JPH07102998A - Fuel supply control method for gas turbine - Google Patents

Abstract

PURPOSE:To prevent fluctuation of a load, misfire of a burner, and damage of high temperature part by determining a mixing ratio through previous setting of calory, multiplying a fuel control signal of a gas turbine thereby, controlling an opening of a fuel rate control valve previously based on the signal, and correcting the mixing ratio based on the feedback signal from a calorimeter. CONSTITUTION:A low heat generation gas (B gas) main pipe 16 is connected to a mixer 21 through a B gas interruption valve 17. A calorimeter 30 is arranged on a down course of an electric dust collector 18. A high heat generation gas (M gas) mother pipe 25 is connected to an inlet of the mixer 21 sequentially through an M gas flowmeter 24, a flow rate control valve 20, and a gas interruption valve 15a. In order to mix the B gas with the M gas through the flow rate control valve 20, a mixing ratio is previously determined by calory setting. A fuel control signal of a gas turbine is multiplied thereby. According to the signal, an opening of the flow rate control valve is previously controlled, and the mixing ratio is corrected by a feedback signal from the calorimeter 30. It is thus possible to prevent fluctuation of a load, misfire of a burner, and damage of high temperature parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control method for a gas turbine which uses a low calorific value gas such as blast furnace gas as a main fuel.

[0002]

Gas turbine gas fuels include natural gas, liquefied natural gas (LNG) and liquefied petroleum gas (LP).
G), petroleum secondary gas, coke oven gas, underground methane gas, blast furnace gas, coal gasification gas, etc. are used. Of these, blast furnace gas has a low calorific value and is on the order of 600 kcal / Nm ³ LHV. For this reason, a single-cylinder can-type combustor with a low combustion load factor is used in order to achieve a stable combustion in a wide load range with a large flow rate of fuel gas.

FIG. 5 is a system diagram of a blast furnace gas-fired gas turbine. Air compressor 1, turbine 2 and combustor 3 are simple 1
The shaft gas turbine 4 is configured. The gas turbine is connected to the generator 6 and the blast furnace gas (hereinafter referred to as B gas) via the main gear unit 5.
The compressor 7 is driven, and the starting prime mover 10 is coupled to the shaft end of the generator via the auxiliary gear device 8 and the clutch 9.

The discharge gas of the B gas compressor 7 is an emergency shutoff valve 1.
3 is led to the combustor 3, and a part of it is introduced into the flow control valve 11, the pressure control valve 12, the gas cooler 14, and the shutoff valve 15.
It is refluxed to the B gas mother pipe 16 via. From the B gas mother pipe, B gas is sent to the gas compressor 7 via the shutoff valve 17 and the electrostatic precipitator 18.

Further, the gas turbine exhaust gas is an exhaust gas boiler 1.
9 and sent to steam generation.

In the starting system of this system, a pilot system that uses a high calorific value gas (oil) is ignited, and then a main system that uses a low calorific value gas mainly containing B gas is ignited.

In operation, the pilot system acts as a pilot fire and prevents the gas turbine from misfiring.

[0008]

In the above-mentioned conventional apparatus, although the single cylinder can type is used as the combustor, there are the following problems in the fuel combustion process.

(1) If the calorific value of the fuel becomes unstable, the load fluctuates and stable operation cannot be performed.

(2) If the calorific value becomes too small, the combustor will misfire, and if it becomes too large, the combustion gas temperature in the combustor will rise.
Gas turbine hot parts are damaged.

[0011]

The present invention takes the following means in order to solve the above problems.

(1) In a gas turbine using a low calorific value gas as a main fuel, when mixing a low calorific value gas with a high calorific value gas through a flow control valve, a mixing ratio is determined in advance by calorie setting, and A fuel supply control method for a gas turbine, wherein a fuel control signal for the gas turbine is applied, the opening of the flow control valve is controlled in advance by the signal, and the mixing ratio is corrected by a feedback signal from a calorimeter.

(2) In the fuel supply control method for a gas turbine according to the above (1), a fuel pressure control method for a gas turbine in which a valve differential pressure is corrected in a flow control valve to improve an unstable mixing ratio.

[0014]

[Action]

(1) In the invention 1, the high calorific value gas is supplied and mixed with the low calorific value gas of the gas turbine which uses the low calorific value gas as the main fuel through the flow control valve. At that time, the mixing ratio is determined in advance by the calorie setting. Then, it is multiplied by the fuel control signal of the gas turbine, and the opening of the flow control valve is controlled in advance by the signal. Further, the mixing ratio is corrected by the feedback signal from the calorie meter that detects the calories after mixing.

Therefore, even if the calorific value of the low calorific value gas is unstable, the mixture ratio is determined in advance by the calorie setting, and the opening of the flow control valve is controlled in advance by the signal, and the high calorific value gas is controlled. Are mixed. Further mixing is corrected by feedback. Therefore, the calorific value of the mixed fuel to the gas turbine is maintained at a predetermined value, and the output (load) of the gas turbine becomes stable.

