Process for preparing molybdenum powder by reducing high-impurity molybdic acid

Abstract

The present invention discloses a process for preparing molybdenum powder by reducing high-impurity molybdic acid, belonging to the technical field of the process for preparing molybdenum powder. The process includes: performing first hydrogen reduction on the raw material high-impurity molybdic acid in a four-tube furnace, performing second hydrogen reduction on the obtained reduction product, and then successively performing hot alkali washing and hot acid washing to obtain high-purity molybdenum powder. The present invention can use molybdic acid to replace traditional ammonium molybdate as the raw material for producing molybdenum powder, significantly shortening the production process flow and reducing the production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of the process for preparing molybdenum powder, and particularly relates to a process for preparing molybdenum powder by reducing molybdic acid with a relatively high impurity content. Background Art

[0002] Molybdenum is one of the important alloying elements added to stainless steel, which can effectively improve the corrosion resistance and strength of stainless steel and enhance its antibacterial and anticorrosion ability. Therefore, in high-end stainless steel products, especially those with high requirements for corrosion resistance, abrasion resistance, etc., a relatively high content of molybdenum is usually added. For example, Mo stainless steel widely used in marine engineering, sewage treatment, chemical industry and other fields has a molybdenum content of 3-4%. On the other hand, low-alloy stainless steel with an appropriate addition of molybdenum element can also be used to prepare stainless steel materials with high strength, high toughness and good wear resistance, and can be applied to the automotive industry, aerospace and other fields.

[0003] At present, the common process for preparing molybdenum powder in industry uses ammonium molybdate as the raw material and obtains molybdenum powder through hydrogen reduction method. However, this preparation process will result in high production costs and low profits. Therefore, in order to obtain higher production profits of molybdenum powder, seeking a lower-cost process method is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] Aiming at the defects of the prior art, the purpose of the present invention is to provide a new process for preparing molybdenum powder by reducing high-impurity molybdic acid, which can use molybdic acid with a relatively high impurity content as the raw material to obtain high-purity molybdenum powder, and significantly reduce the production cost of molybdenum powder preparation.

[0005] The technical solution of the present invention is as follows:

[0006] A process for preparing molybdenum powder by reducing high-impurity molybdic acid, which includes:

[0007] (1) Performing first hydrogen reduction on the raw material high-impurity molybdic acid in a four-tube furnace at a reduction temperature of 400-700 °C to obtain a first reduction product;

[0008] (2) Performing second hydrogen reduction on the first reduction product at a reduction temperature of 800-1200 °C to obtain a second reduction product;

[0009] (3) Heating and alkali-washing the second reduction product with an alkali solution, and then filtering and drying to obtain an alkali-washed product;

[0010] (4) Heating and acid-washing the alkali-washed product with an acid solution, and then filtering and drying to obtain an acid-washed product, i.e., molybdenum powder;

[0011] Among them, the high-impurity molybdic acid includes Ca with a content greater than 5000 ppm, Si with a content greater than 5000 ppm, V with a content greater than 5000 ppm, and W with a content greater than 5000 ppm.

[0012] According to some preferred embodiments of the present invention, it further includes:

[0013] (5) Screening the pickling product to obtain the finished molybdenum powder.

[0014] According to some preferred embodiments of the present invention, in the first hydrogen reduction, the flow rate of hydrogen is 4-12 m 3 / h, the loading amount of the raw material high-impurity molybdic acid per boat is 2.0-5.0 kg / boat, and the boat-pushing speed is 10-20 min / channel.

[0015] According to some preferred embodiments of the present invention, in the second hydrogen reduction, the flow rate of hydrogen is 15-30 m 3 / h, the loading amount of the first reduction product per boat is 1.0-3.0 kg / boat, and the boat-pushing speed is 20-30 min / channel.

[0016] According to some preferred embodiments of the present invention, the alkali solution is an aqueous solution of sodium carbonate, and its concentration is 0.3-0.6 wt%.

[0017] According to some preferred embodiments of the present invention, the mass ratio of the second reduction product to the alkali solution is 1:(4-10).

[0018] According to some preferred embodiments of the present invention, the heating temperature of the heated alkali washing is 60-100 °C, and the heating time is 20-40 min.

[0019] According to some preferred embodiments of the present invention, the acid solution is selected from one or more of sulfuric acid, nitric acid, and hydrochloric acid, and the concentration of the acid solution is 20-40 wt%.

[0020] According to some preferred embodiments of the present invention, the mass ratio of the alkali-washed product to the acid solution is 1:(4-10).

