Corner block for glass melting furnace

Description

technical field

[0001] The invention relates to an angle block for a glass furnace, and a glass furnace comprising such an angle block. State of the art

[0002] Many glass products are manufactured by melting and refining a vitrifiable mixture of raw materials, including compounds such as oxides, carbonates, sulfates, and nitrates. These two steps are carried out in furnaces whose main components are refractory materials capable of withstanding the high temperatures and stresses encountered within these furnaces. Glass furnaces thus generally contain a large number of refractory materials, arranged in different locations according to their properties. For each part of the furnace, the material chosen is the one that does not cause defects rendering the glass unusable (which would reduce production yields) and that is durable enough to ensure a satisfactory furnace lifespan.

[0003] A glass furnace, in particular a float furnace, comprises an elongated basin 4, surmounted by a vault ( figure 1). From upstream to downstream, we distinguish a high-temperature melting and refining zone 6, a constricted section, called a "corset" 8 in a float oven, and then a lower-temperature conditioning zone 10.

[0004] A glassable mixture of raw materials is introduced into the upstream melting and refining zone. This mixture is transformed into molten glass by means of heating devices such as burners (not shown), arranged in the side walls of the tank and operating alternately. The molten glass then passes through the sprue into the conditioning zone, where it is brought to a suitable temperature for drawing, for subsequent shaping operations such as forming, drawing, or floating.

[0005] Basin 4 comprises a vertical side wall 14 and a horizontal floor 16. The side wall 14 is conventionally made up of several sections in lateral blocks, connected to each other by corner blocks 20.

[0006] The part of the side wall 14 which connects two substantially flat sections of the side wall of the basin is called the "corner block".

[0007] We distinguish the furnace corner blocks 20 1, the melting end corner blocks 20 2, and the entry corner blocks 20 3 and exit corner blocks 20 4 of the corset.

[0008] Corner blocks are subjected to significant stress and sometimes develop pronounced cracking, both vertically and horizontally. Once cracked, a corner block is subject to increased corrosion due to molten glass seeping into the cracks. This accelerated corrosion leads to premature wear, which can result in major glass leaks and ultimately furnace shutdown.

[0009] The corner block must also withstand strong thermal stresses since part of the block is in an environment at temperatures close to ambient temperature, usually thanks to air blow cooling, while the part inside the furnace is at temperatures of around 1500°C.

[0010] Furthermore, the corner block undergoes thermal cycles due to maintenance operations, such as operations called "plating", which require stopping and then restarting the external cooling of the furnace, or due to the loading of the vitrifiable mixture.

[0011] The corner block must also resist corrosion from aggressive furnace vapors and condensate. Furthermore, the loading corner blocks must resist erosion caused by the passage of raw materials.

[0012] To withstand these stresses, the corner block is made of a refractory product.

[0013] Among refractory products, a distinction is made between molten and sintered products. Unlike sintered products, molten products most often contain an intergranular glassy phase connecting crystallized grains. The problems posed by sintered and molten products, and the technical solutions adopted to address them, are therefore generally different. A composition developed to manufacture a sintered product is thus not a prioriIt can be used as is to manufacture a molten product, and vice versa. Molten products, often called "electrofused," are obtained by melting a mixture of suitable raw materials in an electric arc furnace or by any other technique adapted to these products. The molten material is then poured into a mold, and the resulting product undergoes a controlled cooling cycle.

[0014] Currently, fused products are mainly used to make corner blocks, particularly Alumina-Zirconia-Silica (AZS) type products containing 30 to 45% zirconia. The microstructure of these products is essentially composed of alpha-alumina crystals, free zirconia crystals, corundum-zirconia eutectic crystals, and an intercrystalline glassy phase.

[0015] Furthermore, to increase the furnace's lifespan, the assembly of the refractory blocks must be "dry," meaning without jointing cement. To ensure a watertight seal, the blocks must therefore have very precise dimensions and a good surface finish. The blocks, and in particular the corner blocks, are thus always machined to ensure close contact with adjacent blocks. A glass furnace with wall blocks and corner blocks having a concave inner surface is described in patent DE717505C.

[0016] However, the resistance to cracking of corner blocks is sometimes insufficient to meet the current evolving needs of glassmakers, who require an extension of furnace life.

[0017] Therefore, there is a need for a corner block with improved resistance to cracking and / or an increased lifespan. One aim of the invention is to meet this need. Summary of the invention

[0018] The invention relates to an angle block for a glass furnace basin according to claim 1.

