HIGH TEMPERATURE PROCESSING OF COMPLEX ORES

Processing of Complex Materials in the Copper Industry:Challenges and Opportunities Ahead

GERARDO ALVEAR FLORES ,1,4 CARLOS RISOPATRON,2

and JOE PEASE3

1.—Independent Consultant, Hamburg, Germany. 2.—International Copper StudyGroup, ICSG, Lisbon, Portugal. 3.—Mineralis Consultants, Brisbane, QLD, Australia.4.—e-mail: galvear1963@hotmail.com

With the gradual decrease in the grade of copper ores being processed, copperconcentrates have become more complex with higher impurity and ganguecontent. This trend has had a detrimental effect on smelters as they have toincrease throughput to maintain copper metal production, while increasingoperating costs due to processing the increased amounts of secondary products(slag, acid) and stabilizing waste streams. This paper discusses impacts fromthe increased complexity of resources from mine to smelters, highlighting theneed for an integrated processing approach to achieve sustainable and com-petitive multi-metal recovery.

INTRODUCTION

Processing of complex materials in non-ferroussmelting has traditionally been approached as aniche opportunity to capture the economic valuecontained in the mining resources. Depending onthe nature and complexity of the resources, minershave sometimes adopted processing options at themine site, such as ultra-fine grinding, alternativeflotation circuits, or hydrometallurgical processes,to reduce the concentration of elements that wouldreduce the value of their product. Meanwhile, theircustomers, the smelters, addressed complexityeither by developing new processes or by modifyingoperating conditions to enhance the removal ofdeleterious elements. In some cases, synergies andcooperation between base metal processing facilitieshave improved recovery and waste management.However, in most cases, the copper industry hasused dilution as the main response, either byblending of complex materials in central facilitiesor by diluting small quantities in large feed streamsto smelters.

Copper is recognized a cornerstone element tosupport the move towards a more sustainablesociety with eco-efficient living standards, e-mobil-ity, efficient house designs, environmentally–friendly public spaces, transportation designs, andmedical applications to reduce disease transmission.

At the time of writing, the global economy facesan unprecedented shock from the impact of coron-avirus which has reduced copper demand andprices. This will change as global stimulus andinfrastructure programs lift the economy, and thiswill be an opportunity to stress the positive aspectsof copper, not only in the traditional applications ofinfrastructure but also in less widespread applica-tions in hospitals and public spaces to reduce therisk of disease transmission.

It is therefore essential that the copper industryprepares itself by getting a clear understanding offuture supply volume and resource quality. If weface increased copper demand, we need to under-stand the expected complexity in supply and howthis will impact processing facilities in terms ofrecoveries, product quality, and waste management.This analysis should also consider the increasingpressure to process urban mining resources inexisting industrial facilities, since these resourceswill bring additional complexity that will impactbusiness performance.

UNDERSTANDING THE SUPPLY

Trends Affecting Copper Mines

Table I shows a list of identified trends in thecopper industry in recent years.1 It identifies chal-lenges from:

JOM, Vol. 72, No. 10, 2020

https://doi.org/10.1007/s11837-020-04255-9� 2020 The Minerals, Metals & Materials Society

(Published online July 6, 2020) 3447

� Resource complexity and regulatory pressures.� Increases in impurity content in concentrates.� Bottlenecks derived from recycling restrictions.� Energy and water access and cost.

What type of complex materials will copper smelterspotentially receive in the coming years? Whatimpurities are going to increase in the copperconcentrates? How will size distribution for libera-tion of copper species in the concentrator impactpyrometallurgical processing? What synergiesbetween base metals processors will be required tooptimize recoveries and minimize environmentalimpact? Addressing these queries will allow smel-ters to understand how they should adjust theiroperations to maximize the recovery of copper andother valuable elements, and the impact on sec-ondary streams such as slag, acid and dust.

Copper Content in Ores and Concentrates

A global copper mine-by-mine review undertakenby ICSG found that the global average copper oregrade was as low as 0.45% copper in reportedreserves and only 0.65% copper in 2015 copper mineproduction. Global weighted average of copper

concentrate output in a large sample of plants wasaround 25% copper in 2015 data. There are signif-icant data published on the falling copper ore gradesin recent decades, but a factor of concern is that theore grades in recently operational mines are notover 0.53%, while copper grades in new projects andin undeveloped mines are not over 0.43% copper onaverage.2

The results of the copper mine ore grades surveycarried out by the ICSG are shown in Fig. 1. Areview of the copper reserves in million tonnes ofcopper and the copper ore grades (percentage ofcopper) using the latest data for the top 56 coppermines of the world, ranked by reserves, producedthe following findings: only 9 of the 56 copper mineswith the largest reserves of copper presented copperore grades over 1% copper content; and only 7 of the56 copper mines with more copper reserves pre-sented reserves over 40 million tonnes each. So, in40 cases, representing almost 73% of the coppermines with important reported reserves, the copperore grades are below 1% copper and the reserves arebelow 40 million tonnes copper content.

