JP2005264319A - PROCESS FOR PRODUCING Ti OR Ti ALLOY BY REDUCTION OF Ca - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing high-purity metallic Ti or Ti alloy at high efficiency in an economic manner without using an expensive reducing agent. <P>SOLUTION: The process comprises, while retaining a molten salt containing CaCl<SB>2</SB>and having Ca fused in a reaction vessel 1, electrolyzing the molten salt of the reaction vessel and feeding a metal chloride containing TiCl<SB>4</SB>into the molten salt so as to react with any Ca generated on the negative electrode 3 side by the electrolysis to thereby produce granular Ti or Ti alloy in the molten salt. The Ti or Ti alloy is separated from the molten salt at the inside of the reaction vessel or at the outside of the reaction vessel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for producing Ti or Ti alloy by Ca reduction in which a metal chloride containing titanium tetrachloride (TiCl ₄ ) is reduced with Ca to produce metal Ti or a Ti alloy.

As an industrial method for producing titanium metal, a crawl method in which TiCl ₄ obtained by chlorinating titanium oxide (TiO ₂ ) is reduced with Mg is generally used. In this crawl method, a reduction step of reducing TiCl ₄ with Mg in the reaction vessel, and unreacted Mg and by-product magnesium chloride (MgCl ₂ ) are removed from the spongy metal Ti produced in the reaction vessel. The metal Ti is manufactured through a vacuum separation process.

In the reduction step, molten Mg is filled in the reaction vessel, and TiCl ₄ liquid is supplied to the liquid surface from above. As a result, TiCl ₄ is reduced by Mg in the vicinity of the molten Mg liquid surface, and particulate metal Ti is generated, and at the same time, molten MgCl ₂ is by-produced in the vicinity of the liquid surface. The produced metal Ti sequentially settles downward, and the molten MgCl ₂ also sinks downward because the specific gravity is larger than the molten Mg, and the molten Mg appears on the liquid surface. By this specific gravity difference replacement, molten Mg is continuously supplied to the liquid surface, and the reduction reaction of TiCl ₄ proceeds continuously.

In the production of metal Ti by the crawl method, a high-purity product is produced, but the production cost increases and the product price becomes very high. One of the causes of increased manufacturing cost is that it is difficult to increase the supply rate of TiCl ₄ . The following (a) to (c) can be considered as the reason for limiting the supply rate of TiCl ₄ .

(A) To increase the productivity in the crawl method, it is effective to increase the supply rate of TiCl ₄ , that is, the supply amount per unit area or unit time of molten Mg to the liquid surface. However, if the supply rate of TiCl ₄ is increased too much, the above-described specific gravity difference replacement cannot be made in time, and MgCl ₂ remains on the liquid surface and TiCl ₄ is supplied thereto. As a result, the supplied TiCl ₄ is discharged to the outside of the reaction vessel as unreacted TiCl ₄ gas or lower chloride gas such as TiCl ₃ (hereinafter referred to as “unreacted gas”). ₄ utilization efficiency decreases. In addition, generation of unreacted gas is accompanied by a rapid increase in the internal pressure of the container, and thus must be avoided. Therefore, the supply rate of TiCl ₄ is limited.

(B) When the supply rate of TiCl ₄ is increased, the Mg vapor generated from the molten Mg liquid surface reacts with the TiCl ₄ vapor to increase the amount of Ti deposited on the inner surface of the reaction vessel above the molten Mg liquid surface. On the other hand, as the reduction of TiCl ₄ proceeds, the liquid level of molten Mg rises, so that Ti deposited on the upper inner surface of the reaction vessel is immersed in molten Mg in the latter half of the reduction process, and the effective area of the liquid level decreases. As a result, the reaction rate decreases. In order to suppress this, it is necessary to limit the TiCl ₄ supply rate and suppress Ti precipitation on the inner surface of the upper portion of the container as much as possible.

Patent Document 1 proposes a method in which liquid TiCl ₄ is dispersedly supplied to the liquid surface where molten Mg is present to increase the reaction efficiency and suppress the precipitation of Ti on the upper inner surface of the reaction vessel. However, it is not sufficient as a measure for suppressing the Ti precipitation.

