Patent Application
20220074592
The present invention relates to an assembly for injecting a gaseous combustion agent into a combustion zone, a burner comprising such an assembly and the use of such an assembly/burner in a combustion method.
In industrial combustion methods, for example, in order to transform a load (melting, heating, recycling furnace, etc.), certain flame characteristics are sought, in particular a flame shape and length adapted to the combustion chamber and/or to the load intended to be heated, in order to obtain a determined thermal transfer profile and to optimize the production quality and the lifetime of the equipment.
The flame characteristics are particularly determined by the nature of the combustion agents (fuel and oxidant) and how they are introduced into the combustion zone (flows, speeds, space distribution, etc.).
Thus, a burner is known from EP-A-0763692 that comprises a first internal passage for supplying oxygen-rich oxidant (at least 80% O2), an intermediate passage for supplying fuel externally surrounding the first oxidant supply passage and a second external passage for supplying oxidant externally surrounding the passage for supplying fuel. According to EP-A-0763692, the burner comprises a means for varying the flow rate of oxidant injected through the first internal passage, this allows a characteristic of the flame, such as the flame length and the luminosity, to be controlled.
Similarly, the use of a burner is known from EP-A-1016825 that comprises a first internal passage for supplying oxidant, an intermediate passage for supplying fuel externally surrounding the first oxidant supply passage and a second external oxidant supply passage externally surrounding the fuel supply passage for heating a molten glass transfer channel during glass production and for regulating the flame length generated by means of said burner by modifying the proportion of the total flow of oxidant passing through the first oxidant supply passage.
The aforementioned burners are burners with concentric and adjacent injection of fuel and oxidant generating a flame with an essentially circular cross-section.
Other burners generate flames called “flat flames” and/or inject at least some of the oxidant at a distance from the injection of the fuel, and even inject at least some of the fuel at a distance from the injection of the oxidant.
Thus, EP-A-2143999 describes a burner comprising:
This known burner also comprises:
According to EP-A-2143999, the at least two gaseous fuel passages each comprise an internal passage and a coaxial external passage.
A means for controlling the flow of gaseous fuel regulates the flow of gaseous fuel respectively through the internal passages and the external passages by means of a gaseous fuel distributor.
This allows both the thermal transfer profile and the flame length to be controlled.
If it is thus known that it is possible to modify certain characteristics, and in particular the generated flame length, by adjusting the distribution of the flow of fuel or of oxidant on a plurality of concentric passages/injectors, the known burners do not comprise any feedback means allowing the operation of the burner, and therefore the targeted characteristic of the flame, to be adjusted in real time.
Surprisingly, it has now been discovered that it is possible to produce such a feedback system on the basis of a detected pressure of the gaseous combustion agent before it is distributed.
The present invention relates to an assembly for injecting a gaseous combustion agent into a combustion zone, which gaseous combustion agent is selected from gaseous fuels and gaseous oxidants.
The assembly comprises a chamber and the agent is introduced into the assembly via an inlet of this chamber.
The assembly comprises at least one primary injector for conveying a primary flow of the agent from the chamber toward the combustion zone and for injecting said primary flow into the combustion zone. To this end, the at least one primary injector is fluidly connected to the chamber by means of at least one passage, called primary passage.
The assembly also comprises at least one secondary injector for conveying a secondary flow of the agent from the chamber toward the combustion zone and for injecting said secondary flow into the combustion zone. The at least one secondary injector is in turn fluidly connected to the chamber by means of at least one passage, called secondary passage. The at least one secondary passage has an adjustable flow section.
A regulating system, for example, in the form of a valve, allows this flow section of the at least one secondary passage to be regulated.
The assembly also comprises a pressure detector for detecting a pressure or a variation in gas pressure in the chamber, as well as a control system connected to the pressure detector.
The control system is also connected to a system for regulating and controlling said regulating system, so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the variation in pressure detected by the pressure detector of the assembly.
According to one embodiment, the control system, which can be an analogue or digital control system, is adapted to control the regulating system so that the gas pressure in the chamber is located in a predetermined pressure zone by regulating the flow section of the at least one secondary passage.
According to another embodiment, the control system is adapted to control the regulating system so that the gas pressure in the chamber corresponds to a value that is predetermined by regulating the flow section of the at least one secondary passage.
