CORNER BLOCK FOR GLASS FURNACE

Abstract

A corner block for a glass furnace tank. The corner block has an outer surface including: upper and lower surfaces delimiting the length of the corner block, right and left surfaces to be in contact with corresponding surfaces of adjacent blocks, a hot face to be in contact with the environment inside the tank, and a cold face, opposite the hot face. A main portion of the corner block extends, over more than 80% of the length of the corner block, between two limiting upper and lower transverse planes. The hot face is edge-free. An edge is a line along which the hot face has a break in slope greater than 25°. The hot face has a profile that is convex in any transverse sectional plane in the main portion.

Claims

1. A corner block for a glass furnace tank, said corner block having an outer surface comprising: upper and lower surfaces delimiting the length of the corner block, right and left surfaces intended to be in contact, in the operational position, with corresponding surfaces of adjacent blocks, a hot face intended to be in contact, in the operational position, with the environment inside said tank, a cold face opposite the hot face, the corner block being characterized in that in a main portion of the corner block extending, over more than 80% of the length of the corner block, between two limiting upper and lower transverse planes, the hot face is edge-free, an edge being a line along which the hot face has a break in slope greater than 25°, the hot face having a profile that is convex in any transverse sectional plane in the main portion.

2. The corner block as claimed in claim 1, wherein the main portion extends from the upper surface to a base part intended to be integrated in a floor of the tank in the operational position.

3. The corner block as claimed in claim 1, wherein, in the main portion, the hot face is devoid of an edge marking a break in slope greater than 10°.

4. The corner block as claimed in claim 1, having, in a median longitudinal sectional plane (Pl.sub.50), in the main portion, a thickness decreasing from the limiting lower transverse plane to the limiting upper transverse plane.

5. The corner block as claimed in claim 1, wherein, in the main portion, a point of the profile of the hot face in a median longitudinal sectional plane becomes increasingly distant from a vertical line passing through the upper end of the said profile, the closer said point is moved towards the lower surface.

6. The corner block as claimed in claim 1, wherein, in the main portion, the profile of the hot face in a median longitudinal sectional plane is rectilinear and forms, with the vertical direction V, an angle α of less than 30° and greater than 2°.

7. The corner block as claimed in claim 6, wherein the angle α is less than 20° and greater than 5°.

8. The corner block as claimed in claim 1, wherein the hot face is strictly convex in the main portion.

9. The corner block as claimed in claim 1, wherein, in any transverse sectional plane in the main portion, the hot face has a convex profile in the form of a circular arc, optionally extended, at one or both of its ends, by a straight segment.

10. The corner block as claimed in claim 1, 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. The corner block as claimed in claim 1, 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 sectional plane.

12. The corner block as claimed in, claim 1, 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. The corner block as claimed in claim 1, wherein in the main portion the cold face is edge-free.

14. The corner block as claimed in claim 1, wherein a first thermally insulating material having a thermal conductivity of less than 7.0 W.m.sup.−10.1<.sup.−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. A corner device comprising a corner block as claimed in claim 1 and an adapter block having a first face in contact with the left surface or the right surface 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. A glass furnace comprising a tank comprising a side wall comprising two segments and a corner block as claimed in claim 1, said corner block or said corner device connecting said two segments.

17. The glass furnace as claimed in claim 16, wherein the tank defines a corset, the corner block being disposed at the corset entrance.

18. A glass furnace comprising a tank comprising a side wall comprising two segments and a corner device as claimed in claim 15, said corner device connecting said two segments.

19. The glass furnace as claimed in claim 18, wherein the tank defines a corset, the corner device being disposed at the corset entrance.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0104] Further features and advantages of the invention will become apparent from the following detailed, non-limiting description and from an examination of the attached drawing in which:

[0105] FIG. 1 shows a schematic plan view of a glass melting tank;

[0106] FIG. 2 shows schematically, in perspective, a first embodiment of a corner block according to the invention;

[0107] FIG. 3 shows schematically, in perspective, a second embodiment of a corner block according to the invention;

[0108] FIG. 4 shows schematically, in perspective, a third embodiment of a corner block according to the invention;

[0109] FIG. 5 shows schematically, in perspective, a fourth embodiment of a corner block according to the invention;

[0110] FIG. 6 shows schematically, in perspective, a fifth embodiment of a corner block according to the invention;

[0111] FIG. 7 shows schematically, in perspective, a sixth embodiment of a corner block according to the invention;

[0112] FIG. 8 shows schematically, in perspective, a seventh embodiment of a corner block according to the invention;

[0113] FIG. 9 schematically shows, in perspective, a corner device according to the invention comprising a corner block according to the invention and adapter blocks, in the operational position; and

[0114] FIG. 10 illustrates the definition of an edge.

