Novel chromium separation method and system for laterite-nickel ore

Abstract

The invention belongs to the technical field of laterite-nickel ore dressing, and particularly relates to a novel chromium dressing method and system for laterite-nickel ore. The method comprises the steps of laterite-nickel ore washing, hydrocyclone desliming, screening, low-intensity magnetic separation, high-intensity magnetic separation, shaking table gravity separation and chromium concentrate obtaining. The novel chromium separation system for the laterite-nickel ore comprises an ore washing and grading system, a desliming device, a magnetic separation system, a gravity separation system, a regrinding device, a secondary magnetic separation device and a secondary gravity separation system. The comprehensive grade of Cr2O3 in the first chromium concentrate and the second chromium concentrate obtained through the new chromium separation process ranges from 33.82% to 42%, and the recovery rate of the qualified chromium concentrate Cr2O3 ranges from 20.36% to 35.21% and is far higher than the index of 5%-10% of the recovery rate of Cr2O3 in the process of the prior art.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laterite nickel ore dressing, and particularly relates to a novel chrome ore dressing method and system for laterite nickel ore. BACKGROUND

[0002] Laterite nickel ore is a surface weathering crust type deposit, and is a weathering-leaching-deposition product of a nickel-containing basic-ultrabasic rock mass. Due to the oxidation of iron after weathering of the deposit, the ore is red, and thus is commonly known as laterite nickel ore. Globally, about 70% of nickel is currently extracted from sulfide nickel ore, but the nickel contained in laterite nickel ore accounts for 65% to 70% of nickel reserves. With the gradual reduction of sulfide nickel resources and high-grade laterite nickel resources, the economic development of a large amount of laterite nickel ore with a grade of about 1% is increasingly concerned by people. The main valuable elements in the ore are nickel, cobalt and iron, and the associated valuable element is chromium. In the process of recovering nickel and cobalt by a wet method, the chromite has a large momentum due to its large density and high stability, which will bring adverse effects on the pipe wall and the lining of the autoclave in the process of slurry transportation and high-pressure leaching. Therefore, the chromite is usually recovered before the recovery of nickel and cobalt by the wet method.

[0003] The commonly used chrome ore dressing process for laterite nickel ore in the industry is: laterite nickel ore→washing operation→screening operation→cyclone classification→spiral chute→shaking table roughing→shaking table scavenging→weak magnetic separation→chromium concentrate, which specifically includes the following steps: laterite nickel ore with a particle size of less than 350 mm is fed into a drum washer through a plate feeder for washing, and the ore is classified by a drum washer screening section, and the ore is classified by 25 mm, +25 mm is large gravel, and -25 mm slurry is fed into a 3 mm linear screen, the oversize +3 mm to 25 mm is small gravel, and -3 mm slurry is fed into a cyclone for classification, the classification overflow particle size is more than 85% of -53 microns, and is fed into a hydrometallurgical operation, the classification underflow is fed into a spiral chute for Cr2O3 pre-enrichment, the coarse mineral of the spiral chute is fed into a shaking table for roughing, the heavy mineral of the roughing shaking table is fed into a weak magnetic separator for further Cr2O3 enrichment, and a chromium concentrate with a Cr2O3 grade of more than 38% is obtained; the light mineral of the roughing shaking table is fed into a hydrometallurgical operation through a classification regrinding operation, the middlings of the roughing shaking table are fed into a shaking table for reprocessing, the heavy mineral of the reprocessing shaking table is fed into a weak magnetic separator for further Cr2O3 enrichment, a chromium concentrate with a Cr2O3 grade of more than 38% is obtained, and the middlings of the reprocessing shaking table are taken as waste slag, and the light mineral of the reprocessing shaking table is fed into a hydrometallurgical operation through a classification regrinding operation. Figure 1 .

[0004] With the existing method, the theoretical recovery rate of Cr2O3 is 39.27%, but in actual production, the recovery rate of Cr2O3 is only 5% to 10%, which is greatly different from the theoretical recovery rate, and it can be seen that the existing process has the defect of low recovery rate. SUMMARY

[0005] The raw material processed in this invention is a "wet" laterite nickel ore from Indonesia, which is mainly composed of limonite, with a limonite content of 57% to 78%. The chromium minerals are mainly chromite and chromite spinel, with a content of 2% to 4%. Other metallic minerals include magnetite and manganese oxides, as well as trace amounts of pyrolusite, manganese potassium ore, and manganese nickel ore. The non-metallic minerals are mainly serpentine, talc, chlorite, and quartz, with small amounts of diopside, tremolite, forsterite, and trace amounts of boehmite and apatite.

[0006] In the raw materials described in this invention, the particle size of chromite is mainly distributed in the range of 0.02 to 1 mm, which is within the beneficiation range. The +0.045 mm particle size, which is easily beneficiated by gravity separation, accounts for about 40%. The chromite in the +0.5 mm particle size has extremely low liberation. The chromite in the -0.5 mm particle size has good liberation. The total liberation of the raw ore is above 86%. The chromium grade above +1 mm is low, only below 0.8%.

[0007] The determination of chromium's occurrence states indicates that chromium accounts for 40%–65% in chromite and chromite spinel, 50%–30% in limonite, and very little in chlorite, magnetite, and pyrolusite. Chromium in limonite is difficult to recover through physical beneficiation, and chromium in chromite and chromite spinel with a particle size of -0.02 mm is also extremely difficult to recover; therefore, the theoretical recovery rate of chromium is around 40%. Nickel, apart from a very small amount in goethite, is mostly dispersed in pyrolusite, limonite, and various clay minerals and iron-magnesium silicate minerals.

