A multi-stage combined leaching method for ultra-low grade laterite nickel ore

Abstract

This invention provides a multi-stage combined leaching method for ultra-low grade lateritic nickel ore, comprising: high-pressure acid leaching of the raw lateritic nickel ore slurry to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium, and high-pressure leaching solution containing nickel, cobalt, and manganese, wherein the nickel content in the raw lateritic nickel ore slurry is less than 1.0%; multi-stage atmospheric pressure leaching of the mixture obtained by mixing the high-pressure leaching solution, the raw lateritic nickel ore slurry, and the acid solution, followed by concentration treatment to obtain a final stage concentrated atmospheric pressure leaching solution and a final stage concentrated atmospheric pressure leaching slurry, wherein the slurry concentration of the final stage concentrated atmospheric pressure leaching slurry is the same as that of the raw lateritic nickel ore slurry; sequentially subjecting the final stage concentrated atmospheric pressure leaching solution and the high-pressure leaching tailings to circulating leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum, and chromium removal treatment, and MHP precipitation treatment to obtain nickel-cobalt hydroxide product; and returning the final stage concentrated atmospheric pressure leaching slurry to the high-pressure acid leaching treatment, which can effectively inhibit the scaling rate of conventional high-pressure acid leaching treatment and extend the production cycle.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Background Technology

[0002] Currently, the demand for Ni, Co, and Mn metals in ternary materials for new energy is increasing, and the development of laterite nickel ore with large reserves but ultra-low nickel grades is gradually becoming a hot topic in the industry. Hydrometallurgical route using sulfuric acid leaching under high temperature and high pressure is one of the mainstream smelting processes for ultra-low grade laterite nickel ore.

[0003] However, during the high-pressure, high-temperature leaching process, due to Fe... 3+ And Al 3+ Hydrolysis and precipitation of metal ions, precipitation of low-solubility substances such as CaSO4, and precipitation of solid impurities such as SiO2 in minerals can all lead to scale buildup on the walls of high-pressure reactors, the blades of agitators, the inner walls of reactor discharge pipes, and valves. This scale causes a series of problems that are detrimental to production, including blockage of discharge pipes and valves, increased pressure drop, and reduced reactor volume. Currently, the main method for dealing with scale buildup in actual production is to periodically shut down the high-pressure reactor for cleaning. However, frequent start-ups and shutdowns can reduce production efficiency and cause fluctuations in production process parameters.

[0004] Therefore, how to effectively reduce the scaling rate of the high-pressure reactor and extend the production time during the leaching process of laterite nickel ore is a technical problem that urgently needs to be solved by those in the field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a multi-stage combined leaching method for ultra-low grade lateritic nickel ore, which solves the technical problem of low production efficiency of nickel hydroxide cobalt products due to the rapid scaling rate of the high-pressure reactor during the high-pressure acid leaching process of ultra-low grade lateritic nickel ore.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a multi-stage combined leaching method for ultra-low grade lateritic nickel ore, comprising: S10, subjecting the lateritic nickel ore slurry to high-pressure acid leaching to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium, and high-pressure leaching solution containing nickel, cobalt, and manganese, wherein the mass percentage of nickel in the lateritic nickel ore slurry is less than 1.0%; S20, mixing the high-pressure leaching solution, the lateritic nickel ore slurry, and an acidic solution to obtain a mixed solution, and subjecting the mixed solution to multi-stage atmospheric pressure leaching, followed by concentration treatment to obtain a final stage concentrated atmospheric pressure leaching solution. The process involves: S20, where the final stage concentrated atmospheric leaching slurry and the high-pressure leaching tailings are subjected to sequential circulating leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum, and chromium removal treatment, and MHP precipitation treatment to obtain nickel-cobalt hydroxide product; wherein, after step S20 is completed, the process further includes: returning the final stage concentrated atmospheric leaching slurry to step S10 for the high-pressure acid leaching treatment.

[0008] This invention involves mixing the high-pressure leachate obtained from high-pressure acid leaching of laterite nickel ore slurry, the laterite nickel ore slurry, and an acidic solution, and then performing multi-stage atmospheric pressure leaching. This avoids scaling in the high-pressure reactor due to excessive accumulation of the high-pressure leachate during high-pressure acid leaching. Furthermore, since the reaction conditions of multi-stage atmospheric pressure leaching are milder than those of high-pressure acid leaching, it effectively suppresses the scaling rate of the high-pressure leachate, thereby extending the acid leaching treatment time. Ultimately, this improves the production efficiency of nickel-cobalt hydroxide products and reduces their production costs.

[0009] Specifically, the mass percentage of nickel in the laterite nickel ore in the laterite nickel ore slurry is less than 1.0%, for example, it can be 0.99%, 0.98%, 0.97%, 0.95%, 0.92%, 0.9%, 0.88%, 0.85%, 0.80%, 0.75%, or 0.70%, etc.

[0010] The preparation of laterite nickel ore slurry in this invention includes: providing natural laterite nickel ore raw material, and obtaining ultra-low grade laterite nickel ore through pretreatment processes such as beneficiation and grinding; wherein, the beneficiation steps specifically include gravity separation and magnetic separation.

[0011] Generally, nickel in ultra-low grade lateritic nickel ore is difficult to leach, and methods such as pyrometallurgical leaching, atmospheric pressure leaching, and bioleaching can be used. Pyrometallurgical leaching carries away metals such as cobalt and scandium from the lateritic nickel ore into the slag, which cannot be recovered. Atmospheric pressure leaching consumes a large amount of acid, typically over 700 kg / ton of lateritic nickel ore, and the leachate contains high levels of impurities such as Fe and Al. Bioleaching takes extremely long times, sometimes measured in months. Therefore, high-pressure acid leaching is used industrially. However, the high reaction pressure of high-pressure acid leaching easily leads to the leaching and hydrolysis of aluminum and iron, resulting in significant scaling. Unlike lateritic nickel ore of normal grade, ultra-low grade lateritic nickel ore, in addition to its low nickel content, also has a correspondingly higher content of aluminum and iron, leading to more severe scaling.

[0012] This invention employs a thickener to concentrate the mixture after multi-stage atmospheric pressure leaching, yielding a final-stage concentrated atmospheric pressure leaching solution and a final-stage concentrated atmospheric pressure leaching slurry. The slurry concentration of the final-stage concentrated atmospheric pressure leaching slurry is the same as that of the original laterite nickel ore slurry. The thickener ensures that the slurry concentration of the final-stage concentrated atmospheric pressure leaching slurry is identical to that of the original laterite nickel ore slurry, thus meeting the slurry conditions for high-pressure acid leaching and facilitating recycling.

[0013] The final stage concentrated atmospheric leaching slurry obtained by this invention meets the slurry conditions for high-pressure acid leaching and can be returned to step S10 to be mixed with the laterite nickel ore slurry for high-pressure acid leaching. This recycling method helps maintain the balance of materials in the system, enabling the entire process to operate continuously and stably, and reducing process fluctuations and potential problems caused by material imbalance.

