JPH0337085B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler feed water pump device, and more particularly to a boiler feed water pump device that eliminates the risk of flushing occurring as the load decreases.

Conventional boiler feed pump devices have had a technical problem in that flushing occurs when the load of the prime mover plant in which the boiler feed pump device is installed is reduced.

FIG. 1 shows an example of a conventionally commonly used boiler feed pump system. Group A and group B are systems of water pumps 34a and 34b, respectively, corresponding to 50% of the rating of the boiler, and group C is a system of water pumps 34c, corresponding to 25% of the rating. 3 of A, B, and C above
A boiler feed water pump device 1 is formed by the group. 10 is a condenser, 11 is a condensate pump,
13 is a feed water heater, 21 is a deaerator, and 22 is a deaerator water storage tank.

During plant operation, condensate in the condenser 10 is sent to the deaerator 21 by the condensate pump 11 via the condensate pipe 12, the feed water heater 13, and the check valve 14.

The condensate sent to the deaerator 21 is heated and degassed with heated steam supplied from the steam pipe 24 and stored in the deaerator water storage tank 22, and is then transferred to the downcomer pipes 23a, 23.
It is supplied to the boiler feed water pump device 1 through b and 23c.

Group A configuring the water supply pump device 1
The booster pump inlet valve 31a, the booster pump 32a, the water supply pump suction pipe 33a, the water supply pump 34a, the water supply pump discharge pipe 35a, the water supply pump outlet check valve 36a, and the water supply pump outlet valve 37a are connected in series, and the above-mentioned The discharge port of the water supply pump outlet valve 37a is communicated with the header 38, and a warming pipe 41a, a warming valve 42a, and an oil pipe 43a are connected in series between the header 38 and the water supply pump 34a. . Group B and group C that constitute the water supply pump device 1 are also constructed in the same manner as group A described above. 44a, 44b, and 44c are blow valves connected to the water supply pumps 34a, 34b, and 34c, respectively.

In the conventional boiler feed pump system (FIG. 1) configured as described above, starting is started from the small capacity group C feed pump 34c as follows.

That is, by opening the blow valve 44c, the water stored in the deaerator water storage tank 22 is transferred to the downcomer pipe 23c, the booster pump inlet valve 31c, the booster pump 32c, the water supply pump suction pipe 33c, and the water supply pump 34c, depending on the pressure inside the deaerator and the height difference. The water is allowed to flow down through the water to warm the water supply pump 34c. and water pump 3
When the difference between the metal temperature of 4c and the temperature of the water supply becomes equal to or less than a certain value, the water supply pump 34c is started.

After starting the water supply pump 34c in this way, the warming valves 42a and 42b are opened, and a part of the water discharged from the water supply pump 34c is transferred to the water supply pump 34a,
34b, the deaerator water storage tank 22 via the booster pumps 32a, 32b and the downcomer pipes 23a, 23b.
The boiler feed water pumps 34a and 34b are warmed by reverse flow and circulation, and after warming is completed, the water feed pumps 34a and 34b are started.

After starting up as described above, the plant load is
When it is 50% or more, the water supply pumps 34a and 34b are operated, and the water supply pump 34c is stopped. Further, when the load of the plant is less than 50%, only one of the water supply pumps 34a and 34b is operated, and the other is stopped. For convenience of explanation, an example will be described below in which the water supply pump 34a is operated and the water supply pumps 34b and 34c are stopped.

While the water supply pump 34a is in operation, a portion of the discharged water is sent from the header 38 to the warming valve 42b and the warming valve 42.
The water is supplied through the orifices 43b and 43c to the inactive water pumps 34b and 34c to continue warming, so that the water pumps 34b and 34c can be activated at any time as the plant load increases.

Warming valves 42b, 42 as described above
The flow rate of the warming water circulated to the water supply pumps 34b and 34c through the water supply pump 34b and 34c is very small, for example, about 1% of the water supply pump rating.

As mentioned above, even if the warming water flow rate is extremely small, it is sufficient to maintain the metal temperature of the water supply pump when it is stopped at the same level as the temperature of the water supply. Suction pipes 33b, 33c and downpipe 23 of the water supply pump
It takes a long time for the supply water remaining in b and 23c to be replaced by the circulating water flow.

In this way, the water in the suction line of the water pump is replaced only gradually, so when the plant load suddenly decreases, water stagnates in the suction line of the stopped water pump. There is a technical problem in that the hot water in the area causes flashing, causing water hammer and cavitation.

Next, the reason why the above-mentioned flushing phenomenon occurs will be explained with reference to FIG. In this chart, the horizontal axis shows the passage of time, and the vertical axis shows changes in temperature and pressure due to plant load.

