A gravity separation system and method for low-grade chromite

Abstract

The present invention discloses a gravity separation system and method for low-grade chromite. The separation system comprises a spiral chute for roughing, a spiral chute for first-stage cleaning, a spiral chute for second-stage cleaning, a spiral chute for first-stage scavenging, and a spiral chute for second-stage scavenging. The roughing spiral chute has an aspect ratio A of 0.50 and a lateral inclination angle B of 8.7° or 9.3°. The first-stage cleaning spiral chute and the second-stage cleaning spiral chute have an aspect ratio A of 0.58 or 0.62 and a lateral inclination angle B of 9.5° or 10.5°. The first-stage scavenging spiral chute and the second-stage scavenging spiral chute have an aspect ratio A of 0.43 or 0.47 and a lateral inclination angle B of 8.2° or 8.6°. The use of the above-mentioned sorting system for roughing, concentrating and scavenging can greatly improve the mineral processing capacity and the grade and recovery rate of chromite concentrate. The present invention has the advantages of simple production operation, low consumption, greenness and stable indicators. It can adapt to the large-scale chromite mineral processing production requirements and has excellent production indicators.

Description

Technical Field

[0001] The present invention belongs to the field of mineral processing, and in particular relates to a gravity separation system and method for low-grade chromite. Background Art

[0002] Chromite resources are primarily distributed in Africa, with South Africa and Zimbabwe accounting for 97% of the world's total. Due to its scarcity, my country imports large quantities of chromite annually, initially primarily in the form of high-grade lump ore. However, as high-grade lump ore resources gradually decrease, obtaining sufficiently high-grade lump ore becomes increasingly difficult, while the amount of discarded low- and medium-grade chromite ore in mines continues to grow. Consequently, there is an urgent need to develop effective beneficiation methods to separate high-grade chromite concentrate from low- and medium-grade chromite ore. Although there are many methods for beneficiation of chromite, such as gravity separation, magnetic separation, flotation and chemical separation, flotation has the disadvantages of high cost and reagent pollution, magnetic separation has the disadvantage of poor selectivity, and chemical separation has the problems of high cost and high pollution. Therefore, the gravity separation method of chromite is the most effective and main beneficiation method. Shaking tables, jigging and spiral chutes are all used, but shaking tables are the most widely used. Jigging is often only suitable for the beneficiation of lump ores and cannot adapt to the beneficiation of fine-grained minerals. When using conventional spiral chutes to separate chromite, due to the limitations of the enrichment performance of conventional spiral chutes, it is impossible to directly obtain chromite concentrate of sufficiently high grade. A shaking table must be configured for selection to obtain qualified chromite concentrate. However, the shaking table has the disadvantages of small single-machine processing capacity (0.3-1t / h. unit) and high water consumption (1-3m 3 The existing chromite beneficiation process, which relies on a shaking table or a spiral chute + shaking table configuration, is no longer suitable for large-scale chromite beneficiation. Due to its high technical requirements, the existing process requires a large number of workers, occupies a large area, and is difficult to deploy in large quantities. As the scale of chromite beneficiation increases, the existing beneficiation process using a shaking table or a spiral chute + shaking table configuration is no longer able to meet the needs of large-scale production. There is an urgent need to develop a chromite beneficiation process and method that is simple to operate, easy to maintain, low in energy consumption, clean, and easy to implement for large-scale production. Summary of the Invention

