Method for producing raw material for ferronickel smelting from low grade nickel oxide ore

1. A method for producing a ferronickel raw material, the method forming the ferronickel raw material from a nickel sulfide or a mixed sulfide containing nickel sulfide and cobalt sulfide, wherein treatments are performed through the following steps:

(1) a redissolution step, wherein a nickel sulfide or a mixed sulfide of nickel sulfide and cobalt sulfide is made into a slurry, and an oxidizing agent is added to the slurry to obtain a concentrate containing nickel or nickel and cobalt;

(2) a deferrization step, wherein an alkali is added to the concentrate to obtain a neutralized precipitate and a post-neutralization solution;

(3) a solvent extraction step, wherein the post-neutralization solution is mixed with an organic extractant to separate into an extracted organic matter and a raffinate, and then a back-extraction solution and an organic matter after back-extraction are obtained from the extracted organic matter;

(4) a hydroxylation step, wherein alkali is added to the raffinate and mixed to form nickel hydroxide;

(5) a roasting step, wherein the nickel hydroxide is heated and roasted in a temperature range of not less than 230° C. and not more than 870° C. to form nickel oxide; and

(6) a washing and calcining step, wherein the nickel oxide is water-washed with water at a temperature of not less than 50° C., and then calcined at a temperature of not less than 50° C. to form a post-washing nickel oxide.

2. The method for producing ferronickel raw material according to claim 1 , wherein a particle size of the nickel sulfide or the mixed sulfide is in a range of 15 to 100 μm in mean volume diameter (MV).

3. The method for producing ferronickel raw material according to claim 1 , wherein redissolution is performed in a temperature range of not less than 60° C. and not more than 160° C.

4. The method for producing ferronickel raw material according to claim 1 , wherein the oxidizing agent is at least one of air, oxygen, a hydrogen peroxide solution, and ozone.

5. The method for producing ferronickel raw material according to claim 1 , wherein roasting is performed under an inert atmosphere or an oxygen partial pressure inside a reaction vessel of not more than 10 −8 atm.

6. The method for producing ferronickel raw material according to claim 1 , wherein a sulfurizing agent is added to the back-extraction solution to obtain cobalt sulfide.

7. The method for producing ferronickel raw material according to claim 1 , wherein soda ash is added to the back-extraction solution to obtain cobalt carbonate.

8. The method for producing ferronickel raw material according to claim 1 , wherein alkali is added to the back-extraction solution to obtain cobalt hydroxide.

9. The method for producing ferronickel raw material according to claim 1 , wherein a reducing agent and a binder in an amount of 0.1 to 8.0% by weight with respect to the post-washing nickel oxide are added to the post-washing nickel oxide, and kneaded, followed by calcining at a temperature of not less than 50° C. to obtain a nickel oxide pellet.

10. The method for producing ferronickel raw material according to claim 9 , wherein the reducing agent is at least one of fine coal, powdered coal, and coke breeze.

11. The method for producing ferronickel raw material according to claim 9 , wherein the binder is at least one of bentonite and low grade nickel oxide ore.

12. The method for producing ferronickel raw material according to claim 1 , further comprising

providing the nickel sulfide or the mixed sulfide containing nickel sulfide and cobalt sulfide by high-temperature pressure leaching of a nickel oxide ore using sulfuric acid to form a leachate, neutralizing the leachate, separating into a precipitate containing impurities and a filtrate, adding a sulfurizing agent to the filtrate to separate a zinc sulfide precipitate, and then blowing a sulfurizing agent into a residual filtrate separated from the zinc sulfide.

13. The method for producing ferronickel raw material according to claim 1 , further comprising

providing the nickel sulfide or the mixed sulfide containing nickel sulfide and cobalt sulfide by leaching at least one of nickel hydroxide, nickel oxide, cobalt hydroxide, and cobalt oxide with sulfuric acid to form a leachate, and then blowing a sulfurizing agent into the leachate.