WO2003006905A1

WO2003006905A1 - Ring-type baking furnace

Info

Publication number: WO2003006905A1
Application number: PCT/EP2002/006643
Authority: WO
Inventors: Peter Van Varik; Willem Venus; Peter Sommer
Original assignee: Alcan Technology & Management Ltd.
Priority date: 2001-07-10
Filing date: 2002-06-17
Publication date: 2003-01-23

Abstract

The invention relates to a ring-type baking furnace (1) having two parallel rows of baking chambers which are situated in trough-shaped constructions (2a, 2b), where the trough-shaped constructions (2a, 2b) exhibit outer walls (3a, 3b) and are separated from each other by a partition (100). The partition (100) contains two inner walls (4a, 4b) which form an interlying space (101). The ring-type baking furnace (1) is characterised by way of its modular construction with outer wall elements fitted together to form outer walls (3a, 3b) and inner wall elements fitted together to form inner walls (4a, 4b).

Description

Ring-Type Baking Furnace

The invention relates to a ring-type baking furnace for manufacturing shaped blocks containing carbon, in particular electrodes for aluminium molten flux electrolysis, containing two rows of baking chambers which are situated in trough- shaped constructions running parallel to each other, whereby the trough-shaped constructions exhibit outer walls and are separated from each other by a partition; the invention relates also to a process for manufacturing such a ring-type baking furnace.

Multi-chamber furnaces for baking carbon blocks, employed in particular as anodes for the electrolytic production of aluminium, are known. They are made up of a plurality of stationary chambers which are arranged in one or more rows and are usually arranged in trough-shaped, basin-like or tub-shaped constructions.

The baking chambers are delimited with respect to each other by way of walls running perpendicular to the rows and to the direction of fire progression and with respect to the outside by way of the outer walls of the trough-shaped constructions.

The baking chambers are also sub-divided into compartments by way of fire shaft walls running in the direction of the rows and in the direction of fire progression. These vertical compartments accommodate the carbon blocks - whereby, as a rule, a plurality of such carbon blocks is stacked one on top of the other in each compartment. Depending on the design the chambers are open or are closed off at the top by removable covers.

The compartments are normally lined on the inside of the outer walls and on the floor with thermally insulating material such as e.g. insulating stones such as foamed bricks, rounded-off stones, moler stone or calcium silicate bricks. The individual compartments or firing shaft walls are of refractory bricks such as fireclay bricks.

Ring-type baking furnaces are used widely. These are characterised by way of the parallel arrangement of two rows of baking chambers which are arranged in trough- shaped constructions and separated by means of a partition. The firing shaft systems of both rows of baking chambers are bridged at the ends of the rows of baking cham-bers, with the result that the firing shaft systems have a ring shape. The bridging is normally effected such that all firing shafts join up to a collective channel or are diverted in groups. Separate diversion of each individual firing shaft is of course also conceivable.

Differentiation is made between open ring-type baking furnaces and closed ring- type baking furnaces, whereby the difference lies in the constructive details of the chamber walls and in the manner in which the hot air is circulated around the compartments. The basic principle of two parallel rows of baking chambers arranged in a trough-shaped construction and bridged at the end faces is the same in both cases.

The rows of baking chambers in a ring-type baking furnace are normally built up in parallel, trough-shaped constructions which are rectangular in shape. The trough- shaped constructions stand on a load-bearing foundation and feature outer and end walls. On their inner lying sides the both trough-shaped contructions of a ring- type baking furnace may feature separate side walls which are spaced apart or may feature a common partition in the form of a integral inner wall. The walls and the floor or the foundation of the trough-shaped constructions are normally made of concrete.

The effects of heat from the firing process can be damaging to the trough-shaped constructions and to the furnace lining. Measures must be taken therefore to protect the concrete structure from any long term damage. This is done on the one hand, as already mentioned, by cladding the inner facing of the walls and the floor with refractory, thermally insulating material. On the other hand this is done by active or passive cooling of the walls, in particular the inner walls or partition on the sides turned away from the baking chambers and by active or passive cooling the floor.