(C) In the crawl method, the reaction is performed only in the vicinity of the molten Mg liquid level in the reaction vessel, so that the heat generating region is narrow and the temperature rises locally. Therefore, cooling becomes difficult and the supply rate of TiCl ₄ is limited.

In addition, although it is not a problem that directly affects the supply rate of TiCl ₄ , in the crawl method, Ti powder generated in the form of particles near the liquid surface of molten Mg aggregates due to wettability (adhesiveness) of molten Mg. It settles in a state and sinters with the heat of the melt during the sedimentation to grow grains. Therefore, it is difficult to take out the produced Ti as a fine powder out of the reaction vessel and collect it, and it is difficult to continuously perform the production, and the improvement in productivity is hindered. This is why Ti is produced in a batch manner as sponge titanium in the reaction vessel.

Regarding Ti production methods other than the crawl method, Patent Document 2 describes that, for example, Ca other than Mg can be used as a reducing agent for TiCl ₄ . Further, in Patent Document 3, as a Ti production method using a reduction reaction with Ca, a molten salt of CaCl ₂ is held in a reaction vessel, and metallic Ca powder is supplied into the molten salt from above, And a method of reacting dissolved Ca and TiCl ₄ in a molten salt of CaCl ₂ by supplying CaCl ₂ from below and supplying TiCl ₄ gas.

In the reduction by Ca, metal Ti is generated from TiCl ₄ by the reaction of the following formula (1), and CaCl ₂ is by-produced along with it.

TiCl ₄ + 2Ca → Ti + 2CaCl ₂ .. (1)
Ca has a stronger affinity for Cl than Mg and is in principle suitable as a reducing agent for TiCl ₄ . In particular, in the method described in Patent Document 3, although used by dissolving Ca in the molten CaCl _2, this manner, when a Ca reduction reaction in molten CaCl _2, as Kroll method reaction Compared with the case where TiCl ₄ is supplied to the liquid surface of the reducing agent in the container, the region where the reaction occurs (reaction field) is expanded and the heat generation region is expanded, so that cooling is facilitated. Therefore, the supply rate of TiCl ₄ can be greatly increased, and an improvement in productivity can be expected.

  However, the method described in Patent Document 3 cannot be established as an industrial Ti production method. In this method, since extremely expensive metal Ca powder is used as the reducing agent, the manufacturing cost is higher than that of the crawl method.

Furthermore, as another Ti production method, Patent Document 4 describes a method (Orson's method) in which TiO ₂ is directly reduced by Ca without passing through TiCl ₄ . This method is a kind of direct oxide reduction method and is highly efficient. However, since high-purity TiO ₂ must be used, it is not suitable for producing high-purity Ti.

JP-A-8-295955 US Pat. No. 2,205,854 U.S. Pat. No. 4,820,339 U.S. Pat. No. 2,845,386

  An object of the present invention is to economically produce high-purity metallic Ti or Ti alloy with high efficiency and without using an expensive reducing agent.

In order to achieve this object, the present inventors consider that reduction of TiCl ₄ with Ca is indispensable, and use Ca dissolved in a molten salt of CaCl ₂ as described in Patent Document 3 described above. We examined how to do this.

  In this case, in the reduction reaction vessel, Ca in the molten salt is consumed as the reaction of the formula (1) proceeds. In order to compensate for this, the method described in Patent Document 3 It is necessary to continue supplying the powder into the reduction reaction vessel. However, the present inventors need to economically (ie, inexpensively) replenish Ca in the molten salt consumed in the reduction reaction in order to industrially establish a method for producing Ti by Ca reduction. As a means to solve this problem, a method of manipulating the dissolved Ca concentration in the molten salt by electrolysis was devised.

That is, when the molten CaCl ₂ is electrolyzed in the reaction vessel, the electrode reaction of the following formulas (2) and (3) proceeds to generate Cl ₂ gas in the vicinity of the surface of the anode and Ca in the vicinity of the surface of the cathode. Is generated, the Ca concentration in the molten salt can be increased. Therefore, when TiCl ₄ is supplied into the molten CaCl ₂ so as to react with the Ca generated on the cathode side, Ca consumed for Ti generation is replenished as needed. Extraction of the metal Ti becomes unnecessary, and economical production of the metal Ti becomes possible.

