Device and method for preparing low-oxygen and narrow-distribution superfine molybdenum powder through vapor phase reduction

Abstract

The invention discloses a device and a method for preparing low-oxygen and narrow-distribution superfine molybdenum powder through gas phase reduction, and the method comprises the following steps of: controlling the density difference of hydrogen and water vapor and the partial pressure of the hydrogen and the water vapor through arranging a rising bin and an inverted circular truncated cone-shaped reducer in a furnace body; a mixture of gas-phase MoO3 and argon and hydrogen jointly enter the inverted-truncated-cone-shaped reducer along the bottom of the inverted-truncated-cone-shaped reducer in the tangential direction to be subjected to a reduction reaction, on the basis of the micro-fluidic technology, particle size distribution of superfine molybdenum powder is guaranteed, effective separation of water vapor is achieved, and the purpose of reducing the molybdenum powder is achieved. Industrial molybdenum trioxide or high-purity molybdenum trioxide is used as a raw material to directly prepare the superfine molybdenum powder with uniform particle size and low oxygen content, the equipment investment and the operation cost are greatly reduced, and low-oxidation, narrow-particle-size-distribution, high-efficiency, low-cost and green preparation of the superfine molybdenum powder is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrafine powder preparation, and relates to a method and device for ultrafine molybdenum powder, and specifically to a device and method for preparing low-oxygen and narrow-distribution ultrafine molybdenum powder by gas phase reduction. Background Art

[0002] Ultrafine molybdenum powder with a particle size of less than 1.5μm has more superior mechanical, electrical, magnetic, thermal, optical and chemical (including catalytic) properties. Ultrafine powders are usually used in powder metallurgy and the production of metal ceramic pressings, alloys, special ceramics and electrical components. They are good fillers, abrasives, pigments, catalysts, and can also be used for corrosion-resistant, wear-resistant and heat-resistant coatings. Adding 3-5% ultrafine molybdenum powder to molybdenum powder of normal particle size for pressing and sintering can greatly reduce the sintering temperature and obtain high-density molybdenum and molybdenum alloy products. The particle size and oxygen content of molybdenum powder have a great influence on the chemical properties of molybdenum powder. Studies have shown that molybdenum powders of different particle sizes and oxygen contents have different sintering activities and catalytic activities. Therefore, obtaining low oxygen and narrow distribution characteristics is one of the most important indicators of ultrafine molybdenum powder.

[0003] Existing methods for preparing ultrafine molybdenum powder are mainly divided into thermal decomposition and reduction methods. The thermal decomposition method first reacts chlorine with molybdenite to produce MoCl6, which is then decomposed by high-temperature heating to produce ultrafine molybdenum powder. The reduction method is further divided into carbon reduction and hydrogen reduction. The carbon reduction method involves high-energy ball milling carbon and MoO3 to first produce MoO2 in a low-temperature stage, and then further reduction in a high-temperature stage to produce ultrafine molybdenum powder. The hydrogen reduction method uses hydrogen as a reducing agent to reduce industrial molybdenum oxide, molybdenum carbonyl, or molybdenum chloride in a closed, high-temperature environment to produce ultrafine molybdenum powder.

[0004] In addition, ultrafine molybdenum powder can also be obtained by reducing ultrafine precursors such as sublimed molybdenum trioxide, ultrafine ammonium octamolybdate and other raw materials.

[0005] Currently, this type of technology has some shortcomings and limitations, specifically:

[0006] 1) The thermal decomposition method uses molybdenum pentachloride as the raw material and produces ultrafine molybdenum powder by high-temperature decomposition. However, chlorine is used in the preparation and purification of molybdenum pentachloride. Chlorine gas is a concern for atmospheric pollution and its harmful effects on humans, animals, and plants. Therefore, this method is not suitable for large-scale industrial production of molybdenum powder.

[0007] 2) The carbon reduction of MoO₃ experimental process begins with mechanical mixing of MoO₃ and carbon. The uniformity of this mixing affects the contact area between the reactants, the nucleation rate of the products, and the diffusion rate of the reactants through the product phase, directly influencing the reaction rate and progress. Furthermore, controlling the amount of carbon added is very difficult: too much can easily introduce impurities, while too little can lead to incomplete reduction. Furthermore, carbon reduction produces CO₂ gas emissions, which are inconsistent with the country's "dual carbon" goals and will be subject to future restrictions.

