SUPER CRITICAL TECHNOLOGY IN NTPC
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Transcript of SUPER CRITICAL TECHNOLOGY IN NTPC
SUPER CRITICAL SUPER CRITICAL TECHNOLOGY IN TECHNOLOGY IN
NTPCNTPC
PRESENTATION CONTENTSPRESENTATION CONTENTS
What is critical condition??What is critical condition?? Types of boilers.Types of boilers. Major differences between drum type & once Major differences between drum type & once
through boilers.through boilers. Advantages of once through boiler.Advantages of once through boiler. Effect of advanced cycles on boiler Effect of advanced cycles on boiler
components.components. Conclusion.Conclusion.
Definition of critical Condition
CRITICAL CONDITION IS THERMODYNAMIC
EXPRESSION DESCRIBING THE STATE OF A
SUBSTANCE BEYOUND WHICH THERE IS NO
CLEAR DISTINCTION BETWEEN THE LIQUID
AND GASEOUS PHASE.
SUPERCRITICAL PARAMETERSSUPERCRITICAL PARAMETERS
Tem
per
a tu
re (
C)
Entropy
Critical Point
Pr = 225.56 kg/cm2
T = 374.15 Deg.C
538 Deg C
Subcritical
Supercritical
Types of boilersTypes of boilers
Drum typeDrum type
Once-through typeOnce-through type
Design TypesDesign Types
NATURAL
STEAM DRUM
FURNACEWALLS
ECON.
CONTROLLED
TO SUPERHEATER
CIRC.PUMP
SEPARATOR
CIRC.PUMP
ECON.
DISTRIB.HEADER
ONCE THROUGH
• Natural circulation - well suited for < 175 kg/cm2
• Controlled circulation - optimum solution for reliable high-pressure subcritical operation• Once-through technology
• Suitable for sub and supercritical cycles
Drum type boilerDrum type boiler Natural Circulation BoilerNatural Circulation Boiler
Circulation thru water walls by Circulation thru water walls by
thermo-siphon effectthermo-siphon effect
Controlled Circulation BoilerControlled Circulation Boiler
At higher operating pressures At higher operating pressures
just below critical pressure levels, just below critical pressure levels,
thermo-siphon effect supplementedthermo-siphon effect supplemented
by pumpsby pumps
Drum type boilerDrum type boiler
Steam generation takes place in furnace Steam generation takes place in furnace
water walls. water walls.
Steam -water separation takes place in Steam -water separation takes place in
the drum.the drum.
Separated water mixed with incoming Separated water mixed with incoming
feed water. feed water.
Supercritical Boilers in NTPC Supercritical Boilers in NTPC
SIPAT(3x660 SIPAT(3x660 MW)MW)
BARH (3x660 BARH (3x660 MW) MW)
SupplierSupplier Doosan, KoreaDoosan, Korea TPE, RussiaTPE, Russia
TypeType Two pass,spiral-Two pass,spiral-walledwalled
Two pass,spiral-Two pass,spiral-walledwalled
CapacityCapacity 2225T/hr.2225T/hr. 2225T/hr.2225T/hr.
Steam ParametersSteam Parameters(at boiler outlet)(at boiler outlet)
256kg/cm2/540/568 256kg/cm2/540/568 deg.Cdeg.C
256kg/cm2/540/568 256kg/cm2/540/568 deg.Cdeg.C
Coal Firing Coal Firing Tangential firedTangential fired Front & Rear firedFront & Rear fired
OrderOrder March, 2004March, 2004 March, 2005March, 2005
CommissioningCommissioning 20072007 20082008
Once -thru BoilerOnce -thru Boiler
Requirements :Requirements : Stringent water quality Stringent water quality
Sophisticated control systemSophisticated control system
Low load circulation system Low load circulation system
Special design to support the spiral Special design to support the spiral
furnace wall weightfurnace wall weight
Higher design pressure for components Higher design pressure for components
from feed pump to separator from feed pump to separator
Once Through BoilerOnce Through Boiler
Water flowing through water walls gets Water flowing through water walls gets
converted into steam in one circulation. converted into steam in one circulation.
