EP2161502A1 - Pre-mix burner for a low calorie and high calorie fuel - Google Patents

Abstract

The burner (1b) has a premixing air duct extending along a burner axis, where combustion air is supplied through the duct. A swirl device (5) e.g. swirl vane, is arranged in the duct. The device injects high calorific fuel e.g. natural gas, into the duct via an inlet stage including an inlet opening. The swirl device includes another inlet stage including an inlet opening i.e. borehole, for injecting low calorific fuel e.g. synthesis gas. A distributor opening i.e. distributor borehole (27), is formed with a trapezoidal surface area, where the surface area includes roundings at two sides.

Description

The invention relates to a premix burner for combustion of a low calorific fuel, in particular a synthesis gas and a high calorie fuel.

In view of the global efforts to reduce the pollutant emissions of combustion plants, especially in gas turbines, burners and operating methods for burners have been developed in recent years, which have particularly low emissions of nitrogen oxides (NO _X ). It is often emphasized that such burners are not only with a fuel, but possibly with different fuels, such as oil, natural gas and / or low calorific fuel, which is also referred to as syngas, either or even in combination operable to to increase security of supply and flexibility of operation.

Synthesis gas burners are characterized by the fact that synthesis gases are used as fuel in them. Compared with the traditional gas turbine fuels natural gas and petroleum, which consist essentially of hydrocarbon compounds, the combustible constituents of synthesis gas are essentially carbon monoxide and hydrogen. For selectively operating a gas turbine with syngas from a gasifier and a secondary or substitute fuel, the burner in the gas turbine associated combustion chamber must then be designed as a two- or multi-fuel burner, both with the synthesis gas and with the second fuel, such as natural gas or fuel oil can be applied as needed. The respective fuel is supplied via a fuel passage in the burner of the combustion zone.

Depending on the gasification process and overall plant concept, the calorific value of the synthesis gas is about five to ten times smaller compared to the calorific value of natural gas. Main constituent in addition to CO and H ₂ are inert components such as nitrogen and / or water vapor and possibly also carbon dioxide. Due to the low calorific value consequently high volume flows of fuel, that is, for example, larger Eindüsequerschnitte must be supplied through the burner of the combustion chamber. As a result, one or more separate fuel passages must be made available for the combustion of low calorific fuels, such as synthesis gas.

However, diffusion burners designed as synthesis gas burners can not meet the increasing demands on the exhaust gas emissions of gas turbines, even in synthesis gas operation. One requirement, for example, is to get along with as little dilution as possible for the fuel in the synthesis gas operation.

In view of increasingly stringent requirements on the emission of nitrogen oxides, premix combustion is becoming increasingly important also in the combustion of low calorific gases.

Premix burners typically include a premix zone in which air and fuel are mixed before passing the mixture into a combustion chamber. The introduced into the combustion chamber air mass flow is typically twisted by means of a swirl device. In this twisted air mass flow of high-calorie fuel is injected via one or more juxtaposed or successively arranged circular rows of holes in the twisting device.

There, the mixture burns, producing a hot gas. This hot gas is forwarded to the turbine. In connection with the operation of premix burners, it is particularly important to keep the nitrogen oxide emissions low and to avoid a flashback. In the case of premix combustion can the formation of follow-up areas or Heißgasrückströmgebieten within the burner, for example, reduced by suitable shaping of Eindüsbohrungen, but not avoided in principle.

Such as premix burner designed synthesis gas burners are for example in the EP 1 645 807 A1 and in the EP 1 723 369 B1 disclosed.

With regard to nitrogen oxide minimization, it is customary in particular to add inert mass streams as dilution medium into the air mass flow or the fuel mass flow. The use of lean premix technology enables the reduction in the amount of diluent used, increasing plant economics. Due to the then missing inertization but then there is a highly reactive fuel.

In order to ensure a safe premixing operation, flow separation or a backflow region within the premixing zone of the burner must be avoided at all costs. But at least potential return flow areas are to be designed in such a way that no damage to the burner takes place. As a rule, the backflow areas occur in near-wall zones in the wake of the fuel gas jets.

The object of the present invention is to provide an advantageous premix burner which enables safe operation of high-calorie and low-calorie fuel.

