MIXING DEVICE FOR A GAS HEATER

Abstract

The invention relates to a gas heater mixing device for a gas heater, comprising a mixing element for mixing gas and 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 moveable valve body, wherein the valve body is arrangeable between different positions for controlling the mixed gas flow that can flow through an 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 by means of the fuel gas line into the chamber depends on the position of the valve body in the chamber.

Claims

1.-15. (canceled)

16. A gas heater mixing device comprising: a mixing element for mixing gas and 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 moveable valve body, wherein the valve body is arrangeable between different positions for controlling the mixed gas flow that can flow through an outlet opening of the mixing element; wherein the valve body is formed such that the supply of fuel gas by means of the fuel gas line into the chamber depends on the position of the valve body in the chamber.

17. The gas heater mixing device according to claim 16, wherein: a. the valve body closes the fuel gas line when the valve body is arranged in a first position; and/or b. a fuel gas can be supplied into the chamber when the valve body is not arranged in the first position; and/or c. the fuel gas amount that can be supplied into the chamber is dependent on the valve body position in the chamber.

18. The gas heater mixing device according to claim 16, wherein the fuel gas line guides the movement of the valve body from a first position to a second position or vice versa.

19. The gas heater mixing device according to claim 16, wherein the valve body comprises a valve shaft that: a. is inserted within a cavity of the fuel gas line; and/or b. has an outer diameter that is smaller than an outer diameter of the fuel gas line; and/or c. is at least partly surrounded by the fuel gas line; and/or d. extends in a length direction of the mixing element from a head portion of the valve body; and/or e. a length of protrusion of the valve shaft into the cavity of the fuel gas line depends on a position of the valve body in the chamber.

20. The gas heater mixing device according to claim 16, wherein the fuel gas line comprises at least one fuel gas opening through which fuel gas can be supplied into the chamber.

21. The gas heater mixing device according to claim 20, wherein: a. the opening is arranged such that fuel gas can be supplied into the chamber transverse to a length axis of the mixing element; and/or b. fuel gas openings are arranged at a distance from each other along the length axis of the mixing element; and/or c. the fuel gas line is configured such that fuel gas is directed in a radial outward direction when it leaves the fuel gas opening; and/or d. the at least one fuel gas opening is arranged such that a movement direction of the valve body differs from a direction of fuel gas when it leaves the fuel gas opening.

22. The gas heater mixing device according to claim 20, wherein: a. the valve body closes the fuel gas opening or all fuel gas openings if the valve body is arranged in a first position; and/or b. the valve body does not close at least one fuel gas opening if it is arranged in a second position; and/or c. a number of fuel gas openings that are not closed by the valve body increases when the valve body moves towards the second position; and/or d. the valve body moves in a linear direction.

23. The gas heater mixing device according to claim 16, wherein a fuel gas line portion: a. is arranged coaxial, tangential, parallel or at an angle between 90? and 0? to a length axis of the mixing element; and/or b. comprises the at least one fuel gas opening; and/or c. is surrounded by the chamber.

24. The gas heater mixing device according to claim 16, wherein the chamber has a form of a venturi nozzle.

25. The gas heater mixing device according to claim 16, wherein the fuel gas line is arranged such that: a. fuel gas can be supplied in an area of the mixing element having the smallest flow cross section in the mixing element; and/or b. fuel gas can be supplied in an area of the mixing element having a smaller flow cross section than a part of the mixing element downstream and/or upstream of the area.

26. A gas heater comprising a gas heater mixing device according to claim 16 and a burner that is arranged downstream of the mixing device and that is fluidically connected with the mixing device.

27. The gas heater according to claim 26, wherein the valve body is arranged in the first position if a pressure at an end of the mixing device facing the burner is higher than a pressure at another end of the mixing device facing away from the burner.

28. The gas heater according to claim 26, wherein the gas heater is configured to use fuel gas which comprises at least 10 mol % hydrogen.