If we consider only the top 20 copper mines withthe most important reserves of copper (over 1,000million tonnes of copper reserves) the average

Table I. Challenges for copper miners

Challenge Existing operations

Resource complexityand regulatory pressures

New mines and plants more complex, deeper and more expensive with lower-ore gradesMore complex and finer-sized copper concentratesOpportunity to recover valuable by-productsLimited expansion in operational mines and new mine capacity constraint 2018–2024Large amounts of mineral waste can pose threats to public perceptions of health and

safetyFalling copper content in concentrates traded: more impurities adding to higher

downstream processing costsPotentially more international agreements on a global regulation of mineral waste

after approval of Minamata ConventionIncreasing community pressure and legislation requirements to operate

Increase in impuritycontent

In 2021, over 60% of smelting capacity will be in Asia: potential requirements to dealwith impurities before smelting

Higher levels of impurities such as Hg, As, and Bi, increasing smelter flue dust andother hazardous wastes

More demand for smelter products, but concentrates contain increased units of As, Pb,Bi, and other metals that need to be removed

� 50% of fabrication capacity in China in 2018; raw material imports dependency tocontinue

Global bottleneck in recycledcopper raw materialsin 2018

No more recycled copper waste to China. EU/US/others scrap/waste to be processedsomewhere

Worldwide fabricators demand high-grade scrap, but only refined copper available at aprice

Impurity solution viamarket mechanisms?Only blending works

Falling prices in exchanges 2011–2016, but ICSG reports deficits of refined copperevery year

The current practice of blending dirty concentrates with clean concentrates will becomeincreasing challenging as overall impurity levels rise

Energy Energy shortage and high costsWater Competition with society for water access depending on geographic location

Water for agriculture or mining?

Flores, Risopatron, and Pease3448

copper ore grade of this group is only 0.76% copper,including deposits with a high average copper oregrade, such as Tenke Fungurume with 2.32%Cu,Resolution with 1.5%Cu, Taimyr Peninsula (Nor’-ilsk-Talnakh) with 1.45%Cu and Udokan with0.97%Cu. Other mines with relatively high oregrades include the Ertsberg-Grasberg Group with0.88%Cu, Rosario–Rosario Oeste with 0.82%Cu,Collahuasi with 0.81%Cu, and Olympic Dam with0.78%Cu. Lower ore grades are reported in mineswith high reserves, such as Los Bronces-Los Bron-ces Sur with 0.64%Cu), Andina with 0.62%Cu, butwith the largest reported reserves, El Teniente with0.56%Cu, Escondida-Main Mine with 0.54%Cu, thelargest producer in recent decades, and Los Pelam-bres with 0.51%Cu.

If we look at mines with high reserve volumes andlower copper contents, we can report Butte Groupwith 0.48%Cu. The reserves in the expansion ofEscondida-Pampa Escondida only report 0.45%Cu,meanwhile Chuquicamata report 0.43%Cu, similarto Buenavista del Cobre (Cananea) reporting0.42%Cu, and Radomiro Tomic also reporting0.42%Cu. Lower grades in large reserves arereported by the Pebble project with only 0.34%Cuand Morenci with 0.25%Cu.

Ore Grades and Technologies

Many copper resources and reserves in mineraldeposits report higher copper content than porphyrydeposit, however, the most abundant low-gradeporphyry deposits were mined first, and this is thereason why global copper ore grades went down onaverage during 1990–2018. Current technology toextract low-grade copper reserves indicates thathigher-grade copper deposits are not necessarilymined first. Many low ore grade deposits remainoperating as is the case of Morenci, Toquepala,Cerro Verde, Centinela, Quebrada Blanca, Cuajone,Radomiro Tomic, and Los Bronces. The grade

produced from established mines tends to reducewith age. Other relatively low-grades deposit, suchas Quellaveco, are advancing in the project pipeline.However other high-grade deposits, such as theOlympic Dam expansions, Pokowice, Oyu Tolgoy,Grasberg Underground, and other higher ore gradeprojects, are slowly advancing to the productionstage.3

Higher throughput rates and more efficient min-eral processing has maintained copper output;however, with lower feed copper content andincreasing energy and water use per unit of output,extraction costs have been increasing in importantcopper mines. Using the Chilean copper miningindustry as an example, the use of fossil fuelsincreased over 33% in 2010–2018, while the use ofelectricity increased by around 38% in this sameperiod.4

From the mine processing point of view, thereduction in ore grades and mineralogy changessuggest the need to adapt current mining andmineral processing techniques to maintain produc-tion targets of metal units and quality. However, insome cases, opposite strategies have been followed.For example, some Chinese operations have pro-cessed low-grade copper concentrates.5 These trendssuggest a dynamic balance between copper minesand processers in terms of defining where to investand where is the best place to remove each impu-rity. This requires a balance between metal recov-ery, processing cost, acid production, and slaggeneration.

