JPH11304101A - Waste heat recovery boiler and operating method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drainage control and piping system arrangement in which water hammer is prevented at the time of drainage during banking or restart of a waste heat recovery boiler. SOLUTION: At the time of drainage during hot banking, for example, difference between the steam pressure (pressure gauge 15) in the outlet steam pipe 10 of a superheater and the steam pressure (pressure gauge 14) in a steam drum 14 is operated. When the operated differential pressure reaches a set level, a drain valve 12 in the outlet steam pipe 10 of the superheater is opened so that steam is not entrained into the outlet steam pipe of the superheater at the time of drainage thus preventing water hammer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting an exhaust heat recovery boiler, and more particularly, to preventing a water hammer generated in an exhaust heat recovery boiler supplying steam generated in a steam drum to a steam turbine through a main steam pipe. It is related to the optimal drain discharge to perform.

[0002]

2. Description of the Related Art FIG. 8 shows a system diagram of an exhaust heat recovery boiler according to the prior art. First, water supplied by the water supply pump 1 passes through the economizer 2 and is supplied to the steam drum 3.
The water of the steam drum 3 passes through the downcomer 4 and the evaporator 5 and returns to the steam drum 3. The steam generated from the steam drum 3 is connected to a steam drum outlet connecting pipe 6, a superheater inlet port 7, a superheater 8,
The steam is supplied to a steam turbine (not shown) through a superheater outlet shifter 9, a superheater outlet steam pipe 10, and a superheater outlet stop valve 11.

On the other hand, high-temperature exhaust gas from a gas turbine (not shown) exchanges heat with a superheater 8, an evaporator 5 and a economizer 2 installed in a flue 13 to generate steam.

By the way, during banking, the turbine side is stopped, and drain condenses in the superheater outlet steam pipe 10. A drain valve 12 is provided for discharging the drain.

Conventionally, drainage is performed by opening the drain valve 12 when the turbine is started up. However, when the boiler is started up, especially when cold start is performed after a long stoppage, a large amount of drainage is accumulated and the drum pressure is increased. Drainage could not be sufficiently discharged because of the small size. For this reason, Japanese Patent Application Laid-Open Nos. 6-101802 and 6-249
As described in Japanese Patent Publication No. 402, while the residual pressure is high during hot banking, the drain valve is fully opened for a certain period of time to drain the drain. However, in order to enhance the banking effect, the superheater outlet stop valve 11 is often installed in the outlet steam pipe 10 of the superheater 8 in recent years. In order to install the stop valve 11 on the sidewalk or the like, the outlet steam pipe 10 of the superheater 8 may have a U-shaped pipe configuration.

[0006]

In this case, as shown in FIG. 9, the interior of the first vertical portion 10a, the first horizontal portion 10b and the second vertical portion 10c of the superheater outlet steam pipe 10 and the second horizontal portion are provided. When the drain is accumulated in the second horizontal portion 10d before the superheater outlet stop valve 11 provided in 10d, the superheater outlet stop valve 11 provided in the second horizontal portion 10d is closed, Even if the drain valve 12 provided in the pipe connected to the first horizontal portion 10b is opened, the drain valve 12 stays in the superheater outlet steam pipe 10 having a U-shaped pipe configuration as shown in FIG. The drain on the superheater 8 side comes off first, and a head difference H is generated between the superheater 8 side and the superheater stop valve 11 side.

When the drain on the side of the superheater 8 reaches the first horizontal portion 10b, the drain on the side of the stop valve 11 suddenly flows to the side of the superheater 8 due to the above-mentioned head difference H. The steam on the side of the superheater 8 is entrained in the air, and the entrained steam is cooled by the drain and rapidly drained.
At this time, as shown in FIG. 10B, the drain water collides with the drain water in an attempt to fill the space formed by the rapid drainage of steam, and a strong impact (referred to as a water hammer) occurs. .

If a water hammer occurs in the U-tube horizontal section 10b, there is a problem that the steam pipe 10 at the outlet of the superheater is damaged by vibration or impact.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to control draining and to configure a piping system so that a water hammer does not occur during draining of a waste heat recovery boiler during banking and restarting. To provide.

