Mixing device for gas heaters

Abstract

The invention relates to a gas heater mixing device for a gas heater, comprising a mixing element for mixing gas and a fuel gas, a gas line for supplying gas into a chamber of the mixing element, a fuel gas line for supplying fuel gas into the chamber, and a movable valve body, the valve body being displaceable between different positions to control the mixed gas flow that can flow through the outlet opening of the mixing element. The gas heater mixing device is characterized in that the valve body is formed such that the supply of fuel gas into the chamber by the fuel gas line depends on the position of the valve body in the chamber.

Description

Technical Field

[0001] The present invention relates to a mixing device for a gas heater. Furthermore, the present invention relates to a gas heater and a boiler provided with such a mixing device.

Background Art

[0002] A plurality of gas heaters are known from the prior art. A gas heater typically comprises a mixing device having a chamber in which gas, particularly air, is mixed with fuel gas. The mixed gas is supplied to the burner of the gas heater. Such a gas heater can be used, for example, in a boiler. A boiler comprises a heat exchanger in which water is heated by the gas heater.

[0003] In known gas heaters, there is a problem of flashback. This problem particularly exists when the fuel gas is hydrogen or has a high molar fraction of hydrogen. Flashback can lead to damage to other components of the gas heater, such as the fuel gas valve and the fan. Therefore, it is necessary to suppress flashback.

[0004] A generally known solution for a mixing apparatus is disclosed, for example, in European Patent Application Publication No. 2664849, which aims to provide a mixing apparatus relating to International Publication No. 2012 / 007823, teaching a mixing apparatus comprising a venturi nozzle having two air ducts, each having a gas supply section for guiding air in each case, and a closure unit with a flap, wherein the mixture is not concentrated in the transition region. The closure unit is formed such that the flap closes the latter air duct or the latter gas supply section in the closed position during operation at low air mass flow rates. The air velocity in the region of the latter gas supply section in the transition region between low air mass flow rates and high air mass flow rates is very low so that concentration of the combustion gas-air mixture does not occur. The flap is designed so that the fuel gas-air mixture is not concentrated in the transition region. The flap has an opening for this purpose, which allows air to flow through the opening when the flap is partially closed, which prevents high flow velocities from occurring in the region of the second gas supply section. However, the solution disclosed in European Patent Application Publication No. 2664849 does not protect against flashback because the air and gas supply sections are still open to allow flashback to pass through.

[0005] U.S. Patent Application Publication No. 2020284473 discloses a gas heater that uses hydrogen as a fuel gas to mitigate combustion-related problems and includes a valve to suppress flashback. The valve is located upstream of the burner and downstream of a mixer in which the fuel gas and air are mixed. The valve is movable and can be positioned in an open position in which the gas mixture flows into the burner. Furthermore, the valve can be positioned in a closed position when a flashback occurs. In the closed position of the valve, the valve fluidically isolates the burner from the rest of the gas heater and thus prevents the components from being damaged by the flashback.

[0006] "Design improvement of compressed natural gas (CNG)-Air mixer for diesel dual fuel engines using computational fluid dynamics," by Hassan Sadah Muhssen et al., Energy, Volume 216, February 1, 2021, 118957, tests the performance of existing secondary fuel premix controllers (SFPMCs) and commercially available mixers and aims to modify the design with respect to the air-to-fuel ratio (AFR) and CNG-air mixture homogeneity (CAMH) considering the operating speed of the internal combustion engine. The document discloses an SFPMC comprising an air inlet, a CNG inlet, a main controller body, a mixture outlet, a control valve, a spring, a plastic washer, and a CNG outlet hole in a hollow housing. Incoming air passes through the air inlet, presses the control valve against a spring force to open the air inlet, and presses the control valve against a spring force to open the air and CNG paths, while the mixer outlet discharges the CNG-air mixture into the engine manifold during operation. The main controller body includes a housing that supports the axial movement of the control valve and includes a CNG manifold with a CNG inlet, a CNG distribution chamber, and seven CNG outlet ports. The operating principle of the mixer is represented by the fixed CNG inlet pressure, and the amount of CNG entering the mixer is controlled by the surface design of the control valve shaft, which opens and closes the CNG path during the movement of the control valve. The control valve opens and closes the inner end of the CNG inlet according to the requirements of the engine speed and air-fuel ratio during operation. The movement of the control valve depends on the pressure of the air drawn in by the operating internal combustion engine and passing through the mixer.

