US 3022159 A
Description (OCR text may contain errors)
4 Sheets-Sheet 1 C. J. HOWARD ETAL PRODUCTION OF TITANIUM METAL II I Feb. 20, 1962 Filed Sept. 24, 1959 INVENTORS CARLTON J. HOWARD EDMUND W. SOBOLEWSKI BY ya ATTORNEY Feb. 20, 1962 c. J. HOWARD ETAL v 3,022,159
PRODUCTION OF TITANIUM METAL Filed Sept. 24, 1959 4 Sheets-Sheet 2 lNVEN-TORS CARLTON J. HOWARD EDMUND W. SOBOLEWSK ATTORNEY 1962 c. J. HOWARD ETAL 3,022,159
PRODUCTION OF TITANIUM METAL Filed Sept. 24, 1959 4 Sheets-Sheet 3 g :i. I o if I I I I INVENTORS CARLTON J. HOWARD EDMUND W.SOBOLEWSK ATTORNEY 'IIIIIIIII'I Feb- 20, 1962 I c. J. HOWARD ETAL 3,022,159
PRODUCTION OF TITANIUM METAL 4 Sheets-Sheet 4 Filed Sept. 24, 1959 INVENTORS CARLTON J. HOWARD EDMUIB W. SOBOLEWSKI III/III).
l I I I I I I u I I I I I I I u I ATTORNEY 3,022,159 PRGDUCTION (BF TETANKUM METAL Carlton J. Howard, Liverpool, and Edmund W. Sobolewski, Syracuse, N.Y., assignors to Allied Chemical Corporation, New York, N.Y., a corporation of New York Filed Sept. 24, 1959, Ser. No. 842,103
4 Claims. (Cl. 75-84.5)
This invention relates to processes for making metallic titanium.
The prior art has proposed production of metallic titanium by reaction of metallic sodium and titanium tetrachloride by a two-stage operation-involving relatively low temperature reaction of TiCl, and metallic sodium dispersed on a carrier to form a particulate reaction product comprising principally NaCl and metallic titanium in unstable form, followed by a high temperature stabilization procedure carried out at temperatures above the melting point of NaCl for the purpose of converting the initially unstable metallic titanium to titanium sponge which is stable in air. Processes of this type are disclosed for example in Hansley U.S.P. 2,824,799 of February 25,1958, Quin U.S.P. 2,827,371 of March 18, 1958, and 1n Follows-Keene U.S.P. 2,882,144 of April 14, 1959. The Follows-Keene patent discloses a continuous method for carrying out the low temperature reaction to form the low temperature reaction product containing sodium chloride and unstable metallic titanium. According to prior art, the high temperature stabilization has been carried out as an expensive, time consuming, batch operation.
During high temperature stabilization, the physical forms of material present in the stabilizing zone include liquid NaCl, a pasty gummy mixture of partly melted NaCl and solids, and solid granules or agglomerates of metallic titanium. Under most conditions, the mass undergoing stabilization is highly adherent to metal surfaces. The economic advantages of putting the stabilization step on a continuous basis are self-evident. However, because of the inherent gummy and relatively immobile characteristics of the material being stabilized, any continuous stabilizing apparatus of necessity involves use of mechanical facilities made of metal to carry or work the material undergoing stabilization thru the high temperature stabilization zone. However, the tenacity with which such material adheres to metal surfaces is so great that this factor of high adherence has been major cause of nullifying prior attempts to develop satisfactory continuous stabilization.