[0019] As will be seen in more detail later in the description, the inventors discovered that the absence of an edge reduces cracking and increases the lifespan of the corner block. A corner block according to the invention may also include one or more of the following optional features: the main section extends from the upper surface to a base part intended to be integrated into a basin floor in the service position, or even extends from the upper surface to the lower surface of the corner block; in the main section, the hot face is devoid of an edge marking a break in slope greater than 10°; in the median longitudinal section plane, the corner block has, in the main section, a thickness decreasing from the lower limiting transverse plane to the upper limiting transverse plane, or has a constant thickness; in the main section, a point of the profile of the hot face in the median longitudinal section plane is further from a vertical line passing through the upper end of said profile the closer said point is to the lower surface;The hot face profile in a median longitudinal cutting plane is straight and, preferably, forms in the service position, with the vertical direction, an angle α less than 30° and greater than 2°; the angle α is less than 20°, preferably less than 10%, or even less than 5% and / or greater than 3°; the hot face is strictly convex in the main section; in any transverse cutting plane in the main section, the hot face has a convex profile in the shape of an arc of a circle, optionally extended, at one or both of its ends, by a straight line segment; the hot face has, in a transverse cutting plane, a profile whose general shape is identical regardless of the transverse cutting plane considered in the main section;The hot face, in a cross-sectional plane of the main section, has a profile that is longer the closer said cross-sectional plane is to the lower limiting cross-sectional plane; the corner block has the general shape of a quarter of a truncated cylinder with a circular base, or a quarter of a truncated cone, or a quarter of a truncated cylinder with an annular base; in the main section, the cold face is edgeless.

[0020] According to a second main, optional aspect, of the invention, at least part of the cold face is thermally insulated.

[0021] An angle block according to the second main aspect of the invention may further include one or more of the following optional features: a first thermally insulating material is disposed, preferably glued, on at least part of the cold face, preferably so as to cover at least part of the cold face which, in the service position, extends from the upper surface of the corner block to the waterline, preferably so as to cover at least the entire part of the cold face which, in the service position, extends from the upper surface of the corner block to the waterline; preferably, the part of the cold face covered by the first thermally insulating material extends, preferably from the upper surface of the corner block, to more than 300 mm, preferably more than 400 mm, preferably more than 500 mm, and / or less than 800 mm, preferably less than 600 mm from the upper surface; preferably, the first thermally insulating material is in the form of a slab;Preferably, the first thermally insulating material has a thermal conductivity of less than 1.0 Wm⁻¹·K⁻¹, or even less than 0.7 Wm⁻¹·K⁻¹, or even less than 0.5 Wm⁻¹·K⁻¹; according to another variant, the first thermally insulating material is made of a refractory material having a thermal conductivity of less than 7.0 Wm⁻¹·K⁻¹; preferably, the thickness of the first thermally insulating material, preferably in the form of a slab, is less than or equal to 100 mm, or even less than or equal to 50 mm, or even less than or equal to 30 mm, or even less than or equal to 20 mm, or even less than or equal to 10 mm, or even less than 5 mm and / or greater than 1 mm;a second thermally insulating material is disposed, preferably bonded, on at least part of the cold face, preferably so as to cover at least part of the cold face which, in the service position, extends below the waterline, preferably so as to cover at least all of the part of the cold face which, in the service position, extends below the waterline; preferably, the part of the cold face covered by the second thermally insulating material extends, preferably from the lower surface of the corner block, to more than 500 mm, preferably more than 600 mm, preferably more than 700 mm, and / or less than 800 mm from the lower surface; preferably, the second thermally insulating material is in the form of a slab;preferably, the second thermally insulating material has a thermal conductivity of less than 8 Wm⁻¹.K⁻¹, or even less than 6 Wm⁻¹.K⁻¹, or even less than 1 Wm⁻¹.K⁻¹; the second insulating material is an AZS type material comprising more than 80% ZrO₂ by mass percentage, and preferably in which, by mass percentages on the basis of oxides, the total content Al₂O₃ + ZrO₂ + SiO₂ represents more than 80.0%, preferably more than 84.0%, preferably more than 86.0%, and / or less than 97.0%, or even less than 95.0%, or even less than 94.0%; preferably, the thickness of the second thermally insulating material, preferably in the form of a slab, is less than or equal to 200 mm, or less than or equal to 100 mm, or less than or equal to 50 mm, or less than or equal to 30 mm, or less than or equal to 20 mm, or less than or equal to 10 mm, or less than 5 mm and / or greater than 1 mm;Preferably, the thickness and / or thermal conductivity of the second thermally insulating material layer are such that the thermal insulation is greater than that provided by the first thermally insulating material layer; the entire cold face is covered by a thermally insulating material, the upper part of the cold face being more thermally insulated, preferably with said first thermally insulating material, than the lower part of the cold face, preferably insulated with said second thermally insulating material, the boundary between the areas covered by the first thermally insulating material and by the second thermally insulating material being preferably in a band of less than 20 cm, preferably less than 10 cm high in the waterline area.

