Molybdenum powder preparation method based on molybdenum trioxide one-step reduction and molybdenum powder

Abstract

The invention discloses a molybdenum powder preparation method based on molybdenum trioxide one-step reduction and molybdenum powder. The preparation method comprises the following steps: carrying out primary reduction reaction on molybdenum trioxide in a primary reduction furnace to obtain molybdenum powder; wherein the primary reduction furnace comprises three temperature zones, and the temperatures of the three temperature zones are set to be 450-600 DEG C, 750-850 DEG C and 900-1100 DEG C respectively; intermittent boat pushing is adopted in the primary reduction reaction, and the boat pushing period is 15-23 min / time. According to the method, the molybdenum powder which is uniform in granularity, high in purity and high in yield can be prepared through one-step continuous hydrogen reduction of the raw material molybdenum trioxide, and the production cost and the energy consumption are remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of molybdenum powder preparation methods, and particularly to a molybdenum powder preparation method and molybdenum powder based on one-step reduction of molybdenum trioxide. Background Art

[0002] As an important metal material, molybdenum powder has a wide range of applications in the metallurgical industry. Its unique physical and chemical properties make it a key component for improving material performance. Currently, the mainstream method for preparing molybdenum powder is the multi-step hydrogen reduction method, including: the first step: reducing molybdenum powder raw materials to molybdenum dioxide in a hydrogen atmosphere at 400 - 600 °C; the second step: secondarily reducing molybdenum dioxide to metallic molybdenum powder at 900 - 1100 °C. Although this preparation method has mature technology and wide application, it requires multiple pieces of equipment, multiple operators, and step-by-step production, resulting in problems such as high energy consumption, low efficiency, large raw material consumption, and long production cycle, and it is difficult to meet the market's demand for high-performance and low-cost molybdenum powder preparation.

[0003] For example, the prior art CN102601385A discloses a method for preparing molybdenum powder, which includes reducing molybdenum trioxide in a four-zone or five-zone primary reduction furnace at 340 °C - 660 °C, pushing the boat once every 30 minutes for reduction to obtain molybdenum dioxide, and then reducing molybdenum dioxide in a four-zone or five-zone secondary reduction furnace at 920 °C - 1080 °C, pushing the boat once every 0.5 minutes - 2 minutes for reduction to obtain molybdenum powder.

[0004] Or, for example, the prior art CN103203455A discloses a method for preparing molybdenum powder, which includes performing primary reduction of molybdenum trioxide in a reduction furnace with 4 temperature zones to obtain molybdenum dioxide powder, and then performing secondary reduction of molybdenum dioxide powder in a reduction furnace with 5 temperature zones to obtain molybdenum powder.

[0005] The above prior arts all require at least two reduction furnaces with multiple temperature zones for step-by-step production, and it is difficult to realize the process of continuously reducing raw materials to obtain molybdenum powder. The steps are complex, the cost is high, and the consumption is large.

[0006] Therefore, it is urgently needed in the art to develop a more economical and efficient method for preparing molybdenum powder by one-step reduction of raw materials. Summary of the Invention

[0007] Aiming at the defects of the prior art, the purpose of the present invention is to provide a new method for preparing molybdenum powder by one-step reduction method, which can obtain molybdenum powder with uniform particle size, high purity, and high yield through one-step continuous hydrogen reduction of the raw material molybdenum trioxide.

[0008] The technical solution of the present invention is as follows: A method for preparing molybdenum powder by one-step reduction of molybdenum trioxide, which includes: placing the raw material molybdenum trioxide in a boat and putting it into a primary reduction furnace with hydrogen flowing through for a primary reduction reaction to obtain molybdenum powder; the primary reduction furnace includes three temperature zones, and the temperature settings are respectively: the first temperature zone: 450 - 600 °C, the second temperature zone: 750 - 850 °C, the third temperature zone: 900 - 1100 °C; in the primary reduction reaction, intermittent boat pushing is adopted, the boat pushing period is 15 - 23 min / time, and the residence time in each temperature zone is 1.25 - 1.92 h.

