WO2012100340A1

WO2012100340A1 - Anode and connector for a hall-heroult industrial cell

Info

Publication number: WO2012100340A1
Application number: PCT/CA2012/000084
Authority: WO
Inventors: Mario FAFARD; Olivier TREMPE; Patrice GOULET; Dave Martin
Original assignee: Universite Laval
Current assignee: Universite Laval
Priority date: 2011-01-28
Filing date: 2012-01-27
Publication date: 2012-08-02
Anticipated expiration: 2013-07-28

Abstract

The present invention provides a combination of an anode and its connector for use in an electrolysis industrial cell in a Hall-Heroult process. The combination of the connector and the anode comprises a yokeless connector made of a conductive material for transmitting electrical current to the anode, the connector having an inverted T-shape, and an anode comprising a groove extending longitudinally along the a top surface of the anode and being sized and shaped to receive a longitudinal bar of the connector. The combination also comprises a pourable conductive material for filling the groove and bonding the longitudinal bar of the connector to the anode. The present invention also relates to a method of connecting the connector to the anode.

Description

ANODE AND CONNECTOR FOR A HALL-HEROULT INDUSTRIAL CELL

FIELD OF THE INVENTION

The present invention relates to the field of aluminum production, and more particularly concerns an anode and its connector for use in an electrolysis industrial cell in a Hall-Heroult process. The present invention further relates to a method for connecting the anode to its connector.

BACKGROUND

There are two primary anode technologies in the Hall-Heroult process: Soderberg and prebaked anodes. Soderberg technology uses a continuously created anode made by addition of paste on top of the anode while prebaked technology is named after its anodes, which are baked beforehand in very large anode baking furnaces at high temperature, before being rodded to an electrical connector and lowered into the electrolytic solution. Those anodes are consumed due to the oxidation reaction during the electrolysis process. The anodes become thinner and must be replaced after approximately 26 days. At the end of the lifetime of the anode, there remains a non-consumed part named butt. This non-consumed part of the anode is not usable to produce aluminum. Generally, butts are cleaned and crushed before being reused to fabricate new anodes.

Referring to Figures A and 1B, a prior art connector 0 and its anode 12 as currently used in the Hall-Heroult process are shown. Electrical current from a bus bar (not shown) is transmitted to the anode 12 using an aluminum rod clamped to the bus bar. The aluminum rod is affixed to a steel yoke 14 using a bimetallic joint. Two to six stubs 16 (three are shown in Figures 1A and 1 B) extend from the yoke 14 and are inserted within stub holes in the anode 12. Stubs are also known in the art as "studs". The stub holes include flutes 18 allowing the current to be transmitted from the bus bar to the anode 12, while supporting the anode 12 at the same time. Cast iron 20 is used to fill in the space between the stubs 16 and the stub holes in order to seal the stubs within the anode 12.

US patent 4,612,105 (LANGON) describes another configuration of an anode and steel conductor connection. The anode and steel conductor described in this patent aims at reducing the contact resistance of the connection to avoid a voltage drop in the anodic system.

It is known that the electrical resistivity at the anode interface is function of the pressure and temperature at the interface¹. The degradation of the steel stubs during the aluminum electrolysis has also an effect on energy losses at the steel, cast iron, and carbon interfaces, while the tensile cracking of the anode depends on relative thermal expansion of steel, cast iron and carbon.

It has also been found that there is a high electrical resistance, and thus energy losses, at the interfaces of the steel stubs, the cast iron and the stub holes of the carbon anode. Indeed, modeling of the current distribution over the surfaces of the connector has shown that several locations on the surfaces presented peaks of current density. The energy losses at the interface are defined as:

•2

Q

Where:

Q = Power density at the interface in W/m²

R = Electrical surface resistance at the interface in Ohms^*m²

j = Current density at the interface in A/m²

It can be seen that having a more uniform current distribution around the surfaces of the connector, thus lowering the electrical current density (j), , would help to reduce energy losses at the connector-anode interfaces.

1 Richard D., Fafard M., Lacroix R., Clery P. & Maltais Y„ 2003. «Carbon to cast iron electrical contact resistance constitutive model for finite element analysis ». Journal of Materials Processing Technology, vol 132, no 1-3, p. 119-131.) It is also known that voltage drops² in the order of 100 to 150 mV occur at the interfaces of the steel stubs, cast iron and stub holes flutes. Energy losses resulting from these voltage drops occur due to the Joule effect and are proportional to the square of the current density (in A/m²).

