JP2961073B2 - Gas turbine exhaust reburn complex plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined gas turbine exhaust reburning plant using gas turbine exhaust as combustion air for a boiler furnace.

[0002]

2. Description of the Related Art FIG. 5 is a schematic system diagram showing an example of a conventional gas turbine exhaust reburning combined plant.

The air (atmosphere) (101) is a compressor (2)
0) and is sent to the combustor (21) as pressurized air (121). The gas turbine fuel (120) is also supplied to the combustor (21) and burns to generate a gas turbine inlet gas (122) having a high temperature and a high pressure. The gas turbine inlet gas (122) drives the gas turbine (22) and generates electric power by a gas turbine generator (23). The gas turbine exhaust (12) whose energy has been recovered by the gas turbine (22)
Since 3) contains about 14% oxygen, it is put into the boiler (4) furnace from the wind box (3) together with the fuel (104) as furnace combustion air for the boiler (4). The boiler outlet exhaust gas (105) discharged from the furnace of the boiler (4) exchanges heat with feed water and condensate in a gas high-pressure feed water heater (25) and a gas low-pressure feed water heater (26) and exchanges with the exhaust gas (106). Become a chimney (5)
Is released into the atmosphere from

On the other hand, in the case of a water supply line, a low-pressure turbine exhaust (107)
Is condensed (108) by the condenser (6) and is pressurized by the condensate pump (7). This condensate pump outlet water supply (109)
Is heated by steam in the low-pressure feedwater heater (8), and is introduced into the low-pressure gas feedwater heater (26) as the low-pressure feedwater heater water supply (225). The gas low pressure feed water heater outlet feed water (132) heated again by the gas low pressure feed water heater (26)
Water is supplied to the deaerator outlet water supply (111) through the deaerator (9), and the pressure is further increased by the water supply pump (10) to become a gas high-pressure water supply heater water supply (233). The boiler feedwater (139) further heated by the gas high-pressure feedwater heater (25) is introduced into the boiler (4) via the economizer (12).

[0005]

The conventional plant has the following problems to be solved.

1) In a gas feed water heater designed at a rated point, the feed water temperature and the exhaust gas temperature cannot be sufficiently controlled at a partial load. Therefore, as shown by the broken line in FIG. 6, the feedwater temperature rises too much and steaming occurs in the economizer, or the exhaust gas temperature falls too much as shown by the broken line in FIG.
Low temperature corrosion of the gas feed water heater may occur.

[0007] 2) As the cumulative operation time of the boiler becomes longer, the inside of the gas feed water heater becomes dirty with the boiler exhaust gas, so that heat transfer is reduced as shown in FIG. Can not be obtained.

[0008]

In order to solve the above-mentioned conventional problems, the present inventor uses the exhaust gas of a gas turbine as combustion air for a boiler furnace, and also uses the turbine bleed air.
In a gas turbine exhaust reburning combined plant in which a plurality of gas feed water heaters for heating boiler feed water by exhaust gas from the boiler furnace separately from the feed water heater system to be heated are provided, the feed water is the gas feed water heater and the feed water heating. a bypass line for bypassing vessel <br/> respectively, a water supply circulation line from the outlet of the upstream side of the gas feed water heater returning part of the water supply to the inlet, and a water supply circulation pump provided in the water supply circulation line gas turbine repowering combined plant characterized by comprising; and with use of the exhaust gas turbine as combustion air of the boiler furnace, turbine
Separately from the feed water heater system that heats by bleeding, in a gas turbine exhaust reburn complex plant in which a plurality of gas feed water heaters that heat boiler feed water by exhaust gas from the boiler furnace are installed in series, the plurality of gas feed water heaters Between the deaerator and the pressure of the deaerator
The inlet temperature of the feed water heater rises to the pressure at which the required temperature is reached.
A deaerator circulation line that pressurizes and returns a part of the feedwater at the outlet of the deaerator to the inlet of the gas feedwater heater on the upstream side, and a deaerator circulation pump provided in the deaerator circulation line. It is intended to propose a gas turbine exhaust gas reburning combined plant characterized by comprising:

In the first solution, the bypass line is provided for supplying water to the gas feed water heater and the feed water heater, respectively. Therefore, when the boiler is operated at a partial load, the bypass line is provided. By opening the valve, the amount of water flowing into the gas feed water heater can be controlled. Therefore, the boiler inlet feedwater temperature can be controlled, and steam saving of the economizer can be prevented. Also, as the cumulative operation time of the boiler becomes longer, the inside of the gas feedwater heater becomes contaminated with the boiler exhaust gas.However, at the beginning of the boiler operation, the bypass amount is increased, and the operation proceeds, and the inside of the gas feedwater heater becomes dirty and becomes hot. When the amount of absorption decreases, the supply water temperature at the economizer inlet can be controlled by reducing the amount of bypass.

[0010] Further, since there is provided a feed water circulation line for returning a part of the feed water from the outlet to the inlet of the gas feed water heater on the upstream side, and a feed water circulation pump provided in the feed water circulation line, the plant has a partial load. When the flow rate and temperature of the boiler exhaust gas decrease, the exhaust gas temperature at the outlet of the gas feed water heater can be controlled by opening the valve of the feed water circulation line and driving the feed water circulation pump, preventing low temperature corrosion of the gas feed water heater. it can.

In the extremely low load zone, the internal pressure of the low-pressure feed water heater is extremely low, and there is a concern that the temperature cannot be increased to a required temperature even if the feed water is circulated through the feed water circulation line. Heat the gas supply water with the pressure of the deaerator
A deaerator circulation line for raising the inlet temperature of the deaerator to a required temperature and returning a part of the feed water at the outlet of the deaerator to the inlet of the gas feed water heater on the upstream side; Since it has a deaerator circulation pump provided in the circulation line, by opening the valve of the deaerator circulation line and driving the deaerator circulation pump, even in an extremely low load zone, the gas feed water heater The inlet feedwater temperature can be raised to a temperature at which sulfuric acid corrosion does not occur. In other words, if the water in the deaerator storage tank has a higher pressure than the upstream gas feed water heater in the low load zone, the temperature of the upstream gas feed water heater inlet water can be easily raised, and the deaerator internal pressure can be increased. Is pressurized with auxiliary steam, the temperature can be reliably raised to the required temperature. In addition, the same device can cope with both the steam alone operation and the combined operation.

[0012]

FIG. 1 is a schematic system diagram showing a first embodiment of the present invention. In this figure, the same parts as those of the conventional one described with reference to FIG. 5 are denoted by the same reference numerals.

In this embodiment, as in the prior art,
The air (atmosphere) (101) is pressurized by the compressor (20) and sent to the combustor (21) as pressurized air (121). Gas turbine fuel (120) for combustor (21)
Also supplied and burned, high temperature and high pressure gas turbine inlet gas
(122) occurs. The gas turbine inlet gas (122) drives the gas turbine (22) and the gas turbine generator (2).
3) generates electric power. The gas turbine exhaust (123) whose energy has been recovered by the gas turbine (22) is fed into the boiler (4) from the wind box (3) together with the fuel (104) as combustion air for the boiler (4) furnace. The exhaust gas (105) generated by the combustion of the fuel (104) is recovered as heat by the gas high-pressure feed water heater (25) and the gas low-pressure feed water heater (26), and then discharged from the chimney (5) as the exhaust gas (106). Is done.

