1. Outokumpu HydroCopper Process
O. Hyvärinen, M. Hämäläinen, R. Leimala
Outokumpu Research Oy, Pori, Finland
Chloride Metallurgy, 2002
Montreal, Quebec, Canada
October 21, 2002

2. Outokumpu HydroCopper Process Block Diagram
Copper Concentrate
Gold
Silver
By-Products
Leach Residue
NaCl Solution
Leaching of Concentrate
Leaching
Purification
Precipitation
Regeneration of
Chemicals
Chlor-alkali Electrolysis
Cl2 (g)
NaOH
Cu2O
Metal Production
Reduction
Melting
Casting
Copper Product
H2 (g)
10 November 2018

3. Counter Current Leaching
Air
Leach Residue
Concentrate
Counter Current Leaching Au
Cu2+
Cu+
Oxidation of Cu+
CaCO3
NaOH
Cu2+
Precipitation Hg
Cl2 Cu
Silver
Removal Ag
(Zn,Pb)CO3
Na2CO3
Metal
Precipitation
HCl
Ion
Exchange
NaOH
Cu2O
Precipitation
Chlor-alkali
Electrolysis
NaCl H2
Reduction
Melting
Casting
Copper Product
10 November 2018

4. Leaching Conditions
Three-stage counter current atmospheric leaching of concentrate in agitated reactors
lixiviant g/l NaCl
oxidants are cupric ions and oxygen (air)
solids content 150 – 300 g/l
temperature oC
pH 1.0 – 2.5
total leaching time typically 10 – 20 h
10 November 2018

5. Leaching Reactions Dissolution of chalcopyrite
CuFeS2 + 3 Cu2+ = 4 Cu+ + Fe S
Sulfide minerals
MeS + 2 Cu2+ = Me Cu+ + S
where Me = Cu, Zn, Pb, Ni, Co, Ag, etc.
10 November 2018

6. Gold Recovery
Gold is leached in the third stage where the redox potential is at its highest
Au + 3 Cu Cl- = AuCl4- + 3Cu+ + 2 Cl-
Gold ions are adsorbed on activated carbon
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7. Iron Oxidation Removal of iron is carried out by oxidation
3 Cu+ + ¾ O2 + 3 H+ = 3 Cu2+ + 1½ H2O
Cu2+ + Fe2+ = Cu+ + Fe3+
Fe H2O = FeOOH + 3 H+
The overall reaction of chalcopyrite leaching is
CuFeS2 + Cu2+ + ¾ O2 + ½ H2O = 2 Cu+ + FeOOH +2 S
10 November 2018

8. Leaching Yields Base metals 98 % Gold and silver >92 %
About 10 % of sulfur is oxidized to sulfate
Pyrite is refractory
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9. Leach Residue Small grain size, but filterable, consisting of:
Elemental sulfur
Goethite or hematite
Gypsum, silica, etc.
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10. Solution Purification
Sulfate is controlled by adding limestone
Cu2+ is removed as hydroxy-chloride, pH = 3 –5,
4 CuCl2 + 6 NaOH = 3 Cu(OH)2* CuCl2 + 6 NaCl
or by reduction with copper powder
Cu2+ + Cu = 2 Cu+
Silver is cemented out with Cu powder and mercury as amalgam
Multivalent metals are precipitated as hydroxides or carbonates, pH = 6 – 7
Traces of these metals are removed by ion exchange
10 November 2018

11. Precipitation of Cuprous Oxide
Cuprous oxide is precipitated with sodium hydroxide, pH =
2 CuCl + 2 NaOH = Cu2O + 2 NaCl + H2O
Impurities in the purified cuprous chloride solution have to be well below 0.1 mg/l
10 November 2018

12. Reduction, Melting and Casting
Cuprous oxide is reduced by hydrogen gas at T = 400 – 550 oC in a rotary kiln (Outokumpu Demo Plant)
Cu2O(s) + H2(g) = 2 Cu(s) + H2O(g)
Copper powder is melted in an induction furnace and cast into wire rod using the renowned Outokumpu Upcast® Technology
10 November 2018

13. Lixiviant Regeneration
NaCl solution from the Cu2O-precipitation is fed into a membrane Chloralkali Electrolyzer
2 NaCl + 2 H2O = 2 NaOH + Cl2 + H2
Products of the electrolyzer are recirculated
NaOH to Cu2O precipitation
H2 to Cu2O reduction
Cl2 to oxidize cuprous to cupric before leaching
½ Cl2 + Cu+ = Cu Cl-
10 November 2018

14. Chlor-alkali Electrolyzer
Chlor-alkali cell in HydroCopperTM Process replaces copper EW cell
Compared with the EW cell the highly advanced Chlor-alkali cell is
proven technology
operates at a higher current density
copper is not in contact with the cell and is not harvested from it
the cell is compact and needs less maintenance
10 November 2018