[0009] In the above technical solution, the residence time in each temperature zone is the total residence time including the boat pushing time. For example, if the length of each temperature zone is set to be approximately the length of 5 boats, when a boat enters a certain temperature zone and the boat is pushed 5 times in succession to push it to the next temperature zone, then the residence time of the boat in this temperature zone is the time of 5 boat pushings.

[0010] The inventors unexpectedly found that through specific hydrogen kinetics regulation, such as in the hydrogen reduction reaction, by synergistically controlling a specific boat pushing speed (15 - 23 min / time) and a specific temperature zone setting (the first temperature zone: 450 - 600 °C, the second temperature zone: 750 - 850 °C, the third temperature zone: 900 - 1100 °C), precise control of the reaction rate of reducing molybdenum trioxide to molybdenum powder and the water vapor partial pressure during the reaction can be achieved, thereby effectively controlling the formation rate and morphology of the products during the reaction, eliminating phenomena such as caking and agglomeration of materials and sublimation of raw materials during the reaction, and obtaining a one-step reduction product with a very high sieving rate and finished product rate.

[0011] The reaction formula of the primary reduction reaction carried out in the above preparation method is as follows: 3MoO3 + 3H2 → 3Mo + 3H2O According to some preferred embodiments of the present invention, the loading amount of molybdenum trioxide in the boat is 1.0 - 1.5 kg / boat.

[0012] According to some preferred embodiments of the present invention, the inlet flow rate of hydrogen is 250 - 500 L / min, the dew point is -10 °C to 20 °C, and the purity ≥ 99.99%.

[0013] According to some preferred embodiments of the present invention, the preparation method further includes: sieving the product obtained from the primary reduction reaction through an 80 - mesh sieve to obtain the molybdenum powder.

[0014] According to some preferred embodiments of the present invention, the purity of the particle size of molybdenum trioxide ≥ 99.9%, and the particle diameter is 8 - 20 μm.

[0015] According to some preferred embodiments of the present invention, in the primary reduction reaction, the furnace pressure in the primary reduction furnace is 2.2 - 2.8 KPa.

[0016] The present invention further provides molybdenum powder prepared according to the above method.

[0017] The obtained molybdenum powder has a particle size of 2.0 - 6.0 μm, uniform distribution, an oxygen content of ≤0.2%, and a sieving rate of ≥95% after passing through a 80 - mesh sieve after the first reduction.

[0018] The present invention has the following beneficial effects: The present invention can directly convert molybdenum trioxide into high - quality molybdenum powder through a one - step reduction reaction using a single reduction furnace, reducing the generation of intermediate molybdenum dioxide and the reaction process, realizing continuous reduction production of molybdenum powder, significantly shortening the preparation cycle, energy consumption, and equipment and personnel costs of molybdenum powder; The molybdenum powder obtained by the present invention has a uniform particle size distribution, high purity, and a high sieving rate of the finished product, maintaining or even improving the product quality while reducing costs; Compared with the traditional two - step reduction preparation method, the total preparation cycle of the present invention is shortened by more than 30%, the energy consumption is reduced by more than 20%, and the investment in personnel and equipment is reduced by more than 50%. Description of the Drawings

[0019] Figure 1 It is a SEM image of the molybdenum powder obtained in Example 2 magnified 30 times; Figure 2 It is a SEM image of the molybdenum powder obtained in Example 2 magnified 500 times; Figure 3 It is a SEM image of the molybdenum powder obtained in Example 2 magnified 1000 times; Figure 4 It is a SEM image of the molybdenum powder obtained in Example 2 magnified 5000 times; Figure 5 It is the material caking phenomenon that appears in Comparative Example 1, where (a) is the caking phenomenon of the lower - layer material and (b) is the caking phenomenon of the upper - layer material; Figure 6 It is the phenomenon that the lower - layer material in Comparative Example 1 adheres to the boat; Figure 7 It is the sublimation phenomenon of the bottom - layer material that appears in Comparative Example 1. Detailed Embodiments

[0020] Next, the technical solutions in the present invention will be further described in combination with the embodiments and drawings of the present invention. The following described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the scope of protection of the present invention.