Curve J represents the plant load. This chart is
When the plant load J suddenly decreases from time t ₁ to time t ₃ , the temperature and pressure of the feed water over the above period and before and after it are shown.

Curve M is the deaerator internal pressure, curve O is the booster pump inlet pressure, and curve P is the water pump inlet pressure. More details are as follows.

Since the inlet pressure of the booster pump 32a and the inlet pressure of the booster pump 32b are always equal, this is expressed as a curve O(a)(b)
It is expressed as

Curve P(a) represents the inlet pressure of the water supply pump 34a,
Curve P(b) represents the inlet pressure of the water supply pump 34b, and curves P(a) and (b) represent the pressures when the inlet pressures of the water supply pumps 34a and 34b are equal.

Curve K is the temperature of the feed water in the deaerator water storage tank 22.

When the plant load J decreases at a constant rate from time t ₁ to time t ₂ , the deaerator internal pressure M decreases at the same time, and the booster pump inlet pressure O(a)(b) and The feed water temperature K in the deaerator water storage tank also decreases at the same timing.

Curve L(a) represents the inlet temperature of the water supply pump 34a,
Curve L(b) shows the inlet temperature of the water supply pump 34b, and curves L(a) and (b) show the temperatures when the inlet temperatures of the water supply pumps 34a and 34b are equal.

When the plant load J is constant (before time t ₁ ), the feed water pump inlet temperature L(a)(b) is the same as the feed water temperature K in the deaerator water storage tank, but when the plant load J is t ₁ When the water supply pump inlet temperature L(a)(b) starts to fall at this point, the water pump inlet temperature L(a)(b) starts to fall after a delay of time lag _t4 . This time lag _t4 means that the water supply in the deaerator water storage tank, which has cooled down, is
(Fig. 1) to reach the inlets of the water supply pumps 32a, 32b.

As mentioned above, when the water supply pump inlet temperature L(a)(b) starts to fall after a time lag of _t4 , the saturation pressure N of water corresponding to the water supply pump inlet temperature increases.
(a) and (b) also begin to fall.

When the plant load J further decreases to 50% or less, the water supply pump 34b is stopped as described above. This time point is defined as _t2 .

If the plant load J continues to decrease until the time _t3 even after the time _t2 , the booster pump inlet pressure O(a)(b) also continues to decrease until the time _t3 .

The inlet pressure P(a) of the water supply pump 34a, which continues to operate, also decreases almost parallel to the deaerator internal pressure curve M until time _t3 .

However, since the booster pump 32b is also stopped when the water supply pump 34b is stopped, the pressure difference between the outlet and inlet of the booster pump 32b disappears, and the inlet pressure curve P(b) of the water supply pump 34b rapidly decreases to t. After time ₂ , the inlet pressure O(a)(b) of the booster pump 32b overlaps.

In this way, the inlet pressure P(b) of the water supply pump 32b decreases rapidly, but the inlet temperature L(b) of the water supply pump 32b remains approximately constant after time _t2 due to the pump being stopped. Therefore, the saturated steam pressure N(b) corresponding to the feedwater pump inlet pressure also remains approximately constant after time _t2 .

For this reason, the water supply pump 34 is
The inlet pressure P(b) of water supply pump 34 becomes equal to the saturated steam pressure N(b) corresponding to the inlet temperature of the same pump, and thereafter becomes lower than the saturated steam pressure N(b).
The water supply in the suction side pipe b is flushed.

As is clearly understood from the above explanation, the flushing phenomenon in the water supply pump suction line is more likely to occur as the absolute value of the drop in plant load increases and the rate of drop increases.

As one method to prevent the above-mentioned flushing phenomenon, the orifice 43 shown in FIG.
If the diameters of a, 43b, and 43c are increased to increase the amount of warming circulating water in the suction side pipe of the stopped water supply pump, the heat in the water supply pump suction side pipe will be reduced when the load decreases as described above. Flushing can be suppressed by quickly replacing the water with low-temperature feed water, but it is not preferable to constantly circulate a large amount of water for warming in this way because it increases power loss.

In addition, as another method to prevent the above-mentioned flushing phenomenon, even if the plant load decreases to 50% or less, one of the water supply pumps is not stopped at time t ₂ in Figure 2, and the plant load is increased. settles down
It is conceivable to continue operating two water supply pumps until time t ₃ , but this would result in a large power loss and would not be easy to control and manage the water supply system.

It is also conceivable to install the deaerator water storage tank at a high place and use its water pressure to suppress flushing, but this would significantly increase plant construction costs and is therefore impractical.

