Gravity Separation Technology for White Tungsten Ore Based on Density Differences

The gravity separation process for white tungsten ore is a physical mineral processing method that achieves separation based on the density differences between white tungsten ore and gangue minerals. It offers significant advantages such as a simple process flow, low cost, and environmental friendliness. Although its recovery efficiency and concentrate grade are limited when applied alone, it plays an irreplaceable role in the pre-treatment of white tungsten ore, the recovery of coarse-grained minerals, and integrated mineral processing flows. The density of scheelite is significantly higher than that of gangue minerals such as quartz and calcite, providing a solid foundation for gravity separation. Through scientific equipment selection and process design, efficient pre-concentration and recovery of resources can be achieved.

I. Core Principles of White Tungsten Ore Gravity Separation

The core principle of the gravity separation process is to achieve separation by utilizing the differences in settling velocities of various minerals in a medium (typically water), where settling velocity depends on factors such as mineral density, particle size, and shape. The density of white tungsten ore is 6.8 g/cm³, which is significantly higher than that of common gangue minerals such as quartz (2.65 g/cm³) and calcite (2.71 g/cm³). Its specific gravity ratio relative to gangue minerals ranges from 2.08 to 2.78, classifying it as a type of ore that is relatively easy to process via gravity separation. This provides a solid material foundation for gravity separation.

The suitability of gravity separation for wolframite is primarily reflected in two aspects: First, it is suitable for wolframite with coarse-grained distribution. For ores with relatively coarse grain sizes that can achieve single-particle liberation through grinding, gravity separation can directly recover qualified minerals, resulting in a short process flow and low costs; Second, it is suitable for pre-treatment and pre-concentration. Gravitational separation can pre-remove a large amount of low-density gangue minerals, reducing the feed load on subsequent processes such as flotation and thereby lowering production costs. However, white wolframite is brittle and prone to overgrinding during the grinding process, resulting in a large amount of fine-grained minerals. Since the difference in sedimentation rates among fine-grained minerals is reduced, the recovery efficiency of gravity separation is significantly lowered. This characteristic limits the standalone application of gravity separation, leading to its more frequent use in combination with other processes.

II. Selection and Application of Key Equipment for White Tungsten Ore Gravity Separation

The selection of gravity separation equipment directly impacts the recovery efficiency and performance indicators of white tungsten ore and must be determined comprehensively based on factors such as ore particle size, density differences, and production scale. Currently, commonly used equipment for white tungsten ore gravity separation includes spiral chutes, fine sand shaking tables, jigs, and centrifuges, each with its own suitable applications and operational characteristics.

The spiral chute is one of the preferred pieces of equipment for white tungsten ore beneficiation. It utilizes the combined effects of gravity, centrifugal force, and water flow to achieve the stratification and separation of minerals. This equipment offers advantages such as high throughput, a small footprint, no power requirements, and simple operation, making it suitable for the pre-concentration and tailings disposal of fine-grained white tungsten ore. The working principle of the spiral chute involves feeding the slurry from the top of the chute, where it flows along the spiral surface. Under the combined effects of gravity and centrifugal force, high-density white tungsten ore moves toward the outer side of the chute bottom, while low-density gangue minerals flow toward the inner side of the chute. Ultimately, the two types of minerals are separated via a discharge mechanism. In practical applications, parameters such as the spiral angle and chute width must be adjusted according to the ore particle size to ensure effective separation.

Fine sand shaking tables (including fine slurry grooved shaking tables) are suitable for the recovery of fine- and ultrafine-grained white tungsten ore. They utilize the reciprocating motion of the bed surface and the flushing action of transverse water flow to achieve mineral stratification and separation. Shaking tables offer high separation precision and can effectively recover fine-grained white tungsten ore that is difficult to recover using other equipment; however, their processing capacity is relatively small, making them suitable for small-scale production or concentration operations. During operation, parameters such as the bed angle, stroke, frequency, and transverse water flow velocity must be precisely controlled. By adjusting these parameters to alter the movement trajectory of minerals on the bed surface, efficient separation of white tungsten ore from gangue minerals is achieved.

Jigging machines are suitable for the recovery and rejection of coarse-grained white tungsten ore. They utilize the pulsating action of water to stratify mineral particles by density, with high-density white tungsten ore particles sinking to the bottom of the bed to form the heavy product, while low-density gangue minerals float to the surface to form the light product. Jigging machines offer high throughput and high separation efficiency, enabling the rapid removal of large amounts of low-density gangue. They are suitable for the pre-concentration of white tungsten ore and are particularly effective in scenarios where over-grinding of white tungsten ore needs to be avoided. For fine tungsten slurry, centrifugal concentration is an effective recovery method. By utilizing the centrifugal force generated through high-speed rotation, it amplifies the density difference between white tungsten ore and gangue minerals, achieving efficient separation of fine-grained minerals. It is a crucial piece of equipment for solving the challenges of recovering fine tungsten slurry.