A method for reducing nickel and cobalt content in tailings from hydrometallurgical processing of laterite nickel ore

Abstract

This invention relates to a method for reducing the nickel and cobalt content in tailings from hydrometallurgical processing of laterite nickel ore, comprising the following steps: Leaching slurry obtained from hydrometallurgical processing of laterite nickel ore is subjected to sequential circulating leaching and pre-neutralization treatments to obtain a pre-neutralized slurry. This is followed by multi-stage CCD washing. The resulting CCD overflow undergoes sequential primary and secondary iron and aluminum removal processes. The primary iron and aluminum removal underflow is recycled to the multi-stage CCD washing process and co-settled with the pre-neutralized slurry. The resulting CCD underflow is then discharged after tailings neutralization and pressure filtration treatment. This invention directly reuses the primary iron and aluminum removal underflow to the multi-stage CCD washing process and dilutes it with water, allowing the iron and aluminum slag in the original primary iron and aluminum removal underflow to co-settle with the tailings in the pre-neutralized slurry. This not only eliminates the need for pressure filtration and washing recycling of the primary iron and aluminum removal underflow in existing technologies but also effectively washes both types of slag, reducing the nickel and cobalt content in the final tailings.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical processing of laterite nickel ore, and more particularly to a method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgical processing. Background Technology

[0002] Lateritic nickel ore is a type of ore rich in nickel and cobalt, primarily formed under warm and humid climatic conditions. This nickel-rich lateritic layer is formed when ultramafic rocks are weathered and leached at or near the surface. The mining and processing of lateritic nickel ore is crucial to the global nickel supply, especially given its increasingly widespread use in the stainless steel and battery manufacturing industries.

[0003] Hydrometallurgy is a technique for extracting metals from ores, particularly suitable for processing ores with high water content and loose structure, such as laterite nickel ore. This method primarily involves a series of chemical reactions to dissolve the metals in the ore into a solution, followed by recovery of the metals from the solution through steps such as precipitation, extraction, or ion exchange. In processing laterite nickel ore, hydrometallurgical techniques mainly include high-pressure acid leaching (HPAL), atmospheric pressure acid leaching (ATM), and atmospheric pressure sulfuric acid leaching (LSX).

[0004] Because laterite nickel ore contains not only abundant nickel and cobalt but also other impurities such as iron, aluminum, and chromium, impurity removal is a crucial process in existing hydrometallurgical processes for laterite nickel ore, directly affecting the efficiency of subsequent metal recovery and product quality. Furthermore, during the iron and aluminum removal process, iron and aluminum in the underflow often exist in colloidal form in the leachate, making them difficult to separate using simple filtration methods. Current treatment involves multi-stage washing and pressure filtration, followed by discharge as slag. However, the presence of iron and aluminum colloids in this slag easily causes blockages during these processes, and the process is time-consuming and labor-intensive. Therefore, a new process method is urgently needed to address these problems. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for reducing the nickel and cobalt content in the tailings of laterite nickel ore hydrometallurgy. The first-stage iron and aluminum removal underflow is directly recycled to the multi-stage CCD washing process and diluted with water, so that the iron and aluminum slag in the original first-stage iron and aluminum removal underflow and the tailings in the pre-neutralized slurry settle together. This not only eliminates the need for the pressure filtration-washing cycle treatment of the first-stage iron and aluminum removal underflow in the prior art, but also effectively washes the two types of slag materials, reducing the nickel and cobalt content in the final tailings.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy, comprising the following steps:

[0008] (1) Take the leaching slurry obtained by hydrometallurgical treatment of laterite nickel ore, and perform cyclic leaching treatment and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. Then, perform multi-stage CCD washing to obtain CCD overflow liquid.

[0009] (2) The CCD overflow liquid is subjected to a first stage of iron and aluminum removal and a second stage of iron and aluminum removal in sequence. The resulting iron and aluminum removal underflow is recycled to the multi-stage CCD washing and is co-settled with the pre-neutralized slurry to obtain the CCD underflow. The CCD underflow is then subjected to tailings neutralization and pressure filtration treatment in sequence before the tailings are discharged.

[0010] In existing technologies, the primary iron-aluminum removal underflow is typically treated multiple times through a filter press and washing process before being discharged. However, the presence of iron and aluminum slag colloids in this underflow easily causes blockages during these processes, and the treatment is time-consuming and labor-intensive. This invention directly reuses the primary iron-aluminum removal underflow in a multi-stage CCD washing process and dilutes it with water. This allows the iron and aluminum slag in the original primary iron-aluminum removal underflow to settle together with the tailings in the pre-neutralized slurry. This not only eliminates the need for the filter press and washing cycle in existing technologies but also effectively washes both types of slag, reducing the nickel and cobalt content in the final tailings.