[0014] The reasons why the combined high-pressure acid leaching and multi-stage atmospheric pressure leaching treatment in this invention can inhibit scaling are as follows: 1) Mild reaction conditions: The reaction conditions under atmospheric pressure are relatively mild, without the drastic physicochemical changes seen under high pressure. Some reactions and precipitation processes that easily lead to scaling are slowed down or less likely to occur. 2) Differences in ion solubility: Under atmospheric pressure and lower temperatures, the solubility of some substances is relatively high, making it difficult to reach saturation and precipitate to form a scale layer. However, high pressure and high temperature may cause changes in solubility, promoting scale formation. 3) Fluid dynamics: The flow state of fluids under atmospheric pressure is relatively stable, unlike the complex flow changes that may occur under high pressure, reducing the possibility of material deposition and scaling due to local flow anomalies. 4) Reaction rate: The lower reaction rate allows some potential scaling components more time to remain in a dissolved state or be uniformly dispersed, rather than rapidly precipitating and accumulating. 5) Impurity behavior: The reaction and transformation behavior of impurities under atmospheric pressure differs from that under high pressure, and some impurity reaction pathways that may lead to scaling are inhibited or altered. 6) Difficulty in process control: Atmospheric pressure processes are relatively easier to control, with smaller parameter fluctuations, thereby reducing the risk of scaling caused by process instability and process parameter disturbances.

[0015] Preferably, in step S10, the concentration of the laterite nickel ore slurry is 30-40%, for example, it can be 30%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, and the slurry-to-product ratio is 100-200m³. 3 / ton of metallic nickel, for example, could be 100m 3 / ton of metallic nickel, 112m 3 / ton of metallic nickel, 123m 3 / ton of metallic nickel, 134m 3 / ton of metallic nickel, 145m 3 / ton of metallic nickel, 156m 3 / ton of metallic nickel, 167m 3 / ton of metallic nickel, 178m 3 / ton of metallic nickel, 189m 3 / ton of metallic nickel or 200m 3 / ton of metallic nickel, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0016] The present invention preferably controls the slurry concentration of laterite nickel ore slurry within the above-mentioned range, which can ensure sufficient solid content to maintain the efficiency of subsequent reactions and processing, and also ensure that the slurry has suitable fluidity and operability.

[0017] Preferably, in step S10, the process conditions for the high-pressure acid leaching treatment are: temperature 220–260°C, for example, 220°C, 225°C, 229°C, 234°C, 238°C, 243°C, 247°C, 252°C, 256°C, or 260°C, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable; pressure 2.0–6.0 MPa, for example, 2.0 MPa, 2.5 MPa, 2.9 MPa, 3.4 MPa, 3.8 MPa, 4.3 MPa, 4.7 MPa, 5.2 MPa, 5.6 MPa, or 6.0 MPa, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] Preferably, the acid consumption for the high-pressure acid leaching treatment is 15 to 25 tons / ton of nickel, for example, it can be 15 tons / ton of nickel, 17 tons / ton of nickel, 18 tons / ton of nickel, 19 tons / ton of nickel, 20 tons / ton of nickel, 21 tons / ton of nickel, 22 tons / ton of nickel, 23 tons / ton of nickel, 24 tons / ton of nickel or 25 tons / ton of nickel, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] Preferably, the pH of the high-pressure acid leaching treatment is 0.5 to 2.0, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 1.9 or 2.0.

[0020] Specifically, the process of high-pressure acid leaching of laterite nickel ore slurry includes:

[0021] (1) The raw nickel ore slurry of laterite is subjected to high-pressure acid leaching treatment, and high-pressure leaching slurry is obtained through multi-stage flash heat exchange; wherein, the process conditions of high-pressure acid leaching treatment are: temperature of 220~260℃, pressure of 2.0~6.0MPa, and acid consumption of 15~25 tons / ton of nickel.

[0022] Specifically, multi-stage flash heat exchange can achieve more efficient heat transfer, rapidly increase the temperature of the slurry to meet the requirements of subsequent processes, and at the same time, fully recover and utilize the waste heat in the system, reduce overall energy consumption, and improve energy utilization efficiency.

[0023] (2) The high-pressure leaching slurry is subjected to solid-liquid separation treatment to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching solution containing nickel, cobalt and manganese.

[0024] Preferably, a reducing agent and a leaching accelerator are also added during the high-pressure acid leaching process.

[0025] Preferably, the reducing agent comprises any one or a combination of at least two of lignite, ferrous sulfate, sodium sulfite, or sodium bisulfite, wherein typical but non-limiting combinations are a combination of lignite and ferrous sulfate, a combination of sodium sulfite and ferrous sulfate, a combination of lignite and sodium bisulfite, or a combination of sodium bisulfite and ferrous sulfate.

[0026] Preferably, the leaching accelerator includes sodium sulfate and / or copper sulfate.

[0027] It is worth noting that adding a reducing agent can inhibit the transformation of divalent manganese ions to higher valence states, which is beneficial for the subsequent extraction of manganese. On the other hand, it is beneficial for converting hexavalent chromium to trivalent chromium in the subsequent multi-stage neutralization process, which facilitates chromium removal. Introducing a leaching promoter can promote the leaching of nickel, cobalt, and manganese.

[0028] Preferably, the amount of the leaching promoter added is 1.0 to 2.5 wt% of the laterite nickel ore slurry, for example, it can be 1.0 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, or 2.5 wt%.

[0029] The high-pressure acid leaching treatment results in a high-pressure leaching tailings containing iron, aluminum, and magnesium with a Ni content of less than 0.05%, for example, 0.049%, 0.048%, 0.045%, 0.042%, 0.04%, 0.038%, or 0.035%; a Co content of less than 0.005%, for example, 0.004%, 0.003%, 0.002%, or 0.001%; ​​and a Mn content of less than 0.05%, for example, 0.049%, 0.048%, 0.047%, 0.046%, 0.044%, 0.04%, 0.038%, 0.035%, 0.03%, or 0.028%.

[0030] Preferably, in step S20, the mass ratio of the high-pressure leaching solution, the lateritic nickel ore slurry, and the acidic solution is 1:(0.8-1.2):(1-2). The proportions of the lateritic nickel ore slurry can be, for example, 0.8, 0.83, 0.85, 0.87, 0.89, 0.92, 0.94, 0.96, 0.98, 1, 1.1, 1.15, 1.18, or 1.2, but are not limited to the listed values; other unlisted values ​​within this range are also applicable. The proportions of the acidic solution can be, for example, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2, but are not limited to the listed values; other unlisted values ​​within this range are also applicable. The above mass ratio ensures that the relative content of each component is within a suitable range, guaranteeing both sufficient reaction and economic rationality of the process.

[0031] Preferably, the acidic solution comprises sulfuric acid or hydrochloric acid. Both acids effectively promote the relevant reactions. Sulfuric acid has wide applications and good reactivity, while hydrochloric acid may also have specific advantages in certain situations.

[0032] Preferably, the mass ratio of the final stage concentrated atmospheric leaching slurry to the laterite nickel ore slurry in step S10 is (0.8-1.2):(1-2). The number of parts of the final stage concentrated atmospheric leaching slurry can be, for example, 0.8, 0.82, 0.83, 0.85, 0.88, 0.9, 0.92, 0.95, 1.0, 1.05, 1.1, 1.15, or 1.2. The number of parts of the laterite nickel ore slurry can be, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0.

[0033] Preferably, the total mass content of iron, aluminum and magnesium in the laterite nickel ore slurry is 45-55 wt%, for example, it can be 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, or 55 wt%.

[0034] Preferably, the total mass content of iron, aluminum and magnesium in the final stage concentrated atmospheric pressure leaching slurry is 30-44 wt%, for example, it can be 30 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 42 wt%, 43 wt% or 44 wt%, etc.

