Extractive Metallurgy
Introduction
The History of Man Can Be Broadly Classified into Three Divisions –
1-The Stone Age: where the old man used the non-metallic
Material like Stone and Quartz to manufacture his own tools like cutting tools, weapons
and for making Fire.
2- The Bronze Age: The Transition from The stone Age Discover of the copper in around
8000 B.C. - Can be consider one of the most significant phases of human Age as it was
discovered that by adding the arsenic to copper and to tin will increase the mechanical
properties of copper around 4000 B.C. and this was the beginning of bronze age. The
bronze was used in huge quantity to manufacture special tools beside it's use in
manufacturing weapons.
3- The Iron Age: the Iron Metal was faster oxides by appearing free with air and humidity,
so it is appear in Nature as oxide
The Iron Age was very important as it's extension to our age.
Source of metals
Three main sources of metals and their compounds are the earth's crust, the
sea, and scrap metal, the most important one being the earth's crust. The sea,
which on an average, 3.5% of dissolved solids. In the cultivating specific marine
organisms which would concentrate one or more elements withen their bodies
by inherent biological activity. In addition, cover large areas of the sea floor.
Finally, scrap metal is becoming increasingly important and a freely available
source of metal in view of the rapid industrial growth all over the world. (The
metal recovered from scrap metal are called secondary metals), in current steelmaking processes a significant portion of the "charge" consists of scrap metal.
1-Earth's Crust
The most common element in the nature that is represent it in the earth's crust
are formed from molten rock (magmas). Magmas are the source of the igneous
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rock, which is represent the organs of other type of rocks from these rocks the
earth's crust are formed with a thickness about (33 Km).
The rock that formed the earth crust can be classified into three types:
1-Igneous rock: is formed through the cooling and solidification of magma.
2- Sedimentary rock: is A type of rock that formed by The sedimentation
disintegration of material at the earth's surface and withen bodies of water. The
disintegration occurs by withering or corrosion.
3- Metamorphic minerals: are those that form only at the high temperatures
and pressures associate with the process and metamorphism.
2- Sea as source of metals:
Sea water can be considered a dilute solution containing valuable minerals and
chemicals compound . About (70) element have so far been discovered in sea
water.
3- Scrap:
The History of extraction metallurgy can be divided into two period – the
ancient period / when A small number of metals was known, and the recent
period of about the last two centuries, when almost metals have become
available commercially.
Many important metals are present in nature combined with sulfure as metal
sulfides; These include cadmium cobalt, copper, lead, nickel, zinc and gold
group, metals are associated with sulfides base metal ores essential factor in the
creation and development level of civilization.
The first step in recovery metals from their ores is that of finding are – bodies in
which metal sulfides are present in a sufficient quantity, and at a sufficient
concentration for mining to be economic. The discovery of metals by depended
on their being easily found, easily recognized as ores and easily reduced from
these ores.
Extraction metallurgy is not confined to the production of a single metal from
each ore, metals and sometimes non-metals , present in ores in very
proportions may be Concentrated into slags or dust which are sometimes of
great value .
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Ores: is a material non-organic which is finding in geology natural circumstances
by Processed natural, Their have chemical structure limiting and crystal
structure.
An or most contain materials that are:
1-Valuable.
2- In concentration that can be profitably Mined transported, milled and
processed.
3- Able to be extracted from waste rock by mineral processing techniques.
The basic extraction of are deposits fellows the steps:
1-Prospecting or exploration to find ores.
2-Conduct resource estimation to mathematically and grade of the deposit.
3-Conduct A feasibility study to determine the theoretical economic of the ore
deposit.
4-Conduct a feasibility study to evaluate the financial viability.
5-Development to create access to an ore bodies and building of mine plant and
equipment.
6-Reclamation to make land where a mine had been suitable for future use.
Our Types:
1-Oxides ores
2-Sulfide ores
3-Italides ores
4-CrystalLine ores
1-oxidesores: consider from important group and more presence in natural. For
example the formation of iron oxides. (Magnetite Fe3O4, hematite Fe2O3).
