Multi-mode equipment set and use thereof

Abstract

Equipment set comprising a burner for burning fuel with a combustion oxidant and for heating a combustion zone, a valve unit (100), an oxidant-gas source (110) and a reducing-gas source (120), the burner comprising a multitude of injectors for injecting fluid jets into a downstream combustion zone, the burner including at least one first injector (11), a second fuel injector (21) surrounding the at least one first injector (11), and a third combustion-oxidant injector (31) surrounding the second injector (21), each first injector (11) being equipped with a laval nozzle for supersonic fluid injection into the combustion zone, the at least one first injector (11) being fluidly connected, via a valve unit (100), to an oxidant-gas source (110) and to a reducing-gas source (120), the valve unit (100) being adapted to switch between modes of fluid supply to the at least one first injector (11).

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 (a) and (b) to European Patent Application No. 25166038.7, filed Mar. 25, 2025, the entire contents of which are incorporated herein by reference.BACKGROUND

[0002] The present invention relates to burners and their use.

[0003] Burners are and remain commonly used devices for heating industrial processes and equipment by burning a fuel with an oxidant.

[0004] Traditionally, ambient air has been used as the combustion oxidant and fossil fuels as the fuel.

[0005] More recently, oxygen-enriched air and oxygen have been used as combustion oxidants, for example in order to increase the efficiency of the heating process compared to combustion with air.

[0006] Also, in recent years, the use of fossil fuels in particular, and of carbon-based fuels in general, has come under scrutiny, because of the greenhouse gases generated during their combustion. For this reason, the use of non-carbon-based fuels, such as hydrogen or ammonia, is increasingly being promoted.

[0007] There is thus a need to provide new combustion equipment and processes specifically adapted for the use of non-carbon-based fuels.

[0008] A number of industrial processes in which a charge is treated require, in addition to being supplied with thermal energy for heating the furnace and / or the charge, also the supply of a reducing agent (also referred to as “reductant” or “reducer”) for reducing the charge. A reducing agent causes the chemical reduction of the charge by electron donation to the charge. In the process, the reducing agent is itself oxidized. Examples of substances that are common reducing agents include CH4, pulverized coal, NH3 and carbon monoxide.

[0009] For such processes, it would be useful to be able to supply thermal heat and reducing agent by means of a same piece of equipment.

[0010] Similarly, a number of industrial processes in which a charge is treated require, in addition to being supplied with thermal energy for heating the furnace and / or the charge, also the supply of an oxidizing agent (also referred to as “oxidants” or “oxidizers”) for oxidizing the charge or of at least one element thereof. An oxidizing agent causes the chemical oxidation of the charge or the element and is itself chemically reduced in the process. Oxygen (used alone or in the form of a mixture with other components, as is, for example, the case for ambient air) is the most commonly used oxidizing agent.

[0011] For such processes, it would be useful to be able to supply thermal heat and oxidizing agent by means of a same piece of equipment.

[0012] In EP-B-0866138 a method and device for introducing gas, such as oxygen, nitrogen, argon carbon dioxide, hydrogen, and hydrocarbon gas, into a liquid pool, such as of molten metal, aqueous liquid or corrosive liquid, are known. According to said known method, the gas is injected from a lance having a converging and diverging nozzle, the tip of the lance being spaced from the surface of the liquid pool, thereby forming a gas stream having a supersonic velocity. The gas stream is surrounded with a flame envelope having a velocity less than that of the gas stream. The gas stream passes from the lance tip to the liquid pool surface and contacts the liquid pool surface with supersonic velocity so that gas from the gas stream passes through the surface of the liquid pool and into the liquid pool. EP-B-0866138 discloses in particular a lance having a central conduit, a first annular passageway and a second annular passageway, each of the annular passageways being coaxial with the central conduit. The central conduit terminates at an injection end or tip of the lance to form a main orifice. The first and second annular passageways also terminate at the injection end. The first and second annular passageways each form annular orifices around the main orifice or terminate in sets of first and second injection holes arranged in a circle around the main orifice. The central conduit communicates with a source of main gas. The second annular passageway communicates with a source of oxygen. The first annular passageway communicates with a source of fuel. The fuel may be any fuel, preferably a gaseous fuel and most preferably is natural gas or hydrogen. The nozzle used to eject the gas from the lance is a converging / diverging nozzle.

[0013] EP-B-1102003 discloses an apparatus for establishing a single coherent jet from a plurality of gas streams. The apparatus comprises a lance having a lance axis and having an end with a plurality of nozzles. Each of said nozzles have a nozzle axis at an inward angle to the lance axis. The apparatus further comprises means for passing at least one of fuel and oxidant out from the lance peripheral to said plurality of nozzles comprising:

[0014] a first ring of holes around the nozzles on the lance face for the flow of fuel and a second ring of holes around the first ring of holes on the nozzle face for the flow of oxidant or

[0015] a first ring of holes around the nozzles on the lance face for the flow of oxidant and a second ring of holes around the first ring of holes on the nozzle face for the flow of fuel.

[0016] EP0777751B1 discloses a burner / injector means of an electric arc furnace for use in a method of steelmaking using ferrous metallic scrap, the burner / injector means having a liquid-cooled body.

[0017] The corresponding method of steelmaking comprises the steps of:

[0018] a) heating the furnace using an electric arc to at least partially melt a portion of the scrap;

[0019] b) directing a controllable flow of a compressed auxiliary oxidizing gas having an average oxygen content between 20% and 50% and a controllable flow of fluid hydrocarbon fuel through respective third and second supply conduits located inside of the liquid-cooled body of the burner / injector means and further through respective third outlet opening and second outlet nozzle toward the interior of the furnace, wherein the auxiliary oxidizing gas and the hydrocarbon fuel mix and create a mixture which travels in the direction along a central axis of the third outlet opening and toward the interior of the furnace;

[0020] c) simultaneously directing a controllable flow of an oxygen rich compressed first oxidizing gas having average oxygen content of at least 80% through a first supply conduit located inside of the burner / injector means, through a plurality of first outlet nozzles adjacent to the discharge opening of the second outlet nozzle, and toward the furnace interior in a direction about and partially toward the discharged mixture to mix and form a flame envelope, wherein the first oxidizing gas participates in burning of the hydrocarbon fuel, thereby creating a high velocity impinging flame directed toward scrap located in a predetermined area of the furnace in front of the third outlet opening;

[0021] d) maintaining the controllable flows of the hydrocarbon fuel and the first oxidizing gas to provide initially a ratio of total oxygen provided by the first oxidizing gas and auxiliary oxidizing gas to hydrocarbon fuel near and preferably above the stoichiometric combustion ratio until a portion of scrap located in the predetermined area of the furnace is at least partially melted thereby creating an iron-carbon melt and a slag layer covering the iron-carbon melt;

[0022] e) directing toward the slag layer a stream of solid particles including carbonaceous fuel carried by the auxiliary compressed gas through the third supply conduit to participate in combustion inside of the formed flame envelope which is directed toward the predetermined area of the furnace previously occupied by the charged scrap when it has partially melted, wherein the first oxidizing gas partially burns the injected solid particles, and wherein the first oxidizing gas has a velocity sufficient to participate in burning the hydrocarbon fuel and combustible components of the injected solid particles and to enhance the penetrating ability and delivery range of the unburned portions of the injected solid particles;

[0023] f) after a portion of the scrap has been melted, of providing a controllable flow of a high velocity additional oxidizing gas having an average oxygen content in excess of 90% toward the iron-carbon melt through an additional supply conduit located inside the liquid-cooled body of the burner / injector means and then through an additional discharge opening disposed adjacent to the third outlet opening, and then toward the predetermined area of the furnace previously occupied by scrap that has been at least partially melted, wherein the additional oxidizing gas contacts and at least partially reacts with the carbon in at least one the of iron-carbon melt or the slag, thereby formed hot CO;

[0024] g) maintaining the step of directing the stream of solid particles and the stream of the first oxidizing toward the slag layer during the step of providing the additional oxidizing gas toward the iron-carbon melt; and

[0025] h) refining the iron-carbon melt to obtain a steel melt.SUMMARY

[0026] In response to the challenges described hereinabove, the present invention provides an equipment set comprising a burner, a valve unit, an oxidant-gas source and a reducing-gas source.

[0027] The burner comprises a multitude of injectors for injecting fluid jets into a downstream combustion zone. The multitude of injectors includes (i) at least one first injector (i.e. a single first injector or more than one first injector), (ii) a second injector surrounding the at least one first injector, and (iii) a third injector surrounding the second injector.

[0028] The second injector is an injector for injecting fuel into the combustion zone. Thereto, the second injector is fluidly connected to a source of the fuel.

[0029] The third injector is an injector for injecting a combustion oxidant into the combustion zone. Thereto, the third injector is fluidly connected to a source of the combustion oxidant.

[0030] Each first injector is equipped with a laval nozzle for supersonic fluid injection into the combustion zone. The at least one first injector is furthermore fluidly connected, via the valve unit, to the oxidant-gas source and to the reducing-gas source. The valve unit is adapted to switch between different modes of fluid supply to the at least one first injector.

[0031] The valve unit is more specifically adapted to switch between the following operation modes of fluid supply to the at least one first injector:

[0032] a first mode during which neither oxidant gas from the oxidant-gas source nor reducing gas from the reducing-gas source is supplied to the at least one first injector for supersonic injection thereof into the combustion zone,

[0033] a second mode during which oxidant gas is supplied from the oxidant-gas source to at least one first injector of the at least one first injectors for supersonic injection thereof into the combustion zone and

[0034] a third mode during which reducing gas from the reducing-gas source is supplied to at least one first injector of the at least one first injectors for supersonic injection thereof into the combustion zone.

[0035] According to a structurally less complex embodiment, the at least one first injector consists of, i.e. is, one first injector. In that case, the single first injector receives oxidant gas from the oxidant-gas source for its supersonic injection during the second mode, whereas the same single first injector receives reducing gas from the reducing-gas source for its supersonic injection during the third mode. The valve unit is then adapted to switch between different modes of fluid supply to the single first injector. The single first injector, the second injector and the third injector may advantageously be parallel injectors and more specifically coaxial injectors.

[0036] Alternatively, the at least one first injector may consist of two or more than two first injectors.

[0037] More specifically, according to such an alternative embodiment, the at least one first injector comprises at least one first oxidant injector (i.e. one or more than one first oxidant injectors) for supersonic injection of the oxidant gas into the combustion zone during the second mode and at least one first reducing-gas injector (i.e. one or more than one reducing-gas injectors) for supersonic injection of the reducing gas into the combustion zone during the third mode. Different first injectors are then used for the supersonic injection of oxidant gas into the combustion zone and for the supersonic injection of the reducing gas into the combustion zone. The valve unit is then adapted to switch between different modes of fluid supply to the multitude of first injectors. In such a case, the at least one first oxidant-gas injector is connected to the oxidant-gas source via the valve unit and the at least one first reducing-gas injector is connected to the reducing-gas source via said valve unit.

[0038] The second and third injectors are preferably coaxial injectors.

[0039] The at least one first, second and third injectors advantageously extend along parallel longitudinal axes.

[0040] The combustion oxidant is typically selected from the group consisting of oxygen, air, oxygen-enriched air and a gas obtained by mixing oxygen with an inert gas. The combustion oxidant is preferably oxygen.

[0041] Similarly, the oxidant gas from the oxidant-gas source is typically selected from the group consisting of oxygen, air, oxygen-enriched air and a gas obtained by mixing oxygen with an inert gas.

