Single stage pressure leach hydrometallurgical method for upgrade of copper concentrates

Abstract

A hydrometallurgical method 80 for the removal at least one of iron, aluminum, arsenic, sulfur, nickel, cobalt, zinc and cadmium (impurities) from a copper concentrate to produce an upgraded copper concentrate 92, the method comprising the step of: subjecting the copper concentrate to an acidic leaching process (NONOX leach 120) in a multi-compartment autoclave using a copper sulfate containing lixiviant under lowered electrochemical conditions, to implement a controlled removal of between 20% and 99% of at least one of the impurities to produce the upgraded copper concentrate. The NONOX leach 120 is conducted to produce the majority of required soluble copper sulfate from a partial oxidation of the feed copper concentrate in a first compartment 200 of the multi-compartment autoclave under particular conditions.

1 . A hydrometallurgical method for the removal at least one of iron, aluminum, arsenic, sulfur, nickel, cobalt, zinc and cadmium (impurities) from a copper concentrate to produce an upgraded copper concentrate, the method comprising the step of:
 subjecting the copper concentrate to an acidic leaching process (NONOX leach) in a multi-compartment autoclave using a copper sulfate containing lixiviant under lowered electrochemical conditions, to implement a controlled removal of between 20 and 99% of at least one of iron, aluminum, arsenic, sulfur, nickel, cobalt, zinc and cadmium (impurities) to produce the upgraded copper concentrate, with reduced soluble copper losses in the discharge stream, and wherein the NONOX leach is conducted:
 to produce the majority of required soluble copper sulfate from a partial oxidation of the feed copper concentrate in a first compartment of the multi-compartment autoclave; 
 to pass the partially oxidised slurry from the first compartment into the second and ensuing compartments of the multi-compartment autoclave; 
 such that a division between the first compartment and the second and ensuing compartments does not permit transfer of unused oxidant gas from the first compartment to the second and ensuing compartments; 
 to provide a non-oxidising atmosphere in the second and ensuing compartments such that a majority of the soluble copper in the partially oxidised slurry from the first compartment is uploaded onto the partially leached solids to provide the upgraded concentrate; 
 employing elevated temperature and elevated pressure to suppress boiling in the leaching process; and 
 utilising acid generated from the hydrolysis of ferric iron in the first compartment to re-dissolve the ferric iron in the non-oxidising conditions of the second and ensuing compartments. 
   
     
     
         2 . A hydrometallurgical method as defined in  claim 1 , wherein the leaching process (NONOX leach) is conducted at an electrochemical potential of greater than 150 mV (Ag/AgCl 3.8M KCl). 
     
     
         3 . A hydrometallurgical method as defined in  claim 2 , wherein the leaching process (NONOX leach) is conducted at an electrochemical potential in the range of between about 175 mV and 450 mV (Ag/AgCl 3.8M KCl). 
     
     
         4 . A hydrometallurgical method as defined in  claim 1 , wherein the electrochemical potential of the NONOX leach is controlled by the presence of, or the addition to the NONOX leach of, one or more of cupric sulfate, ferric ion, air, oxygen, pyrolusite, or hematite. 
     
     
         5 . A hydrometallurgical method as defined in  claim 1 , wherein the copper sulfate containing lixiviant typically comprises one or more of the following solutes: sulfuric acid, sodium sulfate, copper sulfate, the copper sulfate containing lixiviant being obtained from within the NONOX leach, or from a source external to the NONOX leach. 
     
     
         6 . A hydrometallurgical method as defined in  claim 5 , wherein the copper sulfate containing lixiviant also contains some chloride anions. 
     
     
         7 . A hydrometallurgical method as defined in  claim 1 , wherein the NONOX leach is conducted between about 100° C. and 240° C. 
     
     
         8 . A hydrometallurgical method as defined in  claim 7 , wherein the NONOX leach is conducted between about 160° C. and 240° C. 
     
     
         9 . A hydrometallurgical method as defined in  claim 1 , wherein copper-iron-sulfides are transformed in the NONOX leach, and the NONOX leach is conducted under conditions to transform 50% to 99% of the copper-iron-sulfides to iron-depleted copper sulfides and covellite and to a sulfur-depleted variant (digenite/chalcocite). 
     
     
         10 . A hydrometallurgical method as defined in  claim 9 , wherein pyrite and pyrrhotite are substantially altered under NONOX conditions to iron depleted copper-iron-sulfides. 
     
     
         11 . A hydrometallurgical method as defined in  claim 1 , wherein the NONOX leach is conducted at a pressure in the range of 500-3500 kPa. 
     
     
         12 . A hydrometallurgical method as defined in  claim 11 , wherein the retention time of the NONOX leach is between about 0.5 and 8 hours. 
     
     
         13 . A hydrometallurgical method as defined in  claim 1 , wherein the partial oxidation of the feed copper concentrate in the first compartment of the multi-compartment autoclave employs oxygen, oxygen enriched air or air as the oxidant. 
     
     
         14 . A hydrometallurgical method as defined in  claim 1 , wherein the first compartment of the multi-compartment autoclave is preferably divided from the other compartments by a divider construction that restricts the free flow of the autoclave vapour phase from the first compartment to other compartments, i.e. the divider construction forms the division between the first compartment and the second and ensuing compartments so that the transfer of unused oxidant gas from the first compartment to the second and ensuing compartments is minimised or not permitted. 
     
     
         15 . A hydrometallurgical method as defined in  claim 14 , wherein a counter current vapour flow within the autoclave is usually present such that the second and remaining compartments have a vapour phase that is essentially free of oxygen. 
     
     
         16 . A hydrometallurgical method as defined in  claim 1 , further comprising feeding into the NONOX leach a copper sulfate slurry from a crystalliser or a copper sulfate leach liquor from an external pressure oxidation reactor (PROX reactor), or copper sulfate solution from an external source, or a copper sulfate leach slurry direct from a PROX reactor. 
     
     
         17 . A hydrometallurgical method as defined in  claim 16 , wherein the copper sulfate slurry typically comprises copper sulfate, iron sulfate and sulfuric acid. 
     
     
         18 . A hydrometallurgical method as defined in  claim 1 , wherein the copper sulfate can be added to more than one compartment in the NONOX leach reactor. 
     
     
         19 . A hydrometallurgical method as defined in  claim 1 , wherein the copper aqueous concentration levels within the discharge liquor from the NONOX leach reactor are less than 5 g/L and more typically less than 1 g/L.