[0022] An angle block according to the invention may also include one or more of the following optional features: the angle block has a chemical composition, in mass percentage on the basis of oxides, such that: Al 2 O 3 + ZrO 2 + SiO 2 > 80.0%; the angle block has a chemical composition comprising, in mass percentage on the basis of oxides, more than 0.5% and less than 10.0% of a zirconia stabilizer; the corner block has a chemical composition, in mass percentages on the basis of oxides, such that, for a total of 100%: Al 2 O 3 + ZrO 2 + SiO 2: more than 84.0% and less than 99.7%, Y 2 O 3: less than 5.0%, Na 2 O + K 2 O: less than 1.5%, B 2 O 3: less than 0.6%, oxide species other than Al 2 O 3 , ZrO 2 , SiO 2 , Y 2 O 3 , Na 2 O , K 2 O and B 2 O 3: less than 10.0%; the oxide species other than Al 2 O 3 , ZrO 2 , SiO 2 , Y 2 O 3 , Na 2 O, K 2 O and B 2 O 3 are CaO, MgO, SrO, BaO, TiO 2 , Fe 2 O 3 , and SnO 2 , one or more of these species may be absent;The angle block has a chemical composition, in mass percentages based on oxides, such as: ZrO2: more than 12.0% and less than 45.0%, SiO2: more than 8.0% and less than 24.0%, Al2O3: more than 35.0% and less than 60.0%.

[0023] A manufacturing process comprises the following successive steps: a) mixing of raw materials so as to form a starting charge; b) melting of said starting charge until a bath of molten material is obtained; c) pouring of said molten material into a mold, preferably at room temperature, and solidification of said molten material by cooling, so as to obtain an intermediate piece having the general shape of an angle block; d) demolding of the intermediate piece, then e) preferably machining, preferably partial, of the outer surface of the intermediate piece, so as to obtain an angle block according to the invention or a piece of an angle block according to the invention.

[0024] Preferably, the mold is made by 3D printing, so as to obtain a block with the desired shape.

[0025] The invention further relates to an angle device comprising an angle block according to the invention and an adapter block having a first face in contact with the left surface or the right surface of the angle block, and a second face, parallel and opposite to the first face, and having a different shape from said first face.

[0026] The shape of the left surface or the right surface is preferably that of the surface of an adjacent block with which said left surface or said right surface is in contact in the service position.

[0027] A method for manufacturing a furnace comprising an angle block according to the invention is described.

[0028] The invention also relates to a glass furnace comprising a basin having a side wall having two sides and an angle block according to the invention, or an angle device according to the invention, connecting said two sides.

[0029] Preferably, the corner block or corner device is positioned at the inlet of the chamber or at the loading point. Preferably, the corner block is a loading corner block.

[0030] When the glass furnace is in operation, the corner block or corner device is at least partially in contact with molten glass. Definitions

[0031] The "service position" is the position in which the corner block is integrated into a side wall of a glass furnace basin, so as to connect two sections of said side wall to each other.

[0032] The waterline height varies when the glass furnace is in operation. The "waterline zone" is defined by the maximum and minimum waterline heights when the glass furnace is in operation.

[0033] The adjectives "right" and "left", "hot" and "cold" are used for clarity. Before the furnace is put into service, the "hot" side is the side that is intended to be exposed to the environment inside the furnace, i.e., to the highest temperatures after commissioning.

[0034] "Lower" and "upper", "inner" and "outer", "horizontal" and "vertical" refer to orientations or positions when the corner block is in its service position, in a glass furnace.

[0035] By "horizontal" and "vertical" we mean an orientation forming with a perfectly horizontal and vertical plane, respectively, an angle of less than 5°, or even less than 2°, or even less than 1°.

[0036] The length direction of a corner block is the direction that extends vertically when the corner block is in the service position. This direction is represented by arrow V in the figures.

[0037] A transverse plane is a plane perpendicular to the direction of the length of the angle block.

[0038] The median transverse plane is the transverse plane at mid-length of the corner block.

[0039] In a cross-sectional plane, the width of a corner block is measured along the line extending midway between the hot and cold faces. In the figures, this line, called the "width line", is represented by line X.

[0040] In a cross-sectional plane, the thickness is measured perpendicular to the X line of the width.

[0041] A longitudinal plane is a plane that includes the direction of length and, in a transverse plane, is perpendicular to the width line X of the corner block. The median longitudinal plane is the longitudinal plane at mid-width, the width being defined in the median transverse cutting plane.

[0042] A "cutting" plane is a plane that cuts through a block and provides a view of the block thus cut.

[0043] The "edges" of a surface are the points on that surface where a line of steepest descent exhibits a slope change, also called a "break in slope," greater than 25°. By extension, we also say that the surface has a break in slope greater than 25°. For example, the Figure 10represents a surface S on which the line of greatest slope G exhibits a break in slope of θ at every point MA on the line A. If the angle θ is greater than 25° for all points on the line A, the line A is an edge. In practice, the slope change can be measured between two points M1 and M2 on the line of greatest slope separated by a distance of 3 mm, the 3 mm distance being measured along said line.

[0044] "Machining" refers to an operation by which the surface of a refractory part is machined to obtain a precise surface geometry. Typically, and in a particular embodiment of the invention, machining involves removing at least the outer skin.

[0045] For clarity, the chemical formulas of oxides are used to designate the contents of these oxides in a composition. For example, "ZrO2", "SiO2" or "Al2O3" designate the contents of these oxides and "zirconia", "silica" and "alumina" are used to designate phases of these oxides made up of ZrO2, SiO2 and Al2O3, respectively.

