| 摘要 |
<p>1,186,439. Treating chromium ores. FARBENFABRIKEN BAYER A.G. 23 June, 1967 [12 July, 1966], No. 29020/67. Heading C1A. Chromium ore, after the addition of a leaning agent, is heated to 500‹ C. then treated with NaOH solution or fused NaOH and the mixture reacted at 900‹ to 1200‹ C. in the presence of a free oxygen-containing gas to give a chromatecontaining product. The NaOH solution is preferably not less than 30% by weight and advantageously 40 to 60% by weight. Leaning agents may be dolomite, iron oxide or residue from a previous caustic treatment according to the invention and the alkali used may contain some Na2CO3. A preferred embodiment comprises a 3-stage process wherein only part of the alkali required is added in each stage. In an example, leaning agent (iron oxide) is added only to the third stage of a three-stage process comprising also intermediate leaching.</p> |
