CA2138001A1 - Method and device for replacing anodes in a dry method aluminum electrolysis process involving heat recovery - Google Patents
Method and device for replacing anodes in a dry method aluminum electrolysis process involving heat recoveryInfo
- Publication number
- CA2138001A1 CA2138001A1 CA002138001A CA2138001A CA2138001A1 CA 2138001 A1 CA2138001 A1 CA 2138001A1 CA 002138001 A CA002138001 A CA 002138001A CA 2138001 A CA2138001 A CA 2138001A CA 2138001 A1 CA2138001 A1 CA 2138001A1
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- Canada
- Prior art keywords
- anodes
- residual
- accordance
- molten bath
- anode rods
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
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Classifications
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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
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
- C25C3/12—Anodes
- C25C3/125—Anodes based on carbon
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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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces
- F27B3/08—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces heated electrically, with or without any other source of heat
- F27B3/085—Arc furnaces
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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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)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
The invention relates to a method and to a device suitable for use in the replacement of anodes in a dry-method aluminum electrolysis process involving heat recovery. New carbon anodes, which are arranged on the anode rods, can be preheated by utilizing the residual heat of the residual anodes that have been removed from the molten bath and/or the hot bath material that has been taken from the molten bath and subsequently preheated and transferred to the molten bath.
Heat is recovered and exchanged with the aid of a heat exchanger which may be a multi-chamber system.
Heat is recovered and exchanged with the aid of a heat exchanger which may be a multi-chamber system.
Description
2~3800~
Method and Device for Replacing Anodes in a Dry Method Aluminum Electrolysis Process Involvinq Heat Recovery This invention relates to a method and apparatus for replacing anodes.
More particularly, one aspect of this invention relates to a method for replacing carbon anodes arranged on anode rods in a dry method aluminum electrolysis process, during which heat is recovered. According to another aspect of this invention, there is provided an apparatus suitable for carrying out the above method.
During the dry electrolysis of aluminum, carbon anodes (anode blocks), which are arranged on anode rods, are consumed to a considerable extent during the electrolysis. This necessitates periodic replacement of the carbon anodes. The used or residual anodes, as they are commonly referred to, are caked with a mixture of aluminum oxide and electrolyte. They exhibit extremely high temperatures when removed from the molten bath of the electrolytic cell, and produce heavy emissions of toxic substances, particularly fluorine gases.
The hot, residual anodes, after being removed from the electrolytic cell, are generally taken to distant processing locations where the above-mentioned baked-on materials are removed; thereafter the residual anodes are scraped in order to recover valuable carbon material from the nipples of the anode rods. Following additional processing, the latter are fitted with new carbon anodes (if required).
When the anodes are exchanged, not only are the residual anodes removed, but spent bath material is also removed from the electrolytic cell. The quantity of bath material removed from the latter for each residual anode, corresponds minimally to the quantity of baked-on bath material; the latter, during the burning process, accumulates on top of the carbon anode. When the spent bath material is removed, electrolyte (which is still 2~3800~
partially in liquid form) is also removed from the bath. The emissions produced by this method are considerable.
The carbon anodes employed in the dry method electrolysis process are manufactured conventionally from green artificial carbon bodies which must subsequently be burned at a high temperature inside a furnace. DE-OS 35 38 151 discloses a procedure in which green carbon anodes are preheated by using the heat recovered during the subsequent cooling of the consumed carbon anodes, following which such green carbon anodes are burned by means of induction. The new carbon anodes produced after cooling are fitted with anode rods and then tranferred to the electrolytic cell to replace the consumed anodes.
One object of the present invention is to provide an improved method and apparatus in which heat, which is advantageous for further processing, can be recovered during anode replacement and, during which, the emission of toxic substances can simultaneously be suppressed to a large extent.
The method of the present invention involves the arrangement of the new carbon anodes on the anode rods, followed by preheating and, in a preheated state, they are taken to the molten bath. The preheating having been accomplished with the aid of the heat recovered from the residual anodes removed from the molten bath and/or from the hot bath material that has been removed from the electrolytic cell.
In accordance with a broad aspect of the invention, there is provided a method of exchanging carbon anodes utilized in a dry-method aluminum electrolysis process involving heat recovery and in which new carbon anodes associated with anode rods are exchanged for residual anodes, comprising the steps of:
providing new carbon anodes arranged on associated anode rods;
removing residual anodes from a molten bath of an electrolytic cell to recover heat therefrom; and with heat from said residual 2~3ROOl -anodes or heat from material from said molten bath, prior to utilizing said new carbon anodes.
The method is preferably implemented so as to permit the new carbon anodes, together with the anode rods bearing them, to be placed inside the preheating chamber of a heat exchanger. The air contained in the heat exchanger is heated by means of the hot residual anodes taken from the molten bath and/or by means of the hot bath material that has been removed from the electrolytic cell.
In accordance with another aspect of this invention, there is provided an apparatus suitable for carrying out the above method; more particularly, this invention provides an apparatus for exchanging carbon anodes comprising a heat exchanger for cooling on one side of residual anodes and their associated anode rods which have been removed from a molten bath or hot bath material removed from said molten bath, and, on the other side, for the preheating new carbon anodes arranged on associated anode rods, which are adapted to be transported to a molten bath.
It is proposed that the new carbon anodes to be used to replace the burned anodes in the molten bath are, after being attached to the anode rods, heated or preheated by using the considerable residual heat of the residual anodes removed from the molten bath and/or the bath material which, like furnace waste, is removed in order to replenish the molten bath.
The preheating of the new anodes using the residual heat from the residual anodes or molten spent bath material, is advantageous in that the introduction of the preheated new anodes will cause the process to start sooner than would otherwise occur if only unheated anodes were to be employed. Moreover, the temperature shock normally encountered during insertion of new anodes is considerably reduced and less heat energy is drawn from the molten bath for heating the new anodes. Furthermore, current flows more readily through the newly-installed new anodes during -the heating phase. With the aid of the proposed method, it is, of course, possible to heat the new anodes to approximately 200C, or higher, by employing the residual heat contained in the residual anodes and/or in the electrolyte. The preheating process takes place inside a closed chamber of a heat exchanger or similar apparatus without use of complicated technology. It is also proposed that environmentally-harmful emissions will be extensively suppressed by this method.
In particular, the method of the present invention permits the residual anodes which, together with their anode rods, have been removed from the molten bath and, preferably together with the bath material removed ~rom the molten bath, to be transferred to a cooling chamber which, in order to facilitate heat exchange, is connected to a preheating chamber in which the new carbon anodes are preheated.
In this arrangement, the cooling chamber and the preheating chamber constitute a heat exchanger. The new carbon anodes to be preheated (which are arranged on the anode rods) are transferred through the preheating chamber in a continuous operation; while the hot residual anodes (arranged on their anode rods and removed from the molten bath) are transported in continuous fashion in the opposite direction through the cooling chamber. The method of this invention thus advantageously affords the possibility of including in the process at least a rough cleaning of the residual anodes of the caked-on bath material; i.e. effecting the cleaning-off of the residual anodes inside the closed chamber constituted by the cooling chamber, cooling tunnel, or prechamber. In this arrangement, the time required to recover heat from the residual anodes in the cooling section of the heat exchanger can at least be employed in rough cleaning the residual anodes.
