Method for leaching laterite-nickel ore and removing iron from ferronickel leachate in cooperation with laterite-nickel ore leaching

Abstract

The invention discloses a method for leaching laterite-nickel ore and removing iron from ferronickel leachate, which comprises the following steps of: performing high-pressure leaching on the laterite-nickel ore by using ferronickel normal-pressure pickle liquor or a composition of the ferronickel normal-pressure pickle liquor and sulfuric acid as a leaching agent under the leaching conditions that the oxygen partial pressure is 0.1-0.6 Mpa, the temperature is 220-260 DEG C, the acid-ore ratio is 230-310g / Kg, and the liquid-solid ratio is 2-6mL: 1g; wherein the ferronickel normal-pressure pickle liquor is obtained by carrying out normal-pressure leaching on a ferronickel product obtained by carrying out a pyrogenic process on laterite-nickel ore by using sulfuric acid. According to the method, the ferronickel normal-pressure pickle liquor is adopted as a leaching agent to conduct high-pressure leaching on the upper-layer low-grade high-iron low-magnesium laterite-nickel ore, and efficient leaching of the low-grade high-iron low-magnesium laterite-nickel ore and removal of iron in the ferronickel normal-pressure pickle liquor are achieved. Compared with sulfuric acid serving as a leaching agent, the leaching temperature required for achieving the same leaching rate by adopting the ferronickel normal-pressure acid leaching solution as the leaching agent is lower.

Description

Technical Field

[0001] The invention relates to a nickel ore smelting method, and in particular to a method for removing iron by leaching laterite nickel ore in coordination with nickel-iron leaching solution. Background Art

[0002] Laterite nickel ore is formed by long-term weathering, leaching and metamorphism of nickel-containing olivine and serpentine. Because the ore contains iron, the iron is oxidized to trivalent state after weathering, making the ore red, so it is called laterite ore. Laterite nickel ore resources are mainly distributed in tropical countries within 30 degrees north and south of the equator, especially in the tropical and subtropical regions around the Pacific Ocean.

[0003] The laterite nickel ore layer is usually divided into three layers, namely: ① The upper layer of limonite-type laterite nickel ore: the main characteristics are low content of nickel, silicon and magnesium, and high content of iron and cobalt, among which the content of iron is usually 35-50wt%. ② The lower layer of silicon-magnesium-type laterite nickel ore: high content of silicon and magnesium, low content of iron and cobalt, but high content of nickel, among which the content of magnesium is usually 15-35wt%. ③ The middle transition layer: the content of each main metal is between the upper and lower layers.

[0004] The processing technology of laterite nickel ore is mainly divided into three categories: pyrometallurgy, hydrometallurgy and combined pyrometallurgy and hydrometallurgy. The siliceous-magnesium laterite nickel ore mainly composed of silicate minerals is suitable for pyrometallurgical process, while the limonite type deposit is suitable for hydrometallurgical process. The intermediate transition type ore can be treated by pyrometallurgy or hydrometallurgy.

[0005] Hydrometallurgy currently mainly uses acid leaching processes, including atmospheric pressure acid leaching, heap leaching and high pressure acid leaching, among which:

[0006] The heap leaching process uses leaching of ore at room temperature, but the ore dissolution rate is slow and the nickel-cobalt leaching rate is low. It is only suitable for processing laterite nickel ore with high magnesium content.

[0007] Atmospheric pressure acid leaching is carried out at a temperature higher than room temperature. The leaching process consumes a large amount of acid, and there is a high concentration of residual acid in the leachate, which must be neutralized by adding alkali solution before subsequent separation. However, the alkali neutralization process is prone to produce a large amount of Fe(OH)3 colloid, which makes filtration difficult. In addition, the neutralization process prevents the residual acid from being recycled, resulting in a waste of acid. For laterite nickel ore with a high iron content, since the dissolution rate of iron minerals is very slow, a very high concentration of acid must be used to leach at a temperature close to the boiling point to dissolve the iron minerals. Therefore, atmospheric pressure acid leaching is more suitable for treating laterite nickel ore with a high magnesium content.

[0008] The high-pressure acid leaching process is generally carried out under high temperature and high pressure (230-270°C, 3-5MPa). The ore dissolution rate is fast. During the leaching process, the nickel, cobalt and iron in the minerals first dissolve into the leaching solution, and then the iron in the leaching solution is hydrolyzed into hematite and precipitated. The leaching process realizes the separation of nickel, cobalt and iron. Therefore, the high-pressure acid leaching process is particularly suitable for processing high-iron and low-magnesium ores. Since the acid released during the iron deposition process can continue to leach undissolved ore, the acid consumption of this process is relatively low.