The object is achieved by a premix burner for combustion of a low calorific (SG) and high calorific fuel (NG), with a along a burner axis extending premix air duct on the combustion air can be fed and arranged with a arranged in the premix air duct swirl device from the hochkalorischer Fuel via an inlet stage comprising at least an inlet opening into which the premixing channel can be injected, wherein the swirling device comprises at least one further inlet stage, comprising at least one inlet inlet for low calorific fuel (SG).

The swirl device is referred to below as a swirl blade. But it can also be understood as other spin-producing means.

For the first time, a targeted radial fuel distribution into an axial or diagonal flow channel becomes possible with the premix burner of the invention. It is thus possible to keep the fuel away from the channel walls of the premix channel, which can serve as potential ignition ranges. This avoids the risk of flashback in boundary layers. Additional air-side pressure loss through separation areas behind the fuel jets is largely prevented in the premix burner according to the invention.

In a preferred embodiment, a distributor opening, in particular distributor bore, is present. As a result of this, the low-calorie fuel, in particular the synthesis gas, flows to the inlet openings and is thus injected into the premixing channel.

Preferably, the distribution opening has a substantially trapezoidal base. This causes a low pressure loss and a more uniform fuel distribution. In a preferred embodiment, the base further has rounded portions on both sides. Also, the base may have semicircles, in particular etched semicircles. The fillets are preferably radii or semicircles. The trapezoidal base surface is particularly advantageous, since the approximately parallelism of the wall of the distributor opening hereinafter referred to as distributor hole, and the surface of the swirl device so the swirl blade, resulting in approximately equal opening lengths for the inlet openings. As a result, the resistance coefficient of the openings is approximate same, and this results in a very uniform fuel distribution. This is especially the case when all inlet opening diameters have the same diameter.

Preferably, the distributor opening, in particular therefore the distributor bore, has a slot shape or an oval shape. This is particularly advantageous in order to achieve the largest possible area for the distributor bore, without falling below the minimum required wall thickness.

In a preferred embodiment, the at least one inlet opening is a bore. This is manufacturing technology particularly easy to implement.

Preferably, at least two inlet openings are present, wherein the at least two inlet openings form an axial (that is to say in blade height) inlet opening row (RW1). Preferably, at least two rows of inlet openings (RW1, RW2) are present, which are arranged offset to one another. Alternatively or additionally (depending on the row number), the inlet opening rows can also be arranged in parallel. This may depend on the configuration of the swirl device, in particular swirl blade. Also, multiple rows of intake ports (RW1, ..., RWn) may be present. For an odd number of rows, about three rows (RW1, RW2, RW3), e.g. Also, the second row RW2 to the first row RW1 and the third row RW3 be offset, while the first row RW1 and the third row RW3 are arranged in parallel or in a row. For example, all three rows RW1, RW2, RW3 can also be arranged offset from one another / parallel to one another. The distance between the individual rows should preferably comprise at least one bore diameter. The inlet opening rows can each have a different number of inlet openings.

In a preferred embodiment, the at least two rows of inlet openings (RW1, RW2) have the same inlet opening diameters (∅RW1, ∅ RW2) of the inlet ports. If the inlet opening lengths of the inlet openings are also approximately the same, this results in an approximately equal coefficient of resistance of the inlet openings, and thus also a very uniform fuel distribution.

The at least two rows of inlet openings (RW1, RW2) are preferably designed with different inlet opening diameters (∅RW1, ∅ RW2) of the inlet openings. Fuel jets with a larger diameter have a greater penetration depth. This can preferably be provided for a uniform distribution on the circumference, since thus a different penetration depth of the fuel jets is achieved.

In a preferred embodiment, the ratio of the area of the inlet openings to the area of the distributor opening, in particular the distributor bore, is 1: 4. This is particularly advantageous because of the large mass flows required for the low calorific fuel, in particular synthesis gas. The lower limit here is a ratio of the area of the inlet openings to the area of the distributor opening, in particular the distributor hole 1: 1. However, at such a ratio, it is desirable that the inlet ports have a different size axially (that is, at blade height). This counteracts an uneven distribution of the fuel due to the ratio 1: 1.

The distributor opening, in particular the distributor bore, preferably has an inlet mouth. This has the advantage that the flow is evened over a longer distance and especially separation zones, which can form at the inlet, do not extend to the inlet openings.

In a preferred embodiment, the inlet mouth into the distributor opening, in particular the distributor bore into it. This means that the Rückströmgebiete that start at the inlet mouth, away from the first inlet openings.

