NO345291B1

NO345291B1 - An aluminium production anode yoke, an anode hanger, and a carbon anode

Info

Publication number: NO345291B1
Application number: NO20181193A
Authority: NO
Inventors: Per-Arne Klingenberg
Original assignee: Hmr Hydeq As
Priority date: 2018-09-12
Filing date: 2018-09-12
Publication date: 2020-11-30
Also published as: EP3850128B1; NO20181193A1; EP3850128A1; WO2020055266A1

Description

The present invention relates to a yoke and a hanger for an anode used in connection with aluminium production. Furthermore, the invention relates to a carbon anode for such an anode hanger, an anode hanger with such an anode.

Specifically, the present invention relates reducing the losses and thus the required amount of energy used in aluminium production. Due to the low resistance and high currents, the loss is typically measured in millivolts of voltage drop during production rather than in ohm. The amount of energy required is typically calculated in kWh used pr. kg aluminium produced. A typical number is 13,9 kWh/kg produced aluminium, and it is a target of the present invention to reduce this number to below 13 kWh/kg.

Furthermore, it is a purpose of the present invention to simplify the process of changing the carbon anode, including removing the remaining carbon (butts), crust and impurities and install a new carbon anode. This process is normally performed in a separate portion of a smelting plant or in a separate factory, the so-called anode rodding shop. The carbon anode must typically be changed every 20-30 days, and a cell typically includes 18 anodes making the change of carbon anodes a substantial, power consuming and continuous part of aluminium production.

Traditional anode hangers with yokes include vertical, cylindrical steel stubs or nipples on the yokes that are inserted into corresponding bores in the carbon anode. Molten cast iron alloy is then poured into the cavity between stubs and the carbon anode to fix the anode to the yoke and to provide a good contact surface between the stubs and the carbon. Melting metal for this process is however, power consuming and cleaning off old carbon and deposits of yokes before a new carbon anode can be installed is time consuming and complicated. Due to the different coefficient of expansion of the metal in the yokes, the metal that is poured into the cavity between the yoke and the carbon anode and the carbon anode itself, can the interface area between the carbon anode and the yoke be reduced and thus the ability to transfer high current. In this context it is also relevant to consider that the operating temperature of such anodes is around 900°C.

NO 933197, discloses an anode hanger for holding and supplying a carbon anode with electric current in a Hall- Héroult electrolytic cell. The contact between the anode and the hanger is achieved in that two inclined plates secured to the hanger are inserted in corresponding recesses in an upper part of the anode. The plates are forced apart with a pressing mechanism until they contact the outer edges of the recesses.

WO 2016130014 discloses an anode for use in production of aluminium in cells of Hall-Héroult type. The anode comprises a body of calcinated carbonaceous material connected to an electrical current lead. The current lead is connected to an anode rod being a part of an anode hanger. The current lead includes at least one metallic suspension plate with vertically oriented rodding plates at least partly embedded in corresponding recesses in the top of the carbonaceous body and further connected by mechanical fixation means.

CN 102400178 relates to a clamping device for connecting an aluminum guide rod and an anode carbon block. The aluminium guide rod is connected to the anode carbon block with two clamping plates. A central part of each of the two clamping plates is hinged to a respective connecting piece. The other end of each of two connecting pieces is hinged through pins. The two connecting pieces are formed by two intersected connecting rods.

It is the purpose of the present invention to provide an anode hanger, a carbon anode for such an anode hanger, and an anode hanger with such an anode. The present invention alleviates at least some of the issues addressed above and reduces power consumption compared with traditional hangers.

Specifically, the invention concerns an anode hanger with an aluminium production anode yoke for an aluminium production carbon anode with two recesses with tapered sidewalls. The aluminium production anode yoke includes two anode yoke parts, each including a beam attachment portion with a beam contact area and an anode yoke transition portion forming an electricity conducting transition between the beam attachment portion and a yoke blade with an anode attachment portion with an anode contact area. A beam, wherein the anode attachment portion of each of the two anode yoke parts form an angle in relation to a longitudinal axis of the beam in a range from 3°-45°. The anode attachment portion includes a substantially straight bottom edge between two end portions extending at an angle from the bottom edge a first plane side portion at a first side of the anode attachment portion and a second plane side portion at a second side of anode attachment portion. The first plane side portion and the second plane side portion form a slight taper in a range of 0,4°-10° off parallel.

