MHP precipitation method based on compound alkali precipitant

Abstract

The invention relates to an MHP precipitation method based on a compound alkali precipitator, which comprises the following steps: adding a compound alkali solution into a laterite-nickel ore liquid after iron and aluminum are removed, and carrying out precipitation reaction to obtain cobalt nickel hydroxide slurry; the compound alkali in the compound alkali solution comprises a mixture of sodium carbonate and sodium hydroxide; and carrying out post-treatment separation on the cobalt nickel hydroxide slurry to obtain the MHP. According to the method, a sodium hydroxide and sodium carbonate compounded system is used as a precipitator, and the MHP is prepared under the cooperation of sodium carbonate and sodium hydroxide, so that the problem of local over-alkalinity caused by direct use of strong-alkalinity sodium hydroxide is solved, the content of manganese in the obtained MHP is reduced, the content of nickel and cobalt in the MHP is increased, and the cost of subsequent MHP refining for preparing crystals is conveniently reduced; meanwhile, the reaction rate is more controllable, and the obtained MHP is better in filterability and lower in water content.

Description

Technical Field

[0001] The invention relates to the field of hydrometallurgy, and in particular to a MHP precipitation method based on a composite alkali precipitant. Background Art

[0002] MHP, a mixed nickel-cobalt hydroxide precipitate, serves as an intermediate in the hydrometallurgical process of laterite nickel ore. Its primary metal components are Ni, Co, Mn, and Mg. The content of these metals directly determines MHP's quality, affecting both its transportation costs and the costs of subsequent extraction and refining. Sodium hydroxide and magnesium oxide are commonly used as precipitants in the hydrometallurgical process for producing MHP.

[0003] Sodium hydroxide is widely used as a precipitant in the preparation of MHP because it is widely available, reacts quickly when precipitating MHP, and does not introduce additional harmful impurities. It is currently the most commonly used precipitant in the industry. However, the use of sodium hydroxide also has some problems: (1) Overalkalinity problem: In large-scale industrial production, the strong alkalinity of sodium hydroxide can cause the reaction system to be locally overalkaline, which will increase the manganese content in MHP and correspondingly reduce the nickel and cobalt contents.

[0004] (2) Excessive precipitation rate problem: The precipitation rate of metal ions such as nickel, cobalt, and manganese is too fast, resulting in a high nucleation rate of MHP, which in turn produces MHP particles with small particle size and uneven distribution, making it difficult for MHP to be effectively settled and filtered, resulting in a high moisture content in the filter cake.

[0005] (3) Increased subsequent processing costs: Higher water content increases the transportation cost of MHP; high manganese content increases the cost of subsequent refining, especially the cost of using P204 extractant to extract impurities (calcium, copper, manganese, zinc, etc.) to separate the nickel and cobalt sections.

[0006] Magnesium oxide, with its relatively low price, has become the second most popular precipitant in the industry, replacing sodium hydroxide, for the production of MHP. However, magnesium oxide is poorly soluble in water, resulting in a high magnesium content and low nickel content in the resulting MHP. This increases the cost of transporting the MHP and the subsequent P507 extraction and magnesium removal process during refining. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above technical deficiencies and provide a MHP precipitation method based on a composite alkali precipitant to solve the technical problems of high manganese content, low nickel and cobalt content, and high water content in the preparation of MHP in the prior art.

[0008] In order to achieve the above technical objectives, the technical solution provided by the present invention is: In a first aspect, the present invention provides a method for precipitating MHP using a composite alkali precipitant, comprising the following steps: S1, adding a composite alkali solution to a laterite nickel ore solution after iron and aluminum removal to carry out a precipitation reaction to obtain a nickel-cobalt hydroxide slurry; the composite alkali in the composite alkali solution comprises a mixture of sodium carbonate and sodium hydroxide; S2, post-treating and separating the nickel-cobalt hydroxide slurry to obtain MHP.

[0009] In some embodiments, the laterite nickel ore liquor after iron and aluminum removal comprises 2-7 g / L Ni, 0.15-0.8 g / L Co, and 1-5 g / L Mn.

[0010] In some embodiments, the compounding base comprises 15-95% sodium carbonate and 5-85% sodium hydroxide, calculated by mass percentage.

[0011] In some embodiments, the mass fraction of the compound alkali in the compound alkali solution is 1-20%.

[0012] In some embodiments, the prepared alkali solution is prepared by adding the prepared alkali to water or industrial water and mixing uniformly. In some embodiments, the ratio of the total molar amount of the prepared alkali to the total molar amount of nickel and cobalt is 1.4 to 2.5. In some embodiments, the precipitation reaction conditions are: a temperature of 55 to 70°C and a reaction time of 1 to 7 hours. In some embodiments, post-treatment includes thickening and filtration.

