JPH041270B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cooling water system in a one-tube bundle two-pass condenser.

[Conventional technology]

In a power generation plant, the turbine exhaust gas that has completed its work in the turbine is led to a condenser, where it is cooled and condensed, becoming condensed water and being reintroduced to the boiler or heat exchanger.

The condenser is 1 if the turbine displacement is small.
If the condenser is configured with one tube bundle and the required amount of cooling water is small, the number of condensate cooling pipes in the condenser is small and the length of the cooling pipes is required to be long, so one tube bundle is divided into two sections. A 1-tube bundle, 2-pass type condenser is used in which the cooling water is divided into two sections and the cooling water reciprocates within the tube bundle.

Seawater is normally used as the cooling water for condensers, but seawater contains foreign objects such as shellfish and wood chips, so these foreign objects can clog the cooling pipes or block the entrances of the cooling pipes. There is a risk of blocking the side.

Therefore, in power plants, a so-called backwash operation is performed in which cooling water is flowed from the opposite direction of cooling pipes in order to remove foreign substances. The number of times this backwash operation is performed varies depending on the amount of foreign matter, but if there is a large amount, it is performed once a day.

In systems that perform backwash operation, a backwash valve is used that has four ports and changes the direction of water flow by switching a built-in valve body.

FIG. 1 shows a one-tube bundle two-pass type condenser cooling water system equipped with this backwash valve. In the figure, a condenser 1 includes a water chamber 2 and an intermediate water chamber 3, and the water chamber 2 is divided by a partition plate 4 into an inlet water chamber 2a and an outlet water chamber 2b. Further, the plurality of cooling pipes arranged in the condenser 1 are divided into an inlet pipe bundle 5a that connects the inlet water chamber 2a and the intermediate water chamber 3, and an outlet pipe bundle 5b that connects the intermediate water chamber 3 and the outlet water chamber 2b. Separated.

During forward washing operation, the cooling water introduced into the water intake pipe 7 by the water intake pump 6 is passed through a stop valve 8, a backwash valve 9,
It flows into the inlet water chamber 2a through the water supply pipe 10, and further flows into the inlet bundle 5a, intermediate water chamber 3, and outlet tube bundle 5 in the condenser 1.
After exchanging heat with the turbine exhaust gas, the water is discharged through the outlet water chamber 2b, the drain pipe 11, the backwash valve 9, the water discharge pipe 12, and the first valve 13.

During backwash operation, as shown in FIG. 2, the direction of flow of cooling water is reversed by rotating the valve body 9a of the backwash valve 9 by 90 degrees. That is, the cooling water sent to the backwash valve 9 by the water intake pump 6 is introduced from the drain pipe 11, and is then introduced into the outlet water chamber 2b and the outlet pipe bundle 5.
After flowing through the intermediate water chamber 3 and the inlet pipe bundle 5a in this order to exchange heat, the water flows through the inlet water chamber 2a, the water supply pipe 10, the backwash valve 9, the water discharge pipe 12, and the first valve 13 to be drained. Ru.

By the way, when the backwash valve 9 shifts from the normal wash state to the backwash state, as shown in FIG.
The cooling water flowing in from the water supply pipe 10, which has a lot of resistance,
The water does not flow into the drain pipe 11, but directly drains from the water discharge pipe 12.

Figure 4 shows that the flow rate of cooling water flowing into condenser 1 is determined by valve 9.
This shows how the valve body 9a changes depending on the displacement of the valve body 9a. As is clear from this figure, the cooling water that was flowing as a 100% normal flow when the valve body 9a was facing the forward flushing side gradually decreased as the valve body changed, and once the flow rate reached zero, , begins to flow to the backwash side, 100%
It increases until.

[Problem to be solved by the invention]

The condenser is installed for the purpose of condensing the turbine exhaust, so if a state of zero cooling water flow occurs even for a short period of time, as mentioned above, it will not be able to bear 100% of the load, and the vacuum level will decrease. will drop and the power plant will trip.

To avoid this situation, conventionally, before starting backwash operation, the set load of the power plant is reduced to about 30%, and then the backwash operation is started. This also applies to the transition from backwash operation to forward wash operation.

