NO313897B1 - Wall structure for use in a stove or equivalent and method of forming the same - Google Patents

Abstract

The present invention concerns a wall structure and a method for constructing such an anchored wall structure. The wall structure is designed for use in a furnace or the similar, where the structure is exposed to cyclical thermal load. The structure consists of a row of individual elements which are placed in the longitudinal direction of the structure and are arranged in one or more courses, one resting on the other. The individual elements may consist of bricks of refractory material and the wall structure may also be provided with internal flue gas ducts. The wall structure is also designed to be able to compensate for longitudinal changes and any vertical changes as a consequence of cyclical thermal load. The wall structure's longitudinal changes are compensated for in a connection (2) arranged at least one end of the wall structure. The structure's individual elements are fixed to each other in the horizontal direction by means of mutually interacting contact elements. This produces a structure which remains stable after repeated thermal cycles, and costs related to restoration and stoppages can be reduced.

Description

The present invention relates to a wall construction for use in an incinerator or similar, for example an incinerator for calcining carbon bodies. The invention also relates to a method for forming such a wall structure. In particular, but not exclusively, the invention relates to walls or partial walls with internal flue gas ducts.

Combustion furnaces for the calcination of carbon anodes used in the production of aluminum according to the Hall-Héroult process can be constructed with several chambers arranged in two parallel rows. Such furnaces have a firing cycle that is moved relative to the chambers as the carbon material is calcined. The chambers are successively connected to each other with channels to be able to conduct hot combustion gas or flue gas through the furnace structure. Each chamber can be divided into several smaller chambers using dividing walls or so-called cassette walls. These dividing walls are equipped with several flue gas channels through which hot gas is conducted, in order to efficiently distribute heat to objects placed in the chambers so that the calcination process is as homogeneous as possible. A problem with such ovens, where the dividing walls can have an extent of several meters both vertically and horizontally, is that the walls lose their parallelism over time as a result of heating/cooling cycles with large temperature differences. In the worst case, bulging and sagging can cause problems with operating the oven in a satisfactory manner. This is due to leakage and fire or because it can be difficult to insert/remove objects as a result of large geometric deviations in the chambers.

WO 92/22780 relates to a wall construction for use in an oven, where expansion joints are arranged between segments in the wall. According to this solution, expansion and contraction movements must be accommodated in the expansion joint in each individual layer of segments. If the joints in all layers are aligned along the same vertical axis, this continuous joint can contribute to unwanted instability in the wall. On the other hand, if the joints in each layer are mutually offset in relation to each other, this can reduce the number of flue gas channels that can be obtained in the wall, and thus reduce the wall's ability to transfer heat.

CH 258544 shows an incinerator where a dividing wall can include flue gas channels (fig. 3). In this solution, a longitudinal change of the dividing wall is sought as a result of thermal heating/cooling absorbed in vertical joints between each stone while the ends of the wall are firmly clamped. One problem that will become apparent over time when using this principle for expansion/contraction is that particles from material that fills the oven can settle into the joints and completely or partially prevent the intended expansion. If the wall has a certain clearance in its attachment to the rest of the structure in the oven, this clearance will gradually be used up as the partial wall gets a permanent extension as a result of the aforementioned mechanism. Over time, a construction of this type could therefore bulge out and lose its parallelism. Further problems that can occur are that rock can be completely or partially crushed by the necessary expansion not being allowed after a given number of thermal cycles. A subsequent erosion of stone can thus occur, which will entail the need for costly remedial work as well as put the furnace completely or partially out of operation for a period.

With the present invention, the above-mentioned problems can be completely or partially avoided. In accordance with the present invention, the necessary expansion/contraction of the wall in its longitudinal direction as a result of thermal cycles will be compensated for at at least one end of the wall, while the stones are mutually locked to each other. Walls in accordance with the present invention have been shown to be very stable over repeated temperature cycles, and the costs related to the rehabilitation of masonry and any downtime of the furnace will thus be able to be considerably reduced.

These and further advantages can be achieved with the invention as defined in the attached patent claims 1-11.

