JPH0733887B2 - Steam turbine plant - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a steam turbine plant, and more particularly to a drain pump up system for a feed water heater, a control method therefor, and a drain spray nozzle.

[Conventional technology]

A steam turbine plant that has been widely adopted in the past,
For example, in the condensate system of a nuclear power plant described in JP-A-59-71902, a system is adopted in which all the cascade drains in the feed water heater are recovered in the condenser. In this system, the reactor (steam generator)
All of the water is supplied to the condenser through a condenser to remove oxygen dissolved in the drain in the condenser, that is, after being deaerated, and further supplied through a condenser treatment apparatus. Therefore, it is an advantageous system from the viewpoint of improving water quality,
It is not always an optimal system in terms of increasing the capacity of the low-pressure condensate pump provided in the condensate system and increasing the capacity of the condensate treatment device.

Therefore, recently, Japanese Patent Laid-Open Nos. 61-41807 and 62-62
As described in Japanese Patent Publication No. 5003, a nuclear plant using a new drain recovery system in which a cascade drain of a feed water heater is directly recovered by a drain pump in a water supply system (condensate system) is planned. According to this, it is possible to reduce the capacity of the low-pressure condensate pump and the capacity of the condensate demineralizer in the condensate treatment device by about 40%. Of course, when adopting this new system configuration, it is necessary to take special measures to degas the cascade drain, that is, to remove dissolved oxygen in the drain, and in general, degas the drain downstream of the feedwater heater. A tank is installed and dissolved oxygen is removed in this drain degassing tank and collected in the water supply system.

[Problems to be Solved by the Invention]

However, even with this configuration, although some degassing is possible with the degassing tank, overall degassing is not sufficient, that is, when the load of the steam turbine is large, it is sufficiently degassing, but the load is small ( When the load is light, deaeration is not sufficiently performed, and the deaeration capacity is generally low.

Explaining this point in a little more detail, it is known that the degassing efficiency is generally improved by increasing the surface area of the liquid to be degassed. From this point, drainage from the feed water heater is required for efficient degassing. Is atomized in the deaeration tank (by jetting a nozzle, etc.). However, in this type of steam turbine plant, the pressure for jetting at the time of atomization is determined by the height between the feed water heater and the degassing tank, and the drain amount varies depending on the turbine load. From the jet pressure varies depending on the load,
Especially when the load is light, atomization is not performed and degassing efficiency is lowered, which is disliked.

The present invention has been conceived in view of the above, and an object of the present invention is to provide a steam turbine plant having such a deaerator capable of obtaining a predetermined deaerating performance even when the load of the steam turbine changes. And providing a control method thereof.

That is, the present invention divides the spray nozzle device arranged in the deaeration tank into a plurality of nozzle systems for each of a plurality of nozzles, and makes the number of operations of the divided nozzle systems proportional to the load of the steam turbine. It is designed to achieve the intended purpose without being operated.

The number of operations of the divided nozzle system may be determined by the drain amount of the feed water heater or the drain pipe pressure of the feed water heater.

Further, in the nozzle in the above-mentioned nozzle system, when the nozzle hole is made to have a cross-sectional shape of sudden expansion-reduction-expansion so that a part of the drain is boiled under reduced pressure immediately before jetting from the nozzle tip,
It is effective because the drain can be made into finer particles.

[Means for Solving the Problems]

The steam turbine plant of the present invention includes a feed water heater that heats feed water to a steam generator, and a deaeration tank that performs deaeration of the drain of the feed water heater, and the drain of the feed water heater, The deaeration tank is used for deaeration, and the drain pump collects it in the condensate system on the downstream side of the condenser.The inflow drain from the feed water heater is introduced into the deaeration tank. A plurality of nozzle systems that atomize the jets are arranged side by side in the direction in which the drain drops, and except for the nozzle systems that are arranged in the uppermost row, the drain inflow that stops the drain that flows into the nozzle systems is at the inlet of each nozzle system. The present invention is characterized in that stop means is provided and the drain inflow stop means is sequentially stopped as the amount of drain of the feed water heater decreases.

Further, it is preferable that the ejection amount of each of the nozzles is increased as it is arranged below, and the stop operation of the drain inflow stopping means detects the pressure of steam withdrawn into the feed water heater. However, it is preferable to open and close the drain inflow stopping means by this detection signal.

