Process for heating metal semi-finished products, especially steel semi-finished products, and hybrid power heating plant
The hybrid heating plant integrates electric preheating of combustible fluids with heat exchangers to enhance energy efficiency and reduce emissions, addressing the limitations of hydrogen and induction heating in metal furnaces.
Patent Information
- Authority / Receiving Office
- KR · KR
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2026-07-21
Smart Images
Figure PCT00001_ABST
Abstract
Description
Technology Field
[0001] The present invention relates to a process and a heating plant for heating metal semi-finished products, particularly steel semi-finished products, using a hybrid combustible material and electric energy.
[0002] The present invention relates to the field of metallurgical heating furnaces used in the steel industry to heat metal semi-finished products before they undergo hot plastic working processes such as rolling.
[0003] In particular, the present invention relates to continuous type metal heating furnaces, which generally consist of a longitudinally extended straight or circular working chamber having a first opening for introducing semi-finished products to be heated and a second opening for discharging the heated semi-finished products. Inside the working chamber, there is an advancing assembly for moving the semi-finished products to be heated from the first opening to the second opening. This advancing assembly varies according to the typology of the semi-finished products (slabs, billets, rods, etc.) and may be a walking beam, a roller hearth, or other type. To heat semi-finished products, open flame burners or radiant tube burners are generally used depending on the application, and are powered by combustible materials that may be, for example, fossil fuels (natural gas), combustible materials that can be produced from renewable sources (biogas, hydrogen produced from water electrolysis), combustible materials that can be recovered from other processes (coke oven gas), or mixtures thereof. Background Technology
[0004] The working chamber of a furnace is generally divided into two zones, Zone 1 and Zone 2, which are arranged sequentially along the advancing direction of the semi-finished products. Typically, one or more burners are placed in Zone 2 to generate thermal energy through the combustion of combustible gases. Combustion products (flue gases) travel in the opposite direction to the advance of the semi-finished products, passing through Zone 2 to reach Zone 1. Zone 1 generally lacks thermally active elements, and preheating of the semi-finished products occurs while simultaneously cooling the flue gases passing through it. These cooled flue gases are drawn in along the flue gas plant and released into the atmosphere through the chimney.
[0005] To improve plant performance, heat exchangers are commonly installed, and flue gases discharged from the furnace release heat by preheating combustible material (typically air).
[0006] In response to industrial processes, particularly the decarbonization and energy transition policies of the steel industry, there is a problem of reducing the total carbon dioxide emissions (carbon footprint) of these metal furnaces.
[0007] The first known solution involves the use of combustible gases produced from renewable sources. In particular, the use of hydrogen produced by the electrolysis of water in electrolytic cells powered by renewable electricity has been proposed and industrially tested; when used in a pure form, this fuel reduces CO₂ emissions to virtually zero. While this solution has the advantage of being applicable to existing metal furnaces without significant structural changes, it has the disadvantage that the efficiency of power utilization is not optimized. In fact, considering the current performance of electrolysis processes and modern metal furnaces, it can be inferred that only 40% to 60% of the power used to produce hydrogen is actually transferred to the semi-finished products in the form of thermal energy.
[0008] Another known solution involves directly utilizing electricity within the furnace by introducing systems that heat metal semi-finished products by induction: that is, specific electric windings carrying alternating currents are installed to generate variable magnetic fields, which induce current within the semi-finished product, heating it by the Joule effect. On the other hand, this system has the advantage of utilizing electricity more efficiently than the previous case. Conversely, the use of induction heating is limited by two aspects:
[0009] First, above the Curie temperature (about 750°C), steel semi-finished products lose their magnetic properties, making induction heating inefficient.
[0010] - In addition, if an oxidizing atmosphere is present (such as in the first preheating zone where the oxygen concentration is higher than in the second zone where the burners are installed due to an inevitable inlet of air), a significant amount of metal oxides (scale) will form on the surface of the semi-finished products if the temperature exceeds 900°C, which will not be suitable for subsequent plastic processing processes (e.g., rolling).
[0011] Therefore, it is necessary to develop plants and processes that can overcome the problems arising from the above technology, reduce carbon dioxide emissions from fossil combustible materials, maintain the quality of heated semi-finished products, and increase the utilization efficiency of energy sources.
[0012] These objectives according to the present invention are achieved by providing a heating plant and process for heating metal semi-finished products, particularly steel semi-finished products, as specified in the independent claim.
[0013] Additional features are provided in dependent claims.
[0014] The features and advantages of the heating plant and process for metal semi-finished products, particularly steel semi-finished products, according to the present invention will become more apparent from the following exemplary and non-limiting description with reference to the attached schematic drawings: Brief explanation of the drawing
[0015] FIG. 1 is a schematic diagram of a first possible embodiment of a plant according to the present invention; FIG. 1a is a schematic diagram of a possible embodiment of a plant according to the present invention as an alternative to FIG. 1; FIG. 2 is a graphic representation of a plane showing the exchanged heat (Q) on the x-axis and the temperature (T) on the y-axis of a first embodiment of a process according to the present invention that can be implemented in a plant according to FIG. 1 or FIG. 1a; FIG. 3 is a schematic diagram of a second possible embodiment of a plant according to the present invention; FIG. 3a is a schematic diagram of a possible embodiment of a plant according to the present invention as an alternative to FIG. 3; FIGS. 4 and 5 are graphic representations of a plane showing the heat exchange amount (Q) on the x-axis and the temperature (T) on the y-axis of two possible variations of a second embodiment of a process according to the present invention that can be implemented in a plant according to FIG. 3 or FIG. 3a; FIG. 6 is a block diagram of a process according to the present invention; FIG. 7 is a schematic diagram of a first possible embodiment of a burner of a plant according to the present invention, wherein the electric unit is an integral part of the burner, and the burner includes a recuperative type heat exchanger; FIGS. 8a and 8b are schematic diagrams illustrating two different operational configurations of a second embodiment of a burner of a plant according to the present invention, wherein the electric unit is an integral part of the burner, and the burner also includes a regenerative type heat exchanger; FIGS. 9a and 9b are schematic diagrams illustrating two different operational configurations of a third embodiment of a burner of a plant according to the present invention, wherein the electric unit is a unit separated from the burner and is integrated into an adjacent regenerative type heat exchanger; Specific details for implementing the invention
[0016] Referring to the attached drawing, a heating plant 10 for heating metal semi-finished products SM, particularly steel semi-finished products, before undergoing subsequent processing processes, particularly hot plastic processing processes such as rolling, is schematically illustrated.
[0017] Metal semi-finished products SM can consist of, for example, steel slabs, billets, rods, blooms, etc.
[0018] Heating plant 10 is:
[0019] - Metal heating furnace for heating metal semi-finished products SM 20 - The metal heating furnace,
[0020] - A work chamber 201 having at least one inlet opening 202 for an inlet of metal semi-finished products SM to be heated and at least one outlet opening 203 for an outlet of metal semi-finished products SM heated,
[0021] - A transfer assembly 204 that advances metal semi-finished products SM along work chamber 201 from inlet 202 to outlet 203,
[0022] - comprising at least one burner 30 coupled to a metal furnace 20, having at least one outflow opening 302 for a combustible fluid fluid fluidly connected directly or indirectly to a combustion chamber fluidly, and at least one outflow nozzle 301 for a combustible fluid fluid fluidly connected directly or indirectly to a combustion chamber fluidly, wherein the combustion chamber is defined by a working chamber 201, or is in a state of fluid communication or heat exchange with the working chamber 201; and
[0023] - First supply duct 40 supplying combustible fluid - The first supply duct 40 is fluidly connected to the outlet nozzle 301 of burner 30 at the outlet, and connected to the source 400 of combustible fluid at the inlet -;
[0024] - Second supply duct 50 supplying combustible fluid - The second supply duct 50 is fluidly connected to the outlet 302 of burner 30 at the outlet, and connected to a source 500 of combustible material having a feeding temperature T0 at the inlet -;
[0025] - A suction duct 60 for sucking in at least one fraction of the atmosphere inside the working chamber 201 and / or combustion products from the burner 30 - the suction duct 60 is fluidly connected to the combustion chamber and / or working chamber 201 at the inlet and connected to the flue gas treatment and suction unit 600, 601 at the outlet -; comprises.
[0026] According to the present invention, the heating plant 10 further comprises at least one heat-generating electric unit 70 disposed along a second supply duct 50 upstream of the outlet 302 of the burner 30.
[0027] The electric unit 70 is coupled to the electric power source 700 and converts the electric power into thermal energy to generate heat that preheats the combustible fluid supplied to the burner 30 to a final pre-heating temperature T2, which is higher than the feeding temperature T0 of the combustible material.
[0028] The electric unit 70 includes one or more electric heaters that may be of the type having one or more electric resistors, electric arc type, or plasma type.
[0029] Preferably, the electric unit 70 includes one or more electric resistors 701, and the power supplied thereto is converted into thermal energy by the Joule effect.
[0030] One or more electric resistors 701 may be in direct contact with the flow of a combustible fluid or may be thermally connected to ducts 702 through which the flow of the combustible fluid passes. Ducts 702 are integral parts of the second supply duct 50 or are fluidly connected to the second supply duct 50.
[0031] Alternatively, the electric unit 70 is an electric arc type and heats the combustible fluid directly or indirectly.
[0032] According to additional alternatives, the electric unit 70 is one or more plasma torch types.
[0033] In any case, the electric unit 70 converts the supplied power into thermal energy to generate heat that heats a combustible fluid directly or indirectly without changing its chemical composition.
