US2828201A

US2828201A - Method for producing titanium and zirconium

Info

Publication number: US2828201A
Application number: US189917A
Authority: US
Inventors: Gordon R Findlay
Original assignee: Nat Res Corp
Current assignee: National Research Corp
Priority date: 1950-10-13
Filing date: 1950-10-13
Publication date: 1958-03-25
Anticipated expiration: 1975-03-25

Description

March 25, 1958 Y G. R. FINDLAY 2,828,201

METHOD FOR PRoDuoING TITANIUM AND ZIRCONIUM Filed oct. 1s, 195o s sheets-sheet 1 n l l l 1 1 1 r I 1 1 l 1 n 1 www,

` ATTORNEY" March 2.5, 1.958

G. R. -FlNDLAY METHOD FOR PRODUCING TITANIUM AND ZIRCO-NIUM Filed Oct. 13. 1950 5 Sheets-Sheet 2 AW? Aug. Tic24) [AUD 84 Sloroge l Meiering 28? Pump or Valve Pressure A(g) Relief Valve l (66 v I "'38 Vnporizalipn B(g)- of A '4\ flg) Heclll" Condensalion l Temp lOOOoC for (Slorhng) of B Q A+B@ Free Arpressure l- 50 Mcrns Algl Argon Press. I Qlm.

-fAm l d6 LBun B Helm 326 /88 \|ngol 6B l -I Pump 957 (c g. Ti) Y or ,8(1) Valve Condensohon of' A f90 gBu) l El cl'rol sis of e y Fll'er Bk'g No) V B Halde Sl'oroge ocuum 9| Pump L 82 l CO L 92 L-/Halogen V Crude A (2) Formalion of A (e.g. reoclion of l Aal Vlflcllsagen wl'h C+ TiOg) 'y {94 l I Fraclonolion Slrpper A Crude A 4 Purifying i of Column Sl'uroge f Agel g5-l l y Y l Impurl'ies (c g. SiC/i4) INVENT0R L y Y x60/'don E f/'na//ay Residue B FIG. 3

Y @mw muy@ ATTORNEY M arch 225, 1 958 G. R. FINDLAY METHOD FOR PRODUCING TITANIUM AND ZIRCONIUM Filed ocr. 13. 195o 3 Sheets-Sheet 5 :IUU

FIG. 4

ATTORNEY United States Patent f Research Corporation, -Middlesexr County, Mass., a corporation ofMassa'chstts Application oet-ebene, 195o, srralN $9,911 "2 Claims. (ci. 75'-84.4`)

`Thisinvention relates to the production of'me'tals and `more pagicularly to processes Iand apparatus forproduclVa metal compounmparticularly a halideof one' of the metals titanium` or zirconium, is vaporizedA and fedinto a reaction gzone. A reducing metal, preferably -sodiur'n "or other alkali or alkalinefearth metal,V is'als'o'vaporize'd and fed into the `same reaction zone. The alkaline' :earth inetalsinl-ude `ma-gnesinn-1- as Well as calcium `(see Latimer and Hildebrand., Reference Book of 1Inorganic ChemisL try, New York, Macmillan Company, 193'6 ted., p. 'For simplicity; tlre invention will be initially described tu connect-ion with :the use of alkali metals. ATIh'e 'vae purs of the grou-pVa'metal halide and the: alkali "nietal are thoroughly intermixed `as they enter t-he `.reaction Zone to form a single `stream of thetwo vapors-in which the ltwo vapors -burnV with intense `heat to Vreduce the metal halide to the `group' IX/Ta met-al and :to -forin va halL 1de of the alkali metal `as. a byeprodct.- The above processV ishighly exothermic and requires careful 'con'- ntrol of the temperatures obtained lduring the reaction; It also requires careful control of temperatures adjacent the reaction zone so as to permit `formation of "ari in-got of the group IVa metal and to fachieve sepanate condensation of the lay-products 'of the reactionarid unreacted starting materials.

1tA is a principal object of the ,present invention vto prof- Avide an improved apparatus and process for practicing ythe -inventiondescribed in `my abovementioned fcoprendmg application. f Y A nother object of the present invention is to 'provide an improved apparatus of the above type having a 'high thermal `efliciency, ease of control, Iand simplicity of fconstruction.

