PROCESS DESIGN
The FLSmidth RC™ technology is based on
dense-media separation and is combined with a
lamella plate design, which is unique to the
RC™ and, therefore, allows for the recovery of
the valuable material in the processing plant
Processing performance
Paul Moore looks at some mineral processing developments,
designs and initiatives with a focus on innovation
ack in October 2015, the inauguration
celebration for a pilot plant for a dry iron
ore concentration process, developed by
New Steel of Brazil, took place in Ouro Preto,
Minais Gerais, Brazil. New Steel has developed a
revolutionary new process called Fines Dry
Magnetic Separation (FDMS) for iron ore
concentration that utilises Loesche grinding
technology and is considered 100% sustainable
and New Steel believes it to be unprecedented
in the world.
The New Steel FDMS pilot plant uses a mobile
ore grinding plant (OGPmobile) which consists
of three 40 ft ocean containers. The machinery
for grinding, classifying, product separation and
material transport is installed in two of the
containers. The third container contains the
process control system and the central control
room. This container can also be used as a
laboratory and for spare parts and equipment
storage. The concept behind the OGPmobile
also enables it to be used in hostile geographic
B
The Loesche OGPmobile at New Steel's pilot
66 International Mining | JANUARY 2018
at and climatic conditions, and allows the
individual containers to be assembled and
dismantled easily. A power supply and a good
foundation is all that is required for operation.
For New Steel, the OGPmobile allows it to
produce up to 300 t of grinding product for
direct treatment in subsequent processing
stages. Grinding tests are performed to
determine the specific grindability factor and
the optimum process parameters, such as
grinding pressure, grinding energy, wear values
and flow rate of process gas. These provide the
basis for scale-up in industrial grinding plants.
The OGPmobile provides the user with a means
of calculating the effect of Loesche grinding
technology on the overall material flow in their
processing plant and is a convincing way to
demonstrate its benefits.
Things are now moving rapidly with New
Steel’s FDMS. It uses a mechanical dryer,
powered by environmentally friendly natural gas
or biomass, to reduce the ore’s moisture
content; the product is
then classified into
various fractions and
separated
magnetically. It
bypasses the
traditional wet
method of steel
processing, which
uses at least 1,000
litres of water in the
separation of each
tonne of ore. Dry
processing enables
higher mass and
metallic recovery, and
allows access to
smaller iron ore deposits without losses due to
water dislodging. New Steel told S&P Global
Platts in September 2017 that it was imminently
expecting a permit to build its first commercial
size FDMS plant, with Loesche grinding
technology, to be located in Minas Gerais state
in southeast Brazil, and which will reprocess
tailings produced by Vale. The plant is expected
to start operations in 2019 and New Steel says
that interest in the dry processing has grown
both in Brazil and elsewhere, following the
Samarco tailings dam failure. Aside from Brazil,
New Steel has patented the FDMS process in
Australia, Mexico, Argentina, Ukraine,
Kazakhstan, Armenia, Azerbaijan, Belarus,
Kyrgyzstan, Turkmenistan, the USA, Russia,
Saudi Arabia, South Africa and Mongolia.
Orway helps optimise grinding at
Kevitsa
The Kevitsa open-pit mine in Finland is located
approximately 142 km north-northeast of
Rovaniemi, the capital of Finnish Lapland. The
mine hosts significant quantities of nickel-
copper-cobalt-PGE (platinum group elements)
ore and is one of the largest ever mineral
discoveries in Finland. The operation was
commissioned in 2012, and consists of a partial
secondary crushing circuit followed by an AG-
pebble grinding circuit with two partially closed-
circuit AG mills and a single closed-circuit
pebble mill. The ore is variable and can range
from average competency to extreme. As a result,
the circuit can swing from being AG limited to
pebble mill limited. When processing extremely
competent ore, the circuit becomes AG mill limited,
restricting throughput. This prompted the staff at
Kevitsa to approach Orway Mineral Consultants
(OMC) to model the circuit and conduct
simulations to confirm optimisation strategies to
maximise throughput during these periods and to
provide new insights and suggestions.
Prior to optimisation, the primary crushed
product was partially secondary crushed, with
the -100 mm/+25 mm secondary crushed prior
to feeding the AG mill. The +100 mm lump
material and -25 mm fines reported directly to
the AG mill feed. The proportion of +100 mm
material in the primary crushed product was
very high, at approximately 40% of the total
primary crusher product. This material was
building up in the AG mills, limiting throughput.
The classification efficiency for the AG mill
cyclones was also observed to be very poor.
These cyclones were operating at very high
circulating loads in an attempt to improve the