Improvements in treating iron-bearing materials

摘要

Ferric oxide is produced by subjecting iron-bearing material to the action of sulphuric acid and forming a concentrated aqueous solution of ferrous sulphate from which solid hydrated ferrous sulphate is obtained, e.g. by evaporation or cooling, heating the solid hydrated ferrous sulphate by hot gases passed in contact therewith for dehydration, heating the anhydrous product out of contact with the air and combustion gases for decomposition to substantially pure ferric oxide and a gaseous product consisting essentially of sulphur dioxide and sulphur trioxide, oxidizing the sulphur dioxide to sulphur trioxide, absorbing all the sulphur trioxide in concentrated sulphuric acid to regenerate the acid used in treating the iron-bearing material. Aqueous ferrous sulphate may be obtained by treating iron-bearing material with aqueous sulphuric acid or with water free acid at elevated temperature with subsequent water-leaching of the product. Dehydration may be effected in a rotary kiln at 400-450 DEG C. in a countercurrent of hot gas. The anhydrous product may be decomposed in a muffle furnace at 480-1300 DEG C. by hot combustion gases and the waste gases may be passed to the rotary kiln. Specification 656,142 is referred to.