If the trough-shaped constructions have inner walls that are separated and spaced apart from each other, then these are cooled by active or passive cooling of the interlying space. If the trough-shaped constructions have a common integral inner wall, then this exhibits spaces therein e.g. in the form of cooling channels for circulation of a cooling medium. In the case of small interlying spaces and integral inner walls with spaces therein, it is necessary to have active cooling in order to have efficient removal of heat. This is achieved e.g. by forced circulation of air through the interlying spaces or wall spaces by means of ventilators. A typical trough-shaped construction to accommodate a series of baking chambers has a length e.g. of 100 - 200 m, in particular 70 - 200 m, a breadth of around 11 - 13 m, in particular 9 - 13 m, and a height of around 4 - 6 m. The overall breadth of a ring-type baking furnace is e.g. 25 - 30 m. The dimensions are only nominal values, not exact dimensions.

The production of carbon blocks involves shaping into blocks - in a press or vibrating device - a dough-like mixture of a mass of petroleum coke, anthracite, soot or graphite containing a binder such as tar and/or pitch, and then transferring these blocks to the compartments of the baking furnace. These green-strength carbon blocks are stacked one on top of the other in the chambers of the baking furnace. The shaped blocks are embedded completely in a filler powder e.g. of coke such as petroleum coke or anthracite in order to prevent the blocks from sticking to each other during the heating process and to prevent deformation and, by providing an atmosphere that is as non-oxidising as possible, to avoid burning off of the charge in the upper temperature range of the baking process. This way the shaped blocks stacked on top of each other in the compartments are separated completely from each other and from the firing shaft walls and the base.

The baking of the anodes is carried out indirectly by heating the firing shafts with external mobile burners. During baking, several baking chambers are grouped together as a unit or so called "fire" which is connected via a waste gas extractor to a waste gas pipe-line which normally runs round the whole furnace. In general a so called fire comprises a sealing chamber, a pre-heat chamber, a heating zone of about three chambers and a cooling zone of about six chambers. The shaped blocks to be baked are first pre-heated, then exposed to the high temperature of the firing region and finally cooled in the cooling zone.

The number of chambers taken as a group forming a so called fire depends both on the geometry of the compartments and the firing shafts and on the manner of baking. The number of fires on the other hand depends on the size of the furnace i.e. on the number of chambers.

As the baking process progresses the fires move cyclically and - in a manner - continuously round the furnace. During baking the binder is converted to coke by means of which the desired mechanical and electrical properties are achieved. The interaction with the carbon containing powder enables the oxidation of the carbon block to be prevented during the baking process.

The heating is carried out as a rule using gas, oil or liquid petroleum gas (LPG). The baking process lasts several days, whereby the temperature of the carbon blocks reaches 1100°C for a period of time.

The baked shaped blocks are employed e.g. as electrodes, in particular as anodes for aluminium molten flux electrolyisis according to the Hall-Heroult process.

The service life of such ring-type baking furnaces is limited, with the result that they must be completely renewed after some years of service. Apart from replacement and reconstruction of the baking chambers, maintenance as a rule also includes renewal of the trough-shaped construction. In particular the inner walls or partition, which are especially exposed to high thermal loads, must normally be replaced and built up anew.

During such replacement work production should be impaired as little as possible - in particular not interrupted - therefore efforts are made to keep the time for construction work as short as possible. Of course also in the case of the installation of new ring-type baking furnaces, it is desirable to be able to put them into service after the shortest possible construction period.

The object of the invention is, therefore, to propose a ring-type baking furnace which requires a relatively short period of on-site time for its construction. Further, as a result of improvements in design, the ring-type furnace and in particular its partition should achieve the longest possible service life.