In order to transfer , without harmful emissions, the hot residual anodes removed from the electrolytic cell and/or waste bath material into the heat exchange system and place the 2~38001 preheated new anodes inside the electrolytic cell rapidly and without noticeable heat loss, this invention may use transport containers that are effectively transported by means of a transport vehicle; in particular, a forklift truck, etc.
Examples of such transport containers which are preferably designed as multi-chamber containers, have already been suggested in the art. In order to be used in the process of the present invention, such transport containers are designed to comprise at least one receptacle for a residual anode and an additional receptacle for the waste bath material removed from the electrolytic cell. As mentioned above, the transport containers are also effectively employed to transfer the preheated new anodes from the heat exchanger to the electrolytic cell.
The method of the present invention can be implemented in heat exchange systems of differing design. One preferred design of the apparatus for implementation of the method of the present invention includes a heat exchange unit which, closing toward the outside, comprises a cooling zone for cooling down the residual anodes together with their anode rods (having been removed from the molten bath and/or the hot bath material that has been removed from the molten bath) on one side; and, on the other side, a preheating zone for preheating the new anodes arranged on the anode rods and destined for the molten bath. It is preferred that the heat exchanger comprises a parallel arrangement of a cooling tunnel forming the cooling zone, and a preheating tunnel forming the preheating zone. In this arrangement, the two tunnels are connected in order to permit the exchange of heat. The heat exchanger comprising a cooling tunnel and preheating tunnel, is designed to permit the anode rods, which are fitted with new anodes, to transit the preheating tunnel in the direction opposite to that in which the anode rods, which are fitted with the residual anodes, transit the cooling tunnel.
2~3~1 -It is also proposed that inside the heat exchanger (or inside a prechamber of same) a cleaning device serving to remove the bath material clinging to the residual anodes exist. The cooling tunnel and preheating tunnel both connect via a transfer tunnel to a common prechamber to which the residual anodes and the bath material, which is removed from the furnace as waste are transferred; and from which the preheated new anodes are taken and then transported to the electrolytic cell, preferably by means of the transport containers. Both the cooling tunnel and preheating tunnel feature the necessary transfer equipment. It is preferable that transfer be accomplished with the aid of transfer pallets and a pallet conveyor. The facility should also be designed so that its equipment can be operated from a protected location. Further preferred embodiments of the present invention are hereinafter illustrated and described in greater detail.
Having thus generally described the invention, reference will now be made to the accompanying drawings, illustrating preferred embodiments and in which:
Fig. 1 is a schematic view of one embodiment of the processing sequence in conjunction with a proposed device;
Fig. 2 is a longitudinal section through one embodiment of a transport container employed in the process; and Fig. 3 is a cross-section through one embodiment of a transport container employed in the process.
Fig. 1 illustrates the processing sequence employed to exchange anodes and recover heat, as well as the equipment used to implement the method in the heat exchange system. In this arrangement, a facility in accordance with the invention, as shown in drawings A, C, and D, illustrate a selection of vertical cross-sections through its prechamber or, a vertical longitudinal section through the cooling tunnel (Drawing C) and the preheating 2~3800~
tunnel (Drawing D). Drawing B illustrates a vertical longitudinal section through the prechamber. The flow lines, which are indicated by arrows, show the direction in which the process operates.
As shown in Fig. 1, by reference numeral 1, the furnace building encloses the melting baths used in the dry method aluminum electrolysis process. The apparatus employed for heat recovery and preheating of the new carbon anodes destined for the melting bath located inside building 1, comprises a closed system that constitutes a heat exchanger. The latter comprises a prechamber 2, which, as shown in drawings A, C, and D, is closed or capable of being locked toward the outside in a variety of vertical cross-sections; and, in drawing B, in vertical longitudinal sections. Connected to prechamber 2 is a cooling tunnel 3 (Drawing C) and, arranged parallel to the latter, a preheating tunnel 4. Situated between cooling tunnel 3, or rather, preheating tunnel 4 and common prechamber 2, is a transfer tunnel 5 or 6 that is provided with means for transferring the anode rods that are fitted with either the residual anodes or the new anodes. A pallet conveyor 8 is employed to transport (in the process direction shown by the arrow X) the anode rods-7, which bear the residual anodes, from prechamber 2 through transfer tunnel 5 and cooling tunnel 3.
Anode rods 7 which are fitted with the residual anodes are held in upright position on pallets 9. As illustrated, for example, each pallet 9 carries a group of three anode rods 7. The latter, which are fitted with the residual anodes, thus transit inside cooling tunnel 3 during which they radiate the heat originating from the molten bath. The cooled-off residual anodes together with the anode rods, having left cooling tunnel 3, are transported in the direction indicated by the arrow X' to the non-illustrated anode preparation facility. In Drawing D, the anode rods 7, having arrived from the anode preparation facility with new carbon anodes 10, are also grouped on pallets 11 which are placed in the centre of pallet conveyor 12 and are transported in the direction of arrow Y through preheating tunnel 4 and transfer tunnel 6 into prechamber 2 i.e., opposite to the transport direction X, in which the hot residual anodes move.
Located inside prechamber 2 is a sieve grate 13 extending in a longitudinal direction of the former and also arranged below said sieve grate, a conveyor 14 which, for example, may be a chain conveyor, plate belt or similar device. Also arranged inside prechamber 2 are manipulators 15, capable of pivoting about a vertical axis and an articulated arm 16 comprising a gripper 17. Manipulators 15 serve to handle anode rods 7 that are fitted with the residual anodes and with the new carbon anodes, a procedure that will hereinafter be described in greater detail As illustrated in Drawing B, arranged above grate 13 are a crushing apparatus 18 and a cleaning apparatus 19; which, for example, comprise a breaker, a press, or similar equipment which serves to rough-clean the hot, residual anodes of the molten bath material that clings to their top side. Such caked-on bath material is indicated by means of reference numeral 20 in Drawing A, with respect to the residual anode 21. Finally, also arranged inside prechamber 2 is a further pallet conveyor 23 forming the means of transfer for pallet conveyors 8 and 12 from the cooling tunnel and the preheating tunnel.
Transfer of the hot residual anodes 21, together with their anode rods 7 from the molten bath contained in furnace building 1 to prechamber 2 of the heat exchange system (as well as that of the new carbon anodes that have been preheated inside preheating zone 4 from prechamber 2) to the molten bath housed in the furnace building 1 is accomplished, (as indicated by arrows 24 and 25) with the aid of a transport vehicle 26. The latter may be a forklift truck, platform wagon, or the like which provides shuttle transfer between furnace building 1 and the heat exchange facility, or its prechamber 2. Situated in the transfer path between the furnace building and prechamber 2 are the hot residual anodes 21 as well as the preheated new anodes 10 in the receptacles of a transport container 27. The operating sequence of this system is as follows:
213~
The burnt anodes, or in other words, the hot residual anodes 21 with their anode rods 7 (having been taken from the molten bath located inside the furnace building) are removed by means of a gripper or similar implement (not shown) and are placed inside transport container 27. The latter has a plurality of closeable receptacles for a plurality of residual anodes on whose top side bath material 20 is caked. When the anodes are replaced, the bath material 30 (which is located in the vicinity of and also underneath the removed anode [Fig. 2])) is removed from the electrolytic cell as furnace waste which may still contain hot electrolyte. Furnace waste 30 is placed inside a separate receptacle of transport container 27 (Fig. 2) which can also be locked. Loaded transport container 27 is then picked up by means of the lifting forks of transport vehicle 26 and then transferred, in the direction indicated by arrow 24, to prechamber 2. Drawing A of Fig. 1 illustrates transport vehicle 26 at prechamber 2 in position to transfer its load. In this example, prechamber 2 features in its side wall an insertion opening 28 through which the transport fork can be inserted and the transport container 27 carried thereupon. This arrangement permits the latter to be placed inside prechamber 2 while transport vehicle 26 remains outside. Insertion opening 28 can be locked by means of a locking element, e.g., a sliding gate or roll-up gate which may be opened to permit placement of the transport container inside prechamber 2. Transport vehicle 26 can also, as illustrated, feature a locking plate 29, which, after the former has achieved the transfer position, serves to close insertion opening 28. Thus, transport container 27, placed inside prechamber 2 is opened after which manipulator 15 with its gripper 17, grabs a protruding anode rod 7 and its hot, residual anode 21. These are lifted out of the receptacle of transport container 27 and then, as illustrated in Drawing B, laid flat upon grate 13 and positioned vis-à-vis relative to a cleaning apparatus 19.