[0034] Power source 700 has the advantage of being of a type generated from a renewable source. "Power source 700" refers to any electric plant, unit, or circuit that provides power to electric unit 70, such as, for example, a dedicated electric generator or a branch of an electric supply line.
[0035] As explained in detail below, the heating plant 10 is:
[0036] - At least one central electric unit 70, i.e., an electric unit 70 separated from and located externally from one or more burners 30 and positioned along a section of a second supply duct 50 upstream of each burner 30 to preheat the combustible fluid supplied to the inlet of each burner 30 (Figs. 1 and 3); or
[0037] - At least one electric unit 70 located locally to one or more burners 30, i.e., an electric unit 70 positioned upstream of each outlet 302 along a section of a second supply duct 50 that is integrated onboard to the burner 30 or connected in proximity to it, for preheating a combustible fluid supplied through each outlet 302 (Figs. 1a, 3a and 7 to 9b).
[0038] The reason this latter embodiment is preferred is that by electrically preheating the combustible fluid near outlets 302, the length of the section of the second supply duct 50 extending from the electric unit 70 to outlets 302 is reduced; thus, heat dispersion occurring along the section is limited and, consequently, thermal insulation costs are reduced. This preferred embodiment further improves the flexibility of the operation management of individual burners, making it possible for the local electric unit 70 to be activated / deactivated or controlled separately and independently from the other burners.
[0039] In a preferred embodiment, the heating plant 10 is:
[0040] - Includes at least one heat exchanger 80 fluidly connected to a second supply duct 50 and / or suction duct 60, and preheating a combustible material to a first preheating temperature T1 lower than a final preheating temperature T2, which at least partially recovers residual sensible heat of at least one fraction of the inhaled atmosphere and / or inhaled combustion products from the burner inside the work chamber from the feeding temperature T0. The heat exchanger 80 is equipped with at least one inlet 801 of the combustible material to be preheated and at least one outlet 802 of the preheated combustible material. If the heating plant 10 includes the heat exchanger 80, an electric unit 70 is positioned along the second supply duct 50 downstream of the inlet 801 of the combustible material to be heated to the heat exchanger 80. Advantageously, for heat exchange efficiency, the electric unit 70 is positioned along the second supply duct 50 downstream of outlet 802 from the heat exchanger 80 where the combustible material is preheated.
[0041] The heat exchanger 80 can be of the recuperative or regenerative type.
[0042] A recovery type heat exchanger refers to a heat exchanger in which thermal energy is directly released from the heating fluid to the heated fluid through a wall between them. In this case, the heat exchanger 80 is fluidly connected simultaneously with the second supply duct 50 and the suction duct 60 (Figs. 1, 1a, 3a, and 7).
[0043] A regenerative type heat exchanger refers to a heat exchanger in which a heat storage and exchange unit exists, wherein thermal energy is first stored (storage or heating stage) while a heating fluid passes through it, and then thermal energy is released to the fluid while a fluid to be heated passes through it (release or cooling stage). In this case, the heat exchanger 80 is fluidly connected to a second supply duct 50, alternatively a suction duct 60 (Figs. 8a-8b and 9a-9b). For a regenerative type heat exchanger, two storage and exchange units are generally provided, which operate alternately and selectively in the storage and heat release stages via a valve assembly to ensure continuous operation. As is known, the storage and exchange units are composed of metal sheets or packs of elements, or a matrix made of refractory or ceramic material, etc.
[0044] As explained in detail below, the heating plant 10 is:
[0045] - At least one central heat exchanger 80, i.e., separated from and external to one or more burners 30, and a heat exchanger 80 positioned along a section of the second supply duct 50 upstream of the electric unit 70 if the electric unit 70 is acquired as a central unit (regardless of whether it is integrated into the heat exchanger itself, FIG. 1 and FIG. 3, or positioned upstream of each burner 30 if the electric unit 70 is acquired as a unit adjacent to the burner 30, FIG. 1a and FIG. 3a) or
[0046] - Includes at least one heat exchanger 80 adjacent to one or more burners 30, that is, to preheat combustible material supplied from an inlet to each electric unit 70, a heat exchanger 80 (Figs. 7 to 9b) which is built into or connected adjacently to the burner 30 and is positioned upstream of each electric unit 70 adjacent thereto along a section of a second supply duct 50 that is integrated into or connected adjacently to the same burner 30.
[0047] In a preferred embodiment, the heating plant 10 comprises at least one central heat exchanger 80 (advantually of a recovery type) and, for one or more burners 30, each electric unit 70 adjacent to the burner 30 (Figs. 1a and 3a). In an alternative embodiment, the heating plant 10 comprises:
[0048] - Includes a bypass line 90 that is fluidly connected to the suction duct 60 through at least one bypass valve 900 and connected to the second supply duct 50 upstream of the electrical unit 70.
[0049] Advantageously, if the heating plant 10 includes a heat exchanger 80 and a bypass line 90, the latter is connected to a second supply duct 50 downstream of outlet 802 from the heat exchanger 80 of the combustible material preheated therein.
[0050] The bypass valve 900 is controlled to provide at least one recirculation fraction of the inhaled atmosphere inside the work chamber 201 and / or the inhaled combustion products from the burner 30 to the second supply duct 50 and the suction duct 60. In this case, the combustible fluid supplied, which is heated by the electric unit 70 and then discharged through the outlets 302, is a mixture of the recirculation fraction and the combustible fluid that can be preheated to temperature T1.
[0051] In a preferred embodiment, the bypass valve 900 is controlled to provide the entire amount of the inhaled fraction of the atmosphere inside the work chamber 201 and / or the inhaled combustion products from the burner 30 to the second supply duct 50 and the suction duct 60. In this case, the combustible material supplied, which is heated by the electric unit 70 and then discharged through the outlets 302, is a mixture of combustible material and recirculated fluid, or consists only of recirculated fluid, excluding the heat exchanger 80 available from the circuit. As mentioned, the electric unit 70 may be obtained as a unit separate from the burner 30 or as an integral part of the burner 30.
[0052] In particular, the electric unit 70 can be obtained as a central unit separated from each burner 30, or preferably as a local unit integrated with one or more burners 30.
[0053] Likewise, the heat exchanger 80 can be obtained as a unit separate from the burner 30 or as a unit integrated into the burner 30.
[0054] In particular, the heat exchanger 80 can preferably be obtained as a central unit separated from each burner 30, or as a local unit integrated with one or more burners 30, in the latter case, one or more burners 30 are equipped with an electric unit 70 adjacent to the burner 30.
[0055] Where there is a heat exchanger 80 obtained as a central unit separated from the burner 30, the electric unit 70 may be obtained as a unit separated from the heat exchanger or as a unit integrated with the heat exchanger. In any case, the electric unit 70 is placed downstream of inlet 801, preferably downstream of outlet 802 of combustible material from the heat exchanger. Where the electric unit 70 is obtained as a unit separated from the heat exchanger 80, it may be obtained as a central unit separated from the burner 30 or as a local unit integrated with one or more burners 30.
[0056] If there is a heat exchanger 80 obtained as a local unit integrated into one or more burners 30, provided, an electric unit 70 is obtained as a local unit integrated into the burner 30 itself. In any case, the electric unit 70 is placed downstream of inlet 801, and preferably downstream of outlet 802 of combustible material from heat exchanger 80.
[0057] In a preferred embodiment, the heating plant 10 is:
[0058] - Includes at least one temperature sensor 211 for measuring the temperature inside a work chamber 201 connected to a control and processing electronic unit 100 and / or at least one oxygen concentration measuring device 210 for measuring the oxygen concentration inside the work chamber 201, and the control and processing electronic unit 100 controls an electric unit 70 and a burner 30 according to the measured oxygen concentration and / or temperature. The measured temperature is an input parameter of a temperature regulator that manages the power of one or more burners 30 to reach a desired temperature. The measured oxygen concentration may be used to control each burner to manage the ratio of combustible material to flammable material.
[0059] If a bypass line 90 is also present, the control and processing electronic unit 100 controls the electric unit 70, burner 30, and bypass valve 900 according to the measured oxygen concentration and temperature. As will be discussed below, in particular, if the metal furnace 20 is fluid-tight and a suction device capable of handling fluid current at flow rates and temperatures (>700°C) that characterize such a metal furnace is available, the electronic unit 100 controls the burner 30, electric unit 70, and valve 900 to supply only flue gas of appropriate temperature and oxygen content while operating without combustible material.
[0060] The heating plant 10 and its operation are described in more detail with reference to the attached drawings.
[0061] The expressions “upstream” and “downstream” each mean preceding and following a determined reference point taken along the direction of flow of fluid flow, such as the direction of flow of a combustible fluid flowing along the second supply duct 50 from the source 500 of combustible material to the outlet 302, or along the direction of movement of metal semi-finished products SM.
[0062] Combustible substances refer to combustible fluids, and generally refer to gaseous combustible substances such as natural gas, LPG, hydrogen, gases produced in primary processes such as coke oven gas and blast furnace gas, and mixtures thereof.
[0063] A combustible substance refers to a fluid that chemically reacts with a combustible substance to oxidize (combust); the combustible substance may be, for example, air or oxygen-enriched air (i.e., air in which the oxygen content is generally 21% or more by volume). If the combustible substance is air, the source of the combustible substance 500 consists of the environment outside the metal heating furnace 20.
[0064] The first supply duct 40 includes a set of ducts through which fluid flow of a combustible material flows, starting from a source 400 of combustible fluid and supplied to an outlet nozzle 301. The first supply duct 40 may connect the source 400 of combustible fluid to the outlet nozzle 301 and may be provided at least partially inside the burner 30.
