MELTING SYSTEM AND METHOD FOR MELTING ALUMINUM WASTE

Description

Technical field of the invention

[0001] The present invention relates to the field of aluminum waste recycling and more particularly, to the field of aluminum waste melting systems for melting aluminum waste.

[0002] The present invention also relates to the field of aluminum waste melting processes by an aluminum waste melting system. State of the art

[0003] In the field of aluminum waste recycling, rotary kilns, or tilting rotary kilns, are commonly used. This technology is specifically designed to process oxidized waste, such as foundry dross, or materials containing organic coatings, including coated coils, manufacturing scrap, or materials composed of small individual particles, such as beverage cans, or UBCs (Used Beverage Cans) in established Anglo-Saxon terminology. Before being introduced into the rotary kiln, the beverage cans are generally compacted to form a load with an overall parallelepiped or cubic shape. Since beverage cans are coated with varnish and paint, organic residues are invariably found in these loads.The residual carbon content in each batch is therefore highly variable and depends on the amount of varnish and paint present on the crushed beverage cans in the batch and the process control conditions.

[0004] During the melting of aluminum scrap, in addition to the liquid aluminum intended for recovery and casting, oxides, which are impurities present in the molten mass, are also formed. To remove these oxides, it is known from the prior art to use salts that both limit the oxidation of the aluminum and separate these oxides from the molten mass by forming a slag on the surface of the molten metal.

[0005] To remove organic coatings, different methods can be used. One method, as described in document US2017 / 0051914A1, consists of evaporating the organic coatings by heating, then carrying out afterburning in a separate chamber before melting the metal in a second furnace.

[0006] Alternatively, as described in documents WO2005 / 085732A1 and EP1243663A2, organic coatings can be removed by descaling beverage cans through direct combustion in the metal melting furnace. In such an operation, the stoichiometry of the oxidizer and fuel is crucial, as it influences the composition of the combustion fumes and the quality of the resulting liquid metal. If the amount of oxidizer is insufficient, combustion is incomplete, producing volatile organic compounds (VOCs) rather than carbon dioxide.

[0007] Document EP4092390 describes an apparatus capable of monitoring and adjusting a combustion condition in a furnace in real time, comprising: a furnace having a heating chamber, a combustion chamber, a loading door, an exhaust gas outlet, and an exhaust gas outlet pipe and two sensors of the same type disposed at different positions in the exhaust gas outlet pipe and a control device receiving signals from the two sensors and adjusting, according to a difference between the signals, the quantity of fuel and / or oxygen-containing gas entering the combustion chamber.

[0008] Document US2005 / 103159 describes a process for melting aluminum, which consists of introducing solid aluminum into a furnace, melting the aluminum to form an aluminum bath, detecting variations in carbon monoxide (CO) and / or hydrogen (H2) concentration and the temperature of the fumes exiting the furnace, deducing the formation of aluminum oxide on the surface of the aluminum bath by regulating the melting process according to the formation of aluminum oxide.

[0009] Document WO 01 / 33200 relates to processes and apparatus using tunable diode lasers to monitor and / or control a high-temperature process using an oxidant containing O2 and an organic fuel.

[0010] US2020 / 284513 relates to a method for regulating combustion in a furnace heated by a burner equipped with at least one oxygen lance, wherein fuel is supplied via a burner fuel supply and oxygen is supplied at least in part with a high velocity of 100 m / s or more by the oxygen lance(s), and oxygen in a superstoichiometric range is supplied.

[0011] Document DE102013012831 relates to a process for melting contaminated aluminum in a rotary drum furnace. The rotary drum furnace is heated by means of a burner, the burner being ignited with a gaseous mixture of fuel, oxygen, and air, the burner being ignited with a gaseous mixture in a ratio of fuel, oxygen, and air such that the burner is ignited in a superstoichiometric combustion ratio with a lambda value greater than 1.

[0012] US2011 / 154949 relates to a process for operating a furnace, in which a feed material comprising at least one metallic element is melted, the feed material being heated by at least one burner which operates with a volumetric flow rate of fuel and a volumetric flow rate of an oxidant.

[0013] Document WO2021 / 220802 relates to a melting / refining furnace for cold iron sources and a method of operating a melting / refining furnace, by which it becomes possible to improve the heating efficiency of a raw material and to reduce the amount of electrical energy required to melt the raw material without causing oxidation of the raw material, and to reduce melting / refining time, and to improve productivity and reduce costs.

[0014] Volatile organic compounds (VOCs) refer to all organic molecules containing at least one carbon atom bonded to hydrogen, nitrogen, oxygen, sulfur, chloride, etc., with the exception of carbon monoxide (CO), carbon dioxide (CO2), water (H2O), and nitrogen oxides (NOx). A primary problem with VOC formation is that it contributes to lowering the temperature inside the furnace. A second problem stems from the fact that some VOCs are toxic. It is therefore crucial to limit their formation or drastically reduce their concentration before venting combustion fumes from the melting system. Furthermore, most industrial processes are subject to regulatory requirements that govern VOC emission limits.

[0015] However, if the conditions are highly oxidizing (i.e., with a greater quantity of oxidant than fuel), all organic matter is burned to form carbon dioxide, but it is possible to oxidize the liquid aluminum, thus generating oxides. One consequence of this oxide generation is that they can be incorporated into the molten metal, degrading the quality of the metal obtained after solidification. Document WO2005 / 085732A1 therefore proposes a reduction phase to prevent the oxidation of liquid aluminum and thus avoid oxide formation. However, such a reduction phase has the disadvantage of increasing the amount of fuel released (e.g., methane), which is a volatile organic compound.

[0016] It is therefore clear that, given the highly variable carbon content in each charge, controlling the maximum amount of charge introduced into the furnace to guarantee both optimal combustion and efficient metal melting, while simultaneously limiting VOC emissions outside the melting system, is very difficult. Furthermore, since the oxidizer flow rate is technically limited by the furnace's capacity, it is sometimes impossible to supply enough oxidizer to prevent incomplete combustion, particularly if the carbon content in the charge is too high.

[0017] Furthermore, in fusion devices such as those described in document WO2005 / 085732A1, the combustion fumes produced are introduced into a duct for cooling. This cooling method generally results in the formation of toxic dioxins, which should be prevented. Object of the invention

[0018] The present invention aims to provide a solution that addresses all or some of the aforementioned problems. In particular, the fusion system according to the invention aims to: limit the formation of VOCs; limit the formation of dioxins; achieve the melting of aluminium and the combustion of organic coatings inside the same furnace, while limiting the formation of oxides; achieve the melting of an optimal quantity of aluminium waste in a large furnace.

