Download - Management of Minor Elements
Management of Minor Management of Minor Elements in the Elements in the Production of Base MetalsProduction of Base Metals
Sharif Jahanshahi, Warren Bruckard, Chunlin Chen and Frank Jorgensen Mission: To progressively
eliminate waste and emissions in the minerals cycle, while
enhancing business performance and meeting community expectations
Presentation by Sharif Jahanshahi PhD, FAusIMM
Sharif Jahanshahi has over 30 years experience in R&D across; high temperature processing of ferrous and base metals, thermodynamics and kinetics of high temperature systems, melt chemistry, process modelling, simulation and development
Currently consulting for leading global players in the metallurgical industry through Meta-Logical Solutions Pty Ltd.
Website: http://www.metalogical.solutionsEmail: [email protected]
Green Processing 2006: 5-6 June 3
BackgroundBackground
Australia exports ~ 3 millions of tpa of copper, nickel, lead and zinc in form of concentrate and refined metals.
Base metal ores contain low levels (1- 104 ppm) of toxic/ hazardous elements (As, Sb, Bi, Cd, Hg, Se, Te…, Th, U)
Clean, coarsely-grained ore bodies becoming depleted
Ore bodies of future becoming more complex, finer-grained and containing higher amount of minor/toxic elements.
Worldwide industry mines and process 100s million tonnes of base metal ores each year
Accumulated mass of minor elements in biosphere is large and could have a significant environmental impact
Green Processing 2006: 5-6 June 4
Industry ContextIndustry Context
Minor elements present technical and environmental problems as well as being costly
Smelters impose treatment charges and penalty payment on minor elements in concentrates
Governments becoming increasingly sensitive to emissions
Community pressure for more sustainable processing
Smelters setting tighter penalty specifications for minor elements
Imperative to develop alternative treatments for selective removal of toxic elements at the mine site before despatch of concentrate to smelters
Green Processing 2006: 5-6 June 5
Options for Dealing with Toxic Options for Dealing with Toxic Elements in OresElements in Ores
Primarily determined by mineralogy and grain size
Occurrence - association with other elements
Distribution between phases
For widely and uniformly dispersed minor elements in mineral phases treatment option is limited
Separation and removal in waste/residue streams produced in metal extraction
If concentrated in discrete phases, options exists for early removal by physical and chemical means
Having separated and concentrated the toxic elements, consideration has to be given to their use or safe disposal
Green Processing 2006: 5-6 June 6
ArsenicArsenic
Is one impurity element found in most base metal ores and concentrates
Lowers metal quality, if not removed from product metal
Contributes to health concerns during metallurgical processing
Causes environmental concerns during disposal of tailings and wastes
High arsenic levels in an ore can make the deposit economically unviable
Blending of high and low arsenic concentrates has been practiced by industry. Can we continue this in the future?
Green Processing 2006: 5-6 June 7
Mineralogy Consideration Mineralogy Consideration
In copper ores arsenic occurs asEnargite (Cu3AsS4) Tennanite (3Cu2S.As2S3)
Arsenopyrite (FeAsS) Cobaltite (CoAsS)
In nickel systemsGersdorffite (NiAsS) Niccolite (NiAs)
Arsenopyrite (FeAsS) Cobaltite (CoAsS)
Physical separation of arsenic bearing minerals from non-arsenic bearing minerals is difficult Similar specific gravity, non-magnetic, strongly floatable with
conventional collectors etc.