It is to be noted that the zone or predetermined pressure range can be constant over time, but that it can also vary over time, for example:
The above statements are also applicable to the predetermined value of the gas pressure.
As indicated above, the system for controlling the assembly can be an analogue or digital system. It can be mechanical, for example, pneumatic or hydraulic. Preferably, the control system is digital. According to a preferred embodiment, the control system is programmable. In this case, in order to implement the injection assembly according to the invention, the control system is programmed so as to control the regulating system so as to activate the regulating system as a function of the pressure or of the variation in pressure detected by the pressure detector. The gas pressure or the variation in gas pressure detected by the pressure detector is then transferred to the programmable control system: for example, by means of a wired connection or by means of a wireless connection.
The regulating system can comprise various means for regulating the flow section of the at least one secondary passage, such as one or more adjustable valves positioned in the at least one secondary passage between the chamber and the at least one secondary injector, or the movement of a mechanical element acting as a valve for the at least one secondary passage, with this movement being generated, for example, by translation, by rotation (screwing) or by deformation of a mechanical element connected to the valve or even by modifying the magnetic state of a metal element.
According to a simple and reliable embodiment, the regulating system is provided with at least one valve capable of regulating the flow section of the at least one secondary passage by at least partially plugging said passage.
Such a regulating system can particularly assume the following form. The at least one secondary passage fluidly connecting the at least one secondary injector to the chamber has an internal surface in the form of a funnel and the regulating system comprises a valve with a corresponding external surface and that can be moved along the longitudinal axis of the secondary passage. When the valve is thus moved along said longitudinal axis, the external surface of the valve moves toward or away from the internal surface of the secondary passage and the flow section of said passage is respectively reduced or enlarged.
It is also to be noted that it can be advantageous for the regulating system to be designed so that the flow section of the at least one secondary passage is never fully closed. Indeed, in order to provide sufficient cooling for the at least one secondary injector, and/or to avoid clogging the at least one secondary injector (for example, due to deposits of condensable substances present in the atmosphere of the combustion zone or due to the formation of soot originating from the overheating of the gaseous fuel in contact with at least one secondary injector), a minimal gas flow through the at least one secondary injector can be necessary. However, it is also possible to contemplate that such a minimal gas flow is ensured using means other than the regulating system defined above such as, for example, fluid passages that short-circuit the valve and that are small so as to simply ensure this minimum flow.
The assemblies are typically made from metal, with the injectors, or at least the downstream ends (injection ends), often advantageously being made of high heat and oxidation resistant metals, such as Inconel® type nickel-chromium austenitic steel alloys or Kanthal® type nickel-free alloys.
The assembly according to the invention can more specifically comprise at least one pair of a primary injector with a secondary injector, in which pair one from among the primary injector and the secondary injector surrounds the other one from among the primary injector and the secondary injector.
The primary injector thus can surround the secondary injector or the secondary injector can surround the primary injector of the pair.
According to an advantageous embodiment, the primary injector of the pair is surrounded by the secondary injector of the pair.
According to a particular embodiment, the primary injector and the secondary injector of the pair are concentric. However, in some cases, a non-concentric arrangement can be useful.
It is to be noted that such a configuration in pairs does not exclude the presence of other elements, and in particular the presence of one or more other injectors in or around either one of the injectors of the pair.
For example, according to a particular embodiment, the fluid can be a gaseous oxidant, such as a gas containing at least 80 vol %, and preferably at least 90 vol %, of oxygen. The primary injector of the pair is located at the center and is surrounded by the secondary injector of the pair, preferably concentrically. An injector for injecting fuel into the combustion zone is located between the primary injector and the secondary injector of the pair, so that the fuel injector surrounds the primary oxidant injector and is surrounded by the secondary oxidant injector, the assembly thus forms part of a burner for the combustion (at least partial) of the fuel with the oxidant, and wherein the flow section of the secondary injector, and therefore also the distribution of the oxidant between the primary flow and the secondary flow, are regulated by the control system by means of the regulating system as a function of the gas pressure or the variation in gas pressure in the chamber of the assembly detected by the pressure detector.
