Multi-stage combined leaching method for ultralow-grade laterite-nickel ore

Abstract

The invention provides an ultralow-grade laterite-nickel ore multistage combined leaching method which comprises the steps that firstly, high-pressure acid leaching treatment is conducted on laterite-nickel ore raw ore pulp, high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching liquid containing nickel, cobalt and manganese are obtained, and the mass percent of nickel in the laterite-nickel ore raw ore pulp is smaller than 1.0%; secondly, mixing the high-pressure leachate, the laterite-nickel ore raw ore pulp and an acid solution to obtain a mixed solution, performing multi-stage normal-pressure leaching treatment on the mixed solution, and performing concentration treatment to obtain a final-stage concentrated normal-pressure leachate and final-stage concentrated normal-pressure leaching slurry with the same ore pulp concentration as the laterite-nickel ore raw ore pulp; and finally, the final-stage concentrated normal-pressure leaching liquid and the high-pressure leaching tailings are sequentially subjected to circulating leaching, multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment, and the cobalt nickel hydroxide product is obtained. According to the method, the scaling rate of conventional high-pressure acid leaching treatment can be effectively inhibited, and the production period is prolonged.

Description

Technical Field

[0001] The present application relates to the field of metallurgy technology, and in particular to a multi-stage combined leaching method for ultra-low-grade laterite nickel ore. Background Art

[0002] With the booming development of my country's new energy vehicle industry and the gradual depletion of high-quality nickel and cobalt resources, demand for Ni, Co, and Mn metals in new energy ternary materials is increasing. The development of laterite nickel ores, which have large reserves but ultra-low nickel grades, has become a hot topic in the industry. The hydrometallurgical route of sulfuric acid leaching under high-temperature and high-pressure conditions is currently one of the mainstream smelting processes for ultra-low-grade laterite nickel ores.

[0003] However, during the high pressure and high temperature leaching process, due to the 3+ and Al 3+ The hydrolysis and precipitation of metal ions, the precipitation of low-solubility substances such as CaSO4, and the precipitation of solid-phase impurities such as SiO2 in minerals can form scale on the walls of high-pressure reactors, the impeller surfaces, the inner walls of reactor discharge pipes, and valves. This can lead to a series of production-damaging problems, including blockage of discharge pipes and valves, increased pressure drop, and reduced reactor volume. Currently, the main method for combating scale formation in actual production is to regularly shut down the autoclave for scale removal. However, frequent shutdowns and starts can reduce production efficiency and cause fluctuations in production process indicators.

[0004] Therefore, in the high-pressure leaching process of laterite nickel ore, how to effectively reduce the scaling rate of the high-pressure reactor and extend the production time is a technical problem that needs to be solved urgently by people in this field. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which aims to solve the technical problem of low production efficiency of nickel cobalt hydroxide products due to the rapid scaling rate of the high-pressure reactor during the high-pressure acid leaching process of existing ultra-low-grade laterite nickel ore.

[0006] The present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, comprising: S10, performing high-pressure acid leaching on the laterite nickel ore pulp to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and a high-pressure leaching solution containing nickel, cobalt and manganese, wherein the mass percentage of nickel in the laterite nickel ore pulp is less than 1.0%; S20, mixing the high-pressure leaching solution, the laterite nickel ore pulp and the acidic solution to obtain a mixed solution, and subjecting the mixed solution to a multi-stage normal pressure leaching treatment, to obtain a final-stage concentrated normal pressure leaching solution and a final-stage concentrated normal pressure leaching slurry after concentration treatment, wherein the pulp concentration of the final-stage concentrated normal pressure leaching slurry is the same as the pulp concentration of the laterite nickel ore pulp; S30, subjecting the final concentrated atmospheric pressure leachate and the high pressure leach tailings to cyclic leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment, and MHP precipitation treatment in sequence to obtain a nickel cobalt hydroxide product; After step S20 is completed, the process further includes returning the final concentrated atmospheric pressure leaching slurry to step S10 for high-pressure acid leaching.

[0007] Preferably, in step S10, the slurry concentration of the laterite nickel ore slurry is 30-40%, and the slurry capacity ratio is 100-200m 3 / ton of metallic nickel.

[0008] Preferably, in step S10, the process conditions for the high-pressure acid leaching treatment are: temperature 220-260° C., and pressure 2.0-6.0 MPa.

[0009] Preferably, in step S20, the mass ratio of the high-pressure leaching solution, the laterite nickel ore slurry and the acidic solution is 1: (0.8-1): (1-2); the acidic solution includes sulfuric acid or hydrogen chloride.

[0010] Preferably, in step S20, the temperature of the multi-stage atmospheric pressure leaching treatment is 60-90°C.

[0011] Preferably, in step S20, a thickener is used to concentrate the mixed liquor after the multi-stage atmospheric pressure leaching treatment to obtain a final-stage concentrated atmospheric pressure leachate and a final-stage concentrated atmospheric pressure leaching slurry.

[0012] Preferably, in step S20, the number of normal pressure leaching stages of the multi-stage normal pressure leaching treatment is 2 to 10.

[0013] Preferably, in the cyclic leaching and multi-stage pre-neutralization treatment in step S30: the controlled temperature of the cyclic leaching is 70~90°C; the pH of the multi-stage pre-neutralization is 0.8~2, and the neutralizing agent of the multi-stage pre-neutralization is an alkaline mixture of any one or more of lime milk, limestone, sodium hydroxide, magnesia ore, and magnesium hydroxide.

[0014] Preferably, in step S30, the number of washing stages of the countercurrent washing treatment is 3 to 9; the process conditions for iron, aluminum and chromium removal are: the number of process stages is 2 to 7, the control temperature is 55 to 90° C., and the pH value is 2.5 to 5.5.

