improves the production efficiency and reduces the production cost.

Drawings

FIG. 1 shows the magnesium reduction curve corresponding to the pellet sample

1# represents the pellet sample of comparative example 1

2# pellet sample of example 1

Detailed Description

The word "embodiment" as used herein, is not necessarily to be construed as preferred or advantageous over other embodiments, including any embodiment illustrated as "exemplary". Performance index tests in the examples of this application, unless otherwise indicated, were performed using routine experimentation in the art. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; other test methods and techniques not specifically mentioned in the present application are those commonly employed by those of ordinary skill in the art.

The terms "substantially" and "about" are used throughout this disclosure to describe small fluctuations. For example, they may mean less than or equal to ± 5%, such as less than or equal to ± 2%, such as less than or equal to ± 1%, such as less than or equal to ± 0.5%, such as less than or equal to ± 0.2%, such as less than or equal to ± 0.1%, such as less than or equal to ± 0.05%. Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. Such range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of "1 to 5%" should be interpreted to include not only the explicitly recited values of 1% to 5%, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values, such as 2%, 3.5%, and 4%, and sub-ranges, such as 1% to 3%, 2% to 4%, and 3% to 5%, etc. This principle applies equally to ranges reciting only one numerical value. Moreover, such an interpretation applies regardless of the breadth of the range or the characteristics being described.

In this disclosure, including the claims, all conjunctions such as "comprising," including, "" carrying, "" having, "" containing, "" involving, "" containing, "and the like are to be understood as being open-ended, i.e., to mean" including but not limited to. Only the conjunctions "consisting of … …" and "consisting of … …" are closed conjunctions.

In the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present application may be practiced without some of these specific details. In the examples, some methods, means, instruments, apparatuses, etc. known to those skilled in the art are not described in detail in order to highlight the subject matter of the present application. On the premise of no conflict, the technical features disclosed in the embodiments of the present application may be combined arbitrarily, and the obtained technical solution belongs to the content disclosed in the embodiments of the present application.

In some embodiments, a magnesium smelting process includes:

(1) mixing a magnesium-containing raw material, a reducing agent, a mineralizer and a pore-forming agent according to a certain proportion to obtain a raw material mixture; generally, raw materials such as a magnesium-containing raw material, a reducing agent, a mineralizer, a pore-forming agent and the like are mixed according to a certain proportion, then the mixture is prepared into powder, and then mixed powder with proper granularity is selected; in order to mix the raw material powder uniformly, the raw material mixture generally needs to be sufficiently stirred and ground, and for example, the raw material mixture may be ball-milled and mixed in a ball mill to achieve sufficient uniform mixing between the raw material particles; generally, the particle size selection can be carried out by screening through a screen, and the selected particle size of the raw material is determined by selecting a proper mesh size of the screen;

(2) pressing and forming the raw material mixture under the pressure of 50-300 MPa to obtain raw material pellets; the general compression molding method can comprise compression molding, double-roller compression molding and the like, and the proper raw material pellet can be obtained;

(3) carrying out heat treatment on the raw material pellets at the temperature of not higher than 1000 ℃, and carrying out heat preservation for a certain time to obtain porous pellets; in the heat treatment process of the raw material pellets, the pore-forming agent reacts and/or changes phase state to generate gas, the gas escapes from the raw material pellets, and mutually communicated channels are formed in the raw material pellets to form porous pellets; after the temperature is kept for a certain time at the set temperature, the gas completely escapes from the raw material pellets;

(4) under the condition that the temperature of the porous pellets is higher than 1100 ℃, the magnesium-containing raw material interacts with a reducing agent and a mineralizing agent to react to generate metal magnesium, the metal magnesium escapes from a channel of the raw material pellets in a steam state at high temperature, and the escaped magnesium steam further enters a crystallizer to be condensed to obtain crystallized magnesium.

In some embodiments, the raw material powder is mixed and ground, and then is molded into raw material pellets. In the process of forming raw material powder into pellets by compression molding, the forming pressure has important influence on heat and mass transfer in the smelting process, the pellet strength is small due to undersize pressure, the particles are not tightly contacted with each other, the diffusion mass transfer of substance molecules is not facilitated, the chemical reaction is not facilitated, diffusion space channels are reduced due to overlarge pressure, the escape resistance of gas or metal vapor is increased, the reduction efficiency of metal magnesium is reduced, and the whole smelting period is prolonged. As an alternative embodiment, the molding pressure is usually selected to be between 50 and 300 MPa. Further preferably, the molding pressure is set to 130 to 170 MPa.

