JP2021004399A - Method for producing sponge titanium - Google Patents

Abstract

To provide a method for producing sponge titanium which can suppress formation of thick wall surface production sponge titanium onto an inner surface of a side wall of a metallic reduction reaction vessel.SOLUTION: A method for producing sponge titanium includes a reduction step of supplying titanium tetrachloride to a molten bath containing metal magnesium in a metallic reduction reaction vessel to produce a sponge titanium lump, in the reduction step, every time 10 mass% of the titanium tetrachloride based on the total supply amount is supplied until the supply amount of the titanium tetrachloride reaches at least 50 mass% of the total supply amount of the titanium tetrachloride, the total movement distance of the bath surface of the molten bath is set at 0.12 or more in terms a ratio to an effective space height in the metallic reduction reaction vessel, and a temperature of the side wall of the metallic reduction reaction vessel at the position of the bath surface in the height direction is within a range of 700-950°C.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing titanium sponge by supplying titanium tetrachloride to a molten bath containing metallic magnesium to generate titanium sponge lumps in a metal reduction reaction vessel.

For example, in order to produce titanium sponge by the Kroll process, which is widely used in industry, metallic magnesium in a molten state is stored in advance in a metal reduction reaction vessel to form a molten bath, and titanium tetrachloride is formed on the bath surface. Is dropped to perform a reduction step. In the reduction step, metallic magnesium acts as a reducing material to reduce titanium tetrachloride to metallic titanium, and the metallic titanium grows as a sponge titanium mass inside the metallic reduction reaction vessel.

Here, it is considered that the following reaction occurs in the metal reduction reaction vessel. Titanium tetrachloride dropped from the upper side reacts with metallic magnesium near the bath surface, where metallic titanium and magnesium chloride are produced. This magnesium chloride generated near the bath surface settles deeper than the bath surface due to the difference in specific gravity with the metallic magnesium, while the metallic magnesium floats toward the bath surface. As a result of this bath flow, metallic magnesium is present on the bath surface, and the reduction reaction of titanium tetrachloride by metallic magnesium continues to occur in the vicinity of the bath surface.

After the reduction step, a separation step is generally performed. In the separation step, magnesium chloride in the metal reduction reaction vessel and, if residual, metallic magnesium are drained, and then, for example, the metal reduction reaction vessel is heated to a high temperature while the pressure inside the metal reduction reaction vessel is reduced. By the separation step, the metallic magnesium remaining in the metal reduction reaction vessel, magnesium chloride as a by-product, and the like are separated from the sponge titanium mass in the metal reduction reaction vessel. Then, the titanium sponge mass is taken out from the metal reduction reaction vessel and crushed to obtain granular titanium sponge.

Patent Documents 1 and 2 describe techniques focusing on the discharge of magnesium chloride from the metal reduction reaction vessel in the reduction step and the supply of metallic magnesium into the metal reduction reaction vessel.
Specifically, Patent Document 1 "provides a method for producing titanium sponge that enables an increase in productivity by preventing a decrease in yield due to a tap operation of MgCl ₂ and a charge operation of molten Mg". For the purpose of "when producing sponge titanium by dropping and adding TiCl ₄ to the molten Mg contained in the reaction vessel, a tap operation for extracting the by-product MgCl ₂ from the vessel is performed intermittently, and at the same time. A method for producing titanium sponge, characterized in that the tapping amount of MgCl ₂ is reduced in the latter half of the reaction than in the first half of the reaction, is disclosed.

Further, in Patent Document 2, "The object of the present invention is to increase the utilization rate of molten Mg charged during the reduction operation to improve productivity (titanium yield), and to suppress quality deterioration due to charging. The purpose is to provide a high-quality and economical method for producing titanium sponge. "" When producing titanium sponge in a reduction reaction vessel by the crawl method, the supply of TiCl ₄ was temporarily stopped during the reduction reaction, and the supply thereof was stopped. We are proposing a method for producing titanium sponge, in which molten Mg is additionally charged into the container from above the reduction reaction container while it is stopped.