[0019] This goal can be achieved through the implementation of an aluminum waste melting system to melt aluminum waste, the melting system comprising: a melting furnace intended for melting said aluminum waste, and comprising: a drum internally delimiting a melting chamber intended to receive said aluminum waste to be melted; a burner comprising an ignition device, at least one oxidizer injector, and at least one fuel injector, said oxidizer injector being configured to inject a flow of oxidizer into the melting chamber, said fuel injector being configured to inject a flow of fuel into the melting chamber, and the ignition device being configured to start combustion of the oxidizer and fuel injected into the melting chamber, to bring heat into the melting chamber;means of evacuation configured to allow the extraction of all or part of the combustion fumes from inside the melting enclosure to an open air area located outside the melting enclosure and where the air is free to circulate;an extraction hood disposed outside the melting enclosure and intended to capture by suction all or part of said combustion fumes present in the open air zone, said extraction hood further comprising a control line including a carbon monoxide sensor configured to measure a value of a carbon monoxide concentration in said combustion fumes captured by the extraction hood, the carbon monoxide sensor comprising a laser emitter configured to emit laser radiation, and a laser receiver configured to receive said emitted laser radiation, and to measure an absorption spectrum of said received laser radiation, the value of the carbon monoxide (C) concentration being determined from said absorption spectrum thus measured;a control device configured to receive input information representative of the carbon monoxide concentration value measured by the carbon monoxide sensor, and to control said oxidant flow rate injected by said oxidant injector and / or said fuel flow rate injected by said fuel injector, according to said input information, the oxidant and fuel flow rates being controlled to keep the VOC level at the outlet of the melting furnace below a safety value.

[0020] The previously described provisions allow for the development of an aluminum scrap melting system capable of melting aluminum scrap to obtain liquid aluminum, while simultaneously burning volatile organic compounds (VOCs) within the melting chamber. Furthermore, the presence of a carbon monoxide sensor communicating with the control system enables the regulation of oxidizer and fuel flow rates to keep VOC levels at the melting furnace outlet below a safe threshold.

[0021] Advantageously, using a fume hood at the melting furnace exhaust system allows for rapid cooling of the combustion fumes by mixing them with the open air directly at the furnace outlet, while simultaneously capturing the combustion fumes. This method limits the formation of dioxins in the combustion fumes, while ensuring that all cooled combustion fumes are captured as they exit the melting furnace.

[0022] The fusion system may also have one or more of the following characteristics, taken alone or in combination.

[0023] In one embodiment, the melting furnace includes a material inlet door configured to allow the introduction of aluminum scrap into the melting chamber. In this case, the material inlet door is opened to introduce the aluminum scrap into the melting chamber.

[0024] By "controlling", we mean that the control device is capable of regulating or varying the flow rates of oxidizer and / or fuel introduced into the furnace chamber, for example via one or more valves.

[0025] According to one embodiment, the control device is an automated system configured to automatically control the flow rate of oxidant injected by the oxidant injector, and / or the flow rate of fuel injected by the fuel injector, and / or optionally the rotational speed of the rotary drum, for example, according to an algorithm stored in the control device's memory. Such an algorithm may include instructions corresponding to operating modes of a control step in the fusion process according to the invention.

[0026] According to one embodiment, the melting furnace is a rotary furnace comprising a rotating drum configured to be rotated.

[0027] In this way, it is possible to accelerate or slow down the combustion of organic coatings by rotating the rotating drum.

[0028] According to another embodiment, the melting furnace is a multi-chamber furnace.

[0029] According to one embodiment, the means for evacuating the melting furnace include at least one opening provided in a wall of the melting furnace.

[0030] According to one embodiment, at least one opening is disposed at the level of a door of the melting furnace, for example on an upper portion of said door.

[0031] The previously described provisions allow for the design of a door that is not airtight against combustion fumes. The design and manufacture of such a door is therefore simplified compared to aluminum scrap melting systems where the door is airtight. This makes it possible to design and manufacture large rotary melting furnaces capable of handling a greater quantity of aluminum scrap.

[0032] Advantageously, the presence of the extraction hood also prevents the escape of combustion fumes outside the aluminum waste melting system, and thus limits diffusion in the workshop where the melting furnace is located.

[0033] The carbon monoxide sensor includes a laser emitter configured to emit laser radiation, and a laser receiver configured to receive said emitted laser radiation, and to measure an absorption spectrum of said received laser radiation, the value of the carbon monoxide concentration being determined from said absorption spectrum thus measured.

[0034] In other words, the carbon monoxide sensor measures the value of the carbon monoxide concentration by a measurement method by laser absorption spectrometry, also called TDLAS for "Tunable diode laser absorption spectroscopy" according to the established Anglo-Saxon terminology.

[0035] Advantageously, using a laser absorption spectrometry measurement method with the carbon monoxide sensor allows for the measurement of carbon monoxide concentration with a sensitivity of approximately 0.3 ppm in less than 1 second. This is particularly advantageous for near real-time control of the melting furnace to monitor the combustion of volatile organic compounds.

[0036] Furthermore, such a carbon monoxide sensor has the advantage of being a non-contact measurement method, facilitating maintenance.

[0037] Finally, this online spectrometry measurement method limits interference from other gases, making the measurement reliable.

[0038] According to one embodiment, the melting furnace includes an additional oxidizer lance separate from at least one oxidizer injector, and configured to allow the introduction of an additional flow of oxidizer into the melting chamber.

[0039] According to one embodiment, the additional oxidizer lance has a maximum oxidizer introduction flow rate into the fusion chamber that is strictly greater than a maximum oxidizer introduction flow rate of at least one oxidizer injector.

[0040] The previously described provisions make it possible to propose a melting furnace with improved oxidant injection capabilities, which is particularly suitable for improving the combustion of volatile organic compounds inside the melting chamber.

[0041] According to one embodiment, the oxidant injector is an industrially pure oxygen injector.

[0042] According to one embodiment, the additional oxidizer lance is an industrially pure oxygen lance.

[0043] In this way, it is possible to improve the combustion of volatile organic compounds without cooling the inside of the melting furnace. This is particularly advantageous for reducing the time and therefore the energy required to melt a given quantity of aluminum scrap compared to a melting furnace using an oxidant containing less than 100% oxygen, typically air or oxygen-enriched air.

[0044] In one embodiment, the control duct for the extraction hood comprises an extraction end at which combustion fumes are captured, and a filtration end, opposite the extraction end, said filtration end being equipped with a dust filter configured to filter combustion products separate from the VOCs remaining in the combustion fumes, at the filtration end. Advantageously, the dust filter may be a lime filter configured both to capture the remaining dust in the combustion fumes and to neutralize acidic fumes such as hydrochloric acid (HCl).

[0045] In this way, it is possible to filter the combustion fumes before they escape outside the aluminum waste melting system.

[0046] According to one embodiment, the fusion system includes a carbon dioxide trap disposed at the filtration end, said carbon dioxide trap being configured to trap all or part of the carbon dioxide present in the combustion fumes before they are evacuated from the fusion system.

[0047] The objective of the invention can also be achieved through the implementation of a process for melting aluminum waste using an aluminum waste melting system, the melting process comprising: a step of making available an aluminium waste melting system as described above; a first introduction step in which a first quantity of said aluminium waste is introduced into the melting chamber of the melting furnace; a melting step in which the ignition device is lit so that the burner supplies heat to the melting chamber of the melting furnace when it is supplied with oxidizer and fuel respectively by the oxidizer injector and by the fuel injector, said melting step leading to the formation by melting of liquid aluminium,and to the formation of combustion fumes; a measurement step in which the carbon monoxide sensor measures the value of the carbon monoxide concentration in the combustion fumes captured by the extraction hood; a control step in which the control device receives input information representative of the value of the carbon monoxide concentration measured by the carbon monoxide sensor, and controls the flow rate of oxidant injected by the oxidant injector, and / or controls the flow rate of fuel injected by the fuel injector, according to said input information; the process further comprising a preliminary calibration step (E11), in which a correlation law is established between: an average carbon monoxide concentration (Cm) measured by the carbon monoxide sensor (37),and an average concentration of volatile organic compounds (VOCs) measured at the filtration end (35) by a volatile organic compound (VOC) sensor, said correlation law being established on the basis of at least three average carbon monoxide concentration values ​​(Cm) measured by the carbon monoxide sensor (37), each associated with an average volatile organic compound concentration value ([VOC]m) measured over the same time interval. in which the oxidizer and fuel flow rates are controlled to keep the volatile organic compound (VOC) levels at the outlet of the melting furnace below a safety value.

