DE3000672A1 - GAS TURBINE BURNER AND OPERATING METHOD - Google Patents

Description

Gas turbine burners and operating procedures

The invention relates to a burner and a burner assembly for a stationary gas turbine and a method for operating the same.

In recent years, gas turbine manufacturers have increasingly had to deal with pollutant emissions. The emissions of nitrogen oxides (NO) were of particular importance because these oxides are a precursor to air pollution are.

It is known that the formation of nitrogen oxides increases with increasing flame temperature and with increasing residence time. It is therefore theoretically possible to reduce nitrogen oxide emissions by adjusting the flame temperature and / or the time that the reacting gases remain at the peak temperatures can be reduced. In practice it is however, because of the vortex diffusion flame properties

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difficult to achieve by modern gas turbine burners. In such burners the combustion takes place in a thin, evaporating droplet of liquid fuel surrounding layer at a fuel / air equivalence ratio close to unity regardless of the equivalence ratio of the entire reaction zone. Since this is the state which leads to the highest flame temperature, relatively large amounts of nitric oxide are produced. Consequently can with the traditional single-stage atomizing fuel nozzle burners the recently issued emission regulations are not complied with, regardless how lean the nominal equivalence ratio of the reaction zone is.

It is known that the injection of substantial amounts of water or steam thus reduces nitric oxide production can that the requirements of a low nitrogen oxide emission can be met with the conventional burners can. However, this injection also has many disadvantages, including an increase in system complexity, an increase the operating costs due to the need for water treatment and the deterioration of other performance parameters.

Attempts to achieve a homogeneous lean reaction zone by external pre-evaporation and pre-mixing of fuel and air with lean equivalence ratios have led to limited useful results. These designs are typically for clean, very volatile fuels such as gasoline, jet fuel, etc., for a regenerative cycle (increased burner inlet temperature) and at reduced pressures (less than 10.1 bar (10 atmospheres)) been used. In addition to the increase in complexity, a major disadvantage of this solution is the risk of self-ignition

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and a flair setback. At a pressure of 10.1 bar (10 atmospheres) is the residence time required for distillate fuel to completely evaporate, and the time to self-ignition is almost the same, see e.g. the ASME preprint 77-GT-69.

The problem of reducing nitrogen oxide emissions adds further complexity when it is necessary to comply with other combustion design criteria. These criteria include good ignition properties, good cross-firing ability, Stability over the entire load range, a large percentage minimum throughput, a low traverse number, long life and the ability to work safely.

Some of the factors that lead to the formation of nitrogen oxides from fuel nitrogen and atmospheric nitrogen are known and efforts have been made to adapt various burner operations to these factors, cf. E.g. the US-PSs 3 958 416, 3 958 413 and 3 946 553. However, the methods used so far are either not adaptable for use in a burner for a stationary gas turbine or for the reasons given below not suitable.

The object of the invention is to provide a new two-stage combustion system with two modes of operation for a gas turbine that contribute to the entire gas turbine cycle Flame temperatures works at which when using various gaseous and distillate fuels the Pollutant emissions are significantly reduced to acceptable levels.

Two embodiments of the invention are described below

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described in more detail with reference to the accompanying drawings. It shows

1 shows a schematic cross section of a first embodiment of the invention,

2 shows a schematic cross section of a second embodiment of the invention,

Fig. 3 is a schematic representation of three burners according to the invention, which is a high-load ignition system have and

Fig. 4 is a diagram showing the fuel supply during operation the burner shows as a function of time.

The invention relates to a burner for a stationary gas turbine and, for example, to an arrangement of burners as well as a method for operating them, to reduce nitrogen oxide emissions. In particular, the burner has two combustion chambers that have a neck part are connected to each other, separate fuel inlet devices for each section and means for regulating the fuel supply to each fuel injector relative to the others. In the event that a flameout occurs, the burners are equipped with a high-load ignition system provided by every first section from adjacent burners and every other section from adjacent Burners are connected to one another by cross-ignition tubes. The burner is operated by first using fuel is only introduced into the first section and burned therein. Subsequently, the fuel supply switched to the second section until the combustion

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nen stops in the first section, whereupon the fuel distribution it is switched back to the first section for mixing purposes until the desired nitrogen oxide reduction is achieved has been achieved.