Concentrate Quality

Figure 2 shows data on the composition of 32major traded concentrates, with the mineral com-position calculated from publicly available assaydata (which should therefore be considered to beapproximate).6 Expanding the data to 180 tradedconcentrates shows an average grade of 27% Cu,even though concentrates average only around 55–60% copper sulfides. This is due to the presence ofthe minerals chalcocite (79.9%Cu) and covellite(66.4%Cu), which are much higher grade thanchalcopyrite (34.6%Cu).

However, chalcocite and covellite are secondarycopper sulfides that occur in higher proportions inthe close-to-surface ore zones. As the shallowerzones are depleted, more mines are moving intodeeper areas with increased primary mineraliza-tion, that is, a higher proportion of copper iscontained in chalcopyrite (New African depositsare the exception to the industry trend towardshigher chalcopyrite, but concentrates from Africanmines are rarely traded internationally.) This willcause a gradual decrease in the copper concentrategrade of traded concentrates, unless efforts aremade to make concentrates mineralogically cleaner;that is, the proportion of copper sulfides would have

Fig. 1. Copper mine reserves versus copper ore grades; survey byICSG.2

Processing of Complex Materials in the Copper Industry: Challenges and Opportunities Ahead 3449

to increase above the current level of 55–60% byremoving more iron sulfides and non-sulfide gangueminerals. To achieve this, concentrators would needto increase the mineral processing ‘‘power’’, includ-ing finer regrinding and more intense flotationcleaning of the concentrates. These modificationsto grinding and flotation require more capitalinvestment and increase operating costs at themine site, so many operators will choose to passthe lower-grade concentrates to smelters instead, solong as their concentrate is marketable and thepenalties are less than the required capital andoperating costs. This is reflected in the increase inthe use of blending facilities as the primary tool toreduce the impact of complexity in smelters. Fig-ure 3 shows the blending facilities strategicallylocated around the globe.

COMPLEXITY IN COPPER CONCENTRATESAND POTENTIAL COUNTER MEASURE

IN COPPER SMELTING

Table II summarizes the effects on copper smelt-ing of this trend to the increasing proportion ofcopper from chalcopyrite from deeper copper mines.

Increases in gangue and sulfur content directlyimpact the production of slag and sulfuric acid, bothconsidered secondary products in copper production.Minor element concentration will not only affect thesecondary products but also the main output of thesmelter, copper anodes. Figure 4 shows a compar-ison for copper anode impurities between 2007 and2019:8 arsenic, tellurium, bismuth, selenium,nickel, and antimony concentrations in copperanodes have all increased.

Fig. 2. Estimated mineral composition of major traded copper concentrates; Ccp chalcopyrite, Cc chalcocite, Cv covellite, Py pyrite and Popyrrhotite.

Flores, Risopatron, and Pease3450

Fig. 3. Recent blending facilities1,7 (map source: https://commons.wikimedia.org/wiki/File:Worldmap_wdb_combined.svg, licensed under CCBY-SA).

Table II. Concentrate complexity and impact on copper smelting

Concentrateoutput Impact on copper smelting

Lower copperconcentrate(general)

Potential impact on furnace heat balance due to increase sulfur content potentially balanced by ganguecontent in the concentrate

Increased slag generationIncreased copper losses as slag amounts increaseIncreased acid production (higher sulfur content)

Increase ingangueconcentration(specific)

Alumina: An increment in alumina content in the feed will increase slag viscosity. Copper lossespotentially impacted due to increased matte entrained (i.e., increase in Al2O3 content in slag over

4% could drastically increases slag viscosity)Magnesia: Impact on slag liquidus temperature required to increase operating temperature to keep

slag with required fluidity, depending on smelting technologyIron oxide: Will require addition fluxing agent (silica) to keep Fe/SiO2 target

Increase in pyrite Increase in slag generationDirect impact on heat balance of the furnace might result in reducing copper matte grade or addi-

tional cooling agents (reverts) to balance heat, replacing new feed, and reducing produced copperunits

Increase inPb and Zn

ZincIncrease in zinc content in slag (bath smelting) and dust (flash furnace) might allow options to

recover via dust leachingLead

Increase in dust concentration during converting process might also option for recovery via dustleaching in an integrated Cu-As-Pb-Zn recovery circuit

Potential requirement for a lead removal stage at the end of copper blowing by adding silica-containing fluxes. Slag will need to be recycled to smelting unit

Increase in theconcentration ofdeleteriouselements

Arsenic: Increase in arsenic concentration in streams from primary smelting reactor:Requirements for additional operating costs in gas cleaningIncrease in arsenic concentration in slag could jeopardize slag disposal or use in secondary appli-

cationsIncrease in arsenic in anode could require use of fluxing to meet anode standardsHalogens: Increase in mercury, fluorine, and chlorines in concentrate:

Additional gas cleaning requiredPrecious metal losses to gas might increase due to volatilization as chloridesCorrosion of gas-cleaning equipment

Processing of Complex Materials in the Copper Industry: Challenges and Opportunities Ahead 3451

This increase in impurities in the copper anodeshas not only affected the electrorefining process butalso intermediate streams, sub-product quality, andthe options for dust and residue recycling to thesmelting furnace. This has increased the need toincorporate bleeding options or synergies with otherbase metal operations to achieve more sustainablemetal recovery, waste stabilization, and overallsustainable processing.