[0007] U.S. Patent Application Publication No. 20110226218 relates to a controller for mixing combustible gases or gas mixtures, including natural gas (CNG), propane, butane, LPG, hydrogen, and octane, used as a secondary fuel mixture supplied to the intake manifold of an internal combustion engine used in vehicles such as generators, ships, cranes, airplanes, and helicopters, in order to reduce the fuel consumption of primary fuels, which may include octane, diesel, ethanol, and kerosene. The document discloses a secondary fuel controller having a hollow air inlet that screws into one end of a hollow main controller body and into an air / fuel mixture outlet. Inside the controller are a coaxially aligned pneumatic valve positioned close to the inlet end of the air inlet and a secondary fuel air / air blender positioned close to the outlet end of the air / fuel mixture outlet. The valve and air blender are held together by a coaxially aligned connector screw, thereby moving together as a unit within the secondary fuel manifold formed inside the main controller body. An airflow resistance spring is positioned between the pneumatic valve and the secondary fuel manifold to maintain this configuration in the closed position, with the air blender seated against the outlet port of the secondary fuel manifold. The secondary fuel manifold includes a laterally oriented secondary fuel inlet to which secondary fuel sources such as natural gas (NGV), liquefied petroleum (LPG), and hydrogen can be connected. Other fuel sources such as ethanol and biofuels are also conceivable within the scope of this invention. When connected to a secondary fuel source, pressurized fuel is available in the secondary fuel inlet, but flows only when the air blender is moved to the variable open position. The opening of the air blender is controlled by the inlet air flowing into the air inlet colliding with the convex outer surface of the pneumatic valve. The greater the airflow regulated by engine demand, the greater the opening of the air blender. The secondary or alternative fuel source, entering the controller through the secondary fuel inlet and then passing through the air blender, mixes with the inlet air in the outlet for discharge from the outlet in the form of a mixed or blended gas.Next, this mixed air / secondary fuel mixture flows into the intake manifold of the internal combustion engine for proper blending with primary fuel sources, which are supplied separately to the engine's intake manifold. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2012 / 007823 [Patent Document 2] European Patent Application Publication No. 2664849 [Patent Document 3] U.S. Patent Application Publication No. 2020284473 [Patent Document 4] U.S. Patent Application Publication No. 20110226218 [Non-patent literature]

[0009] [Non-Patent Document 1] Design improvement of compressed natural gas (CNG)-air mixer for diesel dual fuel engines using computational fluid dynamics, Hassan Sadah Muhssen et al., Energy, Volume 216, February 1, 2021, 118957. [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a gas heater mixer that is safe from flashback damage to its components, particularly when hydrogen is used as fuel, and that can achieve a compact structure for the gas heater mixer. [Means for solving the problem]

[0011] This objective is solved by a gas heater mixing device comprising a mixing element for mixing a gas and a fuel gas, a gas line for supplying gas into a chamber of the mixing element, a fuel gas line for supplying fuel gas into the chamber, and a movable valve body, wherein the valve body is configurable between different positions to control the mixed gas flow that can flow through the outlet opening of the mixing element, and the valve body is formed such that the supply of fuel gas into the chamber by the fuel gas line depends on the position of the valve body in the chamber.

[0012] The gas heater mixing device of the present invention has the advantage of a compact structure because, since the valve body is located within the chamber of the mixing element, it requires less space compared to gas heater mixing devices of known gas heaters. Furthermore, it can prevent damage to the components of the gas heater mixing device due to flashback.

[0013] The mixed gas is the output gas exiting the gas heater mixer. The mixed gas may include gas and fuel gas. Alternatively, the mixed gas may consist only of gas if fuel gas is not introduced into the chamber.

