JPS5953471B2 - Condenser cooling water flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling water flow rate control device for a condenser that performs vacuum degree control and heated drainage control in a thermal or nuclear power plant.

Generally, in thermal and nuclear power plants, steam that has expanded and performed work in a steam turbine is led to a condenser.

This condenser is a device that cools and condenses the steam turbine's exhaust gas into water, creates a high vacuum state, lowers the back pressure, and increases the heat drop in the steam turbine, increasing the output and efficiency of the turbine. be.

Therefore, such a condenser is maintained at a degree of vacuum to achieve the best efficiency according to the load factor, and the flow rate of cooling water in the condenser is controlled to obtain this degree of vacuum. .

On the other hand, seawater is generally used as cooling water for the condenser, and the seawater that has undergone heat exchange with the turbine exhaust is discharged into the groove again.

However, since the temperature of this waste water is higher than the temperature of the nearby seawater, it causes various adverse effects, so it is necessary to keep the temperature difference between the cooling water intake and outlet below the specified value by combining the heated waste water with the newly taken cooling water. It is also necessary to control the flow rate of heated wastewater so that it is mixed with some water before being discharged.

FIG. 1 is a cooling water system diagram of a general condenser.

In the figure, cooling water is supplied from water intake 1 through two systems, and circulating water pumps 2A and 2 are provided for each system.
The water is pumped up by B and passes through condenser valves 3A and 3B. The valve openings of the condenser valves are controlled by electric motors 4A and 4B, and the cooling water flow rate is adjusted.

The cooling water that has passed through the condenser artificial valve enters the condenser water chambers 5A and 5B and is heated by exchanging heat with the exhaust gas of the steam turbine 7 while traveling in the direction of the arrow through the cooling pipe group (not shown) in the condenser 6. The water is discharged to the drain port 8.

That is, by controlling the flow rate of cooling water in the condenser, the degree of vacuum in the condenser described above is maintained at an optimum state.

On the other hand, a portion of the new cooling water taken in by the circulating water pumps 2A and 2B passes through the condenser bypass valves 9A and 9B, where the valve opening is controlled by the electric motors 10A and IOB and is returned as bypass cooling water. It is mixed with the warm waste water that has passed through the water dispenser and is discharged to the drain port 8.

This condenser bypass valve is controlled by a wastewater temperature control device.

However, 1. The condenser bypass valve provided for controlling the temperature of the waste water required a large-capacity one, which resulted in an increase in construction costs and a number of maintenance items.

Furthermore, even if we assume a configuration in which the condenser bypass valve is removed and the condenser artificial valve also controls the waste water temperature in order to reduce maintenance items, a flow rate greater than that required by the bypass valve will still be ensured. Since a large-capacity population valve is required, the disadvantage of increased construction costs remains unsolved.

In addition, in plants where operations are performed manually by operators, condenser input valves and condenser This method has the disadvantage that it is necessary to operate both bypass valves, which causes a great deal of stress on the operator.

The present invention has been made to eliminate the above-mentioned drawbacks, and includes controlling the vacuum level of the condenser to improve turbine efficiency, and keeping the temperature difference between the condenser cooling water intake and outlet below a specified value. The purpose of the present invention is to provide a cooling water flow rate control device for a condenser that performs both drainage temperature control and water temperature control only by controlling a circulating water pump, thereby reducing equipment costs for a cooling water system and reducing the number of manual operation parts.

FIG. 2 is a cooling water system diagram of a condenser to which the cooling water flow rate control device according to the present invention is applied.

In the figure, the cooling water at the water intake 1 is supplied to a circulating water pump 2A whose blade opening is adjusted by electric motors 11A and 11B.
and 2B, and directly led as they are to condenser water chambers 5A and 5B, and the outlet flow rate of the condenser is measured by flow rate detectors 12A and 12B.

FIG. 3 is a block diagram showing the configuration of an embodiment of a cooling water flow rate control device for a condenser according to the present invention.

101 constituting this cooling water flow rate control device 100 is a well-known circuit called an optimum degree of vacuum control flow rate setting circuit, which will be briefly explained below.

In other words, in order to operate the turbine efficiently, it is desirable to increase the degree of vacuum in the condenser and lower the back pressure.
In order to increase the degree of vacuum, the circulating water pump must be operated to increase the amount of cooling water, and the power consumption for driving the circulating water pump, that is, the power transmission end loss increases, making the control meaningless.

Therefore, the degree of vacuum in the condenser is calculated based on the turbine exhaust volume, exhaust temperature, condenser cooling area, cooling water temperature, etc. in addition to the turbine load factor, and the cooling water flow rate to obtain this degree of vacuum is calculated. The circuit that outputs the flow rate signal is the optimum vacuum degree control flow rate setting circuit.

Similarly, 102 is a well-known circuit called a drainage temperature control flow rate setting circuit, and its outline will be explained below.

