Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/42—Details of construction of furnace walls, e.g. to prevent corrosion; Use of materials for furnace walls
  • C03B5/43—Use of materials for furnace walls, e.g. fire-bricks
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping

Definitions

• the present invention relates to techniques for melting thermoplastic materials with a high melting point, such as glass. It relates more particularly to an oven intended for melting such materials, and its use. Such a furnace for melting materials such as glass must be designed so that its walls suitably insulate the molten bath from the outside so as to guarantee good thermal efficiency, avoiding any migration of the molten glass towards the outside.
• a typical furnace wall construction provides, on the outside a sufficient thickness of insulating material, and on the inside, surfaces of refractory material resistant to corrosion by glass.
• refractory materials are installed in the furnace in the form of slabs or blocks, placed one next to the other, between which it is necessary to make watertight seals to prevent the penetration of glass.
• the slabs of refractory material which have a high thermal conductivity rest on blocks of insulating material by means of an unshaped layer which provides a base having a perfectly horizontal level. It is generally a concrete based on a hydraulic binder.
• the temperature profile in the operating oven is such that the temperature below the refractory is close to the crystallization temperature of the glass, or at least is such that the viscosity of the glass becomes very high, so that if the glass crosses the refractory thickness, it freezes or crystallizes (devit ⁇ fication) at the top d e the insulator and its migration is then stopped
• Such a passage through glass can happen in particular when a block of refractory cracks under the effect of thermal expansion constraints, or when a joint between two blocks has been poorly closed. This can also occur when the glass introduced into the solid state in the oven contains residue metallic. In fact, the corrosion of refractory materials is accelerated when a drop of molten metal is present at the interface between the refractory and the glass, and veins can form through which the glass quickly penetrates towards the insulating material.
• the object of the invention is to reduce these risks, and to provide oven walls having improved glass sealing, in particular when metal residues are introduced into the glass bath.
• shot of refractory material is meant in the present application, in the usual way, a refractory material in particulate or granular form which can be obtained in particular by grinding or crushing.
• the subject of the invention is an oven for melting a material with a high melting point, such as glass, this oven comprising a hearth and side walls delimiting a bath of molten material, and being characterized in that at least part of the surface of the hearth, and possibly of the side walls which is in contact with the molten material is initially constituted by at least one layer comprising shot of refractory material
• a wall surface made from a particulate material such as refractory shot has an improved glass seal compared to a surface made up of the juxtaposition of preformed articles such as slabs.
• this expression generally designates any fusible mineral material, natural or artificial, in particular glass but also rock.
• the refractory material may advantageously be of any type resistant to corrosion by glass (the degree of resistance may be higher or lower), in particular of the type based on chromium oxide or based on zirconium oxide. , silicon and / or aluminum (AZS type).
• the shot usable according to the invention can be derived from refractory recovered material.
• the particle size of the shot is variable and may advantageously be less than 50 mm, for example of the order of 1 mm to 50 mm. Particles greater than 50 mm may nevertheless also be useful.
• These particle sizes are understood as the smallest mesh size of a sieve allowing the sieving of the particulate material.
• the surface in contact with the glass can consist essentially of shot.
• the particle size thereof can be advantageously chosen, depending on the nature of the glass present in the bath, in particular its viscosity at the temperature of the wall and its surface tension, so that the shot is not or very little wettable by the glass of the bath and therefore that the progression of the glass in the interstices between the particles of shot is prevented.
• a shot is all the more advantageous as it contains particles of fine particle size, since the layer thus formed is all the more compact.
• the shot may advantageously comprise a mixture of particles of different particle sizes, suitable for obtaining maximum filling or compactness of the layer or optimized for forming a tight layer.
• the layer or at least one of the layers of the surface in contact with the glass contains, in addition to the shot, a mineral binder compatible with the molten glass bath, which may be of the chemical or ceramic setting type, in particular a mineral binder formed from molten oxide (s) or vitreous material (s).
• a mineral binder compatible with the molten glass bath which may be of the chemical or ceramic setting type, in particular a mineral binder formed from molten oxide (s) or vitreous material (s).
• the interstices between the particles of shot are at least partially filled with said binder, to constitute a composite material.
• the binder is preferably initially mixed with the shot in particulate form in at least one of said layers.
