JPH0921329A - Exhaust gas reverse flow prevention device for gas turbine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the exhaust gas reverse flow prevention device for a gas turbine system, which can enhance reliability, and automate its operations while the device is being made small in size. SOLUTION: When a part of a gas turbine 2 is operated, introduction of air into the inside of an exhaust passage 6 through a gap between a closed switching damper 10 and a closed seal damper 12 at the side of the suspended gas turbine 2, prevents exhaust gas reversely flowing from the junction part of the exhaust gas passage 6 from leaking out of the closed seal damper 12 to the switching damper 10 side. Therefore, sealing can thereby be surely accomplished, and since no gas is emitted out of a space between the switching damper 10 and the seal damper 12, an air bleed damper, an air bleed duct and a related silencer can thereby be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cogeneration system having a plurality of gas turbines mainly used for power generation and a single exhaust heat boiler using the exhaust gas as a heat source. The present invention relates to a combined cycle gas turbine system that rotates a steam turbine with steam to generate electricity, and an exhaust gas backflow prevention device for the combined cycle gas turbine system.

[0002]

2. Description of the Related Art In a gas turbine system having a plurality of gas turbines and a single exhaust heat boiler using the exhaust gas as a heat source, the exhaust gas discharged from the plurality of gas turbines is merged through each exhaust gas passage to form a single exhaust heat exchanger. Attempts have been made to recover the waste heat from an exhaust heat boiler to effectively use the exhaust heat of exhaust gas.

In this case, since the exhaust gas discharged from the gas turbine has a constant static pressure (about 250 mmAq), for example, when one gas turbine is stopped, the other gas turbines in operation are operated. The exhaust gas flows backward and is applied as back pressure to the exhaust gas passage on the downstream side of the gas turbine at rest. For this reason, it becomes difficult to smoothly restart the gas turbine that is stopped under the influence of this back pressure, and a system for preventing this becomes necessary.

FIG. 5 shows an example of a conventional exhaust gas backflow prevention device for a gas turbine system. In this device, one exhaust heat boiler 4 is provided for a plurality (two in this example) of gas turbines, and a three-way exhaust damper 10 and an extraction damper 20 are provided in an exhaust gas passage 6 of each gas turbine 2. And a slide gate damper 18 are provided.

For example, it is assumed that the gas turbine 2 of the first unit is in operation and the gas turbine 2 of the second unit is at rest. 2
The slide gate damper 18 of Unit 1 drives a hydraulic cylinder (not shown) with a manual switch (not shown) to move the shut-off gate 56 downward to close it, so that the exhaust gas discharged from the exhaust gas passage 6 of Unit 1 is discharged to Unit 2 Cut off so that it does not flow to the side. On the other hand, Unit 3 three-way exhaust damper 10
As shown in the figure, the exhaust heat boiler 4 side is closed by the shut-off gate 46 so that the exhaust gas from the Unit 1 can restart the Unit 2 smoothly even if the exhaust gas passage 6 of the Unit 2 has a positive pressure. Then, the side of the bypass duct 11 is opened and the exhaust gas is discharged from the bypass duct 11 to the outside.

At this time, since the complete sealing cannot be achieved only by shutting off by the three-way exhaust damper 10 and the slide gate damper 18, the exhaust gas circulates through the gap between the shutoff gates 46, 56, and the gas turbine 2 is stopped. There may be back pressure. For this reason, in order to discharge the exhaust gas that has come around, the bleed air damper 20 and the bleed air duct 21 are provided between them, and the bleed air damper 20 is opened by a manual switch (not shown) so as to be discharged to the outside from the bleed air duct 21. .

[0007]

However, in the above-mentioned conventional system, there is a problem that the structure becomes complicated because the number of constituent devices for preventing backflow of exhaust gas increases. In addition to the bypass duct 11, the extraction duct 21
Since the exhaust gas is also emitted to the atmosphere, a silencer for the bleed air duct 21 is required in addition to the silencer for the bypass duct 11 for noise reduction, which causes a problem that the installation space becomes large.

Further, if the bleed air damper 20 and the slide gate damper 18 are automatically driven, there is a problem that the structure becomes complicated and it is difficult in terms of cost.

Further, in the extraction damper 20, since the exhaust gas is released by the ventilation force of the extraction duct 21, the back pressure of the gas turbine 2 in the stopped state does not become 0 or less, and the reliability of the leakage prevention of the exhaust gas is reduced. There was also the problem of poor sex.