PROCESSING OF COPPER COMPLEXMATERIALS IN THE COPPER INDUSTRY

Pyrometallurgical processing of complex copperconcentrates has been traditionally associated withthe smelting of specific materials containing sub-stantial concentrations of deleterious elements,such as arsenic and/or smelted polymetallic basemetal concentrates containing relevant quantities ofcopper, lead, and zinc as carrier metals, associatedwith precious metals and other elements. In mostcases, such materials have been processed in facil-ities integrated with or close to the mine site.Examples include the processing of Cu-As concen-trates in Kosaka in Japan, the roasting of Cu-Asconcentrates at El Indio in Chile, and the processingof Cu-As concentrates from the Consolidated Minein The Philippines at the Lepanto Roaster.9 Most ofthese plants have had a limited operating life, asthey were originally designed to treat specific mineresources with a limited mine life. However, withthe commissioning of the Ministro Hales roaster inChile, a renewed interest in roasting has emergedas a niche solution for processing high-arsenicconcentrates. This could potentially allow simplerand more cost-effective integrated metallurgicalplants using one-step pyrometallurgical processing,i.e., direct-to-blister processing of roaster calcine. Inprinciple, the overall capital cost of such a facilityshould be competitive considering the reduction inequipment and material handling.

In the case of polymetallic concentrates, a morerobust approach to increase metal recovery andmulti-metal production has been to develop multi-metal recovery facilities. The main goals of thesefacilities are to achieve maximum metal recoveriesand optimum waste and effluent management bythe exchange of metal flows between the differentmetallurgical circuits. This principle, shown inFig. 5, is applied in metallurgical integrated plants,such as the Kazzinc Ust-Kamenogorsk Metallurgi-cal Complex in Kazakhstan,10 the Boliden RonnskarSmelter,11 or in multi-integrated sites in Japan,12

Germany13 and Korea,14 among others.However, even in these integrated facilities, it

still not yet feasible to recover elements such as W,Mo, V, Mn, Cr, Nb, Ta, Li, and the rare earths.Considering the future challenges that will arisefrom processing increasing quantities of batteries,additional efforts will be required to adapt metal-lurgical circuits to recover new elements.

Additional efforts have been made in countrieslike Japan and Germany to develop technologies torecover rare metals from waste from small elec-tronic and electric appliances, prioritizing pre-pro-cessing of these materials before being fed intocopper smelting circuits.16 The aim is to improverecovery rates and the range of elements that can beeconomically recovered.

Table III shows a compilation of metallurgicalcomplex processing plants that were or are cur-rently operating in the western world, aiming to usebase metal carrier properties to optimize and max-imize precious metal recovery. In most of theseplants, base metal volume production is not asrelevant as the concentration of valuable preciousmetals. These plants can potentially process indus-trial wastes, city incinerator metallic sub-products,recycling oils, and others. Countries like Korea andJapan have been pioneers in this approach at theirnon-ferrous operating plants.

Example 1: Japanese Approach Primaryand Secondary Materials IntegratedComplexity; JX Nippon Mining Flowsheet12

Metallurgical plants in Japan are using a similarapproach by integrating primary and secondarycomplex processing sites and maximizing synergiesbetween them to increase metal recovery. In thecase of Japan, special emphasis has been made toprocess complex secondary raw materials andindustrial waste using the ability of existing smelt-ing facilities to recover valuable metals. Figure 6shows the concept applied by JX Nippon Mining tocombine primary resources with secondary andindustrial waste resources.

Example 2: Aurubis Primary and SecondaryMaterials Processing Systems

Figure 7 shows the process flowsheet of the leadsecondary copper smelter.20 The flowsheet allows

Fig. 4. Global copper anode impurity growth 2007–20198.

Flores, Risopatron, and Pease3452

the integration and transfer of materials with theprimary copper smelter. The lead smelter andrefinery involve:

� Smelting of complex copper lead concentrates inan electric furnace.

� Converting of copper lead matte in a Peirce-Smith converter.

� Refining of lead bullion.� Integration with anode slime plant.� Integration with precious metal refinery.

On the secondary copper side, one of the mostsuccessful expressions of an integrated recyclingsystem has been the implementation of the KayserRecycling System (KRS+). This flowsheet, whichwas developed to recover copper, lead, tin, andprecious metals, has been in operation since 2002 inLunen, Germany. Figure 8 shows the Lunen pro-cess flowsheet.23

The flowsheet encompasses the following unitoperations:

� ISAMELTTM furnace for smelting reduction.� Settling furnace for copper recovery.� Pb-Sn furnace for Pb-Sn alloy production.� TBRC for copper conversion.� Anode furnace.

