AU618541B2

AU618541B2 - Method for producing metallic titanium and apparatus therefor

Info

Publication number: AU618541B2
Application number: AU19044/88A
Authority: AU
Inventors: Eiichi Fukasawa; Takefumi Irie; Kazuhiko Kobayashi; Shigenori Okudaira; Hiroshi Uchida; Masanori Yamaguchi
Original assignee: Toho Titanium Co Ltd
Current assignee: Toho Titanium Co Ltd
Priority date: 1987-07-17
Filing date: 1988-07-14
Publication date: 1992-01-02
Anticipated expiration: 2008-07-14
Also published as: DE3875411D1; EP0299791B1; DE3875411T2; EP0299791A1; CA1328561C; AU1904488A

Description

Declared at Tokyo this 4th day of July 1988 Signature of Declarant(s) 11/81 SFP4 To: The Commissioner of Patents ft IIIU- ~LI- 1P I S F Ref: 64553 FORM V0 CO ONWEALTH OF AUSTRALIA SPATENTS ACT 1952 SCOMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: 4444 4r 4 4 1 4 4 4 £r 4 Name and Address of Applicant: Address for Service: Toho Titanium Co., Ltd.

13-31, Konan 2-chome Minato-ku Tokyo

JAPAN

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Method for Producing Metallic Titanium and Apparatus Therefor The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 'I

ABSTRACT

A method for producing metallic titanium by the reduction of titanium tetrachloride with a reducing metal agent, capable of continuously producing metallic titanium on an industrial scale. The temperature and pressure of the reaction region are kept above the melting point of metallic titanium and at least above the vapour pressure of the reducing metal agent, 10 respectively, so that the reducing metal agent and its chloride may be kept in a molten state but without S".o boiling.

0 00 (Figure 1) o 2 0 0 0 a 0 0 000 _i METHOD FOR PRODUCING METALLIC TITANIUM AND APPARATUS THEREFOR This invention relates to a method for producing metallic titanium and an apparatus therefor, and more particularly to a method and apparatus for producing metallic titanium from titanium tetrachloride at a reaction temperature above the melting point of titanium.

4444 1 0 In the known "Kroll" process, metallic titanium is 4 produced by the reduction of titanium tetrachloride by 0a4 metallic magnesium.

040o In the Kroll process, the reduction is generally o00 carried out at a temperature below the melting point of metallic titanium while keeping the reduction vessel at normal pressure to produce spongy metallic titanium.

000 The spongy metallic titanium product is subjected to 4 0-00.

0ooo vacuum separation or leaching to remove any excess 0 00 metallic magnesium and magnesium chloride (by-product) 0 20 remaining in the fine internal voids of the metallic titanium product and is thus purified. The purified metallic titanium is then crushed and formed into a shape suitable for melting. After melting, an ingot of titanium is obtained.

As can be seen, the Kroll process is a batch type process. Accordingly, producing the metallic titanium ingot according to the Kroll process requires at least four discontinuous or independent steps comprising'a reduction step, a vacuum separation step, a crushing step and a melting step.

The Kroll process also has the following disadvantages.

The spongy metallic titanium which is the reaction 1 2 product is firmly adhered to a reduction vessel, so that much labour and time are required for removing the deposited reaction product from the vessel.

Another disadvantage is that it is difficult to remove the heat of reaction from the reaction system during the reduction step sufficiently rapidly.

A further disadvantage is that the titanium is produced at a sufficiently elevated temperature to increase its activity. Accordingly, it is readily 10 contaminated with the material of the reaction vessel .wall.

o Still another disadvantage is that the separation o o step for purification of the titanium requires much attention in order to prevent contaminated of the S 15 titanium with moisture, air and the like. Accordingly, removal of the unreacted reactant and the by-product must be carried out in a vacuum or argon atmosphere.

For the purpose of reducing metal halide with a reducing metal agent without using the Kroll process, other methods are proposed in each of which the reduction is carried out at a reaction temperature above the melting point of the metal to be produced and the product is continuously removed from the reaction vessel. The metal product is then obtained in a molten state or in the form of an ingot by cooling the molten metal product for solidification.

As an example, Japanese Patent Application Laying- Open Publication No.35733/1981 discloses a method for producing metallic titanium which comprises the steps of introducing titanium chloride and a reducing metal agent both in the vapour state into a reaction vessel to react both under conditions so that a liquid metallic titanium product is obtained together with the I i 3 vapour. The chloride by-product of the reducing metal agent is separated from the titanium product for recovery and the metallic titanium product is solidified in a mould kept at a temperature below the melting point of the metallic titanium product to obtain an ingot which is removed from the reaction vessel.

