New chromium beneficiation method and system for lateritic nickel ore

Abstract

The present invention relates to the technical field of lateritic nickel ore beneficiation. Disclosed are a new chromium beneficiation method for lateritic nickel ore, the method comprising: lateritic nickel ore → ore washing → hydrocyclone desliming → screening → low-intensity magnetic separation → high-intensity magnetic separation → gravity separation using a shaking table → chromium concentrate; and a new chromium beneficiation system for lateritic nickel ore, the system comprising: an ore washing and classification 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. In a first chromium concentrate and a second chromium concentrate obtained by using the new chromium beneficiation process flow, the comprehensive grade of Cr2O3 is 33.82%-42%, and the recovery rate of a standard-compliant chromium concentrate Cr2O3 is 20.36%-35.21%, which is much higher than the indicator of the recovery rate of Cr2O3 being 5-10% in a related technical process flow.

Description

New type method and system for selecting chromium from laterite nickel ore TECHNICAL FIELD

[0001] The present application belongs to the technical field of laterite nickel ore beneficiation, and particularly relates to a new type method and system for selecting chromium from laterite nickel ore. BACKGROUND

[0002] Laterite nickel ore is a surface weathering crust type deposit, which is a weathering-leaching-deposition product of a nickel-containing basic-ultrabasic rock body. 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 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 ore 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 process flow for selecting chromium from 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 cylindrical washing machine through a plate feeder for washing, and the ore is classified by a cylindrical washing machine 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, which is fed into a hydrometallurgical operation, the classification underflow is fed into a spiral chute for Cr2O3 pre-enrichment, the coarse-grained 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 enrichment of Cr2O3, 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 enrichment of Cr2O3, and a chromium concentrate with a Cr2O3 grade of more than 38% is obtained, the middlings of the reprocessing shaking table are treated as waste slag, and the light mineral of the reprocessing shaking table is fed into a hydrometallurgical operation through a classification regrinding operation, as shown in FIG. 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 flow has the defect of low recovery rate. SUMMARY

[0005] The raw material treated in the present application is a "wet type" laterite nickel ore in Indonesia, which is mainly composed of limonite, and the content of limonite reaches 57% to 78%; the chromium minerals therein are mainly chromite and chromium iron spinel, and the content is 2% to 4%. Other metal minerals are magnetite and manganese oxide, and there are also trace amounts of manganite, manganokalite, and manganickelite; non-metallic minerals are mainly serpentine, talc, chlorite, and quartz, and there are also small amounts of diopside, tremolite, and peridot, as well as trace amounts of diaspore and apatite.

[0006] In the raw material described in the present application, the particle size of chromite is mainly distributed in the range of 0.02 to 1 mm, which is in the range of selection, and the gravity separation of the easily selected particle size of +0.045 mm accounts for about 40%, the degree of dissociation of chromite in the +0.5 mm particle size is extremely low, and the chromite below the -0.5 mm particle size has good dissociation, and the total dissociation degree of the raw ore is more than 86%, and the chromium grade above +1 mm is low, only below 0.8%.

[0007] The occurrence state of chromium shows that the chromium in chromite and chromium iron spinel accounts for 40% to 65%, the chromium in limonite accounts for 50% to 30%, and the chromium in chlorite, magnetite, and hard manganese ore accounts for a very small proportion. The chromium in limonite is difficult to recover by physical beneficiation, and the chromium in the -0.02 mm particle size of chromite and chromium iron spinel is also extremely difficult to recover, so the theoretical recovery rate of chromium is about 40%. Except for a small amount of needle nickel, most of the nickel is dispersed in hard manganese ore, limonite, and various clay minerals and iron-magnesium silicate minerals.

[0008] The average content of Cr2O3 in chromite and chromium spinel is 37%, and the highest can reach 47%, which is the main purpose mineral for chromium selection, and the 0.02 mm above particle size of chromite and chromium spinel is mainly recovered. Chromite and spinel belong to the spinel family of minerals, and the isomorphism substitution between Mg 2+ and Fe 2+ , Al 3+ and Cr 3+ , Fe 3+ is very extensive, forming chromite subfamily and spinel subfamily minerals, which have strong magnetic properties to weak magnetic properties, most of which enter the magnetic product at a field strength of 0.1 to 0.48T, and a few enter the magnetic product at 0.56T. Most of the chromite and chromium spinel are granular or fragmented granular monomer particles, and part of the chromite is intergrown with serpentine, olivine, and limonite, and the chromite and spinel are gradually changed in growth.