Further, it is preferable that the nozzle for ejecting and atomizing the inflow drain from the feed water heater is a spray nozzle having a divergent cross-sectional shape, and a plurality of nozzles are arranged in a honeycomb shape.

Furthermore, the drain deaeration system of the steam turbine plant of the present invention, a feed water heater for heating the feed water to the steam generator,
And a deaeration tank for deaeration of the drain of the feedwater heater, wherein the drain of the feedwater heater is deaerated in the deaeration tank, and a drain pump is used for the condensate system on the downstream side of the condenser. A spray nozzle provided in the degassing tank is provided with a drain pipe for introducing the drain of the feed water heater in a plurality of systems, and the plurality of drain pipes are provided. By using an overflow-type drain piping path that has steps, the drain water level from the spray nozzle becomes almost constant even when the load of the steam turbine is changed, and the drain jet speed from the nozzle becomes constant. It is characterized by doing so.

[Action]

According to this configuration, when the load decreases and the drain flow rate decreases, some operations of the spray system can be stopped to control the drain ejection amount per spray nozzle to be substantially the same. Even if the nozzle opening area is fixed, the drain jet speed can be controlled to be almost constant,
That is, since the deaeration performance by the spray nozzle system shows a characteristic that is substantially proportional to the drain jet velocity, the constant drain jet velocity keeps the deaeration performance constant. Therefore, it becomes possible to obtain a predetermined degassing performance even when the load changes.

〔Example〕

The present invention will be described in detail based on the illustrated embodiments.

FIG. 1 shows a main part of the steam turbine plant as a system. In the figure, the drain deaeration system of the feed water heater is such that the low-pressure feed water heaters 6 and 7 and the drain deaeration tank 1 that stores the drain of the feed water heater are connected by drain pipes 21 and 22 of the feed water heater. The pipe 21 is provided with a water level control valve, that is, a water level control valve 23 for opening and closing control by a signal from a water level controller 24 provided in the feed water heater 6. Further, the drain deaeration tank 1 and the upstream side of the high-pressure condensate pump 4 (downstream side of the condenser) are connected by a low-pressure drain pump up recovery system 25, and the low-pressure drain pump up recovery system has a low pressure. A drain pump 26 and a drain water level control valve 29 that is opened and closed by a signal from a drain water level controller 28 provided in the drain degassing tank 1 are interposed. Further, a feed water heater side vent steam pipe 31 connecting the drain deaeration tank 1 and the feed water heater 7 via a check valve 30, the drain tank 1 and a condenser (not shown).
And Olyphus 32 for steam flow control valve and steam on-off valve 33
A vent steam system 34 configured by a condenser-side vent steam pipe 36 connected via a condenser, the feed water heater 7 and a condenser (not shown) via an orifice 37 for adjusting a steam flow rate. The feed water heater vent system 38 to be connected is provided, while the condensate sent from a low pressure condensate pump (not shown) is
After removing impurities through the filter demineralizer 2 and the tape head demineralizer 3 which are condensate filters, the low pressure feed water heaters 7 and 6 are heated by the extraction steam flowing from the extraction pipes 8 and 9. It is sent to the high pressure feed water heater system.

In the drain deaeration tank 1, the drain of the feed water heater 7 on the low pressure side was sprinkled from the upper portion, and the drain of the feed water heater 6 on the high pressure side of the feed water heater 7 was generated from the drain by flushing from the lower portion. A sprinkling pipe 10 and a flush pipe 11 for scavenging the depressurization flash vapor from below to above;
A plurality of spray nozzles 12 and 13 provided above the sprinkling pipe 10 and the flush pipe 11, and the drain pipe 21 of the water heater.
And the water spray pipe 10 for connecting the water spray side drain spray pipe
14, the drain pipe 22 of the feed water heater and the slush tube
A plurality of drain spray systems 16 and 17 configured by a flush-side drain spray pipe 15 that connects 11 and 11 are provided. In addition, the drain spray systems 16 and 17 are provided with extraction steam pressure detectors 18 and 19 provided in the extraction pipes 8 and 9, respectively.
And a drain valve 40-a, 40-b, 41-a, 41-b for inflowing and stopping the drain into each drain spray system 16, 17, and the drain valve 40- by a signal from the detector 18, 19. Valve switches 42 and 43 for controlling the opening and closing of a, 40-b and 41-a, 41-b are provided.

