1Schematic Diagram of the New Steam Temperature Control

2IS

Temperature atFurnace Exit

3IS

WW 3SH 4SH ECO1,2SH

DSDT

Main SteamTemperature

Water-to-fuel Ratio(Fuel)

DSDT = T3SO -T4S H

The new steam temperature control is a system which uses fuel to control the temperature at the furnace exit, and which uses the 3IS valve (SH spray valve) to control the main steam temperature.

T3SO

Temperature atFurnace Exit

Main SteamTemperature

T4SH

3SO

TWWO

TFSO

BFP

2Comparison of the New Steam Temperature Controland the Conventional Control

Main Steam Temperature

Temperature at Furnace Exit

Fuel(water-to-fuel ratio, WFR)

Temperature at Furnace Exit

Temperature at Exit of Tertiary Superheater

Secondary Spray

De-Superheater Decreased

Temperature (DSDT)

Main Steam TemperatureTertiary Spray

Conventional Control New ControlOperational

AreaObject of Control

Substantial changes of control circuitTheoretical verification only result in insufficient quantitative verification

Conduct prior verification using Conduct prior verification using highhigh--precision simulatorprecision simulator

3Simulation of the New Steam Temperature ControlA

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15 min

10 degrees

Deviation of A-D main steam temperature

MWD

Settling Time: at least 15 minMax. Deviation:

10 degrees

: Deviation to main steam temperature

MWD

10 min

4 degrees

Deviation to main steam temp.

Settling Time: 25 min

Max. Deviation: 8 degrees

: Deviation to main steam temperature

MWD

15 min

Deviation of A-D main steam temperature

10 degrees

Settling Time: 10 min

Max. Deviation: 5 degrees

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: Deviation to main steam temperature

10 min

4 degrees

Deviation to main steam temp.

Settling Time: 10 min

Max. Deviation: 4 degrees

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: Deviation to main steam temperature

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Able to verify validity of improvements to control, by prior verAble to verify validity of improvements to control, by prior verification of new controlification of new control Improve temperature control at furnace Improve temperature control at furnace

exit using waterexit using water--toto--fuel ratiofuel ratio Reduce deviation to main steam Reduce deviation to main steam

temperature & Improve settling timetemperature & Improve settling time

4Observed from Results of Simulation and Actual Operation

Results of prior verification

Circuit changeIncrease of accuracy to parameter default values

Reliable reconstruction in a short time (prior case studies)Reliable reconstruction in a short time (prior case studies)Reduction of trial operation durationReduction of trial operation duration

Conventional Control(Response Time)

Temperature at Furnace Exit Temperature at Exit of Tertiary Superheater

De-Superheater Decreased Temperature (DSDT)

Main Steam Temperature(20 seconds)

(7 seconds)

(45 seconds)

(60 seconds)

Main Steam Temperature Temperature at Furnace ExitFuel(water-to-fuel ratio, WFR)

Secondary Spray

Tertiary Spray

New ControlObject of ControlOperational

Area (Response Time)

(37 seconds)(190 seconds)

5New Steam Temperature Control(Verification of Default Parameters)

2.5

21:38Jun 23, 1997

15:45Jun 23, 1997

Test No. T-S-0 T-S-1

Time 22:15Jun 22, 1997(Current circuit)

TFSO:TWWO100

(Proposed circuit)TFSO:TWWO

5:5

TFSO

MAX(dev.)

545.6(+4.6)

546.3(+5.3)

MIN(dev.)

533.2(7.8)

536.4(4.6)

F3IS

MAX 19.4 16.4MIN 1.8 0.7MAX 84 89

MAX65 680 0

Remarks 3IS Break

3IS Break

MIN

Tsat

F2IS

T-S-720:23

Jun 23, 1997

3IS Cascade Gain

545.3(+4.3)538.4(2.6)18.1

828211

No further gain increase possible

T-S-8

Superheat setting

545.0(+4.0)539.1(1.9)24.17.01109027

further improved by increasing the

additional spray

Test Conditions

Schematic Diagram of the New Steam Temperature ControlComparison of the New Steam Temperature Control and the Conventional ControlSimulation of the New Steam Temperature ControlObserved from Results of Simulation and Actual OperationNew Steam Temperature Control(Verification of Default Parameters)