WO2015089672A1

WO2015089672A1 - Process, apparatus and saw blade for processing anode blocks, and prebaked anode blocks for aluminum production

Info

Publication number: WO2015089672A1
Application number: PCT/CA2014/051239
Authority: WO
Inventors: Alain Jacques
Original assignee: 9293-3720 Québec Inc.
Priority date: 2013-12-20
Filing date: 2014-12-19
Publication date: 2015-06-25

Abstract

An anode block for aluminum production in an electrolysis cell, comprises a calcined carbon body having a wear surface with at least one groove defined therein, the at least one groove having at least a lower groove section with a lower section width and extending upwardly from the wear surface, and an upper groove section with an upper section width narrower than the lower section width, the upper groove section being continuous with the lower groove section. There is also provided an apparatus and a process for processing anode blocks.

Description

PROCESS, APPARATUS AND SAW BLADE FOR PROCESSING ANODE BLOCKS, AND PREBAKED ANODE BLOCKS FOR ALUMINUM PRODUCTION

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of United States provisional patent application no. 61/918.871 which was filed on December 20, 2013. The entirety of the aforementioned application is herein incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to the field of calcined carbon bodies. More particularly, it relates to a process, an apparatus and a specific saw blade for processing calcined carbon bodies and, even more particularly, for processing grooves in calcined carbon bodies, such as prebaked anode blocks for aluminum production. It also relates to prebaked anode blocks for aluminum production manufactured using the above described process, apparatus, and/or saw blade.

BACKGROUND

[0003] In the field of aluminum production, it is known to perform aluminum smelting using industrial process, such as the Hall-Heroult process. In such a process, electrolysis of an electrolyte (commonly being a molten mixture of alumina (Al₂0₃), cryolite (Na₃AIF₆), and aluminum fluoride (AIF₃)) is performed in an electrolysis cell, using an anode including at least one anode block, to conduct electricity and produce the aluminum. During electrolysis, oxidation of the anode block produces carbon dioxide (C0₂) thereat, which tends to accumulate at a wear (or consumable) surface of the anode block. Such gas accumulation increases the electrical resistance (thereby reducing the current efficiency) and causes instabilities and variations in the electrical contact between the anode block and the electrolyte.

[0004] One of the existing solutions for reducing gas accumulation at the wear surface of the anode block is to cut at least one groove (or slot) in the wear surface thereof, for example and without being limitative, using a circular saw in a dry milling process. The at least one groove allows the drainage of the gas from the wear surface of the anode block as it defines a gas evacuation path for the gas to flow into and away from the wear surface. The at least one groove however negatively impacts the lifetime of the anode block in the electrolysis cell and reduces the working surface thereof, as a result of the decrease in the calcined carbon mass caused by the cutting of the at least one groove therein. There is thus a need to make the grooves narrower in order to limit the decrease in the calcined carbon mass.

[0005] In view of the above, there is a need for an improved anode block, apparatus and/or saw blade for processing anode blocks as well as a process for the manufacture of an anode block which would be able to overcome or at least minimize some of the above- discussed prior art concerns.

BRIEF SUMMARY OF THE INVENTION

[0006] According to a general aspect, there is provided an anode block for aluminum production in an electrolysis cell. The anode block comprises a calcined carbon body having a wear surface with at least one groove defined therein. The at least one groove has at least a lower groove section with a lower section width and extending upwardly from the wear surface, and an upper groove section with an upper section width narrower than the lower section width, the upper groove section being continuous with the lower groove section.

[0007] In an embodiment, each one of the at least one groove has a groove depth ranging between about 250 mm and about 450 mm. The groove depth can range between about 300 mm and about 400 mm.

[0008] In an embodiment, the lower groove section of each one of the at least one groove has a lower groove section depth ranging between about 125 mm and about 250 mm.

[0009] In an embodiment, the upper groove section of each one of the at least one groove has an upper groove section depth ranging between about 125 mm and about 200 mm.

[0010] In an embodiment, the lower section width of the lower groove section of each one of the at least one groove ranges between about 8 mm and about 20 mm. The lower section width of the lower groove section of each one of the at least one groove can range between about 8 mm and about 14 mm. [0011] In an embodiment, the upper section width of the upper groove section of each one of the at least one groove ranges between about 4 mm and about 10 mm. The upper section width of the upper groove section of each one of the at least one groove can range between about 4 mm and about 8 mm.

[0012] In an embodiment, the anode block has a first lateral face and a second lateral face opposed to the first lateral face and wherein each one of the at least one groove extends continuously longitudinally from the first lateral face to the second lateral face.

[0013] In an embodiment, two grooves are defined in the wear surface.

[0014] According to another general aspect, there is provided a saw blade for cutting a groove in a wear surface of a prebaked anode block for aluminum production. The saw blade comprises a circular saw blade disc with at least a first set of teeth having a first tooth width and a second set of teeth having a second tooth width, wherein each one of the first set of teeth and the second set of teeth protrude laterally outwardly of the saw blade disc and are radially spaced apart from one another, the second set of teeth being positioned inwardly of the first set of teeth and the first tooth width being narrower than the second tooth width.

[0015] In an embodiment, the circular saw blade disc includes at least an outer annular disc having an inner edge and an outer edge and an inner annular disc having an outer edge, the outer annular disc extending radially from the outer edge of the inner annular disc and the at least one first set of teeth and second set of teeth each being associated with a respective one of the outer annular disc and the inner annular disc. The teeth of the first set of teeth can be circumferentially spaced apart along the outer edge of the outer annular disc and the teeth of the second set of teeth can be circumferentially spaced apart along the outer edge of the inner annular disc. The outer annular disc can have a plurality of spaced-apart recesses defined along the inner edge thereof and extending inwardly into the outer annular disc and wherein each one of the teeth of the second set of teeth can be positioned in a respective one of the recesses.

[0016] In an embodiment, each one of the inner annular disc and the outer annular disc has a thickness, the thickness of each one of the inner annular disc and the outer annular disc being substantially constant along a radial length thereof. [0017] In an embodiment, each one of the inner annular disc and the outer annular disc tapers along a radial length thereof.

