EP4008954A2 - Burner assembly for combustion of hydrogen-containing fuel gas and burner body - Google Patents

Abstract

The invention relates to a burner arrangement for burning a mixture of air and a fuel gas containing hydrogen or essentially pure hydrogen in a combustion chamber (10) into which the mixture can exit from a burner body (7), the burner body (7) being designed in this way that during operation, flames (24) occur more frequently and/or more intensely in at least one predefinable partial flame area (25) of a flame area (8) available for flames (24) around the burner body (7) than in other partial flame areas (23) and wherein at least one optical sensor (17) is present, which can detect light from a partial flame area (25) with more or stronger flames (24). A corresponding burner body (7) has a large number of channels (14), the channels (14) having different cross sections and/or being distributed inhomogeneously over the burner body (7) and/or pointing in different directions. Alternatively or in addition, the burner body (7) may not be formed in a rotationally symmetrical manner, but rather have a substantially rectangular, polygonal, oval or a cross section delimited by differently curved sections. The invention makes it possible to increase the light yield and/or the informative value of optical measurements on flames (24) of a combustion process without increasing the expense for sensors.

Description

The invention relates to a (burner) arrangement for the combustion of fuel gas containing hydrogen, preferably with a hydrogen content greater than 10%, in particular greater than 50%, very preferably greater than 97%. Hydrogen as a fuel gas or as an admixture to fuel gases is becoming more and more important, and great efforts are being made to upgrade new or existing burners of heating devices for operation with it. It is not only a question of large systems, but also of wall-mounted units for heating water and, in general, heaters for heating buildings and/or providing hot water.

During its combustion (with ambient air), hydrogen differs in several respects from previously used fuel gases, in particular a hydrogen flame is almost invisible to the human eye, emits less heat than flames produced with carbonaceous fuels, and hydrogen flames require different measuring systems than the ones to monitor them other fuels. In particular, ionization measurements do not provide reliable signals when the proportion of hydrogen in the fuel gas is high. The present invention is therefore particularly, but not only, applicable to heaters that are operated with pure hydrogen or with fuel gas that consists of more than 50% hydrogen.

A use of optical sensors (for the visible, but especially for the ultraviolet range of light) for flame monitoring and control of combustion using optical filters is for applications in heaters that are operated with hydrogen-containing fuel gas, for example from DE 10 2019 101 329 A1 known. Also the EP 2 223 016 B1 , the U.S. 5,829,962 A and the DE19 509 704 A1 deal extensively with optical measurement systems for flame monitoring, but not specifically for hydrogen flames or for flames of hydrogen-containing fuels.

It was newly recognized that a disadvantage for the optical monitoring of flames of a burner is the design of such burners, which typically (mainly because of the necessary heat transfer to a heat transfer medium) strive for an approximately uniform distribution of the flames over a large flame area, in particular an almost Rotationally symmetrical distribution around a cylindrical burner body with openings for a mixture of air and fuel gas evenly distributed on its cylinder surface. As a result, an optical sensor, which should be located at a certain distance from the flames, especially outside of a combustion chamber behind a window, because of the temperatures occurring in the combustion chamber, only detects a certain, usually very small proportion of z. B. can detect 1 to 10% of the flame. This limits the light output (the portion of the light generated by the flame that reaches the sensor) of the sensor and makes precise monitoring difficult. This can only partially be improved by optical lenses or a geometrically favorable arrangement of the sensor. Although it is known that this can be compensated for by several or even many sensors (connected in parallel) for different partial flame areas of the flame, this requires a great deal of effort without improving the yield of each individual sensor.

The object of the present invention is to at least partially solve the problems outlined with reference to the prior art and to create a burner arrangement and a burner body which enable a greater luminous efficiency of sensor arrangements.

A burner arrangement and a burner body according to the independent claims serve to solve this problem. Advantageous refinements and developments of the invention are specified in the respective dependent claims. The description, in particular in connection with the drawing, illustrates the invention and specifies further exemplary embodiments.

