Dark radiator

Abstract

The invention relates to a dark radiator, comprising a burner (1, 5, 6, 7), a blower (2) and a radiant tube (3) connected to an exhaust gas discharge line, wherein the burner (1) is connected to a fuel gas supply, wherein the blower (2) is configured to supply combustion air to the burner (1), wherein the burner (1) is configured to emit a flame into the radiant tube (3, 3'), and wherein the fuel gas supply is connected to a hydrogen source.

Description

[0001] The invention relates to a dark radiator, comprising a burner, a blower and a jet tube, wherein the burner is connected to a fuel gas supply, wherein the blower is configured to supply combustion air to the burner, and wherein the burner is configured to emit a flame into the jet tube.

[0002] In commercial and industrial settings, radiant heaters are frequently used to heat production and storage facilities. These heaters consist of one or more radiant tubes, each equipped with at least one burner. A flame is generated by burning a mixture of fuel gas and air within the burner, and this flame can be distributed along the entire length of the radiant tube by means of a fan. The fuel gas is natural gas or liquefied petroleum gas (LPG), which is mixed in a predetermined ratio in a mixing chamber before being introduced into the combustion chamber through a nozzle and ignited. A grid or mesh acts as a backdraft preventer, guiding the fuel-air mixture and simultaneously restraining the flame.The radiant tubes are regularly connected linearly or in a U-shape downstream of the burner and are designed to radiate the heat generated by the flame evenly along the entire length of the tube. The radiant tube is heated uniformly by the flame and generates thermal radiation that is emitted onto the area to be heated. Reflectors are frequently used to increase efficiency. The exhaust gases produced by combustion are removed from the radiant tube by a fan and, for example, discharged to the outside air via exhaust pipes. Such dark radiators are described, for example, in DE 1064671 B and DE 9207435 U1.

[0003] To minimize the pollutants produced during fuel combustion, there is a constant effort to achieve an optimal stoichiometric ratio between fuel gas and air in order to achieve the most complete combustion possible, thereby minimizing pollutant emissions. For example, DE 10 2014 019 765 A1 proposes controlling the blower and gas valve by means of a control device to ensure complete combustion of the fuel gas-air mixture. EP 2 708 814 A1 further proposes equipping the burner with a mixer and at least one secondary air duct, whereby the burner is configured so that part of the air supplied by the blower is directed to the mixer and another part of the air is directed to a secondary air duct, in order to supply a portion of the combustion air to the flame without fuel.In DE 10 2014 019 766 A1 it is further proposed to use a sensor to detect the current mixing ratio and / or the type of gas, particularly with regard to the admixture of other gas types, and to supply gas and / or air to the burner depending on the comparison result between the measured and the required mixing ratio, until the required mixing ratio is achieved.

[0004] The aforementioned solutions have proven successful in practice, resulting in dark radiators exhibiting relatively low emissions and high efficiency today. The present invention aims to provide a dark radiator whose emissions are further reduced while maintaining at least the same efficiency. According to the invention, this objective is achieved by the features of claim 1.

[0005] The invention provides a dark radiator that exhibits an efficiency at least equivalent to that of the prior art and with reduced pollutant emissions. Because the fuel gas supply is preferably connected exclusively to a hydrogen source, the exhaust gas theoretically contains no carbon-containing pollutants such as carbon monoxide, carbon dioxide, or hydrocarbons, since hydrogen does not contain carbon.

[0006] The burner comprises a gas nozzle and a mixing tube, which is supplied with hydrogen by the gas nozzle. Combustion air is drawn into the mixing tube by the blower, and the gas nozzle and mixing tube together form an ejector. The ejector's propellant is hydrogen introduced through the gas nozzle, and the combustion air drawn into the mixing tube is combustion air. An ignition device for igniting the hydrogen-combustion air mixture is located downstream of the mixing tube, spaced in the direction of the flame. This allows for the supply of a hydrogen-combustion air mixture in a defined ratio. Because the hydrogen and combustion air are mixed outside the blower, only within the mixing tube, the requirements for the blower material are reduced, as there is no risk of flame flashback into the blower.Preferably, a backdraft arrestor is arranged in the mixing tube at its end facing the flame direction. This prevents flame flashback into the mixing tube.

