Chromium separation method for laterite-nickel ore

Abstract

The invention provides a chromium separation method for laterite-nickel ore, which comprises the following steps: carrying out first-stage cyclone classification on the laterite-nickel ore to obtain first-stage coarse raw ore pulp and first-stage fine raw ore pulp; sequentially performing low-intensity magnetic separation and high-intensity magnetic separation on the primary crude raw ore pulp to obtain chromium pre-concentrate; the first-stage fine raw ore pulp is subjected to second-stage rotational flow classification, and second-stage coarse raw ore pulp and second-stage fine raw ore pulp are obtained; and mixing the chromium pre-concentrate with the secondary coarse raw ore pulp to obtain a pre-concentrate, and sequentially carrying out spiral chute classification, gravity concentration and post-low intensity magnetic separation on the pre-concentrate to obtain the chromium concentrate. The integrated physical separation method adopted by the invention shows excellent performance, has high selectivity, high chromium recovery efficiency and stable chromium concentrate quality, and does not need additional chemical reagents.

Description

Technical Field

[0001] The invention belongs to the technical field of mining and metallurgy engineering, and particularly relates to a method for separating chromium from laterite nickel ore. Background Art

[0002] Nickel is a non-ferrous metal widely used in the production of electrical and electronic equipment. Global demand for nickel continues to grow due to increasing industrial applications and consumer demand, particularly in battery production. Nickel is derived from nickel ore, which is processed through hydrometallurgical or pyrometallurgical extraction techniques. There are two main types of nickel ore: laterite nickel ore and sulfide ore. Approximately 70% of global nickel reserves are located in laterite nickel deposits. In laterite nickel ore, nickel is primarily found in goethite, serpentine, olivine, and iron oxide minerals, enriched through isomorphous substitution during the weathering of ultramafic rocks. Therefore, traditional mineral separation and beneficiation techniques are difficult to extract from laterite nickel ore. Because laterite nickel ore is typically located near the surface and widely distributed, open-pit mining is generally used to mine nickel resources. Therefore, the processing of laterite nickel ore requires careful consideration and in-depth research.

[0003] Laterite nickel ore is mainly composed of iron oxide minerals and often contains chromite as a secondary mineral. These ores are characterized by a high chromium content, with chromium grades reaching 70,000 mg / kg, far exceeding the average grade of 35 mg / kg in the continental crust. The presence of chromite is of concern because it is chemically stable and insoluble under high pressure acid leaching (HPAL) conditions, which leads to its accumulation in HPAL residues. Although trivalent chromite (Cr) can be readily absorbed by the environment if properly managed, it can be readily absorbed by the environment. 3+ ) are harmless to the environment, but when these residues are exposed to oxidizing conditions, they can lead to hexavalent chromium (Cr 6+ ) is formed. 6+ ) is a highly toxic, carcinogenic and water-soluble substance that can contaminate groundwater and ecosystems, posing environmental risks.

[0004] In addition to its environmental impact, the presence of chromite in laterite nickel ore slurries significantly increases mechanical wear on production equipment, particularly in high-pressure acid leaching (HPAL) systems. Due to its high hardness and abrasiveness, chromite causes continuous physical erosion of critical components such as pipes, pumps, and autoclave reactors. This erosion accelerates equipment wear, leading to thinning of reactor walls and potentially causing system failure due to leaks or structural damage. Consequently, the presence of chromite increases equipment maintenance frequency, shortens equipment life, and increases operating costs. Therefore, pre-treatment with chromite prior to HPAL is highly recommended.

[0005] Beneficiation of laterite nickel ore is a critical step prior to hydrometallurgical or pyrometallurgical processing, aiming to effectively separate nickel-containing minerals from chromium-containing minerals. Chromium recovery from laterite nickel ore can be successfully achieved through physical separation methods such as hydrocyclones, spiral chutes, shaking tables, and magnetic separators. A chromite concentrate with a Cr2O3 grade of 37.67% and a recovery of 6.28% was obtained by combining classification (hydrocyclones), gravity separation (spiral chutes and shaking tables), and magnetic separation. This integrated approach not only facilitates chromite recovery but also actively supports the downstream HPAL process by generating high-nickel tailings suitable for further leaching. However, despite its advantages, this process also faces challenges, particularly low chromite recovery efficiency, primarily attributed to poor performance of the hydrocyclones during the initial classification stage. This low efficiency reduces the feed quality to the spiral concentrator, thereby limiting overall recovery.

