JPH0861013A - Device for draining outlet of exhaust heat recovery boiler - Google Patents

Abstract

PURPOSE: To provide a draining device capable of efficient and automatic drainage to the outside of a system. CONSTITUTION: A steam pressure and temperature on the prior stage side of main steam stop valves 27 to 29 are detected, the measured values are introduced into a temperature-entropy chart calculation device 40, and it is judged whether the steam at the time of measurement is in wet area or dry area. When it is in wet area, the main steam stop valves 27 to 29 are closed and, at the same time, a drain valve 30 on the prior stage side of the main steam stop valves is opened so as to exhaust drain automatically to the outside of a system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat recovery boiler outlet drain removing device for automatically removing a large amount of drain generated at the time of starting a combined cycle power plant out of the system.

[0002]

2. Description of the Related Art FIG. 4 shows a steam-water system of an exhaust heat recovery boiler and a steam turbine in a conventional combined cycle power plant. Air from the atmosphere is the air compressor 1
Is compressed into high pressure air and supplied to the combustor 2, mixed with fuel and burned, and then becomes high temperature and high pressure gas, which is supplied to the gas turbine 3. This high-temperature high-pressure gas rotates the gas turbine impeller while adiabatically expanding to near the atmosphere in the gas turbine to generate power for the gas turbine.

The exhaust gas after working with a gas turbine is
Exhaust heat is recovered in the exhaust heat recovery boiler 4 and released into the atmosphere through the chimney 5. On the other hand, the steam from the low-pressure turbine 35 is condensed in the condenser 17 that is always in a vacuum state during operation to be condensed water. The condensate is heated by the low-pressure feed pump 18 by the low-pressure economizer 7 provided in the exhaust heat recovery boiler 4, and is supplied to the low-pressure steam drum 19. The feed water supplied to the low-pressure steam drum 19 is heated in the low-pressure evaporator 8 to become steam, which is further heated in the low-pressure superheater 9 and is passed through the low-pressure main steam pipe 26 and the low-pressure main steam stop valve 29 to the low-pressure turbine 35. Is supplied to. In addition, a part of the feed water that has left the low-pressure economizer 7 is supplied by the medium-pressure feed pump 22 to the medium-pressure economizer 1.
It is heated at 0 and supplied to the medium pressure steam drum 20. The feed water supplied to the intermediate-pressure steam drum 20 is heated in the intermediate-pressure evaporator 12 to become steam, which is further heated in the intermediate-pressure superheater 13 to drive the intermediate-pressure main steam pipe 25 and the intermediate-pressure main steam stop valve 28. Through the intermediate pressure turbine 34. Further, a part of the feed water that has exited from the low-pressure economizer 7 is heated by the high-pressure feed pump 23 by the high-pressure primary economizer 11 and the high-pressure secondary economizer 14, and is supplied to the high-pressure steam drum 21.

The water supplied to the high-pressure steam drum 21 is
It is heated in the high-pressure evaporator 15 to become steam, further heated in the high-pressure primary superheater 6, and supplied to the high-pressure turbine 33 via the high-pressure main steam pipe 24 and the high-pressure main steam stop valve 27.

The steam leaving the high-pressure turbine 33 is reheated by the reheater 1.
After being reheated in 6, the steam that has been heated in the intermediate pressure superheater 13 merges and is supplied to the intermediate pressure turbine 34. The steam exiting the intermediate-pressure turbine 34 joins the steam heated in the low-pressure superheater 9, is supplied to the low-pressure turbine 35, works in the low-pressure turbine, and then is condensed in the condenser 17 to generate condensed water. Thus, a circulation system to be supplied to the low pressure steam drum 19 is formed.

At the time of starting the plant, a large amount of steam condensation doin is generated because the equipment and the entire piping system are cooled, which causes various harmful effects. For this reason, drainage is provided in the piping and the reservoir of the equipment, and it is common to perform drainage outside the system at the time of startup.

In the combined cycle power plant, as shown in the starting characteristic of FIG. 5, the uncombusted fuel gas remaining in the gas turbine and the exhaust heat recovery boiler in the starting process is compressed by an air compressor before ignition of the gas turbine. 1
Purge operation is performed to discharge the compressed air from the system. This combined cycle power plant is characterized in that the plant is frequently started and stopped because it has excellent starting characteristics as compared with a general thermal power plant.

