can training boiler

8/18/2019 CAN Training Boiler

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February 2003February 2003

Training

ÇAN THERMAL POWER PLANT


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Steam Generator

with Circulating FBC

Untertitel (Arial 22 bis 24)

Training CAN Seite 4

Customer TEAS

Plant location CAN / Turkey

Firing capacity 358,6 MW

Steam data SH RH

485 t/h 437 t/h

175 bar 38 bar

543 °C 542 °C

Fuel turkish lignite

Year of Commissioning 2003


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Steam Generator

Cross section furnace centre



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Steam Generator

Circulating Fluidized Bed


furnace

nozzle grid

primary air

flue gas

cyclone


7/207

General description

process - fluidization


Combustion air is mainly divided in

primary air - air through nozzle grid

secondary air - air through air nozzles above grid

bed material consists of approx. 98 % ash or sand

nozzle grid causes for a homogenous fluidization of

bed material


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General description

process - fluidization


primary air transports bed material in direction of

ceiling

coarse bed material falls down along sidewalls

other material is separated in cyclones

separated material returns to furnace through loop

seals with fluidization air

flue gas leaves cyclones through exit tubes to 2nd

pass

fly ash is separated in electrostatic precipitator


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General description

process flow

Process flow schematic



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General description

process - fuel supply


crushed raw lignite is stored in four coal bunkers

coal is discharged through coal feeders to 8 feedingpoints of the four double ash loop seals for a

uniform disribution of the fuel across nozzle grid

mixing with hot ash in loop seals predries coal

already

Coal feeding system


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General description

process - limestone supply


Limestone powder is stored in two limestone

bunkers

limestone is discharged through fluidizing

conveyors to the 8 coal drag link chain conveyors

Limestone system


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General description

process - bed material supply


for first start up of boiler or after revision, furnace is

filled up with sand or available bed material

bed material is discharged through a rotary feeder

and a drag link chain conveyor to furnace

for a uniform distribution of bed material,there shallbe a minimum primary air flow during feeding


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General description

process - bed material discharge


bed ash is discharged via four openings in bottom

of furnace

ash flow from furnace to the two ash coolers are

controlled with L-valves

bed ash is fluidized in ash cooler and cooled downthrough feeding water and condensate

cooled down bed ash can conveyed to bed materialsilo

L-valve

Ash cooler


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General description

particle size characteristics


Particle size distribution mainly depends on :

particle size of the supplied coal

particle size of the limestone

particle size of the externally supplied bed material separation characteristics of the cyclones

abrasion characteristics of ash

Grain size distr


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General description

particle size characteristics


Expected particle size distribution

m a te r ia l m a x . g ra in s iz e (m m ) m a in p a r t ic le (m m )

C o a l < 2 0 4 -5

L im e s to n e < 1 0 ,1 -0 ,1 5B e d a s h < 1 0 ,2 -0 ,5

approx. values for

initial adjustment


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General description

Steam generator data

Steam dataSteam data

Steam capacity SH / RH 457 / 407 t/h

Pressure SH / RH 190 / 39.8 bar

Temperature SH / RH 543 / 542 °C

Feedwater temperature 250 °C

Waste gas temperature 138 °C



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H-p diagram


Fuel Data:Fuel Data:

Fuel: Brown Coal

LCV: 10.890 MJ/kg

Ash: 32.0 %

Water: 22.0 %

Eco

Evaporator

SH 1/1SH 1/2SH 1/3INJ-1

SH 2-PL

INJ-2SH 3

..

.

....

..

..

.

RH 1RH-INJ

RH 2-PL

.

..

.

Pressure

0 50 100 150 200 250 300 bar 400

E n t h a l p y

4,000

3,600

3,200

2,800

2,400

2,000

1,600

1,200

800

400

kJ/kg

100 °C

150 °C

200 °C

250 °C

300 °C

350 °C

375 °C

40 0 ° C

45 0 ° C

5 0 0 ° C

5 5 0 ° C

600 °C

650 °C

7 00 °C

750 °C


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General description



Fuel dataFuel data

Brown coal

Calorific value (NCV) 10.9 MJ/kg Ash 32 %

Moisture 22%

Sulphur 4.0 % (max. 7.0 %) Fuel capacity 128 t/h

Desulphurization 95 %

SO2 Emission 1,000 mg/m3

s.t.p. (5 % O2) Fuel ash composition SiO2 50 %, Al2O3 30 %,

FeO3 15 %, other const 5 %


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Flue Gas Temperature

Versus Load Nozzle Grid/Furnace


1000

900

800

700

600

500

400

300

200

100

0

0 40 60 80 100

Steam output (%)

F l u e g a s t e m

p e r a t u r e ( ° C )

20

Furnace

Nozzle Grid

Fuel DataFuel Data::

Fuel: Brown Coal

LCV: 10.890 MJ/kg

Ash: 32.0 %

Water: 22.0 %

approx. values for

initial adjustment


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Description of systems

Water / steam system

components


feedwater supply

feedwater preheating

evaporator

superheater reheater

high pressure heatersash coolers

economiser

heating surfaces

drum


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Natural circulation boiler


Feedwater control

Level

Feedwater

Steam flow m•

EvaEco

T


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Water steam scheme



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Feedwater supply

2 controlled feed pumps

for controlling of sufficient differential pressure

between inlet and outlet of the

feedwater control station

2 feedwater control valves

one start up feed control valve (up to 30 % )

one full load feed control valve

for controlling of required feedwater flow



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feedwater supply

P&I feedwater control station



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Feedwater preheating

HP heater 6 and 7

feeded from bleeding or CRH steam

cooling of HP ash coolers with feedwater

normal boiler operation:

all feedwater is sent through ash coolers

if one ash cooler out of operation,

bypass available

economiser

arranged in second pass flue gas

last heating surface upstream flue gas air heater



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Ash cooler



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evaporator

Wall heating surfaces of the furnace



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superheater

Two parallel steam lines

SH 1/1 supporting tubes of the second pass

SH 1/2 walls of second pass

SH 1/3 convective heating surface in second pass spray attemperator 1

SH 2 platen heating surface in furnace

spray attemperator 2

SH 3 convective heating surface in second pass


D i i f


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P&I attemperator


D i ti f t


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Live steam piping

One SH safety valve (≈30 % MCR flow)

one SH standstill cooling valve (≈10% GCC flow)

one HP bypass control valve (70 % MCR flow)

with safety function

two HP turbine valves (2 x 50 % MCR flow)


