co2 emissivity 1

[almostbroken]

I am sizing a flare stack and the height is a function of the heat generated at ground level as per API 521. The heat at ground level is a function of emissivity. The default seems to be 0.2. However a heavier gas should have a higher number and a gas high in methane and H2S would have much less.

Does anyone know where I can get emissivity of individual gases?

 

[Flareman]

almostbroken
Go to

http://www.geocities.com/flareman_xs.

Navigate to Main Index|Downloads and get the paper "Making the Flare Safe". You will find an approach to emissivity which is more reflective of the real world than using standard default values. In all cases the true "emissivity" or fraction of heat radiated, usually falls between 0.09 for a flame you can't see (H2?) to a maximum of 0.4 (very rare) for an "almost clean" flame but with a lot of radiative carbon (think low velocity ethylene). The method uses the carbon mass of the molecule as a predictor, along with velocity and tip diameter. It isn't entirely sound because there should also be a stability parameter based on the heat of formation characteristics, but I really haven't been able to characterize that satisfactorily at this time.
Your heading mentioned CO2 emissivity. That's barely even a factor. The heat radiated from the flame comes primarily from the transient carbon solids released in the hot core of the flame before the gases have diffused out toward the ambient air.
Hope it helps
David