A method for extracting iron concentrate from a laterite nickel ore hydrometallurgical residue

Abstract

The present application relates to a kind of laterite nickel ore hydrometallurgy slag iron concentrate extraction method, the extraction method includes the following steps: (1) biomass is heated to 350-600 ℃ under nitrogen atmosphere, carbonization treatment 80-160 min, again heated to 350-600 ℃ under carbon dioxide atmosphere, activation treatment 40-70 min, after grinding and sieving, obtain biomass charcoal;(2) laterite nickel ore hydrometallurgy slag, additive and the biomass charcoal obtained in step (1) are mixed after reduction roasting under argon atmosphere, obtain roasting product;The roasting product is mixed with dispersing agent and ball milled, then add water to slurry, after magnetic separation, dry, obtain iron concentrate.The present application uses modified biomass charcoal as reducing agent, and improves roasting and magnetic separation operation under the condition of biomass charcoal, realizes the efficient recovery of iron concentrate.

Description

Technical Field

[0001] This invention relates to the field of slag recycling technology, specifically to a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. Background Technology

[0002] Nickel is a strategic reserve metal with wide applications and plays a vital role in the socio-economic sphere. As a key material in the production of new energy batteries, the demand for nickel resources is constantly increasing with the rapid development of the new energy industry.

[0003] With the large-scale consumption of nickel sulfide ore resources, these resources are gradually becoming depleted, and internationally, the focus of nickel resource development has shifted to laterite nickel ore. Currently, the processing of laterite nickel ore mainly relies on hydrometallurgical processes, which are effective for processing low-grade ores. However, hydrometallurgical processing of laterite nickel ore generates a large amount of metallurgical slag, and current slag disposal methods primarily include tailings dam stacking, underground pressure filtration backfilling, and deep-sea landfilling, which suffer from high processing costs, environmental pollution, and resource waste. The chemical composition of laterite nickel ore hydrometallurgical slag is complex, but its iron content exceeds 40%. Therefore, recovering iron resources from laterite nickel ore hydrometallurgical slag is an effective solution.

[0004] Currently, the main method for recovering iron concentrate from laterite nickel ore hydrometallurgical slag is reduction roasting-magnetic separation. For example, CN116926312A discloses a method for preparing high-grade iron concentrate by microwave roasting laterite nickel ore hydrometallurgical slag. The method involves mixing laterite nickel ore hydrometallurgical slag and calcium-containing additives evenly, then placing the mixture in a microwave roasting furnace in powder form or pelletized form for microwave reduction roasting. The obtained microwave reduction roasting product is then ground and magnetically separated to obtain high-grade iron concentrate.

[0005] For the recovery and utilization of laterite nickel ore hydrometallurgical slag, coal, coke, and natural gas are currently commonly used as reducing agents. The reducing agent is a key factor determining the roasting effect and thus affecting iron recovery efficiency. For example, CN110616315A discloses a method for preparing nickel-iron concentrate from laterite nickel ore, including: drying and crushing the laterite nickel ore, mixing it with coal powder to form pellets; drying the pellets, mixing them with coal particles, and roasting them to obtain reduction products; grinding the reduction products and then subjecting them to at least one magnetic separation to obtain nickel-iron concentrate. Compared to non-renewable petrochemical resources such as coal and coke, biochar has the advantages of wide distribution, low price, and environmental friendliness. Therefore, utilizing biochar to recover iron concentrate from laterite nickel ore hydrometallurgical slag is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag, using biochar as a reducing agent and improving roasting and magnetic separation operations under biochar conditions, thereby achieving efficient recovery of iron concentrate.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for extracting iron concentrate from hydrometallurgical slag of laterite nickel ore, the extraction method comprising the following steps:

[0009] (1) The biomass is first heated to 350-600℃ in a nitrogen atmosphere and carbonized for 80-160 min, then heated to 350-600℃ in a carbon dioxide atmosphere and activated for 40-70 min. After grinding and sieving, biochar is obtained.

[0010] (2) The laterite nickel ore wet metallurgical slag, additives and biomass char obtained in step (1) are mixed and then reduced and roasted under an argon atmosphere to obtain roasted product; the roasted product is mixed with dispersant, ball-milled and then water is added to make slurry, magnetic separation is performed and then dried to obtain iron concentrate.