With its articulated gripping tongs 17, manipulator 15 holds the anode rod in place during the hot cleaning procedure, in -- Z13~30~
which the hot bath material 20 (which has been deposited upon the residual anode) is removed with the aid of cleaning apparatus 19.
Bath material 20 then falls through grate 13 onto conveyor 14.
Subsequently, the furnace waste (bath material 30) which is held inside a separate receptacle of transport container 27, is dumped onto grating 13, which is indicated by means of reference numeral 30 in Drawing B. Furnace waste 30 is crushed on top of grating 13 with the aid of crushing apparatus 18 and also falls onto conveyor 14. Crushing apparatus 18 can be provided with a powered pressure plate that serves to press hot furnace waste 30 through grate 13. All of the bath material that has fallen onto the conveyor 14 is conveyed by the latter into a cooling zone in order to be cooled down. This cooling zone, as illustrated in Drawing B, adjoins the front wall of prechamber 2 and advantageously comprises a rotating cooling drum 31. Bath material 32 which is cooled-off inside the latter is finally transferred from the cooling zone, by cooling drum 31, in the direction indicated by arrow Z for further treatment.
Furnace waste 30 can also be emptied out of transport container 27, as illustrated in Drawing C (if the container is tipped) which permits the furnace waste to fall onto grate 13.
This emptying action can also be effected in another manner, e.g.
through a trapdoor fitted to the bottom of the receptacle of the transport container.
Residual anode 2I, having been rough-cleaned in the manner described above, is (as illustrated in Drawing B) then picked up by means of manipulator 15 from the processing zone and, as is illustrated in Drawing C, placed inside a transport pallet 9 that sits on top of pallet conveyor 23. Pallet 9 is then (after receiving its load) transported with the aid of pallet conveyor 8 via transfer tunnel 5 through cooling tunnel 3. Drawing C
illustrates that the length of the cooling tunnel 3 permits accomodation of a plurality of transport pallets at the same time. After having sufficiently cooled-off, the residual anodes - 2~3~001 are (together with their anode rods) transferred in the direction of the arrow X' out of cooling tunnel 3 and to another facility for additional processing. It will, of course, be appreciated that a closeable insertion opening for the anode rods, and for transport pallets 9, can also be provided on external front wall 33. The same applies with respect to front wall 34 of preheating tunnel 4. Transfer tunnels can also be provided in this case.
Anode rods 7 after being provided with new carbon anodes 10, are loaded onto pallets 11 and then transferred in the direction of arrow Y through the insertion opening in front wall 34, into preheating tunnel 4, and, with the aid of pallet conveyor 12, conveyed through the preheating zone. Thereafter they are conveyed through transfer tunnel 6 into prechamber 2, where they are placed on top of pallet conveyor 23. Anode rods 7 and preheated new anodes 10 are, with the aid of a second manipulator 15, picked up and, as Drawing D illustrates, placed inside transport container 27 that sits on top of the transport forks of a transport vehicle 26. The receptacles of transport container 27 are then closed. The latter, now holding the preheated new carbon anodes 10, is then transferred with the aid of transport vehicle 26 (in the direction of arrow 25) to the furnace building whereupon the preheated new anodes are brought to the molten bath, in order to replace the previously-removed residual anodes.
Preheating of new anodes 10, during their transit in preheating tunnel 4, is effected with the aid of the heat given off by the hot, residual anodes when transiting cooling tunnel 3 i.e., during their cooling-down stage. The transfer of heat between cooling tunnel 3 and preheating tunnel 4 can be effected in a number of ways. A simple means of effecting heat transfer is to have cooling tunnel 3 joined to preheating tunnel 4 in such a way that the hot chamber air formed inside the cooling tunnel is allowed to reach preheating tunnel 4. This serves to sufficiently heat up the chamber air inside the latter. Cooling 2l3ao~
tunnel 3 with transfer tunnel 5, and preheating tunnel 4 with transfer tunnel 6, are advantageously arranged parallel to one another and are connected to each other transversely in order to facilitate heat transfer. Another effective method can be to arrange both tunnels 3 and 4 with their transfer tunnels adjoining in a wall-to-wall relationship i.e., with a common wall between them. In yet another arrangement, hot chamber air is sucked out of cooling tunnel 3 and transfer tunnel 5 and forced into preheating tunnel 4 and transfer tunnel 6.
The heat radiated by loose bath material 32 inside the cooling zone or cooling drum 31 can also be utilized effectively to heat up the preheating zone or to preheat new anodes 10. To this end, it is also possible to connect the cavity of cooling drum 31 to the preheating tunnel 4. By means of recovering heat from residual anodes that have been removed from the molten bath and the remaining furnace waste, the new anodes which are destined for the molten bath can be preheated in an energy-efficient manner to temperatures that can far exceed 200C. In this way, the temperature shock, which would normally impact on the new anodes when placed inside the electrolytic cell or its melting bath, is considerably reduced; moreover, current flow through the new anodes in the heat-up phase is accelerated.
In spite of this however, the molten bath does not unnecessarily lose heat energy when the new anode 10 is being heated up. The method of this invention also prevents the unavoidable fluorine emissions into the outside air when the residual anodes and residual furnace material are removed from the molten bath.
Figs. 2 and 3 illustrate an example of an individual transport container 27 suitable for use in the method described in the present invention. In this example, transport container 27 features three adjacent receptacles 35 of which each of external receptacles 35 accomodates at least one hot residual anode 21 which has been removed from thev molten bath. The residual anode carries on its upper side a hot bath material deposit 20. The middle receptacle 35 can, in this arrangement, 213F~0~)1 serve to hold the furnace waste (hot bath material) 30. Each of receptacles 35 is formed from a housing having, on its top side, a cover 36 that tightly closes the insertion opening. In this arrangement, the receptacles 35 are connected to a sub-transport unit by means of a common substructure 37. The latter is designed as a transport pallet which permits transport container 27 to be picked up and transported by means of a forklift vehicle. Situated in the region of the floor of the receptacles holding the residual anodes is a dumping area placed in the form of a grate, and on which residual anodes 21 are placed. ~hen receptacles 35 are closed, the anode rods 7 protrude upwardly out of the receptacles so that the protuding rods are snugly surrounded by the covers 36.
