US3551308A - Operation of furnace for the electrolytic fusion recovery of aluminum - Google Patents

Operation of furnace for the electrolytic fusion recovery of aluminum Download PDF

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Publication number
US3551308A
US3551308A US718704A US3551308DA US3551308A US 3551308 A US3551308 A US 3551308A US 718704 A US718704 A US 718704A US 3551308D A US3551308D A US 3551308DA US 3551308 A US3551308 A US 3551308A
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Prior art keywords
furnace
anode
crust
gas
alumina
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Expired - Lifetime
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US718704A
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English (en)
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Wolfgang Capitaine
Martin Bard
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Alcan Holdings Switzerland AG
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Alusuisse Holdings AG
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium

Definitions

  • the anode effect is eliminated by supplying the gas film or barrier layer below the anode by using movements of the bath which are produced by mechanical or pneumatic means.
  • the elimination of the anode effect is therefore normally composed of two successively performed opera tions which are partly carried out manually:
  • the anode effect persists for about 3 to 10 minutes, because after the optical or acoustic signal has been given an operator must first set a crust breaker in operation, drive it to the appropriate furnace (in some cases this may mean long distance where large sheds are involved) and then as described, break the crust. Only after this can the 3,551,308 Patented Dec. 29, 1970 ice anode effect be eradicated by means of wooden rods or compressed air.
  • the breaking of the crust in order to introduce alumina into the bath is not only carried out after an anode effect occurs, but that it is expedient to perform this operation one or more times between two anode effects, so as to operate the furnace at as constant a voltage as possible.
  • the crust is broken at intervals of, for instance, 2 to 4 hours. So as to produce the anode effect about once a day, the addition of alumina is reduced by taking suitable steps on some of the occasions when the bath is serviced.
  • the mechanical breaking of the crust be automated, both on the servicing of the furnace carried out after an anode effect and on the servicing thereof carried out between two anode effects, and that the increase in voltage occurring before or during the anode effect be used as an initiating means for the remedial measures.
  • the anodes be divided into two half groups, one on each side of an interspace in the longitudinal axis of the furnace, and that a mechanically driven crust-breaking apparatus extending over the entire length of the anode zone be arranged in this interspace.
  • Acording to the invention in a method of operating a furnace for the recovery of aluminium by fusion electrolysis, the anode effect is eliminated by piercing the crust on the surface of the electrolyte with at least one mechan ically driven tool and supplying gas to the electrolyte through at least one duct located in the piercing tool.
  • the present inventive method makes it possible to eliminate the anode effect or even partly or completely avoid it in a considerably shorter time than by the methods heretofore known and nevertheless obtain the favourable 3 state of the contents of the bath (purification effect) which has heretofore been attributed to an action of the anode effect, so that the disadvantageous consequences of the anode effect do not have to be accepted.
  • This method can be employed both in furnaces with prebaked anodes and in furnaces with self-baking anodes.
  • anode effect within the definition of the present invention it is understood to mean both the eradication of the completed anode effect, with disappearance of the excess electric voltage, and the prevention and avoidance of the appearance of the completed anode effect, as well as the prevention, or limitation, of the detrimental consequences in its initial period (time of incipient voltage increase).
  • the eradication time that is the duration of the anode effect
  • the method according to the invention operates in a reliable and quantitatively regular manner.
  • the method has the advantage, inter alia, that it is not tied to specific designs, or divisions of the space, of the electrolytic cell, as is the case with previous proposals for automation and mechanisation, and is capable of general application.
  • gases may be employed when the method according to the invention is carried into effect.
  • gases for example, compressed air gives good results.
  • the gaseous agent is injected for at least 5 seconds, preferably for more than seconds, at a pressure of more than 2 atmospheres gauge pressure, preferably more than 4 atmospheres gauge pressure.
  • the present invention also includes an apparatus for carrying the method according to the invention into effect, the apparatus comprising at least one mechanically driven tool for piercing the surface crust of the electrolyte, the tool including at least one duct for feeding gas into the electrolyte.
  • the piercing tool according to the invention is in the form of a blowing chisel which includes the ducts for the supply of gas in the form of bores or attached tubes. At least that part of the gas ducts which extends in the longitudinal direction of the blowing chisel may also be formed by assembling suitably preformed parts of the blowing chisel.
  • One such chisel or a number of them is or are attached by the upper end to the piston rod of a pressure cylinder or to some other suitable motive means which in turn is mounted, for example, on a crust-breaker truck, or preferably is mounted stationarily on the furnace, for instance on the structure supporting the anode system or else on a support erected on the edge of the furnace tank or beside the latter.
  • the gas feed duet extending in the longitudinal direction of the chisel advantageously has a lateral connection in the upper part of the chisel, below the point where the chisel is attached to the piston rod, and extends into the region of the tip of the chisel, where it may have its outlet at the actual tip, but preferably discharges a little above the tip through laterally directed branch ducts.
