JP7220186B2 - Method for producing titanium powder, method for producing sponge titanium, titanium powder and gas collector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing titanium powder, a method for producing titanium sponge, a titanium powder and a gas collecting device when reducing titanium tetrachloride in a metallic reduction reaction vessel, for example in the production of titanium sponge. be. In particular, this invention proposes a technique capable of producing titanium powder by a novel method.

In producing sponge titanium, for example, titanium tetrachloride such as purified titanium tetrachloride obtained by continuous distillation of crude titanium tetrachloride produced from a raw material ore is supplied into a metal reduction reaction vessel. A reduction process takes place in which the titanium tetrachloride is reduced.

In the reduction process by the Kroll method, which is often used industrially, for example, molten metal magnesium is stored in advance in a metal reduction reaction vessel, and titanium tetrachloride is continued over a certain amount of time on the molten metal magnesium. drop on a regular basis. This magnesium metal acts as a reducing agent to reduce titanium tetrachloride to titanium metal. Such metallic titanium is obtained as a sponge-like large mass, and the crushed sponge titanium mass is generally called sponge titanium. Reduction of titanium tetrachloride produces magnesium chloride as a by-product.

Here, more specifically, the following reactions are thought to occur within the metal reduction reactor. Titanium tetrachloride dropped from above reacts with metallic magnesium near the bath surface, where metallic titanium and magnesium chloride are produced. The magnesium chloride produced near the bath surface sinks deeper than the bath surface due to the difference in specific gravity from metallic magnesium, while metallic magnesium rises toward the bath surface. As a result, metallic magnesium is usually present on the bath surface, and the reduction reaction of titanium tetrachloride with metallic magnesium occurs continuously near the bath surface.

Incidentally, as a technique related to the production of this kind of titanium sponge, there is one described in Patent Document 1 and the like. In Patent Document 1, for the purpose of "reducing the average chlorine concentration of the entire mass of titanium sponge and thus of the titanium sponge", it is described that "titanium tetrachloride is supplied onto molten magnesium in a reaction vessel by the Kroll method to produce a titanium sponge mass. At least a part of the titanium sponge produced is produced within a period of time t from the time when metallic magnesium on the surface of the reaction bath is depleted and titanium lower chlorides begin to dissolve in magnesium chloride. Meanwhile, a method for producing sponge titanium by continuously supplying titanium tetrachloride has been proposed.

Regarding the detailed mechanism of such a reduction process of titanium tetrachloride, knowledge such as that described in, for example, Patent Document 2 has been obtained so far.

WO2018/110617 Japanese Patent Application Laid-Open No. 2003-306726

By the way, titanium powder mainly containing metallic titanium is generally produced from sponge titanium obtained by the above-mentioned reduction process or titanium shavings using a hydrodehydrogenation method or the like. If titanium powder can be produced by a method other than this, it may be used in a wider range of applications depending on the unique properties derived from the production.

An object of the present invention is to provide a method for producing titanium powder, a method for producing sponge titanium, a titanium powder, and a gas collecting device by a novel technique.

The inventor conducted various investigations on the reduction reaction mechanism of titanium tetrachloride in a metal reduction reaction vessel. As a result, the inventors found that the internal gas is collected from the internal space above the bath surface in the metal reduction reactor during the step of conducting the reduction reaction, and the titanium powder is obtained from the powder present in this internal gas. Found it.

Based on this knowledge, the method for producing titanium powder of the present invention collects an internal gas containing powder from the internal space of the metal reduction reaction vessel in the process of reducing titanium tetrachloride in the metal reduction reaction vessel. It has a gas collection step and a powder separation step of separating powder containing titanium powder present in the internal gas from the internal gas.

Here, in the powder separation step, it is preferable to use dry separation in which the powder in the internal gas is captured during transfer of the internal gas.

Here, the method for producing titanium powder of the present invention further includes an acid treatment step of treating the powder with an acid after the powder separation step, and dissolving and removing at least a part of the different powder different from the titanium powder. It is preferable to further have.
In this case, the different powder may contain one or more of metallic magnesium and magnesium chloride.
In this case, the acid is preferably at least one selected from the group consisting of nitric acid, hydrochloric acid and sulfuric acid.

