CA1328561C - Method for producing metallic titanium and apparatus therefor - Google Patents
Method for producing metallic titanium and apparatus thereforInfo
- Publication number
- CA1328561C CA1328561C CA000571625A CA571625A CA1328561C CA 1328561 C CA1328561 C CA 1328561C CA 000571625 A CA000571625 A CA 000571625A CA 571625 A CA571625 A CA 571625A CA 1328561 C CA1328561 C CA 1328561C
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- titanium
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- reaction vessel
- reducing metal
- reaction
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/10—Obtaining titanium, zirconium or hafnium
- C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
- C22B34/1263—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds, e.g. by reduction
- C22B34/1268—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds, e.g. by reduction using alkali or alkaline-earth metals or amalgams
- C22B34/1272—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds, e.g. by reduction using alkali or alkaline-earth metals or amalgams reduction of titanium halides, e.g. Kroll process
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- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
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, respectively, so that the reducing metal agent and its chloride may be kept in a molten state but without boiling.
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, respectively, so that the reducing metal agent and its chloride may be kept in a molten state but without boiling.
Description
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.
In the known "Kroll" process, metallic titanlum i8 produced by the reduction of titanium tetrachloride by metalllc magnesium.
In the Kroll process, the reduction is generally 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.
The spongy metallic titanium product is sub~ected to vacuum separation or leaching to remove any excess metallic magneslum and magnesium chloride (by-product) remaining in the fine internal voids of the metallic titanium product and 18 thus purifled. The purlfied metalllc titanlum 18 then crushed and formed lnto a shape sultable for meltlng. After meltlng, an lngot of tltanium 18 obtalned.
As can be seen, the Kroll process 18 a batch type process. Accordlngly, produclng the metalllc tltanlum lngot accordlng to the Kroll process requlres at least four dlscontlnuous or lndependent steps comprlsing a reduction step, a vacuum separatlon step, a crushing 9tep and a melting step.
The Kroll process also has the following dlsadvantages.
The spongy metalllc titanlum whlch is the reaction - , .
1 32856~
product is firmly adhered to a reduction vessel, 80 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 contaminated with the material of the reaction vessel wall.
Still another disadvantage is that the separation step for purification of the titanium requires much attention ln order to prevent contaminated of the 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 whlch the reduction i8 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 19 then obtalned ln a molten state or ln the form of an lngot by coollng the molten metal product for solldlflcatlon.
As an example, Japanese Patent Appllcatlon Laylng-Open Publlcatlon No.35733/1981 dlscloses a method for produclng metalllc tltanlum whlch comprlses the steps of lntroduclng tltanlum chlorlde and a reduclng metal agent both ln the vapour state lnto a reactlon vessel to react both under condltlons 80 that a llquid metallic titanium product is obtained together with the .
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chloride of the reducing metal agent in the form of a 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 obtain a metallic titanium product and chloride by-product of the reducing metal agent ln a moltenstate 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 the problems of the Kroll process by reducing the metal halide with the reducing metal agent while keeping the reaction temperature above the melting point of the metal product to obtain the molten metallic product.
However, while these methods are disclosed in patent literatures, they have not been commerciallzed on an lndustrlal scale. The reason 18 belleved to be that lt 18 very dlfflcult to select a materlal for the reactlon vessel whlch wlthsatands a sufflclently hi8h temperature to produce actlve metal of a higher meltlng polnt such as tltanlum, zlrconlum or the llke ln the reactlon veosel and to keep it in a molten state.
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More particularly, for example, the method disclosed in Japanese Patent Publication No.19761/1971 is to reduce titanium tetrachloride with magnesium to produce metallic titanium while keeping the temperature in the reaction zone at about 1730C and the pressure in the reaction vessel at about 5 atms 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 1730C and its pressure is about 5 atms which is substantially equal to the vapour pressure of the magnesium chloride, produced in liquid form. This results in the magnesium being boiled which leads to a failure to keep 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 which often produces lower chlorides of titanium such as titanium trichloride, titanium dichloride and the like.
Also, ln thls method, the reactants (titanium tetrachloride in the form of a gas and magnesium in the form of a liquld) are supplied through graphite plpes to a molten layer of the reactlon product on a bottom of the reaction vessel to carry out the reaction ln the molten layer. Thls causes the 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, since the reaction is a reduction taking place in the molten layer of titanium, the titanium product is contaminated wlth S
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Moreover, the lack of magnesium in the reaction zone leads to a decrease in reaction efficiency per a reaction sectional area.
It is an ob;ect of the present invention to provide a method and apparatus for producing metallic titanium by the reduction of titanium tetrachloride with a reducing metal agent which are capable of continuously producing metallic titanlum at a lower energy cost and on an industrlal scale.
According to one aspect of the invention, there is provided a method for producing titanlum by the reduction of titanium tetrachloride with a reducing metal agent characterised by the steps of: maintaining the temperature and pressure in a reaction zone in a ; reaction vessel above the melting point of the metallic titanium to be produced and above the vapour pressure of the reducing metal agent at that temperature;
supplying titanium tetrachloride and the reducing metal agent to the reaction vessel to react to produce a metallic titanium product and a chloride by-product of the reducing metal agent while maintaining the product and the by-product ln a molten state; separating the metallic titanium product and the chloride by-product of the reducing metal agent from each by making use of the difference in their densities; collecing the metallic tltanium product at the bottom of the reaction vessel; and contlnuously drawlng out the metalllc titanium product from the bottom of the reactlon vessel.
Preferably, the titanium product is solidified by coollng as lt is withdrawn.
Preferably, a molten bath of chloride of the reducing metal agent and optionally also of the .
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1 ~28561 reducing metal agent 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 agent are supplied to the reaction region. Preferably the titanium tetrachloride is supplied in liquid from the top of the reaction vessel and the reducing metal agent is supplied either in the same way or is injected into the bath.