Japanese Patent Publication No.19761/1971 discloses a method for producing metal comprising the steps of introducing titanium tetrachloride vapour and a liquid reducing metal agent into liquid metal in a reaction vessel, heating a reaction zone to a temperature above the melting point of titanium to t" obtain a metallic titanium product and a chloride by- 1 product of the reducing metal agent in a molten state under a vapour pressure of the reducing metal agent at the relevant temperature, separating the product and by-product from each other using the difference in their gravities, and separately removing them from the reaction vessel.

Various similar methods have attempted to solve ll the problems of the Kroll method by reducing the metal halide withi the reducing metal agent while keeping the reaction temperature above the melting point of the metal product to obtain the molten metallic titanium product Hlowever,_while these methods are disclosed in the patent literatures, they have not been commercialised on an industrial scale.

41 j er~-aaun a More particularly, for example, the method tau'ght in Japanese Patent Publication No.19761/1971 is to i reduce titanium tetrachloride with magnesium to produce metallic titanium while keeping the temperature in the reaction zone at about 1730 0 C and the pressure in the reaction vessel at about 5 arms corresponding to a partial pressure of the magnesium chloride by-product.

at that temperature to produce the metallic titanium product and the magnesium chloride by-product in a molten state. Thus, in the method the reaction zone temperature is about 1720 0 C and its pressure is about ams which is substantially equal to the vapour Sipressure of the magnesium chloride, produced in liquid S 15 form. This results in the magnesium boiling which leads to a failure to maintain the magnesium in an amount sufficient to reduce titanium tetrachloride in the reaction zone fully. This causes the reaction to take place in the presence of insufficient magnesium 2 which often produces lower chlorides of titanium such as titanium trichloride, titanium dichloride and the like.

Also, in this method, the reactants (titanium S C tebrachloride in the form of a gas and magnesium in the Sform of a liquid) are supplied through graphite pipes to a molten layer .of the reac.tion product the bottom of Q oa °io 0 l the reaction vessel to carry out th'e reaction in the molten layer. This causes, ihe open end of the graphite pipes to be corroded by the active molten titanium product. Also, the.molten titanium product contacts each of the reactants at a relatively low temperature at the open end of the pipes, solidifying the reactants, and so clogging the pipes. Furthermore,

C.)

S Isince the reaction is a reduction reaction taking place in the molten layer of titanium, the titanium product is contaminated with unreacted reactants, the by-product and the like. Moreover, the lack of magnesium in the reaction zone leads to a decrease in reaction efficiency per a reaction sectional area.

It is an object of the present invention to provide a method and apparatus for producing metallic titanium by the reduction of titanium tetrachloride by a reducing metal which are capable of continuously producing metallic titanium at a lower energy cost and on an industrial scale.

According to one aspect of the present invention, there is provided a method for producing titanium by the reduction of titanium tetrachloride with a reducing metal which comprises the steps of: o maintaining the temperature in a reaction zone in a reaction vessel above 0 o 15 the melting point of the metallic titanium to be produced; supplying titanium tetrachloride and the reducing metal to the reaction vessel to react to produce a metallic titanium product and a reducing metal halide as a by-product while maintaining the product and the reducing metal halide in a molten state; separating the metallic titanium product and the reducing metal halide from each other by making use of the :0 differences in their densities; collecting the metallic titanium product at the bottom of the reaction vessel; and continuously drawing off the metallic product from the bottom of the reaction vessel; characterised in that the pressure in the reaction zone is maintained above the vapour 25 pressure of the reducing metal and the reducing metal halide at the temperature in the reaction zone.

Preferably, the titanium product is solidified by cooling as it is withdrawn.

Preferably, a molten bath of chloride of the reducing metal and optionally also of the reducing metal itself is previously formed in the reaction vessel so that the surface of the molten bath constitutes the reaction zone and titanium tetrachloride and the reducing metal are supplied to the reaction zone. Preferably the titanium tetrachloride is supplied in liquid form from the top of the reaction vessel and the reducing metal is supplied either in the same way or is injected into the bath.

W:1537y VNTO -6- Preferably, the chloride by-product of the reducing metal is discharged from the reaction vessel at a rate arranged to maintain the position of the reaction zone substantially constant. The method may also include the steps of inserting a titanium ingot into the bottom of the reaction vessel resulting in the coalescence of the separated metallic titanium metal product with the titanium ingot and drawing the metallic titanium product out continuously together with the titanium ingot at a rate corresponding to the amount of the metallic titanium product being coalesced with the titanium ingot.

According to another aspect of the invention, there is provided an apparatus for producing metallic titanium by the reduction of titanium tetrachloride with a reducing metal according to a method as claimed in any one of the preceding claims, the apparatus comprising: a reaction S vessel having a reaction zone in which a temperature above melting point of the titanium product is defined and which is kept at a pressure sufficient to prevent boiling of the reducing metal and its halide at that temperature; a reducing metal feed pipe for supplying the reducing metal in the form of a liquid from the side or the top of the reaction vessel to the reaction zone; a titanium tetrachloride feed pipe for supplying titanium tetrachloride from the top of the reaction vessel to the reaction zone; a discharge pipe for discharging the halide by-product of the reducing metal from the side of the reaction vessel; heating means positioned outside the reaction vessel at a position corresponding to the reaction zone; and a withdrawal section at the bottom of the reaction vessel for continuously drawing out the metallic titanium product, characterised in that the reaction vessel comprises a plurality of longitudinal segments separated by slits thereby dividing the reaction vessel in its longitudinal direction each of the slits being filled with an electrically insulating and heat resistant material.

