US3761379A - Aluminum production apparatus - Google Patents

Abstract

APPARATUS HAVING A POT IN WHICH ALUMINA AND CRYOLITE ARE ELECTRICALLY HEATED, COMPRISING: TWIN CARBONACEOUS ANODE BLOCKS, HAVING ALIGNED HORIZONTAL BORES; STEEL CARBON-BLOCK HOLDING, VERTICAL STEMS; AND A JOINED HORIZONTAL STEEL PIN THAT FITS IN THE ALIGNED BORES, WITH A SLIP-FIT CLEARANCE IN ASSEMBLY AT ROOM TEMPERATURE, AND TIGHT, CURRENT-CONDUCTING CONTACT WHEN IN THE HEATED MATERIALS. THE INVENTION COMPRISES: MEANS FOR MANUALLY OR AUTOMATICALLY JACKING ANODES UP OR DOWN SEPARATELY OR TOGETHER; MEANS FOR MAINTAINING A PREDETERMINED VOLTAGE ACROSS EACH POT OF A POT LINE, EACH OF THESE VOLTAGES BEING SET FOR EFFICIENCY OF A PARTICULAR POT; A CARBON-BLOCK ANODE HAVING A VERTICAL FACE FOR FITTING AGAINST THE SIMILAR FACE OF A TWIN BLOCK, AND A PIN-FITTING, HORIZONTAL BORE TERMINATING AT THE VERTICAL FACE; AND A METHOD OF REPLACEMENT OF A HEAT-WORN CARBON-BLOCK BUTT BY JACKING IT UP, COOLING THE PIN UTIL IT HAS CLEARANCE IN THE BORE, REMOVING THE BUTT, AND REPLACING A BLOCK ON THE PIN.

Description

Sept., 25, 1973 c. H. ELLIOTT 3,76,379

ALUMINUM- PRODUCT I ON APPARATUS mgl EHAR LES H. ELLIOTT,

' INVENTOR.

17. WWW-s ATTORN EY.

Sept. 25, 1973 c. H. ELLIOTT ALUMINUM-PRODUCTION APPARATUS 3 Sheets-Sheet 2 Filed July 20, 1971 AUTUMATI C ALL MOTORS CONTROL 4IJOWER SOURCE OVERR IDE OF CONTROL CENTER MANUAL OVERRIDE FIC-5.4

^HARLES H. ELLIOTT, l Fl G' 2 INVENTOR.

- WFM/' ATTORN EY.

3 Sheets-Sheet 5 TNVENTOR ATTORN EY..

AuToMATlc VOLTAGE SYSTEM (COMPUTER) A .c. pou/ER souRcE PSHI/ARLES H. ELLIOTT,

C. H. ELLIOTT ALUMINUM-PRODUCTION APPARATUS ANODE E ws 2 C 4. D I 5 7 S Y E G T 5 U .LLNAL 5 B `nu LLIMO m E a A o K o n B N D f U R c T T R TE O N T O U N m O I ANLAO D. H M N N T OBFC I O A .C O W C C T I m m A. T M n E L n JM l N O w 2 ,am m L 7 m A wm w .w

Filed July 20,. 1971 METERING UNIT sept. 25, 1973 DOWN REFERENCE SIGNAL BARS CURRENT THRU ALL BUS METERING UNIT FOR POT LINE FIG. 5

United States Patent O U.S. Cl. 204--225 y14 Claims ABSTRACT F THE DISCLOSURE Apparatus having a pot in which alumina and cryolite are electrically heated, comprising: twin carbonaceous anode blocks, having aligned horizontal bores; steel carbon-block holding, vertical stems; and a joined horizontal steel pin that lits in the aligned bores, with a slip-lit clearance in assembly at room temperature, and tight, current-conducting contact when in the heated materials. The invention comprises: means for manually or automatically jacking anodes up or down, separately or together; means for maintaining a predetermined voltage across each pot of a pot line, each of these voltages being set for eiliciency of a particular pot; a carbon-block anode having a vertical face for tting against the similar face of a twin block, and a pin-fitting, horizontal bore terminating at the vertical face; and a method of replacement of a heat-worn carbon-block butt by jacking it up, cooling the pin until it has clearance in the bore, removing the butt, and replacing a block on the pin.

