AMIT 135: Lesson 1 Introduction

Introduction

Insert intro narrative or video.

Objectives

By the end of this lesson students should be able to:

  • Explain the role of Extractive Metallurgy and its sub disciplines in mining industry.
  • Explain mineral processing and processes involved.
  • Distinguish between ore, mineral and rocks.
  • List different physical properties of ore and how they are exploited in beneficiation process.
  • Develop an understanding how beneficiation process works based on a typical example flowsheet of various ore.

Reading

The economical production of metals and non-metals has never been as important and as difficult as it is today. In the twentieth century, annual copper production increased by a factor of 250 to an amount exceeding 8 million tons per year. A greater increase was realized by aluminum with similar trends also observed for other metals such as lead, zinc and tin. Occurring simultaneously with the increase in demand of most metals, industrial minerals and fuels, the quality of the ore reserves have depreciated substantially.

Iron ore on a conveyor
Iron Ore on a conveyor [image 135-1-1]
Digging ore from the earth is only half the battle. Often just as challenging and costly is the processing of the ore, which takes place in mills, smelters and refineries. Processing requires crushing and grinding to liberate the minerals. After liberation, separation processes are used to concentrate the valuable mineral. The final step removes water from the concentrate and tailings.

 

Copper ore
Copper ore, image courtesy of Aibyek Khamkhash
[image (135-1-2.1]
Photograph of pyrite stacked cubes, from the National Mineral Collection
Photograph of pyrite stacked cubes (R18657) from the National Mineral Collection
[image 135.1.2.2]
Uranium ore
Uranium ore
[image 135-1-2.3]
Chromite
Chromite
[image 135-1-2.4]
 

Today’s ore reserves are lower in grade and the minerals are more finely disseminated, thereby making minerals processing of the material more complex and costly. Finely disseminated ores require substantial comminution costs to liberate the valuable minerals. In 1986, it was estimated that 35% of selling price for copper was associated with the crushing and grinding of host ore.

A copper mine
A copper mine, image courtesy of Aibyek Khamkhash
[image 135-1-3]
 

Extractive Metallurgy

The study of the processes used in the separation and concentration (benefication) of raw materials. The field is an applied science, covering all aspects of the physical and chemical processes, used to produce mineral-containing and metallic materials, sometimes for direct use as a finished product, but more often in a form that requires further physical processing which is generally the subject of physical metallurgy, ceramics, and other disciplines within the broad field of materials science.

Sub-disciplines:

  • Minerals Processing
  • Hydrometallurgy
  • Pyrometallurgy
  • Electrometallurgy

Mineral Processing

The science and art of converting a run-of-mine ore into a saleable and/or usable product by means that do not destroy the physical and chemical identity of the minerals.

Distinct objectives include:

  • Production of a saleable material having a specified particle size distribution (e.g. aggregate industry).
  • Liberation of components for subsequent processing (e.g. exposing surfaces for leaching processes).
  • Generation of a material having a specified composition, e.g.,
    • Elimination of components that would hinder the efficiency of downstream processes.
    • Elimination of components that would limit the feasibility of using the materials as a saleable product.
  • Objective ‘c’ involving the production of a final concentrate tends to be the most complex and difficult forms of mineral processing since it involves several distinctly different operations, i.e.,
    • Liberation (crushing and grinding);
    • Particle Size Control (screening and classification);
    • Composition Control (solid-solid separations);
    • Product and Tailings Dewatering (solid-liquid separations).

 

A diagram of mineral processing
A diagram of mineral processing [image 135-1-4]
 

Aggregate

The term “aggregate” is defined as gravel, sand, clay, shale, stone, limestone, sandstone, marble, granite, “rock”.

In the definition of aggregate the term “rock” excludes metallic ores and the non-metallic ores: barite, coal, diamond, graphite, gypsum, kaolin, magnesite, mica, salt and talc.

The production of aggregates is relatively simple. The process typically involves a series of crushers and screens to produce material having various particle sizes.

Importance of Aggregates

  • Aggregates touch our lives everyday, from the driveway to the workplace. We drive, sit, stand and walk on aggregates.
  • Many products that enrich our daily lives contain aggregates. They are found in paint, paper, plastics and glass. In powder form, aggregates are used as mineral
    supplements for agriculture, medicines and household products.
  • Aggregates are also used to protect the environment by controlling soil erosion, assisting in water purification and reducing sulfur dioxide emissions generated by power plants.

Aggregate Production

At the beginning of the 20th century, production of aggregates in the United States was minimal and its uses limited. Today, aggregates are produced in every state, and aggregates production tonnage ranks first in the non-fuel minerals industry.

More than two billion tons of aggregates are used annually in the United States. This equals ten tons of aggregates for every American!