• the composite material based on refractory shot and the binder is a fairly coherent material which does not allow or hardly allow the passage of a molten material such as glass between the particles of shot. It is also a material whose corrosion by glass is slow and which therefore has an improved lifespan.
• the grain size of the shot is less critical in this embodiment because the particles are retained by the binder.
• the use of relatively fine shot nevertheless remains advantageous because it makes it possible to create a compact layer with a high contact surface between the particles and the binder, making the composite layer a very tight barrier against glass and other residues which may be present. in the molten bath.
• the surface of the sole (or at least a part) and possibly of the walls comprises only a single layer containing refractory shot.
• the particle size of the latter is preferably less than 50 mm, in particular 30 mm, in particular 20 mm.
• the shot may advantageously comprise a mixture of particles of different particle sizes, suitable for obtaining maximum filling or compactness of the layer or optimized for forming a tight layer.
• the shot is not too fine so as to avoid any risk of entrainment of the shot in the molten glass bath as a result of significant stirring on the surface of the hearth and the walls. , a risk which would be detrimental to the quality of the molten glass.
• a first layer comprising a first shot and, under said contact layer, at least one other layer called “lower” comprising another shot, the granulometry of the shot of the contact layer being greater than that of the shot or of the mixture of shots of the or each lower layer.
• the shot of the contact layer is advantageously such that it cannot be entrained by the stirring of the bath and protects the lower layer from this stirring.
• the layer in contact with the molten bath preferably comprises shot having a particle size greater than 10 mm, in particular of the order of 10 to 50 mm, in particular of the order of 20 to 50 mm, and the or each lower layer preferably comprises grain size shot less than 20 mm or 10 mm as appropriate, in particular of the order of 1 to 10 mm, very preferably less than 5 mm, where applicable a mixture of particle sizes.
• the or at least one lower layer contains an inorganic binder as mentioned above, while the contact layer consists essentially of the relatively large shot.
• a layer of the surface coating comprises a binder ensuring cohesion between the particles of shot
• this binder can be formed from various mineral materials, in particular from oxides or from vitreous materials such as glass, possibly partially devitrified, or rock such as basalt
• the glass can be identical to or different from the glass present in the bath. It can in particular be at least partly a recovery glass (cullet) or advantageously a dense glass absorbing radiation in the field. infrared
• the binder can be advantageously chosen, in particular as a function of its viscosity at the temperature of the wall and of its surface tension, so as to be able to seal (seal) at least partially the interstitial spaces between the particles of shot
• the binder can be chosen so that its density (in particular at the temperature of the hearth) is greater than the density of the glass present in the furnace. An effective physical separation is thus achieved between the binder glass and the molten glass produced in the oven
• the binder can be chosen such that its viscosity is greater than the viscosity of the glass present in the oven.
• the binder glass thus has a sufficiently high viscosity at the temperature of the sole to retain the particles of pellets well and the difference in viscosity avoids mixing of the binder with the molten glass produced in the oven.
• the binder can be chosen so that its thermal conductivity is lower than that of the molten glass produced in the oven, thus ensuring a temperature under the layer. of fairly low shot, the kinetics of corrosion by the glass of the constituent materials of the furnace can be slowed down.
• the mineral binder can be more or less chemically inert with respect to shot
• the binder glass or other binder material
• the binder reacts with the refractory material in shot, corroding the latter with a passage of oxide elements from the refractory material to the binder phase
• This enrichment of the binder in elements refractory oxide generally has the effect of modifying the devit ⁇ fication and / or viscosity characteristics of the interstitial mineral binder
• the cohesion of the layer thus formed is linked at least in part to the progressive modification of the chemical composition of the binder, which would lead to an increase in viscosity and / or devitrification of the latter at the temperature of the sole or the wall, preventing the glass of the molten bath from infiltrating between the refractory particles.
• This enrichment of the interstitial glass (or other material) is generally all the more pronounced as the surface of exchange with the refractory material is high, that is to say that the granulometry of the shot is fine.
• the refractory shot material is relatively resistant or insensitive to corrosive attack by the glass.
• the refractory material is resistant to both binder glass and bath glass.
• the refractory shot used for this contact layer contains chromium oxide, preferably at a rate of at least 10%, in particular at least 30% by weight, for example at least 60%.
• a refractory material at least partially attackable by the interstitial binder very particularly a material containing alumina.
• a refractory material at least partially attackable by the interstitial binder very particularly a material containing alumina.
