Support device for firing ceramic pieces

Abstract

The invention relates to a 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) having 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 (P1), - 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). Figure to be published with the abbreviation: [Fig. 2]

Description

Title of the invention: 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 construction 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. The firing temperatures of the terracotta products range from 900°C to 1200°C, depending on the raw materials used and the products to be fired.

[0004] Several tunnel furnace designs exist depending on the applications and markets, but in all cases, they consist of walls that provide thermal insulation and must at the same time 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 oven such as burners, sight glasses, recirculation fans and other air injection or smoke extraction nozzles. - For the upper wall, possibly support equipment such as fluid manifolds and circulation platforms.

[0005] They are traversed by wagons on which the products are placed and undergo a predefined cooking cycle during their movement. The transfer time, and therefore the cooking time, of the products varies greatly depending on the nature of the raw materials used; it ranges 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 having to be "reheated" each time they pass through the oven (leading to accelerated degradation of the refractories).

[0007] Furthermore, the wagons, and more specifically the insulating and refractory lining they carry, represent a significant mass to be heat-treated, equivalent to or even greater than the mass of the "products and supports" carried. These wagons, using known 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 penalizing in 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 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, in the vertical direction and from bottom to top: insulating panels 2 of calcium silicate, a dense base layer 3 of concrete, a layer 4 of loose 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 of the known technique therefore essentially consists of a structure formed by successive stacking of structural and insulating layers, with a basic structural layer of concrete providing rigidity and also conferring 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, in particular for firing ceramic parts in a kiln, comprising:

[0013] - a chassis extending in a first direction, a second direction and a third direction perpendicular in pairs, the chassis comprising a support plane, the chassis possibly comprising a support structure comprising 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 chassis,

[0014] - a plurality of studs supported by the chassis, preferably by the support structure, and arranged in rows, each extending along the first direction and spaced from each other along the second direction (L2),

[0015] - a continuous layer supported by the chassis and which can be formed on the plane of support, this continuous layer being formed between said studs (16) and being intended to support thermal insulation.

[0016] 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.

[0017] According to another feature, said continuous layer may 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 may overlap the edges of other sheets. Some of the edges of the sheets may be arranged opposite each other.

[0018] According to another feature, a thermally insulating frame can 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 continuous layer or said plurality of sheets a cup for receiving a thermally insulating insulator, preferably in the form of a filling material, the insulating frame having a thermal conduction along the third direction of less than 0.5 Wm*.K', preferably between 0.05 and 0.3 Wm*.K'.

[0019] This configuration allows for a lightweight frame, preferably with the aforementioned plates described above, surrounded by a thermally insulating frame which, together with the continuous layer, forms a recess for receiving insulation. The thermal properties of the frame allow it to limit heat transfer in the vertical direction, that is, along the third direction.

[0020] Note that the use of loose material as a filler is preferable for achieving good thermal insulation. However, it is understood that it would be possible to use another type of insulation, such as panels arranged in the basin.

[0021] According to yet another feature, the thermally insulating frame may comprise a first thermally insulating layer with a closed contour and having a thermal conductivity coefficient between 0.05 and 0.15 Wm'.K' and a second layer covering the first layer which also has a closed contour closed and exhibits a cold crush resistance after baking at 800°C of between 1 and 2 MPa, preferably between 1.5 and 1.8 MPa, preferably about 1.6 MPa.

[0022] The first thickness may comprise a plurality of layers of first thermally insulating panels, said layers being arranged in a staggered pattern.

[0023] The panels can be made of compressed fibrous materials.

[0024] The insulating panels may have a density of less than 350 kg / m3. The insulating panels have a fibrous structure.

[0025] The second layer may comprise a plurality of structural slabs, preferably made of lightweight concrete, placed side by side so as to form a closed contour.

[0026] Each support block can be mounted in a tray supported directly by the chassis.

[0027] Each tray may include a bottom wall supporting a support block, each bottom wall being arranged below the first support plane.

[0028] A collar can surround each tray and is mounted to rest on the chassis, preferably on the support structure.

