Hydrogen burners and methods for operating such a hydrogen burner

Abstract

Hydrogen burner (1) comprising a front plate (2) and a combustion chamber (3) adjoining the front plate (2), wherein the front plate (2) has at least one first inlet opening (4) for supplying hydrogen and at least one second inlet opening (5) for supplying oxygen into the combustion chamber (3), and wherein the front plate (2) has a cooling system with at least one cooling channel (6) through which water can flow and which has a cooling water inlet (8) at a first end (7) and a cooling water outlet (10) at a second end (9). and wherein at least one third inlet opening (11) for supplying water to the combustion chamber (3) is provided in the end plate (2) and the third inlet opening (11) is connected to the at least one cooling channel (6) of the cooling system, wherein a valve (12) is arranged within the third inlet opening (11), characterized in that the valve (12) is pressure actuated and can be controlled by the pressure in the combustion chamber (3).

Description

[0001] The invention relates to a hydrogen burner according to the preamble of independent patent claim 1 and to a method for operating such a hydrogen burner according to the preamble of independent patent claim 5.

[0002] Hydrogen is playing an increasingly important role in energy storage and energy conversion into electricity, especially in renewable energies where the timing of energy supply, for example from wind or solar power, does not always coincide with the time of energy demand. The energy provided by renewables can be used to split water into hydrogen and oxygen using electrolysis and then temporarily store it until electricity and / or heat are needed.

[0003] If energy is needed, the hydrogen can be reacted with the oxygen in a hydrogen burner through controlled oxidation. Such a hydrogen burner is known, for example, from DE 29 33 932 A1. The hydrogen burner is designed so that hydrogen and oxygen can be injected through a front plate with at least two openings into a combustion chamber arranged downstream in the direction of flow and brought into contact within the combustion chamber. Oxidation releases a high level of thermal energy, which can be used to drive an expansion machine (turbomachine, piston engine), which in turn generates electrical power via a generator.

[0004] During hydrogen oxidation, the flame is applied directly to the faceplate and does not lift off, unlike, for example, a natural gas burner. For this reason, the faceplate is subject to particularly high thermal stress and requires continuous cooling. Before starting the hydrogen burner, the cooling system must first be activated and checked for proper functioning; otherwise, there is a risk of total burner failure.

[0005] To cool the front plate, DE 29 33 932 A1 provides a cooling channel in the front plate, which is connected to a cooling water inlet and a cooling water outlet and through which cooling water can be passed. Holes lead from the cooling channel into the combustion chamber, through which water enters the combustion chamber.

[0006] The problem with this type of cooling is that the cooling water either leaves the unignited hydrogen burner toward the turbine, collects there, and causes damage to the turbine, or remains in the hydrogen burner and causes damage through sudden evaporation upon ignition. Both scenarios must therefore be avoided at all costs.

[0007] DE 197 00 994 A1 discloses a control unit that ensures continuous steam turbine operation through continuous measurement of the steam quality and immediate evaluation, as well as the associated valve control. The amount of water added is regulated by a water inlet valve, which is opened by a control unit when a specified pressure is reached in the combustion chamber.

[0008] The object of the invention is to eliminate the problems known from the prior art and to provide a hydrogen burner and a method for operating such a hydrogen burner in which reliable cooling of the front plate of the hydrogen burner is guaranteed.

[0009] The problem is solved with regard to the burner by the features of independent patent claim 1. With regard to the method, the problem is solved by the features of independent patent claim 5.

[0010] The hydrogen burner according to the invention, comprising an end plate and a combustion chamber adjoining the end plate, wherein at least one first inlet opening for supplying hydrogen and at least one second inlet opening for supplying oxygen into the combustion chamber is provided in the end plate, and wherein the end plate has a cooling system with at least one cooling channel through which water can flow and which has a cooling water inlet at a first end and a cooling water outlet at a second end, and wherein at least one third inlet opening for supplying water into the combustion chamber is provided in the end plate and the third inlet opening is connected to the at least one cooling channel of the cooling system, is characterized in that a valve is arranged within the third inlet opening.