The prior art suggests carrying out the low temperature TiCh-dispersed Na reaction in such ways that the reaction product contains total sodium in a range vary ing'from a few percent stoichiometric deficiency (i.e. an excess of TiCl to the stoichiometric equivalent, and thru afew-percent sodium excess over stoichiometric requirements. It will be understood that low temperature reaction product which may be made in accordance With prior art proposals contains Na of NaCl. In most operations there is some relatively small incomplete reaction, and in this situation the reaction product contains a small amount of subchlorides of Ti and a correspondingly small amount of unreacted stoichiometric sodium. If the reaction product was made under conditions in which sodium was fed in quantity in small excess of stoichiometric requirements, the reaction product contains, in addition to Na of NaCl and any unreacted stoichiometric Na, a further quantity of Na in amount corresponding to such excess over stoichiometric. In the case of a low temperature process in which a stoichiometric deficiency of Na has been employed, total sodium of the reaction product includes only the Na of NaCl and the Na which corresponds to whatever the small subchlorides content may be. Hence, as used herein, the expression total sodium includes free and combined Na, i.e. of NaCl, any unreacted stoichiometric Na which corresponds to small subchloride content, and any Na which was charged to the low temperature reaction in excess of stoichiometric requirements for the TiCl fed. Free sodium designates Na in excess of stoichiometric Na, and excludes stoichiometric and unreacted Na. From another viewpoint, low temperature reaction products suggested by the prior art, with respect to total sodium,
may be said to have a negative titre i.e. deficient in stoichiometric Na (excess TiC14), ora neutral titre i.e. contains a stoichiometric amount of Na, or a positive titre i.e. contains some free Na in excess of stoichiometric requirements. r
Investigations on which the present invention are based show' that successful continuous high temperature stabilization, looking mostly toward controlling the degree of adherence of material undergoing stabilization to metal equipment used in a continuous furnace and forming quality product, depends largely upon factors such as the physical form of the low temperature reaction prod. net to be stabilized, e.g. whether particulate or otherwise, the total sodium content of the low temperature reaction product, and the temperature prevailing at the point Where the stabilized material is .finally removed mechanically from contact with the metal apparatus elements employed to continuously carry or work the material to be stabilized thru the stabilization zone.
The object of this invention is to provide a process by which the unstable metallic titanium of material consisting initially of a non-adherent particulate reaction prod! uct containing NaCl and unstable Ti, and having certain compositions with regard to total sodium content whether negative, neutral or positive titres, and formed by dryway reaction of metallic sodium and titanium tetrachloride at reactive elevated temperature above the melting point of sodium and substantially below the, melting point of sodium chloride, may be continuously stabilized in compacted form at temperature above the melting point of sodium chloride.
The invention, objects and advantages thereof, may be understood from consideration of the following description taken in conjunction with the accompanying drawings diagrammatically illustrating an embodiment of apparatus in which practice of the invention process may be effected. In the drawings:
FIG. 1 is a vertical longitudinal section of a furnace adapted for continuous high temperature stabilization of the low temperature reaction product under consideration;
FIG. 2 shows mostly in elevation a cooler-crusher into which heat treated material from the furnace of FIG. 1 may be discharged, crushed and cooled;
FIG. 3 is a vertical section taken approximately on the line 3-3 of FIG. 1;
FIG. 4 is anenlarged sectional detail of apparatus for feeding material to be treated into one end of the furnace;
FIG. 5 is an enlarged sectional detail of a seal for withdrawing by-product sodium chloride as liquid from the furnace; and
FIG. 6 is a diagrammatic longitudinal vertical section of a compactor for pelletizing initially particulate low temperature reaction product.
Referring to FIG. 1, 10 indicates an elongated openended muffie, circular in transverse vertical section, which may be made of any satisfactory heat and corrosion resistant material, such as Incoloy plate, of suitable thickness. The mufile is provided with end plugs 11 and 12 which may consist of hollow metallic shells of Incoloy plate filled with insulating brick to the inner sides of which are attached electric grid-type heaters 13 and 14. The plugs are formed with flanges for bolting to the muflle ends to make a gas-tight unit. Tubes 16 in the end plugs accomodate sight glasses. The muflle is provided on the top side with a solid material feed nozzle 18, a cleanout nozzle 19, and on the bottom side with a liquid salt (NaCl) discharge nozzle 21, a downwardly directed liquid salt drain pipe 23 (FIG. and a heat-treated material discharge nozzle 24 (FIG. 1) the bottom of which opens into a discharge leg 25 having on the lower periphery a flange 26.
FIG. 4 illustrates in vertical section an arrangement which may be employed in conjunction with nozzle 18 (FIG. I) for feeding pelleted low temperature reaction product into mufile 10. The feeder of FIG. 4 may comprise a chute 30 including a circular flange 31 adapted to register with flange 33 of nozzle 18. The rear lower end 35 of the chute extends downwardly and terminates just clear of a belt surface in the mufile as indicated at 36, FIG. 1, while the lower forward end of the chute is cut away as at 38, FIG. 4, to afford a relatively large opening which provides for mowing-up of pellets on the feed end of the belt.