D i ti f t


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P&I live steam


D i ti f t


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HP safety devices

Safety device MCRflow

MCR operatingpressure

One HP safety valve atdrum

70 % +17 bar

One HP bypass controlvalve at SH 3 outlet

70 % + 10 bar

One HP safety valve atSH 3 outlet

Approx.30 %

+ 17 bar


LP safety devices

Pressure control



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reheater

Two parallel steam lines

RH 1 convective heating surface in second pass

spray attemperator 1

RH 2 platen heating surface in furnace




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Hot reheat steam piping

One LP start up standby control valve

( 30 % GCC)

one RH safety valve (MCR flow)

one LP bypass control valve

( > 315 t/h at 39.2 bar)

two LP turbine interceptor valves

(2 x 50 % MCR flow)




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LP safety device

Safety device MCR

flow

MCR operating

pressure

One HP safety

valve at drum

70 % +17 bar

Training CAN Seite 35 Pressure control



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HP auxiliary systems

Filling line

Desalting system

start up drain system ( drum, flash tank,

boiler condensate tank )

drain system of heating surfaces

venting system




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P&I SH drain station




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air fluegas system

components


2 secondary air (SA) fans with vane guide

function: supply of the CFB system withsecondary air

capacity: 2 x 70%

2 primary air (PA) fans with vane guide

function: supply of the CFB system with

primary air

capacity: 2 x 70%



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P&I PA / SA fan




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air fluegas system

components


4 steam air heaters (SAHs)

function: heating up the combustion air for start up and to prevent flue gas

temperature falling below dew point

2 regenerative air heaters (RAH)

function: heating up combustion air



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air fluegas system

components


3 fluidizing air fans

function: fluidization of loop seals,supply of flame scanners, ignitors

and oil lances with cooling and

ignition air capacity: 3 x 50%



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air fluegas system

components


2 ash coolers with immersed cooling surfaces

and 2 ash cooler fansfunction: cooling of the extracted bed ash from

850°C to 60°-140°C

capacity: 2 x 100%



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p y

air fluegas system

components


2 electrostatic precipitators (ESP)

function: cleaning flue gas from ash particles capacity: 2 x 70%

2 induced draught (ID) fans with vane guide

function: leading flue gas to chimney

control flue gas pressure at cyclone

outlet

capacity: 2 x 70%



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p y

start-up burner

Use of start up burner


start up burners are used for heating up of the

bed material in the furnace until the releasetemperature for coal feeding is reached

HFO shall be used with an combustion air temperature of at least 120 °C



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p y

start-up burner

components


number of burners 8 (3 front wall, 3 rear wall,

1 left and 1 right side wall)

number of levels 1

fuel heavy oil N° 6/ light oil N° 2

type of burner jet burner

atomising system pressure atomisation

fitting position 30 °



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y

start-up burner

Releases


LFO ignition permit time is running

(boiler is purged)or

>7 bed temperature >570° C

or

start up burner is on

HFO see LFOand

temperature HFO > 90°C



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start-up burner

Technical data light oil


oil flow max. 1656 kg/h

oil flow min. 828 kg/h

oil pressure max. 75 bar

oil pressure min. 20 bar

control range 1 : 2



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start-up burner

Technical data heavy oil






control range 1 : 2



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start-up burner

operation


Either light oil operation or heavy oil operation

can be preselected.Then oil supply must be started.

The start up burner can be started or stopped

manually from local panel in the field or controlroom.



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start-up burner

operation


If oil lance is empty and heavy oil operation is

preselected, oil lance will be prewarmed for 90sec with steam

Signal "lance prewarmed" is displayed for 600

sec, if steam cleaning valves have been open for at least 80 sec



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start-up burner

operation


If oil lance is empty, safety time is running for 12

secIf oil lance is not empty ( filled lance ) safety time

is running for 5 sec


t t b


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start-up burner

operation


Start up burner shuts down automatically with FG

boiler shutdown or if ignition trial failed Scavenging is done with steam valve opened

and ignition in operation for 15 sec, then 5 min

without ignition.


t t b


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start-up burner


impeller

oil lance

ignitor

flame scanner

core air


t t b


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start up burner

P&I start up burner



start up burner


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start up burner

burner station



bed lances


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bed lances

Use of bed lances


ignition of bed lances possible with at least

500° C / 550 °C bed temperature

bed lances are used for heating up of the bed

material in the furnace until the releasetemperature for coal feeding is reached

bed lances are used for maintaining a constant

bed material temperature at low loads


bed lances


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bed lances

components


number of burners 8 (2 front wall, 2 rear wall,

2 left and 2 right side wall)

number of levels 1

fuel heavy oil N° 6/ light oil N° 2

atomising system pressure atomisation

max. load 15 % of boiler load

fitting position 30 °


bed lances


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bed lances

Technical data light oil






control range 1 : 2


bed lances


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bed lances

Technical data heavy oil






control range 1 : 2


bed lances


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bed lances

Releases


LFO start up burner in operationand

>7 bed temperature >500° Cor >7 bed temperature >570° C

HFO start up burner in operation

and>7 bed temperature >550° Cand


or >7 bed temperature >570° Cand


approx. values for

initial adjustment


start-up burner / bed lances


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start up burner / bed lances



ash cooler


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ash cooler

components


The bed ash discharge system extracts the bed

ash from the furnace automatically depending

on the pressure above primary air nozzle grid

The bed ash system is equipped with 4

horizontal L-valves , 2 to each ash cooler.

general


ash cooler


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ash cooler

pressure above nozzle grid versus load


80

90

100

110

120

130

0 10 20 30 40 50 60 70 80 90 100

load BMCR (%)

p r e s s u r e a

b o v e g r i d ( m b a r )

setpoint 1

setpoint 2

setpoint 3

setpoint 4

general

description

L-valve

approx. values for

initial adjustment


P&I ash cooler


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P&I ash cooler


furnace

from

ash cooler fan

general


ash cooler


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overview

Training CAN Seite 65 general


ash cooler


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components


The bottom ash discharge via horizontal L-valve

is done discontinuously. The horizontal L-valve

is set into a basic position. The opening

sequence and amplitude of the horizontal L-

valve is controlled by the reference value,

pressure above primary air nozzle grid. During

normal operation both horizontal L-valves are in

operation and work alternating for each

sequence. The horizontal L-valve is kept at itsbasic position when the reference value is

below a specified minimum set point.

