JPH0445571B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for refining refractory metals, particularly TiCl ₄ , ZrCl ₄
The present invention relates to a method for separating and removing magnesium chloride and magnesium metal from a reaction product obtained by a reduction method of metal chloride with molten magnesium (so-called Kroll method).

A method for heating and separating unreacted metallic magnesium and magnesium chloride from the metal produced by the Chlor method is to carry Mg and MgCl ₂ in a circulating flow of inert gas and take them out of the system. is also known (Japanese Patent Publication No. 43-29861), but a method using vacuum distillation is more commonly adopted.

In the former method, since the operation is carried out in a positive pressure Ar atmosphere, the evaporation rate of Mg and MgCl ₂ is low, and the circulating gas carrying these substances is cooled, and solidified Mg and MgCl ₂ are removed by a filter. Since it is collected, a complicated equipment configuration is required. In addition, the collected Mg and MgCl ₂ particles adhere to the cloth, which requires time and effort to collect, and the recovered material is highly contaminated, making it difficult to reuse.

On the other hand, in the vacuum distillation process, the entire system is evacuated using a vacuum pump.
Continue heating. First, Mg vapor is generated from the spongy metal housed in the retort, which is led to a cooling section provided outside the retort and solidified.
The pressure inside the retort while Mg vapor is generated is relatively high, sometimes reaching several + mmHg.
When most of the Mg has evaporated and MgCl ₂ vapor is generated, the vapor pressure is an order of magnitude lower than that of Mg, so the degree of vacuum inside the device increases considerably.
And that period is long. Therefore, if there is a defect in the airtightness of the device at this stage, the product will be contaminated by the intruding outside air. The risk of such contamination is extremely high when the metal being refined is Ti or other refractory metals, which have a strong affinity for oxygen and nitrogen and are used as getters to obtain a high degree of vacuum.

Therefore, a high degree of airtightness must be ensured in the equipment used in the vacuum distillation process, and for this reason, these equipments are usually tested for airtightness using pressurized gas prior to raising the temperature. However, in actual equipment with complex configurations, this test requires a great deal of effort and time and is often impractical, and depending on the shape of the sealing material, it may not be possible to maintain a high positive pressure state in the exhaust system. be.

In this way, it is often difficult to completely check the airtightness of the entire system, and if a leak occurs after the vacuum distillation operation has started, the entire system is under reduced pressure, so it is difficult to find the leak location. This is extremely difficult, and as a result, in the conventional precision process using vacuum distillation, some degree of product contamination is unavoidable, and the yield of high-quality products is low.

Therefore, one of the main objectives of the present invention is to eliminate the drawbacks of both the above-mentioned prior art, the gist of which is to:
A refractory metal lump mixed with Mg and MgCl ₂ is heated in a space separated from the outside air and vaporized or liquefied.
In a method for separating Mg and MgCl ₂ from solid metals, at least in the latter half of the separation process when the partial pressures of Mg and MgCl ₂ are significantly reduced, an inert gas flow is introduced into the space to create a negative pressure. A refractory metal refining method characterized by continuing heating in an inert gas atmosphere.

When operating according to the method of the present invention, backflow of air from the connections and exhaust system of the distillation apparatus into the apparatus is prevented and contamination of product metals is minimized.

When carrying out the method of the present invention, the metal ingot to be refined is, for example, Japanese Patent Publication No. 48-34646,
Using a device as described in No. 174530, it is placed above or below the internal space of the distillation device, and the bottom or top is used as a cooling section to collect evaporated Mg and MgCl _{2 .}
can be solidified and adhered here. Alternatively, in order to perform distillation operations such as Mg reduction of metal chlorides in the same apparatus, for example, Japanese Patent Publication No. 55-36255 and
The devices described in each publication of USP3684264 can be modified and used. When the reduction process is performed in a separate device, a double cylinder configuration using an inner cylinder is convenient for transporting the metal lump.

When carrying out the method of the present invention using the various apparatuses described above, several further embodiments are available. For example, regarding the point where inert gas is introduced (injected), the flow rate of the gas used is small, and there is almost no leakage from the retort body of the distillation device, so from the original purpose of preventing air intrusion, It is sufficient that the inert gas is introduced (injected) on the same side of the metal mass to be purified as the vacuum suction side (for example, above the apparatus). in this case,
This is advantageous in that a device with a relatively simple structure is obtained. On the other hand, it is more preferable to introduce the gas on the side opposite to the suction because it is expected that the introduced airflow will transport Mg and MgCl ₂ to the cooling section, thereby making it possible to shorten the vacuum distillation time. At this time, in the case of a vacuum distillation device that heats the metal lump to be purified by placing it below the container, the pipe for introducing the inert gas should extend along the wall of the container and have an opening near the bottom of the container. It is best to place them in advance. For example, when a dedicated distillation retort having a heating section below is used and an inner cylinder containing metal is placed inside the retort, a conduit having an opening is provided at the bottom of the retort. In addition, when the reduction operation and the distillation operation are carried out using a common retort (for example, as described in JP-A-59-133335), the piping used for discharging the by-product MgCl ₂ during the reduction operation is It can be used as an inert gas introduction. By doing this, while the inert gas passes through the inlet pipe,
Since it is sufficiently preheated by a furnace heated to over 900°C, there is no need for any special equipment to preheat the introduced gas to prevent solidification of MgCl ₂ or Mg.

In order to simplify the structure, the opening of the inlet pipe can be provided in the lower part of the cooling section in the above device. In this case, Mg and
The MgCl ₂ vapor will be cooled to some extent, but since the amount of gas introduced is small, the vapor will not solidify and fall, but rather it will have a slight effect of promoting the solidification and adhesion of the vapor to the cooling wall. .

