EP1864056B1 - Premix burner for a gas turbine combustion chamber - Google Patents

Description

The invention relates to a premix burner for a combustion chamber of a gas turbine, in particular in a power plant, at least comprising a mixing space limiting housing, an oxidant supply for supplying a gaseous oxidizer in the mixing chamber, a gas fuel supply for supplying a gaseous fuel into the mixing chamber and a liquid fuel supply means for feeding a liquid fuel into the mixing chamber, comprising a centrally disposed burner lance extending from a burner head into the mixing space, and an outlet opening for the exit of the fuel / air mixture.

State of the art

A premix burner of the type mentioned is out EP 0 433 790 known. The known burner has a built-up of several nested shells housing which surrounds a mixing chamber. The staggered arrangement of the half-shells slots for tangentially supplying an oxidizer, in particular combustion air, formed in the mixing chamber. As a result of the tangential incidence of combustion air, a swirling flow is formed in the mixing chamber, which at the burner outlet due to a Cross-sectional jump becomes unstable and merges into an annular swirling flow with a backflow in the core. This backflow allows the stabilization of a flame front downstream of the burner outlet. Within the inlet slots for the combustion air injectors are provided for injecting a gaseous fuel into the combustion air. This injection, in conjunction with the turbulent swirl flow within the mixing chamber, leads to good mixing of the gaseous fuel with the combustion air. Good mixing in such burners is one of the prerequisites for low NO _x emissions during combustion. In addition, the burner is equipped with a central lance for supplying a liquid fuel which extends from the burner head into the mixing chamber. The lance has at its free-standing, axial end an injection port through which the liquid fuel in the mixing chamber and in the combustion chamber arranged downstream of the combustion chamber of a combustion chamber can be injected.

In this burner, the injection of the liquid fuel into the mixing chamber is parallel to the burner axis and the injection of the gaseous fuel into the combustion air parallel to the flow direction. Thus, the characteristic of the injection with respect to penetration depth and mixing of the fuel jets and the fuel distribution along the combustion air inlet slots and the burner axis are given. The arrangement of the outlet openings determines the quality of mixing of fuel and combustion air as well as the fuel distribution at the burner outlet. But these variables have a significant influence on the NO _x emissions and extinguishing limit of the burner and its stability with regard to combustion pulsations. The problem with the operation of premix burners, in particular those in connection with gas turbine plants, is the partial load range, since in this case only comparatively small amounts of fuel are added to the combustion air. In the complete mixing of the fuel with the entire combustion air but creates a mixture, which is just in the lower part load range is no longer flammable or only forms a very unstable flame. This leads to undesirable combustion pulsations or possible extinguishment of the flame.

One way to reduce these adverse effects is to deliver the entire required amount of fuel through the central lance. The burner is then operated at very high air ratios as a diffusion burner. This results in high flame stability on the one hand, but also very high NO _x emissions on the other hand.

A further development of the burner discussed above is the subject of EP 1 292 795 , which discloses a burner that can be operated stably even with changes in load or fuel quality with approximately constant low emission levels. This premix burner comprises a housing composed of a plurality of shells, a mixing space into which combustion air is introduced via tangentially arranged slots, which merges into a swirling flow in the mixing space, means for introducing fuel into the combustion air flow, these means being a first group substantially parallel to the first Burner axis aligned fuel outlet openings for a first fuel and at least a second group comprises substantially aligned parallel to the burner axis fuel outlet openings for a second fuel, wherein the first and the second group are acted upon independently, and these means are preferably arranged in the region of the combustion air inlet slots.

To further increase the flame stability pilot fuel can also be introduced via a lance.

