WO2004088001A1 - Method and apparatus for dispersing alumina in a molten electrolyte contained in an aluminum reduction cell - Google Patents

Method and apparatus for dispersing alumina in a molten electrolyte contained in an aluminum reduction cell Download PDF

Info

Publication number
WO2004088001A1
WO2004088001A1 PCT/CA2004/000459 CA2004000459W WO2004088001A1 WO 2004088001 A1 WO2004088001 A1 WO 2004088001A1 CA 2004000459 W CA2004000459 W CA 2004000459W WO 2004088001 A1 WO2004088001 A1 WO 2004088001A1
Authority
WO
WIPO (PCT)
Prior art keywords
alumina
molten electrolyte
gas
electrolyte
crust
Prior art date
Application number
PCT/CA2004/000459
Other languages
French (fr)
Inventor
Marcel Collard
Paul Desclaux
Original Assignee
Alcan International Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcan International Limited filed Critical Alcan International Limited
Publication of WO2004088001A1 publication Critical patent/WO2004088001A1/en

Links

Classifications

    • 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
    • C25C3/14—Devices for feeding or crust breaking

Definitions

  • This invention relates to a method and apparatus for supplying and dispersing alumina into the molten electrolyte of a reduction cell used for the production of aluminum.
  • Aluminum is produced on the industrial scale by the electrolytic reduction of alumina dissolved in molten cryolite in the Hall-Heroult process. As the electrolysis proceeds, the concentration of alumina in the electrolyte diminishes and fresh alumina has to be added to the cell from time to time. At the surface of the cell, the electrolyte normally solidifies to form a crust which must be broken to allow the fresh alumina to reach the molten electrolyte. This is usually done by means of a point breaker feeder having a vertically movable chisel made of heat — resistant steel which plunges through the crust and forms a hole of suitable size to receive a charge of alumina powder from an associated feeding apparatus.
  • the incorporation of electrolyte into the alumina and the freezing of the resulting aggregate dilutes the alumina in the fresh charge and thus changes the intended concentration of the alumina in the molten electrolyte since some alumina remains undissolved in the crust; the diminution of the alumina in the electrolyte could lead to an "anode effect", i.e. a shorting of the cell at one or more anodes.
  • large solid aggregates of alumina may fall to the bottom of the cell and may penetrate the metal pad formed at the bottom wall in contact with the cathode, leading to the formation of a sludge beneath the pad and consequently to decreased cell efficiency.
  • a method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises steps of: (a) delivering a predetermined amount of alumina onto a surface of the molten electrolyte through a crust formed on the surface; and (b) directing a stream of gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
  • a method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises steps of: (a) creating a hole in a crust of solidified electrolyte formed on the surface of the molten electrolyte; (b) delivering through the created hole a predetermined amount of alumina into the molten electrolyte; and (c) blowing a compressed gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
  • a method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises steps of: (a) delivering a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte, which is formed on the surface of the molten electrolyte; (b) pushing the delivered alumina into the molten electrolyte while breaking the crust; and (c) blowing a compressed gas to the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the alumina into the molten electrolyte.
  • the compressed gas may be blown at multiple points in such a manner that the blown gas causes a vortex in the molten electrolyte.
  • the compressed gas may be also blown beneath the surface of the molten electrolyte wherein the electrolyte is agitated by bubbling of the blown gas.
  • the compressed gas may be brought into proximity of the reduction cell prior to being blown, thereby to be pre-heated, for example, to 40 to 50 °C.
  • the compressed gas is air or nitrogen.
  • an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises: (a) means for delivering a predetermined amount of alumina onto a surface of the molten electrolyte through a crust formed on the surface; and (b) a gas supplying device for directing a stream of gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
  • an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises: (a) a crust breaker for forming a hole in a crust of solidified electrolyte formed on the surface of the molten electrolyte, the crust breaker being capable of moving into and away from the molten electrolyte; (b) an alumina feeder being adapted to charging a predetermined amount of alumina into the molten electrolyte through the hole formed above; and (c) a gas supplying device for blowing a compressed gas to the charged alumina and the molten electrolyte in such a manner to cause agitation in the molten electrolyte, whereby dispersion and dissolution of the charged alumina into the molten electrolyte is accelerated.
  • the gas supplying device includes a gas nozzle which is adapted to blow the compressed gas to the molten electrolyte.
  • the gas supplying device may include a plurality of gas nozzles arranged to blow the compressed gas in such a manner to cause a vortex in the molten electrolyte, thereby to further accelerate the dispersion and dissolution of the alumina into the molten electrolyte.
