Method for manufacturing glass and hybrid glass furnace for implementing said manufacturing method
By giving priority to the use of combustion energy and electrical energy in the heating zone of the mixed glass furnace, the thermal barrier problem caused by foam formation is solved, the heating efficiency and recycling capacity are improved, and more efficient glass production is achieved.
Patent Information
- Application Number
- CN202380077357.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-09-14
- Filing Date
- 2023-09-13
- Publication Date
- 2025-06-20
AI Technical Summary
In existing mixed glass furnaces, foam formation leads to a thermal barrier, limiting heating efficiency and recycling capabilities, and existing mitigation measures are inefficient, affecting glass production.
By preferentially using combustion energy and electrical energy in the heating zone of the mixed glass furnace, the energy ratio is controlled in the first and second heating zones, respectively, to limit foam formation and maximize the heating efficiency of each energy.
It effectively limits the emergence of foam, improves the heating efficiency and recycling capacity of the furnace, reduces energy consumption, and extends the service life of the furnace refractory materials.
Smart Images
Figure CN120187674A_ABST
Abstract
Description
Prior art
[0001] The present invention belongs to the general field of glass manufacturing. More particularly, the present invention relates to a manufacturing method comprising the step of melting a vitrifiable material in order to be able to manufacture glass. The present invention also relates to a hybrid glass furnace configured to implement said manufacturing method. The present invention finds a particularly advantageous application in the case where the glass to be produced is borosilicate glass, but is in no way limiting.
[0002] In the present specification, "vitrifiable material" is understood to mean all materials, natural ores or synthetic products that can enter into the composition of a glass furnace fed (feeds) for (intended for) the manufacture of glass, derived from recycled materials such as cullet, etc.
[0003] Similarly, "glass" is understood to mean glass in a broad sense, i.e. covering any material having a vitreous, glass-ceramic or ceramic matrix.
[0004] Furthermore, the term "manufacture" includes the indispensable step of melting the vitrifiable material, as well as all subsequent steps of refining / conditioning the molten glass if necessary to bring it to its final form, in particular in the form of flat glass (assembled glass), hollow glass (bottles, jars), glass in the form of mineral wool (in particular rock wool or glass wool) used for its thermal insulation or sound insulation properties, or even glass in the form of textile yarns optionally used for reinforcement materials.
[0005] From the prior art, different examples of furnace designs for melting vitrifiable materials are known, thus obtaining a bath of molten material, also commonly called a "batch mixture" or "composition", from which glass can be manufactured. More specifically, and in particular to meet the ecological challenge of reducing carbon dioxide (CO2) emissions, it is known to use fuel combustion furnaces (via burners) with electric auxiliary heating (via electrodes embedded in the bath). Furnaces of this design thus combine several energies, namely, for example, the combustion energy of fossil origin (usually natural gas) and electrical energy. Such furnaces are also called "hybrid" glass furnaces.
[0006] Conventional hybrid glass furnaces comprise a hot top tank which is (virtually or physically by means of suitable vertical walls) divided into two heating zones. The term "heating zone" refers to the parts of the tank that are distributed from upstream to downstream with respect to the flow direction of the vitrifiable material introduced into the tank and that differ from each other in terms of the proportion of combustion energy (or electrical energy, respectively) used for heating the vitrifiable material.
[0007] More specifically, the current design of the hybrid glass melting furnace tank includes an upstream heating zone and a downstream heating zone. The upstream heating zone is designed to melt the vitrifiable material and is mainly supplied with electrical energy. The downstream heating zone is designed more for refining the glass composition (i.e., improving the glass quality so that it contains as few unmelted particles or as few bubbles as possible) and is mainly supplied with combustion energy.
[0008] This design optimizes the heating efficiency (or heat transfer) in the upstream and downstream heating zones of the hybrid glass melting furnace. Electrical energy is also preferred in the upstream heating zone for melting the vitrifiable material because approximately 99% of the power is transferred to the glass bath via the electrodes. In contrast, the power transferred to the vitrifiable material through the burners in the upstream heating zone is much lower, approximately 60%, depending on the fuel / oxidizer mixture, especially the oxygen content and / or the use of preheating. This is one of the reasons why this type of hybrid glass melting furnace has become the benchmark for glass production.
[0009] During operation, "foaming" is typically observed on the surface of the molten bath in the glass melting furnace. The presence of this foam is especially due to the content of the vitrifiable material. For recycling purposes, they usually contain used materials such as household or apartment broken glass and / or glass wool (e.g., glass wool waste or scrapped products from the production line). However, these used materials contribute to increasing the proportion of carbon chains (e.g., organic contamination on bottle broken glass or binders in mineral wool) and sulfates in the bath. However, especially near the electrodes, but not limited to this, the foaming phenomenon is thermally activated, and the sulfates are desorbed by reacting with the added carbon, thereby generating the foam in question.
[0010] The present inventors have demonstrated that, for reasons detailed below, foam formation is a thermal barrier that is particularly harmful to the overall heating efficiency of such hybrid glass melting furnaces.
[0011] In the upstream heating zone, where foam formation is encouraged due to the mainly use of electrical energy for heating, the foam forms a thermal barrier at the interface between the glass bath and the floating vitrifiable material that has not yet melted. As a result, this thermal barrier limits the transfer of heat generated by the electrodes to the vitrifiable material newly introduced onto the surface of the glass bath. Those materials are thus only partially melted in the tank, making tonnage management more complex and increasing the risk of bath overflow outside the tank.