[0035] It is worth noting that, from the total mass content of iron, aluminum and magnesium in the above-mentioned laterite nickel ore slurry and the final stage concentrated atmospheric pressure leaching slurry, it can be seen that, under the same slurry concentration, the content of iron, aluminum and magnesium decreases by about 10% percentage points. That is, the present invention can better leach iron, aluminum and magnesium metals through atmospheric pressure leaching process, thereby reducing the total mass content of iron, aluminum and magnesium in the final stage concentrated atmospheric pressure leaching slurry. Then, mixing the final stage concentrated atmospheric pressure leaching slurry with the laterite nickel ore slurry for high-pressure acid leaching can significantly alleviate the phenomenon of iron, aluminum and magnesium leaching and hydrolysis under the severe conditions of high-pressure acid leaching, which leads to a large amount of scaling.

[0036] Compared to leaching under normal pressure first and then under high pressure, this invention directly performs high pressure leaching first, which can achieve efficient leaching of nickel, cobalt and manganese in the high pressure leaching step, resulting in higher overall leaching efficiency. It can not only ensure leaching efficiency, but also delay the scaling treatment cycle and improve production efficiency.

[0037] Preferably, in step S20, the temperature of the multi-stage atmospheric pressure leaching treatment is 60–90°C, for example, 60°C, 64°C, 67°C, 70°C, 74°C, 77°C, 80°C, 84°C, 87°C, or 90°C, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The relatively mild temperature range of the multi-stage atmospheric pressure leaching treatment helps control the reaction rate and selectivity, while also reducing equipment requirements and operating costs. The pressure is close to atmospheric pressure, simplifying process operation and equipment requirements.

[0038] Preferably, the pH of the multi-stage atmospheric pressure leaching treatment is 0.5 to 2.0, for example, it can be 0.5, 0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8 or 2.0.

[0039] Preferably, in step S20, a thickener is used to concentrate the mixture after the multi-stage atmospheric pressure leaching treatment to obtain the final stage concentrated atmospheric pressure leaching solution and the final stage concentrated atmospheric pressure leaching slurry.

[0040] Preferably, in step S20, the number of atmospheric pressure leaching stages in the multi-stage atmospheric pressure leaching treatment is 2 to 10, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10. This reflects the design concept of completing the leaching process step by step through multiple stages. Multi-stage treatment can improve the leaching effect and efficiency, making the reaction more complete and thorough, and also facilitates fine control and optimization of the reaction at different stages. By increasing the number of stages, the degree of leaching can be gradually increased, the recovery rate of valuable metals can be improved, and the residue of impurities can be reduced. This multi-stage design provides greater flexibility and controllability to adapt to different ore characteristics and product requirements.

[0041] Specifically, the final concentrated atmospheric pressure leaching slurry obtained through multi-stage atmospheric pressure leaching can leach out a portion of the iron, aluminum, and magnesium. This is partly because some of the Fe... 3+ And Al 3+ During multi-stage atmospheric pressure leaching, metal ions undergo hydrolysis, producing precipitates that form scale on the inner wall of the atmospheric pressure reactor; on the other hand, this is due to another portion of Fe... 3+ And Al 3+ Metal ions dissolve in the final stage concentrated atmospheric pressure leachate.

[0042] Preferably, in the cyclic leaching and multi-stage pre-neutralization treatment of step S30, the controlled temperature of the cyclic leaching is 70–90°C, for example, 70°C, 73°C, 75°C, 77°C, 79°C, 82°C, 84°C, 86°C, 88°C, or 90°C, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The cyclic leaching of this invention reduces the residual acid concentration from 30–50 g / L to below 5 g / L.

[0043] Preferably, the pH of the multi-stage pre-neutralization is 0.8 to 2, for example, it can be 0.8, 1, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 1.9 or 2, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the neutralizing agent for the multi-stage pre-neutralization includes any one or a combination of at least two of lime milk, limestone, sodium hydroxide, or magnesium hydroxide, wherein typical but non-limiting combinations are the combination of lime milk and limestone, the combination of sodium hydroxide and limestone, the combination of lime milk and sodium hydroxide, and the combination of magnesium hydroxide and limestone.

[0045] Preferably, in step S30, the neutralized slurry obtained from the cyclic leaching and multi-stage pre-neutralization treatment is subjected to countercurrent washing to obtain a final liquid phase and a slag phase. The number of washing stages in the countercurrent washing treatment is 3 to 9, for example, 3, 4, 5, 6, 7, 8, or 9. In this step, the ratio of wash water to slag phase in the countercurrent washing treatment is (1-7):1, the Ni content in the final liquid phase is less than 0.1 g / L, and the nickel content in the neutralized slag phase is less than 0.06%. During the multi-stage pre-neutralization treatment, an appropriate amount of neutralizing agent is added to keep the slag phase in a neutral state. The slag phase after neutralization treatment is separated into solid and liquid phases by a thickener to obtain tailings. The tailings have a pH of 6-9 and mainly contain iron. Subsequently, iron metal is recovered by reduction roasting and magnetic separation. The tailings after iron metal recovery meet the direct discharge standards and can be directly discharged, which is in line with the green and environmentally friendly production expectations.

[0046] Preferably, the process conditions for the iron, aluminum, and chromium removal treatment are as follows: the number of process stages is 2 to 7, for example, 2, 3, 4, 5, 6, or 7 stages, and / or the controlled temperature is 55 to 90°C, for example, 55°C, 59°C, 63°C, 67°C, 71°C, 75°C, 79°C, 83°C, 87°C, or 90°C, but not limited to the listed values; other unlisted values ​​within this range are also applicable, and / or the pH value is 2.5 to 5.5, for example, 2.5, 2.9, 3.2, 3.5, 3.9, 4.2, 4.5, 4.9, 5.2, or 5.5, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In this invention, the final liquid phase after multi-stage countercurrent washing undergoes multi-stage iron, aluminum, and chromium removal, thickening, and separation under the condition of adding a neutralizing agent and a precipitation promoter. In this step, the multi-stage iron, aluminum, and chromium removal consists of a first-stage removal and two or more stages. The liquid phase after the first-stage removal is processed by the next stage. The slag phase after the first-stage removal is returned and subjected to multi-stage countercurrent washing again. The slag phase after the second and more stages is reused and subjected to cyclic leaching and multi-stage neutralization treatment again. The process conditions for multi-stage iron, aluminum, and chromium removal are: 2 to 7 stages; controlled temperature of 55 to 90°C; pH of 2.5 to 5.5; the neutralizing agent is any one or a mixture of lime milk, limestone, sodium hydroxide, and magnesium hydroxide; the precipitation promoter is any one or a mixture of organic and inorganic polymers, such as polyacrylamide and polyaluminum chloride, etc., without limitation.

[0048] For example, the process conditions for removing iron, aluminum, and chromium in one stage could be: adding a neutralizing agent, introducing compressed air, controlling the pH at 2.5–4.0, the temperature at 70–90℃, and the reaction time at 1–2 hours. After the first stage of iron, aluminum, and chromium removal is completed, a considerable amount of nickel, cobalt, and manganese remains in the thickened slurry. Returning the slurry after the first stage of iron, aluminum, and chromium removal for multi-stage countercurrent washing is beneficial for the full utilization of nickel, cobalt, and manganese in the slurry. In the first stage of iron, aluminum, and chromium removal, iron, aluminum, and chromium metals are removed simultaneously.

