Support device for firing ceramic parts

Abstract

The invention relates to a support device (10), in particular for firing ceramic parts in a furnace, the support device comprising: - a frame (16) extending in a first direction (L1), a second direction (L2) and a third direction (L3) which are mutually perpendicular, and comprising a support structure (17) that comprises a plurality of first plates (20) extending in the first direction (L1) and second plates (22) extending in the second direction (L2) which intersect one another and together define a support plane (P1); - a plurality of pads (14) carried by the support structure (17) and arranged in rows that each extend in the first direction (L1) and are spaced apart from one another in the second direction (L2); - a continuous layer (42) formed on the support plane (P1) and between the pads (14) and intended to support a thermal insulator (52).

Description

DESCRIPTION TITLE: Support device for firing ceramic pieces Technical field of the invention

[0001] The present invention relates to support devices for firing ceramic pieces and to a kiln incorporating such a device. Previous Art

[0002] The manufacture of building products such as clay tiles and bricks requires high-temperature firing, which is most often carried out in a continuous kiln called a tunnel kiln.

[0003] Due to their production capacity, these kilns are large: up to two hundred meters long, four to ten meters wide, and with a loading height of up to two meters. Firing temperatures for terracotta products range from 900°C to 1200°C, depending on the raw materials used and the products being fired.

[0004] Several tunnel oven designs exist depending on the applications and markets, but in all cases, they consist of walls that provide thermal insulation and must simultaneously fulfill the following functions: - Ensure a tight seal between the inside and outside of the oven. This is crucial to limit unwanted air leaks in negative pressure areas and the diffusion of oven fumes to the outside, which lead to increased energy consumption and corrosion problems. To allow the fixing and support of equipment directly related to the furnace such as burners, sight glasses, recirculation fans and other air injection or fume extraction nozzles. The upper wall may support equipment such as fluid manifolds and circulation platforms.

[0005] These lines are traversed by wagons on which the products are placed, undergoing a predetermined cooking cycle during their journey. The transfer time, and therefore the cooking time, varies considerably depending on the nature of the raw materials used, ranging from eight to forty hours.

[0006] To date, all (99%) of brick and tile production kilns use kiln wagons. Beyond their function of "supporting" the loads to be fired, these wagons constitute the fourth wall of the kiln, with the disadvantage of needing to be "reheated" each time they pass through the kiln (leading to accelerated degradation of the refractories).

[0007] Furthermore, the railcars, and more specifically the insulating and refractory lining they carry, represent a significant mass requiring thermal treatment, equivalent to or even greater than the mass of the "products and materials" on board. These railcars, built using existing technology, exhibit high thermal inertia, which increases energy consumption.

[0008] The products and supports on board have a total exchange surface area much larger than that of the insulating and refractory lining of the wagon, the mass of which is extremely detrimental to the overall energy efficiency of a furnace.

[0009] The refractory and insulating linings of known wagons are made according to a traditional design common to all wagon suppliers and comprising a periphery of the wagon in dense materials (cordierite or concrete), a load transfer of loads in dense materials (cordierite or concrete) resting on a levelling / load distribution slab made of concrete to interface with a chassis.

[0010] Figure 1 illustrates a wagon 1 of a known type comprising, from bottom to top in the vertical direction: insulating panels 2 of calcium silicate, a base layer of dense concrete 3, a layer 4 of loose-fill fiber or insulating material, and a layer of biosoluble material 5. Cordierite pads 6 provide load transfer between the concrete layer 3 and supports 7 for the pieces to be baked. The structure of wagons using this known technique therefore essentially consists of a structure built by successively stacking structural and insulating layers, with a basic structural concrete layer that provides rigidity and also high thermal inertia.

[0011] The invention aims to provide a simple and economical solution to the aforementioned problems. Presentation of the invention

[0012] To this end, it proposes a support device, particularly for firing ceramic pieces in a kiln, comprising: a frame extending along a first direction, a second direction and a third direction perpendicular to each other in pairs, the frame comprising a support plane, the frame being able to comprise a support structure having a plurality of first plates extending along the first direction and second plates extending along the second direction intersecting each other and which together define the first support plane of the frame, a plurality of studs carried by the frame, preferably by the support structure, the studs being preferably arranged in rows each extending along the first direction and said rows being preferably spaced from each other along the second direction (L2), a continuous layer carried by the chassis and which can be formed on the support plane, this continuous layer being formed between said studs (16) and being intended to support thermal insulation.

[0013] According to the invention, the load transfer is achieved by pads directly supported by the chassis and, more specifically, where applicable, by a lightweight support structure formed of interlocking plates. The continuous layer allows for the application of thermal insulation.

[0014] According to another characteristic, this continuous layer can comprise a plurality of sheets, for example, made of steel. The layer is configured to allow insulation against air transfer in the vertical direction. It would also be possible to use ceramic plates. At least some of the edges of the sheets can overlap the edges of other sheets. Some of the sheet edges can be arranged opposite each other.

