Classification and Gravity Concentration in Tin Ore Beneficiation

      Among tin minerals, only cassiterite and stannite have industrial value, with cassiterite being the core raw material for extracting metallic tin. Due to cassiterite's high density, gravity separation remains the mainstream beneficiation process currently. However, placer tin ore is fragile and prone to over-grinding and slime formation, producing a large amount of -10μm slime that seriously interferes with the beneficiation process. Therefore, classified desliming and precise equipment configuration have become the key to cassiterite beneficiation.

      Classified desliming is a necessary step before gravity separation. Using equipment such as water guns, ore washers, and small-diameter hydrocyclones, the particle size of the feed is strictly controlled to maximize the elimination of slime interference. Gravity separation equipment must be adapted to particle sizes: shaking tables can handle the 2～0.037mm particle size, producing high-grade concentrates with a high enrichment ratio and serving as the main equipment for tin beneficiation; spiral concentrators are suitable for recovering the 1～0.074mm particle size, and oscillating spiral concentrators strengthen the loosening of ore particles through a composite force field, achieving significant results in recovering coarse-grained cassiterite in tin tailings treatment; jigs are mostly used for medium-grain separation, and new jigs outperform traditional equipment in enrichment ratio, recovery rate, and processing capacity, and have been extended to cassiterite pre-separation; -37μm slime needs to be separated using centrifuges or belt chutes. In addition, heavy medium pre-separation is gradually applied in tin concentrators, and economic benefits can be generated when the waste rejection rate exceeds 20%～25%.

       The process design follows the principle of "multi-stage grinding and multi-stage separation". A closed-circuit grinding system is formed by combining grinding mills and fine screens to achieve "recover as early as possible and discard as early as possible", avoiding over-crushing of cassiterite. Focusing on gravity separation equipment, combined with particle size adaptation and high-efficiency technologies, is the key to improving cassiterite recovery rate and ensuring the stable operation of concentrators.