[0049] For example, the process conditions for two-stage or higher iron, aluminum, and chromium removal could be: pH controlled at 4.0–5.5, temperature at 55–80℃, and reaction time at 2–10 hours. During two-stage or higher iron, aluminum, and chromium removal, the remaining iron, aluminum, and chromium in the liquid phase can be removed simultaneously, improving the removal efficiency of impurity metal elements and ensuring the subsequent extraction of purer nickel, cobalt, and manganese products. The purpose of reusing the slag phase from two-stage or higher iron, aluminum, and chromium removal for further leaching and multi-stage neutralization is that a certain amount of nickel, cobalt, and manganese elements will still remain in the slag phase after the two-stage or higher iron, aluminum, and chromium removal. Reusing this slag phase allows for the extraction of as much nickel, cobalt, and manganese as possible. Simultaneously, since the pH value after two-stage or higher iron, aluminum, and chromium removal differs significantly from that during leaching and multi-stage pre-neutralization, reusing the slag phase from two-stage or higher iron, aluminum, and chromium removal can reduce the amount of neutralizing agent used during leaching and the first neutralization treatment, thereby saving costs.

[0050] Preferably, in step S30 of the present invention, the tail liquid phase after multiple iron, aluminum, and chromium removal is subjected to MHP precipitation treatment to obtain nickel-cobalt hydroxide product; in the nickel-cobalt hydroxide product of step S30: the nickel mass percentage is 30-40%, for example, it can be 30%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable; the cobalt mass percentage is 3.0-6.0%, for example, it can be 3.0%, 3.4%, 3.7%, 4%, 4.4%, 4.7%, 5%, 5.4%, 5.7%, or 6.0%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0051] Specifically, the aforementioned MHP precipitation process is a multi-stage nickel-cobalt synthesis process, consisting of a first-stage nickel-cobalt synthesis stage and two or more stages. The liquid phase following the first stage of nickel-cobalt synthesis is then used in the next stage. The tail-end liquid phase from the multi-stage iron, aluminum, and chromium removal process undergoes a first-stage nickel-cobalt synthesis treatment, yielding nickel-cobalt hydroxide. This nickel-cobalt hydroxide product from the tail-end of the multi-stage nickel-cobalt synthesis is returned for further leaching and multi-stage neutralization. This allows the remaining trace amounts of nickel and cobalt in the slag phase after multi-stage nickel-cobalt precipitation to re-enter the process for extraction, ultimately improving the extraction rate of nickel and cobalt. Simultaneously, the tail-end liquid phase from the multi-stage nickel-cobalt synthesis is discharged after wastewater treatment.

[0052] For example, the process conditions for synthesizing nickel-cobalt in one stage could be: adding a neutralizing agent, controlling the pH value to be 6.5–7.4, the temperature to be 50–70℃, and the reaction time to be 5–7 hours.

[0053] For example, the process conditions for two-stage or higher synthesis of nickel-cobalt could be: pH value controlled at 7.5–10.0, temperature at 40–90℃, and reaction time at 0.5–1.5 h.

[0054] The present invention does not impose any special restrictions on the solid-liquid separation in the above process. Any device and method known to those skilled in the art for solid-liquid separation can be used. It can also be adjusted according to the actual process. For example, it can be filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0055] The present invention does not impose any special restrictions on the pulverization process described above. Any device and method known to those skilled in the art for pulverization can be used. Adjustments can also be made according to the actual process. For example, it can be grinding, extrusion pulverization, splitting pulverization, or impact pulverization, or a combination of different methods.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects:

[0057] (1) The multi-stage combined leaching method for ultra-low grade laterite nickel ore provided by the present invention combines high-pressure acid leaching and multi-stage atmospheric pressure treatment, and returns the final stage concentrated atmospheric pressure leaching slurry to the high-pressure acid leaching treatment. This can reduce scaling in the high-pressure acid leaching process and extend the growth cycle. Specifically, it is preferred to extend the maintenance and descaling cycle to more than 150 days under the acid consumption condition of 300 kg acid / ton dry ore, and extend the maintenance cycle to more than double. After 60 days of operation, the pressure difference increases to within 0.2 MPa.

[0058] (2) In the high-pressure acid leaching step, the multi-stage combined leaching method for ultra-low grade laterite nickel ore provided by the present invention preferably controls the mass ratio of the final stage concentrated atmospheric pressure leaching slurry to the laterite nickel ore slurry within a reasonable range, which is not only conducive to the efficient leaching of nickel, cobalt and manganese, but also greatly alleviates the scaling phenomenon. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the multi-stage combined leaching method for ultra-low grade laterite nickel ore provided in an embodiment of the present invention.

[0060] Figure 2 This is a schematic diagram of the specific process of the multi-stage combined leaching method for ultra-low grade laterite nickel ore provided in Embodiment 1 of the present invention. Detailed Implementation

[0061] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0063] In the description of the embodiments of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "multi-level" means two or more levels, unless otherwise explicitly defined.

[0064] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0065] In the description of the embodiments of this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0066] It is worth noting that in industrial production, severe scaling requires shutdown for maintenance. On the one hand, for high-pressure acid leaching processes, a single shutdown for descaling takes about 7 days, which consumes manpower and delays production every day. On the other hand, repeated shutdowns and restarts can easily lead to batch-to-batch differences in the entire production process and affect the stability of production. Therefore, it is necessary to minimize scaling as much as possible.

[0067] To address the technical problem of low production efficiency of nickel-cobalt hydroxide products due to rapid scaling in the high-pressure reactor during high-pressure acid leaching of ultra-low-grade lateritic nickel ore, this invention provides a multi-stage combined leaching method for ultra-low-grade lateritic nickel ore. Compared with conventional high-pressure acid leaching, the method provided by this invention has milder reaction conditions, effectively suppressing the scaling rate of the high-pressure leaching solution, thereby delaying the scaling treatment time in high-pressure acid leaching, ultimately improving the production efficiency of nickel-cobalt hydroxide products and reducing their production costs.

[0068] Please see Figure 1 , Figure 1 A schematic diagram of a multi-stage combined leaching method for ultra-low grade laterite nickel ore provided in an embodiment of the present invention; wherein, the multi-stage combined leaching method includes the following steps:

[0069] S10, the laterite nickel ore slurry is subjected to high-pressure acid leaching to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching solution containing nickel, cobalt and manganese, wherein the mass percentage of nickel in the laterite nickel ore slurry is less than 1.0%.

[0070] S20, the high-pressure leaching solution, the laterite nickel ore slurry, and the acidic solution are mixed to obtain a mixed solution, and the mixed solution is subjected to multi-stage atmospheric pressure leaching treatment. After concentration treatment, a final stage concentrated atmospheric pressure leaching solution and a final stage concentrated atmospheric pressure leaching slurry are obtained. The slurry concentration of the final stage concentrated atmospheric pressure leaching slurry is the same as that of the laterite nickel ore slurry.

[0071] S30, the final stage concentrated atmospheric pressure leaching solution and the high pressure leaching tailings are sequentially subjected to circulating leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment to obtain nickel-cobalt hydroxide product; wherein, after the completion of step S20, the final stage concentrated atmospheric pressure leaching slurry is returned to step S10 for the high pressure acid leaching treatment.

[0072] For ease of comparison, the acidic solutions used in the leaching process described below are all 25 wt% sulfuric acid. However, this does not mean that this invention can only use sulfuric acid of this concentration; other concentrations of sulfuric acid are also feasible. The acid consumption referred to in this invention is calculated based on the purchase of high-concentration (generally 98%) sulfuric acid.