On the other hand, in the case of the water supply thread, the low-pressure turbine exhaust (107)
Is condensed (108) by the condenser (6) and is pressurized by the condensate pump (7). This condensate pump outlet water supply (109)
Is a low pressure feed water heater (8) and a gas low pressure feed water heater (2
It branches to 6). In the low-pressure feedwater heater (8), the water is heated by the extracted steam of the steam turbine and becomes the low-pressure feedwater heater outlet feedwater (110). In addition, gas low pressure feed water heater (2
6) Water supply for low-temperature gas low-pressure feedwater heater water supply (1)
25) and a low-temperature gas low-pressure feed water heater bypass feed water (126). The low-temperature gas low-pressure feedwater heater feedwater (125) exchanges heat with the low-temperature part of the low-temperature gas low-pressure feedwater heater (26), then merges with the low-temperature gas low-pressure feedwater heater bypass feedwater (126) and exits at the low-temperature gas low-pressure feedwater heater. The feed water (127) is then branched again into a hot gas low pressure feed water heater feed water (128) and a hot gas low pressure feed water heater bypass feed water (129). The high-temperature gas low-pressure feedwater heater feedwater (128) is heat-exchanged in the high-temperature portion of the gas low-pressure feedwater heater (26), and then is passed through the hot gas low-pressure feedwater heater bypass feedwater (1).
29) Merge with high temperature gas low pressure feed water heater outlet water supply (130)
Becomes The recirculation line to the condensate pump outlet water supply (109) is provided in the line of the high temperature gas low pressure water heater outlet water supply (130), and the gas low pressure water heater recirculation is performed by the recirculation pump (27). The water (131) flows.

The low-pressure feed water heater outlet feed water (110) heated by the low-pressure feed water heater (8) is supplied to the gas low-pressure feed water heater (2).
6) High-temperature gas low-pressure feed water heated at the outlet of the heater (13
0) and becomes the water supply (132) at the outlet of the gas low-pressure water heater. After passing through the deaerator (9), the deaerator outlet water supply (1
11), and after the pressure is increased by the water supply pump (10),
Water supply pump outlet water supply (112). This feedwater pump outlet feedwater (112) is branched to a high-pressure feedwater heater (11) and a gas high-pressure feedwater heater (25).
In 1), the steam is heated by the extracted steam of the steam turbine and becomes high-pressure feed water heater outlet feed water (113). In addition, the feed water for the gas high-pressure feed water heater (25) further includes low-temperature gas high-pressure feed water heater feed water (133) and low-temperature gas high-pressure feed water heater bypass feed water (1).
Branch to 34). And low temperature gas high pressure feed water heater feed water
(133) heat-exchanges in the low temperature part of the gas high pressure feed water heater (25), and then joins with the low temperature gas high pressure feed water heater bypass feed water (134) to become the low temperature gas high pressure feed water heater outlet feed water (135);
The hot water high-pressure feed water heater feed water (136) and the hot gas high-pressure feed water heater bypass feed water (137) are branched again. The high-temperature gas high-pressure feed water heater feed water (136) exchanges heat with the high-temperature portion of the high-pressure gas high-pressure feed water heater (25), and then merges with the high-temperature gas high-pressure feed water heater bypass feed water (137) to supply the gas high-pressure feed water heater outlet water. (138).

The high-pressure feed water heater outlet water (113) heated by the high-pressure feed water heater (11) is supplied to the gas high-pressure feed water heater (2).
It joins with the high-pressure gas supply water heater outlet water supply (138) heated in 5) to become boiler water supply (139) and is supplied to the economizer (12).

In the above system, at the time of partial load, the gas low pressure feed water heater (26) and the gas high pressure feed water heater (2)
5) Controlling the temperature of the feedwater supplied to the economizer (12) by flowing a part of the feedwater through the bypass lines provided in each of the bypass lines, the gas low-pressure feedwater heater (2)
The exhaust gas (106) at the outlet of the gas low-pressure feed water heater (26) by flowing the recirculated water (131) through the feed water recirculation line of 6)
Control the temperature of the Also, at the beginning of the boiler operation, since the insides of the gas low-pressure feed water heater (26) and the gas high-pressure feed water heater (25) have not been contaminated yet, the valves of each bypass line are slightly opened, and as the operation date elapses. If the inside of the gas low pressure / high pressure feed water heaters (25) and (26) becomes dirty, the valve of the gas low pressure / high pressure feed water heaters (25) and (26) is gradually closed by gradually closing the valve of the bypass line. Control the heat absorption.