Still `another object of the invention is to provide novel bigot-casting apparatus and processes which are rparticu- -larly advantageous for 'use in forming ingots of metals sich` as titanium, zirconium,.and theflike.

-Still `another 'object Ao'f `the present invention is to provide' improved temperature controlin `the p'roduction of rhetailsof the abovetype. l

Other objects of `the invention will in 'part 'be obvious and will Vin part appear hereinafter.

The invention accordingly comprises the processinvolvin'g the several lsteps and "the relation and the order of one oi'fmore 'of 'such step's 'with respect t`o` each of the Aothers, and 'the apparatus possessing the construction, combination of elements and arrangement 'of `parts `v'vhich are exempliied iin the Af'ollovvit'tg detailed disclosure, and the scopeY ofthe application of which wi11 be indicated in itl'i :Cla-'IIS.

fFor a fuller understanding `of the nature fand objects `of the invention, reference 'Should be had to the following ldetailed description taken in connection with the accompanying drawings wherein:

2,828,201 Patented Mar. 25, 1958 r. YICC 2 iig. l isv a diagrammatic, schematic, sectional view of one preferredform ofthe invention; r Y,

Fig. 2 is a fragmentary view of a portion of the apparatus of Fig. 1 takenalong the' line 2 2;

Fig". 3 ,islaV flowv sheet showing one .preferred Varrangement or auxiliary equipmentV and the order. ofthe various steps :in Vthe process; and- Y l l l is a 4fraginen tar-y, schematic, sectional view of another embodimentf: the invention.

nsgeneral this inventionrelates to the production of metals, 'an friorparticularly to the production of .metals such as titanium, zirconium, and the like by the red-nef tion'of compounds thereof in an airfree atmosphere. lfiorsimplicity of'illstration the present invention will 'be described hereinafter in `more detail in corinectionwi'th the reduction of titanium. tetrachloride to .titanium `by* sodium. vapors; without; l.intending to limit thescope fof. the invention. thereby. For making ingotsoftitanium, for errant-ple, lthe apparatus of the Vpresent invention preferably corrtpr'isesareaction4 chamber andan ingo't-forming associated this reaction chamberf. Into the reaction chamber' there Ais fed `a vapor of a reducible tif -tanium componnd, such as titanium tetrachloride. yA` vae pt'vr'ized rnetalliclreducing agent, such as sodiumvapors is also fed linto the reaction chamber, the two .feeding .means being arrangedas a torch so that-the vapors are intimately mixed: as they. enter the .reaction cham-ber to cause intense burnir`1`g'fo'f. .the vapors with the `reduction of' the titanium tetrachloride to vtitaniurr-l;and Withvthe Fformation of sodiumA chloride as `a byproduct. Associatedwith` .the `above elements .there is provided `a means for storing a supply of .theametallic reducing agent (.i. fe., sodium) .in molten` condition, amca-ns for confining@ liguidheat-exchange .medium yin contact with 4the walls of the reaction chamber,` and -a means nfor, controllingthe temperature of the walls ofthe reaction chamber by con- Vtrolling the `rate at which the heat-exchange medium .removes Yheat therefrom. ln one `=preferred embodiment the control of the Vremoval of heat .is-achieved byannean's for controlling the vapor .pressure above -theliqnidf-.heatexchange mediufmfthereby controlling the temperature of this liquid hea-t-exchange medium. lInfanother embodiment 1ofthe invent-ion the removal of--heat` is controlled by controlling the area 'of contact between the heaterschange medium Vand. a heat transfer medium V.in hea-ttra-nsfer relationship thereto. Y, ,Y Y in one preferred embodimentof thelinvention the rnetallic lreducing Vagent (i. e., the ,.sodium) -serves *as L.the heat-exchange medium, and the means .for fconningtthe :heacexchange medium win heat-exchangerelationship with -the wallsof the reactionrchamber includes at least a ,porton=of-the -means -forzsto-ring the supply of the reducing agent. 4It is also `preferred tha-t the vapor pressurel controlling means be varranged to maintain thesodium'va- `por pressure suicient-ly highso that the .temperaturepf the sodium -in heat-exchange relationshipp'with the Walls Iof the reaction-chamberrisabove Ythe.meltingpoint ofthe 4sodium chloride formed in the reaction chamber. Asa result Aof this construction the walls of ther'reaction cham.- berare maintained at .a temperature whichdsabove l`the melting point of the sodium chloride-byproduct, tand beylow the tempera-ture -at which -thisysodium chloride .has Van appreciable vapor pressure.y Thus :the-walls-oi.the reaction chamber serve as a condenser for .thesodinm chlorideby-:product. y

