JP2001033004A - Method of draining for waste heat recovery boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of draining water held in a waste-heat recovery boiler therefrom safely and in a short time without stopping a gas-turbine and the like. SOLUTION: In a waste heat recovery boiler, which comprises an economizer 2 having purge gas feed-in means and drain valves 16, 17, and 18, and a steam generator 10 connected to a condenser through a turbine by-pass valve, and generates steam for operating a steam turbine by exhaust gas, the inlet and outlet sides of the economizer 2 are closed in a state that the exhaust gas is fed thereto and purge gas is fed to the economizer 2 from the purge gas feed-in means to drain boiler-retained water in the economizer through the drain valves 16, 17, and 18, and in addition the inlet and outlet sides of the steam generator 10 are closed and the boiler-retained water is evaporated to be discharged into the condenser through a turbine by-pass valve 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for draining water retained in an exhaust heat recovery boiler used in combination with a gas turbine or a diesel engine.

[0002]

2. Description of the Related Art For the purpose of heat recovery of high-temperature exhaust gas from a prime mover such as a gas turbine or a diesel engine,
An exhaust heat recovery boiler is sometimes used in combination. As an example of a power generation application, an exhaust heat recovery combined cycle plant that combines an exhaust heat recovery boiler and steam turbine equipment with a gas turbine burning gas fuel such as LNG is used. In recent years, many are planned and installed.

In such a waste heat recovery combined cycle plant, high-temperature exhaust gas from a gas turbine or the like is guided to an exhaust heat recovery boiler. The thermal energy of the exhaust gas is recovered by the waste heat recovery boiler and heats the water supplied from the water supply system from the steam turbine plant,
Evaporated and used for steam generation. As a result of the heat recovery, the exhaust gas that has passed through the exhaust heat recovery boiler is discharged to the atmosphere after being cooled to about 100 ° C. with a clean fuel such as LNG, depending on the fuel component. The steam generated by the exhaust heat recovery boiler is sent to a steam turbine and used for heat supply such as power generation and heating.

[0004] In the waste heat recovery boiler, when the internal water (hereinafter referred to as boiler holding water) is drained, the water is kept at a temperature lower than 100 ° C so as not to flash and evaporate when discharged into an atmospheric tank or the like. It is common to wait until it cools down before draining. In this case, the boiler is cooled after stopping a gas turbine or the like that generates high-temperature exhaust gas that becomes heat input to the exhaust heat recovery boiler, and the boiler water temperature is reduced to about 100%.
Drainage will be performed after the temperature falls below ℃.

[0005]

However, in the exhaust heat recovery combined cycle plant as described above, the exhaust heat recovery boiler and the steam turbine equipment may be stopped while the gas turbine on the exhaust gas supply side is operated in some cases. However, there has been a need to continue operation with only a prime mover such as a gas turbine.

That is, in the prior art, when draining water from an exhaust heat recovery boiler, the gas turbine or the like is stopped, and after the boiler cools, the boiler water is drained. On the other hand, there has been a demand for a method of safely and quickly draining water held in a boiler without stopping a gas turbine.

SUMMARY OF THE INVENTION The present invention meets the above-mentioned needs and safely and quickly drains the boiler-holding water of an exhaust heat recovery boiler without stopping a turbine or the like so as not to generate steam from the boiler. Also shut down the turbine equipment,
Thereafter, it is an object of the present invention to provide a method of draining an exhaust heat recovery boiler that can perform an operation of passing exhaust gas from a gas turbine or the like and releasing the exhaust gas to the atmosphere as it is without water in the exhaust heat recovery boiler. It is assumed that.

[0008]

Means for Solving the Problems (1) The present invention has been made to solve the above-mentioned problems, and the invention of claim 1 provides a conserving device having a purge gas feeding means and a drain valve. A steam generator connected to the condenser through a turbine bypass valve, and the exhaust heat recovery boiler that generates the working steam of the steam turbine by the exhaust gas. And the outlet side is closed, and purge gas is supplied from the purge gas supply means to pressurize the economizer to a pressure equal to or higher than its saturation pressure, while draining the boiler water in the economizer from the drain valve, and generating the steam. The present invention provides a method for draining a waste heat recovery boiler, comprising closing an inlet side and an outlet side of a device, evaporating boiler water in the device, and discharging the water to a condenser through the turbine bypass valve. .

