Multi-impact flame melting process

Abstract

A melting process in which the unmelted material forms a pile 30 having a free surface 40 inclined relative to the vertical in the furnace 10; said unmelted material is heated by means of flames 51, 52, 53 with regulated power and impulse directed towards the free surface 40 along at least two directions α1, α2, α3 forming different acute angles θ1, θ2, θ3 with the horizontal plane such that the flames 51, 52, 53 define impact zones 41, 42, 43 on the free surface 40 which are located at at least two different vertical levels h1, h2, h3. Abbreviated figure: Fig. 1

Description

Title of the invention: Multi-impact flame melting process

[0001] The present invention relates to melting processes and furnaces.

[0002] It is known in melting processes to introduce the unmelted charge (solid charge), hereafter the “unmelted”, into the furnace by means of chargers.

[0003] While waiting for their melting, the unmelted material then forms a bank or one or more piles of unmelted material (solids) in the furnace.

[0004] For example, in the case of certain known glass melting furnaces, these unmelted materials float on the bath of already molten raw materials like a carpet and break up into several small islands as they move through the furnace before their total melting.

[0005] It is known in melting processes to introduce the unmelted charge into the furnace by means of feeders. The unmelted material then forms a mound or one or more piles of unmelted material in the furnace.

[0006] Depending on the method of loading used, the unmelted material can accumulate in the furnace in the form of one or more slopes of a greater or lesser height, which may even reach the vault of the furnace and of a width which may be equal to the width of the furnace, or even in the form of one or more piles of such a height.

[0007] In all cases, the unmelted deposit has a free surface that is generally inclined with respect to the vertical.

[0008] In what follows, the term "pile" is used to refer to such unsold material deposits of any shape, therefore both unsold material deposits in the shape of a berm and unsold material deposits in the shape of a pile.

[0009] It is known to direct flames towards piles of unmelted material to cause the unmelted material to melt.

[0010] Heating the inclined free surface of a pile with a single flame to obtain controlled and / or more or less uniform melting on the free surface directed towards the flame is a challenge, especially when the unmelted materials have low thermal conductivity.

[0011]

[0012] Indeed, the distribution of energy imparted to the unburned material depends on the geometry of the flame and its orientation towards the target surface. For example, in the case of a horizontal flame with a circular cross-section impacting the free surface of an unburned material embankment, the free surface is not perpendicular to the flame and the intersection of the flame with the target surface is inclined backwards, leading to an energy distribution that disproportionately affects parts of the target surface further from the burner and parts not impacted by the flame.

[0013] This results in uneven heating and an imbalance in the melting of the pile: the area receiving the most energy will melt first, leaving a hollow in the pile. Areas of the pile receiving less energy will lag behind in melting and may, for example, in a continuous furnace, advance with the molten charge towards the furnace outlet.

[0014] The heating heterogeneity thus requires the furnace operator to slow down the loading of raw materials in order to ensure complete melting, and where necessary the refining of the charge molten in the furnace, which results in a decrease in production.

[0015] This problem is particularly pronounced in the case of unmelted materials with low thermal conductivity.

[0016] The present invention aims to remedy at least in part the problem described above.

[0017] To this end, the invention proposes a melting process in which unmelted material is introduced into a furnace by one or more loaders. In the furnace, this unmelted material forms a pile with a free surface inclined with respect to the vertical. The surface area of ​​the base of the pile is therefore greater than the surface area of ​​the top of the pile.

[0018] According to the melting process, the unmelted material in the pile is heated by means of flames directed towards said inclined free surface. Each of these flames impacts the free surface of the pile and thus defines an impact zone on this free surface.

[0019] According to the invention, these flames are directed towards the free surface along at least two directions forming different acute angles with the horizontal plane. In this way, the impact zones defined by the flames on the free surface are located at at least two different vertical levels.

[0020] By vertical level of an impact zone, we understand in the present context the height of the centroid or center of mass of that zone.

[0021] Also according to the invention, the thermal energy transferred to the pile by each of these flames in its impact zone is regulated by regulating the power of the flame.

[0022] Moreover, the impulse of each of these flames is regulated so that the flame impacts the free surface in its impact zone without mechanical degradation by the flame of the structural integrity of the pile in this impact zone.

[0023] The process according to the invention has several advantages.

[0024] The heating by the flames of the unmelted material in the pile is distributed over the height of the pile.

[0025] The thermal energy transferred to each impact zone is regulated. This makes it possible to heat certain impact zones more or less than others, thereby optimizing the melting process. Such regulation also prevents overheating of the unmelted material, which is important because overheating can lead to a decrease in quality.