Numerical simulations performed on a prior art anode demonstrated that current density in this type of anode can vary from 12 000 to 360 000 A/m². When calculating the current going through an anode divided by the transfer surfaces, the mean value is about 20 000 A/m². Simulations have shown that the current actually passes through specific regions, these regions being submitted to a very high current density.

Known to the applicant are patent applications WO 02055761 (TSOMAEV) and US 4659442 (NATERSTAD).

TSOMAEV describes a carbon electrode and a head for suspending the electrode and for supplying electricity to the electrode. The head must be slid into the electrode's groove from one of the end walls of the anode. The head is locked in place by inserting wedge-shaped fixing pins underneath the connector, the fixing pins being made from a material that burns. One of the objectives aimed by TSOMAEV is to eliminate the use of cast iron from the head-electrode connection, in order to facilitate the reuse of the head once the electrode has been consumed.

NATERSTAD describes an inert anode top under which a carbon core is glued and aims at reducing carbon losses. The anode top is provided with a groove for receiving studs from a connector, the studs being attached to a yoke and having a shape complementary to the shape of the groove. The studs of the connector must also be slid into the electrode's groove from one of the end walls of the anode and locked in position therein using a wedge.

Neither NATERSTAD, nor TSOMAEV makes use of cast iron, or any other type of conductive material, for attaching the connector to the anode. NATERSTAD

2 J. Wilkening and S. Cote. Problems of the Stub-Anode Connection. TMS Light Metals, pages 865-873, 2007 and TSOMAEV describe an insertion of the connector into the anode by sliding the connector from one side of the anode, the connector being fixed therein thanks to the complementary shape of the connector and groove of the anode.

Although some improvements have been made in this field, there is still a need to reduce energy losses occurring at the connector-anode interfaces. It would be desirable to obtain a more uniform current distribution at the connector anode interfaces. It would also be desirable to have an even contact pressure over the surface of the connector in order to further reduce the energy losses. It would also be desirable to increase the operational lifetime of the anode. SUMMARY OF THE INVENTION

An object of the present invention is to provide a combination of a connector and an anode addressing the above-mentioned need.

In one aspect of the present invention, there is provided a combination of a connector and an anode for use in a Hall-Heroult industrial cell for producing aluminum. The combination comprises a yokeless connector made of a conductive material for transmitting electrical current to the anode. The connector has an inverted T-shape and comprises a vertical bar for receiving the electrical current, and a longitudinal bar connected to the said vertical bar. The combination also comprises an anode having a longitudinal top surface, and a groove extending longitudinally along the top surface. The groove is sized and shaped to receive the longitudinal bar of the connector. The combination still comprises a pourable conductive material for filling the groove and bonding the longitudinal bar of the connector to the anode. Preferably, the pourable conductive material may be cast iron.

According to an optional aspect of the combination, the groove may open solely at the longitudinal top surface of the anode. The groove may have a width larger than the width of the longitudinal bar so as to enable insertion of the connector from the top surface of the anode. According to an optional aspect of the combination, the groove may open at both top and opposed side surfaces of the anode. The anode may therefore comprise a refractory material for filling two opposed end portions of the groove, each of the two opposed end portions being located between one end of the longitudinal bar of the connector and the corresponding opposed side surface of the anode.

According to an optional aspect of the combination, the connector may comprise a pair of inclined bars, each inclined bar of the pair extending outwardly from one side of the vertical bar towards the longitudinal bar of the connector for connecting the vertical bar to the longitudinal bar. Optionally, the vertical bar may be centrally connected to the longitudinal bar of the connector.

According to an optional aspect of the combination, the combination may comprise a bottom space between the longitudinal bar and a bottom wall of the groove, the pourable conductive material filling said bottom space. The combination may also comprise side spaces between the longitudinal bar and longitudinal side walls of the groove, the pourable conductive material filling said side spaces.

According to an optional aspect of the combination, the longitudinal bar may have a rectangular cross-section, a flared cross-section or an ovoid cross-section. Preferably, the longitudinal bar may have a circular cross-section. Optionally, the groove and the longitudinal bar of the connector may have cross-sections of same shape, the cross-section of the groove being larger than the cross-section of the longitudinal bar. The groove may have a flared cross-section which is narrower near the longitudinal top surface of the anode.

