Basis of MD & PEM

• Mineral processing is a branch of science and technology dealing with

processing of natural and synthetic mineral materials as well as accompanying
liquids, solutions and gases to provide them with desired properties.
• It is a part of technical sciences, although it contains elements originating from
other fields of knowledge, especially natural sciences.
• Mineral processing is based on separation processes and is involved in
performing and description of separations, as well as their analysis, evaluation,
and comparison
Studies of important metallic and
non-metallic minerals
Exploration for mineral deposits
Mineral
• It is a naturally occurring inorganic compound of one or more metals in association with nonmetals such as
oxygen, sulphur, and the halogens.
• A mineral has a fixed composition and well-defined physical and chemical properties. (Ex. Hematite is
mineral of iron)
Ore
• It may be defined as a naturally occurring aggregate or a combination of minerals from which one or more
metals or minerals may be economically extracted.
• The economy of extraction generally depends on fundamental factors such as
a) the percentage of valuable metal in the ore,
b) the form in which the metal occurs,
c) the percentage of impurities in the ore,
d) the physical condition of the ore,
e) the location and magnitude of the ore deposits,
f) the proximity to transport facilities, and
g) the market value of the metal.
Mineral Resources

• Minerals can be grouped under two main categories of metallic and non-metallic on the basis of chemical
and physical properties.
1. Metallic Minerals
• Ferrous
• Non-ferrous
2. Non-metallic Minerals
• Fuel Minerals
• Other Nonmetallic Minerals

Metallic Minerals
• Metallic minerals are the sources of metals and provide a strong base for the development of metallurgical
industry.
• Iron ore, bauxite etc. produces metal and are included in this category.
• Metallic minerals exhibit a metallic shine or lustre in their appearance.
• Metallic minerals can be further divided into ferrous and non-ferrous metallic minerals.
Mineral Resources

Ferrous Minerals
• All those minerals which have iron content are called ferrous minerals.
• Iron ore, manganese and chromites are examples of ferrous minerals.
• Ferrous Minerals account for about three-fourth of the total value of the production of metallic minerals
• These minerals provide a strong base for the development of metallurgical industries, particularly iron, steel
and alloys.
• India is well-placed in respect of ferrous minerals both in reserves and production.

Non-ferrous Minerals
• Minerals which do not contain iron are known as non ferrous mineral.
• Copper, bauxite, etc. are non ferrous minerals.
• India is poorly endowed with non-ferrous metallic minerals, except bauxite.
Mineral Resources

Non-metallic Minerals
• Non-metallic minerals are either organic or inorganic in origin and do not contain extractable metals in their
chemical composition.
• Based on their origin, they are further classified into two categories, i.e., mineral fuel and other non metallic
minerals.
• India is endowed with a large number of non-metallic minerals, but only a few of these are commercially
important.
• They are limestone, dolomite, mica, kyanite, sillimanite, gypsum and phosphate.
• These minerals are used in a variety of industries such as cement, fertilizers, refractories and electrical
goods.
Mineral Fuels
• Mineral fuels are organic in origin and derived from the buried animal and plant life such as coal and
petroleum.
• They are also known as fossil fuels.
Other Non-metallic Minerals
• Other non-metallic minerals are inorganic in origin such as mica, limestone and graphite, etc.
Mineral Resources

Characteristics of Minerals
Basic characteristics of a mineral are following:
• Definite crystalline structure
• Definite chemical composition
• Naturally occurring
• Formed by inorganic processes
• Solid
For a rock to be mineral it has to have at least three of these characteristics. Other characteristics of minerals
are:
• These are unevenly distributed over space.
• There is an inverse relationship in quality and quantity of minerals i.e. good quality minerals are less in
quantity as compared to low quality minerals.
• All minerals are exhaustible over time.
• Minerals take a long time to develop geologically and they cannot be replenished immediately at the time of
need.
Important Ores and Minerals (Iron, Fe)

Important iron ores in hand specimens: a) Hematite; b) Magnetite; c) Pyrite; and d) Ilmenite.
Important Ores and Minerals of
Manganese (Mn)

Fig. 13.4: Ferromanganese nodules.

