WO2020168582A1

WO2020168582A1 - Device and method for directly reducing metal compound to prepare metal or alloy powder

Info

Publication number: WO2020168582A1
Application number: PCT/CN2019/076093
Authority: WO
Inventors: 卡马里•阿里•雷扎
Original assignee: 东北大学
Priority date: 2019-02-21
Filing date: 2019-02-26
Publication date: 2020-08-27
Also published as: CN109853001B; CN109853001A

Abstract

A device and method for directly reducing a metal compound to prepare metal or alloy powder. The method comprises: under a protective atmosphere containing water vapor, taking a metal plate (11) as a cathode, taking graphite (9) as an anode, and taking metal chloride as molten salt (13); placing a metal compound (12) to be treated in the molten salt (13); at a temperature between a melting temperature of the molten salt +10°C and a boiling temperature of the molten salt -100°C, performing electrochemical electrolysis reaction at the voltage of 0.5-4.1 V to obtain molten salt containing metal or alloy powder; and cooling to a room temperature along with a furnace, and separating the solidified salt from the metal or alloy powder.

Description

Device and method for preparing metal or alloy powder by directly reducing metal compound

Technical field

The present invention relates to the field of electrochemical technology, in particular to a device and method for preparing metal or alloy powder by directly reducing metal compounds.

Background technique

The use of metal oxide or metal sulfide minerals to produce metal and alloy powders, and in the production process, does not emit greenhouse gases or harmful gases, such as carbon dioxide and sulfur dioxide, etc., is the main direction of future industrial development, especially due to powder metallurgy technology Rising, more and more technologies using powder as raw materials, such as additive manufacturing and 3D printing technology, etc. (References, C. Buchanan, L. Gardner, Application of metal 3D printing in architecture: methods, research, applications, opportunities And challenge discussion[J].Engineering structure,180,(2019):332～348.C.Buchanan,L.Gardner,Metal 3D printing in construction:A review of methods,research,applications,opportunities and challenges,EngineeringStructures 180 (2019)332-348).

At present, the production of steel ingots with carbon as a reducing agent and steel oxide minerals as raw materials will emit a large amount of carbon dioxide. In addition, additional expensive processes, such as atomization, are needed to prepare metal powder from steel ingots. Therefore, more green and more direct methods are needed to prepare metal powder from its minerals.

In the document "Hydrogen reduction WO ₃ and WO _3- NiO powder reduction behavior and powder microstructure analysis" (reference H.Kang, YKJeong, STOh, Hydrogen reduction behavior and microstructural characteristics of WO ₃ and WO ₃ -NiO powders, International Journal of Refractory Metals and Hard Materials, International Journal of Refractory Metals and Hard Materials 88 (2019) 69-72), and published documents in Z.chen et al. "Hematite powder in hydrogen Research on reduction kinetics in atmosphere" (reference Z. Chen, J. Dang, X. Hu, H. Yan, Reduction Kinetics of Hematite Powder in Hydrogen Atmosphere at Moderate Temperatures, Metals 8(2018) 751), all based on Hydrogen acts as a reducing agent, and metal powders such as tungsten, molybdenum, nickel, cobalt, and iron are extracted from their oxide minerals at temperatures exceeding 600°C. However, the production of hydrogen and its transportation to the reduction reactor are costly and dangerous.

Patent US7790014 discloses a molten salt method, which specifically presses and sinters metal mineral powder to obtain a metal mineral disc. Then the prepared metal mineral disc was placed in CaCl ₂ molten salt, and then connected to the negative electrode of the power source. A container filled with molten CaCl ₂ is connected to the positive pole of the power source. In this case, oxygen can be obtained from one end of the metal mineral disc, and the metal mineral disc is reduced to obtain metal powder. There are two limitations to using this method to prepare metal minerals into metals: (1) The preparation of metal mineral discs requires a multi-step process, including pressing metal mineral powder into the disc, and sintering the disc at high temperature to produce Sintered metal mineral tray. This process is time-consuming and energy-consuming. (2) The conductivity of metal minerals is very low, so the kinetics of the electrochemical reaction is very low.