[0008] 3) Chemical vapor reduction (CVR) methods, which utilize molybdenum carbonyl and molybdenum fluoride, are ideal for producing ultrafine, narrowly distributed molybdenum powders. However, the raw materials are very expensive, and molybdenum fluoride generates HF during use. Its highly corrosive and toxic nature places extremely stringent demands on equipment and operators. Similarly, the preparation of molybdenum carbonyl requires a CO2-free environment, placing stringent requirements on the reaction environment and making industrial production difficult.

[0009] 4) The traditional method for preparing molybdenum powder is the H2 reduction of MoO3, which includes one-stage, two-stage, and three-stage reduction. The first-stage reduction reaction is difficult to control, resulting in coarse and poor-quality molybdenum powder. The second-stage reduction, from MoO2 to molybdenum powder, is the most significant process affecting molybdenum powder quality. The crude molybdenum powder produced by the second-stage reduction requires screening and mixing to obtain a finished molybdenum powder with a particle size of 3-4 μm. The three-stage reduction method is primarily used to produce high-purity molybdenum powder with low oxygen content and large particle size. To produce ultrafine molybdenum powder using hydrogen reduction, ultrafine precursors such as sublimated molybdenum trioxide, fine-grained ammonium octamolybdate, and molybdic acid must be used.

[0010] In particular, the above-mentioned ultrafine molybdenum powder reduction technology varies greatly during the reduction process due to the reaction micro-area condition factors (temperature, gas concentration, etc.). For example, in a traditional reactor, the microscopic mixing rate of the reactants is less than the chemical reaction rate, so the reaction process is affected by mass transfer, which leads to inconsistent chemical reaction rates in the entire reactor and local supersaturation differences. At the same time, the gas flow boundary layer in the traditional reactor is thick, the temperature conduction efficiency is very low, and there is a situation where the local temperature is inconsistent with the overall temperature. Under these circumstances, the nanoparticles produced have a large particle size, a wide distribution, and a high probability of agglomeration between particles, which leads to a significant decline in product quality. The ultrafine molybdenum powder produced has a wide particle size distribution, which leads to a significant decline in product quality. In addition, ultrafine molybdenum powder has high surface activity and strong oxygen absorption capacity, which can easily lead to high oxygen content and even natural phenomena.

[0011] The gas source and reducing agent used in traditional gas-phase reduction to prepare ultrafine molybdenum powder are expensive and highly toxic. Summary of the Invention

[0012] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a device and method for preparing low-oxygen and narrow-distribution ultrafine molybdenum powder by gas-phase reduction, which directly prepares ultrafine molybdenum powder with uniform particle size and low oxygen content using industrial molybdenum trioxide or high-purity molybdenum trioxide as raw materials, greatly reducing equipment investment and operating costs, and realizing the low-oxidation and narrow-distribution particle size of ultrafine molybdenum powder - high efficiency, low cost, and green preparation.

[0013] In order to achieve the above object, the present invention adopts the following technical solutions:

[0014] A device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction, comprising a vertically arranged hollow cylindrical furnace body, a sublimation chamber disposed near the top of the furnace body, a feed pipe disposed in the center of the top of the sublimation chamber, the feed pipe extending to the top of the furnace body, a feed port disposed on one side of the feed pipe located outside the furnace body, and a sealing plate disposed on the feed port;

[0015] A sublimation bin discharge pipe is provided near one side of the sublimation bin and extends downward. A partition is vertically provided in the inner cavity of the sublimation bin on the side connected to the sublimation bin discharge pipe. A porous plate inclined toward the middle of the sublimation bin is provided on the top of the partition, and the top of the porous plate is connected to the top wall of the inner cavity of the sublimation bin.