[0042] The composition of the combustion oxidant may be different from or identical to the composition of the oxidant gas. According to a particular embodiment, the combustion oxidant and the oxidant-gas are identical and are both supplied by a same source, i.e. by the oxidant-gas source.

[0043] In the context of the present invention, the term “oxygen” refers to a gas, which may be stored in liquefied form, consisting for at least 90 mol % and for up to 100 mol % of O2.

[0044] In the present context, the expression “inert gas” refers to a gas, which again may be stored in liquefied form that is neither a combustion oxidant nor a fuel under the conditions reigning in the combustion zone. Examples of such “inert gases” may be nitrogen, carbon dioxide and noble gases such as argon. Carbon-free inert gases, such as nitrogen and noble gases, are generally preferred.

[0045] The fuel may be selected from the group consisting of natural gas, hydrogen, ammonia, a mixed gas obtained by ammonia cracking and mixtures of at least two of said fuels. The fuel is preferably selected from the group of non-carbonaceous fuels consisting of hydrogen, ammonia, a mixed gas obtained by ammonia cracking and mixtures of at least two of said fuels.

[0046] Whereas a carbonaceous reducing gas, such as carbon monoxide or methane, may be used, the reducing gas is preferably a non-carbonaceous reducing gas. Said reducing gas may be selected from the group consisting of hydrogen, ammonia, a mixed gas obtained by ammonia cracking, mixtures of at least two of said reducing gases and mixtures of at least one of said reducing gases with at least one inert gas, for example a mixture of hydrogen and nitrogen.

[0047] The composition of the fuel may differ from the composition of the reducing gas. Alternatively, the composition of the fuel may be identical to the composition of the reducing gas. According to a particular embodiment, the fuel and the reducing gas are identical and are both supplied by a same source, i.e. by the reducing-gas source.

[0048] In particular for processes with a high-temperature combustion zone (typically ≥650° C.), the burner advantageously comprises a cooling jacket for cooling the burner by means of a cooling fluid. The cooling jacket surrounds the third injector. A preferred cooling fluid is cooling water, though other cooling fluids may be used.

[0049] The burner may further comprise a jet stabilizing chamber downstream of the first, second and third injectors and upstream of the combustion chamber. Such a stabilization chamber is particularly useful when, during operation, the burner injects fuel and combustion oxidant into the combustion zone so as to supply thermal energy thereto by means of a flame generated by the combustion of the injected fuel with the injected combustion oxidant, while simultaneously injecting a supersonic jet of the oxidizing or of the reducing agent. In that case, the difference in velocity between the supersonic jet and the flame may cause destabilization of the supersonic jet / flame. The presence of a stabilization chamber, as defined hereabove, helps to stabilize the flame and maintain supersonic jet coherence, for example for better penetration of the supersonic jet into the charge.

[0050] According to a preferred embodiment, the stabilization chamber has a cylindrical inner volume with a circular cross section. The cylindrical inner volume advantageously has a length L and a cross-section diameter D, with an L / D ratio between 0.5 and 5.0, preferably between 0.7 and 2.0, more preferably, between 0.8 and 1.5.

[0051] According to one embodiment of the present burner, the second injector terminates towards the combustion chamber in a ring of fuel injection openings, whereby said ring is positioned around the at least one first injector. Such a ring of fuel injection openings may, for example, be obtained when the second injector is formed between an inner and an outer tube, has an annular cross-section and terminates in an equally ring-shaped end-flange extending from the inner to the outer tube, when the end-flange presents a multitude of injection openings evenly distributed around the central void of the ring-shaped end-flange of the second injector.

[0052] Similarly, the third injector may terminate towards the combustion chamber in a ring of combustion-oxidant injection openings, whereby said ring of combustion-oxidant injection openings is positioned around the second injector. The ring of combustion-oxidant injection openings may be obtained using a third injector with ring-shaped end-flange as described above with respect to the second injector, i.e. with a third injector being formed between an inner and an outer tube and terminating in a ring-shaped end-flange extending between said tubes.

[0053] According to a useful embodiment, the third injector terminates towards the combustion chamber in a ring of combustion-oxidant injection openings positioned around the second injector, and said second injector similarly terminates towards the combustion chamber in a ring of fuel injection openings positioned around the at least one first injector. According to an advantageous embodiment thereof, each fuel injection opening of the ring of fuel injection openings is positioned on a bisector of a sector defined by the center and two adjacent combustion-oxidant injection openings of the ring of combustion-oxidant injection openings. In this manner, it is possible to alternate the fuel injection openings and the combustion-oxidant injection openings around the at least one first injector.

[0054] According to a useful embodiment of the burner, the at least one first injector is further connected, via the valve unit, to an inert-gas source. According to said embodiment, the valve unit is further adapted to enable at least one, preferably at least two and more preferably all three of the following:

[0055] supplying a purge-gas flow of inert gas from the inert-gas source to the first injector (when the burner comprises a single first injector) or to a first injector (when the burner comprises a multitude of first injectors) when no oxidant gas from the oxidant-gas source and no reducing gas from the reducing-gas source is supplied to said first injector;and / or

[0056] during the second mode: mixing of the oxidant gas from the oxidant-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector;and / or

[0057] during the third mode: mixing of the reducing gas from the reducing-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector.

[0058] As indicated earlier, the inert gas may be nitrogen, carbon dioxide or a noble gas such as argon, carbon-free inert gases, such as nitrogen and noble gases, being generally preferred.

[0059] The supply, during operation of the burner, of purge gas to a first injector to which neither oxidizing gas nor reducing gas is being supplied helps prevent said first injector being partially or totally blocked due to the deposit thereon of condensable substances from the atmosphere of the combustion zone. Moreover, in the case of a same first injector being used both for the supersonic injection of oxidizing gas during the second mode and for the supersonic injection of reducing gas during the third mode, supplying purge gas to said first injector in between the supersonic injections of these fluids increases the safety of the burner in that it ensures that reducing gas and oxidizing gas are not simultaneously present in said first injector, by sweeping the first injector with inert gas between said modes. Such a step may also be referred to as a further mode, namely a “purge mode”, between the second and third mode, in either order of succession.

[0060] Mixing of the oxidant gas from the oxidant-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector makes it possible, on the one hand, to reduce the concentration with which the oxidant gas is injected into the combustion zone during the second mode (for example in order to prevent excessive charge oxidation) and, on the other hand, to increase the mass flow rate of the gas stream with which the oxidant gas is injected during the second mode (for example to increase penetration of the oxidant gas into the charge).

[0061] Similarly, mixing of the reducing gas from the reducing-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector makes it possible, on the one hand, to reduce the concentration with which the reducing gas is injected into the combustion zone during the third mode (for example in order to prevent excessive charge reduction) and, on the other hand, to increase the mass flow rate of the gas stream with which the reducing gas is injected during the third mode (for example to increase penetration of the reducing gas into the charge).

[0062] The present invention further relates to the use of the equipment set, according to any one of the embodiments described above, for burning the fuel with the combustion oxidant for the heating of the combustion zone and, if present, for heating any charge present in the combustion zone.

[0063] The invention thus also relates to a method of heating the combustion zone and of generating a combustion atmosphere in said combustion zone by means of the equipment set according to any one of the above-described embodiments and whereby the valve unit regulates the fluid supply to the injectors of the burner as described above.

[0064] Said method includes at least one operation stage during which fuel from the fuel source is injected into the combustion zone via the second injector, combustion oxidant from the combustion-oxidant source is injected into the combustion zone via the third injector and the injected fuel is combusted with the injected combustion oxidant in the combustion zone to provide thermal energy thereto.

[0065] According to a preferred embodiment, the method comprises at least two of the following operation stages:

[0066] a heating stage without supersonic injection via the at least one first injector

[0067] During this heating stage, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector.

[0068] The fuel-to-oxygen ratio of the fuel injected into the combustion zone via the second injector and the combustion oxidant injected into the combustion zone via the third injector is controlled for optimal heat generation. Optimal heat generation is normally obtained when the fuel-to-oxygen ratio is substantially stoichiometric, i.e. with a fuel-to-oxygen ratio of the injected fuel and the injection combustion oxidant between 0.8 and 1.2 times the stoichiometric fuel-to-oxygen ratio, preferably between 0.9 and 1.1 times the stoichiometric fuel-to-oxygen ratio.

[0069] In order to ensure the complete combustion of the injected fuel, a slight excess of combustion oxidant may be injected, for example with an fuel-to-oxygen ratio of the injected fuel and the injected combustion oxidant of at least 0.7 times but below 1.0 times the stoichiometric fuel-to-oxygen ratio.

[0070] When ingress of ambient air into the combustion zone cannot be avoided, a fuel-to-oxygen ratio of the injected fuel and the injected combustion oxidant above the stoichiometric fuel-to-oxygen ratio may be used as the ingress air provides additional oxygen for the (complete) combustion of the fuel. In that case, the fuel-to-oxygen ratio may be higher than 1.0 times stoichiometric fuel-to-oxygen ratio and, for example, depending on the level of air ingress up to 1.3 times the stoichiometric fuel-to-oxygen ratio.

[0071] On the other hand, when additional combustible matter is present in the combustion zone, for example because a charge, such as, for example, contaminated scrap metal, is present in the combustion zone that contains and / or releases combustible matter when heated, the fuel-to-oxygen ratio of the injected fuel to the injected combustion oxidant may advantageously be below the stoichiometric fuel-to-oxygen ratio so as to provide oxygen for the combustion of said additional combustible matter as well as for the combustion of the injected fuel. In that case, the fuel-to-oxygen ratio of the injected fuel to the injected combustion oxidant is less than 1.0 times the stoichiometric fuel-to-oxygen ratio and, for example, depending on the amount of combustible matter present in / released from the charge, upwards of 0.7 times the stoichiometric fuel-to-oxygen ratio.

[0072] a neutral heating stage with supersonic injection

[0073] During this heating stage, again, fuel from the fuel source is injected into the combustion zone via the second injector, and thus subsonically, and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected subsonically into the combustion zone via the third injector.

[0074] In addition, oxidant gas from the oxidant-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector.

[0075] Alternatively, when the reducing gas is a gaseous fuel, such as hydrogen, reducing gas from the reducing-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector.

[0076] When the reducing gas is a gaseous fuel and multiple first injectors are present, it is even possible to combine, during this stage, the subsonic injection of fuel from the fuel source into the combustion zone via the second injector and the subsonic injection of combustion oxidant from the combustion-oxidant source into the combustion zone via the third injector, with supersonic injection of both oxidant gas from the oxidant-gas source and reducing gas from the reducing-gas source via the first injectors.

[0077] In the present context, “neutral heating” refers to the heating of the combustion zone by means of fuel combustion, whereby the generated combustion gases are essentially non-reducing and non-oxidizing and therefore do not cause chemical reduction or oxidation of a charge present in the combustion zone.

[0078] Consequently, during the neutral heating stage with supersonic injection, the flow rates into the combustion zone of subsonic fuel from the fuel source and of subsonic combustion oxidant from the oxidant-gas source, as well as of the supersonic oxidant gas from the oxidant-gas source and / or the supersonic reducing gas from the reducing-gas source are regulated so as to generate such an essentially non-reducing and non-oxidizing atmosphere in the combustion zone, taking into account any air ingress or combustible substances present in the charge.

