JP2004293519A - Combustion control method of steam jet gas turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion control method for a steam jet gas turbine capable of increasing the output of the gas turbine by jetting a large quantity of steam to a combustor when the demand for electric power is large, nullifying the injection of steam completely when the power demand remains small and the demand for the steam is large, and maintaining a high combustion efficiency while NOx generation is suppressed at all times. <P>SOLUTION: The combustion control method of the steam jet gas turbine is configured with a pilot burner 12 of diffused combustion type installed in the center, a plurality of main burners 14 of premixed combustion type arranged around the pilot burner, and a steam injection pipe 16 to supply steam to be mixed with the influx air to the pilot burner and the main burners, wherein the ratio (S+A)/F as the sum of the steam S and the air A in the pilot burner and the main burners to the fuel F is held within the stable combustion range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a combustion control method for a steam injection gas turbine that injects steam into a combustor of the gas turbine.
[0002]
[Prior art]
In recent years, Patent Documents 1 to 5 and the like have been proposed as steam injection gas turbines for increasing the output by injecting steam into a combustor of a gas turbine.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 8-26780 [Patent Document 2]
Japanese Patent Application Laid-Open No. H9-125984 [Patent Document 3]
JP-A-10-184393 [Patent Document 4]
JP 2002-4946 A [Patent Document 5]
JP-A-2002-130675
In the two-fluid cycle disclosed in Patent Document 1, as shown in FIG. 12, steam 52 generated by exhaust heat E of gas turbine equipment 51 is mixed with compressed air by a mixer 53, and the mixed gas is exhausted by exhaust heat E. By heating the fuel in the combustor 55 of the gas turbine and injecting it into the combustor 55 of the gas turbine, the power generation output can be increased in accordance with the power demand while supplying the surplus steam 52a as a utility. In this figure, 56 is an exhaust heat recovery boiler, A is air, F is fuel, and W is water supply.
[0005]
As shown in FIG. 13, a "steam injection gas turbine and a control method therefor" disclosed in Patent Document 2 include a compressor 62, a combustor 63 and a turbine 64, steam injection means 65 for injecting steam into the combustor, and a compressor. Air amount control means 66 for adjusting the amount of air flowing into the compressor by adjusting the angle of the stationary blades, and control means 67 for controlling the amount of air flowing into the compressor. It controls the air amount control means 66 so as to reduce the air amount or to suppress the pressure fluctuation of the air compressed by the compressor 62.
[0006]
As shown in FIG. 14, the “control method of a gas turbine power generation device” of Patent Document 3 includes an engine control device 71, a steam control device 72, and an output management device 73, and generates NOx in a combustor 74 from a fuel flow rate. The amount of steam to be suppressed is calculated and adjusted, and the turbine injection steam amount and the fuel flow rate are calculated for the case of giving priority to the electric power and the case of giving priority to the process steam.
[0007]
As shown in FIG. 15, a “heat / electricity ratio control method for a small-capacity gas turbine cogeneration system” disclosed in Patent Document 4 is a steam control valve that supplies a part of steam generated by an exhaust heat recovery boiler 81 to a combustor 82. A steam supply passage 84 having a steam supply passage 83 is provided, and the opening degree of the steam control valve 83 is adjusted according to the heat load of the exhaust heat recovery boiler 81 to control the thermoelectric ratio of the system output.
[0008]
As shown in FIG. 16, a "low NOx combustor for a two-fluid cycle and its operating method" in Patent Document 5 discloses a diffusion combustion type pilot burner 92 disposed at a center portion and a plurality of pilot burners 92 disposed around the pilot burner 92. And a steam injection pipe 96 for supplying steam so as to be mixed with air flowing into the fuel injection valve 9 of the main burner. When performing steam injection to increase output, A part of the steam to be injected is injected from the steam injection pipe 96, mixed with the air flowing into the main injection valve, and supplied to the fuel injection valve.
[0009]
[Problems to be solved by the invention]
In order to protect the environment, it is required to reduce NOx (nitrogen oxides) in the combustion exhaust gas of a gas turbine. In Japan, it is necessary to reduce it to, for example, 20 ppm or less in a large city (for example, Tokyo).