  • gas nozzle(s) may be submerged into the molten electrolyte and blow the compressed gas beneath the surface of the molten electrolyte, wherein the electrolyte is agitated by bubbling action of the gas.
  • the gas supply device blows a compressed gas for an appropriate period of time after substantial completion of the dissolution of the alumina, thereby to prevent blocking of the gas supply device by solidified electrolyte.
  • an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises: (a) an alumina feeder for delivering a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte; (b) means for pushing the delivered alumina into the molten electrolyte while breaking the crust; and (c) a gas supplying device for blowing a compressed gas to the molten electrolyte through a gas nozzle in such a manner to cause agitation in the molten electrolyte, whereby dispersion and dissolution of the alumina into the molten electrolyte is accelerated.
  • the pushing means may be submerged into the molten electrolyte to force part of the delivered alumina below the surface of the molten electrolyte.
  • the gas nozzle may be incorporated into the pushing means at the lower area thereof such that the gas nozzle submerges into the molten electrolyte and blow the compressed gas beneath the surface of the molten electrolyte, wherein the electrolyte is agitated by bubbling action of the gas.
  • an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell comprises: (a) an alumina feeder for charging a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte; (b) a crust breaker being adapted to push the charged alumina into the molten electrolyte while breaking the crust, wherein the crust breaker is submerged into the molten electrolyte and part of the charged alumina is forced below the surface of the molten electrolyte; and (c) a gas supplying device for blowing a compressed gas beneath the surface of the molten electrolyte through a gas nozzle, the gas nozzle being provided in the crust breaker at the lowest point thereof, wherein the blown compressed gas causes agitation in the molten electrolyte, whereby dispersion and dissolution of the alumina into the molten electrolyte is accelerated
  • the invention has the advantages, at least in its preferred forms, that (a) better alumina control is obtained due to the similarity between the amount of alumina added to the cell and the amount of alumina dissolved in the electrolyte; (b) better anode effect control as a consequence of (a); (c) less sludge formed under the metal pad; and (d) the ability to operate the cell at a higher alumina concentration than with a conventional alumina feeder system.
  • a further advantage is that alumina in the form of large particles or lumps can be dispersed without difficulty whereas the conventional method often requires the alumina to be ground to a uniform small particle size for rapid dispersion.
  • Fig. 1 is a cross-section of an upper part of an aluminum reduction cell illustrating a first embodiment of the method and apparatus of the present invention
  • Fig. 2 is a cross-section similar to Fig. 1 illustrating a second embodiment of the invention
  • Fig. 3 is a cross-section similar to Fig. 1 illustrating a third embodiment of the invention.
  • Fig. 4 is a top view of a fourth embodiment of the present invention where two gas supply pipes are utilized.
  • FIG. 1 shows an embodiment of the invention which is employed in conjunction with a conventional crust breaker.
  • a hole 10 is formed in crust 11 by an initial use of a crust breaker (not shown) and an alumina feeding device 12 charges particulate alumina 13 into the molten electrolyte 16 through the hole 10 when the concentration of alumina in the electrolyte has fallen below a predetermined level.
  • a gas supply tube 14 includes at its lower end a gas nozzle 15 sized, positioned and dimensioned to direct a jet of gas (or a compressed gas) onto the alumina 13 fed above or the adjacent area surrounding the alumina 13.
  • the alumina feeding device used in the present invention may be any conventional feeder. If desired, the feeder shown in United States Patent No. 4,435,255 issued to Aluminium de Greece on March 6, 1984 may be employed.
  • the gas nozzle 15 may be a shaped structure or merely an open end of the gas supply tube 14.
  • the gas supply tube 14 has a control valve 17 by means of which the supply of gas can be turned on or off.
  • the gas supply tube 14 is connected to a supply of compressed gas 14a such as a pressurized chamber or a compressor.
  • the valve 17 is operated so that a jet of gas is directed into the delivered alumina 13 and the molten electrolyte 16 to agitate the electrolyte to cause the alumina 13 to disperse and dissolve more efficiently in the molten electrolyte 16.
  • the valve 17 may be operated to turn off the flow of gas.
  • Fig. 3 shows an alternative operation of the embodiment of Fig. 1.
  • the gas supply pipe 15, that is, the gas nozzle 15 is submerged into the molten electrolyte 16 after the delivery of alumina and blow a compressed gas beneath the surface of the electrolyte such that a bubbling action can be generated by the gas to produce agitation of the molten electrolyte and assist in the dispersion and dissolution of the delivered alumina 13 into the molten electrolyte 16.
  • the molten electrolyte 16 may be agitated by directing the compressed gas onto the delivered alumina 13 or the surface of the molten electrolyte 16 from above or by bubbling the gas beneath the surface of the molten electrolyte 16 (see Fig. 3), or possibly by using a combination of both these methods.
