JPH0926125A - Exhaust gas duct device and gas turbine starting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the back-flow of a high temperature exhaust gas from occurring and equipment from being damaged, and secure the safety of work during maintenance inspection time by providing an exhaust gas damper at the outlet of a plurality of waste heat collection boilers, and providing a device which prevents the back-flow of exhaust gas from the other waste heat collec tion boiler at this damper part. SOLUTION: A relief valve 13 provided on a damper 7 is fully closed during the operation of a gas turbine. In the case where one shaft out of a plurality of shafts of combined cycles is stopped, the damper 7 is fully closed, and the relief valve 13 provided in a back flow exhaust gas relief device 12 of the damper 7 is fully opened, thereby discharging a back-flow exhaust gas 11 to the atmosphere, which gas leaks from a gas of a seal plate 16 of a damper blade 15 of the damper 7 to a waste heat collection boiler from an exhaust gas merging duct 8 which shows a positive pressure. This construction makes it possible to prevent a high temperature exhaust gas from flowing into the waste heat collection boiler, even if the back flow exhaust gas 11 leaks from the damper 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas duct device of a system in which outlet flues of a plurality of exhaust heat recovery boilers are gathered and a plurality of combined cycle facilities of a structure having a structure for exhausting air from one chimney are gathered. , An exhaust gas duct device with a structure suitable for preventing burnout of upstream equipment due to backflow of exhaust gas from the other exhaust heat recovery boiler, and ensuring safety during maintenance and inspection of flue and exhaust heat recovery boiler The present invention relates to a method for starting a gas turbine.

[0002]

2. Description of the Related Art FIG. 3 shows a system in which outlet flues of a plurality of conventional heat recovery steam generators are gathered together and a plurality of combined cycle facilities of a plurality of axes having a structure in which they are exhausted by one chimney are gathered together. In the figure, the generator 18 is rotated by operating the gas turbine 20. The exhaust gas 27 discharged from the gas turbine 20 passes through the high-temperature exhaust gas duct 21 and is sent to an exhaust heat recovery boiler (HRSG) 22. HRSG22
The steam is generated at, the steam is sent to the steam turbine 19, and the generator 18 is rotated by the operation of the steam turbine 19. The exhaust gas 27 heat recovered by the HRSG 22 is
It passes through the low-temperature exhaust gas duct 23, the damper 24, and the exhaust gas merging duct 25, and is discharged from the chimney 26 to the atmosphere. Damper 2
4 is installed in the damper frame 29. While the gas turbine 20 is in operation, the damper 24 is fully opened, but when one of the plurality of shafts is stopped (the gas turbine 20 is stopped), the damper 24 of the stopped shaft is fully closed. As a conventional technique, there is, for example, JP-A-61-181937.

[0003]

As described above, in the system in which the exit flues of a plurality of conventional exhaust heat recovery boilers are gathered and a plurality of combined cycle facilities of a structure having a structure of exhausting one chimney are gathered, When the exhaust gas pressure in the merging duct at the chimney inlet is positive, even if the damper is fully closed, high-temperature exhaust gas leaks from the damper and HRSG
There is a problem that the work flows into the duct on the (exhaust heat recovery boiler) side and the work at the time of maintenance and inspection in the duct and in the HRSG is extremely dangerous. Further, when the gas turbine is started, the damper is fully opened. At this time, there is a problem that high-temperature exhaust gas flows backward and burns equipment such as a gas turbine provided in the upstream. Therefore, when one axis is stopped in the combined cycle of a plurality of axes, there is a problem that the wake of the damper at the outlet of the HRSG must be adjusted to a negative pressure so that exhaust gas does not flow backward. . However, if the number of connected combined cycle axes for one chimney increases, in order to reduce the duct internal pressure at the exhaust gas confluence section and the chimney internal pressure to a negative pressure, the exhaust gas confluence duct size and the chimney size must be changed. Need to be bigger. On the other hand, in order to reduce the size of the merging duct and the stack, it is necessary to reduce the number of combined cycle axes connected to one stack, which eventually increases the number of stacks. Also requires a large installation space,
There is a problem that the equipment cost becomes expensive.

