JP2527170B2 - Operation method of gas turbine two-stage combustor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas turbine combustor, and particularly to a significantly low combustor.
The present invention relates to an operation method for achieving optimum NOx-reducing fuel and air conditions in a two-stage combustor to improve combustion performance and reduce NOx.

[Prior art]

Due to increasing social demands for energy saving and resource saving, the recent needs are for construction plans of a combined combined power generation plant of a gas turbine and a steam turbine aiming at high temperature and high efficiency. However, the environmental regulations for exhaust gas from gas turbines are strict, and in particular regarding the emission of nitrogen oxides (NOx), which is said to be an air pollutant, gas turbine combustors generally do not fall within the regulation values, and development of low NOx combustors is an urgent task. ing. As a result of this development, the fuel is divided into two systems, and the head combustion chamber that burns the primary fuel and the rear combustion chamber that burns the secondary fuel in the high load zone downstream of this combustion chamber are provided. Operates only with the primary fuel in the low load range up to about 25%,
Supply and burn both secondary. In the rear combustion chamber, the secondary fuel is ignited by the head combustion chamber fire.

Since each combustion chamber is capable of lean lean combustion with excess air, it is possible to reduce NOx. However, in a gas turbine plant, the fuel flow rate changes almost in proportion to the load change, but since the amount of air from the compressor is almost constant (because the gas turbine speed is constant), there is no air flow inside the combustor. The weight ratio with fuel (called the fuel-air ratio) fluctuates. For this reason, the combustion state in the gas turbine operating range is not constant, and even if it is set to have a preferable fuel air ratio in a certain load zone, the fuel becomes excessively rich in another load state,
NO is produced by thinning or carbon monoxide (C
O) and unburned fuel components (HC) will increase. For this reason, the primary fuel and the air flow rate are controlled so that a constant fuel-air ratio is maintained at all times, as seen in JP-A-61-52523. Then, when the load is above a certain load zone, the fuel of the second stage is introduced.

In this prior art, the primary head combustion chamber has a limited combustion range for premixing fuel and air prior to combustion. For this reason, the primary air flow rate is controlled so that the fuel-air ratio is always constant from ignition. To control the air flow rate, a part of the air from the compressor is extracted and further boosted to adjust the flow rate, which not only reduces efficiency but also needs to adjust the flow rate in a wide range of conditions from ignition to secondary fuel injection. Since there is a possibility that the energy is lost for boosting the pressure, it causes a decrease in efficiency in a wide operating range. On the other hand, because the flow rate of the secondary air is not adjusted, the fuel-air ratio of the secondary fuel and the air is different in the high load zone from the time of the secondary fuel input, so the fuel is supplied when the fuel flow rate at the secondary fuel input is small. Since the concentration becomes low, the secondary fuel is discharged before it reaches the combustible range, and even if it enters the combustion range, CO and HC are often generated when the concentration is low.

[Problems to be solved by the invention]

In the above-mentioned prior art, when the secondary fuel is input, the 2 o'clock fuel is thin so that it deviates from the combustion range, so that unburned components and CO are generated more frequently. However, there were problems such as air flow impact force due to a sudden load change of the gas turbine, damage due to thermal shock, and deterioration of reliability.

An object of the present invention is to facilitate ignition of a secondary fuel from a flame of a primary fuel in a two-stage combustion type gas turbine plant, to eliminate a sudden load change, to improve the combustion performance of the primary combustion, and to reduce CO and HC. By controlling the fuel-air ratio with the secondary air in the secondary combustion while suppressing the generation of NOx, it is intended to improve the combustion performance and realize low NOx over the entire operating load range of the gas turbine.

[Means for solving problems]

The operating method of the present invention created to achieve the above object suppresses rapid load fluctuation due to secondary fuel injection, and
In order to suppress the generation of CO and HC after the injection of secondary fuel, the action of increasing the secondary fuel while reducing the primary fuel while suppressing the sum of the primary and secondary fuel is performed rapidly. Reduce load fluctuations. In addition, by suppressing the reduction of primary fuel and using secondary air flow rate control to realize secondary combustion with a small amount of secondary fuel, the generation of CO and HC is suppressed and secondary combustion is facilitated. To do. Furthermore, when the load is high, the secondary air is increased and the secondary fuel is increased to perform premixed dilution combustion to achieve a significant reduction in NOx while suppressing the increase in primary fuel and reducing NOx in the head combustion chamber. Suppress the occurrence. In this way, after the injection of secondary fuel, the combined use of primary and secondary fuel control and secondary air control suppresses the generation of CO and HC and reduces NOx in the operating load zone of the gas turbine. Can be planned.

