Process for the preparation of low potassium molybdenum powder

Abstract

The application discloses a method for preparing low-potassium molybdenum powder, which comprises the following steps: step 1, adding a small amount of sodium chloride into an ammonia leaching solution of molybdenum ore, and evaporating and crystallizing to prepare ammonium dimolybdate; step 2, preparing molybdenum oxide by calcining the ammonium dimolybdate; and step 3, reducing the molybdenum oxide by hydrogen in two stages to obtain the low-potassium molybdenum powder. The method for preparing the low-potassium molybdenum powder adopts a doping method according to the process conditions of conventional molybdenum powder production, uses a chloride (NaCl) to remove impurities potassium, and makes the potassium overflow after being vaporized and volatilized in a hydrogen reduction environment, so that the low-potassium molybdenum powder is prepared, the use of high temperature (greater than 1000 DEG C) is avoided, the low-potassium molybdenum powder is prepared by only using conventional methods at 800-900 DEG C, energy consumption is reduced, and the molybdenum powder is prevented from being caked, sintered and agglomerated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metal processing methods, and particularly relates to a method for preparing low-potassium molybdenum powder. BACKGROUND

[0002] Molybdenum powder is commonly used for manufacturing molybdenum electrodes, molybdenum targets, molybdenum wires and other high-temperature field products. With the continuous development of science and technology, the application range of molybdenum products is becoming wider and wider, especially in the aspects of super-large integrated circuits, high-definition televisions, LCD liquid crystal display targets and the like. Impurity potassium in molybdenum easily forms a low-melting-point eutectic, and vaporizes to form a pit under high-temperature and high-pressure conditions, which is easily broken into a breakpoint. Therefore, some molybdenum product manufacturers continuously require to reduce the potassium content in molybdenum powder. At present, the mass content of potassium in the commonly sold ordinary molybdenum powder is generally 0.0100-0.0200%, and the molybdenum product manufacturers hope to reduce it to below 0.0020%, which is relatively difficult for molybdenum powder manufacturers.

[0003] The conventional molybdenum powder potassium removal method generally adopts an ultra-high-temperature volatilization method. The ammonia leaching solution of molybdenum ore is evaporated and crystallized, and the obtained ammonium molybdate is reduced into molybdenum powder at high temperature. With the vaporization and volatilization of potassium impurities in the high-temperature heating process, a certain purification effect is achieved. In the above process, the trace potassium in the molybdenum powder comes from the potassium in the ammonia leaching solution, which comes from the potassium feldspar in the molybdenite (see: Tang Junli, Cui Yuqing, Cao Weicheng, et al. Analysis of the source of potassium in ammonium molybdate [J]. China Molybdenum, 2017, 41(6): 36-38). The melting point of potassium feldspar is relatively high, about 1220℃, and the vaporization temperature is high. In order to make the potassium volatilize in large quantities, the temperature of the ordinary molybdenum powder needs to be increased to above 1350℃, which will cause the molybdenum powder to be seriously caked after the treatment, and the molybdenum powder needs to be treated by crushing, ball milling and the like, which will affect the preparation of the molybdenum powder to a certain extent. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing low-potassium molybdenum powder, which solves the problem of serious caking of molybdenum powder caused by the high-temperature vaporization method used in the existing molybdenum powder preparation method to reduce the potassium content.

[0005] The technical solution adopted by the present application is as follows: a method for preparing low-potassium molybdenum powder, comprising the following steps:

[0006] Step 1: a small amount of sodium chloride is added to the ammonia leaching solution of molybdenum ore, and ammonium dimolybdate is prepared by evaporation and crystallization;

[0007] Step 2: ammonium dimolybdate is prepared into molybdenum oxide by calcination;

[0008] Step 3: the molybdenum oxide is reduced by two-stage hydrogen reduction, and low-potassium molybdenum powder is obtained.

[0009] The present application is also characterized in that,

[0010] The amount of sodium chloride incorporated in step 1 is 0.15-1% of the mass of molybdenum in the ammonia leaching solution.

[0011] The evaporation crystallization temperature in step 1 is 95-100°C, and the ammonium dimolybdate crystallized by evaporation is filtered and dried.

[0012] The calcination temperature in step 2 is 450-550°C, and the time is 2-3h.

