JPS5855321B2 - Cooling water control device for condenser in power generation plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling water control device for a condenser in a power plant such as a thermal power plant or a nuclear power plant.

The thermal efficiency of a turbine in a thermal or nuclear power plant is determined by the steam conditions generated from the boiler, the condenser vacuum degree, the feed water temperature, the heat cycle conditions such as the number of feed water heating stages, and the performance of the turbine itself.

In particular, it is known that the degree of vacuum in the condenser has a large effect on the efficiency of the turbine.

In thermal and nuclear power plants, steam generated from a boiler is sent to a turbine, expands within the turbine, performs work, and is then exhausted to a condenser.

This condenser cools and condenses the steam turbine exhaust gas and condenses it, creating a high vacuum state and lowering the exhaust pressure to reduce the heat drop in the steam turbine, increasing the output and efficiency of the turbine. It is a device.

Here, the degree of vacuum of the condenser is the amount of exhaust gas exhausted to the condenser,
It is well known that the temperature varies depending on the exhaust temperature, the temperature and amount of cooling water in the condenser, the shape of the condenser, the cooling area, etc.

The optimum degree of vacuum in the condenser is determined so that the turbine operates at maximum efficiency according to its load.

Next, conventional condenser vacuum control will be explained.

FIG. 1 is a cooling water system diagram of a condenser, and FIG. 2 is a block diagram showing a circuit of a conventional condenser vacuum degree control device.

In Fig. 1, the cooling water of the water intake 1 is supplied to the regulating motor 3A.
, 3B, the required flow rate is supplied to the water chambers 4A, 4B of the condenser 5 by the circulating water pumps 2A, 2B, whose openings are adjusted by the circulating water pumps 2A, 2B, and the cooling pipes (not shown) in the condenser 5 are moved in the direction of the solid line arrow. While passing through the exhaust gas of the steam turbine 6, heat is exchanged with the exhaust gas of the steam turbine 6.

The heated cooling water is discharged from the drainage lower as wastewater.

The degree of vacuum in the condenser in such a condenser cooling water system is controlled by adjusting the amount of cooling water in the condenser.
The flow rate of cooling water is controlled by the optimum vacuum degree control device shown in FIG.

By the way, as mentioned above, the optimum degree of vacuum is determined by the load factor of the turbine 6, while the degree of vacuum of the condenser is determined by the exhaust volume of the steam turbine, the exhaust temperature, the amount of cooling water in the condenser, the temperature of the cooling water,
It is determined by the shape of the condenser and the cooling area.

Therefore, the flow rate of cooling water to obtain the optimum degree of vacuum is determined by the generator load, which is proportional to the load factor (displacement amount) of the steam turbine, and the cooling water temperature.

Since the other factors are constant, they are treated as coefficients.

When adjusting the flow rate, the load value G1 and the cooling water temperature T1 measured by the cooling water inlet temperature detector 8 are input to the flow rate setting circuit 11, and the condenser flow rate setting value Q1 for obtaining the optimum degree of vacuum is set in the setting circuit 11. Calculated.

This flow rate set value Q1 is the condenser flow rate detector 9A.

The condenser flow rates Q2A and Q2B detected by 9B are compared in adders 12A and 12B, respectively.

The deviation value is given to motor drive circuits 13A and 13B, and this input drives the regulating motor 3A.

3B is driven, and the opening degrees of circulation pumps 2A and 2B are adjusted to obtain the required condenser flow rate.

Now, in the condenser vacuum level control method described above, the condenser flow rate, that is, the circulation pump flow rate, is adjusted in order to maintain the vacuum level at an optimal value. The pump power is very large, so even if the optimal air quality is achieved and the turbine efficiency is increased, the pump driving loss will increase, and as a result, the reverse terminal loss of the power generation plant will increase. there were.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a condenser cooling water control device that automatically adjusts the flow rate of condenser cooling water in order to improve the gain at the power transmission end of a power generation plant and effectively utilizes energy. shall be.

The present invention will be explained below with reference to illustrative embodiments.

FIG. 3 is a block diagram showing an example of a cooling water control device according to the present invention.

Reference numeral 14 denotes a rated vacuum degree setting device, which is used to set the rated vacuum degree Vac1 for steam turbine operation.