[0029] 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 first support plane.

[0030] 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....

[0031] At least a plurality of first bars, made of a material capable of mechanically resisting a temperature of at least 1000°C, for example in SiC, can be arranged along the first direction on each of said pads.

[0032] At least a plurality of second bars, made of a material capable of mechanically resisting a temperature of at least 1000°C, for example in SiC, can be arranged along the first direction on each of said pads.

[0033] A thermal insulator, for example in the form of loose material, can be disposed on said plurality of sheets or said continuous layer, the thermal insulator having a thermal conductivity coefficient of less than 0.3 Wm*.K', preferably less than 0.2 Wm*.K'.

[0034] The thermal insulation may comprise at least a first layer and a second layer, the first layer preferably 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 for example, of approximately 75 kg / m3. It would still be possible to use a single material for the filling.

[0035] The second layer has a density between 100 and 120 kg / m3, for example approximately 110 kg / m3.

[0036] Each plot can comprise two distinct parts superimposed one on top of the other along the third direction.

[0037] 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.

[0038] Shims can be inserted between the first part of the block and the second part of the block.

[0039] The first part of the block includes notches for receiving bars mounted in support simultaneously on several blocks.

[0040] A thermally insulating block, such as a brick, can be inserted between a bottom wall of each tray and a block.

[0041] The pads can be made of concrete having a density of between 2 and 3 tonnes per m3.

[0042] This document also relates to a tunnel furnace having an inlet end and an outlet end in which is inserted a device as described above which includes rolling elements, the tunnel furnace including heating means successively comprising five treatment zones: - a first temperature rise zone comprising initial heating means, which may include initial burners. - a second cooking zone including secondary heating means which may include secondary 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 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, - 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. Brief description of the figures

[0043] [Fig.1] [Fig.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);

[0044] [Fig.2] [Fig.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;

[0045] [Fig.3] [Fig.3] is a schematic perspective view of the chassis of the device according to [Fig.3];

[0046] [Fig.4] [Fig.4] is a larger-scale schematic perspective view of the area delimited by dotted lines on [Fig.3];

[0047] [Fig.5] [Fig.5] illustrates a receiving area of ​​a support tray for a stud;

[0048] [Fig.6] [Fig.6] is an isolated schematic view of a receiving tray of a plot;

[0049] [Fig.7] [Fig.7] is a view similar to that of [Fig.5] and illustrating sheet metal surrounding the bins;

[0050] [Fig.8] [Fig.8] is a view similar to [Fig.7] on which plots have been added;

[0051] [Fig.9] [Fig.9] is a schematic axial cross-sectional view of a stud intended for use in a support device according to this document;

[0052] [Fig. 10] [Fig. 10] is a schematic perspective view of the first part of a plot;

[0053] [Fig. 11] [Fig. 11] is a schematic perspective view of the second part of a plot;

[0054] [Fig. 12] [Fig. 12] is a schematic perspective view of a support device according to this document, the thermally insulating filling material not being shown;

[0055] [Fig. 13] [Fig. 13] is a schematic perspective view similar to [Fig. 12] in which is further illustrated a covering thickness of the periphery of the chassis intended to form a structural layer;

[0056] [Fig. 14] [Fig. 14] is a schematic cross-sectional view of a block arranged in the immediate vicinity of the periphery of the support device;

[0057] [Fig. 15] [Fig. 15] is a schematic perspective view similar to [Fig. 13], in which a first layer of thermally insulating material is shown;

[0058] [Fig. 16] [Fig. 16] is a schematic view illustrating a second layer of thermal insulation covering the first layer of thermal insulation of [Fig. 14];

[0059] [Fig. 17]

[0060] [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;

[0061] [Fig. 19] [Fig. 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

[0062] Reference is now made to [Fig. 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.

[0063] 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 (Fig. 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 interlaced with each other and together define by their upper edges the support plane Pb More precisely 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 the operating temperatures of the support device 10.