[0009] In combination with the related technical process and the raw material described in the present application, the existing chromium selection process has the following defects:

[0010] 1. Large-diameter cyclone classifies particle size of 53 microns, and chromite (containing chromite) in +20 micron particle size is in the recoverable range, the classification efficiency decreases with the increase of the proportion of -400 mesh particle size in the raw ore in actual production, the proportion of +20 microns in the overflow of the cyclone is 20% to 40%, causing the tailing loss of +20 micron Cr2O3 recovery rate, and the operating recovery rate of Cr2O3 in the underflow of the cyclone is only 40 to 50%;

[0011] 2. There is residual flocculating agent in the production process water, which is easy to form a group and precipitate at the position of the spiral chute intercepter, causing the intercepter to be blocked, causing the heavy minerals to directly enter the light mineral tailings, causing a large loss of chromite (containing chromite); at the same time, due to the phenomenon of high molecular flocculation precipitation, the separation effect of the spiral chute is reduced;

[0012] 3. The Cr2O3 grade of the middlings in the re-concentration shaking table is about 10%, which is the intergrowth of chromite (containing chromite) and other minerals, directly enters the slag pool and is thrown away without taking measures to recover, causing the loss of chromite;

[0013] 4. In the process of shaking table gravity separation, +1 to -3 mm large particles, especially +2 to -3 mm particle size, exceed the separation range of the shaking table, hinder the formation of chromite concentrate belt on the shaking table bed surface and the movement of chromite to the concentrate discharge direction, causing the movement of chromite to the middlings, causing the loss of chromite.

[0014] The application specifically includes the following contents:

[0015] With the increase of the demand for chromium concentrate smelting, the contradiction with the low chromium recovery rate is increasingly intensified; at the same time, with the gradual increase of the number and scale of nickel hydrometallurgy industrial production projects, the waste of chromium resources caused by the chromium selection process is also increasingly serious, and a new chromium selection technology for laterite nickel ore is urgently needed, which aims to greatly improve the Cr2O3 recovery rate and reduce the influence of chromium impurities on smelting. In view of the problems existing in the related technology, the application provides a new chromium selection method and system for laterite nickel ore, and the specific contents of the application are as follows:

[0016] A new chromium selection method for laterite nickel ore, comprising the following steps:

[0017] (1) Washing and primary screening: washing the raw laterite nickel ore, and then performing 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; since the laterite nickel ore is tightly bonded together by clay minerals such as chlorite, serpentine, soapstone and talc to form particles of different sizes, the application first disperses various minerals by washing to expose the properties of various minerals, which is more conducive to subsequent separation;

[0018] (2) Desliming: the ore slurry with a particle size of <3 mm is subjected to desliming treatment to obtain an underflow slurry with a particle size of >20 pm and an overflow, the solid particles in the overflow having a particle size of <20 pm; the content of the fine particle size in the ore is high, the proportion of the particle size of -0.02 mm in different raw ores is 51.76% to 72.34%, and the grade of Cr2O3 in the mineral particles with a particle size of <0.02 mm is low, with an average grade of 1.19%, which is difficult to be recovered by physical means. Therefore, due to the large difference in the proportion of the particle size of -0.02 mm in different raw ores, it is inevitable to cause large fluctuations in the recovery rate of the chromite, that is, the larger the proportion of the particle size of -0.02 mm in the raw ore, the lower the recovery rate of the chromite. Therefore, the mineral with a particle size of <0.02 mm is removed by desliming operation and does not enter the subsequent chromite selection process;

[0019] (3) Secondary screening: the underflow slurry with a particle size of >20 pm is subjected to secondary screening to obtain oversize material with a particle size of >1 mm and undersize slurry with a particle size of <1 mm; according to the particle size composition analysis results of different raw ores, the Cr2O3 grade of +3 mm and -3~+1 mm particle size is low, with contents of 0.84% and 1.15% respectively, therefore, the +3 mm and -3~+1 mm particle size minerals are pre-removed by secondary screening and do not enter the subsequent chromite selection process;

[0020] (4) Low-intensity magnetic separation: the underflow slurry is subjected to low-intensity magnetic separation, the low-intensity magnetic field strength is controlled to be 0.1-0.15T, and low-intensity magnetic concentrate and low-intensity tailings are obtained;

[0021] (5) High-intensity magnetic separation: the low-intensity tailings are subjected to high-intensity magnetic separation, the magnetic field strength of the high-intensity magnetic field is controlled to be 0.4-0.8T, and high-intensity magnetic concentrate and high-intensity tailings are obtained; since the chromite has weak magnetism, the high-gradient high-intensity magnetic separation can be used for recovery. The high-gradient high-intensity magnetic separation has the characteristics of high magnetic field strength and good recovery effect on fine-grained valuable minerals. The particle size of the chromite in the ore is generally fine, and the high-gradient high-intensity magnetic separation is beneficial to the recovery of the fine-grained chromite. In addition, the content of the fine particle size in the ore is high, the content of the particle size of -0.01 mm is 31.76%, and the content of Cr2O3 in the particle size material accounts for 38.40% of the Cr2O3 in the whole particle size, so much fine mud has a very adverse effect on the gravity separation of the chromite, and the magnetic separation step is set before the gravity separation in the present application, a large amount of fine mud enters the high-intensity tailings in the magnetic separation process, avoiding the entry of the fine mud into the gravity separation. Therefore, the magnetic separation can pre-enrich the chromite, strengthen the recovery of the fine-grained chromite, and reduce the adverse effects of the fine mud on the subsequent gravity separation;

