JPH062806A - Water supplying and heating device - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a feed water heating device capable of performing cleanup and warming in a feed water heater and a feed pipe without reducing the amount of feed water to an exhaust gas cooler even at a partial load. In the feed water heating device in which a feed water heater having steam turbine extraction air as a heating source and an exhaust gas cooler having gas turbine exhaust gas as a heating source are connected in parallel, the feed water heater 15
a recirculation pipe 32 is branched from the water supply pipe 26a between the water supply inlet stop valve 27a and the water supply inlet stop valve 27, the tip of the recirculation pipe 32 is connected to the deaerator 13, and the recirculation pipe 32 is deaerated. A flow rate adjusting valve 34 for controlling the amount of water supplied to the device 13 is provided.

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 Recently, gas turbine power generation facilities have been added to aging existing boilers and steam turbine power generation facilities in order to increase the demand for electricity, increase the number of aging power plants, soaring fuel prices, and tightening environmental regulations for emissions. In order to increase plant output, improve efficiency, extend life, reduce environmental impact, etc., adoption of a repowering system designed to regenerate the plant is one of the important issues for the electric power business. .

FIG. 8 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
It is sent to the deaerator 13 through a, and is further returned to the boiler 1 by the feed water pump 14 through the high pressure feed water heaters 15a, 15b, 15c and the high pressure exhaust gas cooler 12b connected in parallel with this.

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 then 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, bleed air is supplied to the high-pressure feed water heater 15c from the middle stage of the high-pressure turbine 3 via the bleed pipe 21c, and bleed air is drawn from the low-temperature reheat pipe 4 to the high-pressure feed water heater 15b via the bleed 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 stop valve 2 that can fully close the bleed in 2b and 22c respectively
3 and a bleed air check valve 24 for preventing an overspeed of the steam turbine due to the reverse flow of bleed air (the bleed pipes 22a, 22b, 22c are partially omitted from the drawing).

FIG. 9 is a view showing a water supply system around the high-pressure feed water heater, in which drain generated in the high-pressure feed water heater 15c passes through a drain adjusting valve 25a to the primary side high-pressure feed water heater. 15b, high-pressure feed water heater 15
Similarly, the drain generated in b flows through the drain adjusting valve 25b into the high pressure feed water heater 15c, and the drain adjusting valve 2
It is supplied to the deaerator 13 via 5c.

At the outlet side of the water supply pump 14, the water supply pipe 2
6 is branched into two, one of which is connected to the high-pressure feed water heater 15a and the like, and the other of which is connected to the high-pressure exhaust gas cooler 12b. Further, a water supply inlet stop valve 27 is provided on the inlet side of the high pressure water supply heater 15a, a water supply outlet stop valve 28 is provided on the outlet side of the high pressure water supply heater 15c, and an inlet side of the water supply inlet stop valve 27 is further provided. Is high-pressure feed water heater 15
A water supply adjusting valve 29 for adjusting the distribution of the water supply to the a side and the high-pressure exhaust gas cooler 12b is provided. On the other hand, an inlet stop valve 30 and an outlet stop valve 31 are provided at the inlet side and the outlet side of the high-pressure exhaust gas cooler 12b in order to shut off the system by setting the water flow rate to the high-pressure exhaust gas cooler 12b to 0 when the gas turbine is stopped. It is provided.

[0010]

By the way, domestic thermal power plants have recently been required to operate under a wide range of loads for intermediate loads in order to cope with power changes during the day and night, but when operating under such conditions. For easy operation, it is possible to find a gas turbine / steam turbine capacity ratio that cuts all stages of the high-pressure feed water heater and can secure the feed water temperature required by the boiler only by the amount of heat recovered from the gas turbine exhaust gas. Although it is preferable, since it is a combination selected from a limited number of models in reality, it is necessary to switch the service in / out of the high pressure feed water heater at around 75% of the steam turbine load as shown in FIG. In the above, it is usual to supplement the heat quantity of part of the feed water with the quantity of air extracted from the steam turbine.

However, in such an apparatus in which a gas cooler using a gas turbine exhaust gas as a heating source is installed side by side with an ordinary feed water heater, the amount of air compressed by the compressor does not significantly change even under partial load. In other words, the amount of exhaust gas discharged to the high-pressure exhaust gas cooler 12b is almost unchanged 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. As a result, at a partial load, the outlet water supply temperature of the high-pressure exhaust gas cooler 12b is kept below the temperature at which steaming occurs in the economizer (not shown) of the boiler 1, so that the amount of water supplied to the high-pressure exhaust gas cooler 12b is reduced. The amount of water supplied to the high-pressure feed water heater is significantly reduced,
It becomes 0 at a certain load.