As described above, in the present embodiment, by controlling the feedwater flow rate of the bypass lines provided in the gas feedwater heaters (25) and (26), the economizer (12) is used.
As shown by the solid line in FIG. 6, steaming of the economizer can be prevented even when the plant is partially loaded or at the beginning of the plant operation. Also, by controlling the circulating water flow rate of the feed water circulation line provided in the gas low pressure feed water heater (26), the exhaust gas temperature at the outlet of the gas low pressure feed water heater (26) can be controlled.
As shown by the solid line in FIG. 7, low-temperature corrosion of the gas low-pressure feedwater heater (26) can be prevented when the plant is partially loaded.

Next, FIG. 2 is a schematic system diagram showing a second embodiment of the present invention.

The boiler exhaust gas (220) exchanges heat with feed water in a gas high-pressure feed water heater (204), and then exchanges heat with the gas low-pressure feed water heater.
At (203), heat exchange occurs with condensate to become low-temperature gas (222), which is released from the chimney to the atmosphere via an electric dust collector. On the other hand, in the water system, the condensed water condensed in the condenser is heated by the low-pressure feed water heater (201) to become the low-pressure heater outlet feed water, and is introduced into the gas low-pressure feed water heater (203). This water supply must be at a temperature above which the gas low pressure feed water heater (203) does not cause sulfuric acid corrosion.

At partial load, gas low pressure feed water heater
The outlet water supply (212) of (203) can be recirculated by the gas low pressure feed water heater circulation pump (205) to heat the inlet water supply temperature to the required temperature as shown in FIG. In the low load zone, as shown in FIG.
02), the pressure of the gas low-pressure feed water heater (203) is increased to the required temperature, and the deaerator circulation pump (20)
By recirculating according to 6), it is possible to respond. The same method can also be applied to steam-only operation.

As described above, according to the present embodiment, even at a low load, the inlet feedwater temperature of the gas low-pressure feedwater heater can be maintained at a temperature equal to or higher than the dew point at which sulfuric acid corrosion occurs. Also,
Even in steam alone operation, the boiler exhaust gas volume decreases and the temperature of the feedwater at the inlet of the gas low-pressure feedwater heater becomes difficult to rise.However, by circulating the pressurized water in the deaerator storage tank, the partial load is reduced. Can be maintained at a temperature equal to or higher than the dew point.

[0023]

According to the present invention, the temperature of the feedwater supplied to the economizer can be controlled by controlling the feedwater flow rate of the bypass line provided in the gas feedwater heater.
Steaming of the economizer can be prevented even during partial load of the plant or at the beginning of plant operation. Also, by controlling the circulating water flow rate of the feed water circulation line provided in the upstream gas feed water heater, the temperature of the exhaust gas at the outlet of the upstream gas feed water heater can be controlled. Low temperature corrosion of the heater can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic system diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a deaerator saturated water temperature and a deaerator recirculation flow rate for keeping a gas low-pressure feedwater heater inlet feedwater temperature constant.

FIG. 4 is a diagram showing a relationship between a steam turbine load and a deaerator pressure.

FIG. 5 is a schematic system diagram showing an example of a conventional gas turbine exhaust reburn combined plant.

FIG. 6 is a diagram showing a relationship between plant load and enthalpy of water supply at the inlet of the economizer.

FIG. 7 is a diagram showing a relationship between a plant load and a gas feed water heater outlet gas temperature.

FIG. 8 is a diagram showing the relationship between the cumulative operation time of the boiler and the heat absorption of the gas feed water heater.

