Method for recycling iron from high-pressure acid leaching tailings of lateritic nickel ores

Abstract

A method for recycling iron from high-pressure acid leaching tailings of lateritic nickel ores. The method comprises the following steps: subjecting ore pulp containing high-pressure acid leaching tailings of lateritic nickel ores to countercurrent washing, so as to obtain an overflow washing solution and a concentrated underflow; and subjecting the overflow washing solution to a neutralization treatment, and subjecting the concentrated underflow to alkaline washing for a sulfur removal treatment. The recycling method can achieve the recovery of iron from high-pressure acid leaching tailings of lateritic nickel ores, and reduce the discharging of tailings; and in the resulting iron concentrate, the content of sulfur is within 0.1 wt%, the content of SiO2 is within 10 wt%, and the content of iron is stabilized at 60 wt% or higher.

Description

A method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore Technical Field

[0001] The present application belongs to the technical field of hydrometallurgy, and relates to a method for utilizing laterite nickel ore, and in particular to a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. Background Art

[0002] High-pressure acid leaching (HPAL) technology for laterite nickel ore is characterized by reliable process, wide adaptability, low cost and wide application range. HPAL accounts for a considerable proportion of the laterite nickel ore projects that have been built in recent years and are about to be built.

[0003] At present, the mainstream process of HPAL is that the ore of laterite nickel ore is crushed, screened and then concentrated in the beneficiation plant, and then pumped to the high-pressure reactor for leaching. The slurry after leaching is pumped to the pre-neutralization process for residual acid neutralization. The neutralized slurry is washed in countercurrent to collect the overflow liquid; after the overflow liquid undergoes the aluminum removal process, liquid alkali is added to adjust the pH value, and the nickel cobalt hydroxide product is precipitated.

[0004] CN114622102A discloses a method for comprehensive extraction of valuable metals from laterite nickel ore, comprising: adding sulfuric acid to the underflow obtained after ball milling and thickening the laterite nickel ore for pre-leaching to obtain a slurry; adding the slurry to the ore blend and performing pressure leaching to obtain a first leachate and a first leach residue; neutralizing the first leach residue and performing solid-liquid separation to obtain a second leach residue and a second leachate; subjecting the second leach residue to acid washing, extraction, washing, stripping and precipitation to obtain scandium hydroxide; and subjecting the second leachate to alkalization, impurity removal and complex precipitation to obtain nickel, cobalt and manganese hydroxides.

[0005] However, the laterite nickel ore processed by HPAL is generally limonite. The nickel in limonite is associated with iron, and the iron grade is above 40%. However, the HPAL process provided by the existing technology does not involve iron recovery, and discarding the iron will cause a huge waste of resources.

[0006] Therefore, it is necessary to provide a method for recycling iron in laterite nickel ore high-pressure acid leaching tailings, which can recover iron in laterite nickel ore and reduce tailings discharge effect.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of this application is to provide a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. The recycling method can recover iron in high-pressure acid leaching tailings of laterite nickel ore, and the sulfur content of the recovered iron concentrate is within 0.1wt%, the SiO2 content is within 10wt%, and the iron content is stable at more than 60wt%, which meets the standard of magnetite concentrate C60.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] The present application provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, the recycling method comprising the following steps:

[0012] Countercurrent washing of slurry containing high-pressure acid leaching tailings of laterite nickel ore to obtain overflow washing liquid and concentrated underflow; the overflow washing liquid is neutralized and the concentrated underflow is subjected to alkaline washing and desulfurization treatment;

[0013] The alkaline washing and desulfurization treatment comprises:

[0014] (I) concentrating the underflow for solid-liquid separation, mixing the obtained solid-containing material with alkali solution to perform alkali washing, performing solid-liquid separation on the slurry after alkali washing, and filtering the underflow after solid-liquid separation to obtain a filter cake;

[0015] (II) mixing the filter cake obtained in step (I) with a reducing agent, performing a reduction heat treatment under a protective atmosphere, and performing magnetic separation after cooling to obtain an iron concentrate;

[0016] The neutralization treatment includes pre-neutralization treatment, one-stage neutralization to remove iron and aluminum, two-stage neutralization to remove iron and aluminum, one-stage nickel and cobalt precipitation and two-stage nickel and cobalt precipitation which are carried out in sequence.

[0017] The recycling method provided in this application reduces the sulfur content in the concentrated underflow through alkaline washing and desulfurization. After reduction heat treatment and magnetic separation, the resulting iron concentrate has a sulfur content of less than 0.1 wt%, a SiO2 content of less than 10 wt%, and a stable iron content of more than 60 wt%, meeting the C60 standard for magnetite concentrate. Furthermore, the recycling method provided in this application fully utilizes tailings from high-pressure acid leaching of laterite nickel ore, reducing tailings emissions, improving economic efficiency, and being environmentally friendly.

[0018] If not otherwise specified, the solid-liquid separation in the recycling method provided in the present application is carried out in a thickener.

[0019] If not specifically limited, the wash water ratio of the recycling method provided in the present application is the mass ratio of the wash water mass to the mass of the solids in the thickener underflow.

[0020] If not specifically limited, the present application provides an oxygen atmosphere in a recycling method, and the gas used is air.

[0021] For example, the solid-liquid separation method in step (I) of the present application includes but is not limited to filter press. The present application obtains a filter cake containing solid material and a filtrate through filter press.

[0022] The present application does not limit the specific treatment method of the filtrate. For example, the filtrate is mixed with the overflow washing liquid and then neutralized.

[0023] In one embodiment, the alkaline substance in the alkali solution in step (I) includes sodium carbonate and sodium hydroxide.

[0024] In one embodiment, in the alkali solution of step (I), the molar ratio of sodium carbonate to sodium hydroxide is (1-3):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In one embodiment, the concentration of the alkali solution in step (I) is 2.5-3.5 mol / L, for example, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L or 3.5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] In one embodiment, the solid content of the concentrated underflow in step (I) is 36-40 wt%, for example, 36 wt%, 37 wt%, 38 wt%, 39 wt% or 40 wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In one embodiment, after the alkali solution in step (I) is mixed with the solid-containing material, the solid-liquid mass ratio of the resulting system is 1:(7-9), for example, it can be 1:7, 1:7.5, 1:8, 1:8.5 or 1:9, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] The mixing method in step (I) of the present application includes but is not limited to stirring.

[0029] In one embodiment, the mixing in step (I) is carried out at a temperature of 70-80° C. and for a time of 50-70 min.

[0030] The mixing temperature in step (I) is 70-80°C, for example, 70°C, 72°C, 75°C, 78°C or 80°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] The mixing time in step (I) is 50-70 min, for example, 50 min, 55 min, 60 min, 65 min or 70 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] The mixing time in step (I) refers to the stirring time.

[0033] In one embodiment, the reducing agent in step (II) comprises carbon powder.