Since the burner can be operated exclusively with liquid fuel, there is the possibility to maintain or repair the gas fuel supply without the operation of the burner or the combustion chamber must be completely interrupted. This is advantageous for the efficiency of the gas turbine equipped therewith. As already mentioned elsewhere, leads but the injection of liquid fuel into the mixing chamber of the burner or in the combustion chamber of the combustion chamber usually to significantly increased flame temperatures, which is due for example to insufficient atomization, mixing and evaporation of the liquid fuel before its ignition. Increased flame temperatures, however, are accompanied by a disproportionately increased production of NO _x emissions and soot. This disadvantage can be reduced somewhat by adding water or water vapor, for example in a quantitative ratio of 1: 1, to the liquid fuel, and thus injecting a fuel / water emulsion into the mixing space instead of the liquid fuel, which leads to a Delays the combustion reaction and leads to a reduction of the local flame temperatures. The disadvantage here again is that the supply of such a diluent increases the heat transfer in the turbine on the hot gas side, which is associated with a reduction in the lifetime of the turbine. Furthermore, there are sites for power plants where water is too precious to use as a diluent. Taking into account also the comparatively short time in which the burner is actually operated with liquid fuel, so on the occasion of maintenance of the gas fuel supply or in pilot operation, the expenses for the treatment of the water, for example, demineralization plants must be provided, too high.

A generic Vormischbrenner is the subject of EP 1 336 800 which is characterized in particular by measures to further reduce thermoacoustic vibrations within the combustion system and thus increased combustion stability. This burner is based on the basic idea of stabilizing by means of fluidic measures the central backflow zone forming downstream of the burner outlet, within which the fuel / air mixture ignites. For this purpose, the relatively far reaching into the mixing chamber central burner lance in its downstream end region with a widening cross section. The lance has outlet openings for preferably liquid fuel and combustion air and the corresponding feed channels for these media. On the one hand, the proximity of the introduction of fuel prevents the risk of the flame from migrating into the mixing space and, on the other hand, this proximity promotes the swirl breakdown of the fuel / air mixture which propagates in the direction of flow, with the result that the backflow zone is stabilized. Different cross-sectional shapes of the end portion of the lance also affect, to varying degrees, the formation of coherent structures. However, the far reaching into the mixing chamber injection of fuel has the disadvantage of a reduced mixing quality of the fuel / air mixture with the already mentioned elsewhere sequence of increased NO _x emissions.

An alternative solution for reducing combustion-driven thermoacoustic vibrations during operation of a generic burner disclosed DE 10164099 , This proposed solution is based on the idea of injecting the fuel in such a way that the delay time between injection of the fuel into the combustion air stream and its combustion in the flame front corresponds to a systematically varying distribution. This is based on the finding that a slightly varying by an average delay time between injection location and combustion promotes the occurrence of such vibrations, since slight fluctuations in the fuel supply, initiated by pressure fluctuations in the combustion system, are able to increase in this way. According to the solution, the central burner lance, which extends far into the mixing chamber, is equipped with a wide range of fuel injections distributed circumferentially over the mantle surface.

According to an older proposal according to US 5307634 is, unlike the aforementioned embodiments, which consists of at least two nested shells housing surrounding the mixing chamber, not conical, but cylindrical. The staggered arrangement of the cylindrical shells here cylindrical forms the slots for tangentially supplying the combustion air into the mixing chamber. Within the mixing chamber, the swirl flow forms, which merges at the burner outlet into an annular swirl flow with a backflow in the core. Within the air inlet slots injectors are provided for injecting gaseous fuel into the combustion air. Starting from the head end of the burner, a conically tapering central body protrudes into the mixing chamber, whose pointed end is provided with outlet openings for the likewise gaseous pilot fuel. This fuel fraction does not participate in the premix. A steady proportion of 4% to 6% of the total fuel is supplied as pilot fuel during burner operation. This share contributes significantly to an increase in NO _x emissions.

Presentation of the invention

The invention aims to remedy this situation. The invention, as characterized in the claims, the object of the invention to provide for a generic burner, an improved embodiment, which is particularly comparatively inexpensive feasible and thereby allows a reduction of NO _x emissions and soot formation.

According to the invention, this object is achieved by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea, in a generic burner according to EP 1336800 providing the lance with at least one pilot injection hole and part of the injection holes of the liquid fuel, the injection holes (14) of the lance (6) being arranged in at least one row parallel to the main discharge direction (9), and a second liquid fuel supply means in the form of one of the oxidizer stream flow around the tube at least predominantly within or upstream of the inlet opening of the housing.