[0079] The combination of subsonic injection of combustion oxidant by means of the third injector with supersonic injection of oxidant gas by means of the at least one first injector, and thus the repartition of the injected oxygen between the third injector and the at least one first injector, makes it possible to adapt the properties of the generated flame, in particular the velocity of the generated flame. The same is true for the combination of subsonic fuel injection by means of the second injector with supersonic injection of a reducing gas that is a gaseous fuel.

[0080] an oxidizing stage

[0081] During an oxidizing stage, oxidant gas from the oxidant-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector, typically in order to oxidize, within the combustion zone, a charge or elements present in the charge.

[0082] By thus injecting the oxidant gas supersonically, a better contact or deeper penetration of the oxidant gas with / into the charge may be obtained.

[0083] When as is often the case, the combustion zone must also be heated during the oxidizing stage, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector.

[0084] In that case, the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector is advantageously at most equal to, and optionally lower than, the stoichiometric fuel-to-oxygen ratio, so that the heating by fuel combustion does not reduce the amount of oxygen in the combustion zone that is available for other purposes, such as, in particular the oxidation of the charge or elements present therein.

[0085] For example, the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector is less than or equal to the stoichiometric fuel-to-oxygen ratio, preferably below 0.9 times the stoichiometric fuel-to-oxygen ratio and greater than or equal to 0.7 times the stoichiometric fuel-to-oxygen ratio, though, as discussed earlier, adjustments of the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector may be made in order to take into account ingress air.

[0086] a reducing stage

[0087] During a reducing stage, reducing gas from the reducing-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector, typically in order to cause chemical reduction, within the combustion zone, of a charge or elements present in the charge.

[0088] By injecting the reducing gas supersonically, a better contact or deeper penetration of the reducing gas with / into the charge may be obtained.

[0089] When as is typically the case, the combustion zone must be heated during the reducing stage, fuel from the fuel source is injected subsonically into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected subsonically into the combustion zone via the third injector.

[0090] In that case, the fuel-to-oxygen of the fuel injected via the second injector and the combustion oxidant injected via the third injector is advantageously at least equal to, and optionally higher than, the stoichiometric fuel-to-oxygen ratio, so that the heating by fuel combustion does not reduce the amount of reducing agent in the combustion zone that is available for chemically reducing the charge or elements present therein.

[0091] For example, the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector is higher than or equal to 1.0 times, preferably at least 1.1 times, the stoichiometric fuel-to-oxygen ratio and, for example, not more than 1.3 times the stoichiometric fuel-to-oxygen ratio.

[0092] Again, adjustments of the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector may be made in order to take into account other factors, such as ingress air.

[0093] As stated, the method according to the present invention usefully comprises at least two of the following operation stages:

[0094] a heating stage without supersonic injection via the at least one first injector as described above;

[0095] a neutral heating stage with supersonic injection as described above;

[0096] a combined oxidizing and heating stage, i.e. an oxidizing stage, during which in addition to the supersonic injection of oxidant gas via the at least one first injector, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector, as described above;

[0097] a combined reducing and heating stage, i.e. a reducing stage, during which in addition to the supersonic injection of reducing gas via the at least one first injector, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector, as described above.

[0098] As mentioned earlier, during each operating stage of the method of the present invention, the fluid supply to the at least one first injector of the burner, and by extension to all injectors of the burner, is conducted via the valve unit, via which said fluid supply is regulated.

[0099] The present invention thus covers in particular a method as described above:

[0100] comprising or consisting of a heating stage and an oxidizing stage, in particular at least a heating stage and a combined oxidizing and heating stage; whereby, according to a specific embodiment, the heating stage precedes the oxidizing stage / combined oxidizing and heating stage; or

[0101] comprising or consisting of a heating stage and a reducing stage, in particular a heating stage and a combined reducing and heating stage; whereby, according to a specific embodiment, the heating stage precedes the reducing stage / combined reducing and heating stage; or

[0102] comprising or consisting of a heating stage, an oxidizing stage and a reducing stage; in particular a heating stage, an oxidizing stage and a combined reducing and heating stage; and more particularly a heating stage, a combined oxidizing and heating stage and a combined reducing and heating stage; whereby, according to a specific embodiment, the heating stage precedes the oxidizing stage / combined oxidizing and heating stage, in turn preceding the reducing stage / combined reducing and heating stage.

[0103] Methods as discussed above are particularly useful for batch processes with multiple successive process stages as well as for semibatch processes with multiple successive stages between successive charging or successive discharging steps.

[0104] The method of the invention, according to any one of the embodiments described above, is particularly useful when a charge is melted in the combustion zone during the heating step. The molten charge is thereafter subjected to one or more oxidizing and / or reducing stages in the combustion zone.BRIEF DESCRIPTION OF THE DRAWINGS

[0105] The present invention and its advantages are described in more detail in the following non-limiting examples, reference being made to FIGS. 1 to 4, whereby:

[0106] FIG. 1 is a schematic cross-sectional view of an embodiment of a burner of the equipment set according to the invention according to a first plane,

[0107] FIG. 2 is a schematic cross-sectional view of the burner of FIG. 1 according to a second plane perpendicular to the first plane,

[0108] FIG. 3 is a schematic front view into the jet-stabilizing chamber of the burner of FIG. 1, and

[0109] FIG. 4 is a schematic representation of the equipment set including the burner of FIG. 1.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0110] The illustrated burner comprises multiple injectors for injecting fluid jets into a combustion zone located downstream of the burner. The combustion zone is, for example, located in a combustion / heating chamber of a furnace.

[0111] The burner comprises a first, central, injector 11, a second injector 21 that surrounds the first injector 10 and a third injector 31 that surrounds the second injector 21.

[0112] According to the illustrated embodiment, the first, second and third injectors, respectively 11, 21 and 31, are coaxially arranged.

[0113] Second injector 21 is a fuel injector. In use, second injector 21 is connected, via its inlet 20, to a source of fuel, such as a hydrogen tank (not shown).

[0114] Third injector 31 is a combustion-oxidant injector. In use, third injector 31 is connected, via its inlet 30, to a source of combustion oxidant, such as an air blower, or, preferably, an oxygen plant or reservoir.

[0115] First injector 11 is equipped with a laval nozzle 1 to enable first injector 11 to inject fluid supersonically into the downstream combustion zone. D1 is the outlet diameter of laval nozzle 1 and thus also the outlet diameter of first injector 11.

[0116] The inlet 10 of first injector 11 is selectively connected, via valve unit 100, to an oxidant-gas source 110 and to a reducing-gas source 120.

[0117] Valve unit controls 100 the flow of oxidant gas from the oxidant-gas source 110 to first injector 11 and the flow of reducing gas from the reducing-gas source 120 to first injector 11 is likewise controlled by means of said valve unit 100.

[0118] Valve unit 100 is more specifically adapted to switch between the following modes of fluid supply to first injector 11:

[0119] a mode, referred to as “first mode”, during which neither oxidant gas nor reducing gas is supplied to first injector 11 for supersonic injection into the downstream combustion zone,

[0120] a mode, referred to as “second mode”, during which oxidant gas from is supplied from the oxidant-gas source 110 to first injector 11 for supersonic injection of a flow of said oxidant gas into the downstream combustion zone, and

[0121] a mode, referred to as “third mode”, during which reducing gas from the reducing-gas source 120 is supplied to first injector 11 for supersonic injection of a flow of said reducing gas into the downstream combustion zone.

[0122] During the first mode, no supersonic injection of fluid into the combustion zone is performed by first injector 11.

[0123] Typically, during the second mode, only oxidant gas is supersonically injected via first injector 11. Similarly, during the third mode, only reducing gas is typically supersonically injected via first injector 11.

[0124] However, it is also possible for the oxidant gas, respectively the reducing gas, to be injected supersonically together with an additional gas, such as an inert gas or a mainly inert gas, such as ambient air, via first injector 11 during the second, respectively third mode. For example, the addition / admixture of an inert gas may be useful to attenuate the oxidizing effect of the oxidant gas, respectively the reducing effect of the reducing gas on a charge in the combustion zone and / or to increase the amount of gas (in Nm3) that is being supersonically injected.

[0125] FIG. 4 illustrates an embodiment whereby first injector 11 is selectively connected to oxidant-gas source 110 and reducing-gas source 120, but also to inert-gas source 130, the flow of inert gas from inert-gas source 130 to first injector 11 being likewise controlled by valve unit 100.

[0126] In the illustrated embodiment, the burner comprises a single first injector 11 via which oxidant gas is supersonically injected during the second mode and via which reducing gas is supersonically injected during the third mode.

[0127] According to an alternative embodiment, the burner comprises multiple first injectors 11.

[0128] Similarly to the illustrated embodiment, individual first injectors 11 may be used both to supersonically inject oxidant gas during the second mode and to supersonically inject reducing gas during the third mode.

[0129] Alternatively, one or more first injectors 11 (oxidant-gas-only first injectors) may be dedicated for the supersonic injection of oxidant gas during the second mode only, while one or more other first injectors 11 (reducing-gas-only first injectors) are dedicated for the supersonic injection of reducing gas during the third mode only.

[0130] When a first injector 11 is not used for supersonic injection of a fluid into the combustion zone, as is the case during the first mode, but as is also the case for any oxidant-gas-only first injectors during the third mode or any reducing-gas-only first injectors during the second mode, said first injector 11 may inject no fluid into the downstream combustion zone. However, depending on the process for which the combustion zone is used, it may be useful or even necessary, to maintain a subsonic fluid flow through a first injector 11 when not being used for supersonic injection, for example in order to maintain some cooling of the first injector and / or to prevent said first injector from being blocked by deposits formed thereon. The fluid subsonically injected via a first injector 11 during the first mode may be oxidant gas, reducing gas or, preferably, a purge gas.

[0131] Second injector 21 is a subsonic fuel injector. In the illustrated embodiment, second injector 21 terminates in a ring of fuel injection nozzles / openings 2 annularly positioned around laval nozzle 1 of first injector 11. D2 is the diameter of fuel injection nozzles / openings 2. As shown in FIG. 3, said ring of fuel injection nozzles / openings 2 is coaxial / concentric with laval nozzle 1 and fuel injection nozzles / openings 2 are evenly / equidistantly distributed on said ring.

[0132] The edge-to-edge distance L12 between fuel injection nozzles / openings 2 and laval nozzle 1 is preferably between 1.19 and 1.55 times diameter D1 of laval nozzle 1, preferably between 1.29 and 1.45 times, more preferably between 1.32 and 1.42 times diameter D1 of laval nozzle 1.

[0133] Third injector 31 is a subsonic combustion-oxidant injector. As shown in FIG. 3, third injector 31 similarly terminates in a ring of combustion-oxidant injection nozzles / openings 3 annularly positioned around laval nozzle 1 of first injector 11 and around the ring of fuel injection nozzles / openings 2. Said ring of combustion-oxidant injection nozzles / openings 3 is coaxial / concentric with laval nozzle 1, and with the ring of fuel injection nozzles / openings 2. Again, combustion-oxidant injection nozzles / openings 3 are evenly / equidistantly distributed on the ring of combustion-oxidant injection nozzles / openings 3.

[0134] The edge-to-edge distance L13 between oxidant injection nozzles / openings 3 and laval nozzle 1 is greater than the edge-to-edge distance L12 between fuel injection nozzles / openings 2 and laval nozzle 1. Edge-to-edge distance L13 between oxidant injection nozzles / openings 3 and laval nozzle 1 is preferably between 2.40 and 2.80 times diameter D1 of laval nozzle 1, preferably between 2.45 and 2.75 times, more preferably between 2.50 and 2.70 times diameter D1 of laval nozzle 1.

