US2905613A - Methods and apparatus for the electrolytic-refining of titanium metal or zirconium metal - Google Patents

Description

Sept. 22, 1959 TADAO TOMONARI ETTAL 2,

METHODS AND APPARATUS FOR THE ELECTROLYTIC-REFINING OF TITANIUM METAL OR ZIRCONIUM METAL 3 Sheets-Sheet 1 Filed Sept. 19, 1956 INVENTOR 75mm W ATTORNEYS Sept. 2, 1959 TADAO TOMONARI ETAL 2,905,613

METHODS AND APPARATUS FOR THE ELECTROLYTIC-REFINING 0F TITANIUM METAL OR ZIRCQNIUM METAL Filed Sept. 19, 1956 5 Sheets-Sheet 2 ATTORNEYS Sept. 22, 1959 Filed Sept. 19, 1956 TADAO TOMONARI ETAL 2,905,613 METHODS AND APPARATUS FOR THE ELECTROLYTIC-REFINING OF TITANIUM METAL OR ZIRCONIUM METAL 3 Sheets-Sheet 3 9 ylNVENTOR W W wmwzwa BY m/M ATTORNEYS METHODS AND APPARATUS FOR THE ELECTRO- LYTIC-REFINING OF TITANIUM METAL OR ZIRCONIUM METAL Tadao Tomonari, Yokohama, Noboru Ishimoto and Tetsuro Togo, Aniagasaki, and Tamotsu Izumi, Osaka, Japan, assignors to Osaka Titanium Seize Kabushiki Kaisha, Amagasaki, Japan, a corporation of Japan Application September 19, 1956, Serial No. 610,781 1 Claim. (Cl. 204-216) This invention relates to methods and apparatus for the refinement of titanium or zirconium and is more particularly directed to methods and apparatus for the electrolytic-refining of titanium metal or zirconium metal from impure sponges or scraps of titanium or zirconium or scraps of titanium or zirconium alloys.

An object of this invention is to provide a novel method and apparatus whereby good quantity of titanium metal or Zirconium metal may be produced easily, economically and extremely effectively from impure sponges or scraps of titanium or zirconium or scraps of titanium or zirconium alloys. Another object of this invention is to provide an improved apparatus wherewith the chemical corrosion of an electrolytic cell may be extremely diminished. Further another object of the invention is to provide an electrolytic apparatus wherewith an electrolyte may easily be melted by external heating.

According to this invention, an electrolytic cell is made of a conductive metal, for example, stainless steel or the like which is electro-chemically nobler than the metal to be treated, namely, than titanium metal or zirconium metal. And, the said cell is charged with impure sponges or scraps of titanium or zirconium or scraps of titanium or zirconium alloys, namely, with the raw material to be refined, along the inside surface of the wall of the cell so that the raw material covers and closely contacts with the surface of the wall, and thus the raw material and the wall of the cell are made to serve as an anode, while, one or several cathodes are placed in said cell leaving a space from the anode. As described above, the electrolytic cell according to this invention is made of a noble metal and is closely covered with the raw material to be refined, so that the chemical corrosion of the cell with an electrolyte filled therein will be considerably diminished and, even when the exposed parts of the cell into the atmosphere above the electrolytic bath are chemically corroded and the reaction products caused by said corrosion on the inside surface of the wall of the cell are dropped into the bath, such products exert no influences upon the quality of the sponges deposited on the cathode as the same products are immediately reduced by the titanium placed by the wall of the cell. Furthermore, the apparatus and method according to this invention has the advantage that the electrolyte positioned in the cell may easily be melted by external heating, and is free fro-m the disadvantages brought about in the case where an electrolytic cell is required to be made of a refractory material consisting of mainly graphite or oxide. The titanium metal or Zirconium metal deposited on the cathode is properly drawn out of the cell and is given some treatments such as vacuum distillation or leaching.

