topic 1: types of ore bodies and mine processes
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Topic 1: Types of ore Bodies and Mine Processes. Extraction Open Pit Strip Mining Underground Crushing Initial Autogenous Circuit Beneficiation Physical Chemical Electrochemical Smelting. INCO Thompson Ni ore. Snow Lake 0.16 oz Au / tonne. Ekati, NWT, Diamonds. Types of Ore. - PowerPoint PPT PresentationTRANSCRIPT
Topic 1: Types of ore Bodies and Mine Processes
• Extraction– Open Pit– Strip Mining– Underground
• Crushing– Initial – Autogenous Circuit
• Beneficiation– Physical– Chemical– Electrochemical
• Smelting
Types of Ore• Massive: base metal
Cu, Ni, Zn
• Disseminated: gold,
• Diamonds Snow Lake
0.16 oz Au / tonne
INCO Thompson Ni ore
Ekati, NWT, Diamonds
Bissett Au
Bedded Ore bodies
Potash, SaskatchewanSyncrude, Oil sands, Fort McMurray
Black Thunder Coal MineWyoming, USA
Extraction process depend on shape, position and
value of ore body• Open Pit
• Strip Mining
• Underground Mine
• Dissolution: potash, uranium,
• In situ mobilization: oil shale
• Heap Leach
What are the major environmental issues related to each form of extraction?
Open Pit
Bingham Canyon Cu Mine
Ekati Diamond Mine
Note: The amount of waste rock to be removed to provide reasonable gradient for trucks.Only efficient for large ore bodies close to the surfaceCan be useful for dumping mine waste at closure
Strip Mining
Very efficient for high level flat lying ore bodies. Overburden and top soil can be replaced minimizing environmental damage
Underground
Dissolution: potash, uranium In situ mobilization: sulfur, oil shale
NaCl or KCl dissolved in water
Acid in situ leach of metallic ore
Hot water or steam used to mobilize sulfur or oil
Heap Leach
Landusky, Montana, CN Heap Leach Gold Mine 1979-1996
Crushing• Ore bearing and non ore-bearing rock will be separated as soon as
possibleWhat happens to non-ore-bearing rock?• Ore-bearing rock will be crushed to the size necessary to liberate
the required mineral• Heap leach requires only very coarse crushing• Much finer crushing for gold and PGE as they are enclosed within other mineral grains• Initial crushing underground • In mill, crushing in autogenous circuit withfeedback of large particles• Final crushing in rod or ball mills
Beneficiation (Extraction of metal from rock/mineral)
• Physical techniques– Gravity
• Gold from quartz• Diamonds• Tantalum
– Flotation• Sulphides from silicates• Cu and Ni sulphides• NaCl from KCl
• Chemical Techniques– CN leaching– Roaster oxidizes sulphide to SO2
• Smelting• Electrochemical Refining of pure metal
Consider the waste generated at each stage
Gravity Separation
Whiffle tableSeparator
Fine grained waste goes to tailings pond. What does it contain?
Flotation Cells
Ore becomes attached to air bubbles, float, and are collected.Gangue sinks to the bottom of the flotation cells and piped to tailings pond
Chemicals added include:Frothers: pine oils & alcohols promote the formation and stability of bubbles. Collectors promote adherence of air bubbles to the mineral. Conditioners: make the surface of the mineral particle either more or less susceptible to concentration. Activators e.g. copper sulfate, lead nitrate, lead acetateDepressants e.g. sodium cyanide, zinc sulfate
Chemical Separation
• Cyanide leaching for gold– at pH 11– gold retrieved by Merrill
Crowe (precipitation on zinc dust) or Carbon in Pulp (CIP) process
• Roaster oxidizes sulphide to SO2
– Releases metal for refining and SO2 to the atmosphere unless scrubbers are in place
Smelting
• Separates remaining silicates from metals
• Slag (molten silicates) pored off
• Metal pores into bars or sent for final electochemical refining