[0034] In one embodiment, the particle size of the reducing agent in step (II) is less than 200 mesh.

[0035] The particle size of the reducing agent in step (II) of the present application is <200 mesh, which means that the particle size of the reducing agent is <75 μm, for example, it can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm or 74 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] That is, it is sufficient to select a reducing agent that can pass through a 200-mesh sieve.

[0037] In one embodiment, the mass ratio of the filter cake to the reducing agent in step (II) is (5-8):1, for example, 5:1, 6:1, 7:1 or 8:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] The mass ratio of the filter cake to the reducing agent in this application refers to the mass ratio of the solid in the filter cake to the reducing agent.

[0039] In one embodiment, the protective atmosphere in step (II) comprises nitrogen and / or an inert gas.

[0040] In one embodiment, the reduction heat treatment in step (II) includes a first temperature increase, a second temperature increase, and a heat preservation treatment performed sequentially.

[0041] In one embodiment, the first heating rate is 12-18°C / min, and the end temperature is 480-520°C.

[0042] In the present application, the first heating rate is 12-18°C / min, for example, it can be 12°C / min, 13°C / min, 14°C / min, 15°C / min, 16°C / min, 17°C / min or 18°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In the present application, the endpoint temperature of the first heating is 480-520°C, for example, it can be 480°C, 490°C, 500°C, 510°C or 520°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In one embodiment, the second heating rate is 8-12°C / min, and the end temperature is 640-660°C.

[0045] In the present application, the second heating rate is 8-12°C / min, for example, it can be 8°C / min, 9°C / min, 10°C / min, 11°C / min or 12°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In the present application, the end temperature of the second heating is 640-660°C, for example, it can be 640°C, 645°C, 650°C, 655°C or 660°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In one embodiment, the temperature of the insulation treatment is the end temperature of the second heating, and the time is 25-35 minutes, for example, it can be 25 minutes, 27 minutes, 30 minutes, 32 minutes or 35 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In one embodiment, the number of washing stages of the countercurrent washing is at least 4, the overflow liquid of the first stage of countercurrent washing is the overflow washing liquid, and the underflow of the last stage of countercurrent washing is the concentrated underflow.

[0049] The present application uses at least four stages of countercurrent washing to reduce the nickel content in the overflow wash while ensuring the solid content of the concentrated underflow, thereby avoiding excessive nickel inclusion in the underflow; at the same time, the pH value of the overflow wash is increased, enabling more iron to be precipitated subsequently.

[0050] In one embodiment, the wash water ratio of the countercurrent washing is (1.5-1.8):1, for example, it can be 1.5:1, 1.6:1, 1.7:1 or 1.8:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In one embodiment, the pre-neutralization treatment comprises:

[0052] The pH value of the overflow washing liquid is adjusted to be above 2, and the obtained slurry is subjected to neutralization countercurrent washing to obtain neutralized tailings and neutralized overflow liquid;

[0053] The resulting neutralized overflow liquid undergoes subsequent neutralization to remove iron and aluminum.

[0054] In one embodiment, the wash water ratio of the neutralization countercurrent washing is (0.8-1.2):1, for example, it can be 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] In the pre-neutralization treatment of the present application, the pH value of the overflow washing liquid is adjusted to be above 2, for example, it can be 2, 2.2, 2.4, 2.5, 2.7 or 3, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In one embodiment, the filtrate obtained from the pressure filtration in step (I) is mixed with the neutralization tailings.

[0057] In one embodiment, the one-stage neutralization and iron removal of aluminum comprises:

[0058] In an oxygen atmosphere, the pH value of the neutralized overflow liquid is adjusted to 3.6-4, and the obtained slurry is subjected to solid-liquid separation to obtain a first iron-aluminum removal underflow and a first iron-aluminum removal overflow liquid;

[0059] The obtained first iron and aluminum removal overflow liquid is subjected to subsequent two-stage neutralization to remove iron and aluminum.

[0060] In the present application, the pH value of the neutralization overflow liquid in the one-stage neutralization and iron and aluminum removal is adjusted to 3.6-4, for example, it can be 3.6, 3.7, 3.8, 3.9 or 4, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] In one embodiment, part of the obtained first iron removal aluminum bottom flow is mixed with the neutralization tailings; further optionally, 75-85wt% of the obtained first iron removal aluminum bottom flow is used as seeds for a stage of neutralization and iron removal, and the rest is mixed with the neutralization tailings.

[0062] In one embodiment, the pH value of the neutralized overflow liquid is adjusted to 3.6-4 using a calcium carbonate slurry with a mass concentration of 28-32 wt%.

[0063] In the present application, the mass concentration of the calcium carbonate slurry used to adjust the pH value of the neutralized overflow liquid is 28-32wt%, for example, it can be 28wt%, 29wt%, 30wt%, 31wt% or 32wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0064] In one embodiment, the second stage neutralization and removal of iron and aluminum comprises:

[0065] Under an oxygen atmosphere, the pH value of the first deironing aluminum overflow liquid is adjusted to 4.6-5, and the obtained slurry is subjected to solid-liquid separation to obtain a second deironing aluminum underflow and a second deironing aluminum overflow liquid;

[0066] The second iron and aluminum removal overflow liquid obtained is subjected to subsequent nickel and cobalt precipitation.

[0067] In one embodiment, part of the obtained second iron removal aluminum bottom flow is returned to the pre-neutralization treatment; further optionally, 75-85wt% of the obtained second iron removal aluminum bottom flow is used as seeds for the second-stage neutralization iron removal aluminum, and the rest is returned to the pre-neutralization treatment.

[0068] In one embodiment, a calcium carbonate slurry with a mass concentration of 28-32 wt% is used to adjust the pH value of the first iron and aluminum removal overflow liquid to 4.6-5, for example, it can be 4.6, 4.7, 4.8, 4.9 or 5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0069] In the present application, the mass concentration of the calcium carbonate slurry used to adjust the pH value of the first iron and aluminum removal overflow liquid is 28-32wt%, for example, it can be 28wt%, 29wt%, 30wt%, 31wt% or 32wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0070] In one embodiment, the one-stage nickel-cobalt precipitation comprises:

[0071] The pH value of the second iron and aluminum removal overflow liquid is adjusted to 7.6-8, and the obtained slurry is subjected to solid-liquid separation to obtain a nickel and cobalt precipitation underflow and a nickel and cobalt precipitation overflow liquid;

[0072] The overflow liquid obtained from the first stage nickel-cobalt precipitation is used for subsequent second stage nickel-cobalt precipitation.

[0073] In one embodiment, 75-85 wt% of the obtained first stage nickel-cobalt precipitation underflow is used as seed crystals for the first stage nickel-cobalt precipitation, and the rest is used as the finished product.