[0026] Finally, the regulation of the flame impulse ensures that each of the flames directed towards the free surface of the pile reaches, that is to say impacts, this free surface, but with an impulse such that the flame does not mechanically degrade the structural integrity of the pile in its impact zone.

[0027] In this context, a distinction is made between, on the one hand, the desired melting of the unmelted material in the heap and its effect on the shape and structure of the heap and, on the other hand, the mechanical degradation of the heap, in particular by mechanical entrainment of unmelted material from the heap by the flames and combustion gases. Such mechanical degradation may result in particular from (i) the presence of unmelted material in the molten charge discharged from the furnace or from an insufficiently refined molten charge, (ii) the degradation of the interior of the furnace by the entrained unmelted material, and (iii) the loss of unmelted material discharged from the furnace with the combustion fumes.

[0028] As indicated above, the flames are directed towards the free surface along at least two directions forming different acute angles with the horizontal plane. In this way, the impact zones defined by the flames on the free surface are located at at least two different vertical levels. Such a configuration is therefore clearly distinct from a combustion process in which a multitude of flames are generated along at least two directions forming different acute angles with the horizontal plane, but in which the flames merge into a single flame downstream of the burner. Indeed, such a fused flame would define a single impact zone on the free surface and not a multitude of impact zones at different vertical levels.

[0029] It should be noted that the present invention does not preclude the presence in the furnace of heating means other than the aforementioned flames directed towards the free surface. Such other heating means may include, in particular, electric heating elements and / or flames not directed towards the inclined free surface of the pile, for example above or submerged in the molten charge in a refining zone.

[0030] The proposed process, with its regulation of the power of the imparting flames on the one hand and its regulation of the imparting flame impulse on the other, thus makes it possible to resolve the melting imbalance of the heap observed in known processes and consequently to increase furnace production. The melting, better distributed over the free surface of the heap directed towards the flames, will lead to a Optimizing the use of thermal energy, energy savings will be even greater when the process is combined with a system for recovering thermal energy from the fumes expelled from the furnace. The energy thus recovered can advantageously be used to heat one or more combustion reactants (oxidizer and / or fuel) via a heat recovery unit and / or to preheat at least a fraction of the unmelted material before it is introduced into the furnace.

[0031] As indicated above, according to the process of the invention, flames are directed towards the free surface in at least two directions forming different acute angles with the horizontal plane so that said flames define impact zones on the free surface located at at least two different vertical levels.In a preferred embodiment, the impact zones of these flames on the free surface are located at at least three different vertical levels, or even at least four different vertical levels. The number of vertical levels is chosen according to the height of the pile and therefore also its free surface area, as well as the size / shape of the impact zones. The size and shape of an impact zone depend on the geometry of the flame and the impacted free surface, more specifically on the length and cross-section, defined by the burner generating the flame, and the opening angle of the impacting flame, and the shape and inclination of the impacted free surface.

[0032] The impact zones can be positioned relative to each other in different ways.

[0033] For example, impact zones located at a given vertical level can be positioned offset from impact zones located at the vertical level below and / or located at the vertical level above.

[0034] However, for the implementation of the method, it may be advantageous for the impact zones at at least two different vertical levels to have geometric centers that lie in the same vertical plane. Such a configuration can, in particular, be achieved by means of flames directed towards the free surface, whose directions (a) form different acute angles with the horizontal plane and (b) lie in said same vertical plane. In this case, it is possible to use a single burner to generate the multitude of flames whose directions lie in this plane.

[0035] As indicated above, the impacting flames form acute angles with the horizontal plane, and each impacting flame defines an impact zone on the free surface of the pile. Thus, when several such impacting flames have directions located in the same vertical plane, said directions will normally diverge from each other in the direction towards the free surface of the pile in order to prevent said flames from joining and mixing, thus merging into a single flame before impacting said free surface of the pile.

[0036] The impact zones of two adjacent flames may partially overlap.

[0037] According to a preferred embodiment and in order to ensure good distribution of heating and melting of the impacted free surface, each of the impact zones partially covers the nearest impact zone.

[0038] For better management of the melting process, it may be useful to detect the height of the pile in the furnace. To this end, the furnace may be equipped with means for detecting the height or profile of the pile in the furnace.

[0039] According to a useful embodiment, the number of different vertical levels of the impact zones is adjusted according to the height of the pile.

