EP0866269A1 - Boiler for heat generation - Google Patents

Abstract

In a boiler system for heat generation, which essentially consists of a combustion chamber and a burner acting on the head side of the combustion chamber, this combustion chamber is divided into two parts (17, 102a) by inserting an annular disc (103). In the front part (17), a limited inner backflow zone (24) is formed in operative connection with this disc (103). This disc (103) then causes outer return flow zones (106) fed by recirculated flue gases (30) to form inside the front part (17) of the combustion chamber, the flue gases of which are introduced into the combustion process of the burner, said backflow zones (24, 106) are locally separated from each other. This enables better flame stabilization, lower pulsations and significantly lower pollutant emissions to be achieved when the burner is in operation. <IMAGE>

Description

Technical field

The invention relates to a boiler system according to the preamble of claim 1.

State of the art

The flame stabilization of many modern low NOx burners is based on the generation of a backflow bubble or backflow zone (= vortex breakdown). In the case of an unfavorable design of the swirl generator, the swirl number is too high the desired short backflow bubble due to the swirling of the vortex in one long almost cylindrical backflow zone over. When operating the burner without Combustion chamber or too large combustion chamber or with relatively cold combustion chamber walls the return of the flue gases in the core becomes the heat withdrawn. This leads to insufficient flame stabilization, especially at the start and when operating with liquid fuels to an inadequate Pre-evaporation of the fuel drops. This behavior can also affect Burners with passive flue gas recirculation can be observed in the combustion chamber. These problems can lead to flame out or vibrations an undesired special starting procedure is necessary. For heating systems will also be a very long start-up phase with increased emissions necessary in which the whole boiler with its relatively large thermal Inertia must be warmed up until the back-flowing smoke gases have sufficient temperature.

Presentation of the invention

The invention seeks to remedy this. The invention as set out in the claims is characterized, the task is based on a boiler system to propose precautions to avoid excessive cooling of the reacted gases, i.e. of the recirculated flue gases prevented.

This is achieved by using an orifice or a corresponding partition dividing the combustion chamber Means are placed within the combustion chamber. It should be emphasized that the design of this aperture can be varied, and for example not limited to an annular disc. Other means which The effects described below can also trigger this subject of the invention.

With the measure according to the invention, the combustion chamber is divided into two parts, in particular the front part of the combustion chamber relevant to the effect becomes.

As for the above-mentioned front part of the combustion chamber, the one according to the invention Measure in that the effect is achieved that an inner Return flow zone and outer return flow zones are each locally defined to one another can arise, which results in a clear separation of the two.

The main advantage of the invention is that the flow in the Combustion chamber center is accelerated, which leads to a shortening of the inner Backflow zone leads, i.e. this inner backflow zone is limited downstream. This means that hotter flue gases are now on the burner axis arise, and so too much cooling of those formed there reacted Gases is prevented. These gases, which are now at a higher temperature level then flow as recirculated flue gases over the as separated acting and locally defined with respect to the inner backflow zone Backflow zones to an injector system belonging to the burner.

Both effects result in better flame stabilization and fuel evaporation. This in turn leads to significantly lower pulsations during the Starting process and also to significantly lower pollutant emissions in this transient phase.

Advantageous and expedient developments of the task solution according to the invention are characterized in the further dependent claims.

In the following, embodiments of the invention will be described with reference to the drawings explained in more detail. All not necessary for the immediate understanding of the invention Elements have been left out. The same elements are in the different Figures with the same reference numerals. The flow direction the media is indicated by arrows.

Brief description of the drawings

Fig. 1

eine Kesselanlage, welche mit einem Vormischbrenner betrieben wird, mit einer Vorrichtung für die Limitierung der Ausdehnung der Rückströmzone,

Fig. 2

eine weitere Ausgestaltung der Vorrichtung für die Limitierung der Ausdehnung der Rückströmzone,

Fig. 3

einen Vormischbrenner zum Betrieb der Kesselanlage, in perspektivischer Darstellung,

Fig. 4

eine weitere perspektivische Darstellung dieses Vormischbrenners aus anderer Ansicht in vereinfachter Form,

Fig. 5

einen Schnitt durch den Vormischbrenner gemäss Fig.2 oder 3, mit Injektoren bestückt, wobei die Einströmungsebene von Zuführungskanälen parallel zur Brennerachse verlaufen,

Fig. 6

eine Konfiguration des Injektorsystems in Strömungsrichtung,

Fig. 7

eine weitere Ausgestaltung der Einströmungsebene von Zuführungskanälen und

Fig. 8

eine weitere Konfiguration des Injektorsystems in Strömungsrichtung.