[0013] Furthermore, part of the concentrated underflow is returned as seed crystals to be mixed with the nickel cobalt hydroxide slurry.

[0014] Furthermore, the filtration is performed by vacuum filtration or filter press filtration, and the MHP filter cake is washed with distilled water or industrial water during filtration.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a sodium hydroxide and sodium carbonate composite system as a precipitant to prepare MHP. Sodium carbonate serves as a strong electrolyte and a strong base weak acid salt. The MHP is prepared in combination with sodium carbonate and sodium hydroxide, thereby avoiding the problem of local over-alkalinity caused by directly using strongly alkaline sodium hydroxide, reducing the Mn content in the obtained MHP and increasing the nickel and cobalt contents therein, thereby facilitating reduction in the cost of subsequent MHP refining and crystal preparation. The reaction rate is controllable, the obtained MHP has better filterability, and the water content is less than 50%. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] In the prior art, when preparing MHP, the use of sodium hydroxide as a precipitant easily introduces a large amount of manganese into the MHP, thereby reducing the nickel and cobalt contents therein. To address the above drawbacks, the present invention provides an MHP precipitation method based on a composite alkaline precipitant. In this method, a composite system of sodium hydroxide and sodium carbonate is used instead of single sodium hydroxide as a precipitant to prepare MHP. This method increases the nickel and cobalt contents in the resulting MHP, reduces the contents of other components, especially manganese, and facilitates reducing the cost of preparing crystals in the subsequent MHP refining and extraction stage. Furthermore, the reaction rate is controllable, the resulting MHP has better filtration performance, and the water content in the resulting MHP is facilitated to be reduced.

[0018] In a first aspect, the present invention provides a method for precipitating MHP using a composite alkali precipitant, comprising the following steps: S1, adding a composite alkali solution to a laterite nickel ore solution after iron and aluminum removal to carry out a precipitation reaction to obtain a nickel-cobalt hydroxide slurry; the composite alkali in the composite alkali solution comprises a mixture of sodium carbonate and sodium hydroxide; S2, post-treating and separating the nickel-cobalt hydroxide slurry to obtain MHP.

[0019] In some embodiments, the laterite nickel ore liquor after iron and aluminum removal contains 2-7 g / L Ni, 0.15-0.8 g / L Co, and 1-5 g / L Mn.

[0020] In some embodiments, the composite alkali comprises, by weight, 15-95% sodium carbonate and 5-85% sodium hydroxide. A higher sodium carbonate ratio results in less localized over-alkalinity in the precipitation reaction, lower manganese content, higher nickel and cobalt content, and lower moisture content in the resulting MHP.

[0021] In some embodiments, the mass fraction of the composite alkali in the composite alkali solution is 1 to 20%. Specifically, the mass fraction of the composite alkali can be selected from 1%, 2%, 5%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, etc. If the mass fraction of the composite alkali solution is too high, localized over-alkalinity can easily occur. When the proportion of sodium carbonate in the composite alkali solution increases, the concentration of the composite alkali solution can be appropriately increased. If the mass fraction of the composite alkali solution is too low, the nickel-cobalt solution will be severely diluted, which will increase the amount of alkali used in the MHP precipitation process and increase production costs.

[0022] In some embodiments, the compounded alkali solution is prepared by adding the compounded alkali to water or industrial water and mixing them uniformly. In some embodiments, the ratio of the total molar amount of the compounded alkali to the total molar amount of nickel and cobalt is 1.4 to 2.5.

[0023] Among them, if the molar ratio is too low, although the MHP quality is high, the nickel and cobalt precipitation rate is low, resulting in a significant decrease in equipment utilization and product production efficiency. If the molar ratio is too high, the MHP quality will be reduced.

[0024] In some embodiments, the precipitation reaction conditions are: a temperature of 55-70°C and a reaction time of 1-7 hours. Specifically, the reaction temperature can be selected from 55°C, 56°C, 58°C, 60°C, 65°C, and 70°C, and the reaction time can be selected from 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, and 7 hours. When the temperature is too low, crystal growth is slow, resulting in small MHP particle size, poor filtration performance, and a high moisture content. When the reaction temperature is too high, it is necessary to increase the temperature by introducing steam, which increases costs. When the reaction time is too short, the MHP particles are small, the filtration performance is poor, and the moisture content is high. When the reaction time is too long, the manganese in the nickel-cobalt solution is oxidized, accelerating its hydrolysis and significantly increasing the manganese content in the MHP. Furthermore, the nickel-cobalt precipitation rate decreases, resulting in an increased amount of alkali. In some embodiments, post-treatment includes thickening and filtration.