Setpoint L-valves


L-valve


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ash control valve

Training CAN Seite 67 Setpoint L-valves

Plug

Valve Seat

Water Cooled

Valve Shaft

Hydraulic

Actuator

Assembly

Refractory Lined

Valve Bodygeneral


auxiliaries


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arrangement



air preheater


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regenerative air preheater


Air preheaters consist of a large number of heat

transfer plates arranged like the spokes of a

wheel, which slowly rotate at speeds lower than

one revolution per minute and up to approximately

five r/mm from a hot side exhaust environment

into a cold side intake. The cold intake air is thus

"preheated" improving efficiencies and reducing

wasted process energy.


air preheater


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regenerative air preheater


Air flow downstream of APH Flue gas upstream of APH

Air flow upstream of APH Flue gas downstream of APH


cyclones


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Purpose of cyclones


Arrangement downstream of the furnace

cyclone inlets have a spiral shape

cyclones have an interior lining which isfireproof, wear resistant and insulates

particles above an significant size are completely

separated

solid mass flow is transported from the from the

loop seals to the furnace

loop seals prevent a backflow of fluegas from

furnace

flue gas leaves cyclones through exit tubes


cyclones


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Arrangement cyclones


Çan

355.6 MW


cyclones


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Cyclone overview


InclinedDownward

Inlet Duct

High PerformanceRefractory for Inlet Area

Eccentric VortexFinder Arrangement

Advanced VortexFinder Shape

Second Pass


cyclones


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cyclone performance



cyclones


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velocity and dust loading


velocity dust loading


loop seal


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P&I loop seal



loop seal


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loop seal



loop seal


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loop seal


downcomer

lift

line


auxiliaries


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section lower furnace



sootblower


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Rotary long retractable sootblower



sootblower


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Rotary extended lance sootblower



sootblower


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Installation 2nd pass


No Level(m)

KKS-No Fluegastemperature

( °C)

Fluegaspressure(mbar)

Type of construction

1 33.630 01 HCB20 AT001 860 -1.0 Long retractable blower2 33.630 01 HCB20 AT001 860 -1.0 Long retractable blower

3 33.630 01 HCB20 AT001 860 -1.0 Long retractable blower



6 30.560 01 HCB20 AT001 700 -2.0 Long retractable blower7 25.170 01 HCB20 AT001 540 -4.0 Helical blower

8 25.170 01 HCB20 AT001 540 -4.0 Helical blower



11 19.250 01 HCB20 AT001 435 -6.0 Helical blower12 19.250 01 HCB20 AT001 435 -6.0 Helical blower





limestone feeding


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limestone feeding system


two limestone silos

one fluidizing conveyor, divides the conveying

route in two parts

adjustable rotary feeders

adjustable drag link conveyors

two manual operated gate valves

<


limestone feeding


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P&I limestone feeding


limestone silo

fluidizing conveyor

rotary feeders

drag link conveyors

<


coal and limestone feeding


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arrangement coal and limestone feeding



coal feeding


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arrangement


cyclone Coal bunker furnace

Gravimetric

coal feeder

Drag link

chain conveyor

Loop seal

Rotary

feeders

<


coal feeding

l f di t


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coal feeding system


four coal bunkers each with two outflows

altogether eight adjustable gravimetric coal

feeders with clean out conveyor

eight adjustable drag link chain conveyors with

connection with limestone feeding

downstream of drag link conveyors route divides

in two conveying routes

each route is lockable with manual operated shutoff gate valves

<


coal feeding

l f di t


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coal feeding system


each route is lockable with manual operated shut

off gate valves

each route consists of one rotary feeder downstream one manual operated shut off gate

valve

one auto operated shut off gate valve

both shut off gate valves, rotary feeder and drag

link chain conveyors are supplied with adjustable

sealing air

upstream of loop seal both conveying routes are

linked up<

Boiler protection

Boiler protection part I

I t l k


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ID fan protection

SA fan protection

secondary air way release

primary air way release

reheater release

general interlocking

Interlocks


symbols

Logic diagram

Boiler protection

Boiler protection part II

Interlocks


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boiler purge

ignition release

start up burner release

bed lance burner LFO release

bed lance burner HFO release

oil burner purge release

coal feeder release

Interlocks


Boiler protection

ID fan protection

Both ID fans are tripped if


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Both ID fans are tripped if

>=2 furnace pressure < min

>=2 reg air heater speed < min

one of four ID fan bearing temperature

> 90 °C

cooling air flow < min ( for > than 30 min)ID fan motor winding temperature > 140°C

ID fan motor cooling air inlet temperature

> 70°CID fan motor cooling air outlet temperature

> 110°C

ID fan vibration > 11 mm/sTraining CAN Seite 91 approx. values forinitial adjustment

Boiler protection

SA fan protection


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Both SA fans are tripped if

no ID fans in operation and ”command on”

SA fan ≤ 2 furnace pressure > max

SA fan bearing temperature > 95°C

SA fan motor winding temperature > 140°C SA fan motor cooling air inlet temperature

> 70°C

SA fan motor cooling air outlet temperature> 110°C

SA fan vibration > 11 mm/s

Training CAN Seite 92approx. values forinitial adjustment

Boiler protection

Secondary air way release


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Secondary air way release is available if

no boiler emergency switch is activated

furnace pressure is > min and < max

ID fan and SA fan are in operation

fluegas dampers are open

Failure of air and fluegas way release signal leads

to boiler trip.


Boiler protection

Primary air way release

Primary air way release is available if following


94/207

Primary air way release is available, if following

signals are available

secondary air way release

a minimum fluidising air pressure ( 300 mbar)

a minimum secondary air pressure ( 30 mbar) reheater release

water level in the drum < max ( 200 mm)

water level in the drum > min


Boiler protection

Reheater release


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Boiler protection

General interlocking


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master fuel fault is existing, if

failure of the primary air way release signal both PA Fans out of operation

furnace windbox pressure below a minimum( 40 mbar )

primary air flow below minimum (38570 Nm³/h) condenser level not > max


Boiler protection

Boiler purge

The purging is done with 50% MCR air flow


97/207


The purging is done with ~50% MCR air flow(78.5 kg/s). The purge time is set to a value thatmeets the total volume of 3 times boiler fluegas

way volume (16 min). On completion of the presetvolumes i.e. 3 times volume change for fluegaspath the signal boiler purge time completed is

activated. Any interruption during this processresets the boiler purge time relay. In this case thepurge cycle has to start all over again. If the boiler was in operation and the bed temperature at the

nozzle grid level exceeded 570 °C there is noneed to purge the boiler.

approx. values forinitial adjustment

Boiler protection

Ignition release


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Once the purge is completed the ignition permit

time is set and a secondary air flow < 30% is

maintained. For the normal start time a maximumof 3 failstarts is allowed. The start attempts of the

burners is monitored through a fail start counter. If

the burner is not established within the allowedpreset number failstart counts the boiler has to be

purged again.


