EP4194751A1 - Dark radiator - Google Patents

Abstract

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

Description

The invention relates to a dark radiator with a burner, a fan and a radiant tube, the burner being connected to a fuel gas supply, the fan being set up to supply combustion air to the burner, the burner being set up to emit a flame into the radiant tube.

In the commercial and industrial sector, infrared heaters are often used to heat production and storage facilities. Dark radiators have one or more radiant tubes as radiant elements, to which at least one burner is assigned. Combustion of a mixture of combustible gas and air within the burner generates a flame that can be distributed over the entire length of the radiant tube using a fan. Natural gas or liquid gas is used as fuel gas, which is mixed in a mixing chamber in a specified ratio, after which it is fed into the combustion chamber via a nozzle and ignited. As a non-return valve, the fuel-air mixture is guided through a grid or mesh, which also has the task of holding the flame. The radiant tubes are regularly connected to the burner in a linear or U-shaped manner and should radiate the heat generated by the flame evenly over the entire length of the tube. The radiant tube is evenly heated by the flame and generates thermal radiation, which is radiated onto an area to be heated. Reflectors are often used to increase efficiency. The exhaust gases resulting from the combustion are removed from the radiant tube with the help of the blower, for example discharged to the outside air via exhaust pipes.

In order to minimize the pollutants produced during the combustion of the fuel, there is a constant effort to achieve an optimal stoichiometric ratio between fuel gas and air in order to achieve combustion that is as complete as possible and in which pollutant emissions are minimized. For this purpose, for example, in DE 10 2014 019 765 A1 suggested blower and To control gas valve by means of a control device to ensure complete combustion of the mixture of fuel gas and air. In the EP 2 708 814 A1 it is further proposed to equip the burner with a mixer and at least one secondary air duct, the burner being set up so that part of the air supplied by the blower is supplied to the mixer and another part of the air is supplied to a secondary air duct in order to discharge part of the supplied combustion air to the flame without adding fuel. In the DE 10 2014 019 766 A1 is also proposed to use a sensor to record the current mixing ratio and/or the type of gas, in particular with regard to the admixture of other types of gas, and to supply gas and/or air to the burner depending on the comparison result between the measured and the necessary mixing ratio until the necessary mixing ratio is established.

The above solutions have proven themselves in practice, as a result of which dark radiators today have relatively low pollutant emissions while at the same time being highly efficient. The object of the present invention is to provide a dark radiator whose pollutant emissions are further reduced with at least the same level of efficiency. According to the invention, this object is solved by the features of the characterizing part of patent claim 1.

With the invention, a dark radiator is provided which has an efficiency that is at least the same as in the prior art and in which the emission of pollutants is reduced. Due to the fact that the fuel gas supply is preferably connected exclusively to a hydrogen source, the exhaust gas theoretically does not contain any carbon-containing pollutants such as carbon monoxide, carbon dioxide or hydrocarbons, since hydrogen does not contain any carbon.

In a further development of the invention, the blower is connected to an ejector whose suction port is connected to the hydrogen supply, with the combustion air sucked in by the blower serving as the driving medium, so that a mixture of hydrogen and combustion air is supplied to the burner by the blower. This enables the supply of a hydrogen/combustion air mixture in a defined mixing ratio, whereby the flame temperature can be adjusted. By setting a high air ratio, i.e. with a high excess of air, the flame temperature can be reduced. Due to the high reactivity of hydrogen, a high air ratio of 2.5 to 3 is possible. In this way, the flame temperature can be brought below the limit temperatures of nitrogen oxide formation and also of the materials of the radiant tube.

In a further embodiment of the invention, the burner comprises a gas nozzle and a mixing tube, which is fed with hydrogen from the gas nozzle, the mixing tube being flushed with combustion air by the blower, the gas nozzle forming an ejector with the mixing tube, the driving medium of the ejector hydrogen introduced through the gas nozzle and the medium sucked into the mixing tube is combustion air located in the jet tube and an ignition device for igniting the hydrogen-combustion air mixture is connected downstream in the flame direction at a distance from the mixing tube. As a result, it is possible to supply a mixture of hydrogen and combustion air in a defined ratio. Because the hydrogen is first mixed with the combustion air outside of the fan in the mixing tube, the requirements for the material of the fan are reduced, since there is no risk of a flashback into the fan. A non-return lock is preferably arranged in the mixing tube at its end directed in the direction of the flame. This prevents flashback into the mixing tube.

In a further embodiment of the invention, the burner comprises a gas nozzle, the blower being set up for flushing the gas nozzle with combustion air and no combustion gas mixing chamber for premixing combustion gas and combustion air being arranged and the gas nozzle being fed exclusively with combustion gas. This achieves a simpler and less expensive construction of the burner. Surprisingly, it has been shown that due to the high reactivity of hydrogen, complete combustion of the hydrogen is achieved without pre-mixing with combustion air. Until the required mixing of the hydrogen with the combustion air flowing around the blower, there is a large distance between the flame and the gas nozzle, so that there is no thermal impairment of the gas nozzle. In addition, it has been shown that there is also no risk of flashback, which is why the flame holder in the form of a perforated plate or wire mesh required in the prior art is not required.

In a further development of the invention, a combustion air mixing chamber is arranged upstream of the burner in the flame direction and is connected to a combustion air source and the exhaust gas discharge line. By supplying exhaust gases to the combustion air, a reduction in oxygen is achieved, which makes it possible to lower the flame temperature. In addition, the recirculation of the exhaust gas results in a reduction in nitrogen oxide emissions.

In a further development of the invention, the fan is arranged upstream of the burner in the flame direction and the combustion air mixing chamber is arranged inside the fan. This achieves good mixing of combustion air and exhaust gas within the fan.

In an embodiment of the invention, the connection between the exhaust gas discharge line and the combustion air mixing chamber includes a branching device, by which the ratio of the branched off exhaust gas volume flow to the combustion air volume flow is determined. This allows the oxygen content of the combustion air/exhaust gas mixture to be adjusted. The branching device preferably includes an adjusting device, by means of which the ratio of the branched off exhaust gas volume flow to the combustion air volume flow can be adjusted.

In a further development of the invention, the burner serves as a primary burner, which is followed by a secondary burner at a distance in the flame direction in the radiant tube, the fuel gas supply of which has a hydrogen source as the fuel gas source is connected, the secondary burner of the exhaust gas stream of the upstream primary burner is supplied as combustion air. This achieves after-treatment of the exhaust gas from the primary burner, as a result of which emissions of nitrogen oxides are largely minimized. It has been shown that due to the high reactivity of the hydrogen, the remaining oxygen content in the exhaust gas from the primary burner is readily sufficient for the combustion of the hydrogen from the secondary burner. In addition, the combustion process in the secondary burner is favored by the temperature of the exhaust gas flow from the primary burner.

In an 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 jet pipe along the axis, thereby avoiding damage to the jet pipe.

Figur 1

die schematische Darstellung eines Dunkelstrahlers;

Figur 2

die schematische Darstellung eines Dunkelstrahlers in einer weiteren Ausführungsform;

Figur 3

die schematische Darstellung eines Dunkelstrahlers in einer dritten Ausführungsform;

Figur 4

die schematische Darstellung eines Dunkelstrahlers in einer vierten Ausführungsform mit Primär- und Sekundärbrenner und

Figur 5

die schematische Darstellung eines Dunkelstrahlers in einer weiteren Ausführungsform mit Primär- und Sekundärbrenner.

Other developments and refinements of the invention are specified in the remaining dependent claims. Exemplary embodiments of the invention are shown in the drawings and are described in detail below. Show it:

figure 1

the schematic representation of a dark radiator;

figure 2

the schematic representation of a dark radiator in a further embodiment;

figure 3

the schematic representation of a dark radiator in a third embodiment;

figure 4

the schematic representation of a dark radiator in a fourth embodiment with primary and secondary burner and

figure 5

the schematic representation of a dark radiator in a further embodiment with primary and secondary burner.

The dark radiator selected as an exemplary embodiment according to figure 1 comprises a burner 1, which is connected to a blower 2 and to which a jet pipe 3 is connected. The jet pipe 3 is in figure 1 merely implied; the jet pipe 3 can certainly extend over a few meters in length and be formed from several jet pipe elements. In the exemplary embodiment, the jet tube 3 is designed as a highly heat-resistant stainless steel tube. Alternatively, special steels with a thermally applied aluminum oxide layer can also be used. In the exemplary embodiment, the radiant tube 3 is surrounded by a reflector (not shown), which in the exemplary embodiment is made of surface-structured aluminum sheet and has partition plates on both sides to reduce convective losses.

The burner 1 comprises a gas nozzle 11 serving as a gas-air mixture nozzle, which is provided with a non-return lock in the exemplary embodiment and which 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 fan 2 is connected on its suction side to an ejector 21 , the driving connection of which is connected to a combustion air supply 22 and the suction connection of which is connected to a hydrogen supply 23 . The combustion air sucked in by the blower 2 is used here as a driving medium, through which the hydrogen is sucked in. On the pressure side, the blower 2 supplies the gas nozzle 11 with a hydrogen/combustion air mixture, which is ignited by the ignition electrode 12 after exiting through the gas nozzle 11, whereby a flame extending through the jet pipe 3 is generated.

In the embodiment according to figure 2 a burner 4 is arranged, which in turn is connected to a blower 2 and to which a jet pipe 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 central axis of the jet tube 3 . A gas nozzle that is exclusively charged with hydrogen is referred to here as a hydrogen nozzle. The hydrogen nozzle protrudes into a mixing tube 43 which runs coaxially with the jet tube 3, with a radial suction gap between the mixing tube 43 and the hydrogen nozzle 41 is formed by the hydrogen nozzle 41 and the mixing tube 43 formed ejector. The mixing tube 43 is held in the burner 4 by a separating screen 45 that clamps it and is provided with scavenging openings. A non-return lock 431 is arranged in the mixing tube 43 at its end opposite the hydrogen nozzle 41 . Furthermore, a thermal sensor 432 for detecting a possible flashback is arranged in the mixing tube 43 .

The blower 2 is aligned in such a way that combustion air 35 flows around the hydrogen nozzle 41 and the mixing tube 43 . Combustion air 25, which mixes with the hydrogen, is sucked in via the suction gap 44 by the hydrogen flow introduced into the mixing tube 43 via the hydrogen nozzle 41. The hydrogen/combustion air mixture emerging from the mixing tube 43 is ignited by the ignition electrode 46 arranged at a distance from the mixing tube 43, as a result of which a flame is formed which extends into the jet tube 3 over the length thereof. A portion of the combustion air 35 blown into the burner 1 by the blower 2 flows through the scavenging openings of the partitions 45 and washes around the flame extending into the radiant tube 3, which is thereby cooled. The ejector formed by the hydrogen nozzle 41 and the mixing tube 43 is designed in such a way that combustion air with an air ratio of 2.5 is supplied to the hydrogen in the mixing tube, whereby a flame temperature of approximately 900° C. is achieved.

In the embodiment according to figure 3 includes the dark radiator a burner 5, which is connected to a fan 2 and to which a radiant tube 3 is connected. The jet pipe 3 has a U-shaped course, which is followed by a branch pipe 6 which is connected to the blower 2 via a suction pipe 24 . The burner 5 in turn includes a hydrogen nozzle 51 which is connected to a hydrogen supply 52 . The hydrogen nozzle 51 is aligned in the direction of the longitudinal central axis of the jet pipe 3 . An ignition electrode 53 for igniting the hydrogen is positioned at a distance from the hydrogen nozzle 51 .

The ejector tube 6 comprises a main tube section 61, via which the jet tube 3 is connected to the suction tube 24. An exhaust gas discharge pipe 62 branches off from the main pipe section 61 and a combustion air supply pipe 63 is spaced therefrom. The combustion air stream 631 sucked in by the blower 2 via the intake pipe 24 serves as a driving medium for the ejector tube 6 , via which part of the exhaust gas stream 621 is sucked in through the recirculation orifice 64 . The mixture of exhaust gas and combustion air produced in this way is introduced into the burner 5 by the blower 2 , where it flows around the hydrogen nozzle 51 . The proportion of the exhaust gas stream in the combustion air stream can be adjusted by the recirculation orifice 64 , which in turn determines the oxygen content of the mixture of exhaust gas and combustion air stream flowing around the hydrogen nozzle 51 . The main exhaust gas flow is discharged via the exhaust gas discharge pipe 62 .

The burner 5, the radiant tube 3, the ejector tube 6 and the blower 2 connected to the suction tube 24 are each connected to one another via flange connections.

In the embodiment according to figure 4 two burners are arranged in the radiant tube 3, a primary burner 7 and a secondary burner 8 downstream of this in the direction of the flame. The primary burner 7 and the secondary burner 8 correspond to the burner 5 explained in the exemplary embodiment described above a hydrogen supply 72, 82, with an ignition electrode 73, 83 being positioned at a distance from the hydrogen nozzle 71, 81. The primary burner 7 is connected to a fan 2 whose suction port is connected to a combustion air supply 22 . The primary burner 7 is followed by a U-shaped jet tube 3 which is connected to the secondary burner 8 via a compensating element 31 . The secondary burner 8 is in turn followed by a further jet tube 3 ′, which in the exemplary embodiment is again U-shaped.

Combustion air flows around the hydrogen nozzle 71 of the primary burner 7 from the blower 2 . The mixture of hydrogen and combustion air that forms in front of the hydrogen nozzle 71 is ignited by the ignition electrode 73 , as a result of which a first flame forms at a distance in front of the hydrogen nozzle 71 . The exhaust gas flow 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 flow-hydrogen mixture that forms in front of the hydrogen nozzle 81 has a sufficiently high oxygen content so that it can be ignited by the ignition electrode 83, creating a second flame is formed, which extends along the second jet tube 3 '. The exhaust gas stream of this second flame is derived from the second radiant 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, which absorbs the movements of the pipeline along the axis.

In this exemplary embodiment, combustion air is supplied to the primary burner 7 via the blower 2 and 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 according to the first exemplary embodiment, with the intake combustion air serving as the driving medium via which the combustion air is sucked out of the second radiant tube 3′. In a further modified embodiment, the second jet pipe 3' can also be connected to the suction line of the blower 2 via an ejector pipe, as is described in the third exemplary embodiment. The flame temperature of the first flame of the primary burner 7 can also be adjusted in this way. In addition, a further reduction in the nitrogen oxide content of the discharged exhaust gas is made possible in this way.

In the embodiment according to figure 5 is the primary burner 7' corresponding to the burner of the embodiment according to FIG figure 2 formed, wherein the hydrogen nozzle 71 in turn protrudes into a mixing tube 74, so that between hydrogen nozzle 71 and mixing tube 74 a suction gap 75 is formed. A non-return lock 741 is in turn arranged in the mixing tube 74 at its end opposite the hydrogen nozzle 71 . Otherwise, the structure of the dark radiator of this exemplary embodiment corresponds to the dark radiator of the exemplary embodiment according to FIG figure 4 , In this embodiment, too, the embodiments given there for the admixture of part of the exhaust gas flow of the second radiant tube 3 'to the combustion air sucked in by the fan 2 are possible.

Claims (10)

Dark radiator with a burner (1, 5, 6, 7), a fan (2) and a radiant tube (3), which is connected to an exhaust gas discharge line, the burner (1) being connected to a fuel gas supply, the fan ( 2) is set up to supply combustion air to the burner (1), the burner (1) being set up to emit a flame into the radiant tube (3, 3'), characterized in that the fuel gas supply is connected to a hydrogen source. Dark radiator according to Claim 1, characterized in that the fan (2) is connected to an ejector (21), the suction connection of which is connected to the hydrogen supply (23), the combustion air sucked in by the fan (2) serving as the driving medium, so that the A hydrogen/combustion air mixture is supplied to the burner (1) by the blower (2). Dark radiator according to Claim 1, characterized in that the burner (4) comprises a gas nozzle (41) and a mixing tube (43) which is fed with hydrogen from the gas nozzle (41), the mixing tube (43) being driven by the blower (2nd ) is flushed with combustion air, the gas nozzle (41) forming an ejector with the mixing tube (43), the driving medium of the ejector being hydrogen introduced through the gas nozzle and the medium sucked into the mixing tube (43) in the jet tube (3, 3' ) located combustion air and wherein in the flame direction at a distance from the mixing tube (43) an ignition device for igniting the hydrogen-combustion air mixture is connected downstream. Dark radiator according to Claim 1, characterized in that the burner (7) comprises a gas nozzle, the blower (2) being set up for flushing the gas nozzle (71) with combustion air and no combustible gas mixing chamber for premixing combustible gas and Combustion air is arranged and the gas nozzle is fed exclusively with fuel gas. Dark radiator according to Claim 3 or 4, characterized in that a combustion air mixing chamber is arranged upstream of the burner (1, 5, 6) in the flame direction and is connected to a combustion air source and the exhaust gas discharge line. Dark radiator according to Claim 5, characterized in that the fan (2) is arranged upstream of the burner (1) in the direction of the flame and the combustion air mixing chamber is arranged inside the fan (2). Dark radiator according to Claim 5 or 6, characterized in that the connection between the exhaust gas discharge line (62) and the combustion air mixing chamber comprises a branch device (64) which determines the ratio of the branched off exhaust gas volume flow to the combustion air volume flow. Dark radiator according to Claim 7, characterized in that the branching device (64) comprises an adjustment device, by means of which the ratio of the exhaust gas volume flow to the combustion air volume flow can be adjusted. Dark radiator according to one of the preceding claims, characterized in that the burner serves as a primary burner (7), which is followed by a secondary burner (8) at a distance in the flame direction in the radiant tube (3), the fuel gas supply of which is connected to a hydrogen source as the fuel gas source, the Secondary burner (8) the exhaust gas stream of the upstream primary burner (7) is supplied as combustion air. Dark radiator according to claim 9, characterized in that between the primary burner (7) and the secondary burner (7) there is a compensating element (31) for compensating for thermally induced changes in length within the radiant tube (3).

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