RU2430308C2 - Burner for gas turbine, in which gas with low calorific value is used as fuel - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: burner (4) for gas burner includes: swirler (21), plate (58), the first channel (18) via which fuel gas with low calorific value is supplied, and second channel (17) via which combustion air is supplied. The first and the second channels (17, 18) are located concentrically relative to longitudinal axis (2). Output of the first channel (18) is formed with convergent nozzle (50). Swirler (21) is installed at the outlet of the second channel (17). Plate (58) is tightly installed in the first channel (18) upstream nozzle (50) and has many holes (56) with calibrated section of the passage. Holes (56) are inclined in tangential direction relative to longitudinal axis (2) at the specified angle. For fuel gases having flame propagation speed of less than 300 mm/s, plate (58) has 36 to 38 holes (56) the diameter of which is 11.5 to 12.0 mm, and inclination angle of holes (56) is approximately 22°. For fuel gases having flame propagation speed of 300 mm/s to 400 mm/s, plate (58) has 80 holes (56) the diameter of which is 8.5 mm to 9.0 mm, and inclination angle of holes (56) is 17° to 22°. If calorific value of gas with low calorific value from the first channel (18) is less than 4.0 MJ/kg, then natural gas consumption is assumed from pilot line (46). Burner (5) is used only when gases with low calorific value are not available.

EFFECT: high burner flexibility; operation is possible at the gas used with low calorific value and of any type within the whole working range of gas turbine.

12 cl, 3 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a burner for a gas turbine, in which gas with a low calorific value is used as fuel, in particular off-gas produced in the metallurgical industry.

State of the art

The use of exhaust gases from the metallurgical industry in gas turbine burners is part of the prior art. In particular, the well-known burners are intended for the use of fuel gases with a constant composition obtained in the metallurgical industry, in the operating mode, or only gas from blast furnaces, or also gas from blast furnaces, gas from coke ovens and gas from metallurgical plants (LD converters) with a given and constant percentage content. The effective use of known burners on a large scale is limited, on the one hand, by the fact that the calorific value of the gas is very low, and on the other hand, by the fact that the gas composition varies in various steel mills. In fact, often the gas that may be available to power the burner is a mixture of blast furnace gas, metallurgical gas and coke oven gas, the percentage of which varies substantially in accordance with the processes typical of each steel plant.

In other words, the known burners are far from providing satisfactory results, since it has been found that it is difficult to burn gases having a calorific value of less than 4.0 MJ / kg. The second reason is that burners contain many elements that must be designed in a special way, as required in each case, in accordance with the composition and, therefore, in accordance with the calorific value of the gas available at a particular steel plant.

Therefore, there is a need to increase the flexibility of the known burners, in particular for the use of gas mixtures obtained in the metallurgical industry, the calorific value of which is very low, for example, from 3.0 MJ / kg to 4.0 MJ / kg, while combustion stability must be guaranteed.

Disclosure of invention

The aim of the present invention is to provide a burner for a gas turbine in which gas with a low calorific value can be used as fuel and which would meet the above requirements, achieved by a simple and inexpensive method.

According to the present invention, there is provided a gas turbine burner comprising:

a first channel through which fuel gas with low calorific value is supplied during use, and a second channel through which combustion air is supplied during use, wherein the first and second channels are concentric with respect to the longitudinal axis, the exit of the first channel being formed by a tapering nozzle;

swirl mounted at the exit of the second channel;

a plate sealed in the first channel upstream of the nozzle and having many holes with a calibrated passage section, the holes being inclined in a tangential direction relative to the longitudinal axis at a given angle;

moreover, for fuel gases having a flame propagation velocity of less than 300 mm / s, the plate has from 36 to 38 holes, the diameter of which is from 11.5 mm to 12.0 mm, and the angle of inclination of the holes is approximately 22 °; and

for fuel gases with a flame propagation rate of 300 mm / s to 400 mm / s, the plate has 80 holes, the diameter of which is from 8.5 mm to 9.0 mm, and the angle of inclination of the holes is from 17 ° to 22 °.

The burner also preferably comprises detachable connection means for connecting the plate in a fixed position and allowing the plate to be replaced.

In the proposed burner, the nozzle is preferably radially bounded by a wall attached to the plate and carrying detachable connection means.

In the burner of the invention, preferably the disconnecting means of the connection comprises a threaded connection.

In the proposed burner, preferably the holes are located at the same angular distance from each other around the longitudinal axis.

In the proposed burner, preferably the holes are made in the plate along two concentric circles.

The burner also preferably comprises a pilot line through which natural gas is supplied during use.