FIG. 5 shows a liquid salt drain and a gas seal for the mufile. The bottom of the muffie is formed so as to provide gentle slopes from the mufile ends to muffle drain pipe 23 which projects downwardly into a cup 47 tapered to a point at the bottom. Similarly tapered rod 48 depends from the under end of the taper point. The upper outer end of the cup 47 may be welded, as by spaced apart webs 50, to the upper end of a cylindrical sleeve 51 the lower end of which terminates in a flange 53 for attachment to fiange 54 on the bottom of nozzle 21. According to this arrangement, liquid salt fills cup 47, overflows the upper periphery thereof, and runs down thru the annulus 55 between the outer surface of the cup and the inside of the upper end of sleeve 51. Liquid salt collecting in the cup forms a gas seal, and liquid salt in annulus 55 is discharged therefrom via rod 43 and funnel 56 which cooperate to minimize contact of liquid salt with the inner faceof the lower end of sleeve 51 which opens into a liquid salt receptacle not shown.
The heat-treated material discharge nozzle 24 (FIG. 1') may be rectangular in horizontal section and tapered substantially toward the bottom end which opens into discharge leg 25 of eliptical horizontal section. The upper edge of nozzle 24 may be welded to the edge of a corresponding opening in the muffie shell, and near the lower end nozzle 24 has welded thereto the upper periphery of an inverted cone-like apron 60 the lower edge of which is. welded to theupper end of the discharge leg 25. As shown in FIG. l,the lower end of nozzle 24 projects down into the upper end of discharge leg 25, and configuration of the adjacent parts is such as to afford a substantial annulus between the bottom of the discharge nozzle and the inside of the discharge leg, this arrangement being preferred in order to prevent direct contact, with the walls of discharge leg 25, of hot material discharged thru the nozzle 24.
The muffie (FIG. 1), nozzles 18,19, 21 and 24,
and discharge leg 25 are enclosed in an electric furnace assembly comprising an outer steel shell 63, and insulating firebrick 64 the inner surfaces of which are sufiiciently tend over the entire width of the belt.
provided with a bevel knife edge,
spaced from the exteriors of the mutfle, the salt drain, discharge nozzle 24 and the discharge leg 25 to accommodate electric grid-type heaters 66. These heaters, and also heaters 13 and 14 in the end plugs, are arranged in suitable unit relation so that variable amounts and degrees of heat, as desired, may be applied to different parts of the apparatus.
Mufile 10 is provided with an axially disposed endless conveyor extending from beneath feed nozzle 18 to solid material discharge nozzle 24. Since the mechanical structural details of the conveyor constitute no part of this invention, for brevity, conveyor construction illustrated in the drawings is highly diagrammatic. As indicated in FIG. 3, longitudinally disposed angle irons or rails 70 are Welded at their edges to the lower inner circumference of the mufile and afford support for the conveyor and associated elements. In FIG. 3, 71 denotes generally a longitudinal framework which extends axially of the muffle and to which in one way or another all elements of the conveyor assembly are fixedly or movably attached. Lower and upper tracks 73 and 74 support and guide the edges of an endless conveyor belt 75 equipped at the longitudinal outer edges with selvage plates 77, fabricated as known in the conveyor art and functioning to prevent spilling of solid material over the edges of the upper run of the belt.
Suitably journalled in association with the conveyor frame 71 are shafts 78 and 79 (FIG. 1) carrying belt drive drums. One end of each drive shaft projects outwardly thru the furnace shell and thru gas-tight glands to facilitate connection to the source of power for rotating the shafts and the associated belt drive drums. 'Mufile 10 is anchored at the material feed end, and the entire conveyor unit is preferably anchored at the solids discharge end of the muflle while the feed end of the conveyor assembly is free to move axially to provide for varying thermal conditions of expansion and contraction. Further, feed end shaft 78 is mounted so as to permit axial movement with regard to the conveyor frame, the bearings of shaft 78 being yoked to the inner end of a rod 81 (FIG. 1) which is axially movable in gas-tight gland 82. The outer end of rod 81 may be connected to any suitable mechanism, not shown, by which tension of the endless belt may be observed and adjusted. Preferably both shafts 78 and 79 are driven members so that the belt is driven from both ends.
The belt drive drums may be cast out of type ACI-HT stainless steel and provided with lug teeth spanning the width of the drums. The belt preferably employed is of the plate type, as distinguished from mesh type, known in the art and illustrated for example in U.S.P. 2,779,579 of January 29, 1957. Preferably, construction of the plate belt is such that the inner and outer surfaces of the plates are concaved and convexed respectively in accordance with the curvature of the drive drums. The belt plates, belt pins and selvage plates may be made of ACI-H'I' stainless steel (Ni 35--Cr 15). Plate type belts are more or less perforate at the plate and pin linkages, and permit drainage of liquid NaCl thru both upper and lower belt runs.