[0007] In a further development of the invention, a combustion air mixing chamber is arranged upstream of the burner in the direction of the flame, which is connected to a combustion air source and the exhaust gas discharge line. By introducing exhaust gases into the combustion air, an oxygen reduction is achieved, thereby lowering the flame temperature. Furthermore, the recirculation of the exhaust gas reduces nitrogen oxide emissions.

[0008] In a further development of the invention, the blower is arranged upstream of the burner in the direction of the flame, and the combustion air mixing chamber is located inside the blower. This ensures good mixing of combustion air and exhaust gas within the blower.

[0009] In an embodiment of the invention, the connection between the exhaust gas discharge line and the combustion air mixing chamber comprises a branch device by which the ratio of the diverted exhaust gas volume flow to the combustion air volume flow is determined. This allows for adjustment of the oxygen content of the combustion air-exhaust gas mixture. Preferably, the branch device includes an adjustment device by which the ratio of the diverted exhaust gas volume flow to the combustion air volume flow can be adjusted.

[0010] In a further development of the invention, the burner serves as a primary burner, to which a secondary burner is connected in the jet tube at a distance in the direction of the flame. The fuel gas supply to the secondary burner is connected to a hydrogen source, and the exhaust gas stream from the upstream primary burner is supplied to the secondary burner as combustion air. This achieves post-treatment of the primary burner's exhaust gas, thereby largely minimizing nitrogen oxide emissions. It has been shown that, due to the high reactivity of hydrogen, the remaining oxygen content in the primary burner's exhaust gas is readily sufficient for the combustion of the hydrogen in the secondary burner. Furthermore, the combustion process in the secondary burner is favored by the temperature of the primary burner's exhaust gas stream.

[0011] In one embodiment of the invention, a compensating element in the form of a compensator is interposed between the primary burner and the secondary burner to compensate for thermally induced changes in length within the radiant tube. This compensator, which is preferably designed as an axial compensator, absorbs the movement of the radiant tube along its axis, thereby preventing damage to the radiant tube.

[0012] Other embodiments and configurations of the invention are specified in the remaining dependent claims. Exemplary embodiments of the invention are illustrated in the drawings and are described in detail below. The drawings show: Figure 1 the schematic representation of a dark radiator; Figure 2 the schematic representation of a dark radiator in an embodiment according to the invention; Figure 3 the schematic representation of a dark radiator in a design with exhaust gas recirculation; Figure 4the schematic representation of a dark radiator in an embodiment with primary and secondary burners and Figure 5 The schematic representation of a dark radiator in an embodiment according to the invention with primary and secondary burners.

[0013] The dark radiator according to Figure 1 It comprises a burner 1, which is connected to a blower 2 and to which a jet nozzle 3 is attached. The jet nozzle 3 is in Figure 1The blast tube 3 is only indicated here; it can extend over several meters in length and be composed of multiple blast tube elements. In the exemplary embodiment, the blast tube 3 is designed as a high-temperature-resistant stainless steel tube. Alternatively, special steels with a thermally applied aluminum oxide layer can also be used. In the exemplary embodiment, the blast tube 3 is enclosed by a reflector (not shown), which in this embodiment is made of surface-structured aluminum sheet and has baffles on both sides to reduce convective losses.

[0014] The burner 1 comprises a gas nozzle 11 serving as a gas-air mixture nozzle, which in the exemplary embodiment is provided with a non-return valve and is connected to the blower 2. An ignition electrode 12 is arranged in the burner 1 at a distance from the gas nozzle 11. The blower 2 is connected on its suction side to an ejector 21, the drive connection of which is connected to a combustion air supply 22 and its suction connection to a hydrogen supply 23. The combustion air drawn in by the blower 2 serves as the motive medium, causing the hydrogen to be drawn in. On the pressure side, a hydrogen-combustion air mixture is supplied to the gas nozzle 11 by the blower 2. After exiting the gas nozzle 11, this mixture is ignited by the ignition electrode 12, thereby generating a flame extending through the jet tube 3.