The present invention was made in view of the above-mentioned circumstances, and provides a boiler feed pump device that can prevent flushing when the plant load decreases without causing a large power loss or significantly increasing construction costs. The purpose is to provide.

In order to achieve the above object, the present invention provides a boiler feed pump system in which, when the amount and rate of decrease in plant load exceed a certain value, the dehydrator rains on the suction side pipe of the stopped water pump. The water supply pump is characterized in that a pipe line for replacing hot water in the pipe and the water supply pump suction pipe with low-temperature water supply is connected to the suction side of the water supply pump.

The above-mentioned low-temperature water supply means the water supply in the deaerator water storage tank 22 whose temperature has decreased as the load has decreased.

Next, one embodiment of the present invention will be described with reference to FIG. In this figure, the same drawing reference numbers as in FIG. 1 (conventional device) are given to the same or similar constituent members as in the conventional device, so the explanation will be omitted.

In this embodiment, a drainage pipe having three branch pipes 52a, 52b, and 52c is installed so as to be able to cope with the case where the operation of any of the three water supply pumps 34a, 34b, and 34c is stopped when the plant load decreases. The collection pipe 52 is composed of three branch pipes 52a, 5
Condenser drain valves 50a and 5 are installed at 2b and 52c, respectively.
0b, 50c and orifice 51a, 51b, 5
1c is interposed and the tip of each branch pipe is connected to the suction port 34a- of the water supply pump 34a, 34b, 34c.
1, 34b-1, 34c-1, and the collecting pipe portion of the waste water recovery pipe 52 is connected to the condenser 10.

As a result, the condenser drain valves 50a, 50b,
Or, if you open the same 50c, the water supply pump suction pipe 33
The hot water in the down pipes 23a, 33b, or 33c is communicated with the condenser 10 via an orifice, and the hot water in the downcomer pipes 23a, 23b, or 23c is also communicated with the booster pump inlet valve 31a, respectively. 31
b, or 31c, and booster pump 32
a, 32b, or 32c, and are connected to the condenser 10, respectively.

The apparatus of the present invention is constructed as described above, and its usage and operation will be described below with reference to FIG.
FIG. 4 is a diagram corresponding to FIG. 3 for the conventional device, and the meanings of the symbols used are the same.

Similarly to FIG. 1, the load curve J begins to decline from time _t1 , becomes less than 50% at time _t2 , and continues to decline almost uniformly until time _t3 .

Each curve from time t ₁ to just before time t ₂ is the same as in the conventional device (FIG. 2).

Stopping the operation of the water supply pump 34b at time _t2 is also similar to the conventional device, but in this embodiment, after the water supply pump 34b is stopped, the condenser drain valve 50b is opened (see FIG. 3).

When the condenser drain valve 50b is opened, the downpipe 23b,
Booster pump 32b and water pump suction pipe 33
The hot water in b is discharged into the condenser 10 and replaced by the feed water in the deaerator water storage tank 22.

As a result, (see FIG. 4) the water supply pump 34b
The inlet temperature L(b) of the water supply pump 34a continues to decrease even after time _t2 in substantially the same way as the inlet temperature L(a) of the water supply pump 34a. The slight time lag _t5 in the figure corresponds to the time difference between when the water supply pump 34b is stopped and when the condenser drain valve 50b is opened.

As described above, the inlet temperature of the water supply pump 34b decreases in almost the same way as the inlet temperature of the water supply pump 34a, so the saturated steam pressure N(b) corresponding to the inlet temperature of the water supply pump 34b remains unchanged even after time _t2 . The saturated steam pressure N(a) corresponding to the inlet temperature of the booster pump decreases to approximately the same level as the saturated steam pressure N(a), and there is no risk of exceeding the booster pump inlet pressure O(b), and therefore there is no risk of causing a flushing phenomenon.

Note that there is some hot water in the water supply pump 34b, but since the amount is small, it is quickly replaced by the warming circulating water (circulated water via the orifice 43b), and the condenser It is discharged at 10.

In the embodiment shown in FIG. 3 described above, the present invention is applied to a supply pump device in which booster pumps 32a, 32b, 32c are connected in series to three water supply pumps 34a, 34b, 34c, respectively. The present invention can also be applied to a water supply pump device having a configuration in which the booster pumps 32a, 32b, and 32c are omitted in the same manner as described above.

As explained above, the boiler feed pump device according to the present invention has a dehydrator precipitate that hits the suction side pipe of the water pump that is stopped when the amount and rate of decrease in plant load exceeds a preset constant value. The above-mentioned effects are produced by connecting a pipe line for replacing hot water in the pipe and water pump suction pipe with low-temperature water supply to the suction side of the water pump.

