Mineral Processing: Separation Flashcards
Generally accepted as the most simple and economical of all concentration methods
* Mineral particles are separated by virtue of the differences in density - the greater the difference in density between two minerals, the more easily they can be separated
* However, the smaller the particles, the more powerful are fluid and viscous forces relative to gravity
Gravity Concentration
– typified by jigging, which takes advantage of differing rates of settlement
separation in vertical currents
- A process of sizing particles by means of an upward current of fluid
- Reverse of gravity sedimentation; Stokes’ Law applies
- Uses one or more sorting columns where the feed is separated into two fractions by their terminal velocities
- Consider a sorting column with a constant water pressure supply from the bottom, calibrated to separate minerals of separating size d
- Particles < d will move up the column; > d will report to underflow
- “enhanced decantation
Elutriation
particles are immersed in a bath containing a medium of intermediate density so that some particles float and others sink
dense-medium separation
or ‘thin film sizing‘ – shaking table or a spiral separator
separation in streaming currents
- Also known as Gold Panning and Miner’s Pan
- Used as preliminary concentration of heavy-metal ores
- Most commonly used for gold
Panning
- the minerals to be separated are stratified in a bed rendered fluid by a pulsating current below to effect stratification
- The bed “dilates”, accommodating heavier, finer particles to settle through the interstices of larger particles; larger particles experience hindered settling
Jigging
Uses the difference in magnetic properties between minerals
* Separation by applying magnetic fields:
– Magnetic valuable minerals from gangue (Fe3O4 from SiO4)
– Non-magnetic valuable mineral (SnO2 from (Fe,Mn)WO4
– Removal of tramp metals
Magnetic Separation
repelled along the lines of magnetic force to a point where the field intensity is smaller
Diamagnetic
attracted along the lines of magnetic force to points of greater field intensity
Paramagnetic
Ni, Co, Mn, Cr, Ce, Ti, O and Pt group elements also exhibit paramagnetism
* For most cases, PM of minerals is due to the presence of IRON
Ferromagnetism
high surface charge
Insulators
no charging effect
Conductors
- A method of wet concentration of ores in which separation of valuable minerals from gangue is effected by utilizing the surface-chemical properties of the minerals to enable physical separation
- Generally, separation is made possible by attaching a mineral to a bubble and letting it float above the bulk phase, leaving the other “unwanted” mineral submerged
Flotation
– The only flotation process which is of commercial importance
Froth Flotation
When air bubbles are passed through a slurry containing fine mineral particles, with certain minerals capable of attachment to the bubble
Froth Flotation
UNIQUE among applications in metallurgy, as it involves all possible interfaces:
– Air-Water (Gas-Liquid)
– Mineral-Water (Solid-Liquid)
– Air-Mineral (Gas-Solid)
Flotation
is capable of concentrating selectively and successively a number of different minerals which originally coexisted in a given ore deposit
Froth Flotation
- Is the force acting parallel to the surface of a bulk of substance, which opposes any effort to extend the interfacial area
- The natural tendency of a liquid to decrease its surface
- Denoted by γ
Surface Tension
Collection of bubbles; governed by the equation:
FROTH
maintenance of a body of bubbles at and above the upper surface of the pulp
FROTHING
Frothing Agents
* also referred to as
FROTHERS
lowers ST; the reagent concentrates at the bubble surfaces
Organic frothers
increases ST; they concentrate away from the surface
Inorganic Frothers
