Burner and method for combusting a hydrogen-containing fuel

Description

[0001] The invention relates to a burner for combusting a hydrogen-containing fuel, comprising a burner unit accommodated within a supply line for a secondary oxidant, which comprises a fuel supply connected to a supply line for a hydrogen-containing fuel and a supply line for a primary oxidant, and comprising a swirl device arranged in the supply line for the secondary oxidant. Furthermore, the invention relates to a method for combusting a hydrogen-containing fuel with an oxygen-containing oxidant.

[0002] EP 3 333 481 A1 discloses a burner for burning hydrogen. The burner has a coaxial design, with a central fuel supply for hydrogen and coaxially arranged supplies for a primary and a secondary oxygen-containing oxidant. However, additional combustion of fuels other than hydrogen or a swirl device is not provided.

[0003] EP 3 450 843 A1 discloses a burner for burning hydrogen gas, in which an oxidant supply is arranged concentrically within a tubular supply for hydrogen gas. During operation of the burner, a tubular flame is formed within the outer supply. Supplementary combustion of other fuels is also not provided for in this device.

[0004] WO 2009 / 068424 A1 discloses a premix burner for the combustion of a hydrogen-containing synthesis gas. In this burner, hydrogen or a hydrogen-containing synthesis gas and another liquid or gaseous fuel are fed radially into a swirling air stream. The resulting gas mixture is intensively mixed due to the swirling flow and fed into a combustion chamber where it is reacted. However, this device does not envision changing the fuel composition during operation.

[0005] WO 00 / 61992 A1 describes a burner arrangement in which a burner with a fuel supply and an oxidant supply is accommodated in a supply line for a secondary oxidant. To adapt the flow conditions to the respective requirements, rotatably mounted flow elements are arranged in the supply line for the secondary oxidant.

[0006] A burner arrangement for combusting a fuel with an oxidizer is known from IT UB20 156 239 A1. A mixing section is connected upstream of the burner, into which a first supply line for methane and a second supply line for hydrogen flow.

[0007] US 2009 / 111064 A1 describes a burner assembly in which a first oxidant supply is housed within a fuel supply, which in turn is housed within a second oxidant supply. Before entering a furnace chamber, the fuel and oxidant pass through a flame stabilization device, which may be, for example, a swirl device.

[0008] The invention is based on the object of providing a burner and a method for burning a hydrogen-containing fuel with an oxygen-containing oxidizing agent, which can be used flexibly with different fuel compositions, in particular with different hydrogen contents, and which produces good results in a wide range with regard to economic efficiency and pollutant emissions.

[0009] This object is achieved by a burner having the features of patent claim 1 and by a method having the features of patent claim 7. Advantageous embodiments of the invention are specified in the subclaims.

[0010] The burner according to the invention for combusting a hydrogen-containing fuel comprises at least one fuel supply and at least one supply for a primary and a secondary oxidant. The at least one fuel supply and at least one supply for a primary oxidant are accommodated within the supply for a secondary oxidant and are also referred to below as the "burner unit." For example, the fuel supply(s) and the supply(s) for the primary oxidant are designed as concentrically or parallel-arranged tubes closed on the shell side, which are arranged concentrically within a likewise tubular supply for the secondary oxidant.However, other embodiments are also conceivable within the scope of the invention, for example a burner unit in which a central feed for fuel (or for primary oxidant) is radially surrounded by a plurality of feeds for the primary oxidant (or for the fuel) that are axially parallel to one another.

[0011] A mixing section is arranged upstream of the actual fuel supply, into which a supply line for a hydrogen-containing fuel, in particular for pure hydrogen with a purity of over 99 vol.%, and at least one supply line for a second gaseous fuel flow. The mixing section may be, for example, a section of pipe arranged upstream of the fuel supply, a mixing chamber, or a rear section of the fuel supply, spaced apart from the burner outlet into a treatment chamber, such as a furnace chamber or combustion chamber, when the burner is installed.

