Treatment device and treatment method for nickel-containing minerals

Abstract

The invention relates to a nickel-containing mineral treatment device and method, the treatment device comprises a first pipeline, a second pipeline, a third pipeline and at least two vertical autoclaves, each vertical autoclave is provided with a feed port, a discharge port and a steam inlet, each feed port is connected to the first pipeline in parallel, each steam inlet is connected to the second pipeline in parallel, and each discharge port is connected to the third pipeline in parallel. And the discharge ports are connected in parallel to a third pipeline. The treatment device can accurately maintain the time, temperature and pressure required by the ore pulp leaching reaction, accurately control the ore pulp flow in each vertical autoclave, effectively reduce the possibility that the pressure in the autoclave rises suddenly, reduce the potential safety hazard of production, and ensure an excellent leaching effect.

Description

Technical Field

[0001] The present invention relates to a processing device and a processing method for nickel-containing minerals, belonging to the field of hydrometallurgy. Background Art

[0002] Nickel is an important strategic metal for civil and military use, mainly used as raw material for producing various stainless steels, soft magnetic alloys and alloy structural steels, etc. Laterite nickel ore is one of the common nickel-containing minerals and an important raw material for producing nickel iron. Laterite nickel ore resources are surface weathered crust deposits formed by the weathering, leaching and sedimentation of sulfide nickel ore rock masses. Generally, laterite nickel ore contains 1-2% nickel and 20-50% iron. The surface laterite nickel ore has low nickel content and high iron content. The smelting of laterite nickel ore is divided into pyrometallurgy and hydrometallurgy. Pyrometallurgy can be divided into two methods: rotary kiln pre-reduction - electric furnace smelting and sintering machine sintering - blast furnace smelting. The product of the former method is nickel iron (nickel content greater than 7%), which is suitable for processing ores with nickel content above 1-3% and iron content below 25%; the product of the latter method is nickel iron alloy (nickel content less than 3%), which is suitable for processing ores with nickel content of 0.8-1.3% and iron content above 45%. Hydrometallurgy is divided into sulfuric acid method and nitric acid method. Both of these methods use high temperature and high pressure. The temperature and pressure of the sulfuric acid method are higher than those of the nitric acid method. The characteristic of the sulfuric acid method is that the steam produced by using pyrite or sulfur to make acid is used for high temperature and high pressure leaching. The steam produced by making acid can balance the production demand. Under high temperature and high pressure conditions, iron is deposited in the leaching residue. The leaching residue has high iron content but also high sulfur content and cannot be used as iron-making raw material and can only be stockpiled in the slag yard. This method has been used in several industrial plants for production. The characteristic of the nitric acid method is that the temperature and pressure during the leaching process are lower than those of the sulfuric acid method, but separate steam supply is required for heat supplement. Nitric acid can be recycled from the leaching solution. The leaching residue produced under high temperature and high pressure conditions has high iron content and low sulfur content and can be used as iron-making raw material. Currently, the nitric acid method is being applied in industrial production. Generally, the existing nitric acid method adds laterite nickel ore into a multi-chamber horizontal autoclave (see Figure 3 ), adds nitric acid solution, and passes in steam. The pulp enters from the first chamber of the horizontal autoclave and leaves from the last chamber. The pulp flow rate in each chamber is the same, that is, "large flow rate, short cycle". Under high temperature and high pressure conditions, nitrate ions in the pulp are prone to volatilize, and the rapidly volatilized gas will cause the pressure in the autoclave to rise, posing serious potential production safety hazards. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, one of the purposes of the present invention is to provide a processing device for nickel-containing minerals with higher safety and excellent leaching effect; the second purpose of the present invention is to provide a processing method for nickel-containing minerals.

[0004] To solve the above technical problems, the technical solution of the present invention is as follows:

[0005] A processing device for a nickel-containing mineral, comprising:

[0006] A first pipeline for conveying reaction raw materials; and

[0007] At least 2 vertical autoclaves, each of which has a feed inlet, a discharge outlet and a steam inlet, and the feed inlets are connected in parallel to the first pipeline.

[0008] Thus, the nickel-containing mineral pulp containing nitric acid can be continuously input into multiple vertical autoclaves in a parallel flow manner through the first pipeline, that is, with "small flow rate and long cycle", more precisely maintaining the time, temperature and pressure required for the pulp leaching reaction, precisely controlling the pulp flow rate in each vertical autoclave, effectively reducing the possibility of a sharp increase in the pressure inside the autoclave, reducing potential production safety hazards, and ensuring excellent leaching effects.

