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Our aim is to become Australia's leading mineral processing technology
provider and the most successful total solution provider. We plan to
design and deliver total project solutions using exclusive technology
where possible. The speed of response to clients needs and a "technical
capability gap" is critical and central to the new economy. Engineering
services will not be delivered in the future as they were in the past
and technology is the key to the new way of project delivery.
Comminution
Comminution is the term applied to the process by which the particle
size of an ore is progressively reduced. It is one of the first and
perhaps most important steps in the processing of ore from a mine. The
purpose of comminution may be:
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To produce material of a controlled particle size and shape
such as quarry gravels for road building, or sands for the construction
industry or the fine grinding of cement clinker
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To increase the surface area available for chemical reaction such as leaching of low grade gold ores by cyanide solution
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To liberate or free a valuable mineral from worthless gangue material prior to concentration or separation
 Crushing
Crushing is the coarse comminution stage
where "Run-of-mine" (ROM) ore up to 1.5m diameter is reduced in size to
about 5-20mm and this is accomplished by compression or impact of the
ore against rigid surfaces. It is usually a dry process, performed in
several stages with small reduction ratios of between 3 and 6 : 1 in
each stage. It is usually two or three stage operation.
 Grinding
Grinding is the final stage of
comminution designed to reduce the particle size fine enough to
complete liberation of the valuable mineral or produce a high surface
area. The grinding is usually carried out wet in a rotating cylindrical
mill containing a charge of loose grinding medium in the form of either
steel rods or balls.
Flotation
This process involves the introduction of air bubbles by one means or
another into mineral/water pulp. The mineral particles selectively
attach to the air bubbles which act as a balloon to provide the
necessary buoyancy to carry the minerals to the surface of the three
phase pulp (liquid/solid/gas) where stable froth holds the mineral and
can be skimmed off to produce a concentrate.
Gravity Concentration
Gravity concentration is, next to
hand picking, the oldest form of mineral processing. It was the
dominant process for over 2000 years. However, in recent times, its
importance has declined due to the development of other processes.
Gravity concentration is the separation of two or more minerals,
usually of different specific gravity, by their relative movement in
response to the force of gravity and ore or other forces, which is
generally the resistance to motion by a viscous fluid such as water.
 Thickening
Thickening is the removal of suspended
solid particles from a liquid by gravitational settling. Such
operations may be divided up into thickening and classification.
Although governed by similar principles, these processes differ in that
the primary purpose of thickening is to increase the solid
concentration, whereas classification serves to remove solids from a
relatively dilute stream. The most common type of sedimentation unit is
the cylindrical continuous thickener with mechanical sludge-ranking
arms.
 Filtering and Drying
The purpose of filtering slurries or
suspensions of minerals may be to recover the solids, or the clarified
liquor, or both. Examples of the first requirement are for metallic
concentrates and clean coal, and of the second are for cyanide leaching
of gold/silver ores, acid leaching or uranium ores and polishing zinc
sulphide solutions prior to electro deposition. An efficient filtration
system is essential where the products are of high value or where
inefficiency, may cause, for example, and effluent problem. When the
end product has to be dried, the prior mechanical separation of a high
proportion of the liquor will reduce costs by decreasing energy
requirements for drying.
Leaching
Leaching is the process of extracting a soluble constituent from a
solid by means of a solvent. In extractive metallurgy, it is the
process of dissolving a certain mineral (or minerals) from an ore or a
concentrate, or dissolving certain constituents from metallurgical
products such as calcines, mattes, scrap alloys, anodic slimes, etc. In
this respect, either one of two purposes can be achieved.
Adsorption
Understanding the mechanism of gold adsorption
by activated carbon is important because the CIP/CIL processes work as
a result of this chemical occurrence. "Activated Carbon" is a generic
term for a family of highly porous carbonaceous materials that cannot
be defined by a structural formula or chemical analysis. Each particle
possess millions of tiny interlocking holes, and under a microscope
looks like a sponge. Thus the carbon has a very high internal surface
area (ie. one gram of activated carbon which is the amount that would
fit the end of a human thumb, has the same surface area as two football
fields). Activated carbon is the adsorbent that increases the
concentrate of gold, post the leach solution phase.
Stripping and Smelting
Because the absorption of material
onto activated carbon is so efficient, the stripping of that material
off the carbon is critical to recovering it for sale. The material is
stripped by washing the carbon with hot chemicals to make a highly
concentrated solution. This solution is treated in electro-winning
cells to make a solid mud that is dried and smelted to be poured into
bars.
Sampling and Assaying
An often overlooked section of
mining, sampling and assaying is used in almost every facet of
production. The invention of Atomic Adsorption Spectrophotometry (AAS)
is the single most important discovery that has aided the analysis of
ores and minerals in the last twenty years providing results with
incredible accuracy. Sampling is the means whereby a small amount of
material is taken from the main bulk in such a manner that it is
representative of that larger amount. Great responsibility rests on a
very small sample, so it is essential that samples are truly
representative of the bulk. Assaying and chemical analysis involves the
measurement of the amount of a substance in its environment. For
example, the determination of cyanide in CIP solutions or the
determination of gold in mine ores. Analyses are carried out in order
to try to maintain optimum operating conditions in all aspects of mine
and plant production. To this end, assaying for gold is used to
evaluate ore reserves, monitor mine feed to the processing plant, assay
the bullion purity and many other intermediate processes in the mining
and mineral processing of gold.
Magnetic Separation
Magnetic separation processes use the magnetic properties of minerals
to separate them into magnetic and non-magnetic fractions. In mineral
sands, processing the slightly magnetic illmenite is seperated from the
higher value, but non-magnetic, rutile to make a rutile concentrate.
Solvent Extraction
After leaching valuable material from an
ore or concentrate, the valuable material is distributed in the solvent
(usually water plus chemicals). It is often in simillar concentrations
in the solvent as it was in the ore. Some metals will transfer from
this water solution to an organic immissible liquid solution if a
suitable transfer chemical is added to the organic liquid. The two
phases (water and organic) are well mixed and allowed to separate (this
is why it needs to be immissible i.e unmixable). The organic phase is
much smaller in volume than the water phase, so the concentration of
valuable material is much higher and easier to treat by a stripping
process.
Process Control
Automated control systems can help an
operation improve its efficiency. A control system is made up of
several components or subsystems arranged to perform a desired control
function.
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Open Loop or Programmed Control - control action is independent of both the process input and output
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Closed Loop Control Feed Forward - control action is determined by the process input, but is independent of the process output
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Closed Loop Control Feedback - the control action is somehow dependent on the process output
Flowsheets
Flowsheets are the "map" of the operation. They detail the various
processes needed to produce a valuable product from the ore stream.
These flowsheets then become the basis for items such as flow and mass
balancing documentation, process description, and equipment selection
sheets.
Plant Maintenance
It is a fact that a plant's condition
deteriorates with time. "Everything wears out, even holes". The
examination of these deterioration and wears patterns can be a valuable
tool in minimising and reducing plant costs.
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Technology