Important Ores and Minerals of
Copper (Cu)
Lead and Zinc
• Lead and zinc always go together because of their strong
geochemical affinity.
• Zinc is vital for galvanising industry while battery sector
is known for being the major consumer of lead.
Aluminum (Al).
Gold (Au). • Gold occurs principally as a native metal.
• Native gold can occur as sizeable nuggets, as fine
grains or flakes in the alluvial deposits.
• Ores in which gold occurs in chemical
composition with other elements are
comparatively rare.
Radioactive Metals Group • They all occur in the Precambrian rocks of
Dharwar Craton in southern part of India.
• Singhbhum copper belt and the Aravalli rocks in
Udaipur District.
• Thorium along with uranium occurs in the cerium
rich monazite mineral.
• heavy black sands on the sea coasts of India, from
Narmada estuary to Kerala coast and Odisha
coast.
• The uranium mine in Jaduguda village in the
Singhbhum District of Jharkhand was the first
uranium mine in India.
 Minerals, Origin and Application
Metal Ore Location Application or Use
Aluminium Bauxite Major- Orissa and Andhra Deoxidizing , electrical conductor,
(Al) Gibbsite (Al2O3.3H2O) Pradesh roofing industry, Kitchen ware,
Diaspore (Al2O3.H2O) Minor- Jammu and chemical, packaging industry and
Kashmir, Bihar, MP, UP, protective surfaces
TN and Maharashtra
Chromium Chromite (Fe.Cr2O3) Keonjhar (Odisha) Stainless steel
(Cr) Singhbhum district Chromium plating
(Bihar) Paints
Karnataka
Nickel (Ni) Very less exist in India Sukinda (Odisha) Stainless steel
Pentlandite [(NiFe)9S8] Singhbhum (Bihar) Batteries
Violarite (Ni2FeS4) Monel alloy- Oil industry

Copper (Cu) Chalcocite (Cu2S), Jharkhand, Rajasthan, Ornaments, vessels, Electrical

Chalcopyrite (CuFeS2), Madhya Pradesh and industry as conductors etc, alloys
Bornite (Cu5FeS4), Malachite Karnataka. Minor deposits making like bronze, duralumin,
(CuCO3Cu(OH2)), Cuprite in Sikkim, Maharashtra gun metal, building industry,
(Cu2O), Covellite (CuS) and Andhra Pradesh railway industry, power
transmission, Automobile industry
Metal Ore Location Application or Use
Magnesium Dolomite – Salem district of TN, UP, Aircraft Industry
MgCO3.CaCO3 Karnataka Cathodic Protection to Pipelines, storage
Magnesite – MgCO3 tank,deoxidizer
MgCl2 and MgSO4,
Present in sea-water
Brucite – Mg(OH)2
Titanium Ilmenite (FeTiO3), Beach sand Kerala Jet engine components, Air Frames,
Monazite, Rutile (TiO2) Waltair (AP) Missiles and Spacecraft
Lead Galena (PbS; lead Rajasthan, Jharkhand, Used in car batteries, pigments,
sulphide), Anglesite Maharashtra and Andhra ammunition, cable sheathing, weights
(PbSO4; lead sulphate), Pradesh, Odisha, Gujarat, for lifting, weight belts for diving, lead
Cerusite (PbCO3; lead Sikkim, Uttarakhand, crystal glass, radiation protection
Carbonate) and Jammu & Kashmir.
Zinc Sphalerite – ZnS, Zincite Rajasthan, Jharkhand, Used as coating and galvanising iron and
– ZnO, Franklinite- Maharashtra and Andhra steel products to prevent rusting.
ZnO(Fe, Mn)2O3, Pradesh, Odisha, Gujarat, Galvanised steel is used for car bodies,
Calamine –Zn2(OH)2SiO3, Sikkim, Uttarakhand, street lamp posts, safety barriers and
Smithstone – ZnCO3 and Jammu & Kashmir. suspension bridges
 Mica Group

Distribution in India: Uses:

