BURNER AND PROCESS FOR BURNING A HYDROGEN-CONTAINING FUEL

Abstract

A burner for burning a hydrogen-containing fuel is equipped with a burner unit which comprises a fuel feed and a feed for a primary oxidant (oxygen) and which is accommodated in a feed for a secondary oxidant (air). A swirl device whose relative position with respect to the burner unit can be altered is provided in the feed for the secondary oxidant. The relative position of the burner unit and the swirl device may be controlled according to a composition of the fuel, in particular according to the water content thereof and the ratio of primary and secondary oxidant. The burner allows flexible adaptation of the burning to fuels of different composition, even during ongoing operation.

Claims

1. A burner for combustion of a hydrogen-containing fuel, the burner comprising: a burner unit which is accommodated within a feed for a secondary oxidant and comprises a fuel feed connected to an inlet for a hydrogen-containing fuel and a feed for a primary oxidant; and a swirl device disposed in the feed for the secondary oxidant; wherein upstream of the fuel feed of the burner unit is a mixing zone into which there open the inlet for hydrogen and at least one inlet for a second gaseous fuel; and wherein the swirl device and the burner unit are movable relative to one another.

2. The burner as claimed in claim 1, wherein the fuel feed and the feed for the primary oxidant are arranged concentrically to one another in the burner unit, and the latter is disposed concentrically within the feed for the secondary oxidant.

3. The burner as claimed in claim 1, wherein the fuel feed and the feed for the primary oxidant open out flush with one another at a mouth of the burner unit that faces a treatment space.

4. The burner as claimed in claim 1, wherein the burner unit is accommodated within the feed for the secondary oxidant so as to be movable axially with respect to the latter and with respect to the swirl device.

5. The burner as claimed in claim 1, wherein the swirl device is accommodated within the feed for the secondary oxidant so as to the movable axially with respect to the latter and with respect to the burner unit.

6. The burner as claimed in claim 1, wherein the burner unit has at least two fuel feeds.

7. A method of combustion of a hydrogen-containing fuel with an oxygen-containing oxidant in a treatment space using a burner as claimed in claim 1, wherein hydrogen via the inlet for hydrogen and optionally a second gaseous fuel via the inlet for the second gaseous fuel are mixed in the mixing zone and introduced into a treatment space via the fuel feed; a primary oxidant is simultaneously introduced into the treatment space via the feed for the primary oxidant, and optionally a secondary oxidant via the feed for the secondary oxidant; the fuel and the oxidant(s) are mixed with one another and reacted in the treatment space; depending on the chemical composition of the fuel introduced into the treatment space and/or the ratio of primary and secondary oxidant fed to the treatment space, the flow profile of the secondary oxidant introduced into the treatment space, which is determined by the relative position of the swirl device and the burner unit, is varied according to a defined program.

8. The method as claimed in claim 7, wherein the primary oxidant used is oxygen and the secondary oxidant used is air.

9. The method as claimed in claim 7, wherein the second gaseous fuel used is natural gas and/or a lean gas having low calorific value.

10. The method as claimed in claim 7, wherein the ratio of the flow rates of primary and secondary oxidant is controlled depending on a composition of the fuel fed to the treatment space according to a defined program and/or depending on measured parameters.

11. The method as claimed in claim 7, wherein there is flameless combustion in the treatment space.

12. The burner as claimed in claim 1, wherein the burner unit has at least two feeds for the primary oxidant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Working examples of the invention are to be elucidated in detail with reference to the drawings. The figures show, in schematic views:

[0027] FIG. 1 shows a burner of the invention in a first embodiment in longitudinal section in a first operating position,

[0028] FIG. 2 shows the burner from FIG. 1 in a second operating position,

[0029] FIG. 3 shows a burner of the invention in a second embodiment in longitudinal section in a first operating position,

[0030] FIG. 4 shows the burner from FIG. 3 in a second operating position.