[0016] The side of the upper part of the sublimation chamber away from the sublimation chamber discharge pipe is connected to the tail end of the sublimation chamber air inlet pipe, and the head end of the sublimation chamber air inlet pipe is connected to the argon buffer tank arranged outside the furnace body;

[0017] A heating furnace wire is provided outside the sublimation chamber;

[0018] The furnace body is further provided with an inverted truncated cone-shaped reducer located at the lower part of the sublimation bin, and a reducer feed port is tangentially provided along the side wall of the lower part of the inverted truncated cone-shaped reducer, and the reducer feed port is connected to the tail end of the sublimation bin discharge pipe and the tail end of the hydrogen inlet pipe arranged in parallel; the head end of the hydrogen inlet pipe is connected to the hydrogen buffer tank arranged outside the furnace body;

[0019] The bottom of the inverted truncated cone-shaped reducer is provided with an air door system, and the bottom of the air door system is connected to the circulation system through a water vapor outlet pipe;

[0020] A reducer discharge port is provided on the side of the top of the inverted frustum-shaped reducer away from the reducer feed port, and the reducer discharge port is connected to the separation and drying system through the reducer discharge pipe.

[0021] The present invention also has the following technical features:

[0022] Preferably, the circulation system includes a circulating water collection tank, a circulating water cooling tank is provided on one side of the circulating water collection tank, and the top and bottom of the circulating water collection tank and the circulating water cooling tank are connected by pipelines respectively;

[0023] The circulating water cooling box is provided with an exchanger;

[0024] A water outlet is provided on one side of the bottom of the circulating water collection box, and a mixed gas outlet is provided at the center of the top. The mixed gas outlet is connected to the bottom of the first drying chamber through a first mixed gas outlet pipe, and the top of the first drying chamber is connected to the argon / hydrogen separator through a second mixed gas outlet pipe. The hydrogen outlet of the argon / hydrogen separator is connected to the hydrogen buffer tank through a gas pipeline.

[0025] The argon outlet of the argon / hydrogen separator is connected to the argon buffer tank through a gas pipeline.

[0026] Furthermore, a first gas compressor and a second gas compressor are respectively provided on the pipeline between the argon / hydrogen separator and the argon buffer tank, and on the pipeline between the argon / hydrogen separator and the hydrogen buffer tank.

[0027] Preferably, the separation and drying system includes a spiral separator connected to the reducer discharge pipe, a powder collection bin is provided at the bottom of the spiral separator, and the top is connected to the second drying chamber through a hydrogen outlet pipe, and the second drying chamber is connected to the hydrogen buffer tank through a gas pipeline.

[0028] Furthermore, a third gas compressor is provided on the hydrogen outlet pipe between the spiral separator and the second drying chamber.

[0029] Furthermore, an air cooling jacket is provided on the reducer discharge pipe.

[0030] Preferably, the inner wall of the inverted frustum-shaped reducer is provided with a spiral guide groove.

[0031] The present invention also protects a method for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder using the above-mentioned device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction, comprising the following steps:

[0032] Step 1: Add MoO3 powder to the sublimation chamber through the feed port, close the sealing plate, open the sublimation chamber inlet pipe, and introduce argon gas into the sublimation chamber until the sublimation chamber is full. Then turn on the heating furnace and set the heating temperature to 900℃.

[0033] Step 2: When the temperature of the sublimation chamber reaches 700-800°C, hydrogen is introduced, and at the same time, the cyclone separator, the circulation system, the first gas compressor, the second gas compressor, the third gas compressor and the air cooling jacket are turned on.

[0034] Preferably, the gas flow rate ratio of argon and hydrogen is 3:2.

[0035] Furthermore, the gas flow rate of the argon gas is 300 cm / min, and the gas flow rate of the hydrogen gas is 200 cm / min.

[0036] Compared with the prior art, the present invention has the following technical effects:

[0037] Based on microfluidic technology and in combination with the requirements of hydrogen reduction and rapid separation of its product water vapor, the present invention has developed a technical machine device for preparing ultrafine, low-oxygen and narrowly distributed molybdenum powder by hydrogen reduction of gas-phase molybdenum trioxide. The core of the device is to utilize the density difference between hydrogen and water vapor and the difference in air pressure inside the inverted frustum-shaped spiral reducer to ensure the particle size distribution of ultrafine molybdenum powder and achieve effective separation of water vapor. This allows the direct preparation of ultrafine molybdenum powder with uniform particle size and low oxygen content using industrial molybdenum trioxide or high-purity molybdenum trioxide as raw material, significantly reducing equipment investment and operating costs, and achieving the high efficiency, low cost and green production of ultrafine molybdenum powder with low oxidation and narrow particle size distribution.

