US20080078674A1

US20080078674A1 - Module busbar arrangement for powerful aluminum electrolytic cells

Info

Publication number: US20080078674A1
Application number: US11/981,983
Authority: US
Inventors: Vitaliy Platonov; Vitaliy Pingin; Victor Mann
Original assignee: Russian Engineering Co LLC; Pratt and Whitney Rocketdyne Inc
Current assignee: Russian Engineering Co LLC; Aerojet Rocketdyne of DE Inc
Priority date: 2005-05-04
Filing date: 2007-10-31
Publication date: 2008-04-03
Also published as: WO2007004075A2; CA2607479A1; CN101248218A; WO2007004075A3; RU2288976C1; AU2006264501A1

Abstract

A busbar arrangement for an electrolytic cell utilized for the production of aluminum by electrolysis of molten cryolite salt where the cells are arranged in a side-by-side relationship. In the busbar, the upstream cathode collector and the downstream cathode collector of the upstream cell, the electric connecting arrangements, and the anode risers associated with the downstream cell are combined in the individual busbar modules. In each module, at least one anode riser is situated at the upstream side of the downstream cell and at least one anode riser is situated at the downstream side of the downstream cell. The anode risers at the upstream side are connected to the cathode rods of the upstream and downstream sides of the upstream cell. The anode risers at the downstream side of the downstream cell are connected to the cathode rods and cathode collectors of the downstream side of the upstream cell. The upstream and downstream anode risers are substantially symmetrical about the short planar axis of the cell.

Description

FIELD OF THE INVENTION

This invention relates to aluminum production, in general, and more particular to aluminum production by electrolysis of molten cryolite salts in electrolytic cells arranged in side-by-side relationship.

