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