Further, the turbine extraction amount to the high-pressure feed water heater 12b is controlled by the drain adjusting valves 25a, 25b, 25c by observing the drain level of the feed water heater, so that the drain condensation amount is reduced as the feed water amount decreases. , The drain adjustment valves 25a, ... Are closed, and when the water supply to the high-pressure feed water heater is 0, the drain adjustment valves 25a ,.

When the engine is operated while the load is further reduced, the extraction valve 23, the feed water inlet stop valve 27 and the feed water outlet stop valve 28 are fully closed.

However, if the load is once increased and then the load is increased and water is supplied to the feed water heater, the following problems occur. (A) The water that has accumulated in the water heater and the water supply pipe for a long time and is soiled is sent to the boiler 1. (B) Since there is a time delay in heat exchange in the feed water heater,
For a while after passing water, cold water at the outlet temperature of the deaerator is sent and mixed with the hot water at the outlet of the high-pressure exhaust gas cooler that has become hot. The temperature difference here may exceed 100 ° C., the thermal stress of the water supply pipe becomes excessive, and the life of the water supply pipe may be significantly shortened depending on the frequency of load changes.

For partial load, there is a method of constantly supplying a small amount of feed water to the feed water heater to heat the feed water, but since the feed water amount to the high pressure exhaust gas cooler decreases, the feed water temperature to the boiler rises. When steaming occurs in the economizer, or when a small amount of water is passed, the amount of bleed air also becomes small, so the controllability of the drain adjustment valves 25a, ... There is a problem that the stop valve 24 causes hunting and the operability deteriorates.

In view of the above points, the present invention is a feed water heating apparatus capable of performing cleanup and warming in a feed water heater and a feed pipe without reducing the amount of feed water to an exhaust gas cooler even under partial load. Aim to get.

[0017]

The first invention of the present invention is as follows:
In a feedwater heating device in which a feedwater heater that uses steam turbine bleed air as a heating source and an exhaust gas cooler that uses a gas turbine exhaust gas as a heating source are connected in parallel, from the feedwater pipe between the feedwater heater and the feedwater stop valve to the recirculation pipeline. Is branched and led out, the tip of the recirculation line is connected to the deaerator, and a flow rate adjusting valve for controlling the amount of water supplied to the deaerator is provided in the recirculation line.

A second aspect of the invention is to heat the feed water with the exhaust gas from the boiler, wherein the exhaust gas from the gas turbine is heat-exchanged with the feed water before it is supplied to the boiler to lower the temperature. A second exhaust gas cooler is connected in series, the water supply pipe between the two exhaust gas coolers is connected between the water supply heaters by a gas cooler water supply bypass pipe having a stop valve, and is provided at the outlet of the final stage water supply heater. It is characterized in that a flow rate adjusting valve is provided in parallel with the water supply outlet stop valve.

In a third aspect of the present invention, a recirculation pipe is branched from a water supply pipe between the feed water heater and the water supply outlet valve, and the recirculation pipe is connected to a deaerator via a flow control valve. The extraction valve is provided with a control valve for controlling a small amount of heated steam.

Further, a fourth aspect of the invention is to provide a water supply pump bypass pipe which bypasses the water supply pump, the water supply adjusting valve and the water supply inlet stop valve, and connects the outlet side of the water supply buster pump and the inlet side of the water supply heater with the water supply pump. The bypass pipe is provided with a water supply stop valve and a check valve.

A fifth aspect of the present invention is characterized in that the feed water inlet portion of the exhaust gas cooler and the feed water heater outlet side are communicated with each other through a flow rate adjusting valve.

In a sixth aspect of the present invention, a recirculation pipe is branched and led out from a water supply pipe between a feed water heater and a feed water stop valve, and the recirculation pipe is connected to a condenser via a flow control valve and a pressure reducing device. It is characterized by being connected.

[0023]

In the feed water heating apparatus according to the first aspect of the present invention, when a partial load is applied and the feed water amount is reduced, the entire feed water amount is passed to the high pressure exhaust gas cooler to recover the exhaust heat, and the operation is continued for a long time. First, the water supply inlet stop valve is closed with the water supply outlet stop valve opened, and the extraction valve to the high-pressure feed water heater is fully closed. Therefore, a small amount of feed water flows back through the high pressure feed water heater from the confluence of the outlet of the high pressure exhaust gas cooler and the feed water heater, and is collected in the deaerator having a low pressure through the recirculation pipe.

Thus, a part of the high temperature feed water on the outlet side of the high pressure exhaust gas cooler is recovered to the deaerator through the water supply pipe and the high pressure feed water heater, and the high temperature feed water constantly circulates in the high pressure feed water heater. To do.

