JPS5953562B2 - Power plant equipment cooling water control method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for controlling cooling water for various equipment in a power plant.

[Background of the invention]

Each device in a power plant, such as pumps, motors, and generators, generates heat during operation, so in order to ensure stable operation of each device, it is necessary to absorb the generated heat and cool each device to prevent its temperature from rising too high. Therefore, an equipment cooling water system is installed.

The equipment cooling water system uses a pump to pump up cooling water, cools it to a specified temperature through a cooling water cooler, and supplies it to a cooler attached to the equipment, which has been reduced to a specified pressure.

It is often planned that the cooled water attached to the equipment is returned to the cooling water source and pumped up again by a pump to be circulated as cooling water. FIG. 1 is a cooling water system diagram for explaining a conventional power plant equipment cooling water control device.

The cooling water is sent to the cooling water cooler 3 by the cooling water pump 2a or 2b to lower the water temperature, and further, by the action of the cooling water temperature control valve 31, the cooling water is cooled before passing through the cooling water cooler bypass piping 13. It is mixed with water and adjusted to a specified temperature. A cooling water temperature controller 41 is disposed downstream of the cooling water temperature control valve 31 . The cooling water adjusted to the specified temperature is further reduced in pressure to the specified pressure by the cooling water pressure regulating valve 32 and sent to the cooling water supply main pipe 14. A cooling water pressure regulator 42 having a manual setting function is disposed downstream of the cooling water pressure regulating valve 32 so that the specified pressure can be set manually. The cooling water is branched from the cooling water supply main pipe 14 and sent to the main turbine oil cooler 4, the generator hydrogen cooler 5, and the turbine-driven feedwater pump cooler 6 via temperature control valves 33a, 33b, and 33c, respectively. It will be done. In addition, the cooling water
[Cooling water supply main pipe] Branched from 4 and immediately connected to miscellaneous equipment cooler 7,
7". The cooling water that has cooled each of these equipment coolers passes through the cooling water return main pipe 15, returns to the cooling water pump 2, and is circulated again as cooling water. Reference numeral 1 refers to the head tank. However, the cooling water has the function of absorbing the effects of expansion and contraction depending on the temperature.By the way, there are five units of each device shown in Figure 1, and three of them are temperature control valves.
3a, 33b, etc. are shown, but in reality, there are approximately 40 devices in a large-capacity power plant that require cooling water, and the required amount of cooling water is approximately 2200
Approximately 10% of the total number of devices is T/H and has a temperature control valve that automatically adjusts the amount of water in the cooler attached to the device according to the amount of heat generated by the device itself. The amount of water is about 1600T/H, which is about 73%.

For this reason, if the equipment with the automatic temperature control valve is out of operation, the amount of cooling water required for the power plant will be 27% of the rated amount, and as a result, the discharge amount of the cooling water pump will decrease. This increases the pump head and reduces system pressure loss by reducing the water flow rate in the piping and each cooler. For this reason, the differential pressure at the inlet and outlet of the cooling water pressure control valve 32 increases, and together with the decrease in flow rate, the opening degree of the control valve decreases (
(13% when fully open), even a slight change in the valve opening will result in a large change in flow rate, and this large change in flow rate will increase the pressure fluctuation downstream of the cooling pressure control valve 32, making it difficult to control the cooling water pressure. If a hunting phenomenon occurs and automatic operation of the cooling supply device becomes difficult or pressure fluctuations are too large, there is a problem that each control valve 32, 33a, 33b, 33c or pressure regulator 42 may be damaged. [Object of the invention] The object of the present invention is to solve this problem and to
A method for controlling cooling water for power plant equipment that can increase the amount of water to be controlled by the pressure regulating valve 32 even during shutdown, minimize fluctuations in cooling water pressure, and safely continue operation;
The object of the present invention is to provide an apparatus for carrying out this method.

[Summary of the invention]

To achieve this object, the power plant equipment cooling water control method and device of the present invention include a method for opening a stable start valve to bypass cooling water from upstream to downstream of the cooler, and for carrying out this method. The device is characterized by comprising a pipe connecting upstream and downstream of the cooler, and a stable start valve provided in the pipe and opened when the amount of water required for the cooler is small. do.

In other words, the cooling water pressure control valve focuses on the fact that when there is a large amount of cooling water flowing through the pressure control valve, even if there is a fluctuation in the amount of cooling water, the adjusted pressure on the downstream side is less likely to fluctuate. When the local turbines and power plants are not operating,
A safety activation valve inserted in parallel to the cooler was opened to increase the amount of cooling water passing through the control valve.