Additionally, the above-mentioned flushing phenomenon is likely to occur when the plant load is reduced, but it is more likely to occur when the deaerator installation height is low and the water head is small, or when the downcomer pipe is long. Therefore, there is a risk that a flushing phenomenon may occur even if the water supply pump is not stopped.However, even in such a case, the device according to the present invention can promote the replacement of hot water in the water supply pump suction pipe. Flushing can be prevented.

Next, an embodiment different from the above embodiment will be described with reference to FIG.

The difference from the above embodiment (Fig. 3) is 3.
The suction sides of the water supply pumps 34a, 34b, 34c are connected to each other by pipes 61, 62, 63, and a valve 6 for warming communication is installed in each of the pipes.
4, 65, 66 and orifice 67, 68, 6
This is the point where 9 is connected via an intervening connection.

With this configuration, for example, when the water supply pump 34b is stopped, the warming valve 64
When opened, the water supply pump 34a continues to operate.
Some of the water discharged from the booster pump 32a for
4 and the water pump suction pipe 3 via the orifice 67
3b, since it circulates to the downcomer pipe 23b, the hot water in the suction pipe of the stopped water supply pump 34b is replaced with low-temperature supply water, and flushing is prevented. Since the booster pump described above has a lower head (for example, about 1/30) than the water supply pump, as in this embodiment, the discharge water of the booster pump 32a, 32b, or 32c is circulated to replace the stagnant hot water. As a result, the power loss is significantly smaller than when the water discharged from the water pump is circulated.

FIG. 6 shows a further different embodiment. This embodiment is an example in which the present invention is applied to a steam motor plant having a deaerator equipped with a deaerator circulation pump 73.

The above-mentioned deaerator circulation pump 73 was originally installed in the deaerator water storage tank 2 prior to starting the water supply pump device 1.
This embodiment is provided for heating and deaerating the water supplied in the steam pipe 24 by the heated steam supplied by the steam pipe 24 while circulating it in the downcomer pipes 23a, 23b, and 23c. In order to construct the apparatus of the present invention using the deaerator circulation pump 73, the deaerator circulation pump suction pipe 71 is formed with three branch pipes 71a, 71b, and 71c, and the above three branch pipes booster pumps 32a, 32b, 32, respectively.
Connect it to the point as close as possible to the inlet of c. A deaerator circulation pump inlet valve 72 , a pressure air circulation pump 73 , a check valve 74 , a circulation pump outlet valve 75 and a deaerator circulation pump discharge pipe 76 are sequentially connected to the suction pipe 71 . The deaerator 2
Connect to 1.

With the above configuration, when any of the water supply pumps 34a, 34b, or 34c is stopped due to a decrease in the plant load, the deaerator circulation pump 73 is operated to perform deaeration. By forcibly circulating the water supply in the water storage tank 22 into the downcomers 23a, 23b, and 23c to replace the stagnant hot water, the downdown pipes 23a, 23b, 23
This can prevent flashing from occurring within c.

In this embodiment, the existing deaerator circulation pump 73 can be used, and the pipe line provided for replacing the hot water can be simple.
The operation is simple because the same operation (operation of the deaerator circulation pump 73) can be performed even when a, 34b, or 34c is stopped. However, in the device of this example, the water supply pump suction pipes 33a, 33
Since it is not possible to forcefully circulate the stagnant hot water in the orifices 43a, 43b, 43
It is desirable to make the flow resistance of c slightly smaller than that in the conventional device (FIG. 1) and to slightly increase the amount of circulating water for warming described above.

FIG. 7 is a control block diagram of each of the embodiments described above (the embodiments of FIGS. 3, 5, and 6).

As previously explained with reference to FIGS. 1 and 2, there is a risk that a flushing phenomenon will occur if the load on the plant drops significantly and rapidly. Therefore, even if the amount of load drop is large, there is no risk of flashing occurring if the load drops gradually, and even if the load drops rapidly, if the width of the drop is small, there is no risk of flashing occurring. None.

Based on the above considerations, as shown in Figure 7A,
Blocks 81, 82, 83, and 84 are ANDed, and separately, blocks 91 and 92 are ANDed.
The device according to the present invention is controlled to operate when either of the above two AND conditions is established.

