Dry coke composed of 4% inert solids (ash), 90% carbon, and 6% hydrogen is burned in a furnace with dry air. The solid refuse left after combustion contains 10% carbon and 90% inert ash (and no hydrogen). The inert ash content does not enter into the reaction.
The Orsat analysis of the flue-gas gives 13.9% CO2, 0.8% CO, 4.3% O2, and 81.0% N2. Calculate the percent of excess air based on complete combustion of the coke.