Low Grade Ores - Smelt, leach or concentrate?

1

Sharif Jahanshahi and Terry Norgate

Meta-Logical Solutions

Decline in Australian Ore Grades

2

0

5

10

15

20

25

30

35

40

1840 1855 1870 1885 1900 1915 1930 1945 1960 1975 1990 2005

Ore

Gra

des

(Cu,

Pb,

Zn,

Au,

Ni,

U, D

iam

onds

)

0

325

650

975

1,300

1,625

1,950

2,275

2,600

Ore

Gra

de (A

g)

Copper (%Cu)

Gold (g/t)

Lead (%Pb)

Zinc (%Zn)

Uranium (kg/t U3O8)

Nickel (%Ni)

Diamonds (carats/t)

Silver (g/t)

general trend

(kg/t U3O8)

(Ag, 1884 - 3,506 g/t)

Source: G. Mudd, The sustainability of mining in Australia: Key production trends and their environmental implications for the future, Research Report, October 2007 (http://civil.eng.monash.edu.au/about/staff/muddpersonal/rr5/

Processing Routes for Copper Ores

Ore deposit

Mining

Crushing & grinding

Mineral processing

Smelting

Converting

Refining

Refined metal

Smelting

Pyrometallurgical route

Hydrometallurgical route

In-situ leaching

Leaching (heap, pressure)

Solvent extraction & electrowinning

Refined metal

Crushed/ground ore

Matte

Crushed/ground ore

Concentrate

Matte

LCA Based Energy Consumption - Excludes mining

-

5,000

10,000

15,000

20,000

25,000

Concentrator Smelter Refinery Total

Ener

gy c

onsu

mpt

ion

(MJ/

t Cu) Ore grade 3% Cu

Concentrate recovery 93.7%Smelter recovery 97.1%Overall recovery 90.5%

-

10,000

20,000

30,000

40,000

50,000

Crushing Leach & SX EW TotalEn

ergy

con

sum

ptio

n (M

J/t C

u) Ore grade 2% CuHeap leach recovery 70%SX recovery 93%Overall recovery 64.8%

Concentrate, Smelt, Refine Heap leach, SX, EW

Energy consumption will increase with decreasing ore grade through the concentrator and mining

Energy consumption will increase with decreasing ore grade through leaching and mining

Effect of Ore Grade on Energy Consumption - Pyromet route

0

100

200

300

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5Em

bodi

ed e

nerg

y (M

J/kg

Cu)

Ore grade (% Cu)

Liberation/grain size 75 um

Australia

World

USA

Effect of Ore Grade - Including Mining

0

30

60

90

120

150

0.5% Cu 3.0% Cu

Embo

died

ene

rgy

(MJ/

kg C

u)

RefiningSmeltingMineral processingMining

6 times higher energy consumption for mining and mineral processing

Comparison of Alternative Routes

0

400

800

1200

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Embo

died

ene

rgy

(MJ/

kg C

u)

Ore grade (wt% Cu)

Smelt & conc (75 um)

Smelt & conc (5 um)

Pressure acid leach

In-situ leaching

Heap leaching

Direct smelt

❖ With waste heat recovery from slags, direct smelting becomes even more energy efficient

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: sharif@metalogical.solutions