Preferably, the chloride by-product of the reducing metal agent ls discharged from the reactlon vessel at a rate arranged to maintain the position of the reaction zone substantlally 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 tltanlum product being coalesced with the titanium lngot.
Accordlng to another aspect of the lnvention, there is provided an apparatus for producing metallic tltanlum by the reductlon of tltanlum tetrachlorlde with a reducing metal agent characterlsed by: a reactlon vessel having reaction zone in which a temperature above a melting point of the titanium product i8 defined and which is kept at a pressure sufficient to prevent boiling o~ the reducing metal a8ent and its chloride at that temperature; a reducing metal agent feed pipe for supplying the reducing metal agent 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 :
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of the reaction vessel to the reaction zone; a discharge pipe for discharging the chloride by-product of the reducing metal agent from the side of the reaction vessel; heating means arranged outside the reaction vessel at a position corresponding to the reaction zone; and a withdrawing section at the bottom of the reaction vessel for continuously drawing out the metallic titanium product.
One preferred embodiment of the invention includes a reaction vessel made of a thick titanium plate in which a reaction zone is defined and which is kept at a pressure sufficient to prevent boiling of a reducing metal agent and its chloride. A reducing metal agent feed pipe supplies the reducing metal agent in the form of 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 agent extends from the side of the reaction vessel. Heating means are arranBed outside the reaction vessel at a position corresponding to the reaction zone for carrying out electromagnetic induction heating, resistance heating or the like, and a mould section i9 arranged at a bottom of the reaction vessel for solidifying the molten metallic titanium product by cooling and continuously drawing out lt from the reaction vessel.
An alternative reaction vessel structure includes a reaction vessel made of metal 8uch as copper or a ceramic material such as alumina, zirconia or the like in which a reaction zone is defined and which is kept at a pressure sufficient to prevent boiling of the ~: , `
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reducing metal agent and the chloride of the reducing metal agent. 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 the reaction zone. The vessel also includes a removal section with heating means for heating a molten material which carries out - 10 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 use as the reactlon vessel in the present invention which includes ; 20 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 ' 25 reaction te9t in order to evaluate the reaction efficlency for reducing titanium tetrachloride with metallic magnesium according to the present invention.
; 30 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 1350C by ., , . ~ ~ , .
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` ' g electromagnetic induction heating or resistance heating to form a molten magnesium bath in the reaction vessel.
Immediately after the heating, 1340g liquid titanlum tetrachloride was fed to the molten magnesium for 50 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 99% and the reaction efficiency per unit sectlonal area of the reaction vessel was 62.7kmol/hr.m2. For comparison, the Kroll process was carried out and was found to give a reaction efficiency per unit sectional area of a reaction vessel of 1.3kmol/hr-m2.
The efficiency of reaction between titanium tetrachloride and metallic magnesium in the gas phase is calculated in an article entitled "Gas Phase Reaction Test Report" by Prof. Takeuchi of Tohoku University, Journal of Japan Institute of Metals, 23, pp625-637 (1965), as follows:
In the reactlon test, the volume of a tltanlum rlbbon for growing titanium on was 0.057m3 and the deposition rate of tltanium to the titanium ribbon was ! 3.45kg/hr (72mol/hr). Accordingly, its volume efflclency i8 72/0.057 ~ 1263mol/hr-m3 and lts reactlon efficiency i per area 19 1.263kmol/hr-m2.
I It may not be strlctly falr slmply to compare the ; reactlon efflclency of the present lnvention to the reaction efflciency calculated ln thls way because - 30 reactlon condltlons such as temperature, a feed rate of feedstocks and the llke were set dlfferently. However, lt wlll be noted that the reactlon between the tltanlum tetrachlorlde and meta111c =agnesluc ln the pre~ent '., .
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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.
A temperature of the reactlon 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 keep~ng it in a molten state, it is desirable to keep the reaction vessel at a temperature which is about 100-200C 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 the reducing metal agent and its chloride.
More preferably, when titanium ~melting point of 1670C) ls 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 temperature of at least 1670C and more preferably 1827C, 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 1827C.
For reduction of titanium tetrachloride, the reducing metal agent may be fed in a stoichiometric amount. However, in order to carry out the reduction . .
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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:
Pigure l is a vertical section through a first embodiment according to the present invention;
Figure 2 is a view similar to Figure l showing a second embodiment; and Figure 3 i8 a partially cutaway perspective view generally showing an example of a reaction vessel incorporated in the apparatus shown in Pigure 2.
i 15 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 Pigure l includes a reaction vessel structure A which also serves as a pressure vessel. The reaction vessel structure A
lncludes an ou~er shell or outer wall l made of a steel plate, an inner wall made of titanlum serving as a reaction vessel 3 and a heat lnsulatlng materlal 2 between the outer shell 1 and the reactlon vessel 3.
' An inert gas (e.g., argon) ls lntroduced to the '~ reactlon vessel 3 from a pressure ad~usting pipe 4 through a valve 5, 80 that the interior of the reactlon vessel 3 is set and kept at a pressure sufficient to prevent substantially any boillng of the magneslum and - magneslum chlorlde, even when the temperature in a reaction zone deflned ln the reaction vessel 3 rises above the melting point of titanium. Por example, the , :`' . ~ ~ :
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reaction vessel 3 is kept at a pressure of about 50 atms when the temperature of the bath in the reaction vessel 3 is 1827C. 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 reducing metal agent feed pipe 6 extending through the side wall of the reaction vessel structure A and into the reaction vessel 3. Similarly, liquid titanium tetrachloride is supplied to the reaction zone through 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 i8 provided at an intermediate part of its outer periphery (in a vertical direction) surrounding the reaction zone with a heater or heating means 8 adapted to carry out electromagnetic induction heating, re9istance heating or the like`to ad~ust the temperature of the reaction region in the reaction vessel 3 to a level above 1670C, corresponding to the melting point of titanium. A discharge tube 9 is connected to the reaction vessel 3 ad~acent to the heating means 8, for dlscharglng magneslum chloride by-product formed by the reduction.
