RU2783785C2 - Furnace with immersible burner with self-lining walls - Google Patents

Abstract

FIELD: melting.

SUBSTANCE: present invention relates to a furnace for melting of vitrifiable material, in particular glass, with an immersible burner. The furnace contains a wall cooled with cooling fluid, while a surface of the wall, facing inside the furnace, has, before melting of vitrifiable material in the furnace, binding texture for devitrified vitrifiable material with the possibility of furnace self-lining, and binding texture contains solid sections and voids with a size of at least 5 mm in a direction perpendicular to the wall. A method for melting of vitrifiable material in the furnace is disclosed.

EFFECT: reduction in corrosion of a metal wall and elongation of a service life of its surface due to stabilization of a self-lining layer of a furnace, stabilization of a melting process, improvement of energy efficiency due to stabilization and minimization of heat transfer, deflection of unburnt gases to a bath of vitrifiable material, and minimization of a number of unburnt gases passing between the metal wall and self-lining.

13 cl, 9 dwg

Description

DESCRIPTION OF THE INVENTION

2420-563378EN/42

IMMERSION BURNER FURNACE WITH SELF-LINED WALLS

The present invention relates to the field of immersion burner furnaces with metal walls cooled by a cooling fluid, which are known to those skilled in the art as a water jacket. These furnaces are designed to melt a vitrified material, typically of the oxide type, typically containing at least 30% by weight of silica such as glass or silicate such as alkali and/or alkaline earth silicate. The glass may in particular be soda-lime glass or stone, often referred to by those skilled in the art as "black glass".

The water jacket cooling system is used for the immersion burner furnace in order to contain the temperature to which its structure is exposed. The molten vitrified material, which may in particular be molten glass, devitrifies (i.e. solidifies) in contact with these cooled (T°C < 100°C) walls and forms a hard crust between the body of vitrified material and the metal wall. This crust of devitrified vitrified material provides natural wall protection. It is highly compatible with fusible glass material because it has the same composition, only it is solidified. Consequently, this crust forms a "self-lining" for the vitrified material in the furnace. However, this self-liner has been found to crack, fragment and fall off in sheets during operation. Even if the area of the self-lining that has fallen off is restored by contact with the vitrified material, the corresponding metal surface of the wall is nevertheless subjected to erosion/corrosion by the very hot molten vitrified material for some time, and very intense heat exchange between the molten vitrified material, in particular molten glass, and the cooled wall occurs locally all the time until the self-lining is restored. In addition, sheets of solid self-liner that have fallen off into the molten material are melted, which also uselessly absorbs energy and lowers the temperature of the molten mass. All these unpredictable heat transfers destabilize the melting process.

It has been thought that the poor retention of the self-liner on the wall is due to the chemical and physical nature of the wall, especially the fact that it is too smooth, as well as the high thermal stress to which it is subjected. In addition, it was found that the self-lining has a poorly formed structure at its interface with the metal wall due to the rapid curing of the vitrified material. The surface of the self-liner in contact with the metal does not adhere well to it, is porous, and contains real channels. The molten material protrudes continuously and powerfully against the walls due to the high levels of agitation caused by the operation of the submerged burner. These protrusions exert high pressure on the combustion gases, and it has been found that the combustion products pass between the self-liner and the metal wall and exit the self-liner next to the vitrified material at some height from the bottom of the tank, which is random and perhaps even reaches the level of the roof. Here, the expression "combustion gases" means gases formed after combustion and/or unburned fuel and/or oxidant. Analysis of these combustion products showed that they contain a lot of water, which is particularly corrosive to the wall metal. In addition, unburned gases leaving the self-liner at a particular height combust as soon as they leave the self-liner, but transfer less energy to the melting vitrified material than if they burned at the bottom of the tank, as is usually the case.

The present invention relates to a furnace for melting a vitrified material (in particular glass) with an immersion burner comprising a wall cooled by a cooling fluid, wherein the wall surface facing the interior of the furnace has, before melting the vitrified material in the furnace, a fastening texture for a so-called self-lining of devitrified vitrified material to cover the inner wall of the furnace, as soon as it begins to function to melt the vitrified material. The present invention provides in particular the following advantages:

- stabilization of the self-lining layer of the furnace;

- stabilization of the melting process;

- stabilization and minimization of heat transfers, and consequently improvement of energy efficiency;

- deflection of unburned gases to the glass material bath and minimization of the amount of unburned gases passing between the metal wall and self-lining;

- reduction of corrosion of a metal wall and prolongation of service life of its surface.

