JP3922115B2 - Low NOx combustion method for gas turbine and low NOx combustor - Google Patents

Description

[0001]
BACKGROUND 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, and improves the stability of lean combustion of a low equivalent ratio gas. The present invention relates to a low-NOx combustion method for a gas turbine and a low-NOx combustor for a gas turbine that achieve a sufficiently low NOx and the like.
[0002]
[Prior art]
In recent years, in a combustor of a device that requires large heat energy such as a high-temperature incinerator or a boiler, it is also referred to as a fiber mat burner (“metal fiber mat burner”) that is a surface combustion type high radiation type gas burner. ) Is often used. Here, the fiber mat is obtained by sintering a metal fiber having a strand diameter of 15 to 50 μm into a mat having a thickness of several millimeters 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 supplies a gas (premixed gas) premixed with fuel and air to the combustion chamber and burns it red on the surface of the fiber mat. The mat surface is uniformly red hot and high At the same time as generating radiant heat, exhaust gas of about 1000 ° C. is discharged.
In addition, 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 surface and a low thermal conductivity in the thickness direction. Also have.
Therefore, the fiber mat burner has so far been mainly used in a field aiming at utilization of the radiant heat and combustion exhaust gas, for example, a field aiming at heating and drying of an object.
[0003]
Fiber mat burner
(1) High uniformity of combustion surface and no uneven temperature distribution.
(2) Since the flame does not rise, it is difficult to misfire, and soot is hardly generated.
(3) NOx concentration generated in combustion under certain conditions is extremely low.
(4) Excellent backfire resistance in the combustion chamber,
(5) Combustion load per unit area is higher than conventional burners.
(6) The ratio obtained as radiant heat in the input heat amount is high, and heating and drying can be made more efficient.
It has the features such as. Therefore, when this is applied to devices such as furnaces and boilers, uniform and stable flammability and backfire resistance are improved, and the use of radiant heat increases the efficiency of heating and drying of the object, in other words. Therefore, it is possible to reduce the size of the apparatus and to reduce the NOx of the combustion exhaust gas, which contributes to environmental protection.
[0004]
[Problems to be solved by the invention]
However, so far, the surface combustion type fiber mat burner has not been used in a gas turbine combustor that uses the kinetic energy of combustion exhaust gas.
The reason is
(1) Since the gas turbine drives the gas turbine by combustion exhaust gas generated by burning 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.
(2) When a premixed gas with a high equivalence ratio (equivalent ratio of about 1) is burned, it is necessary to lower the combustion temperature in the fiber mat that performs surface combustion in order to reduce NOx. If an attempt is made to lower the combustion temperature by releasing 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 very high combustion stability, the concentration of NOx generated under a certain condition is extremely low, and the backfire in the combustion chamber can be avoided. It has excellent characteristics. Therefore, if this can be applied to a combustor for a gas turbine while considering the problem of energy efficiency, a very excellent combustor can be provided.
[0006]
The present invention has been developed to solve the above-described problems. That is, the present invention improves the energy efficiency by recovering radiant heat from the surface combustion method that has not been applied to the conventional gas turbine in consideration of the problem of energy efficiency, and at the same time the red surface of the fiber mat. Provided are a low-NOx combustion method for gas turbines and a low-NOx combustor for gas turbines capable of simultaneously reducing the temperature and improving the combustion stability of premixed lean gas, reducing NOx, and improving the resistance to flashback. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention supplies a premixed gas (1) having a high equivalent ratio from one side of the felt mat-like first fiber mat (4) and burns red on the surface of the other side, A felt fiber-like second fiber mat (6) disposed opposite to the other surface side of the first fiber mat with a certain gap (8), and red heat on the other surface side of the first fiber mat. Heat exchange with the surface, a pre-mixed gas (2) having a low equivalent ratio is supplied to the gap through the second fiber mat to preheat, and then the red hot surface is pilot pilot (12 The low-NOx combustion method for gas turbines is characterized in that 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, and a small amount of a high-equivalence ratio premixed gas (hereinafter referred to as “high-equivalence ratio gas”). The surface of the first fiber mat on the air gap side is burned red, and this is used as a pilot (flame holding) burner. At this time, radiant heat is released from the red hot surface, and this radiant heat is absorbed by the gas in the second fiber mat and the gap facing each other. Since the temperature of the red hot surface of the first fiber mat decreases due to the release of radiant heat, it is possible to reduce NOx generated in large quantities during high temperature combustion of the high equivalent ratio gas.
