Combustion furnace and assembly

Abstract

Combustion assembly and furnace comprising at least one such combustion assembly, the combustion assembly comprising a non-metallic refractory block (10) extending over a height h between a lower end (11) and an upper end (12), having an inlet face (14) and an outlet face (13) opposite the inlet face (14), the block (10) being divided over its height h into several stages (et1, et2, et3, et4), each stage (et1, et2, et3, et4) being pierced by at least one passage (p) for the injection of fuel and / or oxidizer, each passage (p) extending from the inlet face (14) to the outlet face (13) and terminating in at least one injection opening (21, 22, 23) in the outlet face (13) of the block, the at least one injection opening (21, 22, 23) of each floor (et1, et2, et3,et4) defining on the outlet face (13) a contact rectangle (25) two segments of which are parallel to the direction of height h and two segments of which are perpendicular to the direction of height h, the assembly also comprising burners capable of generating flames (f1, f2, f3, f4) whose length can be varied at constant flame power at a rate of one burner per stage (et1, et2, et3, et4), each burner having at least one injector for injecting a fuel (31) fluidly connected to a fuel inlet of the burner and at least one injector for injecting an oxidizer (32, 33) fluidly connected to an oxidizer inlet of the burner, each burner being mounted on the corresponding stage (et1, et2, et3, et4) of the block (10) such that the fuel and oxidizer injectors (31, 32, 33) of the burner are inserted into at least one passage (p) of said stage (et1, et2, et3,et4) corresponding and such that the fuel and oxidizer inlets of the burner are located on the side of the inlet face (14) of the block (10), the at least one passage (p) of the different stages (et1, et2, et3, et4) being oriented and spaced so that when the burners generate flames (f1, f2, f3, f4) downstream of the outlet face (13), the flames (f1, f2, f3, f4) generated by the different burners are spaced apart and non-convergent, the contact rectangle (25) defined on the outlet face (13) at the stage (et1) contiguous to the lower end (11) of the block (10) having segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h.,

Description

[0001] The present invention relates to a combustion unit and a furnace equipped with at least one such combustion unit.

[0002] In industrial thermal processes, it is known to heat a load in a furnace by means of one or more flames generated by the combustion of a fuel with an oxidizer.

[0003] The intensity, orientation, length and cross-section of the flame(s) are generally adapted to the load and the position of the load relative to the burners generating the flames.

[0004] For example, the orientation and length of a flame can be chosen to impact the load in order to improve heat transfer to the load. When the load has a large surface area facing the burner, the width and height of the flame can be chosen so that the load is heated across its entire surface.

[0005] However, the optimization of certain industrial thermal processes requires more flexibility, for example, when the distance between the load and the burner and / or the height of the load vary over time during the operation of the furnace.

[0006] From US-A-11598522, it is known that in a tilting rotary batch melting furnace, a first burner producing a first flame at a first power is operated, and a second burner, mounted above the first burner, producing a second flame, is operated at a second power. The known melting process comprises two phases. In the first phase, the solid charge in the furnace obstructs the first flame. During this phase, the second power is greater than the first power. In a subsequent phase, the charge is melted to a sufficient extent so as not to obstruct the development of the first flame. The two burners are then regulated so that the first power, i.e., the power of the first flame, which is closer to the charge, is greater than the second power, i.e., the power of the second flame.

[0007] This process improves the melting efficiency of a batch-type tilting rotary melting furnace, to which it is limited. Furthermore, its adaptability to different loads remains limited.

[0008] The present invention aims to remedy, at least in part, the drawbacks of known methods.

[0009] The object of the present invention includes more particularly providing a combustion assembly for the reliable realization of adaptable / flexible, or even more adaptable / flexible, combustion, as well as an adaptable / flexible furnace equipped with at least one such combustion assembly.

[0010] To this end, the present invention proposes a combustion assembly comprising a non-metallic refractory block and several burners.

[0011] The refractory block extends over a height h between a lower end (or bottom) and an upper end (or top).

[0012] The block has an entry face and an exit face opposite the entry face. The exit face and the entry face are separated by a thickness ep, called the block thickness.

[0013] When the block is installed in a furnace, the exit face is directed towards the combustion zone and therefore constitutes the so-called "hot" face of the block, while the entrance face is located outside this combustion zone.

[0014] Along its height h, the block is divided into several floors or levels.

[0015] Each stage is pierced by at least one passage, i.e., one or more passages, for the injection of fuel and / or oxidizer (combustion oxidizer). Each passage extends from the inlet face to the outlet face and terminates in at least one injection opening in the outlet face of the block.