On the other hand, Patent Document 3 states, "In the method for producing sponge titanium by reducing magnesium tetrachloride, the reaction vessel is filled with molten magnesium, and the wall surface of the reaction vessel is in contact with the vicinity of the reaction surface of the molten magnesium bath in which the reduction reaction proceeds. A method for producing titanium sponge, which comprises maintaining the average temperature of magnesium chloride below the melting point of magnesium chloride and supplying the titanium tetrachloride to the vicinity of the reaction surface of the molten magnesium bath ”is described. According to this, "high-purity titanium sponge can be efficiently produced, and as a result, high-purity titanium can be produced with good yield."

Japanese Unexamined Patent Publication No. 2004-43872 Japanese Unexamined Patent Publication No. 2012-184476 Japanese Unexamined Patent Publication No. 2008-190024

By the way, in the reduction step, as the reduction reaction progresses, as shown in FIG. 4, the titanium sponge lump TS grows on the bottom 53 side in the metal reduction reaction vessel 51, and the bath surface is on the upper side of the inner surface of the side wall 52. A substantially annular wall-generated sponge titanium WS that rises from the inner surface is formed near the position of Sb.

When this wall surface-generated sponge titanium WS is formed by being greatly raised inward as shown in FIG. 5, for example, there are the following problems.
Since the temperature near the bath surface Sb in the metal reduction reaction vessel 51 becomes high due to the heat generated by the reduction reaction, the metal is used for the purpose of reducing damage to the lid and for controlling the inside of the vessel to the desired temperature range. It may be cooled by air cooling or the like from the outside of the reduction reaction vessel 51. However, the wall surface-generated sponge titanium WS formed as a thick layer from the inner surface of the side wall 52 toward the inside in the vicinity of the bath surface Sb reduces the effect of this cooling in the vicinity of the bath surface Sb.

Further, when a large wall surface-generated sponge titanium WS is formed in the vicinity of the bath surface Sb, the area of the bath surface Sb is reduced, so that the above-mentioned bath flow of metallic magnesium and magnesium chloride is not smoothly performed, and the reduction reaction occurs. Is inhibited.
Further, since the wall surface-generated titanium sponge WS formed by swelling from the inner surface of the side wall 52 to the inside hinders the removal of the sponge titanium lump TS from the metal reduction reaction vessel 51, the workability of taking out the sponge titanium lump TS To make it worse.

At present, no effective countermeasure or solution has been found for the formation of such a large wall-generated sponge titanium WS and the problems caused by the formation. In Patent Documents 1 to 3, the above-mentioned wall surface-generated sponge titanium WS has not been studied at all.

An object of the present invention is to provide a method for producing titanium sponge, which can suppress the formation of thick wall-formed titanium sponge on the inner surface of the side wall of a metal reduction reaction vessel.

As a result of diligent studies, the inventor made a large fluctuation in the height of the bath surface of the molten bath while maintaining the bath surface of the molten bath at a specific temperature within a predetermined period from the beginning to the middle of the reduction process. , It was found that the formation tendency of wall surface-generated sponge titanium can be changed.

Based on such knowledge, a reduction step of supplying titanium tetrachloride to a molten bath containing metallic magnesium to form a sponge titanium mass in a metal reduction reaction vessel is included, and the titanium tetrachloride is supplied in the reduction step. Every time 10% by mass of titanium tetrachloride is supplied, the total moving distance of the bath surface of the molten bath is calculated until the amount reaches at least 50% by mass of the total supply of titanium tetrachloride. The ratio of the effective space height in the metal reduction reaction vessel to the effective space height is 0.12 or more, and the temperature of the side wall of the metal reduction reaction vessel at the position of the bath surface in the height direction is 700 ° C. to 950. It is to be within the range of ° C.

In the reduction step, it is preferable that magnesium chloride produced in the metal reduction reaction vessel is intermittently discharged from the metal reduction reaction vessel.

Further, in the reduction step, metallic magnesium can be intermittently supplied into the metal reduction reaction vessel.

According to the method for producing titanium sponge of the present invention, it is possible to suppress the formation of thick wall-generated titanium sponge on the upper side of the inner surface of the side wall of the metal reduction reaction vessel.

