JPS609533Y2 - Saturated water circulation device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a saturated water circulation device for a once-through boiler, and particularly to a saturated water circulation device that can be suitably implemented in a variable pressure Penson boiler that can be used over a wide load range.

For variable pressure once-through boilers that can be used over a wide load range, such as the variable pressure Penson boiler, a storage tank is placed in the startup bypass system to store saturated water, and this saturated water is mixed with feed water and supplied to the boiler. ing.

Fig. 1 shows the saturated water circulation system in the Penson boiler.As the load is restored, saturated water 10 in the storage tank 4 flows into the water supply pipe 2 via the downcomer pipe 5 by the boiler circulation pump 1, and together with the supply water W. Sent to boiler 3.

In this case, the cross-sectional area of the downcomer pipe 5 connecting the storage tank 4 and the circulation pump 1 is determined based on the maximum flow rate because the boiler is operated in a wide load range.

However, for example, if a steam turbine or other equipment that uses steam breaks down, fuel supply to the reboiler 3 may be stopped, or cooling water may be introduced into the storage tank 4 through the cooling water pipe 8 to cope with a sudden load drop. Then, the static pressure inside the storage tank 4 drops rapidly.

For this reason, the velocity of the saturated water flowing down the downcomer pipe 5 decreases, and the saturated water evaporates in the downdown pipe 5 before reaching the circulation pump 1 (
As a result, the saturated water flowing into the pump 1 contains air bubbles, causing cavitation.

The object of this invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a saturated water circulation device that does not cause flushing of saturated water between a storage tank and a downcomer pipe.

In short, this idea involves placing multiple small-diameter downcomers between the storage tank and the circulation pump, installing a stop valve on each of these downcomers, and operating the stop valves to adjust the pressure according to the depressurization ratio in the storage tank. The number of downcomers used is increased or decreased to allow saturated water to flow down the downdown pipes at a certain speed or higher.

Here, the term "small diameter" is a name in contrast to the diameter of a conventional downcomer pipe, and the total cross-sectional area of the plurality of small diameter pipes corresponds to at least the cross-sectional area of the conventional downcomer pipe.

Embodiments of this invention will be described below with reference to the accompanying drawings.

In FIG. 2, small-diameter downcomers 5a, 5b, 5c, and 5d are arranged between the storage tank 4 and the circulation pump 1, and these downcomers have stop valves 6at and 6b, respectively.
6C! 6d is provided.

In this circulation system, the control box 7 detects the pressure inside the can with a pressure detector 9 disposed in the storage tank 4, and operates each stop valve 6a...6c according to this inside pressure.

This determines the number of downcomers to be used, and controls the flow rate of the saturated water 10 to be equal to or higher than a certain rate.

In this case, the optimum flow rate depends on the depressurization rate in the storage tank 4, but for example, the flow rate of saturated water with a gauge pressure of 200 atg is 500 yr'/h, the length of the downcomer pipe is 2
59 and the pressure reduction rate is 15 at/min, the optimum flow rate is 57 FL/S.

Also, as the pressure reduction rate decreases, the optimal flow rate also decreases, so
The control box 7 determines the number of downcomers to be used by increasing or decreasing the decompression rate.

Note that 11 in the figure is a superheater that superheats the steam discharged from the storage tank 9.

According to this invention, the number of downcomer pipes used is increased or decreased in accordance with the depressurization rate of the storage tank, so there is no flushing within the downcomer pipes, and therefore cavitation in the circulation pump does not occur.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a conventional saturated water circulation device, and FIG. 2 is a system diagram showing a saturated water circulation device according to this invention. 1...Circulation pump, 3...Boiler, 4
...Storage tank, 5,5at 5bt
5ct 5d""" Downpipe, 6a* 6b, 6
ct 6d...Stop valve, 7...Control box, 9...Inner pressure detector.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a system that re-supplies saturated water in a storage tank to a boiler using a circulation pump, the storage tank and the circulation pump are connected by multiple small-diameter downcomer pipes each having a stop valve. Water circulation device. 2 Utility Model Registration Scope of Claims In the saturated water circulation device according to claim 1, an in-can pressure detector is disposed in the storage tank, and the in-can pressure detector and the stop valve are each connected to a control box, and the storage The system is configured to automatically determine the number of downcomers to be used according to changes in the decompression rate inside the tank.