Super critical power plants operate above the critical point where there is no distinction between liquid and gas phases. They have higher efficiencies of around 45-47% compared to 38% for subcritical plants due to higher turbine inlet temperatures and pressures above 240 atm. Once-through boilers without drums are better suited for supercritical conditions as they allow forced circulation through all sections compared to drum-type boilers. Super critical plants improve efficiency but have higher capital costs.

1. Super critical
power plant
BY SRIDURGA
08761A0351

2. 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

3. What is super
critical power
plant???
The power plant which
operates above the critical
condition is a ”SUPER
CRITICAL POWER PLANT”

4. 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.

6. WHY ADVANCED SUPERCRITICAL?
• Efficiency of the Rankine Cycle
increases with increasing Turbine inlet
Temperature and Pressure
• Cycle efficiency of typical sub-critical
plant is 38% whereas today’s
supercritical technology increases this
to around 45-47%

10. 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

11. Types of boilers
 Drum type
 Once-through type

12. Design Types
NATURAL CONTROLLED
STEAM DRUM TO SUPERHEATER
ECON.
CIRC.
PUMP
FURNACE
WALLS
ONCE THROUGH
SEPARATOR
• Natural circulation - well suited for < 175
kg/cm2
ECON.
• Controlled circulation - optimum solution for
reliable high-pressure subcritical operation
• Once-through technology
CIRC.
PUMP • Suitable for sub and supercritical cycles
DISTRIB.
HEADER

13. 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

14. 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

15. Once Through Boiler-Concept
Once through system
Super Critical Boilers

16. 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
Super Critical Boilers

17. Once-thru Boiler
Major differences from Drum type boiler :
 Evaporator system
 Low load circulation system
 Separator

18. 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.

19. LOW LOAD SYSTEM WITH CIRCIRCULATION PUMP

20. 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

21. 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

22. conclusion
Super critical power plants are the
efficient plants to produce greater
out put although it has some
drawbacks ….