[0018] According to a further general aspect, there is provided an apparatus for processing anode blocks for use in connection with the electrolytic production of aluminum. The apparatus comprises: at least one saw blade having a saw blade disc with at least two sets of teeth, a first one of the sets of teeth being peripherally mounted to the saw blade disc and comprising a plurality of teeth having a first tooth width and a second one of the sets of teeth comprising a plurality of teeth having a second tooth width, larger than the first tooth width, the teeth of the second one of the sets being mounted inwardly of the teeth of the first one of the sets and being radially spaced-apart therefrom.

[0019] In an embodiment, the saw blade disc includes at least an outer annular disc having an inner edge and an outer edge and an inner annular disc having an outer edge, the outer annular disc extending radially from the outer edge of the inner annular disc and the first one of the sets of teeth and the second one of the sets of teeth each being associated with a respective one of the outer annular disc and the inner annular disc. The teeth of the first one of the sets of teeth can be circumferentially spaced apart along the outer edge of the outer annular disc and the teeth of the second one of the sets of teeth can be circumferentially spaced apart along the outer edge of the inner annular disc. The outer annular disc can have a plurality of spaced-apart recesses defined along the inner edge thereof and extending inwardly into the outer annular disc and wherein each one of the teeth of the second one of the sets of teeth can be positioned in a respective one of the recesses.

[0020] In an embodiment, each one of the inner annular disc and the outer annular disc has a thickness, the thickness of each one of the inner annular disc and the outer annular disc being substantially constant along a radial length thereof.

[0021] In an embodiment, each one of the inner annular disc and the outer annular disc tapers along a radial length thereof.

[0022] According to still another general aspect, there is provided an apparatus for processing anode blocks for use in connection with the electrolytic production of aluminum.

The apparatus comprises: at least two saw blades mounted in a series configuration with a first one of the saw blades comprising a first saw blade disc with a first diameter and peripherally mounted teeth having a first tooth width and a second one of the saw blades comprising a second saw blade disc with a second diameter and peripherally mounted teeth having a second tooth width, the second diameter being larger than the first diameter and the second tooth width being narrower than the first tooth width.

[0023] In an embodiment, the first diameter of the first saw blade disc ranges between about 250 mm and about 850 mm.

[0024] In an embodiment, the second diameter of the second saw blade disc ranges between about 500 mm and about 1300 mm

[0025] In an embodiment, the first tooth width of the peripherally mounted teeth of the first saw blade disc ranges between about 8 mm and about 20 mm. The first tooth width of the peripherally mounted teeth of the first saw blade disc can range between about 8 mm and about 14 mm.

[0026] In an embodiment, the second tooth width of the peripherally mounted teeth of the second saw blade disc ranges between about 4 mm and about 10 mm. The second tooth width of the peripherally mounted teeth of the second saw blade disc can range between about 4 mm and about 8 mm.

[0027] In an embodiment, each one of the first saw blade disc and the second saw blade disc has a thickness, the thickness of at least one of the first saw blade disc and the second saw blade disc being substantially uniform along a corresponding one of the first diameter and the second diameter.

[0028] In an embodiment, at least one of the first saw blade disc and the second saw blade disc tapers along the corresponding one of the first diameter and the second diameter.

[0029] According to another general aspect, there is provided a process for the manufacture of an anode block for use in an aluminum electrolysis cell. The process comprises the step of: cutting at least one groove in the anode block, the at least one groove having a lower groove section with a lower section width and extending upwardly from a wear surface of the anode block, and an upper groove section with an upper section width narrower than the lower section width and, the upper groove section being continuous with the lower groove section.

[0030] In an embodiment, the step of cutting the at least one groove comprises inserting a saw blade in the anode block to cut simultaneously the lower groove section and the upper groove section.

[0031] In an embodiment, the step of cutting the at least one groove comprises initially cutting the lower groove section by inserting an upstream saw blade in the anode block and subsequently cutting the upper groove section by inserting a downstream saw blade in the anode block along the lower groove section.

[0032] According to still another general aspect, there is provided a saw blade for cutting a groove in a wear surface of a prebaked anode block for aluminum production. The saw blade comprises a circular saw blade disc having a tapered profile, being thicker close to a center thereof and thinner close to a periphery thereof and at least a first set of teeth peripherally mounted to the circular saw blade disc.

[0033] In an embodiment, the saw blade disc comprises a central disc having a uniform thickness and two tapered shaped discs, each one being superposed on a respective side of the central disc.

[0034] In an embodiment, the saw blade disc is between about 0.5 mm and about 2 mm thicker close to the center than at its periphery.

[0035] In an embodiment, the angle defined between a centrally extending plane and an outer face ranges between about 0.1° and about 5° and, in an alternative embodiment, between about 0.1° and about 0.3°.

[0036] According to still another general aspect, there is provided a method for producing aluminum in a Hall-Heroult cell with prebaked carbon anodes, each one of the anodes having a wear surface. The method comprises draining gas away from the wear surface by forming at least one continuous groove in the wear surface of the anodes, the gas drainage being performed by the at least one groove having a first groove section with a first section width and a second groove section with a second section width narrower than the first section width, the second groove section being continuous with the first groove section.

DESCRIPTION OF THE FIGURES

[0037] Other objects, advantages and features will become more apparent upon reading the following non-restrictive description of embodiments thereof, given for the purpose of exemplification only, with reference to the accompanying drawings in which:

[0038] Figure 1 is a perspective view of an anode block of an anode for aluminum production, in accordance with an embodiment.

[0039] Figure 2 is a side elevation view of the anode block of Figure 1.

[0040] Figure 3 is a side elevation view of a saw blade for cutting a groove in an anode block, in accordance with an embodiment where the saw blade includes an inner annular disc and an outer annular disc and two sets of teeth radially spaced-apart from one another.

[0041] Figure 4 is a cross-sectional perspective view of the saw blade of Figure 3, according to an embodiment where the inner annular disc and an outer annular disc have a substantially constant width.

[0042] Figure 5 is a cross-sectional perspective view of the saw blade of Figure 3, according to an embodiment where the inner annular disc and an outer annular disc each have a tapered profile.

[0043] Figure 6 is a perspective view of two saw blades of Figure 3, mounted on a spindle, in a parallel configuration, for making two parallel grooves in the anode block.

[0044] Figure 7 is a side elevation view of a set of two saw blades, in accordance with an embodiment, and mounted to spindles in a series configuration for making a groove in the anode block.