This design distributes the liquid fuel injection to several injection holes, reducing the flow rate at the single injection hole. In this way, the atomization effect of the individual injection holes can be improved. At the same time, this results in improved mixing and improved evaporation of the liquid fuel. The arrangement of the injection holes in series and parallel to the main outflow direction inevitably results in a part of the injection holes being relatively far removed from the outlet opening of the mixing chamber. The liquid fuel injected there has therefore an increased residence time in the mixing chamber, which favors the mixing and evaporation of the fuel. Also particularly advantageous for the mixing and evaporation is the radial component of the main injection direction at the respective injection hole. Because this measure intensifies the mixing and evaporation of the liquid fuel.

The construction according to the invention thus results in a significant improvement in the atomization, the mixing and the evaporation of the liquid fuel. This delays the ignition of the liquid fuel and reduces the risk of locally excessive flame temperatures. As a result, NO _x formation is reduced; In addition, less soot is produced. It is of particular advantage in this case that the described improvement of the emission values can be achieved without the liquid fuel being required for this purpose Water or steam or other diluent would have to be supplied. As a consequence, the burner according to the invention does not require water for operation with liquid fuel. The proportion of water in the liquid fuel (so-called "ω value") is therefore low and is preferably zero. Since no such diluent is needed for the operation of the burner with liquid fuel, corresponding facilities for the preparation of such a diluent accounted for. The cost of implementing such a burner are therefore comparatively low.

By arranging a plurality of fuel injection holes along the at least one tangential inlet opening for the oxidizer, the admixing of the liquid fuel takes place within the tangential inlet opening of the mixing space or immediately upstream thereof. This injection, in conjunction with the turbulent swirl flow within the mixing space, leads to an intensive mixing of fuel and oxidizer. At the same time thereby extends the residence time of the injected liquid fuel, which also improves the mixing and especially the evaporation of the liquid fuel.

By having at least one liquid fuel passage connected to the main supply line for liquid fuel and formed in a tube extending along the at least one tangential inlet port located upstream of the respective inlet port with respect to the oxidant flow, the injection of the liquid fuel is enabled by the second liquid fuel supply device via such a tube an optimal distribution of the injection of the liquid fuel along the respective inlet opening. This also supports the atomization, mixing and evaporation of the liquid fuel.

In a particular development, the said pipe can additionally be used to supply the same to the oxidator stream via the pipe upstream of the respective inlet opening for the operation of the burner with gas fuel. For this purpose, the tube contains at least one gas fuel channel in addition to the liquid fuel channel. The injected at this point gas fuel thus also has a particularly long residence time in the burner, which intensifies the mixing with the Oxidatorstrom. The integration of the liquid fuel channel and the at least one gas fuel channel into a common tube thereby reduces the manufacturing cost of the burner.

Other important features and advantages of the burner according to the invention will become apparent from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

Brief description of the drawings

Fig. 1

einen stark vereinfachten, prinzipiellen Längsschnitt durch einen Brenner nach der Erfindung,

Fig. 2

einen Querschnitt durch den Brenner gemäss Fig. 1 entsprechend Schnittlinien IX - IX,

Fig. 3

einen Querschnitt durch den Brenner gemäss Fig. 1 entsprechend Schnittlinien X - X,

Fig. 4

eine vergrößerte Ansicht auf ein Detail XI aus Fig. 2,

Fig. 5

eine Ansicht auf ein Detail XII aus Fig. 1,

Fig. 6

eine vergrößerte Ansicht auf ein Detail XIII aus Fig. 5.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components. Show, in each case schematically,

Fig. 1

a greatly simplified, fundamental longitudinal section through a burner according to the invention,

Fig. 2

a cross section through the burner according to Fig. 1 according to section lines IX - IX,

Fig. 3

a cross section through the burner according to Fig. 1 according to section lines X - X,

Fig. 4

an enlarged view of a detail XI Fig. 2 .

Fig. 5

a view on a detail XII Fig. 1 .

Fig. 6

an enlarged view of a detail XIII Fig. 5 ,

Ways to carry out the invention

Corresponding Fig. 1 a burner 1 according to the invention comprises a mixing space 3 delimited by a housing 2. The burner 1 also has a burner head 4, which is arranged opposite an outlet opening 5 of the mixing space 3. At the burner head 4, a lance 6 is mounted, which projects centrally into the mixing chamber 3.