The method for producing titanium powder according to the present invention can be carried out together with the production of sponge titanium lumps by reduction of titanium tetrachloride in the metal reduction reactor.

Further, a method for producing titanium sponge according to the present invention involves any one of the methods for producing titanium powder described above.

The titanium powder of the present invention has an average particle size d50 of 5.0 μm or less.

Here, the titanium powder of the present invention preferably has a 10% particle size d10 of 0.7 μm to 1.0 μm.
Here, the titanium powder of the present invention preferably has an average particle size d50 of 2.5 μm or less and a 90% particle size d90 of 3.0 μm to 12.0 μm.

The gas collection device of the present invention collects internal gas from the internal space of a metal reduction reaction vessel for reducing titanium tetrachloride, communicates with the internal space, and passes the internal gas from the internal space. It has a gas flow path and a powder collecting section provided in a part of the gas flow path for collecting powder in the internal gas.

Here, the gas collection device of the present invention has a tubular flow path member connected to a metal reduction reaction vessel and having the gas flow path formed therein, and a part of the tubular flow path member in the axial direction has , it is preferable that the powder collector is provided.

According to this invention, titanium powder can be produced by a novel technique.

1 is a schematic cross-sectional view of a metal reduction reaction vessel showing a reduction process of titanium tetrachloride in which a method for producing titanium powder according to one embodiment of the present invention can be performed; FIG. 1 is a schematic cross-sectional view showing a gas collecting device capable of sending internal gas collected in a gas collecting step of a method for producing titanium powder according to one embodiment of the present invention; FIG.

Embodiments of the present invention will be described below.
A method for producing a titanium powder according to one embodiment of the present invention is a method for producing a titanium powder containing metallic titanium (Ti), wherein when titanium tetrachloride is reduced in a metal reduction reactor, It has a gas collection step of collecting internal gas containing powder from the internal space of the metal reduction reaction vessel, and a powder separation step of separating powder containing titanium powder present in the internal gas from the internal gas. .

Here, in many cases, the above-described method for producing titanium powder can be suitably carried out during the reduction process of titanium tetrachloride when producing titanium sponge. Therefore, the reduction process of titanium tetrachloride is first described in detail here.

(Reduction process of titanium tetrachloride)
In this reduction process, generally, titanium tetrachloride is supplied into a metal reduction reaction vessel, and the titanium tetrachloride is reduced in the metal reduction reaction vessel to produce a sponge titanium mass.

Titanium tetrachloride (TiCl ₄ ) can be, for example, liquid titanium tetrachloride (also referred to as “purified titanium tetrachloride”) after being purified in a rectification column. This refined titanium tetrachloride is obtained, for example, by purifying crude titanium tetrachloride produced by reducing raw material ore such as titanium ore in a rectifying column. Specifically, the raw material ore is reduced with coke at a high temperature, and titanium oxide in the raw material ore is reacted with chlorine to obtain crude titanium tetrachloride. Since crude titanium tetrachloride contains other volatile chlorides and the like as impurities, it is purified by continuous distillation in a rectifying column. Thereby, high purity purified titanium tetrachloride with most of such impurities reduced is obtained.

The metal reduction reaction vessel used for the reduction of titanium tetrachloride in the reduction process can be a known one that has been used for similar reductions. For example, a metal reduction reaction vessel 1 schematically shown in FIG. A raw material supply pipe 4 provided in the lid member 3 so that titanium tetrachloride can be supplied from above toward the bath surface Sb, and a byproduct discharge for discharging magnesium chloride and the like produced by the reduction reaction of titanium tetrachloride. a tube 5;

Furthermore, in this metallic reduction reaction vessel 1, the cover member 3 is provided with a gas collection pipe 6 for collecting an internal gas Gi, which will be described later, from the internal space Si of the metallic reduction reaction vessel 1. As shown in FIG. The gas sampling pipe 6 can also function as a depressurization pipe. That is, the depressurization pipe may be separately provided in the lid member 3, or the gas sampling pipe 6 may also have the depressurization function.
Although not shown, the metal reduction reaction vessel 1 is usually provided with a heating mechanism, a cooling mechanism, and the like around it, so that the inside is adjusted to an appropriate temperature. The metal reduction reaction vessel 1 is generally made of stainless steel, steel, or the like.