Reference numeral 15 denotes an optimum degree of vacuum calculation circuit, into which the load value G1 detected by the generator load detector 10 is input as a signal proportional to the displacement of the steam turbine 6, and the optimum degree of vacuum value ac2 is calculated according to the generator load factor. Calculate.

The rated vacuum degree Vac1 (setting value) and the optimum vacuum degree value Vac1 obtained as above are input to the adder 16, and the adder 16 calculates the difference value V between both values Vac1 and Va c 2.
ac3 is calculated, and this difference value Vac3 is input to the steam turbine output increase calculation circuit 17.

The turbine output increase calculation circuit 17 has a generator load value G1.
is also input, and the increase in output of the steam turbine when the steam turbine is operated at the optimum degree of vacuum is calculated as a power value to obtain Pl.

On the other hand, the inlet temperature T1 of the condenser cooling water intake 1 is detected by the temperature detector 8, and the difference between this inlet temperature I and the degree of vacuum Va
c3 is input to the cooling water increase calculation circuit 18.

Then, an increase in the amount of cooling water Q3 in the rated vacuum state that should be flowed in order to perform optimal vacuum control is calculated.
Q3 is output to the circulating water pump power increase calculation circuit 19.

Further, the opening value η and the pump head M of the circulating water pump are also input to the circuit 19 for calculating the increased power of the circulating water pump, and the increased power of the circulating water pump caused by performing the optimum vacuum degree control is calculated as the power value P2. is output from the calculation circuit 19 as .

The circulating water pump power increase power value P2 and the steam turbine efficiency increase power value P are input to an adder 20 to determine the power difference P3 between the two values, and the cooling water flow rate increase calculation circuit 2
1 is input.

The opening value η and the pump head M of the circulating water pump are also input to this calculation circuit 21, and the calculation circuit 21 calculates that the power difference P3 is positive polarity, that is, the pump power increase power value P2 is the efficiency increase power value Only when the level is higher than P1, a corrected cooling water flow rate Q4 proportional to the power loss difference P3 is output.

On the other hand, the optimum degree of vacuum value Vac2 and the input temperature T1 are input to the optimum vacuum degree control required cooling water flow rate calculation circuit 22, and the calculation circuit 22 calculates the necessary cooling water flow rate Q5 for optimum vacuum degree control.

Then, the corrected cooling water flow rate Q4 is subtracted from the required cooling water flow rate Q, and the total cooling water amount setting value Q1 is determined.

The control system after Q1 is the same as the conventional flow rate control system of a circulating water pump, and will therefore be omitted.

Incidentally, the rated vacuum degree Vacl of the condenser is determined as a limit value for steam turbine operation based on condenser cooling water temperature fluctuations, the average value of the turbine load factor, and the like.

On the other hand, the optimum degree of vacuum to obtain the optimum efficiency of the turbine is
As mentioned above, it is determined by the turbine load factor (turbine displacement), exhaust temperature, condenser cooling area, condenser cooling water amount (circulating water pump flow rate), its temperature, etc.

Among these, the exhaust temperature is generally considered to be a constant temperature,
Furthermore, the cooling area of the condenser 5 is also a fixed value.

Furthermore, since the exhaust gas temperature is constant, the turbine load factor, ie, the turbine displacement, has a value proportional to the generator load.

Therefore, it is clear that the condenser cooling water flow rate to obtain the optimum degree of vacuum Vac2 is determined by the generator load, cooling water temperature variables, and other fixed coefficients.

In this way, the optimum degree of vacuum calculation circuit 15 in FIG. The amount of cooling water for temperature control, that is, the circulating water pump flow rate Q, can be obtained.

On the other hand, the difference Vac3 between the rated vacuum degree Vq c 1 and the optimum vacuum degree Vac2 is input to the steam turbine output increase calculation circuit 17, and by controlling the optimum vacuum degree, the difference between the efficiency of the steam turbine and the steam turbine efficiency under the rated vacuum degree is calculated. According to the generator load G1 at that time, an increase P1 in generated power due to efficiency improvement is obtained.

