Multi-stage combined leaching method for ultralow-grade laterite-nickel ore

Abstract

The invention provides a multistage combined leaching method for ultralow-grade laterite-nickel ore, which comprises the following steps: carrying out high-pressure acid leaching treatment on raw ore pulp of the laterite-nickel ore to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching liquid containing nickel, cobalt and manganese, and the nickel content in the raw ore pulp of the laterite-nickel ore is less than 1.0%; a mixed solution obtained after the high-pressure leaching solution, the laterite-nickel ore raw ore pulp and an acid solution are mixed is subjected to multi-stage normal-pressure leaching treatment, a final-stage concentrated normal-pressure leaching solution and final-stage concentrated normal-pressure leaching slurry are obtained after concentration treatment, and the ore pulp concentration of the final-stage concentrated normal-pressure leaching slurry is the same as that of the laterite-nickel ore raw ore pulp; the final-stage concentrated normal-pressure leaching solution and the high-pressure leaching tailings are sequentially subjected to circulating leaching, multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment, and a cobalt nickel hydroxide product is obtained; and the final-stage concentrated normal-pressure leaching slurry is returned to the high-pressure acid leaching treatment, so that the scaling rate of the conventional high-pressure acid leaching treatment can be effectively inhibited, and the production period is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a multi-stage combined leaching method for ultra-low-grade laterite nickel ore. Background Art

[0002] At present, the new energy industry has an increasing demand for Ni, Co, and Mn metals in new energy ternary materials. The development of laterite nickel ore with large reserves but ultra-low nickel grade has gradually become a hot spot in the industry. The hydrometallurgical route of sulfuric acid leaching under high temperature and high pressure conditions is currently one of the mainstream smelting processes for ultra-low-grade laterite nickel ore.

[0003] However, during the high pressure and high temperature leaching process, due to the Fe 3+ and Al 3+ The hydrolysis and precipitation of metal ions, the precipitation of low-solubility substances such as CaSO4, and the precipitation of solid impurities such as SiO2 in minerals will form scale on the walls of the autoclave, the impeller surface, the inner wall of the reactor discharge pipe, and the valve, causing a series of problems that are not conducive to production, such as blockage of the discharge pipe and valve, increased pressure drop, and reduced reactor volume. At present, the method to deal with scaling in actual production is mainly to shut down the autoclave regularly to clean the scale, but frequent startup and shutdown will reduce production efficiency and cause fluctuations in production process indicators.

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

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, aiming to solve the technical problem that the production efficiency of nickel cobalt hydroxide products is too low due to the rapid scaling rate of the high-pressure reactor during the high-pressure acid leaching process of the existing ultra-low-grade laterite nickel ore.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The invention provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, comprising: S10, performing high-pressure acid leaching treatment on the raw ore pulp of the laterite nickel ore 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 in the raw ore pulp of the laterite nickel ore is less than 1.0%; S20, mixing the high-pressure leaching solution, the raw ore pulp of the laterite nickel ore and an acidic solution to obtain a mixed solution, and performing multi-stage atmospheric pressure leaching treatment on the mixed solution, and obtaining a final concentrated atmospheric pressure leaching solution after concentration treatment. The method comprises the following steps: preparing a final concentrated atmospheric pressure leaching slurry and a final concentrated atmospheric pressure leaching slurry, wherein the slurry concentration of the final concentrated atmospheric pressure leaching slurry is the same as the slurry concentration of the laterite nickel ore original slurry; S30, subjecting the final concentrated atmospheric pressure leaching liquid and the high pressure leaching tailings to cyclic leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment in sequence to obtain a nickel cobalt hydroxide product; wherein, after the completion of the S20 step, the method further comprises: returning the final concentrated atmospheric pressure leaching slurry to the S10 step for the high pressure acid leaching treatment.

[0008] The invention mixes the high-pressure leaching solution obtained by high-pressure acid leaching treatment of laterite nickel ore pulp, the laterite nickel ore pulp and the acidic solution, and then performs multi-stage atmospheric pressure leaching treatment, which can avoid scaling of the high-pressure reactor due to excessive accumulation of the high-pressure leaching solution in the high-pressure acid leaching treatment. At the same time, since the reaction conditions of the multi-stage atmospheric pressure leaching treatment are milder than those of the high-pressure acid leaching treatment, the scaling rate of the high-pressure leaching solution can be effectively suppressed, thereby extending the treatment time of the acid leaching treatment, and finally improving the production efficiency of the nickel cobalt hydroxide product and reducing the production cost of the nickel cobalt hydroxide product.

[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 the raw ore pulp of laterite nickel ore in the present invention comprises: providing natural laterite nickel ore raw material, and obtaining ultra-low-grade laterite nickel ore through the pre-treatment steps of ore dressing and ore grinding; wherein the ore dressing step is specifically gravity separation and magnetic separation.