[0045] Figure 7a and 7b are respectively a perspective view, enlarged, of a tooth of a first saw blade and a tooth of the second saw blades of the set of two saw blades of Figure [0046] Figure 8 is a cross-sectional perspective view of a second saw blade of the set of two saw blades of Figure 7.

[0047] Figure 9 is a cross-sectional perspective view of a saw blade for making a groove in the anode block, in accordance with an embodiment where the saw blade includes a single saw blade disc having a tapered profile.

DETAILED DESCRIPTION

[0048] In the following description, the same numerical references refer to similar elements. The embodiments, geometrical configurations, materials mentioned and/or dimensions shown in the figures or described in the present description are embodiments only, given solely for exemplification purposes.

[0049] Moreover, although the embodiments of the anode block and/or apparatus for processing anode blocks and corresponding parts thereof consist of certain geometrical configurations as explained and illustrated herein, not all of these components and geometries are essential and thus should not be taken in their restrictive sense. It is to be understood, as also apparent to a person skilled in the art, that other suitable components and cooperation thereinbetween, as well as other suitable geometrical configurations, may be used for the anode block and/or apparatus for processing anode blocks, as will be briefly explained herein and as can be easily inferred herefrom by a person skilled in the art. Moreover, it will be appreciated that positional descriptions such as "forward", "rearward", "above", "below", "left", "right" and the like should, unless otherwise indicated, be taken in the context of the figures and should not be considered limiting.

[0050] Referring generally to Figures 1 and 2, there is shown an embodiment of an anode block 20 of an anode (not shown) used for aluminum production. In the embodiment shown, the anode block 20 is a calcined carbon body connectable to an anode hanger (not shown) configured to retain the anode block 20 and conduct the electric current thereto. In an embodiment, an upper surface 29 of the anode block 20 includes at least one fitting recess (not shown) to allow the anode hanger to be connected to the anode block 20.

[0051] In the embodiment shown, the anode block 20 has a substantially rectangular prism shape with bevelled upper edges and straight (90°) side and lower edges. However, it is appreciated that, in alternative embodiments, the shape of the anode block 20 can differ from the embodiment shown. For example, in an embodiment, the anode block 20 can have a prism shape different from the rectangular prism shape of the embodiment shown, and each one of the edges can be straight, bevelled, rounded, or the like.

[0052] The anode block 20 comprises two grooves 22 cut into a lower surface (or underside) of the anode block 20, also known as the "wear surface" 24, and extending upwardly therefrom. In other words, each one of the two grooves 22 extends inwardly into the anode block 20, from the wear surface 24. In the course of the present description, the term "groove" refers to a recess extending inwardly into the anode block 20.

[0053] In the embodiment shown, the anode block 20 comprises two grooves 22, however, it is appreciated that, in alternative embodiments, the anode block 20 can comprise more or less than the two illustrated grooves 22. Moreover, in the embodiment shown, the two grooves 22 are substantially evenly spaced-apart along a length of the anode block 20; i.e. the two grooves 22 are substantially parallel to one another. However, it is appreciated that, in an embodiment, the distance between the grooves 22 can vary along the length of the anode block 20. Furthermore, in embodiments where more than one groove 22 is provided, the grooves 22 can be substantially similar to one another or can differ in size, shape, orientation, or the like.

[0054] In the embodiment shown, each one of the grooves 22 extends continuously longitudinally from a first lateral face 25a of the anode block 20 to a second lateral face 25b, opposed to the first lateral face 25a. Hence, each one of the grooves 22 defines a recess opened at the wear surface 24 and both lateral faces 25a, 25b of the anode block 20. One skilled in the art will however understand that, in an alternative embodiment (not shown), at least one of the grooves 22 can extend inwardly from the wear surface 24, without being opened at one or both of the lateral faces 25a, 25b. Moreover, in the embodiment shown, each one of the grooves 22 extend upwardly inside the anode block 20, substantially normal to the wear surface 24. However, one skilled in the art will understand that, in an alternative embodiment (not shown), at least one of the grooves 22 can be inclined with respect to the wear surface 24 of the anode block 20, i.e. at least one of the grooves 22 can define an oblique angle (an angle other than a right angle), with the wear surface 24 of the anode block 20. [0055] In the embodiment shown, each one of the grooves 22 includes two groove sections along a groove depth 22a thereof: a lower groove section 26 and an upper groove section 28. In the present specification, the terms "lower" and "upper" refers to the orientation of the anode block 20 in an electrolysis cell. The lower groove section 26 has a lower groove section depth 26c and extends upwardly between a lower end 26a, corresponding with the wear surface 24 of the anode block 20, and an upper end 26b distal from the wear surface 24. The upper groove section 28 has an upper groove section depth 28c and extends upwardly between a lower end 28a, corresponding with the upper end 26b of the lower groove section 26, and an upper end 28b. As can be seen in the Figures, the upper end 28b of the upper groove section 28 is inwards with respect to the lower end 28a thereof, and is positioned between the upper end 26b of the lower groove section 26 and the upper surface 29 of the anode block 20.

[0056] For example and without being limitative, in an embodiment, the groove depth 22a of each one of the grooves 22 can range between about 250 mm and about 450 mm. In an alternative embodiment, the groove depth 22a of each one of the grooves 22 can range between about 300 mm and about 400 mm. Along the groove depth 22a of the groove 22, in an embodiment, the lower groove section depth 26c can range between about 125 mm and about 250 mm and the upper groove section depth 28c can range between about 125 mm and about 200 mm. It will be understood that, in different embodiments, the lower groove section depth 26c and the upper groove section depth 28c can be substantially similar to one another or different from one another, with either one of the lower groove section depth 26c and the upper groove section depth 28c being the longer. In an embodiment, a ratio between a length of the lower groove section depth 26c and the upper groove section depth 28c ranges between about 30% and about 70%. In another embodiment, the ratio between a length of the lower groove section depth 26c and the upper groove section depth 28c ranges between about 40% and about 60%. In still another embodiment, the ratio is around 50%.

