JPH0588362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for controlling the temperature of a moisture separation heater for a steam turbine, and is used in, for example, a nuclear power plant.

Prior Art FIG. 5 shows a conventional temperature control method for a two-stage reheat moisture separation heater in a nuclear power plant. In the figure, 1 is a high-pressure turbine, 2 is a low-pressure turbine, 3 is a generator, 4 is a main steam system, 5 is a high-pressure turbine extraction system, 6 is a heating system using main steam, 7 is a control valve, and 8 is moisture separation heating 9 is a high pressure turbine exhaust system.

Saturated steam supplied from the steam generator expands and performs work in the high-pressure turbine 1 and leaves as moist steam. Therefore, before supplying this to the low-pressure turbine 2, it is heated in the moisture separation heater 8. This is used to create superheated steam to prevent corrosion within the low-pressure turbine and prevent a drop in efficiency.

In current typical moisture separation heaters, the first stage is heated by a high pressure turbine extraction system 5, and the second stage is heated by a heating steam system 6 branched from main steam.

If the low-pressure turbine inlet steam temperature is too low, the steam humidity will increase in the low-pressure turbine 2, causing erosion, and thermal efficiency will deteriorate. Inconveniences may occur, such as abnormal gaps. Therefore, the inlet steam temperature of the low pressure turbine must be controlled to an appropriate value.

On the other hand, since a sudden temperature change in the low pressure turbine causes thermal stress to occur, the rate of change in temperature of the steam at the outlet of the moisture separation heater 8 must be appropriately controlled at startup or when the load changes.

Taking a typical nuclear power plant as an example, when the second-stage side heating of the moisture separation heater 8 is not utilized (that is, when heating is performed only by the bleed air of the high-pressure turbine), the low-pressure turbine 2 The inlet steam temperature is at point Q of the load-temperature curve in FIG. 2 at the initial load. On the other hand, the inlet steam temperature of the low-pressure turbine 2 is controlled by the control device according to the set value on the load following operation curve shown by the broken lines A, B, C, D, and E in FIG. At times, from point Q to R
The temperature must be raised to the set point. At this time, the rate of change in inlet steam temperature is limited to a certain upper limit due to limitations on thermal stress of the low pressure turbine 2.

Conventional control methods corresponding to the above matters are as follows.

Once the turbine reaches rated speed and is joined to the power system, it takes on the initial load. The low pressure turbine inlet steam temperature is increased at a predetermined temperature change rate starting from point Q in FIG. Then, it intersects line AB at point R. Thereafter, the load follow-up operation curve is followed and restricted within a predetermined time or when there is another limiting factor from the steam generator side or the like.

Problems to be Solved by the Invention Problems in the conventional control method described above are as follows.

When the turbine is taking full load, for example, the inlet temperature is at point E. Therefore, when the operation is temporarily stopped after full-load operation and then restarted, the low-pressure turbine 2 is cooled, and its metal temperature becomes a certain value between point E and point Q. On the other hand, the steam temperature increases from the temperature at the time of entry (point Q) to the temperature corresponding to the load over a period of time at a certain rate of temperature change.

During this time, the inside of the low-pressure turbine is between the above-mentioned points E and Q.
From the metal temperature intermediate between the point and point, the metal is cooled by steam toward the low-pressure turbine inlet steam temperature (point Q) at the time of co-input, that is, at the initial load, and is then heated. Not only is this initial cooling process completely wasteful, but the low pressure turbine
Limiting the rate of temperature change to reduce thermal stress results in a complete waste of time.

The object of the present invention is to eliminate the first wasteful cooling process, that is, the wasteful warm-up operation.

Means for Solving the Problems The present invention employs the following means to solve the above-mentioned problems. That is, the present invention
In the temperature control method when restarting a two-stage reheat moisture separation heater that uses main steam and high-pressure turbine bleed air as heating steam sources, the metal temperature inside the low-pressure turbine is measured, and this temperature is set at the initial load. The control valve of the heating steam source using the main steam is opened until the set temperature on the load following operation curve of the low pressure turbine in the region close to is reached, and the low pressure turbine inlet steam temperature is rapidly increased in steps until this temperature is reached. Then, the temperature is raised at a predetermined rate of temperature change up to the set temperature on the load following operation curve.

Effect: According to the above-described means, it is possible to quickly start up and perform metal matching without the above-mentioned wasteful cooling process when restarting.

Embodiments Next, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 1 shows the sequence of the present invention.