The main cause of NOx generation is so-called thermal NOx, in which nitrogen in the air is oxidized by a high-temperature flame during combustion. To reduce this thermal NOx, hot spots in the flame are reduced to generate high-temperature flame. It is effective to eliminate
[0010]
For this reason, in Patent Documents 1 to 4 described above, means for lowering the flame temperature by injecting steam is used, and a "diffusion combustor" capable of performing stable combustion even when injecting steam is used in the combustor. .
However, when steam is injected into the diffusion combustor, if the amount of water vapor is reduced too much, the amount of generated NOx may increase and exceed the regulation value. Therefore, there is a problem that the steam injection is always required, and accordingly, the amount of the utility steam is reduced and the fuel consumption is increased.
[0011]
On the other hand, as a combustor capable of reducing NOx, a "lean premixed combustor" disclosed in Patent Document 5 is known in addition to the above-described steam injection diffusion combustor. This lean premixed combustor premixes fuel with a sufficient amount of air to homogenize it, and burns it lean.Therefore, since it is burned with a large amount of air, it has no hot spots and eliminates the generation of high-temperature flames. Low NOx can be realized.
[0012]
Therefore, by applying the conventional lean premixed combustor to the steam injection gas turbine, the NOx generation amount can be kept within the regulation value even if the steam injection is eliminated, and the steam injection is eliminated as necessary, The utility vapor amount can be increased and the fuel consumption can be reduced.
[0013]
However, this lean premixed combustor does not require steam to reduce NOx, but has a problem that combustion tends to be unstable. For this reason, simply injecting steam into the lean premixed combustor will cause the flame temperature to drop too low to make stable combustion difficult and cause misfire, or if the fuel is increased to stabilize combustion, the fuel will become excessive in the fuel region. However, there is a problem that the original lean combustion cannot be performed, the amount of generated NOx increases, and the combustion efficiency decreases.
[0014]
The present invention has been made to solve such a problem. That is, an object of the present invention is to increase the output of a gas turbine by injecting a large amount of steam into a combustor when power demand is large, and to completely eliminate steam injection when power demand is small and steam demand is large. It is an object of the present invention to provide a combustion control method for a steam injection gas turbine that can maintain high combustion efficiency while always suppressing the generation of NOx.
[0015]
[Means for Solving the Problems]
According to the present invention, a diffusion combustion type pilot burner arranged in the center, a plurality of premixed combustion type main burners arranged therearound, and a mixture with air flowing into the pilot burner and the main burner are mixed. A steam injection pipe for supplying steam,
A combustion control method for a steam injection gas turbine, wherein a ratio (S + A) / F of a sum of steam S and air A and fuel F in a pilot burner and / or a main burner is maintained in a stable combustion range. You.
[0016]
According to the present invention described above, the ratio (S + A) / F of the sum of the steam S and the air A and the fuel F in the pilot burner and / or the main burner is maintained in the combustion stable range, so that stable combustion can be always realized. A reduction in combustion efficiency can be prevented, and a reduction in NOx can be achieved. Therefore, this combustion control method can eliminate unstable phenomena such as oscillating combustion, reduction in combustion efficiency, and runout.
[0017]
According to a preferred embodiment of the present invention, the fuel flow to the pilot burner is increased according to the increase in the steam injection amount, and the ratio (S + A) / F of the sum of steam S and air A and fuel F in the pilot burner is increased. Keep within stable combustion range.
[0018]
In general, in a low NOx combustor, the combustion power of the central burner located around the center enables lean combustion of the main burner. However, when the steam injection amount increases, the combustion of the pilot burner becomes weak, and the main burner also becomes improper. Become stable.
According to the present invention described above, the fuel flow to the pilot burner, which becomes the ignition source, is increased continuously or stepwise in accordance with the increase in the steam injection amount. Therefore, the sum of steam S and air A and the fuel F in the pilot burner are increased. (S + A) / F can be maintained in the combustion stable range, stable combustion of the pilot burner and the main burner can be realized, a decrease in combustion efficiency can be prevented, and a reduction in NOx can be achieved.