[0135] As shown in FIG. 3, in the illustrated preferred embodiment, each fuel injection opening 2 is positioned on a bisector of a sector defined by the center, corresponding to the location of laval nozzle 1, and two adjacent combustion-oxidant injection openings 3 of the ring of combustion-oxidant injection openings 3. This provides for optimized mixing of fuel injected via fuel injection openings 2 with combustion oxidant injected via combustion-oxidant injection openings 2, when second injector 21 and third injector 31 simultaneously inject fuel, respectively combustion oxidant into the combustion zone, for the combustion of the injected fuel with the injected combustion oxidant therein.

[0136] The outlet of first injector 11, fuel injection openings 2 forming the outlet(s) of the second injector 21 and combustion-oxidant injection openings 3 forming the outlet(s) of the second injector 31 are located in a same plane 51.

[0137] The illustrated burner further comprises a jet-stabilizing chamber 5, downstream of first injector 11, second injector 21 and third injector 31, but upstream of the combustion zone. When second injector 21 and third injector 31 simultaneously inject fuel, respectively combustion oxidant, into the combustion zone for the combustion of the injected fuel with the injected combustion oxidant therein, initial mixing of the injected fuel with the injected combustion oxidant can take place in jet-stabilizing chamber 5 of the burner.

[0138] Jet-stabilizing chamber 5 shields the injected fluids at their respective points of injection 1, 2 and 3 from the frequently turbulent atmosphere in the combustion zone. Moreover, when, in addition to the injection of fuel via second injector 21 and the injection of combustion oxidant via third injector 31, one or more supersonic fluid jets are injected by means of the at least one first injector 11, the presence of jet-stabilizing chamber 5 reduced interference by the supersonic jet and / or dilution by the combustion-chamber atmosphere, thereby improving flame stability.

[0139] Jet-stabilizing chamber 5 is a cylindrical chamber with an axial dimension L in the axial direction of the first injector 11 and a diameter D perpendicular to the axial dimension L. Plane 51 forms the basis of said cylindrical chamber.

[0140] According to a preferred embodiment the L / D ratio of jet-stabilizing chamber 5 is between 0.90 and 1.34, preferably between 1.00 and 1.24, for example between 1.08 and 1.16.

[0141] In order to protect the burner against thermal damage due to the high temperatures in the combustion chamber, the illustrated burner is equipped with a cooling jacket 41 to cool the burner with a cooling fluid, such as, for example, cooling water, in which case the cooling jacket 41 is a water jacket. Cooling jacket 41 surrounds third injector 31 at least towards the downstream / injection end of the burner. It comprises a cooling-fluid inlet 40a and a cooling-fluid outlet 40b. During operation of the burner, cooling fluid is supplied to cooling-fluid inlet 40a and is caused to flow in inner sleeve 41a of cooling jacket 41 all around third injector 31 in the direction towards combustion-oxidant injection nozzles / openings 3 and then all around stabilizing chamber 5, before flowing back through outer sleeve 41b to cooling-fluid outlet 40b.

[0142] The usefulness and flexibility of the equipment set according to the present invention is illustrated by the non-limiting example hereafter in which the burner is inter alia used to heat a combustion zone of a furnace combustion chamber in which a charge is to be treated.

[0143] In order to raise the temperature in the combustion zone gradually to its operation temperature without causing thermal damage to the refractory material of the combustion chamber, the combustion zone is heated up without supersonic fluid injection. During said heating-up stage, fuel is injected into the combustion zone via second injector 21 and combustion oxidant injected into the combustion zone via third injector 31 at a substantially stoichiometric fuel-to-oxygen ratio. As there is no risk of thermal damage to or deposits onto the first injector 11 at this stage, one may choose not to inject any gas into the combustion zone via first injector 11 at this stage. Alternatively, a subsonic fluid jet may be injected by first injector 11 during this stage.

[0144] Once the combustion zone has reached the desired operation temperature, the charge is introduced into the combustion chamber and the burner is used to heat the charge in the combustion zone. In order to enhance the penetration of the flame into the charge or, more generally, improve the contact between the flame and the charge, the burner is now used to heat the charge by heating with supersonic injection. During this stage, oxidant-gas from oxidant-gas source 110 is injected into the combustion zone at supersonic velocity via first injector 11, fuel is injected subsonically into the combustion zone via second injector 21 and combustion oxidant is injected subsonically into the combustion zone via third injector 31. The fuel-to-oxygen ratio of, on the one hand, the fuel injected into the combustion zone via second injector 21 and, on the other hand, the combustion oxidant injected into the combustion zone via third injector 31 and the oxygen-gas injected into the combustion zone via the first injector 11 corresponds to the stoichiometric ratio, unless air ingress into the combustion chamber justifies a higher fuel-to-oxygen injection ratio. However, if during this stage, combustion of combustible substances (contaminants) present in the charge is desired, the fuel-to-oxygen injection ratio is selected so that an excess of oxygen is available in the combustion zone for the combustion of said combustible substances therein. If, on the other hand, it is important to avoid oxidation of the charge at this stage, the fuel-to-oxygen injection ratio is selected so as to avoid an excess of oxygen in contact with the charge in the combustion zone.

[0145] Such a heating stage with supersonic injection may, for example, be a melting stage.

[0146] Once the charge is heated and depending on the nature of the charge and the nature of the treatment to which the charge is to be subjected, the next step may be an oxidizing heating stage, during which the charge is heated and oxidized, or a reducing heating stage, during which the charge is heated and reduced, or even a succession of an oxidizing heating stage and a reducing heating stage in any given order.

[0147] During such an oxidizing heating stage, oxidant-gas from the oxidant-gas source 110 is injected into the combustion zone at supersonic velocity via first injector 11, whereby the supersonic injection velocity enables the oxygen gas to penetrate into the charge. Meanwhile, fuel is injected subsonically into the combustion zone via second injector 21 and combustion oxidant is injected subsonically into the combustion zone via third injector 31. Given that the charge is to be oxidized, the fuel-to-oxygen ratio of, on the one hand, the fuel injected into the combustion zone via second injector 21 and, on the other hand, the combustion oxidant injected into the combustion zone via third injector 31 and the oxygen-gas injected into the combustion zone via the first injector 11 is kept below the stoichiometric ratio in order to make sure that, in spite of the oxygen consumed by fuel combustion, oxygen remains available for the oxidation of the charge.

[0148] During a reducing heating stage, reducing gas from the reducing-gas source 120 is injected into the combustion zone at supersonic velocity via first injector 11. Meanwhile, fuel is injected subsonically into the combustion zone via second injector 21 and combustion oxidant is injected subsonically into the combustion zone via third injector 31. Given that reduction of the charge is to be achieved and thus oxidation of the charge is to be avoided at this stage, the fuel-to-oxygen ratio of the fuel injected into the combustion zone via second injector 21 and the combustion oxidant injected into the combustion zone via third injector 31 is kept at or above the stoichiometric ratio so that the reducing agent is not consumed by the combustion oxidant and / or oxygen from air ingress into the combustion chamber.

[0149] If, thereafter, the charge is to be maintained in the combustion chamber at high temperature, for example in order to keep the charge from solidifying, the burner may be used to avoid cooling of the charge whereby fuel is injected into the combustion zone via second injector 21 for its combustion in the combustion zone with combustion oxidant injected via third injector 31. Depending on the level of heating required and depending on the risk of undesired oxidation, respectively reduction of the charge, the burner may then be operated without supersonic injection (as during the heating-up stage) or with supersonic injection and a non-oxidizing or non-reducing atmosphere in the combustion zone (as during the heating-up stage). If the burner is used without supersonic injection at this stage, it is advisable to inject a subsonic fluid stream via first injector 11 at this stage to prevent said first injector 11 from being blocked by deposits thereon.

[0150] During the entire process, the fluid supply to the injectors 11, 21 and 31 is regulated by the valve unit 100 of the equipment set, for example under the control of an accordingly programmed control unit 101.

[0151] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0152] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0153] “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.

[0154] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0155] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0156] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0157] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

Examples

Embodiment Construction

[0110]The illustrated burner comprises multiple injectors for injecting fluid jets into a combustion zone located downstream of the burner. The combustion zone is, for example, located in a combustion / heating chamber of a furnace.

[0111]The burner comprises a first, central, injector 11, a second injector 21 that surrounds the first injector 10 and a third injector 31 that surrounds the second injector 21.

[0112]According to the illustrated embodiment, the first, second and third injectors, respectively 11, 21 and 31, are coaxially arranged.

[0113]Second injector 21 is a fuel injector. In use, second injector 21 is connected, via its inlet 20, to a source of fuel, such as a hydrogen tank (not shown).

[0114]Third injector 31 is a combustion-oxidant injector. In use, third injector 31 is connected, via its inlet 30, to a source of combustion oxidant, such as an air blower, or, preferably, an oxygen plant or reservoir.

[0115]First injector 11 is equipped with a laval nozzle 1 to enable firs...

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 (a) and (b) to European Patent Application No. 25166038.7, filed Mar. 25, 2025, the entire contents of which are incorporated herein by reference.BACKGROUND

[0002] The present invention relates to burners and their use.

[0003] Burners are and remain commonly used devices for heating industrial processes and equipment by burning a fuel with an oxidant.

[0004] Traditionally, ambient air has been used as the combustion oxidant and fossil fuels as the fuel.

[0005] More recently, oxygen-enriched air and oxygen have been used as combustion oxidants, for example in order to increase the efficiency of the heating process compared to combustion with air.

[0006] Also, in recent years, the use of fossil fuels in particular, and of carbon-based fuels in general, has come under scrutiny, because of the greenhouse gases generated during their combustion. For this reason, the use of non-carbon-based fuels, such as hydrogen or ammonia, is increasingly being promoted.

[0007] There is thus a need to provide new combustion equipment and processes specifically adapted for the use of non-carbon-based fuels.

[0008] A number of industrial processes in which a charge is treated require, in addition to being supplied with thermal energy for heating the furnace and / or the charge, also the supply of a reducing agent (also referred to as “reductant” or “reducer”) for reducing the charge. A reducing agent causes the chemical reduction of the charge by electron donation to the charge. In the process, the reducing agent is itself oxidized. Examples of substances that are common reducing agents include CH4, pulverized coal, NH3 and carbon monoxide.

[0009] For such processes, it would be useful to be able to supply thermal heat and reducing agent by means of a same piece of equipment.

[0010] Similarly, a number of industrial processes in which a charge is treated require, in addition to being supplied with thermal energy for heating the furnace and / or the charge, also the supply of an oxidizing agent (also referred to as “oxidants” or “oxidizers”) for oxidizing the charge or of at least one element thereof. An oxidizing agent causes the chemical oxidation of the charge or the element and is itself chemically reduced in the process. Oxygen (used alone or in the form of a mixture with other components, as is, for example, the case for ambient air) is the most commonly used oxidizing agent.

[0011] For such processes, it would be useful to be able to supply thermal heat and oxidizing agent by means of a same piece of equipment.

