Melting method using multiple impact flames

Abstract

The invention relates to a melting method in which unmelted material forms a material slope 30 which abuts on one side against an upstream wall 11 of a furnace 10 and which has a free surface 40 on the opposite side; the unmelted furnace material is heated by means of at least three flames 51, 52, 53 at regulated power and momentum and the flames are directed towards the free surface 40 to define impact zones 41, 42, 43 on the free surface 40 over at least three different distances l1, l2, l3 of one of the side walls 13, 13'of the furnace 10.

Description

Technical Field

[0001] This invention relates to melting methods and furnaces. Background Technology

[0002] In melting methods, known practices include introducing unmelted furnace charge (solid charge), hereinafter referred to as "unmelted charge", into the furnace via a feeder.

[0003] During melting, the unmelted charge forms an unmelted charge bank, which is equal in width to the furnace and has a variable height that may even reach the top of the furnace.

[0004] For example, in the case of some known glass melting furnaces, the unmelted furnace charge floats like a carpet on the already molten bath of raw materials before it is fully melted and breaks into several small islands as it moves through the furnace.

[0005] The material slope has a free surface that is typically inclined relative to the vertical direction.

[0006] In the case of a combustion furnace, at least some of the thermal energy required for the progressive melting of the solid charge in the charge slope is provided by one or more burners installed in the furnace. It is particularly known to direct the flame toward the unmelted charge slope, especially toward the inclined free surface of the slope, to melt the unmelted charge. In this case, the inclined free surface forms the melting front of the unmelted charge in the charge slope.

[0007] In order to ensure high quality for any product manufactured from molten charge originating from the furnace, the molten charge must be homogeneous and, in particular, free of any trace amount of unmelted charge at the furnace outlet.

[0008] Therefore, it is crucial that the melting front of the material slope is located at a certain distance from the furnace outlet.

[0009] However, in known methods, variations in the position and / or shape of the melting front can be observed across the width of the furnace, and thus variations in the distance between the unmelted charge slope and the furnace outlet can be observed across that width.

[0010] The cause of such distance differences may be the accidental (e.g., unplanned) collapse of a portion of the free surface of the material slope, or, for example, due to friction between the material slope and the sidewall, or structural collapse when unmelted charge is introduced or discharged through the sidewall instead of along the longitudinal axis of the furnace.

[0011] In principle, the furnace can be operated to move the free surface of the feed ramp further away from the furnace outlet. However, in this case, the furnace's productivity decreases.

[0012] In addition, some furnace materials deteriorate when their temperature exceeds the limit.

[0013] Therefore, it is crucial to properly control the heating and melting of the solid furnace charge present in the feed slope.

[0014] Heating the sloping free surface of the feed slope with a single or two flames pointing towards it to achieve controlled melting of the melting front is challenging, especially when the unmelted charge has low thermal conductivity.

[0015] In fact, the thermal energy distribution imparted to the unmelted charge depends on the geometry of the flame and its orientation toward the target surface. Thermal energy is primarily imparted to the unmelted charge by the flame at the point where it intersects with the free surface, disadvantaging other parts of the free surface unaffected by the flame. Furthermore, when the point where the flame intersects with the free surface includes areas closer to the burner and areas further away from it, this results in a thermal energy distribution that favors the areas closer to the burner and disadvantages the areas further away from it.

[0016] This results in uneven heating and an imbalance in melting of the feed ramp: the area receiving the most energy melts first, leaving voids in its location within the ramp. The melting of the less energy-receiving areas of the ramp will be delayed, and these areas may, for example, move forward with the molten charge toward the furnace outlet in a continuous furnace.

[0017] Therefore, uneven heating requires furnace operators to slow down the feeding of raw materials to ensure complete melting and, depending on the specific circumstances, slow down the refining of the molten charge in the furnace, which leads to a decrease in production.

[0018] This problem is particularly pronounced with unmelted charge having low thermal conductivity. In fact, with solid charge having low thermal conductivity, the particles of unmelted charge transfer little or no heat to each other, and the heat of combustion received by the free surface of the charge slope does not reach the unmelted charge inside the charge slope or only reaches it slowly. Summary of the Invention

[0019] The purpose of this invention is to at least partially overcome the above-mentioned problems.

[0020] Therefore, this invention proposes a melting method in a furnace. The furnace has a melting zone located between an upstream wall, a downstream wall opposite to the upstream wall, a first side wall, a second side wall, a top, and a bottom. The two side walls connect the upstream wall and the downstream wall. The distance between the two side walls defines the width l of the furnace. The distance between the upstream wall and the downstream wall defines the length L of the furnace. The distance between the bottom and the top corresponds to the height of the furnace.

[0021] According to the invention, unmelted furnace charge is introduced into the furnace via one or more feeders through or on the upstream wall side.

