CHAMBRE EN FORME DE CASSETTE ET BRIQUE MOULEE DANS UN FOUR REFRACTAIRE

CASSETTE CHAMBER AND SHAPED BRICK IN A REFRACTORY FURNACE

Abrégé anglais

The invention relates to a cassette chamber (1) of a refractory furnace, in
particular, for firing anode blocks using a cover grit with an essentially
rectangular plan each with two vertical opposing chamber longitudinal walls
(3, 4) and chamber transverse walls (5, 6) and at least one vertical cassette
wall (7) running perpendicular to the chamber transverse walls (5, 6) or
chamber longitudinal walls (3, 4) fixed to said chamber walls (3, 4, 5, 6)
made up of individual essentially square mineral fire-resistant shaped bricks
(11, 11), wherein gas channels (9) are moulded in the shaped bricks (11, 11a)
running upwards in the cassette wall (7), said shaped bricks (11, 11a) being
made from refractory concrete.

Revendications

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Claims
1. A cassette chamber (1) in a refractory furnace, in
particular for the baking of anode blocks, using
covering grit, which has an essentially rectangular
base area and has in each case two vertical opposite
chamber longitudinal walls (3, 4) and chamber
transverse walls (5, 6) and at least one vertical
cassette wall (7) which extends perpendicularly to the
chamber transverse walls (5, 6) or chamber longitudinal
walls (3, 4) and is connected to the respective chamber
walls (3, 4, 5, 6) and which is constructed from
individual mineral, essentially cuboidal refractory
shaped bricks (11, 11a), there being provided in the
cassette wall (7) gas ducts (9) which are continuous
from the bottom upward and are incorporated into the
shaped bricks (11, 11a), characterized in that the
shaped bricks (11, 11a) consist of refractory concrete.
2. The cassette chamber as claimed in claim 1,
characterized in that the refractory concrete has at
least one refractory granulated product as aggregate,
in particular Al2O3 granulates, such as, for example,
mullite-rich materials and/or fireclay and/or
andalusite, at least one refractory flour-like product
as additive, such as, for example, aluminum oxide
and/or clay and/or mullite-containing components and/or
non-oxidic materials, at least one consolidated mineral
binder, such as, for example, aluminum oxide cement
and/or microsilica and/or reactive aluminum oxide, and,
if appropriate, at least one addition, such as, for
example, a liquefier and/or binding regulator and/or
organic and/or inorganic fibers.

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3. The cassette chamber as claimed in claim 1 and/or
2, characterized in that the refractory concrete is a
refractory concrete of type ULCC (Ultra Low Cement
Castables) with a CaO content of at most 0.2 to 1.0% by
weight.
4. The cassette chamber as claimed in one or more of
claims 1 to 3, characterized in that the refractory
concrete has an Fe2O3 content < 2% by weight, preferably
< 1% by weight.
5. The cassette chamber as claimed in one or more of
claims 1 to 4, characterized in that the refractory
concrete has the following thermomechanical,
thermochemical and physical properties:

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<IMG>
6. The cassette chamber as claimed in one or more of
claims 1 to 5, characterized in that the shaped bricks
(11, 11a) have two wide sides (12, 13), two end faces
(16, 17) and an underside (14) and a top side (15) and
the following dimensions:
width: 190 to 350 mm, in particular 200 to 300 mm
height: 500 to 1000 mm, in particular 600 to 800 mm
length: 600 to 2000 mm, in particular 1000 to 1900 mm.

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7. The cassette chamber as claimed in one or more of
claims 1 to 6, characterized in that shaped bricks
(11, 11a) arranged one above the other are connected to
one another by means of groove/tongue connections,
preferably without bricking-in.
8. The cassette chamber as claimed in claim 7,
characterized in that the shaped bricks (11, 11a) have
in their top side (15) in each case a fixing groove
(18) with an expediently trapezoidal cross section.
9. The cassette chamber as claimed in claim 8,
characterized in that the shaped bricks (11, 11a) have
in their underside (14) in each case a fixing tongue
(18) matching the fixing groove (18).
10. The cassette chamber as claimed in one or more of
claims 1 to 9, characterized in that shaped bricks
(11, 11a) arranged so as to be lined up in a row next
to one another are connected to one another by means of
groove/tongue connections, preferably without bricking-
in.
11. The cassette chamber as claimed in claim 10,
characterized in that the shaped bricks (11, 11a) have
on at least one end face (16, 17) in each case a
connecting groove (24) or a connecting tongue (25) with
an expediently trapezoidal cross section.
12. The cassette chamber as claimed in claim 10 and/or
11, characterized in that the shaped bricks (11, 11a)
have on the end face (16) in each case the connecting
groove (24) with an expediently trapezoidal cross
section.
13. The cassette chamber as claimed in claim 11 and/or
12, characterized in that the shaped bricks (11, 11a)

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have on the end face (17) in each case the connecting
tongue (25) matching the connecting groove (24).
14. The cassette chamber as claimed in one or more of
claims 1 to 13, characterized in that the shaped bricks
(11,11a) have 3 to 10, in particular 6 to 8 gas ducts
(9) extending continuously from the underside (14) to
the top side (15).
15. The cassette chamber as claimed in one or more of
claims 1 to 14, characterized in that the gas ducts (9)
have an essentially rectangular cross section with
rounded duct edges (31).
16. The cassette chamber as claimed in one or more of
claims 1 to 15, characterized in that the cassette wall
(7) is connected to the chamber walls (3, 4, 5, 6), at
least on one cassette wall end face (40), by means of
at least one connecting device, the connecting device
having a connecting groove (36) extending vertically in
the chamber walls (3, 4, 5, 6), a connecting end face
(100) of a connecting shaped brick (11a), an expansion
joint (41) delimited by the connecting groove (36) and
the connecting end face (100), a slot (45) delimited by
the wide side (12) of the connecting shaped brick (11a)
and the connecting groove (36) and preferably a gap
(44) delimited by the wide side (13) and the connecting
groove (36).
17. The cassette chamber as claimed in claim 16,
characterized in that the connecting device has a
sealing device sealing off the slot (45).
18. The cassette chamber as claimed in claim 16 and/or
17, characterized in that the connecting device has a
sealing device sealing off the gap (44).

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19. The cassette chamber as claimed in claim 17 and/or
18, characterized in that the sealing device has, in
the region of the connecting groove end face (100), a
vertically extending sealing groove (47, 57) and a
vertically extending sealing element (53, 61) arranged
in the sealing groove (47, 57).
20. The cassette chamber as claimed in claim 19,
characterized in that the sealing groove (47, 57) is
provided in the respective wide side (12, 13) of the
connecting shaped brick (11a).
21. The cassette chamber as claimed in claim 19 and/or
20, characterized in that the sealing groove (47, 57)
is provided in the respective connecting groove side
face (38, 39).
22. The cassette chamber as claimed in one or more of
claims 19 to 21, characterized in that the sealing
groove (47) has a rectangular cross section.
23. The cassette chamber as claimed in one or more of
claims 19 to 22, characterized in that the sealing
groove (47) is arranged, at least in part regions,
within the connecting groove (36).
24. The cassette chamber as claimed in one or more of
claims 19 to 23, characterized in that the sealing
element (53) is a sealing cuboid (53).
25. The cassette chamber as claimed in claim 24,
characterized in that the sealing cuboid (53) is
arranged in the sealing groove (47) with an interlock
or with a slight interference fit.
26. The cassette chamber as claimed in one or more of
claims 19 to 25, characterized in that the sealing
device in the sealing groove (47) has a vertically

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extending strip-shaped elastic, preferably ceramic
fiber mat (51) which expediently bears with a fiber mat
underside (52) against a sealing groove bottom (48) and
with a fiber mat surface (55) against a sealing cuboid
rear side (54) and which preferably extends over the
entire width of the sealing groove (47).
27. The cassette chamber as claimed in one or more of
claims 24 to 26, characterized in that the sealing
cuboid (53) bears slidably and sealingly over a large
area with a sealing cuboid sliding face (56) lying
opposite the sealing cuboid rear side (54), at least in
part regions, against the respective connecting groove
side face (38, 39).
28. The cassette chamber as claimed in one or more of
claims 19 to 21, characterized in that the sealing
groove (57) is a U-shaped sealing cylinder groove (57).
29. The cassette chamber as claimed in claim 28,
characterized in that the sealing element (61) is a
cylindrical sealing rod (61).
30. The cassette chamber as claimed in claim 29,
characterized in that the sealing rod (61) is arranged
with a form fit or with a slight press fit in the
sealing cylinder groove (57).
31. The cassette chamber as claimed in one or more of
claims 29 to 30, characterized in that the depth of the
sealing cylinder groove (57) is less than the diameter
of the sealing rod (61), so that the sealing rod (61)
preferably bears linearly against the respective
connecting groove side face (39) and seals off.
32. The cassette chamber as claimed in one or more of
claims 16 to 31, characterized in that the connecting
device has a storage device for the covering grit.