It is a vertical cross-sectional view which shows an example of the metal reduction reaction vessel which can be used in the reduction step of the manufacturing method of sponge titanium which concerns on one Embodiment of this invention together with a reduction furnace. It is an enlarged vertical cross-sectional view which shows typically the wall surface-generated sponge titanium produced in the reduction step of the manufacturing method of sponge titanium which concerns on one Embodiment of this invention. 3 (a) and 3 (b) are examples of graphs showing a part of the change in the ratio of bath surface height (Hs / He) to the supply amount of titanium tetrachloride. It is a vertical cross-sectional view of the metal reduction reaction vessel which shows the sponge titanium mass and the wall surface formation sponge titanium produced in the metal reduction reaction vessel in the conventional reduction step. It is an enlarged vertical sectional view which shows typically the wall surface formation sponge titanium produced by the conventional reduction process.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing titanium sponge according to one embodiment of the present invention includes a reduction step of supplying titanium tetrachloride to a molten bath containing metallic magnesium in a metal reduction reaction vessel to produce titanium sponge lumps. In particular, in the reduction step, every time 10% by mass of titanium tetrachloride is supplied, at least until the supply amount of titanium tetrachloride reaches at least 50% by mass of the total supply amount of titanium tetrachloride. The total moving distance of the bath surface of the melting bath is 0.12 or more as a ratio to the effective space height in the metal reduction reaction vessel, and the metal reduction at the position of the bath surface in the height direction. The temperature of the side wall of the reaction vessel is set in the range of 700 ° C. to 950 ° C.

After the reduction step, in many cases, the liquid magnesium chloride and metallic magnesium in the metallic reduction reaction vessel are extracted, and then the pressure in the metallic reduction reaction vessel is further reduced to reduce the metallic magnesium from the titanium sponge mass. And a separation step of separating magnesium chloride is performed. The titanium sponge mass is taken out of the metal reduction reaction vessel after undergoing a separation step and crushed into granular titanium sponge.

(Reduction process)
In the reduction step, a metal reduction reaction vessel 1 as illustrated in FIG. 1 is used. The metal reduction reaction vessel 1 has a cylindrical or other tubular side wall 2, a bottom portion 3 that seals one end side (lower end side in FIG. 1) of the side wall 2 in the axial direction, and the other end side of the side wall 2 in the axial direction. It is provided with a lid 4 attached to the opening (upper end side in FIG. 1). The side wall 2 is provided with a by-product discharge pipe 5 connected to a portion of the side wall 2 near the bottom 3, and the lid 4 is provided with a raw material supply pipe 6. Generally, as shown in the illustrated example, a rostrum 7 that operates to push up the sponge titanium block TS when the sponge titanium block TS is taken out from the metal reduction reaction container 1 is arranged on the bottom 3 side of the metal reduction reaction container 1. Will be done. The metal reduction reaction vessel 1 is arranged in the reduction furnace 8 and the reduction step is performed. Although not shown, the reduction furnace 8 is provided with a plurality of air cooling ports that can be independently controlled along the height direction, and air is blown from the air cooling ports to the side wall 2 to make a metal reduction reaction vessel. 1 can be cooled. In the present embodiment, it is preferable to cool the metal reduction reaction vessel 1 at least at the height portion where the bath surface Sb is present.

To perform the reduction step using the metal reduction reaction vessel 1, for example, metallic magnesium as a reducing material is stored in the metal reduction reaction vessel 1 in a molten state, and the inside of the metal reduction reaction vessel 1 is melted. Let the bath be Bm. Then, while heating the metal reduction reaction vessel 1 in the reduction furnace 8, cooling is also locally performed, and titanium tetrachloride, which is a raw material, is used from above via the raw material supply pipe 6 provided in the lid 4. TiCl ₄ ) is dropped onto the bath surface Sb of the melting bath Bm and supplied. The titanium tetrachloride dropped in this way comes into contact with the metallic magnesium, and the titanium tetrachloride is reduced by the metallic magnesium based on the reaction of the formula: TiCl ₄ + 2Mg → Ti + 2MgCl ₂ .

