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

• the present invention relates to a device for controlling the stroke of a pointerolle of a point feed system of an electrolysis cell intended for the production of aluminum.
• the devices used usually allow the alumina and / or electrolyte to be fed to one or more feed points per cell: these products are introduced into the electrolyte bath through a hole made by a driller who goes down periodically and breaks the crust or keeps the hole open.
• the breaker's stroke is normally of fixed length and determined by the mechanical system which ensures its vertical movement.
• Such a device has disadvantages. Indeed, depending on the hardness of the crust and the level of the free surface of the electrolyte, it may happen that the stroke of the breaker is insufficient to break the crust and allow the introduction of alumina.
• the active end of the piercer also called chisel
• the chisel carries with it part of the solidified bath in the form of a deposit which becomes more important with each descent of the piercer. Prolonged contact between the chisel and the electrolyte degrades the chisel because of the high temperature and the chemically aggressive nature of the bath.
• the chisel being guided by a sheath, solidified bath deposition on the chisel can, despite the presence of a scraper, form a bead that can prevent the chisel to go back completely into the sheath. This can result in a blockage of the chisel in the device, leading to a plugging of the alumina feed hole and / or electrolyte.
• This phenomenon of clogging and blocking can also cause breakage and / or wear of the chisel, mechanical shocks due to the rise in tension of the cylinder controlling the movement of the drill, as well as damage to the material, serving as electrical insulation, as a result of thermal shocks and lateral forces that occur when the solidified bath meets the scraper.
• the device can not work anymore.
• the control of the penetration of the chisel in the electrolyte is also made difficult because of the variation of electrolyte level, resulting in particular from the operations performed on the tank and variations in distance between the electrolyte. anodes and metal, caused in particular by regulating the resistance of the electrolysis cell.
• Supply means for supplying alumina to an electrolytic cell producing aluminum have been described in the documents FR 2 483 965, FR 2 614 320, US Pat. No. 4,563,255 and WO 0106039.
• the documents FR 2 483 965 and WO 0106039 each describe a device for establishing an electrical contact to raise the chisel when it comes into contact with the electrolyte. However, these documents do not indicate ways to establish such contact.
• the present invention aims to remedy these problems by proposing a device for controlling the movement of the choke of the particularly rigorous pointer to accurately detect the moment of contact between the chisel with the bath, and this through the establishment of a very reliable electrical contact between the electric circuit and the chisel.
• the object of the present invention is a device for controlling the stroke of a chisel of a feed system of an electrolysis cell intended for the purpose of.
• said cell comprising an electrolysis bath covered with a crust
• the chisel being carried by a rod fixed to the rod of an actuator ensuring the vertical movement of the chisel between a high position in which it is at above the crust and a low position intended to perforate the crust and to come into contact with the bath
• the device comprising means for detecting the crust and electrical contact between the chisel and the bath, these means comprising an electrical circuit capable of making an electrical measurement between the chisel and a point of the cell taken as electrical reference, and to act immediately on the actuator to cause a vertical movement of the pointing upwards, when a predetermined value of an electrical measurement is reached, characterized in that said electrical circuit is connected to the chisel, to the chisel pin or to the actuator rod by connecting means adapted to create a point contact in at least one point between the circuit and the chisel, the chisel pin or the actuator rod, these connecting means being subjected to elastic means pushing them respectively in
• the device according to the invention makes it possible to carry out an electrical measurement, such as a measurement of voltage or a measurement of current between the chisel, the stem of the chisel or the rod of the actuator and the bath in a particularly reliable way and precise. It is possible to make electrical contact with only one of these parts while enjoying a sufficient measurement quality.
• the electrical contact is preferably established on the chisel or on the chisel pin, as these parts are firmly connected to one another with a great electrical continuity.
• the connecting means are in the form of a piece of conductive material whose section decreases in the direction of contact with the stem of the chisel, said part being subjected to the action of said elastic means.
• the piece of conductive material has a spherical bearing head, such as a ball or a spherical end ball.
• the connecting means are in the form of a cylinder axis forming an angle (preferably a right angle) with the axis of the chisel, the rod thereof or the rod of the actuator.
• the connecting means are in the form of a generally diabolo-shaped piece having an element delimited by two convergent convex surfaces able to bear in two points on the chisel, the stem of that or the actuator rod.
• the connecting means are in the form of a metal part, such as steel or copper, or a non-conductive metal part, such as silicon carbide. The electrical contact thus made is particularly reliable.
• a material such as steel is particularly resistant to high temperatures and the corrosive atmosphere prevailing above the electrolyte bath.
• the hardness of the conductive material part has a Brinell hardness of between 285 and 370, measured with a tungsten carbide ball under a weight of 3000 kg, corresponding to a Rockwell hardness of 30 to 40 HRC.
• the elastic means are in the form of a helical spring.
• this spring has a pressure less than or equal to 50 N. The contact between the electric circuit and the chisel pin is thus particularly reliable while avoiding wear of the chisel pin.
• the piece of conductive material and the coil spring are mounted inside a bushing made of conductive material, the piece of conductive material protruding from one end of the sleeve and the end of the sleeve opposite the ball being equipped with a contact.