[0012] A swirl device is provided in the feed for the secondary oxidant and preferably radially on the outside of the burner unit, by means of which, in a conventional manner, the flow of secondary oxidant introduced into the treatment chamber can be forced into a helical path and a flow direction can thereby be specified. The swirl device is arranged such that the burner unit and swirl device are movable relative to one another, i.e. the swirl device relative to the burner unit and the feed for the secondary oxidant and / or the burner unit relative to the swirl device and the feed for the secondary oxidant. The movement of the burner unit and / or swirl device takes place by means of a manually operated or motor-driven displacement device.For example, the swirl device is a body equipped with air guiding elements, arranged around the burner unit, which body is axially movable relative to the burner unit and / or relative to which the burner unit is, and in which a continuous movement of the swirl device and / or the burner unit between a first position in which the swirl device and the mouth of the burner unit are close to one another, and a second position in which the swirl device is set back relative to the mouth of the burner unit in the feed for the second oxidizing agent is possible.

[0013] During operation of the burner, hydrogen or a mixture of hydrogen and a second gaseous fuel previously produced in the mixing section is introduced into a treatment chamber. Means such as valves are provided by which the flow rates of hydrogen and the second fuel, as well as their ratio, can be variably adjusted. The primary and secondary oxidants are introduced into the treatment chamber via the corresponding feed lines and only reacted with the fuel there. The flow rates of primary and secondary oxidants, as well as their ratios, can also be adjusted independently of one another using suitable means such as valves. By changing the relative positions of the swirl device and the burner unit, the flow pattern of the secondary oxidant introduced into the treatment chamber can be specifically modified.

[0014] The primary oxidant is preferably pure oxygen, and the secondary oxidant is air. In the context of this invention, "pure oxygen" is understood to mean oxygen with a purity of at least 90 vol.%. The hydrogen-containing fuel is preferably pure hydrogen with a purity of at least 99 vol.%. The second gaseous fuel preferably contains no or only negligible amounts of hydrogen. For example, it is natural gas and / or a gas or gas mixture with a high inert gas content and low calorific value (lean gas).

[0015] In a preferred embodiment, at least one fuel supply and one supply for the primary oxidant are designed as concentrically extending cylindrical tubes that have no flow connection to one another. Preferably, one fuel supply is arranged centrally within a supply for the primary oxidant. In a particularly preferred embodiment, the fuel supply and the supply for the primary oxidant open in alignment with one another at a burner mouth of the burner unit in the direction of the treatment chamber.

[0016] The burner unit is preferably arranged concentrically within the likewise cylindrical supply for the secondary oxidant. In the installed state, the opening of the burner unit is preferably recessed from the opening of the supply for the secondary oxidant into the treatment chamber in order to protect the burner unit from heat exposure from the treatment chamber. The supply for the second oxidant is either designed as a tube installed in a burner holder (burner block) or is formed by a corresponding cylindrical bore in the burner block itself.

[0017] An advantageous embodiment of the burner according to the invention provides that the burner unit has at least two fuel inlets and / or at least two inlets for the primary oxidant. Such an arrangement provides, in particular, a further possibility for influencing the geometry or temperature of a flame forming in the treatment chamber.

[0018] The burner according to the invention is preferably used in a process for burning a hydrogen-containing fuel with an oxygen-containing oxidizing agent in a treatment chamber, which is characterized by the following steps: Hydrogen is supplied via the hydrogen supply line and, if necessary, mixed in the mixing section upstream of the burner supply with a second gaseous fuel, which was supplied via the supply line for the second gaseous fuel, and the hydrogen or the mixture (hereinafter generally referred to as "fuel") is introduced into a treatment chamber via the fuel supply line. At the same time, a primary oxidant, for example pure oxygen, is introduced into the treatment chamber via the supply line for the primary oxidant and, if necessary, a secondary oxidant, for example air, is introduced into the treatment chamber via the supply line for the second oxidant. In the treatment chamber, the fuel and the oxidant(s) are reacted with one another, depending on the chemical composition of the fuel introduced into the treatment chamber, in particular its hydrogen content or its calorific value.and / or the ratio of primary and secondary oxidant supplied from the treatment chamber, the flow pattern of the secondary oxidant introduced into the treatment chamber is changed according to a predetermined program, whereby the change in the flow pattern is achieved by varying the relative position of the swirl device and the burner unit.

[0019] The relative position of the burner unit and the swirl device is controlled, for example, as follows: Due to the low ignition temperature and high flame speed during hydrogen combustion, a high hydrogen content in the fuel leads to higher temperatures in the area where the burner enters the treatment chamber. In this case, it is advantageous to delay the thorough mixing of the oxidizing agent and fuel as much as possible. This is particularly true when the oxidizing agent contains high oxygen content, as this results in higher reaction temperatures and a lower flow rate driving the flame away from the burner mouth.In the limiting case of pure, or almost pure, hydrogen-oxygen combustion, the swirl device, which in this case is of only minor importance due to the low proportion of secondary oxidant, is then preferably retracted in the burner holder, as far away as possible from the flame and the mouth opening of the burner unit.