[0015] According to another feature, a thermally insulating frame may surround said studs and be arranged on the periphery of said chassis, preferably on the periphery of the support structure, so as to form with said plurality of sheets a recess for receiving thermally insulating material, preferably in the form of a filling material, the insulating frame having a thermal conductivity in the third direction of less than 0.5 W.m' 1 .K' 1 , preferably between 0.05 and 0.3 W.m' 1 .K' 1 .

[0016] This configuration allows for a lightweight frame, preferably with the aforementioned plates, surrounded by a thermally insulating frame that, together with the continuous layer, forms a recess for insulation. The thermal properties of the frame limit heat transfer in the vertical direction, that is, along the third direction.

[0017] Note that using loose-fill material is preferable for achieving good thermal insulation. However, it is understood that other types of insulation, such as panels arranged within the basin, could be used.

[0018] According to yet another characteristic, the thermally insulating frame may include a first thermally insulating layer with a closed contour and having a thermal conductivity coefficient between 0.05 and 0.15 W.m' 1 .K' 1 and a second layer covering the first layer which is also closed contour and has a cold crush resistance after baking at 800°C (indicate the standard) of between 1 and 2 MPa, preferably between 1.5 and 1.8 MPa, preferably about 1.6 MPa.

[0019] The thickness referred to as "first layer" and "second layer" is defined along the third direction. The dimensions of the first and second layers are measured along the third direction. The term "closed contour" refers to a layer extending continuously 360° around the perimeter of the frame.

[0020] The second layer preferably represents between 2 and 30% of the sum of the first and second layers.

[0021] The sum of the first and second thicknesses will preferably be between 200 and 500 mm, to have sufficient thermal protection for the metal frame.

[0022] When the dimension of the second thickness is less than or equal to 10% of the sum of the thicknesses of the first and second thicknesses, the second thickness must have a bending strength of at least 20 MPa. A material such as silicon carbide could be suitable.

[0023] The first layer may comprise a plurality of layers of first thermally insulating panels, said layers being arranged in a staggered pattern.

[0024] The panels can be made from compressed fibrous materials.

[0025] Insulating panels can have a density of less than 350 kg / m³ 3 The insulating panels have a fibrous structure.

[0026] The second layer may comprise a plurality of structural slabs, preferably made of lightweight concrete, placed side by side to form a closed contour.

[0027] The structural slabs can be poured in place using formwork. A protective film is preferably placed on top of the first layer to prevent moisture from the poured concrete from transferring to the first layer. The concrete for the second layer can have a density between 400 and 600 kg / m³.

[0028] Each support block can be mounted in a tray supported directly by the chassis.

[0029] Each tank may include a bottom wall supporting a support block, each bottom wall being arranged below the first support block.

[0030] A collar can surround each tray and is mounted to rest on the chassis, preferably on the support structure.

[0031] The first and second plates may include collar receiving recesses associated with each tray so that the upper surface of the collar is coplanar with the foreground of support.

[0032] Thus formed, the collars together with the upper ends of the first and second plates form a common surface for receiving sheets arranged side by side to form a continuous surface for receiving sealing means in the form of bulk material, such as granules, flakes... .

[0033] At least a plurality of first bars, made of a material capable of mechanically resisting a temperature of at least 1000°C, for example SiC, can be arranged along the first direction on each of said pads.

[0034] At least a plurality of second bars, made of a material capable of mechanically resisting a temperature of at least 1000°C, for example SiC, can be arranged along the first direction on each of said pads.

[0035] Thermal insulation, for example in the form of loose material, can be placed on said plurality of sheet metal, the thermal insulation having a thermal conductivity coefficient of less than 0.3 W.m' 1 .K' 1 , preferably less than 0.2 W.m' 1 .K' 1 .

[0036] The thermal insulation may comprise at least a first layer and a second layer, the first layer being placed between the sheets and the second layer, the layers being such that the first layer has a lower density than the second layer. The first layer may have a density between 65 and 85 kg / m³ 3 for example, approximately 75 kg / m 3It would still be possible to use a single material for the filling.

[0037] The second layer has a density between 100 and 120 kg / m³ 3 for example approximately 110 kg / m 3 .

[0038] To obtain a good compromise of bulk along the third direction and avoiding heat transfer to the chassis of the device, preferably including rolling elements, the device will be such that the sum of the first thickness and the second thickness represents between 65 and 90% of the dimension measured, along the third direction, between the sheets and the upper surface of the bars.

[0039] The dimension of the thermal insulation along the third direction can be between 90 and 95% of the sum of the first and second thicknesses.

[0040] Each plot can comprise two distinct parts superimposed one on top of the other along the third direction.

[0041] The first part and the second part can cooperate by shape connection so as to block the second part of the block on the first part along the first direction and the second direction.

[0042] Shims can be inserted between the first part of the block and the second part of the block.

[0043] The first part of the block includes notches for receiving bars mounted simultaneously on several blocks.