[0019]
Further, according to the present invention, the number of main burners used is changed in accordance with an increase in the steam injection amount, and the ratio (S + A) / F of the sum of steam S and air A and fuel F in the main burner to be used is burned. Keep in stable range.
It is preferable that the number of main burners used is gradually reduced in accordance with an increase in the steam injection amount.
[0020]
In general, a plurality of premixed combustion type main burners (multi-injection valves) of a low NOx combustor enable lean combustion by lean mixing of air and fuel in an excess air state in a premixing pipe. When the steam injection amount increases, the fuel becomes more lean and the combustion efficiency decreases.
According to the present invention described above, the number of main burners used is changed in accordance with an increase in the steam injection amount, the fuel flow rate per one multi-injection valve used is increased, and the steam S and air in the main burner used are increased. Since the ratio (S + A) / F of the sum of A and the fuel F is kept within the stable combustion range, a decrease in combustion efficiency can be prevented, and a reduction in NOx can be achieved.
That is, by determining the optimal number of multi-injection valves to be used in accordance with the steam injection amount, a decrease in combustion efficiency is suppressed, and steam injection up to the steam injection amount specific to the engine can be performed without being affected by the conditions of the combustor.
[0021]
According to the combustion control method of the present invention described above, in the steam injection gas turbine, in an operation state in which steam injection for increasing output is not performed, the low NOx combustor operates as a conventional lean premixed combustor, Even if injection is eliminated, the amount of generated NOx can be kept within the regulation value, and the amount of utility steam can be increased accordingly.
[0022]
Also, when performing steam injection to increase the output, the steam to be injected is injected from the steam injection pipe and mixed with the air flowing into the pilot burner and the main burner, so that the steam and the air are sufficiently mixed uniformly. Can be introduced. Therefore, even if steam is injected into premixed combustion that is relatively unstable in combustion, stable combustion can be performed.
[0023]
Furthermore, by increasing the steam injection amount in accordance with the increase amount of the fuel, the combustion amount can be increased while suppressing the generation of NOx, and the output of the gas turbine can be increased. Note that the remaining steam is preferably injected into a position relatively not involved in combustion, such as a thin hole in a combustor liner.
[0024]
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.
[0025]
FIG. 1 is an overall configuration diagram of a steam injection gas turbine to which the combustion control method of the present invention is applied. As shown in FIG. 1, the steam injection gas turbine includes an air compressor 1, a gas turbine 2, a combustor 3, a speed reducer 4, a generator 5, a waste heat boiler 6, a mist separator 7, and the like. By injecting the steam S generated by the exhaust heat E into the combustor 3, the power generation output can be increased according to the power demand while supplying the surplus steam as a utility. In this figure, A is air, F is fuel, and W is water supply.
[0026]
FIG. 2 is a specific example of the thermoelectric output characteristics of the steam injection gas turbine of the present invention. In this figure, the horizontal axis represents the amount of supplied steam that can be supplied to the outside as a utility, and the vertical axis represents the output of the power generation terminal. A in the figure is a dry operation line that does not inject steam into the combustor, and B is a maximum output line that injects steam into the combustor to maximize the output.
From this figure, this steam-injected gas turbine can obtain a power generation terminal output of about 2000 kW without injecting steam into the combustor, and at that time, supplies a maximum of about 6000 kg / h of steam as a utility to the outside. it can. In addition, it can be seen that by injecting a part of the steam into the combustor, it is possible to obtain a power generation end output of up to about 2500 kW.
[0027]
FIG. 3 is an overall configuration diagram of a low NOx combustor to which the present invention is applied. As shown in this figure, the low NOx combustor 3 includes a pilot burner 12 disposed at the center and a plurality (six in this example) of main burners 14 disposed around the pilot burner 12. In this figure, 21 is a scroll, 22 is a combustor liner, 23 is a casing, 24 is a spark plug (igniter), and air A compressed by the air compressor 1 flows between the casing 23 and the liner 22. The gas reaches the burners 12 and 14 and flows through the burners and other parts into the liner 22 to form flames 27a and 27b, and the generated combustion gas passes through a scroll portion (not shown) and passes through a gas turbine (not shown). 2 to drive it.