Summary of the invention

In view of the above-mentioned problems, the present invention provides an apparatus and method for preparing metal or alloy powder by directly reducing metal compounds. The method is an electrochemical method, in particular, placing metal minerals in a molten salt medium in a humid atmosphere and directly Converted into the corresponding metal powder. There is no need to press and sinter the metal mineral powder to obtain the metal mineral disc. In the method of the present invention, metal minerals are not used as the cathode. Instead, a metal plate immersed in molten salt is used as the cathode. The high conductivity of the metal plate greatly improves the kinetics of the reaction.

The method for preparing metal or alloy powder by directly reducing a metal compound of the present invention includes the following steps:

Step 1: Electrochemical electrolysis reaction

In a protective atmosphere containing water vapor, the metal plate is used as the cathode, graphite is used as the anode, and the metal chloride is used as the molten salt. The metal compound to be treated is placed in the molten salt and heated to make the molten salt in a molten state. Molten salt melting temperature +10°C ~ molten salt boiling point temperature -100°C, at 0.5 ~ 4.1V, electrochemical electrolysis reaction is carried out to obtain molten salt containing metal or alloy powder; wherein, the protective atmosphere contains The volume percentage of water vapor is 0.1%-20%, and the balance is argon;

Step 2: Post-processing

The molten salt containing metal or alloy powder is cooled to room temperature along with the furnace to obtain a mixture of solidified salt and metal or alloy powder, and the solidified salt and metal or alloy powder are separated to obtain metal powder.

In the step 1, the time required for the electrochemical electrolysis reaction is t, where t _min ≤ t ≤ t _max , where the minimum reduction time t _min required for the reduction of the metal compound to metal is:

t _min =(ny×3216)/I (1)

Among them, t _min is the shortest reduction time, the unit is min; n is the amount of the metal compound powder, the unit is mol; y is the sum of the number of atoms other than the metal in the metal compound, dimensionless; I is the current, the unit Is A;

The longest reduction time t _max required to reduce the metal compound to metal is:

t _max = t _min × 1.5 (2).

In the step 1, the metal chloride in the molten salt is a metal chloride or a mixture of several metal chlorides, specifically LiCl, CaCl ₂ , NaCl, ZnCl ₂ , KCl or MgCl ₂ One or more.

In the step 1, the melting temperature of the molten salt is less than the melting temperature of the metal compound.

In the step 1, as a preference, the metal plate is a metal plate or an alloy plate made of reduced metal components.

In the step 1, the metal compound is a metal oxide and/or a metal sulfide, specifically Fe ₂ O ₃ , Fe ₃ O ₄ , FeO, NiO, Ni ₂ O ₃ , CoO, Co ₂ O ₃ , MoO ₃ , MoS ₂ , Cr ₂ O ₃ , CrO ₂ , CrO ₃ , FeTiO ₃ , MnO, MnO ₂ , WO ₃ and WO ₂ or a mixture of one or more.

In the step 1, the metal compound can be a metal compound powder with a particle size of 10 nm-100 μm.

In the step 1, the mass of the molten salt is 10-30 times the mass of the metal compound.

In the step 2, the separation treatment can be one of the following two methods:

The first:

Dissolve the mixture of solidified salt and metal or alloy powder in water, and separate solid-liquid to obtain a suspended aqueous solution of metal or alloy powder and salt; the suspended aqueous solution of salt, after evaporation, the obtained salt can be recycled and reused;

The second type:

When the metal or alloy powder is a magnetic metal powder, magnetic separation is used to separate the solidified salt from the metal or alloy powder.

In the method for preparing metal or alloy powder by directly reducing a metal compound of the present invention, the particle size of the prepared metal powder is 2-20 μm, and the current efficiency of the method is 95-100%.