On the other hand, when the load is increased again to feed water from the feed pump outlet to the high-pressure feed water heater for heating, the stop valve provided in the recirculation pipeline to the deaerator is fully closed, and the feed water inlet is closed. The stop valve is opened to allow water to flow through the high-pressure water heater while controlling the water supply flow rate with the water supply adjustment valve, and then the bleed valve is opened to bleed the high-pressure water heater. In this case, the extraction amount increases in accordance with the increase in the amount of water supplied to the high-pressure feed water heater, so that the temperature of the water supply from the outlet of the high-pressure feed water heater can be maintained at an appropriate temperature.

Further, in the second aspect of the present invention, during the partial load operation, the feed water between the first and second exhaust gas coolers flows into the high pressure feed water heater side, and a part thereof passes through a part of the high pressure feed water heater. , Is mixed with the feed water flowing out from the second exhaust gas cooler, and the remaining feed water is collected in the deaerator through another high pressure feed water heater. Then, the high-pressure feed water heater is supplied with feed water at an appropriate temperature and is kept below the maximum operating temperature.On the other hand, the difference between the outlet feed water temperatures of the high-pressure feed water heater and the exhaust gas cooler becomes small, and the thermal stress at the confluence is reduced. Can be made smaller.

In the third aspect of the invention, the feed water that has passed through the high pressure feed water heater during partial load is controlled by the flow rate adjusting valve and collected in the deaerator. Therefore, a part of the water supply always circulates in the water supply pipe and the high pressure water supply heater, and the water supply temperature at the outlet of the high pressure water supply heater is maintained at an appropriate temperature.

Further, in the fourth invention, as in the third invention, part of the feed water is circulated to the feed water heater even under partial load, but in this case, the feed water discharged from the booster pump bypasses the feed pump. It is then supplied to the water heater. Therefore, the power of the pump can be reduced.

In the fifth aspect of the present invention, the feed water that has passed through the feed water heater at the time of partial load is combined with the feed water supplied to the exhaust gas cooler, and the total amount of water supplied is supplied to the boiler via the exhaust gas cooler. Therefore, it is possible to keep the temperature of the feed water heater at a high temperature without accumulating the feed water in the feed water heater, and even if the load is rapidly increased, thermal stress or the like may be applied to the feed water heater and the feed pipe. The impact can be minimized.

Further, in the sixth aspect of the invention, when the load is reduced and the amount of water supplied to the feedwater heater becomes equal to or less than the minimum required amount of water supply of the feedwater heater, the water supply is returned through the recirculation pipe line. The amount of water that is collected in the water heater and flows through the water heater is always kept above a predetermined level.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. 8 and 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a system diagram showing a first embodiment of the present invention, in which a feed water heater side feed pipe 26a branched at the outlet side of the feed pump 14 has a feed water regulating valve 29 and a feed water inlet stop valve. 27 is provided, and three high-pressure feed water heaters 15a, 15b, 15c are provided downstream of the feed water inlet stop valve 27, and the feed water inlet stop valve 27 and the first feed water stop valve 27 of the feed water heater side water supply pipe 26a are provided. The recirculation pipeline 32 is branched from the high-pressure feed water heater 15a. A stop valve 33, a flow rate adjusting valve 34, and an orifice 35 are provided in the middle of the recirculation pipe 32, and the tip end thereof is connected to the deaerator 13.

In this device, however, the stop valve 33 is fully closed during the rated load operation, and the water supply adjusting valve 29
High-pressure feed water heater 15a and high-pressure exhaust gas cooler 12
Water supply distribution to b is controlled, and water supply heater drain adjustment valve 2
5a, 25b, 25c for each high-pressure feed water heater 15
The drain levels of a, ... Are controlled, and the amount of bleed air to each high-pressure feed water heater is controlled correspondingly.

Then, the plant enters the partial load operation,
When the amount of water supplied to the high-pressure feed water heater 15a falls below a certain set flow rate, the water supply inlet stop valve 27 is fully closed and the entire amount of water supply is passed to the high-pressure gas cooler 12b. Therefore, the supply of water to the high-pressure feed water heaters 15a, 15b, 15c becomes 0, the extraction heating steam is not condensed, and the drain level in the feed water heater begins to decrease, and the drain adjustment valves 25a, 25b, 25c.
Is fully closed, and then the bleed valve 23 is fully closed. After that, the stop valve 33 is fully opened and the flow rate adjustment valve 34 is slightly opened.

However, a part of the feed water heated by the high-pressure exhaust gas cooler 12b flows back to the high-pressure feed water heater 15c side from the feed water confluence at the outlet side of the high-pressure exhaust gas cooler 12b having high temperature and pressure, and the flow rate adjusting valve A small amount of feed water controlled by the high pressure feed water heaters 15c, 15
b, 15a sequentially, and through the recirculation line 32, the deaerator 1
Recovered in 3. Then, the feed water flowing into the deaerator 13 is mixed and deaerated in the deaerator 13, again pressurized by the water supply pump 14 and sent to the high-pressure exhaust gas cooler 12b to be heated. In this way, the water supply pipe 26 can be used even under partial load.
The high-temperature feed water is constantly circulated through the "a" and the high-pressure feed water heaters 15a, 15b, 15c.