BACKGROUND OF THE INVENTION

Busbar arrangements for an aluminum electrolytic cells arranged in a side-by-side relationship in the pot room are known in the art. Such busbars typically comprise collecting busbars in combination with associated cathode flexible electrical conductors which are arranged along upstream and downstream longitudinal sides of the cell. Anode risers situated at the upstream side of the cell are provided for transmitting similar electrical currents there-through. The anode busbars of the downstream cell are connected to a neighboring upstream cell by risers. In this manner, the outer risers are connected to the outer cathode collectors of the upstream side of the upstream cell by flexible electrical conductors positioned along the transverse sides of the cell. The outer risers are also connected to collecting cathode busbars or cathode collectors of the downstream side of the upstream cell.
The intermediate risers are connected to the intermediate cathode collectors or collecting busbars of the upstream side of the cell by the flexible cathode conductors positioned symmetrically under the cathode blocks situated in the close vicinity to the end sides of the cell. The intermediate risers are also connected with cathode collectors or collecting cathode busbars of the downstream side of the upstream cell. The busbar situated under the bottom of the cell and disposed in the vicinity of the neighboring row of the cells carries 15% of the current at the upstream side of the cell. On the other hand the other busbar carries 10% of the current at the upstream side. An intermediate busbar is also situated under the bottom of the cell and extends in to the midpoint between the longitudinal axis of the row of the cells and the cell end on the side opposite to the neighboring row of cells. This busbar carries 5% of the current at the upstream side. The busbar arrangement discussed hereinabove is described in French Patent No. 2,552,782.
One of the major disadvantages of the above-discussed prior art busbar arrangement is limited usage in the high power/amperage electrolytic cells, i.e., electrolytic cells operating with amperage exceeding 350 kA. The design of such busbars and risers is subject to various restrictions. One such restriction is that the busbars and risers should be arranged so as to minimize the general magnetic field induced in the cell. In particular, the vertical component of such magnetic field should be minimized. The vertical component of the induced magnetic field interacts with the horizontal component of the electric currents in the molten metal pad giving rise to horizontal forces which can affect different regions of the metal pad in different ways. These forces may result in undesirable metal motion, humping of the metal surface, and wave formation. These disturbances can necessitate maintaining larger than required anode to cathode distance in the cell, in turn, increasing the internal resistance of the cell. In operation of the busbar, it is important to compensate, the vertical component of magnetic field at the ends of the cell by the busbar arrangements enveloping such ends. The vertical component of the magnetic field developed at the ends of the working zone of the cell is typically formed by the horizontal portions of the anode risers, bus connectors between the anode busbars, and the cathode busbars which extend under the bottom of the pot. To achieve the optimum magnitude of the vertical component of the magnetic field at the ends of the cell (so as not to exceed 15-20 G) it is often necessary to pass almost the entire current of the upstream side of the cell through the busbar enveloping the ends of the respective cell. As result, in the aluminum production plant, the busbars extending from the cathode collector bars of the upstream cell to the anode busbars of the neighboring downstream cell are much longer than the portions of the busbars of the collector bars at the downstream side. In order to provide uniform distribution of the current within the cathode collector bars of upstream and downstream sides of the cell and to decrease horizontal currents in the melt, it is necessary to provide equality of resistance in the busbar branches from the cathode collector bars at the upstream and downstream sides of the upstream cell to the anode busbar of the down-stream cell. Such equality in the resistance is reflected in the Expression [1]. $\begin{matrix} R_{upstr .} = R_{downstr} or & [1] \\ \frac{L_{upstr}}{S_{upstr}} = \frac{L_{downstr}}{S_{downstr}} & [2] \end{matrix}$
Since L_upstr>L_downstr, then it follows that S_upstr>S_downstr.
The sectional area of the busbars from collector bars at the upstream side is limited by the density of current they carry. The ratio of such sectional area to the density of the current passing therethrough should not exceed 0.75 A/mm². The sectional area of collector bars at the upstream side is determined by the expression [2].
It should be clear from the above expressions that the higher the required amperage of the cell, the greater the difference in length of the busbar branches at the upstream and down-stream sides, the greater the busbar sectional area at the upstream and downstream sides, and as a consequence, the heavier the busbar. Therefore, in order to accommodate such massive busbars, substantial distance is required between the cells for the busbar installation. Thus, an aluminum production cell utilizing a busbar fabricated and installed based on the above-discussed prior art principles becomes noncompetitive at amperages higher than 350 kA. At such amperages, the weight of the busbars and distance between cells becomes prohibitively large.