[0011] The present invention provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. Firstly, the preparation process of biochar is optimized. Through carbonization under a nitrogen atmosphere, the organic components of biochar are transformed into inorganic carbon after high-temperature treatment. Subsequently, carbon dioxide activation treatment is used to regulate and improve the pore structure, which is beneficial to further improving the purity of the iron concentrate. Compared with carbon sources such as coke and coal, the biochar provided in this application has a comparable or even superior iron concentrate recovery effect. Combined with the use of additives, the melting point can be lowered, saving energy consumption. In addition, the addition of a dispersant in the magnetic separation step can effectively ensure the uniform dispersion of particulate matter in the liquid medium, preventing its precipitation and aggregation.

[0012] Preferably, step (1) specifically includes:

[0013] (a) Crush the biomass, wash it with water, and dry it at 90-100℃ for 400-520 min;

[0014] (b) Under a nitrogen atmosphere, heat to 350-600℃ at a rate of 1-5℃ / min, carbonize for 80-160min, and then cool naturally to room temperature;

[0015] (c) Under a carbon dioxide atmosphere, heat to 350-600℃ at a rate of 1-5℃ / min, activate for 40-70min, and then cool naturally to room temperature;

[0016] (d) After grinding, pass through a 40-300 mesh sieve, wash with water, and dry at 110-120℃ for 680-800 min to obtain biochar.

[0017] The drying temperature described in step (a) is 90-100°C, for example, it can be 90°C, 92°C, 95°C, 98°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] The drying time in step (a) is 400-520 min, for example, it can be 400 min, 450 min, 480 min, 500 min or 520 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] The heating rate in step (b) under nitrogen atmosphere is 1-5℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] The endpoint of the temperature rise in step (b) under nitrogen atmosphere is 350-600℃, for example, it can be 350℃, 400℃, 450℃, 500℃, 550℃, 580℃ or 600℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 500-600℃.

[0021] The carbonization time in step (b) is 80-160 min, for example, it can be 80 min, 100 min, 120 min, 150 min or 160 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 100-150 min.

[0022] When the temperature and time of the carbonization process are within a preferred range, better iron recovery can be achieved.

[0023] The room temperature mentioned in step (b) is 15-35℃, for example, it can be 15℃, 20℃, 25℃, 30℃ or 35℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] The heating rate in step (c) under a carbon dioxide atmosphere is 1-5 °C / min, for example, it can be 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min or 5 °C / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] The endpoint of the temperature rise in step (c) under a carbon dioxide atmosphere is 350-600℃, for example, it can be 350℃, 450℃, 500℃, 550℃ or 600℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 450-550℃.

[0026] The activation treatment time in step (c) is 40-70 min, for example, it can be 40 min, 50 min, 55 min, 60 min or 70 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 50-60 min being preferred.

[0027] When the temperature and time of the activation treatment are within the preferred range, better iron concentrate recovery can be achieved.

[0028] The room temperature mentioned in step (c) is 15-35℃, for example, it can be 15℃, 20℃, 25℃, 30℃ or 35℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] The mesh size of the sieve described in step (d) is 40-300 mesh, for example, it can be 40 mesh, 100 mesh, 200 mesh, 250 mesh or 300 mesh, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] The drying temperature in step (d) is 110-120°C, for example, it can be 110°C, 112°C, 115°C, 118°C or 120°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] The drying time in step (d) is 680-800 min, for example, it can be 680 min, 700 min, 720 min, 750 min or 800 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the biomass in step (1) includes any one or a combination of at least two of coconut shells, wheat straw, corn stalks, bamboo, rice straw, peanut shells or branches. Typical but non-limiting combinations include a combination of coconut shells and wheat straw, a combination of corn stalks, bamboo, rice straw and peanut shells, or a combination of coconut shells, wheat straw, corn stalks, bamboo, rice straw, peanut shells and branches.

[0033] Preferably, the branches include fruit tree branches.

[0034] Preferably, the amount of biochar added in step (2) is 2-5 wt% of the mass of laterite nickel ore hydrometallurgical slag, for example, it can be 2 wt%, 3 wt%, 3.5 wt%, 4 wt% or 5 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3-4 wt%.

[0035] Preferably, the amount of additive added in step (2) is 4-6 wt% of the mass of laterite nickel ore hydrometallurgical slag, for example, it can be 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt% or 6 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the additive in step (2) includes Na2CO3 and / or NaOH, and more preferably a combination of Na2CO3 and NaOH.