A scraperblade 85 (FIG. 1) which may be made of e.g. No. 330 stainless steel plate, is attached rigidly to the end of the conveyor frarnein position as to ex- The blade is and is attached to the frame so that the knife edge is preferably tangential of the belt at a point slightly above the horizontal center line of the drum.
Heat treated material, i.e. spalt, is discharged from the conveyor belt thru discharge nozzle 24 and discharge leg 25 of FIG. 1 into a cooler-crusher shown diagrammatically in FIG. 2. The cooler-crusher assembly comprises a cylindrical steel shell housing a rotating shaft 91 mounted in gas tight bearings and carrying steel spud paddles 93. Stationary stud paddles 94 are welded at their lower ends to the cooler shell to facilitate crushing. An inlet nozzle 96 of elliptical horizontal section provided with a flange 97 for connection to flange 26, affords communication between the bottom of furnace discharge leg '25 and the interior of crusher-cooler 90. Disintegrated solids discharged from the crusher-cooler drop thru an outlet nozzle 99 into a gas-lock chamber 100 outlet ofwhich communicates with a spalt cooling bin 102 which is one of a plurality of parallelly arranged similar bins. The entire cooler-crusher assembly may rest on spring supports 1% to permit vertical expansion, and on roller bearings indicated at 105 to allow for horizontal movement.
FIG. 6 represents diagrammatically a compactor which may be employed to compress non-adherent particulate unstable low-temperature reaction product into pellets. The pelletizer comprises a feed nozzle 111 a piston 111 and a piston 112, a pellet forming chamber 114, and a discharge nozzle 115, the pistons being operated by hydraulic cylinders 116 and 117. Inlet nozzle 110 is connected to the outlet end of a screw conveyor, not shown, which transfers particulate low-temperature reaction product from a storage bin to compactor inlet 110. Known electrical cam-timer arrangements may be used to sequence the movements of the cylinders to facilitate formation of pellets of desired density and size, and also at a desired rate. For example, piston sequence may be as follows: particulate low temperature reaction product falls from inlet 110 into chamber 114, while piston 111 moves out of the chamber and piston 112 moves into the chamber sufficiently to close off outlet 115; piston 111 moves forward in chamber 114 a distance sufiicient to effect pelletizing; piston 112 withdraws to the position shown in FIG. 6; piston 111 completes the forward stroke sufliciently to drop the pellet into outlet 115. The flange 118 of the pelletizer outlet is connected to flange 31 of the chute 31? as indicated in FIG. 4.
It will be understood that the interior of the apparatus described is gas-tight, and that in operation the interior of the entire apparatus, from the interior of the storage bin for the unstable low temperature reaction product up to and including cooling bin 102, is maintained under a relatively low positive pressure of an inert gas e.g. argon, accessories such as piping, valves, inlets, etc. for maintaining an inert atmosphere within the apparatus not being shown. Selection of construction materials not mentioned herein are within the skill of the art.
' One control factor of major importance in successful continuous stabilization of particulate loW temperature reaction product is the composition of the latter with regard to the presence or absence of free Na. For con venience, this control factor is referred to herein as titre, and what is meant by negative, neutral-and positive titres is as previously explained. Titre of any given sample may be determined by any suitable analysis method which takes into account all sodium present except the reacted sodium which has gone over to NaCl in the low temperature reaction. To illustrate, and assuming a sample having a positive titre (i.e. contains Na above stoichiometric requirements), the sample may be treated with water and e.g. hydrochloric acid in excess. n addition of Water, the unreacted Na goes to NaOH and the corresponding amounts of titanium chlorides hydrolyze to TiO and HCl, the HCl tying up with the NaOH to form NaCl. Thuswise, in the case of a sample containing an excess of Na over stoichiometric, the unreacted Na is eliminated from further consideration. Withregard to the Na present over and above stoichiometric, such Na with water goes to NaOH, and the latter reacting with a known amount of HQ! in excess goes to NaCl plus the HCl excess. Back titration with NaOH to neutralize the excess HCl gives the amount of HCl used to tie up with the Na present over and above stoichiometric requirements, this amount of Na being then determinable on a weight basis, The relation between this thus determined weight and the theoretical stoichiometric amount of Na in the given sample provides a percentage value denoting the excess of sodium over stoichiometric and indicated herein as positive percent titre, e.g. a positive 1% titre indicates that the sample as to Na contains an excess of 1% by weight of stoichiometric Na requirements. Similarly, assuming a low temperature reaction product deficient in stoichiometric Na, on treatment of the sample with water and hydrochloric acid, the unreacted Na and the corresponding amounts of titanium chlorides go to NaCl as before. However, because of stoichiometric Na deficiency there is formed a corresponding amount of HCl which amount is the difference between total HCl present and the HCl added to the sample with the Water. The amount of Na reactable with the thus formed HCl to produce NaCl is the weight measure of the stoichiometric deficiency of Na, and the weight relation of such amount of Na to the theoretical stoichiometric amount of Na in the sample gives a negative percent titre, e.g. a negative 1% titre indicates that the sample as to Na is short 1% by weight of stoichiometric Na requirements.