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33. The cassette chamber as claimed in claim 32,
characterized in that the storage device has at least
one preferably vertically oriented storage volume or
oversize volume which is provided as a consequence of
production and/or by virtue of assembly.
34. The cassette chamber as claimed in claim 33,
characterized in that the storage device has a
vertically oriented repository groove (62) as a storage
volume.
35. The cassette chamber as claimed in claim 34,
characterized in that the repository groove (62) is
provided on the connecting end face (100) of the
connecting shaped bricks (11a) and has a, for example,
trapezoidal cross section.
36. The cassette chamber as claimed in claim 34 and/or
35, characterized in that the ratio of storage volume
to expansion joint volume in the repository groove (62)
is 30 to 80%, preferably 40 to 60%, at room
temperature.
37. The cassette chamber as claimed in one or more of
claims 16 to 36, characterized in that the connecting
device has at least one oblique vertically extending
preferably planar end edge (64, 65) which connects the
connecting end face (100) to the respective wide side
(12, 13) and which in each case delimits a storage
volume together with the respective connecting groove
side face (38, 39) and the expansion joint (41).
38. The cassette chamber as claimed in claim 37,
characterized in that the storage volume is a
triangular repository (66, 67) of essentially
triangular cross section.

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39. The cassette chamber as claimed in claim 38,
characterized in that the ratio of storage volume to
expansion joint volume in the triangular repositories
(66, 67) is in each case 30 to 80%, preferably 40 to
60%, at room temperature.
40. The cassette chamber as claimed in one or more of
claims 32 to 39, characterized in that a ceramic fiber
mat strip (63) is provided in the slot (45).
41. The cassette chamber as claimed in one or more of
claims 34 to 36, characterized in that end faces
(68, 69) laterally delimiting the repository groove
(62) have a trapezoidal profile, as seen from the side.
42. The cassette chamber as claimed in claim 41,
characterized in that the end faces (68, 69) have in
each case a preferably planar oblique sloping end face
(71, 72) adjoining the top side (15), a preferably
planar vertical end face (73, 74) adjoining said
sloping end face and a preferably planar oblique
overhang end face (75, 76) which adjoins said vertical
end face and which the underside (14) adjoins.
43. The cassette chamber as claimed in claim 42,
characterized in that the sloping end faces (71, 72)
form with the top side (15) an angle a of preferably
100 to 130°, preferably 105 to 120°.
44. The cassette chamber as claimed in claim 42 and/or
43, characterized in that the overhang end faces (75,
76) form with the underside (14) an angle .beta. of
preferably 100 to 130°, preferably 105 to 120°.
45. The cassette chamber as claimed in one or more of
claims 1 to 44, characterized in that the cassette wall
(7) has at least one suction extraction orifice (77)
which connects the expansion joint (41) and/or the

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storage volume or storage volumes to a cassette space
(8) .
46. The cassette chamber as claimed in claim 45,
characterized in that at least one connecting shaped
brick (11a) has in the lower region a preferably planar
incline (78) extending from the connecting end face
(100) to the underside (14).
47. The cassette chamber as claimed in claim 46,
characterized in that the incline (78) projects
partially beyond the connecting groove side faces (38,
39), so that the suction extraction orifice (77) is
delimited in each case essentially by the incline (78)
of one connecting shaped brick (11a), the top side (14)
of a connecting shaped brick (11a) arranged below it
and a connecting groove outer edge (79).
48. The cassette chamber as claimed in claim 46 and/or
47, characterized in that a slip-off wedge (80), in
particular likewise consisting of refractory concrete,
is arranged below the incline (78) and, in particular,
within the connecting groove (36).
49. The cassette chamber as claimed in claim 48,
characterized in that the slip-off wedge (80) has a
planar wedge bottom (81), two wedge side faces (82, 83)
perpendicular to this, a wedge rear wall (84) likewise
perpendicular to the wedge bottom (81) and to the wedge
side walls (82, 83), a wedge front wall (85) parallel
to said wedge rear wall and preferably two slip-off
faces (86, 87) which adjoin the wedge side walls (82,
83) and which taper toward one another in a roof-shaped
or gable-shaped manner with respect to the wedge bottom
wall (81), and also two wedge ceiling walls (88, 89)
which adjoin the wedge rear wall (84) at right angles
and likewise taper toward one another in a roof-shaped
or gable-shaped manner.

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50. The cassette chamber as claimed in claim 49,
characterized in that the slip-off wedge (80) is
fastened with the wedge rear wall (84) to the
connecting groove bottom (37) by means of adhesive
bonding and/or bricking-in and expediently lies with
its wedge bottom wall (81) on the top side (15) of the
connecting shaped brick (11a) arranged below it.
51. The cassette chamber as claimed in claim 49 and/or
50, characterized in that the slip-off wedge (80) is
dimensioned in such a way that its wedge side walls
(82, 83) terminate flush with the connecting groove
side faces (38, 39) in the horizontal direction, and
the distance between the two wedge side walls (82, 83)
expediently corresponds to the width of the connecting
groove (36).
52. The cassette chamber as claimed in claim 48,
characterized in that the slip-off wedge (80) has a
single planar slip-off face (90), the gradient of which
preferably corresponds in amount to the gradient of the
incline (78).
53. The cassette chamber as claimed in one or more of
claims 1 to 52, characterized in that the cassette wall
(7) has at least one draw-off duct (91) for the
covering grit.
54. The cassette chamber as claimed in claim 53,
characterized in that the draw-off duct (91) extends
away from the connecting end face (100) through the
connecting shaped brick (11a) and issues in each case
into the first smoke gas duct (9), as seen from the
connecting end face (100).
55. The cassette chamber as claimed in claim 54,
characterized in that the draw-off duct (91), in

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particular, flow-connects the storage volume or storage
volumes and/or the expansion joint (41) to the first
smoke gas duct (9).
56. The cassette chamber as claimed in claim 54 and/or
55, characterized in that the draw-off duct (91)
extends away from the connecting end face (100)
obliquely downward, preferably a draw-off duct axis
(92) forming with the vertical an angle .epsilon. of 30 to 60°,
preferably of 40 to 50°, and the draw-off duct axis
(92) expediently running in a brick longitudinal mid-
plane (10).
57. The cassette chamber as claimed in one or more of
claims 54 to 56, characterized in that the draw-off
duct (91) has a conical profile, the cross section of
the draw-off duct (91) preferably widening in the
direction of the smoke gas duct (9).
58. The cassette chamber as claimed in claim 57,
characterized in that a draw-off duct cone angle .phi. is
preferably 10 to 30°, preferably 15 to 20°.
59. A shaped brick for refractory furnace walls, in
particular for cassette walls and/or cassette chamber
walls, characterized by the features of one or more of
claims 1-6, 8, 9, 11-15, 20, 22, 28, 35, 42-44, 46, 54,
56-58.
60. A method for production of a shaped brick for
refractory furnace walls, in particular of a shaped
brick as claimed in claim 59, characterized by the
following method steps:
a) production of an, in particular, castable fresh
refractory concrete,
b) introduction, in particular casting, of the
fresh refractory concrete into a mold,

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c) preferably shaking and/or vibration of the
fresh refractory concrete in the mold,
d) hardening of the fresh refractory concrete in
the mold,
e) removal of the hardened refractory concrete
shaped brick from the mold.