On the other hand, from the second fiber mat heated by radiant heat, a large amount of premixed gas with a low equivalent ratio (hereinafter referred to as “low equivalent ratio gas”) is supplied toward the gap. At that time, the low equivalent ratio gas is indirectly preheated by convection heat transfer with the mat or the like, and its stable combustion range is expanded. Furthermore, the preheated low equivalent ratio gas becomes the second fiber mat because the combustion of the first fiber mat has high uniformity of the combustion surface, the temperature distribution is uniform, and the first fiber mat has a high flame holding property. Stable lean combustion (lean combustion) is performed on the air gap side, and a blue flame with a short flame length that does not release radiant heat is formed in a planar shape as a main frame in the air gap.
As described above, according to the combustion method using the fiber mat of the above-described form, there is no waste in terms of energy efficiency, (1) ensuring the flame holding property of the pilot burner by red heat combustion, and (2) high equivalence ratio gas Reduced NOx by lowering red-hot combustion temperature, (3) Presence of high flame-holding pilot burner and stable lean combustion in main burner due to preheating of low equivalent ratio gas, (4) Lower main burner by stable lean combustion Simultaneously with the NOx conversion, (5) the improvement of the backfire resistance by partitioning the premixed gas supply path and the combustion region with a fiber mat can be realized at the same time.
Further, by mixing the combustion gas of the pilot burner and 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 carrying out the above-described low NOx combustion method for a gas turbine, the present invention supplies a high equivalence ratio premixed gas (1) from one side of a felt mat-like first fiber mat (4). A felt-mat-shaped first burner disposed oppositely with a certain gap (8) between the pilot burner (12) for burning in red on the surface on the other surface side and the other surface side of the first fiber mat. A main burner (14) having a two-fiber mat (6), supplying a premixed gas (2) with a low equivalence ratio from one side of the second fiber mat and performing lean burn in the gap located on the other side And a low NOx combustor for a gas turbine.
[0010]
By arranging the first fiber mat and the second fiber mat facing each other with a certain gap between them, stable combustion in the most basic state, low NOx, improvement in flash 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 from the inner peripheral side of the first fiber mat located inside. The premixed gas (1) with a high equivalent ratio is supplied to the gap (8) side, and the premixed gas (2) with a low equivalent ratio is directed to the gap from the outer peripheral side of the second fiber mat located outside. Shall be supplied.
[0012]
Since the fiber mat has a large degree of freedom in its shape, a combustor having a free shape can be created. Therefore, in view of the recovery efficiency of radiant energy and downsizing of the combustor, the combustor is configured by arranging the first fiber mat and the second fiber mat in a double cylindrical shape, so that the energy efficiency is high and the flame holding property is improved. It is possible to provide a combustor that is excellent in resistance to fire and has high backfire resistance and 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 is located on the inner side. A premixed gas (2) with a low equivalent ratio is supplied from the inner peripheral side toward the gap (8), and a premixed gas (1) with a high equivalent ratio is supplied from the outer peripheral side of the first fiber mat located outside. May be 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 as described above, but their arrangements are reversed. That is, in this embodiment, a red-hot combustion surface is formed on the outer peripheral side of the air gap. Even with such a configuration, a combustor excellent in energy efficiency and the like can be provided as in the above-described combustor.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, 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. A compressor that compresses air taken into the engine on the upstream side and a turbine driven by combustion exhaust gas on the downstream side. Is arranged (not shown).
In addition, this combustor is characterized by adopting a surface combustion method which has not been employed in a gas turbine combustor from the viewpoint of high conversion rate to radiant energy.
[0017]
FIG. 1 is shown for explaining 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 mixed in advance and then burned through another path. Supplied to the vessel.
In each mixer, a relatively small amount of pre-mixed gas (high equivalent ratio gas 1) having a high equivalent ratio (equivalent ratio of about 0.8 to 1) and a large amount of low equivalent ratio (equivalent ratio 0.4 to 0.6). Degree) premixed gas (low equivalent ratio gas 2).