According to another similar embodiment, the fluid is a gaseous fuel, such as natural gas. The primary injector of the pair is located at the center and is surrounded by the secondary injector, preferably concentrically. An injector for injecting oxidant into the combustion zone is located between the primary injector and the secondary injector of the pair, so that the oxidant injector surrounds the primary fuel injector and is surrounded by the secondary fuel injector. The oxidant preferably is a gas containing at least 80 vol %, and more preferably at least 90 vol %, of oxygen. The assembly thus forms part of a burner for the combustion (at least partial) of the fuel with the oxidant, and wherein the flow section of the secondary injector, and therefore also the distribution of the fuel between the primary flow and the secondary flow of fuel, are regulated by the control system by means of the regulating system as a function of the gas pressure or the variation in gas pressure in the chamber of the assembly detected by the pressure detector.
The assembly according to the invention can comprise a single primary injector and a single secondary injector, and in particular a single pair of a primary injector with a secondary injector.
According to an alternative embodiment, the assembly according to the invention comprises a plurality of primary injectors and/or a plurality of secondary injectors, and in particular a plurality of pairs of a primary injector with a secondary injector.
According to a particular embodiment, the at least one secondary injector of the assembly is spaced apart from the at least one primary injector of the assembly, without the at least one primary injector of the assembly surrounding a secondary injector of the assembly and without the at least one secondary injector of the assembly surrounding a primary injector of the assembly.
In this case, the at least one primary injector can particularly extend into a first plane, whereas the at least one secondary injector extends into a second plane, with the second plane being parallel to the first plane. In this way it is possible to inject the primary flow and the secondary flow of the gaseous combustion agent into the combustion zone along two parallel planes.
According to an alternative embodiment, the at least one primary injector extends into a first plane and the at least one secondary injector extends into a second plane, with the first plane and the second plane intersecting downstream of said primary and secondary injectors, i.e. inside the combustion zone into which the gaseous combustion agent is injected.
The assembly according to the invention can comprise at least two primary injectors and/or at least two secondary injectors, preferably at least two primary injectors and at least two secondary injectors. This is particularly advantageous in the case whereby, as described above, the at least one primary injector extends into a first plane and the at least one secondary injector extends into a second plane different from the first plane.
In order to inject gaseous agent into the combustion zone, the inlet of the assembly, which is also the inlet of the chamber of the assembly, is fluidly connected to a gaseous fuel source, preferably a gaseous fuel source selected from natural gas, biogas, propane, butane, the residual gases of steel-making or methane-reforming methods, hydrogen, any mixture of said gaseous fuels, or is fluidly connected to a gaseous oxidant source, preferably with an oxygen content of 21 to 100 vol %, preferably greater than 21 vol %, and in particular at least 80 vol %, more preferably at least 90 vol %.
Such a source can be a tank of the gaseous agent in gaseous form or in liquefied form, a supply duct conveying said gaseous agent or a generator of said gaseous agent.
The invention also relates to an installation comprising a plurality of assemblies according to any one of the embodiments described above. In this case, it can be preferable for this installation to comprise a common control system that is capable of controlling, preferably independently, the system for regulating each assembly of the installation as a function of the gas pressure or the variation in gas pressure detected by the pressure detector of said assembly.
As indicated above, the assembly can be incorporated in a burner.
Such a burner according to the invention therefore comprises an assembly according to any one of the aforementioned embodiments for injecting a gaseous combustion agent into a combustion zone, which gaseous combustion agent is selected from a gaseous fuel and a gaseous oxidant.
Such a burner typically also comprises at least one additional injector for injecting an additional fluid into the combustion zone. As a general rule, when the gaseous agent injected by the assembly is a gaseous fuel, the at least one additional injector is adapted for injecting a gaseous oxidant into the combustion zone, and when the gaseous agent injected by the assembly is a gaseous oxidant, the at least one additional injector is adapted for injecting a fuel (gaseous or non-gaseous) into the combustion zone.
According to one embodiment, the burner comprises a block with an inlet face and an outlet face opposite the inlet face. The combustion zone is located downstream of the outlet face.
Contrary to the assembly, the block is typically made from a refractory material, such as cement, or an electrofusion type material, or a pressed material, mainly made up of alumina and/or zirconium and/or silica and/or magnesia or a mixture of these components in varied proportions as a function of the application method.
