CN101680365A - Gas turbine power generation system and its operation control method - Google Patents

Abstract

The present invention is when the load of gas turbine sharply reduces, can easily suppress the gas turbine generating system of the rotating speed rising of gas turbine, this system possesses gas turbine (2), be connected in the generator (7) of gas turbine (2) with can transmitting rotating force, be used for fuel gas compressors (5) that the fuel gas that offers described gas turbine (2) is compressed, drive the motor (9) of this fuel gas compressors (5) usefulness, from described generator (7) to the 1st driving that described motor (9) provides that electric power uses with feeder (16), and the system controller of the operation usefulness of control gas turbine (2).

Description

Gas turbine power generation system and its operation control method

technical field

The invention relates to a gas turbine power generation system and an operation control method thereof. More specifically, it relates to a gas turbine power generation system provided with a thermal gas compressor for compressing thermal gas supplied to the gas turbine, and in the gas turbine power generation system, for example, when the load suddenly decreases such as load cutoff, it relates to a gas turbine power generation system for preventing the gas turbine from exceeding the specified A method for controlling the operation of a gas turbine power generation system at a rotational speed.

Background technique

Gas turbines generate electricity more efficiently than thermal boilers and emit less carbon dioxide, so their use as environmentally friendly power generation equipment is increasing. On the other hand, in the iron and steel industry as a basic industry, low-calorie by-product gases such as blast furnace gas (referred to as BFG, or Blast Furnace Gas) and converter gas (LDG) are produced. In recent years, gas turbines have been able to combust such low-calorie by-product gases due to technical improvements. There are increasing cases of using it as fuel for gas turbines to generate electricity.

9 to 11 show examples of device configurations of a gas turbine power generation system using the above-mentioned low-calorie by-product gas as a fuel for a gas turbine. Both the power generation system 101 in FIG. 9 and the power generation system 102 in FIG. 10 use the power from the gas turbine 104 to generate power. A power generation system 103 in FIG. 11 is a combined power generation system in which a gas turbine 104 is installed and a steam turbine 105 is also installed, and power generated by both 104 and 105 is used to generate electricity. A fuel gas compressor 106 for compressing fuel gas is attached to the three power generation systems 101 , 102 , and 103 . This is because, in order to use low-calorie by-product gas as fuel, it is necessary to greatly increase the supply amount of fuel gas and to compress it to a high concentration so that it has the calorie value required by the gas turbine.

Both the power generation system 102 of FIG. 10 and the power generation system 103 of FIG. 11 are connected to a fuel gas compressor 106 on a rotary drive shaft 110 from a gas turbine 104 via a transmission gear 111 .

The gas turbine 104 is provided with an air compressor 107 and a combustor 108 for compressing combustion air, and a generator 109 is connected thereto. A compressed air pipe 112 for supplying compressed air from the air compressor 107 and a fuel gas supply pipe 113 for supplying fuel gas from the fuel gas compressor 106 are connected to the combustor 108 . A flow rate control valve 114 is provided on the fuel gas supply pipe 113 . The fuel gas compressor 106 , the air compressor 107 , and the generator 109 are connected to the same shaft so as to be driven by the gas turbine 104 . Furthermore, in the hybrid power generation system 103 of FIG. 11 , the steam turbine 105 is also coaxially connected to the generator 109 .

Thus, in a power generation system that uses low-calorie gas as fuel, a large-capacity fuel gas compressor 106 is required. Furthermore, since it is a large-capacity facility, the power of the gas turbine 104 is used to drive the fuel gas compressor 106 . Since adopting such an equipment configuration requires design of each system (especially design of the shaft), long construction period and high construction cost are unavoidable.

On the other hand, in the case of a gas turbine power generation system using a common fuel such as natural gas, fuel gas (natural gas) is high in calories, so a large-capacity fuel gas compressor is generally not required, and a small-capacity fuel gas compressor is used. Can. In this case, the fuel gas compressor is not connected to the gas turbine, but is installed independently, and is usually driven by a small or medium-sized electric motor. Furthermore, a fuel gas compressor is unnecessary when the pressure of the fuel gas is high.

Fig. 12 and Fig. 13 show an example of equipment arrangement of a gas turbine power generation system using the above-mentioned natural gas as the fuel of the gas turbine. The power generation system 115 in FIG. 12 is a system for generating power using the power from the gas turbine 104 , and the power generation system 116 in FIG. 13 is a combined power generation system in which the gas turbine 104 and the steam turbine 105 are installed side by side. As shown in the figure, the power generation systems 115 and 116 are not equipped with fuel gas compressors, and the fuel gas (natural gas) is directly provided to the burner 108 by the supply source. The same reference numerals are assigned to the same devices as those in the gas turbine power generation system of FIGS. 9 to 11 , and description thereof will be omitted. It is particularly easy to design the shaft of a gas turbine power generation system that burns natural gas (meaning natural gas is used as fuel) and adopts such an equipment configuration. Furthermore, in the case of a new construction system, it is also possible to adopt a method in which a roughly standard existing design is used and only slightly modified.