That objective is achieved by way of the invention in that the trough-shaped constructions exhibit, at least in part, a modular structure and the partition contains two parallel inner walls which are spaced apart and form an interlying space, and the inner walls are made up of prefabricated inner wall elements which stand arranged side-by-side on the foundation, base or base elements, and are formed out of or contain a concrete type of material.

Usefully, a central longitudinal trench is provided or created, running parallel to and between the inner walls, in the foundation or base. Cooling channels, e.g. in the form of pipes running transverse to the partition, are created in or concreted into the foundation or base of the trough-shaped constructions.

The cooling channels discharge into the sides of the central longitudinal trench at the central longitudinal axis (A) of the ring-type baking furnace and emerge from the foundation or base at the outer sides of the ring-type baking furnace.

The inner wall interlying space is preferably continuous i.e. uninterrupted in the longitudinal direction of the ring-type baking furnace. Means for cooling the interlying space are provided in the interlying space and/or in the region of the front ends of the interlying space i.e. in the region of the end walls of the ring-type furnace. The means are preferably ventilators for creating a stream of gas or air in the interlying space.

The interlying space may be closed off at the top by means of covering elements. The covering elements bridge the inner walls transverse to their longitudinal edges. On the one hand, the covering elements stabilise the inner walls from side-ways displacement, and at the same time serve as a work-platform between the two rows of baking chambers. The covering elements usefully lie on the supporting surfaces for them or on the inner wall elements. The covering elements may exhibit openings for the purpose of circulating air; they are however preferably without openings.

In a preferred version the trough-shaped constructions contain outer walls made up of prefabricated outer wall elements on the foundation, base or base elements. The outer walls are made up of outer wall elements arranged and fitted together at the sides.

The prefabricated outer and/or inner wall elements of a first version preferably feature integral feet. The feet are in the form of foot-like broadenings at one or two sides of their base. They should guarantee the, preferably, non-anchored stability of the wall elements. Integral means that the parts in question e.g. wall elements and feet are made of one piece.

In another version of the invention, the prefabricated outer and/or inner wall elements contain recesses in their bottom end faces in the form of slit-shaped openings, bored holes or channels to accommodate anchoring elements, in par- ticular reinforcing rods such as iron reinforcing rods. The above mentioned wall elements in this version are mounted on anchoring elements which are set into and secured, partially, i.e. at one end, to the foundation, the base or base elements. Set means here that the anchoring elements are arranged engaging in the recesses in the wall elements. The anchoring elements are likewise secured in the recesses. Secured means that the anchoring elements are securely and permanently joined to the foundation resp. to the wall element.

The anchoring elements introduced into the recesses in the wall elements are preferably secured in the wall elements by means of attaching material introduced into the recesses via openings at the sides. The openings may be provided in the sides of the inner wall elements facing the baking chambers and/or facing the interlying space. It is self evident that the openings for filling purposes should be connected to the recesses. The attaching material is preferably of a concrete or cement mixture which may be introduced in the fluid state and subsequently hardened.

Of course wall elements exhibiting supporting feet may also be anchored to the foundation, base or base elements in the above described or any other manner using anchoring elements, in particular reinforcing rods.

The partition may also contain base elements. Thereby, the inner wall elements are preferably arranged with their downward facing end faces on the central base elements. The inner wall elements may stand on feet on the central base elements and/or may be securely attached to the central base elements via anchoring elements. The anchoring elements for this are attached or fixed at one end in the central base elements and at the other end in the recesses in the bottom end faces of the inner wall elements.