[0008] Chromite and chromite spinel contain an average of 37% Cr₂O₃, with a maximum of 47%, making them the primary target minerals for chromium beneficiation. The focus is on recovering chromite and chromite spinel with a particle size of 0.02 mm or larger. Chromite and spinel belong to the spinel group of minerals, which contains Mg... 2+ with Fe 2+ Al 3+ With Cr 3+ Fe 3+ Isomorphic substitution is widespread, forming chromite and spinel subgroup minerals. These minerals exhibit strong to weak magnetism, with most becoming magnetic products at a field strength of 0.1–0.48T, and a few at 0.56T. Chromite and chromite spinel mostly occur as granular or fragmented granular single grains. Some chromite is associated with serpentine, olivine, and limonite, showing a gradual growth relationship between chromite and spinel.

[0009] Based on existing technical processes and the raw materials described in the invention, and using process investigation and other technical verification measures, the following defects were found in the existing chromium selection process:

[0010] 1. The large-diameter hydrocyclone classifies particles of 53 micrometers, while chromite (containing chromium spinel) in the +20 micrometer particle size is within the recoverable range. In actual production, the classification efficiency decreases as the proportion of -400 mesh particles in the raw ore increases. The +20 micrometer particle size accounts for 20% to 40% of the hydrocyclone overflow, resulting in tailing losses in the +20 micrometer Cr2O3 recovery rate. The Cr2O3 recovery rate in the hydrocyclone underflow is only 40% to 50%.

[0011] 2. Residual flocculants in the process water are prone to agglomerate and precipitate at the spiral chute collector, causing blockage of the collector and resulting in heavy minerals being directly thrown into the tailings of light minerals, causing a large loss of chromite (containing chromium spinel); at the same time, the separation effect of the spiral chute is reduced due to the precipitation of high molecular flocs.

[0012] 3. The Cr2O3 grade of the ore in the shaking table is about 10%. This part is the intergrowth of chromite (containing chromium spinel) and other minerals. It is directly thrown into the slag pond without any measures to recover it, resulting in the loss of chromite.

[0013] 4. During the shaking table gravity separation process, large particles of +1 to -3mm, especially those of +2 to -3mm, exceed the separation range of the shaking table. They hinder the formation of the chromite concentrate zone and the movement of chromite towards the concentrate discharge direction on the shaking table surface, causing the chromite to move towards the middlings direction, resulting in chromite loss.

[0014] This invention specifically includes the following:

[0015] With the increasing demand for chromium concentrate smelting, the contradiction between the current low chromium recovery rate and the demand is intensifying. Simultaneously, as more nickel hydrometallurgical projects are put into operation and their scale gradually increases, the waste of chromium resources caused by current chromium beneficiation processes is becoming increasingly serious. Therefore, there is an urgent need for a new technology for chromium beneficiation from laterite nickel ore, aiming to significantly improve the Cr2O3 recovery rate while reducing the impact of chromium impurities on smelting. To address the problems of existing technologies, this invention provides a novel method and system for chromium beneficiation from laterite nickel ore. The specific contents of this invention are as follows:

[0016] A novel method for chromium beneficiation in laterite nickel ore includes the following steps:

[0017] (1) Washing and primary screening: The laterite nickel ore is washed and then screened to obtain large gravel with a particle size ≥3mm and slurry with a particle size <3mm. Since the laterite nickel ore is tightly bonded together by clay minerals such as chlorite, serpentine, soapstone, and talc, forming particles of different sizes, this invention first disperses the various minerals by washing, exposing the properties of each mineral, which is more conducive to subsequent beneficiation.

[0018] (2) Desliming: The slurry with a particle size <3mm is deslimed to obtain an underflow slurry and overflow with a particle size ≥20μm. The solid particles in the overflow have a particle size <20μm. The ore has a high content of fine particles, with the proportion of -0.02mm particles reaching 51.76% to 72.34% in different raw ores. However, the Cr2O3 grade in mineral particles with a particle size below -0.02mm is low, with an average grade of 1.19%, making it difficult to recover by physical means. Therefore, due to the large difference in the proportion of -0.02mm particles in different raw ores, the recovery rate of chromite will inevitably fluctuate greatly. That is, the larger the proportion of -0.02mm particles in the raw ores, the lower the recovery rate of chromite. Therefore, this invention removes minerals with a particle size below -0.02mm through desliming, preventing them from entering the subsequent chromite beneficiation process.

[0019] (3) Secondary screening: The underflow slurry with a particle size ≥20μm is subjected to secondary screening to obtain the oversize material with a particle size ≥1mm and the undersize slurry with a particle size <1mm. According to the particle size composition analysis results of different raw ores, the Cr2O3 grade of +3mm and -3 to +1mm particles is low, with contents of 0.84% ​​and 1.15% respectively. Therefore, the present invention uses secondary screening to pre-remove the +3mm and -3 to +1mm particles, so that they do not enter the subsequent chromium beneficiation process.

[0020] (4) Weak magnetic separation: The underflow slurry is subjected to weak magnetic separation, and the weak magnetic field strength is controlled to be 0.1-0.15T to obtain weak magnetic concentrate and weak magnetic tailings;

[0021] (5) Strong magnetic separation: The weak magnetic tailings are subjected to strong magnetic separation, with the magnetic field strength controlled at 0.4-0.8T, to obtain strong magnetic concentrate and strong magnetic tailings. Since chromite has weak magnetism, it can be recovered by high-gradient strong magnetic separation. High-gradient strong magnetic separation has the characteristics of high magnetic field strength and good recovery effect of fine-grained valuable minerals. The chromite particles in the ore are generally fine, and high-gradient strong magnetic separation is beneficial to enhance the recovery of this part of fine-grained chromite. In addition, the ore has a high content of fine particles, with -0.01mm particles accounting for 31.76%, and the Cr2O3 content in this particle size accounts for 38.40% of the total Cr2O3 in the particle size. Such a large amount of fine mud has a very adverse effect on the gravity separation of chromite. This invention sets a magnetic separation step before gravity separation, so that a large amount of fine mud enters the strong magnetic tailings during the magnetic separation process, thus avoiding its entry into gravity separation. Therefore, magnetic separation can be used to pre-enrich chromite, enhance the recovery of fine-grained chromite, and reduce the adverse effects of fine mud on subsequent gravity separation.