• the shot used for this layer can be advantageously chosen from AZS type materials. especially recycled, possibly with a limited amount of chromium oxide.
• the composite layer can be produced in various ways: in particular, it is possible to spread a mixture of refractory shot and mineral material on the surface and to heat this mixture, for example when the oven is started, to form the composite, or else it is possible to arrange first a layer of shot then a layer of mineral material that is melted to impregnate the shot
• the invention also relates to a process for manufacturing an oven, such as a glass oven, in which a bottom and side walls are produced intended to delimit a bath of molten material, characterized in that that it includes the steps of :
• a mineral binder in the first step, can be applied in mixture with the shot of at least one layer, or in a layer surmounting a layer of shot.
• another layer is applied to a layer comprising a binder. essentially comprising shot, with a grain size greater than that of the lower layer or layers
• the second step allows the melting and / or thermal activation of the binder so that at least one composite layer is formed
• the structure of the sole and / or of the walls can be adapted as required, in particular the layer or layers comprising shot (14, 16) can be applied to a base layer, shaped or not, made in particular of slabs or blocks refractory or insulating material
• Shaped means a layer made of shaped articles which are installed in the furnace, as opposed to a layer obtained from a shapeless material deposited or spread in the furnace.
• the layer or layers comprising refractory shot can be applied to slabs or blocks of refractory material usually used to produce the contact surface with the molten bath, the layer or layers comprising refractory shot can be applied in place of a traditional block or slab material, either on a layer of leveling concrete, or directly on the insulating blocks.
• the layer or layers comprising shot can also be used on the interior walls of the furnace in well-defined zones, chosen in particular as a function of the temperature prevailing in the bath or above the bath in the zones considered, or as a function of the quality of the material in the molten bath in the areas considered.
• This second embodiment may prove to be particularly advantageous, when the oven has a low bath height (in particular less than 800 mm, in particular 500 mm) because with a reasonable slope angle, the inclined wall does not occupy a very large bath volume.
• the refractory shot-based composite can be used in all types of ovens, advantageously to constitute the entire surface of the hearth and possibly of the walls of the furnace. Its use can nevertheless vary depending on the type of oven.
• the layer comprising shot can be used over the entire surface of the sole in an electric oven, in particular of the plunging electrode type, whereas it may only be used in the area of charging in a burner oven, in which the downstream area can use conventional slabs in contact with the molten material.
• the hearth it is generally advantageous for the hearth to have a layer comprising refractory shot at least in an area of the furnace where the supply of material to be melted takes place.
• the surface coating according to the invention is perfectly adapted to receive these residues. It can in particular to prevent the progression of these residues to the lower structural levels of the walls, such as insulation blocks.
• the wall surface coating according to the invention has a remarkable advantage when the material to be melted contains metallic residues, in the sense that it withstands corrosion much better than a conventional contact refractory material. melted at a temperature close to its melting point.
• the invention also relates to the use of an oven as described above for melting recovery glass containing metal residues.
• the recovery glass can come from various sources, in particular from mirrors, heated glazing for motor vehicles, in particular rear glasses, or tinned or enamelled glass, in particular for automobile glazing, or also from recycled packaging.
• the metals present in the form of metallic residues in these recovery glasses can be in particular silver, lead, copper, tin or others. It was surprising to note that, depending on the granulometry of the shot used (for a given mineral binder), the liquid metal resulting from the melting of the recovery glass could or not penetrate into the surface layer (s).
• the critical size of the particles of shot depends on the nature of the metal in particular on its viscosity in the molten state at the temperature of the bottom, as well as of the interstitial mineral binder and of the molten glass in the bath.
• the surface of an oven wall can be adapted to recover the metal separated from the glass by fusion, this surface being permeable to said metal.
• the subject of the invention is also a process for the separation of metal present in recovery glass, this process comprising a step consisting in melting the recovery glass in an oven as described above, in which the shot included in the surface layer of the sole which is in contact with the glass has a particle size suitable for making said layer permeable to said metal.
• a space for recovering the liquid metal flowing through said layer there can be provided, immediately under said layer, a space for recovering the liquid metal flowing through said layer.
• a perforated element such as a grid can be placed in the upper part of this space, serving as a support for the contact layer.
• the metal is then trapped at the border between the two shot-based layers and gradually stored during a campaign to use the furnace. After one or more campaigns of use, it suffices to deposit the surface coating of the sole, from which the recovered metal can be easily extracted.
