Hydrogen reduction method for improving reduction efficiency of molybdenum powder

Abstract

The invention discloses a hydrogen reduction method for improving the reduction efficiency of molybdenum powder, which comprises the following steps: preparing molybdenum dioxide subjected to primary reduction into molybdenum dioxide fine powder of which the particle size is not greater than 8 microns, and / or increasing the apparent density of the molybdenum dioxide subjected to primary reduction to 1.5-2.0 g / cm < 3 >; loading the obtained molybdenum dioxide into a porous boat; putting the porous boat filled with molybdenum dioxide into a reduction furnace; closing the reduction furnace, heating the reduction furnace, and introducing hydrogen while heating; water vapor in the reduction furnace is extracted in a pulse mode; and opening the reduction furnace, and taking out the reduced molybdenum powder. By changing the morphology of molybdenum dioxide, the apparent density of molybdenum dioxide is improved, the secondary reduction loading amount is increased, the loading amount is increased by 30-50%, the single-furnace yield is remarkably increased, the secondary reduction process is optimized, the mass transfer efficiency of hydrogen permeation and water vapor overflow is enhanced, the reaction time is shortened, the hydrogen utilization rate is increased by 20% or above, and the reduction time is shortened by 15-25%; the molybdenum powder has uniform particle size (D90 < = 5 microns) and oxygen content < = 0.1%.

Description

Technical Field

[0001] The present invention relates to the technical field of molybdenum powder reduction, and in particular to a hydrogen reduction method for improving the reduction efficiency of molybdenum powder. Background Art

[0002] The traditional hydrogen reduction method for preparing molybdenum powder is usually divided into two stages: primary reduction and secondary reduction. The primary reduction is to reduce MoO3 to MoO2, and the secondary reduction is to reduce the MoO2 after the primary reduction to Mo powder. Problems existing in the existing technology are: first, the amount of the boat loaded in the secondary reduction stage is limited by the bulk density of molybdenum dioxide (MoO2), resulting in low single-furnace output; second, in the secondary reduction process, since the growth mechanism of molybdenum powder is significantly affected by the water vapor partial pressure, the water vapor partial pressure of the material in the traditional process boat gradually increases with the increase of the material layer depth, and the water vapor partial pressure between the material layers differs greatly, resulting in uneven overall particle size distribution of the molybdenum powder, showing the characteristics of small particle size in the upper layer and large particle size in the lower layer; at the same time, hydrogen and the water vapor generated by the reaction counter-current, hinder each other, and the reaction rate is affected by the diffusion mechanism, resulting in low secondary reduction efficiency. These effects lead to high energy consumption, low efficiency and low yield of the current two-stage hydrogen reduction process. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a hydrogen reduction method that improves the reduction efficiency of molybdenum powder.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] A hydrogen reduction method for improving the reduction efficiency of molybdenum powder comprises the following steps:

[0006] S1: preparing the reduced molybdenum dioxide into molybdenum dioxide fine powder with a particle size of no more than 8 μm, and / or increasing the bulk density of the reduced molybdenum dioxide to 1.5-2.0 g / cm 3 ;

[0007] S2: The molybdenum dioxide obtained in step S1 is placed into a porous boat;

[0008] S3: placing the porous boat containing molybdenum dioxide into a reduction furnace;

[0009] S4: closing the reduction furnace and heating the reduction furnace while introducing hydrogen;

[0010] S5: extracting water vapor in the reduction furnace in a pulse manner;

[0011] S6: Open the reduction furnace and take out the reduced molybdenum powder.

[0012] Furthermore, in the step S1, the molybdenum dioxide is placed in a ball mill crusher, and the volume ratio of the crushing balls in the ball mill crusher to the molybdenum dioxide is controlled at 5:1 to 10:1, and after crushing, molybdenum dioxide fine powder with a particle size not greater than 8 μm is obtained.

[0013] Furthermore, the rotation speed of the ball mill crusher is 200-400 rpm, and the crushing time is 30-60 min.

[0014] Furthermore, in the step S1, the molybdenum dioxide is placed in a mixer, and the mixer is controlled to work for 20 to 60 minutes to obtain a bulk density of 1.5 to 2.0 g / cm 3 of the molybdenum dioxide.

[0015] Furthermore, in the step S2, the diameter of the vertical vent holes on the porous boat is 2-5 mm, and the spacing between the vertical vent holes is 10-15 mm.

[0016] Furthermore, in the S4 step, the reduction furnace heating is divided into three stages: the first stage is low-temperature heating, with high-flow hydrogen introduced; the second stage is medium-temperature heating, with medium-flow hydrogen introduced; and the third stage is high-temperature heating, with low-flow hydrogen introduced.