[0022] In the context of this invention, "on the wall side" should be understood to mean within half the length of the furnace adjacent to the wall, preferably within one-third, or even one-quarter or one-fifth of the length of the furnace adjacent to the wall.

[0023] In a furnace, unmelted charge forms a ramp on one side against the upstream wall. On the opposite side, this ramp has a free surface that is generally inclined relative to the vertical direction.

[0024] The unmelted charge in the feed slope is heated by a flame to obtain molten charge, which is then discharged from the furnace through an outlet in or above the downstream wall.

[0025] According to the invention, at least three flames are thus directed toward a free surface, each flame defining an impact zone on the free surface of the material slope. More specifically, the flames are directed toward the free surface to define impact zones on the free surface at at least three different distances from the first sidewall.

[0026] In the context of this invention, the distance between the impact zone and another element, such as a wall, should be understood as the distance between the centroid or center of mass of the impact zone and the other element.

[0027] According to the invention, the heat energy transferred from each of these flames to the material slope in its impact zone is also regulated by adjusting the power of the flames.

[0028] Furthermore, the momentum of each of these flames is adjusted so that the flame impacts the free surface in its impact zone without mechanically damaging the structural integrity of the material slope in the impact zone.

[0029] The method of the present invention has several advantages.

[0030] The heating of the unmelted charge in the furnace slope by the flame is distributed across the width of the furnace and therefore across the width of the furnace slope.

[0031] The heat energy transferred to each impact zone is regulated. Therefore, some impact zones can be heated more or less than others, thus optimizing the melting method in each impact zone and consequently, in the longitudinal position of the melting front of that zone within the furnace. This regulation also prevents overheating of the unmelted charge, which is important in situations where overheating could lead to a decline in quality.

[0032] Finally, the momentum of the flames is adjusted to ensure that each flame pointing towards the free surface of the material slope reaches the free surface, i.e., actually impacts the free surface, but the momentum should be such that the flames do not mechanically damage the structural integrity of the material slope in their impact zone. Attached Figure Description

[0033] Figure 1An embodiment of a furnace in which the method of the present invention is implemented is shown.

[0034] Figure 2 Another embodiment of a furnace in which the method of the present invention is implemented is shown. Detailed Implementation

[0035] In this context, a distinction is made between the required melting of unmelted charge in the charge slope and its effect on the shape and structure of the charge slope, and the mechanical destruction of the charge slope by flames and the mechanical retrieval of any unmelted charge by combustion gases. This mechanical destruction may result in (i) the presence of unmelted charge in the molten charge discharged from the furnace or in insufficiently refined molten charge, (ii) the destruction of unmelted charge retrieved from inside the furnace, and (iii) the loss of unmelted charge discharged from the furnace with the combustion gases.

[0036] As shown above, the flame is directed toward the free surface to define at least three impact zones at different distances from the first sidewall. Therefore, this configuration is distinctly different from combustion methods in which numerous flames are generated, but which merge into a single flame downstream of the burner and upstream of the free surface. In fact, this merging flame defines a single impact zone on the free surface, rather than defining numerous impact zones at different distances from the first sidewall, as is the case with many impact flames according to the invention.

[0037] It should be noted that the present invention does not exclude the presence of heating devices other than the aforementioned flames pointing towards the free surface in the furnace. Such other heating devices may in particular include electric heating elements and / or flames that are not pointing towards the inclined free surface of the charge slope, for example, above or submerged in the molten charge in the refining zone.

[0038] Therefore, the proposed method addresses the positional imbalance of the free surface of the charge slope observed in known melting methods, by adjusting both the power and momentum of the impingement flame, and thus improves the furnace's production while ensuring the uniformity of the molten charge discharged from the furnace and the absence of unmelted charge. Better distribution of melting on the inclined free surface corresponding to the melting front of the charge slope leads to optimized thermal energy utilization of these flames, resulting in even greater energy savings when combined with a system for recovering thermal energy from the flue gas discharged from the furnace. The energy recovered in this manner can advantageously be used to heat one or more combustion agents (oxidizer and / or fuel) via a co-current heat exchanger and / or preheat at least a portion of the unmelted charge before it is introduced into the furnace.

[0039] As shown above, according to the method of the present invention, the flame is directed toward a free surface to define impact zones on the free surface at different distances from the first sidewall (and therefore also at different distances from the second sidewall, wherein the impact zone farthest from the first sidewall is the impact zone closest to the second sidewall).

[0040] According to one embodiment, at least four flames are directed toward a free surface to define at least four impact zones on the free surface at different distances from the first sidewall. Optionally, at least five flames are directed toward a free surface to define at least five impact zones on the free surface at different distances from the first sidewall.

[0041] The number of impact zones selected depends on the furnace width *l* and the shape and size of the impact zones, especially the horizontal dimension. Using a small number of impact zones with a large horizontal dimension simplifies the control of the melting method in the sense that the number of flames whose power and momentum must be adjusted is relatively small. Using a larger number of impact zones allows for more localized and therefore more precise adjustment of the melting front of the material slope, but requires more complex control / adjustment.