Aggregate pile
Aggregate pile
[image 135-1-5]
An aerial view of the Barrick Gold mine
Barrick Gold mine
[image 132-1-5.2]
 

Aggregate Preparation Circuits

  • Grizzly Screens: Removes fines to bypass primary crushers.
  • Crushers: Reduces the size of material.
  • Screens: Separation aggregates into various sizes.
A screen with rock
A screen
[image 135-1-6]
 

A typical mill flowsheet diagram
A Typical Flow Sheet diagram [image 135-1-7]

Iron Ore Processing

The mineral types are:

  • Hemattite (Fe2O3)
  • Magnetite (Fe3O4)

Typical gangue material is silica

In some cases, the iron ore deposit is sufficiently rich and thus no physical processing is required.

Where processing is required, separation processes typically include:

  • Density-based separators
  • Magnetic separators
  • Froth flotation
An iron ore processing plant
An iron ore processing plant
[image 135-1-9]
 

Iron Processing Circuits

  • Grinding (9”- powder-fine)
    • Primary Mill Grinding
    • Pebble Mill Grindin1g
  • Concentrating:
    • Deslime thickeners
    • Magnetic separator
    • Vacuum disc filters
  • Producing Pellets:
    • Balling: The powdery iron ore concentrate is mixed with a small amount of a clay binder called “bentonite” and rolled into marble-sized  pellets.
    • Rotary Kiln: Heat-hardening of pellets at temperatures as high as 2,400 °F.
Iron ore Processing diagram
Iron ore Processing diagram
[image 135-1-10]
 

Iron ore pellets
Iron ore pellets [image 135-1-12]
 

Iron ore processing flowsheet
Iron ore processing flowsheet
[image 135-1-13]

Gold and Silver Processing

  • Grinding and Size Classification.
  • Leaching and Adsorption:
    • Addition of water to form slurry .
    • Addition of lime to the ore and cyanide solution to the slurry, to leach the gold or silver.
    •  Addition of carbon to adsorb dissolved metals.
  • Recovery and Dore Bullion
    • Stripping the metals from the carbon by acid washing .
    • Precipitation of the gold and silver by electro-wining.
    • Smelting of metal products into bars of dore bullion.
    • Pumping of the barren slurry (tailings) to the tailings storage facility.
Silver
Silver
[image 135-1-14.1]
Gold minerals
Gold minerals [image 135-1-14.2]
Gold ore processing flowsheet
Gold ore processing
[image 135-1-15]
 

Nickel Processing

  • Size Reduction: Primary, secondary and tertiary crushers.
  • Magnetic Separation: Separates magnetic ore (pyrrhotite) from non-magnetic ore (copper and nickel concentrates).
  • Froth Flotation: Non-magnetic ore is sent to a series of rougher and cleaner flotation cells to produce nickel concentrate.
  • Drying: Thermal  removal of liquid moisture .
  • Calcining: Thermal decomposition of a material.

Nickel Processing Circuits

  • Roasting: Thermal gas-solid reactions, which can include oxidation, reduction, chlorination, sulfation, and pyrohydrolysis.
  • Smelting: Thermal reactions in which at least one product is a molten phase.
  • Refining: Removal of impurities from materials by a thermal process .
Nickel Ore
Nickel ore
[image 135-1-18.1]
Nickel processing flowsheet
Nickel processing flowsheet
[image 135-1-18.2]
 

Diamond Processing

  • Crushing
  • Screening
  • Heavy-Medium Separation (HMS)
  • X-ray Sorter
Aerial photo of the Ekati diamond mine
Ekati diamond mine
[Image 135-1-19.1]
A rough diamond
A rough diamond [image 135-1-19.2]
A 70 carat white rough diamond
Rough diamond from the Diavik Diamond Mine, 70 carat
[image 135-1-19.3]
A cut diamond
A cut diamond
[image 135-1-19.4]
Diamond processing flowsheet
Diamond processing flowsheet [image 135-1-20]
 

 

Uranium Processing

  • Crushing and Grinding Circuit: Particle size reduction for leaching efficiency.
  • Thickener: Removal of excess water from ground ore.
  • Leaching: Acid is used to dissolve uranium from the ore.
  • Washing and Filtering: Separation of uranium solution from solid waste.
  • Solvent Extraction and Strip Section: Removal of uranium from water ­kerosene solution to aqueous solution.
  • Precipitation Tanks: Uranium precipitates (yellowcake) upon addition of ammonia.
  • Thickener: Excess water is removed.
  • Centrifuge: Moisture removal.
  • Calciner: Removal of ammonia and production of uranium oxide (U3O8).
Uranium yellow cake
Uranium Cake
[Image 135-1-21]
 