According to an optional aspect of the combination, the conductive material of the connector may be a metallic material, such as steel.

According to an optional aspect of the combination, the connector may be made as a one-piece structure.

According to an optional aspect of the combination, the longitudinal bar of the connector may extend along almost an entire length of the longitudinal top surface of the anode for fitting in the corresponding groove. The longitudinal bar may be completely recessed into the groove.

In another aspect of the present invention, there is provided a method for connecting a connector to an anode suitable for use in a Hall-Heroult industrial cell. The method comprises providing a yokeless connector made of a conductive material for transmitting electrical current to an anode. The yokeless connector comprises a vertical bar and a longitudinal bar arranged in an inverted T-shape. The method also comprises providing the anode comprising a groove sized and shaped to receive the longitudinal bar of the connector, the anode having a longitudinal top surface, and the groove extending along the longitudinal top surface and being opened solely at the top surface of the anode. The method still comprises inserting the longitudinal bar of the connector into the groove, from the longitudinal top surface of the anode. Finally, the method comprises pouring a pourable conductive material around the inserted longitudinal bar and into the groove for bonding the connector to the anode.

In another aspect of the present invention, there is provided a method for connecting a connector to an anode suitable for use in a Hall-Heroult industrial cell. The method comprises providing a yokeless connector made of a conductive material for transmitting electrical current to an anode. The yokeless connector comprises a vertical bar and a longitudinal bar arranged in an inverted T-shape. The method also comprises providing the anode comprising a groove sized and shaped to receive the longitudinal bar of the connector, the anode having a longitudinal top surface and opposed side surfaces, and the groove extending along the longitudinal top surface of the anode towards the opposed side surfaces. The method still comprises inserting the longitudinal bar of the connector into the groove, from either the longitudinal top surface of the anode or from one of the opposed side surfaces. The method then comprises filling two opposed portions of the groove with refractory materials, each of the two opposed portions being located between one end of the inserted longitudinal bar of the connector and the corresponding opposed side surface of the anode. Finally, the method comprises pouring a pourable conductive material around the inserted longitudinal bar and into the groove for bonding the connector to the anode.

According to an optional aspect of the methods described above, the pourable conductive material is cast iron.

Advantageously, the combination of the connector and the anode of the invention reduces energy losses at the interfaces of the connector and the anode due to a better current distribution. In addition, since the connector is yokeless and stubless, in some cases the height, and thus the operational life of the anode can be increased. This in turn reduces aluminum manufacturing costs since it reduces inherent costs due to the anode replacement. Energy perturbations are also reduced due to the increase of the time interval between anode replacements.

In addition, the pressure at the interfaces of the connector is more evenly distributed compared to prior art stubs connectors, also contributing to a more uniform current distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages and features of the present invention will become more apparent upon reading the following non-restrictive description of preferred embodiments thereof, given for the purpose of exemplification only, with reference to the following accompanying figures:

Figure 1A is a perspective view of a prior art anode and its connector;

Figure 1 B is a perspective view of the connector illustrated in Figure 1A;

Figure 2A is a top perspective view of a combination anode-connector, according to one embodiment of the present invention;

Figure 2B is a top perspective view of a combination anode-connector, according to another embodiment of the present invention; Figure 3A is a semi-transparent schematic view of a prior art anode and its connector in an electrolytic cell;

Figure 3B is a semi-transparent schematic view of a combination anode- connector according to one embodiment of the present invention;

Figures 4A to 4F are cross-sectional views along line IV of Figure 2A of combinations anode-connectors having various cross-sectional shapes; and

Figures 5A to 5C represents three different schemes of a longitudinal section of a combination anode-connector according to three embodiments of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS

In the following description, similar features in the drawings have been given similar reference numerals. In order to preserve clarity, certain elements may not be identified in some figures if they are already identified in a previous figure.

The present invention aims at solving problems of energy losses at the connector/carbon anode interface with a yokeless and stubless anode connector. In order to be able to use existing industrial lifting systems for sealing operations of the connector to the anode, the connector is insertable from above the anode or from one of the sides of the anode. Preferably, the connector is inserted from above the anode.