Designed to work in conjunction with each receptacle 35 is a filtration device 39 (Fig. 3) which is, in order to connect the receptacle with the surrounding atmosphere, arranged in an air vent 40. The latter is located in the wall of the receptacle in question so that it prevents destructive pressure from building up inside the receptacles due to the high temperatures. The filtration device at the same time prevents the escape of fluorine gases into the surrounding atmosphere.
As illustrated in thè embodiments of the present invention, covers 36 are shown as flip-open covers, each of which feature flap covers 42 and 43 which are mounted so as to be able to pivot on hinges 41. In this way they converge towards the top when in a closed position. In this arrangement, a closure strip 44, which is arranged on top of one of the flap covers 43, is provided with a recess so that by opening towards its edge, it forms the above-mentioned passage for the anode rod. The shape of the recess accomodates the cross-sectional shape of anode rod 7; strip 44 furthermore overlaps the top part of the flap cover 42, so that between the closure surfaces of both flap covers flexible seal 45 is formed serving to seal the receptacle towards the outside. Flap covers 42 and 43 can, when in the closed position, be locked together by means of a locking device (not 2~3~0~i shown). When the locking device is disengaged, both flap covers swing outwardly on hinges 41 to opposite sides in order to permit the anode rods with their residual anodes to be inserted from above into the receptacles 35, or alternatively, to be lifted out of the latter.
Instead of the two-piece flap cover described above, a single-flap cover, also provided on top of each receptacle 35, can serve as the cover 36. In this arrangement, the single-flap I cover 42 is somewhat shorter and stationary, while the other flap cover 43 is capable of swinging upon hinge 41. It will of course be appreciated that the arrangement permits, when in the open position, the residual anodes to be inserted or lifted out in an unhindered manner, into the receptacles.
It will furthermore be appreciated that alternative designs of transport container 27 can be employed and that the number of receptacles carried in each transport container can vary. It is suggested, however, that in order to implement the proposed method, transport containers comprise at least two receptacles so that one of the receptacles can serve to accomodate a residual anode, while the other serves to hold residual furnace waste.
The design of the heat exchange system can also be different from that illustrated in Fig.1. Heat exchange between the hot residual anodes, the hot bath material and a new anode to be preheated could, for example, be accomplished by using the residual heat from the residual anodes or the bath material by using a gaseous or liquid heating medium. The latter could be heated and then used for heating the preheating tunnel. Use of the described heat exchange system does not necessarily require the presence of operating personnel inside prechamber 2. All operating systems can be controlled exteriorly or from a heat-insulated or cooled control cabin.
In order to prevent the absorption of iron through preheating of the new anodes, which could have an undesirable 2~3Ronl ~r~
effect on the aluminum smelting process, the various operating components, such as grate 13, its conveyor 14, cooling drum 31 and/or the transport container, may be clad with aluminum.
Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
Method and Device for Replacing Anodes in a Dry Method Aluminum Electrolysis Process Involvinq Heat Recovery This invention relates to a method and apparatus for replacing anodes.
More particularly, one aspect of this invention relates to a method for replacing carbon anodes arranged on anode rods in a dry method aluminum electrolysis process, during which heat is recovered. According to another aspect of this invention, there is provided an apparatus suitable for carrying out the above method.
During the dry electrolysis of aluminum, carbon anodes (anode blocks), which are arranged on anode rods, are consumed to a considerable extent during the electrolysis. This necessitates periodic replacement of the carbon anodes. The used or residual anodes, as they are commonly referred to, are caked with a mixture of aluminum oxide and electrolyte. They exhibit extremely high temperatures when removed from the molten bath of the electrolytic cell, and produce heavy emissions of toxic substances, particularly fluorine gases.
The hot, residual anodes, after being removed from the electrolytic cell, are generally taken to distant processing locations where the above-mentioned baked-on materials are removed; thereafter the residual anodes are scraped in order to recover valuable carbon material from the nipples of the anode rods. Following additional processing, the latter are fitted with new carbon anodes (if required).
When the anodes are exchanged, not only are the residual anodes removed, but spent bath material is also removed from the electrolytic cell. The quantity of bath material removed from the latter for each residual anode, corresponds minimally to the quantity of baked-on bath material; the latter, during the burning process, accumulates on top of the carbon anode. When the spent bath material is removed, electrolyte (which is still 2~3800~
partially in liquid form) is also removed from the bath. The emissions produced by this method are considerable.
The carbon anodes employed in the dry method electrolysis process are manufactured conventionally from green artificial carbon bodies which must subsequently be burned at a high temperature inside a furnace. DE-OS 35 38 151 discloses a procedure in which green carbon anodes are preheated by using the heat recovered during the subsequent cooling of the consumed carbon anodes, following which such green carbon anodes are burned by means of induction. The new carbon anodes produced after cooling are fitted with anode rods and then tranferred to the electrolytic cell to replace the consumed anodes.
One object of the present invention is to provide an improved method and apparatus in which heat, which is advantageous for further processing, can be recovered during anode replacement and, during which, the emission of toxic substances can simultaneously be suppressed to a large extent.
The method of the present invention involves the arrangement of the new carbon anodes on the anode rods, followed by preheating and, in a preheated state, they are taken to the molten bath. The preheating having been accomplished with the aid of the heat recovered from the residual anodes removed from the molten bath and/or from the hot bath material that has been removed from the electrolytic cell.
In accordance with a broad aspect of the invention, there is provided a method of exchanging carbon anodes utilized in a dry-method aluminum electrolysis process involving heat recovery and in which new carbon anodes associated with anode rods are exchanged for residual anodes, comprising the steps of:
providing new carbon anodes arranged on associated anode rods;
removing residual anodes from a molten bath of an electrolytic cell to recover heat therefrom; and with heat from said residual 2~3ROOl -anodes or heat from material from said molten bath, prior to utilizing said new carbon anodes.
The method is preferably implemented so as to permit the new carbon anodes, together with the anode rods bearing them, to be placed inside the preheating chamber of a heat exchanger. The air contained in the heat exchanger is heated by means of the hot residual anodes taken from the molten bath and/or by means of the hot bath material that has been removed from the electrolytic cell.
In accordance with another aspect of this invention, there is provided an apparatus suitable for carrying out the above method; more particularly, this invention provides an apparatus for exchanging carbon anodes comprising a heat exchanger for cooling on one side of residual anodes and their associated anode rods which have been removed from a molten bath or hot bath material removed from said molten bath, and, on the other side, for the preheating new carbon anodes arranged on associated anode rods, which are adapted to be transported to a molten bath.
It is proposed that the new carbon anodes to be used to replace the burned anodes in the molten bath are, after being attached to the anode rods, heated or preheated by using the considerable residual heat of the residual anodes removed from the molten bath and/or the bath material which, like furnace waste, is removed in order to replenish the molten bath.
The preheating of the new anodes using the residual heat from the residual anodes or molten spent bath material, is advantageous in that the introduction of the preheated new anodes will cause the process to start sooner than would otherwise occur if only unheated anodes were to be employed. Moreover, the temperature shock normally encountered during insertion of new anodes is considerably reduced and less heat energy is drawn from the molten bath for heating the new anodes. Furthermore, current flows more readily through the newly-installed new anodes during -the heating phase. With the aid of the proposed method, it is, of course, possible to heat the new anodes to approximately 200C, or higher, by employing the residual heat contained in the residual anodes and/or in the electrolyte. The preheating process takes place inside a closed chamber of a heat exchanger or similar apparatus without use of complicated technology. It is also proposed that environmentally-harmful emissions will be extensively suppressed by this method.
