JPS61138806A - Steam turbine plant - Google Patents

Abstract

PURPOSE:To prevent the overload operation of a condensate pump from occurring in time of turbine bypass operation, by controlling a condenser level control valve, situated in a condensing pipe line between the condensate pump and a deaerator, according to low pressure bypass water injection valve opening in a low pressure turbine bypass system. CONSTITUTION:During ordinary operation, a water injection valve 25 injecting water into an attemperator 22 in a low pressure bypass pipe line 23 is fully opened, and a condenser lever control valve 14 is controlled with a signal out of a condenser level detector 28 by way of an operational unit. Here, it enters on turbine bypass operation, and when a low pressure bypass valve 21 is opened, a signal out of a temperature detector 27 in the low pressure bypass pipe 23 is transmitted to the water injection valve 25 by way of the operational unit, opening this valve. Simultaneously, an open signal of the water injection valve 25 turns to a control signal for the condenser level control valve 14 according to the function preset in a function operational unit, controlling this valve. With this constitution, the overload operation of a condensate pump in time of the turbine bypass operation is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a steam turbine plant with a low-pressure turbine bypass system.

[Background of the invention]

The conventional steam turbine plant is disclosed in Japanese Patent Application Laid-Open No. 55-5461.
As described in No. 3, a method has been considered in which a deaerator level control valve is controlled according to the discharge pressure or discharge flow rate of a condensate pump. However, no consideration has been given to a method of controlling the condenser water level control valve according to the opening degree signal of the water injection valve.

[Purpose of the invention]

An object of the present invention is to enable a condensate pump to be designed economically by considering only normal operation, and to eliminate the need to set the condensate pump installation level in advance in consideration of overload operation. An object of the present invention is to provide a steam turbine plant that can be designed economically.

[Summary of the invention]

The gist of the present invention is to control the condenser water level control valve according to the opening degree of the low-pressure bypass water injection valve to maintain the discharge flow rate of the condensate pump at a rated value or less.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

1 is the boiler, 2 is the main steam stop valve 3 that directs the steam from the boiler 1
, a main steam pipe leading to the high pressure turbine 5 via the control valve 4, 6
7 is a reheater that heats the steam from the high-pressure turbine 5, and 7 is a high-temperature reheat steam pipe with a combination reheat valve 8 installed in the middle. 9 is an intermediate pressure turbine; 10 is a crossover pipe that leads all the steam from the intermediate pressure turbine 9 to the low pressure turbine 11; and the low pressure turbine 11
The exhaust steam is returned to the boiler 1 via the condenser 12, condensate pump 13, low pressure heater 15, deaerator 16, boiler feed water pump 17, and high pressure heater 18.

A high-pressure bypass valve 19 leads the main steam pipe 2 to the inlet of the reheater 6.

23 is a low-pressure bypass pipe that directly guides the outlet steam of the reheater 6 to the condenser 12, and is provided with a low-pressure bypass valve 21 and a desuperheater 22 in the middle. Reference numeral 24 denotes a water injection pipe for injecting water into the desuperheater 22 in the total low pressure bypass pipe 23 for a portion of the discharge amount of the condensate pump 13, and a water injection valve 25fc& is provided in the middle. In this case, the high pressure bypass cell 19 is opened in response to the load shedding signal (load shedding detector 20), the low pressure bypass valve 21 is opened in response to the pressure of the high temperature reheat pipe 7, and the water injection valve 25 is opened in response to the low pressure It is configured to be opened depending on the temperature of the bypass v23 (temperature director 27). Further, a condenser water level adjustment valve 14 is provided on the way from the condensate pump 13 to the deaerator 16. Further, 28 is a condenser water level detector, and the condenser water level regulating valve 14 is controlled by this signal. Furthermore,
The condenser water level adjustment valve 14 is configured to be controlled also by a signal from a detector 27 that controls the water injection valve 25, based on the present invention.

Details of the control system will be explained with reference to FIG.

During normal operation, the water injection valve 25 is fully closed, and in this case, the condenser water level adjustment valve 14 is controlled by the high level selector 31 by the signal from the condenser water level detector 28 via the calculator 32.
Selected by. For example, when the turbine bypass operation is started due to load shedding and the low pressure bypass valve 21 is opened, a signal from the temperature sensor 27 attached to the low pressure bypass pipe 23 is sent to the water injection valve 25 via the calculator 32, and the water is injected. valve 2
Open 5. At the same time, the water injection valve 25 open signal is converted into a condenser water level adjustment valve 140 control signal according to the function shown in FIG.
The condenser water level adjustment valve 14 is controlled by the condenser water level detection signal.

As shown in Figure 2, before load shedding, condenser water level adjustment valve 1
4, the discharge amount of the condensate pump 13 is kept below the rated value. However, in the conventional technology, when the load is cut off, the condenser water level rises, so the signal of the condenser water level detector 28 As a result, the condenser water level adjustment valve 14 is fully opened, and the discharge amount of the condensate pump 13 exceeds the rated value, resulting in the condensate pump operating under overload. According to the present invention, when a load is cut off, etc., the control system described above converts the open signal of the water injection valve 25 into a throttle 9 signal of the condenser water level adjustment valve 14 by the function calculator 30, and the high-level selector 31 By giving priority to the condenser water level signal and narrowing down the condenser water level adjustment valve 14 according to the opening degree of the water injection valve 250, the discharge IT value of the condensate pump 13 can be controlled within the rated value. In the figure, 14 is a condenser water level adjustment valve, 26 is a pressure detector, 2
9 is a water injection valve opening signal circuit.

〔Effect of the invention〕

According to the present invention, overload operation of the condensate pump during turbine bypass operation can be prevented.

[Brief explanation of drawings]

Fig. 1 is a piping system diagram of a steam turbine plant based on the present invention, Fig. 2 is a characteristic curve diagram of a condensate pump, Fig. 3 is a control system diagram of an embodiment of the present invention, and Fig. 4 is a water injection valve opening diagram. FIG. 5 is a diagram of a piping system of a conventional steam turbine plant. 29...Water injection valve opening signal circuit.

Claims (1)

[Claims] 1. When the load is drastically reduced, the outlet steam of the boiler reheater is directly guided to the condenser via a low pressure turbine bypass system equipped with a low pressure bypass valve, and a condensate pump is connected to the low pressure turbine bypass system. In a steam turbine that continues to operate by injecting a portion of the discharge water, the water level adjustment valve of the condenser installed in the middle of the condensate piping between the condensate pump and the deaerator is operated under load. 1. A steam turbine plant characterized in that, in the event of drastic reduction, the discharge flow rate of the condensate pump is maintained at a rated value or less by controlling according to the opening degree of a water injection valve to the low-pressure turbine bypass system.