JPS5913809A - Method of controlling feedwater of drum boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses PCB (Fast
Cut Back or Fuel Cat Back
) relates to a water supply control method for compensating for a low drum level F at the time of occurrence.

When a thermal power generation unit is disconnected from the grid due to an accident in the transmission tSt system of a thermal power plant, the generator output instantly drops to just a few coefficients of power for the auxiliary equipment in the station, and the turbine also goes unloaded for a short period of time. It will be in operation state.

Upon detection of these conditions, the boiler rapidly throttles and adjusts boiler inputs such as feed water, fuel, and air to the boiler's lowest linearity, allowing the unit to return to single-load operation within the plant.

These operating functions are collectively called PCB.

When a PCB occurs in a drum boiler, the air bubbles in the furnace wall tube are crushed due to the effects of a decrease in furnace heat absorption due to fuel throttling and a transient increase in main steam pressure, resulting in a drop in the drum level. If the feed water flow rate is commensurate with the reduction in F/steam flow rate, the drum level will be low and there is a risk of boiler tripping.

The invention of C is intended to provide a water supply control method that can quickly and accurately compensate for such a drop in boiler level during PCB. As shown in the figure, PCB occurs and the drum level becomes N W L (NormalWater L@
If the flow rate is -1xx (z is any set value, e.g. 3Qs+*) or more than -1xx (z is an arbitrary setting value, e.g. 3Qs+*) F than
Water is supplied at NWL −y tm (
y is an arbitrary set value, y (z, in extreme case y =
When the drum level is restored to (may be Qm), the emotional water supply pump is brought into service and the water supply capacity of the turbine-driven water pump is gradually reduced to reach the desired drum level.

If this method is used incorrectly, the drum level will suddenly drop, causing the FC8 occurrence II! Since water is supplied by the turbine-driven water supply pump after j, it is possible to follow this sudden low F temperature. In addition, once the rE has returned to near the desired level, we switched to an electric water supply pump that has good antibacterial properties for small eyelids and can supply water without steam, so that rE (
tM can be reached.

Hereinafter, embodiments of the present invention will be falsely described with reference to drawings with a lid.

In FIG. 2, a signal S1 indicating the occurrence of PCB is one input terminal of an AND circuit, a delay circuit (here, the delay time is set to 10 seconds) 2, a non-AND circuit 3? The signal is applied to the other input terminal of the AND circuit 1 through the signal line. Therefore, the output of the AND circuit 1 becomes %11 for 10 seconds after the occurrence of FC8. AND circuit 4 outputs the output of AND circuit 1 and a signal S2 indicating that the drum level has become NWL -z 1g or higher.
The drum level is NWL -z between the above river sands.
When Oi reaches F, outputs %11. And l!
] One output signal of J route 4 and five OR circuits are used to drive the turbine-driven water supply pump Wt/h (turbine-driven water supply pump is 2
If there are any units, a sliding signal is used to drive each unit at Σt/h).

The AND circuit 6 is the output of the OR circuit 5 and the drum level is N.
WL-7! Did you come back? The beat signal S3 is input through the NOT circuit 7, and the drum level is set to NWL -y.
The output of the OR circuit 5 is held at %IIK until it returns to normal operation.

When the drum level returns to between N%-7, the OR circuit 5 releases its self-holding state and outputs IQIK. This output %Ol is a knot circuit of 11, a delay circuit (delay time of 1 second)
12 and the NOT circuit 13 to release the self-holding by the AND circuit 14, x#fi&(this delay time
is used to set the output of the OR circuit 8 to IQ# so that two phalanx values do not overlap when switching the phalanx values of the turbine-driven water supply pump. Output IQj of OR circuit 8
is inverted in the knot circuit 9 to become %1#, giving a command for the turbine-driven feedwater pump KOt/h. However, Wt
Change rate limiter 1, dropping from /h to Ot/) at once
I'm at 5 which will gradually drop by 0.

The output of knot circuit 1 is a delay circuit (delay time x - 2 seconds)
15 and is applied to one input terminal of the °C AND circuit 16. The other input terminal of the AND circuit 16 is 0 of the OR circuit 88.
The name output has been added. Therefore, AND circuit 1
From 6, the drum level returned to NWL -y III for well over x-2 seconds. 11 was electric! 1] i@Water bong's eye motion input phalanx is output.

FIG. 3 shows the operation of the circuit of FIG. 2 described above. The operation when a PCB occurs can be briefly explained as follows.

■ PCB Occurrence■ If the drum level or Hirorou Wing Dragon F is reached within 10 seconds of PCB occurrence, turn off the turbine-driven water supply pump to Wt/
Drive at h ■ When the drum level returns to NWL -7ill f, service the electric water supply pump in just over X-2 seconds, and reduce the water supply number of the turbine-driven water pump by 11li on the X erosion control. According to this invention, as soon as a PCB occurs, if the drum level is lower than a certain level -2, the turbine-driven water pump will supply water to the drum circle in a vague manner, and the drum level will reach the skin level. Near level
After returning at ytm 9, we drove the N-motive water supply bong and gradually reduced the water resistance of the WEJ water pump of the turbine body, so we could quickly and accurately compensate for the low F fire at the drum level caused by FCBQIICl and E.

[Brief explanation of drawings]

FIG. 1 is a time chart for explaining the invention in detail, FIG. be. 2, 12, 15...Delay circuit, l(1... Rate of change limiter.

Claims (1)

[Claims] If a PCB occurs in a drum boiler and the drum level drops below the specified value by -i am or more F['F, the turbine-driven water supply pump supplies water at a large flow rate to restore the drum level to -ylly<z) or higher than the specified value. Then, a small flow of water is supplied from the wL dynamic water pump, and the amount of water supplied by the turbine-driven IvI water pump is gradually reduced.