DETAILED DESCRIPTION

[0031] The burner 1 shown in sections in FIGS. 1 and 2 comprises, in a coaxial arrangement, a central fuel feed 2 surrounded radially on the outside by a feed 3 for a primary oxidant, for example oxygen; fuel feed 2 and feed 3 for the primary oxidant together form a hydrogen/oxygen burner unit 4. The burner unit 4 is adjoined radially on the outside, and coaxially thereto, by a feed 5 for a secondary oxidant, for example air. The feeds 2, 3, 5 open out at a burner mouth 6 into a treatment space 7, which is, for example, a combustion chamber or a furnace space. The foremost section of the burner 1 facing the treatment space 7 is framed in a burner receptacle (burner block) 8, retracted with the burner mouth 6 with respect to the treatment space 7.

[0032] The fuel feed 2 is fluidically connected via a pipe section 9 to two inlets 10, 11, via which respectively different gaseous fuels are introduced and are mixed with one another in the pipe section 9, before the resultant fuel mixture is introduced into the treatment space 7 via the fuel feed 2. In particular, pure gaseous hydrogen is introduced via inlet 10, and a second gaseous fuel with a low level of hydrogen, for example natural gas, via inlet 11.

[0033] In the working example shown here, an inlet 12 for pure oxygen (with a purity of more than 90% by volume) which is fluidically connected to an oxygen source (not shown here), for example a stationary tank, opens out into the feed 3 for primary oxidant, and an inlet 13 for air into the feed 5. The feeds 2, 3, 5 have no flow connection with one another over their entire length up to the burner mouth 6. Only upstream of the burner mouth 6 is there mixing of the gases introduced via feeds 2, 3, 5. Not shown in the drawings, but nevertheless present, is an ignition device of customary design for ignition of the fuel-oxidant mixture introduced into the treatment space 7.

[0034] A swirl device 15 is disposed in the feed 5 for the secondary oxidant. The swirl device 15, in the working example shown here, extends coaxially around the burner unit 4 and is equipped with air-guiding elements 16 in a spiral arrangement, by means of which the gas stream introduced via the feed 5 is forced into a swirling motion about a burner axis 17.

[0035] The swirl device 15, in the working example shown in FIGS. 1 and 2, is in an axially movable arrangement within the feed 5, and it can moved even during operation by means of drive mechanics 18 that are merely indicated here by dashedanddotted lines. The swirl device 15 may be moved continuously between a position in which, as shown in FIG. 1, it is deep within the feed 5, away from the burner mouth 6, and a position in which, as shown in FIG. 2, it concludes flush, or at least virtually flush, with the burner mouth 6 by a front face.

[0036] The burner 20 shownonly by its front sectionin FIG. 3 and FIG. 4, in which, incidentally, elements having the same effect have been given the same reference numerals as in the burner 1 in FIGS. 1 and 2, differs from the burner 1 merely in that a swirl device 15 that is not movable axially with respect to the feed 5 is incorporated in the feed 5 for the secondary oxidant. The swirl device 15 is equipped in a customary manner with spiral air-guiding elements 16 and is fixedly connected to a burner receptacle 8 to give a swirl grid. The swirl device 15 here is mounted in a retracted position in the burner receptacle 8 in order to prevent damage by the effect of heat from the treatment space 7.

[0037] At the same time, in the working example according to FIGS. 3 and 4, the burner unit 21 formed from the feeds 2 and 3 is movable axially with respect to the burner receptacle 8, and hence with respect to the swirl device 15. The burner unit 21 may by means of a movement device 23 continuously between a position in which, as shown in FIG. 3, it projects within the burner receptacle 8 in the direction of the treatment space 7 at a distance from the swirl device 15 and a position in which, as shown in FIG. 4, it is retracted with a front face flush, or at least virtually flush, with the swirl device 15 in the burner receptacle 8.

[0038] The burners 1, 20 are intended, in particular, to burn a mixture composed of the components hydrogen and a second gaseous fuel, for instance natural gas and/or a lean gas, in a variable composition that also changes during operation with an oxidant consisting of oxygen or an oxygen-air mixture in likewise variable composition. Since the different compositions of fuel and oxidant lead to different flame geometries and temperatures, it is additionally necessary during operation to adjust the flow ratios implemented by the swirl device 15, 15.