The yokeless and stubless configuration also enables to increase the height of the anode if needed. A pourable conductive material is used for bonding the connector to the anode and ensuring an even distribution of the electrical current from the connector to the anode. It should be understood that the bonding refers to a mechanical bonding, that is, any physical interaction enabling fixation, attachment, anchoring or sealing of the connector to the anode without changing the chemical structure of the connector and/or anode. Preferably, cast iron is used as a conductive and pourable material. The pourable conductive material, such as cast iron, is required in order to be able to reuse the connector, even when the size of the longitudinal bar of the proposed connector is reduced due to corrosion, generally occurring after being in service for a given period of time. The anode is preferably made as a one-piece structure and has dimensions allowing a use in common known electrolytic cells, such as Hall-Heroult cells.

Referring to Figure 2A, a combination of an anode 24 and a connector 22 for use in a Hall-Heroult industrial cell is illustrated. The combination comprises the anode 24, the connector 22 and the conductive pourable material 20, such as cast iron. The conductive pourable material acts as a seal, and fills the groove 32 between the anode 24 and the connector 22. The anode 24, made of carbon, has a longitudinal top surface 25 and a groove 32 which extends longitudinally along the longitudinal top surface 25. The groove 32 may open solely on the longitudinal top surface 25, that is, it does not open at the end walls, also referred herein as side surfaces 27 of the anode. This configuration of the groove 32 also has the advantage of preventing pourable conductive material 20 leakage from the end walls 27 of the anode when poured around the connector 22 to seal it.

Referring to Figure 2B, the groove 32 may also open on both the longitudinal top surface 25 and side surfaces 27 of the anode. The connector 22 is made of a conductive material, in order to transmit the electrical current to the anode 24, required for the electrolysis process. The connector 22 has an inverted T-shape made of a vertical bar 30 which receives the electrical current from an aluminum rod (not shown) and a longitudinal bar 26 connected to the vertical bar 30. The longitudinal bar 26 extends into the groove of the anode. When inserted in the groove 32, the longitudinal bar 26 extends almost over the entire length of the anode. Having the longitudinal bar 26 extending on almost the entire length of the anode allows to better distribute the electrical current within the anode, and especially towards both sides 27 of the anode. The pourable conductive material 20 fills the groove 32 and seals the longitudinal bar 26 of the connector 22 to the anode 24. In order to prevent pourable conductive material 20 from leaking from the groove 32 during bonding of the connector 22 to the anode 24, a closure 29 made of refractory material fills the groove 32 from ends of the longitudinal bar 26 unto the side surfaces 27 of the anode. Furthermore, this refractory material protects the ends of the longitudinal bar 26 against dissolution in the electrolytic solution. With this configuration, the connector can be inserted within the anode from its sides 27 or from the top of the anode.

While in Figures 2 to 5B, the vertical bar 30 is shown centered relative to the longitudinal bar 26, in another embodiment the vertical bar could be offset from the center of the longitudinal bar as shown in Figure 5C. Preferably, the vertical bar is centered to fit into conventional electrolytic cells.

As can be appreciated, the connector 22, because of its yokeless inversed T-bar configuration, provides the advantage of increasing the height of the anode 24, as shown in Figures 3A and 3B. In other words, since the connector 22 does not have a yoke, the height h gained allows the use of thicker anodes (i.e. with an increased height) and the anode replacement cycle, which is generally around 26 days, can be increased.

Having a yokeless connector thus leads to a reduction of the costs that are inherent to an anode replacement, that is, costs due to the workforce required to replace the anode. Increasing the height of the anode (due to the yokeless connector) also helps reducing the energy-related perturbations in electrolytic cells, since the time interval between anode replacements is increased. The height increase of the anode may still be limited by the type of cell which is used. The replacement cycle of the connector-anode combination of the invention could increase by nearly 50% the replacement time. Increasing the replacement cycle length of the anode can also contribute to reducing GHG (Green House Gases).

While one in the art would believe that an increase in the height of the anode would lead to an increase of the energy losses due to the increased resistivity of the anode, it has been discovered that the use of a connector as described above leads to an overall reduction of energy losses in the anode.