[0037] Preferably, the mass ratio of Na2CO3 to NaOH is 1:(0.7-1.2), for example, it can be 1:0.7, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] This invention lowers the melting point and saves energy by adding Na2CO3 and / or NaOH as additives during the roasting process. At the same time, it facilitates the reaction of some substances in the slag to form sulfides, which are then removed by subsequent magnetic separation, ultimately further improving the purity of the iron concentrate.

[0039] Preferably, the mixing method in step (2) is ball milling for 30-120 minutes, for example, 30 minutes, 50 minutes, 70 minutes, 100 minutes or 120 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the reduction roasting in step (2) is performed by heating to 500-900℃ at a rate of 3-6℃ / min under an argon atmosphere and then reducing roasting for 30-180min.

[0041] The heating rate of the reduction calcination is 3-6℃ / min, for example, it can be 3℃ / min, 4℃ / min, 5℃ / min or 6℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] The endpoint of the reduction calcination is 500-900℃, for example, it can be 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] The reduction calcination time is 30-180 min, for example, it can be 30 min, 60 min, 100 min, 120 min or 180 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the argon gas introduction rate is 1-5 mL / min, for example, it can be 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min or 5 mL / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] Compared to nitrogen, using argon as an inert gas is more conducive to improving the purity of iron concentrate.

[0046] Preferably, the amount of dispersant added in step (2) is 3-5 wt% of the mass of the calcined product, for example, it can be 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the dispersant in step (2) includes any one or a combination of at least two of sodium metaphosphate, sodium hexametaphosphate, water glass, caustic starch, or saline water glass. Typical but non-limiting combinations include a combination of sodium metaphosphate and sodium hexametaphosphate, a combination of water glass, caustic starch, and saline water glass, or a combination of sodium metaphosphate, sodium hexametaphosphate, water glass, caustic starch, and saline water glass.

[0048] The term "salt-treated water glass" refers to a mixture of water glass and aluminum sulfate.

[0049] Preferably, the amount of water used in step (2) for slurry preparation is 4-6 times the total mass of the calcined product and the dispersant, for example, it can be 4 times, 5 times or 6 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the intensity of magnetic separation in step (2) is 1000-3000 Gs, for example, it can be 1000 Gs, 1500 Gs, 2000 Gs, 2500 Gs or 3000 Gs, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] As a preferred embodiment of the extraction method of the present invention, the extraction method includes the following steps:

[0052] (1) The biomass is crushed, washed with water, and dried at 90-100℃ for 400-520 min; then, under a nitrogen atmosphere, the temperature is raised to 350-600℃ at a rate of 1-5℃ / min for carbonization treatment for 80-160 min, and then naturally cooled to room temperature; then, under a carbon dioxide atmosphere, the temperature is raised to 350-600℃ at a rate of 1-5℃ / min for activation treatment for 40-70 min, and then naturally cooled to room temperature; after grinding, it is passed through a 40-300 mesh sieve, washed with water, and dried at 110-120℃ for 680-800 min to obtain biochar;

[0053] (2) The laterite nickel ore hydrometallurgical slag, additives, and biochar obtained in step (1) are ball-milled for 30-120 min, and then heated to 500-900℃ at a rate of 3-6℃ / min under an argon atmosphere with a flow rate of 1-5 mL / min, and reduced and roasted for 30-180 min to obtain the roasted product; the amount of biochar added is 2-5 wt% of the mass of the laterite nickel ore hydrometallurgical slag; the amount of additives added is 4-6 wt% of the mass of the laterite nickel ore hydrometallurgical slag; the additives include Na2CO3 and / or NaOH, preferably a combination of Na2CO3 and NaOH, and the mass ratio of Na2CO3 to NaOH is 1:(0.7-1.2);

[0054] The obtained roasted product is mixed with a dispersant, ball-milled, and then water is added to form a slurry. After magnetic separation at an intensity of 1000-3000 Gs, the mixture is dried to obtain iron concentrate. The amount of dispersant added is 3-5 wt% of the mass of the roasted product. The amount of water used to form the slurry is 4-6 times the total mass of the roasted product and the dispersant.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag provided by this invention first optimizes the preparation process of biochar. Through carbonization under a nitrogen atmosphere, the organic components of biochar are transformed into inorganic carbon after high-temperature treatment. Subsequently, carbon dioxide activation treatment is used to regulate and improve its pore structure, which is beneficial to further improve the purity of iron concentrate. The calorific value of the prepared biochar is comparable to that of commercial carbon sources, and it has the advantages of stable performance, low sulfur content, and no heavy metals. More importantly, compared with carbon sources such as coke and coal, the biochar provided in this application has a comparable or even better iron concentrate recovery effect.