Uranium ore processing flowsheet
Uranium ore processing flowsheet
[Image 135-1-22]
 

Platinum Processing

Concentrating:

  • Size reduction: Crushing and milling circuits
  • Rougher and Cleaner Flotation: Separation of platinum from ore
  • Tailings and Concentrate Thickening: Removal of excess water.
  • Filtering: Removal of moisture.
Platinum
Platinum
[Image 135-1-23]

Platinum Processing Circuits

Smelting:

  • Drying: Thermal removal of water
  • Smelting : Thermal reactions in which at least one product is a molten phase

 

Refining:

  • Base Metals Refinery: Nickel, copper and cobalt
  • Platinum Metals Refinery: Platinum, Rhodium, Iridium, Ruthenium, Palladium and gold
Platinum processing flowsheet
Platinum processing flowsheet
[image 135-1-24]
 

Zinc Processing Circuit

  • Size reduction: Crushing and grinding.
  • Flotation: Zinc is separated from the ore.
  • Filtering: Removal of excess water and surface.
Galena
Galena
[image 135-1-25]
Zinc metal
Zinc Metal
[image 135-1-25.2]
Sphalerite
Sphalerite
[image 135-1-25.3]
Zinc flowsheet
Zinc flowsheet
[image 135-1-26]
 

Zinc and lead processing flowsheet
Zinc and lead processing flowsheet
[image 135-1-27]
 

Heavy Mineral Sand

  • Main products of heavy mineral sands processing are:
    • Rutile (TiO2)
    • Ilmenite (FeTiO3)
    • Leucoxene
    • Zircon (ZrSiO4)
  • Titanium Dioxides
    • Paints
    • Plastics
    • Paper
    • Textiles
    • Inks
    • Foodstuffs, cosmetics
Ilmenite
Ilmenite
[image 135-1-28.1]
Zircon
Zircon
[image 135-1-28.2]
 

Zirconium

  • Zircon is generally a minor product obtained from processing heavy mineral sands.
  • Applications
    • Ceramics in opacifiers used in surface glazes and pigments.
    • High melting  point (2200°C) attracts use as a foundry sand in moulds
    • Zirconium metal
      • 90% in nuclear energy
    • Zirconium Metal
    • Zirconium chemicals
Zirconium Metal
Zirconium Metal
[image 135-1-29]
Zirconium silicate powder
Zirconium silicate powder
[image 135-1-29]
 

Heavy Mineral Sand Properties

Mineral Valuable Magnetic Susceptibility Electrical Conductivity SG Chemical Formula
Ilmenite Yes High High 4.5-5.0 FeTiO3
Rutile Yes Low High 4.2-4.3 TiO2
Zircon Yes Low Low 4.7 ZrSiO4
Leucoxene Yes Semi High 3.5-4.1 Fe.TiO3.TiO2
Monazite No Semi Low 4.9-5.3 (Ce,La,Th,Nd,Y)PO4
Staurolite No Semi Low 3.6-3.8 Fe2Al9Si4O22.(OH)
Kyanite No Low Low 3.6-3.7 Al2SiO5
Garnet No Semi Low 3.4-4.2 (Fe,MN,Ca)3.Al2(SiO4)3
Quartz No Low Low 2.7 SiO2

 

Magnetic & Non-Magnetic Density Fractionation

Magnetic Non-Magnetic
SG Mineral SG Mineral
-3.85 Trash -3.79 Quartz, trash
-3.85 + 4.05 Magnetic Leucoxene -3.79 + 4.05 Leocoxene
-4.05 + 4.38 Altered Ilmenite -4.05 + 4.38 Rutile
-4.38 + 4.9 Primary Ilmenite -4.38 + 4.9 Zircon
+4.9 Monazite +4.9
Image of a floating dredge and concentrator
Dredge and floating concentrator (3000-4000tph) [image 135-1-30]
[image of dredge and floating concentrator (3000-4000tph)
Dredge and floating concentrator (3000-4000tph) [image 135-1-31]
A diagram of a spiral concentrator
A spiral concentrator [135-1-32]
A diagram of spiral concentrators
spiral concentrators [135-1-33]
General Heavy Mineral Sand Concentration Process diagram
General Heavy Mineral Sand Concentration Process [image (135-1-34)]

Wet High Intensity Magnets (WHIMS)

After the initial gravity concentration, WHIMS can be used to separate ilmenite from the other heavy minerals.

A diagram of a wet high-intensity magnet
WHIMS [image 135-1-35]
Typical Dry Processing Process Flow Sheet of Heavy Mineral Sands
Typical Dry Processing Process Flow Sheet of Heavy Mineral Sands
[image 136-1-36]
 

High Tension Electrostatic Separators
High Tension Electrostatic Separators [image (135-1-38)]

 

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