[0046] Unless otherwise stated, all oxide contents in an angle block according to the invention are mass percentages based on the oxides. A mass content of an oxide of a metallic element refers to the total content of that element expressed in the form of the most stable oxide, according to the usual industry convention.

[0047] In a molten product, oxides typically represent more than 95%, more than 97%, more than 99%, preferably approximately 100% of the mass.

[0048] HfO₂ is not chemically dissociable from ZrO₂. However, according to the present invention, HfO₂ is not added intentionally. HfO₂ therefore refers only to traces of hafnium oxide, this oxide being always naturally present in zirconia sources at mass contents generally less than 5%, generally less than 2%. In a block according to the invention, the mass content of HfO₂ is preferably less than 5%, preferably less than 3%, preferably less than 2%. For clarity, the total content of zirconium oxide and traces of hafnium oxide may be referred to interchangeably as "ZrO₂" or as "ZrO₂ + HfO₂". HfO2 is therefore not included in the "oxide species other than ZrO2, SiO2, Al2O3, Na2O, B2O3 and Y2O3".

[0049] “Contain”, “define”, “present” or “understand” should be interpreted broadly, not restrictively.

[0050] Unless otherwise specified, the definition of a characteristic applying to the main segment does not exclude that characteristic for the rest of the corner block. Brief description of the figures

[0051] Other features and advantages of the invention will become apparent upon reading the following detailed, non-limiting description and examining the accompanying drawing in which: [ Fig 1 ] there figure 1 schematically represents, as seen from above, a glass melting basin; Fig 2 ] there figure 2 schematically represents, in perspective, a first embodiment of a corner block according to the invention; [ Fig 3 ] there figure 3 schematically represents, in perspective, a second embodiment of a corner block according to the invention; [ Fig 4 ] there figure 4 schematically represents, in perspective, a third embodiment of a corner block according to the invention; [ Fig 5 ] there figure 5schematically represents, in perspective, a fourth embodiment of a corner block according to the invention; [ Fig 6 ] there figure 6 schematically represents, in perspective, a fifth embodiment of a corner block according to the invention; [ Fig 7 ] there figure 7 schematically represents, in perspective, a sixth embodiment of a corner block according to the invention; [ Fig 8 ] there figure 8 schematically represents, in perspective, a seventh embodiment of a corner block according to the invention; [ Fig 9 ] there figure 9 schematically represents, in perspective, an angle device according to the invention comprising an angle block according to the invention and adaptation blocks, in the service position; Fig 10 ] there Figure 10 illustrates the definition of an edge.

[0052] In the various figures, identical or analogous references are used to designate identical or analogous parts or parts of parts. Detailed description Shape

[0053] By definition, an angle block 20 or an angle device 32 connects two sections 141 and 142 of the lateral wall of the basin 14, partially represented on the figure 8 Viewed from above, the two panels join the corner block or corner device according to panel planes P1 and P2, respectively. The panel planes P1 and P2 form an angle greater than 45°, preferably greater than 70°, preferably greater than 80°, and / or less than 135°, preferably less than 110°, preferably less than 120°, classically of about 90°.

[0054] As depicted on the figures 5 and 6A corner block 20 comprises a lateral portion 20l, intended to be integrated into the lateral wall 14 of the basin, and a base portion 20b intended to bear on the ground and be integrated into the basin's floor. The base portion may have edges 21, particularly when it projects beyond the hot face, in the form of a sole, as shown in the figure 5 .

[0055] The base may also be indistinguishable from the side, as on the figures 2 to 4 .

[0056] The outer surface of a 20 angle block comprises: upper surfaces 22s and lower surfaces 22i, conventionally horizontal, delimiting the length L 20 of the corner block; right and left surfaces, 22d and 22g, conventionally vertical, which, in the service position, are in contact with corresponding surfaces of adjacent blocks; an inner lateral surface, or "exposed surface", also called the "hot face" 22c, which belongs to the inner surface of the side wall 14 of the basin and which, in the service position, is in contact with the environment inside the basin; optionally, an inner base surface 22b which, in the service position, is also in contact with the environment inside the basin, but which belongs to the base (see, for example, the figure 5 ), an outer surface, also called the "cold face" 22f, opposite the hot face 22c, which, in the service position, is in contact with the environment outside the basin.

[0057] Preferably, the upper surface 22s, classically flat, delimits the upper edge of the lateral wall of the basin.

[0058] Preferably, the lower surface 22i, which is classically flat, rests on the ground.

[0059] Preferably, the right and left surfaces, 22d and 22g, are planar. Classically, they extend in planes forming an angle greater than 45°, preferably greater than 70°, preferably greater than 80°, and / or less than 135°, preferably less than 110°, preferably less than 120°, classically about 90°.

[0060] The right and left surfaces, 22d and 22g, are classically perpendicular to the planes of pan P 1 and P 2, respectively.

[0061] In a corner block, each of the right and left surfaces 22d and 22g is machined. A machined surface therefore does not exhibit a skin microstructure.