[0003] To meet the demands for large-scale, clean, low-cost, and easy-to-operate chromite beneficiation, this invention has developed a chromite beneficiation method that utilizes a single gravity separation method and a single type of gravity separation equipment. This gravity separation equipment and process not only meets the needs of large-scale chromite production but also provides sufficient enrichment performance, enabling direct production of qualified chromite concentrate with metal recovery rates comparable to those of other beneficiation methods.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A gravity separation system for low-grade chromite, characterized in that the gravity separation system comprises a roughing spiral chute, a first-stage concentrating spiral chute, a second-stage concentrating spiral chute, a first-stage scavenging spiral chute, and a second-stage scavenging spiral chute; the roughing spiral chute, the first-stage concentrating spiral chute, the second-stage concentrating spiral chute, the first-stage scavenging spiral chute, and the second-stage scavenging spiral chute all have slurry inlets at their upper ends, and the roughing spiral chute, the first-stage concentrating spiral chute, the second-stage concentrating spiral chute, the first-stage scavenging spiral chute, and the second-stage scavenging spiral chute all have concentrate discharge outlets, middling discharge outlets, and tailings discharge outlets at their lower ends. The concentrate discharge outlet of the roughing spiral chute and the concentrate discharge outlet of the first-stage scavenging spiral chute are connected to the slurry inlet of the first-stage cleaning spiral chute; the middling discharge outlet and tailings discharge outlet of the roughing spiral chute and the tailings discharge outlet of the first-stage cleaning spiral chute and the tailings discharge outlet of the second-stage cleaning spiral chute are connected to the slurry inlet of the first-stage cleaning spiral chute; the concentrate discharge outlet of the first-stage cleaning spiral chute and the middling discharge outlet of the second-stage cleaning spiral chute are connected to the slurry inlet of the second-stage cleaning spiral chute, and the middling discharge outlet and tailings discharge outlet of the first-stage cleaning spiral chute are connected to the slurry inlet of the second-stage cleaning spiral chute. The spiral chute for roughing has a pitch-to-diameter ratio of 0.50-0.55 and a transverse inclination angle of 8.7°-9.3°; the spiral chute for the first and second stage fine cleaning and the second stage fine cleaning has a pitch-to-diameter ratio of 0.58-0.62 and a transverse inclination angle of 9.5°-10.5°; the spiral chute for the first and second stage sweeping has a pitch-to-diameter ratio of 0.43-0.47 and a transverse inclination angle of 8.2°-8.6°. The pitch-to-diameter ratio A of the spiral chute is the ratio of the pitch H to the diameter D of the spiral chute, where H is the pitch and D is the diameter of the spiral chute; the transverse inclination angle B is the angle between the line connecting the origin and the end point of the cubic parabola and the horizontal line.

[0006] Furthermore, the spiral chute for roughing, the spiral chute for the first stage cleaning, the spiral chute for the second stage cleaning, the spiral chute for the first stage sweeping, and the spiral chute for the second stage sweeping are arranged at the same horizontal position.

[0007] Furthermore, the concentrate discharge outlet of the roughing spiral chute, the concentrate discharge outlet of the first-stage scavenging spiral chute and the slurry inlet of the first-stage concentrating spiral chute are connected to a first slurry pool; the middling discharge outlet of the roughing spiral chute, the tailings discharge outlet and the tailings discharge outlet of the first-stage concentrating spiral chute, the tailings discharge outlet of the second-stage concentrating spiral chute and the slurry inlet of the first-stage scavenging spiral chute are connected to a second slurry pool; the concentrate discharge outlet of the first-stage concentrating spiral chute, the middling discharge outlet of the second-stage concentrating spiral chute and the slurry inlet of the second-stage concentrating spiral chute are connected to a third slurry pool, the middling discharge outlet of the first-stage scavenging spiral chute, the tailings discharge outlet and the slurry inlet of the second-stage scavenging spiral chute are connected to a fourth slurry pool; the first slurry pool, the second slurry pool, the third slurry pool and the fourth slurry pool are all equipped with slurry pumps.

[0008] Furthermore, the number of the spiral chute for roughing, the spiral chute for the first stage cleaning, the spiral chute for the second stage cleaning, the spiral chute for the first stage sweeping, and the spiral chute for the second stage sweeping is single or multiple in parallel.