Then, the load is increased again to supply the water supply pump 14
Water supply is branched from the outlet of the high pressure feed water heater 15a, 1
When inflowing into 5b and 15c as well, first, the stop valve 33 is fully closed, then the feed water inlet stop valve 27 and the extraction valve 23 are fully opened, and the feed water adjusting valve 29 is used to feed water to the high pressure feed water heater 15a. While gradually controlling the flow rate, the opening degree of the water supply adjusting valve 29 is adjusted until the target flow rate is reached. At this time, the feed water temperature at the outlet of the high-pressure feed water heater 15c is heated by bleeding to each high-pressure feed water heater and is maintained at an appropriate temperature.

FIG. 2 is a diagram showing a water supply temperature distribution in the water supply pipe 26a and its change with time when the partial load is changed to the high load. The vertical axis represents temperature, the horizontal axis represents the position of the water supply pipe, A is the confluence point with the high pressure exhaust gas cooler outlet water supply, B is the water supply outlet valve, C to E are the high pressure water supply heater, and F is the position of the water supply inlet stop valve. (The arrow in the figure indicates the flow direction of the water supply).

FIG. 2A shows the temperature distribution of the feed water in the conventional device and its change with time. FIG. 2A shows the state in which the entire amount of feed water is flowing into the high pressure exhaust gas cooler during partial load operation. . The water supply temperature between B and F of the water supply pipe is 0 because the amount of water supplied to the high-pressure water supply heaters 15a, 15b, 15c is 0 and heat exchange is not performed therein, and therefore the temperature at the outlet of the water supply pump 14 (for example, 170 ° C.). ing. On the other hand, the water supply outlet stop valve 28 is fully closed, the temperature of the high-pressure exhaust gas cooler outlet (for example, 270 ° C.) at the confluence A, and the temperature at the water supply outlet stop valve position B is slightly lower than that.

In (b), with the water supply outlet stop valve 28 and the water supply inlet stop valve 27 opened, the water supply at 170 ° C. is mixed with the water supply flowing out from the high-pressure exhaust gas cooler 12b at the confluence A. Therefore, the inlet / outlet temperature difference here is about 100 ° C., and a large thermal stress is generated in the water supply pipe. Further, at the same time, the contaminated feed water that has stayed in the feed pipe between A and F for a long time joins the feed water supplied to the boiler.

In (c), the extraction of air to the high-pressure feed water heater is started thereafter, and the feed water temperature at the outlet of the feed water heater is rising. In (d), the amount of water supplied to the high-pressure feed water heater reaches the target value, and at the same time, the third high-pressure feed water heater 15c
The supply water temperature at the outlet has reached an appropriate temperature (for example, 270 ° C.).

On the other hand, in the device of the present invention, as shown in FIG. 2 (b), during partial load operation (a), since a part of the feed water flows back from the junction point A in the feed pipe, The temperature distribution in the water supply pipe gradually decreases from the outlet temperature of the high-pressure exhaust gas cooler in consideration of the heat radiation. At this time, the water supply inlet stop valve is fully closed, the inlet side of the water supply pump outlet water temperature (170 ° C), and the outlet side temperature of the confluence A (2
(70 ° C) minus the heat radiation of the water supply pipe.

Further, when the water supply inlet stop valve is fully opened, the high-pressure water supply heaters 15a, 15b, 15c are supplied with the water supply at the outlet of the water supply pump 14, and the amount of water supply is made minute by the water supply adjusting valve 29. Controlled, as shown in (b), the temperature distribution gradually increases from the outlet temperature of the feed pump to the downstream side in consideration of the residual heat of the feed pipe. Therefore, at the confluence A, the temperature difference is smaller than that in the conventional device, and the thermal stress of the water supply pipe is small. Further, since the water supply in the water supply pipe is constantly circulated, dirty water supply does not mix.

In (c), the bleeding to the high pressure feed water heater is started and the feed water temperature at the outlet of the feed water heater is rising,
In (d), the amount of water supplied to the high-pressure feed water heater reaches the target value, and at the same time, the water supply temperature at the outlet of the third high-pressure feed water heater 15c also reaches an appropriate temperature (about 270 ° C.).

As described above, during the partial load operation, a slight amount of feed water is made to flow backward in the feed water pipe and is collected in the deaerator, so that when the load shifts from the partial load to the high load, the dirty feed water is mixed. In addition, the temperature difference at the confluence of the water supply pipes can be reduced, and the thermal stress of the water supply pipes can be reduced. Moreover, the additional equipment is only the recirculation pipe 32 branched from the outlet of the feed water inlet stop valve and connected to the deaerator, the stop valve 33, the flow rate adjusting valve 34, and the orifice 35, and the additional remodeling range is small. Well, by recirculating and recovering part of the high-temperature feed water to the deaerator, the amount of water supplied to the high-pressure exhaust gas cooler 12b is increased, and the amount of heat recovery there is increased to the deaerator. It is possible to reduce the amount of turbine bleed air, and it is possible to improve work in the turbine, that is, power generation end output or power generation end efficiency.