• In India best quality mica and the workable • High quality natural sheet mica is used in helium neon
deposits have been recorded mainly from laser as retardation plates.
Jharkhand, Andhra Pradesh and Rajasthan. • Sheet mica are also used in electrical and electronic
• Occurrences of less importance mica is reported industries as insulating materials, such as capacitors,
from Tamil Nadu, Karnataka, Kerala, west Bengal, communicator segments, and high-pressure steam
Madhya Pradesh and Odisha. boilers.
Gypsum
• Gypsum (CaSO4.2H2O) is a hydrated calcium sulphate.
• Gypsum has specific gravity of 2.3.
• It has hardness 2 and can be scratched with finger nail.
• It is divided into five categories:
1) Rock gypsum,
2) Gypsite, a mixed porous type with sand and clay,
3) Alabaster, a fine grained, massive and light coloured,
4) Satin spar, silky and fibrous form,
5) Selenite, crystalline, colourless, transparent silky form
Distribution in India:
• Selenite occurs in Nellore and Guntur and Prakasham Districts of Andhra Pradesh, Jamnagar, Surendranagar,
Bhavnagar, Jamnagar and Kutch Districts of Gujarat.
• Gypsum occurs in Sirmur and Chamba, of Himachal Pradesh, Baramula and Doda, Jammu & Kashmir.
• High-grade gypsum is mostly mined in Rajasthan in Nagaur, Bikaner, Barmer, Churu, Jaisalmer and Pali.
• Gypsum also occurs in Gulbarga District of Karnataka, Shahdol District of Madhya Pradesh and Tiruchirapalli
District of Tamil Nadu.
• Gypsum occurs interbedded with limestone or dolomite in Tehri Garhwal, Dehradun and Nainital Districts of
Uttar Pradesh.
Uses: Gypsum is utilized in three important industries like cement, fertiliser (ammonium sulphate) and Plaster of
Paris.
Magnesite
• Magnesite (MgCO3) is a carbonate of magnesium.
• Commercially the term 'magnesite' refers not only to the mineral,
but also to many products, obtained by calcining the natural
carbonate, e.g., caustic magnesite (magnesia obtained by calcining
crude magnesite at comparatively low temperatures, 700 to
1000oC) and refractory magnesite (magnesia obtained by calcining
magnesite at high temperatures, 1500 to 1800oC).
• Pure magnesite is calcined at still higher temperatures (1600-
1800oC) to expel carbon dioxide completely which is known as
'periclase' (MgO) in the trade.

Distribution in India:
• Almora and Pithoragarh Districts of Uttar Pradesh, Brahmani and Pangi in Himachal Pradesh, Jammu and
Kashmir (Kargil, Ladakh and Udhampur Districts), Karnataka (Coorg and Mysore), Dharmapuri, Nilgiris,
Periyar, Coimbatore, Tirunelveli, Tiruchirapalli and Salem Districts of Tamil Nadu, Salem, Uttarakhand.
Uses:
• Magnesite is used as abrasive for soft polishing of metal and mineral surfaces.
• The refractory industry is the major consumer of magnesite.
• Basic refractories, which could be largely used in the steel industry.
• Fused magnesia finds application as insulating material in tubular heating elements in electrical Industry
Granite
• Granite is a plutonic felsic rock with quartz and feldspar as essential
minerals.
• Granite in the form of building structural and ornamental stones has
acquired important position in the field of modern architecture.
• The word granite has been derived from Latin work ‘Granum’
meaning grain.
• Besides hard and compact nature the texture of granite readily takes
up good polish which gives it beautiful appearance.
• Colour varies from pink, grey, red and black with different textures.

Distribution in India:
• Granite occurs in almost all parts of India such as Anantpur, Chitoor, Guntur, Hyderabad, Warangal Districts
in Andhra Pradesh; Bangalore, Bellary, Tumkur Districts in Karnataka; Ajmer, Alwar, Barmer, Bhilwara
Districts in Rajasthan; Coimbatore, Dharampuri, Salem Districts in Tamil Nadu; Deogarh, Banka, Godda,
Gumla, Hazaribag, Palamu, Ranchi and Singhbhum Districts in Jharkhand.
Uses:
• Magnesite is used as abrasive for soft polishing of metal and mineral surfaces.
• The refractory industry is the major consumer of magnesite.
• Basic refractories, which could be largely used in the steel industry.
• Fused magnesia finds application as insulating material in tubular heating elements in electrical Industry
Marble
• Marble is a calcareous metamorphic rock.
• The word ‘marble’ has been derived from Latin word ‘Marmaros’
which means shining stone.
• Any stone capable of taking polish without any regard to its chemical
composition was designated as marble in early days.
• Marble is a crystalline rock exhibiting sugary (saccharoidal) texture
consisting mainly of calcite or more rarely dolomite.
• Marble is white in colour although due to impurities colour may vary.

Distribution in India:
• Makrana marble is one of the most preferred ornamental and masonry stones from north-west India
Uses:
• Marble is one of the best building materials used for flooring exterior and interiors of walls, monuments,
architecture and other construction applications.
• Famous monuments like Taj Mahal of Agra (one of the Seven Wonders of the World and a UNESCO world
heritage site), Lotus temple of Delhi, Victoria Memorial of Kolkata and are constructed of marble.
• In abroad, Makrana marble has been used in Sheikh Zayed Mosque, Abu Dhabi, UAE, and Moti Masjid,
Lahore, Pakistan.
Marble
• Limestone is a calcareous rock formed both organically and
inorganically.
• It is a carbonate of lime or calcium.
• It can be crystalline, pisolitic, oolitic or earthy.
• The impure limestone may be argillaceous, siliceous, ferruginous,
bituminous or dolomitic in nature.
• Nomenclature of limestone may vary based upon its colour, structure,
locality and formation in which it occurs and its genesis etc