As an alternative embodiment, the magnesium-containing material comprises one or a combination of more of dolomite, magnesite, calcined dolomite or magnesium oxide. The main component of the dolomite raw material is CaCO₃·MgCO_3，The main component of the magnesite raw material is MgCO₃The main component of the calcined dolomite raw material is CaO and MgO, and the main component of the magnesium oxide raw material is MgO. Generally, a single raw material can be selected for smelting to prepare the metal magnesium, and a plurality of different raw materials can be selected as mixed raw materials to prepare the metal magnesium. As an alternative embodiment, the dolomite raw material is selected as the magnesium-containing raw material to smelt the magnesium metal, the dolomite can be firstly calcined and decomposed into calcined dolomite, and then the calcined dolomite is mixed with other raw materials such as a reducing agent, a mineralizing agent, a pore-forming agent and the like to smelt.

As an alternative embodiment, the reducing agent comprises a siliceous reducing agent, wherein the amount of siliceous reducing agent to magnesium-containing source material is in accordance with a molar ratio M_Si:M_2MgOThe silicon-containing reducing agent is determined to be 1.0-1.5, and specifically comprises one or a combination of more of ferrosilicon, silicon-aluminum alloy and silicon-aluminum-iron alloy. The amount of reducing agent is usually determined by the reaction equivalent of silicon atoms in the active reducing component of the reducing agent with magnesium atoms in the magnesium-containing material, and in order to fully utilize the magnesium-containing material and sufficiently reduce the magnesium therein to magnesium atoms, a reducing agent having a molar ratio of greater than the stoichiometric amount, for example, M, is usually used_Si:M_2MgODetermining the amount of active element Si in the reducing agent and the amount of MgO in the magnesium-containing raw material as 1.0-1.5, and further determining the amount of the silicon-containing reducing agent powder raw material and the amount of the magnesium-containing raw material powder raw material. In a more preferred embodiment, the molar ratio M is selected_Si:M_2MgODetermining the quantity of the silicon-containing reducing agent and the magnesium-containing raw material as 1.1-1.3.

Some examples disclose magnesium smelting processesThe reducing agent comprises a carbonaceous reducing agent, wherein the amount of carbonaceous reducing agent to magnesium-containing raw material is in accordance with a molar ratio M_C:M_MgOThe carbon-containing reducing agent is determined to be 1.0-4.5, and specifically comprises calcium carbide and a carbonaceous reducing agent. The amount of reducing agent is usually determined by the reaction equivalent of carbon atoms in the active reducing component in the reducing agent and magnesium atoms in the magnesium-containing material, and in order to fully utilize the magnesium-containing material and fully reduce the magnesium atoms therein, a reducing agent greater than the stoichiometric amount is usually used, and for example, the molar ratio M may be used_C:M_MgODetermining the amount of active elements of carbon and MgO in the reducing agent, and further determining the amount of carbon-containing reducing agent powder raw materials and magnesium-containing raw material powder raw materials, wherein the amount of the active elements of carbon and MgO is 1.0-4.5. In a more preferred embodiment, the molar ratio M is selected_C:M_MgODetermining the amount of the carbonaceous reducing agent and the magnesium-containing raw material as 1.0-4.5. The carbonaceous reducing agent is generally a reducing agent such as activated carbon, coke, petroleum coke, coal and the like.

Some embodiments disclose a magnesium smelting method, wherein the reducing agent comprises calcium and calcium alloy. The quantity of the reducing agent calcium and calcium alloy is according to the molar ratio M_Ca:M_MgDetermined as 1.1-1.5.

As an optional embodiment, the mineralizer is fluorite, and the amount of the fluorite is determined according to the content of calcium fluoride in the fluorite, namely the content of the fluorite in the raw material powder is controlled to be 1-5% calculated by the calcium fluoride. The content mentioned in the present application means the mass percentage of the specific raw material powder in the mixed raw material powder.