A mould section 10 for solidifying the molten metallic titanlum 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 i8 inserted in the : : ; . , .
mould section 10 to close the bottom of the reaction vessel 3 and then magnesium 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 separate from the magnesium chloride.
Subsequently, more argon gas is introduced into the reaction vessel 3 to increase the pressure. Then, liquid titanium tetrachloride is fed to the surface of 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 molten magnesium chloride layer through the magnesium feed pipe 6 connected to the side of the reaction vessel 3. Alternatively, the magnesium feed pipe 6 may be connected to the top of the reaction vessel 3 so that both the tltanium tetrachloride and the magneslum may be supplied ln liquid from the top of the reaction vessel 3 to the reactlon zone (as ln an apparatus of Flgure 2 described herelnafter).
Tltanlum tetrachlorlde supplied to the surface of the molten magneslum layer of the bath reacts as a llquld wlth the llquld magneslum to produce tltanlum 14 and magneslum chlorlde 13. Alternatlvely, lt may react as a vapour with magneslum vapour vapourlsed from the molten magneslum layer of the bath of lndeed wlth llquld magneslum.
The heat of reactlon and the effect of the heater , . .
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~ 328561 - 14 _ 8 cause the temperature of the molten bath in the reaction vessel 3 to rise above the meltlng 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 ln their densities.
The molten metallic titanium product 14 precipitates and sinks through the molten magnesium layer and the i~ 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 drawn out at a suitable rate, during which it is solidified by cooling.
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 ad~usted 80 that the molten bath in the reaction zone 18 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 . -.
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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 3l in the wall of the reaction vessel 3. In the illustrated embodiment, it is divided into twelve segments 32.
Each of the segments 32 is formed of a material of good thermal conductivity, for example, a metal such as copper or the like. The slits 31 are filled in an electrically insulating and heat resistant material to 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 the reaction zone therein. The cooling pipes 33 are connected to one another and between a cooling agnet inlet 34 and a cooling agent outlet 35 to form a path for clrculating a coollng agent.
An upwardly extendlng duct 15 i9 connected to the open top end of the reaction vessel the upper end of which is connected to the exterior through a cylinder section 16 and ln which the reducing agent feed plpe 6 18 located. The titanium tetrachlorlde feed plpe 7 is posltloned wlthln the upper portlon of the reactlon duct 15. Thus, liquid magnesium and llquld tltanium tetrachlorlde are supplled through the feed pipes 6 and 7 to the reactlon zone. The reaction vessel 3 is provlded at a bottom thereof with a mould section l9 at the bottom, through which a tltanlum lngot ll ls inserted into the reaction vessel 3.
The reaction vessel 3 constituted by the segments .~
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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 1670C). 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 constantly ln a molten state during the reaction. Thus, in the illustrated embodiment, the heating means 8 comprises the upper and lower electromagnetic induction heating coils 8a and 8b.
As described above, the embodiment of Figures 2 and 3 is so constructed that the reaction vessel 3 i8 divided into a plurality of the cooled segments 32 and the segments 32 are electrically insulated from one ; another by the slits 31. Such a construction substantially prevents the generation of eddy currents 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 the titanium ingot to be sub~ected 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 oE 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 :`
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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 ll is inserted into the mould section 10 to close the bottom of the reaction vessel 3 and then magnesium and magnesium chloride are 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 titanlum ingot 11 while the upper magnetic inductlon heating coil 8a is operated to melt the magnesium and magnesium chloride charged into the reaction zone,,resulting in a molten bath of magnesium and magnesium chloride being formed in the reaction vessel 3. Molten magnesium 12 floats, above the magnesium chloride due to the difference in their densities and the magnetic field by electromagnetic induction, 80 that it remains separate from the magnesium chlorlde. Part of the molten magnesium chloride flows lnto the gap between the titanlum lngot ll and the inner surface of the reactlon vessel 3 where it solidifies by cooling, to glve pressure sealing and electrical lnsulation actions.
Subsequently, more argon gas 19 lntroduced into the reaction vessel 3 to lncrease the pressure, and liquid magneslum and tltanlum tetrachloride are fed through the magnesium feed plpe 6 and the tltanium tetrachloride ~eed pipe 7 connected to the top of the reactlon ves~el 3 to the surface of the QolteQ
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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 wlth magnesium vapour generated from the molten magnesium layer or with liquid magneslum.
The heat of reaction and the effect of the heater 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, 80 that the magnesium, the titanium product and the magnesium chloride by-product are all kept in a liquid state. Also, the molten bath is vertically separated into three layers, namely, magneslum 12, magnesium chloride 13 and tltanium 14, in that order, due to the difference in their densities.
The molten metallic tltanium product 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 14 of the tltanium lngot 11, where lt remalns ln the molten state and 18 sub~ected to stirring and mixing by the lower electro-magnetic induction heating coil 8b. This results in the molten titanlum product belng 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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the product is cooled and solidified bv 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 ad~usted so that the molten bath at the reaction zone is kept at a constant level. At this time, a part of the magnesium chloride flows into the gap between the titanium ingot ll and the wall of the reaction vessel and solidifies there to form an insulating layer which serves to prevent contact between the ingot ll and the reaction vessel. The insulating layer exhibits heat 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 rapidly flows from the molten magnesium chloride layer into the broken portion of the insulating layer and solidifies to re-form an insulating layer. Also, the molten titanlum is heated by the lower electromagnetic ., induction heating ,coil 8b and tends to levitate at its central portion. Accordingly, magnesium chloride readily flows into the gap between the wall of the reaction vessel and the tltanlum lngot 11 to facllltate formation of the addltlonal lnsulatlng layer.