[0065] An outlet nozzle 301 may be obtained at the end of at least one injection lance 311 mounted on the burner 30. The lance 311 may form part of the first supply duct 40 or be connected to the first supply duct 40 through a fluid connection.
[0066] "Combustible fluid" means a fluid composed solely of combustible material, or a mixture of combustible material and the fraction of air and / or combustion products inside the working chamber 201, which is recirculated and flows along the intake duct 60 as described later.
[0067] The second supply duct 50 includes a set of ducts through which fluid flow of a combustible fluid flows, starting from a source 500 of combustible material and supplied to an outlet 302. The second supply duct 50 connects the source 500 of combustible material to the outlet 302.
[0068] The second supply duct 50 may be provided at least partially inside the burner 30. An outlet 302 may be obtained at the end of at least one duct 312 inside the burner 30. Duct 312 may form part of the second supply duct 50 or be connected to the second supply duct 50 via a fluid connection. In one possible embodiment, two or more outlets 302 are provided, which may be obtained at a distribution head 313 placed at the end of one or more ducts 312. If a single duct 312 exists, it may be coaxial with the lance 311 and outside the lance 311.
[0069] The combustion chamber may be composed of a tubular compartment 314 obtained from the burner 30 and fluidly connected to the working chamber 201, or it may be composed of the working chamber 201 itself.
[0070] The possibility that the combustion chamber is composed of a tubular compartment fluidly connected to a radiant tube disposed inside the work chamber 201 is not excluded. In this case, the combustion chamber may be heat exchanged with the work chamber 201 through the radiant tube.
[0071] In this description, reference is made to cases where the combustion chamber is fluidly connected to the working chamber 201 or consists of the working chamber 201 itself; in such cases, the combustion products form the atmosphere inside the working chamber 201.
[0072] More specifically, this description relates to the case where the burner 30 is of the so-called "open-flame" type.
[0073] The suction duct 60 comprises a set of ducts through which a fluid flow, formed by at least the friction of the atmosphere and / or combustion products inside the working chamber 201 and sucked in and flowing along it, passes. The suction duct 60 may be provided at least partially inside the burner 30.
[0074] In the case where the regenerative type heat exchanger 80'', 80''' is composed of a local unit (Figs. 8a and 8b) integrated into the burner 30'' or a local unit (Figs. 9a and 9b) integrated near it, in the first operation configuration, by the fluid flow formed by at least one sucked fraction of the atmosphere and / or combustion products inside the work chamber 201, and in the second operation configuration, by the flow of the combustible fluid to be heated, the second supply duct 50 and the suction duct 60 are composed of a single section of duct that moves at least partially alternately, and this single section of duct is at least partially an integral part of the burner 30''.
[0075] In the case where the heating plant 10 includes a central heat exchanger 80 of the recovery type (Figs. 1, 1a, 3 and 3a), the second supply duct 50 and the suction duct 60 are each composed of a heat exchange duct that is at least partially part of the heat exchanger or is fluidly connected to the heat exchanger.
[0076] In the case where the recovery type heat exchanger 80' is configured as a local unit integrated into the burner 30' (Fig. 7), these heat exchange ducts are an integral part of the burner 30'.
[0077] The moving assembly 204 supports the metal semi-finished products SM by advancing them along a direction of movement that is straight or at least partially curved from the inlet 202 to the outlet 203. This may be a movable skid type, a roller type, or other types known in the art, so it is not described further.
[0078] Along the work chamber 201, there are at least two zones starting from the inlet 202 toward the outlet 203: a first zone 2011 for preheating metal semi-finished products SM to a first temperature, and a second zone 2012 for heating the preheated metal semi-finished products SM to a second temperature higher than the first temperature.
[0079] In a preferred embodiment, at least one burner 30 is placed in the second zone 2012.
[0080] The combustion products form a fluid flow that moves along the working chamber 201 in the opposite direction to the movement of the metal semi-finished products SM.
[0081] The metal furnace 20 may be equipped with two or more burners 30, which are advantageously placed in a second zone 2012 and do not necessarily have to be identical to each other.
[0082] The fluid flow of combustion products flows from Zone 2 2012 to Zone 1 2011.
[0083] The inlet of suction duct 60 is fluidly connected to Zone 1 2011.
[0084] The outlet of the suction duct 60 is fluidly connected to a chimney 601 or another suction unit, which can be preceded by a treatment unit 600.
[0085] In a preferred embodiment, along the suction duct 60, there is at least one auxiliary suction unit 602 or "exhauster," and the auxiliary suction unit 602 or exhauster comprises, for example, an axial fan or centrifugal fan for moving and recirculating the fraction of air and / or combustion products inside the working chamber 201, which is particularly useful in situations where the flow rate of the recirculation fraction along the possible bypass line 90 is high (in percentage). Where the bypass line 90 is present, the auxiliary suction unit 602 is positioned upstream of the bypass valve 900.
[0086] Referring to the embodiment schematically illustrated in FIG. 1, the heating plant 10 includes a heat exchanger 80 and an electric unit 70 positioned downstream of the heat exchanger 80 and upstream of the burner 30.
[0087] Heat exchanger 80 is a central heat exchanger and is of the recovery type.
[0088] The electric unit 70 is obtained as an independent central separate unit in relation to the heat exchanger 80 and one or more burners 30.
[0089] The electric unit 70 includes one or more electric resistors 701 that are thermally connected to ducts 702 through which a combustible fluid flows. The ducts 702 may be an integral part of the second supply duct 50 or the electric unit 70 and may be fluidly connected to the second supply duct 50.
[0090] Metal semi-finished products SM enter the working chamber 201 through the inlet 202 and pass through the first zone 2011 (preheating zone) at a low temperature, being preheated in the opposite direction by the flow of combustion products generated in the second zone 2012, and the second zone 2012 is located downstream of the first zone 2011 when considering the direction of movement of the metal semi-finished products SM. The second zone 2012 or heating zone at a higher temperature is equipped with at least one burner 30. The burner 30 is:
[0091] - Combustible material through the first feeding duct 401, which is at least part of the first supply duct 40 and fluidly connected to the outflow nozzle 301,
[0092] and
[0093] - A combustible fluid is supplied through at least the second feeding duct 501, which is part of the second supply duct 50 and fluidly connected to the outlet 302, and is preheated to a final preheating temperature T2.
[0094] After passing through Zone 2 2012, the metal semi-finished products SM are discharged from the work chamber 201 through the discharge port 203.
[0095] The combustible material required for combustion is generally air drawn in from the external environment of the heating plant 10.
[0096] Combustible material passes through one or more first exchange ducts 803 inside the heat exchanger 80. The heat exchanger 80 is configured as a central gas-gas heat exchanger of the recovery type, and the combustible material is heated by thermal energy (residual sensible heat) released from cooled combustion products discharged from a metal furnace 20, which passes through the interior of the heat exchanger 80 through one or more second exchange ducts 804 that are thermally connected to the first exchange ducts 803. The second exchange duct 804 is connected to the metal furnace 20 at an inlet through at least a first suction duct 603, the suction duct 603 being part of the suction duct 60 and transferring combustion products or fractions of the atmosphere inside the work chamber 201 from the metal furnace 20 to the heat exchanger 80. The second exchange duct 804 is connected to the treatment plant 600 (if present) at the outlet, and then to the chimney 601 and at least the second suction duct 604, the suction duct 604 being part of the suction duct 60 and transferring the suctioned current discharged from the heat exchanger 80 to the chimney 601.
[0097] The inlet 801 of the first exchange duct 803 is fluidly connected to a source of combustible material 500 through one or more inlet ducts 502, which are part of the second supply duct 50. The outlet 802 of the first exchange duct 803 is fluidly connected to an electrical unit 70 through one or more connecting ducts 503, which are part of the second supply duct 50. The connecting ducts 503 are fluidly connected to ducts 702 of the electrical unit 70. The combustible fluid, which is preheated to a first preheating temperature T1 in the heat exchanger 80 and discharged from the heat exchanger 80, enters ducts 702 and is heated to a final preheating temperature T2 (typically at least 1000°C) due to heat generated by one or more electric resistors 701 as it moves through ducts 702. A combustible fluid preheated to a final preheating temperature T2 discharged from an electric unit 70 is supplied to a burner 30 through a second feeding duct 501 and flows through at least one outlet 302 of the burner 30 in the combustion chamber, and a combustible material supplied through a first feeding duct 401 and discharged from an outlet nozzle 301 is supplied.
[0098] In the embodiment of FIG. 1, the electric unit 70 is obtained as a central independent unit connected to an upstream heat exchanger 80 through each duct (intermediate duct 503 and second feeding duct 501) and further connected to a downstream burner 30 or the outlet 301 of the burner.
[0099] In an alternative embodiment, the electric unit 70 can be obtained as an integral part of the central heat exchanger 80 by installing electric heaters, which are equipped with the central heat exchanger 80, along the path of the combustible material, regardless of whether they are of the register type, electric arc type, or plasma type. In any case, the electric heaters are positioned downstream of the inlet 801 of the combustible material of the heat exchanger 80, preferably downstream of the outlet 802 of the combustible material from the heat exchanger 80. This is to maximize the recovery of residual sensible heat of the atmosphere and / or combustion products inside the work chamber 201. In fact, if the electric unit 70 is placed along the path of the combustible material upstream of the inlet 801 of the combustible material to the heat exchanger 80, the heat exchange between the combustible material and the atmosphere and / or combustion products inside the working chamber will be performed after the electric preheating of the combustible material, and as a result, the residual sensible heat exchanged will inevitably be lower, which is substantially proportional to the temperature difference between the two fluids in which the heat exchange is performed.
