Prof. D.N. ReddyDirector

Centre for Energy TechnologyUniversity College of Engineering

Osmania University.

Thermal performance

• The main impact of the Supercritical Cycle is to

increase the overall plant efficiency by reducing Fuel

consumption for Unit of Power Generated.

Reduction in CO2 emissions to the extent of 15%

sub-critical = 38% supercritical = 45% at 600 oC

Temp 650 – 700oC = 50 – 55%

Steam Cycle performance

• 1969 - 36%

• 1985 - 40%

• 1990 - 43-44%

• 2000 Double Re-heat - 45-46%

Improvement in Efficiency

Increase in Main Steam Pressure and Re-heat Steam

Temp

Final Feed Water Temperature

( Depends on: Increase in No.of Re-heat stages and

Number of Feed Water Heaters)

BOILER EXIT GAS TEMPERATURE

( 20oC reduction increases Efficiency by 1.1%)

Condensor pressure

Reduction of Auxillary Power Consumption

Improvement in Component Efficiencies

Part Load Efficiency

Part load

Reduction on

Efficiency

• Sub-critical 75% - 4%

50% - 10-11%

• Super-critical 75% - 2%

50% - 5.5 –8%

Boiler Design Optimisation

• Sub-Critical Boilers - Drum Boilers Steam

and

Water Separated in the

evaporator

• Super-Critical - Once-through design

Two pass and Tower Design

Combustion Zone - Spirally Wound

Membrane / inclined

tubing preferable

Increase in Pressure - Thicker sections / Higher and

Temp grade composition

Current state of ArtBoiler out let Steam Pressure and

Temperature = 300 bar/580-600 oC

Limitations Boiler Furnace Wall Complex Welding

Vertical Furnace Tube Design

Cheaper and less Complex Furnace Design

Easier Furnace Framing

Lower Pressure Drop (higher efficiency)

Current status of Turbine Design

Shaft Speeds - 3000-3600 rpm

Inlet Steam conditions - 240 bar/565oC

300 bar/600oC

Output = 1100 MW

Feed Water Pumps

Boiler Feed Water Pumps - 3-4% of gross

power output

Feed Water Temperature - 280 – 300oC

Flue Gas Temperature - 120oC

(can be reduced to 80oC using Heat Recovery System)

Upstream Flue gas De-Sulfurization

Improvement in Efficiency

Heat Recovery System = 0.6% Coal Fired

= 1.0% Lignite Fire

Turbine and Cycle Optimisation Improved blading profiles making use of Modern

CFD Technologies

Higher Final Feed Temperature and Bled Steam

Temperature

Bled Steam Tapping off the HP cylinder

Improved Efficiency of Auxillaries

Lower condenser pressures using larger

condensers and large exhaust areas

Large unit sizes improving Turbine Efficiencies

Increasing automation and level of controls

Optimising plant layout

Alternate Boiler Technologies

Gasification Cycles

FBC’s AFBC

PFBC

CFBC

• HRSG to Power a Turbogenerator

Schematic diagram of a steam power plantSchematic Diagram of a Steam Power Plant

Process plant diagramProcess Plant Diagram

Steam turbine cycle

Steam Turbine Cycle

The ideal reheat cycleThe Ideal Reheat Cycle

The ideal regenerative cycleThe Ideal Regenerative Cycle

Regenerative cycle with open feed water heaterRegenerative Cycle with Open Feed Water Heater

Closed Feed Water Heater

Arrangement of heaters in an actual power plant utilizing regenerative feed water heaters

High pressure turbine

Deaerating open feed

water heater

High pressure heater

intermediate pressure heater

Trap Trap

Low pressure heater

Trap

Condenser 5kPa

Low pressure turbine

Generator

Effect of boiler pressure on Rankine-cycle efficiency

Effect of Boiler Pressure on Rankine-Cycle Efficiency

Effect of exhaust pressure on rankine cycle efficiency

Pressure of Turbine Inlet

Steam cycle efficiency and specific steam consumption against steam temperature at turbine entry