In recent years, with the increase in the price of natural gas, which is a fuel that accounts for most of the operating costs of power generation systems, etc., it is desired to abandon gas turbine power generation systems that burn natural gas and build gas turbine power generation systems that burn by-product gases (low-calorie gases), or replace existing Some gas turbine power generation systems that burn natural gas are being transformed into gas turbine power generation systems that burn low-calorie gas, and the number of users is increasing. However, as mentioned above, the power generation system fueled by low-calorie gas has always required a large-capacity fuel gas compressor, and each system needs to be designed (especially the design of the shaft), which inevitably leads to prolongation of the construction period and system construction. high cost.

In addition, even a gas turbine power generation system using such a low-calorie gas as fuel is required to be able to suppress the overheating of the gas turbine when a sudden load reduction such as a load cut occurs, just like a gas turbine power generation system using a high-calorie fuel such as natural gas. speed (excessive increase in speed), while maintaining the specified speed without tripping, and maintaining a state where the speed is controllable.

For example, when the gas turbine is operating at the rated load, if the load is cut off for some reason in the power transmission system or the gas turbine power generation system, the gas turbine will fall into an overspeed state in an instant once it is stepped out from the load. Once the detection device detects such a situation, in order to reduce the fuel supply, it quickly reduces the opening of the flow control valve of the fuel supply system to suppress the overspeed of the gas turbine. The load cut is detected based on input such as an output signal of a generator or a rotational speed signal of a gas turbine. Then, the flow control valve implements a valve closing action, closing the valve to the opening degree required to ensure the minimum fuel flow required to avoid the burner from extinguishing and to maintain the rated speed under no-load conditions. The opening degree control of the flow control valve is performed while monitoring quantities indicative of operating conditions such as the rotational speed of the gas turbine, the output of the generator, the exhaust gas temperature of the gas turbine, and the inlet and outlet pressures of the air compressor. Control at the time of such a load cutoff is disclosed in many documents (see, for example, JP-A-8-165934, JP-A-2002-138856, and JP-A-2002-227610).

In the case of a gas turbine fueled by high-calorie natural gas, the amount of fuel supplied is relatively small, so the diameters of the fuel gas supply piping and the flow rate control valve are small. Thus, control with the flow control valve is not so difficult. However, in the case of a gas turbine power generation system using low-calorie gas as fuel, it is not easy to control the operation when such a load suddenly decreases. Since the fuel gas is a low-calorie gas, the amount of fuel supplied to the gas turbine is large, so a large-diameter fuel gas supply pipe is used. Therefore, a large-diameter flow control valve has to be selected, and the valve form that can be used as a flow control is limited. According to such a flow control valve, unlike the flow control valve for natural gas, it is difficult to stably control the current reduction in the low flow state required at the time of load cutoff. Accordingly, it is difficult to stably reduce the heat input to the gas turbine and maintain the heat input while the load shedding occurs. Furthermore, due to the low calorie value of heat, it is difficult to effectively suppress the overspeed of the gas turbine while preventing flameout.

Therefore, the existing gas turbine power generation system using low-calorie gas as thermal fuel connects the fuel gas compressor and the gas turbine on the same shaft. In this case, the moment of inertia of the entire rotating body of the generator train composed of the gas turbine, the fuel gas compressor, and the generator is also large.

Contents of the invention

The present invention is made to solve such existing problems, and its object is to provide a gas turbine power generation system that burns low-calorie fuels that is easy to design and manufacture by borrowing existing gas turbine power generation systems that use high-calorie fuels such as natural gas. That is, it is easy to provide new manufacturing, and it is also easy to provide a low-calorie gas-burning gas turbine power generation system obtained by modifying an existing high-calorie gas-burning gas turbine power generation system. Furthermore, the gas turbine operation control method can easily suppress the increase in the rotation speed of the gas turbine when a sudden load drop such as a load cut occurs in such a low-calorie gas combustion gas turbine power generation system.

The gas turbine power generation system of the present invention includes a gas turbine, a power generator connected to the gas turbine so as to be capable of transmitting rotational force, a fuel gas compressor for compressing fuel gas supplied to the gas turbine, and a fuel gas compressor for driving the fuel gas compressor. An electric motor, a first drive feeder for supplying electric power from the generator to the electric motor, and a system control device for controlling the operation of the gas turbine.

If a gas turbine power generation system is adopted, the equipment configuration of the existing gas turbine power generation system fueled by high-calorie gas such as natural gas can be used. Thus, a new shaft design is not required or facilitated. As a result, design and manufacture becomes easy, and the construction period and system construction cost can be reduced. In addition, even when the external load suddenly decreases such as load cutoff, since the power consumption of the electric motor for the fuel gas compressor is used as the load, the extreme drop in the load of the gas turbine as in the prior art does not occur. As a result, the increase in the rotation speed of the gas turbine is suppressed in advance, so that the rotation speed control of the gas turbine is facilitated.