  • the gas jet should be strong enough to cause enough stirring of the electrolyte at the surface that any crust which forms from the aluminum charge 13 is dispersed into the molten electrolyte 16.
  • the agitation of the electrolyte should be great enough to cause an appreciable increase in the rate of dispersion or dissolution of the alumina in the molten electrolyte 16, but not so great as to produce splashing of the electrolyte, undue dust formation or other disadvantages.
  • the flow of gas may be confined to the area of the delivered alumina so that localized agitation of the electrolyte in the region of the alumina addition takes place.
  • the type of agitation produced by the gas may include merely forcing the alumina below the surface of the molten electrolyte as well as a stirring, mixing or bubbling action.
  • the agitation should be
  • the flow of gas is commenced after the delivery of the alumina (to reduce dust formation) and continues until the alumina has been fully dispersed.
  • the gas may continue to be delivered after the dispersion of the alumina, if desired, for example to prevent blocking of
  • Fig. 2 shows another embodiment of the invention.
  • a chisel 18 attached to the end of a shaft 19 is capable of being moved up or down to break a hole 10 in the crust 11 when alumina is to be charged to the electrolyte 16.
  • the chisel 18 incorporates a gas nozzle
  • the chisel 18 is preferably first operated to break the crust 11 and is then raised to clear the resulting hole, while blowing the compressed gas in order to prevent the gas nozzle 15 from blocking by a solidified electrolyte. A predetermined amount of alumina is then delivered to the surface of the molten electrolyte 16 from alumina feeding
  • a gas supply tube 14 has a lower end terminating in a gas nozzle 15 positioned at the lowermost point of the chisel 18 and an upper end
  • control valve 17 When the chisel is in its lowermost position or it starts to be lowered, the control valve 17 is operated to turn on the gas flow so that gas bubbles from the nozzle 15 into the molten electrolyte 16 in the region of the delivered alumina 13, thus stirring the
  • Fig. 2 not only disperses the alumina by gas agitation but also forces some of the alumina below the surface of the electrolyte by mechanical action of the chisel.
  • the chisel is then preferably raised to the uppermost position until it is again required for use.
  • the gas flow is preferably maintained until the chisel is fully raised and all electrolyte has been cleared from the gas supply tube 14 and the nozzle 15 in order to prevent blockage of the tube as the electrolyte freezes.
  • the crust breaker used to form a hole in the crust may be any conventional device, such as the chisel in Fig. 2, and the supply means (pipe) for the delivery of the gas may be incorporated into the chisel (such as a crust breaker) or may be independent of it, as illustrated in Figs. 1 and 2 respectively.
  • the alumina 13 may be delivered into a selected area (corresponding to the reference numeral 10) on the crust 11 by means of the feeding device 12, and then the chisel 18 or a conventional crust breaker (not shown in Fig. 1 ) may be operated to push the delivered alumina 13 into the molten electrolyte 16 while breaking the crust 11.
  • the chisel 13 or the crust breaker may be lowered enough to force some of the alumina below the surface of the molten electrolyte 16, and the gas supply tube 14 and the gas nozzle 15 may be operated in the same manner as discussed above or below.
  • Fig. 4 schematically illustrates another embodiment of the invention, where two gas supply pipes 15 are utilized, each pipe having a gas nozzle 15.
  • the gas supply pipes 14 are positioned and angled in such a manner to produce a vortex or circulation at the molten electrolyte 16 to aid the dispersion and dissolution of the alumina 13.
  • the compressed gas may be blown onto the delivered alumina 13 or areas near thereto to generate a vortex or circulation of the molten electrolyte.
  • the gas supply pipes 14, i.e., the gas nozzles 15 may be submerged into the molten electrolyte 16 and blow a compressed gas beneath the surface of the electrolyte to generate a vortex of the electrolyte, together with a bubbling action, thereby to more effectively accelerate the dispersion and dissolution of the delivered alumina 13 into the molten electrolyte. While two gas supply pipe are illustrated in Fig. 4, more than two gas supply pipes may be employed, when required or desired.
  • the crust breaker may be operated to maintain a hole in the crust between alumina charges so that it does not become necessary to break through a thick section of crust before supplying the alumina.
  • any suitable gas may be used to create the necessary agitation provided it does not cause adverse effects on the alumina or the electrolyte nor result in environmental pollution.
  • Air is the preferred gas because of its cheapness and availability, but other gases such as nitrogen can be used.
  • the gas is normally used at ambient temperature but may become heated to 40-50°C prior to its delivery due to its passage through a delivery system which becomes warm as a result of its proximity to the hot cell.
  • the gas utilized in the present invention can be supplied under pressure from any suitable source, e.g. from a compressor or from a pressurized container.
  • the gas can be directed to the outlet jet, nozzle or orifice by suitable tubing, which may be flexible if the outlet jet, nozzle or orifice is movable with the crust breaker.

