Gravity Separation and Flotation Processes for Tin in Tin Tailings

Tin ores are predominantly polymetallic associated deposits; following beneficiation, the tailings retain significant quantities of valuable components such as tin, copper, lead and zinc. As the properties of the ores vary considerably, tailored separation processes are required to recover tin resources. Current mainstream technologies include gravity separation, flotation and combined processes utilising both.

Gravity separation is the fundamental process for tin tailings recovery. Commonly used equipment includes shaking tables, spiral chutes, suspended vibrating conical separators and centrifugal separators. Shaking tables offer a high enrichment ratio and are suitable for the separation of fine-grained tin; chutes feature a simple structure and high throughput; suspended vibrating conical separators utilise the principle of fluidised-film separation to achieve fine-grain enrichment; centrifugal equipment utilises centrifugal force to capture ultrafine tin particles and is primarily used for pre-concentration and scavenging. However, traditional gravity separation is ineffective at recovering ultra-fine cassiterite and yields low overall performance indicators; in actual production, prior classification is required, and multiple pieces of equipment must operate in conjunction. Composite force field-enhanced gravity separation equipment is currently a key focus of technological research and development, as it can significantly improve the recovery rate of fine and ultra-fine cassiterite.

Flotation is specifically designed for fine and ultrafine cassiterite that is difficult to recover using conventional gravity separation, and is subdivided into five categories: conventional, electrolytic, carrier, flocculation and microbial flotation. Conventional flotation relies on reagents to modulate the floatability of minerals; electrolytic flotation alters the slurry interface through water electrolysis to improve separation efficiency; carrier flotation utilises carriers to entrain fine-grained cassiterite for flotation; and flocculation flotation achieves separation through the selective flocculation of impurities using reagents. Whilst each flotation process demonstrates outstanding recovery performance, they all involve high reagent consumption, which can lead to environmental pressures and increased production and operational costs.

In practice, the resource recovery of tin tailings rarely relies on gravity separation or flotation alone; instead, a combined process involving graded pre-treatment is commonly adopted: coarse-grained material undergoes composite force field gravity separation, whilst fine-grained material is fed into the flotation system, with the process optimised using low-pollution, environmentally friendly flotation reagents. By leveraging the complementary strengths of these two processes, it is possible not only to improve the overall tin recovery rate but also to control reagent consumption and environmental management costs, thereby efficiently utilising the associated polymetallic resources within tin tailings and achieving the efficient resource recovery of tailings.