[0040] In this case, the flames corresponding to the impact zones with the highest vertical level are extinguished when the height of the pile falls below a given threshold (thus, for example, moving from impact zones with three vertical levels to impact zones with only the two lowest vertical levels), and the flames corresponding to impact zones with a higher vertical level are ignited when the height of the pile exceeds a given threshold (thus moving, for example, from impact zones with two vertical levels to impact zones with three vertical levels, the added third level being located above the two pre-existing levels). The two thresholds may be the same or different.

[0041] Indeed, the height of the heap in the furnace can vary, for example, depending on the furnace production (also called the "pull" in the case of a continuous melting furnace), depending on the nature of the unmelted material introduced into the furnace and / or the molten charge to be obtained. In the case of a batch furnace (often called a "batch furnace"), or a semi-continuous furnace (often called a "semi-batch furnace"), the height of the heap can vary during the melting process: the heap height is generally at its maximum after the introduction of a "batch" of unmelted material and decreases as the melting of the unmelted material progresses.

[0042] In the present context, a semi-continuous melting process or furnace is understood to be a melting process or furnace in which part of the charge is added or subtracted during the melting cycle.

[0043] As indicated above, the furnace can be equipped with means for detecting the height or profile of the pile within the furnace. The pile height can also be visually verified by the furnace operator through a peephole in the furnace. The pile height and / or its evolution during the melting process can also be estimated based on historical data.

[0044] When the pile has a shape or position in the furnace such that one or more of the flames that are normally directed towards the pile pass totally or partially over or beside the pile, these flames are advantageously extinguished. thus do not impact the free surface of the pile, or even only partially impact the free surface of the pile.

[0045] By extinguishing the flames which are generally directed towards the free surface but pass at least partially over or beside the pile of unmelted material, the efficiency of the furnace is increased and there is no longer a risk that such a flame will impact and overheat, for example, the wall or a stoker of the furnace located behind the pile in the direction of the flame.

[0046] When the pile has a shape or position in the furnace such that a portion of its free surface is not impacted by a flame, but the furnace includes means (such as a burner) for directing an impacting flame towards this portion of the free surface, one or more flames as defined above are advantageously added / ignited to impact this portion of the pile's free surface. For example, by adding one or more flames with an impact zone level closer to the top of the pile as the pile height increases, the heat distribution of the unmelted material is better spread over the free surface of the pile.

[0047] It may also be useful to detect a position of the free surface of the pile in the furnace. In particular, it may be useful to detect positions of the free surface at at least one of the vertical levels of the impact zones defined by the flames directed towards this free surface.

[0048] A position of the free surface allows, for example, to identify the state of advancement or withdrawal of the pile in a continuous melting furnace with respect to the outlet for the molten charge of the furnace, a pile too far advanced towards the outlet of the furnace increasing the risk of the presence of unmelted material in the evacuated molten charge and / or of incomplete refining of the molten charge upstream of this outlet.

[0049] According to an advantageous embodiment, it is detected whether the pile reaches a predefined advance distance in the direction of at least one of the flames directed towards the free surface. This predefined advance distance corresponds to an advance of the free surface, and therefore of the melting front of the pile, relative to its desired position. When the pile reaches this predefined advance distance, the overall power of the flames directed towards the free surface is increased. In this way, it is possible to induce faster melting of the unmelted material in the pile and thus a retreat of the free surface towards its desired position.

[0050] According to another embodiment, which may or may not be combined with the preceding embodiment, the presence of the pile is detected at a predefined recoil distance in the direction of at least one of the flames directed towards the free surface. This predefined recoil distance corresponds to a retraction of the free surface, and therefore of the melting front of the pile, from its desired position. When the pile does not reach this predefined recoil distance, the overall intensity of the flames is reduced. In this way, it is possible to slow down the melting of the unmelted material in the pile and eventually, especially with the introduction of additional unmelted material into the furnace, to bring the free surface towards its desired position.

[0051] As already indicated above, according to the present invention, the impulse of each flame directed towards the free surface is regulated so that the flame impacts the free surface without mechanical degradation of the structural integrity of the pile in the area of ​​flame impact. Consequently, when the position of the free surface of the pile does not correspond or no longer corresponds to its desired position, an adjustment of the impulse of these flames may also be necessary to ensure that the flames impact the free surface in its actual position and / or to avoid mechanical degradation of the structural integrity of the pile in the area of ​​flame impact on the free surface in its actual position.