In addition to the first drive feeder from the generator, a second drive feeder for supplying electric power to the motor from a power source other than the generator may be provided, and the system The control device is configured to be able to switch between feeding the electric motor from the second drive feeder and feeding the motor from the first drive feeder.

A motor starting device having a fixed frequency converter for starting the motor is provided on the second drive feeder. With such a configuration, even when the electric phase and voltage of the two power supply systems of the second drive feeder and the generator are different from each other, the motor can be started without any problem.

The first drive feeder may be connected to a portion of the second drive feeder between the motor and the motor starter.

The first drive feeder may be connected to the second drive feeder; the motor starter may be connected to a portion of the second drive feeder connected to the first drive feeder and the motor. With such a configuration, the gas compression rate of the fuel gas compressor can be adjusted by controlling the frequency of electricity supplied from the generator to the motor.

A generator bus bar for externally supplying power to the generator while driving the gas turbine while sending electric power from the generator may be provided, and the second drive feeder is connected to the generator bus bar. According to such a configuration, since the number of devices to be provided with the second drive feeder can be reduced, it is possible to reduce equipment costs and maintenance costs, which is desirable.

The operation control method of a gas turbine power generation system according to the present invention includes a gas turbine, a generator connected to the gas turbine capable of transmitting rotational force, a fuel gas compressor for compressing fuel gas supplied to the gas turbine, and driving the fuel gas. An operation control method of a gas turbine power generation system for a motor for a gas compressor and a power supply line for supplying electric power to the motor. When the fuel gas compressor is started, power is fed to the motor from the power supply line. The electric motor is fed from the generator when the gas turbine is in operation.

According to this method, even when the external load of the gas turbine suddenly decreases, such as a load cut, the rotation speed of the gas turbine can be easily controlled as described above.

When the load of the gas turbine decreases sharply, it is easier to control the rotation speed of the gas turbine by changing the operating conditions of the fuel gas compressor to adjust the load of the electric motor.

When the load of the gas turbine decreases sharply, the operating conditions of the fuel gas compressor can be changed as described above while reducing the heat input to the gas turbine.

According to the present invention, it is possible to construct a gas turbine power generation system burning low-calorie gas, and to use the equipment configuration of a gas turbine power generation system burning high-calorie gas natural gas or the like that has already been designed as a standard, so that a new shaft design is unnecessary or easy to implement. Therefore, the design and manufacture become easy, and the construction period can be shortened and the construction cost of the system can be reduced. In addition, in such a low-calorie gas combustion gas turbine power generation system, when a sudden load drop such as a load cut occurs, the increase in the rotation speed of the gas turbine can be easily suppressed.

The above and more aspects of the present invention will become apparent from the following description made with reference to the accompanying drawings.

Description of drawings

FIG. 1 is a schematic system diagram of an example of a gas turbine power generation system including an embodiment of the gas turbine power generation system of the present invention.

Fig. 2 is a system diagram showing an example of an electrical system of the gas turbine power generation system of the present invention, showing a state before the start of motion.

Fig. 3 is a system diagram of Fig. 2, showing a normal operating state of the gas turbine power generation system.

Fig. 4 is a system diagram of Fig. 2, showing a state of the gas turbine power generation system at the time of load cut-off.

Fig. 5 is a system diagram showing another example of the electrical system of the gas turbine power generation system according to the present invention, showing the state before the start of operation.

Fig. 6 is a system diagram of Fig. 5, showing a normal operating state of the gas turbine power generation system.

Fig. 7 is a system diagram of Fig. 5, showing a state of the gas turbine power generation system at the time of load cut-off.

Fig. 8(a) is a graph showing the change in load of the gas turbine when the load is cut off, (b) is a graph showing the change in the rotational speed of the gas turbine by heat input control at the time of load cut off, and (c) is a graph showing the change in the rotational speed of the gas turbine according to the load. A graph showing changes in the opening degree of the flow control valve for cutoff control.

FIG. 9 is a system diagram showing an example of a conventional power generation system including a gas turbine that burns low-calorie gas.

Fig. 10 is a system diagram showing another example of a conventional power generation system including a gas turbine burning low-calorie gas.

Fig. 11 is a system diagram showing still another example of a conventional power generation system including a gas turbine burning low-calorie gas.

FIG. 12 is a system diagram showing an example of a conventional power generation system including a gas turbine burning natural gas.

FIG. 13 is a system diagram showing another example of a conventional power generation system including a gas turbine burning natural gas.

Detailed ways

Embodiments of the gas turbine power generation system and the operation control method of the gas turbine according to the present invention will be described below with reference to the above-mentioned drawings.

