COMMINUTION & CRUSHING
Automated feeder control
On the interface between mine and
mill are the primary crusher
installations, which are typically
the first bottleneck of large mining
operations. The production of large
crushers can be enhanced
significantly by optimising the feed
rate control. Historically, this is
achieved by manually controlling
the feed to the crushers, either via
controlling the dump traffic lights
or the apron feeder speed.
indurad radar sensors in its
indurad radar sensors in its iCrusher offering enable real-
iCrusher offering enable real-time
time measurement of the crusher or apron feeder levels,
thereby allowing automatic feeder control
measurement of the crusher or
apron feeder levels, thereby
allowing automatic feeder control. Fabian Riedel, VP Sales & Projects at indurad, confirms:
“Current and previous indurad projects have proven to increase production by up to 20%
sustainably over long periods. The indurad sensor systems can be installed above crusher
chambers to avoid over- and under-filling.” Such installations have successfully been implemented
in Chile, Australia and the US.
Most processes between primary crusher and mill are also constrained by volume flow (silos,
draw points, transfer chutes, etc) and it is therefore paramount to measure actual bulk volumes
within the process plant. Due to fluctuations in bulk density and material moisture, the
measurements achieved by belt scales (mass) are only indicative of the volume and necessitate an
over-design of bulk material handling equipment to avoid spillage and blockages. The indurad iBelt
volumetric belt scale enables real-time volume flow measurement under harsh conditions and does
not require frequent calibration as it is a contactless measurement method. It is therefore a
dependable component in any large plant's automation system. This has been shown in dozens of
installations in bulk material handling operations worldwide.
Riedel states: “indurad thus offers a unique package of autonomous functions for increasing
competitiveness according to specific customer needs. Automation solutions from indurad are
often in the spotlight as the general and safety regulations become stricter for mining companies
around the world.” indurad solutions, he says, not only improve productivity and operating costs,
but overcome several challenges: harsh environmental and process-related conditions, heavy
vibration, thick dust, varying measurement requirements like 1D, 2D, 3D, and high and low refresh
rates.
He said FLSmidth has developed new wear
surface technology that improves the robustness
of these parts and pushes the life of the rollers out
to around 10-12 months (as a goal) in true hard-
rock mining applications, bringing down the
would-be operating costs associated with
operating this grinding technology.
Dziedzina expected the maximum feed size of a
‘mining-ready’ OK Mill to be around the 160 mm
mark, opening the number of applications even
further.
He also saw the machine working in tandem
with FLSmidth’s EcoTails™ filtered tailings
management solution. By removing the difficult to
dewater ultrafines prior to flotation, tailings
filtration will become more efficient and less
expensive making it attractive to mine owners,
FLSmidth says.
“Miners are increasingly on the lookout for
ways to optimise their flowsheets,” the company
said. “Dry grinding and classification are one way
18 International Mining | APRIL 2020
media detritor) are set to play a major role in
achieving its target of lowering GHG emissions by
10% in the most “energy-intensive customer
processes” by 2025.
According to the company, the Vertimill
provides the lowest total cost of ownership
compared with other grinding mills in many
applications thanks to its high energy efficiency,
reduced media consumption, low installation cost
as well as minimal liner wear and maintenance.
Based on a review of the Vertimills currently in
operation and a comparison of their efficiency and
media consumption relative to a ball mill, Metso
estimates some 1.48 million MWh of energy was
saved and 652,000 t of CO 2 emissions were
abated in 2018 using the machines.
Boylston thinks developing a large-scale
comminution circuit that leverages both the HRC
and Vertimill could really display to industry just
how much energy can be saved by using such
equipment.
“We’re really looking for partners to take the
next logical step, which for me on a large plant is
two stage crushing into our HRC, then directly into
a Vertimill to save the most power and media
possible,” he said.
There are other manufacturers of fine grinding
technology that would argue their equipment
should be factored into new energy efficient
designs too.
Glencore Technology has its IsaMill™ fine
grinding technology, which was recently upgraded
with the addition of conical spacers. In tests in an
IsaMill processing pyrite concentrate for gold
recovery, these new spacers displayed specific
energy requirement reductions of 12.7-21.5%
depending on the P80 needs. The greater the fine
grinding duty, the greater the savings recorded,
the company said.
Meanwhile, FLSmidth has its VXP mills, which
to optimise not only the grinding circuit, but also
the flotation and tailings process at the same time.”
Dziedzina expects to provide more insight on were recently selected by Vista Gold as the
preferred fine grinding mill in a flowsheet for its
Mt Todd gold project in the Northern Territory of
OK Mill timelines around MINExpo later this year,
but even at this stage, he could clearly see the
technology having a massive industry impact.
“The development of HPGR in mining has been Australia.
Outotec’s HIGmill ® is also gaining popularity as
miners look for more energy efficient final grind
the biggest technology shift in comminution
during my time within the industry,” he said. “This
VRM technology could be as big – if not bigger –
than that. That is attainable, it is just a matter of
time and money.
“The future of mining is (hopefully) dry
classification and separation technology with the
highest energy efficiency and lowest impact on
our environment.”
The daily grind
Energy efficiency is one of the core attributes of
Metso’s Vertimill technology, hence the reason
why it, the HRC and the company’s SMD (stirred
options.
The Outotec HIGmill has several key
advantages over other fine and ultra-fine grinding
technologies, according to Bjorn Nielsen, Director
– Product Management, Grinding at Outotec.
“The vertical arrangement means that gravity
helps to compress the media bed, ensuring high
contact loads between media and symmetrical
energy transfer throughout the charge. As a result,
the HIGmill has a very broad operating range –
energy efficiency is very similar for a range of
media charge levels and operating speeds.”
This operating flexibility lets the machine deal
with variations in feed particle size while
maintaining efficient operation, according to