[0009] Further, a first valve is provided at the feed inlet, and the inlet end of the first valve is communicated with the first pipeline.

[0010] Further, the processing device further includes a second pipeline, and the steam inlets are connected in parallel to the second pipeline. The second pipeline can be used to convey steam to realize heating and temperature maintenance of the materials in the vertical autoclave.

[0011] Further, a third valve is provided at the steam inlet, and the inlet end of the third valve is communicated with the second pipeline.

[0012] Further, the processing device further includes a third pipeline, and the discharge outlets are connected in parallel to the third pipeline; more preferably, a second valve is provided at the discharge outlet, and the outlet end of the second valve is communicated with the third pipeline.

[0013] Thus, it is convenient to more precisely control the flow rate of the pulp entering the relevant vertical autoclave and parameters such as the temperature and pressure therein, which helps to further reduce potential safety hazards and improve leaching effects. In addition, by opening and closing the relevant valves, some vertical reactors can be selectively put into working or stopped working states, which is convenient for cleaning or repairing the slag and scale in some vertical reactors, and at the same time enables the processing device to still be used for high-temperature and high-pressure leaching without affecting normal production operations, which helps to increase production capacity and is more convenient for industrial production.

[0014] Further, a pump is provided on the first pipeline, and preferably, the pump is arranged at the inlet end of the first pipeline. Thus, it is convenient to pressurize the pulp.

[0015] Further, the number of the vertical autoclaves is 3 - 8, preferably 4 - 7.

[0016] Further, a flash tank is further included, and the inlet of the flash tank is communicated with the outlet end of the third pipeline. Thus, it is convenient to cool and depressurize the pulp after high-temperature and high-pressure leaching.

[0017] Based on the same inventive concept, the present invention also provides a method for treating nickel-containing minerals, which is carried out by using the treatment device described above; the method includes the following steps:

[0018] S1. Crushing the nickel-containing minerals to be treated to obtain fine ore;

[0019] S2. Mixing the fine ore, nitric acid, and water to form a pulp to obtain a slurry;

[0020] Wherein, the initial liquid-solid mass ratio of the slurry is 1.5 - 2:1, and the initial concentration of nitric acid is 170 - 190 g / L;

[0021] S3. Feeding the slurry into the first pipeline so that the slurry enters at least 2 vertical autoclaves, and at the same time introducing steam into the corresponding vertical autoclaves. After high-temperature and high-pressure leaching, cooling and depressurizing are carried out in sequence, and solid-liquid separation is performed to obtain leached residue and leachate;

[0022] Wherein, during high-temperature and high-pressure leaching, the temperature in the vertical autoclave is controlled at 190 - 200 °C, preferably 194 - 198 °C, and the pressure is 1.4 - 1.6 MPa, preferably 1.45 - 1.55 MPa. The leached residue can be stockpiled or sold as iron slag.

[0023] Optionally, the nickel-containing minerals are nickel oxide ore, further laterite nickel ore.

[0024] Optionally, in the laterite nickel ore, the content of Ni is 0.8 - 1.3%, and the content of Co is 0.08 - 0.18%. Further, the content of Mg in the laterite nickel ore is 25 - 30%, and the content of SiO2 in the laterite nickel ore is 30 - 40% (high-magnesium and high-silica type); further, the content of Fe in the laterite nickel ore is 40 - 50% (limonite type).

[0025] Further, in the fine ore, the proportion of solid phase substances with a particle size of 200 mesh in the fine ore is ≥ 90 wt%, preferably not less than 95 wt%.

[0026] Further, in S2, the initial liquid-solid mass ratio of the slurry is 1.6 - 1.8:1, and the initial concentration of nitric acid is 175 - 185 g / L.

[0027] Further, in S3, the time for high-temperature and high-pressure leaching is 1 - 2 h.

[0028] Further, after S3, the leachate is neutralized once and then solid-liquid separated to obtain a primary neutralized liquid with a pH value of 3 - 4; then the primary neutralized liquid is neutralized a second time and then solid-liquid separated to obtain a secondary neutralized residue and a secondary neutralized liquid with a pH value of 7 - 8; then, the secondary neutralized liquid is concentrated and crystallized to obtain magnesium nitrate products.