In particular, the method of the present invention permits the residual anodes which, together with their anode rods, have been removed from the molten bath and, preferably together with the bath material removed ~rom the molten bath, to be transferred to a cooling chamber which, in order to facilitate heat exchange, is connected to a preheating chamber in which the new carbon anodes are preheated.
In this arrangement, the cooling chamber and the preheating chamber constitute a heat exchanger. The new carbon anodes to be preheated (which are arranged on the anode rods) are transferred through the preheating chamber in a continuous operation; while the hot residual anodes (arranged on their anode rods and removed from the molten bath) are transported in continuous fashion in the opposite direction through the cooling chamber. The method of this invention thus advantageously affords the possibility of including in the process at least a rough cleaning of the residual anodes of the caked-on bath material; i.e. effecting the cleaning-off of the residual anodes inside the closed chamber constituted by the cooling chamber, cooling tunnel, or prechamber. In this arrangement, the time required to recover heat from the residual anodes in the cooling section of the heat exchanger can at least be employed in rough cleaning the residual anodes.
In order to transfer , without harmful emissions, the hot residual anodes removed from the electrolytic cell and/or waste bath material into the heat exchange system and place the 2~38001 preheated new anodes inside the electrolytic cell rapidly and without noticeable heat loss, this invention may use transport containers that are effectively transported by means of a transport vehicle; in particular, a forklift truck, etc.
Examples of such transport containers which are preferably designed as multi-chamber containers, have already been suggested in the art. In order to be used in the process of the present invention, such transport containers are designed to comprise at least one receptacle for a residual anode and an additional receptacle for the waste bath material removed from the electrolytic cell. As mentioned above, the transport containers are also effectively employed to transfer the preheated new anodes from the heat exchanger to the electrolytic cell.
The method of the present invention can be implemented in heat exchange systems of differing design. One preferred design of the apparatus for implementation of the method of the present invention includes a heat exchange unit which, closing toward the outside, comprises a cooling zone for cooling down the residual anodes together with their anode rods (having been removed from the molten bath and/or the hot bath material that has been removed from the molten bath) on one side; and, on the other side, a preheating zone for preheating the new anodes arranged on the anode rods and destined for the molten bath. It is preferred that the heat exchanger comprises a parallel arrangement of a cooling tunnel forming the cooling zone, and a preheating tunnel forming the preheating zone. In this arrangement, the two tunnels are connected in order to permit the exchange of heat. The heat exchanger comprising a cooling tunnel and preheating tunnel, is designed to permit the anode rods, which are fitted with new anodes, to transit the preheating tunnel in the direction opposite to that in which the anode rods, which are fitted with the residual anodes, transit the cooling tunnel.
2~3~1 -It is also proposed that inside the heat exchanger (or inside a prechamber of same) a cleaning device serving to remove the bath material clinging to the residual anodes exist. The cooling tunnel and preheating tunnel both connect via a transfer tunnel to a common prechamber to which the residual anodes and the bath material, which is removed from the furnace as waste are transferred; and from which the preheated new anodes are taken and then transported to the electrolytic cell, preferably by means of the transport containers. Both the cooling tunnel and preheating tunnel feature the necessary transfer equipment. It is preferable that transfer be accomplished with the aid of transfer pallets and a pallet conveyor. The facility should also be designed so that its equipment can be operated from a protected location. Further preferred embodiments of the present invention are hereinafter illustrated and described in greater detail.
Having thus generally described the invention, reference will now be made to the accompanying drawings, illustrating preferred embodiments and in which:
Fig. 1 is a schematic view of one embodiment of the processing sequence in conjunction with a proposed device;
Fig. 2 is a longitudinal section through one embodiment of a transport container employed in the process; and Fig. 3 is a cross-section through one embodiment of a transport container employed in the process.
Fig. 1 illustrates the processing sequence employed to exchange anodes and recover heat, as well as the equipment used to implement the method in the heat exchange system. In this arrangement, a facility in accordance with the invention, as shown in drawings A, C, and D, illustrate a selection of vertical cross-sections through its prechamber or, a vertical longitudinal section through the cooling tunnel (Drawing C) and the preheating 2~3800~
tunnel (Drawing D). Drawing B illustrates a vertical longitudinal section through the prechamber. The flow lines, which are indicated by arrows, show the direction in which the process operates.
As shown in Fig. 1, by reference numeral 1, the furnace building encloses the melting baths used in the dry method aluminum electrolysis process. The apparatus employed for heat recovery and preheating of the new carbon anodes destined for the melting bath located inside building 1, comprises a closed system that constitutes a heat exchanger. The latter comprises a prechamber 2, which, as shown in drawings A, C, and D, is closed or capable of being locked toward the outside in a variety of vertical cross-sections; and, in drawing B, in vertical longitudinal sections. Connected to prechamber 2 is a cooling tunnel 3 (Drawing C) and, arranged parallel to the latter, a preheating tunnel 4. Situated between cooling tunnel 3, or rather, preheating tunnel 4 and common prechamber 2, is a transfer tunnel 5 or 6 that is provided with means for transferring the anode rods that are fitted with either the residual anodes or the new anodes. A pallet conveyor 8 is employed to transport (in the process direction shown by the arrow X) the anode rods-7, which bear the residual anodes, from prechamber 2 through transfer tunnel 5 and cooling tunnel 3.
Anode rods 7 which are fitted with the residual anodes are held in upright position on pallets 9. As illustrated, for example, each pallet 9 carries a group of three anode rods 7. The latter, which are fitted with the residual anodes, thus transit inside cooling tunnel 3 during which they radiate the heat originating from the molten bath. The cooled-off residual anodes together with the anode rods, having left cooling tunnel 3, are transported in the direction indicated by the arrow X' to the non-illustrated anode preparation facility. In Drawing D, the anode rods 7, having arrived from the anode preparation facility with new carbon anodes 10, are also grouped on pallets 11 which are placed in the centre of pallet conveyor 12 and are transported in the direction of arrow Y through preheating tunnel 4 and transfer tunnel 6 into prechamber 2 i.e., opposite to the transport direction X, in which the hot residual anodes move.
Located inside prechamber 2 is a sieve grate 13 extending in a longitudinal direction of the former and also arranged below said sieve grate, a conveyor 14 which, for example, may be a chain conveyor, plate belt or similar device. Also arranged inside prechamber 2 are manipulators 15, capable of pivoting about a vertical axis and an articulated arm 16 comprising a gripper 17. Manipulators 15 serve to handle anode rods 7 that are fitted with the residual anodes and with the new carbon anodes, a procedure that will hereinafter be described in greater detail As illustrated in Drawing B, arranged above grate 13 are a crushing apparatus 18 and a cleaning apparatus 19; which, for example, comprise a breaker, a press, or similar equipment which serves to rough-clean the hot, residual anodes of the molten bath material that clings to their top side. Such caked-on bath material is indicated by means of reference numeral 20 in Drawing A, with respect to the residual anode 21. Finally, also arranged inside prechamber 2 is a further pallet conveyor 23 forming the means of transfer for pallet conveyors 8 and 12 from the cooling tunnel and the preheating tunnel.