[0022] (6) Re-selection: the strong magnetic concentrate is subjected to rough table separation to obtain heavy concentrate, middlings and tailings; the middlings are subjected to re-table separation to obtain re-concentrate and tailings; the re-concentrate and the heavy concentrate are combined and subjected to table separation to obtain first chromium concentrate and tailings; the density of the chromite is high, reaching 4-5 g / cm 3 , the density of the limonite, augite and amphibole is less than 3.5 g / cm 3 . In the high gradient magnetic separation process, part of the weakly magnetic minerals such as limonite, augite and amphibole are separated together with the chromite, and the density difference between the chromite and other minerals is used to realize the separation of the monomer state chromite and other minerals by table re-selection. The primary liberation degree of the chromite is as high as 86.29%, and thus most of the chromite can be effectively recovered in this operation.

[0023] (7) Re-grinding: the tailings and the weak magnetic concentrate are combined and ground to obtain a ground product; since the intergrowth state chromite enters the middlings in the table re-selection process, the middlings need to be re-ground and re-selected;

[0024] (8) Secondary weak magnetic separation: the ground product is subjected to weak magnetic separation to control the weak magnetic field strength to be 0.1-0.15 T to obtain iron concentrate and secondary weak magnetic tailings;

[0025] (9) Re-grinding and re-selection: the secondary weak magnetic tailings are subjected to rough table separation to obtain re-grinding tailings and re-grinding concentrate; the re-grinding concentrate is subjected to table separation to obtain second chromium concentrate and re-grinding tailings. The primary fine-grained chromite and the fine-grained chromite produced in the re-grinding process are finally all in the table middlings, and the fine-grained chromite is recovered by table re-selection to effectively improve the recovery rate.

[0026] Further, the ore washing method of step (1) is that the laterite nickel ore and water are put into a stirring tank, the 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.

[0027] Further, at least one of the primary screening and the secondary screening is performed by using a pat-type vibrating screen machine.

[0028] Further, the desliming of step (3) is performed by using a cyclone.

[0029] Further, the weak magnetic separation of step (4) is performed by using a cylindrical weak magnetic separator, the exciting current is controlled to be 1-3 A, the magnetic medium is controlled to be a magnetically conductive stainless steel, and the steel rod spacing of the magnetic medium box is controlled to be 3 mm.

[0030] Further, the strong magnetic separation in step (5) is performed by using a high gradient magnetic separator, the control excitation current is 1-3 A, the magnetic medium is a magnetic conductive stainless steel, and the distance between the steel rods of the magnetic medium box is 3 mm.

[0031] Steps (4)-(5) set the magnetic field strength, magnetic medium and distance of the weak magnetic separation and the strong magnetic separation respectively according to the particle size, characteristics and other factors of the selected mineral in the present application, so as to ensure the optimal demagnetization effect.

[0032] Further, the table roughing in step (6) is performed by using a sand type table, the sand table is used for roughing because the structure and performance of the sand table are more suitable for selecting materials with a large proportion of coarse particles, and the single processing capacity is larger and the economic and technical indicators are higher; at least one of the table reselection and the table cleaning in step (6) is performed by using a fine mud type table, the fine mud table is more suitable for materials with a large proportion of fine particles, and the mineral processing indicators are better.

[0033] Further, at least one of the following conditions is met: the secondary weak magnetic separation in step (8) is performed by using a magnetic separation tube, the magnetic separation tube is used here to more conveniently control and adjust the magnetic field strength, the feed amount and the vibration frequency; at least one of the secondary roughing and the secondary cleaning in step (9) is performed by using a fine mud type table.

[0034] A novel chromium selection 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 washing and grading system includes a stirring storage tank, a primary screening device, a desliming device, and a secondary screening device, the primary screening device and the secondary screening device are respectively provided with a feed inlet and a undersize discharge outlet, 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 with the discharge outlet of the stirring storage tank, the feed inlet of the desliming device is connected with the undersize discharge outlet of the primary screening device, and the discharge outlet of the desliming device is connected with 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 with the undersize discharge outlet of the secondary screening device, and the tailings outlet of the weak magnetic separation device is connected with the feed inlet of the strong magnetic separation device.

[0037] The reselection system comprises a rough selection device, a reselection device and a fine selection device, the rough selection device comprises a feed inlet, a heavy mineral outlet, a middling outlet and a tailing outlet, the feed inlet of the rough selection device is connected with the concentrate outlet of the high-intensity magnetic separation device; the reselection device is provided with a feed inlet, a heavy mineral outlet and a tailing outlet, the feed inlet of the reselection device is connected with the middling outlet of the rough selection device; the fine selection device is provided with a feed inlet, a concentrate outlet and a tailing outlet, the feed inlet of the fine selection device is connected with the heavy mineral outlets of the rough selection device and the reselection device respectively;

[0038] The feed inlet of the regrinding device is connected with the concentrate outlet of the low-intensity magnetic separation device and the tailing outlet of the fine selection device respectively;

[0039] The secondary magnetic separation device is provided with a feed inlet, a concentrate outlet and a tailing outlet, the feed inlet of the secondary magnetic separation device is connected with the discharge outlet of the regrinding device;

[0040] The secondary reselection system comprises a secondary rough selection device and a secondary fine selection device, the secondary rough selection device and the secondary fine selection device are respectively provided with a feed inlet, a concentrate outlet and a tailing outlet, the feed inlet of the secondary rough selection device is connected with the tailing outlet of the secondary magnetic separation device; the feed inlet of the secondary fine selection device is connected with the concentrate outlet of the secondary rough selection device.

