Method for efficiently recovering chromium from low-grade laterite-nickel ore

Abstract

The invention relates to the technical field of laterite-nickel ore beneficiation, in particular to a method for efficiently recovering chromium from low-grade laterite-nickel ore. Comprising the following steps that laterite-nickel ore is washed and screened to remove gravel materials with the particle size of + 3 mm, and materials with the particle size of-3 mm are subjected to primary grading; secondary grading is conducted on the settled sand of the cyclone at the 0.074 mm grading point, and a coarse fraction of + 0.074 mm and a fine fraction of-0.074 mm are obtained; feeding the coarse fraction into a fine sand table, feeding the fine fraction into a slime table, and respectively carrying out reselection; and performing low-intensity magnetic separation on the gravity concentrate to obtain final chromium concentrate. According to the method, through precise secondary grading control and grading gravity separation, the recovery rate of the chromium concentrate is remarkably increased and reaches 20% or above, the chromium resource in the low-grade laterite-nickel ore is fully utilized, and the method has important industrial application value and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of laterite nickel ore beneficiation technology, specifically to a method for efficiently recovering chromium from low-grade laterite nickel ore. Background Technology

[0002] Lateritic nickel ore is a major source of global nickel resources, accounting for approximately 72% of global nickel resources. Low-grade lateritic nickel ore typically contains valuable associated minerals such as chromite, making it significant for comprehensive recovery. Chromium plays a crucial role in the metallurgical industry, primarily used in the production of ferrochrome alloys and metallic chromium, an indispensable material for manufacturing special steels such as stainless steel, acid-resistant steel, and heat-resistant steel. However, China's chromium ore resources are relatively scarce, with over 80% of its annual consumption relying on imports. Therefore, the efficient recovery of chromium concentrate from low-grade lateritic nickel ore has significant economic and strategic importance.

[0003] Currently, some research has been conducted on the separation and recovery technology of chromium from laterite nickel ore. Chinese patent CN111389582B discloses a method for separating chromite from laterite nickel ore. This method includes obtaining a first product after primary classification, performing a secondary classification on the first particle size ore to obtain products of different particle sizes, and then performing gravity separation on the different particle sizes separately. This method employs a secondary classification of the product after primary classification and before the gravity separation step, thereby obtaining different narrow particle size ores. This reduces the influence of particle size differences and overcomes the problem of an excessively wide feed particle size range in existing technologies.

[0004] However, existing processes for beneficiating chromium from low-grade laterite nickel ore still have many problems. The traditional process typically involves: laterite nickel ore → washing → screening → hydrocyclone classification → spiral sluice → shaking table roughing → shaking table scavenging → weak magnetic separation → chromium concentrate and middlings. In actual production, this process achieves a Cr2O3 recovery rate of only 5%–10%, far below the theoretical recovery rate of over 30%, indicating significant room for improvement in chromium recovery. Based on actual production and data analysis, the existing technology has the following key problems: First, the particle size of the minerals classified by the hydrocyclone is above 53μm, while the chromium particles that the equipment can recover are only 20μm in size, resulting in the loss of some target chromium minerals during hydrocyclone classification; Second, in actual production, the recycled water contains flocculants, and the minerals will adhere to the spiral chute under the action of flocculants, resulting in unsatisfactory separation of the target chromium minerals and the loss of some chromium due to tailings; Third, the target minerals can be separated at the critical point of 20μm on the shaking table, but the industry generally uses coarse and fine sand shaking tables, which separate particles above 74μm, resulting in the loss of target chromium minerals below 74μm; Fourth, the industry generally adopts a mixed-feed mode, which cannot achieve the best separation effect of the shaking table, resulting in the loss of target chromium minerals. Summary of the Invention

[0005] To address the problems of low chromium recovery rate and low chromium grade in existing chromium beneficiation processes for low-grade laterite nickel ore, this invention proposes a method for efficiently recovering chromium from low-grade laterite nickel ore, comprising the following steps:

[0006] Step 1: After washing the mixed low-grade laterite nickel ore, screen it to remove the +3mm particle size ore, and obtain the -3mm particle size ore.

[0007] Step 2: Use a hydrocyclone to classify the -3mm particle size mineral material once, and screen it to obtain -0.5mm overflow and +0.5mm gravel underflow.

[0008] Step 3: The overflow of -0.5mm obtained in Step 2 is then classified a second time using a classifier to obtain an overflow of -0.074mm and an underflow of +0.074mm.

[0009] Step 4: The -0.074mm overflow obtained in Step 3 is fed into a slime shaking table for roughing to obtain slime roughing concentrate, slime roughing medium, and slime roughing tailings; the +0.074mm underflow is fed into a fine sand shaking table for roughing to obtain fine sand roughing concentrate, fine sand roughing medium, and fine sand roughing tailings.

[0010] Step 5: The roughing concentrate of slime and the roughing concentrate of fine sand obtained in Step 4 are further subjected to shaking table re-concentration to obtain slime re-concentration concentrate, slime re-concentration tailings, and fine sand re-concentration concentrate and fine sand re-concentration tailings, respectively.

