JP2004044845A - Low nox combustion method for gas turbine, and low nox combustor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously improve combustion stability of premixed lean gas, reduce NOx, and improve flashback resistance. <P>SOLUTION: Premixed gas 1 having a high equivalent ratio is supplied from one surface side of a first fiber mat 4 having a felt mat shape and is glowing-combusted on the other surface, and this is used as a pilot burner 12. Heat exchange is performed between a second fiber mat 6 having a felt mat shape faced to the other surface side of the first fiber mat with a certain clearance 8 and a red heat surface on the other surface side of the first fiber mat, thereby suppressing NOx generated in high temperature combustion. Additionally, premixed gas 2 having a low equivalent ratio is supplied to the clearance via the second fiber mat, and is preheated to expand the stable combustion range, and then lean combustion is performed in the clearance. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a low NOx combustion method for a gas turbine and a low NOx combustor for a gas turbine. More specifically, the present invention employs a surface combustion method using a fiber mat to improve the stability of lean combustion of low equivalent ratio gas and The present invention relates to a low-NOx combustion method for a gas turbine and a low-NOx combustor for a gas turbine that realize a sufficient reduction of NOx and the like.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a combustor of a device requiring a large amount of heat energy, such as a high-temperature incinerator or a boiler, a fiber mat burner which is a surface-burning type high radiation gas burner (also referred to as a “metal fiber mat burner”). ) Is often used.
Here, the fiber mat is obtained by sintering a metal fiber having an element wire diameter of 15 to 50 μm into a mat having a thickness of several mm with a high porosity, and the fiber mat burner is used as a combustion surface. It is a combustor.
Combustion with a fiber mat burner is a method in which a gas (premixed gas) in which fuel and air are mixed in advance is supplied to a combustion chamber, and the gas is red-burned on the surface of the fiber mat. At the same time as generating the radiant heat, the exhaust gas of about 1000 ° C. is discharged.
Since the metal fibers constituting the fiber mat are uniformly oriented in the in-plane direction of the mat, the fiber mat has a high heat uniformity in the plane and a small heat conductivity in the thickness direction. Also have.
Therefore, the fiber mat burner has hitherto been mainly used in a field aiming at utilizing the radiant heat and the combustion exhaust gas, for example, a field aiming at heating and drying of an object.
[0003]
Fiber mat burner
(1) The uniformity of the combustion surface is high and the temperature distribution is not uneven,
(2) It is difficult to misfire because the flame does not rise, and soot hardly occurs.
(3) The concentration of NOx generated during combustion under certain conditions is extremely low.
(4) excellent fire resistance in the combustion chamber;
(5) The combustion load per unit area is higher than the conventional burner,
(6) Of the input heat, the ratio obtained as radiant heat is high, and the efficiency of heating and drying can be improved.
It has features such as. Therefore, when this is applied to an apparatus such as a furnace or a boiler, uniform and stable combustion and flashback resistance are improved, and the use of radiant heat makes the heating and drying of the object more efficient, in other words, If this is the case, the size of the device can be reduced, and the NOx of the combustion exhaust gas can be reduced, which can contribute to environmental protection.
[0004]
[Problems to be solved by the invention]
However, the surface mat type fiber mat burner has not been used in a gas turbine combustor or the like that uses kinetic energy of combustion exhaust gas.
The reason is that
{Circle around (1)} Since the gas turbine drives the gas turbine with combustion exhaust gas generated by combusting air and fuel in a combustor and takes it out as power, the conversion rate to radiant energy (radiant heat) is high, The surface combustion method having a low conversion rate to kinetic energy is not suitable for a gas turbine from the viewpoint of energy efficiency.
{Circle around (2)} When performing combustion of a premixed gas having a high equivalence ratio (equivalent ratio of about 1), it is necessary to lower the combustion temperature in a fiber mat that performs surface combustion in order to reduce NOx. In order to lower the combustion temperature by emitting radiant heat from the surface of the fiber mat, energy efficiency is sacrificed in a gas turbine that does not use radiant heat.
Etc.
[0005]
On the other hand, as described above, the surface combustion type combustor has extremely high combustion stability, the NOx concentration generated under certain conditions is extremely low, and flashback in the combustion chamber can be avoided. Has excellent features. Therefore, if this can be applied to a gas turbine combustor while considering the problem of energy efficiency, a very excellent combustor can be provided.