[0009] In order to extract nickel from laterite nickel ore containing high-grade magnesium, it can be first smelted by a pyrometallurgical process, and then a nickel-iron product (nickel-iron concentrate or nickel-iron powder) with a high nickel purity can be obtained by magnetic separation, such as the invention patent with publication number CN101418388A.

[0010] Nickel iron atmospheric pressure acid leaching solution is obtained by leaching the nickel iron product obtained by pyrometallurgical process from laterite nickel ore at atmospheric pressure with sulfuric acid, wherein containing a large amount of iron ions and sulfuric acid and a small amount of nickel sulfate. For extracting nickel, a large amount of iron ions are not needed, so it is necessary to perform an iron removal operation on it; in addition, it is also hoped that the sulfuric acid in the residual acid leaching solution can be recycled. On the other hand, the leaching agent of laterite nickel ore when high pressure acid leaching is a strong acid (usually sulfuric acid). Based on the above two aspects, the inventor team of the present application, after analysis and testing, believes that the iron removal of nickel iron atmospheric pressure acid leaching solution is realized while high pressure leaching of laterite nickel ore is performed using nickel iron atmospheric pressure acid leaching solution as a leaching agent, and has certain feasibility. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a method for leaching laterite nickel ore in coordination with nickel-iron leaching solution to remove iron. The method uses nickel-iron atmospheric pressure acid leaching solution as a leaching agent to perform high-pressure leaching on the upper low-grade, high-iron, low-magnesium laterite nickel ore, thereby achieving efficient leaching of the low-grade, high-iron, low-magnesium laterite nickel ore and removal of iron in the nickel-iron atmospheric pressure acid leaching solution.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] A method for removing iron by leaching laterite nickel ore in coordination with nickel-iron leaching solution, wherein the laterite nickel ore is subjected to high-pressure leaching using nickel-iron atmospheric pressure acid leaching solution or a combination of nickel-iron atmospheric pressure acid leaching solution and sulfuric acid as a leaching agent, and the leaching conditions are: oxygen partial pressure of 0.1-0.6Mpa, temperature of 220-260°C, acid-ore ratio of 230-310g / Kg, and liquid-solid ratio of 2-6mL:1g; wherein,

[0014] Nickel-iron atmospheric pressure acid leaching solution, also known as nickel-iron leaching solution, is obtained by leaching the nickel-iron product obtained from laterite nickel ore by pyrometallurgical process with sulfuric acid at atmospheric pressure.

[0015] In the method of the present invention, the ferronickel atmospheric pressure acid leaching solution can be obtained by leaching the ferronickel product obtained by reducing and roasting laterite nickel ore in a rotary kiln and then magnetically separating it using sulfuric acid at atmospheric pressure, and the process parameters during atmospheric pressure leaching are the same as those in the prior art.

[0016] In a preferred embodiment, the nickel-iron atmospheric pressure acid leaching solution is obtained by leaching the nickel-iron product obtained by reducing and roasting a laterite nickel ore containing high-grade magnesium in a rotary kiln and then magnetically separating it with sulfuric acid at atmospheric pressure. The effective sulfuric acid concentration in the nickel-iron atmospheric pressure acid leaching solution can be determined as needed, such as 1.1 to 3.1 mol / L. Specifically, the nickel-iron atmospheric pressure acid leaching solution can be obtained by the following method:

[0017] Take nickel iron powder (particle size is preferably less than 100 mesh) and use concentrated sulfuric acid to leach nickel iron. During leaching, the temperature is controlled to be 80-90°C, the acid (sulfuric acid) material (nickel iron powder) ratio is controlled to be 180-220% by mass, the liquid (all liquids, including water and sulfuric acid) solid (nickel iron powder) ratio is 5-7mL: 1g, and the leaching time is usually 7-10h to obtain nickel iron leaching solution. The effective sulfuric acid concentration in the leaching solution obtained under the above leaching conditions is usually 1.1-3.1mol / L.

[0018] In the method described in the present invention, when a combination of nickel-iron atmospheric pressure acid leaching solution and sulfuric acid is used as a leaching agent, the proportion of sulfuric acid can be determined as needed, and it is only necessary to meet the acid-ore ratio and liquid-solid ratio specified in the leaching conditions. The applicant found in the experiment that the leaching rate of nickel and cobalt using a mixed leaching agent with sulfuric acid added is not necessarily better than that using only a single nickel-iron atmospheric pressure acid leaching solution. Furthermore, the applicant also found through experiments that under the same other experimental conditions, the leaching temperature required to obtain the same leaching rate using nickel-iron atmospheric pressure acid leaching solution as a leaching agent is lower than that using sulfuric acid as a leaching agent, which can not only recycle the acid in the nickel-iron atmospheric pressure acid leaching solution, but also effectively reduce energy consumption and production costs.