[0115] In the various figures, identical or similar references are used to designate identical or similar parts or portions of parts.

DETAILED DESCRIPTION

[0116] Form

[0117] By definition, a corner block 20 or corner device 32 connects together two segments 14.sub.1 and 14.sub.2 of the tank side wall 14, partially shown in FIG. 8. When viewed from above, the two segments join the corner block or corner device along segment planes P.sub.1 and P.sub.2, respectively. The segment planes P.sub.1 and P.sub.2 form an angle with each other greater than 45°, preferably greater than 70°, preferably greater than 80°, and/or less than 135°, preferably less than 110°, preferably less than 120°, typically about 90°.

[0118] As shown in FIGS. 5 and 6, a corner block 20 comprises a side part 20.sub.1, intended to be integrated into the side wall 14 of the tank, and a base part 20.sub.b intended to rest on the ground and be integrated in the floor of the tank. The base part can have edges 21, particularly when it projects beyond the hot face, in the form of a flange, as shown in FIG. 5.

[0119] The base part can also be indistinguishable from the side part, as in FIGS. 2 to 4.

[0120] The outer surface of a corner block 20 comprises: [0121] an upper surface 22s and lower surface 22i, typically horizontal, delimiting the length L.sub.20 of the corner block, [0122] right and left surfaces, 22d and 22g, typically vertical, which in the operational position are in contact with corresponding surfaces of adjacent blocks, [0123] an inner side surface, or “exposed surface”, also called the “hot face” 22c, which belongs to the inner surface of the side wall 14 of the tank and which, in the operational position, is in contact with the environment inside the tank, [0124] optionally, an inner base surface 22b which, in the operational position, is also in contact with the environment inside the tank, but which belongs to the floor (see for example FIG. 5), [0125] an outer surface, also called the “cold face” 22f, which is opposite the hot face 22c and which, in the operational position, is in contact with the environment outside the tank.

[0126] Preferably, the upper surface 22s, which is typically flat, delimits the top edge of the side wall of the tank.

[0127] Preferably, the lower surface 22i, which is typically flat, rests on the ground.

[0128] Preferably, the right and left surfaces, 22d and 22g, are flat. Usually, they extend in planes forming between them 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°, usually about 90°.

[0129] The right and left surfaces, 22d and 22g, are usually perpendicular to the segment planes P.sub.1 and P.sub.2, respectively.

[0130] In a corner block, each of the right and left surfaces 22d and 22g is machined. A machined surface therefore does not have a skin microstructure.

[0131] Preferably, only those surfaces which, in the operational position, are in contact with corresponding surfaces of adjacent blocks are machined. Preferably, all surfaces which, in the operational position, are in contact with corresponding surfaces of adjacent blocks are machined.

[0132] The invention relates to the side portion 20.sub.1, which typically extends from the upper surface of the corner block to the base part 20.sub.b, typically over 90% of the length of the corner block. Therefore, the features described below refer to a main portion 24 of the corner block that extends between two limiting upper and lower transverse planes, referenced P.sub.24s and P.sub.24i, respectively, shown in FIG. 4 for example.

[0133] Preferably, the main portion 24 extends, between the two limiting upper and lower transverse planes P.sub.24s and P.sub.24i, over more than 80%, preferably more than 90%, preferably more than 95%, preferably 100% of the length of the block. In particular, in the embodiments shown in FIGS. 2 to 4, the two limiting upper and lower transverse planes can be the upper 22s and lower 22i surfaces, respectively.

[0134] Preferably, the main portion extends from the upper surface. Preferably, the main portion extends, along the length direction, to the base part of the corner block.

[0135] Preferably, the main portion extends from the upper surface to less than 20 cm, preferably less than 10 cm, most preferably less than 5 cm from the lower surface.

[0136] According to the invention, the hot face is edge-free in the main portion.

[0137] The hot face is oriented towards the inside of the tank. It is intended to be placed at least partially in contact with molten glass.

[0138] Preferably, the hot face does not have a soft edge in the main portion, an edge being soft when it delimits a break in slope of less than 15°, preferably less than 10°, preferably less than 5°, preferably less than 1°.

[0139] In the median longitudinal sectional plane Pl.sub.50, the corner block has a length L.sub.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-hand side of FIGS. 2 and 3).

[0140] The corner block 20 has a thickness e.sub.20, measured in the median longitudinal sectional plane Pl.sub.50 and in the median transverse sectional plane Pt.sub.50, preferably greater than 200 mm, preferably greater than 250 mm and/or less than 500 mm, preferably less than 450 mm.