According to the invention, it has been found that low temperature reaction product initially inparticulate' form-whether of negative, neutral or positive titremay be continuously stabilized, by passing the same on. a suitable metal supporting surface moving thru a sta-, bilization zone maintained at stabilizing temperature and for an adequate retention time, and may be satisfactorily disengaged from a metal supporting surface provided that the initially particulate low temperature reaction product is pelleted at certain minimum pressure, and provided that the temperature in the zone of disengagement of the stabilized material from the moving surface, on termination of retention time, is maintained below the melting point of sodium chloride. Briefly, practive of the invention comprises continuously pelletiz ing the initially particulate reaction product'at pressure not less than 3600 lbs/sq. in., continuously feeding the pelleted material into one end of a high temperature stabilizing zone and onto a supporting surface continu: ously moving thru such zone, continuously moving the surface and the pelleted material thereon thru the Zone while subjecting such material to stabilizing temperature substantially above the melting point of sodium chloride, regulating rate of movement of the surface and of the material thru the zone so as to provide a retention time for the material such that, on discharge from the zone of the material and cooling thereof to relatively low temperature, the metallic titanium content of said cooled material is stable in air, continuously disengaging the heat-treated solid material from the surface on termination of said retention time while main taining temperature below the melting point of sodium chloride in the zone of said disengagement, and continuously withdrawing disengaged solid material from said zone, the entire foregoing operation being carried out in an inert atmosphere. I
With regard to the low temperature reaction product utilized, the invention process is directed to stabilizing the unstable metallic titanium of material consisting of an initially non-adherent particulate reaction product containing NaCl and unstable Ti and formed by dryway reaction of metallic sodium andtitanium tetrachloride at reactive elevated temperature above the melting point of sodium and substantially below the melting point of sodium chloride. While the reactiontemperatures employed in the manufacture of the low temperature reaction product may range from above the melting point of sodium to a temperature reasonably below the melting point of sodium chloride, such temperatures are more practicably in the approximate range of 650 C., it being preferred, in practice of the instant invention, to utilize'l'ow temperature reaction product which 7 has been made in the temperature range of 175 C. up to say 300-400 C.
As above indicated, prior art suggests manufacture of low temperature reaction product in such ways that the various particulate products may have negative, substantially neutral, or positive titres. The present invention affords the highly important advantage that the particulate products of the art may be continuously stabilized whether such products with respect to total sodium have negative, neutral or positive titres. It has been found that in order to continuously stabilize low temperature reaction product initially in the non-adherent particulate form and having total sodium ranging from negative titre thru positive titre, one factor upon which successful operation depends is that such product should be pelleted at pressure not less than about 3600 lbs/sq. in.
Titres of low temperature reaction products in particulate form made by methods of the prior art may vary over a relatively broad range and may have a negative titre down to say 3% or more, up thru neutral, and to a positive titre up to 3% or more. On the positive side, the particulate products employed in practice of this invention may have a titre up to about 2%, desirably not more than about 1.75%. Positive titres amounting to more than about 2% are undesirable since investigations indicate that greater excess sodium values atiord no significantly increased disengagement properties, and in some instances appear to deleteriously affect Brinnell hardness number of the ultimate metallic titanium product. Investigations show that, particularly with regard to enhancement of spalt disengagement properties of pelleted materiahlow Brinnell number, ultimate product quality, and low fines contentof ground spalt, use of particulate reaction products having titres in the range of just above neutral i;e. about plus 0.2% down to a moderate negative value afiord significant advantages. Maximum negative titre value, while not appearing to be as notably important as maximum titre value on the positive side, is desirably not higher than about 2.5%. In the better embodiments of the invention in' which the material is subjected to stabilization in pelleted form, it is preferred to utilize, for pelleting, particulate low temperature reduction products which have titres substantially in the range of negative 1.0% up to positive 0.2%, overall best quality ultimate product being obtained when titres are substantially in the range of negative 0.2% to positive 0.2%.