Specifically, the plant load drop width is larger than a preset constant value (block 81), the plant load drop rate is larger than a preset fixed value (block 82), and the plant load after the plant load drop is larger than the preset constant value (block 81). less than the load that would require stopping at least one water pump (block
83) and at least one water pump continues to operate (block 84), the device of the present invention is activated to perform hot water replacement (block 100). Also, from a different perspective than the above conditions, the plant load is tripped (block 91), and
If at least one feedwater pump is in operation (block 92), hot water replacement is performed (block 100) to ensure a minimum boiler flow rate.

The details of the control for performing the above hot water replacement (block 100) are shown in FIGS. 7B to 7C.

In the case of the embodiment shown in FIG. 3, the water supply pumps 34a, 34b whose operation has been stopped as shown in FIG. 7B,
Alternatively, for 34c, the condenser drain valves 50a, 50b, or 50c provided on the respective suction sides are opened (block 101) and closed after an appropriate time by the timer TD (block 102). The above-mentioned appropriate time means the time required for the stagnant hot water in the water supply pump suction side pipe to be replaced with low-temperature supply water by the operation of the device of the present invention, and is set in advance by design or experiment. put.

In the case of the embodiment shown in FIG. 5, as shown in FIG. 7C, the warming communication valve 64, 65 or 66 is opened (block 103) and closed after an appropriate time by the timer TD (block 104).

In the case of the embodiment shown in FIG. 6, the deaerator circulation pump 73 is started as shown in FIG.
105), and the timer TD closes the valve after an appropriate time (block 106).

By automatically controlling as described above, it is possible to effectively and appropriately operate the device of the present invention without requiring any special effort, and to prevent a flushing phenomenon accompanying a decrease in plant load without causing unnecessary power loss.

As explained above, the present invention provides a boiler feed water pump device including a plurality of water feed pumps.
When the amount of decrease in plant load and the rate of decrease in plant load exceed a certain value, the hot water in the dehydrator down pipe and the water pump suction pipe, which correspond to the suction side pipe of the stopped water pump, is replaced with low-temperature feed water. By connecting the replacement pipe to the suction side of the water supply pump, it is possible to prevent flushing when the plant load decreases, and there is no risk of large power loss, reducing equipment costs. There is no risk of a significant increase.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a boiler feed water pump system commonly used in the past, Fig. 2 is a temperature/pressure/time chart for explaining the flushing phenomenon in the above feed water pump system, and Fig. 3 is a system diagram of a boiler feed pump system according to the present invention. A system diagram of the boiler feed water pump device according to the example, FIG. 4 is a temperature/pressure/time chart in the above example,
FIGS. 5 and 6 are system diagrams of boiler feed water pump devices in different embodiments from those described above, and FIGS. 7A to 7D are automatic control block diagrams in each of the embodiments described above. 1,1'... Boiler feed pump device, 10...
Condenser, 21... Deaerator, 22... Deaerator water storage tank, 23a, 23b, 23c... Downpipe, 32
a, 32b, 32c...booster pump, 33
a, 33b, 33c... Water pump suction pipe, 34
a, 34b, 34c...Water pump, 50a, 5
0b, 50c...Condenser drain valve, 51a, 51
b, 51c...orifice, 52a, 52b, 5
2c... Drainage recovery pipe, 61, 62, 63... Warming connection pipe, 64, 65, 66... Warming communication valve, 67, 68, 69... Orifice,
71...Deaerator circulation pump suction pipe, 71a, 71
b, 71c... Branch pipe, 73... Deaerator circulation pump, 74... Check valve.

Claims (1)

[Scope of Claims] 1 In a boiler feed water pump device, this corresponds to the suction side pipe of the feed water pump that is stopped when the amount and rate of load reduction of the prime mover plant in which the above device is installed respectively exceed a certain value. A boiler feed water pump device, characterized in that a pipe line for replacing hot water in a dehydrator downpipe and a water feed pump suction pipe with low-temperature feed water is connected to the suction side of the water feed pump. 2. The pipe line for replacing the hot water is a pipe line that interconnects the suction sides of a plurality of water supply pumps installed in parallel, and a valve is interposed in the pipe line. A boiler feed water pump device according to claim 1. 3. The above-mentioned pipe line for replacing the hot water is a pipe line connecting the suction side of the water supply pump and the deaerator, and a pump is interposed in the pipe line. Boiler feed water pump device according to scope 1. 4. The piping for replacing hot water as described above shall be constructed such that (a) the width of the drop in plant load is above a certain value, the plant load drop rate is above a certain value, the plant load is below a certain value, and An automatic control means is provided to operate water flow when at least one feed pump is in operation, or (b) when the plant load is tripped and at least one feed water pump is in operation. A warming device for a boiler feed water pump suction pipe according to claim 1, claim 2, or claim 3, characterized in that the heating device is a pipe line.