Recycling method of magnesium element in laterite-nickel ore hydrometallurgy

Abstract

The invention discloses a cyclic utilization method of a magnesium element in laterite-nickel ore hydrometallurgy. The method comprises the following steps: atomizing the magnesium sulfate-containing waste liquid obtained in the laterite-nickel ore hydrometallurgy process, and pyrolyzing in a reducing atmosphere to obtain magnesium oxide powder and SO2-containing gas; the method comprises the following steps: regulating magnesium oxide powder to obtain magnesium slurry, returning the magnesium slurry to a leaching solution containing Ni < 2 + > and Co < 2 + > at the front end of laterite-nickel ore hydrometallurgy, and carrying out a nickel cobalt hydroxide precipitation reaction; the SO2-containing gas is dedusted and dried, and concentrated sulfuric acid is prepared by adopting a two-conversion and two-absorption contact method. According to the method, the magnesium-containing waste liquid is subjected to spray pyrolysis, and obtained magnesium oxide and SO2 are respectively fed into a laterite-nickel ore hydrometallurgy production line and an acid making production line, so that not only is zero emission of the magnesium-containing waste liquid realized, but also resource cyclic utilization of the magnesium element is effectively realized, and the method is suitable for industrial production. The technical problems that in the prior art, magnesium-containing waste liquid in laterite-nickel ore hydrometallurgy is high in treatment cost and difficult to recycle are effectively solved.

Description

Technical Field

[0001] This invention relates to a method for recovering magnesium in nickel ore smelting, specifically a method for recycling magnesium in laterite nickel ore hydrometallurgical smelting, belonging to the field of laterite nickel ore hydrometallurgical technology. Background Technology

[0002] Magnesium content in lateritic nickel ore typically accounts for 1-5% of the ore's (dry basis) mass. Conventional hydrometallurgical processes generate a large amount of magnesium-containing wastewater. Existing technologies primarily employ two methods for treating this wastewater: one is direct heating and evaporation to crystallize the magnesium sulfate heptahydrate (MgSO4·7H2O); the other is direct discharge into a wastewater treatment plant for impurity removal. However, both methods suffer from the following technical drawbacks:

[0003] 1) The processing consumes too much energy and has too little economic benefit, often operating at a loss. Moreover, the purity of the recovered magnesium sulfate is limited and it is difficult to reach the 2N level, so its industrial application value is not high. 2) If magnesium is not recovered, although the processing cost will be reduced to a certain extent, it will also waste magnesium resources and increase potential environmental risks. 3) In the hydrometallurgical smelting of laterite nickel ore, an additional alkali agent needs to be added as a precipitant, which cannot make full use of magnesium-containing waste liquid and further increases the production cost of nickel-cobalt hydroxide.

[0004] In summary, existing technologies have not yet established an efficient, economical, and environmentally friendly technical route for the recovery and utilization of magnesium resources during the hydrometallurgical smelting of laterite nickel ore. Therefore, how to efficiently utilize magnesium resources in the hydrometallurgical smelting of laterite nickel ore to achieve resource recycling and environmental friendliness has become a pressing problem for the industry. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore. This method involves spray pyrolysis of magnesium-containing wastewater, with the resulting magnesium oxide and SO2 being fed into a high-pressure acid leaching line and an acid production line for laterite nickel ore, respectively. This not only achieves zero discharge of magnesium-containing wastewater but also effectively realizes the resource-based recycling of magnesium, effectively solving the technical problems of high treatment costs and difficulty in resource utilization of magnesium-containing wastewater in the hydrometallurgical smelting of laterite nickel ore in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore, comprising:

[0007] Step S1: The waste liquid containing magnesium sulfate obtained during the hydrometallurgical process of laterite nickel ore is atomized and then pyrolyzed under a reducing atmosphere to obtain magnesium oxide powder and SO2-containing gas.

[0008] Step S2: After adjusting the magnesium oxide powder to obtain magnesium slurry, return it to the front end of the laterite nickel ore hydrometallurgical process containing Ni. 2+ Co 2+ In the leachate, a nickel-cobalt hydroxide precipitation reaction is carried out;

[0009] Step S3: The SO2-containing gas is subjected to dust removal and drying, and concentrated sulfuric acid is produced by a two-transformation two-absorption contact method.