Boiler protection

Ignition release


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Ignition oil burner release permit is available

provided there are the following

start up burner on

or

bed temperature > 570°C

boiler protection existing

or ignition permit time running

secondary air flow < 30%


Boiler protection

Start up burner release

Oil burner burner release permit is available


100/207

Oil burner burner release permit is availableprovided there are the following:

Primary air way release

Ignition release

Minimum primary air flow available or oil valvesstart up burners closed at least 10 min

Min LFO supply pressure available (if light oiloperation selected)

Min HFO supply pressure available (if heavy oiloperation selected)

control air pressure > min available ( 3,5 bar)


Boiler protection

LFO bed lance burner release

b d l b LFO l it i il bl


101/207

bed lance burner LFO release permit is available

provided there are the following:

Ignition release

boiler protection

Primary air flow > min (38570 Nm³/h)

control air pressure > min ( 3,5 bar)

bed temperature > 500 °C


Boiler protection

HFO bed lance burner release

b d l b HFO l it i il bl


102/207

bed lance burner HFO release permit is available


Ignition release

boiler protection

Primary air flow > min ( 38570 Nm³/h)

control air pressure > min ( 3,5 bar)



Boiler protection

Oil burner purge release

Oil b rner p rge release permit is a ailable


103/207

Oil burner purge release permit is available


bed lance burner LFO release

or

bed lance burner HFO release

or

start up burner release

and minimum purge steam pressure available


Boiler protection

Coal feeder release

Coal feeder release permit is available provided


104/207

Coal feeder release permit is available provided

there are the following

boiler protection existing

ignition release existing

>=2 primary air flow > min 52550 Nm³/h)

>=7 bed temperature > min ( 650° C)


Boiler protection

unit load runback

one of two ID Fan is tripped


105/207

one of two ID Fan is tripped

target: 70 % BMCR not delayed

one of two SA Fan is trippedtarget: 70 % BMCR not delayed

one of two PA Fan is trippedtarget: 70 % BMCR not delayed

one of two FB ash cooler fan

target: 70 % BMCR not delayed

turbine trip

target: 60 % BMCR not delayedTraining CAN Seite 105

approx. values forinitial adjustment

System operation

overview

fi t filli f b il


106/207

first filling of boiler

cold start up boiler

warm start up boiler

hot start up boiler

normal operation

shut down boiler

blackout

failures


System operation

first filling of boiler

Filling line is used for filling the evaporator after a


107/207

Filling line is used for filling the evaporator after a

repair standstill. Evaporator and downcomer are

filled from bottom up to avoid thermal stress of drum during filling operation

all isolating valves upstream of measurementsshall be opened

Filling of eco, evaporator and of drum via fillingline ( 01 LAE10) until drum level > min


System operation

General

Operation conditions for start / stop and


108/207

Operation conditions for start / stop and

monitoring of the boiler is given in the form of

functional group logics whole system is divided into functional groups

and subgroups

function group control can be started in automode or manually.

group control is used to START or STOP in

steps.


System operation

General

every step is activated when its previous step


109/207

every step is activated, when its previous step

command is carried out and the necessary

conditions previous to this step are fulfilled step is overriden or overruled, if the subsequent

conditions meet the overruling criterias to this

step selection control blocks are for either one out of

two or three equipments

some operational conditions require manualintervention (e.g. start of oilburners, coalfeeding)


System operation

Overview function groups


110/207


System operation



111/207


System operation



112/207


System operation

cold start

criterion for cold start up


113/207

p

bed temperature < 100 °C

bed temperature control

The brick lining of the cyclone part admits amaximum rate of temperature change of approx.

100 K /h. Therefore, the bed temperature is used

as most important control variable during the start-up process, the required target being a bed

temperature increase of approx. 100 K/h.


System operation

cold start

Steam pressure control


114/207

p

The life steam pressure is controlled by the HPbypass control valve during start-up of the steam

generator. The hot reheat steam pressure is

controlled by the LP bypass control valve. In caseof failures, a steam flow of 30% at maximum can

be released to atmosphere via SH start-up standby

control valve.


Adj live st

Adj reheat st

System operation

cold start

Steam temperature control


115/207

p

spray attemperators are ready for operation to keepsteam temperatures below given limits

due to the very slow rate of bed temperature increase,

the steam temperature rate of change both of lifesteam and of hot reheat steam normally will be in a

safe range without any spray attemperator operation

as soon as the required turbine coupling temperature

in the life steam line or in the hot reheat line is reached,

the relevant spray attemperator will open and will keep

this temperature.


System operation

cold start

Start-up of fans and of steam air preheater with Adjustment of firing


116/207

Start up of fans and of steam air preheater with

FG air fluegas

Fill-in of required bed material

Purge via secondary air with FG purge


System operation

cold start

Ignition of start-up burner (LFO) with a firing rate Adjustment of firing


117/207

g p ( ) g

of approx. 10%

use HFO start up burners not until combustionair temperature has reached 120 °C

adjustment of primary air minimum flow

minimum air flow for

start-up burner 38570 Nm³/h bed lances 46400 Nm³/h


approx. values for

initial adjustment

System operation

cold start

Ignition of bed lance LFO or HFO (minimum bed Adjustment of firing


118/207

Ignition of bed lance LFO or HFO (minimum bed

temperature for bed lance release LFO 500° C

HFO 550° C )

Firing rate increase to approx 40%. The increase

takes place in steps adapted to avoid a rate of

change of the bed temperature > 100 K/h.

Start-up at least one ash cooler


approx. values for

initial adjustment

System operation

cold start

Start-up of the first coal feeder after Adjustment of firing


119/207

Start up of the first coal feeder after

bed temperature > 650 °C is reached

waiting time until coal ignition (coal ignition is

recognized by fast increasing of bed

temperature)

Increase of coal firing rate, synchronous

reduction of oil firing rate and oil firing turnoff


approx. values for

initial adjustment


120/207

System operation

cold start

SH and RH start-up drains are set to autoDrain system


121/207

operated mode with starting FG air fluegas

condensate obtained in the HP and LP steam

system is automatically discharged


System operation

cold start

controlled with HP bypass control valve Adjustment of live steam pressure


122/207

yp

1. control valve opens to minimum position

pressure will increase in sliding pressure mode

2.pressure control mode with variable target rate

up to turbine coupling pressure3.fixed pressure setpoint (until steam turbine has

taken over all steam)

4.increase steam pressure to operation pressure

Training CAN Seite 122 Steam pr ctrl

System operation

cold start

controlled with LP bypass control valve Adjustment of hot reheat steam pressure


123/207

yp

1. control valve opens to maximum position -


2.pressure control mode with fixed pressure

setpoint (until steam turbine has taken over allsteam)