Distribution in India:
• Limestone is widely distributed in many places such as Andhra Pradesh, Karnataka, Assam, Jharkhand; North
Eastern part of Goa, Gujarat, Haryana, Himachal Pradesh, Uttar Pradesh, Rajasthan, Uttarakhand, Jammu &
Kashmir.
• Limestone and dolomite deposits are located in Raigarh, Janjir- Champa, Bilaspur, Raipur, Durg and
Rajnandgaon Districts.
Uses:
• It is extensively used in cement industries, iron and steel, chemical, sugar and paper industries.
• Limestone is also used in fertiliser, ferro-alloys, glass manufacture, lime manufacture, foundry, refractories,
textile, electrode, ceramic, sponge iron.
Application of Non-metallic minerals
Exploration for mineral deposits
• In ancient times, some minerals must have been spotted on the earth’s
surface itself because of their striking physical characteristics such as
vivid colours and crystalline shapes, whereas those hidden under the
soil would have remained unnoticed.
• Therefore, scientific methods are necessary for a accurate location and
a quantitative estimation of mineral deposits.
• The principal methods employed in mineral exploration are generally
based on the magnetic, electrical, and electromagnetic properties of the
ore bodies.
• Other geophysical methods, namely, gravitational, seismic, and
radioactive methods are normally used for oil exploration.
Magnetic methods
• Magnetic methods are based on the fact that magnetic
ore deposits disturb the earth’s magnetic field in their
vicinity.
• Instruments such as magnetometers and variometers
are capable of detecting buried deposits of magnetite
(iron ore) and nickel- and cobalt-bearing ores.
• Indirectly, they also help in locating alluvial deposits
of gold and platinum which often contain abundant
grains of magnetite.
• A magnetic survey performed by these instruments
yields contour maps of the ore deposits.
• By measuring the variations in the magnetic intensities
in both the vertical and horizontal directions, the
dimensions of the ore very can be estimated.
• The vertical and horizontal intensity curves are easily
related to the location and orientation of the ore body.
 Electrical methods
• Electrical methods are based on the differences between
the electrical conductivities of certain ore deposits and
those of the surrounding rocks.
• These methods are recommended particularly for
certain sulphide minerals which have remarkably high
conductivities- often several thousand times higher than
the conductivity of the surrounding rocks.
• Conductivity measurements directly indicate both
presence and the magnitude of the ore deposits.
• Electrical flow lines, obtained by passing either a direct
or an alternating current into the ground between a pair
of earthed electrodes, crowed in towards any mass of
conducting material.
• if one applies a voltage at different locations and
measures the current flowing and defined that, there is
some place where resistivity’s suddenly dropping, it
means you find, here you go on measuring the current
flowing and take the whole thing from one place to
another and you find there is a place where suddenly the
there is a hint of dropping resistivity.
 Electrical methods
• Conductivity measurements are
supplemented by the measurement of
potentials at the ground surface.
• From these potential data, we can draw
equipotential lines on a map of the area.
• Equipotential lines are always perpendicular
to the lines indicating the flow of current
and diverge from the ore body.
• Modern instruments which measure
conductivity and potential measurements
simultaneously help in determining the
location and orientation of ore bodies.
• There is a rather unique electrical technique
to detect and determine the volume of a Fig. 3.3 Survey of Electrical Flow Lines and Equipotential Lines
sulphide ore body. (after Jones and Williams, 1948)
Sources of Metals
Three main source of Metals
• Earth’s Crust
• The Sea
• Scrap Metal
➢Earth’s Crust:
➢The Sea: Marine organisms
Sea floor nodules
➢ Scrap Metal: The metals recovered from scrap
metals are called secondary metals.
The charge material in current steel making is
“Scrap”
Sources of metals
The main sources of metals and their
compounds are
1. The earth’s crust (most important
one) or land
• O, Si, Al, Fe, Ca, Na, K, Mg elements
account for more than 98% (75% is
composed of Si and O ) of the earth’s
crust.
• Elements that are abundant in the
earth’s crust but have only limited use
include titanium, rubidium, and
vanadium. On the other hand,
elements such as Cu, Zn, and Pb are
far less abundant in the earth’s crust.
• Some rich ore deposits, for example,
the bauxite ores of Kashmir, are
located in areas with poor
transportation facilites, redering their
economic exploitation difficult.
Sources of metals
The main sources of metals and their compounds are
2. The sea – cover more than 70% of the earth’s
surface contain 3.5% of dissolved solids.
• Sea have chlorides deposites- (NaCl after
vaporization of sea water, but it is not pure NaCl, it
is a mixture of other chlorides)
• Sea is homogeneous body of water, these values are,
remarkably, the same all over the globe.
• Juvenile water (along with basalt a form of water)
contains many components of sea-water such as
chlorine, bromine, carbon, boron, nitrogen, and
various trace elements.
• A kind of seaweed contain a very high concentration
of iodine.
• Other sea organisms may contain elements such as
Ba, Co, Cu, Pb, Ni, Ag, and Zn.
Sources of metals Ocean-floor nodules
• Trillion of tons of nodules are scattered
across the ocean floor.
• These nodules whose principle contituents
are manganese, nickel, iron, copper, cobalt,
and siliceous ocean-floor silt are collectively
termed as ‘Manganese nodules’.
• In terms of their nickel content, they can also
be called ‘Nickel nodules’ since they are a
potential source of nickel.
• Mero (1972) has estimated that
approximately one and half trillion tons of
nodules are scattered across the floor of the
Pacific Ocean alone.
Sources of metals
3. Scrap – freely available source of metal – the metal recovered from scrap metal
are called secondary metals.
• Metal manufacturing processes would virtually only refine and recycle
increasingly huge quantities of metals which are periodically used and discarded.
• For instance, in current steel-making processes, a significant portion of the
‘charge’ consists of scrap metal.
Minerals/metals wealth in India
• Adequate to abundant – Ores of Al, Be, Cr, Mn, Mg, Ti, Zr, Th and the
rare earths.
• India continued to be largely self-sufficient in minerals which constitute primary mineral raw
materials that are supplied to industries, such as iron & steel, aluminium, cement, various types
of refractories, china clay-based ceramics, glass, etc.
• Inadequate but present – Ores of Cu, Au, C (graphite), Pb, V, Zn, Cd,
Ni, U and Sn
• India is self-sufficient or near to self-sufficient in bauxite, chromite, limestone, iron ore and
sillimanite.
• Poor to so far unknown – Ores containing Sb, Bi, B, Co, Hg, Mo, Nb,
Ta, P, Se, S, Sr, Te, Ag, W.
• India is deficient in coal, copper concentrate, kyanite, magnesite, rock phosphate, manganese
ore, etc. which are imported to meet the demand
(some non-metals also included here)
Minerals wealth in India
Minerals wealth in India