[0006] Therefore, how to improve the recovery rate of chromium in laterite nickel ore and obtain high-grade chromium concentrate with stable quality is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for chromium separation from laterite nickel ore. The combined physical separation method adopted in the present invention shows excellent performance. First, the method enhances the selective separation of fine-particle chromium minerals through multi-stage hydraulic classification, significantly improving the yield of chromium in the pre-concentrate; second, the method combines the synergistic cooperation of pre-weak magnetic separation and strong magnetic separation, significantly improving the chromium recovery efficiency, and can effectively separate chromium minerals from associated gangue minerals; third, the chromium concentrate obtained by this method shows consistent high grade and recovery rate, thereby minimizing the loss of precious metals commonly seen in traditional separation methods; fourth, the method does not use chemical reagents and is environmentally sustainable. In summary, the method significantly improves the recovery rate of chromium in laterite nickel ore, and shows excellent high selectivity and stable chromium concentrate quality, and has good potential in terms of economic feasibility and environmental protection.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for separating chromium from laterite nickel ore, which comprises the following steps:

[0010] The laterite nickel ore is subjected to a first-level cyclone classification to obtain a first-level coarse ore pulp and a first-level fine ore pulp.

[0011] The first-level coarse ore pulp is subjected to pre-weak magnetic separation and high-intensity magnetic separation in sequence to obtain chromium pre-concentrate; the first-level fine ore pulp is subjected to secondary cyclone classification to obtain secondary coarse ore pulp and secondary fine ore pulp.

[0012] The chromium pre-concentrate and the secondary coarse ore pulp are mixed to obtain a pre-concentrate, and the pre-concentrate is subjected to spiral chute classification, gravity separation and post-weak magnetic separation in sequence to obtain a chromium concentrate.

[0013] The combined physical separation method used in the present invention exhibits excellent performance. First, the method enhances the selective separation of fine-particle chromium minerals through multi-stage hydraulic classification, significantly improving the yield of chromium in the pre-concentrate. Second, the method combines pre-weak magnetic separation with high-intensity magnetic separation to significantly improve the chromium recovery efficiency and can effectively separate chromium minerals from associated gangue minerals. Third, the chromium concentrate obtained by this method exhibits consistent high grade and recovery rate, thereby minimizing the loss of precious metals commonly seen in traditional separation methods. Fourth, the method does not use chemical reagents and is environmentally sustainable. In summary, this method significantly improves the recovery rate of chromium in laterite nickel ore, and exhibits excellent high selectivity and stable chromium concentrate quality, showing good potential in both economic feasibility and environmental protection.

[0014] Preferably, the classification particle size of the first-level cyclone classification is 0.037 mm.

[0015] In the present invention, in the first-stage cyclone classification stage, particle size and density work together to separate, thereby introducing larger and higher-density particles into the underflow part to separate the first-stage coarse ore pulp, and the first-stage fine ore pulp is separated into higher-density fine particles through the second-stage cyclone classification, thereby improving the classification accuracy and reducing the product mismatch problem encountered in the single-stage cyclone classification method; the second-stage coarse ore pulp separated by the second-stage cyclone classification is then mixed with the chromium pre-concentrate to obtain a pre-concentrate, which greatly improves the yield of chromium in the pre-concentrate.

[0016] In the present invention, the non-magnetic material obtained by the pre-weak magnetic separation is subjected to strong magnetic separation, thereby selectively separating chromium minerals from silica and other gangue minerals. The chromium minerals are concentrated in the magnetic part to form a chromium pre-concentrate, while silica and other minerals without significant magnetism remain in the non-magnetic tailings part; the chromium pre-concentrate is then mixed with the secondary coarse ore pulp to obtain a pre-concentrate, which greatly improves the chromium yield and chromium grade in the pre-concentrate.

[0017] Preferably, the feed pressure of the primary cyclone classification is 0.1-0.2 MPa, for example, 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa or 0.2 MPa.

[0018] In the present invention, the appropriate feed pressure can enable the particles to be more fully classified according to their physical properties, reduce mixing, improve the accuracy and purity of classification, and at the same time improve the production capacity and economic benefits of the equipment.

[0019] Preferably, the pre-weak magnetic separation includes: subjecting the primary coarse ore pulp to a first weak magnetic separation to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material, and the first weak magnetic separation non-magnetic material is used for the strong magnetic separation.

[0020] Preferably, the magnetic field strength of the first weak magnetic separation is 1200-1600 Oe, for example, it can be 1200 Oe, 1300 Oe, 1400 Oe, 1500 Oe, 1600 Oe, preferably 1400-1600 Oe.

[0021] In the present invention, the coarse raw ore pulp may contain some magnetic impurities, which can be removed by weak magnetic separation with a specific magnetic field strength to prevent them from interfering with subsequent processes and affecting the quality of the final product.

[0022] It should be noted that Oe (Oersted) is the unit of magnetic field strength in the centimeter-gram-second (CGS) system.

[0023] Preferably, the magnetic field strength of the high-intensity magnetic separation is 6000-8000 Oe, for example, it can be 6000 Oe, 6500 Oe, 7000 Oe, 7500 Oe or 8000 Oe, etc., preferably 7000-7500 Oe.