[0011] It should be noted that the leaching slurry obtained by the hydrometallurgical process of laterite nickel ore described in this invention is preferably a high-pressure leaching slurry of laterite nickel ore.

[0012] As a preferred technical solution of the present invention, in step (1), the process conditions for the cyclic leaching treatment are: pH < 1.5.

[0013] As a preferred technical solution of the present invention, in step (1), the process conditions of the pre-neutralization treatment are: controlling pH = 1.8 to 2.2, for example 1.8, 1.9, 2.0, 2.1 or 2.2, etc. Preferably, the pre-neutralization treatment is performed by adding limestone to adjust the pH to 1.8 to 2.2.

[0014] As a preferred technical solution of the present invention, in step (1), the process conditions for the multi-stage CCD washing are: controlling pH = 2.2 to 4.7, for example 2.2, 2.5, 2.8, 3.0, 3.3, 3.5, 3.8, 4.0, 4.3, 4.5 or 4.7, etc.

[0015] As a preferred technical solution of the present invention, in step (2), the process conditions for the first stage of iron and aluminum removal are: controlling the pH to be 3.5 to 3.8, for example 3.5, 3.6, 3.7 or 3.8, etc., and the process conditions for the second stage of iron and aluminum removal are: controlling the pH to be 4.8 to 5.0, for example 4.8, 4.9 or 5.0, etc.

[0016] As a preferred technical solution of the present invention, the number of stages of the multi-stage CCD washing in step (1) is 2 to 6, for example, 2, 3, 4, 5 or 6. The pre-neutralized slurry in step (2) enters the first stage of the multi-stage CCD washing, and the section of iron-aluminum removal underflow is recycled to the i-th stage of the multi-stage CCD washing, where i ≥ 2 and is an integer. If the section of iron-aluminum removal underflow is also recycled to the first stage of the multi-stage CCD washing, it will result in too much suspended matter in the first stage of the multi-stage CCD washing, which will seriously affect the stable operation of the multi-stage CCD washing. Further experiments have shown that the earlier the stage of iron-aluminum removal underflow is recycled, the better the washing effect, and the lower the content of nickel ions and cobalt ions in the final tailings.

[0017] As a preferred technical solution of the present invention, the iron and aluminum removal underflow is diluted with water before reuse, and the ratio of the volume of water added to the volume of the iron and aluminum removal underflow is controlled to be >1.2, such as 1.3, 1.4, 1.5 or 1.6.

[0018] As a preferred technical solution of the present invention, the concentration of the iron and aluminum removal underflow before dilution with water is 25-30%, such as 25%, 26%, 27%, 28%, 29% or 30%, etc., and the concentration of the iron and aluminum removal underflow after dilution with water is 5-8%, such as 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%, etc.

[0019] As a preferred technical solution of the present invention, in step (2), the specific steps of neutralizing the tailings include: adding lime milk to make the pH of the system 6.8 to 7.2, for example 6.8, 6.9, 7.0, 7.1 or 7.2.

[0020] As a preferred technical solution of the present invention, it further includes:

[0021] Step (2) yields a two-stage iron and aluminum removal underflow and a two-stage iron and aluminum removal overflow. The two-stage iron and aluminum removal underflow is reused and subjected to another cyclic leaching treatment, while the two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0022] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0023] This invention provides a method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy. The first-stage iron and aluminum removal underflow is directly recycled to the multi-stage CCD washing process and diluted with water, so that the iron and aluminum slag in the original first-stage iron and aluminum removal underflow and the tailings in the pre-neutralized slurry settle together. This not only eliminates the need for the pressure filtration-washing cycle treatment of the first-stage iron and aluminum removal underflow in the prior art, but also effectively washes the two types of slag, reducing the nickel and cobalt content in the final tailings. Attached Figure Description

[0024] Figure 1This is a schematic flowchart of a method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy, according to one embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of a process in one embodiment of the present invention, in which the iron and aluminum underflow is recycled to a multi-stage CCD washing process. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] One embodiment of the present invention provides a method for reducing the nickel and cobalt content in tailings from hydrometallurgical processes of laterite nickel ore, such as... Figure 1 As shown, it includes the following steps:

[0028] (1) Take the high-pressure leaching slurry of laterite nickel ore, and perform cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. Then, perform multi-stage CCD washing to obtain CCD overflow liquid.

