JP3335696B2 - Steam generator and method of operating the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam generator such as an exhaust heat recovery boiler, and more particularly to a steam generator having a economizer, and keeping the fluid pressure in the economizer above the saturated vapor pressure of the fluid temperature. Steam generator designed to operate and operation of steam generator
It is about the method .

[0002]

2. Description of the Related Art As part of high-efficiency power generation, development of a combined power generation plant has recently been promoted. This plant
In this system, electric power is generated by a gas turbine, heat retained in exhaust gas discharged from the gas turbine is collected by an exhaust heat recovery boiler, and steam generated by the exhaust heat recovery boiler drives a steam turbine to generate power.

[0003] In addition to such high-efficiency power generation, this plant also has the features of gas turbines, such as easy start-up and high load responsiveness. It is a power plant suitable for operation.

FIG. 4 is a schematic diagram for explaining a system of the combined cycle power plant. 1 in the figure is a gas turbine,
2 is a generator, 3 is a steam turbine, 4 is a condenser, 5 is a waste heat recovery boiler, 6 is a feedwater pump, 7 is a low-pressure economizer, 8 is a low-pressure evaporator, 9 is a low-pressure drum, and 10 is a feedwater pump. , 11 is a high-pressure economizer, 12 is a high-pressure evaporator, 13 is a high-pressure drum, 1
4 is a superheater, 15 and 16 are flow control valves (first and second flow
The amount regulating valve), 17 check valve, 38 is a feed water pump 10 Mi
A minimum flow valve (minimum flow regulating valve) 39 is a minimum flow pipe .

In FIG. 1, an exhaust heat recovery boiler 5 includes a superheater 14, a high-pressure evaporator 12, and a high-pressure economizer 11 on an exhaust gas passage 18 in order to recover exhaust heat from the gas turbine 1 to the maximum. , A low-pressure evaporator 8, a low-pressure economizer 7, and the like. However, particularly when the hot start is started or when the load is low, since the temperature of the gas flowing into the exhaust heat recovery boiler 5 is low, the heat transfer tube group on the relatively low temperature side, that is, the low pressure economizer 7 is used.
And an evaporation phenomenon occurs in the high-pressure economizer 11. When the air- water mixed fluid exists in the low-pressure economizer 7 and the high-pressure economizer 11 , the control of the boiler becomes unstable, making it difficult to continue the operation, and the water hammer phenomenon occurs, and Various problems occur, such as damage to the device.

In order to solve such a problem, as shown in FIG. 1, flow control valves 15 and 16 are provided at the outlet side of the low-pressure economizer 7 and the high-pressure economizer 11, respectively. 10 discharge pressure is increased, low pressure economizer 7, high pressure economizer
The fluid pressure in the vessel 11 is maintained at or above the saturated vapor pressure of the fluid temperature, thereby preventing the occurrence of an evaporation phenomenon.

[0007]

However, such a steam generator has the following problems.

Namely, the low-pressure drum 9 at start by starting the water supply pump 6, 10, but to introduce exhaust gas from the gas turbine 1 at the time when the drum level of the high-pressure drum 13 becomes controllable, low pressure evaporator 8 The volume of the can water in the high-pressure evaporator 12 expands due to the temperature rise, and the water level of the drum rises. For this reason, the flow control valves 15 and 16 are set to 10 to 30 in the initial stage of startup.
Keep closed for minutes. However, during this time, low pressure nodes
Since the water in the charcoal unit 7 and the high-pressure economizer 11 is heated in a sealed state, the volume of the fluid increases at a rate of about 1 to 2% per minute. Since water is an incompressible fluid, the low-pressure economizer 7 and the high-pressure
The pressure in the economizer 11 will increase by about 30 to 50 kg / cm ² per minute, causing a serious accident such as rupture or blasting of equipment.

Therefore, conventionally, an on / off valve 27 and a bypass pipe 26 are provided as a bypass system of the flow control valve 16, and the on / off valve 27 is opened when the flow control valve 16 is closed, so that the low pressure economizer 7 and the high pressure The increased volume of the fluid in the charcoal 11 is discharged to the high-pressure drum 13. However, since the level of the high-pressure drum 13 rises accordingly, the blow valve 3
0 was opened and water was drained out of the system. In this case, since high-temperature pure water is discharged, energy is extremely lost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a steam generator and a method for operating the steam generator , which are highly safe and can save energy.

[0011]

In order to achieve this object, according to the present invention, a check valve is provided from the upstream to an outlet of a water supply pump for supplying water to a economizer disposed in a flow path of a high-temperature gas. A water supply stop valve is provided, and the minimum flow pipe of the water supply pump is taken out from the middle of the valves. Further, a stop valve is provided in the minimum flow pipe instead of the water supply stop valve.

