How much natural gas for burning ACID GAS in a thermal oxidizer

TO combustion chamber temp is usually 900degC. So you can calculate how much natural gas you have to add to your low btu acid gas stream to achieve this flame temp, assuming say 5% excess O2 in the flue gas.
Required inputs are the LHV of the acid gas stream, the LHV of the natural gas stream, and Cp values for N2, O2, CO2, and H20 vapor at ambient temp and 900degC. Write out the chemical reaction for combustion of H2S to SO2 to start with. Ask a chemical engineer or chemist to help if not familiar or not sure. Someone on E-Tips may help to check your completed calcs if required.

The amount of natural gas is really determined by the air flow and the requirement to heat it to at least 1400F. Adding acid gas that has any caloric content to to the air will then reduce the amount of natural gas needed.