[0052] The pile can be in the form of a slope. Such a pile can in particular be obtained when the unmelted material is introduced into a continuous furnace through or on either side of the upstream wall of the furnace and the molten charge is evacuated from the furnace through the downstream wall of the furnace, the furnace being equipped with one or more burners located on the side of the downstream wall and whose flame(s) are directed towards a melting front of the slope forming a free surface inclined with respect to the vertical towards the upstream wall.

[0053] The pile can also be in the form of a stack, such as a stack made of a conical or truncated conical substance. Such a pile can be obtained, in particular, when the unmelted material is introduced into the furnace through the furnace vault.

[0054] The unmelted material can also form several piles in the furnace, each pile having a free surface. In this case, the process according to the invention is used to melt the unmelted material in each pile.

[0055] Impact flames result from the combustion of a fuel with an oxidizer (i.e. a combustion oxidizer).

[0056] The fuel can be a solid, liquid or gaseous fuel.

[0057] The fuel is advantageously a gaseous fuel. Such a gaseous fuel may be a carbonaceous fuel, a non-carbonaceous fuel, or a mixture of carbonaceous and non-carbonaceous fuels. Thus, the fuel may in particular be chosen from among the following gaseous fuels: natural gas, hydrogen, ammonia, synthesis gas, biogas, any gas containing hydrogen and / or carbon monoxide, and combinations of at least two of these gaseous fuels.

[0058] For environmental reasons, non-carbon fuels and renewable fuels with a low carbon footprint.

[0059] The oxidizer / oxidant typically has an oxygen content of 16% to 100% by volume. Oxidizers / oxidants richer in oxygen, for example with a Fuels with an oxygen content of at least 90% by volume are typically more efficient and produce hotter flames, given their low or even absence of ballast gas, which does not participate in combustion. However, for some applications, an oxidizer / oxidizer with a higher ballast content, typically generating more dilute flames, may be preferable.

[0060] In order to generate flames directed towards the free surface of the pile of unmelted material, the furnace is equipped with at least one burner.

[0061] In one useful embodiment, the furnace is equipped with at least one burner that generates a multitude of flames directed towards the free surface. In another useful embodiment, the furnace is equipped with several burners, each generating a single flame directed towards the free surface. A burner of the furnace can thus generate a single impacting flame or several impacting flames. The furnace can also be equipped with a combination of burners, at least one of which generates a single flame and at least one other generates several flames.

[0062] According to an advantageous embodiment, the furnace is equipped with at least one burner which generates flames, i.e. several flames, directed towards the free surface of the pile in at least two directions forming different acute angles with the horizontal plane so that the impact zones defined by these flames generated by this burner on the free surface are located at at least two different vertical levels.

[0063] According to a preferred embodiment, the furnace is equipped with at least one burner which generates at least two flames directed towards the free surface and whose directions a. form different acute angles with the horizontal plane, b. are located in said same vertical plane and c. are divergent from each other in the direction towards the pile / towards the free surface of the pile.

[0064] For the implementation of the process, the melting furnace is generally equipped: • one or more loading machines to introduce the unmelted materials into the oven; • one or more combustion devices, and in particular one or more burners, to generate flames directed towards the free surface; • a control unit enabling: • to regulate the flame intensity and • to regulate the pulse of the flames.

[0065] For the implementation of particular embodiments of the process according to the invention, the oven may also be equipped with one or more of the following equipment: a detector to detect the height or profile of the pile; • a detector to detect a position of the free surface, preferably to detect a position of the free surface at at least one of the vertical levels of the impact zones; • a detector to detect whether the pile reaches a predefined advancement distance or not; • a detector to detect the presence or absence of the pile at a predefined retreat distance.

[0066] It should be noted that the same detector can be used for several detections. For example, it is possible to use a detector that detects the shape and position of a pile-shaped heap or a detector that detects the shape and position of the melting front of a slope-shaped heap.

[0067] When the furnace is equipped with one or more detectors, the furnace advantageously also includes a control unit to control the regulation unit using data detected by the detector(s), for example according to any of the embodiments described above concerning the regulation of the power and pulse of the impacting flames.

[0068] As indicated above, the process can be a continuous process, therefore with a continuous melting furnace, a discontinuous process, therefore with a discontinuous melting furnace or a semi-continuous process, that is to say with a semi-continuous furnace.

[0069] In the case of a batch or semi-continuous process, the melting process may also include a stage during which the heap is substantially or completely melted and during which there are no inclined free surfaces on which flames define impact zones at at least two vertical levels. Depending on the case, there may be no combustion in the furnace during this stage (particularly when this stage is short and / or the furnace heat losses are low) or a certain level of combustion (generally lower) is maintained in order to refine the molten charge or to maintain it at the required temperature above the melting temperature of the charge.