Description

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Cassette chamber and shaped brick in a refractory furnace
The invention relates to a cassette chamber in a
refractory furnace, in particular an annular cassette
refractory furnace, preferably for the baking of
amorphous carbon bodies, in particular of anodes
consisting of high-purity carbon, which serve for the
electrolytic reduction of aluminum or for other
electrometallurgical processes. The invention relates,
moreover, to a shaped brick for refractory furnace
walls and to a method for its production.
The generation of pure aluminum from aluminum oxide
(A1203) usually takes place by means of what is known as
electrolytic smelting. This method is based on
decomposing A1203, dissolved in a molten cryolite bath,
by means of an electrical current which is supplied to
the bath by means of an immersed electrode consisting
of high-purity carbon (anode). In this case, the pure
aluminum obtained is deposited on walls of a crucible
which consists of baked carbon and constitutes the
cathode, and the oxygen obtained travels to the anode
and is burnt with it. For this reason, the anodes have
to be renewed at regular intervals, usually when they
are approximately 3026 worn, and therefore there is a
constant demand for anodes.
In the production of these anodes, first, a viscous
mixture of broken or ground coke or hard coal and of a
suitable binder, for example, coaltar pitch, is pressed
into what are known as "green" anode blocks, and these

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are subsequently baked at a temperature of
approximately 1200 C, so that the anode blocks acquire
the properties required for aluminum production, such
as, for example, electrical conductivity and oxidation
resistance.
The baking of the anode blocks usually takes place in
special refractory furnaces, preferably in annular
cassette refractory furnaces, in the gas-heated
chambers of which the "green" anode blocks are
introduced in stacks and are embedded in what is known
as covering grit or carbon grit, this ensuring that the
baking operation takes place without oxygen. The carbon
grit used for this purpose, which is usually produced
from the residual stocks of incompletely worn anodes,
consist essentially of graphite and alkali fluorides
and has, for example, a grain size of < 3 mm.
An annular cassette refractory furnace of this type for
the baking of anodes is known, for example, from
DE 200 21 089 U1 and is described below by way of
example with reference to figures 35 and 36. This
annular cassette refractory furnace 200 has a
multiplicity of cuboidal cassette chambers 201 which
are arranged both next to one another and one behind
the other in two rows, adjacent cassette chambers 201
being flow-connected to one another via a continuous
gas ring line 202, so that the combustion or smoke
gases are routed from one cassette chamber 201 to the
next (fig. 36). The individual cassette chambers 201
have in each case two vertical, opposite and mutually
parallel chamber longitudinal walls 203 and two
likewise vertical, opposite and mutually parallel
chamber transverse walls 204, the chamber longitudinal
walls 203 and chamber transverse walls 204 being
arranged perpendicularly to one another and forming a
continuous belt wall or chamber wall 205 in which a
plurality of vertically extending smoke gas passages

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212 are provided. Moreover, each cassette chamber 201
is subdivided into parallelepipedal cassettes 207 by
means of likewise vertically oriented cassette walls
206 extending perpendicularly to the chamber
longitudinal walls 203 from one chamber longitudinal
wall 203 to the opposite one. Each of the cassette
walls 206 in this case likewise has a plurality of
vertically extending smoke gas passages 212. The
cassettes 207 serve for receiving the baking stock 218
embedded in the carbon grit bed 217.
Both the cassette walls 206 and the chamber wall 205 in
this case usually consist of relatively small-format
individual wall bricks produced in a complicated way
and consisting of hydraulically pressed, ceramically
bound and essentially gastight fireclay bricks which
are bricked in by hand and grouted with fireclay
mortar. The fixing of the fireclay bricks with respect
to one another takes place via groove/tongue
connections known per se. These fireclay bricks
normally have an AL203 content of approximately 40% and
a length of 200 to 500 mm, a width of 200 to 300 mm and
a height of 130 to 180 mm.
Moreover, each cassette chamber 201 is closed by means
of a chamber cover 208 in such a way as to form an
upper cavity or compensation space 211 between the
chamber cover 208 and upper cassette wall surfaces 210
of the cassette walls 206 and the baking stock 218
located in the cassettes 207. A further, lower cavity
or compensation space 213 is formed in a chamber region
or chamber bottom region 214 of the cassette chambers
201 or of the cassettes 207.
During operation, that is to say during the baking of
the anodes, the smoke gases are routed in the line flow
direction 215 from one cassette chamber 201 to the
adjacent cassette chamber 201 in each case. For this

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purpose, first, fuel is burnt in separate vertical
heating or combustion shafts 216 which are provided in
that chamber longitudinal wall 203 of each cassette
chamber 201 which lies on the entry side with respect
to the line flow direction 215, usually in each case
one heating shaft 216 being present per cassette 207.
The smoke gas thus generated rises upward in the
respective heating shaft 216 and collects in the upper
compensation space 211 where pressure and temperature
compensation takes place. The smoke gas is routed from
there, through the smoke gas passages 212 present in
the cassette walls 206 and the chamber wall 205 and, if
appropriate, through the carbon grit bed 217 downward
into the lower compensation space 213, where pressure
and temperature compensation again takes place. The gas
flows out of the lower compensation space 213 into the
next heating shaft 216 of the cassette chamber 201
which is adjacent in the line flow direction 215, fuel
being supplied in countercurrent. The smoke gases thus
follow an essentially sinusoidal or meander-shaped
profile from cassette chamber 201 to cassette chamber
201.
During operation, a reducing and, because of the carbon
grit, an alkali fluoride-containing baking atmosphere
is present in the individual cassettes 207, whereas an
oxidizing atmosphere prevails in the heating shaft 216.
Usually, when an annular cassette refractory furnace
200 of this type is in operation, always one or two of
the cassette chambers 201 are in this case used as
combustion chambers, while the cassette chambers 201
arranged upstream of them in the line flow direction
215 are operated as heating chambers, and the cassette
chambers 201 lying downstream are operated as cooling
chambers, out of which the baked product is extracted
and into which new baking stock 218 is subsequently
introduced. In this case, a normal baking cycle,

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including the pre-heating and cooling of the anodes,
lasts approximately 14 days.
Owing to the constant change in the operating state of
the cassette chambers 201, the chamber wall 205 and,
above all, the cassette walls 206 are exposed to high
thermal loads and fluctuations, and therefore the
chamber wall 205 and the cassette walls 206 must
possess good thermomechanical properties, such as high
refractoriness under load, low softening under load, a
low flow behavior under load, a low
expansion/contraction behavior and good spalling
resistance.
Problems are, in particular, thermally induced, ever
alternating expansions and contractions in the cassette
walls 206 and the chamber wall 205. The expansions
result, inter alia, in undesirable barreling or bulging
of the cassette walls 206, since these are connected
essentially fixedly to the chamber wall 205 on the end
face and cannot shift. Moreover, owing to the
constantly changing tensile and compressive load, the
joints between the individual fireclay bricks are
broken open and destroyed, so that, in time, individual
fireclay bricks break out from the cassette walls 206.
This effect is also intensified in that the fireclay
bricks are highly susceptible to thermochemical attack
by the alkali fluorides contained in the covering grit.
The alkali fluorides penetrate into the pores of the
fireclay bricks and contribute to undesirable mineral
phase transformations which lead, on the one hand, to
an increased expansion behavior of the material and, on
the other hand, to premature softening under load.
Moreover, the very fine carbon grit, because of its low
grain size, gradually penetrates into the destroyed
joints and prevents and blocks the

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expansion/contraction movement of the cassette walls
206 to an even greater extent. This leads to an even
higher instability of the cassette walls 206 and, in
the end, to the destruction of the cassette walls 206
which then have to be repaired or exchanged completely,
which is highly complicated, time-consuming and cost-
intensive, inter alia because bricking-in has to be
carried out by hand.
In order to counteract this, it is known to mount the
cassette walls 206 in grooves of the chamber
longitudinal walls 203 and to provide expansion joints
which extend vertically in the chamber wall 205 and in
the butting region between the cassette walls 206 and
the chamber wall 205 and which are filled with Styropor
and/or ceramic elastically deformable fiber materials.
In this case, the Styropor serves merely as a spacer
during the mounting of the cassette walls 206 and for
providing a defined width of the expansion joint, since
the Styropor burns away immediately when the annular
cassette refractory furnace 200 is in operation. Both
the expansion joint provided by the Styropor used and
the ceramic elastic fiber material, which is compressed
reversibly in the event of the expansion of the
cassette walls 206, thus make it possible to have a
defined length change of the cassette walls 206 without
deformation.
The problem in this case, however, is that the ceramic
fiber materials possess only a limited period of use.
This is because, inter alia, for mounting and ensuring
freedom of movement of the cassette walls 206, the
width of the grooves is generally somewhat greater than
the width of the cassette walls 206, so that in each
case a gap is present between the cassette outer walls
and groove side walls. The very fine carbon grit also
gradually penetrates through or into these gaps and
into the ceramic fiber material, so that the movement