[0024] In the present invention, the strong magnetic separation process of a specific magnetic field strength can further enrich chromium-containing minerals and improve the grade of chromium concentrate. Therefore, by combining weak magnetic separation of a specific magnetic field strength with strong magnetic separation of a specific magnetic field strength, chromium minerals can be selectively separated from silica and other gangue minerals, thereby improving the recovery rate of chromium.

[0025] Preferably, the feed pressure of the secondary cyclone classification is 0.05-0.10 MPa, for example, it can be 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.10 MPa, preferably 0.06-0.09 MPa.

[0026] In the present invention, an appropriate feed pressure can ensure a stable flow trajectory of the slurry in the cyclone, avoid turbulence or deviation of the slurry, and thus provide good flow conditions for subsequent particle classification.

[0027] Preferably, the classification particle size of the secondary cyclone classification is 0.074 mm.

[0028] Preferably, the following steps are performed before the pre-concentrate is classified in the spiral chute:

[0029] The preconcentrate is introduced into a slightly positive pressure fluidized bed reactor for fluidization mixing to obtain a fluidized mixture.

[0030] In the present invention, a "gas-liquid-solid three-phase fluidized bed" can be formed during the fluidized mixing process. The airflow causes the mineral particles in the chromium pre-concentrate to be suspended, and three-dimensional mixing is achieved with the particles in the secondary coarse ore slurry during turbulent collision, so that the particle size distribution of the material entering the subsequent classification equipment is more uniform.

[0031] Preferably, during the fluidized mixing process, the pressure of the high-pressure air is 0.2-0.5 MPa, for example, 0.2 MPa, 0.3 MPa, 0.4 MPa or 0.5 MPa.

[0032] In this invention, high-pressure air suspends the mineral particles in the chromium pre-concentrate, achieving three-dimensional mixing with the particles in the secondary coarse ore slurry through turbulent collisions. This effectively breaks up particle agglomerates, ensuring better dispersion of the particles before entering the spiral chute. This avoids inaccurate classification caused by particle agglomeration and improves classification efficiency and accuracy. Furthermore, at a specific pressure, the high-pressure air dilutes and stirs the slurry, reducing its viscosity. This allows the slurry to flow more smoothly in the spiral chute, facilitates particle settling and separation, reduces particle entrainment caused by viscosity, and improves classification efficiency.

[0033] Preferably, an oxidant is introduced during the fluidized mixing process, and the amount of the oxidant introduced is 0.5-1.5% of the mass of the pre-concentrated material, for example, 0.5%, 0.75%, 1%, 1.25% or 1.5%. For example, the oxidant may be oxygen.

[0034] In the present invention, an oxidant is introduced during the fluidized mixing process to slightly oxidize and modify the surface of the ore particles, thereby creating favorable conditions for subsequent separation processes.

[0035] Preferably, after the spiral chute is classified, chute concentrate and chute tailings are obtained, and the chute concentrate is subjected to the gravity separation.

[0036] Preferably, the gravity separation method includes multi-stage shaking table classification.

[0037] Preferably, the multi-stage shaking table classification includes: subjecting the chute concentrate to a first-stage shaking table separation to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; subjecting the first-stage shaking table concentrate to a second-stage shaking table separation to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings, and a second-stage shaking table tailings.

[0038] In the present invention, the multi-stage shaking table classification significantly improves the chromium recovery rate compared with the traditional method without sacrificing the concentrate quality.

[0039] Preferably, during the one-stage shaking table sorting process, the water flow rate is 8-12 L / min, for example, it can be 8 L / min, 9 L / min, 10 L / min, 11 L / min or 12 L / min.

[0040] Preferably, during the two-stage shaking table sorting process, the water flow rate is 6-10 L / min, for example, it can be 6 L / min, 7 L / min, 8 L / min, 9 L / min or 10 L / min.

[0041] In this invention, the first-stage shaker uses an appropriate water flow rate to initially separate coarse and fine-grained minerals, creating a preliminary distribution of minerals of varying particle sizes and densities across the bed surface. Based on the sorting results from the first-stage shaker, the second-stage shaker employs a higher, more appropriate water flow rate to further refine the minerals. This allows for more precise separation of minerals of varying properties into distinct products, reduces cross-contamination between products, and improves sorting accuracy. The combined effects of these two processes ensure the effective recovery of useful minerals of varying particle sizes and densities, improving the overall recovery rate and avoiding resource waste.

[0042] Preferably, the post-weak magnetic separation includes:

[0043] The second-stage shaking table concentrate is subjected to second weak magnetic separation to obtain second weak magnetic separation non-magnetic material and second weak magnetic separation magnetic material, wherein the second weak magnetic separation non-magnetic material is the chromium concentrate.

