Device for preparing refractory metal by magnesiothermic reduction method

Abstract

The utility model relates to a device for preparing refractory metal by using a magnesiothermic reduction method in the technical field of refractory metal powder preparation, which comprises a magnesium powder evaporator and a heater I of the evaporator, and the evaporator is provided with an air inlet and a magnesium steam outlet; the reaction area comprises a reactor containing diluted salt and a heater II of the reactor, a vacuum suction port and a gas outlet are formed in the reactor, a perforated plate is arranged in the reactor, a gas distribution disc is arranged below the perforated plate, and a refractory metal oxide raw material is laid on the upper surface of the perforated plate; the gas distribution disc is connected to a magnesium steam outlet of the evaporator through a gas path communicating pipe, and the gas distribution disc, the porous plate and the raw materials are all submerged in the diluted salt in the reactor; the gas inlet is used for introducing argon, and the gas outlet is used for discharging redundant magnesium steam and argon. According to the device, tantalum powder and other refractory metal are prepared in the mode that gaseous magnesium reduction is conducted in fused salt, the oxygen content in the refractory metal powder can be reduced, the particle sintering structure is promoted, and the impurity content is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to refractory metal powder preparation technical field, concretely relates to a device for preparing refractory metal by magnesium heat reduction method. BACKGROUND

[0002] Refractory metal generally refers to the metal with the melting point higher than 1650 DEG C, mainly including tungsten, tantalum, molybdenum, niobium, rhenium and the like.Tantalum is a kind of rare metal with black ash, has high melting point, belongs to refractory metal, has excellent corrosion resistance (especially can form dense oxide film in acidic medium) and good biocompatibility, and its high specific surface area characteristics make it become the core material for manufacturing micro high capacity tantalum capacitor, is widely used in consumer electronics, communication equipment and automotive electronics field.Niobium is a kind of rare high melting point metal with silver gray, has good superconductivity, corrosion resistance, wear resistance and the like, is widely used in steel, superconducting material, aerospace, atomic energy and the like field.The main application of tantalum is to make tantalum capacitor, as the raw material of tantalum capacitor, the performance of tantalum powder determines the level of tantalum capacitor performance.

[0003] Taking the preparation of tantalum powder as an example, the current industrialized production method of metal tantalum powder mainly includes sodium reduction potassium fluorotantalate method and magnesium reduction tantalum oxide method.Sodium reduction potassium fluorotantalate method uses potassium fluorotantalate (K2TaF7) as raw material and sodium as reducing agent to generate metal tantalum powder in high-temperature molten state (700-900 DEG C) by displacement reaction.But the reaction speed of the process is fast, the heat release is large, the concentration gradient exists in liquid-liquid reduction system, and the reaction controllability is poor, so that the particle size of product tantalum powder is uneven and the impurity content is high.

[0004] Magnesium reduction tantalum oxide method can be divided into magnesium heat self-propagating method and gaseous magnesium reduction method according to different reduction modes.The tantalum powder obtained by magnesium heat self-propagating method has the defects of uneven particle, serious sintering between particles and poor controllability.Gaseous magnesium reduction method utilizes magnesium vapor to react with raw material, the heat release is small, the controllability is good, the specific surface area of obtained tantalum powder is large, and high specific capacity tantalum powder can be prepared, but the tantalum powder also has the problems of high oxygen content, which usually needs secondary reduction, and poor sintering resistance, and it is difficult to form sintering structure between particles. UTILITY MODEL CONTENTS

[0005] In view of the problems of gaseous magnesium reduction method, such as small heat release, slow reaction speed, small tantalum powder particle, high oxygen content and difficult to form sintering structure, the utility model provides a device for preparing refractory metal by magnesium heat reduction method, the addition and existence of molten salt in the reaction process in the device can improve the surface activity of tantalum powder particle and reduce the impurity content on the surface of tantalum powder.

[0006] In order to realize the above object, the utility model adopts the following technical scheme:

[0007] A device for preparing refractory metal by magnesium thermal reduction method, comprising a magnesium evaporation zone and a reaction zone, the magnesium evaporation zone comprises an evaporator for containing magnesium powder raw material and a heater one arranged outside the evaporator, and the evaporator is provided with an air inlet and a magnesium vapor outlet.

[0008] The reaction zone comprises a reactor containing dilute salt inside and a heater two arranged outside the reactor, and the reactor is provided with a vacuum suction port and an air outlet, and the vacuum suction port is connected to a vacuum system for vacuumizing the inside of the reactor.

[0009] A perforated plate is horizontally arranged at the lower part of the inside of the reactor, and a gas distribution plate with a plurality of air outlets uniformly arranged on the upper wall is arranged below the perforated plate, the upper surface of the perforated plate is used for laying refractory metal oxide raw material, the air inlet of the gas distribution plate is connected to the magnesium vapor outlet of the evaporator through an air path communication pipe, and the gas distribution plate, the perforated plate and the refractory metal oxide raw material are all submerged in the dilute salt in the reactor.