Here, magnesium chloride (MgCl ₂ ) as a by-product settles downward from the bath surface Sb due to its higher specific gravity than metallic magnesium. On the other hand, the metallic magnesium in the bath floats toward the bath surface Sb because of its relatively small specific gravity. Due to such a difference in specific gravity between magnesium chloride and metallic magnesium, a bath flow is generated and metallic magnesium is located on the bath surface Sb, and the reaction continues between this metallic magnesium and the dropped titanium tetrachloride. The sponge titanium lump TS grows mainly in the bath. Magnesium chloride precipitated downward may be discharged to the outside of the metal reduction reaction vessel 1 through the by-product discharge pipe 5 on the bottom 3 side of the metal reduction reaction vessel 1.

The titanium tetrachloride used in the reduction step can be, for example, a liquid purified titanium tetrachloride after being purified in a rectification column. This purified titanium tetrachloride is obtained by refining crude titanium tetrachloride produced by reacting a raw material ore such as titanium ore with a carbon source such as coke and chlorine gas in a rectification tower. However, titanium tetrachloride is not limited to the above-mentioned purified titanium tetrachloride as long as it can be used in the reduction step.
Further, magnesium chloride produced in the reduction step can be decomposed into metallic magnesium and chlorine gas by subjecting it to molten salt electrolysis in an electrolytic cell. The metallic magnesium thus obtained can be used again in the reduction step.

When such a reduction step proceeds, the titanium sponge lump TS grows on the bottom 3 side in the metal reduction reaction vessel 1, and the wall surface forming sponge is placed at a height position near the bath surface Sb on the inner surface upper side of the side wall 2. Titanium WS may be formed by rising inward from its inner surface.
When the wall surface-generated sponge titanium WS near the bath surface Sb is formed thickly, the presence of the wall surface-generated sponge titanium WS causes insufficient cooling of the bath surface Sb by air cooling or the like performed around the side wall 2, and heat generation of the reduction reaction occurs. There is a concern that the temperature rise of the bath surface Sb due to the above cannot be satisfactorily suppressed.

Further, the larger the area of the bath surface Sb of the molten bath Bm, the smoother the bath flow due to the movement of metallic magnesium and magnesium chloride in the bath. In particular, from the middle to the final stage of the reduction step, not only the temperature of the bath surface Sb tends to rise, but also the amount of metallic magnesium in the molten bath Bm decreases, so that a smooth bath flow is important. The bath flow also has an advantage of suppressing a temperature rise of the bath surface Sb. However, the presence of thickly formed wall surface-generated sponge titanium WS near the bath surface Sb reduces the surface area of the bath surface Sb and impedes the bath flow.

Further, after the reduction step and the separation step are completed, the lid 4 is removed from the metal reduction reaction vessel 1 and the rostrum 7 is raised to take out the sponge titanium lump TS from the metal reduction reaction vessel 1. At this time, if the wall surface-generated sponge titanium WS is formed so as to be greatly raised from the inner surface of the side wall 2, the sponge titanium lump TS and the wall surface-generated sponge titanium WS interfere with each other, and the sponge titanium lump TS can be easily taken out. You won't get it.

In order to deal with such a problem, in this embodiment, the height of the bath surface Sb and the temperature of the bath surface Sb of the molten bath Bm are generated as a result of the wall surface generation in a predetermined period from at least the early stage to the middle stage of the reduction step. Adjust so that the sponge titanium WS is formed thin over a relatively wide area.
Specifically, until at least 50% by mass of the total supply of titanium tetrachloride supplied in the entire reduction step is reached, 10% by mass of the total supply of titanium tetrachloride is supplied each time the molten bath Bm is supplied. The total moving distance of the bath surface Sb is 0.12 or more as a ratio to the effective space height He in the metal reduction reaction vessel. Further, during the predetermined period, the temperature of the side wall 2 of the metal reduction reaction vessel 1 at the position of the bath surface Sb in the height direction is set within the range of 700 ° C. to 950 ° C. Here, the ratio of the total moving distance of the bath surface Sb to the effective space height He is also referred to as the ratio of the total moving distance of the bath surface Sb.

According to this, during the predetermined period after the reduction step is started, the bath surface Sb largely changes in the height direction while being maintained within a specific temperature range. As a result, as schematically shown in FIG. 2, the wall surface-generated sponge titanium WS is formed by thinly depositing on the upper side of the inner surface of the side wall 2 near the bath surface Sb, and swells inward of the metal reduction reaction vessel 1. Will be suppressed.