[0048] In an advantageous embodiment, the oxidant flow rate injected by the oxidant injector, and / or pilot the fuel flow rate injected by the fuel injector are adjusted to maintain an oxidation stoichiometry for the gas injection.

[0049] The provisions described above make it possible to propose a melting process which allows both the formation of liquid aluminium from aluminium waste and the limitation of the quantity of volatile organic compounds in the combustion fumes evacuated from the melting chamber of the melting furnace by the thermolysis of said volatile organic compounds in-situ in the melting furnace.

[0050] The fusion process may also have one or more of the following characteristics, taken alone or in combination.

[0051] According to one embodiment, the first introduction step further includes the introduction of at least one salt, so as to obtain a slag denoted "L" covering the liquid aluminum and comprising alumina and said at least one salt during the melting step.

[0052] Advantageously, the introduction of at least one salt during the first introduction step makes it possible to trap solid residual organic compounds that come from the thermolysis of organic materials present in aluminum waste.

[0053] According to one embodiment, the melting process includes a melting furnace emptying step, in which all or part of the liquid aluminum contained in the melting chamber is extracted from the melting chamber, typically by tipping or siphoning.

[0054] According to one embodiment, during the piloting stage, the control device controls the flow rate of oxidant injected by the oxidant injector, and / or the flow rate of fuel injected by the fuel injector according to the following operating modes: a first mode of operation in which the oxidant flow rate and the fuel flow rate are chosen to introduce the oxidant and the fuel into the fusion chamber in stoichiometric proportions, the first mode of operation being established if the value of the carbon monoxide concentration is strictly less than a first threshold;a second mode of operation in which a ratio between the oxidant flow rate and the fuel flow rate is varied between an initial ratio corresponding to an introduction under stoichiometric conditions of oxidant and fuel into the fusion chamber respectively by the oxidant injector and the fuel injector, and a maximum ratio corresponding to a zero flow rate of fuel introduced by the fuel injector into the fusion chamber and a maximum oxidant flow rate introduced by the oxidant injector into the fusion chamber, said ratio between the oxidant flow rate and the fuel flow rate being varied according to the value of the measured carbon monoxide concentration, the second mode of operation being established if the value of the carbon monoxide concentration is strictly less than a second threshold and greater than or equal to the first threshold;a third operating mode in which the oxidizer flow rate is set to the maximum oxidizer flow rate value, the fuel flow rate is stopped, and the ignition device is switched off, the third operating mode being established if the value of the carbon monoxide concentration is strictly less than a third threshold and greater than or equal to the second threshold; a fourth operating mode in which the oxidizer flow rate is set to a maximum flow rate value, the fuel flow rate is stopped, the ignition device is switched off, the fourth operating mode being established if the value of the carbon monoxide concentration; carbon is strictly greater than the third threshold, said thresholds being determined to limit emissions of volatile organic compounds VOCs below defined thresholds.

[0055] According to one embodiment, if the melting furnace is a rotary furnace comprising a rotating drum, the fourth operating mode further includes the variation, and in particular the reduction, of the rotational speed of the rotating drum.

[0056] According to one embodiment, the first threshold is strictly less than the second threshold.

[0057] According to one embodiment, the second threshold is substantially equal to five times the value of the first threshold.

[0058] According to one embodiment, the second threshold is strictly less than the third threshold.

[0059] According to one embodiment, the third threshold is substantially equal to twice the value of the second threshold.

[0060] According to one embodiment, the first threshold is approximately equal to 30 ppm.

[0061] According to one embodiment, the second threshold is substantially equal to 150 ppm.

[0062] According to one embodiment, the third threshold is approximately equal to 300 ppm.

[0063] By "approximately equal", we mean "within 10%".

[0064] Advantageously, controlling the oxidizer and fuel injectors allows both the limitation of volatile organic compound (VOC) formation and protection against the risk of over-oxidation. Indeed, if the oxidizer and fuel injectors are operating in the second, third, and fourth modes, the excess oxidizer is consumed to limit the formation of VOCs and does not oxidize the liquid aluminum. Furthermore, and advantageously, if the melting process includes the introduction of at least one salt, the resulting slag acts as a shield against the oxidation of the liquid aluminum by the injected oxidizer.

[0065] According to one embodiment, the fourth operating mode further includes the introduction of an additional flow of oxidizer into the fusion chamber by the additional lance.

[0066] In this way, it is possible to increase the amount of oxidant introduced into the melting chamber, and to destroy by combustion a greater quantity of volatile organic compounds without decreasing the melting temperature of the melting furnace.

[0067] According to one embodiment, the first operating mode includes implementing a second introduction step in which a second quantity of aluminum scrap is introduced into the melting chamber of the smelting furnace. For example, the second introduction step may be implemented when the control device drives the oxidizer flow rate and the fuel flow rate in the first operating mode directly after having driven the oxidizer flow rate and the fuel flow rate in an operating mode selected from the second, third, or fourth operating mode.

[0068] Therefore, it is possible to adjust the amount of aluminum scrap introduced into the melting chamber without first measuring the amount of volatile organic compounds in the aluminum scrap. This increases the melting yield of liquid aluminum.

[0069] According to one embodiment, during the piloting step, if the ignition device is off, and if the carbon monoxide concentration is strictly below a restart threshold value, then the ignition device is switched on, the restart threshold value being strictly greater than the first threshold and strictly less than the second threshold. For example, the restart threshold value is approximately 1.5 times the value of the first threshold.

[0070] According to one embodiment, the restart threshold value is substantially equal to 45 ppm.

[0071] Advantageously, reigniting the ignition device once the carbon monoxide concentration falls below a sufficiently low threshold allows the aluminum melting process to restart and limits the formation of oxides on the surface of the liquid aluminum. This arrangement takes into account potential hysteresis phenomena during the melting of the metal and the combustion of organic coatings, which are related to the inertia of the melting furnace.

[0072] The fusion process includes a preliminary calibration step, in which a correlation law is established between: an average carbon monoxide concentration measured by the carbon monoxide sensor, and an average volatile organic compound concentration measured at the filtration end by a volatile organic compound sensor, said correlation law being established on the basis of at least three average carbon monoxide concentration values ​​measured by the carbon monoxide sensor, each associated with an average concentration value of volatile organic compounds measured over the same time interval. In one embodiment, the correlation law is in the form of a linear equation and is established by a linear regression method. Indeed, the applicant surprisingly found that it was possible to establish a linear relationship between the average carbon monoxide concentration at the outlet of the melting furnace and the average VOC concentration at the filtration end. This correlation law is particularly dependent on the melting system used, as it depends specifically on the melting furnace, the extraction hood, and the dilution rate of the combustion fumes in the open air before their capture by the extraction hood.