[0012] In EP-B-0866138 a method and device for introducing gas, such as oxygen, nitrogen, argon carbon dioxide, hydrogen, and hydrocarbon gas, into a liquid pool, such as of molten metal, aqueous liquid or corrosive liquid, are known. According to said known method, the gas is injected from a lance having a converging and diverging nozzle, the tip of the lance being spaced from the surface of the liquid pool, thereby forming a gas stream having a supersonic velocity. The gas stream is surrounded with a flame envelope having a velocity less than that of the gas stream. The gas stream passes from the lance tip to the liquid pool surface and contacts the liquid pool surface with supersonic velocity so that gas from the gas stream passes through the surface of the liquid pool and into the liquid pool. EP-B-0866138 discloses in particular a lance having a central conduit, a first annular passageway and a second annular passageway, each of the annular passageways being coaxial with the central conduit. The central conduit terminates at an injection end or tip of the lance to form a main orifice. The first and second annular passageways also terminate at the injection end. The first and second annular passageways each form annular orifices around the main orifice or terminate in sets of first and second injection holes arranged in a circle around the main orifice. The central conduit communicates with a source of main gas. The second annular passageway communicates with a source of oxygen. The first annular passageway communicates with a source of fuel. The fuel may be any fuel, preferably a gaseous fuel and most preferably is natural gas or hydrogen. The nozzle used to eject the gas from the lance is a converging / diverging nozzle.

[0013] EP-B-1102003 discloses an apparatus for establishing a single coherent jet from a plurality of gas streams. The apparatus comprises a lance having a lance axis and having an end with a plurality of nozzles. Each of said nozzles have a nozzle axis at an inward angle to the lance axis. The apparatus further comprises means for passing at least one of fuel and oxidant out from the lance peripheral to said plurality of nozzles comprising:

[0014] a first ring of holes around the nozzles on the lance face for the flow of fuel and a second ring of holes around the first ring of holes on the nozzle face for the flow of oxidant or

[0015] a first ring of holes around the nozzles on the lance face for the flow of oxidant and a second ring of holes around the first ring of holes on the nozzle face for the flow of fuel.

[0016] EP0777751B1 discloses a burner / injector means of an electric arc furnace for use in a method of steelmaking using ferrous metallic scrap, the burner / injector means having a liquid-cooled body.

[0017] The corresponding method of steelmaking comprises the steps of:

[0018] a) heating the furnace using an electric arc to at least partially melt a portion of the scrap;

[0019] b) directing a controllable flow of a compressed auxiliary oxidizing gas having an average oxygen content between 20% and 50% and a controllable flow of fluid hydrocarbon fuel through respective third and second supply conduits located inside of the liquid-cooled body of the burner / injector means and further through respective third outlet opening and second outlet nozzle toward the interior of the furnace, wherein the auxiliary oxidizing gas and the hydrocarbon fuel mix and create a mixture which travels in the direction along a central axis of the third outlet opening and toward the interior of the furnace;

[0020] c) simultaneously directing a controllable flow of an oxygen rich compressed first oxidizing gas having average oxygen content of at least 80% through a first supply conduit located inside of the burner / injector means, through a plurality of first outlet nozzles adjacent to the discharge opening of the second outlet nozzle, and toward the furnace interior in a direction about and partially toward the discharged mixture to mix and form a flame envelope, wherein the first oxidizing gas participates in burning of the hydrocarbon fuel, thereby creating a high velocity impinging flame directed toward scrap located in a predetermined area of the furnace in front of the third outlet opening;

[0021] d) maintaining the controllable flows of the hydrocarbon fuel and the first oxidizing gas to provide initially a ratio of total oxygen provided by the first oxidizing gas and auxiliary oxidizing gas to hydrocarbon fuel near and preferably above the stoichiometric combustion ratio until a portion of scrap located in the predetermined area of the furnace is at least partially melted thereby creating an iron-carbon melt and a slag layer covering the iron-carbon melt;

[0022] e) directing toward the slag layer a stream of solid particles including carbonaceous fuel carried by the auxiliary compressed gas through the third supply conduit to participate in combustion inside of the formed flame envelope which is directed toward the predetermined area of the furnace previously occupied by the charged scrap when it has partially melted, wherein the first oxidizing gas partially burns the injected solid particles, and wherein the first oxidizing gas has a velocity sufficient to participate in burning the hydrocarbon fuel and combustible components of the injected solid particles and to enhance the penetrating ability and delivery range of the unburned portions of the injected solid particles;

[0023] f) after a portion of the scrap has been melted, of providing a controllable flow of a high velocity additional oxidizing gas having an average oxygen content in excess of 90% toward the iron-carbon melt through an additional supply conduit located inside the liquid-cooled body of the burner / injector means and then through an additional discharge opening disposed adjacent to the third outlet opening, and then toward the predetermined area of the furnace previously occupied by scrap that has been at least partially melted, wherein the additional oxidizing gas contacts and at least partially reacts with the carbon in at least one the of iron-carbon melt or the slag, thereby formed hot CO;

[0024] g) maintaining the step of directing the stream of solid particles and the stream of the first oxidizing toward the slag layer during the step of providing the additional oxidizing gas toward the iron-carbon melt; and

[0025] h) refining the iron-carbon melt to obtain a steel melt.SUMMARY

[0026] In response to the challenges described hereinabove, the present invention provides an equipment set comprising a burner, a valve unit, an oxidant-gas source and a reducing-gas source.

[0027] The burner comprises a multitude of injectors for injecting fluid jets into a downstream combustion zone. The multitude of injectors includes (i) at least one first injector (i.e. a single first injector or more than one first injector), (ii) a second injector surrounding the at least one first injector, and (iii) a third injector surrounding the second injector.

[0028] The second injector is an injector for injecting fuel into the combustion zone. Thereto, the second injector is fluidly connected to a source of the fuel.

[0029] The third injector is an injector for injecting a combustion oxidant into the combustion zone. Thereto, the third injector is fluidly connected to a source of the combustion oxidant.

[0030] Each first injector is equipped with a laval nozzle for supersonic fluid injection into the combustion zone. The at least one first injector is furthermore fluidly connected, via the valve unit, to the oxidant-gas source and to the reducing-gas source. The valve unit is adapted to switch between different modes of fluid supply to the at least one first injector.

[0031] The valve unit is more specifically adapted to switch between the following operation modes of fluid supply to the at least one first injector:

[0032] a first mode during which neither oxidant gas from the oxidant-gas source nor reducing gas from the reducing-gas source is supplied to the at least one first injector for supersonic injection thereof into the combustion zone,

[0033] a second mode during which oxidant gas is supplied from the oxidant-gas source to at least one first injector of the at least one first injectors for supersonic injection thereof into the combustion zone and

[0034] a third mode during which reducing gas from the reducing-gas source is supplied to at least one first injector of the at least one first injectors for supersonic injection thereof into the combustion zone.

[0035] According to a structurally less complex embodiment, the at least one first injector consists of, i.e. is, one first injector. In that case, the single first injector receives oxidant gas from the oxidant-gas source for its supersonic injection during the second mode, whereas the same single first injector receives reducing gas from the reducing-gas source for its supersonic injection during the third mode. The valve unit is then adapted to switch between different modes of fluid supply to the single first injector. The single first injector, the second injector and the third injector may advantageously be parallel injectors and more specifically coaxial injectors.

[0036] Alternatively, the at least one first injector may consist of two or more than two first injectors.

[0037] More specifically, according to such an alternative embodiment, the at least one first injector comprises at least one first oxidant injector (i.e. one or more than one first oxidant injectors) for supersonic injection of the oxidant gas into the combustion zone during the second mode and at least one first reducing-gas injector (i.e. one or more than one reducing-gas injectors) for supersonic injection of the reducing gas into the combustion zone during the third mode. Different first injectors are then used for the supersonic injection of oxidant gas into the combustion zone and for the supersonic injection of the reducing gas into the combustion zone. The valve unit is then adapted to switch between different modes of fluid supply to the multitude of first injectors. In such a case, the at least one first oxidant-gas injector is connected to the oxidant-gas source via the valve unit and the at least one first reducing-gas injector is connected to the reducing-gas source via said valve unit.

[0038] The second and third injectors are preferably coaxial injectors.

[0039] The at least one first, second and third injectors advantageously extend along parallel longitudinal axes.

[0040] The combustion oxidant is typically selected from the group consisting of oxygen, air, oxygen-enriched air and a gas obtained by mixing oxygen with an inert gas. The combustion oxidant is preferably oxygen.

[0041] Similarly, the oxidant gas from the oxidant-gas source is typically selected from the group consisting of oxygen, air, oxygen-enriched air and a gas obtained by mixing oxygen with an inert gas.

[0042] The composition of the combustion oxidant may be different from or identical to the composition of the oxidant gas. According to a particular embodiment, the combustion oxidant and the oxidant-gas are identical and are both supplied by a same source, i.e. by the oxidant-gas source.

[0043] In the context of the present invention, the term “oxygen” refers to a gas, which may be stored in liquefied form, consisting for at least 90 mol % and for up to 100 mol % of O2.

[0044] In the present context, the expression “inert gas” refers to a gas, which again may be stored in liquefied form that is neither a combustion oxidant nor a fuel under the conditions reigning in the combustion zone. Examples of such “inert gases” may be nitrogen, carbon dioxide and noble gases such as argon. Carbon-free inert gases, such as nitrogen and noble gases, are generally preferred.

[0045] The fuel may be selected from the group consisting of natural gas, hydrogen, ammonia, a mixed gas obtained by ammonia cracking and mixtures of at least two of said fuels. The fuel is preferably selected from the group of non-carbonaceous fuels consisting of hydrogen, ammonia, a mixed gas obtained by ammonia cracking and mixtures of at least two of said fuels.

[0046] Whereas a carbonaceous reducing gas, such as carbon monoxide or methane, may be used, the reducing gas is preferably a non-carbonaceous reducing gas. Said reducing gas may be selected from the group consisting of hydrogen, ammonia, a mixed gas obtained by ammonia cracking, mixtures of at least two of said reducing gases and mixtures of at least one of said reducing gases with at least one inert gas, for example a mixture of hydrogen and nitrogen.

[0047] The composition of the fuel may differ from the composition of the reducing gas. Alternatively, the composition of the fuel may be identical to the composition of the reducing gas. According to a particular embodiment, the fuel and the reducing gas are identical and are both supplied by a same source, i.e. by the reducing-gas source.

[0048] In particular for processes with a high-temperature combustion zone (typically ≥650° C.), the burner advantageously comprises a cooling jacket for cooling the burner by means of a cooling fluid. The cooling jacket surrounds the third injector. A preferred cooling fluid is cooling water, though other cooling fluids may be used.

[0049] The burner may further comprise a jet stabilizing chamber downstream of the first, second and third injectors and upstream of the combustion chamber. Such a stabilization chamber is particularly useful when, during operation, the burner injects fuel and combustion oxidant into the combustion zone so as to supply thermal energy thereto by means of a flame generated by the combustion of the injected fuel with the injected combustion oxidant, while simultaneously injecting a supersonic jet of the oxidizing or of the reducing agent. In that case, the difference in velocity between the supersonic jet and the flame may cause destabilization of the supersonic jet / flame. The presence of a stabilization chamber, as defined hereabove, helps to stabilize the flame and maintain supersonic jet coherence, for example for better penetration of the supersonic jet into the charge.

[0050] According to a preferred embodiment, the stabilization chamber has a cylindrical inner volume with a circular cross section. The cylindrical inner volume advantageously has a length L and a cross-section diameter D, with an L / D ratio between 0.5 and 5.0, preferably between 0.7 and 2.0, more preferably, between 0.8 and 1.5.

