US3640800A

US3640800A - Electrolytic cell

Info

Publication number: US3640800A
Application number: US54829A
Authority: US
Inventors: Arthur F Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-07-14
Filing date: 1970-07-14
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08

Abstract

An improved electrolytic cell having collector elements arranged horizontally in the cell and extending to the sides thereof, and a slab of aluminum disposed horizontally at the bottom of the cell to which the collector elements are connected.

Description

[ Feb. 8, 1972 United States Patent Johnson [541 ELECTROLYTIC CELL 3,063,919 11/1962 Jouguetetal..................... 3,385,778 5/1968 Johnson............................

Primary Examiner-John H. Mack Assistant Examiner-D. R. Valentine [22] Filed:

Attorney-Pennie, Edmonds, Morton, Taylor and Adams [57] ABSTRACT An improved electrolytic cell having collector elements ar- .204/67, 204/243 M, 204/244 ------C 3/ (322d ranged horizontally in the cell and extending to the sides Field of 243-247, th r of, and a slab of aluminum disposed horizontally at the 2 4/2 M bottom of the cell to which the collector elements are connected.

[51] Int.

29 Claims, 6 Drawing Figures Reierences Cited UNITED STATES PATENTS 2,999,801 9/1961 Wleugel................................

ELECTROLYTIC CELL BACKGROUND OFTI-IE INVENTION In. the electrolytic reduction of fusions to produce aluminum in electrolytic cells disposed in a potline, the concept of carrying current from the collector elements through the steel potshell sides and to the pot-to-pot bus was incorporated in the'earliest Hall-cells. In'these early constructions, the collector elements .were bolted to the potshell sides which were, in turn, riveted to a bottom much thinner than the sides. This resulted in practically all the current flowing horizontally along the potshell sides in a manner causing high vertical magnetic flux density in the cavity containing the fused electrolyte and underlyingreduced-aluminum. This high flux density was especially prevalent at the so-called long arm or upstream corners of the cell where current was collected in a copper bus leading endwise of the cell to join the short arm bus,'connected to the downstream-comers of-the cell. The flow of current around" the sides of cells of this construction, being generally at the level-of the'cavity containing the molten aluminum, produces unwanted heaping of the molten metal-and unpredictable electromagnetic circulation of the molten metal andotherwise decreasesthe efficiency of the reducing operation.

Many of todays potlines have vertical magnetic flux densities-in the moltenmetal'pad equal to or greater than those of back and forth on themselves but such methods require much more prefabricated aluminum bus which is expensive to fabricate and requires considerable space.

Illustrations of cells having lateral cathode and anode bus structure and utilizing either Soderberg or prebaked electrodes in end-to-end or side-by-side arrangement in the potlines are containedin'thefollowing U.S. Pat. Nos.: 2,761,830; 2,804,429; 2,874,ll; 3,385,778; 3,404,081 and 3,415,724. In addition to the constructions disclosed in the above-listed patents, my earlier US. Pat. Nos. 3,434,957 and 3,434,958 disclose cell constructions with improved flux density patterns produced by directing the current directly downwardly throughthe potlining to an underlying slab of aluminum. Constructions of this type, however, require vertically disposed collector elements and thus complete overhauling of. existing cells using.horizontally disposed collector elements.

SUMMARY OF THE INVENTION The improved'electrolytic cell constructed in accordance with. the teachings of the present invention may be advantageously used in the construction of new potlines of high amperage such as 200,000 amperes or more and may also be used for converting at low cost potshells now in use.

Generally, the improved electrolytic cell includes a rectangular steel or aluminum potshell having a cathode carbon potlining with a cavity for'containing fused electrolyte'and an underlying layer of reduced aluminum. Horizontally disposed iron collector elements are embedded in the potlining and extend normal to the sides of the cell for collecting cathode current'and leading it to the pot-to-pot bus means-connecting the cell to the next cell in a line of cells. Instead of collecting the current flowing from the collector elements in-the conventional cathode ring bus encircling the cell at the level ofthe cavity, this structure is eliminated and the current is all directed from the collector elements to a slab of aluminum disposed at the bottom of the cell in underlying relationship with the cavity. Portions of the slab extendalong certain areas.

of the sides of the cell for connection to the collector elements and the slab is shapedso as to direct current'from the collector elements along paths which produce a vertical electromagnetic flux density as measured along the potlining cavity which is generally uniform along the cavity and less than the horizontal electromagnetic flux density.

The improved electrolytic cell construction not only eliminates the need for complicated-cathode ring bus structurebut also eliminates the need for the usual flexibles which are normally used to attach the collector elements to the bus structure. The elimination of the horizontally running bus structure generally reduces unwanted electromagnetic circulation and heaping of the molten metal in the cavity and provides more room between potshells for repairs and maintenance. Also, with the current flow being. controlled to produce low vertical electromagnetic fluxdensity, the reduction process is made more efficient due to the less heaping of the molten aluminum. The anodes require little if any adjustment due to uneven burning in different parts of the cell. Theoretically, with a level molten cathode, each anode should adjust itself to draw current at equal current densities which is not possible with conventionalconstructions due to the unpredictable heaping of the molten aluminum. The efficiency of the reduction process is alsoincreased since the temperature under the anodes can-be maintained more uniform due to the reduction in the magnitude of the vertical flux density and the creation of more uniform flux density throughout the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph comparing the vertical flux density produced in the improved cell of the present invention with the flux density of conventional cells;

FIG. 2 is a cross-sectional view of one embodiment of the improved cell'ofthe present invention;

FIG. 3 is a plan view showing the orientation of the improved cell of FIG. 2 disposed in side-by-side relation in a line of cells;