Patent document SU 1595345 discloses a busbar arrangement for electrolytic cells arranged in two side-by-side rows. This busbar comprises the anode busbar connected to the anodes by the anode rods. It also includes the cathode busbar collectors with the associated cathode rods and flexible electrical connectors extending outwardly at the upstream and downstream sides of the cathode shell. This prior art busbar also includes connecting busbars which provide connection between cathode and anode busbars and the busbar of the magnetic field correction circuit. These elements are disposed in parallel to the transverse axis of the aluminum electrolytic cell at the ends of the cathode shell. The connection between the cathode busbar of the upstream cell and the anode busbar of the downstream cell is carried out as busbar modules consisting of two half-risers. One of the half risers is rigidly connected to the cathode collector at the upstream side of the cell. This side is connected with four flexible electrical connectors. The other half-riser is connected by busbars situated under the bottom of the cathode shell and also connected to the flexible cathode connectors at the upstream side of the cell. It should be noted that the connecting busbars situated under the cathode shell bottom are disposed in parallel to the transverse axis of the aluminum electrolytic cell and in parallel to each other. Electrical current is supplied to the correction circuit in the direction coinciding with the direction of the current in the potline. Preferable magnetic field correction current is between 20 and 80% of the potline current.
One of the disadvantages of the prior art busbar discussed in SU 1595245 is utilization of the independent magnetic field correction arrangement. The arrangement consists of two conductors extending along both ends of the cells in the circuit in the direction of potline current. The correction current is between 20 and 80% of the potline current. For example, with the potline current at the level of 500 kA, the correction current can be as high as 400 kA. The busbar arrangement is heavy due to the presence of the above-discussed corrective busbars. The additional weight is about 14 tons for each electrolytic cell. Utilization of the above-discussed heavier correction circuits causes an increase in the electric power consumption due to the voltage drop in the correction circuit. All of the above ultimately result in increased costs associated with construction and maintenance of the production areas associated with the correction circuits. For example, when the amperage is at the level of 400 kA, the correction busbars arrangement may consist of 16 busbars each having cross-sectional area of 650×70 mm. The total width of such massive busbar arrangement is about 2 meters.
The passage of the electric current in the power supply conductors and in the conducting portions of the cell generates magnetic fields which cause undesirable movements in the liquid bath which causes deformation of the metal-electrolysis bath interface. These movements of metal agitate the electrolytic bath placed underneath the anodes and can short-circuit this element of the bath when contact occurs between the liquid metal and the anode. In such instances the electrolysis yield greatly diminishes and power consumption increases.
It is known that the metal-bath interface and the movements of the liquid metal are closely dependent on the values of the vertical component of the magnetic field and symmetry of the horizontal components. Minimizing the value of the vertical component in the magnetic field causes substantial reduction in the depth between the highest and lowest points of the metal layer and reduction of the magnetic forces which cause disturbances in this layer. Thus, it is highly desirable to minimize the vertical component of the magnetic fields in the liquid metal and to reduce the circulation of liquid metal and of liquid bath in the cell.
One of the objects of the invention is to reduce operational costs by increasing unit capacity of an electrolytic cell by increasing the amperage and decreasing the busbar weight.
Another object of the invention is to mitigate adverse magneto-hydrodynamic effects in the melt, to eliminate the correction circuit, to optimize the magnetic field and to reduce specific electric power consumption. A further object of the invention is to provide an arrangement capable of placing the cells as close to each other as possible. This is highly desirable in order to reduce specific operational costs for the potrooms and to retain sufficient free access for personal movement and maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of the cell modules of the invention;
FIG. 2 is a cross-section view showing two adjacent cells illustrating conveyance of current from upstream to downstream cells in the module of the invention;
FIG. 3 is a graph illustrating a perspective view of the vertical component (Bz) of the magnetic field at the metal pad of the cell having the busbar configuration of FIGS. 2 and 3;
FIG. 4 is a graph illustrating distribution of the vertical magnetic field component (Bz) in the metal pad according to the invention, with no current being provided in the down-stream anode risers of the downstream cell;
FIG. 5 is a graph illustrating distribution of the vertical magnetic field component (Bz) in the metal pad according to the invention, with no current being provided in the upstream anode risers of the downstream cell;
FIG. 6 is a graph illustrating distribution of the vertical magnetic field component (Bz) in the metal pad according to the invention, with the electrical current being provided in the upstream and downstream anode risers of the downstream cell; and
FIG. 7 is a schematic diagram showing the upstream and downstream cells in the module of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1, 2, and 7, which show the electrolytic cells disposed transversely in rows with their long sides situated perpendicular to the general direction of the current. The elements of the invention are referred to as upstream or downstream, depending on whether they are originated from the upstream or the downstream side of the respective cell or within the row of cells, with respect to the direction of the current which is taken as the reference.