• the sleeve is screwed into a threaded hole formed in the wall of a sheath surrounding the rod.
• This arrangement assures easy assembly, easy replacement in case of wear or damage, and an adjustment of the pressure exerted by the piece of conductive material on the chisel, the chisel pin or the shank of the chuck. actuator, depending on the importance of screwing the socket into the threaded hole of the sheath.
• This arrangement allows the equipment of existing stitching devices, with minor adjustments.
• the piece Conductive material is thus held firmly in safe and definite contact with the chisel, the chisel pin or the actuator rod.
• the device according to the invention comprises two pieces of conductive material arranged facing each other, bearing against the chisel, the rod thereof or the actuator rod, on either side of that -this.
• the reliability of the electrical contact is optimal.
• the opposing pressures of the two sockets cancel out and prevent the deflection of the rod.
• the point of the cell taken as a reference is located on the cathode.
• FIG. 1 is a schematic sectional view of an electrolysis cell for producing aluminum by the Hall-Héroult process
• FIG. 2 is a sectional view of the stitching device equipped with an embodiment of the device according to the invention, in which the chisel is in the low position,
• FIG. 3 is a partial sectional view of the stitching device equipped with an embodiment of the device according to the invention, in which the chisel is in the up position;
• FIG. 4 is a sectional view on an enlarged scale; , the socket of. device according to a preferred embodiment of the device according to the invention.
• FIG. 1 shows an electrolysis cell 1 intended for the production of aluminum by the Hall-Héroult method.
• This cell 1 comprises a cathode 2 formed of several cathode blocks, a melt of molten aluminum 3, a bath of molten electrolyte 4 above which is a crust 5 formed of solid electrolyte and alumina, anodes 6 plunging into the electrolyte, a positive bar 7 which distributes the electric current to the anodes, cathode bars 8, sealed in the cathode blocks 2 and which allow the output of the electric current of the cathode 2, at least one negative bar which collects the current of the cathode bars 8 and a superstructure 10 on which is typically fixed the control device according to the invention, shown schematically in this figure, next to a feed system 12 of alumina and / or electrolyte .
• the installation comprises a chisel 13 carried by a rod 14.
• the chisel 13 can be fixed to the rod 14, for example by screwing, or form a single piece with the rod 14.
• This chisel 13 is vertically movable between a high position (see Figure 3) in which it is above the crust 5 and a low position in which it has perforated the crust and comes into contact with the electrolysis bath 4, as shown in this figure.
• the upward or downward vertical movement of the chisel 13 is controlled by an actuator, here constituted by a double-acting jack 15 provided with a piston 16 whose rod 17 is connected to the rod 14 of the chisel 13 by means of a connecting member 18.
• the rod 14 is mounted inside a sheath 30, within which is mounted a guide sleeve 11. Outside the sheath 30 is disposed a tube 34, with the interposition of elements 35 forming electrical insulators. At the end of the sheath 30 is mounted a scraper element 36.
• the control device comprises means for detecting the electrical contact between the chisel 13 and the electrolysis bath 4 in the form of an electrical circuit 19 able to measure the voltage between the chisel 13 and a point 20 of the cell taken as the reference potential, this point 20 being located on the cathode 2 in this figure.
• This electrical circuit 19 typically comprises a resistor 21, a voltmeter 22 and connecting conductors 9, 9 '.
• the measuring circuit 19 is connected to the rod of the jack 17, to the rod 14 carrying the chisel or to the chisel 13 by connecting means 23 able to create a reliable and point-to-point contact 24 between the circuit 19 and said stems or chisel.
• FIG. 2 illustrates a preferred embodiment in which said bridge contact is located on the rod 14 carrying the chisel. -. . .
• the connecting means 23 may be in the form of a metal part, typically made of steel, the section of which decreases towards the contact 24 with the rod 14 of the chisel 13, in particular in the form of a ball as shown in this figure, and are subjected to elastic means 25, shown in the form of a helical spring in this figure, pushing them towards the rod 14 of the chisel 13.
• the ball 23 and the spring 25 can be mounted inside a bushing 26 made of conductive material, such as steel or copper, the end opposite the ball being
• the sleeve 26 has an external thread 29 and is thus screwed into a threaded hole formed in the wall of the sheath 30 surrounding the rod 14. The sleeve is thus fixed firmly opposite the rod 14 and the contact 24 established between the ball 23 and the rod 14 is particularly safe and constant.
• Figure 3 is shown a portion of a device according to the invention wherein the chisel 13 is in the up position, the lower position being shown in phantom.
• a second sleeve 31 also comprising a ball and a helical spring is screwed into the sheath 30 surrounding the rod 14 of the chisel 13, facing the first bushing 26.
• the counter-pressures of the bushing 26 and the bushing 31 cancel each other out and prevent the deflection of the stem 14.
• the chisel 13 descends, from its upper position, to the crust 5 and the electrolysis bath 4, under the action of the cylinder 15. During this descent, the ball is in reliable contact with the movable rod 14 of the chisel 13 through elastic means 23 which push it towards the rod 14. The voltmeter does not detect at that time significant voltage, the circuit 19 is not closed.
• the voltmeter 22 detects the crossing of a voltage threshold due to the point contact 24 between the measuring circuit 19 and the rod 14 by means of of the ball 23.
• the device according to the invention thus makes it possible to avoid the repeated deposits of solidified bath on the chisel and the clogging and blocking phenomena which result from it, and provides a certain advantage over the control devices of the prior art.
• the invention is not limited to the sole embodiment of this control device described above by way of example, it encompasses all variants.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)
• Furnace Details (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=34981571

