Convert H2S to SOx

[clsengr]

How do I calculate the SO2 stack emission from a natural fired heater from ppm H2S?

 

[AggieCHEN04]

Do you know the composition and BTU value of your fuel gas?

I've performed similar conversions by determining the stoichiometric ratios of the combustion products (CO2, SO2, H2O) to each component in the fuel gas. This is a somewhat tedious process because it involves balancing a combustion reaction for each component in the fuel gas.

The complete/ideal combustion of fuel gas doesn't account for NOx, CO, and other SOx emissions. The concentration of these compounds is dependant on the type of burner used and the flame temperature. Usually the burner manufacturer will provide estimates for these types of emissions in ppm or lb/BTU.

You would need to know:
-fuel gas rate
-fuel gas composition
-destructive efficiency of the burner
-manufacturer estimates of CO, NOx, SO, SO3, etc in the vent
-the % excess Oxygen required for determining combustion air required and ultimately the amount of inerts vented.

 

[25362]

For example, a rough estimate of perfect combustion would result in a volume of combustion gases, in relation to one volume of the fuel gas, all taken at the same T,P conditions, as follows:

excess air % 0 10 20

Methane 10.5 11.5 12.4
Ethane 18.2 19.8 21.5
Propane 25.8 28.2 30.6

Dividing the original ppm by these factors would give the ppm of SO2 in the combustion flue gases.

 

[clsengr]

Do you have a feel for percentage of accuracy by simply assuming complete combustion as in the following:
lb SO2/MMBtu = (xxx mol H2S / 10E6 mol Refinery Gas) x (1 mol SO2 / 1 mol H2S) x (64 lb SO2 / mol SO2) x (mol Refinery Gas / 379 SCF) x (SCF Refinery Gas / xxxx BTU) x (10^6 Btu / MMBtu).
Thanks.