[0029] Optionally, magnesia is used to perform primary neutralization on the leaching solution. Optionally, during primary neutralization, the reaction temperature is controlled at 40 - 80°C, further 70 - 80°C. The primary neutralization slag generated during primary neutralization can be further treated to recover elements such as aluminum. The primary neutralization time is generally 1 - 1.5 h.

[0030] Optionally, magnesia is used to perform secondary neutralization on the primary neutralization solution. Optionally, during secondary neutralization, the reaction temperature is controlled at 40 - 80°C, further 70 - 80°C. The secondary neutralization time is generally 1 - 1.5 h. Generally, the secondary neutralization slag is a nickel-cobalt concentrate and can be used for further recovery of nickel and cobalt.

[0031] Optionally, the magnesium nitrate product is pyrolyzed at a low temperature of 500 - 600°C for 1 - 1.5 h to obtain magnesia and NO x gas. The magnesia can be returned to the neutralization process, and the generated NO x gas can be used for nitric acid regeneration to produce nitric acid.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) By using the treatment device of the present invention, the ore pulp can be fed into the multi-chamber horizontal autoclave in the mode of "large flow rate, short cycle", and changed to the mode of "small flow rate, long cycle" into multiple single vertical autoclaves, that is, the ore pulp is fed into one chamber with a large flow rate and changed to a small flow rate and parallelly fed into multiple relatively independent vertical autoclaves, reducing the ore pulp flow rate in the autoclave, which is equivalent to increasing the single chamber volume and reducing the degree of rapid volatilization of nitrate ions in the solution. When the ore pulp flow rate is constant, the time to enter one chamber is short (short cycle), the ore pulp flow velocity is fast (large flow rate), and when nitrate ions volatilize, it is difficult to adjust and control the pressure of the horizontal autoclave, and safety hazards are likely to occur; on the contrary, when the ore pulp enters multiple vertical autoclaves for a long time (long cycle), the ore pulp flow velocity is relatively slow (small flow rate), and when nitrate ions volatilize, the pressure of the vertical autoclave is easy to adjust and control. The way that the ore pulp enters multiple vertical autoclaves in parallel flow greatly improves the production safety performance of the treatment device, and can more accurately control conditions such as the high-temperature and high-pressure leaching temperature, time, and pressure, making the leaching effect more ideal and stable, which is beneficial to industrial production.

[0034] (2) The treatment device and method of the present invention have a wide adaptability to raw materials. Magnesia can be recovered from high-magnesium laterite nickel ore, and iron slag can be produced and sold externally for limonite laterite nickel ore.

[0035] (3) The nickel and cobalt recovery rates of the treatment device and method of the present invention are as high as over 94%, and other elements such as aluminum and scandium can also be comprehensively recovered.

[0036] (4) In the present invention, the secondary neutralization liquid is treated by evaporation crystallization, thermal decomposition, etc., and NO can be produced x gas, which is sent to the subsequent nitric acid regeneration process, enabling the recycling of nitric acid and contributing to cost savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flow chart of a method for treating laterite nickel ore according to the present invention.

[0038] Figure 2 is a schematic structural diagram of a device for treating laterite nickel ore according to the present invention.

[0039] Figure 3 is a schematic structural diagram of an existing device for treating laterite nickel ore. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be described in detail below with reference to embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. For the convenience of description, words such as "upper", "lower", "left", and "right" in the following text only indicate the same direction as the upper, lower, left, and right directions of the drawings themselves, and do not limit the structure. Unless otherwise specified, the relevant percentages refer to mass percentages.

[0041] Embodiment 1

[0042] Refer to Figure 2 , the device for treating laterite nickel ore in this embodiment includes a first pipeline 4, a second pipeline 5, a third pipeline 6 and at least 2 vertical autoclaves 2. The vertical autoclaves 2 have a feed inlet, a discharge outlet and a steam inlet. Each feed inlet is connected in parallel to the first pipeline 4, each steam inlet is connected in parallel to the second pipeline 5, and each discharge outlet 3 is connected in parallel to the third pipeline 6. A first valve 21 is provided at the feed inlet, a second valve 22 is provided at the discharge outlet, and a third valve 23 is provided at the steam inlet. The inlet end of the first valve 21 is connected to the first pipeline 4, the outlet end of the second valve 22 is connected to the third pipeline 6, and the inlet end of the third valve 23 is connected to the second pipeline 5. A pump 1 is provided on the first pipeline 4, and the pump 1 is arranged at the inlet end of the first pipeline 4. The number of the vertical autoclaves 2 is 6. A flash tank 3 is further included, and the inlet of the flash tank 3 is connected to the outlet end of the third pipeline 6. A fourth valve 7 is provided on the downstream side of the pump 1; a fifth valve 8 is provided at the inlet end of the second pipeline 5; a sixth valve 9 is provided at the inlet of the flash tank 3. A stirring mechanism is provided in each vertical autoclave.

