Integrated hydrometallurgical and pyrometallurgical processing of base-metal sulphides

Abstract

The present invention relates to the recovery of base metals, in particular but not exclusively copper, via integrated hydrometallurgical and pyrometallurgical processing of base-metal sulphides, in particular but not exclusively iron-containing base-metal sulphides.

1 . A method for the recovery from a metal value bearing concentrate of one or more metal values including at least a primary metal value, the method using an integrated hydrometallurgical and pyrometallurgical process and including the steps of:
 i. performing a separation grading step by subjecting the metal-bearing concentrate to one or more beneficiation steps to enable the formation of at least three separate metal-bearing fractions including a high-grade metal concentrate fraction, a low-grade metal concentrate fraction, and a tailing fraction;   ii. subjecting the low-grade metal concentrate fraction to an acidic leaching process to enable formation of an acidic upgrading solution containing a solubilised form of the primary metal value;   iii. subjecting the high-grade metal concentrate fraction to a metal value upgrading step via reaction with at least a portion of the acidic upgrading solution formed in step (ii) to produce an upgraded metal concentrate fraction having a higher w/w concentration of the primary metal value; and   iv. subjecting the upgraded metal concentrate fraction derived from step (iii) to a smelting process to obtain at least the primary metal value.   
     
     
         2 . The method according to  claim 1 , wherein the primary metal value present in the metal value-bearing concentrate is copper. 
     
     
         3 . The method according to  claim 2 , wherein in step (ii) the acidic upgrading solution is an acidic copper sulphate solution. 
     
     
         4 . The method according to  claim 1 , wherein the one or more beneficiation steps of step (i) include milling, gravity, magnetic and/or flotation processes. 
     
     
         5 . The method according to  claim 1 , further including the step of subjecting the tailing fraction obtained in step (i) to an acidic leaching process to form an acidic solution for use in the processes of step (ii) or step (iii). 
     
     
         6 . The method according to  claim 5 , further including the step of subjecting the tailing fraction to further hydrometallurgical treatment to recover any additional soluble metal values that may be present. 
     
     
         7 . The method according to  claim 1 , further including the step of subjecting smelter flue dust or slag derived from the smelting process of step (iv) to hydrometallurgical treatment with an acid solution to form an underflow stream containing insoluble components and an overflow stream containing soluble forms of the primary metal value, wherein the underflow stream is recycled for use in step (iii) or step (iv) and/or the overflow stream is recycled for processing with the low-grade metal concentrate fraction or tailing fraction for facilitating recovery of any contained metal value. 
     
     
         8 . The method according to  claim 7 , wherein the step of treating the smelter flue dust or slag is a one or two stage process, whereby in the second stage the underflow product formed is further treated, prior to use in step (iii) or step (iv), by reaction with a stronger acid solution to facilitate further removal of any ferric iron or other leachable impurities that may be present. 
     
     
         9 . The method according to  claim 7 , wherein the underflow stream is further treated through regrinding and/or flotation processes to provide a concentrate feed for use in step (iii) or step (iv) for combination with the high-grade metal concentrate fraction. 
     
     
         10 . The method according to  claim 1 , wherein the acidic leaching process of step (ii) includes a pressure oxidation circuit where an oxidative leach reaction is continued until substantially all of the primary metal value present in the low-grade metal concentrate fraction is dissolved in the acidic upgrading solution and the ferric ion concentration of the acidic upgrading solution is below about 10 g/L. 
     
     
         11 . The method of  claim 10 , wherein any leach residues formed in the pressure oxidation circuit are further processed or recycled with the tailing fraction. 
     
     
         12 . The method according to  claim 1 , wherein the metal value-bearing concentrate includes a precious metal value, and wherein any leach residues formed in any of the hydrometallurgical and pyrometallurgical steps are further processed for recovering the precious metal value. 
     
     
         13 . The method according to  claim 12 , wherein the further process for recovering the precious metal value is via cyanide leaching. 
     
     
         14 . The method according to  claim 1 , wherein the metal value-bearing concentrate is an ore slurry containing at least one of the minerals selected from the group consisting of covellite, chalcocite, chalcopyrite, bornite and enargite. 
     
     
         15 . The method according to  claim 1 , wherein the high-grade metal concentrate fraction includes greater than 20-35% w/w of the primary metal value and the low-grade metal concentrate fraction includes less than 20-35% w/w of the primary metal value. 
     
     
         16 . The method according to  claim 1 , wherein step (i) includes subjecting the separated high-grade metal concentrate fraction and/or low-grade metal concentrate fraction to further processing including grinding, flotation, filtering, dilution, thickening, washing and/or other cleaning processes. 
     
     
         17 . The method according to  claim 1 , wherein prior to step (iii) or step (iv), the difference between the concentration of the primary metal value in the high-grade metal concentrate fraction compared to that in the low-grade metal concentrate fraction is increased through further processing to facilitate the recovery of the primary metal value. 
     
     
         18 . The method according to  claim 1 , wherein the hydrometallurgical upgrading step (iii) comprises the use of a single or multi-compartmented autoclave or digestor to produce an upgraded metal concentrate fraction having an increased primary metal value concentration. 
     
     
         19 . The method according to  claim 1 , wherein a source of sulphur dioxide obtained from off-gases of the smelting process of step (iv) is used in the hydrometallurgical upgrading step (iii) to facilitate reduction of any ferric ions that may be present. 
     
     
         20 . The method according to  claim 19 , wherein the primary metal value concentration in the upgraded metal concentrate fraction is increased to a concentration of greater than above about 45-50% w/w. 
     
     
         21 . The method according to  claim 1 , wherein prior to the smelting process step (iv), the upgraded metal concentrate fraction obtained in step (iii) is further processed by at least one of washing, flotation, dewatering, or drying and mixing with fluxes. 
     
     
         22 . The method according to  claim 1 , wherein prior to the smelting process step (iv), the upgraded metal concentrate fraction obtained in step (iii) is subjected to further separation grading to form a further upgraded feed for the smelting process step (iv) and a secondary recycle feed for step (iii). 
     
     
         23 . The method according to  claim 1 , further including the recovery of the metal values of uranium, cobalt, nickel, gold and/or silver, when present in the metal value bearing concentrate. 
     
     
         24 . The method according to  claim 1 , further including the transformation of any arsenic, when present in the metal value bearing concentrate, into an environmentally safe form.