2012 americas school of mines · pdf filebasics of mining and mineral processing. ... fraser...

2012 Americas School of Mines

W Scott DunbarUniversity of British Columbia

• www.pwc.com

Basics of Mining and Mineral Processing

Agenda

Geological Concepts

Mining Methods

Mineral Processing Methods

Mine Waste Management

Mining and Money

A Future of Mining

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A Future of Mining: The Topics

Drivers of innovation in mining

Automation, rapid excavation

In situ and underground processing

Some different concepts

A Future of Mining 3

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Sustainable Mining and Mineral Processing

Energy use

Social Impact

Waste disposal

Resource depletion

Can all this be done without jeopardizing the ability of future generations to meet their needs?

Or the ability of the industry to continue operating?

Environmental Impact

Mining and Mineral Processing


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The call of the reserves – trend to underground

0 500 1000 1500 2000 2500 3000 35000.2

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GrasbergNorthparkes

Palabora

AndinaEl Teniente

Codelco Norte

Highland Valley

Antamina

Minto

BagdadCerro VerdeBingham CanyonMorenci

Resolution

Galore Creek

Oyu Tolgoi

New Afton

Fungurume

Legend Proven + Probable Reserves Measured + Indicated Resources

Aver

age

Cop

per G

rade

(%)

Reserves or Resources (Mt)

All near end of mine life

No sign of these kinds of deposits (yet)

Most large new copper mines are

underground mines


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Notes: The call of the reserves

To obtain reserves mining companies must take on some significant unsystematic risks (risks notrelated to market changes) associated with exploration, project feasibility and constructability of newprojects in places where there is little geological knowledge or infrastructure. One way to diversifythese risks and still attract investment is to have a steady flow of cash from existing operations, someof which can be used to provide opportunities for development of new projects. If the unsystematicrisks cause the new projects to fail, the existing operations provide a “safety net”.The large grades and/or resources of some copper deposits shown here attract large miningcompanies, but there are significant unsystematic risks:•Freeport McMoran: Fungurume in the Congo. Political risks as well as social and health issues•Rio Tinto, Ivanhoe Mines: Oyu Tolgoi in Mongolia. No infrastructure and uncertainty about whatroyalties the Mongolian government will charge•Rio Tinto: Resolution project east of Phoenix. Orebody at a depth of 2 km in rock where thetemperatures are 80C. Feasibility of any mining method under these conditions is uncertain.•Teck Cominco, Novagold: Galore Creek in northwestern BC. No roads, no power and significant watermanagement issues at the proposed mine.


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MINECOs balance sheet


1.85%4.42%

70.5%

7%9.47%

6.8%

Cash Receivables Inventories PP & E Investments Other

Property, plant and equipment

This is the average from the annual reports of five mining companies in 2005. Mining companies have a lot of their balance sheet tied up in physical assets. This affects return on equity and return on invested capital.

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Creating value

Revenues‐CostsReturn on Equity

Assets

Usual approach to increase RoEis to reduce operating costs


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Mine Automation

Why? To reduce costs. Also safer

Possible, in principle, to automate any part of the mine cycle more efficient use of assets and labor

• Tele‐operation:• tele‐operated LHDs, three drills, one operator above ground

• some success at Vale (formerly INCO) mines in Sudbury, Ontario

• Autonomous trucks and shovels:• BHP and Rio Tinto

• for application to coal and iron ore mines


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There have been some significant advances in mine automation over the last decade. Forexample, Komatsu has provided autonomous 290 tonne haul trucks (930E‐4AT) to bothCodelco in Chile and Rio Tinto in Australia. Caterpillar is also working on developing anautonomous 700 tonne (!) truck.Deep underground mines have a strong incentive to be involved in mine automationbecause of long travel times of workers to and from work areas and the difficult, possiblyunsafe, work conditions at large depths.

Notes: Mine Automation – to reduce costs


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This LHD has no driver


Light rope guidance system

www.canadianminingjournal.com

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Notes: This LHD has no driver …

In some cases, tele‐operation can be slower than directly operated machines. However, it isreliable and that is very important in a mining operation which depends on a regular feedof material.One Canadian prime minister (Jean Chretien) was shown operating a LHD in a mine inSudbury, Ontario from a conference hall in Toronto. So if a politician can do it, there is noend to the possibilities.


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Autonomous trucks (and shovels one day)

Source: www.komatsu.com/CompanyInfo/press/2008122516111923820.html

Rio Tinto’s West Angeles iron mine, Australia


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Rapid excavation – for rapid development

Roadheader Roadheader cycleNo drilling and blasting


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Notes: Rapid excavation – for rapid development

Most of these technologies have been applied to tunnel construction but have not yetbeen applied in mining construction or development.Other technologies such as water jets and projectiles have been tested as a means of rapidexcavation.


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Does cost cutting really work? 19

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Basic Materials (includes mining) Consumer Services Consumer Goods Oil and Gas Financials Health Care Industrials Technology Telecommunications Utilities

Not really, if comparisons made to other industries

Also …Energy and equipment costs are significant

Dow‐Jones Total Return Indices


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What about the assets?

Capital Operating productivityproductivity

Revenues‐Costs Revenues‐Costs OutputAssets Output Assets

With existing technology it is possible to find ways of using assetsmore efficiently or to use less of them.

Industry focus


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Process Integration – mine to mill or mill to mine

Waste‐ore separation at face

or at pit wall

metal

Mine Mill

Concentrate to surface

Existing technologies metal

the “wall”

Current paradigm

The subject of a lot of research


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Notes: Process Integration

Mine Ore type Separation method % Waste rejectedMcCreedy East, ON Narrow vein copper Optical sorting

Dense media55.9%

McCreedy West, ON

Massive nickel sulfide Conductivity sortingDense media

21.6%

Fraser Mine, ON Narrow vein copper Dense media 44.3%

Thayer Lindsley, ON Massive/ banded nickel sulfide

Dense media 14.2%

Some trials of pre‐concentration (waste‐ore separation) at underground mines in Ontario

Ore and waste minerals often have different optical properties (i.e., they respond to aparticular kind of light differently), different electrical conductivities, and differentdensities. Thus ore and waste minerals will reflect a particular kind of light differently. Inthe presence of an electrical current, one will resist the current (typically the waste) andthe other will pass the current. If a dense medium is mixed with the ore, the lighterminerals (typically the waste minerals) will float to the top. Thus each of these differencesin properties can be used to separate the two types of minerals.


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Develop radically different technologies that can do mining andmineral processing with small (micro) assets

minimize material handlingcheap and disposable machines

Why not reduce assets?


In‐situ or near‐situ processing

metal

New technologies

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But one could also ask:


DO WE NEED MACHINES?

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Ants cleaning their nest


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Notes: Ants Cleaning their Nest

1500 dead ants were put into a 10 cm diameter dish located in an artificial ant colony. Afew worker ants from the colony were released. The workers then proceeded to clean thenest by moving the dead ants into separate piles. Within 36 hours three distinct piles weremade. After 72 hours, there was one pile.

There is no “foreman ant”. An individual worker ant moves ants around based on cues suchas the ease with which a dead ant can be moved; if it is too hard to move, it’s likely in a pileso leave it alone, if it’s easily moved then pick it up and put it in a place where it is hard tomove which should be a pile.


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Why not sort minerals this way?

Construct a swarm of small machines that can detect or inferparticle size or weightEach machine has a simple instruction set:

• pick up a particle if it is heavy

• drop a particle near similar particles, or

• move around to find a pile of similar particles

It is actually very difficult to do this a re‐think is necessary.Nature might have done some of the work for us (the D of the R&D)


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Mining and Remediation with Plants

Plant nickel accumulators

Nickel mine waste rock

Harvest, then plant native species

Phyto‐mining of gold mine tailings, South Africa


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Notes: Mining and Remediation with Plants Plants transpire large amounts of water from the soil to facilitate photosynthesis and will accumulateany soluble metals present in soil water during transpiration. The amount of accumulation increaseswith the concentration of metals in the soil, with the ambient temperature, and with an increase inplant biomass. This can be exploited to induce hyperaccumulation of metals in the following way:

wait until the plant is fully grownwhen the ambient temperature is high, induce a high concentration of metals in the soil byapplication of a suitable chemical (thiocyanate in the case of gold or acids in the case of somebase metals)harvest the plants (which are probably dead due to the high metal concentration), burn them andrecover the metals from the ashes.