In the reduction process, the above-mentioned titanium tetrachloride is supplied from the raw material supply pipe 4 into the metal reduction reaction vessel 1, and the titanium tetrachloride is reduced to obtain the titanium sponge mass TS.
An example of the reduction process will be described in detail. First, liquid molten metallic magnesium is stored in a metallic reduction reaction vessel 1 whose interior is maintained at a predetermined high temperature. Then, titanium tetrachloride is dropped onto the bath surface Sb from the upper side of the molten magnesium metal to supply it.

As a result, titanium tetrachloride and metallic magnesium come into contact with each other near the bath surface Sb, and metallic titanium is produced together with magnesium chloride as a by-product. It is thought that a reaction (formula (a) below) occurs between molten magnesium in the bath and titanium tetrachloride. At this time, it is assumed that a certain proportion of reaction between gases occurs in the region above the bath surface Sb. guessed. The produced metallic titanium can float in the internal space Si inside the metallic reduction reactor 1 as fine powder.
TiCl ₄ (gas, liquid) + Mg (liquid) → Ti (solid) + MgCl ₂ (liquid) (a)
TiCl ₄ (gas) + Mg (gas) → Ti (solid) + MgCl ₂ (liquid) (b)

Of these, magnesium chloride settles downward from the bath surface Sb due to its higher specific gravity than metallic magnesium. On the other hand, metallic magnesium in the bath floats toward the bath surface Sb due to its relatively small specific gravity. Due to such a difference in specific gravity between magnesium chloride and metallic magnesium, a bath flow occurs, metallic magnesium is positioned on the bath surface Sb, and the reaction continues between this metallic magnesium and the dropped titanium tetrachloride. A titanium sponge mass TS grows mainly in the bath.

Since the reactions of the above formulas (a) and (b) occur favorably at the beginning and middle of the reduction process, the supply rate of titanium tetrachloride into the metallic reduction reaction vessel 1 can be increased to some extent.
On the other hand, the above reaction proceeds in the reduction process, and at the end of the reduction process, metallic magnesium in the bath is consumed and its amount decreases. Further, as illustrated in FIG. 1, the titanium sponge mass TS grows large in the bath, and the top of the titanium sponge mass TS may reach the bath surface Sb onto which titanium tetrachloride is dripped. This makes it easier for metallic magnesium to be trapped in the sponge titanium mass TS, and together with the decrease in the amount of metallic magnesium, the floating of metallic magnesium due to the above-described bath flow is prevented, and metallic magnesium reaches the bath surface Sb. It takes time to do so. As a result, the speed of the reduction reaction of titanium tetrachloride with metallic magnesium in the vicinity of the bath surface Sb may decrease. Therefore, in the final stage, it may be necessary to reduce the supply rate of titanium tetrachloride into the metallic reduction reactor 1 .

As a result of investigating the detailed mechanism of such a reduction reaction, the inventor found that while reducing titanium tetrachloride in the metal reduction reaction vessel 1, the bath surface Sb in the metal reduction reaction vessel 1 A new knowledge was obtained that titanium powder is contained in the internal gas Gi containing powder collected from the internal space Si on the upper side. Based on such knowledge, the inventor devised a method for producing titanium powder as described in detail below.

(Method for producing titanium powder)
In the method for producing titanium powder according to one embodiment of the present invention, an internal gas Gi containing powder is obtained from the internal space Si while titanium tetrachloride is being reduced in the metal reduction reactor 1. It has a gas collection step. Since the internal gas Gi contains powder containing titanium powder, a powder separation step for separating the powder from the internal gas Gi is performed after the gas collection step.

In the gas collection step, in the reduction process described above, a predetermined amount of gas is collected during the period from when titanium tetrachloride is supplied into the metallic reduction reaction vessel 1 to when the supply of titanium tetrachloride is stopped and the collection of titanium sponge lumps is completed. , the internal gas Gi can be collected from the internal space Si.
In particular, it is preferable to collect the internal gas Gi from the internal space Si at the beginning and middle of the reaction. This facilitates production of titanium powder having a small particle size as described later. Here, more specifically, the early stage of the reaction refers to the timing when the cumulative supply amount (mass basis) of titanium tetrachloride is 0% to 64% of the total planned supply amount, and the middle stage of the reaction is 65% to 75%. % timing. Therefore, the internal gas Gi may be collected until the cumulative supply of titanium tetrachloride is 75%.