[0057] (2) The present invention uses carbon dioxide as an activator, the process is relatively simple, the generated waste gas is mainly carbon dioxide and water vapor, which has little environmental pollution, and the final biochar product has a high specific surface area, well-developed pore structure, and wide range of applications.

[0058] (3) By adding Na2CO3 and / or NaOH as additives during the roasting process, the present invention can reduce the melting point and save energy. At the same time, it is beneficial for some substances in the slag to react and generate sulfides, which are easy to remove through the subsequent magnetic separation process, and ultimately further improve the purity of the iron concentrate. Meanwhile, compared with nitrogen, using argon as an inert gas is more conducive to improving the purity of the iron concentrate. In addition, adding a dispersant in the magnetic separation step can effectively ensure that the particulate matter is uniformly dispersed in the liquid medium and prevent its precipitation and agglomeration.

[0059] (4) The present invention can recover iron concentrate products from the hydrometallurgical slag of laterite nickel ore, and the obtained non-magnetic substances can be used to produce building materials or cement products, which improves the resource utilization rate and economic benefits of laterite nickel ore, and plays a positive role in solving the environmental problems caused by the long-term stockpiling and landfilling of laterite nickel ore hydrometallurgical slag.

[0060] (5) The extraction method provided by the present invention can better realize the recovery of iron concentrate from laterite nickel ore hydrometallurgical slag, while having the characteristics of being environmentally friendly, low cost, and high cost performance, and has good application prospects. Detailed Implementation

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] This invention aims to explore a more environmentally friendly method for the resource utilization of lateritic nickel ore hydrometallurgical slag by replacing existing reducing agents such as coal and coke with biochar. This invention also provides a method for extracting iron concentrate from lateritic nickel ore hydrometallurgical slag, comprising the following steps:

[0063] (1) The biomass is crushed, washed with water, and dried at 90-100℃ for 400-520 min; then, under a nitrogen atmosphere, the temperature is raised to 350-600℃ at a rate of 1-5℃ / min for carbonization treatment for 80-160 min, and then naturally cooled to room temperature; then, under a carbon dioxide atmosphere, the temperature is raised to 350-600℃ at a rate of 1-5℃ / min for activation treatment for 40-70 min, and then naturally cooled to room temperature; after grinding, it is passed through a 40-300 mesh sieve, washed with water, and dried at 110-120℃ for 680-800 min to obtain biochar;

[0064] (2) The laterite nickel ore hydrometallurgical slag, additives, and biochar obtained in step (1) are ball-milled for 30-120 min, and then heated to 500-900℃ at a rate of 3-6℃ / min under an argon atmosphere with a flow rate of 1-5 mL / min, and reduced and roasted for 30-180 min to obtain the roasted product; the amount of biochar added is 2-5 wt% of the mass of the laterite nickel ore hydrometallurgical slag; the amount of additives added is 4-6 wt% of the mass of the laterite nickel ore hydrometallurgical slag; the additives include Na2CO3 and / or NaOH, preferably a combination of Na2CO3 and NaOH, and the mass ratio of Na2CO3 to NaOH is 1:(0.7-1.2);

[0065] The obtained roasted product is mixed with a dispersant, ball-milled, and then water is added to form a slurry. After magnetic separation at an intensity of 1000-3000 Gs, the mixture is dried to obtain iron concentrate. The amount of dispersant added is 3-5 wt% of the mass of the roasted product. The amount of water used to form the slurry is 4-6 times the total mass of the roasted product and the dispersant.

[0066] Based on the characteristics of laterite nickel ore hydrometallurgical slag, this invention uses biomass raw materials and sequentially processes them under high-temperature conditions in nitrogen and carbon dioxide atmospheres to obtain biochar that can effectively reduce iron in laterite nickel ore hydrometallurgical slag. Based on the biochar, the invention improves the additives and their types, the heating conditions, the reaction atmosphere and other reduction roasting conditions, as well as the dispersant and magnetic separation conditions, such as magnetic separation intensity. This achieves the goal of replacing conventional reducing agents with biochar, and the recovery effect of this invention has industrial value.

