Mineral Processing: LIBERATION Flashcards
- an inorganically formed, naturally
occurring homogenous solid having a
definite chemical composition and an
orderly crystal structure.
Minerals
- is a mineral deposit w/c can be
ECONOMICALLY EXPLOITED to become a
source or supply of a particular material
Ore
all minerals having NO
ECONOMIC VALUE
Gangue
also known as Mineral Dressing, Ore Dressing, Mineral
Beneficiation, Milling
Mineral Processing
- Mechanical Separation of valuable
minerals from valueless minerals
Mineral Processing
“de-stresses” the transition between the
mineral source, to the final metal product
Mineral Processing
- To bring valuable mineral or the
final product into suitable
technical condition as required
by the process - Undesired constituents of the
original ore must be removed or
reduced below the specified
units
TECHNICAL
- To provide the cheapest way to
eliminate the unwanted
minerals - Reduce unit material handling
costs
ECONOMIC
- Concentration of desired mineral =
Freight Savings
Waste Rock Minimization =
Improved
Metal Purity!
Effective Material Reduction =
Reduced
Treatment Charges!
- particle size reduction by breaking,
crushing, or grinding of ore, rock, coal, or
other materials - It is a critical component in most mineral
processing flowsheets and can serve
several purposes - Goals: LIBERATION and SEPARATION
COMMUNITION
- Segregation of Materials into products
characterized by difference in size - Screening and Classification
SIZING
- Separation of valuable minerals
- Based on the physical characteristics of
minerals
CONCENTRATION
- Solid/liquid separation by thickeners and filters
DEWATERING
- Bins, conveyors, feeders, pumps, etc.
AUXILIARY OPERATIONS
- output is the mineral form of the valuable
minerals and its liberation size - identification of the mineral form by
comparison with known samples of
minerals and linear testing under the
microscope
ORE MICROSCOPY
- A beam of electrons is focused on to a
point on the surface of the sample - The elements being detected both
qualitatively and quantitatively by their
resulting x-ray spectra
ELECTRON PROBE ANALYSIS
- Measure the average spacing between
layers or rows of atoms - Determine the orientation of a single
crystal or grain - Find the crystal structure of an unknown
material - Measure the size, shape and internal
stress of small crystalline regions
XRD
- Mineral Dressing consists of two steps:
LIBERATION AND SEPARATION
impracticable if the 1st step
has not been successfully accomplished!
SEPARATION
The essential prerequisite for the
separation of an ore into valuable and waste
fractions
LIBERATION
Incomplete liberation limits either ____________
GRADE OR RECOVERY
Uncrushed rock
Grains, Grain size
**
Crushed rock
Particles, Particle size
Particles can consist of a single mineral;
FREE PARTICLES
When a particle consists of 2 or more
minerals, this is called
LOCKED PARTCLES
The percentage of a mineral or phase
occurring as free particles
DEGREE OF LIBERATION
the percentage of minerals that exist as locked particles
DEGREE OF LOCKING
– Happens when the interface between
grainsis weak
– Fracture at the grain boundaries; liberation
at the mineral grain
INTERGRANULAR
- Multiple separating tests
*Microscope counting techniques - Polarized light mineragraphy
QUANTIFYING F
– Fracture occur across the grain; occurs
when mineral has weak structure
– Most common liberation problem
TRANSGRANULAR
– Localized stresses (@ the surface)
–Occurs when insufficient energy is applied
to cause significant fracture of the particles
ABRASION
- Contains both valuable and gangue
minerals! - A large proportion of the difficulties
experienced in mineral separation are
associated with the treatment of these
particles
MIDDLINGS
– Impact
– The applied energy is well in excess of
which is required for fracture
– Under these conditions, many parts of the
particle is overloaded
– Comparatively large number of particles
with a wide range of sizes
SHATTER
– Slow compression
– Occurs when energy applied is just
sufficient to load comparatively few regions
of the particles to the fracture point
– Only a few new particles produced
CLEAVAGE
TYPES OF MIDDLINGS
further size reduction increase liberation
RECTILINEAR
TYPES OF MIDDLINGS
further reduction will increase liberation but a significant part are still very hard to liberate
SHELL
TYPES OF MIDDLINGS
difficult to liberate
VEIN
TYPES OF MIDDLINGS
very fine reduction treatment
OCCLUSIONS
- Occurs by preferential fracturing
- No further liberation may be obtained by
additional comminution - Possible if mineral has:
– Macrostructural weakness (coal beds)
– Microstructural weakness (schists)
– Microstructural differences in physical
properties of adjacent minerals (galena and
quartz)
LIBERATION BY DETACHMENT
- An empirical relationship between energy
consumed during size reduction has been
proposed by Hukki;
Energy-Size Reduction Relationship
- Concerned with the relationship between
energy input and the particle size made from
a given feed size - Various theories were put forward; none
was individually satisfactory
COMMINUTION THEORY
considered to be proportional to one side of
that area; therefore, it is inversely
proportional to the square root of the
diameter
crack length in unit volume
Applicability of Energy Laws
- For Crushing (>1cm)
KICK’s
Applicability of Energy Laws
-For Fine Grinding (10 - 1000μm) →
RITTINGER’s
Applicability of Energy Laws
-For Rod Mill and Ball Mill grinding →
BOND’s
Applicability of Energy Laws
For ranges approaching grinding limit →
No practical application!
- For crushing, it is often taken as the ratio of
the feed opening (gape) to the discharge
opening (set) of equipment
clue work: “ratio”
Reduction Ratio