[0017] Furthermore, the temperature of the low-temperature heating is 400-600°C, the temperature of the medium-temperature heating is 600-800°C, and the temperature of the high-temperature heating is 800-1000°C.

[0018] Furthermore, the low flow rate of hydrogen is 3 to 5 L / min, the medium flow rate of hydrogen is 5 to 8 L / min, and the high flow rate of hydrogen is 8 to 12 L / min.

[0019] Furthermore, the water vapor in the reduction furnace is extracted by a vacuum pump, and the working interval of the vacuum pump is 28 to 32 minutes.

[0020] Furthermore, the vacuum pump operates once for 5 to 6 minutes.

[0021] The beneficial effects of the present invention are:

[0022] By changing the molybdenum dioxide morphology, the bulk density is increased, and the secondary reduction boat capacity is increased by 30-50%, significantly boosting single-furnace output. The secondary reduction process is optimized, enhancing the mass transfer efficiency of hydrogen infiltration and water vapor overflow, shortening reaction time, increasing hydrogen utilization by over 20%, and reducing reduction time by 15-25%. The molybdenum powder has a uniform particle size (D90 ≤ 5μm) and an oxygen content ≤ 0.1%. The new process reduces energy consumption, improves efficiency, and increases yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0025] See Figure 1 , the present invention provides a technical solution:

[0026] A hydrogen reduction method for improving the reduction efficiency of molybdenum powder comprises the following steps:

[0027] (1) The reduced molybdenum dioxide is made into a molybdenum dioxide fine powder with a particle size of not more than 8 μm, and / or the bulk density of the reduced molybdenum dioxide is increased to 1.5 to 2.0 g / cm 3 . Put molybdenum dioxide into a ball mill crusher. The volume ratio of the crushing balls in the ball mill crusher to molybdenum dioxide is controlled at 5:1 to 10:1. After crushing, fine molybdenum dioxide powder with a particle size not greater than 8 μm is obtained. The speed of the ball mill crusher is 200 to 400 rpm, and the crushing time is 30 to 60 minutes. Put molybdenum dioxide into a mixer, control the mixer to work for 20 to 60 minutes, and obtain a loose density of 1.5 to 2.0 g / cm 3 Of molybdenum dioxide. Reducing the density of molybdenum dioxide and increasing the density of molybdenum dioxide are two different methods. Either method can be used to produce molybdenum dioxide, or the two methods can be combined. The ball mill crusher and mixer are both equipment in the prior art.

[0028] (2) The molybdenum dioxide obtained in step (1) is placed in a porous boat. The vertical vent holes on the porous boat have a diameter of 2 to 5 mm and a spacing of 10 to 15 mm. The porous boat is a conventional boat, and the vent holes are arranged as needed.

[0029] (3) Place the porous boat containing molybdenum dioxide into a reduction furnace. The reduction furnace is a furnace in the prior art, and the upper temperature limit can be 1200°C.

[0030] (4) Close the reduction furnace and heat it, while introducing hydrogen. The reduction furnace heating is divided into three stages: the first stage is low-temperature heating, with high-flow hydrogen introduced; the second stage is medium-temperature heating, with medium-flow hydrogen introduced; and the third stage is high-temperature heating, with low-flow hydrogen introduced. The temperature of low-temperature heating is 400-600°C, the temperature of medium-temperature heating is 600-800°C, and the temperature of high-temperature heating is 800-1000°C. The low-flow hydrogen is 3-5 L / min, the medium-flow hydrogen is 5-8 L / min, and the high-flow hydrogen is 8-12 L / min. Among them, heating in a step-by-step manner can achieve better heating. The amount of hydrogen introduced is large at first and then small, which avoids hydrogen waste and allows hydrogen to fully react, saving costs. Low-temperature heating includes 400°C but not 600°C, medium-temperature heating includes 600°C but not 800°C, and high-temperature heating includes 800°C and also 1000°C.

[0031] (5) The water vapor in the reduction furnace is extracted in a pulsed manner. The water vapor in the reduction furnace is extracted by a vacuum pump, and the working interval of the vacuum pump is 28 to 32 minutes. The vacuum pump works once for 5 to 6 minutes. Among them, the vacuum pump is a device in the prior art. Generally, the vacuum pump is turned on once every 30 minutes and works for 5 minutes each time. When the vacuum pump is working, the water vapor and hydrogen in the reduction furnace are extracted. Through subsequent processing, the hydrogen can be filtered out for secondary use, further saving costs.

[0032] (6) Open the reduction furnace and take out the reduced molybdenum powder. The generated molybdenum powder is cooled in the reduction furnace. After cooling, the molybdenum powder and the porous boat are taken out of the reduction furnace together, and finally the molybdenum powder is taken out of the porous boat.