The tltanlum lngot 11 ls drawn out at a rate correspondlng to the amount of tltanium preclpltated on the tltanlum lngot by means of rollers (not shown).
Accordlngly, the posltlon of the molten titanlum product above the titanium lngot ll ls kept substantlally constant. A part of heat of reactlon ln the reaction vessel ls removed upwards from the reactlon vessel 3 by :, .
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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 temperature, so that boiling of the reduclng metal agent and its chloride may be substantially prevented to keep them at a liquid state in the reaction vess.el, resulting in the reduction being carried out efficiently.
The present invention also allows the metallic titanium to be produced in the form of a liquid. The separation of the metallic titanium product and the chloride by-product of the reducing metal agent is simple, as is the recovery of the by-product, and the titanium ingot may be directly removed, enabling the whole production apparatus to be small-sized.
Furthermore, the present lnvention permits producing of metallic titanium to be continuously carried out, 80 that the separating, crushing and melting steps requlred in the conventlonal Kroll process may be eliminated, leading to a significant decrease in manufacturing costs whlle 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.
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The example was carried out using an apparatus constructed in accordance with Figure 1.
A reaction vessel having an inner diameter of 20cm was used and a titanium ingot having an inner diameter of 10cm was inserted into the mould section of the reaction vessel to close the bottom. 20kg magnesium chloride and 4.6kg magnesium were charged into the reaction vessel, which was then fully closed.
An atmoqphere in the reaction vessel was replaced with argon, the magnesium chloride and magnesium were heated to 1000C by electromagnetic induction heating and the reaction vessel was pressurized to about 5Oatms.
Immediately after such conditions were established titanium tetrachloride and liquid magnesium kept at 800C were supplied to the reaction vessel at feed rates of 4.0Q/min (7.0kg/min) and 1.2Q/min (1.8kg/min), respectively. This caused a temperature of the bath to - rise rapldly to 1827C, and so the power for the electromagnetic induction heating was decreased to keep the temperature at 1827~50C.
~; Subsequently, the ingot was drawn out downwardly at an average veloclty of 4.9cm/min. The operation was continued for 3 hours, resulting in a tltanium ingot belng produced ln an amount of 0.3 ton.
The magnesium chloride by-product produced during the operation was continuously discharged from the reactlon vessel at the appropriate rate to keep the depth of the bath in the reaction vessel constant.
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l 328561 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 figures are in wt% and the balance is titanium.
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This example was carried out using an apparatus constructed in accordance with Figures 2 and 3.
A reaction vessel having an inner diameter of 20cm 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, 20kg magnesium chloride and 4.6kg magnesium were charged into the reaction vessel, which was then fully closed.
The at~osphere in the,reaction,vessel was replaced ; with argon and the top of the titanium ingot ànd the reaction vessel were heated by electromagnetic induction heating to heat magnesium chloride and magnesium in the reaction zone to a temperature of 1000C. The magnesium chloride melted by the heating flowed 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 50 atms. Immedlately after such conditions were attained, titanium tetrachloride and liquid magnesium kept at 800C were supplied to the reaction vessel at feed rates of 4.0Q/min (7.0kg/min) and 1.2Q/min (1.8kg/min), respectively. This caused the temperature of the bath to rlse rapldly to 1827C, and 80 the power for the electromagnetlc inductlon heating waA decreased to keep the temperature of 1827C~50C.
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 belng manufactured ln an amount of 0.2 ton.
The magnesium chlorlde by-product produced durlng the operatlon was continuously discharged from the .
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reaction vessel at 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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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.
In the known "Kroll" process, metallic titanlum i8 produced by the reduction of titanium tetrachloride by metalllc magnesium.
In the Kroll process, the reduction is generally 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.
The spongy metallic titanium product is sub~ected to vacuum separation or leaching to remove any excess metallic magneslum and magnesium chloride (by-product) remaining in the fine internal voids of the metallic titanium product and 18 thus purifled. The purlfied metalllc titanlum 18 then crushed and formed lnto a shape sultable for meltlng. After meltlng, an lngot of tltanium 18 obtalned.
As can be seen, the Kroll process 18 a batch type process. Accordlngly, produclng the metalllc tltanlum lngot accordlng to the Kroll process requlres at least four dlscontlnuous or lndependent steps comprlsing a reduction step, a vacuum separatlon step, a crushing 9tep and a melting step.
The Kroll process also has the following dlsadvantages.
The spongy metalllc titanlum whlch is the reaction - , .
1 32856~
product is firmly adhered to a reduction vessel, 80 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 contaminated with the material of the reaction vessel wall.
Still another disadvantage is that the separation step for purification of the titanium requires much attention ln order to prevent contaminated of the 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 whlch the reduction i8 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 19 then obtalned ln a molten state or ln the form of an lngot by coollng the molten metal product for solldlflcatlon.
As an example, Japanese Patent Appllcatlon Laylng-Open Publlcatlon No.35733/1981 dlscloses a method for produclng metalllc tltanlum whlch comprlses the steps of lntroduclng tltanlum chlorlde and a reduclng metal agent both ln the vapour state lnto a reactlon vessel to react both under condltlons 80 that a llquid metallic titanium product is obtained together with the .
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chloride of the reducing metal agent in the form of a 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 obtain a metallic titanium product and chloride by-product of the reducing metal agent ln a moltenstate 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 the problems of the Kroll process by reducing the metal halide with the reducing metal agent while keeping the reaction temperature above the melting point of the metal product to obtain the molten metallic product.
However, while these methods are disclosed in patent literatures, they have not been commerciallzed on an lndustrlal scale. The reason 18 belleved to be that lt 18 very dlfflcult to select a materlal for the reactlon vessel whlch wlthsatands a sufflclently hi8h temperature to produce actlve metal of a higher meltlng polnt such as tltanlum, zlrconlum or the llke ln the reactlon veosel and to keep it in a molten state.