FIG. 1 is a schematic system diagram of a gas turbine power generation system 1 including an embodiment of the gas turbine power generation system of the present invention. The fuel of the gas turbine 2 used in the gas turbine power generation system 1 (hereinafter also referred to as "power generation system 1") is low-calorie by-product gas (low-calorie gas) BGF generated by the blast furnace S as a gas generation source. Further, it includes a combustor 3 , a fuel gas supply pipe 4 for supplying fuel gas to the combustor 3 , a fuel gas compressor 5 for compressing the fuel gas, an air compressor 6 for supplying compressed air to the combustor 3 , and a generator 7 . The fuel gas supply pipe 4 is connected from the gas generation source S to the burner 3 via a fuel gas compressor 5 . A flow rate control valve 10 is provided in a portion of the fuel gas supply pipe 4 between the fuel gas compressor 5 and the burner 3 .

During normal operation of the power generation system 1, the system control device 70 takes, for example, the output value of the generator 7, the rotational speed of the gas turbine 2, the inlet and outlet pressure of the air compressor 6, the temperature of the exhaust gas of the gas turbine 2, etc. The opening degree of the valve is used to input heat to the gas turbine 2.

The air compressor 6 and the generator 7 are coaxially connected to the gas turbine 2 so as to be driven by the rotary shaft 2 a of the gas turbine 2 . The configuration of the above equipment is the same as the existing gas turbine power generation system burning natural gas. Therefore, the design and manufacture of the system are easy to carry out. Furthermore, unlike the gas turbine power generation system that burns natural gas, the gas turbine power generation system 1 that heats low-calorie gas is provided with a large-capacity fuel gas compressor 5 as described above. The fuel gas compressor 5 is not coaxially connected to the gas turbine 2, but is installed independently. This point is one of the characteristics of the present invention. Therefore, no new shaft design is required when a large-capacity thermal gas compressor 5 is installed. This also facilitates design and manufacture. The independently configured fuel gas compressor 5 is driven not by the gas turbine 2 but by its dedicated electric motor 9 . Furthermore, as will be described below, power is supplied to the electric motor 9 from a feeder line (bus bar) inside the power plant, and at the same time, power can also be supplied from the above-mentioned generator 7 . This point is also a feature of the present system 1 .

FIG. 2 shows an electrical system for driving the gas turbine 2 and the fuel gas compressor 5 in the power generation system 1 and supplying electric power from the generator 7 . Illustration of the system control device 70 is omitted. In this power plant, a first bus 11 used for supplying electric power from a generator to the outside and a second bus 12 used for supplying electric power to the motor 9 of the fuel gas compressor 5 are provided.

A generator bus 13 is provided between the first bus 11 and the generator 7 . The generator bus 13 is used to transmit electric power from the generator 7 to the first bus 11 , and is also used to supply power from the first bus 11 to the generator 7 when the gas turbine 2 is started. Also, a breaker 14a used for starting and a breaker 14e used for cutting off a load are provided on the generator bus 13 . A bypass bus 15 a including a starter device 15 for the gas turbine 2 is also provided on the generator bus 13 to bypass the breaker 14 a. A breaker 14b is also installed on this bypass bus 15a, and a circuit breaker 14f is also installed. The starting device 15 described above is a device for starting the gas turbine 2 using the generator 7 as a synchronous motor. The starting device 15 may also use, for example, a static frequency converter.

A first drive feeder 16 is provided between the generator 7 and the motor 9 for the fuel gas compressor 5 , and a second drive feeder 17 is provided between the second bus 12 and the motor 9 . Both feeders 16, 17 are provided with breakers 14c, 14d. The first drive feeder 16 is a bus bar for driving the fuel gas compressor 5 by feeding power from the generator 7 to the motor 9 when the gas turbine 2 is in operation. The second drive feeder 17 is a bus for driving the fuel gas compressor 5 by feeding power to the electric motor 9 from the second bus 12 when the gas turbine 2 is started. A motor starter 18 for starting the motor 9 is provided on the second drive feeder 17 . The motor starting device 18 adopts a static frequency converter, so even if the phase and voltage of the electricity from the second bus 12 and the electricity from the generator 7 are different from each other, the motor 9 can be started without any problem. This is also one of the characteristics of this system. Transformers 8 are installed at appropriate places on the drive feeders 16 and 17 , the generator bus 13 , and the bypass bus 15 a.

Next, the operation control of the gas turbine power generation system 1 performed by the system control device 70 will be described with reference to FIG. 2 . Before the start of the operation, the circuit breakers 14a, 14b, 14c, 14d, 14e and the circuit breaker 14f on all wiring lines are turned off. That is, cut off the power supply. Also in order to start the gas turbine 2, the breaker 14e as well as the breaker 14b and the circuit breaker 14f on the bypass bus 15a are closed. Then, the starter 15 changes the frequency and supplies power to the generator 7, thereby rotating the generator 7 as a synchronous motor and rotating the gas turbine 2. At this time, the gas turbine 2 is started by temporarily supplying natural gas NG or the like to the combustor 3 of the gas turbine as fuel at the time of startup.