2-sulfide ores: the major class of ore is probably the most common and is found
on the sites at which it was deposited. This group associate with iron almost
always present for Ex. Cadmium is found associated with Zinc, Iron with Copper,
Copper, Iron with Nickel.
3. Halides Ores :( Salt Rock) ex. Sodium and magnesium chloride.
4-Crystalline ores: contain number different from metals, which have crystal
content for ex. Chalcopyrite (CuFeS2).
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The Wining of ores:
The first stage in the wining of ores is to find the:
1-Traditionally Prospectors: were hardly enterprising mine seeking their
fortunes with a clever eye for the tell-tale signs of valuable minerals.
2-Modern prospecting: is organized by large mining companies by geologist and
geophysicists who add skill sophisticated techniques.
There Are Three Techniques for modern prospection:
A-Electrical Methods.
B-Magnetic Methods.
C-Chemical Methods.
A-Electrical Methods: involve the measurement of soil resistance or natural
currents in soil surrounding.
B-Magnetic Methods: include Declination and inclination over wide areas from
surface and geological formation thousands of feet below the surface.
C-Chemical Methods: include the analysis of vegetation and sand from rivers to
trace sources of minerals.
The Physical and chemical characteristics of ores:
Importance of properties which is depending on it extraction process for ores, is
properties which distinguish ore every metal of other.
There are two types of properties:
1-physical properties: include specific weight, color, shape, size of particles and
surface area.
2-Chemical properties: include process of separation for ores of metals, is
depending on chemical interaction between ores of metals and some chemical
material.
The Evaluation of ore:
1-Exploration cost.
2-Wining cost.
3-Concetration cost
4-Transportation cost.
5-Waste deposal cost.
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6-Extraction cost.
7-Refining.
8-Marketing cost
Several considerations should be taken to evaluate the ore deposit and can be
divided into two groups:
1-Geological Considerations: Can be summarized to:
a-The Size, the shape and the deposit ore.
b-the concentration of the metal or the metals into the ore.
c-The amount of the material which could be found in the ore deposit and the
ability to extract them as by product like gold and silver, or gangue mineral in
ore.
2-Non Geological Consideration: can be summarized to:
a-The cost of mining operation, which consist of mineral Extractive.
b-The cost of consideration processes, the chooses of concentration process
depend on ore nature and gangue mineral.
c-The cost of Transport waste away from working position.
d-The cost of assisting materials which is association in extraction process.
e-The Amount of energy needed in the sum of the free energy of the reduction
of the compound of the metal as found in the ore to the metallic state. And the
energy required for all mechanical to carry out.
F-workers: the cost of the workers are different from location to another (from
country to another) and almost unskilled workers were used in mining
operation, but in some cases it was necessary to used a skilled workers in in
extraction operation.
Ore dressing
Is a process of mechanically separating the grains of ore minerals from the
gangue minerals, to produce a concentrate containing most of the ore minerals
and a tailing containing the bulk of the gangue minerals. These process a
physical and chemical treatment or a combination of the two which aimed to
altering the physical and chemical nature of the mineral so that the final
combination of the minerals can be economically treated for metal extraction.
This Process Conduct for:
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1-Transport a small amount from ore which contain high portion of mineral.
2-Production a small amount from which contain high portion of mineral.
3-Obtian on a small amount of waste after extraction process.
Commination
The size to which ore particles must be reduced is dictated by requirements of
the next stage of the process, these in term depending on the particle size of
the grains of the several minerals in the untreated ore.
The ore world be broken down until every particle was either entirely valuable
mineral or entirely gangue.
This could occur only fractures were to pass along the interfaces between
grains.
In this case, the ore and gangue minerals would be said to be non-coherent and
it would suffice to release the valuable particles.
Basically commination serves two purposes:
1-it detaches dissimilar minerals particles from each other.
2- Liberate the valuable components and it produced small-sized mineral
particles which are more suitable than large-size ore for subsequent operations.
There are two principal kinds of commination – crushing down to about 7mm
(Max), and grinding to smaller sizes, large lumps may have been weaken by
cracks introduced during mining or by the existence of bedding planes, and
these may make the ore appear to break more easily at the crushing stage than
during grinding, but the mechanics of fracture essentially the same in each
stage.