That is, according to the first aspect of the present invention, in an exhaust heat recovery boiler provided with a economizer which is not designed in consideration of evaporation inside, the operation of a device on the exhaust gas supply side such as a gas turbine is performed. It is possible to discharge the boiler water and its steam inside the exhaust heat recovery boiler while continuing the exhaust gas through the exhaust heat recovery boiler.

(2) A second aspect of the present invention provides a condensate preheater and a economizer, each having a purge gas supply means and a drain valve, and steam connected to the condenser via a turbine bypass valve. A waste heat recovery boiler that includes a generator and generates the working steam of the steam turbine by the exhaust gas.In the state where the exhaust gas is passed, the inlet side and the outlet side of each of the condensate preheater and the economizer are closed, The purge gas is supplied from the purge gas supply means to drain the boiler water from the drain valve, close the inlet side and the outlet side of the steam generator, evaporate the boiler water in the apparatus, and remove the turbine bypass valve. And a drainage method for a waste heat recovery boiler, wherein the wastewater is discharged to a condenser via a condenser.

That is, according to the second aspect of the present invention, in an exhaust heat recovery boiler provided with a condensate preheater and a economizer which is not designed in consideration of evaporation inside, an exhaust gas supply side of a gas turbine or the like is provided. It is possible to discharge the boiler water and its steam inside the exhaust heat recovery boiler while the operation of the apparatus is continued and the exhaust gas is passed through the exhaust heat recovery boiler.

(3) The invention according to claim 3 includes a economizer and a steam generator connected to a downstream side of the economizer and connected to a condenser via a turbine bypass valve. In the exhaust heat recovery boiler that generates the working steam of the steam turbine by the exhaust gas, the inlet side of the economizer and the outlet side of the steam generator are closed with the exhaust gas passing through, and the interior of the economizer and the interior of the steam generator The present invention also provides a method for draining an exhaust heat recovery boiler, wherein the boiler-owned water is evaporated and discharged to a condenser through the turbine bypass valve.

That is, according to the third aspect of the present invention, in the exhaust heat recovery boiler provided with the economizer designed in consideration of evaporation inside, the operation of the exhaust gas supply side device such as the gas turbine is continued. Then, it is possible to discharge the boiler water and its steam inside the exhaust heat recovery boiler while passing the exhaust gas through the exhaust heat recovery boiler.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a system diagram schematically showing a water / steam system of an exhaust heat recovery boiler, and shows an example in which a recirculation system is provided in a saver, and shows a normal operation state in which steam is sent to a steam turbine. . FIG. 2 shows a state in which the boiler-owned water is being drained in the same system diagram. In addition,
The valves in the figure indicate an open state when the valve is white, and indicate a closed state when black.

In FIG. 1, the water supply from a condensate pump (not shown) passes through a economizer inlet stop valve 1 on the inlet side of the economizer and is supplied to an economizer 2 of the exhaust heat recovery boiler. Is supplied to the steam drum 6 through a water supply control valve 4 and a water supply control valve outlet valve 5 installed in a water supply pipe 3 on the outlet side. The opening of the water supply control valve 4 is adjusted so that the drum level in the steam drum 6 becomes constant. The water supply control valve bypass valve 7 may be installed in consideration of, for example, a failure of the water supply control valve 4.

Further, in order to keep the feedwater temperature at the inlet of the economizer above a certain temperature, part of the feedwater at the outlet of the economizer 2 is recirculated by the economizer recirculation pump 8. The amount of recirculation is adjusted by the economizer recirculation control valve 9.

The steam drum 6, the evaporator 10, and the heater 11 constitute a steam generator of an exhaust heat recovery boiler ("steam generator" in this specification including the claims means the same). The boiler water in the steam drum 6 circulates through the evaporator 10 and returns to the steam drum 6 again. During this circulation, the boiler water is heated in the evaporator 10 so that two phases of water and steam are formed. It returns to the steam drum 6 as a flow. In the steam drum 6, the water is separated into water and saturated steam, the water is circulated again to the evaporator 10, and the saturated steam is guided to the superheater 11 to be superheated, and then the boiler outlet steam stop valve provided in the main steam pipe 12. 13 to a steam turbine (not shown).