Some As minerals contain high concentration of copper and nickel e.g. enargite (Cu3AsS4) has 48% Cu
Green Processing 2006: 5-6 June 8
Mineral Recovery in 1 minuteMineral Recovery in 1 minute
0
10
20
30
40
50
60
70
80
90
100
-500 -400 -300 -200 -100 0 100 200 300 400 500
Pulp potential (mV vs SHE)
Min
eral
rec
ove
ry a
t 1
min
(%
) Enargite (pH 8)
Chalcopyrite (pH 8)
0
10
20
30
40
50
60
70
80
90
100
-500 -400 -300 -200 -100 0 100 200 300 400 500
Pulp potential (mV vs SHE)
Min
eral
rec
ove
ry a
t 1
min
(%
) Enargite (pH 8)
Chalcopyrite (pH 8)
Senior et al J. Min Eng. Int, In press
Green Processing 2006: 5-6 June 9
Selective RoastingSelective Roasting
Roasting has been used to remove arsenic from ores and concentrates
A number of treatment options have been developed and reviewed in literature
Operating windows for selective removal of arsenic from copper concentrates identified through thermodynamic modelling
Green Processing 2006: 5-6 June 10
Effect of Roasting Temperature Effect of Roasting Temperature
100
80
60
40
20
0
500 600 700 800 900
Temp. (°C)
Rem
ova
l o
f A
rsen
ic (
%)
0.055%As
0.54%As
5.3%As
O2:Chalcopyrite = 2 CuFeS2:FeS2: FeS ~ 10:1.7:1
58% desulfurisation
100
80
60
40
20
0
500 600 700 800 900
Temp. (°C)
Rem
ova
l o
f A
rsen
ic (
%)
0.055%As
0.54%As
5.3%As
O2:Chalcopyrite = 2 CuFeS2:FeS2: FeS ~ 10:1.7:1
58% desulfurisation
Nakazawa, Yazawa & Jorgensen Met Trans 30B, 1999
Green Processing 2006: 5-6 June 11
Effect of Oxygen Supply at 700 CEffect of Oxygen Supply at 700 C
100
80
40
60
20
01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
O2 : chalcopyrite (mol:mol)
Re
mo
val
of
Ars
en
ic (
%)
5.3% As
0.54% As
0.055% As
700 ° C
FeAsO4
100
80
40
60
20
01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
O2 : chalcopyrite (mol:mol)
Re
mo
val
of
Ars
en
ic (
%)
5.3% As
0.54% As
0.055% As
700 ° C
FeAsO4
Nakazawa, Yazawa & Jorgensen Met Trans 30B, 1999
Green Processing 2006: 5-6 June 12
Effect of Oxygen Supply at 900 CEffect of Oxygen Supply at 900 C
100
80
40
60
20
01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
O2 : chalcopyrite (mol:mol)
Re
mo
val
of
Ars
en
ic (
%)
5.3% As
0.54%
0.055%
900 °C
100
80
40
60
20
01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
O2 : chalcopyrite (mol:mol)
Re
mo
val
of
Ars
en
ic (
%)
5.3% As
0.54%
0.055%
900 °C
Nakazawa, Yazawa & Jorgensen Met Trans 30B, 1999
Green Processing 2006: 5-6 June 13
Arsenic Removal from Copper Arsenic Removal from Copper Concentrate during RoastingConcentrate during Roasting
Smelter Roaster* Temp.(°C)
Arsenic in feed
(wt %)
Arsenic removal
(%)
Sulphur removal
(%)
US EPA MH 540 0.2 27 -
US EPA FB 540 to 620 0.02 15 -
El Indio MH 720 max. 6.4 >90 56
Saganoseki FB 685 to 705 5 to 6 85 to 90 60 to 70
Lepanto FB 700 1.3 82 60
Oroya MH 700 2.6 76 53
Boliden FB 700 to 720 2 92 56
*MH = multi-hearth and FB = fluidized bed
Green Processing 2006: 5-6 June 14
Distribution of As, Bi, Pb during Distribution of As, Bi, Pb during SmeltingSmelting
40 45 50 55 600
25
50
75
100T=1573 KPSO2=0.1 atmIron silicate slag
bBi
Gas
Matte
40 45 50 55 600
25
50
75
100T=1573 KPSO
2=0.1 atm
Calcium ferrite slag
T=1573 KPSO
2=0.1 atm
Calcium ferrite slag
eBi
Gas
Matte
wt% Cu in matte
40 45 50 55 600
25
50
75
100T=1573 KPSO
2=0.1 atm
Iron silicate slag
aAs
Slag
Gas
Matte
Dis
trib
utio
n (
%)
40 45 50 55 600