[0011] Step 6: Combine the concentrates obtained in Step 4 and Step 5 and then perform shaking table cleaning to obtain mud concentrate and fine sand concentrate;

[0012] Step 7: Combine the concentrate from the slime and the concentrate from the fine sand and perform weak magnetic separation to obtain chromium concentrate.

[0013] Furthermore, the grade of Cr2O3 in the low-grade laterite nickel ore is no higher than 5 wt%.

[0014] Furthermore, the operating pressure of the hydrocyclone in step 2 is 0.15 MPa.

[0015] Furthermore, the Cr2O3 grade in the -0.5mm overflow ore is not less than 5wt%.

[0016] Furthermore, in step 4, the overflow of -0.074mm is concentrated and then fed into the slime shaking table.

[0017] Furthermore, the magnetic field strength for weak magnetic selection is 1200–1600 GS.

[0018] Furthermore, the obtained chromium concentrate has a grade greater than 40 wt%.

[0019] This invention offers the following beneficial technical effects: Based on the particle size and metal distribution of low-grade lateritic nickel ore, the gravity separation process is optimized: the mixed feeding method is changed to a graded feeding method, and a suitable grading range is designed to effectively reduce the loss of the target mineral chromium. Through secondary grading and graded feeding, the problem of low efficiency in mixed feeding is solved. The configuration of +200 mesh feed to fine sand shaking table and -200 mesh feed to slime shaking table significantly improves the separation effect. The weak magnetic separation process further optimizes the chromium concentrate grade and chromium-iron ratio. The chromium recovery rate of this method is significantly improved, from 5%-10% in the prior art to over 20%, and high-grade chromium concentrate is obtained, with a Cr2O3 grade of over 40%. This provides an effective technical solution to the problem of chromite resource shortage, fully utilizes the chromium resources in low-grade lateritic nickel ore, and has significant industrial application value and economic benefits. Attached Figure Description

[0020] The embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

[0021] Figure 1 A flowchart illustrating the method of the present invention is shown;

[0022] Figure 2 A flow chart of the chromium beneficiation process in Example 1 is shown (the washing step is omitted);

[0023] Figure 3 A flow chart of the chromium beneficiation process in Example 2 is shown (the washing step is omitted);

[0024] Figure 4 A flow chart of the chromium beneficiation process in Example 3 is shown (the washing step is omitted).

[0025] in, Figures 2-4 In the diagram, the upper left of the crosshair represents the yield, the upper right of the crosshair represents the Cr2O3 grade, and the lower right of the crosshair represents the recovery rate. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] A method for efficiently recovering chromium from low-grade lateritic nickel ore, wherein the Cr2O3 grade of the ore is no higher than 5 wt%, includes the following steps:

[0028] Step 1: After washing the mixed low-grade laterite nickel ore, screen it to remove the +3mm particle size ore to obtain the -3mm particle size ore (i.e., hydrocyclone sediment).

[0029] Step 2: Use a fine sand hydrocyclone to classify the -3mm particle size mineral material once, and screen it to obtain -0.5mm overflow and +0.5mm gravel underflow.

[0030] Step 3: Then, the overflow of -0.5mm obtained in Step 2 (Cr2O3 grade not less than 5wt%) is further classified using a hydrocyclone to obtain an overflow of -0.074mm and an underflow of +0.074mm. In the attached figure, 200 mesh is 0.074mm.

[0031] Step 4: The -0.074mm overflow obtained in Step 3 is concentrated. The concentrated ore solution (i.e., the underflow in the attached diagram, where the overflow is water) enters a slime shaking table for roughing to obtain slime roughing concentrate, slime roughing medium, and slime roughing tailings. The +0.074mm underflow enters a fine sand shaking table for roughing to obtain fine sand roughing concentrate, fine sand roughing medium, and fine sand roughing tailings.

[0032] Step 5: The ore in the slime and the ore in the fine sand obtained in Step 4 are further subjected to shaking table re-selection to obtain slime re-selection concentrate, slime re-selection tailings, and fine sand re-selection concentrate and fine sand re-selection tailings, respectively.

[0033] Step 6: Combine the concentrates obtained in Step 4 and Step 5 and then perform shaking table cleaning to obtain slime concentrate and fine sand concentrate, as well as slime tailings and fine sand tailings; the tailings from roughing, re-cleaning and cleaning are combined into chromium tailings (combined).

[0034] Step 7: Combine the slime concentrate and the fine sand concentrate for weak magnetic separation (magnetic field strength of 1200-1600GS, preferably 1500GS) to obtain chromium concentrate and chromium middlings.

[0035] Example 1

[0036] The raw limonite ore (Ore 1) from a certain region in Indonesia was dried, mixed, and then used for chromium concentrate beneficiation using this method. The particle size distribution and metal distribution of Ore 1 are shown in Table 1 below. The magnetic field strength during the weak magnetic separation stage was 1500 GS.