[0074] In one embodiment, a sodium hydroxide solution with a mass concentration of 8-12 wt% is used to adjust the pH value of the second iron and aluminum removal overflow liquid to 7.6-8, for example, it can be 7.6, 7.7, 7.8, 7.9 or 8, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0075] In the present application, the mass concentration of the sodium hydroxide solution used to adjust the pH value of the second iron and aluminum removal overflow liquid is 8-12wt%, for example, it can be 8wt%, 9wt%, 10wt%, 11wt% or 12wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0076] In one embodiment, the second stage nickel-cobalt precipitation comprises:

[0077] The pH value of the first stage nickel-cobalt precipitation overflow liquid is adjusted to above 8.5, and the obtained slurry is subjected to solid-liquid separation to obtain the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow liquid.

[0078] The present application does not further limit the specific use of the overflow liquid of the second-stage nickel-cobalt precipitation. For example, part of the overflow liquid of the second-stage nickel-cobalt precipitation is used as washing water for countercurrent washing, and the remaining is discharged after treatment.

[0079] In one embodiment, part of the obtained second-stage nickel-cobalt precipitation bottom flow is returned to the pre-neutralization treatment; further optionally, 75-85wt% of the obtained second-stage nickel-cobalt precipitation bottom flow is used as seeds for the second-stage nickel-cobalt precipitation, and the rest is returned to the pre-neutralization treatment.

[0080] In one embodiment, lime milk with a mass concentration of 18-22 wt% is used to adjust the pH value of the first stage nickel and cobalt precipitation overflow liquid to above 8.5, for example, it can be 8.5, 8.6, 8.8, 8.9 or 9, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0081] In the present application, the mass concentration of lime milk used to adjust the pH value of the first stage nickel and cobalt precipitation overflow liquid is 18-22wt%, for example, it can be 18wt%, 19wt%, 20wt%, 21wt% or 22wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0082] In one embodiment, the pre-neutralization treatment includes at least 2 stages of pre-neutralization;

[0083] The pH value of the second iron and aluminum removal underflow and / or the second nickel and cobalt precipitation underflow used in the first stage pre-neutralization is adjusted;

[0084] The final stage is pre-neutralization to adjust the pH value to above 2.

[0085] Further optionally, the pre-neutralization treatment described in the present application includes 4-stage pre-neutralization.

[0086] Different from the 6-stage pre-neutralization in the prior art, since the high-pressure slag is separated during the countercurrent washing process, the purpose of early separation and dilution is achieved; and the pH value of the overflow washing liquid is increased, achieving a certain pre-neutralization effect. Therefore, the pre-neutralization treatment in this application only requires 4 stages of pre-neutralization.

[0087] In one embodiment, the neutralization countercurrent washing has at least two washing stages, the overflow liquid of the first stage of neutralization countercurrent washing is the neutralization overflow liquid, and the bottom flow of the last stage of neutralization countercurrent washing is the neutralization tailings.

[0088] In one embodiment, the slurry containing high-pressure acid leaching tailings of laterite nickel ore is prepared by the following method:

[0089] (a) crushing laterite nickel ore into ore powder, re-selecting to obtain chromium concentrate, and concentrating the remaining slurry to a solid content of 36-40wt%;

[0090] (b) The concentrated slurry is heated to 200-210° C. and subjected to high-pressure acid leaching to obtain leached nickel and a slurry containing high-pressure acid leaching tailings of laterite nickel ore.

[0091] In one embodiment, the particle size of the mineral powder in step (a) is 100-300 mesh, that is, the mineral powder can pass through a 100-mesh sieve but cannot pass through a 300-mesh sieve.

[0092] In one embodiment, the high-pressure acid leaching is performed at a temperature of 250-260° C., a pressure of 4.6-5.0 MPa, and a time of 50-60 min.

[0093] In the present application, the temperature of high-pressure acid leaching is 250-260°C, for example, it can be 250°C, 252°C, 255°C, 258°C or 260°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0094] In the present application, the absolute pressure of high-pressure acid leaching is 4.6-5.0 MPa, for example, 4.6 MPa, 4.7 MPa, 4.8 MPa, 4.9 MPa or 5 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0095] In the present application, the high-pressure acid leaching time is 50-60 minutes, for example, it can be 50 minutes, 52 minutes, 55 minutes, 58 minutes or 60 minutes, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0096] In one embodiment, the acid used in the high-pressure acid leaching is sulfuric acid, and the acid-ore ratio is 280-320 g / t, where "t" represents ton.

[0097] In the present application, the sulfuric acid used in high-pressure acid leaching is 98 wt% concentrated sulfuric acid, and the acid-ore ratio is 280-320 g / t, for example, 280 g / t, 290 g / t, 300 g / t, 310 g / t or 320 g / t, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0098] As an optional technical solution of the recycling method of the present application, the recycling method comprises the following steps:

[0099] (1-1) Crushing the laterite nickel ore into ore powder with a particle size of 100-200 mesh, re-selecting to obtain chromium concentrate, and concentrating the remaining slurry in a thickener to a solid content of 36-40wt%;

[0100] (1-2) The concentrated slurry is heated to 200-210° C. and subjected to high-pressure acid leaching to obtain leached nickel and a slurry containing high-pressure acid leaching tailings of laterite nickel ore;

[0101] The high-pressure acid leaching temperature is 250-260°C, the pressure is 4.6-5.0 MPa, and the time is 50-60 minutes;

[0102] The acid used in the high-pressure acid leaching is 98wt% concentrated sulfuric acid, and the acid-ore ratio is 280-320g / t;

[0103] (2) countercurrent washing a slurry containing high-pressure acid leaching tailings of laterite nickel ore to obtain an overflow wash liquid and a concentrated underflow having a solid content of 36-40 wt%; the countercurrent washing has at least four stages, the overflow liquid of the first stage of countercurrent washing is the overflow wash liquid, and the underflow of the last stage of countercurrent washing is the concentrated underflow;

[0104] The wash water ratio of the countercurrent washing is (1.5-1.8):1;

[0105] The overflow washing liquid is neutralized and the concentrated underflow is subjected to alkaline washing and desulfurization treatment; the neutralization treatment and alkaline washing and desulfurization treatment are not prioritized;

[0106] The neutralization treatment includes pre-neutralization treatment, first-stage neutralization to remove iron and aluminum, second-stage neutralization to remove iron and aluminum, first-stage nickel and cobalt precipitation, and second-stage nickel and cobalt precipitation.

[0107] (3-1) Pre-neutralization treatment: at least two stages of pre-neutralization are performed, and the pH value of the second iron and aluminum removal underflow and / or the second stage nickel and cobalt precipitation underflow used in the first stage of pre-neutralization is adjusted; in the final stage of pre-neutralization, the pH value of the overflow washing liquid is adjusted to be above 2; the resulting slurry is subjected to at least two stages of neutralization countercurrent washing with a wash water ratio of (0.8-1.2):1, the overflow liquid of the first stage of neutralization countercurrent washing is the neutralization overflow liquid, and the underflow of the final stage of neutralization countercurrent washing is the neutralization tailings; the resulting neutralization overflow liquid is subjected to a subsequent one-stage neutralization to remove iron and aluminum;

[0108] (3-2) One-stage neutralization and aluminum removal: Under air aeration, the pH of the neutralization overflow liquid is adjusted to 3.6-4 using a calcium carbonate slurry having a mass concentration of 28-32 wt%. The resulting slurry is subjected to solid-liquid separation in a thickener to obtain a first aluminum-removed underflow and a first aluminum-removed overflow liquid. The resulting first aluminum-removed overflow liquid is subjected to subsequent two-stage neutralization and aluminum-removal.