[0044] A thermally insulating block, such as a brick, can be inserted between a bottom wall of each container and a block.

[0045] The pads can be made of concrete with a density of between 2 and 3 tonnes per m³ 3 .

[0046] This document also relates to a tunnel furnace having an inlet end and an outlet end into which is inserted a device as described previously which includes rolling elements, the tunnel kiln comprising heating means successively comprising five treatment zones: a first temperature rise zone comprising first heating means which may include first burners, a second firing zone comprising second heating means which may include second burners, a third active or passive cooling zone, a fourth passive cooling zone, and a fifth active cooling zone which may include hot air recovery means which may be carried by the vault and / or the walls of the tunnel kiln, the main airflow passing through the kiln counter-currently (from the outlet to the tunnel inlet) being injected at this point, in which the second zone corresponds to less than 10% of the length of the kiln measured between the inlet end and the outlet end,the fourth cooling zone corresponding to less than 20% of the said length of the oven. Brief description of the figures [Fig. 1] Figure 1 represents a wagon for transporting parts according to the known technique, in particular in ceramics for firing in a kiln, according to a first cutting plane (part A) and according to a second cutting plane perpendicular to the first cutting plane (part B); [Fig. 2] Figure 2 represents a wagon for transporting parts, including ceramics, for firing in a kiln, according to a second cutting plane perpendicular to the first cutting plane; [Fig. 3] Figure 3 is a schematic perspective view of the chassis of the device according to Figure 3; [Fig. 4] Figure 4 is a larger-scale schematic perspective view of the area outlined in dotted lines in Figure 3; [Fig. 5] Figure 5 illustrates a receiving area of ​​a support tray for a stud; [Fig. 6] Figure 6 is an isolated schematic view of a receiving tray of a plot; [Fig. 7] Figure 7 is a view similar to that of Figure 5 and illustrating sheets surrounding the trays; [Fig. 8] Figure 8 is a view similar to Figure 7 on which plots have been added; [Fig. 9] Figure 9 is a schematic axial cross-sectional view of a stud intended for use in a support device according to this document; [Fig. 10] Figure 10 is a schematic perspective view of the first part of a plot; [Fig. 11] Figure 11 is a schematic perspective view of the second part of a plot; [Fig. 12] Figure 12 is a schematic perspective view of a support device according to this document, the thermally insulating filling material not being shown; [Fig. 13] Figure 13 is a schematic perspective view similar to Figure 12 in which is further illustrated a covering thickness of the periphery of the chassis intended to form a structural layer; [Fig. 14] Figure 14 is a schematic cross-sectional view of a block arranged in the immediate vicinity of the periphery of the support device; [Fig. 15] Figure 15 is a schematic perspective view similar to Figure 13, in which a first layer of thermally insulating material is shown; [Fig. 16] Figure 16 is a schematic view illustrating a second layer of thermal insulation covering the first layer of thermal insulation of Figure 14; [Fig. 17] [Fig. 18] Figures 17 and 18 are schematic perspective views of the device illustrating two finishing stages of the support device according to this document; [Fig. 19] Figure 19 represents a graph illustrating the thermal behavior of the device according to the invention compared to the known technique. Detailed description of the invention

[0047] We now refer to Figure 2, which represents a support device 10 intended to support ceramic parts. As can be seen, the support device 10 comprises a plurality of bars 12 supported by pads 14 carried by a frame 16.

[0048] Figure 3 illustrates the frame 16 of the support device 10. The frame 16 extends along a first direction L1, a second direction L2, and a third direction L3, which are perpendicular to each other. The first direction L1 can be described as the longitudinal direction, the second direction L2 as the transverse direction, and the third direction L3 as the vertical direction. The frame 16 includes a support plane Pi (Figure 4). The frame 16 may include a support structure 17 comprising a plurality of first plates 20 extending along the first direction L1 and second plates 22 extending along the second direction L2. The first plates 20 and the second plates 22 are interlocked and together define the support plane Pi by their upper edges.More specifically, the first plates 20 and the second plates 22 are nested within each other by means of notches made in the plates 20, 22. The chassis 18 is supported by rolling elements 24, preferably capable of withstanding high temperatures, at least up to operating temperatures of the support device 10.

[0049] As can be seen in Figure 4, the first plates 20 oriented along the first direction, L1, can all be identical. The second plates 22 oriented along the second direction can include secondary primary plates 22a and secondary secondary plates 22b. The secondary primary plates 22a can be arranged in pairs such that one primary plate 22a is arranged on one side of a rolling element 24 and another primary plate 22a is arranged on the opposite side. Secondary secondary plates 22b are arranged between secondary primary plates 22a, more precisely between one primary plate 22a arranged on one side of a wheel 24 and another primary plate 22a arranged on the other side of an adjacent wheel along the direction L1. The secondary secondary plates 22b are arranged in pairs.We observe that a first pair of secondary 22b plates and a second pair of secondary 22b plates are arranged side by side. The distance between the 22b plates of a pair is less than the distance separating two secondary 22b plates of two adjacent pairs.