However, increasing the load each time the transition to backwashing or forward washing operation complicates the operation of the power plant, and load control cannot be performed in a short period of time, which improves the thermal efficiency of the power plant throughout the year. This results in a bottleneck in improving plant thermal efficiency. In addition, the number of plant load operations required to switch between forward and backwash operations is much greater than load operations for other reasons, which is a factor in reducing the reliability of the power plant.

The present invention has been made to eliminate the drawbacks of the prior art described above, and an object of the present invention is to provide a condenser cooling water system that eliminates the need to reduce the plant load when transitioning to backwash operation and forward wash operation. That is.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a cooling water system for a condenser of a one-tube bundle two-pass type in which an inlet water chamber and an outlet water chamber that are separated from each other are connected by a tube bundle via an intermediate water chamber. , equipped with a backwash valve for switching the flow direction of the cooling water supplied to the condenser between forward and reverse depending on the position of the valve body, and a discharge end of the water intake pipe that takes in the cooling water by the water pump; , a suction end of a water supply pipe that introduces cooling water into the inlet water chamber, a discharge end of a discharge pipe that leads out cooling water from the outlet water chamber, and a suction end of a water discharge pipe that leads the cooling water to the water discharge side, respectively. In the condenser cooling water system connected to each of the four ports of the above-mentioned backwash valve, a first valve is provided in the middle of the above-mentioned water discharge pipe, and the terminal end of the bypass pipe drawn out from the above-mentioned intermediate water chamber of the condenser is It is characterized in that it is connected to the downstream side of the first valve of the water discharge pipe via a second valve.

[Effect]

According to the present invention, by opening and closing the first valve and the second valve, the water supply pipe and the drain pipe can be separated even when the valve body of the backwash valve is in the neutral position in the forward and reverse directions of the cooling water flow. By leading the cooling water that has been introduced into the condenser from the bypass pipe to the discharge pipe, at least half of the normal flow rate of the cooling water is secured, and on the other hand,
Normal full flow flows through the condenser except when the valve body is in the neutral position.

〔Example〕

Embodiments of the present invention and their effects will be described below with reference to FIGS. 5 to 11. In addition, in these figures, white valves indicate an open state, and black valves indicate a closed state.

In FIG. 5, the condenser 1 shows a 1-tube bundle 2-pass type condenser, and this condenser 1 has a water chamber 2 and an intermediate water chamber 3.
The water chamber 2 is divided by a partition plate 4 into an inlet water chamber 2a and an outlet water chamber 2b. Further, the inlet water chamber 2a and the outlet water chamber 2b communicate with each other via the intermediate water chamber 3 by a tube bundle of a plurality of cooling tubes arranged in the condenser 1, and this tube bundle is connected to the inlet water chamber 2.
an inlet pipe bundle 5a that connects the intermediate water chamber 3 and the intermediate water chamber 3; and an outlet pipe bundle 5b that connects the intermediate water chamber 3 and the outlet water chamber 2b.
It is made up of.

Next, a cooling system that supplies and discharges cooling water to such a condenser 1 will be explained. Water intake pump 6
A water intake pipe 7 is connected to the discharge side of the water intake pipe 7, and its discharge end is connected via a stop valve 8 in the middle to one port of a backwash valve 9 having four ports. The other two ports of this backwash valve 9 are respectively connected to the inlet water chamber 2a.
and the outlet water chamber 2b.
and is connected by a drain pipe 11. Further, a water discharge pipe 12 is connected to the remaining ports of the backwash valve 9, and the outlet end is guided to the discharge side, while a first valve 13 is installed on the pipe. Note that the backwash valve 9 selectively switches the flow direction of the cooling water circulating in the condenser 1 between forward and reverse by switching the flow path according to the rotational position of the valve body 9a. be able to.

According to the present invention, a bypass pipe 15 is led out from the intermediate water chamber 3 of the condenser 1, and the end of the pipe is connected to the water discharge pipe 12 downstream of the first valve 13. A second valve 16 is installed on this bypass piping 15.

Next, the operating procedure from forward washing to backwashing will be explained with reference to Figs. 5 to 11. Fig. 5 shows the state during normal washing, and Fig. 11 shows the state during backwashing. ,
6 to 10 show the state at the time of delivery.

