US1043154A - Electrolytic production of light metals. - Google Patents

Description

. l INVENTORS i 0- :f WITNESSES:

G. 0. SEWARD, P. VON KGELGEN & I. VON BIDDER. ELBGTROLYTIG PRODUCTION 0F LIGHT METALS. APPLICATION FILED MAY 10, 1909.

1,043, 154. Patented Nov. 5, 1912.

Z SHEETS-BHBET 1.

G. 0. SEWARD, F. VON KGELGEN (Y: F. VON BIDDER. BLECTROLYTIC PRODUCTION 0F DIGHT METALS. APPLICATION FILED MAY 10, 1909.

Patented Nov. 5, 1912.

2 SHEETS-SHEET 2.

WITNESSES:

'UNITED STATES PATENT oEEIoE.

GEORGE-o. sEWARD, OE EAsT ORANGE', NEW JERSEY, AND FRANZ von KGELGEN AND ERI'rz von RIDDER, OE HoLoolvIBs ROOK, VIRGINIA, AssIGNoRs To VIRGINIA LABO- RATORY COMPANY, OE NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTROLYTC PRODUCTION OF LIGHT METALS.

To all whom 'it may concern:

Be it known that we, GEORGE O. SEWARD, a ,citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, FRANZ VON KGELGEN, a subject of the German Emperor, residing at Holcombs Rock, in the county of Bedford and State of Virginia, andF RITZ VON BID- DEP., a subject of the Russian Emperor, residing in Holcombs Rock aforesaid, have jointly invented certain new and useful-Improvements in lElectrolytic Production of Light Metals, of which the following isa specification.

This invention relates in general tov the electrolysis of molten salts where the metal or alloy produced is of lower specific gravity than the electrolyte, and specically to the production of sodium from sodium-chlorid or common salt, the ore of sodium which is found in most abundance and in an almost pure state.

The production of the metal sodiumfdirectly by the electrolysis of sodium-chlorid has not, to our knowledge, been accomplished` in a commercial way prior to our invention; though many excellent suggestions as to the -form of apparatus and much valuable data have been published.

The apparatus is illustrated, in vits essential details, by the accompanying drawing, Figure 1 of. which is avertical diamet-rical section 'of the furnace, and Fig. 2 isa horizontal section on the line 2-2 in' Fig. 1.

through the sides of the riveted steel case a and connect by threaded joints with carbon or graphite plates b b which fit together to form -a polygonalanode which also serves as the sides of the Crucible. This sectional ,construction of the anode is convenient, but it may be made monolithic if desired.. f

The space between the anode and the furnace case is filled with a thoroughly tamped agglomerate a of {ire-clay, asbestos-fiber, and cement, and the bottom of the-Crucible d is also conveniently Vmade of this material which -isa good insulating lining and which resists the action of the anode gas and of the electrolyte well.

By limiting the height of the anode a protective layer of salt may be maintained over; the top, preventing oxidatlon and disin f tegration of the carbon.

Specication of Letters Patent.

bestos twine on the tubes.

Patented Nov. 5, 1912.

' Application mea May 1o, 1909. serial No. 495,016.

coil is embedded in the crucible bottom as shown and also tends to maintain the integrity of the latter by its cooling effect.

A nipple c in the top of the cathode re-4 ceives At-he molten metal as its level rises within the sodium-chamber and. directsl its course so that it will drop clear of the walls of the cathode-cavity and fall into the receiver e, from whence it may be tapped at intervals through tap-hole e.

The sodium is collected within the watercooled and salt-incrusted curtain g which dips below the electrolyte and divides the space above it into a sodium-chamber and a chlorin-chamber. g is in no sense a pole cell as it is kept totally inactive b the layer of chilled salt n maintained there` on through the cooling action of the water circulating within the curtain. This` curtain is conveniently made of two separate coils of seamless copper tubing which are rst the run-and is conveniently made by closely Graphite pencils b lead in the' current wrapping two `or more layers of strong as- The multiple-coil construction of the curtain which is shown in the drawing is a further insurance against activity, as, even in case the upper coil comes in contact with the negatively-charged sodium in the sof dium-chamber, the isolation will still bev ac- The correct.

complished by the lower coil.- dtermination of the size of this curtain is important as the area of the floating sodium is controlled thereby and, in a measure, the current density at the iron-sodium cathode which is preferably high, for example 10 amperes per sq. inch Of total surface of active iron and. sodium.