[0019] The ferrous sulfate in the ferronickel atmospheric pressure acid leaching solution is decomposed into sulfuric acid and ferric oxide during the pressure leaching process. The sulfuric acid is used for the efficient leaching of low-grade high-iron and low-magnesium laterite nickel ore and the removal of iron in the ferronickel atmospheric pressure acid leaching solution.

[0020] The reaction principle of the present invention is:

[0021] 4FeSO4+O2+4H2O=2Fe2O3+4H2SO4

[0022] NiFe2O4+H2SO4=NiSO4+Fe2O3+H2O

[0023] The overall reaction is: 4NiFe2O4+4FeSO4+O2+4H2O=4NiSO4+6Fe2O3+4H2O

[0024] The method of the present invention is carried out in an autoclave, and oxygen or oxygen-enriched air is introduced into the autoclave to make the oxygen partial pressure in the autoclave reach 0.1-0.6Mpa, preferably 0.2-0.3Mpa. Under the conditions defined in the present invention, when the high-pressure leaching time is greater than or equal to 30min, the laterite nickel ore can obtain a higher nickel and cobalt leaching rate. Under other certain conditions, increasing the time of the oxidation leaching reaction can increase the leaching rate. The applicant has found through experiments that a relatively satisfactory nickel and cobalt leaching rate can be obtained when the high-pressure leaching time is controlled at 50-60min.

[0025] In the method of the present invention, during high-pressure leaching, the preferred acid-ore ratio is 250-270 g / Kg, the preferred liquid-solid ratio is 3-4 mL:1 g, and the preferred temperature is 230-250°C.

[0026] The method of the present invention is particularly suitable for high-pressure leaching of limonitic laterite nickel ore (i.e. high-iron and low-magnesium laterite nickel ore), and is more suitable for leaching of low-grade limonitic laterite nickel ore (Ni content is less than 1.5%).

[0027] Compared with the prior art, the present invention is characterized in that:

[0028] 1. The nickel-iron atmospheric pressure acid leaching solution is used as a leaching agent to carry out high-pressure leaching of the upper low-grade high-iron and low-magnesium laterite nickel ore. On the one hand, the acid in the nickel-iron atmospheric pressure acid leaching solution is recycled; on the other hand, a large amount of ferrous ions in the nickel-iron atmospheric pressure acid leaching solution are oxidized to form ferric oxide and precipitated into the leaching residue to be removed, which realizes the efficient leaching of the low-grade high-iron and low-magnesium laterite nickel ore and also enables the removal of iron in the nickel-iron atmospheric pressure acid leaching solution; furthermore, the nickel-cobalt leaching rate of this method is high, because a large amount of ferrous ions in the nickel-iron atmospheric pressure acid leaching solution are oxidized to form ferric oxide and precipitated into the leaching residue, which also increases the grade of iron in the leaching residue (compared with using sulfuric acid as a leaching agent), which is more conducive to the use of the leaching residue as iron ore.

[0029] 2. Compared with sulfuric acid as a leaching agent, the leaching temperature required to achieve the same leaching rate using nickel-iron atmospheric pressure acid leaching liquid as a leaching agent is lower. A specific experiment by the applicant shows that the leaching rate of nickel and cobalt can reach 97% when leaching at 230°C using the method of the present invention; when sulfuric acid is used as a leaching agent, the temperature required to achieve this leaching rate is about 250°C. DETAILED DESCRIPTION

[0030] In order to better explain the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0031] The ferronickel acid leaching solution used in the following embodiments is obtained by leaching ferronickel powder (100 mesh sieve, quantitative analysis of chemical composition shows that the nickel content is 5.63% and the iron content is 69.29%) obtained by reduction roasting of high-grade magnesium-containing laterite nickel ore in a rotary kiln and then magnetic separation using concentrated sulfuric acid according to the following process:

[0032] Take nickel iron powder and use concentrated sulfuric acid to leach at normal pressure. During leaching, the temperature is controlled to be 85°C, the acid (sulfuric acid) material (nickel iron powder) ratio is controlled to be 200% by mass, the liquid (all liquids, including water and sulfuric acid) solid (nickel iron powder) ratio is 6mL:1g, and the leaching time is 8h to obtain nickel iron atmospheric pressure acid leaching solution. The effective sulfuric acid concentration in the acid leaching solution is 1.2mol / L, and the concentrations of iron, nickel, cobalt, and chromium ions are 61.316g / L, 4.938g / L, 0.147g / L, and 3.796g / L, respectively.