[0025] Furthermore, part of the concentrated underflow is returned as a seed crystal to be mixed with the nickel cobalt hydroxide slurry; that is, part of the concentrated underflow is returned to the MHP precipitation reaction system as a seed crystal to promote the growth of MHP grains and thus improve the filtration performance of MHP.

[0026] Furthermore, the filtration is performed by vacuum filtration or filter press filtration, and the MHP filter cake is washed with distilled water or industrial water during filtration; wherein the MHP filter cake is washed with distilled water or industrial water to remove soluble impurities such as sulfate and improve the purity of MHP.

[0027] The present invention will be further described in detail below by way of specific examples. To avoid redundancy, the laterite nickel ore iron and aluminum removal liquid used in the examples and comparative examples is described below: The laterite nickel ore iron and aluminum removal liquid used in the present invention is the liquid phase obtained after the laterite nickel ore is subjected to acid leaching and two-stage iron and aluminum removal, wherein the main components are shown in Table 1 below.

[0028] Table 1 Composition of laterite nickel ore liquid after iron and aluminum removal (g / L)

[0029] Comparative Example 1 A MHP precipitation method comprises the following steps: (1) Preparation of precipitant solution: 38.37 g of sodium hydroxide as a precipitant was added to industrial water and stirred for 10 min to obtain a precipitant solution with a mass fraction of 10%; (2) Precipitation of MHP: Add the prepared precipitant solution to 10 L of laterite nickel ore after iron and aluminum removal to react, that is, according to the amount of substance, the ratio of the added amount of sodium hydroxide to the total molar amount of nickel and cobalt is 1.6:1; wherein, the reaction temperature is 60 ° C, and the reaction time is 2 h, to obtain MHP slurry; (3) Thickening: The MHP slurry is thickened to obtain the thickened supernatant and MHP underflow; (4) Filtration: Filter the MHP underflow and wash the MHP filter cake with industrial water.

[0030] Example 1 An MHP precipitation method based on a composite alkali precipitant, which differs from Comparative Example 1 in that sodium hydroxide is replaced with an equal mass of composite alkali as a precipitant, wherein the composite alkali includes 10 wt% sodium carbonate and 90 wt% sodium hydroxide; specifically comprising the following steps: (1) Preparation of a composite alkali solution: 38.37 g of composite alkali as a precipitant was added to industrial water and stirred for 10 min to obtain a composite alkali solution. The mass fraction of the composite alkali solution was 10%, and the composite alkali solution included 10 wt% sodium carbonate and 90 wt% sodium hydroxide. (2) Precipitation of MHP: Add the prepared compound alkali solution to 10 L of laterite nickel ore after iron and aluminum removal for reaction at a temperature of 60 °C for 2 h to obtain MHP slurry; (3) Thickening: The MHP slurry is thickened to obtain the thickened supernatant and MHP underflow; (4) Filtration: Filter the MHP underflow and wash the MHP filter cake with industrial water.

[0031] Example 2 The only difference from Example 1 is that the composite alkali is adjusted to 15 wt% sodium carbonate and 85 wt% sodium hydroxide; the other steps and conditions are the same as those in Example 1.

[0032] Example 3 The only difference from Example 1 is that the composite alkali is adjusted to 20 wt% sodium carbonate and 80 wt% sodium hydroxide; the other steps and conditions are the same as those in Example 1.

[0033] Example 4 The only difference from Example 1 is that the composite alkali is adjusted to 35 wt% sodium carbonate and 65 wt% sodium hydroxide; the other steps and conditions are the same as those in Example 1.

[0034] Example 5 The only difference from Example 1 is that the composite alkali is adjusted to 60 wt% sodium carbonate and 40 wt% sodium hydroxide; the other steps and conditions are the same as those in Example 1.

[0035] Example 6 The only difference from Example 1 is that the composite alkali is adjusted to 85 wt% sodium carbonate and 15 wt% sodium hydroxide; the other steps and conditions are the same as those in Example 1.

[0036] Comparative Example 2 The only difference from Comparative Example 1 is that sodium hydroxide is replaced by sodium carbonate of equal mass; other steps and conditions are the same as those in Comparative Example 1.

[0037] Comparative Example 3 The only difference from Comparative Example 1 is that sodium hydroxide is replaced with 1.5 times the mass of sodium carbonate; other steps and conditions are the same as those in Comparative Example 1.