Training CAN Seite 123 Steam pr ctrl

System operation

cold start


124/207


System operation

warm start

criterion for warm start up


125/207

drum temperature > 100 °Cbed temperature < 650 °C


System operation

warm start

start-up of fans and of steam air preheater with

FG air fluegas

Adjustment of firing


126/207

FG air fluegas

if bed temperature < 570 °C :purge via secondary air

if bed temperature > 570 °C :

ignition of the oil firing ignition of the oil firing ( start-up burner ) with a

firing rate of approx. 10%

adjustment of primary air minimum flow( see cold start )


approx. values for

initial adjustment

System operation

warm start

Ignition of bed lance LFO or HFO (minimum bed



127/207

temperature for bed lance release LFO 500° C

HFO 550° C )

Firing rate increase to approx. 40%. First the

increase is accelerated to reach quickly thesame bed temperature value, that was measured

before purge. The following increase takes place

in steps adapted to avoid a rate of change of the

bed temperature > 100 K/h.


approx. values for

initial adjustment

System operation

warm start

start-up of the first coal feeder after both bed



128/207

temperature > 650 °C is reached and the cooling

of one FB-ash cooler at least is in service.

increase of coal firing rate, synchronous

reduction of oil firing rate and oil firing turnoff


approx. values for

initial adjustment

System operation

warm start

usual feedwater flow control during start-up of

Feedwater supply


129/207

the firing

discharge of obtained excess water from drum

by the drum blow down system

normally the feedwater will always be sent

through FB-ash coolers. However it is allowed to

send the feedwater via ash cooler bypass aslong as bed temperature < approx. 200 °C.


System operation

warm start

SH and RH start-up drains are set to auto

Drain system


130/207

operated mode with starting FG air fluegas

condensate obtained in the HP and LP steam

system is automatically discharged


System operation

warm start

controlled with HP bypass control valve

Adjustment of live steam pressure


131/207

1. control valve opens to minimum position -


2.pressure control mode with variable target rate

up to turbine coupling pressure

3.fixed pressure setpoint (until steam turbine has

taken over all steam)

4.increase steam pressure to operation pressure


System operation

warm start

controlled with LP bypass control valve

Adjustment of hot reheat steam pressure


132/207

1. control valve opens to minimum position

2.pressure control with pressure setpoint approx.

equal to the HRH pressure value at ignition until

LP bypass reaches maximum position

( approx.50% )

3.pressure control mode with fixed pressure

setpoint (until steam turbine has taken over allsteam)


System operation

warm start


133/207


System operation

hot start

criterion for hot start up


134/207



System operation

hot start

restart of fans, adjustment of primary air

minimum flow ( > 52550 Nm³/h)



135/207

minimum flow ( 52550 Nm /h)

restart of first coal feeder rapid increase of firing rate to approx 40% in

order to keep the bed temperature above 650 °C.


approx. values for

initial adjustment

System operation

hot start

Feedwater supply


136/207

feedwater supply and drum blow down are

working in the warm start-up manner.

due to the high bed temperature the feedwater

shall always sent through FB ash cooler.


System operation

hot start

Drain system

Adjustment of live steam pressure

Adjustment of hot reheat steam pressure


137/207


beginning at a higher pressure level

actions to be taken in warm start-up manner

System operation

hot start


138/207


System operation

Normal operation

feedwater supply and drum blow down

desalting of boiler water

overview


139/207

desalting of boiler water

steam pressure

steam temperature

control O2

air distribution

primary air control

steam air preheater


System operation

Normal operation

pressure and temperature condition in the

furnace

overview


140/207

grain size distribution of the bed

sootblowing

limestone feeding desulphurization

formation of NOx


System operation

Normal operation

boiler feedwater pumps have the control task to

ensure an appropriate differential pressure

Feedwater supply and drum blow down


141/207

between inlet and outlet of the feedwater control

station respectively between inlet of feedwater

control station and drum.

the feedwater control valve in service has to

adjust the feedwater mass flow. All feedwater is

normally sent through the FB-ash cooler.

overfed water is automatically discharged fromdrum by drum emergency blow down system.


System operation

Normal operation

blow down valve is used for keeping conductivity

of boiler water below 50 µS/cm

Desalting of boiler water


142/207

of boiler water below 50 µS/cm

blow down valve can be operated intermittent or

continuously.

blow down valve shall be closed when boiler is

not in operation


System operation

Normal operation

During normal operation the total live steam flow

and the total hot reheat steam flow are sent to

Steam pressure


143/207

turbine. If the turbine is not able to take the total

steam flow, HP bypass and LP bypass take the

remaining steam flow up to 70% MCR. In this

case the load capability is restricted to approx.

70% MCR.

Fixed-pressure operation in the HP system

combined with sliding-pressure operation in the

LP system is the usual operation mode within the

whole range of load. Bypass operation at 70%

MCR load requires 100% hot reheat pressure.Training CAN Seite 143 Safety devices

System operation

Normal operation

At ignition the HP bypass control valve opens to a

given start-up minimum position

Superheated steam pressure control


144/207

The first part of the pressure rise takes place insliding pressure mode with this HP bypass position

Then HP bypass is switched to pressure control

mode. The pressure setpoint is increased infunction of steam flow and pressure until required

steam turbine coupling pressure is reached

further pressure increase up to normal operationpressure after steam turbine has taken over all the

steam


System operation

Normal operation

After ignition the LP bypass opens to a given start-

up maximum position

reheated steam pressure control


145/207

the HRH pressure is rising in sliding pressuremode up to the required turbine coupling pressure

After that the start-up maximum position limit is

eliminated. The LP bypass is switched to pressurecontrol mode, setpoint being the required turbine

coupling pressure value

set-point is set somewhat above the operatingpressure. Thus, the LP bypass is kept close during

the further turbine load operation.


System operation

Normal operation

life steam temperature is controlled by SH spray

attemperators 2.1 / 2.2. A constant temperature

i id d i th l d f 50 100 % GCC

Steam temperature


146/207

is provided in the load range of 50-100 % GCC.

The task of the spray attemperators 1.1/ 1.2 is to

keep the control valve position of the spray

attemperators 2.1 / 2.2 within a well suited range.

hot reheat steam temperature is controlled by

RH spray attemperators. A constant temperature

is provided in the load range of 50-100 % GCC.