The burner also preferably comprises a third channel, through which natural gas is supplied during use, the first, second and third channels being concentrically relative to each other.

In the proposed burner, preferably the second channel is located in the radial direction between the first channel and the third channel.

The present invention also provides a gas turbine burner assembly comprising a burner made in the above manner in combination with a coaxial pre-mix burner fed using natural gas.

The present invention also provides a method of supplying fuel gas to a burner, in which the flow rate of natural gas from the pilot line is established if the calorific value of gas with a low calorific value from the first channel is less than 4.0 MJ / kg.

In the proposed method, it is preferable that the flow of natural gas from the pilot line (46) is continuously changed as a function of the calorific value and / or the composition of the gas with a low calorific value.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings, which illustrate an example of a variant of its implementation, not limiting the scope of the invention, and in which:

Figure 1 is a cross-sectional view of a burner of a gas turbine according to a preferred embodiment of the present invention with some elements not shown for clarity;

FIG. 2 is an enlarged cross-sectional view of the burner element shown in FIG. 1; and

Figure 3 is a section along the line III-III in figure 2.

Preferred Embodiment

Figure 1 shows the burner assembly, indicated by 1, which is part of a gas turbine (not shown), with which, when used, the shaft of an electric machine (not shown) is rotated to generate electrical energy.

The assembly 1 extends along the longitudinal axis 2 and, when used in the chamber 3 (partially shown), provides combustion and comprises a central burner 4 and a peripheral burner 5 of the “pre-mix” burner type, coaxial with the burner 4 and installed around it.

The burner 5 contains a device 6 with blades for creating vortices, or turbulence, usually called a "swirl", which (vortices) are transmitted to the chamber 3 by the so-called "diagonal" combustion air flow coming from channel 9.

Burner 5 also includes a line 13 for supplying fuel gas, i.e. natural gas. Line 13 supplies fuel gas to the compartments between the blades of the swirler 6 to obtain a mixture of gas and air, while the amount of air is greater than the theoretical stoichiometric ratio to ensure combustion of the pre-cooked mixture.

Burner 4 (see FIG. 1) comprises a channel 17 for supplying combustion air and a channel 18 for supplying fuel gas, i.e. gas with low calorific value, in particular gas obtained in the metallurgical industry. The channels 17, 18 are circular, arranged concentrically with respect to axis 2 and are separated from each other by a tubular body 20, the axis of which is also axis 2.

In particular, the outlet of the channel 17 is formed by a device 21 with blades (“swirl”), with the help of which create vortices, or turbulence, in the flow of combustion air. In the channel 17 there is a ignition electrode 24 and an electric power line of a known type for generating an ignition spark in the compartments between the blades of the swirler 21.

Channel 18 is radially bounded externally by the tubular body 32, and channel 17 is radially bounded internally by the tubular body 33, which terminates in a conical portion 34.

The housing 33 extends along axis 2 and is mounted around a gas-oil, or fuel, nozzle 35, which protrudes axially from the center of swirl 21 to chamber 3.

The housing 33 and the nozzle 35 form in the radial direction relative to each other an annular channel 36, through which the flow of fuel gas, i.e. natural gas that enters the compartments between the blades of the swirl 21 through the outlet openings (not shown) made in part 34, for burning it with combustion air coming from the channel 17, and to obtain a diffusion flame.

In the channel 36, there are many tubes 46 parallel to the axis 2, isolated from the gas passing through the channel 36, which form the so-called “pilot line” and which have corresponding ends crossing part 34 for supplying an additional fuel gas stream, i.e. natural gas, under special operating conditions of a gas turbine. In particular, the gas from the pilot line 46 is supplied for mixing with the combustion air coming from the channel 17, and it burns together with the gas coming from the channel 18 (“co-combustion”), and a pilot flame is formed, which stabilizes the diffusion flame generated gas coming from channel 18.

The outlet of the channel 18 is an annular hole formed by a tapering nozzle 50, i.e. having a cross section of the passage, which narrows to accelerate the flow of gas with low calorific value.

The nozzle 50 is bounded from the inside in the radial direction by the cylindrical axial end of the housing 20 and the outer annular wall 51 of the swirl 21, and from the outside by the wall 52.

The wall 52 comprises a conical front part 53 and a cylindrical rear part 54, which is removably attached to the axial end of the housing 32, in particular by means of a threaded connection 55.

Channel 18 (see FIGS. 2 and 3) is connected to a plurality of holes 56 made in the annular plate 58 and having calibrated passage sections for accurately determining the flow rate of fuel gas, which then passes through the nozzle 50.