Referringfnow :more-particularly to .the drawings, where likeinumbers .refer to like elements in all the |gure` s,fth e apparatus comprises sa reaction vessel .1'0 deui-ng therewithinY a reaction chamber 12. Surrounding the reac- 'tion vessel 1'0 there 'is preferably positioned 'a second vessel 41f4, the space v116 between these two vessels b arranged "to hold a 'liquid' heat-exchange rrediur T8Q Near the bottom of the reaction chamber 12 there is located an ingot-forming mold 20 in which a titanium ingot 21 is formed during the reaction. For achieving intimate mixture of the titanium tetrachloride and sodium vapors there is provided a torch 22 which separately feeds the two vapors into the reaction chamber and directs these two vapors together as they enter the chamber so as to form a flame 23 in which the reduction takes place. This flame 23 serves as the reaction zone and achieves complete reduction of the titanium tetrachloride to metallic titanium. Since the llame 23 is directed towards the ingot mold 20, the resultant titanium is caused to impinge on the surface of an ingot in the mold and to coalesce on this surface, the flame being sufficiently hot to maintain at least the upper surface of the ingot in molten condition.

The reaction chamber 12 includes a vacuum-pumping port 24 connected to a suitable vacuum-pumping system, not shown, which can evacuate the reaction chamber 12 to a low free air pressure on the order of less than .O01 mm. Hg abs. Located near the bottom of the reaction chamber, and spaced to one side of the ingot mold, is an outlet pipe 26 for removing liquid sodium chloride 27.

The vapor pressure of the heat-exchange medium 18 is controlled by a pressure relief valve. generally indicated at 28, the setting of this pressure relief valve 28 controlling the temperature of the liquid heat-exchange medium as a function of the vapor pressure in the space 16a thereabove. The liquid heat-exchange medium, as indicated previously, is preferably sodium since sodium has excellent thermal conductivity at high temperatures, and also since it must be vaporized for use in the preferred reaction described above. In the preferred arrangement shown the sodium vapors existing in the space 16a above the surface of the liquid sodium 18 are used as a source of supply for the sodium vapors fed to the torch 22. This torch 22 comprises, in the preferred form shown, a rod 30 preferably formed of a refractory metal, such as molybdenum, having a plurality of holes 32 near the periphery thereof see Fig. 2). A central hole 34 is also provided in the rod 30, the holes 32 being for the purpose of feeding sodium vapors into the reaction zone, and the hole 34 being for the purpose of feeding titanium tetrachloride vapors into the reaction zone. This torch provides a short ame in which there is through intermixing of the sodium and titanium tetrachloride vapors. This ame 23 is preferably a forced diffusion type of llame which achieves complete reaction, in a highly concentrated zone, between the sodium and titanium tetrachloride vapors. The sodium vapors are fed to the holes 32 by means of a distributing collar 36 in communication with the upper ends thereof, while titanium tetrachloride vapors are fed to the hole 34 by means of a tube 38 connected to the upper end of this hole 34. A pipe 40 leads from the space 16a above the level of the molten sodium, this pipe 40 being connected to the collar 36 and the flow of sodium vapor through this pipe being controlled by a valve 42. This valve 42 is preferably provided with a long stem 44 having an exteriorly positioned operating handle 46 and a water-cooled seal 48.

The pressure relief valve 28 for controlling the vapor pressure of the sodium in the chamber 16 comprises a valve 52, the degree of opening of which is controlled by a pressure responsive device, such as a spring 54. A pipe 56 is included for permitting escape, to a suitable receptacle, of excess sodium vapors generated in space 16a by the exothermic reaction which occurs within the reaction chamber 12.