[0051] According to one embodiment of the present burner, the second injector terminates towards the combustion chamber in a ring of fuel injection openings, whereby said ring is positioned around the at least one first injector. Such a ring of fuel injection openings may, for example, be obtained when the second injector is formed between an inner and an outer tube, has an annular cross-section and terminates in an equally ring-shaped end-flange extending from the inner to the outer tube, when the end-flange presents a multitude of injection openings evenly distributed around the central void of the ring-shaped end-flange of the second injector.

[0052] Similarly, the third injector may terminate towards the combustion chamber in a ring of combustion-oxidant injection openings, whereby said ring of combustion-oxidant injection openings is positioned around the second injector. The ring of combustion-oxidant injection openings may be obtained using a third injector with ring-shaped end-flange as described above with respect to the second injector, i.e. with a third injector being formed between an inner and an outer tube and terminating in a ring-shaped end-flange extending between said tubes.

[0053] According to a useful embodiment, the third injector terminates towards the combustion chamber in a ring of combustion-oxidant injection openings positioned around the second injector, and said second injector similarly terminates towards the combustion chamber in a ring of fuel injection openings positioned around the at least one first injector. According to an advantageous embodiment thereof, each fuel injection opening of the ring of fuel injection openings is positioned on a bisector of a sector defined by the center and two adjacent combustion-oxidant injection openings of the ring of combustion-oxidant injection openings. In this manner, it is possible to alternate the fuel injection openings and the combustion-oxidant injection openings around the at least one first injector.

[0054] According to a useful embodiment of the burner, the at least one first injector is further connected, via the valve unit, to an inert-gas source. According to said embodiment, the valve unit is further adapted to enable at least one, preferably at least two and more preferably all three of the following:

[0055] supplying a purge-gas flow of inert gas from the inert-gas source to the first injector (when the burner comprises a single first injector) or to a first injector (when the burner comprises a multitude of first injectors) when no oxidant gas from the oxidant-gas source and no reducing gas from the reducing-gas source is supplied to said first injector;and / or

[0056] during the second mode: mixing of the oxidant gas from the oxidant-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector;and / or

[0057] during the third mode: mixing of the reducing gas from the reducing-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector.

[0058] As indicated earlier, the inert gas may be nitrogen, carbon dioxide or a noble gas such as argon, carbon-free inert gases, such as nitrogen and noble gases, being generally preferred.

[0059] The supply, during operation of the burner, of purge gas to a first injector to which neither oxidizing gas nor reducing gas is being supplied helps prevent said first injector being partially or totally blocked due to the deposit thereon of condensable substances from the atmosphere of the combustion zone. Moreover, in the case of a same first injector being used both for the supersonic injection of oxidizing gas during the second mode and for the supersonic injection of reducing gas during the third mode, supplying purge gas to said first injector in between the supersonic injections of these fluids increases the safety of the burner in that it ensures that reducing gas and oxidizing gas are not simultaneously present in said first injector, by sweeping the first injector with inert gas between said modes. Such a step may also be referred to as a further mode, namely a “purge mode”, between the second and third mode, in either order of succession.

[0060] Mixing of the oxidant gas from the oxidant-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector makes it possible, on the one hand, to reduce the concentration with which the oxidant gas is injected into the combustion zone during the second mode (for example in order to prevent excessive charge oxidation) and, on the other hand, to increase the mass flow rate of the gas stream with which the oxidant gas is injected during the second mode (for example to increase penetration of the oxidant gas into the charge).

[0061] Similarly, mixing of the reducing gas from the reducing-gas source with inert gas from the inert-gas source at a controlled ratio upstream of the at least one first injector makes it possible, on the one hand, to reduce the concentration with which the reducing gas is injected into the combustion zone during the third mode (for example in order to prevent excessive charge reduction) and, on the other hand, to increase the mass flow rate of the gas stream with which the reducing gas is injected during the third mode (for example to increase penetration of the reducing gas into the charge).

[0062] The present invention further relates to the use of the equipment set, according to any one of the embodiments described above, for burning the fuel with the combustion oxidant for the heating of the combustion zone and, if present, for heating any charge present in the combustion zone.

[0063] The invention thus also relates to a method of heating the combustion zone and of generating a combustion atmosphere in said combustion zone by means of the equipment set according to any one of the above-described embodiments and whereby the valve unit regulates the fluid supply to the injectors of the burner as described above.

[0064] Said method includes at least one operation stage during which fuel from the fuel source is injected into the combustion zone via the second injector, combustion oxidant from the combustion-oxidant source is injected into the combustion zone via the third injector and the injected fuel is combusted with the injected combustion oxidant in the combustion zone to provide thermal energy thereto.

[0065] According to a preferred embodiment, the method comprises at least two of the following operation stages:

[0066] a heating stage without supersonic injection via the at least one first injector

[0067] During this heating stage, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector.

[0068] The fuel-to-oxygen ratio of the fuel injected into the combustion zone via the second injector and the combustion oxidant injected into the combustion zone via the third injector is controlled for optimal heat generation. Optimal heat generation is normally obtained when the fuel-to-oxygen ratio is substantially stoichiometric, i.e. with a fuel-to-oxygen ratio of the injected fuel and the injection combustion oxidant between 0.8 and 1.2 times the stoichiometric fuel-to-oxygen ratio, preferably between 0.9 and 1.1 times the stoichiometric fuel-to-oxygen ratio.

[0069] In order to ensure the complete combustion of the injected fuel, a slight excess of combustion oxidant may be injected, for example with an fuel-to-oxygen ratio of the injected fuel and the injected combustion oxidant of at least 0.7 times but below 1.0 times the stoichiometric fuel-to-oxygen ratio.

[0070] When ingress of ambient air into the combustion zone cannot be avoided, a fuel-to-oxygen ratio of the injected fuel and the injected combustion oxidant above the stoichiometric fuel-to-oxygen ratio may be used as the ingress air provides additional oxygen for the (complete) combustion of the fuel. In that case, the fuel-to-oxygen ratio may be higher than 1.0 times stoichiometric fuel-to-oxygen ratio and, for example, depending on the level of air ingress up to 1.3 times the stoichiometric fuel-to-oxygen ratio.

[0071] On the other hand, when additional combustible matter is present in the combustion zone, for example because a charge, such as, for example, contaminated scrap metal, is present in the combustion zone that contains and / or releases combustible matter when heated, the fuel-to-oxygen ratio of the injected fuel to the injected combustion oxidant may advantageously be below the stoichiometric fuel-to-oxygen ratio so as to provide oxygen for the combustion of said additional combustible matter as well as for the combustion of the injected fuel. In that case, the fuel-to-oxygen ratio of the injected fuel to the injected combustion oxidant is less than 1.0 times the stoichiometric fuel-to-oxygen ratio and, for example, depending on the amount of combustible matter present in / released from the charge, upwards of 0.7 times the stoichiometric fuel-to-oxygen ratio.

[0072] a neutral heating stage with supersonic injection

[0073] During this heating stage, again, fuel from the fuel source is injected into the combustion zone via the second injector, and thus subsonically, and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected subsonically into the combustion zone via the third injector.

[0074] In addition, oxidant gas from the oxidant-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector.

[0075] Alternatively, when the reducing gas is a gaseous fuel, such as hydrogen, reducing gas from the reducing-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector.

[0076] When the reducing gas is a gaseous fuel and multiple first injectors are present, it is even possible to combine, during this stage, the subsonic injection of fuel from the fuel source into the combustion zone via the second injector and the subsonic injection of combustion oxidant from the combustion-oxidant source into the combustion zone via the third injector, with supersonic injection of both oxidant gas from the oxidant-gas source and reducing gas from the reducing-gas source via the first injectors.

[0077] In the present context, “neutral heating” refers to the heating of the combustion zone by means of fuel combustion, whereby the generated combustion gases are essentially non-reducing and non-oxidizing and therefore do not cause chemical reduction or oxidation of a charge present in the combustion zone.

[0078] Consequently, during the neutral heating stage with supersonic injection, the flow rates into the combustion zone of subsonic fuel from the fuel source and of subsonic combustion oxidant from the oxidant-gas source, as well as of the supersonic oxidant gas from the oxidant-gas source and / or the supersonic reducing gas from the reducing-gas source are regulated so as to generate such an essentially non-reducing and non-oxidizing atmosphere in the combustion zone, taking into account any air ingress or combustible substances present in the charge.

[0079] The combination of subsonic injection of combustion oxidant by means of the third injector with supersonic injection of oxidant gas by means of the at least one first injector, and thus the repartition of the injected oxygen between the third injector and the at least one first injector, makes it possible to adapt the properties of the generated flame, in particular the velocity of the generated flame. The same is true for the combination of subsonic fuel injection by means of the second injector with supersonic injection of a reducing gas that is a gaseous fuel.

[0080] an oxidizing stage

[0081] During an oxidizing stage, oxidant gas from the oxidant-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector, typically in order to oxidize, within the combustion zone, a charge or elements present in the charge.

[0082] By thus injecting the oxidant gas supersonically, a better contact or deeper penetration of the oxidant gas with / into the charge may be obtained.

[0083] When as is often the case, the combustion zone must also be heated during the oxidizing stage, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector.

[0084] In that case, the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector is advantageously at most equal to, and optionally lower than, the stoichiometric fuel-to-oxygen ratio, so that the heating by fuel combustion does not reduce the amount of oxygen in the combustion zone that is available for other purposes, such as, in particular the oxidation of the charge or elements present therein.

[0085] For example, the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector is less than or equal to the stoichiometric fuel-to-oxygen ratio, preferably below 0.9 times the stoichiometric fuel-to-oxygen ratio and greater than or equal to 0.7 times the stoichiometric fuel-to-oxygen ratio, though, as discussed earlier, adjustments of the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector may be made in order to take into account ingress air.

[0086] a reducing stage

[0087] During a reducing stage, reducing gas from the reducing-gas source is injected into the combustion zone at supersonic velocity via the at least one first injector, typically in order to cause chemical reduction, within the combustion zone, of a charge or elements present in the charge.

[0088] By injecting the reducing gas supersonically, a better contact or deeper penetration of the reducing gas with / into the charge may be obtained.

[0089] When as is typically the case, the combustion zone must be heated during the reducing stage, fuel from the fuel source is injected subsonically into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected subsonically into the combustion zone via the third injector.

[0090] In that case, the fuel-to-oxygen of the fuel injected via the second injector and the combustion oxidant injected via the third injector is advantageously at least equal to, and optionally higher than, the stoichiometric fuel-to-oxygen ratio, so that the heating by fuel combustion does not reduce the amount of reducing agent in the combustion zone that is available for chemically reducing the charge or elements present therein.

[0091] For example, the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector is higher than or equal to 1.0 times, preferably at least 1.1 times, the stoichiometric fuel-to-oxygen ratio and, for example, not more than 1.3 times the stoichiometric fuel-to-oxygen ratio.

[0092] Again, adjustments of the fuel-to-oxygen ratio of the fuel injected via the second injector and the combustion oxidant injected via the third injector may be made in order to take into account other factors, such as ingress air.

[0093] As stated, the method according to the present invention usefully comprises at least two of the following operation stages:

[0094] a heating stage without supersonic injection via the at least one first injector as described above;

[0095] a neutral heating stage with supersonic injection as described above;

[0096] a combined oxidizing and heating stage, i.e. an oxidizing stage, during which in addition to the supersonic injection of oxidant gas via the at least one first injector, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector, as described above;

[0097] a combined reducing and heating stage, i.e. a reducing stage, during which in addition to the supersonic injection of reducing gas via the at least one first injector, fuel from the fuel source is injected into the combustion zone via the second injector and is combusted in the combustion zone with combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector, as described above.