Indeed, the replacement of prior art stubs 16 with a longitudinal bar 26 (best shown in Figure 3B) extending preferably on almost the entire length of the anode 24 provides the advantage of increasing the surface of the interface between the connector 22 and the anode 24 (and provide a better distribution of current), in addition to increasing the height of the anode 24 (increasing the lifetime of the anode).

As shown in Figures 2A, 2B, 3B, 5A and 5C, two inclined bars, or stringers 28, connect the longitudinal bar 26 with the vertical bar 30 of the, connector 22. This "trident" configuration provides the advantage of further distributing the current flow from the aluminum anode rod bar to the anode 24 and obtaining a better mechanical behavior of the connector 22 during the pourable conductive material 20 bonding operation and during the use of the combination inside the cell. Indeed, the current flowing through the inclined bars 28 reaches the extremities of the longitudinal bar 26, which in turn reaches extremities of the anode, which results in the current being distributed more evenly in the anode.

The connector is made of a conductive material, preferably a metallic material, such as steel. The longitudinal, inclined and vertical bars may preferably be formed as a one-piece structure, i.e. without any welding between the vertical, inclined and longitudinal bar. Of course, other metals for the connector can be used or other methods to assembly the longitudinal, inclined and vertical bars can be also used. The vertical bar is preferably provided with a bi-metallic joint for linking the connector to the aluminum rod as commonly used in the aluminum electrolysis process. Another advantage of the connector and the groove is the reduction of the carbon required for anode manufacturing and thus a reduction in the energy used for baking the anode. Carbon waste management (butts) is also reduced, with an overall reduction of GHG emissions. In the prior art connector, the carbon between the stubs is not used to produce aluminum being a part of the butt. While using the connector and groove according to the present invention, a reduction of up to 5% in terms of the volume of carbon is obtained, when compared to a 3-stub prior art connector.

Now referring to Figures 4A to 4F, different cross-sections of the connector 22 and the groove 32 are shown. The connector 22 may have a rectangular cross- sectional shape, but it can also take different cross-sectional shapes, such as flared, circular or ovoid cross-sectional shapes. Of course, the groove 32 can also take different cross-sectional shapes, including a trapezoidal cross-section. Preferably, the connector 22 may have a circular cross-sectional shape (as shown on Figure 4B) for providing a more even current distribution at the interface of the connector and the pourable conductive material, such as cast iron.

Referring to Figure 4A, the groove 32 preferably has a flared shape, narrower near the top of the anode. This particular configuration provides a better structural joint of the connector 22 with the anode 24, once the pourable conductive material 20 has solidified and shrunk within the groove 32 of the anode 24.

Referring to Figures 3B, 4A and 4F, the groove 32 has preferably rounded corners for smoothing the rough edges and avoid weakening and/or cracking of the anode. The variants shown in Figures 4B, 4C, 4E and 4F also help in reducing peaks of pressure at specific points of the surface of the connector 22, further improving the current distribution at the interface of the connector and the anode.

Referring to Figure 4A, when the longitudinal bar 26 is to be inserted from the longitudinal top surface 25 of the anode 24, the width W_bar of the longitudinal bar 26 is slightly smaller than the width of the narrowest section of the trapezoidal section (i.e. the width of the top portion of the groove 32, W_groove)- The same size relation of course applies to other connector-groove configurations. This size restriction is not needed, when the longitudinal bar is to be inserted from one of the side surfaces of the anode.

Still referring to Figure 4A, since the groove 32 has an upper section narrower than its lower section, the thickness of the pourable conductive material 20 in the upper section is thinner than the thickness in the lower section. When solidifying, the shrinkage of the pourable conductive material 20 will be more important in the lower section of the groove 32 than in the upper section. This will in turn lead to a contact pressure higher in the upper section of the groove 32, helping the current 34 to flow towards the top of the anode 24. Since steel is more conductive than the carbon of the anode, the current generally tends to flow towards the bottom of the steel bar. By having a higher mechanical pressure towards the top of the anode 24, the contact resistivity in this region is decreased, leading to a more uniformly distributed current density on the highest portion of the longitudinal bar 26. The results have shown that the use of a connector-anode combination as illustrated in Figure 4A has a lower voltage drop in this combination, of up to 15% per cell compared to prior art, which in turn leads to a reduction of the production costs in terms of electricity consumption. As shown in Figures 4B and 4C, the groove 32 and the longitudinal bar 26 can have same cross-sections, the cross-section of the groove being larger than the cross-section of the longitudinal bar 26. When the connector is combined to the anode, there is a bottom space between the longitudinal bar and the bottom wall of the groove, and pourable conductive material 20 may or may not fill this bottom space. There are also side spaces between the longitudinal bar 26 and longitudinal sidewalls of the groove 32, the pourable conductive material 20 also preferably filling these side spaces too.