(1) During normal washing (see Fig. 5) In this state, the stop valve 8 and the first valve 13 are opened, and the second valve 16 is closed. Therefore, the cooling water introduced into the water intake pipe 7 from the water intake pump 6 passes through the stop valve 8, the backwash valve 9, and the water supply pipe 1.
0, it is introduced into the condenser 1 through the inlet water chamber 2a, absorbs heat from the turbine exhaust gas flowing outside at the inlet tube bundle 5a, and passes through the intermediate water chamber 3 to the outlet tube bundle 5.
When flowing through b, after absorbing heat from the turbine exhaust again, the drain pipe 11, the backwash valve 9, the water discharge pipe 12, the first
is discharged into the sea via the valve 13.

(2) During transit (state shown in FIGS. 6 to 10) First, from the state shown in FIG. 5, the second valve 16 is fully opened. Then, the cooling water introduced into the intermediate water chamber 3 from the inlet pipe bundle 5a is divided into two parts, and a part of it is passed through the outlet pipe bundle 5b, the drain pipe 11, the backwash valve 9, and the first valve 13 to the water discharge pipe. 12, and the remaining part flows from the intermediate water chamber 3 into the bypass pipe 15, and passes through the second valve 16 to the water discharge pipe 1.
Join the flow within 2. A portion of the cooling water flows through the outlet tube bundle 5b, while the entire amount of cooling water flows through the inlet tube bundle 5a (see FIG. 6).

Next, leaving the valve body 9a of the backwash valve 9 as it is, the first
Fully close valve 13. Then, the entire amount of cooling water introduced into the intermediate water chamber 3 from the inlet pipe bundle 5a flows out from the bypass pipe 15, passes through the second valve 16, and is discharged into the water discharge pipe 12, and during this time, the cooling water flowing through the outlet pipe bundle 5b The flow rate becomes zero (see Figure 7).

Next, when the valve body 9a of the backwash valve 9 is switched to the neutral position as shown in FIG. It flows in parallel in the sink, water supply pipe 10, and drain pipe 11, flows into the inlet water chamber 2a and outlet water chamber 2b, flows in the direction of the arrow in the inlet pipe bundle 5a and outlet pipe bundle 5b, and flows in the intermediate water chamber 3. and flows out into the water discharge pipe 12 via the bypass pipe 15 and the second valve 16 (see FIG. 8). In this state, 50% of the total flow rate of the cooling water flows through the inlet tube bundle 5a and the outlet tube bundle 5b, and backwashing in the outlet tube bundle 5b is started.

Next, when the valve body 9a of the backwash valve 9 is rotated 45 degrees clockwise and placed in the position shown in FIG. , is introduced into the outlet water chamber 2b through the drain pipe 11, the entire amount flows in the outlet pipe bundle 5b in the backwash direction, and the intermediate water chamber 3, the bypass pipe 15, the second valve 1
6 and is discharged from the water discharge pipe 12 (see Fig. 9).

Furthermore, when only the first valve 13 is fully opened from the state shown in FIG.
Flows in the backwash direction inside the inlet water chamber 2a, water supply pipe 1
0, is discharged through the backwater valve 9, the first valve 13 and the water discharge pipe 12. In this state, although the flow rate decreases, the remaining cooling water flows through the bypass pipe 15 and is discharged from the water discharge pipe 12 via the second valve 16 (see FIG. 10).

Finally, from the state shown in FIG.
When only the water supply pipe 10 is fully closed, the discharge via the bypass pipe 15 is stopped, so the entire amount of cooling water introduced into the intermediate water chamber 3 flows through the inlet pipe bundle 5a in the backwash direction, and the water supply pipe 10 and the backwash flow are completely closed. It is discharged through the valve 9, the first valve 13 and the water discharge pipe 12. In this state, the entire amount of cooling water flows in the inlet tube bundle 5a and the outlet tube bundle 5b in the backwash direction (see FIG. 11).

In addition, the valve operation from backwashing to normal/reversal can be performed by performing the above-mentioned operation in reverse, and the flow of cooling water will be exactly the same.

In this way, the entire amount of cooling water always flows through either or both of the inlet tube bundle 5a and the outlet tube bundle 5b, except during the time of passage shown in FIG. 8, and as a result, more than half of the condenser tube bundle will always exhibit normal condensing performance.