FIG. 3 shows another embodiment of the present invention, in which the high pressure exhaust gas cooler is the first high pressure exhaust gas cooler 12 shown in FIG.
In addition to b, a second high-pressure exhaust gas cooler 36 for lowering the temperature of the gas turbine exhaust gas to recover heat is provided.

Exhaust gas from the gas turbine is supplied to the second high-pressure exhaust gas cooler 36, where the temperature of the exhaust gas is lowered by heat exchange with the feed water and then supplied to the boiler 1. The exhaust gas from the boiler 1 is the first
Is supplied to the high pressure exhaust gas cooler 12b.

The first high pressure exhaust gas cooler 12b and the second high pressure exhaust gas cooler 12b
The gas cooler feed water bypass pipe 37 is branched from the water feed pipe between the high-pressure exhaust gas coolers 36, and its tip is connected to the feed pipe between the high-pressure feed water heaters 15b and 15c. The gas cooler feed water bypass pipe 37 has a stop valve. 38 are provided. Further, the extraction pipe 22b for supplying the heating steam to the high-pressure feed water heater 15c is connected to the extraction stop valve 23 and the extraction check valve 2.
4 is provided with a bleed air second valve 39 and a bleed air second check valve 40 that control a minute amount of bleed air, and a drain pipe 41 that collects the drain of the high pressure feed water heater 15c into the condenser 8. The drain pipe 41 is provided with a stop valve 42 and a pressure reducing orifice 43. Further, the water supply outlet stop valve 28 is also provided with a flow rate adjusting valve 44 in parallel with the water supply outlet stop valve 28 for adjusting a minute amount of water supply.

During the rated load operation, however, the stop valves 33, 38, 42, the bleeding second valve 39 and the flow rate adjusting valve 44 are fully closed, and the other valves are operated in the same manner as shown in FIG. By performing the above, the flow becomes the same as that shown in FIG.

On the other hand, the high pressure feed water heater 15 becomes a partial load.
When the amount of water supplied to a falls below a certain set flow rate, the water supply inlet stop valve 27 is fully closed, and the total amount of water supply is the first high-pressure exhaust gas cooler 1
2b, the high-pressure feed water heater drain adjustment valve 25a,
After the valves 25b and 25c are fully closed, the bleed valve 23 is fully closed. Therefore, the stop valve 33 is fully opened, and the flow rate adjusting valve 34 is slightly opened to provide the same flow as in FIG.

After that, the stop valve 38 is further fully opened, the water supply outlet stop valve 28 is fully closed, and the flow rate adjusting valve 44 is slightly opened, whereby a part of the water supply from the outlet of the first high pressure exhaust gas cooler 12b is supplied to the gas cooler water supply bypass pipe. 37 to flow into the water supply pipe 26a, part of which flows backward through the water supply pipe 26a, and passes through the high-pressure water supply heaters 15b and 15a and the recirculation pipe 32, and the deaerator 13
The other is passed through the high pressure feed water heater 15c and the flow rate adjusting valve 44, mixed with the outlet feed water of the second high pressure exhaust gas cooler 36, and then sent to the boiler 1.

In this case, the feed water which merges with the gas cooler outlet feed water via the flow rate adjusting valve 44 is heated and controlled by opening the second extraction valve 39 and the stop valve 42, and is kept at an appropriate temperature.

In this way, the high pressure feed water heater 15b,
The supply water having an intermediate temperature at the outlet of the first high-pressure exhaust gas cooler 12b flows into 15a and the deaerator 13, and the temperature can be kept below the maximum operating temperature of each device. Further, since the feed water temperature at the outlet of the high pressure feed water heater 15c is heated and controlled by extraction air, the temperature difference from the feed water at the outlet of the second high pressure exhaust gas cooler 36 can be minimized.

On the other hand, when the load is increased again and the amount of water supplied to the boiler is increased, the operation can be performed in the reverse order of the above.

However, also in this embodiment, as in the case shown in FIG. 1, during the partial load operation, the feed water always flows to the feed water pipe and the high pressure feed water heater, and the high pressure feed water heater 15a,
The feed water having an intermediate temperature flows into 15b and the deaerator 13 and is kept at the maximum operating temperature or lower. Further, during the transition from the partial load to the high load, the feed water temperature at the outlet of the high-pressure feed water heater 15c is always kept appropriate, and the difference from the outlet feed water temperature of the high-pressure exhaust gas cooler 12b is minimized to reduce the thermal stress of the feed pipe. Can be made smaller.