[0009] A method for beneficiating chromite using the gravity separation system comprises the following steps:

[0010] After two stages of crushing, the raw ore enters the ball mill for grinding, and then after classification, the part with particle size greater than 0.5mm returns to the ball mill for re-grinding, and the raw ore with particle size less than 0.5mm enters the roughing spiral chute. The concentrate after roughing is discharged through the concentrate outlet of the roughing spiral chute and enters the slurry inlet of the first-stage concentrating spiral chute. The middlings and tailings after roughing are discharged and enter the inlet of the first-stage sweeping spiral chute; the concentrate obtained from the first-stage concentrating enters the slurry inlet of the second-stage concentrating spiral chute, the middlings obtained from the first-stage concentrating are returned to the ball mill for re-grinding, and the first-stage concentrating is discharged. The tailings obtained by the selection enter the slurry inlet of the spiral chute for the first stage of scavenging; the concentrate obtained by the second stage of scavenging is used as the final concentrate; the middlings obtained by the second stage of scavenging enter the slurry inlet of the spiral chute for the second stage of scavenging, and the tailings obtained by the second stage of scavenging enter the slurry inlet of the spiral chute for the first stage of scavenging; the concentrate obtained by the first stage of scavenging enters the slurry inlet of the spiral chute for the first stage of scavenging, and the middlings and tailings obtained by the first stage of scavenging enter the slurry inlet of the spiral chute for the second stage of scavenging. The concentrate obtained by the second stage of scavenging is returned to the ball mill for re-grinding, and the middlings and tailings obtained by the second stage of scavenging are directly discarded.

[0011] The beneficial effects of the present invention are as follows: the present invention utilizes spiral chutes with different pitch-to-diameter ratios and lateral inclinations to form a coarse, fine, and scavenging gravity separation process. In the concentrating operation section, the configured spiral chute has a larger pitch-to-diameter ratio and lateral inclination, resulting in a higher slurry flow rate and greater centrifugal force, which can effectively improve the grade of the concentrate. Conversely, in the scavenging operation section, the configured spiral chute has a smaller pitch-to-diameter ratio and lateral inclination, resulting in a lower slurry flow rate, which can effectively improve the recovery of fine-grained chromite. Furthermore, the present invention has the advantages of simple production and operation, low consumption, environmental friendliness, and stable performance indicators. It can meet the requirements of large-scale chromite ore beneficiation production and has excellent production indicators. For example, in Zimbabwe, the present invention was used to transform a shaking table chromite beneficiation plant that originally processed 50 tons of raw ore per day. Ten spiral chutes involved in the present invention were used to replace the original 50 shaking tables, and a chromite beneficiation plant with a daily processing capacity of 500 tons of raw ore was built. The processing capacity was increased by 10 times, the grade of chromite concentrate reached 49.56%, and the recovery rate was 90.16%. Compared with the original shaking table gravity separation process, the indicators were significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the layout of the gravity sorting system.

[0013] Figure 2 Schematic diagram of the process flow of the present invention.

[0014] Figure 3 Schematic diagram of the aspect ratio A of a spiral chute.

[0015] Figure 4 Schematic diagram of the cross-sectional curve and lateral inclination angle B of the spiral chute.

[0016] Among them, 1 is a spiral chute for roughing, 2 is a spiral chute for first-stage selection, 3 is a spiral chute for second-stage selection, 4 is a spiral chute for first-stage sweeping, 5 is a second-stage spiral chute, 6 is the first slurry pool, 7 is the second slurry pool, 8 is the third slurry pool, 9 is the fourth slurry pool, and 10 is a slurry pump. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] Implementation 1