As an optional implementation mode, the particle sizes of the magnesium-containing raw material powder, the reducing agent powder and the mineralizer powder can be controlled, so that the mutual uniform distribution of various powders is promoted, the reaction speed is increased, and the magnesium smelting efficiency is improved. Further, as an alternative embodiment, the particle diameters of the magnesium-containing raw material powder, the reducing agent powder and the mineralizer powder are substantially equivalent, so that effective contact between particles is achieved after the powders are mixed, and for example, the particle diameter of each raw material powder can be controlled within a certain range. The smaller the particle size of the raw material is, the more favorable the reaction is theoretically, but the too small particle size lowers the economical efficiency of production. For example, the particle size of the raw material particles containing magnesium is generally selected to be 100 mesh or larger, the particle size of the reducing agent is controlled to be 100 mesh or larger, and the particle size of the mineralizer particles is controlled to be 100 mesh or larger.

As an alternative embodiment, the pore-forming agent has a pyrolysis temperature of not more than 1000 ℃ and a volume content of not more than 50%, for example, the pore-forming agent may be selected from one or a combination of more of inorganic ammonium salt, carbonate, chloride salt, plant dust, rice hull, starch, urea, polypropylene carbonate, dextrin, and sucrose. The pore-forming agent is generally selected from substances which can generate gas at the temperature of not more than 1000 ℃, and the generated gas can escape from the pellets without being left in the raw material pellets, and other substances which have side effects on smelting magnesium are not generated after the gas is generated. Inorganic ammonium salts typically include ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium chloride, ammonium bisulfate, ammonium nitrate, carbonates typically include sodium carbonate, potassium carbonate, and chloride salts typically include sodium chloride, potassium chloride, calcium chloride. Gas molecules generated after pyrolysis of the pore-forming agent particles escape from the pellets, cavities are generated in situ in the pore-forming agent particles, the pore-forming agents uniformly distributed in the pellets are communicated with one another, and after the generated gas molecules escape, cavities with high mutual communication are formed in the pellets, namely, three-dimensional cavity channels uniformly distributed in the pellets can be used as channels for metal magnesium vapor to escape, so that the escape resistance of metal magnesium is reduced, the generation efficiency of metal magnesium is improved, and the smelting efficiency is improved.

In an alternative embodiment, the pore former preferably has a volume content of 3 to 30%. A three-dimensional cavity channel can be formed in the pellet, the volume of the cavity channel is not too large, and smelting efficiency is not reduced.

Further, as an alternative embodiment, the pore former has a particle size of less than 3 mm. The particle size of the pore-forming agent is controlled to be directly related to the size and the position of a cavity formed by the pore-forming agent, the particle size of the pore-forming agent is usually selected to be not more than 3mm, because the cavity formed by the pore-forming agent with overlarge particle size in the pellet is overlarge, the formed cavity cannot penetrate through all reaction raw materials in the pellet, part of reaction raw material particles are still closely adjacent, a channel for magnesium vapor to escape does not exist, and magnesium vapor generated by the reaction of the magnesium-containing raw material and the reducing agent cannot escape in time, so that the magnesium smelting efficiency is influenced.

Further as an optional embodiment, the particle size of the pore-forming agent particles is equivalent to the particle size of the magnesium-containing raw material, the reducing agent raw material and the mineralizing agent raw material, so that the pore-forming agent particles are uniformly distributed in the reaction raw material, and cavities formed after the gas is generated by pyrolysis of the pore-forming agent can be uniformly distributed in the raw material pellets. In an alternative embodiment, the ratio of the particle size of the pore-forming agent particles to the particle size of the magnesium-containing raw material powder particles is set to 0.9 to 1.5: 1. In a more preferred embodiment, the pore former particles have a particle size of 1.0 to 1.3: 1.

As an alternative embodiment, the heat treatment process of the raw material pellets is performed under a vacuum condition, and the heat treatment under the vacuum condition is favorable for reaction and formation of porous pellets.

As an alternative embodiment, the heat treatment process of the raw material pellets is performed under air, argon, nitrogen atmosphere or a mixture atmosphere thereof.

Usually, the porous pellets are subjected to chemical reaction at the temperature higher than 1100 ℃ to produce metal magnesium, so that the smelting process of the magnesium is realized. The high-temperature treatment temperature of smelting is usually determined according to the properties of raw materials and equipment, and the low temperature can result in slow reaction rate, incomplete reaction, long reaction time and high production cost; the service life of the equipment is influenced by overhigh temperature, and the production cost is increased; typically when using a siliceous reducing agent with a heat resistant alloy steel tank body, the reaction temperature is selected to be above 1100 ℃. As an optional implementation mode, the temperature range of 1100-1250 ℃ can be selected for carrying out chemical reaction to smelt magnesium. When using carbonaceous reductant with high temperature refractory alloy cans or non-metallic cans, the reaction temperature is selected to be above 1100 ℃. As an alternative embodiment, the temperature range of 1400-1600 ℃ can be selected for carrying out the chemical reaction.