[0006]
The present invention has been made to solve the above-mentioned problem. That is, the present invention improves the energy efficiency by recovering the radiant heat in consideration of the energy efficiency problem, while simultaneously improving the surface combustion method that has not been applied to the gas turbine. Provided is a low-NOx combustion method for a gas turbine and a low-NOx combustor for a gas turbine capable of simultaneously lowering the temperature and simultaneously improving the combustion stability of a premixed lean gas, reducing NOx, and improving flashback resistance. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides a premixed gas (1) having a high equivalent ratio from one surface side of a first fiber mat (4) in the form of a felt mat and causing the surface on the other surface side to red-heat and burn. A second fiber mat (6) in the form of a felt mat, which is disposed opposite to the other side of the first fiber mat with a certain gap (8) therebetween, and a red heat on the other side of the first fiber mat; The pre-heating is performed by supplying a heat exchange with the surface and a pre-mixed gas (2) having a low equivalent ratio through the second fiber mat to the gap, and thereafter, the glowing surface is connected to the pilot burner (12). The present invention provides a low NOx combustion method for a gas turbine, wherein lean combustion is performed in the gap.
[0008]
According to the present invention, the first fiber mat and the second fiber mat are arranged to face each other with a certain gap therebetween, and a small amount of a premixed gas having a high equivalent ratio (hereinafter, referred to as “high equivalent ratio gas”). Red heat combustion is performed on the surface of the first fiber mat on the void side, and this is used as a pilot (flame holding) burner. At this time, radiant heat is emitted from the red heat surface, and the radiant heat is absorbed by the gas in the opposing second fiber mat and the gap. The emission of the radiant heat lowers the temperature of the glowing surface of the first fiber mat, so that it is possible to reduce NOx, which is generated in large quantities when the high equivalent ratio gas is burned at a high temperature.
On the other hand, from the second fiber mat heated by the radiant heat, a large amount of a premixed gas having a low equivalent ratio (hereinafter, referred to as a “low equivalent ratio gas”) is supplied toward the gap. At this time, the low equivalent ratio gas is indirectly preheated by convection heat transfer with the mat or the like, and the stable combustion range is expanded. Further, since the combustion surface becomes highly uniform, the temperature distribution is uniform, and the red-hot combustion in the first fiber mat having high flame holding properties becomes a pilot, the preheated low equivalent ratio gas becomes the second fiber mat. A stable lean burn (lean burn) is performed on the side of the gap, and a blue flame with a short flame length that does not emit radiant heat is formed in a plane as a main frame in the gap.
As described above, according to the combustion method using the fiber mat of the above-described embodiment, there is no waste in energy efficiency, (1) securing the flame holding property of the pilot burner by red-hot combustion, and (2) high-equivalence ratio gas. NOx reduction by lowering red heat combustion temperature; (3) Stable lean combustion in main burner due to presence of pilot burner with high flame holding properties and preheating of low equivalent ratio gas; (4) Low main burner due to stable lean combustion In addition to NOx conversion, (5) improvement of flashback resistance by separating the premixed gas supply path and the combustion area by the fiber mat can be realized at the same time.
Furthermore, by mixing the combustion gas of the pilot burner with the low equivalent ratio gas, a combustion gas recirculation effect can be expected, and it is possible to further reduce NOx.
[0009]
As a specific combustor for performing the above-mentioned low NOx combustion method for a gas turbine, the present invention supplies a premixed gas (1) having a high equivalent ratio from one surface side of a first fiber mat (4) in the form of a felt mat. Further, a felt mat-shaped second burner (12), which is disposed opposite to the other surface side of the first fiber mat, with a fixed gap (8) between the pilot burner (12) for burning red heat on the other surface side. A main burner (14) having a two-fiber mat (6) and supplying a low-equivalent-ratio premixed gas (2) from one surface side of the second fiber mat and causing lean combustion in the gap located on the other surface side; And a low NOx combustor for a gas turbine.
[0010]
By arranging the planar first fiber mat and the second fiber mat so as to face each other with a certain gap, stable combustion in the most basic form, reduction of NOx, improvement of flashback resistance, etc. are realized. A combustor can be provided.
[0011]
According to a preferred embodiment of the present invention, the first fiber mat (4) and the second fiber mat (6) are formed in a coaxial double cylinder, and are arranged from the inner peripheral side of the inner first fiber mat. The premixed gas (1) having a high equivalent ratio is supplied to the space (8), and the premixed gas (2) having a low equivalent ratio is directed toward the space from the outer peripheral side of the second fiber mat located outside. Supplied.