In the currently common reduction of aluminum from bauxite the steel bulbs that support the carbon anode blocks are bonded to the molten cast iron in the spaces between the stubs and carbon. This structure entails necessity, in replacement of the mostly burned carbon butts, of removing the anode-supporting steel stubs and rods with the butts. Then in the rodding room the butts are crushed olf the stubs, the stubs are mechanically cleaned, and new blocks are fixed to the stubs by re-pouring cast non.

In view of this laborous procedure, an object of this invention is to provide horizontally apertured anode blocks and horizontal steel pins, having a slip iit in their assembly at room temperature and at aluminumpot temperature having tight mechanical and electrical contact. Some other objects of the invention are to provide: (1) aluminum-pot sets 0f independently jacked anode assemblies, each assembly comprising an anode-supporting rod, twin steel pins, twin carbon blocks, and a flexible connector that is electrically connected to the elongated bus bar which supplies current to all the assemblies; (2) the combination of a xed anode-supporting frame, a bus bar, a plurality of jacks supported by the frame, steel block-holding means swivel-mounted on each jack stem, and flexible connectors between the said steel means and the bus bar; (3) the combination as in (2) above, comprising a current-sensing device around each flexible connector, and electrical means responsive to a signal from this device for operating the associated jack; and (4) the combination as in (3) above having: a plurality of bus bars; a manual override for each jack motor and alternately for all the jack motors; and an automatic override for all jack motors. Other objects of the invention will be apparent from the following detailed specication and the attached drawings.

In these drawings: FIG. l is a side elevational view, partly in vertical section, of one aluminum-reduction cell or pot according to the invention; FIG. 2 is a sectional view of the structure of FIG. l from the plane indicated at 2-2 in FIG. l, but showing in a block diagram the invented system for controlling the jack motors; FIG. 3 is a detail view of structure for providing cooling of vriCe the anode-block supporting pins before detachment of the spent carbon blocks or butts; FIG. 4 is a detailed elevational View, partly in vertical section, showing the sWiveled anode-supporting stem and structure for its rotation; and FIG. 5 is a schematic and block-diagram illustration of the invented control circuit for the jack motors.

In FIGS. l and 2 the invented structure is shown as comprising: a pair of I-beams 1 that are directly o1' indirectly supported by the building structure; an anodesupporting frame 2; a bus bar 3; a plurality of reversible jack motors 4 (optionally pneumatic or electrical); an anodesupporting jack 5, selectively operable up or down by each motor; steel carbon-block-holding means 6, having an upper portion that is swivelly mounted in the combined thrust and rotary bearing 7; twin carbon anode blocks 8, in operation linally burning into butts or spent carbon blocks, 9; a plurality of exible, preferably laminated-aluminum connectors 12; springs 13, each being connected to the top of a jack screw and electrically insulated from the connector, for maintaining it in a desirable configuration; a bimetallic connection 14 between the flexible connector and the steel block-holding means, comprising an aluminum plate 16 pre-Welded to a steel plate 18 that is Welded to the steel means 6; anodecurrent-sensing devices 20; and circuitry (briey indicated in FIG. 2 and more in detail in FIG. 5) for selective individual or mass-operation control of the jack motors.

The twin carbon anode blocks 8 usually weigh approximately a ton apiece. Each has: a molded and bore aperture from end to end; a planar face 22 that'abuts the similar face 22 of the adjacent block; and a shoulder 24, preferably extending from end to end of the block. Between the vertical shoulders 24 extends the lower end of the steel block-holder stem 2.6; and to the bottom of 26 the steel pin 28 is welded, this pin being in the block bores and in ljuxtaposition with the ledges at the bottom of the shoulders.