Example 3: Ust-Kamenogorsk MetallurgicalComplex10,24,25

The Ust-Kamenogorsk Metallurgical Complex is amulti-metal recovery plant combining lead, copperand zinc base metal metallurgy. The plant consistsof:

� Zinc refinery with a capacity of 190,000 tpa.� Lead smelter and refinery with a lead bullion

production capacity of 144,000 tpa.� Copper smelter and refinery with a copper

cathode production capacity of 70,000 tpa.

A precious metal plant is also integrated into thebase metal operation to produce gold and silver. TheUst-Kamenogorsk metallurgical complex is able toprocess highly complex materials with high recov-eries given by the integrated nature of the plant.Figure 9 shows a simplified process flowsheet.

THE ARSENIC CHALLENGE

Arsenic has been a recurrent challenge in themanagement of deleterious elements in the process-ing of copper concentrates. Arsenic content hasgradually increased in copper concentrates to levelsthat are almost above the standard arsenic blendingconcentrations that most western smelters inEurope, Asia (excluding China), and North Americacan operate. A clear example of the gradual increaseof arsenic in copper concentrates can be demon-strated by the behavior in the blends processed inJapan. According to the Metals Economics Instituteof Japan, arsenic content in copper concentratesprocessed in Japanese smelters has graduallyincreased since 1991 from 400 ppm to over1,000 ppm in 2016, while the copper content in theconcentrates decreased from near 33% to 27%Cu.26

This represents a 3 times increase in the units of Asper unit of Cu in the feed. The same reportestimates that standard copper concentrate blendscould increase to 3,000 ppm if new high As-contain-ing deposits are brought into operation. Introducing

Fig. 5. Multi-metal recovery flows in a Cu-Pb-Zn integrated copper plant (modified from Nakamura15).

Processing of Complex Materials in the Copper Industry: Challenges and Opportunities Ahead 3453

Table

III.

Meta

llurgicalin

tegrated

plants,exclu

din

gChin

a10, 11, 17–22

Plantand

company

Base

meta

lsFurnacety

pe

Application

Products

Operation

active

La

Oro

ya

Doe

Ru

nP

eru

Cu

,P

b,

Zn

Cu

Rev

erber

ato

ryfu

rnace

Pei

rce–

Sm

ith

con

ver

ter

Pb

Sin

ter

pla

nt-

bla

stfu

rnace

Zn

Roa

stin

gE

W

Pol

ym

etall

icco

nce

ntr

ate

sC

u,

Pb,

Zn

PM

Bi,

As,

Sb

On

hol

d

La

Cari

dad

Gru

po

Mex

ico

Cu

Ten

ien

teco

nver

ter

Fla

shfu

rnace

Pei

rce–

Sm

ith

con

ver

ter

Cu

con

cen

trate

sC

uY

es

Kos

ak

aD

owa

Cu

,P

bC

uF

lash

furn

ace

Ele

ctri

cfu

rnace

Pie

rce–

Sm

ith

con

ver

ter

Pb

Ele

ctri

cfu

rnace

Hig

hA

sco

pp

erco

nce

n-

trate

sR

esid

ues

from

Zn

pla

nt

Cu

,P

b,

Pre

ciou

sm

et-

als

,S

nR

epu

rpos

edto

sec-

ond

ary

Ust

Kam

enog

orsk

Kazz

inc

Cu

,P

b,

Zn

Cu

ISA

SM

EL

T—

Pie

rce–

Sm

ith

con

ver

ter

An

ode

furn

ace

Pb

ISA

SM

EL

TB

last

furn

ace

Zn

Roa

ster

EW

Pol

ym

etall

icco

mp

lex

con

-ce

ntr

ate

sR

esid

ues

Cu

,P

b,

Zn

Pre

ciou

sm

etals

Yes

Ham

bu

rgS

mel

ter

Au

rubis

Cu

,P

bC

u-P

bE

lect

ric

furn

ace

Pei

rce–

Sm

ith

con

ver

ter

Com

ple

xC

u-P

bco

nce

n-

trate

sC

um

att

eP

bbu

llio

nY

es

Hor

ne

Gle

nco

reC

uC

uN

oran

da

Rea

ctor

Nor

an

da

Con

ver

ter

An

ode

Fu

rnace

Com

ple

xC

uco

nce

ntr

ate

sR

ecycl

ing

mate

rials

Cu

Yes

Hob

oken

um

icor

ep

reci

ous

met

als

Cu

,P

b,

Zn

,N

iC

uIS

AS

ME

LT

Lea

chin

g-E

WP

bIS

AS

ME

LT

Bla

stF

urn

ace

Com

ple

xC

u-P

bco

nce

n-

trate

sR

esid

ues

Cu

,P

bbu

llio

nP

reci

ous

met

als

Yes

JX

Nip

pon

Min

ing

Cu

,P

bC

uF

lash

furn

ace

Pei

rce–

Sm

ith

con

ver

ters

An

ode

furn

ace

Sta

nd

ard

cop

per

con

cen

-tr

ate

sIn

du

stri

al

resi

du

esW

EE

E

Cu

,A

uP

GM

,S

e,T

eY

es

Flores, Risopatron, and Pease3454

Table

III.