25
50
75
100T=1573 KPSO2=0.1 atmCalcium ferrite slag
d
Matte
As
Slag
Gas
Dis
trib
utio
n (
%)
wt% Cu in matte
40 45 50 55 600
25
50
75
100cT=1573 K
PSO2=0.1 atm
Iron silicate slag
Pb
Gas
Matte
40 45 50 55 600
20
40
60
80
100
fPb
Gas
Matte
wt% Cu in matte
Chen et al Sohn Intl Symp , 2006
Green Processing 2006: 5-6 June 15
Simulated FlowsheetSimulated Flowsheet
Converting1st & 2nd Stages
Smelting
Fire-refining1st & 2nd Stages
CopperConc
Slag
Slag
Matte
Blister Copper
Anode Copper
Gas
Gas
Gas
Air + Flux
Air + Flux
Air/Methane
Green Processing 2006: 5-6 June 16
Arsenic Distribution Arsenic Distribution - - From Concentrate to Anode CopperFrom Concentrate to Anode Copper
0
25
50
75
100
Smelting Convert 1 Convert 2 Fire-ref 1 Fire-ref 2
Processing Step
Ars
en
ic D
istr
ibu
tion
(%
)
Gas
Slag
Matte/ Copper0.1 wt% As in Conc
Iron silicate slag
Green Processing 2006: 5-6 June 17
Arsenic Deportment Arsenic Deportment - From Concentrate to Anode Copper- From Concentrate to Anode Copper
0
25
50
75
100
Smelting Convert 1 Convert 2 Fire-ref 1 Fire-ref 2
Processing Step
Ars
en
ic D
ep
ort
me
nt (
wt%
)
Gas
Slag
Matte/Copper
0.1 wt % As in ConcIron silicate slag
Green Processing 2006: 5-6 June 18
Copper Production from Sulfide Copper Production from Sulfide OresOres
Ore
Tailing Dam
Anode Slimes
Smelting
Air, Flux, Coal Air, Flux
Acid Plant
Concentrate Matte Blister
AnodeCopperr Copper
99.99%
AnodeSlimes
Air, Natural Gas
Air, Flux
Slag
SlagSlagSlag
Acid
Dore Metal (Ag-Au)
Tailings
Gypsum
Tailing Dam
Tailing Dam
Flotation Smelting 2-stage Converting
Fire-refining Electro-refining
Green Processing 2006: 5-6 June 19
Safe Disposal of Toxic ElementsSafe Disposal of Toxic Elements
Production of arsenic and other toxic elements is well in excess of market demand
Typically concentrated in form of fumes, dross, precipitates and slags
Disposal of surplus in a safe and environmentally acceptable manner
Thus conversion to a less hazardous form and longer term solutions are required conversion into calcium arsenate, ferric arsenate etc.
encapsulation in concrete or locking in silicate slags
Careful assessment of these options is required
Green Processing 2006: 5-6 June 20
The Early Removal OptionsThe Early Removal Options
TailingDam
Flotation
Roaster
Smelter
Low As Conc
High AsConc
Low AsConc
Safe Disposal e.g mine backfill
Ore
Arsenic Fumes
Green Processing 2006: 5-6 June 21
ConclusionsConclusions
Increasing pressure on metal producers to reduce emissions and manage toxic elements deportment
Challenge - orebodies with higher levels of minor elements, which are difficult to process
Early removal option offers competitive advantage
Several options for safe disposal of low volume highly toxic streams, which could be linked with the early removal
We believe, it is time to put current capability into practice by examining the integrated flowsheets to deal with the management of the minor elements in a more sustainable way.
Green Processing 2006: 5-6 June 22
AcknowledgementAcknowledgement
Some of the work and findings presented were generated
through a project carried out under the auspice and
financial support of the Cooperative Research Centre for
Sustainable Resource Processing, which was established
and is supported under the Australian Government's
Cooperative Research Centres Program