According to the FIGS. 2 and 3 the housing 2 is designed in the embodiments shown here so that the mixing chamber 3 has two inlet openings 7 for the oxidizer. These inlet openings 7 are arranged and designed so that forms a tangential inflow and thus a concentric vortex system for the mixing chamber 3. This is achieved here by a half-shell construction of the housing 2, wherein the half-shells are arranged offset in their parting plane with respect to a longitudinal center axis of the housing 2 eccentrically to each other. Furthermore, the housing 2 is formed substantially conically with a cross-section widening towards the outlet opening 5. However, the conical design of the housing 2 is not mandatory. It may also be cylindrical, wherein it is expedient in such an embodiment of the housing 2, a conical to arrange tapered inner body within the mixing chamber 3, as in the cited above EP 1 292 795 is explained in more detail.

The burner 1 is used to supply a combustion chamber, not shown, of a gas turbine, in particular in a power plant, with an oxidizer-fuel mixture. For this purpose, the burner 1 is connected to said combustion chamber, in such a way that the outlet opening 5 opens at a combustion chamber 8 of the combustion chamber. In this case, the oxidizer-fuel mixture at the outlet opening 5 on a main outflow direction 9, which extends parallel to the longitudinal direction of the mixing chamber 3 and which is substantially perpendicular to the outlet opening 5.

The burner 1 is equipped with an oxidant supply device 10, which in the Fig. 1, 2, 3 symbolized by an arrow. The Oxidatorzuführeinrichtung 10 is used for supplying a gaseous oxidizer, usually air, in the mixing chamber 3. The inventive burner 1 is designed for operation with liquid fuel, such as fuel oil. For this purpose, the burner 1 has a first liquid fuel supply device 12, with the aid of which liquid fuel can be introduced into the mixing chamber 3.

This first liquid fuel supply device 12 is equipped with at least one main supply line 13, which supplies the liquid fuel to a plurality of injection holes 14. Through these injection holes 14, the liquid fuel can be introduced into the mixing chamber 3. In this case, the injection holes 14 are arranged or distributed such that at least a plurality of injection holes 14 are arranged with respect to the main outflow direction 9 in at least one row. Furthermore, it is particularly important that the individual injection holes 14 are configured in such a way that a main injection direction 15 of the respective injection hole 14 symbolized here by an arrow has a radial component which extends radially to the main outflow direction 9. When "Main injection direction" is understood to mean that direction which has a spray jet with or without spin on average.

By this structure or by this configuration and arrangement of the injection holes 14 results in a distributed in the longitudinal direction of the mixing chamber 3 arrangement of the injection holes 14. This is to achieve improved atomization, mixing and evaporation of the injected liquid fuel advantage.

The injection holes 14 are formed on the lance 6, whereby the injection of liquid fuel into the swirl flow, which is due to the tangential supply of the oxidizer in the mixing chamber 3, quasi from the inside.

Preferably, the injection holes 14 are arranged in more than one row parallel to the main outflow direction 9, for example in two diametrically opposite rows. According to Fig. 2 lie the injection holes 14, for example, in the parting plane of the two housing halves 2, within which the two housing halves 2 are arranged eccentrically offset from each other and the slot-shaped inlet openings 7 form.

The number of rows of injection holes 14 suitably corresponds to the number of inlet openings 7 of the mixing space 3. In this way, each group of the injection holes 14 can be assigned specifically to an inlet opening 7. However, this is not mandatory. As well, more or less rows of injection holes 17 may be arranged, or the rows may be offset from the inlet opening 7 upstream or downstream.

While the injection holes 14 mounted in two opposite rows, as shown in FIG FIG. 2 are arranged in pairs in the same longitudinal plane, the injection holes of the opposite rows also be offset to each other. In this case, the lined-up injection holes 14 of each row preferably have a uniform spacing from one another.

The liquid fuel supply device 12 is equipped with a pilot supply line 16, by means of which at least one pilot injection hole 17 liquid fuel can be supplied. In contrast to the other injection holes 14, the at least one pilot injection hole 17 is designed such that it has a main injection direction 18, indicated by an arrow, which exclusively has an axial component which extends parallel to the main discharge direction 9. In the pilot operation of the burner 1, liquid fuel can thus be injected into the mixing chamber 3 or directly into the combustion chamber 8 axially, ie, parallel to the main outflow direction 9 with or without swirl.

