Spirals, the most common equipment for the separation of heavy minerals such as chromite, are greatly affected by size distribution and the liberation degree (hence the specific gravity and size) of the feed particles. In this study, the efficiency of spirals in separation of low-grade chromite particles has been investigated by studying the distribution of grade, size distribution and liberation degree of feed, concentrate, and tailings of spiral. For this purpose, mass balance constraints were applied to the spiral-containing chromite processing circuit. Afterwards, the grade variations and size distributions have been investigated. According to the results, when the feed to the spiral has a larger size distribution, the enrichment ratio of the feed is 1.32 and, with the smaller feed size, this value has increased to 1.99. When the spiral feed has a larger size distribution and higher specific gravity, the recovery of chromite increases with increasing particle size up to 250 microns, and then with increasing particle size, recovery decreases with a relatively steep slope. Evaluation of spiral efficiency with respect to particle liberation degree has also shown that despite the high degree of liberation of spiral feed in size fractions smaller than 75 microns (88.9%), the liberation degree of spiral concentrate and tail in this faction is equal to and less than that of feed, which can indicate poor spiral performance in these size fractions.

中文翻译：

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低品位铬铁矿加工中粒度分布和游离度对工业螺旋分离性能的影响

螺旋是分离重矿物（例如铬铁矿）的最常用设备，它受进料颗粒的粒度分布和解离度（因此是比重和粒度）的影响很大。在这项研究中，通过研究螺旋的品位分布、粒度分布和进料、精矿和尾矿的释放度，研究了螺旋分离低品位铬铁矿颗粒的效率。为此，对含螺旋的铬铁矿处理电路应用了质量平衡约束。之后，研究了等级变化和尺寸分布。结果表明，当进入螺旋的进料粒度分布较大时，进料的浓缩比为1.32，随着进料粒度的减小，该值增加到1.99。当螺旋进料具有较大的粒度分布和较高的比重时，铬铁矿的回收率随着粒径增加到250微米而增加，然后随着粒径的增加，回收率以相对陡峭的斜率下降。与颗粒释放度相关的螺旋效率评估也表明，尽管粒径小于 75 微米 (88.9%) 的螺旋进料高度释放，但该部分中螺旋精矿和尾料的释放度等于和小于进料，这可能表明这些粒度级分的螺旋性能较差。恢复以相对陡峭的斜率下降。与颗粒释放度相关的螺旋效率评估也表明，尽管粒径小于 75 微米 (88.9%) 的螺旋进料高度释放，但该部分中螺旋精矿和尾料的释放度等于和小于进料，这可能表明这些粒度级分的螺旋性能较差。恢复以相对陡峭的斜率下降。与颗粒释放度相关的螺旋效率评估也表明，尽管粒径小于 75 微米 (88.9%) 的螺旋进料高度释放，但该部分中螺旋精矿和尾料的释放度等于和小于进料，这可能表明这些粒度级分的螺旋性能较差。