[0050] The first plates 20 have notches shaped to receive the second secondary plates 22b. The second primary plates 22a have notches that receive the first plates 20. The notches in the first plates 20 and the second plates 22a and 22b are formed so as to open onto an edge of the plates oriented along a first direction of the third direction L3, this first direction being upwards. The plates 20 and 22 are nested successively along this first direction of the third direction L3, such that the second primary plates 22a receive the first plates 20 in their notches, and then the second secondary plates 22b are engaged in the notches of the first plates 20. It is observed that the notches in the first plates 20 are such that they allow the second secondary plates 22b to be fully received.

[0051] The rolling elements 24 intended to allow the movement of the chassis are mounted in rotation on axes (not shown) carried by first plates 20 arranged on either side of each rolling element 24.

[0052] The first plates 20 and second plates 22 can each be formed from a single piece or from several pieces, for example two, assembled together along the main extension direction L2 or L3 along which the plates extend.

[0053] As can be seen in Figures 3 and 4, the first plates 20 and the second plates 22 together define a first support plane Pi. More precisely, the upper edges of the second plates 22 and the upper edges of the first plates 20 define the first support plane Pi. In other words, the edges of said plates 20 and 22 are thus positioned at the same height along the third direction L3.

[0054] Figure 3 illustrates a plurality of trays 26 intended to receive pads 28 supporting the bars 12 (Figure 2). Each tray 26 is supported by two first adjacent plates 20 along the second direction L2 and by two second adjacent secondary plates 22b along the first direction L1.

[0055] Figure 5 shows a receiving area for a support tray 26 of a stud 14 and a part B which is an isolated schematic view of a receiving tray 26 of a stud 14. The first plates 20 and two adjacent secondary plates 22b have recesses 28 formed in their upper edges. The length (along L1 and L2) and thickness (along L3) of the recesses 28 in the first plate 20 and the secondary plates 22b are such that they allow a collar 30 of a receiving tray to be received, as illustrated in Figure 5.

[0056] As illustrated in Figure 6, each container 26 comprises side walls 32 extending along the third direction L3, the lower ends of which are joined together by a substantially flat bottom wall 34 extending in a plane formed by the first direction L1 and the second direction L2, i.e., parallel to the support plane Pi. The collar 30 is formed around the side walls 32 of the container 26 and is supported by them. This collar 30, which can be described as annular, extends in a plane formed by the first direction L1 and the second direction L2. This collar 30 is arranged at mid-height of the side walls 32. The collar 30 can be formed by a ring having portions 36 projecting on the inner circumference of the ring, the projections 36 being engaged in housings in the side walls 32 for retaining the collar 30 on the side walls 32.It is observed that at least some or all of the side walls 32 may include slots 38 opening onto their upper edges, the other end of which opens into a substantially circular opening 40. The slots 38 and the openings 40 facilitate the thermal expansion of the side walls 32 of the trays 26 and thus prevent their deformation in a baking oven.

[0057] Each receiving tray 26 of a block is positioned so that the flange 30 is fully engaged in the recesses 28 of the upper edges of the first plates 20 and the second secondary plates 22b. Furthermore, the flange 30 and the recesses 28 are dimensioned so that the upper surface of the flange 30 is coplanar with the first support plane Pi. This support plane Pi is thus formed by the upper edges of the first plates 20 and the second secondary plates 22b. Moreover, the bottom wall 34 of each tray 26 is arranged below the first support plane Pi, which reduces the overall size of the trays 26 along the third direction L3 and gives the support device 10, as described in this document, greater compactness.

[0058] Figure 7 illustrates a plurality of receiving trays 26 arranged on the support structure 17 of the frame 16. These trays 26 are arranged in rows along the first direction L1 which are spaced from each other along the second direction L2. Each tray 26 is intended to receive a plot 14 which will be described below, which therefore have an identical arrangement along the first direction L1 and the second direction L2.

[0059] Figure 7 also illustrates a continuous layer 42 carried by the frame 16 and which can be formed on the support plane Pi. This continuous layer 42 is formed between the aforementioned pads 14 and is intended to support a thermal insulation which will be described later.

[0060] As illustrated in Figure 7, the continuous layer 42 can comprise a plurality of sheets 42a, for example made of steel, arranged on the support plane Pi and between the trays 26, and configured to form a continuous layer or surface. In a particular configuration, the edges of the sheets 42a can overlap the edges of other sheets to form a continuous surface. The continuous layer or the sheets 42a are arranged to surround the trays 26, and some of them are positioned on the flanges 30 of the trays 26.

[0061] Figure 8 represents a plurality of pads 14 mounted in the trays 26 described previously. Each pad 14 comprises a first part 14a (figure 10) or lower part and a second part 14b (figure 11) or upper part arranged on the lower part 14a.

[0062] Figure 9 represents a plot 14 according to a cross-sectional view along a plane including the second direction L2 and the third direction L3.

