A precipitation method for MHP based on a composite alkali precipitant

Abstract

The present invention discloses a precipitation method for MHP based on a composite alkali precipitant, which includes the following steps: A composite alkali solution is added to the liquid from laterite nickel ore after iron and aluminum removal to initiate a precipitation reaction, resulting in a nickel-cobalt hydroxide slurry; the composite alkali in the solution is a mixture of sodium carbonate and sodium hydroxide. The nickel-cobalt hydroxide slurry is subsequently processed and separated to obtain MHP. The invention employs a composite system of sodium hydroxide and sodium carbonate as the precipitant to prepare MHP, addressing the issues associated with the direct use of the strongly alkaline sodium hydroxide, which can lead to local over-alkalinity. This method reduces the manganese content in the resulting MHP, increases the nickel and cobalt content, facilitates the reduction of subsequent costs for refining MHP into crystals, and makes the reaction rate more controllable, resulting in better filter property and lower water content of the MHP.

Description

[0001] Description

[0002] A PRECIPITATION METHOD FOR MHP BASED ON A COMPOSITE ALKALI PRECIPITANT

[0003] Field Of The Disclosure

[0004] The present invention relates to the field of hydrometallurgy, speci fically to a precipitation method for MHP based on a composite alkali precipitant .

[0005] Background

[0006] MHP, a mixed nickel-cobalt hydroxide precipitate , serves as an intermediate in the hydrometallurgical process of laterite nickel ore . Its main metallic components , Ni , Co , Mn, and Mg, directly determine the quality of MHP, af fecting its transportation costs and the costs of subsequent extraction and refining processes . In the preparation of MHP intermediates from laterite nickel ore by hydrometallurgy technology, sodium hydroxide and magnesium oxide are used as the commonly precipitants .

[0007] Sodium hydroxide is widely used as a precipitant in the preparation process of MHP because of its broad availability, fast reaction rate in precipitating MHP, and the absence of introducing additional harmful impurities . However, there are several issues associated with the use of sodium hydroxide :

[0008] ( 1 ) Over-alkalinity problem : The strong alkalinity of sodium hydroxide in large-scale industrial production can lead to local over-alkalinity in the reaction system, which increases the manganese content in MHP and correspondingly reduces the content of nickel and cobalt .

[0009] ( 2 ) Excessive precipitation rate problem : The precipitation rate of metal ions such as nickel , cobalt , and manganese is too fast , leading to a high nucleation rate of MHP, resulting in small and unevenly distributed MHP particles , making it di f ficult to ef fectively settle and filter, thus leading to a higher moisture content in the filter cake . ( 3 ) Increased subsequent treatment costs : The higher moisture content increases the transportation cost of MHP ; the high manganese content increases the cost in the subsequent refining process , especially when using P204 extractant for the extraction and separation of nickel and cobalt .

[0010] Magnesium oxide , relatively low in price , has become the second most used precipitant in the industry for the preparation of MHP . However, magnesium oxide is poorly soluble in water , resulting in a higher magnesium content and lower nickel content in the prepared MHP, increasing the transportation cost of MHP and the cost of subsequent refining when using P507 for magnesium extraction .

[0011] SUMMARY

[0012] The purpose of the present invention is to overcome the above technical deficiencies and provide a precipitation method for MHP based on a composite alkali precipitant , solving the technical problems of high manganese content and low nickel and cobalt content , and high moisture content in the preparation of MHP .

[0013] To achieve the above technical obj ectives , the present invention provides the following technical solution

[0014] The present invention provides a precipitation method for MHP based on a composite alkali precipitant , including the following steps : S I , a composite alkali solution is added to the liquid from laterite nickel ore after iron and aluminum removal for a precipitation reaction, resulting in a nickel-cobalt hydroxide slurry; the composite alkali in the solution includes a mixture of sodium carbonate and sodium hydroxide ; S2 , the nickel-cobalt hydroxide slurry is processed and separated to obtain MHP .

[0015] In some embodiments , the liquid from laterite nickel ore after iron and aluminum removal includes 2-7 g / L Ni , 0 . 15-0 . 8 g / L Co , and 1-5 g / L Mn .

[0016] In some embodiments , by mass percentage , the composite alkali includes 15-95% sodium carbonate and 5-85% sodium hydroxide .

[0017] In some embodiments , the mass fraction of the composite alkali in the solution is 1-20% . In some embodiments , the composite alkali solution is obtained by uni formly mixing the composite alkali with water or industrial water .

[0018] In some embodiments , the molar ratio of the total amount of composite alkali to the total amount of nickel and cobalt is 1 . 4-2 . 5 .