[0109] 75-85wt% of the obtained first iron-removal aluminum underflow is used as seeds for the first stage of neutralization and iron-removal aluminum, and the remainder is mixed with the neutralization tailings;

[0110] (3-3) Second-stage neutralization and deironing: Under air ventilation, the pH of the first deironing overflow is adjusted to 4.6-5 using a calcium carbonate slurry having a mass concentration of 28-32 wt%. The resulting slurry is subjected to solid-liquid separation in a thickener to obtain a second deironing underflow and a second deironing overflow. The resulting second deironing overflow is then subjected to subsequent first-stage nickel and cobalt precipitation.

[0111] 75-85wt% of the obtained second iron and aluminum removal bottom flow is used as seed crystals for the second stage of neutralization and iron and aluminum removal, and the rest is returned to the pre-neutralization treatment;

[0112] (3-4) One-stage nickel and cobalt precipitation: The pH of the second iron and aluminum removal overflow solution is adjusted to 7.6-8 using an 8-12 wt% sodium hydroxide solution. The resulting slurry is subjected to solid-liquid separation in a thickener to obtain a first-stage nickel and cobalt precipitation underflow and a first-stage nickel and cobalt precipitation overflow solution. The first-stage nickel and cobalt precipitation overflow solution is then subjected to a subsequent second-stage nickel and cobalt precipitation.

[0113] 75-85wt% of the obtained first stage nickel-cobalt precipitation underflow is used as seed crystals for the first stage nickel-cobalt precipitation, and the rest is used as the finished product;

[0114] (3-5) Second stage nickel and cobalt precipitation: The pH value of the overflow liquid from the first stage nickel and cobalt precipitation is adjusted to above 8.5 using lime milk having a mass concentration of 18-22 wt %. The resulting slurry is subjected to solid-liquid separation in a thickener to obtain a second stage nickel and cobalt precipitation underflow and a second stage nickel and cobalt precipitation overflow liquid;

[0115] 75-85wt% of the obtained second-stage nickel-cobalt precipitation underflow is used as seed crystals for the second-stage nickel-cobalt precipitation, and the remainder is returned to the pre-neutralization treatment;

[0116] The alkaline washing and desulfurization treatment comprises:

[0117] (4-1) Concentrating the underflow and performing filter pressing to obtain a filter cake containing solid material and a filtrate, stirring and mixing the alkali solution and the solid material at 70-80° C. to perform alkali washing, performing solid-liquid separation on the slurry after alkali washing, and performing filter pressing to obtain a filter cake and a filtrate after the solid-liquid separation; the filtrate is mixed with the neutralization tailings;

[0118] The stirring time is 50-70 minutes;

[0119] The concentration of the alkali solution is 2.5-3.5 mol / L, and the alkaline substance includes sodium carbonate and sodium hydroxide in a molar ratio of (1-3):1;

[0120] After the alkali solution is mixed with the concentrated underflow, the solid-liquid mass ratio of the resulting system is 1:(7-9);

[0121] (4-2) mixing the filter cake obtained in step (4-1) with carbon powder having a particle size of less than 200 mesh in a mass ratio of (5-8):1, performing a reduction heat treatment under a protective atmosphere, and performing magnetic separation after cooling to obtain an iron concentrate;

[0122] The reduction heat treatment includes a first temperature increase, a second temperature increase and a heat preservation treatment performed in sequence;

[0123] The first heating rate is 12-18°C / min, and the end temperature is 480-520°C;

[0124] The second heating rate is 8-12°C / min, and the end temperature is 640-660°C

[0125] The temperature of the heat preservation treatment is the end temperature of the second heating, and the time is 25-35 minutes.

[0126] Compared with the prior art, this application has the following beneficial effects:

[0127] The recycling method provided in this application reduces the sulfur content in the concentrated underflow through alkaline washing and desulfurization. After reduction heat treatment and magnetic separation, the resulting iron concentrate has a sulfur content of less than 0.1wt%, a SiO2 content of less than 10wt%, and a stable iron content of more than 60wt%, meeting the C60 standard for magnetite concentrate. Furthermore, the recycling method provided in this application fully utilizes the tailings from high-pressure acid leaching of laterite nickel ore, reducing tailings emissions, improving economic efficiency, and being environmentally friendly.

[0128] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0130] FIG1 is a flow chart of the process of the method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore provided in Example 1. DETAILED DESCRIPTION

[0131] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0132] In order to clearly illustrate the technical solution of the present application, the composition of the laterite nickel ore processed in the present application includes 1.2wt% nickel, 0.1wt% cobalt, 40wt% iron and 20wt% SiO2. The composition of the laterite nickel ore is only for the purpose of clearly illustrating the technical solution and is not regarded as a further limitation of the laterite nickel ore.

[0133] Example 1

[0134] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. The process flow chart of the recycling method is shown in FIG1 , comprising:

[0135] (1-1) Crushing the laterite nickel ore into ore powder with a particle size of 100-200 mesh, re-selecting to obtain chromium concentrate, and concentrating the remaining slurry in a thickener to a solid content of 38wt%;

[0136] (1-2) The concentrated slurry is heated to 205° C. and subjected to high-pressure acid leaching to obtain leached nickel and a slurry containing high-pressure acid leaching tailings of laterite nickel ore;

[0137] The high-pressure acid leaching temperature is 255°C, the pressure is 4.8 MPa, and the time is 55 minutes;

[0138] The acid used in the high-pressure acid leaching is 98 wt% concentrated sulfuric acid, and the acid-ore ratio is 300 g / t;

[0139] (2) countercurrent washing a slurry containing high-pressure acid leaching tailings of laterite nickel ore to obtain an overflow wash liquid and a concentrated underflow with a solid content of 38 wt%; the countercurrent washing comprises four stages, which are respectively carried out in thickeners CCD1, CCD2, CCD3, and CCD4, wherein the overflow liquid of the first stage countercurrent washing is the overflow wash liquid, and the underflow of the fourth stage countercurrent washing is the concentrated underflow;

[0140] The wash water ratio of the countercurrent washing is 1.6:1;

[0141] The overflow washing liquid is neutralized and the concentrated underflow is subjected to alkaline washing and desulfurization treatment; the neutralization treatment and alkaline washing and desulfurization treatment are not prioritized;

[0142] The neutralization treatment includes pre-neutralization treatment, first-stage neutralization to remove iron and aluminum, second-stage neutralization to remove iron and aluminum, first-stage nickel and cobalt precipitation, and second-stage nickel and cobalt precipitation.

