Converting

Matte Feed

Process used for Cu, Ni extractionCopper• Cu: 35 – 65 wt.%• Fe: 10 – 40 %• S: 20 – 25%• O: 2 – 3%• Zn, Pb: 0 – 5%; As: 0 – 0.5%; Bi: 0 – 0.1%• Au: 1.5 x 10-5 ; Ag: 0 – 0.1%

Objective

• Produce blister copper (98.5 – 99.5% pure)• Fe: 0.1%; S: 0.02 – 0.1%; O: 0.5 – 0.8%• Au: 0 – 0.01%; Ag: 0 – 0.1%• Blister copper has to be purified further for

electrical applications (99.999% pure) by electrolysis.

• Au, Ag can be recovered.

Converter

Stages in convertingSlag forming stage• Preferential oxidation of FeS to FeO, Fe3O4

which combines with silica to form slag.• Cu2O formed is re-sulfidized to Cu2S.

FeS (M) + Cu2O (S) = FeO (S) + Cu2S (M); K=104

• Towards the end of stage aFeS↓ – Cu2O (S)↑• Matte is added in two stages after discarding slag.

Metal making stage• Cu2S (l) + 1.5O2 = Cu2O(s) + SO2

• Cu2S (l) + 2Cu2O(s) = 6Cu(l) + SO2

• Two layers of liquid– Sulfide rich phase on top.– Liquid blister copper at the bottom.– Finally sulfide layer is consumed.

• Solubility of S and O in final blister copper given by: – [S] + 2[O] = SO2 ; K = 40 at 1200 C

– S: 0.02% ; O: 0.5% (PSO2 = 0.1 atm)

– [S] ~ 1% and [O] ~ 0.4% forms SO2 voids during

solidification. WHY?