[0010] Before the reaction starts, the dilute salt is laid on the lower part of the perforated plate, then the refractory metal oxide raw material is laid on the perforated plate, and then the dilute salt is continuously added above the refractory metal oxide raw material, and the amount of the added salt is enough to ensure that the height of the dilute salt after melting (i.e. molten salt) still exceeds the height of the refractory metal oxide raw material on the perforated plate.

[0011] The air inlet is used for introducing atmosphere gas into the evaporator, and the air outlet is used for discharging excess magnesium vapor and the atmosphere gas. During the reaction, the reactor is heated first, and then the magnesium evaporator is heated after the dilute salt is completely melted. Then the argon gas carrying the magnesium vapor enters the reactor, reacts with the refractory metal oxide raw material through diffusion, and the excess argon gas and magnesium vapor are discharged from the air outlet.

[0012] Preferably, the refractory metal in the utility model mainly refers to tantalum powder or niobium powder, and the refractory metal oxide raw material mainly refers to tantalum oxide or niobium oxide. The device for preparing refractory metal by magnesium thermal reduction method provided by the utility model can be used for preparing metal tantalum powder, metal niobium powder, and other refractory metals such as tungsten, molybdenum and rhenium.

[0013] Preferably, the evaporator and the reactor are both closed cylindrical volume cavities, which are composed of a cylindrical tank body and a circular cover body sealedly connected.

[0014] Preferably, the material of the reactor and the perforated plate is nickel-based alloy, which still has high strength and anti-oxidation corrosion ability under high temperature conditions.

[0015] Preferably, the dilute salt is one or more of potassium chloride, sodium chloride, magnesium chloride, calcium chloride, or a rare earth salt such as lanthanum chloride.

[0016] Preferably, the atmosphere gas is argon. After vacuumizing the reactor and the evaporator, the argon is purged, and the argon is passed into the evaporator at a certain flow rate and can pass into the reactor through the gas passage communication pipe. After repeated purging, the internal environment of the reactor and the evaporator is completely replaced.

[0017] The utility model also includes other components that enable it to be used normally, which are all conventional means in the field, and in addition, the devices or components not specified in the utility model, such as dilute salt, evaporator, reactor, heater, and vacuum system, all adopt the existing technology in the field.

[0018] The utility model has the beneficial effects as follows:

[0019] The device for preparing refractory metal by using magnesium hot reduction method provided by the utility model adopts the process mode of gaseous magnesium reduction in molten salt. The addition of molten salt can further absorb the heat released during the reaction and slow down the reaction speed. Meanwhile, the addition of molten salt can promote the diffusion sintering of refractory metal powder such as tantalum powder and niobium powder, thereby promoting the reaction, reducing the oxygen content in the refractory metal powder, and promoting the formation of sintering structure between particles. The presence of molten salt can improve the surface activity of refractory metal powder and reduce the impurity content of refractory metal powder. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structure schematic view of the device for preparing refractory metal by using magnesium hot reduction method in the embodiment.

[0021] In the figure: 1. evaporator; 2. heater one; 3. gas inlet; 4. reactor; 5. heater two; 6. gas outlet; 7. vacuum system; 8. perforated plate; 9. gas distribution disc; 10. gas passage communication pipe; 11. magnesium powder raw material; 12. dilute salt; 13. refractory metal oxide raw material. DETAILED DESCRIPTION

[0022] The technical scheme of the utility model will be clearly and completely described below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the utility model, but not all the embodiments.

[0023] Embodiment 1

[0024] As Figure 1As shown in the figure, the device for preparing refractory metal by magnesium thermal reduction method comprises a magnesium evaporation zone and a reaction zone. The magnesium evaporation zone comprises an evaporator 1 for containing magnesium powder raw material 11 and a heater 1 2 arranged outside the evaporator. The evaporator is provided with an air inlet 3 and a magnesium vapor outlet.

[0025] The reaction zone comprises a reactor 4 containing dilute salt 12 and a heater 2 5 arranged outside the reactor. The reactor is provided with a vacuum suction port and an air outlet 6. The vacuum suction port is connected to a vacuum system 7 for vacuumizing the interiors of the evaporator and the reactor which are in communication with each other. The vacuum system adopts a vacuum pump.

[0026] The evaporator and the reactor are both closed cylindrical volume cavities which are composed of a cylindrical tank body and a circular cover body sealedly connected. The air inlet is used for introducing atmosphere gas into the evaporator, and the air outlet is used for discharging excess magnesium vapor and the atmosphere gas. The atmosphere gas adopts argon.

[0027] A perforated plate 8 is horizontally arranged at the lower part of the inside of the reactor. The materials of the reactor and the perforated plate are both nickel-based alloy. A gas distribution plate 9 with a plurality of air outlets uniformly arranged on the upper wall is arranged below the perforated plate. The upper surface of the perforated plate is used for laying refractory metal oxide raw material 13. This embodiment is mainly used for preparing metal tantalum powder. The refractory metal in this embodiment specifically refers to metal tantalum, and the refractory metal oxide raw material specifically refers to tantalum oxide raw material.