[0041] Further, at least one of the following conditions is met:

[0042] The desliming device is a cyclone desliming device;

[0043] The low-intensity magnetic separation device is a cylindrical low-intensity magnetic separator;

[0044] The high-intensity magnetic separation device is a high-gradient magnetic separator;

[0045] The rough selection device is a mineral sand type shaking table;

[0046] At least one of the reselection device and the fine selection device is a fine slurry type shaking table;

[0047] The regrinding device is a grinding machine;

[0048] The secondary magnetic separation device is a magnetic separation tube;

[0049] At least one of the secondary rough selection device and the secondary fine selection device is a LY-0.5㎡ fine slurry type shaking table. BRIEF DESCRIPTION OF DRAWINGS

[0050] FIG. 1 is a process flow diagram of a new type of chromium selection method for laterite nickel ore in the related art;

[0051] FIG. 2 is a process flow diagram of a new type of chromium selection method for laterite nickel ore disclosed in the present application; ​

[0052] Fig. 3 is a structural schematic diagram of a new type of chromium separation system for laterite nickel ore disclosed by the present application;

[0053] Table 1 is a desliming data index of Example 1;

[0054] Table 2 is the analysis results of the oversize and undersize slurry after the secondary screening of Example 1;

[0055] Table 3 is a magnetic separation index table of Example 1;

[0056] Table 4 is a table of table parameters of Example 1;

[0057] Table 5 is a table of table parameters of Example 1;

[0058] Table 6 is an index table of the regrinding and magnetic separation combined process of Example 1;

[0059] Table 7 is a chromium separation process index of laterite nickel ore with a-20 micron ratio of 63% in Example 2;

[0060] Table 8 is a chromium separation process index of laterite nickel ore with a-20 micron ratio of 72% in Example 3;

[0061] Table 9 is a chromium separation process index of laterite nickel ore with a-20 micron ratio of 57% in Example 4. DETAILED DESCRIPTION

[0062] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments shown below do not limit the invention described in the claims in any way. In addition, the entire content of the embodiments shown below is not limited to being necessary for the solution of the invention described in the claims.

[0063] Referring to Fig. 2, a new type of chromium separation method for laterite nickel ore includes the following steps:

[0064] (1) Washing and primary screening: Put the laterite nickel ore and water into the 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, and then perform washing and primary screening to obtain large gravel with a particle size of ≥3 mm and a slurry with a particle size of <3 mm; the present application pre-removes +1 mm size gravel with a Cr2O3 grade of less than 1% through washing and primary screening, and the chromium iron ore of-1 mm particle size entering the chromium separation process is pre-enriched, thereby improving the Cr2O3 grade of the weak magnetic separation slurry;

[0065] (2) Desliming: The slurry with a particle size of <3 mm is subjected to desliming treatment to obtain an underflow slurry with a particle size of ≥20 μm and an overflow, and the particle size of the solid particles in the overflow is <20 μm;

[0066] (3) Secondary screening: the undersize slurry with particle size ≥20 μm is subjected to secondary screening to obtain oversize with particle size ≥1 mm and undersize slurry with particle size <1 mm;

[0067] (4) Low-intensity magnetic separation: the undersize slurry is subjected to low-intensity magnetic separation by using a cylindrical low-intensity magnetic separator, the low-intensity magnetic field strength is controlled to be 0.1-0.15 T, the excitation current is controlled to be 1-3 A, the magnetic medium is type 3 (magnetic conductive stainless steel), the steel rod spacing of the magnetic medium box is controlled to be 3 mm, and low-intensity magnetic concentrate and low-intensity tailings are obtained;

[0068] (5) High-intensity magnetic separation: the low-intensity tailings are subjected to high-intensity magnetic separation by using a high-gradient magnetic separator, the magnetic field strength of the high-intensity magnetic field is controlled to be 0.4-0.8 T, the excitation current is controlled to be 4-7 A, the magnetic medium is type 3 (magnetic conductive stainless steel), the steel rod spacing of the magnetic medium box is controlled to be 3 mm, and high-intensity magnetic concentrate and high-intensity tailings (i.e. tailings 1 in FIG. 2) are obtained; through the combined process of low-intensity magnetic separation and high-intensity magnetic separation, coarse-grained chromite is recovered, and the high-intensity magnetic separator can effectively recover fine-grained chromite, thereby expanding the range of recovered particle size of chromite and improving the recovery rate of chromite;