Corresponding FIG. 1 If appropriate, the injection holes 14 may also be configured such that their respective main injection direction 15 also has an axial component in addition to the radial component, which therefore extends parallel to the main outflow direction 9. In this way, for example, the mixing with the oxidizer flow can be improved.
In addition, the injection holes 14 may also be configured such that the respective main injection direction 15 also has a peripheral component in addition to the radial component. This peripheral component or tangential component extends transversely to the main outflow direction 9 and transversely to the radial component. In this case, this peripheral component is expediently oriented in the direction of rotation of the swirl flow, which forms due to the tangential inflow of the oxidizer in the mixing chamber 3. Also, the perimeter component can help improve the mixing of the liquid fuel with the oxidizer. It is understood that the injection holes 14 may be configured such that the main injection direction 15 has the axial component and the circumferential component cumulatively or alternatively in addition to the radial component.

For the arrangement, positioning and dimensioning of the injection holes 14 and for the orientation of the main injection direction 15, an optimum is advantageously sought, which leads to a particularly good atomization, mixing and evaporation of the liquid fuel in the oxidizer gas. For this purpose, it may in particular also be necessary to design the individual injection holes 14 differently with regard to the hole cross section and / or the main injection direction and / or the mutual spacing in order to be able to optimally adapt each individual injection hole to the locally prevailing flow conditions in the extreme case. Furthermore, it is clear that the injection holes 14 must have a specific ratio of length to diameter in order to be able to represent the respective desired main injection direction clean. It is quite possible that it will be necessary to choose the wall thickness of the lance 6 larger than is the case, for example, in a conventional lance 6 for injecting liquid fuel.

Each inlet opening 7 is associated with a tube 19, see also the FIGS. 2 and 3 , The tubes 19 are arranged inside or with respect to the oxidizer flow upstream of the respective associated inlet opening 7 and extend quasi parallel along the entire respective inlet opening 7. The tubes 19 are expediently not provided with a circular cross-section, but have in adaptation to the space. and flow conditions within or immediately upstream of the inlet port 7 have a long-round, oval or streamline profile.

A gas fuel supply device 11 comprises at least one supply line; In the present case, two supply lines are provided, namely a first supply line 20 and a second supply line 21. With the supply lines 20, 21 can be supplied to several injection holes 22, 23 gas fuel. In this case, first injection holes 22 are supplied by the first supply line 20, while second injection holes 23 are supplied from the second supply line 21. The injection holes 22, 23 are arranged upstream of the respective inlet opening 7 with respect to the oxidizer flow. The respective tube 19 contains at least one gas fuel channel which is connected to the respective supply line 20, 21 and which leads to the respective associated injection holes 22, 23. In the present case, a first gas fuel channel 24 is therefore contained in each tube 19, which communicates the first supply line 20 with the first injection holes 22 in a communicative manner. Correspondingly, each tube 19 also includes a second gas fuel passage 25 communicating the second feed line 21 with the second injection holes 23.

In the embodiments shown here, the first injection holes 22 are arranged in a first longitudinal section of the mixing chamber 3, which is remote from the outlet opening 5 and adjoins the burner head 4, thereby forming a first burner stage. In contrast, the second injection holes 23 are arranged in a second longitudinal section of the mixing chamber 3 adjoining the outlet opening 5 and thereby form a second burner stage, which is arranged downstream of the first burner stage with respect to the main outflow direction 9. About the separate supply lines 20, 21, the two burner stages can be controlled independently. In that regard, it is in the embodiment of the Fig. 1 around a two-stage burner 1.

Within each tube 19, both the first group of injection holes 22 and the second group of injection holes 23 are individually arranged in at least one row, which extend substantially along the respective inlet opening 7.

