Modern Mining June 2016

60 / 64

PRODUCT News
58 MODERN MININGJune 2016
in extreme acidic conditions on a copper
processing operation in the Middle East.
“The outcome of this project was yet
another derivative of these mills. In this
instance, we adapted the VXPmill’s design
to work in severe process conditions,”
says Terence Osborn, Sales & Marketing
Manager for sub-Saharan Africa at
FLSmidth.
He says the VXPmill is a vertically ori-
ented stirred media mill that is open to
the atmosphere and designed with a
modular impeller that has removable discs
and spacers. Slurry enters at the bottom,
travels upward through the mill chamber,
and overflows through a media retention
screen at the top. The rotating polyure-
thane discs activate inert ceramic grinding
media inside the milling chamber. This flui-
dises the media bed, attrition grinding the
particles in the slurry.
Osborn says the system is designed
to allow changes to the distribution of
the media and energy within the mill
by altering the number and spacing
between the impeller discs when the mill
is commissioned.
Assembly of the two mills will start
in August this year, followed by testing
at FLSmidth’s facility in Johannesburg.
The mills will then be containerised and
shipped to site and commissioned by
FLSmidth before the end of the year
where after they will play their role in
helping the copper producer improve the
VXPmills to be used in “severe process conditions”
Because they operate at a power intensity
that is higher than low speed mills and
overlaps that of high speed mills, one of
the major traits of VXPmills is their flex-
ibility, allowing them to be engineered
and manufactured for a host of grinding
applications.
This important characteristic has been
demonstrated again, with FLSmidth’s
South African operation in Roodepoort
involved in the engineering design and
manufacturing that will see VXPmills used
This VXP2500 in Zimbabwe was the first of the updated
VXP2500 mill series.
recovery of very fine copper particles.
Because the mills will be exposed to
pulp, they had to be engineered specifi-
cally for extremely acidic environments,
with a PH of 2,5. This meant the compo-
nents of the VXPmills had to be made from
a variety of materials that would not only
withstand arduous operating conditions
but also ensure that the plants could be
built within budget.
Osborn says this was a complex under-
taking providing various challenges for
the company’s local engineers. The South
African team also made extensive use of
the expertise of FLSmidth’s design engi-
neers in India.
Osborn describes the end result as an
ingenious solution. “We did not go for one
specific material selection, such as stainless
steel, but rather opted for a combination
of many different materials based on the
principal operational requirements of each
component as well as the suitability to
withstand the acidic environment. We do
not believe that there are many engineers
who would have been able to achieve this
outcome, over the time period and within
budget,” he says.
The end result saw only a 7 % increase
on the initial costing of the mills, with the
solution comprising a combination of
mild steels, austenitic and duplex stainless
steels, fibre reinforced plastics, as well as
polyurethane and polyurea coatings.
FLSmidth, tel (+27 10) 210-4820