FIG. 1 illustrates an arrangement with large numbers of electrolytic cells laid out in lines in the electrolysis pot rooms electrically connected in series using connecting conductors in order to optimize the occupancy of factory floors. It is further illustrated in FIG. 1 that the cells are arranged so as to form least two parallel lines which are electrically connected to each other by the conductors. The electrolysis current therefore passes in the cascade fashion from one cell to the next. The length and mass of the conductors should be as small as possible in order to limit investment and operating costs. The conductors are also configured such as to reduce or offset the effects of magnetic fields produced by the electrolysis current.
As illustrated in FIG. 7, the “right-hand head of the cell” refers to the side of the cell situated on the right-hand side of an observer placed in the axis of the line of cells and looking in the direction of the current traversing this line of cells. The term “left-hand head of the cells” refers to the other side of the cell.
As best illustrated in FIGS. 1, 2 and 7, aluminum electrolytic cells are structures having long or longitudinal axis Y-Y and short or transverse axis X-X. Each cell comprises a metal casing or a cathode shell 8 which is formed with a bottom portion 21 and side portions 22, 23 extending outwardly therefrom. An interior of the shell 8 is lined with insulating material adapted to support a cathode assembly which is formed by a plurality carbonaceous blocks 24. Embedded in the carbonaceous blocks are cathode metal collector bars 4 extending within the cell transversely to the longitudinal axis Y-Y. The cathode metal bars 4 are electrically connected at one end to a negative conductor or cathode connecting conduit 6 and at another end to a cathode connecting conduit 7. The connection between the cathode collector bars 4 and the cathode collectors 6 and 7 is by means of flexible electrical conductors 5. Fixed on the shell 8 is a superstructure containing an anode assembly comprising anode busbars 1 extending along the longitudinal axis Y-Y of the cell. Carbon anodes 2 are suspended from the anode busbars by means of metal anode rods 3.
The arrangement of the invention is subdivided into a plurality of busbar modules. In this respect FIG. 1 illustrates the busbar subdivided into four modules: A, B, C, and D. Each module comprises an anode busbars assembly with the metal anode rods 3 adapted for supplying current to the carbonaceous anodes 2. In each module the upstream cell is formed with the upstream cathode collector 6 disposed at the upstream side of the upstream cell and the downstream cathode collector 7 provided at the downstream side thereof. The cathode bars 4 by means of the flexible electrical conductors 5 are connected to the respective cathode collectors 6 and 7.
As best illustrated in FIGS. 1 and 2 each cell is formed with two parallel lines of anodes 2 supported by the rods 3. The anode busbar 1 is formed by upstream and downstream bar elements 1A and 1B respectively, connected by equi-potential rods. The anode busbars 1 of the downstream cell receive the current collected by the cathode rods 4 through the upstream 6 and downstream 7 cathode collectors of the upstream cell. The current is transferred by means of connecting busbars 9 to the upstream riser 10 of the downstream cell. The risers or rising connections 10 and 11 are typically formed having horizontal and vertical portions, so as to rise over the ends or over the respective sides of the cell, forming the elevated structures ultimately connecting the anode busbars 1 of the downstream cell and the cathode collector busbars 6, 7 which are disposed lower around the upstream cells. Each upstream riser 10 is formed having double-branch structure. More specifically, each raiser 10 comprises a branch 10A connected to the downstream cathode collector 7 of the upstream cell and a branch 10B connected to the upstream cathode collector 6 by at least one connecting busbar 9 passing under the bottom of the cell.
In each module the anode busbars 1 and ultimately the anodes 2 are supplied with electrical current by means of the risers 10 and 11 which are positioned symmetrically to the short or transverse axis X-X of the cell. As illustrated in FIG. 1, the upstream anode risers 10 associated with the upstream side 1A of the anode busbar of the downstream cell are connected to the cathode rods 4 and the respective cathode collectors 6 and 7 of both the upstream and downstream sides of the upstream electrolytic cell. The downstream anode risers 11 associated with the downstream side 1B of the anode busbar are connected to the cathode rods 4 and the downstream cathode collector 7 of the upstream cell. The electric connecting busbar or arrangements 9 are disposed primarily under the bottom portion 21 of the cathode shell 8. Portions of the connecting arrangements 9 of the outer busbar modules A and D envelop the end areas of the respective electrolytic cell, so as to extend substantially vertically approximately up to the level of molten metal in the cell.
FIGS. 1 and 2 illustrate an embodiment of the busbar arrangement of the invention having risers 10 associated with the upstream side 1A of the anode busbar connected to about ⅔ of the collector bars of the busbar module. The risers 11 at the downstream side 1B of the anode busbar are connected to about ⅓ of collector bars of the busbar module.
Although the busbar arrangement of the invention is illustrated in FIG. 1 as having four busbar modules, a busbar arrangement consisting of any reasonable number of busbar modules depending on the required power of the cell is within the scope of the invention.
