The following flue gas analysis was obtained: CO2 10%, CO 0.5%, O2 4.5%, N2 85%, all percentages by volume for burning natural gas (composition 90% methane, 10% nitrogen) in a furnace. Calculate the...

The following flue gas analysis was obtained: CO2 10%, CO 0.5%, O2 4.5%, N2 85%, all percentages by volume for burning natural gas (composition 90% methane, 10% nitrogen) in a furnace. Calculate the percentage excess air flow (percentage above stoichiometric). Reaction: CH4 + 2O2 ⟶ CO2 + 2H2O