[0043] Refer to Figure 1, calculated based on the combined total volume of 30 liters of 6 vertical autoclaves with a volume of 5 liters each (single water-cooled), take 20 Kg / h of laterite nickel ore (Ni: 1.2%, Co: 0.1%, Fe: 10%, Mg: 18%, SiO2: 36%, Al: 1.4%). Crush and grind the laterite nickel ore until the mineral particle size is 90% of 200 mesh, add 30 L / h of nitric acid solution (nitric acid concentration 180 g / L), mix and adjust the pulp (liquid-solid mass ratio 1.5:1) to obtain pulp; pump the adjusted pulp into 6 vertical autoclaves in a parallel flow manner, introduce steam for high-temperature and high-pressure leaching, control the leaching temperature at 190 °C, the pressure at 1.4 MPa, and the reaction time at 1 h. After the reaction is completed, the pulp is cooled and depressurized, and liquid-solid separation is carried out to produce 30 L / h of leaching solution (Ni: 7.62 g / L, Co: 0.63 g / L, Mg: 118.8 g / L, Al: 8.49 g / L). After calculation, among them, the nickel leaching rate is 95.20%, the cobalt leaching rate is 94.30%, the magnesium leaching rate is 99%, and the aluminum leaching rate is 91%. After neutralizing the leaching solution once with magnesium oxide at 50 °C, liquid-solid separation is carried out to obtain a primary neutralized solution with a pH value of 3 - 4; then neutralize the primary neutralized solution with magnesium oxide at 50 °C for a second time, followed by liquid-solid separation to obtain a second neutralized slag and a second neutralized solution with a pH value of 7 - 8; then, concentrate and crystallize the second neutralized solution to obtain magnesium nitrate product. Then, thermally decompose the magnesium nitrate product. Among them, the thermal decomposition conditions are: decomposition temperature: 500 °C, decomposition time: 1 h, and the quality of the thermally decomposed product magnesium oxide: 96%.

[0044] Example 2

[0045] Calculated based on the combination of 6 vertical autoclaves with a volume of 5 liters each (single water-cooled) and a total volume of 30 liters, 10 Kg / h of laterite nickel ore (Ni: 1.0%, Co: 0.12%, Fe: 12%, Mg: 19%, SiO2: 37%, Al: 1.5%) is taken. The laterite nickel ore is crushed and ground until the mineral particle size is 90% of 200 mesh. 20 L / h of nitric acid solution (nitric acid concentration 190 g / L) is added, and they are mixed and slurried (liquid-solid mass ratio 2:1) to obtain pulp. The prepared pulp is pumped into 6 vertical autoclaves in a parallel flow manner, and steam is introduced for high-temperature and high-pressure leaching. The temperature is controlled at 200 °C, the pressure is 1.6 MPa, and the reaction time is 1.5 h. After the reaction is completed, the pulp is cooled and depressurized, and liquid-solid separation is carried out to produce 20 L / h of leaching solution (Ni: 4.78 g / L, Co: 0.57 g / L, Mg: 94.05 g / L, Al: 6.9 g / L). Through calculation, among them, the nickel leaching rate is 95.50%, the cobalt leaching rate is 94.80%, the magnesium leaching rate is 99%, and the aluminum leaching rate is 92%. After neutralizing the leaching solution with magnesium oxide at 50 °C for the first time and then carrying out liquid-solid separation, a first neutralized solution with a pH value of 3 - 4 is obtained; then, the first neutralized solution is neutralized with magnesium oxide at 50 °C for the second time and then liquid-solid separation is carried out to obtain a second neutralized slag and a second neutralized solution with a pH value of 7 - 8; then, the second neutralized solution is concentrated and crystallized to obtain magnesium nitrate product. Then, the magnesium nitrate product is thermally decomposed. Among them, the thermal decomposition conditions are: decomposition temperature: 550 °C, decomposition time: 1.5 h, and the quality of the thermally decomposed product magnesium oxide: 97%.