An object of the present invention is to solve the above-mentioned problems in the prior art, in which a plurality of exhaust heat recovery boiler outlet flues are combined and exhausted by one chimney. In a system in which cycle equipment is assembled, when one axis is stopped in a combined cycle of multiple axes, the size of the merging duct and chimney for increasing the negative pressure of the wake of the damper at the HRSG outlet, or the number of chimneys Without increasing the backflow of high-temperature exhaust gas to prevent burnout of equipment arranged in the upstream,
Effective backflow of high temperature exhaust gas from the merging duct when starting the exhaust gas duct device with a structure that can ensure the safety of work during maintenance and inspection in the duct and in the HRSG and the gas turbine that is stopped To provide a method to prevent.

[0005]

In order to achieve the above-mentioned object of the present invention, the present invention has a constitution as set forth in the claims. That is, according to the present invention, as described in claim 1, in an exhaust gas duct device having a structure in which outlet flues of a plurality of exhaust heat recovery boilers are gathered and exhausted by one chimney, Exhaust gas having a structure in which each outlet part is provided with an exhaust gas damper that can be opened and closed independently, and the exhaust gas damper part is provided with an exhaust gas escape device for preventing backflow of exhaust gas from the other exhaust heat recovery boiler. It is a duct device. Further, as described in claim 2, the present invention provides the exhaust gas escape device according to claim 1, wherein at least the exhaust pipe and the exhaust gas escape provided outside the seal plate portion of the damper blade of the slide damper for preventing backflow of the exhaust gas. The exhaust gas duct device comprises a valve or an exhaust pipe, an exhaust gas relief valve, and a ventilation fan. Further, according to the present invention, as described in claim 3, one chimney, at least a generator, a gas turbine,
In a method of starting a gas turbine in a stopped state in a combined cycle power plant to which a plurality of outlet flues consisting of an exhaust heat recovery boiler are connected, the output of the other operating gas turbine is reduced, that is, the amount of exhaust gas is reduced. After adjusting the exhaust gas pressure in the confluence duct section to which a plurality of outlet flues are connected to a negative pressure, by starting the gas turbine stopped, the exhaust heat recovery boiler of the other operating gas turbine is started. This is a method for starting a gas turbine that prevents backflow of high-temperature exhaust gas from the engine.