[0057] Each one of the lower groove section 26 and the upper groove section 28 has a section width 26d, 28d, with the lower section width 26d being wider than the upper section width 28d. For example and without being limitative, in an embodiment, the lower section width 26d can range between about 8 mm and about 20 mm. In an alternative embodiment the lower section width 26d can range between about 8 mm and about 14 mm. For example and without being limitative, in an embodiment, the upper section width 28d can range between about 4 mm and about 10 mm. In an alternative embodiment, the upper section width 28d can range between about 4 mm and about 8 mm. In an embodiment, the upper section width 28d is between about 2 mm and 4 mm narrower than the lower section width 26d.

[0058] In view of the above, in the embodiment shown, each one of the grooves 22 is divided into two continuous groove sections, 26, 28, each having a different width 26d, 28d. However, one skilled in the art will easily understand that, in an alternative embodiment, each one of the grooves 22 can include more than two groove sections, each being characterized a different width. Moreover, in the embodiment shown, the upper groove section 28 is centered with respect to the lower groove section 26. One skilled in the art will however understand that, in an alternative embodiment, the upper groove section 28 can be offset with respect to the centered configuration shown. For example and without being limitative, in an embodiment, the upper groove section 28 can be horizontally aligned with either one of the sides of the lower groove section 26.

[0059] As mentioned above, the lower groove section 26 and the upper groove section 28 are continuous, i.e. the upper groove section 28 is consecutive to the lower groove section 26, with the upper end 26b of the lower groove section 26 and the lower end 26a of the upper groove section 28 being located at a junction therebetween. In the embodiment shown in Figures 1 and 2, the joining edges 27 positioned at the junction of the upper end 26b of the lower groove section 26 and the lower end 28a of the upper groove section 28 are substantially straight edges, i.e. edges extending substantially horizontally. However, one skilled in the art will understand that, in an alternative embodiment, the joining edges 27 can have a different configuration from the embodiment shown, such as, without being limitative, a bevelled configuration.

[0060] Referring now to Figures 3 to 5, there is shown an embodiment of a saw blade 40 for cutting grooves 22 in the anode block 20, as shown in Figures 1 and 2. In order to allow the saw blade 40 to cut into the anode block 20, the saw blade 40 is securable on a spindle (not shown), such as to be used in a machining unit (not shown), a processing machine (not shown), or the like. [0061] The saw blade 40 has a circular saw blade disc 42 which includes an inner annular disc 43 and an outer annular disc 45. The inner annular disc 43 has an outer edge 43a and an inner edge 43b defining a central aperture 41 sized and shaped to receive the spindle (not shown). The outer annular disc 45 has an inner edge 45b and an outer edge 45a, with a plurality of spaced-apart recesses 51 defined along the inner edge 45b and extending inwardly into the outer annular disc 45. The outer annular disc 45 extends radially from the outer edge 43a of the inner annular disc 43, such as to project beyond the outer edge 43a of the inner annular disc 43.

[0062] In an embodiment, the circular saw blade disc 42 is manufactured as a single piece component where the inner annular disc 43 and the outer annular disc 45 are integral to one another. One skilled in the art would however understand that, in an alternative embodiment, the inner annular disc 43 and the outer annular disc 45 can be manufactured independently and subsequently be connected to one another, for example and without being limitative, through brazing, welding or the like. Moreover, it will be understood that the configuration of the saw blade 40 which is illustrated in Figures 3 to 5 is provided solely for the purpose of illustration and that, in alternative embodiments, the size and shape of the saw blade disc 42 of the saw blade 40 can depart from the embodiment shown. For example and without being limitative, in an alternative embodiment, the saw blade disc 42 can include more than two annular discs connected to one another or manufactured as a single piece component.

[0063] Referring to Figures 4, in an embodiment, each one of the inner annular disc 43 and the outer annular disc 45 has a substantially constant width along a radial length thereof. In an embodiment, the inner annular disc 43 is wider than the outer annular disc 45 (see Figure 4). One skilled in the art will however understand that, in an alternative embodiment (not shown), the inner annular disc 43 and the outer annular disc 45 can have substantially the same width.

[0064] Referring to Figure 5, in an alternative embodiment, each one of the inner annular disc 43 and the outer annular disc 45 has a tapered profile, i.e. the profile of each one of the inner annular disc 43 and the outer annular disc 45 tapers along a radial length thereof. Indeed, as can be seen in Figure 5, in the embodiment shown, the profile of each one of the inner annular disc 43 and the outer annular disc 45 tapers radially outward, i.e. each one of the inner annular disc 43 and the outer annular disc 45 is wider a its inner edge 43b, 45b than at its outer edge 43a, 45a. For example and without being limitative, in an embodiment, the angle defined by the tapered profile of each one of the inner annular disc 43 and the outer annular disc 45 can range between about 0.1° and about 5° and, in an alternative embodiment, between about 0.1° and about 0.3°. One skilled in the art will understand that, in an alternative embodiment, only one of the inner annular disc 43 and the outer annular disc 45 can have a tapered profile, while the other one has a substantially constant thickness along a radial length thereof.

[0065] In an embodiment, each of the inner annular disc 43 and the outer annular disc 45 is between about 0.5 mm and about 2 mm thicker close to its inner diameter than at its outer diameter. In an embodiment, each of the inner annular disc 43 and the outer annular disc 45 is approximately 1 mm thicker close to its inner diameter than at its outer diameter.

[0066] In the embodiment shown, the thickness of the outer annular disc 45 at the inner edge 45b is greater than the thickness of the inner annular disc 43 at the outer edge 43a, i.e. the outer annular disc 45 is wider than the inner annular disc 43 at a junction of both annular discs 43, 45. One skilled in the art would however understand that, in alternative embodiments (not shown), the thickness of the outer annular disc 45 at the inner edge 45b can be substantially similar to the thickness of the inner annular disc 43 at the outer edge 43a or the thickness of the outer annular disc 45 at the inner edge 45b can be smaller than the thickness of the inner annular disc 43 at the outer edge.

[0067] For example and without being limitative, in an embodiment, the thickness of the inner annular disc 43 can range between about 8 mm and about 14 mm at the inner edge 43b and between about 5 mm and about 11 mm at the outer edge 43a thereof, while the thickness of the outer annular disc 45 can range between about 4 mm and about 8 mm at the inner edge 45b, and between about 2 mm and about 7 mm at the outer edge 45a thereof.