Specifically, in collecting the internal gas Gi, for example, an inert gas Ga such as argon gas is supplied to the internal space Si of the metal reduction reactor 1 through the gas supply pipe 12 or the like, and the inert gas is The internal gas Gi can be pushed out from the gas sampling tube 6 at .

The internal gas Gi collected from the internal space Si of the metallic reduction reaction vessel 1 can be sent to a gas collecting device 7 as illustrated in FIG.
The illustrated gas collection device 7 includes a gas collection pipe 6 as a tubular channel member in which a gas channel communicating with the internal space Si and passing the internal gas Gi from the internal space Si is formed, and a part of the gas channel. and a powder collecting portion 6a provided in the internal gas Gi for collecting powder in the internal gas Gi.

Here, the powder collector 6a can be, for example, a stainless flexible hose or the like that extends over a predetermined area of the gas sampling pipe 6. As shown in FIG. The powder collector 6a is not particularly limited as long as it can catch the powder contained in the internal gas Gi. or an air classifier. The powder collector may be a simple container-like one into which the internal gas Gi is fed, in which the powder is accumulated and the gas is discharged. That is, any material can be used as long as it can shut off the outside air and withstand a predetermined high temperature.
As a result, when the internal gas Gi passes through the powder collecting portion 6a of the gas sampling pipe 6, the powder in the internal gas Gi is collected by the powder collecting portion 6a as dry separation using no liquid. be.

In addition to the gas sampling pipe 6, the gas collecting device 7 further includes a tank-like liquid contact portion 8 to which the gas sampling pipe 6 is connected for performing required analysis of the internal gas Gi, and a liquid contact portion. 8, a liquid circulation pipe 10 for circulating the liquid ejected from the nozzle portion 9 and accumulated in the liquid contact portion 8 to the nozzle portion 9, and a gas for discharging the remaining gas. and an exhaust pipe 11 . However, such additional configuration is not necessarily required.

Alternatively, the powder may be separated from the internal gas Gi by wet separation. As an example of wet separation, the internal gas Gi that has flowed into the liquid contact portion 8 is brought into contact with the liquid ejected from the nozzle portion 9 . As a result, the powder of the internal gas Gi accumulates also in the liquid contact portion 8, so that the powder can be separated by removing the powder from the liquid. This liquid can be, for example, water, specifically tap water, industrial water, distilled water, purified water, ion-exchanged water, pure water, ultrapure water, or the like. It is enough. The powder obtained by the wet separation may contain a relatively large amount of another powder described later containing Mg or the like. The powder may be subjected to an acid treatment step, which will be described later. However, such wet separation tends to increase the hydrogen concentration of the titanium powder. Therefore, the above dry separation may be preferable depending on the application. Dry separation is also superior to wet separation in that the amount of different powders in the powder is reduced.

The powder collected by the powder collection unit 6a may contain, in addition to titanium powder containing metallic titanium, powder of one or more of metallic magnesium and magnesium chloride. This is presumably because the reduction of titanium tetrachloride with metallic magnesium in the reduction process is an exothermic reaction, and the magnesium in the metallic reduction reaction vessel 1 becomes easier to evaporate. In some cases, the powder may contain powder of titanium hydride (TiH).

If the powder collected by the powder collection unit 6a contains different powders of one or more of metal magnesium (Mg) and magnesium chloride (MgCl ₂ ), the powder is removed after the powder separation step. It is preferable to perform an acid treatment step of treating with an acid to dissolve and remove at least a portion of the different powder.
The acid used at this time may be at least one selected from the group consisting of nitric acid, hydrochloric acid and sulfuric acid. Among them, nitric acid is preferred because it is an oxidizing acid. This is because an oxidizing acid forms a stable oxide film on the surface of the titanium powder. When hydrochloric acid or sulfuric acid is used, it is desirable to dilute it (for example, a concentration of 5% by mass or less) and keep it at room temperature as much as possible.

The acid treatment in the acid treatment step can be performed, for example, at room temperature, preferably 30° C. or less, for 15 to 60 minutes.