[0073] Example 1

[0074] This embodiment provides a multi-stage combined leaching method for ultra-low grade lateritic nickel ore. (See also...) Figure 2 The multi-stage combined leaching method includes the following steps:

[0075] (1) A certain limonite-type laterite nickel ore was selected as the test object. After testing (the following are mass percentages), the content of nickel in the ore was 0.4%, cobalt 0.15%, Cr2O3 3.78%, MnO 2.13%, Al2O3 10.86%, SiO2 25.42%, Fe 30.54%, and Mg 5.23%. According to the test results, the sample is a typical limonite-type ultra-low grade laterite nickel ore. The ultra-low grade laterite nickel ore was mixed with water to prepare the laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0076] (2) Lignite powder was added to the laterite nickel ore slurry at a mass ratio of 1000:1 to lignite, and sodium sulfate (leaching promoter, added at 1.5 wt% of the laterite nickel ore slurry) was fed into a high-pressure reactor. The high-pressure leaching reaction was carried out under the conditions of 255℃, 4.0 MPa, pH 1.0, and acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching solution containing nickel, cobalt and manganese.

[0077] (3) The high-pressure leaching solution containing nickel, cobalt and manganese, the laterite nickel ore slurry and the acid solution are mixed in a mass ratio of 1:1:1.5 to obtain a mixed solution, and the mixed solution is transferred to an atmospheric pressure reactor for multi-stage atmospheric pressure leaching treatment; the process conditions for each stage of the multi-stage atmospheric pressure leaching treatment are: temperature 80℃, pressure 0.1MPa, pH 1.2, and number of atmospheric pressure leaching stages 5.

[0078] (4) The mixture after multi-stage atmospheric pressure leaching is concentrated using a thickener to obtain the final stage concentrated atmospheric pressure leaching solution and the final stage concentrated atmospheric pressure leaching slurry. The slurry concentration of the final stage concentrated atmospheric pressure leaching slurry is 35%. The final stage concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry at a mass ratio of 1.0:1 for high-pressure acid leaching treatment (i.e., high-pressure leaching).

[0079] (5) The final concentrated atmospheric pressure leachate is mixed with the high pressure leaching tailings and then leached in a circulating manner and pre-neutralized in multiple stages. Then, a multi-stage countercurrent washing process is adopted, with 6 washing stages and a ratio of washing water to slag phase of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizing agent is added to the slag phase to make the slag phase neutral at pH 6.8. Then, metallic iron is recovered and the tailings are discharged.

[0080] (6) The liquid phase obtained from multi-stage countercurrent washing is further subjected to a first-stage iron, aluminum, and chromium removal process (with the addition of sodium hydroxide). The process conditions for this first-stage iron, aluminum, and chromium removal are: controlled temperature of 85℃, pH of 3.0, and reaction time of 1h. The slag phase after the first-stage iron, aluminum, and chromium removal is recycled for another continuous multi-stage countercurrent washing. The liquid phase after the first-stage iron, aluminum, and chromium removal is subjected to a second-stage iron, aluminum, and chromium removal process (with the addition of sodium hydroxide). The process conditions for the second-stage iron, aluminum, and chromium removal are: controlled temperature of 79℃, pH of 4.8, and reaction time of 3h. The slag phase after the second-stage iron, aluminum, and chromium removal is recycled for another leaching and neutralization.

[0081] (7) A neutralizing agent (sodium hydroxide) is added to the liquid phase after the second-stage removal of iron, aluminum, and chromium to carry out a first-stage synthesis of nickel and cobalt. The resulting nickel-cobalt hydroxide product is obtained. The process conditions for the first-stage synthesis of nickel and cobalt are: pH 7.0, reaction temperature 66℃, and reaction time 3h. The process conditions for the second-stage synthesis of nickel and cobalt are: pH 8.0, reaction temperature 50℃, and reaction time 1.0h. The obtained nickel-cobalt hydroxide product contains 31.13% nickel and 3.51% cobalt by mass.

[0082] Example 2

[0083] This embodiment provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore, the multi-stage combined leaching method comprising the following steps:

[0084] (1) A certain limonite-type laterite nickel ore was selected as the test object. After testing (the following are mass percentages), the content of nickel in the ore was 0.6%, cobalt 0.25%, Cr2O3 2.48%, MnO 1.86%, Al2O3 9.45%, SiO2 18.67%, Fe 35.14%, and Mg 8.38%. According to the test results, the sample is a typical limonite-type ultra-low grade laterite nickel ore. The ultra-low grade laterite nickel ore was mixed with water to prepare the laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 30%.

[0085] (2) Lignite powder was added to the laterite nickel ore slurry at a mass ratio of 900:1 to lignite, along with sodium sulfate (leaching promoter, added at 2.5 wt% of the laterite nickel ore slurry) and fed into a high-pressure reactor. The leaching reaction was carried out under high-pressure leaching conditions of 260℃, 2.0 MPa, pH 0.8, and acid consumption of 25 tons / ton of nickel. The high-pressure leaching slurry was obtained by multi-stage flash heat exchange. The high-pressure leaching slurry was then filtered to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium, and high-pressure leaching solution containing nickel, cobalt, and manganese.

[0086] (3) The high-pressure leaching solution containing nickel, cobalt and manganese, the laterite nickel ore slurry and the acid solution are mixed in a mass ratio of 1:0.8:2 to obtain a mixed solution, and the mixed solution is transferred to an atmospheric pressure reactor for multi-stage atmospheric pressure leaching treatment; the process conditions for each stage of the multi-stage atmospheric pressure leaching treatment are: temperature 60℃, pressure 0.1MPa, pH 1.2, and number of atmospheric pressure leaching stages 2.

[0087] (4) The mixture after multi-stage atmospheric pressure leaching is concentrated using a thickener to obtain the final stage concentrated atmospheric pressure leaching solution and the final stage concentrated atmospheric pressure leaching slurry. The slurry concentration of the final stage concentrated atmospheric pressure leaching slurry is 30%. The final stage concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry at a mass ratio of 1.2:1 for high-pressure acid leaching.

[0088] (5) The final stage concentrated atmospheric pressure leachate is mixed with the high pressure leaching tailings and then leached in a cycle and neutralized in multiple stages. Then, a multi-stage countercurrent washing process is adopted, with 6 washing stages and a washing water to slag ratio of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizing agent is added to the slag phase to make the slag phase neutral at pH=7.0. Then, metallic iron is recovered and the tailings are discharged.

[0089] (6) The liquid phase obtained from multi-stage countercurrent washing is further subjected to a first-stage iron, aluminum, and chromium removal process (with the addition of sodium hydroxide). The process conditions for this first-stage iron, aluminum, and chromium removal are: controlled temperature of 60℃, pH of 2.5, and reaction time of 1.5h. The slag phase after the first-stage iron, aluminum, and chromium removal is recycled for another continuous multi-stage countercurrent washing. The liquid phase after the first-stage iron, aluminum, and chromium removal is subjected to a second-stage iron, aluminum, and chromium removal process (with the addition of sodium hydroxide). The process conditions for the second-stage iron, aluminum, and chromium removal are: controlled temperature of 80℃, pH of 4.0, and reaction time of 3h. The slag phase after the second-stage iron, aluminum, and chromium removal is recycled for another leaching and neutralization.