The method for preparing metal or alloy powder by directly reducing a metal compound according to the present invention has a mechanism as follows: water from a protective atmosphere containing water vapor, that is, a humid atmosphere, dissolves into molten salt to generate hydrogen ions. The hydrogen ions are reduced to hydrogen gas on the metal cathode plate placed in the molten salt. As a result, the generated hydrogen moves upward and reduces the metal compound suspended in the molten salt to the corresponding metal and produces water. The resulting water is dissolved in the molten salt, and this process continues. The reaction process involved is as follows:

H ₂ O (moist atmosphere) → 2[H ⁺ ]+[O ^2- ] (soluble in molten salt) (3)

2[H ⁺ ]+2e→H ₂ (on the metal plate used as the cathode) (4)

H ₂ +MeO (metal oxide powder in molten salt)→Me+H ₂ O (5)

H ₂ +MeS (metal sulfide powder in molten salt)→Me+H ₂ S (6)

The method for preparing metal or alloy powder by direct reduction of metal compounds uses a device for preparing metal or alloy powder by directly reducing metal compounds, including a reaction vessel, a reaction vessel cover, a ceramic tube, a ceramic cover, a ceramic plate, a graphite crucible, and a ceramic Crucible and metal plate;

The reaction vessel and the reaction vessel cover are closed to form a reaction chamber; the ceramic tube, ceramic cover, ceramic plate, graphite crucible, ceramic crucible and metal plate are all arranged in the reaction chamber;

Among them, the ceramic tube, the ceramic cover, and the ceramic disc form a protective atmosphere cavity; the graphite crucible, the ceramic crucible, and the metal plate are all set in the protective atmosphere cavity; the protective atmosphere cavity is provided with an inlet for a protective atmosphere containing water vapor and a protective atmosphere containing water vapor Atmosphere outlet

The graphite crucible is provided with a ceramic crucible, and the ceramic crucible is used for containing metal compounds; the ceramic crucible is provided with a metal plate, and the metal plate is connected to the negative electrode of the power supply and serves as the cathode of the device; the graphite crucible is connected The positive pole of the power supply serves as the anode of the device.

The reaction vessel cover is provided with an air inlet, an air outlet, a first cathode lead through hole and a first anode lead through hole, and the ceramic cover is provided with an air inlet containing a protective atmosphere of water vapor, The air outlet of the protective atmosphere of water vapor, the second cathode wire through hole and the second anode wire through hole; the air inlet corresponds to the air inlet of the protective atmosphere containing water vapor and is provided with an air inlet pipe, so The air outlet hole corresponds to the air outlet of the protective atmosphere containing water vapor and is provided with an air outlet pipe. The first cathode wire through hole and the second cathode wire through hole correspond to each other and are provided with a cathode wire. An anode wire through hole corresponds to the second anode wire through hole and is provided with an anode wire.

The device for preparing metal or alloy powder by directly reducing metal compounds also includes a protective atmosphere system containing water vapor, a power source and a melting furnace, and the air inlet of the air inlet pipe is connected with the protective atmosphere system containing water vapor; The cathode wire is connected to the negative electrode of the power source, and the anode wire is connected to the positive electrode of the power source; the devices for directly reducing metal compounds to prepare metal or alloy powder are all set in the furnace.

Wherein, the capacity of the ceramic crucible<the capacity of the graphite crucible.

The ceramic tube and the ceramic disc can be integrated or separated.

Compared with the prior art, the device and method for directly reducing metal compounds to prepare metal or alloy powder of the present invention have the following advantages:

In the method, the metal compound to be processed is placed in the molten salt in a humid inert gas protective atmosphere, and a voltage is applied between the cathode and the anode to directly reduce the metal compound suspended in the molten salt to the corresponding metal powder. If a metal compound mixture of two or more metal compound components is added to the molten salt, the metal compound mixture will be reduced to produce a metal alloy powder or an intermediate composition powder. The method directly adds the metal compound to the molten salt to prepare the metal powder, and has the advantages of simple process, high efficiency and significant economic benefit. The current efficiency of the method is very high, close to 100%.

Description of the drawings

Figure 1 is a schematic diagram of the structure of the device for preparing metal or alloy powder by directly reducing metal compounds according to the present invention;

In the figure, 1 is the reaction vessel, 2 is the reaction vessel cover, 3 is the gas inlet pipe, 4 is the gas outlet pipe, 5 is the power supply, 6 is the ceramic tube, 7 is the ceramic cover, 8 is the ceramic plate, 9 is the graphite crucible, and 10 It is a ceramic crucible, 11 is a metal plate, 12 is a metal compound, 13 is a molten salt, 14 is a furnace, 15 is an anode wire, and 16 is a cathode wire.