The solution described in this patent application also has a relatively low cost and is easy to implement.

The wall is usually vertical, but may also be inclined. In general, the wall provides a connection between the hearth and the roof of the furnace. The wall together with the hearth allows the furnace to contain the vitrified material melted in the furnace.

The fastening texture contains solid particles and voids with a size preferably of at least 5 mm in a direction perpendicular to the wall. This means that if a smooth surface is placed against a textured surface parallel to a wall, said smooth surface being composed of generators parallel to each other (vertical if the wall is vertical), then the space between the wall and said smooth surface contains recesses of at least 5 mm and preferably at least 1 cm, and more preferably at least 2 cm. These recesses can even accommodate a virtual sphere with a diameter of at least 5 mm, preferably at least 1 cm, and more preferably at least 2 cm. Texture fastening is visible to the naked eye. A smooth and flat metal plate is considered to have no attachment texture.

The wall usually contains a metal plate, optionally vertical if the wall is vertical, and the fastening texture is created by means of a fastening system containing protruding metal elements attached to that surface of said plate that faces the inside of the furnace. Initially, the metal plate is usually smooth and does not have any particular pattern, and it is the attachment system of the present invention attached to this plate that creates the texture. The other surface of the metal plate (facing the outside of the furnace) is cooled, in particular in contact with a cooling fluid, which is usually cold water, i.e. water at a temperature usually in the range of 1 to 20° C. inclusive (cooling line inlet temperature).

Vitrified materials melted in a furnace typically have a temperature of 800°C - 1590°C inclusive.

The wall texturing elements may specifically comprise metal sections such as a solid round rod, an iron angle, a (tubular or solid) metal square rod, etc. The metal profile is preferably attached to the metal plate such that the main direction in which it extends (its main direction perpendicular to its section) is substantially horizontal. In particular, in the case of a corner iron, it is preferably secured by means of its outer edge. This outer edge forms an obtuse angle at the junction of the two flat metal wings of the angle. The iron corner is preferably attached such that the edge is substantially horizontal. The metal profile can usually be attached to the metal plate by welding.

The wall texturing elements may also be localized elements (particularly without much extension in any particular direction parallel to the wall) attached to the wall, such as pins inserted into or welded to the plate.

The texture preferably comprises protrusions forming spaces locally on the wall that can be filled with devitrified glassy self-lining material that is trapped in these spaces between at least a portion of the protrusion and a wall surface further to the periphery of the furnace (i.e. further from the interior of the furnace) than this part of the protruding element.

The texturing elements are preferably attached to the metal wall plate so that they protrude from the metal plate to a depth of at least 1 cm and preferably at least 2 cm.

In addition, the texturing elements effectively prevent the flow of gas along the metal wall and under the self-lining, rising some distance from the bottom of the furnace. To this end, the texturing element, in particular of the profile type, is preferably positioned closer to the bottom of the oven, and extends substantially horizontally around the oven. It is preferably a profile whose direction of extension is substantially horizontal (a localized element on the wall surface of the pin type is not preferred for this barrier function). This belt of texturing element actually forms a combustible gas deflecting barrier so that much less combustible gas passes under the self-liner above this barrier. These texturing elements, which form, if necessary, a full belt on the inner perimeter of the metal wall, are preferably located at a distance of 5-20 cm from the lowest point of the hearth. Therefore, the installation of this deflecting barrier forces the gases back into the liquid bath, which has two consequences: 1) unburned gases burn in the vitrified material, 2) water no longer passes along the metal wall, the corrosion of which is thereby reduced. Thus, the texture in accordance with the present invention may include a substantially horizontal band extending from the lowest point of the hearth (outside the self-lining on the hearth) from 5 cm to 20 cm, inclusive. This lowest point of the hearth is the point that is in contact with the vitrified materials before the formation of the self-liner. It should be noted that the self-lining can be formed on the hearth in the same way.

