Pyrite containing 80% FeS 2 and 20% gangue is burned in excess air to produce a gas with a complete analysis of 7.78% SO 2 , 1.39% O 2 , 82.06% N 2 , 4.92% SO 3 and 3.85% H 2 0. Analysis of the cinder...

Pyrite containing 80% FeS₂
and 20% gangue is burned in excess air to produce a gas with a complete analysis of 7.78% SO₂, 1.39% O₂, 82.06% N₂, 4.92% SO₃
and 3.85% H₂0. Analysis of the cinder shows a total sulfur content of 6.46% due to the presence of unburned FeS₂
and SO₃
absorbed by Fe₂O₃. Air supplied is at 27°C, 745 mm Hg and saturated with vapor. The burner gases then enter a converter together with 30% excess secondary air (supplied at the same conditions as primary air) based on the complete conversion of all SO₂
to SO₃. 75% of the SO₂
actually burns to SO₃. The converter gases enter an absorber and absorbed in acid solution. The waste gases formed has a partial orsat analysis of 0.7% SO₂. Calculate per kg of pyrite

Find % excess air (FeS₂
to SO₂)

ANS.(10.17)