Recovery of zinc from ore or concentrate - involves thermal treatment in fluidised bed before forming soln. for further treatment

摘要

Zinc is recovered from ores and sulphated concentrates contg. iron sulphate by (a) calcining in a fluidised bed at 620-700 deg.C with 20-60% stoichiometric excess of air, mean retention time over 1 hr. and gas velocity 25-150 cm/sec. to obtain a calcined prod. contg. zinc mainly as sulphate and oxy-sulphate, and iron mainly as haemalite, (b) lixiviating with water or dil. sulphuric acid at below 80 deg.C to partially extract the zinc cpds., (c) separating the liq. for recovery and purification of the zinc, (d) lixiviating the residue with hot conc. sulphuric acid soln. at above 80 deg.C so that most of the zinc ferrite and sulphide are converted to zinc sulphate and iron sulphate which dissolve, (e) separating the soln. and (f) recycling this to the fluidised bed, (g) washing the solid residue from (e) with water, (h) separating the soln. and (i) recycling this partially to stage (b) and/or the fluidised bed.