[0011] Generally speaking, nickel in ultra-low-grade laterite nickel ore is difficult to leach, and can be leached by pyrometallurgy, atmospheric pressure leaching, bioleaching and other methods. Since the pyrometallurgy will bring metals such as cobalt and scandium in the laterite nickel ore into the slag and cannot be recovered, atmospheric pressure leaching consumes a lot of acid, generally more than 700kg / ton of laterite nickel ore, and the content of impurities such as Fe and Al in the leachate is high, and the bioleaching time is extremely long, measured in months, so high-pressure acid leaching is used in industry. However, the reaction pressure of high-pressure acid leaching is high, which easily leads to the leaching and hydrolysis of aluminum and iron, thereby generating a large amount of scaling. Unlike general-grade laterite nickel ore, in addition to the low nickel content in ultra-low-grade laterite nickel ore, the content of aluminum and iron will also increase accordingly, which also leads to more serious scaling of ultra-low-grade laterite nickel ore.

[0012] The present invention uses a thickener to concentrate the mixed solution after multi-stage atmospheric pressure leaching treatment to obtain a final concentrated atmospheric pressure leaching solution and a final concentrated atmospheric pressure leaching slurry, and the slurry concentration of the final concentrated atmospheric pressure leaching slurry is the same as the slurry concentration of the laterite nickel ore slurry. The thickener can make the slurry concentration of the final concentrated atmospheric pressure leaching slurry the same as the slurry concentration of the laterite nickel ore slurry, so that the final concentrated atmospheric pressure leaching slurry meets the slurry conditions of high-pressure acid leaching treatment and is convenient for recycling.

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

[0014] The reasons why the combined treatment of high-pressure acid leaching and multi-stage atmospheric pressure leaching in the present invention can inhibit scaling are as follows: 1) Mild reaction conditions: The reaction conditions under atmospheric pressure are relatively mild, and there are no drastic physical and chemical changes like those under high pressure. Some reactions and precipitation processes that easily lead to scaling will be slowed down or less likely to occur. 2) Differences in ion solubility: At atmospheric pressure and relatively low temperatures, the solubility of some substances is relatively large, and it is not easy to reach saturation and precipitate to form a scale layer, while high pressure and high temperature may change the solubility and promote the formation of scaling. 3) Fluid dynamics: The flow state of the fluid under atmospheric pressure is relatively stable, unlike the complex flow changes that may occur under high pressure, which reduces the possibility of material deposition and scaling due to local flow anomalies. 4) Reaction rate: The lower reaction rate allows some potential scaling components to have more time to remain dissolved or be evenly dispersed, rather than quickly precipitating and accumulating. 5) Impurity behavior: The reaction and transformation behavior of impurities under atmospheric pressure is different from that under high pressure, and some impurity reaction pathways that may cause scaling are suppressed or changed. 6) Difficulty of process control: The atmospheric pressure process is relatively easier to control, and the parameter fluctuations are small, thereby reducing the risk of scaling caused by process instability and process parameter disturbances.

[0015] Preferably, in the step S10, the slurry 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, and other values ​​not listed in the range are also applicable. The slurry capacity ratio is 100-200m 3 / ton of nickel metal, for example, 100m 3 / ton of nickel metal, 112m 3 / ton of nickel metal, 123m 3 / ton of nickel metal, 134m 3 / ton of nickel metal, 145m 3 / ton of nickel metal, 156m 3 / ton of nickel metal, 167m 3 / ton of nickel metal, 178m 3 / ton of nickel metal, 189m 3 / ton of nickel metal or 200m 3 / ton of metallic nickel, etc., but are not limited to the listed values, and other unlisted values ​​within the range are also applicable.

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

[0017] Preferably, in the step S10, the process conditions of 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, and other values ​​not listed within the range are equally 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, and other values ​​not listed within the range are equally applicable.

[0018] Preferably, the acid consumption of 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, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0019] Preferably, the pH of the high pressure acid leaching treatment is 0.5 to 2.0, for example, it may 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 the raw slurry of laterite nickel ore specifically includes:

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

[0022] Specifically, multi-stage flash heat exchange can achieve more efficient heat transfer, quickly increase the slurry temperature, and meet subsequent process requirements. At the same time, it can fully recycle and utilize 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 liquid 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, and a combination of sodium bisulfite and ferrous sulfate.

[0026] Preferably, the leaching promoter comprises sodium sulfate and / or copper sulfate.

[0027] It is worth noting that the addition of reducing agents can, on the one hand, inhibit the transformation of divalent manganese ions to a high-valent state, which is beneficial to the subsequent extraction of manganese; on the other hand, it is beneficial to the subsequent multi-stage neutralization process, converting hexavalent chromium into trivalent chromium, which is convenient for chromium removal; the introduction of leaching promoters can promote the leaching of nickel, cobalt and manganese.

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

[0029] Among them, after high-pressure acid leaching treatment, the Ni content in the obtained high-pressure leaching tailings containing iron, aluminum and magnesium is less than 0.05%, for example, it can be 0.049%, 0.048%, 0.045%, 0.042%, 0.04%, 0.038% or 0.035%, etc.; the Co content is less than 0.005%, for example, it can be 0.004%, 0.003%, 0.002% or 0.001%, etc., and the Mn content is less than 0.05%, for example, it can be 0.049%, 0.048%, 0.047%, 0.046%, 0.044%, 0.04%, 0.038%, 0.035%, 0.03% or 0.028%, etc.

[0030] Preferably, in the 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), wherein the number of portions of the laterite 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, etc., but not limited to the listed values, and other values ​​not listed in the range are also applicable. The number of portions 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, etc., but not limited to the listed values, and other values ​​not listed in the range are also applicable. The above mass ratio ensures that the relative content of each component is within an appropriate range, which can not only ensure the full progress of the reaction, but also achieve the economic rationality of the process.