[0100] In an alternative embodiment within the scope of the claimed invention, the electric unit 70 is obtained as a local unit dedicated to each burner 30, preferably as a local unit obtained as an integral part of each burner 30 (Figs. 1a, 3a and Figs. 7 to 9b).
[0101] This alternative embodiment provides additional advantages that increase the flexibility of preheating and that the combustible material is preheated to a final preheating temperature T2 (1000°C or higher) in a part of the appropriately insulated burner body 30, or preferably inside or onboard the burner body 30, because the heat loss that inevitably occurs along the sections of the second supply duct 50 connecting the electric unit 70 to the burner 30 (i.e., outlet 302) is reduced, even if it is insulated, when the electric unit 70 is obtained as a central unit separated from the burner 30.
[0102] For the same reason, in an additional advantageous alternative embodiment within the scope of the claimed invention, an electric unit 70 and a heat exchanger 80 are obtained as local units for each burner 30, and more preferably as local units that are integral parts of each burner 30.
[0103] FIG. 7 schematically illustrates an alternative embodiment in which the burner 30' is equipped with a so-called self-recuperative type, i.e., a local heat exchanger 80' of the recovery type.
[0104] In fact, as is known, the self-recovering burner 30' includes, in addition to the ducts necessary to supply combustible and combustible fluids, at least one intake duct 60' for the fraction of combustion products drawn from the atmosphere inside the combustion chamber and / or the working chamber 201 of the metal furnace 20. The intake duct 60' is part of the intake duct 60 or is fluidly connected to the intake duct 60.
[0105] The self-recovering burner 30' is further equipped with a heat exchanger 80', through which the friction of the atmosphere and / or combustion products inside the working chamber 201 sucked in along the suction duct 60' releases heat to the combustible fluid so that the combustible fluid is preheated to a first preheating temperature T1.
[0106] According to the present invention, a self-recovering type burner 30' is positioned downstream of an inlet 801' of combustible fluid to a heat exchanger 80', preferably downstream of an outlet 802' of combustible fluid from the heat exchanger 80', and includes an electric unit 70 adjacent to and integrated with the burner 30', positioned upstream of an outlet 302.
[0107] In the embodiment illustrated in FIG. 7, the self-recovering type burner 30' is:
[0108] - At least one lance 311 that is part of the first supply duct 40 or fluidly connected to the first supply duct 40 and ends in one or more outflow nozzles 301;
[0109] - At least one feeding duct 312 for combustible fluid that is part of the second supply duct 50 or fluidly connected to the second supply duct 50 and ends at one or more outlets 302;
[0110] It includes at least one suction duct 60' that is part of or fluidly connected to the supply duct 60, fluidly connected to the atmosphere inside the combustion chamber or work chamber 201 at the inlet, and fluidly connected to the treatment and suction unit 600, 601 at the outlet - the suction duct 60' is heat exchange connected to the feeding duct 312 of the combustible fluid and advantageously forms a countercurrent type heat exchanger 80' together with it.
[0111] The inlet 801' of the combustible fluid to the heat exchanger 80' consists of the inlet end of the combustible fluid feeding duct 312 or the section of the feeding duct 312 where the heat exchange connection with the suction duct 60' begins.
[0112] The combustible fluid outlet 802' from heat exchanger 80' consists of a section of combustible fluid feeding duct 312 where the heat exchange connection between combustible fluid feeding duct 312 and suction duct 60' ends.
[0113] The feeding duct 312 can advantageously be a single duct that is coaxial with the lance 311 and located outside the lance 311.
[0114] The suction duct 60' can advantageously be a single duct that is coaxial with duct 312 and outside of duct 312.
[0115] The electric unit 70 is positioned downstream of the inlet 801' of the combustible fluid to the heat exchanger 80', preferably downstream of the outlet 802' of the combustible fluid from the heat exchanger 80', and upstream of the outlet 302. It may include one or more electric heaters positioned along a section of the feeding duct 312 connecting the outlet 802' of the heat exchanger 80' to the outlet 302.
[0116] This section of the feeding duct 312 is insulated from the intake duct 60' and / or the combustion chamber or working chamber 201, for example, through insulation 703. The insulation 703 consists of a tubular element having a base on which a head 313 is obtained, for example, by externally surrounding one or more electric resistors 701. In this way, the thermal energy generated by one or more electric resistors 701 is released primarily into the combustible fluid to be preheated, limiting the amount of heating of the atmosphere and / or combustion products inside the working chamber 201 drawn along the intake duct 60' by conduction through the burner walls.
[0117] FIGS. 8a-8b schematically illustrate a possible alternative embodiment in which a burner 30'' is of the so-called regenerative type, that is, a regenerative type heat exchanger 80'' integrated adjacent to the burner 30''.
[0118] As is known, a regenerative burner comprises, in addition to a duct (a duct consisting of a lance 311 in the exemplified form) required to supply combustible material to an outlet nozzle 301, a regenerative type heat exchanger 80'' comprising at least one heat storage and exchange unit in which thermal energy is first stored (storage or heating stage) while a heating fluid inside passes through, and then thermal energy is released (release or cooling stage) while a fluid to be heated passes through. The heating fluid consists of at least one fraction of the atmosphere and / or combustion products inside the working chamber 201 drawn in along the intake duct 60.
[0119] The fluid to be heated consists of a combustible fluid supplied along the second supply duct 50.
[0120] The flow of the heating fluid and the flow of the fluid to be heated move alternately through the heat storage and exchange units, and preferably in opposite directions to each other.
[0121] A valve system (not shown) controls the passage of two fluids through a heat exchanger 80''. According to the present invention, a regenerative type burner 30'' includes an electric unit 70 obtained as an integral part of the burner 30''. The electric unit 70 is installed between the heat exchanger 80'' and the outlet 302.
[0122] The electric unit 70 is positioned downstream of the inlet 801'' of the combustible fluid to the heat exchanger 80'', and advantageously downstream of the outlet 802'' of the combustible fluid from the heat exchanger 80''.
[0123] In this case, the second supply duct 50 and the suction duct 60 are composed of at least partially identical single sections 510 and 610 of the duct, and at least partially identical single sections 510 and 610 of the duct are integral parts of the burner 30'' and are alternately moved by a fluid flow formed by at least one suctioned fraction of the atmosphere and / or combustion products inside the working chamber 201 that is discharged through the suction duct 60 after passing through the heat exchanger 80'' in the first operating configuration (Fig. 8b), and by a flow of combustible fluid to be heated that is supplied to the outlet 302 after passing through the heat exchanger 80'' in the second operating configuration (Fig. 8a).
[0124] The electric heating unit 70 includes electric heaters of electric resistor type 701 arranged along such sections 510, 610 of the duct between the heat exchanger 80'' and the outlet 302, for example.
[0125] Preferably, the electric unit 70 includes at least one on / off type switch 704 controllable between an open (off) position that cuts off the supply of power to the electric heaters and a closed (on) position that allows the supply of power to the electric heaters.
[0126] Switch 704 is controlled by the control and processing electronic unit 100.
[0127] In the first operation configuration (Fig. 8b), the electric unit 70 is deactivated and the switch 704 is in the open (off) position.
[0128] In the second operation configuration (Fig. 8a), the electric unit 70 is activated and the switch 704 is in the closed (on) position.
[0129] In the first operation configuration (Fig. 8b), the combustible supply is stopped.
[0130] In the second operation configuration (Fig. 8a), the supply of combustible material is activated.
[0131] Referring to the embodiment illustrated in FIGS. 8a and 8b, the burner 30'' comprises a lance 311 having at least one outlet nozzle 301 of a combustible material fluidly connected directly to a working chamber 201 or through a tubular compartment 314 at one end. The opposite end of the lance 311 is fluidly connected to a source 400 of combustible fluid, and the lance 311 is part of a first supply duct 40 or is fluidly connected to the first supply duct 40.
[0132] Then, the burner 30'' includes sections 510 and 610 of a duct that are generally located outside the lance 311 and coaxial with the lance 311, and sections 510 and 610 of the duct are fluidly connected at one end to the working chamber 201 through at least one opening, either directly or indirectly through tubular compartment 314. This opening alternatively serves as an outlet 302 (Fig. 8a) and a suction opening (Fig. 8b).
[0133] Along sections 510 and 610 of the duct, a regenerative heat exchanger 80'' is arranged, and the regenerative heat exchanger 80'' is fluidly connected to sections 510 and 610 of the duct and includes a heat storage and exchange unit obtained from materials that are gas-passable and resistant to high temperatures.
[0134] The electric unit 70 is placed along sections 510 and 610 of the duct between the heat exchanger 80'' and the opening for fluid connection between the working chamber 201 and sections 510 and 610 of the duct, along with its own electric heaters.
[0135] Sections 510 and 610 of the duct on the opposite side from the part fluid-connected to the working chamber 210 are optionally fluid-connected alternately as follows:
[0136] - Source of combustible material 500 through the second supply duct 50 (with at least one valve located therein),
[0137] and
[0138] - Processing unit 600 through suction duct 60 (with at least one valve located therein).