[0022] (6) Gravity separation: The strong magnetic concentrate is subjected to shaking table roughing to obtain roughed heavy ore, roughed medium ore, and roughed tailings; the roughed medium ore is subjected to shaking table re-separation to obtain re-separated heavy ore and re-separated tailings; the roughed heavy ore and the re-separated heavy ore are combined and then subjected to shaking table cleaning to obtain first chromium concentrate and cleaned tailings; chromite itself has a high density, reaching 4-5 g / cm³. 3 The density of minerals such as limonite, pyroxene, and amphibole is less than 3.5 g / cm³. 3 Some weakly magnetic minerals in the ore, such as limonite, pyroxene, and amphibole, enter the strong magnetic product along with chromite during the high-gradient strong magnetic separation process. To separate the chromite from other minerals, a shaking table gravity separation method is used, leveraging the density difference between chromite and other minerals. Chromite has a primary liberation degree as high as 86.29%, therefore, most of the chromite can be effectively recovered in this process.

[0023] (7) Regrinding: The selected tailings and the weak magnetic concentrate are combined and then ground to obtain the grinding product; since the chromite in the intergrowth state enters the middlings during the shaking table gravity separation process, the middlings need to be regrinded and re-selected.

[0024] (8) Secondary weak magnetic separation: The grinding product is subjected to weak magnetic separation, and the weak magnetic field strength is controlled to be 0.1-0.15T to obtain iron concentrate and secondary weak magnetic tailings.

[0025] (9) Regrinding and Gravity Separation: The secondary weak magnetic tailings are subjected to shaking table roughing to obtain regrinding roughing tailings and regrinding roughing concentrate; the regrinding roughing concentrate is then subjected to shaking table cleaning to obtain a second chromium concentrate and regrinding cleaned tailings. The primary fine-grained chromite and the fine-grained chromite produced during regrinding will ultimately enter the shaking table middle ore. This invention uses shaking table gravity separation to enhance the recovery of this portion of fine-grained chromite, effectively improving the recovery rate.

[0026] Preferably, the ore washing method in step (1) is as follows: put laterite nickel ore and water into a stirring tank, start stirring, control the liquid-solid ratio to be (3-4):1, the stirring intensity to be 280-380 r / min, and the stirring time to be 10-15 min.

[0027] Preferably, the primary screening and / or secondary screening are performed using a tapping vibrating screen.

[0028] Preferably, the desliming in step (3) is carried out using a hydrocyclone.

[0029] Preferably, the weak magnetic separation in step (4) is carried out by a cylindrical weak magnetic separator, with the excitation current controlled at 1-3A, the magnetic medium being magnetically conductive stainless steel, and the spacing between the steel bars in the magnetic medium box being 3mm.

[0030] Preferably, the strong magnetic separation in step (5) is carried out using a high gradient magnetic separator, with the excitation current controlled at 1-3A, the magnetic medium being magnetically conductive stainless steel, and the spacing between the steel rods in the magnetic medium box being 3mm.

[0031] Steps (4)-(5) based on the particle size, characteristics and other factors of the minerals selected according to the present invention, the magnetic field strength, magnetic medium and spacing of weak magnetic separation and strong magnetic separation are set respectively, which can ensure that the optimal demagnetization effect is achieved.

[0032] Preferably, the roughing process of the shaking table in step (6) is carried out using a sand-type shaking table. The reason for using a sand-type shaking table for roughing is that the structure and performance of the sand-type shaking table are more suitable for separating materials with a large proportion of coarse particles, and the single unit has a larger processing capacity and higher economic and technical indicators. The re-selection and / or fine selection of the shaking table in step (6) is carried out using a fine mud-type shaking table. The fine mud-type shaking table is more suitable for separating materials with a large proportion of fine particles and has better mineral processing indicators.

[0033] Preferably, the secondary weak magnetic separation in step (8) is carried out using a magnetic separator tube, which makes it easier to control and adjust the magnetic field strength, feed rate and vibration frequency; and / or, the secondary roughing and / or secondary cleaning in step (9) is carried out using a fine mud-type shaking table.

[0034] A novel chromium beneficiation system for laterite nickel ore includes a washing and grading system, a magnetic separation system, a gravity separation system, a regrinding device, a secondary magnetic separation device, and a secondary gravity separation system.

[0035] The ore washing and grading system includes a stirring tank, a primary screening device, a desliming device, and a secondary screening device. The primary and secondary screening devices are respectively provided with a feed inlet and a discharge outlet for undersize material. The desliming device is provided with a feed inlet, an overflow outlet, and a discharge outlet. The feed inlet of the primary screening device is connected to the discharge outlet of the stirring tank, and the feed inlet of the desliming device is connected to the discharge outlet for undersize material of the primary screening device. The discharge outlet of the desliming device is connected to the feed inlet of the secondary screening device.

[0036] The magnetic separation system includes a weak magnetic separation device and a strong magnetic separation device. The weak magnetic separation device and the strong magnetic separation device are respectively provided with a feed inlet, a concentrate outlet and a tailings outlet. The feed inlet of the weak magnetic separation device is connected to the undersize outlet of the secondary screening device, and the tailings outlet of the weak magnetic separation device is connected to the feed inlet of the strong magnetic separation device.

[0037] The gravity separation system includes a roughing device, a re-separation device, and a cleaning device. The roughing device includes a feed inlet, a heavy ore outlet, a middlings outlet, and a tailings outlet. The feed inlet of the roughing device is connected to the concentrate outlet of the high-intensity magnetic separator. The re-separation device is provided with a feed inlet, a heavy ore outlet, and a tailings outlet. The feed inlet of the re-separation device is connected to the middlings outlet of the roughing device. The cleaning device is provided with a feed inlet, a concentrate outlet, and a tailings outlet. The feed inlet of the cleaning device is connected to the heavy ore outlets of both the roughing device and the re-separation device.

