steam circulation system
TRANSCRIPT
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HARSH SRIVASTAVA
DY. SUPDT.(OPERATION,STG III)
BE ( MECH.).BIET,JHANSI(UP)
ET- 98 (22nd BATCH)
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Steam circuit diagram
Super Heater
De-superheater /Attemperator
Re-heater
IBR
Super Critical Boiler
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FROM BFP
DISCHARGE
500MW WATER AND
STEAM CIRCUIT
CC
Pump
Bank I
Bank II
Economizer
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BOTTOM RNG HDR& Z-PANEL 1ST PASS W.W
1ST PASS W.W O/L HDRS ROOF I/L HEADER
2ND PASS UPPER C-HDR 2nd PASS LOWER C-HDRS
LTSH I/L HEADER LTSH O/L HEADER
D.P.I/L HEADER D.P.O/L HEADER
S.H. HEADER R.H.HEADER
2ND PASS ROOF O/L HDR(REAR ECONOMISER
M.S
H.
R.
HC.R.H
FROM F.R.S
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Pendant type
Horizontal type
Radiant Superheater
ConvectionSuperheater
CombinedSuperheater
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SUPER HEATER
WATER IS HEATED TO RAISE STEAM TO HIGHER TEMPERATURE
ARRANGED IN 3 STAGES
LTSH LOCATED ABOVE ECONAMISER
RADIANT PENDENT TYPE (DIV PANEL)
ABOVE FURNACE
CONVECTIVE FINAL SUPER HEATER
ABUVE FURNACE IN CONV PATH
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Super heaters
Super heater heats the high-pressure steam from itssaturation temperature to a higher specified
temperature.
Super heaters are often divided into more than one
stage.
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Hot Flue
GasThermal Structure
SH
Steam
Convection &
Radiation HT
Convection HT
Drop in Enthalpy
of Flue Gas
Rise in Enthalpy of
Steam
Mechanism of Heat Transfer
Source/Supply Thermal Structure Sink /Demand
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Rate of heat transfer from hot gas to cold steam is
proportional to:
Surface area of heat transfer
Mean Temperature difference between Hot Gas and ColdSteam.
Thot gas,in
Tcold steam,in
Thot gas,out
Tcold steam,out
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Thot gas,in
Tcold steam,in
Thot gas,out
Tcold steam,out
Thot gas,in
Tcold steam,in
Thot gas,out
Tcold steam,out
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Platen Superheater : Flat panels
of tubes located in the upper part
of the furnace, where the gas
temperature is high.
The tubes of the platen SH
receive very high radiation as
well as a heavy dust burden.
Mechanism of HT : HighRadiation & Low convection
Thermal Structure:
No. of platens
No. of tubes in a platen
Dia of a tube
Length of a tube
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The outer diameter of platen SH is in the range of 32 42
mm.
The platens are usually widely spaced, S1 = 500 900 mm.
The tubes within a platen are closely spaced, S2/d = 1.1. The number of parallel tubes in a platen is in the range of
15 35.
Design Constraints: Max. allowable steam flow rates.
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Convective super heaters are vertical
type (Pendant ) or horizontal types.
The Pendant SH is always arranged
in the horizontal crossover duct.
Pendant SH tubes are widely spaceddue to high temperature and ash is
soft.
Transverse pitch : S1/d > 4.5
Longitudinal pitch : S2/d > 3.5.
The outside tube diameter : 32 51mm
Tube thickness : 3 7mm
S1S2
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The horizontal SH are located in the back pass.
The tubes are arranged in the in-line configuration.
The outer diameter of the tube is 32 51 mm.
The tube thickness of the tube is 3 7 mm.
The transverse pitch : S1/d = 2 3.
The longitudinal pitch :S2/d = 1.6 2.5.
The tubes are arranged in multiple parallel sets.
The desired velocity depends on the type of SH and operating steam
pressures. The outside tube diameter : 32 51mm
Tube thickness : 3 7mm
S1S2
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CRH FROM
HPT
MS TO HPT HRH TO IPT
DRUM
PLATEN SH1
PRI. SH
ECONOMISER
ECONOMISER
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Steam drum-SH connecting tube-Radiant roof inletheader-First pass roof front-rear-radiant roof outletheader-SH SCW inlet header side-back pass side
wall tube-backpass bottom headers-backpass frontand rear-backpass screen-backpass roof-backpaasSH & Eco supports-SH/Eco support headers-LTSHsupport tubes-SH rear roof tubes-SH SC rear walltubes-LTSH inlet header-LTSH Banks- LTSH outletheaders-SH /DESH link- SH/DESH-division panel-Division panel outlet header- Pendant assembly-outlet header
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Basically the control of temperature is to protect thesuperheater by preventing the metal temperatures reaching adangerously high level reducing mechanical strength andleading to failure. Water flowing through a tube conducts heataway much more effectively than steam due to its higherspecific heat capacity. This means that tubes carrying waterhave a metal temperature much closer to the fluid passingthrough it.
For superheat temperatures alloys of chrome molybdenumsteels are used (upto 560oC), difficulties in welding means
that there use is restricted to only within the highesttemperature zone and a transition piece fitted to connect toremaining mild steel tubing.
Superheat temperature control is therefore fitted to ensuresuperheat temperature does not exceed design limits.
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The preferred location ofdesuperheater, especially fortemperature above 450 deg C isbetween sections of superheater. Thesteam is first passed through a
primary superheater where it is raisedto intermediate temperature. It is thenpassed through the desuperheater andits temperature reduction is controlledso that, after continuing through thesecondary or final stage of the
superheater, the required constantconditions are maintained at theoutlet.