[0016] Because each stage is pierced by at least one passage, each stage has at least one injection opening in the exit face of the block.

[0017] The at least one injection opening of each stage defines a contact rectangle (also called an "intouch rectangle") on the outlet face. Two segments or sides of the contact rectangle are parallel to the direction of height h. The other two segments or sides are perpendicular to the direction of height h. Each injection opening of the corresponding stage is located entirely within said contact rectangle, and each segment or side of the contact rectangle is in contact with the contour of at least one of the injection openings of the corresponding stage.

[0018] The combustion unit comprises several burners, one per stage. Therefore, the number of burners is equal to the number of burners.

[0019] Each burner has injectors, including: at least one injector for injecting a fuel and at least one injector for injecting an oxidizer.

[0020] At least one fuel injector for each burner is fluidly connected to a burner fuel inlet, and at least one oxidizer injector for each burner is fluidly connected to a burner oxidizer inlet. Each burner is mounted on the corresponding stage of the block such that the fuel and oxidizer injectors of said burner are inserted into at least one passage of the corresponding stage, and so that the burner's fuel and oxidizer inlets are located on the inlet face of the block.

[0021] Each burner is capable of generating flames by combustion of the fuel with the oxidizer downstream of the outlet face of the block. According to the present invention, each burner is capable of generating such flames whose length can be varied while maintaining a constant flame intensity.

[0022] Also according to the invention, the at least one injection passage of the different stages are oriented and spaced so that when the burners generate flames downstream of the outlet face of the block by combustion of the fuel with the oxidizer, the flames generated by the different burners are spaced apart from each other and non-convergent.

[0023] With regard to the floor adjacent to the lower end of the block, the contact rectangle defined on the exit face at the floor adjacent to the lower end of the block has segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h.

[0024] For the operation of the combustion assembly, the fuel inlets are connected to a fuel source, for example a fuel tank or pipeline, and the oxidizer inlets are connected to an oxidizer source, for example an air blower, air gas separation unit, or an oxygen tank or pipeline.

[0025] The block can be a rectangular parallelepiped, also called a "rectangular block". The passages for injecting fuel and / or oxidizer into the block determine the direction of the flames generated in the combustion zone downstream of the block's outlet face.

[0026] According to the invention, the contact rectangle defined on the exit face of the floor adjacent to the lower end of the block has segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h. However, one or more other floors may also have such a contact rectangle. In one embodiment, the contact rectangles of all floors have segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h.

[0027] Such a contact rectangle defined on the exit face at the floor adjacent to the lower end of the block has segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h makes it possible in particular to produce flames whose cross-section has a dimension in the direction perpendicular to the direction of height h greater than its dimension in the direction of height h.

[0028] In one particular embodiment, the assembly has only two stages and therefore only two burners. In this case, one of the two stages is adjacent to the lower end of the block, and the other is adjacent to the upper end of the block. In another useful embodiment, the assembly has exactly three stages and therefore three burners. In this case, one of the three stages is adjacent to the lower end of the block, another two stages are adjacent to the upper end of the block, and the third stage is located between the two aforementioned stages.

[0029] As indicated above, the at least one injection passage of the different stages is oriented and spaced such that when the burners generate flames downstream of the block's outlet face by combustion of the fuel with the oxidizer, the flames generated by the different burners are not converging with respect to each other. In one embodiment, the at least one injection passage of the different stages is oriented and spaced such that when the burners generate flames by combustion of the fuel with the oxidizer, at least two of the flames generated by the different burners are parallel. In another embodiment, the at least one injection passage of the different stages is oriented and spaced such that when the burners generate flames by combustion of the fuel with the oxidizer, at least two of the flames generated by the different burners are diverging.The two embodiments described above can also be combined in a single combustion unit comprising at least three stages. In this case, the at least one injection passage of the different stages is oriented and spaced such that when the burners generate flames by combustion of the fuel with the oxidizer, at least two of the flames generated by the different burners are parallel and at least two of the flames generated by the different burners are divergent.

[0030] Depending on the specific embodiment, all the generated flames are parallel to each other or all the generated flames are divergent from each other.

[0031] In an advantageous embodiment, the at least one injection passage of the different stages is positioned such that when the burners generate flames downstream of the block's outlet face by combustion of the fuel with the oxidizer, the flames generated by the different burners are aligned. Thus, in a particularly preferred embodiment, the contact rectangles defined on the block's outlet face have centers of gravity aligned in the direction of the height h.