29. The gas heater according to claim 26, wherein: a. the gas heater comprises a fan for supplying the gas to the gas heater mixing device; and/or b. the gas heater comprises a fuel gas valve for controlling the fuel gas supplied into the gas heater mixing device.

30. A boiler for heating a liquid, wherein the boiler comprises a gas heater according to claim 26, and a heat exchanger with a combustion chamber, wherein the burner of the gas heater is at least partly arranged within the combustion chamber.

Description

[0040] FIG. 1 a side section view of a mixing device according to an embodiment of the invention, wherein a valve is arranged in a second position,

[0041] FIG. 2 a side section of the mixing device according to the embodiment of the invention, wherein the valve is arranged in a first position,

[0042] FIG. 3 a schematic view of a gas boiler comprising a mixing device as shown in FIGS. 1 and 2.

[0043] A mixing device 1 shown in FIG. 1 comprises a mixing element 3 for mixing fuel gas and gas. Additionally, the mixing device 1 comprises a gas line 4 for supplying gas into a chamber 6 of the mixing element 3. The gas can be ambient air. The mixing device 1 also comprises a fuel gas line for supplying fuel gas into the chamber 6 of the mixing element 3 and a moveable valve body 7. The valve body 7 is arranged within the chamber 6 and can be moved between different positions for controlling the mixed gas flow that can flow through an outlet opening 17 of the mixing element 3. FIG. 1 shows a state of the valve body 7 in which the valve body 7 is arranged in a second position. In said position mixed gas can flow through the outlet opening 17 of the mixing element 3. As is explained below in more detail, the supply of fuel gas by way of the fuel gas line 5 into the chamber 6 of the mixing element 3 depends on the position of the valve 7.

[0044] The moveable valve body 7 comprises a valve head 25 and a valve shaft 8 extending from the valve head 25 in a direction. In particular, the valve shaft 8 extends from the valve head 25 such that it is arranged coaxial to a length axis M of the mixing element 3.

[0045] In a position shown in FIG. 1, the valve body 7 is not in contact with a wall 21 of the mixing element 3. Thus, a flow area 22 exists between the valve body 7 and the wall 21 in axial direction of the mixing element 3 so that the mixed gas can flow through said flow area 22 towards the outlet 17.

[0046] The wall 21 defines at least a part of the chamber 6 along the length axis M of the mixing element 3. An outer cross section of the valve body 7 is smaller than an inner cross section of the chamber 6. This secures that the mixed gas can flow to the outlet opening 17 between the valve body 7 and the wall 21 of the mixing element 3 in radial direction.

[0047] The mixing element 3 has an inlet opening 23 through which gas enters the chamber 6. The gas is supplied by the fan 14 shown in FIG. 3. Downstream the inlet opening 23, a part of the chamber 6 is formed as a venturi nozzle 24 in this embodiment. In alternative non-shown embodiments, the chamber does not have a venturi nozzle. The chamber 6 has a portion with a tapering section, a portion with a constant cross section and a widening section.

[0048] The fuel gas pipe 5 comprises a fuel gas line portion 11 that extends coaxially to the length axis of the mixing element 3. The fuel gas line portion 11 comprises a plurality of fuel openings 10 that are arranged at a distance to each other along the length axis M of the mixing element 3. Additionally, the holes 10 are arranged such that they are arranged on opposite portions of the fuel gas line portion 11 referring to the length axis M of the mixing element 3.

[0049] The valve shaft 8 is arranged within a cavity 9 of the fuel gas line 5. The valve portion 8 protrudes into the cavity 9 to different extents dependent on the position of the valve body 7. In the partly opened position of the valve shown in FIG. 1 the valve shaft 8 enters the hole such that only a part of the holes 10 are covered. In a non-shown opened position of the valve body 7, the valve shaft 8 does not cover any hole 10.

[0050] The fuel gas leaves the fuel gas line via the holes 10. The holes 10 and/or the fuel gas line portion are positioned such that the flow direction of the fuel gas when leaving the holes 10 is perpendicular to the flow direction of the gas. After the fuel gas left the holes 10 it is mixed with the gas in the venturi nozzle 24 part of the chamber 6. The mixed gas leaves the mixing device 1 through the outlet opening 17.