When the superheated steam exiting the superheater 11 has an imbalance between the evaporation amount of the exhaust heat recovery boiler and the swallowing amount of the steam turbine, for example, when all the steam cannot be supplied to the steam turn, such as at the time of startup, The surplus steam is collected by a condenser (not shown) via a turbine bypass valve 14. An air vent valve 15 at each top of the boiler and a drain valve 1 at each bottom
6, 17 and 18 are installed and opened and closed when filling and draining the boiler. Normally, the air vent valve 15
An N ₂ (nitrogen gas) system 19 is connected so that nitrogen gas as a purge gas can be charged in consideration of rust prevention on the inner surface of the boiler during a long-term shutdown of the boiler.

As described above, FIG. 1 shows a system diagram showing a water / steam system of an exhaust heat recovery boiler having a economizer recirculation system, and has described a normal operation state in which generated steam is sent to a steam turbine. In order to drain the boiler water from the exhaust heat recovery boiler as shown in FIG. 1, in the conventional method as described above, first, a gas turbine or the like that discharges high-temperature exhaust gas as a heat input source is stopped, Eliminate heat input to the boiler,
Let the boiler cool down. In this state, wait for the boiler tube and other pressure-resistant parts to cool, and then reduce the boiler water
When it cools down to less than 00 ° C., the air vent valve 15 and the drain valves 16, 17, 18 of each part are opened, and the boiler water is drained from the drain valves 16, 17, 18. Cooled boiler water drained from the drain valves 16, 17, and 18 is collected in an open-to-atmosphere tank such as a blow tank (not shown) and can be treated by a concrete drain tank used in a wastewater treatment facility. To about 60 ° C. or less. This cooling is often performed by injecting industrial water or the like as cooling water.

On the other hand, in the case where the water stored in the boiler is drained without stopping the heat input source to the exhaust heat recovery boiler such as a gas turbine, it is impossible to drain the water in a state where the temperature of the boiler water is cooled below 100 ° C. Therefore, the conventional method cannot be adopted.

Therefore, in the present invention, the steam generated from the boiler is recovered to the condenser via the turbine bypass valve 14 in a state where the water supply to the boiler is stopped, thereby evaporating the water held in the boiler. is there. Of course, the pressure-resistant parts such as the boiler tubes are designed so that the boiler is empty (meaning that the boiler water is not filled up to the specified water level) and that there is no problem with passing exhaust gas from gas turbines etc. Is a prerequisite. However, the necessity of draining the boiler's water with the exhaust gas passing is when the boiler is required to operate a gas turbine, etc. in an empty state. Considered above and already satisfied.

FIG. 2 shows a state in which the drainage method of the present invention is carried out, the supply of water to the boiler is stopped, and steam generated by the boiler is collected in a condenser via a turbine bypass valve.
The drainage method according to the first embodiment of the present invention will be specifically described below with reference to FIG. In FIG. 2, components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In the normal operation state shown in FIG. 1, the economizer inlet stop valve 1 on the inlet side of the economizer and the water supply control valve outlet valve 5 on the outlet side are fully closed. Thereby, the water supply from the boiler water supply pump is stopped, and the water supply in the economizer 2 is isolated from the steam drum 6 side.

[0024] As long as the mixed fluid of the evaporator 10 to the water-steam is present, since it is not the water pressurized in the economizer 2 is evaporated, the air vent valve 15 near the N ₂ gas filled line 1
9, by pressurizing and purging with N ₂ gas to a saturation pressure equivalent to or higher than the feedwater temperature enclosed in this portion, the economizer inlet stop valve 1, feedwater control valve outlet valve 5, and feedwater control valve bypass The water supply trapped between the valves 7 can be discharged to a blow tank (not shown) via the drain valve 16 without self-evaporation.

On the other hand, the evaporator 10 and the steam drum 6, which are downstream from the water supply control valve outlet valve 5 and the water supply control valve bypass valve 7, and the connecting pipe portion connecting them are originally designed for the purpose of evaporating. The mixture of water and steam accumulated in this portion is positively evaporated, and the steam is recovered in the condenser via the heater 11 to discharge the internal fluid in this portion. It is possible to
It is possible to substantially drain the boiler-owned water.

That is, the water supply control valve outlet valve 5 and the water supply control valve bypass valve 7 on the inlet side of the steam generator are fully closed to stop supplying water to the steam drum 6, and then the boiler on the outlet side is stopped. The outlet steam stop valve 13 is closed, or, if this valve is not installed, the steam turbine control valve (not shown) is closed to isolate the steam from flowing to the steam turbine, and at the same time, the turbine bypass valve 14 is opened. Then, the steam from the boiler is collected in a condenser (not shown).
Here, the boiler outlet steam stop valve 13 and the control valve of the steam turbine constitute an outlet side valve device.