continued

Plant

and

company

Base

meta

lsFurnacety

pe

Application

Products

Operation

active

Kor

eaZ

inc

Cu

,P

b,

Zn

,N

i.P

bT

SL

au

smel

tQ

SL

react

orZ

nT

SL

au

smel

tC

u

Com

ple

xP

b-Z

nco

nce

ntr

ate

san

dre

sid

ues

Cu

,P

b,

Zn

,A

g,

Au

,In

,B

i,S

b,

Cd

,T

e,S

e,C

oY

es

Ron

skar

Sm

elte

rB

olid

enC

u,

Pb,

Zn

,N

i.C

—P

roce

ssli

ne

1D

ryer

Fla

shfu

rnace

Pei

rce–

Sm

ith

con

ver

ters

An

ode

furn

ace

Refi

ner

yC

u—

Pro

cess

lin

e2

Flu

idiz

edbed

roast

erE

lect

ric

furn

ace

Set

tlin

gfu

rnace

Pb

Dry

erK

ald

op

lan

tL

ead

refi

ner

yZ

nF

um

ing

furn

ace

Cli

nk

erp

lan

t

Cu

ble

nd

edco

nce

ntr

ate

sC

omp

lex

con

cen

trate

sS

econ

dary

mate

rial

con

cen

trate

sL

ead

con

cen

trate

Ele

ctro

nic

scra

p

Cu

,C

uan

dN

isu

lfate

s,A

u,

Ag,

Se

Cop

per

matt

eto

pro

cess

lin

e1

Sla

gto

Zn

fum

ing

Pb

Zn

clin

ker

Processing of Complex Materials in the Copper Industry: Challenges and Opportunities Ahead 3455

such complex high-arsenic copper concentrateswould require large amounts of clean concentratesto dilute the arsenic contents to levels accept-able from the technical and economic points of viewby copper smelter.27

The impact of a small increase in the tonnes ofhigh-arsenic concentrates is illustrated in Fig. 10.28

Because of the more than tenfold higher arsenicunits per unit of concentrate, what appears to be asmall increase in the amount of high-arsenic con-centrates forecast in Mayhew et al.28 almost doublesthe arsenic units at smelting. Even if there weresufficient low-arsenic concentrates to dilute theaverage arsenic to acceptable limits, the smeltingindustry would still face a significant increase in theunits (tonnes) of arsenic to be processed and dis-posed. This would appear to be an unsustainableposition for the predominantly urban-located smelt-ing industry. It indicates that technologies need tobe adopted to reduce the arsenic content of copperconcentrates at mine sites.

Strategies to Process Complex ArsenicContaining Materials

A large amount of fundamental work has beenconducted to understand the behavior of arsenic in

copper smelting. Thermodynamic and kineticaspects as well as strategies to optimize captureand stabilization were summarised by Piret et al.,who conducted an extensive review on the state ofthe art in 1989.29 The main conclusions of the Piretreview are:

� Metallurgical slags offer a limited capacity tocapture arsenic, mainly due to the reducingconditions in which they are treated.

� Gas phase elimination and subsequent process-ing of condensed dust are more suitable forarsenic capture.

� Arsenic capture as speiss form is advantageous.� Recycling of intermediate products should be

directed to processes in which arsenic can beeffectively separated from the metal phase.

� Hydrometallurgical processing is the most suit-able process route for separate processing ofintermediate arsenic-containing materials.

� Effluent processing techniques allow the sepa-ration and recovery of arsenic in intermediateproduct. However, safe disposal of these arsenicintermediate streams will require developingenvironmentally stable compounds.

� Wet gas cleaning is an unavoidable step if lowergas emission standards are applied.

Fig. 6. JX Nippon Mining Flowsheet (reprinted with permission of JX Nippon Mining).12

Flores, Risopatron, and Pease3456

Most of the above criteria have been graduallyapplied to modern smelting operations, with newtechnologies being used for arsenic recovery, andsafe disposal from copper smelting dust, refineryeffluents, gas cleaning, and wastewater processingbeing gradually achieved.

In the last 30 years, a great deal of effort has alsobeen made to develop alternative technologies toprocess high-arsenic-containing materials. Focushas been on:

� Developing niche technologies for processingspecific ore bodies from mine to cathode using a

Fig. 7. Aurubis lead smelter flowsheet for processing of Cu-Pb complex concentrates (reprinted from Extraction 2018).20

Fig. 8. Kayser recycling system (KRS+) (reprinted from Rewas 2013).23

Processing of Complex Materials in the Copper Industry: Challenges and Opportunities Ahead 3457

combination of hydrometallurgical techniquesand solvent extraction and electrowinning.

� Selective flotation to depress and concentratehigh-arsenic streams.

� Renewed interest in roasting of high-arsenic-containing materials.

� Leaching of high-arsenic copper concentrates(alkaline and acid environments).

� Stabilization of arsenic residues in crystallinestable structures such as scorodite.

