Vit154 Xs00 Laa20 System Rev_b

8/12/2019 Vit154 Xs00 Laa20 System Rev_b

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DRAWING/DOCUMENT STATUS: FOR CONSTRUCTION

b 2006-03-24 Doosan Specific Revision Traynor Fuchs Schobert

a 2005-11-30 First Issue Traynor Fuchs Schobert

Rev. DATE DESCRIPTIONBearb.Coord.

GeprftChecked

APPD.

PROJECT :

CAMAU 1 750MW COMBINED CYCLE POWER PLANT

OWNER : OWNERS ENGINEER :

PETRO VIETNAMCPMB

CONTRACTOR : CONTRACTORS ENGINEER :

LILAMA CORPORATION FICHTNER

SUBCONTRACTORS NAME : SUBCONTRACTORS SUPPLIER :

sPOWER GENERATION

DRAWING TITLE :

Bypass Deaeration

PKZ UAS Contents Code Reg. No. UNID

Ursprung/Original Ursprung-Nr./Original-No.Urspr.-PKZ-Nr.Orig.-PC

LAA20ZA rev.fProjekt/Project PKZ/PC


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System-Beschreibung

System Description

Projekt/Anlage:Project/Plant: Ca Mau 1

CCPP

Rev b

System

System

Nebenstrom-Entgasung

Bypass Deaeration

Seiten/Pages:

Anlagen/Appendices:

10

6

VIT154 XS00 LAA20UNID

423 201 855Proj.-Kennz./Proj. Code UA/Doc. Inhaltskennzeichen/Contents Code

LAA20ZA rev. f PG W712, Dr. Scht tlerUrsprung / Original Modulverantwortl icher / Module Coordinator

Zugehrige Schaltplne/Related P & I Diagrams:

Handhabung:Handling:

NUR FR INTERNEN GEBRAUCHFOR INTERNAL USE ONLY

VIT154 - XG02 - LAA20 1/1 UNID 422 938 264 Bypass Deaeration

geprft und freigegeben durch /reviewed and released by

In-dexRev.

DatumDate

Erstellung bzw.nderungen (Seiten)

Issue resp.Modifications (Pages).

DienststelleOffice

bearbeitet durchprepared by

intern1)

Internal

extern2)

external

a 2005-11-30Ersterstellung

First Issue E913 G. Traynor T. Fuchs B. Schobert3)

Gez. Traynor Gez. Fuchs Gez. Schobert 4)

b 2006-03-24

Doosan Spec. Rev. E913 G. Traynor T. Fuchs B. Schobert

Gez. Traynor Gez. Fuchs Gez. Schobert


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System BeschreibungProjekt/Anlage:Project/Plant: Ca Mau 1 CCPP

System DescriptionSystem LAA20

Seite/Page 2

Index/Revision b

I Table of Contents

II Systems, Abbreviations

1 Task, Function and Design

2 Modes of Operation

2.1 Preparations

2.2 Start-up and Shutdown

2.3 Operation, Closed and Open Loop Controls

3 Appendices


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Seite/Page 3

Index/Revision b

II Systems, Abbreviations

Systems

LAA Deaeration, Storage

LAB Feedwater Piping System (excl. Feedwater Pump andFeedwater Heating System)

Abbreviations

B/P Bypass

CEP Condensate Extraction Pump

CLC Closed Loop Control

CPH Condensate Preheater

CTRL-V Control Valve

D/A Deaerator

GT Gas Turbine

HP High Pressure

HRSG Heat Recovery Steam Generator

IP Intermediate PressureLP Low Pressure

SGC Sub Group Control

YFH Function Chart Overview Level


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Seite/Page 4

Index/Revision b

1 Task, Function and Design

The objectives of the system are :

- to remove non condensable gases like carbon dioxide and oxygen from the con-densate during start-up and normal operation of the plant if required by the con-ductivity of the condensate to meet the following criteria:- cation conductivity of the feedwater, LP/IP and HP steam < 0.2 S/cm- oxygen content of the condensate and feedwater < 100 ppb

- heat up the condensate during oil firing of the GT

During filling of the HRSG and during start-up of the plant the bypass deaerator is putinto operation to remove non condensable gases in the water/steam cycle. With thebypass deaerator in operation the start-up time can be reduced because the requiredsteam quality for the ST start-up can be reached earlier.