FIG. 4 is a view showing still another embodiment of the present invention. The water supply pipe 26a is provided with a water supply outlet second stop valve 45 immediately before the confluence with the high pressure exhaust gas cooler outlet water supply pipe 26b. The recirculation pipe line 46 branches out from the water supply pipe on the inlet side of the water supply outlet second stop valve 45, and the tip thereof is connected to the deaerator 13. Then, in the recirculation pipe line 46, as in the first embodiment, the stop valve 33 and the flow rate adjusting valve 3 are provided.
4, an orifice 35 is provided.

On the other hand, the extraction pipe 2 to the high-pressure feed water heater 15a
The bleed valve 23 and the bleed check valve 24 are provided in parallel with the bleed valve 23 and the bleed check valve 24. A feed water heater second drain adjustment valve 49 is provided in parallel with the feed water heater drain adjustment valve 25c provided in the drain pipe.

During the rated load operation, however, the stop valve 33, the bleed air second valve 47 and the feed water heater second drain adjustment valve 49 are fully closed, and the other stop valves are fully opened. It operates in the same manner as the embodiment.

Therefore, the partial load operation is started, and the amount of water supplied to the high-pressure water heaters 15a, 15b, 15c is adjusted by the water supply adjusting valve 2.
When the flow rate controlled by 9 falls below a set flow rate, the stop valve 3
3 is fully opened and the water supply outlet second stop valve 45 is fully closed. Therefore, the high-pressure feed water heaters 15a, 15b, and 15c are supplied with the water having the flow rate adjusted by the flow rate adjusting valve 34.
To the deaerator 13 via the recirculation line 46. At the same time, each high-pressure feed water heater 15a, 15b, 1
Bleed valve 23 to 5c, and feed water heater drain adjustment valve 2
5a, 25b, 25c are fully closed, and the extraction air second valve 47 and the feed water heater second drain adjustment valve 49 are opened. Therefore, the feed water flowing into the high-pressure feed water heater 15a is heated and controlled by the minute amount of bleed air flowing from the bleed air second valve 47 having a small diameter, and is maintained at an appropriate temperature.

However, also in this embodiment, the water supply pipe 26a and the high-pressure water supply heaters 15a, 15 are operated during the partial load operation.
A small amount of feed water always flows to b and 15c, and the feed water temperature at the outlet of the high-pressure feed water heater is maintained at an appropriate temperature.

When increasing the load from the partial load operation to increase the amount of water supplied to the boiler, first, the flow rate adjusting valve 3
In step 4, the recirculation flow rate is increased to a certain flow rate, each extraction valve 23 to the high-pressure feed water heaters 15a, 15b, 15c is opened, the extraction second valve 47 is closed, and each drain adjustment valve 25
a, 25b, 25c are opened, and the feed water heater second drain adjustment valve 49 is fully closed.

Therefore, the feed water temperature at the outlet of the high-pressure feed water heater 15c is raised to a predetermined temperature due to the increase in the extraction amount, and the temperature difference from the high-pressure exhaust gas cooler outlet feed water becomes small. Therefore, the water supply outlet second stop valve 45 is opened, and the stop valve 33
When is fully closed, the recirculation water supply to the deaerator is switched to the water supply to the boiler and mixed with the outlet water supply of the high-pressure exhaust gas cooler 12b to increase the amount of water supply to the boiler.

As described above, during the partial load operation, a small amount of feed water is recovered from the recirculation pipeline to the deaerator through the feed pipe and the high pressure feed water heater, and the feed water temperature at the outlet of the high pressure feed water heater is
The temperature is maintained at an appropriate temperature by controlling a small amount of bleed air, and the influence on the performance is minimized to allow continuous water supply to the water supply pipe and the high-pressure water supply heater.

Further, when shifting from a partial load to a high load, the feed water temperature at the outlet of the high pressure feed water heater 15c can be raised to an appropriate temperature and then mixed with the high temperature feed water at the outlet of the high pressure exhaust gas cooler. The thermal stress due to the temperature difference between the tubes can be reduced.

FIG. 5 shows a modified example of FIG.
A recirculation pipe line 46 for recirculating the water supply is branched from a water supply pipe 26a between the high-pressure water supply heater 15c and the water supply outlet stop valve 28, and is connected in parallel with the water supply outlet stop valve 28. 50 and a pressure reducing orifice 51 are provided. Further, the water supply pipe 26 is provided with a bypass pipe 52 that bypasses the water supply pump 14, the water supply adjusting valve 29, and the water supply inlet stop valve 27 from between the water supply pump 14 and the water supply booster pump 14 a provided upstream thereof. It is branched. The bypass pipe 52 includes a stop valve 53 and a check valve 54.
Is provided, and the tip is connected to the water supply pipe 26a on the inlet side of the high-pressure water heater 15a. Other points are shown in Figure 4.
Is the same as

During the rated load operation, however, the stop valve 53 and the flow rate adjusting valve 50 are fully closed, and the other valves are operated in the same manner as in FIG. 4 to perform the same operation. be able to.