Further other objects and features of this invention will be made clear by the following description of the embodiments shown on the accompanying drawings, in which:

Figs. 1 and 2 illustrate an embodiment of this invention; Figs. 3 and 4 illustrate another embodiment of the 2,905,613 Patented Sept. 22, 1959 2 invention; Figs. 5 to 10 inclusive illustrate further another embodiment of the invention.

Fig. 1 is a diagrammatical plane view of an apparatus of the invention.

Fig. 2 is a diagrammatical section view on the line 11-11 in Fig. 1.

Fig. 3 is a diagrammatical plane view of a modified form of apparatus according to this invention.

Fig.4 is a diagrammatical section view on the line IV-IV in Fig. 3.

Fig. 5 is a side view, partly in section, of another modified form of apparatus according to this invention.

Fig. 6 is a front view, partly in section, of the apparatus. A

Fig. 7 is a sectional side view showing the relation between an electrolytic cell and a grating.

Fig. 8 is a plane view of the cell in Fig. 7.

Fig. 9 is a sectional side view showing a modified form of relation between the electrolytic cell and the grating.

Fig. 10 is a plane view of the cell shown in Fig. 9.

First, one example of the invention will be explained with reference to Figs. 1 and 2. The cylindrical elec trolytic cell 8 made of Ni 20-Cr 18 stainless steel is provided with the grating 14 made of the same material as said cell in such a manner that the grating 14 is placed along the inside surface of the wall of the cell 8 leaving the space 13 between the cell 8 and grating 14. And the said cell 8 is filled with an electrolyte so that the grating 14 is situated under the surface of the electrolyte.

The space 13 formed between the grating 14 and the wall of the cell 8 is filled with a certain amount of impure sponges of titanium so that the sponges may be dissolved anodically by being supplied with electric current from the positive pole of an electric source through the Wall of the cell 8. The cylindrical cathode 16 made of a titanium plate is placed in said cell 3 concentrically with the same and is connected with the negative pole of the electric source. When a fair quantity of titanium metal has been deposited on the cathode 16, the electric supply is cut off and the cathode is drawn out of the cell 8 together with the titanium metal deposited there'- on and is carried into a cooling chamber, though chamber is not illustrated. Inthis cooling chamber, the cathode 16 with the deposited metal is cooled to a temperature under C. and then is carried out of the chamber into the air and, as the next step, the same is carried into a furnace, not illustrated, for a vacuum treatment. In this furnace, the cathode with the deposited metal is heated to a temperature of about 800 C. for the purpose of evaporating the electrolyte adhered thereon and also of disproportionating the titanium su-bchlor-ide included in the adhered electrolyte into titanium and titanium tetrachloride. After these treatments, the same cathode with the deposited metal is cooled and thus the final products may be obtained.

Next, another example of this invention will be described with reference to Figs. 3 and 4. The rectangular form of electrolytic cell 8 made of 18-8 stainless steel is divided into several small compartments, which compartments are in communication with each other at their lower portions so that the electrolyte may be used in common to all compartments. Each compartment is pro vided with a grating 14 placed along the inside surface of the wall of the compartment leaving the space 13 be tween the two, and every space 13 is filled with a certain quantity of titanium impure sponges to be refined. Furthermore, each compartment is provided with the cathode 16 made of a titanium metal plate. The operation in this embodiment is the same as for that of the modification mentioned above. v