The mold 20 in which the titanium ingot 21 is formed comprises a curved flange portion 60 surrounding a central cylindrical portion 62, these two portions being preferably integral and formed of a refractory metal, such as molybdenum. At the bottom of the central cylindrical section 62 there is included a reducing die 64 which reduces the diameter of the titanium ingot 21 as it is withdrawn by a pair of rolls-656. This reducing die 64 thus serves as a vacuum seal to prevent passage of air into the reaction zone between the boundaries of the forming ingot and the mold surface. Surrounding the mold is a liquid sodium guide 66 which serves to cause flow of liquid sodium into heat-exchange relationship with the exterior surfaces of

mold portions

60 and 62, this sodium being introduced through a pipe 68 and, in one preferred form of the invention, the entering liquid sodium being at a lower temperature than the remainder of the sodium 18 in the space 16 so as to remove heat from the mold walls at a high rate.

A sight tube 70 is positioned near the top of the reaction chamber, this sight tube extending through the inner and

outer vessels

10 and 14 respectively, and through a layer of insulation 72 which preferably surrounds the whole apparatus. At the top of the sight tube there is provided a sight glass 74 adjacent to which is positioned a water-cooling coil 76. Argon or other inert gas is preferably introduced through a pipe 7S so as to cause a flow of argon gas down the sight tube 70 to remove any vapors which might otherwise diffuse up the tube 70 and condense either as a smoke within tube 70 or as a coating on the inner surface of the sight glass 74. The sight glass 74 is preferably also provided with a wiper (not shown) for removing from the inner surface of the sight glass any condensed material which reaches the sight glass despite the argon ow.

The preferred operation of the device of Fig. l, and the arrangement of the auxiliary equipment, is illustrated best in the flow diagram of Fig. 3 wherein like numbers refer to like elements in the other figures. In this Fig. 3 there is provided a storage chamber for holding the reducible metal compound A (e. g. titanium tetrachloride). A supply tank for holding the molten metallic reducing agent B (e. g. sodium) is indicated at 82. A pump or valve 84 is included for feeding the titanium tetrachloride from the supply 80 to a vaporizer 86 therefor, while a pump or valve 88 is included for transferring molten sodium from supply 82 to the space 16 surrounding the reaction vessel 10. For electrolyzing the sodium chloride reaction product the pipe 26 leads to an electrolysis chamber 90, the sodium formed in this charnber 90 being piped to supply 82 through a filter 91 for removing impurities such as oxides. The chlorine gen erated in chamber 90 is piped to a reaction vessel 92 in which the titanium tetrachloride is formed by reaction with titanium dioxide and carbon. This manufacture of titanium tetrachloride is well described in chapter 17 of y'fitanium, Its Occurrence, Chemistry and Technology by Barksdale, published (1949) by the Ronald Press Co., New York. The resultant crude titanium tetrachloride is then piped to a crude storage tank 93 at which point a purifying agent such as oleic acid may be added. From the crude storage tank the crude titanium tetrachloride goes to a stripper 94 where some impurities, such as silicon tetrachloride, are removed. It then passes through a fractionation column 9S, and the thus purified titanium tetrachloride is then pumped to storage chamber 80. For initially heating the sodium in the space 16 to a desired high temperature on the order of 1000 C. there is provided a heater 96 which heats the sodium to 1000 C., the vapors of the sodium condensing at the top of the space 16 and the condensed sodium being recirculated Vthrough the heater until the sodium in space 16 has `been brought up to the desired temperature.

l assegni in'ispace 16to thedesired! temperature, preferably about 10001 C. During the heat-up time the'ractionfchmbr 12* vispreferably` being evacuatedl bymeansA of lvaci'tnn pump '99 to afree air pressure on the order ydffless than about 1= micron Hg abst In lieul of evacuat'ng chamber 12`1tfrnaytbe purged of air bylsweeping with argon introduced through pipe78 ata pres-sureslightlyin excess of atmosphericpressure.`