An object of the present invention is to solve the above problems and to provide an exhaust gas backflow prevention device for a gas turbine system which can be automated while improving reliability and downsizing.

[0011]

In order to achieve the above object, the invention of claim 1 or claim 6 of the present invention comprises a plurality of gas turbines, a single exhaust heat boiler using exhaust gas as a heat source, An exhaust gas passage that joins the exhaust gas from the plurality of gas turbines and introduces it into the exhaust heat boiler, a bypass passage that is connected to each exhaust gas passage and discharges the exhaust gas to the outside, and an exhaust gas from the gas turbine to the exhaust heat boiler. A switching damper selectively set at an operating position to be introduced and a bypass position to be introduced into the bypass passage, and a seal damper provided on the downstream side of the switching damper in the exhaust gas passage for opening and closing the exhaust gas passage, and partly When operating only the gas turbine of the, the pressure higher than the pressure of the exhaust gas in the exhaust gas passage from between the closed switching damper and the seal damper on the stopped gas turbine side. The introduction of air, so that the exhaust gas flowing back to the exhaust gas channel from the merging portion of the exhaust gas passage is prevented from leaking from the closed to seal the damper to the switching damper side.

According to a second aspect of the present invention, in the first aspect, the air sealing device includes a plurality of blowers that are selectively operated, and when the pressure of the introduced air is below a set value,
It has a blower automatic switching means for automatically starting the blower that has been stopped.

According to a third aspect of the present invention, in the second aspect, the opening / closing valve and the check valve located upstream of the opening / closing valve are provided in the individual air passages for introducing the air from the blower into the exhaust gas passage of each gas turbine. And the individual air passages communicate with each other by a communication passage between the check valve and the on-off valve.

According to a fourth aspect of the present invention, in the first aspect, the seal damper has a duct portion forming a part of the exhaust gas passage, and the duct portion is provided with an air introduction port for introducing air into the exhaust gas passage. Has been formed.

According to a fifth aspect of the present invention, in the first aspect, there is provided drive means for driving the switching damper and the seal damper in conjunction with the operation of each gas turbine.

[0016]

According to the invention of claim 1 or claim 6, when only a part of the gas turbine is operated, the inside of the exhaust gas passage is opened from between the closed switching damper and the seal damper on the gas turbine side which is stopped. By introducing air having a pressure higher than the pressure of the exhaust gas into the exhaust gas passage, it is possible to prevent the exhaust gas flowing back through the exhaust gas passage from leaking from the closed seal damper to the switching damper side. Therefore,
Since reliable sealing is possible and exhaust gas is not emitted between the switching damper and the seal damper, the extraction damper and extraction duct and the silencer thereof are not required. Accordingly, it is possible to provide an exhaust gas backflow prevention device or an exhaust gas backflow prevention method for a gas turbine system, which can improve reliability and can be downsized.

According to the second aspect of the invention, the air sealing device automatically operates the plurality of blowers that are selectively operated and the blower that has been stopped when the pressure of the introduced air is below a set value. It has a blower automatic switching means for additional activation. Therefore, it is possible to stably prevent backflow of exhaust gas even if the blower fails during operation.

According to the third aspect of the present invention, an opening / closing valve and a check valve located upstream of the opening / closing valve are provided in the individual air passage for introducing the air from the blower into the exhaust gas passage of each gas turbine. The individual air passages communicate with each other through the communication passage between the check valve and the on-off valve. Therefore, the air passage for switching the blower is simplified.

According to the invention of claim 4, the seal damper has a duct portion forming a part of the exhaust gas passage, and an air inlet for introducing air into the exhaust gas passage is formed in the duct portion. . Therefore, since the seal damper and the air inlet are configured as one unit, the number of parts is reduced, the structure is simplified, and the installation space is also reduced.

According to the invention of claim 5, there is provided a drive means for driving the switching damper and the seal damper in conjunction with the operation of each gas turbine. Therefore, it becomes possible to automate the backflow prevention of exhaust gas.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an exhaust gas backflow prevention device for a gas turbine system according to an embodiment of the present invention. In this gas turbine system, a plurality (two in this example) of gas turbines 2 are driven by the pressure of combustion gas, and for example, the rotor of a generator 3 is rotated to obtain generated power. On the other hand, the exhaust gas discharged from each gas turbine 2 is joined by the exhaust gas passage 6 and sent to the single exhaust heat boiler 4 which uses the exhaust gas as a heat source, and the supplied water is supplied as shown in the side view of FIG. After being preheated by the economizer 14 inserted in the exhaust duct 15, it is vaporized in the waste heat boiler 4, and this steam is sent as a process steam or is sent to a separately provided steam turbine for power generation in order to effectively use the waste heat. .

