Mineral Processing 2 Slides

8/12/2019 Mineral Processing 2 Slides

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AGGLOMERATION:

The act or process of converting separate particles into mass or cluster. An enormous amount of fines is generated during mining and ore processing

operations. Since the fines can not be used directly in the blast furnace. It is necessary to agglomerate them into lumps; pellets and briquettes. The particulate matter may require size enlargement to make it sellable or to improve

its physical properties

The process is used for changing the size of concentrate particles, when the particle sizeof an ore is too small for the use in latter stage of treatment (e.g. in the blast furnace), it

must be reformed to lumps of appropriate size and strength.

Most of the mineral products are agglomerated by four basic processes.a) Sinteringb) Pelletizing

c) Briquetting

d)Nodulizing

(1) SINTERING:

The sintering of iron ore is one of the most important methods of ore treatment

It may be defined as the process of heating concentrate particles to an elevatedtemperature below its melting point.

It is one of the processes in which a bed of small ore particles is bonded into clinker byhigh temperature fuel combustion.

Excessive fine material in an ore will result in a greater fine dust loss at blast furnace The rate of temperature is controlled by drying and blowing air through the bed. The

temperature approaching 1400C in the narrow combustion zone.

Sintering has the largest industrial application and many million tons of iron oreconcentrate are annually converted into sinters by this process.

(2) BRIQUETTING :

It can be defined as a process of agglomeration where by particulate matter isconsolidated into briquettes

Iron ore fines ------> binder -------->Mixing--->Mechanical pressure = iron ore Briquettes


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The kiln used may be 100ft long 6 ft in diameter at entrance and 10ft diameter at thedischarge end.

It is slightly inclined to the horizontal and rotates at the speed of 1to 2 rpm. The agglomeration continues as the ore proceeds through the kiln and heated at

temperature of 1200 to 1500C. A great cooler usually cools the nodules. The size of nodules depend upon the temp:, quality of tar and speed of rotation of kiln.

MAGNETIC SEPARATION:

It is one of the methods applied in mineral processing for separation of magneticminerals from non-magnetic minerals.

Initially it was employed to separate strongly magnetic ores(magnetite) from gangue. Before 1939,only few ferromagnetic materials were available for industrial application. With the advancement of technology and design of machines , this method is adopted

now for the separation of ores which are feebly magnetic.

For Example:

Hematite, limonite, siderite, etc, can now be separated from their gangue by application

of high intensity magnetic fields.

Magnetic separation is a method of concentration of an ore used when:1) The ore is magnetic but gangue is non-magnetic

2) The ore is non-magnetic but gangue is magnetic

The magnetic separation is effective due to distinct movement of magnetic particlestowards the magnetic field and non-magnetic particles away from it.

Broadly minerals can be classified into three groups on the basis of their behaviour in amagnetic field:

1) Attracted

2) Repelled or

3) Unaffected

Further more, there are three main classifications of magnetic minerals w.r.t theirinteraction with the magnetic field:


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1) Paramagnetic Minerals (Feebly Attracted)

2) Ferromagnetic Minerals(Strongly Attracted)

3) Diamagnetic Minerals (Non-magnetic)

PARAMAGNETIC MINERALS:

These minerals are slightly attracted by the magnetic field and dont retain theirmagnetic properties when the external field is removed.

These minerals are attracted in the direction in which the magnetic field increases( i.e.towards a concentrated magnetic field).

A magnetic response is obtained at a flux density greater than 2000 gauss and less than20000 gauss.

Examples include:

Chromite, Hematite, Limonite, Monazite, Aluminum, Tin, Platinum

FERROMAGNETIC MINERALS:

These are themselves magnets and have very high susceptibility to magnetic force andthey exhibit the strong attraction to the magnetic field.

They are attracted in the same way, however they can be quite easily magnetized by alow intensity of magnetic field.

A magnetic response is obtained at a flux density of


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GAUSS:

The amount of magnetism induced in a body by a magnetic force is called Flux densityand is measured in gauss.

The intensity of a magnetic field refers to the no. of lines of flux passing through a unitarea .

Lines of flux are measured in gauss( lines/cm2 orTesla) 1 Tesla = 10,000 gauss.TYPES OF MAGNETIC SEPARATORS:

INTRODUCTION:

various material compositions on the

basis of their magnetic properties. They are used in industries like mining, and smaller versions

are utilized in scientific labs to process some types of samples. Numerous companies make

magnetic separators for various applications, and there are several different styles available for

people to choose from, depending on the application and their needs.

kind. As materials are passed below,

over, through, or around the magnetic separator, it attracts undesirable impurities, pulling

them out and cleaning the process stream.