Further another embodiment of this invention will be" explained with reference to Figs. to inclusive. Referring to the drawings, numeral 1 is an electric furnace having the electric heating elements 2 placed along the semi-spherical concave recess made in the center thereof, and the air-tight cover 3 is mounted on the top of the furnace 1 so that the chamber 4 to be filled with inert gas may be formed within said cover 3. The raw material feeding device 5 introduces impure titanium sponges, the raw material to be refined, into the electrolytic cell 8, which will be explained more particularly hereinafter, from the vacuum tank 6 through the feeding pipe 7 by means of, for example, a feeding screw at a certain constant feeding velocity without exposing the treated raw material to the air. The electrolytic cell 8 .of a dish type, which is placed along the inside surface of the. semi-spherical concave recess of the furnace 1, is provided with the revolving shaft 9 projecting downwards from the center of the bottom thereof and is rotatably supported by the support 11 of the furnace 1 by way of placing the flange 10 provided around the upper parts of the outside of the cell 8 on walls 12 on said support 11. The grating dish 14 of a semi-spherical form is supported in the furnace 1 concentrically with the cell 8 leaving the space 13 from the inside surface of said cell 8. And, the cathode 16 having the form of a spherical shell is rotatably supported within the grating dish 14 concentrically with the same leaving the space from the inside of said dish 14. Said cathode 16 is provided with the horizontal revolving shaft 17 projected therefrom as one body in alignment with a diameter thereof, and said shaft 17 is rotatably supported at its both ends on the furnace 1. The revolving shafts 9 and 17 of both the electrolytic cell 8 and the cathode 16 are provided with the gaskets 18 and 19 respectively for scaling up the interiors of the furnace 1 and the cover 3 hermetically against the air, and these shafts 9 and 17 are connected with the driving means 20 and 21 respectively so as to be revolved slowly thereby.

The wall of the electrolytic cell 8, which serves as a part of an anode, is supplied with an electric current through the revolving shaft 9 and the brush 22 on said shaft 9 from the positive pole of an electric source, and the electric current flows to the cathode 16 through the electrolyte filled in the cell 8 and then runs out towards the negative pole of the electric source passing through the revolving shaft 17 and the brush 23 provided on said shaft 17.

The device 24 for collecting products is projected towards the spherical cathode 16 from the front thereof in the opposite direction of revolution of the cathode 16. By this device 24, the products deposited on the cathode 16 may be carried out into the vacuum tank 25 placed at the outside of the furnace 1 through the valve 26 and other means. The device 24 shown in the drawings is of the type of an inclined trough of which the top end is placed near the upper surface of the cathode 16. The top end of the feeding pipe 7 is inserted into the space 13 between the cell 8 and the grating dish 14, and several pushing plates 27 are projected from said dish 14 into the space obliquely against the direction of revolution of the cell 8.

By this embodying apparatus, an electrolytic operation may be carried out as follows:

A certain quantity of impure titanium sponges, the raw material to be refined, of the size less than two meshes is carried into the vacuum tank 6, in which its moisture, air and the like are removed. Then, the raw material is sent into the feeding pipe 7 at a constant feeding speed by means of the feeding device 5 by way of opening a valve at the inlet of the pipe, whereby the space 13 between the cell 8 and the grating dish 14 is filled with the raw material. While, the cell 8, which has been filled with titanium dichloride and melted salt such as MgCl KCl, NaCl and others, is revolved by the revolving shaft 9. At the same time, the cathode 16 also is revolved gently by the revolving shaft 17 so that the surface of the cathode 16 may be immersed in the electrolyte. The raw material sent into the space 13 revolves together with the revolving cell 8, while the grating dish having the pushing plates 27 is kept stationary, and therefore the raw material is led with the pushing plates 27 and is pushed away towards the bottom of the cell 8. It is proper to revolve the cell 8 at the speed of one to five times a day. Because the raw material is pushed downwards by the pushing plates 27 automatically in this apparatus as described above, the density of electric current within the vessel scarcely changes. If, on the contrary, there is no pushing means such as the pushing plates 27, the filling density of the raw material in the cell 8 is gradually reduced with the advance of electrolysis, and consequently the density of electric current and the velocity of electrolysis are unavoidably reduced.