[0031] Preferably, the acidic solution includes sulfuric acid or hydrochloric acid. These two acids can effectively promote the relevant reactions. Sulfuric acid has a wide range of applications and good reaction performance, and hydrochloric acid may also have specific advantages in some cases.

[0032] Preferably, the mass ratio of the final concentrated atmospheric leaching slurry to the laterite nickel ore slurry in step S10 is (0.8-1.2):(1-2), and the number of portions of the final 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, etc. The number of portions 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, etc.

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

[0034] Preferably, the total mass content of iron, aluminum and magnesium in the final concentrated atmospheric pressure leaching slurry is 30-44wt%, for example, it can be 30wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 42wt%, 43wt% or 44wt%, 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 concentrated atmospheric pressure leaching slurry, it can be seen that at 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 the atmospheric pressure leaching process, thereby reducing the total mass content of iron, aluminum and magnesium in the final concentrated atmospheric pressure leaching slurry, and then mixing the final concentrated atmospheric pressure leaching slurry with the laterite nickel ore slurry for high-pressure acid leaching, which can significantly alleviate the phenomenon of leaching and hydrolysis of iron, aluminum and magnesium under the severe conditions of high-pressure acid leaching to produce a large amount of scaling.

[0036] Compared with leaching at normal pressure first and then at high pressure, the present invention directly performs high pressure leaching first, which can achieve efficient leaching of nickel, cobalt and manganese in the high pressure leaching step, and the overall leaching efficiency is higher, which can not only ensure the leaching efficiency, but also delay the scaling treatment cycle, thereby improving the production efficiency.

[0037] Preferably, in the 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, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable. The temperature range of the multi-stage atmospheric pressure leaching treatment is relatively mild, which helps to control the reaction rate and selectivity, and also reduces the requirements for equipment and operating costs. The pressure is close to normal pressure, which simplifies the 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 the step S20, a thickener is used to concentrate the mixed liquor after the multi-stage atmospheric pressure leaching treatment to obtain the final-stage concentrated atmospheric pressure leaching liquor and the final-stage concentrated atmospheric pressure leaching slurry.

[0040] Preferably, in the step S20, the number of normal pressure leaching stages of the multi-stage normal pressure leaching treatment is 2 to 10, for example, it can be 2, 3, 4, 5, 6, 7, 8, 9 or 10. This reflects the design idea of ​​gradually completing the leaching process through multiple stages. Multi-stage treatment can improve the effect and efficiency of leaching, make the reaction more sufficient and thorough, and also facilitate fine control and optimization of reactions 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 increased, and the residual 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 by multi-stage atmospheric pressure leaching treatment can leach a portion of iron, aluminum and magnesium. This is because part of the Fe 3+ and Al 3+ During the multi-stage atmospheric pressure leaching process, metal ions are hydrolyzed and precipitated, forming scale on the inner wall of the atmospheric pressure reactor. On the other hand, due to the fact that another part of Fe 3+ and Al 3+ The metal ions are dissolved in the final concentrated atmospheric pressure leachate.

[0042] Preferably, in the cyclic leaching and multi-stage pre-neutralization treatment of step S30: the control 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, etc., but not limited to the listed values, other values ​​not listed in the range are also applicable. The cyclic leaching of the present invention reduces the residual acid concentration from 30-50g / L to below 5g / L.

[0043] Preferably, the pH of the multi-stage pre-neutralization is 0.8-2, for example, 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, and other values ​​not listed within the range are also applicable.

[0044] Preferably, the neutralizing agent for the multi-stage pre-neutralization comprises 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 a combination of lime milk and limestone, a combination of sodium hydroxide and limestone, a combination of lime milk and sodium hydroxide, and a combination of magnesium hydroxide and limestone.

[0045] Preferably, in the step S30, the neutralized slurry obtained by the cyclic leaching and multi-stage pre-neutralization treatment is subjected to countercurrent washing treatment to obtain a final liquid phase and a slag phase. The number of washing stages of 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 to 7): 1, the Ni content of the terminal liquid phase is less than 0.1 g / L, and the nickel content of the slag phase after neutralization is less than 0.06%; during the multi-stage pre-neutralization treatment, the slag phase is in a neutral state by adding an appropriate amount of neutralizing agent, and the slag phase after neutralization is separated by solid-liquid separation in a thickener to obtain tailings, the pH of the tailings is 6 to 9, and the tailings mainly contain iron elements, and then the iron metal is recovered by reduction roasting and magnetic separation. The tailings after the recovery of iron metal meet the direct discharge standard and can be directly discharged, which meets the production expectations of green environmental protection.

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

[0047] In the present invention, the final liquid phase after multi-stage countercurrent washing is subjected to multi-stage iron removal, aluminum chromium concentration and separation under the condition of adding a neutralizer and a precipitation promoter. In this step, the multi-stage iron removal of aluminum chromium consists of a first stage of iron removal of aluminum chromium, a second stage and above of iron removal of aluminum chromium, and the liquid phase after the first stage of iron removal of aluminum chromium is subjected to the second stage of iron removal of aluminum chromium treatment, the slag phase after the first stage of iron removal of aluminum chromium is returned and subjected to multi-stage countercurrent washing again, and the slag phase after the second stage and above of iron removal of aluminum chromium is reused and subjected to cyclic leaching and multi-stage neutralization treatment again. Among them, the process conditions for multi-stage iron removal of aluminum chromium are: the number of process stages is 2 to 7 stages, the control temperature is 55 to 90°C, and the pH is 2.5 to 5.5; the neutralizer is a mixture of any one or more of lime milk, limestone, sodium hydroxide, and magnesium hydroxide: the precipitation promoter is a mixture of any one or more of organic polymers and inorganic polymers, such as polyacrylamide, polyaluminum chloride, etc., which are not limited here.