[0143] (3-1) Pre-neutralization treatment: 4-stage pre-neutralization is performed in 4 pre-neutralization tanks connected in series. The pH value of the second iron and aluminum removal underflow and the second nickel and cobalt precipitation underflow used in the first stage pre-neutralization are adjusted. In the subsequent pre-neutralization process, a calcium carbonate slurry with a mass concentration of 30% is continuously added to adjust the pH value of the overflow washing liquid to 2. The resulting slurry is subjected to a second-stage neutralization countercurrent washing with a wash water ratio of 1:1, which is carried out in thickeners CCD5 and CCD6 respectively. The overflow liquid of the first stage neutralization countercurrent washing is the neutralization overflow liquid, and the underflow of the second stage neutralization countercurrent washing is the neutralization tailings. The resulting neutralization overflow liquid is subjected to the subsequent first-stage neutralization to remove iron and aluminum.

[0144] (3-2) One-stage neutralization and aluminum removal: Under air aeration, the pH of the neutralization overflow liquid was adjusted to 3.8 using a 30 wt% calcium carbonate slurry. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a first aluminum-removed underflow and a first aluminum-removed overflow liquid. The resulting first aluminum-removed overflow liquid was subsequently subjected to two-stage neutralization and aluminum-removal.

[0145] 80 wt% of the obtained first iron-aluminum removal underflow is used as seeds for the first stage of neutralization and iron-aluminum removal, and the rest is mixed with the neutralization tailings;

[0146] (3-3) Second-stage neutralization and deironing: Under air ventilation, the pH of the first deironing overflow was adjusted to 4.8 using a 30 wt% calcium carbonate slurry. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a second deironing underflow and a second deironing overflow. The resulting second deironing overflow was then subjected to subsequent first-stage nickel and cobalt precipitation.

[0147] 80 wt% of the obtained second iron and aluminum removal bottom flow is used as seed crystals for the second stage of neutralization and iron and aluminum removal, and the rest is returned to the pre-neutralization treatment;

[0148] (3-4) One-stage nickel and cobalt precipitation: The pH value of the second iron and aluminum removal overflow liquid is adjusted to 7.8 using a 10 wt% sodium hydroxide solution. The resulting slurry is subjected to solid-liquid separation in a thickener to obtain a first-stage nickel and cobalt precipitation underflow and a first-stage nickel and cobalt precipitation overflow liquid. The first-stage nickel and cobalt precipitation overflow liquid is then subjected to a subsequent second-stage nickel and cobalt precipitation.

[0149] 80 wt% of the obtained first stage nickel-cobalt precipitation underflow is used as seed crystals for the first stage nickel-cobalt precipitation, and the rest is used as the finished product;

[0150] (3-5) Second stage nickel and cobalt precipitation: The pH value of the overflow liquid from the first stage nickel and cobalt precipitation was adjusted to 8.5 using 20 wt% lime milk, and the resulting slurry was subjected to solid-liquid separation in a thickener to obtain a second stage nickel and cobalt precipitation underflow and a second stage nickel and cobalt precipitation overflow liquid;

[0151] 80 wt% of the obtained second-stage nickel-cobalt underflow is used as seed crystals for the second-stage nickel-cobalt precipitation, and the remainder is returned to the pre-neutralization treatment;

[0152] The alkaline washing and desulfurization treatment comprises:

[0153] (4-1) Concentrating the underflow and performing filter pressing to obtain a filter cake containing solid material and a filtrate, stirring and mixing the alkali solution and the solid material at 75° C. to perform alkali washing, performing solid-liquid separation on the slurry after alkali washing, and performing filter pressing to obtain a filter cake and a filtrate after the solid-liquid separation; the filtrate is mixed with the neutralization tailings;

[0154] The stirring time is 60 min;

[0155] The concentration of the alkali solution is 3 mol / L, and the alkaline substance includes sodium carbonate and sodium hydroxide in a molar ratio of 2:1;

[0156] After the alkali solution is mixed with the concentrated underflow, the solid-liquid mass ratio of the resulting system is 1:8;

[0157] (4-2) mixing the filter cake obtained in step (4-1) with carbon powder having a particle size of less than 200 mesh in a mass ratio of 6:1, performing a reduction heat treatment under a nitrogen atmosphere, and then water cooling and magnetic separation at a magnetic field strength of 50 mT to obtain an iron concentrate;

[0158] The reduction heat treatment includes a first temperature increase, a second temperature increase and a heat preservation treatment performed in sequence;

[0159] The first heating rate is 15°C / min, and the end temperature is 500°C;

[0160] The second heating rate is 10°C / min, and the end temperature is 650°C

[0161] The temperature of the heat preservation treatment is the end temperature of the second heating, and the time is 30 minutes.

[0162] Example 2

[0163] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, the recycling method comprising:

[0164] (1-1) Crushing the laterite nickel ore into ore powder with a particle size of 100-200 mesh, re-selecting to obtain chromium concentrate, and concentrating the remaining slurry in a thickener to a solid content of 36wt%;

[0165] (1-2) The concentrated slurry is heated to 200° C. and subjected to high-pressure acid leaching to obtain leached nickel and a slurry containing high-pressure acid leaching tailings of laterite nickel ore;

[0166] The high-pressure acid leaching temperature is 250°C, the pressure is 4.6 MPa, and the time is 60 minutes;

[0167] The acid used in the high-pressure acid leaching is 98 wt% concentrated sulfuric acid, and the acid-ore ratio is 280 g / t;

[0168] (2) countercurrent washing a slurry containing high-pressure acid leaching tailings of laterite nickel ore to obtain an overflow wash liquid and a concentrated underflow with a solid content of 36 wt%; the countercurrent washing comprises four stages, which are respectively carried out in thickeners CCD1, CCD2, CCD3, and CCD4, wherein the overflow liquid of the first stage countercurrent washing is the overflow wash liquid, and the underflow of the fourth stage countercurrent washing is the concentrated underflow;

[0169] The wash water ratio of the countercurrent washing is 1.5:1;

[0170] The overflow washing liquid is neutralized and the concentrated underflow is subjected to alkaline washing and desulfurization treatment; the neutralization treatment and alkaline washing and desulfurization treatment are not prioritized;

[0171] The neutralization treatment includes pre-neutralization treatment, first-stage neutralization to remove iron and aluminum, second-stage neutralization to remove iron and aluminum, first-stage nickel and cobalt precipitation, and second-stage nickel and cobalt precipitation.

[0172] (3-1) Pre-neutralization treatment: 4-stage pre-neutralization is performed in 4 pre-neutralization tanks connected in series. The pH value of the second iron and aluminum removal underflow and the second nickel and cobalt precipitation underflow used in the first stage pre-neutralization are adjusted. In the subsequent pre-neutralization process, a calcium carbonate slurry with a mass concentration of 28% is continuously added to adjust the pH value of the overflow wash liquid to 2. The resulting slurry is subjected to a second-stage neutralization countercurrent washing with a wash water ratio of 0.8:1, which is carried out in thickeners CCD5 and CCD6 respectively. The overflow liquid of the first stage neutralization countercurrent washing is the neutralization overflow liquid, and the underflow of the second stage neutralization countercurrent washing is the neutralization tailings. The resulting neutralization overflow liquid is subjected to the subsequent first-stage neutralization to remove iron and aluminum.

[0173] (3-2) One-stage neutralization and aluminum removal: Under air aeration, the pH value of the neutralization overflow liquid was adjusted to 4 using a 28 wt% calcium carbonate slurry. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a first aluminum-removed underflow and a first aluminum-removed overflow liquid. The resulting first aluminum-removed overflow liquid was subsequently subjected to two-stage neutralization and aluminum-removal.

[0174] 75 wt% of the obtained first iron-aluminum removal underflow is used as seeds for the first stage of neutralization and iron-aluminum removal, and the rest is mixed with the neutralization tailings;

[0175] (3-3) Second-stage neutralization and deironing: Under air ventilation, the pH of the first deironing overflow was adjusted to 5 using a 28 wt% calcium carbonate slurry. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a second deironing underflow and a second deironing overflow. The resulting second deironing overflow was then subjected to a subsequent first-stage nickel and cobalt precipitation.

[0176] 75wt% of the obtained second iron and aluminum removal bottom flow is used as seed crystals for the second stage neutralization and iron and aluminum removal, and the rest is returned to the pre-neutralization treatment;

[0177] (3-4) One-stage nickel and cobalt precipitation: The pH value of the second iron and aluminum removal overflow liquid is adjusted to 8 using an 8 wt% sodium hydroxide solution. The resulting slurry is subjected to solid-liquid separation in a thickener to obtain a first-stage nickel and cobalt precipitation underflow and a first-stage nickel and cobalt precipitation overflow liquid. The resulting first-stage nickel and cobalt precipitation overflow liquid is then subjected to a subsequent second-stage nickel and cobalt precipitation;

[0178] 75 wt% of the obtained first stage nickel-cobalt precipitation underflow is used as seed crystals for the first stage nickel-cobalt precipitation, and the rest is used as the finished product;

[0179] (3-5) Second stage nickel and cobalt precipitation: The pH value of the overflow liquid from the first stage nickel and cobalt precipitation was adjusted to 8.5 using 18 wt% lime milk, and the resulting slurry was subjected to solid-liquid separation in a thickener to obtain a second stage nickel and cobalt precipitation underflow and a second stage nickel and cobalt precipitation overflow liquid;

[0180] 75wt% of the obtained second-stage nickel-cobalt underflow is used as seed crystals for the second-stage nickel-cobalt precipitation, and the remainder is returned to the pre-neutralization treatment;

[0181] The alkaline washing and desulfurization treatment comprises:

[0182] (4-1) The bottom flow is concentrated and filtered to obtain a filter cake containing solid material and a filtrate, and the alkali solution and the solid material are stirred and mixed at 70° C. to perform alkali washing. The slurry after alkali washing is subjected to solid-liquid separation, and the bottom flow after solid-liquid separation is filtered to obtain a filter cake and a filtrate; the filtrate is mixed with the neutralization tailings;

[0183] The stirring time is 70 min;

[0184] The concentration of the alkali solution is 2.5 mol / L, and the alkaline substance includes sodium carbonate and sodium hydroxide in a molar ratio of 1:1;

[0185] After the alkali solution is mixed with the concentrated underflow, the solid-liquid mass ratio of the resulting system is 1:7;

[0186] (4-2) mixing the filter cake obtained in step (4-1) with carbon powder having a particle size of less than 200 mesh in a mass ratio of 5:1, performing a reduction heat treatment under a nitrogen atmosphere, and then water-cooling and magnetic separation at a magnetic field strength of 50 mT to obtain an iron concentrate;

[0187] The reduction heat treatment includes a first temperature increase, a second temperature increase and a heat preservation treatment performed in sequence;

[0188] The first heating rate is 12°C / min, and the end temperature is 480°C;

[0189] The second heating rate is 8°C / min, and the end temperature is 640°C

[0190] The temperature of the heat preservation treatment is the end temperature of the second heating, and the time is 35 minutes.

[0191] Example 3

[0192] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, the recycling method comprising:

[0193] (1-1) Crushing the laterite nickel ore into ore powder with a particle size of 100-200 mesh, re-selecting to obtain chromium concentrate, and concentrating the remaining slurry in a thickener to a solid content of 40wt%;

[0194] (1-2) The concentrated slurry is heated to 210° C. and subjected to high-pressure acid leaching to obtain leached nickel and a slurry containing high-pressure acid leaching tailings of laterite nickel ore;

[0195] The high-pressure acid leaching temperature is 260°C, the pressure is 5.0 MPa, and the time is 50 minutes;

[0196] The acid used in the high-pressure acid leaching is 98 wt% concentrated sulfuric acid, and the acid-ore ratio is 320 g / t;

[0197] (2) countercurrent washing a slurry containing high-pressure acid leaching tailings of laterite nickel ore to obtain an overflow wash liquid and a concentrated underflow with a solid content of 36 wt%; the countercurrent washing comprises four stages, which are respectively carried out in thickeners CCD1, CCD2, CCD3, and CCD4, wherein the overflow liquid of the first stage countercurrent washing is the overflow wash liquid, and the underflow of the fourth stage countercurrent washing is the concentrated underflow;

[0198] The wash water ratio of the countercurrent washing is 1.8:1;

[0199] The overflow washing liquid is neutralized and the concentrated underflow is subjected to alkaline washing and desulfurization treatment; the neutralization treatment and alkaline washing and desulfurization treatment are not prioritized;

[0200] The neutralization treatment includes pre-neutralization treatment, first-stage neutralization to remove iron and aluminum, second-stage neutralization to remove iron and aluminum, first-stage nickel and cobalt precipitation, and second-stage nickel and cobalt precipitation.

[0201] (3-1) Pre-neutralization treatment: 4-stage pre-neutralization is performed in 4 pre-neutralization tanks connected in series. The pH value of the second iron and aluminum removal underflow and the second nickel and cobalt precipitation underflow used in the first stage pre-neutralization are adjusted. In the subsequent pre-neutralization process, a calcium carbonate slurry with a mass concentration of 32% is continuously added to adjust the pH value of the overflow wash liquid to 2. The resulting slurry is subjected to a second-stage neutralization countercurrent washing with a wash water ratio of 1.2:1, which is carried out in thickeners CCD5 and CCD6 respectively. The overflow liquid of the first stage neutralization countercurrent washing is the neutralization overflow liquid, and the underflow of the second stage neutralization countercurrent washing is the neutralization tailings. The resulting neutralization overflow liquid is subjected to the subsequent first-stage neutralization to remove iron and aluminum.