1537y 7 One preferred embodiment of the invention includes a reaction vessel made of thick titanium plate in which a reaction zone is defined and which is kept at a pressure sufficient to prevent boiling of the reducing metal and its chloride. A reducing metal feed pipe supplies the reducing metal in the form of a liquid from the side or top of the reaction vessel to the reaction zone, and a titanium tetrachloride feed pipe supplies titanium tetrachloride from the top of the reaction vessel to the reaction zone. A discharge pipe for discharging a chloride by-product of the reducing metal extends from the side of the reaction vessel. Heating means are arranged outside the reaction vessel at a position corresponding to the reaction zone for carrying out S electromagnetic induction heating, resistance heating or the like, and a 1 5mould section is arranged at the bottom of the reaction vessel for solidifying the molten metallic titanium product by cooling and continuously drawing reducing metal and the chloride of the reducing metal. The reaction vessel has a vertically extending hollow shape and is open at the top and bottom. The reaction vessel includes a cooling agent circulating path for cooling the inner surface of the reaction vessel and portions of its outer periphery at a position corresponding to S 20 the reaction zone. The vessel also includes a removal section with heating means for heating a molten material which carries out electromagnetic induction heating, resistance heating or the like.

In the present invention, a suitable reaction vessel provided with the heating means may comprise a crucible, as disclosed in U.S. Patent No. 3,755,091 which is adapted to melt titanium chips, titanium sponge or the like for preparing a titanium ingot and is used in an evacuated inert atmosphere. Such a crucible may be incorporated in a pressure vessel for i use as the reaction vessel in the present invention which includes the reaction zone for reducing titanium tetrachloride and the mould section for solidifying the metallic titanium product by cooling and continuously removing it therefrom.

The present inventors have conducted the following reaction test in order to evaluate the reaction efficiency for reducing titanium tetrachloride with metallic magnesium according to the present invention.

T :1537y -8- REACTION TEST A pressure in the reaction vessel was kept at 50 atms. The reaction vessel was charged with 845g metallic magnesium, which was heated to 1350*C by oa 0 o fc 0 sonoo SooA KJono1 KXW:1537y 9 electromagnetic induction heating or resistance heating to form a molten magnesium bath in the reaction vessel.

Immediately after the heating, 1340g liquid titanium tetrachloride was fed to the molten magnesium for seconds at a feed rate of 1608g/min.

The temperature of the bath reached the melting point of titanium in 15 seconds after the beginning of the addition of titanium tetrachloride, thereby producing liquid titanium. The yield of titanium was o 10 99% and the reaction efficiency per unit sectional area 2 of the reaction vessel was 62.7kmol/hr.m For o° *o comparison, the Kroll process was carried out and was found to give a reaction efficiency per unit sectional °o o 2 area of a reaction vessel of 1.3kmol/hr*m S° 15 The efficiency of reaction between titanium tetrachloride and metallic magnesium in the gas phase is calculated in an article entitled "Gas Phase S~o Reaction Test Report" by Prof. Takeuchi of Tohoku University, Journal of Japan Institute of Metals, 23, S" 20 pp6 2 5-6 3 7 (1965), as follows: In the reaction test, the volume of a titanium 3 ribbon for growing titanium on was 0.057m and the deposition rate of titanium to the titanium ribbon was 3.45kg/hr (72mol/hr). Accordingly, its volume efficiency r 3 is 72/0.057 1263mol/hr-m and its reaction efficiency 2 per area is 1.263kmol/hr'm It may not be strictly fair simply to compare the reaction efficiency of the present invention to the reaction efficiency calculated in this way because reaction conditions such as temperature, a feed rate of feedstocks and the like were set differently. However, it will be noted that the reaction between the titanium tetrachloride and metallic magnesium in the present

'I

1 10 0*0*00 0 o 0000 O of~ 00 0SD 00000 0 C- C0 00 o i S0 0: '0 jl 00r 0 0 000 0000o 0 0 invention exhibits a reaction efficiency at least 49.6 (62.7/1.263) times that of the above described gas phase reaction and 48.2 (62.7/1.3) times as much as that of the Kroll process. The fact that the present invention exhibits such higher reaction efficiency is believed to be due to the liquid metallic magnesium and liquid titanium tetrachloride being supplied to the reaction region kept there at a higher temperature and a higher pressure.