As time elapses while maintaining this state, the water held in the boiler decreases due to evaporation, and at the same time, the pressure in the boiler also decreases. When the pressure in the boiler falls slightly below the atmospheric pressure, the turbine bypass valve 14 is fully closed. Since high-temperature exhaust gas is continuously supplied to the boiler, at this point, most of the boiler-owned water has evaporated and is collected in the condenser.

When the drainage of the steam drum 6, the evaporator 10 and the like after the water supply control valve outlet valve 5 and the water supply control valve bypass valve 7 is completed, the water supply control valve bypass valve 7 is fully opened.
The separation between the economizer 2 side and the evaporator 10 side is eliminated, and the drainage operation of the boiler possession water is completed. It should be noted that at this time, the water supply control valve outlet valve 4 should be kept fully closed in the unlikely event that a small amount of drain or the like remains on the side of the economizer 2 and the two-phase flow of water and steam evaporated from the water supply. This is because when passing through the control valve 3, there is a risk that internal components such as an internal valve having a complicated structure may be damaged, and this can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.
The form will be described. FIG. 3 is an example of a system diagram of an exhaust heat recovery boiler in a case where a condensate preheater is provided in a stage preceding the economizer.
3 shows a state in which the drainage method of the present invention is being performed. FIG.
Parts having the same functions as those described above are given the same reference numerals, and description thereof is omitted.
The valves in the figure indicate an open state when the valve is white, and indicate a closed state when black.

In FIG. 3, the water supply from a not-shown condensate pump (not shown) is preheated by a condensate preheater 21 before entering the economizer 2 and then goes to the economizer 2. Becomes The water supply from the condensate pump passes through a condensate preheater inlet valve 20, is guided to a condensate preheater 21, is heated by exhaust gas, and is sent to a deaerator (not shown) via a condensate preheater outlet valve 22. Can be Part of the feed water heated by the condensate preheater 21 is recirculated by the condensate preheater recirculation pump 23 in order to keep the inlet temperature of the condensate preheater 21 at a certain temperature or higher. The amount of recirculation is adjusted by a condensate preheater recirculation control valve 24. Reference numeral 25 denotes an air vent valve, and reference numeral 26 denotes an N ₂ (nitrogen gas) system as a purge gas, which is connected between the condensate preheater inlet valve 20 and the condensate preheater 21.
27 is a drain valve.

The feed water heated by the condensate preheater 21 is sent to a deaerator (not shown) and a boiler feed pump.
Water is supplied to the boiler again. This water supply is supplied to the economizer 2 through the economizer inlet stop valve 1, and the feedwater heated by the ecommerce 2 is supplied to the water supply control valve 4 and the water supply control valve outlet valve 5 installed in the water supply pipe 3. , And water is supplied to the steam drum 6. The opening of the water supply control valve 4 is adjusted so that the drum level in the steam drum 6 becomes constant. The water supply control valve bypass valve 7 may be installed in consideration of, for example, a failure of the water supply control valve 4. The configuration after the steam drum 6 is the same as that in FIG. 2 showing the first embodiment.

The drainage method in the waste heat recovery boiler having the condensate preheater and the recirculation system of FIG. 3 described above is as follows.

From the normal operation state, the condensate preheater inlet valve 20 and the condensate preheater outlet valve 22 on the inlet side and the outlet side of the condensate preheater 21 are fully closed to isolate around the condensate preheater 21. .
Similarly, the inlet / outlet valve 1, the water supply control valve outlet valve 5, and the water supply control valve bypass valve 7, which are the inlet side and outlet side of the economizer 2, are fully closed. Thereby, the water supply from the boiler water supply pump is stopped, and the water supply in the economizer 2 is isolated from the steam drum 9 side.

As long as the mixed fluid of water and steam is present in the evaporator 10, the pressurized feedwater in the condensate preheater 21 and the economizer 2 does not evaporate.
The condensate preheater inlet valve 20 is pressurized from the nearby N ₂ gas filling lines 26 and 19 with N ₂ gas at a pressure higher than the saturation pressure corresponding to the temperature of the feedwater sealed in these parts.
From the condensate preheater outlet valve 22
In addition, the water confined between the economizer inlet stop valve 1, the water supply control valve outlet valve 4 and the water supply control valve bypass valve 5 is supplied to the blow tank (not shown) via the drain valves 27 and 16 without self-evaporation. It is possible to discharge.