If material is compressed between two plane surfaces it will first deform
elastically and then fracture suddenly along the planes of principal shear stress
if the lead is with dawn immediately the fracture occurs then the material will
be found to have broken into a small number of small pieces.
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Fig: the fracture of ore under compressive leading
Advantage of Commination:
1-Ability to transport and storage the ores.
2-Release of various mineral ores from ores.
3-Production with appropriate size and shape for separation.
4-Increasing surface area for ores or pulp to facilitate contact with chemical
solvents.
Stages of Commination:
1-Crushing.
2-Grinding.
Crushing
The Crushing Stages are:
1-Primary Crushing: (course crushing): In Primary crushing, ore or run-of mine
ore (up to 1m in size) is crushed down to about 10cm and it is done in a jaw or
gyratory crusher.
2-Secondary Crushing: (intermediate crushing):in this case ore is crushed prom
10cm to less than 1-2cm size, for this purpose Jaw, cone or roll crushers are
used. These secondary crushers consume more power than primary crushers.
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3-Tertiary crushing: (fine Crushing): By tertiary crushers ore is crushed from 12cm to less than 0.5cm. Cone crushers, roll crushers, hammer mills can be used
for this purpose.
There are three types of crushers:
1-Jaw crushers.
2-Gyratory crushers.
3-Roll Crusher.
1-Jaw Crusher: Contain two crushing plate and space between a fixed crushing
plate and moving one. In Jaw crushers the ore is squeezed until it breaks and
fragments fall down to a narrower part of the wedge to be squeezed again,
repeatedly, until they can escape through the minimum gap of the bottom. They
are capable of processing up to 500 tons of ore per hour.
Fig: schematic Jaw Crusher
2-Gyratory Crusher: is similar in effect, but the relative of the crushing face is
due to the gyratory by shaft and some tangential force is applied in this case as
well as simple squeeze.
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Interaction Between particle occurs so that ore is broken against ore producing
some fines and reducing, gyratories are built to handle up to 5000 tons of ore
per hour.
Gyratories operate best on hard, brittle material and do not work well on soft
plastic minerals like clay while Jaw crusher can deal these material much better.
Fig: Schematic Gyratory Crushes
3-Roll Crusher: rolls draw the ore lumps down into The gap between them with
smooth rolls this limit the reduction ratio to about 3:1, but using slugger rolls,
the reduction ratio can be above 4:1.
Fracture of ore between rolls is again mainly by squeezing and must occur by
stages as the material is drawn into the narrowing space.
Introduction between ore particles is much less than in Jaw and gyratory
crushers and the proportion of fines produces is smaller.
Roll crusher used to high moisture contain or clay nature.
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Fig: Schematic roll crusher
The Choice between Jaws and Gyratories is an economic:
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1-Jaws can be built to handle large material.
2-Gyratories have a higher rate of production but the handle a small material.
3-Rate of production in size in the Jaws crushers small than gyratories Crushers.
4-Jaw crusher is favorite for work and more flexible cheaper to maintain and
run.
Grinding
The grinding stages are:
1-Coarse Grinding: Rod mills are generally used as coarse grinding machines.
They are capable of taking feed as large as 50mm and making a product as fine
as 300 microns.
2-Fine Grinding: Fine Grinding, which is the final stage of comminution, is
performed in ball mills using steel balls as the grinding medium. The ball mill,
after feeding 0.5mm material may give a product that is less than 100 microns.
The principle purposes of grinding are:
1-To obtain the correct degree of liberation in mineral processing.
2-To increase the specific surface area of valuable minerals for
hydrometallurgical treatment, i.e. leaching.
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There are for types of mills:
1-ball mills.
2-Tube mills.
3-Pebble mills.
4-Rod mills.
1-Ball mills: Ball mill is a barrel – shaped vessel rotating on its horizontal axis,
and is loaded with balls of steel or cast iron.