[0021] According to some preferred embodiments of the present invention, the heating temperature of the heated pickling is 40-70 °C, and the heating time is 20-40 min.

[0022] The beneficial effects of the present invention include:

[0023] The process method for preparing molybdenum powder by reducing high-impurity molybdic acid provided by the present invention uses molybdic acid to replace traditional ammonium molybdate as the raw material for producing molybdenum powder, significantly shortening the production process flow, reducing the production cost, and without the intervention of ammonia in the whole process flow, no ammonia gas is generated, and no pollutants are discharged.

[0024] The process method of the present invention first uses high-temperature reduction to remove volatile substances in the raw materials, then uses alkaline washing of molybdenum powder to remove impurities such as Ca and Si brought by high-impurity raw materials, and then uses acid washing of molybdenum powder to remove impurities such as V and W brought by high-impurity raw materials. Finally, the purity of the prepared molybdenum powder can reach more than 99%, meeting the requirements of molybdenum powder for superalloy additives. Specific Embodiments

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the 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 skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0026] Example 1

[0027] Molybdenum powder is prepared through the following process steps:

[0028] (1) 50 kg of high-impurity molybdic acid is subjected to hydrogen reduction in a four-tube furnace to obtain molybdenum dioxide. Among them, the temperature of hydrogen reduction is 500 °C, the flow rate is 8 m 3 / h, the loading amount of high-impurity molybdic acid per boat is 2.0 kg / boat, and the boat-pushing speed is 11 min / channel; in the used high-impurity molybdic acid, the contents of Ca, Si, V, and W are 0.5680%, 0.4992%, 0.6321%, and 0.5910% respectively;

[0029] (2) The obtained molybdenum dioxide is subjected to hydrogen reduction in a high-temperature reduction furnace to obtain reduced molybdenum powder. Among them, the temperature of hydrogen reduction is 950 °C, the flow rate is 20 m 3 / h, the loading amount of molybdenum dioxide per boat is 1.5 kg / boat, and the boat-pushing speed is 20 min / channel;

[0030] (3) 50 ml of an aqueous solution of Na2CO3 with a concentration of 0.43 wt% is added to 10 g of the reduced molybdenum powder for heating and alkaline washing. The heating temperature is 70 °C, and the heating time is 30 min. After washing, it is filtered and dried to obtain molybdenum powder after alkaline washing;

[0031] (4) 50 ml of a sulfuric acid solution with a concentration of 20 wt% is added to the molybdenum powder after alkaline washing for heating and acid washing. The heating temperature is 40 °C, and the heating time is 30 min. After washing, it is filtered and dried to obtain molybdenum powder after acid washing;

[0032] (5) The molybdenum powder after acid washing is sieved to obtain the finished molybdenum powder.

[0033] Example 2

[0034] Molybdenum powder is prepared through the following process steps:

[0035] (1) 50 kg of high-impurity molybdic acid is subjected to hydrogen reduction in a four-tube furnace to obtain molybdenum dioxide. Among them, the temperature of hydrogen reduction is 550 °C, the flow rate is 8 m 3 / h, the loading amount of high-impurity molybdic acid per boat is 2.0 kg / boat, and the boat-pushing speed is 11 min / channel; in the used high-impurity molybdic acid, it contains Ca: 0.6180%, Si: 0.5795%, V: 0.6399%, W: 0.6210%;

[0036] (2) The obtained molybdenum dioxide is subjected to hydrogen reduction in a high-temperature reduction furnace to obtain reduced molybdenum powder. Among them, the temperature of hydrogen reduction is 1000 °C, the flow rate is 20 m 3 / h, the loading amount of molybdenum dioxide per boat is 1.5 kg / boat, and the boat-pushing speed is 20 min / channel;

[0037] (3) 60 ml of an aqueous Na2CO3 solution with a concentration of 0.43 wt% is added to 10 g of the reduced molybdenum powder for heating and alkali washing. The heating temperature is 80 °C, the heating time is 25 min. After washing, it is filtered and dried to obtain the molybdenum powder after alkali washing;

[0038] (4) 60 ml of a sulfuric acid solution with a concentration of 20 wt% is added to the molybdenum powder after alkali washing for heating and acid washing. The heating temperature is 50 °C, the heating time is 25 min. After washing, it is filtered and dried to obtain the molybdenum powder after acid washing;

[0039] (5) The molybdenum powder after acid washing is sieved to obtain the finished molybdenum powder.