[0098] As mentioned earlier, during each operating stage of the method of the present invention, the fluid supply to the at least one first injector of the burner, and by extension to all injectors of the burner, is conducted via the valve unit, via which said fluid supply is regulated.

[0099] The present invention thus covers in particular a method as described above:

[0100] comprising or consisting of a heating stage and an oxidizing stage, in particular at least a heating stage and a combined oxidizing and heating stage; whereby, according to a specific embodiment, the heating stage precedes the oxidizing stage / combined oxidizing and heating stage; or

[0101] comprising or consisting of a heating stage and a reducing stage, in particular a heating stage and a combined reducing and heating stage; whereby, according to a specific embodiment, the heating stage precedes the reducing stage / combined reducing and heating stage; or

[0102] comprising or consisting of a heating stage, an oxidizing stage and a reducing stage; in particular a heating stage, an oxidizing stage and a combined reducing and heating stage; and more particularly a heating stage, a combined oxidizing and heating stage and a combined reducing and heating stage; whereby, according to a specific embodiment, the heating stage precedes the oxidizing stage / combined oxidizing and heating stage, in turn preceding the reducing stage / combined reducing and heating stage.

[0103] Methods as discussed above are particularly useful for batch processes with multiple successive process stages as well as for semibatch processes with multiple successive stages between successive charging or successive discharging steps.

[0104] The method of the invention, according to any one of the embodiments described above, is particularly useful when a charge is melted in the combustion zone during the heating step. The molten charge is thereafter subjected to one or more oxidizing and / or reducing stages in the combustion zone.BRIEF DESCRIPTION OF THE DRAWINGS

[0105] The present invention and its advantages are described in more detail in the following non-limiting examples, reference being made to FIGS. 1 to 4, whereby:

[0106] FIG. 1 is a schematic cross-sectional view of an embodiment of a burner of the equipment set according to the invention according to a first plane,

[0107] FIG. 2 is a schematic cross-sectional view of the burner of FIG. 1 according to a second plane perpendicular to the first plane,

[0108] FIG. 3 is a schematic front view into the jet-stabilizing chamber of the burner of FIG. 1, and

[0109] FIG. 4 is a schematic representation of the equipment set including the burner of FIG. 1.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0110] The illustrated burner comprises multiple injectors for injecting fluid jets into a combustion zone located downstream of the burner. The combustion zone is, for example, located in a combustion / heating chamber of a furnace.

[0111] The burner comprises a first, central, injector 11, a second injector 21 that surrounds the first injector 10 and a third injector 31 that surrounds the second injector 21.

[0112] According to the illustrated embodiment, the first, second and third injectors, respectively 11, 21 and 31, are coaxially arranged.

[0113] Second injector 21 is a fuel injector. In use, second injector 21 is connected, via its inlet 20, to a source of fuel, such as a hydrogen tank (not shown).

[0114] Third injector 31 is a combustion-oxidant injector. In use, third injector 31 is connected, via its inlet 30, to a source of combustion oxidant, such as an air blower, or, preferably, an oxygen plant or reservoir.

[0115] First injector 11 is equipped with a laval nozzle 1 to enable first injector 11 to inject fluid supersonically into the downstream combustion zone. D1 is the outlet diameter of laval nozzle 1 and thus also the outlet diameter of first injector 11.

[0116] The inlet 10 of first injector 11 is selectively connected, via valve unit 100, to an oxidant-gas source 110 and to a reducing-gas source 120.

[0117] Valve unit controls 100 the flow of oxidant gas from the oxidant-gas source 110 to first injector 11 and the flow of reducing gas from the reducing-gas source 120 to first injector 11 is likewise controlled by means of said valve unit 100.

[0118] Valve unit 100 is more specifically adapted to switch between the following modes of fluid supply to first injector 11:

[0119] a mode, referred to as “first mode”, during which neither oxidant gas nor reducing gas is supplied to first injector 11 for supersonic injection into the downstream combustion zone,

[0120] a mode, referred to as “second mode”, during which oxidant gas from is supplied from the oxidant-gas source 110 to first injector 11 for supersonic injection of a flow of said oxidant gas into the downstream combustion zone, and

[0121] a mode, referred to as “third mode”, during which reducing gas from the reducing-gas source 120 is supplied to first injector 11 for supersonic injection of a flow of said reducing gas into the downstream combustion zone.

[0122] During the first mode, no supersonic injection of fluid into the combustion zone is performed by first injector 11.

[0123] Typically, during the second mode, only oxidant gas is supersonically injected via first injector 11. Similarly, during the third mode, only reducing gas is typically supersonically injected via first injector 11.

[0124] However, it is also possible for the oxidant gas, respectively the reducing gas, to be injected supersonically together with an additional gas, such as an inert gas or a mainly inert gas, such as ambient air, via first injector 11 during the second, respectively third mode. For example, the addition / admixture of an inert gas may be useful to attenuate the oxidizing effect of the oxidant gas, respectively the reducing effect of the reducing gas on a charge in the combustion zone and / or to increase the amount of gas (in Nm3) that is being supersonically injected.

[0125] FIG. 4 illustrates an embodiment whereby first injector 11 is selectively connected to oxidant-gas source 110 and reducing-gas source 120, but also to inert-gas source 130, the flow of inert gas from inert-gas source 130 to first injector 11 being likewise controlled by valve unit 100.

[0126] In the illustrated embodiment, the burner comprises a single first injector 11 via which oxidant gas is supersonically injected during the second mode and via which reducing gas is supersonically injected during the third mode.

[0127] According to an alternative embodiment, the burner comprises multiple first injectors 11.

[0128] Similarly to the illustrated embodiment, individual first injectors 11 may be used both to supersonically inject oxidant gas during the second mode and to supersonically inject reducing gas during the third mode.

[0129] Alternatively, one or more first injectors 11 (oxidant-gas-only first injectors) may be dedicated for the supersonic injection of oxidant gas during the second mode only, while one or more other first injectors 11 (reducing-gas-only first injectors) are dedicated for the supersonic injection of reducing gas during the third mode only.

[0130] When a first injector 11 is not used for supersonic injection of a fluid into the combustion zone, as is the case during the first mode, but as is also the case for any oxidant-gas-only first injectors during the third mode or any reducing-gas-only first injectors during the second mode, said first injector 11 may inject no fluid into the downstream combustion zone. However, depending on the process for which the combustion zone is used, it may be useful or even necessary, to maintain a subsonic fluid flow through a first injector 11 when not being used for supersonic injection, for example in order to maintain some cooling of the first injector and / or to prevent said first injector from being blocked by deposits formed thereon. The fluid subsonically injected via a first injector 11 during the first mode may be oxidant gas, reducing gas or, preferably, a purge gas.

[0131] Second injector 21 is a subsonic fuel injector. In the illustrated embodiment, second injector 21 terminates in a ring of fuel injection nozzles / openings 2 annularly positioned around laval nozzle 1 of first injector 11. D2 is the diameter of fuel injection nozzles / openings 2. As shown in FIG. 3, said ring of fuel injection nozzles / openings 2 is coaxial / concentric with laval nozzle 1 and fuel injection nozzles / openings 2 are evenly / equidistantly distributed on said ring.

[0132] The edge-to-edge distance L12 between fuel injection nozzles / openings 2 and laval nozzle 1 is preferably between 1.19 and 1.55 times diameter D1 of laval nozzle 1, preferably between 1.29 and 1.45 times, more preferably between 1.32 and 1.42 times diameter D1 of laval nozzle 1.

[0133] Third injector 31 is a subsonic combustion-oxidant injector. As shown in FIG. 3, third injector 31 similarly terminates in a ring of combustion-oxidant injection nozzles / openings 3 annularly positioned around laval nozzle 1 of first injector 11 and around the ring of fuel injection nozzles / openings 2. Said ring of combustion-oxidant injection nozzles / openings 3 is coaxial / concentric with laval nozzle 1, and with the ring of fuel injection nozzles / openings 2. Again, combustion-oxidant injection nozzles / openings 3 are evenly / equidistantly distributed on the ring of combustion-oxidant injection nozzles / openings 3.

[0134] The edge-to-edge distance L13 between oxidant injection nozzles / openings 3 and laval nozzle 1 is greater than the edge-to-edge distance L12 between fuel injection nozzles / openings 2 and laval nozzle 1. Edge-to-edge distance L13 between oxidant injection nozzles / openings 3 and laval nozzle 1 is preferably between 2.40 and 2.80 times diameter D1 of laval nozzle 1, preferably between 2.45 and 2.75 times, more preferably between 2.50 and 2.70 times diameter D1 of laval nozzle 1.

[0135] As shown in FIG. 3, in the illustrated preferred embodiment, each fuel injection opening 2 is positioned on a bisector of a sector defined by the center, corresponding to the location of laval nozzle 1, and two adjacent combustion-oxidant injection openings 3 of the ring of combustion-oxidant injection openings 3. This provides for optimized mixing of fuel injected via fuel injection openings 2 with combustion oxidant injected via combustion-oxidant injection openings 2, when second injector 21 and third injector 31 simultaneously inject fuel, respectively combustion oxidant into the combustion zone, for the combustion of the injected fuel with the injected combustion oxidant therein.

[0136] The outlet of first injector 11, fuel injection openings 2 forming the outlet(s) of the second injector 21 and combustion-oxidant injection openings 3 forming the outlet(s) of the second injector 31 are located in a same plane 51.

[0137] The illustrated burner further comprises a jet-stabilizing chamber 5, downstream of first injector 11, second injector 21 and third injector 31, but upstream of the combustion zone. When second injector 21 and third injector 31 simultaneously inject fuel, respectively combustion oxidant, into the combustion zone for the combustion of the injected fuel with the injected combustion oxidant therein, initial mixing of the injected fuel with the injected combustion oxidant can take place in jet-stabilizing chamber 5 of the burner.

[0138] Jet-stabilizing chamber 5 shields the injected fluids at their respective points of injection 1, 2 and 3 from the frequently turbulent atmosphere in the combustion zone. Moreover, when, in addition to the injection of fuel via second injector 21 and the injection of combustion oxidant via third injector 31, one or more supersonic fluid jets are injected by means of the at least one first injector 11, the presence of jet-stabilizing chamber 5 reduced interference by the supersonic jet and / or dilution by the combustion-chamber atmosphere, thereby improving flame stability.

[0139] Jet-stabilizing chamber 5 is a cylindrical chamber with an axial dimension L in the axial direction of the first injector 11 and a diameter D perpendicular to the axial dimension L. Plane 51 forms the basis of said cylindrical chamber.

[0140] According to a preferred embodiment the L / D ratio of jet-stabilizing chamber 5 is between 0.90 and 1.34, preferably between 1.00 and 1.24, for example between 1.08 and 1.16.

[0141] In order to protect the burner against thermal damage due to the high temperatures in the combustion chamber, the illustrated burner is equipped with a cooling jacket 41 to cool the burner with a cooling fluid, such as, for example, cooling water, in which case the cooling jacket 41 is a water jacket. Cooling jacket 41 surrounds third injector 31 at least towards the downstream / injection end of the burner. It comprises a cooling-fluid inlet 40a and a cooling-fluid outlet 40b. During operation of the burner, cooling fluid is supplied to cooling-fluid inlet 40a and is caused to flow in inner sleeve 41a of cooling jacket 41 all around third injector 31 in the direction towards combustion-oxidant injection nozzles / openings 3 and then all around stabilizing chamber 5, before flowing back through outer sleeve 41b to cooling-fluid outlet 40b.

