US2890953A - Continuous process for the manufacture of titanium metal - Google Patents

Description

June 16,1959 Y K. M. HILL ETAL 2,890,953

CONTINUOUS PROCESS FOR THE MANUFACTURE OF TITANIUM METAL Filed Nov. 14, 1955 V 2 Sheets-Sheet l 7 FIG. I a

I [nve tow KENNETH MRS/l H L ll P5727? JD/l/V LY/VS aE) S Ana-7X a yq' tt or neyn June 16, 1959 I K. M. HILL ETAL 2,890,953

CONTINUOUS PROCESS FOR THE MANUFACTURE OF TITANIUM METAL Filed NOV. 14, 1955 2 Sheets-Sheet 2 Inventor/ EN 5 f/ Mil/25W ll/LL 2 23 J'O/l/V LXA/SK Y By I M United States CONTINUOUS PROCESS FOR THE MANUFACTURE OF TITANIUM METAL Application November 14, 1955, Serial No. 546,692

Claims priority, application Great Britain November 16, 1954 4 Claims. (Cl. 75-845) This invention relates to a continuous process for the manufacture of ductile titanium by reduction of titanium tetrachloride by means of sodium metal and to an apparatus for effecting this process. The apparatus is so designed that the products of reaction are in a free-flowing non-adherent form so that their removal from a primary reaction vessel to a subsequent process stage is a relatively straight forward matter.

Titanium is normally produced by the reduction of titaniurn tetrachloride using a molten metal, usually sodium or magnesium, as the reducing metal. A major setback to the economic application of this process is the tendency of the titanium metal so produced to form a single block of metal of sponge-like form, which commonly adheres to the walls of the primary reaction vessel used to contain the reactants, thus making withdrawal of the titanium difiicult.

A principal object of the present invention is to provide a process and apparatus whereby the reduction of titanium tetrachloride by means of sodium metal to ti tanium metal may be carried out effectively and economically without the reaction taking place adjacent to the wall of the containing vessel. A further object of the present invention is to produce the titanium metal, sodium chloride and excess sodium metal in a form Which facilitates the subsequent removal of the latter two components.

According to the present invention, a process for the manufacture of ductile titanium comprises reacting together titanium tetrachloride in liquid or vapour phase with sodium metal in atomised liquid phase in an inert atmosphere, the rate of admixture of the reactants being so adjusted that the sodium metal is present in excess over the stoichiometric equivalent.

The process for the production of ductile titanium according to the invention comprises introducing titanium tetrachloride in liquid or vapour phase into a reaction chamber within the confines of which an inert atmosphere prevails, introducing sodium metal in atomised liquid phase into said reaction chamber at a rate sufiicient to ensure that the sodium metal is present in slight excess over the stoichiometric equivalent of titanium tetrachloride, the two reactants being arranged to commingle out of physical contact with the walls of the reaction chamber, whereby to avoid localised titanium sponge deposition.

It is an essential feature of the invention that the sodium metal shall be present in the reaction chamber in excess, albeit slight, over the stoichiometric equivalent of titanium tetrachloride. A 5% excess is particularly suitable.

In accordance with the invention apparatus for the production of ductile titanium by reduction of titanium tetrachloride by means of sodium metal comprises a gastight reaction chamber, means for introducing titanium tetrachloride in liquid or vapour phase into said chamber, means for introducing molten sodium in an atomate ised liquid phase into said chamber, and means for withdrawing the products of reaction from said reaction chamher.

The inert atmosphere may comprise a noble gas such as helium or argon.

Apparatus in accordance with the invention consists of a containing chamber which shall be gas-tight and so constructed that it may be completely filled with an inert atmosphere, for example argon or helium. The upper portion of the reaction chamber is fitted with a liquid atomising device, through which the sodium metal, as a liquid, is fed into the apparatus. The atomising device used may be chosen from one of the several types available for the atomisation of liquids, for example, gas atomising nozzles of a design currently used for the spraying of paints, pressure atomising nozzles of various types such as are used for water atomisation, for the spraying of crops and similar duties, and spinning disc atomisers commonly in use in spray drying apparatus. Of these several types of nozzle, examples of each of which have been used for the spraying of sodium, the pressure atomising type operated with a liquid pressure of 25/30 lbs. per square inch has been used the most extensively. The upper portion of the apparatus is also fitted with a duct through which titanium tetrachloride is fed into the apparatus. It is advantageous to so design the titanium tetrachloride inlet system that the concentration of titanium tetrachloride is sensibly constant at all points on the periphery of the reaction chamber. If this is not so, there may be a tendency for a local excess of titanium tetrachloride over sodium metal, leading to the formation of lower chlorides of titanium which are undesirable. Among the possible ways of obtaining this homogeneity may be mentioned the use of a piezometer ring or, alternatively, the injection of titanium tetrachloride vapour tangentially, thus causing a vapour stream to travel completely round the periphery of the reaction chamber.