During normal constant plant operation deaeration of the condensate is performed in

the condenser. If increased oxygen level in the condensate or feedwater or if in-creased conductivity in the condensate, feedwater or steam is detected additionaldeaeration can be performed in the bypass deaerator which is located downstream ofthe condensate preheaters.

With reference to full load, up to 50% of the condensate can be deaerated. If morethan these 50% condensate pass through the preheaters the surplus condensate isrouted directly to the both LP drums and to the feedwater pumps. Deaeration is per-formed by delivering condensate to the deaerator and heating it up to its saturationtemperature with auxiliary steam by direct contact. The deaerator temperature is con-trolled by a control valve in the auxiliary steam supply line.

The condensate flow to the deaerator is controlled by the level control of the deaera-tor. The deaerator is designed as a spray type (Stork) / tray type deaerator. Inside thedeaerator steam flows in counter current direction to the condensate drizzling down.At the top of the deaerator column almost all the steam is condensed. The non con-densable gases like oxygen and carbon dioxide are released to atmosphere via a

vent pipe. The deaerated condensate is fed back to the outlet pipe of the condensatepreheaters by a deaerator pump via a flow control valve and is routed to the suctionside of the feedwater pumps.

The deaerator is constructed as a vertical vessel with deaeration and storage sectionin one shell. The unit consists of a cylindrical carbon steel shell and carbon steel


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Seite/Page 5

Index/Revision b

If deaeration is required due to increased conductivity in the condensate the tempera-ture at the condensate preheater outlet is reduced to about 8K below the saturationtemperature in the bypass deaerator by the condensate preheater temperature con-trol. The temperature difference of 8K ensures an optimal deaeration process in thedeaerator.

Carbon dioxide (CO2) can only be removed from the condensate if the deaeratortemperature is kept above 135C because CO2will form to a salt (ammonium bicar-

bonate) when ammonia or other caustic material is present. This salt is relatively sta-ble below 135C and can only be broken down at higher temperatures in order to setfree the gaseous CO2which can be eliminated afterwards by deaeration.

If one of the GTs is operating in oil firing mode the bypass deaerator is put into opera-tion and used as an external condensate preheater. The condensate in the deaeratoris heated up, so that the mixture of cold condensate coming from the condensatepreheaters and the heated up condensate coming from the bypass deaerator reachesthe required inlet temperature for the HP- and IP-economizers as well as the LPdrums.


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Seite/Page 6

Index/Revision b

2 Modes of Operation

2.1 Preparations

Before starting the bypass D/A the auxiliary steam supply must be ensured to warm-up the D/A. The condensate supply as well as the condensate preheating systemmust be in operation. For cooling of the D/A pump the closed cooling water systemmust be in operation.

2.2 Start-up and Shutdown

Start-up

Before HRSG filling and start-up the Unit Coordination Program starts the SGC B/PDEAERATION. The SGC must be started manually if additional deaeration is re-quired during load operation owing to increased condensate or feedwater oxygenlevel or increased condensate, feedwater or steam conductivity.

At the beginning of the start-up procedure all valves are closed, the controls for ventvalve and emergency drain valve as well as the temperature control via the auxiliarysteam CTRL-V are taken into operation.