[0029] In step (1), the process conditions for the cyclic leaching treatment are: pH < 1.5; the process conditions for the pre-neutralization treatment are: pH = 1.8 to 2.2; and the process conditions for the multi-stage CCD washing are: pH = 2.2 to 4.7.

[0030] (2) The CCD overflow liquid is subjected to a first stage of iron and aluminum removal and a second stage of iron and aluminum removal in sequence. The resulting iron and aluminum removal underflow is recycled to the multi-stage CCD washing and is co-settled with the pre-neutralized slurry to obtain the CCD underflow. The CCD underflow is then discharged after being neutralized by tailings and filtered by pressure.

[0031] (3) The two-stage iron and aluminum removal process yields a two-stage iron and aluminum removal underflow and a two-stage iron and aluminum removal overflow. The two-stage iron and aluminum removal underflow is reused and subjected to cyclic leaching treatment again, and the two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0032] In step (2), the process conditions for the first stage of iron and aluminum removal are: pH is controlled at 3.5 to 3.8, and the process conditions for the second stage of iron and aluminum removal are: pH is controlled at 4.8 to 5.0.

[0033] In step (2), a section of the iron and aluminum removal underflow is recycled to the multi-stage CCD washing process. Figure 2One embodiment is shown, including the following: the number of stages of the multi-stage CCD washing in step (1) is 6; the pre-neutralized slurry in step (2) enters the first stage of the multi-stage CCD washing; the iron-aluminum removal underflow is recycled to the second stage of the multi-stage CCD washing; the iron-aluminum removal underflow is diluted with water in the second stage of the multi-stage CCD washing, and the ratio of the volume of water added to the volume of the iron-aluminum removal underflow is controlled to be >1.2; more specifically, the overflow liquid of the next stage CCD washing is used as water to dilute the iron-aluminum removal underflow and is then settled in the previous stage CCD washing section; for example, the overflow liquid of the third stage CCD washing can be recycled, used as water to dilute the iron-aluminum removal underflow, and introduced into the second stage CCD washing section for settling; in other embodiments, similar overflow recycling methods or other water addition methods can also be used, which are not limited here. In this process, the concentration of the iron and aluminum removal underflow before dilution with water is 25-30%. If the concentration of the iron and aluminum removal underflow is too high, it will be difficult to transport and may cause pipeline blockage. At the same time, the ratio of the volume of water added to the volume of the iron and aluminum removal underflow also needs to be controlled. The concentration of the iron and aluminum removal underflow reused after dilution with water is 5-8%. If the volume of water added is too small, it will be difficult to fully dilute the iron and aluminum removal underflow, which will also lead to the mixed solution concentration being too high and difficult to settle in the secondary CCD washing section.

[0034] In step (3), the two-stage iron and aluminum removal process yields the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow. The two-stage iron and aluminum removal underflow is recycled to the circulating leaching process. The residual temperature and acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the recycled two-stage iron and aluminum removal underflow. The residual metal elements such as Ni and Co in the two-stage iron and aluminum removal underflow re-enter the reaction system, thereby improving the subsequent extraction rate of metal elements such as Ni and Co.

[0035] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0036] The mass percentage of each element in the laterite nickel ore used in the following examples and comparative examples is shown in Table 1 below. After the raw ore is prepared into a slurry, it is subjected to high-pressure acid leaching to obtain a laterite nickel ore high-pressure acid leaching slurry. The conditions for high-pressure acid leaching are: 250℃, pressure 4.5MPa, acid consumption 25 tons / ton of nickel. The multi-stage CCD washing process specifically includes 6 stages of countercurrent washing.

[0037] Table 1 Composition of Laterite Nickel Ore

[0038]

[0039] Example 1

[0040] A method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy includes the following steps:

[0041] (1) The high-pressure leaching slurry of laterite nickel ore is subjected to cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. The pH of the cyclic leaching treatment is controlled at <1.5, and the pH of the pre-neutralization treatment is controlled at 1.8 to 2.2. Then, a 6-stage CCD washing is performed to obtain CCD overflow liquid. The pH of the first stage CCD washing section of the multi-stage CCD washing is controlled at 2.2 to 2.5, and the pH of the sixth stage CCD washing section is controlled at 4.5 to 4.7.