In the busbar arrangement of the invention operates in the following manner. By means of the flexible electrical conductors 5 the electrical current in the upstream cell is directed from the cathode rods 4 to the respective upstream 6 and downstream 7 cathode collectors. The horizontal sections of the upstream anode risers 10, as well as the elements associated with the respective upstream cell, such as the connecting busbars 9 extending under the bottom of cathode shell 8, the cathode rods 4 and the respective flexible electric conductors 5 at the downstream side create in the metal-electrolysis bath interface a vertically oriented component or vector of the magnetic field (Bz). More specifically, this vertically oriented component of the magnetic field (Bz) is directed upwardly in the left hand head of the electrolytic cell (according to direction of the current in the potline). This vertical component of the magnetic field is directed downwardly in the right hand head of the cell. The horizontal sections of the downstream anode risers 11, the connecting busbars 9 of the outer modules A and D, and the cathode rods 4 with the respective flexible electrical conductors 5 at the upstream side of the upstream cell create in the melt the vertical component of the magnetic fields (Bz) having orientation opposite to that of the above discussed conductors. That is, the vertical component of the magnetic field (Bz) is directed downwardly at the left hand head of the cell and upwardly at the right hand head of the cell. Mutual compensation of the magnetic field (according to the axis Bz) from both groups of the above-discussed conductors assures the optimum value of the magnetic field which does not exceed 15-20 G. Significantly, the anode risers 11 associated with the downstream side 1B of the anode busbar eliminate the necessity to install the independent lines of conductors adapted for the correction the magnetic field, as discussed by the prior art.
Each horizontal section of the upstream risers 10 and downstream risers 11 create in the melt on the right side from their location (according to the direction of the electrical current in the riser) a magnetic field directed downwardly relative to the axis (Bz) and directed upwardly relative to the (Bz) axis on the left side from their location. This arrangement provides for frequent sign alternation (positive or negative) according to the direction of the vertical component of the magnetic field extending along the longitudinal sides of the cell. As illustrated in FIG. 1, the upstream risers 10 and downstream risers 11 associated with upstream branch 1A and the downstream branch 1B respectively are positioned opposite each other. Thus, the sign alteration relative to the axis (Bz) along the longitudinal sides of the cell is asymmetric about planar axes of the cell. In each module the current distribution in the anode risers is chosen in such a manner that the maximum value of the magnetic field in the melt does not exceed 15-25 G.
The electrical current distribution in the upstream anode risers 10 of the downstream cell is between ½ and ¾ of the module current. The electrical current distribution in the downstream anode risers 11 of the downstream cell is between ½ and ¼ of the module current. The above arrangement provides the relative equality of the volume and transverse electromagnetic forces in the metal. This enhances development of the symmetric metal pad topography, symmetric ledge, and freeze in the work zone, so as to improve positive effect on MHD stability of the melt. Relatively small anode-cathode distance in the module and relatively small weight of the busbar are accomplished in view of the fact that the current is transferred in the shortest distance from the upstream to the downstream cell. This also occurs in view of the similarity in the length between the busbar branches disposed at the upstream and downstream sides of the cell. The above discussed arrangement enables the invention to provide in the busbar branches the maximum permissible electrical current density, while maintaining the minimum cross-section area thereof.
In the invention, the modular design makes it possible to develop a busbar arrangement adaptable for the amperages of 500 kA and greater, while maintaining a relatively small weight. Magnetic field optimization is based on the following principles. The vertical component of the magnetic field (Bz) acts on the molten metal layer is of the same direction (positive or negative) over a substantial area of the cell (particularly along its longitudinal axis) forming coherent and increased oscillation of the molten metal surface. This occurs because of the longitudinal moment buildup along the cell. Therefore, in the present invention, the magnetic field is optimized by frequent sign alterations along the vertical component (Bz). This occurs at least along the longitudinal sides of the cell, where the signs are altered from positive to negative and negative to positive, relative to the planar axes of the cell.
As illustrated in the diagram of FIG. 3, the module busbar of the invention creates in the melt nine the sign alternations according to the direction of the vertical component (Bz) of the magnetic field at the upstream side, and eleven sign alternations at the downstream side. The magnetic field according to the axis (Bz) is asymmetrical relative to the planar axes of the cell and does not exceed 25 G.
Utilization of the above-discussed busbar of the invention results in increased capacity of the cell. This is achieved in view of the amperage increase to the level up to 500 kA and higher, while maintaining the efficiency of between 93% and 95% and specific electric power consumption between 12300 and 13500 kWh/t.