Further, even when the load state suddenly changes to the no-load state, the fuel control signal applied to the mixing ratio decreases, so that the flow control valve is throttled. On the other hand, since the flow control valve for the low heat value gas is also throttled by the fuel control signal, the mixing ratio after mixing is kept constant. As a result, the minimum calorie for maintaining the no-load operation is maintained, and the smooth transition to the no-load operation is performed.

(2) In the second aspect of the invention, the valve differential pressure on the inlet and outlet sides of the flow control valve is detected, and the signal is used to correct the valve differential pressure.

Therefore, even if the supply pressures of the high calorific value gas and the low calorific value gas fluctuate, the flow rate characteristics are corrected according to the fluctuation, and stable mixing is always performed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

The parts described in the conventional example are denoted by the same reference numerals and the description thereof will be omitted, and the parts relating to the present invention will be mainly described.

In FIG. 1, a low exothermic gas (B gas) mother tube 16
Is connected to the mixer 21 via the B gas cutoff valve 17. The outlet of the mixer 21 passes through the electrostatic precipitator 18 and the gas compressor 1
Connected to. The calorimeter 30 is an electric dust collector 18
It is installed on the downstream side.

The outlet of the gas compressor 1 of the gas turbine is connected to the combustor 3. The fuel gas flow valve 11 is also branched to
It is connected to the outlet of the shutoff valve 17 via the pressure control valve 12.

The high exothermic gas (M gas) mother pipe 25 is connected to the inlet of the mixer 21 through the M gas flow meter 24, the flow control valve 20, and the gas cutoff valve 15a in this order. Also, the flow control valve 20
A control valve differential pressure gauge 22 is provided between the inlet and outlet of the valve. Further, a bypass line having a gas starting valve 23 is connected between the inlet and outlet of the shutoff valve 15a.

A block diagram of the control circuit of the M gas flow control valve 20 is shown in FIG.

The output 31s (calorific value Cs of mixed gas) of the calorie setting unit 31 is sent to the subtractor 32. Also subtractor 3
The output of the calorimeter 30 is subtracted and input to 2. The output of the subtractor 32 is sequentially sent to the multiplier 36 through the multiplier 33, the PI calculator 34, and the adder 35. Also, the multiplier 36
A fuel control signal (CSO) 60s is input to the. The output of the multiplier 36 is the valve opening setting device 37, the multiplier 38, the I / E.
It is sent to the flow control valve 20 through the converter 39 in sequence.

The output of the differential pressure detector 22 at the inlet and outlet of the flow control valve 20 is sent to the multiplier 38 through the E / I converter 40 and the function generator 41 in sequence. Further, the outputs of SG43 and SG44 are input to the valve opening setting device 37 via the double relay 42.

The CSO signal 60s is sent to the multiplier 33 via the function generator 47. Further, the Cs signal 31s is subtracted from the subtracter 4
It is sent to the divider 50 via 8. In addition, the subtractor 48 has B
The output of SG49 that generates gas calorific value C _B is input. Further, the divider 50 has the M gas calorific value C _M to C
SG51 which generates the signal which subtracted _B is inputted.
The output of the divider 50 is the P calculator, the multiplier 53, and the adder 54.
Are sequentially transmitted to the adder 35.

Further, the CSO signal 60s is sent to the multiplier through the function generator 55. Further, the rotation speed signal 61s is sent to the adder 54 via the function generator 56.

The lower limit of calories required for stable combustion changes depending on the operating condition of the gas turbine 4. That is, when the gas turbine is started up and accelerated, the amount of fuel injection is small and combustion tends to be unstable, so high calories are required. However, during rated load operation, the amount of fuel injection is also maximum and combustion is most stable, so calories can be reduced. However, since there is a moment when the vehicle goes into a no-load state due to an electric accident or the like, it is necessary to maintain at least the minimum calorie required in a no-load state even under load operation.

Before starting the gas turbine, the pre-ignition heat increase control is performed by the calorie UP input operation until the fuel reaches the calorie required for ignition. In the pre-start heat increase control, the SG 43 outputs an M gas flow rate control valve opening setting signal based on the sequence control, and is sent to the valve opening setting device 37 via the double relay 42. Due to this signal, M gas is mixed in the loop to increase heat. That is, M gas flow rate control valve 2
The opening degree of 0 is controlled to the set opening degree, and when the predetermined amount of heat is reached, the valve is automatically closed (see FIGS. 2A and 3).

A loop passing through the mixer 21, the gas compressor 1, the fuel gas flow rate control valve 11 and the pressure control valve 12 is heated by the pre-ignition heat increase control to supply a high calorific value fuel necessary for ignition acceleration. To do.