10 A temperature of the reaction zone is set above a melting point of titanium. In order to precipitate stably the metallic titanium product onto the bottom of the reaction vessel while keeping it in a molten state, it is desirable to keep the reaction vessel at a temperature which is about I00-200°C higher than the melting point of titanium and to keep the pressure of the reaction region at least above the vapour pressure of the reducing metal agent at the reaction temperature and preferably above the sum of the vapour pressures of 20 the reducing metal agent and its chloride.

More preferably, when titanium (melting point of 1670'C) is to be produced using titanium tetrachloride as the feedstock and magnesium as the reducing metal agent, the bath in the reaction vessel is kept at a 25 temperature of at least 1670'C and more preferably 18270C, and at a pressure above 42.6 atms, corresponding to a partial pressure of magnesium and more preferably above 48.6 atms corresponding to the total sum of the partial pressure of magnesium (42.6 atms) and magnesium chloride (5.98 atms) at the temperature of 18270C.

For reduction of titanium tetrachloride, the reducing metal agent may be fed in a stoichiometric amount. However, in order to carry out the reduction 11 fully, it is desirable to feed a predetermined excess of the reducing metal agent in the reaction region to inhibit the production of lower titanium chlorides.

The invention may be carried into practice in various ways and some embodiments will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a vertical section through a first embodiment according to the present invention; Figure 2 is a view similar to Figure 1 showing a second embodiment; and ~Figure 3 is a partially cutaway perspective view aoo generally showing an example of a reaction vessel Sincorporated in the apparatus shown in Figure 2.

In the present invention, titanium tetrachloride and a reducing metal agent are supplied in liquid form to a reaction zone for reaction. Magnesium or sodium may be used as the reducing metal agent.

The apparatus shown in Figure 1 includes a o 20 reaction vessel structure A which also serves as a pressure vessel. The reaction vessel structure A includes an outer shell or outer wall 1 made of a steel plate, an inner wall made of titanium serving as a reaction vessel 3 and a heat insulating material 2 between the or er shell 1 and the reaction vessel 3.

An inert gas argon) is introduced to the reaction vessel 3 from a pressure adjusting pipe 4 through a valve 5, so that the interior of the reaction vessel 3 is set and kept at a pressure sufficient to prevent substantially any boiling of the magnesium and magnesium chloride, even when the temperature in a reaction zone defined in the reaction vessel 3 rises above the melting point of titanium. For example, the 12reaction vessel 3 is kept at a pressure of about atms when the temperature of the bath in the reaction vessel 3 is 18270C. When the pressure in the reaction vessel 3 is above or below the set value, an automatic pressure adjusting valve (not shown) is operated to keep the pressure at the set value automatically.

Liquid magnesium for use as the reducing metal agent is supplied to the reaction zone through a j reducing metal agent feed pipe 6 extending through 0 0ri a 0n a0 10 the side wall of the reaction vessel structure A and into the reaction vessel 3. Similarly, liquid titanium 0000 o 0 tetrachloride is supplied to the reaction zone through 00 0o 0 a titanium tetrachloride feed pipe 7 extending through the top of the reaction vessel structure A and into the vessel 3.

The reaction vessel 3 is provided at an intermediate oo part of its outer periphery (in a vertical direction) o V surrounding the reaction zone with a heater or heating means 8 adapted to carry out electromagnetic induction 00 20 heating, resistance heating or the like to adjust the temperature of the reaction region in the reaction vessel 3 to a level above 1670'C, corresponding to the melting point of titanium. A discharge tube 9 is connected to the reaction vessel 3 adjacent to the heating means 8, for discharging magnesium chloride by-product formed by the reduction.

A mould section 10 for solidifying the molten metallic titanium product is connected at the bottom of the reaction vessel, for cooling and drawing out the titanium product.

The production of metallic titanium using the apparatus shown in Figure 1 will now be described.

Firstly, a titanium ingot 11 is inserted in the 5845/3 13 mould section 10 to close the bottom of the reaction vessel 3 and then magnesi-a and magnesium chloride are charged in small amounts into the reaction vessel 3.

The atmosphere in the reaction vessel 3 is replaced with argon gas and then the heater 8 is operated to melt the magnesium and magnesium chloride, resulting in a molten bath of magnesium and magnesium chloride being formed in the reaction vessel 3. The molten magensium 12 floats above the magnesium chloride due to the difference in their densities, so that it may remain 10 separate from the magnesium chloride.

th Subsequently, more argon gas is introduced into S° °the reaction vessel 3 to increase the pressure. Then, liquid titanium tetrachloride is fed to the surface of 0 the molten magnesium 12 through the titanium tetrachloride feed pipe 7 connected to the top of the reaction vessel 3. Liquid magnesium is supplied to the oO molten magnesium chloride layer through the magnesium feed pipe 6 connected to the side of the reaction 00 vessel 3. Alternatively, the magnesium feed pipe 6 may be connected to the top of the reaction vessel 3 so that both the titanium tetrachloride and the magnesium 0440 may be supplied in liquid from the top of the reaction vessel 3 to the reaction zone (as in an apparatus of Figure 2 described hereinafter).