[0044] The ore in the second-stage shaking table is subjected to third weak magnetic separation to obtain third weak magnetic separation magnetic material and third weak magnetic separation non-magnetic material. The second weak magnetic separation magnetic material and the third weak magnetic separation magnetic material are both magnetic iron concentrate.

[0045] Preferably, the magnetic field strength of the second weak magnetic separation is 1000-1400 Oe, for example, it can be 1000 Oe, 1100 Oe, 1200 Oe, 1300 Oe or 1400 Oe.

[0046] Preferably, the magnetic field strength of the third weak magnetic separation is 1000-1400 Oe, for example, it can be 1000 Oe, 1100 Oe, 1200 Oe, 1300 Oe or 1400 Oe.

[0047] Preferably, the non-magnetic materials separated by the third weak magnetic separation flow back to the second-stage shaking table for separation.

[0048] In the present invention, since the non-magnetic material in the third weak magnetic separation has a high chromium content, it is returned to the second-stage shaking table for separation to further recover the chromium minerals therein, thereby improving the chromium recovery rate and reducing resource waste.

[0049] Preferably, the chromium selection method comprises the following steps:

[0050] (1) The laterite nickel ore is subjected to a first-level hydrocyclone classification with a classification particle size of 0.037 mm to obtain a first-level coarse ore pulp and a first-level fine ore pulp.

[0051] The first-level coarse ore pulp is subjected to a first weak magnetic separation with a magnetic field strength of 1400 to 1600 Oe to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material. The first weak magnetic separation non-magnetic material is then subjected to a strong magnetic separation with a magnetic field strength of 7000 to 7500 Oe to obtain a strong magnetic separation non-magnetic material and a chromium pre-concentrate; wherein the first weak magnetic separation magnetic material is a magnetic iron concentrate.

[0052] The first-level fine ore pulp is subjected to second-level cyclone classification with an ore feeding pressure of 0.06-0.09 MPa and a classification particle size of 0.074 mm to obtain a second-level coarse ore pulp and a second-level fine ore pulp.

[0053] (2) The chromium pre-concentrate and the secondary coarse ore pulp are mixed, and then introduced into a slightly positive pressure fluidized bed reactor for fluidized mixing to obtain a fluidized mixture; the pressure of the high-pressure air introduced into the slightly positive pressure fluidized bed reactor is 0.2 to 0.5 MPa.

[0054] (3) The fluidized mixture is subjected to spiral chute classification to obtain chute concentrate and chute tailings; the chute concentrate is subjected to a first-stage shaking table sorting to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; and the first-stage shaking table concentrate is subjected to a second-stage shaking table sorting to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings and a second-stage shaking table tailings; wherein the stroke of the first-stage shaking table sorting is greater than the stroke of the second-stage shaking table sorting.

[0055] (4) performing a second weak magnetic separation on the second-stage shaking table concentrate, with a magnetic field strength of 1000 to 1400 Oe, to obtain a second weak magnetic separation non-magnetic material and a second weak magnetic separation magnetic material, wherein the second weak magnetic separation non-magnetic material is a chromium concentrate, and the Cr2O3 grade of the chromium concentrate is ≥40% (for example, it can be 40%, 41%, 42%, 43%, 44% or 45%, etc.).

[0056] The ore in the second-stage shaking table is subjected to a third weak magnetic separation with a magnetic field strength of 1000 to 1400 Oe to obtain a third weak magnetic separation magnetic material and a third weak magnetic separation non-magnetic material; the second weak magnetic separation magnetic material and the third weak magnetic separation magnetic material are both magnetic iron concentrates, and the third weak magnetic separation non-magnetic material is returned to the second-stage shaking table for sorting.

[0057] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The combined physical separation method used in the present invention exhibits excellent performance. First, the method enhances the selective separation of fine-particle chromium minerals through multi-stage hydraulic classification, significantly improving the yield of chromium in the pre-concentrate. Second, the method combines pre-weak magnetic separation with high-intensity magnetic separation to significantly improve the chromium recovery efficiency and can effectively separate chromium minerals from associated gangue minerals. Third, the chromium concentrate obtained by this method exhibits consistent high grade and recovery rate, thereby minimizing the loss of precious metals commonly seen in traditional separation methods. Fourth, the method does not use chemical reagents and is environmentally sustainable. In summary, this method significantly improves the recovery rate of chromium in laterite nickel ore, and exhibits excellent high selectivity and stable chromium concentrate quality, showing good potential in both economic feasibility and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a process flow chart provided for Example 1 of the present invention. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0062] Example 1

[0063] This embodiment provides a method for separating chromium from laterite nickel ore, and its process flow chart is as follows: Figure 1 As shown, the chromium selection method includes the following steps:

[0064] (1) A hydrocyclone is used to perform first-level hydrocyclone classification on the laterite nickel ore, with a classification particle size of 0.037 mm and an ore feed pressure of 0.12 MPa to obtain a first-level coarse ore slurry and a first-level fine ore slurry.