2 is an XRD pattern of Fe prepared by direct reduction of Fe ₂ O ₃ in Example 1 of the present invention;

Fig. 3 is a graph showing changes in voltage and current during the entire experiment in Example 2 of the present invention;

4 is an XRD pattern of Fe prepared by direct reduction of Fe ₂ O ₃ in Example 2 of the present invention;

In FIG. 5, (a) is an SEM image of Fe ₂ O ₃ as a raw material in Example 2 of the present invention; (b) is an SEM image of Fe powder prepared in Example 2 of the present invention;

Figure 6 is an XRD pattern of Fe ₂ O _{3 as a} raw material and Fe as a product in Example 3 of the present invention;

7 is an SEM image of Fe powder prepared by direct reduction of Fe ₂ O ₃ in Example 3 of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the embodiments.

Example 1

A device for directly reducing metal compounds to prepare metal or alloy powder. The schematic diagram of the structure is shown in Figure 1. It specifically includes a reaction vessel 1, a reaction vessel cover 2, a ceramic tube 6, a ceramic cover 7, a ceramic plate 8, a graphite crucible 9, and a ceramic crucible 10 and metal plate 11;

The reaction vessel 1 and the reaction vessel cover 2 are closed to form a reaction cavity; the ceramic tube 6, the ceramic cover 7, the ceramic plate 8, the graphite crucible 9, the ceramic crucible 10 and the metal plate 11 are all arranged in the reaction cavity;

Among them, the ceramic tube 6, the ceramic cover 7, the ceramic plate 8 form a protective atmosphere cavity; the graphite crucible 9, the ceramic crucible 10, and the metal plate 11 are all set in the protective atmosphere cavity; the protective atmosphere cavity is provided with an inlet for a protective atmosphere containing water vapor And the outlet of a protective atmosphere containing water vapor;

The graphite crucible 9 is provided with a ceramic crucible 10, and the ceramic crucible 10 is used to contain metal compounds; the ceramic crucible 10 is provided with a metal plate 11, and the metal plate 11 is connected to the negative electrode of the power supply 5 and serves as the cathode of the device The graphite crucible 10 is connected to the anode of the power supply 5 as the anode of the device.

The reaction vessel cover 2 is provided with an air inlet, an air outlet, a first cathode wire through hole and a first anode wire through hole, and the ceramic cover is provided with an air inlet of a protective atmosphere containing water vapor, The air outlet of the protective atmosphere containing water vapor, the second cathode wire through hole and the second anode wire through hole; the air inlet hole corresponds to the air inlet of the protective atmosphere containing water vapor and is provided with an air inlet pipe 3 , The air outlet hole corresponds to the air outlet of the protective atmosphere containing water vapor and is provided with an air outlet pipe 4, and the first cathode wire through hole corresponds to the second cathode wire through hole and is provided with a cathode wire 16, The first anode wire through hole and the second anode wire through hole correspond to each other and an anode wire 15 is provided.

The device for preparing metal or alloy powder by directly reducing metal compounds also includes a protective atmosphere system containing water vapor, a power source 5 and a furnace 14, the air inlet of the air inlet pipe 3 and a protective atmosphere system containing water vapor The gas outlet of the gas outlet pipeline 4 is connected to the natural gas extraction system, the cathode wire 16 is connected to the negative electrode of the power source 5, and the anode wire 15 is connected to the positive electrode of the power source 5; the direct reduction metal The powder electrochemical devices are all set in the furnace.

The materials of the reaction vessel 1 and the reaction vessel cover 2 are stainless steel.

The material of the ceramic tube 6, the ceramic cover 7, and the ceramic disc 8 is alumina.