Titanium tetrachloride supplied to the surface of the molten magnesium layer of the bath reacts as a liquid with the liquid magnesium to produce titanium 14 and magnesium chloride 13. Alternatively, it may react as a vapour with magnesium vapour vapourised from the molten magnesium layer of the bath of indeed with liquid magnesium.

The heat of reaction and the effect of the heater

:I

14 8 cause the temperature of the molten bath in the reaction vessel 3 to rise above the melting point of titanium. However, the reaction vessel 3 is kept at a pressure above a vapour pressure of magnesium at that temperature, so the titanium product 14, the magnesium chloride by-product 13 and the magnesium 12 are all kept in a liquid state. Also, the molten bath is vertically separated into three layer, namely magnesium 12, magnesium chloride 13 and titanium 14, in that order, due to the difference in their densities.

The molten metallic titanium product 14 precipitates and sinks through the molten magnesium layer and the molten magnesium chloride layer to the bottom of the reaction vessel 3 and reaches the top of the titanium ingot 11 to coalesce with it as it is produced.

Correspondingly, the titanium ingot 11 is continuously so drawn out at a suitable rate, during which it is o solidified by cooling.

The magnesium chloride by-product 13 is discharged 00 20 through the discharge pipe 9 connected to the side of the reaction vessel 3 at a discharge rate which is adjusted so that the molten bath in the reaction zone is kept constant in depth. The titanium ingot 11 is drawn out at a rate corresponding to the amount of titanium precipitated on the titanium ingot (or the precipitation rate of the titanium) by means of rollers (not shown). Accordingly, the position of the molten titanium product above the titanium ingot 11 is kept substantially constant.

The apparatus shown in Figures 2 and 3 is constructed in substantially the same manner as that of Figure 1 except for the construction of the reaction vessel 3, the arrangement of the reducing agent feed 15 pipe 6 and the construction of the heating or heating means 8.

More particularly, the reaction vessel 3 is formed as a vertically extending cylindrical shape, the top and bottom of which are open and is divided into two or more segments 32 by means of vertical slits 31 in the wall of the reaction vessel 3. In the illustrated embodiment, it is divided into twelve segments 32.

0 Each of the segments 32 is formed of a material of good root 10 thermal conductivity, for example, a metal such as' copper or the like. The slits 31 are filled in an Selectrically insulating and heat resistant material to 0o00 I insulate the segments 32 from one another electrically.

The segments 32 are each provided with an internal cooling pipe 33 for supplying a cooling agent through them to cool the wall of the reaction vessel 3 defining I °the reaction zone therein. The cooling pipes 33 are oo connected to one another and between a cooling agnet inlet 34 and a cooling agent outlet 35 to form a path 0 20 for circulating a cooling agent.

An upwardly extending duct 15 is connected to the open top end of the reaction vessel the upper end of .oo which is connected to the exterior through a cylinder 4 6 4 4 section 16 and in which the reducing agent feed pipe 6 is located. The titanium tetrachloride feed pipe 7 is positioned within the upper portion of the reaction duct 15. Thus, liquid magnesium and liquid titanium tetrachloride are supplied through the feed pipes 6 and 7 to the reaction zone. The reaction vessel 3 is provided at a bottom thereof with a mould section 19 at the bottom, through which a titanium ingot 11 is inserted into the reaction vessel 3.

The reaction vessel 3 constituted by the segments

L

16 32 has at its upper part on the outer periphery at a position corresponding to the reaction zone in the reaction vessel 3, an upper electromagnetic induction heating coil 8a for raising a temperature of the reaction zone above the melting point of titanium (or 1670'C). On its lower part, the vessel 3 has a lower electromagnetic induction heating coil 8b for melting the top of the titanium ingot 11 and the magnesium chloride adjacent the top to keep the top of the ingot 1 0 constantly in a molten state during the reaction. Thus, r04* in the illustrated embodiment, the heating means 8 004,comprises the upper and lower electromagnetic induction 000oo oo heating coils 8a and 8b.

As described above, the embodiment of Figures 2 and 3 is so constructed that the reaction vessel 3 is divided into a plurality of the cooled segments 32 and the segments 32 are electrically insulated from one U 0 another by the slits 31. Such a construction 0u substantially prevents the generation of eddy currents 20 in each segment 32 due to electromagnetic induction heating, thereby permitting the molten materials in the reaction zone of the reaction vessel 3 and the top of o0 the titanium ingot to be subjected to induction heating without heating the segments 32. The apparatus includes a discharge pipe 9 for discharging the magnesium chloride by-product which is connected to a substantially central portion of a side of the reaction vessel, in this case between the upper and lower electromagnetic induction heating coils 8a and 8b.