[0028] The air inlet end of the gas distribution plate is connected to the magnesium vapor outlet of the evaporator through a gas path communication pipe 10. The gas distribution plate, the perforated plate and the tantalum oxide raw material are all submerged in the dilute salt in the reactor.

[0029] The dilute salt is single potassium chloride, sodium chloride, magnesium chloride, calcium chloride or rare earth salt such as lanthanum chloride or a mixture of a plurality of different rare earth salts. For example, before the reaction starts, potassium chloride and sodium chloride can be uniformly mixed in a molar ratio of 1:1, spread on the lower part of the perforated plate, and then the tantalum oxide raw material is laid on the perforated plate. Then the mixed salt of potassium chloride and sodium chloride is continuously added on the raw material, so that the height of the mixed salt after melting exceeds the height of the tantalum oxide raw material, that is, the tantalum oxide raw material is always submerged below the molten salt liquid level during the reaction. At the same time, twice excess magnesium powder is added in the evaporator.

[0030] Before the reaction starts, the dilute salt is spread on the lower part of the perforated plate, and then the tantalum oxide raw material is laid on the perforated plate. Then the dilute salt is continuously added above the tantalum oxide raw material. The amount of the dilute salt added should ensure that the height of the dilute salt after melting (i.e. molten salt) also exceeds the height of the tantalum oxide raw material. The addition of molten salt can promote the growth and sintering of tantalum powder particles, which is beneficial to the formation of sintered structure and the reduction of impurity content.

[0031] The reactor and the evaporator are vacuumized (to below 10 Pa) and then cleaned by argon gas, the argon gas is circulated at a flow rate of 800 ml / min, the cleaning is repeated for multiple times until the internal environment of the reactor and the evaporator is completely replaced, and then the vacuum system is closed. During the reaction, the reactor is first heated to 1000℃ at a heating rate of 10℃ / min, after the temperature is increased to the set temperature, the evaporator is heated, the temperature is increased to 900℃ to make the magnesium powder gasify; the argon gas carries the magnesium vapor to the reactor to react with the tantalum oxide, and the temperature is kept for 6h; after the reaction is completed, the furnace is cooled to room temperature to obtain the product, the product is washed with water and acid to obtain the tantalum powder, and the excess argon gas and the magnesium vapor are discharged from the gas outlet.

[0032] Example 2

[0033] The difference between the embodiment and the embodiment 1 is that the embodiment is mainly used for preparing the metal niobium powder, the refractory metal in the embodiment is specifically the metal niobium, and the refractory metal oxide raw material is specifically the niobium oxide raw material.

[0034] The technical scheme of the utility model is not limited to the restriction of the above specific embodiments, and many modifications and changes are obvious to those skilled in the art without deviating from the scope and spirit of the described embodiments, and any technical modification made within the spirit and principles of the utility model falls within the protection scope of the utility model.

Claims

1. An apparatus for preparing refractory metals using a magnesothermic reduction method, comprising a magnesium evaporation zone and a reaction zone, characterized in that: The magnesium evaporation zone includes an evaporator for holding magnesium powder raw materials and a heater 1 located outside the evaporator. The evaporator is equipped with an air inlet and a magnesium vapor outlet. The reaction zone includes a reactor containing diluted salt and a heater 2 located outside the reactor. The reactor is equipped with a vacuum suction port and an air outlet. The vacuum suction port is connected to a vacuum system for evacuating the reactor. A perforated plate is horizontally mounted on the lower inner side of the reactor. Below the perforated plate is a gas distribution plate with a plurality of evenly spaced air outlets on its upper wall. The upper surface of the perforated plate is used to lay refractory metal oxide raw materials. The air inlet of the gas distribution plate is connected to the magnesium vapor outlet of the evaporator through a gas passage connecting pipe. The gas distribution plate, the perforated plate, and the refractory metal oxide raw materials are all submerged in the diluted salt inside the reactor. The air inlet is used to introduce atmospheric gas into the evaporator, and the air outlet is used to discharge excess magnesium vapor and the atmospheric gas.

2. The apparatus for preparing refractory metals using the magnesothermic reduction method according to claim 1, characterized in that: Both the evaporator and the reactor are closed cylindrical cavities.

3. The apparatus for preparing refractory metals using the magnesothermic reduction method according to claim 1, characterized in that: Both the reactor and the perforated plate are made of nickel-based alloys.

4. The apparatus for preparing refractory metals using the magnesothermic reduction method according to claim 1, characterized in that: The refractory metal is tantalum powder or niobium powder; the refractory metal oxide raw material is tantalum oxide or niobium oxide.

5. The apparatus for preparing refractory metals using the magnesothermic reduction method according to claim 1, characterized in that: The diluent is potassium chloride, sodium chloride, magnesium chloride, calcium chloride, or lanthanum chloride.

6. The apparatus for preparing refractory metals using the magnesothermic reduction method according to claim 1, characterized in that: The atmospheric gas is argon.

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