  • the chisel has such a length and such a range of depth that the gas outlet orifices can preferably be immersed to a point below the anodes.
  • Gas can be injected into the electrolyte at such a pressure by means of the apparatus according to the invention than an area of the bath of about 2-4 sq. m., possibly even somewhat larger, is set in motion.
  • an anode area of about 10 to sq. m. it is generally sufficient to install 2 to 6 tools per furnace.
  • the piercing tools may, for example, be arranged at the ends of the furnace, for instance two at each end. This arrangement will be a possibility in particular in furnaces with continuous, self-baking electrodes, or in furnaces with elongated prebaked anodes mounted across the width of the furnace and disposed close to one another. In this case, care should be taken that the gas jets are so arranged in relation to one another that their in dividual effects are additive i.e., as seen from the centre of the furnace, they set all parts of the bath in like rotary motion.
  • the method and apparatus according to the invention can be employed with advantage in the electrolytic furnaces mentioned in the preamble, the anodes of which are divided into two groups by an interspace provided along the longitudinal axis of the furnace, for example by securing the chisels with gas inlet bores to a beam which extends over the entire length of the anode zone and is adapted to be moved up and down mechanically.
  • the arrangement of the tools in the longitudinal axis of the furnace has the advantage that gas can be blown out in all directions, which increases the range of action of the individual tools accordingly, since no blowing directions are blocked by walls.
  • the blowing orifices of the chisels may be directed downwardly; in this way, the purifying action of an anode effect can be intensified and a purifying action may also be expected when the injection of gas is effected outside the time of an anode effect.
  • the blowing orifices are advantageously so arranged that they are directed horizontally or approximately horizontally and blow under the anodes in the lowered position of the chisels.
  • blowing chisels arranged in the longitudinal axis of the furnace, that it is more favourable to direct the blowing orifices not parallel to the furnace axes, but obliquely with respect thereto, for example at an angle of -60, preferably 50.
  • FIG. 1 shows a blowing chisel in longitudinal section
  • FIG. 2 is a cross-section through the blowing chisel shown along lines 22 of FIG. 1;
  • FIG. 3 shows in elevation the lower portion of a modified blowing chisel shown in perspective
  • FIG. 4 shows in elevation the lower portion of another blowing chisel also in perspective
  • FIG. 5 is cross-section through the blowing chisel shown along the lines 55 of FIG. 4;
  • FIG. 6a is a longitudinal section through the lefthand half of an electrolytic furnace having an interspace be tween the two longitudinal rows of anodes, the blowing chisels being shown in the raised position;
  • FIG. 6b is a similar view of the righthand half showing the blowing chisels in the lowered position.
  • blowing chisel 1 shown in FIGS. 1 and 2 con sists of a solid cylindrical piece, for example of steel, with an axial bore 2 which is worked out from above and is subsequently sealed.
  • the chisel 1 is secured by means of the overlapping socket 3 to the pistol rod 4 of a pressure cylinder 5.
  • the chisel has a lateral bore 6 opening into the longitudinal bore 2 and to which a gas feed pipe 7 is connected.
  • the longitudinal bore 2 divides into four radial bores 8, which serve as outlet orifices for the gas.
  • these outlet orifices are arranged at right angles to the longitudinal axis of the vertically operating chisel, that is they are arranged horizontally, but, as already mentioned, it is possible to direct these orifices obliquely downwards or slightly upwards.
  • the chisel tip proper which wears out during operation, may be replaceable.
  • blowing chisels are also able to initiate the flow of the alumina lying on the crust of the electrolyte into the electrolyte by means of the holes made by them in the crust.
  • FIGS. 4 and 5 Another example is the winged blowing chisel shown in FIGS. 4 and 5, made from a flat section 10 which is pointed at the bottom and to each of the flat sides of which a longitudinally split tube 11 is Welded, the tube being closed in conical form at the bottom and being provided with blowing orifices 8.
  • FIG. 6 shows diagrammatically an example of the application of the invention to an aluminium electrolysis furnace the anodes of which are divided centrally into two groups by an interspace extending in the longitudinal axis of the furnace.
  • the electrolytic furnace consists essentially of a pot 12 with an iron-plate shell 13 in combination with a hollow peripheral reinforcement 14 and iron reinforcing members 15, as well as a brick insulating lining 16 and a cathodic carbon lining 17 in which the cathode bus bars 18 are embedded.
  • Two rows'of prebaked anodes 2,3 which are disposed close to one another dip into the layer of electrolyte 20.
  • only each two outer anodes 23 of the rear row are shown in the drawing, but not the way in 6 which they are suspended from the anode bus bars, or the bus bars and the further details of the anode system as these are well known.
  • the supporting pillars 25 for the anode system which stand onthe shed floor 24.
  • a bracket 26 mounted on each of these supporting pillars 25 is a bracket 26 directed towards the centre of the furnace, to which brackets there is attached, with the interposition of the two vertically adjustable pressure cylinders 27, a beam 28 extending above the interspace between the rows of anodes.
  • Other thrust-producing means such as, for example, toggle levers or eccentric drives, may also be used instead of the pressure cylinders 27.
  • the beam 28 is equipped with four blowing chisels 1, which are fed through a separate main gas line 29 and the connections 7. This arrangement has the advantage, inter alia, that all the chisels can be actuated together with only two pressure cylinders.