[0019] In some embodiments , the conditions for the precipitation reaction are : a temperature of 55-70 ° C and a time of 1-7 hours .

[0020] In some embodiments , the subsequent treatment includes thickening and filtration .

[0021] Furthermore , a portion of the underflow after thickening is returned as seed crystals and mixed with the nickel-cobalt hydroxide slurry .

[0022] Furthermore , the filtration uses vacuum filtration or pressure filtration, and the MHP filter cake is washed with distilled water or industrial water during filtration .

[0023] Compared with the existing technology, the beneficial ef fects of the present invention include :

[0024] The invention uses a composite system of sodium hydroxide and sodium carbonate as the precipitant to prepare MHP . Sodium carbonate , as a strong electrolyte and a salt of a weak acid and a strong base , avoids the local over-alkalinity problem caused by the direct use of the strongly alkaline sodium hydroxide , reduces the manganese content in the resulting MHP, increases the nickel and cobalt content , facilitates the reduction of subsequent costs for refining MHP into crystals ; and makes the reaction rate controllable , resulting in better filterability of the obtained MHP, with a moisture content lower than 50% .

[0025] Detailed Description Of Preferred Embodiments

[0026] To make the purpose , technical solution, and advantages of the present invention clearer, the following provides further detailed description of the invention in conj unction with embodiments . It should be understood that the speci fic embodiments described here are only for the purpose of explaining the invention and do not limit the invention . In the existing technology for preparing MHP, using sodium hydroxide as a precipitant tends to introduce more manganese into MHP, reducing the content of nickel and cobalt. To address the above shortcomings, the present invention provides a precipitation method for MHP based on a composite alkali precipitant, replacing the single sodium hydroxide with a composite alkali system to prepare MHP, increasing the nickel and cobalt content in the obtained MHP, reducing other components, especially the manganese content, facilitating the reduction of subsequent costs for refining MHP extraction section to prepare crystals; and making the reaction rate controllable, resulting in better filterability of the obtained MHP, and facilitating the reduction of the moisture content in the obtained MHP.

[0027] The first aspect, the present invention provides a precipitation method for MHP based on a composite alkali precipitant, including the following steps: SI, a composite alkali solution is added to the liquid from laterite nickel ore after iron and aluminum removal for a precipitation reaction, resulting in a nickel-cobalt hydroxide slurry; the composite alkali in the solution includes a mixture of sodium carbonate and sodium hydroxide; S2, the nickel-cobalt hydroxide slurry is processed and separated to obtain MHP.

[0028] In some embodiments, the liquid from laterite nickel ore after iron and aluminum removal contains 2-7 g / L Ni, 0.15-0.8 g / L of Co, and 1-5 g / L Mn.

[0029] In some embodiments, by mass percentage, the composite alkali includes 15-95% sodium carbonate and 5-85% sodium hydroxide. The higher the ratio of sodium carbonate, the less the degree of local over-alkalinity in the precipitation reaction, the lower the manganese content in the obtained MHP, the higher the nickel and cobalt content, and the lower the moisture content of MHP.

[0030] In some embodiments, the mass fraction of the composite alkali in the solution is 1-20%. 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, it is easy to form local over-alkalinity. When the proportion of sodium carbonate in the composite alkali solution increases, the concentration of the composite alkali solution can be moderately 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 the production cost.

[0031] In some embodiments, the composite alkali solution is obtained by uniformly mixing the composite alkali with water or industrial water .

[0032] In some embodiments, the molar ratio of the total amount of composite alkali to the total amount of nickel and cobalt is 1.4-2.5. If the molar ratio is too low, although the quality of MHP is high, the precipitation rate of nickel and cobalt is low, resulting in a significant decrease in equipment utilization and product production efficiency. If the molar ratio is too high, it will reduce the quality of MHP.

[0033] In some embodiments, the conditions for the precipitation reaction are: a temperature of 55-70°C and a time of 1-7 hours. Specifically, the reaction temperature can be selected from 55°C, 56°C, 58°C, 60°C, 65°C, and70°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 . If the temperature is too low, the crystal growth is slow, resulting in small MHP particles with poor filtration performance and higher moisture content. If the reaction temperature is too high, it will require additional measures such as steam injection to increase the temperature, which will increase costs. If the reaction time is too short, the MHP particles are small, with poor filtration performance and higher moisture content. If the reaction time is too long, manganese in the nickel-cobalt solution will be oxidized, accelerating the hydrolysis of manganese, leading to a significant increase in manganese content in MHP, and also reducing the precipitation rate of nickel and cobalt, resulting in increased alkali consumption.