In what follows, the invention shall be described in more detail with examples and figures where:

Fig.l shows, in section, seen from above, details regarding the attachment of one end of a dividing wall i

relation to adjacent masonry,

Fig. 2 shows a section view from above of two parallel dividing walls with fixings at their ends towards

adjacent masonry,

Fig. 3 shows a detail of the fastening of the ends of the partition walls,

Fig. 4 shows a detail at the end of the dividing wall,

Fig. 5 shows a further detail at the end of the dividing wall,

Fig. 6 shows a detail of the structure of the dividing wall.

Figure 1 shows a cross-section from above of a brickwork 1 which can be a so-called belt wall in an incinerator which can be built up from a number of single stones. The masonry as shown in the figure is adapted to the attachment of partition walls 3', 3", 3"', 3"" (only four are partially shown in the figure). The connection 2 between partition wall 3' and the masonry 1 is shown in an enlarged section in the lower part of the figure. In this section, an end stone 4 can be seen in the dividing wall 3', a connecting stone 6 and an anchoring stone 5 which form part of the masonry 1 and are firmly connected to it. The connecting stone 6 can suitably have a rectangular cross-section and have side surfaces 10, 10' which cooperate with respective surfaces 8, 9 and 8', 9' in the end stone and in the anchoring stone, respectively. The anchoring stone 5 and the end stone 4 are mutually movable and an expansion of the dividing wall of which the end stone is a part is permitted above the expansion opening 7 between the end surface 14 of the connecting stone and the surface 11 of the end stone. Contraction that may occur in the wall construction can be compensated for by allowing the end stone 4 to be moved away from anchoring stone 5 while maintaining the connection via connecting stone 6. It should be understood that the connection in an alternative embodiment can be made up of only two elements, i.e. without the connecting stone by a geometry corresponding to said stone being designed as an integral part of either the anchoring stone or the end stone. The size of the expansion opening 7 is adapted based on experience depending on the stone material, operating conditions for the application in question or other conditions. The same will apply to the longitudinal intervention in connection 2 with regard to contraction of the wall construction.

Appropriately, the cooperating surfaces in connection 2 run along the entire vertical extent of the partition wall, i.e. all stone shifts in the partition wall and corresponding shifts in the masonry are designed in the manner shown in the figure. An advantage of such a design is that variations in the length of the wall construction can also be accommodated in its vertical direction in connection 2.

In the example shown in the figure, the adjacent surfaces 13, 12 in the anchoring stone 5 and the end stone 4 respectively are designed slightly sloping so that the surfaces form a V-shape. The purpose of such a V-shape is that particulate material which may lie close to the dividing wall and which can consequently be pressed towards the connection, will be able to be drained out of this area by an expansion (extension) of the dividing wall. It is also advantageous that the surfaces have a mutual V-shape during emptying/cleaning of the chamber. Appropriately, the angle formed between the surfaces can be 30° or more. The size of this angle will depend, among other things, on the material to be drained away and the surface pressure the surfaces are designed for. Furthermore, the connection 2 will include sealing surfaces to the extent that there will be no problems with penetration of material into the connection during a contraction-related movement of the end piece 4.

Figure 2 shows a section view from above of two parallel dividing walls 114, 115, which are fixed at their ends against adjacent masonry 101, 102. In this embodiment, the connections are designed by the anchoring stones 103, 104, 105, 106 having a geometry where the design of the connecting stone is included as an integral part of the anchoring stone and where this thus interacts directly with the adjacent end stone 107, 108, 109, 110 respectively.

It is clear from the figure that the shift that appears in dividing wall 114 is different from that appearing in dividing wall 115 with regard to the design of the stones. In the first-mentioned dividing wall, the end stone 107 is equipped with one flue gas passage 111, while the end stone 108 in dividing wall 115 is equipped with two flue gas passages 112, 113. A similar arrangement is shown at the opposite ends of the dividing walls. Furthermore, it appears that stone 116 with flue gas channels 118, 119 in dividing wall 114 is similarly designed as stone 117 with flue gas channels 120, 121 in dividing wall 115, but the horizontal position in the respective wall is different.