In practice, the particulate material to be stabilized preferably is continuously pelleted as in a compactor such as that of FIG. 6 under pressure conditions not less than 3600 lbs/sq. in., and preferably of the order of 3800-4200 lbs/sq. in. It has been found that pelletizing pressures, and initial pellet size to a significant extent, contribute critically to the disengagement properties of the spalt on termination of stabilizing furnace retention time. For best structural stability, preferably the pellets employed are made in cylindrical form at the pressures noted and so as to have a diameter/length ratio not greater than about 1.4. In practice, pellets about 1.4 inches in diameter and one inch or less in length have been employed successfully,
The pelleted material is continuously fed into a stabilizing zone of the type described, eg via a feed device such as exemplified in FIG. 4.
Stabilization temperature is above the melting point (804 C.) of sodium chloride, a practicable working low temperature limit being about 850 C. Stabilization temperature may vary within the range of about 850-l000 0., although average temperatures of around 900 C. are preferred, and temperatures above about 950 C. are undesirable because of increased tendency for spalt to adhere to and incipiently alloy with metal of the conveying surface.
Pelletized material fed into the stabilizer thru chute 30 drops onto the receiving end of the moving supporting surface e.g. the belt, and largely because of the form of opening in the lower end of the chute, spreads out in relatively layer form mowing up at the center of the belt and tapering oil at the edges. In usual practice, pellets on the beltmay mow up to about 6 in. deep at the center and taper oii to a single pellet depth toward the edges.
Retention time of material being stabilized in the stabilizing zone is variable as is appreciated by the skill of the art. In any event, retention time is such that the metallic Ti content of the spalt produced in and discharged from the stabilizing zone, when cooled to relatively low temperatures, is stable in air. With this objective in view, depending upon the capacity of the particular apparatus at hand, desirable stabilizing temperature and other operating factors apparent to the skill of the art, rate of movement of pelleted material thru the stabilizing zone and retention time therein may be established by test run for any given set of conditions. In procedures such as exemplified herein, retention time preferably should be not less than 3 hours. Temperature to which the spalt should be'cooled before exposure to air, e.g. spalt collecting in the spalt cooling bin 102 of FIG. 2, may lie in the range of from say 40-80 (3-, and is preferably not more than 100 C.
A marked advantage resulting from herein continuous stabilization is that lay-product NaCl may be continuously drained from solids or semi-solids all during the passage of the same thru the stabilization zone. Notwithstanding the relatively high pressure of pelleting and the resulting density of pellets, a major portion of the by-product NaCl drains out of the pellets. In practice as illustrated, about 75 to of the total salt content of the material fed may be drained away and separately removed from the system. There is no relative movement as between the more or less perforate carrying belt and the material thereon while the two are moving thru the. stabilizing zone.
ln'addition to the previously described total sodium content factor of the material ted to the stabilizing zone, it has been found that, with respect to providing satisfactory conditions 'for disengagement of spalt from its supportlng surface at the end of retention time, another equally important and controlling factor lies in the temperature existing in the zone of disengagement of the spalt from the moving metal supporting surface. In this connection, when stabilizing the material described in pellet form, it has been found that the zone at and m the immediate vicinity of spalt disengagement should be maintained at a temperature substantially below the melt ng point of NaCl. This temperature, a practicable maximum, should be a workable number of degrees C. below the melting point of NaCl, and ordinarily should not be more than about 775 C., and a good operating maximum temperature is about 750 C. Depending upon the operating facilities at hand, the lower this temperature the better since friability of the cluster-like spalt increases at lower temperatures and greatly improves spalt disengagement and crushing. Comparable temperatures are desirably maintained While the spalt is being transferred, e.g. thru the discharge nozzle 24 and discharge leg 25 of FIG. 1 into a crusher-cooler such as illustrated in FIG. 2.
The following Example 1 illustrates practice of the invention. The apparatus employed was substantially the same as described. In the mufile, a plate-type continuous belt about 15 inches wide was used. The length of the belt, strung over 10 in. OD. drive drums, was such that the drum drive shafts were about 9 ft. apart (cold furnace). Data given are based on averages of a 23-day continuous run.