Family Applications (1)

Country Status (14)

Families Citing this family (14)

Family Cites Families (8)

• 2005
  • 2005-04-19 FR FR0503877A patent/FR2884524B1/fr not_active Expired - Fee Related
  • 2005-09-08 US US11/220,905 patent/US7429314B2/en not_active Expired - Fee Related
  • 2005-09-09 CA CA2604971A patent/CA2604971C/fr not_active Expired - Fee Related
  • 2005-09-09 ZA ZA200709034A patent/ZA200709034B/xx unknown
  • 2005-09-09 BR BRPI0520068-7A patent/BRPI0520068A2/pt not_active IP Right Cessation
  • 2005-09-09 AU AU2005330635A patent/AU2005330635B2/en not_active Ceased
  • 2005-09-09 NZ NZ562768A patent/NZ562768A/en not_active IP Right Cessation
  • 2005-09-09 EP EP05805577A patent/EP2097560A2/fr not_active Withdrawn
  • 2005-09-09 RU RU2007142375/02A patent/RU2378418C2/ru not_active IP Right Cessation
  • 2005-09-09 CN CN200580050099.5A patent/CN101198725B/zh not_active Expired - Fee Related
  • 2005-09-09 WO PCT/FR2005/002244 patent/WO2006111622A2/fr not_active Ceased
• 2006
  • 2006-04-17 AR ARP060101500A patent/AR055911A1/es active IP Right Grant
• 2007
  • 2007-10-21 EG EGNA2007001129 patent/EG24773A/xx active
  • 2007-11-13 NO NO20075819A patent/NO20075819L/no not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events