Furthermore, the vacuum difference Vac3 and the cooling water temperature T1 are input to the cooling water flow rate increase calculation circuit 18, and the increase Q3 of the cooling water flow rate from the rated vacuum level control to achieve the optimum vacuum level control is calculated. It is input to the circulating water pump power increase calculation circuit 19, and the circulating water pump power increase P2 required to flow the increased flow rate Q is obtained from the opening value η and head M of the circulating water pump at that time.

Then, gain power P1 and pump power increase due to efficiency improvement (
The difference P3 from P2 (power loss) is obtained by the adder 20, and this power difference P3 is input to the cooling water flow increase calculation circuit 21, and the corrected cooling is calculated from the opening value η and head M of the circulating water pump at that time. A water flow rate Q4 is obtained.

Note that the flow rate Q4 outputs a signal only when the loss power P2 is higher than the gain power P1.
When is higher than the power loss P2, it becomes zero.

Then, the corrected cooling water flow rate is subtracted by the adder 23 from the flow rate Q5 necessary for optimum vacuum degree control to obtain Ql, which is used as the flow rate setting of the circulating water pump.

Above Q) In the example, the steam turbine displacement is obtained from the generator load, but it is possible to obtain the same effect by placing a flow rate detector at the steam exhaust point of the turbine and inputting the steam flow rate instead of the load. can.

As described above, according to the present invention, the output increase (outside of power gain) due to the improvement in turbine thermal efficiency obtained by performing optimal vacuum degree control and the power increase of the circulating water pump (power loss),
Since the flow rate of the circulation pump is controlled so that the power output of the power generation plant always produces a positive gain,
Electric power at the transmission end of the power generation plant is output with maximum efficiency, and energy can be used more effectively.

[Brief explanation of the drawing]

Fig. 1 is a condenser cooling water system diagram, Fig. 2 is a block diagram of a conventional condenser optimum vacuum level control device, and Fig. 3 is an embodiment of a condenser cooling water control device according to the present invention. FIG. 1...Water intake, 2A, 2B...Circulation pump, 3A, 3B...Circulation pump adjustment electric motor, 4A. 4B... Condenser chamber, 5... Condenser,
6...Steam turbine, 7...Drain port,
8...Cooling water inlet temperature detector, 9A, 9B...
...Condenser inlet cooling water amount detector, 10...
Generator load detector, 11...Flow rate setting circuit, 1
2A, 12B...Adder, 13A. 13B...Motor drive circuit, 140.198.
Rated vacuum degree setting device, 15... Optimal degree of vacuum calculation circuit, 16... Adder, 11... Turbine output increase calculation circuit, 18... Cooling water flow rate increase calculation circuit, 19... Pump power increase calculation circuit, 20... Cooling water flow rate increase calculation circuit, 2
1... Cooling water amount calculation circuit for optimal vacuum degree control, V
ac,... Rated vacuum degree, Vac2...
Optimal degree of vacuum, Vac3... Difference in degree of vacuum, Pl...
... Gain power, P2 ... Loss power, P3.
...Power difference, T, ...Cooling water intake inlet temperature, Q, ~Q5...Cooling water flow rate value.

Claims (1)

[Claims] 1 In a cooling water control system for a condenser in a thermal or nuclear power plant, the rated vacuum setting device sets the rated vacuum of the condenser, and a signal proportional to the turbine displacement is input to determine the optimum level for turbine operation. An optimum degree of vacuum calculation circuit that calculates the degree of vacuum, an adder that calculates the deviation between the rated degree of vacuum and the optimum degree of vacuum, and an increase in turbine output due to improvement in thermal efficiency of the turbine based on the obtained degree of vacuum deviation. A circuit for calculating an increase in turbine output; a circuit for calculating an increase in pump power for circulating condenser cooling water due to vacuum adjustment based on the vacuum degree deviation; An adder that calculates the deviation between the increase in pump power and the increase in pump power and outputs only when the increase in pump power is higher than the increase in turbine peak, and a cooling function that calculates the increase in cooling water flow rate to be corrected based on the increase deviation. Condensing water in a power generation plant equipped with a water flow rate increase calculation circuit, an adder that subtracts this corrected cooling water flow rate increase from the cooling water flow rate required for optimal vacuum adjustment and outputs a comprehensive cooling water flow rate adjustment signal. Cooling water control device for the vessel.