[0014] The outlet opening of the mixing element is the opening through which the mixed gas flows to be supplied to the burner. The outlet opening can be located at one end of the mixing device. The inlet opening of the mixing device is the opening through which gas supplied, for example by a fan, flows into the chamber of the mixing element. The inlet opening can be located at the other end of the mixing device. Both openings can be located in their respective planes extending perpendicular to the length axis of the mixing element.

[0015] The fuel gas can be natural gas, methane, ethylene, propane, butane, coal gas, biogas, mixtures thereof, and hydrogen or mixtures thereof further containing hydrogen, especially pure hydrogen. The fuel gas may contain more than 20 mol% hydrogen. Pure hydrogen is present if the fuel gas contains at least 98 mol% hydrogen. The gas can be air.

[0016] If the gas is air, the gas source corresponds to the surrounding air drawn in by the fan. The fuel gas can be stored in a fuel gas tank, fuel gas line, or fuel gas grid, or it can be generated in situ by an electrolytic cell or the like.

[0017] In the following, the terms "downstream" and "upstream" refer to the direction of gas flow from the fan of the gas heater to the burner, or the direction of fuel gas flow from the fuel gas valve to the burner. The burner may be a premixed burner. Premixing means that a mixture of fuel gases is supplied to the burner.

[0018] According to embodiments of the present invention, the valve body can close the fuel gas line when the valve is positioned in a first position, thereby preventing fuel gas from being supplied into the chamber. In particular, the valve body can close the fuel gas line so that when the valve is positioned in a first position, gas cannot flow through the outlet opening at all or can flow only in a limited manner. The valve position has the advantage of increasing the safety of the gas heater. In particular, when the valve body is positioned in a first position, flashback travel to the fuel gas valve is prevented.

[0019] When the valve body is not in the first position, fuel gas can be supplied into the chamber. In particular, the amount of fuel gas that can be supplied into the chamber depends on the valve body position. Therefore, by controlling the valve position, the amount of fuel gas supplied into the chamber can be easily controlled. Thus, the composition of the mixed gas can be easily controlled.

[0020] The fuel gas line can guide the movement of the valve body from the first position to the second position or vice versa. In particular, the valve shaft can be inserted into the cavity of the fuel gas line. Thus, at least a part of the valve shaft is surrounded by the fuel gas line in the circumferential direction of the valve shaft. In such an embodiment, the outer diameter of the valve shaft is smaller than the outer diameter of the fuel gas line. In particular, the outer diameter of the valve shaft is slightly smaller than the inner diameter of the fuel gas line so that the valve shaft can move relative to the fuel gas line. The length of the protrusion of the valve shaft into the cavity of the fuel gas line depends on the position of the valve body in the chamber.

[0021] Alternatively, the movable valve shaft can surround the fuel gas line in the circumferential direction of the valve shaft. In such an embodiment, the valve shaft is hollow to receive at least a part of the fuel gas line. Thus, the valve shaft surrounds at least a part of the fuel gas line, particularly the entire fuel gas line, in the circumferential direction.

[0022] In both embodiments, the valley shaft can move relative to the fuel gas line, and the fuel gas line guides the movement of the valve shaft and thus the valve body. In particular, the valve body can move in a linear direction. Thus, the valve body can move along the longitudinal axis of the mixing element. The valve shaft can have a circular cross-section. Alternatively, the valve shaft can have a different cross-section, particularly a square cross-section.

[0023] The valve shaft can extend in the longitudinal direction of the mixing element from the valve head of the valve body. The valve head can have a diameter larger than the movable valve shaft. Thus, since the guide is provided by the fuel gas line already present for supplying fuel gas into the chamber, there is no need to provide a separate guide for the valve. Thus, a simple structure of the gas heater is achieved.

[0024] The fuel gas line may have at least one fuel gas opening, particularly several fuel gas openings, such as holes or slots, through which fuel gas can be supplied into the chamber. Providing several fuel gas openings has the advantage that the amount of fuel gas supplied into the chamber can be easily controlled by the position of the movable valve shaft. The fuel gas openings are arranged at a distance from each other, particularly along the longitudinal axis of the mixing element. Thus, the supply of fuel gas can be ensured through the axial portion of the mixing element so that the mixing of fuel gas and air in the chamber of the mixing element is improved.