A "pulp" of ore with 20 – 50% of water is fed into it in same designs a grate is
provide holes between 3 to 10mm in diameter to control the size in the over
flow, preventing the early escape of coarse particles.
The lining and well have been made of high alloyed steels including 13%Mn, the
section being designed for easy replacement in so far.
There is now a strong trend toward the use of rubber for linings. This is said to
wear well and to allow mills to be driven harder to give higher productivity and
replacement is faster and cheaper rubber cannot be used in large mills or where
the ball are bigger than 85mm in diameter and in any case the thickness of the
rubber must be adequate to with stand damage by its being cut through by the
balls.
The choice between special steel balls and cheap cast iron, an economic, steal
would last longer, but cost it, there is an occasional chance that contamination
in special steel balls might be injurious to the later parts of the process .
Fig: schematic representation of ball mill
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2-Tube Mills: tubes mills divided by grids into compartment containing different
sizes of balls, in say, three stages. This should be more attention to keep it
efficient, but it needs more attention to keep it efficient.
Tube mills are longer and narrower than ball mills.
3-Pebble Mills: These have porcelain or rubber lining and filled with porcelain
ball suitable flint pebbles. These mills are narrower than ball mills to avoid
excessive breakage of the pebbles. Pebble mills are used in the ceramic
industries and the preparation of gold ores, because iron inhibit amalgamation
of gold particles in once process.
4-Rod Mills: rod mill which is a similar barrel. Shaped vessel, perhaps a little
longer than a ball mill of same diameter, laid parallel with axis filled with steel
bars, 75-100mm in diameter which is more troubles some to operate than a ball
mill because rods wear and break, but it more production.
Ore dressing – Sizing and sorting
A-Screen according ….. Sizing
B-Sorting
Classification
Flotation
Magnetic
Screening: is mechanical process used to separate particle size, which produce
from broken processes, another hand, separation on base size.
Particles can be separated into two groups an oversize which is unable to pass
through the screen and under size which does pass, can be obtained on this
type from separation from through passage ore on aperture surface, this
apertures allowed with passage particles through it. Particles oversize which
larger from holes of sieving stay on the surface of sieving while the particles
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under size which smaller from holes of sieving pass from through sieving
apertures
Use of Screening in wining process for here reasons:
1-Preventing entry the large rock.
2-Remove a small size in order to increase efficiency of Subsequent processes.
3-Production the requirement size for concentration and separation processes.
The Major specification for standard sieves:
1-The American society for testing materials (ASTM) the apertures is only 30%
of the total screen area.
2-The Institution of mining and metallurgy (I.M.M) (London), The apertures is
only 25% of the total screen area.
Screening Surfaces:
There are three types from screening surfaces:
1-Parallel rod screening: They are made from iron rods, this is the rods is equal
and parallel.
2-Sieves plates: They are made of steel sheet from special alloys, strength of the
corrosion those sieves welded or woven to give square or any engineering
shapes.
3-Wires screening: they are made from copper wires or brass either welded or
woven to give different apertures and different diameters.
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Fig: Schematic of screening surface
Types of screening:
1-Constant screening: They are made from parallel iron rods, it is using to
remove fine materials, which produce from crusher process. Particle size can be
sieved in this screen about (20 – 30)Mm.
2-Movable screening: A-Rotary Screening: They are made from rotary apertures
cylinder. This screening rotate on a slightly inclined about axis, it is using in
classification rocks and pebble.
B-Vibrating screening the motion in this screening is vibration and it occurs with
normal shape by using electromagnetic equipment.
The screening is inefficiency process because:
First: Mineral
1-Total density for ore.
2-Particle shape.
3-Humidity percentage in pulp.
Second: Screen
1-Area of screen (surface of screen & size and shape of aperture).
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2-Thickness of screen.
3-vibration of screen.
4-Inclination of screen.
5-Way of feeding screen and quality.
6-Way of contact particles with surface of screen.
7-Time of screening
We can Obtain on good screening by:
1-Remove wet and stacking materials.
2-The good vibration.
3-suffecient gradient for prevent close the aperture.
4-Must be vibration movement opposite the flow of material.
5-speed of inlet & thickness is constant.