[0068] In an embodiment, the saw blade disc 42 includes a first set of teeth 50 and a second set of teeth 52, radially spaced apart from one another. The first set of teeth 50 and the second set of teeth 52 are each associated with a respective one of the outer annular disc 45 and the inner annular disc 43. In the embodiment shown, the teeth of the first set of teeth 50 and the second set of teeth 52 are engageable directly with the saw blade disc 42. One skilled in the art will however understand that, in an alternative embodiment (not shown), the teeth of either one of the first set of teeth 50 and the second set of teeth 52 can rather be secured to tooth holders (not shown) received in recesses (not shown) defined in the saw blade disc 42. Moreover, in another alternative embodiment (not shown), the teeth of either one of the first set of teeth 50 and the second set of teeth 52 can be permanently mounted to the saw blade disc 42, for example and without being limitative through brazing, welding or the like. Furthermore, the shape and the configuration of the teeth of either one of the first set of teeth 50 and the second set of teeth 52 can differ from the embodiment shown. One skilled in the art will understand that, in an alternative embodiment (not shown), the saw blade disc 42 can include more than the two set of teeth of the embodiment shown, such as to cut grooves having more than two sections of different widths, as will be better understood in view of the description below.

[0069] In the embodiment shown, the teeth of the first set of teeth 50 are located at the outer edge 45a of the outer annular disc 45 (which corresponds to a periphery of the saw blade disc 42). More particularly, the teeth of the first set of teeth 50 are circumferentially spaced apart along the outer edge 45a of the outer annular disc 45. A gullet 47 is defined between each consecutive teeth of the first set of teeth 50, along the outer edge 45a of the outer annular disc 45, such that a gullet 47 is associated with each tooth of the first set of teeth 50 and extends forwardly thereof. In the course of the present description, the term "forward", when used in reference to the saw blade 40, refers to the direction where the teeth of the first set of teeth 50 and the second set of teeth 52 are intended to face during use.

[0070] The teeth of the second set of teeth 52 are located radially inwardly of the saw blade disc 42 and define a circular pattern. More particularly, the teeth of the second set of teeth 52 are located at the outer edge 43a of the inner disc 43, with each tooth of the second set of teeth 52 being positioned in a respective one of the recesses 51 defined in the outer annular disc 45. In other words, each one of the teeth of the second set of teeth 52 is associated with a respective one of the recesses 51 extending upwardly and forwardly thereof with respect to the rotation direction of the saw blade disc 42. Hence, the teeth of the second set of teeth 52 are spaced-apart from one another along the outer edge 43a of the inner disc 43 with a gullet 55 being defined peripherally of the inner annular disc 43, between each consecutive teeth of the second set of teeth 52. Once again, a gullet 55 is associated with each tooth of the second set of teeth 52 and extends forwardly thereof. Each gullet 55 is associated with a respective one of the recesses 51 such that each combination of the gullet 55 and the associated recess 51 defines a cavity 57 in the saw blade disc 42. The cavities 57 are sized and shaped to receive and temporarily retain carbonaceous material removed from the anode block 20 by the saw blade 40 during the cutting of the groove 22 therein.

[0071] In an embodiment, the teeth of each one of the first set of teeth 50 have a first tooth width 50a and the teeth of the second set of teeth 52 have a second tooth width 52a. Each one of the first tooth width 50a and the second tooth width 52a are thicker than the respective one of the annular discs 43, 45 to which the associated set of teeth is connected, i.e. the teeth of the first set of teeth 50 are thicker than the thickness of the outer annular disc 45 while the teeth of the second set of teeth 52 are thicker than a thickness of the inner annular disc 43. Hence, the teeth of each one of the first set of teeth 50 and the second set of teeth 52 protrude outwardly on the sides of the saw blade disc 42, to allow the required clearance for the saw blade disc 42 to rotate into the anode block 20 during the cutting of the groove 22 by the saw blade disc 40.

[0072] For a predetermined width (or clearance) of the teeth of each one of the first set of teeth 50 and the second set of teeth 52, the tapered configuration of the inner annular disc 43 and/or the outer annular disc 45 (as shown in Figure 5) increases the stiffness of the saw blade disc 42, as opposed to a saw blade disc 42 where the inner annular disc 43 and/or the outer annular disc have a substantially uniform thickness.

[0073] Referring to Figures 1 to 5, the width of each groove section 26, 28 of the grooves 22 cut in the anode block 20 is determined by the first tooth width 50a and the second tooth width 52a of the teeth of each one of the first set of teeth 50 and the second set of teeth 52 of the saw blade 40. Therefore, in order to cut a groove 22 with a lower groove section 26 having a greater width than the consecutive upper groove section 28, the first tooth width 50a is narrower than the second tooth width 52a, i.e. the teeth of the first set of teeth 50 of the saw blade 40 are narrower than the teeth of the second set of teeth 52 such that the teeth of the second set of teeth 52 extend laterally outwardly past the teeth of the first set of teeth 50 in the saw blade disc 42 of the saw blade 40. Hence, the teeth of the second set of teeth 52 define a wider groove section in the anode block 20 (corresponding to the lower groove section 26 of the grooves 22) than the teeth of the first set of teeth 50 (corresponding to the upper groove section 28) when the above-described saw blade 40 is used to cut into the anode block 20.

[0074] In view of the above, a saw blade 40 such as described above can be used in a process for the manufacture of an anode block 20 to be used in an aluminum electrolysis cell. In such a process, one or more grooves 22 can each be cut in the anode block 20 by inserting the saw blade 40 in the anode block to cut simultaneously the lower groove section 26 and the upper groove section 28 therein.

[0075] Referring now to Figure 6, in an embodiment, a plurality of saw blades 40 can be mounted to a spindle 60 of a machining unit or a processing machine (not shown), in a parallel configuration, such as to cut multiple spaced-apart grooves in a single anode block 20 or a single groove in each one of a plurality of anode blocks 20 positioned side by side. For example, in the embodiment shown, two saw blades 40 are mounted to the spindle 60 of a machining unit or a processing machine (not shown), in a parallel configuration. It will be appreciated that the configuration of the saw blades 40 illustrated in Figure 6 is provided solely for the purpose of illustration and several alternative embodiments can be foreseen. For example and without being limitative, in an embodiment each one of the saw blades 40 can be mounted to a different spindle 60 or more than two saw blades 40 can be mounted to the spindle 60 in the parallel configuration.