The anode attachment portion may have a substantially uniform cross section along its length between the two end portions, whereby the anode attachment portion includes a first substantially plane side portion at the first side of the anode attachment portion and a second substantially plane side portion at the second side of the anode attachment portion.

Each anode yoke part may include an angled portion between the anode attachment portion and the beam attachment portion.

Each substantially straight bottom edge may include a rounded bottom portion.

The anode yoke may be made of steel or cast iron.

The taper may be in a range from 1°to 5° off parallel.

The taper may be in a range from 1,5° to 3° off parallel.

The taper may be 2° off parallel.

Furthermore, the invention relates to an anode hanger with an aluminium production anode yoke with two anode yoke parts as defined above. The anode hanger comprises a beam, wherein an anode attachment portion of each of the two anode yoke parts form an angle in relation to a longitudinal axis of the beam in the range from 3°-45°.

The angle may be 20°.

At least one of said two anode yoke parts may be fixed to the beam with a releasable connection.

The beam may be assembled of at least a first and a second individual, longitudinal beam part joined along the longitudinal axis. Each of said two anode yoke parts may be fixed to each of the at least first and second individual, longitudinal beam parts. Releasable mechanical fasteners secure the first beam part to the second beam part.

One of the at least first and second individual, longitudinal beam parts may include an aluminium cell connecting top bracket.

The anode hanger may further include an anode wherein the anode includes at least two tapered substantially parallel recesses.

Each of the at least two tapered substantially parallel recesses may be angled at an angle in the range from 3°-45° in relation to the longitudinal axis of the beam.

Each of the at least two tapered substantially parallel recesses may be angled at an angle in the range from 5° to 30° in relation to the longitudinal axis of the beam.

Each of the at least two tapered substantially parallel recesses may be angled at an angle in the range from 15° to 25° in relation to the longitudinal axis of the beam.

The angle of each of the at least two tapered substantially parallel recesses may be 20°.

The invention furthermore relates to an aluminium production carbon anode for an anode hanger defined above comprising two recesses parallel to a longitudinal axis and inclined in relation to a transversal axis.

The two recesses include tapered sidewalls.

Short description of the enclosed figures:

Fig. 1 is a front elevation of an anode hanger with an anode of an embodiment of the invention;

Fig. 2 shows the embodiment of fig.1 in cross section;

Fig. 3 is a side elevation of the embodiment of fig.1 and 2;

Fig. 4 is a cross section of an alternative embodiment to the invention of figs.1-3; Fig. 5 is a side elevation of the embodiment of fig.4;

Fig. 6 shows a detail of an anode and a yoke of the invention; and

Fig 7 shows a detail the alternative embodiment of a yoke from the side and the front.

Detailed description of an embodiment of the invention with reference to the enclosed figures:

An anode is changed in an automatic process. The automatic process is performed in an anode rodding shop, and the anode of the invention simplifies the rodding process including the removal of a used anode or butt, the cleaning of the yoke and the attachment of a new anode.

Fig. 1 is a front elevation of an anode hanger with an anode 5 of calcined carbon material. The anode 5 is made as a rectangular block with a transversal axis 10 aligned with a longitudinal beam axis of an aluminium rod, stem or beam 3 of the anode-hanger. The anode hanger further includes a yoke 1 holding the anode 5 to the beam 3. The yoke 1 includes two yoke parts, both secured to the beam 3 through a bi metal coupling. One of the two yoke parts is permanently fixed to the beam 3 and the other is fixed to the beam with releasable and mechanical fasteners 2 such as bolts or a pin and wedge structure. The mechanical fastener or fasteners are typically adapted for automated assembly and disassembly for exchanging a used anode or butt 29 with a new and unused anode 5. The interface between the yoke and the beam includes a bimetal connection to enable welding of the different metals and to ensure proper contact between the components and thus sufficient area to allow the high currents to pass from the beam 3 to the yoke 1. The bi metal coupling also prevents galvanic corrosion in the interface between the metals. The yoke1 is typically made of steel and the beam 3 is typically made of aluminium. Each of the two yoke parts include a transition portions 32 formed as carrier plates that form a transition between a yoke blade with an anode attachment portion 12 and a beam attachment portion and transfers current between beam attachment portion and the anode attachment portion 12.