[0038] The present invention conducts matching research on the reducer structure and process to achieve effective control of the oxygen content, particle size and distribution of ultrafine molybdenum powder, thereby ensuring the large-scale production of high-quality ultrafine powder.

[0039] The raw materials of the invention are widely available, have good adaptability, are safe and environmentally friendly, have a simple production process, are non-toxic and non-corrosive, and can be produced continuously and on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the overall structure of the device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction of the present invention;

[0041] The meanings of the numbers in the figure are: 1-furnace body, 2-sublimation chamber, 3-feed pipe, 4-feed port, 5-sealing plate, 6-sublimation chamber discharge pipe, 7-partition, 8-porous plate, 9-sublimation chamber air inlet pipe, 10-argon buffer tank, 11-inverted frustum-shaped reducer, 1101-reducer feed port, 12-hydrogen inlet pipe, 13-hydrogen buffer tank, 1102-damper system, 30-water vapor outlet pipe, 1103-reducer discharge port, 14-reducer Original device discharge pipe, 15-circulating water collection box, 16-circulating water cooling box, 17-water outlet, 18-first mixed gas outlet pipe, 19-first drying chamber, 20-second mixed gas outlet pipe, 21-argon / hydrogen separator, 22-first gas compressor, 23-spiral separator, 24-powder collection bin, 25-hydrogen outlet pipe, 26-second drying chamber, 27-second gas compressor, 28-third gas compressor, 29-air cooling jacket. DETAILED DESCRIPTION

[0042] The specific contents of the present invention are further explained in detail below with reference to the embodiments.

[0043] Example 1

[0044] like Figure 1 As shown, this embodiment provides a device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas-phase reduction, comprising a vertically arranged hollow cylindrical furnace body 1, a sublimation chamber 2 being provided near the top of the furnace body 1, a feed pipe 3 being provided in the center of the top of the sublimation chamber 2, the feed pipe 3 extending to the top of the furnace body 1, a feed port 4 being provided on one side of the feed pipe 3 located outside the furnace body 1, and a sealing plate 5 being provided on the feed port 4;

[0045] A sublimation bin discharge pipe 6 is provided near one side of the sublimation bin 2 and extends downward. A partition 7 is vertically provided in the inner cavity of the sublimation bin 2 on the side connected to the sublimation bin discharge pipe 6. A porous plate 8 is provided on the top of the partition 7 and is inclined toward the middle of the sublimation bin 2. The top of the porous plate 8 is connected to the top wall of the inner cavity of the sublimation bin 2. In order to control the separation size of the sublimated molybdenum oxide, a porous plate 8 is provided at the outlet of the sublimation bin 2.

[0046] The upper part of the sublimation bin 2 is connected to the tail end of the sublimation bin air inlet pipe 9 on the side away from the sublimation bin discharge pipe 6, and the head end of the sublimation bin air inlet pipe 9 is connected to the argon buffer tank 10 arranged outside the furnace body 1; in order to ensure the stability of the air pressure in the sublimation bin 2 and prevent hydrogen from entering, argon is introduced into the sublimation bin 2 to maintain a relative positive pressure with the inverted frustum-shaped reducer 11.

