JPH01224494A - Circulating water controlling apparatus - Google Patents

Abstract

PURPOSE:To make water discharged by a pump unchanged by controlling an angle of a blade of the pump so as to control the amount of circulating water discharged by the pump by means of water level detected at a water cutlet of the pump as a control signal of the angle of the blade. CONSTITUTION:Steam discharged from a steam turbine 1 is cooled and condensed by a condenser 2. Water level is detected by a water level detecter 8 provided at a water outlet. An output signal of the detecter 8 is converted by a converter 12 into a change signal of a blade of a pump corresponding to the amount of changing water level. The change signal is supplied to a blade angle control-operating apparatus 6 so as to control the angel of the blade. The amount of the water discharged by the pump is thus controlled so as to be unchanged without respect to fluctuation of the water level of the circulating water at the outlet.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Wi ring water pump for a steam power plant, and in particular,
The present invention relates to a control device that optimally controls the amount of circulating water sent to a condenser of a steam turbine.

[Conventional technology]

Steam power plants are equipped with movable vane-type pumps that can arbitrarily change the pump discharge volume by changing the angle of the pump blades, and the pump discharge volume is controlled according to the operating conditions of the steam power plant. There is.

Regarding the control of the blade angle, for example, 1.
As shown in No. 6-36889, the cooling water temperature is detected and the amount of cooling water supplied to the condenser is controlled so that maximum efficiency is achieved in the turbine cycle.

[Problem to be solved by the invention]

In this conventional technology, control is performed by assuming that the discharge amount of the circulating water pump has a certain relationship with the angle of the pump blades, but in reality, the water level at the pump intake port changes. For example, since the pump discharge amount changes widely, there is a problem that controlling only the cooling water temperature condition causes a large error in the optimal circulating water amount required for high efficiency of the turbine plant, making it impossible to perform suitable control.

The above problem is 1. Typically, when the steam turbine condenser is installed at a position considerably higher than the pump water intake level, the siphon pressure at the top of the condenser ice chamber does not exceed the limit. This problem becomes noticeable in circulating water systems where the circulating water recovery tank is installed at a position higher than the pump water intake level.

In such a circulating water system, the circulating water pump has a discharge head that is sufficient to cover the total loss, which is the pressure loss of the condenser, the pressure loss of the circulating water piping, and the valves, plus the level difference between the pump intake water level and the recovery tank. For example, if the pump water intake water level changes from a low water level to a high water level, the overall loss of the circulation system will decrease, and the pump discharge rate will increase due to the pump characteristics. The change in the discharge amount becomes larger as the change in the intake water level increases.
This impedes the above-mentioned optimal circulating water flow control.

An object of the present invention is to provide a circulating water system that can obtain the most preferable pump discharge amount for a circulating water system or a steam power plant including a turbine plant even if the water level at the circulating water pump water intake fluctuates. There is a particular thing.

[Means to solve the problem]

The above object is achieved by detecting changes in the water level of the circulating water pump water intake and controlling the blade angle of the pump.

[Effect]

To control the blade angle of a circulating water pump, a water level detection instrument is installed at the pump water intake to detect changes in water level, and its output signal is replaced with a pump blade change signal corresponding to the amount of water level change.
This is done by driving the blade angle adjustment device. As a result, the discharge amount of the pump can be controlled regardless of fluctuations in the intake water level, or depending on the fluctuating water level.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a condenser 2 that cools and condenses exhaust steam from a steam turbine 1, and a circulating water pump system that supplies cooling water to the condenser. In the circulating water pump system, water discharged from a movable vane type circulating water pump 3 having a vane angle adjustment drive device 6 is supplied to an ice chamber of a condenser 2 through a circulating water pipe 4, and after passing through the condenser, is sent to a recovery tank 5. released.

In addition, Fig. 2 shows the water volume-head curve A l of the circulating water pump.
It is a graph showing the relationship between + A x and circulating water system pressure loss curves Bt and B2.