[0063] Preferably, the first part 14a and the second part 14b can cooperate by form connection so as to lock the second part 14b of the block onto the first part 14a along the first direction L1 and the second direction L2. The upper surface of the first part 14a of the block 14 can thus include a first imprint formed of longitudinal and transverse grooves Ri, in which longitudinal and transverse ribs Ni of the lower face of the second part 14b of the block 14 are engaged.

[0064] The first part 14a of the block 14 may include a recess 44 formed on its lower face to limit the mass of the first part 14a and reduce the heat transfer between the first part 14a of the block 14 and the container 26. The ends, along the second direction L2, of the first part 14a and of the second part 14b may include recesses 46 to facilitate their handling.

[0065] The first part 14a of the block 14 has two opposing flanks along the longitudinal direction L1, converging towards each other in the direction of the second part 14b of the block 14. The second part 14b of the block 14 has a roughly parallelepiped shape. The load transfer between the first part 14a and the second part 14b is achieved solely by the longitudinal ribs Ni of the second part 14b, which bear in the longitudinal grooves Ri of the first part 14a. The other structural elements provide a restraint, limiting any movement in the plane formed by the directions Longitudinal and transverse. Shims 46 (not shown) can be inserted between the first part 14a and the second part 14b of each block 14. These shims can be mounted between the longitudinal grooves Ri of the first part 14a of the block and the longitudinal ribs Ni of the second part 14b of the block 14, and allow for compensating for manufacturing tolerances of the first part 14a and the second part 14b of the block 14 and ensuring the flatness of the bars 12 mounted on the second part 14b of the block 14 (Figure 9). These shims can be made of refractory steel / alloy, ceramic (mica, for example), or a material resistant to temperatures exceeding 1000°C.

[0066] Figure 9 also illustrates bars 12 mounted on the second part 14b of each block 14, in the case shown two bars 12. These bars 12 can support a support plate 48 intended to receive a ceramic element to be fired in a kiln. The upper surface of each second part 14b of the block 14 comprises at least one longitudinal groove Vi, here two longitudinal grooves, in which a support bar 12 is mounted.

[0067] As shown in Figure 12, each stud 14 is covered by a skirt 50 which prevents the filler material intended for the sheets 42a from seeping between the first part 14a and the second part 14b of each stud 14 and entering the trays 26. The arrangement of the studs 14 in two parts facilitates the replacement of only one part of each stud 14, in this case the second part, which is most exposed to the high temperature in the baking oven. Replacing the second part 14b of each stud 14 allows the first part to remain in position and the insulating filler material to stay in place.

[0068] According to this document, a thermally insulating frame 52 surrounds the studs 14 and is positioned on the periphery of the chassis 14, more specifically on the periphery of the support structure 17, so as to form, together with the continuous layer 42, more particularly with said plurality of sheets 42a, a recess for receiving thermal insulation 54 in the form of a filling material, such as a loose material. The thermally insulating frame 42 may have a thermal conductivity along the third direction L3 of less than 0.5, preferably between 0.05 and 0.3 (Figures 12 and 13).

[0069] The proposed arrangement with 14 supports supported by a chassis 16 and combined with a specific peripheral frame 52 allows for decoupling between the mechanical support of the ceramic parts to be fired and the thermal transfer compared to the previous technique.

[0070] The thermally insulating frame 52 may comprise, as illustrated in Figures 12 and 13, a first thermally insulating layer 52a and a second layer 52b covering the first layer 52a. The first thermally insulating layer 52a may have a closed contour and exhibit a thermal conductivity coefficient between 0.05 and 0.15 W.nr 1 .K' 1 , preferably between 0.6 and 0.11 W.nr 1 .K' 1 The first thickness 52a can exhibit a tensile strength of between 0.5 MPa and 1 MPa, preferably between 0.7 MPa and 0.9 MPa under ambient conditions of 23°C, 50% humidity, atmospheric pressure and for a thickness of 50 mm.

[0071] The second layer 52b can cover the first layer 52a and can have a closed contour and can have a cold crush resistance after baking at 800°C (according to ISO 1927-6) of between 1 and 2 MPa, preferably between 1.5 and 1.8 MPa, preferably about 1.6 MPa.

[0072] In one variant, the thermally insulating frame 52 could comprise only one layer having the properties of the aforementioned second layer 52b.

[0073] The second layer, 52b, provides increased mechanical strength compared to the first layer, 52a, and ensures resistance to impacts from ceramic elements. Furthermore, the combination of two layers as described offers a better compromise between thermal insulation and mechanical strength.