[0042] (2) The CCD overflow is subjected to a first-stage iron and aluminum removal treatment (pH controlled at 3.5-3.8) and a second-stage iron and aluminum removal treatment (pH controlled at 4.8-5.0) in sequence. The concentration of the first-stage iron and aluminum removal underflow is 29%. The third-stage CCD washing overflow is reused as water to dilute the first-stage iron and aluminum removal underflow. It is then reused in the second-stage CCD washing section and co-sedimented with the pre-neutralized slurry. The volume ratio of the added water to the first-stage iron and aluminum removal underflow is 1.3. The concentration of the reused first-stage iron and aluminum removal underflow after dilution is 5-8%. After co-sedimentation, the CCD underflow is obtained by being discharged from the sixth-stage CCD washing section. The CCD underflow is neutralized by tailings (pH adjusted to 7 by adding lime milk) and then subjected to pressure filtration. Finally, the tailings are discharged.

[0043] (3) After the two-stage iron and aluminum removal process, the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow are obtained. The two-stage iron and aluminum removal underflow is reused and subjected to a circulating leaching process again. The residual temperature and residual acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the returned two-stage iron and aluminum removal underflow. The two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0044] Example 2

[0045] A method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy includes the following steps:

[0046] (1) The high-pressure leaching slurry of laterite nickel ore was subjected to cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. The pH of the cyclic leaching treatment was controlled at <1.5, and the pH of the pre-neutralization treatment was controlled at 1.8 to 2.2. Subsequently, a 6-stage CCD washing was performed to obtain CCD overflow liquid. The pH of the first stage CCD washing section of the multi-stage CCD washing was controlled at 2.2 to 2.5, and the pH of the sixth stage CCD washing section was controlled at 4.5 to 4.7.

[0047] (2) The CCD overflow is subjected to a first-stage iron and aluminum removal treatment (pH controlled at 3.5-3.8) and a second-stage iron and aluminum removal treatment (pH controlled at 4.8-5.0) in sequence. The concentration of the first-stage iron and aluminum removal underflow is 29%. The fourth-stage CCD washing overflow is reused as water to dilute the first-stage iron and aluminum removal underflow. It is then reused in the third-stage CCD washing section and co-sedimented with the pre-neutralized slurry. The volume ratio of the added water to the volume of the first-stage iron and aluminum removal underflow is 1.3. The concentration of the reused first-stage iron and aluminum removal underflow after dilution is 5-8%. After co-sedimentation, the CCD underflow is discharged from the sixth-stage CCD washing section. The CCD underflow is neutralized by tailings (pH adjusted to 7 by adding lime milk) and then subjected to pressure filtration. Finally, the tailings are discharged.

[0048] (3) After the two-stage iron and aluminum removal process, the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow are obtained. The two-stage iron and aluminum removal underflow is reused and subjected to a circulating leaching process again. The residual temperature and residual acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the returned two-stage iron and aluminum removal underflow. The two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0049] Example 3

[0050] A method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy includes the following steps:

[0051] (1) The high-pressure leaching slurry of laterite nickel ore was subjected to cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. The pH of the cyclic leaching treatment was controlled at <1.5, and the pH of the pre-neutralization treatment was controlled at 1.8 to 2.2. Subsequently, a 6-stage CCD washing was performed to obtain CCD overflow liquid. The pH of the first stage CCD washing section of the multi-stage CCD washing was controlled at 2.2 to 2.5, and the pH of the sixth stage CCD washing section was controlled at 4.5 to 4.7.

[0052] (2) The CCD overflow is subjected to a first-stage iron and aluminum removal treatment (pH controlled at 3.5-3.8) and a second-stage iron and aluminum removal treatment (pH controlled at 4.8-5.0) in sequence. The concentration of the first-stage iron and aluminum removal underflow is 29%. The fifth-stage CCD washing overflow is reused as water to dilute the first-stage iron and aluminum removal underflow. It is then reused in the fourth-stage CCD washing section and co-sedimented with the pre-neutralized slurry. The volume ratio of the added water to the first-stage iron and aluminum removal underflow is 1.3. The concentration of the reused first-stage iron and aluminum removal underflow after water dilution is 5-8%. After co-sedimentation, the CCD underflow is discharged from the sixth-stage CCD washing section. The CCD underflow is neutralized by tailings (pH adjusted to 7 by adding lime milk) and then subjected to pressure filtration. Finally, the tailings are discharged.