[0062] Preferably, only the surfaces that, in the service position, are in contact with corresponding surfaces of adjacent blocks are machined. Preferably, all surfaces that, in the service position, are in contact with corresponding surfaces of adjacent blocks are machined.

[0063] The invention relates to the lateral portion 20l which typically extends from the upper surface of the corner block to the base portion 20b, typically over more than 90% of the length of the corner block. Therefore, the features described below refer to a main section 24 of the corner block which extends between two upper and lower limiting transverse planes, referenced P24s and P24i, respectively, shown in the figure. figure 4 For example.

[0064] Preferably, the main section 24 extends, between the two upper and lower transverse boundary planes P24s and P24i, over more than 80%, preferably more than 90%, preferably more than 95%, preferably 100% of the block's length. Particularly in the embodiments shown in the figures 2 to 4 , the two upper and lower limit transverse planes can be the upper surface 22s and lower surface 22i, respectively.

[0065] Preferably, the main section extends from the upper surface. Preferably, the main section extends, along its length, to the base of the corner block.

[0066] Preferably, the main section extends from the upper surface to within 20 cm, preferably within 10 cm, preferably within 5 cm of the lower surface.

[0067] According to the invention, the hot face does not have an edge in the main section.

[0068] The hot side is oriented towards the inside of the basin. It is intended to be at least partially in contact with molten glass.

[0069] Preferably, the warm face does not have a gentle edge in the main section, an edge being gentle when it delimits a break in slope of less than 15°, preferably less than 10°, preferably less than 5°, preferably less than 1°.

[0070] In the median longitudinal section plane Pl 50, the corner block has a length L 20 preferably greater than 0.5 m, preferably greater than 0.8 m, preferably greater than 1.0 m, preferably greater than 1.2 m, and / or less than 2.0 m, preferably less than 1.7 m (the section in this plane is shown on the left part of the figures 2 And 3 ).

[0071] The corner block 20 has a thickness e 20, measured in the median longitudinal cutting plane Pl 50 and in the median transverse cutting plane Pt 50, preferably greater than 200 mm, preferably greater than 250 mm and / or less than 500 mm, preferably less than 450 mm.

[0072] Preferably, the thickness em of the corner block, measured at the intersection between the median transverse cutting plane Pt 50 and the longitudinal cutting plane passing through a point M on the width line X of the corner block, varies by less than 20%, preferably less than 10%, preferably less than 5%, preferably less than 1% with respect to e 20 when the point M travels along the width line X. In other words, the m -e 20 | / e 20 < 20%, preferably |em - e 20 | / e 20 < 10%, preferably |em - e 20 | / e 20 < 5%, preferably |em - e 20 | / e 20 < 1%, regardless of the thickness em measured along the width line X.

[0073] In the median longitudinal section plane Pl 50, the corner block can have a constant thickness regardless of the position considered along the length direction of the corner block, that is, regardless of the transverse section plane considered, at least in the main section, as shown for example on the figure 2 The manufacturing of the corner block is simplified.

[0074] In the median longitudinal section plane Pl 50, the corner block 20 can have a variable thickness depending on the position considered along the direction of the length of the corner block.

[0075] Preferably, in the median longitudinal section plane Pl 50, the corner block has, at least in the main section, an increasing thickness, preferably regularly increasing, as one descends along the length of the corner block, as shown for example on the figure 3 .

[0076] Preferably, (e max - e min ) / e min > 10%, and / or, preferably, (e max - e min ) / e min < 30%, or even (e max - e min ) / e min < 20%, e max and e min denoting respectively the maximum and minimum thicknesses in the median longitudinal section plane Pl 50 (see figure 2 ). The lifespan of the corner block is significantly improved.

[0077] In a preferred embodiment, the Lc profile of the hot face in the median longitudinal cutting plane Pl 50 is substantially straight. Preferably, it forms an angle α with the vertical direction V that is less than 30°, preferably less than 20°, preferably less than 10°, or even less than 5°, and / or preferably greater than 2°, preferably greater than 3° (as shown, for example, on the figure 3 ).

[0078] In one embodiment, the Lc profile of the hot face in the median longitudinal cutting plane Pl 50, for example concave or straight, is shaped to move inwards towards the basin as one approaches the lower surface 22i.

[0079] As shown, for example, on the figure 4 , a point of the profile Lc of the hot face, in the median longitudinal cutting plane Pl 50, can be further removed from a vertical line Δ passing through the upper end of said profile Lc the closer said point is to the lower surface 22i.

[0080] In one embodiment, the Lf profile of the cold face in the median longitudinal cutting plane is substantially rectilinear. Preferably, it forms an angle of less than 10°, preferably less than 5°, preferably less than 2°, and preferably substantially zero with the vertical direction V, as shown, for example, on the figure 3 .

[0081] In the median transverse section plane Pt 50, the hot face presents a Tc profile, reflected in the right part of the figures 2 to 4 for clarity.