Anode: 2Cl ⁻ → 2e ⁻ + Cl ₂ (2)
Cathode: Ca ²⁺ + 2e ⁻ → Ca (3)
A method of replenishing Ca consumed for reduction of TiCl ₄ with Ca generated by electrolysis is also performed by causing reduction and electrolysis to be performed in a reduction tank and an electrolysis tank, respectively, and circulating molten CaCl ₂ between both tanks. Is possible. However, if TiCl ₄ is supplied into the molten CaCl ₂ in the reaction tank so as to react with Ca generated on the cathode side by electrolysis, the reaction tank serves as both a reduction tank and an electrolytic tank, and both tanks are provided. This is not necessary, and is very advantageous in terms of equipment cost as compared with the case where molten CaCl ₂ is circulated between the reduction tank and the electrolytic tank.

  The present invention has been made on the basis of such consideration, and the gist thereof is the following method for producing Ti or Ti alloy.

That is, a method for producing Ti or a Ti alloy using a reduction reaction with Ca, in which a molten salt containing CaCl ₂ and dissolved in Ca is held in a reaction vessel, and electrolysis is performed in the molten salt in the reaction vessel. Reduction electrolysis in which a metal chloride containing TiCl ₄ is supplied into the molten salt so that it reacts with Ca generated on the cathode side by electrolysis, and Ti or Ti alloy is generated in the molten salt. And a Ti separation step of separating the Ti or Ti alloy from the molten salt in the reaction vessel or outside the reaction vessel.

In the method for producing Ti or Ti alloy by Ca reduction of the present invention, for example, when molten CaCl ₂ is held in the reaction vessel as a molten salt and TiCl ₄ is supplied into the molten salt in the reaction vessel, the TiCl ₄ is Reduced by Ca dissolved in the molten salt, granular and / or powdery metal Ti (hereinafter referred to as “Ti grains”) is generated. Although the dissolved Ca in the molten salt is consumed as the Ti grains are generated, the electrolysis of the molten CaCl ₂ proceeds simultaneously with the reduction reaction in the reaction tank, so Ca is generated and consumed on the cathode side. Dissolved Ca is replenished.

Conventionally, one of the reasons that Ca has not been used for industrial production of metal Ti is that separation of Ca and CaCl ₂ is difficult. Mg is produced by electrolyzing MgCl ₂ , but since Mg is hardly dissolved in MgCl ₂ , the produced Mg can be efficiently recovered. Na can also be efficiently produced by electrolyzing NaCl in the same manner as Mg. On the other hand, Ca is produced by electrolysis of CaCl ₂ , but the produced Ca is dissolved in CaCl ₂ by about 1.5%. Therefore, it is difficult to produce only efficiently Ca, dissolved Ca generates CaCl ₂ in back reaction (reaction back to CaCl ₂ and Ca generated on the cathode side is coupled with Cl ₂ generated on the anode side) Since the phenomenon is added, the manufacturing efficiency is poor. A technique for increasing the recovery rate of Ca by means such as cooling the electrode is also used, but the production cost of Ca must still be high.

However, in the method for producing Ti or Ti alloy by Ca reduction of the present invention, Ca dissolved in molten CaCl ₂ is used and it is not necessary to separate Ca, so that the electrolytic production cost of Ca can be reduced. .

Further, if Ca reduction in molten CaCl ₂ is used, the reduction reaction field is widened, and at the same time, the heat generation area is widened. Furthermore, while the vapor pressure at 850 ° C. is Mg of 6.7 kPa (50 mmHg), Ca is as extremely low as 0.3 kPa (2 mmHg). Therefore, the amount of Ti deposited on the upper inner surface of the reaction tank is When Ca is used for the reduction, it is much less than Mg. Therefore, in the method for producing Ti or Ti alloy by the Ca reduction of the present invention, the TiCl ₄ supply rate can be greatly increased.