[0012]
Since the fiber mat has a large degree of freedom in shape, a combustor having a free shape can be created. Therefore, in consideration of radiant energy recovery efficiency, downsizing of the combustor, etc., the first fiber mat and the second fiber mat are arranged in a double cylinder to constitute the combustor, so that the energy efficiency is high and the flame holding property is high. It is possible to provide a combustor which is excellent in heat resistance, has high flashback resistance, and realizes low NOx.
[0013]
According to another preferred embodiment of the present invention, the first fiber mat (4) and the second fiber mat (6) are formed in a coaxial double cylinder, and the second fiber mat (4) located inside is formed. A low equivalence ratio premixed gas (2) is supplied from the inner peripheral side toward the gap (8), and a high equivalence ratio premixed gas (1) is supplied from the outer peripheral side of the first fiber mat located on the outside. Is supplied to the gap side.
[0014]
In this embodiment, the first fiber mat and the second fiber mat are formed in a double cylindrical shape in the same manner as described above, but the arrangement is reversed. That is, in the present embodiment, a red-hot combustion surface is formed on the outer peripheral side of the gap. However, even with this configuration, it is possible to provide a combustor excellent in energy efficiency and the like as in the above-described combustor.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each of the drawings, common portions are denoted by the same reference numerals, and redundant description is omitted.
[0016]
The low NOx combustor of the present invention is mainly intended for use in a gas turbine, and a compressor for compressing air taken into the engine on the upstream side and a turbine driven by combustion exhaust gas on the downstream side. (Not shown).
In addition, this combustor is characterized by adopting a surface combustion system which has not been adopted in a combustor of a gas turbine because of its high conversion rate to radiant energy.
[0017]
FIG. 1 illustrates the principle of a low NOx combustion method for a gas turbine and a low NOx combustor according to the present invention, and shows a basic internal configuration of the low NOx combustor.
[0018]
Two mixers (not shown) are provided on the upstream side of the combustor 10, and in each mixer, air and fuel compressed by a compressor (not shown) are uniformly mixed in advance, and then burned through another path. Supplied to the vessel.
In each mixer, a relatively small amount of the premixed gas (high equivalent ratio gas 1) having a high equivalent ratio (approximately 0.8 to 1) and a large low equivalent ratio (equivalent ratio 0.4 to 0.6) are used. ) Of premixed gas (low equivalent ratio gas 2).
[0019]
The combustor 10 comprises a felt mat-shaped first fiber mat 4 and a second fiber mat 6 in which metal fibers arranged opposite to each other with a certain gap are sintered at a high porosity into a mat having a thickness of several mm. And a frame tube 16 which covers them to form the outer shape of the combustor. The first fiber mat 4 has a relatively small amount of the high equivalent ratio gas 1 from the surface opposite to the surface facing the second fiber mat 6. A high equivalence ratio gas supply pipe 18 is connected to supply a large amount of low equivalence ratio gas 2 to the second fiber mat 6 from the surface opposite to the surface facing the first fiber mat 4. A low equivalent ratio gas supply pipe 22 is connected.
[0020]
The frame tube 16 is formed by the first fiber mat 4 and the second fiber mat 6, the first space 24 to which the high equivalent ratio gas supply pipe 18 is connected, and the void space 8 between the first fiber mat and the second fiber mat. Has a layer structure partitioned into three spaces of a third space 26 to which the low equivalent ratio gas supply pipe 22 is connected, and exhausts combustion exhaust gas to the downstream end of the frame tube 16 in the space 8. Exhaust port 28 is open.
[0021]
The high equivalence ratio gas 1 supplied from the high equivalence ratio gas supply pipe 18 connected to the frame tube 16 diffuses uniformly in the first space 24, passes through the first fiber mat 4, and heads toward the void space 8, and Red heat combustion occurs on the first fiber mat surface on the space side to form a pilot frame.
On the other hand, the low equivalent ratio gas 2 supplied from the low equivalent ratio gas supply pipe 22 connected to the frame tube 16 diffuses uniformly in the third space, passes through the second fiber mat 6, and is supplied to the void space 8, The main frame is formed by performing lean combustion in the void space.
[0022]
As described above, the low NOx combustor 10 has a structure in which the pilot burner 12 is configured on one side (the lower side in the figure) and the main burner 14 is configured on the other side (the upper side in the figure) with the gap space as a boundary. .