[0046] Example 3

[0047] Calculated based on the combination of 6 vertical autoclaves with a volume of 5 liters each (single water-cooled) and a total volume of 30 liters, take 20 Kg / h of laterite nickel ore (Ni: 1.1%, Co: 0.09%, Fe: 48%, Mg: 2.8%, Al: 3.4%, Sc: 76 g / t). Crush and grind the laterite nickel ore until the mineral particle size reaches 90% passing through 200 mesh. Add 30 L / h of nitric acid solution (nitric acid concentration 180 g / L), mix and adjust the pulp (liquid-solid mass ratio 1.5:1) to obtain pulp; pump the adjusted pulp into 6 vertical autoclaves in a parallel flow manner, introduce steam for high-temperature and high-pressure leaching, control the temperature at 190 °C, pressure at 1.4 MPa, reaction time at 1 h. After the reaction is completed, cool down and depressurize the pulp, separate the liquid and solid, and produce 30 L / h of leaching solution (Ni: 6.99 g / L, Co: 0.57 g / L, Mg: 17.92 g / L, Al: 20.85 g / L, Sc: 0.042 g / L). Through calculation, among them, the nickel leaching rate is 95.3%, the cobalt leaching rate is 94.4%, the magnesium leaching rate is 96%, the aluminum leaching rate is 92%, the scandium leaching rate is 82%. The leaching solution is sent to the subsequent process, and the leaching residue contains iron: 56%. Use magnesium oxide to conduct primary neutralization of the leaching solution at 50 °C, then separate the solid and liquid to obtain a primary neutralization solution with a pH value of 3 - 4; then use magnesium oxide to conduct secondary neutralization of the primary neutralization solution at 50 °C, separate the solid and liquid to obtain secondary neutralization slag and a secondary neutralization solution with a pH value of 7 - 8; then, concentrate and crystallize the secondary neutralization solution to obtain magnesium nitrate product. Then, thermally decompose the magnesium nitrate product, among which, the thermal decomposition conditions are: decomposition temperature: 500 °C, decomposition time: 1 h, and the quality of the magnesium oxide obtained from thermal decomposition is 96%.

[0048] Example 4

[0049] Calculated based on the combination of 6 vertical autoclaves with a volume of 5 liters each (single water-cooled) and a total volume of 30 liters, 10 Kg / h of laterite nickel ore (Ni: 1.2%, Co: 0.11%, Fe: 47%, Mg: 3.6%, Al: 4.2%, Sc: 88 g / t) is taken. The laterite nickel ore is crushed and ground until the mineral particle size of 200 mesh accounts for 90%. 20 L / h of nitric acid solution (nitric acid concentration 190 g / L) is added, and mixed and slurried (liquid-solid mass ratio 2:1) to obtain pulp. The adjusted pulp is pumped into 6 vertical autoclaves in a parallel flow manner, and steam is introduced for high-temperature and high-pressure leaching. The temperature is controlled at 200 °C, the pressure is 1.6 MPa, and the reaction time is 1.5 h. After the reaction is completed, the pulp is cooled and depressurized, and liquid-solid separation is carried out to produce 20 L / h of leaching solution (Ni: 5.75 g / L, Co: 0.52 g / L, Mg: 17.46 g / L, Al: 19.53 g / L, Sc: 0.037 g / L). After calculation, among them, the nickel leaching rate is 95.8%, the cobalt leaching rate is 94.6%, the magnesium leaching rate is 97%, the aluminum leaching rate is 93%, and the scandium leaching rate is 83%. The leaching solution is sent to the subsequent process, and the leaching residue contains 55% iron. After neutralizing the leaching solution with magnesium oxide at 50 °C for the first time, liquid-solid separation is carried out to obtain a first neutralized solution with a pH value of 3 - 4; then, the first neutralized solution is neutralized with magnesium oxide at 50 °C for the second time, and liquid-solid separation is carried out to obtain a second neutralized residue and a second neutralized solution with a pH value of 7 - 8; then, the second neutralized solution is concentrated and crystallized to obtain magnesium nitrate product. Then, the magnesium nitrate product is thermally decomposed. Among them, the thermal decomposition conditions are: decomposition temperature: 550 °C, decomposition time: 1.5 h, and the quality of the thermally decomposed product magnesium oxide is 97%.

[0050] Comparative Example 1

[0051] Repeat Example 1, with the only difference being that the treatment device used is a horizontal autoclave 10 with a volume of 30 liters and 6 chambers (single chamber water-cooled) (see Figure 3 ).