WHERE MAGNETIC SEPARATORS COULD BE USED?

Magnetic Separators could be used in two cases: The ore is magnetic but gangue is non-magnetic The ore is non-magnetic but gangue is magnetic All the materials are affected in some way when placed in the vicinity of magnetic field,

although with most substances the effect is too slight to be detected.

The mechanism for the separation is distinctive movement of magnetic particlestowards the magnetic field and non-magnetic particles away from it.

APPLICATION OF MAGNETISM AS SEPARATOR:

For the removal of tramp iron in coarse and intermediate-crushing circuits, as aprotection to the crushing machinery.

For the concentration of magnetite ores For the concentration of iron ore other than magnetite, after preliminary conversion of

iron minerals to artificial magnetite by suitable Roasting

For the removal of small quantities of iron ore minerals form ceramic raw materials.


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ELEMENTS OF DESIGN OF MAGNETIC SEPARATORS:Following are the elements while selection and designing of a magnetic separator:

Production of suitably converging magnetic field Even feeding of ore particles as a stream or sheet Control of speed of passage of ore thorough the magnetic field Avoidance and/ or correction of occlusion or non-magnetic material between or within

magnetic flux

Provision of suitable means for disposing off separated products Provision for production of a middling Elimination or reduction to a minimum of moving (wearing) parts

CLASSIFICATION OF MAGNETIC SEPARATORS:Magnetic separators can be classified according to:

the medium in which the separation is made the mode of presentation of the feed the mode of disposal of the products and whether the magnets are stationary or moving

On such basis some might be as:

High intensity magnetic separators Low intensity magnetic separators Dry separators Wet separators etc

IMPORTANT TYPES OF MAGNETIC SEPARATORS:There are many types of magnetic separators but some important types are described as under:

EDISON SEPARATOR:

This magnetic separator consists of a bar magnet. The ore as thin stream falls in front ofthe poles, susceptible particles being deflected towards and non-susceptible particles

continuing to fall un-deflected.

This magnetic separator was not wholly successful because of inability of control flow ofsolid in a thin sheet, and because of lack of control over the speed of the falling

particles.

MAGNETIC DRUM SEPARATOR: These are important magnetic separators that remove ferrous metal from dry bulk

products in free-flowing processing systems. They are self cleaning unit consisting of

drums and housing normally of stainless steel. The magnets used by the magnetic drum

separators are either ceramic magnets or rare earth magnets. The magnetic drum

separators are available both in single or double drum configuration.


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HOW IT WORKS?

The processing materials enter the top of the magnetic drum separator and flow acrossthe surface of the drum. The rotary drum in the magnetic field captures the ferrous

tramps whereas the nonferrous falls free from the drum into the cleaned material flow.

As the drum rotates, the ferrous metal so captured is carried past the diverter and

released outside of the magnetic field.

TYPES:

Its types are as under:

Electro drum separators Wet drum separators Single drum separators Double drum separators

APPLICATIONS:

The magnetic drum separator is ideal for separating iron particles from granules and powders;it is widely used in the following industries:

Glass Ceramic Chemical Fertilizer Plastic Food industry Iron and steel slag treatment Reduced pyrite ash separation Calcined limestone production Metal powder production

BALL NORTON SEPARATOR:Unlike most magnetic separators which are used to remove relatively small amounts of metal,

the ball Norton separator is designed to handle large amounts of ferrous material removing

other undesirable elements. A unique combination of alternating magnetic poles and vibratory

conveying works to clean the magnetic material.

APPLICATIONS:

Its applications include: Foundry shot Crushed borings Slag and magnetic ores


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ROLLER TYPE MAGNETIC SEPARATOR: This is meant to separate ferrous contaminants from the flimsy magnetized dry granular

metallic and non-metallic materials. It has wide applications in industries and mineral

processing. This separator uses high powered rare earth magnets with very low

dimensional tolerance. The other components of machine are conveyor and vibratory

feeder. The magnetic rolls are available in different widths and magnetic strength.

HOW IT WORKS?