[0023]
According to the low NOx combustor 10 having the above-described configuration, first, the glowing surface of the first fiber mat 4 having excellent flame holding properties functions as a pilot, so that a large amount of low equivalent ratio gas supplied through the second fiber mat 6 is provided. 2 can be stably lean burned in the void space 8. In lean combustion, a short blue flame that does not emit radiant heat is formed in a plane.
Further, the second fiber mat 6 facing the first fiber mat 4 is heated by radiant heat from the glowing surface of the first fiber mat, and a large amount of low equivalent ratio gas 2 supplied to the void space 8 is mat (the second fiber mat). (1, 2 fiber mats), etc., and the stable combustion range is expanded. In other words, the conventional problem of energy efficiency is solved by recovering radiant heat generated at a high conversion rate in the surface combustion method using the fiber mat for preheating the low equivalent ratio gas.
Furthermore, since the radiant heat from the glowing surface can be recovered and the combustion temperature of the high equivalence ratio gas 1 on the glowing surface can be reduced, the generation of a large amount of NOx during high-temperature combustion can be suppressed.
In addition, since the supply path of the premixed gas (high equivalent ratio gas and low equivalent ratio gas) and the combustion region (void space) are separated by the fiber mat, the flashback resistance can be improved.
Further, by mixing the combustion exhaust gas of the high equivalent ratio gas with the low equivalent ratio gas, further reduction of NOx due to the combustion gas recirculation effect can be expected.
[0024]
FIG. 2 is a schematic diagram showing a preferred embodiment in which the above-described principle of the low NOx combustor is applied to a combustor for an actual gas turbine. FIG. 2A is an axial sectional view, and FIG. Is a sectional view in the radial direction.
[0025]
The outer shape of the combustor 20 is formed by a frame tube 16 having a hollow cylindrical shape. Inside the frame tube, a first fiber mat 4 formed in a cylindrical shape coaxial with the frame tube and a first fiber mat are fixed. A second fiber mat 6 that covers the space 8 with a gap 8 is disposed.
That is, the inside of the frame tube 16 includes a space inside the cylindrical first fiber mat 4 (first space 24), a space between the first fiber mat and the second fiber mat (gap space 8), and a second fiber mat. It has a layer structure divided into three layers of a space (third space 26) between the inner circumference of the frame tube.
[0026]
A high equivalent ratio gas supply pipe 18 for supplying the high equivalent ratio gas 1 generated by one mixer (not shown) to the first space 24 is connected to the center of the frame tube 16 from the axial direction at the upstream end face side. Four low equivalence ratio gas supply pipes 22 for supplying the low equivalence ratio gas 2 generated by another mixer (not shown) to the third space 26 are connected to the outer peripheral side of the pipes from the axial direction.
An exhaust port 28 for exhausting combustion exhaust gas is annularly opened at a portion corresponding to the gap space 8 on the downstream end face side of the frame tube 16.
[0027]
According to the combustor 20 having such a configuration, the high equivalence ratio gas 1 supplied from the high equivalence ratio gas supply pipe 18 to the first space 24 is diffused in the first space, and then the first fiber mat 4 is moved into the void space 8. Side, and burns red-hot on the fiber mat surface on the void space side to form a pilot frame. Further, the low equivalent ratio gas 2 supplied from the low equivalent ratio gas supply pipe 22 to the third space 26 diffuses in the third space, and then passes through the second fiber mat toward the void space 8, and in the void space. Perform lean combustion.
[0028]
By forming the combustor in a cylindrical shape in this way, and configuring the pilot burner 12 adopting the surface combustion method and the main burner 14 performing the lean combustion therein, the same effect as the low NOx combustor 10 described above is obtained. And a small, low NOx combustor with high radiant heat recovery efficiency can be realized.
[0029]
3A and 3B are configuration diagrams schematically showing a low NOx combustor according to another embodiment, in which FIG. 3A is an axial sectional view, and FIG. 3B is a radial sectional view.
[0030]
The configuration of this combustor 30 is similar to that of the combustor 20 shown in FIG. 2, but the second fiber mat 6 is located inside and the first fiber mat 4 is located outside. That is, the high equivalent ratio gas 1 is supplied from the outer peripheral side of the first fiber mat 4 located on the outside to the gap 8 side, and the low equivalent ratio gas 2 is supplied from the inner peripheral side of the second fiber mat 6 located on the inside. Is supplied toward the void space 8.