[0139] In the first operation configuration (Fig. 8b):
[0140] - Electric unit 70 is preferably deactivated, and advantageously, switch 704 is in the open (off) position;
[0141] - The supply of combustible fluid is interrupted along sections 510 and 610 of the duct;
[0142] - The supply of flammable material according to Lance 311 is stopped;
[0143] - Since sections 510 and 610 of the duct are fluidly connected to the processing and suction units 600 and 601, at least fractions of the atmosphere and / or combustion products inside the working chamber 201, which pass through the heat exchanger 80'' and release heat to the storage unit of the heat exchanger 80'', are sucked through sections 510 and 610 of the duct.
[0144] In the second operation configuration (Fig. 8a):
[0145] - Electric unit 70 is activated and switch 704 is in the closed (on) position;
[0146] - Duct sections 510 and 610 are fluidly connected to source 500 of combustible material;
[0147] - Lance 311 is fluid-connected to source 400 of flammable fluid;
[0148] - The combustible fluid passing through the heat exchanger 80'' is preheated until it reaches a first preheating temperature T1 using heat stored in the storage unit, and then undergoes additional preheating until it reaches a final preheating temperature T2 using heat generated in the electric unit 70, after which it is inlet into the combustion chamber through the outlet 302.
[0149] Advantageously, the metal heating furnace 20 is equipped with at least one pair of regenerative type burners 30'' that operate alternately in a first operation configuration and a second operation configuration.
[0150] FIGS. 9a and 9b show additional alternative embodiments in which a regenerative type heat exchanger 80''' is used exclusively for each burner 30 but is obtained as a separate local unit, and an electric unit is also obtained as an integral part of the same heat exchanger 800''' as a local unit.
[0151] Preferably, in this case, the heat exchanger 80''' is placed right next to the burner 30. FIGS. 9a and 9b illustrate two different operational configurations similar to those shown in FIGS. 8a and 8b.
[0152] The embodiment of the heating plant 10 in FIG. 1a differs from the embodiment of FIG. 1 in that one or more burners 30 are adjacent to burner 30 and are dedicated to burner 30 and advantageously integrated into burner 30. As will be easily understood by a person skilled in the art, the electrical circuit diagrammed in FIG. 1a can be replaced by equivalent circuits.
[0153] The embodiment of the heating plant 10 in FIG. 3 differs from the embodiment of FIG. 1 due to the presence of a bypass line 90 and a possible auxiliary suction device 602. It is clear that the bypass line 90, illustrated and described with reference to FIG. 3, can also be provided in the embodiment of FIG. 1a as schematically illustrated in FIG. 3a.
[0154] Another object of the present invention is a process 1000 for heating metal semi-finished products SM, particularly steel semi-finished products, comprising the following steps (Fig. 6):
[0155] a) Step (1001) of providing metal semi-finished products SM to be heated at the inlet of the working chamber 201 of a metal heating furnace 20;
[0156] b) providing at least one combustible current comprising at least one combustible fluid (1002);
[0157] c) a step (1003) of providing a combustible current containing at least one combustible material at a feeding temperature (T0) - the combustible material burns a combustible material that generates high-temperature combustion products at a temperature (Tpc0) -;
[0158] d) a step (1030) of forming a current of a high-temperature combustible fluid having a final preheating temperature (T2) higher than the feeding temperature (T0) of the combustible material using a combustible flow;
[0159] e) supplying a combustible flow and a high-temperature combustible fluid flow to at least one outlet nozzle 301 and at least one outlet 302 of at least one burner 30 coupled to a metal furnace 20, respectively, to cause combustion that generates high-temperature combustion products at a temperature (Tpc0) (1004);
[0160] f) a step (1005) of heating metal semi-finished products SM moving along the work chamber 201 using at least one fraction of the sensible heat of the inlet high-temperature combustion products or atmosphere, which is cooled from a temperature Tpc0 to a first cooling temperature Tpc1 and obtains the inlet high-temperature metal semi-finished products SM discharged from the work chamber 201;
[0161] g) Step 1006 of inhaling at least one fraction of the cooled combustion products and / or the atmosphere inside the working chamber 201,
[0162] Step d), which is Step 1030 forming a flow of a high-temperature combustible fluid at a final preheating temperature T2, comprises at least the following Step 1033:
[0163] d1) A step of providing heat obtained from a power source 700 to a flow of combustible fluid by an electric unit 70 that converts electric power into thermal energy.
[0164] In a preferred embodiment of process 1000, step d), which is step 1030 forming a flow of a high-temperature combustible fluid at a final preheating temperature T2, further comprises at least one of the following steps prior to step 1033:
[0165] d1a) a step (1031) of preheating a combustible flow from a feeding temperature (T0) to a first preheating temperature (T1) using at least one fraction of residual sensible heat of the atmosphere inside the work chamber 201 or the combustible flow preheated to a first preheating temperature (T1) in step g) by means of a heat exchanger (80, 80', 80'', 80'''), and combustible products or combustible fraction of the atmosphere inside the work chamber 201 at a final cooling temperature Tpc2 lower than the first cooling temperature Tpc1, thereby obtaining the combustible flow preheated to a first preheating temperature (T1) in step g),
[0166] d1b) A step (1032) of mixing the combustible flow with at least one recirculation fraction of the atmosphere inside the working chamber and / or the combustible flow, which obtains the combustible fluid flow at a temperature (T'1) higher than the feeding temperature (T0) of the combustible material during step g).
[0167] In a possible embodiment, step d) which is step 1030 forming a flow of a high-temperature combustible fluid at a final preheating temperature T2 comprises only step d1a) which is step 1031 preheating before step 1033.
[0168] In a possible embodiment, step d) which is step 1030 forming a flow of a high-temperature combustible fluid at a final preheating temperature T2 comprises only step d1b) which is step 1032 mixing prior to step 1033.
[0169] In an additional possible embodiment, step d) which is step 1030 forming a flow of a high-temperature combustible fluid at a final preheating temperature T2 comprises both step d1a) which is step 1031 preheating and step d1b) which is step 1032 mixing, and step d1a) which is step 1031 preheating is performed before step d1b) which is step 1032 mixing.
[0170] In a preferred embodiment, step f) of heating metal semi-finished products SM moving along the work chamber 201 is performed by generating high-temperature combustion products or by generating a fluid flow that brushes past the metal semi-finished products SM in the opposite direction to the movement of the metal semi-finished products SM by inleting it into the work chamber 201.
[0171] In this case, advantageously, process 1000 further includes step 1007:
[0172] - A step of measuring the oxygen concentration present in the atmosphere inside at least the working chamber 201, and / or
[0173] - Step of measuring the internal temperature of the working chamber 201,
[0174] - A step of controlling step d) which is step 1030 and step e) which is step 1004, depending on the measured oxygen concentration and / or temperature.
[0175] If the recirculated fraction in step d1b) which is the mixing step 1032 corresponds to the intake fraction of the atmosphere inside the working chamber 201 during step g) and / or the entire intake of the intake combustion products ― if step d1a) which is the preheating step 1031 is interrupted or omitted, in step 1007, it is provided as follows:
[0176] - If the measured oxygen concentration is lower than a prefixed threshold (e) (e.g., 3%-5%), step e) of supplying a combustible flow and a high-temperature combustible fluid flow to at least one outlet nozzle 301 and at least one outlet 302 of at least one burner 30 coupled to a metal furnace 20, respectively, is stopped;
[0177] - If the measured oxygen concentration is higher than a predetermined threshold (e.g., 3%-5%), step e) of supplying step 1004 is maintained or restored.
[0178] In a possible embodiment, step f) of heating metal semi-finished products SM moving along the work chamber 201, which is step 1005, is performed by generating or inleting high-temperature combustion products into radiating tubes through which combustion products flow in order to transfer heat by irradiation to the metal semi-finished products SM.
[0179] In this case, advantageously, process 1000 further includes step 1007:
[0180] - Step of measuring the internal temperature of the working chamber 201,
[0181] - A step of controlling step d) which is step 1030 and step e) which is step 1004, according to the measured temperature.
[0182] In this case, the metal furnace 20 is of the indirect heating type: the flue gas flows within the radiant tubes and does not come into contact with the metal semi-finished products SM, thereby making the oxygen content present therein irrelevant and the possibility of recirculation. By providing at least one electric unit 70 downstream of the heat exchanger 80 and advantageously positioning it in the radiant tubes, the flexibility of plant management can be increased, reducing operating costs and contributing to decarbonization. The following cases may occur:
[0183] - Fuel costs are low; in this case, electric unit 70 is turned off and burner 30 operates in standard mode;
[0184] - During the combustion phase, burner 30 operates and electric unit 70 is switched on, helping to raise the temperature of the combustible material already preheated by the flue gas of the heat exchanger, thereby aiding in decarbonization;
[0185] - Combustible materials are expensive and CO₂ generation must be reduced or eliminated. In such cases, burner 30 is supplied with only combustible material and no combustible material, and electric unit 70 operates at a higher power than in the previous case to reach the required temperature in the working chamber through the radiation tube.
[0186] As described above, process 1000 can be implemented using heating plant 10 including all possible variations, and a description of heating plant 10 is referenced herein.
[0187] In particular, the heat exchanger 80, 80', 80'', 80''' may be of the recovery type or regeneration type, and may be obtained as a separate, central, local unit adjacent to or integrated into the burner 30.
[0188] The electric unit 70 can be obtained as a separate unit, a central unit, a local unit, or a local unit integrated into the burner 30.
[0189] Now, some steps of a possible embodiment of process 1000 implemented using the heating plant 10, which is diagrammed in FIG. 2 and diagrammed in FIG. 1 or FIG. 1a, are described in more detail. For reference, the reference characters shown in the graph of FIG. 2 are also shown in the corresponding sections of the diagram of FIG. 1.