The material is discharged on the belt by the feeder. The magnetic roll is enveloped bythe conveyor. The Para and Ferro magnetic ingredients remain stuck to the belt whereas

non-magnetic ingredients pass freely at the end of the conveyor.

APPLICATIONS:

It has applications in the following areas like:

Glass industries Abrasive refractory Quartz cleaning Upgrading of graphite Recovery of metals from slag removal of Ferro silicates Chemical industry.

GRAVIT FEED MAGNETIC SEPARATOR:

This separates ferrous tramp metal through gravity system; these magnets areconstructed out of welded stainless steel structure. The gravity magnet comes in

different shapes and sizes and is ideal for narrow chute applications. Gravity feed

magnets are normally used in vertical flow system.

APPLICATIONS:

Gravity magnetic separators have different industrial and commercial usage. They are applied

in industries like:

Food industry Chemical industry Grain processing industries Pharmaceutical industries

MAGNETIC COOLANT SEPARATOR: It is a device which cleans the coolant liquid of very fine ferrous particles. It removes

the iron chips from the milling or grinding liquid. It is light and compact structure having

strong magnetic power which can remove very fine ferrous particles. For precise

grinding operations uninterrupted flow of oil is must. The coolant magnetic separator

ensures the uninterrupted flow of the liquid.


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WET DRUM SEPARATOR: Wet drum magnets have high magnetic recovery and discharge. The feed slurries

recover the magnetic. These are available in single or multiple drum applications. These

recover magnetic solids in as clean a magnetic concentrate as possible. Permanent

magnet assembly eliminates coil burn-outs. The magnet/pole elements are bolted to amild steel shaft. The drum is made from thick stainless steel for long service of life. Wet

drum separators are available in different configuration like single drum, double drum

and multiple drum. In double drum two separators are arranged back to back with a

common feedback.

APPLICATIONS:

Glass industry Chemical industry Plastic industry Mining industry Food industry Pharmaceutical industry Foundry industry

FROTH FLOTATION: Floatation is the process by which mineral particles are induced to become attached to

the air bubble & float and other particles to sink, so that valuable mineral are

concentrated and separated from the worthless gangue or waste.

Floatation is widely used in mineral processing industry with the aim of concentratingvaluable to obtain high grade concentrate and simultaneously separate gangue.

Before floatation the mined ore is mechanically ground, to powder of desired grain sizeand mixed with water and chemicals to form slurry or pulp for flotation process.

In the floatation cell air is introduced into slurry to produce air bubble that naturallymove upward and produce froth on the top of the slurry .

The mineral grains depending on their mineral contents tend either to float or sink inthe liquid .

During the floatation process particles of desired mineral which are commonlyhydrophobic attached to the rising air bubble from bottom of the cell where air is

injected with the particles of gangue material (which are hydrophilic) remain in slurry or

pulp and discarded through tailing gate. Froth flotation can be adapted to a broad range of mineral separations, as it is possible

to use chemical treatments to selectively alter mineral surfaces so that they have the

necessary properties for the separation. It is currently in use for many diverse

applications, with a few examples being:

separating sulfide minerals from silica gangue (and from other sulfide minerals);separating potassium chloride (sylvite) from sodium chloride (halite);

separating coal from ash-forming minerals;


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removing silicate minerals from iron ores; separating phosphate minerals from silicates Flotation process can be categorized as:

1) PLAIN FLOTATION:

It was 1st practiced in MP to obtain one type of concentrate from sulfide ore.

2) BULK FLOATATION:

Generally mineral ores contain more than one valuable mineral. In case of sulphides,minerals usually occur together e.g. chalcopyrite and galena, chalcopyrite and pyrite. In

some ore bodies many minerals may floats out together and discard the gangue.

Such flotation process in which more than one valuable mineral ore floated together iscalled bulk flotation.

Or the rising of a mineralized froth, of more than one mineral, in a single operation.3) DIFFERENTIAL FLOTATION: Later on this mixture of valuable minerals is further floated afterbulk floatation to recover individual mineral one by one is called differential flotation.

It was later developed to recover progressively more than two kinds of concentratefrom complex sulfide ore bearing many valuable minerals.

In differential flotation , valuable minerals are recovered individually. In this , sulfide concentrate is accomplished by 1stdestroying the hydrophobic coating

and then by recovering another concentrate.

FLOTATION EQUIPMENT: Flotation can be performed in rectangular or cylindrical mechanically agitated cells or

tanks. Mechanical cells use large mixer at the bottom of the tank to introduce air and

providing mixing action.