[0015] Preferably, in the nickel cobalt hydroxide product of step S30, the mass percentage of nickel is 30-40%, and the mass percentage of cobalt is 3.0-6.0%.

[0016] The beneficial effect of the present application is that, unlike the prior art, the present application mixes the high-pressure leachate obtained after high-pressure acid leaching treatment of laterite nickel ore pulp, the laterite nickel ore pulp and the acidic solution and then performs multi-stage atmospheric pressure leaching treatment, which can avoid scaling of the high-pressure reactor due to excessive accumulation of the high-pressure leachate during the high-pressure acid leaching treatment. At the same time, since the reaction conditions of the multi-stage atmospheric pressure leaching treatment are milder than those of the high-pressure acid leaching treatment, the scaling rate of the high-pressure leachate can be effectively suppressed, thereby extending the treatment time of the acid leaching treatment, and ultimately improving the production efficiency of the nickel cobalt hydroxide product and reducing the production cost of the nickel cobalt hydroxide product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0018] Figure 1 A schematic flow chart of a multi-stage combined leaching method for ultra-low-grade laterite nickel ore provided in an embodiment of the present application; Figure 2 This is a schematic diagram of the specific process of the multi-stage combined leaching method for ultra-low-grade laterite nickel ore provided in Example 1 of the present application. DETAILED DESCRIPTION

[0019] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0021] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0022] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0024] In order to solve the technical problem that the production efficiency of nickel cobalt hydroxide products is too low due to the rapid scaling rate of the high-pressure reactor during the high-pressure acid leaching process of existing ultra-low-grade laterite nickel ore, the present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, wherein the reaction conditions of the above method are milder than those of conventional high-pressure acid leaching treatment, and the scaling rate of the high-pressure leachate can be effectively suppressed, thereby delaying the treatment time of the high-pressure acid leaching treatment, and ultimately improving the production efficiency of the nickel cobalt hydroxide product and reducing the production cost of the nickel cobalt hydroxide product.

[0025] See also Figure 1 , Figure 1 A schematic flow chart of a multi-stage combined leaching method for ultra-low-grade laterite nickel ore provided in an embodiment of the present application; wherein the method comprises the following steps: S10, performing high-pressure acid leaching on the laterite nickel ore pulp to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and a high-pressure leaching solution containing nickel, cobalt and manganese, wherein the mass percentage of nickel in the laterite nickel ore pulp is less than 1.0%.

[0026] Specifically, step S10 further includes: First, natural laterite nickel ore raw material is provided. After pre-treatment steps of ore dressing and ore grinding, ultra-low-grade laterite nickel ore is obtained, and the mass percentage of nickel in the ultra-low-grade laterite nickel ore is less than 1.0%. Among them, the ore dressing steps specifically include gravity separation and magnetic separation.

[0027] Afterwards, the ultra-low-grade laterite nickel ore is mixed with water to prepare laterite nickel ore slurry. The slurry concentration of the laterite nickel ore slurry is 30-40%, and the slurry capacity ratio is 100-200m 3 / ton of metallic nickel, the mass percentage of nickel in the laterite nickel ore slurry is less than 1.0%; such concentration selection is based on comprehensive considerations, which require both ensuring sufficient solid content to maintain the efficiency of subsequent reactions and treatments, and ensuring that the slurry has appropriate fluidity and operability.

[0028] Finally, the laterite nickel ore pulp is subjected to high-pressure acid leaching treatment to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching liquid containing nickel, cobalt and manganese. The process of high-pressure acid leaching treatment of the laterite nickel ore pulp specifically includes: (1) The raw ore pulp of laterite nickel ore is subjected to high-pressure acid leaching treatment, and the leached ore pulp is obtained by multi-stage flash preheating; wherein, the process conditions of high-pressure acid leaching treatment are: temperature 220~260℃, pressure 2.0~6.0MPa, and acid consumption 15-25 tons / ton of nickel.

[0029] Specifically, multi-stage flash preheating can achieve more efficient heat transfer, quickly increase the slurry temperature, and meet subsequent process requirements. At the same time, it can fully recycle and utilize waste heat in the system, reduce overall energy consumption, and improve energy utilization efficiency.

[0030] (2) subjecting the leached slurry to solid-liquid separation to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese. After the high-pressure acid leaching treatment, the high-pressure leaching tailings containing iron, aluminum, and magnesium have a Ni content of less than 0.05%, a Co content of less than 0.005%, and a Mn content of less than 0.05%.

[0031] Specifically, a reducing agent and a leaching accelerator are added during the high-pressure acid leaching process. The reducing agent includes lignite, ferrous sulfate, sodium sulfite, sodium bisulfite, etc., and the leaching accelerator is any one or more of sodium sulfate and copper sulfate.

[0032] Among them, the addition of reducing agents can, on the one hand, inhibit the transformation of divalent manganese ions to a high-valent state, which is beneficial to the subsequent extraction of manganese; on the other hand, it is beneficial to the subsequent multi-stage neutralization process, converting hexavalent chromium into trivalent chromium, which facilitates chromium removal; the introduction of leaching promoters can promote the leaching of nickel, cobalt and manganese.

[0033] S20, mixing the high-pressure leaching solution, the laterite nickel ore slurry and the acidic solution to obtain a mixed solution, and performing multi-stage atmospheric pressure leaching treatment on the mixed solution. After concentration treatment, a final concentrated atmospheric pressure leaching solution and a final concentrated atmospheric pressure leaching slurry are obtained, and the pulp concentration of the final concentrated atmospheric pressure leaching slurry is the same as the pulp concentration of the laterite nickel ore slurry.