When thereaction^ chamber 12 has been brought to itsidesired temperature of about 1000* C. the feed of argon'throug-h'pipe 7-8 anddown'the sight tube 70 is commenced. The valve 42 isopened'to allow-sodium vapors toenterY the distributingcollar 362 and to pass down the outer holes 32 in the torchl 22;` Ati the same time the titanium tetrachloride is fed into th'elpipe 38 by pumping titanium tetrachloride from the supply tank 80 to the vaporizer 86; The thusvaporizedtitanium tetrachloride enters the central hole 34` inthe torch 22 and mixes intimately'with the* sodium as the two vapors issue from the"endfofithetorch; The feed of the sodium and the titanium tetrachloride vapors ispreferably accomplished withfa stoichiometric relationship therebetween. If desired an excess offsodiurn may be fed tothe reaction zone, thisexcess being helpful in preventing formation of lower chlorides resulting yfrom incomplete reduction of the titanium tetrachloride. During thetravel of the titanium tetrachloride vapor down pipe 38L and through the hole 34` in the torch, this vapor is preferably superheated by the heat of the reaction chamber to atemperature on the order of about.1000 C. The two hot vapors issuing from theA end ofthe torch ignite with anhighly exoth'erinic reaction to give an intensely hot flame 23 in which the sodium reduces `thetitaniurrr tetrachloride to metallic tita nium with sodiumchloride as a byproduct. The flame temperature is preferably about 2000" C. so that the titanium'formed therein isV subjected to a temperature above its melting point. This ame is directed towards the top ofthe` ingo't 21-4 in the mold 20 and maintains the uppersurfaceof this titaniurningot in molten condition. The metallictitanium formed bythe reduction reaction isA driven by the flame', and the `initial velocity of the reactants,` towards the surface ofthe ingot where it coalescjes on thesurface of this ingot. Since the temperatureof'the llame23 is extremely high the by-product sodium chloride 27remains in the Vapor phase and is completely separated from the metallic titanium formed in the llame. The sodium chloride 27 is condensed on' the walls of the reaction chamber, runs down these walls and isi withdrawn from the. reaction chamber 12 by means of pipe"2'6. This s'odiumchloride 27 passes'to the electrolysis chamber 90 where it is el'ectrolyzed, by usual techniques, to sodium and chlorine. The resultant sodium is recirculated to the sodium supply 82 while'the chlorine is passed to the reaction chamber for forming titanum tetrachloride by reaction with carbon and titanium dioxide. This titanium tetrachloride is then puried and fed to the titanium tetrachloridel supply 80. Any unreacted sodium and titanium tetrachloride are separately condensed in conden'sers 97 C and 98` and fed back to their respective supplies.

During the reaction the total pressure in the system is maintained at about atmospheric pressure by the argon which trav'elsdown sight glass tube 70, this argon being removed at a` constantrate by the pump 99; The vapor pressure offtheA sodium in space 16 is maintained essentially constant" during the process by the operation of the `pressure relief valve 28. The sodium vapors which `passthrough pressure relief valve 28 are condensed in condenser 97`and then fed back to thesodium supply 82. Thefheat of condensation of the sodium may conveniently vbeutilized. for-vaporizing the titanium tetrachloride and maintaining.y the sodium supply molten by use of a suitableheat-exchange device (not shown).

Aaztheititaniumgformed linthe flame 23, coalesces on the `upper .surface of the fingot -21 in the mold 120, 'the sffi'z of the ingot increases. Consequently, the ingot is withdrawn by rolls 65 aslthe titaf m t, nie'level ofthe top :of :the i t being preferably p constant during 'thiswithdrawaL The lccmtrol of Itheingot withdrawalmaybe' achieved bytli'elu'se 'of th'mocuples (not shown) which measure the :temperature in the mold wall 62 and thus vindicate 'the level of fitaniui'n therein.

Referring now toPig. 4- there is fshb'vv-n another embodiment of the invention which lis of particular vante for those installationsvwhere n is undesirable tofcentf'ol 'highltemperature sodiunivpdr pressures b se ofay pressure relief valve. In thise'ihodiiriet oft on, 'where like' numbers refer to like elements in the preceding figures, there are three separare `bodies or heat-exchange liquid concentric'ally arranged around the" reaction chamber. The second body` of heatexch'ange` liquid "servesV as a variable-area heatltijsfer'inedium between the lir'st and thirdrbodies of heat-'exchange liquid. The effective area of the heat-transfer inediurt between the` first and third heat-exchange liquids preferably controlletlas' a direct function of the vapor pressure above the first heat-'exchange liquid (i.V e; that body of heat-exchange liquid closest to the reaction chamber. in av preferred forni of this embodiment` the Hfst and second bodies of heat:- exchange liquid are two portions of the sodium supply.