[0074] The first layer 52a has a dimension along the third direction L3, or vertical direction, of between 150 and 300 mm. The second layer 52b has a dimension along the third direction L3, or vertical direction, of between 20 and 100 mm. Preferably, the vertical dimension of the second layer 52b is less than 40% of the vertical dimension of the first layer 52a. This ensures a good compromise in terms of overall dimensions along the vertical direction L3, resulting in a cold crush resistance after curing at 800°C (EN ISO 1927-6) of between 1 and 2 MPa, preferably between 1.5 and 1.8 MPa, preferably around 1.6 MPa, and a thermal conductivity of between 0.05 and 0.15 W / m. 1 .K' 1. The panels of the first thickness 52a preferably have a thickness of less than 50 mm for a width between 200 and 500 mm and a length between 500 and 1000 mm in order to avoid deformation by bimetallic effect leading to the formation of a convex curvature on the hottest face and a concave curvature.

[0075] The first layer 52a may comprise a plurality of layers of first thermally insulating panels 54, said layers being arranged in a staggered pattern around the periphery of the frame 14, more specifically the support structure 17. The insulating panels may be arranged to form a stepped assembly extending from the inside of the support device outwards (Figure 13). This arrangement provides stability to the stacking of the layers of first thermally insulating panels. The panels may be made of compressed fibrous materials. They may have a density of less than 350 kg / m³. They may have a fibrous structure.

[0076] The second layer 52b may comprise a plurality of structural slabs, preferably made of concrete or ceramic, placed end to end to form a closed contour. Preferably, the second layer 52b will comprise only a single layer of structural slabs to avoid deformation due to the bimetallic effect of slabs embedded within the second layer 52b.

[0077] Figure 14 shows a cross-sectional view of a block 14 arranged near the periphery of the frame. The panels 54 of the first layer 52a are arranged in a stepped pattern, but reversed to conform to the shape of the sides of the block 14. It can also be seen that the blocks 14 can be placed on thermally insulating blocks 56. These thermally insulating blocks 56 can have a thermal conductivity coefficient between 0.2 and 0.5 W.m' 1 .K' 1and a cold crush resistance after baking at 800°C (according to ISO 1927-6) of between 3 and 6 MPa.

[0078] Figures 15 and 16 illustrate the arrangement of thermal insulation 58 above the continuous layer 42, that is, more specifically above the sheets 42a. In the illustrated variant, the thermal insulation comprises at least two layers. It should be noted that it could also comprise only one. The thermal insulation is in the form of a material suitable for filling the internal space delimited by the peripheral frame 52 and the continuous layer 42 or the sheets 42a. This thermal insulation can be a loose material or a plurality of panels arranged side by side in an arrangement that limits thermal conduction between the panels. The thermal insulation can have a thermal conductivity coefficient of less than 0.3 W / m². 1 .K' 1, preferably less than 0.2 W.m' 1 .K' 1 .

[0079] The thermal insulation may comprise at least one layer, preferably at least two layers, such that the first layer is positioned between the sheets and the second layer. In one embodiment, the first layer 58a has a lower density than the second layer 58b, thereby limiting heat accumulation in the lower part of the support structure. The first layer 58a may have a density between 65 and 85 kg / m³. 3 For example, approximately 75 kg / m³. It would still be possible to use a single material for the infill. The second layer, 58b, can have a density between 100 and 120 kg / m³. 3 for example approximately 110 kg / m 3 Assuming a single layer, the density would be less than 120 kg / m³ 3 , preferably between 85 kg / m 3 and 100 kg / m 3 .

[0080] As illustrated in Figures 15 and 16, support blocks 60, such as bricks, can be placed between the rows of pads 14. Figure 17 illustrates the addition of support slabs 62 mounted on the blocks 60. These support blocks 60 and the slabs have sufficient mechanical characteristics to allow the passage of a man.

[0081] A fiber mat can be placed on the second layer 58b of thermal insulation. A layer made of concrete, or ceramic, or of a material such as that composing the first layer 52a, covers the second insulating layer 58b, and where applicable, the fiber mat (Figure 18).

[0082] We now refer again to Figure 2, which shows a plurality of first bars 12, made of a material capable of mechanically resisting a temperature of at least 1000°C, for example SiC, arranged along the first direction L1 on each of said pads 14. In the embodiment shown in Figure 2, at least a plurality of second bars 12, made of a material capable of mechanically resisting a temperature of at least 1000°C, for example SiC, are arranged along the first direction L1 on each of said pads. In the example shown, each pad carries exactly two bars 12. Several bars 12 can be arranged end to end when the length of a single bar does not have a dimension along the first direction L1 sufficient to go from the first pad 14 to the last pad 14 of a row.

[0083] We now refer to Figure 19, which illustrates two curves: a first curve Ci (solid line) and a second curve C2 (dashed line), each showing the temperature of a support device as a function of time when placed in a tunnel kiln for firing ceramic pieces at temperature T1. More precisely, the first curve Ci illustrates the temperature of a support device 10 according to the invention, and the second curve C2 illustrates the temperature of a support device of the prior art as shown in Figure 1. The unit of time is used on the x-axis, which is equivalent to a unit of time, considering the movement of the support device at a constant speed in a tunnel kiln. Indeed, the unit of time is preferable since it is representative of the operating time of the tunnel kiln. The terms "duration" and "length" in relation to the zones are therefore equivalent.