Abstract

The invention provides a method and apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The apparatus comprises: (a) an alumina feeder (12) for charging a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte (11); (b) a crust breaker (18, 19) being adapted to push the charged alumina into the molten electrolyte while breaking the crust; and (c) a gas supplying device (14) for blowing a compressed gas beneath the surface of the molten electrolyte through a gas nozzle (15) such that the blown compressed gas causes agitation in the molten electrolyte to accelerate dispersion and dissolution of the alumina into the molten electrolyte. The gas nozzle is preferably provided in the crust breaker at the lowest point thereof.

Description

Method And Apparatus For Dispersing Alumina In A Molten Electrolyte Contained In An Aluminum Reduction Cell
TECHNICAL FIELD
This invention relates to a method and apparatus for supplying and dispersing alumina into the molten electrolyte of a reduction cell used for the production of aluminum.
BACKGROUND ART
Aluminum is produced on the industrial scale by the electrolytic reduction of alumina dissolved in molten cryolite in the Hall-Heroult process. As the electrolysis proceeds, the concentration of alumina in the electrolyte diminishes and fresh alumina has to be added to the cell from time to time. At the surface of the cell, the electrolyte normally solidifies to form a crust which must be broken to allow the fresh alumina to reach the molten electrolyte. This is usually done by means of a point breaker feeder having a vertically movable chisel made of heat — resistant steel which plunges through the crust and forms a hole of suitable size to receive a charge of alumina powder from an associated feeding apparatus.
The added alumina gradually sinks into the molten electrolyte and eventually becomes evenly distributed throughout the melt. However, since the charge of alumina sinks into the electrolyte very slowly, it tends itself to form a crust incorporating solidified electrolyte and this leads to several disadvantages. Firstly, the formation of solidified alumina aggregates greatly reduces the rate of dissolution of the alumina in the electrolyte. Secondly, the incorporation of electrolyte into the alumina and the freezing of the resulting aggregate dilutes the alumina in the fresh charge and thus changes the intended concentration of the alumina in the molten electrolyte since some alumina remains undissolved in the crust; the diminution of the alumina in the electrolyte could lead to an "anode effect", i.e. a shorting of the cell at one or more anodes. Thirdly, large solid aggregates of alumina may fall to the bottom of the cell and may penetrate the metal pad formed at the bottom wall in contact with the cathode, leading to the formation of a sludge beneath the pad and consequently to decreased cell efficiency.
There is accordingly a need for a more efficient way of adding alumina to and distributing alumina throughout the electrolyte of a cell and it is an object of the present invention to satisfy this need.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention, there is provided a method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The method comprises steps of: (a) delivering a predetermined amount of alumina onto a surface of the molten electrolyte through a crust formed on the surface; and (b) directing a stream of gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
According to another aspect of the present invention, there is provided a method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The method comprises steps of: (a) creating a hole in a crust of solidified electrolyte formed on the surface of the molten electrolyte; (b) delivering through the created hole a predetermined amount of alumina into the molten electrolyte; and (c) blowing a compressed gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
According to another aspect of the present invention, there is provided a method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The method comprises steps of: (a) delivering a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte, which is formed on the surface of the molten electrolyte; (b) pushing the delivered alumina into the molten electrolyte while breaking the crust; and (c) blowing a compressed gas to the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the alumina into the molten electrolyte.
The compressed gas may be blown at multiple points in such a manner that the blown gas causes a vortex in the molten electrolyte. The compressed gas may be also blown beneath the surface of the molten electrolyte wherein the electrolyte is agitated by bubbling of the blown gas.
Further, the compressed gas may be brought into proximity of the reduction cell prior to being blown, thereby to be pre-heated, for example, to 40 to 50 °C. The compressed gas is air or nitrogen.
According to another aspect of the present invention, there is provided an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The apparatus comprises: (a) means for delivering a predetermined amount of alumina onto a surface of the molten electrolyte through a crust formed on the surface; and (b) a gas supplying device for directing a stream of gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
According to another aspect of the present invention, there is provided an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The apparatus comprises: (a) a crust breaker for forming a hole in a crust of solidified electrolyte formed on the surface of the molten electrolyte, the crust breaker being capable of moving into and away from the molten electrolyte; (b) an alumina feeder being adapted to charging a predetermined amount of alumina into the molten electrolyte through the hole formed above; and (c) a gas supplying device for blowing a compressed gas to the charged alumina and the molten electrolyte in such a manner to cause agitation in the molten electrolyte, whereby dispersion and dissolution of the charged alumina into the molten electrolyte is accelerated.
The gas supplying device includes a gas nozzle which is adapted to blow the compressed gas to the molten electrolyte. The gas supplying device may include a plurality of gas nozzles arranged to blow the compressed gas in such a manner to cause a vortex in the molten electrolyte, thereby to further accelerate the dispersion and dissolution of the alumina into the molten electrolyte.
Further, the gas nozzle(s) may be submerged into the molten electrolyte and blow the compressed gas beneath the surface of the molten electrolyte, wherein the electrolyte is agitated by bubbling action of the gas.
In operation, the gas supply device blows a compressed gas for an appropriate period of time after substantial completion of the dissolution of the alumina, thereby to prevent blocking of the gas supply device by solidified electrolyte.
According to another aspect of the present invention, there is provided an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The apparatus comprises: (a) an alumina feeder for delivering a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte; (b) means for pushing the delivered alumina into the molten electrolyte while breaking the crust; and (c) a gas supplying device for blowing a compressed gas to the molten electrolyte through a gas nozzle in such a manner to cause agitation in the molten electrolyte, whereby dispersion and dissolution of the alumina into the molten electrolyte is accelerated.