Sorting operation
1-Classification
2-Flotation
3-Separation
Classification
Classification is sorting process for particles which is depending on velocity fall
ore particles through fluid media or other medium is air.
The depending velocity of particles fall in the fluid on many forces effecting it.
1-Mass of particle.
2-Mass of fluid displaced
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3-liquid resistance.
When a choice velocity of fall particles with other particles is depending on the
following:
1-If equal density of grains deposite more velocity from a small grains.
2- is equal diameters of grains and different the density, grains have a higher
density fall more velocity from grains Have a smaller density.
3-If equal density and size of grains, regular shapes fall more velocity from
grains have non-regular shapes.
Classifiers
The depending principle operate of classifiers which is using in classification on
put of particles in path from water and contain pulp.
The Different mainly between classifiers is how ro remove the production from
the path.
There are three type of classifiers:
1-Mechanical classifiers: was a tank fed with pulp at one end, and the other end
is sloping, where the particles is low density and light particles remove from
higher, while the particles is high density and heavy particles deposited in the
tank bottom.
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2-Hydrualic Classifier: is the rectangular tank, which is containing on many
rooms in the tank bottom, pulp is fed near the top water is fed on the same
side, where coarse particles deposite in the room which is near from feed either
fine particles is deposite in the last room which is depending on the density and
size.
Fig. Schematic hydraulic classifier
3-Cyclones classifier: contain two part, one part is the cylindrical in the top and
the other part is conical vessel in the bottom. Cylindrical part contain the
aperture cover from top, which pass through central pipe called "Vortex finder"
which is using to remove over flow from pulp-pulp is injected tangentially with
very high velocity at the top a conical vessel.
The fluid is moved a spiral path toward the apex; therefor, start the coarse
particles go down to the cone bottom and overflow is go up to the top by
"Vortex Finder"
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Fig. Schematic of Cyclones classifier.
Flotation
Froth flotation: is process for separating minerals from gangue.
The surfaces of selected minerals are made hydrophobic the hydrophobic
particles become attached to air bubbles that are introduced into pulp and are
carried to the froth layer.
Froth flotation is process to remove particles from limiting ore in fluid media by
using anther media is air.
Add chemical agents in flotation process to make ore particles hydrophobic.
Froth flotation is completed by using suitable chemical agents.
Chemical Agents:
Using The chemical agents in the froth flotation process for two reasons:
1-To make the contact between air bubbles and ore particles.
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2-To separate the float metal in the top flotation cell and stay the metal which is
not float in the bottom.
There are five groups from chemical agents:
1-Collectors.
2-Depressant.
3-Frothers.
4-Activation.
5-Deactivation
1-Collectors: Use the collectors for easily contact ore particles with air bubbles
by design film on provided ore- But without effecting on gangue or other ores in
flotation cell.
From type of collectors:
1-Sulphonate
2-Marcapton
3-Amine
The choice of collector for a particular job. It depends on many factor. The
nature of the minerals involved, their degree of oxidation and the presence of
even traces of other heavy metals in the pulp.
Methods of Collections work on mineral surface:
There are three types of theories to interpreting this phenomena.
1-Chemical Theory.
2-Ionic adsorption theory.
3-Natural Molecule adsorption theory.
2-Frothers: a frothers must also be added to ensure the formation of a stable
froth with sufficient buoyancy to carry the load of floatable mineral these
contain compounds comprising polar and non-polar groups which are adsorbed
strongly at water-air interfaces, the polar groups toward the water. When two
bubbles come together their surfaces films meet with non-polar groups facing
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each other and they tend to repel each other rather than coalesce. This gives
the froth stability. It is essential that the froth is not to stable, as it must be
easily dispersed to release immediately it has been removed from the cell. From
type of frothers :CH3OH.
3-Depressants: use the depressants to prevent float ores that not favorable, it
Prevents from contacted gangue with air bubbles in flotation cell, and
separation metal ore which it favorable from types of depressants; sulphide.
4-Activation: use the activation for some metals ores which is not reaction their
surfaces with collecton presence chemical materials in the pulp, may it reaction
easily with collectors. These activators effect on surface ore particles which are
made hydrophobic.