[0084] A tunnel kiln includes an extension direction running between an inlet end and a second outlet end. The tunnel kiln is designed to allow the movement of a ceramic part support device between the inlet end and the outlet end, the second direction L2 of the support device being collinear with the extension direction of the kiln. The tunnel kiln of the invention and of the prior art successively comprises at least five zones. The five zones are designated Z1, Z2, Z3, Z4, Z5 for the purposes of this document and Z a , Zt>, Z c , Zd, Z e Regarding the previous technique, a first zone Z1, Z a , temperature rise including primary heating means, such as primary burners, a second cooking zone Z2, Zb including secondary heating means such as secondary burners, The second heating means may include burners capable of generating an axial and radial flame along the burner axis. The burner has a principal direction of extension and is supported by a kiln vault such that its principal direction of extension is oriented in a plane perpendicular to the direction of extension of the tunnel kiln; a third zone Z3, Z c active cooling including means for injecting cooling air as well as possible means for recovering hot air which can be carried by the tunnel kiln roof; a fourth passive cooling zone Z4, Zd, i.e. a zone without cooling air injection, and a fifth zone Z5, Z eactive cooling including means for recovering hot air which can be supported by the vault and / or the walls of the tunnel furnace, the main airflow passing counter-currently through the furnace (from the outlet to the tunnel inlet) being injected at this point,

[0085] In the case of the dotted curve, we observe that the first zone is longer than the first zone of the tunnel furnace using a support device according to the invention since the support device according to the present document has a lower thermal inertia.

[0086] We observe that the first zone Z1 has a slope greater than that of the first zone Z aThe first zone of the kiln corresponds to the area where the ceramic pieces are brought to a firing temperature plateau T1, which marks the beginning of the second zone. The second zone is where the ceramic pieces are fired; it is the firing zone itself, during which the temperature remains relatively constant. The duration of the second firing zone is shorter compared to previous techniques.

[0087] The use of a support device according to the invention makes it possible to reduce the duration of the second zone Z2 compared to the length of the second zone Zb of the prior art.

[0088] It is observed that the third cooling zone Z3, which lowers the firing temperature to a temperature T2 above the quartz point temperature, has a shallower slope compared to that of the third zone Zc. Also, the length of the third zone Z3 is greater compared to the length of the third zone Z c of the prior art. The "quartz point" is the temperature of 573 °C at which a-quartz (low-temperature polymorph) transforms into p-quartz (high-temperature polymorph). This is the point at which crystalline silica transforms into vitreous silica while simultaneously reaching its point of maximum thermal expansion.

[0089] It is observed that the fourth cooling zone Z4 has a slope very similar to that of the fourth zone Zd. The length of the fourth zone Z4 is increased compared to the length of the fourth zone Zd of the previous technique.

[0090] Finally, the fifth zones Z5, Z e are essentially identical in terms of length and slope.

[0091] According to the invention, the second zone Z2 corresponds to less than 15%, preferably less than 10%, of the tunnel kiln length measured between the inlet and outlet ends. The fourth cooling zone Z4 corresponds to less than 25%, preferably less than 20%, of the tunnel kiln length. The combination of the tunnel kiln and a support device reduces energy consumption in the kiln by heating, since the temperature rise is faster. Zone Z1 is smaller compared to the prior art, and the firing time is also shorter due to improved thermal uniformity within the parts being fired, as the support device retains less heat. The injection of cold air at the third zone Za can thus be carried out over a longer period.At the end of the third zone, we move into the fourth zone, which is uncooled. This zone represents a waiting period for the quartz point to pass. It is important that the temperature decrease over time is gradual as the quartz point passes, which explains the shallow slope.

[0092] The configuration of the support device 10 according to the invention allows the cooking temperature T1 to be reached more quickly, cooking to be faster, and active cooling (third zone Z3) to begin earlier. The low thermal inertia of the device allows less cold air to be injected into the third zone compared to the prior art, which limits energy consumption by the heating elements in the first and second zones Z1 and Z2.

Claims

DEMANDS 1. Support device (10) particularly for firing ceramic pieces in a kiln, comprising: a frame (16) extending along a first direction (L1), a second direction (L2) and a third direction (L3) perpendicular to each other, and comprising a support structure (17) comprising a plurality of first plates (20) extending along the first direction (L1) and second plates (22) extending along the second direction (L2) intersecting each other and together defining a support plane (Pi), a plurality of pads (14) carried by the support structure (17) and arranged in rows each extending along the first direction (L1) and spaced from each other along the second direction (L2), a continuous layer (42) formed on the support plane (P1) and between said pads (14) and intended to support a thermal insulation (52).

2. Device according to claim 1, wherein said continuous layer (42) comprises a plurality of sheets (42a).

3. Device according to claim 1 or 2, wherein a thermally insulating frame (52) surrounding said studs and disposed on the periphery of said chassis (16) so as to form with said continuous layer (42) a recess for receiving a thermally insulating material (58), preferably in the form of a filling material, the insulating frame having a thermal conductivity along the third direction (L3) of less than 0.5 W.m' 1 .K' 1 , preferably between 0.05 and 0.3 W.m' 1 .K' 1 .