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of the cassette walls 206 is blocked again, thus
leading once more to the problems described above.
Problems in such annular cassette refractory furnaces
known per se are therefore, on the one hand, the
thermally induced damage to the refractory furnace
walls, such as the barreling of the cassette walls and
the breaking open of the joints between the fireclay
bricks, this being further intensified due to the
susceptibility of the fireclay bricks to thermochemical
attack by the alkali fluorides contained in the carbon
grit.
Moreover, the production of the refractory furnace
walls by the manual bricking-in of the many individual
fireclay bricks is highly time-consuming and cost-
intensive, and also the repair of the damaged
refractory furnace walls is possible only in a highly
complicated way.
The CO resistance of the fireclay bricks is also
insuf f icient .
The object of the present invention is to provide a
cassette chamber for a refractory furnace, in
particular an annular cassette refractory furnace or
the like, in particular for the baking of amorphous
carbon bodies, in which the thermally and chemically
induced damage to the refractory furnace walls, such
as, for example, barreling and crack formation, is
minimized, while the refractory furnace walls can be
produced and repaired simply and cost-effectively.
Moreover, the object of the invention is to provide a
shaped brick for such refractory furnace walls, which
can be produced more simply, has good thermochemical
and thermomechanical properties and experiences less
thermally and chemically induced damage.

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Furthermore, a simple and cost-effective method for
production of such a shaped brick for refractory
furnace walls is to be specified.
These objects are achieved, with regard to the cassette
chamber, by means of the features of claim 1, with
regard to the shaped brick by means of the features of
claim 59 and, with regard to the method, by means of
the features of claim 60. Advantageous developments are
characterized in the accompanying subclaims.
The invention is explained in more detail below by way
of example with reference to the drawing in which:
fig. 1 shows a diagrammatic perspective view
from above of a cassette chamber according to the
invention,
fig. 2 shows a side view of a shaped brick
according to the invention with a longitudinal
sectional cutout along a brick longitudinal mid-
plane,
fig. 3 shows a top view of a shaped brick
according to the invention,
fig. 4 shows a longitudinal section of the
shaped brick according to fig. 3 along the line A-
A,
fig. 5 shows a side view of a shaped brick
according to the invention in a further
embodiment, with a longitudinal sectional cutout
along the brick longitudinal mid-plane,

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fig. 6 shows a longitudinal section of the
shaped brick according to fig. 5 along the line B-
B,
fig. 7 shows a view of a detail of the cutout
marked in fig. 6 by C,
fig. 8 shows a cross-sectional view of a
cassette chamber according to the invention in a
first embodiment with regard to the connection of
cassette walls and chamber wall along a horizontal
plane coplanar with a top side of an upper shaped
brick,
fig. 9 shows a longitudinal section of the
cassette chamber according to fig. 8 along the
line D-D,
fig. 10 shows a view of a detail of the cutout
marked in fig. 8 by E,
f ig . 11 shows a top view of a connecting shaped
brick used in the first embodiment with regard to
the connection of cassette walls and chamber wall,
fig. 12 shows a view of a detail, corresponding
to the view in the form of a detail illustrated in
fig. 10, according to a second embodiment of the
cassette chamber with regard to the connection of
cassette walls and chamber wall,
fig. 13 shows a top view of a connecting shaped
brick used in the second embodiment with regard to
the connection of cassette walls and chamber wall,
fig. 14 shows a perspective view from above of
the connecting shaped brick according to fig. 13,
arranged in a connecting groove of a chamber

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longitudinal wall illustrated in the form of a
cutout,
fig. 15 shows a view of a detail, corresponding
to the view in the form of a detail illustrated in
fig. 10, according to a third embodiment of the
cassette chamber with regard to the connection of
cassette walls and chamber wall,
fig. 16 shows a top view of a connecting shaped
brick used in the third embodiment with regard to
the connection of cassette walls and chamber wall,
fig. 17 shows a perspective view from above of
the connecting shaped brick according to fig. 16,
arranged in a connecting groove of a chamber
longitudinal wall illustrated in the form of a
cutout,
fig. 18 shows a top view of a connecting shaped
brick used in a fourth embodiment with regard to
the connection of cassette walls and chamber wall,
fig. 19 shows a perspective view from above of
the connecting shaped brick according to fig. 18,
arranged in a connecting groove of a chamber
longitudinal wall illustrated in the form of a
cutout,
fig. 20 shows an end view of a connecting shaped
brick used in a fifth embodiment of the cassette
chamber with regard to the connection of cassette
walls and chamber wall,
fig. 21 shows a side view of the connecting
shaped brick according to fig. 20,

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fig. 22 shows a perspective view from above of
two connecting shaped bricks according to fig. 18
arranged one above the other, arranged in a
connecting groove of a chamber longitudinal wall
illustrated in the form of a cutout,
fig. 23 shows a longitudinal section,
corresponding to the longitudinal section
according to fig. 9, of a cassette chamber
according to a sixth embodiment of the cassette
chamber with regard to the connection of cassette
walls and chamber wall,
fig. 24 shows a view in the form of a detail of
the cutout marked in fig. 23 by F,
fig. 25 shows a perspective view from above of
two connecting shaped bricks, arranged one above
the other, according to the sixth embodiment of
the cassette chamber with regard to the connection
of cassette walls and chamber wall, arranged in a
connecting groove of a chamber longitudinal wall
illustrated in the form of a cutout,
fig. 26 shows a side view of a connecting shaped
brick according to fig. 25,
fig. 27 shows a side view of the connecting
shaped brick according to fig. 26,
fig. 28 shows a perspective view from above of
two connecting shaped bricks arranged one above
the other, in each case with a slip-off wedge,
according to a seventh embodiment of the cassette
chamber with regard to the connection of cassette
walls and chamber wall, arranged in a connecting
groove of a chamber longitudinal wall illustrated
in the form of a cutout,

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fig. 29 shows a longitudinal section along the
brick longitudinal mid-plane of a connecting
shaped brick with a slip-off wedge according to
fig. 28, arranged in the connecting groove of the
chamber longitudinal wall illustrated in the form
of a cutout,
fig. 30 shows a top view of the connecting
shaped brick according to fig. 29, arranged in the
connecting groove of the chamber longitudinal wall
illustrated in the form of a cutout, with a
modified slip-off wedge,
fig. 31 shows a perspective view from above of
the slip-off wedge according to fig. 30,
fig. 32 shows a perspective view from above of a
connecting shaped brick according to an eighth
embodiment of the cassette chamber with regard to
the connection of cassette walls and chamber wall,
arranged in a connecting groove of a chamber
longitudinal wall illustrated in the form of a
cutout,
fig. 33 shows a side view of the connecting
shaped brick according to fig. 32 with a
longitudinal sectional cutout along the brick
longitudinal mid-plane,
fig. 34 shows a top view of the connecting
shaped brick according to fig. 33,
fig. 35 shows a diagrammatic perspective view
from above of a refractory furnace according to
the prior art,

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fig. 36 shows a section along a vertical plane,
parallel to cassette walls, through four cassette
chambers of the refractory furnace according to
fig. 35.
A refractory furnace has at least one, preferably 10 to
20 cuboidal cassette chambers 1 or cassette chambers 1
of rectangular base area, which are flow-connected to
one another (fig. 1, 8, 9, 23). Each of the cassette
chambers 1 consists of a continuous belt wall or
chamber wall 2 which is formed by two chamber
longitudinal walls 3, 4 oriented vertically and
parallel to one another and arranged so as to be spaced
apart from one another in the horizontal direction and
by two chamber transverse walls 5, 6 likewise oriented
vertically and parallel to one another and spaced apart
from one another in the horizontal direction, but
arranged perpendicularly to the chamber longitudinal
walls 3, 4.
Moreover, the cassette chamber 1 has at least one,
preferably 4 to 8 cassette walls 7 which are oriented
parallel to the chamber transverse walls 5, 6 and which
extend from one chamber longitudinal wall 3, 4 to the
opposite chamber longitudinal wall 3, 4 and subdivide
the cassette chamber 1 into a plurality of cuboidal
cassette spaces 8.
Alternatively to this, the cassette walls 7 are
oriented parallel to the chamber longitudinal walls 3,
4 and extend from one chamber transverse wall 5, 6 to
the opposite chamber transverse wall 5, 6 (not
illustrated).
A plurality of vertically extending heating shafts 101
of rectangular cross section are formed in the chamber
longitudinal wall 3, usually one heating shaft 101
being present per cassette space 8.