[0012] Foam may also be present in the downstream heating zone. This may be due to the transfer of foam from the upstream zone and / or the presence of unmelted particles from the upstream heating zone - which sustains the foaming phenomenon, and / or due to the high temperatures reached in this downstream zone. Insofar as combustion energy is mainly used there, the problem of heat transfer from the burner to the bath is an important issue. The foam forms a thermal barrier between the burner and the glass bath that is heated and refined in the said downstream heating zone.
[0013] The following non-limiting examples are given to show the consequences of the barrier created due to the presence of foam, which forms the thermal barrier. In the case of an overhead burner, for a power input of 200 kW / m 2 , it is estimated that in the presence of foam that forms the thermal barrier, approximately 40 kW / m 2 (plus or minus + / - 10 kW / m 2 ) will be transferred to the glass bath, whereas, in contrast, for the vitrifiable material present on the surface of the glass bath, the power input is approximately 120 kW / m 2 (plus or minus + / - 10 kW / m 2 ). In the case of electrodes, for a power input of 200 kW / m 2 , we know that approximately 198 kW / m 2 will be transferred to the glass bath (due to the above design of the hybrid glass furnace), but we estimate that only approximately 40 kW / m 2 (more or less + / - 10 kW / m 2 ) will be transferred to the glass material to be melted present on the surface of the bath, again due to the thermal barrier formed by the foam.
[0014] Thus, limiting the overall heating efficiency of the hybrid furnace means that the foaming phenomenon is an obstacle to using cullet and / or glass wool-based products as vitrifiable materials (i.e., for recycling). In other words, foaming limits the recycling capacity of the hybrid furnace and results in a significant increase in energy consumption, or even leads to a temperature increase - which causes premature wear of the furnace refractories.
[0015] Current attempts to mitigate this foaming problem are far from optimal as they involve countermeasures such as adding solid oxidants like sodium nitrate (NaNO3) and manganese dioxide (MnO2). In fact, the use of oxidants itself is restricted, especially due to NOx emissions and the need to maintain a significantly bio-soluble glass target. Therefore, increasing the amount of oxidant is not feasible and in fact results in limiting the recycling of vitrifiable materials.
[0016] It should be noted that the foaming phenomenon - although it exists regardless of the composition of the vitrifiable material - is more particularly problematic (in terms of the amount of foam generated) when the glass to be manufactured is borosilicate glass. Summary of the Invention
[0018] The object of the present invention is to remedy some or all of the drawbacks of the prior art, in particular those disclosed above, by proposing a solution that maximizes the heating efficiency (or heat transfer) of each energy used (combustion, electricity) and the recycling capacity within the mixing furnace.
[0019] For this purpose, and according to a first aspect, the present invention relates to a method for manufacturing glass, the method comprising the step of melting a vitrifiable material for manufacturing the glass, the vitrifiable material containing a proportion of carbonaceous organic matter in the range of 0.5% to 10%, wherein the step of melting the vitrifiable material is carried out by means of a mixing glass furnace comprising a hot top tank, the tank comprising, from upstream to downstream:
[0020] - A first heating zone, which comprises combustion heating means,
[0021] - A second heating zone, which comprises electrodes immersed in a bath of molten material,
[0022] The melting step is carried out such that the proportion of combustion energy used for melting the vitrifiable material in the first zone is at least 50%, and the proportion of electrical energy used for melting the vitrifiable material in the second zone is at least 50%, with combustion energy being preferentially used in the first heating zone to limit foaming in the first heating zone, and conversely, electrical energy being preferentially used in the second heating zone to maximize the heating efficiency of each energy used in the furnace.
[0023] Advantageously, during the melting step, the preference for combustion energy in the first heating zone and conversely the preference for electrical energy in the second heating zone are determined according to the proportion of carbonaceous organic matter contained in the vitrifiable material.
[0024] According to an important feature, for a person skilled in the art, the method for manufacturing glass according to the present invention involves a paradigm shift in the design of the glass furnace for implementing the method. In fact, as previously mentioned, the design of the mixing glass furnace according to the prior art is based on the principle of using electrical energy in the upstream heating zone and combustion energy in the downstream heating zone, which is respectively attributed to the obtained heat transfer efficiency.
[0025] Therefore, it prevents a person skilled in the art from modifying this furnace design, especially when the implementation of the present invention results in the use of electrical energy and combustion energy in the heating zones of the tank, which counterintuitively reverses the dominant energy in each zone, i.e., the exact opposite situation.
[0026] The manufacturing method according to the invention thus makes it possible to preferentially use combustion energy in the first heating zone and, conversely, to preferentially use electrical energy in the second heating zone.
[0027] This greatly reduces the risk of interaction between the sulfates contained in the vitrifiable material and the carbon chains also contained in the vitrifiable material, avoiding the presence of very hot localized spots within the glass. In other words, this advantageously limits foaming in the first heating zone.
[0028] Furthermore, if foam is indeed formed, the main heating means (burner or electrode) in each zone is not separated from the heating means intended to heat by a foam layer forming a heat-insulating screen (i.e., the screens or heat-insulating screens previously existing in the prior art).
