JPS61209918A - Concentrating device for molybdenum or tungsten solution - Google Patents

Abstract

PURPOSE:To obtain a concentrating device capable of prepg. high purity powder of Mo or W by providing a closed vessel for heating and concentrating solution of Mo or W capable of performing evaporation of the soln. under reduced pressure. CONSTITUTION:A concentration device is provided with a closed vessel 1, a heating means 3 provided to the external periphery of the vessel 1, and an evacuating means 4 connected to the vessel 1. For example, a vessel 2a contg. Mo soln. 2 to be concentrated is laid in the bottom of a box 1a and an upper cover 1b is set to the box 1a air-tightly. A means 4 is then operated to evacuate the inside of the vessel 1, and a means 3 is also operated. Thus, heating and concentration is performed under specified reduced pressure and temp. When the water in the soln. 2 is removed by evaporation, the operation of the means 3, 4 are stopped and cocks 4a, 5a are changed over. Clean air through an air filter 5 is introduced into the vessel 1 to return the pressure to the normal pressure, then the cover 1b is removed and concentrated solid product is taken out. When the product is reduced with H2, Mo powder having high purity is obtd.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention involves concentrating No or distillate powder produced in the manufacturing process of high-purity molybdenum (No) or tungsten (trade) powder to obtain solids of WO03 and WO3. Concerning a concentrator for

[Technical background of the invention and its problems] MOS-LSI, especially ultra-L with more than 258 bits
The circuit conductor portion of the SI element is usually formed by applying a sputtering method using a target made of MO or -. It is essential that the target used at this time be of high purity.

For example, if the target material contains impurities such as uranium or thorium, the operational reliability of the obtained VLSI device will be significantly lowered due to damage from alpha rays from these radioactive elements. Therefore, the permissible amount of these radioactive elements is P
It is necessary to have Pb order. In addition, alkali metals such as sodium and potassium easily migrate in the gate insulating film of the device and deteriorate the MOS interface characteristics, so the permissible amount must be on the order of several tens of ppb.Furthermore, iron, Since heavy metals such as nickel cause leakage phenomena at interface joints, the permissible amount thereof is also required to be on the order of several tens of ppb.

By the way, the above-mentioned target is generally manufactured by sintering No or - powder. Therefore, in order to obtain a high-purity No/W target with few impurities, the No powder or W powder used as a raw material must be of extremely high purity and do not contain the above-mentioned impurities. This is necessary.

No powder is usually produced by dissolving No ore in an alkaline solution such as caustic soda, adding nitric acid to the resulting solution such as sodium molybdate to form molybdenum trioxide (Mo03), and dissolving this Mo03 in aqueous ammonia. It is produced by a method in which this solution is heated and concentrated to precipitate crystals of ammonium baramolybdate salt, which are recovered and then reduced with hydrogen in a hydrogen furnace. The same applies to the case of catfish powder.

In this step, the liquid obtained by dissolving Mo03 in aqueous ammonia is heated and concentrated by a method in which the liquid is poured into an open container and then heated to dissipate the water content.

However, in this method, since the container is in an open state, external contamination by dust and the like cannot be avoided, and since the container is heated under normal pressure, it takes a relatively long time and a large amount of thermal energy to evaporate the water content. Especially in industrial scale production, these problems cannot be ignored.

For this reason, it is extremely difficult to remove the impurities mentioned above and reduce the impurities to the order of PPb using the above-mentioned conventional methods, and in particular, it is virtually impossible to remove radioactive elements. As a high purification treatment in the above method, a recrystallization method is applied to crystals of paramolybdate or paratungstate. A precipitation method is also known.

However, even when applying the recrystallization method,
Both paramolybdates and paratungstates have the unique property of adsorbing impurity elements, which makes them impractical due to their low impurity removal efficiency, and also creates dust and impurities in the purification process. Since it takes a long time and requires complicated incidental equipment, the obtained No powder, W
The powder becomes extremely expensive.

As described above, it is not easy to produce MO or powder with a sufficiently high purity on an industrial scale using conventional methods and equipment used therein.

In order to solve this problem, the inventors of the present invention have conducted intensive research and have developed the following method, which makes it possible to produce extremely high purity No powder or powder, and has already filed a patent application.

