JPH0579819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas turbine control device, and more particularly to a gas turbine fuel control device that can suppress the generation of nitrogen oxides, etc., which are air pollutants.

[Conventional technology]

Gas turbine combustor nitrogen oxides (hereinafter referred to as
The main purpose of reducing NOx (referred to as NOx) is to uniformly mix fuel and air during the combustion process, shorten the time for NOx generation, and achieve uniform low-temperature combustion. As a means of establishing this combustion form, the combustor uses premixing of fuel and air,
Methods of fuel dispersion and multistage introduction are known in the art. However, the above-mentioned known technology is a NOx reduction technology for a single combustor, and is installed in a power plant.
The fuel system and its control when load control is performed as part of the power system have not been studied.

[Problem that the invention seeks to solve]

Figure 4 shows the main equipment configuration of the gas turbine power plant. Air compressor 1, combustor 2, turbine 3,
In a gas turbine power plant configured with a generator 4, the generated electric power is supplied to the grid via a bow disconnector 5. This power control is performed by the fuel adjustment valve 6. Next, FIG. 5 shows the relationship between the ratio of fuel and air supplied to the combustor (fuel-air ratio) and the amount of NOx generated. In diffusion combustion, when fuel is injected, even if there is a lot of air around it, the air necessary for stable combustion is used, and the remaining air is used for dilution.
Diffusion combustion allows stable combustion even at low fuel-air ratios, but
NOx generation is high. In premix combustion, the fuel and air are mixed in advance, so the degree of mixing between the fuel and air is improved, the fuel-air ratio can be made leaner, and NOx can be reduced. In actual combustors, diffusion combustion with high combustion stability is used in the low fuel-air ratio region, and diffusion combustion is used in the high-fuel-air ratio region.
Premixing that can reduce NOx is added to keep the amount of NOx below a certain value from low fuel-air ratio range to high fuel-air ratio range. FIG. 6 shows such a control method using the fuel-air ratio as a parameter.

Here, F ₁ shown by a solid line is a fuel that performs diffusion combustion, and F ₂ shown by a dotted line is a fuel that performs premix combustion, and F1 + F2 = 100%. The amount of NOx generated increases as the fuel-air ratio of diffusion combustion increases, but by premixing a portion of the fuel, the NOx value in the high fuel-air ratio region can be lowered.

As described above, in the low NOx combustor, premix combustion is added to the diffusion combustion, whereas conventional combustion was limited to diffusion combustion, and two fuel systems corresponding to these are required.

In other words, it is necessary to divide the total fuel command value for the purpose of load control into a command to a fuel system that performs diffusion combustion for the purpose of NOx control, and a command to another fuel system that performs premix combustion. become. In this division, it is important not to cause load fluctuations, to appropriately select the switching point from diffusion combustion to premix combustion, and to manage the amount of NOx generated within a limit value.

Generally, it is difficult to accurately measure the air flow rate of a gas turbine, and it is difficult to divide the fuel command value using the fuel-air ratio as a parameter as shown in FIG.

An object of the present invention is to accurately perform the switching according to the set value when shifting from only diffusion combustion to combined operation of diffusion combustion and premix combustion when performing load control as part of an electric power system. An object of the present invention is to provide a gas turbine fuel control device that can suppress the amount of fuel generated within a control value.

[Means for solving problems]

The gas turbine fuel control device of the present invention has a pipe for supplying fuel according to the load, a first fuel pipe for performing diffusion combustion, and a second fuel pipe for performing premix combustion. branch out,
In a gas turbine fuel control device that controls to perform only diffusion combustion or diffusion combustion and premix combustion via these first and second fuel pipes, the gas turbine fuel control device is provided in the first fuel pipe and performs diffusion combustion. a first fuel adjustment valve that adjusts the fuel flow rate to perform premix combustion; a second fuel adjustment valve that is installed in the second fuel pipe and adjusts the fuel flow rate to perform premix combustion; an atmospheric temperature detecting means for detecting; a correcting means for correcting the fuel requirement value according to the turbine air amount determined based on the detected output of the atmospheric temperature detecting means when the gas turbine speed is constant; The corrected fuel requirement value is taken in and the fuel flow rate for diffusion combustion is indicated based on the fuel flow rate control characteristic that is stored in advance and indicates the supply ratio of the fuel for diffusion combustion and the fuel for premix combustion with respect to the fuel requirement value depending on the load. a first calculating means for generating a fuel command value; and generating a value obtained by subtracting the fuel command value output from the first calculating means from the fuel request value as a fuel command value indicating a fuel flow rate for premix combustion. a second calculation means; a first drive means for driving the first fuel adjustment valve to open and close based on the fuel command value output from the first calculation means; and second driving means for driving the second fuel adjustment valve to open and close based on the fuel command value.

