JPS61215405A - Temperature control for moisture-content separating heater - Google Patents

Abstract

PURPOSE:To enable a nuclear turbine to be started quickly in its warming up by controlling the opening action of a control valve within a heating steam supply system for a moisture-content separating heater in accordance with the results of measuring the metal temperature within a low pressure turbine. CONSTITUTION:In a nuclear turbine, a high pressure turbine 1 is driven by saturated steam supplied through a main steam system 4 from a steam generator, and wet steam after finishing the work is heated in a moisture-content separating heater 8, and then fed to a low pressure turbine 2. In the above, the metal temperature within the low pressure turbine 2 is measured, and when the temperature remains in a range between 204 deg.C and 110 deg.C, a control valve 7 within a heating system 6 related to said heater 8 is opened so that the temperature rises step by step from the set value of steam temperature at the inlet of the low pressure turbine up to 180 deg.C, and then the temperature is controlled to rise at a rate of change within 45 deg.C/hr. In addition, when the metal- temperature is at more than 204 deg.C, the set value is raised step by step up to 204 deg.C, and then the steam temperature is allowed to follow up a set value corresponding to the load.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature control method for a moisture separation heater of a steam turbine. On the other hand, the steam temperature increases to a temperature corresponding to the load. During this time, the low pressure turbine is cooled down and then
There was wasted time due to heating, but it is used in the technical field to eliminate this.

Conventional technology FIG. 5 shows a method of controlling the temperature of the moisture separator.

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, 8 is a moisture separation heater, and 9 is a high-pressure turbine exhaust system.

In nuclear turbines, saturated steam is supplied from a steam generator. When the high-pressure turbine expands and performs work, it exits the high-pressure turbine as wet steam, so in order to prevent corrosion in the low-pressure turbine and reduce efficiency, it is heated in a moisture separation heater 8 to become superheated steam. .

In a current typical example, 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.

Next, if the low-pressure turbine inlet temperature is too low, steam humidity will increase in the low-pressure turbine, causing double lotion and poor thermal efficiency. If it exceeds this, problems such as abnormal gaps between internal parts will occur, so the inlet temperature of the low-pressure turbine must be controlled to an appropriate value.

On the other hand, since sudden temperature changes in the turbine cause thermal stress, the moisture separation heater 8
The rate of change of the outlet temperature must be properly controlled.

Taking a typical nuclear power plant as an example, when the second stage side heating of the moisture separation heater 80 is not utilized (that is, when it is heated only by the bleed air of the high pressure turbine), the inlet steam of the low pressure turbine 2 The temperature is approximately 90° C. without load. On the other hand, the low-pressure turbine 20 inlet steam temperature is controlled by the control device as shown in A and B in FIG.

The temperature is controlled according to the set values of the broken lines C, D, and E, but during warm-up operation, the temperature is raised from point 9 to point R to reach the set value. The vertical axis is temperature, and the -horizontal axis is load. On the other hand, due to thermal stress limitations of the low pressure turbine 2, the rate of change in inlet steam temperature is limited to 56° C./hour.

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

The turbine reaches its rated speed and takes an initial load of 5 cm when it is joined to the power system. Starting from point 9 in FIG. 2, the low pressure turbine inlet steam temperature is increased at a rate of change of 45° C./hour. Then, line AB (204°C) intersects K at point R. From then on 5
The set temperature is followed and controlled within 6°C/hour or when there is another limiting factor from the steam generator side or the like.

The problems with this control method are as follows.

When the turbine is taking full load, for example, the inlet temperature is at point E. Therefore, when restarting after full-load operation, the low-pressure turbine 2 is cooled down from point E and the metal temperature of the low-pressure turbine 2 is at a certain value between E and Q. On the other hand, the steam temperature was 11
The temperature is increased from 0°C to 204°C at a rate of 45°C/hour, that is, in about 2 hours, to the temperature corresponding to the load.

During this period, the inside of the low-pressure turbine is first cooled from 180°C to 110°C by steam, and then heated (the metal temperature is considered to be 180°C in EQMIIC). The reason for limiting the temperature increase rate is to reduce thermal stress in the low pressure turbine 2.

From this point of view, the initial cooling process is a complete waste of time.

Problems to be Solved by the Invention The present invention aims to eliminate the above-mentioned initial cooling time, that is, unnecessary warm-up operation.