[0067] The composition of the laterite nickel ore hydrometallurgical slag (with sulfuric acid as the leaching medium) used in the following examples and comparative examples is shown in Table 1.

[0068] Table 1

[0069]

[0070] Unless otherwise specified, the techniques or conditions described in the following examples are based on those described in the literature or the product instructions. Unless otherwise specified, the reagents or instruments used are all commercially available products.

[0071] Example 1

[0072] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag, the extraction method comprising the following steps:

[0073] (1) The coconut shell was crushed to less than 3 cm, washed with deionized water to remove surface impurities, and dried at 95°C for 480 min. Then, under a nitrogen atmosphere, the temperature was raised to 550°C at a rate of 3°C / min and carbonized for 120 min, and then naturally cooled to room temperature. Then, under a carbon dioxide atmosphere, the temperature was raised to 500°C at a rate of 3°C / min and activated for 55 min, and then naturally cooled to room temperature. After grinding, the shell was passed through a 200-mesh sieve, washed three times with deionized water to remove impurities, and then dried at 115°C for 720 min to obtain biochar.

[0074] (2) The lateritic nickel ore hydrometallurgical slag, Na2CO3, NaOH and the biochar obtained in step (1) are ball-milled for 70 min, and then heated to 700℃ at a rate of 5℃ / min under an argon atmosphere with a flow rate of 3 mL / min, and reduced and roasted for 120 min to obtain the roasted product; the amount of biochar added is 3.5 wt% of the mass of the lateritic nickel ore hydrometallurgical slag; the total amount of Na2CO3 and NaOH added is 5 wt% of the mass of the lateritic nickel ore hydrometallurgical slag; the mass ratio of Na2CO3 to NaOH is 1:1;

[0075] The obtained roasted product was mixed with sodium metaphosphate and ball-milled for 30 minutes. Water was added to form a slurry, and the mixture was separated by magnetic separation at an intensity of 2000 Gs and then dried to obtain iron concentrate. The amount of sodium metaphosphate added was 4 wt% of the mass of the roasted product. The amount of water used to form the slurry was 5 times the total mass of the roasted product and sodium metaphosphate.

[0076] Example 2

[0077] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag, the extraction method comprising the following steps:

[0078] (1) The corn stalks were crushed to less than 3 cm, washed with deionized water to remove surface impurities, and dried at 90°C for 520 min. Then, under a nitrogen atmosphere, the temperature was raised to 500°C at a rate of 1°C / min and carbonized for 150 min, and then naturally cooled to room temperature. Then, under a carbon dioxide atmosphere, the temperature was raised to 450°C at a rate of 1°C / min and activated for 60 min, and then naturally cooled to room temperature. After grinding, the stalks were passed through a 300-mesh sieve, washed three times with deionized water to remove impurities, and then dried at 110°C for 800 min to obtain biochar.

[0079] (2) The lateritic nickel ore hydrometallurgical slag, Na2CO3, NaOH and the biochar obtained in step (1) are ball-milled for 30 min, and then heated to 500℃ at a rate of 3℃ / min under an argon atmosphere with a flow rate of 1 mL / min, and reduced and roasted for 180 min to obtain the roasted product; the amount of biochar added is 3 wt% of the mass of the lateritic nickel ore hydrometallurgical slag; the total amount of Na2CO3 and NaOH added is 4 wt% of the mass of the lateritic nickel ore hydrometallurgical slag; the mass ratio of Na2CO3 to NaOH is 1:0.7;

[0080] The obtained roasted product was mixed with sodium hexametaphosphate, ball-milled, and then water was added to form a slurry. After magnetic separation at an intensity of 1000 Gs, the mixture was dried to obtain iron concentrate. The amount of sodium hexametaphosphate added was 3 wt% of the mass of the roasted product. The amount of water used to form the slurry was 4 times the total mass of the roasted product and sodium hexametaphosphate.