As shown in FIG. 1, the exhaust gas backflow prevention device of this system is provided with a bypass duct (bypass passage) 11 which is connected to each exhaust gas passage 6 and discharges the exhaust gas to the outside.
And a switching damper 10 such as a three-way exhaust damper selectively set at an operating position P1 for introducing the exhaust gas from the gas turbine 2 into the exhaust heat boiler 4 and a bypass position P2 for introducing the exhaust gas to the bypass duct 11. There is.

Here, when the apparatus further operates only a part of the gas turbine 2 and a seal damper 12 arranged downstream of the three-way exhaust damper 10 in the exhaust gas passage 6 to open and close the exhaust gas passage 6, Closed three-way exhaust damper 10 and seal damper 1 on the gas turbine 2 side
By introducing air between the two, the air seal device 16 that prevents the exhaust gas that flows back from the exhaust gas passage 6 from the merging portion of the exhaust gas passage 6 from leaking from the closed seal damper 12 to the three-way exhaust damper 10 side. It has and.

This air sealing device 16 (for example, 16A,
16B (two units) are provided with two motor-driven blowers (blowers) 30 that generate air, and each blower 30 and the corresponding seal damper 12 are connected by an individual air passage 35. In each of the first and second individual air passages 35A and 35B, a check valve 32 that blocks a reverse flow of air, and a seal air switching valve 3 that switches ON / OFF of the inflow of air.
4 and a pressure switch 36 provided between the check valve 38 and the seal air switching valve 34. Normally, the seal air switching valve 34 of the individual air passage 35 connected to the seal damper 12 of the operating gas turbine 2 is closed, and the resting seal air switching valve 34 is open. In addition, these individual air passages 35A, 35B
Communicate with each other through the communication passage 40 between the check valve 32 and the seal air switching valve 34.

Further, the controller 24 controls the entire system and detects the pressure signal S3 when the pressure of the pressure switch 36 of the air circuit 35 falls below a set value for some reason and outputs the pressure signal S3. Based on the blower, the blower switching means 26 for automatically starting the blower that has been stopped to maintain the air supply is provided. However, at the time of a thermal trip of the blower that was operating, this blower is stopped and the blower that was paused is automatically started.

The configuration of each device will be described in detail below. First, a plan view of the three-way exhaust damper 10 is shown in FIG.
The side view is shown in FIG. The three-way exhaust damper 10 shown in FIG. 3B has a duct portion 42 forming a part of the exhaust gas passage 6.
And a drive means 44 for selectively driving the exhaust damper cutoff gate 46.

The drive means 44 is provided at one end of the exhaust damper main body 42 on the side of the bypass duct 11 with the exhaust damper cutoff gate 4
A support shaft 48 to which 6 is fixed is rotatably arranged.
Frame 43 attached to the other end on the exhaust damper body 42
The motor cylinder 50 is rotatably supported by
A drive motor M1 is connected to the motor cylinder 50. In addition, an arm 52 is attached to the motor cylinder 50.
Are joined together, and the tip of the arm 52 and the support shaft 48 are fixed.

When the drive motor M1 is driven and the motor cylinder 50 rotates, the arm 52 rotates in the A and B directions. When the arm 52 moves in the A direction, the support shaft 48 rotates counterclockwise, and at the operating position P1, the bypass duct 11 side is closed and the exhaust heat boiler 4 side is opened. In this operating state, the exhaust gas from the gas turbine 2 is introduced into the exhaust heat boiler 4. On the contrary, when it rotates in the B direction, the support shaft 48
Rotates clockwise, and at the bypass position P2, the exhaust heat boiler 4 side is closed and the bypass duct 11 side is opened.

This three-way exhaust damper 10 is placed in the bypass position P.
Normally, the number 2 is set when the exhaust heat boiler 4 fails, or when the exhaust heat boiler 4 is stopped due to a decrease in the feed water pressure to the exhaust heat boiler 4, etc. It is also necessary to overcome the back pressure of the exhaust gas passage 6 at the time of restart of 2. At the tip of the bypass duct 11,
A silencer 13 (see FIG. 2) is attached and has a sound deadening effect.