In other words, the method is to decompose crude No or So powder, which is produced by a conventional method and still contains a large amount of impurities, with hydrogen peroxide solution, and No and - are complex ions, and other elements are cations. A step of preparing an aqueous solution (first step), a step of bringing this aqueous solution into contact with a cation exchange resin to adsorb impurity elements that have become cations, and obtaining an eluate of No or lily complex ions (second step). ), a step of heating this eluate to evaporate water to obtain a concentrated solid (third step), and finally a step of reducing this concentrated solid (Mo03 or w03) with hydrogen (fourth step). ing.

In order to obtain high-purity MO or pure powder in which the impurities are on the order of pPb, it is necessary to take care to prevent external contamination as much as possible in each of the above steps. Furthermore, when considering industrial-scale production, reducing energy costs is an important factor.

For this reason, the present inventors investigated each of the above steps and found that the third step is the step that has the greatest impact on the problem of external contamination and the problem of energy cost reduction. We have now developed a concentrator that can solve these problems.

[Objective of the Invention] The present invention generally provides an apparatus for concentrating an MO or W solution, and specifically, for use in the third step in a method for producing high-purity No or W powder consisting of the above-mentioned steps; h
The object of the present invention is to provide an apparatus for concentrating a No. or Mo. solution in a method for producing Mo or W powder.

[Summary of the Invention] The concentrating device of the present invention includes: a closed container containing a molybdenum or tungsten solution to be concentrated; a heating means disposed around the outer periphery of the closed container; and a device connected to the closed container to reduce the pressure inside the container. The invention is characterized by comprising: decompression means for.

The apparatus of the present invention will be described in detail based on a schematic diagram illustrating the apparatus. In Fig. 0, numeral 1 denotes a closed container, which is basically composed of a lower box body 1a and an upper lid tb. The lower box body 1a and the upper lid 1b are removably connected to each other by bolts and nuts, for example, at the flange IC. The upper lid 1b is provided with an exhaust section 1d connected to a pressure reducing means, which will be described later. Inside the closed container 1 is housed a container 2a filled with a solution 2 of 0 or 10% to be concentrated.

3 is a heating means disposed around the outer periphery of the closed container 2,
For example, a mantle heater that covers the entire four containers is a suitable means because it suppresses heat loss during heating and contributes to reducing energy costs.

4 is connected to the exhaust part 1d provided in the upper lid tb via the conduit Pl, the flow path switching cock 4a, and the conduit P2,
A pressure reducing means for reducing the pressure inside the closed container 1.

A common vacuum pump may be used as the pressure reduction means, but as will be described later, in the process of heating and concentrating solution 2a, steam and water are inevitably generated, so the structure must be such that its function will not be inhibited by these. For example, a trap may be added in the middle of the conduit P2, or, as the simplest means, an aspirator using running water may be used.

5 is an air filter and conduit P3. Cock 5a, conduit P
4. The cock 4a is connected to the exhaust section 1d via a conduit P1. This is an auxiliary equipment for restoring the inside of the container 1 to normal pressure before taking out the produced concentrated solids from the closed container 1 after completing the heating concentration process under reduced pressure.

In addition, if an umbrella 1e is provided in the container 1 to cover the entire upper part of the melt 112a and connect the exhaust part 1d to the upper part as shown in the figure, external contaminants may settle from the exhaust part 1d for some reason. It is effective in preventing contamination of the solution 2a and, by extension, the concentrated solid matter even if the solution 2a is mixed.

The device of the invention operates as follows.

For example, the No. or So solution 2a to be concentrated is placed in the lower box 1a.
, and set the upper lid 1b airtight thereon. Thereafter, the pressure reducing means 4 is activated to reduce the pressure inside the container 1, and the heating means 3 is activated. Heat concentration under reduced pressure is carried out at a predetermined pressure and temperature. When the water in the solution 2a is evaporated and removed, heating means 3. Stop the operation of the pressure reducing means 4 and close the cock 4a.
, 5a is switched to introduce air purified by the air filter 5 into the container 1 to bring the inside of the container 1 to normal pressure, and then the upper lid 1b is removed and the concentrated solids are taken out.