The pushing means may be submerged into the molten electrolyte to force part of the delivered alumina below the surface of the molten electrolyte. The gas nozzle may be incorporated into the pushing means at the lower area thereof such that the gas nozzle submerges into the molten electrolyte and blow the compressed gas beneath the surface of the molten electrolyte, wherein the electrolyte is agitated by bubbling action of the gas.
According to another aspect of the present invention, there is provided an apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell. The apparatus comprises: (a) an alumina feeder for charging a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte; (b) a crust breaker being adapted to push the charged alumina into the molten electrolyte while breaking the crust, wherein the crust breaker is submerged into the molten electrolyte and part of the charged alumina is forced below the surface of the molten electrolyte; and (c) a gas supplying device for blowing a compressed gas beneath the surface of the molten electrolyte through a gas nozzle, the gas nozzle being provided in the crust breaker at the lowest point thereof, wherein the blown compressed gas causes agitation in the molten electrolyte, whereby dispersion and dissolution of the alumina into the molten electrolyte is accelerated.
The invention has the advantages, at least in its preferred forms, that (a) better alumina control is obtained due to the similarity between the amount of alumina added to the cell and the amount of alumina dissolved in the electrolyte; (b) better anode effect control as a consequence of (a); (c) less sludge formed under the metal pad; and (d) the ability to operate the cell at a higher alumina concentration than with a conventional alumina feeder system. A further advantage is that alumina in the form of large particles or lumps can be dispersed without difficulty whereas the conventional method often requires the alumina to be ground to a uniform small particle size for rapid dispersion.
A further understanding, aspects and advantages of the present invention will be realized by reference to the following description, appended claims and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in more detail below with reference to the accompanying drawings, in which:
Fig. 1 is a cross-section of an upper part of an aluminum reduction cell illustrating a first embodiment of the method and apparatus of the present invention; and
Fig. 2 is a cross-section similar to Fig. 1 illustrating a second embodiment of the invention;
Fig. 3 is a cross-section similar to Fig. 1 illustrating a third embodiment of the invention; and
Fig. 4 is a top view of a fourth embodiment of the present invention where two gas supply pipes are utilized.
BEST MODES FOR CARRYING OUT THE INVENTION
Fig. 1 shows an embodiment of the invention which is employed in conjunction with a conventional crust breaker. A hole 10 is formed in crust 11 by an initial use of a crust breaker (not shown) and an alumina feeding device 12 charges particulate alumina 13 into the molten electrolyte 16 through the hole 10 when the concentration of alumina in the electrolyte has fallen below a predetermined level. A gas supply tube 14 includes at its lower end a gas nozzle 15 sized, positioned and dimensioned to direct a jet of gas (or a compressed gas) onto the alumina 13 fed above or the adjacent area surrounding the alumina 13.
The alumina feeding device used in the present invention may be any conventional feeder. If desired, the feeder shown in United States Patent No. 4,435,255 issued to Aluminium de Greece on March 6, 1984 may be employed.
The gas nozzle 15 may be a shaped structure or merely an open end of the gas supply tube 14. The gas supply tube 14 has a control valve 17 by means of which the supply of gas can be turned on or off. The gas supply tube 14 is connected to a supply of compressed gas 14a such as a pressurized chamber or a compressor. After a charge of alumina 13 has been delivered to the surface of the electrolyte 16 through the hole 10 formed in the crust 11 , the valve 17 is operated so that a jet of gas is directed into the delivered alumina 13 and the molten electrolyte 16 to agitate the electrolyte to cause the alumina 13 to disperse and dissolve more efficiently in the molten electrolyte 16. After the alumina has been dispersed in this way, the valve 17 may be operated to turn off the flow of gas.
Fig. 3 shows an alternative operation of the embodiment of Fig. 1. In Fig. 3, the gas supply pipe 15, that is, the gas nozzle 15 is submerged into the molten electrolyte 16 after the delivery of alumina and blow a compressed gas beneath the surface of the electrolyte such that a bubbling action can be generated by the gas to produce agitation of the molten electrolyte and assist in the dispersion and dissolution of the delivered alumina 13 into the molten electrolyte 16.
As described above, the molten electrolyte 16 may be agitated by directing the compressed gas onto the delivered alumina 13 or the surface of the molten electrolyte 16 from above or by bubbling the gas beneath the surface of the molten electrolyte 16 (see Fig. 3), or possibly by using a combination of both these methods. In any event, the gas jet should be strong enough to cause enough stirring of the electrolyte at the surface that any crust which forms from the aluminum charge 13 is dispersed into the molten electrolyte 16. In other words, the agitation of the electrolyte should be great enough to cause an appreciable increase in the rate of dispersion or dissolution of the alumina in the molten electrolyte 16, but not so great as to produce splashing of the electrolyte, undue dust formation or other disadvantages.
The flow of gas may be confined to the area of the delivered alumina so that localized agitation of the electrolyte in the region of the alumina addition takes place. The type of agitation produced by the gas may include merely forcing the alumina below the surface of the molten electrolyte as well as a stirring, mixing or bubbling action. Preferably, the agitation should be
5 sufficient to prevent substantial caking (crust formation) of the alumina before it disperses in the molten electrolyte. The flow of gas is commenced after the delivery of the alumina (to reduce dust formation) and continues until the alumina has been fully dispersed. The gas may continue to be delivered after the dispersion of the alumina, if desired, for example to prevent blocking of
10 the gas jets or nozzles by frozen electrolyte.
Fig. 2 shows another embodiment of the invention. In this embodiment, a chisel 18 attached to the end of a shaft 19 is capable of being moved up or down to break a hole 10 in the crust 11 when alumina is to be charged to the electrolyte 16. As depicted in Fig. 2, the chisel 18 incorporates a gas nozzle
15 15 at the lowest point of the chisel 18. The chisel 18 is preferably first operated to break the crust 11 and is then raised to clear the resulting hole, while blowing the compressed gas in order to prevent the gas nozzle 15 from blocking by a solidified electrolyte. A predetermined amount of alumina is then delivered to the surface of the molten electrolyte 16 from alumina feeding