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According to the invention, the cassette walls 7 in
this case consist of individual large-format inner
shaped bricks 11 and of the connecting shaped bricks
lla which, arranged so as to be offset one above the
other and lined up in a row next to one another, in
each case form a cassette wall 7 (fig. 1-34). These
shaped bricks 11, lla in each case have two planar and
mutually parallel wide sides 12, 13, an underside 14, a
top side 15 and two opposite end faces 16, 17.
Furthermore, vertically extending continuous smoke gas
ducts 9 of essentially rectangular cross section are
introduced into the shaped bricks 11, lla. In this
case, the shaped bricks 11, lla of the assembled
cassette chamber 1 are arranged in such a way that the
smoke gas ducts 9 lie vertically in alignment with one
another. Preferably, the smoke gas ducts 9 are in this
case symmetrical with respect to a brick longitudinal
mid-plane 10.
The length of the shaped bricks 11, lla according to
the invention, that is to say the distance between the
opposite end faces 16, 17, is in this case preferably
600 to 2000 mm, preferably 1000 to 1900 mm, and the
width, that is to say the distance between the opposite
wide sides 12, 13, is preferably 190 to 350 mm,
preferably 200 to 300 mm, the height, that is to say
the distance of the underside 14 from the top side 15,
preferably being 500 to 1000 mm, preferably 600 to
800 mm. Consequently, the shaped bricks 11, lla
according to the invention are markedly larger than the
building bricks conventionally used and therefore,
inter alia, much simpler to handle.
According to the invention, the shaped bricks 11, lia
consist of a refractory concrete which consists
essentially of a refractory granulated product as

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aggregate, in particular A1203 granulates, such as, for
example, mullite-rich materials and/or fireclay and/or
andalusite, of a refractory flour-like product as
additive, such as, for example, aluminum oxide and/or
clay and/or mullite-containing components and/or
non-oxidic materials, of mineral binders, such as, for
example, aluminum oxide cements and/or microsilica
and/or reactive aluminum oxides, and also of additions,
such as, for example, liquefiers and/or binding
regulators and/or organic and/or inorganic fibers.
The use of a refractory concrete of type ULCC (Ultra
Low Cement Castables), with a CaO content of 0.2 to
1.0% by weight, has proved to be particularly
advantageous within the scope of the invention.
By such a refractory concrete of type ULCC being used
for the shaped bricks according to the invention, in
particular, a synergistic effect is achieved. On the
one hand, the shaped brick 11, lla according to the
invention has a low softening under load and low flow
under load which are characteristic of ultra low cement
refractory concrete. On the other hand, because of the
low water requirement of the refractory concrete during
production, the shaped bricks have very low open
porosity, so that the shaped bricks 11, lla possess low
gas permeability and are thereby resistant to the
absorption and attack of the alkali fluorides contained
in the carbon grit.
In order to achieve the Co resistance required for use
in the refractory furnace, moreover, the refractory
concrete has only an Fez03 content < 2% by weight,
preferably < 1% by weight.
In particular, preferably, a refractory concrete with
the following thermomechanical, thermochemical and

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physical properties is used as a material for the
shaped bricks 11, lla according to the invention:
Physical In particular
properties
Open porosity 12-20 13-17 [%]
after 400 C
combustion
Reversible 0.4 - 1.0 0.5 - 0.7 [%]
expansion up to
1000 C after
1300 C combustion
Irreversible -0.5 - +0.2 -0.2 - +0.2 [~]
expansion after
1200 C combustion
Strength after > 50 > 90 [MPa]
1300 C combustion
Thermomechanical
properties
Softening under > 1400 > 1500 [ C]
load T05 after
1300 C combustion
Refractoriness > 1500 > 1600 [ C]
under load ta
after 1300 C
combustion
Flow under load < 0.01 < 0.005 [o/h]
at 1280 C between
14 and 24 h
Spalling > 50 > 100 []
resistance
Thermochemical
properties
Alkali/fluorine Alkali- and fluorine- []
resistance resistant according to
DIN 51069-2
CO resistance A-B - []
according to
ASTM C 288,
500 C, 200 h
The production of the shaped bricks 11, lla in this
case takes place preferably by the customary concrete
technology, that is to say, for example, by the
introduction or casting of a previously produced fresh
refractory concrete into a mold, preferably subsequent
shaking or vibration, hardening of the fresh refractory

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concrete and removal of the hardened shaped bricks 11,
lla from the mold. By means of this production method,
in principle, any desired three-dimensional shape of
the shaped bricks 11, lla can be produced, and there
can be a simple, rapid and flexible reaction to changed
requirements with regard to the three-dimensional
shape. Moreover, this production is highly cost-
effective, since the casting molds or formwork required
can be produced likewise cost-effectively from wood or
plastic.
In the installed state, the shaped bricks 11, lla
arranged one above the other are fixed with respect to
one another by means of groove/tongue connections, a
fixing groove 18 being provided in the top side 15 and
a fixing tongue 19 matching this being provided in the
underside 14. Both the fixing groove 18 and the fixing
tongue 19 are in this case arranged preferably
symmetrically with respect to the brick longitudinal
mid-plane 10 and are therefore interrupted by the smoke
gas passages 9. In this case, fixing groove side faces
20 or fixing tongue side faces 21 are expediently not
perpendicular to a fixing groove bottom 22 or fixing
tongue bottom 23, but, instead, form an obtuse angle
with the respective bottom 22; 23, so that the fixing
groove 18 and the fixing tongue 19 have a trapezoidal
cross section.
The shaped bricks 11, lla arranged next to one another
are likewise connected to one another by means of
groove/tongue connections, in each case a connecting
groove 24 being provided on one end face 16 and a
matching connecting tongue 25 being provided on the
opposite end face 17 in each case. Here, again,
connecting groove side faces 26 or connecting tongue
side faces 27 are expediently not perpendicular to a
connecting groove bottom 28 or connecting tongue bottom

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29, so that the connecting groove 24 and the connecting
tongue 25 also have a trapezoidal cross section.
According to a further embodiment illustrated by way of
example in fig. 6, 7, 20, 21, 26, 27 and 33, the shaped
brick 11, ila has no centrally arranged fixing tongue
19 described above, but, instead, two semi-cylindrical
adaptor tongues 30 running in each case next to the
smoke gas ducts 9 and parallel to the brick
longitudinal mid-plane 10. These adaptor tongues 30
correspond in their shape and dimensions to tongues
conventionally used, so that these shaped bricks 11,
lla can be used as adaptor bricks, for example in the
lower row in a known refractory furnace.
As already explained above, the smoke gas ducts 9
provided in the cassette wall 7 and consequently in the
shaped bricks 11, lla have an essentially rectangular
cross section symmetrical with respect to the brick
longitudinal mid-plane 10 and having rounded duct edges
31. In particular, the smoke gas ducts 9 have a cross-
sectional length L in the direction of the brick
longitudinal mid-plane 10 of 80 to 250 mm, preferably
of 100 to 200 mm, and a cross-sectional width B
perpendicularly to the brick longitudinal mid-plane 10
of 80 to 250 mm, preferably of 100 to 200 mm.
In a cassette wall 7, the shaped bricks 11, lla are in
this case dimensioned and arranged in such a way that
vertical wall joints 33 of a horizontal shaped brick
row 34, which are present between the individual shaped
bricks 11, lla, are arranged so as to be offset with
respect to the wall joints 33 of a shaped brick row 34
arranged above or below it. A good strength and
stability of the cassette wall 7 are thereby achieved,
without the shaped bricks 11, lla being bricked in with
one another, thus affording, during assembly, an
enormous benefit in terms of cost and time, as compared