As a result, since the wall surface-generated sponge titanium WS is thin to some extent, the vicinity of the bath surface Sb can be effectively cooled by air cooling from around the container. Further, since the decrease in the area of the bath surface Sb due to the swelling of the wall surface-generated sponge titanium WS is suppressed, the bath flow is smoothly performed. Further, the presence of the thin wall-generated sponge titanium WS improves the workability of taking out the sponge titanium lump TS from the metal reduction reaction vessel 1 after the separation step.

Here, the total moving distance of the bath surface Sb of the molten bath is based on the initial height of the molten salt bath Sb in the metal reduction reaction vessel 1 before the supply of titanium tetrachloride is started, and the total movement distance of the titanium tetrachloride is based on the initial height. The amount of supply (drop amount), the inner diameter of the side wall 2 of the metal reduction reaction vessel 1, and the amount of magnesium chloride discharged and / or metallic magnesium when magnesium chloride is discharged and / or metallic magnesium is supplied in the reduction step. It can be obtained by using the supply amount of.
For example, when neither the discharge of magnesium chloride nor the supply of metallic magnesium is performed, the bath surface Sb of the molten bath continuously rises with the supply of titanium tetrachloride during the reduction step. Therefore, in this case, the moving distance of the bath surface Sb in the direction in which the bath surface Sb of the melting bath rises is obtained based on the supply amount of titanium tetrachloride and the inner diameter of the side wall 2 of the metal reduction reaction vessel 1. Let this be the total movement distance of the bath surface Sb.
Alternatively, when the magnesium chloride is discharged and / or the metallic magnesium is supplied, not only the moving distance in the bath surface ascending direction due to the supply of titanium tetrachloride as described above, but also the bath surface descending direction due to the magnesium chloride discharge. The total moving distance of the bath surface Sb of the molten bath is calculated in consideration of the moving distance and / or the moving distance in the bath surface rising direction due to the supply of metallic magnesium.

In the reduction step, the bath surface when the titanium tetrachloride is supplied is changed by changing the ratio (Hs / He) of the height Hs of the bath surface Sb of the melting bath to the effective space height He in the metal reduction reaction vessel 1. It can represent the fluctuation of the height of Sb.

Here, the height Hs of the bath surface Sb is along the height direction (vertical direction, vertical direction in FIG. 1) from the position of the bottom surface of the sponge titanium block TS formed in the reduction step to the position of the bath surface Sb. Means length. In the illustrated example, the titanium sponge mass TS is formed on the surface 7a of the rostrum 7, and the bottom surface of the titanium sponge mass TS is located on the surface 7a of the rostrum 7. Therefore, the height Hs of the bath surface Sb of the melting bath Is the length in the height direction from the position of the surface 7a of the rostrum 7 to the position of the bath surface Sb.
The height Hs of the bath surface Sb is the amount of titanium tetrachloride supplied and the metal reduction reaction vessel 1 from the initial height of the molten salt bath Sb in the metal reduction reaction vessel 1 before supplying titanium tetrachloride. It can be obtained by using the inner diameter of the side wall 2 and the amount of magnesium chloride discharged and / or the amount of metallic magnesium supplied when magnesium chloride is discharged and / or metallic magnesium is supplied in the reduction step.

Further, here, the effective space height He in the metal reduction reaction vessel 1 is the maximum in which the bath surface Sb can rise from the surface 7a of the rostrum 7 in which the bottom surface of the titanium sponge ingot TS contacts in the vertical direction. Means height. In the case of the figure, since the raw material supply pipe 6 protrudes from the lid 4 toward the space in the metal reduction reaction vessel 1, the effective space height He is the position of the surface 7a of the rostrum 7 (sponge titanium lump TS). It is the length in the height direction from the position of the bottom surface of the raw material supply pipe 6 to the position of the lower end of the raw material supply pipe 6.