Further, the high-temperature gas discharged from the gas turbine is
A low-pressure economizer and a high-pressure economizer in the
Water supply to the high-pressure economizer between the low-pressure economizer and the high-pressure economizer
Install a water supply pump to supply low pressure to the low pressure economizer.
Connect the drum and connect the high pressure drum to the high pressure economizer
And a first flow between the low pressure economizer and the low pressure drum.
A quantity regulating valve is provided to connect the high-pressure economizer with the high-pressure drum.
A second flow control valve is provided in between, and at the outlet of the water supply pump
A check valve and a water supply stop valve are provided from the upstream, and the check valve and the water supply stop valve are provided.
Between the water pump and the minimum flow pipe.
The minimum flow pipe was provided with a minimum flow valve.
In the method for operating a steam generator, the gas turbine
Open the above minimum flow valve before starting and
From the start of the turbine, the low pressure drum and high pressure drum
Until the fluctuation of the water level of the
The flow control valve 2 is fully closed.

[0013]

By installing the minimum flow pipe as described above, the minimum flow of the water supply pump is performed, and at the same time, when the steam is increased or decreased in the steam generator, or when both are reduced, This means that a system for releasing the volume expansion of the fluid to be heated (water) in the economizer has been realized. This can prevent energy loss due to the outflow of high-temperature pure water,
The possibility of laceration of equipment such as economizers can now be prevented.

[0014]

FIG. 1 shows a system diagram of a steam generator according to the present invention.

First, although not shown, combustion air from an air supply pipe and fuel from a fuel supply pipe are mixed and burned in a combustion chamber, and the combustion gas is used to rotate the gas turbine 1 to generate power. The exhaust gas used for rotating the gas turbine 1 is introduced into an exhaust gas passage 18 of the exhaust heat recovery boiler 5. The exhaust gas passage 18 includes a low-pressure boiler including a low-pressure economizer 7, a low-pressure evaporator 8, and a low-pressure drum 9, and a high-pressure economizer 11, a high-pressure evaporator 12,
A high-pressure boiler including a high-pressure drum 13 and a superheater 14 is provided.

On the other hand, the water to be heated is supplied by a water supply pump 6.
Is supplied to the low-pressure economizer 7 through the water supply pipe 19, is heated to a predetermined temperature, and is introduced into the low-pressure drum 9 via the flow control valve 15. The water supplied to the low-pressure drum 9 is circulated naturally or forcibly in the order of the low-pressure evaporator 8 and the low-pressure drum 9, while being heated and separated into water and steam in the low-pressure drum 9. Then, the separated steam is supplied to the steam turbine 3 through the low-pressure main steam pipe 21.

On the other hand, a part of the high-temperature water diverted at the outlet side of the low-pressure economizer is supplied to the high-pressure economizer 11 through the high-temperature water supply pipe 22 by the water supply pump 10 and is heated to a predetermined temperature. Is supplied to the high-pressure drum 13 through a drum water supply pipe 23 having a flow control valve 16. The hot water supplied to the high-pressure drum 13 is circulated in the order of the high-pressure evaporator 12 and the high-pressure drum 13, and the steam separated in the high-pressure drum 13 is
After being sent to the superheater 14 via the drum steam outlet pipe 24 and further heated here, the air is sent from the high-pressure main steam pipe 25 to the steam turbine 3.

In this way, power is generated by the steam turbine 3. Then, the steam used for rotating the steam turbine 3 becomes water in the condenser 4, and is supplied again to the exhaust heat recovery boiler 5 by the water supply pump 6.

Here, the flow control valves 15 and 16 are connected to a low pressure
The fluid pressure (water pressure) in the economizer 7 and the high-pressure economizer 11 is adjusted to be equal to or higher than the saturated vapor pressure of the fluid temperature,
Steam generation in the vessel is suppressed.

In this embodiment, a water stop valve 32 is provided downstream of the check valve 17 at the outlet of the water supply pump 10, and a minimum flow connecting the condenser 4 from the space between the check valve 17 and the water stop valve 32. Pipe 29 and minimum flow valve (minimum flow adjustment
Valve 28 ) .

FIG. 2 is a characteristic diagram of gas turbine output and drum level. In the figure, curve A indicates the water level of the high pressure drum, curve B indicates the water level of the low pressure drum, and curve C indicates the output of the gas turbine. As shown in this figure, when the gas turbine 1 starts, the water level of the low-pressure drum 9 and the high-pressure drum 13 fluctuates. Therefore, the steam generation according to the present invention
In the operation method of the raw device, the flow control valve 15 is used for a certain time T from the start of the gas turbine 1 until the fluctuation of the water level of the low-pressure drum 9 and the high-pressure drum 13 stops.
16 is fully closed .