By placing alternating shifts corresponding to what is shown in the section of partition wall 114 and what is shown in the section of partition wall 115 above each other when constructing partition walls, the stones will be mutually anchored to each other via upper/lower shifts by means of mutually interacting engagement elements among otherwise by means of the design of the flue gas ducts. This will be explained in more detail in figures 4-6.

Figure 3 shows details of the fastening of the ends of the partition walls, more specifically an appropriate design of an anchoring stone. The upper part of the figure shows in perspective the underside of a stone 150, while the lower part shows in perspective the upper side of a corresponding stone 150'. The outer geometry of the stones corresponds to that shown in previous figures, but figure 3 also shows interacting elements which will ensure mutual retention between the various shifts of anchoring stones. In the example shown, the anchoring stone 150 is equipped with rotationally symmetrical recesses 151 which interact with rotationally symmetrical elevations 151' in the anchoring stone 150'. Appropriately, the interacting elements can have a semi-spherical shape or a rounded cone shape, but other geometric shapes can also be used. As can further be seen from the figure, the protruding parts 153, 153' of the stones (corresponding to the integrated connecting stone in 6 in Figure 1) are equipped with cooperating elements 152, 152'. In the embodiment shown, the element 152 is made up of a rotationally symmetrical recess, while the corresponding element 152' is made up of a rotationally symmetrical elevation. Appropriately, these elements have a mainly cylindrical design. A build-up of anchoring stones as shown here will provide a stable masonry, where forces that can occur locally on, for example, one or more stones can be partially distributed over the stones in an upper/underlying stone shift. This will be especially beneficial for the protruding parts of the stones, where, for example, forces arising against the protruding part 153 in the stone 150 can be distributed to the underlying stone 150' via cooperating elements 152, 152' and in a similar way to any overlying stone (not shown).

Figure 4 shows a stone corresponding to stone 107 as shown in Figure 2. The upper part of the figure shows the stone seen from above, the lower part of the figure shows the stone seen in section from the side. The figure shows flue gas flue 111 which has a raised end 200 on its upper side, and a cut-out 201 on its lower part. The raised cut-out 200 is adapted to a corresponding cut-out in a stone arranged to be placed on the stone 107, while the cut-out 201 is arranged to be able to fit an elevation in an underlying stone (not shown). Said elevated terminations and recesses will contribute to the flue gas duct having a tight connection between the stone shifts, while at the same time they will contribute to a good mutual anchoring of the stones. Furthermore, the stone 107 can be equipped with transverse beads 202, 202' on its upper side and corresponding transverse recesses 203 on its lower side for further stabilization of the stone.

Figure 5 shows a stone corresponding to stone 108 in Figure 2, where the upper part of the figure shows the stone seen from above and the lower part of the figure shows the stone seen in section from the side. The figure shows flue gases 112, 113 which have raised ends 250, 251 on their upper side and recesses 252, 253 on their lower part. The raised ends 250, 251 are adapted to corresponding recesses in one or two stones arranged to be placed on the stone 108 , while the recesses 252, 253 are designed to fit elevations in one or two underlying Stones (not shown). Said elevated terminations and recesses will help ensure that the flue gas ducts have a tight connection between the stone shifts, while at the same time they will contribute to a good mutual anchoring of the stones. As in the previous figure, the stone 108 can be equipped with transverse beads 254, 254' on its upper side and corresponding transverse recesses 255 on its lower side for further stabilization of the stone.

Figure 6 shows a stone corresponding to stone 116 in Figure 2, where the upper part of the figure shows the stone seen from above and the lower part of the figure shows the stone seen in section from the side. Flue gas flow is shown in the figure

118, 119 which on its upper side have raised ends 300, 301 and on its lower part have recesses 302, 303. The raised ends 300, 301 are adapted to corresponding recesses in one or two Stones designed to be placed on the stone 116, while the recesses 302 , 303 is designed to be able to fit elevations in one or two underlying Steners (not shown). Said elevated terminations and recesses will help ensure that the flue gas ducts have a tight connection between the stone shifts, while at the same time they will contribute to a good mutual anchoring of the stones. However, it should be understood that it may be appropriate to use mortar or a sealant to further stabilize the connections between the stones.