Next, the breaker 14b and the circuit breaker 14f on the bypass bus 15a are turned off, and the activation device 15 ends its function. On the other hand, the breaker 14a on the generator bus 13 is closed, and the electric power generated by the generator 7 is transmitted to the first bus 11, and distributed to user points inside and outside the power plant. Next, the breaker 14d on the second drive feeder 17 is closed, and power is supplied from the second bus 12 to the motor starter 18 . The motor starter 18 then drives the electric motor 9 for the fuel gas compressor 5 until the rated speed is reached. The fuel gas compressor 5 is activated by means of the rotation of the electric motor 9 .

Next, as shown in FIG. 3 , the motor starter 18 synchronizes the phase and voltage of the electricity from the second bus 12 and the electricity generated by the generator 7 . The breaker 14c on the first drive feeder 16 is closed, and the electric motor 9 is powered from the generator 7 . The breaker 14d on the second drive feeder 17 is turned off, and the power supply from the second bus 2 to the motor starter 18 is stopped. That is, the power supply path to the motor 9 is switched from the second drive feeder 17 to the first drive feeder 16 . When the electric motor 9 is supplied with normal power from the generator 7, the fuel gas compressor 5 is switched to normal operation. Then, fuel gas (low-calorie gas) is supplied to the combustor 3 through the fuel gas supply pipe 4, and the gas turbine 2 starts normal operation. At this time, the supply of natural gas for start-up is stopped.

Next, the operation control of the load cut test as an example of a sudden decrease in the load of the gas turbine 2 will be described. It is obliged to confirm by means of a load cut-off test that in an industrial gas turbine power generation system, in the case of a load cut-off during rated load operation, the speed control device can function so that the gas turbine does not exceed the maximum allowable speed (usually load operation 110% of the rated speed). Operation is only allowed after confirming that there is no problem with the function of the speed control device. The speed regulating device includes, for example, a system control device for adjusting the opening degree of a flow control valve on a fuel gas supply pipe, and the like.

In the load cutoff test, as shown in FIG. 4 , the load cutoff breaker 14 e is suddenly opened to cut off the external load of the gas turbine 2 , while the other electrical systems maintain normal operation. That is, the generator 7 continues to supply power to the electric motor 9 for the fuel gas compressor 5 . On the other hand, the gas turbine 2 is disconnected from the load instantaneously, but the heat input to maintain the rated operation cannot be reduced instantaneously so far. The remaining portion of the input heat generates the acceleration torque of the rotating body to accelerate the gas turbine 2 and increase the rotation speed. Even in such a case, it is necessary to drastically reduce the heat input so that the rotational speed of the gas turbine 2 does not exceed the allowable maximum rotational speed.

In the case of a conventional natural gas-fired gas turbine, since the load actually becomes zero at the same time as the load is cut off, the remaining portion of the heat input is large. On the other hand, in the case of the system 1 of the present invention, even if the load is cut off, the generator 7 still supplies power to the motor 9 for the fuel gas compressor 5 normally, so even if the external load is cut off, the load is not substantially zero. . It is only 20 to 40% of the rated load, for example. Compared with the conventional gas turbine that does not supply power to the electric motor from the generator, the increase in the rotation speed of the gas turbine 2 is suppressed accordingly. Therefore, it is not necessary to reduce the supply amount of the fuel gas sharply and extremely. That is, even if it is a flow control valve 10 with a large diameter, it is easy to control it, and it is easy to control the rotation speed of the gas turbine 2 .

Furthermore, if the power consumed by the electric motor 9 is large, the residual load of the gas turbine 2 becomes large when the load suddenly decreases. Thus, by taking advantage of this fact, changing the operating conditions of the fuel gas compressor 5 when the load decreases sharply makes it possible to more easily control the rotation speed of the gas turbine 2 .

Fuel gas compressors generally use axial flow compressors. The fuel gas compressor 5 of this embodiment is also an axial flow compressor, and the pressure of the fuel gas is adjusted by changing the inclination angle of the guide vanes on the fluid inlet side.

In the electrical system shown in FIGS. 2 to 4 , the first bus bar 11 used for the power supply for starting the gas turbine 2 and the power supply for the generator 7 to the outside, and the power for starting the electric motor 9 for the fuel gas compressor The second bus bar 12 used for the supply belongs to a different system. However, as shown in FIG. 5 , it is also possible to realize two power supplies using a single system (bus bar) 11 .

Comparing with FIG. 2, it can be seen that in the system shown in FIG. 5, the second bus bar 12 is not provided. By connecting the second drive feeder 17 to the generator bus 13 , starting power is supplied to the motor 9 for the fuel gas compressor from the first bus 11 through the generator bus 13 and the second drive feeder 17 . The portion connected to the generator bus 13 of the second drive feeder 17 is between the connection point of the bypass bus 15 a and the transformer 8 . Of course, it is not limited to this position. With such a configuration, the number of breakers 14d and transformers 8 can be reduced, and only one bus bar is required. The difference from the electrical system shown in FIGS. 2 to 4 is only the above-mentioned parts, and the other structures are the same, so the same symbols are assigned to the same members, and their descriptions are omitted.

