FIRED HEATERS
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FIRED HEATERS
Chemical reactions and processes take place at high temperatures and hence heat sources are required.
Various sources of heat
Direct fired heaters
Steam heaters
Thermal fluid heaters, e.g., Dowtherm
Electrical heaters
Fluid In Fluid Out
DIRECT FIRED HEATER
Typical examples are Crude heaters, vacuum heaters, Platformer Rx charge heaters etc.
Steam to various usersincluding turbines, charge heaters,Reboilers etc.
Condensate returnto boilers
Typical examples can be seen in almost all plants
Fluid In Fluid Outtoheatexchangers
THERMAL FLUID HEATER
Typical example in LAB plant in PG and polyesterplants in HZ & PGThermal fluid used is Dowtherm A
Fluid In
Fluid Out
Electrical Power IN
Typical examples areAir heaters, Lube oil heaters, vaporizers
RADIATION ZONE
FUEL OIL
FUEL GAS
STEAM
CONVECTION ZONE
STACK
DAMPER
AIR
Radiation Zone is the section where there is a naked flame and about 2/3rd of the heat transfer is by radiation mode
Convection zone is the section where about 2/3rd of the heat transfer is by convection mode
1300–1600 C
800 – 900 C
CLASSIFICATION OF HEATERS BASED ON AIR FLOW
FOR COMBUSTION
RADIATION ZONE
BURNERS
CONVECTION ZONE
STACK
DAMPERNATURAL DRAFT
FIRED HEATER
AIR
PRESS
DIFF
RADIATION ZONE
BURNERS
PLENUM CHAMBER
CONVECTION ZONE
STACK
FD FAN
DAMPER
FORCED DRAFT FIRED HEATER
AIR FROM ATMOS.
RADIATION ZONE
BURNERS
PLENUM CHAMBER
CONVECTION ZONE
STACK
ID FAN
FD FAN
DAMPER
BALANCED DRAFT FIRED HEATER
RADIATION ZONE
BURNERS
PLENUM CHAMBER
CONVECTION ZONE
STACK
AIR PREHEATER
ID FAN
FD FAN
DAMPER
STEAM APH
CLASSIFICATION OF HEATERS BASED ON
BURNER LOCATION
BOTTOM OR UPFIRED
SIDE OR END FIRED
TOP OR DOWNFIRED
CYLINDRICAL HEATER WITH VERTICAL COIL
CLASSFICATION BASED ON TYPE OF RADIANT COIL
Radiant tubes are always bare
Example: Crude, vacuum heaters, xylene col. reboiler
IN
OUT
SECTION
CLASSFICATION BASED ON TYPE OF RADIANT COIL
Arbor type
Inlet header Outlet header
CLASSFICATION BASED ON TYPE OF RADIANT COIL
Example : Isomar charge heater at JG, LAB charge heater at PG
U tube
CLASSFICATION BASED ON TYPE OF RADIANT COIL
Example : Platformer heaters
HORIZONTAL RADIANT COILS
Example : Coker heaters
CLASSFICATION BASED ON TYPE OF RADIANT COIL
FINNED TUBES - CONVECTION
STUDDED TUBES - CONVECTION
Maximize heat transfer by increasing area.
Convection tubes are always horizontal
Baretubes
Burner floor refractory
Air register
Pilot burner
Burner tile
BURNER ASSEMBLY
Atomizing steam + Fuel Oil OR fuel gas
Burner floor refractory
Air register
Fuel gas
Fuel oilPilot burner
Burner tile
BURNER ASSEMBLY
Atomizing steam
HEAT SHIELD
150mm TO 200mm thick castable refractory
Bottom floor 200mm thick castable refractory with one layer of brick lining
1300 - 1600 C
800 - 900 C
350 - 450 C
CERAWOOL LINING CAN BE APPLIED INSTEAD OF REFRACTORY
DETAIL OF CERAWOOL LINING
Heater steel external shell
Bitumastic paint coating
SS304 foil 0.2mm thick forcorrosion resistance
25mm thick cerawoolpads laid one after another.
Cerawool blankets hold down bolts
Cerawool is not used in furnaces with oil fired burners.
Cost is high
METALLURGY OF TUBES
Depends on the fluid inside and the temperature to which the fluid is to be heated
Tube metallurgy Max. temp (C)Carbon steel 5401.25% Cr - 0.5%Mo 5952.25% Cr - 1%Mo 6505%Cr-1%Mo 6509%Cr-0.5%Mo 705SS304,SS316,SS321,SS347815HK40(25Cr-20Ni) 1010
For any selected metallurgy of tubes the minimum design life shall be minimum 100 000 hours
Metallurgy of tube supports
Tube metallurgy Max. temp (C)Carbon steel 427 C2.25%Cr-1%Mo 64919%Cr-9%Ni 81625%Cr-12%Ni (Plate) 87125%Cr-12%Ni (cast) 98225%Cr-20%Ni(Plate) 87125%Cr-20%Ni(Cast) 109350%Cr-50%Ni 982
If the fuel oil has more than 100ppm vanadium then the supports shall be 50%Cr-50%Ni or refractory lined for corrosion resistance purposes.
IMPORTANT DOCUMENTS TO BE REFERRED
Process licensor datasheet
Vendor datasheet
API 560 - Fired heaters for general refinery services
API 530 - Calculation of heater tube thickness
Equipment drawings for individual heater for more details
END
RADIATION ZONE
FUEL OIL
FUEL GAS
STEAM
PLENUM CHAMBER
CONVECTION ZONE
STACK
AIR PREHEATER
ID FAN
FD FAN
DAMPER
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