In order to further reduce corrosion of the metal in the wall by molten glass material, in particular molten glass, the wall, including its texturizing elements, may be coated with refractory concrete, preferably containing alumina. This concrete covers the wall, forming a self-lined boundary. This concrete provides a chemical bond to the self-lining. In fact, the alumina migrates into the vitrified material of the self-liner, which in particular may be glass, which leads to an increase in the devitrification temperature of this vitrified material, and consequently to a very strong chemical attachment of the self-liner. In particular, this concrete contains more than 50% and preferably more than 80% alumina. Suitable concretes are sold as 6P or F15R by Thermbond, T96HT or T95G3 by Calderys, Erplast 20 or Ersol 50 by Sefpro. The concrete can be applied in a substantially uniform thickness, incl. and on the texturing elements, so that the surface facing the interior of the furnace retains the texture due to the presence of the texturing elements pre-applied to the metal wall. The presence of these texturing elements contributes to the retention of concrete on the wall. The surface of the concrete facing the interior of the kiln is preferably textured due to the presence of texturing elements pre-applied to the metal wall. Not enough concrete is usually applied to level the surface of the concrete facing the interior of the kiln. In fact, it is preferable to preserve the texture on that surface of the concrete that borders the self-lining. The concrete layer may have a thickness ranging from 5 mm to 70 mm inclusive.

It is possible to produce a furnace wall according to the present invention, one surface of which faces the interior of the furnace, and the other surface of which is cooled, in particular in contact with a cooling fluid, by fastening, in particular by welding, texturizing, in particular metal elements, to a smooth the surface of the metal plate, and then providing said surface with said texturing elements intended to face the interior of the furnace and be self-lined when the furnace is in operation. The present invention also relates to a method for manufacturing a furnace according to the present invention, including placing texturing elements on a smooth surface of a metal plate, and then positioning the plate, if necessary vertically, so that the surface provided with texturing elements forms the inner surface of the furnace wall.

The present invention also relates to a process for the production of a vitrified material, in particular glass, comprising melting the vitrified material in a furnace according to the present invention. The raw material is introduced into the furnace and then melted in the furnace in order to produce a molten vitrified material, which is then removed from the furnace by exhausting it through an orifice.

Fig. 1 shows the interior of a prior art metal-walled water jacket type immersion burner furnace after it has been shut down. The metal walls were smooth before the operation of the furnace, that is, they consisted of a steel sheet without any texture. The photo shows that a layer of devitrified glass stuck to the wall randomly fell off in sheets on the hearth of the furnace.

Fig. 2 represents a) the wall of a furnace in accordance with the present invention, as viewed from the inside, and b) its cross section. The vertical and initially smooth metal wall plate 1 is covered with metal elements 2 attached to said plate. These metal elements have a profile type and are attached to the plate by welding. They are installed so that the main direction in which they run is essentially horizontal. They form an attached texture containing solid areas and voids with size p (at least 5 mm) perpendicular to the surface of the metal plate 1. In fact, if a smooth surface 5 parallel to the wall, made up of vertical generators parallel to each other, is placed opposite the textured surface , the space between the wall and said smooth surface contains recesses 6 of at least 5 mm in size perpendicular to the wall (the depth p is considered to be perpendicular to the wall). The other surface 3 of the metal plate 1 is in contact with the cooling water 4.

Fig. 3 shows a wall of a furnace in accordance with the present invention in cross section. The initially smooth vertical metal wall plate 20 is covered with metal elements 21 attached to said plate. These metal elements are of the type of an angle iron profile and are attached to the plate by welding their outer edge at the junction of two flat wings of the iron angle. They are installed so that the main direction in which they run is essentially horizontal. The other surface of the metal plate 20 is in contact with the cooling water 22. The refractory concrete 23 was applied to the metal wall after the iron angles 21 were fixed on it. show depressions and solid areas with depth p measured perpendicular to the wall. The devitrified vitrified material of the self-liner 24 adheres to the concrete and forms a new contact surface 26 for the meltable materials 25. The depth of the solids and depressions of the self-liner surface 26 is generally less than that of the wall (concrete) surfaces 27 prior to the melting of the vitrified material.

Fig. 4 shows the inner wall of an immersion burner furnace prior to the melting of the vitrified material in the furnace. The metal mesh that forms the texture of the self-lining attachment was welded to a metal plate, behind which cooling water circulates.

Fig. 5 shows the inner wall of the immersion burner furnace shown in FIG. 4, after melting the glass in the furnace and emptying it. In this photo, the surface of the self-lining and the metal mesh are visible under the devitrified glass. It was found that the devitrified glass filled most of the space between the metal grid and the metal plate.