[0042] The distance between the impact zone and the first sidewall is preferably distributed over the entire width l of the furnace. The impact zones can, for example, be distributed over the width l of the furnace in a substantially equidistant manner (i.e., the distance difference between the impact zone and the first sidewall is the same for each pair of consecutive impact zones).

[0043] In the case of an odd number of impact zones, one of the impact zones is usually located at the transverse center of the furnace (i.e., the distance from the first (and second) sidewalls corresponds to half the width l of the furnace), and the other impact zones are usually located on each side of the central impact zone in equal numbers.

[0044] According to a preferred embodiment, the distance between the impact zone and the first sidewall is symmetrically distributed over the width l of the furnace relative to half of the width l.

[0045] Two adjacent impact zones can partially overlap.

[0046] According to the preferred embodiment and in order to ensure a good distribution of heating and melting on the impacted free surface, each impact zone partially overlaps with the nearest impact zone.

[0047] The size and shape of the impact zone depend on the geometry of the flame and the impacted free surface, and more specifically on the length of the flame (the distance between the flame source and its impact zone on the free surface of the material slope), the flame cross-section defined by the burner that generates the flame, the opening angle of the impacting flame, and the shape and slope of the impacted free surface.

[0048] According to one embodiment, the flame is a staggered fuel and / or oxidizer injection flame. Staggered combustion is described in the references entitled "Oxygen-Enhanced Combustion," first edition: ISBN 0-8493-1695-2, page 52, and "Oxygen-Enhanced Combustion," second edition: ISBN 978-1-4398-6228-5, page 458, both edited by Charles E. Baukal Jr. It significantly reduces the amount of NOx produced during combustion. Furthermore, proper positioning of the staggered fuel and / or oxidizer injections (e.g., positioning the staggered injections to be spaced apart on the horizontal plane of the one or more main injections) allows for flames with specific cross-sections, such as a cross-section whose horizontal dimension is greater than its vertical dimension, like a "flat flame."

[0049] Other devices can also be implemented, such as a burner with a single nozzle having a horizontal dimension greater than its vertical dimension, to obtain the flame.

[0050] As shown above, the number of impact zones selected depends particularly on the horizontal dimension of the impact zones, which in turn depends on the cross-sectional width of the flame when it impacts the free surface of the material slope. The larger the horizontal dimension of the impact zones, the fewer impact zones are required to cover the free surface of the material slope across the entire width l of the furnace.

[0051] Therefore, according to a useful implementation, the cross-section of one or more flames corresponding to the impact zone not adjacent to the sidewall, or even all impact flames, has a horizontal dimension and a vertical dimension, wherein the horizontal dimension is greater than the vertical dimension, as is especially true for flat flames.

[0052] The cross-section of the one or more flames can be essentially rectangular.

[0053] The horizontal dimension of a cross-section or region should be understood as the dimension along the longest horizontal straight line from one end of the cross-section or region to the other. The vertical dimension of a cross-section or region should be understood as the dimension along a straight line perpendicular to the horizontal line and therefore lying in a vertical plane.

[0054] To better manage this melting method, it may also be worthwhile to examine the location of a portion of the free surface along the length of the furnace, where this portion advantageously corresponds to the impact zone. This location is also referred to as the "forward-moving state" because it corresponds to the state in which the unmelted charge moves forward toward the furnace outlet towards the molten charge. This location can be expressed, for example, as the distance between the upstream wall and this portion; a larger distance between the upstream wall and this portion indicates that the portion under consideration has moved closer to the furnace outlet. The location can also be expressed as the distance between this portion and the downstream wall, in which case a shorter distance indicates that the portion and the furnace outlet have moved closer together.

[0055] According to the preferred embodiment, the positions of several parts of the free surface, or even the parts of the free surface corresponding to the impact zone, are detected.

[0056] The location of one or more portions of the free surface of the material slope can be detected by means of thermal or optical imaging, or even a combination of both.

[0057] As shown above, locations that are too close to the furnace outlet increase the risk of unmelted charge being present in the discharged molten charge and / or the molten charge being incompletely refined upstream of the outlet.

[0058] According to an advantageous embodiment, the method includes detecting whether the portion has reached a predetermined forward movement distance corresponding to the portion and the downstream wall moving closer to a permitted maximum value. This predetermined forward movement distance corresponds to the considered portion moving forward toward the downstream wall beyond its desired position. When the portion reaches this predetermined forward movement distance, the flame power in the impact zone corresponding to that portion increases. In this way, the unmelted charge near the portion can be caused to melt more rapidly, thus causing the portion to move backward from the free surface to its desired position.

