JPH10306920A - Waste gas duct device and waste heat recovering boiler equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reverse flow of high-temperature waste gas to prevent instruments, arranged in the upstream side, from burning and ensure safety of work upon maintenance and inspection in a duct as well as a waste heat recovering boiler (HRSG). SOLUTION: Low-temperature waste gas ducts 6 of a plurality of HRSGs are collected to a waste gas joining duct 8 to obtain a waste gas duct device for exhausting it through a chimney 9 while an exhaust fan 12 is arranged at least in one of the waste gas joining duct 8 and the chimney 9 whereby the number of axis of the waste gas duct 6, joined and connected to one set of chimney 9, is increased. In this case, danger of reverse flow of high- temperature waste gas is reduced even under a condition that an internal pressure in the waste gas joining duct 8 becomes a positive pressure whereby safe property upon maintenance and inspection can be ensured. At the same time, the burning of instruments in the upstream side of the duct due to the reverse flow of the high-temperature waste gas can be prevented whereby the sizes of the waste gas joining duct 8 and the chimney 9 can be set so as to be small and effect of making a charge for installation inexpensive can be obtained.

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 system for a system in which a plurality of exhaust cycle ducts of a plurality of exhaust heat recovery boilers are assembled and a plurality of combined cycle facilities having a structure exhausted by one chimney are assembled. The present invention also relates to an exhaust gas duct device suitable for preventing burning of upstream equipment due to backflow of exhaust gas from the other exhaust heat recovery boiler and ensuring safety during maintenance and inspection of the flue and exhaust heat recovery boiler.

[0002]

2. Description of the Related Art FIG. 3 shows a system in which exit flues of a plurality of conventional exhaust heat recovery boilers are assembled, and a plurality of combined cycle facilities having a structure exhausted by one chimney are assembled. In FIG. 3, the generator 18 is rotated by the operation of 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. HRSG2
The steam is generated in 2, and 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
The gas 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.

[0003]

As described above, a low-temperature exhaust gas duct 23 of a plurality of conventional exhaust heat recovery boilers 22 is gathered in an exhaust gas merging duct 25 and exhausted by one chimney 26. In a system in which cycle equipment is assembled, there are the following problems.

That is, when the exhaust gas pressure in the exhaust gas merging duct 25 at the entrance of the chimney 26 is positive, the damper 2
Even when the valve 4 is fully closed, the high-temperature exhaust gas leaks from the damper 24 as shown by the arrow 28 and flows into the low-temperature exhaust gas duct 23 on the HRSG (exhaust heat recovery boiler) 22 side. This is a problem that the work during maintenance and inspection inside the HRSG 22 is extremely dangerous.

Further, when the gas turbine 20 is started,
The damper 24 is fully opened. At this time, the high-temperature exhaust gas flows backward and the other gas turbine
However, there is a problem that the devices such as the above are burned.

Therefore, when one shaft in a combined cycle of a plurality of shafts is stopped, the wake of the damper 24 at the outlet of the HRSG 22 must always be adjusted to a negative pressure to prevent exhaust gas from flowing back. There is.

However, if the number of combined cycle shafts connected to one chimney 26 increases, the size of the exhaust gas merging duct 25 and the size of the Needs to be increased in size. On the other hand, in order to reduce the size of the exhaust gas merging duct 25 and the size of the chimney 26,
It is necessary to reduce the number of axes of the combined cycle connected to one chimney 26, and eventually increase the number of chimneys 26. In any case, a large installation space is required and equipment costs are reduced. There is a problem that is expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and it is an object of the present invention to combine a plurality of exhaust heat recovery boiler outlet flues and exhaust the exhaust gas with a single chimney. In a system where cycle equipment is assembled, when one axis in a combined cycle of multiple axes is stopped, the size of the merging duct and chimney to reduce the pressure downstream of the damper at the HRSG outlet and the number of chimneys, or the number of chimneys Without increasing the temperature, prevent backflow of high-temperature exhaust gas and prevent burnout of equipment placed upstream,
It is an object of the present invention to provide an exhaust gas duct device having a structure capable of ensuring work safety during maintenance and inspection in a duct and in an HRSG.

[0009]

In order to solve the above-mentioned problems of the present invention, the present invention employs the following configuration. That is, a low-temperature exhaust gas duct of a plurality of exhaust heat recovery boilers is assembled into an exhaust gas merging duct, and the exhaust gas duct device has a structure in which the exhaust gas is exhausted by one chimney. An exhaust fan is arranged in at least one of the exhaust gas merging duct and the chimney. It is a flue gas duct device.