5-deactivation: involve these deactivators to remove effecting activation from
surface ores.
Stages added of chemical agents in flotation cell:
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Flotation Cell
In flotation cell pulp agitated and air either injected to form many bubbles by
"impeller" which rise through the cell, air is dissolved into the flotation solution
under high pressure. Under the solution is released into the flotation chamber,
the reduced pressure cause much of the dissolved air to come out of solution to
form bubbles.
Pulp is continuously pumped into the next of about ten cells in series for
repeated treatments.
Mineral particle assemble as a froth on top and this is scraped off into a launder
and discharged with water spray.
Fig. Schematic flotation cell.
Magnetic Separation:
Magnetic separation: is a physical separation process which is depending on
magnetic property, about used to concentrate iron minerals with high efficiency
may be classification of materials by the depending on magnetic property as
following:
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1-Ferromagnetic materials: have high magnetic property which is attracted
toward magnet like magnetite.
2-Paramagnetic Materials: have moderately magnetic property like hematite.
3-Damagnetic Materials: is a materials which cannot attracted toward magnet.
Use of process magnetic separation for two reasons:
1-Remove iron compounds from feed which is entered to crushing or grinding to
protect from waste and remove iron compounds from ceramic materials.
2-Cocentration some iron ores like magnetite and concentration other iron ores
like hematite by hardly high magnets.
Note: Magnetic field may be obtained user either permanents magnets or
electromagnets.
May Be Classification of process magnetic separation for two types:
1-Dry magnetic separation: dry magnetic separation gives a more complete
separation of magnetic from non-magnetic materials and used to separate a
large from particles
at size > 5mm.
when mixture of magnetic and non-magnetic particles is carried across a
magnetic flied the magnetic particles tend to
remain in the field while the other pass through magnetic separators simply
provide two path-gravitation path for non-magnetic particles and a magnetic
path for magnetic materials.
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2-Wet magnetic separation: In this separation, used the water with ores which
the particles is small. At size < 10Mm. this is derived homogenous particles
distribution and easily separation.
Fig. Schematic wet magnetic separator.
Electrostatic Separation
Mineral have a wide range of electrical conductivity and can be distinguished by
that property. If several kinds of particles are given an electrostatic charge and
then brought into contact with an electrical conduct at earth potential the
charge will leak away from the good conductors much more rapidly than from
the poor conductors. While the charge remains the electrostatic attraction.
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Fig: Electrostatic separation
Agglomeration
When the particle size of an ore or concentrate is too small for use in a later
stage of treatment (e.g. in the blast furnace). It is must be re-formed into lumps
of appropriate size and strength.
This may be done by briquetting or by pelletizing at ordinary temperature or by
sintering pelletizing and sometimes they are used together , fine ore being
pelletizing as feed for the sinter plant.
These agglomeration are usually required for blast furnaces and especially in the
case of the iron blast furnace but the large quantity of fines produced must first
be agglomerated. Some ores are so fine when mined as to require
agglomeration others need to be agglomerated only after mineral dressing.
There are three methods for agglomeration process:
1-Pelletizing.
2-Sentering.
3.Briquetting.
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1- Pelletizing: is a pressure mechanical process for mixture from metal particles
and water with presence suitable binding material. Which is produced in
different shape like mold shape.
Some small pressure is necessary to consolidate the molds as they form but this
comes mainly from their weight applied to each small particles are bonded
together by surface tension force in the moisture between them.
Types of binding Materials:
1-Non-organic Materials.
Ex: (cement, clays, metals salts)
2-Organic Materials.
Ex: oil, wood pulp.
2- Sintering
Consider from importance agglomeration process in industry applying. Which is
used high temperature and bellow the melting point to allow diffusion for the
purpose of the particles. It is applied to bond:
1-Metal – ceramic
2-Metal – Metal
3-Ceramic – Ceramic
There are two types for sintering.
1-Sintering Diffusion.
2-Liquid – phase sintering.
3-Briquetting: is a essentially mechanical process of agglomeration fine ores
particles.
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