Fig. 2 is a cross section of fig.1 showing the anode 5, the yoke 1 and beam 3 of the anode hanger. The anode 5 includes two longitudinal anode recesses 16 with a tapered profile. The taper of each tapered anode recess 16 corresponds to the taper of the tapered anode attachment portion 12 of each of the yoke blades 13 to ensure proper contact between the anode 5 and the yoke 1 to maintain a large contact area for the high currents transferred between the yoke 1 and the anode 5. The tapered transition also ensures proper mechanical and electrical contact between the tapered anode attachment portion 12 of each yoke blade 13 and the two tapered anode recesses 16.

Each of the two anode blades 13 is inclined with an angle of 20° in relation to a transversal axis along the beam 3 or 110° in relation to a horizontal line (as shown in fig 6). A current distribution stiffener plate 14 in the longitudinal direction of the anode 5 and the yoke blades 13 improves current distribution over the yoke 1 and stiffens the yoke blades 13. The angle of the carrier plates positively locks the anode 5 to the yoke 1 and increases the area of the interface between the yoke blades and the anode recesses 16.

Fig. 3 is a cross section perpendicular to the anode hanger with anode of figs.1, 2. The transversal axis 10 along the beam 3 is perpendicular to the longitudinal axis of the anode 5. The anode recess 16 is shown with dotted lines. The stiffener plate 14 of each yoke part along each yoke blade 13 extend parallel to the longitudinal axis 9 of the anode 5. Mechanical fasteners 2 (illustrated with horizontal lines) secure one of the yoke parts to the beam 3 while the other yoke part is permanently fixed to the beam 3.

The yoke 1 shown in figs.1-3 is made up of a first and a second yoke part that are installed/inserted into the anode 5 individually before they are fixed in the position shown in the figs.1-3 to hold the anode 5 in place. An electrically conductive compound may be smeared on the yoke parts and or in the recesses 16 of the anode 5 to ensure that the entire area of the interface between the anode 5 and the anode attachment portion 12 of the yoke inserted into the anode 5 is in electrical contact to reduce power losses and heat generation due to increased electrical resistance.

In figures 1-3 is one of the two yokes 1 permanently fixed to the beam 3 through a bi-metal transition, and the other of the two yokes 1 can be attached with releasable mechanical fasteners and can thus be released during exchange of the anode.

Figs. 4-7 shows an alternative embodiment of the invention. In figs.4-7 are each yoke fixed to an individual beam and the individual beams are assembled when the used anode/butt is exchange with the new anode in an automatic process involving an anode changing plant.

Fig. 4 is a cross section of the invention. One of the individual beams 3 is permanently secured to a top bracket 6 and two upper mechanical fasteners 8 hold the two beam parts together after installation of the anode. The two upper mechanical fasteners 8 are typically bolts. A stiffening steel spacer 4 is sandwiched between the two individual beam parts. A lower mechanical fastener 2 including a clamp and a wedge hold the two beam parts together above angled beam portions of each individual beam. A permanent bimetal connection 7 fixes each of the individual beams to each of the two parts of the yoke 1.