[0019] A low-grade gravity sorting system, such as Figure 1As shown, it includes a roughing spiral chute 1, a first-stage concentrating spiral chute 2, a second-stage concentrating spiral chute 3, a first-stage sweeping spiral chute 4, a second-stage sweeping spiral chute 5 and a first slurry pool 6, a second slurry pool 7, a third slurry pool 8 and a fourth slurry pool 9; the roughing spiral chute 1, the first-stage concentrating spiral chute 2, the second-stage concentrating spiral chute 3, the first-stage sweeping spiral chute 4 and the second-stage sweeping spiral chute 5 are arranged at the same horizontal position, and the upper ends of the roughing spiral chute 1, the first-stage concentrating spiral chute 2, the second-stage concentrating spiral chute 3, the first-stage sweeping spiral chute 4 and the second-stage sweeping spiral chute 5 are all provided with a slurry inlet, and the lower ends of the roughing spiral chute 1, the first-stage concentrating spiral chute 2, the second-stage concentrating spiral chute 3, the first-stage sweeping spiral chute 4 and the second-stage sweeping spiral chute 5 are all provided with a concentrate discharge outlet, a middling discharge outlet and a tailings discharge outlet. 1. The concentrate discharge outlet of the spiral chute 4 for the first stage sweeping and the slurry inlet of the spiral chute 2 for the first stage cleaning are connected to a first slurry pool 6. The middling discharge outlet, tailings discharge outlet of the roughing spiral chute 1, the tailings discharge outlet of the first stage cleaning spiral chute 2 and the tailings discharge outlet of the second stage cleaning spiral chute 3 and the slurry inlet of the spiral chute 4 for the first stage sweeping are connected to a second slurry pool 7; the concentrate discharge outlet of the first stage cleaning spiral chute 2, the middling discharge outlet of the second stage cleaning spiral chute 3 and the slurry inlet of the second stage cleaning spiral chute 3 are connected to a third slurry pool 8, the middling discharge outlet and tailings discharge outlet of the spiral chute 4 for the first stage sweeping and the slurry inlet of the spiral chute 4 for the second stage sweeping are connected to a fourth slurry pool 9. The first slurry pool 6, the second slurry pool 7, the third slurry pool 8 and the fourth slurry pool 9 are all equipped with a slurry pump 10, which transports the slurry in each slurry pool to the slurry inlet of each spiral chute through the slurry pump 10.

[0020] like Figure 3 、 4 As shown, the diameters of spiral chute 1 for roughing, spiral chute 2 for first-stage cleaning, spiral chute 3 for second-stage cleaning, spiral chute 4 for first-stage sweeping, and spiral chute 5 for second-stage sweeping are 1500mm, the aspect ratio A of spiral chute 1 for roughing is 0.55, and the lateral inclination angle B is 9°; the aspect ratio A of spiral chute 1 for roughing, spiral chute 2 for first-stage cleaning, spiral chute 3 for second-stage cleaning, spiral chute 4 for first-stage sweeping, and spiral chute 5 for second-stage sweeping are 0.60, and the lateral inclination angle B is 10°; the aspect ratio A of spiral chute 4 for first-stage sweeping and spiral chute 5 for second-stage sweeping are 0.45, and the lateral inclination angle B is 8.5°.

[0021] The above-mentioned sorting system is used for sorting, such as Figure 2As shown, the specific process flow is as follows: the chromite ore with a grade of 26.75% (Cr2O3) is crushed in two stages and enters the ball mill for grinding. Then, after classification, the part with a particle size greater than 0.5 mm is returned to the ball mill for re-grinding, and the ore with a particle size less than 0.5 mm enters the roughing spiral chute 1. The concentrate after roughing enters the first pulp pool 6 through the concentrate discharge port. The slurry pump 10 pumps the slurry in the first pulp pool 6 into the slurry inlet of the first-stage concentrating spiral chute 2. The middlings and tailings after roughing are discharged from the discharge port and enter the second pulp pool 7. The slurry in the second pulp pool 7 is pumped into the inlet of the first-stage sweeping spiral chute 4 by the slurry pump 10; the concentrate obtained by the first stage concentrating is discharged and pumped into the slurry inlet of the second-stage concentrating spiral chute 3 through the third pulp pool 8 and the slurry pump 10. The middlings obtained by the first stage concentrating are returned to the ball mill for re-grinding. The tailings obtained from the first stage of concentration pass through the second pulp pool 7 and the pulp pump 10 into the pulp inlet of the first stage scavenging spiral chute 4; the concentrate obtained from the second stage of concentration is used as the final concentrate; the middlings obtained from the second stage of concentration enter the third pulp pool 8 and are pumped into the pulp inlet of the second stage of concentration spiral chute 3 through the pulp pump 10, the tailings obtained from the second stage of concentration enter the second pulp pool 7 and are pumped into the pulp inlet of the first stage of concentration spiral chute 4 through the pulp pump 10; the concentrate obtained from the first stage of scavenging enters the first pulp pool 6 and is pumped into the pulp inlet of the first stage of concentration spiral chute 2 through the pulp pump 10, the middlings and tailings obtained from the first stage of scavenging enter the fourth pulp pool 9 and are pumped into the pulp inlet of the second stage of scavenging spiral chute 5 through the pulp pump 10, the concentrate obtained from the second stage of scavenging is returned to the ball mill for re-grinding, and the middlings and tailings obtained from the second stage of scavenging are directly discarded. The chromite concentrate obtained has a grade of 49.56% (Cr2O3), a yield of 48.67%, and a recovery rate of 90.16%.