'Ifhev main body of the sodium is inV contact with the Walls of the reaction chamber and the other portion is between the-main body and the thirdV body'of heat-exchange liquid, this second'por'tionof 's'odiuln serving as the variable-area heat-exchange medium. As the vapor pressure (and temperature) ofthe main body of sodium rises it forces some of the sodium into the second body thereof to increase the area of the second body of sodium between the main body andthe third body 'of heat-exchange liquid, thus increasingA thefratev of' heat` removal from the main body of liquidsodiun.

In Fig. 4 there is provided a third vessel Vllttl outside of vessel 14, vessel forming a third chamber 102 in which a relatively small body of sodium- 18a" is confined, there being small passages 104 between

chambers

102 and 16. Outside of vessel 100 is a fourthves'sellllG defining a fourth chamber 108 with the vessel 100 for holding a third heat-exchange liquid 110'.' The. space 112 above liquid sodium 18a is iilled with a predetermined inert gas pressure to maintain a pressure difference above the two bodies of

sodium

18 and 18a. Space 1'14 above the heatexchange liquid 110 is lled with vapors of this liquid 110. For controlling the level of sodium 18 in chamber 16 there is a level-responsive device, such as a resistance element 116, connected to a measuring means 118. The measuring means 118 is preferably arranged `to control a valve 120 in the sodium feed line 68. 'The vapor pressure in space 114 Vis controlled by a pressure relief valve 122 to allow escape of the vapors of liquid 110 Vfrom space 114 to prevent heat-exchange liquid 11i) from reaching a temperature above its decomposition point. The condensed heat-exchange liquid is fed back into chamber 108 by means of a pipe 124.

The operation of the Fig. 4 arrangement isV essentially the same as the operation of the apparatus described in Figs. 1, 2, and 3, with the difference, however, that the control of the temperature of the wall ofthe reaction chamber is achieved in` a somewhat modified manner. 1n Fig. 4 the change in the vapor pressure of the sodium 18 adjacent the reaction chamber is used to control the removal of heat by changing the rate of heat transfer from this sodium 1S. The level of the sodium 1S is maintained substantially constant by the resistance element 116, the measuring system 118, and the valve 120. In a preferred arrangement the valve 120 is normally open sufficiently to permit the entrance of anamount of sodium equal to that being used by the process. Any changes in the level of sodium in chamber 1 6, then cause 7 zgorrecting change in the amount of opening of valve In the Fig. 4 embodiment of the invention the heatexchange liquid 110 is preferably Dowtherm (a eutectic mixture of phenyl ether and diphenyl) and the heat imparted thereto is utilized to heat the titanium tetrachloride, maintain the sodium in liquid condition, and to heat steam for power purposes where there is considerable excess heat available. In both the Fig. l and Fig. 4 embodiments of the invention, the various parts of the apparatus are preferably constructed of 310 stainless steel except the torch 22 and

mold

60, 62, which are preferably made of molybdenum.

While the invention has been specifically described in connection with the use of the preferred titanium tetrachloride as the reducible product-metal compound and the preferred sodium as the metallic reducing agent, numerous other materials may be employed. The essential attributes for the metallic reducing agent (B in Fig. 3), which enable it to achieve a satisfactory reduction of a reducible product-metal halide, are set forth below:

(1) The heat of reaction of the metallic reducing agent with the reducible product-metal halide must be great enough, at a temperature corresponding to the melting point of the product metal, to supply at least enough heat for:

(a) the total heat capacity of the reactant materials and the by-products of the reaction between the preheat temperature and the melting point of the product metal;

(b) the heat of vaporization of the by-product halide of the metallic reducing agent;

(c) the heat of fusion of the product-metal;

(d) the heat loss in the cold mold 20 or its equivalent; and

(e) the radiation heat loss from the reaction flame.