[0081] Example 3

[0082] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag, the extraction method comprising the following steps:

[0083] (1) Crush the rice straw to less than 3 cm, wash it with deionized water to remove surface impurities, and dry it at 100℃ for 400 min; then, under a nitrogen atmosphere, heat it to 580℃ at a rate of 5℃ / min and carbonize it for 100 min, and then cool it naturally to room temperature; then, under a carbon dioxide atmosphere, heat it to 550℃ at a rate of 5℃ / min and activate it for 50 min, and then cool it naturally to room temperature; grind it and pass it through a 40-mesh sieve, wash it three times with deionized water to remove impurities, and then dry it at 120℃ for 680 min to obtain biochar.

[0084] (2) The lateritic nickel ore hydrometallurgical slag, Na2CO3, NaOH and the biochar obtained in step (1) are ball-milled for 120 min, and then heated to 900℃ at a rate of 6℃ / min under an argon atmosphere with a flow rate of 5 mL / min, and reduced and roasted for 30 min to obtain the roasted product; the amount of biochar added is 4 wt% of the mass of the lateritic nickel ore hydrometallurgical slag; the total amount of Na2CO3 and NaOH added is 6 wt% of the mass of the lateritic nickel ore hydrometallurgical slag; the mass ratio of Na2CO3 to NaOH is 1:1.2;

[0085] The obtained roasted product was mixed with water glass, ball-milled, and then water was added to form a slurry. After magnetic separation at an intensity of 3000 Gs, the mixture was dried to obtain iron concentrate. The amount of water glass added was 5 wt% of the mass of the roasted product. The amount of water used to form the slurry was 6 times the total mass of the roasted product and water glass.

[0086] Example 4

[0087] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this embodiment and Embodiment 1 is that, except for adjusting the carbonization temperature in step (1) to 350°C, the rest is the same as in Embodiment 1.

[0088] Example 5

[0089] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this embodiment and Embodiment 1 is that, except for adjusting the carbonization temperature in step (1) to 600°C, the rest is the same as in Embodiment 1.

[0090] Example 6

[0091] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Embodiment 1 is that, except for adjusting the activation treatment temperature in step (1) to 350°C, the rest is the same as in Embodiment 1.

[0092] Example 7

[0093] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this embodiment and Embodiment 1 is that, except for adjusting the activation temperature in step (1) to 600°C, the rest is the same as in Embodiment 1.

[0094] Example 8

[0095] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Embodiment 1 is that, except for adjusting the amount of biochar added in step (2) to 2wt% of the mass of laterite nickel ore hydrometallurgical slag, the rest is the same as in Embodiment 1.

[0096] Example 9

[0097] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Embodiment 1 is that, except for adjusting the amount of biochar added in step (2) to 5 wt% of the mass of laterite nickel ore hydrometallurgical slag, the rest is the same as in Embodiment 1.

[0098] Example 10

[0099] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Embodiment 1 is that, except for replacing Na2CO3 and NaOH in step (2) with Na2CO3, the rest is the same as in Embodiment 1.

[0100] Example 11

[0101] This embodiment provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Embodiment 1 is that, except for replacing Na2CO3 and NaOH in step (2) with NaOH in equal mass, the rest is the same as in Embodiment 1.

[0102] Comparative Example 1

[0103] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Example 1 is that step (1) is omitted, and the biochar in step (2) is replaced with coke. All other steps are the same as in Example 1.

[0104] Comparative Example 2

[0105] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this method and Example 1 is that step (1) does not include an activation treatment step, while the rest is the same as Example 1.

[0106] Comparative Example 3

[0107] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Example 1 is that no additives are added in step (2), while the rest is the same as in Example 1.

[0108] Comparative Example 4

[0109] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference from Example 1 is that the reduction roasting in step (2) is carried out under a nitrogen atmosphere, while the rest is the same as in Example 1.

[0110] Comparative Example 5

[0111] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this method and Example 1 is that, except for adjusting the carbonization temperature in step (1) to 300°C, the rest is the same as in Example 1.

[0112] Comparative Example 6

[0113] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this method and Example 1 is that, except for adjusting the carbonization temperature in step (1) to 650°C, the rest is the same as in Example 1.

[0114] Comparative Example 7

[0115] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this method and Example 1 is that, except for adjusting the activation temperature in step (1) to 300°C, the rest is the same as in Example 1.

[0116] Comparative Example 8

[0117] This comparative example provides a method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag. The difference between this method and Example 1 is that, except for adjusting the activation temperature in step (1) to 650°C, the rest is the same as in Example 1.