In the illustrated embodiment, the reaction vessel 3 is made of a metal material in view of economic efficiency and maintenance. However, it may be formed of a ceramic material such as alumina, zirconia or the '17 F- 17 like. In such a case, it would not be necessary to divide the reaction vessel 3 into segments.

The operation of the apparatus shown in Figures 2 and 3 will now be described. Basically, operation of the apparatus of Figures 2 and 3 is similar to that of Figure 1.

First, a titanium ingot 11 is inserted into the mould section 10 to close the bottom of the reaction vessel 3 and then magnesium and magnesium chloride are 0i charged in small amounts into the reaction vessel 3.

Then, the atmosphere in the reaction vessel 3 is replaced with argon gas and the lower magnetic induction heating coil 8b is operated to melt the top of the titanium ingot ii while the upper magnetic :a induction heating coil Ba is operated to melt the Smagnesium and magnesium chloride charged into the reaction zone, resulting in a molten bath of reaction vessel 3. Molten magnesium 12 floats above 20 qthe magnesium chlorid t e t o the difference in their densities and the magnetic field by electromagnetic induztion, so that it remains separate from the Sthmagnesium chloride. Part of the molten magnesium S chloride flows into the ga ect the titanium ingot 1 and the inner surface of the reaction vessel 3 where I it solidifies by cooling, to give pressure sealing and electrical insulation actions.

Subsequently, more argon gas is introduced into the reaction vessel 3 to increase the pressure, and liquid magnesium and titanium tetrachloride are fed through the magnesium feed pipe 6 and the titanium tetrachloride feed pipe 7 connected to the top of the reaction vessel 3 to the surface of the molten 18 magnesium 12, forming an upper layer of the molten bath or the reaction region. Alternatively, the magnesium feed pipe 6 may be connected to the side of the reaction vessel 3 as in the apparatus of Figure 1.

Titanium tetrachloride in the reaction zone or at the surface of the molten magnesium layer of the molten bath reacts in liquid form with the liquid magnesium to produce titanium and magnesium chloride.

Alternatively, it may react as vapour with magnesium ti i0 vapour generated from the molten magnesium layer or 4 I rwith liquid magnesium.

ag* The heat of reaction and the effect of the heater o o 8 cause the temperature of the molten bath in the reaction vessel 3 to rise above the melting point of titanium. However, the reaction vessel 3 is kept at a pressure above a vapour pressure of magnesium at that o temperature, so that the magnesium, the titanium product and the magnesium chloride by-product are all kept in a liquid state. Also, the molten bath is 20 vertically separated into three layers, namely, magnesium 12, magnesium chloride 13 and titanium 14, in that order, due to the difference in their densities.

o, The molten metallic titanium product precipitates 0 and sinks through the molten magnesium layer and the molten magnesium chloride layer to the bottom of the reaction vessel 3 and reaches the top 14 of the titanium ingot 11, where it remains in the molten state and is subjected to stirring and mixing by the lower electromagnetic induction heating coil 8b. This results in the molten titanium product being homogeneous.

The titanium product is coalesced with the top of the titanium ingot 11 and the titanium ingot 11 is continuously drawn out at a suitable rate, during which

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f <W:1537y T 0< 19 the product is cooled and solidified by the cooling agent circulated in the cooling pipes 33 of the segments 32.

The magnesium chloride by-product 13 is discharged through the discharge pipe 9 connected to the side of the reaction vessel 3 at a discharge rate which is adjusted so that the molten bath at the reaction zone is kept at a constant level. At this time, a part of 0000 0 the magnesium chloride flows into the gap between the 1 0 titanium ingot 11 and the wall of the reaction vessel 00' and solidifies there to form an insulating layer which serves to prevent contact between the ingot 11 and the o0 o reaction vessel. The insulating layer exhibits heat o insulating and pressure sealing actions. The insulating layer may be partially broken by mechanical friction when the titanium ingot 11 is downwardly drawn out, however, when this happens, the magnesium chloride 0o rapidly flows from the molten magnesium chloride layer into the broken portion of the insulating layer and 00 20 solidifies to re-form an insulating layer. Also, the molten titanium is heated by the lower electromagnetic induction heating coil 8b and tends to levitate at its 0 central portion. Accordingly, magnesium chloride 0 0 readily flows into the gap between the wall of the reaction vessel and the titanium ingot 11 to facilitate formation of the additional insulating layer.

The titanium ingot 11 is drawn out at a rate corresponding to the amount of titanium precipitated on the titanium ingot by means of rollers (not shown).

Accordingly, the position of the molten titanium product above the titanium ingot ii is kept substantially constant. A part of heat of reaction in the reaction vessel is removed upwards from the reaction vessel 3 by 4 ~LL -e 20 radiation and convection, however, a large part of the heat is outwardly removed by the cooling agent circulated in the circulation pipes 33 at the segments 32 constituting the reaction vessel 3.