The block y8 may be formed either in a mold by use of a high-pressure hydraulic press, or in a mold in which carbon compaction is obtained by jarring the mold on an anvil while maintaining a moderate pressure With a hydraulic press. In either event, the mold has two separated shoulders, one to form space for the depending, supporting part for a mold core, and the other to form the shoulder or recess 24. The aperture for the blockholding pin is approximately formed in the mold by: either a heat-consumable, Wooden or aluminum cylindrical core that is held in molding position by the said depending part; or by a retractable steel cylinder extended into a wall of the mold. After the molding operation the carbon is baked, disposing of the core if it is of the consumable type; and the pin aperture is then finish-bored with a diamond cutting tool in a boring mill. The linishedbore diameter is such as to provide a clearance between the pin 28 and the carbon block when the block and the pin are at room temperature.

In use, at pot-operation temperature the diterence between coeiicients of expansion of the carbon and steel causes their unequal expansions to the extent that the pin is very tightly gripped. This interference fit provides excellent mechanical, block-steadying contact and excellent electrical contact of the `current-conducting carbon and steel.

CHANGING OF ANODES When the twin carbon anode blocks 8 have burned into butts, indicated at 9, they are replaced by new anodes. This is accomplished by: (l) operating the appropriate jack motor 4 in the direction for raising the block-holding means 6, this motor driving the jack, which elevates the twin butts 9; (2) attaching the :compressed-air hose 30 (FIG. 3) to the coupling 32 on the end of pin 28 and blowing air (optionally cooled at a point near the pin by a vortex cooler) thru the aperture in the pin, to the extent necessary to so reduce the pin temperature as to eliminate the holding friction between the steel and carbon; (3) removing the hose; (4) an anode-carrying boom supported by an overhead crane or vehicle then is brought into alignment with the pin, a forked hydraulic ram is dropped into position straddling the stem 26, with lingers that engage the shoulder 24 and pull the block olf the pin and onto the boom; (5) the vehicle or crane transfers the butt 9 to a transport vehicle; (6) the boom picks up a new anode 8, realigns with the pin and a pneumatically operated collar pushes the new anode off the boom and onto the pin; (7) the steel holding means 6 is then rotated 180 degrees: by means of the manually operated pin bar 34, temporarily litting in one of the recesses or holes 36 (preferably three annular recesses); or alternatively by means of the pneumatic or electric motor 38 (FIG. 4), manually controlled, rotating the stem 26 by the worm shaft 40, engaging worm wheel 42; (8), (9), (10) and (11)-the above steps 4 to 7 are now repeated in removal of the second one of the twin carbon blocks; and (l2) operating the jack motor 4 in the direction for lowering the block-holding means 6, until the new blocks are moved thru the opening that was formed in the crust of alumina during raising of the butts 9, and until the blocks are immersed in the cryolite.

During this anode-changing operation the weight on the combined thrust and rotary bearing 7 becomes unbalanced relative to the axis of the stem 26. This may be due to the temporary necessity of having only one butt 9 on the stem and pin 28, or by having one butt and only one new buttreplacing carbon block 8 on the pin. The stem 26 is then prevented from transmitting its deflection to the jack screw by the stabilizer 43. An optional limit switch, 43L, mounted on the stabilizer, normally closed, is opened when the jack screw reaches the end of its travel in the upward direction, thus preventing the possible jamming of the thrust bearing against the stabilizer.

CONTROL OF THE JACK MOTORS In the above-described changing of anodes the jack motors 4 preferably are manually controlled. Irrespective of whether they are pneumatic or electric they are controlled by means of electrical coils. When they are pneumatic each of these coils is in a solenoid that operates a valve; when they are electrical each of the coils operates a switch. Each of these coil means (comprising a solenoid coil and valve or a solenoid coil and switch) is selectively connectible either to manually operated means or electrical means in an electrical circuit which preferably is of the type indicated briey in FIG. 2 and more in detail in FIG. 5.

The controls indicated in the diagramatic blocks in FIG. 2 optionally may comprise a single large box, mounting the control center 44 and the override components of the circuitry of FIG. 2 or FIG. 5; or these components alternatively may be supported by a plurality of boxes.