FIG. 4 shows a side view of the seal damper 12. This seal damper 12 is provided with an air inlet 12a into which air flows from the individual air passage circuit 35, a duct portion 62 connected in the middle of the exhaust gas passage 6, and a drive means 64 for driving a seal damper cutoff gate 66. ing.

In the drive means 64, a support shaft 68 having a seal damper cutoff gate 66 fixed thereto is rotatably arranged at one end of the duct portion 62 on the exhaust heat boiler 4 side. Duct part 6
A motor cylinder 70 is rotatably supported by a frame 73 provided below the motor cylinder 2, and a drive motor M2 is connected to the motor cylinder 70. An arm 72 is connected to the motor cylinder 70,
The tip of the arm 72 and the support shaft 68 are fixed.

When the drive motor M2 is driven to rotate the motor cylinder 70, the arm 72 is rotated in the C and D directions. When the arm 72 rotates in the C direction, the support shaft 68 rotates counterclockwise, and the exhaust heat boiler 4 side is opened at the operating position P3. In this operating state, the exhaust gas from the gas turbine 2 is introduced into the exhaust heat boiler 4. On the contrary, when the support shaft 48 rotates clockwise when it rotates in the D direction, the exhaust heat boiler 4 side is closed at the air seal position P4.

Next, the operation of the exhaust gas backflow prevention device of this system will be described. In FIG. 1, for example, when the first unit of the gas turbine 2 is in operation and the second unit is at rest, the control signal a from the controller 24 causes the three-way exhaust damper 10 of the first unit to have the bypass duct 11 side closed, The exhaust heat boiler 4 side is switched to the operating position P1 in the open state (see FIG. 3 (A)). Also, the seal damper 12 of Unit 1
, The blower 30 of the first individual air passage 35A is stopped and the seal air switching valve 34 is closed, so that air does not flow in, and the control signal b from the controller 24 causes the seal damper 1 to move.
The seal air shutoff gate 66 of No. 2 is switched to the operating position P3 (see FIG. 4) where the exhaust heat boiler 4 side is in the open state.
Therefore, the exhaust gas of Unit 1 is sent to the exhaust heat boiler 4 through the exhaust gas passage 6. Then, as shown in FIG. 2, the water supplied to the exhaust heat boiler 4 is preheated by the economizer 14 inserted into the exhaust duct 15 and then vaporized in the exhaust heat boiler 4, and the steam is process steam. As
Alternatively, it is sent to a separately provided steam turbine for power generation.

At this time, the three-way exhaust damper 10 of the No. 2 machine is closed by the control signal a of the controller 24 so that the exhaust heat boiler 4 side is closed so that no back pressure is applied to the No. 2 machine of the gas turbine 2 at rest in FIG. Then, the bypass duct 11 side is switched to the bypass position P2 in the open state (FIG. 3).
(A)). Along with this, the seal damper 1 of Unit 2
2 is switched to the air seal position P4 in which the exhaust heat boiler 4 side is closed by the control signal b of the controller 24 (see FIG. 4).

The controller 24 is mounted on the drive motor M1 of the three-way exhaust damper 10 in order to prevent the exhaust gas from flowing from the operating gas turbine through the gap between the gates 46 and 66. From the sensor, the exhaust damper shutoff gate 46 is moved to the bypass position P2
The position signal S1 indicating that the seal damper 12 is located at the air seal position P4, and a position sensor (not shown) attached to the drive motor M2 of the seal damper 12 indicates that the seal damper cutoff gate 66 of the seal damper 12 is at the air seal position P4. When the signal S2 is received, the seal damper 12
The blower 30 in the second individual air passage 35B is operated, and the seal air switching valve 34 is opened to allow air to flow in.
As a result, the air from the blower 30 flows into the seal damper 12 of the Unit 2 and fills the duct portion 62, thereby air-sealing, and the exhaust gas at the confluent portion of the exhaust gas passage 6 to the gas turbine 2 of the Unit 2. It is prevented from flowing around and flowing in.

