Dense Media Separation

Dense Media Separation/Dense Medium Separation/Heavy Media Separation

1 What is a dense media separation?

Description
Dense media separation (DMS for short) is a widely used in the mining industry by densitometry errand valuable minerals and non-valuable rock separation process. The process can be conducted at particle sizes as coarse as 300 mm and as fine as 500 μm with high separation efficiency, depending on the liberation characteristics of the valuable minerals. Dense media separation also referred to as heavy media separation.

Application of dense media separation plant
The DMS can be used in the jewelry industry, because of the diamond body denser than rock, and may also be used in the iron ore industry, since hematite more dense than silica. In the coal industry, where the denseness of coal is less than silica, it can also be used DMS.

Working principle of DMS technology
The heavy medium separation process relies on a medium of specific density (specific gravity) that is between the density of the minerals targeted for separation. Once the minerals are submerged in the medium, the small density minerals float up, and the larger density minerals sink down.
There are three stages of the dense medium separation process: feeding material pre-concentration, dense medium separation, and ferrous-based media recovery.

Advantages of heavy media separation mining
1. High separation efficiency and accuracy The HMS efficiency mainly depends on the specific gravity of ore particles, less affected by the size and shape of ore particles.
2. Wide processible particle size from 300 mm to 500 μm.
3. Easy to operate and control, low investment in equipment.

2 DMS processing flowsheet

In short, feed preparation ⇒ dense medium separation ⇒ ferrous based media recovery.

2.1 Feed Preparation

Feed preparation includes a process of particle size reduction and grading to ensure that an appropriate particle size range is provided to the heavy media separation vessel. The feed preparation process is involving crushing/breaking, washing/scrubbing, desliming, etc.

Raw ore material is commonly reduced in size using stone crusher such as cone crusher, jaw crusher, gyratory crusher, impact crusher. The crushed material can be scrubbed to break clays and agglomerated particles or rubbed to break down fragile gangue minerals for further removal by screening.
Slimes may cause inefficiencies in the DMS process through increased slurry viscosity, affecting the movement of fine particles.
For materials that do not require scrubbing or other pretreatments, crushed product direct sent to the horizontal screen deck of the DMS plant to remove the fine particles/slimes.

Related equipment: stone crushers, classification screens, scrubber, cyclone, feed hopper, vibratory feeder, conveyor belt, thickener.

2.2 Dense Medium Separation

In short, the DMS process is to concentrate the target minerals and to discharge the reject items. Thanks to the preparation, the reject items is discharged and minimize the processing requirement, the separator machine is the heart of the DMS plant.
There are two types of DMS separator vessels, static one, namely open bath vessel, is commonly used to separate coarse particle, by using of the nature gravity settling velocity; another one is dynamic type, usually used for finer particle, make use of centrifugal forces that enforces the settling velocity in the heavy medium slurry.

The working principle of DMS cyclone is similar to that of a common hydrocyclone. Ore is submerged in a dense medium, move under pressure, the particles with higher density than the slurry will move along the wall of the hydrocyclone and down to the top of the hydrocyclone, finally passing through the bottom flow of the hydrocyclone, while the particles with lower density will enter the vortex and finally move up through the overflow of the hydrocyclone.

related equipment: DMS Plant, pump-fed cyclone, dense medium cyclone

2.3 Ferrous-based Media Recovery

The medium recovery of heavy media separation plant composes of two portions, the medium recovery circuit and dilute medium circuit. the float and sink slurry from the separator machine separately flow to vibrating screens, which is fitted with a sieve plate with a pore size smaller than that of the feed preparation screen. The first part of the screen is used to drain the high-density medium. The screen is too small and is then reported through the degaussing coil to the circulation medium tank, where it is mixed with the newly imported feed. The second part of the screen contains a water spray that flushes any remaining ferromagnetic particles from the solid particles in the two streams before leaving the circuit.
The size of the screen tube is too small, report to the dilution medium loop from the flushing part of the screen tube, and then guide it to the low-intensity magnetic drum separator for the recovery of ferromagnetic heavy medium particles.

3 DMS processing plant cases

DMS Processing of 25 tonnes hard rock lithium

Dense media separation equipment

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