In addition, Ca is inferior in wettability (adhesiveness) to Mg, and Ca adhering to the precipitated Ti particles dissolves in CaCl ₂ , so there is much less aggregation of produced titanium particles and grain growth due to sintering. The produced Ti can be taken out of the reaction vessel in a powder state, and a continuous Ti production operation is also possible.

The supply form of TiCl ₄ into the molten CaCl ₂ solution, to directly supplied in the gaseous state a TiCl ₄ into the molten CaCl ₂ solution is higher contact efficiency TiCl ₄ to Ca in the molten CaCl ₂ solution, especially This is a desirable form. However, the present invention is not limited to this, and TiCl ₄ in a liquid or gas state is supplied to the liquid surface of the molten CaCl ₂ liquid, or the liquid surface or liquid state of the molten Ca liquid held on the molten CaCl ₂ liquid. It is also possible to supply TiCl ₄ .

When supplying the TiCl ₄ liquid to the molten Ca liquid surface held on the molten CaCl ₂ liquid to cause a reduction reaction, the molten Ca liquid is kept thin enough to use the Ca in the molten CaCl ₂ liquid Is desirable. If the Ca layer is thin, Ca in the molten CaCl ₂ solution is also involved in the reaction, so the reaction is carried out from the molten Ca layer to the molten CaCl ₂ layer, and the specific gravity difference substitution cannot be made in time due to the increase in the supply rate of TiCl _4. Can continue to produce Ti.

Regarding the supply of the TiCl ₄ gas, it will be described that the method for producing Ti or Ti alloy by Ca reduction of the present invention is more advantageous than the crawl method.

In the crawl method, a TiCl ₄ liquid is supplied to the surface of the molten Mg liquid, but an attempt was made to supply a TiCl ₄ gas into the liquid of the molten Mg liquid in order to expand the reaction field. However, as described above, since the vapor pressure of Mg is high, Mg vapor enters the TiCl ₄ gas supply pipe and reacts with TiCl ₄ to block the supply pipe.

On the other hand, although an attempt was made to supply the TiCl ₄ gas into the molten MgCl ₂ liquid, the frequency of closing the supply pipe is reduced, but the situation of the pipe closing still remains. This is because the molten product may be stirred by bubbling TiCl ₄ gas and molten Mg may reach the supply pipe. In addition, even if TiCl ₄ is supplied into the molten MgCl ₂ solution, Mg hardly dissolves in the molten salt, so that the reduction reaction hardly occurs.

On the other hand, in the method using Ca reduction, the supply pipe is hardly clogged and TiCl ₄ gas can be supplied into the molten CaCl ₂ liquid. It is assumed that the supply pipe is less likely to be clogged due to the low vapor pressure of molten Ca.

That is, in the method for producing Ti or Ti alloy by the Ca reduction of the present invention, it is particularly desirable to supply TiCl ₄ directly in a gaseous state into the molten CaCl ₂ liquid, but this supply form is not problematic in actual operation. It can be implemented. In addition, a liquid surface of the molten CaCl ₂ liquid, a liquid surface of the molten Ca liquid held on the molten CaCl ₂ liquid, and a form of supplying a TiCl ₄ liquid or gas into the liquid may be employed.

The separation from Ti particles in the molten CaCl ₂ solution produced in the molten CaCl ₂ solution can be implemented either reactor or reaction vessel outside. However, since it becomes a batch system when carried out in the reaction tank, in order to increase productivity, using the fact that the produced Ti is obtained in the form of particles, it is extracted out of the reaction tank together with the molten CaCl ₂ solution, and outside the reaction tank. It is better to separate the Ti particles from the molten CaCl ₂ solution. The Ti particles can be easily separated from the molten CaCl ₂ liquid by a drawing operation by mechanical compression or the like.

When Ti is produced by the production method of the present invention, TiCl ₄ is used as a raw material, but it is also possible to produce a Ti alloy by using a mixture of TiCl ₄ and other metal chlorides. is there. Since TiCl ₄ and other metal chlorides are simultaneously reduced by Ca, a Ti alloy can be produced by this method. The other metal chloride may be used in a gaseous state or a liquid state.

