GB660778A - Improvements in roasting of sulfide ore - Google Patents

Abstract

<PICT:0660778/III/1> Sulphide ores, e.g. of zinc, copper and iron, are roasted by introducing the ore particles having a size within the range of through 6 and on 65 mesh into the upper portion of a vertically disposed grateless chamber 1, and maintaining the mass in the form of a fluid column by introducing air at vertically spaced intervals within the chamber, e.g. through pipes 4, 5, 6, the introduction being such as to provide different degrees of agitation in at least two zones. The apparent density of the mass in the three zones A, B, C may be 75-90 per cent, 55-75 per cent and 50-60 per cent respectively that of the bulk density of the ore particles. The chamber may be enlarged at the top to form a zone D, having about the same activity as zone B. This fourth zone prevents loss of fine particles blown upwardly, and constitutes a preliminary roasting stage. Air is supplied to this zone through pipes 13. In a modification, upper chamber 3 is continued as an upper roasting furnace, which is further enlarged at the top, so that there may be formed further zones corresponding to zones B, C, D. The furnace is surrounded by a jacket 10 for cool air, water &c. or for heating gas. Fine ores may be aggregated by wetting with sulphite liquor and extruding; other binders specified are zinc sulphate and bentonite. The plastic mass may alternatively be pressed between rollers. The amount of air used in the process is up to 1.5 times, and suitably 1.1 times, the theoretical amount. For zinc sulphide ores, roasting temperatures of 900-1200 DEG C may be used.