[0029] As a result, the invention maximizes the heating efficiency or the heat transfer efficiency of each type of energy used in the furnace. In fact, since the appearance of foam is greatly limited in the first heating zone, the problem of poor heat transfer between the bath and the vitrifiable material is also greatly limited, which greatly facilitates the melting of the vitrifiable material introduced into the tank.
[0030] In the second heating zone, where the energy used is mainly electrical energy, the glass bath actually contains no carbonaceous vitrifiable material and sulfates, making the electrical heating efficient without the risk of poor heat transfer.
[0031] Furthermore, if foam residues do form on the surface of the bath in the second heating zone, this will have no harmful effect on glass production. On the contrary, such foam residues form a thermal barrier against the heat generated by the electrodes below the surface of the bath, contributing to good thermal insulation of the bath. The thermal barrier formed by the foam was a drawback in the second heating zone with burners, but becomes an advantage in the case of electrodes.
[0032] In a particular embodiment, the melting method may further comprise one or more of the following features, taken in isolation or according to any technically possible combination.
[0033] In a particular embodiment, the proportion of combustion energy used for melting the vitrifiable material in the first zone is at least 60%, and the proportion of electrical energy used for melting the vitrifiable material in the second zone is at least 60%.
[0034] In a particular embodiment, the proportion of combustion energy used in the first zone is at least 70%.
[0035] In a particular embodiment, the melting energy used in the first zone is only combustion energy.
[0036] In certain embodiments, the first heating zone further includes an electrode immersed in a bath of molten material, and the melting step is carried out such that the proportion of electrical energy used in the first zone can keep the bath temperature above a given temperature (e.g., the crystallization temperature of the glass).
[0037] In certain embodiments, the proportion of electrical energy used in the second zone is at least 70%.
[0038] In certain embodiments, the melting energy used in the second zone is only electrical energy.
[0039] In certain embodiments, the second heating zone further includes a combustion heating device, and the melting step is carried out in such a way that the proportion of combustion energy used in the second zone can keep the crown temperature above a given temperature (e.g., the condensation temperature of sodium borate).
[0040] In certain embodiments, the proportion of combustion energy used in the first zone is equal to the proportion of electrical energy used in the second zone.
[0041] In certain embodiments, the proportion of combustion energy used in the first zone and the proportion of electrical energy used in the second zone are different, one being greater than the other, or vice versa.
[0042] In certain embodiments, the combustion energy in the first zone and / or the second zone is obtained by burning hydrogen.
[0043] In certain embodiments, the vitrifiable material is selected to enable the manufacture of borosilicate glass.
[0044] In certain embodiments, the proportion of carbonaceous organic matter contained in the vitrifiable material is less than or equal to 10%, being 0.75% to 10%, more preferably 1% to 10%, and even more preferably 2% to 10%.
[0045] In certain embodiments, the vitrifiable material contains recycled materials, such as cullet with a proportion less than or equal to 90%, and / or mineral wool with a proportion less than or equal to 100%.
[0046] In certain embodiments, the combustion flue gas generated in the first heating zone is discharged towards the second heating zone until the exhaust chimney arranged downstream of the second heating zone, so as to be able to keep the crown temperature in the second heating zone above a given temperature, especially the condensation temperature of sodium borate, by means of the flue gas.
[0047] According to a second aspect, the present invention relates to a hybrid glass furnace configured to implement a method for manufacturing glass, the furnace comprising a control unit for separately controlling at least a combustion heating device in a first heating zone and an electrode immersed in a bath of molten material in a second heating zone according to the proportion of carbonaceous organic substances contained in the vitrifiable material, preferentially using combustion energy in the first heating zone to limit foaming in this first heating zone and, conversely, preferentially using electrical energy in the second heating zone, so as to maximize the heating efficiency of each type of energy used in the furnace.
[0048] In a particular embodiment, the hybrid glass furnace may further comprise one or more of the following features, individually or in any technically possible combination.
[0049] In a particular embodiment, the furnace comprises a vertical partition configured to:
[0050] - block the flow of the melt between the first and second zones on the surface of the bath of molten material,
[0051] - allow the melt to circulate between the first and second zones at the hearth of the furnace.
[0052] The ability of the partition (due to its suitable height) to block the circulation of the molten material between the zones at the surface of the bath of molten material advantageously prevents the foam generated in the second heating zone from migrating to the first heating zone. In other words, the presence of the vertical partition further optimizes the heating efficiency of the hybrid furnace.
[0053] In a particular embodiment, the roof height in the second heating zone is less than the roof height in the first heating zone.
[0054] In a particular embodiment, the bath height in the second heating zone is less than the bath height in the first heating zone.
[0055] In a particular embodiment, the furnace further comprises an exhaust chimney arranged in the downstream part of the second heating zone and configured to discharge the combustion flue gas generated in the first heating zone into the second heating zone.
[0056] Summary of the Drawings
[0057] Other features and advantages of the present invention will become apparent from the non-limiting description given below with reference to the accompanying drawings, which show exemplary embodiments thereof. In the drawings:
[0058] - Figure 1 Schematically shows a particular embodiment of a hybrid glass furnace according to the present invention;
[0059] - Figure 2 Schematically shows another embodiment of a hybrid glass furnace according to the present invention;
[0060] - Figure 3 Schematically shows yet another embodiment of the hybrid glass furnace according to the present invention;
[0061] - Figure 4 Schematically shows an embodiment of the hybrid glass furnace according to the present invention;
[0062] - Figure 5 Schematically shows an embodiment of the hybrid glass furnace according to the present invention.