The exhaust fan makes it possible to easily achieve a negative pressure in the exhaust gas merging duct or the chimney. As a result, the number of shafts to which the exhaust gas duct is merged and connected to one chimney is increased, and even under conditions where the internal pressure of the exhaust gas merge duct is positive, there is no danger of high-temperature exhaust gas flowing backward. In addition to ensuring safety at the same time, even if the damper is fully opened at the time of startup, it is possible to prevent burning of the upstream equipment due to the backflow of high-temperature exhaust gas, and the size of the exhaust gas merging duct and chimney can be set small, so equipment costs Has the effect of being inexpensive. Also,
The present invention also includes an exhaust heat recovery boiler provided with the exhaust gas duct device at an outlet.

[0011]

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. As shown in FIG. 1, an exhaust fan 12 is provided in a chimney 9 in contrast to the above-described conventional structure shown in FIG. In FIG. 1, the generator 1 is rotated by the operation of the gas turbine 3. The exhaust gas 10 discharged from the gas turbine 3 passes through the high-temperature exhaust gas duct 4 and is sent to the HRSG 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 heat recovered by the HRSG 5 is
The gas passes through the low-temperature exhaust gas duct 6, the damper 7 (fully open), and the exhaust gas merging duct 8, and is discharged from the chimney 9 to the atmosphere. The pressure of the exhaust gas in the exhaust gas merging duct 8 and the chimney 9 during such normal operation is indicated as positive pressure.

When one shaft in the combined cycle of a plurality of shafts is stopped (the gas turbine 3 is stopped), the internal pressure in the exhaust gas merging duct 8 can be reduced to a negative pressure by activating the exhaust fan drive motor 13. HRSG5 can be prevented from flowing back to the HRSG5 side, so that the work can be performed safely when the inside of the ducts 4, 6 and the HRSG5 are inspected.

When the gas turbine 3 is started, the damper 7 must be opened.
In the case of a positive pressure, the exhaust fan drive motor 13 is activated to start the exhaust gas confluence duct 8.
Since the exhaust gas pressure in the inside and the chimney 9 can be easily made a negative pressure, burning of the gas turbine 3 by the backflow exhaust gas 11 can be prevented. At this time, the exhaust gas pressure in the exhaust gas merging duct 8 has a characteristic that varies depending on the atmospheric temperature or the plant output. Can be adjusted to a negative pressure. Note that a flow straightening plate 14 is provided in the chimney 9 to smoothly discharge exhaust gas.

FIG. 4A is a graph showing the relationship between the atmospheric temperature and the pressure in the exhaust gas merging duct 8 when one of the plurality of gas turbines 3 is stopped and the other gas turbines 3 are operated. However, this graph shows that when the atmospheric temperature exceeds a certain temperature, the exhaust gas pressure in the exhaust gas merging duct 8 becomes positive. FIG. 4B is a graph showing the relationship between the plant output and the exhaust gas pressure in the exhaust gas merging duct 8. It is clear that the exhaust gas pressure in the exhaust gas merging duct 8 becomes negative when the plant output decreases. Is shown.

As described above, even if the number of axes of the combined cycle connected to one chimney 9 increases, the pressure of the exhaust gas in the exhaust gas merging duct 8 and the chimney 9 can be adjusted to a negative pressure. Therefore, it is possible to prevent the backflow of the high-temperature exhaust gas and to reduce the size of the exhaust gas merging duct 8 and the size of the chimney 9,
Installation space is reduced and equipment costs are lower.

As an embodiment of the present invention, the exhaust fan 12 is installed in the chimney 9 in FIG. 1, but the exhaust fan 12 may be arranged in the exhaust gas merging duct 8 as shown in FIG.

[0018]

According to the exhaust gas duct device of the present invention, in an exhaust gas duct device having a structure in which outlet flue of a plurality of exhaust heat recovery boilers is gathered and exhausted by one chimney, an exhaust fan is provided in the chimney or duct. Since the pressure in the exhaust gas merging duct can be adjusted to negative pressure even if the number of combined cycle axes connected to one chimney increases, the size of the exhaust gas merging duct and the size of the chimney And the installation space is reduced, and the equipment cost is reduced. 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 the 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 a structure of an exhaust gas duct device according to another embodiment of the present invention.

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

FIG. 4 is a graph showing the relationship between the internal pressure of a merging duct, atmospheric temperature, and plant output in a plurality of conventional combined cycles.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Generator 2 Steam turbine 3 Gas turbine 4 High temperature exhaust gas duct 5 Exhaust heat recovery boiler 6 Low temperature exhaust gas duct 7 Damper 8 Exhaust gas merging duct 9 Chimney 10 Exhaust gas 11 Backflow exhaust gas 12 Exhaust fan 13 Exhaust fan drive motor 14 Rectifier plate

Claims (2)

[Claims] 1. An exhaust gas duct device having a structure in which low-temperature exhaust gas ducts of a plurality of exhaust heat recovery boilers are assembled into an exhaust gas merging duct and exhausted by one chimney, wherein exhaust gas is exhausted to at least one of the exhaust gas merging duct and the chimney. An exhaust gas duct device comprising a fan. 2. An exhaust heat recovery boiler provided with the exhaust gas duct device according to claim 1 at an outlet portion.