  • the stroke of the pressure cylinders and the length of the individual blowing chisels are so calculated that, in the raised or inoperative position of the beam, the tips of the chisels are located above the crust formed on the electrolyte (left-hand side of FIG. 6) and, in the lowered position of the beam, the outlet orifices 8 of the blowing chisels 1 are located below the anodes 23 (right-hand side of FIG. 6).
  • the electrolytic furnaces in a shed are so operated by feeding them with alumina by means of conventional mechanical crustbreaking devices. that about 1 /2 anode effects are obtained per furnace per day.
  • the surface crust is broken open by portable conventional pneumatic drills, first on one longitudinal side of the furnace tank 12, then on the other longitudinal side and then on the two transverse sides, and in the process alumina is pushed into the bath, after which, after the new crust has solidified, fresh alumina is heaped upon the latter.
  • the anode effect may be provoked when desired.
  • the blowing chisel apparatus located over the interspace between the two rows of anodes is set in operation, i.e. the beam 28 and its chisels 1 are forced downward under the action of the pressure cylinders 27, the gas feed ducts of the chisels being first fed with compressed air at a small part of the pressure subsequently employed.
  • the beam descends, the crust is pierced locally by the chisels, the alumina lying thereon is introduced into the melt and the blowing orifices of the chisels are brought below the anodes.
  • the duct system of the blowing chisels is now fed with compressed air at a higher pressure, for example at about 5 atmospheres gauge for 10-20 seconds, which produces a corresponding boiling or bubbling and circulation of the bath.
  • the air consumption is between 2 and 4 cu.m. (measured at N.T.P.)/min. If the time required for the response of the control system and the downward movement of the apparatus (3-5 seconds) is added, the anode effect persists fully for about 10 to 25 seconds. This time has proved in the tests to be fully adequate for purifying the bath. Before the apparatus is raised, the compressedair pressure is again reduced to such an extent that it is suflicient to prevent with certainty any penetration of melt into the blowing orifices.
  • alumina is advantageously introduced into the bath to suffice until the next planned crust-breaking operation, which can be effected by suitable choice of the nature and number of the piercing tools.
  • a Suiciently thick layer of alumina is again placed thereon for heat insulation and to prepare for the next eradication operation.
  • the method according to the invention solves the problems of effecting the elimination of anode effects and purification of the contents of the bath rapidly, reliably and without manual or mechanical agitation, in trouble-free interplay with the rest of the conventional operation of a furnace, in particular with the supply of the alumina. It is even possible to carry out the supply of the alumina and the eradication of the anode effect in one and the same operation and approximately simultaneously.
  • alumina can be introduced into the bath by means of the blowing chisels described during normal operation, i.e. in the periods between the anode effects, so that a separate supplementary crust-breaking arrangement and operation of a crust-breaker or other arrangements known per se for feeding alumina into them are unnecessary.
  • the operation of the apparatus can be automated with advantage by a programming switching mechanism being switched on, for example by the voltage which is increased on the occurrence of the full anode effect or even earlier by the increase in voltage preceding the anode effects, thus, for instance, at a cell voltage of 20 volts or still earlier, the programming switching mechanism controlling the individual steps of breaking open the crust, immediately following injection of gas and so on.
  • the method according to the invention also facilitates the full automation of the electrolysis of aluminium which is to be aimed at Gantry-like frames travelling along the series of furnaces are already known which are equipped with crust-breakers and alumina chargers for operation at the sides of the furnaces.
  • Such constructions can be automated, but can only be used for periodic operation, since they are too heavy to be moved rapidly to a furnace showing the anode effect.
  • an automatable apparatus according to the invention which is present at the furnace is best suited to intervene without any loss of time, and in fact even when anode effects occur simultaneously in a plurality of furnaces.
  • a particularly favourable method of operating an aluminium electrolysis furnace therefore consists in that, in combination, the anode effects are eliminated by applying the method described and the furnace is fed with raw ma terials by known methods between the anode effects.
  • the supply of the raw materials, in particular alumina, whether at the time of an anode effect or outside this time, may be carried out in manner known per se, such as by depositing it on the crust of the bath and breaking the crust, by supply and forcing in by means of screws or worms, but it may also be carried out by pnuematic forcing by means of rapidly flowing gases.
  • the method according to the invention also has the advantage that, due to the vigorous bubbling and the fine distribution of the raw materials supplied in the melt, which are caused by the gas blown in at the same time, rapid dissolution of these raw materials is obtained and rapid sinking thereof and the undesired formation of undissolved compact crusts of A1 0 on the bottom and on the walls of the bath are counteracted.
  • a method of operating a furnace for the recovery of aluminium by fusion electrolysis wherein the anode effect is eliminated by piercing the crust on the surface of the electrolyte with at least one mechanically driven tool and supplying gas to the electrolyte through at least one duct located in the piercing tool.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Containers Having Bodies Formed In One Piece (AREA)
US718704A 1967-04-07 1968-04-04 Operation of furnace for the electrolytic fusion recovery of aluminum Expired - Lifetime US3551308A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH499067A CH496100A (de) 1967-04-07 1967-04-07 Verfahren und Vorrichtung zum Betreiben eines Ofens für die schmelzelektrolytische Gewinnung von Aluminium