A method for preparing metal or alloy powder by directly reducing a metal compound includes the following steps:

Step I:

Put the metal compound powder 12 (15g Fe ₂ O ₃ powder) to be processed in the ceramic crucible 10 and cover the metal plate 11;

Add 320 g of lithium chloride molten salt 13 into the graphite crucible 9 and cover it on the metal compound powder 12; wherein the graphite crucible has an inner diameter of 6 cm and a height of 13.5 cm; the metal plate 11 is a stainless steel disc with a diameter of 5 cm;

Place the entire device in the melting furnace 14 and heat it to a temperature of 670°C to obtain molten salt;

Step II:

When the molten salt is in a molten state, through the gas inlet pipe 3, a protective gas containing water vapor is introduced into the protective atmosphere cavity formed by the ceramic tube 6, ceramic cover 7, and ceramic disc 8, so that the protective atmosphere cavity is filled with water vapor. Protective atmosphere, where the volume percentage of water vapor in the protective atmosphere is 10%, and the balance is argon;

The metal plate 11 is connected to the negative electrode of the power source 5 through the cathode wire 16 as a cathode, and the graphite crucible 9 is connected to the positive electrode of the power source 5 through the anode wire 15 as an anode. Electrochemical electrolysis reaction 2.5h;

Step III:

After the electrochemical electrolysis reaction is over, the furnace is cooled to room temperature to obtain a mixture of solidified salt and metallic Fe powder;

Dissolve the mixture of solidified salt and metallic Fe powder in water, filter solid-liquid separation to obtain a suspended aqueous solution of metallic Fe powder and salt; the suspended aqueous solution of salt, after evaporation, the obtained salt can be recycled and reused; metallic Fe powder is vacuum dried, The dried Fe powder was obtained. After being adsorbed and purified by a magnet, the XRD pattern was analyzed. The obtained XRD pattern is shown in Figure 2. From Figure 2, it can be seen that the diffraction peak of Fe is clear and there is no impurities, indicating that the prepared metal Fe The powder has high purity, and the raw material Fe2O3 is all reduced to Fe. In this embodiment, the current efficiency is 95%.

Example 2

A device for directly reducing metal compounds to prepare metal or alloy powder is the same as in Example 1.

A method for directly reducing metal compounds to prepare metal or alloy powder, same as Example 1, except that:

(1) The total electrochemical electrolysis time is 1.5h.

(2) The maximum voltage of the power supply is adjusted to 3.8V.

Figure 3 shows the voltage and current curve during the entire experiment. It can be seen from the change curve that the current maintains a constant 10A during this process. After the electrochemical electrolysis is over, the current fluctuates violently and the voltage changes to a certain extent, the maximum is 3.8V;

The XRD of the Fe powder product prepared in this example can be seen in Figure 4, indicating that the Fe powder prepared is pure iron.

From this embodiment, it can be calculated that the current efficiency of the process is 98%.

In this embodiment, the SEM image of the Fe ₂ O ₃ raw material is shown in Figure 5 (a), and the SEM image of the Fe powder product is shown in Figure 5 (b). The particle size of the raw material Fe ₂ O ₃ powder is 100-300 nm. The particle size of the iron powder product is 2-7μm. This is because the iron powder agglomerates together in the high-temperature molten salt, and the particle size becomes larger.

Example 3

(1) Take 5g Fe ₂ O ₃ as raw material.

(2) The voltage is fixed at 0.97V.

(3) The total electrochemical electrolysis time is 10h.

In this embodiment, the XRD analysis of the Fe ₂ O ₃ raw material and the prepared iron powder product is shown in FIG. 6. Prove that the raw material is Fe ₂ O ₃ and the product is Fe. The results show that iron powder is directly produced from Fe ₂ O ₃ powder at a low voltage of 0.97V.

In this embodiment, the scanned electronic image of the prepared iron powder is shown in FIG. 7. The particle size of the iron product is 5-20 μm. In this example, the particle size of the Fe powder product is larger than that of Example 2. This is because it takes a long time to generate Fe at a lower voltage.

Example 4

A device for directly reducing metal compounds to prepare metal or alloy powder, which is the same as Example 1, except that:

(1) The ceramic tube 6 and the ceramic disc 8 are integrated.

(2) The materials of the reaction vessel 1 and the reaction vessel cover 2 are nickel alloy.

(3) The material of the ceramic tube 6, the ceramic cover 7, and the ceramic disc 8 is zirconia.

(1) The raw material is a mixture of Fe ₂ O ₃ + NiO + Cr ₂ O ₃ ;

(2) The prepared Fe-Ni-Cr alloy is composed of Fe (60wt%)-Ni (30wt%)-Cr (10wt%).