As shown in FIG. 2, the drain spray charging system 16 has a plurality of spray nozzles 12 having a divergent cross-sectional shape with a good drain atomization efficiency as a drain spray mechanism and arranged in a honeycomb shape to improve the drain atomization volumetric efficiency and deionization. The drainage deaeration tank 1 is reduced in size and weight by improving the energy effect. The drain spray system 17 is also composed of similar devices. Further, the spray nozzles 12 and 13 are rapidly expanded so that a part of the drainage is boiled under reduced pressure immediately before jetting from the spray nozzle, as shown in an enlarged cross section in FIG.
It has a two-stage decompression spray nozzle structure with a cross-sectional shape that shrinks and expands toward the end.

The valve switch 42 for opening and closing the drain valves 40-a, 40-b (see FIG. 1) is a pressure setter 45, 46 as shown in FIG.
A signal from the pressure detector 18 and the pressure setting device 45, 4
It is constituted by valve operation signal oscillators 49, 50 which output valve operation signals 47, 48 for opening and closing the drain valves 40-a, 40-b in response to the signal from 6. The valve switch 43 (FIG. 1) has the same structure.

With the system configured in this way, efficient degassing performance can be obtained even if the load on the steam turbine changes for the following reasons, in other words, the amount of drain from the feed water heater changes. is there. That is, as for the degassing characteristics having the drain spray type degassing mechanism, as a result of conducting various experiments, the effect of the drain jet velocity from the drain spray nozzle is the strongest, and the degassing performance is expressed by the following formula (1). By definition, it was found that this degassing performance NTU shows a characteristic that increases almost in proportion to the drain jet velocity.

To show such characteristics means that in order to improve the degassing performance, it is better to increase the drain jet velocity, promote the atomization of the drain, and increase the drain degassing surface area. To increase the speed, there are restrictions on the device configuration and operation. In this point, the conventional spray system uses the spray nozzle with a constant opening area as shown in FIGS. 5 and 6, and the nozzle drain jet velocity v _W according to the change of the drain flow rate with respect to the generator output (load). Since the operating range of is too wide, there is a load zone where the specified degassing performance N ₁ is not obtained, which makes it difficult to operate when changing the load.

On the other hand, the drain degassing system 16 and 17 of the present invention (Fig. 1)
As described above, multiple drain spray systems 16,1
Drain valve 40-a, 40-b, 41
Since the opening / closing control of -a and 41-b is performed, the drain ejection amount per spray nozzle can be made substantially constant. As a result, as shown in FIGS. 7 and 8, the drain jet velocity v _W from the nozzle becomes almost constant (narrow) with respect to the change in the generator output (turbine output), so even if the load changes The degassing performance of N ₁ can be obtained. In particular, the effect is exerted in the case of a system configuration in which the spray differential pressure cannot be sufficiently secured.

In the above description, an example in which three drain spray systems are used has been described, but it goes without saying that more stable deaeration performance can be obtained as the number of systems increases.

Further, in the drain deaeration system of the present invention, the drain from the high temperature / high pressure side feed water heater 6 becomes flush steam and is heated and deaerated by heating the drain from the low pressure feed water heater 7 dropping from the upper sprinkler pipe 10. Water supply due to the effect and the depressurization deaeration effect by lowering the internal pressure in the drain degassing tank 1 to a pressure lower than the saturated steam pressure with respect to the drain water heater drain temperature flowing into the drain degassing tank 1 by the vent steam system It is possible to reduce the amount of dissolved oxygen in the drain collected in the system, and to prevent corrosion of the feed water heater, steam generator, etc. after drain collection.

Further, when the drain degassing system of the present invention is provided with the expanded passage 12a, that is, when the two-stage depressurizing spray nozzle 12 is provided, as shown in FIG. 3, the drain in the nozzle due to flash vapor from the drain is used. Due to the stirring effect, atomization of the drain ejected from the nozzle can be promoted even under a low differential pressure, and the effect of improving the deaeration performance of the drain spray system having a small drain system head is achieved. According to the result of the experiment, the diameter of the enlarged passage 12a is 3 to 5 times as large as that of the ejection passage 12b.

