JPH06241402A - Combustion system for exhaust recombustion boiler of gas turbine - Google Patents

Abstract

PURPOSE:To provide an apparatus which enables the continuation of a stable operation of a boiler able to withstand a turbulence such as change in air for combustion with a relatively simple device in case of abnormal stoppage of a gas turbine. CONSTITUTION:Air can be supplied concentratedly near a nozzle of a burner 8 of a boiler 3 with a small-capacity ventilator 6 with a short starting time from a duct 2 divided with a partition 7 even against a turbulence in an air system for combustion in case a gas turbine 1 stops, which enables the continuation of a stable operation with the stabilization of a flame. Here, a large capacity ventilator 5 can not supply the air quickly to the burner 8 because of a long starting time thereof. But the air for combustion can be supplied from the large-capacity ventilator 5 while the gas turbine 1 rotates by inertia to supply the air. In this case, the temperature of the air supplied to the burner 8 lowers and hence, a volumetric flow rate thereof drops. Thus, a part of a supply passage for combustion of the burner 8 is closed with dampers 9 and 10 thereby securing a necessary burner different pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler combustion system for a gas turbine exhaust gas re-combustion boiler, which requires continuous operation of the boiler alone even when the gas turbine is stopped.

[0002]

2. Description of the Related Art Recently, since the exhaust gas of a gas turbine contains a considerable amount of oxygen, research and development of a gas turbine exhaust gas reheating system for reusing the gas turbine exhaust gas as combustion gas for a boiler has been actively conducted. (Japanese Patent Laid-Open No. 6
4-75803, etc.). In the gas turbine exhaust gas reheat system, the boiler alone operation is required when the gas turbine is stopped, but in the conventional apparatus, as shown in FIG. 4, the boiler alone operation is provided between the outlet of the gas turbine 21 and the boiler 23. The duct 22 from the ventilator 31 is connected, and when the gas turbine 21 is stopped, the ventilator 31 is activated to supply combustion air and operate the boiler 23 alone. Since the exhaust gas for combustion of the boiler 23 during operation of the gas turbine 21 has a high gas temperature of about 500 ° C. and the oxygen concentration in the exhaust gas is low, the combustion exhaust gas is burned as compared with the operation of the boiler 23 by the operation of the blower 31. The volume flow rate of the exhaust gas for use becomes large. During operation of the blower 31, the windproof damper 25 provided on the duct 24 branched to the duct 22 and the damper 26 provided at the gas turbine outlet are closed, and the duct 32 connecting the outlet of the blower 31 and the duct 22 is closed. Damper 2 provided
Open 7. As described above, the required burner throw area is significantly different between the operation of the gas turbine 21 and the operation of the boiler 23 alone. For this reason, as shown in FIG.
The combustion air supply passage (duct) 22 of 8 is divided into two, and for gas turbine exhaust gas of high temperature and low oxygen content, the dampers 29 and 30 are opened to use both passages, and the boiler by the ventilator 31 is used. In the isolated operation, one of the dampers 29 and 30 is closed to operate in one flow path, the flow velocity of the burner throw section is secured, and a stable combustion state is secured.

[0003]

In the above gas turbine exhaust gas reheating system, when the gas turbine 21 abnormally stops (trips), the boiler 23 continues to operate, so that the air supply due to the inertia of the gas turbine 21 is stopped. Before doing so, it is necessary to immediately start the air blower 31 and supply combustion air for the boiler 23. For this reason, in order to start the fan 31 and supply combustion air to the boiler 23 during a short time during which air is continuously supplied due to the inertia of the gas turbine 21, a motor larger than usual is used for the fan 31. Need to be installed. Further, in order to maintain stable combustion of the burner 28 of the boiler 23, each damper 2
It is necessary to install an interlock system for 9 and 30 operations and a blow-off facility. The present invention provides a gas turbine exhaust gas reheating system that can withstand a disturbance such as a change in combustion air with a relatively simple device during a gas turbine emergency stop, and a gas turbine exhaust gas that can continue stable operation of a boiler. An object is to provide a combustion system for a reburning boiler.