[0047] A heating furnace wire is provided outside the sublimation chamber 2; MoO3 sublimates significantly above 800°C, and the MoO3 is heated to about 900°C for sublimation to form a gas-phase molybdenum source as a raw material source for gas-phase reduction;

[0048] The furnace body 1 is further provided with an inverted truncated cone-shaped reducer 11 located at the lower part of the sublimation bin 2. A reducer feed port 1101 is tangentially provided along the side wall of the lower part of the inverted truncated cone-shaped reducer 11. The reducer feed port 1101 is connected to the tail end of the sublimation bin discharge pipe 6 and the tail end of the hydrogen inlet pipe 12 arranged in parallel; the head end of the hydrogen inlet pipe 12 is connected to the hydrogen buffer tank 13 arranged outside the furnace body 1; the reducer feed port 1101 is output from the sublimation bin 2 by a mixed gas containing gaseous molybdenum oxide and argon. The hydrogen and gaseous molybdenum trioxide are transported from the bottom of the inverted truncated cone-shaped reducer 11 through the same tangential direction of the horizontal position of the reducer feed port 1101 to the interior thereof for mixing and reaction;

[0049] The bottom of the inverted frustum-shaped reducer 11 is provided with an air door system 1102, and the bottom of the air door system 1102 is connected to the circulation system through the water vapor outlet pipe 30;

[0050] Hydrogen and gaseous molybdenum trioxide are transported from the same tangential direction at the bottom horizontal position of the inverted truncated cone reducer 11 to the inside of the inverted truncated cone reducer 11 for mixing and reaction. The reaction path is caused by the centrifugal force, gravity, cylinder wall support force and friction generated by the rotation of the gas inside the inverted truncated cone reducer 11, and the gas moves upward in a spiral motion, and the hydrogen gas flow is continuously input. This ensures the continuity of the spiral gas flow power and the gas flow is always in a higher hydrogen partial pressure environment, thereby accelerating the reduction process. Due to the rotational motion of the main gas flow, A low-pressure area is formed at the axial position of the inverted frustum-shaped reducer 11, which creates dynamic conditions for the diffusion of water vapor from the high-pressure area on the inner wall of the cylinder to the low-pressure area on the axis, thereby accelerating the separation of water vapor from the cylinder wall of the inverted frustum-shaped reducer 11 toward the axis. Then, in the axial direction of the inverted frustum-shaped reducer 11, due to the low density of hydrogen and the high density of water vapor, the water vapor continuously moves to the lower part of the inverted cone, while the hydrogen is at the upper part. At this time, the damper system 1102 at the bottom center of the inverted frustum-shaped reducer 11 becomes the main channel for water vapor to overflow.

[0051] A reducer discharge port 1103 is provided on the side of the top of the inverted frustum-shaped reducer 11, away from the reducer feed port 1101. The reducer discharge port 1103 is connected to the separation and drying system via the reducer discharge pipe 14. The ultrafine powder and the continuously replenished hydrogen in an upward spiral motion flow out from the reducer discharge port 1103 in the tangential channel at the top of the inverted frustum-shaped reducer 11, thereby completely achieving the separation of the ultrafine powder, hydrogen and water vapor in the inverted frustum-shaped mixing reactor, thereby ensuring that the ultrafine molybdenum powder is in a hydrogen environment with a higher partial pressure, completing the low-oxygen reduction process of the ultrafine molybdenum powder.

[0052] The circulation system includes a circulating water collecting tank 15, a circulating water cooling tank 16 is provided on one side of the circulating water collecting tank 15, and the top and bottom of the circulating water collecting tank 15 and the circulating water cooling tank 16 are connected by pipelines respectively;

[0053] An exchanger is provided in the circulating water cooling box 16;

[0054] A water outlet 17 is provided on one side of the bottom of the circulating water collection box 15, and a mixed gas outlet is provided at the center of the top. The mixed gas outlet is connected to the bottom of the first drying chamber 19 through a first mixed gas outlet pipe 18. The top of the first drying chamber 19 is connected to the argon / hydrogen separator 21 through a second mixed gas outlet pipe 20. The hydrogen outlet of the argon / hydrogen separator 21 is connected to the hydrogen buffer tank 13 through a gas pipeline.

[0055] The argon outlet of the argon / hydrogen separator 21 is connected to the argon buffer tank 10 through a gas pipeline.

[0056] The water vapor and argon / hydrogen mixture discharged from the center hole at the bottom of the inverted frustum-shaped reducer 11 are condensed into water by the cooler and collected, while the remaining argon / hydrogen mixture is dried and enters the argon buffer tank and hydrogen buffer tank for recycling.