[0063] Description of the embodiment
[0064] Figure 1 Schematically shows a particular embodiment of the glass furnace 100 according to the present invention in its environment. In particular, Figure 1 A side view of the furnace 100 is shown.
[0065] In the remainder of the specification, the longitudinal, vertical, and transverse orientations will be used non - restrictively with reference to the axis system (L, V, T) shown in the figures.
[0066] By convention, the terms "upstream" and "downstream" and "left" and "right" are used with reference to the longitudinal orientation. The terms "up" and "down" or "top" and "bottom" or "above" and "below" are used with reference to the vertical orientation.
[0067] More particularly, in this specification, the terms "upstream" and "downstream" correspond to the direction of glass flow in the furnace, where the glass flows from upstream to downstream, or in other words, from left to right with respect to the depiction of the furnace 100 in Figure 1 the figures.
[0068] According to the present invention, the furnace 100 includes a hot top trough 110, which is generally made of refractory material, such as made of alumina - zirconia - silica or chrome.
[0069] The concept of "hot top" in glass - making furnaces is well - known to those skilled in the art and will not be further explained here. As a reminder, according to this design, the vitrifiable material is usually introduced into the trough 110 from the side (i.e., along its longitudinal orientation) by means of a loading device (not shown in the figures) also called a "loader".
[0070] In Figure 1 the embodiment shown, the trough 110 has a horizontally - extending bottom wall 111, which forms the hearth of the furnace 100. Similarly, according to other examples, it is not excluded to consider a lower wall inclined with respect to the horizontal plane, for example in the form of a downward - pointing cone or inclined plane, so as to promote driving the molten vitrifiable material towards the bottom of the trough 110 at the start of melting.
[0071] The furnace 100 is configured to melt the vitrifiable material introduced into the tank 110 to form a bath 120 of molten vitrifiable material. The material thus melted is used to manufacture glass, and the furnace 100 is integrated into a glass manufacturing apparatus for this purpose, which glass manufacturing apparatus includes various devices (not shown in the figure) capable of carrying out steps of refining and / or homogenizing and / or thermally conditioning and / or final shaping of the glass in zones other than the zone where the furnace 100 is implemented. Such steps are well known to those skilled in the art and will not be further described here.
[0072] For the remainder of the description, considered in a non - limiting manner, the glass intended to be manufactured from the molten material in the furnace 100 is borosilicate glass. However, considering the manufacture of this glass is only one variant of the present invention. Thus, generally, there is no limitation on the type of glass produced from the melt in the furnace 100 according to the present invention.
[0073] It should be noted that the composition of the vitrifiable material enabling the manufacture of borosilicate - type glass is well known to those skilled in the art and will not be described in detail here. Of course, this observation also applies to all other types of glass that can be manufactured according to the present invention. In addition, aspects regarding the proportion of carbonaceous organic matter that can be included in the vitrifiable material used are described in more detail subsequently.
[0074] According to the present invention, the glass furnace 100 is of a hybrid type. In other words, two different energy sources are used, namely combustion energy and electrical energy, to melt the vitrifiable material in the tank 110 to form the bath 120. Each of these energies is used by means of suitable heating devices of a type known per se, namely:
[0075] - an overhead burner for combustion energy arranged between the furnace roof 110 and the surface of the bath 120, and
[0076] - electrodes embedded in the bath 120 for electrical energy, which are made of a refractory material such as molybdenum.
[0077] Combustion can be achieved in a known manner by combining different types of fuel and oxidizer. Thus, oxygen in air is generally used as the oxidizer, and the air can be enriched with oxygen to obtain oxygen - enriched air. In the specific case of oxy - fuel combustion, even pure oxygen can be used as the oxidizer.
[0078] In terms of combustion, the fuel used is generally natural gas, or possibly other fossil fuels, such as petroleum products, such as fuel oil.
[0079] Of course, the use of fossil fuels directly affects the carbon footprint of glass production, especially in terms of carbon dioxide (CO2) emissions from combustion. To improve this carbon balance, green fuels, especially biogas - a gas consisting essentially of methane and carbon dioxide produced by methanation, can be used as an alternative to fossil fuels.
[0080] Alternatively, the fuel used in all or part of the furnace 100 can be hydrogen (H2), which advantageously contains no carbon compared to biogas.
[0081] In its general principle, the mixing furnace 100 differs from the mixing furnaces of the prior art in that the trough 110 contains two heating zones, a first heating zone Z_1 and a second heating zone Z_2, from upstream to downstream, which are configured to carry out the melting step (not shown in the figure) of the vitrifiable material according to the glass manufacturing method of the present invention.
[0082] The step of melting the vitrifiable material for manufacturing the glass, the vitrifiable material containing a proportion of carbonaceous organic matter of 0.5% to 10%, is carried out in such a way that:
[0083] - The proportion of combustion energy for melting the vitrifiable material in the first zone Z_1 is at least 50% (i.e., the total melting energy for melting the vitrifiable material in the first zone Z_1 contains at least 50% of combustion energy), and
[0084] - The proportion of electrical energy for melting the vitrifiable material in the second zone Z_2 is at least 50% (i.e., the total melting energy for melting the vitrifiable material in the second zone Z_2 contains at least 50% of electrical energy).