A burner arrangement is proposed for burning a mixture of air and a fuel gas containing hydrogen or essentially pure hydrogen in a combustion chamber into which the mixture can exit from a burner body. The burner body is designed in such a way that during operation, flames occur more frequently and/or more intensely in at least one predeterminable partial flame area of a flame area around the burner body that is available for flames than in other partial flame areas, and there is at least one optical sensor that detects light from the partial flame area with more or stronger flames.

In typical burner arrangements according to the prior art, the aim is to achieve a homogeneous distribution of the flames in a flame area surrounding the burner body (this does not have to be the entire space surrounding the burner body) during operation. Most burner bodies have an inlet side and an opposite end face without channels or openings for mixture, with a lateral surface (which does not necessarily have to be cylindrical) between these two sides includes an interior and can be provided with channels for the exit of the mixture. A homogeneous distribution of the flames on the outside of this lateral surface also seems sensible at first glance, because heat is then evenly distributed during combustion and can be evenly transferred to a heat transfer medium in a heat exchanger. A disadvantage, however, is that with an optical sensor, especially one that is (for temperature reasons) located far outside the flame area, usually even outside a housing of the combustion chamber behind a window, you only see a small part of the flame area with a correspondingly low yield can observe in light. This can be remedied by designing the flame area (viewed globally) to be inhomogeneous and observing at least one sub-area of the flame area in which more and/or larger flames are present than in other sub-areas. Surprisingly, any disadvantages of an inhomogeneous distribution of the flames around a burner body are acceptable because they are largely balanced out by radiation, convection (turbulence) and heat conduction, so that good heat transfer to a heat transfer medium can nevertheless be ensured. On the other hand, when measuring with an optical sensor, a higher light output and/or significance for the entire flame can be achieved because a larger proportion of the flames is observed. This effect can be multiplied even more if there are several sensors, each observing flame areas with more and/or larger flames. Only the maximum temperatures occurring in these partial flame areas should remain so limited that no impermissible production of nitrogen oxides takes place.

The invention also covers cases in which no flames or only extensions of adjacent flames occur in partial areas around a burner body, in which there would be flames according to the prior art, because a very inhomogeneous distribution of the flames takes place. In this context, the flame area also includes areas around the burner body that are potentially suitable for flames but not used.

The burner body is preferably designed in such a way that more and/or stronger flames occur in two, three or more partial flame areas and optical sensors for or for detecting light from two, three or more such partial flame areas are present. In this way, redundancy and a higher light yield can be achieved during measurements, which is particularly important for wavelength-selective measurements in the ultraviolet range, because only small amounts of light are incident and can or must be processed.

In particular, the burner body is designed in such a way that during operation there is a difference in energy release (proportional to the number and size of the flames) in different partial flame areas of 20 to 100%, preferably 40 to 60%. This has a direct effect on the light yield in optical measurements. This means in particular that there can be flame sub-regions with little to almost no flames, while there are correspondingly more flames in other flame sub-regions.

The invention is particularly suitable for high proportions of hydrogen in the fuel gas if each optical sensor is designed for the detection of predefinable spectral ranges in the ultraviolet spectrum of light. Typical emissions of OH* radicals and CH* radicals, which are particularly suitable for the desired monitoring and regulation according to the prior art, are in this range. In the case of pure hydrogen, the radiation from OH* radicals in particular can be used.

In a special embodiment, all optical sensors are connected to a control and regulation unit that can evaluate sensor signals and process them for flame monitoring and regulation of the combustion process.

According to another aspect, a burner body is also proposed, in particular for the burner arrangements described, the burner body enclosing an interior space and having a plurality of channels for the passage of a mixture of air and fuel gas from the interior space into a combustion chamber. The channels have different cross sections and/or are distributed inhomogeneously over the surface of the burner body and/or point in different directions. In this way, different quantities of the mixture can flow into different partial flame areas around the burner body. The features specified here, which can be used individually or in various combinations with one another, relate to all channels (also often called burner nozzles) with the design and arrangement of which the desired inhomogeneous distribution of the fuel mixture and thus the flames can be achieved. The shape of the burner body itself can remain unchanged, particularly as is known from the prior art.