FIG. 4 is a plan view of the aluminum slab employed in the embodiment of the present invention shown in FIG. 2 with the side portions thereof folded outwardly and showing the amount and direction of currentflow therethrough;

FIG. 5 is a plan view of a modified embodiment of the aluminum slab structure used in the improved cell of the present invention; and

FIG. 6 is a perspective view of the improved collector element of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shownin FIGS. 1 and 2, the improved electrolytic cell as constructed for side-by-side arrangement in a potline includes a generally rectangular potshell 1 having relatively upright sides defined by elongated.

sidewalls

2 and 3 connected together by end walls 4 and 5 and a generally flat bottom 6. The-potshell contains an electrically conductive cathode potlining 7 having a cavity 8 for holding fused electrolyte 9 and an underlyinglayer of reduced molten aluminum 10. The fused electrolyte has a crust 9' frozen on its upper surface. An inwardly extending rim on the potshell forms a reinforced deck plate 11 which is bolted down after the carbonaceous potlining is rammed into place. Disposed at the bottom of the cell and in underlying relation with the cavity 8 is a slab of aluminum 12. The aluminum slab includes portions extending along certain 'areas at. the side of the cell along the sidewalls and end walls as will be more fully described below. Disposed between the slab of aluminum and the potlining is a layer of heat insulation brick 13. There is also a thin refractory electric insulation 14 under the aluminum slab to prevent the slab from contributing to the electrical conductivity of the underlining bottomzof the potshell. The insulation 14 is, however, thin enough to permit the flow of heat from the slab to the bottom of the potshell.

Extending through the crust-9' and into the fused electrolyte contained-in the cavity 8 are pairs of carbon anodes 15. Multiple pairs'of anodes extend the length of the cell and are disposed at a distance of about 1.5 inches above the molten aluminum. Asshown in FIG. 1, the anodes are mechanically 8 Average having an encircling bus structure at the level of the cavity is 19 made to show the points at which the vertical flux density is where a multiple number of flexible aluminum sheets 20 are welded for-lowing the bus bar to a riser bus 21 connecting Table I below sets forth the values of the vertical flux density at eight points along the upstream edge and downstream edge of the conventional cell arranged in side-by-side relation in a potline. The values for the eight points along the upstream edge and downstream edges represent eight points disposed on both sides of the transverse centerline of the cell. The flux alue as the density on the left half of the cavity and is only op ppsite in sign or From the values of Table I, the net vertical flux density along the upstream and downstream edges of the cell is In FIG. 1, curves representing the vertical flux density along the upstream and downstream edges of the improved cell con- I Table II below sets forth the values of the vertical flux density on which

curves

26 and 27 are based. The values were calculated at the same eight points in the cavity of the cell as patlining cavity bus structure connecting the cell in line with other cells. Preparatory to determining the shape of the slab shown in FIG. 4, evaluation of the flux density of the conventional cell de most troublesome.

density at any point on the right half of the cavity is the same 15 in v plotted in FIG. I. The values of the vertical flux density of the shown by the dotted lines 26 while the values of the vertical flux density along the downstream edge of the conventional cell are shown by the dotted lines 27. In FIG. 4, the outline of the potshell is shown by the dash lines 24 and the points along the edges of the cavity 8 where the vertical flux density is mea-.

.Sured r h wn xt eee ir lei nu struction of the present invention are shown by the solid lines 28 and 29, respectively. The curves 28 and 29 are calculated in the same manner as used for the

curves

26 and 27.

were used for determining the flux density in the conventional cell.

Vertical flux density components in gauss calculated at points along left upstream edge of In accordance with the teachings of the present invention, the current is withdrawn from the cell through a plurality of horizontal collector elements 23 disposed rigidly normal to the sides of the cell as by welding their ends to the cell sides.

FIG. 4 shows the particular construction of the aluminum slab used in the embodiment of the invention shown in FIG. 1.

The particular shape of the aluminum slab including the portions to be disposed below the cell and those to be disposed along its sides, produces a substantially uniform and low elec- Conductor causing vertical flux density joined to stubs 16. The stubs which may be made of steel are, in turn, connected as by welding or bolting to one endof rod members 17. The rod members which may be of aluminum or copper are adjustably secured at their other ends to an ano bus bar 18. The bus is formed into a ring bus at its ends cell to the downstream bus 22 of the next upstream cell in the potline. A superstructure from which the anode ring bus is suspended by vertically adjustable jacks is not shown. As shown in FIG. I, the downstream bus 22 is connected to the cell aluminum slab underlying the cell. Referring to FIG. 3, it will be seen that each cell includes two downstream bus means 22 extending from the downstream side of the cell in diverging relation with respect to each other.

downwardly into the underlying portion of the aluminum slab l2 and from there to the downstream bus means 22.

In FIG. 4, the aluminum slab is shown in plan view with the side portions which would extend along the sides of the cell folded outwardly. In FIG. 4, the outline of the potshell is shown by the dash line 24. Also, the outline of the edges of the cavity 8 is shown by the dash line 25.

tromagnetic flux density along the cavity. The shape is determined on a trial and error basis by calculating the vertical flux density at various points in the cavity as caused by current flowing through different segments of thecell and adjoining TABLE I.-VE RTICAL MAGNETIC FLUX DENSITY OF CONVENTIONAL CELL IN SID E-BY-SIDE ARRANGEMENT IN POTLINE Current in conductor, (M amps.) 1

34 56 055 4nm w2 2 3 L2 wnaumw maaaea Vertical flux density compontents in gauss calculated at points along left downstream edge of potlining cavity Totalflux downward Totalfluxupward Net vertical flux density.