[0085] More specifically, in the embodiments described herein, the two heating zones Z_1, Z_2 are in fluid communication and there is no barrier between them.
[0086] In addition, each of the heating zones Z_1, Z_2 is advantageously configured to be able to use both combustion energy and electrical energy. As Figure 1 shown, the first heating zone Z_1 includes three overhead burners 130_1, 130_2, 130_3 and two electrodes 140_1, 140_2. The second heating zone Z_2 includes a single overhead burner 150 and four electrodes 160_1, 160_2, 160_3, 160_4 at the same time.
[0087] The burners 130_1, 130_2, 130_3, 150 are so-called lateral burners, which are usually so named due to their lateral arrangement (perpendicular to the glass flow in the furnace 100).
[0088] In Figure 1In the illustrated embodiment, the electrodes 140_1, 140_2, 160_1, 160_2, 160_3, 160_4 are so-called rising electrodes, which are commonly so named due to their vertical arrangement from the bottom 111 of the trough 110. However, one or more electrodes may have a different orientation, such as an inclined orientation.
[0089] However, considering such a number of burners and electrodes in each of the heating zones Z_1, Z_2 is only a variant of the present invention. Generally speaking, there is no limit to the number of burners and electrodes in each heating zone, as long as the proportion of combustion energy (correspondingly, electrical energy) used in the first zone Z_1 (correspondingly, in the second zone Z_2) is at least 50%.
[0090] Implementing the melting step of such a method for manufacturing glass by means of the mixing furnace 100 thus makes it possible to preferentially use combustion energy in the first heating zone Z_1 in order to limit foaming in the first heating zone Z_1, and conversely, to preferentially use electrical energy in the second heating zone Z_2, so as to maximize the heating efficiency (i.e., heat transfer) of each type of energy used in the furnace 100.
[0091] This greatly reduces the risk that sulfates contained in the vitrifiable material precipitate near the electrodes in the first heating zone Z_1 and interact with the carbon chains also contained in the vitrifiable material. In other words, this advantageously limits foaming in the first heating zone Z_1, i.e., the consequences of the thermal barrier formed by said foam.
[0092] As a result, the present invention maximizes the heating efficiency of each type of energy used in the furnace 100. In fact, since the appearance of foam is greatly limited in the first heating zone Z_1, the problem of poor heat transfer between the bath and the vitrifiable material is also greatly limited, which greatly promotes the melting of the vitrifiable material introduced into the trough 110.
[0093] According to the present invention, the energy source (combustion or electrical) is advantageously never separated from the energy source intended to be heated by the foam, thereby compensating for the disadvantages of the prior art described in the preamble caused by the shield or thermal insulation screen formed by said foam.
[0094] In fact, the foam - at least limited in the first heating zone - does not rise onto the vitrifiable material to be melted, and thus no longer forms a thermal insulation screen, so that the melting mainly achieved by means of burners according to the present invention is no longer affected. Similarly, in the second heating zone, where heating and refining are mainly carried out by means of electrodes, the possible presence of foam no longer acts as a thermal barrier to the (electrical) energy source as in the case of using burners in the prior art.
[0095] In the second heating zone Z_2, where the energy used is mainly electrical energy, the bath 120 contains little carbonaceous material and sulfate, making the electrical heating efficient without the risk of poor heat transfer. Additionally, if foam residues do form on the surface of the bath 120 in the second heating zone Z_2 (e.g., as shown in Figure 1 ), this will not have a harmful effect on the production of glass. On the contrary, the foam residues form a thermal barrier against the heat generated by the electrodes below the surface of the bath 120, contributing to good thermal insulation of the bath 120.
[0096] In a more particular exemplary embodiment of the melting step, the proportion of combustion energy used to melt the vitrifiable material in the first zone is at least 60%, and the proportion of electrical energy used to melt the vitrifiable material in the second zone is at least 60%.
[0097] According to a more particular exemplary embodiment of the melting step, the proportion of combustion energy used in the first zone Z_1 is at least 70%, for example, the proportion of combustion energy used in the first zone Z_1 is 75% or 85%.
[0098] The melting step can also be carried out in such a way that the proportion of electrical energy used in the first zone Z_1 can keep the bath temperature there above a given temperature (e.g., the glass crystallization temperature).
[0099] Generally speaking, there is no limit to the proportion of combustion energy used in zone Z_1 as long as it is greater than or equal to 50%. Thus, for example, it is not possible to prevent the melting energy used in the first zone Z_1 from being only combustion energy (i.e., the proportion of combustion energy = 100%). In this regard, it should be understood that the presence of electrodes in the first heating zone Z_1 is not essential for the present invention.
[0100] In the second heating zone Z_2, in addition to the above examples of the proportion of combustion energy used in the first heating zone Z_1, the proportion of electrical energy is at least 70%, for example, the proportion of electrical energy used in the second zone Z_2 is 75% or 85%.
[0101] In a more specific embodiment, the melting step can also be carried out in such a way that the proportion of combustion energy used in the second zone Z_2 can keep the furnace roof temperature above a given temperature.
[0102] For example, the temperature corresponds to the condensation temperature of sodium borate at about 1200 °C. This compound is known for its corrosive properties, and if the temperature above the bath 120 is insufficient, it can condense on the walls of the furnace roof.