(2) The free energy change of the reaction (AF), at a temperature corresponding to the melting point of the product-metal, must be favorable or a satisfactory yield must be possible by regulation of the pressure at which the reaction is carried out.

(3) The vapor pressure of the halide of the metallic reducing agent, which is a by-product of the reaction, shall be high in comparison with the vapor pressure of the product-metal at the melting point of the productmetal so as to achieve vaporization of this halide of the metallic reducing agent.

(4) The vapor pressure of the metallic reducing agent should be high because of the necessity for:

(a) vaporizing the metallic reducing agent for the reaction; and

b) preventing the metallic reducing agent from remaining in the product-metal, particularly if there is any appreciable solubility of the two metals.

(5) The chosen metallic reducing agent should have no solubility, or very little solubility, in the productmetal at the melting point of the product-metal and, in addition, the metallic reducing agent should not react with the product-metal to form intermetallic compounds.

(6) It is not essential, but it is considered important from an economic standpoint, that the metallic reducing agent (a) have a low melting point;

(b) have a small ratio of atomic weight to valence;

(c) be easy to prepare from its halide by means such as electrolysis;

(d) be capable of being prepared in, or purified to, a high state of purity free from nitrides and oxides in particular;

(e) be noiicorrosive or nonreactive with available materials or" construction at the temperatures required;

(f) be relatively abundant so that the capital investment in metallic reducing agent required for circulation in the system be low;

(g) have good thermal conductivity; and

(h) have a low heat of vaporization.

In preferred forms of the invention the reducible product-metal compound (A in Fig. 3) is a product-metal halide and preferably meets the following requirements:

(l) The product-metal halide is preferably volatile and preferably has a boiling point less than about 800 C. The product-metal halide does not decompose into lower halides at its volatilization temperature.

(2) The product-metal halide must be capable of being purified to a high degree to remove product-metal oxide or oxyhalide salts. The product-metal should have a vapor pressure or boiling point substantially different from any oxide or oxyhalide salt that the product-metal might forni so that purilication of the product-metal halide can be effected by distillation.

(3) The product-metal should have a vapor pressure which is low at its melting point and is low with respect to the pressure in the reaction zone to minimize loss of the product-metal by evaporation.

(4) The product-metal halide should have a satisfactory high heat of reaction with the chosen reducing agent.

When materials other than the preferred titanuim tetrachloride and sodium are used, the temperature of the walls ofthe reaction chamber is adjusted so that it is above the melting point of the by-product compound formed during the reducing reaction and below that temperature at which the vapor pressure of the by-product compound is an appreciable portion of the total pressure in the reaction chamber. In order to achieve the above operating conditions it is only necessary to control the rate of heat removal by controlling the vapor pressure above the heat-exchange medium surrounding the reaction chamber in the Fig. 1 form of the invention, or by adjusting the heat-transfer area of the intermediate heatexchange liquid in the Fig. 4 embodiment.

While the invention has been described primarily in connection with the manufacture of pure metals, it is equally adaptable to the manufacture of alloys. In this latter case a mixture of two reducible metal compounds may be fed into the reaction zone through the pipe 38 so that the two metallic compounds may be simultaneously reduced to form the desired binary alloy. Equally, tertiary and quaternary alloys may be formed, if desired, by by the above process. Accordingly, the word metal used in the appended claims is intended to include alloys as well as the pure metal.

Since certain changes may be made in the above process and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description, o1' shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. In a process for producing a group IV metal from the class consisting of titanium and zirconium by reduction of a group IV metal tetrahalide with a metallic reducing agent from the group consisting of the alkali metals and the alkaline earth metals, the improvement which comprises mixing vapors of the tetrahalide and vapors of the reducing agent in a reaction zone in a reaction chamber so that the vapors react with intense heat to form a highly heated reaction flame which is at a temperature above the melting point of the group IV metal and above the vaporization temperature of the byproduct halide, directing said reaction flame against the surface of the group IV metal body to maintain said surface molten by transfer of heat from the llame to the surface and to collect on the molten group IV metal surface liquid group IV metal carried in the flame, simultaneously removing heat from the group IV metal body to solidify liquid group IV metal at the solid-liquid interface, separately withdrawing the product group IV metal and the by-product halide from the reaction zone, confining a first liquid heat-exchange medium in contact with, and outside of, the walls of a reaction chamber, maintaining a second liquid heat-exchange medium in heat-transfer relationship between said rst heat-exchange medium and a third heat-exchange medium, and controlling the degree of heat transfer through said second heat-exchange medium as a direct function of the vapor pressure of said rst heat-exchange medium.