[0020] The lower the hydrogen content in the fuel and / or the higher the air content in the oxidant, the lower the flame temperature becomes, and the flame moves away from the burner mouth due to the larger mass flow. In this situation, intensive mixing of fuel and oxidant by means of the swirl device as close as possible in front of the burner mouth is advantageous. According to the invention, this is achieved, for example, by the swirl device and burner mouth approaching one another, i.e. either, in the case of a movable swirl device, this is pushed forward towards the burner mouth, or, in the case of a movable burner, the latter is pushed back relative to the swirl device fixed in a swirl cabinet in the burner holder, in the direction away from the combustion chamber.

[0021] Furthermore, with the burner according to the invention it is also possible to regulate the ratio and the absolute values of the mass flows of primary oxidant (in particular pure oxygen) and secondary oxidant (in particular air) as a function of a composition of the fuel supplied to the treatment chamber according to a predetermined program and / or as a function of measured parameters.

[0022] The burner according to the invention can be operated in particular with a fuel mixture consisting of hydrogen and natural gas and / or another gaseous fuel, in particular lean gas, as well as with pure oxygen as the first and air as the second oxidizing agent, wherein the ratio of hydrogen to natural gas and / or the ratio of oxygen to air can be changed to a wide extent even during operation.

[0023] The burner according to the invention or the method according to the invention is preferably also suitable for inducing flameless combustion in the treatment chamber. For this purpose, the streams of fuel and the primary and / or secondary oxidant are introduced into the treatment chamber with such a high momentum that intensive recirculation of the exhaust gases in the treatment chamber occurs, resulting in flameless combustion.

[0024] Embodiments of the invention will be explained in more detail with reference to the drawings. Schematic views show: Fig. 1 : A burner according to the invention in a first embodiment in longitudinal section in a first operating position, Fig. 2 : Turn off the burner Fig. 1 in a second operating position, Fig. 3 : A burner according to the invention in a second embodiment in longitudinal section in a first operating position, Fig. 4 : Turn off the burner Fig. 3 in a second operating position.

[0025] The one in the Fig. 1 and 2The burner 1, shown in detail, comprises, in a coaxial arrangement, a central fuel feed 2, which is surrounded radially on the outside by a feed 3 for a primary oxidizing agent, for example oxygen; fuel feed 2 and feed 3 for the primary oxidizing agent together form a hydrogen / oxygen burner unit 4. Radially on the outside of the burner unit 4 and coaxial with it is a feed 5 for a secondary oxidizing agent, for example air. The feeds 2, 3, 5 open at a burner mouth 6 into a treatment chamber 7, which is, for example, a combustion chamber or a furnace chamber. The front section of the burner 1 facing the treatment chamber 7 is set back with the burner mouth 6 relative to the treatment chamber 7 and enclosed in a burner receptacle (burner block) 8.

[0026] The fuel supply 2 is fluidly connected via a pipe section 9 to two supply lines 10, 11, through which different gaseous fuels are introduced and mixed with each other in the pipe section 9 before the resulting fuel mixture is introduced into the treatment chamber 7 via the fuel supply 2. In particular, pure gaseous hydrogen is introduced via the supply line 10, and a second, gaseous and low-hydrogen fuel, for example natural gas, is introduced via the supply line 11.

[0027] In the exemplary embodiment shown here, a supply line 12 for pure oxygen (with a purity of over 90 vol.%), which is fluidly connected to an oxygen source not shown here, for example a stationary tank, opens into the supply line 3 for primary oxidant, and a supply line 13 for air opens into the supply line 5. The supplies 2, 3, 5 have no flow connection to one another along their entire length up to the burner mouth 6. The gases introduced via the supplies 2, 3, 5 are only mixed upstream of the burner mouth 6. Not shown in the drawings, but present, is an ignition device of conventional design for igniting the fuel-oxidant mixture introduced into the treatment chamber 7.

[0028] A swirl device 15 is arranged in the supply line 5 for the secondary oxidant. In the embodiment shown here, the swirl device 15 extends coaxially around the burner unit 4 and is equipped with spirally arranged air guide elements 16, by means of which the gas flow introduced via the supply line 5 is forced into a vortex-like movement around a burner axis 17.