[0025] Each of the fuel gas openings can be positioned so that fuel gas can be supplied into the chamber in a direction laterally to the longitudinal axis of the mixing element. In particular, at least one fuel gas opening can be positioned so that fuel gas can be supplied into the chamber along a direction perpendicular to the longitudinal axis of the mixing element. Such a fuel gas supply unit has the advantage that the mixing of the fuel gas and the gas is increased within the chamber of the mixing element. In an alternative embodiment, the fuel gas can be supplied into the chamber along a direction having an angle different from 90° with respect to the longitudinal axis of the mixing element. It is also possible for the fuel gas to be supplied along the tangential direction of the mixing element.

[0026] The fuel gas line can be configured such that the fuel gas is directed radially outward as it exits the fuel gas opening. Radially outward is understood to mean a direction away from the longitudinal axis of the mixing element, which can be the central axis of the mixing element. Therefore, the fuel gas is not supplied to the chamber from the walls of the mixing element. In this case, the fuel gas is directed radially inward, i.e., toward the longitudinal axis of the mixing element. At least one fuel gas opening is positioned such that the direction of movement of the valve body is different from the direction of the fuel gas as it exits the fuel gas opening. Such a fuel gas line has the advantage that the fuel gas can be mixed very well with the gas flowing in the chamber.

[0027] A movable valve body, particularly the valve stem, closes the fuel opening or all fuel openings when the valve body is positioned in a first position. In the first position, the valve stem covers all fuel gas openings so that fuel gas cannot flow into the chamber. Thus, it is ensured in a compact and safe manner that no fuel gas is supplied into the chamber when the valve body is positioned in the first position.

[0028] The movable valve body does not close at least one fuel gas opening when positioned in the second position. In particular, in the second position, the valve stem does not close any fuel opening. The valve body can be coupled to a fuel gas line such that the number of fuel openings not closed by the valve stem increases as the valve body moves away from the first position and / or toward the second position. Thus, it is ensured that fuel gas is supplied into the chamber of the mixing element in the second position and / or intermediate positions between the first and second positions of the valve.

[0029] The valve body is movable to multiple positions. These positions have different flow areas through which the gas mixture can flow. In the first position of the valve, the valve, particularly the valve head, is in contact with the wall of the mixing element, thus preventing the gas mixture from flowing through the outlet opening of the mixing element. Alternatively, the first position of the valve body is set to allow a predetermined gap, also known as a quenching gap, which can remain between the valve head and the wall of the mixing element. Thus, even with the valve body in the first position, a limited gas mixture flow can be generated. The gap is designed to ensure that flames are extinguished and therefore functions as a flame suppressor to improve the safety of systems operated by flammable gases or liquids. The quenching gap is defined based on room temperature from 80°C to 90°C and can range from 0.5 mm to 2.5 mm, particularly from 0.5 mm to 1.5 mm. For hydrogen applications, the quenching gap is preferably less than 0.65 mm.

[0030] When the valve is in the open position or moved away from the first position, the flow area corresponds to the area between the walls of the mixing element and the valve, particularly the valve head. In the second position of the valve body, the flow area between the walls of the mixing element and the valve is greater than the flow area when the valve body is in the first position. The mixed gas flow increases as the distance between the valve body and the mixing element increases. The maximum mixed gas flow is achieved when the valve body is in the maximum open position. In this position, the valve stem does not cover any fuel gas openings in the fuel gas line.

[0031] According to embodiments of the present invention, the fuel gas line may comprise fuel gas line portions arranged coaxially, parallel to, or tangentially with respect to the longitudinal axis of the mixing element, or at angles from 90° to 0° with respect to the longitudinal axis of the mixing element. Alternatively, the fuel gas line may have different orientations with respect to the longitudinal axis of the mixing element. The fuel gas line portion may comprise at least one fuel gas opening, which may be, for example, a hole or a slot. In particular, the fuel gas line portion may comprise fuel gas openings arranged opposite each other, especially in the diametrical direction. The fuel gas line portion has the advantage of being able to supply fuel gas to the central region of the chamber, thereby improving the mixing of the fuel gas and the gas. In particular, the fuel gas line portion may be arranged to surround the chamber. The fuel gas line portion may surround the mixing element in a tangential direction with respect to the longitudinal axis. The longitudinal axis of the fuel gas line portion is parallel to or coaxial with the longitudinal axis of the mixing element. As described above, the longitudinal axis of the mixing element may be the central axis of the mixing element.