When the plant is shut down, the low, medium, and high pressure steam drums 19-2 are provided in order to make the next startup quicker.
1. The hot banking method in which high-temperature steam is sealed in the low pressure superheater 9, the medium pressure superheater 13 and the high pressure primary superheater 6 is generally adopted. When the plant is started from such a state, during the purging operation peculiar to the combined cycle power plant, the low, medium and high pressure steam drums 19 to 21, the low pressure superheater 9, the medium pressure superheater 13 and the high pressure primary superheater 6 are provided. The contained steam is cooled and condensed by the gas turbine exhaust gas (at this point, the gas turbine is not ignited, so the exhaust gas temperature is around 50 ° C. only due to the temperature increase due to compression), and a large amount of drain is generated. If the main steam stop valves 27 to 29 at the steam turbine inlet that do not completely remove this drain are opened, a large amount of drain will flow into the steam turbine, causing excessive thermal stress to the steam turbine due to rapid cooling and the turbine casing. It causes serious damage to the steam turbine such as deformation due to large temperature difference between the upper and lower half of the steam turbine. This is the generally called water induction phenomenon of steam turbines.

For this purpose, each drain valve 3 is provided in front of the high pressure main steam stop valve 27, the intermediate pressure main steam stop valve 28, and the low pressure main steam stop valve.
0 to 32 are provided, and after the gas turbine is ignited at the time of startup, each drain valve is opened for a certain period of time to remove the drain of the high-pressure main steam pipe 24, the intermediate-pressure main steam pipe 25, and the low-pressure main steam pipe 26 from outside the system. Is performed to prevent the drain from flowing into the steam turbines 33 to 35.

[0010]

However, according to the drain elimination method according to the above method, the drain is not reliably discharged in a plant such as a combined cycle power plant where a large amount of drain is generated by performing a purge operation or the like. there is a possibility. In particular, the amount of drain generated is greatly affected by the operating conditions at that time, the outside air temperature, and the like, and drainage cannot be reliably discharged from the system by the opening / closing management of the drain valves 30 to 32 over time. Further, if the drain valves 30 to 32 are kept open for a long time, the drain in the system can be completely discharged, but during this time, a large amount of high temperature steam is also discharged, which causes a large energy loss. Become.

The present invention has been made based on such a point, and an object thereof is to prevent a large amount of drain generated at the time of start-up of a combined cycle power plant from flowing into a steam turbine, or to prevent steam from being wet. It is an object of the present invention to provide a drain elimination device at the exit of a heat recovery steam generator that continuously detects the drain amount and automatically discharges the drain amount.

[0012]

In order to achieve the above object, exhaust heat of a gas turbine is recovered by an exhaust heat recovery boiler,
In a combined cycle power plant that starts a steam turbine with this recovered heat, at the start of this plant, it is arranged in front of the main steam stop valve provided on the inlet side of the steam turbine, and measures the steam pressure and temperature. The detector and steam pressure and temperature measured by this detector are input, and it is determined whether the steam at the time of measuring the steam pressure and temperature is in a wet or dry state, and in the case of a wet state, A temperature-entropy diagram calculator is provided automatically for giving a close command to the main steam stop valve and at the same time giving an open command to the drain valve arranged on the upstream side of the main steam stop valve. This is a drain removal device at the exit of the exhaust heat recovery boiler, which is characterized by removing the drain outside the system.

In order to achieve the above object, the exhaust heat of the gas turbine is recovered by an exhaust heat recovery boiler, and the combined cycle power plant that starts the steam turbine with the recovered heat is provided on the inlet side of the steam turbine. A drain pot that is provided in a part of the drain pipe on the upstream side of the main steam stop valve to store the drain and the presence or absence of drain in this drain pot are detected.If a drain is present, it is placed on the inlet side of the steam turbine. It is equipped with a level controller that gives a close command to the main steam stop valve provided and at the same time gives an open command to the drain valve arranged in front of this main steam stop valve. This is a drain elimination device at the exhaust heat recovery boiler outlet, which is characterized in that it is excluded from the system.

[0014]

According to the invention corresponding to claim 1, the steam pressure and temperature on the upstream side of the main steam stop valve are detected, and the measured values are guided to the temperature-entropy diagram calculation device so that the steam at the time of measurement becomes wet. If it is wet, the main steam stop valve is closed, and at the same time, the drain valve on the upstream side of the main steam stop valve is opened, and the drain is automatically removed from the system. The water induction phenomenon caused by the inflow of drain into the steam turbine of the combined cycle power plant is drastically reduced, and the reliability of the entire plant is improved.