In a preferred version the partition contains central base elements situated over the central longitudinal trench. The central base elements thereby cover the central longitudinal trench, whereby channel-type openings in the central base elements, in particular vertical channel-type openings ensure that an exchange of gas can take place between the central longitudinal trench and the interlying space in the inner wall. The inner wall elements may be arranged either on or beside the central base elements. The ring-type baking furnace according to the invention preferably exhibits dimensions of the orders of magnitude mentioned at the start. The inner wall space usefully has a breadth i.e. dimension transverse to the longitudinal axis of the furnace, of 30 - 300 cm. The breadth of the inner wall space is preferably 40 - 200 cm, in particular 50 - 150 cm. The wall thickness of the outer and inner wall elements is e.g. 15 - 35 cm, in particular 20 - 30 cm. The length of the outer and inner wall elements i.e. in the direction of the furnace longitudinal axis, may e.g. amount to 300 - 1000 cm, in particular 400 - 800 cm.

The outer and inner wall elements, the base elements and the covering elements are usefully made of a concrete-type of material, preferably reinforced concrete, in particular concrete reinforced with steel. The reinforcement is preferably in the form of iron rods or grids of iron rods. The elements mentioned are preferably prefabricated concrete parts made e.g. by casting methods.

In a further development of the invention also the end walls of the ring-type baking furnace are made of end wall elements arranged and fitted together at the sides. The end wall elements can be secured on the foundation using the same methods as the outer and inner wall elements i.e. with supporting feet and/or anchoring elements, in the manner described above. The end wall elements preferably have the same dimensions as the outer and inner wall elements. The end wall elements are usefully made of a concrete type of material, preferably reinforced concrete, in particular concrete reinforced with steel or iron. The elements mentioned are preferably prefabricated concrete parts.

The wall elements are usefully fitted together e.g. by filling the joints with concrete.

The trough-shaped construction is preferably built up on a load bearing foundation, whereby the foundation may be multi-layered. The foundation may therefore contain a series of layers of different kinds of concrete such as lean concrete, gravel concrete and/or insulating concrete. Further, it is also possible to have unattached layers or intermediate layers in the foundation e.g. of sand or gravel. Above the foundation, covering the whole or part of the base area, there may be one or more base elements or base slabs of concrete, in particular of concrete reinforced with steel or iron. The base slab or slabs may also be part of the foundation. The exact structure of the foundation is of secondary importance for the present invention, for which reason detailed descriptions thereof will be omitted here.

In addition to the cooling channels further pipes may be provided in the foundation such as facilities for measuring e.g. temperature or for tension rods.

For cooling the inner walls air is preferably drawn in by the above mentioned ventilators in the region of the end walls of the trough-shaped construction and forced into the interlying space in the inner wall. As the partition is preferably closed off by covering elements, the air thus supplied passes via the central longitudinal trench and through the cooling channels to the outer side of the ring-type baking furnace, whereby the stream of air exits to the atmosphere via the cooling channels on the outer longitudinal trenches at the side of the baking furnace. The stream of air produced by the ventilators cools the inner walls by passing through the interlying space in the inner walls and also the base or foundation on passing through the cooling channels.

Usefully, the outer walls are also cooled, whereby the cooling can take place by natural circulation of air on the outer side of the walls. The cooling may also take place by forced air cooling generated by ventilators.

Another version is such that the cooling of the base and the partition takes place in separate systems. The structure of the ring-type baking furnace is essentially that in the versions described above with the exception that the cooling channels in the foundation of the ring-type baking furnace run from one side to the other side without any connection to the inner wall space.

The invention relates also to a process for manufacturing a ring-type baking furnace with two rows of baking chambers which are situated in trough-shaped, tub-shaped or basin-like constructions running parallel to each other, whereby the trough-shaped con-structions exhibit outer walls and are separated from each other by a partition.

The manufacturing process is characterised in that the partition contains two inner walls that run parallel to each other, are spaced apart and form an interlying space, and each inner wall is formed by fitting inner wall elements together at the sides; the inner wall elements are securely situated on the foundation, base or base elements via integral feet and/or are anchored in the foundation, base or base elements via anchoring elements, and the interlying space is closed off towards the top by means of covering elements bridging the inner walls transverse to its longitudinal edges.