[0103] Generally speaking, there is no limit to the proportion of electrical energy used in the second zone Z_2, as long as it is greater than or equal to 50%. Thus, for example, it is not possible to prevent the melting energy used in the second zone Z_2 from being only electrical energy (i.e., the proportion of electrical energy = 100%). In this regard, it should be understood that the presence of burners in the second heating zone Z_2 is not essential for the present invention.
[0104] As a supplement or alternative to maintaining the roof temperature above a given temperature by adjusting the combustion energy used in the second heating zone Z_2, the furnace may further comprise an exhaust chimney 180 configured to discharge the combustion flue gas generated in the first heating zone Z_1 to the second heating zone Z_2.
[0105] Advantageously, the chimney 180 is arranged or connected to the downstream part of the second heating zone Z_2. However, there are no restrictions on the configuration (shape, geometry, arrangement) of the chimney 180, which may, for example, take the form of an opening cut into the roof of the slot 110 to form a flue gas discharge channel.
[0106] Such a chimney 180, by discharging the flue gas into the second zone Z_2, also makes it possible to keep the temperature there above a given temperature and thus can also help to avoid the corrosion effects associated with the condensation of sodium borate on the roof of the furnace 100.
[0107] Advantageously, the circulation of the flue gas (from the first heating zone Z_1) through the second heating zone Z_2 before being discharged downstream via the flue 180 can keep the roof temperature above a given temperature (such as the condensation temperature of sodium borate) and may even enable the burner 130_4 to be dispensed with, which then particularly helps to reduce the roof height in the second heating zone Z_2 of the furnace 100.
[0108] As previously mentioned, the melting step of the method for manufacturing glass according to the present invention maximizes the heating efficiency of each of the energies used in the furnace 100. Thus, the present invention can use more recycled materials than the prior art, thereby maximizing the recycling capacity of the furnace 100.
[0109] Thus, according to a specific embodiment of the melting step, the proportion of carbonaceous organic matter contained in the vitrifiable material introduced into the slot 110 is less than or equal to 10%.
[0110] According to an important feature of the present invention, the vitrifiable material for manufacturing glass contains a proportion of carbonaceous organic matter of 0.5% to 10%, preferably 0.75% - 10%, more preferably 1% to 10%, and even more preferably 2% to 10%.
[0111] The vitrifiable material for manufacturing glass may include recycled materials, such as cullet (e.g., household cullet, ground cullet, etc.) in a proportion less than or equal to 90%, and / or mineral wool in a proportion less than or equal to 100% (e.g., glass filler corresponding to 100% recycled glass wool, which may contain up to 10% binder).
[0112] The furnace 100 includes a control unit UC for respectively controlling the combustion heating devices 130_1, 130_2, 130_3 in the first heating zone Z_1 and the electrodes 160_1, 160_2, 160_3, 160_4 immersed in the bath 120 of the molten material in the second heating zone Z_2 according to the proportion of carbonaceous organic substances contained in the vitrifiable material.
[0113] Preferably, and according to the first embodiment, during the melting step, when the vitrifiable material contains approximately 0.5% proportion of carbonaceous organic substances, the proportion of combustion energy for melting the vitrifiable material in the first heating zone Z_1 is 50%, and the proportion of electrical energy for melting the vitrifiable material in the second heating zone Z_2 is 50%. In other words, in each of the heating zones Z_1; Z_2, the share of combustion energy and the share of electrical energy are respectively equal to 50%.
[0114] Alternatively, the proportion of combustion energy and the proportion of electrical energy are not equal. For example, the proportion of combustion energy in the first heating zone Z_1 is 50%, while the proportion of electrical energy in the second heating zone Z_2 is greater than 50%, such as 70% or even 100%.
[0115] Of course, the proportion of combustion energy in the first zone Z_1 can also alternatively be greater than the proportion of electrical energy in the second zone Z_2, especially when the proportion of electrical energy is 50% and the proportion of combustion energy is greater than 50%, such as equal to 70% or even 100%.
[0116] Preferably, and according to the second embodiment, during the melting step, when the vitrifiable material contains approximately 5% proportion of carbonaceous organic substances, the proportion of combustion energy for melting the vitrifiable material in the first heating zone Z_1 is 75%, and the proportion of electrical energy for melting the vitrifiable material in the second heating zone Z_2 is 75%. In other words, in each of the heating zones Z_1; Z_2, the share of combustion energy and the share of electrical energy are respectively equal to 75% in this case.
[0117] Preferably, during the melting step, when the vitrifiable material contains a proportion of 10% carbonaceous organic substances, the proportion of combustion energy for melting the vitrifiable material in the first heating zone Z_1 is 100%, and the proportion of electrical energy for melting the vitrifiable material in the second heating zone Z_2 is 100%.
[0118] In other words, in each of the heating zones Z_1 ; Z_2 , the proportion of combustion energy and the proportion of electrical energy are in this case each equal to 100%.
[0119] According to the variant just described for the first embodiment, the share of combustion energy and the share of electrical energy may differ from the second or third embodiment, one being greater than the other or vice versa, each of said energy shares being at least 50%.
[0120] Thanks to the control unit UC, the furnace 100 can be controlled by preferentially using combustion energy in the first heating zone Z_1 in order to limit bubbling in said first heating zone Z_1, and conversely, preferentially using electrical energy in the second heating zone Z_2 in order to maximize the heating efficiency (i.e. heat transfer) of each of said energies used in the furnace 100.