Sixs countries, namely, the U.S.A., the U.S.S.R., Canada, South Africa, Australia, and
China possess most of the world’s mineral reserves and consequently, dominate the
production of minerals.
Status of Mineral beneficiation Industry In
India
Central Organisation
• Geological Survey of India.
• Indian Institute of Science , Bangalore.
• Regional Research Laboratory, Bhubaneswar and Jorhat (Now
known as CSIR- Institute of Minerals and Materials Technology
and CSIR-North and East institute of science and technology
respectively)
• CSIR- National Metallurgical Laboratory, Jamshedpur.
Public Sector Undertaking Private Sector
1.Andhra Pradesh Mining Corporation Ltd. 1. Bharat Aluminium Co. Ltd.
2. Bhilai Steel Plant 2. Binani Cements Ltd.
3. Fertilizers Corporation of India Ltd. 3. Dempo Mining Corporation Ltd.
4. Gujarat Minerals Development Corporation 4. Ferro Alloys Corporation Ltd.
5. Hindustan Copper Ltd. 5. Hindustan Zinc Ltd.
6. Madhya Pradesh State Mining Corporation 6. Ispat Industries Ltd.
Ltd. 7. Keshoram Cements .
7. Maharashtra State Mining Corporation Ltd. 8. Madras Cements Ltd.
8. Mineral Exploration Corporation Ltd. 9. Mangalam Cements Ltd.
9. National Mineral Development Corporation 10. Oswal Chemcials and Fertilizers Ltd.
Ltd. 11. Sesa Goa Pvt. Ltd.
10. Orissa Mining Corporation. 12. Tamilnadu Minerals
11. Rajasthan State Mines & Minerals Ltd. 13. Tata Iron & Steel Co. Ltd.
12. Rajasthan State Tungsten Development
Corporation.
13. Sikkim Mining Corporation Ltd.
14. Uttar Pradesh Mineral Development
Corporation Ltd.
15. West Bengal Mineral Development
Corporation Ltd.
 Flow sheet of Mineral Processing