[0040] Example 3

[0041] The molybdenum powder is prepared through the following technological steps:

[0042] (1) 50 kg of high-impurity molybdic acid is subjected to hydrogen reduction in a four-tube furnace to obtain molybdenum dioxide. Among them, the temperature of hydrogen reduction is 600 °C, the flow rate is 8 m 3 / h, the loading amount of high-impurity molybdic acid per boat is 2.0 kg / boat, and the boat-pushing speed is 10 min / channel; in the used high-impurity molybdic acid, it contains Ca: 0.7590%, Si: 0.7213%, V: 0.5312%, W: 0.8100%;

[0043] (2) The obtained molybdenum dioxide is subjected to hydrogen reduction in a high-temperature reduction furnace to obtain reduced molybdenum powder. Among them, the temperature of hydrogen reduction is 1050 °C, the flow rate is 20 m 3 / h, the loading amount of molybdenum dioxide per boat is 1.5 kg / boat, and the boat-pushing speed is 18 min / channel;

[0044] (3) Add 50 ml of an aqueous solution of Na2CO3 with a concentration of 0.43 wt% to 10 g of reduced molybdenum powder and perform heating and alkali washing. The heating temperature is 80 °C and the heating time is 25 min. After washing, filter and dry to obtain molybdenum powder after alkali washing;

[0045] (4) Add 60 ml of a sulfuric acid solution with a concentration of 30 wt% to the molybdenum powder after alkali washing and perform heating and acid washing. The heating temperature is 50 °C and the heating time is 25 min. After washing, filter and dry to obtain molybdenum powder after acid washing;

[0046] (5) Screen the molybdenum powder after acid washing to obtain the finished molybdenum powder.

[0047] The above embodiments of the present invention can significantly reduce the production cost of molybdenum powder. Chemical composition analysis is performed on the finished molybdenum powder obtained in the above Examples 1-3. After testing, the purity of the molybdenum powder is between 99.4% and 99.7%, where Ca < 0.030%, Si < 0.030%, V < 0.040%, and W < 0.050%.

[0048] The above embodiments are the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A process for preparing molybdenum powder by reducing high-impurity molybdic acid, characterized in that, It includes: (1) First, perform a first hydrogen reduction on the raw material high-impurity molybdic acid in a four-tube furnace at a reduction temperature of 400 - 700 °C to obtain a first reduction product; (2) Then, perform a second hydrogen reduction on the first reduction product at a reduction temperature of 800 - 1200 °C to obtain a second reduction product; (3) Heat and wash the second reduction product with an alkali solution, then filter and dry it to obtain a product after alkali washing; (4) Heat and wash the product after alkali washing with an acid solution, then filter and dry it to obtain a product after acid washing, namely molybdenum powder; Among them, the high-impurity molybdic acid includes Ca with a content greater than 5000 ppm, Si with a content greater than 5000 ppm, V with a content greater than 5000 ppm, and W with a content greater than 5000 ppm.

2. The process method according to claim 1, characterized in that, It also includes: (5) Screen the product after acid washing to obtain finished molybdenum powder.

3. The process method according to claim 1, characterized in that, In the first hydrogen reduction, the flow rate of hydrogen is 4 to 12 m 3 / h, the loading amount of the raw material high-impurity molybdic acid per boat is 2.0 to 5.0 kg / boat, and the boat-pushing speed is 10 to 20 min / channel.

4. The process method according to claim 1, characterized in that, In the second hydrogen reduction, the flow rate of hydrogen is 15 to 30 m 3 / h, the loading amount of the first reduction product per boat is 1.0 to 3.0 kg / boat, and the boat-pushing speed is 20 to 30 min / channel.

5. The process method according to claim 1, wherein The alkali solution is an aqueous solution of sodium carbonate with a concentration of 0.3 - 0.6 wt%.

6. The process method according to claim 1, characterized in that, The mass ratio of the second reduction product to the alkali solution is 1:(4 - 10).

7. The process method according to claim 1, characterized in that, The heating temperature for the heat and alkali washing is 60 - 100 °C, and the heating time is 20 - 40 min.

8. The process method according to claim 1, characterized in that, The acid solution is selected from one or more of sulfuric acid, nitric acid, and hydrochloric acid, and the concentration of the acid solution is 20 - 40 wt%.

9. The process method according to claim 1, characterized in that, The mass ratio of the product after alkali washing to the acid solution is 1:(4 - 10).

10. The process method according to claim 1, characterized in that, The heating temperature for the heat and acid washing is 40 - 70 °C, and the heating time is 20 - 40 min.