[0032] As previously mentioned, each burner is capable of generating flames by burning fuel with an oxidizer downstream of the outlet surface of the block, the length of which can be varied while maintaining a constant flame intensity. This allows the flame intensity and length to be adapted to the position of the fuel charge relative to the combustion unit, and this can be done at several levels, each level corresponding to a stage of the block and its corresponding burner.

[0033] Burners capable of generating flames of varying lengths at constant flame intensity are known in the state of the art. For example, burners exist that allow the flame length to be varied by modifying the flow cross-section for at least one of the combustion reactants (fuel and / or oxidizer).

[0034] Il is notably known to modify the flow section mechanically, as, for example, described in EP-A-2118565.

[0035] Il is also known to provide injectors of different flow sections for the same combustion reactant and to vary the flame length by choosing the injector and therefore also the flow section through which the combustion reactant is injected into the combustion zone.

[0036] In a preferred embodiment, the burner capable of varying the flame length at constant flame power comprises several injectors for the same combustion propellant and a control system for distributing the combustion propellant to be injected into the combustion zone among said injectors. For example, when such a burner has two oxidizer injectors, the control system allows the oxidizer to be directed to the first oxidizer injector, to the second oxidizer injector, or even to be distributed between the first and second oxidizer injectors, preferably at adjustable ratios. When such a burner has two fuel injectors, the control system allows the fuel to be directed to the first fuel injector, to the second fuel injector, or even to be distributed between the first and second fuel injectors, preferably at adjustable ratios.

[0037] The burner's combustion reagent injectors can usefully be coaxial injectors.

[0038] Such burners are, for example, described in document US-A-5743723, the contents of which are incorporated by reference into this patent application.

[0039] By equipping such a burner with coaxial injectors of cross-section whose width is at least twice its width and by mounting said coaxial injectors in a passage of the block of corresponding shape with an injection opening defining on the outlet face a contact rectangle whose length x of the segments perpendicular to the direction of height h is at least twice the length y of the segments parallel to the direction of height h, it is possible to use the burner as such to generate a wide flame, that is to say a flame whose cross-section has a dimension in the direction perpendicular to the direction of height h which is wider than its dimension in the direction of height h, whose length can be varied at constant flame power.

[0040] Such burners are also described in document WO-A-2010 / 003866, the contents of which are also incorporated by reference in this patent application. The burners described in the latter document are particularly suited for installation in a stage where the contact rectangle defined on the outlet face of the stage adjacent to the lower end of the block has segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h, as is notably the case for the stage adjacent to the lower end of the block.

[0041] IlIt is also possible to create a defined contact rectangle on the outlet face at the stage adjacent to the lower end of the block, which has segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h, by means of a staged combustion burner by staggering the injection of at least one combustion reactant through the outlet face of the block in the direction perpendicular to the direction of height h. According to such an embodiment, the burner comprises on the one hand a primary burner, capable of generating a primary flame, secondary injectors, for example two in number, for the combustion reactant to be staged located on either side of the primary burner in the direction perpendicular to the direction of height h and a control system capable of regulating the distribution of the reactant to be staged between the primary burner and the secondary injectors.The primary burner may, for example, be capable of generating a primary flame with a substantially circular cross-section. In particular, the primary burner may be a burner capable of varying the length of the primary flame while maintaining a constant primary flame intensity, for example, a burner such as that described in US-A-5743723.

[0042] One advantage of such an embodiment is that, depending on the setting of the distribution of combustion reactants, the burner is capable of generating both a wide flame, as defined above, whose length can be varied at constant flame power, and a narrower flame, for example with a cross-section in a circular substance, but whose length can still be varied at constant flame power.

[0043] The present invention also covers a combustion furnace equipped with at least one combustion unit according to any one of the embodiments described above. The at least one combustion unit according to the invention is mounted in the furnace with the lower end of the block facing downwards, the upper end of the block facing upwards, and the outlet face of the block facing a combustion zone inside the furnace. In this way, when the burners generate flames downstream of the outlet face of the block by burning the fuel with the oxidizer, the flames generated by the various burners are located within the combustion zone.

[0044] Such a furnace advantageously comprises several combustion sets according to the invention, with, for example, two such combustion sets positioned opposite each other and / or two such combustion sets next to each other.

[0045] The oven can be a batch oven, a continuous oven or a semi-continuous oven, also called a semi-batch oven.

[0046] In one important embodiment, the furnace is a static furnace and therefore not a rotary furnace. In another interesting implementation, the furnace is a melting furnace.