Furthermore, if the connection between the heating and retort section and the cooling cylinder is completely airtight, the opening of the introduction pipe may be provided near the lid of the cooling cylinder. This also prevents exhaust gas from flowing back into the vacuum system due to leaks in the lid and vacuum system piping.

On the other hand, for a reduced pressure distillation apparatus in which the metal to be refined is placed in the upper part and the lower part is used as a cooling section, the arrangement of the introduction pipes may be reversed to the above-mentioned cases.

In the method of the present invention, an inert gas is introduced at least in the latter stage of the vacuum distillation operation, thereby reducing the degree of vacuum in the vacuum system to a certain extent, thereby making it impossible to detect or This prevents contamination of refined metals during vacuum distillation operations due to the ingress of small amounts of air through difficult leak points. Therefore, a small amount of gas is enough to function satisfactorily. For example, during a distillation operation, Ar may be introduced to maintain a pressure of around 1 Torr while continuing to evacuation, but to obtain a higher distillation rate it is necessary to operate at a lower pressure, i.e. with less introduced gas. This is desirable. Generally, it is preferable to introduce Ar gas so that the degree of vacuum reached just before the start of the distillation operation (for example, about 10 ^-2 Torr) is maintained throughout the operation.

In this way, the method of the present invention performs distillation operation at a relatively low degree of vacuum, and therefore does not require a large-capacity high-vacuum pump unlike distillation operations at a high degree of vacuum, so the exhaust system can be configured simply. I can do it. Furthermore, since the airtightness test before operation can be simplified, the time and labor required for this can be reduced.

In the method of the present invention, since the distillation operation is performed at a low degree of vacuum, the efficiency of the vacuum separation operation itself is somewhat reduced due to the difference in vapor pressure from impurities, but on the other hand, the thermal conductivity due to the gas present in the system is Because of this increase, the final impurity removal efficiency decreases little. In addition, since inert gas is constantly introduced into the system, even if there is a problem with the exhaust system and it becomes necessary to create positive pressure in the system, appropriate measures can be taken to prevent contamination of refined metals. It is possible to take prompt action, maintain high quality, and prevent a decrease in yield despite such troubles.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a longitudinal sectional view of a separation device suitable for carrying out the method of the invention. At the lower part of the vacuum separator, which is designated as 1 in the figure as a whole, there is arranged an electric heating furnace 2 of essentially closed construction and connected to suitable vacuum means (not shown). A vertically elongated cylindrical body 3 is installed in the furnace 2, and a reduction reaction vessel 5 holding a reaction mixture 4 consisting of produced metal-Mg- _MgCl2 obtained by the Kroll method is accommodated in the lower part of the cylinder. The upper part of the cylindrical body 3 that protrudes from the furnace 2 can be separated from the lower part placed in the furnace, and an exhaust pipe 6 for decompression is installed at the top, and a water canopy 7 for cooling is installed around the top. An inert gas introduction pipe 8 extends along the vessel wall at the lower part of the cylinder 3 and has an opening at the bottom. A removable heat shield 9 is attached to the middle part of the cylinder. An empty reduction reaction vessel 11 is fixed to the lid 10 of the cylinder 3 with bolts.
is suspended, and solidified substances such as Mg and MgCl ₂ are adhered to the inner surface. An example using a device having such a configuration is as follows.

Example A lower cylindrical body made of SUS316 with an inner diameter of 1.6 m and a wall thickness of 32 mm is installed in an electric furnace having an essentially cylindrical space with an inner diameter of 2 m and a depth of 4 m. The outline placed inside this
The reaction vessel, which is 1.4 m long, 16 mm thick, and 2.4 m long, made of SUS410, holds approximately 4 tons of titanium sponge and a mixture containing small amounts of MgCl ₂ and Mg. An empty reduction reaction vessel of the same type as the one placed at the bottom of the cylinder (but with the bottom plate removed) is suspended from the lid, placed over the bottom of the cylinder, and joined. A vacuum is drawn through the tube at the top, and the lower part of the cylinder is heated to 950°C in a furnace.
Heat to ~1000°C while cooling the top.

Maintain the above temperature for 20 hours, and when the degree of vacuum at the suction port of the vacuum pump reaches 2 × 10 ^-2 Torr,
A small amount of Ar gas was supplied through a conduit extending along the lower part of the cylinder and opening at the bottom to maintain the degree of vacuum at the above position at 2 to 5 x 10 ^-2 Torr. This state was maintained for 72 hours to complete the separation operation.

The average analysis values of the entire titanium sponge mass obtained were as follows.

Oxygen 500ppm Nitrogen 30ppm Mg 120ppm Chlorine 250ppm Hardness 80BHN This quality was almost the same as that obtained with a conventional completely airtight device, and there was no major difference in the total operating time.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view schematically showing a vacuum separation apparatus suitable for carrying out the method of the present invention. 1... Separation device (whole), 2... Electric heating furnace, 3...
... Cylindrical body, 4 ... Reaction mixture, 5 ... Reduction reaction vessel, 6 ... Exhaust pipe, 7 ... Water mantle, 8 ... Gas introduction pipe, 9 ... Heat shield, 10 ... Lid, 11 ... ...Reduction reaction vessel.

Claims (1)

[Claims] 1. A method for heating a refractory metal lump mixed with Mg and MgCl ₂ in a space separated from the outside air and separating vaporized or liquefied Mg and MgCl ₂ from solid metal, at least: A refractory metal characterized by introducing an inert gas flow into the space during the latter half of the separation process when the partial pressures of Mg and _MgCl2 drop significantly, and continuing heating in a negative pressure inert gas atmosphere. Purification method. 2. The method for refining a refractory metal according to claim 1, wherein the inert gas is a gas containing argon as a main component.