According to FIGS. 1 and 2, the burner 1 according to the invention has a total of a first combustion zone or section 2, which is connected to a throat or throat section or zone 3, which in turn is connected to a second combustion zone or section 4.

The first combustion zone 2 can be of conventional lean burn design be, in which a single, preferably axially symmetrical fuel nozzle 5 is used. The second combustion zone 4 is supplied with fuel from a plurality of fuel nozzles 6. In Figs. 1 and 2 there are four radial nozzles are shown arranged symmetrically on the burner circumference, but any number of nozzles can be used if necessary to be used. Air from the gas turbine compressor (not shown) is fed into the burner at elevated pressure, typically from about 10.1 to 30.4 bar (10-30 atmospheres). For example, the air can have one or more Air inlet openings 7, 7 'are introduced. The openings 7, which are located in the first combustion zone 2, are preferably arranged so that they cause a flow circulation that leads to stable combustion in a wide range of operations. Precautions are taken to avoid the products of combustion in Zone 4 to cool quickly with a suitable heat exchange fluid. For example, quenching air can enter zone 4 over several Holes 8 are embedded. The amount of heat exchange fluid used is sufficient to cool the combustion products so that the fluid temperature is at the desired one Gas turbine combustion temperature is reduced.

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The zones 2, 3 and 4 are preferably circular Cross-section, however, any desired configuration can be used. The building material can be metal or ceramic and the zones can be surface-cooled by various methods, for example by Water cooling, through cooling in a closed system, through steam film cooling and through conventional air film cooling. A usable arrangement of rows of rings of schematically spaced baffles longitudinally the zone walls for generating an air film cooling is for example in US Pat. No. 3,777,484, while a useful arrangement of slot cooling, for example in U.S. Patent 3,728,039.

It can be seen that the neck or the constriction 3 as an aerodynamic separator or isolator between the first combustion zone 2 and the second combustion zone 4 In order for the neck 3 to perform this function properly, it must have a sufficiently reduced diameter with respect to the first zone 2 and the second zone 4. Generally a ratio of the diameter the first combustion zone 2 or the second combustion zone 4, whichever is smaller, to the diameter of neck zone 3 of at least 1.2: 1, and preferably at least about 1.5: 1. To facilitate a smooth The transition between the first combustion zone 2 and the neck 3 is made by the part located furthest downstream 2a of zone 2 has a uniformly decreasing diameter, i.e. a conical cross-section. The length of the neck 3 in the direction of its longitudinal axis is not critical and any length that the separating function as well as the throttling function of the neck 3 can be used. In general, the length of the first combustion zone 2 is in the direction of the longitudinal axis at least about three times the length of the

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Neck 3 and preferably at least about five times the length of neck 3 has the same overall configuration as the first zone 2, of course, with the exception that the conical transition part is the most upstream part 4a of zone 4 which connects it to neck 3.

A second and preferred embodiment of the invention is shown in FIG. 2, in which like parts bear like reference numerals as in FIG. The one shown in FIG The arrangement differs from that shown in Fig. 1 in the following respects. First is the diameter of the constriction 3 has been reduced to the mean air speed by enlarging the zone, which results in a structure which is advantageous in terms of preventing flashback is more effective. Second is the height (i.e. the length in the direction of the longitudinal axis) of the convergent conical Part 2a has been enlarged. In this embodiment are the fuel nozzles 6 relocated from the constriction 3 to the divergent conical part 4a of the second zone 4 and in Mini combustion chambers or vortex cups 9 have been reset, in which the operation of the secondary fuel nozzles 6 is more stable and the likelihood of it becoming a Flame failure comes, is less.

Fig. 3 shows as an example three interconnected burners according to the invention. The first combustion zone 2 each Burner 1 is adjacent to the first combustion zone 2 Burner 1 connected in a conventional manner via a cross-ignition tube 1O. In addition, is in the invention the second combustion zone 4 of each burner 1 with the Second combustion zone 4 of each adjacent burner 1 is connected via a cross-ignition tube 11. At the design high

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load operating states of the burner according to the invention takes place, which is described in more detail below, the Burn only in the second zone 4 and no burning occurs in the first zone 2. If for any reason In conventional arrangements, the flame breaks out in a chamber under such high load conditions Cross-ignition take place because the standard cross-ignition tubes 10 are arranged upstream of the reaction zone 4 and because the throat 3 is used to prevent flashback. In the embodiment shown in Fig. 3, the second group is used of cross-ignition tubes 11 as a high-load ignition system. It is Although it is preferable to use both sets of cross-ignition tubes (i.e. tubes 10 and 11), if necessary Any high-load re-ignition system must be built into the burner system.