[0082] The profile of the hot face can be the same regardless of the transverse cutting plane chosen in the main section, as for example on the figures 2 And 4 Preferably, it results from a homothetic deformation of the profile Tc (defined in the median transverse cutting plane Pt 50) as for example on the figure 3 or on the figure 5 Preferably, the homothety ratio increases, preferably regularly, from the upper limiting transverse plane to the lower limiting transverse plane. In other words, the profile lengthens as one moves down the corner block, while maintaining its general shape, as for example on the figures 3 And 5 .

[0083] Preferably, the Tc profile is strictly convex over more than 80%, preferably more than 90%, preferably 100% of its length. In one embodiment, the hot face does not have a flat area, as on the figures 1 to 3 .

[0084] Preferably, the Tc profile does not include a strictly concave portion.

[0085] Preferably, the Tc profile does not have a singular point, i.e., no break in slope.

[0086] Preferably, the Tc profile is substantially symmetrical with respect to the median longitudinal cutting plane, as in the embodiments of figures 1 to 4 .

[0087] In one embodiment, the Tc profile has the shape of a circular arc ( figures 2 And 3 The arc of a circle can be extended by straight line segments ( figure 4 ).

[0088] In the median transverse section plane Pt 50, the cold face presents a profile Tf, transferred to the right part of the figures 2 to 4 for clarity.

[0089] Preferably, the cold face profile is the same regardless of the cross-section plane chosen in the main section.

[0090] The Tf profile can be strictly convex ( figures 2 And 3 Preferably, however, the Tf profile is flat or strictly concave ( figure 4 ), which improves mechanical strength.

[0091] Preferably, the Tf profile does not have a singular point, i.e., no break in slope.

[0092] Preferably, the Tf profile is substantially symmetrical with respect to the median longitudinal plane, as in the embodiments of figures 2 to 4 .

[0093] In one embodiment, the profile Tf has the shape of a circular arc ( figures 2 And 3The arc of a circle can be extended by straight line segments ( figure 4 ).

[0094] In one embodiment, in the median cross-section plane, the distance between the profiles of the hot and cold faces is constant, regardless of the longitudinal section plane considered.

[0095] The characteristics described above relating to the shape of the corner block and defined with reference to the median longitudinal cutting plane are preferably applicable in any longitudinal cutting plane between two limiting longitudinal planes defined with respect to the width line X (in the median transverse cutting plane), the distance between the limiting longitudinal planes being preferably greater than 60%, preferably greater than 70%, preferably greater than 80%, preferably greater than 90% of the width of the corner block (distance between the right and left faces, following the width line X in the median transverse cutting plane).

[0096] The characteristics described above relating to the shape of the corner block in the median longitudinal cutting plane are preferably applicable regardless of the longitudinal cutting plane considered.

[0097] The characteristics described above and defined with reference to the median cross-section plane are preferably applicable regardless of the cross-section plane considered in the main section.

[0098] The right and left surfaces are typically the same shape as the surfaces of the lateral blocks with which they are in contact. Thus, internally, the basin does not present any irregularities resulting from a step between the blocks. Typically, the surfaces of the adjacent lateral blocks are approximately rectangular in outline. This is particularly true when the Lc profile causes a widening of the corner block in the lower part ( figure 4(for example), it is therefore necessary to join a rectangular contour in the longitudinal planes in which the right and left surfaces extend, as shown on the figure 7 For example.

[0099] The corner block 20 can be made up of one or more pieces. In particular, it can be an assembly of several elementary blocks 341, 342 and 343, the faces at the right and left ends of the assembly being oriented perpendicular to the planes P1 and P2, respectively.

[0100] In one embodiment, adapter blocks 301 and 302 are added to the angle block according to the invention, so as to constitute an angle device 32 according to the invention, as shown in the figure 8 . The adaptation blocks can in particular be configured so that the right surface and the left surface of the corner device are identical to those of the adjacent side blocks 14 1 and 14 2, respectively.

[0101] The angle device 32 can therefore comprise a one-piece angle block or, as shown in the figure 8 , an assembly of elementary blocks, and one or more adaptation blocks so as to adapt the shape of the surfaces at the right and left ends of the corner device to the faces of the adjacent blocks opposite.

[0102] In the implementation of the figure 2 , the corner block has the general shape of a quarter of a truncated cylinder with a circular base and a vertical axis, a quarter of such a cylinder being a piece of the truncated cylinder after it has been cut by two planes perpendicular to each other and passing through its axis.

[0103] In the implementation of the figure 3, the corner block has the general shape of a quarter of a truncated cone with a vertical axis, a quarter of a truncated cone being a piece of the truncated cone after it has been cut by two planes perpendicular to each other and passing through its axis.

[0104] In the implementation of the figure 4 , the corner block has the general shape of a quarter of a truncated cylinder with an annular base and a vertical axis, a quarter of such a cylinder being a piece of the truncated cylinder after it has been cut by two planes perpendicular to each other and passing through its axis.

[0105] According to one embodiment, the corner block is provided with an anchoring device in the metal casing of the glass furnace. This anchoring device is, for example, made up of a screw, a hook, a metal plate, or a notch.