Below this load range, usually the hot reheat

steam temperature is lower and not yet

controlled, the spray control valves are closed.Training CAN Seite 146

System operation

Normal operation

The main steam temperature downstream of SH 3is controlled and adjusted to setpoint by means of

4 desuperheaters ( two downstream of SH 3 and

Superheated steam temperature control


147/207

4 desuperheaters ( two downstream of SH 3 and

two downstream of SH 2)

maximum setpoint is 543 °C

or is set manually

or is set by unit master controller ( lower setpoint

during startup of boiler)

The spray mass flow for the four injections is

extracted by the feedwater control valvesTraining CAN Seite 147

System operation

Normal operation

The reheater steam temperature downstream of

RH2 is controlled and adjusted to setpoint by

means of 2 attemperators (downstream of RH 1)

reheated steam temperature control


148/207

means of 2 attemperators (downstream of RH 1)

maximum setpoint is 542 °C

or is set manuallyor is set by unit master controller ( lower setpoint

during startup of boiler)

The spray mass flow for the two injections is

extracted by the feedwater control valves


System operation

Normal operation

The air flow must be regulated in accordance

with the fuel flow

If th f l fl i t ll d ll h i

Control O2


149/207

If the fuel flow is controlled manually, changes in

the fuel flow carried out too quickly are to be

avoided.


System operation

Normal operation

Control O2

O2-content in flue gas downstream

2nd passapprox values for


150/207


11,31

3,44

0

2

4

6

8

10

12

0 20 40 60 80 100

GCC Load [%]

O

2 - c o n t e n t d r y [ V o l . - % ]

approx. values for

initial adjustment

System operation

Normal operation

Air distribution

70,00

80,00

The diagram gives approx.

values

for the initial adjustment.


151/207


0,00

10,00

20,00

30,00

40,00

50,00

60,00

40 50 60 70 80 90 100GCC [%]

a i r m a

s s f l o w

[ k g / s ]

primary air

upper secondary air

burner air

lower secondary air

coal feeding air

ash cooler fluidization

sealing air, cooling air ingnitor, flamescanner, limestone feeding air

ash loop seal fluidization

System operation

Normal operation

Primary air control

Primary air flow setpoint is formed of

an function of unit load demand of unit master


152/207


controller and primary air flow (valid for bedtemperatures > 650°C)

and an function of bed temperature and primary

air flow (valid for bed temperatures< 650°C)

there is a possibility to adjust primary air flowmanually

approx. values for

initial adjustment

System operation

Normal operation

Steam air preheaters

The task of steam air heater is

to keep constant the air outlet temperature


153/207


to avoid the operation of the regenerative air preheater below the flue gas dew point

System operation

Normal operation

During normal operation both ash coolers are in

operation. The bottom ash discharge from the

furnace is controlled automatically depending on

Pressure and temperature in the furnace


154/207

furnace is controlled automatically depending on

the pressure above nozzle grid. The bedpressure in the lower level is supposed to be

between 80 and 90 mbar with 100 % BMCR.

The horizontal L-valves are opened alternating.

The bed temperature shall be

approx. 840 - 860 °C.


approx. values for

initial adjustment

System operation

Normal operation

Pressure in the furnace

120

130

r )approx. values for

initial adjustment


155/207


80

90

100

110

0 10 20 30 40 50 60 70 80 90 100

load BMCR (%)

p r e s s u r

e a b o v e g r i d ( m b

a r

setpoint 1

setpoint 2

setpoint 3

setpoint 4

Descr ash cooler

initial adjustment

System operation

Normal operation

Grain size distribution of bed

30

Case 1 Case 2

m


156/207


+ 30

+ 20

+ 10

0 20 40 60 80 100 mbar

System operation

Normal operation

Tendency to a fine bed

to be recognized by:



157/207

decreasing bed temperature increased bed pressures on the upper levels

Measures

reduce ash cooler cooling air flow (min. flow)

feed coarse bed material


System operationNormal operation

Tendency to a coarse bed

to be recognized by



158/207

increasing bed temperature low pressures on the upper levels

Measures

increase ash cooler air flow

increase primary air portion



Particle size distribution of solid inventory0.11.0(%)

10.020.030.040 0

solids


159/207


10 µm100 1000Grain size d

40.0

50.060.070.0

80.0

90.0

99.0

99.9

R e s i d u e R

approx. values for

initial adjustment


Particle size distribution of lignite

Acceptable particle size

distribution:

99,9 % < 6.0-9.0 mm

0,1

1

10

20%

99,9

99

90

80%

0,1 0,2 0,5 1 2 5 20 50 100106


160/207


,

55 % < 1.0 mm


161/207

- the boiler load

- the fouling of the heating surfaces

(CO increase)- the increase of fluegas temperature

The complete cycle is to be operated at leastonce per shift.



Even if the control is off, the limestone feeding

has to be carried out such that the admissible

SO2 limit values are kept in every operating

Limestone feeding


162/207

phase if possible.



The task of the limestone control is to reduce the

SO2 content in the flue gas to a predefined value

control SO2 content


163/207

by dosing limestone

To improve the dynamic response of the

controlled system due to its inertia - from

limestone dosing into boiler to SO2-

measurement in the stack - the lignite flow is

used as a feedforward signal


CFB DesulfurizationChemical Reaction Basics

1. Calcination of LimestoneCaCO3 => CaO + CO2for temperatures above ca. 750 °CEndothermic reaction DH = +178 kJ/mol


164/207


Endothermic reaction DH 178 kJ/mol

2. Sulfur Dioxide Reaction

S + O2 => SO2

for temperatures above ca. 650 °CExothermic reaction, DH = - 297 kJ/mol

3. Desulfurization Reaction

CaO + 1/2 O2 + SO2 => CaSO4for temperatures between 750 °C and 900 °CExothermic Reaction DH = - 500 kJ/mol

CFB Desulfurizationreaction inside particles

macro pores

sulfated lime

unreacted


165/207


Calcination and Desulphurization Reaction inside Limestone Particles

micro pores lime

- CO2

CaCO3 CaO CaSO4

+ SO2 +1/2 O2

CFB Boiler - SO2 Capture

Achieved by limestone injection

CaCO3 --> CaO + CO2Optimum temperature:

CaO + SO2 + ½ O2 --> Ca SO4 850 °C


166/207


• Main parameter :

Furnace temperature control

- Limestone consumption varies enormously with

furnace temperature

No low cost remedial measure to

a poor furnace temperaturecontrol

790 810 830 850 890870 910

Temperature

Ca/S

Desulphurization Rate vsCFB Furnace Temperature

6

5

a t e


167/207


4

3

2

1

0

650 700 750 800 850 900 950 1000

Temperature (°C)