It shows:

Fig. 1

a boiler system which is operated with a premix burner, with a device for limiting the extent of the backflow zone,

Fig. 2

a further embodiment of the device for limiting the extent of the backflow zone,

Fig. 3

a premix burner for operating the boiler system, in perspective,

Fig. 4

another perspective view of this premix burner from another view in a simplified form,

Fig. 5

3 shows a section through the premix burner according to FIG. 2 or 3, equipped with injectors, the inflow plane of supply channels running parallel to the burner axis,

Fig. 6

a configuration of the injector system in the direction of flow,

Fig. 7

a further embodiment of the inflow plane of supply channels and

Fig. 8

a further configuration of the injector system in the flow direction.

WAYS OF CARRYING OUT THE INVENTION, INDUSTRIAL APPLICABILITY

1 shows a boiler system 100 belonging to the prior art, as is customary is used for heating systems. This boiler system 100 exists essentially from a combustion chamber formed from a flame tube 101 102, which is surrounded by a heat-resistant partition 105. The boiler system is operated here by a premix burner, the description of which 3 and 4 can be seen in more detail. The operation of this boiler system can be but do not do it alone with this burner; other types of burners each with flame stabilization can also be used. The Fig. 1 mainly wants the aforementioned almost cylindrical elongated Show backflow zone 24a, which leads to the disadvantages mentioned there, and which are canceled by the proposal according to FIG. 2.

Fig. 2 shows the subdivision of the combustion chamber by an acting as an aperture annular disc 103, the steps 104 a boundary of the inner backflow zone 24 effect. This inner backflow zone 24 is thus in the direction of flow limited within the front part 17 of the combustion chamber what excessive cooling of the reacted gases prevented. The second part 102a of the combustion chamber, downstream of the aperture 103, serves as an exhaust zone. The current itself becomes within the first part 17 of the combustion chamber in the center of the combustion chamber accelerates, which then results in a compact and shortened inner backflow zone 24 leads, as can be seen quite clearly from FIG. 2. By hotter Flue gases on the burner axis leading to the burner will be a better one Flame stabilization reached. Through the through the annular disk 103 Subdivision of the combustion chamber also creates outer backflow zones 106 of reacted gases acted as recirculated flue gases via injectors (See Fig. 5-8) in the combustion process of the one used here Premix burner (see Fig. 3-4). Because these fumes 30 because of the limitation given by the annular disk 103 experienced minimized cooling can be experienced by the higher temperature level these flue gases 30 achieve increased fuel evaporation, which increases better flame stabilization and significantly lower pollutant emissions leads. The inner backflow zone 24 and the outer backflow zones 106 are separated from one another in a locally defined manner. The distance of this annular disk 103 and the means used for this purpose from the front wall of the burner depends on the respective operation. The The same also applies to the degree of step 104 of the annular disk 103, i.e. the degree of cross-sectional reduction triggered by such means resp. the degree of reduction in flow passage. The simplicity of here proposed means, especially as regards the annular disc related adjustments without further ado.

Fig. 3 shows a premix burner in perspective. For the better Understanding the subject matter is beneficial if at the same time when capturing 3 at least also FIG. 4 is used. These two figures have mainly the purpose, the type and the functioning of such Stake out Brenners.

The premix burner according to FIG. 3 consists of two hollow conical partial bodies 1, 2, which are nested offset from one another and with a gaseous and / or liquid fuel is operated. Under the term Not only the one shown here becomes "conical" due to a fixed opening angle understood cone shape, but also includes other configurations the partial body with a, such a diffuser or diffuser-like shape as well a confuser or confuser-like shape. These forms are not present Specifically shown, since they are familiar to those skilled in the art. The dislocation the respective central axis or longitudinal axis of symmetry of the partial bodies 1, 2 to each other (see Fig. 4, Pos. 3, 4) creates on both sides, in mirror image Arrangement, each a tangential air inlet duct 5, 6 free, through which the Combustion air 7 in the interior of the premix burner, i.e. in the cone cavity 8 streams. The two conical partial bodies 1, 2 each have a cylindrical one Initial part 9, 10, which is also, analogously to the aforementioned partial bodies 1, 2, offset run to each other so that the tangential air inlet channels 5, 6 over the entire length of the premix burner is available. In the area of the cylindrical Initially there is a nozzle 11 for preferably atomizing a liquid Fuel 12 housed, such that their injection approximately with the narrowest cross-section of the cone cavity formed by the partial bodies 1, 2 8 coincides. The injection capacity and the operating mode of this nozzle 11 depends on the specified parameters of the respective premix burner. The fuel 12 injected through the nozzle 11 can, if necessary, with a recirculated exhaust gas are enriched; then it is also possible through the Nozzle 11 to accomplish the complementary injection of a quantity of water.