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More particularly, for example, the method disclosed in Japanese Patent Publication No.19761/1971 is to reduce titanium tetrachloride with magnesium to produce metallic titanium while keeping the temperature in the reaction zone at about 1730C and the pressure in the reaction vessel at about 5 atms 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 1730C and its pressure is about 5 atms which is substantially equal to the vapour pressure of the magnesium chloride, produced in liquid form. This results in the magnesium being boiled which leads to a failure to keep 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 which often produces lower chlorides of titanium such as titanium trichloride, titanium dichloride and the like.
Also, ln thls method, the reactants (titanium tetrachloride in the form of a gas and magnesium in the form of a liquld) are supplied through graphite plpes to a molten layer of the reactlon product on a bottom of the reaction vessel to carry out the reaction ln the molten layer. Thls causes the 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, since the reaction is a reduction taking place in the molten layer of titanium, the titanium product is contaminated wlth S
.
.~ ~. '. ', 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 ob;ect of the present invention to provide a method and apparatus for producing metallic titanium by the reduction of titanium tetrachloride with a reducing metal agent which are capable of continuously producing metallic titanlum at a lower energy cost and on an industrlal scale.
According to one aspect of the invention, there is provided a method for producing titanlum by the reduction of titanium tetrachloride with a reducing metal agent characterised by the steps of: maintaining the temperature and pressure in a reaction zone in a ; reaction vessel above the melting point of the metallic titanium to be produced and above the vapour pressure of the reducing metal agent at that temperature;
supplying titanium tetrachloride and the reducing metal agent to the reaction vessel to react to produce a metallic titanium product and a chloride by-product of the reducing metal agent while maintaining the product and the by-product ln a molten state; separating the metallic titanium product and the chloride by-product of the reducing metal agent from each by making use of the difference in their densities; collecing the metallic tltanium product at the bottom of the reaction vessel; and contlnuously drawlng out the metalllc titanium product from the bottom of the reactlon vessel.
Preferably, the titanium product is solidified by coollng as lt is withdrawn.
Preferably, a molten bath of chloride of the reducing metal agent and optionally also of the .
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1 ~28561 reducing metal agent 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 agent are supplied to the reaction region. Preferably the titanium tetrachloride is supplied in liquid from the top of the reaction vessel and the reducing metal agent is supplied either in the same way or is injected into the bath.
Preferably, the chloride by-product of the reducing metal agent ls discharged from the reactlon vessel at a rate arranged to maintain the position of the reaction zone substantlally 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 tltanlum product being coalesced with the titanium lngot.
Accordlng to another aspect of the lnvention, there is provided an apparatus for producing metallic tltanlum by the reductlon of tltanlum tetrachlorlde with a reducing metal agent characterlsed by: a reactlon vessel having reaction zone in which a temperature above a melting point of the titanium product i8 defined and which is kept at a pressure sufficient to prevent boiling o~ the reducing metal a8ent and its chloride at that temperature; a reducing metal agent feed pipe for supplying the reducing metal agent 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 :
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of the reaction vessel to the reaction zone; a discharge pipe for discharging the chloride by-product of the reducing metal agent from the side of the reaction vessel; heating means arranged outside the reaction vessel at a position corresponding to the reaction zone; and a withdrawing section at the bottom of the reaction vessel for continuously drawing out the metallic titanium product.
One preferred embodiment of the invention includes a reaction vessel made of a thick titanium plate in which a reaction zone is defined and which is kept at a pressure sufficient to prevent boiling of a reducing metal agent and its chloride. A reducing metal agent feed pipe supplies the reducing metal agent in the form of 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 agent extends from the side of the reaction vessel. Heating means are arranBed outside the reaction vessel at a position corresponding to the reaction zone for carrying out electromagnetic induction heating, resistance heating or the like, and a mould section i9 arranged at a bottom of the reaction vessel for solidifying the molten metallic titanium product by cooling and continuously drawing out lt from the reaction vessel.
An alternative reaction vessel structure includes a reaction vessel made of metal 8uch as copper or a ceramic material such as alumina, zirconia or the like in which a reaction zone is defined and which is kept at a pressure sufficient to prevent boiling of the ~: , `
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reducing metal agent and the chloride of the reducing metal agent. 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 the reaction zone. The vessel also includes a removal section with heating means for heating a molten material which carries out - 10 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 use as the reactlon vessel in the present invention which includes ; 20 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 ' 25 reaction te9t in order to evaluate the reaction efficlency for reducing titanium tetrachloride with metallic magnesium according to the present invention.
; 30 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 1350C by ., , . ~ ~ , .
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` ' g electromagnetic induction heating or resistance heating to form a molten magnesium bath in the reaction vessel.
Immediately after the heating, 1340g liquid titanlum tetrachloride was fed to the molten magnesium for 50 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 99% and the reaction efficiency per unit sectlonal area of the reaction vessel was 62.7kmol/hr.m2. For comparison, the Kroll process was carried out and was found to give a reaction efficiency per unit sectional area of a reaction vessel of 1.3kmol/hr-m2.
The efficiency of reaction between titanium tetrachloride and metallic magnesium in the gas phase is calculated in an article entitled "Gas Phase Reaction Test Report" by Prof. Takeuchi of Tohoku University, Journal of Japan Institute of Metals, 23, pp625-637 (1965), as follows:
In the reactlon test, the volume of a tltanlum rlbbon for growing titanium on was 0.057m3 and the deposition rate of tltanium to the titanium ribbon was ! 3.45kg/hr (72mol/hr). Accordingly, its volume efflclency i8 72/0.057 ~ 1263mol/hr-m3 and lts reactlon efficiency i per area 19 1.263kmol/hr-m2.