• FIG. 1 shows a schematic view in partial longitudinal section of an oven according to the invention
• FIG. 2 shows an enlarged detail of the silk of the oven of Figure 1;
• FIG. 3 shows a schematic view in longitudinal section of another oven according to the invention.
• the oven 1 shown in Figure 1 consists essentially of a hearth 2, side walls 3 and a roof 4, defining a bath 5 of a molten material such as glass. It further comprises supply means 6. such as a conveyor, of material to be melted 7 and a channel 8 for flow of the molten material.
• the means for melting the material 7 are not shown.
• the material may consist of recovery glass (cullet) and / or of a powdery oxide composition
• the sole 2 consists essentially, from the outside towards the inside, of a wall made of insulating blocks 9 arranged on one or more rows (only one row being shown), an optional layer 10 of refractory concrete on which are optionally placed slabs 11 of refractory material, then a first layer 12 and a second continuous layer 13 based refractory material
• the detail of layers 12 and 13 is visible on the enlargement of FIG. 2.
• the first layer 12, or lower layer comprises shot 14 of refractory material, in particular of AZS or chromium oxide type, of a relatively granulometry. fine, in particular less than 20 mm, advantageously 10 mm, in particular 5 mm, embedded in or surrounded by a binder 15 formed from oxides or a vitreous material such as glass.
• the second layer 13, or contact layer comprises another shot 16 of refractory material, of composition identical or different from that of shot 14, in particular at least 10 mm, advantageously at least 20 mm, but with a grain size greater than that of said first shot 14, the shot particles 16 being surrounded by an ore binder 17, of composition identical or different from that of the contact layer 12
• the glass melted from the cullet interacts with the surface of the shot and becomes charged element (s) of refractory oxide (s), for example Al Zr, Si in the case of AZS shot, or Cr in the case of chrome shot
• refractory oxide for example Al Zr, Si in the case of AZS shot, or Cr in the case of chrome shot
• the glass enriched in refractory oxide elements becomes more viscous and possibly may finally devitnfier in the free interstitial spaces, the viscous material devit ⁇ fié preventing the passage of glass from the bath 5 to the lower layers
• a separating element such as a grate or a refractory metal screen could be interposed between the two layers of shot, and possibly a similar element could be placed on the second layer so as to maintain the respective levels of the layers
• a retaining grid could be used to apply one or more similar layers to the side walls 3
• layers 14 and 16 are deposited in layers 12 and 13 in intimate mixture with the binder 15 and 17 respectively.
• the binder in fusion coats the particles of shot ensures the cohesion of the whole.
• the granulometry of the shot 16 and the quality of the bonding glass 17 are such that the layer 13 is permeable to the metal 18
• the granulometry of the shot 14 and the quality of the bonding glass 15 are such that the layer 12 is impermeable to the metal 18
• the metal 18 present in the molten state in the bath 5 flows by gravity to the bottom 2, penetrates through the layer 13 by making a passage between the particles of shot 16, and is blocked at the border between layers 13 and 12, where it accumulates in the form of drops whose size gradually increases
• FIG. 3 shows another embodiment of the invention.
• the oven 20 of FIG. 3 comprises elements identical or equivalent to those of the oven 1, these elements are designated by the same reference numeral.
• the essential differences with the first embodiment relate to the structure of the sole and the walls.
• the sole consists of three layers comprising refractory shot
• the lower layer 21 (analogous to the lower layer 12 of the furnace 1) comprises a binder and relatively fine shot, for example having a particle size of the order of 0 to 5 mm, of a type which can be relatively attacked by a binder based on glass, for example of the AZS type which may optionally contain a limited amount of chromium oxide
• This layer is impermeable to glass, in particular because the fine shot settles very compactly and saturates the interstitial glass with refractory oxides thanks to the high exchange surface; it is also very resistant to corrosion. It plays in particular the role of a concrete, hence the optional nature of the layer 10 of refractory concrete.
• the middle layer 22 comprises a binder and a larger shot than that of the layer 21, for example having a particle size of the order of 10 to 30 mm, and of a type which is relatively attackable by a glass-based binder, identical or different from the type of shot of layer 21.
• this shot can be of the AZS type which can contain up to 30% chromium oxide.