[0076] As can be seen in Figure 6, in an embodiment one or more blade stabilizers 62 can be mounted close to each one of the saw blade 40, in order to stabilize the corresponding saw blade 40 during rotation thereof. The blade stabilizer 62 is mounted to the machining unit or processing machine (not shown) which includes the saw blade 40. In an embodiment, the blade stabilizer 62 is adapted to exert a force on the saw blade 40 in a direction substantially perpendicular to a cutting plane defined by the saw blade 40. Each blade 40 can include one or more blade stabilizers 62.

[0077] Each blade stabilizer 62 can include a pair of stabilizer pads 63 or other devices positioned on opposite sides of the saw blade 40 and contributing to the stabilization thereof. The stabilizer pads can be any suitable stabilizer including and without being limitative stabilizers including bearings and/or rollers. In the embodiment shown, each blade stabilizer 62 is aligned with the outer annular disc 45 of the corresponding saw blade disc 42 and exerts a force thereagainst to achieve the desired stabilization of the saw blade 40. It is appreciated that the configuration of the blade stabilizer 62 illustrated in Figure 6 is provided solely for the purpose of illustration and, once again, several alternative embodiments can be foreseen. For example and without being limitative, in an alternative embodiment (not shown), the blade stabilizer 62 can be spaced-apart from the saw blade 40 and apply gas pressure on the lateral faces of the saw blade disc 42, such as to stabilize the saw blade 40 laterally without contacting the saw blade 40.

[0078] Now referring to Figures 7 to 9, in an alternative embodiment, a first (upstream) saw blade 70 and a second (downstream) consecutive saw blade 72 mounted in a series configuration can be used to cut the groove 22 with the lower groove section 26 having a greater width 26d than the continuous upper groove section 28, in the anode block 20 as shown in Figures 1 and 2. Indeed, rather than the above described single saw blade 40 having the first set of teeth 50 and the second set of teeth 52, the first and the second consecutive saw blades 70, 72 of different diameter and each having a peripheral set of teeth 76, 78 can be used to cut the above described groove 22 in the anode block 20, as will be described in more details below.

[0079] One skilled in the art will understand that, in an alternative embodiment (not shown), more than two saw blades can be configured in a series configuration, in order to define more than two groove sections of different widths. Furthermore, in another alternative embodiment (not shown) one or more saw blades having two or more sets of teeth can be combined with one or more saw blades in a series configuration.

[0080] Figures 7, 7a and 7b show a schematic representation of the first and the second saw blades 70, 72 mounted in a series configuration and configured to cut the groove 22 with the lower groove section 26 and the upper groove section 28 of different widths 26d, 28d in the anode block 20. Each one of the first and the second saw blades 70, 72 is operatively mounted to its own spindle 88, 89. The first saw blade 70 is mounted upstream of the second saw blade 72 and is characterized by a smaller diameter and a larger width of the associated set of teeth than the second saw blade 72, mounted downstream of the first saw blade 70 with respect to a travel direction 74 of the anode blocks 20.

[0081] Each one of the first and the second saw blades 70, 72 comprises a respective saw blade disc 80, 82 having an outer (peripheral) edge 80a, 82a. As mentioned above, each one of the first and the second saw blades 70, 72 has a set of peripherally mounted teeth 76, 78. The set of teeth 76 of the saw blade disc 80 of the first saw blade 70 is mounted at the outer edge 80a thereof. The set of teeth 78 of the saw blade disc 82 of the second saw blade 72 is mounted at the outer edge 82a thereof.

[0082] The saw blade disc 80 of the first saw blade 70 has a first diameter 80b and the set of teeth 76 of the saw blade disc 80 of the first saw blade 70 has a first tooth width 76a. Similarly, the saw blade disc 82 of the second saw blade 72 has a second diameter 82b and the set of teeth 78 of the saw blade disc 82 of the second saw blade 72 has a second tooth width 78a. The second diameter 82b is larger than the first diameter 80b and the second tooth width 78a is narrower than the first tooth width 76a. In other words, the set of teeth 76 of the saw blade disc 80 of the first saw blade 70 extended inwardly further into the anode block 20 and are thicker than the teeth of the set of teeth 78 of the saw blade disc 82 of the second saw blade 72. Hence, the width of the groove section cut by the first saw blade 70 (which corresponds to the lower groove section 26) is wider than the width of the groove section performed by the second saw blade 72 (which corresponds to the upper groove section 28).

[0083] For example and without being limitative, in an embodiment, the first diameter 80b of the saw blade disc 80 of the first saw blade 70 can range between about 250 mm and about 850 and the second diameter 82b of the saw blade disc 82 of the second saw blade 72 can range between about 500 mm and 1300 mm. Moreover, for example and without being limitative, in an embodiment, the first tooth width 76a can range between about 8 mm and about 20 mm. In an alternative embodiment the first tooth width 76a can range between about 8 mm and about 14 mm. For example and without being limitative, in an embodiment, the second tooth width 78a can range between about 4 mm and about 10 mm. In an alternative embodiment, the second tooth width 78a can range between about 4 mm and about 8 mm.

[0084] The radius of the saw blade disc is typically greater than the groove performed in the anode block 20. For instance and without being limitative, a second blade having a diameter of about 1300 mm can perform a groove having a 450 mm depth. The first blade could be characterized by a diameter of about 850 mm (1300 mm - 450 mm). Thus, the first blade, i.e. the one having the smallest diameter, can have a diameter which corresponds to the diameter of the second blade minus the depth of the groove performed by the second blade. [0085] In view of the above, the first and the second saw blades 70, 72 configured in the series configuration can be used in a process for the manufacture of an anode block 20 to be used in an aluminum electrolysis cell. In such a process, one or more grooves 22 can each be cut in the anode block 20 by initially cutting the lower groove section 26 using the first saw blade 70 and subsequently cutting the upper groove section 28 by inserting the second saw blade 72 in the anode block 20, along the lower groove section 26. For example, in the embodiment shown in Figure 7, the anode blocks 20 (see Figure 1) in which the groove 22 is to be cut can be displaced with respect to the first and the second saw blades 70, 72 in direction of arrow 74. Hence, the first saw blade 70 firstly engages the anode block 20 and the second saw blade 72 engages the anode block subsequently to the initial engagement by the first saw blade 70 (along the first groove section cut by the first saw blade 70). In other words, a first section of the groove 22 (which corresponds to the lower groove section 26 of the groove 22 in Figure 1) is initially cut by the first saw blade 70. Subsequently, a second section of the groove 22, continuous with the first section, (which corresponds to the upper groove section 28 of the groove 22 in Figure 1) is cut by the second saw blade 72.