[0010]

The object of the present invention is solved by the following constitutions. (1) An evaporator disposed in an exhaust gas channel, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and an exhaust gas flow for superheating the steam from the steam drum In a waste heat recovery boiler provided with a superheater disposed in a passage and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe includes A stop valve for stopping the flow of steam, and a superheater outlet pressure gauge for measuring the superheater outlet steam pressure upstream of the stop valve are provided, and a drain valve is connected to the superheater outlet steam pipe. The steam drum is provided with a drum pressure gauge for measuring the steam pressure in the drum.From the measured values of the superheater outlet pressure gauge and the drum pressure gauge at the time of drain discharge of the superheater outlet steam pipe, the superheater outlet steam pressure and Calculate the pressure difference from the steam drum pressure, Heat recovery boiler provided with a control device which is differential pressure opens the drain valve of the superheater outlet steam pipe reaches the set value.

(2) An evaporator disposed in the exhaust gas channel, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a device for superheating the steam from the steam drum In a waste heat recovery boiler provided with a superheater disposed in the exhaust gas flow path of the above and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe is connected to the superheater outlet. From a substantially U-shaped tube comprising a first vertical portion, a first horizontal portion following the first vertical portion, a second vertical portion following the first horizontal portion, and a second horizontal portion following the second vertical portion. A stop valve for stopping the flow of steam in the superheater outlet steam pipe is installed at the second horizontal portion or the second vertical portion of the superheater outlet steam pipe, and a drain valve is connected to a lower portion of the first horizontal portion; A differential pressure gauge for measuring a differential pressure of the vapor pressure between the horizontal portion and the second horizontal portion or the second vertical portion on the upstream side of the stop valve is provided, During draining of the heat outlet steam pipe, when the detected value of the differential pressure gauge reaches the target pressure difference heat recovery steam control device provided for opening the drain valve.

(3) An evaporator disposed in the exhaust gas channel, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a device for heating the steam from the steam drum A superheater disposed in the exhaust gas flow path of the steam drum, a steam drum outlet connecting pipe serving as a vapor flow path provided between the steam drum and the superheater, and a superheater for guiding the steam from the superheater to the outside of the exhaust gas flow path In an exhaust heat recovery boiler provided with an outlet steam pipe, the superheater outlet steam pipe has a first vertical portion of the superheater outlet, a first horizontal portion following the first vertical portion, and a second vertical portion following the first horizontal portion. And a second horizontal portion following the second vertical portion, a substantially U-shaped tube, and a stop valve for stopping the flow of steam in the superheater outlet steam pipe is installed at the second horizontal portion of the superheater outlet steam pipe. And a drain valve connected to the lower portion of the first horizontal portion, and connected to a steam drum or a steam drum outlet. Tube or superheater installed heat recovery steam balance pipe to contact the second horizontal portion of the upstream side of any and check valve of the outlet steam pipe.

(4) An evaporator disposed in the exhaust gas channel, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a device for superheating the steam from the steam drum In a waste heat recovery boiler provided with a superheater disposed in the exhaust gas flow path of the above and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe is connected to the superheater outlet. From a substantially U-shaped tube comprising a first vertical portion, a first horizontal portion following the first vertical portion, a second vertical portion following the first horizontal portion, and a second horizontal portion following the second vertical portion. The drain valve is connected to a lower portion of the first horizontal portion, and a stop valve for stopping the flow of steam in the superheater outlet steam pipe is connected to the second horizontal portion of the superheater outlet steam pipe downstream of the connection position of the drain valve. The first vertical section of the superheater steam pipe near the superheater outlet and the upstream side of the stop valve installation position Heat recovery boiler provided with a communication pipe serving as a steam flow path between the two horizontal portions.

(5) An evaporator disposed in the exhaust gas channel, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a device for heating the steam from the steam drum In a waste heat recovery boiler provided with a superheater disposed in the exhaust gas flow path of the above and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe is connected to the superheater outlet. From a substantially U-shaped tube comprising a first vertical portion, a first horizontal portion following the first vertical portion, a second vertical portion following the first horizontal portion, and a second horizontal portion following the second vertical portion. The drain valve is connected to the lower part of the first horizontal portion, and a stop valve for stopping the flow of steam in the superheater outlet steam pipe is connected to the first superheater outlet steam pipe.
Exhaust heat recovery boiler installed downstream from the drain valve connection position in the horizontal section.

(6) An evaporator disposed in the exhaust gas channel, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a device for superheating the steam from the steam drum In a waste heat recovery boiler provided with a superheater disposed in an exhaust gas flow path of the superheater and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, when drain in the superheater outlet steam pipe is discharged. When the pressure difference between the steam pressure in the superheater outlet steam pipe and the steam drum pressure reaches a set value while the flow of steam in the superheater outlet steam pipe is stopped, the exhaust heat recovery drains the drain from the superheater outlet steam pipe. How to operate the boiler.

