JPH03194131A - Fuel switching device for gas turbine - Google Patents

Abstract

PURPOSE:To enable smooth change-over without generating the load fluctuation or the like of a gas turbine at the time of performing change-over between gas fuel and liquid fuel by switching circuit into a specified position, and after this switching, opening a closed fuel valve gradually and closing an opened fuel valve gradually. CONSTITUTION:A fuel switching device for a gas turbine controls a gas fuel control valve 6 and a liquid fuel bypass control valve 11 by control signals outputted from a gas fuel control circuit 14 and a liquid fuel control circuit 15 on the basis of fuel control signals S1 from a fuel control circuit 13 for controlling the speed and load of the gas turbine so as to switch fuel. In this case, there are provided with a switching circuit 16 for switching the fuel control signals S1 to be inputted into the respective control circuits 14, 15, and a fluctuation preventing circuit 17 for preventing the fluctuation of the fuel control signals at the time of switching fuel. The fuel control signals having passed function generators 18a, 18b are then inputted into a closed side fuel valve control circuit to open a fuel valve gradually and close the opened fuel valve gradually.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel switching device for a gas turbine, and in particular to a fuel switching device for a gas turbine.
A gas turbine that can easily switch fuels without stopping the gas turbine and without causing load fluctuations in the gas turbine when alternately switching between gas fuel such as G and liquid fuel such as kerosene. This invention relates to a fuel switching device.

(Prior art) Conventionally, liquid fuels such as light oil and kerosene have been generally used as fuel for gas turbines, but from the perspective of diversifying energy resources, liquefied natural gas (LNG) or propane have been used as fuel for gas turbines. , liquefied petroleum gas (LPG) such as butane
) and other gas fuel operations have begun to increase in recent years.

Gas turbines can be operated in various ways, including for exclusive combustion of liquid fuel, for mixed combustion of liquid fuel and gas fuel, and for exclusive combustion of gas fuel.The optimal operation mode is determined by taking into account the installation area of each plant and the energy situation of each power plant. has been adopted.

The system configuration will be described below with reference to FIG. 4, taking as an example a gas turbine power generation system configured with two types of fuel systems: gas fuel such as LNG and liquid fuel such as kerosene.

A gas turbine power generation system is basically configured by coaxially arranging a compressor 1 for compressing combustion air, a gas turbine 2, and a generator 3. The gas turbine 2 is rotated by mixing air compressed by the compressor 1 with fuel injected into the combustor 4 and then combusting the mixture.

The fuel system is composed of a gas fuel system and a liquid fuel system, and the fuel system supplies gas fuel from a gas fuel supply source (not shown) to the combustor 4 through a gas fuel stop valve 5 and a gas fuel control valve 6. On the other hand, the liquid fuel system supplies liquid fuel from a liquid fuel source (not shown) through a liquid fuel stop valve 7, a fuel pump 8, a flow divider 9, and a check valve 10.
The fuel is supplied to the combustor 4 through the combustor 4. A liquid fuel bypass control valve 11 and a liquid fuel relief valve 12 are disposed in the two pipes that bypass the fuel pump 8, respectively.

The operation of the gas turbine 2 is controlled by adjusting the flow rate of fuel flowing into the combustor 4.

That is, when gas fuel is used, the gas fuel control valve 6 is opened and closed, while when liquid fuel is used, the liquid fuel bypass control valve 11 is opened and closed. Furthermore, the gas fuel stop valve 5 and the liquid fuel stop valve 7 function as quick shutoff valves that emergencyly stop the supply of each fuel when an abnormality occurs in the gas turbine.

Although Fig. 4 shows an example of the configuration of a gas turbine generator system in which the gas turbine 2 and the generator 3 are directly connected through a single shaft, the exhaust heat of the gas turbine 2 is further recovered by an exhaust heat recovery boiler (not shown). However, a similar fuel system is also provided in a combined cycle power generation plant where the generated steam is introduced into a steam turbine (not shown) directly connected to the same shaft as the gas turbine to increase the operating efficiency of the generator 3. .

Next, a typical operation pattern of a gas turbine when using gas fuel will be explained.

A starting device including a motor or the like via a torque converter or the like is disposed at the shaft end of the gas turbine, and the gas turbine 2 starts rotating by this starting device. Then, when air purging and the like in the gas turbine 2 are completed, the gas fuel stop valve 5 and the gas fuel control valve 6 are opened, and gas fuel is supplied into the combustor 4. Immediately after the gas fuel is ignited, the gas turbine 2 is speeded up after a certain period of warm-up operation, and after reaching the rated rotation speed, the combustor 4 is operated until the rated load is reached after joining the power system and increasing the load. The amount of gaseous fuel flowing in is gradually increased. Note that in the combined cycle power plant, the exhaust heat recovery boiler is warmed up when the gas turbine 2 reaches a certain rotational speed during the speed increase. During this time, the rotational speed of the gas turbine is held constant.