[0034] In some embodiments, subsequent treatment includes thickening and filtration. Furthermore, a portion of the underflow after thickening is returned as seed crystals to mix with the nickel-cobalt hydroxide slurry; that is, a portion of the underflow after thickening is returned to the MHP precipitation reaction system as seed crystals to promote the growth of MHP crystals, thereby improving the filtration performance of MHP.

[0035] Furthermore, filtration is carried out using vacuum filtration or pressure filtration, and the MHP filter cake is washed with distilled water or industrial water during filtration; this washing with distilled water or industrial water removes soluble impurities such as sulfates, thereby improving the purity of MHP.

[0036] Below is a detailed description of the invention through specific examples to further illustrate the invention. To avoid redundancy, the following description of the liquid from laterite nickel ore after iron and aluminum removal used in the examples and comparatives is as follows:

[0037] The liquid from laterite nickel ore after iron and aluminum removal used in this invention is the liquid phase obtained after acid leaching and two-stage iron and aluminum removal of laterite nickel ore, with the main components shown in Table 1 below. Table 1 Composition of the liquid from laterite nickel ore after iron and aluminum removal (g / L)

[0038] Ni Co Mn Fe Al Zn Cu Ca Mg

[0039] 3.21 0.31 2.02 0.0007 0.004 0.0028 0.007 0.57 8.98

[0040] Comparative Example 1

[0041] A method for precipitating MHP, including the following steps:

[0042] (1) Preparation of the precipitant solution: 38.37 g of sodium hydroxide as the precipitant is added to industrial water and stirred for 10 minutes to obtain the precipitant solution, with a mass fraction of 10%;

[0043] (2) MHP precipitation : The prepared precipitant solution is added to 10 L of the liquid from laterite nickel ore after iron and aluminum removal for reaction. According to the molar quantity calculation, the amount of sodium hydroxide added is in a ratio of 1.6:1 to the total molar amount of nickel and cobalt; the reaction temperature is 60°C, and the reaction time is 2 hours to obtain the MHP slurry;

[0044] (3) Thickening: The MHP slurry is subjected to thickening treatment to obtain the supernatant and MHP underflow after thickening; (4) Filtration: The MHP underflow is filtered, and the MHP filter cake is washed with industrial water.

[0045] Example 1

[0046] A precipitation method for MHP based on a composite alkali precipitant, different from Comparative Example 1 in that: sodium hydroxide is replaced with an equal mass of composite alkali as the precipitant, with the composite alkali containing 10 wt% sodium carbonate and 90 wt% sodium hydroxide; the specific steps include:

[0047] (1) Preparation of the composite alkali solution: 38.37 g of composite alkali as the precipitant is added to industrial water and stirred for 10 minutes to obtain the composite alkali solution, with a mass fraction of 10%, containing 10 wt% sodium carbonate and 90 wt% sodium hydroxide;

[0048] (2) MHP precipitation: The prepared composite alkali solution is added to 10 L of the liquid from laterite nickel ore after iron and aluminum removal for reaction. The reaction temperature is 60°C, and the reaction time is 2 hours to obtain the MHP slurry;

[0049] (3) Thickening: The MHP slurry is subjected to thickening treatment to obtain the supernatant and MHP underflow after thickening;

[0050] (4) Filtration: The MHP underflow is filtered, and the MHP filter cake is washed with industrial water.

[0051] Example 2

[0052] The difference from Example 1 is only: the composite alkali is adjusted to 15 wt% sodium carbonate and 85 wt% sodium hydroxide; other steps and conditions are the same as in Example 1.

[0053] Example 3

[0054] The difference from Example 1 is only: the composite alkali is adjusted to 20 wt% sodium carbonate and 80 wt% sodium hydroxide; other steps and conditions are the same as in Example 1.

[0055] Example 4

[0056] The difference from Example 1 is only: the composite alkali is adjusted to 35 wt% sodium carbonate and 65 wt% sodium hydroxide; other steps and conditions are the same as in Example 1.

[0057] Example 5 The difference from Example 1 is only: the composite alkali is adjusted to 60 wt% sodium carbonate and 40 wt% sodium hydroxide; other steps and conditions are the same as in Example 1.

[0058] Example 6

[0059] The difference from Example 1 is only: the composite alkali is adjusted to 85 wt% sodium carbonate and 15 wt% sodium hydroxide; other steps and conditions are the same as in Example 1.

[0060] Comparative Example 2

[0061] The difference from Comparative Example 1 is only: sodium hydroxide is replaced with an equal mass of sodium carbonate; other steps and conditions are the same as in Comparative Example 1.

[0062] Comparative Example 3

[0063] The difference from Comparative Example 1 is only: sodium hydroxide is replaced with 1.5 times the mass of sodium carbonate; other steps and conditions are the same as in Comparative Example 1.