[0038] The feed inlet of the regrinding unit is connected to the concentrate outlet of the weak magnetic separator and the tailings outlet of the fine separation unit, respectively.

[0039] The secondary magnetic separation device is equipped with a feed inlet, a concentrate outlet, and a tailings outlet. The feed inlet of the secondary magnetic separation device is connected to the discharge outlet of the regrinding device.

[0040] The secondary gravity separation system includes a secondary roughing device and a secondary cleaning device. The secondary roughing device and the secondary cleaning device are respectively provided with a feed inlet, a concentrate outlet and a tailings outlet. The feed inlet of the secondary roughing device is connected to the tailings outlet of the secondary magnetic separation device; the feed inlet of the secondary cleaning device is connected to the concentrate outlet of the secondary roughing device.

[0041] Preferred,

[0042] The desliming device is a hydrocyclone desliming device; and / or,

[0043] The weak magnetic separation device is a cylindrical weak magnetic separator; and / or...

[0044] The strong magnetic separation device is a high-gradient magnetic separator; and / or,

[0045] The roughing device is a sand-type shaking table; and / or,

[0046] The re-selection device and / or the finer selection device is a fine-slurry type shaking table; and / or...

[0047] The regrinding device is a grinding mill; and / or...

[0048] The secondary magnetic separation device is Magnetic separator; and / or

[0049] The secondary coarsening device and / or secondary fine-selection device is an LY-0.5㎡ type fine mud shaking table.

[0050] The beneficial effects of this invention are:

[0051] (1) This invention pre-discards +1mm gravel with a Cr2O3 grade of less than 1% by washing and primary screening, so that -1mm chromite entering the chromium beneficiation process is pre-enriched, thereby increasing the Cr2O3 grade entering the weak magnetic beneficiation slurry.

[0052] (2) This invention uses a hydrocyclone for desliming. By selecting the best classification conditions and equipment, a large amount of chromite in the -20 micron particle size that is difficult to recover can be pre-discarded, so that the chromite can be pre-enriched in the second stage. At the same time, in industrial production applications, it can reduce the number of subsequent process equipment and the equipment processing capacity, effectively reduce infrastructure and equipment investment, and increase enterprise profits.

[0053] (3) The present invention uses a combination of weak magnetic and strong magnetic processes to recover coarse chromite while the strong magnetic separator can effectively recover fine chromite, thereby expanding the recovery particle size range of chromite and improving the chromite recovery rate.

[0054] (4) Through three-stage gravity separation on a shaking table, based on the distribution pattern of chromite of different particle sizes, we focus on strengthening the recovery of each particle size. The shaking table roughing adopts a fine sand type shaking table to prioritize the separation of high-grade chromite in the 0.074mm to 1mm particle size. The fine mud type shaking table is used to recover chromite in the 0.02mm to 0.074mm particle size in the roughing shaking table. The low-grade coarse particles are thrown out by 1mm screening, which can solve the problem of coarse particles affecting the shaking table separation efficiency on the shaking table surface and avoid loss of chromite concentrate recovery rate.

[0055] (5) This invention improves the degree of liberation of intergrowth chromite in the tailings and weak magnetic concentrate by re-grinding and re-selection, so that it can be recovered through the shaking table gravity separation process. In addition, magnetite is recovered by weak magnetic separation, further improving the grade index of chromite concentrate.

[0056] (6) In actual industrial production, lateritic nickel ore from multiple mining areas is often piled together, making precise ore blending difficult. This results in significant fluctuations in the proportion of -20 micrometer particles in the raw ore. For lateritic nickel ore with over 70% of particles at -20 micrometers, it becomes difficult to improve the grade of chromium concentrate, leading to low chromium recovery. The new chromium beneficiation method of this invention is more adaptable to this type of difficult-to-beneficiate lateritic nickel ore than other processes in the prior art. The comprehensive Cr2O3 grade in the first and second chromium concentrates obtained by the new chromium beneficiation process of this invention is 33.82%-42%, and the recovery rate of Cr2O3 in the qualified chromium concentrate is 20.36%-35.21%, far exceeding the 5-10% Cr2O3 recovery rate of existing processes. Attached Figure Description

[0057] Figure 1 This is a process flow diagram of a novel chromium beneficiation method for laterite nickel ore in the existing technology;

[0058] Figure 2This is a process flow diagram of the novel chromium beneficiation method for laterite nickel ore disclosed in this invention;

[0059] Figure 3 This is a schematic diagram of the structure of the novel chromium beneficiation system for laterite nickel ore disclosed in this invention. Detailed Implementation

[0060] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments shown below do not limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations illustrated in the following embodiments are not limited to those necessary for the solution of the invention as described in the claims.

[0061] Reference Appendix Figure 2 A novel method for chromium beneficiation from laterite nickel ore includes the following steps:

[0062] (1) Washing and primary screening: Put the laterite nickel ore and water into the mixing tank, start the stirring, control the liquid-solid ratio to be (3-4):1, the stirring intensity to be 280-380 r / min, and the stirring time to be 10-15 min, wash the ore, and then perform primary screening to obtain large gravel with a particle size ≥3mm and slurry with a particle size <3mm.

[0063] (2) Desliming: The slurry with a particle size <3mm is deslimed to obtain underflow slurry and overflow with a particle size ≥20μm, wherein the particle size of the solid particles in the overflow is <20μm;

[0064] (3) Secondary screening: The underflow slurry with a particle size ≥20μm is subjected to secondary screening to obtain the oversize material with a particle size ≥1mm and the undersize slurry with a particle size <1mm;

[0065] (4) Weak magnetic separation: The underflow slurry is subjected to weak magnetic separation using a cylindrical weak magnetic separator. The weak magnetic field strength is controlled to be 0.1-0.15T, the excitation current is 1-3A, the magnetic medium is type 3 (magnetic stainless steel), and the spacing between the steel bars of the magnetic medium box is 3mm, to obtain weak magnetic concentrate and weak magnetic tailings.