[0010] The technical solution provided by this invention adopts spray pyrolysis technology, which not only realizes rapid and thorough pyrolysis of magnesium-containing waste liquid, but also significantly shortens the process time and reduces the process energy consumption. Furthermore, the particle size of magnesium oxide can be controlled by controlling the process parameters of pyrolysis, and the resulting SO2 concentration is high, so there is no need for enrichment and it can be used directly as a raw material for acid production.

[0011] As a preferred embodiment, the concentration of magnesium sulfate in the waste liquid is 10~60 g / L.

[0012] As a preferred embodiment, the droplet size of the atomized waste liquid is 20~85μm.

[0013] The particle size of the atomized waste liquid directly affects the amount of waste liquid processed per unit time and the particle size of the resulting magnesium sulfate. If the atomized particle size is too fine, it will seriously reduce the amount of waste liquid processed, prolong the process time, and increase energy consumption. If the atomized particle size is too coarse, it will result in the magnesium oxide powder having an excessively large particle size, reducing the subsequent nickel-cobalt precipitation efficiency.

[0014] As a preferred embodiment, the reducing atmosphere is at least one of methane, carbon monoxide, and hydrogen.

[0015] As a preferred embodiment, the pyrolysis conditions are: a temperature of 700~1300℃ and a residence time of 2~30s.

[0016] The process conditions for spray pyrolysis must be strictly followed according to the above requirements, as they directly affect the particle size of magnesium oxide powder. Only within the above range can magnesium oxide powder with a particle size of 100~300nm be obtained.

[0017] As a preferred embodiment, the magnesium oxide powder has a purity of ≥98% and a particle size of 100~300nm.

[0018] As a preferred embodiment, the concentration of SO2 in the SO2-containing gas is 8-12 vol%. The SO2 obtained by spray pyrolysis according to the present invention has high purity and can be used as a raw material for acid production without further enrichment.

[0019] As a preferred embodiment, the conditions for preparing the magnesium oxide powder slurry are as follows: deionized water and magnesium oxide powder are thoroughly mixed within 5-20 minutes to obtain a magnesium slurry with a solid content of 5-15 wt%. More preferably, the pH of the magnesium slurry is 10-11.

[0020] As a preferred embodiment, the conditions for the nickel-cobalt hydroxide precipitation reaction are as follows: magnesium slurry containing Ni is added under stirring. 2+ Co 2+ The temperature in the leachate is 40~60℃ and the time is 60~120min.

[0021] After a short period of slurry preparation, the pH of magnesium oxide powder is adjusted to a suitable range for the precipitation reaction of nickel-cobalt hydroxide. Using this powder as a precipitant, high-grade nickel-cobalt hydroxide products can be obtained. This process not only significantly improves the recycling of magnesium resources but also effectively reduces the amount of external precipitant required, lowering production costs by 30-42% during the precipitation process.

[0022] As a preferred embodiment, the magnesium slurry consumption per unit volume, calculated based on Ni in the leachate, is 0.75~0.9 t / t. Ni Further preferably, the magnesium slurry consumption per unit volume, calculated based on Ni in the leachate, is 0.75~0.9 t / t. Ni The magnesium slurry obtained by this invention undergoes a precipitation reaction. Because the magnesium oxide prepared by the spray pyrolysis process has a small particle size and high activity, and because the self-made magnesium oxide avoids the problem of reduced activity due to water absorption during transportation of purchased magnesium oxide, this method is significantly more efficient than the traditional process of 1.2~1.4 t / t. Ni The magnesium oxide consumption was reduced by about 30%, and the magnesium recovery rate was ≥95%, achieving efficient recycling of magnesium resources.

[0023] As a preferred embodiment, the sum of the mass fractions of Ni and Co in the nickel-cobalt hydroxide is ≥42%, and the mass fraction of Mg is ≤1.5%.

[0024] As a preferred embodiment, the conditions for the two-conversion-two-absorption contact method are: conversion temperature of 450–550 ℃, catalyst of vanadium pentoxide, and total conversion rate ≥99.5%. Based on the high-purity SO2-containing gas obtained from the spray pyrolysis process, after acid production via the two-conversion-two-absorption contact method, the concentration of the obtained sulfuric acid is ≥98%, the SO2 conversion rate is ≥99.5%, and the residual SO2 emission is ≤50 mg / m³. 3 It meets the requirements of the "Emission Standard for Air Pollutants" (GB 16297-1996) and basically achieves zero emissions of exhaust gas.