20 device 12. The chisel 18 is then lowered again to the extent that the lower end of the chisel projects below the surface of the molten electrolyte 16 and this pushes some of the delivered alumina into the electrolyte to help to disperse it. A gas supply tube 14 has a lower end terminating in a gas nozzle 15 positioned at the lowermost point of the chisel 18 and an upper end
25 connected by means of a flexible hose (shown in broken lines) to a source of compressed gas 14a via a control valve 17. When the chisel is in its lowermost position or it starts to be lowered, the control valve 17 is operated to turn on the gas flow so that gas bubbles from the nozzle 15 into the molten electrolyte 16 in the region of the delivered alumina 13, thus stirring the
30 electrolyte and quickly dispersing the alumina. Advantageously, the embodiment of Fig. 2 not only disperses the alumina by gas agitation but also forces some of the alumina below the surface of the electrolyte by mechanical action of the chisel.
After the alumina has been dispersed in this way, the chisel is then preferably raised to the uppermost position until it is again required for use. The gas flow is preferably maintained until the chisel is fully raised and all electrolyte has been cleared from the gas supply tube 14 and the nozzle 15 in order to prevent blockage of the tube as the electrolyte freezes.
According to the present invention, the crust breaker used to form a hole in the crust may be any conventional device, such as the chisel in Fig. 2, and the supply means (pipe) for the delivery of the gas may be incorporated into the chisel (such as a crust breaker) or may be independent of it, as illustrated in Figs. 1 and 2 respectively.
In an alternative operation of the embodiments of Figs. 1 and 2, the alumina 13 may be delivered into a selected area (corresponding to the reference numeral 10) on the crust 11 by means of the feeding device 12, and then the chisel 18 or a conventional crust breaker (not shown in Fig. 1 ) may be operated to push the delivered alumina 13 into the molten electrolyte 16 while breaking the crust 11. Similarly, the chisel 13 or the crust breaker may be lowered enough to force some of the alumina below the surface of the molten electrolyte 16, and the gas supply tube 14 and the gas nozzle 15 may be operated in the same manner as discussed above or below.
Fig. 4 schematically illustrates another embodiment of the invention, where two gas supply pipes 15 are utilized, each pipe having a gas nozzle 15. As shown in Fig. 4, the gas supply pipes 14 are positioned and angled in such a manner to produce a vortex or circulation at the molten electrolyte 16 to aid the dispersion and dissolution of the alumina 13. According to the present invention, the compressed gas may be blown onto the delivered alumina 13 or areas near thereto to generate a vortex or circulation of the molten electrolyte. Alternatively, the gas supply pipes 14, i.e., the gas nozzles 15 may be submerged into the molten electrolyte 16 and blow a compressed gas beneath the surface of the electrolyte to generate a vortex of the electrolyte, together with a bubbling action, thereby to more effectively accelerate the dispersion and dissolution of the delivered alumina 13 into the molten electrolyte. While two gas supply pipe are illustrated in Fig. 4, more than two gas supply pipes may be employed, when required or desired.
If desired, the crust breaker may be operated to maintain a hole in the crust between alumina charges so that it does not become necessary to break through a thick section of crust before supplying the alumina.
According to the invention, in the embodiments discussed above, any suitable gas may be used to create the necessary agitation provided it does not cause adverse effects on the alumina or the electrolyte nor result in environmental pollution. Air is the preferred gas because of its cheapness and availability, but other gases such as nitrogen can be used. The gas is normally used at ambient temperature but may become heated to 40-50°C prior to its delivery due to its passage through a delivery system which becomes warm as a result of its proximity to the hot cell.
As noted above, the gas utilized in the present invention can be supplied under pressure from any suitable source, e.g. from a compressor or from a pressurized container. The gas can be directed to the outlet jet, nozzle or orifice by suitable tubing, which may be flexible if the outlet jet, nozzle or orifice is movable with the crust breaker.
While the present invention has been described with reference to several preferred embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and variations may occur to those skilled in the art, without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS:
1. A method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the method comprising steps of: (a) delivering a predetermined amount of alumina onto a surface of the molten electrolyte through a crust formed on the surface; and (b) directing a stream of gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
2. A method according to claim 1 , wherein the step of delivering includes steps of: (a) creating an opening in the crust; and (b) charging through the opening the predetermined amount of alumina into the molten electrolyte.
3. A method according to claim 1 , wherein the step of delivering includes steps of: (a) charging the pre-determined amount of alumina into a pre-selected area on the crust; and (b) pushing the charged alumina into the molten electrolyte while breaking the crust.
4. The method according to claim 3, wherein, in the step of pushing, part of the alumina is pushed below the surface of the molten electrolyte.
5. The method according to anyone of claims 1 to 4, wherein the gas is directed to multiple points in such a manner that the gas causes a vortex in the molten electrolyte.
6. The method according to anyone of claims 1 to 5, wherein the gas is directed beneath the surface of the molten electrolyte whereby the electrolyte is agitated by bubbling of the gas.
7. A method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the method comprising steps of: (a) creating a hole in a crust of solidified electrolyte formed on the surface of the molten electrolyte; (b) delivering through the created hole a predetermined amount of alumina into the molten electrolyte; and (c) blowing a compressed gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
8. The method according to claim 7, wherein the compressed gas is blown at multiple points in such a manner that the blown gas causes a vortex in the molten electrolyte.
9. The method according to claim 7 or 8, wherein the compressed gas is blown beneath the surface of the molten electrolyte whereby the electrolyte is agitated by bubbling of the blown gas.
10. The method according to claim 7, wherein the compressed gas is brought into proximity of the reduction cell prior to being blown.
11. The method according to claim 10, wherein the compressed gas is pre-heated to 40 to 50 °C.
12. The method according to claim 7, wherein the compressed gas includes air or nitrogen.
