SUPER HEATING• HEATING STEAM

ABOVE SATURATION TEMPERATURE

– IMPROVES THERMAL CYCLE EFFICIENCY

– STEAM CAN BE RETAINED IN VAPOUR FORM TILL THE LAST STAGE OF TURBINE

– NO CONDENSATION OF STEAM BETWEEN BOILER AND TURBINE

SUPER HEATERS

CLASSIFICATION

RADIANT CONVECTIVE

SUPER HEATERS

SUPER HEATERS CLASSIFICATION

H O R IZO N T AL L SH APED

DRAINABLE

VER T C AL

NON DRAINABLE

SUPER HEATERS

SUPER HEATERS CLASSIFICATION

PARALLEL FLOW COUNTER FLOW

SUPER HEATERS

SUPER HEATERS DESIGN CONSIDERATIONS

• STEAM TEMPERATURE REQUIRED• SUPER HEATER SURFACE AREA

REQUIRED• RATE OF STEAM FLOW THROUGH

TUBES (MASS FLOW)• MATERIAL BEST SUITED• GAS TEMPERATURE ZONES WHERE THE

SURFACES ARE TO BE LOCATED• ARRANGEMENT OF SURFACES

– SPACING OF TUBES

SUPER HEATERS DESIGN CONSIDERATIONS

• STEAM TEMPERATURE– MINIMUM

• BASED ON APPLICATION AND ECONOMICS

– MAXIMUM• BASED ON METALLURGICAL

LIMITATIONS

SUPER HEATERS DESIGN CONSIDERATIONS

• SURFACE AREA– GIVE MINIMUM PRESSURE DROP WITHOUT

INCREASING METAL TEMPERATURE

– GIVE HIGH MASS FLOW TO KEEP METAL TEMPERATURE LOW

– REQUIRE ALLOY OF LESSER COST

– PROPER SPACING WITH REFERENCE TO FUEL CHARACTERISTICS

– LOW DRAUGHT LOSS

SUPER HEATERS DESIGN CONSIDERATIONS

• MASS FLOW– HIGHER THAN NECESSARY

• PRESSURE LOSS WILL BE MORE

• LESS EFFICIENCY

– LESSER• HIGH TUBE METAL TEMPERATURE

– PRESSURE DROP NOT MORE THAN 10%

– STEAM FILM TEMPERATURE NOT MORE THAN 380C

MATERIALS USED FOR S.H.

ASME CODE NOMINAL

COMPOSITION

TEMP.LIMIT 0C

SA 213 CARBON STEEL 450

SA 213 T1 C-1/2 Mo. 470

SA 213 T11 11/4 Cr. –1/2 Mo. 550

SA 213 T22 21/4 Cr.-1 Mo. 580

SA 213 T9 9 Cr.-1 Mo. 635

SA 213 TP 304 H 18 Cr.-8 Ni. 705

SA 213 TP 347 H 18 Cr.-10 Ni. 705

SA 213 TP 316 H 16 Cr.-12 Ni.-2

Mo.

705

S.H.SECTIONS IN C.E BOILERS

• STEAM COOLED WALL AND ROOF SECTION

• LOW TEMPERATURE SUPER HEATER

• PLATEN SUPER HEATER

• FINAL SUPER HEATER

500 MW BOILER

C.E.DESIGN

TOWER TYPE BOILER

STEIN DESIGN

OPERATING FACTORS AFFECTING STEAM TEMPERATURE

• BOILER LOAD

• EXCESS AIR

• FEED WATER TEMPERATURE

• USE OF SATURATED STEAM

• BLOW DOWN

• BURNER OPERATION

• HEATING SURFACE CLEANLINESS

• FUEL

MEANS FOR CONTROLLING STEAM TEMPERATURE

• SEPARATELY FIRED SUPER HEATER

• EXCESS AIR

• GAS RECIRCULATION

• BURNER SELECTION

• TILTING BURNERS

• ATTEMPERATION

300 UPWARDS HORIZONTAL 300 DOWNWARDS

DESUPERHEATING

• CONTROL OF STEAM TEMPERATURE BY INJECTING WATER– SURFACE TYPE– DIRECT MIXING

• ATTEMPERATION

SUPER HEATER LENGTH

TE

MP

ER

AT

UR

E

3400C

4100C

3600C

5400C

6000C

CONCEPT OF ATTEMPERATION

ATTEMPERATION WATER STANDARDS

• PURITY– AS PURE AS THAT OF STEAM

• PRESSURE– HIGHER THAN STEAM PRESSURE

• TEMPERATURE– SATURATION TEMPERATURE

CORRESPONDING TO STEAM PRESSURE

ATTEMPERATION WATER SOURCES

• BOILER CONDENSER

• FEED WATER TAPPED BEFORE FEED CONTROL STATION