Example 1

FIG. 4 illustrates distribution of the vertical magnetic field component (Bz) as depicted in the melt of the electrolytic cell with no current being provided at the anode risers on the downstream side 1B of the anode busbar of the downstream cell. This figure actually illustrates an experimental example of the calculated magnetic induction vector (Bz) of the electrolytic cell having the busbar arrangement of the invention. In this example the electrical current in the anode risers at the downstream side 1B is equal to zero. The current provided by the anode risers 10 to the upstream side 1A of the busbar is equal to predetermined values. It is apparent from the graph in FIG. 4 that the (Bz) component of the magnetic field from the risers 10 that it is accumulated at the ends of the cell can reach the value up to ±50 G. The magnetic field from the busbars enveloping the ends of the cell is insufficient to compensate the vertical (Bz) component generated by the upstream risers 10. The magnetic field from the side of the risers is of the wave nature, whereas at the opposite side it changes almost linearly.
This example resembles a typical situation in the prior art anode busbar structures for the side-by-side cell arrangement. In the prior art the magnetic field at the ends of the cell is typically compensated by the magnetic field from the stack plates enveloping the ends of the cell. However, the prior art method of compensation causes substantial increase in the weight of the busbar and leads to the increase in the distance between the cells. There is also known compensation pattern by means of individual conductors extending along the short side of the cell and directed along the direction of current running in the potline. In this instance, the amperage is between 80 and 120 kA. This prior art method of compensation is expensive and requires additional power supplies.

Example 2

FIG. 5 illustrates another experimental example of the calculated magnetic induction vector Bz of the electrolytic cell utilizing the busbar arrangement of the invention. The current in the anode risers at the upstream side 1A is zero. The current in the anode risers 11 at the downstream side 1B is equal to the predetermined values. It is apparent from the graph of FIG. 5 that the Bz component of the magnetic field is accumulated from the anode risers 11 at opposite ends of the cell, so as to reach value up to ±50 G. The magnetic field at the risers 11 is of the wave nature, while at the side opposite to the risers the magnetic field changes almost linearly.

Example 3

FIG. 6 represents a graph illustrating an example of distribution of the vertical magnetic field component (Bz) according to the invention with the electrical current being provided in the upstream 10 and downstream 11 anode risers. It is shown in this graph that the sign of the vertical component (Bz) of the magnetic field alternates many times in the direction along the longitudinal sides of the cell. The alternations indicated by the “+” and “−” signs are asymmetrical relative to the long axis of the cell. In this example the value of the component (Bz) does exceed ±25 G.
There are many benefits of positioning the risers on both upstream 1A and down-stream 1B sides of the anode busbar, in accordance with the invention. In the arrangement of the invention it is not necessary to compensate the magnetic induction vector (Bz) at the cell ends by providing individual busbars or busbars enveloping the ends of the cell. This results in substantial reduction of the weight of the busbar. The asymmetrical and multiple alternations of the sign of the vertical component (Bz) along longitudinal sides and the desirable range of its value (which does not exceed 20 G) are the prerequisites of stable cell operation at the amperage of 500 kA and higher. Unlike the prior art, the current to the anode risers 10 at the upstream side 1A of the downstream cell is directed from the upstream cathode collectors 6 and the cathode bars 4 of the upstream cell, while the current to the anode risers 11 at the downstream side 1B of the downstream cell is delivered from the downstream cathode collectors 7 and cathode bars 4 of the upstream cell. This arrangement assures the relative equality in the length of the most busbar branches and makes it possible to maintain the highest possible current density and also to reduce the total weight of the busbar. The modular type of the busbar of the invention facilitates assembly from such modular and electrolytic cells having practically any required power.
In the production of aluminum by electrolysis of molten cryolite salts in the electrolytic cells arranged in the side-by-side relationship in a pot room, it is essential to increase unit capacity of a cell by increasing the amperage, decreasing the busbar weight, so as to ultimately reduce the operational costs. In the invention, these objects are achieved by providing the busbar assembly where the upstream cathode collectors 6 and the downstream cathode collectors 7 of the upstream cell; the electric connecting arrangements or connecting busbars 9, and the anode risers 10 and 11 associated with the downstream cell are combined in the individual busbar modules. In the invention, in each module at least one anode riser 10 is situated at the upstream side 1A of the downstream electrolytic cell and at least one anode riser 11 is situated at the downstream side 1B thereof. The anode risers 10 at the upstream side 1A are connected to the cathode rods 4 and cathode collectors 6 and 7 of the upstream and downstream sides of the upstream cell. The anode risers 11 at the downstream side 1B are connected to the cathode rods 4 and the cathode collector 7 of the downstream side of the upstream cell. Each busbar module of the invention is adapted for passage between 10 and 100% of the pot line electrical current. In the preferred embodiment each busbar is adapted for passage between 18 and 30% of the pot line electrical current. The anode risers 10 at the upstream side 1A are arranged to distribute between 50 and 75 percent of the module current. On the other hand, the anode risers 11 at the downstream side 1B are arranged to distribute between 50 and 75% of the module current. The anode risers 10 and 11 are substantially symmetrical about the short planar axis of the cell. The electric connecting arrangement or connecting busbars 9 are disposed under the bottom portion 21 of the cell. At least a portion of the connecting busbars 9 of the outer modules (modules A and D, for example) envelops the end areas of the respective cells, so as to be located, at least, at the level of the molten metal. The number of the cathode rods 4 connected to the electrical connecting arrangements 9 on the portion of the cell closest to the neighboring row of the cells exceeds the number of the cathode rods connected to the electrical connecting arrangements 9 on the opposite side.

