Arsenical oxidic iron ores and roasted iron pyrites are dearsenicated by subjecting them to a reducing roast at at least 800 DEG C. exclusively with solid reducing agents, in which the atmosphere above the material being roasted is as nearly neutral as possible, and in which the reducing agent consists of a sulphidic reducing agent present in an amount equivalent to between 1% and 4% FeS2, and a carbonaceous reducing agent, in the form of anthracite or coal, present in an amount equivalent to between 1.8% and 3.6% carbon, exclusive of any solids added as fuel to provide heat for the process by being burnt. The ore may be mixed with the reducing agent, and if desired pelleted, and this may then be in addition sintered, either by using more of the reducing agent, or by supplying the extra heat by hot gases. The throughput of air is preferably between 5 and 10 cubic metres per square metre of suction surface per hour at least during its first stages of the treatment, and may after about half the duration of the treatment be raised to above 50 and preferably above 80 cubic metres per hour. If the ore contains sulphur as sulphate, this sulphur may be used to form some of the sulphidic reducing agent in situ. Suitable carbonaceous reducing agents include anthracite, brown coal, or charcoal.
展开▼
