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Патент USA US3024187

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March 6, 1962
M. 6:. SEM
PROCESS FOR OPERATING SODERBERG ANODES
WITH VERTICAL CONTACT STUDS
3,024,1 78
Filed March 5, 1959
FIG. 2.
,, IN VEN TOR.
MATHIAS OVROM SEM
BY
é‘ Wm Yifcd’“
ATTORNEYS.
United States Patent
3,924,173
Patented Mar. 6, 1962
l
2
3 024 178
procedure is safe enough but it causes a higher voltage
drop in the anode. The inventor has found that one
can operate with an average voltage drop of about 0.45
PROCESS FOR OPERATINEI SODERBERG ANODES
WITH YERTIOAL CONTACT STUDS
volt if the contact rods are allowed to reach the 15 cm.
Mathias Ovrom Sem, Smestad, Oslo,v Norway, assignor to
Elektrokemisk A/S, Oslo, Norway, a corporation of
Norway
Filed Mar. 5, 1959, Ser. No‘. 797,387
Claims priority, application Norway Apr. 19, 1958
5 Claims. (Cl. 204-67)
level above the anode bottom while the voltage drop is
usually 0.154120 volt higher at the 25 cm. level. One
can thus save at least about 0.15 volt if the tips of the
contact rods are allowed to reach the 15 cm. level. This
means a saving in current of 3% with the same am
10 perage output, or about 500 kw.-h. per ton of Al. An
When using Siiderberg anodes in aluminium furnaces
it is now customary to arrange the contact studs ver
advantage of equal importance is attained in that the
contact rods can operate for a longer time in the anode
without having to be withdrawn. As the anode con
tically in the anode. The contact studs pass through a
sumption is usually about 2 cm. per day a 5 days longer
layer of raw electrode paste which may for example be
25 centimeters deep. This paste is molten and rests di 15 operating time in the anode is attained by letting the
tip of the rod go down to 10 cm. above the anode bot
rectly on the baking zone where the transformation to
solid electrode takes place at about 420° C. The bak
ing zone is a well de?ned limitation between baked and
tom before being withdrawn.
into the same hole, but in a higher position, ‘for exam
ple 25~3O cm. higher up in the electrode. The rod
until it reaches the baking zone. The two halves of
the shield can if desired, be connected with a suitable
will be baked into the anode by means of raw electrode
paste which is ?lled into the bottom of said hole. If
soon as the shield is in place the contact rod can be
Applicant has found a way to make use of this pos
sibility by shielding the hole left by the rod against the
unbaked paste which can easily be localized by insert
20 soft electrode paste by means of a shield which is placed
ing an iron rod into the electrode from above.
in the soft paste around the rod before it is withdrawn.
The contact studs are ?rmly ?xed in the baked elec
The shield may be of metal, preferably a non-magnetic
trode paste by the baking and thus supply the electric
metal, for example aluminium. It is usually made of
current to the anode. The studs must be twisted loose
two halves which are hinged together and closed around
from the anode and pulled up before they contact the
liquid ?uoride bath. A new contact rod is then inserted 25 the rod and then pushed through the soft electrode paste
tong which permits an easy handling of the shield. As
thick ?owing electrode paste is used the hole left by the 30 twisted loose and withdrawn, for example by means of
stud is usually left open for a while after the stud has
m‘
a crane.
The small quantity of liquid paste which un
der these circumstances will ?ow into the hole will in
been withdrawn, as the thick electrode paste will not
stantaneously become baked at the bottom of the hole
?ow down by itself and ?ll the hole. A suitable spe
without penetrating into the ?uoride bath. The further
cial electrode paste can then be ?lled into the hole be
fore inserting the stud into the anode. This paste may 35 procedure can then be to ?ll the rod hole with a spe
cial paste, for example in the ‘form of cold, crushed
for example be introduced in the molten state. This
pieces, or one can let the electrode paste in the top of
is the method which has previously been customary. It
the electrode ?ow into the hole at a suitable speed. One
has however been found that a better quality of anode
may also ?ll some dry special paste into the lower part
has been attained by employing a thin-?owing electrode
paste containing more binding agent that previous types. 40 of the rod hole and tamp this paste before the soft paste
is introduced. Such a shield of non-magnetic metal is
Usually such paste contains between 28-33% pitch. The
removed from the anode as soon as the bottom of the
paste will at the temperature in question at the top of
rod hole has been secured against penetration of soft
the anode be so thin-?owing that the paste will auto
electrode paste.