[0032] The chamber may have a shape symmetrical with respect to the longitudinal axis. Alternatively, the chamber may have an asymmetrical shape, particularly asymmetrical with respect to the longitudinal axis. The chamber may have the form of a venturi nozzle. The fuel gas line may be arranged so that the fuel gas can be supplied to a region of the mixing element having the smallest flow cross-sectional area. This may be a nozzle portion having a constant cross-section along the axial extension of the venturi nozzle. Additionally or alternatively, the fuel gas may be supplied to a region of the mixing element having a smaller flow cross-sectional area than parts of the mixing element downstream and / or upstream of that region. The supply of fuel gas to the region of the mixing element has the advantage that the gas velocity is higher in that region than in other regions of the mixing element. This improves the mixing of the fuel gas and the gas. Furthermore, the venturi nozzle allows the gas heater to be equipped with a pneumatic fuel gas valve instead of an electronic or electronic gas valve.

[0033] In an advantageous embodiment of the present invention, a gas heater is provided. The gas heater has a burner located downstream of the mixing device and fluidly connected to the mixing device.

[0034] The valve can be positioned in a first position when flashback or other undesirable flue gases flow from the combustion chamber toward the fan. In the above situation, the pressure upstream of the valve body, i.e., on the burner side, is higher than the pressure downstream of the valve body, i.e., on the fan side.

[0035] Alternatively, if the pressure at the other end of the mixing device facing outward from the burner is higher than the pressure at the end of the mixing device facing the burner, the valve may be in the second position or move from the first position to the second position.

[0036] In this embodiment, the gas heater is configured to use a gaseous fuel containing 10 mol% to 100 mol%, particularly 50 mol% to 100 mol%, preferably 95 mol% to 100 mol%, and more preferably 95 mol% to 98 mol% of hydrogen. The gas heater according to the present invention is not limited to the use of a gaseous fuel containing hydrogen. Any type of fuel gas, such as natural gas, methane, ethylene, propane, butane, coal gas, biogas, and mixtures thereof, and hydrogen or mixtures thereof further containing hydrogen, particularly pure (at least 98 mol%) hydrogen, can be used as fuel. In this embodiment, the gaseous fuel also contains hydrogen, preferably 95 mol% or more. However, any combination of hydrogen and, for example, natural gas can be used.

[0037] The gas heater may be equipped with a fan for supplying gas to the mixing device. The position of the valve in the chamber, in particular the valve position, can be controlled by the fan of the gas heater. In particular, the valve position depends on the fan output. This is possible because the pressure applied to the valve depends on the fan output. When it is detected that the valve body is in a first position, the fuel gas valve can be closed and / or the fan can be stopped. The position of the valve body can be detected by changes in the mixed gas flow and / or the fan speed.

[0038] Furthermore, the gas heater includes a fuel gas valve for controlling the fuel gas supplied into the chamber of the mixing device. The fuel gas valve can be electronic or an electronic gas valve, particularly when the chamber of the mixing element does not have a venturi nozzle configuration. Alternatively, the fuel gas valve can be a pneumatic gas valve, in which case steering pressure is required to open the fuel gas valve.

[0039] In a particular advantageous embodiment of the present invention, a gas boiler for heating water is provided. The gas boiler comprises a gas heater of the present invention and a heat exchanger having a combustion chamber, wherein the burner of the gas heater is at least partially located within the combustion chamber.

[0040] The diagram schematically illustrates the subject matter of the present invention, and elements that are identical or function similarly are usually given the same reference numerals. (Brief explanation of the drawing) (Figure 1) This is a side cross-sectional view of a mixing device according to an embodiment of the present invention, in which the valve is located in a second position. (Figure 2) This is a side cross-section of a mixing device according to an embodiment of the present invention, in which the valve is located in a first position. (Figure 3) This is a schematic diagram of a gas boiler equipped with the mixing device shown in Figures 1 and 2.