26706959 200 1 0 &0 &

323 455 42 23 0m0mL2 1 Dim- 2 2 1 in pstream riser to anode bus. End bus from upstream lateral Pot-to-pot bus segment. Downstream lateral bus Adjacent downstream lateral bus Downstream anode bus.. Upstream anode bus.

TABLE IL-VERTICAL MAGNETIC FLUX DENSITY OF IMPROVED CELL OF PRESENT INVENTION IN SIDE-BY-SIDE Vertical flux density components In gauss calculated at points along left upstream edge of potlining cavity 8 Average ARRANGEMENT IN POTLINE Total flux downward Total flux upward Net vertical flux density" Conductor causing vertical flux density Current in 35527241 am mnZsaa VERTICAL MAGNETIC FLUX DENSITY OF IMPROVED CELL OF PRESENT INVENTION IN SIDE-BY-SIDE ARRANGEMENT IN POTLINE-Continued Vertical flux density components in gauss calculated at points along left upstream edge urreul. in f tlin' t conductor, Conductor causing vertical p0 mg ca y (M amps.) flux density 1 2 3 4 5 6 T 5 Average Vertical flux density components in gauss calculated at points along left downstream edge of potlim'ng cavity 60.... Upstream riser to anode bus. 6.8 8.3 7.4 6.1 4. 5 3. 5 2. 2 0.6 4.9 02-0-62 Ends of potshell.... 13. 9 3. 9 1. 5 0. 7 0. 4 0. 2 0.1 0. 0 2. 6 0-12.5-0 Middle bottom slab. 6.1 10.3 13. 7 15.3 13. 6 10. 5 6. 7 1. 1 9. 7 50-.. Pot-to-pot bus at so 1.7 8.0 6.9 10.3 9.4 7.2 6.3 2.6 0. 4 .6.2-0-6.2 Downstream potshell side. 0.-& 1.1 3. 6 12. 7 -21. 2 19.4 -10. 4 2. 7 8. 9 -0 Downstream anode bus... 4.3 4.6 4.6 4.0 3.3 2.4 -1. 5 0. 5 3. 1 26-0 Upstream anode bus 7.2 7.6 7.4 -6.7 -l5.5 4.1 2. 5 0.9 -6.2

Total flux downward 43. 7 21.3 16.4 23.4 30. 0 25. 9 -14.4 4. 1 22. 3 Total flux upward 26. 8 22. 5 29. 5 32. 4 27. 9 21. 4 15. 3 4. 8 22. 6

Net vertical flux density 16. 9 1. 2 9. 0 4. 5 0. 9 0.2 0.2

In determining the vertical flux densities of both the conventional and the improved cell, a cell having a length of 25% feet and a width of 8 feet has been used. Also, 100,000 amperes is the potline electrical current on which Tables I and II and FIG. 1 are based. The calculation necessary to determine the values for the vertical magnetic flux density arising from current flowing through different parts of the cell are well known, and therefore, not described in detail herein. In making these calculations, however, one skilled in the art will recognize that the vertical flux density component of flux at any certain point along one of the edges of the cavity 8; namely, at any encircled point (l-8), is proportional to the currentcarrying segment of the conductor structure under consideration and to the differences in the values of the sines of the angles formed, first, between a perpendicular line extending from the point to the segment under consideration, or to the segment extended, and a line drawn from the point to the far end of the segment under consideration; and, secondly, the sine of the angle formed between the above-mentioned perpendicular line and a line drawn from the point to the near end of the current conductor segment under consideration. Similarly, the vertical flux density caused is directly proportional to the ratio h/a where:

a is the perpendicular distance from the point at which the vertical flux density is to be determined to the segment under consideration, and h is the length of the horizontal side of a right triangle constructed in a vertical plane through line a with line u having the hypotenuse of the triangle. When a current conductor is at the same level as the point along the cavity edge where the flux density is being measured, h=a and the vertical flux density at this point is at a maximum as compared to the horizontal flux density which is zero. Also, the vertical flux density at this point is directly proportional to the current in the segment under consideration and to the above calculated sine differences and is inversely proportional to the perpendicular distance a from the point to the segment.

When a current-carrying segment is directly beneath and parallel to the line of encircled points (1-8) along the edge of the cavity, h=0. Accordingly, the vertical flux density is zero at'these points regardless of the amount of current carried in the conductor segment.

When a comparatively long conductor extends on bothsides and is relatively close to a particular point in the cavity at which the flux density is being measured, the sine differences between the angles as calculated in the manner described above approaches 2.0 which is the sum of the sines of two 90 angles and the maximum effect which can be exerted by a straight conductor with a given current. The smaller the angle subtended between the lines drawn from the point at which the flux density is to be measured to the opposite ends of the current-carrying segment of the conductor under consideration, the less the sine differences defined above andthe less the effect of the current in the segment on the vertical flux density at the point under consideration.

The aluminum slab shown in FIG. 4 is disposed directly underneath the potshell cavity with the side portions disposed along the sidewalls and end walls of the potshell. This construction compels the current to flow in the amounts and directions indicated in FIG. 4. The current values in FIG. 4 are in thousands of amperes; and for purposes of simplicity no electrical current is shown flowing in the steel potshell where it is bare of aluminum since the amount of such current is small compared to that current in the aluminum slab. For example, in practice it may be assumed that steel has an electrical conductivity of about 20 percent of that of aluminum. Accordingly, using an aluminum slab which is thick enough to result in a current density of 400 amperes per square inch of aluminum conductor cross section, the steel potshell can be assumed to be conducting amperes per square inch of aluminum. With a potshell bottom of five-eighths of an inch thick steel and an aluminum slab cast on top of the bottom and having a thickness of 1% inches, the latter will carry percent of the current.