[0004]

The above object of the present invention can be achieved by the following constitutions. In the combustion system of a gas turbine exhaust gas re-combustion boiler that supplies the exhaust gas of the gas turbine as combustion air for the burner of the boiler through a duct, the duct is connected to the combustion air flow path from the large capacity air blower and the small capacity air blower. The combustion air flow passage from the small-capacity air blower is configured so that it can be centrally supplied as combustion air near the fuel injection port of the burner of the boiler. Gas turbine exhaust re-combustion boiler with a mechanism for adjusting the amount of air supplied to the gas turbine exhaust gas re-combustion boiler, or gas turbine exhaust gas re-combustion boiler that supplies exhaust gas from the gas turbine as combustion air for the burner of the boiler via a duct In this combustion system, a duct is provided with a combustion air flow path from a relatively large capacity air blower, and each burner of the boiler is supplied with combustion air for comparison. Is a gas turbine exhaust afterburning boiler combustion system having a small capacity ventilator.

[0005]

According to the present invention, even with respect to the disturbance of the combustion air system when the gas turbine is stopped, the air of the small capacity fan is concentrated near the burner nozzle of the boiler by the small capacity fan with a short start-up time. Since it can be supplied to, the flame can be stabilized, and stable operation can be continued. At this time, the large-capacity aerator is started at the same time as the small-capacity aerator, but since the start-up time is long, it is not possible to supply the combustion air for the burner of the boiler immediately, but the gas turbine turns by inertia, Combustion air from a large capacity fan can be supplied to the burner while supplying air. In this case, the temperature of the air supplied to the burner decreases, and the volume flow rate thereof also decreases, so that a part of the combustion supply flow path of the burner is closed by the damper, and the required burner differential pressure is secured. By providing a combustion stabilizing air ventilator for each burner instead of the small capacity ventilator, the stable combustion of the burner can be maintained even when the combustion air fluctuates during a trip of the gas turbine.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. First, the embodiment shown in FIGS. 1 and 2 will be described. FIG. 1 of the present embodiment shows an overall configuration diagram of the gas turbine exhaust reburning system, and FIG. 2 shows a detailed view of the burner portion of FIG. Exhaust gas from the gas turbine 1 is supplied to the wind box 4 of the boiler 3 through the duct 2. Two ducts, a large capacity ventilator 5 and a small capacity ventilator 6, are provided in the duct 2. The duct 2 is divided by a partition plate 7 so as to fit the two fans 5 and 6. The air supplied from the large-capacity air blower 5 to the burner 8 is supplied from the divided flow passage of the duct 2 having the inlet damper 14 to the secondary air air register 12 with the damper 9 in the wind box 4 and the damper. 10 is divided and supplied to the air register 13 for the tertiary air at the inlet portion, and the air from the small capacity air blower 6 is supplied to the damper 15
When the damper 11 in the vicinity of the burner 8 is opened from the other divided flow path of the duct 2 with a certain structure, it is supplied as combustion air intensively in the vicinity of the fuel injection port of the burner 8 provided in the boiler 3. Is. The gas turbine 1 is provided with an outlet damper 16 which is closed when the exhaust gas from the gas turbine 1 is stopped from being supplied to the boiler 3. Further, dampers 17 and 18 are provided at the outlets of the large-capacity fan 5 and the small-capacity fan 6 respectively, and are closed when the supply of the air from the fans 5 and 6 into the duct 2 is stopped.

With the above structure of this embodiment, when the air is supplied to the burner 8 of the boiler 3, the combustion air flow path (duct 2) of the burner 8 is divided into three parts. Then, when the exhaust gas from the gas turbine 1 having a high temperature and a low oxygen concentration is supplied to the boiler 3, the dampers 9 and 10 installed in the wind box 4 of the burner 8 are opened and all the flow paths of the duct 2 are operated. When supplying the combustion air from the atmosphere having a low temperature and a high oxygen concentration to the boiler 3, the dampers 9 and 10 are used.
The open / close control partially stops the supply of the combustion air, optimizes the air flow velocity in the burner throw section, and secures stable combustion. Note that the combustion air flow path of the burner 8 may be finely divided into three or more as necessary.