2. In a process for producing a group IV metal from the class consisting of titanium and zirconium by reduction of a group IV metal tetrahalide with a metallic reducing agent from the group consisting of the alkali metals and the alkaline earth metals, the improvement which comprises mixing vapors of the tetrahalide and vapors of the reducing agent in a reaction zone in a reaction chamber so that the vapors react with intense heat to form a highly heated reaction llame which is at a temperature above the melting point of the group IV metal and above the vaporization temperature of the by-product halide, directing said reaction flame against the surface of the group IV metal body to maintain said surface molten by transfer of heat from the ame to the surface and to collect on the molten group IV metal surface liquid group IV metal carried in the flame, simultaneously removing heat from the group IV metal body to solidify liquid group IV metal at the solid-liquid interface, separately withdrawing the product group IV metal and the by-product halide from the reaction zone, and

References Cited in the file of this patent UNITED STATES PATENTS 1,305,726 Leonard June 3, 1919 1,306,568 Weintraub June 10, 1919 1,499,852 Cerini July 1, 1924 1,519,582 Harris Dec. 16, 1924 1,670,965 Heron May 22, 1928 1,698,624 Dale Jan. 8, 1929 1,747,070 Grain Feb. 11, 1930 1,748,518 Midgley Feb. 25, 1930 1,840,588 Knox Ian. 12, 1932 1,894,982 Eppensteiner J an. 24, 1933 1,929,520 Rudorff Oct. 10, 1933 2,365,194 Hodson et al. Dec. 19, 1944 2,482,127 Schlechten et a1 Sept. 20, 1949 2,564,337 Maddex Aug. 14, 1951 FOREIGN PATENTS 253,161 Great Britain June 7, 1926

Claims

2. IN A PROCESS FOR PRODUCING A GROUP IV METAL FROM THE CLASS CONSISTING OF TITANIUM AND ZIRCONIUM BY REDUCTION OF A GROUP IV METAL TETRAHALIDE WITH A METALLIC REDUCING AGENT FROM THE GROUP CONSISTING OF THE ALKALI METALS AND THE ALKALINE EARTH METALS, THE IMPROVEMENT WHICH COMPRISES MIXING VAPORS OF THE TETRAHALIDE AND VAPORS OF THE REDUCING AGENT IN A REACTION ZONE IN A REACTION CHAMBER SO THAT THE VAPORS REACT WITH INTENSE HEAT TO FORM A HIGHLY HEATED REACTION FLAME WHICH IS AT A TEMPERATURE ABOVE THE MELTING POINT OF THE GROUP IV METAL AND ABOVE THE VAPORIZATION TEMPERATURE OF THE BY-PRODUCT HALIDE, DIRECTING SAID REACTION FLAME AGAINST THE SURFACE OF THE GROUP IV METAL BODY TO MAINTAIN SAID SURFACE MOLTED BY TRANSFER OF HEAT FROM THE FLAME TO THE SURFACE AND TO COLLECT ON THE MOLTEN GROUP IV METAL SURFACE LIQUID GROUP IV METAL CARRIED IN THE FLAME, SIMULTANEOUSLY REMOVING HEAT FROM THE GROUP IV METAL BODY TO SOLIDIFY LIQUID GROUP IV METAL AT THE SOLID-LIQUID INTERFACE, SEPARATELY WITHDRAWING THE PRODUCT GROUP IV METAL AND THE BY-PRODUCT HALIDE FROM THE REACTION ZONE, AND CONTROLLING THE REMOVAL OF HEAT FROM SAID REACTION CHAMBER BY REGULATING THE PRESSURE OG THE VAPOR OF A HEATEXCHANGE LIQUID CONFINED IN HEAT-EXCHANGE RELATIONSHIP WITH THE OUTSIDE OF THE REACTION CHAMBER.