[0202] (3-2) One-stage neutralization and aluminum removal: Under air-aeration conditions, the pH value of the neutralization overflow liquid was adjusted to 3.6 using a 32 wt% calcium carbonate slurry. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a first aluminum-removed underflow and a first aluminum-removed overflow liquid. The resulting first aluminum-removed overflow liquid was subsequently subjected to two-stage neutralization and aluminum-removal.

[0203] 85 wt% of the obtained first iron- and aluminum-removing underflow is used as seeds for the first stage of neutralization and iron- and aluminum-removing, and the remainder is mixed with the neutralization tailings;

[0204] (3-3) Second-stage neutralization and deironing: Under air ventilation, the pH of the first deironing overflow was adjusted to 4.6 using a 32 wt% calcium carbonate slurry. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a second deironing underflow and a second deironing overflow. The resulting second deironing overflow was then subjected to subsequent first-stage nickel and cobalt precipitation.

[0205] 85wt% of the obtained second iron and aluminum removal bottom flow is used as seed crystals for the second stage neutralization and iron and aluminum removal, and the rest is returned to the pre-neutralization treatment;

[0206] (3-4) One-stage nickel and cobalt precipitation: The pH of the second iron and aluminum removal overflow solution was adjusted to 7.6 using a 12 wt% sodium hydroxide solution. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a first-stage nickel and cobalt precipitation underflow and a first-stage nickel and cobalt precipitation overflow solution. The first-stage nickel and cobalt precipitation overflow solution was then subjected to a subsequent second-stage nickel and cobalt precipitation.

[0207] 85 wt% of the obtained first stage nickel-cobalt precipitation underflow is used as seed crystals for the first stage nickel-cobalt precipitation, and the rest is used as the finished product;

[0208] (3-5) Second stage nickel and cobalt precipitation: The pH value of the overflow liquid from the first stage nickel and cobalt precipitation was adjusted to 8.5 using lime milk having a mass concentration of 22 wt %. The resulting slurry was subjected to solid-liquid separation in a thickener to obtain a second stage nickel and cobalt precipitation underflow and a second stage nickel and cobalt precipitation overflow liquid;

[0209] 85wt% of the obtained second-stage nickel-cobalt underflow is used as seed crystals for the second-stage nickel-cobalt precipitation, and the remainder is returned to the pre-neutralization treatment;

[0210] The alkaline washing and desulfurization treatment comprises:

[0211] (4-1) Concentrating the underflow and performing filter pressing to obtain a filter cake containing solid material and a filtrate, stirring and mixing the alkali solution and the solid material at 80° C. to perform alkali washing, performing solid-liquid separation on the slurry after alkali washing, and performing filter pressing to obtain a filter cake and a filtrate after the solid-liquid separation; the filtrate is mixed with the neutralization tailings;

[0212] The stirring time is 50 min;

[0213] The concentration of the alkali solution is 3.5 mol / L, and the alkaline substance includes sodium carbonate and sodium hydroxide in a molar ratio of 3:1;

[0214] After the alkali solution is mixed with the concentrated underflow, the solid-liquid mass ratio of the resulting system is 1:9;

[0215] (4-2) mixing the filter cake obtained in step (4-1) with carbon powder having a particle size of less than 200 mesh in a mass ratio of 8:1, performing a reduction heat treatment under a nitrogen atmosphere, and then water cooling and magnetic separation at a magnetic field strength of 50 mT to obtain an iron concentrate;

[0216] The reduction heat treatment includes a first temperature increase, a second temperature increase and a heat preservation treatment performed in sequence;

[0217] The first heating rate is 18°C / min, and the end temperature is 520°C;

[0218] The second heating rate is 12°C / min, and the end temperature is 660°C

[0219] The temperature of the heat preservation treatment is the end temperature of the second heating, and the time is 25 minutes.

[0220] Example 4

[0221] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, which is the same as that of Example 1 except that the alkaline substance in step (4-1) is only sodium carbonate.

[0222] Example 5

[0223] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, which is the same as that of Example 1 except that the alkaline substance in step (4-1) is only sodium hydroxide.

[0224] Example 6

[0225] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. Except that in step (4-1), the alkali solution is mixed with the concentrated underflow and the solid-liquid mass ratio of the obtained system is 1:6, the rest is the same as Example 1.

[0226] Example 7

[0227] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. Except that in step (4-1), the alkali solution is mixed with the concentrated underflow and the solid-liquid mass ratio of the obtained system is 1:10, the rest is the same as Example 1.

[0228] Example 8

[0229] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. Except for directly heating the temperature to 650°C at a rate of 15°C / min and then performing a heat preservation treatment for 30 minutes, the rest is the same as Example 1.

[0230] Example 9

[0231] This embodiment provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore. Except for directly heating the temperature to 650°C at a rate of 10°C / min and then performing a heat preservation treatment for 30 minutes, the rest is the same as Example 1.

[0232] Comparative Example 1

[0233] This comparative example provides a method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, which is the same as Example 1 except that no alkali washing is performed, but the solids in the concentrated underflow are dried and then step (4-2) is directly performed.

[0234] The Fe content, Si content and S content in the iron concentrates obtained in Examples 1-9 and Comparative Example 1 were tested, and the Fe content, Si content and S content in the high-pressure acid leaching tailings of the laterite nickel ore obtained were tested. The results are shown in Table 1.

[0235] Among them, the test method for Fe content is obtained by titration using the titanium trichloride-potassium dichromate method specified in GB / T 6730.65-2016;

[0236] Sulfur content is obtained according to the barium sulfate weight method specified in GB / T 6730.16-2016;

[0237] The silicon content was obtained using the molybdenum blue colorimetric method specified in GB / T 6730-2016.

[0238] Table 1

[0239] In the above embodiments and comparative examples, the mass percentage of the neutralized tailings as the high-pressure acid leaching tailings of laterite nickel ore and the recovery rate of Fe were tested, and the results are shown in Table 2.

[0240] Table 2

[0241] In summary, the recycling method provided by this application reduces the sulfur content in the concentrated underflow through alkaline washing and desulfurization. After reduction heat treatment and magnetic separation, the sulfur content of the resulting iron concentrate is within 0.1wt%, the SiO2 content is within 10wt%, and the iron content is stable at above 60wt%, meeting the C60 standard for magnetite concentrate. In addition, the recycling method provided by this application can fully utilize the tailings from high-pressure acid leaching of laterite nickel ore, reducing tailings emissions, improving economic efficiency, and being environmentally friendly.

[0242] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for recycling iron in high-pressure acid leaching tailings of laterite nickel ore, the recycling method comprising the following steps: Countercurrent washing of ore pulp containing high-pressure acid leaching tailings of laterite nickel ore to obtain overflow washing liquid and concentrated underflow; the overflow washing liquid is subjected to neutralization treatment, and the concentrated underflow is subjected to alkaline washing and desulfurization treatment; The alkaline washing and desulfurization treatment comprises: (I) concentrating the underflow for solid-liquid separation, mixing the obtained solid-containing material with alkali solution for alkali washing, performing solid-liquid separation on the slurry after alkali washing, and filtering the underflow of the solid-liquid separation to obtain a filter cake; (II) the filter cake obtained in step (I) is mixed with a reducing agent, subjected to reduction heat treatment under a protective atmosphere, and subjected to magnetic separation after cooling to obtain an iron concentrate; The neutralization treatment includes pre-neutralization treatment, first-stage neutralization to remove iron and aluminum, second-stage neutralization to remove iron and aluminum, first-stage nickel and cobalt precipitation and second-stage nickel and cobalt precipitation which are carried out in sequence.

2. The recycling method according to claim 1, wherein: The alkaline substance in the alkali solution of step (I) includes sodium carbonate and sodium hydroxide; Optionally, in the alkali solution of step (I), the molar ratio of sodium carbonate to sodium hydroxide is (1-3):1; Optionally, the concentration of the alkali solution in step (I) is 2.5-3.5 mol / L.

3. The recycling method according to claim 1 or 2, wherein: The solid content of the concentrated underflow in step (I) is 36-40wt%; Optionally, after the alkali solution in step (I) is mixed with the solid-containing material, the solid-liquid mass ratio of the obtained system is 1:(7-9); Optionally, the mixing temperature in step (I) is 70-80° C. and the mixing time is 50-70 min.

4. The recycling method according to any one of claims 1 to 3, wherein: The reducing agent in step (II) comprises carbon powder; Optionally, the particle size of the reducing agent in step (II) is less than 200 mesh; Optionally, the mass ratio of the filter cake to the reducing agent in step (II) is (5-8):1; Optionally, the reduction heat treatment in step (II) includes a first heating, a second heating and a heat preservation treatment performed sequentially; Optionally, the first heating rate is 12-18°C / min, and the end temperature is 480-520°C; Optionally, the second heating rate is 8-12°C / min, and the end temperature is 640-660°C; Optionally, the temperature of the heat preservation treatment is the end point temperature of the second heating, and the time is 25-35 minutes.

5. The recycling method according to any one of claims 1 to 4, wherein: The number of washing stages of the countercurrent washing is at least 4, the overflow liquid of the first stage of countercurrent washing is the overflow washing liquid, and the underflow of the last stage of countercurrent washing is the concentrated underflow; Optionally, the wash water ratio of the countercurrent washing is (1.5-1.8):

1.

6. The recycling method according to any one of claims 1 to 5, wherein: The pre-neutralization treatment comprises: The pH value of the overflow washing liquid is adjusted to be above 2, and the obtained slurry is subjected to neutralization countercurrent washing to obtain neutralized tailings and neutralized overflow liquid; The obtained neutralized overflow liquid is subjected to subsequent neutralization to remove iron and aluminum; Optionally, the wash water ratio of the neutralization countercurrent washing is (0.8-1.2):

1.

7. The recycling method according to claim 6, wherein: The one-stage neutralization and iron removal includes: In an oxygen atmosphere, the pH value of the neutralized overflow liquid is adjusted to 3.6-4, and the obtained slurry is subjected to solid-liquid separation to obtain a first iron-removal aluminum underflow and a first iron-removal aluminum overflow liquid; The obtained first iron-aluminum-removing overflow liquid is subjected to subsequent two-stage neutralization to remove iron and aluminum; Optionally, a calcium carbonate slurry having a mass concentration of 28-32 wt% is used to adjust the pH value of the neutralized overflow liquid to 3.6-4; Optionally, the second stage neutralization and iron removal includes: In an oxygen atmosphere, the pH value of the first iron removal and aluminum removal overflow liquid is adjusted to 4.6-5, and the obtained slurry is subjected to solid-liquid separation to obtain a second iron removal and aluminum removal underflow and a second iron removal and aluminum removal overflow liquid; The obtained second iron and aluminum removal overflow liquid is subsequently subjected to a first stage of nickel and cobalt precipitation; Optionally, the pH value of the first iron and aluminum removal overflow liquid is adjusted to 4.6-5 using calcium carbonate slurry with a mass concentration of 28-32wt%.

8. The recycling method according to claim 7, wherein: The one-stage nickel-cobalt precipitation comprises: The pH value of the second iron and aluminum removal overflow liquid is adjusted to 7.6-8, and the obtained slurry is subjected to solid-liquid separation to obtain a section of nickel and cobalt precipitation underflow and a section of nickel and cobalt precipitation overflow liquid; The obtained first stage nickel-cobalt precipitation overflow liquid is subsequently subjected to second stage nickel-cobalt precipitation; Optionally, a sodium hydroxide solution with a mass concentration of 8-12 wt% is used to adjust the pH value of the second iron and aluminum removal overflow liquid to 7.6-8; Optionally, the second stage nickel-cobalt deposition includes: The pH value of the first stage nickel-cobalt precipitation overflow liquid is adjusted to be above 8.5, and the obtained slurry is subjected to solid-liquid separation to obtain the second stage nickel-cobalt precipitation underflow and the second stage nickel-cobalt precipitation overflow liquid; Optionally, lime milk with a mass concentration of 18-22 wt % is used to adjust the pH value of the first stage nickel-cobalt precipitation overflow liquid to above 8.

5.

9. The recycling method according to claim 8, wherein: The pre-neutralization treatment includes at least 2 levels of pre-neutralization; The pH value of the second iron and aluminum removal underflow and / or the second nickel and cobalt precipitation underflow used in the first stage pre-neutralization is adjusted; The final stage is pre-neutralization, adjusting the pH value to above 2; Optionally, the neutralization countercurrent washing has at least two washing stages, the overflow liquid of the first stage of neutralization countercurrent washing is the neutralization overflow liquid, and the underflow of the last stage of neutralization countercurrent washing is the neutralization tailings.

10. The recycling method according to any one of claims 1 to 9, wherein: The slurry containing high pressure acid leaching tailings of laterite nickel ore is prepared by the following method: (a) crushing laterite nickel ore into ore powder, re-selecting to obtain chromium concentrate, and concentrating the remaining slurry to a solid content of 36-40wt%; (b) the concentrated slurry is heated to 200-210° C. and subjected to high pressure acid leaching to obtain leached nickel and a slurry containing high pressure acid leaching tailings of laterite nickel ore; Optionally, the high pressure acid leaching has a temperature of 250-260°C, a pressure of 4.6-5.0 MPa, and a time of 50-60 min; Optionally, the acid used in the high-pressure acid leaching is sulfuric acid, and the acid-ore ratio is 280-320 g / t.

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