[0048] For example, the process conditions for the first-stage iron, aluminum and chromium removal are: adding a neutralizing agent, charging compressed air, controlling the pH to 2.5-4.0, the temperature to 70-90°C, and the reaction time to 1-2 hours; wherein, after the first-stage iron, aluminum and chromium removal step is completed, a considerable portion of nickel, cobalt and manganese still exists in the concentrated slurry, and the slurry after the first-stage iron, aluminum and chromium removal is returned for multi-stage countercurrent washing, which is beneficial to the full utilization of nickel, cobalt and manganese in the slurry; in the first-stage iron, aluminum and chromium removal process, the simultaneous removal of iron, aluminum and chromium metals is achieved.

[0049] For example, the process conditions for the second and above iron, aluminum and chromium removal are: controlling the pH to be 4.0-5.5, the temperature to be 55-80°C, and the reaction time to be 2-10h. In the process of the second and above iron, aluminum and chromium removal, the remaining iron, aluminum and chromium in the liquid phase can be further removed synchronously, which improves the removal efficiency of impurity metal elements to ensure that a purer nickel, cobalt and manganese product can be extracted later; and the purpose of recycling the slag phase of the second and above iron, aluminum and chromium removal and re-circulating leaching and multi-stage neutralization treatment is that a certain amount of nickel, cobalt and manganese elements will still remain in the slag phase after the second and above iron, aluminum and chromium removal, and re-recycling can extract as much nickel, cobalt and manganese as possible; at the same time, due to the large difference in pH value between the second and above iron, aluminum and chromium removal and the cyclic leaching-multi-stage pre-neutralization treatment, the recycling of the slag phase of the second and above iron, aluminum and chromium removal can reduce the use of neutralizers in the cyclic leaching-first neutralization treatment to a certain extent, thereby achieving the purpose of cost saving.

[0050] Preferably, in step S30 of the present invention, the tail liquid phase after multi-stage iron, aluminum and chromium removal is subjected to MHP precipitation treatment to obtain a nickel cobalt hydroxide product; in the nickel cobalt hydroxide product of step S30: the mass percentage of nickel 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 values ​​not listed in the range are equally applicable; the mass percentage of cobalt 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 values ​​not listed in the range are equally applicable.

[0051] Specifically, the above-mentioned MHP precipitation treatment is a multi-stage nickel-cobalt synthesis process, which consists of a first-stage nickel-cobalt synthesis, a second-stage nickel-cobalt synthesis and above, and the liquid phase after the first-stage nickel-cobalt synthesis is subjected to the second-stage nickel-cobalt synthesis. The tail liquid phase of the multi-stage iron, aluminum and chromium removal is subjected to a first-stage nickel-cobalt synthesis treatment, and a nickel-cobalt hydroxide product is obtained after the first-stage nickel-cobalt synthesis. The nickel-cobalt hydroxide product synthesized in the tail stage of the multi-stage nickel-cobalt synthesis is returned and circulated for leaching and multi-stage neutralization treatment again, so that the small amount of nickel and cobalt remaining in the slag phase after the multi-stage nickel-cobalt precipitation can be extracted again in the process flow, so that the final extraction rate of nickel and cobalt elements is improved; at the same time, the tail liquid phase of the multi-stage nickel-cobalt synthesis is discharged after wastewater treatment.

[0052] For example, the process conditions for one-stage synthesis of nickel and cobalt may be: adding a neutralizing agent, controlling the pH value to be 6.5 to 7.4, the temperature to be 50 to 70° C., and the reaction time to be 5 to 7 hours.

[0053] For example, the process conditions for synthesizing nickel and cobalt in the second stage and above may be: controlling the pH value to be 7.5 to 10.0, the temperature to be 40 to 90° C., and the reaction time to be 0.5 to 1.5 h.

[0054] The present invention has no special limitation on the solid-liquid separation in the above process. Any device and method for solid-liquid separation known to those skilled in the art can be used, and can also be adjusted according to the actual process, such as filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0055] The present invention has no special limitation on the crushing in the above process. Any device and method known to those skilled in the art can be used for crushing, and it can also be adjusted according to the actual process. For example, it can be grinding, extrusion crushing, splitting crushing or impact crushing, etc., 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 can reduce scaling during high-pressure acid leaching and extend the growth cycle by combining high-pressure acid leaching and multi-stage atmospheric pressure treatment, and returning the final concentrated atmospheric pressure leaching slurry to the high-pressure acid leaching. Specifically, it is preferably possible to extend the maintenance and descaling cycle to more than 150 days under the acid consumption condition of 300 kg acid / ton of dry ore, and the maintenance cycle is extended to more than one time, and the pressure difference increases to within 0.2 MPa after 60 days of operation;

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

[0059] Figure 1 A schematic flow chart of a 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 specific process schematic diagram of the multi-stage combined leaching method for ultra-low-grade laterite nickel ore provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0061] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0063] In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multi-level" is more than two levels, unless otherwise clearly and specifically defined.