The operation of the burners according to the invention is shown graphically in FIG. Combustion begins with ignition a mixture of hydrocarbon fuel and air in the first combustion zone 2. This is done in conventional Way achieved by means of a spark plug 12, which is arranged in the vicinity of the fuel nozzle 5 in the first combustion zone 2 is. In typical conventional systems ten burners are arranged in a ring and usually are from the burners only two provided with spark plugs 12 while the remaining eight burners are ignited by cross-ignition via the cross-ignition tubes 10. During ignition and cross-ignition and also during the low load operation of the burners, only the primary fuel nozzle 5 guides the burner 1 fuel too. Up to this point the combustion has the single-stage, heterogeneous vortex diffusion flame combustion characteristic from conventional burners.

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With a load condition in the middle range, its exact timing on the stability limits and the Pollutant emission properties of each operating mode and the Fuel allocation is based on the stages, the Secondary fuel nozzles 6 activated. The transition of the ignited Fuel from the first zone 2 into the second zone 4 leads to ignition in the second zone 4. The burner now works in a two-stage heterogeneous operating mode that continues until the desired basic load is achieved is. After allowing a short period of time to stabilize and warm up, the mode of operation turns off a two-stage heterogeneous combustion is converted into a single-stage homogeneous combustion. This procedure begins by simultaneously increasing and decreasing the amount of fuel supplied to the secondary nozzles 6 the amount of fuel supplied to the primary nozzle 5 while the total fuel supply remains constant. The relative quantities the fuel supply to the nozzles 5 and 6 can be controlled by a fuel supply controller 13, which is connected between the nozzle 5 and the nozzles 6. The change in fuel distribution continues until the Flame in the first combustion zone 2 goes out, which in most cases occurs when the entire fuel supply has been switched to the secondary nozzles 6.

The fuel supply to the nozzle 5 is then resumed or increased and the supply to the nozzles 6 is reduced, while the total fuel supply is substantially is kept constant. The burner 1 is designed so that there is no flashback during normal operation comes by making the first zone 2 long enough so that the flow area equals that of a full formed turbulent pipe flow, and by making the constriction 3 narrow enough so that the speed is increased to a value, above which the

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Flame speed cannot be overcome. Consequently there is a premixing of the majority of the fuel and the air in the first stage (i.e. in the first. Zone 2) and for homogeneous combustion in the second stage, i.e. in the second zone 4. Switching the fuel distribution from the secondary nozzles 6 to the primary nozzle 5 remains until the desired low pollutant emission values are reached. The desired values are achieved when the majority of the fuel supply is on the Nozzle 5 goes, and in most cases if at least 60% of the fuel supply goes through nozzle 5.

It should be noted that an important feature of the burner according to the invention is that when it becomes a Should there be a flashback, it is not a hardware catastrophe as is the case with typical designs with premixing. However, there would be a considerable increase in the production of nitrogen oxides and control steps would have to be taken in order to carry out the switchover procedure again and to operate in the homogeneous operating mode again to record.

During the shutdown of the gas turbine, steps are carried out to re-ignite the first zone 2 because there is only a small minimum throughput in the homogeneous operating mode gives. The re-ignition of the first stage means a return to the heterogeneous two-stage combustion takes place at which the system has a large minimum flow rate that allows the turbine to be shut down slowly, to reduce unwanted thermal stress.

To illustrate the reduction in nitrogen oxide emissions ionon, which is achieved by the invention, a burner manufactured according to the invention with a conventional,

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Compared to commercially available burners with MS 7001E equipment. The burner according to the invention had the structure shown in FIG. 1 and a single air atomizing nozzle MS 7001E was used as the primary nozzle 5 and four smaller pressure atomizing secondary nozzles 6 were used. Data (corrected for radiation losses at the thermocouples) was added at about 1138 ⁰ C (2O8O ° F), the laboratory-scale equivalent of the nominal load. Under these conditions, the conventional standard burner in the laboratory had a nitrogen oxide emission of 120 vol.ppm (ppmv), while a burner according to the invention only emitted 56 vol.ppm. This test was conducted using a used air supply, meaning that the products of combustion from a direct heater (such as a propane heater), which served to raise the air temperature to the proper inlet levels, were used as the oxidizer for combustion during the test. The nitrogen oxide emissions are therefore lower than they would be achieved with unused air. Based on these laboratory results, it is to be expected that the operation of the burner according to the invention under field conditions (ie when the turbine is actually used with unused air) in the homogeneous operating mode would show a comparable reduction in nitrogen oxide emissions. It can therefore be assumed that burners according to the invention meet the requirements of a low nitrogen oxide emission.