[0053] (3) After the two-stage iron and aluminum removal process, the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow are obtained. The two-stage iron and aluminum removal underflow is reused and subjected to a circulating leaching process again. The residual temperature and residual acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the returned two-stage iron and aluminum removal underflow. The two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0054] Example 4

[0055] A method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy includes the following steps:

[0056] (1) The high-pressure leaching slurry of laterite nickel ore is subjected to cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. The pH of the cyclic leaching treatment is controlled at <1.5, and the pH of the pre-neutralization treatment is controlled at 1.8 to 2.2. Then, a 6-stage CCD washing is performed to obtain CCD overflow liquid. The pH of the first stage CCD washing section of the multi-stage CCD washing is controlled at 2.2 to 2.5, and the pH of the sixth stage CCD washing section is controlled at 4.5 to 4.7.

[0057] (2) The CCD overflow is subjected to a first-stage iron and aluminum removal treatment (pH controlled at 3.5-3.8) and a second-stage iron and aluminum removal treatment (pH controlled at 4.8-5.0) in sequence. The concentration of the first-stage iron and aluminum removal underflow is 29%. The second-stage CCD washing overflow is reused as water to dilute the first-stage iron and aluminum removal underflow. It is then reused in the first-stage CCD washing section and settled together with the pre-neutralized slurry. The volume ratio of the added water to the volume of the first-stage iron and aluminum removal underflow is 1.3. The concentration of the first-stage iron and aluminum removal underflow after dilution is 5-8%. After co-settling, the CCD underflow is obtained by being discharged from the sixth-stage CCD washing section. The CCD underflow is neutralized by the tailings (pH adjusted to 7 by adding lime milk) and then subjected to pressure filtration. Finally, the tailings are discharged.

[0058] (3) After the two-stage iron and aluminum removal process, the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow are obtained. The two-stage iron and aluminum removal underflow is reused and subjected to a circulating leaching process again. The residual temperature and residual acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the returned two-stage iron and aluminum removal underflow. The two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0059] Example 5

[0060] A method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy includes the following steps:

[0061] (1) The high-pressure leaching slurry of laterite nickel ore is subjected to cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. The pH of the cyclic leaching treatment is controlled at <1.5, and the pH of the pre-neutralization treatment is controlled at 1.8 to 2.2. Then, a 6-stage CCD washing is performed to obtain CCD overflow liquid. The pH of the first stage CCD washing section of the multi-stage CCD washing is controlled at 2.2 to 2.5, and the pH of the sixth stage CCD washing section is controlled at 4.5 to 4.7.

[0062] (2) The CCD overflow is subjected to a first-stage iron and aluminum removal treatment (pH controlled at 3.5-3.8) and a second-stage iron and aluminum removal treatment (pH controlled at 4.8-5.0). The concentration of the iron and aluminum removal underflow in the first stage is 29%. It is directly reused in the second-stage CCD washing section without dilution. After co-sedimentation, the CCD underflow is discharged from the sixth-stage CCD washing section. The CCD underflow is neutralized by tailings (pH adjusted to 7 by adding lime milk) and then subjected to pressure filtration. Finally, the tailings are discharged.

[0063] (3) After the two-stage iron and aluminum removal process, the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow are obtained. The two-stage iron and aluminum removal underflow is reused and subjected to a circulating leaching process again. The residual temperature and residual acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the returned two-stage iron and aluminum removal underflow. The two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0064] Comparative Example 1

[0065] A hydrometallurgical method for laterite nickel ore includes the following steps:

[0066] (1) The high-pressure leaching slurry of laterite nickel ore is subjected to cyclic leaching and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. The pH of the cyclic leaching treatment is controlled at <1.5, and the pH of the pre-neutralization treatment is controlled at 1.8 to 2.2. Then, a 6-stage CCD washing is performed to obtain CCD overflow liquid. The pH of the first stage CCD washing section of the multi-stage CCD washing is controlled at 2.2 to 2.5, and the pH of the sixth stage CCD washing section is controlled at 4.5 to 4.7.

[0067] (2) The CCD overflow is subjected to a first-stage iron and aluminum removal treatment (pH controlled at 3.5-3.8) and a second-stage iron and aluminum removal treatment (pH controlled at 4.8-5.0) in sequence; the first-stage iron and aluminum removal underflow is directly discharged and washed separately, and is not reused; the pre-neutralized slurry is directly fed into the first-stage CCD washing section of the multi-stage CCD washing, and the CCD underflow is discharged from the sixth-stage CCD washing section. After the tailings neutralization treatment (pH adjusted to 7 by adding lime milk), the CCD underflow is then subjected to pressure filtration treatment. The filter residue obtained by pressure filtration is mixed with the tailings after the first-stage iron and aluminum removal underflow washing and discharged as the final tailings.