The obtained concentrated solid is transferred to the next hydrogen reduction step and No.
It goes without saying that it is also reduced to W powder.

The operating conditions such as the degree of pressure reduction in the container 1 and the heating temperature may be appropriately set depending on the type, concentration, amount, etc. of the solution 2a. For example, in the case of the solution obtained in the second step,
The pressure inside the container 1 is 10 to 50 mHg.

It goes without saying that the temperature is preferably about 70 to 100°C, and the treatment time is the time required for the solution 2a to evaporate and convert into a concentrated solid.

[Effects of the Invention] As is clear from the above explanation, by heating and concentrating using the apparatus of the present invention, ■ No. or So solution to be concentrated, which is housed in a closed container, will not be contaminated from the outside. No, ■
Since the evaporation process is performed under reduced pressure, it can be concentrated in a much shorter time than under normal pressure.

■In addition, the temperature during heating can be lower than that under normal pressure, which greatly contributes to the high purity of No or So powder and the reduction of energy costs, and its industrial value is high. .

[Examples of the Invention] Example 1 1 kg of crude No. powder (average particle size 5%) containing the indicated amounts of the impurities shown in the table was placed in a container whose inner wall was made of tetrafluoroethylene polymer, 500 g of water was added thereto and the whole was stirred. Then, while cooling the container under running water,
2. Add 30% hydrogen peroxide solution into the container at an addition rate of about 1.0 u/hr. IJll was added to dissolve all the crude No powder. At this time, the temperature of the reaction system was maintained at 40°C or lower. After that, water was added to the whole to make the total amount ton. Next, we used a strongly acidic polystyrene sulfonic acid H-type cation exchange resin (trade name, Diaion SK Cloud 19 particle size 50-10
0 mesh: manufactured by Mitsubishi Kasei ■) was prepared. After 400 g of this cation exchange resin was sufficiently swollen with water, it was packed into a polypropylene column with an inner diameter of 35 layers and a layer length of 400 mm to produce an ion exchange column.

The aqueous solution was passed through this ion exchange column to obtain a No. eluate to be concentrated.

This solution was divided into two parts, one of which was divided into SOS 31B as shown in the figure.
The container was set in a sealed container 1 (inner volume: 40M) made by the manufacturer.

Using an aspirator as a pressure reducing means, the container 1 was embedded in a mantle heater, and a concentrated solid was obtained in 105 hours by heating and concentrating at a pressure of 25 Hg and a temperature of 95°C. This solid was heated to 900° C. in a hydrogen furnace to obtain 98.0 g of powder. Yield 98%.

The obtained No powder was quantitatively analyzed, and the quantitative values of impurity elements excluding Mo were measured. The e unit in which the results are shown in the table is pp garden.

As Comparative Example 1, the other MO eluate was treated with the same <SOS
The mixture was placed in a container made of 31B with an open top, and the whole was concentrated under normal pressure by heating at a pressure of 25 mmHg and a temperature of 95°C.

It took 15 hours to obtain a concentrated solid.

The analysis results are shown in Table 1.

In addition, as Comparative Example 2, the analysis results using the conventional precipitation method are also shown.

Example? Purified W powder was obtained in the same manner as in Example 1, except that crude W powder containing the impurities shown in Table 2 was used. The quantitative analysis results are shown in Table 2. Comparative Example 3 shows the results of Example 1 phased with Comparative Example 1.

[Brief explanation of drawings]

The figure is a schematic diagram showing an example of the device of the present invention. l: Airtight container, la: Lower box body. lb...Top lid 1c...Flange part. ld...exhaust section. 2...No or W solution to be concentrated. 2a...Container, 3...Heating means. 4... Pressure reduction means.

Claims (1)

[Claims] 1. A closed container containing a molybdenum or tungsten solution to be concentrated; a heating means disposed around the outer periphery of the closed container; a decompression means connected to the closed container to reduce the pressure inside the container;
An apparatus for concentrating a molybdenum or tungsten solution, comprising: 2. The concentrating device according to claim 1, wherein the molybdenum or tungsten solution is an eluate obtained by dissolving molybdenum or tungsten powder in a hydrogen peroxide solution and then passing the solution through a cation exchange resin.