[0073] According to one embodiment, the average concentration of volatile organic compounds measured at the filtration end by a volatile organic compound sensor is measured downstream of the dust filter, i.e. after the dust filter has filtered the combustion fumes.

[0074] For example, the time interval corresponds to a melting cycle, which is the time between the introduction of the first quantity of aluminum scrap and the draining of the molten aluminum. During this melting cycle, an average carbon monoxide concentration is measured by calculating the arithmetic mean of the carbon monoxide concentration values ​​measured by the carbon monoxide sensor over the same melting cycle. Similarly, an average VOC concentration is measured over the same melting cycle by calculating the arithmetic mean of the VOC concentration values ​​measured by the VOC sensor. This average VOC concentration is then compared to the average carbon monoxide concentration.This operation is repeated at least three times to obtain at least three pairs of average concentration values ​​for carbon monoxide and VOCs, allowing a linear equation to be established in the form [. VOCs ] m = α * Cm where [VOC]m is the average VOC concentration measured over a cycle expressed in milligrams of carbon equivalent per normal cubic meters (mg / Nm³), Cm is the average carbon monoxide concentration measured over a cycle expressed in ppm, and α is a positive real coefficient. For example, the coefficient α is approximately equal to 0.4.

[0075] The restart threshold value, the first threshold, the second threshold, and the third threshold are determined at the end of the calibration step. These thresholds are determined to limit emissions of volatile organic compounds below defined limits, for example, by usage or by regulatory requirements.

[0076] For example, the first threshold could correspond to the following formula: S 1 = 2 5 α COV max

[0077] The second threshold can correspond to the following formula: S 2 = 2 α COV max

[0078] The third threshold can correspond to the following formula: S 3 = 4 α COV max

[0079] The restart threshold value can correspond to the following formula: Sr = 3 5 α COV max where α is the coefficient determined by establishing the linear equation described above, and where [VOC]max is a maximum average VOC concentration value over A fusion cycle, arbitrarily set by the user, or by regulatory or normative requirements.

[0080] According to A In this embodiment, the melting process further includes a cooling stage, in which the combustion fumes are diluted and cooled in open air outside the melting chamber. It is well understood that on AThe melting cycle, cooling stage and measurement stage can be implemented simultaneously and continuously.

[0081] The previously described arrangements allow the combustion fumes to be cooled outside the melting chamber in open air. This cooling step is particularly advantageous because it dilutes and cools the combustion fumes, minimizing the formation of toxic dioxins.

[0082] For example, the cooling stage includes an evacuation stage in which the evacuation means are operated to allow the evacuation of combustion fumes produced during the melting stage outside the melting chamber and into the open air, and a suction stage in which the suction hood captures by suction the combustion fumes present in the open air outside the melting furnace.

[0083] According to one embodiment, the piloting step is carried out after the measurement step within the same phase and said phase is repeated over time, in particular in a cyclical or periodic manner.

[0084] According to one embodiment, the measurement step is implemented several times over a piloting time interval, so as to implement the piloting step several times over said piloting time interval.

[0085] In one embodiment, the measurement and control steps are implemented continuously and in real time over the control interval. This allows for real-time control of the melting furnace during the control process. In this way, the melting time of the aluminum scrap can be optimized while minimizing the amount of volatile organic compounds released from the melting chamber. Brief description of the drawings

[0086] Other aspects, objectives, advantages, and features of the invention will become clearer upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which: [ Fig. 1 ] There figure 1 is a schematic view of a fusion system according to a particular embodiment of the invention. Fig. 2 ] There figure 2 is a schematic view of a melting process according to a particular embodiment of the invention. Detailed description

[0087] In the figures and throughout the description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not drawn to scale to ensure clarity. Moreover, the different embodiments and variants are not mutually exclusive and can be combined.

[0088] As illustrated on the figure 1 The invention relates to a system for melting aluminum waste. Such aluminum waste can, for example, consist of beverage cans that have been compacted together to form a mass of waste to be melted.

[0089] The melting system 1 includes, firstly, a melting furnace 10 intended to melt the said aluminum waste. According to one variant, the melting furnace 10 is a rotary furnace, but such a variant is not limiting and it is also possible that the melting furnace 10 is a multi-chamber furnace, or any other furnace suitable for melting aluminum, that is to say, capable of placing a mass of waste at a temperature above 660°C.

[0090] The melting furnace 10 includes a drum 11 which internally delimits a melting chamber 13 for receiving the aluminum scrap to be melted. According to the previously described variant in which the melting furnace 10 is a rotary furnace, the drum 11 is a rotating drum configured to be set in motion. In this way, it is possible to accelerate or slow down the combustion of the organic coatings by rotating the drum 11.

[0091] The melting furnace 10 also includes a burner 20 comprising an ignition device 21, at least one oxidizer injector 23, and at least one fuel injector 25.

[0092] The oxidizer injector 23 is configured to inject an oxidizer flow into the melting chamber 13. It is generally coupled to an oxidizer supply located outside the melting furnace 10, and to an oxidizer valve for varying the oxidizer flow rate injected into the melting chamber 13. This oxidizer valve can advantageously be actuated automatically, so as to control or automatically vary the oxidizer flow rate injected into the combustion chamber 13. In one embodiment, the burner 20 comprises a central oxidizer injector 23 located near the ignition device 21, and four peripheral oxidizer injectors 23 arranged at equal distances from the central oxidizer injector 23. However, this configuration is not limited, and the burner 20 may comprise one or more oxidizer injectors 23 arranged in a different manner.

[0093] Advantageously, the oxidant injector 23 can be an injector of industrially pure oxygen. In this way, it is possible to improve the combustion of volatile organic compounds (VOCs) without cooling the inside of the melting furnace 10. This is particularly advantageous for reducing the time and therefore the energy required to melt a given quantity of aluminum scrap compared to a melting furnace 10 using an oxidant containing less than 100% oxygen, typically air or oxygen-enriched air.

[0094] The fuel injector 25 is configured to inject a flow of fuel into the melting chamber 13. It is generally coupled to a fuel supply located outside the melting furnace 10, as well as to a fuel valve for varying the flow of fuel injected into the melting chamber 13. Such a fuel valve can also be actuated automatically, so as to be able to control or automatically vary the flow of fuel inserted into the combustion chamber 13. In one embodiment, the burner 20 may include a single fuel injector 25 located near the central oxidizer injector 23 and the ignition device 21.

[0095] The ignition device 21 is configured to start combustion of the oxidizer and fuel injected into the melting chamber 13, in order to supply heat to the melting chamber 13. Thus, the burner 20 is able to allow the melting of the aluminum waste in the melting chamber 13. Furthermore, the melting furnace 10 allows the combustion of the organic compounds present in the aluminum waste.