[0021] Example 1

[0022] The molybdenum powder is prepared through the following steps: (1) Take 1.2 kg of loose powder of MoO3 and place it in a boat. The boat used is a boat cast from Gr28Ni48 alloy, with dimensions of 500 mm × 80 mm × 80 mm and a thickness of 5 mm. Continuously introduce hydrogen through a hydrogen purification circulation system and control the hydrogen flow rate to be 300 L / min and the hydrogen dew point to be 20°C; (2) Push the boat into a reduction furnace with three temperature zones. The length of each temperature zone is approximately 5 times the length of a boat. The temperatures of the three temperature zones are set at 450°C, 850°C, and 1100°C respectively. Adjust the pressure in the reduction furnace to 2.5 kPa, control the boat pushing rate to be 18 min / time, and the residence time in each temperature zone to be 1.5 h to obtain the product molybdenum powder.

[0023] Pass the obtained product molybdenum powder through an 80-mesh sieve, and the sieving rate reaches 98%. Detect the oxygen content of the obtained molybdenum powder by the "inert gas fusion infrared absorption method - thermal conductivity method" in GB / T 4325 "Methods for Chemical Analysis of Molybdenum", and the oxygen content is 0.10%, meeting the requirements of GB / T3461-2016.

[0024] Example 2

[0025] The molybdenum powder is prepared through the following steps: (1) Take 1.2 kg of loose powder of MoO3 and place it in a boat. The boat used is a boat cast from Gr28Ni48 alloy, with dimensions of 500 mm × 80 mm × 80 mm and a thickness of 5 mm. Continuously introduce hydrogen through a hydrogen purification circulation system and control the hydrogen flow rate to be 300 L / min and the hydrogen dew point to be 20°C; (2) Push the boat into a reduction furnace with three temperature zones. The length of each temperature zone is approximately 5 times the length of a boat. The temperatures of the three temperature zones are set at 550°C, 850°C, and 1050°C respectively. Adjust the pressure in the reduction furnace to 2.5 kPa, control the boat pushing rate to be 16 min / time, and the residence time in each temperature zone to be 1.333 h to obtain the product molybdenum powder.

[0026] Pass the obtained product molybdenum powder through an 80-mesh sieve, and the sieving rate reaches 99%. Detect the oxygen content of the obtained molybdenum powder by the "inert gas fusion infrared absorption method - thermal conductivity method" in GB / T 4325 "Methods for Chemical Analysis of Molybdenum", and the oxygen content is 0.08%, meeting the requirements of GB / T3461-2016.

[0027] The SEM images of the obtained product molybdenum powder are as shown in the appendix Figures 1-4 as follows, where Figure 1 is an image magnified 30 times (30×), Figure 2 is an image magnified 500 times (500×), Figure 3 is an image magnified 1000 times (1000×), Figure 4It is an image magnified 5000 times (5000×). It can be seen that the obtained molybdenum powder has uniform particle size, uniform dispersion, high purity, and no adhesion or caking phenomenon.

[0028] Comparative Example 1

[0029] Molybdenum powder was prepared through the following steps: (1) Take 1.4 kg of loose powder of MoO3 and place it in a boat. The boat used is a boat cast from Gr28Ni48 alloy, with dimensions of 500 mm × 80 mm × 80 mm and a thickness of 5 mm. Continuously introduce hydrogen through a hydrogen purification circulation system and control the hydrogen flow rate to be 250 L / min and the hydrogen dew point to be -10°C; (2) Push the boat into a reduction furnace with three temperature zones. The length of each temperature zone is approximately 5 times the length of the boat. The temperatures of the three temperature zones are set at 700°C, 900°C, and 1050°C respectively. Adjust the pressure in the reduction furnace to 2.9 kPa, control the boat pushing rate to be 29 min / time, and the residence time in each temperature zone to be 2.41 h to obtain the product molybdenum powder.