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with the bricks conventionally used which are bricked
in by hand.
In order to prevent the barrelings occurring in the
prior art, according to the invention the cassette
walls 7 consisting of a plurality of shaped bricks 11,
lla are connected on the end face, displacably in the
horizontal cassette longitudinal direction 35, to the
chamber longitudinal walls 3, 4, in each case by means
of connecting devices. In order to ensure that this
displacably is not blocked in the long term, even
during operation, and remains operable for as long as
possible, a plurality of variants are provided
according to the invention.
On the inside of the chamber, vertically oriented and
continuous connecting grooves 36 of the connecting
device, in each case with a connecting groove bottom 37
and with two mutually parallel connecting groove side
faces 38, 39, are provided in the chamber longitudinal
walls 3, 4. The depth of the connecting grooves 36 in
this case is preferably 30 to 200 mm, preferably 60 to
150 mm, the distance between two connecting groove
bottoms 37 opposite one another in the horizontal
direction being greater than the length of the cassette
wall 7 arranged between them, that is to say the
distance between their cassette wall end faces 40 in
the horizontal direction, so that in each case a free
space or an expansion joint 41 is formed as a further
element of the connecting device between the cassette
wall end faces 40 and the connecting groove bottoms 37,
and the cassette wall 7 is connected to the chamber
longitudinal walls 3, 4 displacably by a limited amount
in the cassette longitudinal direction 35.
The distance between the two connecting groove side
faces 38, 39 is in this case likewise somewhat greater
than the width of the cassette walls 7, that is to say

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than the distance between cassette wall sides 42, 43 or
than the width of the shaped bricks 11, lla, so that
there is in each case a small gap 44 or slot 45 between
the cassette wall sides 42, 43 and the connecting
groove side faces 38, 39. In this case, the gaps 44
preferably have a width of 2 to 5 mm, preferably 1.8 to
2.4 mm, and the slots 45 preferably have a width of 5
to 25 mm, preferably 9 to 13 mm. The gaps 44 and slots
45 are expedient, in order to ensure as low-friction a
mounting as possible of the cassette walls 7 in the
connecting grooves 36 and as low-friction a movement as
possible of the cassette walls 7 in the cassette
longitudinal direction 35, even in the event of a
thermally induced width expansion of the cassette walls
7, and in order to compensate manufacture-related
inaccuracies. Gaps 44 and slots 45 are likewise in each
case an integral part of the connecting devices.
In order to provide an expansion joint 41 of defined
depth, for example, in each case a Styropor strip 46
bearing against the connecting groove bottoms 37 is
provided for mounting the cassette walls 7, is burnt
completely when the cassette chamber 1 is put into
operation and leaves behind the expansion joint 41 with
a depth of preferably 5 to 50 mm, preferably 15 to
40 mm.
According to the invention, in each case one of the two
end faces 16, 17 of the connecting shaped bricks lla
have no connecting groove 24 or connecting tongue 25,
but, instead, elements for the connection of the
connecting shaped bricks lla to the chamber walls 3, 4.
This end face 16 or 17 is designated below as a
connecting end face 100 and is a further integral part
of the connecting device.
According to a preferred embodiment of the invention
with regard to the connection of cassette walls 7 and

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chamber longitudinal walls 3, 4, the connecting device
has a sealing device which prevents carbon grit from
penetrating into the expansion joint 41.
For this purpose, in each case, a vertically extending
sealing groove 47 is provided in the wide side 12 as an
element of the sealing device in the region of the
connecting end face 100 (fig. 8-11).
This sealing groove 47 has a rectangular cross section,
a sealing groove bottom 48 running parallel to the wide
sides 12, 13. The depth of the sealing groove 47 is
preferably 15 to 120 mm, preferably 30 to 80 mm, and
the width of the sealing groove 47, that is to say the
distance between sealing groove side faces 49, 50, is
preferably 60 to 200 mm, preferably 100 to 150 mm.
In the assembled cassette chamber 1 (fig. 8, 9), the
connecting shaped bricks lla are arranged in the
cassette walls 7 in such a way that the sealing grooves
47 are arranged vertically in alignment one above the
other. Moreover, the sealing grooves 47 lie, at least
in part regions, within the connecting grooves 36 and,
with respect to the connecting groove side faces 38,
39, on the side of the slot 45 delimited by the
connecting groove side face 38 and the wide side 12.
This overlapping of the connecting grooves 36 and of
the sealing grooves in part regions is dimensioned in
such a way that it is maintained even in the event of
the thermally induced contraction of the cassette
walls.
Provided as a further element of the sealing device in
the sealing grooves 47 is, for example, in each case a
vertically extending strip-shaped, elastically flexible
or resilient ceramic fiber mat 51 which bears with its
fiber mat underside 52 against the respective sealing
groove bottom 48 and preferably extends over the entire

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sealing groove width. The thickness of the fiber mats
51 is in this case preferably 2 to 40 mm, preferably 5
to 20 mm.
Moreover, in=each case a sealing element, in particular
a cuboid vertically extending sealing cuboid 53, is
seated as a further element of the sealing device,
preferably with an interlock or a slight interference
fit, in the sealing grooves 47 and bears slidably and
sealingly over a large area with its sealing cuboid
rear side 54 against a fiber mat surface 55 and with
its sealing cuboid sliding face 56 lying opposite the
sealing cuboid rear side 54, at least in part regions,
against the respective connecting groove side face 39.
In this case, the width of the sealing cuboids 53
corresponds essentially to the width of the sealing
grooves 47 and the thickness of the sealing cuboids 53
is preferably 20 to 100 mm, preferably 30 to 80 mm. The
length of the sealing cuboids 53 is preferably 500 to
1000 mm, preferably 600 to 800 mm, so that a plurality
of sealing cuboids 53 are expediently provided one
above the other in a sealing groove 47 of a connecting
shaped brick lla (fig. 9).
Moreover, the sealing cuboids 53 preferably consist of
lightweight refractory bricks and/or fireclay bricks
and/or aluminum oxide bricks and are produced by
pressing and/or casting.
Since the sealing cuboids 53 bear slidably and
sealingly over a large area with their sealing cuboid
sliding faces 56 at least partially against the
respective connecting groove side face 39, the carbon
grit used for the baking of anodes does not penetrate
through the slots 45 into the expansion joints 41, and
the movement of the cassette walls 7 in the cassette
wall longitudinal direction 35 under the thermally

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induced expansions and contractions is not impeded by
penetrating carbon grit. In this case, a long-term
uniform pressure force of the sealing cuboids 53
against the connecting groove side faces 39 is achieved
by the use of the elastic flexible fiber mats 51.
According to a further embodiment of the sealing
device, the connecting shaped bricks lla have in the
connecting end faces 100 in each case a vertically
extending U-shaped sealing cylinder groove 57 with a
semi-cylindrical cylinder groove bottom 58 and two
mutually parallel cylinder groove side faces 59, 60 in
the wide side 12 which adjoin these tangentially and
are perpendicular to the wide sides 12, 13.
In the assembled cassette chamber 1, the sealing
cylinder grooves 57, too, are arranged vertically in
alignment one above the other and lie on the side of
the slot 45. Moreover, the sealing cylinder grooves 57
are arranged in such a way that, even in the event of
the contraction of the cassette walls 7, they lie at
least half within the connecting grooves 36.
A cylindrical sealing rod 61 as a sealing element is
arranged in the sealing cylinder grooves 57 in each
case, for example, with a form fit or with a slight
press fit. A form fit means that the radius of the
sealing rods 61 corresponds to the radius of the
sealing cylinder grooves 57. In this case, the depth of
the sealing cylinder grooves 57 is less than the
diameter of the sealing rods 61, so that the sealing
rods 61 bear linearly against the respective connecting
groove side face 39 (linear contact) and seal off, so
that the carbon grit does not penetrate through the
slots 45 into the expansion joints 41. In the event of
a movement of the cassette wall 7 in the cassette wall
longitudinal direction 35 on account of the thermally
induced expansions and contractions, the sealing rods