The circuitry of FIG. 5 comprises the control center 44, receiving signals from several sources and converting these signals into jack-motor-operating power, selectively for operating a single jack or all the jacks of one cell or pot, and also selectively for operating the jack means in up or down direction.

The manual override comprises two sets (46 and 48) of switches operable `by pushbuttons or the like (here shown as twelve, for twelve twin anode blocks in a pot), one set for raising any one or all of the anode blocks in a cell; and the other set for lowering any or all of the blocks of the cell. One of the pushbuttons (50, 50) is for each of the twin-anode assemblies of a pot (twelve of these assemblies are indicated in FIGS. 1 and 2, but for ease of illustration there are shown in FIG. 5: only one of these assemblies at 52, only four of the twelve jack motors, and only one of the twelve anode-current-sensing devices Each of the pushbuttons S4 and 54 is for simultaneous or gang operation, up or down, of all twelve of the jack motors of a pot.

Optionally and preferably, there are two types of automatic controls: (l) an automatic control system for maintaining Via each of the anodes equal current distribution among the anodes, by individually raising or lowering the anode, thus changing the length of the path thru the cryolite and the resistance to current from the anode to the cathode 60, comprising a plurality of current-sensing devices 20 and of metering units 56; and (2) the automatic voltage control system 58.

In the individually controlled equal-current distribution system the current-sensing device 20 encompasses a portion of each individual conductor 12, which may be a solid part of the conductor, but as shown is preferably part of a exible laminated-aluminum element. The device 20 comprises: an iron magnetic core 61 encompassing the conductor 12; a plurality of coils 62 in which current is circulated to produce a ux in opposition to the flux in the core that is caused by the anode current owing thru the conductor 12.

The metering unit 56, of one of the commercially obtainable types, is associated with the device 20 and performs three functions: (l) it supplies flux-producing current to the coils 62; 2) it sense the interrelation between the ux from the current in coils 62and the flux caused by the conductor 12; and (3) it continually sends a signal, which is proportional to the anode current, to the control center 44. In this center a time-controlled, periodic comparison is made of the signal from each anode with a signal from the pot-line metering unit 64.

The commercially obtainable unit 64 receives a signal from the current-sensing device 66 which encompasses the common direct-current supply line (which may comprise the bus bars 68), thru which current ows to all the pots. This device 66 is similar to the device 20. The unit 64 supplies to the control center 44 a signal that is proportional to the main pot-line current thru all the pots.

The control center 44 periodically compares the signals from S6 and 64 by placing them in opposition in a coil or coils. When these signals are unequal a signal current in the center is caused. When this current reaches a predetermined value it causes the associated center follow-up elements to send a signal to the jack motor of the anode being tested, for operating the jack up or down. These follow-up elements may be a combination of coil-operated switches or of solid-state components such as the transistors, diodes and resistors of an integrated circuit. The predetermined value may be set (for example at a difference of 1% of the smaller full-load value of the two compared signals) by means of a silicon-controlled diode that triggers a supply current to the jack-motor control involved when the diodes control element is energized by the predetermined difference. An amplifier in the control center amplies the jack-motor controlling current. When the above-mentioned coil-operated switches are optionally used, the predetermination is accomplished by a contactmaking voltmeter that closes the appropriate one of the switches indicated in FIG. 5 in the control center-for example the switch 70.

AUTOMATIC VOLTAGE CONTROL The voltage-control system 58 maintains a predetermined voltage across each cell or pot on the pot-line. The voltage across the Various cells is predetermined for each pot according to that which is best for efliciency in that particular pot. For example, a pot may be recently re-lined, involving higher internal resistance which requires higher voltage for eiciency. The system 58 holds the voltage across each pot at the value established by the operator at the pot by manually setting an adjustable reference voltage means, for example a variable resistor, 71, in a battery and voltmeter circuit, to the predetermined value on the voltmeter. This circuit is connected with and sends a signal, via conductor 72, to the computer of the system 58. The computer also sequentially receives another signal, via conductor 73, of the actual voltage across the pot being tested, this voltage being indicated by the voltmeter 74. These two signals are cornpared in the computer by bucking one against the other, as in a bridge circuit. The resultant signal of the dilerence, if any, is transmitted to the control center 44, via conductors 78 and 79, closing all the switches of the center in either the up or down mode, to cause the jack motors to raise or lower all the anodes of that pot.