This eliminates hunting of the pressure regulating valve and stabilizes the pressure downstream of the regulating valve. [Embodiments of the Invention] Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows an apparatus for carrying out the method for controlling cooling water for power plant equipment according to the present invention, and the difference from the conventional cooling water system for power plant equipment is that each equipment is on the cooling water supply main pipe 14. The upstream side of the attached cooler group 8 and the downstream side of the cooler group 8 on the cooling water return main pipe 15 are connected by a stable start pipe 16. A valve 36 and a flow rate regulating orifice 37 are provided.

Furthermore, when the main turbine and generator are stopped, there is no heat generation from the main turbine oil cooler 4, generator hydrogen cooler 5, and turbine-driven cooling pump 6, so the temperature control valve of each cooler 33a, 33b, and 33C are fully closed to cut off the inflow of cooling water. At this time, the stable start valve 36 is opened by the control circuit shown in FIG.
To explain the control logic in FIG. 3 in more detail, in the same figure, when the amount of cooling water required for each cooler decreases and the opening degree of the cooling water pressure regulating valve 32 becomes less than the specified value, 0R
The safety activation valve 36 is opened by the logic circuit A and the 0R logic circuit C. Once there is an output from the 0R logic circuit A, even if the opening degree of the regulating valve 36 exceeds the specified value, the system will safely start up as long as the conditions for generator connection (that is, the generator is in load operation) are not met. Valve 36 is adapted to remain open. Furthermore, if conditions are met during main turbine turning (when the main turbine and generator are not in operation), the safety start valve 36 is opened by the OR logic circuit C.

Note that the wipeout logic W in FIG. 3 means that this circuit is opened when the conditions for the addition of a generator are met. Now, the temperature control valves 33a, 33b, 33c of each cooler are fully closed to block the inflow of cooling water, and the stable start valve 36 is opened by the control logic shown in FIG. By flowing the cooling water in the main pipe 14 through the orifice 37 of the stable startup pipe 16 and into the cooling water return main pipe 15, the flow rate of water flowing through the cooling water pressure control valve 32 is increased.

That is, in Fig. 4, the vertical axis shows the cooling water flow rate Q as a percentage with the maximum value of 100, the horizontal axis shows the operating status of only miscellaneous equipment in section D from the origin, and section E shows the operating status of the turbine. Considering the operating conditions, and assuming that the numbers in this section are numbers indicating each output as a percentage, with the maximum output of the generator as 100, the cooling water pressure regulating valve is closed until the generator starts output operation. The water flow rate of No. 32 is 50%, which is shown by the straight line F. After that, during output operation, the water flow rate is varied from 50% to 100% by automatic adjustment of the temperature control valves 33a, 33b, and 33c of each cooler. The curve G varies between % and %. When calculating the conventional water flow rate using these coordinates, as shown by the two-dot chain lines H and I in the figure, when the turbine is operating only miscellaneous equipment before starting operation, the water flow rate is 27%, and This value rises rapidly to 50% when the turbine starts operating. That is, the two-dot chain line H is the amount of cooling water when conventional turbines, generators, and electric machines are stopped, and is equal to the amount of cooling water for miscellaneous equipment.The difference of 1 between the solid line F and this two-dot chain line H indicates that the cooling water is stable. Equal to the flow rate of the starting valve. Also, the symbol J is the amount of cooling water in the equipment cooler equipped with a temperature control valve that automatically adjusts the amount of cooling water, and the sum with the amount of cooling water H for miscellaneous equipment in the previous season is slightly lower than the cooling water pump design point P. It is configured as follows. In Fig. 5, the horizontal axis shows the cooling water amount Q in %, and the vertical axis shows the cooling water pressure p in Kg/Cm2, where A is the discharge pressure characteristic of the cooling water pumps 2a and 2b, and B is: Similarly, C indicates the inlet pressure characteristic of the pressure regulating valve 32, C indicates the outlet pressure characteristic, and D indicates the pressure characteristic of the return main pipe 15.

The difference N between the characteristic curves A and B represents the resistance loss in the pipe from the discharge side of the cooling water pumps 2a, 2b to the inlet of the control valve 32, and indicates that the loss increases as the flow rate increases. ing. The difference T between the characteristic curves C and D is the set pressure given to the pressure regulator 42, and in this embodiment is set to 0.5 kg/Cnl2. L is the cooling water pump 2a, 2b (7) from the return main pipe 15.
) represents the pressure loss in the pipeline leading to the suction side. The difference between characteristic curves B and C indicates the differential pressure at the inlet and outlet of the control valve 32, and when the amount of cooling water is 0, the inlet pressure is 6 kg/c] The difference between N2 and outlet pressure 25 kg/Cm2 is 3.5 kg/Cnl2. For hot items, cooling water amount Q is 27%, 50%, 100%
As the pressure changes, the differential pressure M1=3.4kg/
Cm・, M2=2.9kg/Cm2, M3=0.7kg
/Cnl2.