� Vitrification of high-arsenic-containing materi-als in smelting slags.

Table IV shows the level of development of sometechnology responses for processing complexarsenic-containing materials.30, 31 Most of thesetechnologies have been developed to process high-arsenic-containing streams. However, with blend-ing continuing to be the most popular approach, agradual increase in arsenic content in copper con-centrates—and a faster increase in the tonnes ofarsenic processed—should be expected. This willexert more pressure on smelters, increasing theiroperating costs, jeopardizing their competitiveness,and increasing environmental compliancerequirements.

Complexity, therefore, can be understood not onlyin terms of supply but also in terms of the effect onthe business need to invest in peripherical equip-ment to increase capture, reduce emissions, andstabilize residues according to local regulations.

This gradual increase associated with operationalprocedures aimed to minimize waste outlets hasgradually increased arsenic concentration in slagsand, subsequently, reduced market opportunitiesfor sub-products. Several efforts are currentlyundergoing in Chile, Germany, Australia, Japan,and Canada, among others, to develop pre-process-ing alternatives for safe arsenic removal prior tosmelting or processing of secondary streams gener-ated in the copper smelting processes.

The last two items in Table IV should be the firstinvestigated in any integrated industry response. Itis almost always more efficient to remove animpurity at ambient temperature and pressure inmineral processing rather than in smelting—so longas that impurity is in a discrete identifiable mineral.When arsenic in the current ‘‘baseload’’ of tradedconcentrates occurs in the form of arsenopyrite(FeAsS), or is apparently dissolved in iron sulfides,

Fig. 9. Kazzinc Ust-Kamenogorsk Metallurgical Complex flowsheet (reprinted from extraction 2018).24

Fig. 10. Actual and predicted arsenic levels of concentrates(calculated by the authors from a graph of actual and forecastconcentrate arsenic levels reported by Mayhew et al.28).

Flores, Risopatron, and Pease3458

then it can be reduced by mineral separation apply-ing modern fine regrinding and washed-froth clean-ing. This is more technically efficient than removingthe arsenic in smelting, but it is not always moreeconomic for the miner. Though the technology iswell proven, it requires capital investment andincreases mine-site operating costs. Current concen-trate contracts do not generally reward this invest-ment—that is, they do not send the correct cost‘‘signals’’ to achieve the most efficient solution for theoverall processing industry. Usually mine sites onlyadopt these technologies if they are essential tomarket their concentrate—for example, some of thesites that produce the highest quality concentrates inFig. 2 do so in order to achieve limits on impuritiessuch as U or F. The mineral processing steps toreduce the impurities to acceptable levels for mar-keting coincidentally reduce other mineral contam-ination, resulting in a significantly higherconcentrate grade in high copper recovery (thoughin a finer-grained concentrate). If more accurateeconomic signals were sent through concentratecontracts, or if the copper industry agreed to an‘‘arsenic code’’, then the average arsenic level ofcurrently traded concentrates could also be reduced.

A much more difficult mineral processing chal-lenge is the selective flotation of arsenic-bearingcopper minerals (e.g., enargite, Cu3AsS4, and ten-nantite, (Cu, Fe)12As4S13). These minerals haveflotation characteristics very similar to non-arsenic-bearing copper minerals (chalcopyrite, chal-cocite and bornite). Very small chemical ‘‘windows’’for partial separation have been demonstrated inlaboratory work, but these do not appear robust

enough for practical application. Even if they were,they would still only split the same amount ofarsenic between a low-arsenic copper concentrateand a high-arsenic copper concentrate. Either way,a new processing technology needs to be adopted ifthe copper industry is to avoid the transport andsmelting of increased units of arsenic from thesedeposits. The atmospheric leaching processes inTable IV appear the most likely candidates, andthey could be applied on-site or at a central facilityto reduce arsenic content and dispose it locally andsafely before transport to smelters.

RECOGNIZING COMPLEXITY AS A DRIVERFOR THE FUTURE

Primary and secondary sources of base metals aregradually increasing in complexity. This complexityincludes lower grade ore, lower grade concentrates,and increases in the concentration of minor metalsand slagging elements. This pattern has clearlyaffected non-ferrous metal production, increasingoperating costs, environmental compliance pres-sures, and the investment required to ensure asustainable production of metals.

Alvear et al.32 discussed some key elementsassociated with the increasing complexity for pri-mary copper production. This has been observed inthe operation of secondary materials, such as theKayser Recycling System, with increasing complex-ity and reduction in the concentration of base andprecious metals in the sourced raw materials.