[0022] Example 2

[0023] Based on Example 1, the number of spiral chute 1 for roughing, spiral chute 2 for first-stage cleaning, spiral chute 3 for second-stage cleaning, spiral chute 4 for first-stage scavenging, and spiral chute 5 for second-stage scavenging are all 3. The aspect ratio A of the spiral chute 1 for roughing is 0.50, and the lateral inclination B is 8.7°; the aspect ratio A of the spiral chute 2 for first-stage cleaning and the spiral chute 3 for second-stage cleaning is 0.62, and the lateral inclination B is 10.5°; the aspect ratio A of the spiral chute 4 for first-stage scavenging and the spiral chute 5 for second-stage scavenging is 0.43, and the lateral inclination B is 8.2°. After the chromite with a grade of 26.75% (Cr2O3) is sorted, the resulting chromite concentrate has a grade of 49.71% (Cr2O3), a yield of 47.56%, and a recovery rate of 88.38%.

[0024] Example 3

[0025] Based on Example 1, the number of spiral chute 1 for roughing, spiral chute 2 for first-stage cleaning, spiral chute 3 for second-stage cleaning, spiral chute 4 for first-stage scavenging, and spiral chute 5 for second-stage scavenging are all 4. The aspect ratio A of the spiral chute 1 for roughing is 0.50, and the lateral inclination B is 9.3°; the aspect ratio A of the spiral chute 2 for first-stage cleaning and the spiral chute 3 for second-stage cleaning is 0.58, and the lateral inclination B is 9.5°; the aspect ratio A of the spiral chute 4 for first-stage scavenging and the spiral chute 5 for second-stage scavenging is 0.47, and the lateral inclination B is 8.6°. The chromite concentrate obtained has a grade of 48.81% (Cr2O3), a yield of 49.12%, and a recovery rate of 89.63%.

[0026] The technical solution of the present invention enables the spiral chute in the beneficiation section to have a larger pitch-to-diameter ratio and lateral inclination, resulting in a higher slurry flow rate and greater centrifugal force, effectively improving the concentrate grade. Conversely, the spiral chute in the scavenging section has a smaller pitch-to-diameter ratio and lateral inclination, resulting in a lower slurry flow rate, effectively improving the recovery of fine-grained chromite. Through the rational configuration of processes and equipment, while ensuring the chromite's beneficiation indicators, the production scale of chromite ore beneficiation is effectively increased, making it easier to achieve large-scale production, simpler to operate, and with more stable indicators than traditional chromite beneficiation processes.

Claims

1. A gravity separation system for low-grade chromite, wherein the Cr2O3 grade of the low-grade chromite is 26.75%, characterized in that: The gravity sorting system includes a spiral chute for roughing, a spiral chute for first-stage cleaning, a spiral chute for second-stage cleaning, a spiral chute for first-stage scavenging, and a spiral chute for second-stage scavenging; the aspect ratio of the spiral chute for roughing is 0.50, and the lateral inclination angle is 8.7° or 9.3°; the aspect ratio of the spiral chute for first-stage cleaning and the spiral chute for second-stage cleaning is 0.58 or 0.62, and the lateral inclination angle is 9.5° or 10.5°; the aspect ratio of the spiral chute for first-stage scavenging and the spiral chute for second-stage scavenging is 0.43 or 0.47, and the lateral inclination angle is 8.2° or 8.6°; The concentrate discharge outlet of the chute and the concentrate discharge outlet of the first-stage scavenging spiral chute are connected to the slurry inlet of the first-stage beneficiation spiral chute; the middling discharge outlet and tailings discharge outlet of the roughing spiral chute and the tailings discharge outlet of the first-stage beneficiation spiral chute and the tailings discharge outlet of the second-stage beneficiation spiral chute are connected to the slurry inlet of the first-stage scavenging spiral chute; the concentrate discharge outlet of the first-stage beneficiation spiral chute and the middling discharge outlet of the second-stage beneficiation spiral chute are connected to the slurry inlet of the second-stage beneficiation spiral chute, and the middling discharge outlet and tailings discharge outlet of the first-stage scavenging spiral chute are connected to the slurry inlet of the second-stage scavenging spiral chute.