Ore from Mines

Crushing

Screening Mineral Extraction Tailings

(Separation/ Gangue
Concentration)
Grinding Mineral concentrates

Chemical Extraction
Classification (extract valuable
element from mineral) Metal
Flowchart of extraction of metals
• The ultimate goal in the production of
metals is to yield metals in their purest
form.
• Step-1: mining
• Step-2 and 3: Physical processing
• Step-5 and 7: low temperature chemical
processing (hydrometallurgy)
• Step-4 and 6: These steps are not included
under the heading of mineral processing
(high-temperature smelting and refining
means pyrometallurgy)
• Step-1,2,3,5 are considered as the part of
mineral processing.
Simple block flowsheet

• Block diagram in which all operations of similar

character are grouped.
• Comminution deals with all crushing, grinding and
initial rejection.
• Separation groups the various treatments incident to The simple line flowsheet is for most purposes
production of concentrate and tailing. sufficient, and can include details of machines,
• Product handing covers the disposal of the products. settings, rates, etc.
Methods of beneficiation
• Mineral dressing (according to Gaudin in 1951) is the processing of raw materials to yield
marketable products and waste by means that do not destroy the physical and chemical identity of
the minerals.
• Ore dressing is mineral dressing applied to ores.
• Taggart (1951) defines ore dressing as the sum total of treatments to which ore are subjected in
order to separate and discard their worthless fractions by essentially physical means.
• Traditionally, ore dressing had been confined to physical operations, but technology has widened
considerably in recent years to also include certain chemical beneficiation techniques.
• In these techniques, not only is the physical appearance or the chemical composition of the mixture
of minerals altered but limited changes in the chemical nature for the minerals may also be brought
about.
• For example, in magnetizing roasting, the FeO impurity can be oxidized to Fe3O4 which is
magnetically separated in a subsequent operation.
• Metallurgical wastes such as off-grade ores and slags are, at present, being beneficiated by
employing chemical reactions such as chlorination.
• Accordingly, ore dressing may be defined as the physical or chemical treatment or a combination
of the two which aims at altering the physical and chemical nature of the minerals so that the final
combination of the minerals can be economically treated for metal extraction.
Unit Operations in mineral dressing
Process Description Properties of mineral exploited

Comminution
Crushing, grinding Subdivision of mineral lumps and Brittleness
particles into smaller sizes
Sizing
Sorting or hand-picking, screening Separation according to size Size difference among particles
Hydraulic classification Settling in fluid Relatives difference in size and
density among mineral particles
Concentration
Gravity concentration
Heavy media separation and Settling in liquid Relative difference in density
Jigging among particles
Tabling Frictional movement along wet Density, size, shape, and coefficient
vibrating solid surface of friction
Magnetic separation Separation due to magnetic field in Magnetic permeability and
dry or wet condition magnetic susceptibility of particles
Unit Operations in mineral dressing
Process Description Properties of mineral exploited
Electrostatic separation Charging and charge loss of particles and Conductivity and charge-retention
their deflections in electrostatic field characteristics
Flotation Attachment of gas bubbles to mineral in Surface properties
aqueous pulp containing surfactants and Affinity for specific surface-active
frothers. reagents
Subsequent preferential froth flotation for
some minerals
Dewatering
Sedimentation thickening Settling of particles Nonspecific
Coagulation Neutralization of charge or repulsive forces Adsorption properties of minerals
may lead to beneficiation
filtration Solid-liquid separation Nonspecific
Drying Removal of moisture from moist solid Nonspecific
Agglomeration
Pelletizing, nodulizing, Obtaining bigger lumps from small particles Solid-solid reaction at interfaces of
sintering through adhesion or incipient fusion of particles
particles
Comminution (Size reduction)
• Comminution basically serves two purposes:
1) It detaches dissimilar mineral particles from each other so as to ‘Liberate’ the valuable components.
2) It produces small-sized mineral particles which are more suitable than large-sized ores for subsequent
beneficiation operations.

Libration
• The particles of an ore may consist either of a single material or of two or more minerals.
• The former are termed free particles and the latter locked particles.
According to Gaudin (1951),
• Degree of liberation: it is the percentage of the mineral or phase occurring as free particles in relation to the
total of that mineral occurring in free and locked forms.
• Degree of locking: it is the percentage occurring as locked particles in relation to the total occurring in the
free and locked forms.

