Method and combusting fuel and burner therefor

Abstract

Method and burner for combusting a main fuel with a main oxidizer, whereby flows of the main fuel and the main oxidizer are injected via an injector end, comprising at least one metallic injector, said injector end being positioned in the upstream section of a main passage of a refractory block and whereby multiple jets are injected into the downstream section of the main passage to increase mixing and turbulence of the flows of the main fuel and the main oxidizer.

Claims

1. A method of combusting fuel with oxidizer by means of a burner comprising a main injector assembly and a refractory burner block, whereby the main injector assembly terminates in an injection end which comprises at least one metallic injector, the block comprises a main passage bordered by a surrounding passage surface and extending along an axis from a cold face of the block to a hot face of the block opposite the cold face, the main passage defines a main injection direction X parallel to the axis and has an upstream section adjacent the cold face and a downstream section downstream of the upstream section and adjacent the hot face, said downstream section terminating in a main injection opening in the hot face of the block, and the injection end of the main injector assembly is positioned in the upstream section of the main passage so that the upstream section surrounds the at least one metallic injector, a flow of main fuel and flow of main oxidizer are injected according to main injection direction X towards and into the downstream section of the main passage by means of the injector end of the main injector assembly, characterized in that: the burner block further comprises multiple auxiliary passages terminating in the downstream section via n auxiliary openings in the surrounding surface of the main passage, whereby n2 and n jets of agitating gas are injected into the downstream section via the n auxiliary openings so as to interact with the flow of main fuel and the flow of main oxidizer and to increase turbulence and mixing thereof.

2. The method of claim 1, whereby the n jets of agitating gas are injected so as to decrease the momentum of the flow of main fuel and the flow of main oxidizer in the main injection direction X.

3. The method of claim 1, whereby the n auxiliary openings are positioned in axial symmetry around the axis.

4. The method of claim 1, whereby: the n agitating gas jets are directed towards the axis, or the n agitating gas jets are injected according to a same sense of rotation around the axis.

5. The method of claim 1, whereby the agitating gas jets are injected according to an injection direction forming an angle of between 30 and 105 with the main injection direction X, preferably between 45 and 105 , more preferably between 45 and 105, and most preferably between 65 and 85.

6. The method of claim 1, whereby the refractory block is a refractory ceramic block or a refractory metallic block.

7. The method of claim 1, whereby the agitating gas is selected from: a substantially inert gas, a secondary oxidizer and a secondary gaseous fuel.

8. The method of claim 1 whereby: at least part of the main fuel is injected around the main oxidizer, or least part of the main oxidizer is injected around the main fuel.

9. A burner comprising a metallic injector assembly and a refractory burner block, the injector assembly comprising an injection end and terminating in at least one metallic injector, the block comprising a main passage bordered by a surrounding surface and extending along an axis from a cold face of the block to a hot face of the block opposite the cold face, the main passage having a longitudinal axis, an upstream section adjacent the cold face and a downstream section adjacent the hot face and downstream of the upstream section, said downstream section terminating in a main injection opening in the hot face of the block, the injection end of the injector assembly being positioned in the upstream section of the main passage for injecting fuel and oxidizer towards and into the downstream section of the main passage said upstream section surrounding the at least one metallic injector, characterized in that: the burner block further comprises multiple auxiliary passages for transporting an agitating gas through the burner block and for injecting agitating gas jets into the downstream section of the main passage, the multiple auxiliary passages terminating in the downstream section of the passage through n auxiliary openings in the surrounding surface of the main passage, with n2, the multiple auxiliary passages being positioned and oriented so that, in operation, the n agitating gas jets injected via said n auxiliary openings interact with the main fuel and the main oxidizer injected by the injector assembly inside or downstream of the downstream section so as to generate increased turbulence and mixing of the main fuel with the main oxidizer.

10. The burner of claim 9, whereby the n auxiliary openings are evenly distributed around the longitudinal axis.

11. The burner of claim 9, whereby the multiple auxiliary passages are positioned and oriented so that, in operation, the n agitating gas jets are injected via said n auxiliary openings: with injection directions directed towards the longitudinal axis, or with injection directions presenting a same sense of rotation around the axis.

12. The burner of claim 9, whereby the multiple auxiliary passages are positioned and oriented so that, in operation, the n agitating gas jets are injected via said n auxiliary openings with injection directions forming an angle of between 30 and 105 with the main injection direction X, preferably between 45 and 105, more preferably between 60 and 105, and most preferably between 65 and 85.

13. The burner of claim 9, whereby the injection end of the injector assembly comprises an oxidizer injector and a fuel injector, whereby the injection end of the injector assembly preferably comprises (a) an oxidizer injector which surrounds a fuel injector or (b) a fuel injector which surrounds an oxidizer injector.

14. The burner of claim 9, whereby the refractory block is a refractory ceramic block or a refractory metallic block.

15. The furnace comprising at least one burner of claim 9, said burner being mounted in a furnace wall so that the hot face of the burner block faces a combustion zone of the furnace and so that the cold face of the burner block faces away from the combustion zone.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic representation of a partial cross section of a burner according to the invention and

(2) FIG. 2 is a schematic hot-side front view of the burner of FIG. 1.

(3) FIG. 3 is a schematic representation of a partial cross section of an alternative embodiment of the burner according to the invention and

(4) FIG. 4 is a schematic hot-side front view of the burner of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

(5) The illustrated burners comprise a main injector assembly of which the injection end 100 is shown.

(6) The injection end 100 comprises a central metallic oxidizer injector 120 for the injection of industrially pure oxygen (at least 90% vol O.sub.2) mixed with recycled flue gas as the main oxidizer and a surrounding metallic fuel injector 110 for the injection of a gas-entrained particulate solid fuel as the main fuel.