The two beams 3 are fixed to each other with upper mechanical fasteners 8 when the anode 5 is changed. The steel spacer 4 located between the two aluminium beams is isolated by a dielectric sintered film between the spacer 4 and the aluminium beams 3 to prevent any galvanic corrosion issues. The upper mechanical fasteners 8 are also installed in a manner preventing electrical contact between the steel and aluminium. A lower mechanical fastener 2 include a wedge and clamp connection to simplify automatic change of anode 5 and to avoid typical problems related to threaded connections used in the environment of the present invention. Permanent bi-metal couplings 7 between the aluminium beams 3 and the steel yokes 1 ensures good and predictable electrical contact between the beams 3 and the yokes 1. Using individual aluminium beams 3 permanently connected to the yokes 1, prevent disassembly and assembly of an electrically conducting connecting surface between the yoke1 and the beam 3 when the anode 5 is changed. The aluminium beams 3 also form a split beam better conforming to the shape of a current rail and thus improves the transfer of current between the current rail and the aluminium beams 3, thus reducing the voltage drop. Each yoke 1 is formed as blade of steel and includes a blade shaped and tapered anode attachment portion adapted to be inserted into the anode 5.

Fig. 4 shows how the two yoke parts are installed into the anode 5 and how the angle of the tapered attachment portion 12 of the yoke blades positively lock the anode 5 to the yoke 1 and increases the area of the interface between the carrier plates 11 and the anode recesses 16 without reducing the size of the usable part of the anode.

Figure 5 is a side elevation, partly in cross section of fig.4 and show the invention including the yoke 1 completely from the side. The top bracket 6 attaches the beam 3 to the aluminium producing electrolysis cell. The plate shaped stiffening steel spacer 4 sandwiched between the two portions of the beam 3 includes a widened, curved portion to increase the stiffness of the assembled beam 3. The lower mechanical fastener 2 includes a clamp structure including a wedge to clamp the beam parts and to simplify automatic assembly and disassembly during exchange of the anode 5. The upper mechanical fasteners 8 include bolts. The yoke 1 is shown installed in a tapered recess cast and milled in the anode 5. The taper of the recesses correspond to the taper of the anode attachment portions (12 on fig 8). During assembly, the yokes 1 are pressed into the recesses along with a contact compound filled into the recess. Each of the two yoke parts include a yoke blade 13.

Fig. 6 shows a detail of the tapered attachment portion 12 of each yoke blade 13 of the yoke and the corresponding recess 16 in the anode 5. Similarly, with the tapered attachment portion 12, is the taper of the sides in the recess 16, 2° off parallel. The taper ensures positive contact between the anode and the yoke and prevents play between the anode and yoke as the yoke is worn. The tapered attachment portion 12 is formed by a first substantially plane side portion 30, at a first side of the yoke blade 30 and a second substantially plane side portion 31, at a second, opposite side of the yoke blade 13. The first plane side portion 30 and the second plane side portion 31 form the slight taper of 2° off parallel. “Off parallel” is intended to describe how much the angle of the sides deviate from a line parallel to the centreline. For instance, 2° off parallel means that each side deviate 1° from a line parallel to the centreline as shown in the fig. The taper could be in a range of 0,4°-10° off parallel. The recesses 16 and the tapered attachment portion 12 are angled 110° in relation to a horizontal line.

Fig. 7 shows a yoke part from the side to the left and in an elevated view to the right. A beam attachment portion 25 include a beam contact area and an anode yoke transition portion 32 forming an electricity conducting transition between the beam attachment portion 25, the yoke blade13 with the tapered anode attachment portion 12 with the anode contact area. The tapered anode attachment portion 12 include a substantially straight bottom edge 20 and a substantially uniform cross section along its length between two end portions 21, 22 extending at an angle from the bottom edge 20. The bottom edge 20 is rounded to form a blunt edge 26 to prevent the edge from deforming or fracturing the anode in the event the tapered anode attachment portion 12 bottoms out in the anode during installation and to prevent current peaks. The angle between two end portions 21, 22 and the bottom edge 20 is 90°. The first substantially plane side portion 30, at a first side of the tapered anode attachment portion 12 and the second substantially plane side portion 31 at the second side of the tapered anode attachment portion 12 form the main contact areas with the anode. These side portions 30, 31 form the slight taper in a range of 0,4°-10° off parallel,

A yoke transition portion 32 forms a transition between each yoke blade 13 and each beam attachment portion 25 and transfers current between beam attachment portion 25 and the anode attachment portion 12. The beam attachment portion 25 attaches the yoke 1 to the beam 3.