In one form of the invention, the atomisation of the liquid sodium metal is efiected by means of a noble gas under pressure and titanium tetrachloride in liquid or vapour phase is introduced into the reaction chamber so as to commingle with the atomised liquid spray of sodi um metal. Alternatively, titanium tetrachloride vapour may be used as the means for atomising the sodium meal.

In order to initiate the reaction it is desirable to preheat the reaction chamber and the reactants. Satisfactory results have been obtained with the reaction chamber and titanium tetrachloride feed arm pro-heated to 500 C. and with the liquid sodium pre-heated to 400 C. Almost immediately upon the commingling of the reactants the effect of the exothermic heat of reaction is noticed and the external heat sources may be removed and cooling means (for example a blast of cold air) may even be substituted. The degree of cooling necessary is of course a function of the rate of addition of the reactants.

The diameter of the reaction chamber is a function of the size and type of atomising spray, but should be sufiiciently large to ensure that the spray atomised metal does not impinge upon the side walls, otherwise at the point of impingement a growth of titanium sponge is likely to develop. Such growths could eventually block the reaction chamber.

The product of reaction is particulate and relatively free-flowing so that its removal from the reaction chamber is not a difficult operation. The removal is achieved successfully by means of a broken flight screw conveyor mounted at the lower extremity of a preferably hopper shaped bottom section of the reaction chamber. This whole lower section of the reaction chamber may conveniently be cooled in order to prevent any tendency for sodium chloride to become sticky through melting and thus binding the product together.

It may be found convenient to fit vibrators to the hopper walls in order to ensure a complete clearance of material from the hopper Walls and thereby, incidentally, to ensure eflicient cooling of the products of reaction. The actual mechanism of the reaction between titanium tetrachloride and atomised liquid sodium metal is open to some question.

In order that the titanium produced by the reaction shall be in the form of a fairly coarse powder to facilitate collection and subsequent processing, there are grounds for believing that the particle size of the drops of sodium metal should be controlled. It is thought that the formation of very fine drops of sodium metal or of sodium vapour in the reaction chamber may give rise to a titanium powder which is too fine for practical purposes. It seems logical to presume that drops of sodium metal of different particle size differ in the time required to react with the titanium tetrachloride, and that, in order to facilitate complete reaction, the particle size should be as uniform'as possible. Against this hypothesis, however, it must be recognised that although the sodium metal is introduced into the reaction chamber as a liquid and the reaction is initiated whilst the sodium is in liquid phase, sodium has a very high vapour pressure and as soon as the reaction gets going properly, temperatures as high as 1000 C. have been recorded. There is thus a possibility that the greater proportion of the reaction is a vapour phase one and if this is so, the actual size of the drops of sodium metal would not appear to have any significant effect on the particle size of the product. Whatever the true mechanism of the reaction, the use of atomised liquid sodium metal as one reactant is an essential feature of the process according to the invention. It will generally be found convenient to arrange for the mixture of particles of titanium and sodium chloride produced by the reaction to be cooled below the melting point of the sodium chloride before the particles contact one another or the walls of the reaction vessel. However, the possibility of keeping the sodium chloride in a molten state deliberately in order that it shall serve as a conveying medium for solid titanium particles must not be excluded.

The products of reaction removed from the apparatus hereinbefore described are essentially titanium metal and sodium chloride, together with a small excess of sodium metal and the titanium may then be purified by leaching or vacuum distillation techniques.

The invention will now be more particularly described with reference to the accompanying drawings, in which Figs. 1 and 2 illustrate two different embodiments of an apparatus each capable of providing operating conditions in which the process according to the invention may be carried out.

Referring to the first embodiment illustrated in Fig. 1, a reaction space 1 is enclosed by a reaction or spray chamber ( members 2, 3, 4 and 5), the main reaction space being that enclosed by the portion of the vessel 2 which is of such diameter that the cone of sprayed reactants does not impinge on the walls until reaction is substantially complete, and of such length that reaction is complete before the hopper bottom 4 is reached.