[0190] Step c) of step 1003, which provides a combustible flow containing at least one combustible material at a feeding temperature T0, includes providing the combustible material necessary for combustion and optionally controlling it. The combustible material may be air, and in this case, it must be made into a suitable condition for subsequent steps. Alternatively, the combustible material may be oxygen-rich air. Generally, the inlet temperature of the combustible material of the heating plant 10, i.e., the feeding temperature T0, is similar to the temperature of the ambient environment. For reference, the feeding temperature T0 is equivalent to 25°C.
[0191] Step d), which is Step 1030 forming a flow of a high-temperature combustible fluid at a final preheating temperature T, is continuously:
[0192] - Step d1a) Step 1031 of preheating a combustible flow from a feeding temperature T0 to a first preheating temperature T1 using at least one fraction of the residual sensible heat of the suction fraction by a heat exchanger 80, and
[0193] - Step d1) includes step 1033, which provides heat obtained from power source 700 by electric unit 70 until a final preheating temperature T2 is reached, in this case, to a flow of combustible fluid consisting of a combustible flow heated to a first preheating temperature T1.
[0194] Referring to the diagram in FIG. 2, step d1a), which is the preheating step 1031, is represented by section AB, where state A corresponds to the combustible material entering the heating plant 10 and state B corresponds to the combustible material exiting the heat exchanger 80. The temperature of the combustible material discharged from the heat exchanger 80, i.e., the first preheating temperature T1, may be approximately 550-650°C. The first preheating temperature T1 of the combustible material depends on the efficiency of the heat exchanger 80 and the temperature of the atmosphere and / or combustion products fraction inside the working chamber 201, which is drawn in and supplied from the inlet of the heat exchanger 80. On the x-axis (Q), heat Q A-B silver, (heat Q E-F The residual sensible heat removed from the friction of the atmosphere and / or combustion products inside the working chamber 201, which is drawn in and supplied from the inlet of the cooling heat exchanger 80, is provided.
[0195] After step d1a), which is the preheating step 1031, step 1033 is provided, which provides heat obtained from the power source 700 by the electric unit 70 until the final preheating temperature T2 is reached in step d1), to a flow of combustible fluid consisting of a combustible flow heated to a first preheating temperature T1 in this case. This step 1033 may be performed in the electric unit 70 obtained as a central unit separated from the heat exchanger 80, as described above and as shown in FIG. 1, or in the central electric unit obtained as an integral part of the heat exchanger 80, or more advantageously in a local electric unit, preferably a local electric unit integrated into the burner 30 (Fig. 1a). In any case, according to the present invention, this step 1033 is obtained using power converted into thermal energy according to any possible manner. Preferably, the power supplied to the electric unit 70 is converted into thermal energy by the Joule effect by one or more electric heaters of the form of register 701, which are connected to heat exchange with one or more ducts 702 through which the flow of combustible fluid flows. Alternatively, the flow of combustible fluid may be heated directly or indirectly by electric-arc electric heaters or by one or more plasma torch types.
[0196] In this step 1033, the combustible fluid is heated to a final preheating temperature T2 equal to at least 800°C, preferably at least 1000°C, more preferably at least 1200°C. Where the combustible fluid is air, it is desirable that the final preheating temperature T2 in this preheating step not exceed 1350-1400°C to prevent the generation of nitrogen oxides (NOx).
[0197] In the diagram of FIG. 2, this step 1033 is represented as section BC, and the combustible fluid moves from state B, corresponding to the combustible fluid discharged from heat exchanger 80, to state C, corresponding to the combustible fluid discharged from electric unit 70. Q in FIG. 2 EL Column Q expressed as B-C It is provided by power.
[0198] In step e) of the supplying step 1004, to cause combustion of the combustible flow and the high-temperature combustible fluid flow that generates high-temperature combustion products at temperature Tpc0, the combustible flow and the high-temperature combustible fluid flow are supplied to the outlet nozzle 301 and outlet 302 of at least one burner 30 coupled to the metal heating furnace 20, respectively.
[0199] During combustion, the conditions of the flow of the combustible fluid graphically represented by point C are converted into the conditions of the inlet of the combustion products to the working chamber 201 represented by point D. The temperature Tpc0 is approximately 2650°C (adiabatic flame temperature).
[0200] Heat Q C-D In the case of the most common hydrocarbon combustion, it corresponds to the chemical energy released by a simple and ideal form of combustion reaction, and is as follows:
[0201] O2+ N2+ C x H y -> CO2 + H2O + N2
[0202] From the ideal reaction reported above, it can be seen that since the combustion products are generally non-oxidizing, the scale formation phenomenon, which is particularly pronounced when exceeding 900°C, is limited. In practice, the atmosphere inside the working chamber 201 aims to maintain an oxygen presence of no more than 3%-5%.
[0203] According to the prior art, that is, in the absence of electric heating of the combustible fluid, the chemical energy required to reach the conditions of point D, i.e., the transformation to BD, is Q B-D It is identical to. According to the present invention, energy Q B-D Part of the power Q that preheats the combustible fluid to the final preheating temperature T2. E It is provided by. Therefore, the chemical energy required for the process according to the present invention is only the energy required for CD conversion, and this is Q C-D It is identical to, and in the drawing, Q COMB It is indicated as (combustion). As shown in Figure 2, since the required combustion energy is lower than that of the prior art, the combust flow rate must be reduced in order to maintain the amount of oxygen within the limits presented above.
[0204] In step f), which is step 1005, heating metal semi-finished products SM moving along work chamber 201 using at least one fraction of the sensible heat of the combustion products, the combustion products are advantageously generated in a second zone 2012 of work chamber 201 and generally move along work chamber 201 in a direction opposite to the direction of movement of the metal semi-finished products SM to be heated. A first zone 2011 preheating the metal semi-finished products SM facilitates heat exchange by convection between the combustion products and the metal semi-finished products SM. In this step f), the combustion products, or the atmosphere inside the furnace, transition from the state diagrammed by point D in FIG. 2 to the state diagrammed by point E, which corresponds to the combustion products and the atmosphere inside the furnace, or at least their inhaled fractions, being discharged from work chamber 201 and also to such inhaled fractions entering the inhalation duct 60.
[0205] Heat Q D-E Most of the metal semi-finished products SM passing through the metal furnace 20 are released, and some of it is dispersed through the walls of the metal furnace 20. The temperature of the combustion products discharged from the metal furnace 20 (first cooling temperature Tpc1) can be about 650–700°C. This temperature is generally lower than the corresponding temperature that appears in a process according to the prior art (i.e., a process without electric heating), and since more energy is required for combustion in the prior art, the flow rate of combustible material is higher, and consequently, the flow rate of combustion products is also higher. As is known, for the same heat exchange with the metal semi-finished products, the higher the flow rate of combustion products, the smaller the decrease in the temperature of the combustion products discharged from the metal furnace 20.
[0206] In step d1a), which is the preheating step 1031, the fraction of air and / or combustion products inside the working chamber 201, which is cooled to a first cooling temperature Tpc1 and sucked outside of the metal heating furnace 20, is further cooled to a final cooling temperature Tpc2 due to heat exchange with the combustible material preheated in the heat exchanger 80.
[0207] The fraction of combustion products discharged from metal furnace 20 (point E) is heat Q in heat exchanger 80. E-F It emits heat, and most of this heat is transferred to combustible material undergoing preheating AB.
[0208] Finally, step g) of step 1006, which involves inhaling at least one fraction of cooled atmosphere and / or cooled combustion products inside the working chamber 201, and step 600, which involves transferring the inhaled fraction to a flue gas treatment unit, wherein the combustion products are treated and released into the atmosphere (section FG) at a temperature close to room temperature.
[0209] The embodiment of the heating plant 10 in Fig. 3 differs from the embodiment of Fig. 1 due to the presence of a bypass line 90 and a possible auxiliary suction device 602.
[0210] A bypass valve 900 is positioned along a first suction duct 603 that connects the outlets of the atmosphere and / or combustion products inside the working chamber 201 from the metal furnace 20 to the heat exchanger 80 using their inlets. The operation of this bypass valve 900 or a similar diversion system is similar to the operation of a three-way valve: the fraction of the atmosphere and / or combustion products inside the working chamber 201 sucked in from the section of the first suction duct 603 upstream of the first suction duct 603 is transferred to one or both of the following:
[0211] - A section of the first suction duct 603 downstream of the first suction duct 603 supplying such suctioned fraction at the inlet of heat exchanger 80,
[0212] - Bypass line 90 supplying the suctioned fraction along the second supply duct 50 downstream of outlet 802 of the preheated combustible material from heat exchanger 80 and upstream of the inlet of the combustible fluid to electric unit 70.
[0213] The bypass valve 900 may be configured and controlled to completely block the suctioned fraction from passing along the section of the first suction duct 603 downstream of the first suction duct 603 or along the bypass line 90; or may be configured and controlled to regulate the flow rate of the suctioned fraction supplied along the section of the first suction duct 603 downstream of the first suction duct 603 and / or recirculated along the bypass line 90 (the flow rate of the recirculated fraction is between 0% and 100% of the total flow rate of the suctioned fraction).
[0214] Optionally, upstream of the bypass valve 900, a “exhaust device” 602 consisting of an axial fan or a centrifugal fan for moving and recirculating flue gas may be provided, for example, which is useful in situations where the flow rate of the recirculating fraction is high (in percentage).
[0215] By providing a bypass line 90, at least one fraction (recirculation fraction) of the atmosphere and / or combustion products inside the working chamber 201, which is sucked in to form a combustible fluid and discharged from the furnace, can be recirculated by mixing with the combustible material.