The tube 19 additionally includes a liquid fuel channel 26 which extends parallel to the gas fuel channels 24, 25. The liquid fuel channel 26 establishes a communicating connection between the main supply pipe 13 and the injection holes 14. The integration of the injection holes 14 in the tube 19 results in a particularly simple structure for the burner 1, which can be operated both with gaseous fuel and with liquid fuel. At the same time results in this type of injection of the liquid fuel a particularly long residence time for the liquid fuel in the mixing chamber 3, whereby the atomization, mixing and evaporation of the liquid fuel is improved.

It will be appreciated that in another embodiment, the at least one tube 19 may contain only the liquid fuel channel 26, wherein then the introduction of the gas fuel may be carried out by means of a separate tube or in any other suitable manner.

Corresponding FIG. 4 the tube 19 has a dreikammerigen structure in the region of the first gas fuel channel 24, wherein each chamber forms one of the channels 24, 25, 26. The cut for the presentation according to Fig. 4 is selected such that a pair of opposite first injection holes 22 communicating with the first gas fuel channel 24, a pair of opposite second injection holes 23 communicating with the second gas fuel channel 25 and a plurality of injection holes 14 communicating with the liquid fuel channel 26 can be seen ,

In this case, it can be seen that in each case a plurality of injection holes 14 are again combined into groups, which are each arranged one behind the other in a row parallel to the main outflow direction 9. In this case, all of the injection holes 14 are each designed such that their respective main injection direction 15 has a radial component with respect to the main outflow direction 9 of the burner 1. In addition, a plurality of injection holes 14 are arranged along a trailing edge of the tube 19 and thereby configured such that their respective main injection direction 15 runs parallel to a main inflow direction of the burner 1. This Haupteinströmrichtung is symbolized in Fig. 11 by an arrow and denoted by 27. The main inflow direction 27 has the oxidizer flow flowing into the mixing chamber 3 at the respective inlet opening 7. In addition, here two rows of injection holes 14 are provided, each of which is designed so that their respective main injection direction 15 with respect to the main inflow 27 has a transverse component. In this way, the injection takes place directly into the oxidizer flow, which flows around the tube 19 and enters the mixing chamber 3 downstream of the tube 19 through the inlet opening 7.

According to the FIGS. 5 and 6 the injection holes 14 and the second injection holes 23 formed on the same side of the tube 19 are offset relative to each other with respect to the main discharge direction 9 so as to avoid mutual overlap. The same applies expediently also for the relative position between the injection holes 14 and the first injection holes 22. The staggered arrangement can be avoided, for example, that an ignitable mixture passes through the injection holes 14 in the liquid fuel supply 12 during operation of the burner 1 with gas fuel.

LIST OF REFERENCE NUMBERS

1

burner

2

casing

3

mixing room

4

burner head

5

outlet

6

lance

7

inlet port

8th

combustion chamber

9

Hauptausströmrichtung

10

Oxidatorzuführeinrichtung

11

Gasbrennstoffzuführeinrichtung

12

first liquid fuel supply device

13

main supply

14

Injection hole

15

Hautpeinspritzrichtung

16

Pilotzuführleitung

17

Pilot injection hole

18

Main outflow direction of 17

19

pipe

20

first supply line

21

second supply line

22

first injection hole

23

second injection hole

24

first gas fuel channel

25

second gas fuel channel

26

Liquid fuel passage

27

main inflow

Claims (13)

1. Premix burner for a combustion chamber of a gas turbine, comprising

   - a housing (2) for defining a mixer chamber (3) for premixing an oxidator with a gaseous fuel and/or liquid fuel,

   - an oxidator feed device (10) for feeding the oxidator into the mixer chamber (3), which has at least one inlet opening (7), which is designed and arranged so that the oxidator which is fed through this at least one inlet opening (7) to the mixer chamber (3) flows basically tangentially into the mixer chamber (3),

   - a gaseous fuel feed device (11) for feeding the gaseous fuel into the mixer chamber (3),

   - a first liquid fuel feed device (12) for feeding the liquid fuel into the mixer chamber (3), comprising a centrally arranged lance (6) which extends from a burner head (4) into the mixer chamber (3),

