MINERAL PROCESSING SITEby Eren Caner ORHAN |
This site is visited times since 15 October
1997
The OUTOKUMPU Flotation Concept consists of packages made up of products from the OK Flotation Machine Family. These are grouped under the following headings:
Flotation equipment comprises standard products from the OK flotation machine family:
Controlled air flow
An external blower is standard on OK flotation machines, to
ensure a well regulated air flow.
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Optimum size air
bubbles The specially designed OK mechanism produces the right size of buble from the supplied air, whatever the aeration rate. Sufficient
number of collisions |
Fast froth collection
Internal launders provide fast froth collection. Froth
crowders can be used to improve collection in special cases.
Low power draw
Less than 1 kW/sq.m is typical for large OK flotation
machines.
OK-TC flotation machines incorporate all the proven features of conventional OK flotation machines. They can be used instead of them, depending on the lay-out and space requirements.
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Uniform conditions
for mixing The cylindrical tank design maximises the amount of collisions between the mineral particles and air bubbles and minimises short circuiting. Effective
frothbed control |
Flexible and simple lay-out
The cylindrical tank gives the flotation section a flexible
and simple lay-out since all directions are equal with regard to
the feed and discharge points.
Flash flotation takes place in the grinding circuit. The liberated, easy floating particles from the classifier sands are recovered or skimmed by SK(Skim-Air) flotation machines.
Minimal overgrinding
The liberated valuable minerals are floated while still
relatively coarse, which prevents overgrinding.
High grade concentrates
These are produced in one stage to become part of the final
concentrate.
Improved dewatering
Coarse SK concentrates mixed with final concentrates improve
dewatering.
Proven benefits
Flash flotation has been successfully utilised with Ag, Au,
Pt, Cu, Ni and Pb ores.
Less cell volume required
Flash flotation recovers considerable amounts of valuable
minerals, so less cell volume required, or an existing flotation
circuit gains extra capacity.
Energy savings
The coarser final concentrate and the reduction in total cell
volume give energy savings in flotation and dewatering.
HG(High Grade) flotation machines are deeper in design than conventional flotation machines. They have been specially designed for cleaner flotation and are fitted with froth washing facilities and froth crowders.
High grade concentrates
The thicker froth bed and effective froth washing procedure
high grade concentrates with lower slime contents.
Reduced MgO contents
MgO content is reduced in Ni-concentrates
Simplified flotation circuits
More effective cleaner flotation simplifies flotation
circuits and reduces circulation loads.
For the cleaning stage OK developed the HG flotation machine. Essentially, the function of cleaning is to remove the last valuable ore particles as selectively as possible, and as any remaining pulp is lost to the ta,ilings after this stage. The design of the lower part of the HG cell is based on the OK cell to guarantee high recovery. The most distinctive difference from a conventional OK machine is in the upper part, where the rising froth is forced to pass through a tapered channel inclined so that the area through which the concentrate leaves the channel is considerably smaller than the surface area of the pulp. In the HG cell there is an abundance of finely dispersed air: The amount of air is higher than in conventional flotation and the froth layer remarkably thicker. The froth is washed by water sprayed through special nozzles, which distribute the water gently throughout the froth without collapsing it. The aim of this is to create conditions favorable to difficult flotation tasks, e.g. fine particle flotation.
In the selection of cells, size is a very important factor. In addition to this there have been dramatic increases in the size of individual floatation cells. These large cells have been designed using hydrodynamic scale-up criteria and have had wide industry acceptance. There are various sized cells manufactured by flotation equipment manufactureres.
After the determination of total volume required in the flotation, the individual cell sizes are determined. For example in a concentration unit there are two possibilities:
In this selection there are some factors that sould be taken in consideration:
There are some disadvantages of the large cells. First of all the conditioning will be more difficult than in the smaller cells. As the size is large, to supply the same yield in conditioning, a larger and complex motor, rotor and stator should be used and this will cause a more power consumption. The other thing is the repair of the more complex equipment will be more difficult. Another disadvantage is that they will cost more than a smaller cell.
Besides, larger cells have important advantages as they will increase the capacity of the process. Even if they are expensive than smaller ones, as they increase capacity an optimum number of cells and cost could be determined.
Eren Caner
Orhan
Hacettepe University
Ankara, Turkey
The Outokumpu Flotation Concept, http://www.tumsas.com/THEOUTOKUMPUFLOTATION.HTM