[0019]
The combustor 10 includes a first fiber mat 4 and a second fiber mat 6 in the form of a felt mat obtained by sintering metal fibers arranged opposite to each other with a predetermined gap into a mat having a high porosity and a thickness of several mm. The first fiber mat 4 has a relatively small amount of the high equivalent ratio gas 1 from the side opposite to the surface facing the second fiber mat 6. A high equivalent ratio gas supply pipe 18 is connected to supply the second fiber mat 6 with a large amount of low equivalent ratio gas 2 from the opposite side of the surface facing the first fiber mat 4. A low equivalent ratio gas supply pipe 22 is connected.
[0020]
The frame tube 16 includes a first space 24 to which a high equivalent ratio gas supply pipe 18 is connected by the first fiber mat 4 and the second fiber mat 6, and a gap space 8 between the first fiber mat and the second fiber mat. In addition, it has a layered structure partitioned into three spaces of a third space 26 to which a 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 gap space 8 portion. An exhaust port 28 is opened.
[0021]
The high equivalent ratio gas 1 supplied from the high equivalent 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 toward the gap space 8, and the gap It burns red on the surface of the first fiber mat 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 lean combustion in the void space.
[0022]
Thus, the low NOx combustor 10 has a structure in which the pilot burner 12 is formed on one side (lower side in the figure) and the main burner 14 is formed on the other side (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, a large amount of low equivalent ratio gas supplied through the second fiber mat 6 is obtained because the red hot surface of the first fiber mat 4 excellent in flame holding function functions as a pilot. 2 can be stably burned in the void space 8. In lean combustion, a blue flame with a short flame length that does not release radiant heat is formed in a planar shape.
The second fiber mat 6 facing the first fiber mat 4 is heated by the radiant heat from the red surface of the first fiber mat, and a large amount of the low equivalent ratio gas 2 supplied to the gap space 8 is the mat (first Preheated by convection heat transfer or the like with 1, 2 fiber mat), and the stable combustion range is expanded. In other words, by recovering the radiant heat generated at a high conversion rate in the surface combustion method using the fiber mat for preheating the low equivalent ratio gas, the conventional problem of energy efficiency is solved.
Furthermore, since the radiant heat from the red hot surface can be recovered and the combustion temperature of the high equivalent ratio gas 1 on the red hot surface can be lowered, it is possible to suppress the generation of a large amount of NOx generated during high temperature combustion.
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 partitioned by the fiber mat, the resistance to flashback can be improved.
Further, by mixing the high-equivalent-ratio combustion exhaust gas and the low-equivalent-ratio gas, further reduction in NOx due to the combustion gas recirculation effect can be expected.
[0024]
FIG. 2 is a configuration diagram schematically showing a preferred embodiment in which the principle of the low NOx combustor described above is applied to an actual gas turbine combustor, where (a) is an axial sectional view, and (b). FIG.
[0025]
The outer shape of the combustor 20 is formed by a cylindrical hollow frame tube 16. A first fiber mat 4 formed in a cylindrical shape coaxial with the frame tube and a first fiber mat are fixed inside the frame tube. The second fiber mat 6 is disposed so as to cover the gap 8.
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 the second fiber mat. It has a layered structure divided into three layers of the space (third space 26) between the inner periphery 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 upstream end surface of the frame tube 16 from the axial direction. In addition, four low equivalent ratio gas supply pipes 22 for supplying the low equivalent ratio gas 2 generated in another mixer (not shown) to the third space 26 are connected to the outer peripheral side from the axial direction.
An exhaust port 28 for exhausting combustion exhaust gas is annularly opened in 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, after the high equivalent ratio gas 1 supplied from the high equivalent ratio gas supply pipe 18 to the first space 24 diffuses in the first space, the first fiber mat 4 is allowed to pass through the gap space 8. The pilot frame is formed by burning red heat on the surface of the fiber mat on the gap space side. 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 gap space 8. Perform lean combustion.
[0028]
In this way, the combustor is formed in a cylindrical shape, and the pilot burner 12 adopting the surface combustion method and the main burner 14 for performing lean combustion are formed therein, thereby achieving the same effect as the low NOx combustor 10 described above. And a small low-NOx combustor with high radiant heat recovery efficiency.
[0029]
FIG. 3 is a configuration diagram schematically showing a low NOx combustor according to another embodiment, in which (a) is an axial sectional view and (b) is a radial sectional view.