[0025] Compared with the prior art, the beneficial technical effects of the technical solution provided by the present invention are as follows:

[0026] 1) The method provided by the present invention sprays magnesium-containing waste liquid for pyrolysis, and sends the resulting magnesium oxide and SO2 to the hydrometallurgical and acid production lines of laterite nickel ore respectively. This not only achieves zero discharge of magnesium-containing waste liquid, but also effectively realizes the resource recycling of magnesium element. It effectively solves the technical problems of high treatment cost and difficulty in resource utilization of magnesium-containing waste liquid in hydrometallurgical laterite nickel ore.

[0027] 2) In the technical solution provided by this invention, the obtained magnesium oxide can replace the alkali agent as a precipitant and be added to the Ni-containing process of laterite nickel ore hydrometallurgy. 2+ Co 2+ The concentrated sulfuric acid obtained from the SO2 produced in the leachate can also be used as a strong acid in the leaching process of laterite nickel ore hydrometallurgical, which not only realizes the resource utilization of magnesium-containing waste liquid, but also significantly reduces the production cost of laterite nickel ore hydrometallurgical. Attached Figure Description

[0028] Figure 1 The flowcharts are for the methods provided in Embodiments 1 and 2 of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying tables. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for recycling magnesium in the hydrometallurgical process of laterite nickel ore. The specific steps are as follows:

[0032] Step S1: Take magnesium-containing waste liquid from the hydrometallurgical processing of a laterite nickel ore mine in Indonesia. The magnesium content is 35 g / L, the pH is 6.5, and the temperature is room temperature. Atomize the magnesium sulfate solution into droplets with an average particle size of 50 μm using an ultrasonic atomizer and spray it into a spray pyrolysis furnace. Natural gas (CH4 volume fraction 92%) is introduced as a reducing agent, the furnace temperature is controlled at 850℃, and the residence time is 15s. Pyrolysis yields magnesium oxide powder and SO2 gas. The obtained magnesium oxide powder has a purity of 99.1% and an average particle size of 220 nm. The SO2 gas concentration is 10.5 vol%.

[0033] Step S2: Add deionized water to magnesium oxide powder to adjust the solid content to 10 wt%, slurry for 5 minutes to obtain magnesium slurry with a pH of 10.5. Then, add the magnesium slurry to the Ni-containing front end of the laterite nickel ore hydrometallurgical process while stirring. 2+ Co2+ In the leachate, a nickel-cobalt hydroxide precipitation reaction was carried out at a temperature of 50℃ for 60 minutes; wherein, Ni in the leachate... 2+ The concentration was 3.2 g / L, Co 2+ The concentration was 0.35 g / L, and the magnesium oxide consumption was 0.85 t / t. Ni The obtained nickel-cobalt hydroxide precipitate was analyzed, and its Ni+Co content was 44.5 wt%, Mg content was 1.07 wt%, and Ni+Co recovery rate was 98.2%.

[0034] Step S3: The SO2-containing gas is subjected to dust removal and drying, and concentrated sulfuric acid is produced using a two-conversion, two-absorption contact method. The process conditions for acid production are: conversion temperature 480℃, and vanadium pentoxide catalyst. The final product is concentrated sulfuric acid with a concentration of 98.5 wt%, a total conversion rate of 99.6%, and an SO2 emission concentration of 42 mg / m³. 3 .

[0035] Example 2

[0036] Step S1: Take magnesium-containing waste liquid from the hydrometallurgical processing of a laterite nickel ore mine in Indonesia. The magnesium content is 43 g / L, the pH is 6.8, and the temperature is room temperature. Atomize the magnesium sulfate solution into droplets with an average particle size of 60 μm using an ultrasonic atomizer and spray it into a spray pyrolysis furnace. Use CO as a reducing agent, control the furnace temperature at 900℃, and the residence time is 12 s. Pyrolysis yields magnesium oxide powder and SO2 gas. The obtained magnesium oxide powder has a purity of 98.5% and an average particle size of 150 nm. The SO2 gas concentration is 11.2 vol%.