[0086] It will be understood that, in an embodiment, the disc 80 of the first saw blade 70 can either have a substantially uniform thickness or can have a tapered configuration, as shown in Figure 9, which will be described in more details below.

[0087] In the embodiment shown in Figures 7 and 8, the disc 82 of the second saw blade 72 includes two components: an inner annular disc 84, defining a central aperture to receive the spindle 88 of the machining unit (not shown) and an outer annular disc 86 mounted at a periphery of the inner disc 84. In such an embodiment, only the outer annular disc 86 includes a set of teeth 78 to cut a groove section (corresponding to the upper groove section 28 in Figure 1) in the anode block 20. The inner disc 84 includes a plurality of cogs 90 mounted at its outer periphery. The cogs 90 mesh with an inner edge of the outer disc 86 to drive the outer disc 86 in rotation. The inner disc 84 is thicker than the outer disc 86 and has a thickness that is substantially similar or narrower than the width of a groove section previously cut in the anode block 20 by the first saw blade 70 (which corresponds to the lower groove section 26 in Figure 1).

[0088] Moreover, in an embodiment (not shown), either one or both the first and the second saw blades 70, 72 can include at least one blade stabilizer (not shown). In an embodiment, the at least one blade stabilizer prevents lateral displacement of the outer annular disc 86 with respect to the annular inner disc 84 of the second saw blades 72.

[0089] Referring now to Figure 9, there is shown an embodiment of a saw blade 100 having a saw disc 102 with a tapered profile and a single set of teeth 108 at an outer edge thereof. In the embodiment shown, the saw disc 102 comprises three components superposed and secured together. More particularly, the saw disc 102 comprises a central disc 104 and two tapered shaped discs 106, each one being superposed on a respective side of the central disc 104. The teeth of the set of teeth 108 extend outwardly from the central disc 104. One skilled in the art will however understand that, in an alternative embodiment, the saw disc 102 can be manufactured as a single piece component, with the central disc 104 and the two tapered shaped discs 106 being unitary with one another.

[0090] In an embodiment, the saw disc 102 is between about 0.5 mm and about 2 mm thicker close to the central aperture 41 than at its periphery. In an embodiment, the saw disc 102 is approximately 1 mm thicker close to the central aperture 41 than at its periphery. The angle defined by each of the tapered shaped discs 106 is between about 0.1° and about 5° and, in an alternative embodiment, between about 0.1° and about 0.3°. These ranges also apply for single piece discs having a tapered profile. Thus, the angle defined between a plane extending centrally in the disc and the outer face of the disc on a side thereof can range between about 0.1° and about 5° and, in an alternative embodiment, between about 0.1° and about 0.3°.

[0091] In an embodiment where a plurality of saw blades are mounted in a series configuration, the saw blade 100 having a saw disc 102 with a tapered profile and a single set of teeth 108 shown in Figure 9, can be used to cut any of the above described groove sections. For example and without being limitative, in an embodiment such as shown in Figure 7, the saw blade 100 having a saw disc 102 with a tapered profile and a single set of teeth 108 can be used for either one or both of the first and the second saw blades 70, 72. The disc 102 is thicker close to a center thereof, corresponding to the central aperture 41 , which is sized and shaped to receive the spindle (not shown), and thinner close to the outer periphery. [0092] It is appreciated that features of each one of the above described embodiments can be combined with features of the other embodiments or alternative which are described above and are not limited to the respective embodiments described.

[0093] Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An anode block for aluminum production in an electrolysis cell, the anode block comprising a calcined carbon body having a wear surface with at least one groove defined therein, the at least one groove having at least a lower groove section with a lower section width and extending upwardly from the wear surface, and an upper groove section with an upper section width narrower than the lower section width, the upper groove section being continuous with the lower groove section.

2. The anode block of claim 1 , wherein each one of the at least one groove has a groove depth ranging between about 250 mm and about 450 mm.

3. The anode block of claim 2, wherein the groove depth ranges between about 300 mm and about 400 mm.

4. The anode block of any one of claim 1 to 3, wherein the lower groove section of each one of the at least one groove has a lower groove section depth ranging between about 125 mm and about 250 mm.

5. The anode block of any one of claim 1 to 4, wherein the upper groove section of each one of the at least one groove has an upper groove section depth ranging between about 125 mm and about 200 mm.

6. The anode block of any one of claims 1 to 5, wherein the lower section width of the lower groove section of each one of the at least one groove ranges between about 8 mm and about 20 mm.

7. The anode block of claim 6, wherein the lower section width of the lower groove section of each one of the at least one groove ranges between about 8 mm and about 14 mm.

8. The anode block of any one of claims 1 to 7, wherein the upper section width of the upper groove section of each one of the at least one groove ranges between about 4 mm and about 10 mm.

9. The anode block of claim 8, wherein the upper section width of the upper groove section of each one of the at least one groove ranges between about 4 mm and about 8 mm.

10. The anode block of any one of claims 1 to 9, wherein the anode block has a first lateral face and a second lateral face opposed to the first lateral face and wherein each one of the at least one groove extends continuously longitudinally from the first lateral face to the second lateral face.

11. The anode block of any one of claims 1 to 10 , wherein two grooves are defined in the wear surface.

12. A saw blade for cutting a groove in a wear surface of a prebaked anode block for aluminum production, the saw blade comprising a circular saw blade disc with at least a first set of teeth having a first tooth width and a second set of teeth having a second tooth width, wherein each one of the first set of teeth and the second set of teeth protrude laterally outwardly of the saw blade disc and are radially spaced apart from one another, the second set of teeth being positioned inwardly of the first set of teeth and the first tooth width being narrower than the second tooth width.