When the above-mentioned bath surface height ratio (Hs / He) was calculated while titanium tetrachloride was supplied into the metal reduction reaction vessel 1, a part thereof was added to each of FIGS. 3 (a) and 3 (b). A graph showing the change in the ratio of bath surface height (Hs / He) to the supply amount of titanium tetrachloride (Hs / He) as illustrated may be obtained. In the graphs of FIGS. 3A and 3B, the ratio of bath surface heights (Hs / He) from the time when 10% by mass of the total supply of titanium tetrachloride to the time when 30% by mass was supplied, respectively. ) Is shown. Here, every time a relatively short period of time elapses, magnesium chloride is intermittently discharged from the metal reduction reaction vessel 1, metal magnesium is intermittently supplied to the metal reduction reaction vessel 1, and the like. As a result, as shown by the solid line in FIGS. 3A and 3B, the bath surface height ratio (Hs / He) fluctuates up and down to some extent in a short span. The total moving distance of the bath surface Sb corresponds to the sum of the sizes of the components in the vertical axis direction of the polygonal line shown in FIG. Using this total movement distance and effective space height, the effective space in the metal reduction reaction vessel is the total movement distance of the bath surface of the melting bath every time 10% by mass is supplied with respect to the total supply amount of titanium tetrachloride. The ratio to the height is calculated, and this ratio is set to 0.12 or more.

Until the supply of titanium tetrachloride reaches 50% by mass of the total supply, the ratio of the total distance traveled by the bath surface Sb for every 10% by mass of titanium tetrachloride may be less than 0.12. In this case, the fluctuation of the bath surface Sb is insufficient, and the wall-generated sponge titanium WS is formed in a relatively narrow range in the height direction inside the metal reduction reaction vessel 1, so that the above-mentioned problem occurs. From the viewpoint of moving the bath surface Sb appropriately and significantly, the ratio of the total moving distance of the bath surface Sb every time 10% by mass of titanium tetrachloride is supplied is preferably 0.16 or more. There is no particular preferable upper limit of the ratio of the total moving distance of the bath surface Sb, but it may be, for example, 0.30 or less.

Further, when the temperature of the side wall 2 at the position of the bath surface Sb becomes less than 700 ° C. until the supply amount of titanium tetrachloride reaches 50% by mass of the total supply amount, it is expected that TiCl ₄ + 2Mg → Ti + 2MgCl ₂ In addition to the reaction, a reaction for producing lower titanium chloride such as TiCl ₂ occurs, and the ratio of this reaction tends to increase. In addition, the bath surface temperature is too close to the melting point of magnesium. On the other hand, when the temperature of the side wall 2 exceeds 950 ° C., the evaporation of metallic magnesium proceeds, and the ratio of the reduction reaction of titanium tetrachloride in the gas phase tends to increase. By setting the temperature of the side wall 2 at the position of the bath surface Sb to 800 ° C. to 950 ° C., the reaction of lower titanium chloride such as TiCl2 can be further reduced. The temperature of the side wall 2 can be measured by a thermometer such as a thermoelectric pair installed on the outside of the container on the side wall 2.

After the supply amount of titanium tetrachloride reaches 50% by mass of the total supply amount of titanium tetrachloride, the ratio of the total moving distance of the bath surface Sb and the temperature of the side wall 2 are controlled as described above. No need to do. However, even within a certain period after the supply amount of titanium tetrachloride reaches 50% by mass of the total supply amount of titanium tetrachloride, the ratio of the total movement distance of the bath surface Sb and / or the temperature of the side wall 2 May be controlled in the same manner.

The period from the start of the supply of titanium tetrachloride to the supply of 50% by mass of titanium tetrachloride is the height Hs of the bath surface Sb, which is the highest during the period, that is, the maximum value Hsmax, and during the period. The lowest height Hs of the bath surface Sb, that is, the lowest value Hsmin, preferably has a relationship of (Hsmax-Hsmin) /He≥0.15, more preferably (Hsmax-Hsmin) /He≥0.20. Try to satisfy the relationship. In this case, since the bath surface Sb changes more reliably in the height direction, the wall surface-generated sponge titanium WS is formed thinly. As will be described later, when the metallic magnesium is supplied into the metal reduction reaction vessel 1 in the reduction step, the height of the bath surface Sb at the start of the supply of titanium tetrachloride can be set low. (Hsmax-Hsmin) / He can exceed 0.30.

As described above, in order to control the ratio of the total movement distance of the bath surface Sb, for example, in the metal reduction reaction vessel 1 until the supply amount of titanium tetrachloride reaches at least 50% by mass of the total supply amount. One or more of the operations of supplying metallic magnesium to the metal and the operation of discharging magnesium chloride from the metallic reduction reaction vessel 1 can be performed.