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AT (1) AT280626B (enrdf_load_html_response)
CH (1) CH496100A (enrdf_load_html_response)
FR (1) FR1562422A (enrdf_load_html_response)
GB (1) GB1164090A (enrdf_load_html_response)
IS (1) IS795B6 (enrdf_load_html_response)
NL (1) NL158855B (enrdf_load_html_response)
NO (1) NO119119B (enrdf_load_html_response)
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3714002A (en) * 1970-09-02 1973-01-30 Reynolds Metals Co Alumina reduction cell and improved anode system therein
US4049529A (en) * 1975-07-10 1977-09-20 Gewerkschaft Eisenhutte Westfalia Apparatus with crust piercing and gas feeding means for use with electrolytic furnaces
US4069115A (en) * 1977-04-27 1978-01-17 Maskin A/S K. Lund & Co. Method and arrangement for removing a gas cushion
US4111764A (en) * 1977-05-17 1978-09-05 Aluminum Company Of America Method for feeding a subliming material into a liquid
US4172018A (en) * 1977-06-28 1979-10-23 Swiss Aluminium Ltd. Process and device for the production of aluminum
US4317595A (en) * 1979-09-10 1982-03-02 Swiss Aluminium Ltd. Chisel for a crust breaking facility
US4328085A (en) * 1979-09-10 1982-05-04 Swiss Aluminium Ltd. Device for servicing electrolytic cells
US4392926A (en) * 1980-05-30 1983-07-12 Showa Aluminum Industries K.K. Process and apparatus for production of aluminum
WO1992006228A1 (en) * 1990-10-04 1992-04-16 Northwest Aluminum Company Continuous ore feeder for soderberg aluminum reduction cells
US5759382A (en) * 1995-09-21 1998-06-02 Canadian Liquid Air Ltd/Air Liquide Canada Ltee Injection of powdered material into electrolysis cells