The manually controlled means 80 for blocking the automatic controls comprises a multiple-contact relay connected with the conductor 78, for switching off the periodic current from 58, and also connected with the conductor 76, for switching off the currents from 56. This relay is operated by current that is switched on by a manually-operated switch. The resulting blocking enables jacking and removal of an anode by manual means (not interfered with by automatic controls)-by Closing one of the switches actuated by a pair of the push buttons, 50 and 50.

I claim:

1. Apparatus for the production of aluminum from alumina, comprising:

a crucible, adapted to hold cryolite, alumina and molten aluminum;

a cathode, electrically connected with said molten aluminum;

means for conducting current from said cathode out of said apparatus;

anode means electrically connected with said cryolite,

alumina and aluminum, comprising: anode-supporting structure, having upright, metallic, current-Conducting, carbon-block-holding means and a substantially horizontal, current-conducting, metallic pin means; and carbon anode block means, comprising carbon portions surrounding said pin means; the said carbon block means having at least one, substantially horizontal bore of a diameter suflciently greater than that of said pin to provide a slip-fit clearance between the pin means and bore at room temperature and to provide a tight, current-conducting fit between the pin means and carbon at temperatures of the contents of the Crucible when the apparatus is in operation; and

means for conducting current to said anode means.

2. Apparatus as set forth in claim 1, in which said pin means has a hollow central space, comprising means for transmitting cooling uid thru said hollow space, quickening formation of said clearance between the heated pin and blocks.

3. Apparatus as set forth in Claim 1, in which said anode block means comprises a pair of twin Carbon blocks, having aligned bores on and separately detachable from said pin.

4. Apparatus as set forth in claim 3, in which each of said twin blocks has a vertical face abutting the similar face of the other twin block.

5. Apparatus as set forth in claim 3, in which the said anode-supporting structure comprises: jack means, forcetransmittingly connected to said upright, carbon-blockholding means; combined radial and thrust bearing means between said upright means and jack means; and structure providing for rotation of said upright means on its axis, after removal of one of said twin blocks from said pin means at one side of said Crucible, for facilitating removal of the second twin block from the pin means at the said side of the Crucible.

6. Apparatus for the production of aluminum from alumina, comprising:

a crucible, adapted to hold cryolite, alumina and molten aluminum;

a cathode, electrically connected with said molten aluminum;

means for conducting current from said cathode out of said apparatus;

anode means, electrically connected with the contents of said Crucible, comprising: anode-supporting jack means; upright, metallic, current-conducting, carbonblock-holding means, swivelly connected to said jack means; a substantially horizontal, current-conducting, metallic pin means; and twin carbon anode blocks, each comprising carbonaceous material. surrounding said pin means; and

means for conducting current to said anode means; and

structure providing for turning of said upright means on its axis, after removal of one of said two blocks at one side of said crucible, facilitating removal of the second twin block from the pin means at the said side of the Crucible.

7. Apparatus as set forth in claim 6, comprising means for stabilizing said upright, carbon-bloCk-holding means after the said removal from'the pin means of said one of the twin blocks.

8. Apparatus as set forth in claim 6, in which: each of said blocks has a bore permitting its sliding removal from said pin means at a temperature lower than that of the contents of said Crucible during its operation; and the said pin means has a hollow central space, adapted for the transmission of cooling fluid thru the pin and blocks.

