Hydrometallurgical process for nickel oxide ore

Abstract

Provided is a hydrometallurgical process for nickel oxide ore for recovering nickel and cobalt using a high pressure acid leach process, the process achieving simplification and durability improvement of production facilities, achieving cost reduction and suppression of environmental risk by the compression of the capacity of a tailings dam for storing wastes, and being capable of recycling and effectively utilizing the wastes as a resource. The hydrometallurgical process for nickel oxide ore for recovering nickel and cobalt using a high pressure acid leach process includes an ore processing step, a leaching step, a solid-liquid separation step, a neutralization step, a zinc removal step, a sulfurization step, and a final neutralization step, and further includes step (A), or further includes step (A) and, step (B- 1 ) and/or step (B- 2 ) after step (A).

1 . A hydrometallurgical process for nickel oxide ore for recovering nickel and cobalt using a high pressure acid leach process comprising an ore processing step, a leaching step, a solid-liquid separation step, a neutralization step, a zinc removal step, a sulfurization step, and a final neutralization step, the hydrometallurgical process further comprising,
 step (A): a step of separating chromite particles from an ore slurry produced in the ore processing step by a recovery process including specific gravity separation, and then classifying the chromite particles to recover a high-concentration chromite concentrate having a grade of chromium(III) oxide of at least more than 50% by weight.   
     
     
         2 . A hydrometallurgical process for nickel oxide ore for recovering nickel and cobalt using a high pressure acid leach process comprising an ore processing step, a leaching step, a solid-liquid separation step, a neutralization step, a zinc removal step, a sulfurization step, and a final neutralization step, the hydrometallurgical process further comprising:
 step (A): a step of separating chromite particles from an ore slurry produced in the ore processing step by a recovery process including specific gravity separation, and then classifying the chromite particles to recover a high-concentration chromite concentrate having a grade of chromium(III) oxide of at least more than 50% by weight; followed by at least one of:   step (B- 1 ): a neutralization step of subjecting a leachate to neutralization with at least one of a calcium-based neutralizing agent and a magnesium-based neutralizing agent, the leachate being produced by subjecting the ore slurry, in which the chromium grade has been reduced by separating the chromite particles in step (A), sequentially to the leaching step and the solid-liquid separation step; and   step (B- 2 ): a neutralization step of subjecting a leach residue slurry to neutralization with a magnesium-based neutralizing agent, the leach residue slurry being produced by subjecting the ore slurry, in which the chromium grade has been reduced by separating the chromite particles in step (A), sequentially to the leaching step and the solid-liquid separation step, to thereby recover hematite particles from the leach residue slurry.   
     
     
         3 . The hydrometallurgical process for nickel oxide ore of  claim 2 , wherein step (A) is followed by step (B- 1 ) and step (B- 2 ). 
     
     
         4 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein the recovery process in step (A) comprises subjecting the ore slurry to classification with a cyclone to form a particulate iron-leaned ore slurry in which fine iron hydroxide particles have been reduced, and then recovering chromite particles contained in the particulate iron-leaned ore slurry from the particulate iron-leaned ore slurry as a chromite concentrate using specific gravity separation. 
     
     
         5 . The hydrometallurgical process for nickel oxide ore according to  claim 4 , wherein the recovery process in step (A) comprises subjecting the ore slurry to classification with a cyclone without diluting the slurry concentration of the ore slurry. 
     
     
         6 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein the recovery process in step (A) comprises collecting a whole amount of the chromite excluding unavoidable loss into an underflow in the classification with the cyclone. 
     
     
         7 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein the specific gravity separation comprises a step of using a density separator. 
     
     
         8 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein the specific gravity separation comprises a step of using a spiral concentrator. 
     
     
         9 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein the specific gravity separation comprises a step of using a density separator and a step of using a spiral concentrator. 
     
     
         10 . The hydrometallurgical process for nickel oxide ore according to  claim 7 , wherein the step of using a density separator comprises treating a concentrated slurry with the density separator twice or more. 
     