In this way, from the ignition stage of the gas turbine 2, the speed increases, joins,
Control of the gas fuel flow rate required from the load increase operation to the rated load operation is performed by opening and closing the gas fuel control valve 6. However, the flow rate control range required at each operating stage of the gas turbine is very wide, and it may be difficult to control the flow rate by opening and closing only the gas fuel control valve 6.

In particular, when the gas fuel flow rate is low and the gas turbine rotates at low speed, such as during ignition or warm-up operation, the opening degree of the gas fuel control valve 6 becomes very small, which may make stable flow control difficult. In order to eliminate this unstable flow control, the gas fuel stop valve 5 is provided with a control function that increases or decreases the fuel pressure on the secondary side of the gas fuel stop valve 5 in proportion to the rotation speed of the gas turbine 2. A method to do so is also adopted. As a result, when the gas turbine rotates at low speed, the fuel pressure on the secondary side of the fuel stop valve 5, that is, the fuel pressure on the primary side of the gas fuel control valve 6, is controlled to be low. Therefore, even in a low flow rate range, it is possible to operate the gas fuel control valve 6 with a large opening degree, and it is possible to avoid instability of flow rate control.

The valve opening degree of the gas fuel control valve 6 is controlled by a command signal from a gas turbine control circuit (not shown).

A predetermined valve opening setting signal is output during ignition and warm-up operation of the gas turbine, while a valve opening setting signal necessary for speed and load control is output during speed and load increase operation to control the required flow rate. You can get fuel. In addition to the ignition signal, the fuel tank 4
A certain minimum valve opening signal and the like are also set in order to prevent blow-out.

Next, the operation pattern when using liquid fuel will be explained.

As a means for transferring the liquid fuel, a fuel pump 8 usually formed by a gear pump or the like is used. This fuel pump 8
is connected to the turbine main shaft via a gear reduction device and is configured to rotate in conjunction with the turbine. Therefore, the discharge flow rate of liquid fuel discharged from the fuel pump 8 is proportional to the pump rotation speed, that is, the rotation speed of the gas turbine. Therefore, fuel other than the fuel necessary for operating the gas turbine is returned to the suction side of the fuel pump 8 via the liquid fuel bypass control valve 11. The liquid fuel system is also equipped with a liquid fuel relief valve 12 for returning fuel on the discharge side to the suction side when the discharge pressure of the fuel pump 8 exceeds a certain allowable value.

The liquid fuel discharged from the fuel pump 8 is supplied into the combustor 4 through a flow divider 9 for uniformly distributing the liquid fuel to the combustor 4 and a check valve 10 for preventing backflow. As described above, in the liquid fuel system, the operation control from ignition of the gas turbine to speed increase, merging, and load increase is performed by adjusting the opening degree of the liquid fuel bypass control valve 11. The liquid fuel stop valve 7 does not have the function of controlling the fuel pressure on the secondary side like the gas fuel stop valve 5, but has the function of a shielding valve that simply stops the fuel supply in an emergency when an abnormality occurs.

In this way, both the valve opening setting signal for controlling the gas fuel control valve 6 and the valve opening setting signal for controlling the liquid fuel bypass control valve 11 are signals for controlling the speed and load of the gas turbine. Therefore, the same fuel control signal passes through each fuel valve control circuit and is output as a valve opening setting signal for each fuel valve.

Switching between the gas fuel system and the liquid fuel system is performed by selecting one of the fuel types using a gas turbine control panel (not shown) when the gas turbine is stopped.

(Problem to be Solved by the Invention) However, in the conventional fuel selection switching type gas turbine plant as described above, each time the gas fuel is switched from the gas fuel to the liquid fuel or vice versa, the gas turbine is turned off once. The fuel switching operation requires a lot of effort and time, and a quick response cannot be achieved. Furthermore, as gas turbines are frequently started and stopped, fatigue of gas turbine components tends to progress.
There is also the problem of shortening the life of the plant.

Furthermore, because the fuel switching operation is complicated, it is difficult to quickly respond to social demands for diversifying the fuels used, and there is also the problem that the plant has little flexibility and lacks responsiveness.