[0141] Preferably, the thickness e.sub.m of the corner block, measured at the intersection between the median transverse sectional plane Pt.sub.50 and the longitudinal sectional plane passing through a point M of 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.sub.20 as the point M traverses the width line X. That is to say, |e.sub.m−e.sub.20|/e.sub.20<20%, preferably |e.sub.m−e.sub.20|/e.sub.20<10%, preferably |e.sub.m−e.sub.20|/e.sub.20<5%, preferably |e.sub.m−e.sub.20|/e.sub.20<1%, regardless of the thickness e.sub.m measured along the width line X.

[0142] In the median longitudinal sectional plane Pl.sub.50, the corner block can have a constant thickness in any position considered in the direction of the length of the corner block, i.e., in any transverse sectional plane considered, at least in the main portion, as shown for example in FIG. 2. This simplifies the production of the corner block.

[0143] In the median longitudinal sectional plane Pl.sub.50, the corner block 20 may have a varying thickness depending on the position considered along the length direction of the corner block.

[0144] Preferably, in the median longitudinal sectional plane Pl.sub.50, the corner block has, at least in the main portion, an increasing thickness, preferably a steadily increasing thickness, as it descends in the direction of the length of the corner block, as shown for example in FIG. 3.

[0145] Preferably, (e.sub.max−e.sub.min)/e.sub.min>10%, and/or, preferably, (e.sub.max−e.sub.min)/e.sub.min<30%, or (e.sub.max−e.sub.min)/e.sub.min<20%, with e.sub.max and e.sub.min designating, respectively, the maximum and the minimum thickness in the median longitudinal sectional plane Pl.sub.50 (see FIG. 2). This significantly improves the service life of the corner block.

[0146] In a preferred embodiment, the profile Lc of the hot face in the median longitudinal sectional plane Pl.sub.50 is substantially rectilinear. Preferably, it forms, with the vertical direction V, an angle α of less than 30°, preferably less than 20°, preferably less than 10°, or less than 5°, and/or preferably more than 2°, preferably more than 3° (as shown, for example, in FIG. 3).

[0147] In one embodiment, the profile Lc of the hot face in the median longitudinal sectional plane Pl.sub.50, for example concave or rectilinear, is shaped to run inwardly into the tank as it approaches the lower surface 22i.

[0148] As shown, for example, in FIG. 4, a point on the profile Lc of the hot face, in the median longitudinal sectional plane Pl.sub.50, may become increasingly distant from a vertical line A passing through the upper end of said profile Lc, the closer said point is moved towards the lower surface 22i.

[0149] In one embodiment, the profile Lf of the cold face in the median longitudinal sectional plane is substantially rectilinear. Preferably, it forms, with the vertical direction V, an angle of less than 10°, preferably less than 5°, preferably less than 2°, preferably substantially zero, as shown, for example, in FIG. 3.

[0150] In the median transverse sectional plane Pt.sub.50, the hot face has a profile Tc, which is shown on the right-hand side of FIGS. 2 to 4 for clarity.

[0151] The profile of the hot face can be the same, regardless of the transverse sectional plane chosen in the main portion, as for example in FIGS. 2 and 4. Preferably, it results from a homothetic deformation of the profile Tc (defined in the median transverse sectional plane Pt.sub.50), for example as in FIG. 3 or in FIG. 5. Preferably, the homothety ratio increases, preferably evenly, from the limiting upper transverse plane to the limiting lower transverse plane. In other words, the profile lengthens whilst moving down the corner block, maintaining its general shape, for example as in FIGS. 3 and 5.

[0152] Preferably, the profile Tc 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 zone, as in FIGS. 1 to 3.

[0153] Preferably, the profile Tc does not have a strictly concave portion.

[0154] Preferably, the profile Tc has no singular point, i.e., no break in slope.

[0155] Preferably, the profile Tc is substantially symmetrical with respect to the median longitudinal sectional plane, as in the embodiments of FIGS. 1 to 4.

[0156] In one embodiment, the profile Tc has the shape of a circular arc (FIGS. 2 and 3). The circular arc can be extended by straight line segments (FIG. 4).

[0157] In the median transverse sectional plane Pt.sub.50, the cold face has a profile Tf, shown on the right-hand side of FIGS. 2 to 4 for clarity.

[0158] Preferably, the profile of the cold face is the same regardless of the transverse sectional plane chosen in the main portion.

[0159] The profile Tf can be strictly convex (FIGS. 2 and 3). Preferably, however, the profile Tf is flat or strictly concave (FIG. 4), which improves the mechanical strength.

[0160] Preferably, the profile Tf has no singular point, i.e. no break in slope.

