PROCEDE POUR LE CHAUFFAGE DE BLOCS ANODIQUES, ET CONCEPTION DU CHAUFFAGE DE BLOCS ANODIQUES

METHOD FOR THE HEATING OF ANODE BLOCKS, AND AN ARRANGEMENT FOR THE HEATING OF ANODE BLOCKS

Abrégé français

Procédé destiné à chauffer des blocs anodiques, lesquels blocs anodiques (2) sont utilisés lors de la production d'aluminium et comprennent des trous (3) de contact dans lesquels on décide de fixer des contacts électriques. L'invention est caractérisée en ce que les trous (3) sont amenés à être chauffés au moyen d'une chaleur radiative à partir d'éléments résistants électriques (4, 5, 6) conçus pour être utilisés à de hautes températures, en ce que le câble électrique des éléments (4, 5, 6) se trouve sous la forme de tiges dotées de deux ou plus de tronçons, en ce que chacun des éléments (4, 5, 6) est amené à être disposé dans une cuvette (7, 8, 9) dotée d'une surface d'extrémité ouverte, et en ce qu'une cuvette (7, 8, 9) pour chaque trou (3) dans le bloc anodique (2) est amenée à reposer devant le trou (3) en question. L'invention se rapporte également à une conception.

Abrégé anglais

A method for the heating of anode blocks, which anode blocks (2) are used during the production of aluminium and comprise contact holes (3) into which it is arranged that electrical contacts are to be attached. The invention is characterised in that the holes (3) are caused to be heated by means of radiative heat from electri- cal resistive elements (4, 5, 6) arranged to be used at high temperatures, in that the wire of the elements (4, 5, 6) is in the form of shanks with two or more legs, in that each one of the elements (4, 5, 6) is caused to be arranged in a cup (7, 8, 9) with an open end surface, in that one cup (7, 8, 9) for each hole (3) in the anode block (2) is caused to lie in front of the hole(3) in question. The invention relates also to an arrangement.

Revendications

6,
Claims
1. A method for heating anode blocks, which anode blocks (2)
are used in the production of aluminium and comprise contact
holes (3) into which it is arranged that electrical contacts
are to be attached, characterise ci in that the holes
(3) are caused to be heated by means of radiative heat from
electrical resistive elements (4, 5, 6) arranged to be used
at high temperatures, in that the wire of the elements (4, 5,
6) is in the form of shanks with two or more legs, in that
each one of the elements (4, 5, 6) is caused to be arranged
in a cup (7, 8, 9) with an open end surface, in that one cup
(7, 8, 9) for each hole (3) in the anode block (2) is caused
to lie in front of the hole in question (3) and n that the
said cup (7, 8, 9) is caused to be of a fibre insulating
material comprising Al2O3 and/or SiO2.
2. A method according to claim 1, characterised in
that the said elements (4, 5, 6) are caused to be a high-
temperature element.
3. A method according to claim 1 or 2, characterised
in that each resistive element (4, 5, 6) is caused to de-
velop a power of approximately 10-2 0 kW.
4. A method according to any one of claims 1 to 3,
characterised i n that the distance between the said
open end surface and the anode block (2) is caused to exceed
a couple of millimetres and to lie below a couple of centime-
tres.
5. An arrangement for the heating of anode blocks, which
anode blocks (2) are used in the production of aluminium and

7
comprise contact holes (3) into which it is arranged that
electrical contacts are to be attached, characterised
i n that the arrangement comprises electrical resistive ele-
ments (4, 5, 6) arranged to be used at high temperatures, in
that the wire of the elements (4, 5, 6) is in the form of
shanks with two or more legs, in that each one of the ele-
ments (4, 5, 6) is arranged in a cup (7, 8, 9) with an open
end surface, in that the cups (7, 8, 9) with the resistive
elements (4, 5, 6) are equal in number to the number of holes
(3) in the anode block (2) , and in that the cups (3) are
placed into a holder (10) that is common for all the cups
such that one cup (7, 8, 9) for each hole (3) in the anode
block (2) is caused to lie in front of the hole in question
(3) and i n that the said cup (7, 8, 9) is manufactured from
a fibre insulating material comprising A1203 and/or Si02=
6. An arrangement according to claim 5, characterised
i n that the said element (4, 5, 6) is a high-temperature
element.
7. An arrangement according to claim 5 or 6, charac-
terised in that each resistive element (4, 5, 6) is
arranged to develop a power of approximately 10-20 kW.
8. An arrangement according to any one of claims 5 - 7,
characterised in that the distance between the said
open end surface and the anode block (2) is caused to exceed
a couple of millimetres and to lie below a couple of centime-
tres.