[0033] Implementation Example 1

[0034] (1) The MoO2 after primary reduction was mixed in a high energy mixer for 25 min, and the bulk density was increased from 1.03 g / cm 3 Increased to 1.65g / cm 3 .

[0035] (2) The density is 1.65g / cm 3 The MoO2 is loaded into a porous boat having a pore size of 3 mm, and then the porous boat containing MoO2 is pushed into the reduction furnace.

[0036] (3) During the low-temperature heating stage, 10 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 6 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 4 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 800°C for 2 hours.

[0037] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0038] The final oxygen content of molybdenum powder is 0.08%, and the single furnace output is increased by 35%.

[0039] Implementation Example 2

[0040] (1) The MoO2 after primary reduction was mixed in a high energy mixer for 35 min, and the bulk density was increased from 1.03 g / cm 3 Increased to 1.81g / cm 3 .

[0041] (2) The density is 1.81g / cm 3 The MoO2 is loaded into a porous boat having a pore size of 3 mm, and then the porous boat containing MoO2 is pushed into the reduction furnace.

[0042] (3) During the low-temperature heating stage, 10 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 6 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 4 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 800°C for 2 hours.

[0043] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0044] The final oxygen content of molybdenum powder is 0.08%, and the single furnace output is increased by 41%.

[0045] Implementation Example 3

[0046] (1) The reduced molybdenum dioxide was placed in a ball mill. The volume ratio of the crushing balls to the molybdenum dioxide in the ball mill was controlled at 8:1. The speed of the ball mill was 300 rpm. The crushing time was 35 min. Fine molybdenum dioxide powder with a particle size of 5 μm was obtained.

[0047] (2) MoO2 with a particle size of 5 μm is loaded into a porous boat with a pore size of 3 mm, and then the porous boat filled with MoO2 is pushed into the reduction furnace.

[0048] (3) During the low-temperature heating stage, 10 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 6 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 4 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 800°C for 2 hours.

[0049] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0050] Final restore time is shortened by 20%.

[0051] Implementation Example 4

[0052] (1) The reduced molybdenum dioxide was placed in a ball mill. The volume ratio of the crushing balls to the molybdenum dioxide in the ball mill was controlled at 8:1. The speed of the ball mill was 300 rpm. The crushing time was 35 min. The particle size of the molybdenum dioxide fine powder was reduced from 30 μm to 5 μm. The 5 μm molybdenum dioxide fine powder was then placed in a high-energy mixer and mixed for 35 min. The bulk density was reduced from 1.00 g / cm 3 Increased to 1.80g / cm 3 .

[0053] (2) The bulk density is 1.80 g / cm 3 The MoO2 is loaded into a porous boat having a pore size of 3 mm, and then the porous boat containing MoO2 is pushed into the reduction furnace.

[0054] (3) During the low-temperature heating stage, 8 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 5 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 3 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 920°C for 4 hours, with a material layer thickness of 1.5 cm.

[0055] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0056] The final molybdenum powder oxygen content is 0.08%, the molybdenum powder diameter is 4.5μm, and the single furnace output is increased by 41.25%.

[0057] Implementation Example 5

[0058] (1) The reduced molybdenum dioxide was placed in a ball mill. The volume ratio of the crushing balls to the molybdenum dioxide in the ball mill was controlled at 7:1. The speed of the ball mill was 320 rpm. The crushing time was 30 min. The particle size of the molybdenum dioxide fine powder was reduced from 30 μm to 8 μm. The 8 μm molybdenum dioxide fine powder was then placed in a high-energy mixer and mixed for 25 min. The bulk density was reduced from 1.00 g / cm 3 Increased to 1.50g / cm 3 .

[0059] (2) The bulk density is 1.50 g / cm 3 The MoO2 is loaded into a porous boat having a pore size of 3 mm, and then the porous boat containing MoO2 is pushed into the reduction furnace.

[0060] (3) During the low-temperature heating stage, 8 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 5 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 3 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 920°C for 4 hours, with a material layer thickness of 1.5 cm.

[0061] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0062] The final molybdenum powder has an oxygen content of 0.12%, a diameter of 6.8 μm, and a single furnace output increased by 35%.

[0063] Implementation Example 6

[0064] (1) The reduced molybdenum dioxide was placed in a ball mill. The volume ratio of the crushing balls to the molybdenum dioxide in the ball mill was controlled at 8:1. The speed of the ball mill was 300 rpm. The crushing time was 35 min. The particle size of the molybdenum dioxide fine powder was reduced from 30 μm to 5 μm. The 5 μm molybdenum dioxide fine powder was then placed in a high-energy mixer and mixed for 35 min. The bulk density was reduced from 1.00 g / cm 3 Increased to 1.80g / cm 3 .