[0033] The laterite nickel ore used for leaching nickel and cobalt in the following embodiments is a limonitic laterite nickel ore, and its composition, by mass percentage, contains Ni 0.83%, Fe 44.97%, Co 0.07%, Mg 1.02%, Si 1.34%, Al2O3 3.08%, Ca0.06%, and Mn 0.69%.

[0034] In the following embodiments, leaching is performed in an autoclave. After leaching is completed, the material is discharged, filtered, and the filtrate and leached residue are collected respectively. The leached residue is washed and dried to detect the nickel and cobalt ion contents. During the leaching process, the nickel, cobalt and magnesium in the laterite nickel ore enter the solution (a small amount of aluminum also enters the solution), and the iron remains in the leached residue. The obtained filtrate can be sent to a subsequent nickel-cobalt recovery process, and the obtained leached residue is used as an iron concentrate product or further used to produce an iron product after desulfurization.

[0035] The method for detecting the concentration of nickel ions and cobalt ions in the leached residue is as follows: take 2.0g of the filter residue in a conical flask, pour in aqua regia, keep heating until the leached residue is completely melted (about 4-5 hours), cool and filter, collect the filtrate and place it in a volumetric flask and make up the volume, and then the concentration and content of the metal nickel and cobalt in the solution can be obtained through ICP detection. The leaching rate of metal nickel and cobalt in laterite nickel ore can be calculated from this.

[0036] Calculation method for iron grade in leaching slag: The mass of iron element in the leaching slag is obtained through chemical element analysis, and then divided by the total mass of the leaching slag to obtain the iron grade in the leaching slag.

[0037] Example 1

[0038] The laterite nickel ore was leached under high pressure using nickel-iron atmospheric pressure acid leaching solution as the leaching agent. The leaching conditions were: oxygen partial pressure of 0.2 MPa, temperature of 230°C, acid (sulfuric acid) ore (limonitic laterite nickel ore) ratio of 268.8 g / Kg, liquid (total amount of sulfuric acid and water) solid (limonitic laterite nickel ore) ratio of 3 mL:1 g, leaching time of 1 h, and rotation speed of 400 rpm.

[0039] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 96.8%, the leaching rate of cobalt is 96.2%, and the iron grade in the leached slag is 52.3%.

[0040] Comparative Example 1-1

[0041] Using sulfuric acid as the leaching agent, high pressure leaching of laterite nickel ore was carried out under the same leaching conditions as in Example 1.

[0042] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 95.2%, the leaching rate of cobalt is 94.3%, and the iron grade in the leached slag is 52.1%.

[0043] Comparative Example 1-2

[0044] The laterite nickel ore was leached under high pressure using sulfuric acid as the leaching agent. The leaching conditions were: oxygen partial pressure of 0.2 MPa, temperature of 250°C, acid-ore ratio of 268.8 g / Kg, liquid-solid ratio of 3 mL:1 g, leaching time of 1 h, and rotation speed of 400 rpm.

[0045] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 96.6%, the leaching rate of cobalt is 96.4%, and the iron grade in the leached slag is 53.6%.

[0046] Example 2

[0047] Example 1 was repeated, except that the acid-ore ratio during leaching was changed to 230.5 g / Kg.

[0048] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 82.1%, the leaching rate of cobalt is 95.2%, and the iron grade in the leached slag is 53.8%.

[0049] Example 3

[0050] Example 1 was repeated, except that the leaching temperature was changed to 250°C during leaching.

[0051] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 98.2%, the leaching rate of cobalt is 97.1%, and the iron grade in the leached slag is 53.3%.

[0052] Example 4

[0053] High-pressure leaching of laterite nickel ore was carried out using a combination of nickel-iron atmospheric pressure acid leaching solution and sulfuric acid as a leaching agent (the total acid content of the leaching agent was 260 g / Kg, of which the concentration of sulfuric acid was 25 g / L). The leaching conditions were: oxygen partial pressure of 0.2 MPa, temperature of 250°C, acid-ore ratio of 260 g / Kg (the total acid content of the leaching agent was 260 g / Kg, of which the concentration of sulfuric acid was 25 g / L), liquid-solid ratio of 3 mL:1 g, leaching time of 1 h, and rotation speed of 400 rpm.