[0059] According to another embodiment, which may or may not be combined with the preceding embodiments, the method includes detecting whether the portion has reached a predetermined distance, referred to as a "reverse movement distance," corresponding to the portion and the upstream wall moving closer to a permitted maximum value. This predetermined reverse movement distance corresponds to the portion's retraction from the free surface relative to its desired position. When the portion under consideration fails to reach this predetermined reverse movement distance, the flame in the impact zone corresponding to that portion is reduced. In this way, the melting of unmelted charge in that portion can be slowed and ultimately, especially with the introduction of additional unmelted charge into the furnace, the portion on the free surface is brought to its desired position.

[0060] As described above, according to the present invention, the momentum of each flame pointing towards the free surface is adjusted such that the flame impacts the free surface in its impact zone without mechanically damaging the structural integrity of the material slope within the flame impact zone. Therefore, when the position of a portion of the free surface of the material slope does not correspond to or no longer corresponds to its desired position, it may also be necessary to adjust the momentum of the corresponding flame to ensure that the flame impacts that portion of the free surface at its actual position and / or to prevent the flame from mechanically damaging the structural integrity of that portion of the material slope.

[0061] When the position of several parts of the inclined free surface of the material slope is detected in this manner, the predetermined forward movement distance and / or predetermined backward movement distance may be the same or different for each part, depending on the specific structure of the furnace, such as the center or eccentric positioning of the furnace charge outlet.

[0062] The actual position of a portion of the inclined free surface of the charge ramp within the furnace can vary, for example, as a function of furnace output (also referred to as "draw" in the case of a continuous furnace), depending on the nature of the unmelted charge introduced into the furnace and / or the molten charge to be obtained. In the case of discontinuous furnaces (often referred to as "batch furnaces") or semi-continuous furnaces (often referred to as "semi-batch furnaces"), the positions of these portions of the inclined free surface are particularly variable during the melting process, where the melting front thus moves forward to the furnace outlet after a "batch" of unmelted charge is introduced and moves backward toward the upstream wall as the unmelted charge melts. Therefore, in such methods, the desired positions of these portions of the inclined free surface change over time. According to an embodiment suitable for discontinuous or semi-continuous furnaces, predetermined forward and / or predetermined backward distances can be used, which also change over time simultaneously with the evolution of their desired positions.

[0063] In the context of this invention, a semi-continuous melting method or furnace should be understood as a melting method or furnace in which some of the furnace charge is added or removed during the melting cycle.

[0064] The impingement flame is obtained by the combustion of fuel with an oxidant (i.e., a combustion oxidant).

[0065] The fuel can be solid, liquid, or gaseous.

[0066] Advantageously, the fuel is a gaseous fuel. This gaseous fuel can be a carbon-based fuel, a non-carbon-based fuel, or a mixture of carbon-based and non-carbon-based fuels. Therefore, the fuel can be particularly selected from the following gaseous fuels: natural gas, hydrogen, ammonia, syngas, biogas, any gas containing hydrogen and / or carbon monoxide, and combinations of at least two of these gaseous fuels.

[0067] For environmental reasons, non-carbon fuels and renewable fuels with a low carbon footprint can be chosen.

[0068] Oxidizers typically have an oxygen content of 16-100% by volume. For example, more oxygen-enriched oxidizers with an oxygen content of at least 90% by volume are generally more effective and provide a hotter flame, given their low or no content of ballast gases that do not participate in combustion. However, for some applications, oxidizers with a higher content of ballast gases may be preferred, which typically produces a more diluted flame.

[0069] In order to generate flames pointing towards the free surface of the unmelted charge slope, the furnace is equipped with at least one burner.

[0070] A furnace may be equipped with at least one burner that produces several streams of flame directed and impacting a free surface. A furnace may also be equipped with at least one burner that produces a single stream of flame directed and impacting a free surface. A furnace may also be equipped with at least one burner that produces several streams of flame directed and impacting a free surface, and a combination of at least one burner. According to a useful embodiment, the furnace is equipped with multiple burners, each producing a single stream of flame directed and impacting a free surface. Therefore, the burners in the furnace can produce a single stream of impact flame or several streams of impact flame. The furnace may also be equipped with a combination of burners, including at least one burner producing a single stream of flame and at least one burner producing several streams of flame.

[0071] To implement this method, furnaces are typically equipped with:

[0072] ●One or more feeders for introducing unmelted furnace charge into the furnace;

[0073] ● One or more combustion devices, especially one or more burners, for producing a flame directed toward a free surface;

[0074] ●Control unit, used for:

[0075] ○ Adjusting the flame power; and

[0076] ○ Adjust the momentum of the flame.

