GB1186836A - A process for the purification by chlorination of roasted iron sulphide materials - Google Patents

Abstract

1,186,836. Purification by chlorination of roasted iron ores. BOLIDEN A.B. 25 June, 1968, No. 30128/68. Heading C1A. A sulphide bound ferruginous material, which may be mixed with oxide bound ferruginous material, and which contains Cu, Zn, Sn, Pb, Co, Ni, Au, Ag, As, Bi, Sb and S compounds, is roasted (as described in Specification 1,116,519) in a fluidized bed at 700-1100‹ C. with such an amount of oxygen that the oxygen pressure in the resulting roaster gas lies within prescribed limits (set out in claim 1), whereafter the material, in that condition, is separated from the roaster gases and treated, while still hot, with chlorine, or another gas containing chlorine or chlorine compounds, or material giving off gas containing chlorine or chlorine compounds. Free oxygen may be excluded during the chlorinating stages. The evolved substances may be recovered from the waste gases and the chlorine content may also be recovered and recirculated. The chlorination is usually carried out at 600‹ to 1100‹ C., preferably in a fluidized bed, but other suitable reactor types are discussed. When chlorine is used as the chlorinating agent and the roasted material contains sulphides and magnetite, then free oxygen usually in the form of air, is added to the chlorine. Steam may also be employed as an additive to reduce chlorination of iron oxides. If the roasted material contains no sulphide the chlorine may be diluted with an inert gas, e.g. nitrogen, carbon dioxide. If hydrogen chloride is used as the chlorinating agent less oxidizing conditions may be employed than in the case of chlorine but there must be sufficient oxygen to drive off all the sulphur. The roasted material may also be desulphurized in a separate reactor before passing to the chlorinating reactor by treatment with an oxygen containing gas or a solid oxidant such as ferric oxide. If an oxygen containing gas is used this may be diluted with an inert gas to reduce conversion of the magnetite in the roasted material to haematite. Iron oxide may also be added during the desulphurization stage and sulphide may be added to help drive off arsenic. Owing to the heat evolved in the oxidation of magnetite to haematite cooling may be necessary in the desulphurization and/or chlorination stages and various means of achieving this are disclosed.