[0066] (5) Strong magnetic separation: The weak magnetic tailings are subjected to strong magnetic separation using a high-gradient magnetic separator. The magnetic field strength is controlled at 0.4-0.8T, the excitation current at 4-7A, the magnetic medium is type 3 (magnetic stainless steel), and the spacing between the steel bars in the magnetic medium box is 3mm, to obtain strong magnetic concentrate and strong magnetic tailings (i.e., Figure 2 Middle tailings 1);

[0067] (6) Gravity separation: The strong magnetic concentrate is roughed using a sand-type shaking table to obtain roughed heavy ore, roughed medium ore, and roughed tailings (i.e., tailings 2); the roughed medium ore is further separated using a fine mud-type shaking table to obtain further separated heavy ore and further separated tailings (i.e., tailings 3); the roughed heavy ore and the further separated heavy ore are combined and then further separated using a fine mud-type shaking table to obtain the first chromium concentrate (i.e., chromium concentrate 1) and the cleaned tailings;

[0068] (7) Regrinding: The selected tailings and the weak magnetic concentrate are combined and then ground to obtain the grinding product;

[0069] (8) Secondary weak magnetic separation: The grinding product is subjected to weak magnetic separation using a magnetic separator tube, and the weak magnetic field strength is controlled to be 0.1-0.15T to obtain iron concentrate and secondary weak magnetic tailings.

[0070] (9) Regrinding and gravity separation: The secondary weak magnetic tailings are roughed by shaking table using a fine mud type shaking table to obtain regrinding roughed tailings (i.e., tailings 4) and regrinding roughed concentrate; the regrinding roughed concentrate is cleaned by shaking table using a fine mud type shaking table to obtain second chromium concentrate (i.e., chromium concentrate 2) and regrinding cleaned tailings (i.e., tailings 5).

[0071] A novel chromium beneficiation system for laterite nickel ore that can implement the above-mentioned chromium beneficiation method includes a washing and grading system, a magnetic separation system, a gravity separation system, a regrinding device, a secondary magnetic separation device, and a secondary gravity separation system;

[0072] The ore washing and grading system includes a stirring tank, a primary screening device, a desliming device, and a secondary screening device. The primary and secondary screening devices are respectively equipped with a feed inlet and a discharge outlet for undersize material. The desliming device is equipped with a feed inlet, an overflow outlet, and a discharge outlet. The feed inlet of the primary screening device is connected to the discharge outlet of the stirring tank, and the feed inlet of the desliming device is connected to the discharge outlet for undersize material of the primary screening device. The discharge outlet of the desliming device is connected to the feed inlet of the secondary screening device. Preferably, the desliming device is a hydrocyclone desliming device.

[0073] The magnetic separation system includes a weak magnetic separator and a strong magnetic separator. The weak magnetic separator and the strong magnetic separator are respectively provided with a feed inlet, a concentrate outlet, and a tailings outlet. The feed inlet of the weak magnetic separator is connected to the undersize outlet of the secondary screening device, and the tailings outlet of the weak magnetic separator is connected to the feed inlet of the strong magnetic separator. The weak magnetic separator is a cylindrical weak magnetic separator, and the strong magnetic separator is a high-gradient magnetic separator.

[0074] The gravity separation system includes a roughing device, a re-separation device, and a cleaning device. The roughing device includes a feed inlet, a heavy ore outlet, a middlings outlet, and a tailings outlet. The feed inlet of the roughing device is connected to the concentrate outlet of the strong magnetic separator. The re-separation device has a feed inlet, a heavy ore outlet, and a tailings outlet. The feed inlet of the re-separation device is connected to the middlings outlet of the roughing device. The cleaning device has a feed inlet, a concentrate outlet, and a tailings outlet. The feed inlet of the cleaning device is connected to the heavy ore outlets of both the roughing and re-separation devices. The roughing device is a sand-type shaking table, while the re-separation and cleaning devices are fine mud-type shaking tables. The feed inlet of the regrinding device is connected to the concentrate outlet of the weak magnetic separator and the tailings outlet of the cleaning device.

[0075] The feed inlet of the regrinding device is connected to the concentrate outlet of the weak magnetic separation device and the tailings outlet of the fine separation device, respectively; the regrinding device is a grinding mill.

[0076] The secondary magnetic separation device is equipped with a feed inlet, a concentrate outlet, and a tailings outlet. The feed inlet of the secondary magnetic separation device is connected to the discharge outlet of the regrinding device. Magnetic separator;

[0077] The secondary gravity separation system includes a secondary roughing device and a secondary cleaning device. The secondary roughing device and the secondary cleaning device are each equipped with a feed inlet, a concentrate outlet, and a tailings outlet. The feed inlet of the secondary roughing device is connected to the tailings outlet of the secondary magnetic separation device; the feed inlet of the secondary cleaning device is connected to the concentrate outlet of the secondary roughing device. Both the secondary roughing and secondary cleaning devices are LY-0.5㎡ type fine mud shaking tables.

[0078] Example 1

[0079] Reference Appendix Figure 2 A novel method for chromium beneficiation from laterite nickel ore includes the following steps:

[0080] (1) Washing and primary screening: The laterite nickel ore and water are placed in a stainless steel mixing tank, the mixing is turned on, and the ore is washed. Then, the 25mm and 3mm screening is carried out by a tapping vibrating screen, and finally large gravel with a particle size of +25mm, small gravel with a particle size between -25mm and +3mm, and slurry with a particle size of <3mm are obtained.

[0081] (2) Desliming: The slurry with a particle size <3mm is deslimed using a hydrocyclone. The hydrocyclone consists of a 3 / 2C-AH slurry pump and an Smax-150 to obtain underflow slurry with a particle size ≥20μm and overflow. The particle size of the solid particles in the overflow is <20μm.