[0030] Sieve the obtained product molybdenum powder through an 80-mesh sieve, and the sieving rate is 20%. Observe the pushed-out boat. The lower-layer material is severely caked and there is a situation of sticking to the boat. At the same time, some molybdenum trioxide at the bottom layer has sublimated, as shown in the appendix Figures 5-7 shown, where Figure 5 (a) in it is the caking phenomenon of the lower-layer material, Figure 5 (b) in it is the caking phenomenon of the upper-layer material, Figure 6 is the phenomenon of sticking to the boat of the lower-layer material, Figure 7 is the sublimation phenomenon of the bottom-layer material.

[0031] Detect the oxygen content of the obtained molybdenum powder by "Inert Gas Fusion Infrared Absorption Method - Thermal Conductivity Method" in GB / T 4325 "Methods for Chemical Analysis of Molybdenum", which is 0.5%, not meeting the requirements of GB / T3461-2016.

[0032] Comparative Example 2

[0033] Molybdenum powder was prepared through the following steps: (1) Take 1.3 kg of loose powder of MoO3 and place it in a boat. The boat used is a boat cast from Gr28Ni48 alloy, with dimensions of 500 mm × 80 mm × 80 mm and a thickness of 5 mm. Continuously introduce hydrogen through a hydrogen purification circulation system and control the hydrogen flow rate to be 280 L / min and the hydrogen dew point to be -10°C; (2) Push the boat into a reduction furnace with three temperature zones. The length of each temperature zone is approximately equal to the length of 5 boats. The temperatures of the three temperature zones are set at 650 °C, 950 °C, and 1000 °C respectively. Adjust the pressure inside the reduction furnace to 2.7 kPa, control the boat-pushing rate at 24 min / time, and the residence time in each temperature zone is 2.0 h to obtain the product molybdenum powder.

[0034] Screen the obtained product molybdenum powder through an 80-mesh sieve. The sieving rate is 30%. Observe the pushed boat. The caking of the lower-layer material is reduced compared to Comparative Example 1. At the same time, some molybdenum trioxide has sublimated.

[0035] Detect the oxygen content of the obtained molybdenum powder by "Inert Gas Fusion Infrared Absorption Method - Thermal Conductivity Method" in GB / T 4325 "Methods for Chemical Analysis of Molybdenum", which is 0.35%, not meeting the requirements of GB / T3461-2016.

[0036] Comparative Example 3

[0037] Prepare molybdenum powder through the following steps: (1) Take 1.2 kg of loose powder of MoO3 and place it in a boat. The boat used is a boat cast from Gr28Ni48 alloy, with dimensions of 500 mm × 80 mm × 80 mm and a thickness of 5 mm. Continuously introduce hydrogen through a hydrogen purification circulation system and control the hydrogen flow rate at 300 L / min and the hydrogen dew point at -10 °C; (2) Push the boat into a reduction furnace with three temperature zones. The length of each temperature zone is approximately equal to the length of 5 boats. The temperatures of the three temperature zones are set at 600 °C, 900 °C, and 950 °C respectively. Adjust the pressure inside the reduction furnace to 2.4 kPa, control the boat-pushing rate at 18 min / time, and the residence time in each temperature zone is 1.5 h to obtain the product molybdenum powder.

[0038] Screen the obtained product molybdenum powder through an 80-mesh sieve. The sieving rate is 55%. Observe the pushed boat. The caking of the lower-layer material is reduced compared to Comparative Example 2, and a small amount of incompletely reduced material appears at the bottom.