[0090] (7) A neutralizing agent (sodium hydroxide) is added to the tail-end liquid phase after the second-stage iron, aluminum, and chromium removal process to perform a first-stage nickel-cobalt synthesis and a second-stage nickel-cobalt-manganese synthesis to obtain nickel-cobalt hydroxide product. The process conditions for the first-stage nickel-cobalt synthesis are: pH 6.5, reaction temperature 70℃, and reaction time 5h. The liquid phase from the first-stage nickel-cobalt synthesis is used for the second-stage nickel-cobalt synthesis. The slag phase from the second-stage nickel-cobalt synthesis is recycled for further leaching and neutralization treatment. The liquid phase from the second-stage nickel-cobalt synthesis is discharged after wastewater treatment. The process conditions for the second-stage nickel-cobalt synthesis are: pH 10.0, reaction temperature 40℃, and reaction time 1.5h. The obtained nickel-cobalt hydroxide product contains 36.52% nickel and 5.32% cobalt by mass.

[0091] Example 3

[0092] This embodiment provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore, the multi-stage combined leaching method comprising the following steps:

[0093] (1) A certain limonite-type laterite nickel ore was selected as the test object. After testing (the following are mass percentages), the content of nickel in the ore was 0.8%, cobalt 0.45%, Cr2O3 4.12%, MnO 1.58%, Al2O3 9.81%, SiO2 12.18%, Fe 33.27%, and Mg 6.25%. According to the test results, the sample is a typical limonite-type ultra-low grade laterite nickel ore. The ultra-low grade laterite nickel ore was mixed with water to prepare the laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 40%.

[0094] (2) Lignite powder was added to the laterite nickel ore slurry at a mass ratio of 1100:1 and sodium sulfate (leaching promoter, added at 1.0 wt% of the laterite nickel ore slurry) together with the lignite powder. The leaching reaction was carried out under high pressure leaching conditions of 220℃, 6.0 MPa, pH 1.0, and acid consumption of 15 tons / ton of nickel to obtain high pressure leaching tailings containing iron, aluminum and magnesium and high pressure leaching solution containing nickel, cobalt and manganese.

[0095] (3) The high-pressure leaching solution containing nickel, cobalt and manganese, the laterite nickel ore slurry and the acidic solution are mixed at a mass ratio of 1:0.9:1 to obtain a mixed solution, and the mixed solution is transferred to an atmospheric pressure reactor for multi-stage atmospheric pressure leaching treatment; the process conditions for each stage of the multi-stage atmospheric pressure leaching treatment are: temperature 90℃, pressure 0.1MPa, pH 0.5, and number of atmospheric pressure leaching stages 10.

[0096] (4) A thickener is used to concentrate the mixture after multi-stage atmospheric pressure leaching to obtain the final stage concentrated atmospheric pressure leaching solution and the final stage concentrated atmospheric pressure leaching slurry. The slurry concentration of the final stage concentrated atmospheric pressure leaching slurry is 40%. The final stage concentrated atmospheric pressure leaching slurry is returned to step (2) and mixed with the laterite nickel ore slurry at a mass ratio of 0.8:1 for high-pressure acid leaching.

[0097] (5) The final concentrated atmospheric pressure leachate is mixed with the high pressure leaching tailings and then leached in a cycle and neutralized in multiple stages. Then, a multi-stage countercurrent washing process is adopted, with 6 washing stages and a washing water to slag ratio of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizing agent is added to the slag phase to make the slag phase neutral at pH=6.8. Then, metallic iron is recovered and the tailings are discharged.

[0098] (6) The liquid phase obtained from multi-stage countercurrent washing is further subjected to a first-stage iron, aluminum, and chromium removal process (with the addition of sodium hydroxide). The process conditions for this first-stage iron, aluminum, and chromium removal are: controlled temperature of 60℃, pH of 4.0, and reaction time of 2.0h. The slag phase after the first-stage iron, aluminum, and chromium removal is recycled for continuous multi-stage countercurrent washing again. The liquid phase after the first-stage iron, aluminum, and chromium removal is subjected to a second-stage iron, aluminum, and chromium removal process (with the addition of sodium hydroxide). The process conditions for the second-stage iron, aluminum, and chromium removal are: controlled temperature of 55℃, pH of 2.5, and reaction time of 4h. The slag phase after the second-stage iron, aluminum, and chromium removal is recycled for cyclic leaching and neutralization again.

[0099] (7) A neutralizing agent (sodium hydroxide) is added to the tail-end liquid phase after the second-stage iron, aluminum, and chromium removal process to carry out the first-stage nickel-cobalt synthesis. The resulting product is nickel-cobalt hydroxide. The process conditions for the first-stage nickel-cobalt synthesis are: pH 7.4, reaction temperature 50℃, and reaction time 7h. The liquid phase from the first-stage nickel-cobalt synthesis is used for the second-stage nickel-cobalt synthesis. The slag phase from the second-stage synthesis is recycled for further leaching and neutralization. The liquid phase from the second-stage synthesis is discharged after wastewater treatment. The process conditions for the second-stage nickel-cobalt synthesis are: pH 10.0, reaction temperature 40℃, and reaction time 0.5h.

[0100] The obtained nickel-cobalt hydroxide product contained 38.12% nickel and 4.96% cobalt by mass.

[0101] Example 4

[0102] This invention provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for step (3), in which the mass ratio of high-pressure leaching solution containing nickel, cobalt, and manganese, laterite nickel ore slurry, and acidic solution is 1:0.7:1.5, the rest of the method is the same as in Example 1.

[0103] Example 5

[0104] This invention provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for step (3), in which the mass ratio of high-pressure leaching solution containing nickel, cobalt, and manganese, laterite nickel ore slurry, and acidic solution is 1:1.4:1.5, the rest of the method is the same as in Example 1.

[0105] Example 6

[0106] This invention provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for the high-pressure acid leaching temperature of 280°C in step (2), the method is the same as in Example 1.

[0107] Example 7

[0108] This invention provides a multi-stage combined leaching method for ultra-low grade lateritic nickel ore. Except for the mass ratio of the final stage concentrated atmospheric pressure leaching slurry to the lateritic nickel ore slurry being 1.5:1, which is relatively high, the method is the same as in Example 1.

[0109] Example 8

[0110] This invention provides a multi-stage combined leaching method for ultra-low grade lateritic nickel ore. Except for the mass ratio of the final stage concentrated atmospheric pressure leaching slurry to the lateritic nickel ore slurry, which is 0.5:1 (which is relatively low), the method is the same as in Example 1.

[0111] Example 9

[0112] This invention provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for the fact that the number of stages of multi-stage atmospheric pressure leaching is 10, the method is the same as in Example 1.

[0113] Example 10

[0114] This invention provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for the temperature of the multi-stage atmospheric pressure leaching being 90°C, the method is the same as in Example 1.

[0115] Comparative Example 1

[0116] This comparative example provides a multi-stage combined leaching method for ultra-low grade lateritic nickel ore. Except for the absence of multi-stage atmospheric pressure leaching and the use of high-pressure acid leaching for all lateritic nickel ore pulp, the multi-stage combined leaching method is the same as that in Example 1.

