Method and means for using microwave energy to oxidize sulfidic copper ore into a prescribed oxide-sulfate product

Abstract

The present invention is directed to the microwave treatment of a class of selected metal ores and concentrates, particularly those known as chalcopyrite, in a fluidized bed reactor. The end product is commonly a mixture of copper oxide and copper sulfate, both of which are liquid soluble and directly recoverable by known techniques. The ratio of the oxide-sulfate mixture end product may be controlled by suitable control of microwave parameters.

1 . A process for recovering a selected metal from a sulfidic material, comprising:
 (a) passing microwave energy through a bed of the sulfidic material while the material is positioned in a fluidized bed reactor;   (b) during step (a), passing a fluidizing gas through the reactor to fluidize the bed of sulfidic material to oxidize selected metal sulfides in the sulfidic material and form an oxidized selected metal-containing material; and   (c) removing the oxidized selected metal-containing material from the fluidized bed reactor.   
     
     
         2 . The process of  claim 1 , wherein the oxidized selected metal-containing material, after removal from the fluidized bed reactor, has a ratio of selected metal oxides to selected metal sulfates ranging from about 0.3:1 to about 8:1 and a sulfide sulfur content ranging from about 1 to about 0.5 wt. %. 
     
     
         3 . The process of  claim 1 , wherein the sulfide sulfur content of the sulfidic material is at least about 7 wt. % and wherein a maximum temperature of the bed of sulfidic material and of the selected metal sulfides is no more than about 690° C. 
     
     
         4 . The process of  claim 1 , wherein the selected metal is at least one of copper, nickel, cobalt, and manganese, wherein the fluidized bed is positioned above an inert bed of particulate material, the inert bed of particulate material being too heavy to be fluidized by the fluidizing gas in step (b), wherein the material has a P 80  size ranging from about 35 microns to about 75 microns, and wherein the particulate material in the inert bed has a P 80  size ranging from about 200 microns to about 300 microns. 
     
     
         5 . The process of  claim 1 , wherein the oxidized material, when removed from the fluidized bed reactor, comprises no more than about 5 wt. % selected metal ferrites and wherein at least most of the selected metal in the oxidized material is in the form of a sulfate. 
     
     
         6 . The process of  claim 1 , wherein the oxidized material, when removed from the fluidized bed reactor, has a maximum sulfide sulfur content of no more than about 1 wt. % and wherein at least most of the selected metal in the oxidized material is in the form of XO, where X is the selected metal. 
     
     
         7 . The process of  claim 1 , wherein the selected metal-containing components of the selected metal-containing material are heated to a temperature ranging from about 580 to about 680° C., wherein a microwave energy source comprising one or more individual generating units generating the microwave energy has a power level in the range of about 1 kw to about 150 kw per generating unit, operates at a frequency ranging from about 300 MHz to about 3 GHz, wherein the reaction chamber has an unloaded Q value ranging from about 1,000 to about 25,000, wherein the microwave energy delivered to the sulfidic material ranges from about 250 to about 300,000 Joules/gm, and wherein at least most of the microwave energy has a frequency of about 915 MHz. 
     
     
         8 . The process of  claim 1 , wherein the selected metal-containing sulfidic material has a sulfide sulfur concentration of no more than about 6 wt. % and wherein a residence time of the material in the reactor is no more than about 30 minutes. 
     
     
         9 . The process of  claim 1 , wherein the fluidized bed reactor operates as a bubbling bed fluidized system, wherein a volumetric fluidizing gas-to-solids ratio is at least about 1:1, and wherein microwave interaction with the material occurs primarily within the selected metal-containing material. 
     
     
         10 . A selected metal recovered by the process of  claim 1 . 
     
     
         11 . A process for recovering a selected metal from a sulfide sulfur-containing material, comprising:
 (a) passing microwave energy through a bed of the sulfide sulfur-containing material while the material is positioned in a fluidized bed reactor;   (b) during step (a), passing a fluidizing gas through the reactor to fluidize the bed of sulfide sulfur-containing material to oxidize selected metal sulfides in the sulfide sulfur-containing material and form an oxidized selected metal-containing material; and   (c) removing the oxidized selected metal-containing material from the fluidized bed reactor, wherein the fluidized bed is positioned above an inert bed of particulate material, the inert bed of particulate material being too heavy to be fluidized by the fluidizing gas in step (b).   
     
     
         12 . The process of  claim 11 , wherein the oxidized selected metal-containing material, after removal from the fluidized bed reactor, has a ratio of selected metal oxides to selected metal sulfates ranging from about 0.3:1 to about 8:1 and a sulfide sulfur content ranging from about 1 to about 0.5 wt. %. 
     
     
         13 . The process of  claim 11 , wherein the sulfide sulfur content of the sulfide sulfur-containing material is at least about 7 wt. % and wherein a maximum temperature of the bed of sulfide sulfur-containing material and of the selected metal sulfides is no more than about 690° C. 
     
     
         14 . The process of  claim 11 , wherein the selected metal is at least one of copper, nickel, cobalt, and manganese, wherein the sulfide sulfur-containing material has a P 80  size ranging from about 35 microns to about 75 microns, and wherein the particulate material in the inert bed has a P 80  size ranging from about 200 microns to about 300 microns. 
     
     
         15 . The process of  claim 11 , wherein the oxidized material, when removed from the fluidized bed reactor, comprises no more than about 5 wt. % selected metal ferrites and wherein at least most of the selected metal in the oxidized material is in the form of a sulfate. 
     
     
         16 . The process of  claim 11 , wherein the oxidized material, when removed from the fluidized bed reactor, has a maximum sulfide sulfur content of no more than about 1 wt. % and wherein at least most of the selected metal in the oxidized material is in the form of XO, where X is the selected metal. 
     
     
         17 . The process of  claim 11 , wherein the selected metal-containing components of the selected metal-containing material are heated to a temperature ranging from about 580 to about 680° C., wherein a microwave energy source comprising one or more individual generating units generating the microwave energy has a power level in the range of about 1 kw to about 150 kw per generating unit, operates at a frequency ranging from about 300 MHz to about 3 GHz, wherein the reaction chamber has a Q value ranging from about 1,000 to about 25,000, wherein the microwave energy delivered to the sulfur-containing material ranges from about 250 to about 300,000 Joules/gm, and wherein at least most of the microwave energy has a frequency of about 915 MHz. 
     
     
         18 . The process of  claim 11 , wherein the selected metal-containing and sulfide sulfur-containing material has a sulfide sulfur concentration of no more than about 6 wt. 
     
     
         19 . The process of  claim 11 , wherein the fluidized bed reactor operates as a bubbling bed fluidized system and wherein microwave interaction with the selected metal-containing material occurs primarily within a lean phase medium. 
     
     
         20 . A selected metal recovered by the process of  claim 11 .