[Effect]

The correction means corrects the fuel requirement value in accordance with the output request of the gas turbine in accordance with the turbine air amount determined based on the detected output of the atmospheric temperature detection means when the gas turbine speed is constant.

Until a predetermined NOx value is reached, the first fuel regulating valve is controlled to open and close so that the fuel flow rate supplied to the combustor matches 100% of the fuel requirement value in order to perform diffusion combustion. In this case, the fuel command value for controlling the first fuel regulating valve incorporates the corrected fuel demand value from the correction means, and the diffusion combustion fuel and fuel for the fuel demand according to the load stored in advance. It is generated by the first calculation means based on the fuel flow rate control characteristic indicating the supply ratio of the premix combustion fuel, and is output to the first fuel adjustment valve via the first drive means.

On the other hand, when a predetermined NOx value is reached, the fuel command value for the first fuel adjustment valve is lowered from 100% to a predetermined percentage. At the same time, the second calculation means generates a value obtained by subtracting the fuel command value output from the first calculation means from the fuel request value as a fuel command value indicating the fuel flow rate for premix combustion. This fuel command value is output to the second fuel adjustment valve via the second drive means, and the fuel flow rate for premix combustion is adjusted.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, FIG. 1 shows the fuel system of the present invention.

F ₁ shows the fuel injected into the diffusion combustion zone, and F ₂ shows the fuel injected into the premix combustion zone. F ₁ is ejected from a nozzle from a fuel supply port through a pressure regulating valve (PCV1) 103, a pressure detector 105, and a flow regulating valve (FCV1) 104.

The F ₂ 's fuel system is also the same as the F ₁ .

In such a system, the so-called governor signal F ₀ , which is the total required value of the fuel amount, is 1, so it is necessary to allocate this signal to F ₁ and F ₂ .
FIG. 2 shows a control block diagram of the fuel regulating valve in the fuel system.

The atmospheric temperature detected by the detector 121 is
It is connected to a function generator 122, and the multiplier 12 uses this output to calculate the total fuel demand value F ₀ from the governor.
Correct in 4. Function generator 125 determines the fuel ratio of F ₁ based on the revised fuel requirement value F ₀ '. The idea here will be explained with reference to FIG.

The sum F ₀ of the fuel command value F ₁ given to the fuel regulating valve FCV1 of the diffusion combustion fuel system and the fuel command value F ₂ given to the fuel regulating valve FCV2 of the premix combustion fuel system is always determined by the governor control signal. One thing is that when the fuel pressure regulating valve FCV2 is opened, the variation in the fuel pressure on the FCV1 side can be controlled by the fuel pressure regulating valve PCV1, so there is no load variation when switching between _F1 and _F2 .

Next, we will discuss how to determine F ₁ and F ₂ . When the fuel command value F ₀ is small, diffusion combustion is performed and F ₀
= _F1 . As F ₀ increases, the amount of NOx generated increases, so based on the specified data when the specified NOx value is reached, F ₁ is made smaller than F ₀ in order to use premix combustion in combination. _{, F 2 =}
Let F ₀ −F ₁ .

FIG. 7 shows the division of fuel commands when atmospheric temperature is used as a parameter related to the gas turbine air amount. The gas turbine air amount is determined by the gas turbine speed and atmospheric temperature, but F ₁ and
Since _F2 switching is performed after the gas turbine generator is turned on, the speed remains constant. Therefore, the gas turbine air flow rate at the time of switching is influenced only by the atmospheric temperature; as the atmospheric temperature decreases, the air flow rate increases, and conversely, as the atmospheric temperature increases, the air flow rate decreases. shows this relationship,
Based on the atmospheric temperature of 15°C, the air flow rate at this time is normalized and expressed as "1". Note that the reference temperature may be any degree Celsius. is for modifying the fuel command value F ₀ (governor control signal).

The calculation result is F ₀ ′ = 273℃ + 15℃ / 273℃ + x℃F ₀ = YF ₀ , and if the atmospheric temperature rises above 15℃, F ₀ ′ becomes F ₀
If it becomes smaller, and vice versa, F ₀ ′ becomes larger than F ₀ .

Now, based on F ₀ ′, calculate F 1 and F ₁ using the method described above.
Allocate fuel command to F ₂ . Here, A and B are switching points at an atmospheric temperature of 15°C. Point A is the point at which combined use of premixed combustion is started to reduce NOx from a state of 100% diffusion combustion, and point B is the point where premixed combustion starts at point A, when premixed combustion fuel F ₂ is increased or decreased, and after combustion stabilizes, F ₂ is decreased, and this represents the starting point of this decrease. F ₀ =F ₁ +
The F ₂ relationship is preserved. When the atmospheric temperature rises above 15°C, the switching points YA and YB move to the side where F ₀ ' becomes smaller. In other words, since Y is smaller than 1, the value becomes smaller than the switching point when the atmospheric temperature is 15°C, and vice versa. It becomes a large value if the atmospheric temperature drops below 15℃. This is equivalent to switching between F ₁ and F ₂ depending on the fuel/air ratio. In this way, according to this embodiment, switching between F ₁ and F ₂ can be performed accurately according to the set value.