R e l a t i v e

S o r b e n t F l o w r a

Main Factors of influence

System operation

CFB NOX Emissions

Fuel Characteristics- Increase of NOx with fuel nitrogen content

- Increase of NOx with fuel volatile matter content


168/207


Furnace Temperature- Decrease of NOx with low temperature in furnace

( approx. 850 °C )

Excess Air - Decrease of NOx with low excess air level ( 20 % )

Air Staging- Decrease of NOx with low primary air feeding

Fuel / Air Mixing- Decrease of NOx with intense and homogeneous

fuel / air mixing

System operationshut down

Two different cases


169/207

Shut-down with fast cooling down

(repair standstill)

Shut-down with pressure maintaining

(hot standby standstill)


System operationshut down

load reduction to minimum load approx. 30%

the change from turbine mode to HP/LP bypass

First part


170/207

mode takes place before the steam temperature

drops. During and after this change HP bypass

and LP bypass keep the operating pressure

values of life steam and of HRH steam.

turn off of the coal feeders


System operationCooling down with pressure maintaining

To manage pressure maintaining without the risk

of excessive SH wall temperatures rise, a

i i b t

general


171/207

compromise is necessary between

some cooling down of the cyclone refractory

lining on the one hand

and

maintaining hot the bed material on the other

hand



After the turn off of the coal feeders the followingactions have to be done:

Primary air fan OFF. Lower secondary air

d l d

Air fluegas system


172/207

dampers closed

The secondary air fan and the induced draught

fan remain in operation for a period of several

minutes. Some secondary air flow is adopted inorder to obtain sufficient cooling of the refractoy

lining. At the same time the bed temperature in

both FB ash coolers has to be reducedto < approx. 400 °C

Then all fans OFFTraining CAN Seite 172


The feedwater supply remains in operation,adjusting the drum level to a constant value. The

feedwater is still sent through the FB-ash cooler.

feedwater


173/207

Shut-down of the feedwater supply not before the

response of the enabling criteria

maximum outside tube wall temperature of SH 1/1

< approx. 400°C for > 15 minutes

Some adjusting of the drum level before shut-downof the feedwater supply may be advantageous for

the following standstill and the restartTraining CAN Seite 173


HP bypass and LP bypass are switched to

pressure limiting control mode. Their task is

li iti f th lif t d HRH

HP and LP bypass


174/207

limiting of the life steam pressure and HRH

pressure to values close below the response

pressure values of the safety devices



After shut-down of the induced draught fan, theSH standstill cooling valve has to do a

temperature limiting control task. That means: In

case of maximum outside tube wall temperature

SH standstill cooling valve


175/207

case of maximum outside tube wall temperatureof SH 1/1 > approx. 430°C,

it is opened to cooling position

Thus, a small steam flow of approx. 2,5 % BMCR

is produced and released via SH standstill

cooling valve to the ambient air, which ensures asufficient longterm cooling of the critical SH 1

heating surfaceTraining CAN Seite 175


The SH relief valve is closed again by the criterion

SH standstill cooling valve


176/207

maximum outside tube wall temperature

of SH 1/1 < approx. 400°C


System operationfast cooling down

The task is to cool the steam generator down as

f t ibl i h kf

general


177/207

fast as possible in a shockfree manner.

After the turn off of the coal feeders the following

actions have to be done



Air fluegas system

All fans remain in operation.

The cooling is practised with small air flow rates

of approximately 30 50 % of the GGC secondary


178/207


of approximately 30-50 % of the GGC secondaryair flow.

This cooling operation mode is continued untilthe bed temperature has dropped to the required

value.


feedwater

The feedwater supply remains in operation,adjusting the drum level to a constant value.

The feedwater ist still sent through the

ash cooler


179/207


ash cooler.

Shut-down of the feedwater supply not before

the response of the enabling criteria :

maximum outside tube wall temperature

of SH 1/1 < approx. 400°C for > 15 minutes

The cooling down process may possibly besupported by continuing the feedwater supply for

some time


HP and LP bypass

Cooling down of the water-steam system by well-

directed pressure reduction down to depressurized

state


180/207


state The operator has to open slowly HP bypass and

LP bypass to position values, that ensure to get a

rate of pressure change within the safe range.

In case of condenser being out of service the

pressure can be reduced manual via RH start-up

standby control valve.

System operationblack out

general

In case of a failure of the main power supply, asafe state of the plant must be achieved.

Besides an emergency shutdown of the firing it ist th fl id t d i th


181/207


Besides an emergency shutdown of the firing it isnecessary to use the fluid stored in the

HP system for well-directed long-term cooling of

endangered heating surfaces (support tubes at

the transition cyclone 2nd pass).

Any other loss of stored HP fluid is to be

prevented.


Safe state water steam system

Final control element Safe state

Drum emergency blow down control

valve

Closed


182/207


valveDrum emergency blow down gate valve Closed

Demine drum gate valve Closed

SH standstill cooling valve controlledcooling position

Gate valve upstream SH standstill

cooling valve

Open

HP bypass control valve Closed


First measures

If the failure of the main power supply cannot be

eliminated within approx 15 minutesth f ll i l t ti ti h t


183/207


eliminated within approx. 15 minutes,the following manual protection actions have to

be carried out


measures

Final control element action target

swirl dampers of induceddraught fans,

swirl dampers of secondary air fans

open upto 100%

cooling by natural draught


184/207


y

upper secondary air dampers,

oil burner air dampers

open upto 100%

cooling by natural draught

manual shut-off valve01HAC10AA403Hin the economiser-

evaporator short circuitline

open The water contained in theeconomiser (approx. 29 t) isdrained into the evaporator.

Thus this water can be usedfor emergency coolingpurpose of the endangeredheating surfaces.


Second measures

If the failure of the main power supply cannot be

eliminated within approx 45 minutes


185/207


eliminated within approx. 45 minutes,

the following manual protection actions can be

done for better cooling :


measures

Final control element action target

cover of manhole,

arranged betweenf d l

open

withti

improved cooling

by natural draught


186/207


arranged betweenfurnace and cyclone

withcaution

by natural draught

upper secondary air

dampers

reduce

opening

keeping sub-

atmosphericpressure in thefurnace

Failuresleakages

Leakage boiler pressure parts

tube leaks or tube ruptures will ultimately lead toa boiler shut down

it is up to the operator or shift charge engineer

to decide when


187/207


to decide when

Generally boiler operation may continue for

some time if a tube leak is negligible small, easyto locate and easy to watch

Failuresleakages

Leakage evaporator

take the firing system out of service

separate the boiler from the common main steam

line

stop limestone dosing


188/207


stop limestone dosing

discharge bed material

reduction of the main steam pressure observingthe admissible gradient

maintain water level in the drum

by make-up feeding

Failuresleakages

Leakage evaporator

cooling of the boiler by means of the fans -observing the admissible temperature gradient in

the cyclone area

open overfire and oilburner air dampers to 50%


189/207


p pand set the minimum primary air flow

at a bed temperature of approx. 400°C

the make-up feeding can be stopped

Failuresleakages

Leakage evaporator

unpressurize boiler with attention toadmissible gradient

further cooling of the boiler by means of the

primary air fan until inspection temperature has


190/207


p y p pbeen reached

draining of evaporator or superheater

Failuresleakages

Leakage economizer

Small leaks are not very easy to detect (sounddetectors may help) and deviation of feedwater to

steam ratio or decreasing flue gas temperatures

after eco can only be noticed if leakage hasid bl i d


191/207


y gconsiderably increased.