Phyto‐remediation is the use of plants which accumulate contaminant metals to clean mine waste.Phyto‐mining is the use of the plants which accumulate valuable metals to extract these metals intothe tissue mass of the plant. The process can be repeated until the metals are completely extracted.However, the concentrations of metals required to make the process economic have apparently notbeen achieved. It is an area of active research. Plant species could be genetically engineered toenhance their capabilities to absorb metals.

Source: Anderson et al, 1999. Phytomining for nickel, thallium and gold. Journal of GeochemicalExploration, 67:407‐415


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Nuggets in the desert

Bill Southern, owner of retail outlet in Morristown between Phoenix and Wickenburg on the

way to Bagdad minewww.nuggetshooter.com

For a video of an Aussie finding a nugget see www.youtube.com/watch?v=x5nv1lcbN54


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How did they get there?

• Detrital – loose fragments worn away from the “Mother lode”• But gold is relatively heavy and not that mobile

• Where’s the “Mother lode”?

• Chemical accretion – crystallization from solution• But gold is not that reactive (remember it’s a noble metal)

• Where’s the water? How would it get into solution?

There must be another way.


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A nugget up close (electron microscope)

Source: Reith et al, 2006. Biomineralization of gold: Biofilms on bacterioform gold. Science, 313: 233‐236

Looks like gold‐encrustedbacteria – white arrowsshow cell wall structureGenetic analysis of biofilmson gold showed evidence ofbacteria

(Just like they do DNA analysis on CSI)


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And the most pervasive bacterium is

something called Ralstonia metallidurans

Incubate R. metallidurans with gold chloride for 5 days at 30CElectron micrograph of single microbe shows embedded gold particle

Source: Reith et al, 2006. Biomineralization of gold: Biofilms on bacterioform gold. Science, 313: 233‐236


gold particle

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Notes: And the most pervasive bacterium is

The genetic analysis showed that the bacteria in the biofilms on the gold nugget belongedto as many as 30 species, most of which could not be found in the soil surrounding thenugget. The most pervasive species was genetically nearly identical to the bacteriumRalstonia metallidurans, a microbe well‐known for its ability to precipitate some heavymetals from solution.R. mellidurans was incubated with a gold chloride (HAuCl4) at 30C for 5 days. The goldchloride is toxic to bacteria and so initially the bacterial count decreased. However, thebacteria count eventually increased rapidly indicating it developed a resistance to the goldchloride. The backscatter electron micrograph of the bacteria in the culture shows energypeaks corresponding to carbon, oxygen and metallic gold. The gold either accumulated inthe cell walls of the bacterium or appeared to cover the bacterium entirely.


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Sulfate-reducing bacteria (SRB)


Metal sulfidesprecipitate

SRBs catalyze the reduction of sulfatesMetal sulfates are

present in contaminated water

Carbon source

SRBs exist naturally but need a carbon source to be active

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Notes: Sulfate-reducing bacteria (SRB)


SRB use carbon source and reduce sulfates in contaminated water:

Sucrose + acid + sulphate + water hydrogen sulphide + carbonic acidC12H22O11 + 12H+ + 6SO4

−2 + H2O 6H2S(aq) + 12H2CO3(aq)

Metal ion + hydrogen sulphide metal sulphide + hydrogen ionMe2+ + H2S(aq) MeS(solid) + 2H+

A carbon source is not usually present SRB are dormant.A simple carbon source: add sugar

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Notes: Sulfate-reducing bacteria (SRB)Oxidation is an energy‐releasing process, and organisms make use of the energy to live. Oxygen is themost common oxidizer; it wants electrons and once it has stripped them off some helpless ion, itcombines with hydrogen to produce water. However, sulfate‐reducing bacteria (SRB) use sulfate as anoxidizer, reducing the sulfate to sulfide.

SRB metabolism requires an organic carbon source (as food) and some growth substrate forattachment since the bacteria cannot survive in open water. SRB metabolism causes sulfide minerals toprecipitate in marine sediments, wetlands, lake sediments, or wherever there are sources of metalions, sulfate ions and carbon. SRB are used as a method for treating acid mine drainage which containssulfates and metal ions in solution. See www.bioteq.com

The biological names of common SRBs are Desulfovibrio and Desulfotomaculum.

