# US 9,752,211 B2 · Neutralization method and neutralization plant > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,211 B2 - Document ID: US9752211B2 - Status: Granted - Kind: B2 - Application number: 14/382,737 - Filed: 2013-03-01 - Published: 2015-01-22 - Granted: 2017-09-05 - Earliest claimed: 2012-03-06 - Assignees: Sumitomo Metal Mining Co., Ltd. - Applicants: Sumitomo Metal Mining Co., Ltd. - Inventors: Hiroyuki Mitsui; Osamu Nakai; Satoshi Matsubara - Web page: https://patentgrep.com/patent/US9752211B2 ## CPC - C22B 23/0461: {by chemical methods} - C22B 3/04: by leaching (C22B3/18 takes precedence) - C22B 23/0423: {Halogenated acids or salts thereof} - Y02P 10/20: Recycling - C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract A method for improving the filterability in separating a zinc sulfide, produced by applying sulfurization treatment to a post-neutralization solution containing zinc together with nickel and cobalt in a dezincification step in a hydrometallurgical process for nickel oxide ore. The method includes a neutralization reaction step of neutralizing leachate in a neutralization tank, a separation step of separating neutralized slurry into a neutralized sediment and a post-neutralization solution by adding flocculant to the neutralized slurry, a measuring step of measuring the viscosity of the post-neutralization solution, a step of storing the post-neutralization solution in a storage tank, and a transfer step of transferring the stored post-neutralization solution to a dezincification reaction tank used in a dezincification step subsequent to a neutralization step. ## Claims ### Claim 1 A neutralization method used in a neutralization step of neutralizing leachate produced by leaching nickel oxide ore, and producing neutralized sediment containing impurities and a post-neutralization solution containing zinc together with nickel and cobalt, in a hydrometallurgy process for nickel oxide ore, the method comprising: a neutralization reaction step of neutralizing the leachate in a neutralization reaction tank; a separation step of separating neutralized slurry into neutralized sediment and the post-neutralization solution by adding flocculant to the slurry; a viscosity measuring step of measuring the viscosity of the post-neutralization solution produced through the separation step; a storing step of temporarily storing the post-neutralization solution in a storage tank; and a flow-feeding step of transferring the stored post-neutralization solution to a dezincification reaction tank used in a dezincification step subsequent to the neutralization step, wherein in the flow-feeding step, when the post-neutralization solution has a viscosity, as measured in the viscosity measuring step such that the rate for passing 50 mL of the post-neutralization solution through a membrane filter having a mesh opening size of 0.45 μm, that is higher than 0.10 sec/cm2·mL, a flow rate of the post-neutralization solution to be transferred to the dezincification reaction tank is controlled, and the post-neutralization solution is circulated by returning back a predetermined rate of the post-neutralization solution to the neutralization reaction tank, and when the viscosity of the post-neutralization solution measured in the viscosity measuring step is higher than 0.10 sec/cm2·mL, a flow rate of the post-neutralization solution to be transferred to the dezincification reaction tank used in the dezincification step is set to 60 to 80% for the total flow rate, and a flow rate of the post-neutralization solution to be circulated by returning back the post-neutralization solution to the neutralization reaction tank is set to 20 to 40% for the total flow rate. ### Claim 2 (depends on 1) The neutralization method according to claim 1, wherein in the flow-feeding step, when the post-neutralization solution is circulated by returning back the predetermined rate of the post-neutralization solution to the neutralization reaction tank, the flocculant is not added in the separation step. ### Claim 3 (depends on 1) The neutralization method according to claim 1, wherein the storage tank has a capacity corresponding to an amount of storage of more than 3 hours with respect to the flow rate of the post-neutralization solution. ### Claim 4 (depends on 1) The neutralization method according to claim 1, wherein the hydrometallurgy process for nickel oxide ore further comprises: a leaching step of leaching slurry of the nickel oxide ore, under high temperature and high pressure, by adding sulfuric acid to the slurry of the nickel oxide ore; a solid-liquid separating step of separating residue while multistage cleaning the leached slurry to produce leachate containing impurity elements together with nickel and cobalt; a neutralization step of separating the neutralized sediment containing the impurity elements by controlling pH of the leachate to produce the post-neutralization solution containing zinc together with nickel and cobalt; a dezincification step of producing a zinc sulfide by applying sulfurization treatment to the post-neutralization solution and separating the zinc sulfide to produce a mother liquid for nickel recovery containing nickel and cobalt; and a nickel recovery step of producing a mixed sulfide containing nickel and cobalt by applying sulfurization treatment to the mother liquid for nickel recovery. ### Claim 5 (depends on 4) The neutralization method according to claim 4, wherein the neutralized sediment separated in the neutralization step is repeatedly added in multistage cleaning in the solid-liquid separating step.