13. A method of supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the method comprising steps of: (a) delivering a predetermined amount of alumina into a pre-selected area on a crust of solidified electrolyte, which is formed on the surface of the molten electrolyte; (b) pushing the delivered alumina into the molten electrolyte while breaking the crust; and (c) blowing a compressed gas to the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the alumina into the molten electrolyte.
14. The method according to claim 13, wherein, in the step (b), part of the delivered alumina is pushed below the surface of the molten electrolyte.
15. The method according to claim 13, wherein the compressed gas is blown at multiple points in such a manner that the blown gas causes a vortex in the molten electrolyte.
16. The method according to claim 13 or 15, wherein the compressed gas is blown beneath the surface of the molten electrolyte whereby the electrolyte is agitated by bubbling of the blown gas.
17. The method according to claim 13, wherein the compressed gas is brought into proximity of the reduction cell prior to being blown.
18. The method according to claim 13, wherein the compressed gas is pre-heated to 40 to 50 °C.
19. The method according to claim 13, wherein the compressed gas includes air or nitrogen.
20. An apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the apparatus comprising: (a) means for delivering a predetermined amount of alumina onto a surface of the molten electrolyte through a crust formed on the surface; and (b) a gas supplying device for directing a stream of gas to the delivered alumina and the molten electrolyte such that the gas agitates the molten electrolyte, whereby the agitation of the electrolyte accelerates dispersion and dissolution of the delivered alumina into the molten electrolyte.
21. The apparatus according to claim 20, wherein the means for delivering includes (a) a crust breaker for creating an opening in the crust; and (b) an alumina feeding device for charging through the opening the predetermined amount of alumina into the molten electrolyte.
22. The apparatus according to claim 20, wherein the means for delivering includes (a) an alumina feeding device for charging the predetermined amount of alumina into a pre-selected area on the crust; and (b) means for pushing the charged alumina into the molten electrolyte while breaking the crust.
23. The apparatus according to claim 22, wherein the means for pushing is adapted to force part of the alumina below the surface of the molten electrolyte.
24. The apparatus according to anyone of claims 20 to 23, wherein the gas supplying device is adapted to blow the gas at multiple points in such a manner that the gas causes a vortex in the molten electrolyte.
25. The apparatus according to anyone of claims 20 to 24, wherein the gas supplying device is adapted to direct the gas beneath the surface of the molten electrolyte whereby the electrolyte is agitated by bubbling of the gas.
26. An apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the apparatus comprising: (a) a crust breaker for forming a hole in a crust of solidified electrolyte formed on the surface of the molten electrolyte, the crust breaker being capable of moving into and away from the molten electrolyte; (b) an alumina feeder being adapted to charging a predetermined amount of alumina into the molten electrolyte through the hole formed above; and (c) a gas supplying device for blowing a compressed gas to the charged alumina and the molten electrolyte in such a manner to cause agitation in the molten electrolyte, whereby dispersion and dissolution of the charged alumina into the molten electrolyte is accelerated.
27. The apparatus according to claim 26, wherein the gas supplying device includes a gas nozzle which is adapted to blow the compressed gas to the molten electrolyte.
28. The apparatus according to claim 26, wherein the gas supplying device includes a plurality of gas nozzles, the gas nozzles being arranged to blow the compressed gas in such a manner to cause a vortex in the molten electrolyte, thereby to further accelerate the dispersion and dissolution of the alumina into the molten electrolyte.
29. The apparatus according to claim 26, wherein the gas supplying device includes a gas nozzle being adapted to submerge into the molten electrolyte and blow the compressed gas beneath the surface of the molten electrolyte, wherein the electrolyte is agitated by bubbling action of the gas.
30. The apparatus according to claim 26, wherein, in operation, the gas supply device is adapted to blow a compressed gas for an appropriate period of time after substantial completion of the dissolution of the alumina, thereby to prevent blocking of the gas supply device by solidified electrolyte.
31. The apparatus according to claim 26, wherein the crust breaker incorporates a gas nozzle provided in the gas supply device.
32. An apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the apparatus comprising: (a) an alumina feeder for delivering a predetermined amount of alumina into a preselected area on a crust of solidified electrolyte; (b) means for pushing the delivered alumina into the molten electrolyte while breaking the crust; and (c) a gas supplying device for blowing a compressed gas to the molten electrolyte through a gas nozzle in such a manner to cause agitation in the molten electrolyte, whereby dispersion and dissolution of the alumina into the molten electrolyte is accelerated.
33. The apparatus according to claim 32, wherein the pushing means is adapted to be submerged into the molten electrolyte to force part of the delivered alumina below the surface of the molten electrolyte.
34. The apparatus according to claim 32, wherein the gas nozzle is incorporated into the pushing means at the lower area thereof such that the gas nozzle submerges into the molten electrolyte and blow the compressed gas beneath the surface of the molten electrolyte, wherein the electrolyte is agitated by bubbling action of the gas.
35. The apparatus according to claim 32, wherein the gas supply device is operated to blow a compressed gas for an appropriate period of time after substantial completion of the dissolution of the alumina, thereby to prevent blocking of the gas nozzle by solidified electrolyte.
36. An apparatus for supplying and dispersing alumina into a molten electrolyte in an aluminum reduction cell, the apparatus comprising: (a) an alumina feeder for charging a predetermined amount of alumina into a preselected area on a crust of solidified electrolyte; (b) a crust breaker being adapted to push the charged alumina into the molten electrolyte while breaking the crust, wherein the crust breaker is submerged into the molten electrolyte and part of the charged alumina is forced below the surface of the molten electrolyte; and (c) a gas supplying device for blowing a compressed gas beneath the surface of the molten electrolyte through a gas nozzle, the gas nozzle being provided in the crust breaker at the lowest point thereof, wherein the blown compressed gas causes agitation in the molten electrolyte, whereby dispersion and dissolution of the alumina into the molten electrolyte is accelerated.
PCT/CA2004/000459 2003-04-03 2004-03-26 Method and apparatus for dispersing alumina in a molten electrolyte contained in an aluminum reduction cell WO2004088001A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA2,424,388 2003-04-03
CA 2424388 CA2424388A1 (en) 2003-04-03 2003-04-03 Method and apparatus for dispersing alumina in a molten electrolyte contained in an aluminum reduction cell