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Purpose: RE-HEAT THE STEAM FROM HP TURBINE TO
540 DEG
COMPOSED OF THREE SECTIONS
RADIANT WALL REHEATER ARRANGED IN FRONT &SIDE WATER WALLS
REAR PENDANT SECTION ARRANGED ABOVE
GOOSE NECK
FRONT SECTION ARRANGED BETWEEN UPERHEATER PLATEN & REAR WATER WALL HANGER
TUBES
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Calculate the efficiency of Rankine cycle, Rankine.
Calculate mean effective temperature of heat
addition, Tm,in using
Find out pressure corresponding to Tm,in and
entropy at HP turbine inlet.
Add reheating at this pressure and calculate
efficiency of the Reheat Cycle.
Repeat above steps for few iterations.
inm
cCarnotEqRankine
TT
,
.
1==
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The arrangement and construction of a re-
heater is similar to that of a super-heater. In
large modern boiler plant, the reheat sections
are mixed equally with super-heater sections.
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The pressure drop inside re-heater tubes has an importantadverse effect on the efficiency of turbine.
Pressure drop through the re-heater should be kept as low aspossible.
The tube diameter : 42 60mm.
The design is similar to convective super-heaters.
Overall Heat Transfer Coefficient : 90 110 W/m2 K.
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Device attached to a boiler for
automatically relieving the pressure
of steam before it becomes great
enough to cause bursting. Thecommon spring-loaded type is held
closed by a spring designed to open
the valve when the internal
pressure reaches a point in excess
of the calculated safe load of theboiler. Safety valves are installed on
boilers according to strict safety
norms and IBR recommendation
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Locacation SetPressure(Kg/sq cm
RelivingCapacityT/Hr
Drum 175.8 177.1
179.3 180.6
181.1 182.5
Super Heater 163.3 154.0
Re-heater
inlet
45.0
45.5
46.3
Re-heater
outlet
42.70
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History
Scope (cover regulations on):
Electric-Resistance-Welded Steel Boiler And Super-Heater
Tubes
Boiler Tubes Subject To External Pressure
The Working Pressure To Be Allowed On Various Parts Of
Boilers
Welded And Seamless Forged Drums For Water TubeBoilers And Super Heaters
Requisite Mountings, Fittings and Auxiliaries
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Boiler And Super Heater Tubes, HeadersAnd Other Pressure Parts Tubes
Steam-Pipes And Fittings
Registration Of Boilers And Inspection OfBoilers
Safety Of Persons Inside Boilers
Qualification Tests For Welders Engaged InWelding Of Boilers
Feed Water For Boiler
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WHY SUPERCRITICAL
PRESSURE Increasing the pressure will mean increase in saturation
temperature at which steam evaporates thus increasing
the average temperature of heat addition.
A Boiler operating at a pressure above critical point is
called SUPERCRITICAL BOILER
A point where boiling water and dry saturated lines
meet so that associated latent heat is zero, this point iscalled Critical Point.
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CRITICAL CONDITION
Definition
CRITICAL is a thermodynamic expressiondescribing the state of a substance beyond
which there is no clear distinction between theliquid and gaseous phase.
The critical pressure & temperature for water are
Pressure = 225.56 Kg / cm2
Temperature = 374.15 C
http://var/www/apps/conversion/current/tmp/scratch2695/D:/UTSAV/STAGE1/CRITICAL.ppthttp://var/www/apps/conversion/current/tmp/scratch2695/D:/UTSAV/STAGE1/CRITICAL.ppt -
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T S DIAGRAM
Boilin
gWate
r
DryS
aturatedSteam
Entropy KJ / Kg K
Tempe
rature
(
0
C
)
-2730
240c
A
B C
D
E
F
OUTPUT INCREASE Basic Rankine Cycle
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256K
g/cm2
0
100
200
300
400
500
600 540C568C
ENTROPY
TEMPSUPER CRITICAL
BOILER CYCLE WITHSH, RH & Regeneration
of SIPAT 3 x 660 MW
Steam flow :2225 T/Hr
Steam temp : 540 c
Steam Pres : 256 kg/cm2
RH pre : 51.6 Kg/cm2
RH Temp : 568c
Feed water Temp : 291c
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SUPERCRITICAL BOILER
Supercritical pressure boiler has no drum and heat absorbing
surface being, in effect, one continuous tube, hence called
once through Supercritical pressure boilers.
The water in boiler is pressurized by Boiler Feed Pump, sensibleheat is added in feed heaters, economizer and furnace tubes,
until water attains saturation temperature and flashes
instantaneously to dry saturated steam and super heating
commences.
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Pressure Parts Material
SA210C, T12, T23Reheater
Tube
Final
Section
Economizer Tube SA210C
Spiral SA213T22EvaporatorTube/Water
Wall Vertical SA213T22
Primary SA213T23, T91
Secondary
SA213T12, T23, T91Superheater
Tube
Final SA213T23, T91, T92
Primary
SA213T23, T91
SUPER304H
Separator SA302C
SH outlet SA335P91Header
RH outlet SA335P91
SIPAT 500 MW PlantMaterial Oxidation Criteria,
SA-210C 454
SA-213T2 482
SA-213T12 552
SA-213T22 593
SA-213T23 593
SA-213T91 649
SA-T92 649
SUPER304H 760
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