The assembly is then attached to the inlet face of the block so that the injectors of the burner, and therefore also the injectors of the assembly, are positioned in one or more perforations that pass through the block from the inlet face to the outlet face.
Thus, a burner according to the invention can, for example, comprise such a block with one or more first perforations, which terminate at a first level in the outlet face of the block, as well as one or more additional perforations, which terminate in the outlet face at a second level located below or above the first level. The assembly comprises at least two, and preferably at least three, primary injectors and secondary injectors for conveying and injecting gaseous fuel into the combustion zone. Each of the primary injectors forms a pair with one of the secondary injectors. According to one embodiment, each of the primary injectors surrounds one of the secondary injectors. According to a preferred embodiment, each of the secondary injectors surrounds one of the primary injectors. These pairs, for example, in triplicate, are positioned in the one or more first perforation(s) that terminate at the first level. The burner also comprises a plurality of additional injectors for conveying and injecting oxidant into the combustion zone. Said additional injectors are positioned in the one or more additional passages of the block so as to allow oxidant to be injected into the combustion zone above or below the gaseous fuel. The additional injectors can extend into a plane parallel to the plane of the pairs of a primary injector with a secondary injector. According to another embodiment, the additional injectors can define an injection plane for the oxidant that intersects the plane of the pairs in the combustion zone downstream of the outlet face where the oxidant injected by the additional injectors mixes and reacts with the fuel injected by the pairs.
As already indicated above, other, and in particular one or more injector(s) other than the primary injector and the secondary injector of the pair, can be present in or around either one from among the primary injector and the secondary injector of the pair.
According to a first embodiment, the one or more additional passage(s) terminate in the outlet face of the block above the one or more first passage(s). According to another embodiment, the one or more additional passage(s) terminate in the outlet face of the block below the one or more first passage(s).
According to a third embodiment, the block comprises one or more additional passage(s), which terminate in the outlet face at a level located above the first level and in which at least two, and preferably at least three, additional injectors for the oxidant are located, as well as one or more additional passage(s), which terminate in the outlet face of the block below the first level and in which at least two, and preferably at least three, additional injectors for the oxidant are also located. This embodiment allows, according to the requirements of the method, oxidant to be injected into the combustion zone above, below or above and below the gaseous fuel.
The invention also relates to a furnace comprising an internal combustion zone and equipped with at least one assembly according to the invention for injecting a gaseous combustion agent into said combustion zone, which gaseous combustion agent is selected from gaseous fuels and gaseous oxidants. As indicated above, the at least one assembly can form part of a burner according to the invention, in which case the furnace is equipped with at least one burner according to the invention.
The present invention particularly advantageously can be implemented in a furnace selected from furnaces for manufacturing or heating glass or enamels, furnaces for manufacturing or recycling or heating metals, such as rotary furnaces, or reverberatory furnaces for aluminum, copper or lead, cast iron, steel, etc.
Another aspect of the present invention is a combustion method, in which a gaseous combustion agent is injected into a combustion zone by means of an assembly according to the invention, which gaseous combustion agent is selected from gaseous fuels and oxidants, said assembly being able to form part of a burner according to the invention.
According to this method, the pressure detector of each assembly detects the gas pressure or a variation in the gas pressure in the chamber of this assembly, the system for regulating the assembly regulates the flow section of its at least one secondary passage, and the control system controls the regulating system so that the flow section of the at least one secondary passage of each assembly is regulated as a function of the pressure or of the variation in pressure detected by the pressure detector of this assembly.
As already described above within the context of the installation and of the furnace according to the invention, in the case whereby a plurality of assemblies is used in the method, each assembly can have its own control system connected to the pressure detector and to the regulating system, with the control system controlling the regulating system so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the variation in pressure detected by the pressure detector of said assembly. However, in an often advantageous manner, a common control system can control the system for regulating each assembly as a function of the pressure or of the variation in pressure detected by the pressure detector of the relevant assembly.
As has also already been previously indicated, the system for regulating the assembly can be controlled so that the gas pressure in the chamber of the assembly is located in a predetermined pressure zone or even so that the gas pressure in the chamber of the assembly corresponds to a predetermined value.