13. The saw blade of claim 12, wherein the circular saw blade disc includes at least an outer annular disc having an inner edge and an outer edge and an inner annular disc having an outer edge, the outer annular disc extending radially from the outer edge of the inner annular disc and the at least one first set of teeth and second set of teeth each being associated with a respective one of the outer annular disc and the inner annular disc.

14. The saw blade of claim 13, wherein the teeth of the first set of teeth are circumferentially spaced apart along the outer edge of the outer annular disc and the teeth of the second set of teeth are circumferentially spaced apart along the outer edge of the inner annular disc.

15. The saw blade of claim 14, wherein the outer annular disc has a plurality of spaced-apart recesses defined along the inner edge thereof and extending inwardly into the outer annular disc and wherein each one of the teeth of the second set of teeth is positioned in a respective one of the recesses.

16. The saw blade of any one of claims 13 to 15, wherein each one of the inner annular disc and the outer annular disc has a thickness, the thickness of each one of the inner annular disc and the outer annular disc being substantially constant along a radial length thereof.

17. The saw blade of any one of claims 13 to 15, wherein each one of the inner annular disc and the outer annular disc tapers along a radial length thereof.

18. An apparatus for processing anode blocks for use in connection with the electrolytic production of aluminum, the apparatus comprising: at least one saw blade having a saw blade disc with at least two sets of teeth, a first one of the sets of teeth being peripherally mounted to the saw blade disc and comprising a plurality of teeth having a first tooth width and a second one of the sets of teeth comprising a plurality of teeth having a second tooth width, larger than the first tooth width, the teeth of the second one of the sets being mounted inwardly of the teeth of the first one of the sets and being radially spaced-apart therefrom.

19. The apparatus of claim 18, wherein the saw blade disc includes at least an outer annular disc having an inner edge and an outer edge and an inner annular disc having an outer edge, the outer annular disc extending radially from the outer edge of the inner annular disc and the first one of the sets of teeth and the second one of the sets of teeth each being associated with a respective one of the outer annular disc and the inner annular disc.

20. The apparatus of claim 19, wherein the teeth of the first one of the sets of teeth are circumferentially spaced apart along the outer edge of the outer annular disc and the teeth of the second one of the sets of teeth are circumferentially spaced apart along the outer edge of the inner annular disc.

21. The apparatus of claim 20, wherein the outer annular disc has a plurality of spaced- apart recesses defined along the inner edge thereof and extending inwardly into the outer annular disc and wherein each one of the teeth of the second one of the sets of teeth is positioned in a respective one of the recesses.

22. The apparatus of any one of claims 19 to 21 , wherein each one of the inner annular disc and the outer annular disc has a thickness, the thickness of each one of the inner annular disc and the outer annular disc being substantially constant along a radial length thereof.

23. The apparatus of any one of claims 19 to 21 , wherein each one of the inner annular disc and the outer annular disc tapers along a radial length thereof.

24. An apparatus for processing anode blocks for use in connection with the electrolytic production of aluminum, the apparatus comprising: at least two saw blades mounted in a series configuration with a first one of the saw blades comprising a first saw blade disc with a first diameter and peripherally mounted teeth having a first tooth width and a second one of the saw blades comprising a second saw blade disc with a second diameter and peripherally mounted teeth having a second tooth width, the second diameter being larger than the first diameter and the second tooth width being narrower than the first tooth width.

25. The apparatus of claim 24, wherein the first diameter of the first saw blade disc ranges between about 250 mm and about 850 mm.

26. The apparatus of claim 24 or 25, wherein the second diameter of the second saw blade disc ranges between about 500 mm and about 1300 mm

27. The apparatus of any one of claims 24 to 26, wherein the first tooth width of the peripherally mounted teeth of the first saw blade disc ranges between about 8 mm and about 20 mm.

28. The apparatus of claim 27, wherein the first tooth width of the peripherally mounted teeth of the first saw blade disc ranges between about 8 mm and about 14 mm.

29. The apparatus of any one of claims 24 to 28, wherein the second tooth width of the peripherally mounted teeth of the second saw blade disc ranges between about 4 mm and about 10 mm.

30. The apparatus of claim 29, wherein the second tooth width of the peripherally mounted teeth of the second saw blade disc ranges between about 4 mm and about 8 mm.

31. The apparatus of any one of claims 24 to 30, wherein each one of the first saw blade disc and the second saw blade disc has a thickness, the thickness of at least one of the first saw blade disc and the second saw blade disc being substantially uniform along a corresponding one of the first diameter and the second diameter.

32. The apparatus of any one of claims 24 to 30, wherein at least one of the first saw blade disc and the second saw blade disc tapers along the corresponding one of the first diameter and the second diameter.

33. A process for the manufacture of an anode block for use in an aluminum electrolysis cell, the process comprising the step of: cutting at least one groove in the anode block, the at least one groove having a lower groove section with a lower section width and extending upwardly from a wear surface of the anode block, and an upper groove section with an upper section width narrower than the lower section width and, the upper groove section being continuous with the lower groove section.

34. The process of claim 33, wherein the step of cutting the at least one groove comprises inserting a saw blade in the anode block to cut simultaneously the lower groove section and the upper groove section.

35. The process of claim 33, wherein the step of cutting the at least one groove comprises initially cutting the lower groove section by inserting an upstream saw blade in the anode block and subsequently cutting the upper groove section by inserting a downstream saw blade in the anode block along the lower groove section.

36. A saw blade for cutting a groove in a wear surface of a prebaked anode block for aluminum production, the saw blade comprising a circular saw blade disc having a tapered profile, being thicker close to a center thereof and thinner close to a periphery thereof and at least a first set of teeth peripherally mounted to the circular saw blade disc.

37. The saw blade of claim 36, wherein the saw blade disc comprises a central disc having a uniform thickness and two tapered shaped discs, each one being superposed on a respective side of the central disc.

38. The saw blade of one of claims 36 and 37, wherein the saw blade disc is between about 0.5 mm and about 2 mm thicker close to the center than at its periphery.

39. The saw blade of any one of claims 36 to 38, wherein the angle defined between a centrally extending plane and an outer face ranges between about 0.1° and about 5°.

40. The saw blade of any one of claims 36 to 38, wherein the angle defined between a centrally extending plane and an outer face ranges between about 0.1° and about 0.3°.