In the method for producing Ti or Ti alloy by Ca reduction of the present invention, Ca in molten CaCl ₂ (Ca produced on the cathode side or unreacted Ca) is combined with Cl ₂ produced on the anode side to return to CaCl ₂ . Back reaction and wear of the furnace material due to the high reactivity of Ca become problems.

When the back reaction occurs, the electrolysis current is consumed, and the current efficiency is lowered. For this problem, in particular, for the back reaction in which Ca produced on the cathode side is combined with Cl ₂ produced on the anode side, a partition wall having an opening at the lower part is provided in the reaction tank (see below). 1), it is desirable to divide the tank into an anode side and a cathode side.

Further, for the problem of wear of the furnace material, it is effective to lower the melting point of the molten salt as a mixed salt instead of CaCl ₂ alone and to lower the temperature of the molten salt (that is, the bath temperature).

That is, in the method for producing Ti or Ti alloy by Ca reduction according to the present invention, CaCl ₂ having a melting point of 780 ° C. is usually used as the molten salt, but a binary melting system of CaCl ₂ -NaCl and CaCl ₂ -KCl is used. Like salt or CaCl ₂ -NaCl-KCl ternary molten salt, CaCl ₂ is mixed with one or more of other salts (for example, NaCl, KCl, LiCl and CaF ₂ ), A multi-component molten salt is also possible. Thereby, since melting | fusing point of salt falls, it becomes possible to reduce the temperature (bath temperature) of molten salt. For example, when CaCl ₂ and NaCl (melting point: about 800 ° C.) are mixed, the melting point can be lowered to a minimum of about 500 ° C.

  As a result, it is possible to extend the life of the furnace material, reduce the furnace material cost, and further suppress the evaporation of Ca and salt from the liquid surface.

Since the production method of Ti or Ti alloy by Ca reduction of the present invention is a method of reducing TiCl ₄ that is easily obtained in high purity, high purity metal Ti or Ti alloy can be produced.

Since Ca is used as the reducing agent and the metal chloride containing TiCl ₄ reacts with Ca in the molten salt containing CaCl ₂ , the supply rate of TiCl ₄ can be increased. Furthermore, since Ti grains or Ti alloy grains are produced in CaCl ₂ , there is very little aggregation between grains and grain growth due to sintering, and these can be taken out of the reaction tank, enabling continuous operation. is there. In addition, the reduction reaction and the electrolytic reaction are allowed to proceed simultaneously in the reaction tank, and Ca consumed by the reduction reaction is supplemented by the electrolytic reaction, so that the Ca can always be used in a state dissolved in the molten salt.

  Therefore, according to the production method of the present invention, high-purity metal Ti or Ti alloy can be produced efficiently and economically.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a metal Ti manufacturing apparatus showing an embodiment of the present invention. In this embodiment, the reaction tank 1 that performs the reduction reaction and the electrolytic reaction simultaneously is used. The reaction tank 1 holds Ca-rich molten CaCl ₂ in which Ca is dissolved in a relatively large amount as a molten salt. CaCl ₂ has a melting point of about 780 ° C., the molten salt is heated above its melting point.

In the reaction tank 1, molten CaCl _2, which is a molten salt, is electrolyzed by energizing between the anode 2 and the cathode 3, Cl ₂ gas is generated on the anode 2 side, and Ca is generated on the cathode 3 side. . In this example, the inside of the reaction vessel 1 is divided into an anode side and a cathode side by a partition wall 4. However, the lower part of the partition wall 4 has an opening so that the movement of the molten salt is not hindered.

In the reaction tank 1, in parallel with the electrolysis of the molten salt, gaseous TiCl ₄ is dispersed and injected into the molten salt on the cathode side in the tank. Thereby, the injected TiCl ₄ is reduced by the dissolved Ca in the molten salt, and particulate metal Ti is generated. The produced Ti particles settle due to the difference in specific gravity and accumulate on the bottom of the reaction vessel 1 on the cathode side.