Next, the operation and effect of the present invention will be described. According to the present invention, as described in claim 1, in an exhaust gas duct device having a structure in which the outlet flues of a plurality of exhaust heat recovery boilers are gathered and exhausted by one chimney, the outlets of the plurality of exhaust heat recovery boilers are provided. The exhaust gas damper that can be independently opened and closed, and the exhaust gas damper unit is provided with an exhaust gas escape device for preventing backflow of the exhaust gas from the other exhaust heat recovery boiler, Backflow due to leakage can be released from the damper unit to another system (for example, in the atmosphere). This eliminates the risk of hot exhaust gas flowing backward even if the number of exhaust gas merging and connecting shafts for one chimney increases, even if the internal pressure of the exhaust gas merging duct and the internal pressure of the chimney become positive. ,
It is possible to ensure safety during maintenance and inspection, and even if the damper is fully opened at startup, it is possible to prevent burnout of the upstream equipment due to the backflow of high-temperature exhaust gas, and to set the size of the exhaust gas confluence duct and chimney small. Therefore, there is an effect that the equipment cost becomes low. Further, according to the present invention, as described in claim 2, in claim 1, the exhaust gas escape device is:
A structure including at least an exhaust pipe and an exhaust gas relief valve, or an exhaust pipe, an exhaust gas relief valve, and a ventilation fan provided outside the seal plate portion of the damper blade of the slide damper that prevents the backflow of the exhaust gas. Due to the structure, the backflow due to the leakage of exhaust gas,
It is possible to provide an exhaust gas escape device that can be quickly released from the damper part, for example, into the atmosphere, has a simple structure, and has excellent functionality. Further, according to the present invention, as described in claim 3, for example, as shown in FIG. 5B, even when one gas turbine is stopped, when the pressure in the confluence duct at the chimney inlet is positive, By reducing the output of the other operating gas turbine, that is, by reducing the exhaust gas amount of the gas turbine, the pressure loss in the merging duct and the chimney can be reduced, so that the inside of the merging duct can be adjusted to a negative pressure. It will be possible. Since the exhaust gas pressure in the merging duct can be adjusted in this manner, the exhaust gas pressure in the merging duct can be controlled to a negative pressure when restarting the gas turbine that is not operating. It is possible to prevent burnout of the upstream equipment due to the backflow of high-temperature exhaust gas. Further, as shown in FIG. 5A, for example, the output of the gas turbine can be reduced (the amount of exhaust gas can be reduced) depending on the atmospheric temperature, so that the inside of the merging duct can be adjusted to a negative pressure. Further, in the present invention, it is also possible to reduce and adjust the output of the gas turbine by the pressure in the merging duct at the chimney inlet. Further, in the present invention, it is also possible to reduce the output of the gas turbine by the plant output and adjust the exhaust gas pressure in the confluence duct at the chimney inlet portion.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a system in which a plurality of combined cycle facilities are assembled in one chimney as an example of an embodiment of the present invention. In contrast to the conventional structure shown in FIG. 3 described above, as shown in FIG. 1, the damper 7 is provided with a backflow exhaust gas escape device 12 provided with an escape valve 13 and the like. In the figure, the generator 1 is rotated by operating the gas turbine 3. Exhaust gas 10 discharged from the gas turbine 3 passes through a high temperature exhaust gas duct 4 and is sent to an HRSG (exhaust heat recovery boiler) 5. The HRSG 5 generates steam, sends the steam to the steam turbine 2, and rotates the generator 1 by operating the steam turbine 2. The exhaust gas 10 that has been heat-recovered by the HRSG 5 passes through the low-temperature exhaust gas duct 6, the damper 7 (fully opened), and the exhaust gas confluence duct 8, and is discharged from the chimney 9 to the atmosphere. The relief valve 13 provided in the damper 7 is fully closed during the operation of the gas turbine 3. The pressure of the exhaust gas in the exhaust gas confluence duct 8 and the chimney 9 at the time of such normal operation shows a positive pressure. Stops one axis during a combined cycle of multiple axes (gas turbine 3
When it is stopped, the damper 7 is fully closed as shown in FIGS. 2 (a) and 2 (b). Then, the relief valve 13 provided in the reverse-flow exhaust gas escape device 12 of the damper 7 is fully opened, and the HRSG 5 is discharged from the exhaust gas merging duct 8 showing a positive pressure.
The backward flow exhaust gas 11 leaking from the gap of the seal plate 16 of the damper blade 15 of the damper 7 to the side is discharged to the atmosphere. Thus, even if the backflow exhaust gas 11 leaks from the damper 7, it is possible to prevent the high-temperature exhaust gas from flowing into the HRSG 5 side, so that the work can be safely performed during the internal inspection of the inside of the duct and the HRSG and the like. Further, when the gas turbine 3 is started, the relief valve 13 must be closed and the damper 7 must be opened. However, when the pressure in the exhaust gas confluence duct 8 is detected, if the pressure is positive, the operation of other shafts is performed. By reducing the load a little and reducing the exhaust gas flow rate in the chimney 9, the exhaust gas pressure in the exhaust gas confluence duct 8 and the chimney 9 can be easily made negative. Can be prevented. At that time, the exhaust gas pressure in the exhaust gas joining duct 8 is
Since there is a characteristic that it changes depending on the atmospheric temperature or the plant output, by reducing the load of the gas turbine 3 depending on the atmospheric temperature or the plant output, the exhaust gas merging duct 8
It is also possible to adjust the exhaust gas pressure inside. For example,
FIG. 5 (a) is a graph showing the relationship between the atmospheric temperature and the pressure in the exhaust gas confluence duct when one gas turbine is stopped and the other gas turbine is in operation. It shows that the pressure becomes positive. Further, FIG. 5B is a graph showing the relationship between the plant output and the exhaust gas pressure in the exhaust gas joining duct, and shows that the exhaust gas pressure in the joining duct becomes negative when the plant output becomes low. . Thus, even if the number of axes of the combined cycle connected to one chimney increases, it is possible to adjust the pressure of the exhaust gas in the exhaust gas confluence duct 8 and the chimney 9 to a negative pressure or a positive pressure. The backflow of high-temperature exhaust gas can be prevented, the size of the exhaust gas joining duct 8 and the size of the chimney 9 can be reduced, and the installation space can be reduced and the equipment cost can be reduced. As an embodiment of the present invention, in FIG. 1, the backflow exhaust gas escape device 12 is installed on the side part of the damper 7, but it may be arranged on the upper part or another position. Further, as shown in FIG. 2C, the backflow exhaust gas escape device 12 may be provided with a ventilation fan 17 to forcibly exhaust the exhaust gas, which has an effect of rapidly releasing the backflowing high temperature exhaust gas.

