143 rd SME Annual Meeting 26 February 2014 Mike Albrecht, PE Teaching new employees about...

143rd SME Annual Meeting 26 February 2014Mike Albrecht, PE www.smartdogmining.com

Teaching new employees about processing equipment

What it is and how it works


What are these?

Storage tanks, surge tanks, float cells, or leach tanks?


Some recent questions

– How do you separate magnetite from beach sands?

– How does a dense media system work?– What are the key parameters to control in cyclone

separation of solids, for a SAG mill discharge? – Can somebody give me a good orientation of

how a cyclone separation works? – Does anyone have any experience in Magnetic

separation in the aqueous phase?


What it is and how it works

• We use some large and unusual equipment. • Understanding it is important to good

operations• How do you teach a new employee. • This presentation will be an introduction – in particular to gravity separating equipment.


Jigs

• Principles of particle motion under pulsed-flow hindered-settling conditions.

• Separating mechanisms are: – hindered settling, – differential acceleration, – and consolidation trickling.


Jigs

• The particles became rearranged in layers of increasing density from bottom to top.

• Jigging can be applied to a wide size-range of particles with top sizes up to 200 +mm.


Jigs


Dense Media Vessels

• Feed is slurried in a medium with a specific gravity close to that of the desired separation. – The lighter fraction floats – and the heavier fraction sinks.

• Heavy medium are suspensions of magnetite or ferrosilicon in water.


Dense Media Vessels


Dense Media Cyclone

• Similar to a vessel, a slurry of ore and medium (magnetite or ferrosilicon dispersed in water) is admitted at a tangent to the cyclone.

• The higher specific gravity moves along the wall of the cone and is discharged at the apex.

• The lighter particles of lower specific gravity move toward the longitu dinal axis of the cyclone and through the vortex finder.


Dense Media Cyclone


Tables

• Separation is by flowing film. • The feed fans out over the table deck by:– differential motion – and gravitational flow

• The particles become stratified in layers behind the riffles.


Tables

• This stratification is followed by the removal of successive layers from the top downward by cross-flowing water as the stratified bed travels toward the outer end of the table


Tables


Water-only Cyclone

• Similar in operation to Dense Media cyclones, but with no media, using only water and inertia, because of the wide angle or angles in its conical bottom.

• Predominately used in coal, and a few other applications.


Water-only Cyclone


Launders/Sluices

• Launders/Sluices have been used for mineral processing almost as long as jigs (or perhaps longer).

• They are simple to build and operate, but require a relatively large amount of space for processing anything more than a few pounds an hour of material.


Launders/Sluices


Spirals

• Spirals are a more recent development than launderers and date from the mid 20th Century (CE).

• While essentially a spiral launder the force on the particles from the centripatel action enhances separation.


Spirals


Centrifugal Concentrators

• Particles >0.5 mm a water based gravity separation process is very efficient.

• 0.5 mm to 0.1 mm efficiency drops off, but the devices can still be effective.

• < 0.1 mm or with a small density difference, the speed with which the particles will move apart maybe less than the speed at which the water is flowing.



• One solution - increase the force on the particles by speeding up their movement.

• Centrifugal concentrators can increase the force to 50 to 150 times

• They can separate particles which previously where impossible to separate by other than flotation or chemical processes.


Flotation

• Flotation - a physicochemical method. • It involves chemical treatment of a pulp to

create conditions favorable for the attachment of particles to air bubbles.

• Some particles are not readily wetted by water (hydrophobic),

• While others are readily wetted by water (hydrophilic).


Flotation

• By the addition of chemicals these proper ties can be enhanced.

• Air bubbles are created by the agitator mechanism which draws air down the shaft.

• The air bubbles carry the hydrophobic particles to the surface of the pulp

• Form a froth which is skimmed off • The hydrophilic particles remain in the pulp.


Flotation


What are these?

• Float Cells


More Information

• Agricola, Georgius. (1556). “De re metallica.” Translated 1950 translated by: H. C. Hoover, L.H. Hoover. Dover, NY.

• Albrecht, M. C. (2013), “A Mining Engineers Notebook”, http://www.smatdogmining.com, 2013

143 rd SME Annual Meeting 26 February 2014 Mike Albrecht, PE Teaching new employees about...

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