The entry plane for the fuel into the distribution well is thus artificially shifted further away from the inlet ports, into the distribution well.

Preferably, the area of the distributor opening, in particular of the distributor bore, is reduced in the flow direction. Thus, the flow rate is changed, in particular kept the same, so that a better uniform distribution of the fuel is achieved. Furthermore, thus secondary flows can be suppressed.

FIG 1a

einen Längsschnitt durch einen Vormischbrenner nach dem Stand der Technik,

FIG 1b

einen Längsschnitt durch einen Vormischbrenner gemäß der Erfindung,

FIG 2

einen erfindungsgemäßer Vormischbrenner mit Verteilerbohrungen für hoch- und niederkalorischen Brennstoff,

FIG 3

eine Drallschaufel mit Einlassöffnungen für niederkalorischen Brennstoff,

FIG 4

Eindüsungsöffnungen und Verteilerbohrung für hoch- und niederkalorischen Brennstoff in der Drallschaufel,

FIG 5

eine Drallschaufel mit Einlaufmündung für niederkalorischen Brennstoff und Verteilerbohrung (schematisch),

FIG 6

verschiedene Muster der Eindüsungsöffnungen.

Further features, properties and advantages of the present invention will be described below by means of an embodiment with reference to the accompanying figures. Showing:

FIG. 1a

a longitudinal section through a Vormischbrenner according to the prior art,

FIG. 1b

a longitudinal section through a premix burner according to the invention,

FIG. 2

an inventive premix burner with distributor bores for high and low calorific fuel,

FIG. 3

a swirl vane with low calorie fuel inlet ports,

FIG. 4

Injection holes and distributor hole for high and low calorific fuel in the swirl blade,

FIG. 5

a swirl bucket with inlet mouth for low calorific fuel and distribution well (schematic),

FIG. 6

different patterns of injection ports.

FIG. 1a shows a premix burner 1a according to the prior art, which is approximately rotationally symmetrical with respect to a burner axis 12. A directed along the burner axis 12 pilot burner 9 with a fuel supply channel 8 and a concentrically enclosing this air supply annular channel 7 is concentrically surrounded by a fuel ring channel 3. This fuel ring channel 3 is partially concentrically enclosed by a premixed air channel 2. Der premix air duct 2 is designed as an annular channel 14, which has an outer channel wall 15. The central axis 12 facing side of the premixing channel 2 is hereinafter referred to as the hub-side channel wall 16.

In this premix air duct 2 a - shown schematically - ring of swirl vanes 5 is installed, which forms a swirl device. Preferably, at least one of these swirl blades 5 is formed as a hollow blade 5a. It has an inlet formed by a plurality of small openings 6 for a fuel supply ( FIG. 1a ) on. The inlet openings 6 is connected to the fuel channel 3. The hollow blade 5a is designed for the supply of high-calorie fuel 11, for example natural gas or fuel oil. The fuel ring channel 3 opens into this hollow blade 5a.

The premix burner 1a can be operated via the pilot burner 9 as a diffusion burner. Usually, however, it is used as a premix burner, that is, fuel and air are first mixed and then sent to combustion. The pilot burner 9 serves to maintain a pilot flame, which stabilizes the combustion during premix burner operation with a possibly changing fuel-air ratio.

In the combustion of high calorie fuel 11, i. e.g. Natural gas or fuel oil, combustion air 10 and the high-calorie fuel 11 are mixed in the premixed air channel 2 and then fed to the combustion. In the exemplary embodiment shown here, the high-calorie fuel 11 is conducted from the fuel ring channel 3 into a hollow blade 5a of the swirl vane ring 5 and from there via which the inlet opening 6 is introduced into the combustion air 10 in the premix air channel 2.

In the premix burner 1b of the invention ( FIG. 1b ) is also the combustion of a low calorific fuel SG, for example, a synthesis gas from a coal gasification process, possible. For this purpose, a further injection stage comprising at least one, but preferably a plurality of inlet openings 40, designed here as a bore 40, is provided in the swirl blade 5, 5 a. The injection via further inlet openings 40 on the swirl blade 5, 5 a enables a radial fuel distribution in an axial or diagonal flow channel. This makes it possible to keep the fuel from the endangered channel walls, which can serve as a potential Zündungsbereich. The inlet openings 40 are connected to a gas distribution ring 17 via a distributor opening, hereinafter referred to as a distributor bore 27, which surrounds the premixed air channel 2 at least partially radially outwardly.