[0034] Specifically, step S20 further includes: First, a high-pressure leaching solution, a laterite nickel ore pulp and an acidic solution are mixed to obtain a mixed solution, and the mixed solution is subjected to a multi-stage atmospheric pressure leaching treatment to obtain a mixed solution; wherein, the high-pressure leaching solution, the laterite nickel ore pulp and the acidic solution are mixed in a specific proportion. This mixing method is to adjust the composition and conditions to facilitate the subsequent multi-stage atmospheric pressure leaching treatment.

[0035] Preferably, the mass ratio of the high-pressure leaching solution, the laterite nickel ore slurry and the acidic solution is 1: (0.8~1): (1~2); the above mass ratio ensures that the relative content of each component is within an appropriate range, which can not only ensure the sufficient progress of the reaction, but also achieve the economic rationality of the process.

[0036] Preferably, the acidic solution includes sulfuric acid or hydrogen chloride; they are common strong acids that can effectively promote the relevant reactions. Sulfuric acid has a wide range of applications and good reaction performance, while hydrogen chloride may also have specific advantages in certain situations.

[0037] Preferably, the process conditions for each stage of the multi-stage atmospheric pressure leaching process are: temperature 60-90°C and pressure 0-0.1 MPa. This relatively mild temperature range helps control reaction rate and selectivity, while also reducing equipment requirements and operating costs. The pressure is close to atmospheric pressure, simplifying process operations and equipment requirements.

[0038] Preferably, the number of atmospheric pressure leaching stages in a multi-stage atmospheric pressure leaching process is 2 to 10. This reflects the design concept of gradually completing the leaching process through multiple stages. Multi-stage processing can improve leaching effectiveness and efficiency, ensuring a more complete and thorough reaction. It also facilitates precise control and optimization of reactions at different stages. By increasing the number of stages, the degree of leaching can be gradually increased, the recovery rate of valuable metals can be improved, and residual impurities can be reduced. This multi-stage design provides greater flexibility and controllability to adapt to different ore characteristics and product requirements.

[0039] Afterwards, a thickener is used to concentrate the mixed liquor after the multi-stage atmospheric pressure leaching treatment to obtain a final-stage concentrated atmospheric pressure leachate and a final-stage concentrated atmospheric pressure leaching slurry. The pulp concentration of the final-stage concentrated atmospheric pressure leaching slurry is the same as the pulp concentration of the laterite nickel ore pulp. The thickener can make the pulp concentration of the final-stage concentrated atmospheric pressure leaching slurry the same as the pulp concentration of the laterite nickel ore pulp, so that the final-stage concentrated atmospheric pressure leaching slurry meets the pulp conditions for high-pressure acid leaching treatment and is easy to recycle.

[0040] Specifically, the final concentrated atmospheric leaching slurry obtained by multi-stage atmospheric leaching can leach a portion of iron, aluminum and magnesium. This is because part of the Fe 3+ Mg 2+ and Al 3+ During the multi-stage atmospheric pressure leaching process, metal ions are hydrolyzed and precipitated, forming scale on the inner wall of the atmospheric pressure reactor. On the other hand, due to the other part of Fe 3+ Mg 2+ and Al 3+ The metal ions are dissolved in the final concentrated atmospheric pressure leachate.

[0041] Finally, the final concentrated atmospheric leaching slurry obtained meets the slurry conditions for high-pressure acid leaching treatment and can be returned to step S10 to be mixed with the laterite nickel ore slurry for high-pressure acid leaching treatment; this recycling method helps to maintain the balance of materials in the system, allowing the entire process to operate continuously and stably, reducing process fluctuations and potential problems caused by material imbalance.

[0042] In this step, the reasons why multi-stage atmospheric pressure leaching treatment can inhibit scaling are as follows: 1) Mild reaction conditions: The reaction conditions under normal pressure are relatively mild, without the drastic physical and chemical changes that occur under high pressure. Some reactions and precipitation processes that easily lead to scaling will be slowed down or less likely to occur.

[0043] 2) Difference in ion solubility: Under normal pressure and low temperature, the solubility of some substances is relatively large, and it is not easy to reach saturation and precipitate to form a scale layer. However, high pressure and high temperature may change the solubility and promote the formation of scale.

[0044] 3) Fluid dynamics: The flow state of the fluid under normal pressure is relatively stable, unlike the complex flow changes that may occur under high pressure, which reduces the possibility of material deposition and scaling due to local flow anomalies.

[0045] 4) Reaction rate: A lower reaction rate gives some potential scaling components more time to remain dissolved or evenly dispersed rather than quickly precipitating and accumulating.

[0046] 5) Impurity behavior: The reaction and transformation behavior of impurities at normal pressure is different from that at high pressure. Some impurity reaction pathways that may cause scaling are inhibited or changed.

[0047] 6) Difficulty of process control: The atmospheric pressure process is relatively easier to control, and the parameter fluctuations are smaller, thereby reducing the risk of scaling caused by process instability and process parameter disturbances.

[0048] S30, the final concentrated atmospheric pressure leachate and the high pressure leaching tailings are sequentially subjected to cyclic leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment to obtain nickel cobalt hydroxide product.

[0049] Specifically, step S30 further includes: First, the final concentrated atmospheric leachate is mixed with the high-pressure leach tailings and then subjected to cyclic leaching and multi-stage neutralization to obtain a neutralized slurry. In this step, the cyclic leaching process conditions are: controlling the temperature at 70-90°C and reducing the residual acid concentration from 30-50g / L to below 5g / L; the multi-stage pre-neutralization process conditions are: controlling the pH at 0.8-2 by adding a neutralizing agent; the neutralizing agent is an alkaline mixture of one or more of lime milk, limestone, sodium hydroxide, magnesia ore, and magnesium hydroxide.