Local heating of the electrolyte between the curtain and the cathode is necessary in order to limit `the cooling effect of the for- -merand avoid chilling ofthe electrolyte and obstruction of the entrance for the sodium into the sodium-chamber. The function of the cooling medium circulating within the curtain is to maintain an` insulating and protective layer of solid salt thereon and its trically connected to the negative terminal may be introduced through the cover of the 'sodium-chamber and. into the electrolyte through the floating sodium to give further control of .cathodie activity if desired. Local heating may be also accomplished by the use of heating bodies within the sodiumchamber whichl give control independently of the electrolyzlng current. Hollow iron or pressed steel members heated by an internal electric resistance coil or by other than electric means are convenient and, if

heated by gas after the manner of gasolene flat-irons or soldering-irons, effect an economy iary thereto.

An iron plate c', insulated from the furnace case and from the metal of the curtain,

4covers both the sodium and the chlorin- 'chamberg The cooling effect of the air, to-

gether with a protective deposit of con.

densed salt-vapor on its under side, keeps the cover z' from being attacked by the dry chlorin.

An opening through the cover at its c'en ter gives access to the sodium-chamber and to the cathode-cavity through the nipple c'. andv is normally closed by the plug i. Other openings through the cover into the chlorinchamber are rovided for feeding in salt and for breaking up salt crusts if any form. The -chlorin is drawn out through the stack 0, a slight suction being preferably maintained.

The crucible may be quickly emptied when desired through the tap-hole m. l

An approximation to atmospheric pressure is maintained within the cathode-cav-n ity and equilibrium between that 'and the sodium-chamber by the system of pipes 7c and la and the kerosene seal s, whereby the effects of sudden generation of gas'or ebullition of the electrolyte are. neutralized and any tendency for the cathode nipple to Siphon when full offalling sodium overcome. By using tees in the construction of the system of pipes cleaning out is facilitated. l V

of current and may be used as an auxil-A The yelectrical connections to the cathode andl anode are indicated in the drawing and may be made in any convenient manner, preferably so that either direct `or alternating current may be used interchangeably., When using alternating current, We can pass it through'the electrodes shown or one pole of the current may be iron rods of small cross-section whereby a current of comparatively high voltage and low amperage may be used.

The procesa-Alternating current is preferably. used in melting and! keeping molten the velectrolyte at the beginning c'f a run inl order to defer separation of sodium until the level of the electrolyte is so high that it will collect entirely within the sodiumchamber. The curtain is then incrusted with salt by repeatedly ladling on of molten electrolyte or .by repeated immersion therein until a sufficiently thick coating has been formed over the preliminary vinsulating layer. rAn electrolyte which'melts at about 600 degrees C. is preferably used, suitable fluxes being added. for this purpose and the `electrolysis is conducted at a temperature of between 630 and 670 degrees C. Practically nothing but sodium-chlorid is decomposed, but in a long run Aslight volatilization and decompositionof the fluxes occur and occasionaladdition of the same is necessary. After the direct current has replaced the alternating the output is poor until all moisture is eliminated from the lining, etc., and the electrolyte is completely dehydrated. The separation of sodium soon starts however and grows larger and soon the receiver' becomes heated up from the overiow of sodium therein which, when using a current of .over 3000 amperes, is rapid enough to maintain the metal in a molten state so that it can readily be drawn off through the taphole e. By adding some suitable hydrocarbon, such as paraiin, to .the ladle before tapping, the sodium is pre-vented from burning by the covering which is thereby formed. Fromthe tapping-ladle the sodium is conveniently poured into large cast-iron cal-' drons kept hot by small ires and from thence into the molds at convenient times.

' The process requires little attention beyond keeping the electrolyte at the proper Y .of the electrolyte until the salt-incrustation is melted off the sodium bridges will be rei. leased, after which a new coatingy of salt may be formed on the curtain by cooling the electrolyte to its normal temperature.

It is preferable to replace the direct with alternating current during this operation so as to avoid separation of sodium and hasten the result though not entirely necessary.

The appearance of sodium outside of the curtain may alsoindicate that accumulated impurities on the Crucible bottom have become active and are separating sodium so remote fro-m the cathode that it rises outside the sodium-chamber.

A preliminary refining of the salt, however, renders the accumulation of 4impurities so slow that the above condition only appears at long intervals. This is conveniently effected by melting the salt in a small,

electric furnace with a current of comparatively high pressure and low volume. The

insoluble impurities settle to the bottom of the melt and the soluble impurities which are less electro-positive than sodium are decomposed (by the'current if direct current is used and by bringing sodium into contact with the melt if alternating current is used) and then settle to the bottom. By using the dehydrated and purified salt from the upper part of the melt, practically pure material is obtained for feeding into the electrolysis furnace.

