The Spiral Chute: Structure, Function, and Application in Mineral Processing

The spiral chute is a fundamental and highly efficient gravity separation device widely employed in the mineral processing industry. It is primarily used in the roughing and cleaning stages for separating fine-grained minerals, typically handling particle sizes ranging from 0.3 mm down to 0.02 mm. Its effectiveness is maximized when there is a sufficient specific gravity difference between the target mineral and the gangue (waste rock).

This versatile equipment can process a broad spectrum of minerals. It is extensively applied in separating iron ores (like hematite and magnetite), tungsten, tin, tantalum-niobium, and beach sand minerals such as zircon, rutile, and ilmenite. It is also effective for gold, platinum, chrome ore, and various other non-ferrous and rare metal ores.

Spiral chutes are commonly integrated into complex processing flowsheets. A classic application is in iron ore beneficiation within stage-grinding, coarse-fine separation, and combined gravity-magnetic-anionic reverse flotation circuits. They often serve as a pre-concentration step ahead of magnetic separation or flotation, improving overall plant efficiency and reducing the load on downstream processes.

The working principle is based on gravity differentials. A slurry of ore and water is fed to the top of a vertically mounted, downward-spiraling trough. As the slurry flows down, minerals are subjected to combined forces: gravity, centrifugal force, and friction. Denser particles settle toward the inner part of the spiral channel, while lighter gangue particles are carried by the water flow toward the outer rim. This spatial separation allows for the collection of concentrate, middlings, and tailings from different discharge points at the bottom.

The key advantages of spiral chutes drive their popularity. First, they require no external power for separation, operating solely on gravity, which makes them energy-efficient. They feature a simple structure, are easy to install and operate, and have a large processing capacity. Additionally, they offer high recovery rates (up to 95% for some ores), low water consumption, and a small footprint. Modern innovations, like rotating spiral chutes with PLC control, further enhance separation precision and adaptability for fine-particle recovery.

In summary, the spiral chute remains a cornerstone of gravity concentration due to its robust, cost-effective, and efficient design for separating a wide array of minerals based on density differences.