A zinc concentrate analyzing 63% ZnS, 6% PbS, 3% CdS, 4% FeS, 6% FeS2, 11% SiO2, and 7% H2O is roasted in a fluid-bed roaster. The roasted product contains CdO, Fe2O3, PbO, PbSO4, SiO2, ZnO, and ZnO•Fe2O3. Assuming lead is evenly distributed between PbO and PbSO4, find:
a) The theoretical air requirement.
b) The volume (in m3 at STP) and composition of the off-gases when air 20% (by volume) in excess of the theoretical requirement is used.
c) The volume (in m3 at STP) and composition of the off-gases when oxygen-enriched (30% O2 by volume) air 10% (by volume) in excess of the theoretical requirement is used.