Mineral Processing

Dense Medium Separation

The dense medium cyclone (DMC) is the most ubiquitous of the DMS vessels in use, and deservedly so. It is efficient (when run properly), can process both coarse and fine sizes, and has a relatively small footprint. Unlike other forms of gravity concentration, it also makes a positive separation at a desired density cut-point, due to the presence of the medium whose density is easily controlled.

DMS Introduction

Dense media separation is usually employed for coarse gangue rejection, but can also be used to produce mineral concentrates from high-grade ores. Flotation is used for processing fine particle size feed, and where high-grade concentrates are required.  Magnetic separation is used to remove large quantities of iron-bearing gangue minerals to make the concentrate suitable for use in ceramics and glass manufacturing.  The dense medium separation(DMS) process is a mature technology and is widely used in mineral and coal processing. 

Processing Flow

The beneficiation of pegmatite ore in the presence of other valuable minerals such as those containing tin and tantalum in addition to the lithium minerals increases the complexity of processing. This may in-volve additional operation to remove these minerals as by products. For example, in the treatment of Bernic lake pegmatite, spiral circuits are used to remove and concentrate tantalum minerals (Ferguson et al., 2000). Also, in the processing of Greenbushes’ pegmatite ore, the bulk flotation concentrate is treated with gravity separation techniques such as spiral and shaking table to remove heavy minerals, e.g., SnO2, Ta2O5 and Fe2O3 (Bale and May, 1989).

Dense media separation (DMS) or heavy media separation is a pre-concentration technique used to reject gangue minerals prior to grinding. DMS exploits the difference in specific gravity between the target and gangue minerals, and is commonly used in the separation of spodumene from other gangue silicates. The specific gravity of spodu-mene is between 3.1 and 3.2; this makes it slightly heavier than most gangue minerals such as quartz (2.65), albite (2.60) and muscovite (2.8). The spodumene, therefore, sinks while gangue minerals float in dense medium of appropriate specific gravity, and thus separated from each other.

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