matically ?ow into the hole when the contact stud is
The invention is schematically illustrated in appended
withdrawn from the anode. This is of course a very 45
FIGS. I and II which show a hinged shield of above de~
practical solution. Several serious difficulties are how
scribed type. FIG. I shows a vertical ‘section through a
ever connected therewith due to the fact that the anode
rod with shield and FIG. II a corresponding horizontal
has a tendency to crack in its lower part, especially at
section. In the ?gures, 1 is a contact rod penetrat
the bottom of the hole for the contact rod, during the
ing into the baked part of the anode 2. 3 is the soft
strains to which the anode is subjected when the contact
paste on top of the anode and 4 indicates the boundary
rod is twisted loose, as a force up to 10—20 tons must
zone between the two layers. As mentioned above this
zone is called the baking zone. 5 is the shield which
is so dimensioned that there will be a clearing 6 between
by a contact rod which is surrounded by open cracks of 55 it and the rod. 7 indicates a tongs for handling the
shield. The tongs can be separate or built together with
this kind a part of the paste will penetrate through the
the shield.
cracks into the ?uoride bath whereby an instantaneous
Instead of making the shield of metal it may be made
development of tar fumes will take place. If the cracks
of other material, for example wood or silicone rubber.
are large such development of fumes will have the char
One can also cast ‘the shield in two halves from a dry
acter of a small explosion which can throw a part of
electrode paste which for example contains 14% bind
the liquid ?uoride bath out of the furnace. This may
then be used on a single contact rod.
Such cracks can
be so large that they form slots through the anode.
When the liquid electrode paste ?ows into a hole left
lead to burnings and similar accidents.
The usual procedure to avoid such holes right through
the anode is to withdraw the rod from the anode when
the lower tip of the rod is so high above the bottom 65
surface of the anode that no through cracks are formed.
With such early withdrawing of the rod, the paste plug
ging the hole under the rod will have time to be baked
ing agent. This has the advantage that it will soon be
dissolved in the electrode paste and be incorporated in
it. It will, however, protect the rod hole against the
soft electrode paste until the bottom of the rod hole is
su?iciently secured. The shield can then simply be
pushed aside in the paste, thus permitting the soft paste
to ?ow into the rod hole. .
One can also employ shields of usual electrode paste.
The shields should then be cooled for example to about
70
such cases the rod is usually raised when its tip is lo
0° C. before being inserted. This has the effect that
cated about 25 cm. above the bottom of the anode. This
the melting of the shield will require so long time that
before reaching the bath through possible cracks. In
3,024,178
there will be time to displace the rod before such paste
shield has been destroyed.
I claim:
1. In the process of operating Stiderberg anodes with
vertical contact studs, the steps incident to the removal
and replacement of such a stud, of surrounding a por
4
by the fact that the sleeve is of non-magnetic metal which
is removed from the anode after the bottom of the hole
left by the stud has been secured against penetration by
soft electrode paste.
3. A process as speci?ed in claim 1, in which the
sleeve is formed in two parts.
4. A process as speci?ed in claim 3, in which the
tion of the stud above the anode with a cylindrical sleeve
sleeve formed of two parts has a handle on each part
having an inside diameter larger than the stud while
to facilitate handling.
the lower portion of the stud is embedded in the baked
portion of the anode, forcing such sleeve down through 10 5. A process as speci?ed in claim 1, in which the
sleeve is formed of hardened electrode paste which
the unbaked portion of the electrode mass until it meets
gradually becomes incorporated in the raw electrode
the baking zone of the anode, removing such stud while
the sleeve is in place, adding unbaked paste into the
paste on top of the anode.
hole left by the stud to ?ll the bottom of the hole, re
References Cited in the ?le of this patent
turning a stud to such hole at a higher position than 15
the original stud but with its end still in the baked por
FOREIGN PATENTS
tion of the anode and permitting unbaked paste to sur
Great
Britain _________ __ July 11, 1947
590,250
round such returned stud to seal the same in place.
Great Britain ________ __ Sept. 11, 1957
782,605
2. A process as speci?ed in claim 1, characterized
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