Next, at the time of partial load operation, the feed water stop valve 2
7 is fully closed, and the stop valve 53 and the flow rate adjusting valve 50 are slightly opened. Therefore, the feedwater having a low pressure at the outlet of the feedwater booster pump 14a is supplied to the high-pressure feedwater heaters 15a, 15b, 15
The exhaust gas cooler 12b having a high pressure and temperature while being collected in the deaerator 13 through the recirculation pipe 46.
After a part of the feed water on the outlet side is decompressed by the orifice 51, it joins the feed water on the outlet of the high-pressure feed water heater 15c and is collected by the deaerator 13.

In this embodiment, however, the water supply pipes and the high-pressure water heaters 15a, 15b, 15c are always supplied with water, and the high-pressure water heaters are supplied with water bypassing the water supply pump 14. Therefore, the pump power can be saved. Moreover, the recirculation line 46
Since it was branched from the pipe between the high-pressure feed water heater 15c and the feed water outlet stop valve 28, it can be branched inside the turbine building, and only a relatively short pipe needs to be additionally installed. Unlike the case of 4), there is no need to run the pipe from the vicinity of the water supply confluence outside the turbine building.

FIG. 6 is a view showing still another embodiment of the present invention, in which the water supply pipe 26a between the water supply outlet of the high-pressure water supply heater 15c and the water supply outlet stop valve 28 has a flow control valve 55. A pipe 56 is connected to the inlet side of the high pressure exhaust gas cooler 12b.

On the other hand, a stop valve 57, a pressure reducing orifice 58 and a stop valve 59 are provided in parallel with the exhaust gas cooler water supply pipe 26b branched on the outlet side of the water supply pump 14 so as to bypass the inlet stop valve 30. A conduit 60 having is provided.

However, the stop valve 57,
By fully closing the flow control valve 59 and the flow control valve 55, the same operation as in the first embodiment can be performed.

Therefore, during the partial load operation, the feed water outlet stop valve 28, the inlet stop valve 30 and the extraction valve 23 are closed, and the stop valves 57 and 59 and the flow rate control valve 55 are controlled in the opening direction. Therefore, the high pressure feed water heater 15
The feed water that has passed through a, 15b, and 15c is guided to the inlet of the high-pressure exhaust gas cooler 12b via the bypass pipe 56, and the stop valve 57
It is introduced into the high-pressure exhaust gas cooler 12b by merging with the feed water that has passed through the above. In this case, the pressure of the feed water flowing from the bypass pipe 56 into the high pressure exhaust gas cooler 12b inlet is 1
While the water passes through 5a, 15b, and 15c, it becomes low, or the water supply flowing through the exhaust gas cooler water supply pipe 26b is also decompressed by the orifice 58, so that the above merging is performed without any trouble.

In the above embodiment, the extraction valve 23 is fully closed so that the high-pressure feed water heaters 15a, 15b, 15c are not heated, but the partial load operation is switched to the normal load operation. High-pressure feed water heater 15c
In order to reduce the difference between the outlet water supply temperature of the exhaust gas and the outlet water supply temperature of the high-pressure exhaust gas cooler 12b, one of the extraction valves 23 is opened or partially opened, and the operation of raising the temperature of the water supply flowing through the water supply pipe 26a is performed. Good. Further, in the above embodiment, the feed water stop valve 28 is closed and the entire amount of feed water flowing out from the high pressure feed water heater 15c is sent to the bypass pipe 56.
The water supply outlet stop valve 28 and the flow rate control valve 55 may be simultaneously opened to control the water supply flowing through the bypass pipe 56 and the flow rate flowing through the water supply outlet stop valve 28.

In addition, FIG. 7 shows the embodiment shown in FIG. 6 in which a recirculation line 46 is further provided. That is, the recirculation pipe line 46 is branched and led out from the water supply pipe connecting the high-pressure water supply heater 15c at the final stage and the water supply outlet stop valve 28, and the tip end thereof is connected to the condenser 8 and the recirculation pipe thereof. The passage 46 is also provided with the flow rate adjusting valve 34 and the pressure reducing orifice 35.

However, when the load is reduced and the amount of feed water flowing in the high pressure feed water heater is reduced to the flow rate required to ensure the minimum flow rate and the minimum temperature at the outlet of the feed water heater 15c, the flow rate adjusting valve 34 is gradually opened and the feed water heater 15c
The feed water flowing out of the tank is returned to the condenser 8 via the recirculation pipe line 46, and the required minimum amount of water supply is secured in the high-pressure feed water heater.