2. The gravity separation system according to claim 1, characterized in that: The spiral chute for roughing, the spiral chute for the first stage cleaning, the spiral chute for the second stage cleaning, the spiral chute for the first stage sweeping and the spiral chute for the second stage sweeping are arranged at the same horizontal position.

3. The gravity separation system according to claim 1, characterized in that: A first slurry pool is connected between the concentrate discharge outlet of the roughing spiral chute, the concentrate discharge outlet of the first-stage scavenging spiral chute and the slurry inlet of the first-stage concentrating spiral chute; a second slurry pool is connected between the middling discharge outlet and tailings discharge outlet of the roughing spiral chute and the tailings discharge outlet of the first-stage concentrating spiral chute, the tailings discharge outlet of the second-stage concentrating spiral chute and the slurry inlet of the first-stage scavenging spiral chute; a third slurry pool is connected between the concentrate discharge outlet of the first-stage concentrating spiral chute, the middling discharge outlet of the second-stage concentrating spiral chute and the slurry inlet of the second-stage concentrating spiral chute; a fourth slurry pool is connected between the middling discharge outlet and tailings discharge outlet of the first-stage scavenging spiral chute and the slurry inlet of the second-stage scavenging spiral chute; the first slurry pool, the second slurry pool, the third slurry pool and the fourth slurry pool are all equipped with slurry pumps.

4. The gravity separation system according to claim 1, characterized in that: The number of the spiral chute for roughing, the spiral chute for the first stage cleaning, the spiral chute for the second stage cleaning, the spiral chute for the first stage sweeping and the spiral chute for the second stage sweeping can be single or multiple in parallel.

5. A method for beneficiating chromite using the gravity separation system according to any one of claims 1 to 4, characterized in that: The following steps are involved: After two stages of crushing, the raw ore enters the ball mill for grinding, and then after classification, the part with particle size greater than 0.5mm returns to the ball mill for re-grinding, and the raw ore with particle size less than 0.5mm enters the roughing spiral chute. The concentrate after roughing is discharged through the concentrate outlet of the roughing spiral chute and enters the slurry inlet of the first-stage concentrating spiral chute. The middlings and tailings after roughing are discharged and enter the inlet of the first-stage sweeping spiral chute; the concentrate obtained from the first-stage concentrating enters the slurry inlet of the second-stage concentrating spiral chute, the middlings obtained from the first-stage concentrating are returned to the ball mill for re-grinding, and the first-stage concentrating is discharged. The tailings obtained by the selection enter the slurry inlet of the spiral chute for the first stage of scavenging; the concentrate obtained by the second stage of scavenging is used as the final concentrate; the middlings obtained by the second stage of scavenging enter the slurry inlet of the spiral chute for the second stage of scavenging, and the tailings obtained by the second stage of scavenging enter the slurry inlet of the spiral chute for the first stage of scavenging; the concentrate obtained by the first stage of scavenging enters the slurry inlet of the spiral chute for the first stage of scavenging, and the middlings and tailings obtained by the first stage of scavenging enter the slurry inlet of the spiral chute for the second stage of scavenging. The concentrate obtained by the second stage of scavenging is returned to the ball mill for re-grinding, and the middlings and tailings obtained by the second stage of scavenging are directly discarded.

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