[0065] (2) The bulk density is 1.80 g / cm 3 The MoO2 is loaded into a porous boat having a pore size of 3 mm, and then the porous boat containing MoO2 is pushed into the reduction furnace.

[0066] (3) During the low-temperature heating stage, 8 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 5 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 3 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 920°C for 4 hours, with a material layer thickness of 1.5 cm.

[0067] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0068] Finally, the oxygen contents of the molybdenum powder in the upper and lower layers of the boat were detected to be 0.10% and 0.35% respectively.

[0069] Implementation Example 7

[0070] (1) The reduced molybdenum dioxide was placed in a ball mill. The volume ratio of the crushing balls to the molybdenum dioxide in the ball mill was controlled at 8:1. The speed of the ball mill was 300 rpm. The crushing time was 35 min. The particle size of the molybdenum dioxide fine powder was reduced from 30 μm to 5 μm. The 5 μm molybdenum dioxide fine powder was then placed in a high-energy mixer and mixed for 35 min. The bulk density was reduced from 1.00 g / cm 3Increased to 1.80g / cm 3 .

[0071] (2) The bulk density is 1.80 g / cm 3 The MoO2 is loaded into a porous boat having a pore size of 3 mm, and then the porous boat containing MoO2 is pushed into the reduction furnace.

[0072] (3) During the low-temperature heating stage, 12 L / min of hydrogen was introduced into the reduction furnace; during the medium-temperature heating stage, 8 L / min of hydrogen was introduced into the reduction furnace; during the high-temperature heating stage, 4 L / min of hydrogen was introduced into the reduction furnace, and the temperature was kept at 920°C for 4 hours, with a material layer thickness of 1.5 cm.

[0073] (4) The vacuum pump is turned on every 30 minutes and works for 5 minutes each time.

[0074] The final oxygen contents of the molybdenum powder in the upper and lower layers of the boat were 0.08% and 0.15%, respectively.

[0075] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder, characterized in that: The following steps are involved: S1: preparing the reduced molybdenum dioxide into molybdenum dioxide fine powder with a particle size of no more than 8 μm, and / or increasing the bulk density of the reduced molybdenum dioxide to 1.5-2.0 g / cm 3 ; S2: The molybdenum dioxide obtained in step S1 is placed into a porous boat; S3: placing the porous boat containing molybdenum dioxide into a reduction furnace; S4: closing the reduction furnace and heating the reduction furnace while introducing hydrogen; S5: extracting water vapor in the reduction furnace in a pulse manner; S6: Open the reduction furnace and take out the reduced molybdenum powder.

2. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to claim 1, characterized in that: In the step S1, the molybdenum dioxide is placed in a ball mill, and the volume ratio of the crushing balls in the ball mill to the molybdenum dioxide is controlled at 5:1 to 10:1, and after crushing, fine molybdenum dioxide powder with a particle size of no more than 8 μm is obtained.

3. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to claim 2, characterized in that: The rotation speed of the ball mill crusher is 200-400 rpm, and the crushing time is 30-60 min.

4. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to claim 1, characterized in that: In the step S1, the molybdenum dioxide is placed in a mixer, and the mixer is controlled to work for 20 to 60 minutes to obtain a bulk density of 1.5 to 2.0 g / cm 3 of the molybdenum dioxide.

5. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to any one of claims 1 to 4, characterized in that: In the step S2, the diameter of the vertical vent holes on the porous boat is 2-5 mm, and the spacing between the vertical vent holes is 10-15 mm.

6. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to any one of claims 1 to 4, characterized in that: In the step S4, the reduction furnace heating is divided into three stages: the first stage is low-temperature heating, with high-flow hydrogen introduced; the second stage is medium-temperature heating, with medium-flow hydrogen introduced; and the third stage is high-temperature heating, with low-flow hydrogen introduced.

7. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to claim 6, characterized in that: The temperature of the low-temperature heating is 400-600°C, the temperature of the medium-temperature heating is 600-800°C, and the temperature of the high-temperature heating is 800-1000°C.

8. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to claim 6, characterized in that: The low flow rate of hydrogen is 3 to 5 L / min, the medium flow rate of hydrogen is 5 to 8 L / min, and the high flow rate of hydrogen is 8 to 12 L / min.

9. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to any one of claims 1 to 4, characterized in that: The water vapor in the reduction furnace is extracted by a vacuum pump, and the working interval of the vacuum pump is 28 to 32 minutes.

10. A hydrogen reduction method for improving the reduction efficiency of molybdenum powder according to claim 9, characterized in that: The vacuum pump works once for 5 to 6 minutes.

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