JPH0610619A - Water heater - Google Patents

Abstract

(57) [Summary] [Purpose] In a plant that combines a steam turbine and a gas turbine, the final boiler feedwater temperature is maintained at a predetermined temperature even during partial load operation of the plant, and the heat of the gas turbine exhaust gas is fully utilized. What I was able to do. In a feed water heating device in which a feed water heater 15 using steam turbine bleed air as a heating source and an exhaust gas cooler 12b using a gas turbine exhaust gas as a heating source are connected in parallel, a flash tank 28 is provided from a feed water outlet of the exhaust gas cooler 12b.
A bypass tank 27 for a flash tank that guides the water supply to the tank was branched and led out, and the flash tank 28 was connected to a water supply pump driving turbine 29 and also connected to the condenser 8 via a pressure reducing device 32 and a control valve 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed water heating apparatus in an exhaust gas recombustion combined cycle plant in which a gas turbine power plant is additionally provided in a steam turbine power plant.

[0002]

2. Description of the Related Art Generally, the exhaust gas of a gas turbine is usually 50.
The temperature is 0 ° C., and how to utilize this exhaust heat has become an important issue. As one of the means, it has been proposed to use the gas turbine exhaust as the combustion gas of the boiler.

FIG. 2 is a conventional system configuration diagram of a combined cycle adopting an exhaust gas re-combustion system, in which steam generated in a boiler 1 is supplied to a high-pressure steam turbine 3 via a main steam pipe 2 and expanded there to work. The steam that has been subjected to (1) is returned to the boiler 1 through the low temperature reheat pipe 4 and reheated. The reheated reheated steam is sent to the medium-pressure steam turbine 6 and the low-pressure steam turbine 7 via the high-temperature reheat pipe 5, where expansion work is performed and then the water is condensed in the condenser 8. The work performed by each turbine is extracted as electric energy by the steam turbine generator 9.

The condensate condensed by the condenser 8 is supplied to the low-pressure feed water heaters 11a, 11b, 11 by the condensate pump 10.
c and the low-pressure exhaust gas cooler 12 connected in parallel with it
a is sent to the deaerator 13, and the water supply pump 14
Is recirculated to the boiler 1 via the high-pressure feed water heaters 15a, 15b, 15c and the high-pressure exhaust gas cooler 12b connected in parallel therewith.

On the other hand, the compressed air compressed by the compressor 15 is sent to the combustor 17, and the fuel supplied to the combustor 17 is combusted to form a high-pressure mixed gas, which is supplied to the gas turbine 18 where it expands and works. And is taken out as electric energy by the gas turbine generator 19.
Further, the exhaust gas that has worked in the gas turbine 17 is sent to the boiler 1 and used there as combustion air.

Exhaust gas from the boiler 1 passes through the high-pressure exhaust gas cooler 12b and the low-pressure exhaust gas cooler 12a, exchanges heat with the supply water and the condensate, and then is discharged from the chimney 20.

By the way, the high-pressure feed water heater 15c is supplied with extraction air from the middle stage of the high-pressure turbine 3 via the extraction pipe 21c, and the high-pressure feed water heater 15b is extracted from the low temperature reheat pipe 4 via the extraction pipe 21b. The high pressure feed water heater 15a is supplied with bleed air from the middle stage of the intermediate pressure turbine 6 via the bleed pipe 21a, and the low pressure feed water heaters 11a, 11b and 11c are supplied with low pressure respectively. From the middle paragraph of the turbine 7 to the extraction pipes 22a, 22b, 2
Bleed air is supplied through 2c. And each extraction pipe 21a, 21b, 21c and 22a, 2
A bleed valve 23 that can completely close bleed air in 2b and 22c, respectively.
Further, a bleed air check valve 24 is provided to prevent overspeed of the steam turbine due to bleed air reverse flow (the bleed pipes 22a, 22b, 22c are partially omitted from the drawing).

[0008]

However, in such a system in which a gas cooler using a gas turbine exhaust gas as a heat source is installed in parallel with an ordinary feed water heater, the amount of air compressed by the compressor is partially reduced. The load does not change so much, and the amount of exhaust gas discharged to the high-pressure exhaust gas cooler hardly changes from that during rated operation. On the other hand, in the steam turbine cycle system, when the load becomes partial, the amount of water flowing through the condensate pipe and the water supply pipe decreases depending on the load. Therefore, in a gas cooler using a gas turbine exhaust gas as a heating source, a small amount of boiler feed water and a large amount of gas turbine exhaust gas are heat-exchanged, and the final boiler feed water temperature rises significantly, causing problems such as steaming in the boiler. is there.

In view of the above points, the present invention provides a feed water heating device that keeps the final boiler feed water temperature below a predetermined temperature even during partial load operation, and that can sufficiently utilize the heat of the gas turbine exhaust gas. The purpose is to

[0010]

The present invention provides a feed water heating apparatus in which a feed water heater using steam turbine bleed air as a heating source and an exhaust gas cooler using gas turbine exhaust gas as a heating source are connected in parallel. The flash tank bypass pipe that guides the water supply from the water supply outlet to the flash tank is branched and led out, and the flash tank is connected to the water supply pump drive turbine and connected to the condenser via the pressure reducing device and the control valve. And

[0011]

When the final boiler feed water flow rate decreases during partial load operation, part of the feed water from the exhaust gas cooler is guided to the flash tank, and the steam generated in the flash tank is sent to the feed water pump drive turbine. The steam drives the feedwater pump drive turbine. Then,
The amount of bleed air from the steam turbine can be reduced. Then, when the amount of steam generated in the flash tank exceeds the amount required for the feed water pump driving turbine, it is discharged to the condenser via the pressure reducing device or the like, and it is possible to cope with all partial load operations.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The same parts as those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The condensed water condensed by the condenser 8 is heated by the low-pressure feed water heater 11 and then sent to the high-pressure feed water heater 15 side by the feed water pump 14. On the discharge side of the water supply pump 14, the water supply pipe 26 is branched into a high pressure water heater side water supply pipe 26a and a gas cooler side water supply pipe 26b, and the high pressure water supply heater side water supply pipe 26a is connected to the high pressure water supply heater 15a. Is connected, and the high-pressure exhaust gas cooler 12b is connected to the gas cooler side water supply pipe 26b. Then, the feedwater discharged from the feedwater pump 14 is sent to the high-pressure feedwater heater 15 and the high-pressure exhaust gas cooler 12b, where they are respectively heated and combined, and then supplied to the boiler 1.