The distribution bore 27 for synthesis gas has a substantially trapezoidal base ( fig2 and fig3 ). As a result, the fuel-side pressure loss is kept small and provided a uniform fuel distribution. A trapezoidal base with rounding, for example radii or semicircles, on both sides is particularly advantageous. The trapezoidal base is particularly advantageous because approximately equal bore lengths for the fuel bores 40 are provided by the approximate parallelism of the wall of the manifold bores 27 and the blade surface. As a result, the resistance coefficient of the holes 40 is approximately equal and thus the fuel distribution is very uniform. This is especially true when the fuel holes 40 are made with the same bore diameter. The distributor bore 27 has a slot shape 42 (FIG. fig2 and fig3 ), through which the synthesis gas is supplied to the inlet ports 40 at the swirl vanes 5, 5a. This has the advantage of achieving the largest possible area for the distributor bore 27, without falling below the minimum wall thickness required.

The injection stage of the swirl blade 5 for high-calorie and low-calorie fuel consists of several inlet openings 6 and 40. The inlet openings 6 are shown below for the injection of high-calorie fuel, in particular natural gas. The inlet openings 6 are-as described above-supplied with fuel from the fuel channel 3. Within the blade 5, 5a, a bore 50, which in particular has a round cross-sectional area ( FIG. 2 and FIG. 4 ) and which is separate from the distribution bore 27 made. In the following, certain features will be described only for the synthesis gas inlet port 40 and the manifold bore 27. However, they may nevertheless be applied to the corresponding high calorific fuel inlet port 6 and bore 50 as well. These inlet openings 40 can thereby different patterns for the injection (see. FIG. 3 and FIG. 6 ) and also have different diameters for the inlet openings. The inlet openings 40 for low calorific fuel are arranged in an axial row RW1. Preferably, a plurality of axial rows RW1 and RW2 are present. The axial rows RW1 and RW2 can be arranged either offset from each other or parallel or in a row. With an odd number of rows, for example, RW1, RW2, RW3, the second row RW2 may also be offset from the first row RW1 and third row RW3 while the first row RW1 and the third row RW3 are arranged in parallel or in a row. For example, all three rows RW1, RW2, RW3 can also be arranged offset from each other. Such patterns are for example in FIG6 in Examples 1 (Var1) to 6 (Var 6). The distance between the individual rows should preferably comprise at least one bore diameter.

If the bore diameter (∅RW1, ∅ RW2) of the inlet openings 40 of, for example, two rows (RW1, RW2) is the same, this is particularly advantageous if the holes 40 have the same bore length. Thus, namely, the resistance value of the holes 40 is approximately equal and the fuel distribution is very uniform.

The bore diameter (∅ RW1, ∅ RW2) of the inlet openings 40 of, for example, two rows (RW1, RW2) may also be different, since fuel jets having a larger hydraulic diameter have a greater penetration depth. Thus, this can be used to achieve an even distribution at the periphery by means of different penetration depth of the fuel jets.

Of course, the bore diameter (∅ RW1) of the inlet ports 40 of a single row can also be adjusted to the characteristics / physical characteristics of the individual premix burner 1b.

For the ratio of the surfaces of the fuel bores 40 to the distributor bore 27, a ratio of 1: 4 is desirable due to the mass flows for the synthesis gas. As a lower limit for the ratio of the surfaces of the fuel bores 40 to the distributor opening, in particular the distributor bore 27, a ratio of 1: 1 is to be achieved. To distribute the fuel equally at this ratio, it is further advantageous to make the fuel bores 40 axially different in size.

The surface of the distributor bore 27 may decrease with increasing distance from entry of the low calorie fuel, that is to say in the flow direction. Thus, a better uniform distribution of the fuel is achieved. Furthermore, it is thus possible in particular to suppress secondary flows. For further suppression of secondary flows, the distributor bore 27 can be subdivided into two sub-channels from about half of the distributor height (not shown). This can be done for example by means of a separating plate.

The introduction of an inlet mouth 45 to the distributor bore 27 has proved to be advantageous ( FIG. 5 ). The inlet opening 45 causes the flow to be evened out over a longer distance, and in particular to detachment zones, which can form at an inlet, does not extend to the holes 40. The inlet plane, that is to say the plane at which the fuel enters the distributor bore 27, is thus artificially displaced away from the inlet openings 40.

