FLOTATION TECHNOLOGY
Eriez StackCell two stage flotation
It has been known for some time that
conventional flotation is inefficient for
floating ore particles that are too small or
too large. This is a result of the inherent
inability of conventional flotation tank cells
to be simultaneously optimised for fine and
coarse particle flotation. This phenomenon
has been reported anecdotally in a number
of plants where recovery was measured as a
function of size. By increasing the rotor
speed in a conventional cell, the recovery of
fine particles could be increased. However, at
the same time, the recovery of coarse
particles was decreased.
Eriez says it has addressed this problem by
commercialising the StackCell “two stage”
flotation device. The two stages are two separate
functional chambers within the StackCell. The
first stage introduces high energy which is
optimal for contacting and attachment of bubbles
and particles. The second stage, which receives
the aerated pulp from the first chamber, has low
energy which is optimal for bubble-particle
flotation with minimised drop-back, a major
cause for the low recovery of coarse particles. By
keeping the stages isolated, high shearing
energy can be introduced into the first cell alone
without passing that energy into the second
stage where it is detrimental.
The attached image shows a cutaway of the
StackCell and each stage. Ore pulp and air are
mixed with high specific energy in the inner tank
or contacting chamber. After a short residence
time, they are ejected evenly into a second tank
or separation chamber. Centrifugal and shear
forces prevent aerated pulp from returning to the
contacting chamber. In the separation chamber,
low forced convection facilitates successful
transport by buoyancy into the froth phase. Plant
trials with the StackCell on a variety of metal
sulphide ores, including nickel and copper, have
shown that the StackCell can achieve equivalent
grade and recovery in about 20% of the time
required by conventional mechanical cells.
“Reducing the working volume of a mechanical
cell by five times will have a dramatic impact on
the costs of a flotation facility. As an example,
we share herein a case study which compares
the costs of Eriez’ StackCell-70 against a
conventional 70 m 3 generic tank cell. The
StackCell-70, which is currently operating at
several sites, has the equivalent process
capability of a roughly 70 m 3 conventional tank
cell. For this case study, we are considering that
six cells are required in series, which is a typical
configuration for rougher/scavenger. The owner
of the operation therefore has the choice of
installing six StackCell-70s or six generic 70
m 3 conventional cells. For the comparison, we
will assume the conventional tank cells are
32 International Mining | NOVEMBER 2019
gangue or direct flotation steps to recover
lithium-rich micas, such as lepidolite and
petalite or the spodumene itself. Dr Pablo
Dopico, Global Technical Manager for
industrial minerals for Clariant Mining
Solutions states: “Clariant Mining
Solutions has developed an expertise in
the beneficiation of lithium ores by direct
and reverse flotation using customised
FLOTIGAM and FLOTINOR collectors and
FLOTANOL frothers, and a number of
spodumene operators globally have found
that Clariant flotation reagents provide
the optimal combination of recovery,
grade, and value.”
While a few lithium projects around the globe
are being delayed and some previously operating
mines have been idled, AMG Mineração in
Nazareno, Minas Gerais, Brazil remains a bright
spot in the developing story of spodumene
mining. They became a major producer of
tantalum from pegmatite ores in 2009. “When
AMG Mineração decided to expand their mining
of pegmatite ores to enter the spodumene
market, Clariant Mining Solutions was ready with
a suite of reagents to support AMG Mineração’s
development of the flowsheet for the
beneficiation of their complex spodumene ore.
After evaluating several reagents in their pilot
plant, the best performing combination of
collectors and frothers from Clariant Mining
Solutions was identified, including a spodumene
collector that is part of Clariant’s EcoTain family
of products. Clariant’s EcoTain products follow a
systematic, in-depth screening across 36 criteria
and significantly exceed market standards in
sustainability, have best-in-class performance,
and contribute to the sustainability efforts of
Clariant’s customers and Clariant itself.”
AMG Mineração started production of
spodumene concentrate in 2018, and Clariant
Mining Solutions supported the start-up by
making its global resources available, including
Clariant’s technical team at its flagship Mining
Application and Development Centre (CADM) in
Belo Horizonte, Minas Gerais. Helen Martins,
Technical Sales Engineer with Clariant Mining
Solutions in Minas Gerais, stated: “Clariant aided
in the start-up offering technical know-how in the
handling of collectors and their application in
mining while also being flexible, adapting
packaging to the needs of the operation during
the ramp-up mode, and even providing
temporary dosage equipment.”
Pedro Rollo, Head of Clariant’s CADM, added
that, “the location of our laboratory in the heart
of the mining industry in Brazil is really
conducive to working with our customers,
allowing their metallurgists and process
engineers to visit our lab and witness the
flotation tests.” IM
Illustration of the industrial-
scale StackCell
connected with a 300 mm drop between each
pair with a 1,000 mm drop between each
StackCell as a worst case. For estimating the
building envelope, we will define the highest
point in the elevation as the distance to remove
the mechanism in one piece from the highest cell
in the train. The bank of StackCells in this
comparison will occupy less than 50% of the area
and volume compared with conventional cells.
The foundations will also require about 25% of
the load requirements when the tanks are filled
with pulp. The installed motor power is about
40% lower for the StackCell, although it is more
than 200 times higher in the bubble-particle
contacting chamber, where more energy is good,
and zero in the bubble-particle separation
chamber, where more energy is bad.”
Since capital building costs such as concrete,
steel and piping will scale with area and
operating costs such as ventilation and heating
will scale with volume, shrinking the footprint by
50% and reducing the load requirements to 25%
will lead to a dramatic reduction in plant
construction costs. Additionally, reducing the
electric motor power by 40% and the building
envelope by 50% will significantly lower
operating costs.
Clariant solutions for hard rock
lithium flotation
Flotation reagents are at the heart of the
process. In the face of the growing demand for
lithium for the manufacture of electric vehicles, a
significant number of lithium mining projects are
being developed across the globe. Lithium salts
have been traditionally extracted from salt flats,
however a growing share of the global
production of lithium is now coming from
spodumene ores.
Spodumene is a lithium aluminum inosilicate
found in pegmatite ores and the beneficiation of
spodumene ores to produce spodumene
concentrates is very dependent on the nature of
the deposit. The flow sheets are as diverse as the
number of deposits where they often include
either reverse flotation steps to remove mica