[0016] According to the above-mentioned respective solutions, steam is not entrained in the horizontal pipe during draining during banking or when the boiler is restarted, so that a water hammer can be prevented.

[0017]

Embodiments of the present invention will be described. FIG. 1 shows an example of an exhaust heat recovery boiler provided with a control device that controls a drain valve based on a differential pressure of a pressure gauge and does not generate a water hammer. In the exhaust heat recovery boiler shown in FIG. 1, components having the same functions as those of the boiler described in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

A drum pressure gauge 14 for measuring the pressure in the drum 3 and a superheater outlet pressure gauge 15 for measuring the pressure in the superheater outlet steam pipe 10 are provided, and the pressure obtained by the two pressure gauges 14 and 15 is provided. The values are converted into electric signals by pressure transmitters 16 provided in the control device 19, and the pressure difference between the pressure gauges 14 and 15 is compared by the pressure comparator 17 based on the electric signals. The signal based on the pressure difference is used as an output of the control device 19 to control the opening and closing of the drain valve 12. For example, the drain valve 12 and 10-20% opening when the pressure difference between the pressure gauge 14 and 15 were approximately 1.5mH ₂ O, to discharge the drain.

FIG. 4 shows the timing at which the drain valve 12 is opened. Drum 3 measured by drum pressure gauge 14
And the outlet pressure of the superheater 8 measured by the superheater outlet pressure gauge 15, the drain accumulates during the banking. Therefore, the drain pressure of the superheater 8 in the U-shaped superheater outlet evaporating pipe 10 increases with the passage of time. And a pressure difference corresponding to the head is generated. When the pressure difference reaches the set pressure, the drain valve 12 is set to 10-20% from the pressure comparison device 17.
An electric signal to be opened is transmitted, and the drain valve 12 is slowly opened. As the drain comes off, the pressure difference generated from the water head is alleviated, the pressure difference between the pressure of the drum 3 and the outlet pressure of the superheater 8 becomes small, and when all the drain comes out of the superheater outlet steam pipe 10, the pressure difference becomes almost zero. It becomes 0. At this time, a control signal for completely closing the drain valve 12 is given, and the drain valve 12 is closed. Further, since the drain accumulates with the passage of time, a pressure difference is generated. By incorporating the control device 19 as described above, the drain can be effectively discharged without causing a water hammer.

Also, as shown in FIG.
The pressure difference between the second horizontal portion 10d of the superheater outlet steam pipe 10 and the first horizontal portion 10b of the superheater outlet steam pipe 10 on the upstream side is measured by a differential pressure gauge 18, and the control device 19 is determined from the differential pressure value.
The water hammer can be similarly prevented by estimating the drain amount by controlling the opening degree of the drain valve 12 by a method similar to the control procedure shown in FIG. 4 described above.

As shown in FIG. 3, even when the superheater outlet stop valve 11 is installed in the vertical portion 10c on the downstream side of the first horizontal portion 10b, the vertical stop portion 10c on the upstream side is also provided. A differential pressure gauge 18 is installed, a pressure difference between the first horizontal portion 10b and the vertical portion 10c is measured by the differential pressure gauge 18, a drain amount is estimated from the differential pressure value, and the same as the control procedure shown in FIG. 4 described above. The water hammer can be similarly prevented by controlling the opening of the drain valve 12 by a method.

By installing such a control system, it is possible to prevent water hammer in the superheater outlet steam pipe 10 during banking.

The embodiment of the present invention shown in FIG. 5 has an exhaust heat recovery boiler having a piping system when the balance pipe 20 is installed between the steam drum outlet connection pipe 6 and the superheater outlet stop valve 11 upstream side. An example will be described. In the heat recovery steam generator shown in FIG. 5, components having the same functions as those of the boiler described with reference to FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

When the balance pipe 20 is installed between the steam drum outlet connection pipe 6 and the superheater outlet steam pipe 10 on the upstream side of the superheater outlet stop valve 11, the steam bypasses the superheater 8 during normal operation. Therefore, it is necessary to adjust the flow rate of the bypass steam or not to flow the bypass steam. For this purpose, the balance pipe 20 may be provided with an orifice 22 or a valve (not shown). When draining is performed during banking, since the drains of the vertical portions 10a and 10c decrease almost at the same time, steam is not involved in the U-tube horizontal portions 10b and 10d unlike the case where the balance pipe 20 is not installed. , No water hammer. Note that the take-out position of the balance pipe 20 may be the steam drum 3 instead of the steam drum outlet connection pipe 6.