The low temperature Na-TiCl reaction product subjected to stabilization was made in a conjunctive continuous run in accordancewith the process described in the above-mentioned Follows-Keene patent. In the low temperature reaction vaporous TiCl and sodium dispersed on reaction product of a previous cycle were reacted at temperatures in the range of about 230-260 C. This reaction product consisted of 12-14% unstable metallic Ti, the balance including relatively small amount of subchlorides of titanium and a corresponding small amount of unreacted sodium, average titre was in the range of about negative 0.55% to positive 0.01%, the remainder being sodium chloride. A typical screen analysis of material of this nature is as follows:
The low temperature product was made and maintained under an argon blanket.
The free-flowing, particulate low temperature reaction product was transferred under argon blanket from a storage bin by a screw conveyor, held at internal temperature of about 125 C., to the feed inlet of a hydraulic compactor unit such as illustrated in FIG. 6. This compactor was operated by sequencemechanism known in the art to punch out pellets about 1.4 in. in diameter and about %-2 in. long under pressure of 4000 lbs./in. at rate of 4-6 pellets per minute. These pellets were dropped into the feed mechanism of the furnace via a chute such as 30 of FIG. 4. Rate of feed of pelletizcd reaction product to the stabilizing furnace was such that 30-40 lbs./hr. of incoming material was dropped onto the receiving end of the belt conveyor. Electrically generated heat was applied to the mufiie in quantity such that temperature in approximately the front 8 feet of the belt was maintained at about 900 C. while the temperature in approximately the rear one foot of the belt and in the zone of disengagement of spalt at the discharge end of the belt was maintained below about 740 C. No heat was applied to the spalt discharge nozzle 24 or to the furnace discharge leg 25. The material on the belt was forwarded thru the stabilizing zone at a rate of about 2.0 to 2.25 ft./hr., thus providingan overall retention 'time of titanium material on the belt of about 44.5
During this period 20-25 lbs./hr. of liquid NaCl drained away from the material on the belt, flowed into the salt sealin the bottom of the mufile and was discharged from the apparatus. Hence, about 75 to 85 weight percent of the total NaCl present in the stabilizing zone drained away from the material on the belt and was removed from the system as liquid NaCl. While most of the pellets sinter together superficially at points and lines of contact, in general the pellets retained their shape and shrank to about one-fifth original size. The spalt in chunks, appearing mostly in the form of semi-fused together clusters of grapes, was satisfactorily stripped from the end of the belt by means of a scraper blade positioned, with respect to the belt, substantially as previously described. Stripped spalt dropped thru the discharge nozzle 24 and the discharge leg 25 into the cooler-crusher. Rate of discharge of spalt off the belt was about 15 lbs./hr., and the spalt contained in the range of 45-60% metallic titanium. In the coller-crusher, the paddle shaft was driven at a rate of about 100 rpm, and the spalt was broken up into chunks of about one inch maximum dimension, i.e. small enough to be handleable in the succeeding operation. The broken spalt product of the cooler-crusher was conveyed to and dropped into one of a' plurality of parallelly arranged-cooling chambers which when filled was isolated in the cooler-crusher atmosphere.
In the cooling chamber, the material was allowed to cool to about 40 C. Up to this point, the entire stabilizing operation was carried out under a positive pressure of argon of about 3-4 in. of water.
On completion of cooling, the argon blanket was re leased and the metallic titanium of the spalt was stable in air. The spalt was then crushed to maximum size of about in. The splat was salt leached by washing 3 times in water containing about 1% of Hcl, the quantity of acidified water used in each wash being roughly 1.25 times the Weight of solids. The residual, stable metallic titanium sponge was vacuum dried at temperature not in excess of about 100 C. After arc melting, as known in the art, the metallic titanium product had averageBrinnell hardness number of 125. In the course of the run about 11,800 lbs. of particulate low temperature reaction product of the bulk density of about 7075 lbs/ft. were fed to the process; about 7700 lbs. of NaCl were drained out as liquid thru the salt seal; about 4100 lbs. of spalt ously fed to the (crushed bulk density about 103 lbs./ft. were discharged from the belt; and sponge titanium recovery was about 1900 lbs., i.e. about 94% of theory. Bulk density of the sponge was about 66 lbs./ft.