[0077] To implement a particular embodiment of the method of the present invention, the furnace may also be equipped with one or more of the following devices:

[0078] ● A detector for detecting one or more portions of a free surface, preferably corresponding to the location of one or more portions of the free surface within an impact zone defined by a flame impacting the free surface; and

[0079] ● Control unit, for the portion corresponding to the impact zone, compares the detection position with a predetermined forward movement distance and / or compares the detection position with a predetermined backward movement distance, and based on the comparison, transmits a control signal to the control unit to adjust the power and momentum of the flame in the impact zone corresponding to that portion.

[0080] As mentioned above, the method can be a continuous method, i.e., using a continuous furnace; a discontinuous method, i.e. using a discontinuous furnace; or a semi-continuous method, i.e. using a semi-continuous furnace.

[0081] In the case of discontinuous or semi-continuous methods, the melting method may also include a step in which the charge is substantially or completely melted and there is no free surface on which the flame defines the impact zone. Depending on the specific circumstances, there may be no combustion in the furnace during this step (especially when the step is short and / or heat loss from the furnace is low) or a certain degree (usually a low degree) of combustion may be maintained to refine the molten charge or to maintain it at a required temperature above the melting temperature of the charge.

[0082] The impingement flame can be directed from various parts of the furnace towards the free surface of the charge ramp. Therefore, the flame can be directed towards the free surface via the downstream wall, via the side walls, or via the top of the furnace. Combinations of such impingement flames can also be used. For example, one or more impingement flames corresponding to an impingement zone not adjacent to one of the side walls can be directed towards the free surface via the downstream wall or via the top, while the impingement flame corresponding to an impingement zone adjacent to one of the side walls can be directed towards the free surface via that adjacent side wall.

[0083] With regard to a flame that defines an impact zone adjacent to a sidewall, it is worthwhile to prevent the flame from partially pointing towards or impacting the sidewall, as such an impact could damage the wall.

[0084] Therefore, it may be worthwhile to use flames with various cross-sections for the impact zone adjacent to one of the sidewalls and for one or more impact zones not adjacent to the sidewalls. For example, according to one embodiment, one or more impact zones not adjacent to the sidewalls are defined by symmetrically staggered flames of staggered injection of propellant, which are symmetrically positioned relative to one or more main injections, while the impact zone adjacent to the sidewalls is defined by asymmetrically staggered flames of one or more staggered injections of propellant, which are positioned only on one or more main injection sides opposite to the adjacent sidewall.

[0085] The method of the present invention is preferably a method for melting glass, a method for melting enamel, a method for melting non-ferrous metals such as aluminum, lead, copper, etc., and especially a method for secondary melting of non-ferrous metals, more specifically in the context of recycling one or more non-ferrous metals, for melting hydraulic binders, or for vitrifying waste. Therefore, the furnace is preferably selected from glass melting furnaces, enamel melting furnaces, non-ferrous metal melting furnaces, hydraulic binder melting furnaces, and waste vitrification furnaces.

[0086] According to a particularly preferred embodiment of the invention, any of the embodiments described above can be combined with the method described in French patent application FR 2405259, filed May 23, 2024, according to which the flame is directed toward a free surface to define impact zones at at least two different vertical heights on the free surface. This combination not only has the advantage of providing a better distribution of heat transfer from the flame to the unmelted charge in the slope across the width l of the furnace, as obtained by the invention, but also has the advantage of providing a better distribution of heat transfer from the flame to the unmelted charge in the slope across the height h of the slope, and thus providing even more effective control over the melting of the unmelted charge near the melting front of the slope.

[0087] The present invention and its advantages will be referred to in accordance with the following non-limiting embodiments. Figure 1 and 2 To better understand, these figures illustrate two embodiments of a furnace in which the method of the present invention is implemented, in cross-section and top view.

[0088] Figure 1 More specifically, a continuous furnace 10 for melting glass is shown.

[0089] The furnace 10 has an upstream wall 11 through which unmelted charge (i.e., solid vitrifiable composition) is introduced into the furnace 10, and a downstream wall 12 opposite to the upstream wall 11 through which molten glass 50 is discharged from the furnace 10.

[0090] The two sidewalls 13 and 13' connect the upstream wall 11 and the downstream wall 12.

[0091] The furnace 10 also has a top and a bottom (not shown in the figure), wherein the melting zone is located between the upstream wall 11, the downstream wall 12, the side walls 13 and 13', the top and the bottom.

[0092] This solid vitrifiable composition consists of or contains small particles with low thermal conductivity compared to that of metals. Therefore, these particles transfer little or no heat between themselves.

[0093] For example, unmelted charge is introduced into furnace 10 via upstream wall 11 using a worm gear 20. In the illustrated embodiment, the feeder 20 is located at the center of upstream wall 11. The unmelted charge forms a pile in the form of a ramp 30 inside furnace 10, which extends above molten glass 50. On the upstream side of furnace 10, the ramp 30 of unmelted charge abuts against upstream wall 11. Towards the downstream side, the ramp 30 terminates at a free surface 40 inclined relative to the vertical direction and curves toward downstream wall 12.