[0118] The yield of the iron concentrates obtained in Examples 1-11 and Comparative Examples 1-8 was calculated by (mass of the target material after magnetic separation / initial mass of laterite nickel ore metallurgical slag) * 100%, and the purity was calculated by (mass of the target material after magnetic separation / mass of the material after magnetic separation) * 100%. The results are shown in Table 2.

[0119] Table 2

[0120]

[0121]

[0122] As shown in Table 2, the extraction method provided by this invention can better realize the recovery of iron concentrate from laterite nickel ore hydrometallurgical slag. Moreover, this method has the characteristics of being environmentally friendly, low-cost, and cost-effective, and has good application prospects.

[0123] A comparison of Example 1 with Examples 4-7 and Comparative Examples 5-8 shows that when the carbonization or activation temperature is within the preferred range, higher iron concentrate purity can be obtained; when the temperature exceeds the specified range, the iron concentrate purity will be significantly reduced. A comparison of Example 1 with Examples 8 and 9 shows that when the amount of biochar added is within the preferred range, higher iron concentrate purity can be obtained. A comparison of Example 1 with Examples 10 and 11 shows that, using a compound additive, the iron concentrate obtained after reduction roasting and magnetic separation has higher purity than that obtained with a single additive.

[0124] A comparison of Example 1 and Comparative Example 1 shows that using coke as a reducing agent significantly reduces the purity of iron concentrate. A comparison of Example 1 and Comparative Example 2 shows that the lack of activation treatment during biochar preparation prevents optimization of its pore structure, thus reducing the purity of iron concentrate. A comparison of Example 1 and Comparative Example 3 shows that without additives, the purity of iron concentrate cannot be further improved. A comparison of Example 1 and Comparative Example 4 shows that reduction roasting under a nitrogen atmosphere results in a decrease in the purity of the obtained iron concentrate compared to an argon atmosphere.

[0125] In summary, the method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag provided by this invention first optimizes the preparation process of biochar. Through carbonization under a nitrogen atmosphere, the organic components of biochar are transformed into inorganic carbon after high-temperature treatment. Subsequently, carbon dioxide activation treatment is used to regulate and improve its pore structure, which is beneficial to further improve the purity of iron concentrate. The calorific value of the prepared biochar is comparable to that of commercial carbon sources, and it has advantages such as stable performance, low sulfur content, and no heavy metals. More importantly, compared with carbon sources such as coke and coal, the biochar provided in this application has a comparable or even better iron concentrate recovery effect.

[0126] This invention uses carbon dioxide as an activator, the process is relatively simple, the generated waste gas is mainly carbon dioxide and water vapor, which has little environmental pollution, and the final biochar product has a high specific surface area, well-developed pore structure, and a wide range of applications.

[0127] This invention lowers the melting point and saves energy by adding Na2CO3 and / or NaOH as additives during the roasting process. It also facilitates the reaction of some substances in the slag to form sulfides, which are easily removed by subsequent magnetic separation, ultimately improving the purity of the iron concentrate. Furthermore, using argon as an inert gas, compared to nitrogen, is more beneficial for improving the purity of the iron concentrate. In addition, adding a dispersant in the magnetic separation step effectively ensures that particulate matter is uniformly dispersed in the liquid medium, preventing precipitation and agglomeration.

[0128] This invention can recover iron concentrate products from laterite nickel ore hydrometallurgical slag, and the obtained non-magnetic substances can be used to produce building materials or cement products, thereby improving the resource utilization rate and economic benefits of laterite nickel ore. It also plays a positive role in solving the environmental problems caused by the long-term stockpiling and landfilling of laterite nickel ore hydrometallurgical slag.

[0129] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for extracting iron concentrate from laterite nickel ore hydrometallurgical slag, characterized in that, The extraction method includes the following steps: (1) The biomass is first heated to 500-600℃ under nitrogen atmosphere and carbonized for 100-150 min, then heated to 450-550℃ under carbon dioxide atmosphere and activated for 50-60 min, and then ground and sieved to obtain biochar. (2) The wet metallurgical slag of laterite nickel ore, additives and biochar obtained in step (1) are mixed and then reduced and roasted under an argon atmosphere to obtain roasted products; the roasted products are mixed with dispersant, ball-milled, and then water is added to make a slurry. After magnetic separation, the mixture is dried to obtain iron concentrate. The additive is a combination of Na2CO3 and NaOH, wherein the mass ratio of Na2CO3 to NaOH is 1:(1.1-1.2). The amount of the additive added is 5.5-6 wt% of the mass of laterite nickel ore hydrometallurgical slag, excluding 6 wt%.