[0096] As illustrated on the figure 1The melting furnace 10 may also include an additional oxidizer lance 27, separate from at least one oxidizer injector 23, and configured to allow the introduction of an additional flow rate of oxidizer into the melting chamber 13. This additional oxidizer lance 27 is not generally included in the burner 20. It may, for example, have a maximum flow rate of oxidizer introduction into the melting chamber 13 that is strictly greater than the maximum flow rate of oxidizer introduction from at least one oxidizer injector 23. Similar to the oxidizer injector 23, the additional oxidizer lance 27 may be a lance of industrially pure oxygen.The arrangements described above make it possible to propose a melting furnace 10 with improved oxidant injection capabilities, which is particularly suitable for improving the combustion of volatile organic compounds VOCs inside the melting chamber 13.

[0097] The melting furnace 10 also includes exhaust means 17 configured to allow the extraction of all or part of the combustion fumes, denoted "F", from inside the melting chamber 13 to an open air zone located outside the melting chamber 13 and where air is free to circulate. As illustrated in the figure 1The melting furnace 10 may include a material inlet door 15 configured to allow the introduction of aluminum scrap into the melting chamber 13 when this door 15 is open. For example, the discharge means 17 of the melting furnace 10 may consist of at least one opening in a wall of the melting furnace 10, for example at the door 15 of the melting furnace 10 used for material inlet. On the figure 1The evacuation means 17 comprise a single opening located on an upper portion of the door 15; however, it is understood that the evacuation means 17 may also include several openings. The arrangements described above allow for a door 15 that is not airtight against combustion fumes F. The design and manufacture of such a door 15 is therefore simplified compared to aluminum scrap melting systems in which the door 15 is airtight. It is thus possible to design and manufacture large rotary melting furnaces 10 capable of receiving a greater quantity of aluminum scrap.

[0098] The aluminum waste melting system 1 further includes a suction hood 30 located outside the melting chamber 13 and designed to capture, by suction, all or part of the combustion fumes F present in the open air zone. The suction hood 30 includes a control duct 31 which may include a suction outlet 33 at which the combustion fumes F are captured. For example, this suction outlet 33 may be located at the exhaust means 17 of the melting furnace 10. In this way, it is possible to rapidly cool the combustion fumes F by mixing them with the open air directly at the furnace outlet, while simultaneously capturing said combustion fumes F. The formation of dioxin by de novo synthesis in the combustion fumes F is thus limited, and the combustion fumes F are cooled and captured directly at the outlet of the melting furnace 10.In other words, the presence of the extraction hood 30 prevents the escape of combustion fumes F outside the aluminum waste melting system 1 and thus limits the diffusion in the workshop in which the melting furnace 10 is located.

[0099] The control line 31 of the extraction hood 30 may also include a filter end 35 opposite the extraction end 33. This filter end 35 may advantageously be equipped with a dust filter 39 configured to filter combustion products separate from the VOCs remaining in the combustion fumes F, at the level of the filter end 35. Advantageously, the dust filter 39 may be a lime filter configured both to capture the remaining dust in the combustion fumes and to neutralize acidic fumes such as hydrochloric acid (HCl). In this way, it is possible to filter the combustion fumes F before they escape from the aluminum waste melting system 1.According to an unrepresented variant, the fusion system 1 includes a carbon dioxide trap disposed at the filtration end 35, said carbon dioxide trap being configured to trap all or part of the carbon dioxide present in the combustion fumes F before they are evacuated from the fusion system 1.

[0100] The control line 31 includes a carbon monoxide sensor 37 configured to measure a carbon monoxide concentration value, denoted "C", in the combustion fumes F captured by the extraction hood 30. The carbon monoxide sensor 37 includes a laser emitter configured to emit laser radiation, and a laser receiver configured to receive said emitted laser radiation and to measure an absorption spectrum of said received laser radiation, the value of the carbon monoxide concentration C being determined from said absorption spectrum thus measured. In other words, the carbon monoxide sensor 37 measures the value of the carbon monoxide concentration C by a laser absorption spectrometry measurement method, also known as TDLAS for "Tunable diode laser absorption spectroscopy" according to established Anglo-Saxon terminology.Advantageously, the use of laser absorption spectrometry with the carbon monoxide sensor 37 allows for the measurement of carbon monoxide concentration (C) with a sensitivity of approximately 0.3 ppm in less than one second. This is particularly advantageous for near real-time control of the melting furnace 10 to monitor the combustion of volatile organic compounds. Furthermore, such a carbon monoxide sensor 37 offers the advantage of being a non-contact measurement method, simplifying maintenance. Finally, this online spectrometric measurement method minimizes interference from other gases, ensuring reliable measurements.

[0101] Finally, the aluminum waste melting system 1 includes a control device 50 configured to receive input information representing the carbon monoxide concentration (C) measured by the carbon monoxide sensor 37, and to control the flow rate of oxidizer injected by said oxidizer injector 23 and / or the flow rate of fuel injected by said fuel injector 25, based on said input information. The oxidizer and fuel flow rates are controlled to keep the VOC levels at the outlet of the melting furnace below a safety value. "Control" means that the control device 50 is capable of regulating or varying the flow rates of oxidizer and / or fuel introduced into the furnace chamber, for example, via one or more valves.In general, the control device 50 is an automaton configured to automatically control the flow rate of oxidant injected by the oxidant injector 23 and / or the flow rate of fuel injected by the fuel injector 25, and / or optionally the rotation speed of the rotating drum 11, for example according to an algorithm stored in a memory of the control device 50. Such an algorithm may include instructions corresponding to operating modes of a control step E6 of the fusion process which will be described later.

[0102] The provisions described above make it possible to propose an aluminum waste melting system 1 capable of melting aluminum waste to obtain liquid aluminum marked "M", while allowing the burning of volatile organic compounds VOCs inside the melting chamber 13. The presence of the carbon monoxide sensor 37 communicating with the control device 50 makes it possible to control the oxidizer and fuel flow rates to keep the VOC level at the outlet of the melting furnace 10 below a safety value.

[0103] The invention also relates to a process for melting aluminum waste using an aluminum waste melting system 1. At the end of the melting process, a step is generally carried out to empty the melting furnace 10 (not shown), in which all or part of the liquid aluminum M contained in the melting chamber is extracted from the melting chamber 13, typically by tipping or siphoning.

[0104] One embodiment of the fusion process is presented, for example, at the figure 2 The melting process first includes a step E1 of making available a melting system 1 of aluminium waste of the type of one of those described previously.

[0105] Prior to the implementation of other steps in the melting process, a calibration step E11 is carried out, in which the control parameters of the melting furnace 10 are determined. As we will see later, these control parameters can be used in a control step E6, which is then implemented differently depending on these furnace control parameters, i.e., depending on the type of melting furnace 10 used, or depending on the size of this melting furnace 10. During the calibration step E11, a correlation law, for example in the form of a linear equation, is established between: an average carbon monoxide concentration Cm measured by the carbon monoxide sensor 37, and an average volatile organic compound [VOC] concentration m measured at the filtration end 35 by a volatile organic compound VOC sensor.

[0106] For example, such a correlation law is established by a linear regression method based on at least three average carbon monoxide concentration values ​​Cm determined from measurements of the carbon monoxide sensor 37, each associated with an average volatile organic compound (VOC) concentration value m determined over the same time interval. Indeed, the applicant surprisingly found that it was possible to establish a linear relationship between the average carbon monoxide concentration Cm at the outlet of the melting furnace 10 and the average VOC concentration m at the filtration end 35. This correlation law is dependent on the melting system 1 used, as it depends in particular on the melting furnace 10, the extraction hood 30, and the dilution rate of the combustion fumes F in the open air before their capture by the extraction hood 30.