The gaseous combustion agent injected into the combustion zone by means of the assembly is a gaseous fuel selected from natural gas, biogas, propane, butane, the residual gases of steel-making or methane-reforming methods, hydrogen or any mixture of the aforementioned gases, or is a gaseous oxidant, preferably with an oxygen content of 21 to 100 vol %, preferably greater than 21 vol %, and in particular at least 80 vol %, more preferably at least 90 vol %.
The method according to the invention is particularly useful for generating combustion inside a combustion zone within the context of a method such as manufacturing or recycling glass or enamels, manufacturing or recycling or heating metals, such as aluminum, copper, lead, cast iron, steel, etc.
The invention and its advantages will be better understood in the light of the following examples: (with reference to
The primary injectors (21) are fluidly connected to the chamber (11) by the primary passages (23). The secondary injectors (22) are fluidly connected to the chamber (11) by the secondary passages (24). The secondary passage has an adjustable flow section. A regulating system (32) allows this flow section of the secondary passage (24) to be regulated by virtue of a valve (33). A pressure detector (30) is present for detecting a pressure or a variation in gas pressure in the chamber (11). A control system (31) is connected to the pressure detector (30). This control system is also connected to and controls the regulating system (32).
In
The automatic regulation by the feedback system according to the present invention advantageously can be implemented in various combustion methods, such as for glass production.
The glass production furnaces mainly use air preheated to over 1000° C. as an oxidant. This hot air is obtained by passing through regenerators (stack of refractory bricks). The amount of oxidant injected into the furnace at this temperature level involves a significant amount of movement.
During the campaign of a furnace, production may need to be increased beyond the capacity of the regenerators, which cannot provide a greater amount of hot air due to the limitation of the draw of the fans. A similar problem occurs when the state of the bricks does not allow or no longer allows the desired preheating temperatures to be obtained.
The burner installation operating with an oxygen-rich oxidant (oxy-burner) then appears to be a particularly suitable solution. These burners are generally installed in the openings available dose to the regenerators. With the oxy-combustion (i.e. combustion with an oxidant containing at least 80 vol %, and preferably at least 90 vol %, of oxygen) generating an amount of smoke that is 4 times lower than air combustion and with at least equivalent efficiency, the flames originating from oxy-burners, hereafter called “oxy-flames”, are severely disrupted by the flames, called “aero-flames”, originating from regenerators operating with hot air, due to the lower amount of movement of the oxy-flames. These disruptions can lead to the oxy-flame interfering with the molten solid material and unburnt materials and thus to glass quality or energy efficiency problems. These problems are even more significant when the power (and therefore the flows of the combustion agents) of the oxy-burners is reduced for lower increased production phases. It is therefore essential to maximize the pulse or the amount of movement of the oxy-flames throughout the entire power range of the oxy-burners.
Systems, such as those described in document EP 2143999, allow manual regulation of the flow of gaseous fuel between two injections (primary and secondary) in order to maximize the pulse of the fuel and thus ensure the stability of the flame of the oxy-burner. However, these manual systems require constant adjustment of the fluid distribution by the operators, without being able to easily assess the impact of these adjustments on the method in real-time. In order to avoid these adjustments and any quality problems, the operators most often adjust the power on the air burners (regenerator), causing excessive oxygen consumption and an increase in the production costs.
The present invention advantageously can be used in this case by defining a predefined pressure range or a predefined pressure allowing automatic distribution to be ensured of the flow between the primary and secondary injections, so as to maximize the pulse of the oxy-flame irrespective of the total flow of fuel,
For example, in the case of a 4% production increase, the power of an oxy-burner can be 800 kW, whereas for an 8% oxygen increase, the power of an oxy-burner can be 1.8 MW. It has been determined that a pressure of 300 mbarg in the distribution chamber between the two fuel injections allows a highly stable flame to be provided both at 800 kW and at 1800 kW. The automatic regulation, according to the invention, of the distribution of the fuel, as a function of the gas pressure in the chamber when the power varies, will thus allow the production costs to be optimized, quality defects to be limited and energy consumption to be optimized.
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18306820.4 | Dec 2018 | EP | regional |
This application is a 371 of International Application No. PCT/EP2019/082987, filed Nov. 28, 2019 which claims priority to European Patent Application No. 18306820.4, filed Dec. 18, 2018, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/082987 | 11/28/2019 | WO | 00 |