[0011] The valve prevents uncontrolled water from entering the combustion chamber via the cooling channel and, if applicable, a turbine connected to the combustion chamber. The valve essentially allows the burner to operate in two different modes: 1. The valve is closed, allowing water to enter the cooling channel exclusively through the cooling water inlet and exit through the cooling channel outlet. This operating mode can be described as "closed operation." The water only performs the cooling function of the front plate. 2. The valve is fully open, allowing water to enter the cooling channel via the cooling water inlet and flow completely into the combustion chamber via the nozzle and the third inlet opening. This operating mode can be referred to as "open operation." The water initially continues to cool the front plate before entering the combustion chamber. To achieve this, the cooling channel must be designed accordingly, for example, with a spiral or meandering shape within the front plate, ensuring complete cooling of the front plate before the water enters the combustion chamber.

[0012] In addition to these two operating modes, there is a transition region in which the valve is partially opened so that part of the water can enter the cooling channel via the cooling water inlet and exit via the cooling channel outlet and part of the water enters the combustion chamber via the valve.

[0013] In operating modes where the valve is partially or fully open, the water can fulfill a conditioning function for the combustion steam in addition to cooling the front plate.

[0014] Combustion steam is the steam that is formed during the oxidation of hydrogen with oxygen. By adding water via the third inlet opening, the temperature of the combustion steam produced by the oxidation of hydrogen with oxygen is significantly reduced, so that the steam emerging from the hydrogen burner is suitable for expansion in other turbomachines, for example a steam turbine. By adding water, which is characterized by a significantly lower temperature than the combustion steam, not only does the temperature of the steam formed from the combustion steam and the water drop, but the pressure of the escaping steam also increases considerably. This steam can advantageously be expanded in a steam turbine. In contrast to expansion in a gas turbine, the expansion of steam in a steam turbine allows expansion to condensation conditions, i.e.down to the negative pressure range, which allows significantly higher efficiencies to be achieved.

[0015] One embodiment of the invention provides for the valve to be pressure-actuated and controllable by the pressure in the combustion chamber. This eliminates the need for complex, expensive, and error-prone control technology. Since very high thermal loads exist in the area of ​​the front plate, the use of nozzles actuated by electromagnetic or piezo actuators, for example, is very problematic.

[0016] If the valve is designed as a spring-loaded valve, the opening pressure can be easily adjusted using a suitable spring characteristic.

[0017] A further embodiment of the invention provides that the valve is designed and arranged in such a way that it closes the third inlet opening while relieving pressure. This ensures that water only enters the combustion chamber at a specific opening pressure specified by the valve.

[0018] A further embodiment of the invention provides that the hydrogen burner includes a pilot nozzle for igniting the burner. The pilot nozzle enables gentle start-up of the hydrogen burner. For this purpose, the burner is ignited at the pilot nozzle, for example, at atmospheric pressure, and the pressure is subsequently increased with a certain transient. Before, during, and for an initial period after the pilot nozzle is ignited, the front plate is operated in closed mode. As soon as the pilot nozzle is burning stably, the burner switches to open mode as quickly as possible.

[0019] The method according to the invention for operating the hydrogen burner described in more detail above is characterized by the following process steps: - Supplying water via the cooling water inlet into the cooling channel and discharging the water via the cooling water outlet; - Ignition of the hydrogen burner; - Subsequent increase in the pressure at which combustion takes place; - Automatic opening of the valve when a set pressure is reached in the combustion chamber due to the pressure inside the combustion chamber; - Injecting water from the cooling channel through the third inlet opening into the combustion chamber.

[0020] The method according to the invention ensures that, before the burner is started, the burner is cooled by water flowing through the cooling channel, thus preventing heat-related damage to the burner. At the same time, it is ensured that the water from the cooling channel is only injected into the combustion chamber when the burner is burning stably, which can be determined by the rising pressure in the combustion chamber without additional measuring technology. The pressure in the combustion chamber then causes the valve located within the third inlet opening to open automatically, allowing water to enter the combustion chamber via the third inlet opening and be available to condition the steam.