[0008]

As described in detail above, according to the exhaust gas duct device of the present invention, in the exhaust gas duct device having a structure in which the outlet flues of a plurality of exhaust heat recovery boilers are gathered and exhausted by one chimney, Each of the plurality of exhaust heat recovery boilers is provided with an exhaust gas damper that is opened and closed independently at each outlet, and the exhaust gas damper is provided with an exhaust gas escape device that prevents backflow of exhaust gas from the other exhaust heat recovery boiler. Therefore, even if the number of axes of combined cycles connected to one chimney increases, the pressure of the exhaust gas in the exhaust gas confluence duct and in the chimney can be adjusted to a positive pressure. Also, the size of the chimney can be reduced, and the installation space can be reduced to reduce the equipment cost. Further, since the high-temperature exhaust gas does not flow backward, the upstream device is not burned, and safety during maintenance and inspection in the duct and the exhaust heat recovery boiler can be ensured.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a structure of an exhaust gas duct device exemplified as an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the structure of the backflow exhaust gas escape device of FIG.

FIG. 3 is a schematic diagram showing a configuration of a plurality of conventional combined cycles.

FIG. 4 is a schematic diagram showing the structure of a conventional exhaust gas duct device.

FIG. 5 is a graph showing the relationship between the pressure in the merging duct, the atmospheric temperature, and the plant output in a plurality of conventional combined cycles.

[Explanation of symbols]

 1 ... Generator 2 ... Steam turbine 3 ... Gas turbine 4 ... High temperature exhaust gas duct 5 ... HRSG (exhaust heat recovery boiler) 6 ... Low temperature exhaust gas duct 7 ... Damper 8 ... Exhaust gas joining duct 9 ... Chimney 10 ... Exhaust gas 11 ... Reverse flow exhaust gas 12 Backflow exhaust gas escape device 13 Relief valve 14 Damper frame 15 Damper blade 16 Seal plate 17 Ventilation fan 18 Generator 19 Steam turbine 20 Gas turbine 21 High temperature exhaust gas duct 22 HRSG (Exhaust heat recovery boiler) 23 ... Low temperature exhaust gas duct 24 ... Damper 25 ... Exhaust gas merging duct 26 ... Chimney 27 ... Exhaust gas 28 ... Backflow exhaust gas 29 ... Damper frame

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fumihiko Kane No. 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Ltd. Kure Factory (72) Tatsuzo Enomoto 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Stock Company Kure Factory

Claims (3)

[Claims] 1. In an exhaust gas duct device having a structure in which outlet flues of a plurality of exhaust heat recovery boilers are gathered and exhausted by one chimney, the outlet parts of the plurality of exhaust heat recovery boilers are independently provided. An exhaust gas duct device comprising an exhaust gas damper that can be opened and closed, and an exhaust gas escape device for preventing backflow of exhaust gas from the other exhaust heat recovery boiler is disposed in the exhaust gas damper portion. 2. The exhaust gas escape device according to claim 1,
An exhaust gas duct device comprising at least an exhaust pipe and an exhaust gas relief valve, or an exhaust pipe, an exhaust gas relief valve, and a ventilation fan provided outside a seal plate portion of a damper blade of a slide damper for preventing exhaust gas from flowing backward. 3. A method of starting a gas turbine in a stopped state in a combined cycle power plant, wherein a plurality of outlet flues including at least a generator, a gas turbine, and an exhaust heat recovery boiler are connected to one chimney. The output of the gas turbine during operation is reduced, that is, the amount of exhaust gas is reduced, and the exhaust gas pressure in the confluent duct section to which a plurality of outlet flues are connected is adjusted to a negative pressure. A start-up method for a gas turbine, wherein the start-up prevents backflow of high-temperature exhaust gas from the exhaust heat recovery boiler of the other operating gas turbine.