Means for Solving the Problems The present invention employs the following means to solve the above-mentioned problems. In other words, the metal temperature inside the low-pressure turbine is measured, and when the metal temperature is between 204°C and 110°C, the control valve is opened so that the temperature reaches 180°C in steps from the low-pressure turbine inlet steam temperature set value. Then, the temperature should be raised at a rate of change of 45°C/hour. If the metal temperature is above 204°C, increase the set value in steps until it reaches 204°C, and then increase the steam temperature at a predetermined rate. The low-pressure turbine inlet steam temperature is instantaneously changed to follow the set value corresponding to the load.

According to the above-described means, the metal temperature of the low-pressure turbine is inserted into the control logic according to the restart erroneous time, rapid startup is performed, and the above-mentioned wasted time can be eliminated.

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.

Symbol lO is a turbine load signal, 11 is a load/steam pressure function setter, 12 is a rate of change setter, 13 is a pressure setting value,
14 is a control valve rear pressure signal, 15 is an analog changeover switch, 16 is a turbine metal temperature signal, 17 is an analog changeover switch, 18 is a metal temperature/control valve rear pressure function setting device, 19 is a circuit breaker, and 20 is a one-shot switch. Pulse 21 is the warm-up initial opening degree finger ◆.

The present invention measures the metal temperature inside the low-pressure turbine and instantaneously changes the low-pressure turbine inlet steam temperature to that temperature, thereby eliminating the above-mentioned wasted time.

That is, referring to FIG. 2, if the metal temperature is 20
When the temperature is between 4℃ and 110℃ (for example, 9 points 180℃
) Control valve 7 (Figure 5) so that the low-pressure turbine inlet steam temperature is set to 180°C in steps.
After that, the temperature was controlled to increase at a rate of change of 45° C./hour.

If the low pressure turbine metal temperature is 204°C or higher, the set value is increased stepwise up to 204°C, and then the steam temperature is made to follow the set value corresponding to the load at a predetermined rate.

Note that while temperature control is performed in step 5, pressure control is actually performed using isenthalpic This is because when making a change, pressure and temperature correspond, and temperature can be represented by pressure. When temperature is actually measured and controlled, there is a time delay due to the heating of the thermometer part, so pressure control has a better response.

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

The circuit breaker 19 detects the combination, and the one-shot pulse 20
When the signal is emitted, from k, the turbine metal temperature signal 1
The temperature signal measured at 6 becomes a signal corresponding to the metal temperature of the low pressure turbine 2 at the control valve post-pressure function setting device 1B. Initial warm-up opening index Gives a pressure increase signal at a rate.

Effects of the 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 low-pressure turbine inlet) is inserted into the control logic according to the restart recommendation time since the previous operation, and a thermal shock is applied to the low-pressure turbine. It performs rapid startup without any hassle and eliminates wasteful warm-up operations.

[Brief explanation of drawings]

Figure 1 is a system diagram of the present invention, Figure 2 is a diagram of control that increases temperature at a constant rate of change, Figure 3 is a diagram showing the relationship between load and pressure, and Figure 4 is a pressure function setting device after the control valve. A diagram showing the function of
FIG. 5 is a system diagram showing a temperature control method of a conventional moisture separation heater. 2...Low pressure turbine, 8...Moisture separation heater, lO...
Turbine load signal, 11. Load/steam pressure function setting device, 12. Rate of change setting device, 13. Pressure setting value, 14.
・Pressure signal after control valve, 15...Analog changeover switch,
16...Turbine metal temperature signal, 17...Analog changeover switch, 18...Metal temperature/control valve pressure function setter, 19--breaker, 20...One-shot pulse, 21--Engineer or one person) Figure 2 Burden

Claims (1)

[Claims] The metal temperature inside the low-pressure turbine is measured, and when the metal temperature is between 204℃ and 110℃, the control valve is opened so that the temperature reaches 180℃ in steps from the low-pressure turbine inlet steam temperature set value, and then the temperature is increased to 45℃. / time, and if the metal temperature above is 204℃ or higher, increase the set value in steps until it reaches 204℃, and then adjust the steam temperature to the load at a predetermined rate. A temperature control method for moisture separation heaters that instantly changes the low-pressure turbine inlet steam temperature to a set value by following the set value.