Example 5

(1) The material of the ceramic tube 6, the ceramic cover 7, and the ceramic disc 8 is magnesium oxide.

(1) The raw material is a mixture of NiO+Cr ₂ O ₃ +Fe ₂ O ₃ +MoO ₃ +WO ₃ ;

(2) The prepared 48Ni-22Cr-18Fe-9Mo-W alloy.

Example 6

(1) The materials of the reaction vessel 1 and the reaction vessel cover 2 are molybdenum alloy.

(2) The material of the ceramic tube 6, the ceramic cover 7, and the ceramic disc 8 is silica.

(3) The metal plate 11 is made of molybdenum.

(1) The raw material is a mixture of MoO ₃ + MoS ₂ ;

(2) The volume percentage of water vapor contained in the protective atmosphere is 0.1%;

(3) Mo powder is prepared.

Example 7

(1) Molten salt is a mixture of NaCl-CaCl ₂ at molar ratio, NaCl:CaCl ₂ =0.479:0.521;

(2) In the protective atmosphere, the volume percentage of water vapor is 5%;

(3) The electrochemical electrolysis reaction temperature is the eutectic melting temperature of NaCl-CaCl ₂ + 60°C, and the heating rate is 1°C/min.

(4) Cooling the molten salt containing metal powder to room temperature along with the furnace to obtain a mixture of solidified salt and metal powder, grinding and pulverizing the mixture of solidified salt and metal powder, and magnetic separation to obtain metal powder.

Example 8

(1) The raw material is 160 g Fe ₂ O ₃ , and the current is 20 A, and the electrochemical electrolysis time is 321.6 min-482.4 min, and 6 h is selected in this embodiment.

(2) The molten salt is a mixture of NaCl-KCl-MgCl ₂ in molar ratio, NaCl: KCl: MgCl ₂ = 0.33: 0.216: 0.454;

(3) The electrochemical electrolysis reaction temperature is the eutectic melting temperature of NaCl-CaCl ₂ + 40°C, and the heating rate is 20°C/min.

Example 9

A device for directly reducing metal compounds to prepare metal or alloy powder is the same as in Example 8.

A method for directly reducing metal compounds to prepare metal or alloy powder, the same as that in Example 8, except that:

(1) The raw material is 160g Fe ₂ O ₃ , the current is 10A, and the electrochemical electrolysis time is 643.2min-964.8min, and 12h is used in this embodiment.

Claims

A method for preparing metal or alloy powder by directly reducing a metal compound is characterized in that it comprises the following steps:

Step 1: Electrochemical electrolysis reaction

In a protective atmosphere containing water vapor, the metal plate is used as the cathode, graphite is used as the anode, and the metal chloride is used as the molten salt. The metal compound to be treated is placed in the molten salt and heated to make the molten salt in a molten state. Molten salt melting temperature +10°C ~ molten salt boiling point temperature -100°C, at 0.5 ~ 4.1V, electrochemical electrolysis reaction is carried out to obtain molten salt containing metal or alloy powder; wherein, the protective atmosphere contains The volume percentage of water vapor is 0.1%-20%, and the balance is argon;

Step 2: Post-processing

The molten salt containing metal or alloy powder is cooled to room temperature with the furnace to obtain a mixture of solidified salt and metal or alloy powder, and the solidified salt and metal or alloy powder are separated to obtain metal or alloy powder.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein in the step 1, the electrochemical electrolysis reaction requires a time t, where t min ≤ t ≤ t max , where the minimum reduction time t min required to reduce the metal compound to metal is:

t min =(ny×3216)/I (1)

Among them, t min is the shortest reduction time, the unit is min; n is the amount of the metal compound powder, the unit is mol; y is the sum of the number of atoms other than the metal in the metal compound, dimensionless; I is the current, the unit Is A;