In a preferred version of the invention the outer walls are also formed by fitting together outer wall elements at the sides, whereby the outer wall elements are securely situated on the foundation, base or base elements via feet and/or are anchored in the foundation, base or base elements via anchoring elements.

In a further development of the invention the outer and/or inner wall elements are securely situated in the foundation, base or base elements via anchoring elements, in particular reinforcing rods such as iron reinforcement, whereby the wall elements contain, in their bottom end faces, recesses in the form of slit-shaped openings, holes or channels to accommodate the anchoring elements, and at one end the anchoring elements are set into the foundation, base or base elements, and the pre-fabricated wall elements are set onto the foundation, base or base elements, whereby the anchoring elements engage at the other end in the recesses in the wall elements.

In a special further development attachment material, in particular binding and hardenable material preferably in fluid form, is charged into the recesses via side openings in the wall elements to fix the anchoring elements in the recesses.

The ring-type baking furnace according to the invention, built in a modular manner, and the process for manufacturing such a furnace permits fast construction or assembly of the ring-type baking furnace. Furthermore, the structure of the partition according to the invention permits more efficient cooling of the inner walls, which considerably extends the service life of the individual elements of the trough- shaped construction and the lining.

The invention is explained in greater detail by way of example and with reference to the accompanying drawings. These show:

Fig. 1 : schematic cross-sectional view of the trough-shaped constructions of a first ring-type baking furnace; Fig. 2: schematic cross-sectional view of the trough-shaped constructions of a second ring-type baking furnace;

Fig. 3: perspective view of part of the central base element;

Fig. 4: perspective view of part of a partition during construction; Fig. 5: perspective view of part of the central base element over the central longitudinal trench;

Fig. 6: perspective view of part of a ring-type baking furnace during construction;

Fig. 7: schematic perspective of a ring-type baking furnace shown in plan view; Fig. 8: schematic cross-sectional view of a trough-shaped construction of a first ring-type baking furnace featuring baking chambers;

Fig. 9: schematic cross-sectional view through another version of a partition.

The ring-type baking 1 furnace shown in figure 1 contains two trough-shaped con- structions 2a, 2b each accommodating a row of baking chambers 51 (see also figure 7). The trough-shaped constructions 2a, 2b contain outer walls 3a, 3b (see fig. 6) made up of pre-fabricated wall elements 102 and are delimited from each other by a partition 100. The partition contains two inner walls 4a, 4b set a distance from each other apart and forming an inner wall space 101. Like the partition 110, shown in figure 4, the inner walls are made up of pre-fabricated inner wall elements. Towards the top the inner wall space 101 is bridged over by a plurality of plate-shaped, pre-fabricated covering elements 8 which run transverse to the longitudinal edges of the inner walls 4a, 4b.

In the region of the upper ends of the inner wall elements of the inner walls 4a, 4b the inner wall elements feature a balcony type projection 14a, 14b on the side facing the inner wall space 101 on which the plate-shaped covering elements 8 rest.

The outer and inner wall elements of the outer and inner walls 3a, 3b, 4a, 4b exhibit at their bottom end regions integral feet 11 a-d in the form of foot-like broadening at both sides by means of which the wall elements 3a, 3b, 4a, 4b are set on the foundation 6. A layer 5 of insulating concrete is provided on the foundation between each outer and inner wall of a trough-like construction.

Further, the outer and inner wall elements also feature at their top ends projections 12a, 12b, 13a, 13b in the form of a nose, in each case pointing towards the baking furnace. The projection is preferably an integral part of the outer and/or inner wall element and serves the purpose of covering an insulating layer on the inside e.g. of insulating stones such as foamed stones, rounded-off stones, molar or calcium silicate stones.

A central longitudinal trench 16, 36 is provided in the foundation 6, 26 between the inner walls 4a, 4b, 24a, 24b of the partition 100, 110 or along the central longitudinal axis A of the ring-shaped chamber furnace 1 , 21. Cooling channels 7, 27 in the form of pipes in the foundation 6, 26, and running transverse to the central longitudinal axis, join up to the longitudinal trench 16, 36 at its sides. Each of the cooling channels runs out into a longitudinal trench 17, 37 situated at the side of the ring-shaped baking furnace and running parallel to the outer wall 3a, 3b, 23a, 23b (Fig. 1 and 2).