Similar to the piping system shown in FIG. 5, a piping system having the configuration shown in FIG. 6 does not generate a water hammer because the same operation as described above is obtained. In this case, if a bypass pipe 23 connecting the first vertical pipe 10a and the second horizontal pipe 10d of the superheater outlet steam pipe 10 near the superheater outlet header 9 is provided, when draining is performed during banking,
Since the drains of the vertical portions 10a and 10c decrease almost at the same time, steam is not involved in the U-tube horizontal portions 10b and 10d unlike the case where the bypass pipe 23 is not installed, so that no water hammer occurs.

In the embodiment shown in FIG. 7, a drain valve 12 is provided in a horizontal portion 10b of a superheater outlet steam pipe 10, and a superheater outlet valve 11 is provided in a horizontal portion 10b downstream of the drain valve 12. The piping system diagram is shown. In this case, FIG.
And since it is a piping system which does not cause steam entrainment as described in FIG. 10 (b), drain can be discharged without causing a water hammer. further,
The water hammer can be prevented beforehand by using the configurations shown in the above drawings together.

[0027]

According to the present invention, since the piping system does not cause entrainment of steam, the drain can be discharged from the steam piping without causing a water hammer at the time of banking or the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an exhaust heat recovery boiler that controls an opening of a drain valve from a differential pressure of a pressure gauge according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an exhaust heat recovery boiler that controls an opening degree of a drain valve based on a differential pressure value of a differential pressure gauge of a superheater outlet steam pipe according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of an exhaust heat recovery boiler that controls an opening degree of a drain valve based on a differential pressure value of a differential pressure gauge of a superheater outlet steam pipe according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a timing of opening a drain valve according to the embodiment of the present invention.

FIG. 5 is a schematic diagram of an exhaust heat recovery boiler showing a piping system when the balance piping according to the embodiment of the present invention is installed.

FIG. 6 is a schematic diagram of an exhaust heat recovery boiler showing a piping system when a bypass pipe according to an embodiment of the present invention is installed.

FIG. 7 is a schematic diagram of an exhaust heat recovery boiler showing a piping system according to an embodiment of the present invention.

FIG. 8 is a diagram showing a system of an exhaust heat recovery boiler according to a conventional technique.

FIG. 9 is a diagram showing a drain retention state during banking of an exhaust heat recovery boiler according to a conventional technique.

FIG. 10 is a diagram showing a drain discharge state and a state when a hammer occurs due to opening of a drain valve of a waste heat recovery boiler according to a conventional technique.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 feedwater pump 2 economizer 3 steam drum 4 downcomer 5 evaporator 6 steam drum outlet connecting pipe 7 superheater inlet 8 superheater 9 superheater outlet header 10 superheater outlet steam pipe 10 a first vertical pipe 10 b first Horizontal part 10c Second vertical pipe 10d Second horizontal part 11 Superheater outlet stop valve 12 Drain valve 13 Flue 14 Drum pressure gauge 15 Superheater outlet pressure gauge 16 Pressure transmitter 17 Pressure comparison device 18 Differential pressure gauge 19 Control device 20 Balance Piping 22 Orifice 23 Bypass piping

Continued on the front page (72) Inventor Norio Shimono 6-9 Takara-cho, Kure City, Hiroshima Prefecture Inside Babcock Hitachi Kure Factory (72) Inventor Toshinori Shigenaka 6-9 Takara-cho Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory Inside

Claims (6)