[0064] MHP Composition Testing

[0065] 1. The composition of MHP obtained from the above examples and comparatives was tested, and the results are shown in Table 2 below.

[0066] Table 2 The effect of sodium carbonate mass fraction on the precipitation rate of Ni, Co, and Mn, and the composition of MHP

[0067]

[0068] From Table 2 , it can be seen that compared with Comparative Example 1, the addition of sodium carbonate in Examples 1-6 has a significant impact on the precipitation rate of nickel, cobalt, and manganese, and the composition of MHP . Within a certain range, as the mass fraction of sodium carbonate in the composite alkali (10%-85wt%) increases, the nickel and cobalt content in the prepared MHP continuously increases, and the manganese content continuously decreases, with little change in magnesium content.

[0069] Compared to Example 6, in Comparative Example 2, where all sodium carbonate is used, and when the amount of sodium carbonate is increased to 1.5 times the amount of sodium hydroxide used for precipitating MHP, the manganese content in MHP rapidly increases to 9.21%, causing the nickel content in the precipitate to decrease to 31.17%, and the cobalt content also decreases. Obviously, using sodium carbonate alone as a precipitant results in MHP with significantly increased manganese and magnesium content, and clearly lower nickel and cobalt content. Therefore, the quality of MHP prepared using only sodium carbonate as a precipitant is significantly inferior compared to that prepared using a composite system of sodium hydroxide and sodium carbonate. The moisture content of the MHP filter cakes obtained from the above examples and comparatives was tested after drying, and the results are shown in Table 3 .

[0070] Table 3 Moisture Content of MHP Filter Cakes from Comparatives and Examples

[0071] From Table 3 , it is evident that the method of the present invention, using a composite alkal i as a precipitant , can prepare high-quality MHP, with the moisture content of the MHP filter cake optimi zed to approximately 46% . This indicates that the MHP produced by the method of the present invention has good filtration performance , which is beneficial for reducing the moisture content .

[0072] Comparative Example 4

[0073] The di f ference from Example 1 is only that the liquid from laterite nickel ore after iron and aluminum removal is concentrated to hal f the volume , with other steps and conditions being the same as in Example 1 .

[0074] It was found that the resulting MHP had a decrease in nickel and cobalt content and an increase in manganese content . This indicates that the method of the present invention is more suitable for preparing MHP using nickel and cobalt solutions with relatively low concentrations .

[0075] The speci fic embodiments described above do not constitute a limitation on the scope of protection of the present invention . Any other corresponding changes and modi fications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention .

Claims

What Is Claimed Is1. A precipitation method for Mixed Hydroxide Precipitate (MHP) based on a composite alkali precipitant, characterized by the following steps :SI: A composite alkali solution is added to the liquid from laterite nickel ore after iron and aluminum removal to carry out a precipitation reaction, resulting in a nickel-cobalt hydroxide slurry; the composite alkali in the solution comprises a mixture of sodium carbonate and sodium hydroxide.S2 : The nickel-cobalt hydroxide slurry is processed and separated to obtain MHP.

2. The precipitation method for MHP based on a composite alkali precipitant according to claim 1, characterized in that the liquid from laterite nickel ore 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 precipitation method for MHP based on a composite alkali precipitant according to claim 1, characterized in that, by mass percentage, the composite alkali comprises 15-95% sodium carbonate and 5-85% sodium hydroxide.

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

5. The precipitation method for MHP based on a composite alkali precipitant according to claim 1, characterized in that the composite alkali solution is obtained by uniformly mixing the composite alkali with water or industrial water.

6. The precipitation method for MHP based on a composite alkali precipitant according to any one of claims 1 to 5, characterized in that the molar ratio of the total amount of composite alkali to the total amount of nickel and cobalt is 1.4-2.5.7 . The precipitation method for MHP based on a composite alkali precipitant according to claim 1 , characteri zed in that the conditions for the precipitation reaction are : a temperature of 55-70 ° C and a time of 1-7 hours .8 . The precipitation method for MHP based on a composite alkali precipitant according to claim 1 , characteri zed in that the subsequent treatment includes thickening and filtration .9 . The precipitation method for MHP based on a composite alkali precipitant according to claim 8 , characteri zed in that a portion of the underflow after thickening is returned as seed crystals to be mixed with the nickel-cobalt hydroxide slurry .10 . The precipitation method for MHP based on a composite alkali precipitant according to claim 8 , characteri zed in that the filtration uses vacuum filtration or pressure filtration, and the MHP filter cake is washed with distilled water or industrial water during filtration .

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