JPH049961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the temperature of a moisture separation heater in a nuclear power plant.

The control of the conventional moisture separating heater is based on a patent application filed in 1982.
No. 205835 proposes the configuration shown in FIG.

In FIG. 1, reference numeral 1 indicates warm start mode selection display, 2 indicates cold start mode selection display, 3 indicates pressure set value calculator, 4 indicates pressure set value change rate limiter,
5 is a pressure change rate generator, 6 is a deviation generator, 7 is a
PI controller, 8 is electric/air converter, 9 is pressure detector, 10 is second stage heating steam control valve, MSH is moisture separation heater, HPT is high pressure turbine, LPT is low pressure turbine, GEN is a generator,
LP is the low pressure turbine inlet steam temperature, LM is the first
LH indicates the cycle steam temperature after passing through the stage heater, and LH indicates the high pressure turbine exhaust temperature.

In the control device shown in FIG. 1, the pressure after the second stage heating steam control valve is detected by the pressure detector 9 and the pressure is set for each operation mode, that is, cold start mode, warm start mode, or low load operation mode. The pressure change rate generator 5 outputs the pressure set value change rate limiter 4 so that the set pressure output from the value calculator 3 is obtained.
The set pressure is output through , the deviation is taken by the deviation generator 6, and the second stage heating steam control is performed by the PI controller 7 and the electric/air converter 8 so that the set pressure is the set pressure output from the pressure set value calculator 3. Valve 1
0, thereby controlling the low-pressure turbine inlet steam temperature LP, which is the control target.

However, in the control shown in FIG. 1, the low-pressure turbine inlet steam temperature LP was controlled only by the second-stage heating steam control valve 10, which was insufficient in the following points.

(1) During normal operation, the first stage heating steam control valve remains fully open without any control, so there is a rise in the temperature of the cycle steam due to the first stage heater, but this was not taken into consideration.

(2) Temperature change rate limit for cycle steam low-pressure turbine inlet steam temperature 56°C/Hr (limiting the change rate of low-pressure turbine inlet steam temperature is to reduce thermal stress generated in the turbine due to steam temperature change) (The change rate of 56°C/Hr is one of the typical values actually used.)
However, the limit value is 56℃/Hr due to the reason (1) because it is not vulnerable to the load change rate.
may exceed.

The present invention has been made in view of the above circumstances, and in controlling the second stage heating steam control valve of the moisture separating heater MSH, the first stage heating steam control valve of the moisture separating heater MSH
The purpose of this project is to provide a highly reliable temperature control method that takes into account the temperature increase effect of the stage heater and controls the low-pressure turbine inlet steam temperature within a limit value, reducing thermal stress and thermal strain in the low-pressure turbine. shall be.

Hereinafter, a preferred embodiment of the present invention illustrated in FIG. 2 will be described in detail.

In a nuclear power plant, saturated steam enters a steam turbine, and as the steam expands inside the turbine, it becomes wet steam and separates water droplets. When these water droplets collide with the wings and cabin walls at high speed,
It also erodes the blades and does no work on the blades, reducing the efficiency of the turbine. In order to eliminate such damage, a moisture separation heater is installed to reheat the steam that exits the high-pressure turbine during the expansion of the turbine, using main steam and high-pressure turbine extraction air, and sends it as superheated steam to the low-pressure turbine. things are being done. In moisture separation heaters, in order to increase plant thermal efficiency, two-stage heating is performed in which the steam exiting the high-pressure turbine is first heated by the high-pressure turbine's extraction air, and then a portion of the turbine inlet steam is passed through and further heated. . In this case, the initial heating by the high-pressure turbine bleed air reaches the bleed air temperature until the bleed air amount is balanced so that the heat amount of the bleed air is balanced with the amount of heat that heats the high-pressure turbine exhaust, so the bleed air amount cannot be controlled during normal operation. Instead, the main steam flow rate for second-stage heating is adjusted to control the temperature at the outlet of the moisture separation heater.

The present invention relates to outlet temperature control of this moisture separation heater, and attempts to control the temperature by paying attention to the fact that the steam (i.e., bleed air) temperature of the first stage heating depends on the load of the steam turbine. It is something to do.

FIG. 2 shows the configuration of temperature control according to the present invention, in which reference numeral 11 is a load change rate calculator, 12 is a pressure change rate calculator, 13 is a deviation generator, and L is a turbine. Each shows the load. Other elements are designated by the same reference numerals as corresponding elements in FIG.

In FIG. 2, the turbine load change rate calculator 1
1 samples the continuously inputted turbine load L at certain set time intervals, calculates the rate of change using the least squares method, and calculates the average rate of change. Next, the pressure change rate calculation unit 12 calculates the pressure change rate by the first stage heater that is commensurate with the load change rate of the uncontrolled first stage heater, and the deviation generator 13 generates the pressure change rate. Find the deviation from the value of device 5, and find that the rate of temperature change due to the second stage heater is the limit value 56
2nd stage heating steam control valve 1 so that the temperature is within °C/Hr.
Controls 0.

According to the present invention, when controlling the outlet temperature of the two-stage heater in consideration of the rate of temperature change caused by the first-stage heater of the moisture separation heater, that is, the low-pressure turbine inlet temperature, the turbine load is detected and the load changes. Rate calculator 1
1 and the pressure change rate calculator 12, and this deviation signal is added to the signal of the pressure change rate generator 5, it is possible to control the low pressure turbine inlet steam temperature to prevent the temperature change rate from being excessive. Therefore, it is possible to provide a control method useful for reducing thermal stress and thermal strain in a low-pressure turbine.

In addition, in this control, the second
When adjusting the main steam temperature to the stage heater, the after-valve pressure control of the second stage heating steam control valve 10 is performed near the main steam conditions of the nuclear turbine (i.e., for saturated steam at a pressure of around 70ata). ), depends on the fact that steam pressure and temperature correspond with isenthalpic change with sufficient accuracy in practice.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a temperature control system of a conventional moisture separation heater, and FIG. 2 is a diagram similar to FIG. 1 according to the present invention. 1...Warm start mode selection display, 2...Cold start mode selection display, 3...Pressure set value calculator, 4
...Pressure set value change rate limiter, 5...Pressure change rate generator, 6...Difference generator, 7...PI controller, 8...Electrical/air converter, 9...Pressure detector, 10... ...Second stage heating steam control valve, 11...Load change rate calculator, 12...Pressure change rate calculator, 1
3... Deviation generator, MSH... Moisture separation heater,
HPT...High pressure turbine, LPT...Low pressure turbine, GEN...Generator, LP...Low pressure turbine inlet steam temperature, LM...Cycle steam temperature, LH...
High pressure turbine exhaust temperature, L...Turbine load.

Claims (1)

[Claims] 1. In a temperature control method for a moisture separation heater that performs two-stage heating, in which steam exiting a high-pressure turbine is heated with the extracted air of the high-pressure turbine, and then further heated with a part of the turbine inlet steam, the turbine load is detected. Find the rate of change in the load, and from this find the rate of pressure change commensurate with the rate of change in the load of the first stage heater.
A temperature control method for a moisture separation heater, characterized in that this is added as a deviation value to the pressure setting change rate to control a second stage heating steam control valve.