setting mass fraction...pliz help
 

i am trying to model a simulation of so2 dispersion from single stack (power plant). coal is used for fuel, and the contain of coal from data are sulfur (0.3%), carbon (49%), dust (6%), and other gas. i used turbulent model (spalart allmaras), energy, natural converction, and species transport without reactions.

if i determine top of stack as mass flow inlet and i calculate so2 flow rate for input of mass flow rate. Am i right if i set the materials only air & so2, and set the value of so2 mass fraction is 1 in mass flow inlet????(my assumption: gas which come out from stack to the atmosphere is only so2, no air)

Thanks anybody in advance for help

vickrenz