Operation method for dezincification plant

An operation method for a dezincification plant, the method including a hydrometallurgical method for a nickel oxide ore comprising:

• a leaching step wherein sulfuric acid is added to a slurry of the nickel oxide ore to perform leaching under high temperature and high pressure;
• a solid-liquid separation step wherein multistage washing is applied to the slurry to separate a residue therefrom, whereby a leachate containing an impurity element together with nickel and cobalt is obtained;
• a neutralization step wherein a pH of the leachate is adjusted to separate a neutralized precipitate containing the impurity element therefrom, whereby a post-neutralization solution containing zinc together with nickel and cobalt is obtained;
• a dezincification step wherein a sulfurization treatment is applied to the post-neutralization solution to form a zinc sulfide, and said zinc sulfide is separated therefrom to obtain a mother liquor for nickel recovery which contains nickel and cobalt;
• and
• a nickel recovery step wherein a sulfurization treatment is applied to the mother liquor for nickel recovery to form a mixed sulfide containing nickel and cobalt,
• wherein, when, upon start-up of the dezincification plant, a slurry containing the zinc sulfide formed by adding a sulfurizing agent to the post-neutralization solution is supplied to a filter for filtration and separation,
• an adjustment is performed in such a manner that a flow rate of the slurry supplied to the filter is increased in stages to reach a target slurry flow rate in a time T2, which satisfies the following relational expression (i),
• 3×T1≦T2≦5×T1 (i)
• where T1 represents a minimum time between starting a slurry supply and attaining the target slurry flow rate in the case of transferring the slurry at a maximum liquid transfer capacity of a pump configured to transfer the slurry.