2. The extraction method according to claim 1, characterized in that, Step (1) specifically includes: (a) Crush the biomass, wash it with water, and dry it at 90-100℃ for 400-520 min; (b) Under a nitrogen atmosphere, heat to 500-600℃ at a rate of 1-5℃ / min, carbonize for 100-150min, and then cool naturally to room temperature; (c) Under a carbon dioxide atmosphere, heat to 450-550℃ at a rate of 1-5℃ / min, activate for 50-60min, and then cool naturally to room temperature; (d) After grinding, pass through a 40-300 mesh sieve, wash with water, and dry at 110-120℃ for 680-800 min to obtain biochar.

3. The extraction method according to claim 1, characterized in that, The biomass mentioned in step (1) includes any one or a combination of at least two of the following: coconut shells, wheat straw, corn stalks, bamboo, rice straw, peanut shells, or tree branches.

4. The extraction method according to claim 1, characterized in that, The amount of biochar added in step (2) is 2-5 wt% of the mass of laterite nickel ore hydrometallurgical slag.

5. The extraction method according to claim 4, characterized in that, The amount of biochar added in step (2) is 3-4 wt% of the mass of laterite nickel ore hydrometallurgical slag.

6. The extraction method according to claim 1, characterized in that, The mixing method described in step (2) is ball milling for 30-120 minutes.

7. The extraction method according to claim 1, characterized in that, The reduction roasting in step (2) is as follows: under an argon atmosphere, the temperature is increased to 500-900℃ at a rate of 3-6℃ / min, and the reduction roasting is carried out for 30-180min.

8. The extraction method according to claim 1, characterized in that, The argon gas is introduced at a rate of 1-5 mL / min.

9. The extraction method according to claim 1, characterized in that, The amount of dispersant added in step (2) is 3-5 wt% of the mass of the calcined product.

10. The extraction method according to claim 1, characterized in that, The dispersant in step (2) includes any one or a combination of at least two of sodium metaphosphate, sodium hexametaphosphate, water glass, caustic starch, or saline water glass.

11. The extraction method according to claim 1, characterized in that, The amount of water used in step (2) to adjust the slurry is 4-6 times the total mass of the roasted product and the dispersant.

12. The extraction method according to claim 1, characterized in that, The intensity of magnetic separation in step (2) is 1000-3000 Gs.

13. The extraction method according to claim 1, characterized in that, The extraction method includes the following steps: (1) The biomass is crushed, washed with water and dried at 90-100℃ for 400-520 min; then, under a nitrogen atmosphere, the temperature is raised to 500-600℃ at a rate of 1-5℃ / min and carbonized for 100-150 min, and then naturally cooled to room temperature; then, under a carbon dioxide atmosphere, the temperature is raised to 450-550℃ at a rate of 1-5℃ / min and activated for 50-60 min, and then naturally cooled to room temperature; after grinding, it is passed through a 40-300 mesh sieve, washed with water and dried at 110-120℃ for 680-800 min to obtain biochar; (2) The laterite nickel ore hydrometallurgical slag, additives and biochar obtained in step (1) are ball-milled for 30-120 min, and then heated to 500-900℃ at a rate of 3-6℃ / min under an argon atmosphere with a flow rate of 1-5 mL / min, and reduced and roasted for 30-180 min to obtain the roasted product; the amount of biochar added is 2-5 wt% of the mass of the laterite nickel ore hydrometallurgical slag; the amount of additive added is 5.5-6 wt% of the mass of the laterite nickel ore hydrometallurgical slag and does not include 6 wt%; the additive is a combination of Na2CO3 and NaOH, and the mass ratio of Na2CO3 to NaOH is 1:(1.1-1.2); The obtained roasted product and dispersant are mixed and ball-milled, then water is added to form a slurry. After magnetic separation at an intensity of 1000-3000 Gs, the mixture is dried to obtain iron concentrate. The amount of dispersant added is 3-5 wt% of the mass of the roasted product. The amount of water used to form the slurry is 4-6 times the total mass of the roasted product and the dispersant.

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