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DBT 203Metal Extractive Technology

Topic 1:

Extracting Metal from Ores

Noor Mariamadzliza binti

Mohd Nan15062012

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Syllabus:

Define of ores, minerals and

rocks.

Describe purpose andprocesses involved in mineral

processing

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Introduction

The art of extracting metals from their oresdates back to the dawn of human civilization.

The first metals used by man were gold andcopper, which were found in nature in metallicor native form.Around 4000 B.C man learned to produce

copper and bronze by the smelting of copperand tin ores in a charcoal fire.

Throughout the history of mankind, theprocesses of extractive metallurgy weredeveloped further by trial and error.

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What is Metal Extractive..

The practice of extracting metal from ore,

purifying it and recycling it.

Or

The practice of beneficiating valuable

minerals from their ores

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Mineral..

Mineral by definition are:- Natural inorganic substances possessing definite

chemical compositions and atomic structure.

Many minerals exhibit isomorphism, where

substitution of atoms within the crystal structure bysimilar atoms takes place without affecting theatomic structure.

Also can exhibit as polymorphism, differentminerals having the same chemical composition,but different physical properties due to differencein crystal structure.

Examples: chalcopyrite (CuFeS2) , galena (PbS)

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Ore..

According to traditional definition:- An ore is a rock which can be mined economically to

serve as raw material for the production of metals.

Types of ore:-

Oxides:iron ores, which usually contain the mineral hematite, Fe2O3, but

which also may contain magnetite, Fe3O4Other heavy metals which are mainly produced from oxide ores

are manganese, chromium, titanium, tungsten and tin.

Sulfides:Copper ore, which often consist of mixed sulfides of copper and

iron.

Other metals which are mainly derived from sulfides are nickel,zinc, lead, mercury and molybdenum.

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Halides

Such as rock salt for sodium, and magnesium

chloride brine which, together with seawater, serve

as sources for magnesium.

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Rock..

An aggregate of minerals and need not

have a specific chemical composition.

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Metal Extractive Technology..

Mineral processing

Hydrometallurgy

Pyrometallurgy Electrometallurgy

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Mineral Processing..

As-mined or run-of-mine consists of valuablemetallic minerals and waste (gangue)

Mineral processing, sometimes called ore dressing,mineral dressing, or milling follows mining and

prepares the ore for extraction of the valuable metal toproduce a commercial end product.

It is a process of physically separating the grains ofvaluable minerals from the gangue minerals, toproduce an enriched portion, or concentrate,

containing most of the valuable minerals, and discard,or tailing, containing predominantly the gangueminerals.

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Mineral processing reduces the bulk and

weight of material which must be

transported to the smelter, thus reducing

shipping and handling costs; smeltingcosts are greatly reduced due to the

reduced tonnage which must be treated;

the lack of undesirable waste materialsincreases the smelter recovery, due to the

production of less metal-bearing slag.

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There are two fundamental operations in mineral

processing,

namely the release, or liberation, of valuable

minerals from their waste gangue minerals,and

separation of these values from the gangue,

this latter process being known as

concentration.

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Fig. 1: Simple block flowchart

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Comminution

Separation

Concentrate

Run-of-mine ore

Tailing

Product Handling

(Midling)

Disposal

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Comminution..

The first part in any ore-dressing process.

Involve crushing and grinding.

A process where each mineral grain is free or

practically free.

Crushing and grinding are usually carried out

in a sequence of operations by which the

lump size is reduced step by step.

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One of the major objective of comminution is the

liberation, or release, of the valuable minerals from the

associated gangue minerals at the coarsest possible

particle size.

The degreeof liberationrefers to the percentage of the

mineral occurring as free particles in the ore in relation to

the total content.

A high degree of liberation may only be possible by

intensive fine grinding, which may reduce the particles tosuch a fine size that separation becomes very inefficient.

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Figure show a cross section through a typical

ore particle, and illustrate effectively the

liberation dilemma often facing the mineral

processor.

Region A represent valuable mineral, and

region AA is rich in valuable mineral, but

highly intergrown with the gangue mineral.

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Comminution produces a range of fragment, ranging from fully

liberated mineral and gangue particles.

Particle of type 1 are rich in mineral, and classes as

concentrate as they have an acceptable degree of locking

with the gangue which limits to the concentrate grade. Particles of type 4 would likewise be classed as tailing, the

small amount of mineral present reducing the recovery of

mineral into the concentrate.

Particles of type 2 and 3, however, would probably be classedas middlings, although the degree of regrinding needed to

promote economic liberation of mineral from particle 3 would

be greater than that in particle 2.

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Crushing..

Crushing is the first mechanical stage in the processoff comminution which the main objective is theliberation of the valuable minerals from the gangue.

Generally a dry operation and is usually performed in

two or three stages. Lumps of run-of-mine ore can be as large as 1.5m

across and then are reduced in the primary crushingstage to 10-20 cm in heavy-duty machines.

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Primary crushing

Commonly designed to operate 75% of theavailable time, mainly because of interruptionscause by sufficient crusher feed and by mechanical

delays in the crusher. to reduce the run-of-mine down to about 100mm.

Always operate in open circuit, with or withoutheavy-duty screens.

Jaw crushers, gyratory crushers or impact crusher.

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Secondary and tertiary crushing

Also operate with dry feeds, and their purpose is toreduce the ore to a size suitable for grinding.

From 100mm to less than 10mm lump size.

Cone crushers, roll crushers and hammer mills.

In some case, the crushing in rolls and hammermills is carried on to product sizes below 1mm.

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Grinding..

The final reduction in size usually takes place in rod mills

or ball mills where the finely crushed ore is ground

between rods or balls in a revolving drum.

Combination of impact and abrasion.

The latter may give a product which is less than 0.1mm

in diameter.

These grinding operations may be done on dry material,

but usually carried out wet, i.e., the ore is mixed with

enough water to give a thick pulp which is passed on to

further ore-dressing processes.

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The grinding medium may be steel rods,,

or ball, hard rock or in some cases, the ore

itself.

A recent development in the comminution

field is the autogeneous mill, where coarse

ore is reduced to fine product in one step

by abrasion in a revolving mill drum.

It is used extensively for iron ore grinding

and is expanding into other fields.15062012

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Closed and Open Circuits..

Open Circuit

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Closed Circuit

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