Note: Descriptions are shown in the official language in which they were submitted.
105'~844
The present invention relates to electrical smelting
furnaces and in particular to a gas collection system
therefor.
Furnaces for the melt electrolytic production of
metals are well known in the art. These furnaces are
usually equipped. with a permanent iron casing through
which an electrod.e can be introduced into the operative
part of the furnace. The electrode establishes a current
through the charge thereby melting it and the electrod.e
is gradually consumed.during the smelting process. As it
is consumed it is lowered. into the charge,
During the smelting process, there are a considerable
amount of furnace gases produced.. These furnace gases are
generally collected. in a gas collection ring which surrounds
the electrode at the bath surface. An alternative or
additional means of collection is to have an annular body
about the circumference of the furnace pot to collect the
gases. In both of the above instances, the wall of the gas
collecting member rests on the crust which is formed. on
~0 the bath surface. In order to prevent undesirable escape
of gases, there is usually employed. sealing means such as
granular aluminum oxide between the lower portion of the
-gas collecting member and the crust. It is quite important
to have a good seal since the gases which are produced
will frequently include CO, tar fumes, fluorine vapors
lOSb~344
and dust, all of which are detrimental to the environment
and to the working conditions of the employees in the
plant.
While the aforementioned. procedure for collecting
gas has been in use for a great number of years and.
works quite well, there are, unfortunately, drawbacks
to this system which are especially important in larger
plants. One of the drawbacks is that when the crust is
broken from time to time to allow for supply of additional
material to the charge, the gas collecting member will
frequently become open thus permitting the escape o
noxious gases and. dust mentioned. previously. This
breaking of the crust can also take place at other times
such as when anod.e effect occurs, i.e., when the contents
of the molten bath has been reduced to such a low level
that the voltage across the bath is raised. thereby causing
disruption of the crust. This action will frequently
result in the release of noxious gases and. d.ust into the
pot room.
A further problem with this arrangement is that
the layer of sealing material used. on the surface of the
crust, e.g., aluminum oxide, is never completely gas
tight and. this can lead to the release of gases, especially
along the lining of the furnace pot.
In accord.ance with the present invention, the
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disadvantages of these known gas collecting systems are
substantially eliminated by a gas collecting member which
is positioned. beyond the circumference of the pot at its
lower portion and partly closes the furnace in order to
obtain a chimney effect so that gases are drawn upwards
within the gas collection enclosure. The hot fluorine
and tar containing gases will thus be cond.ucted. upwards
above the lower work level and the gases will be prevented
from escaping into the working area of the urnace operators.
At the same time, the gas collection apparatus of the
A p~o fec~
f~ present invention helps to p~w ~t against heat radiation
from the furnace into the working area thus red.ucing the
undesirably high working temperatures which are normally
associated. with electric smelting furnaces.
The lower end. of the gas collecti.ng apparatus of the
present invention is spaced. from the wall of the furnace
pot thus permitting the entry of air therebeneath. The
gas collecting apparatus then tapers toward.s the anode hold.er
but is spaced. from the anode holder sufficient d.istance
so that gases and the like rising in the gas collecting
apparatus can escape through the top thereof. Suitable
collection apparatus such as ducts or the like may be
provided. at the top for collection of the escaping
gases if desired.
An important feature of the present invention is
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105'~84~
that it comprises at least two sections, one above the other, each
of wh-ich is movable with respect to the other. That is preferably
done with two sections, which are either articulated or slidable with
respect to each other. This construction permits access for breaking
of the crust, tapping, service of the burner or the like in connection
with the lower portion of the gas collecting apparatus and refilling of
the anode paste, stud pulling, jack slipping and the like with respect
to the upper portion of the gas collecting apparatus.
In one particular aspect the present invention provides
in an electric smelting furnace for the melt electrolytic production
of aluminum including a furnace pot having an outer side wall and anode
section disposed above the furnace pot and being of lesser dimensions
than the dimensions of the furnace pot the improvement comprising a gas
collecting hood, said gas collecting hood comprising upper and lower
portions each of which comprises a plurality of sections and each
plurality of sections in combination forming a closed shape and each
said section of each plurality of sections being movable with respect
to any other section independently of the other to permit access to
said furnace pot, each of said sections in the lower portion having a
slope upwardly towards the anode section and the lower end of the lower
portion being of greater dimension than the dimension of the outer wall
of t~e furnace pot and being spaced outward from the outer wall of the
furnace pot to permit entry of air, the upper portion being disposed
at least in part outward from the anode section and being spaced along
its length from the anode section to permit upward egress of gases
evolved from the smelting process.