Publications (1)

Publication Number Publication Date
WO2004088001A1 true WO2004088001A1 (en) 2004-10-14

Family

ID=33035000

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA2004/000459 WO2004088001A1 (en) 2003-04-03 2004-03-26 Method and apparatus for dispersing alumina in a molten electrolyte contained in an aluminum reduction cell

Country Status (2)

Country Link
CA (1) CA2424388A1 (en)
WO (1) WO2004088001A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013075376A1 (en) * 2011-11-22 2013-05-30 中国铝业股份有限公司 Method and system for inhibiting perfluorocarbon formation in aluminum electrolysis cell due to non-anode effect
CN110496828A (en) * 2019-09-06 2019-11-26 中冶赛迪重庆信息技术有限公司 Using cold and hot deformation difference from broken shell descaling method, device and crust-breaking chips
CN114703510A (en) * 2022-04-08 2022-07-05 遵义铝业股份有限公司 Method and device for cooling striking hammer head

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102409357B (en) * 2011-12-20 2014-02-19 登封电厂集团铝合金有限公司 Hyperconcentrated phase conveyer device
CN107497793B (en) * 2017-09-30 2024-03-12 中冶赛迪技术研究中心有限公司 Ultrasonic vibration cleaning device and method for aluminum groove crust-breaking hammer

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4049529A (en) * 1975-07-10 1977-09-20 Gewerkschaft Eisenhutte Westfalia Apparatus with crust piercing and gas feeding means for use with electrolytic furnaces
US5759382A (en) * 1995-09-21 1998-06-02 Canadian Liquid Air Ltd/Air Liquide Canada Ltee Injection of powdered material into electrolysis cells

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4049529A (en) * 1975-07-10 1977-09-20 Gewerkschaft Eisenhutte Westfalia Apparatus with crust piercing and gas feeding means for use with electrolytic furnaces
US5759382A (en) * 1995-09-21 1998-06-02 Canadian Liquid Air Ltd/Air Liquide Canada Ltee Injection of powdered material into electrolysis cells

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013075376A1 (en) * 2011-11-22 2013-05-30 中国铝业股份有限公司 Method and system for inhibiting perfluorocarbon formation in aluminum electrolysis cell due to non-anode effect
CN110496828A (en) * 2019-09-06 2019-11-26 中冶赛迪重庆信息技术有限公司 Using cold and hot deformation difference from broken shell descaling method, device and crust-breaking chips
CN110496828B (en) * 2019-09-06 2023-08-15 中冶赛迪信息技术(重庆)有限公司 Method and device for removing scale by utilizing cold and hot deformation variation and crust breaking hammer
CN114703510A (en) * 2022-04-08 2022-07-05 遵义铝业股份有限公司 Method and device for cooling striking hammer head

Also Published As

Publication number Publication date
CA2424388A1 (en) 2004-10-03

Similar Documents

Publication Publication Date Title
JP4550977B2 (en) Direct smelting method
CA2121215C (en) Injection equipment
KR20110030632A (en) Method and device for output of granulate from the bottom of a tank that in addition to granulate holds liquid
AU654307B2 (en) Jet flow device for injecting gas into molten metal
JP2001192717A (en) Stable stop operation in method for manufacturing molten metal
JP2001192717A5 (en)
WO2004088001A1 (en) Method and apparatus for dispersing alumina in a molten electrolyte contained in an aluminum reduction cell
JP2005068506A (en) Desulfurization method and equipment for molten iron
WO2002022900A2 (en) Process and rotary device for adding particulate solid material and gas to molten metal bath
AU2001293540A1 (en) Process and rotary device for adding particulate solid material and gas to molten metal bath
US20070138714A1 (en) Device for melting down metal-containing material
US1422135A (en) Method of manufacturing calcium carbide
JPWO2013046854A1 (en) Blasting apparatus and blasting method
CN113941399B (en) Sintered ore crushing and collecting device
BG103935A (en) Device and method for water granulation with rock or slag
AU711027B2 (en) Injection of alumina into soderberg cells
CN219837178U (en) Granulating system for metals and alloys
US3396494A (en) Removal of protrusions formed on carbon anodes
KR20140064714A (en) Direct smelting process
JP2002146412A (en) Trough for molten slag
KR102224147B1 (en) device for discharging water-granulated slag using a water wheel
WO2001026793A1 (en) Method for separation of a molten mixture
JP3630051B2 (en) Method and equipment for producing granulated slag
WO2008019226A1 (en) Coal reclamation apparatus and method
GB1578570A (en) Stirrer for metallurgical melts

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NA NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): BW GH GM KE LS MW MZ SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LU MC NL PL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DPEN Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed from 20040101)
122 Ep: pct application non-entry in european phase