The plate 58 is located perpendicular to the axis 2, is attached to the rear end of the part 54, in particular by spot welding and is sealed in the channel 18. In particular, the tightness is guaranteed, on the one hand, by using a threaded connection 55, and on the other hand, by mating the inner cylindrical surface 59 of the plate 58 with the housing 20.

The number of holes 56 and their passage section is determined so that the ratio between the pressure loss on the plate 58 and the pressure in the chamber 3 is more than 5% under the minimum load provided by the operating mode, when using gas coming from the channel 18 (the greater the pressure loss , the lower the susceptibility to such a possible phenomenon as pressure fluctuation in the chamber 3).

In particular, holes 56 are represented by two hole rings 56a, 56b formed along respective concentric circles. In each ring 56a, 56b, the holes are located at the same angular distance from each other around axis 2. The axis of the holes 56 are straight and inclined in a tangential direction relative to axis 2 at a given angle. Said angle of inclination tells the gas stream the turbulent motion of the vortex, similar to that created by the blades in the nozzle 50. The direction in which the holes are inclined relative to axis 2 is the same in the two rings 56a and 56b.

In particular, in the case where the gas supplied through the channel 18 contains a relatively large amount of gas from the blast furnace, it is necessary to achieve relatively high turbulence to provide a higher degree of mixing with air.

The flow rate of fuel gas with a low calorific value entering the nozzle 50 is adjusted and pre-set accordingly by determining, at the beginning of the burner life, the number and cross section of the aperture 56 of the holes, in accordance with the calorific value and / or the composition of the available fuel gas with low calorific value.

As an example, two different types of configurations are described that can be set as alternatives to each other:

- for fuel gas having a flame propagation velocity of less than 300 mm / s, corresponding essentially to the initial conditions under which the fuel gas has a percentage of gas from the blast furnace, which provides thermal energy of at least 70% of the total thermal energy (or effective thermal power), and the percentage of coke oven gas and gas from metallurgical plants (LD converters), which is no more than the remaining 30%, the number of holes 56 is 36 to 38, the holes have a diameter of 11.5 mm d about 12.0 mm, and they are positioned at an angle of inclination of approximately 22 °;

- for fuel gas having a flame propagation rate in the range from 300 mm / s to 400 mm / s, corresponding essentially to the initial conditions under which the fuel gas has a percentage of blast furnace gas, which reports thermal energy of less than 70% of the total heat energy (or effective thermal power), and the percentage of coke oven gas and gas from metallurgical plants (LD converters), which is more than the remaining 30%, the number of holes 56 is 80, the holes have a diameter from 8.5 mm to 9.0 mm, and they are positioned at an angle of inclination of 17 ° to 22 °.

The following describes the operation of node 1.

Ignition of unit 1 is carried out by supplying natural gas through a feed line formed by channel 36. An increase in the speed of a gas turbine is performed again by supplying natural gas via line 36 until a load of 50% of the maximum load is reached.

Further, there is a transition from an action consisting in the diffusion of natural gas to an action using gas with a low calorific value (obtained in the metallurgical industry) by supplying said gas through channel 18.

The gas supply is as follows:

- if the calorific value of the gas leaving channel 18 is greater than 4.0 MJ / kg, then the flow rate of natural gas supplied through a pilot line formed from tubes 46 is 0;

- if the calorific value of the gas leaving the channel 18 is from 3.0 MJ / kg to 4.0 MJ / kg, then the natural gas supplied through the pilot line 46 is used to stabilize the achieved combustion: the flow rate contributes to the total effective thermal power in volume not exceeding 10%, under conditions of maximum load (for example, the flow rate is up to a maximum of 1 kg / s).

In particular, the flow of natural gas through the pilot line 46 is continuously controlled and changed as a function of the composition and / or calorific value of the low calorific value gas supplied through channel 18.

The composition and / or calorific value is determined using sensors of a known type (calorimeter, gas chromatographs, etc.).

In the case where a break in the load is required, the flow rate of gas with low calorific value supplied through channel 18 is reduced to a predetermined minimum and, at the same time, the flow rate of natural gas supplied through pilot line 46 is increased to a predetermined maximum that is sufficient for a gas turbine to operate under without load. A subsequent increase in load, starting under these conditions, is produced by supplying gas with a low calorific value through channel 18 without using natural gas supplied through line 36.

The pre-mix burner 5 is used to burn natural gas in case of inaccessibility of gas with low calorific value. This eliminates the use of steam and / or inert gases (e.g. nitrogen), which would be necessary to limit the emissions of nitrogen oxides present in the exhaust gases if, for example, line 36 was used.