[0142] The usefulness and flexibility of the equipment set according to the present invention is illustrated by the non-limiting example hereafter in which the burner is inter alia used to heat a combustion zone of a furnace combustion chamber in which a charge is to be treated.

[0143] In order to raise the temperature in the combustion zone gradually to its operation temperature without causing thermal damage to the refractory material of the combustion chamber, the combustion zone is heated up without supersonic fluid injection. During said heating-up stage, fuel is injected into the combustion zone via second injector 21 and combustion oxidant injected into the combustion zone via third injector 31 at a substantially stoichiometric fuel-to-oxygen ratio. As there is no risk of thermal damage to or deposits onto the first injector 11 at this stage, one may choose not to inject any gas into the combustion zone via first injector 11 at this stage. Alternatively, a subsonic fluid jet may be injected by first injector 11 during this stage.

[0144] Once the combustion zone has reached the desired operation temperature, the charge is introduced into the combustion chamber and the burner is used to heat the charge in the combustion zone. In order to enhance the penetration of the flame into the charge or, more generally, improve the contact between the flame and the charge, the burner is now used to heat the charge by heating with supersonic injection. During this stage, oxidant-gas from oxidant-gas source 110 is injected into the combustion zone at supersonic velocity via first injector 11, fuel is injected subsonically into the combustion zone via second injector 21 and combustion oxidant is injected subsonically into the combustion zone via third injector 31. The fuel-to-oxygen ratio of, on the one hand, the fuel injected into the combustion zone via second injector 21 and, on the other hand, the combustion oxidant injected into the combustion zone via third injector 31 and the oxygen-gas injected into the combustion zone via the first injector 11 corresponds to the stoichiometric ratio, unless air ingress into the combustion chamber justifies a higher fuel-to-oxygen injection ratio. However, if during this stage, combustion of combustible substances (contaminants) present in the charge is desired, the fuel-to-oxygen injection ratio is selected so that an excess of oxygen is available in the combustion zone for the combustion of said combustible substances therein. If, on the other hand, it is important to avoid oxidation of the charge at this stage, the fuel-to-oxygen injection ratio is selected so as to avoid an excess of oxygen in contact with the charge in the combustion zone.

[0145] Such a heating stage with supersonic injection may, for example, be a melting stage.

[0146] Once the charge is heated and depending on the nature of the charge and the nature of the treatment to which the charge is to be subjected, the next step may be an oxidizing heating stage, during which the charge is heated and oxidized, or a reducing heating stage, during which the charge is heated and reduced, or even a succession of an oxidizing heating stage and a reducing heating stage in any given order.

[0147] During such an oxidizing heating stage, oxidant-gas from the oxidant-gas source 110 is injected into the combustion zone at supersonic velocity via first injector 11, whereby the supersonic injection velocity enables the oxygen gas to penetrate into the charge. Meanwhile, fuel is injected subsonically into the combustion zone via second injector 21 and combustion oxidant is injected subsonically into the combustion zone via third injector 31. Given that the charge is to be oxidized, the fuel-to-oxygen ratio of, on the one hand, the fuel injected into the combustion zone via second injector 21 and, on the other hand, the combustion oxidant injected into the combustion zone via third injector 31 and the oxygen-gas injected into the combustion zone via the first injector 11 is kept below the stoichiometric ratio in order to make sure that, in spite of the oxygen consumed by fuel combustion, oxygen remains available for the oxidation of the charge.

[0148] During a reducing heating stage, reducing gas from the reducing-gas source 120 is injected into the combustion zone at supersonic velocity via first injector 11. Meanwhile, fuel is injected subsonically into the combustion zone via second injector 21 and combustion oxidant is injected subsonically into the combustion zone via third injector 31. Given that reduction of the charge is to be achieved and thus oxidation of the charge is to be avoided at this stage, the fuel-to-oxygen ratio of the fuel injected into the combustion zone via second injector 21 and the combustion oxidant injected into the combustion zone via third injector 31 is kept at or above the stoichiometric ratio so that the reducing agent is not consumed by the combustion oxidant and / or oxygen from air ingress into the combustion chamber.

[0149] If, thereafter, the charge is to be maintained in the combustion chamber at high temperature, for example in order to keep the charge from solidifying, the burner may be used to avoid cooling of the charge whereby fuel is injected into the combustion zone via second injector 21 for its combustion in the combustion zone with combustion oxidant injected via third injector 31. Depending on the level of heating required and depending on the risk of undesired oxidation, respectively reduction of the charge, the burner may then be operated without supersonic injection (as during the heating-up stage) or with supersonic injection and a non-oxidizing or non-reducing atmosphere in the combustion zone (as during the heating-up stage). If the burner is used without supersonic injection at this stage, it is advisable to inject a subsonic fluid stream via first injector 11 at this stage to prevent said first injector 11 from being blocked by deposits thereon.

[0150] During the entire process, the fluid supply to the injectors 11, 21 and 31 is regulated by the valve unit 100 of the equipment set, for example under the control of an accordingly programmed control unit 101.

[0151] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0152] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0153] “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.

[0154] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0155] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0156] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0157] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

Examples

Embodiment Construction

[0110]The illustrated burner comprises multiple injectors for injecting fluid jets into a combustion zone located downstream of the burner. The combustion zone is, for example, located in a combustion / heating chamber of a furnace.

[0111]The burner comprises a first, central, injector 11, a second injector 21 that surrounds the first injector 10 and a third injector 31 that surrounds the second injector 21.

[0112]According to the illustrated embodiment, the first, second and third injectors, respectively 11, 21 and 31, are coaxially arranged.

[0113]Second injector 21 is a fuel injector. In use, second injector 21 is connected, via its inlet 20, to a source of fuel, such as a hydrogen tank (not shown).

[0114]Third injector 31 is a combustion-oxidant injector. In use, third injector 31 is connected, via its inlet 30, to a source of combustion oxidant, such as an air blower, or, preferably, an oxygen plant or reservoir.

[0115]First injector 11 is equipped with a laval nozzle 1 to enable firs...

Claims

1. An equipment set comprising a burner, a valve unit (100), an oxidant-gas source (110) and a reducing-gas source (120):the burner comprising a multitude of injectors for injecting fluid jets into a downstream combustion zone, including:at least one first injector (11),a second injector (21) surrounding the at least one first injector (11), anda third injector (31) surrounding the second injector (21),wherein:the second injector (21) is fluidly connected to a source of a fuel,the third injector (31) is fluidly connected to a source of a combustion oxidant, andthe at least one first injector (11) is equipped with a laval nozzle for supersonic fluid injection into the combustion zone, the at least one first injector (11) being fluidly connected, via the valve unit (100), to the oxidant-gas source (110) and to the reducing-gas source (120), the valve unit (100) being adapted to switch between the following modes of fluid supply to the at least one first injector (11):a first mode during which neither oxidant gas nor reducing gas is supplied to the at least one first injector for supersonic injection into the combustion zone,a second mode during which oxidant gas is supplied from the oxidant-gas source (110) to at least one of the at least one first injectors (11) for supersonic injection of the oxidant gas into the combustion zone, anda third mode during which reducing gas from the reducing-gas source (120) is supplied to at least one of the at least one first injectors (11) for supersonic injection of the reducing gas into the combustion zone.

2. The equipment set according to claim 1, wherein the at least one first injector (11) consists of a single first injector (11), wherein the single first injector (11), the second injector (21) and the third injector (31) are coaxial.

3. The equipment set according to claim 1, wherein the at least one first injector (11) comprises at least one first oxidant injector for supersonic injection of the oxidant gas into the combustion zone during the second mode and at least one first reducing-gas injector for supersonic injection of the reducing gas into the combustion zone during the third mode, whereby the second and third injectors (21, 31) are coaxial injectors, and the at least one first, the second and the third injectors (11, 21, 31) extend along parallel longitudinal axes.

4. The equipment set according to claim 1, wherein the fuel is selected from the group consisting of natural gas, hydrogen, ammonia, carbon monoxide, carbon dioxide, a mixed gas obtained by ammonia cracking and combinations thereof.

5. The equipment set according to claim 1, in which the burner further comprises a cooling jacket (41) for cooling the burner by means of a cooling fluid, said cooling jacket (41) surrounding the third injector.

6. The equipment set according to claim 1, wherein the first, second and third injectors (11, 21, 31) extend longitudinally in a first direction and terminate in a same plane (5) perpendicular to said first direction.

7. The equipment set according to claim 1, in which the burner further comprises a jet-stabilizing chamber (5) downstream of the first, second and third injectors (11, 21, 31) and upstream of the combustion chamber.

8. The equipment set according to claim 1, wherein the third injector (31) terminates towards the combustion chamber in a ring of combustion-oxidant injection openings (3), wherein said ring of combustion-oxidant injection openings (3) is positioned around the second injector (21).

9. The equipment set according to claim 1, wherein the second injector (21) terminates towards the combustion chamber in a ring of fuel injection openings (2), wherein said ring of fuel injection openings (2) is positioned around the at least one first injector (11).

10. The equipment set according to claim 1, further comprising an inert-gas source (130) and wherein the at least one first injector (11) is further fluidly connected, via the valve unit (100), to the inert-gas source (130), the valve unit (100) being further adapted to enable all three of the following:supplying a purge-gas flow of inert gas from an inert-gas source (130) to an injector of the at least one first injector (11) when no oxidant gas from the oxidant-gas source (110) and no reducing gas from the reducing-gas source (120) is supplied to said first injector (11), said purge-gas flow being subsonically injected into the combustion zone via said injector (11);during the second mode: mixing of the oxidant gas from the oxidant-gas source (110) with inert gas from the inert-gas source (130) at a controlled ratio upstream of the at least one first injector (11); andduring the third mode: mixing of the reducing gas from the reducing-gas source (120) with inert gas from the inert-gas source (130) at a controlled ratio upstream of the at least one first injector (11).

11. A method of heating a combustion zone and generating a combustion atmosphere therein using the equipment set according to claim 1, the method comprising at least two of the following operation stages during which fuel from the fuel source is injected into the combustion zone via the second injector (21) and is combusted in the combustion zone with a combustion oxidant from the combustion-oxidant source that is injected into the combustion zone via the third injector (31):a heating stage without supersonic injection into the combustion zone via the at least one first injector (11)a neutral heating stage with supersonic injection into the combustion zone via the at least one first injector (11) whereby a non-oxidizing and non-reducing atmosphere is generated in the combustion zonean oxidizing heating stage, during which oxidant gas from the oxidant-gas source (110) is injected into the combustion zone at supersonic velocity via the at least one first injector (11), anda reducing heating stage, during which reducing gas from the reducing-gas source (120) is injected into the combustion zone at supersonic velocity via the at least one first injector (11),the valve unit (100) regulating the fluid supply to the at least one first injector (11) and furthermore the fluid supply to the second injector (21) and to the third injector (31) during each operation stage.

12. The method according to claim 11, comprising at least a heating stage and an oxidizing stage, whereby the heating stage precedes the oxidizing stage.

13. The method according to claim 11, comprising at least a heating stage and a reducing stage, wherein the heating stage precedes the reducing stage.

14. The method according to claim 11, comprising at least a heating stage and wherein a charge is melted in the combustion zone during the heating stage.

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