The same effect as the combustor shown in FIG. 2 can be achieved also by the combustor having such a configuration.
In the case of the present embodiment, the glowing surface due to surface combustion is formed inside the first fiber mat near the cylindrical frame tube. However, the fiber mat has a characteristic that thermal conductivity in the thickness direction is small, so that energy efficiency is low. The above problem does not occur.
[0031]
As described above, according to the combustor of the present invention, it is possible to secure the flame holding property, to improve the energy efficiency by collecting the secured radiant heat, to expand the stable combustion range by preheating the low equivalent ratio gas, and to reduce the low NOx due to the decrease in the temperature of the red hot surface. , Improvement in flashback resistance and the like can be realized at the same time.
[0032]
It should be noted that the present invention is not limited to the above-described embodiments and examples, and it is needless to say that various changes can be made without departing from the spirit of the present invention.
[0033]
【The invention's effect】
As described above, in the present invention, the stability of lean combustion in the main burner is improved by using the glow surface in the surface combustion method as a pilot burner by using the fiber mat, and the radiant energy generated by the surface combustion is efficiently reduced. Recovering and preheating low equivalence ratio gas (lean premixed gas) to expand the stable combustion area, and reducing NOx generation by lowering the combustion temperature on the red hot surface by radiant heat recovery from the red hot surface Can be.
Therefore, according to the present invention, low NOx for gas turbines that can simultaneously achieve the flame retention of lean combustion, improve energy efficiency, reduce NOx, secure kinetic energy of combustion gas, and improve flashback resistance. A combustion method and a low NOx combustor are provided.
[Brief description of the drawings]
FIG. 1 is a principle diagram of a low NOx combustor for explaining a principle of a low NOx combustion method for a gas turbine and a low NOx combustor of the present invention.
FIG. 2 is a configuration diagram of a preferred embodiment of a low NOx combustor for a gas turbine of the present invention.
FIG. 3 is a configuration diagram of another preferred embodiment of the low NOx combustor for a gas turbine of the present invention.
[Explanation of symbols]
1 High equivalent ratio premixed gas (high equivalent ratio gas)
2 Low equivalent ratio premixed gas (low equivalent ratio gas)
4 First fiber mat 6 Second fiber mat 8 Void (void space)
10, 20, 30 Combustor 12 Pilot burner 14 Main burner 16 Frame tube 18 High equivalent ratio gas supply tube 22 Low equivalent ratio gas supply tube 24 First space 26 Third space 28 Exhaust port

Claims (4)

A premix gas (1) having a high equivalent ratio is supplied from one surface side of the first fiber mat (4) in the form of a felt mat, and the surface of the other surface side is subjected to red heat combustion,
A second fiber mat (6) in the form of a felt mat, which is disposed opposite to the other side of the first fiber mat with a predetermined gap (8) therebetween; Heat exchange with the glowing surface,
Supplying a premixed gas (2) having a low equivalent ratio to the gap through a second fiber mat to perform preheating thereof, and then performing lean combustion in the gap using the glowing surface as a pilot burner (12); A low NOx combustion method for a gas turbine. A pilot burner (12) which supplies a high-equivalence ratio premixed gas (1) from one side of a first fiber mat (4) in the form of a felt mat and burns it on the other side with red heat;
A premixed gas having a low equivalent ratio, having a second fiber mat (6) in the form of a felt mat which is disposed opposite to the other side of the first fiber mat with a certain gap (8) therebetween. A main burner (14) for supplying (2) from one side of the second fiber mat and performing lean combustion in the gap located on the other side. . The first fiber mat (4) and the second fiber mat (6) are formed in a coaxial double cylinder, and a high equivalent ratio premixed gas (1) is formed from the inner peripheral side of the first fiber mat located inside. ) Is supplied to the gap (8) side, and a low equivalent ratio premixed gas (2) is supplied toward the gap from the outer peripheral side of the second fiber mat located on the outside. The low NOx combustor for a gas turbine according to claim 2. The first fiber mat (4) and the second fiber mat (6) are formed as coaxial double cylinders, and a low equivalent ratio premixed gas (2) is formed from the inner peripheral side of the second fiber mat located inside. ) Is supplied toward the gap (8), and a premixed gas (1) having a high equivalent ratio is supplied to the gap side from the outer peripheral side of the first fiber mat located on the outside. The low NOx combustor for a gas turbine according to claim 2.

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