JPS5928804B2 - Superheater desuperheater water injection pipe water hammer prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing the generation of water in a superheater desuperheater water injection pipe and a superheater communication pipe when a once-through boiler is started or during forced cooling when the boiler is stopped.

Conventionally, such water hammers have been dealt with by increasing the startup speed, that is, the time it takes to start up, or by slowing down the forced cooling speed, but the problem still remains that it is difficult to prevent water hammers. there were.

This invention confirms that the primary cause of water hammer is the movement of steam in the water injection pipe of the superheater and desuperheater, and proposes the following water hammer prevention device.

First, the once-through boiler, superheater attemperator, and related pipe lines will be explained with reference to FIG.

Steam from the cage 1 passes through the primary superheater 2, enters the superheater attemperator 8, injects water from the superheater attemperator water injection nozzle 9 to adjust the temperature, and passes through the superheater stop valve 4 to the secondary superheater 5. sent to.

Also, at startup, pipe line 15.2 branches from overheating connecting pipe 3.
Secondary superheater bypass valve 14. Flushes to flash tank 7 via secondary superheater bypass pipe 6.

At this time of startup, the superheater communication pipe 3 and the superheater desuperheater water injection pipe 10 are filled with water, and the temperature of the superheater desuperheater water injection pipe 10 is significantly lower.

Further, as the startup time elapses, the temperature of the superheater communication pipe 3 rises, and finally turns into steam.

However, the superheater desuperheater water injection pipe 10 has a horizontal pipe section located at a level higher than the level of the superheater communication pipe 3, and the pipe slope slopes downward toward the superheater desuperheater water injection adjustment valve 12. Therefore, a portion of the water in the horizontal pipe portion flows into the superheater connecting pipe 3 through the superheater desuperheater water injection nozzle 9 due to the hydrostatic head while replacing steam in the superheater connecting pipe 3.

At this time, water and steam mix in the vertical pipe section near the water injection nozzle 9 of the superheater/desuperheater water injection pipe 10, generating a small water hammer.

It is also believed that this pressure fluctuation causes the water in the horizontal pipe to mix with steam in the two-layer steam section, resulting in an even larger water hammer.

During forced cooling when the boiler is stopped, the pressure in the superheater communication pipe 3 and the pressure in the superheater desuperheater water injection pipe 10 are the same.

Regarding the temperature, at the point where forced cooling is completed, the fluid in the superheater communication pipe 3 is as low as, for example, 80°C, but the water accumulated in the superheater desuperheater water injection pipe 10 is not forcedly cooled but is naturally cooled. In that case, the temperature is as high as about 200°C.

For this reason, when the fluid temperature in the superheater connecting pipe 3 reaches a layer level and the forced cooling is completed, and the boiler feed water pump is stopped, the pressure in the superheater connecting pipe 3 instantly decreases, and the pressure in the superheater desuperheater Flushing occurs in the water accumulated in the water pipe 10, and steam is ejected from the superheater desuperheater water injection nozzle 9 into the superheater connecting pipe 3, generating water in the superheater connecting pipe 3.

When water hammer occurs, piping, supports, and valves.

It is desirable to prevent this from happening as it may cause damage to the heat insulating material.

This invention was developed based on the confirmation that water hammer is caused by the temperature difference between the superheater communication pipe 3 and the superheater desuperheater water injection pipe 10 as described above. As shown in FIG. 3, a temperature balancing pipe is provided which can be flushed from the superheater/desuperheater water injection pipe 10 to the flash tank in order to balance the temperature of these two pipes.

In FIG. 2, a superheater desuperheater water injection pipe 10 between the superheater desuperheater water injection stop valve 11 and the superheater desuperheater water injection nozzle 9 is shown.
The more branched temperature balance line 13 is connected to a bypass valve 16 which in turn connects via line 17 with the flush tank 7 .

FIG. 3 shows a case where a stop valve 18 is provided in the temperature balance pipe 13 and connected to the conduit 15, and the bypass valve 16 and conduit 17 in FIG. 2 are unnecessary.

By providing such a temperature balance pipe 13, at the time of startup or forced cooling, the fluid in the superheater communication pipe 3 is transferred from the superheater desuperheater water injection nozzle 9 to the superheater desuperheater water injection pipe 10.
Since the water flows into the water and flashes to the flash tank 7 via the temperature balance pipe 13, there is no difference in pressure and temperature between the superheater communication pipe 3 and the superheater desuperheater water injection pipe 10, thereby preventing water hammer. can do.

In addition, in Figures 2 and 3, the flow rate for temperature balancing the superheater connection pipe 3 and the superheater desuperheater water injection pipe 10 is extremely small, but considering economic efficiency, it is flushed to the flash tank 7, and the final The water is then collected into a condenser (not shown) and used again as boiler water supply.

Further, FIG. 4, which is another embodiment of the present invention, is a case where there is no need to particularly consider economic efficiency.
3.17 and the pressure reducing valve 16, the drain flows into the blow tank 23, where it is separated into water and air.The drain passes through the drain pipe 19 and the drain pipe 20, and is discharged from the drain pipe 21.

Further, the steam generated in the blow tank 23 is discharged to the atmosphere through the steam pipe 22.

In short, this invention provides a temperature equilibrium pipe branching from the water injection pipe connecting the superheater desuperheater water injection valve and the superheater desuperheater water injection nozzle, and at the time of startup or forced boiler cooling, the temperature equilibrium pipe is connected to the flash tank. The present invention is characterized by a device that prevents water from being generated in the water injection pipe and the superheater communication pipe by flushing the water or discharging it outside the boiler circulation system.

By implementing this invention, water hammer that occurs in the superheater communication pipe and the superheater desuperheater water injection pipe during startup or forced cooling can be prevented, and related pipes, attached valves, desuperheaters, etc. It also ensures safety and has a great effect on boiler operation safety.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the concept of the relationship between the superheater pipe line and the superheater desuperheater water injection pipe of a conventional once-through boiler. Fig. 2 and Fig. 3 are diagrams showing the pipe line when the temperature balance pipe according to the present invention is installed. FIG. 4 is a drawing showing a pipe line when a blow tank 23 is provided when there is no need to particularly consider economic efficiency. 1... Cage, 2... Primary superheater, 3
...Superheater connection pipe, 4...Superheater stop valve, 5...Secondary superheater, 6...Secondary superheater bypass pipe, 7 ...Flash tank, 8
......Superheater desuperheater, 10...Superheater desuperheater water injection pipe, 11...Superheater desuperheater water injection stop valve, 13... Temperature balance pipe, 14... Secondary superheater bypass valve, 16... Bypass valve, 17
... Pipe line, 18 ... Stop valve, 19 ...
...Drain pipe, 20...Drain tank, 21...
...Drain pipe, 22...Exhaust pipe, 23...
...Blow tank.

Claims (1)

[Claims] The 11th superheater, the superheater desuperheater, and the secondary superheater are located in order in the steam flow direction, and the flash tank 7 branches from the superheater communication pipe 3 that connects the superheater desuperheater and the secondary superheater. In a boiler equipped with a pipe line connected to a superheater desuperheater water injection valve 11 and a superheater desuperheater water injection nozzle 9, the water in the pipe is branched from the superheater desuperheater water injection pipe 10 and the water in the pipe is discharged. A superheater/desuperheater/water injection pipe water hammer prevention device characterized in that a pipe 13 is provided.