The present invention was made in order to solve the above problems, and it is possible to reduce the load on the gas turbine during fuel switching without stopping the gas turbine even when the gas turbine is in operation, and at any load on the gas turbine. It is an object of the present invention to provide a fuel switching device for a gas turbine that can alternately switch between gas fuel and liquid fuel at an arbitrary preset speed without causing fluctuations or the like.

[Structure of the invention]

(Means for Solving the Problems) To achieve the above object, the present invention provides a gas fuel control circuit and a liquid fuel valve control circuit based on a fuel control signal from a fuel control circuit for controlling the speed and load of a gas turbine. The valve opening degrees of the gas fuel control valve and liquid fuel bypass control valve are controlled by the gas fuel valve control signal and liquid fuel valve control signal output from the gas fuel valve control signal, and the valve opening degrees of the gas fuel control valve and liquid fuel bypass control valve are switched between gas fuel and liquid fuel, and the gas supplied to the gas turbine is controlled. A turbine fuel switching device includes a switching circuit that switches a fuel control signal input to the gas fuel valve control circuit and liquid fuel valve control circuit, and a fuel control signal or turbine load fluctuation during fuel switching performed during gas turbine operation. The switching circuit inputs a fuel control signal via a function generator to the fuel valve control circuit on the side of the fuel valve that was closed, thereby switching the fuel valve that had been closed. While opening the valve, the fuel valve was opened by inputting a subtracted fuel control signal obtained by subtracting the fuel control signal output from the function generator to the fuel valve control circuit on the fuel valve side that had been opened. The fuel valve is characterized in that it is configured to close the fuel valve.

(Operation) In the gas turbine fuel switching device according to the above configuration,
When switching between gas fuel and liquid fuel during gas turbine operation, the switching circuit is switched to a predetermined position. After switching, a fuel control signal proportional to the output of the function generator is input to the fuel valve control circuit on the fuel valve side that had been closed, so that the fuel valve that had been closed gradually opens.

On the other hand, a subtracted fuel control signal obtained by subtracting the fuel control signal output from the function generator is input to the fuel valve control circuit on the side of the fuel valve that was open, so that the fuel valve that was open becomes a function It gradually closes in response to the output from the generator, and the switching operation between gas fuel and liquid fuel progresses.

Further, during the switching operation, there is a risk that the speed and load of the gas turbine and the fuel control signal from the fuel control circuit may fluctuate greatly, but the fuel control signal and the gas turbine load are held constant by the fluctuation prevention circuit.

Therefore, according to the present invention, even if the gas turbine is operating under any load conditions, it is possible to smoothly switch between gas fuel and liquid fuel, and it is possible to quickly diversify the fuels used. This makes it possible to significantly improve the responsiveness of gas turbine plants. Furthermore, there is little load variation in the gas turbine during switching operations, and stable operation control is possible.

(Example) Next, an example of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a system diagram showing a first embodiment of a fuel switching device for a gas turbine according to the present invention. Note that the same reference numerals are used for the same elements as in the conventional example shown in FIG.

That is, the gas turbine fuel switching device according to the first embodiment controls the gas fuel control circuit 14 and the liquid fuel valve control based on the fuel control signal S1 from the fuel control circuit 13 for controlling the speed and load of the gas turbine 2. The valve opening degrees of the gas fuel control valve 6 and the liquid fuel bypass control valve 11 are controlled by the gas fuel valve control signal S and the liquid fuel valve control signal S3 outputted from the circuit 15, and the gas fuel and the liquid twisted material are mutually controlled. In the gas turbine fuel switching device for supplying the gas turbine 2 to the gas turbine 2, the switching circuit 16 switches the fuel control signal S4 input to the gas fuel valve control circuit 14 and the liquid fuel valve control circuit 15, and when switching the fuel A fluctuation prevention circuit 17 is provided to prevent fluctuations in the fuel control signal S1 at
By inputting the fuel control signal S5, 86 via the terminal b, the previously closed fuel valve is opened, and the function generator 1 is connected to the fuel valve control circuit on the open fuel valve side.
Adder 1 adds the fuel control signals output from 8a and 18b.
9a, 19b subtracted fuel control signal S7.
The fuel valve is configured to close by inputting S8.

The switching circuit 16 is composed of a pair of circuit elements A and B in which the paths of signals input to the gas fuel valve control circuit 14 and the liquid fuel valve control circuit 15 are set to be opposite to each other.

Circuit element A is selected when switching from liquid fuel to gas fuel, while circuit element B is a circuit selected when switching from gas fuel to liquid fuel, and they are configured to be able to switch freely between them.