[0028]
In FIG. 3, a pilot burner 12 is a diffusion combustion burner for diffusing and burning fuel F in the combustion chamber 11.
The main burner 14 includes a main injection valve 14a and a premixing pipe 14b which are arranged coaxially with each other. Fuel F is supplied to the main injection valve 14a from the outside through the casing 23 of the low NOx combustor 3. As this fuel, for example, gas fuel is used. The premix tube 14b is a cylindrical tube having an open lower end in this figure, and facilitates mixing of fuel and air inside each other. That is, the main burner 14 is a premix lean burner constituted by the main injection valve 14a and the premix pipe 14b.
According to this configuration, the fuel F can be injected into the premixing pipe 14b by the main injection valve 14a, and the fuel F can be premixed with a sufficient amount of air in the premixing pipe 14b to perform lean combustion.
[0029]
The low NOx combustor 3 to which the present invention is applied further includes a steam injection pipe 16 that supplies steam so as to be mixed with air flowing into a fuel injection valve (main injection valve 14a) of the main burner 14.
A plurality (for example, six) of the steam injection pipes 16 are attached around the casing 3a of the low NOx combustor 3 to supply steam mixed with air flowing into the pilot burner 12 and the main burner 14. I have.
[0030]
In the present invention, the amount of steam supplied from the plurality of steam injection tubes 16 is always substantially equal, and only the total amount is variably controlled by a steam flow control valve (not shown). Furthermore, the steam injected from the steam injection pipe 16 into the combustor is mixed with air as completely as possible and supplied to the pilot burner 12 and the main burner 14.
Also, the flow rate of fuel supplied to the pilot burner 12 disposed at the center (hereinafter, referred to as pilot fuel flow rate) is variably controlled by a steam flow control valve (not shown).
Further, the total amount of fuel flow supplied to a plurality of (six in this example) main burners 14 (hereinafter referred to as main fuel flow) is variably controlled by a steam flow control valve (not shown).
In addition, each of the plurality of main burners 14 is provided with an independent on-off valve, so that the number of main burners used can be freely changed. In this case, the mixed gas of the air and the steam flows almost uniformly to all the main burners 14, and the fuel is additionally supplied only to the main burners to be used.
[0031]
According to the configuration of the present invention described above, the flame burn source of the main burner 14 can be formed by performing diffusion combustion by the pilot burner 12. Further, generation of NOx can be suppressed by premix combustion in the premix pipe 15 of the main burner 14.
[0032]
【Example】
Hereinafter, an embodiment of a steam injection gas turbine including the above-described low NOx combustor 3 will be described.
[0033]
FIG. 4 is a diagram showing the relationship between the power output of the steam injection gas turbine shown in FIGS. 1 to 3 and the fuel flow rate. In this figure, the horizontal axis represents the power generation end output, the vertical axis represents the fuel flow rate, and the symbol ◆ in the figure represents the operating conditions under which stable combustion was obtained.
From this figure, it is understood that stable combustion can be achieved by increasing the fuel flow rate substantially in proportion to the increase in the output of the power generation end.
[0034]
FIG. 5 is a diagram showing the relationship between the output of the power generation terminal and the flow rate of steam under the same conditions. In this figure, the horizontal axis is the power output end, the vertical axis is the steam flow rate, and the symbol ◆ in the figure is the operating conditions under which stable combustion was obtained.
From this figure, as shown in FIG. 2, in this steam injection gas turbine, it is possible to obtain a power generation end output of about 1500 kW or more even under dry conditions in which steam is not injected into the combustor. It can be seen that a maximum output power of about 2500 kW can be obtained.
[0035]
FIG. 6 is a diagram showing the relationship between the output of the power generation end and the flow rate of the pilot fuel. In this figure, the horizontal axis represents the power generation end output, the vertical axis represents the fuel flow rate, and the symbols ■ and の in the figure represent the operating conditions under which stable combustion was obtained. In addition, ■ indicates the case where all six main burners are used (N = 6), and ○ indicates the case where only four of the six main burners are used (N = 4).