[0107] According to one embodiment, the average concentration of volatile organic compounds measured at the filtration end 35 by a volatile organic compound sensor is measured downstream of the dust filter 39, i.e. after the dust filter 39 has filtered the combustion fumes F.

[0108] For example, the time interval corresponds to a melting cycle, which is the time between the introduction of the first quantity of aluminum scrap and the emptying step of the liquid aluminum M. During this melting cycle, an average carbon monoxide concentration value Cm is measured by calculating the arithmetic mean of the carbon monoxide concentration values ​​C measured by the carbon monoxide sensor 37 over said melting cycle. Over the same melting cycle, an average VOC concentration value [VOC]m is measured by calculating the arithmetic mean of the VOC concentration values ​​[VOC] measured by the VOC sensor.

[0109] This average VOC concentration value [VOC] m is then associated with the average carbon monoxide concentration value Cm. This operation is repeated at least three times to obtain at least three pairs of average carbon monoxide concentration values ​​Cm and VOC [VOC] m, allowing a linear equation to be established in the form [ VOCs ] m = α * Cm where [VOC]m is the average VOC concentration measured over a cycle, expressed in milligrams of carbon equivalent per normal cubic meters (mg / Nm³), Cm is the average carbon monoxide concentration measured over a cycle, expressed in ppm, and α is a positive real coefficient. For example, the coefficient α determined in this case is equal to 0.4.

[0110] It is then possible to determine a restart threshold value Sr, a first threshold S1, a second threshold S2, and a third threshold S3 at the end of the calibration step E11, which constitute the control parameters that can be used in the control step E6. These thresholds are determined to limit emissions of volatile organic compounds (VOCs) below defined thresholds, for example by use, or by normative requirements.

[0111] For example, the first threshold S1 could correspond to the following formula: S 1 = 2 5 α COV max

[0112] The second threshold S2 can correspond to the following formula: S 2 = 2 α COV max

[0113] The third threshold S3 can correspond to the following formula: S 3 = 4 α COV max

[0114] The restart threshold value Sr can correspond to the following formula: Sr = 3 5 α COV max where α is the coefficient determined by establishing the linear equation described above, and where [VOC]max is a maximum average VOC concentration value over a cycle, arbitrarily set by the user, or by regulatory or normative requirements.

[0115] Although such values ​​are not limiting, setting such thresholds by the correlation law, based on the maximum average VOC concentration value over a cycle, arbitrarily set by the user, or by regulatory or normative requirements, ensures that VOC emissions will remain on average over a melting cycle contained at concentrations below a safety value and will be below regulatory thresholds.

[0116] The melting process then includes a first introduction step E21 in which an initial quantity of said aluminum waste is introduced into the melting chamber 13 of the melting furnace 10. The first introduction step E21 may also include the introduction of at least one salt along with the aluminum waste. Thus, during the melting step described later, it is possible to obtain a slag L covering the liquid aluminum M and comprising alumina and said at least one salt. Advantageously, the introduction of at least one salt during the first introduction step E21 makes it possible to trap residual solid organic compounds (polycyclic aromatic hydrocarbons, soot, etc.) that result from the thermolysis of the organic materials present in the aluminum waste.This L slag also has the advantage of forming a protective layer against oxidation which is particularly useful during all stages of the melting process, and especially during the E6 pilot stage.

[0117] Once the initial materials required for melting have been introduced into the furnace, the melting process includes a melting step E3 in which the ignition device 21 is lit so that the burner 20 supplies heat to the melting chamber 13 of the melting furnace 10 when it is supplied with oxidizer and fuel respectively by the oxidizer injector 23, and by the fuel injector 25. This melting step E3 thus leads to the formation by melting of liquid aluminum M, and to the formation of combustion fumes F, but also of slag L if a salt has been introduced into the melting chamber 13.

[0118] The melting process generally includes a cooling stage E4, in which the combustion fumes F are diluted and cooled in open air outside the melting chamber 13. As can be seen on the figure 1The cooling stage E4 may include an exhaust stage in which the exhaust means 17 are activated to allow the exhaust of the combustion fumes F produced during the melting stage E3 to the outside of the melting chamber 13 and into the open air. Subsequently, a suction stage may be implemented, in which the extraction hood 30 captures the combustion fumes F present in the open air outside the melting furnace 10 by suction. The arrangements described above allow the combustion fumes F to be cooled outside the melting chamber 13 in the open air. This cooling stage E4 is particularly advantageous because it allows the combustion fumes F to be diluted and cooled while minimizing the formation of toxic dioxins.

[0119] Once the combustion fumes F are captured by the extraction hood 30, the melting process includes the measurement step E5, in which the carbon monoxide sensor 37 measures the carbon monoxide concentration C in the combustion fumes F. This measurement step E5 allows for the real-time determination of the carbon monoxide concentration C in the combustion fumes F, very quickly after these fumes F have been formed. This is particularly advantageous because it allows for the rapid determination of the VOC concentration in the combustion fumes F, for example, by referring to the formula established during the calibration step E11. It is understood that in a melting cycle, the cooling step E4 and the measurement step E5 can be implemented simultaneously and continuously.

[0120] The melting process also includes the pilot stage E6, in which the control device 50 receives input information representing the carbon monoxide concentration (C) measured by the carbon monoxide sensor 37, and controls the flow rate of oxidizer injected by the oxidizer injector 23, and / or controls the flow rate of fuel injected by the fuel injector 25, based on said input information. The oxidizer and fuel flow rates are controlled to keep the VOC levels at the outlet of the melting furnace below a safety value. "Control" means that the control device 50 is capable of regulating or varying the flow rates of oxidizer and / or fuel introduced into the furnace chamber, for example, via one or more valves.

[0121] In particular, and as detailed in the non-exhaustive embodiment of the figure 2, during the piloting step E6, the control device 50 controls the flow of oxidant injected by the oxidant injector 23, and / or the flow of fuel injected by the fuel injector 25 according to the following operating modes.

[0122] A first operating mode Mod1 involves selecting the oxidizer flow rate and fuel flow rate to introduce the oxidizer and fuel into the melting chamber 13 in stoichiometric proportions. This first operating mode Mod1 is established if the carbon monoxide concentration (C) is strictly below the first threshold S1, for example, as determined during calibration step E11. In one embodiment, the first threshold S1 is substantially equal to 25 ppm, 30 ppm, 35 ppm, or 40 ppm. Optionally, the first operating mode Mod1 may also include a second introduction step E22 in which a second quantity of aluminum scrap is introduced into the melting chamber 13 of the melting furnace 10.For example, it can be planned that the second introduction step E22 is implemented when the control device 50 drives the oxidizer flow rate and the fuel flow rate in the first operating mode directly after having driven the oxidizer flow rate and the fuel flow rate in an operating mode selected from a second, third, or fourth operating mode described below. Thus, it is possible to adjust the amount of aluminum scrap introduced into the melting chamber 13 without first measuring the amount of volatile organic compounds (VOCs) in the aluminum scrap. The melting yield of liquid aluminum M is thereby increased.