[0047] The combustion assembly and furnace according to the present invention are particularly suitable and useful for implementing the processes described in the applicant's unpublished patent applications FR2405260 and FR2405259, the teachings of which are incorporated by reference in the present application.

[0048] The present invention and its advantages are illustrated in the following non-limiting examples, with reference to figures 1 to 2 , of which there figure 1 is a schematic representation of a front view of a combustion assembly according to the invention, from the side of its outlet face, the figure 2is a schematic representation of a cross-section of the combustion assembly of the figure 1 when the combustion unit is in operation.

[0049] The combustion assembly illustrated in the figures comprises a non-metallic refractory block 10 in the shape of a rectangular parallelepiped, which extends over a height h between its lower end 11 and its upper end 12.

[0050] The exit face 13 of block 10 is opposite the inlet face 14 of block 10, the exit face 13 and the inlet face 14 being spaced apart from each other by a thickness ep.

[0051] Block 10 is distributed along its height h into four floors et1, et2, et3 and et4. Floor et1 is contiguous to the lower end 11 and floor e4 is contiguous to the upper end 12.

[0052] Each floor et1 to et4 is pierced by one or more passages p extending from the entrance face 14 to the exit face 13.

[0053] Floors et1 and et2 are each pierced by three passages p and floors et3 and et4 each by a single passage p.

[0054] In stages et1 and et2, the passages p terminate in the exit face 13 in a central injection opening 21 for the injection of fuel and oxidizer flanked in the direction perpendicular to the direction of height h by two injection openings 22 for the injection of stage oxidizer.

[0055] In stages et3 and et4, the single passage p terminates in the outlet face 13 in a single injection opening 23 for the injection of fuel and oxidizer.

[0056] A burner is mounted on each stage et1, et2, et3, et4. The fuel injector(s) 31 and the oxidant injector(s) 32 of the burner are inserted into at least one passage p of the corresponding stage et1, et2, et3, et4.

[0057] Each burner is capable of generating a flame f1, f2, f3, f4 whose length can be modified at constant flame power.

[0058] The orientation of the passage(s) p of the stage determines the direction in which the flame f1, f2, f3, f4 extends downstream of the exit face 13.

[0059] The flames f1, f2, f3 and f4 are non-convergent. The flames f2 and f3 are parallel, the flames f1 and f4 are divergent with respect to each other and with respect to the other flames f2 and f3.

[0060] The burners of stages et3 and et4 each have a fuel injector 31 in the center, surrounded by a second fuel injector 31, which is in turn surrounded by an oxidizer injector 32. By modifying the fuel distribution between the two fuel injectors 31, it is possible to modify the length of the flame f3, f4 generated at constant flame power. The burners of stages et1 and et2 are burners that allow for staged combustion through staggered fuel injection. They differ from the burners of stages et3 and et4, respectively, in that they have additional injectors 33 for controlled staggered oxidizer injection in the plane perpendicular to the height direction h via the two injection openings 22 for staggered oxidizer injection.

[0061] At each stage et1, et2, et3, et4, at least one injection opening 21, 22, 23 defines a contact rectangle 25 on the outlet face 13 whose segments parallel to the direction of height h have a length y and the segments perpendicular to the direction of height h have a length x. In the illustrated embodiment, the contact rectangles defined on the outlet face 13 have centers of gravity c aligned in the direction of height h.

[0062] At the lower level et1 and at levels et2 and et3, the ratio between x and y is greater than 2, which makes it possible to produce wide flames f1, f2 and f3 whose cross-sectional dimension perpendicular to the direction of height h is greater than its dimension in the direction of height h. When a load is located in front of the combustion assembly, such a flame f1, f2 and f3 makes it possible to heat the surface of the load over a greater distance in this direction perpendicular to height h, but over a reduced height.

[0063] At the upper stage et4 of the illustrated embodiment, the ratio between x and y is substantially equal to 1. The flame f4 generated by the corresponding burner is a flame with a substantially circular cross-section.

[0064] The dimension x at floor et4 is less than the dimension x at floor et3 which is in turn less than the dimension x at floor et2.

[0065] This type of embodiment is particularly suitable when the combustion unit is used to heat a charge opposite the unit, which is packed into a conical or truncated conical pile, the cross-section of which therefore decreases towards the apex. Indeed, such a configuration allows the flames f1, f2, f3, f4 to be directed solely towards the charge to be heated, thus making the heating process more efficient.