[0106] Of course, the dimensions and shapes described above are not exhaustive. Composition

[0107] Preferably, the corner block according to the invention comprises, and is preferably made of, an electrofused material consisting, for more than 80% of its mass, of alumina, zirconia, silica, and optionally a zirconia stabilizer, in particular yttrium oxide. The material may be of the AZS type or have a very high zirconia content (typically comprising more than 80% ZrO₂ by mass percentage).

[0108] In one embodiment, the angle block according to the invention comprises more than 0.5%, more than 1.5%, more than 3.0%, more than 4.0%, more than 5.0%, or even more than 6.0%, and / or less than 10.0%, less than 9.0%, or even less than 8.0% of zirconia stabilizer, in particular CaO and / or Y2O3 and / or MgO and / or CeO2, preferably Y2O3 and / or CaO, preferably Y2O3.

[0109] Preferably, the corner block according to the invention has a chemical composition, expressed as mass percentages based on oxides, such that, for a total of 100%, Al₂O₃ + ZrO₂ + SiO₂: more than 80.0%, preferably more than 84.0%, preferably more than 86.0%, and / or less than 97.0%, or even less than 95.0%, or even less than 94.0%, and / or Y₂O₃: more than 0.5%, more than 1.5%, more than 2.0% and / or less than 5.0%, less than 4.0%, or even less than 3.0%, and / or Na₂O: more than 0.1%, or even more than 0.2%, and / or less than 0.6%, preferably less than 0.5%, or even less than 0.4%, and / or B₂O₃: more than 0.1%, or even more than 0.2%, and / or less than 0.6%, preferably less than 0.5%, or even less than 0.4%, and / or oxide species other than Al2O3, ZrO2, SiO2, Y2O3, Na2O and B2O3: less than 10.0%, preferably less than 9.0%, preferably even less than 8.0%, less than 5.0%, or even less than 3.0%, or less than 2.0%, or less than 1.0%, or less than 0.5%.

[0110] According to one embodiment, the corner block according to the invention has a chemical composition such that: ZrO2: more than 12.0%, preferably more than 20.0%, preferably more than 25.0% and / or less than 80.0%, or even less than 75.0% and / or SiO2: more than 6.0%, preferably more than 10.0% and / or less than 24.0%, or even less than 20.0%, and / or Al2O3: more than 18.0%, preferably more than 25.0% and / or less than 60.0%, preferably less than 50.0%.

[0111] According to one embodiment, the corner block according to the invention has a chemical composition such that: ZrO₂: more than 12.0%, preferably more than 15.0%, preferably more than 18.0%, or even more than 22.0%, and / or less than 45.0%, or even less than 40.0%, or even less than 35.0%, or even less than 30.0%, or even less than 25.0%, and / or SiO₂: more than 8.0%, preferably more than 10.0%, preferably more than 12.0%, and / or less than 24.0%, or even less than 20.0%, less than 17.0%, or even less than 14.0%, and / or Al₂O₃: more than 35.0%, preferably more than 38.0%, or even more than 40.0%, and / or less than 60.0%, preferably less than 55.0%, or even less than 50.0%, less than 46.0%, or even less than 44.0%.

[0112] According to one embodiment, the corner block according to the invention has a chemical composition such that: ZrO2: more than 80.0%, preferably more than 83.0%, preferably more than 86.0%, and / or less than 97.0%, or even less than 95.0%, or even less than 94.0%, and / or SiO2: more than 0.5%, preferably more than 1.5%, preferably more than 2.5%, preferably more than 4.0%, or even more than 6.0%, more than 8.0%, more than 8.5%, and / or less than 15.0%, or even less than 12.0%, less than 10.0%, or even less than 8.0%, and / or Al2O3: more than 0.2%, preferably more than 1.0%, and / or less than 3.0%, preferably less than 2.0%. Examples

[0113] Modeling tests were carried out using finite element analysis software (Ansys 17.0).

[0114] Using this software, we determined the temperature and stress fields of AZS refractory blocks, 1300 millimeters long and with a chemical composition containing 40% ZrO₂ (ER 1711 from Saint-Gobain SEFPRO), when the hot face of the block is at a temperature of 1500°C, with heat dissipation by blowing air at ambient temperature (20°C) and with a heat transfer coefficient of 125 W / (m².K). Three block geometries were compared: a rectangular prism (parallelepiped block), with a square base measuring 450 millimeters on each side ("reference" in Table 1 below); a rounded block, representing a quarter of a cone, of the type shown on the figure 3, the radius of the hot face profile being 450 millimeters at the top surface and 550 millimeters at the bottom surface (example 1); the block in example 1 having, on the cold face, a plate of insulating material 10 millimeters thick (thermal conductivity of 0.5 W / (mK) (example 2).