[0037] Table 1. Particle size distribution and metal distribution rate of raw ore 1

[0038]

[0039] The yield, recovery rate, and Cr2O3 grade at each stage of the preparation process are shown in the attached figure. Figure 2 As shown, the hydrocyclone sediment accounts for approximately 32% of the original ore yield. Compared to the -3mm particle size ore, the chromium concentrate yield is 4.07%, and the recovery rate is 33.93%. Compared to the original ore yield of 1.30% and the recovery rate of 26.21%, the chromium concentrate grade is 42.87%, indicating excellent chromium concentrate properties.

[0040] Example 2

[0041] A low-grade laterite nickel ore (Ore 2) from Indonesia was dried and mixed, and then beneficiated using this method for chromium concentrate. The particle size distribution and metal distribution of Ore 2 are shown in Table 2 below. The magnetic field strength during the weak magnetic separation stage was 1500 GS.

[0042] Table 2. Particle size distribution and metal distribution rate of raw ore 2

[0043]

[0044]

[0045] The yield, recovery rate, and Cr2O3 grade at each stage of the preparation process are shown in the attached figure. Figure 3 As shown, the hydrocyclone sediment accounts for approximately 32% of the original ore yield. Compared to the -3mm particle size ore, the chromium concentrate yield is 4.63%, and the recovery rate is 36.71%. Compared to the original ore yield of 1.48% and recovery rate of 20.49%, the chromium concentrate grade is 43.29%, indicating excellent chromium concentrate properties.

[0046] Example 3

[0047] A low-grade laterite nickel ore (origin 3) from Indonesia was dried, mixed, and then used for chromium concentrate beneficiation using this method. The particle size distribution and metal distribution of ore 3 are shown in Table 3 below. The magnetic field strength during the weak magnetic separation stage was 1500 GS.

[0048] Table 3. Particle size distribution and metal distribution rate of raw ore 3

[0049]

[0050] The yield, recovery rate, and Cr2O3 grade at each stage of the preparation process are shown in the attached figure. Figure 4 As shown, the hydrocyclone sediment accounts for approximately 32% of the original ore yield. Compared to the -3mm particle size ore, the chromium concentrate yield is 7.23%, and the recovery rate is 36.92%. Compared to the original ore yield of 2.31% and the recovery rate of 29.14%, the chromium concentrate grade is 43.58%, indicating excellent chromium concentrate properties.

[0051] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for efficiently recovering chromium from low-grade laterite nickel ore, characterized in that, Includes the following steps: Step 1: After washing the mixed low-grade laterite nickel ore, screen it to remove the +3mm particle size ore, and obtain the -3mm particle size ore. Step 2: Use a hydrocyclone to classify the -3mm particle size mineral material once, and screen it to obtain -0.5mm overflow and +0.5mm gravel underflow. Step 3: The overflow of -0.5mm obtained in Step 2 is then classified a second time using a classifier to obtain an overflow of -0.074mm and an underflow of +0.074mm. Step 4: The -0.074mm overflow obtained in Step 3 is fed into a slime shaking table for roughing to obtain slime roughing concentrate, slime roughing medium, and slime roughing tailings; the +0.074mm underflow is fed into a fine sand shaking table for roughing to obtain fine sand roughing concentrate, fine sand roughing medium, and fine sand roughing tailings. Step 5: The roughing concentrate of slime and the roughing concentrate of fine sand obtained in Step 4 are further subjected to shaking table re-concentration to obtain slime re-concentration concentrate, slime re-concentration tailings, and fine sand re-concentration concentrate and fine sand re-concentration tailings, respectively. Step 6: Combine the concentrates obtained in Step 4 and Step 5 and then perform shaking table cleaning to obtain mud concentrate and fine sand concentrate; Step 7: Combine the concentrate from the slime and the concentrate from the fine sand and perform weak magnetic separation to obtain chromium concentrate.

2. The method for efficiently recovering chromium from low-grade laterite nickel ore according to claim 1, characterized in that, The grade of Cr2O3 in the low-grade laterite nickel ore is no higher than 5 wt%.

3. The method for efficiently recovering chromium from low-grade laterite nickel ore according to claim 1, characterized in that, The operating pressure of the hydrocyclone in step 2 is 0.15 MPa.

4. The method for efficiently recovering chromium from low-grade laterite nickel ore according to claim 1, characterized in that, The Cr2O3 grade in the overflow ore of -0.5mm is not less than 5wt%.

5. The method for efficiently recovering chromium from low-grade laterite nickel ore according to claim 1, characterized in that, In step 4, the overflow of -0.074mm is concentrated and then fed into the slurry shaking table.

6. The method for efficiently recovering chromium from low-grade laterite nickel ore according to claim 1, characterized in that, The magnetic field strength for weak magnetic separation is 1200–1600 GS.

7. The method for efficiently recovering chromium from low-grade laterite nickel ore according to claim 1, characterized in that, The obtained chromium concentrate has a grade greater than 40 wt%.

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