Fig. 6 shows a wall of a furnace in accordance with the present invention in cross section. An angled iron profile (51, 52) was attached to a smooth vertical metal plate 50 forming the furnace wall. This profile contains two flat wings 51 and 52 connected to each other orthogonally. This corner profile was welded to the inside surface of a smooth metal plate by its outer corner edge. This corner profile has been installed so that the direction in which it runs is horizontal. The angled flat wings are protruding elements forming locally on the wall spaces 53, 54 which can be filled with devitrified vitrified self-lining material 55 that is captured in these spaces 53, 54 between at least the protruding flat wings and the wall surface 56, 57 located farther from the center of the furnace than the protruding flat wings 51, 52. Thus, along a straight line 58 starting from the interior of the furnace 59 and passing through the flat wing 51, the self-lining 53 is actually then caught between the flat wing 51 and the surface zone 56 (initially smooth) plate, located further to the periphery of the furnace, in the direction from the interior of the furnace 69.

Fig. 7 shows in perspective a bottom corner of the interior of a immersion burner furnace. Submersible burners 60 and 61 are located on the hearth of the furnace. A metal profile belt 62 extends around the furnace tank. This belt is located at a distance d (usually 5 to 20 cm) from the deepest point of the hearth. This belt forms a barrier to gases passing under the self-lining between the hearth and the belt. This belt itself has a height h, usually in the range from 5 to 50 mm inclusive.

Fig. 8 shows the change in energy flows over time in an immersion burner furnace according to the present invention, the inner wall of which is textured as shown in FIG. 2. The following energy loss streams can be measured from temperature measurements of various cooler circuits cooling various locations in the furnace:

- a): total flow

- b): vault and chimney

- c): right wall

- d): left wall

These streams are very regular and constant over time.

Fig. 9 shows the change in energy flows over time in a furnace with an immersion burner identical to that shown in FIG. 3, except that the inner wall was a smooth metal plate with no texture. It can be seen that these flows are much less regular than in the case of the furnace in FIG. 8. In particular, when the self-liner sheet separates, this can be seen very clearly, since the flow curve of the wall affected by this separation shows a sudden increase, such as in region 90.

Claims (13)

1. A furnace for melting a vitrified material with an immersion burner, comprising a wall cooled by a cooling fluid, characterized in that the surface of the wall facing the inside of the furnace has, before melting the vitrified material in the furnace, a fastening texture for a devitrified vitrified material with the possibility of self-lining of the furnace, while fastening texture contains solid areas and voids of at least 5 mm in size in the direction perpendicular to the wall. 2. A furnace according to Claim. 1, characterized in that the wall includes a metal plate, and the fastening texture is created using a fastening system containing protruding metal elements attached to said surface of the plate facing the inside of the furnace. 3. Furnace according to claim 2, characterized in that the metal elements contain a metal profile. 4. Furnace according to claim. 3, characterized in that the metal profile is attached to said plate so that the main direction in which it runs is essentially horizontal. 5. Furnace according to claim 3 or 4, characterized in that the metal profile is an iron corner. 6. The furnace according to claim 5, characterized in that the iron corner is attached to the metal plate with its outer edge at the junction of its two flat wings. 7. Furnace according to any one of the preceding claims, characterized in that the texture comprises protruding elements forming spaces locally on the wall, made with the possibility of filling them with devitrified vitrified self-lining material, which is captured in these spaces between at least part of the protruding element and the wall surface, located farther to the periphery of the furnace than this part of the protruding element. 8. A furnace according to any one of the preceding claims, characterized in that the texture comprises a substantially horizontal band extending from 5 to 20 cm, inclusive, from the lowest point of the hearth outside the self-lining on the hearth. 9. A furnace according to any one of the preceding claims, characterized in that the wall is covered with concrete to form a self-lined boundary. 10. A furnace according to claim 9, characterized in that the concrete contains more than 50 wt.% and preferably more than 80 wt.% alumina. 11. Furnace according to any one of the preceding claims, characterized in that the wall is vertical. 12. Method for the production of a molten vitrified material, in particular molten glass, characterized in that the melting of the vitrified material, in particular glass, is carried out in a furnace according to any one of the preceding claims. 13. A method of manufacturing a furnace according to any one of paragraphs. 1-11, characterized in that texturing elements are fastened to a smooth surface of a metal plate, and then this plate is positioned so that the surface provided with texturing elements forms the inner surface of the furnace wall.

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