• Generally, grain and grain size are used with reference to uncrushed rock and particles and particles size with reference
to crushed or ground rock.
• There are two ways in which a large lump of rock may break.
1) It may break along the grain boundaries between adjacent dissimilar mineral if the bonds along these boundaries are
weak. In such a case, the mineral is liberated by detachment.
2) If the bonds are not very weak or are at least comparable with the cohesive energy of the individual minerals, then the
bond between adjacent dissimilar minerals may not rupture. It would be liberated by size reduction.
Comminution (Size reduction)
Liberation by Size Reduction

• If there is a fracture across grain along

regular planes, some locked particles are
automatically freed.
• Guadin (1951) has used a simple analytical
procedure to show that when a mixture of
two phases is crushed, the less abundant
phase is not freed at all unless the particles
are finer in composition than the original
grain size.
• The particles must be much finer than the
grain size if the less abundant phase is to
be freed to any appreciable extent.
• An important point to be noted here is that
the more abundant phase is always freer
than the less abundant phase.
Crushing and Grinding
• Crushing: the comminution of an ore to about 6 mm (maximum).
• Grinding: the comminution of an ore to less than 6 mm.
• Machines such as jaw crushers, gyratory crushes, and rolls carry out the crushing of an ore as it is
mined.
• In these machines, the ore is crushed in a wedge-shaped space between two hard crushing surfaces-
one fixed and the other moving.
• The smaller fragments of the crushed ore particles are collected as they fall through an opening
provided in the machine.
• Grinding, a process that is slower than crushing, is usually carried out in a ball mill or in an
equipment similar to it, namely, a tube mill, a pebble mill or a rod mill.
• These mills are closed chambers containing hard balls, rods, or pebbles, which are used in
grinding.
• In the rotating mill, the ore particles are subjected to various forces which cause fracture such as
(1) cataracting (impact with balls, rods, or pebble), (2) cascading (attrition among rolling balls) (3)
interparticle collisions and rubbing, and (4) frictional forces at the lining of the mill.
Crushing and Grinding