[0050] Next, the neutralized slurry obtained through cyclic leaching and multi-stage pre-neutralization is subjected to countercurrent washing to produce a final liquid phase and a slag phase. The number of countercurrent washing stages ranges from 3 to 9. In this step, the ratio of wash water to slag phase is (1 to 7):1. The nickel content of the final liquid phase is less than 0.1 g / L, and the nickel content of the neutralized slag phase is less than 0.06%. During the multi-stage pre-neutralization process, an appropriate amount of neutralizing agent is added to neutralize the slag phase. The neutralized slag phase undergoes solid-liquid separation in a thickener to produce tailings with a pH of 6 to 9. The tailings primarily contain iron. The iron metal is then recovered through reduction roasting and magnetic separation. The tailings after iron metal recovery meet direct discharge standards and can be discharged directly, meeting environmentally friendly production expectations.

[0051] Afterwards, the final liquid phase after multi-stage countercurrent washing is subjected to multi-stage iron removal, aluminum chromium concentration and separation under the condition of adding a neutralizing agent and a precipitation promoter. In this step, the multi-stage iron removal consists of a first stage of iron removal, aluminum chromium removal, and a second stage and above of iron removal, and the liquid phase after the first stage of iron removal undergoes a second stage of iron removal, the slag phase after the first stage of iron removal is returned and subjected to multi-stage countercurrent washing again, and the slag phase after the second stage and above of iron removal is reused and subjected to cyclic leaching and multi-stage neutralization treatment again. Among them, the process conditions for multi-stage iron removal are: the number of process stages is 2 to 7, the control temperature is 55 to 90 ° C, and the pH is 2.5 to 5.5; the neutralizing agent is a mixture of any one or more of lime milk, limestone, sodium hydroxide, magnesia ore, and magnesium hydroxide; the precipitation promoter is a mixture of any one or more of organic polymers and inorganic polymers, such as polyacrylamide, polyaluminum chloride, etc., which are not limited here.

[0052] In a specific embodiment, the process conditions for the one-stage iron, aluminum and chromium removal are as follows: adding a neutralizing agent, charging compressed air, controlling the pH to 2.5-4.0, the temperature to 70-90°C, and the reaction time to 1-2 hours; wherein, after the one-stage iron, aluminum and chromium removal step is completed, a considerable portion of nickel, cobalt and manganese still exists in the slag phase, and the slag phase after the one-stage iron, aluminum and chromium removal is recycled and subjected to multi-stage countercurrent washing again, which is conducive to the full extraction of nickel, cobalt and manganese in the slag phase; in the one-stage iron, aluminum and chromium removal process, the simultaneous removal of iron, aluminum and chromium metals is achieved.

[0053] In a specific embodiment, the process conditions for the second and higher iron, aluminum and chromium removal are as follows: controlling the pH to be 4.0-5.5, the temperature to be 55-80°C, and the reaction time to be 2-10 hours. During the second and higher iron, aluminum and chromium removal process, the remaining iron, aluminum and chromium in the liquid phase can be further removed simultaneously, thereby improving the removal efficiency of impurity metal elements, thereby ensuring that a purer nickel, cobalt and manganese product can be extracted subsequently. The purpose of recycling the slag phase after the second and higher iron, aluminum and chromium removal and then performing the cyclic leaching and multi-stage neutralization treatment is that a certain amount of nickel, cobalt and manganese elements will still remain in the slag phase after the second and higher iron, aluminum and chromium removal, and recycling it again can extract as much nickel, cobalt and manganese as possible. At the same time, due to the large difference in pH value between the second and higher iron, aluminum and chromium removal and the cyclic leaching-multi-stage pre-neutralization treatment, recycling the slag phase after the second and higher iron, aluminum and chromium removal can reduce the amount of neutralizer used in the cyclic leaching-first neutralization treatment to a certain extent, thereby achieving the purpose of cost saving.

[0054] Finally, the tail liquid phase after multiple stages of iron, aluminum and chromium removal is subjected to MHP precipitation treatment to obtain a nickel cobalt hydroxide product; wherein the nickel cobalt hydroxide product has a nickel mass percentage of 30-40% and a cobalt mass percentage of 3.0-6.0%.

[0055] Specifically, the above-mentioned MHP precipitation treatment is a multi-stage nickel-cobalt synthesis process, which consists of a first-stage nickel-cobalt synthesis, a second-stage and above nickel-cobalt synthesis, and the liquid phase after the first-stage nickel-cobalt synthesis undergoes the second-stage nickel-cobalt synthesis, and the tail-stage liquid phase of the multi-stage iron, aluminum and chromium removal undergoes a first-stage nickel-cobalt synthesis treatment. After the first-stage nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The nickel-cobalt hydroxide product synthesized in the tail stage of the multi-stage nickel-cobalt synthesis is returned and subjected to a circular leaching and multi-stage neutralization treatment again, so that a small amount of nickel and cobalt remaining in the slag phase after the second-stage nickel and cobalt production can enter the process flow again for extraction, thereby improving the final extraction rate of nickel and cobalt elements; at the same time, the tail-stage liquid phase of the multi-stage nickel-cobalt synthesis is discharged after wastewater treatment.

[0056] In one embodiment, the process conditions for the one-stage synthesis of nickel and cobalt are: adding a neutralizing agent, controlling the pH value to 6.5-7.4, the temperature to 50-70° C., and the reaction time to 5-7 hours.

[0057] In one specific embodiment, the process conditions for the second-stage and above nickel-cobalt synthesis are: controlling the pH value to 7.5-10.0, the temperature to 40-90° C., and the reaction time to 0.5-1.5 h.