[0123] A second operating mode involves varying the ratio between the oxidizer flow rate and the fuel flow rate. This ratio varies between an initial ratio corresponding to the introduction of the oxidizer and fuel under stoichiometric conditions into the fusion chamber 13, and a maximum ratio corresponding to a zero fuel flow rate introduced into the fusion chamber 13 and a maximum oxidizer flow rate introduced into the fusion chamber 13 by the oxidizer injector 23. This ratio between the oxidizer flow rate and the fuel flow rate is varied according to the carbon monoxide concentration C measured by the carbon monoxide sensor 37. It is therefore clear that in the second operating mode Mod2, the oxidizer is always introduced either under stoichiometric conditions with respect to the fuel or in excess.To achieve this, it is possible either to increase the flow rate of oxidizer introduced into the fusion chamber 13 by the oxidizer injector 23, or to decrease the flow rate of fuel introduced into the fusion chamber 13 by the fuel injector 25, or both. The variation in the ratio between the fuel flow rate and the oxidizer flow rate introduced into the fusion chamber 13 can be proportional to the carbon monoxide concentration C, or related to the carbon monoxide concentration by an exponential relationship or any other relationship determined by those skilled in the art, for example, experimentally. This second operating mode Mod2 is established if the value of the carbon monoxide concentration C is strictly less than a second threshold S2 and greater than or equal to the first threshold S1. Thus, the first threshold S1 is strictly less than the second threshold S2.In one embodiment, the second threshold S2 is approximately equal to 125 ppm, 150 ppm, 175 ppm, or 200 ppm. More generally, the second threshold S2 may be approximately equal to five times the value of the first threshold S1. By "approximately equal to," we mean within ±10%.

[0124] A third operating mode, Mod3, involves setting the oxidizer flow rate to its maximum value, stopping the fuel flow, and shutting off the ignition device 21. This third operating mode, Mod3, is established if the carbon monoxide concentration (C) is strictly less than a third threshold, S3, and greater than or equal to the second threshold, S2. Thus, the second threshold, S2, is strictly less than the third threshold, S3. In one embodiment, the third threshold, S3, is substantially equal to 250 ppm, 300 ppm, 350 ppm, or 400 ppm. More generally, the third threshold, S3, can be substantially equal to twice the value of the second threshold, S2.

[0125] Since the third operating mode Mod3 includes switching off the ignition device, it is sometimes necessary to restart the melting step E3 once the measured carbon monoxide concentration C has fallen below a certain threshold, thus saving time on the aluminum scrap melting process. Therefore, if the ignition device 21 is switched off, and if the carbon monoxide concentration C is strictly less than a restart threshold value Sr, then the ignition device 21 is switched on. The restart threshold value Sr is generally strictly greater than the first threshold S1 and strictly less than the second threshold S2. In one embodiment, the restart threshold value Sr is substantially equal to 37.5 ppm, 45 ppm, 52.5 ppm, or 60 ppm. More generally, the restart threshold value Sr is substantially equal to 1.5 times the value of the first threshold S1.Advantageously, reigniting the ignition device 21 once the carbon monoxide concentration C is below a sufficiently low threshold allows the melting of the aluminum waste to be restarted, and limits the formation of oxides on the surface of the liquid aluminum M. This arrangement makes it possible to take into account possible hysteresis phenomena during the melting of the metal and the combustion of the organic coatings, which are linked to the inertia of the melting furnace 10.

[0126] Finally, a fourth operating mode, Mod4, involves setting the oxidizer flow rate to its maximum value, stopping the fuel flow rate, and switching off the ignition device 21 if it has not already been switched off. This fourth operating mode, Mod4, is activated if the carbon monoxide concentration (C) is strictly greater than the third threshold, S3. Advantageously, if the melting furnace 10 is a rotary furnace comprising a rotating drum 11, the fourth operating mode, Mod4, also includes varying, and in particular decreasing, the rotational speed of the rotating drum 11. Furthermore, if the melting furnace 10 includes an additional oxidizer nozzle 27, then the fourth operating mode, Mod4, also includes introducing an additional flow of oxidizer into the melting chamber 13 through the additional nozzle 27.In this way, it is possible to increase the amount of oxidant introduced into the melting chamber 13, and to destroy by combustion a greater quantity of volatile organic compounds VOCs without decreasing the melting temperature of the melting furnace 10.

[0127] The control of the oxidizer and fuel injectors 23, 25 both limits the formation of volatile organic compounds (VOCs) and protects against the risk of over-oxidation. Indeed, if the oxidizer and fuel injectors 23, 25 are positioned in the second, third, and fourth operating modes (Mod2, Mod3, and Mod4), thus in stoichiometric oxidation for gas injection, the excess oxidizer is consumed to limit the formation of VOCs and does not oxidize the liquid aluminum M. Furthermore, and advantageously, if the melting process includes the introduction of at least one salt, the slag L formed acts as a shield against the oxidation of the liquid aluminum M by the injected oxidizer.

[0128] It is understood that the melting process steps described above can be repeated or implemented continuously throughout the entire duration of the aluminum scrap melting process. In particular, the pilot step E6 is carried out after the measurement step E5 within the same phase, and this phase can be repeated over time, notably cyclically, periodically, or continuously. For example, the measurement step E5 can be implemented several times over a pilot time interval, so as to implement the pilot step E6 several times over said pilot time interval. Similarly, the measurement step E5 and the pilot step E6 are implemented simultaneously and / or continuously and in real time over the pilot interval. Thus, it is possible to control the melting furnace 10 in real time during the pilot process.In this way, it is possible to optimize the melting time of the quantity of aluminum waste, while limiting the amount of volatile organic compounds (VOCs) released from the melting chamber 13.

[0129] All the provisions described above make it possible to propose a melting process which allows both the formation of liquid aluminium M from aluminium waste and the limitation of the quantity of volatile organic compounds in the combustion fumes F evacuated from the melting chamber 13 of the melting furnace 10 by the thermolysis of said volatile organic compounds in-situ in the melting furnace 10.

Claims

1. Aluminum scrap melting system (1) for melting aluminum scrap, the melting system (1) comprising: - a melting furnace (10) intended to melt said aluminum scrap, and comprising: - a drum (11) internally delimiting a melting chamber (13) intended to receive said aluminum scrap to be melted; - a burner (20) comprising a firing device (21), at least one oxidant injector (23), and at least one fuel injector (25), said oxidant injector (23) being configured to inject an oxidant flow inside the melting chamber (13), said fuel injector (25) being configured to inject a fuel flow inside the melting chamber (13), and the firing device (21) being configured to start a combustion of the oxidant and the fuel injected into the melting chamber (13), to supply heat into the melting chamber (13); - evacuation means (17) configured to make it possible to extract all or some of the combustion fumes (F) from inside the melting chamber (13) to a vent zone located outside the melting chamber (13) and where air is free to circulate; - a suction hood (30) disposed outside the melting chamber (13) and intended to capture by suction all or some of said combustion fumes (F) present in the vent zone, said suction hood (30) furthermore comprising an inspection pipe (31) comprising a carbon monoxide sensor (37) configured to measure a value of a carbon monoxide concentration (C) in said combustion fumes (F) captured by the suction hood (30), the carbon monoxide sensor comprising a laser emitter configured to emit a laser radiation, and a laser receiver configured to receive said emitted laser radiation, and to measure an absorption spectrum of said received laser radiation, the value of the carbon monoxide concentration (C) being determined on the basis of said absorption spectrum thus measured; - a control device (50) configured to receive an item of input information representative of the value of the carbon monoxide concentration (C) measured by the carbon monoxide sensor (37), and to pilot said oxidant flow injected by said oxidant injector (23) and / or said fuel flow injected by said fuel injector (25), according to said item of input information, the oxidant and fuel flows being piloted to contain the volatile organic compound content (VOC) at the output of the melting furnace at concentrations less than a safety value.