It should be understood that although the examples show a dividing wall with flue gas ducts, corresponding advantages and principles of the invention can also be utilized in wall constructions without continuous ducts where the construction is otherwise exposed to large thermal loads. This may, for example, be relevant for wall constructions that are placed inside a furnace chamber to divide it.

In the embodiments shown, the engagement elements are designed so that elevations are placed on the upper side of the stones, while recesses are placed on the underside of the stones. However, it would be within the scope of the present invention for the elevations to be placed on the underside and the recesses on the upper side or possibly a combination thereof.

According to the present invention, the movements that occur in the wall construction are mainly taken up at at least one end which can be attached to other masonry in a furnace. It should be understood that between the wall construction and its underlying facility, for example a fixed floor construction, a certain relative movement must be allowed between them.

Claims (11)

1. Method for creating an anchored wall structure for use in an incinerator or equivalent where the structure is exposed to cyclic thermal loading, the structure being formed from a number of single elements that are placed in the longitudinal direction of the structure and that are placed in one or more shifts, one bearing the second, since the individual elements can be made of stone of refractory material and where the wall construction can further be designed with internal flue gas channels, the wall construction is further arranged to be able to compensate for longitudinal changes as a result of cyclic thermal load, characterized by that the lengthwise changes of the structure, possibly also changes in the vertical direction, are compensated for in a connection (2) placed at at least one end of the wall structure, and that the individual elements of the structure are otherwise held together in the horizontal direction by means of interacting interlocking elements. 2. Procedure in accordance with claim 1, characterized by that the wall construction is allowed both contraction movement and expansion movement at the connection (2) over cooperating connection surfaces running mainly parallel to the longitudinal direction of the wall construction. 3. Procedure in accordance with claim 2, characterized by that the wall structure can be moved in its longitudinal direction in relation to an underlying support such as a floor. 4. Wall construction for use in an incinerator or equivalent where the construction is exposed to cyclical thermal load, as the construction consists of a number of single elements that can be made of stone of refractory material and where the wall construction can include internal flue gas channels, the wall construction is further arranged to be able to compensate for longitudinal changes as a result of cyclic thermal loading, characterized by the construction's longitudinal changes and any changes in the vertical direction are taken up in a connection (2) placed at at least one end of the wall construction, and that the individual elements of the construction are otherwise firmly anchored to each other in the horizontal direction by means of interacting interlocking elements. 5. Wall construction in accordance with requirement 4, characterized by that the connection (2) comprises at least one end stone (4) and an anchoring stone (5) arranged for mutual movement in the longitudinal direction of the wall construction. 6. Wall construction in accordance with requirement 5, characterized by that the connection (2) is also arranged for a mutual movement between the end stone (4) and anchoring stone (5) in the vertical direction. 7. Wall construction in accordance with requirement 5, characterized by that the end stone (4) and anchoring stone (5) are mutually connected by means of a connecting stone (6). 8. Wall construction in accordance with requirements 5 or 7, characterized by that the end stone (4), the anchoring stone (5) and possibly the connecting stone (6) are designed with interacting connecting surfaces which essentially run parallel to the longitudinal direction of the wall construction. 9. Wall construction in accordance with requirement 5, characterized by that the anchoring stone (5) is firmly connected to a brickwork, such as a belt wall, and is further unguided with engagement elements at its top and bottom. 10. Wall construction in accordance with requirement 5, characterized by that the anchoring stone (5) and the end stone (4) are designed with surfaces (13,12) which mutually form a V-shape for drainage of any material away from the connection. 11. Wall construction in accordance with one or more of the preceding claims 4-10, characterized in that it comprises stones (116, 117) with interacting engagement elements and where the stones are mutually offset in relation to each other in adjacent shifts, whereby a mutual anchoring is obtained in the horizontal direction between the stones.