Super criticalpower plant BY SRIDURGA 08761A0351
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 whichoperates above the criticalcondition is a ”SUPERCRITICAL POWER PLANT”
Definition of criticalCondition 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 CriticalDescription Sub Critical Super CriticalFull Load Pressure <190 atm >240 atmFlow in Water wall 2-Phase 1-PhaseCycle efficiency Base + 2 - 3 % ApproxFuel saving Base +8 - 10 % ApproxBoiler weight Base + 10 %Stages of reheat 1 2 Preferred
Types of boilers Drum type Once-through type
Design Types NATURAL CONTROLLED STEAM DRUM TO SUPERHEATERECON. 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 technologyCIRC.PUMP • Suitable for sub and supercritical cycles DISTRIB. HEADER
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 Super Critical Boilers
Once-thru BoilerMajor 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.
Once -thru BoilerSeparator : 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 BoilerAdvantages :- 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
conclusionSuper critical power plants are theefficient plants to produce greaterout put although it has somedrawbacks ….