Accordingly, the present invention is carried out under conditions where the temperature of the reaction zone is kept above the melting point of the metallic titanium product and its pressure is kept at least at the vapour pressure of the reducing metal agent at that 10 temperature, so that boiling of the reducing metal 0000 agent and its chloride may be substantially prevented to keep them at a liquid state in the reaction vessel, Soresulting in the reduction being carried out oefficiently.

The present invention also allows the metallic 0 titanium to be produced in the form of a liquid. The separation of the metallic titanium product and the oo chloride by-product of the reducing metal agent is simple, as is the recovery of the by-product, and the O0 20 titanium ingot may be directly removed, enabling the whole production apparatus to be small-sized.

00 Furthermore, the present invention permits 0° producing of metallic titanium to be continuously *o0 carried out, so that the separating, crushing and melting steps required in the conventional Kroll process may be eliminated, leading to a significant decrease in manufacturing costs while providing titanium of a high quality.

The above description has been made in connection with producing of titanium. However, the present invention can also be applied to the production of metals such as zirconium, hafnium, niobium and their alloys, silicon, and the like.

l KXN:1537y 21 The present invention will now be illustrated with reference to the following non-limiting Examples.

EXAMPLE 1 The example was carried out using an apparatus constructed in accordance with Figure 1.

A reaction vessel having an inner diameter of was used and a titanium ingot having an inner diameter of 10cm was inserted into the mould section of the O, 10 reaction vessel to close the bottom. 20kg magnesium S oochloride and 4.6kg magnesium were charged into the reaction vessel, which was then fully closed.

G °0 An atmosphere in the reaction vessel was replaced e with argon, the magnesium chloride and magnesium were heated to 10000C by electromagnetic induction heating o and the reaction vessel was pressurized to about a I o, Immediately after such conditions were established titanium tetrachloride and liquid magnesium kept at I 20 800°C were supplied to the reaction vessel at feed rates of 4.0,/min (7.0kg/min) and 1.2/min (1.8kg/min), respectively. This caused a temperature of the bath to Srise rapidly to 18270.C and so the power for the electromagnetic induction heating was decreased to keep the temperature at 1827°±500C.

Subsequently, the ingot was drawn out downwardly at an average velocity of 4.9cm/min. The operation was continued for 3 hours, resulting in a titanium ingot being produced in an amount of 0.3 ton.

The magnesium chloride by-product produced during the operation was continuously discharged from the reaction vessel at the appropriate rate to keep the depth of the bath in the reaction vessel constant.

KXW:1537y 22 The titanium ingot so produced was compared to titanium sponge produced by the Kroll process. It was found that the titanium ingot had a high purity and quality as indicated in Table 1, in which the figurea are in wt% and the balance is titanium.

I 0 01 ao a 4 a a 4 404 4 4 OGO 4 004 a 0 4 a a 00 a c a O 0000 a 0 4 4 a a a 9 0 0 00 9 0 4 9 o a 900 4 49 0 4 904 400 44 TablIe 1 Chemical Composition TypeT 0 C H N S i F e Al1 C r N i C u S n Present Invention 0.010 0. 005 i0. 001 0.001 0.007 0.O-010 0.006 001 0O 005 0.005 0.01 Sponge Ti by Kroll a:0. 06 i0. 01 2>0. 003 01 0. 02 L0. 05 L>0. 03 0. 01 0. 02 005 02 Process i II 24 EXAMPLE 2 This example was carried out using an apparatus constructed in accordance with Figures 2 and 3.

A reaction vessel having an inner diameter of was used and a titanium ingot having an inner diameter of 19.5cm was inserted into the mould section of the reaction vessel to close the bottom. Then, magnesium chloride and 4.6kg magnesium were charged into the reaction vessel, which was then fully closed.

The atmosphere in the reaction vessel was replaced o, with argon and the top of the titanium ingot and the reaction vessel were heated by electromagnetic 44 4 induction heating to heat magnesium chloride and c magnesium in the reaction zone to a temperature of 1000'C. The magnesium chloride melted by the heating CIflowed into the gap between a wall of the reaction vessel and the titanium ingot to form an insulating layer which also exhibited a pressure sealing action.

The reaction vessel was then pressurized to about 20 50 atms. Immediately after such conditions were attained, titanium tetrachloride and liquid magnesium kept at 800'C were supplied to the reaction vessel at feed rates of 4.0t/min (7.0kg/min) and 1.2t/min 0 o (1.8kg/min), respectively. This caused the temperature of the bath to rise rapidly to 1827°C, and so the power for the electromagnetic induction heating was decreased to keep the temperature of 1827 0 C±50 0

C.

Subsequently, the ingot was drawn out downwardly at an average velocity of 1.3cm/min. The operation was continued for 2 hours, resulting in titanium ingot being manufactured in an amount of 0.2 ton.