[0069] (6) Gravity separation: the high-intensity magnetic concentrate is subjected to rough shaking table separation by using a sand-type shaking table to obtain gravity concentrate, middlings and tailings (i.e. tailings 2); the middlings are subjected to re-shaking table separation by using a fine-silt type shaking table to obtain re-concentrate and re-tailings (i.e. tailings 3); the gravity concentrate and the re-concentrate are combined and subjected to fine-silt type shaking table separation to obtain first chromite concentrate (i.e. chromite concentrate 1) and fine-silt type shaking table tailings; through three-stage gravity separation by using a shaking table, different particle sizes of chromite are recovered according to the distribution law of the particle sizes, the coarse sand type shaking table is used for rough shaking table separation to preferentially separate high-grade chromite in the particle size range of 0.074 mm-1 mm, and the fine-silt type shaking table is used for re-shaking table separation to recover chromite in the particle size range of 0.02 mm-0.074 mm; through 1 mm screening, low-grade coarse particles are thrown out, which can solve the problem of coarse particles affecting the separation efficiency of the shaking table and avoid loss of the recovery rate of chromite concentrate;

[0070] (7) Re-grinding: the fine-silt type shaking table tailings and the low-intensity magnetic concentrate are combined and subjected to grinding to obtain a grinding product;

[0071] (8) Secondary low-intensity magnetic separation: the grinding product is subjected to low-intensity magnetic separation by using a magnetic separation tube, the low-intensity magnetic field strength is controlled to be 0.1-0.15 T, and iron concentrate and secondary low-intensity tailings are obtained;

[0072] (9) Re-grinding gravity separation: the secondary low-intensity tailings are subjected to rough shaking table separation by using a fine-silt type shaking table to obtain re-grinding rough shaking table tailings (i.e. tailings 4) and re-grinding rough shaking table concentrate; the re-grinding rough shaking table concentrate is subjected to fine-silt type shaking table separation to obtain second chromite concentrate (i.e. chromite concentrate 2) and re-grinding fine-silt type shaking table tailings (i.e. tailings 5).

[0073] In actual industrial production, the laterite nickel ore piles of multiple mining areas exist together, it is difficult to accurately match the ores, so the phenomenon of large fluctuation range of the proportion of-20 microns in the raw ore occurs. When the particle size of-20 microns is more than 70%, it is difficult to improve the grade of chromium concentrate, and the chromium recovery rate is low. The new chromium selection method of the application has better adaptability than other processes in the related art when facing such refractory laterite nickel ore. The comprehensive grade of Cr2O3 in the first chromium concentrate and the second chromium concentrate obtained by the new chromium selection process of the application is 33.82%-42%, and the recovery rate of qualified chromium concentrate Cr2O3 is 20.36%-35.21%, which is much higher than the index of 5-10% of the related art process.

[0074] A new type of laterite nickel ore chromium selection system capable of realizing the above-mentioned chromium selection method, comprising 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.

[0075] The washing and grading system comprises a stirring tank, a primary screening device, a desliming device, and a secondary screening device. The primary screening device and the secondary screening device are respectively provided with a feed inlet and an undersize discharge outlet. 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 with the discharge outlet of the stirring tank, and the feed inlet of the desliming device is connected with the undersize discharge outlet of the primary screening device. The discharge outlet of the desliming device is connected with the feed inlet of the secondary screening device. The desliming device is preferably a cyclone desliming device. By desliming through the cyclone, the best grading conditions and equipment selection can be selected to pre-throw a large amount of chromium-iron ore that is difficult to recover in the-20 micron size fraction, so as to pre-enrich the chromium-iron ore. At the same time, in industrial production application, the number of subsequent process equipment and the equipment processing capacity can be reduced, the capital construction and equipment investment can be effectively reduced, and the enterprise profit can be improved.

[0076] 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 discharge outlet of the secondary 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 weak magnetic separation device is a cylindrical weak magnetic separator, and the strong magnetic separation device is a high gradient magnetic separator.

[0077] The reselection system comprises a rough selection device, a reselection device, and a fine selection device. The rough selection device comprises a feed inlet, a heavy mineral outlet, a middling outlet, and a tailing outlet. The feed inlet of the rough selection device is connected with the concentrate outlet of the strong magnetic selection device. The reselection device is provided with a feed inlet, a heavy mineral outlet, and a tailing outlet. The feed inlet of the reselection device is connected with the middling outlet of the rough selection device. The fine selection device is provided with a feed inlet, a concentrate outlet, and a tailing outlet. The feed inlet of the fine selection device is connected with the heavy mineral outlets of the rough selection device and the reselection device. The rough selection device is a sand type shaking table. The reselection device and the fine selection device are fine mud type shaking tables. The feed inlet of the regrinding device is connected with the concentrate outlet of the weak magnetic selection device and the tailing outlet of the fine selection device.

[0078] The feed inlet of the regrinding device is connected with the concentrate outlet of the weak magnetic selection device and the tailing outlet of the fine selection device. The regrinding device is a grinding machine.