[0065] The first-level coarse ore pulp is subjected to a first weak magnetic separation with a magnetic field strength of 1400Oe to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material, and then the first weak magnetic separation non-magnetic material is subjected to a strong magnetic separation with a magnetic field strength of 7000Oe to obtain a strong magnetic separation non-magnetic material and a chromium pre-concentrate; wherein, the first weak magnetic separation magnetic material is a magnetic iron concentrate.

[0066] The first-level fine ore pulp is subjected to second-level hydrocyclone classification by using a hydrocyclone, with a feed pressure of 0.07 MPa and a classification particle size of 0.074 mm, to obtain second-level coarse ore pulp and second-level fine ore pulp.

[0067] (2) The chromium pre-concentrate and the secondary coarse ore pulp are mixed to obtain a pre-concentrate, and then the pre-concentrate is subjected to spiral chute sorting to obtain a chute concentrate and a chute tailings.

[0068] (3) The chute concentrate is subjected to a first-stage shaking table separation at a water flow rate of 10 L / min to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; then the first-stage shaking table concentrate is subjected to a second-stage shaking table separation at a water flow rate of 8 L / min to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings and a second-stage shaking table tailings; wherein the stroke of the first-stage shaking table separation is greater than the stroke of the second-stage shaking table separation.

[0069] (4) The second-stage shaking table concentrate is subjected to a second weak magnetic separation with a magnetic field strength of 1200 Oe to obtain a second weak magnetic separation non-magnetic material and a second weak magnetic separation magnetic material. The second weak magnetic separation non-magnetic material is a chromium concentrate. The Cr2O3 grade of the chromium concentrate is 42.68%, and the recovery rate is 19.41%.

[0070] The second-stage shaking table middlings are subjected to third weak magnetic separation with a magnetic field strength of 1200 Oe to obtain third weak magnetic separation magnetic material and third weak magnetic separation non-magnetic material; the second weak magnetic separation magnetic material and the third weak magnetic separation magnetic material are both magnetic iron concentrates, collectively referred to as chromium middlings; the third weak magnetic separation non-magnetic material is returned to the second-stage shaking table for sorting.

[0071] Example 2

[0072] This embodiment provides a method for separating chromium from laterite nickel ore, the method comprising the following steps:

[0073] (1) A hydrocyclone is used to perform first-level hydrocyclone classification on the laterite nickel ore, with a classification particle size of 0.037 mm and an ore feed pressure of 0.12 MPa to obtain a first-level coarse ore slurry and a first-level fine ore slurry.

[0074] The first-level coarse ore pulp is subjected to a first weak magnetic separation with a magnetic field strength of 1500Oe to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material, and then the first weak magnetic separation non-magnetic material is subjected to a strong magnetic separation with a magnetic field strength of 7500Oe to obtain a strong magnetic separation non-magnetic material and a chromium pre-concentrate; wherein, the first weak magnetic separation magnetic material is a magnetic iron concentrate.

[0075] The first-level fine ore pulp is subjected to second-level hydrocyclone classification by using a hydrocyclone, with a feed pressure of 0.06 MPa and a classification particle size of 0.074 mm, to obtain second-level coarse ore pulp and second-level fine ore pulp.

[0076] (2) The chromium pre-concentrate and the secondary coarse ore pulp are mixed to obtain a pre-concentrate, and then the pre-concentrate is subjected to spiral chute sorting to obtain a chute concentrate and a chute tailings.

[0077] (3) The chute concentrate is subjected to a first-stage shaking table separation at a water flow rate of 8 L / min to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; then the first-stage shaking table concentrate is subjected to a second-stage shaking table separation at a water flow rate of 9 L / min to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings and a second-stage shaking table tailings; wherein the stroke of the first-stage shaking table separation is greater than the stroke of the second-stage shaking table separation.

[0078] (4) The second-stage shaking table concentrate is subjected to a second weak magnetic separation with a magnetic field strength of 1000 Oe to obtain a second weak magnetic separation non-magnetic material and a second weak magnetic separation magnetic material. The second weak magnetic separation non-magnetic material is a chromium concentrate. The Cr2O3 grade of the chromium concentrate is 40.35%, and the recovery rate is 20.33%.

[0079] The second-stage shaking table middlings are subjected to third weak magnetic separation with a magnetic field strength of 1000 Oe to obtain third weak magnetic separation magnetic material and third weak magnetic separation non-magnetic material; the second weak magnetic separation magnetic material and the third weak magnetic separation magnetic material are both magnetic iron concentrates, collectively referred to as chromium middlings; the third weak magnetic separation non-magnetic material is returned to the second-stage shaking table for sorting.