On proceeding with the electrolysis, titanium ions move upwards passing through the grating dish 14 and are electrodeposited on the cathode after passing through the space 15. If, in this case, the circumferential speed of the cathode 16 is kept less than 28 cm./hr., the electrolyte is not stirred, and therefore such a speed of the cathode is suitable for the electrolysis. If the revolution speed of the cathode 16 is kept to such a maximum as described above, the electrolyte in the cell 8 hardly attaches to the surface of the cathode but the greater part of the electrolyte in the cell remains in the cell 8, and so the quantity of the electrolyte in the cell is kept almost constant at all times. Therefore, it is sufficient to supplement the waste of the electrolyte only about once a week. The products deposited on the cathode 16 are separated from the surface of the same and are sent into the vacuum tank 25 by means of the collecting device 24 and then the products are sent into a tank filled with algon gas after being given a vacuum treatment, although this tank is not illustrated.

For the purpose of securing the uniformity of thickness and filling density of the raw material in the electrolytic cell 8, the pushing plates 27 which may lead and push away the raw material revolving together with the cell 8, are mounted on the stationary grating dish 14 in this embodiment, but such an operation of the pushing plates may be performed also by such a mechanism as is shown by Figs. 9 and 10. Namely, the electrolytic cell 8 is stationary while the grating dish 14 is rotatable by the driving means 29, and the pushing plates 27 are mounted on said stationary cell 8. By this mechanism, the raw material may be distributed uniformly and be pushed away towards the bottom of the cell by the pushing plates 27 to a constant filling density and thickness. In a second modification thereof, both the cell 8 and the grating dish 14 are connected with driving means respectively so that they may be revolved in the same or reverse directions respectively, and each of these is provided with one or several pushing plates, though this modification is not illustrated.

As it is usual in this embodying apparatus that the electrolytic cell 8 is compactly filled with the raw material, there is the advantage that the chemical corrosion loss of the cell 8 may be greatly reduced. It is usual, furthermore, in this apparatus to have the filling density of the raw material in the cell 8 and the contact area of the same with the surface of the wall of the cell 8 kept almost constant at any time, so that the local increase of the density of electric current is avoidable and consequently a constant electrolytic velocity may be expected.

According to the result of our experiments, the chemical corrosion loss of the electrolytic cell 8 is less than 0.12 gr./m. per 400 hours in case when the cell is made of stainless steel, and is less than 0.42 gr./rn. per 400 hours in case when the cell is made of silicon cast steel. When the circumferential speed of the electrolytic cell 8 is raised, there gives rise to a stirring in the electrolyte and good electrolysis cannot be; expected. According to our tests, which was done in connection with titanium, the speed of the cell of 13-52 cm./hr. is proper. Furthermore, a time interval between one to six hours is suitable for immersing the surface of the cathode in the electrolyte.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention.

Having thus described our invention, what we claim is:

An apparatus for the electrolytic-refining of impure titanium metal and zirconium metal comprising a fixedly supported electrolytic cell of a dish configuration which is made of an electrical current conducting metal electro-chernically nobler than the metal to be treated and capable of being filled with an electrolyte, a source of electrical current having the positive pole thereof connected to said cell, a semi-spherical grating dish rotatably supported along the inside surface of said cell leaving a space therebetween with said space being adapted to be filled with the raw material to be treated so that, the raw material and the cell serve as an anode, driving means for rotating said dish, a spherical cathode rotatably mounted along the inside surface of said grating dish leaving a space therebetween, said cathode being connected with the negative pole of said source of electrical current, driving means for revolving said cathode, and means carried by said dish for uniformly distributing the raw material.

References Cited in the file of this patent UNITED STATES PATENTS 1,012,470 Steinbuch Dec. 19, 1911 2,707,169 Steinborg et a1. Apr. 26, 1955 2,707,170 Wainer Apr. 26, 1955 2,732,339 Webster et a1. Jan. 24, 1956 2,734,856 Schultz et a1. Feb. 14, 1956 2,785,066 Dean Mar. 12, 1957 FOREIGN PATENTS 28,339 Germany Aug. 14, 1884 667,252 France Oct. 15, 1929 713,446 Great Britain Aug. 11, 1954

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