[0216] Advantageously, by providing a bypass line 90, the entire amount of air and / or combustion products inside the working chamber 201 that are sucked in and discharged from the furnace can be mixed with combustible material or recirculated in a closed circuit.
[0217] This solution is particularly useful when a sufficient amount of power is available at a low cost, as it can reduce combustible consumption while maintaining an appropriate flow rate of high-temperature flue gas inside the metal furnace 20 to preheat metal semi-finished products, and also maintain a protective atmosphere inside the working chamber 201 to limit the formation of scale on the surface of the metal semi-finished products SM.
[0218] In a possible operating condition corresponding to the process diagrammed in FIG. 4 (the reference characters shown in the graph of FIG. 4 also indicate corresponding sections of the diagram in FIG. 3), the bypass valve 900 is controlled to transfer the entire fraction of air and / or combustion products inside the working chamber 201, sucked along the first suction duct 603, toward the bypass line 90.
[0219] The inhaled fraction is completely recirculated and mixed with combustible material (step d1b, which is the mixing step 1032). In this case, the combustible material of the ambient conditions (point A) is not preheated—that is, step d1a, which is the preheating step 1031) is absent or interrupted—because the entire inhaled fraction is recirculated and is not supplied from the inlet of the heat exchanger 80.
[0220] The entire inhaled fraction is recirculated to mix with the combustible material at a feeding temperature T0, forming a combustible fluid at a temperature T'1 higher than the feeding temperature T0 of the combustible material (point E').
[0221] The combustible fluid formed in step d1b), which is mixing step 1032, is preheated to a final preheating temperature T2 in the subsequent step 1033, which consists of step d1), which provides heat obtained from an electric power source 700 by an electric unit 70 to the flow of the formed combustible fluid. The flow of the combustible fluid is provided with heat (heat Q) generated by the electric unit 70. EL It is preheated to the final preheating temperature T2 (section E'-C of the graph) by ).
[0222] In step e) of the supplying step 1004, to cause combustion of the combustible flow and the high-temperature combustible fluid flow that generates high-temperature combustion products at temperature Tpc0, the combustible flow and the high-temperature combustible fluid flow are supplied to the outlet nozzle 301 and outlet 302 of at least one burner 30 coupled to the metal heating furnace 20, respectively.
[0223] During combustion, the conditions of the combustible fluid flow graphically represented by point C are converted into the conditions of the combustion products inlet to the working chamber 201 represented by point D (combustion heat Q COMB Emission). The temperature Tpc0 is approximately 2650°C (adiabatic flame temperature).
[0224] Afterwards, in step f) which is the heating step 1005, the atmosphere and / or combustion products inside the work chamber 201 release heat to the metal semi-finished products SM, cool to state E, and then mix again with the combustible material provided to the process.
[0225] FIG. 5 graphically illustrates an additional embodiment of a process according to the present invention that can be implemented using the heating plant 10 of FIG. 3.
[0226] Even in this case, the bypass valve 900 is controlled as described above in relation to FIG. 4, that is, the inhaled fraction is completely recirculated in step 1032, which is mixing step d1b), while combustion is stopped or does not exist in step 1031, which is preheating step d1a).
[0227] When the power supplied to the electric unit 70 is sufficient to meet the total thermal energy requirements of the metal furnace 20 and the desired compositional conditions of the atmosphere inside the working chamber 201 are achieved, particularly regarding the oxygen content that limits the formation of scale, step 1004, which supplies a combustible flow and a flow of a high-temperature combustible fluid to at least one outlet nozzle 301 and at least one outlet 302 of at least one burner 30 coupled to the metal furnace 20 to cause combustion, can be stopped. That is, it is possible to turn off the burner 30.
[0228] Under these operating conditions, the heating plant 10 is an ideally closed system, the atmosphere inside the work chamber 201 is continuously recirculated, and the energy released to the metal semi-finished products SM and the inevitable heat losses are completely balanced by the thermal energy generated by the electric unit 70 by converting the power supplied to the electric unit 70.
[0229] However, in reality, when metal semi-finished products SM enter and exit the metal heating furnace 20, ambient air enters the working chamber 201 through the inlet 202 and outlet 203. When ambient air is introduced, the chemical composition of the internal atmosphere of the working chamber 201 changes, and in particular, the oxygen content tends to increase.
[0230] Therefore, the burner 30 must be periodically reignited to restore the atmospheric conditions necessary to minimize scale formation (step e, which is step 1004, supplying a combustible flow and a flow of a high-temperature combustible fluid to at least one outlet nozzle 301 and at least one outlet 302 of at least one burner 30 coupled to the metal furnace 20, respectively, to restore combustion). Thus, during these steps, the system returns to the operating conditions illustrated in FIG. 4 or FIG. 2.
[0231] As described above, the present invention relates to a heating plant and process for heating metal semi-finished products, particularly steel semi-finished products, and enables the effective combination of thermal energy generated by the combustion of combustible materials and thermal energy generated from electricity.
[0232] In particular, the plant according to the present invention includes a metal furnace for heating steel semi-finished products, and the metal furnace is equipped with one or more burners for burning a mixture of a combustible material (generally a gas) and a combustible fluid (generally air).
[0233] Generally, a thermal recovery system (heat exchanger) is installed to recover at least one fraction of the residual sensible heat of flue gas discharged from the furnace (atmosphere and / or combustion products inside the furnace's working chamber) to preheat combustible material supplied to the burners (simultaneously in the case of a recovery type heat exchanger, later in the case of a regenerative type heat exchanger).
[0234] The plant according to the present invention is characterized by having an electric unit for preheating a combustible fluid supplied by power downstream of a possible heat recovery system and upstream of a combustion chamber supplied by burners. In particular, such electric unit 70 may include one or more electric heaters of the electric resistor type, electric arc type, or plasma type, and advantageously may be adjacent to each burner and dedicated to the burner, and preferably integrated into the burner.
[0235] The process according to the present invention may include at least the following steps:
[0236] - A step of preheating combustible material in one or more heat exchangers by thermal energy subtracted from flue gas from a blast furnace (step d1a);
[0237] - Step of further preheating a combustible material or combustible fluid by an electric unit 70 (step d1);
[0238] - A step of burning a combustible material using a preheated combustible fluid to generate combustion products circulating in the working chamber of the furnace to heat metal semi-finished products moving inside the furnace (by radiation and convection) (steps e and f);
[0239] - A step of sucking combustion products out of the furnace and a step of cooling combustion products discharged from the furnace for incoming combustible material (step d1a and step g).
[0240] The principle of the present invention directly reduces the consumption of combustible material by at least partially replacing the chemical energy released from the combustible material of the burner with power supplied to one or more electric heating systems (heating electric units).
[0241] In addition, considering that the performance of such electric heating systems can reach 95–98%, there is a clear advantage compared to known solutions that, for example, use hydrogen obtained from water electrolysis as a combustible material. Furthermore, by placing the electric heating means along the supply and preheating path of the combustible material instead of placing it directly inside the furnace (as in the prior art), a non-oxidizing atmosphere in the working chamber of the furnace can be maintained constant, which is necessary to prevent the exacerbation of scale formation phenomena.
[0242] The main advantages of the plant and process according to the present invention are:
[0243] - The possibility of reducing CO₂ emissions by replacing at least a portion of the chemical energy provided by fossil combustible materials with electricity produced from renewable sources in a simple and flexible manner.
[0244] - More efficient use of power required for heating compared to solutions using hydrogen from water electrolysis.
[0245] - The possibility of utilizing chemical energy produced from renewable sources (e.g., hydrogen), and the possibility of further reducing greenhouse gas emissions.
[0246] - Maintaining the atmosphere inside the furnace's working chamber under non-oxidizing conditions.
[0247] - For example, the possibility of implementing existing systems by combining them with hydrogen burners or induction pre-heating.
[0248] - The possibility to secure maximum flexibility at the power distribution level.
[0249] - When the burner is controlled in an on / off mode, the electrical unit connected to each burner may be activated only when the burner is in operation.
[0250] It should be noted that the heating plant 10 and process 1000 can be manufactured and implemented even after remodeling an existing heating plant by installing one or more electric units as described above in the supply duct of the combustible material and / or the heat exchanger and / or the burner constituting the furnace installed together, or by replacing the existing burner with a burner modified into one of the forms exemplified in FIGS. 7 to 9b.
[0251] The plant and process conceived in this invention are subject to various modifications and variations within the scope of the invention; furthermore, all details may be replaced with technically equivalent elements. The materials and sizes actually used may be anything depending on technical requirements.