[0070] According to particular embodiments, the process is a continuous or semi-continuous process, the furnace having an upstream wall, through which or on the side of which the unmelted materials are introduced into the furnace, and a downstream wall opposite the upstream wall, through which or on the side of which the molten charge is evacuated from the furnace.

[0071] According to a particular embodiment, the impacting flames are directed towards the free surface of the pile through the downstream wall or the side of the downstream wall, for example through the arch and / or through one or more of the side walls connecting the upstream wall to the downstream wall.

[0072] In the present context, "on the side of a wall" means: in half the length of the furnace adjacent to said wall, preferably in the third, or even in the quarter or in the fifth, of the length of the furnace adjacent to said wall.

[0073] The process according to the invention is preferably a process for melting glass, a process for melting enamel, a process for melting non-ferrous metals, such as aluminum, lead, copper, etc., and in particular such a process for the secondary melting of non-ferrous metals, more particularly in the context of recycling one or more non-ferrous metals, for melting hydraulic binders, or for vitrifying waste. Therefore, the furnace is preferably a furnace selected from among glass melting furnaces, enamel melting furnaces, non-ferrous metal melting furnaces, hydraulic binder melting furnaces, and waste vitrification furnaces.

[0074] The present invention and its advantages will be better understood in the light of the following non-limiting example, with reference to [Fig.1], which is a schematic cross-sectional representation of a furnace in which the process according to the invention is implemented.

[0075] Fig. 1 shows more particularly a continuous furnace 10 for melting glass.

[0076] Ovens of the illustrated type are parallelepiped in shape and generally have a length of less than 10 meters, a width of less than 5 meters and a height of less than 3 meters.

[0077] The furnace 10 has an upstream wall 11, through which the unmelted (i.e. the solid vitrifiable composition) is introduced into the furnace 10, and a downstream wall 12 opposite the upstream wall 11 and through which the molten glass 50 is evacuated from the furnace 10.

[0078] Two lateral walls connect the upstream wall 11 and the downstream wall 12, the rear lateral wall 13 being visible on the [Fig.1].

[0079] The furnace 10 also has a vault 14 and a floor 15, the melting zone being located between the upstream wall 11, the downstream wall 12, the side wall 13 and the other side wall, the vault 14 and the floor 15.

[0080] The solid vitrifiable composition is composed of, or comprises, small particles with low thermal conductivity compared to the thermal conductivity of metals. These particles therefore transmit little or no thermal energy between them.

[0081] The unmelted material is introduced into the furnace 10 through the upstream wall 11, for example by means of a screw conveyor 20. Inside the furnace 10, it forms a pile 30 in the shape of a slope with a height h (measured from the hearth 15) that extends above the molten glass 50. On the upstream side of the furnace 10, the slope 30 of unmelted material rests against the upstream wall 11. Downstream, the slope 30 ends in a free surface 40 inclined with respect to the vertical.

[0082] For heating and melting the unmelted material, the free surface 40 is attacked at different vertical levels by the flames 51, 52, 53 positioned in a fan shape and generated by one or more burners 55 mounted in the downstream wall 12. The free surface 40 therefore forms a melting front for the unmelted material in the furnace 10.

[0083] The furnace 10 illustrated in [Fig. 1] is a small furnace; the melting slope 30 is located on the upstream side of the wall 11, and the burner(s) 55 are on the opposite downstream side 12. The burner(s) 55 are chosen to emit a flame length appropriate to the length of the furnace 10. The molten material 50 moves along the hearth 15 of the furnace 10 in the direction of the burner 55, below which is an outlet hole (not shown) for the molten material 50. The molten material 50 thus moves under the flames 51, 52, 53, which keep it molten until it exits the furnace 10.

[0084] For larger furnaces, the melting slope 30 remains on the upstream wall 11 side, but additional burners are added. These additional burners can, for example, be installed on the side walls 13 connecting the upstream wall 11 and the downstream wall 12, in the vault 14 or in the hearth 15, for so-called "submerged burners".

[0085] Each flame 51, 52, 53 defines an impact zone 41, 42, 43 on the free surface 40 and causes the unmelted material to melt there.

[0086] The flames 51, 52, 53 are directed towards the free surface 40 in different directions a1, a2, a3 (represented by the axes of the flames 51, 52, 53) forming different acute angles 01, 02, 03 with the horizontal plane. In this way, the respective impact zones 41, 42, 43 of the flames 51, 52, 53 are located at different vertical levels hl, h2, h3 (as defined above) of the free surface 40.