[0094] In order to heat and melt the unmelted charge, the free surface 40 is attacked by fan-shaped flames 51, 52, and 53 generated by burners 55 installed in the downstream wall 12. Therefore, the free surface 40 forms a melting front for the unmelted charge in the furnace 10.

[0095] Figure 1 The furnace 10 shown is a small furnace.

[0096] The furnace of the type shown in the diagram is parallelepiped in shape and typically has a length L of less than 10 meters (between upstream wall 11 and downstream wall 12), a width l of less than 5 meters (between side wall 13 and side wall 13'), and a height of less than 3 meters.

[0097] The material slope 30 to be melted is located on the upstream wall 11 side, and the burner 55 is located on the opposite downstream wall 12. The burner 55 is selected to emit a flame length that matches the length of the furnace 10. The molten material 50 moves toward the burner 55 at the bottom of the furnace 10, below which an outlet hole (not shown) is provided for the molten material 50. The molten material 50 thus moves below flames 51, 52, and 53, which keep it molten until it leaves the furnace 10.

[0098] For larger furnaces, the material slope 30 to be melted remains on the upstream wall 11 side, but additional burners are added. These additional burners may, for example, be installed on the side walls 13, 13' connecting the upstream wall 11 and the downstream wall 12, either at the top or at the bottom (for "submerged burners").

[0099] Each flame 51, 52, 53 defines an impact zone 41, 42, 43 on the free surface 40, in which it causes the unmelted furnace charge to melt.

[0100] Flames 51, 52, and 53 point towards the free surface 40 in different directions α1, α2, and α3 (described by the axes of flames 51, 52, and 53), forming various acute angles (≥0°) θ1, θ2, and θ3 with the vertical plane through the longitudinal axis of the furnace. In this way, the corresponding impact zones 41, 42, and 43 of flames 51, 52, and 53 are each located at different distances l1, l2, and l3 from the first sidewall 13 (and therefore also at different distances from the second sidewall 13'). In the illustrated case, the direction α2 of flame 52 lies within the vertical plane including the longitudinal axis of the furnace 10, while the directions α1 and α3 of flames 51 and 53 are located on opposite sides of this vertical plane and form acute angles with it. Therefore, in Figure 1 In the embodiment shown, angle θ2 is 0° and is therefore not visible in the figure.

[0101] Depending on the width l of the furnace 10 and the horizontal dimensions of the flames 51, 52, and 53, a larger number of impact flames may be required to ensure that the impact zones 41, 42, and 43 adequately cover the free surface 40 of the material slope 30 across the entire width l of the furnace. If necessary, additional burners can be installed in the furnace 10 to generate these additional flames.

[0102] like Figure 2 As shown, each impact flame 51, 52, 53 can also use a burner 55, 56, 57. According to Figure 2 Each impact flame 51, 52, 53 has a direction α1, α2, α3 that is parallel to the sidewalls 13, 13' and therefore also parallel to the aforementioned vertical plane.

[0103] However, other configurations can be considered. For example, according to an embodiment not shown, flame 52 is generated by a burner 56 located in the downstream wall 12 and has the following characteristics: Figure 2 The direction α2 is shown. Conversely, flame 53 is produced by a burner 57 mounted in the side wall 13, but the direction α3 of flame 53 is chosen so that flame 53 is defined relative to... Figure 2 The same impact zone 43, wherein flame 51 is generated by a burner 55 mounted in another side wall 13', the direction α1 of flame 51 is selected such that flame 51 is defined within... Figure 2 The same impact zone 41.

[0104] The heat energy transferred from each flame 51, 52, 53 to the unmelted charge in the feed slope 30 via their respective impact zones 41, 42, 43 is regulated by adjusting the power of the respective flames 51, 52, 53. Adjusting the power of the flames 51, 52, 53 also regulates the melting rate of the unmelted charge near the respective impact zones 41, 42, 43. This particularly prevents the free surface 40 from advancing too far towards the downstream wall 12 near the impact zones 41, 42, 43, or even from moving too far backward towards the upstream wall 11 near the impact zones 41, 42, 43.

[0105] The momentum of each flame 51, 52, and 53 is also adjusted. More specifically, this momentum is adjusted so that the flames 51, 52, and 53 impact the free surface 40 of the feed slope 30, which allows for more effective heating of the unmelted furnace charge, while on the other hand, it does not mechanically damage the structural integrity of the feed slope 30.

[0106] Because the momentum of flames 51, 52, and 53 is adjusted so that they impact the free surface 40, the flames corresponding to the impact zone furthest from the source of flames / burners 55, 56, and 57 generally have stronger momentum than the flames corresponding to the impact zone closer to the source of flames / burners 55, 56, and 57.