[0121] and Figure 1 Compared with the design shown, the following will describe Figures 2 to 5 Other designs are shown, in which the control unit UC, or even the exhaust chimney, is not shown, but only for the sake of simplicity. Figures 2 to 5 The furnace shown may further comprise a control unit UC for controlling the energy priority, or even an exhaust chimney for discharging the combustion fumes.
[0122] So far the hybrid furnace according to the invention has been described with regard to a specific geometry according to which there is no physical separation between the two heating zones Z_1 , Z_2 . However, other alternatives are also possible.
[0123] Figure 2 Another specific embodiment of a glass melting furnace 200 according to the present invention is schematically shown in its environment.
[0124] Similar to reference Figure 1 The arrangement of the described arrangement, the mixing furnace 200 comprises a tank 210, in which the vitrifiable material for making glass is melted to form a bath 220. More specifically, the tank 220 comprises two heating zones Z_1, Z_2 from upstream to downstream, and the step of melting the vitrifiable material is performed by means of:
[0125] - three overhead burners 230_1 , 230_2 , 230_3 and two electrodes 240_1 , 240_2 in the first heating zone Z_1 ,
[0126] - An overhead burner 250 and four electrodes 260_1 , 260_2, 260_3, 260_4 in the second heating zone Z_2.
[0127] Furthermore, in this further embodiment, and if Figure 2As shown by way of non-limiting example, the furnace comprises a vertical partition 270 configured to:
[0128] - block the flow of the melt between a first zone and a second zone Z_1, Z_2 on the surface of the bath 220 of molten material,
[0129] - allow the melt to circulate between the first and second zones Z_1, Z_2 in the hearth 211 of the furnace 200.
[0130] The vertical partition 270 is made, for example, of a refractory material such as magnesia and / or chrome, or of the alumina-zirconia-silica type (whether fused or not).
[0131] Alternatively, the vertical partition 270 may comprise an external metal casing (also called an "armature"), which is formed by two partitions between which a cooling fluid (such as water) flows (walls of a so-called "water jacket").
[0132] In other words, the vertical partition 270 is configured to create an opening at the bottom of the furnace 200 such that the molten material in the first heating zone Z_1 can flow towards the second heating zone Z_2 and then be discharged from the furnace 200.
[0133] It should be noted that the ability of the partition 270 (due to its appropriate height) to block the circulation of the molten material between the zones Z_1, Z_2 at the surface of the bath 220 of molten material advantageously prevents the foam generated in the second heating zone Z_2 from migrating to the first heating zone Z_1. In other words, the presence of the vertical partition 270 further optimizes the heating efficiency of the mixing furnace 200.
[0134] As previously mentioned, it is conceivable that the melting energy used in the first zone Z_1 is only combustion energy (i.e., the share of combustion energy = 100%). Such arrangements are advantageous in the context of this embodiment because they promote the generation of convective movements in the bath 220 to help the molten material circulate between the first zone Z_1 and the second zone Z_2 in the hearth 211 of the furnace 200.
[0135] When the furnace 200 comprises a flue gas exhaust chimney similar to Figure 1 the chimney 180 shown in, the vertical partition 270 is then provided at the top with at least one opening (not shown) to allow the flue gas to flow from the first heating zone Z_1 to the second heating zone Z_2 until the said exhaust chimney arranged downstream.
[0136] Figure 3 and Figure 4 Other specific embodiments of the glass furnaces 300, 400 according to the invention are schematically shown in their environment.
[0137] In particular, the furnace 300 (correspondingly, the furnace 400) differs from the furnace 100 (correspondingly, the furnace 200) in Figure 1 in that the roof height in the second heating zone Z_2 is lower than the roof height in the first heating zone Z_1. Figure 1 The furnace 100 (correspondingly, Figure 2 the furnace 200) in that the roof height in the second heating zone Z_2 is lower than the roof height in the first heating zone Z_1.
[0138] So far, the hybrid furnace according to the invention has been described based on the bath height in the first zone Z_1 being the same as the bath height in the second zone Z_2. However, such an arrangement does not limit the invention and does not exclude embodiments in which the bath height in the second zone Z_2 is lower than the bath height in the first zone Z_1. Although there is such a difference in bath height between zones Z_1 and Z_2, the minimum bath height in the second zone Z_2 can be, for example, 200 mm to 300 mm.
[0139] Having a lower glass height in the second zone Z_2 advantageously reduces the construction cost of the furnace because it minimizes the amount of refractory material. In addition, it minimizes the energy requirement because it reduces the volume of the glass to be heated by minimizing the heat loss through the refractory walls.
[0140] Preferably, when the bath height in the second zone Z_2 is lower than the bath height in the first zone Z_1, the melting energy used in the second zone Z_2 is only electrical energy, which enables the second zone Z_2 to be designed with a roof whose height is flush with the bath surface.
[0141] In a non-limiting manner, Figure 5 Another embodiment of the hybrid glass furnace 500 according to the invention is schematically shown, in which the bath height in the second zone Z_2 is lower than the bath height in the first zone Z_1. As can be seen in Figure 5 the height of the furnace hearth 500 is different between zones Z_1 and Z_2, such that the desired bath height difference can be achieved in this embodiment.