[0066] The fact that the combustion unit has a row of burners in the direction of height h allows the heating of the load to be adapted to the height of the pile, in particular by switching off or on the burners of the upper stages et2, et3, et4, or of the stages et3 and et4, or even only of the stage et4, depending on the height of the pile.

Claims

1. Combustion assembly comprising: • a non-metallic refractory block (10), said block (10): ∘ extending over a height h between a lower end (11) and an upper end (12), ∘ having an inlet face (14) and an outlet face (13) opposite the inlet face (14), the outlet face (13) and the inlet face (14) being separated by a thickness ep, ∘ the block (10) being distributed over its height h in several stages (et1, et2, et3, et4), each stage (et1, et2, et3, et4) being pierced by at least one passage (p) for the injection of fuel and / or oxidizer, each passage (p) extending from the inlet face (14) to the outlet face (13) and ending in at least one injection opening (21, 22, 23) in the outlet face (13) of the block, at least one injection opening (21, 22, 23) of each stage (et1, et2, et3,et4) defining on the outlet face (13) a contact rectangle (25) two segments of which are parallel to the direction of height h and two segments of which are perpendicular to the direction of height h, each injection opening (21, 22, 23) of the corresponding stage (et1, et2, et3, et4) being located entirely within said contact rectangle (25) and each segment of the contact rectangle (25) being in contact with the contour of at least one of the at least one injection openings (21, 22, 23) of the corresponding stage (et1, et2, et3, et4), • several burners at a rate of one burner per stage (et1, et2, et3, et4), each burner having injectors (31, 32, 33) of which: ∘ at least one injector for the injection of a fuel (31) fluidly connected to a fuel inlet of the burner and ∘ at least one injector for injecting an oxidant (32, 33) fluidly connected to an oxidant inlet of the burner, each burner being mounted on the stage (et1, et2, et3,et4) corresponding to the block (10) such that the fuel and oxidizer injectors (31, 32, 33) of the burner are inserted into at least one passage (p) of said stage (et1, et2, et3, et4) corresponding and such that the fuel and oxidizer inlets of the burner are on the side of the inlet face (14) of the block (10), each burner is capable of generating flames (f1, f2, f3, f4) by combustion of the fuel with the oxidizer downstream of the outlet face (13) of the block (10) whose length can be varied at constant flame power, the at least one passage (p) of the different stages (et1, et2, et3, et4) are oriented and spaced so that when the burners generate flames (f1, f2, f3, f4) downstream of the outlet face (13) of the block (10) by combustion of the fuel with the oxidizer, The flames (f1, f2, f3, f4) generated by the different burners are spaced apart and non-convergent.and the contact rectangle (25) defined on the exit face (13) at the floor (et1) adjacent to the lower end (11) of the block (10) have segments perpendicular to the direction of height h whose length x is at least twice the length y of the segments parallel to the direction of height h.

2. Combustion assembly according to claim 1, wherein the assembly has two stages (et1, et2, et3, et4) and comprises two burners.

3. Combustion assembly according to claim 1 or 2, wherein at least one passage (p) of the different stages (et1, et2, et3, et4) are oriented and spaced so that when the burners generate flames (f1, f2, f3, f4) by combustion of the fuel with the oxidizer, at least two of the flames (f1, f2, f3, f4) generated by the different burners are divergent.

4. Combustion assembly according to any one of the preceding claims, wherein the contact rectangles (25) defined on the outlet face (13) of the block (10) have centers of gravity (c) aligned in the direction of height h.

5. Combustion furnace equipped with at least one combustion assembly according to any one of the preceding claims, said combustion assembly being mounted in the furnace with the lower end (11) of the block (10) directed downwards, the upper end (12) of the block (10) directed upwards, the outlet face (13) of the block (10) directed towards a combustion zone inside the furnace so that when the burners generate flames (f1, f2, f3, f4) downstream of the outlet face (13) of the block (10) by combustion of the fuel with the oxidizer, the flames (f1, f2, f3, f4) generated by the different burners are located in the combustion zone.

6. Oven according to claim 5, comprising several combustion assemblies according to any one of claims 1 to 4.

7. Oven according to claim 6, comprising two combustion sets according to any one of claims 1 to 4 positioned opposite each other.

8. Oven according to claim 6 or 7, comprising two combustion sets according to any one of claims 1 to 4 positioned side by side.

9. Oven according to any one of claims 5 to 8, wherein the oven is a static oven.

10. Furnace according to any one of claims 5 to 9, wherein the furnace is a melting furnace.

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