These and other features of the present invention may be
more fully understood with reference to the drawings wherein:
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105;~84~
Fig. 1 shows partly in cross section one form of
embodiment of ~he gas collecting apparatus of the present invention;
Fig. 2 is a side view of the apparatus of Fig. 1 sbowing
the preferred shape of the upper and lower sections of the gas
collection apparatus; and
Fig. 3 shows in cross section an alternative embodiment
of the gas collection apparatus of the present invention.
Referring now to Fig. 1 there is shown a furnace 10 with
a substantially annular outer wall 12 and charge 14 with crust 16
at the top thereof. The primary gas collection apparatus 18
surrounds the anode 20. Floor 22 surrounds
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lOS'~844
the furnace 10 In accordance with the present invention,
gas collection apparatus 24 is used. in ad.d.ition to primary
gas collection apparatus 18. In this embod.iment the gas
collection apparatus comprises upper member 26 and. lower
member 28 articulated at 30. The lower member 28 rests
on a ridge 32 of the floor 22. A space 34 is provided.
between the outer wall 12 of the furnace and the floor
22 to permit the free entry of a draft from the basement
(not shown) of the furnace. While this is the preferred
form of embod.iment, it is also possible to eliminate space
34 by positioning member 28 above t~e floor 22 so that an
opening along the floor to act as a drat entrance way
is provided. The lower member 28 extends from beyond the
wall 12 of the furnace 10 in a sloped. position to articulatea
~oint 30 which is spaced from but closely adjacent the anode
20. Extending upward.ly from the articulated joint in
substantially vertical direction is member 26. As gases
are released from the charge 14 they will tend to rise. Due
to the opening 34 or similar opening there will be a natural
chimney effect which will lift the gases through channel 36
between anode member 20 and upper portion 26 so that the
gases are carried away from the furnace room and. the
operator. At the same time, due to the lower member 28,
the gases and radiated heat will also be prevented. from
escaping into the operating room. Further gas collecting
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105'~ 8 44
apparatus such as a hooded. exhaust fan could be provided
above members 26 if desired to collect the gases which
escape from the furnace.
Members 26 and. 28 are movable independ.ent o each
other to permit accessibili-ty to the appropriate part
of the furnace on an as need.ed basis and for the purposes
as d.escribed hereinbefore. Lower member 28 and.upper member
26 preferably comprise a series of adjacent plates forming
substantially an annulus about the furnace 10. While the
plates may be straight if d.esired., it is preferred for
best operation that they have an appropriate curvature and
it is further preferred that lower members 28 be in the
form of truncated. triangles in order to insure a gas
tight fit and proper functioning of the apparatus, see
especially Fig. 2.
In Fig. 3 there is again shown the furnace 10 with
outer wall 12 and floor 22, charge 14 with crust 16 and
primary gas collection apparatus 18. In this case in the
anode section 20 are shown a plurality of electrod.es 40
suspended by rods 42. The anode section itself 20 is
suspended by rods 44 from an anode frame 46. The upper and.
lower sections 48 and 50 of the gas collection apparatus
are slidable with respect to each other on the anod.e frame
46. As with the embodiment of Fig. 1, a space 34' is
provided below member 50 for the introduction of air necessary
~ 05~844
for the chimney effect o the gas collection apparatus of
the present invention.
The upper section 48 can be moved. d.ownwards for access
while the lower section 50 can correspondingly be moved
upwards. .In this embodiment sections 48 and. 50 preferably
have the shape of lower sections 28 of Fig. 2 and are
suitably movable in outward direction with respect to
each other in ad.dition to being slidable up and d.own so
that ad.~acent panels do not interfere with each other
when access is d.esired.
In order to insure proper ~as collection, it is
essential that the lower member 28 or 50 of the gas
collection apparatus be sloped with respect to the vertical.
The slope may range from a minimum of about 10 to a
maximum of about 60.
It will be understood that the claims are intend.ed.
to cover all changes and modificat.ons of the preferred
embod.iment of the invention, herein chosen for the
purpose of illustration, which d.o not constitute d.epartures
from the spirit and scope of the invention.