Transfer of the hot residual anodes 21, together with their anode rods 7 from the molten bath contained in furnace building 1 to prechamber 2 of the heat exchange system (as well as that of the new carbon anodes that have been preheated inside preheating zone 4 from prechamber 2) to the molten bath housed in the furnace building 1 is accomplished, (as indicated by arrows 24 and 25) with the aid of a transport vehicle 26. The latter may be a forklift truck, platform wagon, or the like which provides shuttle transfer between furnace building 1 and the heat exchange facility, or its prechamber 2. Situated in the transfer path between the furnace building and prechamber 2 are the hot residual anodes 21 as well as the preheated new anodes 10 in the receptacles of a transport container 27. The operating sequence of this system is as follows:
213~
The burnt anodes, or in other words, the hot residual anodes 21 with their anode rods 7 (having been taken from the molten bath located inside the furnace building) are removed by means of a gripper or similar implement (not shown) and are placed inside transport container 27. The latter has a plurality of closeable receptacles for a plurality of residual anodes on whose top side bath material 20 is caked. When the anodes are replaced, the bath material 30 (which is located in the vicinity of and also underneath the removed anode [Fig. 2])) is removed from the electrolytic cell as furnace waste which may still contain hot electrolyte. Furnace waste 30 is placed inside a separate receptacle of transport container 27 (Fig. 2) which can also be locked. Loaded transport container 27 is then picked up by means of the lifting forks of transport vehicle 26 and then transferred, in the direction indicated by arrow 24, to prechamber 2. Drawing A of Fig. 1 illustrates transport vehicle 26 at prechamber 2 in position to transfer its load. In this example, prechamber 2 features in its side wall an insertion opening 28 through which the transport fork can be inserted and the transport container 27 carried thereupon. This arrangement permits the latter to be placed inside prechamber 2 while transport vehicle 26 remains outside. Insertion opening 28 can be locked by means of a locking element, e.g., a sliding gate or roll-up gate which may be opened to permit placement of the transport container inside prechamber 2. Transport vehicle 26 can also, as illustrated, feature a locking plate 29, which, after the former has achieved the transfer position, serves to close insertion opening 28. Thus, transport container 27, placed inside prechamber 2 is opened after which manipulator 15 with its gripper 17, grabs a protruding anode rod 7 and its hot, residual anode 21. These are lifted out of the receptacle of transport container 27 and then, as illustrated in Drawing B, laid flat upon grate 13 and positioned vis-à-vis relative to a cleaning apparatus 19.
With its articulated gripping tongs 17, manipulator 15 holds the anode rod in place during the hot cleaning procedure, in -- Z13~30~
which the hot bath material 20 (which has been deposited upon the residual anode) is removed with the aid of cleaning apparatus 19.
Bath material 20 then falls through grate 13 onto conveyor 14.
Subsequently, the furnace waste (bath material 30) which is held inside a separate receptacle of transport container 27, is dumped onto grating 13, which is indicated by means of reference numeral 30 in Drawing B. Furnace waste 30 is crushed on top of grating 13 with the aid of crushing apparatus 18 and also falls onto conveyor 14. Crushing apparatus 18 can be provided with a powered pressure plate that serves to press hot furnace waste 30 through grate 13. All of the bath material that has fallen onto the conveyor 14 is conveyed by the latter into a cooling zone in order to be cooled down. This cooling zone, as illustrated in Drawing B, adjoins the front wall of prechamber 2 and advantageously comprises a rotating cooling drum 31. Bath material 32 which is cooled-off inside the latter is finally transferred from the cooling zone, by cooling drum 31, in the direction indicated by arrow Z for further treatment.
Furnace waste 30 can also be emptied out of transport container 27, as illustrated in Drawing C (if the container is tipped) which permits the furnace waste to fall onto grate 13.
This emptying action can also be effected in another manner, e.g.
through a trapdoor fitted to the bottom of the receptacle of the transport container.
Residual anode 2I, having been rough-cleaned in the manner described above, is (as illustrated in Drawing B) then picked up by means of manipulator 15 from the processing zone and, as is illustrated in Drawing C, placed inside a transport pallet 9 that sits on top of pallet conveyor 23. Pallet 9 is then (after receiving its load) transported with the aid of pallet conveyor 8 via transfer tunnel 5 through cooling tunnel 3. Drawing C
illustrates that the length of the cooling tunnel 3 permits accomodation of a plurality of transport pallets at the same time. After having sufficiently cooled-off, the residual anodes - 2~3~001 are (together with their anode rods) transferred in the direction of the arrow X' out of cooling tunnel 3 and to another facility for additional processing. It will, of course, be appreciated that a closeable insertion opening for the anode rods, and for transport pallets 9, can also be provided on external front wall 33. The same applies with respect to front wall 34 of preheating tunnel 4. Transfer tunnels can also be provided in this case.
Anode rods 7 after being provided with new carbon anodes 10, are loaded onto pallets 11 and then transferred in the direction of arrow Y through the insertion opening in front wall 34, into preheating tunnel 4, and, with the aid of pallet conveyor 12, conveyed through the preheating zone. Thereafter they are conveyed through transfer tunnel 6 into prechamber 2, where they are placed on top of pallet conveyor 23. Anode rods 7 and preheated new anodes 10 are, with the aid of a second manipulator 15, picked up and, as Drawing D illustrates, placed inside transport container 27 that sits on top of the transport forks of a transport vehicle 26. The receptacles of transport container 27 are then closed. The latter, now holding the preheated new carbon anodes 10, is then transferred with the aid of transport vehicle 26 (in the direction of arrow 25) to the furnace building whereupon the preheated new anodes are brought to the molten bath, in order to replace the previously-removed residual anodes.
Preheating of new anodes 10, during their transit in preheating tunnel 4, is effected with the aid of the heat given off by the hot, residual anodes when transiting cooling tunnel 3 i.e., during their cooling-down stage. The transfer of heat between cooling tunnel 3 and preheating tunnel 4 can be effected in a number of ways. A simple means of effecting heat transfer is to have cooling tunnel 3 joined to preheating tunnel 4 in such a way that the hot chamber air formed inside the cooling tunnel is allowed to reach preheating tunnel 4. This serves to sufficiently heat up the chamber air inside the latter. Cooling 2l3ao~
tunnel 3 with transfer tunnel 5, and preheating tunnel 4 with transfer tunnel 6, are advantageously arranged parallel to one another and are connected to each other transversely in order to facilitate heat transfer. Another effective method can be to arrange both tunnels 3 and 4 with their transfer tunnels adjoining in a wall-to-wall relationship i.e., with a common wall between them. In yet another arrangement, hot chamber air is sucked out of cooling tunnel 3 and transfer tunnel 5 and forced into preheating tunnel 4 and transfer tunnel 6.
The heat radiated by loose bath material 32 inside the cooling zone or cooling drum 31 can also be utilized effectively to heat up the preheating zone or to preheat new anodes 10. To this end, it is also possible to connect the cavity of cooling drum 31 to the preheating tunnel 4. By means of recovering heat from residual anodes that have been removed from the molten bath and the remaining furnace waste, the new anodes which are destined for the molten bath can be preheated in an energy-efficient manner to temperatures that can far exceed 200C. In this way, the temperature shock, which would normally impact on the new anodes when placed inside the electrolytic cell or its melting bath, is considerably reduced; moreover, current flow through the new anodes in the heat-up phase is accelerated.