[0080] Example 3

[0081] This embodiment provides a method for separating chromium from laterite nickel ore, the method comprising the following steps:

[0082] (1) A hydrocyclone is used to perform first-level hydrocyclone classification on the laterite nickel ore, with a classification particle size of 0.037 mm and an ore feed pressure of 0.14 MPa to obtain a first-level coarse ore slurry and a first-level fine ore slurry.

[0083] The first-level coarse ore pulp is subjected to a first weak magnetic separation with a magnetic field strength of 1500Oe to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material, and then the first weak magnetic separation non-magnetic material is subjected to a strong magnetic separation with a magnetic field strength of 7500Oe to obtain a strong magnetic separation non-magnetic material and a chromium pre-concentrate; wherein, the first weak magnetic separation magnetic material is a magnetic iron concentrate.

[0084] The first-level fine ore pulp is subjected to second-level hydrocyclone classification by using a hydrocyclone, with a feed pressure of 0.08 MPa and a classification particle size of 0.074 mm, to obtain second-level coarse ore pulp and second-level fine ore pulp.

[0085] (2) The chromium pre-concentrate and the secondary coarse ore pulp are mixed to obtain a pre-concentrate, and then the pre-concentrate is subjected to spiral chute sorting to obtain a chute concentrate and a chute tailings.

[0086] (3) The chute concentrate is subjected to a first-stage shaking table separation at a water flow rate of 10 L / min to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; then the first-stage shaking table concentrate is subjected to a second-stage shaking table separation at a water flow rate of 8 L / min to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings and a second-stage shaking table tailings; wherein the stroke of the first-stage shaking table separation is greater than the stroke of the second-stage shaking table separation.

[0087] (4) The second-stage shaking table concentrate is subjected to a second weak magnetic separation with a magnetic field strength of 1400 Oe to obtain a second weak magnetic separation non-magnetic material and a second weak magnetic separation magnetic material. The second weak magnetic separation non-magnetic material is a chromium concentrate. The chromium grade of the chromium concentrate is Cr2O3, the grade is 42.27%, and the recovery rate is 22.12%.

[0088] The second-stage shaking table middlings are subjected to third weak magnetic separation with a magnetic field strength of 1400 Oe to obtain third weak magnetic separation magnetic material and third weak magnetic separation non-magnetic material; the second weak magnetic separation magnetic material and the third weak magnetic separation magnetic material are both magnetic iron concentrates, collectively referred to as chromium middlings; the third weak magnetic separation non-magnetic material is returned to the second-stage shaking table for sorting.

[0089] Example 4

[0090] The difference between this embodiment and embodiment 1 is that the following steps are further performed between step (2) and step (3):

[0091] The preconcentrate is introduced into a slightly positive pressure fluidized bed reactor for fluidized mixing to obtain a fluidized mixture; during the fluidized mixing process, the pressure of the high-pressure air is 0.3 MPa.

[0092] The remaining chromium selection methods and parameters are consistent with those in the embodiment.

[0093] Example 5

[0094] The difference between this embodiment and embodiment 4 is that oxygen is also introduced during the fluidized mixing process, and the mass of the introduced oxygen accounts for 1% of the mass of the pre-concentrated material.

[0095] The remaining chromium selection methods and parameters were the same as those in Example 4.

[0096] Example 6

[0097] The difference between this embodiment and embodiment 1 is that the ore feeding pressure of the first-stage cyclone classification is 0.05 MPa.

[0098] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0099] Example 7

[0100] The difference between this embodiment and embodiment 1 is that the feed pressure of the first-stage cyclone classification is 0.25 MPa.

[0101] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0102] Example 8

[0103] The difference between this embodiment and embodiment 1 is that the magnetic field strength of the strong magnetic separation is 5500 Oe.

[0104] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0105] Example 9

[0106] The difference between this embodiment and embodiment 1 is that the magnetic field strength of the strong magnetic separation is 8500 Oe.

[0107] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0108] Example 10

[0109] The difference between this embodiment and embodiment 1 is that the feed pressure of the secondary cyclone classification is 0.05 MPa.

[0110] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0111] Example 11

[0112] The difference between this embodiment and embodiment 1 is that the feed pressure of the secondary cyclone classification is 0.12 MPa.

[0113] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0114] Comparative Example 1

[0115] The difference between this comparative example and Example 1 is that the primary fine ore pulp is not subjected to secondary cyclone classification, but the chromium pre-concentrate is directly subjected to subsequent spiral chute classification.

[0116] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that no high-intensity magnetic separation is performed.

[0119] The remaining chromium selection methods and parameters were the same as those in Example 1.

[0120] Performance Testing

[0121] The Cr2O3 grade in the chromium concentrate and chromium midd ore obtained in the above examples and comparative examples was determined by titration, and the corresponding recovery rate was calculated. The specific results are shown in Table 1.