  Ti particles accumulated at the bottom on the cathode side in the reaction tank 1 are extracted from the reaction tank 1 together with the molten salt present at the bottom, and sent to a Ti separation step (not shown). In the Ti separation step, Ti particles extracted from the reaction tank 1 together with the molten salt are separated from the molten salt. Specifically, the molten particles are squeezed out by compressing the Ti grains. Ti particles obtained in the Ti separation step are melted to form a Ti ingot.

  On the other hand, the molten salt separated from the Ti grains in the Ti separation step is a used molten salt, and Ca is consumed and the Ca concentration is lowered. This molten salt is preferably returned to the reaction vessel and reused, and is usually introduced to the anode side in the reaction vessel 1 together with the used molten salt separately extracted from the reaction vessel 1.

On the cathode side in the reaction tank 1, Ca in the molten salt is consumed as Ti particles are generated by the reduction reaction. However, due to the simultaneous electrolysis in the tank, Ca is generated near the surface of the cathode 3 in the tank, thereby supplementing the consumption of Ca. That is, TiCl ₄ supplied into the molten salt is directly and sequentially reduced by Ca generated in the vicinity of the surface of the cathode 3.

  On the other hand, the used molten salt is sent from the Ti separation step to the anode side in the reaction tank 1 as a desirable form. As a result, a one-way flow of molten salt from the anode side to the cathode side is formed in the reaction tank 1, and the inflow of Ca generated on the cathode side to the anode side is avoided. If the partition wall 4 shown in FIG. 1 is provided, the combination with the formation of the unidirectional flow functions more effectively to prevent Ca from flowing into the anode side. Thus, the molten salt introduced to the anode side in the reaction tank 1 moves to the cathode side, is supplemented with Ca, becomes Ca-rich, and is reused for the reduction reaction.

Cl ₂ gas generated in the anode side of the reaction tank 1, by treating chloride TiO _2, it is desirable to reuse in the process chloride to produce a TiC1 ₄ which is a raw material of Ti (not shown). The produced TiCl ₄ is introduced into the reaction vessel 1 and recycled for producing Ti particles by Ca reduction.

As described above, in this embodiment, generation of Ti particles by Ca reduction in the reaction tank 1, that is, consumption of Ca and replenishment of Ca by electrolysis are performed simultaneously, so that in a solid state There is no need to replenish or take out Ca, and high quality Ti grains by Ca reduction are produced continuously and economically. In addition, the reaction tank 1 also serves as a reduction tank and an electrolytic tank, and has great economic merit in terms of equipment. Further, in the reaction tank 1, since the inflow of Ca generated on the cathode side to the anode side is avoided, back reaction in which Ca reacts with the Cl ₂ gas generated on the anode side can be prevented.

During the operation, the temperature of the molten salt in the reaction vessel 1 is controlled to be higher than the melting point of CaCl ₂ (about 780 ° C.).

According to the method for producing Ti or Ti alloy by Ca reduction of the present invention, the supply rate of TiCl _{4 as} a raw material can be increased, and continuous production is possible. In addition, since the reduction reaction and the electrolytic reaction can proceed simultaneously in the reaction tank and Ca consumed in the reduction reaction can be supplemented by the electrolytic reaction, it is not necessary to handle Ca itself alone.

  Therefore, the production method of the present invention can be effectively used as a means for efficiently and economically producing high-purity metal Ti or Ti alloy.

It is a block diagram of the metal Ti manufacturing apparatus which shows embodiment of this invention.

Explanation of symbols

1: Reaction tank 2: Anode 3: Cathode 4: Partition wall

Claims (1)

A method for producing Ti or a Ti alloy using a reduction reaction with Ca, wherein a molten salt containing CaCl ₂ and dissolved in Ca is held in a reaction vessel, and electrolysis is performed in the molten salt in the reaction vessel. And a reduction electrolysis step of supplying a metal chloride containing TiCl ₄ into the molten salt so as to react with Ca generated on the cathode side by the electrolysis, and generating Ti or Ti alloy in the molten salt; And a Ti separation step of separating the Ti or Ti alloy from the molten salt inside or outside the reaction vessel, and a method for producing Ti or Ti alloy by Ca reduction.

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