If the plant is started from cold conditions and the D/A is cold the auxiliary steamCTRL-V is set to a start-up position. When the D/A has achieved a minimum tem-perature by the incoming steam and the temperature difference between the D/A andthe CPH outlet ensures a sufficient subcooling of condensate at the D/A inlet the aux-

iliary steam CTRL-V as well as the condensate inlet CTRL-V is set to CLC mode andcondensate intake is started. When the level in the D/A has achieved the requiredrelease value the D/A pump is started and the feedwater outlet CTRL-V is set to CLCmode. Now the CPH content can be warmed-up and deaerated by means of a cyclecontaining the feedwater pumps (in minimum flow operation; the boiler inlet valvesare closed), the CPH, the D/A including the D/A pump and the D/A bypass. A part ofthe condensate is bypassed across the D/A because the condensate inlet CTRL-V isrestricted in its open position as long as the feedwater pump operates in minimum

flow mode.If the plant is in normal operation and the D/A is in stand-by mode (reduced D/A tem-perature and reduced D/A level) the start-up of the D/A is performed in the sameway. The auxiliary steam CTRL-V is opened to its start-up position. If the D/A tem-perature is high enough for a minimum subcooling of condensate at the D/A inlet theauxiliary steam CTRL-V as well as the condensate inlet CTRL-V is set to CLC mode


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Seite/Page 7

Index/Revision b

For D/A shutdown the SGC B/P DEAERATION has to be set to the standstill pro-gram. It can be done manually during normal plant operation if no deaeration is nec-essary or by the unit coordination program during plant shutdown.

When the D/A is shutdown the setpoint for the D/A level is lowered to the standbylevel, the D/A outlet flow control setpoint is ramped down to zero, then the feedwateroutlet CTRL-V as well as the condensate inlet CTRL-V are closed and switched tomanual operation. Afterwards the D/A pump is switched off and the condensate inletisolating valve is closed.

If the D/A standby mode is manually set (in case of normal operation of the plantwithout bypass deaeration), the shutdown sequence is ended and the D/A tank iskept under pressure by means of auxiliary steam via the auxiliary steam CTRL-V.

If stand-by mode is not selected the CTRL-V in the auxiliary steam supply line is thenclosed, the D/A temperature control is switched off as well as the vent valve control isturned off. The emergency drain valve control remains on.

2.3 Operation, Closed and Open Loop Controls

Deaerator Level Control:The level in the D/A is controlled by the condensate inlet CTRL-V, which is locatedupstream of the D/A.

The condensate inlet CTRL-V will be closed by protection signal if: the D/A level exceeds the value MAX3 or the inlet condensate subcooling is TOO LOW (only if spray type D/A (Storck)) or CEP limitation is actuated (not enough CEP in operation)Mass Flow Control:The mass flow through the D/A is controlled by the feedwater outlet CTRL-V, which islocated downstream of the D/A pump. The non-return valve in the main condensateline avoids back flow or recirculation of deaerated feedwater coming from the D/A.

The feedwater outlet CTRL-V will be closed by protection signal if:

the D/A outlet flow exceeds the value MAX1 or the water level of the LP drum is TOO HIGH

Deaerator Temperature Control:The D/A temperature is controlled by the auxiliary steam CTRL-V. The valve is lo-cated upstream of the D/A.


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Index/Revision b

The shutoff valve is opened if the level control deviation is exceeding a determinedvalue or the D/A inlet CTRL-V is not closed. It is closed if the level control deviation isdecreasing this determined value and the D/A inlet CTRL-V is closed for more than 3minutes.

The shutoff valve will be closed by protection signal if: the D/A level exceeds the value MAX4.

Emergency Drain Valve Control:If the D/A level exceeds the value MAX2 during normal operation the drain valve isopened. As soon as the level falls below the value MAX1 the drain valve will closeagain.

The drain valve will be opened by protection signal if: the D/A level exceeds the MAX3 value.

The drain valve will be closed by protection signal if:

the D/A level falls below the MIN2 value while the D/A pump is in operation.