[0058] The effect of the multi-stage combined leaching method for ultra-low-grade laterite nickel ore is described below through specific examples.

[0059] Example 1: See also Figure 2 , Figure 2A schematic diagram of a specific process for a multi-stage combined leaching method for ultra-low-grade laterite nickel ore provided in Example 1 of the present application; wherein the method specifically comprises: (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (the following is the mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0060] (2) Lignite powder was added to the laterite nickel ore slurry with a mass ratio of 1000:1 to lignite, and the mixture was sent into a high-pressure reactor together with a sodium sulfate leaching promoter. The leaching reaction was carried out under high-pressure leaching conditions of a temperature of 255°C, a pressure of 4.0 MPa, and an acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese.

[0061] (3) The high-pressure leaching solution, the laterite nickel ore slurry and the acid solution were mixed in a mass ratio of 1:1:1.5 to obtain a mixed solution, and the mixed solution was transferred to a normal pressure reactor for multi-stage normal pressure leaching treatment; the process conditions of each stage of the multi-stage normal pressure leaching treatment were: temperature 80°C, pressure 0.1 MPa, and normal pressure leaching stage number 5.

[0062] (4) The mixed liquor after the multi-stage atmospheric pressure leaching treatment is concentrated by a thickener to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry. The ore pulp concentration of the final concentrated atmospheric pressure leaching slurry is 35%. The final concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry for high-pressure acid leaching treatment.

[0063] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leach tailings and then circulated for leaching and multi-stage neutralization. A multi-stage countercurrent washing process is then adopted with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in the thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to keep the slag phase in a neutral state with a pH of 6.8. The metallic iron is then recovered and the tailings are discharged.

[0064] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal, aluminum removal and chromium removal. The process conditions for the first stage of iron removal are as follows: temperature control of 85°C, pH of 3.0, and reaction time of 1 hour. The slag phase after the first stage of iron removal is recycled and subjected to continuous multi-stage countercurrent washing again. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal, aluminum removal and chromium removal. The process conditions for the second stage of iron removal are as follows: temperature control of 79°C, pH of 4.8, and reaction time of 3 hours. The slag phase after the second stage of iron removal is recycled and subjected to cyclic leaching and neutralization again.

[0065] (7) A neutralizing agent is added to the tail liquid phase after the second stage iron, aluminum and chromium removal to perform a first stage nickel-cobalt synthesis. After the first stage nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The process conditions for the first stage nickel-cobalt synthesis are: pH 7.0, reaction temperature 66°C, and reaction time 3 hours. The process conditions for the second stage nickel-cobalt synthesis are: pH 8.0, reaction temperature 50°C; wherein, the nickel-cobalt hydroxide product obtained has a nickel mass percentage of 31.13% and a cobalt mass percentage of 3.51%.

[0066] Example 2: Example 2 of the present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which specifically includes: (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (the following is the mass percentage), the nickel content in the ore was 0.6%, the cobalt content was 0.25%, the Cr2O3 content was 2.48%, the Al2O3 content was 9.45%, the SiO2 content was 18.67%, the Fe content was 35.14%, and the Mg content was 8.38%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0067] (2) Lignite powder was added to the laterite nickel ore slurry with a mass ratio of 1000:1 to lignite, and the mixture was sent into a high-pressure reactor together with a sodium sulfate leaching promoter. The leaching reaction was carried out under high-pressure leaching conditions of a temperature of 255°C, a pressure of 4.0 MPa, and an acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese.

[0068] (3) The high-pressure leaching solution, the laterite nickel ore slurry and the acid solution were mixed in a mass ratio of 1:1:1.5 to obtain a mixed solution, and the mixed solution was transferred to a normal pressure reactor for multi-stage normal pressure leaching treatment; the process conditions of each stage of the multi-stage normal pressure leaching treatment were: temperature 80°C, pressure 0.1 MPa, and normal pressure leaching stage number 5.

[0069] (4) The mixed liquor after the multi-stage atmospheric pressure leaching treatment is concentrated by a thickener to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry. The ore pulp concentration of the final concentrated atmospheric pressure leaching slurry is 35%. The final concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry for high-pressure acid leaching treatment.

[0070] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leach tailings and then circulated for leaching and multi-stage neutralization. A multi-stage countercurrent washing process is then adopted with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in the thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to keep the slag phase in a neutral state of pH = 6.8. The metallic iron is then recovered and the tailings are discharged.

[0071] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal, aluminum removal and chromium removal. The process conditions for the first stage of iron removal are as follows: temperature control of 85°C, pH of 3.0, and reaction time of 1 hour. The slag phase after the first stage of iron removal is recycled and subjected to continuous multi-stage countercurrent washing again. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal, aluminum removal and chromium removal. The process conditions for the second stage of iron removal are as follows: temperature control of 79°C, pH of 4.8, and reaction time of 3 hours. The slag phase after the second stage of iron removal is recycled and subjected to cyclic leaching and neutralization again.

[0072] (7) A neutralizing agent is added to the tail liquid phase after the second stage of iron, aluminum and chromium removal, and a first stage of nickel-cobalt synthesis and a first stage of nickel-cobalt-manganese synthesis are performed to obtain a nickel-cobalt hydroxide product. The process conditions for the first stage of nickel-cobalt synthesis are: pH value 7.0, reaction temperature 66°C, and reaction time 3h. The liquid phase of the first stage of nickel-cobalt synthesis is subjected to a second stage of nickel-cobalt synthesis, and the slag phase of the second stage of nickel-cobalt synthesis is recycled for cyclic leaching and neutralization treatment again. The liquid phase of the second stage of nickel-cobalt synthesis is discharged after wastewater treatment. The process conditions for the second stage of nickel-cobalt synthesis are: pH value is controlled at 8.0, reaction temperature is 50°C; wherein, the nickel mass percentage of the obtained nickel-cobalt hydroxide product is 35.23%, and the cobalt mass percentage is 4.89%.