[0013] In the two-stage hydrogen reduction in step 3, the first-stage reduction temperature is 550-600°C to prepare molybdenum dioxide, and the second-stage reduction temperature is 850-900°C to prepare low-potassium molybdenum powder.

[0014] The method for preparing low-potassium molybdenum powder provided by the application adopts a doping method according to the process conditions of conventional molybdenum powder production, uses a chloride salt (NaCl) to remove impurities potassium, and the potassium is overflowed after being vaporized and volatilized in a hydrogen reduction environment, so that low-potassium molybdenum powder is prepared, high temperature (>1000°C) is avoided, and low-potassium molybdenum powder is prepared by a conventional method at 800-900°C, so that energy consumption is reduced, and molybdenum powder is prevented from caking, sintering and agglomeration. DETAILED DESCRIPTION

[0015] The application will be described in detail below in combination with specific embodiments.

[0016] The application provides a method for preparing low-potassium molybdenum powder, which specifically comprises the following steps:

[0017] (1) Doping ammonium dimolybdate is prepared by evaporation crystallization of molybdenum ore ammonia leaching solution, the molybdenum content in the ammonia leaching solution is 230-260g / L, and the pH is 8-9. Other impurities are in the content range of the conventional production method, a trace amount of agent is a chloride salt (NaCl), the addition amount is 0.15-1% of the mass of molybdenum, the evaporation crystallization temperature is 95-100°C, and the ammonium dimolybdate crystallized by evaporation is filtered and dried to enter the next process;

[0018] (2) Molybdenum oxide is prepared by calcination of ammonium dimolybdate, the calcination temperature is 450-550°C, and the time is 2-3h;

[0019] (3) Molybdenum dioxide is prepared by first-stage reduction of molybdenum oxide at a temperature of 550-600°C, and low-potassium molybdenum powder is prepared by second-stage reduction at a temperature of 850-900°C.

[0020] Through the above-mentioned method, the method for preparing low-potassium molybdenum powder provided by the application does not require high temperature above 1000°C, and in the process of reducing molybdenum dioxide to molybdenum powder in a conventional hydrogen reduction environment at 800-900°C, according to the Le Chatelier's principle of chemical equilibrium movement-high boiling point / melting point preparation boiling point / melting point, the chloride salt (NaCl) incorporated reacts with potassium feldspar at 800-900°C to form potassium chloride with a lower boiling point and sodium feldspar with a lower melting point, so that the potassium is volatilized and overflowed in the process of molybdenum powder reduction, and the potassium is removed.

[0021] NaCl + KAlSi3O8 = KCl + NaAlSi3O8

[0022] Example 1

[0023] (1) Ammonia leaching solution evaporation crystallization to prepare doped ammonium dimolybdate, the molybdenum content in the ammonia leaching solution is 230-260 g / L, and the pH is 8-9. Other impurities are in the content range of the conventional production method, a trace amount of a dopant is a chloride salt (NaCl), the addition amount is 0.15% of the mass of molybdenum, evaporation crystallization is performed at 95-100°C, evaporation crystallization is performed to 1 / 3 of the mother liquor, ammonium dimolybdate is filtered and dried, and then the potassium content is detected to be 80-150 ppm, and after packaging, it enters the calcination process;

[0024] (2) Ammonium dimolybdate is calcined to prepare molybdenum oxide, the calcination temperature is 450-550°C, and the calcination time is 2-3 h, and molybdenum oxide is obtained;

[0025] (3) Molybdenum oxide is reduced by two-stage hydrogen reduction. Molybdenum dioxide is prepared at a first reduction temperature of 550-600°C, molybdenum powder is prepared at a second reduction temperature of 850-900°C, the impurity content (wt%) in the molybdenum powder is K 0.0018, Na 0.0017, Cu 0.0003, Ca 0.0005, Mg 0.0002, and W 0.0057; the blank control molybdenum powder (without adding a chloride salt, and the remaining processes are the same) is K 0.0058, Na 0.0010, Cu 0.0004, Ca 0.0008, Mg 0.0002, and W 0.0069. It can be seen that the potassium is obviously reduced, and the other elements are not affected.