Though -our invention is particularly applicable to the production of metals of the alkali group, and specically to sodium, certain features of it are of great value in the production of alkali-earth metals and of other metals of specific-gravity low enough to float to the surface of the electrolyte employed in their manufacture.

Having described our invention, we now claim as new in the production of a metal y from a fused compound thereof of greater specific gravity: y

l. Producing metals lighter than their fused salts, by electrolyzing the fused salt of such metal by current between an outer V anode and an inner cathode, the. anolyte and catholyte being. partially separated by a 'chilled salt-incrusted curtain inclosing the cathode, the latter being of large mass to diminish heating, and approaching the cathode-so closely as to form a limited annular Zone of electrolyte between, maintaining apool of produced metalwithin such curtain to form an-extension'of the cathodeso that a preponderance of cathodic activity takes place in the upper part of the catholyte, and regulating the current density to keep the resistant electrolyte in said zone heated to such fluidity as to facilitate the ascent of produced metal, and to limit the -thickness. of salt crust on the curtain.

2. Producing metals lighter than their fused salts,by electrolyzing the fused salt of suchmetal by current between an outer anode and an inner cathode, the anolyte and catholytebeing partially separated by a chilled salt-incrusted curtain inclosing the cathode, the cathode being of relatively large mass to avoid heating, and closely approached by the curtain, so that the heat generated in the electrolyte adjacent to the cathode limits the thickness of salt crust on the curtain.

3. Producing metals lighter than theii` fused salts, by electrolyzing the fused saltof such metal by current between an outer anode and an inner cathode, the anolyte and catholyte being partially separated by a chilled salt-incrusted curtain inclosing the cathode, the space within the curtain being covered over to form a cathode chamber, the produced metal descending from such chamber through a discharge passage, and maintaining atmospheric pressure in this chamber and in the discharge passage, to prevent siphoning ofthe produced metal.

4t. Producing metals lighter than their fused salts, by electrolyzing the fused salt of such metal by currentbetween an outer anode and an inner cathode, the anolyte and catholyte being partially separated by a chilled salt-incrusted curtain inclosing the cathode, the anode being of limited height, and protecting the anode by covering it with the electrolyte.

5. Separating the catholyte from the anolyte by a cooled curtain rendered nonactive first by a layer of solid insulating material and secondly by an outer incrustation of salt maintained solid by the cool- 1n Separating the catholyte yfrom the anolyte by a cooled curtain rendered nonactive first by a layer of solid infusible insulating material and secondly by an outer incrustation of salt maintainedv solid by the cooling. 5

7. Separating the catholyte from the anolyte by a cooled curtain rendered nonactiveirst by wrapping with asbestos and secondly by an outer incrustation of salt maintained solid by the cooling. i

8. Separating the metal at an upwardly projecting cathode, between which and the anode is a cooled salt-incrusted curtain, confininv the floating metal within the curtain and 1n contactwith the cathode to form an extension of the latter, the combined cathode having such dimensions as to maintain a preponderance of cathode activity at the upper part, and' consequently maintaining a from solidifying the electrolyte between the cathode and the curtain.

l9. Confining the separated metal by a cooled saltfincru'sted curtain comprising upper and lower sections mutually insulated substantially as and for the purpose described.

l0. Separating the metaly at an upwardly projecting cathode made hollow to form a discharge conduit, coniining it within a cooled curtain and maintaining a substantial equilibrium between the'atmos yhere of the sodium-chamber, cathode-cham er, and exterior to the furnace by the means and for the urpose described.

11. rlhe described electrolytic'apparatus, comprising a tubular ring curtain arranged between a central upwardly projecting cathode and an annular anode, the cathode projecting within the curtain and above the electrolyte, and confined within a Vertical yprojection of the curtain, to insure that the produced metal shall ascend within the curtain, the cathode being lof relatively large mass, and being closely approached by the curtain.

12. An electrolytic apparatus comprising 13. An electrolytic apparatus comprising a tubular ring curtain, a central cathode within it and an anode exterior to it, the space within the curtain being covered over to form a cathode chamber, and the cathode being hollow to form a discharge passage through it, with a connection between the cathode chamber and the discharge passage to equalize the pressures therein, and a seal interposed between said parts vand the outer air to maintain them at substantially ratmospheric pressure.

In witness. whereof, we have hereunto signed our names in thev subscribing witnesses.

GEORGE O. SEWARD. FRJANZ VON KUGELGEN. FRITZ voN BIDDER. i

Witnesses as to George O. Seward:

D. ANTHONY UsINA, FRED WHITE. `Witnesses as to Franz vonKgelgen and Fritz von Bidder: l

. J. H. WEBB,-

E. F. SCALES, Jr.

presence of two.

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