[Explanation of symbols]

 (3) Wind box (4) Boiler (5) Chimney (6) Condenser (7) Condenser pump (8) Low-pressure feedwater heater (9) Deaerator (10) Feedwater pump (11) High-pressure feedwater heater (12) Economizer (20) Compressor (21) Combustor (22) Gas turbine (23) Gas turbine generator (25) Gas high pressure feed water heater (26) Gas low pressure feed water heater (27) Recirculation pump (101) ) Air (atmosphere) (104) Boiler fuel (105) Exhaust gas from boiler (106) Exhaust gas (107) Low pressure turbine exhaust (108) Condensate water (109) Condensate pump outlet water supply (110) Low pressure feedwater heater outlet water supply (111) ) Deaerator outlet feedwater (112) Feedwater pump outlet feedwater (113) High-pressure feedwater heater outlet feedwater (120) Gas turbine fuel (121) Pressurized air (122) Gas turbine inlet gas (123) Gas turbine exhaust (125) Low-temperature gas low-pressure feed water heater feed water ( 126) Low-temperature gas low-pressure feedwater heater bypass feedwater (127) Low-temperature gas low-pressure feedwater heater outlet feedwater (128) High-temperature gas low-pressure feedwater heater feedwater (129) High-temperature gas low-pressure feedwater heater bypass feedwater (130) High-temperature gas low-pressure feedwater heating Unit outlet water supply (131) Gas low pressure feed water heater recirculating water (132) Gas low pressure feed water heater outlet water supply (133) Low temperature gas high pressure feed water heater feed water (134) Low temperature gas high pressure feed water heater bypass feed water (135) Low temperature gas High pressure feed water heater outlet water supply (136) High temperature gas high pressure feed water heater water supply (137) High temperature gas high pressure feed water heater bypass water supply (138) Gas high pressure feed water heater outlet water supply (139) Boiler feed water (201) Low pressure feed water heater ( 202) Deaerator (203) Gas low pressure feed water heater (204) Gas high pressure feed water heater (205) Gas low pressure feed water heater circulation pump (206) Deaerator circulation pump (211) Low pressure feed water heater outlet water supply (212 ) Low pressure gas feed water heater outlet Water (213) Circulating water for low-pressure gas feed water heater (214) Circulating water for deaerator (220) Boiler exhaust gas (221) Gas high-pressure feed water heater outlet gas (222) Gas low-pressure feed water heater outlet gas (225) Gas low-pressure feed water Heater water supply (233) Gas high pressure water heater water supply

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasuko Osawa 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (72) Inventor Masatoshi Shibata 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries (56) References JP-A-8-312905 (JP, A) JP-A-6-10621 (JP, A) JP-A-6-82003 (JP, A) JP-A-4-116306 (JP, A) A) JP-A-62-196506 (JP, A) JP-A-61-128510 (JP, U) JP-A-1-119803 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) F01K 23/10 F02C 6/18 F22D 11/00

Claims (2)

(57) [Claims] An exhaust gas from a gas turbine is used as combustion air for a boiler furnace and heated by turbine bleed.
Separately from the feedwater heater system, in a gas turbine exhaust reburning combined plant in which a plurality of gas feedwater heaters for heating boiler feedwater by the exhaust gas from the boiler furnace are installed in series, the feedwater uses the gas feedwater heater and the feedwater heater. A bypass line for bypassing, a feedwater circulation line for returning a part of feedwater from an outlet of the gas feedwater heater on the upstream side to an inlet, and a feedwater circulation pump provided in the feedwater circulation line. Gas turbine exhaust reburn complex plant. 2. The exhaust gas of a gas turbine is used as combustion air for a boiler furnace and is heated by turbine extraction.
In a gas turbine exhaust reburn complex plant in which a plurality of gas feed water heaters for heating boiler feed water by exhaust gas from the boiler furnace separately from the feed water heater system, a feed line between the plurality of gas feed water heaters A deaerator provided in the gas supply water heater and the pressure of the deaerator
A deaerator circulation line that raises the inlet temperature of the gas to a required temperature and returns a part of the feedwater at the outlet of the deaerator to the inlet of the gas feedwater heater on the upstream side; A combined gas turbine exhaust reburn plant comprising a deaerator circulation pump provided in a line.