Also, in the above explanation, when controlling the opening and closing of the drain valve, the pressure of the steam discharged from the turbine was used, but it is not always necessary to control by this pressure, and pressure changes in other parts and the generator It may be possible to capture the electrical output.

One example is shown in FIG. That is, in the case of this embodiment, the internal pressure of the feed water heater 7 and the drain valve 40
-A and 40-b are provided with differential pressure detectors 51 and 52 in order to detect the pressure difference with the fluid pressure in the drain pipe immediately before the drain pipe, and the signal from the differential pressure detector is used to detect the drain pressure. Valve 40-
Operate the valve switch 50 that controls the opening and closing of a and 40-b, and control the presence or absence of water flow to each drain spray system 16 and 17 according to the change in the drain flow rate due to the load change, and the spray nozzle 1
The drain jet speed from 2 is made to be almost constant, and even with this configuration, the same effect as that of the drain spray system which detects the extracted steam pressure and opens and closes each drain valve is obtained. be able to.

Further, FIG. 10 shows still another embodiment, in which, in this case, the level switch which operates according to the drain water level in this drain pipe is provided in the drain pipe 22 portion having a head.
55,56,57,58 are provided and this level switch 55,56
The drain valve 40-a is controlled by a signal from the drain switch 40-a, and the drain valve 40-b is controlled by a signal from the level switches 57 and 58 to control the drain valve 40-b. By controlling the drain water level in the drain pipe 22 that is determined by the number of nozzles 12 to be substantially constant, the drain jet velocity from the spray nozzle 12 is almost constant even when the drain flow rate changes with load changes. The same effect as that of the drain spray system can be obtained by controlling so that

FIG. 11 shows another embodiment. In this case, instead of the drain valves 40-a and 40-b provided in the drain spray systems 16 and 17 shown in FIG. 1, as shown in the figure, the descending drain piping parts of the drain spray piping 70 and 71 are provided. Overflow type drain pipes 72 and 73 are installed in the to limit the drain that descends the overflow pipes 70 and 71 according to changes in the drain flow rate, and keep the drain flow rate currencyd per spray nozzle as constant as possible. In this way, the purpose is achieved without changing the drain jet velocity. In other words, since the overflow type drain pipes 72, 73 are provided, when the load decreases and the drain amount decreases, the spray system 71 in which the drain water level in the drain pipe does not reach the end of the overflow pipe 73 is formed, and Then, the drain supply to the spray nozzle 12 is cut off, and the drain water level commensurate with the drain flow rate is balanced.
In this case, the maximum positions of the drain pipes 72 and 73 are slightly shifted to stabilize the water level, but the absolute values of the drain water level in the drain pipe 22 for each load are set to be substantially the same. Therefore, the height of the drain water level is kept substantially constant, and the drain jet speed is also kept substantially constant.

Although the low-pressure feed water heater system is shown as an example of the present invention, the present invention can be applied to the high-pressure feed water heater system with exactly the same components, and in this case, the low-pressure feed water heater on the downstream side is used. The capacity can be reduced, and the drain cooler (not shown) can be reduced, so that a greater effect can be expected.

Further, in the above description, it has been stated that the number of actuations of the spray nozzle system is actuated according to, for example, the load of the steam turbine, the drain pressure of the feed water heater or the amount of the drain,
According to the results of in-depth experiments, it is effective to operate the nozzle system at about 32% when the steam turbine load is 50%.

That is, FIG. 12 and FIG. 13 are the experimental results at that time, and in FIG. 12, the degassing performance against the fluctuation of the load of the steam turbine (the load of the generator directly connected to the turbine) is shown. Generally, as is clear from the line DN, the degassing performance NTU according to the change in load, that is, the lighter load.
Will fall. This means that the degassing performance also decreases as the drain temperature decreases as the load becomes lighter. The straight line shown as DT in the figure is the drain temperature shown for reference.

In order to obtain the deaeration performance indicated by the dotted line x (a substantially constant deaeration performance regardless of the size of the load), the nozzle system operation ratio (NC curve) in FIG. 13 is obtained. That is, in FIG. 13, for example, when the load is 75%, the ratio is 61% and the load is 50%.
In the case of, the ratio is 32%, which means that the degassing performance can be kept constant against load fluctuations.