According to the second aspect of the invention, the drain pot is arranged in the drain pipe on the upstream side of the main steam stop valve, and the presence or absence of the drain is detected by using the drain level detector, and the drain is present. In this case, the main steam stop valve was closed, and at the same time, the drain valve in front of the main steam stop valve was opened to automatically remove the drain out of the system.Therefore, the drain was placed in the steam turbine of the combined cycle power plant. The water induction phenomenon caused by the inflow of water is drastically reduced, and the reliability of the entire plant is improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is a schematic system diagram showing a first embodiment of the present invention, and FIG. 2 is a system diagram showing only essential parts thereof. The difference from the conventional example of FIG. 4 is that a temperature detector 37, a pressure detector 38, and a temperature-entropy diagram calculation device 40 are newly added.

In FIG. 1, a pressure detector 38 and a temperature detector 37 are installed in front of the high-pressure main steam stop valve 27 installed in the high-pressure main steam pipe 24.
The measured values of the temperature and pressure of the main steam detected on the upstream side of the main steam stop valve 27 are guided to the temperature-entropy diagram calculation device 40 to determine whether the steam at the time of measurement is in the wet region or the dry region. Determine continuously. When it is determined from the measurement results of the temperature and pressure of the main steam that the steam at the time of measurement is in a dry state, the drain valve 30 is automatically closed by a command signal from the temperature-entropy diagram calculation device 40. At the same time, each main steam stop valve 27 is opened, and steam not containing drain is ventilated to the steam turbine 33.

On the other hand, when it is determined from the measurement results of the temperature and pressure of the main steam that the steam at the time of measurement is in a wet state, the drain valve 30 is automatically operated by a command signal from the temperature-entropy diagram calculation device 40. The main steam stop valve 27 is closed at the same time. This makes it possible to prevent the drain from flowing into the steam turbine.

The drain valve 30 maintains a normally open state while the measured steam is determined to be in the wet region, and incorporates a sequence in which the drain valve 30 is closed at the time when the measured steam changes to a dry state, so that a reliable steam turbine 33 is provided. It is possible to prevent the inflow of drain into the inside, and since there is no transient drain removal operation (open state for a long time), it is possible to reduce the amount of high-temperature high-pressure steam discharged outside the system. The configuration described above is applied to the high pressure steam turbine 33.
Between the exhaust heat recovery boiler 4 and the exhaust heat recovery boiler 4, and a configuration similar to this (configuration shown in FIG. 2) is added to A and B of FIG. 1, and these operational effects are the same as those described above. Is.

In the combined cycle power generation plane in which the drain removing device of the first embodiment described above is installed,
Efficiently discharging the drain, which is generated at startup and causes the water induction of the steam turbines 33, 34, 35, to the outside of the system regardless of the plant startup conditions (cold, warm and hot start) and atmospheric temperature changes, etc. Is possible.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, the drain pot 36 is provided in a part of the pipe on the upstream side of the high-pressure main steam stop valve 27 installed in the high-pressure main steam pipe 24, and the drain level detector 39 causes the drain generated at the start-up of the plant. Configured for continuous level monitoring.

In this case, while the drain level is detected in the drain pot 36, it is determined that the drain is in the generated state, and the drain valve 30 is automatically opened by the signal from the drain level detector 39. , At the same time main steam stop valve 2
7 is closed. This makes it possible to prevent the drain from flowing into the steam turbine 33. On the other hand, when the drain level is not detected in the drain pot 36, it is determined that the drain is not in the generated state, and the drain valve 30 is automatically closed by the signal from the drain level detector 39.
At the same time, the main steam stop valve 27 is opened, and the steam containing no drain is ventilated to the steam turbine.

The drain valve 30 maintains a normally open state when there is a drain in the drain pot 36, and incorporates a sequence in which the drain valve 30 is closed when there is no drain or the drain amount does not increase. Therefore, it is possible to reliably prevent the drain from flowing into the steam turbine 33, and it is possible to reduce the discharge amount of the high-temperature and high-pressure steam from the outside of the system because there is no transient drain removal operation (open state for a long time).