[0015] In the exemplary embodiment according to Figure 2A burner 4 is arranged, which in turn is connected to a blower 2 and to which a jet tube 3 is connected. The burner 4 includes a hydrogen nozzle 41, which is connected to a hydrogen supply 42 and which in turn is aligned with the longitudinal center axis of the jet tube 3. Here, a hydrogen nozzle is defined as a gas nozzle that is exclusively supplied with hydrogen. The hydrogen nozzle projects into a mixing tube 43, which runs coaxially to the jet tube 3, with a radial suction gap formed between the mixing tube 43 and the hydrogen nozzle 41, forming an ejector created by the hydrogen nozzle 41 and the mixing tube 43. The mixing tube 43 is held in the burner 4 by a separating orifice plate 45, which clamps the mixing tube and is provided with purge openings. A non-return valve 431 is arranged in the mixing tube 43 at its end opposite the hydrogen nozzle 41.Furthermore, a thermosensor 432 is arranged in the mixing tube 43 for detecting a possible flame flashback.

[0016] The blower 2 is oriented such that it supplies combustion air 35 to the hydrogen nozzle 41 and the mixing tube 43. The hydrogen flow introduced into the mixing tube 43 via the hydrogen nozzle 41 draws in combustion air 25 through the suction gap 44, which mixes with the hydrogen. The hydrogen-combustion air mixture exiting the mixing tube 43 is ignited by the ignition electrode 46, which is located at a distance from the mixing tube 43, thus forming a flame that extends along the length of the jet tube 3 into the tube. A portion of the combustion air 35 blown into the burner 1 by the blower 2 flows through the purge openings of the baffles 45 and cools the flame extending into the jet tube 3.The ejector formed by the hydrogen nozzle 41 and the mixing tube 43 is designed such that combustion air with an air ratio of 2.5 is supplied to the hydrogen in the mixing tube, thereby achieving a flame temperature of about 900 °C.

[0017] In the example according to Figure 3 The dark radiator comprises a burner 5 connected to a blower 2, to which a jet tube 3 is attached. The jet tube 3 has a U-shaped profile, to which a branch pipe 6 is attached, which is connected to the blower 2 via a suction pipe 24. The burner 5 in turn includes a hydrogen nozzle 51 connected to a hydrogen supply 52. ​​The hydrogen nozzle 51 is aligned along the longitudinal center axis of the jet tube 3. An ignition electrode 53 for igniting the hydrogen is positioned at a distance from the hydrogen nozzle 51.

[0018] The ejector tube 6 comprises a main tube section 61, through which the jet tube 3 is connected to the intake pipe 24. An exhaust gas discharge pipe 62 branches off from the main tube section 61, and a combustion air supply pipe 63 is spaced apart from it. A recirculation orifice 64 is arranged in the main tube section 61 between the exhaust gas supply pipe 62 and the combustion air supply pipe 63. The combustion air flow 631, drawn in by the blower 2 via the intake pipe 24, serves as the motive medium for the ejector tube 6, through which a portion of the exhaust gas flow 621 is drawn in via the recirculation orifice 64. The exhaust gas-combustion air mixture thus generated is introduced by the blower 2 into the burner 5, where it flows around the hydrogen nozzle 51. The proportion of the exhaust gas flow in the combustion air flow can be adjusted by means of the recirculation orifice 64, which in turn determines the oxygen content of the exhaust gas-combustion air flow mixture flowing around the hydrogen nozzle 51.The main exhaust gas flow is discharged via the exhaust gas discharge pipe 62.

[0019] The burner 5, the jet tube 3, the ejector tube 6 and the blower 2 connected to the suction pipe 24 are each connected to each other via flange connections.

[0020] In the example according to Figure 4Two burners are arranged in the jet tube 3: a primary burner 7 and a secondary burner 8 downstream of it in the direction of the flame. The primary burner 7 and the secondary burner 8 correspond to the burner 5 described in the previously described embodiment. These in turn comprise a hydrogen nozzle 71, 81, which is connected to a hydrogen supply 72, 82, with an ignition electrode 73, 83 positioned at a distance from the hydrogen nozzle 71, 81. The primary burner 7 is connected to a blower 2, the suction port of which is connected to a combustion air supply 22. A U-shaped jet tube 3 connects to the primary burner 7 and is connected to the secondary burner 8 via a compensating element 31. A further jet tube 3', which in this embodiment is also U-shaped, connects to the secondary burner 8.