[0117] The specific steps include:

[0118] (1) A certain limonite-type laterite nickel ore was selected as the test object. After testing (the following are mass percentages), the content of nickel in the ore was 0.4%, cobalt 0.15%, Cr2O3 3.78%, MnO 2.13%, Al2O3 10.86%, SiO2 25.42%, Fe 30.54%, and Mg 5.23%. According to the test results, the sample is a typical limonite-type ultra-low grade laterite nickel ore. The ultra-low grade laterite nickel ore was mixed with water to prepare the laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0119] (2) Lignite powder was added to the laterite nickel ore slurry at a mass ratio of 1000:1 to lignite, and fed into a high-pressure reactor along with sodium sulfate. The leaching reaction was carried out under high-pressure leaching conditions of 255℃, 4.0MPa, pH 1.0, and acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching solution containing nickel, cobalt and manganese.

[0120] (3) The high-pressure leaching slurry is circulated and neutralized in multiple stages. Then, a multi-stage countercurrent washing process is adopted, with 6 washing stages and a ratio of washing water to slag phase of 5:1. After solid-liquid separation by thickener, an appropriate amount of lime milk neutralizing agent is added to the slag phase to make the slag phase neutral at pH 6.8. Then, metallic iron is recovered and tailings are discharged.

[0121] (4) The liquid phase obtained from multi-stage countercurrent washing is further subjected to a first-stage iron, aluminum, and chromium removal process. The process conditions for this first-stage iron, aluminum, and chromium removal are: controlled temperature of 85℃, pH of 3.0, and reaction time of 1h. The slag phase after the first-stage iron, aluminum, and chromium removal is recycled for continuous multi-stage countercurrent washing again. The liquid phase after the first-stage iron, aluminum, and chromium removal is subjected to a second-stage iron, aluminum, and chromium removal process. The process conditions for the second-stage iron, aluminum, and chromium removal are: controlled temperature of 79℃, pH of 4.8, and reaction time of 3h. The slag phase after the second-stage iron, aluminum, and chromium removal is recycled for cyclic leaching and neutralization again.

[0122] (5) A neutralizing agent is added to the liquid phase after the second-stage removal of iron, aluminum, and chromium to carry out the first-stage synthesis of nickel-cobalt. After the first-stage synthesis of nickel-cobalt, nickel-cobalt hydroxide product is obtained. The process conditions for the first-stage synthesis of nickel-cobalt are: pH value 7.0, reaction temperature 66℃, and reaction time 3h. The process conditions for the second-stage synthesis of nickel-cobalt are: pH value controlled at 8.0, reaction temperature at 50℃, and reaction time at 1.0h.

[0123] Comparative Example 2

[0124] This comparative example provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for the first stage of atmospheric pressure leaching followed by high pressure acid leaching, the multi-stage combined leaching method is the same as that in Example 1.

[0125] The specific steps include:

[0126] (1) A certain limonite-type laterite nickel ore was selected as the test object. After testing (the following are mass percentages), the content of nickel in the ore was 0.4%, cobalt 0.15%, Cr2O3 3.78%, MnO 2.13%, Al2O3 10.86%, SiO2 25.42%, Fe 30.54%, and Mg 5.23%. According to the test results, the sample is a typical limonite-type ultra-low grade laterite nickel ore. The ultra-low grade laterite nickel ore was mixed with water to prepare the laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0127] (2) The raw nickel ore slurry and sulfuric acid solution were mixed at a mass ratio of 1:1.5 to obtain a mixed solution, and the mixed solution was transferred to an atmospheric pressure reactor for atmospheric pressure leaching treatment. The process conditions for atmospheric pressure leaching treatment were: temperature 80℃, pressure 0.1MPa, pH 1.2, atmospheric pressure leaching stage number 5. After pressure filtration, atmospheric pressure leachate and leaching tailings were obtained.

[0128] (3) Add lignite powder at a mass ratio of 1000:1 between laterite nickel ore slurry and lignite, and feed it together with sodium sulfate into a high-pressure reactor at a mass ratio of 1:1 between the mixed laterite nickel ore slurry and atmospheric pressure leachate. The leaching reaction is carried out under high-pressure leaching conditions of 255℃, 4.0MPa, pH 1.0, and acid consumption of 20 tons / ton of nickel to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leachate containing nickel, cobalt and manganese.

[0129] (4) The high-pressure leaching slurry is circulated and neutralized in multiple stages. Then, a multi-stage countercurrent washing process is adopted, with 6 washing stages and a ratio of washing water to slag phase of 5:1. After solid-liquid separation by thickener, an appropriate amount of lime milk neutralizing agent is added to the slag phase to make the slag phase neutral at pH 6.8. Then, metallic iron is recovered and tailings are discharged.

[0130] (5) The liquid phase obtained from multi-stage countercurrent washing is further subjected to a first-stage iron, aluminum, and chromium removal process. The process conditions for this first-stage iron, aluminum, and chromium removal are: controlled temperature of 85℃, pH of 3.0, and reaction time of 1h. The slag phase after the first-stage iron, aluminum, and chromium removal is recycled for continuous multi-stage countercurrent washing again. The liquid phase after the first-stage iron, aluminum, and chromium removal is subjected to a second-stage iron, aluminum, and chromium removal process. The process conditions for the second-stage iron, aluminum, and chromium removal are: controlled temperature of 79℃, pH of 4.8, and reaction time of 3h. The slag phase after the second-stage iron, aluminum, and chromium removal is recycled for cyclic leaching and neutralization again.

[0131] (6) A neutralizing agent is added to the liquid phase of the tail section after the removal of iron, aluminum, and chromium in the second stage to carry out the first-stage synthesis of nickel-cobalt. After the first-stage synthesis of nickel-cobalt, nickel-cobalt hydroxide product is obtained. The process conditions for the first-stage synthesis of nickel-cobalt are: pH value 7.0, reaction temperature 66℃, and reaction time 3h. The process conditions for the second-stage synthesis of nickel-cobalt are: pH value controlled at 8.0, reaction temperature at 50℃, and reaction time at 1.0h.

[0132] Comparative Example 3

[0133] This comparative example provides a multi-stage combined leaching method for ultra-low grade laterite nickel ore. Except for recycling the final stage concentrated atmospheric pressure leaching slurry to the first stage atmospheric pressure leaching, the multi-stage combined leaching method is the same as in Example 1.

[0134] Specifically, the final stage concentrated atmospheric pressure leaching slurry of Examples 1-10 was converted to dry ore, and the mass percentages of iron, aluminum, magnesium, nickel, and cobalt in the dry ore were calculated, resulting in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] In step (2), a comparative test was conducted on the scale inhibition effect of Examples 1-10 and Comparative Examples 1-4. Examples 1-10 and Comparative Examples 1-4 were set to run for 60 days according to the process steps described above. The difference between the pressure inside the high-pressure reactor and the pressure at the inlet of the flash tank (referred to as pressure difference) was tested. The specific statistical results are shown in Table 2.

[0139] Table 2

[0140]

[0141]

[0142] The following points can be observed from Tables 1 and 2:

[0143] As can be seen from Examples 1-3 and Examples 9-10, the final stage concentrated atmospheric leaching slurry obtained by the multi-stage combined leaching method for ultra-low grade laterite nickel ore provided by the present invention has a lower iron, aluminum, and magnesium content than its corresponding laterite nickel ore slurry. That is, the multi-stage atmospheric leaching process can leach more of the above metals to remove some iron, aluminum, and magnesium. The conditions in the multi-stage atmospheric leaching process are relatively mild, which results in less scaling of iron, aluminum, and magnesium during the multi-stage atmospheric leaching process. This improves the overall maintenance cycle caused by scaling. After 60 days of operation, the pressure difference increases to within 0.2 MPa, and the overall acid consumption of the process is only 300 kg acid / ton of dry ore, which is significantly lower than that of atmospheric leaching.

