Fired Heater Basics

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


Arbor type

Inlet header Outlet header


Example : Isomar charge heater at JG, LAB charge heater at PG

U tube


Example : Platformer heaters

HORIZONTAL RADIANT COILS

Example : Coker heaters


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

RADIATION ZONE

FUEL OIL

FUEL GAS

STEAM

PLENUM CHAMBER

CONVECTION ZONE

STACK

AIR PREHEATER

ID FAN

FD FAN

DAMPER

Fired Heater Basics

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