• layer 22 The role of layer 22 is to enrich the interstitial glass with refractory oxides to make it on the one hand less aggressive when it reaches the lower layer 21, and on the other hand more viscous to limit the convection and the diffusion of aggressive oxides,
• the upper layer 23 (which can be brought closer to the contact layer 13 of the oven 1) comprises a relatively large shot, for example at least 50 mm in which the fine particles have been carefully removed, of a type resistant to corrosion by glass, for example single-phase and rich in chromium oxide Its main function is to block convection on the lower layers; it is not carried away by glass currents and does not create defects thanks to its high particle size.
• the shot of layers 21, 22 and 23 can be recycling materials.
• Each wall is constituted by a lower part made of insulating blocks 9 placed if necessary on the optional layer 10 of refractory concrete. This lower part is surmounted by an upper part made of blocks 3 of refractory material (as used to constitute the walls of the furnace 1).
• the surface of the walls directed towards the glass bath comprises a coating comprising refractory shot which is in continuity with the upper layer 23.
• This coating is inclined relative to the vertical by an angle corresponding to the slope angle of the particulate material used to form the layer 23. It is intended to isolate the blocks 3 and 9 from the glass bath.
• the shot-based layers 21, 22 can be produced by first preparing a mixture of the shot concerned and the corresponding glass-based binder in particulate form, in particular cullet, and successively extending: a compact horizontal layer of the mixture for the lower layer 21;
• the upper layer 23 is produced by depositing a horizontal layer of coarse shot which exceeds the level of separation between refractory block 3 and insulating block 9, and finally by applying the coarse shot along the vertical walls in the form of an embankment.
• one begins to heat the oven to cause the melting of the binder or binders and constitute the layers 21 and 22 respectively.
• the chemical exchanges between binder glass and refractory shot can continue for a certain time during the soaking or the starting of the oven before reaching a state ensuring the desired level of tightness. Thanks to the shot-based coating on the interior walls of the furnace, it is possible to reduce the thickness of the refractory blocks 3 and to replace the refractory blocks 3 lower of the furnace 1 with insulating blocks 9 which are less expensive and significantly reduce the cost of the furnace. , without prejudice to thermal insulation or corrosion resistance.
• the invention which has just been described in the particular case of a glass furnace, the hearth of which, of given structure, is provided over its entire surface with at least two layers based on shot, is in no way limited to this embodiment.
• the indications given in the detailed description can be extended to the other embodiments, in particular to the following cases: the sole has another structure (in particular the insulating blocks, the concrete and / or the slabs are absent); only one layer based on shot is used; the layer (s) are only applied to part of the sole.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Furnace Housings, Linings, Walls, And Ceilings (AREA)
• Glass Melting And Manufacturing (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Glass Compositions (AREA)
• Ceramic Products (AREA)
• Joining Of Glass To Other Materials (AREA)

Priority Applications (8)

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Citations (5)

• 1998
  • 1998-05-19 FR FR9806322A patent/FR2778910A1/fr active Pending
• 1999
  • 1999-05-18 PL PL99338081A patent/PL338081A1/xx not_active Application Discontinuation
  • 1999-05-18 CA CA002296754A patent/CA2296754A1/fr not_active Abandoned
  • 1999-05-18 BR BR9906464-2A patent/BR9906464A/pt not_active Application Discontinuation
  • 1999-05-18 WO PCT/FR1999/001185 patent/WO1999059926A1/fr not_active Application Discontinuation
  • 1999-05-18 KR KR1019997012561A patent/KR20010014390A/ko not_active Application Discontinuation
  • 1999-05-18 EP EP99920884A patent/EP1007483A1/fr not_active Withdrawn
  • 1999-05-18 JP JP2000549548A patent/JP2002515396A/ja active Pending
  • 1999-05-18 SK SK49-2000A patent/SK492000A3/sk unknown
  • 1999-05-18 CN CN99800789A patent/CN1272097A/zh active Pending
  • 1999-05-18 HU HU0003124A patent/HUP0003124A3/hu unknown
  • 1999-05-18 AU AU38294/99A patent/AU3829499A/en not_active Abandoned
  • 1999-05-19 AR ARP990102373A patent/AR016039A1/es unknown
• 2000
  • 2000-01-14 ZA ZA200000145A patent/ZA200000145B/xx unknown
  • 2000-01-18 NO NO20000240A patent/NO20000240D0/no not_active Application Discontinuation

Patent Citations (5)

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