Claims

1. A busbar arrangement for electrical connection between two successive cells in a series of cells arranged in two rows in a side-by-side configuration and adopted for the production of aluminum by electrolysis, comprising:

an upstream cell and a downstream cell, an anode busbar of at least said downstream cell connected to anodes by respective anode bars, said anode busbar having an upstream side and downstream side;

a cathode busbar of at least said upstream cell comprising a plurality of cathode rods extending outwardly from a cathode shell for connection with respective upstream and down-stream cathode collecting conduits, flexible electrical conductors being provided between said cathode rods and the respective upstream and downstream cathode collecting conduits; and a plurality of current supply conductors or risers associated with the anode busbar of the downstream cell; and

said busbar arrangement further comprising upstream and downstream cathode collecting conduits of the upstream cell, connecting busbars, the anode risers associated with the downstream cell are joined so as to form a plurality of integral busbar modules; in each said module at least one anode riser is associated with the upstream side and at least one anode riser is associated with the downstream side of the anode busbar of the downstream cell; said at least one anode riser at the upstream side of the downstream cell is connected to the cathode rods and the respective upstream and downstream cathode collecting conduits of the upstream cell, whereas said at least one anode risers at the downstream side of the downstream cell is connected with the cathode rods and the respective downstream cathode collecting conduit of the upstream cell.

2. The busbar arrangement of claim 1, wherein each said module is adapted for passing between 10 and 100 percent of the potline current.

3. The busbar arrangement of claim 2, wherein each said module is adapted for passing between 18 and 30 percent of the potline current.

4. The busbar arrangement of claim 1, wherein said at least one anode risers at the upstream side is adapted to distribute between ½ and ¾ of the module current.

5. The busbar arrangement of claim 4, wherein said at least one anode risers at the downstream side are adapted to distribute between ½ and ¼ of the module current.

6. The busbar arrangement of claim 1, wherein said at least one upstream and down stream anode risers are symmetrical about the short transverse axis of the downstream cell.

7. The busbar arrangement of claim 1, wherein said connecting busbars are disposed under a bottom portion of said upstream cell and at least a portion of the connecting busbars of the outer modules envelopes the end portion of the respective cell, so as to extend at least at the level of molten metal in said cell.

8. The busbar arrangement of claim 1, wherein there are more cathode rods at the upstream side connected to the collecting busbars at the portion of the cell closest to the neighbor row than the connecting busbars at the other end.

9. The busbar of claim 1, wherein the electric connecting busbar is disposed under the bottom portion of the cell and at least a portion of the connecting busbar of the outer modules envelopes the end areas of the respective cells so as to be located at least at the level of the molten metal within the cell.

10. The busbar arrangement of claim 1, wherein a vertically oriented component of the magnetic field Bz is directed upwardly in a left hand head of the electrolytic cell, according to direction of the current in the potline, said vertical component of the magnetic field is directed downwardly in the right hand head of the cell.

11. The busbar arrangement of claim 10, wherein horizontal sections of said at least one downstream anode riser, the connecting busbars of the outer modules, and the cathode rods with the respective flexible electrical conductors at the upstream side of the upstream cell create in the melt the vertical component of the magnetic fields Bz directed downwardly at the left hand head of the cell and upwardly at the right hand head of the cell.

12. The busbar arrangement of claim 1, wherein each horizontal section of said at least one upstream riser and said at least one downstream riser create in the melt on the right side from their location, according to the direction of the electrical current in the riser, a magnetic field directed downwardly relative to the axis Bz and directed upwardly relative to the axis Bz on the left side from their location.