Description

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Method for the heating of anode blocks, and an arrangement
for the heating of anode blocks.
The present invention relates to a method for the heating of
anode blocks, and to an arrangement for the heating of anode
blocks.
During the production process for primary aluminium, objects
known as "anode blocks" are used. The blocks consist of
/o granulated graphite. Holes are present in these blocks in
order to attach electrical contacts of iron, known as
"yokes", by moulding. The sizes of the blocks may vary, and
the number of contact holes into which contacts are to be
attached may also vary. There is normally between three and
six holes. The blocks may have different dimensions: the
dimensions may, for example, be 1300 x 500 x 500 millimetre.
The anode blocks are exchanged at regular intervals. The
anode blocks are then renovated and stored until they are to
be reused.
Water can collect in the holes in the blocks as a result of
precipitation, since the blocks are often stored outdoors, to
a certain extent. The blocks, furthermore, are also exposed
to moist air. Water is sucked into the blocks, or is absorbed
into the blocks, since the material of the blocks is porous.
Water must be removed and the blocks must be dried before a
secure attachment of contacts by moulding can be carried out.
This is currently carried out through first the removal of
liquid water by blowing with pressurised air, and then the
heating of the block with the aid of gas burners in order to
dry it. The problem with this procedure is that the gas in

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the burners contains a certain amount of water vapour that
initially condenses onto the block before the temperature of
the block has been sufficiently raised. A result of this is
that it takes far too long to dry the blocks.
It is one requirement that the drying time be considerably
reduced. The present invention solves this problem.
The present invention thus relates to a method for heating
m anode blocks, which anode blocks are used in the production
of aluminium and comprise contact holes into which it is
arranged that electrical contacts are to be attached, and it
is characterised in that the holes are caused to be heated by
means of radiative heat from electrical resistive elements
is arranged to be used at high temperatures, in that the wire of
the elements is in the form of shanks with two or more legs,
in that each one of the elements is caused to be arranged in
a cup with an open end surface, and in that one cup for each
hole in the anode block is caused to lie in front of the hole
20 in question.
Furthermore, the invention relates to an arrangement
in which the electrical resistive elements are high
temperature elements
The invention will be described in more detail below, par-
tially with reference to an embodiment of the invention shown
in the attached drawings, where:
- Figure 1 shows an arrangement according to the invention
seen from the side with an anode block that lies beneath
it,

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- Figures 2 and 3 show different perspective sketches of
the arrangement according to the invention and an anode
block.
Figure 1 shows an arrangement 1 for the heating of anode
blocks 2, which anode blocks are used during the production
of aluminium and which comprise contact holes 3 into which it
is arranged that electrical contacts are to be attached.
/0 According to the invention, the arrangement 1 comprises elec-
trical resistive elements 4, 5, 6, shown in Figure 3, ar-
ranged to be used at high temperatures. It is preferred to
use resistive elements that are manufactured by KANTHAL AB,
Sweden, and that are marketed under the name "Kanthal Super".
This element can be heated in operation up to 1900 C. The
wires of the elements 4-6 are formed as shanks with two or
more legs. Each one of the elements 4-6 is arranged in a
cylindrical cup 7, 8, 9 with an open end surface. It is pref-
erable that the cup is cylindrical. The cups 7-9 with the
resistive elements 4-6 are equal in number to the number of
holes 3 in the anode block 2. The cups 7-9 are placed into a
holder 10 that is common for all cups such that one cup 7-9
for each hole 3 in the anode block 2 is caused to lie in
front of the hole 3 in question.
The use by this arrangement of radiative heat from high-
temperature elements entails a method of heating of much
greater efficiency than the previous art technology that has
been described, since no water is added at the beginning of
the heating process. A much higher power can be achieved over
a limited surface through the use of high-temperature ele-
ments, and this also contributes to a more rapid heating and
drying of the anode blocks.

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According to one preferred embodiment of the invention, the
said elements are caused to be a high-temperature element.
According to another preferred embodiment, the said cup is
caused to be of a fibre insulation material comprising A1203
and/or Si02.
According to a further preferred embodiment, each resistive
/o element is caused to develop a power of approximately 10-20
kW.
According to another further preferred embodiment, the dis-
tance between the said open end surface and the anode block
is caused to exceed a couple of millimetres and to lie below
a couple of centimetres.
This method has been shown to be able to reduce significantly
the drying time for anode blocks from that required by the
prior art technology. The drying time is as short as approxi-
mately 4 minutes with the dimensions of the anode block given
above as examples.
The present invention thus solves the problem described in
the introduction.
It has, in addition, proved to be the case when testing the
arrangement that the drying time can be further reduced by
blowing air, in association with the heating process, through
the cups down into the holes of the anode block using a suit-
able and previously known blowing arrangement.

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The present invention is not by any means limited to a method
or an arrangement to be used with anode blocks having three
holes. The invention can be used for all designs of anode
block with holes.
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Several embodiments have been described above. However, the
invention can be varied in ways that will be obvious for one
skilled in the art, and thus the invention is not to be seen
as limited to the embodiments described above, since it can
/0 be varied within the scope of the attached patent claims.

Dessin représentatif