A flash tank bypass pipe 27 is branched from the gas cooler side water supply pipe 26b at the water supply outlet side of the high-pressure exhaust gas cooler 12b, and the tip of the bypass pipe 27 is connected to a flash tank 28. The upper portion of the flash tank 28 is connected to an extraction pipe 30 to a feed water pump driving turbine 29 via a conduit 31, and the conduit 31 is provided in the middle of the decompression device 3.
2 and the control valve 33, and is connected to the condenser 8.

The lower portion of the flash tank 28 is connected to the low-pressure feed water heater 11 by a drain pipe 34, and the drain pipe 34 is also connected to the condenser 8 via a control valve 35. In the figure, reference numeral 36 is a control valve provided on the flash tank bypass pipe 27,
Reference numeral 7 denotes a control valve provided on the gas cooler side water supply pipe 26b.

By the way, the extraction pipe 2 for supplying heating steam to the high-pressure feed water heater 15 and the low-pressure feed water heater 11, respectively.
1, 22 and extraction water flow meters 38a and 38b and a temperature / flow rate sensor 39 are provided on the water supply pipes downstream of the confluence of the high pressure water supply heater side water supply pipe 26a and the gas cooler side water supply pipe 26b, respectively. The flash tank 28 is provided with a level meter 40, and detection signals thereof are input to the control device 41, and the control signals from the control device 41 control the respective control valves 33, 35, 36, 37. I am doing it.

However, during the rated load operation, the control valve 3
3, 35 and 36 are fully closed, and the feedwater sent by the feedwater pump 14 is heated by the high-pressure feedwater heater 15 or the high-pressure exhaust gas cooler 12b, respectively, and then merges and is supplied to the boiler 1. On the other hand, from the boiler 1 Exhaust gas is high pressure exhaust gas cooler 1
After the temperature is reduced in 2b, it is released from the chimney 20 into the atmosphere.

Then, the plant enters the partial load operation,
When the amount of water supplied to the boiler 1 becomes less than or equal to a predetermined flow rate or the temperature of the supplied water becomes more than a predetermined amount, the control valve 36 is controlled in the opening direction. Therefore, a part of the high-pressure water that has become high temperature in the high-pressure exhaust gas cooler 12b is sent to the flash tank 28, and the steam that is flushed there is sent to the water supply pump drive turbine 29 via the conduit 31 and the water supply pump drive turbine 29.
It is used for driving. On the other hand, the drain accumulated in the flash tank 28 is sent to the low pressure feed water heater 11.

Further, the load is further reduced and the amount of air extracted to the high-pressure feed water heater 15 disappears, which indicates that the air flow meter 38a.
When detected by the control valve 37, the control valve 37 controls so that most of the feed water is sent to the high-pressure exhaust gas cooler 12b. In addition, the low pressure feed water heater 1 is controlled by the extraction flow meter 38b.
When it is detected that the amount of bleed air to 1 is 0, the control valve 35 is opened, and the drain amount of the flash tank 28 is detected by the level meter 40, and the amount exceeds the flash tank capacity. Also in this case, the control valve 35 is opened and the drain is discharged to the condenser 8.

On the other hand, the steam for driving the feed water pump drive turbine is sufficient from the flash tank, that is, the steam from the steam turbine 42 to the feed water pump drive turbine 29.
If the bleed air to the boiler is 0 and the temperature and flow rate of the final boiler feed water are detected by the temperature / flow rate sensor 39 and become too high or the flow rate becomes too high, the control valve 33 is opened. The steam generated in the flash tank 28 is decompressed by the decompression device 32 and sent to the condenser 8.

[0021]

Since the present invention is constructed as described above, after using the gas turbine exhaust as the gas for boiler combustion,
The boiler feed water is heated by the exhaust gas cooler, and the heated high-temperature water is flushed by the flash tank as needed,
The steam can drive the feed water pump drive turbine, prevent an abnormal rise in the final boiler feed water temperature, and reduce the extraction amount from the steam turbine.
The output of the plant can be increased. Further, when the flash steam remains, the steam can be sent to the condenser, and the partial load operation range of the plant can be expanded.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of a feed water heating apparatus of the present invention.

FIG. 2 is a schematic system diagram of a conventional feed water heating device.

[Explanation of symbols]

 1 Boiler 8 Condenser 11 Low pressure feed water heater 12b High pressure exhaust gas cooler 14 Water feed pump 15 High pressure water feed heater 18 Gas turbine 27 Flash tank bypass pipe 28 Flash tank 29 Water feed pump drive turbine 33, 35, 36, 37 Control valve

Claims (1)

[Claims] 1. A feed water heating device in which a feed water heater using steam turbine bleed air as a heating source and an exhaust gas cooler using gas turbine exhaust gas as a heating source are connected in parallel, and water is fed from a feed water outlet of the exhaust gas cooler to a flash tank. A bypass tank for a flash tank that leads to the water tank is branched and connected, and the flash tank is connected to a feed water pump driving turbine and connected to a condenser via a pressure reducing device and a control valve.