Flotation cells use spargers to introduce air at the bottom of the cell. Most of the minerals usually do not possess enough floatability and it is difficult to float

these minerals without the aid of chemical agent.

In order to achieve satisfactory separation of valuable minerals from gangue variousfloatation reagents classified as collector, frothers and modifiers are used.

1) COLLECTORS/SURFACTANTS:

Collectors are reagent that adsorb on the mineral surface to form a thin ,coating andmake them hydrophobic .

Collectors provide hydrophobicity on the mineral surface to enhance the mineral to airbubble attachment .

Hydrophobicity has to be imparted to the most of the minerals in order to float them . in order to achieve hydrophobicity ,surfactants known as collectors are added to the

slurry and time is allowed for adsorption during agitation that is its conditioning period


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COLLECTORS:


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2) FROTHERS:

Frothers are reagents used to produce froth of adequate stability and its main functionis tostabilize the bubble that transport the hydrophobic valuable minerals to the surface

of froth zone where they can easily be separated.

Froth generation require the use of frothers and they must be to some extent soluble inH2O,otherwise they would be distributed very unevenly in an aqueous solution and

their surface active properties would not be fully effective.

The most effective frothers include:

Pine oil Cresol (cryslic acid) Aliphatic alcohol Polyglycol Hydroxyle ,carboxyle ,carbonyle Esters Apart from the ability of frothers to form froth, they have other important roles

including:

Creating finer bubbles, whereby the dispersion of air in the flotation cell also improves. Reducing the rate of bubble rise from the mixing zone to the froth zone Increasing the strength of the bubbles and stability of the froth

3) MODIFIERS/REGULATORS:

Modifiers are used extensively in flotation to modify the action of collectors. The function of modifiers is neither collecting nor frothing but the main function of

modifier is to modify the action of collector either by enhancing or by reducing itshydrophobic effect on the mineral surface.

In the presence of modifiers, the collector only adsorb on the particles that are targetedfor recovery and make the collector action more selective towards certain mineral.

The purpose of regulator or modifier is to prepare the surface of various solids forselective adsorption of the surfactants in such a manner that only the desired particles

are made hydrophobic.

According to their function the modifying reagents may be classified into the following groups:

Activators Depressants PH Regulators

ACTIVATORS:

Activators are reagents that alter the surface of mineral so that it can more readilyadsorb a collector and float.


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DISPERSION:

It is the uniform mixture of solid particles in a liquid, where the solids are insoluble inthat liquid.

In dispersion, the suspended particles are uniformly distributed in suspension with theindividual particles being essentially separate.

In dispersion, the suspended particles remain in suspension for longer period of timeduring which the pulp is processed.

Dispersants or dispersing agents are used to improve the separation of the particles andto prevent settling or clumping of the particles.

Dispersants include: Sodium Silicate Sodium hexametaphosphate Sodium Polyacrylate

FLOCCULATION: Flocculation refers to the process by which fine particles are caused to clump together

to form floc.

In this process, the suspended particles in slurry come closer to each other, makingcluster and settle to the bottom of the liquid or float to the top of the liquid depending

on their weight.

Mineral industry world wide need to process finely mineralized ores and recovermineral values from slimes.

Mostly desired minerals in the form of concentrate of coarse particles are recovered whereas

the slimes may be discarded while containing mineral values.

Because of losses of mineral values, it is necessary to convert slimes into coarser particles by

the process of flocculation. Flocculation is achieved by agitation and flocculants which encourage the clumping of

slime.

Once, suspended particles are flocculated into larger particles they can usually beremoved from liquid by filtration.

FACTORS AFFECTING THE FLOCCULATION ARE: concentration of particles in the pulp (pulp density) temperature of pulp PH of pulp Size of particles

Rate of flocculation

Depends upon the following factors:

(a) Particle population in the fluid.

(b) Size of the particles.

(c) Sequence of other events.


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If some other phenomenon happens before flocculation the condition may change and may

affect the subsequent rate of flocculation.

Flocculants or flocculating agents are chemicals used to facilitate the settling ofsuspended particles in slurry.