[0021] Depending on the valve position, the burner is operated in “closed mode”, “open mode” or in partial load mode, in which only part of the water is injected into the combustion chamber to condition the steam and the remaining part of the water flows out via the cooling water outlet.

[0022] One embodiment of the method according to the invention provides for the ignition of the hydrogen burner with the aid of the pilot ignition chamber. The pilot ignition chamber comprises a pilot nozzle and enables a more gentle start-up of the hydrogen burner. The combustion process is initially started in the pilot ignition chamber. At the same time, hydrogen and oxygen are fed into the combustion chamber at a throttled rate. The hot combustion gases entering the combustion chamber from the pilot ignition chamber then ignite the hydrogen / oxygen mixture in the combustion chamber. However, this does not result in a sudden, but rather a continuous pressure increase in the combustion chamber, thus avoiding damage to the combustion chamber and a downstream turbine. As soon as the flame in the combustion chamber is burning steadily, the gas supply can be increased to the nominal value.

[0023] Further embodiments of the invention are explained below with reference to the figures. They show: - Fig. 1: A schematic representation of a hydrogen burner according to the invention in plan view; - Fig. 2: A sectional view of the Fig. 1 hydrogen burner along the line AA; - Fig. 3 A detailed view of the valve located in the third inlet port.

[0024] The illustrations are not necessarily to scale, but serve only to illustrate the invention. Identical or functionally identical components are provided with the same reference numerals throughout the figures.

[0025] Fig. Figure 1 shows a schematic and highly simplified representation of a hydrogen burner 1 according to the invention in a plan view. The hydrogen burner comprises a front plate 2 to which a combustion chamber 3 (see Fig. 2). The combustion chamber further comprises a pilot ignition chamber 13, which enables a more gentle start-up of the hydrogen burner 1. The end plate 2 is round in the exemplary embodiment, but can also have any other shape, for example a square or rectangular shape. The end plate 2 has several burner units. Each burner unit comprises a first inlet opening 4 for supplying hydrogen and a second inlet opening 5 for supplying oxygen into the combustion chamber 3. Instead of a burner unit, the first and second inlet openings 4, 5 can also be incorporated separately in the end plate 2.

[0026] Since, as already described, the flame in a hydrogen burner 1 does not lift off from the end plate 2, high thermal loads act on the end plate 2. To ensure that the thermal loads do not lead to damage to the end plate 2, it must always be cooled. For this purpose, a cooling system is formed in the end plate 2. In the exemplary embodiment, the cooling system has a cooling channel 6 through which water can flow. For this purpose, the channel has a cooling water inlet 8 at a first end 7 and a cooling water outlet 10 at a second end 9, so that the water can flow into the end plate 2 at the coolant inlet 8 and leave it again at the coolant outlet 10. The cooling channel 6 must be arranged such that the entire end plate can be sufficiently cooled. In the exemplary embodiment, the cooling channel 6 is designed in a spiral shape, for example.Depending on the size and shape of the face plate and the thermal load, several cooling channels can also be provided.

[0027] The end plate 2 has a third inlet opening 11 through which water from the cooling channel 6 can be injected into the combustion chamber 3. A valve 12 is arranged in the third inlet opening 11, with the help of which the flow into the combustion chamber 3 can be regulated. This effectively prevents the problems that have previously occurred with hydrogen burners, namely that the cooling water either leaves the not yet ignited hydrogen burner in the direction of the turbine, collects there and causes damage to the turbine, or remains in the hydrogen burner and causes damage there upon ignition through sudden evaporation. The hydrogen burner according to the invention and the corresponding inventive method for operating such a hydrogen burner thus ensure increased operational reliability.