An evaporator 10 constituting a steam generator downstream from the water supply control valve outlet valve 5 and the water supply control valve bypass valve 7.
For the steam drum 6 and the connecting pipe portion connecting them, the boiler water can be discharged in the same manner as in the case of the first embodiment described above with reference to FIG.

Next, a third embodiment of the present invention will be described with reference to FIG.
The form will be described. FIG. 4 is an example of a system diagram of an exhaust heat recovery boiler in which the feedwater control valve 4 is installed on the upstream side of feedwater of the economizer 2 and a part of feedwater is allowed to evaporate at the outlet of the economizer 2. Shows a state in which the drainage method of the present invention is performed.
The parts having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The valves in the figure indicate an open state when the valve is white, and indicate a closed state when black.

In FIG. 4, water supplied from a boiler water supply pump (not shown) is supplied to an economizer inlet stop valve 1 on the inlet side of the economizer 2.
After passing through the water supply control valve 4, the water is supplied to the economizer 2, and the feedwater heated by the economizer 2 is supplied to the steam drum 6. The water supply control valve 4 installed upstream of the economizer 2 has a constant drum level in the steam drum 6 as in the first embodiment of FIG. 2 and the second embodiment of FIG. Adjust the opening so that Steam drum 6
Subsequent steps are the same as in the case of FIG. 2 showing the first embodiment.

A water supply control valve as shown in FIG. 4 described above is installed upstream of the economizer to allow a part of feedwater to evaporate at the economizer outlet. The drainage method is as follows.

From the normal operation state, the economizer inlet stop valve 1 is fully closed. Thereby, the water supply from the boiler water supply pump is stopped. On the other hand, in the case of a system configuration in which the feedwater control valve 4 is installed upstream of the economizer 2, the feedwater warmed by the economizer 2 is allowed to partially evaporate at its outlet. Often designed. In general, there is no isolation valve installed between the economizer 2 and the steam drum 6, so that the water supply in the economizer 2 is also controlled by the evaporator 10 and the steam drum 6 and the communication between them. As in the case of the pipe section, the water stored in the boiler is discharged in the same manner as in the first embodiment described with reference to FIG.

That is, the economizer inlet stop valve 1 is fully closed,
After the water supply to the economizer 2 and the steam drum 6 is stopped, the boiler outlet steam stop valve 13 is closed, or, if this valve is not installed, the steam turbine control valve (not shown) is closed to close the steam generator. Isolate the turbine so that steam does not flow, and at the same time open the turbine bypass valve 14,
The steam from the boiler is collected in a condenser not shown.

As time elapses while maintaining this state, the water held in the boiler decreases due to evaporation, and at the same time, the pressure in the boiler also decreases. When the pressure in the boiler falls slightly below the atmospheric pressure, the turbine bypass valve 14 is fully closed. Since high-temperature exhaust gas is continuously supplied to the boiler, at this point, most of the boiler-owned water has evaporated and is collected in the condenser.

As described above, the first embodiment of the present invention is described.
In any of the embodiments to the third embodiment, the operation of the exhaust gas supply side device such as a gas turbine is continued, and while the exhaust gas is passed through the exhaust heat recovery boiler, the boiler water and the steam inside the exhaust heat recovery boiler are discharged. It is possible to discharge safely and in a short time.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes may be made to the specific structure within the scope of the present invention. Needless to say.

[0044]

(1) As described above, according to the first aspect of the present invention,
A method for draining a waste heat recovery boiler is provided, comprising: a economizer having a purge gas inlet and a drain valve; and a steam generator connected to a condenser via a turbine bypass valve. In the exhaust heat recovery boiler that generates the gas, the inlet side and the outlet side of the economizer are closed and the purge gas is fed from the purging gas supply means while the exhaust gas is passed to drain the boiler water in the economizer. The system is configured to drain water from the valve, close the inlet and outlet sides of the steam generator, evaporate the water held by the boiler in the steam generator, and discharge it to the condenser through the turbine bypass valve. Even in an exhaust heat recovery boiler equipped with a economizer that is not designed to take into consideration the exhaust gas supply side device such as a gas turbine, the operation continues, and the exhaust gas is passed through the exhaust heat recovery boiler. Boiler held water inside the heat recovery boiler and it is possible to discharge the steam safely and in a short time.

