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24 March 2014 PMI Revision 00 1
SteamCirculation
System
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Presentation Plan Steam circuit diagram
Super Heater
De-superheater /Attemperator
Re-heater
IBR
Super Critical Boiler
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FROM BFP
DISCHARGE
DRUM
500MW WATER AND
STEAM CIRCUIT
CC
Pump
Bank I
Bank II
Economizer
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BOTTOM RNG HDR & Z-PANEL 1STPASS W.W
1STPASS W.W O/L HDRS ROOF I/L HEADER
2NDPASS UPPER C-HDR 2ndPASS 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.HEADER2NDPASS ROOF O/L HDR(REAR ECONOMISER
M.S
H.
R.
HC.R.H
FROM F.R.S
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Types of Super Heaters 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 HEATERABUVE 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. The enthalpy rise of steam in a given section should
not exceed
250420 kJ/kg for High pressure. > 17 MPa
< 280 kJ/kg for medium pressure. 7 Mpa17MPa
< 170 kJ/kg for low pressure. < 7 MPa
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Transfer of Energy
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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Mechanism of Heat Transfer :
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 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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Geometry of Thermal Structure :Platen SH The outer diameter of platen SH is in the range of 3242
mm.
The platens are usually widely spaced, S1= 500900
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
1535.
Design Constraints: Max. allowable steam flow rates.
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Convective SuperheaterPendant) 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 : 3251mm
Tube thickness : 37mm
S1S2
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Convective Superheater Horizontal) 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 3251 mm.
The tube thickness of the tube is 37 mm.
The transverse pitch : S1/d = 23.
The longitudinal pitch :S2/d = 1.62.5.
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 : 3251mm
Tube thickness : 37mm
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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SuperheaterTemperature Control Basically the control of temperature is to protect the
superheater by preventing the metal temperatures reachinga dangerously high level reducing mechanical strength andleading to failure. Water flowing through a tube conductsheat away much more effectively than steam due to itshigher specific heat capacity. This means that tubescarrying water have a metal temperature much closer to thefluid passing through 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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Locating the desuperheater The preferred location of
desuperheater, 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 the outlet.
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Reheater 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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Reheater
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Procedure to DetermineOptimum Reheat Pressure Calculate the efficiency of Rankine cycle, Rankine.
Calculate mean effective temperature of heat
addition, Tm,inusing
Find out pressure corresponding to Tm,inand
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
,
. 1hh
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Arrangement andConstruction
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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Reheater
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 lowas possible.
The tube diameter : 4260mm.
The design is similar to convective super-heaters.
Overall Heat Transfer Coefficient : 90110 W/m2K.
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Safety ValvesDevice 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 the boiler.Safety valves are installed on
boilers according to strict safety
norms and IBR recommendation
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Safety Valve Settings of aTypical 200 MW BoilerLocacation Set
Pressure
(Kg/sq cm
Reliving
Capacity
T/Hr
Drum 175.8 177.1179.3 180.6
181.1 182.5
Super Heater 163.3 154.0Re-heater inlet 45.0
45.5
46.3
Re-heateroutlet 42.70
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Indian Boiler Regulations 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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Indian Boiler RegulationsContinued)
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 iscalled SUPERCRITICAL BOILER
A point where boiling water and dry saturated lines
meet so that associated latent heat is zero, this point
is called 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://d/UTSAV/STAGE1/CRITICAL.ppthttp://d/UTSAV/STAGE1/CRITICAL.ppt8/12/2019 Steam Circulation System of pulverized coal fired boiler.
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T S DIAGRAM
Entropy KJ / Kg K
Temperatu
re(0C
)
-2730
240c
A
B C
D
E
F
OUTPUT INCREASE Basic Rankine Cycle
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0
100
200
300
400
500
600 540C568C
ENTROPY
TEMP
SUPER CRITICAL
BOILER CYCLE WITH
SH, 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 drumand 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, sensible
heat 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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THANK YOU