[0028] Fig. 2 shows a sectional view of the Fig. 1 along the line AA. In this view, the combustion chamber 3 adjoining the end plate 2 can be clearly seen, in which the oxygen is oxidized (combusted) with the hydrogen. For this purpose, hydrogen is introduced into the combustion chamber 3 through first inlet openings 4 and oxygen through second inlet openings 5. The flames that arise during combustion at the individual burner units 14 sit directly on the end plate 2, which subjects it to considerable thermal stress. The cooling of the end plate 2 by means of the cooling system integrated in the end plate 2, comprising the spirally arranged cooling channel 6 through which water can flow, ensures that the thermal load does not exceed a permissible value. This can effectively prevent damage to the hydrogen burner 1 and in particular to the end plate 2 due to thermal overload.The water from the cooling channel 6 can be injected into the combustion chamber 3 via the valve 12 through the third inlet opening and used there to condition the fuel gas produced during the combustion of hydrogen with oxygen. The exact structure and function of one embodiment of such a valve 12 is described in . Fig. 3 is explained in more detail.

[0029] The pilot ignition chamber 13 associated with combustion chamber 3 enables a more gentle start-up of the hydrogen burner 1. The combustion process is initially initiated in the pilot ignition chamber 13. At the same time, hydrogen and oxygen are fed into the combustion chamber at a reduced rate. The hot combustion gases entering the combustion chamber from the pilot ignition chamber then ignite the hydrogen / oxygen mixture in the combustion chamber. However, this does not result in a sudden, but rather a continuous pressure increase in the combustion chamber, thus avoiding damage to the combustion chamber and any downstream turbine.

[0030] Fig. 3 shows a detailed view of an exemplary embodiment, a valve 12 arranged in the third inlet opening 11. Its structure will be explained in more detail below. The valve 12 is designed as a pressure-actuated valve and comprises a valve housing 14 in which a valve needle 16 is arranged for axial movement within a valve bore 15 formed in the valve housing 14. The valve needle 16 has a valve tip 17 with which the valve needle 16, in the closed state, rests in a valve seat 18 formed in the valve housing 14 and closes the third inlet opening 11. On the side of the valve needle 16 opposite the valve tip 17, the valve needle 16 has a valve plate 19. A valve spring 20 is supported with a first end against the outside of the valve plate 19 and with a second end against an adjusting nut 21 screwed into the valve housing 14.By adjusting the adjusting nut 21, the spring preload and thus the necessary opening pressure of the valve 12 can be adjusted. The valve spring 20 presses the valve tip 17 against the valve seat 18. When pressure is relieved, the valve needle 16 lies in the valve seat 18 and closes the third inlet opening 11. A projection 22 in the valve housing 14 creates two pressure chambers between the valve housing 14 and the valve needle 16: a first pressure chamber 23 which is delimited in the axial direction by the valve plate 19 on one side and the projection 22 on the other side, and a second pressure chamber 24 which is delimited on one side by the projection 22 and on the other side, in the closed state, by the valve tip 17 and the valve seat 18.

[0031] The first pressure chamber is connected to the combustion chamber 3 via at least one pressure line 24. In the exemplary embodiment, two pressure lines 25 are provided. The second pressure chamber 24 is connected to the cooling channel 6, wherein the cooling water can flow from the cooling channel 6 into the second pressure chamber 24 via a supply line 26 and from the second pressure chamber 24 into the cooling channel 6 via a discharge line 27.

[0032] Below we describe the procedure for operating the hydrogen burner 1 in conjunction with the Fig.1 to 3. Before the hydrogen burner is started, i.e. before the hydrogen is introduced through the first inlet opening 4 and the oxygen through the second inlet opening 5 into the combustion chamber and brought about oxidation, the cooling system is started. For this purpose, water is introduced through the cooling water inlet 8 into the cooling channel 6 of the cooling system. The water flows through the cooling channel and leaves the cooling channel 6 via the cooling water outlet 10. At this point in time, the pressure in the combustion chamber corresponds approximately to atmospheric pressure; this pressure is not sufficient to open the valve 12 against the pressure of the valve spring 20 and to release the third inlet opening 11 so that the water from the cooling channel 6 can reach the combustion chamber 3. Instead, the water flows via the supply line 26 into the second pressure chamber 24 of the valve 12 and from there via the discharge line back into the cooling channel 6.