The magnesium chloride by-product produced during the operation was continuously discharged from the '4 25 reaction vessel the appropriate rate to keep the depth of the bath in the reaction vessel constant.

The titanium ingot so produced was compared to titanium sponge produced by the Kroll process. It was found that the tianium ingot had a high purity and quality similar to that shown in Table 1.

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Claims

1. A method for producing titanium by the reduction of titanium tetrachloride with a reducing metal which comprises the steps of: maintaining the temperature in a reaction zone in a reaction vessel above the melting point of the metallic titanium to be produced; supplying titanium tetrachloride and the reducing metal to the reaction vessel to react to produce a metallic titanium product and a reducing metal halide as a by-product while maintaining the product and the reducing metal halide in a molten state; separating the metallic titanium product and the reducing metal halide from each other by making use of the differences in their densities; collecting the metallic titanium product at the bottom of the reaction vessel; and continuously drawing off the metallic product from the bottom of the reaction vessel; characterised in that the pressure in the reaction zone is maintained above the vapour pressure of the reducing metal and the reducing metal halide at the temperature in the reaction zone.

2. A method as claimed in Claim 1, characterised in that the titanium product is solidified by cooling as it is withdrawn.

3. A method as claimed in Claim 1, characterised in that a molten bath of halide of the reducing metal and optionally also of the reducing metal is previously formed in the reaction vessel so that the surface of the molten bath constitutes the reaction zone and titanium tetrachloride and the reducing metal. S4. A method as claimed in Claim 3, characterised in that the titanium tetrachloride is supplied as a liquid from the top of the reaction vessel and the reducing metal is supplied either in the same way or is injected into the bath. A method as claimed in any one of the preceding claims, characterised in that the halide by-product of the reducing metal is discharged from the reaction vessel at a rate arranged to maintain the position of the reaction zone substantially constant.

6. A method as claimed in any one of the preceding claims, characterised by the steps of inserting a titanium ingot into the bottom of the reaction vessel resulting in the coalescence of the metallic titanium metal product with the titanium ingot and drawing the metallic titanium product out continuously together with the titanium ingot at a rate corresponding to the amount of the metallic titanium product being 1- coalesced with the titanium ingot. Wr"W: 1 537y 0 )A 27

7. A method as claimed in any one of the preceding claims, characterised in that the reducing metal is magnesium or sodium.

8. A method as claimed in any one of the preceding claims, characterised in that the reaction pressure is above the total sum of the vapour pressures of the reducing metal and its halide at the reaction temperature.

9. An apparatus for producing metallic titanium by the reduction of titanium tetrachloride with a reducing metal according to a method as claimed in any one of the preceding claims, the apparatus comprising: a reaction vessel having a reaction zone in which a temperature above melting point of the titanium product is defined and which is kept at a pressure sufficient to prevent boiling of the reducing metal and its halide at that temperature; a reducing metal feed pipe for supplying the reducing metal in the form of a liquid from the side or the top of the reaction vessel to the reaction zone; a titanium tetrachloride feed pipe for supplying titanium tetrachloride from the top of the reaction vessel to the reaction zone; a discharge pipe for discharging the halide by-product of the reducing metal from the side of the reaction vessel; heating means positioned outside the reaction vessel at a position 20 corresponding to the reaction zone; and a withdrawal section at the bottom of the reaction vessel for continuously drawing out the metallic titanium product, characterised in that the reaction vessel comprises a plurality of longitudinal segments separated by slits thereby dividing the reaction vessel in its longitudinal direction each of the slits being filled with an electrically insulating and heat resistant material. An apparatus as claimed in Claim 9, characterised in that the withdrawal section is a mould section at the bottom of the reaction vessel for solidifying the molten metallic titanium product by cooling as it is continuously drawn out from the reaction vessel.

11. An apparatus as claimed in Claim 10, characterised by cooling means located in the wall of the reaction vessel for circulating a cooling agent at least from the reaction zone to the mould section.

12. An apparatus as claimed in Claim 10 or Claim 11, characterised by heating means arranged on portions of the outer periphery of the reaction vessel at positions corresponding to the reaction zone and the Smould section. ':1537y 28

13. A method for producing titanium by the reduction of titanium tetrachloride with a reducing metal, substantially as herein described with reference to Example 1 and Fig 1 or Example 2 and Figs 2 and 3.

14. Titanium whenever produced by the method of any one of claims 1 to 8 or 13. An apparatus for producing metallic titanium by the reduction of titanium tetrachloride with a reducing metal, substantially as herein described with reference to Fig 1 or Figs 2 and 3. DATED this FIFTEENTH day of OCTOBER 1991 Toho Titanium Co., Ltd. Patent Attorneys for the Applicant SPRUSON FERGUSON 4 :1 NT N: 1537y L.