SMART DOG MININGTM
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Tonnage vs Volume
A Weighty Subject that speaks volumes or what
is the true plant capacity
What is the capacity of your operations? Ask this question at any
mine operation and you will get an answer of so many tons (or
tonnes) per hour, day, or year.
While it is easy to measure the weight of the material being feed to
a plant by using a scale, most (if not all) processing equipment are
basically volumetric in operation. The equipment has fixed
dimensions, which allow it to process a certain volume over time.
And yes even crushers are designed to pass a certain volume per unit
time. Taking the volume over time and a given (or assumed – more
late) builk density (more precisely, the volumetric mass density,
the mass per unit volume) of the material you have the weight
capacity.
Some equipment is often sized by its volumetric capacity. Belt
conveyors and feeders are close to pure volumetric process and often
have their capacity expressed in volumetric units (or as a certain
mass per unit time at a given bulk density). Flotation cells are
usually given as having a certain volumetric capacity (80 cubic
feet, 300 cubic meters, etc.) and then using the actual (or assumed)
retention time and (again given or assumed) bulk density, you have
the weight capacity.
Stockpiles have a capacity, often expressed in tons, but actually a
volume based on the length, width, height, and bulk density. And
this can change depending on a lot of factors.
Now the issue of given or assumed bulk density. A problem occurs
because a material will have a different bulk density depending on
where it is in the process. Before mining, during mining, or after
sitting in a stockpile, and then during processing as it is
concentrated. This can affect the apparent bulk density by a
significant amount. Variations of + and – 10% are common. This is
often taken into account in the mining operations where the bulk
density in place, loose, and compacted are accounted for. But the
changing in size of the material also impacts the bulk density. As
the material is reduced in size (crushing and grinding) the space
between particles is also reduced generally increasing the bulk
density. Adding water to create a slurry also impacts it.
So understanding the actual plant capacity is more than just looking
at the ratede tonnage capacity. Actually many operational problems
can be related to not taking this in to account. Feeding a piece of
equipment at a higher volumetric rate than it can handle or at a
lower volumetric rate than the material needs can lead to poor
performance. While the over feeding is an easy one to spot as grade
and recovery often suffer, the under feeding can be harder to
identify. It most often is noted in grinding (over grinding), but
can effect other processes. In flotation producing a lower grade
than expected, byt floating more gangue than planned maybe harder to
spot.
As ore changes this whole issue can change, which requires periodic
review and checking.
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40+ years’ experience in the mining industry with strong mineral
processing experience in precious metals, copper, industrial
minerals, coal, and phosphate
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Operational experience in precious metals, coal, and phosphate plus
in petrochemicals.
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Extensive experience performing studies and determining feasibility
in the US and international (United States, Canada, Mexico, Ecuador,
Columbia, Venezuela, Chile, China, India, Indonesia, and Greece).
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E-mail:
info@smartdogmining.com