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

[0065] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0066] It is worth mentioning that in industrial production, due to severe scaling, the process needs to be shut down for maintenance. On the one hand, for the high-pressure acid leaching process, it takes about 7 days to shut down for descaling each time, and each day consumes manpower costs and delays production operations; on the other hand, repeated shutdowns and restarts are prone to differences between process batches and affect production stability for the entire production process, so scaling needs to be reduced as much as possible.

[0067] In order to solve the technical problem that the production efficiency of nickel cobalt hydroxide products is too low due to the rapid scaling rate of the high-pressure reactor during the high-pressure acid leaching process of the existing ultra-low-grade laterite nickel ore, the present invention provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, wherein the reaction conditions of the method provided by the present invention are milder than those of conventional high-pressure acid leaching treatment, and the scaling rate of the high-pressure leachate can be effectively inhibited, thereby delaying the scaling treatment time in the high-pressure acid leaching treatment, and ultimately improving the production efficiency of the nickel cobalt hydroxide products and reducing the production cost of the nickel cobalt hydroxide products.

[0068] See also Figure 1 , Figure 1 A schematic flow chart 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 comprises the following steps:

[0069] S10, performing high-pressure acid leaching on the raw slurry of laterite nickel ore 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 raw slurry of laterite nickel ore is less than 1.0%;

[0070] S20, mixing the high-pressure leaching solution, the raw ore pulp of the laterite nickel ore and the acidic solution to obtain a mixed solution, and performing multi-stage normal pressure leaching treatment on the mixed solution, and obtaining a final concentrated normal pressure leaching solution and a final concentrated normal pressure leaching slurry after concentration treatment, wherein the pulp concentration of the final concentrated normal pressure leaching slurry is the same as the pulp concentration of the raw ore pulp of the laterite nickel ore;

[0071] S30, subjecting the final concentrated atmospheric pressure leachate and the high pressure leaching tailings to cyclic leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment in sequence to obtain a nickel cobalt hydroxide product; wherein, after the completion of the S20 step, it also includes: returning the final concentrated atmospheric pressure leaching slurry to the S10 step for the high pressure acid leaching treatment.

[0072] For the sake of comparison, the acidic solution used in the following leaching is 25wt% sulfuric acid. However, this does not mean that the present invention can only use sulfuric acid of this concentration, and other concentrations of sulfuric acid are also feasible. The acid consumption referred to in the present invention is the acid consumption calculated based on the purchased high concentration (generally 98%) sulfuric acid.

[0073] Example 1

[0074] This embodiment provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, see Figure 2 , the multi-stage combined leaching method comprises the following steps:

[0075] (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (hereinafter referred to as mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the MnO content was 2.13%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%; thus, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore; the ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0076] (2) adding lignite powder to a mass ratio of 1000:1 between the raw slurry of laterite nickel ore and lignite, and feeding the mixture into a high-pressure reactor together with sodium sulfate (leaching promoter, the addition amount is 1.5wt% of the raw slurry of laterite nickel ore), and carrying out high-pressure leaching reaction under high-pressure leaching conditions of temperature 255°C, pressure 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 liquid containing nickel, cobalt and manganese.

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

[0078] (4) using a thickener to concentrate the mixed liquor after the multi-stage atmospheric pressure leaching treatment to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry, wherein the slurry concentration of the final concentrated atmospheric pressure leaching slurry is 35%, and the final 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 leachate is mixed with the high-pressure leaching tailings and then circulated for leaching and subjected to multi-stage pre-neutralization. A multi-stage countercurrent washing process is then adopted, with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to make the slag phase in a neutral state with a pH of 6.8. The metallic iron is then recovered and the tailings are discharged.

[0080] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal (adding sodium hydroxide). The process conditions for the first stage of iron removal are: the temperature is controlled at 85°C, the pH is 3.0, and the reaction time is 1h. The slag phase after the first stage of iron removal is reused for continuous multi-stage countercurrent washing. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal (adding sodium hydroxide). The process conditions for the second stage of iron removal are: the temperature is controlled at 79°C, the pH is 4.8, and the reaction time is 3h. The slag phase after the second stage of iron removal is reused for cyclic leaching and neutralization.

[0081] (7) A neutralizing agent (sodium hydroxide) is added to the tail liquid phase after the second stage of iron, aluminum and chromium removal to perform a first stage of nickel-cobalt synthesis. After the first stage of nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The process conditions for the first stage of nickel-cobalt synthesis are: pH value is 7.0, reaction temperature is 66°C, and reaction time is 3h. The process conditions for the second stage of nickel-cobalt synthesis are: pH value is controlled to be 8.0, reaction temperature is 50°C, and reaction time is 1.0h; wherein, the nickel-cobalt hydroxide product obtained has a nickel mass percentage of 31.13% and a cobalt mass percentage of 3.51%.

[0082] Example 2

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

[0084] (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (hereinafter referred to as mass percentage), the nickel content in the ore was 0.6%, the cobalt content was 0.25%, the Cr2O3 content was 2.48%, the MnO content was 1.86%, the Al2O3 content was 9.45%, the SiO2 content was 18.67%, the Fe content was 35.14%, and the Mg content was 8.38%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 30%.