Titanium powder can be produced through the above-described gas collection step, powder separation step, and, if necessary, acid treatment step. Details of the titanium powder will be described later.
Such a method for producing titanium powder is preferably carried out together with the production of sponge titanium lumps by reduction of titanium tetrachloride in the metallic reduction reactor 1 . In other words, by reducing titanium tetrachloride in the metal reduction reaction vessel 1, it is possible to produce titanium sponge lumps and titanium powder. As a result, not only sponge titanium lumps but also titanium powder can be produced by reduction of titanium tetrachloride.

(Titanium powder)
Although the reason is not necessarily clear, the titanium powder produced as described above has a smaller particle size than those produced by other production methods.
Specifically, the average particle size d50 of the titanium powder is 5.0 µm or less, preferably 3.0 µm or less, and more preferably 2.5 µm or less. Such small-diameter titanium powder may be effectively used in certain existing applications or new applications. On the other hand, the average particle diameter d50 of such titanium powder may be, for example, 1.0 μm or more, typically 1.5 μm or more.

Also, the 10% particle size d10 of the titanium powder is preferably 0.7 μm to 1.0 μm. Also, the 90% particle size d90 of the titanium powder is preferably 3.0 μm to 12.0 μm. Also, the 90% particle diameter d90 is preferably 3.0 μm to 7.0 μm, more preferably 3.0 μm to 5.0 μm.

The average particle diameter d50 referred to here can also be referred to as a so-called median diameter. Measurement of the average particle size d50, 10% particle size d10 and 90% particle size d90 of titanium powder is a particle size distribution graph obtained by measurement with a laser diffraction / scattering type particle size distribution measuring device, and the volume-based frequency is determined by determining the particle size at which the accumulation of 50%, 10% and 90%.

As for the composition of the titanium powder, the purity of metallic titanium may be, for example, 97.0% by mass to 99.0% by mass, typically 98.0% by mass to 99.0% by mass.
Impurities that may be contained in the titanium powder include at least one selected from the group consisting of iron, magnesium, chlorine, hydrogen and oxygen. The total content of these impurities is generally 3% by mass or less, and in some cases 1% by mass or less in some cases. Among these elements, iron and magnesium concentrations are measured by inductively coupled plasma emission spectroscopy (ICP-OES), chlorine concentration is measured by silver nitrate titration method, hydrogen concentration is measured by inert gas fusion - gas chromatography, oxygen concentration is measured by inert gas fusion - Each can be measured by an infrared absorption method.

(Method for manufacturing sponge titanium)
As an example, a method for producing titanium sponge in the Kroll method includes a reduction process, a vacuum separation process, and a crushing process. In the reduction process, as described above, the aforementioned titanium tetrachloride is added dropwise to the molten metallic magnesium charged into the metal reduction reaction vessel 1 under inert conditions to form sponge titanium lumps. . In the next vacuum separation process, molten magnesium chloride as a by-product and, if remaining, molten magnesium chloride are extracted from the metal reduction reaction vessel 1 through a metal pipe, and then the sponge titanium mass is extracted. Apply a vacuum separation process. The crushing process crushes the titanium sponge chunks. Thereby, sponge titanium is obtained.

Next, the present invention was implemented on a trial basis, and its effects were confirmed, which will be described below. However, the description herein is for illustrative purposes only and is not intended to be limiting.

A reduction process was performed by storing molten metal magnesium in a metal reduction reaction vessel as shown in FIG. At that time, using a gas collection device having a configuration as shown in FIG. The steps and acid treatment steps were performed sequentially.

When the amount of titanium tetrachloride added to the total amount of titanium tetrachloride dropped in the reduction process reaches 25% (at the beginning of the reaction), 67% (at the middle of the reaction), and 92% (at the end of the reaction). , performed a gas collection step to collect the internal gas. From this reduction process, an 8t sponge titanium mass was produced. In order to confirm the reproducibility, the gas collection at the time of 25% of the dropping amount was performed from each of the three reactors A, B, and C which were reacted under the same conditions.

Then, the internal gas collected in the gas collection process was subjected to a powder separation process and an acid treatment process to produce titanium powder. In the gas collection step, argon gas is introduced into the metal reduction reaction vessel at a rate of 100 L/min to 200 L/min, and is directed from the internal space of the metal reduction reaction vessel to the gas collection device through the gas collection pipe. , the internal gas was pumped in for 3 minutes. At this time, powder contained in the internal gas was collected (dry separation) with a SUS flexible hose (caliber 10A) as a powder collector provided in the middle of the gas sampling pipe. The acid treatment step was performed under the conditions of powder: 2 g, 3% by mass diluted nitric acid: 150 ml, dissolution time: 60 min, and temperature: room temperature.