[0161] Even more preferably, the profile Tf is substantially symmetrical with respect to the median longitudinal plane, as in the embodiments of FIGS. 2 to 4.

[0162] In one embodiment, the profile Tf has the shape of a circular arc (FIGS. 2 and 3). The circular arc can be extended by straight segments (FIG. 4).

[0163] In one embodiment, in the median transverse sectional plane, the distance between the profiles of the hot and cold faces is constant, regardless of the longitudinal sectional plane considered.

[0164] The features described above relating to the shape of the corner block and defined with reference to the median longitudinal sectional plane are preferably applicable in any longitudinal sectional plane between two limiting longitudinal planes defined with respect to the width line X (in the median transverse sectional plane), the distance between the limiting longitudinal planes preferably being 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 sectional plane).

[0165] The features described above relating to the shape of the corner block in the median longitudinal sectional plane are preferably applicable regardless of the longitudinal sectional plane considered.

[0166] The features described above and defined with reference to the median transverse sectional plane are preferably applicable regardless of the transverse sectional plane considered in the main portion.

[0167] The right and left surfaces are usually the same shape as the surfaces of the side blocks with which they are in contact. Thus, internally, the tank does not have any roughness resulting from a gap between the blocks. Usually, the surfaces of the adjacent side blocks are substantially rectangular in outline. In particular, when the profile Lc causes a widening of the corner block in the lower part (FIG. 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 in FIG. 7 for example.

[0168] The corner block 20 can be formed of one or more pieces. In particular, it can be an assembly of a plurality of elementary blocks 341, 342 and 343, the faces at the right and left ends of the assembly being oriented perpendicularly to the planes P.sub.1 and P.sub.2, respectively.

[0169] In one embodiment, adapter blocks 301 and 302 are added to the corner block according to the invention, so as to form a corner device 32 according to the invention, as shown in FIG. 8. In particular, the adapter blocks can be configured so that the right and left surfaces of the corner device are identical to those of adjacent side blocks 14.sub.1 and 14.sub.2, respectively.

[0170] The corner device 32 may thus comprise a one-piece corner block or, as shown in FIG. 8, an assembly of elementary blocks, and one or more adapter blocks so as to match the shape of the surfaces at the right and left ends of the corner device to the faces of adjacent, facing blocks.

[0171] In the embodiment shown in FIG. 2, the corner block has the general shape of a quarter-cylinder with a circular base and vertical axis, a quarter of such a cylinder being a piece of the cylinder body after it has been cut by two planes perpendicular to each other and passing through its axis.

[0172] In the embodiment shown in FIG. 3, the corner block has the general shape of a quarter-cone with a vertical axis, a quarter-cone being a piece of the cone after it has been cut by two planes perpendicular to each other and passing through its axis.

[0173] In the embodiment shown in FIG. 4, the corner block has the general shape of a quarter-cylinder with an annular base and vertical axis, a quarter of such a cylinder being a piece of the cylinder body after it has been cut by two planes perpendicular to each other and passing through its axis.

[0174] According to one embodiment, the corner block is provided with an anchoring device for anchoring in the metal shell of the glass furnace. This anchoring device is for example a screw, a hook, a metal plate, or a notch.

[0175] Of course, the dimensions and shapes described above are not limiting.

[0176] Composition

[0177] Preferably, the corner block according to the invention comprises, preferably consists of, an electrofused material consisting, for more than 80% of its mass, of alumina, zirconia, silica and possibly a zirconia stabilizer, in particular yttrium oxide. The material can be of the AZS type or with a very high zirconia content (typically comprising more than 80% of ZrO.sub.2 in weight percent).

[0178] In one embodiment, the corner 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 more than 6.0%, and/or less than 10.0%, less than 9.0%, or less than 8.0% of zirconia stabilizer, in particular CaO and/or Y.sub.2O.sub.3 and/or MgO and/or CeO.sub.2, preferably Y.sub.2O.sub.3 and/or CaO, preferably Y.sub.2O.sub.3.

[0179] Preferably, the corner block according to the invention has a chemical composition, in weight percent on an oxide basis, such that, for a total of 100%, [0180] Al.sub.2O.sub.3+ZrO.sub.2+SiO.sub.2: more than 80.0%, preferably more than 84.0%, preferably more than 86.0%, and/or less than 97.0%, or less than 95.0%, or less than 94.0%, and/or [0181] Y.sub.2O.sub.3: more than 0.5%, more than 1.5%, more than 2.0% and/or less than 5.0%, less than 4.0%, or less than 3.0%, and/or [0182] Na.sub.2O: more than 0.1%, or more than 0.2%, and/or less than 0.6%, preferably less than 0.5%, or less than 0.4%, and/or [0183] B.sub.2O.sub.3: more than 0.1%, or more than 0.2%, and/or less than 0.6%, preferably less than 0.5%, or less than 0.4%, and/or [0184] oxide species other than Al.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2, Y.sub.2O.sub.3, Na.sub.2O and B.sub.2O.sub.3: less than 10.0%, preferably less than 9.0%, preferably less than 8.0%, less than 5.0%, or less than 3.0%, or less than 2.0%, or less than 1.0%, or less than 0.5%.