[0085] (2) adding lignite powder to a mass ratio of laterite nickel ore slurry to lignite of 900:1, and feeding the mixture into a high-pressure reactor together with sodium sulfate (leaching promoter, the addition amount is 2.5wt% of the laterite nickel ore slurry), carrying out leaching reaction under high-pressure leaching conditions of temperature 260°C, pressure 2.0MPa, pH 0.8, and acid consumption of 25 tons / ton of nickel, and obtaining high-pressure leaching slurry through multi-stage flash evaporation and heat exchange, and filtering the high-pressure leaching slurry to obtain high-pressure leaching tailings containing iron, aluminum and magnesium and high-pressure leaching liquid containing nickel, cobalt and manganese.

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

[0087] (4) using a thickener to concentrate the mixed liquor after the multi-stage atmospheric pressure leaching treatment to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry, wherein the slurry concentration of the final concentrated atmospheric pressure leaching slurry is 30%, and the final 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 treatment.

[0088] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leaching tailings and then circulated for leaching and multi-stage neutralization, followed by a multi-stage countercurrent washing process with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to make the slag phase in a neutral state of pH = 7.0, and then the metallic iron is recovered and the tailings are discharged.

[0089] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal (adding sodium hydroxide). The process conditions for the first stage of iron removal are: the temperature is controlled at 60°C, the pH is 2.5, and the reaction time is 1.5h. The slag phase after the first stage of iron removal is reused for continuous multi-stage countercurrent washing. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal (adding sodium hydroxide). The process conditions for the second stage of iron removal are: the temperature is controlled at 80°C, the pH is 4.0, and the reaction time is 3h. The slag phase after the second stage of iron removal is reused for cyclic leaching and neutralization.

[0090] (7) A neutralizing agent (sodium hydroxide) is added to the tail liquid phase after the second stage of iron, aluminum and chromium removal, and a first stage of nickel-cobalt synthesis and a first stage of nickel-cobalt-manganese synthesis are performed to obtain a nickel-cobalt hydroxide product. The process conditions for the first stage of nickel-cobalt synthesis are as follows: pH value is 6.5, reaction temperature is 70°C, and reaction time is 5h. The liquid phase of the first stage of nickel-cobalt synthesis is subjected to a second stage of nickel-cobalt synthesis, and the slag phase of the second stage of nickel-cobalt synthesis is recycled for cyclic leaching and neutralization treatment again, and the liquid phase of the second stage of nickel-cobalt synthesis is discharged after wastewater treatment. The process conditions for the second stage of nickel-cobalt synthesis are as follows: pH value is controlled to be 10.0, reaction temperature is 40°C, and reaction time is 1.5h; wherein, the nickel-cobalt hydroxide product obtained has a nickel mass percentage of 36.52% and a cobalt mass percentage of 5.32%.

[0091] Example 3

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

[0093] (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (hereinafter referred to as mass percentage), the nickel content in the ore was 0.8%, the cobalt content was 0.45%, the Cr2O3 content was 4.12%, the MnO content was 1.58%, the Al2O3 content was 9.81%, the SiO2 content was 12.18%, the Fe content was 33.27%, and the Mg content was 6.25%. Therefore, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore. The ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 40%.

[0094] (2) adding lignite powder to a mass ratio of laterite nickel ore slurry to lignite of 1100:1, and feeding the mixture into a high-pressure reactor together with sodium sulfate (leaching promoter, the addition amount is 1.0wt% of the laterite nickel ore slurry), and carrying out leaching reaction under high-pressure leaching conditions of temperature 220°C, pressure 6.0MPa, 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 liquid 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 in a mass ratio of 1:0.9:1 to obtain a mixed solution, and the mixed solution is transferred to a normal pressure reactor for multi-stage normal pressure leaching treatment; the process conditions of each stage of the multi-stage normal pressure leaching treatment are: temperature 90°C, pressure 0.1MPa, pH 0.5, and normal pressure leaching stage number 10.

[0096] (4) using a thickener to concentrate the mixed liquor after the multi-stage atmospheric pressure leaching treatment to obtain a final concentrated atmospheric pressure leaching liquor and a final concentrated atmospheric pressure leaching slurry, wherein the ore pulp concentration of the final concentrated atmospheric pressure leaching slurry is 40%, and the final 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 treatment.

[0097] (5) The final concentrated atmospheric leachate is mixed with the high-pressure leaching tailings and then circulated for leaching and multi-stage neutralization, followed by a multi-stage countercurrent washing process with 6 washing stages and a ratio of wash water to slag phase of 5:1. After solid-liquid separation in a thickener, an appropriate amount of lime milk neutralizer is added to the slag phase to make the slag phase in a neutral state of pH = 6.8, and then the metallic iron is recovered and the tailings are discharged.

[0098] (6) The liquid phase obtained by multi-stage countercurrent washing is further subjected to the first stage of iron removal (adding sodium hydroxide). The process conditions for the first stage of iron removal are: the temperature is controlled at 60°C, the pH is 4.0, and the reaction time is 2.0h. The slag phase after the first stage of iron removal is reused for continuous multi-stage countercurrent washing. The liquid phase after the first stage of iron removal is subjected to the second stage of iron removal (adding sodium hydroxide). The process conditions for the second stage of iron removal are: the temperature is controlled at 55°C, the pH is 2.5, and the reaction time is 4h. The slag phase after the second stage of iron removal is reused for cyclic leaching and neutralization.