[0057] A first gas compressor 22 and a second gas compressor 28 are respectively provided on the pipeline between the argon / hydrogen separator 21 and the argon buffer tank 10 and on the pipeline between the argon / hydrogen separator 21 and the hydrogen buffer tank 13 .

[0058] The separation and drying system includes a spiral separator 23 connected to the reducer discharge pipe 14. A powder collection bin 24 is provided at the bottom of the spiral separator 23, and the top is connected to the second drying chamber 26 through a hydrogen outlet pipe 25. The second drying chamber 26 is connected to the hydrogen buffer tank 13 through a gas pipeline.

[0059] A third gas compressor 27 is provided on the hydrogen outlet pipe 25 between the spiral separator 23 and the second drying chamber 26 .

[0060] An air cooling jacket 29 is provided on the reducer discharge pipe 14 .

[0061] The inner wall of the inverted frustum-shaped reducer 11 is provided with a spiral guide groove.

[0062] Example 2

[0063] This embodiment provides a method for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by using a device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction, comprising the following steps:

[0064] Step 1: Add MoO3 powder to the sublimation chamber 2 through the feed port 4, close the sealing plate 5, open the sublimation chamber air inlet pipe 9, and introduce argon gas into the sublimation chamber 2 until the sublimation chamber 2 is full. Then, turn on the heating furnace wire and set the heating temperature to 900°C.

[0065] Step 2: When the temperature of the sublimation chamber 2 reaches 700-800°C, hydrogen is introduced, and at the same time, the cyclone separator 23, the circulation system, the first gas compressor 22, the second gas compressor 27, the third gas compressor 28 and the air cooling jacket 29 are turned on.

[0066] The gas flow rate ratio of argon and hydrogen is 3:2. Specifically, the gas flow rate of argon is 300 cm / min, and the gas flow rate of hydrogen is 200 cm / min.

[0067] When the furnace temperature rises to above 800°C, as the gaseous molybdenum oxide sublimates, the gas pressure in the sublimation chamber 2 increases, and the sublimated gaseous molybdenum oxide passes through the porous plate 8 together with the argon gas, and is finally transported by the sublimation chamber discharge pipe 6 to the bottom horizontal tangential inlet of the inverted frustum-shaped reducer 11 and the reducer feed port 1101 and hydrogen, and rotates and mixes in the same direction clockwise / counterclockwise tangentially along the inner wall of the inverted frustum-shaped reducer 11, and a reduction reaction occurs at the same time to generate ultrafine molybdenum powder and water vapor. Under the combined action of the external pressure of the gas, gravity, the supporting force of the inner wall of the inverted frustum-shaped reducer 11 and the friction force, the two products make a spiral motion upward along the inner wall of the inverted frustum-shaped reducer 11; the whole process not only ensures that the ultrafine molybdenum powder always follows the same running trajectory, but also ensures a reducing atmosphere environment, creates the same reaction conditions for the full reduction of the ultrafine molybdenum powder, and achieves the full reduction of the gaseous molybdenum oxide;

[0068] In the early stage of reduction, due to the small bottom radius of the inverted frustum-shaped reducer 11, the rotation speed is high under the same inlet gas velocity, so the centrifugal force is large, causing the gaseous molybdenum oxide and part of the generated ultrafine molybdenum powder, hydrogen, water vapor and argon to spiral upward at the same time. As the horizontal diameter of the inverted frustum-shaped reducer 11 increases, the rotation speed decreases, and the air pressure at the axis position of the frustum decreases. At this time, the ultrafine molybdenum powder with the largest mass and the hydrogen with the highest speed and the lowest density will continue to spiral upward along the inside of the inverted frustum. It moves until it enters the clockwise / counterclockwise tangential reducer outlet 1103 at the top of the inverted frustum-shaped reducer 11 and is discharged outward. At this time, the water vapor and argon will move in the opposite direction, from the high-pressure area of ​​the side wall to the low-pressure area of ​​the axis, thereby realizing the water vapor inside the inverted frustum-shaped reducer 11. Since its upper part is occupied by hydrogen, the water vapor and pressure will gather to the bottom of the inverted frustum-shaped reducer 11 under the influence of partial pressure, and be discharged downward at the damper system 1102 at the center of the bottom of the inverted frustum-shaped reducer 11.