In an alternative embodiment, which can also be used in combination with the above changes to the channels, the burner body, in particular for one of the burner arrangements described, is not formed in a rotationally symmetrical manner. The burner body preferably has an essentially rectangular, polygonal, oval or a cross section formed from differently curved sections. In particular, the torch body is non-cylindrical, but z. B. cuboid or a hollow body with one of the cross-sections described and a predetermined extent in an axial direction.

The burner body preferably has an inlet side for the mixture to enter its interior and an end face opposite the inlet side, each without channels, and is provided with channels on all other sides in such a way that a flame area surrounding these other sides can be flowed in an inhomogeneous manner by the mixture. The invention therefore includes all measures that can be taken on the burner body in order to make the inflow of the mixture into the combustion chamber (seen globally) inhomogeneous and thus to generate flame areas of different strengths, whose strong areas enable a higher light yield when monitored with optical sensors .

In particular, a burner body is designed in such a way that during its operation the inhomogeneity of the flames between different partial flame areas surrounding it is between 20 and 100%, preferably between 40 and 60%.

Fig. 1:

ein Heizgerät mit einer optischen Beobachtung eines Flammenbereiches,

Fig. 2:

einen Querschnitt durch einen Verbrennungsraum gemäß Fig. 1 entlang der Linie I-I zur schematischen Veranschaulichung der Erfindung,

Fig. 3:

einen Querschnitt durch Fig. 1 entlang der Linie I-I zur schematischen Veranschaulichung einer weiteren Ausführungsform,

Fig. 4:

einen Querschnitt durch Fig. 1 entlang der Linie I-I zur schematischen Veranschaulichung einer noch weiteren Ausführungsform, und

Fig. 5:

eine schematische perspektivische Darstellung eines Brennerkörpers.

Schematic exemplary embodiments of the invention, to which this is not limited, the technical environment and the mode of operation will now be explained in more detail with reference to the drawing. They represent:

Figure 1:

a heater with a visual observation of a flame area,

Figure 2:

according to a cross section through a combustion chamber 1 along line II to schematically illustrate the invention,

Figure 3:

a cross section 1 along the line II for the schematic illustration of a further embodiment,

Figure 4:

a cross section 1 along line II to schematically illustrate yet another embodiment, and

Figure 5:

a schematic perspective view of a burner body.