As an alternative to the combinations illustrated in Figures 2A to 4F, the longitudinal bar 26 can be completely recessed into the groove 32. When solidifying, the pourable conductive material 20 will entrap the connector 22 in the anode 24, and thus the anode 24 will be supported by the connector 22. Since the longitudinal bar 26 preferably extends on almost the entire length of the anode 24, the support (or contact) surface is increased compared to prior art stub connectors. This larger contact area leads to a reduction of energy losses. An increase of 40% of the contact surface is expected with the combination of the present invention in comparison with known combinations.

Referring to Figures 4A, 4E and 4F, the internal lower edges of the groove are preferably rounded so as to avoid any crack in the anode.

Furthermore, the surface of the longitudinal bar may be irregular for optimizing the mechanical bond with the pourable conductive material. Now referring to Figures 5A to 5C, different models of connector-anode combination are shown. Figures 5A to 5C are longitudinal cross-sections of three variants of a connector-anode combination according to the present invention. The current and pressure distribution, along with energy losses have been simulated in comparison with known connector-anode combination. The results have shown that at the interface of the anode and the connector, energy losses are less than those of known combinations, and the pressure at the anode- connector interface is more evenly distributed.

The objective of known combination is often to eliminate the cast iron but the present invention aims at using a pourable conductive material, such as cast iron, to enhance the reduction of energy consumption and allows the re-use of the new connector even though the shape of the bar becomes irregular due to corrosion. The present invention also enables to thicken the anode. Furthermore, the present combination anode-connector may preferably be protected against corrosion with a groove with closed ends and possibly ramming paste (made of a blend of pitch, light oil diluent and an aggregate comprising a mixture of anthracite and calcined coke) on the top. The new connector of the present invention is also advantageously re-usable.

As seen on Figure 5C, the vertical bar 30 may not be centered on the longitudinal bar 26 for fitting specific size and geometry requirements of various electrolytic cells.

In one other aspect of the present invention, there is provided a method for combining the connector to the anode. The method may comprise the following steps of: a) providing a yokeless connector and an anode as described above; b) inserting the longitudinal bar of the connector into the groove; and c) pouring a pourable conductive material, such as cast iron, over and around the inserted longitudinal bar, into the groove. More particularly, the insertion of the longitudinal bar of the connector into the groove may be done from the longitudinal top surface or from one of the side surfaces of the anode. Preferably, the insertion is done from the longitudinal top surface of the anode.

Additionally, when the insertion of the connector into the groove is performed from one of the side surfaces of the anode, the method may comprise an additional step of filling two opposed portions of the groove with refractory materials before pouring the pourable conductive material, such as cast iron. Each of the two opposed portions 29 being located between one end of the inserted longitudinal bar 26 of the connector 22 and the corresponding opposed side surface 27 of the anode 24 as better seen in Figure 2B.

As above-mentioned, an insertion of the connector from one of the sides of the anode requires that the groove extends along the longitudinal top surface of the anode unto the side surfaces of the anode, thereby creating a corresponding opening on the side surfaces. After inserting the connector into the groove from one of the sides of the anode, the method thus further comprises filling each of the two portions of the groove with a refractory material to create a closure (29, Figure 2B) between the ends of the longitudinal bar of the connector and the end walls (also referred as side surfaces 27 of the anode, Figure 2B) of the anode. The pouring of the conductive material, such as cast iron, may then be performed to bond the connector to the anode.

As it can be appreciated, the combination and the method of combining the connector and the anode as described in the present application advantageously allow a more uniform current distribution at the anode/ pourable conductive material/connector interfaces which translates into a reduction of energy losses and thus a more efficient electrolysis process.

Of course, numerous modifications could be made to these previously described embodiments above without departing from the present invention.