[0052] As a result, it is necessary to frequently turn on the single-chamber cooling water for cooling and depressurization to ensure the safe production of the autoclave; while in Example 1, since the pulp enters 6 vertical autoclaves in a parallel flow manner, for a single vertical autoclave, the pulp flow rate is small and the flow velocity is slow, and the temperature and pressure of the vertical autoclave are easy to control. It is not necessary to turn on the single cooling water for cooling and depressurization to ensure the production safety performance of the treatment device.

[0053] The content clarified in the above embodiments should be understood that these embodiments are only used to illustrate the present invention more clearly, rather than to limit the scope of the present invention. After reading the present invention, various equivalent forms of modification by those skilled in the art fall within the scope defined by the appended claims of this application.

Claims

1. A processing device for a nickel-containing mineral, characterized in that, Comprising: A first pipeline (4); And At least two vertical autoclaves (2), each of the vertical autoclaves (2) having a feed inlet, a discharge outlet and a steam inlet, and the feed inlets are connected in parallel to the first pipeline (4).

2. The processing device according to claim 1, characterized in that, The feed inlet is provided with a first valve (21), and the inlet end of the first valve (21) is communicated with the first pipeline (4).

3. The processing device according to claim 1, characterized in that The processing device further comprises a second pipeline (5), and the steam inlets are connected in parallel to the second pipeline (5).

4. The processing device according to claim 3, characterized in that The steam inlet is provided with a third valve (23), and the inlet end of the third valve (23) is communicated with the second pipeline (5).

5. The processing device according to claim 1, characterized in that, The processing device further comprises a third pipeline (6), and the discharge outlets (3) are connected in parallel to the third pipeline (6).

6. The processing device according to claim 5, characterized in that The discharge outlet is provided with a second valve (22), and the outlet end of the second valve (22) is communicated with the third pipeline (6).

7. The processing device according to claim 1, characterized in that, A pump (1) is provided on the first pipeline (4).

8. The processing device according to claim 7, characterized in that, The pump (1) is arranged at the inlet end of the first pipeline (4).

9. The processing device according to any one of claims 1 to 3, characterized in that, The number of the vertical autoclaves (2) is 3 - 8.

10. The processing device according to any one of claims 1-3, characterized in that, The number of the vertical autoclaves (2) is 4 - 7.

11. The processing device according to claim 5 or 6, characterized in that, The processing device further comprises a flash tank (3), and the inlet of the flash tank (3) is communicated with the outlet end of the third pipeline (6).

12. A method for treating a nickel-containing mineral, characterized in that, Carried out by using the processing device according to any one of claims 1 - 11; comprising the following steps: S1. Crushing the nickel-containing mineral to be processed to obtain fine ore; S2. Mixing and slurrying the fine ore, nitric acid and water to obtain slurry; Wherein, the initial liquid-solid mass ratio of the slurry is 1.5 - 2:1, and the initial concentration of nitric acid is 170 - 190 g / L; S3. Inputting the slurry into the first pipeline (4) so that the slurry enters at least two vertical autoclaves (2), and at the same time introducing steam into the corresponding vertical autoclaves, after high-temperature and high-pressure leaching, sequentially cooling and depressurizing, and solid-liquid separation to obtain leaching residue and leaching solution; Wherein, when carrying out high-temperature and high-pressure leaching, controlling the temperature in the vertical autoclave to be 190 - 200 °C and the pressure to be 1.4 - 1.6 MPa.

13. The processing method according to claim 12, wherein In the fine ore, the proportion of the solid phase with a particle size of 200 mesh in the fine ore is ≥ 90 wt%.

14. The processing method according to claim 12, wherein In S2, the initial liquid-solid mass ratio of the slurry is 1.6 - 1.8:1, and the initial concentration of nitric acid is 175 - 185 g / L.

15. The processing method according to claim 12, wherein In S3, the time of high-temperature and high-pressure leaching is 1 - 2 h.

16. The processing method according to claim 12, characterized in that, After S3, the leaching solution is neutralized once and then solid-liquid separated to obtain a primary neutralized solution with a pH value of 3 - 4; then the primary neutralized solution is neutralized a second time and then solid-liquid separated to obtain a secondary neutralized residue and a secondary neutralized solution with a pH value of 7 - 8; then, the secondary neutralized solution is concentrated and crystallized to obtain magnesium nitrate product.

17. The processing method according to claim 12, characterized in that, The nickel-containing mineral is laterite nickel ore.

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