Need equation for sizing a blower motor 1

[zomg11one]

We've got an enclosed flare that is sized to vent 44.62 MMSCFD of syngas. GPSA says 3-7 lb of air should be used for smokeless operations; this means we've got to move air at 100,157 ACFM. That being said, is there a handy equation for finding the horsepower of the electric motor used in the blower?

Thanks!

 

[Flareman]

zomg11one
Blower Power =
air mass flow rate (mass/time) x
the equivalent height of a column of air which provides the same pressure as the blower (length)

This gives units M L/T
Convert to whatever power units you need with standard conversions.
Increase the motor size according to the efficiency factor of the blower/motor (usually around 70%)

HOWEVER
Regardless of what GPSA says, if you have an enclosed flare you should check with the supplier what HE says you need. He may not be using blown air at all, particularly for syngas which shouldn't have transient solid component leading to smoke formation.
Most enclosed flares work by natural draft. The hot gases in the stack are light and create a chimney effect which sucks air in to the base below the burners.

David