[Action]

The primary fuel is reduced in order to avoid a sudden load change due to secondary combustion when the secondary fuel is input. Gas tabin
When starting the secondary fuel injection at 25% load, the primary fuel is approx.
While reducing to 60-70%, supplement the reduced amount with secondary fuel. By not increasing the reduction amount of the primary fuel, it is possible to suppress the development of air in the head combustion chamber that is excessive in air, so that it is possible to suppress the generation of CO and HC from the head combustion chamber. Further, by reducing the secondary air, it is possible to put a small amount of secondary fuel into the combustible range, and it is possible to easily ignite the secondary fuel. On the other hand, in the state where the combustion amount at the rated time is large, the secondary air flow rate can be increased and the secondary fuel can be increased following this, so that it is possible to always perform premixed fuel with an excess of air, thus reducing NOx. Diffusion combustion by increasing the ratio of secondary premixed combustion while suppressing the increase of primary fuel
Generation of NOx due to secondary combustion can also be suppressed.

〔Example〕

FIG. 1 shows the configuration of a gas turbine combustor to which the method of the present invention is applied.

The gas turbine is composed of a compressor 1, a turbine 2, a combustor 3, etc., and the air 1a compressed by the compressor 1 passes through a casing 4 and is guided to the combustor 3. The combustor 3 has an outer cylinder 5
It is made up of main materials such as a, 5b, liners 6a, 6b, head combustion chamber 7 and rear combustion chamber 8 having a diameter larger than that. Primary fuel 9 is supplied to the head combustion chamber 7. Primary fuel nozzle 10
Is attached to the cover 11 and supplies fuel through the liner cap 13 to the annular portion between the inner cylinder 12 and the liner 6a. The liner 6a is provided with a plurality of air holes for primary combustion in a plurality of rows, and further has air holes for cooling the wall surface, which are also opened in the inner cylinder. A secondary air supply hole 14 is provided in the head combustion chamber 7, the rear combustion chamber 8, and the connecting portion 13, and the secondary fuel 16 is supplied from the secondary fuel nozzle 15 to this air passage portion, and the air passage portion 17 is secondary. The premixed gas of the secondary air and the secondary fuel, which has become the premixed portion of the air and the fuel and is premixed, is supplied to the rear combustion chamber 8, and the flame 18 from the head combustion chamber 7 is used as the ignition source for the secondary combustion. Form a burning fire 19. Although not shown, ignition of the primary fuel is performed by an ignition plug and detected by a flame detector. For detection of the secondary combustion flame, a flame detector for detecting the rear combustion chamber 8 flame 19 of all combustors is attached.

 FIG. 2 shows a detailed structure of the combustor 3.

An air flow rate adjusting slide ring 21 is attached which covers the inlet 20 of the secondary air passage 17 and moves back and forth to change the area of the air inlet to change the secondary air flow rate. Supports 22 are attached to the slide ring 21 at four locations around the circumference, and an annular member 23 adjacent to the wall side of the outer cylinder 6b is connected to the support member 22. When the outer lever 24 of the outer cylinder 6b moves in the direction of the arrow in the annular member 23, the inner lever 25A moves opposite to the outer lever 24 via the support shaft 25. Then, the inner lever 25A is connected to the annular member 23 by the connecting member 26, and accordingly, by moving the outer lever 24,
The slide ring 21 moves back and forth to change the secondary air opening area. The secondary fuel 16 is introduced into the fuel manifold chamber 28 that penetrates the secondary flange 27.
Then, the secondary fuel is supplied to the inside of the air passage from the combustion injection port 29 opened near the tip of the secondary fuel nozzle 15 located in the secondary air passage 17, and the inside of the passage 17 is mixed with the air. The secondary air flow rate can be arbitrarily determined by the opening degree of the slide ring 21.