As an alternative embodiment, the porous pellets are subjected to heat treatment under vacuum to undergo chemical reaction to obtain crystalline magnesium. The reaction favorable for gas generation is usually carried out under vacuum conditions to accelerate the reaction speed, and for this reason, the porous pellets can be placed in a vacuum reaction furnace to be heated and reacted at a set high temperature.

As an alternative embodiment, the porous pellets are heat treated in an argon atmosphere to carry out a chemical reaction to obtain crystalline magnesium. In order to promote the reaction, the porous pellets can be arranged to react in a flowing argon atmosphere, and the flowing argon facilitates the magnesium vapor to flow and escape, and migrate to a cooling area to be condensed and crystallized, so that the reaction process is accelerated.

Generally, porous pellets are obtained after the raw material pellets are heated and the pore-forming is finished, the temperature is directly raised to a higher smelting temperature in the same reaction vessel, and magnesium-containing raw materials generate magnesium metal vapor at the smelting temperature, so that the reaction process can be shortened, and the smelting efficiency can be improved.

As an alternative embodiment, the pellets can be prepared into porous pellets, then the temperature of the porous pellets is reduced, the porous pellets are transferred into a reactor to be heated to smelting temperature, magnesium-containing raw materials interact with a reducing agent and a mineralizer to generate magnesium metal vapor, and the reaction conditions can be controlled so as to further control the smelting process. For example, the process of pore-forming by reaction of the pore-forming agent and the smelting process of magnesium metal by reduction of the magnesium-containing raw material can be carried out in different reaction vessels.

As an alternative embodiment, the control of the reaction process is further realized by controlling the temperature rise condition of the heat treatment process. For example, in the pore-forming process, the temperature rise speed, the temperature and the heat preservation time can be adjusted, the pore-forming process can be controlled, the internal structure of the pellet at the position is stable, a cavity and a channel with stable structure are formed, and the escape process of magnesium vapor in the subsequent process cannot be blocked. And the too fast pore forming rate can cause the internal structure of the pellet to be damaged or collapsed. The pore-forming temperature is usually 50-100 ℃ higher than the theoretical decomposition or phase transition temperature of the pore-forming agent. The heat preservation time is related to the size of the pellets generally, and is about 0.5-2 hours when the size equivalent of the pellets is 30-50 mm.

The technical details are further illustrated in the following examples.

Example 1

Weighing a certain amount of dolomite with uniform granularity, and calcining the dolomite in a muffle furnace at 1150 ℃ for 90min to obtain calcined dolomite with the activity of 30g and the burnout rate of 47.4%;

grinding calcined dolomite and 75 ferrosilicon into powder, sieving with 100 mesh sieve, and mixing at a molar ratio of M_Si:M_2MgO1.2, mixing, namely mixing the fluorite with 3 mass percent, and then fully and uniformly mixing;

adding 5% of pore-forming agent ammonium bicarbonate into the mixed raw materials, and preparing a pellet sample with the weight of about 10g under the forming pressure of 150 MPa;

placing the material ball sample in a vacuum tube furnace capable of recording weight change in real time, vacuumizing to enable the pressure to reach 10Pa, and heating the sample from 100 ℃ to 1400 ℃ at the heating rate of 2 ℃/min to obtain a weight loss curve of the material ball sample under the reaction condition;

and converting the weight loss curve of the material ball sample into a magnesium reduction rate curve, and calculating the reduction rate.

Comparative example 1

preparing a pellet sample with the weight of about 10g from the mixed raw materials under the molding pressure of 150 MPa;

FIG. 1 is a magnesium reduction rate curve corresponding to a pellet sample, wherein the abscissa is temperature, the ordinate is reduction rate, the # 2 is the pellet sample of example 1, and the # 1 is the pellet sample of comparative example 1, and it can be calculated from the graph that when the reduction rate is 80%, the time required by the # 1 pellet sample is 90min, the time required by the # 2 pellet sample is 53min, and the reduction rate is improved by 42%; when the reduction rate is 90%, the time required by the 1# material ball is 109min, the time required by the 2# material ball is 68min, and the reduction rate is improved by 38%.

Therefore, the experimental results of example 1 and comparative example 1 show that the chemical reaction rate and the reduction efficiency are significantly improved in the technical scheme of example 1.