[0041] (Modes for carrying out the invention) The mixing device 1 shown in Figure 1 comprises a mixing element 3 for mixing fuel gas and other gases. Furthermore, the mixing device 1 comprises a gas line 4 for supplying gas into the chamber 6 of the mixing element 3. The gas can be ambient air. The mixing device 1 also comprises a fuel gas line 5 for supplying fuel gas into the chamber 6 of the mixing element 3 and a movable valve body 7. The valve body 7 is located in the chamber 6 and can be moved between different positions to control the flow of the mixed gas that can flow through the outlet opening 17 of the mixing element 3. Figure 1 shows the state of the valve body 7 when it is positioned in a second position. In this position, the mixed gas can flow through the outlet opening 17 of the mixing element 3. As will be described in more detail below, the supply of fuel gas to the chamber 6 of the mixing element 3 via the fuel gas line 5 depends on the position of the valve 7.

[0042] The movable valve body 7 comprises a valve head 25 and a valve stem 8 extending in a certain direction from the valve head 25. In particular, the valve stem 8 extends from the valve head 25 so as to be coaxial with the length axis M of the mixing element 3.

[0043] At the position shown in Figure 1, the valve body 7 is not in contact with the wall 21 of the mixing element 3. Therefore, a flow region 22 exists between the valve body 7 and the wall 21 in the axial direction of the mixing element 3, allowing the mixed gas to flow through the flow region 22 toward the outlet 17. The wall 21 defines at least a portion of the chamber 6 along the longitudinal axis M of the mixing element 3. The outer cross-section of the valve body 7 is smaller than the inner cross-section of the chamber 6. This ensures that the mixed gas can flow radially toward the outlet opening 17 between the valve body 7 and the wall 21 of the mixing element 3.

[0044] The mixing element 3 has an inlet opening 23 through which the gas enters the chamber 6. The gas is supplied by a fan 14 shown in Figure 3. Downstream of the inlet opening 23, a portion of the chamber 6 is formed as a venturi nozzle 24 in this embodiment. In an alternative embodiment not shown, the chamber does not have a venturi nozzle. The chamber 6 has a portion with a tapered section and a portion with a constant cross-section and a widened section.

[0045] The fuel gas pipe 5 includes a fuel gas line portion 11 that extends coaxially with the length axis of the mixing element 3. The fuel gas line portion 11 includes a plurality of fuel openings 10 that are spaced apart from each other along the length axis M of the mixing element 3. Furthermore, the openings 10 are positioned on opposing portions of the fuel gas line portion 11 with respect to the length axis M of the mixing element 3.

[0046] The valve stem 8 is positioned within the cavity 9 of the fuel gas line 5. The valve portion 8 protrudes into the cavity 9 to a different degree depending on the position of the valve body 7. In the partially open position of the valve shown in Figure 1, the valve stem 8 enters the hole 10 such that only a portion of it is covered. In the open position of the valve body 7 (not shown), the valve stem 8 does not cover the hole 10.

[0047] The fuel gas exits the fuel gas line through the hole 10. The hole 10 and / or portion of the fuel gas line are positioned such that the direction of fuel gas flow when exiting the hole 10 is perpendicular to the direction of gas flow. After exiting the hole 10, the fuel gas is mixed with the gas in the venturi nozzle 24 portion of the chamber 6. The mixed gas exits the mixing device 1 through the outlet opening 17.

[0048] Figure 1 shows a state in which no flashback occurs in the burner 13 shown in Figure 3. This means that the pressure applied to the valve body 7 from downstream, i.e., the fan side, is higher than the pressure applied to the valve body 7 from upstream, i.e., the burner side. The pressure is mainly supplied by the gas mixture indicated by the arrows in Figure 1.