[0122] Table 1

[0123]

[0124] analyze:

[0125] As can be seen from Table 1, the method adopted by the present invention enhances the selective separation of fine particles through optimized multi-stage hydraulic classification, significantly increasing the yield of chromium in the pre-concentrate. Secondly, the method combines the synergistic combination of pre-weak magnetic separation and high-intensity magnetic separation to significantly improve the chromium recovery efficiency and effectively separate chromium minerals from associated gangue minerals. Thirdly, the chromium concentrate obtained by this method exhibits consistent high grade and recovery rate, thereby minimizing the loss of precious metals commonly found in traditional separation methods.

[0126] By comparing Example 1 with Examples 6-7, it can be seen that if the feed pressure of the first-stage cyclone classification is too small, it is not conducive to sufficient sedimentation and effective classification of the particles, and the recovery rate and grade of Cr2O3 are low; if the feed pressure of the first-stage cyclone classification is too large, it not only affects the separation effect of chromium minerals and gangue minerals, thereby reducing the grade of Cr2O3, but also wastes energy, and makes the equipment unable to fully play its due role and cannot meet the needs of large-scale production, thereby affecting the efficiency of the entire production process and increasing production costs.

[0127] By comparing Example 1 with Examples 8-9, it can be seen that if the magnetic field strength of the strong magnetic separation is too small, the capture rate of chromium will decrease, resulting in a lower Cr2O3 recovery rate and a lower Cr2O3 grade; if the magnetic field strength of the strong magnetic separation is too large, some non-magnetic or weakly magnetic impurities may also be adsorbed, reducing the Cr2O3 grade, and at the same time increasing equipment energy consumption and production costs.

[0128] By comparing Example 1 with Examples 10-11, it can be seen that if the feed pressure of the secondary cyclone classification is too low, the slurry flow rate is slow, the processing capacity is reduced, and the classification efficiency is reduced, resulting in a decrease in Cr2O3 grade and recovery rate; if the feed pressure of the secondary cyclone classification is too high, the equipment wear is aggravated, energy consumption increases, and excessively high pressure will cause the slurry to flow too violently in the cyclone, generating excessive turbulence and eddy currents, which will interfere with the normal sedimentation and classification process of the particles, affect the classification effect, and thus lead to a decrease in Cr2O3 grade.

[0129] By comparing Example 1 with Comparative Example 1, it can be seen that if only the single-stage cyclone classification method is adopted and only the first-stage coarse ore pulp obtained by the first-stage cyclone classification is subsequently processed, the recovery rate of Cr2O3 is greatly hindered, the overall recovery effect is limited, and the Cr2O3 grade is reduced.

[0130] From the comparison between Example 1 and Comparative Example 2, it can be seen that if high-intensity magnetic separation is not performed, the chromium recovery rate decreases, and the chromium grade of the chromium concentrate is greatly affected, making it difficult to achieve a high purity effect. In addition, the impurity content in the minerals in the subsequent processing steps is high, which increases the difficulty and cost of subsequent operations.

[0131] It should be noted that while the present invention illustrates the process method through the above-described embodiments, the present invention is not limited to the above-described process steps, and does not necessarily rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for separating chromium from laterite nickel ore, characterized in that: The chromium selection method comprises the following steps: The laterite nickel ore is subjected to a first-level cyclone classification to obtain a first-level coarse ore pulp and a first-level fine ore pulp; The first-level coarse ore pulp is subjected to pre-weak magnetic separation and high-intensity magnetic separation in sequence to obtain chromium pre-concentrate; the first-level fine ore pulp is subjected to secondary cyclone classification to obtain secondary coarse ore pulp and secondary fine ore pulp; The chromium pre-concentrate and the secondary coarse ore pulp are mixed to obtain a pre-concentrate, and the pre-concentrate is subjected to spiral chute classification, gravity separation and post-weak magnetic separation in sequence to obtain a chromium concentrate.

2. The chromium selection method according to claim 1, characterized in that: The feed pressure of the first-stage cyclone classification is 0.1-0.2 MPa.

3. The chromium separation method according to claim 1 or 2, characterized in that: The pre-weak magnetic separation comprises: subjecting the primary coarse raw ore pulp to a first weak magnetic separation to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material, wherein the first weak magnetic separation non-magnetic material is used for the strong magnetic separation; Preferably, the magnetic field strength of the first weak magnetic separation is 1200 to 1600 Oe, preferably 1400 to 1600 Oe.

4. The chromium separation method according to any one of claims 1 to 3, characterized in that: The magnetic field strength of the strong magnetic separation is 6000-8000 Oe, preferably 7000-7500 Oe.

5. The chromium separation method according to any one of claims 1 to 4, characterized in that: The feed pressure of the secondary cyclone classification is 0.05-0.10 MPa, preferably 0.06-0.09 MPa.