   - an outlet opening (5) of the housing (2) for discharge of the oxidator-fuel mixture from the mixer chamber (3) into the combustion chamber,

   wherein the first liquid fuel feed device (12) has a main feed line (13) with more than one injection orifice (14) for liquid fuel, and at least the predominant part of the injection orifices, or all of these injection orifices (14), are designed so that a main injection direction (15) of the respective injection orifice (14) has a radial component which extends perpendicularly to a main outflow direction (9) of the burner, wherein the main outflow direction (9) of the burner is to be understood as a direction of the oxidator-fuel mixture, which flows from the mixer chamber (3), at the outlet opening (5) of the mixer chamber (3), characterized in that the lance (6) has at least one pilot injection orifice (17) and some of the injection orifices (14), wherein the injection orifices (14) of the lance (6) are arranged in at least one row parallel to the main outflow direction (9), and in that a second liquid fuel feed device is arranged in the form of a tube (19) which is flow-washed around by the oxidator flow at least for the most part inside or upstream of the inlet opening (7) of the housing (2).
2. Premix burner according to Claim 1, characterized in that

   - a first number of these injection orifices (14) are arranged along a first row parallel to the main outflow direction (9),

   - a second number of these injection orifices (14) are arranged along a second row parallel to the main outflow direction (9), and

   - the two rows of injection orifices (14) of the first liquid fuel feed device (12) lie diametrically opposite each other.
3. Premix burner according to one of Claims 1 and 2, characterized in that

   - the injection orifices (14) are at least for the most part designed so that the main injection direction (15) of the respective injection orifice (14) additionally has an axial component in the direction of the main outflow direction (9), and/or

   - the injection orifices (14) are at least for the most part designed so that the main injection direction (15) of the respective injection orifice (14) additionally has a tangential component in a swirl direction in the mixer chamber (3).
4. Premix burner according to Claim 1, characterized in that

   - the lance (6) is equipped with a main feed line (13) and a pilot feed line (16),

   - the pilot feed line (16) feeds a pilot injection orifice (17) which is arranged on the free end of the lance (6), and its main injection direction (18) is oriented parallel to the main outflow direction (9),

   - the main feed line (13) feeds at least one row of injection orifices (14) which extend parallel to the main outflow direction (18) over the generated surface of the lance (6), and the main injection direction (15) of which has a radial component.
5. Premix burner according to Claim 4, characterized in that the lance (6) has two diametrically opposite rows of injection orifices (14).
6. Premix burner according to Claim 4 or 5, characterized in that the injection orifices (14) have a main injection direction (15) with a radial component and with an axial component and/or a tangential component.
7. Premix burner according to Claim 1, characterized in that the tube (19) has an oval-shaped cross sectional form.
8. Premix burner according to Claim 1, characterized in that

   - a number of the injection orifices (14) are designed so that a main injection direction (15) of the respective injection orifice (14) extends parallel to the main inflow direction (27) of the oxidator flow which flows into the mixer chamber (3), and/or

   - a number of the injection orifices (14) are designed so that a main injection direction (15) of the respective injection orifice (14) has a transverse component which extends at least approximately perpendicularly to the main inflow direction (27) of the oxidator flow in the inlet opening (7).
9. Premix burner according to Claim 1, characterized in that the tube (19) has at least one liquid fuel passage (26) which feeds a plurality of injection orifices (14) of the liquid fuel feed device (12).
10. Premix burner according to Claim 9, characterized in that at least one gaseous fuel passage (24, 25), which feeds injection orifices (22, 23) and which is connected to at least one feed line (20, 21) for the gaseous fuel, is formed in the tube (19) parallel to the liquid fuel passage (26).
11. Premix burner according to Claim 10, characterized in that

    - a first gaseous fuel passage (24), which is connected to a first feed line (20) and which feeds a first group of injection orifices (22) with gaseous fuel, is formed in the tube (19) parallel to the liquid fuel passage (26),

    - a second gaseous fuel passage (25), which is connected to a second feed line (21) and which feeds a second group of injection orifices (23) with gaseous fuel, is formed in the tube (19) parallel to the liquid fuel passage (26).
12. Premix burner according to Claim 11, characterized in that the second group of injection orifices (23) is arranged downstream of the first group of injection orifices (22) with regard to the main outflow direction (9).
13. Premix burner according to Claim 12, characterized in that the two groups of injection orifices (22, 23) are arranged in at least one row on the generated surface of the tube (19).

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