Of course, the premix burner can be purely conical, i.e. without a cylindrical one Initial parts 9, 10 may be formed. The sub-bodies 1, 2 also each have one Fuel line 13, 14, which runs along the tangential inlet channels 5, 6 are arranged and provided with injection openings 15, through which preferably a gaseous fuel 16 in the combustion air flowing there 7 is injected, as is symbolized by arrows 16, wherein this injection also the fuel injection level (see FIG. 4, item 22) of the Systems forms. These fuel lines 13, 14 are preferably at the latest placed at the end of the tangential inflow, before entering the cone cavity 8, this to ensure an optimal air / fuel mixture.

On the combustion chamber side, the premix burner has an anchorage for the partial bodies 1, 2 serving front panel 18 with a number of holes 19 through which if necessary, a mixed or cooling air 20 the front part of the combustion chamber 17th or whose wall is fed.

If, as already described, the premix burner is used solely by means of a liquid Operated fuel 12, this is done via the central nozzle 11, wherein this fuel 12 then enters the cone cavity 8 at an acute angle or is injected into the combustion chamber 17. The nozzle 11 thus forms a tapered fuel profile 23 rotating from the tangentially flowing Combustion air 7 is enclosed. In the axial direction, the concentration of the injected fuel 12 continuously through the incoming combustion air 7 broken down into an optimal mixture.

If you want to operate the premix burner with a gaseous fuel 16, so this can in principle also be done via the central fuel nozzle 11, however, such an operating mode should preferably be via the injection openings 15 be made, the formation of this fuel / air mixture directly at the end of the air inlet ducts 5, 6.

When the liquid fuel 12 is injected via the nozzle 11, the end the premix burner the optimal, homogeneous fuel concentration over the Cross section reached. Is the combustion air 7 additionally preheated or with a recycled exhaust gas enriched, this supports the evaporation of the liquid fuel 12 sustainably within the length of the premix burner induced premix section. As for the admixture of a returned Concerning flue gas, reference is made to FIGS. 5-8.

The same considerations also apply if the fuel lines 13, 14 instead of gaseous liquid fuels should now be supplied.

In the design of the conical part body 1, 2 with respect to the increase the flow cross-section and the width of the tangential air inlet ducts 5, 6 are strict limits to be observed so that the desired flow field the combustion air 7 at the outlet of the premix burner can. The critical swirl number is set at the outlet of the premix burner: A backflow zone 24 (vortex breakdown) also forms there with one opposite the flame front 25 acting there stabilizing effect, in which Meaning that the backflow zone 24 functions as a disembodied flame holder takes over.

The optimal fuel concentration across the cross section is only in the area the vortex runout, that is, in the area of the backflow zone 24. First a stable flame front 25 is then created at this point Effect results from the swirl number in in the cone cavity 8 Flow direction along the cone axis. A backlash of the flame into that This prevents the interior of the premix burner.

In general it can be said that minimizing the flow opening of the tangential Air inlet channels 6, 7 is predestined, the backflow zone 24 from the end of Form premixing section. The design of the premix burner is suitable furthermore excellent, the flow opening of the tangential air inlet ducts 5, 6 to change as required, which means without changing the overall length of the premix burner a relatively large operational bandwidth can be covered. Of course, the partial bodies 1, 2 are also in a different plane to one another displaceable, which even overlaps the air inlet plane into the cone cavity 8 (see FIG. 4, item 21) of the same in the area of the tangential air inlet channels 5, 6, as shown in Fig. 4, accomplished can be. It is then also possible for the partial bodies 1, 2 to be counter-rotating to interleave rotating movement in a spiral.

Through a more homogeneous mixture formation achievable in this premix burner achieved between the injected fuels 11, 12 and the combustion air 7 lower flame temperatures and thus lower pollutant emissions, in particular lower NOx values. Then reduce these lower temperatures the thermal load on the material on the burner front and make for example special treatment of the surface is not mandatory.