The water supply flow rate / temperature sensor 6 is provided in each of the water supply pipes 26a and 26b at the water supply outlet of the high-pressure water supply heater 15c and the water supply outlet of the high-pressure exhaust gas cooler 12b.
1, 62 are provided, an exhaust gas temperature sensor 63 is provided in the exhaust gas pipe of the high-pressure exhaust gas cooler 12b, and the detection signal from each sensor is input to the control device 64. Then, each valve is controlled by an output signal from the control device 64. Further, in each of the embodiments, the vicinity of the high-pressure feed water heater has been described, but the same may be applied to the vicinity of the low-pressure feed water heater.

[0076]

Since the present invention is configured as described above,
Water can be circulated in the water heater and water heater even under partial load, and the water pipe and water heater can be cleaned up without reducing the amount of water supplied to the high-pressure exhaust gas cooler. It is possible to prevent dirty water from mixing in the water supply when shifting from low load operation to high load operation, and also to minimize the temperature difference between the feed water temperature at the outlet of the feed water heater and the feed water temperature at the exhaust gas cooler outlet. Therefore, the thermal stress in the water supply pipe can be reduced.

[Brief description of drawings]

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

FIG. 2 is an explanatory view of the relationship between the temperature distribution of the water supply pipe of the conventional device and the device of the present invention and its change over time.

FIG. 3 is a schematic system diagram of another embodiment of the present invention.

FIG. 4 is a schematic system diagram of still another embodiment of the present invention.

FIG. 5 is a schematic system diagram of another embodiment of the present invention.

FIG. 6 is a schematic system diagram of still another embodiment of the present invention.

FIG. 7 is a schematic system diagram of another embodiment of the present invention.

FIG. 8 is a system diagram of a conventional combined cycle turbine plant.

FIG. 9 is a system diagram around a conventional high-pressure feed water heater.

[Explanation of symbols]

1 Boiler 3 High Pressure Steam Turbine 8 Condenser 10 Condensate Pump 11a, 11b, 11c Low Pressure Feed Water Heater 12a Low Pressure Exhaust Gas Cooler 12b High Pressure Exhaust Gas Cooler 13 Deaerator 14 Water Pump 14a Water Supply Booster Pump 15a, 15b, 15c High Pressure Water Heating Container 17 Gas turbine 21a, 21b, 21c, 22a, 22b, 22c Extraction pipe 23 Extraction valve 24 Extraction check valve 26 Water supply pipe 27 Water supply inlet stop valve 28 Water supply outlet stop valve 29 Water supply adjusting valve 30 Inlet stop valve 31 Outlet stop valve 32,46 Recirculation pipeline 33,38,42 Stop valve 34,44,50 Flow control valve 36 Second high-pressure exhaust gas cooler 37 Gas cooler feed water bypass pipe 39 Extraction second valve 41 Drain pipe 45 Water supply outlet second stop valve 47 Bleed air second valve 52,56 Bypass pipe 55 Flow control valve

Claims (6)

[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 a feed pipe between the feed water heater and the feed water inlet stop valve. From the recirculation pipeline,
A feed water heating device characterized in that a tip of the recirculation pipe is connected to a deaerator and a flow rate adjusting valve for controlling the amount of feed water flowing into the deaerator is provided in the recirculation pipe. 2. A first exhaust gas cooler that lowers the temperature by exchanging heat with the feed water before supplying the exhaust gas from the gas turbine to the boiler, and a second exhaust gas cooler that heats the feed water with the exhaust gas from the boiler. Are connected in series, the water supply pipe between the two exhaust gas coolers is connected between the water supply heaters by a gas cooler water supply bypass pipe having a stop valve, and a water supply outlet stop valve provided at the outlet of the final stage water supply heater. The feed water heating apparatus according to claim 1, further comprising a flow rate adjusting valve provided in parallel with the flow rate adjusting valve. 3. 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 from a feed pipe between a feed water heater and a feed water outlet valve. Water supply characterized by branching out the recirculation line, connecting the recirculation line to the deaerator through a flow rate adjusting valve, and providing a control valve for controlling the minute heating steam in the extraction pipe Heating device. 4. A water supply pump bypass pipe, which bypasses the water supply pump, the water supply adjusting valve, and the water supply inlet stop valve, and connects the outlet side of the water supply buster pump and the inlet side of the water supply heater,
The feedwater heating apparatus according to claim 3, wherein the feedwater pump bypass pipe is provided with a feedwater stop valve and a check valve. 5. 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, wherein a feed water inlet part of the exhaust gas cooler and a feed water heater outlet are provided. The feed water heating device is characterized in that the side and the side are communicated with each other via a flow rate adjusting valve. 6. A recirculation pipeline is branched from a water supply pipe between a feed water heater and a feed water stop valve, and the recirculation pipeline is connected to a condenser via a flow control valve and a pressure reducing device. The feedwater heating device according to claim 5, which is characterized in that: