Method and device for separating nickel and cobalt in laterite-nickel ore

Abstract

The invention discloses a method and a device for separating nickel and cobalt in laterite-nickel ore, and relates to the technical field of hydrometallurgy, the method comprises the following steps: carrying out acid leaching on laterite-nickel ore pulp, then carrying out CCD countercurrent washing on leaching residues, separating out the leaching residues, and then carrying out pre-neutralization, iron and aluminum removal and nickel and cobalt precipitation, the particle size of gypsum particles in the discharged underflow in the leaching residue CCD countercurrent washing step can be increased after leaching residue CCD countercurrent washing and then pre-neutralization is performed, so that when solid-liquid separation is performed on the leaching residue CCD underflow, a relatively good filtration aiding effect is achieved, the tailing filter pressing time can be shortened, the water content of a tailing filter cake can be reduced, and the separation efficiency can be improved. Therefore, the production capacity of the whole line is improved, the investment of tailing filter pressing equipment is reduced, and meanwhile, the tailing stockpiling efficiency and safety are improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method and a device for separating nickel and cobalt from laterite nickel ore. Background Art

[0002] The processes for producing nickel products using laterite nickel ore as raw material mainly include hydrometallurgy and pyrometallurgy. Among them, high pressure acid leaching (HPAL) of laterite nickel ore is the most important hydrometallurgy process for laterite nickel ore. The traditional HPAL smelting process has the following problems:

[0003] (1) The first stage of iron and aluminum removal underflow uses a filter press for solid-liquid separation and washing, and the washing efficiency is low;

[0004] (2) Tailings treatment is only for slurry neutralization. After neutralization, the tailings slurry can only be landfilled in the deep sea or wet piled, which has a great impact on the environment and high risks;

[0005] (3) The ore pulp from high-pressure acid leaching is first pre-neutralized and then CCD slag-liquid separation is performed. The tailings filter press efficiency is low and the tailings filter cake has a high moisture content.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The object of the present invention is to provide a method and device for separating nickel and cobalt from laterite nickel ore, which is beneficial to shortening the tailings filter pressing time and reducing the moisture content of the tailings filter cake.

[0008] The present invention is achieved in that:

[0009] In a first aspect, the present invention provides a method for separating nickel and cobalt from laterite nickel ore, comprising:

[0010] Acid leaching is performed on the pretreated laterite nickel ore pulp to obtain acid leached ore pulp;

[0011] The acid leaching pulp is subjected to solid-liquid separation by using leaching residue CCD countercurrent washing to obtain leaching residue CCD overflow and leaching residue CCD underflow; the leaching residue CCD underflow is subjected to solid-liquid separation to obtain tailings;

[0012] Pre-neutralizing and thickening the leached residue CCD overflow to obtain a pre-neutralized slurry;

[0013] The pre-neutralized slurry is subjected to a stage of iron removal and aluminum thickening to obtain a stage of iron removal and aluminum underflow and a stage of iron removal and aluminum overflow;

[0014] The first stage of iron and aluminum removal underflow is transferred to the leached residue CCD countercurrent washing step;

[0015] The first stage iron removal and aluminum removal overflow is subjected to second stage iron removal and aluminum thickening to obtain a second stage iron removal and aluminum underflow and a second stage iron removal and aluminum overflow;

[0016] The overflow from the second stage of iron and aluminum removal is subjected to nickel and cobalt precipitation to obtain a nickel-cobalt-containing product.

[0017] In an optional embodiment, at least one of the following features is met:

[0018] a. The solid content of the laterite nickel ore slurry is 30wt%-45wt%, specifically 30wt%, 33wt%, 36wt%, 39wt%, 42wt%, 45wt% or any value between 30wt%-45wt%, and the nickel content of the solid in the laterite nickel ore slurry is 0.8wt%-2.0wt%, specifically 0.8wt%, 1.1wt%, 1.4wt%, 1.7wt%, 2.0wt% or any value between 0.8wt%-2.0wt%;

[0019] b. The acid-ore ratio of the acid leaching step is 200kg / t-400kg / t, specifically 200kg / t, 250kg / t, 300kg / t, 350kg / t, 400kg / t or any value between 200kg / t-400kg / t, the reaction temperature is 240°C-270°C, specifically 240°C, 250°C, 260°C, 270°C or any value between 240°C-270°C, the reaction pressure is 4MPa-6MPa, specifically 4MPa, 4.5MPa, 5MPa, 5.5MPa, 6MPa or any value between 4MPa-6MPa, the reaction time is 0.5h-2h, specifically 0.5h, 1h, 1.5h, 2h or any value between 0.5h-2h;

[0020] c. The number of stages of CCD countercurrent washing of the leached residue is 3-8, specifically 3, 4, 5, 6, 7 or 8, and the wash water ratio is 2-4:1, specifically 2:1, 3:1, 4:1 or any value between 2-4:1;

[0021] d. The pre-neutralization reaction time is 1 h-15 h, specifically 1 h, 3 h, 6 h, 9 h, 12 h, 15 h or any value between 1 h and 15 h, and the reaction pH is 1.0-3.0, specifically 1.0, 1.5, 2.0, 2.5, 3.0 or any value between 1.0 and 3.0.

[0022] In an optional embodiment, the iron-aluminum removal step includes: performing iron-aluminum slag CCD countercurrent washing on the first stage of the iron-aluminum removal underflow to obtain an iron-aluminum slag CCD underflow and an iron-aluminum slag CCD overflow, and transferring the iron-aluminum slag CCD underflow to the leaching slag CCD countercurrent washing step;

[0023] Preferably, the iron-aluminum slag CCD underflow is discharged to the second stage and subsequent one or more stages of the leached slag CCD countercurrent washing;

[0024] Preferably, the iron-aluminum slag CCD overflow is transferred to the second stage iron and aluminum removal step.

[0025] In an optional embodiment, the reaction time of the first stage of iron and aluminum removal is 1h-15h, specifically 1h, 3h, 6h, 9h, 12h, 15h or any value between 1h-15h, and the reaction pH is 3.5-4.5, specifically 3.5, 3.7, 3.9, 4.1, 4.3, 4.5 or any value between 3.5-4.5;

[0026] And / or, the number of stages of the CCD countercurrent washing of the iron-aluminum slag is 3-8, specifically 3, 4, 5, 6, 7 or 8, and the washing water ratio is 2-4:1, specifically 2:1, 3:1, 4:1 or any value between 2-4:1;

[0027] And / or, the second-stage iron and aluminum removal bottom flow is returned to the pre-neutralization step;

[0028] And / or, the reaction time of the second-stage iron and aluminum removal is 1h-10h, specifically 1h, 3h, 6h, 9h, 12h, 15h or any value between 1h-15h, and the reaction pH is 4.5-5.5, specifically 4.5, 4.7, 4.9, 5.1, 5.3, 5.5 or any value between 4.5-5.5.

[0029] In an optional embodiment, the nickel-cobalt precipitation step includes: performing a stage of nickel-cobalt precipitation and thickening on the second stage iron-aluminum removal overflow to obtain a stage of nickel-cobalt precipitation underflow and a stage of nickel-cobalt precipitation overflow;

[0030] The nickel-cobalt bottom flow of the first stage is filtered and washed to obtain a nickel-cobalt-containing product and a filtrate and washing liquid of the product.

[0031] In an optional embodiment, the reaction time of the nickel-cobalt precipitation is 1h-15h, specifically 1h, 3h, 6h, 9h, 12h, 15h or any value between 1h-15h, and the reaction pH is 7.0-7.6, specifically 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6 or any value between 7.0-7.6;

[0032] And / or, the water content of the nickel-cobalt-containing product is 45wt%-60wt%, specifically 45wt%, 50wt%, 55wt%, 60wt% or any value between 45wt% and 60wt%, and the nickel content on a dry basis of the nickel-cobalt-containing product is 35wt%-45wt%, specifically 35wt%, 37wt%, 39wt%, 41wt%, 43wt%, 45wt% or any value between 35wt% and 45wt%.

[0033] In an optional embodiment, the method further comprises: neutralizing and thickening the leached residue CCD underflow to obtain a tailings thickening underflow and a tailings thickening overflow;

[0034] The dense underflow of tailings is filtered through tailings filter press to obtain tailings filter cake and tailings filtrate.

[0035] In an optional embodiment, the first stage nickel-cobalt precipitation overflow and the filtrate washing liquid of the product filter press washing are subjected to second stage nickel-cobalt precipitation and thickening to obtain the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow;

[0036] The second stage nickel and cobalt precipitation bottom flow returns to the acid leaching slurry;

[0037] The overflow from the second stage nickel and cobalt precipitation is used as washing water or slurrying liquid in the steps of CCD countercurrent washing of leached slag, CCD countercurrent washing of iron and aluminum slag, tail gas washing, and limestone slurrying, or discharged to the tailings neutralization process.

[0038] In an optional embodiment, the reaction time of the second-stage nickel-cobalt precipitation is 1h-10h, specifically 1h, 3h, 6h, 9h, 10h or any value between 1h-10h, and the reaction pH value is 7.6-8.2, specifically 7.6, 7.8, 8.0, 8.2 or any value between 7.6-8.2;

[0039] And / or, the reaction time of the tailings neutralization is 1h-10h, specifically 1h, 3h, 6h, 9h, 10h or any value between 1h-10h, and the reaction pH is 6.0-9.0, specifically 6.0, 7.0, 8.0, 9.0 or any value between 6.0-9.0;

[0040] And / or, the moisture content of the tailings filter cake after the tailings filtration is 27wt%-33wt%, specifically 27wt%, 29wt%, 31wt%, 33wt% or any value between 27wt% and 33wt%.

[0041] In a second aspect, the present application provides a separation device for nickel and cobalt in laterite nickel ore applicable to the method described in any one of the aforementioned embodiments, including an acid leaching unit, a leached residue CCD countercurrent washing unit, a pre-neutralization and thickening unit, a first-stage iron and aluminum removal and thickening unit, a second-stage iron and aluminum removal and thickening unit, a first-stage nickel and cobalt precipitation and thickening unit, a product filter press unit, a second-stage nickel and cobalt precipitation and thickening unit and a tailings treatment unit; wherein,

[0042] The acid leaching unit is provided with a leached slurry outlet, the leached slurry outlet is connected to the feed inlet of the leached slag CCD countercurrent washing unit, and the external underflow outlet of the leached slag CCD countercurrent washing unit is connected to the feed inlet of the tailings treatment unit;

[0043] The external overflow port of the leached residue CCD countercurrent washing unit is connected to the feed port of the pre-neutralization and thickening unit, and the reaction tank slurry outlet, underflow port and overflow port of the pre-neutralization and thickening unit are all connected to the feed port of the first stage iron and aluminum removal and thickening unit;

[0044] The underflow port of the first stage iron removal and aluminum thickening unit is connected to the feed port of the leached residue CCD countercurrent washing unit; the overflow port of the first stage iron removal and aluminum thickening unit is connected to the feed port of the second stage iron removal and aluminum thickening unit;

[0045] The overflow port of the second stage iron removal and aluminum concentration unit is connected to the feed port of the first stage nickel and cobalt precipitation and concentration unit;

[0046] The bottom flow port of the first stage nickel-cobalt precipitation and concentration unit is connected to the feed port of the product filter press unit, and the filter cake outlet of the product filter press unit discharges the nickel-cobalt-containing product; the overflow port of the first stage nickel-cobalt precipitation and concentration unit is connected to the feed port of the second stage nickel-cobalt precipitation and concentration unit.

[0047] In an optional embodiment, the underflow port of the first stage iron-aluminum removal and thickening unit is connected to the feed port of the iron-aluminum slag CCD countercurrent washing unit, and the external underflow port of the iron-aluminum slag CCD countercurrent washing unit is connected to the feed port of the second stage and subsequent one or more stages of the leached slag CCD countercurrent washing; the external overflow port of the iron-aluminum slag CCD countercurrent washing unit is connected to the feed port of the second stage iron-aluminum removal and thickening unit;

[0048] And / or, the tailings treatment unit comprises a tailings neutralization and thickening unit, a tailings filter press unit and a wastewater treatment unit; the external underflow outlet of the leached residue CCD countercurrent washing unit is connected to the feed inlet of the tailings neutralization and thickening unit; the underflow outlet of the tailings neutralization and thickening unit is connected to the feed inlet of the tailings filter press unit, and the overflow outlet of the tailings neutralization and thickening unit is connected to the feed inlet of the wastewater treatment unit; the filter cake outlet of the tailings filter press unit discharges the tailings filter cake, and the filtrate outlet of the tailings filter press unit is connected to the wastewater treatment unit;

[0049] And / or, the underflow port of the second-stage iron removal and aluminum concentration unit is connected to the feed port of the pre-neutralization and concentration unit;

[0050] And / or, the filtrate outlet of the product filter press unit is connected to the feed inlet of the second-stage nickel-cobalt precipitation and thickening unit;

[0051] And / or, the bottom flow outlet of the second-stage nickel-cobalt precipitation and thickening unit is connected to the discharge outlet of the acid leaching unit, the overflow outlet of the second-stage nickel-cobalt precipitation and thickening unit is connected to the feed inlet of the tailings neutralization and thickening unit, and the overflow discharged from the overflow outlet of the second-stage nickel-cobalt precipitation and thickening unit is also connected to the washing water inlet of the leaching slag CCD countercurrent washing unit, the washing water inlet of the iron-aluminum slag CCD countercurrent washing unit, the washing water inlet of the tail gas washing device, and the slurry liquid inlet of the limestone slurrying device.

[0052] The present invention has the following beneficial effects:

[0053] In the implementation mode of the present application, after the laterite nickel ore slurry is acid-leached, the leached residue CCD countercurrent washing is then carried out to separate the leached residue, and then pre-neutralization, iron and aluminum removal, and nickel and cobalt precipitation are carried out. The leached residue CCD countercurrent washing and then the pre-neutralization are beneficial to increase the particle size of the gypsum particles in the underflow discharged from the leached residue CCD countercurrent washing step, thereby achieving a better filtering effect when the leached residue CCD underflow is subjected to solid-liquid separation, shortening the tailings filtration time, and reducing the moisture content of the tailings filter cake, thereby increasing the overall production capacity, reducing the investment in tailings filtration equipment, and improving the tailings storage efficiency and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0055] Figure 1 This is a flow chart of the method for separating nickel and cobalt from laterite nickel ore of the present application;

[0056] Figure 2 This is a schematic diagram of the structure of the device for separating nickel and cobalt from laterite nickel ore in the present application.

[0057] Diagram: 1-acid leaching unit; 2-leached residue CCD countercurrent washing unit; 3-pre-neutralization and thickening unit; 4-first stage iron and aluminum removal and thickening unit; 5-iron and aluminum slag CCD countercurrent washing unit; 6-second stage iron and aluminum removal and thickening unit; 7-first stage nickel and cobalt precipitation and thickening unit; 8-product filter press unit; 9-second stage nickel and cobalt precipitation and thickening unit; 10-tailings neutralization and thickening unit; 11-tailings filter press unit; 12-wastewater treatment unit. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0059] Normally, nickel and cobalt in laterite nickel ore are separated by pre-neutralization followed by CCD countercurrent washing of the leaching residue to fully remove the solids. However, since the solid particle size in the CCD underflow obtained in the CCD countercurrent washing step is small, solid-liquid separation is difficult, resulting in low separation efficiency and high moisture content of the tailings filter cake.

[0060] The present invention provides a method for separating nickel and cobalt from laterite nickel ore, comprising:

[0061] Acid leaching is performed on the pretreated laterite nickel ore pulp to obtain acid leached ore pulp;

[0062] The acid leaching pulp is subjected to solid-liquid separation by using leaching residue CCD countercurrent washing to obtain leaching residue CCD overflow and leaching residue CCD underflow; the leaching residue CCD underflow is subjected to solid-liquid separation to obtain tailings;

[0063] Pre-neutralizing and thickening the leached residue CCD overflow to obtain a pre-neutralized slurry;

[0064] The pre-neutralized slurry is subjected to a stage of iron removal and aluminum thickening to obtain a stage of iron removal and aluminum underflow and a stage of iron removal and aluminum overflow;

[0065] The first stage of iron and aluminum removal underflow is transferred to the leached residue CCD countercurrent washing step;

[0066] The first stage iron removal and aluminum removal overflow is subjected to second stage iron removal and aluminum thickening to obtain a second stage iron removal and aluminum underflow and a second stage iron removal and aluminum overflow;

[0067] The overflow from the second stage of iron and aluminum removal is subjected to nickel and cobalt precipitation to obtain a nickel-cobalt-containing product.

[0068] In the implementation mode of the present application, after the laterite nickel ore slurry is acid-leached, the leached residue CCD countercurrent washing is then carried out to separate the leached residue, and then pre-neutralization, iron and aluminum removal, and nickel and cobalt precipitation are carried out. The leached residue CCD countercurrent washing and then the pre-neutralization are beneficial to increase the particle size of the gypsum particles in the underflow discharged from the leached residue CCD countercurrent washing step, thereby achieving a better filtering effect when the leached residue CCD underflow is subjected to solid-liquid separation, shortening the tailings filtration time, and reducing the moisture content of the tailings filter cake, thereby increasing the overall production capacity, reducing the investment in tailings filtration equipment, and improving the tailings storage efficiency and safety.

[0069] In an optional embodiment, at least one of the following features is met:

[0070] a. The solid content in the laterite nickel ore slurry is 30wt%-45wt%, and the nickel content in the solid in the laterite nickel ore slurry is 0.8wt%-2.0wt%; solid content and nickel content within this range are conducive to taking into account both production capacity and slurry rheological properties. In some embodiments, the laterite nickel ore is washed, pulped, beneficiated and slurry thickened to obtain the laterite nickel ore slurry.

[0071] b. The acid-ore ratio of the acid leaching step is 200kg / t-400kg / t, the reaction temperature is 240°C-270°C, the reaction pressure is 4MPa-6MPa, and the reaction time is 0.5h-2h; wherein the acid-ore ratio refers to the ratio of the dry mass of the original ore corresponding to sulfuric acid and laterite nickel ore slurry. When the acid leaching step meets the above conditions, it is beneficial to ensure the leaching rate and leaching efficiency of the nickel element. Compared with normal pressure acid leaching, high pressure acid leaching has more advantages.

[0072] c. The number of stages of CCD countercurrent washing of the leached residue is 3-8, and the washing water ratio is 2-4:1; wherein the washing water ratio refers to the ratio of the mass of the added washing water to the mass of the solids in the slurry to be washed. The reasonable setting of the washing stages and the washing water ratio is conducive to taking into account both the washing effect and efficiency.

[0073] d. The reaction time of the pre-neutralization is 1h-15h, and the reaction pH is 1.0-3.0. The neutralizing agent used can be one or more of limestone, lime, soda lime, and lime milk. The neutralizing agent can be added directly in the form of a solid, or it can be added after being pre-mixed into a slurry.

[0074] In an optional embodiment, the first stage of iron-aluminum removal underflow is subjected to iron-aluminum slag CCD countercurrent washing to obtain iron-aluminum slag CCD underflow and iron-aluminum slag CCD overflow, and the iron-aluminum slag CCD underflow is transferred to the leaching slag CCD countercurrent washing step.

[0075] Compared with filter pressing, the use of iron-aluminum slag CCD countercurrent washing is more conducive to improving washing efficiency. At the same time, the obtained iron-aluminum slag CCD underflow can be directly transferred to the leaching slag CCD countercurrent washing step, and there is no need to slurry the filter cake, which is conducive to improving efficiency.

[0076] In an optional embodiment, the iron-aluminum slag CCD underflow is discharged to the second stage and subsequent one or more stages of the leached slag CCD countercurrent washing;

[0077] And / or, the iron-aluminum slag CCD overflow is transferred to the second stage iron and aluminum removal step.

[0078] The underflow of the iron-aluminum slag CCD is transferred to the leaching slag CCD countercurrent washing step, where the gypsum particles can be fully mixed with the leaching slag and used as a filter aid to improve the filter pressing efficiency of the tailings and reduce the moisture content of the tailings filter cake. The impurities such as iron and aluminum that have not yet been precipitated in the overflow of the iron-aluminum slag CCD can be further removed in the second-stage iron and aluminum removal step.

[0079] In an optional embodiment, the reaction time of the iron and aluminum removal is 1h-15h, and the reaction pH is 3.5-4.5;

[0080] And / or, the number of stages of the CCD countercurrent washing of the iron-aluminum slag is 3-8, and the washing water ratio is 2-4:1;

[0081] And / or, the second-stage iron and aluminum removal bottom flow is returned to the pre-neutralization step;

[0082] And / or, the reaction time of the second-stage iron and aluminum removal is 1h-10h, and the reaction pH value is 4.5-5.5.

[0083] The solid precipitated in the first stage of iron and aluminum removal has a high content of impurities such as iron and aluminum, and contains a certain amount of gypsum particles, but a low content of mixed nickel and cobalt, and can be directly returned to the leaching slag CCD countercurrent washing step for solid-liquid separation; the second stage of iron and aluminum removal further increases the pH of the reaction, and iron, aluminum, etc. are further precipitated, and a small amount of valuable metals nickel and cobalt are precipitated, and gypsum is generated at the same time, which is returned to the pre-neutralization step as a seed crystal, and the valuable metals nickel and cobalt are recovered by dissolution.

[0084] In an optional embodiment, the nickel-cobalt precipitation step includes: performing a stage of nickel-cobalt precipitation and thickening on the second stage iron-aluminum removal overflow to obtain a stage of nickel-cobalt precipitation underflow and a stage of nickel-cobalt precipitation overflow;

[0085] The nickel-cobalt bottom flow of the first stage is filtered and washed to obtain a nickel-cobalt-containing product and a filtrate and washing liquid of the product.

[0086] The solid obtained in one of the nickel-cobalt precipitation steps has a high content of nickel-cobalt hydroxide and can be used as a nickel-cobalt-containing product after dense pressure filtration.

[0087] In an optional embodiment, the reaction time of the nickel-cobalt precipitation is 1h-15h, and the reaction pH is 7.0-7.6; both the precipitation efficiency and the quality of the nickel-cobalt product are taken into consideration.

[0088] In an optional embodiment, the water content of the nickel-cobalt-containing product is 45wt%-60wt%, and the nickel content of the nickel-cobalt-containing product on a dry basis is 35wt%-45wt%.

[0089] In an optional embodiment, the method further comprises: neutralizing and thickening the leached residue CCD underflow to obtain a tailings thickening underflow and a tailings thickening overflow;

[0090] The dense underflow of tailings is filtered through tailings filter press to obtain tailings filter cake and tailings filtrate.

[0091] If the acid leaching slurry is pre-neutralized before the leaching residue CCD countercurrent washing, the obtained gypsum particles are only a few microns and the particle size is small, which cannot play a filtering role on the tailings. Therefore, it is difficult to separate the solid and liquid from the tailings, the separation efficiency is low, the separation effect is poor, the investment in the filter press equipment is large, and the tailings have a high moisture content, which is not easy to transport and store, and the transportation and storage costs of the tailings are high. In the embodiment of the present invention, the leaching residue CCD countercurrent washing is first performed and then pre-neutralized, and the pre-neutralization process realizes the pre-neutralization of the slag through the seed circulation. The gypsum particles grow up and provide seeds for the first stage of iron removal and aluminum, promoting the growth of gypsum in the first stage of iron removal and aluminum slag. The gypsum particles in the bottom flow slag of the second stage of iron removal and aluminum are coarse, and return to the pre-neutralization process to further increase the number of pre-neutralization seeds. The gypsum particles in the bottom flow slag of the second stage of nickel and cobalt precipitation are fine, and return to the acid leaching slurry before the leaching slag CCD, so that most of the gypsum particles can grow to 20-40μm in size, which can be used as a filter aid to facilitate the solid-liquid separation of the bottom flow of the leaching slag CCD to obtain the tailings filter cake, which can effectively improve the separation efficiency and separation effect. In addition, the tailings in the present invention are stored in a dry stack, which effectively reduces the impact of traditional deep-sea landfill or wet stacking on the environmental impact.

[0092] In an optional embodiment, the first stage nickel-cobalt precipitation overflow and the filtrate washing liquid of the product filter press washing are subjected to second stage nickel-cobalt precipitation and thickening to obtain the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow;

[0093] The second stage nickel and cobalt precipitation bottom flow returns to the acid leaching slurry;

[0094] The overflow from the second stage nickel and cobalt precipitation is used as washing water or slurrying liquid in the steps of CCD countercurrent washing of leached slag, CCD countercurrent washing of iron and aluminum slag, tail gas washing, and limestone slurrying, or discharged to the tailings neutralization process.

[0095] The filtrate of the product filter press and the overflow of the first nickel-cobalt precipitation contain some impurities or a small amount of nickel and cobalt, which can be transferred to the second nickel-cobalt precipitation step. The nickel-cobalt hydroxide precipitated in the second nickel-cobalt precipitation contains many impurities and is not suitable for direct use as a product. Therefore, the bottom flow of the second nickel-cobalt precipitation is returned to the acid leaching slurry and enters the leaching slag CCD countercurrent washing step. The gypsum particles in the bottom flow of the second nickel-cobalt precipitation are fine. If it is returned to the pre-neutralization step, it will affect the growth of gypsum in the pre-neutralization step. Therefore, the bottom flow of the second nickel-cobalt precipitation is returned to the acid leaching slurry before the leaching slag CCD, which is beneficial to the filtration of the tailings; at the same time, the acidity of the leaching slag CCD countercurrent washing step is relatively high, which is beneficial to dissolve the soluble components in the solids in the bottom flow of the second nickel-cobalt precipitation, and then it is beneficial to improve the yield of nickel and cobalt.

[0096] In an optional embodiment, the reaction time of the second-stage nickel-cobalt precipitation is 1h-10h, and the reaction pH is 7.6-8.2; while the nickel and cobalt in the solution are precipitated as fully as possible, the amount of alkaline substance added is considered, taking into account the recovery rate and cost of nickel and cobalt.

[0097] In an optional embodiment, the reaction time of the tailings neutralization is 1h-10h, and the reaction pH value is 6.0-9.0; the solute content in the discharged waste liquid is minimized to meet environmental protection requirements.

[0098] In an optional embodiment, the moisture content of the tailings filter cake after the tailings filter press is 27wt%-33wt%.

[0099] In the implementation mode of the present application, the leached residue CCD countercurrent washing is first performed, the leached residue is separated, and then pre-neutralization is performed. The pre-neutralization process realizes the growth of gypsum particles in the pre-neutralization residue through seed circulation, and provides seeds for the first stage of iron removal and aluminum, promoting the growth of gypsum in the first stage of iron removal and aluminum slag. The gypsum particles in the second stage of iron removal and aluminum bottom flow slag are coarse, and the number of pre-neutralization seeds is further increased by returning to the pre-neutralization process. Larger gypsum particles are present in the first stage of iron removal and aluminum bottom flow, and are transferred to the leached residue CCD countercurrent washing step after solid-liquid separation. At this time, the particle size of the gypsum particles can reach more than 20-40μm (the particle size of the gypsum particles generated by the pre-neutralization reaction in the method of pre-neutralization and then leached residue CCD countercurrent washing is only a few microns), so that when the leached residue CCD bottom flow is separated by solid and liquid, it has a better filtering effect, which can shorten the tailings filter press time and reduce the moisture content of the tailings filter cake, thereby improving the full-line production capacity, reducing the investment in tailings filter press equipment, and improving the tailings storage efficiency and safety.

[0100] In the second aspect, the present application provides a separation device for nickel and cobalt in laterite nickel ore suitable for the method described in any one of the aforementioned embodiments, including an acid leaching unit 1, a leached residue CCD countercurrent washing unit 2, a pre-neutralization and thickening unit 3, a first-stage iron and aluminum removal and thickening unit 4, a second-stage iron and aluminum removal and thickening unit 6, a first-stage nickel and cobalt precipitation and thickening unit 7, a product filter press unit 8, a second-stage nickel and cobalt precipitation and thickening unit 9 and a tailings treatment unit; wherein,

[0101] The acid leaching unit 1 is provided with a leached slurry outlet, the leached slurry outlet is connected to the feed port of the leached slag CCD countercurrent washing unit 2, and the external underflow outlet of the leached slag CCD countercurrent washing unit 2 is connected to the feed port of the tailings treatment unit;

[0102] The external overflow port of the leached residue CCD countercurrent washing unit 2 is connected to the feed port of the pre-neutralization and thickening unit 3, and the reaction tank slurry outlet, underflow port and overflow port of the pre-neutralization and thickening unit 3 are all connected to the feed port of the first stage iron and aluminum removal and thickening unit 4;

[0103] The underflow port of the first stage iron removal and aluminum thickening unit 4 is connected to the feed port of the leached residue CCD countercurrent washing unit 2, and the overflow port of the first stage iron removal and aluminum thickening unit 4 is connected to the feed port of the second stage iron removal and aluminum thickening unit 6;

[0104] The overflow port of the second stage iron removal and aluminum concentration unit 6 is connected to the feed port of the first stage nickel and cobalt precipitation and concentration unit 7;

[0105] The bottom flow port of the first stage nickel-cobalt precipitation and concentration unit 7 is connected to the feed port of the product filter press unit 8, and the filter cake outlet of the product filter press unit 8 discharges the nickel-cobalt-containing product; the overflow port of the first stage nickel-cobalt precipitation and concentration unit 7 is connected to the feed port of the second stage nickel-cobalt precipitation and concentration unit 9.

[0106] In an optional embodiment, the underflow port of the first stage iron removal and aluminum thickening unit 4 is connected to the feed port of the iron aluminum slag CCD countercurrent washing unit 5, and the external underflow port of the iron aluminum slag CCD countercurrent washing unit 5 is connected to the feed port of the second stage and subsequent one or more stages of the leached slag CCD countercurrent washing; the external overflow port of the iron aluminum slag CCD countercurrent washing unit 5 is connected to the feed port of the second stage iron removal and aluminum thickening unit 6;

[0107] And / or, the tailings treatment unit comprises a tailings neutralization and thickening unit 10, a tailings filter press unit 11 and a wastewater treatment unit 12, the external underflow outlet of the leached residue CCD countercurrent washing unit 2 is connected to the feed inlet of the tailings neutralization and thickening unit 10; the underflow outlet of the tailings neutralization and thickening unit 10 is connected to the feed inlet of the tailings filter press unit 11, and the overflow outlet of the tailings neutralization and thickening unit 10 is connected to the feed inlet of the wastewater treatment unit 12; the filter cake outlet of the tailings filter press unit 11 discharges the tailings filter cake, and the filtrate outlet of the tailings filter press unit 11 is connected to the wastewater treatment unit 12;

[0108] And / or, the underflow port of the second-stage iron removal and aluminum concentration unit 6 is connected to the feed port of the pre-neutralization and concentration unit 3;

[0109] And / or, the filtrate outlet of the product filter press unit 8 is connected to the feed inlet of the second-stage nickel-cobalt precipitation and thickening unit 9;

[0110] And / or, the bottom flow outlet of the second-stage nickel-cobalt precipitation and thickening unit 9 is connected to the discharge port of the acid leaching unit 1, the overflow outlet of the second-stage nickel-cobalt precipitation and thickening unit 9 is connected to the feed port of the tailings neutralization and thickening unit 10, and the overflow discharged from the overflow outlet of the second-stage nickel-cobalt precipitation and thickening unit 9 is also connected to the washing water inlet of the leaching slag CCD countercurrent washing unit 2, the washing water inlet of the iron-aluminum slag CCD countercurrent washing unit 5, the washing water inlet of the tail gas washing device, and the slurry liquid inlet of the limestone slurrying device.

[0111] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0112] Example 1

[0113] This embodiment provides a method for separating nickel and cobalt from laterite nickel ore, such as Figure 1 As shown, the device used is as Figure 2 As shown, the specific steps include:

[0114] Take the pre-treated laterite nickel ore slurry, the solid content is 37.5%, and the nickel content in the solid is 1.25%;

[0115] The above-mentioned laterite nickel ore pulp is subjected to high-pressure acid leaching, with an acid-ore ratio of 310kg / t, a reaction pressure of 4.6MPa, and a reaction time of 1h to obtain a high-pressure acid leaching pulp;

[0116] The leached pulp from high pressure acid leaching is subjected to 6-stage leaching residue CCD countercurrent washing, with a washing water ratio of 2.3, to obtain leaching residue CCD overflow and leaching residue CCD underflow;

[0117] The leached residue CCD overflow was pre-neutralized and thickened, the reaction pH value was 2.0, the reaction time was 4h, and the pre-neutralized slurry was obtained;

[0118] After pre-neutralization, the slurry undergoes a stage of iron removal and aluminum thickening, the reaction pH value is 3.7, the reaction time is 4 hours, and a stage of iron removal and aluminum underflow and a stage of iron removal overflow are obtained;

[0119] The first stage of iron and aluminum removal underflow is subjected to 6-stage iron and aluminum slag CCD countercurrent washing, with a washing water ratio of 2.5, to obtain iron and aluminum slag CCD underflow and iron and aluminum slag CCD overflow;

[0120] The iron and aluminum slag CCD underflow is discharged to the 5th stage of leached slag CCD countercurrent washing;

[0121] The overflow of the first stage of iron and aluminum removal and the overflow of iron and aluminum slag CCD enter the second stage of iron and aluminum removal and thickening together. The reaction pH value is 4.8 and the reaction time is 3h. The second stage of iron and aluminum removal bottom flow and the second stage of iron and aluminum removal overflow are obtained.

[0122] The second stage iron and aluminum removal bottom flow returns to the pre-neutralization process;

[0123] The overflow of the second stage of iron and aluminum removal is used for a stage of nickel and cobalt precipitation and thickening, the reaction pH value is 7.4, the reaction time is 4h, and a stage of nickel and cobalt precipitation underflow and a stage of nickel and cobalt precipitation overflow are obtained;

[0124] The nickel-cobalt bottom flow of the first stage is filtered and washed by pressure to obtain a nickel-cobalt hydroxide product (MHP) and a filtrate and washing liquid, wherein the water content of the MHP product is 50.5%, and the nickel content of the nickel-cobalt hydroxide product on a dry basis is 41.2%;

[0125] The overflow from the first stage nickel-cobalt precipitation and the filtrate from the product filter press washing are used together for the second stage nickel-cobalt precipitation and thickening, the reaction pH value is 8.0, the reaction time is 3 hours, and the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow are obtained;

[0126] The bottom flow of the second stage nickel and cobalt precipitation returns to the leaching residue CCD countercurrent washing process for leaching;

[0127] Part of the overflow from the second stage nickel and cobalt precipitation is returned to the leaching slag CCD, iron and aluminum slag CCD, tail gas washing, limestone slurrying and other processes as washing water or slurrying liquid, and the rest is discharged to the tailings neutralization process;

[0128] The leached slag CCD underflow and the remaining second-stage nickel-cobalt precipitation overflow are used for tailings neutralization and concentration, the reaction pH value is 7.8, the reaction time is 4h, and the tailings concentrated underflow and tailings concentrated overflow are obtained;

[0129] The dense underflow of tailings is filtered through tailings filter press to obtain tailings filter cake and tailings filtrate. The moisture content of tailings filter cake is 30.3%. The tailings filter cake is discharged to the tailings pond for storage, and the tailings filtrate is discharged after wastewater treatment.

[0130] Comparative Example 1

[0131] This comparative example provides a method for separating nickel and cobalt from laterite nickel ore, which is different from Example 1 mainly in that the countercurrent washing of the leached residue CCD is carried out after the pre-neutralization step, and the solid-liquid separation is carried out on the iron-removing aluminum underflow by means of filter pressing, which specifically comprises the following steps:

[0132] The pre-treated laterite nickel ore pulp was taken, the solid content was 37.3%, and the nickel content in the solid was 1.26%;

[0133] The above-mentioned laterite nickel ore pulp is subjected to high-pressure acid leaching, with an acid-ore ratio of 310kg / t, a reaction pressure of 4.6MPa, and a reaction time of 1h to obtain a high-pressure acid leaching pulp;

[0134] The ore pulp leached out by high pressure acid leaching is pre-neutralized, the reaction pH value is 2.0, the reaction time is 4h, and the pre-neutralized ore pulp is obtained;

[0135] The pre-neutralized slurry is subjected to 6-stage leaching residue CCD countercurrent washing with a washing water ratio of 2.3 to obtain leaching residue CCD overflow and leaching residue CCD underflow;

[0136] After pre-neutralization, the slurry undergoes a stage of iron removal and aluminum thickening, the reaction pH value is 3.7, the reaction time is 4 hours, and a stage of iron removal and aluminum underflow and a stage of iron removal overflow are obtained;

[0137] The first stage of iron and aluminum removal underflow is subjected to iron and aluminum slag filter pressing to obtain iron and aluminum slag filter cake and iron and aluminum slag filter washing liquid;

[0138] The iron and aluminum slag filter cake is slurried and then discharged to the tailings neutralization process;

[0139] The first stage iron and aluminum removal overflow and the iron and aluminum slag filtrate and washing liquid are used together for the second stage iron and aluminum removal and thickening, the reaction pH value is 4.8, the reaction time is 3h, and the second stage iron and aluminum removal bottom flow and the second stage iron and aluminum removal overflow are obtained;

[0140] The second stage iron and aluminum removal bottom flow returns to the pre-neutralization process;

[0141] The overflow of the second stage of iron and aluminum removal is used for a stage of nickel and cobalt precipitation and thickening, the reaction pH value is 7.4, the reaction time is 4h, and a stage of nickel and cobalt precipitation underflow and a stage of nickel and cobalt precipitation overflow are obtained;

[0142] The nickel-cobalt underflow of the first stage is filtered and washed by pressure to obtain a nickel-cobalt hydroxide product (MHP) and a filtrate and washing liquid, wherein the water content of the MHP product is 50.6%, and the nickel content of the nickel-cobalt hydroxide product on a dry basis is 40.9%;

[0143] The overflow from the first stage nickel-cobalt precipitation and the filtrate from the product filter press washing are used together for the second stage nickel-cobalt precipitation and thickening, the reaction pH value is 8.0, the reaction time is 3 hours, and the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow are obtained;

[0144] The bottom flow of the second stage nickel and cobalt precipitation returns to the pre-neutralization process;

[0145] Part of the overflow from the second stage nickel and cobalt precipitation is returned to the leaching residue CCD, tail gas washing, limestone slurrying and other processes as washing water or slurrying liquid, and the rest is discharged to the tailings neutralization process;

[0146] The leached slag CCD underflow, the iron-aluminum slag slurry and the excess second-stage nickel-cobalt precipitation overflow are used to neutralize and thicken the tailings. The reaction pH value is 7.8 and the reaction time is 4 hours to obtain the tailings thickening underflow and tailings thickening overflow.

[0147] The dense underflow of tailings is filtered through tailings filter press to obtain tailings filter cake and tailings filtrate. The moisture content of tailings filter cake is 33.8%. The tailings filter cake is discharged to the tailings pond for storage, and the tailings filtrate is discharged after wastewater treatment.

[0148] By comparing the above Example 1 with Comparative Example 1, it can be seen that adjusting the order of CCD countercurrent washing and pre-neutralization of the leached residue will increase the difficulty of solid-liquid separation in the tailings filter press step and increase the moisture content of the tailings filter cake. This may be because the generated gypsum particles have a smaller particle size and a smaller filtering effect.

[0149] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for separating nickel and cobalt from laterite nickel ore, characterized in that: include: Acid leaching is performed on the pretreated laterite nickel ore pulp to obtain acid leached ore pulp; The acid leaching pulp is subjected to solid-liquid separation by using leaching residue CCD countercurrent washing to obtain leaching residue CCD overflow and leaching residue CCD underflow; the leaching residue CCD underflow is subjected to solid-liquid separation to obtain tailings; Pre-neutralizing and thickening the leached residue CCD overflow to obtain a pre-neutralized slurry; The pre-neutralized slurry is subjected to a stage of iron removal and aluminum thickening to obtain a stage of iron removal and aluminum underflow and a stage of iron removal and aluminum overflow; The first stage of iron and aluminum removal underflow is transferred to the leached residue CCD countercurrent washing step; The first stage iron removal and aluminum removal overflow is subjected to second stage iron removal and aluminum thickening to obtain a second stage iron removal and aluminum underflow and a second stage iron removal and aluminum overflow; The overflow from the second stage of iron and aluminum removal is subjected to nickel and cobalt precipitation to obtain a nickel-cobalt-containing product.

2. The method for separating nickel and cobalt from laterite nickel ore according to claim 1, characterized in that: Meet at least one of the following characteristics: a. The solid content of the laterite nickel ore slurry is 30wt%-45wt%, and the nickel content of the solid in the laterite nickel ore slurry is 0.8wt%-2.0wt%; b. The acid-ore ratio of the acid leaching step is 200kg / t-400kg / t, the reaction temperature is 240°C-270°C, the reaction pressure is 4MPa-6MPa, and the reaction time is 0.5h-2h; c. The number of stages of CCD countercurrent washing of the leached residue is 3-8, and the washing water ratio is 2-4:1; d. The pre-neutralization reaction time is 1h-15h, and the reaction pH value is 1.0-3.

0.

3. The method for separating nickel and cobalt from laterite nickel ore according to claim 1, characterized in that: The first stage of iron-aluminum removal underflow is subjected to iron-aluminum slag CCD countercurrent washing to obtain iron-aluminum slag CCD underflow and iron-aluminum slag CCD overflow, and the iron-aluminum slag CCD underflow is transferred to the leaching slag CCD countercurrent washing step; preferably, the iron-aluminum slag CCD underflow is discharged to the second stage and one or more subsequent stages of the leaching slag CCD countercurrent washing; Preferably, the iron-aluminum slag CCD overflow is transferred to the second stage iron and aluminum removal step.

4. The method for separating nickel and cobalt from laterite nickel ore according to claim 3, characterized in that: The reaction time of the first stage of iron and aluminum removal is 1h-15h, and the reaction pH value is 3.5-4.5; And / or, the number of stages of the CCD countercurrent washing of the iron-aluminum slag is 3-8, and the washing water ratio is 2-4:1; And / or, the second-stage iron and aluminum removal bottom flow is returned to the pre-neutralization step; And / or, the reaction time of the second-stage iron and aluminum removal is 1h-10h, and the reaction pH value is 4.5-5.

5.

5. The method for separating nickel and cobalt from laterite nickel ore according to claim 1, characterized in that: The nickel-cobalt precipitation step comprises: performing a nickel-cobalt precipitation and thickening step on the second-stage iron-aluminum removal overflow to obtain a nickel-cobalt precipitation underflow and a nickel-cobalt precipitation overflow; The nickel-cobalt bottom flow of the first stage is filtered and washed to obtain a nickel-cobalt-containing product and a filtrate and washing liquid of the product.

6. The method for separating nickel and cobalt from laterite nickel ore according to claim 5, characterized in that: The reaction time of the nickel-cobalt precipitation is 1h-15h, and the reaction pH value is 7.0-7.6; and / or, the water content of the nickel-cobalt-containing product is 45wt%-60wt%, and the nickel content of the nickel-cobalt-containing product on a dry basis is 35wt%-45wt%; And / or, it also includes: neutralizing and thickening the leached slag CCD underflow to obtain a tailings thickening underflow and a tailings thickening overflow; The dense underflow of tailings is filtered through tailings filter press to obtain tailings filter cake and tailings filtrate.

7. The method for separating nickel and cobalt from laterite nickel ore according to claim 6, characterized in that: The first stage nickel-cobalt precipitation overflow and the filtrate washing liquid of the product filter pressing washing are subjected to second stage nickel-cobalt precipitation and thickening to obtain the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow; The second stage nickel and cobalt precipitation bottom flow returns to the acid leaching slurry; The overflow from the second stage nickel and cobalt precipitation is used as washing water or slurrying liquid in the steps of CCD countercurrent washing of leached slag, CCD countercurrent washing of iron and aluminum slag, tail gas washing, and limestone slurrying, or discharged to the tailings neutralization process.

8. The method for separating nickel and cobalt from laterite nickel ore according to claim 7, characterized in that: The reaction time of the second stage nickel-cobalt precipitation is 1h-10h, and the reaction pH value is 7.6-8.2; And / or, the reaction time of the tailings neutralization is 1h-10h, and the reaction pH value is 6.0-9.0; And / or, the moisture content of the tailings filter cake after the tailings filter pressure is 27wt%-33wt%.

9. A device for separating nickel and cobalt in laterite nickel ore applicable to the method according to any one of claims 1 to 8, characterized in that: It includes acid leaching unit, leached residue CCD countercurrent washing unit, pre-neutralization and thickening unit, first-stage iron and aluminum removal and thickening unit, second-stage iron and aluminum removal and thickening unit, first-stage nickel and cobalt precipitation and thickening unit, product filter press unit, second-stage nickel and cobalt precipitation and thickening unit and tailings treatment unit; among which, The acid leaching unit is provided with a leached slurry outlet, the leached slurry outlet is connected to the feed inlet of the leached slag CCD countercurrent washing unit, and the external underflow outlet of the leached slag CCD countercurrent washing unit is connected to the feed inlet of the tailings treatment unit; The external overflow port of the leached residue CCD countercurrent washing unit is connected to the feed port of the pre-neutralization and thickening unit, and the reaction tank slurry outlet, underflow port and overflow port of the pre-neutralization and thickening unit are all connected to the feed port of the first stage iron and aluminum removal and thickening unit; The underflow port of the first stage iron removal and aluminum thickening unit is connected to the feed port of the leached residue CCD countercurrent washing unit, and the overflow port of the first stage iron removal and aluminum thickening unit is connected to the feed port of the second stage iron removal and aluminum thickening unit; The overflow port of the second stage iron removal and aluminum concentration unit is connected to the feed port of the first stage nickel and cobalt precipitation and concentration unit; The bottom flow port of the first stage nickel-cobalt precipitation and concentration unit is connected to the feed port of the product filter press unit, and the filter cake outlet of the product filter press unit discharges the nickel-cobalt-containing product; the overflow port of the first stage nickel-cobalt precipitation and concentration unit is connected to the feed port of the second stage nickel-cobalt precipitation and concentration unit.

10. The device for separating nickel and cobalt from laterite nickel ore according to claim 9, characterized in that: The bottom flow port of the first stage iron removal and aluminum thickening unit is connected to the feed port of the iron aluminum slag CCD countercurrent washing unit, and the external bottom flow port of the iron aluminum slag CCD countercurrent washing unit is connected to the feed port of the second stage and the subsequent one or more stages of the leached slag CCD countercurrent washing; the external overflow port of the iron aluminum slag CCD countercurrent washing unit is connected to the feed port of the second stage iron removal and aluminum thickening unit; And / or, the tailings treatment unit comprises a tailings neutralization and thickening unit, a tailings filter press unit and a wastewater treatment unit; the external underflow outlet of the leached residue CCD countercurrent washing unit is connected to the feed inlet of the tailings neutralization and thickening unit; the underflow outlet of the tailings neutralization and thickening unit is connected to the feed inlet of the tailings filter press unit, and the overflow outlet of the tailings neutralization and thickening unit is connected to the feed inlet of the wastewater treatment unit; the filter cake outlet of the tailings filter press unit discharges the tailings filter cake, and the filtrate outlet of the tailings filter press unit is connected to the wastewater treatment unit; And / or, the underflow port of the second-stage iron removal and aluminum concentration unit is connected to the feed port of the pre-neutralization and concentration unit; And / or, the filtrate outlet of the product filter press unit is connected to the feed inlet of the second-stage nickel-cobalt precipitation and thickening unit; And / or, the bottom flow outlet of the second-stage nickel-cobalt precipitation and thickening unit is connected to the discharge outlet of the acid leaching unit, the overflow outlet of the second-stage nickel-cobalt precipitation and thickening unit is connected to the feed inlet of the tailings neutralization and thickening unit, and the overflow discharged from the overflow outlet of the second-stage nickel-cobalt precipitation and thickening unit is also connected to the washing water inlet of the leaching slag CCD countercurrent washing unit, the washing water inlet of the iron-aluminum slag CCD countercurrent washing unit, the washing water inlet of the tail gas washing device, and the slurry liquid inlet of the limestone slurrying device.

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