In the reduction step, metallic magnesium can be continuously or intermittently supplied into the metal reduction reaction vessel 1. As a result, the depletion of metallic magnesium in the metal reduction reaction vessel 1 can be suppressed, and the productivity can be increased. Further, in this case, since the bath surface Sb of the molten bath rises due to the supply of metallic magnesium, the initial height of the bath surface Sb before the start of supply of titanium tetrachloride can be set relatively low. As a result, it becomes easy to increase the total moving distance of the bath surface Sb of the melting bath. Since it may not be possible to supply titanium tetrachloride and metallic magnesium at the same time, metallic magnesium may be supplied intermittently between the supply of titanium tetrachloride.

Further, when magnesium chloride is discharged from the metal reduction reaction vessel 1 in the reduction step, the discharge of magnesium chloride may be continuous or intermittent. When magnesium chloride is discharged intermittently, there is an advantage that the variation in the height direction of the bath surface Sb of the melting bath and the moving distance can be easily adjusted. For example, if the time interval for discharging magnesium chloride is lengthened to increase the amount of magnesium chloride discharged at one time, the bath surface Sb fluctuates greatly in the height direction at that time. The intermittent discharge of magnesium chloride can be, for example, once during the supply of titanium tetrachloride in an amount of 7% by mass to 10% by mass based on the total supply amount. The amount discharged at one time can be 5% by mass to 12% by mass of the total amount of MgCl ₂ discharged in the entire reduction step.

(Separation process)
After the reduction step is completed, in the metal reduction reaction vessel 1, in addition to the sponge titanium lump TS produced in the reduction step and the wall surface-generated sponge titanium WS, the metallic magnesium remaining without being used in the reduction reaction. There are also magnesium chloride and other impurities produced as a by-product of the reduction reaction. The separation step is performed to remove such impurities in a liquid state and then further reduce the pressure inside the metal reduction reaction vessel 1 to separate the impurities from the sponge titanium lump TS or the like.

In the separation step, after draining the liquid, for example, while heating the metal reduction reaction vessel 1 to about 1000 ° C., the inside of the metal reduction reaction vessel 1 is depressurized to create a vacuum atmosphere or the like. As a result, impurities such as metallic magnesium and magnesium chloride existing in the metal reduction reaction vessel 1 are sucked and removed from the metal reduction reaction vessel 1.

After the separation step, the sponge titanium lump TS on the rostrum 7 or the like provided on the bottom 3 side in the metal reduction reaction vessel 1 is taken out from the metal reduction reaction vessel 1. Then, the sponge titanium lump TS can be crushed into granules to obtain sponge titanium.

Next, the method for producing titanium sponge of the present invention was carried out on a trial basis, and its effect was confirmed, which will be described below. However, the description here is for the purpose of mere illustration, and is not intended to be limited thereto.

A reduction step was carried out using a metal reduction reaction vessel and a reduction furnace as shown in FIG. 1 to generate a sponge titanium mass. As the metal reduction reaction vessel, a cylindrical one having an inner diameter of 1900 mm and an effective space height of 4300 mm was used. In Examples 1 to 4 and Comparative Examples 1 to 3, titanium tetrachloride was supplied in the reduction step, and magnesium chloride was intermittently discharged over the entire period of the reduction step. Magnesium chloride is discharged once while supplying 7% by mass to 10% by mass of titanium tetrachloride with respect to the total supply amount, and the amount discharged at that time is MgCl in the entire reduction process. _{2 The} total emission amount was set within the range of 5% by mass to 12% by mass. Table 1 shows the conditions of Examples 1 to 4 and Comparative Examples 1 to 3. In Example 5, magnesium chloride is not discharged during the reduction step, and every time 10% by mass of titanium tetrachloride is supplied until the dropping of titanium tetrachloride reaches 50% by mass of the total supply amount. The ratio of the total moving distance of the bath surface was set to 0.12, and the side wall temperature at the bath surface position was set to 720 ° C.