[0037] Step S2: Add deionized water to magnesium oxide powder to adjust the solid content to 8 wt%, slurry for 10 min to obtain magnesium slurry with pH 10.8. Then, add the magnesium slurry to the Ni-containing front end of the laterite nickel ore hydrometallurgical process while stirring. 2+ Co 2+ In the leachate, a nickel-cobalt hydroxide precipitation reaction was carried out at a temperature of 45℃ for 75 minutes; Ni in the leachate... 2+ The concentration was 3.5 g / L, Co 2+ The concentration was 0.40 g / L, and the magnesium oxide consumption was 0.81 t / t. Ni The obtained nickel-cobalt hydroxide precipitate was analyzed, and its Ni+Co content was 45.5 wt%, Mg content was 0.99 wt%, and Ni+Co recovery rate was 98.5%.

[0038] Step S3: The SO2-containing gas is subjected to dust removal and drying, and concentrated sulfuric acid is produced using a two-conversion, two-absorption contact method. The process conditions for acid production are: conversion temperature 470℃, and vanadium pentoxide catalyst. The final product is concentrated sulfuric acid with a concentration of 98.4 wt%, a total conversion rate of 99.7%, and an SO2 emission concentration of 38 mg / m³. 3 .

[0039] Comparative Example 1

[0040] This comparative example uses a direct heating evaporation crystallization method to treat the same magnesium-containing waste liquid as in Example 1. The specific process is as follows: a magnesium sulfate solution with a magnesium content of 35 g / L is heated and evaporated to saturation, and then cooled and crystallized to obtain magnesium sulfate heptahydrate (MgSO4•7H2O).

[0041] The energy consumption in this comparative example is mainly used for evaporating water from the waste liquid, approximately 2.5 GJ / t MgSO4•7H2O; the commercial price of the obtained magnesium sulfate is approximately 500 RMB / t; the nickel-cobalt hydroxide precipitation process requires the purchase of an alkali as a precipitant, calculated as sodium hydroxide, with a cost of approximately 5000 RMB / t. Ni .

[0042] Comparative Example 2

[0043] This comparative example is exactly the same as Example 1, except that the spray pyrolysis temperature is adjusted to 600 °C.

[0044] The results showed that the magnesium sulfate pyrolysis in this comparative example was incomplete, the magnesium oxide purity was only 85.2%, and it contained a large amount of unpyrolyzed magnesium sulfate; the SO2 gas concentration was only 3.5 vol%, which could not meet the requirements for acid production; in the subsequent nickel-cobalt precipitation reaction, the magnesium oxide activity was insufficient, the Ni+Co recovery rate was only 85.3%, and the Ni+Co content in MHP was only 35.8%.

[0045] Comparative Example 3

[0046] This comparative example is exactly the same as Example 1, except that the spray pyrolysis temperature is adjusted to 1400 °C.

[0047] The results showed that magnesium sulfate sintered in this comparative example, with an average particle size ≥500nm and reduced activity; in the nickel-cobalt precipitation reaction, magnesium oxide consumption increased to 1.8 t / t Ni, and Ni+Co recovery rate decreased to 88.5%.

[0048] Comparative Example 4

[0049] This comparative example is exactly the same as Example 1, except that the droplet size of the spray pyrolysis is adjusted to 100 μm.

[0050] The results showed that in this comparative example, due to the excessively large droplet size, the pyrolysis was incomplete, and the purity of magnesium oxide was only 90.5%. The pyrolysis time needed to be extended to more than 60 s, the energy consumption increased by 30%, and the concentration of SO2 gas obtained was only 6.2 vol%, which could not be used directly for acid production. It needed to be enriched before concentrated sulfuric acid production, which reduced the efficiency of acid production.

[0051] Comparative Example 5

[0052] This comparative example is exactly the same as Example 1, except that the reaction temperature for the nickel-cobalt hydroxide precipitation is adjusted to 30 °C.

[0053] The results showed that the precipitation reaction rate in this comparative example was too slow, and the reaction time needed to be extended to more than 150 min to achieve the same nickel-cobalt precipitation effect; the magnesium oxide consumption increased to 1.4 t / t Ni; and the Ni+Co recovery rate was only 86.7%.

[0054] Comparative Example 6

[0055] This comparative example is exactly the same as Example 1, except that the reaction temperature for the nickel-cobalt hydroxide precipitation is adjusted to 80 °C.