A second test of the two-stage combustion system of the invention double mode was carried out during which a supply of used air was used and during which the firing temperature remained constant at approximately 1132 ° C (2070 ° F). At one point during the increase in fuel supply to the secondary fuel nozzles 6, when the amount of fuel supply via the primary nozzle 5 was 20% and combustion in both

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the combustion zone 2 as well as in the combustion zone took place, the nitrogen oxide emission was about 95 ppm by volume. After switching from the two-stage heterogeneous combustion mode to the homogeneous combustion mode at a point where about 14% of the fuel Flowing through the primary nozzle (the first stage), the nitrogen oxide emissions were 93.5 vol.ppm. The amount of too fuel flowing through the primary nozzle 5 was then increased from 14% to a point at which approximately 70% the total fuel supply went through the primary nozzle, and the nitrogen oxide emission fell further from 9 3.5 vol.ppm to about 49 vol.ppm.

There was a third test performed in a similar manner as in the above-described first test, but a supply was used to unused air that is indirectly preheated air without combustion products · emitted at a firing temperature of about 1,127 ⁰ C (2O6O ° F), the conventional Burner about 260 ppm by volume nitrogen oxide, while the burner according to the invention, operating in a homogeneous mode, emitted about 65 ppm by volume. The fuel used in each of the above tests was No. 2 distillate.

From the laboratory test data above and in particular from that of the third test, in which a supply of unused If air was used, the skilled person can use the considerable Detect reduction (by a factor of four) in nitrogen oxide emissions achieved by the burner according to the invention became. By using such burners, nitrogen oxide emission levels are considerably reduced and met most nitrogen oxide emission regulations.

Having two embodiments of the invention and their modes of operation is for those skilled in the art

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better understood in which the invention differs from the prior art known from the above-mentioned patents differs. In particular, U.S. Patent 3,946 appears to have a two stage, multiple fuel nozzle burner to describe emissions control. However, the fuel and air are outside the liner wall mixed, which differs from the invention described here. In addition, the burner gives way According to the invention, some conditions in which the reaction can be carried out in a heterogeneous mode of operation without premixing (i.e., during run-up, during partial load and during equalization periods of the basic load), i.e. in one Operating mode which is not possible with the burner described in the aforementioned US-PS. The modes of operation according to the invention facilitate a large percentage minimum throughput, easy ignition and cross-ignition as well as flame stability, what are essential properties of a practical design. In addition, switching from the heterogeneous to the homogeneous mode of operation according to the invention achieved by the fuel distribution on the fuel nozzles the first and the second stage is changed, a feature that is not from the aforementioned US patent is known.

U.S. Patents 3,958,413 and 3,958,416 relate to two-stage burners in which the stages are separated by a converging-diverging Narrowing section are separated. In addition, the first stage in the case of the two patents known burners are used at any time during the cycle as a section in which the combustion occurs, and at times in the cycle other than a section in which the premixing occurs. A flashback therefore does not cause a hardware catastrophe, as is the case with the burner known from US Pat. No. 3,946,533 would be the case. The two US PSs also appear

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a variable air inlet geometry for changing the air supply to describe the stages to the transition from heterogeneous combustion in the first stage or in the first and in the second stage to achieve homogeneous combustion only in the second stage. In contrast, with of the invention with variable fuel supply to the stages using several fuel nozzles (instead of the variable geometry) and changing the fuel distribution worked instead of the air distribution.