The second version of a ring-shaped chamber type furnace 21 - shown in figure 2 - contains two trough-like constructions 22a, 22b (see also Fig. 7) each of which accommodates a row of baking chambers 51. The trough-like constructions 22a, 22b contain outer walls 23a, 23b made up of outer wall elements 102 (see also fig. 6) and are delimited with respect to each other by a partition 110. The partition contains two inner walls 24a, 24b spaced a distance apart and forming an interlying inner wall space 101. The inner walls are made up of inner wall elements 9 (see figure 4). Towards the top the inner wall space 101 is covered over by a plurality of covering elements 28 which bridge the inner walls 24a, 24b transverse to their longitudinal edges.

The covering element 28 is in the form of a hat-shaped section which projects into the inner wall space and features two flanges at the side that rest on the upper ends of the walls. The flanges at the side project a given distance over the inner walls 24a, 24b thereby forming a nose shaped projection 38a, 38b.

Situated over the central longitudinal trench 36 and covering it are central covering elements 33 (see also figure 6) which contain vertical openings 32 to ensure exchange of gas between the inner wall space and the longitudinal trench 36. The central base elements 33 contain an elevated central section 39 which acts as spacer. The base elements further feature two flanges 40 joining the central section 39 at each side by forming a terrace 41. Reinforcing rods 31 are embedded and anchored at one end in the free side flanges 40 (see also Fig. 3). The inner wall elements 9 are mounted on the side flanges 40 and abut the terrace 41 , and are such that the reinforcing rods 31 projecting out of the central base elements 33 engage in recesses in the bottom end faces of the inner wall elements 9. The inner wall elements 9 contain holes 34 at the sides, in line with the said recesses; these holes 34 enable material for fixing the reinforcing rods 31 in place to be poured into the inner wall elements after the inner wall elements have been mounted and positioned.

Towards their top end, the outer wall elements 102 exhibit a projection 29a, 29b in the form of a nose pointing towards the baking chambers. The projection is usefully an integral part of the outer wall elements 102 and, as the projections 38a, 38b of the covering elements 28, serve to cover a layer of insulation on the walls.

A layer of insulating concrete 25 is provided on the foundation 26 between the outer and inner wall of the trough-shaped construction 22a, 22b.

The cooling of the inner walls is achieved by means of ventilator fans 10, 30 which are situated in the inner wall space 101 and which suck air from the ends of the trough-shaped construction. As the partition 100, 110 is closed at the top, the air fed in escapes to the outside via the longitudinal trench 16, 36 through the cooling channels 7, 27. The stream of air escapes from the cooling channels and enters the outside atmosphere via the longitudinal trenches 17, 37 on the outside. The stream of air 115 generated by the ventilator fans 10, 30 cools, on the one hand, by passing through the interlying space the inner walls 4a, 4b, 24a, 24b, and also by flowing along the cooling channels 7, 27 the base or foundation 6, 26. In the second version of ring-type baking furnaces 21 (Fig. 2) the stream of air flows out of the inner wall space 101 through the channel-type passageways 32 in the central base element 33 into the central longitudinal trench 36 and out through the cooling channels 27.

The trough-shaped constructions of the ring-type baking furnaces 1 , 21 according to the first and second versions are closed off at the ends by end walls 35 (Figs. 4 and 6).

The trough-shaped construction 2a fitted out with baking chambers as in figure 8 contains an insulating layer 56 on the outer and inner wall and on the floor facing the baking chambers. The insulating layers on the walls are covered over at the top by the described projection in the wall element. The projection is usefully an integral part of the outer and inner wall elements or, in the case of a partition in a different design also by the covering element (see also figure 2). The baking chambers are subdivided by the firing shafts 54 into individual compartments 52 accom-modating the shaped blocks 55 to be baked.