6. The chromium separation method according to any one of claims 1 to 5, characterized in that: Before the pre-concentrate is subjected to spiral chute classification, the following steps are performed: Passing the preconcentrate into a slightly positive pressure fluidized bed reactor for fluidized mixing to obtain a fluidized mixture; Preferably, during the fluidized mixing process, an oxidant is also introduced, and the mass of the introduced oxidant accounts for 0.5-1.5% of the mass of the pre-concentrated material.

7. The chromium separation method according to any one of claims 1 to 6, characterized in that: After the spiral chute is classified, chute concentrate and chute tailings are obtained, and the chute concentrate is subjected to the gravity separation.

8. The chromium separation method according to claim 7, characterized in that: The gravity sorting method includes multi-stage shaking table classification; Preferably, the multi-stage shaking table classification includes: subjecting the chute concentrate to a first-stage shaking table separation to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; subjecting the first-stage shaking table concentrate to a second-stage shaking table separation to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings and a second-stage shaking table tailings; Preferably, during the first stage of the shaking table sorting process, the water flow rate is 8 to 12 L / min; Preferably, during the two-stage shaking table sorting process, the water flow rate is 6 to 10 L / min.

9. The chromium separation method according to claim 8, characterized in that: The post-weak magnetic separation comprises: Performing a second weak magnetic separation on the second-stage shaking table concentrate to obtain a second weak magnetic separation non-magnetic material and a second weak magnetic separation magnetic material, wherein the second weak magnetic separation non-magnetic material is the chromium concentrate; The ore in the second-stage shaking table is subjected to third-weak magnetic separation to obtain third-weak magnetic separation magnetic material and third-weak magnetic separation non-magnetic material; the second-weak magnetic separation magnetic material and the third-weak magnetic separation magnetic material are both magnetic iron concentrate; Preferably, the magnetic field strength of the second weak magnetic separation is 1000-1400 Oe; Preferably, the magnetic field strength of the third weak magnetic separation is 1000-1400 Oe.

10. The chromium separation method according to any one of claims 1 to 9, characterized in that: The chromium selection method comprises the following steps: (1) subjecting the laterite nickel ore to a first-level hydrocyclone classification with a classification particle size of 0.037 mm and an ore feed pressure of 0.1 to 0.2 MPa to obtain a first-level coarse ore slurry and a first-level fine ore slurry; The primary coarse ore pulp is subjected to a first weak magnetic separation with a magnetic field strength of 1200 to 1600 Oe to obtain a first weak magnetic separation magnetic material and a first weak magnetic separation non-magnetic material, and then the first weak magnetic separation non-magnetic material is subjected to a strong magnetic separation with a magnetic field strength of 7000 to 7500 Oe to obtain a strong magnetic separation non-magnetic material and a chromium pre-concentrate; wherein the first weak magnetic separation magnetic material is a magnetic iron concentrate; The first-level fine ore pulp is subjected to a second-level cyclone classification with an ore feeding pressure of 0.06-0.09 MPa and a classification particle size of 0.074 mm to obtain a second-level coarse ore pulp and a second-level fine ore pulp; (2) mixing the chromium pre-concentrate and the secondary coarse ore pulp, and then passing them into a slightly positive pressure fluidized bed reactor for fluidized mixing to obtain a fluidized mixture; the pressure of the high-pressure air passed into the slightly positive pressure fluidized bed reactor is 0.2 to 0.5 MPa; (3) subjecting the fluidized mixture to spiral chute classification to obtain chute concentrate and chute tailings; subjecting the chute concentrate to a first-stage shaking table separation to obtain a first-stage shaking table concentrate and a first-stage shaking table tailings; and then subjecting the first-stage shaking table concentrate to a second-stage shaking table separation to obtain a second-stage shaking table concentrate, a second-stage shaking table middlings, and a second-stage shaking table tailings; wherein the stroke of the first-stage shaking table separation is greater than the stroke of the second-stage shaking table separation; (4) subjecting the second-stage shaking table concentrate to a second weak magnetic separation with a magnetic field strength of 1000 to 1400 Oe to obtain a second weak magnetic separation non-magnetic material and a second weak magnetic separation magnetic material, wherein the second weak magnetic separation non-magnetic material is a chromium concentrate, and the Cr2O3 grade of the chromium concentrate is ≥40%; The ore in the second-stage shaking table is subjected to a third weak magnetic separation with a magnetic field strength of 1000 to 1400 Oe to obtain a third weak magnetic separation magnetic material and a third weak magnetic separation non-magnetic material; the second weak magnetic separation magnetic material and the third weak magnetic separation magnetic material are both magnetic iron concentrates, and the third weak magnetic separation non-magnetic material is returned to the second-stage shaking table for sorting.

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