[0021] The hydrogen nozzle 71 of the primary burner 7 is supplied with combustion air by the blower 2. The hydrogen-combustion air mixture forming in front of the hydrogen nozzle 71 is ignited by the ignition electrode 73, causing a first flame to form at a distance in front of the hydrogen nozzle 71. The exhaust gas stream of this first flame flows through the compensating element 32 and flows around the hydrogen nozzle 81 of the secondary burner 8. The exhaust gas-hydrogen mixture forming in front of the hydrogen nozzle 81 has a sufficiently high oxygen content to be ignited by the ignition electrode 83, forming a second flame that extends along the second jet tube 3'. The exhaust gas stream of this second flame is discharged from the second jet tube 3'.The compensating element 31, positioned in the section of the radiant tube 3 exposed to a high temperature gradient by the secondary burner 8, serves to compensate for thermally induced changes in length within the radiant tube. In the exemplary embodiment, this is designed as an axial compensator that accommodates the movements of the pipe along its axis.

[0022] Primary burner 7 becomesCombustion air is supplied via the blower 2, which flows around the hydrogen nozzle 71 of the primary burner 7. In a modified embodiment, the blower 2 upstream of the primary burner 7 can also be connected to an ejector, as in the first embodiment, with the intake combustion air serving as the motive medium through which combustion air is drawn from the second jet tube 3'. In a further modified embodiment, the second jet tube 3' can also be connected to the suction line of the blower 2 via an ejector tube, as described in the third embodiment. In this way, the flame temperature of the first flame of the primary burner 7 can also be adjusted. Furthermore, this method enables a further reduction in the nitrogen oxide content of the exhaust gas.

[0023] In the exemplary embodiment according to Figure 5 The primary burner 7' corresponds to the burner of the embodiment according to Figure 2The hydrogen nozzle 71 is designed in such a way that it projects into a mixing tube 74, so that a suction gap 75 is formed between the hydrogen nozzle 71 and the mixing tube 74. A non-return valve 741 is arranged in the mixing tube 74 at its end opposite the hydrogen nozzle 71. Otherwise, the construction of the dark radiator in this embodiment corresponds to the dark radiator in the example according to Figure 4 , whereby in this embodiment, the embodiments mentioned therein for mixing a part of the exhaust gas flow of the second jet tube 3' with the combustion air drawn in by the blower 2 are also possible.

Claims

1. Dark radiator, comprising a torch (1, 5, 6, 7), a blower (2), a combustion gas supply, an exhaust discharge line, and a radiant tube (3) that is connected to the exhaust discharge line, where the torch (1) is connected to the combustion gas supply, where the blower (2) is configured to supply the torch (1) with combustion air, where the torch (1) is configured to output a flame into the radiant tube (3, 3'), where the combustion gas supply comprises a hydrogen source, where the torch (4) comprises a gas nozzle (41) and a mixing tube (43) that is fed with hydrogen by the gas nozzle (41), where the blower (2) flushes combustion air around the mixing tube (43), where the gas nozzle (41) forms an ejector with the mixing tube (43), and where the propellant of the ejector is hydrogen introduced through the gas nozzle and the medium sucked into the mixing tube (43) is combustion air present in the radiant tube (3, 3').

2. Dark radiator in accordance with claim 1, where a combustion air mixing chamber that is connected to a combustion air source and the exhaust discharge line is arranged upstream of the torch (1, 5, 6) in the flame direction.

3. Dark radiator in accordance with claim 2, where the blower (2) is arranged upstream of the torch (1) in the flame direction and the combustion air mixing chamber is arranged inside of the blower (2).

4. Dark radiator according with claim 2 or 3, where the connection between the exhaust discharge line (62) and the combustion air mixing chamber comprises a branching device (64) through which the ratio of the branched-off exhaust volume flow to the combustion air volume flow is determined.

5. Dark radiator in accordance with claim 4, where the branching device (64) comprises an adjustment device through which the ratio of the exhaust volume flow to the combustion air volume flow can be adjusted.

6. Dark radiator according to one of the preceding claims, where the torch serves as primary torch (7) that has a secondary torch (8) arranged in the radiant tube (3) downstream at a distance in the flame direction, the combustion gas supply of which is connected to a hydrogen source as a combustion gas source, where the exhaust flow of the upstream primary torch (7) is supplied to the secondary torch (8) as combustion air.

7. Dark radiator in accordance with claim 6, where a compensation element (31) is switched between the primary torch (7) and the secondary torch (7) to compensate for thermally caused length changes within the radiant tube (3).

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