Also, in connection with determining the flux density values of Table II, the distortion of the magnetic flux pattern at the various points of measurement as caused by the magnetic permeability of the steel potshell is not reflected. The magnetic flux densities as calculated in Table II are nevertheless accurate indications of the relative values of the densities which can be expected to be measured in an actual operating cell. In this regard, it is to be noted that in accordance with the teachings of the present invention, aluminum may be used for all parts of the potshell in place of the steel so as to reduce the distortion of the flux pattern which would otherwise be caused by steel.

With particular reference to Table I above, an examination of the vertical flux densities caused by each current-carrying segment considered in the conventional cell shows that the greatest problem in neutralizing flux density exists along the upstream edge of the cell cavity. Here, on the left end of the cell when facing upstream, the downstream lateral bus structure contributes a negative (downward direction) flux of 10.0 gauss compared to the 204.9 gauss in a positive (upward direction) contributed by the seven other conductor segments considered in the estimates. The flux density variation as produced at this point, as well as the other points along the upstream and downstream edges of the cavity is reduced by eliminating the conventional external bus structure and replacing it with the aluminum slab structure shown in FIG. 4.

The aluminum slab includes a solid middle bottom portion 30 extending the full length of the potshell and a solid downstream bottom portion 31 also extending the full length of the potshell. Along the sides of the cell, the aluminum slab includes solid comer portions 32 and finger portions 33. The portions of the slab disposed on one side of the transverse centerline of the potshell adjacent one end wall are separated electrically from the portions of the slab on the other side of such centerline. The collector elements 23 extending to the sidewalls and end walls of the potshell are connected directly to the aligned portions of the aluminum slab detailed in FIG. 4.

As shown in FIG. 3, there are fourteen collector elements extending to each of the sidewalls of the potshell while there are four collector elements extending to each of the end walls of the potshelluAs shown by Table II, the middle bottom slab portion-30 and the downstream bottom slab portion 31 both contribute downward vertical flux densities to balance the excess upward flux density at the various points along the upstream edge of the cavity. Additional balancing is achieved by the four collector elements extending inwardly from each end wall of the potshell with the electrical current from these being routed along the sidewalls of the potshell.

The currents flowing along the four potshell corner portions 32 of the slab are at the level of the cavity and hence exert the maximum flux balancing effect thereon at points near the ends of the cavity. Also, the aluminum finger portions of the slab are electrically insulated from the potshell with a dielectric paint or thin coating and thus contribute nothing to longitudinalconduction of current through the potshell sidewalls.

To compel the side portions of the aluminum slab disposed along the downstream side of the cell to carry the current in a circuit which is electrically parallel to the bottom slab portion, the thickness of the side and bottom portions are correlated so that the current densities in both will be about equal. With the slab having a downstream side portion of 3 feet in height and carrying 4,690 amperes and a bottom portion totaling feet in width and carrying 14,062 amperes, the side portion of the slab will be 1% inches thick while the bottom portion of the slab will be 2% inches thick. With this construction, both the downstream side portion and bottom portion of the slab will carry I04 amperes per square inch. By proportioning the thickness in this way for a current travel in parallel paths, each segment is compelled to carry the current desired so as to achieve a balance of the flux density.

The amount and direction of vertical flux density at the various points of the cavity is also dependent on the construction and arrangement of the external bus structure connecting the adjacent cells in the potline together. With the construction shown in FIGS. 2, 3 and 4, the downstream bus means 22 includes two arms 22a and 2211 each of which is connected to one of the separate bottom portions of the aluminum slab structure disposed on either side of the centerline of the cell. The connection of the arms is made to the bottom portions of the slab at points spaced from the adjacent end walls and the arms extend toward the next downstream cell in a diverging relation to each other as most clearly shown in FIG. 3. The arms extend at a level below the cell until reaching the upstream side of the next downstream cell at which point the arms are connected to the riser bus means 21.

By comparing the dotted and solid curves of FIG. 1 and the values set out in Tables I and II, it is seen that with the cell construction of the present invention, the average vertical flux density along the upstream edge of the cavity of the cell is reduced by about 90 percent (from 95.8 to 9.0 gauss). On the downstream cavity edge, the reduction in the average vertical flux density with the improved cell of the present invention is from -24 gauss to 0.2 gauss.

With the improved cell construction of FIGS. 2-4 of the present invention, the usual insulation of the collector elements from the potshell sides as found in conventional cells is eliminated. Instead, collector elements 23 are firmly welded to the potshell to make an electrical connection. The collector elements are also welded to the aluminum slab portions with which they are aligned. In the preferred construction, the collector elements are wedge-shaped as shown in FIG. 6. Where the potlining is built up of prebaked carbon blocks, these blocks are made with a wedge-shaped slot. Then, collector elements having a uniform rectangular cross section are positioned within these slots and anchored by pouring in cast iron. This produces a wrought iron-cast iron bar with the desired wedge-shaped horizontal cross section. The wedge-shaped collector elements when firmly welded to the side portions of the aluminum slab and to the sidewalls and end walls of the potshelltend to make a tighter connection, thus, one with lower electrical loses, as the bar lengthens when heating from room temperature to l,000 C. and as the potlining expands during operation and pushes outwardly against the pot sides. The wedge-shaped construction prevents the potlining from shearing away from the collector elements as would tend to occur with conventional collector elements of uniform cross section.

In addition to the connection of the collector elements to the walls of the potcell as well as to the aluminum slab, all or part of the insulation normally disposed between the carbonaceous potlining and the steel potshell of conventional cells may be omitted to permit current to flow laterally to the sidewalls of the potshell.