If, for some reason, the second individual air passage 35B or the blower 30 fails and the pressure of the pressure switch 36 falls below the set value, the controller 24 detects the pressure signal S3. Controller 2
By the blower switching means 26 of No. 4, the first individual air passage 3
The blower 30 of 5 A is additionally activated, and the supply of air to both seal dampers 12 is continued via the communication passage 40. However, during the thermal trip of the No. 2 blower 30,
The blower 30 of No. 1 machine is started, and the blower 30 of No. 2 machine is stopped. By providing the communication passage 40, the air passage for performing the switching operation of the blower 30 can be simplified, and stable air supply can be performed even if the blower 30 has a failure.

[Brief description of drawings]

FIG. 1 is a plan view showing an exhaust gas backflow prevention device of a gas turbine system according to an embodiment of the present invention.

FIG. 2 is a side view showing an exhaust gas backflow prevention device of the gas turbine system.

FIG. 3 is a plan view and a side view showing a three-way exhaust damper.

FIG. 4 is a side view showing a seal damper.

FIG. 5 is a plan view showing an exhaust gas backflow prevention device of a conventional gas turbine system.

[Explanation of symbols]

2 ... Gas turbine, 4 ... Exhaust heat boiler, 6 ... Exhaust gas passage,
10 ... Switching damper (three-way exhaust damper), 11 ... Bypass passage, 12 ... Seal damper, 16 (16A, 16B) ...
Air sealing device.

Claims (6)

[Claims] 1. A plurality of gas turbines, a single exhaust heat boiler that uses exhaust gas as a heat source, an exhaust gas passage that joins the exhaust gases from the plurality of gas turbines and introduces the exhaust heat boiler, and each exhaust gas passage. A bypass passage connected to the exhaust passage for discharging exhaust gas to the outside, a switching damper selectively set at an operating position for introducing the exhaust gas from the gas turbine to the exhaust heat boiler and a bypass position for introducing the bypass passage, and A seal damper that is provided downstream of the switching damper in the exhaust gas passage and opens and closes the exhaust gas passage, and when operating only a part of the gas turbine, exhaust gas is discharged between the closed switching damper and the seal damper on the gas turbine side that has stopped. By introducing air with a pressure higher than the pressure of the exhaust gas into the passage, the exhaust gas that has flowed backward from the confluent portion of the exhaust passage is closed. An exhaust gas backflow prevention device for a gas turbine system, which comprises an air seal device that prevents leakage from a stopped seal damper to the switching damper side. 2. The air seal device according to claim 1, wherein the blower which is in operation is automatically supplemented with a plurality of blowers which are selectively operated and when the pressure of the introduced air is below a set value. An exhaust gas backflow prevention device for a gas turbine system having a blower automatic switching means for starting. 3. An on-off valve and a check valve located upstream of the on-off valve are provided in an individual air passage for introducing air from a blower into an exhaust gas passage of each gas turbine according to claim 2. An exhaust gas backflow prevention device for a gas turbine system, wherein the individual air passages communicate with each other through a communication passage between a check valve and an opening / closing valve. 4. The gas according to claim 1, wherein the seal damper has a duct portion that forms a part of an exhaust gas passage, and an air inlet for introducing air into the exhaust gas passage is formed in the duct portion. Exhaust gas backflow prevention device for turbine system. 5. The exhaust gas backflow prevention device for a gas turbine system according to claim 1, further comprising drive means for driving the switching damper and the seal damper in conjunction with the operation of each gas turbine. 6. A plurality of gas turbines, a single exhaust heat boiler using exhaust gas as a heat source, an exhaust gas passage for introducing exhaust gas from the plurality of gas turbines into the exhaust heat boiler, and exhaust gas passages. A bypass passage connected to the exhaust passage for discharging exhaust gas to the outside, a switching damper selectively set at an operating position for introducing the exhaust gas from the gas turbine to the exhaust heat boiler and a bypass position for introducing the bypass passage, and With a seal damper provided on the downstream side of the switching damper in the exhaust gas passage to open and close the exhaust gas passage, and when only some gas turbines are operated, the switching damper and the seal damper on the gas turbine side that have been stopped are closed,
By introducing air having a pressure higher than the pressure of the exhaust gas into the passage from between these two dampers, the exhaust gas flowing back through the exhaust gas passage from the merging portion of the exhaust gas passage leaks from the closed seal damper to the switching damper side. A method for preventing backflow of exhaust gas in a gas turbine system, which prevents the above-mentioned problems.