The ratio of the total moving distance of the bath surface was obtained every time 10% by mass of titanium tetrachloride was dropped, using the dropping amount, the inner diameter of the metal reduction reaction vessel, and the amount of magnesium chloride discharged. The results of ~ 4 and Comparative Examples 1 to 3 are shown in Table 1. Further, in Examples 1 to 4 and Comparative Examples 1 to 3, (Hsmax-Hsmin) / He during the period from the start of dropping titanium tetrachloride to the dropping of 50% by mass was set to 0.15 or more. In Example 5, (Hsmax-Hsmin) / He up to the dropping of 50% by mass of titanium tetrachloride was set to 0.25 or more.
If the side wall temperature at the bath surface position is set to less than 700 ° C., there is a concern that the temperature will be close to the melting point of metallic magnesium and the reduction reaction cannot be performed properly. Therefore, at such a low temperature. No test was performed.

For each of Examples 1 to 5 and Comparative Examples 1 to 3, the maximum thickness in the radial direction of the metal reduction reaction vessel of the wall-generated sponge titanium generated on the inner surface upper side of the side wall of the metal reduction reaction vessel after the reduction step was determined. It was measured. Here, the maximum thickness of the wall-generated titanium sponge in the radial direction is measured at four points at 90 ° intervals in the circumferential direction of the side wall of the metal reduction reaction vessel, and the points where the maximum adhesion thickness is obtained are measured. The measured values of the points were averaged. Then, the case where the thickness of the wall-generated sponge titanium in the radial direction was 200 mm or less was evaluated as a pass, and the other cases were evaluated as a failure. The results are also shown in Table 1. Further, in Example 5, the thickness evaluation of the wall-generated sponge titanium was passed.

As shown in Table 1, in Examples 1 to 4, the ratio of the total distance traveled was 0.12 for each supply of 10% by mass of titanium tetrachloride in the total amount of titanium tetrachloride dropped up to 50% by mass. In addition to the above, the side wall temperature at the bath surface was set within the range of 700 ° C. to 950 ° C., so that the wall-generated sponge titanium satisfied the acceptance criteria. Similar results could be confirmed in Example 5.
On the other hand, in Comparative Example 1, since the ratio of the total moving distance was less than 0.12, the evaluation result of the wall surface-generated sponge titanium was unacceptable. Comparative Example 2 was rejected because the ratio of the total distance traveled from 40% by mass to 50% by mass of titanium tetrachloride added dropwise to the total supply amount was smaller than 0.12. Comparative Example 3 was rejected because the side wall temperature at the bath surface position up to 50% by mass of titanium tetrachloride dropping with respect to the total supply amount exceeded 950 ° C.

From the above, it was found that according to the present invention, the formation of thick wall-formed sponge titanium on the inner surface of the side wall of the metal reduction reaction vessel can be suppressed.

1,51 Metal reduction reaction vessel 2,52 Side wall 3,53 Bottom 4 Lid 5 By-product discharge pipe 6 Raw material supply pipe 7 Rostle 7a Rostle surface 8 Reduction furnace TS Sponge titanium block WS Wall surface generation Sponge titanium Bm Melting bath Sb Bath surface Hs Height of the bath surface of the melting bath He Height of the effective space in the metal reduction reaction vessel

Claims (3)

A method for producing titanium sponge, which comprises a reduction step of supplying titanium tetrachloride to a molten bath containing metallic magnesium to produce titanium sponge lumps in a metal reduction reaction vessel.
In the reduction step, until the supply amount of titanium tetrachloride reaches at least 50% by mass of the total supply amount of titanium tetrachloride.
Every time 10% by mass of the total supply amount of titanium tetrachloride is supplied, the total movement distance of the bath surface of the melting bath is set to 0.12 or more as a ratio to the effective space height in the metal reduction reaction vessel. And,
A method for producing titanium sponge, wherein the temperature of the side wall of the metal reduction reaction vessel at the position of the bath surface in the height direction is in the range of 700 ° C. to 950 ° C. The method for producing titanium sponge according to claim 1, wherein magnesium chloride produced in the metal reduction reaction vessel is intermittently discharged from the metal reduction reaction vessel in the reduction step. The method for producing titanium sponge according to claim 1 or 2, wherein in the reduction step, metallic magnesium is intermittently supplied into the metal reduction reaction vessel.