[0144] Comparing Examples 1 and 4-5, it can be seen that Example 1 preferably controls the mass ratio of the high-pressure leaching solution containing nickel, cobalt, and manganese, the laterite nickel ore slurry, and the acidic solution within a reasonable range. This is more conducive to improving the removal of iron, aluminum, and magnesium during the multi-stage atmospheric pressure leaching process, thereby reducing scaling and extending the maintenance cycle. Moreover, the overall acid consumption in Example 1 is 300 kg acid / ton of dry ore, while Example 4 requires 450 kg acid / ton of dry ore, indicating a significant increase in acid consumption. This shows that the present invention preferably controls the mass ratio of the high-pressure leaching solution containing nickel, cobalt, and manganese, the laterite nickel ore slurry, and the acidic solution within a reasonable range, which can reduce scaling while reducing acid consumption.

[0145] A comparison of Examples 1 and 6 shows that when the temperature of the high-pressure acid leaching treatment is too high, scaling is more likely to occur during the high-pressure acid leaching process due to the higher temperature, resulting in a shorter maintenance cycle and a greater pressure difference after 60 days of operation.

[0146] Comparing Examples 1 and 7-8, it can be seen that in Example 7, due to the larger proportion of the returned final-stage concentrated atmospheric leaching slurry, the actual amount of laterite nickel ore slurry processed in a single process is reduced. Consequently, the overall acid consumption increases from 300 kg acid / ton of dry ore in Example 1 to 480 kg acid / ton of dry ore. This indicates that the present invention preferably controls the mass ratio of the final-stage concentrated atmospheric leaching slurry to the laterite nickel ore slurry within a reasonable range. The presence of the final-stage concentrated atmospheric leaching slurry in high-pressure acid leaching can significantly alleviate the scaling phenomenon in high-pressure acid leaching and extend the maintenance cycle.

[0147] Comparing Example 9 with Example 1, it can be seen that in the multi-stage atmospheric pressure leaching process, the higher the number of atmospheric pressure leaching stages, the better the leaching effect of iron, aluminum and magnesium metals, and the lower the content of iron, aluminum and magnesium in the final stage concentrated atmospheric pressure leaching slurry.

[0148] Comparing Example 10 with Example 1, it can be seen that in the multi-stage atmospheric pressure leaching process, the higher the atmospheric pressure leaching temperature, the better the leaching effect of iron, aluminum and magnesium metals, and the lower the content of iron, aluminum and magnesium in the final stage concentrated atmospheric pressure leaching slurry.

[0149] As can be seen from Examples 1 and Comparative Examples 1-3, the present invention employs high-pressure acid leaching followed by multi-stage atmospheric pressure leaching. The raw laterite nickel ore slurry is added to both the high-pressure acid leaching and multi-stage atmospheric pressure leaching processes, and the final stage concentrated atmospheric pressure leaching slurry is returned to the high-pressure acid leaching process. This significantly reduces the pressure difference after long-term operation, thereby reducing scaling, while also achieving efficient leaching of nickel and cobalt.

[0150] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A multi-stage combined leaching method for ultra-low grade lateritic nickel ore, characterized in that, include: S10, the laterite nickel ore slurry is subjected to high-pressure acid leaching to obtain high-pressure leaching tailings containing iron, aluminum, and magnesium, and high-pressure leaching solution containing nickel, cobalt, and manganese. The mass percentage of nickel in the laterite nickel ore slurry is less than 1.0%. S20, the high-pressure leaching solution, the laterite nickel ore slurry, and the acidic solution are mixed to obtain a mixed solution, and the mixed solution is subjected to multi-stage atmospheric pressure leaching treatment. After concentration treatment, a final stage concentrated atmospheric pressure leaching solution and a final stage concentrated atmospheric pressure leaching slurry are obtained. The slurry concentration of the final stage concentrated atmospheric pressure leaching slurry is the same as that of the laterite nickel ore slurry. S30, the final stage concentrated atmospheric pressure leachate and the high pressure leaching tailings are sequentially subjected to circulating leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment to obtain nickel-cobalt hydroxide product. After step S20 is completed, the process further includes: returning the final stage concentrated atmospheric pressure leaching slurry to step S10 for the high pressure acid leaching treatment; In step S20, the mass ratio of the high-pressure leaching solution, the laterite nickel ore slurry, and the acidic solution is 1:(0.8~1.2):(1~2); in step S20, the temperature of the multi-stage atmospheric pressure leaching treatment is 60~90℃.

2. The multi-stage combined leaching method according to claim 1, characterized in that, In step S10, the concentration of the laterite nickel ore slurry is 30-40%, and the slurry-to-product ratio is 100-200m³. 3 / ton of metallic nickel.

3. The multi-stage combined leaching method according to claim 1, characterized in that, In step S10, the process conditions for the high-pressure acid leaching treatment are: temperature 220~260℃, pressure 2.0~6.0MPa.

4. The multi-stage combined leaching method according to claim 1, characterized in that, The acid consumption for the high-pressure acid leaching treatment is 15-25 tons / ton of nickel.

5. The multi-stage combined leaching method according to claim 1, characterized in that, The pH of the high-pressure acid leaching treatment is 0.5~2.

0.

6. The multi-stage combined leaching method according to claim 1, characterized in that, The acidic solution includes sulfuric acid or hydrochloric acid.

7. The multi-stage combined leaching method according to claim 1, characterized in that, In step S10, the mass ratio of the final stage concentrated atmospheric pressure leaching slurry to the laterite nickel ore slurry is (0.8~1.2):(1~2).

8. The multi-stage combined leaching method according to claim 1, characterized in that, The pH of the multi-stage atmospheric pressure leaching treatment is 0.5~2.

0.

9. The multi-stage combined leaching method according to claim 1, characterized in that, In step S20, a thickener is used to concentrate the mixture after the multi-stage atmospheric pressure leaching treatment to obtain the final stage concentrated atmospheric pressure leaching solution and the final stage concentrated atmospheric pressure leaching slurry.

10. The multi-stage combined leaching method according to claim 1, characterized in that, In step S20, the number of atmospheric pressure leaching stages in the multi-stage atmospheric pressure leaching treatment is 2 to 10.

11. The multi-stage combined leaching method according to claim 1, characterized in that, In the S30 step, the circulating leaching and multi-stage pre-neutralization treatment is carried out at a controlled temperature of 70~90℃.

12. The multi-stage combined leaching method according to claim 10, characterized in that, The pH of the multi-stage pre-neutralization is 0.8~2.

13. The multi-stage combined leaching method according to claim 10, characterized in that, The neutralizing agent for the multi-stage pre-neutralization includes any one or a combination of at least two of lime milk, limestone, sodium hydroxide, or magnesium hydroxide.

14. The multi-stage combined leaching method according to claim 1, characterized in that, In step S30, the number of washing stages in the countercurrent washing process is 3 to 9.

15. The multi-stage combined leaching method according to claim 1, characterized in that, The process conditions for the iron, aluminum and chromium removal treatment are: 2 to 7 process stages, and / or, a controlled temperature of 55 to 90°C, and / or, a pH value of 2.5 to 5.

5.

16. The multi-stage combined leaching method according to claim 1, characterized in that, In the nickel-cobalt hydroxide product of step S30, the mass percentage of nickel is 30-40% and the mass percentage of cobalt is 3.0-6.0%.

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