Figure 7 shows a schematic arrangement of a ring-type baking furnace 1 , 21 in plan view. The trough-shaped constructions 2a, 2b, 22a, 22b contain baking chambers 51 arranged in two rows which are again subdivided into compartments 52. Firing shafts 54 divide the baking chambers 51 in the longitudinal direction into the individual compartments 52. The baking chambers 51 are separated in the transverse direction by transverse walls 53.

The partition 120 according to figure 9 differs from the examples shown in figures 1 and 2 essentially in that the air-cooling of the inner wall space 101 is separate from the air-cooling of the base of the trough-shaped construction. The inner walls 124a and 124b are, analogous to the example shown in figure 2, anchored to the central base elements 123 by means of reinforcing rods 31. Unlike the example in figure 2, it is not necessary to have channel-type openings in the base elements 123. Analogous to the version shown in figure 1 , the inner walls 124a, 124b may also be set on the trough floor by means of supporting feet.

For air-cooling purposes air is sucked in from the ends of the trough-shaped construction by ventilator fans 10 and expelled to the surroundings via openings in the upper closure part of the partition 120. The upper closure part of the partition 120 may contain covering elements 128 as in examples 1 and 2, whereby in this version the covering elements 128 feature openings for air to escape. Further, covering elements may be dispensed, with the result that the upper part contains an opening slit running parallel to the central longitudinal axis A.

Set into the foundation 126 and running transverse to the central longitudinal axis A are cooling channels 127 which run uninterrupted from one side of the ring-type baking furnace to its opposite side. Provided on one side of the ring-type baking furnace are means, preferably ventilators, for feeding a cooling medium, preferably air, into the cooling channels (not shown here). The cooling medium circulating in the cooling channels 127 exits the cooling channels 127 on the opposite side of the ring-type baking furnace.

Claims

1. Ring-type baking furnace (1) for manufacturing shaped blocks containing carbon, in particular electrodes for aluminium molten flux electrolysis, containing two parallel rows of baking chambers (51) which are arranged in trough-shaped constructions (2a, 2b), where the trough-shaped constructions (2a, 2b) exhibit outer walls (3a, 3b) and are separated from each other by a partition (100), characterised in that, the trough-shaped constructions (2a, 2b) exhibit, at least in part, a modular structure and the partition (100) contains two parallel inner walls (4a, 4b) which are spaced apart and form an interlying space (101), and the inner walls (4a, 4b) are made up of prefabricated inner wall elements (9) which stand arranged on the foundation (6), base or base elements and are fitted together side-by- side, and the inner wall elements (9) are formed out of or contain a concrete type of material.

2. Ring-type baking furnace according to claim 1 , characterised in that, a central longitudinal trench (16), running parallel to and between the inner walls (4a, 4b), is provided in the foundation (6) or base, and cooling channels (7), in particular pipes, running transverse to the partition (100), are provided in the foundation (6) or base of the trough-shaped constructions (2a, 2b), and the cooling channels (7) discharge into the sides of the central longitudinal trench (16) at the central longitudinal axis (A) of the ring-type baking furnace and emerge from the foundation (6) or base at the outer side of the ring-type baking furnace (1).

3. Ring-type baking furnace according to one of the claims 1 to 2, characterised in that ventilators (10) for cooling the interlying space (101) are provided in the interlying space (101) or in the region of the front ends of the interlying space (101).

4. Ring-type baking furnace according to one of the claims 1 to 3, characterised in that the interlying space (101) is closed off at the top by means of one or more covering elements (8) made of or containing a concrete-type material bridging the inner walls (4a, 4b) transverse to the longitudinal edges of the inner walls.