As far as the number of air inlet ducts is concerned, the premix burner is not open the number shown is limited. A larger number is displayed there, for example, when it comes to making the premixing wider, or the Swirl number and thus the dependent formation of the backflow zone 24 by to influence a larger number of air inlet ducts accordingly.

Premix burners of the type described here are also those which are to be achieved a swirl flow from a cylindrical or quasi-cylindrical tube go out, the inflow of combustion air into the interior of the pipe tangential air inlet channels is also accomplished, and inside of the tube a conical body with decreasing in the flow direction Cross section is arranged, which is also critical with this configuration Swirl number at the output of the burner can be achieved.

FIG. 4 shows the same premix burner according to FIG. 3, but from a different one Perspective and in a simplified representation. This Figure 4 is essentially serve to correctly record the configuration of this premix burner. In particular, the displacement of the two partial bodies 1, 2 is shown in FIG. 4 to each other, based on the main central axis 26 (= burner axis) of the premix burner, which corresponds to the main axis of the central fuel nozzle 11, quite clearly visible. This dislocation in itself induces the size of the Flow openings of the tangential air inlet ducts 5, 6. The central axis 3, 4 run parallel to each other here.

Fig. 5 is a section approximately in the middle of the premix burner. The mirror image Tangentially arranged feed channels 27, 28 perform the function of Mixing section in which the combustion air 7, formed from fresh air 29 and recirculated flue gas 30 is perfected. The combustion air 7 is in one Injector system 200 processed. Upstream of each feed channel 27, 28, the serves as a tangential inflow into the interior 8 of the premix burner the fresh air 29 evenly over the entire length of the premix burner Perforated plates 31, 32 distributed. In the direction of flow to the tangential inlet channels 5, 6 these perforated plates 31, 32 are perforated. The perforations fulfill the function individual injector nozzles 31a, 32a, which have a suction effect compared to the surrounding flue gas 30 exert such that each of these injector nozzle 31a, 32a each only sucks a certain proportion of flue gas 30, whereupon over the entire axial length of the perforated plates 31, 32, which corresponds to the burner length, a uniform flue gas admixture takes place. This configuration causes that at the point of contact of the two media, i.e. the fresh air 29 and the flue gas 30, an intimate mixing takes place, so that the up to the tangential air inlet slots 5, 6 reaching flow length of the supply channels 27, 28 can be minimized for the mixture formation. Besides The local injector configuration 200 is distinguished by the fact that the geometry the premix burner, especially what the shape and size of the tangential Air inlet ducts 5, 6 concerns, remains dimensionally stable, i.e. through the evenly dosed distribution of the hot flue gases 30 along the entire axial Length of the premix burner, there are no thermal distortions. The same injector configuration as the one just described here can also be used in the area of the head-side fuel nozzle 11 for an axial supply of a Combustion air can be provided.

6 is a schematic illustration of the premix burner in the flow direction, where in particular the course of the perforated plates belonging to the injector system 31, 32 with respect to the inflow planes 33 of the feed channels 27, 28 is expressed. This course is parallel, with the inflow planes 33 itself over the entire burner length parallel to the burner axis 26 of the Premix burner. This figure also shows how the injector nozzles 31a, 32a their inflow angle with respect to the burner axis 26 of the Change the premix burner in the direction of flow. From an initial spike They gradually align angles at the head stage of the premix burner until it is approximately perpendicular to the burner axis in the area of the outlet 26 stand. With this precaution the mixture quality of the combustion air increased and the backflow zone held stable. Meanwhile, is one such inclination is not essential for every burner. Right-angled inflows can also be used in some cases.

7 and 8 show essentially the same configuration according to FIGS. 5 and 6, the perforated plates 34, 35 with the associated injector nozzles 34a, 35a also parallel to the inflow planes 36 over the entire length of the burner of the feed channels 27, 28 run. Meanwhile, these inflow planes 36 run conically with respect to the burner axis 26 of the premix burner. Of the variable inflow angle of the injector nozzles 34a, 35a in the flow direction also largely corresponds to the configuration according to FIGS. 5 and 6, wherein here the gradual erection of these injector nozzles 34a, 35a into one vertical inflow in the area of the outlet of the premix burner primary opposite the inflow plane 36 of the respective feed channel judges.