XRD, SEM, and other analyzes were performed on the powder after the powder separation process and before the acid treatment process, and it was found that the powder was obtained at any of the dripping amount of 25%, the dripping amount of 67%, and the dripping amount of 92%. It was also found that the main phases of the powder were MgCl ₂ and Ti, and that the X-ray diffraction peak of Ti was relatively small in the powder when the amount of dropping was 92%. The X-ray diffraction peak of MgCl ₂ was large for the powder when the amount of drop was 92%.

Moreover, the same analysis was performed on the powder after the acid treatment step. As a result, the powder after the acid treatment process was mainly Ti, and a small amount of TiH was also detected. Table 1 shows the impurity concentration (% by mass) in the powder after the acid treatment step obtained from each of the reaction vessels B and C at the time of 25% of the dropping amount. The Ti purity is obtained by subtracting the content of each element listed in Table 1 from 100% by mass. 0.1% by mass.
In addition, the average particle size of the powder after the acid treatment process obtained from each of the reaction vessels A and B at the time of 25% of the dropping amount, the reaction vessel A at the time of 67% of the dropping amount, and the reaction vessel A at the time of 92% of the dropping amount. Table 2 shows the diameter d50, the 10% particle size d10 and the 90% particle size d90. Regarding the particle size, the primary particles were about 2 μm on average. Secondary particles of 10 μm to 20 μm were also present. In addition, the rate of the secondary particles was large at the time of 92% of the dropping amount.

REFERENCE SIGNS LIST 1 metal reduction reaction vessel 2 vessel body 3 lid member 4 raw material supply pipe 5 by-product discharge pipe 6 gas sampling pipe (tubular flow path member)
6a powder collection part 7 gas collection device 8 liquid contact part 9 nozzle part 10 liquid circulation pipe 11 gas discharge pipe 12 gas supply pipe Sb bath surface TS titanium sponge mass Gi internal gas Ga inert gas

Claims (9)

In the process of supplying titanium tetrachloride to molten metal magnesium stored in a metal reduction reaction vessel and reducing titanium tetrachloride by the Kroll method ,
a gas collection step of collecting internal gas containing powder from the internal space of the metal reduction reaction vessel;
a powder separation step of separating powder containing titanium powder present in the internal gas from the internal gas ;
has _
Manufacture of titanium powder, wherein the collection of the internal gas in the gas collection step is performed at least partly when the cumulative supply amount (mass basis) of titanium tetrachloride is between 0% and 75% of the total planned supply amount. Method. 2. The method for producing titanium powder according to claim 1, wherein the powder separation step uses dry separation for collecting the powder in the internal gas during transfer of the internal gas. After the powder separation step, the titanium powder according to claim 1 or 2, further comprising an acid treatment step of treating the powder with an acid to dissolve and remove at least a part of the different powder different from the titanium powder. Production method. The method for producing titanium powder according to claim 3, wherein the different powder contains one or more of metallic magnesium and magnesium chloride. The method for producing titanium powder according to claim 3 or 4, wherein the acid is at least one selected from the group consisting of nitric acid, hydrochloric acid and sulfuric acid. The method for producing titanium powder according to any one of claims 1 to 5, which is carried out together with production of sponge titanium lumps by reduction of titanium tetrachloride in the metal reduction reaction vessel. A method for producing sponge titanium, comprising:
A method for producing sponge titanium, which involves the method for producing titanium powder according to any one of claims 1 to 6. A gas collecting device that is used in the method for producing titanium powder according to any one of claims 1 to 6 and collects internal gas from the internal space of a metal reduction reaction vessel that reduces titanium tetrachloride,
a gas flow path communicating with the internal space to pass the internal gas from the internal space; A gas collection device, comprising: It has a tubular flow path member connected to a metal reduction reaction vessel and having the gas flow path formed therein, and the powder collecting section is provided in a part of the tubular flow path member in the axial direction. 9. The gas collection device of claim 8, comprising:

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