The yoke transition portion 32 extends along the anode attachment portion 12 and is angled to fix the centreline of the anode attachment portion 12 at a 20° angle in relation the centreline of the beam 3.

The yoke transition portion 32 include a sloped or rounded edge 23, 24 between the two end portions 21, 22 and the beam attachment portion 25.

The shape of the blade and the attachment portions shown in the figures and as described above are relevant to all embodiments and are interchangeable for solutions with a double rod, with a single rod with one releasable yoke portion and with a single rod with two releasable yoke portions.

Claims

1. An anode hanger with an aluminium production anode yoke (1) for an aluminium production carbon anode with two recesses (16) with tapered sidewalls, the aluminium production anode yoke (1) including:

two anode yoke parts, each including a beam attachment portion (25) with a beam contact area and an anode yoke transition portion (32) forming an electricity conducting transition between the beam attachment portion (25) and a yoke blade (13) with an anode attachment portion (12) with an anode contact area;

a beam (3), wherein the anode attachment portion (12) of each of the two anode yoke parts form an angle in relation to a longitudinal axis of the beam (3) in a range from 3°-45°;

wherein the anode attachment portion (12) includes:

a substantially straight bottom edge (20) between two end portions (21, 22) extending at an angle from the bottom edge (20), a first plane side portion (30) at a first side of anode attachment portion (12), and a second plane side portion (31) at a second side of anode attachment portion (12), wherein the first plane side portion (30) and the second plane side portion (31) form a slight taper in a range of 0,4°-10° off parallel.

2. The anode hanger of claim 1, wherein the anode attachment portion (12) has a substantially uniform cross section along its length between the two end portions (21, 22), whereby the anode attachment portion (12) includes a first substantially plane side portion (30) at the first side of the anode attachment portion (12) and a second substantially plane side portion (31) at the second side of the anode attachment portion (12).

3. The anode hanger of claim 1 or 2, wherein each anode yoke part includes an angled portion (15) between the anode attachment portion (12) and the beam attachment portion (25).

4. The anode hanger of claim 1-3, wherein each substantially straight bottom edge (20) includes a rounded bottom portion (26).

5. The anode hanger of any of the preceding claims, wherein the anode yoke parts are made of steel or cast iron.

6. The anode hanger of any of the preceding claims, wherein the taper is 2° off parallel

7. The anode hanger of claim 6 wherein the angle is 20°.

8. The anode hanger of claim 6 or 7, wherein at least one of said two anode yoke parts are fixed to the beam (3) with a releasable connection.

9. The anode hanger of claim 6 or 7, wherein the beam (3) is assembled of at least a first and a second individual, longitudinal beam part joined along a longitudinal axis of the beam (3);

wherein each of said two anode yoke parts are fixed to each of the at least first and second individual, longitudinal beam parts; and

wherein releasable mechanical fasteners (2, 8) secure the first beam part to the second beam part.

10. The anode hanger of claim 9, wherein one of the at least first and second individual, longitudinal beam parts include an aluminium cell connecting top bracket (6)

11. The anode hanger of any of claims 6-10, and a carbon anode (5) including at least two tapered substantially parallel recesses (16), wherein the anode attachment portion (12) of each of the two anode yoke parts are inserted into each of the two tapered substantially parallel recesses.

12. The anode hanger of claim 11, wherein each of the at least two tapered substantially parallel recesses (16) are angled at an angle in the range from 3°-45° in relation to the longitudinal axis of the beam (3).

13. The anode hanger of claim 12, wherein the angle of each of the at least two tapered substantially parallel recesses (16) is 20°.

14. An aluminium production carbon anode for an anode hanger of claim 1, comprising two recesses (16) parallel to a longitudinal axis and inclined in relation to a transversal axis of the aluminium production carbon anode, and

wherein the two recesses (16) includes tapered sidewalls.