Low Grade Iron Ore Benefication

Spirals

A Spiral Concentrator is a flowing film separation device. General operation is a continuous gravitational laminar flow down on an inclined surface. The mechanism of separation involves primary and secondary flow patterns. The primary flow is essentially the slurry flowing down the spiral trough under the force of gravity. The secondary flow pattern is radial across the trough. Here the upper-most fluid layers comprising higher density particles move away from the centre while the lower-most concentrate layers of higher density particles move towards the centre. Spirals require addition of water at various points down the spiral to assist washing of the concentrate, i.e. transporting away the light gangue from the concentrate band. The amount of wash waster and its distribution down the spiral trough can be adjusted to meet the operating requirements. Point control minimizes the total water requirements by efficiently directing water into the flowing pulp at the most effective angle.

Hydrocyclones / Classifiers

Conventionally, the modelling and simulation of classifiers and cyclones are based on 50% separation size commonly known as d50 size. However, the design and construction of mechanical classifiers are primarily based on limiting / elimination size. The metallurgical performance depends on the key hydrocyclones variables such as pressure, feed density, size of vortex and apex. Depending on the ore characteristics, operating parameters of hydrocyclone can be altered to improve performance. The Hydrosizers (classifiers) allow splitting of the low grade ore into two parts, at roughly 50% plus 0.150 mm and 50% minus 0.150 mm respectively. The desired split size of 0.150 mm is chosen based on the fact that particles below that size are normally small enough for the pelletizing process.

Magnetic Separator

Magnetic separators use composite, permanent magnet materials such as Nd-Fe- By applying a new magnetic force concentration technique, a suitable product can be obtained. It is simple in construction, uses no power to generate the magnetic field and has high processing capacity per unit weight. Some tests on a tungsten ore have shown that , compared to a double-disk magnetic separator, it has four times higher capacity per unit weight and produces a tungsten concentrate with 3.79% higher grade and 5.27% higher recovery.
This new device would be suitable for concentrating weakly magnetic minerals. For fine particles down to around 38 microns, spirals give more satisfactory results. Smaller particles than 38 microns must be upgraded by HGMS or possibly centrifuges. The centrifuge unit until recently had a limited capacity of only 45 dmt/hr and they were operating in batch discharging mode. Now the capacity of centrifuge unit is over 100 dmt/hr and they have continuous discharge. Like HGMS, a centrifuge works much better in a narrow size consist. The final tail is dewatered in a high rate thickener before deposition in the tailing pond.

Concentrate Thickener

The concentrate from the two stages of magnetic and gravity separation is thickened to about 60% - 70% solids. Thickener underflow and hydro-separator underflow are pumped into the agitated slurry storage tanks before filtration.

Flotation

Flotation columns are widely used in mineral processing industry to effect separation between disperse phases based on differences in their affinities for air bubbles. However the effective design and scale-up of flotation columns remain a difficult problem. Their design has been based on the use of analogy with chemical kinetics. Use of this procedure is contrasted with mass transfer.