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2943292A1 (de) * 1979-09-10 1981-03-19 Schweizerische Aluminium AG, 3965 Chippis Meissel fuer eine einschlagvorrichtung

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3714002A (en) * 1970-09-02 1973-01-30 Reynolds Metals Co Alumina reduction cell and improved anode system therein
US4049529A (en) * 1975-07-10 1977-09-20 Gewerkschaft Eisenhutte Westfalia Apparatus with crust piercing and gas feeding means for use with electrolytic furnaces
US4069115A (en) * 1977-04-27 1978-01-17 Maskin A/S K. Lund & Co. Method and arrangement for removing a gas cushion
US4111764A (en) * 1977-05-17 1978-09-05 Aluminum Company Of America Method for feeding a subliming material into a liquid
US4172018A (en) * 1977-06-28 1979-10-23 Swiss Aluminium Ltd. Process and device for the production of aluminum
US4317595A (en) * 1979-09-10 1982-03-02 Swiss Aluminium Ltd. Chisel for a crust breaking facility
US4328085A (en) * 1979-09-10 1982-05-04 Swiss Aluminium Ltd. Device for servicing electrolytic cells
US4380492A (en) * 1979-09-10 1983-04-19 Swiss Aluminium Ltd. Method of using a chisel for a crust breaking facility
US4392926A (en) * 1980-05-30 1983-07-12 Showa Aluminum Industries K.K. Process and apparatus for production of aluminum
WO1992006228A1 (en) * 1990-10-04 1992-04-16 Northwest Aluminum Company Continuous ore feeder for soderberg aluminum reduction cells
US5108557A (en) * 1990-10-04 1992-04-28 Northwest Aluminum Company Ore point feeder and method for soderberg aluminum reduction cells
US5759382A (en) * 1995-09-21 1998-06-02 Canadian Liquid Air Ltd/Air Liquide Canada Ltee Injection of powdered material into electrolysis cells

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AT280626B (de) 1970-04-27
NL6803150A (enrdf_load_html_response) 1968-10-08
GB1164090A (en) 1969-09-10
FR1562422A (enrdf_load_html_response) 1969-04-04
NL158855B (nl) 1978-12-15
CH496100A (de) 1970-09-15
NO119119B (enrdf_load_html_response) 1970-03-23
SE343603B (enrdf_load_html_response) 1972-03-13
IS795B6 (is) 1972-01-21
DE1608232B2 (de) 1976-03-18
IS1727A7 (is) 1968-02-24
DE1608232A1 (de) 1970-12-03

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