2. Aluminum scrap melting system (1) according to claim 1, wherein the melting furnace (10) is a rotary furnace comprising a rotary drum (11) configured to be rotated.

3. Aluminum scrap melting system (1) according to any one of claims 1 or 2, wherein the evacuation means (17) of the melting furnace (10) comprise at least one opening formed in a wall of the melting furnace (10).

4. Aluminum scrap melting system (1) according any one of claims 1 to 3, wherein the melting furnace (10) comprises an additional oxidant lance (27) distinct from the at least one oxidant injector (23), and configured to allow the introduction of an additional oxidant flow inside the melting chamber (13).

5. Aluminum scrap melting system (1) according to any one of claims 1 to 4, wherein the oxidant injector (23) is an industrially pure oxygen injector.

6. Aluminum scrap melting system (1) according to any one of claims 1 to 5, wherein the inspection pipe (31) of the suction hood (30) comprises a suction end (33) at which the combustion fumes (F) are captured, and a filtration end (35), opposite the suction end (33), said filtration end (35) being equipped with a dust filter (39) configured to filter residue remaining in the combustion fumes (F), at the filtration end (35).

7. Process for melting aluminum scrap by an aluminum scrap melting system (1), the melting process comprising: - a step (E1) of providing an aluminum scrap melting system (1) according to any one of claims 1 to 6; - a first introduction step (E21) wherein a first quantity of said aluminum scrap is introduced into the melting chamber (13) of the melting furnace (10); - a melting step (E3) wherein the firing device (21) is fired so that the burner (20) supplies heat into the melting chamber (13) of the melting furnace (10) when it is supplied with oxidant and with fuel respectively by the oxidant injector (23), and by the fuel injector (25), said melting step (E3) resulting in the formation of liquid aluminum (M) by melting, and in the formation of combustion fumes (F); - a measurement step (E5) wherein the carbon monoxide sensor (37) measures the value of the carbon monoxide concentration (C) in the combustion fumes (F) captured by the suction hood (30); - a piloting step (E6) wherein the control device (50) receives an item of input information representative of the value of the carbon monoxide concentration (C) measured by the carbon monoxide sensor (37), and pilots the oxidant flow injected by the oxidant injector (23) and / or pilots the fuel flow injected by the fuel injector (25), according to said item of input information, wherein the oxidant and fuel flows are piloted to contain the volatile organic compound content (VOC) at the output of the melting furnace at concentrations less than a safety value, - the process furthermore comprising a prior calibration step (E11), wherein a correlation law is established between: - a mean carbon monoxide concentration (Cm) measured by the carbon monoxide sensor (37), and - a mean volatile organic compound concentration (VOC) measured at the filtration end (35) by a volatile organic compound sensor (VOC), said correlation law being established on the basis of at least three mean carbon monoxide concentration values (Cm) measured by the carbon monoxide sensor (37), each associated with a mean volatile organic compound concentration value ([VOC]m) measured over the same time interval.

8. Melting process according to claim 7, wherein the first introduction step (E21) furthermore comprises the introduction of at least one salt, so as to obtain a slag (L) covering the liquid aluminum (M) and comprising alumina and said at least one salt during the melting step (E3).

9. Melting process according to any one of claims 7 or 8, wherein, during the piloting step (E6), the control device (50) pilots the oxidant flow injected by the oxidant injector (23), and / or the fuel flow injected by the fuel injector (25) according to the following operating modes: - a first operating mode (Mod1) wherein the oxidant flow and the fuel flow are chosen to introduce the oxidant and the fuel into the melting chamber (13) in stoichiometric proportions, the first operating mode (Mod1) being established if the value of the carbon monoxide concentration (C) is strictly less than a first threshold (51); - a second operating mode (Mod2) wherein a ratio between the oxidant flow and the fuel flow is varied between an initial ratio corresponding to an introduction under stoichiometric conditions of oxidant and fuel into the melting chamber (13) respectively by the oxidant injector (23) and the fuel injector (25), and a maximum ratio corresponding to a zero fuel flow introduced by the fuel injector (25) into the melting chamber (13), and a maximum oxidant flow introduced by the oxidant injector (23) into the melting chamber (13), said ratio between the oxidant flow and the fuel flow being varied according to the value of the carbon monoxide concentration (C) measured, the second operating mode (Mod2) being established if the value of the carbon monoxide concentration (C) is strictly less than a second threshold (S2) and greater than or equal to the first threshold (S1); - a third operating mode (Mod3) wherein the oxidant flow is placed at the maximum oxidant flow value, the fuel flow is stopped, and the firing device (21) is switched off, the third operating mode (Mod3) being established if the value of the carbon monoxide concentration (C) is strictly less than a third threshold (S3) and greater than or equal to the second threshold (S2); - a fourth operating mode (Mod4) wherein the oxidant flow is placed at a maximum oxidant flow value, the fuel flow is stopped, the firing device (21) is switched off, the fourth operating mode (Mod4) being established if the value of the carbon monoxide concentration (C) is strictly greater than the third threshold (S3), - said thresholds being determined to limit the volatile organic compound emissions (VOC) lower than defined thresholds.

10. Melting process according to claim 9, wherein the provision step (E1) comprises providing an aluminum scrap melting system (1) according to claim 5, and wherein the fourth operating mode (Mod4) furthermore comprises introducing an additional oxidant flow inside the melting chamber (13) by the additional lance (27).

11. Melting process according to any one of claims 9 or 10, wherein the first operating mode (Mod1) comprises the implementation of a second introduction step (E22) wherein a second quantity of aluminum scrap is introduced into the melting chamber (13) of the melting furnace (10).

12. Melting process according to any one of claims 9 to 11, wherein during the piloting step (E6), if the firing device (21) is switched off, and if the value of the carbon monoxide concentration (C) is strictly less than a restart threshold value (Sr), then the firing device (21) is switched on, the restart threshold value (Sr) being strictly greater than the first threshold (S1) and strictly less than the second threshold (S2).

13. Melting process according to any one of claims 7 to 12, further comprising a cooling step (E4), wherein the combustion fumes (F) are diluted and cooled in the free air outside the melting chamber (13).

14. Melting process according to any one of claims 7 to 13, wherein the piloting step (E6) is carried out after the measurement step (E5) within the same phase and said phase is repeated over time, in particular cyclically or periodically.

15. Melting process according to any one of claims 7 to 14, wherein the oxidant flow injected by the oxidant injector, and / or the fuel flow injected by the fuel injector are adjusted to maintain an oxidation stoichiometry for the gas injection.