If sucrose (sugar) is the carbon source, the chemical reactions are:

Sucrose + sulfate + acid + water sulfur dioxide + carbonic acid

C12H22O11 + 6SO4−2 + 12H+ + H2O 6H2S(aq) + 12H2CO3(aq)

Metal ion + sulfur dioxide metal sulfide + hydrogen ion

Me2+ + H2S(aq) → MeS(solid) + 2H+

Source: Saunders, J. A. et al. 2005. Geochemical, microbiological, and geophysical assessments ofanaerobic immobilization of heavy metals, Bioremediation Journal, 9:33–48


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SRBs under the electron microscope


SRB biofilm

ZnS

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Remediation by SRBs

See www.bioteq.com


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Resources and Reserves of Metals

Scrap metalScrap circuit boards

already a metal source


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Notes: Resources and Reserves of Metals

Some argue that all the metal needed in the world is above ground. (no reference – stilllooking for it)On left:

Densified Scrap Metal No. 3a, Hamilton, Ontario 1997 www.edwardburtynsky.comOn right:

www.dead‐computers.comSeveral mining companies with smelting capacity have invested in the electronics scrapbusiness. As of 1998 recycling accounts for more than half of the U.S. metal supply byweight and roughly 40 percent by value.Sibley, S. F., 2004. Flow Studies for Recycling Metal Commodities in the United States,Circular 1196‐A‐MUS Geological Survey. Available at:

http://pubs.usgs.gov/circ/2004/1196am/


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Can the industry “grow its own”?

Microbes

METALS

Hot springs hydrothermal zones supergene ore zones Electronic and metal scrap

Contaminated water

Demonstrated at lab scale

Feasible

Not yet tried


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Notes: Can the industry “grow its own”?

Three sources of metals are shown here:

• Contaminated water from mines or other industrial sites

• Hydrothermal waters with sulfates or supergene ore zones (e.g., Morenci mine) wherebacterial leaching is already occurring naturally

• Metal and electronic scrap

The idea of recovering metals from such sources using microbes might seem “crazy”, but really the onlymajor barrier is our poor understanding of the interaction between metals and microbes. The amountsof valuable metals in these sources vary, but could be significant in the case of metal scrap. Metals arealready being recovered from some contaminated waters. There are obvious practical problems withdealing with a hydrothermal zone, but the temperatures are not too high. Order‐of‐magnitudeestimates of bacterial oxidation in one fracture at the Morenci mine in Arizona demonstrated that afew kg of thiobacilli could leach between 0.14 – 0.87 t of Cu annually. (See Enders et al, 2006. The roleof bacteria in the supergene environment of the Morenci porphyry copper deposit, Greenlee County,Arizona. Economic Geology, 101:59‐70)

Experiments have shown that bacteria and fungi grown in the presence of fine‐grained electronic scraplead to acid formation and leaching of metals such as copper, tin, aluminum, lead and zinc. (See BrandlH, Bosshard R, Wegmann M, 2001. Computer‐munching microbes: metal leaching from electronicscrap by bacteria and fungi. Hydrometallurgy, 59:319‐326.)


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It’s fun to think about this:


22nd century mining company

biological agents

mini‐machines

orebodies

metal scrap

tailings and mine waste

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Notes: It’s fun to think about this:


A 22nd century mining company will have swarms of small machines or biologicalagents located at orebodies, tailings ponds, waste dumps or metal scrap yardswhere it owns mineral or metal rights. These swarms would be activated to gainaccess to mineralized zones or metal and carry out in‐situ processing to produceminerals or metal products.

The mining company would be a “metal supply” company that may supply metalfrom ore, from waste, or by recycling, depending on demand and costs. A trulyflexible metals production system.

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Mining in 2100

At a mine site in 2100 there will be a person and a dog.

Person’s jobFeed the dog Dog’s job

Stop the person fiddling with the controls, valves, and pipes.

This picture is not to scale


orebody

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THE END


2012 americas school of mines · pdf filebasics of mining and mineral processing. ... fraser...

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