[0069] The hydrogen and ultrafine powder mixed gas discharged from the reducer discharge port 1103 at the top of the inverted frustum-shaped reducer 11 enters the spiral separator 23 to complete gas-solid separation, and the ultrafine powder settles at the bottom of the spiral separator 23 and is collected into the powder collection bin 24, while the hydrogen is discharged through the hydrogen outlet pipe 25 at the top of the spiral powder separator 23, and then further purified and dried in the second drying chamber 26 before entering the hydrogen buffer tank 12 for recycling.

[0070] The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas-phase reduction of the present invention can be used not only for gas-phase reduction and gas-gas synthesis reactions, but also for gas-solid oxidation and calcination reactions. It overcomes the contradiction between the fully closed nature of microfluidic technology and the online separation technology of generated gas, realizes the dual control technology of narrow distribution and low oxidation of ultrafine molybdenum powder, and constructs a method and device system integrating continuous reduction, gas separation and circulation of ultrafine molybdenum powder. The particle size distribution of ultrafine molybdenum powder is controlled by controlling the gas-phase molybdenum trioxide and hydrogen paths and process parameters to achieve control of particle size and distribution.

[0071] The high specific surface area of ​​ultrafine molybdenum powder significantly increases its physical and chemical adsorption of water vapor, leading to oxidation reactions at high temperatures, resulting in high oxygen content in the ultrafine molybdenum powder. This invention utilizes the density difference and kinetic properties of hydrogen and water vapor to achieve rapid online separation of hydrogen, ultrafine molybdenum powder, and water vapor, effectively reducing the adsorption and oxidation reactions of ultrafine molybdenum powder on water vapor molecules, thereby ensuring the goal of low oxidation.

[0072] This method uses molybdenum trioxide sublimation to separate impurities from the main molybdenum element. Within the temperature range of evaporation and sublimation, these impurities are usually unable to form volatile substances and remain in the lower part of the tank, thereby achieving the separation of the main molybdenum and impurity elements, improving the adaptability of molybdenum smelting raw materials, and avoiding the use of chemical purification processes. In addition, all kinds of waste molybdenum metal recovery, volatile molybdenum trioxide flue gas from molybdenum hot pressure processing processes, etc. can be used as raw materials for the method of the present invention, which greatly expands the adaptability of molybdenum smelting raw materials and reduces smelting costs. Compared with the toxicity, harsh preparation environment, conditions and high cost of fluorides and carbonyl molybdenum, the present invention only uses hydrogen, which greatly improves safety and does not rule out any pollution. The raw materials used in this technology are widely available, the generation process is simple, non-toxic and non-corrosive, and can be produced continuously and on a large scale.

[0073] The device of the present invention can also be used for preparing ultrafine tungsten powder and rhenium powder.

[0074] In the description of the present invention, it should be noted that the terms "top", "bottom", "up", "down", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0075] The above embodiments are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art may modify the technical solutions described in the above embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction, characterized in that: The invention comprises a hollow cylindrical furnace body (1) arranged vertically, a sublimation chamber (2) being arranged near the top of the furnace body (1), a feed pipe (3) being arranged at the center of the top of the sublimation chamber (2), the feed pipe (3) extending to the top of the furnace body (1), a feed port (4) being arranged on one side of the feed pipe (3) located outside the furnace body (1), and a sealing plate (5) being arranged at the feed port (4); A sublimation bin discharge pipe (6) is provided near one side of the sublimation bin (2) and extends downwardly therefrom. A partition (7) is vertically provided in the inner cavity of the sublimation bin (2) on the side connected to the sublimation bin discharge pipe (6). A porous plate (8) inclined toward the middle of the sublimation bin (2) is provided on the top of the partition (7). The top of the porous plate (8) is connected to the top wall of the inner cavity of the sublimation bin (2). The upper part of the sublimation chamber (2) is connected to the rear end of the sublimation chamber air inlet pipe (9) on a side away from the sublimation chamber discharge pipe (6), and the head end of the sublimation chamber air inlet pipe (9) is connected to an argon buffer tank (10) arranged outside the furnace body (1); The sublimation chamber (2) is provided with a heating furnace wire outside; The furnace body (1) is further provided with an inverted truncated cone-shaped reducer (11) located at the lower part of the sublimation chamber (2); a reducer feed port (1101) is provided tangentially along the side wall of the lower part of the inverted truncated cone-shaped reducer (11); the reducer feed port (1101) is connected to the tail end of the sublimation chamber discharge pipe (6) and the tail end of the hydrogen inlet pipe (12) arranged in parallel; the head end of the hydrogen inlet pipe (12) is connected to a hydrogen buffer tank (13) arranged outside the furnace body (1); The bottom of the inverted truncated cone-shaped reducer (11) is provided with a damper system (1102), and the bottom of the damper system (1102) is connected to the circulation system via a water vapor outlet pipe (30); A reducer discharge port (1103) is provided on the top of the inverted frustum-shaped reducer (11) on a side away from the reducer feed port (1101), and the reducer discharge port (1103) is connected to the separation and drying system through the reducer discharge pipe (14).