When circuit element A is selected to switch from liquid fuel to gas fuel, the function generator 18a in circuit element A outputs a fuel control signal S5 to the gas fuel valve control circuit 14. The generated signal from the function generator 1-8a is normally a ramp-like function starting from 0 and ending at the fuel control signal S4 before switching, but it may also be a first-order lag function, a timer function, or a step-like function. It is possible to adopt a function suitable for the driving method, such as a function.

Since the fuel control signal S5 for opening the gas fuel valve 6 is output from the function generator 18a to the gas fuel control circuit 14, it is necessary to reduce the control signal to the liquid fuel bypass control valve 11- side. Therefore, an adder]-9a is arranged, and this adder 19a subtracts the fuel control signal S5 sent to the gas fuel valve control circuit 14 from the fuel control signal S4, and sends this subtracted fuel control signal S7 to the liquid fuel valve control circuit 15. configured to output.

Conversely, when switching from gas fuel to liquid fuel, circuit element B of the switching circuit 16 is selected and switched. Its construction and operation are similar to circuit element A except that the input direction of fuel control signal S4 is reversed.

Further, the fuel control circuit 13 receives a load setting signal S for the gas turbine 2. and the actual load signal S9 in an adder 20, which processes the signal and outputs the fuel control signal S1.

Also, a fluctuation prevention circuit 1 that prevents fluctuations in the fuel control signal S1.
7 is composed of a memory 21, an arithmetic circuit 22, and a multiplier 23, and is configured to output a fuel control signal S1 before fuel switching.
is stored in the memory 21, and compared with the actual fuel control signal Slo during fuel switching, S1o/Sl is calculated in the arithmetic circuit 22, and further multiplied by the multiplier 23, thereby controlling the fuel during the fuel switching. Signal S1
to maintain a constant value and prevent load fluctuations in the gas turbine.

Next, tool 5 when switching from liquid fuel to gas fuel Explain the physical operations.

The circuit element A is selected by the fuel switching selection of the switching circuit 16. Gas fuel valve control circuit 14 by function generator 18a
As the fuel control signal s5 increases, the adder 19
a, the fuel control signal S4 to the fuel control signal S5 is
is subtracted, and a subtracted fuel control signal S7 is output to the liquid fuel valve control circuit 15. Then, the gas fuel valve 6 is gradually opened by the gas fuel valve control signal S2 and the liquid fuel valve control signal S3 output from the gas fuel valve control circuit 14 and the liquid fuel valve control circuit 15, respectively, to increase the gas fuel ratio. At the same time, the liquid fuel bypass control valve 11 also gradually opens to reduce the proportion of liquid fuel supplied to the combustor. Therefore, the total amount of energy of the liquid fuel and the gas fuel flowing into the gas turbine is kept constant even at certain times during fuel switching.

Furthermore, even if load fluctuations of the gas turbine occur due to the nonlinear flow characteristics of each fuel valve during fuel switching, the fluctuation prevention circuit 17 ensures that the total value of the fuel control signal SI remains at the level before the fuel switching. Since it is kept the same, fluctuations in the fuel control signal S4 during fuel switching are also effectively prevented.

Even when switching from gas fuel to liquid fuel, by selecting circuit element B, the direction in which the fuel control signal S4 is input is simply reversed, and the same effect can be achieved without causing load fluctuations in the gas turbine. , fuel switching operations can be carried out quickly and easily.

As explained above, according to the gas turbine fuel switching device according to the present embodiment, it is possible to quickly switch between gas fuel and liquid fuel without stopping the gas turbine in operation, and the switching operation is also possible. In the gas turbine, stable operation can be continued without the risk of causing load fluctuations or the like of the gas turbine.

Next, a second embodiment of the present invention will be described with reference to FIG. The fluctuation prevention circuit 24 of the second embodiment includes a memory 21a that stores the actual load signal S of the gas turbine before the switching operation.
, an arithmetic circuit 22a that calculates the ratio between the actual load signal 89- and the actual load signal S9 during the switching operation, and a multiplier 23 that multiplies the fuel control signal S1 by using the ratio as a correction signal.
It consists of a.

The fluctuation prevention circuit 24 receives the actual load signals from the gas turbine before and after the fuel switching operation, and calculates the ratio between the actual load signal S9 before the fuel switching and the actual load signal S9- during the fuel switching stored in the memory 21a. The calculation is performed by the calculation circuit 22a, and the fuel control signal St is multiplied by the calculation result by the multiplier 23a, thereby effectively preventing load fluctuations of the gas turbine during the fuel switching operation performed during gas turbine operation. be able to.