Next, FIG. 6 shows an electrical system used in a device configuration different from that shown in FIGS. 2 and 5 . This electrical system is also an electrical system for driving the gas turbine 2 and the fuel gas compressor 5 of the gas turbine power generation system 1 described above, and for supplying electric power from the generator 7 . Fig. 6 shows the state before the start of the operation when the breakers 14a, 14b, 14c, 14d, 14e and the circuit breaker 14f on all the wirings are turned off. That is, the power supply is cut off. In the electrical system shown in FIGS. 2 and 5 , the first drive feeder 16 from the generator 7 to the motor 9 for the fuel gas compressor is connected to the second drive feeder 17 for the motor 9 and its starter 18 the part between. However, in the electrical system of FIG. 6 , the first drive feeder 16 is connected to the upstream side of the motor starter 18 of the second drive feeder 17 (the second bus 12 side of the motor starter 18 ).

With such a configuration, the motor starter 18 can be used to change the rotation speed of the fuel gas compressor 5 (the rotation speed of the electric motor 9 ) when the power generation system is normally operated. This is because, as described above, the motor starting device 18 employs a static type frequency converter, and thus can change the rotational speed of the motor 9 by utilizing its function. In this case, the fuel gas compressor 5 can also be the above-mentioned axial flow compressor with guide vanes, but the gas compression rate can be adjusted by the motor starting device 18, so a centrifugal compressor can also be used.

Next, the operation control of the gas turbine power generation system 1 performed by the system control device 70 will be described with reference to FIG. 6 . In the case of using the electrical system of FIG. 6 , compared with the case of using the electrical system of FIG. 2 , operation control in a state where electric power is supplied to the motor 9 from the generator 7 after the motor 9 starts is different from each other. That is to say, in the electrical system of FIG. 6 , the phase and voltage of the electricity from the second bus 12 and the electricity generated by the generator 7 are also synchronized, and the path for supplying power to the motor 9 is switched from the second drive feeder 17 It is the first drive feeder 16 . However, since the power supply from the generator 7 to the motor 9 is performed through the motor starter 18 having a frequency conversion function, the rotation speed of the motor 9 can be changed by utilizing the frequency conversion function of the motor starter 18 . With such a configuration, even if the fuel gas compressor 5 does not have a fluid pressure changing function (guide vane, etc.), the gas compression ratio of the gas compressed by the fuel gas compressor 5 can be changed by the control of the motor starter 18 . Of course, there is no problem with axial flow compressors with guide vanes

FIG. 7 also shows the electrical system capable of powering the electric motor 9 from the generator 7 via the motor starter 18 . Comparing with FIG. 6 , it can be seen that the electrical system shown in FIG. 7 is not provided with a bus bar 12 . By connecting the 2nd drive feeder 17 to the generator bus 13, the electric motor 9 for starting the fuel gas compressor is provided with power for starting the motor 9 from the 1st bus 11 through the generator bus 13 and the 2nd drive feeder 17. The portion connected to the generator bus 13 of the second drive feeder 17 is between the connection point of the bypass bus 15 a and the transformer 8 . Of course, it is not limited to this position. With such a structure, the breaker 14d and the transformer 8 can be saved, and only one bus bar is required. The only difference from the electrical system shown in FIG. 6 is the above-mentioned parts, and the other configurations are the same as those of the electrical system shown in FIG. 6 , so the same reference numerals are assigned to the same components, and their descriptions are omitted.

Next, the effects obtained by the above operation will be described with reference to FIG. 8 .

FIG. 8( a ) shows the load change of the gas turbine 2 at the time of load cut, the horizontal axis represents time, the vertical axis represents the gas turbine load (%), and 100% represents the rated load. Operate with 100% rated load (shown by A0 in the figure) before the load is cut off. After the load is cut off, the load is reduced to the power share (for example, 30%) of the power consumption of the motor 9 shown at point A1. In the case of a gas turbine of a type in which the electric motor for the fuel gas compressor is not supplied with power by the generator, the stepwise decrease to 0% shown at point A2 is shown in the figure for comparison.

FIG. 8( b ) shows the change in the rotational speed of the gas turbine 2 when the rotational speed of the gas turbine increases due to load cutoff, and the heat input control (shown in FIG. 8( c )) is performed by using the flow control valve 10 or the like to suppress the rotational speed increase. . The horizontal axis corresponds to the above-mentioned FIG. 8( a ) and the following FIG. 8( c ), and represents time. The vertical axis represents the rotational speed of the gas turbine, and the ratio of the rotational speed when the rated rotational speed Nrat. is 100% during rated load operation is expressed in percentage.