(7) Various conveyor gases may be used for the particulate solid fuel, such as, for example, air, steam or recycled flue gas, with or without oxygen enrichment.

(8) The burners also comprise a refractory block 200, metallic or ceramic, which is mounted in furnace wall 300. A main passage 250, extending along axis 252, is provided through said burner block 200 from the cold face 201 to the hot face 202 of the block 200. The hot face 202 faces the combustion zone 400 of the furnace. Refractory surrounding surface 251 borders the main passage 250 as it traverses block 200.

(9) The main passage has an upstream section 260 adjacent the cold face 201 and a downstream section 270 downstream (in the flow direction of the main fuel and the main oxidizer) of the upstream section 260 and adjacent the hot face 202.

(10) The injection end 100 of the main injector assembly is positioned in the upstream section of the main passage 250 so that the upstream section 260 surrounds the metallic injectors 110, 120.

(11) In use, a flow of the gas-entrained particulate solid fuel and a flow of the main oxidizer are injected towards and into the downstream section 270 of the main passage 250 by means of the injection end 100 of the main injector assembly, so that the two flows come into contact and mix in said downstream section 270.

(12) In the embodiment illustrated in FIGS. 1 and 2, burner block 200 comprises four auxiliary passages 281, 283. Each of said auxiliary passages terminates in the widening downstream section 270 via an auxiliary opening 291, 292, 293, 294 in the surrounding surface 251 of the main passage 250. The four auxiliary openings are in axial symmetry around the axis 252 defining an angle of 90 between two successive auxiliary openings 291, 292, 293 and 294.

(13) The four auxiliary passages 281, 283 are positioned and oriented so that gas jets injected through the auxiliary openings 291, 292, 293 and 294 into downstream section 270 are injected in a clockwise direction with respect to the axis 252 (as seen from the hot face 202 of the burner block 200).

(14) The four corresponding agitating gas jets have identical velocities and flow rates.

(15) These gas jets impact the flows of fuel and oxidizer injected by the injection end 100 of the main injection assembly and act as agitating gas jets, increasing the turbulence and mixing of said fuel and oxidizer flows. The agitating gas jets more particularly confer a swirling effect to the main fuel and main oxidizer flows, thereby extending the residence time of the particulate solid fuel in the main oxidizer flow. In the present example, gaseous fuel is injected as agitating gas jet and thus also ensures ignition of the combustion of the main fuel with the main oxidizer. Due to the identical velocities and flow rates of the agitating gas jets, the propagation direction of the flame remains unchanged.

(16) The illustrated burners are self-cooled burners, whereby the burners, and in particular the metallic injectors 110, 120 of the burners, are cooled by the media flowing through same. No additional cooling circuit is provided or necessary in view of the heat screening of the metallic injectors 110, 120, by the burner 200.

(17) In the embodiment illustrated in FIGS. 1 and 2, the downstream section 270 of the main passage 250 has a larger cross section than the upstream section 260 and has a funnel shape widening towards the hot face 202, in order to limit impact of the main fuel and the main oxidizer flows and of the resulting flame when the root of the flame is located within the passage on the refractory surface in the downstream section 270.

(18) The four auxiliary passages 281, 283 are positioned and oriented so that gas jets injected through the auxiliary openings 291, 292, 293 and 294 are injected in a clockwise direction with respect to the axis 252 (as seen from the hot face 202 of the burner block 200), but with a vector component towards axis 252, and so that the agitating gas jets injected through said auxiliary openings 291 to 294 impact the flows of main fuel and main oxidizer within the downstream section 270 of the main passage 250.

(19) In the embodiment illustrated in FIGS. 3 and 4, the downstream section 270 of the main passage 250 initially has the same cross section as the upstream section 260, then narrows towards the hot face 202, i.e. towards the combustion zone of the furnace, and terminates in a neck portion 273. This neck portion 273 restricts the amount of radiation and combustion gases from the combustion zone which can penetrate into the main passage 250.

(20) As a consequence, condensable substances from the furnace atmosphere are prevented from reaching the cooler injectors.

(21) Burner block 200 comprises six auxiliary passages 281, 283. Each of said auxiliary passages terminates in the neck portion 273 of section 270 via an auxiliary opening 291, 292, 293, 294, 295, 296 in the surrounding surface 251 of the main passage 250. The six auxiliary openings are in axial symmetry around the axis 252 defining an angle of 60 between two successive auxiliary openings 291, 292, 295, 293, 294, 296.

(22) The six auxiliary passages 281, 283 are positioned and oriented so that the agitating gas jets injected through the auxiliary openings 291 to 296 are injected in a counterclockwise direction with respect to the axis 252 (as seen from the hot face 202 of the burner block 200) impact the flows of main fuel and main oxidizer essentially at or immediately upstream or downstream of the main injection opening of main passage 250.

(23) Due to the orientation of the agitating gas jets, no swirling devices are necessary to ensure a sufficiently long residence time of the particulate fuel in the main oxidizer flow while simultaneously the solid angle of the flow of gas-entrained solid fuel and main oxidizer remains small. In this manner, adequate mixing of the fuel and main oxidizer is achieved. If, in order to increase the swirling effect, the burner is also equipped with a mixing device as described above, the mixing device is preferably located within or immediately downstream of the main oxidizer injector 120 to avoid erosion of said swirling device due to impact by the particulate solid fuel.

(24) 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.

(25) The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

(26) 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 is defined herein as necessarily encompassing the more limited transitional terms consisting essentially of and consisting of; comprising may therefore be replaced by consisting essentially of or consisting of and remain within the expressly defined scope of comprising.

(27) 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.

(28) 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.

(29) 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.

(30) 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.