[0115] The stress state at each point of the block can be represented by a tensor, the stress tensor. The principal stresses are the stresses expressed in a basis such that the stress tensor is a diagonal matrix. The coefficient in this matrix corresponding to the highest (positive) tensile stress is called the "first principal stress." The criticality of the stresses was evaluated by the maximum Rmax of the ratio R of the first principal stress to the ultimate tensile strength (ORS), considering all the R ratios along the most stressed edge. The ORS is measured in air, at the temperature considered, on a specimen measuring 80 x 20 x 20 mm in a three-point bending setup with a distance of 70 mm between the two lower supports and a punch descent rate of 0.5 mm / min. The higher the Rmax, the more probable the failure. The results are given in Table 1. [Table 1] Rmax Decrease compared to the reference Reference 3,0 Example 1 2,0 33 % Example 2 1,3 57 %

[0116] The tests therefore show that an angle block according to the invention makes it possible, in a remarkable way, to limit the stresses.

[0117] The invention is particularly well suited to corset entry blocks.

[0118] It goes without saying that the implementation methods described are only examples and could be modified.

Claims

1. Corner block for a glass furnace tank, said corner block having an outer surface (20) comprising: - upper (22s) and lower (22i) horizontal surfaces delimiting the length (L20) of the corner block, - right (22d) and left (22g) vertical surfaces intended to be in contact, in the operational position, with corresponding surfaces of adjacent blocks, said right (22d) and said left (22g) surfaces being machined and not having a skin microstructure, - an inner side surface, called the hot face (22c), which belongs to an inner surface of a side wall (14) of the tank and which is intended to be in contact, in the operational position, with the environment inside said tank, - a cold face (22f), opposite the hot face (22c) which, in the operational position, is in contact with the environment outside the tank, the corner block being characterized in that in a main portion (24) of the corner block extending, over more than 80% of the length of the corner block, between two limiting upper (P24s) and lower (P24i) transverse planes, the hot face (22c) is edge-free, an edge being a line along which the hot face has a break in slope greater than 25°, the hot face (22c) having a profile (Tc) that is convex in any transverse sectional plane in the main portion (24).

2. Corner block according to the preceding claim, wherein the main portion (24) extends from the upper surface (22s) to a base part (20b) intended to be integrated in a floor of the tank in the operational position.

3. Corner block according to any one of the preceding claims, wherein, in the main portion (24), the hot face (22c) is devoid of an edge marking a break in slope greater than 10°.

4. Corner block according to any one of the preceding claims, having, in a median longitudinal sectional plane (Pl50), in the main portion (24), a thickness decreasing from the limiting lower transverse plane (P24i) to the limiting upper transverse plane (P24s).

5. Corner block according to any one of the preceding claims, wherein, in the main portion (24), a point of the profile (Lc) of the hot face in a median longitudinal sectional plane (Pl50) becomes increasingly distant from a vertical line (Δ) passing through the upper end of the said profile, the closer said point is moved towards the lower surface (22i).

6. Corner block according to any one of the preceding claims, wherein, in the main portion (24), the profile (Lc) of the hot face in a median longitudinal sectional plane (Pl50) is rectilinear and forms, with the vertical direction V, an angle α of less than 30° and greater than 2°.

7. Corner block according to the immediately preceding claim, wherein the angle α is less than 20° and greater than 5°.

8. Corner block according to any one of the preceding claims, wherein the hot face (22c) is strictly convex in the main portion (24).

9. Corner block according to any one of the preceding claims, wherein, in any transverse sectional plane in the main portion (24), the hot face (22c) has a convex profile (Tc) in the form of a circular arc, optionally extended, at one or both of its ends, by a straight segment.

10. Corner block according to any one of the preceding claims, wherein the hot face has, in a transverse sectional plane, a profile of which the general shape is identical whatever the transverse sectional plane considered in the main portion.

11. Corner block according to any one of the preceding claims, wherein the hot face has, in a transverse sectional plane of the main portion, a profile which is longer, the closer said transverse sectional plane is moved towards the lower limiting transverse plane.

12. Corner block according to any one of the preceding claims, having the general shape of a quarter-body cylinder with a circular base, or a quarter-body cone, or a quarter-body cylinder with an annular base.

13. Corner block according to any one of the preceding claims, wherein in the main portion the cold face (22f) is edge-free.

14. Corner block according to any one of the preceding claims, wherein a first thermally insulating material having a thermal conductivity of less than 7.0 W.m-1.K-1 is disposed on a portion of the cold face that extends from the upper surface of the corner block to more than 300 mm from said upper surface.

15. Corner device (32) comprising a corner block (20) according to any one of the preceding claims and an adapter block (301, 302) having a first face in contact with the left surface (22g) or the right surface (22d) of the corner block, and a second face, parallel to and opposite the first face, and having a shape different from said first face.

16. Glass furnace comprising a tank comprising a side wall (14) comprising two segments (141, 142) and a corner block according to any one of Claims 1 to 13 or a corner device according to the immediately preceding claim, said corner block or said corner device connecting said two segments.

17. Glass furnace according to the immediately preceding claim, wherein the tank defines a corset (8), the corner block or corner device being disposed at the corset entrance.