Page 34 - HUB-4 Magazine Issue 79
P. 34

 Washing & Screening
Decanter Centrifuge vs Belt Press vs Filter Press: Which is the best for Tailings Management?
All aggregate and mining operations with a wet processing plant will produce a waste stream. This waste stream consists of tailings – the process water and fine solids, clay and other deleterious material removed during the washing process. Traditionally, these tailings are sent to a settling pond or lagoon to separate the solids from the liquid in the waste stream.
However, settling ponds can be time-consuming and expensive to maintain, take up valuable land space and/or cover up mineable reserves. They are not the best method for tailings management, especially when mechanical dewatering options are available.
Mechanical dewatering equipment improves tailings management by separating the solids from the liquid to produce a solids product that is suitable for mechanical handling. As an added bonus, the recovered water can be reused in the washing process, reducing freshwater requirements for sites where water is scarce or expensive.
Types of mechanical dewatering equipment for tailings include:
• DecanterCentrifuges
• BeltPresses
• FilterPresses
Decanter Centrifuges
Decanter Centrifuges separate solids from liquid in a slurry by means of high centrifugal forces to induce sedimentation. The slurry enters the Decanter Centrifuge via a feed pipe into the inside of a rotating screw conveyor that is tapered at one end. The slurry is then released into a bowl surrounding the screw conveyor that is rotating at a higher speed than the conveyor.
High G-forces cause the solid particles in the slurry to be flung to the walls of the bowl, where the screw conveyor moves them toward the tapered discharge end. The tapered end of the screw allows the solids to dewater as they make their way toward the discharge. The water freely moves to the other end of the machine and discharges via ports.
Decanter Centrifuges produce a solid cake material that is suitable for mechanical handling as well as immediately reusable process water. They discharge a solid material somewhere between that of a Thickener and Filter Press. Decanter Centrifuges are fully automated and enclosed for cleaner operation.
   | p34 | March/April - Issue 79

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