Example 2

sieving calcined dolomite and activated carbon powder with 100 mesh sieve, and mixing according to silica molar ratio M_C:M_MgOProportioning 4, proportioning fluorite according to the mass ratio of 3%, and then fully and uniformly mixing;

placing the material ball sample in a vacuum tube furnace capable of recording weight change in real time, vacuumizing to enable the pressure to reach 10Pa, and heating the sample from 100 ℃ to 1600 ℃ at the heating rate of 2 ℃/min to obtain the weight loss curve of the material ball sample under the reaction condition;

Comparative example 2

The experimental results of example 2 and comparative example 2 show that the chemical reaction rate and reduction efficiency are significantly improved in the technical scheme of example 2.

Example 3

Weighing a certain amount of magnesite with uniform granularity, and calcining the magnesite in a muffle furnace at 850 ℃ for 90 min;

sieving magnesite and activated carbon powder with 100 mesh sieve, and mixing according to silica molar ratio M_C:M_MgO1.2, mixing, namely mixing the fluorite with 3 mass percent, and then fully and uniformly mixing;

Comparative example 3

The experimental results of example 3 and comparative example 3 show that the chemical reaction rate and reduction efficiency are significantly improved in the technical scheme of example 3.

The technical solutions and the technical details disclosed in the embodiments of the present application are only examples to illustrate the concept of the present application, and do not constitute a limitation to the technical solutions of the present application, and all the inventive changes that are made to the technical details disclosed in the present application without inventive changes have the same inventive concept as the present application, and are within the protection scope of the claims of the present application.

Claims

1. A magnesium smelting method is characterized by comprising the following steps:

(1) mixing a magnesium-containing raw material, a reducing agent, a mineralizer and a pore-forming agent according to a certain proportion to obtain a raw material mixture; in the raw material mixture, the magnesium-containing raw material comprises one or more of dolomite, magnesite, calcined dolomite or magnesium oxide, the volume content of the pore-forming agent is not more than 50%, the granularity of the pore-forming agent is less than 3mm, the pyrolysis temperature of the pore-forming agent is not higher than 1000 ℃, and the pore-forming agent specifically comprises one or more of inorganic ammonium salt, carbonate, chloride, plant debris, rice hulls, starch, urea, polypropylene carbonate, dextrin and sucrose;

(3) carrying out heat treatment on the raw material pellets at a temperature 50-100 ℃ higher than the theoretical decomposition or phase change temperature of the pore-forming agent, and carrying out heat preservation for a certain time to obtain porous pellets;

(5) the magnesium vapor enters a low-temperature area for condensation to obtain crystallized magnesium;

wherein, if the magnesium-containing raw material comprises dolomite or magnesite, the method also comprises the step of calcining the dolomite or the magnesite before obtaining the raw material mixture.

2. The magnesium smelting process according to claim 1, wherein the reducing agent includes a silicon-containing reducing agent, and the amount of the silicon-containing reducing agent to the magnesium-containing raw material is in accordance with a molar ratio M_Si:M_2MgOAnd determining the silicon-containing reducing agent by 1.0-1.5, wherein the silicon-containing reducing agent comprises one or more of ferrosilicon, silicon-aluminum alloy and silicon-aluminum-iron alloy.

3. The magnesium smelting process according to claim 1, wherein the reductant comprises a carbonaceous reductant, and the amount of the carbonaceous reductant to the magnesium-containing raw material is in accordance with a molar ratio M_C:M_MgOAnd determining the carbon-containing reducing agent by 1.0-4.5, wherein the carbon-containing reducing agent specifically comprises calcium carbide and a carbonaceous reducing agent.

4. The magnesium smelting method according to claim 1, wherein the reducing agent includes calcium or calcium alloy, and the amount of the calcium or calcium alloy and the magnesium-containing raw material is in accordance with a molar ratio M_Ca:M_MgAnd (5) determining the content of the product by the formula of (= 1.1-1.5).

5. The magnesium smelting method according to claim 1, wherein the heat treatment of the raw material pellets is performed under vacuum condition, or under air, argon, nitrogen atmosphere or a mixture of atmosphere.

6. The magnesium smelting process according to claim 1, wherein the chemical reaction of the porous pellets is carried out under vacuum or in a stream of argon gas.

7. The magnesium smelting method according to claim 1, wherein the content of the mineralizer is set to 1 to 5% by mass.