9. Apparatus as set forth in claim 6, comprising, with said Crucible, cryolite, alumina and aluminum, a plurality of sets of jacks, jack motors, Current-conducting anodes, anode-supporting means and Cathodes, each of these sets comprising a said jack, motor and motor controlling means, a said Cathode and a said anode means, in which the said controlling means for controlling the direction and operation of each of the motors comprising: electric coil means for application of power to the motor; a group of manually operable switches, each of which is connected with said coil means for operating a motor in anode-elevating direction; and a second group of manually operable switches, each of which is connected with said coil means for operating a motor in anodelowering direction.

10. Apparatus for the production of metal from ore, Comprising:

a Crucible, for containing electrically heated ore and molten metal;

a cathode, electrically Connected with said molten metal;

means for conducting Current from said Cathode out of said apparatus;

anode means, electrically Connected with contents of said Crucible, comprising: anode-supporting means above said Crucible; upright, metallic, Current-conducting, carbon-bloCk-holding means; at least one current-conducting, metallic pin; and at least one carbon anode block comprising carbonaceous material surrounding said pin, having a bore permitting its sliding removal from the pin at a temperature lower than that of the contents of said Crucible during its operation; the said pin having a hollow Central space, adapted for the transmission of Cooling uid thru said pin and block.

11. Apparatus as set forth in Claim 10, comprising: a pair of twin carbon blocks, having aligned bores on and separately detachable from said pin; and a coupling on said pin, flow-connected with said hollow space, for attachment of a Huid-supplying conduit to the pin.

12. A system for production of aluminum from alumina, Comprising:

a plurality of Crucibles, each of which is adapted to hold cryolite, alumina and molten aluminum; anode means, comprising a plurality of carbonaceous anode-block means;

means for supplying electric Current to said anode-block means in each Crucible, Comprising a plurality of conductors;

cathode means, electrically Connected with Contents of each Crucible;

the pot-line current in the main electric line to all the auodes, and supplying a signal proportional to the pot-line current;

a control center for each crucible, receiving said individual signals and said pot-line signal, comprising: time-controlled means for periodically and separately comparing the pot-line-current signal with each of said individual signals; individual, anode-positioncontrol switches, each of which is associated with one of said motors; means for closing the appropriate one of said individual switches on a predetermined difference between the compared individual signal and pot-line-current signal; and means for electrically connecting said control center with said metering unit, pot-line-current sensing means and said motors;

an auxiliary current source in the neighborhood of each of said crucibles, comprising variable resistance means, adjustable by the operator at said crucible for predetermining a reference voltage drop across contents of that crucible, supplying a signal of said reference voltage;

an automatic voltage system, maintaining a predetermined voltage across each crucible, comprising a computer, intermittently sending a signal to said control center that overrides all the said individual,

anode-position-control switches and requires raising or lowering of all of said anode-block means in a pertinent one of said crucibles, for increasing or decreasing the voltage across that Crucible;

means comprising instrument conductors for transmitting to said computer a signal of the existing voltage across each crucible to the computer;

a voltmeter in the neighborhood of each of the crucibles, connected to said instrument conductors;

the said voltage system comparing the reference of each of said variable resistance means with said signal of existing voltage at each of said crucibles, and sending a voltage-dilference-caused overriding signal to said control center for the said raising or lowering of all anode-block means of a crucible, in

elimination of the said difference.

13. A system as set forth in claim 12, comprising manually controlled means for blocking said overriding signal,

providing for individual control only of each of said anode-block means in a selected number of said crucibles.

14. A system as set forth in claim 13, comprising manually controlled means for sending a signal to said control center for selectively causing said center to require raising or lowering of any number of said anode-block means in a selected one of said crucibles.

References Cited UNITED STATES PATENTS 2,545,412 3/1951 Perret-Bit 204-228 X 3,052,619 9/1962 Schmitt 204-243 R 3,485,727 l2/l969 Uhrenholdt 204-228 X 3,575,827 4/1971 Johnson 204-225 X 3,674,674 7/1972 Arts et al. 204-228 X JOHN H. MACK, Primary Examiner D. R. VALENTINE, Assistant Examiner U.S. Cl. X.R.

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