5. Ring-type baking furnace according to one of the claims 1 to 4, characterised in that the outer walls (3a, 3b) are made up of prefabricated outer wall elements (102), made of or contain a concrete-type material, which are arranged and

5 fitted together at the sides on the foundation (6) or base or base elements.

6. Ring-type baking furnace according to one of the claims 1 to 5, characterised in that the prefabricated outer and/or inner walls elements (3a, 3b, 4a, 4b) exhibit integral feet (11a-d) in the form of foot-like broadenings at one or both sides of

10 their base.

7. Ring-type baking furnace according to one of the claims 1 to 6, characterised in that at the bottom end faces, the prefabricated outer and/or inner wall elements (24a, 24b) contain recesses in the form of slit-shaped openings, bored holes or

15 channels to accommodate anchoring elements (31), in particular reinforcing rods, and the wall elements (24a, 24b) are set on anchoring elements (31) which are partially set into and secured to the foundation, the base or base elements (33), whereby the anchoring elements (31) are arranged engaging in the recesses in the wall elements (24a, 24b).

20

8. Ring-type baking furnace according to claim 7, characterised in that the anchoring elements (31) introduced into the recesses in the wall elements (24a, 24b) are secured in the wall elements (24a, 24b) by means of attaching material, in particular concrete, introduced into the recesses via openings (34)

25 at the sides.

9. Ring-type baking furnace according to one of the claims 1 to 8, characterised in that the partition (110) contains central base elements (33) which are situated on the central longitudinal trench (36) where the base elements are of or

30 contain a concrete type of material, whereby the inner wall elements (9) are situated on or beside the base elements (33), and the interlying space (101) is connected via channel-shaped openings (32) in the central base elements (33) to the central longitudinal trench (36) such that exchange of gas can take place.

35 10. Ring-type baking furnace according to claim 9, characterised in that the inner wall elements (24a, 24b) are securely connected to the central base elements (33), whereby the connection is made by anchoring elements (31), in particular reinforcing rods, fixed into both the base elements (33) and the recesses in the bottom end faces of the inner wall elements (24a, 24b).

11. Process for manufacturing a ring-type baking furnace containing two rows of 5 burning chambers (51) which are situated in trough-shaped constructions (2a,

2b) running parallel to each other, whereby the trough-shaped constructions (2a, 2b) exhibit outer walls (3a, 3b) and are separated from each other by a partition (100), this according to claim 1 , characterised in that,

10 the partition (100) contains two inner walls (4a, 4b) that run parallel to each other, are spaced apart and form an interlying space (101), and each inner wall is formed by fitting inner wall elements (9) together at the sides, and the inner wall elements (9) are securely situated on the foundation (6), base or base elements via integral feet (11b, 11c) and/or are anchored in the foundation

15 (26), base or base elements via anchoring elements (31), and the interlying space (101) is closed off towards the top by means of one or more covering elements (8) bridging the inner walls transverse to its longitudinal edges.

12. Process according to claim 11 , characterised in that the outer walls (23a, 23b) 20 are formed by fitting together outer wall elements (102) at the sides, and the outer wall elements (102) are securely situated on the foundation, base or base elements via integral feet (11a, 11d) and/or are anchored in the foundation, base or base elements via anchoring elements.

25 13. Process according to one of the claims 11 to 12, characterised in that the outer and/or inner wall elements (24a, 24b) are securely situated in the foundation (26), base or base elements via anchoring elements (31), in particular reinforcing rods, and the wall elements (24a, 24b) contain, in their bottom end faces, recesses in the form of slit-shaped openings, holes or channels to accommo-

30 date the anchoring elements (31), and at one end the anchoring elements are inset into the foundation (26), base or in base elements, and the pre-fabricated wall elements (24a, 24b) are set onto the foundation (26), base or base elements, whereby the anchoring elements (31) engage at the other end in the recesses in the wall elements (24a, 24b), and attachment material for fixing the

35 anchoring elements (31) is charged into the recesses via side openings (34) in the wall elements (24a, 24b).