In spite of this however, the molten bath does not unnecessarily lose heat energy when the new anode 10 is being heated up. The method of this invention also prevents the unavoidable fluorine emissions into the outside air when the residual anodes and residual furnace material are removed from the molten bath.
Figs. 2 and 3 illustrate an example of an individual transport container 27 suitable for use in the method described in the present invention. In this example, transport container 27 features three adjacent receptacles 35 of which each of external receptacles 35 accomodates at least one hot residual anode 21 which has been removed from thev molten bath. The residual anode carries on its upper side a hot bath material deposit 20. The middle receptacle 35 can, in this arrangement, 213F~0~)1 serve to hold the furnace waste (hot bath material) 30. Each of receptacles 35 is formed from a housing having, on its top side, a cover 36 that tightly closes the insertion opening. In this arrangement, the receptacles 35 are connected to a sub-transport unit by means of a common substructure 37. The latter is designed as a transport pallet which permits transport container 27 to be picked up and transported by means of a forklift vehicle. Situated in the region of the floor of the receptacles holding the residual anodes is a dumping area placed in the form of a grate, and on which residual anodes 21 are placed. ~hen receptacles 35 are closed, the anode rods 7 protrude upwardly out of the receptacles so that the protuding rods are snugly surrounded by the covers 36.
Designed to work in conjunction with each receptacle 35 is a filtration device 39 (Fig. 3) which is, in order to connect the receptacle with the surrounding atmosphere, arranged in an air vent 40. The latter is located in the wall of the receptacle in question so that it prevents destructive pressure from building up inside the receptacles due to the high temperatures. The filtration device at the same time prevents the escape of fluorine gases into the surrounding atmosphere.
As illustrated in thè embodiments of the present invention, covers 36 are shown as flip-open covers, each of which feature flap covers 42 and 43 which are mounted so as to be able to pivot on hinges 41. In this way they converge towards the top when in a closed position. In this arrangement, a closure strip 44, which is arranged on top of one of the flap covers 43, is provided with a recess so that by opening towards its edge, it forms the above-mentioned passage for the anode rod. The shape of the recess accomodates the cross-sectional shape of anode rod 7; strip 44 furthermore overlaps the top part of the flap cover 42, so that between the closure surfaces of both flap covers flexible seal 45 is formed serving to seal the receptacle towards the outside. Flap covers 42 and 43 can, when in the closed position, be locked together by means of a locking device (not 2~3~0~i shown). When the locking device is disengaged, both flap covers swing outwardly on hinges 41 to opposite sides in order to permit the anode rods with their residual anodes to be inserted from above into the receptacles 35, or alternatively, to be lifted out of the latter.
Instead of the two-piece flap cover described above, a single-flap cover, also provided on top of each receptacle 35, can serve as the cover 36. In this arrangement, the single-flap I cover 42 is somewhat shorter and stationary, while the other flap cover 43 is capable of swinging upon hinge 41. It will of course be appreciated that the arrangement permits, when in the open position, the residual anodes to be inserted or lifted out in an unhindered manner, into the receptacles.
It will furthermore be appreciated that alternative designs of transport container 27 can be employed and that the number of receptacles carried in each transport container can vary. It is suggested, however, that in order to implement the proposed method, transport containers comprise at least two receptacles so that one of the receptacles can serve to accomodate a residual anode, while the other serves to hold residual furnace waste.
The design of the heat exchange system can also be different from that illustrated in Fig.1. Heat exchange between the hot residual anodes, the hot bath material and a new anode to be preheated could, for example, be accomplished by using the residual heat from the residual anodes or the bath material by using a gaseous or liquid heating medium. The latter could be heated and then used for heating the preheating tunnel. Use of the described heat exchange system does not necessarily require the presence of operating personnel inside prechamber 2. All operating systems can be controlled exteriorly or from a heat-insulated or cooled control cabin.
In order to prevent the absorption of iron through preheating of the new anodes, which could have an undesirable 2~3Ronl ~r~
effect on the aluminum smelting process, the various operating components, such as grate 13, its conveyor 14, cooling drum 31 and/or the transport container, may be clad with aluminum.
Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
Claims (22)
1. A method of exchanging carbon anodes utilized in a dry-method aluminum electrolysis process involving heat recovery and in which new carbon anodes associated with anode rods are exchanged for residual anodes, comprising the steps of:
providing new carbon anodes arranged on associated anode rods;
removing residual anodes from a molten bath of an electrolytic cell to recover heat therefrom; and with heat from said residual anodes or heat from material from said molten bath, prior to utilizing said new carbon anodes.
providing new carbon anodes arranged on associated anode rods;
removing residual anodes from a molten bath of an electrolytic cell to recover heat therefrom; and with heat from said residual anodes or heat from material from said molten bath, prior to utilizing said new carbon anodes.
2. A method in accordance with claim 1, further including the step of placing said new carbon anodes together with said anode rods inside a preheating chamber of a heat exchanger, said chamber being heated by the heat of said residual anodes removed from the molten bath, or material from said molten bath.
3. A method in accordance with claims 1 or 2, further including placing said residual anodes, and associated anode rods with a cooling chamber connected to said preheating chamber to preheat said new carbon anodes.
4. A method in accordance with claim 3, wherein said carbon anodes to be preheated are, together with said anode rods, transferred in a continuous manner through said preheating chamber while said residual anodes, which have been removed from said molten bath, are together with the spent bath material, transported in a continuous manner, in an opposite direction through said cooling chamber.
5. A method in accordance with any one of claims 3 or 4, including the further step of at least rough cleaning said residual anodes associated with said anode rods, of caked-on molten bath material, when said residual anodes and associated anode rods have been removed from the molten bath and placed inside said cooling chamber or a prechamber.
6. A method in accordance with any one of claims 1 to 5, including the further step of placing said residual anodes into a transport container after said residual anodes have been removed from said molten bath, and transferring said transport container to a cooling chamber or a prechamber whereafter said residual anodes are removed from said transport container.
7. A method in accordance with claim 6, which includes a further step of placing hot bath material removed from said molten bath inside said transport container, and transferring said hot bath material to said heat exchanger or to a prechamber whereafter said bath material is removed from said transport container and placed in a cooling zone.
8. A method in accordance with claim 6 or 7, wherein there are provided transport containers for transport of said residual anodes and for transport of bath material, each of said transport containers having a plurality of receptacles, and utilizing said transport containers with said receptacles for the step of transporting the residual anodes.
9. A method in accordance with any one of claims 1 to 8, including the step of transporting preheated new carbon anodes and their associated anode rods by means of a transport container to an electrolytic cell.
10. An apparatus for exchanging carbon anodes comprising a heat exchanger for cooling on one side of residual anodes and their associated anode rods which have been removed from a molten bath or hot bath material removed from said molten bath, and, on the other side, for the preheating new carbon anodes arranged on associated anode rods, which are adapted to be transported to a molten bath.
11. An apparatus in accordance with claim 10, wherein said heat exchanger includes a cooling tunnel and a preheating tunnel, said cooling and preheating tunnels being associated with each other to facilitate heat exchanger.
12. An apparatus in accordance with claim 10 or 11, wherein said apparatus includes means for transporting in opposed directions said residual anodes, and associated anode rods, which have been removed from a molten bath, and said new anodes and their associated anode rods, for transfer to a molten bath.
13. An apparatus in accordance with claim 10 or 12, wherein there is included cleaning means for separating caked-on bath material from said residual anodes.