I It may not be strlctly falr slmply to compare the ; reactlon efflclency of the present lnvention to the reaction efflciency calculated ln thls way because - 30 reactlon condltlons such as temperature, a feed rate of feedstocks and the llke were set dlfferently. However, lt wlll be noted that the reactlon between the tltanlum tetrachlorlde and meta111c =agnesluc ln the pre~ent '., .
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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.
A temperature of the reactlon 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 keep~ng it in a molten state, it is desirable to keep the reaction vessel at a temperature which is about 100-200C 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 the reducing metal agent and its chloride.
More preferably, when titanium ~melting point of 1670C) ls 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 temperature of at least 1670C and more preferably 1827C, 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 1827C.
For reduction of titanium tetrachloride, the reducing metal agent may be fed in a stoichiometric amount. However, in order to carry out the reduction . .
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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:
Pigure l is a vertical section through a first embodiment according to the present invention;
Figure 2 is a view similar to Figure l showing a second embodiment; and Figure 3 i8 a partially cutaway perspective view generally showing an example of a reaction vessel incorporated in the apparatus shown in Pigure 2.
i 15 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 Pigure l includes a reaction vessel structure A which also serves as a pressure vessel. The reaction vessel structure A
lncludes an ou~er shell or outer wall l made of a steel plate, an inner wall made of titanlum serving as a reaction vessel 3 and a heat lnsulatlng materlal 2 between the outer shell 1 and the reactlon vessel 3.
' An inert gas (e.g., argon) ls lntroduced to the '~ reactlon vessel 3 from a pressure ad~usting pipe 4 through a valve 5, 80 that the interior of the reactlon vessel 3 is set and kept at a pressure sufficient to prevent substantially any boillng of the magneslum and - magneslum chlorlde, even when the temperature in a reaction zone deflned ln the reaction vessel 3 rises above the melting point of titanium. Por example, the , :`' . ~ ~ :
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reaction vessel 3 is kept at a pressure of about 50 atms when the temperature of the bath in the reaction vessel 3 is 1827C. 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 reducing metal agent feed pipe 6 extending through the side wall of the reaction vessel structure A and into the reaction vessel 3. Similarly, liquid titanium tetrachloride is supplied to the reaction zone through 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 i8 provided at an intermediate part of its outer periphery (in a vertical direction) surrounding the reaction zone with a heater or heating means 8 adapted to carry out electromagnetic induction heating, re9istance heating or the like`to ad~ust the temperature of the reaction region in the reaction vessel 3 to a level above 1670C, corresponding to the melting point of titanium. A discharge tube 9 is connected to the reaction vessel 3 ad~acent to the heating means 8, for dlscharglng magneslum chloride by-product formed by the reduction.
A mould section 10 for solidifying the molten metallic titanlum 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 i8 inserted in the : : ; . , .
mould section 10 to close the bottom of the reaction vessel 3 and then magnesium 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 separate from the magnesium chloride.
Subsequently, more argon gas is introduced into the reaction vessel 3 to increase the pressure. Then, liquid titanium tetrachloride is fed to the surface of 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 molten magnesium chloride layer through the magnesium feed pipe 6 connected to the side of the reaction vessel 3. Alternatively, the magnesium feed pipe 6 may be connected to the top of the reaction vessel 3 so that both the tltanium tetrachloride and the magneslum may be supplied ln liquid from the top of the reaction vessel 3 to the reactlon zone (as ln an apparatus of Flgure 2 described herelnafter).
Tltanlum tetrachlorlde supplied to the surface of the molten magneslum layer of the bath reacts as a llquld wlth the llquld magneslum to produce tltanlum 14 and magneslum chlorlde 13. Alternatlvely, lt may react as a vapour with magneslum vapour vapourlsed from the molten magneslum layer of the bath of lndeed wlth llquld magneslum.
The heat of reactlon and the effect of the heater , . .
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~ 328561 - 14 _ 8 cause the temperature of the molten bath in the reaction vessel 3 to rise above the meltlng 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 ln their densities.
The molten metallic titanium product 14 precipitates and sinks through the molten magnesium layer and the i~ 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 drawn out at a suitable rate, during which it is solidified by cooling.
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 ad~usted 80 that the molten bath in the reaction zone 18 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 . -.
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1 32~56~
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 3l in the wall of the reaction vessel 3. In the illustrated embodiment, it is divided into twelve segments 32.
Each of the segments 32 is formed of a material of good thermal conductivity, for example, a metal such as copper or the like. The slits 31 are filled in an electrically insulating and heat resistant material to 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 the reaction zone therein. The cooling pipes 33 are connected to one another and between a cooling agnet inlet 34 and a cooling agent outlet 35 to form a path for clrculating a coollng agent.
An upwardly extendlng duct 15 i9 connected to the open top end of the reaction vessel the upper end of which is connected to the exterior through a cylinder section 16 and ln which the reducing agent feed plpe 6 18 located. The titanium tetrachlorlde feed plpe 7 is posltloned wlthln the upper portlon of the reactlon duct 15. Thus, liquid magnesium and llquld tltanium tetrachlorlde are supplled through the feed pipes 6 and 7 to the reactlon zone. The reaction vessel 3 is provlded at a bottom thereof with a mould section l9 at the bottom, through which a tltanlum lngot ll ls inserted into the reaction vessel 3.
The reaction vessel 3 constituted by the segments .~
.
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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 1670C). 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 constantly ln a molten state during the reaction. Thus, in the illustrated embodiment, the heating means 8 comprises the upper and lower electromagnetic induction heating coils 8a and 8b.