[Claims] 1. An evaporator disposed in an exhaust gas passage, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a steam drum for superheating steam from the steam drum. In an exhaust heat recovery boiler provided with a superheater arranged in an exhaust gas flow path and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe includes the steam A stop valve for stopping the flow of steam in the pipe, and a superheater outlet pressure gauge for measuring the superheater outlet steam pressure on the upstream side of the stop valve, and a drain valve connected to the superheater outlet steam pipe, Further, the steam drum is provided with a drum pressure gauge for measuring the steam pressure in the drum, and the superheater outlet steam pressure is measured based on the measured values of the superheater outlet pressure gauge and the drum pressure gauge when the drain of the superheater outlet steam pipe is discharged. Calculate the differential pressure between the Heat recovery steam differential pressure obtained by, characterized in that the control device is provided to open the drain valve of the superheater outlet steam pipe reaches the set value. 2. An evaporator disposed in an exhaust gas passage, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a steam drum for heating the steam from the steam drum. In an exhaust heat recovery boiler provided with a superheater disposed in an exhaust gas flow path and a superheater outlet steam pipe that guides steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe is connected to the superheater outlet. The U-shaped tube comprises a first vertical portion, a first horizontal portion following the first vertical portion, a second vertical portion following the first horizontal portion, and a second horizontal portion following the second vertical portion. Installing a stop valve for stopping the flow of steam in the superheater outlet steam pipe at the second horizontal portion or the second vertical portion of the superheater outlet steam pipe, connecting the drain valve to a lower portion of the first horizontal portion, Pressure gauge to measure the differential pressure of the vapor pressure between the second part and the second vertical part or the second vertical part upstream of the stop valve, During draining of the outlet steam pipe, the exhaust heat recovery boiler, characterized in that the detection value of the differential pressure gauge is provided with a control device to open the drain valve reaches the set pressure differential. 3. An evaporator disposed in an exhaust gas passage, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a steam drum for heating the steam from the steam drum. A superheater arranged in the exhaust gas passage, a steam drum outlet connecting pipe serving as a steam passage provided between the steam drum and the superheater, and a superheater outlet for guiding steam from the superheater to the outside of the exhaust gas passage In a waste heat recovery boiler provided with a steam pipe, a superheater outlet steam pipe has a first vertical portion at a superheater outlet, a first horizontal portion following the first vertical portion, and a second vertical portion following the first horizontal portion. And a second horizontal portion following the second vertical portion, and a stop valve for stopping the flow of steam in the superheater outlet steam pipe is provided at the second horizontal portion of the superheater outlet steam pipe. , A drain valve connected to the lower part of the first horizontal portion, and a steam drum or a steam drum outlet connecting pipe Heat recovery steam Rui, characterized in that it has established a balance pipe connecting the second horizontal portion of the upstream side of any and stop valve of superheater outlet steam pipe. 4. An evaporator disposed in an exhaust gas passage, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a steam drum for superheating steam from the steam drum. In an exhaust heat recovery boiler provided with a superheater disposed in an exhaust gas flow path and a superheater outlet steam pipe that guides steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe is connected to the superheater outlet. The U-shaped tube comprises a first vertical portion, a first horizontal portion following the first vertical portion, a second vertical portion following the first horizontal portion, and a second horizontal portion following the second vertical portion. Also, a drain valve is connected to a lower portion of the first horizontal portion, and a stop valve for stopping the flow of steam in the superheater outlet steam pipe is connected to a second end of the superheater outlet steam pipe downstream of the connection position of the drain valve.
Installed in a horizontal section, the first of the superheater steam pipe near the superheater outlet
An exhaust heat recovery boiler, wherein a communication pipe serving as a steam flow path is provided between a vertical portion and a second horizontal portion upstream of the stop valve installation position. 5. An evaporator disposed in an exhaust gas passage, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a steam drum for superheating steam from the steam drum. In an exhaust heat recovery boiler provided with a superheater disposed in an exhaust gas flow path and a superheater outlet steam pipe that guides steam from the superheater to the outside of the exhaust gas flow path, the superheater outlet steam pipe is connected to the superheater outlet. The U-shaped tube comprises a first vertical portion, a first horizontal portion following the first vertical portion, a second vertical portion following the first horizontal portion, and a second horizontal portion following the second vertical portion. The drain valve was connected to the lower portion of the first horizontal portion, and a stop valve for stopping the flow of steam in the superheater outlet steam pipe was installed on the downstream side of the drain valve connection position of the first horizontal portion of the superheater outlet steam pipe. An exhaust heat recovery boiler characterized in that: 6. An evaporator disposed in an exhaust gas passage, a steam drum for separating steam from a fluid consisting of water and steam heated by the evaporator, and a steam drum for superheating steam from the steam drum. In a waste heat recovery boiler provided with a superheater arranged in an exhaust gas flow path and a superheater outlet steam pipe for guiding steam from the superheater to the outside of the exhaust gas flow path, at the time of drain discharge in the superheater outlet steam pipe, With the flow of steam in the superheater outlet steam pipe stopped, when the pressure difference between the steam pressure in the superheater outlet steam pipe and the steam drum pressure reaches a set value, drain is discharged from the superheater outlet steam pipe. Operating method of waste heat recovery boiler.