Flocculants include: Lime Starch Lime + starch Alum Gypsum Ferric Chloride Aluminum sulphate

HEAP LEACHING OF COPPER ORE:DEFINITION:

Leaching is the process of extracting minerals from a solid by dissolving them in aliquid, either in nature or through an industrial process

OR

Heap leaching means leaching ores that have been mined, crushed, and transportedon impervious pads for leaching by sprinkling and percolation of the solution through

the ore

OR

Heap leaching is a tried and tested mining technique enabling the processing ofdifferent kinds of ores which could not otherwise be exploited under viable economic

conditions

OR The separating or dissolving out the soluble constituents from a rock or ore body by

percolation of water is called Heap Leaching/Leaching.

Leaching is the process by which inorganic, organic contaminants or radio nuclides arereleased from the solid phase into the water phase under the influence of mineral

dissolution, desorption, complexation processes as affected by pH, redox, dissolved

organic matter and (micro) biological activity. The process itself is universal, as any

material exposed to contact with water will leach components from its surface or its

interior depending on the porosity of the material considered.

Leaching is extensively used in metal processing industries. The useful metal may occurin mixtures with very large amounts of undesirable constituents, and leaching is used to

remove the metals as soluble salts. The use of acids is prevalent in the metal processing

industry, Sulphates are normally used to remove metals from the solid phase, and these

produce harmful environmental byproducts such as sulphates.

STEPS IN THE PROCESS OF HEAP LEACHING OF COPPER ORE:

Crushing and throwing of oxide ore on clay lined leach pad


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Showering of weak sulphuric acid on the heap Collection of solution (water+acid+ore) in the pond Transporting solution to the Solvent Extraction Plant toproduce copper cathodes Electrowining process is applied Pure copper is transported and water is recycled back to the pad

HEAP LEACHING PROCESS:

The mined ore is usually crushed into small chunks and heaped on an impermeableplastic and/or clay lined leach pad where it can be irrigated with a leach solution to

dissolve the valuable metals.

While sprinklers are occasionally used for irrigation, more often operations use dripirrigation to minimize evaporation, provide more uniform distribution of the leach

solution, and avoid damaging the exposed mineral.

The solution then percolates through the heap and leaches both the target and otherminerals. This process, called the "leach cycle," generally takes from one or two months

for simple oxide ores (e.g, most gold ores) to two years (for nickel laterite ores).

The leach solution containing the dissolved minerals is then collected, treated in aprocess plant to recover the target mineral and in some cases precipitate other

minerals, and then recycled to the heap after reagent levels are adjusted.

Ultimate recovery of the target mineral can range from 30% of contained (run-of-minedump leaching sulfide copper ores) to over 90% for the easiest to leach ores (some

oxide gold ores).

In recent years, the addition of an agglomeration drum has improved on the heapleaching process by allowing for a more efficient leach.

The rotary drum agglomerator works by taking the crushed ore fines and agglomeratingthem into more uniform particles.

This makes it much easier for the leaching solution to percolate through the pile,making its way through the channels between particles.


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The addition of an agglomeration drum also has the added benefit of being able to pre-mix the leaching solution with the ore fines, to achieve a more concentrated,

homogeneous mixture, and allowing the leach to begin prior to the heap.

COPPER LEACHING COUPLED WITH SX/EW

CONSISTS OF THE FOLLOWING STEPS: Application of a sulfuric acid solution to the top of a heap. Interaction of the leach solution with the ore and gangue minerals within the heap. Stoichiometric exchange of one copper ion for two hydrogen ions in the SX plant. Recirculation of the copper depleted solution back onto the heap. The preceding four points state that oxide copper leaching with SX/EW takes place

within a system that is closed to all elements save copper and sulfur.

Sulfur is added as fresh leach solution. Copper is removed from the system in the SX/EW plant. Sulfide dump or heap leaching, where all acid is derived from the dissolution of pyrite

and other sulfides, is closed to all elements save copper.

For all other elements and compounds, copper heap leaching is a closed system. The characterization of copper leaching as a closed system has profound implications to

the chemistry of leaching.

SOLVENT EXTRACTION AND ELECTROWINING: SOLVENT EXTRACTION: It is more commonly used to refine copper. An organic solvent in which copper is soluble is introduced. As the copper is more soluble in the organic layer than the aqueous, it enters an

organic-copper solution and is separated.

Sulfuric acid is added to strip the copper from the organic solvent into an electrolyticsolution.

ELECTROWINING: The copper is refined by electrolysis. The anodes cast from processed blister copper are placed into an aqueous solution of 3

4% copper sulfate and 1016% sulfuric acid.