(2) According to the second aspect of the present invention, a method of draining an exhaust heat recovery boiler includes a condensate preheater and a economizer, each having a purge gas feeding means and a drain valve, a turbine bypass valve. And a steam generator connected to the condenser through the exhaust heat recovery boiler that generates the working steam of the steam turbine by the exhaust gas. In each case, the inlet side and the outlet side are closed, purge gas is supplied from the purge gas supply means to drain the boiler water from the drain valve, and the inlet side and the outlet side of the steam generator are closed. It is configured to evaporate the boiler-owned water and discharge it to the condenser through the turbine bypass valve.Therefore, it is equipped with a condenser preheater and a economizer that are not designed in consideration of evaporating inside. Exhaustion In the recovery boiler, the operation of the exhaust gas supply side device such as a gas turbine is continued, and the boiler water and its steam inside the waste heat recovery boiler are safely and quickly removed while the exhaust gas is passed through the waste heat recovery boiler. Can be discharged.

(3) According to the third aspect of the present invention, a method for draining an exhaust heat recovery boiler is provided by using a condenser and a condenser connected to a downstream side of the condenser and a turbine bypass valve. A steam generator connected to the exhaust heat recovery boiler that generates working steam for the steam turbine by the exhaust gas, in a state where the exhaust gas is passed, closing the inlet side of the economizer and the outlet side of the steam generator, Since the boiler water in the coal-saving unit and the steam generator is evaporated and discharged to the condenser through the turbine bypass valve, the boiler is designed in consideration of evaporation inside. In an exhaust heat recovery boiler equipped with a charcoal unit, the operation of the exhaust gas supply side device such as a gas turbine is continued, and while the exhaust gas is passed through the exhaust heat recovery boiler, the boiler water inside the exhaust heat recovery boiler and its steam Safely and quickly It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a water / steam system of an exhaust heat recovery boiler according to a first embodiment of the present invention, showing a normal operation state in which steam is sent to a steam turbine.

FIG. 2 is the same schematic system diagram as FIG. 1, showing a state in which boiler-owned water is being drained.

FIG. 3 is a schematic system diagram of a water / steam system of an exhaust heat recovery boiler according to a second embodiment of the present invention.

FIG. 4 is a schematic system diagram of a water / steam system of an exhaust heat recovery boiler according to a third embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 economizer inlet stop valve 2 economizer 4 feedwater control valve 5 feedwater control valve outlet valve 6 steam drum 7 feedwater control valve bypass valve 10 evaporator 11 superheater 13 boiler outlet steam stop valve 14 turbine bypass valve 16,17, 18 Drain valve 19 N ₂ (nitrogen gas) system 20 Condenser preheater inlet valve 21 Condenser preheater 22 Condenser preheater outlet valve 26 N ₂ (nitrogen gas) system 27 Drain valve

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F22B 1/18 F22B 1/18 E F22D 11/00 F22D 11/00 H

Claims (3)

[Claims] A steam generator connected to a condenser via a turbine bypass valve, wherein the steam generator is configured to generate working steam of a steam turbine by exhaust gas. In the heat recovery boiler, with the exhaust gas passing through, the inlet side and the outlet side of the economizer are closed, purge gas is sent from the purge gas supply means, and the boiler water in the economizer is drained from the drain valve. A method for draining an exhaust heat recovery boiler, comprising closing an inlet side and an outlet side of the steam generator, evaporating water contained in the boiler, and discharging the water to a condenser through the turbine bypass valve. 2. A condensate preheater and a economizer, each having a purge gas feeding means and a drain valve, and a steam generator connected to the condenser via a turbine bypass valve. In the exhaust heat recovery boiler that generates the working steam, the inlet side and the outlet side of each of the condensate preheater and the economizer are closed while the exhaust gas is passed, and purge gas is supplied from the purge gas supply means. Draining the boiler water from the drain valve, closing the inlet and outlet sides of the steam generator, evaporating the boiler water in the apparatus, and discharging it to the condenser through the turbine bypass valve. A method for draining an exhaust heat recovery boiler. 3. A steam saver, and a steam generator disposed downstream of the steam saver and connected to a condenser via a turbine bypass valve to generate working steam for a steam turbine by exhaust gas. In the exhaust heat recovery boiler, the inlet side of the economizer and the outlet side of the steam generator are closed with the exhaust gas passing through,
A method for draining an exhaust heat recovery boiler, comprising: evaporating water held in a boiler in the coal saver and in the steam generator and discharging the water to a condenser through the turbine bypass valve.