From the foregoing, it is obvious that with the burner 4 it is also possible to burn gas with a low calorific value by appropriate selection of the shape of the plate 58 and the nozzle 50.

In particular, by means of a connecting device configured to detach, for example, a threaded connection 55, it is possible to give greater flexibility to the design of the burner 4 so that it is only necessary to design and produce in a special way only the holes in the plate 58 and the wall 52 of the corresponding shape, based on the type of available fuel gas with low calorific value.

Then, it is possible to easily modify the already provided configuration by replacing the element represented by the plate 58 and the wall 52, in the case when the composition of the gas with low calorific value should be changed.

In addition, the element represented by the plate 58 and the wall 52 can be used to upgrade the current standard burner for its use using gas with low calorific value.

By calibrating the cross section of the passage in the plate 58 for passing fuel gas with a low calorific value and, if necessary, by using the pilot line 46 to add natural gas to the chamber 3, it is possible to maintain stable combustion even when using gases having a calorific value of 3 , 0 MJ / kg to 4.0 MJ / kg.

In other words, the flexibility of burner 4 is so high that, thanks to the stabilization of combustion achieved with pilot line 46, gas of any calorific value can be burned. In particular, it is also possible to control the supply of natural gas supplied through the pilot line 46 continuously by changing the amount of natural gas supplied in accordance with the composition of the low calorific value gas supplied through the channel 18.

Operation is possible when using gas with low calorific value in the entire operating range of a gas turbine. Burner 5 is used only when gases with low calorific value are not available.

From the above it follows that in the design of the burner 4 and the node 1 described here with reference to the accompanying drawings, changes and additions can be made, not beyond the scope of protection of the present invention.

In particular, the distribution of the holes 56 may be different, for example, the holes 56 may be located in one ring.

Claims (12)

1. A burner (4) of a gas turbine, comprising:
the first channel (18), through which fuel gas with low calorific value is supplied during use, and the second channel (17), through which combustion air is supplied during use, while the first and second channels (17, 18) are concentric with respect to the longitudinal axis (2), wherein the output of the first channel (18) is formed by a tapering nozzle (50);
a swirler (21) installed at the outlet of the second channel (17); a plate (58) hermetically mounted in the first channel (18) upstream of the nozzle (50) and having many holes (56) with a calibrated passage section, while the holes (56) are inclined in a tangential direction relative to the longitudinal axis (2) under a predetermined angle (A); moreover, for fuel gases with a flame propagation velocity of less than 300 mm / s, the plate (58) has from 36 to 38 holes (56), the diameter of which is from 11.5 mm to 12.0 mm, and the angle of inclination (A) holes (56) is approximately 22 °; and
for fuel gases with a flame propagation rate of 300 mm / s to 400 mm / s, the plate (58) has 80 holes (56), the diameter of which is from 8.5 mm to 9.0 mm, and the angle of inclination (A) holes (56) -from 17 ° to 22 °. 2. A burner according to claim 1, characterized in that it comprises a disconnecting means (55) for releasing the plate (58) in a fixed position and for replacing the plate (58). 3. A burner according to claim 2, characterized in that the nozzle (50) is radially bounded by a wall (52) attached to the plate (58) and carrying disconnecting means (55). 4. The burner according to claim 3, characterized in that the means (55) of the connection, made with the possibility of disconnection, contains a threaded connection. 5. Burner according to any one of claims 1 to 4, characterized in that the holes (56) are located at the same angular distance from each other around the longitudinal axis (2). 6. Burner according to any one of claims 1 to 4, characterized in that the holes (56) are made in the plate (58) along two concentric circles. 7. A burner according to any one of claims 1 to 4, characterized in that it comprises a pilot line, through which natural gas is supplied during use. 8. The burner according to claim 7, characterized in that it contains a third channel (36), through which natural gas is supplied during use, while the first, second and third channels (17, 18, 36) are concentrically relative to each other. 9. Burner according to claim 8, characterized in that the second channel (17) is located in the radial direction between the first channel (18) and the third channel (36). 10. A gas turbine burner assembly comprising a burner made according to any one of claims 1 to 9, in combination with a coaxial pre-mix burner fed using natural gas. 11. The method of supplying fuel gas to the burner according to claim 7, characterized in that the flow rate of natural gas from the pilot line (46) is set if the calorific value of gas with low calorific value from the first channel (18) is less than 4.0 MJ / kg . 12. The method according to claim 11, characterized in that the flow rate of natural gas from the pilot line (46) is continuously changed as a function of calorific value and / or composition of gas with low calorific value.

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