[0038] MHP ingredient testing 1. The MHP components obtained in the above examples and comparative examples were tested, and the results are shown in Table 2 below.

[0039] Table 2 Effect of sodium carbonate mass fraction on Ni, Co manganese precipitation rate and MHP composition

[0040] As can be seen from Table 2, compared with Comparative Example 1, the addition of sodium carbonate in Examples 1-6 has a significant impact on the precipitation rates of nickel, cobalt, and manganese, as well as the composition of MHP. Within a certain range, as the mass fraction of sodium carbonate in the composite alkali increases (10%-85wt%), the nickel and cobalt contents in the prepared MHP continue to increase, the manganese content continues to decrease, and the magnesium content does not change much.

[0041] Compared to Example 6, Comparative Example 2 used only sodium carbonate. When the amount of sodium carbonate was increased to 1.5 times the amount of sodium hydroxide used to precipitate MHP, the manganese content in the MHP rapidly increased to 9.21%, while the nickel content in the precipitate decreased to 31.17%. The cobalt content also decreased. Clearly, the MHP prepared using sodium carbonate alone as the precipitant had significantly higher manganese and magnesium contents, while significantly lower nickel and cobalt contents. Therefore, the quality of MHP prepared using only sodium carbonate as the precipitant was significantly inferior to that prepared using a combination of sodium hydroxide and sodium carbonate.

[0042] The MHP filter cakes obtained in the above examples and comparative examples were dried and their moisture content was tested. The results are shown in Table 3.

[0043] Table 3 Moisture content of MHP filter cakes obtained in comparative examples and examples

[0044] As shown in Table 3, the method of the present invention uses the compound alkali as a precipitant to prepare high-quality MHP, and the moisture content of the MHP filter cake can be optimized to about 46%. This shows that the MHP particles prepared by the present invention have good filtration performance and are conducive to reducing the moisture content.

[0045] Comparative Example 4 The only difference from Example 1 is that the laterite nickel ore liquid after iron and aluminum removal is concentrated until the volume is reduced to half, and the other steps and conditions are the same as those in Example 1.

[0046] The results showed that the nickel and cobalt contents in the obtained MHP were uniformly reduced, while the manganese content was increased, which showed that the present invention is more suitable for preparing MHP using a nickel and cobalt solution with a relatively low concentration.

[0047] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A MHP precipitation method based on a composite alkali precipitant, characterized in that: The following steps are involved: S1, adding a composite alkali solution to the laterite nickel ore after iron and aluminum removal to carry out precipitation reaction to obtain a nickel cobalt hydroxide slurry; the composite alkali in the composite alkali solution comprises a mixture of sodium carbonate and sodium hydroxide; S2, the nickel cobalt hydroxide slurry is post-treated and separated to obtain MHP.

2. The MHP precipitation method based on a composite alkali precipitant according to claim 1, characterized in that The laterite nickel ore liquid after iron and aluminum removal contains 2-7 g / L Ni, 0.15-0.8 g / L Co, and 1-5 g / L Mn.

3. The MHP precipitation method based on a composite alkali precipitant according to claim 1, characterized in that: Calculated by mass percentage, the composite alkali includes 15-95% sodium carbonate and 5-85% sodium hydroxide.

4. The MHP precipitation method based on a composite alkali precipitant according to claim 1, characterized in that: The mass fraction of the composite alkali in the composite alkali solution is 1 to 20%.

5. The MHP precipitation method based on a composite alkali precipitant according to claim 1, characterized in that: The compound alkali solution is obtained by adding compound alkali into water or industrial water and mixing them evenly.

6. The MHP precipitation method based on a composite alkali precipitant according to any one of claims 1 to 5, characterized in that: The ratio of the total molar amount of the composite alkali to the total molar amount of nickel and cobalt is 1.4 to 2.

5.

7. The MHP precipitation method based on a composite alkali precipitant according to claim 1, characterized in that: The conditions of the precipitation reaction are: temperature of 55-70° C. and time of 1-7 h.

8. The MHP precipitation method based on a composite alkali precipitant according to claim 1, characterized in that: The post-processing includes thickening and filtration.

9. The MHP precipitation method based on a composite alkali precipitant according to claim 8, characterized in that: Part of the concentrated underflow is returned as seed crystals to be mixed with the nickel cobalt hydroxide slurry.

10. The MHP precipitation method based on a composite alkali precipitant according to claim 8, characterized in that: The filtration is performed by vacuum filtration or filter press filtration, and the MHP filter cake is washed with distilled water or industrial water during filtration.

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