[0029] The swirl device 15 is in the Fig. 1 and 2 In the embodiment shown, it is arranged axially movable within the feed 5, whereby it can also be moved during operation by means of a propulsion mechanism 18, which is only indicated here by dot-dash lines. The swirl device 15 can be continuously moved between a position in which it is as in Fig. 1 shown, located deep in the feeder 5 spaced from the burner mouth 6, and a position in which it, as shown in Fig. 2 shown, with a front surface flush, or at least almost flush, with the burner mouth 6.

[0030] The Fig. 3 and in Fig. 4 - there only with its front section - shown burner 20, in which otherwise identically acting elements were provided with the same reference numbers as in burner 1 in Fig. 1 and 2 , differs from burner 1 only in that a swirl device 15' that cannot be moved axially relative to the feed 5 is installed in the feed 5 for the secondary oxidant. The swirl device 15' is equipped in the usual way with spiral-shaped air guide elements 16' and is firmly connected to a burner holder 8' to form a swirl cabinet. The swirl device 15' is mounted recessed in the burner holder 8' to prevent damage due to heat from the treatment chamber 7.

[0031] At the same time, in the embodiment according to Fig. 3 and 4 The burner unit 21 formed from the feeds 2 and 3 is designed to be axially displaceable relative to the burner receptacle 8', and thus relative to the swirl device 15'. By means of a displacement device 23, the burner unit 21 can be continuously moved between a position in which it is, as shown in Fig. 3 shown, protrudes within the burner holder 8' in the direction of the treatment chamber 7 at a distance from the swirl device 15', and a position in which it, as shown in Fig. 4 shown, with a front surface flush, or at least almost flush, with the swirl device 15' retracted in the burner holder 8'.

[0032] The burners 1, 20 are particularly designed to combust a mixture composed of hydrogen and a second gaseous fuel, such as natural gas and / or a lean gas, in a variable composition that also changes during operation, with an oxidizing agent consisting of oxygen or an oxygen-air mixture, also in a variable composition. Since the different compositions of fuel and oxidizing agent lead to different flame geometries and temperatures, it is also necessary to adapt the flow conditions induced by the swirl device 15, 15' during operation.

[0033] The Fig. 1 and 3show a situation in which a fuel with a high hydrogen content - in the limiting case pure hydrogen - is burned with a primary oxidant (compared to air) that is oxygen-rich - in the limiting case pure oxygen - which is introduced into the treatment chamber 7 via the feed 3. In this case, the combustion not only leads to high flame temperatures, but the comparatively low or completely absent flow of secondary oxidant (air) via the feed 5 leads to the formation of a flame in the treatment chamber 7 close to the burner mouth 6.

[0034] The swirl device 15, 15' is positioned deep within the burner mount 8, 8' to protect it from heat. The high momentum of the gases entering the treatment chamber 7 from the inlets 2, 3 leads to intensive recirculation of parts of the atmosphere in the treatment chamber 7, which can subsequently result in flameless combustion in the treatment chamber 7.

[0035] As the proportion of secondary oxidant (air) introduced through the feed 5 increases in relation to the total oxidant introduced into the treatment chamber 7 (hereinafter collectively referred to as "oxidant"), the mass flow introduced into the treatment chamber 7 increases, the flame shifts away from the burner mouth 6, and the swirl device 15, 15' is cooled by the flow of the second oxidant. To ensure thorough mixing of fuel and oxidant in this case, the swirl device 15, 15' and burner unit 4, 21 are moved such that the front section of the swirl device 15, 15' facing the treatment chamber 7 and the mouth of the burner unit 4, 21 approach each other. The closer the swirl device 15, 15' and the mouth of the fuel feed 2 move together, the stronger the influence of the swirled oxidant flow on the fuel flow. The Fig. 2 and 4The limiting case shown describes in particular a situation in which no or almost no primary oxidant (oxygen) is introduced via feed 3, but the oxidant consists almost exclusively of secondary oxidant (air), which is introduced via feed 5.

[0036] If the composition of fuel and / or oxidant changes, the position of the swirl device 15 or the burner unit 21 can be changed during operation and adapted and regulated to the respective requirements. This is done either manually or via an automatic control system (not shown here) according to a predefined program. For example, the relative position of the swirl device 15, 15' relative to the burner unit 4, 21 can be regulated depending on a measured hydrogen concentration in the supplied fuel or a temperature in the treatment chamber 7. Furthermore, in the limiting case of a maximum input of secondary oxidant via the feed 5, the swirl device 15, 15' does not have to be flush with the opening of the fuel feed 2, as shown here; rather, the preferred position of the swirl device for the combustion process depends on the geometry and orientation of the air guide elements 16, 16'.