[0073] Example 3: Example 3 of the present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which specifically includes: (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (the following is the mass percentage), the nickel content in the ore was 0.8%, the cobalt content was 0.45%, the Cr2O3 content was 4.12%, the MnO content was 1.58%, the Al2O3 content was 9.81%, the SiO2 content was 12.18%, the Fe content was 33.27%, and the Mg content was 6.25%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0074] (2) Lignite powder was added to the laterite nickel ore slurry with a mass ratio of 1000:1 to lignite, and the mixture was sent into a high-pressure reactor together with a sodium sulfate leaching promoter. The leaching reaction was carried out under high-pressure leaching conditions of a temperature of 255°C, a pressure of 4.0 MPa, and an acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese.

[0075] (3) The high-pressure leaching solution, the laterite nickel ore slurry and the acid solution were mixed in a mass ratio of 1:1:1.5 to obtain a mixed solution, and the mixed solution was transferred to a normal pressure reactor for multi-stage normal pressure leaching treatment; the process conditions of each stage of the multi-stage normal pressure leaching treatment were: temperature 80°C, pressure 0.1 MPa, and normal pressure leaching stage number 5.

[0076] (4) The mixed liquor after the multi-stage atmospheric pressure leaching treatment is concentrated by a thickener to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry. The ore pulp concentration of the final concentrated atmospheric pressure leaching slurry is 35%. The final concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry for high-pressure acid leaching treatment.

[0077] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leach tailings and then circulated for leaching and multi-stage neutralization. A multi-stage countercurrent washing process is then adopted with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in the thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to keep the slag phase in a neutral state of pH = 6.8. The metallic iron is then recovered and the tailings are discharged.

[0078] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal, aluminum removal and chromium removal. The process conditions for the first stage of iron removal are as follows: temperature control of 85°C, pH of 3.0, and reaction time of 1 hour. The slag phase after the first stage of iron removal is recycled and subjected to continuous multi-stage countercurrent washing again. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal, aluminum removal and chromium removal. The process conditions for the second stage of iron removal are as follows: temperature control of 79°C, pH of 4.8, and reaction time of 3 hours. The slag phase after the second stage of iron removal is recycled and subjected to cyclic leaching and neutralization again.

[0079] (7) A neutralizing agent is added to the tail liquid phase after the second stage of iron, aluminum and chromium removal to perform a first stage nickel-cobalt synthesis. After the first stage nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The process conditions for the first stage nickel-cobalt synthesis are: pH value 7.0, reaction temperature 66°C, and reaction time 3h. The liquid phase of the first stage nickel-cobalt synthesis is subjected to a second stage nickel-cobalt synthesis. The slag phase of the second stage nickel-cobalt synthesis is recycled for further cyclic leaching and neutralization treatment. The liquid phase of the second stage nickel-cobalt synthesis is discharged after wastewater treatment. The process conditions for the second stage nickel-cobalt synthesis are: pH value controlled at 8.0 and reaction temperature 50°C.

[0080] The obtained nickel cobalt hydroxide product contains 38.63% nickel by mass and 5.25% cobalt by mass.

[0081] Example 4: Example 4 of the present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which specifically includes: (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (the following is the mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the MnO content was 2.13%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0082] (2) Lignite powder was added to the laterite nickel ore slurry with a mass ratio of 1000:1 to lignite, and the mixture was sent into a high-pressure reactor together with a sodium sulfate leaching promoter. The leaching reaction was carried out under high-pressure leaching conditions of a temperature of 255°C, a pressure of 4.0 MPa, and an acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese.

[0083] (3) The high-pressure leaching solution, the laterite nickel ore slurry and the acid solution were mixed in a mass ratio of 1:1:1.5 to obtain a mixed solution, and the mixed solution was transferred to a normal pressure reactor for multi-stage normal pressure leaching treatment; the process conditions of each stage of the multi-stage normal pressure leaching treatment were: temperature 80°C, pressure 0.1 MPa, and the number of normal pressure leaching stages was 8.

[0084] (4) The mixed liquor after the multi-stage atmospheric pressure leaching treatment is concentrated by a thickener to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry. The ore pulp concentration of the final concentrated atmospheric pressure leaching slurry is 35%. The final concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry for high-pressure acid leaching treatment.

[0085] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leach tailings and then circulated for leaching and multi-stage neutralization. A multi-stage countercurrent washing process is then adopted with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in the thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to keep the slag phase in a neutral state with a pH of 6.8. The metallic iron is then recovered and the tailings are discharged.

[0086] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal, aluminum removal and chromium removal. The process conditions for the first stage of iron removal are as follows: temperature control of 85°C, pH of 3.0, and reaction time of 1 hour. The slag phase after the first stage of iron removal is recycled and subjected to continuous multi-stage countercurrent washing again. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal, aluminum removal and chromium removal. The process conditions for the second stage of iron removal are as follows: temperature control of 79°C, pH of 4.8, and reaction time of 3 hours. The slag phase after the second stage of iron removal is recycled and subjected to cyclic leaching and neutralization again.