Curve B1 in FIG. 8( b ) exemplifies the case where the increase in the rotational speed of the gas turbine 2 after load cut is not suppressed and exceeds the maximum allowable rotational speed (a value of 110% of the rated rotational speed) Nmax. For comparison, curve B2 exemplifies that in a gas turbine of a type that does not supply power from the generator to the electric motor for the fuel gas compressor, the increase in the rotational speed after the load is cut off is not suppressed, and the maximum allowable rotational speed (a value of 110% of the rated rotational speed) Nmax is exceeded. .Case. For the same heat input, the rotation speed (B1) of the gas turbine 2 of this embodiment is lower than the rotation speed (B2) of the comparative example. This is because the consumed power of the electric motor 9 for the fuel gas compressor exists as a load. Curve B3 shows the change in rotational speed when the gas turbine 2 according to the present embodiment is controlled according to the fuel flow rate reduction curve C1 in FIG. 8(c) described below at the time of load cut.

FIG. 8( c ) shows changes in the opening degree of the flow rate control valve 10 for suppressing an increase in the rotational speed of the gas turbine 2 when the load of the gas turbine 2 is cut off. The horizontal axis corresponds to the above-mentioned FIG. 8( a ) and FIG. 8( b ), and represents time. The vertical axis represents the opening (%) of the flow rate control valve 10 , but it can also be regarded as the same as the fuel flow rate.

The curve C1 represented by the solid line in Fig. 8(c) is the valve closing curve required to reduce the input heat of the gas turbine to avoid the speed of the gas turbine 2 exceeding the allowable maximum speed Nmax. (Fig. 8(b)) when the load is disconnected , is the heat flow reduction curve. On the other hand, the curve C2 shown by the dotted line is a curve for comparison, and illustrates the gas turbine of the type that does not supply power from the generator to the electric motor for the fuel gas compressor so that the rotation speed of the gas turbine does not exceed the allowable maximum rotation speed Nmax. (Fig. 8(b)) The required valve closing curve.

Before the load is cut off, the gas turbine 2 is operated at a rated opening (100%) Urat. of the flow control valve 10 , that is, a fuel flow rate (rated fuel flow rate) Qrat. capable of realizing the rated heat input of the gas turbine 2 . After the load is cut off, reduce the opening of the control valve 10, and make it not lower than the minimum flow (Qmin.) required to keep the fuel flow not lower than the no-load rated speed of the gas turbine (called the small opening). Minimum opening required) Umin. The required minimum flow Qmin. is the fuel flow set to ensure that the minimum heat input required by the burner 3 does not reach the flameout limit. However, in the power generation system 1 of the present embodiment, since the power consumption of the electric motor 9 exists as a load after the load is cut off, it is possible to realize an opening with a margin relative to the required minimum opening Umin. (see curve C1 and Umin. Difference). On the other hand, in the case of a gas turbine of a type that does not supply power to the electric motor for the fuel gas compressor from the generator, it is necessary to bring the opening of the flow rate control valve close to the necessary minimum opening (see curve C2).

As can be seen from the comparison of these fuel flow reduction curves ( C1 , C2 ), in the gas turbine power generation system 1 of the present embodiment, it is not necessary to reduce the opening degree of the flow control valve 10 as in the system of the comparative example. This is because a considerable amount of fuel is required because the consumed power of the electric motor 9 for the fuel gas compressor exists as a load. In other words, it means that in the gas turbine power generation system 1 of this embodiment, when controlling the rotation speed of the gas turbine 2 at the time of load cutoff, it is possible to control the flow rate control valve to achieve a margin with respect to the flameout limit of the combustor 3. flow.

As above, as shown in Fig. 8(a) to Fig. 8(c), when the load of the gas turbine 2 decreases stepwise from 100% at point A0 in Fig. 8(a) to 0% at point A1 due to load cutoff, the present embodiment In order to suppress a sudden increase in the rotational speed of the gas turbine 2, the system control device 70 of the form sets the opening degree of the flow control valve 10 to an opening degree larger than the required minimum opening degree Umin. (curve C1 of FIG. 8( c ) ). In this way, the input heat of the gas turbine 2 is reduced, and as a result, the gas turbine whose speed starts to rise sharply from load decoupling prevents the speed from exceeding the maximum allowable speed Nmax., and decelerates to the rated speed Around Nrat. (curve B3 of Fig. 8(b)).

The system control device 70 can employ, for example, a known active load imbalance detection method in order to detect that the load of the gas turbine 2 has suddenly decreased. Of course, it is not limited to such a method. If possible, it is also possible to detect a sudden load drop from the speed signal of the gas turbine, the outlet pressure signal of the fuel gas compressor, the interruption signal from the load interruption device, and the like.