[0068] (3) After the two-stage iron and aluminum removal process, the two-stage iron and aluminum removal underflow and the two-stage iron and aluminum removal overflow are obtained. The two-stage iron and aluminum removal underflow is reused and subjected to a circulating leaching process again. The residual temperature and residual acid of the high-pressure acid leaching slurry are used to carry out circulating leaching with the returned two-stage iron and aluminum removal underflow. The two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

[0069] The nickel and cobalt content in the tailings obtained by pressure filtration in step (2) of the above embodiments and comparative examples was tested, and the test results are shown in Table 2.

[0070] Table 2. Statistical table of nickel and cobalt content in tailings obtained from Examples 1-5 and Comparative Example 1.

[0071]

[0072]

[0073] Note: " / " indicates that no operation was performed; "ND" indicates that measurement could not be performed.

[0074] The statistical results in Table 2 show that, in Examples 1-3, using the aforementioned method, after the iron and aluminum slag in the first-stage iron-aluminum removal underflow was co-settled with the tailings in the pre-neutralized slurry, the nickel and cobalt content in the discharged tailings was significantly reduced. Furthermore, in the process of recycling the first-stage iron-aluminum removal underflow for multi-stage CCD washing, the earlier the underflow was recycled, the better the washing effect, and the lower the nickel and cobalt ion content in the resulting tailings. In Example 4, the direct recycling of the diluted first-stage iron-aluminum removal underflow to the first-stage CCD washing section resulted in excessive suspended solids in the first-stage CCD washing section, severely affecting the stability of multi-stage CCD washing and forcing the entire process to shut down. In Example 5, the direct recycling of a 29% concentration first-stage iron-aluminum removal underflow to the second-stage CCD washing section without dilution with water caused blockage in the recycling pipeline, affecting the stability of multi-stage CCD washing and forcing the entire process to shut down.

[0075] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0076] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0078] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy, characterized in that, Includes the following steps: (1) Take the leaching slurry obtained by hydrometallurgical treatment of laterite nickel ore, and perform cyclic leaching treatment and pre-neutralization treatment in sequence to obtain pre-neutralized slurry. Then, perform multi-stage CCD washing to obtain CCD overflow liquid. (2) The CCD overflow liquid is subjected to a first stage of iron and aluminum removal and a second stage of iron and aluminum removal in sequence. The iron and aluminum removal underflow obtained is recycled to the multi-stage CCD washing and is co-settled with the pre-neutralized slurry to obtain the CCD underflow. The CCD underflow is then discharged after being neutralized by tailings and filtered by pressure. In step (1), the number of stages of the multi-stage CCD washing is 2 to 6. In step (2), the pre-neutralized slurry enters the first stage of the multi-stage CCD washing, and the iron and aluminum removal underflow is recycled to the i-th stage of the multi-stage CCD washing, where i ≥ 2 and is an integer.

2. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, In step (1), the process conditions for the cyclic leaching treatment are: pH < 1.

5.

3. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, In step (1), the pre-neutralization process conditions are: pH controlled at 1.8~2.

2.

4. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, In step (1), the process conditions for the multi-stage CCD washing are: pH controlled at 2.2~4.

7.

5. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, In step (2), the process conditions for the first stage of iron and aluminum removal are: pH is controlled at 3.5~3.8, and the process conditions for the second stage of iron and aluminum removal are: pH is controlled at 4.8~5.

0.

6. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, Before reuse, the iron and aluminum removal underflow is diluted with water, and the ratio of the volume of water added to the volume of the iron and aluminum removal underflow is controlled to be >1.

2.

7. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, The concentration of the iron and aluminum removal underflow before dilution with water is 25-30%, and the concentration of the iron and aluminum removal underflow after dilution with water is 5-8%.

8. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, In step (2), the specific steps for neutralizing the tailings include: adding lime milk to make the pH of the system 6.8~7.

2.

9. The method for reducing the nickel and cobalt content in tailings of laterite nickel ore hydrometallurgy according to claim 1, characterized in that, Also includes: Step (2) yields a two-stage iron and aluminum removal underflow and a two-stage iron and aluminum removal overflow. The two-stage iron and aluminum removal underflow is reused and subjected to another cyclic leaching treatment, while the two-stage iron and aluminum removal overflow is subjected to MHP sedimentation treatment.

Images