Combustion Air Blower for Refinery Fired Heaters

The process

Process heaters in refineries and petrochemical plants burn fuel gas with forced draft, often through an air preheater, and balanced draft units add an ID fan. Fans are built to refinery specifications with explosion proof motors and spare capacity.

The gas at the fan

Clean air that has passed through an air heater or recuperator. Density is lower than ambient, so the fan is selected at the hot condition and checked for motor load at cold start.

Selection for this duty

Blade form	Backward curved or aerofoil for the best efficiency on clean gas
Material of construction	Mild steel
Drive and bearings	Direct coupled or belt driven with a shaft cooling disc and bearings outside the casing
Density at the fan	At about 180°C the gas density is close to 0.78 kg/m³, 65% of standard air. Pressure developed and power drawn fall in the same ratio, so the selection is made at this density and the motor is checked at cold start.

Feeds a burner with air at the pressure the burner register needs. Sized for the burner turndown range, and often fitted with an inlet silencer. Client-stated blade types for the Combustion Air Blower in general: Backward curved and radial tipped.

Industries

Other fans in refinery fired heaters

Combustion Air Blower in other processes

Information needed to select or quote

1. Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
2. Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
3. Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
4. Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.