GB756965A - Improvements in the production of gases containing sulphur dioxide - Google Patents

Abstract

Gases containing SO2 are obtained by roasting finely-grained sulphidic ores, e.g. pyrites flotation concentrates of grain size predominantly below 0.2 mm., in a single stage in an undivided bed (as defined) of roasted material which is fluidized by means of the free oxygen-containing gases, e.g. air or oxygen enriched air, necessary for roasting, which are introduced through a grate from below and by means of the roaster gases formed, wherein, in addition to the main supply of oxygen-containing gases introduced uniformly into the bed from below, a subordinate amount, e.g. 10 per cent. of main supply, of oxygencontaining gases is supplied, together with the sulphidic ore introduced into the bed, or at at least one point immediately adjacent the zone within which the sulphidic ore is introduced into the bed, so that some agglomeration of the ore occurs. Where the subordinate amount of oxygen-containing gas is supplied together with the ore a mixing burner may be used. Cinders from the fluidized bed and/or the coarser grained fraction of cinders entrained by the roaster gases and/or roasted ore cinders from other roasting systems may be added together with the additional oxygencontaining gas. Such cinders should preferably be added at the temperature at which they are produced without appreciale heat loss, and may be mixed with the ore and the mixture suspended in the additional oxygen-containing gas, with consequent predrying of the ore and agglomeration, if the cinders are hot. The amount of cinder may be 20-40 per cent. of the cinder produced.