2. The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to claim 1, characterized in that: The circulation system includes a circulating water collecting box (15), a circulating water cooling box (16) is provided on one side of the circulating water collecting box (15), and the top and bottom of the circulating water collecting box (15) and the circulating water cooling box (16) are respectively connected by pipelines; The circulating water cooling box (16) is provided with an exchanger; A water outlet (17) is provided on one side of the bottom of the circulating water collection box (15), and a mixed gas outlet is provided at the center of the top. The mixed gas outlet is connected to the bottom of the first drying chamber (19) through a first mixed gas outlet pipe (18), and the top of the first drying chamber (19) is connected to an argon / hydrogen separator (21) through a second mixed gas outlet pipe (20). The hydrogen outlet of the argon / hydrogen separator (21) is connected to the hydrogen buffer tank (13) through a gas pipeline. The argon outlet of the argon / hydrogen separator (21) is connected to the argon buffer tank (10) through a gas pipeline.

3. The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to claim 2, characterized in that: A first gas compressor (22) and a second gas compressor (28) are respectively provided on the pipeline between the argon / hydrogen separator (21) and the argon buffer tank (10), and on the pipeline between the argon / hydrogen separator (21) and the hydrogen buffer tank (13).

4. The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to claim 1, characterized in that: The separation and drying system includes a spiral separator (23) connected to the reducer discharge pipe (14), a powder collection bin (24) is provided at the bottom of the spiral separator (23), and the top is connected to a second drying chamber (26) through a hydrogen outlet pipe (25), and the second drying chamber (26) is connected to a hydrogen buffer tank (13) through a gas pipeline.

5. The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to claim 4, characterized in that: A third gas compressor (27) is provided on the hydrogen outlet pipe (25) between the spiral separator (23) and the second drying chamber (26).

6. The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to claim 4, characterized in that: An air cooling jacket (29) is provided on the reducer discharge pipe (14).

7. The device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to claim 1, characterized in that: The inner wall of the inverted frustum-shaped reducer (11) is provided with a spiral guide groove.

8. A method for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder using the device for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder by gas phase reduction according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Add MoO3 powder into the sublimation chamber (2) through the feed port (4), close the sealing plate (5), open the sublimation chamber air inlet pipe (9), and introduce argon gas into the sublimation chamber (2) until the sublimation chamber (2) is filled, then turn on the heating furnace wire and set the heating temperature to 900°C; Step 2: When the temperature of the sublimation chamber (2) reaches 700-800°C, hydrogen is introduced, and at the same time, the cyclone separator (23), the circulation system, the first gas compressor (22), the second gas compressor (27), the third gas compressor (28) and the air cooling jacket (29) are turned on.

9. The method for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder as claimed in claim 8, wherein: The gas flow rate ratio of argon and hydrogen was 3:

2.

10. The method for preparing low-oxygen and narrowly distributed ultrafine molybdenum powder according to claim 9, wherein: The gas flow rate of the argon gas is 300 cm / min, and the gas flow rate of the hydrogen gas is 200 cm / min.

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