[0051] FIG. 1 shows a state in which no flashback occurs in a burner 13 shown in FIG. 3. This means, the pressure applied on the valve body 7 from downstream the valve body 7, i.e. from the fan side, is higher than a pressure applied on the valve body 7 from upstream the valve body 7, i.e. from the burner side. The pressure is mainly applied by the mixed gas shown by arrows in FIG. 1.

[0052] FIG. 2 shows a side section of the mixing device 1 according to the embodiment of the invention, wherein the valve body 7 is arranged in a first position. In said position the valve body 7, in particular the valve head 25, is in contact with the wall 21 of the mixing element 3. Thus, there is no flow area between the valve 7 and the wall 21 through which the mixed gas could flow. In a non-shown embodiment the valve body 7 is in a close contact with the widening section when the valve body 7 is in the first position and moves towards the outlet opening 17 when it is transferred to the second position. Close contact means that in the close contact position, there remains a predefined gap, also known as a quenching gap. This gap is designed to ensure that a flame will be extinguished and thus serves as a flame arrester to improve the safety of systems operated with flammable gases or liquid. The quenching gap is defined based at room temperature up to 80-90 degrees Celsius and can be 0.5 and 2.5 mm, in particular in the range of between 0.5 and 1.5 mm. The quenching gap is preferably <0.65 mm for hydrogen applications.

[0053] As is evident from FIG. 2, the moveable valve shaft 8 protrudes in the cavity 9 of the fuel gas line such that it covers all fuel gas openings 10 of the gas line 5 when the valve body 7 is in the first position. Thus, in the first position, no or hardly any fuel gas can be supplied to the chamber 6 via the fuel gas line 5.

[0054] FIG. 2 shows as an example a state in which a flashback occurs in the burner 13 shown in FIG. 3. That means, the pressure applied on the valve body 7 from the burner side is higher than the pressure applied on the valve body 7 from the fan side. Thus, the valve body 7 is pressed against the wall 21 due to the applied pressure. The pressure direction resulted from the flashback is shown by arrows in FIG. 2.

[0055] FIG. 3 is a schematic view of a boiler 18 comprising a gas heater 2 with mixing device 1 as shown in FIGS. 1 and 2. The fan 14 of the gas heater 2 is arranged upstream of the mixing device 1 and sucks ambient air. The sucked air flows through the gas line 4 and the inlet opening 23 into the mixing chamber 6. If there is no flashback, the gas is mixed in the mixing chamber 6 with the fuel gas supplied by the fuel gas line 5 and leaves the mixing device 1 via the outlet opening 17.

[0056] The gas heater 2 comprises a fuel gas valve 15 which controls the fuel gas amount that is supplied into the chamber 6 of the mixing element 3. Additionally, the gas heater 2 comprises the burner 13 that is arranged downstream the mixing device 1. Thus, the mixed gas outflowing of the mixing device 1 is supplied to the burner 13. The burner 13 is partly arranged within a combustion chamber 20 of the boiler 18. The flue leaves the combustion chamber 20 via a non-shown opening.

[0057] The boiler 18 comprises a heat exchanger 19 used for heating a liquid, in particular water, by the heat provided by the burner 13.

REFERENCE SIGNS

[0058] 1 gas heater mixing device [0059] 2 gas heater [0060] 3 mixing element [0061] 4 gas line [0062] 5 fuel gas line [0063] 6 chamber [0064] 7 valve body [0065] 8 valve shaft [0066] 9 cavity [0067] 10 hole [0068] 11 fuel gas line portion [0069] 13 burner [0070] 14 fan [0071] 15 fuel gas valve [0072] 17 outlet opening of mixing element [0073] 18 boiler [0074] 19 heat exchanger [0075] 20 combustion chamber [0076] 21 wall [0077] 22 flow area [0078] 23 inlet opining [0079] 24 venturi nozzle [0080] 25 valve head [0081] M length axis