Reference list

1, 2

Partial conical body

3, 4

Central axis to 1 resp. 2nd

5, 6

Tangential air intake ducts

7

Combustion air

8th

Cone cavity, interior of the burner

9, 10

Cylindrical starting parts of the burner

11

Fuel nozzle

12th

Fuel, liquid fuel

13, 14

Fuel lines

15

Injection openings of the fuel line 13, 14

16

Fuel, gaseous fuel

17th

Front part of the combustion chamber delimited by the aperture 103

18th

Front panel

19th

Holes in the front panel

20th

Air, mixed air, cooling air

21

Air inlet level

22

Fuel injection level

23

Fuel profile

24th

Inner backflow zone, backflow bubble

24a

Backflow zone, backflow bladder without fittings in the combustion chamber

25th

Flame front

26

Main central axis, burner axis

27, 28

Feed channels

29

Fresh air

30th

Recirculated flue gas, reacted gases

31, 32

Perforated plates

31a, 32a

Injector nozzles

33

Inflow plane of the inlet ducts 27, 28

34, 35

Perforated plates

34a, 35a

Injector nozzles

36

Inflow plane of the feed channels 27, 28

100

Boiler system

101

Flame tube

102

Exhaust zone

102a

Exhaust zone, downstream of the aperture 103

103

Annular aperture

104

Graduation of the ring-shaped aperture

105

Partitioning

106

Outer backflow zones

200

Injector system

Claims (12)

Boiler plant for heat generation, consisting essentially of a combustion chamber and a burner acting at the top of the boiler system for operation with a liquid and / or gaseous fuel, the burner having means for introducing the combustion air, which induce flame stabilization in the combustion chamber characterized in that in the combustion chamber of the boiler system (100) at least an aperture-shaped means (103) is installed, which the combustion chamber into a front part (17) and a downstream part (102a) divided, and that the aperture-shaped means (103) within the front Part (17) is a downstream boundary of an inner backflow zone (24) and the formation of recirculated flue gases (30) fed outer backflow zones (106) induced. Boiler system according to claim 1, characterized in that the inner Return flow zone (24 and the outer return flow zones (106) each locally are separated from each other. Boiler system according to claim 1, characterized in that the aperture-shaped Means (103) is an annular disc. Boiler system according to claim 1, characterized in that the burner from at least two tall, conical, nested in the flow direction Partial bodies (1, 2) exist that the central axes (3, 4) these partial bodies (1, 2) run offset from one another, in such a way that neighboring ones Walls of the partial body (1, 2) tangential air inlet channels Form (5, 6) for a combustion air (7), and that the burner with at least a fuel nozzle (11, 15) can be operated. Boiler system according to claim 4, characterized in that the fuel nozzle (11) is arranged on the head side and on the burner axis (26). Boiler system according to claim 4, characterized in that in the area the tangential air inlet channels (5, 6) in the longitudinal extension of the burner a number of spaced apart fuel nozzles (15) are arranged are. Boiler system according to claim 4, characterized in that the flow cross section one of the part bodies (1, 2) formed cone cavity (8) increases uniformly in the direction of flow. Boiler system according to claim 4, characterized in that the flow cross section one of the part bodies (1, 2) formed cone cavity (8) a diffuser, a diffuser-like course, a confuser, a confusor-like course. Boiler system according to claim 4, characterized in that the partial body (1, 2) are nested in a spiral. Boiler system according to claim 4, characterized in that in radial or quasi-radial direction with respect to the air inlet ducts (5, 6) Feed channels (27, 27) extend, each of which has at least one injector system (200) for providing fresh air (29) and responded Gases (30) existing combustion air (7). Boiler system according to claim 10, characterized in that the injector system Perforated perforated plates (31, 32; 34, 35) parallel to the respective inflow plane (33, 36) of the combustion air (7) into the supply channels (27, 28) run that the perforated plates in the area of the inflow planes are provided with injector nozzles (31a, 32a; 34a, 35a), and that the Inlet angle of the injector nozzles in the axial direction of the burner the burner axis (26) can be changed at right angles or continuously is. Boiler system according to claim 11, characterized in that the Flow level of the injector nozzles (31a, 32a; 34a, 35a) in the area of the Head stage of the burner has an acute angle, and that this Angle in the axial direction of the perforated plates (31, 32; 34, 35) gradually increases until this largely in the area of the exit of the burner perpendicular to the inflow planes (33, 36) of the feed channels (25, 26) and / or to the burner axis (26).

Images