[0037] Furthermore, within the scope of the present invention, it is also conceivable to provide a further supply for primary oxidizing agent (oxygen) in the burner unit 4, 21 in order to be able to vary the flame geometry even better.

[0038] Furthermore, the burner 1, 20 according to the invention is particularly suitable for the combustion of lean gases with a low calorific value, which for this purpose is mixed with the second gaseous fuel (natural gas) or used exclusively as a second gaseous fuel and is introduced into the treatment chamber 7 via the feed line 11, the pipe section 9 and the fuel feed 2. Bezugszeichenliste

[0039] 1 Burner 2 Fuel supply 3 Primary oxidant supply 4 Burner unit 5 Secondary oxidant supply 6 Burner mouth 7 Treatment chamber 8, 8 Burner mount 9 Pipe section 10 Supply line (for hydrogen) 11 Supply line (for natural gas) 12 Supply line (for oxygen) 13 Supply line (for air) 14- 15, 15 Swirl device 16, 16 Air guide elements 17 Burner axis 18 Propulsion mechanism 19- 20 Burner 21 Burner unit 22 Outlet (of the burner unit)

Claims

1. Burner for combustion of a hydrogen-containing fuel, comprising a burner unit (4, 21) which is accommodated within a feed (5) for a secondary oxidant and comprises a fuel feed (2) connected to an inlet (10) for a hydrogen-containing fuel and a feed (3) for a primary oxidant, and comprising a swirl device (15, 15') disposed in the feed (5) for the secondary oxidant, characterized in that upstream of the fuel feed (2) of the burner unit (4, 21) is a mixing zone (9) into which there open the inlet (10) for hydrogen and at least one inlet (11) for a second gaseous fuel, and the swirl device (15, 15') and the burner unit (4, 21) are movable relative to one another, wherein the burner unit (4, 21) is accommodated within the feed (5) for the secondary oxidant so as to be movable axially with respect to the latter and with respect to the swirl device (15, 15') and / or the swirl device (15, 15') is accommodated within the feed (5) for the secondary oxidant so as to be movable axially with respect to the latter and to the burner unit (4, 21).

2. Burner according to Claim 1, characterized in that the fuel feed (2) and the feed (3) for the primary oxidant are arranged concentrically to one another in the burner unit (4, 21), and the latter is disposed concentrically within the feed (5) for the secondary oxidant.

3. Burner according to Claim 1 or 2, characterized in that the fuel feed (2) and the feed (3) for the primary oxidant open out flush with one another at a mouth of the burner unit (4, 21) that faces a treatment space (7).

4. Burner according to any of the preceding claims, characterized in that the burner unit (4, 21) has at least two fuel feeds (2) and / or at least two feeds (3) for the primary oxidant.

5. Method of combustion of a hydrogen-containing fuel with an oxygen-containing oxidant in a treatment space using a burner (1, 20) according to any of the preceding claims, characterized in that - hydrogen via the inlet (10) for hydrogen and optionally a second gaseous fuel via the inlet (11) for the second gaseous fuel are mixed in the mixing zone and introduced into a treatment space (7) via the fuel feed (2), - a primary oxidant is simultaneously introduced into the treatment space (7) via the feed (3) for the primary oxidant, and optionally a second oxidant via the feed (5) for the second oxidant, - the fuel and the oxidant(s) are mixed with one another and reacted in the treatment space (7), - depending on the chemical composition of the fuel introduced into the treatment space (7) and / or the ratio of primary and secondary oxidant fed to the treatment space (7), the flow profile of the secondary oxidant introduced into the treatment space (7), which is determined by the axial relative position of swirl device (15, 15') and burner unit (4, 21), is varied according to a defined program.

6. Method according to Claim 5, characterized in that the primary oxidant used is oxygen and the secondary oxidant used is air.

7. Method according to either of Claims 5 and 6, characterized in that the second gaseous fuel used is natural gas and / or a lean gas having low calorific value.

8. Method according to any of Claims 5 to 7, characterized in that 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 (7) according to a defined program and / or depending on measured parameters.

9. Method according to any of Claims 5 to 8, characterized in that there is flameless combustion in the treatment space (7).