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61 slide along on the connecting groove side faces 39
or roll on these, so that the sealing action is
maintained even during the movement of the cassette
walls 7.
The length of a sealing rod 61 in this case is
preferably 500 to 1000 mm, preferably 600 to 800 mm, so
that 1 to 10 sealing rods 61 are expediently likewise
provided one above the other in a sealing cylinder
groove 57 of a connecting shaped brick lla. The radius
of the sealing rods 61 is preferably 10 to 60 mm,
preferably 15 to 30 mm.
Moreover, the sealing rods 61 preferably consist of
fireclay and/or aluminum oxide and/or high alumina
and/or corundum and/or magnesium oxide and are produced
by casting and/or vibration.
Of course, it is in this case also within the scope of
the invention to provide a further sealing device which
seals off the gap 44 delimited by the wide side 13 and
the connecting groove side face 39, the gap 44 then
preferably having the same width as the slot 45 (not
illustrated).
Moreover, it is perfectly expedient to provide the
sealing grooves (47, 57) in the connecting groove side
faces (38, 39) instead of in the wide sides (12, 13),
so that the respective sealing element (53, 61)
sealingly bears against or slides along the wide sides
(12, 13) (not illustrated).
A further idea of the invention is likewise to provide
for the carbon grit, as an integral part of the
connecting device, a storage device which has, for
example, a repository or storage volume or oversize
volume or a storage free space which is provided as a
consequence of production or by virtue of assembly and

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in which a large quantity of carbon grit can collect
before it results in the blockage of the movement of
the cassettes wall 7. As a result, necessary repair
work is postponed and the useful life of the cassette
chamber 1 according to the invention is increased.
According to a third preferred embodiment of the
invention with regard to the connection of cassette
walls 7 and chamber longitudinal walls 3, 4, (fig. 15-
17), this is achieved, for example, in that the
connecting end faces 100 of the connecting shaped
bricks lla have in each case a vertically oriented
storage volume, in particular a vertically oriented
repository groove 62 with, for example, a trapezoidal
cross section and a depth of preferably 15 to 100 mm,
preferably 25 to 50 mm.
During operation, the carbon grit gradually penetrates
through the gaps 44 and slots 45 into the repository
groove 62, collects there and falls downward on account
of gravity in the repository grooves 62, so that the
carbon grit level in the repository grooves 62 rises
slowly from the bottom. In this case, the volume of the
repository grooves 62 always remains essentially
identical independently of the thermally induced
contractions and expansions of the cassette walls 7,
whereas the volume of the expansion joints 41 varies
with the constantly changing contractions and
expansions of the cassette walls 7. The volume of the
expansion joint is in this case defined or fixed in
each case by the connecting groove bottom 37, the
connecting groove side faces 38, 39 and the depth of
the expansion joint 41, that is to say the shortest
distance between the connecting groove end face 100 and
the connecting groove bottom 37.

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Preferably, the ratio of storage volume to expansion
joint volume in the repository grooves 62 is 30 to 80%,
preferably 40 to 60%, at room temperature.
In order to keep the amount of carbon grit penetrating
into the repository groove 62 per unit time as low as
possible, in each case a vertically extending ceramic
fiber mat strip 63 is provided in the slots 45.
According to a fourth preferred embodiment of the
invention (fig. 18, 19) with regard to the connection
of cassette walls 7 and chamber longitudinal walls 3,
4, the connecting shaped bricks lla are chamfered
laterally on the connecting end faces 100 in such a way
that in each case two oblique vertically extending
planar end edges 64, 65 which connect the end faces 16,
17 to the wide sides 12, 13 are formed.
In the assembled cassette chamber 1, the connecting end
faces 100 project into the connecting grooves 36 to an
extent such that a vertically extending storage volume
of essentially triangular cross section, a triangular
repository 66, 67, is formed on both sides of the
connecting shaped bricks lla in each case between one
of the two connecting groove side faces 38, 39, one of
the two end edges 64, 65 and the expansion joint 41. In
this case, the triangular repositories 66, 67 of the
connecting shaped bricks lia lie in each case one above
the other in alignment in the cassette walls 7.
The volume of the triangular repositories 66, 67 also
always remains essentially identical independently of
the thermally induced contractions and expansions of
the cassette walls 7.
Preferably, the ratio of storage volume to expansion
joint volume in the triangular repositories 66, 67 is

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in each case 30 to 80%, preferably 40 to 60%, at room
temperature.
In this embodiment of the invention, too, in each case
a ceramic fiber mat strip 63 is expediently provided
for sealing off in the slot 45 (not illustrated).
Alternatively to this, the end edges 64, 65 are, for
example, curved inwardly or designed concavely, so that
the storage volume is further increased (not
illustrated).
In order further to assist the lowering of the carbon
grit in the repository grooves 62, according to a fifth
embodiment of the invention with regard to the
connection of cassette walls 7 and chamber longitudinal
walls 3, 4, there is provision for configuring the
connecting end faces 100 in such a way that the
slipping off of the carbon grit in the repository
grooves 62 is promoted.
In order to achieve this, end faces 68, 69 laterally
delimiting the repository grooves 62 have a trapezoidal
profile, as seen from the side (fig. 20 - 22). The two
end faces 68, 69 in each case adjoin the top side 15
level with or on the same plane as a repository groove
bottom 70 and initially have in each case a planar
oblique sloping end face 71, 72 which forms with the
top side 15 an angle a of preferably 100 to 130 ,
preferably 105 to 120 . The sloping end face 71, 72 has
adjoining it in each case a likewise planar vertical
end face 73, 74 which has adjoining it in each case a
planar oblique overhang end face 75, 76 which runs out
on the underside 14, level with the repository groove
bottom 70, and forms with the underside 14 an angle
of preferably 100 to 130 , preferably 105 to 120 .

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Preferably, in this case, the sloping end faces 71, 72
and the overhang end faces 75, 76 have the same
gradients, that is to say the angles a and 0 are
expediently identical.
The vertical length of the vertical end faces 73, 74 is
preferably 200 to 600 mm, preferably 300 to 500 mm.
By means of the sloping end faces 71, 72, on the one
hand, the. reception volume for the carbon grit is
further increased and, on the other hand, the slipping
off of the carbon grit is assisted. The undercut
arising due to the overhang end faces 75, 76 also
brings about an increase in volume and, in
accompaniment with this, a higher storage capacity.
So that the carbon grit which has accumulated in the
repository grooves 62 can be removed between the baking
cycles, according to a sixth preferred embodiment of
the invention with regard to the connection of cassette
walls 7 and chamber longitudinal walls 3, 4 the
cassette chamber 1 according to the invention has one
or more suction extraction orifices 77 per cassette
wall 7 which connect the storage volumes, in particular
the repository grooves 62 or the expansion joints 41
(not illustrated), to the cassette space 8, so that the
carbon grit can be sucked away from the repository
grooves 62 in a simple way by means of the suction
extraction orifices 77 between the 14-day baking
cycles.
For this purpose, the connecting end face 100 is
chamfered or undercut in the lower region in such a way
as to form a planar incline 78 which extends from the
connecting end face 100 to the underside 14. In this
case, the incline 78 forms with the underside 14 an
angle y of preferably 30 to 60 , preferably 40 to 50
(fig. 26).