4. Device according to claims 1 to 3, wherein the thermally insulating frame (52) comprises a first thermally insulating layer (52a) with a closed contour and having a thermal conductivity coefficient between 0.05 and 0.15 W.nr 1. K' 1 and a second layer (52b) covering the first layer which is also closed contour and has a cold crush resistance after baking at 800°C (indicate the standard) of between 1 and 2 MPa, preferably between 1.5 and 1.8 MPa, preferably about 1.6 MPa.

5. Device according to claim 4, wherein the second thickness (52b) represents between 2 and 30% of the sum of the first thickness (52a) and the second thickness (52b).

6. Device according to claim 4 or 5, wherein the sum of the first thickness (52a) and the second thickness (52b) is between 200 and 500 mm.

7. Device according to any one of claims 4 to 6, wherein the first thickness (52a) comprises a plurality of layers of first thermally insulating panels (54), said layers being arranged in a staggered pattern.

8. Device according to any one of claims 4 to 7, wherein the panels (54) are made of compressed fibrous materials.

9. Device according to claim 47 or 8, wherein the insulating panels (54) have a density of less than 350 kg / m3.

10. Device according to any one of claims 4 to 9, wherein the insulating panels (54) have a fibrous structure.

11. Device according to any one of claims 4 to 9, wherein the second thickness (52b) comprises a plurality of structural slabs, preferably made of lightweight concrete, juxtaposed one after the other so as to form a closed contour.

12. Device according to any one of the preceding claims, wherein each support stud (14) is mounted in a tray (26) supported directly by the chassis (16).

13. Device according to the preceding claim, in which each tray (26) comprises a bottom wall supporting a support block (14), each bottom wall being arranged below the first support plane (Pi).

14. Device according to claim 12 or 13, in which a collar (30) surrounds each tray (26) and is mounted to rest on the support structure (17).

15. Device according to the preceding claim, in which the first (20) and second (22) plates comprise recesses (28) for receiving the collar (30) associated with each tray (26) so that the upper surface of the collar (30) is coplanar with the first plane (Pi) of support.

16. Device according to any one of the preceding claims, wherein at least a plurality of first bars (12), made of a material capable of mechanically resisting a temperature of at least 1000°C, for example in SiC, are arranged along the first direction on each of said pads.

17. Device according to the preceding claim, in which at least a plurality of second bars (12), made of a material capable of mechanically resisting a temperature of at least 1000°C, for example in SiC, are arranged along the first direction (L1) on each of said pads (14).

18. Device according to any one of the preceding claims, wherein a thermal insulator (58), for example in the form of bulk material, is disposed on said continuous layer, the thermal insulator having a thermal conductivity coefficient of less than 0.3, preferably less than 0.

2.

19. Device according to the preceding claim, wherein the thermal insulation (58) comprises at least a first layer (58a) and a second layer (58b), such that the first layer has a lower density than the second layer (58a).

20. Device according to the preceding claim, wherein the first layer has a density between 65 and 85 kg / m³ 3 for example, approximately 75 kg / m 3 .

21. Device according to claim 19 or 20, wherein the second layer (58b) has a density between 100 and 120 kg / m³ 3 for example, approximately 110 kg / m 3 .

22. Device according to any one of the preceding claims, wherein each stud (14) comprises two distinct parts (14a, 14b) superimposed one on top of the other along the third direction (L3).

23. Device according to the preceding claim, wherein the first part (14a) and the second part (14b) cooperate by form connection so as to lock the second part (14b) of the stud (14) on the first part (14a) along the first direction (L1) and the second direction (L2).

24. Device according to one of the two preceding claims, in which wedges are interposed between the first part (14a) of the block (14) and the second part (14b) of the block (14).

25. Device according to any one of claims 22 to 24, wherein the first part (14a) of block (14) comprises notches for receiving bars mounted in support simultaneously on several blocks (14).

26. Device according to any one of the preceding claims and claim 11, wherein a thermally insulating brick (60) is intercalated between a bottom wall of each tray and a block.

27. A device according to any one of the preceding claims, wherein the blocks (14) are made of concrete having a density of between 2 and 3 tonnes / m³ 3 .

28. Tunnel furnace having an inlet end and an outlet end in which is inserted a device according to one of the claims which includes rolling elements, the tunnel furnace comprising successively five processing zones: a first temperature rise zone (Z1) comprising first heating means, such as first burners, a second firing zone (Z2) comprising second heating means such as second burners, a third active or passive cooling zone (Z3), a fourth passive cooling zone (Z4), and a fifth active cooling zone (Z5), in which the second zone corresponds to less than 15%, preferably less than 10%, of the length of the furnace measured between the inlet end and the outlet end, the fourth cooling zone corresponding to less than 25%, preferably less than 20%, of said length of the furnace.

Images