[0087] The thermal energy transferred to the unmelted material in the embankment 30 by each flame 51, 52, 53 via its respective impact zone 41, 42, 43 is regulated by regulating the power of the corresponding flame 51, 52, 53. By regulating the power of the flames 51, 52, 53, the melting rate of the unmelted material is also regulated at the level of the corresponding impact zone 41, 42, 43. This makes it possible, in particular, to avoid destabilization and therefore mechanical degradation of the embankment 30 by too rapid melting of the unmelted material at the base of the embankment 30, or even by too slow melting of the unmelted material in the middle or at the top of the embankment 30.

[0088] By regulating the overall power of the flames 51, 52, 53 and therefore also the thermal energy transferred to the unmelted material in the slope 30 by all the flames 51, 52, 53 via the different impact zones 41, 42, 43, it is possible to adjust the overall melting rate of the unmelted material and consequently also the height h of the slope 30 and / or the advancement position in the furnace of the free surface 40 of the slope 30.

[0089] The pulse of each flame 51, 52, 53 is also regulated. This pulse is more specifically regulated so that the flames 51, 52, 53, on the one hand, impact the free surface 40 of the embankment 30, which allows for more efficient heating of the unmelted material, and, on the other hand, do not mechanically degrade the structural integrity of the embankment 30.

[0090] Since the pulse of the flames 51, 52, 53 is regulated so that said flames 51, 52, 53 impact the free surface 40, the flames that correspond to impact zones furthest from the root of the flame / burner 55 typically have stronger pulses than the flames that correspond to impact zones closer to the root of the flame / burner 55.

[0091] As previously stated, in the present context, a distinction is made between, on the one hand, the change in the pile by the melting of the unmelted material and, on the other hand, the mechanical degradation of the structural integrity of the pile by high-impulse flames, in particular by the uncontrolled mechanical entrainment of unmelted material from the pile by such flames and / or by the fumes / combustion gases generated by such flames.

[0092] For the regulation of the pulse of the flames 51, 52, 53, account is therefore taken of the distance between the free surface 40 and the root of the flames 51, 52, 53 / the outlet of the burner(s) 55 generating the flames 51, 52, 53 and of the nature of the unmelted.

[0093] Thus, when the embankment consists of large and heavy pieces of non-ferrous metal that are difficult to move, the impulse of the flames can be relatively high.

[0094] On the other hand, when the slope consists of or includes unmelted material in the form of light particles / fines / powders, as in the illustrated embodiment, and in particular such fines / powders which do not stick together when entering the furnace, the impulse of the imparting flames must remain low enough to avoid such entrainment or to avoid significant entrainment of said particles.

[0095] It is recalled that such destabilization / training can result in: i. the presence of unmelted material in the molten charge removed from the furnace or in an insufficiently refined molten charge, which can cause problems in processes downstream of the melting stage, such as shaping solid products from the molten charge, and lead to a reduction in the quality of the solid products manufactured; ii. Degradation of the furnace interior, for example: erosion of the walls by entrained unmelted material and formation of deposits on burners or other equipment in contact with the furnace interior; and / or iii. the loss of unmelted material evacuated from the furnace with the combustion fumes. Such a loss of raw materials is obviously costly. It can also cause blockages in the flue gas ducts and accelerated saturation of the filters used to treat the flue gases upstream of the chimney. When the furnace includes a system for recovering thermal energy from the exhaust gases, the presence of unmelted material in the flue gases also poses problems for heat recovery in the heat recovery or regenerator units used. Moreover, when the charge is a mixture of different ingredients, as is generally the case for glass melting processes, the removal of unmelted material with the combustion gases can be selective, with different removal levels for different ingredients.In this case, the composition of the molten charge obtained does not correspond to that resulting from the composition of the unmelted material introduced into the furnace, with obvious consequences for the molten charge treatment processes downstream of the furnace and on the properties of the final product obtained.

[0096] Burners allowing such dual regulation, on the one hand, of the power of the generated flame(s) and, on the other hand, of the pulse of the generated flame(s), are known. Such burners are described, for example, in WO-A-2010 / 003866. Such a burner allows, for example, the modification of the flame power at constant pulse or the modification of the flame pulse at constant power.