Removal of the insulation is most advantageously effected where the wall is aligned with regions in the potlining which are in turn adjacent the portions of the cavity where the vertical electromagnetic flux density is low in relation to the density in the other areas of the cavity. With conventional cell constructions, lateral conduction of current has generally been avoided since with high vertical flux density in the cavity, lateral current produces the undesired electromagnetic circulation and heaping of the molten metal in unpredictable patterns. With the improved cell construction where low vertical flux densities are attained, it is no longer objectionable to conduct some of the current laterally through the potlining and molten metal contained in the cavity. In order to ensure a good electrical contact of the side portions of the slab with the carbon potlining, such portions are formed with a corrugated inner surface when cast onto the potshell sides.

Where the potshell sidewalls and end walls are not covered by side portions of the aluminum slab, the carbonaceous potlining will be rammed tightly against the potshell walls so that part of the electric current will readily flow thereto. Also, the collector elements of the improved cell construction are made shorter than the conventional collector elements with the advantages that the inner ends of the collector elements are not disposed along the longitudinal centerline of the potshell. I-Iere heaving of the potlining and molten aluminum penetrating through the resulting cracks and dissolving collector elements is usually most severe.

The shape of the aluminum slabs shown in FIG. 4 has been devised to reduce the variations in the vertical flux densities at different points along the cavity of the potshell as well as for the purpose of minimizing these densities. By orienting the conducting segments of the cell as shown in FIG. 4, the vertical flux density at the upstream and downstream edges of the cavity is made substantially uniform as shown by the solid curves in FIG. 1. Also, the value of these densities is kept generally less than 30 gauss and the average under 10 gauss.

The shape of the aluminum slab and associated bus structure has, by channeling the current flow into paths that produce low vertical flux density, increased the horizontal flux density in the improved cell as compared to that which would be found in conventional cells. The horizontal flux density does not, however, produce the undesired heaping and electromagnetic circulation as caused by the vertical flux density and, therefore, is not objectionable.

The shape of the aluminum slab shown in FIG. 4 produces the desired result of reducing and evening out the electromagnetic vertical flux densities in the cell. However, it is to be understood that other similar shapes may be used as long as they produce similarly effective current flow patterns.

In FIG. 5 there is shown an aluminum slab construction 34 adapted for minimizing and evening out the magnetic vertical flux densities in cells adapted to be disposed in end-to-end arrangement in a potline. The shape of the slab is determined in the same way as the shape of the slab shown in FIG. 4 is calculated. Table'lll below shows the calculations of the vertical flux densities caused by current'flowing through various conductor segments of the cell and adjacent bus structure.

b. said slab is shaped to direct the current from said collector elements and through said slab to produce a substantially uniform vertical electromagnetic flux density as TABLE ill. --INVENTION IO'ICELL MAGNETIC FLUX DENSITY IN END-'IO-END ARRANGEMENT IN POTLINE Vertical flux donsltycomponents in gauss calculated at'polnts along right edge of potlinlng cavity when one laces upstream and Conductor causing vertical flux density segment 1 2 3 4 6 6 7 8 9 10 l1 l2 l3 14 Avg Near side slab 24.0 -31.0 36. 5 --40.6 42.0 -42.6 42.8 42.9 -42.9 -42.8 42. 6 4l.9 40.3 35.4 39.2 Near bottom slab. 0 0 0 0 0 0 0 0 O 0 0 0 0 0 Near midbottom slab 0.1 0.1 0.1 0.1 0. 2 0. 2 0.5 0. 9 1.8 3. 7 6. 7 0.7 12. 2 12.3 a. Far mldbottom slabm- 0. 1 0. 1 0. 2 0. 2 0. 3 0. 5 0. 7 1. 2 2. 0 3. 3 5. 0 6.7 7. 7 7. 4 2. 5 For bottom slab-.. 1.3 1.9 2.7 3.7 5.1 6.0 8.1 9.2 10.7 11.4 11.7 11.4 10.6 0.2 7.4 Far side slab 4. 6 5. 5 6. 4 7.0 7. 5 7. 8 8.0 3. 1 8.0 7. 9 7. 6 7. 2 6. 5 5. 6 7. 0 End side or bottom slab" -8.3 3.3 l.2 0.5 0.3 0 0 0 0 0. 5 -l.3 -3.0 -6.7 7.8 '2.3 Collector bars. 3.3 0 3.3 0 0 0 0 O 0 0 0 O 0 0 0 Near anode bus 7. 5 8. 6 8. 7 8. 4 7. 8 7. l 6, 4 5. 5 4. 7 3. 7 3.0 2. 6 1.6 1.0 6. 5 Far anode bus-- 19.0 21.4 22.4 22.3 21.4 19.0 18.0 16.0 13.8 11.6 9. 5 7. 5 5.7 4.2 15.1

Total flux down. -'-32.3 34.3 -41.0 4l. 1 42.3 -42.6 42.8 42.9 -42.9 43.3 43.8 -44.9 --47.0 43.2 4l.5 Total flux up 35.9 37.5 40. 5 41.7 42.3 41.2 41.7 40.9 41.0 41.6 43. 5 45.1 44.3 39.7 41.0

Net vertical flux density in gauss 3.6 3.2 0.5 0.5 0 -1.4 -1. 1 -2.0 1.9 -1.7 -0.3 0.2 -2.7 -3.5 -0.5