[0049] Figure 2 shows a side cross-section of a mixing device 1 according to an embodiment of the present invention, with the valve body 7 positioned in a first position. In this position, the valve body 7, particularly the valve head 25, is in contact with the wall 21 of the mixing element 3. Therefore, there is no flow region between the valve 7 and the wall 21 through which the mixed gas can flow. In embodiments not shown, the valve body 7 is in close contact with the widening section when the valve body 7 is in the first position and moves toward the outlet opening 17 when the valve body 7 is moved to a second position. Close contact means that, in the close contact position, a predetermined gap, also known as a quenching gap, remains. This gap is designed to ensure that flames are extinguished and therefore functions as a flame suppressor to improve the safety of systems operated by flammable gases or liquids. The quenching gap is defined based on room temperature from 80°C to 90°C and can range from 0.5 mm to 2.5 mm, particularly from 0.5 mm to 1.5 mm. For hydrogen applications, the quenching gap is preferably less than 0.65 mm.

[0050] As is clear from Figure 2, the movable valve shaft 8 protrudes into the cavity 9 of the fuel gas line 5 so as to cover all of the fuel gas openings 10 of the gas line 5 when the valve body 7 is in the first position. Therefore, in the first position, no fuel gas can be supplied to the chamber 6 through the fuel gas line 5, or very little.

[0051] Figure 2 shows, as an example, a condition in which flashback occurs in the burner 13 shown in Figure 3. This means that the pressure applied to the valve body 7 from the burner side is higher than the pressure applied to the valve body 7 from the fan side. Therefore, the valve body 7 is pressed against the wall 21 by the applied pressure. The direction of the pressure resulting from the flashback is indicated by the arrow in Figure 2.

[0052] Figure 3 is a schematic diagram of a boiler 18 equipped with a gas heater 2 having a mixing device 1 as shown in Figures 1 and 2. The fan 14 of the gas heater 2 is located upstream of the mixing device 1 and draws in outside air. The drawn-in air flows into the mixing chamber 6 through the gas line 4 and the inlet opening 23. In the absence of flashback, the gas mixes with the fuel gas supplied by the fuel gas line 5 in the mixing chamber 6 and exits the mixing device 1 through the outlet opening 17.

[0053] The gas heater 2 includes a fuel gas valve 15 that controls the amount of fuel gas supplied into the chamber 6 of the mixing element 3. Furthermore, the gas heater 2 includes a burner 13 located downstream of the mixing device 1. Thus, the mixed gas flowing out of the mixing device 1 is supplied to the burner 13. The burner 13 is partially located within the combustion chamber 20 of the boiler 18. The flue exits the combustion chamber 20 through an opening (not shown).

[0054] The boiler 18 includes a heat exchanger 19 used to heat a liquid, particularly water, with heat supplied by the burner 13. [Explanation of symbols]

[0055] 1. Gas heater mixing device 2. Gas heater 3 Mixed elements 4 Gas lines 5. Fuel gas line 6 Chambers 7 Valve body 8 Valve stem 9 Cavity 10 holes 11 Fuel gas line section 13 burners 14 Fans 15 Fuel gas valve 17 Mixing element outlet opening 18 Boiler 19 Heat exchanger 20 Combustion Chamber 21 Wall 22 Flow region 23 Inlet opening 24 Venturi nozzles 25 valve head M length axis

Claims

1. A gas heater mixing device (1) comprising a mixing element (3) for mixing gas and fuel gas, a gas line (4) for supplying gas into a chamber (6) of the mixing element (3), a fuel gas line (5) for supplying fuel gas into the chamber (6), and a movable valve body (7), wherein the valve body (7) is configurable between different positions to control the mixed gas flow that can flow through the outlet opening (17) of the mixing element (3), and the supply of the fuel gas into the chamber (6) by the fuel gas line (5) depends on the position of the valve body (7) in the chamber (6), A gas heater mixing device (1) is characterized in that a 7) is formed, the fuel gas line (5) has a plurality of fuel gas openings (10) into which fuel gas can be supplied into the chamber (6), and the valve body (7) is coupled to the fuel gas line (5) such that when the valve body (7) is positioned in a first position, it closes all fuel gas openings (10), when the valve body (7) is positioned in a second position, it does not close at least one fuel gas opening (10), and as the valve body (7) moves toward the second position, the number of unclosed fuel gas openings (10) increases.