[0026] Example 2

[0027] (1) Ammonia leaching solution evaporation crystallization to prepare doped ammonium dimolybdate, the molybdenum content in the ammonia leaching solution is 230-260 g / L, and the pH is 8-9. Other impurities are in the content range of the conventional production method, a trace amount of a dopant is a chloride salt (NaCl), the addition amount is 0.15% of the mass of molybdenum, evaporation crystallization is performed at 95-100°C, evaporation crystallization is performed to 1 / 3 of the mother liquor, ammonium dimolybdate is filtered and dried, and then the potassium content is detected to be 80-150 ppm, and after packaging, it enters the calcination process;

[0028] (2) Ammonium dimolybdate is calcined to prepare molybdenum oxide, the calcination temperature is 450-550°C, and the calcination time is 2-3 h, and molybdenum oxide is obtained;

[0029] (3) The molybdenum oxide is reduced by two-stage hydrogen. The molybdenum dioxide is prepared at the first-stage reduction temperature of 550-600°C, and the molybdenum powder is prepared at the second-stage reduction temperature of 850-900°C. The impurity content (wt%) in the molybdenum powder is K 0.0028, Na 0.0020, Cu 0.0003, Ca 0.0011, Mg 0.0005, and W 0.0050. The blank control molybdenum powder (without adding the chlorine salt, and the remaining procedures are the same) is K 0.0121, Na 0.0009, Cu 0.0004, Ca 0.0018, Mg 0.0005, and W 0.0058. It can be seen that the potassium is obviously reduced, and the other elements are not affected.

[0030] Example 3

[0031] (1) The doped ammonium dimolybdate is prepared by evaporation crystallization of the ammonia leaching solution. The molybdenum content in the ammonia leaching solution is 230-260 g / L, and the pH is 8-9. The other impurities are in the content range of the conventional production method. A trace amount of the agent, i.e. the chlorine salt (NaCl), is added. The addition amount is 1% of the mass of the molybdenum. The evaporation crystallization is performed at 95-100°C. The evaporation crystallization is performed to 1 / 3 of the mother liquor. The ammonium dimolybdate is detected for the potassium content of 80-150 ppm after filtration and drying, and is packaged to enter the calcination process;

[0032] (2) The ammonium dimolybdate is calcined to prepare the molybdenum oxide. The calcination temperature is 450-550°C, and the time is 2-3 h. The molybdenum oxide is obtained.

[0033] (3) The molybdenum oxide is reduced by two-stage hydrogen. The molybdenum dioxide is prepared at the first-stage reduction temperature of 550-600°C, and the molybdenum powder is prepared at the second-stage reduction temperature of 850-900°C. The impurity content (wt%) in the molybdenum powder is K 0.0028, Na 0.0020, Cu 0.0003, Ca 0.0011, Mg 0.0005, and W 0.0050. The blank control molybdenum powder (without adding the chlorine salt, and the remaining procedures are the same) is K 0.0121, Na 0.0009, Cu 0.0004, Ca 0.0018, Mg 0.0005, and W 0.0058. It can be seen that the potassium is obviously reduced, and the other elements are not affected.

Claims

1. A process for the production of low potassium molybdenum powder, characterized in that, The method comprises the following steps: Step 1, adding trace sodium chloride into the ammonia leaching solution of molybdenum ore, and evaporating and crystallizing to prepare ammonium dimolybdate; Step 2, preparing molybdenum oxide by calcining the ammonium dimolybdate; Step 3, preparing molybdenum dioxide by one-stage reduction of the molybdenum oxide at a temperature of 550-600 DEG C, and preparing low-potassium molybdenum powder by two-stage reduction of the molybdenum oxide at a temperature of 850-900 DEG C.

2. The method of claim 1, wherein the low potassium molybdenum powder is prepared by the steps of: The amount of sodium chloride added in step 1 is 0.15-1% of the mass of molybdenum in the ammonia leaching solution. ​ 3. The method of claim 1, wherein the low potassium molybdenum powder is prepared by the steps of: The evaporation and crystallization temperature in step 1 is 95-100 DEG C, and the ammonium dimolybdate obtained by evaporation and crystallization is filtered and dried.

4. The method of claim 1, wherein the low potassium molybdenum powder is prepared by the steps of: The calcining temperature in step 2 is 450-550 DEG C, and the time is 2-3 h. ​