As shown in FIG. 5, the slab when used in a cell adapted to measured along the potlining cavity. be disposed end-to-end relation in a potline has a bottom por- 4. The improvement in an electrolytic cell according to tion 35 extending inwardly of the opposite sidewalls of the cell claim 3 wherein: by progressively smaller distances as measured along points a. said slab is shaped to direct the current from said colleclocated further from the downstream end of the cell. Also, the tor elements through said slab to produce a vertical elecdownstream end of the cell, the bottom portion 35 of the alutromagnetic flux density as measured along the potlining minum slab extends completely across the bottom of the cavity which is generally less than the horizontal elecpotshell. The bottom portion of the slab terminates at a tromagnetic flux density therealong. distance spaced from the other end wall of the potshell so that 5. The improvement in an electrolytic cell according to there is no underlying portion of the slab disposed along the claim 4 wherein: upstream end of the cell. Also, the

portions

36 and 37 of the a. the slab is shaped to produce a vertical electromagnetic slab disposed along the sides of the cell extend the full length 5 flux density as caused by external current flow through of the sidewalls with a diminishing height adjacent the upadjacent cells and connecting bus means when disposed stream side of the cell. in said line which is substantially uniform and generally The slab construction shown in FIG. 5 is-completed by the less than the horizontal electromagnetic flux density as upstanding end portions disposed along either end wall of the caused by said external current.

'potshell. More particularly, the slab includes an upstandi 40 6. The improvement in an electrolytic cell according to portion 38 disposed centrally of the end wall forming the Claim 5 Whefem! downstream end of the cell and two upstanding po i 39' a. said vertical magnetic flux density as measured at difalong the upstream end wall of the cell. As shown, the portions ferent points along the potlining cavity averages no 39 are disposed adjacent the comers of the cell which are gr ter th n about lOgauss.

formed with the sidewalls. As with the embodiment of the in- Th improvement in an electrolytic cell according to ventionshown in FIGS. 2-4, the collector elements 40 are claimSwherein:

connected directly to the aluminum slab structure aligned a. said potshell is generally rectangular with elongated h i h sidewalls connected together by end walls, said potshell Iclaim: being adapted to be disposed in side-by-side relation with l. in an electrolytic cell for the reduction of aluminum ad-lacent potshenS m sadlfne?and adapted'to be disposed-in aline of electrolytic cells in electrithe pomms 9 531d slab dlsposed to P Side of the cally connected relationshipand having a potshell with relaverse cemeflme of the Potshe *f f end wall tively upright sides and a generally flat bottom, a slab of aluthereof: are f the P of Said Slab the minum at said bottom, a layer-of refractory thermal insulation other s1de of sad cellteflma over the Slab, an electrically conductive cathode potlining The improvement in an electrolytic cell according to having a cavity for containingfused electrolyte and underlying clam 5 wherem1 reducedaluminum, a plurality of cathode collector elements f d P -Y Tecmngular with elongated extending generally normal to at least some of said sides and in F connected PE K Y walls, Sald Potshell :electrical engagement with said potlining, and cathode bus befng adapted to f P l'- relation i h means for connecting said cell to the anode structure-of the adlacem Potshells 531d 11116; and

next downstream cell in said line, the improvement wherein: Said l includes:

a. said collector elements at said sides of the cell are electrimidffle bottom Portions disposed on pp cally connected to said slab for connection through said sides of said transverse centerline and along the middle slab to the anode structure of the next downstream cell. of W bottom of the Potshell,

2. The improvement in an electrolytic cell according to solld downstwam bottom Portions disposed P- claim wherein: posite sides of said transverse centerline and along the a. said cathode bus means includes two arms each of which Side Of i potshell adapted to be the down tream id is connected to the slab on opposite sides of the trans- Ofthe cell in Said line w verse centerline of the cell and both of which extend Come! p i disposed along the sidewalls and end toward the downstream side of the cell in diverging rela- W l at h rn r f Said potshell and electrically tion to each other. connected to the collector elements extending to the 3. The improvement in an electrolytic cell according to side and end walls adjacent said corners, and

l i 1 wh i .4. finger portions electrically connecting the remainder of a. said slab extends along certain areas of the sides of said said collector elements to said middle and downstream i al..-

bottom portions.

9. The improvement in an electrolytic cell according to claim 8 wherein:

a. the portions of said slab disposed to one side of the transverse centerline of the potshell adjacent one end wall thereof are separate from the portions of said slab on the other sideof said centerline.

10. The improvement in an electrolytic cell according to claim 9 wherein:

a. the finger portions connected to the collector elements at the sidewalls of the potshell are contained in planes disposed perpendicular to said sidewalls.

ll. The improvement in an electrolytic cell according to claim 10 wherein:

a. said collector elements are electrically connected to said potshell.

12. The improvement in an electrolytic cell according to claim 11 wherein:

a. said slab is electrically insulated from said potshell.

13. The improvement in an electrolytic cell according to claim 3 wherein:

a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in side-by-side relation with adjacent potshells in said line; and

b. said slab includes a corner end portion disposed along the end wall of said potshell and a comer side portion disposed along the sidewall of said potshell and in electrical contact with said comer end portion.

14. The improvement in an electrolytic cell according to' claim 13 wherein:

a. each of said comer end portions is connected to the bottom portions of said slab solely through its connection with the associated comer side portion of said slab.

15. The improvement in an electrolytic cell according to claim 14 wherein: v

a. the corner side portions of said slab along the sidewall thereof, which is adapted to define the downstream side of the cell insaid line, extend further toward the transverse centerline of said potshell than the comer side portions along the opposite sidewall.

16. The improvement in an electrolytic cell according to claim 3 wherein:

a. said slab is disposed along the inner surface of said potshell; and

b. the side portions of said slab have a corrugated surface defining the interface with the potlining with the corrugations extending in the direction of current flow therethrough.