[0097] The flames 51, 52, 53, and in particular the flame 53 corresponding to the impact zone 43 of the highest vertical level h3, can be extinguished individually, notably depending on the melting state of the pile 30 and / or in particular depending on the height h of the pile 30. Such an embodiment is particularly flexible and efficient and can adapt to changes in the composition or structure (particle size distribution) of the charge and / or the desired furnace productivity level. Such an embodiment is also particularly useful for batch and semi-continuous processes which inherently have the characteristic that the height of the pile(s) 30 varies during the melting of the unmelted material.

[0098] In some cases, the position, height h, or even the shape of the pile 30 in the furnace, and their possible evolution during the melting process are known by the furnace operator.

[0099] However, it is generally desirable to be able to detect one or more of these characteristics because they are characteristics that allow the fusion process to be optimized.

[0100] According to an advantageous embodiment, electromagnetic beams, and in particular laser beams, are used to detect the position of the pile 30, the height h of the pile 30, the free surface 40 or of one or more of the impact zones 41, 42, 43 during the melting process.

[0101] According to the illustrated embodiment, two electromagnetic beams 61, 62 are directed from a side wall towards detectors in the opposite side wall 13.

[0102] When the pile 30 of unmelted material is located opposite one of these beams 61, 62, the pile 30 interrupts this laser beam 61, 62 and no signal is detected by the corresponding detector. When the pile 30 does not interrupt the laser beam 61, 62, the corresponding detector detects the beam 61, 62, which means the absence of a pile of unmelted material at that location in the furnace 10.

[0103] A first electromagnetic beam 62 is directed from one side wall 13 to the other at a position corresponding to a predetermined maximum advance position of the free surface 40 and therefore of the melting front of the pile 30. When, in such a melting furnace 10, there is a melting delay, the unmelted pile 30 advances towards the outlet for the molten charge in the downstream wall 12. With the advancement of the pile 30 towards the furnace outlet, the impact zones 41, 42, 43 on the free surface 40 of the pile 30 approach the root of the corresponding impacting flame 51, 52, 53 of the burner 55 generating this impacting flame 51, 52, 53. When the pile 30 intersects the electromagnetic beam 62 (as illustrated in the figure where the pile intersects the beam 62 at the impact zone 42), a signal is transmitted to a control unit 65 of the furnace 10 in order to signal the progress status of the pile 30.In response, the control unit 65 transmits a control signal to the regulation unit 66 of the burner(s) 55 so that the overall power of the impacting flames 51, 52, 53 is increased while distributing the power of the individual flames 51, 52, 53 so as not to destabilize the structural integrity of the pile 30 at the level of its free surface 40 and risk its uncontrolled collapse.

[0104] Also according to the illustrated embodiment, an electromagnetic beam 61, such as a laser beam, is directed from one side wall to the other 13, at a position which corresponds to a predetermined minimum advancement position of the pile 30 of unmelted material towards the outlet of the furnace 10 for the molten charge 50. When the free surface 40 of the pile 30 is upstream of this minimum advancement position, the electromagnetic beam 61, 62 is not or no longer cut by the unmelted material of the pile 30 and the beam 61 impacts the corresponding detector in the side wall 13.In this case, a corresponding signal is transmitted to the control unit 65 of the furnace 10, which in turn transmits a control signal to the control unit 66 of the burner(s) 55 so that the overall power of the impacting flames 51, 52, 53 is reduced while distributing the power of the individual impacting flames 51, 52, 53 in such a way as not to destabilize the embankment 30 and risk its collapse. This reduction of . the overall power may include the temporary extinguishing by the control unit 66 of one or more impacting flames 51, 52, 53.

[0105] Based on the detection signals obtained, the control unit 65 can then compare the detected distance(s) with a predetermined maximum advance position and / or with a predetermined minimum advance position and transmit to the control unit 66 of the burner(s) 55 a control signal for the regulation of the overall power of the flames 51, 52, 53 as described in more detail above.

[0106] These detection signals can also be used to trigger an individual adjustment, via an increase or decrease, of the pulse and / or power of the impacting flame 51, 52, 53, the distance of which between the flame root 51, 52, 53 / the outlet of the corresponding burner 55 and its impact zone 41, 42, 43 has been detected. For example, depending on the detection signal obtained, the control unit 65 can transmit to the regulation unit 66 of the burner concerned a control signal for adjusting the pulse of the flame 51, 52, 53 in question so that this flame 51, 52, 53 effectively impacts its impact zone 41, 42, 43 on the free surface 40 without degrading the structural integrity of the pile 30.

[0107] It is also possible to detect the height of pile 30.