Claims

1. A combination of a connector and an anode for use in a Hall-Heroult industrial cell for producing aluminum, the combination comprising:

a yokeless connector made of a conductive material for transmitting electrical current to the anode, the connector having an inverted T-shape and comprising

a vertical bar for receiving the electrical current, and

a longitudinal bar connected to said vertical bar; and

an anode having

a longitudinal top surface; and

a groove extending longitudinally along the top surface, the groove being sized and shaped to receive the longitudinal bar of the connector;

a pourable conductive material for filling the groove and bonding the longitudinal bar of the connector to the anode.

2. The combination according to claim 1 , wherein the pourable conductive material is cast iron.

3. The combination according to claim 1 or 2, wherein the groove opens solely at the longitudinal top surface of the anode, the groove having a width larger than a width of the longitudinal bar so as to enable insertion of the connector from the top surface of the anode.

4. The combination according to claim 1 or 2, wherein the groove opens at the top and opposed side surfaces of the anode, the anode comprising a refractory material for filling two opposed end portions of the groove, each of the two opposed end portions being located between one end of the longitudinal bar of the connector and the corresponding opposed side surface of the anode.

5. The combination according to any one of claims 1 to 4, wherein the connector comprises a pair of inclined bars, each inclined bar of the pair extending outwardly from one side of the vertical bar towards the longitudinal bar of the connector for connecting the vertical bar to the longitudinal bar.

6. The combination according to any one of claims 1 to 5, comprising a bottom space between the longitudinal bar and a bottom wall of the groove, the pourable conductive material filling said bottom space.

7. The combination according to any one of claims 1 to 6, comprising side spaces between the longitudinal bar and longitudinal side walls of the groove, the pourable conductive material filling said side spaces.

8. The combination according to any one of claims 1 to 7, wherein the longitudinal bar has a rectangular cross-section, a flared cross-section or an ovoid cross-section.

9. The combination according to any one of claims 1 to 7, wherein the longitudinal bar has a circular cross-section.

10. The combination according to any one of claims 1 to 9, wherein the groove and the longitudinal bar of the connector have same shape cross-sections, the cross-section of the groove being larger than the cross-section of the longitudinal bar.

1 1 . The combination according to any one of claims 1 to 10, wherein the groove has a flared cross-section which is narrower near the longitudinal top surface of the anode.

12. The combination according to any one of claims 1 to 1 1 , wherein the vertical bar is centrally connected to the longitudinal bar of the connector.

13. The combination according to any one of claims 1 to 12, wherein the conductive material of the connector is a metallic material.

14. The combination according to claim 13, wherein the metallic material is steel.

15. The combination according to any one of claims 1 to 14, wherein the connector is made as a one-piece structure.

16. The combination according to any one of claims 1 to 15, wherein the longitudinal bar of the connector extends along almost an entire length of the longitudinal top surface of the anode for fitting in the corresponding groove.

17. The combination according to any one of claims 1 to 16, wherein the longitudinal bar is completely recessed into the groove.

18. A method for connecting a connector to an anode suitable for use in a Hall- Heroult industrial cell, the method comprising

providing a yokeless connector made of a conductive material for transmitting electrical current to an anode, the connector comprising a vertical bar and a longitudinal bar arranged in an inverted T-shape;

providing the anode comprising a groove sized and shaped to receive the longitudinal bar of the connector, the anode having a longitudinal top surface, and the groove extending along the longitudinal top surface and being opened solely at the top surface of the anode;

inserting the longitudinal bar of the connector into the groove, from the longitudinal top surface of the anode; and

pouring a pourable conductive material around the inserted longitudinal bar and into the groove for bonding the connector to the anode.

19. A method for connecting a connector to an anode suitable for use in a Hall- Heroult industrial cell, the method comprising

providing the anode comprising a groove sized and shaped to receive the longitudinal bar of the connector, the anode having a longitudinal top surface and opposed side surfaces, and the groove extending along the longitudinal top surface of the anode towards the opposed side surfaces; inserting the longitudinal bar of the connector into the groove, from either the longitudinal top surface of the anode or from one of the opposed side surfaces; filling two opposed portions of the groove with refractory materials, each of the two opposed portions being located between one end of the inserted longitudinal bar of the connector and the corresponding opposed side surface of the anode; and pouring a pourable conductive material around the inserted longitudinal bar and into the groove for bonding the connector to the anode.

20. The method according to claim 18 or 19, wherein the pourable conductive material is cast iron.