[0082] The experimental conditions for this embodiment were: hydrocyclone diameter 150 mm, hydrocyclone underflow inlet diameter 24 mm, operating pressure 0.15 MPa, and raw slurry concentration 15%. The underflow slurry and overflow obtained in this step were analyzed, and the results are shown in Table 1.

[0083] Table 1 Desliming Data Indicators

[0084] Product name Yield % Cr203 grade in %. Cr2O3 recovery in % Underflow slurry 30.60 4.02 58.30 Overflow 69.40 1.27 41.70 Run-of-mine 100.00 2.11 100.00

[0085] The results show that under the conditions of underflow diameter of 24 mm and operating pressure of 0.15 MPa, the classification efficiency is 59.18%, the classification effect is good, the underflow operation yield is 30.6%, the Cr2O3 grade is 4.02%, and the Cr2O3 operation recovery rate is 58.3%.

[0086] (3) Secondary screening: The underflow slurry with a particle size ≥20μm was subjected to secondary screening using a tapping vibrating screen to obtain oversize material with a particle size ≥1mm (i.e., +1mm particle size) and undersize slurry with a particle size <1mm (i.e., -1mm particle size). The oversize material and undersize slurry after secondary screening were analyzed, and the results are shown in Table 2:

[0087] Table 2. Analysis results of oversize and undersize slurry after secondary screening.

[0088]

[0089]

[0090] As shown in Table 1, the yield of the +1mm particle size fraction was 18.31%, with a Cr2O3 grade of 0.89%, a nickel grade of 1.08%, and a cobalt grade of 0.030%. The metal percentages were 8.61% for Cr2O3, 16.11% for nickel, and 7.84% for cobalt. The yield of the -1mm particle size fraction was 81.70%, with a Cr2O3 grade of 2.11%, a nickel grade of 1.26%, and a cobalt grade of 0.079%. The metal percentages were 91.39% for Cr2O3, 83.89% for nickel, and 92.16% for cobalt. It can be seen that chromium, cobalt, and manganese are concentrated in the -1mm particle size fraction, while silicon is significantly higher in the +1mm particle size fraction. Nickel content is high in both the +1mm and -1mm particle size fractions, at 1.08% and 1.26%, respectively.

[0091] (4) Weak magnetic separation: The underflow slurry is subjected to weak magnetic separation using a cylindrical weak magnetic separator. The weak magnetic field strength is controlled at 0.15T, the excitation current is 1.5A, the magnetic medium is type 3, and the gap is 3mm to obtain weak magnetic concentrate and weak magnetic tailings.

[0092] (5) Strong magnetic separation: The weak magnetic tailings were subjected to strong magnetic separation using a high-gradient magnetic separator. The magnetic field strength was controlled at 0.6T, the excitation current at 5.5A, the magnetic medium at type 3, and the gap at 3mm to obtain strong magnetic concentrate and strong magnetic tailings. The magnetic separation products were analyzed, and the results are shown in Table 3.

[0093] Table 3 Magnetic Separation Indicators

[0094]

[0095] The results show that under an electric field strength of 0.6T, the yield is 32.28%, the Cr2O3 grade is 8.6%, and the Cr2O3 recovery rate is 69.06%.

[0096] (6) Gravity separation: The strong magnetic concentrate is roughed using a sand-type shaking table to obtain roughed heavy ore, roughed medium ore and roughed tailings; the roughed medium ore is further separated using a fine mud-type shaking table to obtain further separated heavy ore and further separated tailings; the roughed heavy ore and the further separated heavy ore are combined and then further separated using a fine mud-type shaking table to obtain first chromium concentrate and cleaned tailings;

[0097] The parameters of the shaker selected in this embodiment are shown in Table 4:

[0098] Table 4 Shaking machine parameter table

[0099]

[0100] The results of the reselection of each material are shown in Table 5.

[0101] Table 5 Shaking Table Reselection Indicators

[0102]

[0103] The results show that under the conditions of shaking table roughing + shaking table re-selection + shaking table cleaning described in this invention, qualified chromium concentrate with an operating yield of 10.4%, a Cr2O3 grade of 43.9%, and a Cr2O3 operating recovery rate of 56.96% can be obtained.

[0104] (7) Regrinding: The selected tailings and the weak magnetic concentrate are combined and then ground to obtain the grinding product;

[0105] (8) Secondary weak magnetic separation: The grinding product is then subjected to... The magnetic separator performs weak magnetic separation, controlling the weak magnetic field strength to 0.12T, to obtain iron concentrate and secondary weak magnetic tailings;

[0106] (9) Regrinding and gravity separation: The secondary weak magnetic tailings are roughed by shaking table using LY-0.5㎡ type fine mud shaking table to obtain regrinding roughed tailings and regrinding roughed concentrate; the regrinding roughed concentrate is cleaned by shaking table using LY-0.5㎡ type fine mud shaking table to obtain second chromium concentrate and regrinding cleaned tailings.

[0107] The Cr2O3 grade of the tailings from the shaking table concentrate reached 22.85%, and the Cr2O3 grade of the weak magnetic concentrate reached 5.63%. These two intermediate products are mostly intergrowths of chromite and other minerals, so they can be effectively recovered through regrinding followed by shaking table gravity separation. To further improve the grade of the chromite concentrate, magnetite was also recovered. The results of the regrinding → secondary weak magnetic separation → regrinding gravity separation process are shown in Table 6.

[0108] Table 6. Indicators for the combined regrinding and magnetic-gravity process

[0109]

[0110] The results show that by using the combined process of finely selected shaking table tailings and weakly magnetic concentrate, and then regrinding and magnetic-gravity co-processing as described in this invention, a qualified chromium concentrate with an operating yield of 8.14%, a Cr2O3 grade of 35.66%, and a Cr2O3 operating recovery rate of 34.64% can be obtained.