Next, a third embodiment of the present invention will be described with reference to FIG. The fluctuation prevention circuit 25 of the gas turbine fuel switching device according to this embodiment is a calculation circuit that calculates the ratio of the actual calorific value Q-, Q, - to the standard calorific value Q, , Q, of gas fuel and liquid fuel, respectively. 22c, 22d, and multipliers 23c, 23d that multiply the control signal S5 and the subtracted fuel control signal S7 by the above ratio.

For gas fuel, it is the ratio Q between the standard calorific value Q, which is known in advance, and the actual calorific value Q' measured by the gas analyzer of the gas fuel actually used.

/Q − is calculated by the calculation circuit 22c, and the calculation result is multiplied by the gas fuel control signal S5 by the multiplier 23c. The same applies to liquid fuel systems.

In this way, since the correction amount due to the difference in the calorific value ratio of gas fuel and liquid fuel is multiplied by each fuel control signal S5 and S7, the correction amount due to the difference in calorific value ratio of each fuel is corrected even during gas turbine operation. Load fluctuations in the gas turbine can be effectively prevented.

〔Effect of the invention〕

As explained above, in the gas turbine fuel switching device according to the present invention, when switching between gas fuel and liquid fuel, the switching circuit is switched to a predetermined position.

After switching, the fuel valve control circuit on the fuel valve side that was closed is
Since a fuel control signal 9 proportional to the output of the function generator is inputted, the fuel valve, which had been closed, gradually opens. On the other hand, the fuel valve control circuit on the fuel valve side that had been closed for a while,
Since the subtracted fuel control signal obtained by subtracting the fuel control signal output from the function generator is input, the open fuel valve gradually closes in response to the output from the function generator, and the gas fuel and the liquid fuel switching operation progresses.

Further, during the switching operation, there is a risk that the speed and load of the gas turbine and the fuel control signal from the fuel control circuit may fluctuate greatly, but the fuel control signal and the gas turbine load are held constant by the fluctuation prevention circuit.

Therefore, according to the present invention, even if the gas turbine is operating under any load conditions, it is possible to smoothly switch between gas fuel and liquid fuel, and the present invention can fully accommodate the diversification of fuels used. This makes it possible to significantly improve the responsiveness of gas plants. Furthermore, there is little load variation in the gas turbine during switching operations, and stable operation control is possible.

0

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a first embodiment of a gas turbine fuel switching device according to the present invention, FIG. 2 is a system diagram showing a second embodiment of the present invention, and FIG. 3 is a system diagram showing a third embodiment of the present invention. FIG. 4 is a system diagram showing an example of the configuration of a conventional gas turbine power generation plant. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Gas turbine, 3... Generator, 4... Combustor, 5... Gas fuel stop valve, 6...
・Gas fuel control valve, 7...Liquid fuel stop valve, 8...
Fuel pump, 9... Flow divider, 10... Check valve, 11... Liquid fuel bypass control valve, 12... Liquid fuel relief valve, 13... Fuel control circuit, 14...
- Gas fuel valve control circuit, 15... Liquid fuel valve control circuit, 16... Switching circuit, 17... Fluctuation prevention circuit, 18
a, 18b...function generator, 19a, 19b, 20-
Adder, 21.21a...Memory, 22.22a, 2
2c, 22d... Arithmetic circuit, 23.23a, 23c,
23d--multiplier, 24.25--fluctuation prevention circuit,
SO...Load setting signal, S...Fuel control signal, S
2... Gas fuel valve control signal, 2 S3... Liquid fuel valve control signal, S4. Ss, S6・
...Fuel control signal, S7. S a...subtraction fuel control signal, S9... actual load signal, S1o... fuel control signal, A, B... circuit element.

Claims (1)

[Claims] Based on the fuel control signal from the fuel control circuit for controlling the speed and load of the gas turbine, the gas fuel is controlled by the gas fuel valve control signal and the liquid fuel valve control signal output from the gas fuel control circuit and the liquid fuel valve control circuit. In a fuel switching device for a gas turbine that controls the valve openings of a control valve and a liquid fuel bypass control valve, and switches gas fuel and liquid fuel to supply the gas turbine, the gas fuel valve control circuit and the liquid fuel valve control circuit described above. A switching circuit that switches the fuel control signal input to the gas turbine, and a fluctuation prevention circuit that prevents fluctuations in the fuel control signal or turbine load during fuel switching performed during gas turbine operation, and the switching circuit is closed. By inputting the fuel control signal via the function generator to the fuel valve control circuit on the fuel valve side, the fuel valve that had been closed is opened, while the fuel valve control circuit on the fuel valve side that was open A fuel for a gas turbine, characterized in that the fuel valve, which has been open, is closed by inputting a subtracted fuel control signal obtained by subtracting the fuel control signal output from the function generator. Switching device.