Here, the symbol K indicates the hydrostatic head of the head tank. Figure 6 shows the relationship between the pressure difference P between the inlet and outlet of the control valve and the flow rate Q when the opening of the control valve is kept constant, where W is the opening of 13% and x is the opening of 24%. , Y indicates the characteristic of an opening degree of 80%.

In other words, it shows the change in the differential pressure p at the inlet and outlet of the control valve with respect to the amount of cooling water, but in the W characteristic, the amount of change a1 in the amount of cooling water
The amount of change P1 in the differential pressure at the inlet and outlet of the control valve when is set to ±1% of the total amount of cooling water shows a value of about 1 kg/Cnl2.
Similarly, curve x is a characteristic curve when the pressure control valve opening degree is 24%, and the amount of change A2 in the amount of cooling water is ±1% of the total amount of cooling water.
When this happens, the amount of change P2 in the differential pressure at the inlet and outlet of the control valve is approximately 0.
It shows a value of 4 kg/Cm・, which is about 1/1 compared to the W characteristic.
This shows that it is possible to keep it to 2 or less. 6th
The characteristics shown in the figure are obtained by keeping the opening degree of the control valve constant and looking at how the differential pressure between the outlet and inlet changes when the flow rate fluctuates. Controller 4
The opening degree of the control valve 32 is adjusted so that the detected pressure in step 2 matches the set pressure. There is a problem in that the pressure on the downstream side changes greatly due to a slight change in the opening degree of the valve, making it difficult to obtain control stability.

In particular, as shown by M1 in FIG.
This tendency is remarkable when a large differential pressure M1 is applied.
The inventors discovered that the amount of cooling water is extremely small (approximately 27% of the maximum flow rate) when the main turbine and generator of the power plant are stopped.
In consideration of this, we decided to open the safety start valve only under these operating conditions.

An orifice 37 is inserted in series with the safety start valve 36, and the size of the orifice 37 is set so that a flow rate I in FIG. 5 flows through the safety start piping 16 when the valve 36 is opened. Therefore, in the present invention, the pressure regulating valve 32 has the pressure H+1 in FIG.
In other words, since 50% of the flow rate will flow, the opening degree of the control valve will be around 24%, and the change in the control valve outlet pressure due to the change in flow rate will be small.

[Effects of the Invention] As described above, according to the present invention, even when the required amount of cooling water in a power plant is small, fluctuations in cooling water pressure can be kept to a minimum and operation can be continued safely.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing a conventional power plant equipment cooling water system.
Fig. 2 is a system diagram showing one embodiment of the present invention, Fig. 3 is a control system diagram of the stable start valve applied to the embodiment, and Fig. 4 is a diagram of the relationship between generator output and cooling water flow rate. , FIG. 5 is a diagram showing the relationship between the amount of cooling water and the pressure of the cooling water, and FIG. 6 is a diagram showing the relationship between the flow rate of the cooling water and the differential pressure at the outlet and outlet of the cooling water pressure regulating valve. 2... Cooling water pump, 3... Cooling water cooler, 8...
・Cooling group attached to each device, 16... Stable startup piping, 32
...Cooling water pressure control valve, 33a, 33b, 33c...
- Temperature control valve, 36... stable start valve.

Claims (1)

[Scope of Claims] 1. The cooling water discharged from the cooling water pump is maintained at a constant differential pressure between the cooling water inlet side and the outlet side of the attached cooler of the power plant equipment by the cooling water pressure control valve. A method for controlling power plant equipment cooling water supplied to an auxiliary cooler, when the amount of water required by the auxiliary cooler is small, opening a stable start valve to bypass the cooling water from upstream to downstream of the auxiliary cooler; A method for controlling cooling water for power plant equipment, characterized in that fluctuations in cooling water pressure are minimized by increasing the amount of water regulated by the cooling water pressure regulating valve. 2 A cooler attached to power plant equipment, a cooling water pump that supplies cooling water to the cooler, and a cooling water pressure control valve that maintains a constant cooling water pressure difference between the inlet and outlet sides of the cooler. In the power plant equipment cooling water control device, the control valve is located on the downstream side of the control valve, connects the upstream and downstream of the attached cooler, and opens when the amount of water required by the attached cooler is small. 1. A power plant equipment cooling water control device, comprising a pipe having a valve, and increasing the amount of water regulated by the cooling water pressure regulating valve to minimize fluctuations in cooling water pressure.