| 摘要 |
<p>-a- This invention relates to a process to recover nonferrous metal such as zinc, lead, copper, and precious metals either directly from their ores or from bulk or dirty concentrates produced from their ores. The development of a variable metallurgical process which would be capable of treating low grade concentrates, bulk concentrates or the ore directly is of interest for massive fine grained sulphide ore found throughout the world. Thus the present specification discloses a method for recovering zinc from sulphidic ores and concentrates comprising the following consecutive steps: a) roasting said material in a subdivided form in a fluidized bed reactor at a temperature from 620 to 700.degree.C, with 20 - 60% excess air or oxygen over the stoichiometric for an average retention time of over 1 hour and at a superficial special velocity of the gas within the bed of 25 - 150 cm per sec at reactor temperature resulting in an atmosphere comprising SO2, SO3, water vapour, and remaining O2 and N2 from the air, to obtain a calcine containing the zinc primarily as sulphates and oxysulphates and most of the iron as hematite; b) leaching said calcine with water or dilute sulphuric acid solution at a temperature below 80.degree.C in such a manner that the sulphates, oxysulphates, and oxides of zinc are leached out in part from the calcine into the water or dilute sulphuric acid solution; c) subjecting the leach pulp resulting from step (b) to a liquid-solid separation step to yield a leach solution suitable for purification-metal recovery steps for zinc; - b d) leaching the solid residue resulting from step (c) with hot, strong sulphuric acid solutions, at a temperature above 80.degree.C but below the boiling point of the solution and with sulphuric acid solution stronger than used in step (b), in such a manner that most of the zinc ferrite and unreacted sulphide of zinc are converted to the sulphates of iron and zinc which dissolve in the leach solution; e) subjecting the pulp resulting from step (d) to a solidliquid separation step to obtain a leach solution containing said sulphates of iron and zinc; f) recycling said sulphates of zinc and iron obtained in step (e) in part into said fluidized bed reactor in a subdivided form to convert the sulphates of iron to hematite, SO2 and SO3; g) washing the solid residue resulting from step (e) with water; h) subjecting any pulp resulting from step (g) to a solidliquid separation step to obtain a washed leach residue and a wash liquor containing zinc and iron sulphates and sulphuric acid; and i) recycling said sulphates of zinc and iron resulting from step (h) in part to step (b) and/or in part to the said fluidized bed reactor in a subdivided form to convert the sulphates of iron to hematite, SO2 and SO3.</p> |