[0107] As shown above, in the context of this invention, it is distinguished that the unmelted furnace charge mechanically destroys the structural integrity of the charge slope by altering the charge slope on the one hand through melting the unmelted charge, and on the other hand by the uncontrolled mechanical picking up of the charge slope by a high-momentum flame, especially by the flame and / or the combustion flue gas / gas generated by the flame.

[0108] Therefore, in order to regulate the momentum of flames 51, 52, 53, the distance between the free surface 40 and the outlet of the one or more burners 55, 56, 57 that generate flames 51, 52, 53 and the properties of the unmelted furnace charge are taken into consideration.

[0109] Therefore, when the material slope is made of large and heavy non-ferrous metal sheets that are difficult to pick up, the momentum of the flame can be relatively high.

[0110] Conversely, when the feed slope is composed of or contains lightweight particles / fine particles / powders, especially unmelted furnace feed in the form of such fine particles / powders that do not stick together when entering the furnace, as shown in the embodiment, the momentum of the impinging flame remains relatively low to avoid pick-up or to prevent significant pick-up of the particles.

[0111] It should be noted that this pickup may result in:

[0112] (i) The molten charge discharged from the furnace contains unmelted or insufficiently refined charge.

[0113] This material, which may cause problems in downstream processes of the melting step, such as from the furnace charge.

[0114] The molding of solid products, and the reduction in the quality of the manufactured solid products;

[0115] (ii) Deterioration inside the furnace, such as walls being eroded by unmelted charge and within the burners or furnace.

[0116] A deposition layer is formed on other equipment in contact with the part; and / or

[0117] (iii) Unmelted charge discharged from the furnace is lost with the combustion flue gas. This loss of raw material is obviously costly. It can also cause blockages in flue gas exhaust pipes and accelerated saturation of filters used for flue gas treatment upstream of the chimney. When the furnace includes a system for recovering heat energy from waste flue gas, the presence of unmelted charge in the flue gas also poses problems for heat recovery in the co-current heat exchangers or regenerators in use. Furthermore,

[0118] When the furnace charge is a mixture of various components, especially as in glass melting methods, the discharge of unmelted charge with the combustion flue gas can be selective, with various components exhibiting different emission levels. In this case, the composition of the resulting molten charge does not correspond to the composition obtained from the unmelted charge introduced into the furnace, which significantly affects the performance of the methods used to process the molten charge downstream of the furnace and the resulting final product.

[0119] Burners that allow for dual regulation of the power of one or more flames produced on the one hand and the momentum of one or more flames produced on the other are known. Such burners are described, for example, in WO-A-2010 / 003866. These burners, for example, allow for changing the power of a constant momentum flame or changing the momentum of a constant power flame.

[0120] It is typically desirable to detect one or more features of the melting method, which allows for optimization of the melting method.

[0121] According to an advantageous embodiment, an electromagnetic beam, in particular a laser beam, is used during the melting process to detect the position of the free surface 40 in the furnace 10, preferably in portions corresponding to one or more impact zones 41, 42, 43.

[0122] according to Figure 1 In the illustrated embodiment, electromagnetic beams 61, 62, and 63, more specifically laser beams, are emitted by emission / detection units 90 and 90' mounted in sidewalls 13 and 13' and directed towards a portion of the free surface 40 of the material slope 30. The beams are reflected by this portion of the free surface 40, and the reflected beams 61', 62', and 63' are detected by emission / detection units 90 and 90'. The position of this portion of the free surface 40 reflecting the laser beams 61, 62, and 63 is determined by emission / detection units 90 and 90' based on the time difference between the emission of laser beams 61, 62, and 63 and the detection of their reflections 61', 62', and 63', which is a measure of the distance the beam travels between its emission and detection. Signals corresponding to the positions of the relevant portions of the free surface 40 are transmitted by emission / detection units 90 and 90' to control unit 65.

[0123] The control unit 65 compares the position of the part detected by the transmission / detection units 90, 90' with a predetermined forward movement distance and / or a predetermined backward movement distance, preferably with the predetermined forward movement distance and the predetermined backward movement distance.

[0124] If the comparison shows that the portion of the free surface 40 has reached a predetermined forward movement distance, corresponding to the portion of the free surface 40 moving closer to the outlet of the furnace 10, then the control unit 65 transmits a control signal to the control units 66, 65', 66', and 67' of the burners 55, 56, and 57 to increase the power of the flames 51, 52, and 53 corresponding to the impact zones 41, 42, and 43 in that portion. This allows for accelerated melting of the unmelted furnace charge near that portion of the free surface 40, thereby causing that portion to move backward toward the upstream surface 11 of the furnace 10.