Feed pump provides the driving headFeed pump provides the driving head
Suitable for sub critical & super critical Suitable for sub critical & super critical
pressurespressures
Once-thru BoilerOnce-thru Boiler
Major differences from Drum type boiler :Major differences from Drum type boiler :
Evaporator systemEvaporator system Low load circulation systemLow load circulation system SeparatorSeparator
Once -thru BoilerOnce -thru Boiler
Evaporator systemEvaporator system : :
Formed by a number of parallel tubesFormed by a number of parallel tubes Tubes spirally wound around the Tubes spirally wound around the
furnace to reduce number of tubes and furnace to reduce number of tubes and to increase the mass flow rate thru’ the to increase the mass flow rate thru’ the tubestubes
Small tube diameterSmall tube diameter Arrangement ensures high mass Arrangement ensures high mass
velocity thru the tubesvelocity thru the tubes
Once - thru BoilerOnce - thru Boiler
Low load circulation system :Low load circulation system :
The excess flow over the once-The excess flow over the once-thru flow separated in separator .thru flow separated in separator .
Recirculated back to the boiler Recirculated back to the boiler directly by the dedicated circulating directly by the dedicated circulating pump.pump.
LOW LOAD SYSTEM WITH CIRCIRCULATION PUMP
Once -thru BoilerOnce -thru Boiler
Separator :Separator :
Separates steam and water during Separates steam and water during
the circulating mode operationthe circulating mode operation
Runs dry in once through flow Runs dry in once through flow
mode.mode.
Smaller in size compared to drum in Smaller in size compared to drum in
a drum type boilera drum type boiler
Once -through BoilerOnce -through Boiler
Advantages :-Advantages :-
Better suited for sliding pressure operationBetter suited for sliding pressure operation
Steam temperature can be maintained over Steam temperature can be maintained over
wider load range under sliding pressurewider load range under sliding pressure
Conservation of fuel resources.Conservation of fuel resources.
Shorter start up timeShorter start up time
Improvement in EfficiencyImprovement in Efficiency
Advanced CyclesAdvanced CyclesEffect on Boiler ComponentsEffect on Boiler Components
Evaporator (Furnace) wallsEvaporator (Furnace) walls SuperheatersSuperheaters Thickwalled boiler componentsThickwalled boiler components
Furnace wallsFurnace walls
Increased operating pressure increases Increased operating pressure increases the medium temperatures.the medium temperatures.
Increased regenerative feed heating Increased regenerative feed heating increases the fluid temp entering.increases the fluid temp entering.
Larger furnaces required for NOLarger furnaces required for NOXX
reduction, increase SH steam reduction, increase SH steam temperature at furnace wall outlet.temperature at furnace wall outlet.
SuperheatersSuperheaters
Tube metal temperatures in final Tube metal temperatures in final sections increase with outlet steam sections increase with outlet steam temperature.temperature.
Susceptibility for high temperature Susceptibility for high temperature corrosion. corrosion.
Susceptibility to steam side oxidationSusceptibility to steam side oxidation
Thick walled componentsThick walled components
Higher pressure & temperature lead to Higher pressure & temperature lead to increased thickness of :increased thickness of : Shells of separator, start-up system Shells of separator, start-up system
components, SHO header..components, SHO header.. Main steam piping.Main steam piping.
Higher thickness results in larger Higher thickness results in larger temperature gradients across walls.temperature gradients across walls.
Subcritical Vs SupercriticalSubcritical Vs Supercritical(A Comparison)(A Comparison)
500 MW Unit Size500 MW Unit Size
(Subcritical)(Subcritical)
660 MW Unit Size660 MW Unit Size
(Supercritical)(Supercritical)
Steam ParametersSteam Parameters
(ata / Deg.C/ Deg.C)(ata / Deg.C/ Deg.C)
169/538/538169/538/538 246/538/566246/538/566
Cost of Boiler & Cost of Boiler & Turbine Generator Turbine Generator BlockBlock
BaseBase 1.5%1.5%
Coal ConsumptionCoal Consumption BaseBase 2.1%2.1%
Plant EfficiencyPlant Efficiency BaseBase 2.1%2.1%
COCO22 Emissions Emissions BaseBase 2.1%2.1%
SOSO22 Emissions Emissions BaseBase 2.1%2.1%
Supercritical Technology - StatusSupercritical Technology - Status• More than 500 Units of various sizes operating
worldwide
• Material technology matured up to 600 Deg.C
temperature
• Availability of the order of 88 – 90% which is
comparable with that of subcritical units
• European union working on program “AD 700” which
aims at temperature up to 700-720 Deg.C and
efficiency target of 50%
• First supercritical unit in India has commissioned in
2007 by NTPC in sipat.
Thank YouThank You