2. a. When the valve body (7) is positioned in the first position, the valve body (7) closes the fuel gas line (5) and / or b. When the valve body (7) is not positioned in the first position, fuel gas can be supplied into the chamber (6), and / or c. The amount of fuel gas that can be supplied into the chamber (6) depends on the position of the valve body (7) within the chamber (6). The gas heater mixing apparatus (1) according to feature 1.

3. The gas heater mixing device (1) according to claim 1 or 2, characterized in that the fuel gas line (5) guides the movement of the valve body (7) from the first position to the second position, or vice versa.

4. The valve body (7) is equipped with a valve stem (8), and the valve stem is a, inserted into the cavity (9) of the fuel gas line (5), and / or b. Having an outer diameter smaller than the outer diameter of the fuel gas line (5), and / or c. At least partially surrounded by the fuel gas line (5), and / or d. Extending from the head portion of the valve body (7) in the longitudinal direction (M) of the mixing element (3), and / or e. The gas heater mixing apparatus (1) according to any one of claims 1 to 3, characterized in that the length of the protrusion of the valve stem (8) into the cavity (9) of the fuel gas line (5) depends on the position of the valve body (7) in the chamber (7).

5. a. The fuel gas opening (10) is positioned such that fuel gas can be supplied into the chamber (6) which spans the longitudinal axis (M) of the mixing element (3), and / or b. The fuel gas openings (10) are arranged at a distance from each other, particularly along the longitudinal axis (M) of the mixing element (3), and / or c. The fuel gas line (5) is configured such that the fuel gas is directed radially outward when it exits the fuel gas opening (10), and / or d. The at least one fuel gas opening (10) is positioned such that the direction of movement of the valve body (7) is different from the direction of the fuel gas when it exits the fuel gas opening (10). A gas heater mixing apparatus (1) according to any one of claims 1 to 4.

6. The valve body (7) moves in a linear direction. A gas heater mixing apparatus (1) according to any one of claims 1 to 5.

7. The fuel gas line section (11) a. Arranged coaxially, tangentially, parallel to, or at an angle between 90° and 0° with respect to the longitudinal axis (M) of the mixed element (3), and / or b. comprising at least one fuel gas opening (10), and / or, c. The gas heater mixing apparatus (1) according to any one of claims 1 to 6, characterized in that it is surrounded by the chamber (6).

8. The gas heater mixing apparatus (1) according to any one of claims 1 to 7, characterized in that the chamber (6) has the form of a venturi nozzle.

9. The aforementioned fuel gas line (5) a. The fuel gas can be supplied to the region of the mixing element (3) having the smallest flow cross-sectional area, and / or b. The gas heater mixer (1) according to any one of claims 1 to 8, characterized in that it is arranged so that fuel gas can be supplied to the region of the mixing element (3) having a smaller flow cross-sectional area than a portion of the mixing element (3) downstream and / or upstream of the region.

10. A gas heater (2) comprising a gas heater mixing device (1) according to any one of claims 1 to 9, and a burner (13) disposed downstream of the mixing device (1) and fluidly connected to the mixing device (1).

11. The gas heater (2) according to claim 10, characterized in that the valve body (7) is positioned at the first position when the pressure at the end of the mixing device (1) facing the burner (13) is higher than the pressure at the other end of the mixing device (1) facing outward from the burner (13).

12. The gas heater (2) according to claim 10 or 11, characterized in that the gas heater (2) is configured to use a fuel gas containing at least 10 mol%, and particularly at least 95 mol%, of hydrogen.

13. a. The gas heater (2) is equipped with a fan (14) for supplying the gas to the gas heater mixing device (1), and / or b. The gas heater (2) is equipped with a fuel gas valve (15) for controlling the fuel gas supplied to the gas heater mixing device (1). A gas heater (2) according to any one of claims 10 to 12, characterized in that it is the gas heater (2) described in any one of claims 10 to 12.

14. A boiler (18) for heating a liquid, comprising a gas heater (2) according to any one of claims 10 to 13, and a heat exchanger (19) having a combustion chamber (20), wherein the burner (13) of the gas heater (2) is at least partially located within the combustion chamber (20).

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