[0079] The secondary magnetic selection device is provided with a feed inlet, a concentrate outlet, and a tailing outlet. The feed inlet of the secondary magnetic selection device is connected with the discharge outlet of the regrinding device. The secondary magnetic selection device is a magnetic selection tube. The secondary magnetic selection device is provided with a feed inlet, a concentrate outlet, and a tailing outlet. The feed inlet of the secondary magnetic selection device is connected with the discharge outlet of the regrinding device. The secondary magnetic selection device is a magnetic selection tube.

[0080] The secondary reselection system comprises a secondary rough selection device and a secondary fine selection device. The secondary rough selection device and the secondary fine selection device are respectively provided with a feed inlet, a concentrate outlet, and a tailing outlet. The feed inlet of the secondary rough selection device is connected with the tailing outlet of the secondary magnetic selection device. The feed inlet of the secondary fine selection device is connected with the concentrate outlet of the secondary rough selection device. The secondary rough selection device and the secondary fine selection device are LY-0.5㎡ fine mud type shaking tables.

[0081] Embodiment 1

[0082] Referring to FIG. 2, a novel chrome selection method for laterite nickel ore comprises the following steps:

[0083] (1) Washing and primary screening: Put the laterite nickel ore and water into a stainless steel stirring tank, start stirring, and then use a patting type vibrating screen to perform 25 mm and 3 mm screening in sequence, so as to obtain large gravel with a particle size of +25 mm, small gravel with a particle size of -25 mm to +3 mm, and slurry with a particle size of <3 mm.

[0084] (2) Desliming: The slurry with a particle size of <3 mm is subjected to desliming treatment by using a cyclone. The cyclone is composed of a 3 / 2C-AH slurry pump and a Smax-150, so as to obtain underflow slurry with a particle size of ≥20 μm and overflow. The particle size of solid particles in the overflow is <20 μm.

[0085] The test conditions of this embodiment: the cyclone diameter is 150 mm, the cyclone underflow port diameter is 24 mm, the operating pressure is 0.15 MPa, and the raw ore pulp concentration is 15%. The underflow ore pulp and overflow obtained in this step are analyzed, and the results are shown in Table 1.

[0086] The results show that under the conditions of underflow port diameter 24 mm and operating pressure 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%.

[0087] (3) Secondary screening: the underflow ore pulp with a particle size of ≥20 μm is subjected to secondary screening by a tapping type vibrating screen to obtain oversize material with a particle size of ≥1 mm (i.e. +1 mm size fraction) and undersize ore pulp with a particle size of <1 mm (i.e. -1 mm size fraction); the oversize material and undersize ore pulp after secondary screening are analyzed, and the results are shown in Table 2.

[0088] As shown in Table 1, the +1 mm size fraction yield is 18.31%, the Cr2O3 grade is 0.89%, the nickel grade is 1.08%, the cobalt grade is 0.030%, and the metal occupancy rates are respectively: Cr2O3 8.61%, nickel 16.11%, and cobalt 7.84%; the -1 mm size fraction yield is 81.70%, the Cr2O3 grade is 2.11%, the nickel grade is 1.26%, the cobalt grade is 0.079%, and the metal occupancy rates are respectively: Cr2O3 91.39%, nickel 83.89%, and cobalt 92.16%; it can be seen that chromium, cobalt and manganese are concentrated in -1 mm, silicon is obviously higher in +1 mm size fraction, and nickel content is high in both +1 mm and -1 mm size fractions, being 1.08% and 1.26% respectively.

[0089] (4) Low intensity magnetic separation: the underflow ore pulp is subjected to low intensity magnetic separation by a cylindrical low intensity magnetic separator, the low intensity magnetic field strength is controlled to be 0.15 T, the excitation current is controlled to be 1.5 A, the magnetic medium is controlled to be type 3, and the gap is controlled to be 3 mm, to obtain low intensity magnetic concentrate and low intensity magnetic tailings;

[0090] (5) High intensity magnetic separation: the low intensity magnetic tailings are subjected to high intensity magnetic separation by a high gradient magnetic separator, the high intensity magnetic field strength is controlled to be 0.6 T, the excitation current is controlled to be 5.5 A, the magnetic medium is controlled to be type 3, and the gap is controlled to be 3 mm, to obtain high intensity magnetic concentrate and high intensity magnetic tailings; the magnetic separation products are analyzed, and the results are shown in Table 3.

[0091] The results show that under the condition of 0.6 T field strength, the operation yield is 32.28%, the Cr2O3 grade is 8.6%, and the Cr2O3 operation recovery rate is 69.06%.

[0092] (6) Re-selection: the strong magnetic concentrate is subjected to roughing by a sand type table, to obtain a heavy concentrate, a middling and a tailing; the middling is subjected to re-roughing by a fine mud type table, to obtain a heavy concentrate and a tailing; the roughing heavy concentrate and the re-roughing heavy concentrate are combined and subjected to cleaning by a fine mud type table, to obtain a first chromium concentrate and a cleaning tailing;

[0093] The table parameters used in the example are shown in Table 4.