[0064] As can be seen in [Fig. 4], the first plates 20 oriented along the first direction are L1 and can all be identical. The second plates 22 oriented along the second direction can comprise 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 L1 direction. 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.

[0065] The first plates 20 include notches shaped to receive the second secondary plates 22b. The second primary plates 22a include notches receiving the first plates 20. The notches in the first plates 20 and the second plates 22a, 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, 22 are nested successively within each other along said first direction of the third direction L3 and 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.

[0066] 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.

[0067] 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.

[0068] As can be seen in [Fig. 3] and [Fig. 4], the first plates 20 and the second plates 22 together define a first support plane Pb. 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, 22 are thus positioned at the same height along the third direction L3.

[0069] Figure 3 illustrates a plurality of trays 26 intended to receive pads 28 supporting the bars 12 (Fig. 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 LL

[0070] Figure 5 represents a receiving area of ​​a support tray 26 of a stud 14 and 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 include recesses 28 formed in their upper edges. These recesses, the length (along L1 and L2) and the thickness (along L3) of the recesses 28 of the first plate 20 and the second secondary plates 22b are such that they allow a collar 30 of a receiving tray to be received, as illustrated in Figure 5.

[0071] As illustrated in [Fig. 6], each tray 26 comprises side walls 32 extending along the third direction L3 and whose lower extremities are connected 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 Pb. 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 positioned 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 recesses 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 and whose other end 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.

[0072] 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 Pb, which reduces the overall size of the trays 26 along the third direction L3 and gives increased compactness to the support device 10 as described in this document.

[0073] 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 stud 14, which will be described below, and which therefore have an identical arrangement along the first direction L1 and the second direction L2.

[0074] Fig. 7 also illustrates a continuous layer 42 carried by the chassis 16 and which can be formed on the support plane Pb. This continuous layer 42 is formed between said studs 14 and is intended to support a thermal insulation which will be described later.

[0075] As illustrated in [Fig.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 arranged so as 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.

[0076] Figure 8 represents a plurality of pads 14 mounted in the trays 26 described previously. Each pad 14 comprises a first part 14a (Fig. 10) or lower part and a second part 14b (Fig. 11) or upper part arranged on the lower part 14a.

[0077] Fig. 9 represents a plot 14 according to a cross-sectional view along a plane comprising the second direction L2 and the third direction L3.

[0078] 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 comprise a first impression formed of longitudinal and transverse grooves Rb in which longitudinal and transverse ribs Ni of the lower face of the second part 14b of the block 14 are engaged.

[0079] 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.

[0080] The first part 14a of the block 14 has two opposing flanks along the longitudinal direction L1 that converge 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 substantially 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 form-coordinating elements ensure a locking mechanism that limits any movement in the plane formed by the longitudinal and transverse directions. 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 in the first part 14a and the second part 14b of the block 14, and for ensuring the flatness of the bars 12 mounted on the second part 14b of the block 14 ([Fig. 9]). These shims... can be made of refractory steel / alloy, ceramic (mica for example), in a material resistant to more than 1000°C.

[0081] Figure 9 also illustrates bars 12 mounted on the second part 14b. Each stud 14, in the case presented, has 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 stud 14 comprises at least one longitudinal groove Vb, here two longitudinal grooves, in which a support bar 12 is mounted.

[0082] As shown in [Fig. 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 makes it easier to replace only one part of each stud 14, in this case the second part, which is most exposed to the hot 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.

[0083] According to this document, a thermally insulating frame 52 surrounds the studs 14 and is arranged on the periphery of the chassis 14, more specifically on the periphery of the support structure 17, so as to form 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).

[0084] The proposed arrangement with studs 14 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 heat transfer compared to the prior technique.

[0085] 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 a thermal conductivity coefficient of between 0.05 and 0.15 Wm*.K', preferably between 0.6 and 0.11 Wm*.K'. The first layer 52a may have 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.

[0086] 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.

[0087] In one variant, the thermally insulating frame 52 could comprise only one thickness having the properties of the aforementioned second thickness 52b.