FIG. 3 shows the change in the secondary air flow rate from the start-up of the gas turbine to the rated load, and FIG. 4 shows the change in the opening of the slide ring that follows this change.

From ignition to 100% turbine speed, the air flow rate increases as the compressor speed increases. At 100% speed, about 25-30% of the total air becomes secondary air. The air flow rate is almost constant because the turbine speed is constant up to 100% load at 0% load at 100% speed. However, as shown in FIG. 3, the secondary air is about 25% or less, and the secondary air for starting the injection of the second stage fuel is less than 1/2. As shown in Fig. 4, the slide ring opening moves toward the closing direction and maintains a constant closing opening until about 40% load, and when the load is more than that, the opening gradually increases and becomes about 75% load. The slide ring is fully opened. The secondary air flow rate increases as the slide ring 21 opens. The fact that the secondary air amount further increases at 75% or more is due to the fact that the air flow rate increases as a whole because the angle of the air guide vanes attached to the inlet of the compressor is in the opening direction. FIG. 5 shows changes in the secondary air and changes in the primary air with respect to the slide ring opening. The change of the secondary air changes by changing the opening of the slide ring, but the amount of primary air decreases by closing the opening of the slide ring. This reduced amount is distributed to the liner 6b and the liner 6a in an increased manner, so that the primary air amount increases. Figure 6 shows the primary and secondary fuel injection plans. From ignition to around 25% of the gas turbine load, combustion is performed with only the primary fuel, and secondary fuel is added at 25% or more. At this time, in order to eliminate a sudden load change, the sum of the primary and secondary fuel flow rates is set to a constant amount according to each load, the primary fuel is reduced, and the secondary fuel commensurate with the reduced amount is injected. Up to about 40% load, the secondary air amount is kept constant (the sludge ring is kept close to the closed position as shown in Figs. 3 and 4), so the amount of secondary fuel can be kept as small as possible. Desirably, this can suppress unburned components such as CO. Fig. 7 shows CO, N from the primary combustion
The characteristics of Ox are shown.

CO is generated when there is a lot of primary fuel and a lot of primary air. This is due to supercooled combustion, but in order to keep CO concentration low, it is impossible to reduce the primary fuel too much so that F / A ₁ = 0.007 or less. Therefore, it is necessary to reduce the opening of the slide ring at the time of introducing the secondary fuel to reduce the secondary fuel as much as possible, and the primary air flow rate increases because the opening of the slide ring is closed. Combustion is performed with the primary fuel flow rate increased more than the flow rate increase.

F / A ₁ is preferably 0.007 or more and 0.012 or less in order to suppress the generation of CO and suppress the NOx concentration to a low level. Fig. 8 shows the CO generation characteristics near the 25-40% load after the secondary fuel injection. F ₁ / A ₂ ratio _{F 1 / F 2 = 6/} 4 becomes large ratio F ₂ when it is possible to suppress decrease the generation of CO as compared to the case of _{1/1, F 1 / F 2 =} 6 / 4 is good. This is F ₁
/ F ₂ = F ₁ less than 4/6 leads to F ₁ misfire, conversely F ₁
Increasing F ₁ above / F ₂ = 7/3 leads to NOx increase and F ₂ misfire. Figure 9 shows the NOxCO characteristics of F ₂ combustion at the rated time. CO increases near F ₂ / A ₂ = 0.045, and when the amount of F ₂ is further decreased, it enters the unstable range and then blows off.
In addition, NOx suddenly started to increase from around F ₂ / A ₂ = 5.3.
_{2 When the} amount is increased, the secondary air passage begins to overheat. The optimum range is preferably 0.045 ≦ F ₂ / A ₂ ≦ 0.053. The 10 CO at high load in the figure, shows the relationship between F ₁ / F ₂ on the NO characteristics F ₁ / F
_{When 1} = 1/1, it is almost the NOx limit value. F ₁ / F ₂ = 0.8 / 1.2
In the case of, the amount of premixed secondary air and fuel increases, and F ₁
Since the amount decreases, NOx generation can be reduced. That is, the F ₁ / F ₂ ratio is good at 1/1 to 0.8 / 1.2, and
_{When the} amount of F ₁ is smaller than ₁ / F ₂ = 0.6 / 1.4, CO is generated and F ₁ /
NOx is generated when the amount of F ₁ is larger than F ₂ = 1/1. In this way, if the F ₁ amount is decreased, the F ₁ fuel becomes air excess, so that it becomes a range where CO is generated, and conversely, if the F ₁ amount is increased, NOx is generated. FIG. 11 shows the NOxCO characteristics when the operation control according to the present invention is used for the gas turbine load.
Especially, after F _{2 is} injected from around 25%, F ₁ / F ₂ = 1 shown by the dotted line
Compared with the case of / 1, CO when F ₁ / F ₂ = 6/4 can be halved, and CO can be almost eliminated in the load zone of about 40%. On the other hand, NOx is slightly higher, but can be kept low overall. Especially in the vicinity of 100% load, F ₁ / F ₂ = 0.8 as compared to the case where F ₁ / F ₂ is 1/1 as shown in Fig. 10.
In the case of /1.2, NOx concentration can be reduced by about 25%. Thus F ₂ by increasing the F ₁ ratio of F ₁ / F ₂ at the time of on, also the CO concentration and NOx concentration at the rated after F ₂ turned by increasing the F ₂ ratio of F ₁ / F ₂ at the time of the rated Can be kept low.