[0125] Conversely, if the comparison shows that the portion of free surface 40 has not reached the predetermined backward movement distance, which corresponds to the portion of free surface 40 moving backward toward the upstream wall 11 of the furnace, then control unit 65 transmits control signals to control units 66, 65', 66', and 67' of burners 55, 56, and 57 to reduce the power of flames 51, 52, and 53 corresponding to impact zones 41, 42, and 43 in that portion. This allows the melting of unmelted furnace charge in that portion to slow down and ultimately, especially with the introduction of additional unmelted furnace charge into the furnace 10, allows that portion of free surface 40 to reach its desired position.

[0126] If necessary, control units 66, 65', 66', and 67' will simultaneously adjust the momentum of one or more related flames so that these flames actually impact the portion of the free surface 40 of the material slope 30 at its actual location, and the flames 51, 52, and 53 will not mechanically damage the structural integrity of the material slope 30.

Claims

1. A melting method in a furnace (10) having a melting zone between an upstream wall (11), a downstream wall (12) opposite the upstream wall (11), a first side wall (13) and a second side wall (13'), a top and a bottom, wherein the two side walls (13, 13') connect the upstream wall (11) and the downstream wall (12), wherein the distance between the upstream wall (11) and the downstream wall (12) defines a length L of the furnace (10) and the distance between the two side walls (13, 13') defines a width l of the furnace (10); In the method: ● Unmelted charge is introduced into the furnace (10) via the upstream wall (11) side or above via one or more feeders (20); ● In the furnace (10), the unmelted furnace charge is formed on one side against the upstream wall (11) and on the opposite side has a free surface (40) inclined relative to the vertical direction, forming a material slope (30); ●Heating the unmelted furnace charge in the feed slope (30) by means of flames (51, 52, 53) to obtain molten furnace charge (50); and ●The molten charge (50) is discharged from the furnace through an outlet in or above the downstream wall (12); Its features are: ● Point at least three flames (51, 52, 53) toward the free surface (40) so that on the free surface (40) The impact zone (41, 42, 43) is defined at at least three different distances (l1, l2, l3) from the first sidewall (13); ● By adjusting the power of the flames (51, 52, 53), the heat energy transferred from each flame (51, 52, 53) to the material slope (30) in its corresponding impact zone (41, 42, 43) is regulated; as well as ● Adjust the momentum of each flame (51, 52, 53) so that the flames (51, 52, 53) impact the free surface (40) in their impact zones (41, 42, 43), while the flames (51, 52, 53) do not impact the free surface (40) in the impact zones (41, 42, 43). 42, 43) Mechanical damage to the structural integrity of the material slope (30).

2. The method of claim 1, wherein at least four flames (51, 52, 53) are directed toward the free surface (40) to define impact zones (41, 42, 43) on the free surface (40) at at least four different distances (l1, l2, l3) from the first sidewall (13), preferably at least five flames (51, 52, 53) are directed toward the free surface (40) to define impact zones (41, 42, 43) on the free surface (40) at at least five different distances (l1, l2, l3) from the first sidewall (13).

3. The method according to any one of the preceding claims, wherein the distances (l1, l2, l3) are distributed over the entire width l of the furnace.

4. The method according to any one of the preceding claims, wherein the distances (l1, l2, l3) are symmetrically distributed over the width l of the furnace with respect to the center of the width l.

5. The method according to any one of the preceding claims, wherein each impact zone (41, 42, 43) partially overlaps with the nearest impact zone (41, 42, 43).

6. The method according to any one of the preceding claims, wherein the one or more flames (51, 52, 53) corresponding to the impact zone (41, 42, 43) not adjacent to the sidewall have a cross-section having a horizontal dimension and a vertical dimension, wherein the horizontal dimension is greater than the vertical dimension.

7. The method according to any one of claims 5 and 6, wherein the cross-section is rectangular.

8. The method according to any one of the preceding claims, wherein the flame (51, 52, 53) is an interleaved fuel and / or oxidizer injection flame.

9. The method according to any one of the preceding claims, wherein the position of a portion of the free surface (40) is detected, said portion preferably corresponding to the impact zone (41, 42, 43).

10. The method of claim 9, wherein several portions of the free surface (40) are detected, preferably corresponding to the positions of the portions of the free surface (40) of the impact zones (41, 42, 43).

11. The method according to any one of the preceding claims, comprising detecting whether a portion of the free surface (40) corresponding to the impact zone (41, 42, 43) has reached a predetermined forward movement distance and comprising increasing the power of the flame (51, 52, 53) corresponding to the impact zone (41, 42, 43) when the portion reaches the predetermined forward movement distance.

12. The method according to any one of the preceding claims, comprising detecting whether a portion of the free surface (40) corresponding to the impact zone (41, 42, 43) has reached a predetermined backward movement distance and comprising reducing the power of the flame (51, 52, 53) corresponding to the impact zone (41, 42, 43) when the portion has not reached the predetermined backward movement distance.

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

14. The method according to any one of the preceding claims is used for melting glass, enamel, nonferrous metals, hydraulic adhesives, or vitrifying waste.

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