The sodium metal is introduced down a duct 7 which is fed from melting and filtration means (not shown). The molten metal is atomised in an externally atomising spray head 6, inert gas, argon or helium, being introduced under pressure through a duct 8, to efiect the atomisation. The atomised sodium metal forms a well defined cone 9. The gaseous titanium tetrachloride under pressure is introduced via a duct 10 into a circular duct 11 from which it is expelled through a series of small holes forming cones 12 of vapour which intermingle and react with cone 9. Alternatively, the titanium tetrachloride may be added as a liquid under pressure, in which case cones 12 will be formed of small liquid droplets.

The inert gas introduced through duct 8 to form the spray leaves through a duct 13 through condensing means (not shown), in which any titanium tetrachloride or lower chlorides of titanium leaving the apparatus are collected. Said inert gas may be recycled if desired. Duct 13 is also used in conjunction with duct 8 for evacuating the apparatus and filling it with an inert atmosphere, prior. to the start of the reaction.

The titanium metal formed in the reaction between the atomised molten sodium metal and the titanium tetrachloride vapour is in the form of discrete particles which fall through the reaction space 1 into the hopper bottom 4 from which they flow via a duct 14 to the next stage of the process.

A screw coveyor 15 is used for removing the product metal and a vibrator mounting 17 is provided to assist the flow of the metal powder. Thermo-couples 16 suitably disposed in the reaction chamber indicate the operating temperature and allow control of the reaction to be maintained and similarly the absolute pressure in the reactor measured through duct 13 also gives an indication of the manner in which the reaction is proceeding.

Suitable heating means for the upper part of the reaction chamber may be provided, if desired.

Referring to the second embodiment illustrated in Fig. 2, the reaction space 18 is enclosed by vessel 19 enclosed partly in a furnace 20. The sodium metal, pre-heated and at a pressure of 20 pounds per square inch, enters through duct 21 to the atomising nozzle 22, a well defined cone 23 of sodium metal particles being produced. Titanium tetrachloride vapour enters through tangentially disposed duct 24.

Noble gas (argon) is also fed into the apparatus through duct 24 and any pressure build up in the apparatus is relieved through duct 25, which passes to condensing means (not shown). During the preparation of the reaction chamber ducts 24 and 25 are used for purging the apparatus of air.

Product particles of titanium, sodium metal chloride. and excess sodium metal mixture pass via duct 26 into screw conveying means 27. a

The following example illustrates a typical run in apparatus of the type described.

Example Titanium tetrachloride was added at a measured rate of 68.7 lbs. per hour through a tangential inlet pipe heated to 500 0.; simultaneously sodium metal, pro-'- heated to 400 C., was added at a rate equivalent to a 5% excess over the stoichiometrical equivalent. The sodium metal was pressurised to 25 lbs. per square inch and atomised through a pressure atomising nozzle. Prior to the addition of reactants, the reaction chamber was heated externally to 600 C. and filled with an inert argon atmosphere. When reaction commenced, all the external heating was stopped and the temperature henceforth was maintained by the heat of reaction. The reaction chamber was operated continuously for 3 hours 50 minutes before being shut down. The product, which was in the form of a free-flowing black powder, was heated to 0 C. which had the efiect of distilling off the excess sodium which had been added and the resulting mass was then crushed and leached, firstly in hydrochloric acid to which ferric chloride had been added, followed by water washing. The product, after arc melting, was analysed, and shown to contain 99.5% titanium. Based on the titanium content of the titanium tetrachloride used in the experiment, the yield of leached metal product was 72%.

Titanium metal prepared in accordance with the process and in the apparatus described hereinbefore has a surface area so large that if it were exposed to .the

air it would collect an adhering film of adsorbed oxygen and nitrogen sufficient in quantity to contaminate the metal. This difiiculty is met by heat treating the products to a temperature in excess of the melting point of the sodium chloride. Presumably this heat treatment first reduces the surface area of the metal, secondly distills off any excess sodium and thirdly distils oft, disproportionates, or causes to react With the excess sodium, any lower chlorides of titanium which may be formed. Each or all of these efiects may contribute to subsequent successful leaching. Alternatively, the titanium metal may be purified by vacuum distillation. In this event the removal of sodium chloride Will automatically demand that temperatures of the order of 95 C. shall be maintained for extended periods, and the advantages of heat treatment will, in such circumstances, be automatic.

The present invention provides a process which may be carried out continuously thus permitting maximum utilisation of the apparatus employed. Continuous reduction means that any accidental residual impurities on the walls of, or in the atmosphere in the reaction chamher will be gettered in the initial working of the process and thereafter the product titanium of the continuous process will attain a higher degree of purity than is normally possible in batch work where each batch runs the risk of contamination.