Also, as shown in FIG. 12, the control signal of the slide ring 21 is
30 not only performs the control and optimal F ₂ / A ₂ become such operation the F ₂ flow through, seen when F ₂ is turned by controlling also Yotsute F ₁ flow to the control signal 30 CO Occurrence can be suppressed.

〔The invention's effect〕

According to the present invention, there is an advantage that the combustion characteristics can be particularly improved after the introduction of F _{2 and} the NOx concentration at the time of rating can be suppressed low. Furthermore, the optimum operation control range of F ₁ / A ₁ and F ₂ / A ₂ can be clarified, and the operation can be performed with the best operation pattern. In addition, there is an advantage that it is possible to prevent a sudden load change due to the introduction of F ₂ .

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a gas turbine combustor, and FIG.
The figure is an enlarged cross-sectional view of the secondary fuel supply section. Figures 3 and 4 are charts showing the slide ring operation plan with respect to the gas turbine load. Figure 5 is the change of the slide ring opening and the amount of A ₁ , A _2. Fig. 6 is a diagram showing a fuel plan for a gas turbine load, Fig. 7 is a diagram showing CO, NO characteristics due to primary combustion, and Fig. 8 is a chart showing characteristics immediately after fuel injection.
Figures 9 and 10 show the CO, NOx characteristics at 100% load, Figure 11 shows the CO, NOx characteristics over the entire load range, and Figure 12 shows the slide ring and F ₁ , F. FIG. 7 is an explanatory diagram of control ₂ ; 7 ... head combustion chamber, 8 ... rear combustion chamber, 9 ... primary fuel, 16 ... secondary fuel, 21 ... slide ring, 17 ... air passage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Uchiyama 502 Kazunachicho, Tsuchiura City Hitachi Ltd. Machinery Research Laboratory (72) Inventor Tomio Kuroda 3-1-1 Sachimachi Hitachi City Hitachi Inside Hitachi Works (72) Inventor Fumiyuki Hirose 3-1-1 Sachimachi, Hitachi City Inside Hitachi Works, Hitachi, Ltd. (56) References JP-A-60-57131 (JP, A) JP-A-61 -52523 (JP, A)

Claims (2)

(57) [Claims] 1. A fuel nozzle for primary combustion provided upstream of a combustion chamber, a fuel nozzle for secondary combustion provided downstream of the fuel nozzle for primary combustion, and an air for secondary combustion. In a method of operating a gas turbine two-stage combustor including means for adjusting a flow rate, when the gas turbine load becomes a load for injecting secondary fuel from the fuel nozzle for secondary combustion, until the load reaches a required load. During the period, the secondary fuel is gradually increased and the primary fuel supplied from the primary combustion fuel nozzle is gradually reduced so that the sum of the primary fuel and the secondary fuel becomes substantially constant. A method for operating a gas turbine two-stage combustor, which is characterized in that 2. The operation of a gas turbine two-stage combustor according to claim 1, wherein the flow rate of the secondary combustion air is gradually reduced corresponding to the reduction of the primary fuel. Method.