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DBT 203Metal Extractive Technology
Topic 1:
Extracting Metal from Ores
Noor Mariamadzliza binti
Mohd Nan15062012
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Syllabus:
Define of ores, minerals and
rocks.
Describe purpose andprocesses involved in mineral
processing
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Introduction
The art of extracting metals from their oresdates back to the dawn of human civilization.
The first metals used by man were gold andcopper, which were found in nature in metallicor native form.Around 4000 B.C man learned to produce
copper and bronze by the smelting of copperand tin ores in a charcoal fire.
Throughout the history of mankind, theprocesses of extractive metallurgy weredeveloped further by trial and error.
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What is Metal Extractive..
The practice of extracting metal from ore,
purifying it and recycling it.
Or
The practice of beneficiating valuable
minerals from their ores
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Mineral..
Mineral by definition are:- Natural inorganic substances possessing definite
chemical compositions and atomic structure.
Many minerals exhibit isomorphism, where
substitution of atoms within the crystal structure bysimilar atoms takes place without affecting theatomic structure.
Also can exhibit as polymorphism, differentminerals having the same chemical composition,but different physical properties due to differencein crystal structure.
Examples: chalcopyrite (CuFeS2) , galena (PbS)
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Ore..
According to traditional definition:- An ore is a rock which can be mined economically to
serve as raw material for the production of metals.
Types of ore:-
Oxides:iron ores, which usually contain the mineral hematite, Fe2O3, but
which also may contain magnetite, Fe3O4Other heavy metals which are mainly produced from oxide ores
are manganese, chromium, titanium, tungsten and tin.
Sulfides:Copper ore, which often consist of mixed sulfides of copper and
iron.
Other metals which are mainly derived from sulfides are nickel,zinc, lead, mercury and molybdenum.
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Halides
Such as rock salt for sodium, and magnesium
chloride brine which, together with seawater, serve
as sources for magnesium.
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Rock..
An aggregate of minerals and need not
have a specific chemical composition.
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Metal Extractive Technology..
Mineral processing
Hydrometallurgy
Pyrometallurgy Electrometallurgy
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Mineral Processing..
As-mined or run-of-mine consists of valuablemetallic minerals and waste (gangue)
Mineral processing, sometimes called ore dressing,mineral dressing, or milling follows mining and
prepares the ore for extraction of the valuable metal toproduce a commercial end product.
It is a process of physically separating the grains ofvaluable minerals from the gangue minerals, toproduce an enriched portion, or concentrate,
containing most of the valuable minerals, and discard,or tailing, containing predominantly the gangueminerals.
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Mineral processing reduces the bulk and
weight of material which must be
transported to the smelter, thus reducing
shipping and handling costs; smeltingcosts are greatly reduced due to the
reduced tonnage which must be treated;
the lack of undesirable waste materialsincreases the smelter recovery, due to the
production of less metal-bearing slag.
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There are two fundamental operations in mineral
processing,
namely the release, or liberation, of valuable
minerals from their waste gangue minerals,and
separation of these values from the gangue,
this latter process being known as
concentration.
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Fig. 1: Simple block flowchart
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Comminution
Separation
Concentrate
Run-of-mine ore
Tailing
Product Handling
(Midling)
Disposal
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Comminution..
The first part in any ore-dressing process.
Involve crushing and grinding.
A process where each mineral grain is free or
practically free.
Crushing and grinding are usually carried out
in a sequence of operations by which the
lump size is reduced step by step.
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One of the major objective of comminution is the
liberation, or release, of the valuable minerals from the
associated gangue minerals at the coarsest possible
particle size.
The degreeof liberationrefers to the percentage of the
mineral occurring as free particles in the ore in relation to
the total content.
A high degree of liberation may only be possible by
intensive fine grinding, which may reduce the particles tosuch a fine size that separation becomes very inefficient.
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Figure show a cross section through a typical
ore particle, and illustrate effectively the
liberation dilemma often facing the mineral
processor.
Region A represent valuable mineral, and
region AA is rich in valuable mineral, but
highly intergrown with the gangue mineral.
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Comminution produces a range of fragment, ranging from fully
liberated mineral and gangue particles.
Particle of type 1 are rich in mineral, and classes as
concentrate as they have an acceptable degree of locking
with the gangue which limits to the concentrate grade. Particles of type 4 would likewise be classed as tailing, the
small amount of mineral present reducing the recovery of
mineral into the concentrate.
Particles of type 2 and 3, however, would probably be classedas middlings, although the degree of regrinding needed to
promote economic liberation of mineral from particle 3 would
be greater than that in particle 2.
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Crushing..
Crushing is the first mechanical stage in the processoff comminution which the main objective is theliberation of the valuable minerals from the gangue.
Generally a dry operation and is usually performed in
two or three stages. Lumps of run-of-mine ore can be as large as 1.5m
across and then are reduced in the primary crushingstage to 10-20 cm in heavy-duty machines.
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Primary crushing
Commonly designed to operate 75% of theavailable time, mainly because of interruptionscause by sufficient crusher feed and by mechanical
delays in the crusher. to reduce the run-of-mine down to about 100mm.
Always operate in open circuit, with or withoutheavy-duty screens.
Jaw crushers, gyratory crushers or impact crusher.
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Secondary and tertiary crushing
Also operate with dry feeds, and their purpose is toreduce the ore to a size suitable for grinding.
From 100mm to less than 10mm lump size.
Cone crushers, roll crushers and hammer mills.
In some case, the crushing in rolls and hammermills is carried on to product sizes below 1mm.
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Grinding..
The final reduction in size usually takes place in rod mills
or ball mills where the finely crushed ore is ground
between rods or balls in a revolving drum.
Combination of impact and abrasion.
The latter may give a product which is less than 0.1mm
in diameter.
These grinding operations may be done on dry material,
but usually carried out wet, i.e., the ore is mixed with
enough water to give a thick pulp which is passed on to
further ore-dressing processes.
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The grinding medium may be steel rods,,
or ball, hard rock or in some cases, the ore
itself.
A recent development in the comminution
field is the autogeneous mill, where coarse
ore is reduced to fine product in one step
by abrasion in a revolving mill drum.
It is used extensively for iron ore grinding
and is expanding into other fields.15062012
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Closed and Open Circuits..
Open Circuit
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Closed Circuit
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