[0094] The materials of the re-selection are analyzed, and the results are shown in Table 5.

[0095] The results show that under the conditions of the table roughing + table re-roughing + table cleaning, a qualified chromium concentrate with a production rate of 10.4%, a Cr2O3 grade of 43.9% and a Cr2O3 recovery rate of 56.96% can be obtained.

[0096] (7) Re-grinding: the cleaning tailing and the weak magnetic concentrate are combined and subjected to grinding, to obtain a grinding product;

[0097] (8) Secondary weak magnetic separation: the grinding product is subjected to weak magnetic separation by a magnetic tube, with a weak magnetic field strength of 0.12T, to obtain an iron concentrate and a secondary weak magnetic tailing;

[0098] (9) Re-grinding re-selection: the secondary weak magnetic tailing is subjected to roughing by a LY-0.5㎡ fine mud type table, to obtain a re-grinding roughing tailing and a re-grinding roughing concentrate; the re-grinding roughing concentrate is subjected to cleaning by a LY-0.5㎡ fine mud type table, to obtain a second chromium concentrate and a re-grinding cleaning tailing.

[0099] The Cr2O3 grade of the table cleaning tailing reaches 22.85%, and the Cr2O3 grade of the weak magnetic concentrate reaches 5.63%. The two intermediate products are mainly intergrowths of chromite and other minerals, so they can be effectively recovered by re-grinding + table re-selection. In order to improve the grade of the chromium concentrate, the magnetite is also recovered. The materials of the re-grinding → secondary weak magnetic separation → re-grinding re-selection are analyzed, and the results are shown in Table 6.

[0100] The results show that by using the re-grinding magnetic re-selection combined process of the cleaning table tailing + weak magnetic concentrate, a qualified chromium concentrate with a production rate of 8.14%, a Cr2O3 grade of 35.66% and a Cr2O3 recovery rate of 34.64% can be obtained.

[0101] Example 2

[0102] A laterite nickel ore sample is taken, with a-20mm particle size accounting for 63% of the raw ore. The chromium is selected according to the method and process of the application, and the whole process indexes are shown in Table 7.

[0103] ​The results show that when the new chromium separation technology is used to separate the relatively coarse particle size laterite nickel ore, a chromium concentrate with a yield of 1.12%, a comprehensive grade of Cr2O3 of 41.86%, and a recovery rate of Cr2O3 of 25.68% can be obtained.

[0104] Example 3

[0105] A laterite nickel ore sample is taken, and the proportion of -20 microns in the raw ore is 72%. The chromium is separated according to the method and process described in the present application, and the whole process indicators are shown in Table 8.

[0106] The results show that when the new chromium separation technology is used to separate the relatively coarse particle size laterite nickel ore, a chromium concentrate with a yield of 1.39%, a comprehensive grade of Cr2O3 of 33.82%, and a recovery rate of Cr2O3 of 20.36% can be obtained.

[0107] Example 4

[0108] A laterite nickel ore sample is taken, and the proportion of -20 microns in the raw ore is 57%. The chromium is separated according to the method and process described in the present application, and the whole process indicators are shown in Table 9.

[0109] The results show that when the new chromium separation technology is used to separate the relatively coarse particle size laterite nickel ore, a chromium concentrate with a yield of 1.87% relative to the raw ore, a comprehensive grade of Cr2O3 of 41.25%, and a recovery rate of Cr2O3 of 31.54% relative to the raw ore can be obtained.

[0110] Example 5

[0111] The difference between this embodiment and Example 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; the magnetic field strength of the secondary weak magnetic separation is 0.1T.

[0112] After detection and analysis, the qualified chromium concentrate with a yield of 7.89%, a Cr2O3 grade of 34.31%, and a Cr2O3 operation recovery rate of 33.87% is obtained.

[0113] Example 6

[0114] The difference between this embodiment and Example 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; the magnetic field strength of the secondary weak magnetic separation is 0.15T.

[0115] After detection and analysis, the qualified chromium concentrate with a yield of 8.52%, a Cr2O3 grade of 36.41%, and a Cr2O3 operation recovery rate of 35.21% is obtained.

[0116] Comparative Example 1

[0117] The difference between the present comparative example and example 1 is that the weak magnetic separation is not performed directly before the strong magnetic separation.

[0118] Through detection analysis, the operation yield of the present example is 0.85%, the Cr2O3 grade is 28.31%, and the qualified chromium concentrate with Cr2O3 operation recovery rate of 16.73% is obtained.

[0119] Comparative example 2

[0120] The difference between the present comparative example and example 1 is that the secondary weak magnetic separation is not performed.

[0121] Through detection analysis, the operation yield of the present example is 0.93%, the Cr2O3 grade is 28.75%, and the qualified chromium concentrate with Cr2O3 operation recovery rate of 17.34% is obtained.

[0122] Comparative example 3

[0123] The difference between the present example and example 1 is that the magnetic field strength of the strong magnetic separation is 0.08T.