[0099] (7) A neutralizing agent (sodium hydroxide) is added to the tail liquid phase after the second stage of iron, aluminum and chromium removal to carry out a first stage of nickel-cobalt synthesis. After the first stage of nickel-cobalt synthesis, a nickel-cobalt hydroxide product is obtained. The process conditions for the first stage of nickel-cobalt synthesis are as follows: pH value is 7.4, reaction temperature is 50°C, and reaction time is 7h. The liquid phase of the first stage of nickel-cobalt synthesis is subjected to a second stage of nickel-cobalt synthesis. The slag phase of the second stage of nickel-cobalt synthesis is recycled for cyclic leaching and neutralization treatment again. The liquid phase of the second stage of nickel-cobalt synthesis is discharged after wastewater treatment. The process conditions for the second stage of nickel-cobalt synthesis are as follows: pH value is controlled at 10.0, reaction temperature is 40°C, and reaction time is 0.5h.

[0100] Among them, the obtained nickel cobalt hydroxide product has a nickel mass percentage of 38.12% and a cobalt mass percentage of 4.96%.

[0101] Example 4

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

[0103] Example 5

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

[0105] Example 6

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

[0107] Example 7

[0108] The present invention provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore. The method is the same as Example 1 except that the mass ratio of the final-stage concentrated atmospheric pressure leaching slurry to the laterite nickel ore original slurry is 1.5:1, which is higher.

[0109] Example 8

[0110] The present invention provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore. The method is the same as Example 1 except that the mass ratio of the final-stage concentrated atmospheric pressure leaching slurry to the laterite nickel ore original slurry is 0.5:1, which is relatively low.

[0111] Example 9

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

[0113] Example 10

[0114] The present invention provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore. The method is the same as Example 1 except that the temperature of the multi-stage normal pressure leaching is 90° C.

[0115] Comparative Example 1

[0116] This comparative example provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore, which is the same as Example 1 except that multi-stage normal pressure leaching is not performed and all the laterite nickel ore slurry is subjected to high-pressure acid leaching.

[0117] The specific steps include:

[0118] (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (hereinafter referred to as mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the MnO content was 2.13%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%; thus, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore; the ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0119] (2) adding lignite powder to a laterite nickel ore slurry with a mass ratio of 1000:1, and feeding the slurry and sodium sulfate into a high-pressure reactor, and carrying out a leaching reaction under high-pressure leaching conditions of a temperature of 255° C., a pressure of 4.0 MPa, a pH of 1.0, and an acid consumption of 20 tons / ton of nickel, to obtain a high-pressure leaching tailing containing iron, aluminum, and magnesium and a high-pressure leaching solution containing nickel, cobalt, and manganese.

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

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

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

[0123] Comparative Example 2

[0124] This comparative example provides a multi-stage combined leaching method for ultra-low-grade laterite nickel ore. The multi-stage combined leaching method is the same as Example 1 except that atmospheric pressure leaching is first performed and then high-pressure acid leaching is performed.

[0125] The specific steps include:

[0126] (1) A limonitic laterite nickel ore was selected as the implementation object. After measurement (hereinafter referred to as mass percentage), the nickel content in the ore was 0.4%, the cobalt content was 0.15%, the Cr2O3 content was 3.78%, the MnO content was 2.13%, the Al2O3 content was 10.86%, the SiO2 content was 25.42%, the Fe content was 30.54%, and the Mg content was 5.23%; thus, according to the measurement results, the sample was a typical limonitic ultra-low-grade laterite nickel ore; the ultra-low-grade laterite nickel ore was mixed with water to prepare a laterite nickel ore slurry, and the laterite nickel ore slurry was concentrated to a concentration of 35%.

[0127] (2) mixing the laterite nickel ore slurry and the sulfuric acid acid solution at a mass ratio of 1:1.5 to obtain a mixed solution, and transferring the mixed solution to a normal pressure reactor for normal pressure leaching treatment; the process conditions of the normal pressure leaching treatment are: temperature 80° C., pressure 0.1 MPa, pH 1.2, normal pressure leaching level 5, and filtering to obtain a normal pressure leaching solution and leaching tailings;

[0128] (3) adding lignite powder to the laterite nickel ore slurry at a mass ratio of 1000:1, and feeding the mixed laterite nickel ore slurry to the atmospheric pressure leaching solution at a mass ratio of 1:1, and feeding the mixture into a high-pressure reactor together with sodium sulfate, and carrying out leaching reaction under high-pressure leaching conditions of temperature 255° C., pressure 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.

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

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

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

[0132] Comparative Example 3

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

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

[0135] Table 1

[0136]

[0137]

[0138] In step (2), a comparative test was conducted on the scale inhibition effects of Examples 1 to 10 and Comparative Examples 1 to 4. According to the process steps described above, Examples 1 to 10 and Comparative Examples 1 to 4 were all run for 60 days, and the difference between the inner cavity pressure of the high-pressure reactor and the inlet pressure 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] From Tables 1 and 2, we can see the following points:

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

[0144] By comparing Example 1 with Examples 4 to 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, which can be more conducive to improving the removal of iron, aluminum and magnesium in the multi-stage atmospheric pressure leaching process, thereby reducing scaling and extending the maintenance cycle; and the overall acid consumption in Example 1 is 300 kg acid / ton of dry ore, while the acid consumption of 450 kg acid / ton of dry ore is required in Example 4, and the acid consumption increases seriously, indicating 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 on the basis of reducing acid consumption.