10 is a turbine load signal, 11 is a function setter, 12 is a rate of change setter, 13 is a set value, 14 is a pressure signal after the control valve, 15 is an analog changeover switch, 16 is a turbine metal temperature detector, 17 is an analog Selector switch, 18 is metal function setting device,
19 is a circuit breaker, 20 is a one-shot pulse, 21
is the initial warm-up opening command.

The present invention aims to eliminate the above-mentioned wasted time by measuring the metal temperature inside the low-pressure turbine and instantaneously changing the low-pressure turbine inlet steam temperature to that temperature.

In other words, referring to Fig. 2, after the previous operation, the low-pressure turbine has cooled down and its metal temperature has decreased to R.
For example, it is assumed that there is a point P (180°C) between point (204°C) and point Q (110°C). At this time, the low-pressure turbine inlet steam temperature setting value is set by PI control so that it suddenly reaches point P (180°C) in steps.
The control valve 7 of the heating steam system 6 that branches off the main steam for heating the second stage of the moisture separation heater 8 shown in FIG. 5 is opened.
After performing metal matching in this way, the inlet steam temperature is set at a certain rate of temperature change (45℃/hour) below the upper limit of the rate of temperature change (56℃/hour) determined by the thermal stress limit of the low-pressure turbine 2. /hour).

If the low pressure turbine metal temperature is R point (204℃)
In the above case, the set value is increased stepwise up to point R (204°C), and then the steam temperature is made to follow the set value corresponding to the load at a predetermined rate.

In addition, when performing temperature control, pressure is actually controlled in saturated steam at the pressure currently used in nuclear power turbines.
This is because when performing an isenthalpic change, pressure and temperature correspond, and temperature can be represented by pressure. When controlling the temperature by actually measuring it, there is a time delay due to heating of the thermometer part, so pressure control has a better response.

FIG. 3 shows the relationship between the load and pressure of the function setting device 11, and FIG. 4 shows the function of the function setting device 18, which indicates the pressure corresponding to the turbine metal temperature.

When the circuit breaker 19 detects the combination and the one shot pulse 20 issues a signal, the temperature signal measured by the turbine metal temperature detector 16 passes through the analog changeover switch 17 and enters the function setting device 18 and is sent to the low pressure turbine 2. The signal corresponds to the metal temperature. This signal is connected to the change rate setting device 12 via the analog changeover switch 15 according to the warm-up initial opening degree command 21 . Until the rate of change setter 12 reaches the upper limit signal sent from the function setter 11, a pressure increase signal is given at a predetermined rate using the signal sent from the function setter 18 as an initial value.

Effects of the Invention According to the present invention, when warming up a nuclear turbine, the metal temperature of the low pressure turbine (temperature at a representative point of the turbine at the inlet of the low pressure turbine) is inserted into the control logic based on the time from the previous operation to restart. This enables rapid startup without applying thermal shock to the low-pressure turbine, eliminating wasteful warm-up operations.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a system implementing the method of the present invention, Fig. 2 is a chart showing the load-temperature curve in a low-pressure turbine, Fig. 3 is a chart showing the relationship between load and pressure, and Fig. 4 is a function diagram. FIG. 5 is a diagram showing the functions of the setting device 18, and is a system diagram showing the high and low pressure turbine system of a nuclear power plant. 1...High pressure turbine, 2...Low pressure turbine, 8
... Moisture separation heater, 10 ... Turbine load signal, 11 ... Function setting device, 12 ... Rate of change setting device, 13 ... Setting value, 14 ... Control valve rear pressure signal, 15 ... Analog switching Switch, 16... Turbine metal temperature detector, 17... Analog changeover switch, 18... Function setting device, 19... Circuit breaker, 20... One shot pulse, 21... Warm-up initial opening command.

Claims (1)

[Claims] 1 In the temperature control method when restarting a two-stage reheat moisture separation heater that uses main steam and high-pressure turbine bleed air as heating steam sources, the metal temperature inside the low-pressure turbine is measured, and this temperature is The control valve of the heating steam source using the main steam is opened until the set temperature on the load-following operation curve of the low-pressure turbine in the region close to the load is reached, and the low-pressure turbine inlet steam temperature is rapidly increased in steps until this temperature is reached. 1. A method for controlling the temperature of a moisture separation heater, the method comprising heating it up and then increasing the temperature at a predetermined temperature change rate up to a set temperature on the load following operation curve.