upgrading and thickeners

In mineralprocessing plant, With upgrading we understand, the further processing of the final products from the enrichment stages in a process.
This is valid both concerning the valuable minerals (the concentrate) and the waste minerals (the tailings).

In the first case upgrading means improving the product value by bringing the concentrate to transportability or into a completely dry form. Processing can also go further to calcining and sintering. On the tailing side upgrading means that waste material (wash water, process effluents etc.) is properly taken care of in order to protect the environment, to recover process water and to turn certain portions into valueables.
Sedimentation
Sedimentation is a continuous solid-liquid separation process with settling of solids by gravity. Clarification is the process for removal of solids from a dilute solid/liquid suspension. Thickening is the process for concentrating particles in a supension by gravity compression
Flocculation
All sedimentation technologies are related to particle size. One way of improving the settling speed generally is therefore to increase the size of the particles.
Fine particles can be connected together by coagulation or flocculation. The settling rate of the combined particles will be higher than that of each individual particle.
Flocculation System
A handling system is needed for flocculant utilisation. This comprises provision to mix, store and dilute the polymer. The dilute polymer is then mixed with the feed slurry and allowed to condition (or age) before a sedimentation or dewatering process.
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Conventional Clarifier
Clarification is achieved when the liquid “upstream” velocity VL is lower than the sedimentation velocity of the solids VS.
Conventional Thickener
Continuous thickening to give the required solids concentration in the underflow depends on balancing the volumetric solids flow rate at a critical concentration with the diameter of the thickener.
Bridge type thickener
For smaller thickeners, up to 30 – 40 m diameter, the rakes and drive mechanism are supported on a bridge superstructure, which straddles the tank as shown.
Centre Pier type thickener
For tanks over 30 – 40 m diameter a bridge structure will be imractical. The mechanism and rakes are therefore supported from a centre pier and the bridge is only used for access and to support feed pipe and launder.
Thickeners Drive mechanism
For bridge and centre pier mounting. Options with and without automatic rake lifting system.
Automatic torque monitoring Slewing ring bearing to accommodate out of balance loads on rakes Worm and wheel and multistage epicyclic gearbox drive.
Control of thickeners
Torque is electronically detected and monitored. Increased torque is a sign that the solids loading in the thickener may be building up. This could indicate a process problem (change in feed, blocked underflow etc.). In all these cases rakes and drive have to be protected.
Sinonine technology team

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