Cathodes are thin rolled sheets of highly pure copper or, more commonly these days,reusable stainless steel starting sheets.

A potential of only 0.20.4 volts is required for the process to commence. At the anode, copper and less noble metals dissolve. More noble metals such as silver and gold as well as selenium and tellurium settle to the

bottom of the cell as anode slime, which forms a saleable by product

Copper ions migrate through the electrolyte to the cathode. At the cathode, coppermetal plates out but less noble constituents such as arsenic and zinc remain in solution.

The reactions are:


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At the anode: Cu(s) Cu2+(aq) + 2e At the cathode: Cu2+(aq) + 2e Cu(s

ENVIRONMENTAL ISSUES CAUSED BY

LEACHING AND THEIR IMPROVEMENTS: Heap leaching systems have the potential to contaminate groundwater. Infiltration of leach solutions must be prevented with the use of appropriate liners and

sub-surface drainage systems to collect and recycle solution for treatment.

Pipelines should be provided with secondary containment and leak detectionequipment should be installed.

Impoundments to hold dirty water or untreated process effluents must also be lined. Groundwater monitoring for contamination levels and quality must be carried out.

ADVANTAGES OF HEAP LEACHING:

Much more environmentally friendly than pyrometallurgy. Compared to pyrometallurgy, only a fraction of the gases liberated into the

atmosphere.

Low capital cost Ability of complex and low grade ores extraction A major advantage of heap leaching is the elimination of expensive milling operations

since the ore body need not be crushed to sizes much smaller than 20 to 25 mm.

DISADVANTAGES OF HEAP LEACHING: Large amount of water used,

greater potential for contamination. Difficulties in solidliquid separation Impurities problems in purification process Much longer time needed for high metal recovery

NAGAR PARKER CHINA CLAY PROCESSING:CHINA CLAY- AN INTRODUCTION:

It is a common name used for Kaolin, and is derived from kaolinite, a Chinese wordmeaning high ridge

This was the name of a hill near Jauchau Fu, China, where kaolin was first mined severalhundred years ago for ceramics.

It is white powdery mineral, containing impurities like silica sand, mica etc The removal of these impurities makes it suitable for various industrial applications. The important properties of china clay are that, it has good plasticity , doesntswell in

water, withstand high temperature ( up to 1300 0C and even above) and is non-

conductor of electricity.


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FORMATION OF CHINA CLAY:

China clay is a white kaolin formed due to alteration of feldspars and also when graniteis changed by hydrothermal metamorphism.

It occurs naturally as hydrated aluminum in the compositions usually 2SiO2.Al2O3.2H2O

NAGAR PARKER CHINA CLAY:

The Geological Survey Of Pakistan discovered the Nagar Parker deposits andinvestigated these deposits with the help of detailed Geological mapping, sampling and

by physical and chemical testing.

In Nagar Parker area, deep weathering and alteration of granitic rocks have producedchina clay.

The china clay is in the form of several large pockets which occur in a plain area atshallow deposits.

The deposits are largely covered by a thin layer of soil and further confirming thatKaolinite is the major constituent of Nagar Parker china clay and the measured reserves

are 3.6 Million tons.

To beneficiate Nagar Parker china clay for various industrial uses, it should be processedfor the removal of undesirable minerals such as quartz, gypsum, calcite etc.

Wet processing is preferred for the beneficiation of Nagar Parker china clay as dryprocess is simpler and produces a lower quality product than wet process.

Wet processing is more efficient in concentrating fine china clay .This method involvestwo main steps of the process:

1) Liberation of particles

2) Separation of particles

PROCESSING MECHANISM : Wet processing of kaolin at Nagar Parker begins with blunging of raw china clay with

water to produce slurry using agitator.

Where china clay is liberated from its impurities through the action of agitation. The slurry is then allowed to pass through tank opening designed at the bottom of the

tank.

The fine china clay particles are carried along the moving steam and coarserparticles(silica sand) are allowed to settle down in channels.

The water carrying china clay particles are then passed through fine sieve to separatesmall size silica particles and stored in settling tanks.

After settlement of kaolin particles , most of the water is removed through pumpingand thick pulp of china clay is left behind.

The water is squeezed off from the pulp using disc type filters. The moist agglomerated china clay is then dried for transportation to consumer or for

further refining.


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USES OF CHINA CLAY: China clay is extremely useful mineral, its properties of white color, softness,

smoothness, small particle size and chemically inertness makes it possible for no. ofdifferent applications.