Moreover, when the system control device 70 controls the opening and closing of the flow control valve 10 after a sudden load drop is detected, it can use the rated speed Nrad. as the target value to perform feedback control on the actual gas turbine speed. Moreover, feedback control can also be performed on other gas turbine motion state quantities. It is also possible to simulate the opening and closing control of the control valve in which the event after a sudden load drop is modeled according to the rated load operation of the gas turbine. Data on the opening degree of the control valve and the like at a sudden load angle obtained from the simulation results are set in advance in the system control device. Therefore, it is possible to select the preset data to execute when the real load drops sharply. Furthermore, it is also possible to replace part or all of the simulated data with actual data obtained through actual operation (including data at the time of load interruption). That is, the data set in advance based on the simulation results may be corrected using the actual operation data and used.

In this way, the system control device 70 stores programs and preset data for executing arithmetic processing required for the above-mentioned control, and is equipped with a RAM for temporarily storing data and numerical values during operation, and a CPU for performing arithmetic processing according to the above-mentioned programs.

The system control device 70 controls the entire operation of the gas turbine operation as described above. That is to say, the system control device 70 governs various operating modes such as startup (including startup preparation, cleaning, ignition, synchronous input, cold startup, and hot startup), rated load operation, partial load operation, stop, cooling, and load cut-off.

In the embodiment described above, the system using only the gas turbine to generate electricity was exemplified, but it is not limited thereto. For example, it may be a hybrid power generation system in which a gas turbine is connected to a generator and a steam turbine is also coaxially connected. Because the equipment configuration of the existing gas turbine power generation system burning high-calorie gas can be used.

In the embodiment described above, the low-calorie by-product gas used was exemplified as BFG (Blast Furnace Gas), but it is not limited thereto. The low-calorie gas includes converter gas (LDG), by-product gas (FINEX gas or COREX gas) generated by direct reduction of iron, and by-product gas generated by smelting reduction ironmaking. In addition, it also includes low-calorie gases other than the iron-making field, such as coal seam gas (COG) contained in coal seams, tail gas generated in the GTL (gas liquefaction) process, by-product gas accompanying the oil refining process of oil sand refining, and garbage Low-calorie gas generated by thermal decomposition, combustible waste gas generated during the fermentation and decomposition of general waste including raw waste, and by-product gas generated by chemical reaction of other similar raw materials gas etc. Of course, in addition to the single gas mentioned above, it may also be a mixed gas of multiple different gases mentioned above.

In addition, the present invention is not limited to the above-mentioned embodiments, and the configuration thereof may be changed, added, or deleted within a range not exceeding the scope of the present invention.

Industrial applicability

The gas turbine power generation system of the present invention has a structure capable of supplying power to the electric motor of the fuel gas compressor from the generator connected to the gas turbine, so when the load decreases sharply, the load does not drop greatly as in the prior art, so thereafter The rotation speed control of the gas turbine is easy to perform. Therefore, it is suitable, for example, for a gas turbine power generation facility that is obliged to perform a load cutoff test.

Claims (9)

1. A gas turbine power generation system, characterized in that it has gas turbine, A generator connected to the gas turbine capable of transmitting rotational force, a fuel gas compressor for compressing fuel gas supplied to said gas turbine, an electric motor for driving the fuel gas compressor, a first drive feeder for supplying electric power from the generator to the motor; and A system control device for controlling the operation of a gas turbine. 2. The gas turbine power generation system according to claim 1, wherein: In addition to the first drive feeder from the generator, a second drive feeder for supplying electric power to the motor from a power source other than the generator is provided, The system control device is configured to be capable of switching between power feeding to the motor from the second drive feeder line and power feed to the motor from the first drive feeder line. 3. The gas turbine power generation system according to claim 2, wherein a motor starting device having a fixed frequency converter for starting the electric motor is provided on the second drive feeder. 4. The gas turbine power generation system according to claim 3, wherein the first drive feeder is connected to a portion of the second drive feeder between the electric motor and the motor starter. 5. The gas turbine power generation system according to claim 3, wherein the first drive feeder is connected to the second drive feeder; the motor starting device is connected to the second drive feeder and the second drive feeder. 1 The part between the connection part of the drive feeder and the motor. 6. The gas turbine power generation system according to claim 2, characterized in that, the generator bus bar is configured to send electric power from the generator to the outside, drive the gas turbine at the same time, and provide power to the generator from the outside, The second drive feeder is connected to the generator bus. 7. An operation control method of a gas turbine power generation system comprising a gas turbine, a generator connected to the gas turbine capable of transmitting rotational force, a fuel gas compressor for compressing fuel gas supplied to the gas turbine, and driving the gas turbine A motor for a fuel gas compressor, and an operation control method for a gas turbine power generation system that supplies power to the motor with a power supply line, is characterized in that, When the fuel gas compressor is driven, the electric motor is fed from the electric power supply line, and when the gas turbine is operated, the electric motor is fed from the generator. 8. The operation control method of the gas turbine power generation system according to claim 7, characterized in that, when the load of the gas turbine decreases sharply, the load of the electric motor is adjusted by changing the operating conditions of the fuel gas compressor. 9 . The operation control method of a gas turbine power generation system according to claim 8 , wherein when the load of the gas turbine decreases sharply, the heat input to the gas turbine is reduced. 10 .

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