[0033] As soon as the cooling system is fully started and the cooling of the front plate 2 is ensured, the hydrogen burner 1 is started. The hydrogen burner 1 is started with the help of the pilot ignition chamber 13. For this purpose, hydrogen and oxygen are introduced into the pilot ignition chamber 13 via separate supply lines and oxidized. At the same time, hydrogen and oxygen are throttled through the first and second inlet openings 4, 5 into the combustion chamber 3. The hot combustion gases entering the combustion chamber 3 from the pilot ignition chamber 13 then ignite the hydrogen / oxygen mixture in the combustion chamber 3. However, this does not result in a sudden, but rather a continuous pressure increase in the combustion chamber 3, thus avoiding damage to the combustion chamber and a downstream turbine. Due to the pressure increase in the combustion chamber 3, the pressure within the first pressure chamber 23 increases and the valve 12 opens, i.e.the valve tip 17 lifts off the valve seat 18 and water can flow from the cooling channel 6 through the third inlet opening 11 into the combustion chamber 3 and perform conditioning tasks there. The valve 12 ensures that water can only flow from the cooling channel 6 into the combustion chamber 3 when the hydrogen burner 1 is running stably. This prevents the cooling water from leaving the hydrogen burner 1, which has not yet been ignited or is not yet running stably, in the direction of the combustion chamber 3 and a downstream turbine, collecting there and causing damage to the turbine, or the water from remaining in the hydrogen burner 1 and causing damage there upon ignition due to the sudden evaporation to be expected. The hydrogen burner 1 according to the invention and the method according to the invention for operating the hydrogen burner 1 thus contribute to increased operational reliability.

Claims

[1] Hydrogen burner (1), comprising a front plate (2) and a combustion chamber (3) adjoining the front plate (2), wherein at least one first inlet opening (4) for supplying hydrogen and at least one second inlet opening (5) for supplying oxygen into the combustion chamber (3) is provided in the front plate (2), and wherein the front plate (2) has a cooling system with at least one cooling channel (6) through which water can flow and which has a cooling water inlet (8) at a first end (7) and a cooling water outlet (10) at a second end (9) and wherein at least one third inlet opening (11) for supplying water into the combustion chamber (3) is provided in the front plate (2) and the third inlet opening (11) is connected to the at least one cooling channel (6) of the cooling system, wherein a valve (12) is arranged within the third inlet opening (11), characterized bythat the valve (12) is pressure-actuated and can be controlled by the pressure in the combustion chamber (3). [2] Hydrogen burner (1) according to claim 1, characterized by that the valve (12) is designed and arranged such that it relieves pressure and closes the third inlet opening (11). [3] Hydrogen burner (1) according to one of claims 1 or 2, characterized by that the hydrogen burner (1) comprises a pilot ignition chamber (13) for igniting the hydrogen burner (1). [4] Method for operating a hydrogen burner (1) according to one of claims 1 to 2, characterized by the following procedural steps: - supplying water via the cooling water inlet (8) into the cooling channel (6) and discharging the water via the cooling water outlet (10); - igniting the hydrogen burner (1); - Subsequent increase in the pressure at which combustion takes place; - Automatic opening of the valve (12) when a fixed pressure is reached in the combustion chamber (3) by the pressure inside the combustion chamber (3); - Injecting water from the cooling channel (6) through the third inlet opening (11) into the combustion chamber (3). [5] A method for operating a hydrogen burner (1) according to claim 4, wherein the hydrogen burner (1) comprises a pilot ignition chamber (13) for igniting the hydrogen burner (1), characterized by that the ignition of the hydrogen burner (1) takes place with the aid of the pilot ignition chamber (13).

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