〔The invention's effect〕

As described above in various ways, the present invention is provided in the deaeration tank,
A plurality of nozzle systems for ejecting and atomizing the inflow drain from the feed water heater are provided.Drain inflow stop means for stopping the drain flowing into the nozzle system is provided at the inlet of each nozzle system, and this drain inflow stop Since the means is sequentially stopped as the drain amount of the feed water heater decreases, even if the drain amount varies, that is, the steam turbine load varies, the drain degassing tank The jet speed inside is kept almost constant, so that even if the load of the steam turbine changes, it is possible to always obtain a turbine plant of this kind having a predetermined degassing performance.

[Brief description of drawings]

FIG. 1 is a system diagram showing a drain degassing system of the present invention, FIG. 2 is a plan view showing one of the drain spray nozzle systems, FIG. 3 is a vertical side view of the drain spray nozzle, and FIG. 4 is a drain valve. Block diagram of switch, FIG. 5 is a drain jet characteristic diagram when one drain spray system is used, FIG. 6 is its deaeration performance characteristic diagram, and FIG. 7 is a drain spray system of the present invention for a plurality of systems. FIG. 8 is a characteristic diagram of the drain jet flow in the case of the presence of water, FIG. 8 is a characteristic diagram of the deaeration performance thereof, FIG. 9 and FIG. 10 are system diagrams showing a modification of the present invention, and FIG. FIG. 12 is a characteristic diagram showing the relationship between load and degassing performance, and FIG. 13 is a characteristic diagram showing relationship between load and head loss. 1 ... Drain degassing tank, 6,7 ... Low-pressure feed water heater, 10
...... Sprinkling pipe, 11 …… Flush tank, 12,13 …… Spray nozzle, 16,17 …… Drain spray system, 18,19 …… Bleed steam pressure detector, 25 …… Drain pump up system, 26…
... Low-pressure drain pump, 40-a, 41-a, 40-b, 41-b ... Drain valve (drain inflow stop means), 42,43 ... Valve switch, 5
1,52 …… Differential pressure detector, 55,56,57,58 …… Level switch, 61 …… Flow control type spray nozzle.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toyohiko Masuda 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi Ltd. Hitachi factory (56) References JP 62-5003 (JP, A) JP-A 61-79905 (JP, A) JP-A 58-106308 (JP, A) JP-A 54-133748 (JP, A) Actual development Sho-58-122806 (JP, U) Actual public Sho-38-2096 (JP, Y1)

Claims (5)

[Claims] 1. A feed water heater for heating feed water to a steam generator, and a deaeration tank for deaerating a drain of the feed water heater, wherein the drain of the water supply heater is deaerated. In a steam turbine plant that has been degassed with a drain pump and recovered in a condensate system on the downstream side of a condenser with a drain pump, the drainage inflow from the feed water heater is jetted into the degassing tank to atomize A plurality of nozzle systems are arranged side by side in the direction in which the drain drops, and except for the nozzle systems arranged in the uppermost row, a drain inflow stopping means for stopping the drain flowing into the nozzle systems is provided at the inlet of each nozzle system. A steam turbine plant, characterized in that the drain inflow stopping means is sequentially stopped as the drain amount of the feed water heater decreases. 2. The steam turbine plant according to claim 1, wherein the ejection amount of each nozzle is increased as it is arranged downward. 3. A feed water heater for heating feed water to a steam generator, and a deaeration tank for deaerating a drain of the feed water heater, wherein the drain of the feed water heater is deaerated. In the drain degassing system of the steam turbine plant, which is degassed by, and is collected by the drain pump in the condensate system on the downstream side of the condenser, in the spray nozzle provided in the degassing tank,
A drain pipe for introducing the drain of the feed water heater is provided in a plurality of systems, and the plurality of drain pipes are used as an overflow type drain pipe path having a step, so that the drain water level from the spray nozzle is increased. A drain degassing system for a steam turbine plant, characterized in that the drain jet velocity from the nozzle is made constant so that it becomes almost constant even when the load of is changed. 4. The stop operation of the drain inflow stopping means includes:
The steam turbine plant according to claim 1, wherein the pressure of the steam withdrawn into the feed water heater is detected, and the drain inflow stopping means is opened / closed by the detection signal. 5. A spray nozzle having a divergent cross-sectional shape, wherein a plurality of nozzles for ejecting and atomizing the inflow drain from the feed water heater are arranged in a honeycomb shape. The described steam turbine plant.