The configuration described above is between the high-pressure steam turbine 33 and the exhaust heat recovery boiler 4 in FIG. 1, and the same configuration is the same in A and B in FIG. 1 as in the first embodiment. . The function and effect in this case are also the same as those in the above-described embodiment.

[0025]

According to the drainage elimination device at the outlet of the exhaust heat recovery boiler of the present invention described above, it is possible to efficiently detect a large amount of drainage generated at startup by continuously detecting the wet state of steam or the amount of drainage, It has become possible to automatically discharge to the outside of the system. As a result, the water induction phenomenon caused by the inflow of drain into the steam turbine of the combined cycle power generation plant is drastically reduced, which has a great effect on improving the reliability of the entire plant.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing a first embodiment of a drain removing device at an exhaust heat recovery boiler outlet of the present invention.

FIG. 2 is a system diagram showing only a main part of the embodiment shown in FIG.

FIG. 3 is a system diagram showing only a main part of a second embodiment of the drain removing device at the exhaust heat recovery boiler outlet of the present invention.

FIG. 4 is a schematic system diagram showing an exhaust heat recovery boiler of a conventional combined cycle power plant and a steam-water system of a steam turbine.

FIG. 5 is a starting characteristic diagram of the combined cycle power plant of FIG. 4.

[Explanation of symbols]

1 ... Air compressor, 2 ... Combustor, 3 ... Gas turbine, 4 ...
Exhaust heat recovery boiler, 5 ... Chimney, 6 ... High pressure primary superheater, 7 ...
Low pressure economizer, 8 ... Low pressure evaporator, 9 ... Low pressure superheater, 10 ...
Medium pressure economizer, 11 ... High pressure primary economizer, 12 ... Medium pressure evaporator, 13 ... Medium pressure superheater, 14 ... High pressure secondary economizer, 15 ...
High-pressure evaporator, 16 ... Reheater, 17 ... Condenser, 18 ... Low-pressure water supply pump, 19 ... Low-pressure steam drum, 20 ... Medium-pressure steam drum, 21 ... High-pressure steam drum, 22 ... Medium-pressure water supply pump,
23 ... High-pressure feed pump, 24 ... High-pressure main steam pipe, 25 ... Medium-pressure main steam pipe, 26 ... Low-pressure main steam pipe, 27 ... High-pressure main steam stop valve, 28 ... Medium-pressure main steam stop valve, 29 ... Low-pressure main steam Stop valve, 30 ... High pressure main steam drain valve, 31 ... Medium pressure main steam drain valve, 32 ... Low pressure main steam drain valve, 33 ... High pressure steam turbine, 34 ... Medium pressure steam turbine, 35 ... Low pressure steam turbine, 36 ... Drain Pot, 37 ... Temperature detector, 38 ... Pressure detector, 39 ... Drain level detector, 40 ... Temperature-entropy diagram calculation device.

Claims (2)

[Claims] 1. A combined cycle power plant in which exhaust heat of a gas turbine is recovered by an exhaust heat recovery boiler and the recovered heat is used to start a steam turbine, which is provided on the inlet side of the steam turbine when the plant is started. A detector that is placed in front of the main steam stop valve and that measures the steam pressure and temperature, and the steam pressure and temperature measured by this detector are input, and the steam at the time of measuring the steam pressure and temperature gets wet. Judgment whether it is in a dry or dry area, and if it is wet, give a closing command to the main steam stop valve,
At the same time, the main steam stop valve was equipped with a temperature-entropy diagram calculator that gives an opening command to the drain valve installed in the upstream side, and the drain was automatically excluded from the system. Drain removal device at the exhaust heat recovery boiler outlet. 2. In a combined cycle power plant in which exhaust heat of a gas turbine is recovered by an exhaust heat recovery boiler and the recovered heat is used to start a steam turbine, a main steam stop valve of an inlet side of the steam turbine is installed. A drain pot provided in a part of the drain pipe on the upstream side for storing drain, and the presence or absence of drain in the drain pot are detected, and if drain is present, the main unit is provided at the inlet side of the steam turbine. Equipped with a level controller that gives a closing command to the steam stop valve and at the same time gives an opening command to the drain valve arranged in front of this main steam stop valve, and automatically removes the drain out of the system. A drain elimination device at the exhaust heat recovery boiler outlet.