Recovery of zinc from zinc bearing sulphidic ores and concentrates by controlled oxidation roasting

A process for the recovery of zinc from sulphidic zinc bearing ores and concentrates, comprising the steps of:

• (a) roasting a sulphidic zinc concentrate in contact with an oxygen bearing gas in the temperature range of 850.degree.-1050.degree. C. to obtain a calcine with a sulphur retention in said calcine between 50-75 wt. % of the sulphur initially present in said sulphidic concentrate;
• (b) leaching said calcine to produce a soluble oxidic fraction and an insoluble sulphidic zinc fraction;
• and,
• (c) roasting said insoluble sulphidic zinc fraction in a second roasting operation in stoichiometric excess oxygen, to obtain a zinc-rich calcine for zinc recovery.

A process for the recovery of zinc from sulphidic zinc bearing ores and concentrates, comprising the steps of:

• (a) roasting a sulphidic zinc concentrate in contact with an oxygen bearing gas in the temperature range of 850.degree.-1050.degree. C. to obtain a calcine with a sulphur retention in said calcine between 50-75 wt % of the sulphur initially present in said sulphidic concentrate;
• (b) subjecting said calcine to a first aqueous sulphur dioxide leach to obtain a first leach residue and a first leachate containing dissolved zinc and iron;
• (c) precipitating the dissolved zinc in the first leachate of step (b) as zinc sulphite
• (d) subjecting said first leach residue to a second aqueous sulphur dioxide leach to obtain a second leachate containing dissolved iron and a second leach residue containing undissolved zinc sulphide;
• (e) precipitating the dissolved iron in the second leachate of step (d) as iron sulphite;
• (f) roasting the second leach residue containing undissolved zinc sulphide in a second roasting operation in excess stoichiometric oxygen, to obtain a zinc-rich calcine for zinc recovery, and,
• (g) converting said precipitated iron sulphite of step (e) to an iron oxide product.

A process for the recovery of zinc from sulphidic zinc bearing ores and concentrates, comprising:

• (a) roasting a sulphidic zinc concentrate in contact with an oxygen bearing gas in the temperature range of 850.degree.-1050.degree. C. to obtain a calcine with a sulphur retention in said calcine between 5-50 wt. % of the sulphur initially present in said sulphidic concentrate;
• (b) leaching said calcine to obtain a leach residue which contains both iron bearing compounds and zinc bearing compounds and a zinc leachate suitable for zinc recovery;
• (c) subjecting said leach residue to magnetic separation to obtain an iron fraction and a zinc fraction;
• (d) subjecting said zinc fraction to froth flotation to remove lead and other base metal sulphides and silicates;
• and,
• (e) returning said zinc fraction to roasting step (a).

A process for the recovery of zinc from sulphidic zinc bearing ores and concentrates, comprising:

• (a) roasting a sulphidic zinc concentrate in contact with an oxygen bearing gas in the temperature range of 850.degree.-1050.degree. C. to obtain a calcine with a sulphur retention in said calcine between 5-50 wt. % of the sulphur initially present in said sulphidic concentrate;
• (b) leaching said calcine to obtain an insoluble iron oxide and an unreacted sulphide fraction and a soluble zinc fraction suitable for zinc recovery;
• (c) leaching said iron oxide and unreacted sulphide fraction for separation of iron bearing compounds from sulphidic zinc bearing compounds;
• (d) recycling said sulphidic zinc bearing compounds to roasting step (a);
• (e) taking a bleed stream off said sulphidic zinc bearing compounds from step (c) to remove silicates and lead sulphides.

A process for the recovery of zinc from sulphidic zinc bearing ores and concentrates, comprising:

• (a) roasting a sulphidic zinc concentrate in contact with an oxygen bearing gas in the temperature range of 850.degree.-1050.degree. C. to obtain a calcine with a sulphur retention in said calcine between 5-50 wt. % of the sulphur initially present in said sulphidic concentrate;
• (b) leaching said calcine to obtain an insoluble iron oxide and an unreacted sulphide fraction and a soluble zinc fraction suitable for zinc recovery;
• (c) subjecting said iron oxide and unreacted sulphide fraction to froth flotation for separation of sulphidic zinc bearing compounds from lead sulphides, iron oxides and silicates;
• and
• (d) returning said sulphidic zinc bearing compounds to roasting step (a).