14. An apparatus in accordance with claim 10 or 11, wherein there is included an anode rod manipulator for manipulation of said anode rods associated with said residual anodes or new carbon anodes.
15. An apparatus in accordance with claim 11, wherein said heat exchanger includes or has associated therewith grate means adapted for supporting, in a cleaning position, anode rods having residual anodes.
16. An apparatus in accordance with claim 11 or 15, wherein said heat exchanger includes or has associated therewith grate means and crushing means, and wherein said crushing means is adapted to crush loose bath material supported by said grate means.
17. An apparatus in accordance with claim 15, wherein there is included conveyor means positioned beneath said grate means, said conveyor means being adapted to convey bath material.
18. An apparatus in accordance with claim 11, wherein there is included a pallet conveyor arranged inside said cooling tunnel and inside said preheating tunnel is a pallet conveyor adapted to transport said anode rods, fitted with said residual anodes or said new anodes.
19. An apparatus in accordance with claim 10 or 17, wherein said cooling tunnel and said preheating tunnel, are parallel relationship, said tunnels being connected through a transfer tunnel.
20. An apparatus in accordance with claim 10 or 18, wherein said heat exchanger optionally includes a prechamber, and said heat exchanger or said prechamber having at least one closeable insertion opening for transport containers, for transporting said anode rods having said residual anodes or said new anodes or furnace waste.
21. An apparatus in accordance with claim 19, wherein said transport containers have a plurality of closeable receptacles.
22. An apparatus in accordance with claim 10 or 20, wherein said heat exchanger includes portions having a protective coating where said portions come into contact with new anodes. provided with a coating of aluminum or a similar substance.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4344036A DE4344036A1 (en) | 1993-12-23 | 1993-12-23 | Anode change with heat recovery during aluminium@ fusion electrolysis |
| DEP4344036.3 | 1993-12-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2138001A1 true CA2138001A1 (en) | 1995-06-24 |
Family
ID=6505901
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002138001A Abandoned CA2138001A1 (en) | 1993-12-23 | 1994-12-13 | Method and device for replacing anodes in a dry method aluminum electrolysis process involving heat recovery |
Country Status (6)
| Country | Link |
|---|---|
| AU (1) | AU8167294A (en) |
| CA (1) | CA2138001A1 (en) |
| DE (1) | DE4344036A1 (en) |
| FR (1) | FR2714394A1 (en) |
| NO (1) | NO944973L (en) |
| RU (1) | RU94044352A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103952723A (en) * | 2014-05-16 | 2014-07-30 | 北方工业大学 | Anode replacement method in aluminum electrolysis process |
| AU2011330972B2 (en) * | 2010-11-18 | 2016-07-21 | Metalysis Limited | Method and system for electrolytically reducing a solid feedstock |
| CN105874482A (en) * | 2013-10-25 | 2016-08-17 | 力拓艾尔坎国际有限公司 | System for managing logistics flows in an electrolysis plant, aluminum smelter comprising the system, vehicle for using the system, and method for introducing said system into a pre-existing electrolysis plant |
| US9725815B2 (en) | 2010-11-18 | 2017-08-08 | Metalysis Limited | Electrolysis apparatus |
| RU2650359C1 (en) * | 2016-11-02 | 2018-04-11 | Федеральное государственное автономное образовательное учреждение высшего образования "Сибирский федеральный университет" | Method for preparation of baked anodes for electrolysis of aluminium |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2754832B1 (en) * | 1996-10-23 | 1998-11-27 | Pechiney Aluminium | PROCESS FOR CHANGING ANODES USED IN ALUMINUM ELECTROLYSIS TANKS AND GAS EFFLUENT COLLECTION DEVICE ALLOWING IT TO BE USED |
| FR3030580B1 (en) * | 2014-12-23 | 2018-10-12 | Rio Tinto Alcan International Limited | CONTAINMENT SYSTEM FOR AN ANODE ASSEMBLY |
| RU2621202C1 (en) * | 2016-02-29 | 2017-06-01 | Общество с ограниченной ответственностью "Объединенная Компания РУСАЛ Инженерно-технологический центр" | Method of replacement of anode in electrolysis of melt in aluminium electrolyser |
| NO20181483A1 (en) | 2018-11-20 | 2020-05-21 | Norsk Hydro As | A method and equipment for storing and transporting hot gas emitting components |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3538151A1 (en) * | 1985-10-26 | 1987-04-30 | Schultze Rhonhof Ernst Dr | Process and apparatus for the manufacture of artificial carbon articles |
| IT1221994B (en) * | 1987-07-09 | 1990-08-31 | Techmo Car Spa | EQUIPMENT FOR THE MECHANIZED CHANGE OF THE ANODES IN THE ELECTROLYTIC CELLS FOR THE PRODUCTION OF ALUMINUM |
-
1993
- 1993-12-23 DE DE4344036A patent/DE4344036A1/en not_active Withdrawn
-
1994
- 1994-12-13 CA CA002138001A patent/CA2138001A1/en not_active Abandoned
- 1994-12-21 NO NO944973A patent/NO944973L/en unknown
- 1994-12-22 AU AU81672/94A patent/AU8167294A/en not_active Abandoned
- 1994-12-22 RU RU94044352/02A patent/RU94044352A/en unknown
- 1994-12-23 FR FR9415601A patent/FR2714394A1/en active Pending
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| AU2011330972B2 (en) * | 2010-11-18 | 2016-07-21 | Metalysis Limited | Method and system for electrolytically reducing a solid feedstock |
| AU2011330972C1 (en) * | 2010-11-18 | 2017-01-19 | Metalysis Limited | Method and system for electrolytically reducing a solid feedstock |
| AP4025A (en) * | 2010-11-18 | 2017-02-04 | Metalysis Ltd | Method and system for electrolytically reducing a solid feedstock |
| US9725815B2 (en) | 2010-11-18 | 2017-08-08 | Metalysis Limited | Electrolysis apparatus |
| CN105874482A (en) * | 2013-10-25 | 2016-08-17 | 力拓艾尔坎国际有限公司 | System for managing logistics flows in an electrolysis plant, aluminum smelter comprising the system, vehicle for using the system, and method for introducing said system into a pre-existing electrolysis plant |
| CN105874482B (en) * | 2013-10-25 | 2020-10-23 | 力拓艾尔坎国际有限公司 | System for managing logistics flows in an electrolysis plant, aluminium smelting plant comprising such a system, vehicle using such a system and method for introducing such a system into an existing electrolysis plant |
| CN103952723A (en) * | 2014-05-16 | 2014-07-30 | 北方工业大学 | Anode replacement method in aluminum electrolysis process |
| CN103952723B (en) * | 2014-05-16 | 2016-03-30 | 北方工业大学 | Anode replacement method in aluminum electrolysis process |
| RU2650359C1 (en) * | 2016-11-02 | 2018-04-11 | Федеральное государственное автономное образовательное учреждение высшего образования "Сибирский федеральный университет" | Method for preparation of baked anodes for electrolysis of aluminium |
Also Published As
| Publication number | Publication date |
|---|---|
| NO944973D0 (en) | 1994-12-21 |
| AU8167294A (en) | 1995-06-29 |
| NO944973L (en) | 1995-06-26 |
| DE4344036A1 (en) | 1995-06-29 |
| FR2714394A1 (en) | 1995-06-30 |
| RU94044352A (en) | 1997-04-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19981214 |