In the following examples, apparatus employed was the same as in Example 1, and operating conditions, except as indicated, were substantially the same as described in Example 1. 7
Example 2.The operation was an 11-day continuous, run. Average titre of the particulate low temperature NaTiCl reaction product employed was plus 0.005%, i.e. substantially neutral titre. About 5600 lbs. of the particulate product were continuously fed to the pelletizer, and the resulting pellets were continuously charged into the stabilizing furnace. During the course of the run, about 4200 lbs. of NaCl were drained away from the material on the moving belt and withdrawn from the furnace thru the liquid salt outlet. Spalt produced and discharged from the furnace amounted to about 1400 lbs. and the spalt contained about 800 lbs. of sponge titanium. The spalt was handled as in Example 1, and after arc melting, the metallic titanium product had an average Brinnell hardness number of 125.
Example 3.The operation was a 2-day continuous run. Average titre of the particulate low temperature NaTiCl reaction product employed was plus 0.28%. About 970 lbs. of the particulate product were continupelletizer, and the resulting pellets were continuously charged into the stabilizing furnace. During the course of the run, about 720 lbs. of NaCl were drained away from the material on the moving belt and withdrawn from the furnace thru the liquid salt outlet. Spalt produced and discharged from the furnace amounted to about 250 lbs., and the spalt contained about lbs. of sponge titanium. The spalt was handled as in Example 1, and after arc melting, the metallic titanium product had an average Brinnell hardness number of 127.
We claim: i
1. The process for continuously stabilizing the unstable metallic Ti of material consisting of a nonadherent particulate reaction product containing NaCl and unstable Ti and formed by dry-way reaction of metallic Na and TiCL, at reactive elevated temperature above the melting point of Na and below the melting point of NaCl, which process comprises continuously at pressure not less than 3600 lbs/sq. in. pelletizing said material having a titre substantially in the range of negative 2.5% to positive 0.28%, continuously feeding said pelletized material into one end of a high temperature stabilizing zone and onto a supporting surface continuously moving thru said zone, continuously moving said surface and the pelletized material thereon thru said zone while subjecting said material to stabilizing temperature above the melting point of NaCl, regulating rate of movement of said surface and of said material thru said zone so as to provide a retention time for said material such that, on discharge from said zone of said material and cooling thereof to temperature not substantially higher than 100 C., the metallic Ti content of said cooled material is stable in air, continuously draining liquid sodium chloride away from said material during passage thereof thru said zone and continuously separately discharging such liquid from said zone, on termination of said retention time continuously mechanically disengaging such heat-treated solid material from said surface while maintaining temperature below about 750 C. in the zone of said disengagement, the entire foregoing operation being carried out in an inert atmosphere, and continuously recovering stabilized metallic Ti.
2. The process of claim 1 in which the material pelletized has a titre substantially in the range of negative 0.2% to positive 028% 3. The process of claim 1 in which the material pelletized has a titre substantially in the range of negative 1.0% to positive 0.28%
4. The process for continuously stabilizing the unstable metallic Ti of material consisting of a non-adherent particulate reaction product containing NaCl and unstable Ti and formed by dry-way reaction of metallic Na and TiCL, at reactive elevated temperature above the melting point of Na and below the melting point of NaCl, which process comprises continuously at pressure of the order of 3800 4200 lbs./ sq. in. pelletizing said material having a titre substantially in the range of negative 1.0% to positive 0.28%, continuously feeding said pelleted material into one end of a high temperature stabilizing zone and onto a supporting surface continuously moving thru said zone,
continuously moving said surface and the pelleted ma-v terial thereon thru said zone while subjecting said material to stabilizing temperature substantially in the range of 850-900 C., regulating rate of movement of said surface and of said material thru said zone so as to provide a retention time for said material not less than about 3 hours but such that, on discharge from said zone of said material and cooling thereof to temperature not substantially higher than C., the metallic Ti content of said cooled material is stable in air, continuously draining liquid sodium chloride away from said material during passage thereof thru said zone and continuously separately discharging such liquid from said zone, on termination of saidretention time continuously mechanically disengaging said heat-treated solid material from said surface While maintaining temperature below about 750 C. in the zone of said disengagement, the entire foregoing operation being carried out in an inert atmosphere, and continuously recovering stabilized metallic titanium.
References Cited in the file of this patent UNITED STATES PATENTS 2,564,337 Maddex Aug. 14, 1951 2,734,244 Herres Feb. 14, 1956 2,827,371 Quin Mar. 18, 1958 2,861,791 Chisholm et al Nov. 25, 1958 2,882,144 Follows et a1 Apr. 14, 1959 2,895,823 Lynskey July 21, 1959 2,944,888 Quin July 12, 1960 FOREIGN PATENTS 720,517 Great Britain Dec. 22, 1954