The calorie setting at the time of heat increase before ignition is generally about 1150 kcal / Nm ³ / LHV for B gas fuel.

During operation, the preceding control for controlling the flow rate ratio with respect to the calorie setting, the calorie setting, and the signal from the calorimeter are compared, and calorie correction is performed to control the deviation (see FIG. 2 (H)). ).

In the preceding control, the flow rate ratio of M gas is calculated with respect to the calorie setting by the following calculation formula.

[0035] _{F M / F S = (C} S -C B) / (C M -C B) ──── where F _M: M gas flow F _S: mixed gas flow rate C _S: mixed gas calorific value C _B : B gas calorific value C _M : M gas calorific value The required amount of M gas is obtained in advance based on this calculation (see FIG. 2C).

During calorie correction, the CSO signal 60s is used as a sensitivity correction signal for calorie correction. This is CS
This is because the correction sensitivity is reduced when O is small, that is, when the fuel amount is small (see FIG. 2G).

Further, since the required calorie of the fuel changes depending on the operating state, the calorie is automatically set according to the number of revolutions when the speed is increased (see FIG. 2 (B)).

The flow rate ratio of M gas obtained as described above is set to CSO.
The signal 60s is applied to control the M gas flow rate control valve 20.

As a result, even when the fuel amount suddenly changes such as when the load is cut off, the CSO signal 60s is narrowed down, so that the M gas flow control valve 20 is narrowed down and the mixing ratio of B gas and M gas can be kept constant. Yes (see FIG. 2 (E)).

Since the discharge flow rate of the gas compressor is small during acceleration, the flow rate control valve at the compressor bypass position is closed at will, and the CSO becomes large despite the small amount of fuel. For this reason, since the amount of heat increase is too large only by the advance control and the calorie correction for the calorie setting, the correction for the rotational speed is performed only at the time of starting and accelerating the speed (see FIG. 2F).

If the supply pressures of the M gas and the B gas fluctuate, the flow rate characteristics deviate and the flow rate is not controlled correctly. Therefore, the differential pressure of the M gas flow rate control valve 20 is measured, and feedback correction is performed using this signal to correct the deviation of the flow rate characteristic (see FIG. 2D).

As described above, the output (load) of the gas turbine 4 is maintained constant even if the calorific value of the B gas becomes unstable. Further, even if the calorific value becomes too small, the combustor 3 will not misfire. Even if it becomes excessive, the temperature of the combustion gas in the combustor 3 will not rise.

A plurality of M gas flow rate control valves, fuel gas flow rate and pressure control valves are provided for the purpose of improving valve control characteristics.

[0044]

As described above, according to the present invention, in a gas turbine that uses a low calorific value gas such as B gas as fuel, by mixing and controlling M gas, the load that has been conventionally generated can be reduced. Problems such as fluctuations, misfires in combustors, and damage to high-temperature parts are eliminated, and the reliability of this type of gas turbine is improved.

[Brief description of drawings]

FIG. 1 is a configuration system diagram of an embodiment of the present invention.

FIG. 2 is a control block diagram of an M gas system of the same embodiment.

FIG. 3 is a flow chart of pre-ignition heat increase of the same embodiment.

FIG. 4 is a characteristic diagram of CSO and rotation speed at the time of speed increase of the embodiment.

FIG. 5 is a system of a conventional B gas-fired gas turbine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Air compressor 2 Turbine 3 Combustor 4 Gas turbine 5 Main gear unit 6 Generator 7 B Gas compressor 8 Auxiliary gear unit 9 Clutch 10 Start prime mover 11 Flow control valve 12 Pressure control valve 13 Emergency shutoff valve 14 Gas cooler 15, 17 Shutoff valve 16 B gas mother tube 18 Electrostatic precipitator 19 Exhaust gas boiler 20 M gas flow control valve 21 Mixer 22 Differential pressure gauge (differential pressure detector) 23 M gas start valve 24 Flow meter 25 M gas mother tube 30 Calorimeter 31 Calorie setter 32,48 Subtractor 33,36,38,53 Multiplier 34 PI calculator 35,54 Adder 37 Valve opening setting device 39 I / E converter 40 E / I converter 41,45 , 47, 55, 56 Function generator 42 Double relay 43, 44, 49, 51, SG 46 Tracker 50 Divider 52 P calculator

Claims (2)

[Claims] 1. In a gas turbine using a low calorific value gas as a main fuel, when mixing the low calorific value gas with the high calorific value gas through a flow control valve, a mixing ratio is determined in advance by calorie setting, and Fuel supply control of a gas turbine, characterized in that a fuel control signal of a gas turbine is applied, the opening of the flow control valve is controlled in advance by the signal, and the mixing ratio is corrected by a feedback signal from a calorimeter. Method. 2. The fuel supply control method for a gas turbine according to claim 1, wherein a valve differential pressure correction for improving an unstable mixing ratio is performed on the flow control valve. .