[0111] Example 2

[0112] A laterite nickel ore sample was taken, with -20mm particle size accounting for 63% of the raw ore. Chromium was selected according to the method and process described in this invention, and the full process indicators are shown in Table 7.

[0113] Table 7 - Indicators for the entire chromium beneficiation process of laterite nickel ore with a 20-micron fraction (63%)

[0114]

[0115]

[0116] The results show that when using the new chromium beneficiation technology described in this invention to beneficiate relatively coarse-grained laterite nickel ore through the whole process, a chromium concentrate with a yield of 1.12%, a comprehensive Cr2O3 grade of 41.86%, and a Cr2O3 recovery rate of 25.68% can be obtained.

[0117] Example 3

[0118] A laterite nickel ore sample was taken, with 72% of the raw ore being -20 micrometers. Chromium was selected according to the method described in this invention, and the full process indicators are shown in Table 8.

[0119] Table 8 - Indicators for Chromium Beneficiation Process of Laterite Nickel Ore (72% of the 20-micron Distillate)

[0120]

[0121] The results show that when using the new chromium beneficiation technology to separate relatively coarse-grained laterite nickel ore through the whole process, a chromium concentrate with a yield of 1.39%, a comprehensive Cr2O3 grade of 33.82%, and a Cr2O3 recovery rate of 20.36% can be obtained.

[0122] Example 4

[0123] A laterite nickel ore sample was taken, with 57% of the raw ore being -20 micrometers. Chromium was selected according to the method described in this invention, and the full process indicators are shown in Table 9.

[0124] Table 9-20 micrometers: 57% of the total chromium beneficiation indicators in laterite nickel ore.

[0125]

[0126]

[0127] The results show that when using the new chromium beneficiation technology to separate relatively coarse-grained laterite nickel ore through the whole process, the laboratory can obtain a chromium concentrate with a yield of 1.87% relative to the original ore, a comprehensive Cr2O3 grade of 41.25%, and a Cr2O3 recovery rate of 31.54% relative to the original ore.

[0128] Example 5

[0129] The difference between this embodiment and Embodiment 1 is that the magnetic field strength of the weak magnetic separation is 0.1T and the excitation current is 1A; the magnetic field strength of the strong magnetic separation is 0.5T and the excitation current is 4A; and the magnetic field strength of the secondary weak magnetic separation is 0.1T.

[0130] According to the test and analysis, the yield of this example is 7.89%, the Cr2O3 grade is 34.31%, and the Cr2O3 recovery rate is 33.87%, which is a qualified chromium concentrate.

[0131] Example 6

[0132] The difference between this embodiment and Embodiment 1 is that the magnetic field strength of the weak magnetic separation is 0.3T and the excitation current is 3A; the magnetic field strength of the strong magnetic separation is 0.7T and the excitation current is 7A; and the magnetic field strength of the secondary weak magnetic separation is 0.15T.

[0133] According to the test and analysis, the chromium concentrate produced in this example has a yield of 8.52%, a Cr2O3 grade of 36.41%, and a Cr2O3 recovery rate of 35.21%.

[0134] Comparative Example 1

[0135] The difference between this comparative example and Example 1 is that strong magnetic separation is performed directly without weak magnetic separation.

[0136] According to the test and analysis, the yield of this example is 0.85%, the Cr2O3 grade is 28.31%, and the Cr2O3 recovery rate is 16.73%, which is a qualified chromium concentrate.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that secondary weak magnetic separation is not performed.

[0139] According to the test and analysis, the yield of this example is 0.93%, the Cr2O3 grade is 28.75%, and the Cr2O3 recovery rate is 17.34%, which is a qualified chromium concentrate.

[0140] Comparative Example 3

[0141] The difference between this embodiment and Embodiment 1 is that the magnetic field strength of the strong magnetic separator is 0.08T.

[0142] According to the test and analysis, the chromium concentrate produced in this example has a yield of 3.51%, a Cr2O3 grade of 30.75%, and a Cr2O3 recovery rate of 19.33%.

[0143] As can be seen from the above embodiments and comparative examples, the grade and recovery rate of Cr2O3 are highest only within the process and parameter range defined by the present invention. The comprehensive grade of Cr2O3 in the first and second chromium concentrates obtained by the method described in the present invention is 33.82%-42%, and the recovery rate of Cr2O3 in qualified chromium concentrate is 20.36%-35.21%, which is much higher than the 5-10% Cr2O3 recovery rate of the existing technology process.

[0144] Unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0145] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A novel method for the beneficiation of chromium from laterite nickel ores, characterized by, The method comprises the following steps: (1) washing and primary screening: the raw laterite nickel ore is washed and then subjected to primary screening to obtain large gravel with particle size of 3 mm or more and ore slurry with particle size of less than 3 mm; (2) desliming: the ore slurry with particle size of less than 3 mm is subjected to desliming treatment to obtain underflow slurry with particle size of 20 microns or more and overflow, and the particle size of solid particles in the overflow is less than 20 microns; (3) secondary screening: the underflow slurry with particle size of 20 microns or more is subjected to secondary screening to obtain oversize with particle size of 1 mm or more and undersize ore slurry with particle size of less than 1 mm; (4) low-intensity magnetic separation: the underflow slurry is subjected to low-intensity magnetic separation, and the low-intensity magnetic field strength is controlled to be 0.1-0.15 T to obtain low-intensity magnetic concentrate and low-intensity magnetic tailings; (5) high-intensity magnetic separation: the low-intensity magnetic tailings are subjected to high-intensity magnetic separation, and the magnetic field strength of the high-intensity magnetic field is controlled to be 0.4-0.8 T to obtain high-intensity magnetic concentrate and high-intensity magnetic tailings; (6) gravity separation: the high-intensity magnetic concentrate is subjected to roughing on a shaking table to obtain gravity concentrate, middlings and tailings; the middlings are subjected to re-concentration on a shaking table to obtain gravity concentrate and tailings; the gravity concentrate and the re-concentrate are combined and subjected to cleaning on a shaking table to obtain first chromium concentrate and cleaning tailings; (7) regrinding: the cleaning tailings and the low-intensity magnetic concentrate are combined and subjected to grinding to obtain a grinding product; (8) secondary low-intensity magnetic separation: the grinding product is subjected to low-intensity magnetic separation, and the low-intensity magnetic field strength is controlled to be 0.1-0.15 T to obtain iron concentrate and secondary low-intensity magnetic tailings; (9) regrinding gravity separation: the secondary low-intensity magnetic tailings are subjected to roughing on a shaking table to obtain regrinding roughing tailings and regrinding roughing concentrate; the regrinding roughing concentrate is subjected to cleaning on a shaking table to obtain second chromium concentrate and regrinding cleaning tailings.

2. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, characterized in that, The washing method in step (1) is as follows: the raw laterite nickel ore and water are put into a stirring tank, stirring is started, the liquid-solid ratio is controlled to be (3-4):1, the stirring intensity is controlled to be 280-380 r / min, and the stirring time is controlled to be 10-15 min.

3. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, characterized in that, The primary screening and / or secondary screening is performed by using a patting type vibrating screen machine; and / or, the desliming in step (3) is performed by using a cyclone.

4. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, characterized in that, The low-intensity magnetic separation in step (4) is performed by using a cylindrical low-intensity magnetic separator, and the excitation current is controlled to be 1-3 A, the magnetic medium is controlled to be magnetically conductive stainless steel, and the steel rod spacing of the magnetic medium box is controlled to be 3 mm.

5. The novel method for selecting chromium from laterite nickel ore according to claim 1, characterized in that, The high-intensity magnetic separation in step (5) is performed by using a high-gradient magnetic separator, and the excitation current is controlled to be 4-7 A, the magnetic medium is controlled to be magnetically conductive stainless steel, and the steel rod spacing of the magnetic medium box is controlled to be 3 mm.

6. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, characterized in that, The roughing on a shaking table in step (6) is performed by using a mineral sand type shaking table; the re-concentration and / or cleaning on a shaking table is performed by using a fine mud type shaking table.

7. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, characterized by the fact that, The secondary low-intensity magnetic separation in step (8) is performed by using a magnetic separation tube; and / or, the secondary roughing and / or secondary cleaning in step (9) is performed by using a fine mud type shaking table.

8. The novel chrome recovery process from laterite nickel ore according to any one of claims 1 to 7, characterized by, The Cr2O3 comprehensive grade of the first chromium concentrate and the second chromium concentrate is 33.82%-42%, and the recovery rate of qualified chromium concentrate Cr2O3 is 20.36%-35.21%.

9. A novel chromium separation system for laterite nickel ore, characterized by, The method comprises a washing and grading system, a magnetic separation system, a gravity separation system, a regrinding device, a secondary magnetic separation device, and a secondary gravity separation system. The ore washing and grading system comprises a stirring tank, a first screening device, a desliming device and a second screening device, the first screening device and the second screening device are respectively provided with a feed inlet and an undersize outlet, the desliming device is provided with a feed inlet, an overflow outlet and an outlet, the feed inlet of the first screening device is connected with the outlet of the stirring tank, and the feed inlet of the desliming device is connected with the undersize outlet of the first screening device; the outlet of the desliming device is connected with the feed inlet of the second screening device; The magnetic separation system comprises a weak magnetic separation device and a strong magnetic separation device, the weak magnetic separation device and the strong magnetic separation device are respectively provided with a feed inlet, a concentrate outlet and a tailings outlet, the feed inlet of the weak magnetic separation device is connected with the undersize outlet of the second screening device, and the tailings outlet of the weak magnetic separation device is connected with the feed inlet of the strong magnetic separation device; The gravity separation system comprises a roughing device, a reprocessing device and a cleaning device, the roughing device comprises a feed inlet, a heavy concentrate outlet, a middling outlet and a tailings outlet, the feed inlet of the roughing device is connected with the concentrate outlet of the strong magnetic separation device; the reprocessing device is provided with a feed inlet, a heavy concentrate outlet and a tailings outlet, the feed inlet of the reprocessing device is connected with the middling outlet of the roughing device; the cleaning device is provided with a feed inlet, a concentrate outlet and a tailings outlet, and the feed inlet of the cleaning device is connected with the heavy concentrate outlets of the roughing device and the reprocessing device; The feed inlet of the regrinding device is connected with the concentrate outlet of the weak magnetic separation device and the tailings outlet of the cleaning device; The secondary magnetic separation device is provided with a feed inlet, a concentrate outlet and a tailings outlet, and the feed inlet of the secondary magnetic separation device is connected with the outlet of the regrinding device; The secondary gravity separation system comprises a secondary roughing device and a secondary cleaning device, the secondary roughing device and the secondary cleaning device are respectively provided with a feed inlet, a concentrate outlet and a tailings outlet, the feed inlet of the secondary roughing device is connected with the tailings outlet of the secondary magnetic separation device, and the feed inlet of the secondary cleaning device is connected with the concentrate outlet of the secondary roughing device.

10. The novel chromium separation system for laterite nickel ore according to claim 9, characterized in that, the desliming device is a cyclone desliming device; and / or the weak magnetic separation device is a cylindrical weak magnetic separator; and / or the strong magnetic separation device is a high gradient magnetic separator; and / or the roughing device is a mineral sand type shaking table; and / or the reprocessing device and / or the cleaning device is a fine mud type shaking table; and / or the regrinding device is a grinding machine; and / or the secondary magnetic separation device is an XCGSφ502 magnetic separation tube; and / or the secondary roughing device and / or the secondary cleaning device is a LY-0.5㎡ type fine mud type shaking table.

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