From this figure, in both cases of N = 6 and N = 4, the fuel flow to the pilot burner (pilot fuel flow) is increased in a substantially linear manner in accordance with the increase in the output of the power generation end, thereby achieving stable combustion. You can see that you can do it.
[0036]
FIG. 7 is a relationship diagram between the steam injection amount and the pilot fuel flow rate. In this figure, the horizontal axis represents the steam injection amount, the vertical axis represents the fuel flow rate, Δ represents the case where all six main burners are used (N = 6), and O represents the case where only four of the six burners are used (N = 4).
In addition, each symbol in the drawing indicates an implementation condition under which stable combustion is obtained, and as described later, is an implementation condition under which low NOx and high combustion efficiency are obtained.
[0037]
From this figure, in both cases of N = 6 and N = 4, the fuel flow rate to the pilot burner (pilot fuel flow rate) is increased in proportion to the first order in accordance with the increase of the steam injection amount, thereby stabilizing. It can be seen that combustion, low NOx, and high combustion efficiency can be obtained. The increase in the pilot fuel flow rate may be continuous or stepwise (stepwise).
That is, by increasing the flow rate of fuel to the pilot burner, which becomes the type of ignition, continuously or stepwise according to the increase in the steam injection amount, the ratio (S + A) of the sum of steam S and air A and fuel F in the pilot burner is increased. ) / F can be maintained in a stable combustion range, stable combustion can be achieved, a decrease in combustion efficiency can be prevented, and a reduction in NOx can be achieved.
[0038]
FIG. 8 is a diagram showing the relationship between the power generation end output and the main fuel flow rate when using six tubes, and FIG. 9 is a diagram showing the relationship between the power generation end output and the main fuel flow amount when using four tubes. In these figures, the horizontal axis represents the power output end, and the vertical axis represents the main fuel flow rate. In addition, each symbol in the figure indicates an implementation condition under which stable combustion is obtained, and as described later, is an implementation condition under which low NOx and high combustion efficiency are obtained.
[0039]
From this figure, when all six main burners are used (N = 6) in a region where the power generation end output for performing steam injection is 1500 kW or more (N = 6), only four of the six burners are used (N = 4). It can be seen that the main fuel flow rate per main burner is relatively smaller than in the case of (1). This is because the fuel flow rate of the used main burners x the total number of the main burners does not change, but as described above, the mixed gas of air and steam flows almost uniformly to all the main burners 14, and the fuel is supplied only to the main burners used. It depends.
[0040]
FIG. 10 is a diagram showing the relationship between the output of the power generation end and the NOx amount, and FIG. 11 is a diagram showing the relationship between the output of the power generation end and the combustion efficiency. In these figures, the horizontal axis is the power generation end output, the vertical axis is the NOx amount or the combustion efficiency, Δ is when all six main burners are used (N = 6), ○ is only four out of six main burners (N = 4).
[0041]
From this figure, by controlling the ratio (S + A) / F of the pilot burner, it is possible to secure low NOx and maintain the combustion efficiency, and to change the number of main burners from six to four when the steam injection amount and output increase. This indicates that the combustion efficiency recovers.
[0042]
All the embodiments described above are based on the same steam injection gas turbine embodiment. From the results of FIG. 8 to FIG. 11, in the region of 1500 kW or more at the power generating end for performing steam injection, particularly in the region of 2200 kW or more where the main fuel flow rate is reduced, when all six are not used and only four are used. It can be seen that is better in both NOx reduction and combustion efficiency.
Therefore, in this example, in a region where the output of the power generation end where steam injection is not performed is low, the number of main burners is increased, for example, to 1, 2,... In the region where the power generation end output is 1500 kW or more, it is preferable to reduce the number to six to four in inverse proportion to the power generation end output.
That is, the number of main burners used is changed in accordance with an increase in the steam injection amount, and the ratio (S + A) / F of the sum of the steam S and the air A and the fuel F in the main burner to be used is maintained in a stable combustion range. Thus, it is possible to simultaneously achieve stable combustion, low NOx, and high combustion efficiency.