• If the speed of rotation of a mill is too high,

then centrifuging takes place. As a result, the
contents of the mill simply stick to the inner
rotating surface, and there is hardly any
grinding.
• Conversely, if the speed of rotation is too
slow, then cataracting does not occur, and
the particles and balls simply roll down the
inner surface. In such a situation, only
limited grinding takes place as a result of
cascading.
Crushing and Grinding
• In the literature, there are a number of empirical and semi-empirical relations
which are the so-called ‘classical’ laws of comminution.
• These laws describe the relationships between the cumulative grinding energy
input and the degree of the size reduction of brittle solids.
• Some of the widely accepted laws are as follows.
Rittinger’s Law
• The energy expended during comminution is proportional to the area of the new
surface produced as a results of particle fragmentation.
Kick’s Law
The energy is proportional to the size reduction ratio.
Bond’s Law
The total work input represented by a given weight of a crushed or ground product
is inversely proportional to the square root of the diameter of the product particles.
Sizing
• Most unit processes are designed to treat ores over certain size ranges.
• For example, the feed for a blast furnace must be lumpy, whereas that for fluid bed roasting must
be rather fine, but not very fine.
• A crude method of selecting the coarser particles from an ore body is sorting or hand-picking.
• This method yields particles (approx. dia. Range 40-500 mm) which are not only ideal for certain
unit processes but may also contain a high concentration of the mineral.
• Hand-picking or sorting: particles are properly classified by continuous movement of ore
particles on the conveyer belt according to their size.
• Another method of selection by sizing is screening where the basis of separation is the particles
size, as indicated by standard apertures. In this way, the particles can be separated into two groups,
namely, oversized and undersized.
• A size distribution can be obtained by using a series of apertures as available in a screen, which is
perforated surface.
• A laboratory testing screen consists of a circular brass shell whose diameter is about 200 mm and
height about 50 mm.
• Another screening device, now widely used, is an automatic shaking device.
Classification and concentration
• Classification is a process by which particles of different sizes and
specific gravities are sorted out into uniform groups.
• Classification differs from sizing in two ways, • Generally, the ores are
• First, it is normally applicable to a very low range of particles size (65- found mixed with earthy
200 mesh). impurities like sand, clay,
• Secondly, it separates particles on the basis of their densities. lime stone etc.
• Thus, if the particles sizes are comparable, then, the settling velocities
of heavier and lighter particles would be different, leading to a • These unwanted
possibility of separation and concentration. impurities in the ore are
• In general, classification depends on the settling rates of the individual called gangue or matrix.
particles in a fluid medium (usually water).
• Types of settling – (1) free settling (2) hindered settling • The process of removal of
• Free settling takes place when the individual particles settle freely gangue from powdered
(means unhindered by other particles). ore is called concentration
• Hindered settling occurs when particles of different sizes, gravities,
or ore dressing.
and shapes, in a crowded mass, are sorted in a rising current of water,
the velocity of which is less than the settling rate of the particles, but
sufficiently high to keep then in a turbulent or fluid condition.
Classification and concentration
The settling of a particle in water depends on several factors which are given below:
Specific gravity – a particle with higher specific gravity settles faster than another
particles with lower specific gravity when other parameters such are comparable.
Shape – A rounded particle settles faster than a long narrow grain or a flat grain.
Size – A large particle settles faster than a small one.
Air bubbles – A particle that does not retain adhering air bubbles settles faster than
one that does.
Magnetism – particles that have a mutual magnetic attraction settle faster than those
that do not have such an attraction.
Density of liquid – The settling rate of a particle is higher in a lighter than in a
heavier liquid.
Viscosity – The settling rate of a particle is higher in a less viscous medium.
Classification and concentration
Heavy media separation
• It is a special concentration process
which depends on the specific gravity of
a particle.
• The light (low specific gravity) earthy
impurities are removed from the heavier
metallic ore particles by washing with
water.
• It is therefore, used for the concentration Gravity separation (Hydraulic washing)
of heavier oxide ores, like hematite
(Fe2O3), tinstone (SnO2), and gold (Au). • The densities of most metallic oxides lie in the
• In this method, the powdered ore is range 3.5-4.5 gm/cc.
agitated with water or washed with a • Silica – main component of gangue – having a
strong current of water. density of 2.65 gm/cc.
• Therefore, during heavy media separation in a
• The heavier ore settles down rapidly in
the grooves and the lighter sandy and liquid whose density approximately 3.0 gm/cc, the
earthy materials (gangue particles) are metallic oxides sink but silica floats.
washed away.
Classification and concentration
Jigging
• In a jig, a thick pulp is supported on a
grid and is stratified by pulsating forces
of water from the bottom of the
apparatus.
• In the jigging, all particles are suspended
and the water is allowed to drain back
though the grid.
• This cycle is continuously repeated.
• Eventually, those particles that are denser
and smaller than others concentrate in the
lower strata.
General scheme of a jig (front view).
Classification and concentration
Tabling
• A concentration table or a riffle table employs principles
similar to jigging in a completely different way.
• In this case, the operation is known as tabling.
• In tabling, an inclined flat surface is divided into narrow
strips by riffles of wood so as form parallel channels.
• These channels are set at right angles to the direction of the
water flow.
• During operation, the entire table is vibrated horizontally,
length-wise, in the direction of the riffles.
• As the ore suspension flows across the vibrating table, the
light particles are carried farther than the heavy particles
across the riffles in the direction of water flow and the heavy
particles themselves are carried, length-wise, along the
riffles to the discharge end.
• Thus, channels that are closer to the feed inlet receive the
coarser particles.
Classification and concentration
Magnetic Separation
• By this method, those ores can be concentrated which either
contain impurities which are magnetic or are themselves
magnetic in nature.
• For example, the tin ore, tin stone (SnO2) itself is non-magnetic
but contains magnetic impurities such as iron tungstate
(FeWO4) and manganese tungstate (MnWO4).
• The finely powdered ore is passed over a conveyer belt moving
over two rollers, one of which is fitted with an electromagnet.
• The magnetic material is attracted by the magnet and falls in a Magnetic Separation
separate heap.
• In this way magnetic impurities are separated from non-
magnetic material.
Classification and concentration
Electrostatic Separation
• The electrostatic separation of one
mineral from another is somewhat
similar to magnetic separation in that it is
brought about by an external field
(electrostatic) in conjunction with a
gravitational field.
• When different types of mineral particles
are given an electrostatic charge and then
brought into contact with a grounded
electrical conductor, the charge leaks
away from a good conductor more
rapidly than from a bad conductor.
• This process of discharging is combined
with a falling of particles in air so as to
separate a mineral which is a good
conductor of electricity from one which
is not.
Classification and concentration
Froth Flotation
• This method is especially applied to sulphide
ores, such as Galena (PbS), Zinc Blende (ZnS),
or Copper Pyrites (CuFeS2) .
• It is based on the different wetting properties of
the surface of the ore and gangue particles.
• The sulphide ore particles are wetted
preferentially by oil and gangue particles by
water.
• In this process, finely powdered ore is mixed
with either pine oil or eucalyptus oil.
• It is then mixed with water.
• Air is blown through the mixture with a great
force.
• Froth is produced in this process which carries
the wetted ore upwards with it.
• Impurities (gangue particles) are left in water
and sink to the bottom from which these are
drawn off
 Thank you !
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