Process fluid is fed to both the east pass and the west pass of the natural draft fired heater. The process fluid is heated in the convection section first and then the radiant section before leaving the furnace.
Fuel is fed to both the east and west burners at the bottom of the furnace where it is ignited and burned.
Air enters the furnace through the air registers by natural draft. The
combustion gases leave the furnace through the stack.
The process feed flow is controlled by flow controller FIC-101. Flow to the east and west passes can be adjusted by varying the positions of valves HCV-101E and HCV-102W respectively. Process inlet temperature is indicated by TI-101. Process outlet temperature is controlled by TIC-102 which modulates fuel flow to the burners. East and west pass outlet temperatures are indicated by TI-102E and TI-102W respectively. East and west pass bridge wall tube temperatures are indicated by TI-101E and TI-101W respectively.
Fuel flow to the burners is controlled by temperature controller TIC-102 which is cascaded to fuel flow controller FIC-201. Fuel flow to the east and west burners can be adjusted by varying the positions of valves HCV-201E and HCV-201W respectively. Fuel inlet temperature is indicated by TI-201.
Temperatures in the east and west radiant sections of the furnace are indicated by TI-301E and TI-301W respectively. Bridge wall temperature is indicated by TI-302. Stack inlet and outlet temperatures are indicated by TI-303 and TI-304 respectively.
Air enters the furnace by natural draft. Air flow through the furnace can be trimmed by varying the positions of the east and west pass air registers and the stack damper, HIC-301E, HIC-301W, and HIC-301 respectively.
The ambient air temperature and pressure is indicated by TI-300 and PI-300 respectively. The draft in the east and west radiant sections of the furnace is indicated by PI-301E and PI-301W respectively. Bridge wall draft is indicated by PIC-302. Stack draft is indicated by PI-303.
Weight percent oxygen in the stack gas is indicated by AIC-301.
The BURNER-E and BURNER-W switches act as both ignitors and flame indicators.