[0039] FIGS. 1 and 3 show a situation in which a fuel having a high hydrogen contentpure hydrogen in the limiting caseis burnt with an oxygen-rich (relative to air) primary oxidantpure oxygen in the limiting casewhich is introduced into the treatment space 7 via the feed 3. In this case, not only does the combustion lead to high flame temperatures, but the comparatively minor or completely absent stream of secondary oxidant (air) via the feed 5 leads to formation of a flame in the treatment space 7 close to the burner mouth 6.

[0040] The swirl device 15, 15 here is in a retracted position deep in the burner receptacle 8, 8 for protection from heat. The high momentum of the gases entering the treatment space 7 from the feeds 2, 3 leads to intensive recirculation of parts of the atmosphere in the treatment space 7, which can subsequently result in flameless combustion in the treatment space 7.

[0041] As the proportion of secondary oxidant (air) introduced via the feed 5 in the overall oxidant introduced into the treatment space 7 (collectively oxidant hereinafter) rises, the mass flow introduced into the treatment space 7 increases, the flame moves away from the burner mouth 6, and the swirl device 15, 15 is cooled by the stream of the second oxidant. In order to assure good mixing of fuel and oxidant in this case, the swirl device 15, 15 and burner unit 4, 21 are moved such that the foremost section of the swirl device 15, 15 facing the treatment space 7 and the mouth of the burner unit 4, 21 converge. The closer the swirl device 15, 15 and the mouth of the fuel feed 2 move together, the greater the influence of the swirled oxidant stream on the fuel stream. What is described in particular by the limiting case shown in FIGS. 2 and 4 is a situation in which virtually no primary oxidant (oxygen), if any, is introduced via the feed 3, and the oxidant instead consists virtually exclusively of secondary oxidant (air) which is introduced via feed 5.

[0042] With varying compositions of fuel and/or oxidant, the position of the swirl device 15 or burner unit 21 may be changed during operation and matched to the respective demands and controlled. This is effected either manually or by means of an automatic controller (not shown here) according to a defined program. For example, the relative position of the swirl device 15, 15 relative to the burner unit 4, 21 may be controlled depending on a measured hydrogen concentration in the fuel fed in or a temperature in the treatment space 7. Incidentally, the swirl device 15, 15, in the limiting case of maximum input of secondary oxidant via the feed 5, need not in any way, as shown here, conclude flush with the mouth of the fuel feed 2. Instead, the position of the swirl device which is preferred for the combustion process depends on the geometry and alignment of the air-guiding elements 16, 16.

[0043] Moreover, it is also conceivable in the context of the present invention to provide a further feed for primary oxidant (oxygen) in the burner unit 4, 21, in order to be able to still better vary the flame geometry.

[0044] In addition, the inventive burner 1, 20 is especially also suitable for combustion of lean gases of low calorific value, which for this purpose is mixed with the second gaseous fuel (natural gas) or used exclusively as second gaseous fuel and introduced into the treatment space 7 via the inlet 11, the pipe section 9 and the fuel feed 2.

LIST OF REFERENCE NUMERALS

[0045] 1 burner [0046] 2 fuel feed [0047] 3 feed for primary oxidant [0048] 4 burner unit [0049] 5 feed for secondary oxidant [0050] 6 burner mouth [0051] 7 treatment space [0052] 8, 8 burner receptacle [0053] 9 pipe section [0054] 10 inlet (for hydrogen) [0055] 11 inlet (for natural gas) [0056] 12 inlet (for oxygen) [0057] 13 inlet (for air) [0058] 14 - [0059] 15, 15 swirl device [0060] 16, 16 air-guiding elements [0061] 17 burner axis [0062] 18 drive mechanics [0063] 19 - [0064] 20 burner [0065] 21 burner unit [0066] 22 mouth (of the burner unit)