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super critical power plant is the power plant which operates at the
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BY SRIDURGA08761A0351
Super critical power
plant
contents Introduction Critical condition Super critical parameters Necessity Comparison of sub critical and super
critical plants Types of boilers Drum type boiler Once through boiler Advantages of once through Conclusion
What is super critical power plant???
The power plant which operates above the critical condition is a ”SUPER CRITICAL POWER PLANT”
Definition of critical Condition
CRITICAL CONDITION IS THERMODYNAMIC
EXPRESSION DESCRIBING THE STATE OF A
SUBSTANCE BEYOND WHICH THERE IS NO
CLEAR DISTINCTION BETWEEN THE LIQUID
AND GASEOUS PHASE.
WHY ADVANCED SUPERCRITICAL?
• Efficiency of the Rankine Cycleincreases with increasing Turbine inletTemperature and Pressure
• Cycle efficiency of typical sub-criticalplant is 38% whereas today’ssupercritical technology increases thisto around 45-47%
Sub-Critical vs Super Critical
Description Sub Critical Super Critical
Full Load Pressure <190 atm >240 atm
Flow in Water wall 2-Phase 1-Phase
Cycle efficiency Base + 2 - 3 % Approx
Fuel saving Base +8 - 10 % Approx
Boiler weight Base + 10 %
Stages of reheat 1 2 Preferred
Types of boilers
Drum type
Once-through type
Design 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
Super Critical Boilers
Drum type boiler
Natural Circulation Boiler Circulation through water walls by thermo-siphon effect
Controlled Circulation Boiler At higher operating pressures (just below critical pressure levels), thermo-siphon effect supplemented by pumps to ensure
safety of furnace wall tubes.
Super Critical Boilers
Drum type boiler
Steam generation essentially takes place in furnace water walls
Fixed evaporation end point - the drum
Steam -water separation takes place in the drum
Separated water mixed with incoming feed water and fed back to water wall lower drum by means of boiler water circulating pumps (BWCPs).
Super Critical Boilers
Once Through Boiler-Concept
Once through system
Super Critical Boilers
Once Through Boiler
Once -through forced flow through all sections of boiler (economizer, water walls & super heater)
Feed pump provides the driving head Suitable for sub critical & super
critical pressures
Once-thru Boiler
Major differences from Drum type boiler :
Evaporator system Low load circulation system Separator
Once - thru Boiler
Low load circulation system :
The excess flow over the once-thru flow separated in separator .
Recirculated back to the boiler directly by the dedicated circulating pump.
LOW LOAD SYSTEM WITH CIRCIRCULATION PUMP
Once -thru Boiler
Separator : Separates steam and water
during the circulating mode operation
Runs dry in once through flow mode.
Smaller in size compared to drum in a drum type boiler
Once -through Boiler
Advantages :-
Better suited for sliding pressure
operation
Steam temperature can be
maintained over wider load range
under sliding pressure
Conservation of fuel resources.
Shorter start up time
Improvement in Efficiency
conclusion
Super critical power plants are the effi cient plants to produce greater out put although it has some drawbacks ….
Thank You