17. The improvement in an electrolytic cell according to claim 3 wherein:

a. said potshell is in electrical contact with said potlining along the inner side and end walls thereof.

18. The improvement in an electrolytic cell according to claim 3 wherein:

a. said collector elements are tapered in horizontal cross section in a direction away from the sides of the cell and are mechanically and electrically attached to the sides of said cell.

19. The improvement in an electrolytic cell according to being adapted to be disposed in end-to-end relation with 70 adjacent potshells in said line; and

b. the portion of said slab at the bottom of said potshell extends inwardly from the opposite sidewalls by progressively smaller distances at points located further from the one end wall adapted to define the downstream side of the cell when disposed in said line of cells.

21. The improvement in an electrolytic cell according to claim 3 wherein:

a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in end-to-end relation with adjacent potshells in said line; and

b. the portion of the slab at the bottom of the potshell:

1. extends completely across said bottom adjacent the one end wall adapted to define the downstream side of the cell,

2. extends inwardly from the opposite sidewalls by progressively smaller distances at points located further from said one end wall; and

3. terminates at a point spaced from the other end wall of said potshell.

22. The improvement in an electrolytic cell according to claim 21 wherein:

a. the portions of the slab disposed along the sidewalls of the potshell extend the full length of the sidewalls with diminishing height adjacent the other end wall of the potshell; and

b. the collector elements extending normal to the sidewalls are connected to the aligned side portions of the slab.

23. The improvement in an electrolytic cell according to claim 22 wherein: Y

a. the side portions of the slab further extend centrally of the one end wall and along the other end wall adjacent the corners formed with the sidewalls.

24. in the production of aluminum by the electrolytic reduction of fluoride fusions of alumina contained in a cavity in a rectangular cell adapted to be disposed in a line of cells and having upright metal sides and a flat bottom and lined at least in part with an electrically conductive lining which serves as a cathode container for the electrolyte and molten aluminum during said reduction and from which current is drawn by horizontally disposed collecting elements to bus means disposed exteriorly of said cell, the improvement of:

a. directing current from said collecting elements to the sides of said cell and thereafter downwardly into an aluminum slab disposed horizontally at the bottom of the cell beneath the fluoride fusion of alumina and from there to said bus means adapted to lead from underneath said cell to the next downstream cell in said line.

25. The method according to claim 24 including:

a. directing said current along paths from said collecting elements to said bus means which produce a vertical electromagnetic flux density as caused by current flowing through said cell and as measured along the cavity which is substantially uniform and generally less than the horizontal electromagnetic flux density therealong.

26. The method according to claim 25 including:

a. directing said current along paths from said collecting means to said bus means which produce a vertical electromagnetic flux density as caused by external current flow through adjacent cells and connecting bus means when disposed in said line which is substantially uniform and generally less than the horizontal electromagnetic flux density as caused by said external current.

27. In the production of aluminum by the electrolytic reduction of fluoride fusions of alumina contained in a cavity in a rectangular cell adapted to be disposed in a line of cells and having upright metal sides and a flat bottom and lined at least in part with an electrically conductive lining which serves as a cathode container for the electrolyte and molten aluminum during said reduction and from which current is drawn by horizontally disposed collecting elements to bus means disposed exteriorly of said cell, the improvement of:

a. directing current laterally from said cavity and to said metal sidewalls through the regions of the potlining adjacent the portions of the cavity where the vertical electromagnetic flux density is low in relation to the density in other portions of the cavity and thereafter to said exteriorly disposed bus means.

lecting elements in the regions of the potlining adjacent said other portions of the cavity where the vertical electromagnetic flux density is high and thereafter to said exteriorly disposed bus means.