[0043]
The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the invention.
[0044]
【The invention's effect】
According to the present invention described above, the ratio (S + A) / F of the sum of the steam S and the air A and the fuel F in the pilot burner and / or the main burner is maintained in the combustion stable range, so that stable combustion can be always realized. A reduction in combustion efficiency can be prevented, and a reduction in NOx can be achieved. Therefore, this combustion control method can eliminate unstable phenomena such as oscillating combustion, reduction in combustion efficiency, and runout.
[0045]
Therefore, the combustion control method of the steam injection gas turbine of the present invention can increase the output of the gas turbine by injecting a large amount of steam into the combustor when the power demand is large, and the power demand is small and the steam demand is large. Occasionally, there are excellent effects such as the ability to completely eliminate steam injection and to maintain high combustion efficiency while always suppressing the generation of NOx.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a steam injection gas turbine to which a combustion control method of the present invention is applied.
FIG. 2 is an example of thermoelectric output characteristics of the steam injection gas turbine of the present invention.
FIG. 3 is an overall configuration diagram of a combustor according to the present invention.
FIG. 4 is a diagram showing the relationship between the output of the power generation end and the fuel flow rate.
FIG. 5 is a diagram showing the relationship between the output of the power generation end and the flow rate of steam.
FIG. 6 is a diagram showing the relationship between the output of the power generation end and the flow rate of the pilot fuel.
FIG. 7 is a relationship diagram between a steam injection amount and a pilot fuel flow rate.
FIG. 8 is a diagram showing the relationship between the output of the power generation end and the flow rate of the main fuel when six fuel tubes are used.
FIG. 9 is a diagram showing the relationship between the output of the power generation end and the flow rate of the main fuel when four fuel cells are used.
FIG. 10 is a relationship diagram between a power generation end output and a NOx amount.
FIG. 11 is a diagram showing the relationship between the output of the power generation end and the combustion efficiency.
FIG. 12 is a configuration diagram of a conventional steam injection gas turbine.
FIG. 13 is a configuration diagram of another conventional steam injection gas turbine.
FIG. 14 is a configuration diagram of another conventional steam injection gas turbine.
FIG. 15 is a configuration diagram of another conventional steam injection gas turbine.
FIG. 16 is a configuration diagram of another conventional steam injection gas turbine.
[Explanation of symbols]
1 air compressor, 2 turbines, 3 combustor (low NOx combustor), 4 reducer,
5 generator, 6 waste heat boiler, 7 mist separator,
12 pilot burner (diffusion combustion burner),
14 Main burner (premixed lean burner),
14a main injection valve, 14b premix pipe,
16 steam injection pipe, 21 scroll, 22 combustor liner,
23 casing, 24 spark plug (igniter),
27a, 27b flame,
A air, E waste heat, F fuel, W feed water, S steam

Claims (4)

A diffusion combustion type pilot burner arranged in the center, a plurality of premixed combustion type main burners arranged therearound, and steam injection for supplying steam mixed with air flowing into the pilot burner and the main burner With a tube,
A combustion control method for a steam injection gas turbine, wherein a ratio (S + A) / F of a sum of steam S and air A and fuel F in a pilot burner and / or a main burner is maintained in a stable combustion range. The fuel flow rate to the pilot burner is increased in accordance with the increase in the steam injection amount, and the ratio (S + A) / F of the sum of steam S and air A and fuel F in the pilot burner is maintained in a stable combustion range. The method for controlling combustion of a steam injection gas turbine according to claim 1, wherein: Changing the number of main burners used in accordance with the increase of the steam injection amount, and maintaining the ratio (S + A) / F of the sum of steam S and air A and fuel F in the main burner to be used in a stable combustion range. The method for controlling combustion of a steam injection gas turbine according to claim 1, wherein: The method for controlling combustion of a steam-injected gas turbine according to claim 3, wherein the number of main burners used is gradually reduced in accordance with an increase in the steam injection amount.

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