[0039] Detect the oxygen content of the obtained molybdenum powder by "Inert Gas Fusion Infrared Absorption Method - Thermal Conductivity Method" in GB / T 4325 "Methods for Chemical Analysis of Molybdenum", which is 0.50%, not meeting the requirements of GB / T3461-2016.

[0040] Comparative Example 4

[0041] Prepare molybdenum powder through the following steps: (1)Take 1.2 kg of loose MoO3 powder and place it in a boat. The boat used is a boat cast from Gr28Ni48 alloy, with dimensions of 500 mm × 80 mm × 80 mm and a thickness of 5 mm. Continuously introduce hydrogen through a hydrogen purification circulation system and control the hydrogen flow rate to be 300 L / min and the hydrogen dew point to be 10 °C; (2)Push the boat into a reduction furnace with three temperature zones. The length of each temperature zone is approximately 5 times the length of the boat. The temperatures of the three temperature zones are set at 550 °C, 850 °C, and 950 °C respectively. Adjust the pressure in the reduction furnace to 2.4 kPa, control the boat-pushing rate to be 13 min / time, and the residence time in each temperature zone to be 1.08 h to obtain the product molybdenum powder.

[0042] Sieve the obtained product molybdenum powder through a 80-mesh sieve, and the sieving rate is 76%. Observe the pushed-out boat. There is a small amount of caking in the lower-layer material, and at the same time, there are many materials that are not completely reduced. Detect the oxygen content of the obtained molybdenum powder by the "inert gas fusion-infrared absorption method-thermal conductivity method" in GB / T 4325 "Methods for Chemical Analysis of Molybdenum", which is 1.20%, not meeting the requirements of GB / T3461-2016.

[0043] Furthermore, compare the preparation method of the present invention (one-step reduction method) with the traditional two-step method, and the results are shown in Table 1 below: Table 1 Overall comparison between one-step reduction method and two-step reduction method

[0044] After calculation, under the same output, the one-step reduction method of the present invention can reduce the comprehensive energy consumption by more than 20% compared with the traditional two-step method, and reduce the equipment and personnel investment by more than half.

[0045] It should be noted that the above are only the preferred embodiments of the present invention, and they should not limit the protection scope of the technical solutions of the present invention. Any modifications made by those of ordinary skill in the art to the technical solutions recorded in the foregoing embodiments and any equivalent replacements of technical features within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing molybdenum powder by one-step reduction of molybdenum trioxide, characterized in that, It includes: Placing molybdenum trioxide as raw material in a boat into a primary reduction furnace with hydrogen flowing through for a primary reduction reaction to obtain molybdenum powder; the primary reduction furnace includes three temperature zones, and the temperature settings are respectively: the first temperature zone: 450 - 600 °C, the second temperature zone: 750 - 850 °C, the third temperature zone: 900 - 1100 °C; intermittent boat pushing is adopted in the primary reduction reaction, the boat pushing period is 15 - 23 min / time, and the residence time in each temperature zone is 1.25 - 1.92 h.

2. The preparation method according to claim 1, wherein, The loading amount of molybdenum trioxide in the boat is 1.0 - 1.5 kg / boat.

3. The preparation method according to claim 1, characterized in that, The inlet flow rate of hydrogen is 250 - 500 L / min, the dew point is -10 °C to 20 °C, and the purity ≥ 99.99%.

4. The preparation method according to claim 1, wherein It also includes: passing the product obtained from the primary reduction reaction through an 80 - mesh sieve to obtain the molybdenum powder.

5. The preparation method according to claim 1, wherein The purity of the particle size of the molybdenum trioxide ≥ 99.9%, and the particle diameter is 8 - 20 μm.

6. The preparation method according to claim 1, wherein In the primary reduction reaction, the furnace pressure in the primary reduction furnace is 2.2 - 2.8 KPa.

7. Molybdenum powder prepared by the preparation method according to any one of claims 1 - 6.

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