Claims
Claim 1 In a heating plant (10) for heating metal semi-finished products (SM), particularly steel semi-finished products, - a metal heating furnace (20) for heating metal semi-finished products (SM) - said metal heating furnace (20) comprises: - a working chamber (201) having at least one inlet (202) for an inlet of metal semi-finished products (SM) to be heated and at least one outlet (203) for an outlet of said heated metal semi-finished products (SM); - a moving assembly (204) for moving said metal semi-finished products (SM) along said working chamber (201) from said inlet (202) to said outlet (203); - at least one burner (30) coupled to said metal heating furnace (20) having at least one outlet (302) of a combustible fluid fluid fluid-fluidly connected to a combustion chamber and at least one outlet nozzle (301) of a combustible fluid fluid fluid-fluidly connected to said combustion chamber; - said combustion chamber is defined by said working chamber (201) or said working In a fluid connection or heat exchange state with the chamber (201) -; Includes, - a first supply duct (40) for supplying a combustible fluid - the first supply duct (40) is fluidly connected to the at least one outlet nozzle (301) of the burner (30) and coupled to the source (400) of the combustible fluid -,- a second supply duct (50) for supplying a combustible fluid - the second supply duct (50) is fluidly connected to the at least one outlet (302) of the burner (30) and coupled to the source (500) of the combustible material at a feeding temperature T0 -,- an intake duct (60) for sucking in at least one fraction of the atmosphere inside the work chamber (201) and / or the combustion products of the burner (30) - the intake duct (60) is fluidly connected to the combustion chamber and / or the work chamber (201) at the inlet and coupled to the intake unit (601) at the outlet -;- A heating plant (10) comprising at least one heat-generating electric unit (70) positioned along the second supply duct (50) upstream of the outlet (302) of the burner (30), wherein the electric unit (70) is coupled to a power source (700) and converts the power into thermal energy to generate heat that heats the combustible fluid to a final preheating temperature T2 higher than the feeding temperature T0 of the combustible material. Claim 2 In claim 1, the method comprises at least one heat exchanger (80, 80', 80'', 80''') that preheats the combustible material to a first preheating temperature T1 lower than the final preheating temperature T2, fluidly connected to the second supply duct (50) and / or the suction duct (60), or obtained along the second supply duct (50) and / or the suction duct (60), and recovers at least partially the residual sensible heat of at least one fraction of the intake of the air inside the work chamber and / or the intake of the combustion products of the burner from the feeding temperature T0, wherein the heat exchanger (80, 80', 80'', 80''') comprises at least one inlet (801, 801', 801'') of the combustible material to be preheated and at least one outlet (802, 802') of the preheated combustible material, A heating plant (10) having at least one heat-generating electric unit (70) is positioned along the second supply duct (50) downstream of the inlet (801, 801', 801'') of the heat exchanger. Claim 3 In paragraph 2, the at least one heat-generating electric unit (70) is a heating plant (10) positioned downstream of the outlet (802, 802', 802'') of the heat exchanger. Claim 4 In paragraph 2 or 3, the heat exchanger (80, 80', 80'', 80''') is a recovery type or a regeneration type, a heating plant (10). Claim 5 A heating plant (10) according to any one of claims 1 to 4, comprising a bypass line (90) fluidly connected to the suction duct (60) by at least one bypass valve (900) and connected to the second supply duct (50) upstream of the electric unit (70), wherein the bypass valve (900) is controlled to provide at least one recirculation fraction of the suctioned air inside the work chamber (201) and / or the suctioned combustion products of the burner to the second supply duct (50). Claim 6 In any one of paragraphs 5 and 2 to 4, the bypass line (90) is connected to the second supply duct (50) downstream of the outlet (802, 802', 802'') of the heat exchanger, in a heating plant (10). Claim 7 In one or more of claims 1 to 6, the electric unit (70) comprises one or more electric heaters of the electric resistor type (701), electric arc type, or plasma type, in a heating plant (10). Claim 8 A heating plant (10) comprising at least one electric unit (70) obtained as a unit separated from at least one burner (30) in one or more of claims 1 to 7. Claim 9 A heating plant (10) comprising at least one electric unit (70) obtained as an integral part of each of the burners (30) in one or more of claims 1 to 8. Claim 10 In claim 8 citing claim 2, the heating plant (10) wherein at least one heat exchanger (80, 80', 80'', 80''') is obtained as a unit separated from the burner (30), and the electric unit (70) is obtained as a unit separated from the heat exchanger or as a unit integrated with the heat exchanger. Claim 11 In item 10, a heating plant (10) comprising a central heat exchanger (80) and at least one central electric unit (70). Claim 12 In claim 9 citing claim 2, the heating plant (10) wherein at least one heat exchanger (80, 80', 80'', 80'') is obtained as a unit separated from the burner (30) or as an integral part of each of the burners (30). Claim 13 A heating plant (10) comprising, for at least one central heat exchanger (80) and one or more burners (30), each electric unit (70) obtained as an integral part of each burner (30). Claim 14 In claim 12, the burner (30', 30'') is of the self-recovery type or regeneration type, and the heat exchanger (80', 80'', 80''') is obtained as an integral part of the heating plant (10). Claim 15 In one or more of claims 1 to 14, at least one of the first supply duct (40), the second supply duct (50) and the suction duct (60) is obtained at least partially integrally with the burner (30), a heating plant (10). Claim 16 In one or more of claims 3 to 15 citing claim 2, at least one of the second supply duct (50) and the suction duct (60) is obtained at least partially integrally with the heat exchanger (80, 80', 80'', 80'''), a heating plant (10). Claim 17 A heating plant (10) comprising, in one or more of claims 1 to 16, at least one oxygen concentration measuring device (210) present in the atmosphere inside the work chamber (201) and at least one temperature sensor (211) for measuring the temperature inside the work chamber (201) connected to a control and processing electronic unit (100), wherein the control and processing electronic unit (100) controls the electric unit (70) and the burner (30) according to the measured oxygen concentration and temperature. Claim 18 In claim 17, citing claim 5 or 6, the control and processing electronic unit (100) controls the electric unit (70), the burner (30), and the at least one bypass valve (900) according to the measured oxygen concentration and temperature, of the heating plant (10). Claim 19 In a process (1000) for heating metal semi-finished products (SM), particularly steel semi-finished products, the method comprises: a) providing metal semi-finished products (SM) to be heated at an inlet to a working chamber (201) of a metal furnace (20) (1001); b) providing at least one combustible flow comprising at least one combustible fluid (1002); c) providing a combustible current comprising at least one combustible material at a feeding temperature (T0) (1003) - said combustible material burns a combustible material that generates high-temperature combustion products at a temperature (Tpc0) -; d) using said combustible flow to form a current of a high-temperature combustible fluid having a final preheating temperature (T2) higher than the feeding temperature (T0) of said combustible material (1030); e) the combustible flow and said high-temperature combustible material to cause combustion that generates the high-temperature combustion products at said temperature (Tpc0). A process (1000) comprising: a step (1004) of supplying a fluid flow to at least one outlet nozzle (301) and at least one outlet (302) of at least one burner (30) each coupled to the metal furnace (20); f) a step (1005) of heating metal semi-finished products (SM) moving along the work chamber (201) using at least one fraction of the sensible heat of the high-temperature combustion products to obtain cooled combustion products and high-temperature metal semi-finished products (SM) discharged from the work chamber (201); g) a step (1006) of inhaling at least one fraction of the cooled combustion products and / or the atmosphere inside the work chamber, wherein step d) comprises at least d1) a step (1033) of providing heat obtained from a power source (700) by an electric unit (70) that converts power into thermal energy to the flow of the combustible fluid. Claim 20 In claim 19, the above step d) further comprises, prior to the above step d1), at least one of the following steps: d1a) a step (1031) of preheating the combustible flow from the feeding temperature (T0) to a first preheating temperature (T1) lower than the final preheating temperature (T2) using at least one fraction of the residual sensible heat of the inhaled air inside the working chamber and / or the inhaled combustion products, thereby obtaining a combustible flow preheated to a first preheating temperature (T1) by a heat exchanger (80, 80', 80'', 80'''); and d1b) a step (1032) of mixing the combustible flow with at least one recirculation fraction of the inhaled air and / or the inhaled combustion products, thereby obtaining a flow of combustible fluid at a temperature (T'1) higher than the feeding temperature (T0) of the combustible material and lower than the final preheating temperature (T2). Including, process (1000). Claim 21 In paragraph 20, the above step d) comprises only the above step d1a) or only the above step d1b) prior to the above step d1), a process (1000). Claim 22 In claim 20, the above step d) includes both the above step d1a) and the above step d1b) prior to the above step d1), and the above step d1a) is performed before the above step d1b), process (1000). Claim 23 In any one of claims 19 to 22, the step f) is performed by inleting or generating the high-temperature combustion products into the work chamber (201) which generates a fluid flow opposite to the movement of the metal semi-finished products (SM), in a process (1000). Claim 24 In any one of claims 19 to 23, the process (1000) comprises—at least the step of measuring the oxygen concentration present in the atmosphere, and / or—the step of measuring the temperature inside the working chamber, wherein steps d) and e) are controlled according to the measured oxygen concentration and / or temperature. Claim 25 In paragraph 24 citing paragraph 20, the entire inhaled fraction of the atmosphere inside the work chamber (201) and / or inhaled combustion products are recirculated in step d1b): - if the measured oxygen concentration is lower than a predetermined threshold value, step e) is stopped; - if the measured oxygen concentration is higher than a predetermined threshold value, step e) is maintained or restored, process (1000). Claim 26 A burner (30) for a heating plant (10) according to one or more of claims 1 to 18, comprising: at least one outlet nozzle (301) of a combustible fluid that is fluidly connected to a combustion chamber at an outlet and fluidly connected to a first supply duct (40) of a combustible fluid at an inlet; at least one feeding duct (312) of a combustible fluid that is fluidly connected to a second supply duct (50) of a combustible fluid at an inlet and fluidly connected to at least one outlet (302) of the combustible fluid at an outlet to the combustion chamber; and at least one electric unit (70) that generates heat along the feeding duct (312) upstream of the outlet (302), wherein the electric unit (70) is connected to a power source (700) and converts the power into thermal energy to generate heat for heating the combustible fluid. Claim 27 In claim 26, a burner (30) comprising at least one heat exchanger (80', 80'') of a recovery type or regeneration type disposed along the feeding duct (312) upstream of the electric unit (70).