During normal operation of the gas turbine 1, the operation of the large capacity fan 5 and the small capacity fan 6 is stopped, and all the exhaust gas of the gas turbine 1 is supplied as combustion air for the burner 8. However, when the gas turbine 1 is abnormally stopped, the small-capacity fan 6 having a short start-up time is immediately started, the damper 15 is closed (only the damper 14 is opened), and the small capacity is concentrated near the fuel injection port of the burner 8. Combustion air is supplied from the ventilator 6. At this time, the large-capacity aerator 5 is also started at the same time as the small-capacity aerator 6, but since the starting time is long, the combustion air cannot be supplied to the burner 8 immediately. However, the combustion air from the large-capacity aerator 5 can be supplied to the burner 8 while the gas turbine 1 rotates by inertia and the air is supplied. In this case, the temperature of the air supplied to the burner 8 decreases, and therefore the volumetric flow rate also decreases,
A part of the combustion supply flow path of the burner 8 is closed by the damper 9 or the damper 10 to secure a necessary burner differential pressure.

Generally, when the combustion air for the burner 8 is backed up by a large-capacity air blower, the supply state (draft, etc.) of the combustion air may change significantly,
In the case of the prior art shown in FIG. 4, the windbreak damper 25 and the gas turbine outlet damper 2 are operated when the large capacity air blower 31 is in operation.
6. It is necessary to reduce the change in draft by controlling the opening / closing of the outlet damper 27 of the ventilator 31. However, in the case of the present embodiment, even if the operation of the large capacity aerator 5 is started, the small capacity aerator 6 is
As a result, the flame of the burner 8 is stabilized, and it is possible to withstand the draft fluctuation. Thus
The present embodiment is a system that can sufficiently withstand changes in the switching state of the combustion air supply system due to operating conditions when the gas turbine 1 is stopped, and the like.

Another embodiment of the present invention is shown in FIG. In this embodiment, each burner 8 is used instead of the small capacity fan 6 of the above embodiment.
Since the combustion stabilizing air ventilator 18 is provided in the above, it is possible to sufficiently withstand fluctuations in the combustion air when switching the combustion air when the gas turbine 1 trips.

[0011]

According to the present invention, in addition to a large-capacity aerator, a small-capacity aerator having a short start-up time is provided, and a sleeve for stabilizing the flame is provided around the burner nozzle. By centrally supplying the air in the vicinity of the burner nozzle, it is possible to stabilize the burner flame at an early stage, even against disturbance of the combustion air system when the gas turbine is stopped,
It is possible to continue stable operation of the burner.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an exhaust gas reburn system according to an embodiment of the present invention.

FIG. 2 is a detailed view of a burner unit in FIG.

FIG. 3 is a detailed view of a burner portion of another embodiment of the present invention in which a fan is installed in each burner instead of the small capacity fan installed in FIG. 1.

FIG. 4 is an overall configuration diagram of a conventional exhaust gas reburn system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gas turbine, 2 ... Duct, 3 ... Boiler, 5 ... Large capacity fan, 6 ... Small capacity fan, 8 ... Burner, 18 ... Combustion stabilizing air fan

Claims (2)

[Claims] 1. In a combustion system of a gas turbine exhaust gas re-combustion boiler, which supplies exhaust gas of a gas turbine as combustion air for a burner of a boiler through a duct, the duct is provided with a combustion air flow path from a large capacity fan. The combustion air flow path from the small-capacity air blower is divided, and the combustion air flow path from the small-capacity air blower is configured to be able to be centrally supplied as combustion air near the fuel injection port of the burner of the boiler. A combustion system for a gas turbine exhaust gas re-combustion boiler, comprising a mechanism capable of adjusting the amount of air supplied to the combustion air flow path. 2. In a combustion system of a gas turbine exhaust gas re-combustion boiler, which supplies exhaust gas of a gas turbine as combustion air for a burner of a boiler through a duct, a combustion air flow from a relatively large-capacity fan to the duct. A combustion system for a gas turbine exhaust gas re-combustion boiler, characterized in that a passage is provided and each burner of the boiler is provided with a relatively small capacity fan for supplying combustion air.