Kaolin has a wide variety of industrial applications including: Ceramics Refractories Insulators Paint industry Paper coating and filling Plastic Rubber and textile industries

Glass industry Dyes and inks Cosmetics Pharmaceuticals Adhesives and cement Chemical industry Medicines Leather Soaps and detergents powder etc.

GLASS MANUFACTURING PROCESS:DEFINITION: Glass is an amorphous, hard, brittle, transparent or translucent super cooled liquid of

infinite viscosity, having no definite melting point obtained by fusing a mixture of a

number of metallic silicates or borates of Sodium, Potassium, Calcium, and Lead.

An inorganic product of fusion which has cooled to a rigid condition withoutcrystallizing.

PROPERTIES OF A GLASS:The following are the properties that are exhibited by the glass:

Brittle Amorphous High viscous Supper Cooled liquid Capacity to absorb different colors without affecting Transparent and translucent Low thermal conductivity Electrical insulator


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Transparency Hardness Chemically inert High refractive index High dispersion


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They are low cost, resistant to water but not to acids. They can melt easily and hence can be hot worked. Uses: Window glass, Electric bulbs, Plate glass, Bottles, Jars, cheaper table wares, test tubes,

reagent bottles etc .

2. COLORED GLASS: Small amounts of metallic oxides are mixed with the hot molten mixture of sand,

sodium carbonate and limestone.

The desired color determines the choice of the metallic oxide to be added, as differentmetallic oxides give different colors to the glass.

USES: Colored glass is much in demand. It is used for decorating walls, making sunglasses, and for making light signals for

automobiles, trains and aero planes.

3. PLATE GLASS: Plate glass is thicker than ordinary glass. It has a very smooth surface. It is made by floating a layer of molten glass over a layer of molten tin. It is used in shop windows and doors.

4. SAFETY GLASS:

It can also be called shatterproof glass. It is made by placing a sheet of plastic such as celluloid between sheets of glass. The special quality of this glass is that in case of breakage the broken pieces stick to the

plastic and do not fly off.

You must have noticed a broken window-pane of a bus or a car still in its place. It is used in automobiles. It is also used for making bulletproof screens.

5. LAMINATED GLASS: It can also be called bulletproof glass.

Several layers of safety glass are bound together with a transparent adhesive. The larger the number of layers used the greater is the strength of the glass. It is stronger than safety glass. It is used in aero planes and windshields of cars.

6. OPTICAL GLASS: Optical glass is softer than any other glass. It is clear and transparent.


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(3) SAMPLING: It is an art of getting representative part (small in size) of an ore. Sampling is the means

where by a small amount of material is taken from the main bulk in such a manner that

it is representative of that large amount. Great responsibility rests on a very small

sample, so it is essential that samples are truly representative of the bulk.

Where ever possible samples should be taken of the material when it has been reducedto the smallest particle size consistent to the process.

To obtain the best sample should be made as homogenous as possible. Ores andconcentrates containing cores particles are less homogenous than those containing five

particles.

Sampling system requires primary sampling devices or cutter, and a system to conveythe collected material to a convenient location for analysis.

(4) WEIGHING: It means to find out the quantity of ore. There are numerous ways to determine the quantity of dry ore. Some of them are as

follows.

By weighing ore cars and trucks and weighing of the tare, this requires an operator. By weighing the concentrate and multiplication of this number by the ratio of ore in

tones is calculated from assay of feed concentrate and failing.

By weighing the ore stream at some convenient point and by making an allowancefor the moisture contents.

(5) ASSAYING: The term assaying means testing of an ore by chemical examination to determine the Nature, proportion etc of ingredients it contains. The ore or concentrate sample must be analyzed or assayed, so that the exact chemical

composition of the material is obtained. Assays are of great importance, as they are

used to control operations and to calculate profitability.

Modern methods of assaying are very accurate on stream X-rays analysis. A new dimension has been added in the last few years by installation of non-stream

analysis enables a change of quality to be detected and corrected rapidly and

continuously, obviating the delays involved in laboratory testing. Basically it consists of

a source of radiation which is absorbed b the sample and consists to give off fluorescent

response of each element; it enters a detector which generated a qualitative output

signal as result measuring the characteristics radiation of one element from the sample.

The detector output signal is generally used to obtain an assay value which can be usedfor process control.

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Mineral Processing 2 Slides