     
         11 . The hydrometallurgical process for nickel oxide ore according to  claim 8 , wherein the step of using a spiral concentrator comprises treating a concentrated slurry with the spiral concentrator twice or more. 
     
     
         12 . The hydrometallurgical process for nickel oxide ore according to  claim 8 , wherein a pulp content of the slurry fed to the spiral concentrator is 15 to 35% by weight of solid. 
     
     
         13 . The hydrometallurgical process for nickel oxide ore according to  claim 7 , wherein an amount of Teeter water fed to the density separator is 0.5 to 7.0 [m 3 ·h −1 /m 2 ]. 
     
     
         14 . The hydrometallurgical process for nickel oxide ore according to  claim 1 , wherein the chromite concentrate separated by the specific gravity separation is subjected to magnetic separation which is a physical separation to remove magnetite from the chromite concentrate as a magnetic material and recover a non-magnetic material as a high-concentration chromite concentrate. 
     
     
         15 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein step (B- 2 ) comprises setting pH after the neutralization at 4 to 7 and after the neutralization, performing final neutralization with an alkali other than the magnesium-based neutralizing agent. 
     
     
         16 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein step (B- 2 ) comprises subjecting the leach residue slurry or a neutralized residue slurry including the leach residue slurry to classification with a cyclone to recover a classified fine particle portion obtained by the classification as a concentrate of hematite. 
     
     
         17 . The hydrometallurgical process for nickel oxide ore according to  claim 2 , wherein
 the ore processing step is a step of performing removal of foreign matter from mined raw ore and particle size adjustment of the ore to form an ore slurry;   the leaching step is a step of adding sulfuric acid to the ore slurry and stirring a resulting mixture at high temperature and high pressure to form a leach slurry composed of a leach residue and a leachate;   the solid-liquid separation step is a step of subjecting the leach slurry to multi-stage washing to obtain a leachate containing nickel and cobalt and a leach residue slurry;   the neutralization step is a step of adding an alkali to the leachate to form a neutralized precipitate slurry containing trivalent iron and a mother liquor for nickel recovery;   the zinc removal step is a step of blowing hydrogen sulfide gas into the mother liquor to form a zinc sulfide precipitate slurry and a mother liquor for nickel and cobalt recovery;   the sulfurization step is a step of blowing hydrogen sulfide into the mother liquor for nickel and cobalt recovery to produce a mixed sulfide containing nickel and cobalt and a barren liquor; and   the final neutralization step is a step of adding excess of the barren liquor to the leach residue slurry and adjusting pH to 8 to 9 to obtain a final neutralized residue.   
     
     
         18 . The hydrometallurgical process for nickel oxide ore according to  claim 17 , wherein the particle size adjustment in the ore processing step is performed by sieving with a particle size of 2 mm or less. 
     
     
         19 . The hydrometallurgical process for nickel oxide ore according to  claim 18 , wherein a grade of chromium(III) oxide in the chromite concentrated is 41% by weight or more. 
     
     
         20 . The hydrometallurgical process for nickel oxide ore according to  claim 1 , wherein
 the ore processing step is a step of performing removal of foreign matter from mined raw ore and particle size adjustment of the ore to form an ore slurry;   the leaching step is a step of adding sulfuric acid to the ore slurry and stirring a resulting mixture at high temperature and high pressure to form a leach slurry composed of a leach residue and a leachate;   the solid-liquid separation step is a step of subjecting the leach slurry to multi-stage washing to obtain a leachate containing nickel and cobalt and a leach residue slurry;   the neutralization step is a step of adding an alkali to the leachate to form a neutralized precipitate slurry containing trivalent iron and a mother liquor for nickel recovery;   the zinc removal step is a step of blowing hydrogen sulfide gas into the mother liquor to form a zinc sulfide precipitate slurry and a mother liquor for nickel and cobalt recovery;   the sulfurization step is a step of blowing hydrogen sulfide into the mother liquor for nickel and cobalt recovery to produce a mixed sulfide containing nickel and cobalt and a barren liquor; and   the final neutralization step is a step of adding excess of the barren liquor to the leach residue slurry and adjusting pH to 8 to 9 to obtain a final neutralized residue.