To ensure that during HRSG filling and start-up the feedwater min-flow recirculationflow is routed partly through the D/A for deaeration and warm-up of the condensatepreheater content it is necessary to keep the D/A condensate inlet valve alwaysslightly open. In case that the D/A tank is filled to its operating level and subsequentlythe D/A condensate inlet Ctrl-V is completely shut it is possible that the feedwatermin-flow pressurizes the CPH to a pressure higher than the D/A pump discharge

pressure and the D/A outlet flow is forced to zero even with open D/A outlet Ctrl-V. Inorder to reduce the CPH pressure by reopening the D/A condensate inlet Ctrl-V theD/A emergency drain valve is opened if the D/A outlet flow falls below a limit ofapprox. 10 kg/s while the D/A outlet Ctrl-V is open and the D/A level exceeds thevalue MIN1 during start-up. The D/A Drain Valve is closed again as soon as the D/Aoutlet flow exceeds 10kg/s or the outlet Ctrl-V is not open any longer or the D/A levelfalls below the value MIN1.

Vent Valve Control:When the D/A pressure reaches a slight overpressure and the condensate inletCTRL-V is not closed and the condensate inlet isolating valve is open the vent valveopens. The vent valve will close if the D/A pressure falls below the ambient pressureor the condensate inlet CTRL-V is closed or the condensate inlet isolating valve isclosed in order to keep the pressure in the D/A and to keep the D/A isolated from at-


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Index/Revision b

The D/A pump can only be switched on if the water level in the D/A exceeds the MIN2value.

The pump will be switched off by protection signal if: the differential pressure at the strainer is TOO HIGH or the D/A level is TOO LOW or the water level of the LP drum exceeds the HIGH HIGH level.


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Index/Revision b

3 Appendices

Descrip tion App KKS

Bypass Deaerator; Closed Loop Control Overview 1 10 LAA 20 DU 001

Bypass Deaerator; Level Control 2 10 LAA 20 DL 001

Bypass Deaerator; Temperature Control 3 10 LAA 20 DT 001 Bypass Deaerator; Flow Control 4 10 LAB 05 DF 001

Bypass Deaerator; SGC Overview 5 10 LAA 20 EC 001

Bypass Deaerator; Vessel Protection Sheet 6 10 LAA 20 BB 001


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PI

S

PI

10LAA20EE501

SLC D/A VENT

10LCA65EE001

SLC D /A C OND INLE

10LAB05EE402

SLC D/A EM ERG Y DR


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Vessel Protection Sheet

MEASURING POINT 10LAA20 CL901 CL001 CL002 REFERENCES FOR APPLICATIONS, OBSERVATIONS

FUNCTIONAL CODE W1 W WARNING YP12

FUNCTIONAL GROUP LIMIT-/ SIGNAL SP SETPOINT

RANGE 0 ... 3263 SETPOINT- OUTPUT A ALARM YP11

REDUNDANCY SETTING (TEXT) Z PROTECTION

SIGNAL IDENTIFICATION CODE mm T TOLERANCE YP13 processing by

XH07 XH07 3000 >MAX4 Z, A Alarm: Level TOO HIGH; Prot. OFF: Condensate Pumps; Prot. CLOSE: 10LCA65AA001/AA101, 10LBG70AA101

10LAA20 XH05 2900 >MAX3 Z, A Alarm: Level HH; Prot. OPEN: 10LAB05AA402; Prot. CLOSE:10LCA65AA101,10LBG70AA101,10LCA19AA001

BB001 XH03 2800 >MAX2 Z, W Warning: Level HIGH; Autom. OPEN: 10LAB05AA402 (SLC)XH01 2500 >MAX1 T Tolerance: Control Range Exceeded

XH51 2500 MIN1 SP Autom. OPEN: 10LAB05AA402 (SLC) during Startup if no flow through D/A

Bypass XH52 800 MIN2 SP Release ON: Deaerator Pump; Startup Fill Level

XH54 700

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Vit154 Xs00 Laa20 System Rev_b

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