This pattern constantly challenges the competi-tiveness of smelters, who need regular evaluation ofcost-effective measures to remain competitive. This

Table IV. Some technology responses for the processing of complex arsenic-containing materials

Category Technology and main feature claims Status of development

Atmospheric leaching FLSmidth Ferric Leaching (ROL process) Pilot scaleAlbion process Industrial scaleGalvanox Pilot scaleToowong process Pilot scalePolysulfide Discontinued for copperINTEC Demonstration scaleHydrocopper Demonstration scaleNikko chlorination Demonstration scaleBioCop Demonstration scaleEquity silver Industrial scaleSumitomo chlorination Industrial scaleSeppon copper process Industrial scale

Pressure leaching POX Industrial scaleCESL Demonstration plantDemonstration plant DiscontinuedPLATSOL Pilot scale

Roasting Boliden Industrial scaleConcentrate processing

Vitrification Dundee Sustainable Technologies Demonstration scaleGlassLock ProcessTM

Mineral processing Fine regrinding, washed-froth cleaning Industrial scale, well-provenSelective flotation Separation of arsenic-bearing from non-arsenic-bearing minerals Laboratory scale

Processing of Complex Materials in the Copper Industry: Challenges and Opportunities Ahead 3459

is the most critical question for producers: How todifferentiate from each other in an industry that hasbeen traditionally regarded as a commodity busi-ness with common technologies.

Clearly, adequate technology transformation,selection and performance will play a crucial rolein this race to enhance (1) superior metallurgicalperformance, (2) a sustainable and environmentallyfriendly operation, (3) adequate impurity manage-ment, and (4) proper product quality.

Asset optimization is key. In a previous publica-tion, we recognized the following elements as essen-tial aspects to adjust metallurgical operations to thechange in supply:

� Flexibility of the process configuration to adaptto new grades: find new operating conditions andadjust production to this reality.

� Interaction with concentrate suppliers and abil-ity to blend and stabilize smelting assets on aregular basis if possible.

� Ability to maximize impurity processing capac-ity.

� Energy utilization: how to adjust operatingconditions for a given feed to optimize energyefficiency and utilization.

� Ultimately, considerations for new/improvedtechnologies to meet the challenge of resourceefficiency.

To this list, we add the need for better integration ofmine-site technologies with smelting, to find themost efficient place for the industry to removeimpurities. This requires constructive dialoguebetween miners and smelters. When the mostefficient technical option is identified, then either

concentrate contracts should send the right marketsignals, or the industry may need to agree to a codeof practice to achieve the most sustainable outcome.

KNOWLEDGE INTEGRATION: FROMFUNDAMENTAL KNOWLEDGE

TO TECHNOLOGY IMPLEMENTATION

Knowledge integration plays a key role in theconceptualization and development of metallurgicalprocesses. As complexity is expected to rise, modi-fications of existing metallurgical processes and/ordevelopments of new ones will be required.Increased amounts of minor elements from coppercomplex concentrates as well as complex e-wastesand industrial residues will require sustainableprocessing.

In addition, with e-mobility as a target for thefuture, new processes able to recycle and recoverbattery elements will be required. These potentialnew processes will benefit from synergies fromexisting metallurgical plants; however, careful eval-uation of the impact on existing streams will berequired. New smelters will need to move from astandard processing that is becoming more compet-itive and less profitable to explore processing ofcomplex urban wastes, metallurgical residues, andcomplex materials to secure profitable business.Competition with low-cost smelters, mostly locatedin China, will become more difficult.

As these operations move to consider new busi-ness opportunities, integrated approaches todevelop technologies will be required. Integrationwill mean not only technical knowledge but alsobusiness expertise in non-traditional materials andfull understanding of supply chains.

Table V. Basic elements required to foster an integrated technology development approach

Basic elements Main features

Marketunderstanding

Understanding main drivers behind metals marketsWho are the main actors and where are they playing?Awareness of commercial, technical, and environmental limitations

Technology roadmapping

Clear understanding of limitations and capabilities of technologies and processesAbility to assess technological status of competitors

Comprehensiveprocessknowledge

Capacity to understand current processes and fundamentals behind themHolistic analytical capabilitiesIntegrated multidisciplinary thinking

Technologicalsupport

Appropriate laboratory and/or pilot plant accessProcess modeling capabilities to properly represent metallurgical processes

Intelligent andeffectivenetworking

To know where to go and what to ask when needed to accelerate learning process

Engineeringdesigncapabilities

Clear awareness of engineering scale-up process to enable proper development, engineering,and transfer of technological innovations

Flores, Risopatron, and Pease3460

Key aspects to consider when analysing the needfor further development of existing assets and/ornew technology to meet the needs from the marketare shown in Table V.

CONCLUDING REMARKS

Sustainable production of metals is of paramountimportance to meet community demand along witha sustainable future of our planet. As demand forcopper and contained valuable metals increases andthe grade of available ores decreases, processing ofmore complex materials will be necessary.

The most efficient technical solutions will involvea combination of mineral processing and hydromet-allurgical and pyrometallurgical processing tech-niques, and will include processing complexmaterials from both primary and secondary sourcesat both mine sites and smelters.

In this framework, a resource-to-cathode visionthat incorporates synergies between mines, concen-trators, smelters, and refineries will be required.This needs to start with open technical dialogue,followed by commercial understanding of the mostefficient ways to remove impurities, and then besupported by the right market signals to achieve themore efficient outcomes.

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