[0088] The second layer 52b provides increased mechanical strength compared to the first layer 52a and ensures resistance to impact of ceramic elements. Furthermore, the combination of two layers as indicated offers a better compromise between thermal insulation and mechanical strength.

[0089] 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. The second layer 52b preferably has a vertical dimension less than 40% of the vertical dimension of the first layer 52a, which ensures a good compromise in terms of overall dimensions along the vertical direction L3 to obtain a cold crush resistance after baking at 800°C (EN ISO 1927-6) of between 1 and 2 MPa, preferably between 1.5 and 1.8 MPa, preferably about 1.6 MPa, and a thermal conductivity of between 0.05 and 0.15 Wm*.K'.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.

[0090] 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 particularly the support structure 17. The insulating panels may be arranged to form a stepped arrangement extending from the inside of the support device outwards ([Fig. 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.

[0091] 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 integrated within the second layer 52b.

[0092] 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 so as 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·K and a cold crush resistance after curing at 800°C (according to ISO 1927-6) between 3 and 6 MPa.

[0093] Figures 15 and 16 illustrate the arrangement of a thermal insulator 58 above the continuous layer 42, that is, more particularly above the sheets 42a. In the illustrated embodiment, the thermal insulator comprises at least two layers. It should be noted that it could also comprise only one. The thermal insulator 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 insulator 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 insulator can have a thermal conductivity coefficient of less than 0.3 W / m².K, preferably less than 0.2 W / m².K.

[0094] 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 device. The first layer 58a may have a density between 65 and 85 kg / m³, for example, approximately 75 kg / m³. It would also be possible to use a single material for the infill. The second layer 58b may have a density between 100 and 120 kg / m³, for example, approximately 110 kg / m³. Assuming a single layer, the density would be less than 120 kg / m³, preferably between 85 kg / m³ and 100 kg / m³.

[0095] As illustrated in Figures 15 and 16, support blocks 60, such as bricks, can be arranged between the rows of pads 14. [Fig. 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.

[0096] 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 ([Fig. 18]).

[0097] We now refer again to [Fig. 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 [Fig. 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 strictly 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.

[0098] Reference is now made to [Fig. 19], which illustrates two curves: a first curve Ci shown in solid lines and a second curve C2 shown in dashed lines, each illustrating the temperature of a support device as a function of time when it is placed in a tunnel kiln for firing ceramic pieces at temperature Tb. 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 illustrated in [Fig. 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.

[0099] A tunnel furnace comprises an extension direction extending between an inlet end and a second outlet end. The tunnel furnace 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 furnace. The tunnel furnace of the invention and of the prior art successively comprises at least five zones. The five zones are designated Zb Z2, Z3, Z4, Z5 with regard to the present document and Za, Zb, Zc, Zd, Ze with regard to the prior art. - a first zone Zb Za, for temperature increase including initial heating means, such as initial burners, - a second cooking zone Z2, Zb including secondary heating means such as secondary burners, • Secondary heating methods may include burners capable of generating an axial and radial flame along the burner axis. The burner includes a principal direction of extension and is supported by a kiln vault so that its principal direction of extension is oriented in a plane perpendicular to the direction of extension of the tunnel kiln; - a third active cooling zone Z3, Zc including means for injecting cooling air as well as possible means for recovering hot air which can be carried by the vault of the tunnel furnace; - a fourth passive cooling zone Z4, Zd, i.e., a zone without cooling air injection, and - a fifth active cooling zone Z5, Ze comprising means of hot air recovery 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,

[0100] In the case of the dotted curve, it is observed 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.

[0101] It is observed that the first zone Zi has a steeper slope than the first zone Za. The first zone of the kiln corresponds to the area during which the ceramic pieces are brought to a firing temperature plateau Ti, which marks the beginning of the second zone. The second zone corresponds to the area during which the ceramic pieces are fired; it is therefore the firing zone itself, during which the temperature remains essentially constant. The duration of the second firing zone is reduced compared to the prior art.

[0102] 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.