[0145] By comparing Example 1 with Example 6, it can be seen that when the temperature of the high-pressure acid leaching treatment is high, scaling is more likely to occur during the high-pressure acid leaching process due to the high temperature, the final maintenance cycle is shorter, and the pressure difference is larger after 60 days of operation.

[0146] By comparing Example 1 with Examples 7 to 8, it can be seen that in Example 7, due to the large proportion of the returned final concentrated atmospheric pressure leaching slurry, the laterite nickel ore slurry actually processed in the single process is reduced, which also causes the overall acid consumption to increase to 480 kg acid / ton of dry ore compared to 300 kg acid / ton of dry ore in Example 1. This shows that the present invention preferably controls the mass ratio of the final concentrated atmospheric pressure leaching slurry to the laterite nickel ore slurry within a reasonable range, and the presence of the final concentrated atmospheric pressure leaching slurry in high-pressure acid leaching can significantly alleviate the scaling phenomenon of high-pressure acid leaching and extend the maintenance cycle.

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

[0148] By 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 leaching iron, aluminum and magnesium metals, and the lower the iron, aluminum and magnesium contents in the final concentrated atmospheric pressure leaching slurry.

[0149] It can be seen from Example 1 and Comparative Examples 1 to 3 that the present invention adopts high-pressure acid leaching first and then multi-stage atmospheric pressure leaching, and the laterite nickel ore slurry is added to the high-pressure acid leaching and multi-stage atmospheric pressure leaching respectively, and the final concentrated atmospheric pressure leaching slurry is returned to the high-pressure acid leaching treatment, which can significantly reduce the pressure difference after long-term operation, that is, reduce scaling, and at the same time achieve efficient leaching of nickel and cobalt.

[0150] The present invention illustrates the detailed features of the present invention through the above embodiments, 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 improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, 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 laterite nickel ore, characterized in that: include: S10, performing high-pressure acid leaching on the raw slurry of laterite nickel ore 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 raw slurry of laterite nickel ore is less than 1.0%; S20, mixing the high-pressure leaching solution, the raw ore pulp of the laterite nickel ore and the acidic solution to obtain a mixed solution, and performing multi-stage normal pressure leaching treatment on the mixed solution, and obtaining a final concentrated normal pressure leaching solution and a final concentrated normal pressure leaching slurry after concentration treatment, wherein the pulp concentration of the final concentrated normal pressure leaching slurry is the same as the pulp concentration of the raw ore pulp of the laterite nickel ore; S30, subjecting the final concentrated atmospheric pressure leachate and the high pressure leaching tailings to cyclic leaching and multi-stage pre-neutralization treatment, countercurrent washing treatment, iron, aluminum and chromium removal treatment and MHP precipitation treatment in sequence to obtain a nickel-cobalt hydroxide product; Wherein, after the completion of step S20, the method further includes: returning the final concentrated atmospheric pressure leaching slurry to step S10 for the high pressure acid leaching treatment.

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

3. The multi-stage combined leaching method according to claim 1, characterized in that: In the step S10, the process conditions of the high pressure acid leaching treatment are: temperature 220-260° C., pressure 2.0-6.0 MPa; Preferably, the acid consumption of the high pressure acid leaching treatment is 15 to 25 tons / ton of nickel; Preferably, the pH of the high-pressure acid leaching treatment is 0.5 to 2.

0.

4. The multi-stage combined leaching method according to claim 1, characterized in that: In the 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); Preferably, the acidic solution comprises sulfuric acid or hydrochloric acid; Preferably, the mass ratio of the final concentrated atmospheric pressure leaching slurry to the laterite nickel ore slurry in step S10 is (0.8-1.2):(1-2).

5. The multi-stage combined leaching method according to claim 1, characterized in that: In the step S20, the temperature of the multi-stage atmospheric pressure leaching treatment is 60-90°C; Preferably, the pH of the multi-stage atmospheric pressure leaching treatment is 0.5 to 2.

0.

6. The multi-stage combined leaching method according to claim 1, characterized in that: In the step S20, a thickener is used to concentrate the mixed solution 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.

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

8. The multi-stage combined leaching method according to claim 1, characterized in that: In the cyclic leaching and multi-stage pre-neutralization treatment of step S30: the control temperature of the cyclic leaching is 70-90°C; Preferably, the pH of the multi-stage pre-neutralization is 0.8 to 2; Preferably, the neutralizing agent for the multi-stage pre-neutralization includes any one of lime milk, limestone, sodium hydroxide or magnesium hydroxide, or a combination of at least two thereof.

9. The multi-stage combined leaching method according to claim 1, characterized in that: In the step S30, the number of washing stages of the countercurrent washing process is 3 to 9; Preferably, the process conditions for the iron, aluminum and chromium removal treatment are: the number of process stages is 2 to 7, and / or the temperature is controlled at 55 to 90° C., and / or the pH value is 2.5 to 5.

5.

10. 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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