Process to thermally upgrade metal-containing limonite or saprolite ores via magnetic separation and the use of the magnetic concentrate as seeds

Abstract

This invention provides a process to thermally upgrade metal-containing ores comprising the following steps: (1) mixing: (i) ore, (ii) from 4 and up to 15% by weight relative to the ore of reducing agent, (iii) sulphur bearing agent, (iv) metallic-bearing seeding agent, and optionally (v) low temperature binder agent to produce a blend; (2) agglomeration and dry, if required, of the blend formed in step 1 to produce agglomerates; (3) calcination the agglomerates formed in step 2 at reducing atmosphere from a partial pressure of oxygen of Log 10 (pO 2 )=−12 to Log 10 (pO 2 )=−15) and at temperature between 950-1150° C. to produce a liquid metallic phase that growth and concentrate into metallic particles within the agglomerates; (4) cooling the agglomerates after step 3 to ambient temperature in reducing or inert atmosphere; (5) crushing and grinding the calcine produced in step 4 to a size amenable for magnetic separation of metallic particles, typically represented by a p80 equal or below 25 μm; and (6) magnetic concentration of metallic particles by known techniques of magnetic separation including but not limited to magnetic separation by wet or dry means, dewatering and drying. The invention also refers to the magnetic concentrate produced by the process and to the use of the magnetic concentrate to produce a ferronickel or highly metalized nickel containing matte for the production of stainless steel.

What is claimed is: 
     
         1 . A process to thermally upgrade metal-containing ores, comprising the following steps:
 (1) mixing: (i) ore, (ii) from 4 up to 15% by weight relative to the ore of reducing agent, (iii) sulphur bearing agent, (iv) metallic-bearing seeding agent, and optionally (v) low temperature binder agent to produce a blend;   (2) agglomeration and dry, if required, of the blend formed in step 1 to produce agglomerates;   (3) calcination the agglomerates formed in step 2 at reducing atmosphere (from a partial pressure of oxygen of Log 10 (pO 2 )=−12 to Log 10 (pO 2 ) =−15) and at temperature between 950-1150° C. to produce a liquid metallic phase that growth and concentrate into metallic particles within the agglomerates;   (4) cooling the agglomerates after step 3 to ambient temperature in reducing or inert atmosphere;   (5) crushing and grinding the calcine produced in step 4 to a size amenable (p 80 ≦25 μm) for magnetic separation of metallic particles; and   (6) magnetic concentration of metallic particles by known techniques of magnetic separation, including but not limited to magnetic separation by wet or dry means, dewatering and drying.   
     
     
         2 . The process of  claim 1 , wherein the ores includes nickel laterites of both limonite and saprolite nature. 
     
     
         3 . The process of  claim 1 , wherein the metal includes nickel and iron. 
     
     
         4 . The process of  claim 1 , wherein the metal-containing ores is nickel containing lateritic ores. 
     
     
         5 . The process of  claim 4 , wherein the nickel containing lateritic ores are of the limonitic type or a blend of limonitic/saprolitic ores with low or high iron to silica ratio. 
     
     
         6 . The process of  claim 4 , applicable to the co-processing of lateritic ores in conjunction with nickel-bearing sulphides that could contain any kind of impurities that can be removed by any known method. 
     
     
         7 . The process of  claim 1 , wherein includes a pretreatment of the ore in order to prepare the ore to adequate the size (below 212 μm) and moisture (10 to 20% by mass), by known means of mineral processing. 
     
     
         8 . The process of  claim 7 , wherein this pretreatment might involve, but might not be limited to: crushing, screening, desliming, flotations as part of silica rejection process in order to produce ore blend with Fe/SiO 2  ratios above 2.0 g/g. 
     
     
         9 . The process of  claim 1 , wherein the reducing agent is solid carbon or liquid hydrocarbon type. 
     
     
         10 . The process of  claim 1 , wherein the sulphur bearing agent is added in amounts from 1 and up to 5 wt % of equivalent contained S relative to the weight of ore. 
     
     
         11 . The process of  claim 1 , wherein the sulphur bearing agent is elemental sulphur, nickel-bearing sulphide concentrate, Iron-bearing concentrate, or a blend of sulphides minerals. 
     
     
         12 . The process of  claim 1 , wherein the metallic-bearing seeding agent is added in amounts as little as 0.1 wt % and as high as 2 wt % relative to the weight of ore. 
     
     
         13 . The process of  claim 1 , wherein the metallic-bearing seeding agent is ferronickel particle, ferronickel concentrate, metallic nickel, nickel powder and metallic iron powder. 
     
     
         14 . The process of  claim 1 , wherein the low temperature binder agent is added in amounts from 0 and up to 5 wt.% relative to the mass of ore. 
     
     
         15 . The process of  claim 1 , wherein the low temperature binder agent is organic binder and silicate binder. 
     
     
         16 . The process of  claim 1 , wherein agglomerates of step (3) are dried or wet. 
     
     
         17 . The process of  claim 16 , wherein the dried or wet agglomerates are calcined for at least one hour to a maximum of three hours in contact with reducing atmosphere (equivalent to Log 10 (pO 2 ) of −12 to −15) to a temperature are in the range of 950-1150° C. 
     
     
         18 . A magnetic concentrate, characterized by being produced by the process as defined in  claim 1 , which consists of 5 to 15 wt % Ni and with varying Fe/Ni ratios in the range of 1/1 and up to 10/1 by mass with metallic particles ranging in size above 20 μm. 
     
     
         19 . Use of the magnetic concentrate, produced by the process as defined in  claim 1 , to produce a ferronickel or highly metalized nickel containing matte for the production of stainless steel.