As described above, the embodiment of Figures 2 and 3 is so constructed that the reaction vessel 3 i8 divided into a plurality of the cooled segments 32 and the segments 32 are electrically insulated from one ; another by the slits 31. Such a construction substantially prevents the generation of eddy currents 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 the titanium ingot to be sub~ected 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 oE 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 :`
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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 ll is inserted into the mould section 10 to close the bottom of the reaction vessel 3 and then magnesium and magnesium chloride are 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 titanlum ingot 11 while the upper magnetic inductlon heating coil 8a is operated to melt the magnesium and magnesium chloride charged into the reaction zone,,resulting in a molten bath of magnesium and magnesium chloride being formed in the reaction vessel 3. Molten magnesium 12 floats, above the magnesium chloride due to the difference in their densities and the magnetic field by electromagnetic induction, 80 that it remains separate from the magnesium chlorlde. Part of the molten magnesium chloride flows lnto the gap between the titanlum lngot ll and the inner surface of the reactlon vessel 3 where it solidifies by cooling, to glve pressure sealing and electrical lnsulation actions.
Subsequently, more argon gas 19 lntroduced into the reaction vessel 3 to lncrease the pressure, and liquid magneslum and tltanlum tetrachloride are fed through the magnesium feed plpe 6 and the tltanium tetrachloride ~eed pipe 7 connected to the top of the reactlon ves~el 3 to the surface of the QolteQ
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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 wlth magnesium vapour generated from the molten magnesium layer or with liquid magneslum.
The heat of reaction and the effect of the heater 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, 80 that the magnesium, the titanium product and the magnesium chloride by-product are all kept in a liquid state. Also, the molten bath is vertically separated into three layers, namely, magneslum 12, magnesium chloride 13 and tltanium 14, in that order, due to the difference in their densities.
The molten metallic tltanium product 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 14 of the tltanium lngot 11, where lt remalns ln the molten state and 18 sub~ected to stirring and mixing by the lower electro-magnetic induction heating coil 8b. This results in the molten titanlum product belng 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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.
the product is cooled and solidified bv 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 ad~usted so that the molten bath at the reaction zone is kept at a constant level. At this time, a part of the magnesium chloride flows into the gap between the titanium ingot ll and the wall of the reaction vessel and solidifies there to form an insulating layer which serves to prevent contact between the ingot ll and the reaction vessel. The insulating layer exhibits heat 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 rapidly flows from the molten magnesium chloride layer into the broken portion of the insulating layer and solidifies to re-form an insulating layer. Also, the molten titanlum is heated by the lower electromagnetic ., induction heating ,coil 8b and tends to levitate at its central portion. Accordingly, magnesium chloride readily flows into the gap between the wall of the reaction vessel and the tltanlum lngot 11 to facllltate formation of the addltlonal lnsulatlng layer.
The tltanlum lngot 11 ls drawn out at a rate correspondlng to the amount of tltanium preclpltated on the tltanlum lngot by means of rollers (not shown).
Accordlngly, the posltlon of the molten titanlum product above the titanium lngot ll ls kept substantlally constant. A part of heat of reactlon ln the reaction vessel ls removed upwards from the reactlon vessel 3 by :, .
, ;
- .,........ . ' ~ ' - ' ' ~ :
.
- : , ., "
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 temperature, so that boiling of the reduclng metal agent and its chloride may be substantially prevented to keep them at a liquid state in the reaction vess.el, resulting in the reduction being carried out efficiently.
The present invention also allows the metallic titanium to be produced in the form of a liquid. The separation of the metallic titanium product and the chloride by-product of the reducing metal agent is simple, as is the recovery of the by-product, and the titanium ingot may be directly removed, enabling the whole production apparatus to be small-sized.
Furthermore, the present lnvention permits producing of metallic titanium to be continuously carried out, 80 that the separating, crushing and melting steps requlred in the conventlonal Kroll process may be eliminated, leading to a significant decrease in manufacturing costs whlle 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.
~ ;, ., : . : --~
.. . . .
~ ~ ; ! ' ; .
~ i ~ ` : . , The present invention will now be illustrated with reference to the following non-limiting Examples.
The example was carried out using an apparatus constructed in accordance with Figure 1.
A reaction vessel having an inner diameter of 20cm was used and a titanium ingot having an inner diameter of 10cm was inserted into the mould section of the reaction vessel to close the bottom. 20kg magnesium chloride and 4.6kg magnesium were charged into the reaction vessel, which was then fully closed.
An atmoqphere in the reaction vessel was replaced with argon, the magnesium chloride and magnesium were heated to 1000C by electromagnetic induction heating and the reaction vessel was pressurized to about 5Oatms.
Immediately after such conditions were established titanium tetrachloride and liquid magnesium kept at 800C were supplied to the reaction vessel at feed rates of 4.0Q/min (7.0kg/min) and 1.2Q/min (1.8kg/min), respectively. This caused a temperature of the bath to - rise rapldly to 1827C, and so the power for the electromagnetic induction heating was decreased to keep the temperature at 1827~50C.
~; Subsequently, the ingot was drawn out downwardly at an average veloclty of 4.9cm/min. The operation was continued for 3 hours, resulting in a tltanium ingot belng produced ln an amount of 0.3 ton.
The magnesium chloride by-product produced during the operation was continuously discharged from the reactlon vessel at the appropriate rate to keep the depth of the bath in the reaction vessel constant.
. .
., ~ '. , ~ ''."' '`" ' , - ~ :
l 328561 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 figures are in wt% and the balance is titanium.
;. .
.
~ . :. , ' ~ _ _ ~
._, ~ ~
_, n IL =
D _ _ __ . _ E~ u~ o M
z o Al l ~ ', ', '' 3 I]) :l~ L. , .. . ~ ~.. .. ... .; - . .~
; . .. . , . ;, ~ ~ .
This example was carried out using an apparatus constructed in accordance with Figures 2 and 3.
A reaction vessel having an inner diameter of 20cm 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, 20kg magnesium chloride and 4.6kg magnesium were charged into the reaction vessel, which was then fully closed.