[0142] According to yet another aspect, the invention also encompasses a glass manufacturing method (not shown in detail in the figures), in which in addition to the step of melting the vitrifiable material, the method includes, for example, a final shaping step of the glass. According to a more specific exemplary embodiment, a refining and / or homogenizing and / or thermal conditioning step of the molten material flowing out of the trough can be carried out before the final shaping step.
Claims
1. A method for manufacturing glass, the method comprising the step of melting a vitrifiable material for manufacturing the glass, the vitrifiable material containing a proportion of carbonaceous organic matter in the range of 0.5% to 10%, wherein the step of melting the vitrifiable material is carried out by means of a mixing glass furnace (100) comprising a hot top tank (110), the tank comprising, from upstream to downstream: - The first heating zone (Z_1), which includes combustion heating devices (130_1, 130_2, 130_3), - The second heating zone (Z_2), which includes electrodes (160_1, 160_2, 160_3, 160_4) immersed in a bath (120) of molten material, The melting step is carried out such that the proportion of combustion energy for melting the vitrifiable material in the first zone is at least 50%, and the proportion of electrical energy for melting the vitrifiable material in the second zone is at least 50%. Combustion energy is preferably used in the first heating zone (Z_1) to limit foaming in the first heating zone (Z_1), and conversely, electrical energy is preferably used in the second heating zone (Z_2) to maximize the heating efficiency of each of the energies used in the furnace.
2. The method according to claim 1, wherein the proportion of combustion energy used in the first zone (Z_1) is at least 70%.
3. The method according to claim 2, wherein the melting energy used in the first zone (Z_1) is only combustion energy.
4. The method according to any one of claims 1 to 2, wherein the first heating zone (Z_1) further comprises electrodes (140_1, 140_2) immersed in a bath of molten material, and the melting step is carried out such that the proportion of electrical energy used in the first zone (Z_1) can maintain the bath temperature at a given temperature there, for example above the crystallization temperature of the glass.
5. The method according to any one of claims 1 to 4, wherein the proportion of electrical energy used in the second zone (Z_2) is at least 70%.
6. The method according to claim 5, wherein the melting energy used in the second zone (Z_2) is only electrical energy.
7. The method according to any one of claims 1 to 5, wherein the second heating zone (Z_2) further comprises combustion heating means (130_4), and the melting step is carried out in such a way that the proportion of combustion energy used in the second zone (Z_2) can maintain the furnace top temperature at a given temperature there, for example above the sodium borate condensation temperature.
8. The method according to any one of claims 1 to 7, wherein the proportion of combustion energy used in the first zone (Z_1) and the proportion of electrical energy used in the second zone (Z_2) are equal or different, one being greater than the other or vice versa.
9. The method according to any one of claims 1 to 8, wherein the combustion energy in the first zone (Z_1) and / or the second zone (Z_2) is obtained by hydrogen combustion.
10. The method according to any one of claims 1 to 9, wherein the vitrifiable material is selected so as to be capable of manufacturing borosilicate glass.
11. The method according to any one of claims 1 to 10, wherein the proportion of carbonaceous organic matter contained in the vitrifiable material is less than or equal to 10%, being from 0.75% to 10%, more preferably from 1% to 10%, and even more preferably from 2% to 10%.
12. The method according to any one of claims 1 to 11, wherein the vitrifiable material comprises recycled materials such as, for example, cullet in a proportion less than or equal to 90%, and / or mineral wool in a proportion less than or equal to 100%.
13. The method according to any one of claims 1 to 12, wherein the combustion flue gas generated in the first heating zone (Z_1) is discharged towards the second heating zone (Z_2) until an exhaust chimney (180) arranged downstream of the second heating zone (Z_2), so as to be able to maintain the roof temperature in the second heating zone (Z_2) at a given temperature, in particular above the sodium borate condensation temperature, by means of said flue gas.
14. A hybrid glass furnace (100, 200, 300, 400, 500) configured to implement the method for manufacturing glass according to any one of claims 1 to 13, said furnace comprising a control unit (UC) for respectively controlling at least combustion heating devices (130_1, 130_2, 130_3) in a first heating zone (Z_1) and electrodes (160_1, 160_2, 160_3, 160_4) immersed in a bath (120) of molten material in a second heating zone (Z_2) based on the proportion of carbonaceous organic matter contained in the vitrifiable material, preferentially using combustion energy in the first heating zone (Z_1) to limit foaming in the first heating zone (Z_1), and conversely, preferentially using electrical energy in the second heating zone (Z_2), so as to maximize the heating efficiency of each of the energies used in the furnace.
15. The furnace according to claim 14, said furnace comprising a vertical partition (270), said vertical partition (270) being configured to: - Block the flow of the melt between the first and second zones (Z_1, Z_2) on the surface of the bath of molten material, - Allow the melt to circulate between the first and second zones on the hearth (211) of the furnace.
16. The furnace (300, 400) according to any one of claims 14 to 15, wherein the roof height in the second heating zone (Z_2) is less than the roof height in the first heating zone (Z_1).
17. The furnace (500) according to any one of claims 14 to 16, wherein the bath height in the second heating zone (Z_2) is lower than the bath height in the first heating zone (Z_1).
18. The furnace according to any one of claims 14 to 17, wherein the furnace further comprises an exhaust chimney (180) disposed in a downstream portion of the second heating zone (Z_2) and configured to discharge combustion flue gas generated in the first heating zone to the second heating zone.