We claim:

1. A process for the production of ductile titanium in solid, particulate, relatively free-flowing form from titanium tetrachloride which consists of introducing a conical spray of atomized liquid sodium under pressure into a chamber containing an atmosphere inert to said sodium and titanium tetrachloride, circumferentially intersecting the periphery of said conical spray at a point spaced from the entry of said spray into said atmosphere and spaced from the walls of said chamber with titanium tetrachloride and substantially completely reacting said atomized liquid sodium with said titanium tetrachloride at substantially the points of the intersection to form solid particulate titanium, lower chlorides of titanium, and sodium chloride, the rate of admixture of the reactants being so adjusted that the sodium metal is present in from 1 to excess over the stoichiometric equivalent of titanium tetrachloride.

2. A process for the production of ductile titanium in solid, particulate, relatively free-flowing form from titanium tetrachloride by means of liquid sodium which consists of separately preheating said ingredients to temperature above the boiling point of titanium tetrachloride but below the boiling point of sodium metal, atomizing said preheated sodium at a pressure within the range of 10 to pounds per square inch, introducing a continuous conical spray of said preheated atomized liquid sodium into a chamber containing an atmosphere inert to said sodium and titanium tetrachloride, circumferentially intersecting the periphery of said spray at a point spaced from the entry of said spray into said atmosphere and spaced from the Walls of said chamber with vaporous titanium tetrachloride and substantially completely reacting said liquid sodium with said titanium tetrachloride at substantially the points of intersection to form solid, particulate titanium, lower chlorides of titanium and sodium chloride, the rate of admixture of the reactants being so adjusted that the sodium metal is present in from 1 to 10% excess over the stoichiometric equivalent of titanium tetrachloride.

3. The process as defined in claim 2 wherein said liquid sodium is preheated to about 400 C. and said titanium tetrachloride is preheated to about 500 C.

4. The process as defined in claim 2 wherein the products of reaction of the atomized liqiud sodium and vaporous titanium tetrachloride are permitted to fall within said inert atmosphere and said atmosphere below said points of reaction is maintained at a temperature which inhibits the melting of the sodium chloride.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,825 Clark May 11, 1954 2,205,854 Kroll June 25, 1940 2,277,067 Brassert Mar. 24, 1942 2,530,077 Ramsing Nov. 14, 1950 2,559,419 Fouquet July 3, 1951 2,564,337 Maddex Aug. 14, 1951 2,618,549 Glasser et a1. Nov. 18, 1952 2,708,158 Smith May 10, 1955 2,782,118 Hood Feb. 19, 1957 2,828,199 Findlay Mar. 25, 1958 FOREIGN PATENTS 296,867 Germany Mar. 13, 1917 505,801 Belgium Sept. 29, 1951 1,074,024 France Mar. 31, 1954 1,088,006 France Sept. 1, 1954 717,930 Great ,Britain Nov. 3, 1954

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF DUCTILE TITANIUM IN SOLID, PARTICULATE, RELATIVELY FREE-FLOWING FORM FROM TITANIUM TETRACHLORIDE WHICH CONSISTS OF INTRODUCING A CONICAL SPRAY OF ATOMIZED LIQUID SODIUM UNDER PRESSURE INTO A CHAMBER CONTAINING AN ATMOSPHERE INERT TO SAID SODIUM AND TITANIUM TETRACHLORIDE, CIRCUMFERENTIALLY INTERSECTING THE PERIPHERY OF SAID CONICAL SPRAY AT A POINT SPACED FROM THE ENTRY OF SAID SPRAY INTO SAID ATMOSPHERE AND SPACED FROM THE WALLS OF SAID CHAMBER WITH TITANIUM TETRACHLORIDE AND SUBSTANTIALLY COMPLETELY REACTING SAID ATOMIZED LIQUID SODIUM WITH SAID TITANIUM TETRACHLORIDE AT SUBSTANTIALLY THE POINTS OF THE INTERSECTION TO FORM SOLID PARTICULATE TITANIUM, LOWER CHLORIDES OF TITANIUM, AND SODIUM CHLORIDE, THE RATE OF ADMIXTURE OF THE REACTANTS BEING SO ADJUSTED THAT THE SODIUM METAL IS PRESENT IN FROM 1 TO 10% EXCESS OVER THE STOICHIOMETRIC EQUIVALENT OF TITANIUM TETRACHLORIDE.

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