Review Topic - Optimising the Efficiency of Primary
Aggregate Production
The UK quarrying industry is under increasing pressure to
improve the sustainability of its operations. Ways in which this
can be achieved include reductions in quarry fines production
and reductions in energy and water consumption. There is no
standard definition for quarry fines, but it is often taken to
be material less than 6mm, for which there is sometimes no
market. The objective of some ALSF projects has been to optimise
the production of primary aggregates from quarry operations,
whilst minimizing the generation of unsaleable mineral wastes
and energy consumption.
Planning and design phase
One way of optimising production is to improve aggregate
reserve definition by use of better, more accurate, exploration
and assessment techniques. ALSF projects have been involved in
developing and comparing different methodologies including
geophysical surveys (electromagnetic and resistivity surveys and
use of ground probing radar) and “match to specification”
analysis, relating the resource to the desired product. This is
important in the increasingly complex glacial deposits that are
now being worked. The new quality assessment and presentation
techniques allow quarry design and scheduling based on yields of
individual products rather than on broader sand, gravel and silt
classifications.
Operational phase
Although no ALSF projects have looked at minimising
fines through blast optimisation, the review considers
the potential application of research carried out
elsewhere.
Several ALSF projects considered opportunities for
minimising fines production through carefully selected
or modified crushing and screening circuits. The
selection and set-up of the appropriate crusher was
shown to be a key factor in optimising the product to
fines ratio in a range of rock types. A number of
comminution flow sheet computational simulations have
been undertaken within case studies in ALSF projects,
with the objective of modelling and then measuring
changes in product and fines output.
The main aim of another ALSF project has been to
identify and appraise process methods for the removal of
quarry fines that do not use, or that conserve the use
of, water (impact on which is a major element of
environmental footprint). Water has also been a major
factor behind projects investigating the potential
benefits of a slurry pump transport and ultrasonic
separation system, and looking at different drying and
attrition technologies to remove clay.
Post-closure phase
Stockpiles of unsaleable products can remain a
problem after an operation ceases, if this material
cannot be used in planned restoration or disposed of in
some way for a beneficial use. However, consideration of
this aspect was beyond the scope of this review.
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the Efficiency of Primary Aggregate Production"
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