[0022] In this case, since the feed water pump 10, it is necessary to ensure a minimum flow for overheat Minimamufu
The low valve 28 is opened. Further, since the water supply stop valve 32 is opened before the gas turbine 1 starts, even if the flow control valve 16 is closed by the minimum flow pipe 29, the inside of the high-pressure economizer 11 expands. The fluid can be discharged to the condenser 4. As a result, abnormal high pressure of the high-pressure economizer 11 can be prevented, and there is no need to provide a blow valve and drain the water to the outside of the system as in the related art, thereby preventing energy loss. In this embodiment, since the minimum flow pipe 29 is connected to the condenser 4, the water supply is sufficiently cooled,
Abnormal overheating of the water supply pump 10 can also be prevented.

Although FIG. 1 shows the case where there are two drums, even if the number of drums is three or more and the number of water supply pumps 10 is plural, the minimum flow pipe 29 of each pump must be checked. The same effect can be obtained by extracting from the downstream of the valve 17.

Embodiment 2 FIG. 3 shows another embodiment according to the present invention.
Here, the water supply stop valve 32 at the inlet of the high-pressure economizer 11 is eliminated, and a stop valve 33 is provided in the minimum flow pipe 29 instead. The reason why the stop valve 33 is provided is to prevent the supply of water in the economizer 11 from flowing out to the condenser 4 during stoppage, thereby preventing the high-pressure economizer 11 from being emptied.

[0025]

As described above , in the steam generator and the operation method of the steam generator according to the present invention, the minimum flow pipe is taken out from the outlet of the feed water pump, so that the economizer using the heat-expanded fluid to be heated can be used. As a result, the explosion damage of the fuel cell can be eliminated, the safety can be ensured, and all the inflation water in the economizer can be recovered in the system.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an exhaust heat recovery boiler according to the present invention.

FIG. 2 is a diagram showing characteristics of a gas turbine output and a drum level.

FIG. 3 is a partial view showing the configuration of another embodiment according to the present invention.

FIG. 4 is a schematic configuration diagram of a conventional exhaust heat recovery boiler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas turbine 2 Generator 3 Steam turbine 4 Condenser 5 Exhaust heat recovery boiler 6 Feed water pump 7 Low pressure economizer 8 Low pressure evaporator 9 Low pressure drum 10 Water pump 11 High pressure economizer 12 High pressure evaporator 13 High pressure drum 14 Superheat Apparatus 15, 16 Flow control valve 17 Check valve 18 Exhaust gas flow path 19 Water supply pipe 21 Low pressure main steam pipe 22 High pressure water supply pipe 23 Drum water supply pipe 24 Drum steam outlet pipe 25 High pressure main steam pipe 26 Bypass pipe 27 Bypass on / off valve 28 Minimum Flow valve 29 Minimum flow pipe 30 Drum blow valve 31 Drum blow pipe 32 Water supply stop valve 33 Stop valve

Continuation of the front page (56) References JP-A-4-116301 (JP, A) JP-A-1-179805 (JP, A) JP-A-5-296409 (JP, A) JP-A-63-5206 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F22D 11/00 F22B 1/18

Claims (3)

(57) [Claims] At least a economizer is disposed in a flow path of a high-temperature gas, and a water supply pump for supplying water to the economizer is installed .
Connect a drum to the economizer, and save the economizer and the drum
In the steam generator provided with a flow control valve in between, a check valve and a water stop valve are provided from the upstream at the outlet of the water supply pump, and between the check valve and the water stop valve, the check valve of the water supply pump is provided. Take out the minimum flow tube and insert it into the minimum flow tube.
A steam generator characterized by having a nimum flow valve . 2. At least a economizer is disposed in a flow path of a high-temperature gas, and a water supply pump for supplying water to the economizer is installed .
Connect a drum to the economizer, and save the economizer and the drum
In the steam generator provided with a flow control valve between the check valve, a check valve is provided on the outlet side of the feed pump, and furthermore, a minimum flow pipe of the feed pump is provided between the check valve and the economizer. Take out, stop valve from the upstream to the minimum flow pipe ,
A steam generator characterized by having a minimum flow valve . 3. A low-pressure economizer and a high-pressure economizer are arranged in a flow path of a high-temperature gas discharged from a gas turbine, and the high-pressure economizer is disposed between the low-pressure economizer and the high-pressure economizer. A water supply pump that supplies water to the vessel is installed, a low-pressure drum is connected to the low-pressure economizer, a high-pressure drum is connected to the high-pressure economizer, and a water pump is connected between the low-pressure economizer and the low-pressure drum. 1 is provided between the high-pressure economizer and the high-pressure drum.
And a check valve and a water stop valve are provided at the outlet of the water supply pump from the upstream, and a minimum flow pipe of the water supply pump is taken out from between the check valve and the water stop valve. In the method for operating a steam generator in which a minimum flow valve is provided in a flow pipe, the minimum flow valve that is closed is opened before the gas turbine is started, and the water level of the low-pressure drum and the high-pressure drum is changed from the start of the gas turbine. A method for operating a steam generator, wherein the first and second flow control valves are fully closed until the fluctuation stops.