1 shows schematically a heater 1, which can be operated with hydrogen or a hydrogen-containing fuel gas. (In the view of 1 the difference between the invention and the prior art is not yet recognizable). Air (usually outside air/ambient air) is sucked in by a blower 3 via an air supply 2 and conveyed via a supply line 13 on an inlet side 12 into an interior space 9 of a burner body 7 . In addition to the inlet side 12 , this burner body has an opposite end face 11 which essentially determines the shape of the burner body 7 . Between them lies the interior space 9 enclosed by the burner body 7 . Via a fuel gas supply 4 and a fuel gas valve 5 , fuel gas is added to the air flow generated by the blower 3 in a mixer 6 (eg a Venturi nozzle). The mixture passes through channels 14 in the burner body 7 from the interior 9 into a combustion chamber 10 which is surrounded by a housing 15 and is burned there, with flames 24 being produced in a flame area 8 . Combustion gases produced are discharged through an exhaust system 16 . A first optical sensor 17 is arranged in such a way that it can observe part of the flames 24 in an observation area 22 . The first sensor preferably observes an approximately conical observation area 22 with a cone angle of the cone of z. B. 5 - 30° [angular degrees], preferably 10 to 20°. It is favorable (because of the high temperatures in the flame area) for measurements during operation of the burner body 7 if the first sensor is clearly outside of the flame area 8, in particular outside of the housing 15, which can be done by light-conducting fibers or, as shown, by a suitable window 21 in the housing 15 can be reached. The first sensor 17 can either be designed to be wavelength-sensitive itself (sensitive only to a specific wavelength range), or an optical filter (not shown) is connected upstream of it, which only allows a specific wavelength range to reach the sensor 17 in which the optical emissions to be observed lie. Depending on the application, this wavelength range can be in the infrared range, in the range of visible light or in the ultraviolet range, where the combustion of fuel gases containing hydrogen generates lines in each case. In general, such a first sensor 17 will not be arranged inside a combustion chamber 10 simply because of its supply lines and its temperature sensitivity, which is why it is preferably located behind a window 21 arranged in the housing 15 . The first sensor 17 does not necessarily have to be aimed at the torch body 7 either. It can also be aligned in such a way that the largest possible proportion of the entire flames 24 can be observed in its observation direction. A control and regulation unit 20, to which the first sensor 17 is connected, evaluates the measurement signals from the first sensor 17 and uses them to monitor the flames 24 and/or regulate the combustion process. The arrangement described can measure optical emissions of the hydrogen and other radicals or molecules formed during combustion, which are excited during combustion. From their intensity, conclusions can be drawn, e.g. B. on the composition of the fuel, the quality of combustion, the performance of the burner and the like can be drawn. It can also be used as a flame monitor and/or to regulate combustion. However, one disadvantage is that the observation area 22 can only cover a small part of a flame area 8 around the burner body 7 that is in principle available. According to the state of the art, most of the flames 24 lie outside of the observation area 22, which can lead to a low light output and low significance of such measurements. With an increase in the number of sensors, the light yield and significance of Measurements can be increased, but only in proportion to the amount of equipment involved. The invention creates additional possibilities for increasing the light yield and informative value, as will be explained in more detail with reference to the following figures.

2 shows in a cross section along the line II 1 an embodiment of the invention in a schematic representation. It can be seen that the burner body 7 has a rectangular, here square, cross section. The interior 9 thus has the shape of a cuboid or cube. In the example shown, there are channels 14 through which the mixture can flow on only two sides of the rectangle. Flames 24 therefore do not form uniformly around the burner body 7, but there are two partial flame areas 25 with more flames 24 and two partial flame areas 23 (hatched) with fewer or no flames 24. Two optical sensors 17, 18 behind windows 21 in the housing 15 observe the flames 24 in their respective observation area 22. With this arrangement, the sensors 17, 18 observe a much larger proportion of the flames 24 than if they were distributed evenly over the entire possible flame area 8. The light yield and thus the significance of the measurement increases as a result. The measured values of the sensors 17, 18 can be sent to the control and regulation unit 20 individually or in combination.

3 Fig. 13 shows another embodiment of the invention, in which the torch body 7 has a cross-section of a triangle with outwardly convex sides. Channels 14 are distributed evenly over the burner body 7 (with the exception of the end face 11 and the inlet side 12), but the shape of the cross section results in partial flame areas 25 with more flames 24 and partial flame areas 23 (hatched) with fewer flames 24. In this Three sensors 17, 18, 19 observe the trap Flame sections 25 with more flames 24, which has the positive effect on the measurement described above.

The embodiment according to has the same favorable effect 4 , in which, regardless of the cross-sectional shape of the burner body 7 (can be round, oval, angular or formed from differently curved boundaries), a concentration of the flames 24 on certain partial flame areas 25 with more flames 24 is achieved by a suitable orientation of the channels 14. A specific number of channels 14 can, for example, be aligned with a suitable point (or, for example, with one of the sensors 17, 18, 19). In this way too, partial flame areas 25 with more flames 24 and others 23 (again shown hatched) with fewer or no flames 24 are created. Even so, the sensors observe a larger proportion of the flames 24 than in the prior art. Alternatively or additionally, a similar effect can also be achieved by a systematically distributed different density of channels 14 or by systematically distributed different cross sections of the individual channels 14 .

figure 5 FIG. 12 illustrates again schematically in a perspective view the principle of the invention using a cuboid burner body 7, which here has channels 14 on only two sides. Even if it had ducts 14 on three or four sides (not including the front side 11 and the inlet side 12), an inhomogeneous distribution of flames 24 would still arise around the burner body 7, with more sensitive measurements being able to be carried out in partial flame areas 25 that are more strongly filled with flames 24 .

The measures described here for concentrating flames 24 in partial flame areas 25 can be used individually or in any combination with one another be applied. The intensity of the inhomogeneity of the flames 24 to be generated depends on the desired light output, the number of sensors and the tolerable non-uniform distribution of the heat generated in the flames 24 .

The present invention makes it possible to increase the light yield and/or the informative value of optical measurements on flames of a combustion process without increasing the outlay for sensors.

Reference List

1

heater

2

air supply

3

fan

4

fuel gas supply

5

fuel gas valve

6

mixer

7

torch body

8th

flame area

9

interior (of the torch body)

10

combustion chamber

11

face

12

entry side

13

supply line

14

channels

15

housing (of the combustion chamber)

16

exhaust system

17

First optical sensor

18

Second optical sensor

19

Third optical sensor

20

control and regulation unit

21

window (wavelength selective)

22

observation area

23

Flame section with fewer or smaller flames

24

Flames

25

Flame section with more or stronger flames

Claims (9)

Burner arrangement for burning a mixture of air and a hydrogen-containing fuel gas or essentially pure hydrogen in a combustion chamber (10) into which the mixture from an interior (9) of a burner body (7), from an inlet side (12) and one of these opposite end face (11) and is delimited by an intervening lateral surface with channels (14), the burner body (7) being designed in such a way that, during operation, flames (24) appear in at least one predeterminable partial flame area (25) of a flame (24) available flame area (8) around the burner body (7) to a greater extent and/or occur more strongly than in other partial flame areas (23) and with at least one optical sensor (17) being present which detects light from a partial flame area (25) with more or stronger flames (24) can detect. Burner arrangement according to claim 1, wherein the burner body (7) is designed so that more and/or stronger flames (24) appear in two, three or more flame sections (25) and optical sensors (17, 18, 19) for detecting light of two, three or more such partial flame areas (25) are present. Burner arrangement according to Claim 1 or 2, in which the burner body (7) is designed in such a way that during operation there is a difference in energy release in different partial flame regions (23, 25) of 20 to 100%. Burner arrangement according to one of the preceding claims, in which each optical sensor (17, 18, 19) is designed for the detection of predeterminable spectral ranges in the ultraviolet spectrum of light. Burner arrangement according to one of the preceding claims, wherein all optical sensors (17, 18, 19) are connected to a control and regulation unit (20) which is set up to evaluate sensor signals and process them for flame monitoring and regulation of the combustion process. Burner body (7), in particular for a burner arrangement according to one of Claims 1 to 5, the burner body (7) having an interior space (9) which is defined by an inlet side (12) and an end face (11) lying opposite thereto and a lateral surface lying in between with a plurality of channels (14) for the passage of a mixture of air and fuel gas from the interior (9) into a combustion chamber (10), and wherein the channels (14) have different cross sections and/or are inhomogeneous across the burner body (7) are distributed and/or point in different directions, so that different quantities of the mixture can flow into different partial flame areas (23, 25) around the burner body (7). Burner body (7), in particular for a burner arrangement according to one of claims 1 to 5, wherein the burner body (7) is not rotationally symmetrical in shape but essentially has a rectangular, polygonal, oval or differently curved cross-section. Burner body (7) according to claim 6 or 7, wherein the burner body (7) has an inlet side (12) for the mixture to enter its interior (9) and an end face (11) opposite the inlet side (12) without channels (14) and is provided with channels (14) on all other sides in such a way that a flame region (8) surrounding these other sides can be flowed in an inhomogeneous manner by the mixture. Burner body (7) according to one of claims 6 to 8, wherein the burner body (7) is designed such that during its operation the inhomogeneity of the flames (24) in different partial flame areas (23, 25) surrounding it is between 20 and 100%.

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