[0124] Through detection analysis, the operation yield of the present example is 3.51%, the Cr2O3 grade is 30.75%, and the qualified chromium concentrate with Cr2O3 operation recovery rate of 19.33% is obtained.

[0125] From the above examples and comparative examples, it can be seen that only in the process and parameter range defined in the present application, the grade and recovery rate of Cr2O3 are the highest, the comprehensive grade of Cr2O3 in the first chromium concentrate and the second chromium concentrate obtained by using the method described in the present application is 33.82%-42%, and the recovery rate of Cr2O3 in the qualified chromium concentrate is 20.36%-35.21%, which is much higher than the index of 5-10% of the recovery rate of Cr2O3 in the related art process.

[0126] Unless otherwise explicitly defined and limited, the terms "arranged", "connected" should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be directly connected, or indirectly connected through an intermediate medium, can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0127] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to 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, wherein, 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 and ore slurry with particle size of <3 mm; (2) desliming: the ore slurry with particle size of <3 mm is subjected to desliming treatment to obtain underflow slurry with particle size of ≥20 μm and overflow, and the particle size of solid particles in the overflow is <20 μm; (3) secondary screening: the underflow slurry with particle size of ≥20 μm is subjected to secondary screening to obtain oversize material with particle size of ≥1 mm and undersize ore slurry with particle size of <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 high-intensity magnetic field strength 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 rough shaking table separation to obtain rough gravity concentrate, rough shaking table middlings and rough shaking table tailings; the rough shaking table middlings are subjected to re-shaking table separation to obtain re-shaking table concentrate and re-shaking table tailings; the rough shaking table concentrate and the re-shaking table concentrate are combined and subjected to fine shaking table separation to obtain first chromium concentrate and fine shaking table tailings; (7) regrinding: the fine shaking table tailings and the low-intensity magnetic concentrate are combined and subjected to grinding to obtain grinding products; (8) secondary low-intensity magnetic separation: the grinding products are 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 rough shaking table separation to obtain regrinding rough shaking table tailings and regrinding rough shaking table concentrate; the regrinding rough shaking table concentrate is subjected to fine shaking table separation to obtain second chromium concentrate and regrinding fine shaking table tailings.

2. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, wherein, 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, wherein, At least one of the following two conditions is met: at least one of the primary screening and the secondary screening is performed by using a patting type vibrating screen machine; and 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, wherein, The low-intensity magnetic separation in step (4) is performed by using a cylindrical low-intensity magnetic separator, and the exciting 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. A novel method for the selective recovery of chromium from laterite nickel ores according to claim 1, wherein, The high-intensity magnetic separation in step (5) is performed by using a high-gradient magnetic separator, and the exciting 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, wherein, The rough shaking table separation in step (6) is performed by using a mineral sand type shaking table; and at least one of the re-shaking table separation and the fine shaking table separation 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, wherein, At least one of the following two conditions is met: the secondary low-intensity magnetic separation in step (8) is performed by using a magnetic separation tube; and at least one of the secondary rough shaking table separation and the secondary fine shaking table separation 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, wherein, 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 system for the beneficiation of chromium from laterite nickel ores, wherein, The washing and grading system, the magnetic separation system, the gravity separation system, the regrinding device, the secondary magnetic separation device, and the secondary gravity separation system; The 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 low-intensity magnetic separation device and a high-intensity magnetic separation device, the low-intensity magnetic separation device and the high-intensity magnetic separation device are respectively provided with a feed inlet, a concentrate outlet, and a tailings outlet, the feed inlet of the low-intensity magnetic separation device is connected with the undersize outlet of the second screening device, and the tailings outlet of the low-intensity magnetic separation device is connected with the feed inlet of the high-intensity magnetic separation device; The gravity separation system comprises a roughing device, a re-roughing device, and a cleaning device, the roughing device comprises a feed inlet, a heavy mineral outlet, a middling outlet, and a tailings outlet, the feed inlet of the roughing device is connected with the concentrate outlet of the high-intensity magnetic separation device; the re-roughing device is provided with a feed inlet, a heavy mineral outlet, and a tailings outlet, the feed inlet of the re-roughing 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, the feed inlet of the cleaning device is connected with the heavy mineral outlets of the roughing device and the re-roughing device; The feed inlet of the regrinding device is connected with the concentrate outlet of the low-intensity 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, 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; the feed inlet of the secondary cleaning device is connected with the concentrate outlet of the secondary roughing device.

10. A novel chrome separation system for laterite nickel ore according to claim 9, wherein, At least one of the following conditions is met: The desliming device is a cyclone desliming device; The low-intensity magnetic separation device is a cylindrical low-intensity magnetic separator; The high-intensity magnetic separation device is a high-gradient magnetic separator; The roughing device is a mineral sand type shaking table; At least one of the re-roughing device and the cleaning device is a fine slurry type shaking table; The regrinding device is a grinding machine; The secondary magnetic separation device is The magnetic separation pipe; At least one of the secondary roughing device and the secondary cleaning device is a LY-0.5㎡ fine slurry type shaking table.

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