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Claims (12)

Patent claims: 1 / Method for operating a gas turbine burner in order to generate a low nitrogen oxide emission, wherein the burner has a first and a second combustion chamber, the are interconnected by a constriction chamber, and wherein the first chamber has a first fuel introduction device while at least one of the throat chamber and the second combustion chamber has a second fuel introducing device, characterized by the following steps: a) continuous introduction of fuel into the first chamber via the first fuel introduction device in order to to burn the fuel in it; b) starting the introduction of fuel into the second chamber via the second fuel introduction device and increasing the amount introduced thereof until the amount of the above all fuel introduction devices introduced fuel about the desired 030030/0715 Fuel inlet quantity corresponds, with the ignition of the fuel in the second chamber as a result of the overflow begins of combustion products from the first chamber to the second chamber; c) reducing the amount of via the first fuel introduction device introduced fuel and a corresponding increase in the amount of on the second fuel introduction device injected fuel, so that the total amount of injected fuel is substantially remains constant until at least the burning of fuel in the first chamber ceases; and d) increasing the amount of over the first fuel introduction device introduced fuel and a corresponding reduction in the amount of over the second fuel introduction device injected fuel, so that the total amount of injected fuel is substantially constant remains until the desired value of the nitrogen oxide emission of the burner is reached. 2. The method according to claim 1, characterized in that the fuel introduction via the first fuel introduction device is reduced in step (c) until the entire fuel introduction via the second fuel introduction device he follows. 3. The method according to claim 2, characterized in that the fuel distribution at the end of step (d) so is that the majority of the fuel is introduced via the first fuel introduction device. 4. The method according to claim 3, characterized in that the fuel distribution at the end of step (d) is such that at least 60% of the total fuel is over 030030 / 071S " ⁴ BAD ORIGINAL the first fuel introduction device can be initiated. 5. The method according to claim 1, characterized in that the fuel distribution at the end of step (d) is so that the majority of the fuel is about the first fuel introducing device is initiated. 6. The method according to any one of claims 1 to 5, characterized in that that an axially symmetrical fuel nozzle is used as the first fuel inlet device and that a plurality of symmetrically arranged fuel nozzles can be used as a second fuel introduction device. 7. Burner for a stationary gas turbine that is able to reduce nitrogen oxide emissions when burning a To produce hydrocarbon fuel, characterized by a first combustion zone (2), by a first hydrocarbon fuel injector (5) which is arranged so that fuel is introduced into the first zone, by means (7) for introducing compressed air into the first zone, by a neck zone (3) which is connected to the first zone and has a cross-sectional area which is smaller than those of the first zone, through a second combustion zone (4), which is connected to the neck zone is connected and has a cross-sectional area greater than that of the neck zone, by devices (7 ¹ ) for introducing compressed air into the second zone, by a second hydrocarbon fuel injector (6) which is arranged so that fuel is introduced into at least one of the throat zone and the second zone will. 030030/0715 300Ü672 by means (8) for introducing a quench of heat exchange fluid into the second zone downstream the devices for introducing compressed air into the second zone, and by means (13) for changing the relative quantities of hydrocarbon fuel that over the first and over flow through the second hydrocarbon fuel introducing device. 8. Burner according to claim 7, characterized in that the first hydrocarbon fuel introduction device is a single axially symmetrical fuel nozzle (5) and that the second hydrocarbon fuel inlet device has several symmetrically arranged fuel nozzles (6) having. 9. Burner according to claim 8, characterized in that the fuel nozzles (6) of the second hydrocarbon fuel Feinleitvorrichtung are each designed so that they introduce fuel into a third combustion zone (4a), the means (7 ") for introducing compressed air into the third combustion zone, and that the third combustion zone is arranged so that the fuel and the air from it go into the second combustion zone (4). 10. Burner according to claim 9, characterized in that the first, the second and the third combustion zone (2, 4, 4a) and the neck zone (3) each have a circular cross-section. 11. Burner arrangement for a stationary gas turbine, with several adjacent burners, each of which is a first and has a second combustion chamber, which is connected through a neck 03Ö0 30 / 071S BATH ORIGINAL are connected to each other, and at least one of which has a device for igniting a fuel in his first chamber has characterized by a plurality of first cross-ignition tubes (10), each of which is the first chamber (2) of a burner (1) with the first chamber (2) of an adjacent burner (1) connects, and by several second cross-ignition tubes (11), each of which connects the second chamber (4) of one burner to the second chamber (4) of an adjacent burner. 12. Burner arrangement according to claim 11, characterized by ten burners, each of which is adjacent to other burners. 030030/0715