[0087] (7) A neutralizing agent is added to the tail liquid phase after the second-stage iron, aluminum, and chromium removal, and nickel-cobalt and nickel-cobalt-manganese synthesis are performed in a first-stage synthesis to obtain a nickel-cobalt hydroxide product. The process conditions for the first-stage synthesis of nickel-cobalt are: pH 7.0, reaction temperature 66°C, and reaction time 3 hours. The process conditions for the second-stage synthesis of nickel-cobalt are: pH 8.0, reaction temperature 50°C; wherein, the nickel-cobalt hydroxide product obtained has a nickel mass percentage of 32.83% and a cobalt mass percentage of 4.78%.

[0088] Example 5: Example 5 of the present application provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which specifically includes: (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (the following is the mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the MnO content was 2.13%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0089] (2) Lignite powder was added to the laterite nickel ore slurry with a mass ratio of 1000:1 to lignite, and the mixture was sent into a high-pressure reactor together with a sodium sulfate leaching promoter. The leaching reaction was carried out under high-pressure leaching conditions of a temperature of 255°C, a pressure of 4.0 MPa, and an acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese.

[0090] (3) The high-pressure leaching solution, the laterite nickel ore slurry and the acid solution were mixed in a mass ratio of 1:1:1.5 to obtain a mixed solution, and the mixed solution was transferred to a normal pressure reactor for multi-stage normal pressure leaching treatment; the process conditions of each stage of the multi-stage normal pressure leaching treatment were: temperature 90°C, pressure 0.1 MPa, and normal pressure leaching stage number 5.

[0091] (4) The mixed liquor after the multi-stage atmospheric pressure leaching treatment is concentrated by a thickener to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry. The ore pulp concentration of the final concentrated atmospheric pressure leaching slurry is 35%. The final concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry for high-pressure acid leaching treatment.

[0092] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leach tailings and then circulated for leaching and multi-stage neutralization. A multi-stage countercurrent washing process is then adopted with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in the thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to keep the slag phase in a neutral state with a pH of 6.8. The metallic iron is then recovered and the tailings are discharged.

[0093] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal, aluminum removal and chromium removal. The process conditions for the first stage of iron removal are as follows: temperature control of 85°C, pH of 3.0, and reaction time of 1 hour. The slag phase after the first stage of iron removal is recycled and subjected to continuous multi-stage countercurrent washing again. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal, aluminum removal and chromium removal. The process conditions for the second stage of iron removal are as follows: temperature control of 79°C, pH of 4.8, and reaction time of 3 hours. The slag phase after the second stage of iron removal is recycled and subjected to cyclic leaching and neutralization again.

[0094] (7) A neutralizing agent is added to the tail liquid phase after the second stage iron, aluminum and chromium removal to perform a first stage nickel-cobalt synthesis. After the first stage nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The process conditions for the first stage nickel-cobalt synthesis are: pH 7.0, reaction temperature 66°C, and reaction time 3 hours. The process conditions for the second stage nickel-cobalt synthesis are: pH 8.0, reaction temperature 50°C; wherein, the nickel-cobalt hydroxide product obtained has a nickel mass percentage of 32.51% and a cobalt mass percentage of 4.23%.

[0095] Comparative Example 1: Comparative Example 1 provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which specifically includes: (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (the following is the mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the MnO content was 2.13%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0096] (2) Lignite powder was added to the laterite nickel ore slurry with a mass ratio of 1000:1 to lignite, and the mixture was sent into a high-pressure reactor together with a sodium sulfate leaching promoter. The leaching reaction was carried out under high-pressure leaching conditions of a temperature of 255°C, a pressure of 4.0 MPa, and an acid consumption of 20 tons / ton of nickel to obtain a high-pressure leaching slurry.

[0097] (3) The high-pressure leaching slurry is circulated and leached and multi-stage neutralized, followed by a multi-stage countercurrent washing process with 6 washing stages and a ratio of washing water to slag phase of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to keep the slag phase in a neutral state of pH 6.8. The metallic iron is then recovered and the tailings are discharged.

[0098] (4) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal, aluminum removal and chromium removal. The process conditions for the first stage of iron removal are as follows: temperature control of 85°C, pH of 3.0, and reaction time of 1 hour. The slag phase after the first stage of iron removal is recycled and subjected to continuous multi-stage countercurrent washing again. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal, aluminum removal and chromium removal. The process conditions for the second stage of iron removal are as follows: temperature control of 79°C, pH of 4.8, and reaction time of 3 hours. The slag phase after the second stage of iron removal is recycled and subjected to cyclic leaching and neutralization again.

[0099] (5) A neutralizing agent is added to the tail liquid phase after the second stage of iron, aluminum and chromium removal to perform a first stage nickel-cobalt synthesis. After the first stage nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The process conditions for the first stage nickel-cobalt synthesis are: pH value 7.0, reaction temperature 66°C, reaction time 3h; the process conditions for the second stage nickel-cobalt synthesis are: pH value controlled at 8.0, reaction temperature 50°C; The obtained nickel cobalt hydroxide product contains 30.1% nickel by mass and 2.85% cobalt by mass.

[0100] Specifically, the final concentrated atmospheric leaching slurry of Examples 1 to 5 was converted to dry ore, and the mass percentages of iron, aluminum, magnesium, nickel, cobalt and manganese in the dry ore were calculated to obtain Table 1: Table 1 Test results of the mass percentage of some metals in the final concentrated atmospheric pressure leaching slurry of Examples 1 to 5

[0101] Specifically, it can be seen from Table 1 that in Examples 1 to 5, the final concentrated atmospheric pressure leaching slurry has lower iron, aluminum and magnesium contents than its respective corresponding laterite nickel ore slurry, which proves that the multi-stage atmospheric pressure leaching process can leach more of the above metals to remove part of the iron, aluminum and magnesium.