Claims

2. solid downstream bottom portions disposed on opposite sides of said transverse centerline and along the side of said potshell adapted to be the downstream side of the cell in said line of cells,
2. extends inwardly from the opposite sidewalls by progressively smaller distances at points located further from said one end wall; and
2. The improvement in an electrolytic cell according to claim 1 wherein: a. said cathode bus means includes two arms each of which is connected to the slab on opposite sides of the transverse centerline of the cell and both of which extend toward the downstream side of the cell in diverging relation to each other.
3. The improvement in an electrolytic cell according to claim 1 wherein: a. said slab extends along certain areas of the sides of said cell; and b. said slab is shaped to direct the current from said collector elements and through said slab to produce a substantially uniform vertical electromagnetic flux density as measured along the potlining cavity.
3. terminates at a point spaced from the other end wall of said potshell.
3. corner portions disposed along the sidewalls and end walls at each corner of said potshell and electrically connected to the collector elements extending to the side and end walls adjacent said corners, and
4. finger portions electrically connecting the remainder of said collector elements to said middle and downstream bottom portions.
4. The improvement in an electrolytic cell according to claim 3 wherein: a. said slab is shaped to direct the current from said collector elements through said slab to produce a vertical electromagnetic flux density as measured along the potlining cavity which is generally less than the horizontal electromagnetic flux density therealong.
5. The improvement in an electrolytic cell acCording to claim 4 wherein: a. the slab is shaped to produce a vertical electromagnetic flux density as caused by external current flow through adjacent cells and connecting bus means when disposed in said line which is substantially uniform and generally less than the horizontal electromagnetic flux density as caused by said external current.
6. The improvement in an electrolytic cell according to claim 5 wherein: a. said vertical magnetic flux density as measured at different points along the potlining cavity averages no greater than about 10 gauss.
7. The improvement in an electrolytic cell according to claim 5 wherein: a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in side-by-side relation with adjacent potshells in said line; and b. the portions of said slab disposed to one side of the transverse centerline of the potshell adjacent one end wall thereof are separate from the portions of said slab on the other side of said centerline.
8. The improvement in an electrolytic cell according to claim 5 wherein: a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in side-by-side relation with adjacent potshells in said line; and b. said slab includes:
9. The improvement in an electrolytic cell according to claim 8 wherein: a. the portions of said slab disposed to one side of the transverse centerline of the potshell adjacent one end wall thereof are separate from the portions of said slab on the other side of said centerline.
10. The improvement in an electrolytic cell according to claim 9 wherein: a. the finger portions connected to the collector elements at the sidewalls of the potshell are contained in planes disposed perpendicular to said sidewalls.
11. The improvement in an electrolytic cell according to claim 10 wherein: a. said collector elements are electrically connected to said potshell.
12. The improvement in an electrolytic cell according to claim 11 wherein: a. said slab is electrically insulated from said potshell.
13. The improvement in an electrolytic cell according to claim 3 wherein: a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in side-by-side relation with adjacent potshells in said line; and b. said slab includes a corner end portion disposed along the end wall of said potshell and a corner side portion disposed along the sidewall of said potshell and in electrical contact with said corner end portion.
14. The improvement in an electrolytic cell according to claim 13 wherein: a. each of said corner end portions is connected to the bottom portions of said slab solely through its connection with the associated corner side portion of said slab.
15. The improvement in an electrolytic cell according to claim 14 wherein: a. the corner side portions of said slab along the sidewall thereof, which is adapted to define the downstream side of the cell in said line, extend further toward the transverse centerline of said potshell than the corner side portions along the oppositE sidewall.
16. The improvement in an electrolytic cell according to claim 3 wherein: a. said slab is disposed along the inner surface of said potshell; and b. the side portions of said slab have a corrugated surface defining the interface with the potlining with the corrugations extending in the direction of current flow therethrough.
17. The improvement in an electrolytic cell according to claim 3 wherein: a. said potshell is in electrical contact with said potlining along the inner side and end walls thereof.
18. The improvement in an electrolytic cell according to claim 3 wherein: a. said collector elements are tapered in horizontal cross section in a direction away from the sides of the cell and are mechanically and electrically attached to the sides of said cell.
19. The improvement in an electrolytic cell according to claim 18 wherein: a. said collector elements include a central elongated core section of uniform cross section and an outer section of cast iron formed in situ between said core section and the wall surface of the openings in said potlining.
20. The improvement in an electrolytic cell according to claim 3 wherein: a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in end-to-end relation with adjacent potshells in said line; and b. the portion of said slab at the bottom of said potshell extends inwardly from the opposite sidewalls by progressively smaller distances at points located further from the one end wall adapted to define the downstream side of the cell when disposed in said line of cells.
21. The improvement in an electrolytic cell according to claim 3 wherein: a. said potshell is generally rectangular with elongated sidewalls connected together by end walls, said potshell being adapted to be disposed in end-to-end relation with adjacent potshells in said line; and b. the portion of the slab at the bottom of the potshell:
22. The improvement in an electrolytic cell according to claim 21 wherein: a. the portions of the slab disposed along the sidewalls of the potshell extend the full length of the sidewalls with diminishing height adjacent the other end wall of the potshell; and b. the collector elements extending normal to the sidewalls are connected to the aligned side portions of the slab.
23. The improvement in an electrolytic cell according to claim 22 wherein: a. the side portions of the slab further extend centrally of the one end wall and along the other end wall adjacent the corners formed with the sidewalls.
24. In the production of aluminum by the electrolytic reduction of fluoride fusions of alumina contained in a cavity in a rectangular cell adapted to be disposed in a line of cells and having upright metal sides and a flat bottom and lined at least in part with an electrically conductive lining which serves as a cathode container for the electrolyte and molten aluminum during said reduction and from which current is drawn by horizontally disposed collecting elements to bus means disposed exteriorly of said cell, the improvement of: a. directing current from said collecting elements to the sides of said cell and thereafter downwardly into an aluminum slab disposed horizontally at the bottom of the cell beneath the fluoride fusion of alumina and from there to said bus means adapted to lead from underneath said cell to the next downstream cell in said line.
25. The method according to claim 24 including: a. directing said current along paths from said collecting elements to said bus meaNs which produce a vertical electromagnetic flux density as caused by current flowing through said cell and as measured along the cavity which is substantially uniform and generally less than the horizontal electromagnetic flux density therealong.
26. The method according to claim 25 including: a. directing said current along paths from said collecting means to said bus means which produce a vertical electromagnetic flux density as caused by external current flow through adjacent cells and connecting bus means when disposed in said line which is substantially uniform and generally less than the horizontal electromagnetic flux density as caused by said external current.
27. In the production of aluminum by the electrolytic reduction of fluoride fusions of alumina contained in a cavity in a rectangular cell adapted to be disposed in a line of cells and having upright metal sides and a flat bottom and lined at least in part with an electrically conductive lining which serves as a cathode container for the electrolyte and molten aluminum during said reduction and from which current is drawn by horizontally disposed collecting elements to bus means disposed exteriorly of said cell, the improvement of: a. directing current laterally from said cavity and to said metal sidewalls through the regions of the potlining adjacent the portions of the cavity where the vertical electromagnetic flux density is low in relation to the density in other portions of the cavity and thereafter to said exteriorly disposed bus means.
28. The method according to claim 27 including: a. directing the current flowing through the metal sidewalls along paths leading underneath said cell and then to said exteriorly disposed bus means.
29. The method according to claim 28 including: a. directing current from said cavity and through said collecting elements in the regions of the potlining adjacent said other portions of the cavity where the vertical electromagnetic flux density is high and thereafter to said exteriorly disposed bus means.