By the way, the degree of vacuum in a condenser in a power generation plant is generally set to about 720 mmHg during rated operation. On the other hand, the trip signal of a power plant due to the vacuum level of the condenser or less is generally set at around 600 mmHg, which has a margin of more than 100 mmHg compared to the rated operation. Therefore, even if the condensing performance of the condenser temporarily decreases and the degree of vacuum of the condenser decreases, it will not be a particular problem as long as the trip signal does not occur. According to the performance study, if half of the condenser tube bundle is exhibiting normal condensing performance for a short period of time during backwashing, normal operation of the power plant will not be possible due to the margin until the trip signal is generated. It is possible. In fact, in many power plants that have two pipe bundles and a condenser cooling water system equipped with a backwash valve, one pipe bundle has a transient supply of cooling water to the condenser during backwash operation. Although it will stop temporarily, the other one exhibits normal condensing performance, so it continues to operate without reducing the load on the power plant.

In the present invention, half of the tube bundles always exhibit the normal condensing performance from normal washing to backwashing, or from backwashing to normal washing, so it is possible to transition without reducing the load on the power plant. .

Further, even in the state shown in FIG. 8, the amount of cooling water in the entire condenser is maintained at a specified amount. At this time, the flow velocity in the cooling pipe is approximately half of the specified value. in general,
It is known that the condensing performance of a condenser is proportional to the cooling area and proportional to the 1/2 power of the flow rate in the cooling pipe. Therefore, it can be seen that the state shown in Figure 8 has a condensing performance approximately 1.4 times higher than the state in which half of the tube bundle is exhibiting normal condensing performance (for example, the state shown in Figure 9). . From this, even in the state shown in FIG. 8, there is no need to change the load during transients.

In the above embodiment, the outlet side of the bypass pipe 15 is connected to the water discharge pipe 12, but the bypass pipe 15 may be directly led to the water discharge side and the second valve 16 may be provided on the pipe. . Further, the stop valve 8, the first valve 13, and the second valve 16 can each be constructed with a solenoid valve, and can be operated fully automatically by sequential control.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is no need to reduce the load of the power generation plant during the transition from the forward washing state to the backwashing state or from the backwashing state to the normal washing state. The number of times is reduced, making plant operation easier. Additionally, the thermal efficiency of the power plant throughout the year is increased, and the reliability of the power plant is improved, extending the plant life.

[Brief explanation of drawings]

Figure 1 is a system diagram showing a conventional condenser cooling system, Figure 2 is an explanatory diagram of its operation during backwashing, and Figure 3 is the neutral state of the valve body of the backwash valve in the conventional condenser cooling system. An explanatory diagram showing the position, Fig. 4 is a diagram showing the relationship between the valve position of the backwash valve and the flow rate of cooling water, and Fig. 5 shows the state of the condenser cooling system during normal washing according to the present invention. System diagrams, Figures 6 to 10 are system diagrams during transition showing the state in the middle of transition from normal washing to backwashing, and Figure 11 is a state of the condenser cooling system during backwashing according to the present invention. FIG. 1... Condenser, 2a... Inlet water chamber, 2b... Outlet water chamber, 3... Intermediate water chamber, 5a... Inlet pipe bundle, 5
b... Outlet pipe bundle, 6... Water intake pump, 7... Water intake pipe, 9... Backwash valve, 10... Water supply pipe, 11... Drain pipe, 12... Water discharge pipe, 13... First valve , 15
...Bypass piping, 16...Second valve.

Claims (1)

[Claims] 1. The position of a valve body in a cooling water system to a one-tube bundle, two-pass type condenser, in which an inlet water chamber and an outlet water chamber, which are separated from each other, are connected by a tube bundle via an intermediate water chamber. a discharge end of a water intake pipe that takes in cooling water by a water pump, and a backwash valve for switching the flow direction of the cooling water supplied to the condenser between forward and reverse; The suction end of the water supply pipe that introduces cooling water into the water chamber, the discharge end of the drain pipe that leads the cooling water from the outlet water chamber, and the suction end of the water discharge pipe that leads the cooling water to the water discharge side are respectively connected to the backwash valve. In the double water unit cooling water system connected to each of the four ports, a first valve is provided in the middle of the water discharge pipe, and a second valve is installed at the end of the bypass pipe led out from the intermediate water chamber of the condenser. A double water device cooling water system, characterized in that it is connected to the downstream side of the first valve of the water discharge pipe through the water discharge pipe.