From the above, it is not necessary to use the gas turbine air flow rate, which has a measurement error of ±10%, for switching between F ₁ and F ₂ , and the amount of NOx generated at the time of switching can be managed with precision.

Note that the parameter may be other than atmospheric temperature; for example, compressor outlet air pressure may be used.

The multiplier 126 calculates the fuel ratio of F ₁ and the fuel command value of F ₁ from F ₀ . Adder/subtractor 131
Then, the electro-hydraulic converter 133 is operated according to the deviation between the (calculated) F ₁ fuel command and the F ₁ fuel adjustment valve opening degree 132, and thereby the fuel adjustment valve 104 is adjusted, and the F ₁ , that is, the diffusion combustion system is activated. Control the fuel flow to.

The difference between the total fuel request value F ₀ and the fuel command of F ₁ is calculated by the adder/subtractor 127, and thereby F ₂ ,
That is, it controls the fuel flow rate to the premix combustion system.

Next, FIG. 3 shows a control block diagram of the fuel pressure regulating valve.

The pressure regulating valve (PCV1) 103 is
In order to increase the opening degree of FCV1 and improve controllability,
Performs FCV1 afterpressure control proportional to gas turbine rotation speed. N is the gas turbine rotation speed, and computing unit 1
41, a proportional calculation is performed, and the value to which the bias is added is set as the pressure setting value. This set value is combined with the actual pressure 105 after FCV1, and a proportional-integral calculation is performed by the calculator 144. Servo valve driver 14
5 controls PCV1.

The pressure regulating valve (PCV2) controls the FCV2 after the gas turbine reaches its rated speed, so constant value control is sufficient. The pressure set value is set by the setting device 151, is correlated with the actual pressure 109 of the PCV2, a proportional integral calculation is performed by the calculator 153, and the PCV2 is controlled by the servo valve driver 154.

According to this embodiment, since the after pressures of PCV1 and PCV2 are controlled respectively, F ₁ and F ₂ can be controlled independently, so when turning on F ₂ in the middle of load operation,
The increase in the _F2 nozzle opening area does not affect the _F1 flow rate, so it does not cause load fluctuations.
NOx reduction is possible.

〔Effect of the invention〕

According to the present invention, diffusion combustion, which is stable combustion, is performed while the required output value is small, and when the required output value increases and NOx exceeds a predetermined value, NOx
This has the excellent effect of suppressing the amount of NOx generated within a predetermined value by using premixed combustion, which generates less, and performs combustion according to the required output value.

[Brief explanation of the drawing]

Fig. 1 is a fuel system diagram of one embodiment of the present invention;
The figure shows the control block diagram of Fig. 1, Fig. 3 shows the control block diagram of Fig. 1, Fig. 4 shows the main equipment configuration of the gas turbine power plant, and Fig. 5 shows the fuel-air ratio and NOx generation amount. 6 and 7 are explanatory diagrams for controlling the combustion method. 103...First fuel flow regulating valve, 104...First fuel pressure regulating valve, 108...Second fuel flow regulating valve, 110...Second fuel pressure regulating valve.

Claims (1)

[Claims] 1. A first fuel pipe for causing diffusion combustion in a pipe for supplying fuel according to the load;
Gas turbine fuel control that branches into a second fuel pipe for performing premix combustion, and controls to perform only diffusion combustion or diffusion combustion and premix combustion via these first and second fuel pipes. In the apparatus, a first fuel regulating valve is provided in the first fuel pipe and adjusts the fuel flow rate to perform diffusion combustion; and a first fuel adjustment valve is provided in the second fuel pipe to perform premix combustion. a second fuel regulating valve that adjusts the fuel flow rate; an atmospheric temperature detection means that detects the atmospheric temperature; and a turbine air amount determined based on the detected output of the atmospheric temperature detection means when the gas turbine speed is constant. a correction means for correcting the fuel demand value accordingly; and a correction means for taking in the corrected fuel demand value from the correction means and supplying the diffusive combustion fuel and the premix combustion fuel to the fuel demand value according to the load, which is stored in advance. a first calculation means for generating a fuel command value indicating a fuel flow rate for diffusion combustion based on a fuel flow rate control characteristic indicating a ratio; and subtracting a fuel command value output from the first calculation means from the fuel request value. a second calculation means for generating the calculated value as a fuel command value indicating a fuel flow rate for premix combustion; and driving the first fuel regulating valve to open and close based on the fuel command value output from the first calculation means. and a second drive means that opens and closes the second fuel regulating valve based on the fuel command value output from the second calculation means. Control device.