[0102] Furthermore, by comparing Example 4 with Example 1, it can be seen that in the multi-stage atmospheric pressure leaching process: the higher the atmospheric pressure leaching stage, the better the leaching effect of iron, aluminum and magnesium metals, and the lower the iron, aluminum and magnesium contents in the final concentrated atmospheric pressure leaching slurry.

[0103] Furthermore, by comparing Example 5 with Example 1, it can be seen that in the multi-stage atmospheric pressure leaching process: the higher the atmospheric pressure leaching temperature, the better the leaching effect of leaching iron, aluminum and magnesium metals, and the lower the iron, aluminum and magnesium contents in the final concentrated atmospheric pressure leaching slurry.

[0104] Furthermore, in step (2), a comparative test was conducted on the scale inhibition effects of Example 1 and Comparative Example 1. According to the process steps described above, both Example 1 and Comparative Example 1 were operated for 60 days, and the difference between the pressure in the inner cavity of the high-pressure reactor and the pressure in the inlet of the flash tank (referred to as the pressure difference) was tested. The specific statistical results are shown in Table 2. Since the smaller the pressure difference change during the continuous operation of the high-pressure reactor, the less scale is formed in the inner cavity of the high-pressure reactor, it can be seen from the data in Table 2 that the combined process of high-pressure acid leaching and multi-stage atmospheric pressure leaching has a better scale inhibition effect than the conventional high-pressure acid leaching process.

[0105] Table 2

[0106] The present invention can effectively reduce the amount of scaling on the inner wall of the high-pressure reactor and the discharge pipe during high-pressure acid leaching of ultra-low-grade laterite nickel ore, thereby achieving the purpose of extending the operating cycle of the laterite nickel ore high-pressure acid leaching system and reducing shutdowns and production reductions due to scale removal; and has good scale inhibition effect, safety and environmental protection, simple operation, easy use and low cost.

[0107] Different from the prior art, the embodiment of the present application mixes the high-pressure leachate obtained after high-pressure acid leaching treatment of the laterite nickel ore pulp, the laterite nickel ore pulp and the acidic solution, and then performs multi-stage atmospheric pressure leaching treatment, which can avoid scaling of the high-pressure reactor due to excessive accumulation of the high-pressure leachate during the high-pressure acid leaching treatment. At the same time, since the reaction conditions of the multi-stage atmospheric pressure leaching treatment are milder than those of the high-pressure acid leaching treatment, the scaling rate of the high-pressure leachate can be effectively suppressed, thereby extending the treatment time of the high-pressure acid leaching treatment, and ultimately improving the production efficiency of the nickel cobalt hydroxide product and reducing the production cost of the nickel cobalt hydroxide product.

[0108] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A multi-stage combined leaching method for ultra-low-grade laterite nickel ore, characterized in that: include: S10, performing high-pressure acid leaching on the laterite nickel ore pulp to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and a high-pressure leaching solution containing nickel, cobalt and manganese, wherein the mass percentage of nickel in the laterite nickel ore pulp is less than 1.0%; S20, mixing the high-pressure leaching solution, the raw laterite nickel ore pulp, and the acidic solution to obtain a mixed solution, and performing multi-stage normal pressure leaching treatment on the mixed solution to obtain a final concentrated normal pressure leaching solution and a final concentrated normal pressure leaching slurry after concentration treatment, wherein the pulp concentration of the final concentrated normal pressure leaching slurry is the same as the pulp concentration of the raw laterite nickel ore pulp; S30, subjecting the final concentrated atmospheric pressure leachate and the high-pressure leaching tailings to cyclic leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment, and MHP precipitation treatment in sequence to obtain a nickel-cobalt hydroxide product; Wherein, after the completion of step S20, the method further includes: returning the final concentrated atmospheric pressure leaching slurry to step S10 for the high-pressure acid leaching treatment.

2. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S10, the slurry concentration of the laterite nickel ore slurry is 30-40%, and the slurry capacity ratio is 100-200m 3 / ton of metallic nickel.

3. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S10, the process conditions of the high-pressure acid leaching treatment are: temperature 220-260° C., and pressure 2.0-6.0 MPa.

4. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S20, the mass ratio of the high-pressure leaching solution, the laterite nickel ore slurry and the acidic solution is 1: (0.8-1): (1-2); the acidic solution includes sulfuric acid or hydrogen chloride.

5. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S20, the temperature of the multi-stage atmospheric pressure leaching treatment is 60-90°C.

6. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S20, a thickener is used to concentrate the mixed solution after the multi-stage atmospheric pressure leaching treatment to obtain the final-stage concentrated atmospheric pressure leachate and the final-stage concentrated atmospheric pressure leaching slurry.

7. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S20, the number of normal pressure leaching stages of the multi-stage normal pressure leaching treatment is 2 to 10.

8. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the cyclic leaching and multi-stage pre-neutralization treatment of step S30, the control temperature of the cyclic leaching is 70-90° C.; the pH of the multi-stage pre-neutralization is 0.8-2, and the neutralizing agent of the multi-stage pre-neutralization is an alkaline mixture of any one or more of lime milk, limestone, sodium hydroxide, magnesia ore, and magnesium hydroxide.

9. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the step S30, the number of washing stages of the countercurrent washing treatment is 3 to 9; the process conditions for the iron, aluminum and chromium removal treatment are: the number of process stages is 2 to 7, the control temperature is 55 to 90° C., and the pH value is 2.5 to 5.

5.

10. The multi-stage combined leaching method for ultra-low-grade laterite nickel ore according to claim 1, characterized in that: In the nickel cobalt hydroxide product of step S30, the mass percentage of nickel is 30-40%, and the mass percentage of cobalt is 3.0-6.0%.

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