Circulating water is usually taken from the sea at steam power plants, but
Sea level fluctuates between low and high water levels day and night and seasonally. Hereinafter, this changing water level will be referred to as the low water level LWL and the high water level HWL.

When the water level at the pump water intake is at LWL, the water level difference between the water intake water level and the recovery tank water level is given as Hl, and the circulating water pump discharges at point a, the intersection of the water volume-head curve At and the system pressure loss curve B1. It is driven by.

Next, when the water intake water level changes to HWL, the water level difference becomes H2, the pump operating point shifts to the intersection of curve A1 and curve B2, and the pump discharge amount changes.

However, if the pump blade angle is changed in the direction of decreasing in this state, the water flow-head curve of the pump can be made as shown in A2, and the intersection point can be moved to the 0 point. In other words, the pump discharge amount is obtained as the same amount as during LWL.

In addition, the difference between the water levels H1 and H2 is about 5 m according to an example of a steam power plant in actual operation, and the pump discharge amount at point 0 at this time increases by about 30% compared to that at point a. There J
This results in the flow velocity in the condenser tubes exceeding the allowable maximum flow velocity by a large margin, which may cause erosion in the tubes and cause tube leaks, causing serious problems for the main engine of the steam power plant. , this is a phenomenon that should be avoided.

Also, for circulating water pumps, when two or more pumps are operated, the pressure drop in the circulating water system is reduced, so the pump is already operating at an increased flow rate compared to the rated capacity of the pump, and the amount of water increases significantly. This means increasing the strength of the pump, increasing the capacity of the power motor, and more.

Various problems arise, such as uneconomical design in terms of efficiency.

Therefore, in order to prevent this phenomenon, it is necessary to adjust the pump discharge amount. A control device that makes this possible will be explained below with reference to FIG.

A differential pressure transmitter 1 detects the difference between the air pressures of the air pressure measuring device 8 installed in the water intake and the same type of measuring device 9 installed in the reference water level tank 10.
1, it is transmitted as a signal of water intake water level. As shown in FIG. 2, this water level signal is transmitted to the converter 12 which has a function of the amount of change in the pump discharge amount to be corrected corresponding to the water level change calculated from the pump's water volume-head characteristics and the system pressure drop characteristics. The signal is replaced with a pump blade angle change signal and transmitted to the blade angle adjustment drive bag @6 to control the pump blade angle. Therefore, by using this control device, even if there is a large change in the water level at the pump water intake, the pump discharge amount can be controlled to be constant. 7 is the blade angle control mechanism. still,
When the blade angle of the circulating water pump is controlled for optimization of turbine plant efficiency, for example, by seawater temperature or condenser vacuum, the blade angle is input to the blade angle adjustment device 6 by the computing unit 13. The signal is corrected using the signal.

According to this embodiment, it is possible to protect the condenser from tube erosion, and it is also possible to provide an optimally designed circulating water pump.

〔Effect of the invention〕

According to the present invention, it is possible to control the pump discharge amount so that it does not change regardless of fluctuations in the water level at the circulating water pump water intake.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram of a circulating water system for cooling a condenser and a circulating water pump according to an embodiment of the present invention, and FIG. 2 is an operational characteristics diagram of the circulating water pump. 1... Steam turbine, 2... Condenser, 3... Circulating water pump, 4... Circulating water pipe, 5... Recovery tank, 6...
・Blade angle adjustment device, 7...Blade angle control mechanism, 8...
Water level detector, 9...Water level detector, 10...Reference water level tank, 11...Differential pressure source Figure 1 Figure 2 Q (Ngpenil)

Claims (1)

[Claims] 1. In a circulating water pump that supplies cooling water to a steam turbine condenser of a steam power plant, the water level at the pump water intake is detected, and the angle of the blades of the pump is adjusted as a control signal for the blade angle of the pump. , A circulating water control device that adjusts the amount of circulating water discharged from the pump.