[0056] The results showed that the precipitation reaction rate in this comparative example was too fast, the precipitate particles were small, and co-precipitation occurred with impurities. The main manifestation was that the Mg content in the nickel-cobalt hydroxide product increased to 4.2%.

[0057] Comparative Example 7

[0058] This comparative example is exactly the same as Example 1, except that natural gas is replaced with air.

[0059] The results showed that a large amount of SO3 was generated during pyrolysis, while the SO2 gas concentration was only 5.3 vol%. This was insufficient to directly meet the process requirements of "two-conversion, two-absorption" acid production. After enrichment to a concentration ≥8 vol%, the conversion rate was only 85.2%, and the total concentration of SO3 and SO2 in the exhaust gas reached as high as 850 mg / m³. 3 The levels are seriously excessive.

[0060] As demonstrated in Examples 1 and 2, the technical solution provided by this invention achieves efficient recycling of magnesium resources, resulting in magnesium oxide with a purity ≥98%, Ni+Co recovery rate ≥98%, (Ni+Co) content in MHP ≥42%, and magnesium oxide consumption as low as 0.75–0.9 t / t. NiAs can be seen from Example 1 and Comparative Example 1, the technical solution provided by the present invention not only significantly reduces energy consumption, but also effectively reduces the production cost of nickel-cobalt hydroxide precipitation reaction. As can be seen from Example 1 and Comparative Examples 2-6, the preset technical effect can only be achieved within the range of process parameters required by the present invention. Any modification or replacement will lead to problems such as increased energy consumption, decreased product quality, or environmental pollution. As can be seen from Example 1 and Comparative Example 7, a reducing atmosphere is a key technical means to achieve a high SO2 conversion rate. Without the use of a reducing gas, the SO2 conversion rate is only 85.2%, which cannot meet environmental protection requirements.

Claims

1. A method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore, characterized in that, include: Step S1: The waste liquid containing magnesium sulfate obtained during the hydrometallurgical process of laterite nickel ore is atomized and then pyrolyzed under a reducing atmosphere to obtain magnesium oxide powder and SO2-containing gas. Step S2: Magnesium oxide powder is mixed into a slurry to obtain magnesium slurry, which is then returned to the Ni-containing front end of the laterite nickel ore hydrometallurgical process. 2+ Co 2+ In the leachate, a nickel-cobalt hydroxide precipitation reaction is carried out; Step S3: The SO2-containing gas is subjected to dust removal and drying, and concentrated sulfuric acid is produced by a two-transformation two-absorption contact method.

2. The method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1, characterized in that: The concentration of magnesium sulfate in the waste liquid is 10~60g / L; the droplet size of the waste liquid after atomization is 20~85μm.

3. The method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1, characterized in that: The reducing atmosphere is at least one of methane, carbon monoxide, and hydrogen; the pyrolysis conditions are: a temperature of 700~1300℃ and a residence time of 2~30s.

4. The method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1, characterized in that: The magnesium oxide powder has a purity of ≥98% and a particle size of 100~300nm; the SO2 concentration in the SO2-containing gas is 8~12 vol.

5. The method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1, characterized in that: The conditions for preparing the magnesium oxide powder slurry are as follows: within 5 to 20 minutes, deionized water and magnesium oxide powder are thoroughly mixed to obtain a magnesium slurry with a solid content of 5 to 15 wt%.

6. A method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 5, characterized in that: The conditions for the nickel-cobalt hydroxide precipitation reaction are as follows: magnesium slurry containing Ni is added under stirring. 2+ Co 2+ The temperature in the leachate is 40~60℃ and the time is 60~120min.

7. A method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1 or 6, characterized in that: The magnesium slurry consumption, calculated based on Ni in the leachate, is 0.75~0.9 t / t. Ni .

8. A method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1, characterized in that: The total mass fraction of Ni and Co in the nickel-cobalt hydroxide is ≥42%, and the mass fraction of Mg is ≤1.5%.

9. A method for recycling magnesium in the hydrometallurgical smelting of laterite nickel ore according to claim 1, characterized in that: The conditions for the two-conversion two-absorption contact method are: conversion temperature of 450–550 ℃, catalyst of vanadium pentoxide, and total conversion rate of ≥99.5%.

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