copper extractive metallurgy in the xxi century (parte 1)

8/14/2019 Copper Extractive Metallurgy in the XXI Century (Parte 1)

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COPPER EXTRACTIVE METALLURGY IN THE XXI CENTURY

Jorge M. Menacho, General Manager, De Re Metallica Ingeniera [email protected]

Extended Summary

An overview on the current and future mining technology is presented. The analysis is set

within the Kondratieff wave theory establishing occurrence of around 50-year social-

economic and technological cycles. These curious cycles are well documented since at

least 300 years ago. Within this frame Figure 1 shows some outstanding innovations in the

mining field along the last century.

Figure 1. Kondratieff cycles.

K-wave theory indicates we are entering a depression economic phase and at same time,

we are living an expanding cluster of technology which would settle the paradigms for the

next decades.

If historian now see the turn of the 19th century as the dawn of the industrial revolution, I

hope they will see the turn of the 21th century as the dawn of the energy revolution (Rob

Routs, Director Royal Dutch Shell, June 2007).

Solar, wind, biomass and clean carbon energy will grow fast within the next 20 years.

Nuclear power is always an option, but it will really grow after 2030. Carbon dioxide

capture and storage (CCS) is expected to occur after 2020.

By 2055 the US and the EU are expected to use about 33% less energy per capita than

today. On that time Chinese energy has also peaked and India is still climbing its energy

laddler.


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The copper mining activity will be faced with stronger environmental constraints as well as

to a much stronger competence from the secondary copper recycle industry compared to

current situation.

Process Options Today

Mineral processing and hydrometallurgy are the usual process routes to bring copperminerals into metallic copper as shown in Figure 1.

Figure 2. Process options today.

Relevant innovations of today and tomorrow are reviewed below.

Better and Bigger Crushers

Crushers are among the most efficient comminution machines and probably they will

continue growing in technology and size as illustrated in the Figure 3 (P. Mujica, Metso,

Personal Communication, October, 2012).

Coarse

crushing

Finecrushing

SAG

Milling

Ball

Milling Flotation

Refinery SmeltingER - Cathode

Tailing

Flotation

HIGH-GRADE

Primary

Sulphide

SecondarySulphide

Oxides

LOW-GRADE

Primary

Sulphide

Secondary

Sulphide

Oxides

(< 0.2% Cu) ?

Coarse

Crushing

FineCrushing

Heap

Leaching

EWEW - Cathode

Ripios

LeachingROM

Leaching

Aglomeration Stacking

SX

MINERALS:


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Figure 3. The new MP-2500 cone crusher.

SAG Milling

The original idea that SAG milling could replace secondary crushing, tertiary crushing and

coarse grinding soon disappeared and now is mainly limited to a non recognised tertiary

crushing. The following question is whether the SAG milling is the best option to perform

this fine crushing task?

Eventhough significant improvements in SAG mill design, operation and control have been

introduced in the last decade, other technological options are moving faster. SAG mills will

probably end up as huge ball mills.

From first POLYCOM to HRC

HPRG is nowadays a real option for fine crushing tasks (Figure 4), either as tertiary or

quaternary step and also as pebble crusher in SABC circuits.


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Figure 4. New generation HPRG machines.

Microwave Assisted Comminution

The ability to alter properties of ores to reduce its strength and improve liberation is

ultimately the only way that step changes in the efficiency of comminution processes will

be made.

One of such ways to change the fundamental properties of the ore is microwave pre-

treatment. Recent microwave experiments have shown that by maximising microwave

power density (volumetric heating rate) and reducing cavity residence time, significant

benefits are attained, with microwave energy inputs of less than 1 kWh/t.

It is hard to conceive industrial applications in the copper industry before 2040. It will take

some time, but microwave or similar force field technology will come anyway.

Same metallurgical concept

but improved mechanical

features (arc-frame, bearing

arrangement and flanges).

CURRENT APPLICATIONS:

Tertiary crusher

Quaternary crusher

Pebble crusher in SABC circuit


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Figure 6. Microwave applicator arrangement (taken from Kobusheshe, Microwave

Enhanced Processing of Ores, Ph.D. Thesis, June 2010, School of Chemical

Environmental & Mining Engineering, University of Nottingham, United Kingdom.

It has been demonstrated that microwave pre-treatment improves beneficiation at sizes

suitable for flotation. Significant improvement in liberation of up to 20% were achieved in

particles treated using a single mode cavity at energy inputs lower than 2 kWh/t. The

liberation benefit affects mainly the coarse fraction of the ore. Some selected results taken

from the Kobusheshe thesis are reproduced in Table 1.

Table 1. Results on microwave pre-treatment of ores according to Kobusheshe.

Comminution Start at the Mine

Electronic initiation in blasting operations is a reality today; this has provided flexibility to

obtain appropriate size distribution profiles from the Mine.


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Plasma fragmentation is another promising technique to improve energy efficiency under

higher safety level. Fragmentation is produced by transforming an electrolyte inside a

barrel from liquid to plasma state by applying 8,000 V in 1 ms. The fast increase in

temperature and volume induce the rock fragmentation. Many options are available today

but still this is a young technology (see Figure 7).

Figure 7. Plasma fragmentation technology.

http://www.dattatreyainc.com/division/turn_key_contract/Rock%20Excvations/Broacher/KA

PRA%20catalog.pdf.

Road Map for Comminution Flowsheets

Figure 8 includes probable comminution flowsheets between year 2000 and 2050. SAG

milling would continue goes down against an increasing predominance of the HPGR

technology. In the long-term microwave devices are expected to arise as the most relevant

breakthrough, working together with much giant ball mills.


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Figure 8. Comminution flowsheet evolution.

Flotation Gigantism continues

Size of flotation machines have increased about 20 times since 1970 up to now. Tendency

clearly indicates that gigantism is still underway and 500 m3cells could be achieved within

few years.

Deterministic is Better than Random

Different approaches will arise from modern bright minds. An outstanding example is the

novel Urzar Cell, where collection occurs within a dynamic gas-pulp mixer filled with low

density bodies free to move followed by a froth separator like a thickener provided with an

inclined bottom to get the tails as shown in Figure 9.

Selective

BlastingPrimary

Crushing

Large Ball

MillingSAG Milling

Pebbles

Crushing

Precrushing

2ry Crushing

Main route in the 2000s:

Selective

Blasting

Primary

Crushing HPGR

SAG

MillingGiant Ball

MillingPrecrushing

2ry Crushing

Possible flowsheet in the 2020s:

Primary

Crushing HPGR

Giant Ball

Milling

Secondary

Crushing

Coupled

Blasting

Intensive 1ry

Crushing Microwaving

Giant Ball

MillingHuge HPGR

Coupled

Blasting

Possible flowsheet in the 2050s

copper extractive metallurgy in the xxi century (parte 1)

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