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In the assembled cassette chamber 1, the inclines 78
project partially beyond the connecting groove side
faces 38, 39, so that the suction extraction orifices
77 are delimited in each case essentially by the
incline 78, the top side 14 of the connecting shaped
brick lia arranged below it and a connecting groove
outer edge 79.
In order to promote the slipping off of the carbon grit
in the direction of the suction extraction orifices 77,
according to a seventh embodiment, illustrated in
fig. 28 - 30, of the invention with regard to the
connection of cassette walls 7 and chamber longitudinal
walls 3, 4, a slip-off wedge 80, preferably likewise
consisting of refractory concrete, is arranged below
the respective incline 78. This slip-off wedge 80 has a
planar wedge bottom 81, two wedge side faces 82, 83
perpendicular to this and a wedge rear wall 84,
likewise perpendicular to the wedge bottom 81 and to
the wedge side faces 82, 83, and a wedge front wall 85
parallel to said wedge rear wall. Moreover, the slip-
off wedge 80 has two slip-off faces 86, 87 which adjoin
the wedge side walls 82, 83 and which taper toward one
another in a roof-shaped or gable-shaped manner with
respect to the wedge bottom wall 81 and intersect one
another at an angle S of preferably 30 to 600,
preferably 40 to 50 . Moreover, the slip-off wedge 80
has two wedge ceiling walls 88, 89 which adjoin the
wedge rear wall 84 at right angles and likewise taper
toward one another in a roof-shaped or gable-shaped
manner.
Preferably, in this case, the slip-off wedge 80 is
fastened with its wedge rear wall 84 to the connecting
groove bottom 37 by means of adhesive bonding and/or
bricking-in and lies with its wedge bottom wall 81 on
the top side 15 of the connecting shaped brick lla

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arranged below it. Moreover, the slip-off wedge 80 is
dimensioned in such a way that its wedge side walls 82,
83 terminate flush with the connecting groove side
faces 38, 39 in the horizontal direction. The distance
between the two wedge side walls 82, 83 preferably
corresponds to the connecting groove width.
Alternatively to the embodiment described above, the
slip-off wedge 80 has a single planar slip-off face 90,
the gradient of which expediently corresponds in amount
to the gradient of the incline 78, so that both are
parallel to one another (fig. 28, 29).
According to an eighth embodiment of the invention,
with regard to the connection of cassette walls 7 and
chamber longitudinal walls 3, 4, the cassette chamber 1
according to the invention has in the cassette walls 7
draw-off ducts 91 which extend away from the connecting
end faces 100 through the connecting shaped brick lla
obliquely downward and issue in each case into the
first smoke gas duct 9, as seen from the connecting end
faces 100. The blow-out ducts to that extent flow-
connect the storage volumes, in the case illustrated
the triangular repositories 66, 67 and/or the expansion
joints 41, to the first smoke gas duct 9. In this case,
the cross section of the draw-off ducts 91 widens in a
funnel-shaped manner in the direction of the respective
smoke gas duct 9, so that the draw-off ducts 91 have a
conical profile. Preferably, a draw-off duct axis 92
forms with the vertical an angle E of 30 to 60 ,
preferably of 40 to 500, the draw-off duct axis 92
expediently running in the brick longitudinal mid-plane
10.
Moreover, a draw-off duct cone angle cp is preferably 10
to 30 , preferably 15 to 200.

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In this case, preferably 2 to 6, preferably 2 to 4
draw-off ducts 91 are present per connecting shaped
brick lla.
The reason for these draw-off ducts 91 is that the
smoke gases flowing from the top downward through the
smoke gas ducts 9 of the cassette walls 7 when the
refractory furnace is in operation generate in the
draw-off ducts 91 a vacuum such that the carbon grit
accumulated in the triangular repositories 66, 67
and/or in the expansion joints 41 is properly sucked
out or drawn off from the triangular repositories 66,
67 and/or the expansion joints 41 and blown out
together with the smoke gas.
In order to obtain this suction effect in the case of
an opposite direction of flow of the smoke gases from
the bottom upward through the smoke gas ducts 9, in
this case the draw-off ducts 91 are correspondingly
arranged so as to be mirror-inverted with respect to a
horizontal plane (not illustrated).
The draw-off ducts 91 thus in a particularly simple and
advantageous way have the effect that, while the
refractory furnace is in operation, the carbon grit is
sucked away continuously from the triangular
repositories 66, 67 or from the expansion joints 41, so
that a blockage of the movement of the cassette walls 7
is prevented.
It is, of course, also within the scope of the
invention to combine the various sealing devices and/or
the various storage devices and/or the suction
extraction orifices 77 and/or the draw-off ducts 91
with one another, for example to combine the draw-off
ducts 91 with the trapezoidal repository grooves 62 or
to provide both repository grooves 62 and triangular
repositories 66, 67.

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Moreover, the shaped bricks according to the invention
are pre-eminently suitable as building bricks for the
remaining refractory furnace walls, in particular the
chamber walls, smoke gas ducts then expediently
likewise being present in the chamber walls.
Finally, it must be pointed out that, by the cassette
chamber being configured according to the invention,
the barreling and destruction of the cassette walls,
presenting problems in the prior art, are prevented in
a particularly advantageous way.
This is achieved in terms of the configuration of the
cassette walls, on the one hand, by the use of
refractory concrete, in particular refractory concrete
of type ULCC, as material for the shaped bricks of the
cassette walls and, on the other hand, by the use of
large-format shaped bricks. The shaped bricks
consisting of refractory concrete possess outstanding
thermochemical, thermomechanical and physical
properties in both a reducing and an oxidizing
atmosphere, have, above all because of the low porosity
of refractory concrete, a very low gas permeability and
excellent resistance to the alkali fluorides contained
in the covering grit or in the "furnace atmosphere",
and can be produced very simply and cost-effectively
and with any desired three-dimensional shapes by means
of casting methods known per se. In particular, the
incorporation of the smoke gas ducts and of the
conically running draw-off ducts is possible very much
more simply in the large-format shaped bricks according
to the invention than in the small-format hydraulically
pressed fireclay bricks used according to the prior
art, since the respective ducts would extend over a
plurality of individual bricks and therefore,
inter alia, many different individual bricks would have
to be manufactured.

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However, the large format of the shaped bricks
according to the invention also contributes, in
addition to the better handling and the accompanying
quicker and easier mounting and repair without bricking
in, also to a minimization of the barreling and
destruction of the cassette walls. Owing to the smaller
number of wall joints, as seen over the entire cassette
wall, a relatively smaller amount of carbon grit
penetrates into the cassette wall, and temperature is
distributed more uniformly over the entire cassette
wall, since each joint forms a heat bridge. Thermally
induced stresses in the cassette wall are also avoided
as a result. Moreover, the connection of the shaped
bricks arranged one above the other by means of the
groove/tongue connection is also configured in such a
way that the connection is maintained reliably and in a
gastight manner in spite of thermally induced
expansions and contractions. Crack formation in the
joints cannot occur, as it does in the prior art.
Moreover, the cassette wall consisting of the large-
format shaped bricks according to the invention
possesses a better moment of inertia and, in
accompaniment with this, higher stability.
With regard to the tie-up of the cassette walls to the
chamber walls, the barreling and the accompanying
destruction of the cassette walls are likewise
prevented in various ways.
By means of the sealing devices illustrated, the
situation is prevented in a particularly simple and
advantageous way where the carbon grit penetrates via
the slots and gaps into the expansion joints, and
therefore the expansion joint is not filled over the
course of time with the carbon grit during baking. The
function of the expansion joint is thus maintained

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permanently, so that the thermally induced expansions
and contractions of the cassette walls are compensated
by the expansion joint and barreling of the cassette
walls no longer occurs.
The storage devices provided as a consequence of
production perform a type of buffer function, in that
they receive a large quantity of carbon grit which
penetrates through the slots and gaps before the
expansion joint is clogged and blocked with carbon
grit. If the storage devices are combined with the
suction extraction devices (suction extraction orifice,
draw-off ducts) according to the invention, by means of
which the accumulated carbon grit is sucked away from
the repositories, for example, in a simple way during
the regular cleaning of the cassette chamber between
the 14-day baking cycles, or is blown out continuously
and automatically with the smoke gases during baking,
the clogging of the expansion joints is likewise
prevented permanently in a particularly simple way.
Consequently, by means of the cassette chamber
according to the invention, by suitable choice of
material and size of the shaped bricks and owing to the
improved tie-up of the cassette walls to the chamber
walls, the useful life of a refractory furnace is
markedly increased, and markedly less repair work which
is merely simpler occurs, with the result that
production stoppages fall drastically and therefore the
production costs are markedly reduced.

Dessin représentatif