[0108] In one embodiment, an electromagnetic beam is directed from one wall to an opposite wall at a position near the top of the pile 30. If this detection reveals that the upper part of the pile 30 targeted by the detection is molten and therefore no longer interrupts the electromagnetic beam, a detection signal is transmitted to the control unit 65. The control unit 65 then transmits a control signal to the regulation unit 66 of the burner(s) 55 so that the flame(s) 51, 52, 53 having a direction a1, a2, a3 aimed at an impact zone 41, 42, 43 on this upper part of the pile 30, and which therefore no longer impact the pile 30, or only partially impact it, when this upper part is molten, are extinguished, in order to maintain high energy efficiency of the furnace 10 and to avoid damaging the walls or other elements of the furnace 10 (such as, for example the loading machine, due to being impacted by this or these flames.

[0109] According to an advanced embodiment, the position and profile / shape of the pile 30 inside the furnace 10 are detected, for example by optical means (in English "optical imaging"), and the power of the impacting flames is regulated accordingly as described above.

[0110] It is possible to detect and remedy excessive or insufficient local melting in one or more impact zones 41, 42, 43 on the free surface 40, or even to remedy localized collapse of the free surface 40, by individually adjusting the power of one or more impacting flames 51, 52, 53 specifically directed towards these impact zones 41, 42, 43 on the surface free of pile 30, without necessarily changing the heat transfer by impacting flames 51, 52, 53 to other areas 41, 42, 43 on the free surface 40 of pile 30.

Claims

Demands

1. A melting process in which: • unmelted materials are introduced into a furnace (10) by one or more feeders (20); • in the furnace (10), the unmelted materials form a pile (30) having a free surface (40) inclined with respect to the vertical; • the unmelted materials in the pile (20) are heated by means of flames (51, 52, 53) directed towards the free surface (40), each flame (51, 52, 53) defining an impact zone (41, 42, 43) on the free surface (40) of the pile (30); characterized in that: • the flames (51, 52, 53) are directed towards the free surface (40) along at least two directions (al1, a2, a3) forming different acute angles (01, 02, 03) with the horizontal plane so that the impact zones (41, 42, 43) defined by the flames (51, 52, 53) on the free surface (40) are located at at least two different vertical levels (hl, h2, h3);and • the thermal energy transferred to the pile (30) by each flame (51, 52, 53) in its respective impact zone (41, 42, 43) is regulated by regulating the power of the flame (51, 52, 53); • the impulse of each flame (51, 52, 53) is regulated so that the flame (51, 52, 53) impacts the free surface (40) in its impact zone (41, 42, 43) without mechanical degradation by the flame (51, 52, 53) of the structural integrity of the pile (30) in this impact zone (41, 42, 43).

2. Method according to claim 1, the flame impact zones on the free surface are located at at least three different vertical levels.

3. A method according to any one of the preceding claims, wherein the impact zones at at least two different vertical levels have their geometric centers in the same vertical plane.

4. A method according to any one of the preceding claims, wherein each impact zone partially overlaps the nearest impact zone.

5. A method according to any one of the preceding claims, wherein the height of the pile is detected.

6. A method according to any one of the preceding claims, wherein the flame or flames whose impact zone exceeds at least in part the height h of the pile (30) are extinguished.

7. A method according to any one of the preceding claims, wherein the number of different vertical levels of the impact zones is adjusted according to the height of the pile.

8. A method according to any one of the preceding claims, wherein a position of the free surface is detected, preferably at at least one of the vertical levels of the impact zones.

9. A method according to any one of the preceding claims, wherein it is detected whether the pile reaches a predefined advancement distance in the direction of at least one of the flames directed towards the free surface and wherein the overall power of the flames is increased when the pile reaches this predefined advancement distance.

10. A method according to any one of the preceding claims, wherein the presence of the pile is detected at a predefined recoil distance in the direction of at least one of the flames directed towards the free surface and wherein the overall power of the flames is reduced when the pile does not reach this predefined recoil distance.

11. A method according to any one of the preceding claims, wherein the pile is in the form of a bank or a stack.

12. A method according to any one of the preceding claims, wherein the furnace is equipped with at least one burner which generates flames directed towards the free surface in at least two directions forming different acute angles with the horizontal plane such that the impact zones defined by these flames generated by this burner on the free surface are located at at least two different vertical levels.

13. A process according to any one of the preceding claims, wherein the process is a continuous, discontinuous or semi-continuous process.

14. A process according to any one of the preceding claims for melting glass, enamel, non-ferrous metal, hydraulic binder or for vitrifying waste.

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