[0103] 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 than the third zone Zc. Also, the length of the third zone Z3 is increased compared to the length of the third zone Zc of the prior art. The "quartz point" is the temperature of 573 °C at which quartz a (low-temperature polymorph) transforms into quartz [3 (high-temperature polymorph). This is the point at which crystalline silica transforms into vitreous silica while simultaneously reaching its point of maximum thermal expansion.

[0104] It is observed that the fourth cooling zone Z4 has a slope substantially 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 prior art.

[0105] Finally, the fifth zones Z5, Ze are substantially identical in terms of length and slope.

[0106] 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 better thermal uniformity within the parts being fired, as the support device retains less heat. The injection of cold air at the third zone Z3 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 corresponds to 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.

[0107] The configuration of the support device 10 according to the invention allows the cooking temperature Ti 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 means in the first and second zones Zb Z2.

Claims

Demands

1. A 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) having 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 (Pi) 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 frame so as to form with said continuous layer (42) a receiving basin for a thermally insulating insulator (58), preferably in the form of a filling material, the insulating frame having a thermal conductivity along the third direction of less than 0.5 Wm'.K1, preferably between 0.05 and 0.3 Wm'.K'.

4. Device according to claim 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 Wm'.K' and a second layer (52b) covering the first layer which is also closed contour and has a crush resistance of

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14.

15. cold after baking at 800°C between 1 and 2 MPa, preferably between 1.5 and 1.8, preferably around 1.

6. Device according to claim 4, wherein the first thickness (52a) comprises a plurality of layers of first thermally insulating panels (54), said layers being arranged in a staggered pattern. Device according to claim 5, wherein the panels (54) are made of compressed fibrous materials. Device according to claim 5 or 6, wherein the insulating panels (54) have a density of less than 350 kg / m3. Device according to any one of claims 4 to 7, wherein the insulating panels (54) have a fibrous structure. Device according to any one of claims 4 to 7, 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. 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). Device according to the preceding claim, wherein each tray (26) comprises a bottom wall supporting a support block (14), each bottom wall being arranged below the first support plane (Pi). Device according to claim 10 or 11, in which a collar (30) surrounds each tray (26) and is mounted to rest on the support structure (17). Device according to the preceding claim, wherein the first (20) and second (22) plates comprise recesses (28) for receiving the collar (30) associated with each tray (26) such that the upper surface of the collar (30) is coplanar with the first plane (Pi) of support. 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. A device according to the preceding claim, wherein at least a plurality of second bars (12), made of a suitable material to mechanically withstand a temperature of at least 1000°C, for example in SiC, are arranged along the first direction (Ll) on each of said pads (14).

16. A device according to any one of the preceding claims, wherein a thermal insulator (48), for example in the form of a loose material, is disposed on said continuous layer, the thermal insulator having a thermal conductivity coefficient of less than 0.3 Wm².K, preferably less than 0.2 Wm².K

17. Device according to the preceding claim, wherein the thermal insulation (48) comprises at least a first layer (48a) and a second layer (48b), such that the first layer has a lower density than the second layer (48a).

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

19. Device according to claim 17 or 18, wherein the second layer (48b) has a density between 100 and 120 kg / m3, for example about 110 kg / m3.

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

21. Device according to the preceding claim, wherein the first part (14a) and the second part (14b) cooperate by form linkage 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).

22. 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).

23. Device according to any one of claims 20 to 22, wherein the first part (14a) of block (14) comprises notches for receiving bars mounted simultaneously to rest on several blocks (14).

24. Device according to any one of the preceding claims and claim 10, wherein a thermally insulating brick (60) is intercalated between a bottom wall of each tray and a block.

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

26. A tunnel kiln having an inlet end and an outlet end in which is inserted a device according to any one of the preceding claims comprising rolling elements, the tunnel kiln successively comprising five processing zones: - a first temperature-rising zone (ZJ) 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 kiln measured between the inlet end and the outlet end, the fourth cooling zone corresponding to less than 25%, preferably less than 20%,of the said length of the oven.