[0030]
The configuration of the combustor 30 is similar to that of the combustor 20 shown in FIG. 2, but the second fiber mat 6 is located on the inner side and the first fiber mat 4 is located on the outer side. That is, the high equivalent ratio gas 1 is supplied from the outer peripheral side of the first fiber mat 4 positioned on the outer side to the gap space 8 side, and the low equivalent ratio gas 2 is supplied from the inner peripheral side of the second fiber mat 6 positioned on the inner side. Is supplied toward the void space 8.
Even with the combustor having such a configuration, the same effect as that of the combustor shown in FIG. 2 can be achieved.
In the case of the present embodiment, the red hot surface due to surface combustion is formed inside the first fiber mat in the vicinity of the cylindrical frame tube. However, since the fiber mat has a characteristic that the thermal conductivity in the thickness direction is small, it is energy efficient. The above problem does not occur.
[0031]
As described above, according to the combustor of the present invention, the flame holding property is ensured, the energy efficiency is improved by collecting the secured radiant heat, the stable combustion range is expanded by the preheating of the low equivalent ratio gas, and the low NOx due to the temperature reduction of the red hot surface. It is possible to simultaneously achieve improvement in resistance to flashback and the like.
[0032]
Note that the present invention is not limited to the above-described embodiments and examples, and can be variously modified without departing from the gist of the present invention.
[0033]
【The invention's effect】
As described above, in the present invention, by using a fiber mat, the red hot surface in the surface combustion method is used as a pilot burner, the stability of lean combustion in the main burner is improved, and the radiant energy generated by the surface combustion is efficiently increased. Recover and preheat low-equivalent gas (diluted premixed gas) to expand the stable combustion area, and reduce the combustion temperature on the red hot surface by radiant heat recovery from the red hot surface to suppress the generation of NOx Can do.
Therefore, according to the present invention, low NOx for gas turbines that can simultaneously achieve the flame holding property of lean combustion, the improvement of energy efficiency, the reduction of NOx, the securing of the kinetic energy of combustion gas, and the improvement of 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 the principle of a low NOx combustion method for a gas turbine and a low NOx combustor according to the present invention.
FIG. 2 is a configuration diagram of a preferred embodiment of a low-NOx combustor for a gas turbine according to the present invention.
FIG. 3 is a configuration diagram of another preferred embodiment of a low-NOx combustor for a gas turbine according to the present invention.
[Explanation of symbols]
1 High equivalence ratio premixed gas (high equivalence ratio gas)
2 Premixed gas with low equivalent ratio (low equivalent ratio gas)
4 First fiber mat 6 Second fiber mat 8 Gap (gap space)
10, 20, 30 Combustor 12 Pilot burner 14 Main burner 16 Frame tube 18 High equivalent ratio gas supply pipe 22 Low equivalent ratio gas supply pipe 24 First space 26 Third space 28 Exhaust port

Claims (4)

A high-equivalent ratio premixed gas (1) is supplied from one side of the felt mat-like first fiber mat (4) and burned red on the other side.
A felt-mat-like second fiber mat (6) disposed opposite to the other side of the first fiber mat with a certain gap (8) between the other side of the first fiber mat and the other side of the first fiber mat. Heat exchange with the red hot surface,
A low-equivalent ratio premixed gas (2) is supplied to the gap through the second fiber mat and preheated, and then lean combustion is performed in the gap with the red hot surface as a pilot burner (12). A low NOx combustion method for a gas turbine. A pilot burner (12) for supplying a high equivalence ratio premixed gas (1) from one side of the felt-mat-shaped first fiber mat (4) and burning it red on the surface of the other side;
A felt fiber-like second fiber mat (6) disposed opposite to the other side of the first fiber mat with a certain gap (8), and having a low equivalent ratio premixed gas A main burner (14) for supplying (2) from one side of the second fiber mat and performing lean burn in the gap located on the other side, and a low NOx combustor for a gas turbine, . 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 premixed gas (2) having a low equivalent ratio is supplied toward the gap from the outer peripheral side of the second fiber mat located 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 in a coaxial double cylinder, and from the inner peripheral side of the second fiber mat located on the inner side, a premixed gas (2 ) Is supplied toward the gap (8), and a premixed gas (1) having a high equivalent ratio is supplied from the outer peripheral side of the first fiber mat located on the outer side to the gap side. The low NOx combustor for a gas turbine according to claim 2.

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