[0185] According to one embodiment, the corner block according to the invention has a chemical composition such that: [0186] ZrO.sub.2: more than 12.0%, preferably more than 20.0%, preferably more than 25.0% and/or less than 80.0% or less than 75.0% and/or [0187] SiO.sub.2: more than 6.0%, preferably more than 10.0% and/or less than 24.0%, or less than 20.0%, and/or [0188] Al.sub.2O.sub.3: more than 18.0%, preferably more than 25.0% and/or less than 60.0%, preferably less than 50.0%.

[0189] According to one embodiment, the corner block according to the invention has a chemical composition such that: [0190] ZrO.sub.2: more than 12.0%, preferably more than 15.0%, preferably more than 18.0%, or more than 22.0%, and/or less than 45.0%, or less than 40.0%, or less than 35.0%, or less than 30.0%, or less than 25.0%, and/or [0191] SiO.sub.2: more than 8.0%, preferably more than 10.0%, preferably more than 12.0%, and/or less than 24.0%, or less than 20.0%, less than 17.0%, or less than 14.0%, and/or [0192] Al.sub.2O.sub.3: more than 35.0%, preferably more than 38.0%, or more than 40.0%, and/or less than 60.0%, preferably less than 55.0%, or less than 50.0%, less than 46.0%, or less than 44.0%.

[0193] According to one embodiment, the corner block according to the invention has a chemical composition such that: [0194] ZrO.sub.2: more than 80.0%, preferably more than 83.0%, preferably more than 86.0%, and/or less than 97.0%, or less than 95.0%, or less than 94.0%, and/or [0195] SiO.sub.2: more than 0.5%, preferably more than 1.5%, preferably more than 2.5%, preferably more than 4.0%, or more than 6.0%, more than 8.5%, and/or less than 15.0%, or less than 12.0%, less than 10.0%, or less than 8.0%, and/or [0196] Al.sub.2O.sub.3: more than 0.2%, preferably more than 1.0%, and/or less than 3.0%, preferably less than 2.0%.

EXAMPLES

[0197] Modeling tests were conducted with a finite element software (Ansys 17.0).

[0198] With this software, the temperature and stresses of AZS refractory blocks, with a length of 1300 mm and a chemical composition with 40% ZrO.sub.2 (ER 1711 from Saint-Gobain SEFPRO), were determined when the hot face of the block is at a temperature of 1500° C., with heat evacuation by air blowing at room temperature (20° C.) and with a heat transfer coefficient of 125 W/(m.sup.2.K). Three block geometries were compared: [0199] a straight block (rectangular parallelepipedic block), with a square base of 450 millimeters on each side (“reference” in table 1 below); [0200] a rounded block, representing a quarter cone, of the type shown in FIG. 3, the radius of the profile of the hot face being 450 millimeters at the upper surface and 550 millimeters at the lower surface (example 1); [0201] the block of example 1 having, on the cold face, a plate of an insulating material 10 millimeters thick (thermal conductivity of 0.5 W/(m.K) (example 2).

[0202] The stress state of each point in the block can be represented by a tensor, the stress tensor. The principal stresses are the stresses expressed in a base such that the stress tensor is a diagonal matrix. The coefficient of this matrix that corresponds 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 stress at failure (MOR), considering all ratios R along the most stressed edge. The MOR is measured in air, at the considered temperature, on a specimen of dimensions 80*20*20 mm.sup.3 in a 3-point bending set-up realized with a distance of 70 mm between the two lower supports, and the punch descent speed is equal to 0.5 mm/min. The higher the Rmax, the more likely the failure. The results are given in Table 1.

TABLE-US-00001 TABLE 1 Rmax Decrease compared to the reference Reference 3.0 Example 1 2.0 33% Example 2 1.3 57%

[0203] The tests thus show that a corner block according to the invention makes it possible to reduce the stresses significantly.

[0204] The invention is particularly well suited to corset entrance blocks.

[0205] It goes without saying that the embodiments described are only examples and could be modified, in particular by substitution of technical equivalents, without thereby departing from the scope of the invention.