The longest reduction time t max required to reduce the metal compound to metal is:

t max = t min × 1.5 (2).
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein in said step 1, the metal chloride in the molten salt is a metal chloride or several metals A mixture of chlorides.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1 or 3, wherein the molten salt is one of LiCl, CaCl 2 , NaCl, ZnCl 2 , KCl or MgCl 2 or Several kinds.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1 or 3, wherein the melting temperature of the molten salt is less than the melting temperature of the metal compound.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein, in the step 1, the metal plate is a metal plate or an alloy plate made of reduced metal components.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein in the step 1, the metal compound is a metal oxide and/or a metal sulfide.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein the metal compound is Fe 2 O 3 , Fe 3 O 4 , FeO, NiO, Ni 2 O 3 , CoO, One or a mixture of Co 2 O 3 , MoO 3 , MoS 2 , Cr 2 O 3 , CrO 2 , CrO 3 , FeTiO 3 , MnO, MnO 2 , WO 3 and WO 2 .
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein in the step 1, the metal compound is a metal compound powder with a particle size of 10 nm-100 μm.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein in said step 1, the mass of the molten salt is 10-30 times the mass of the metal compound.
The method for preparing metal or alloy powder by directly reducing a metal compound according to claim 1, wherein, in the step 2, the separation treatment is one of the following two methods:

The first:

The mixture of solidified salt and metal or alloy powder is dissolved in water, and solid-liquid separation is performed to obtain a suspended aqueous solution of metal or alloy powder and salt; the suspended aqueous solution of salt is evaporated, and the obtained salt is recycled and reused;

The second type:

When the metal or alloy powder is a magnetic metal powder, magnetic separation is used to separate the solidified salt from the metal or alloy powder.
The method for preparing metal or alloy powder by directly reducing a metal compound according to any one of claims 1-3 and 6-11, characterized in that, in the method for preparing metal or alloy powder by directly reducing a metal compound, the current efficiency It is 95-100%.
The method for preparing metal or alloy powder by directly reducing metal compounds according to any one of claims 1-3 and 6-11, the device used for preparing metal or alloy powder by directly reducing metal compounds is characterized in that it comprises a reaction vessel, a reaction vessel Container lid, ceramic tube, ceramic lid, ceramic plate, graphite crucible, ceramic crucible and metal plate;

The reaction vessel and the reaction vessel cover are closed to form a reaction chamber; the ceramic tube, ceramic cover, ceramic plate, graphite crucible, ceramic crucible and metal plate are all arranged in the reaction chamber;

Among them, the ceramic tube, the ceramic cover, and the ceramic disc form a protective atmosphere cavity; the graphite crucible, the ceramic crucible, and the metal plate are all set in the protective atmosphere cavity; the protective atmosphere cavity is provided with an inlet for a protective atmosphere containing water vapor and a protection containing water vapor Atmosphere outlet

The graphite crucible is provided with a ceramic crucible, and the ceramic crucible is used for containing metal compounds; the ceramic crucible is provided with a metal plate, and the metal plate is connected to the negative electrode of the power supply and serves as the cathode of the device; The positive pole of the power supply serves as the anode of the device.
The device for preparing metal or alloy powder by directly reducing metal compounds according to claim 13, wherein the reaction vessel cover is provided with an air inlet, an air outlet, a first cathode lead through hole and a first anode lead Through holes, the ceramic cover is provided with an air inlet for a protective atmosphere containing water vapor, an air outlet for a protective atmosphere containing water vapor, a second cathode wire through hole and a second anode wire through hole; The air hole corresponds to the air inlet of the protective atmosphere containing water vapor and is provided with an air inlet pipe, and the air outlet corresponds to the air outlet of the protective atmosphere containing water vapor and is provided with an air outlet pipe. The cathode wire through hole corresponds to the second cathode wire through hole and is provided with a cathode wire, and the first anode wire through hole is corresponding to the second anode wire through hole and is provided with an anode wire.
The device for preparing metal or alloy powder by directly reducing metal compounds according to claim 13, wherein the device for preparing metal or alloy powder by directly reducing metal compounds further comprises a protective atmosphere system containing water vapor, a power supply, and In the melting furnace, the air inlet of the air inlet pipe is connected to a protective atmosphere system containing water vapor; the cathode wire is connected to the negative electrode of the power source, and the anode wire is connected to the positive electrode of the power source; the direct reduction metal The equipment for preparing metal or alloy powder from the compound is set in the furnace.