With the here disclosed premix burner for synthesis gas and natural gas (low and high calorific fuel) is a targeted radial fuel distribution in an axial or diagonal flow channel possible for the first time. It is thus possible to keep the fuel away from the channel walls of the premix channel, which may serve as a potential firing range. This avoids the risk of flashback in wall boundary layers. The pressure loss is largely prevented in the premix burner according to the invention. Due to the configuration of the fuel holes and the distributor bore a uniform fuel distribution is largely ensured. In the case of the premix burner exemplified here, moreover, the inlet openings for low-calorie combustible gas are farther from the outer channel wall and the hub-side channel wall than the inlet openings for high-calorie fuel gas. This also reduces, for example, the flashback or the inflammation of areas near the channel walls. Different patterns for inlet openings are also provided according to the invention.

Claims (22)

Premix burner (1b) for combustion of a low calorific (SG) and high calorific fuel (NG) with a along a burner axis (12) extending premixed air duct (2) can be fed via the combustion air (10) and with a in the premix air duct ( 2) arranged swirling device (5) from the high-calorie fuel (11) via an inlet stage comprising at least one inlet opening (6), in the premixing channel (2) is injectable characterized in that the swirling means (5) at least one further inlet stage comprising at least an inlet port (40) for low calorific fuel (SG). Premix burner (1b) according to claim 1,
characterized in that a distributor opening, in particular a distributor bore (27) is present. Premix burner (1b) according to one of the preceding claims, characterized in that that the distributor opening, in particular the distributor bore (27) has a substantially trapezoidal base. Premix burner (1b) according to claim 3,
characterized in that the base has rounded portions on both sides. Premix burner (1b) according to claim 3 or 4, characterized in that the base has semicircles, in particular etched semicircles. Premix burner (1b) according to one of claims 1-4,
characterized in that the distributor opening, in particular the distributor bore (27) has a slot shape. Premix burner (1b) according to one of the preceding claims, characterized in that the at least one inlet opening (40) is a bore. Premix burner (1b) according to one of the preceding claims, characterized in that the at least one inlet opening (40) comprises a slot shape. Premix burner (1b) according to one of the preceding claims, characterized in that the at least one inlet opening (40) comprises an oval shape. Premix burner (1b) according to one of the preceding claims, characterized in that at least two inlet openings (40) are present, and the at least two inlet openings (40) form an axial inlet opening row (RW1) relative to the height of the swirl device (5). Premix burner (1b) according to claim 10,
characterized in that at least two rows of inlet openings (RW1, RW2) are present, which are arranged offset to one another. Premix burner (1b) according to claim 10 or 11,
characterized in that at least two rows of inlet openings (RW1, RW2) are present, which are arranged parallel to one another. Premix burner (1b) according to one of claims 9-12,
characterized in that the at least two rows of inlet openings (RW1, RW2) are designed with equal inlet opening diameters (∅RW1, ∅ RW2) of the inlet openings (40). Premix burner (1b) according to one of claims 9-12,
characterized in that the at least two rows of inlet openings (RW1, RW2) are designed with different inlet opening diameters (∅RW1, ∅ RW2) of the inlet openings (40). Premix burner (1b) according to one of the preceding claims, characterized in that the ratio of the area of the inlet openings (40) to the area of the distributor opening, in particular the distributor bore (27), is 1: 4. Premix burner (1b) according to claim 15,
characterized in that as a lower limit, the ratio of the area of the inlet openings (40) to the area of the distributor opening, in particular of the distributor bore (27), is 1: 1. Premix burner (1b) according to one of the preceding claims, characterized in that that the distributor opening, in particular the distributor bore (27) has an inlet mouth (45). Premix burner (1b) according to claim 17,
characterized in that that the inlet mouth (45) into the distribution opening, in particular in the distributor bore (27) has. Premix burner (1b) according to one of the preceding claims, characterized in that a hub side (16) and an outer channel wall (15) are included. Premix burner (1b) according to claim 19,
characterized in that that a fuel supply to the distributor opening, in particular distributor bore (27) of the hub-side channel wall (16) or the outer channel wall side (15) is present. Premixing burner (1b) according to one of the preceding claims, characterized in that the area of the distributor opening, in particular of the distributor bore (27), is reduced in the flow direction. Gas turbine with a premix burner (1b) according to one of the preceding claims.

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