Drainage temperature control is a control that keeps the difference between the cooling water inlet temperature and the drain outlet temperature below a specified value, but the temperature of the drain outlet is determined by measuring the temperature at several points near the drain outlet and averaging it, so it cannot be compared to warm wastewater. It takes a long time for the seawater to mix and for the outlet temperature to settle down to a steady state due to the heat conduction properties of seawater.

In addition, since the water channel from the condenser outlet to the drain port is generally extremely long, changes in the drain port temperature are complicated due to dead time factors. A set value is calculated by adding a predicted value of the amount of cooling water to make the temperature below a specified value and the amount of cooling water corrected from the actual temperature difference.

103 is a high value priority circuit that compares the outputs of the two setting circuits and passes a high level signal; 104A and 104B are adders that connect the condenser outlet flow rate detector 12A;
And 12B is compared with the output of the high value priority circuit and outputs a difference signal. 105A and 105B are regulators that drive electric motors 11A and 11B of circulating water pumps 2A and 2B according to the output of the adder, and add Adjust the flow rate of cooling water pumped up from the water intake so that the output of the device becomes zero.

Hereinafter, the operation of the flow rate control device according to the present invention will be explained.

The output Qv of the optimum vacuum degree control flow rate setting circuit 101 and the output Q1 of the drainage temperature control flow rate setting circuit 102 are given to a high value priority circuit 103, which outputs a cooling water flow rate command Q5 equal to the higher flow rate setting.

This flow rate command Q5 is added to adders 104A and 104B, and the condenser output flow rate Qa is separately input to this adder.
−□ and Qa−n, respectively, and the deviation signal Qε
-□ and Qa-B are obtained.

This deviation signal is applied to regulators 105A and 105B, and a signal that makes this deviation zero is given to electric motors 11A and IIB to adjust the blade opening of the pump and control the flow rate of the cooling water pumped up.

Here, by using the high value priority circuit, the degree of vacuum or the temperature of the drain water is controlled to be higher than the set value, but no problem occurs.

In other words, when Qv>Q□, the amount of cooling water for controlling the drainage temperature will flow more than necessary, but the drainage temperature of the condenser will be correspondingly lower, and the difference between the cooling water inlet temperature and the drainage outlet temperature will become smaller. The effect on the seawater near the drainage outlet will be less.

In addition, when QT>Qv, the amount of cooling water for controlling the vacuum level will flow more than necessary, but this will not cause any harm as the vacuum level of the condenser will increase and the back pressure will decrease, which will improve the turbine efficiency.

In the above embodiment, the flow rate at the outlet of the condenser cooling water was detected and used as the feedback signal, but the same operation can be achieved by using the flow rate at the inlet of the condenser cooling water or the opening degree of the circulation pump.

As is clear from the above explanation, according to the condenser cooling water flow rate control device according to the present invention, only the circulating water pump can be controlled.
It is possible to maintain the degree of vacuum and the temperature of the waste water at appropriate values, making it possible to significantly reduce construction costs without the need for large-capacity valves, and freeing operators from complex manual operations, making turbine plants more efficient. It is possible to operate efficiently and to reduce the harmful effects caused by heated waste water.

[Brief explanation of the drawing]

Fig. 1 is a cooling water system diagram of a general condenser, Fig. 2 is a cooling water system diagram of a condenser to which the device of the present invention is applied, and Fig. 3 is a cooling water system diagram of a condenser according to the present invention. FIG. 1 is a block diagram showing the configuration of an embodiment of a flow rate control device. 1... Water intake, 2A, 2B... Circulating water pump, 3A, 3B... Condenser population valve, 4A,
4B, 10A, IOB, IIA, IIB...
...Electric motor, 5A. 5B... Condenser ice chamber, 6... Condenser,
7...Steam turbine, 8...Drain port,
9A, 9B...Condenser bypass valve, 12A, 1
2B...Flow rate detector, 100...Condenser cooling water flow rate control device, 101...Optimum degree of vacuum control amount setting circuit, 102... Drainage temperature control flow rate setting circuit, 103... High value priority circuit, 104
A, 104B...Adder, 105A, 105B
・・・・・・Adjuster.

Claims (1)

[Claims] 1. In a device that controls the flow rate of cooling water in a condenser using a pump whose blade opening can be adjusted by an electric motor, the cooling water is used to maintain the condenser at an optimal degree of vacuum in order to improve turbine efficiency. a first setting circuit that outputs a flow rate signal; a second setting circuit that outputs a cooling water flow rate signal that maintains a temperature difference between a cooling water intake and a cooling water outlet below a specified value;
a high value priority circuit that compares the outputs of the first setting circuit and the second setting circuit and passes a higher level signal; a detection signal of the cooling water flow rate of the condenser; and an output of the high value priority circuit. A cooling water flow rate control device for a condenser, comprising: a controller that drives the electric motor in response to a deviation signal compared with the deviation signal; and a regulator that adjusts the blade opening of the pump in a direction in which the deviation signal becomes zero. .