The unit should be shut down in the normal way

and feeding should be stopped immediately after "fire out".

Failuresleakages

Leakage superheater, reheater

These leakages may easily be detected bysound detectors.

Decision should be a normal shut down as the

leakage can be neither located or judged


192/207


g j g

Feeding can continue after fire out to equally

decrease temperature in the boiler's water parts.

FailuresHP bypass

HP bypass

If the HP bypass doesn't open adequatelyalthough opening is required,

sufficient cooling of the RH heating surfaces is

impossible.


193/207


In addition, sufficient cooling of the SH heating

surfaces would also be impossible

as long as the pressure is below

the response pressure of the HP safety devices

FailuresHP bypass

HP bypass

In case of high bed temperatures (above approx.600 °C), an emergency firing shutdown must be

initiated within approx. 30 s to avoid damage of

the platen heating surfaces (SH2, RH2) in thefurnace


194/207


furnace.

In case of bed temperatures below approx.

600 °C, the operator shall reduce firing rate

to minimum.

If he does not succeed in opening the HP bypass,

he normally has to initiate a firing shut-down after

a maximum of 10 minutes.

FailuresLP bypass

after turbine trip

In case of turbine trip the load capability of thesteam generator is restricted to

approx. 55 % BMCR

The HP bypass ensures the cooling of theSH h ti f b l i t i t


195/207


SH heating surfaces by releasing steam into

the CRH system

If the LP bypass does not open (e. g. because of

condenser malfunction), the LP start-up standby

control valve is automatically opened, doing

some cooling releasing about 30% steam to

atmosphere

FailuresLP bypass

after turbine trip

The other steam is stored in the RH system, untilthe pressure is high enough to initiate opening of

HRH safety valves.

Then the HRH safety valves ensure a sufficient


196/207


longterm cooling of the the RH heating surfaces.

FailuresLP bypass

during start up

In case of malfunction of both LP bypass and theLP start-up standby control valve,

the RH pressure increase up to the HRH safety

valve response pressure value would take toomuch time because of small start-up steam


197/207


much time because of small start-up steam

production.

In case of high bed temperatures (above approx.600 °C), an emergency firing shutdown must be

initiated within approx. 60 s to avoid damage of

the platen reheat heating surfaces (RH2) in thefurnace during this period of HRH pressure

increase.

FailuresLP bypass

during start up

In case of bed temperatures below approx.600 °C, the operator shall reduce firing rate to

minimum.

If he does not succeed in opening the LP bypassfinally he shall initiate a firing shut down after a


198/207


finally, he shall initiate a firing shut-down after a

maximum of 10 minutes.

FailuresLP bypass

during start up

After a malfunction of the LP bypass only (e. g.because of condenser trip) the LP start-up

standby control valve is automatically opened to

100 % to ensure the cooling of the RH2 As soon as the LP bypass is ready for operation


199/207


As soon as the LP bypass is ready for operation

again, the LP start-up standby control valve has

to be closed manually If the operator does not succeed in opening the

LP bypass finally, he normally has to initiate a

firing shut-down after a short while

Failuresfiring permit signal

emergency fire shut down


200/207


Failuresfiring permit signal

emergency fire shut down

There are 4 possibilities to fulfill reheater release: Bed temperature < 570 °C (7 of 10)

During start-up firing the primary air flow

between 10 and 30 %


201/207


The turbine is in operation and the outlet

temperature of the reheater is < 562 °C

The HP-bypass is opened > 15 % and LP-

bypass is opened > 15 % or reheater start-up

valve is opened > 30 % and temperature of the

reheater is < 562 °C

approx. values for

initial adjustment

Failuresash cooler

temperatures

ash temperature 1st chamber > 500 °C

shut off L-valve and lock hoppering sequence

until temperature < 400 °C


202/207


ash cooler overflow > 200°C

shut off L-valve and rotary seal

until temperature < 150 °C

approx. values for

initial adjustment

Failuresash cooler

operation with one ash cooler

close L-valves

fluidization of the ash cooler has to be


203/207


maintained as sealing against the flue gas

atmosphere from the furnace

In case of worst coal a boiler load reduction

can be necessary

Failuresash cooler

cooling circuit of ash cooler

Detection of leaks

pressure increase in the ash cooler chamber temperature decrease in the ash cooler chamber


204/207


temperature decrease in the ash cooler chamber

increased moisture content of ash which may

lead to an increased plugging tendency

Failuresash cooler

cooling circuit of ash cooler

measures

shut off and emptying of the L-valves

shut off of the cooling water flow through

th h l


205/207


the ash cooler

maximum fluidization of the ash cooler has to bemaintained

emptying the ash cooler via lock hopper system

as fast as possible

Overview symbols

AND gate

OR gate

BISTABLE

PULSE t t

If any of all the inputs to an AND gate are logic 1,

then the output is logic 1 otherwise the output is

logic 0.If any one or more inputs to an OR gate is logic 1

then the output is logic 1, otherwise the output is

logic 0.

If S=1, while R=O then Q=1, Q’ =O, and flip flop is

in SETstate.

If R=1. while S=O then Q=O.Q’ =1, and flip flop isin RESET state.

Output goes to logic 1 immediately when input

goes to logic 1 Output remains at logic 1 for the

&

>=1

R S


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PULSE output

DELAYED ON time

DELAYED OFF time

NOT gate

goes to logic 1. Output remains at logic 1 for the

specified time and then returns to logic 0

regardless of state of input in.

If input goes to logic 1, then after a timedelay of specified duration, output changes

to logic 1.Output goes to logic 0 as soon as

input returns to logic 0.

Output goes to logic 1 immediately when

input goes to logic 1.

When input returns to logic 0, outputremains at logic 1.

Lo

can training boiler

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