The at~osphere in the,reaction,vessel was replaced ; with argon and the top of the titanium ingot ànd the reaction vessel were heated by electromagnetic induction heating to heat magnesium chloride and magnesium in the reaction zone to a temperature of 1000C. The magnesium chloride melted by the heating flowed 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 50 atms. Immedlately after such conditions were attained, titanium tetrachloride and liquid magnesium kept at 800C were supplied to the reaction vessel at feed rates of 4.0Q/min (7.0kg/min) and 1.2Q/min (1.8kg/min), respectively. This caused the temperature of the bath to rlse rapldly to 1827C, and 80 the power for the electromagnetlc inductlon heating waA decreased to keep the temperature of 1827C~50C.
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 belng manufactured ln an amount of 0.2 ton.
The magnesium chlorlde by-product produced durlng the operatlon was continuously discharged from the .
,.
.
. i ~ 32856~
reaction vessel at 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.
. . .
, i . , . ~ .
Claims (8)
1. A method for producing titanium by the reduction of titanium tetrachloride with a reducing metal agent 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 agent to the reaction vessel to react to produce a metallic titanium product and a chloride by-product of the reducing metal agent while maintaining the product and the by-product in a molten state; separating the metallic titanium product and the chloride by-product of the reducing metal agent from each 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 agent at the temperature in the reaction zone.
characterised in that the pressure in the reaction zone is maintained above the vapour pressure of the reducing metal agent 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 chloride of the reducing metal agent and optionally also of the reducing metal agent 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 agent are supplied to the reaction zone.
4. 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 agent is supplied either in the same way or is injected into the bath.
5. A method as claimed in claims 1, 2 or 3, characterised in that the chloride by-product of the reducing metal agent 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 claims 1, 2 or 3, 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 coalesced with the titanium ingot.
7. A method as claimed in claims 1, 2, or 3, characterised in that the reducing metal agent is magnesium or sodium.
8. A method as claimed in claims 1, 2 or 3, characterised in that the reaction pressure is above the total sum of the vapour pressures of the reducing metal agent and its chloride at the reaction temperature.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62-177014 | 1987-07-17 | ||
| JP17701487A JPS6421021A (en) | 1987-07-17 | 1987-07-17 | Production of metallic titanium |
| JP62190186A JP2554888B2 (en) | 1987-07-31 | 1987-07-31 | Manufacturing method of metallic titanium |
| JP62-190186 | 1987-07-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1328561C true CA1328561C (en) | 1994-04-19 |
Family
ID=26497701
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000571625A Expired - Fee Related CA1328561C (en) | 1987-07-17 | 1988-07-08 | Method for producing metallic titanium and apparatus therefor |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0299791B1 (en) |
| AU (1) | AU618541B2 (en) |
| CA (1) | CA1328561C (en) |
| DE (1) | DE3875411T2 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7435282B2 (en) | 1994-08-01 | 2008-10-14 | International Titanium Powder, Llc | Elemental material and alloy |
| CA2196534C (en) * | 1994-08-01 | 2001-04-10 | Donn Reynolds Armstrong | Method of making metals and other elements |
| US7445658B2 (en) | 1994-08-01 | 2008-11-04 | Uchicago Argonne, Llc | Titanium and titanium alloys |
| US5958106A (en) * | 1994-08-01 | 1999-09-28 | International Titanium Powder, L.L.C. | Method of making metals and other elements from the halide vapor of the metal |
| US20070017319A1 (en) | 2005-07-21 | 2007-01-25 | International Titanium Powder, Llc. | Titanium alloy |
| CA2623544A1 (en) | 2005-10-06 | 2007-04-19 | International Titanium Powder, Llc | Titanium or titanium alloy with titanium boride dispersion |
| LV13528B (en) * | 2006-09-25 | 2007-03-20 | Ervins Blumbergs | Method and apparatus for continuous producing of metallic tifanium and titanium-bases alloys |
| US7753989B2 (en) | 2006-12-22 | 2010-07-13 | Cristal Us, Inc. | Direct passivation of metal powder |
| US9127333B2 (en) | 2007-04-25 | 2015-09-08 | Lance Jacobsen | Liquid injection of VCL4 into superheated TiCL4 for the production of Ti-V alloy powder |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2816828A (en) * | 1956-06-20 | 1957-12-17 | Nat Res Corp | Method of producing refractory metals |
| US3847596A (en) * | 1968-02-28 | 1974-11-12 | Halomet Ag | Process of obtaining metals from metal halides |
| US3775091A (en) * | 1969-02-27 | 1973-11-27 | Interior | Induction melting of metals in cold, self-lined crucibles |
| LU81469A1 (en) * | 1979-07-05 | 1981-02-03 | Luniversite Libre Bruxelles | PROCESS AND PLANT FOR THE PRODUCTION OF REACTIVE METALS BY REDUCTION OF THEIR HALIDES |
| US4442083A (en) * | 1982-11-04 | 1984-04-10 | Stauffer Chemical Company | Method of desulfurizing waste gases containing sulfur dioxide |
| US4442082A (en) * | 1982-12-27 | 1984-04-10 | Sri International | Process for obtaining silicon from fluosilicic acid |
| JPS6089529A (en) * | 1983-10-21 | 1985-05-20 | Mitsubishi Metal Corp | Production of metallic titanium |
-
1988
- 1988-07-08 CA CA000571625A patent/CA1328561C/en not_active Expired - Fee Related
- 1988-07-14 AU AU19044/88A patent/AU618541B2/en not_active Ceased
- 1988-07-15 DE DE8888306510T patent/DE3875411T2/en not_active Expired - Fee Related
- 1988-07-15 EP EP88306510A patent/EP0299791B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| AU618541B2 (en) | 1992-01-02 |
| EP0299791B1 (en) | 1992-10-21 |
| EP0299791A1 (en) | 1989-01-18 |
| AU1904488A (en) | 1989-01-19 |
| DE3875411T2 (en) | 1993-04-08 |
| DE3875411D1 (en) | 1992-11-26 |
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