[0054] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 96.8%, the leaching rate of cobalt is 94.8%, and the iron grade in the leached slag is 53.6%.

[0055] Example 5

[0056] High-pressure leaching of laterite nickel ore was carried out using a combination of nickel-iron atmospheric pressure acid leaching solution and sulfuric acid as a leaching agent (the total acid content of the leaching agent was 260 g / Kg, of which the concentration of sulfuric acid was 45 g / L). The leaching conditions were: oxygen partial pressure of 0.2 MPa, temperature of 250°C, acid-ore ratio of 260 g / Kg (the total acid content of the leaching agent was 260 g / Kg, of which the concentration of sulfuric acid was 45 g / L), liquid-solid ratio of 3 mL:1 g, leaching time of 1 h, and rotation speed of 400 rpm.

[0057] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 98.0%, the leaching rate of cobalt is 96.9%, and the iron grade in the leached slag is 54.2%.

[0058] Example 6

[0059] The laterite nickel ore was leached under high pressure with nickel-iron atmospheric pressure acid leaching solution. The leaching conditions were: oxygen partial pressure of 0.3 MPa, temperature of 220°C, acid-ore ratio of 250 g / Kg, liquid-solid ratio of 4 mL:1 g, leaching time of 50 min, and rotation speed of 300 rpm.

[0060] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 93.7%, the leaching rate of cobalt is 92.5%, and the iron grade in the leached slag is 53.4%.

[0061] Example 7

[0062] The laterite nickel ore was leached under high pressure with nickel-iron atmospheric pressure acid leaching solution. The leaching conditions were: oxygen partial pressure of 0.1 MPa, temperature of 240°C, acid-ore ratio of 270 g / Kg, liquid-solid ratio of 6 mL:1 g, leaching time of 40 min, and rotation speed of 400 rpm.

[0063] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 97.0%, the leaching rate of cobalt is 96.4%, and the iron grade in the leached slag is 54.1%.

[0064] Example 8

[0065] The laterite nickel ore was leached under high pressure with nickel-iron atmospheric pressure acid leaching solution. The leaching conditions were: oxygen partial pressure of 0.6 MPa, temperature of 250°C, acid-ore ratio of 250 g / Kg, liquid-solid ratio of 3 mL:1 g, leaching time of 1 h, and rotation speed of 400 rpm.

[0066] According to calculation, in this example, the leaching rate of nickel in the laterite nickel ore is 98.5%, the leaching rate of cobalt is 97.2%, and the iron grade in the leached slag is 53.8%.

Claims

1. A method for removing iron from laterite nickel ore by leaching ferronickel, characterized in that: The laterite nickel ore is subjected to high pressure leaching using nickel-iron atmospheric pressure acid leaching solution or a combination of nickel-iron atmospheric pressure acid leaching solution and sulfuric acid as a leaching agent, and the leaching conditions are: oxygen partial pressure of 0.1-0.6Mpa, temperature of 220-260°C, acid-ore ratio of 230-310g / Kg, liquid-solid ratio of 2-6mL:1g; wherein, Nickel-iron atmospheric pressure acid leaching solution is obtained by leaching the nickel-iron product obtained from laterite nickel ore by pyrometallurgical process with sulfuric acid at atmospheric pressure.

2. The method according to claim 1, characterized in that: The nickel-iron atmospheric pressure acid leaching solution is obtained by leaching the nickel-iron product obtained by reduction roasting of laterite nickel ore in a rotary kiln and then magnetic separation with sulfuric acid at atmospheric pressure.

3. The method according to claim 1, characterized in that: The nickel-iron atmospheric pressure acid leaching solution is obtained by leaching the nickel-iron product obtained by reducing and roasting the laterite nickel ore containing high-grade magnesium in a rotary kiln and then magnetically separating it with sulfuric acid at atmospheric pressure.

4. The method according to any one of claims 1 to 3, characterized in that: The high pressure leaching time is greater than or equal to 30 minutes.

5. The method according to any one of claims 1 to 3, characterized in that: The high-pressure leaching time is 50 to 60 minutes.

6. The method according to any one of claims 1 to 3, characterized in that: The acid-ore ratio during high-pressure leaching is 250-270 g / Kg.

7. The method according to any one of claims 1 to 3, characterized in that: The liquid-to-solid ratio during high-pressure leaching is 3-4 mL:1 g.

8. The method according to any one of claims 1 to 3, characterized in that: The temperature during high pressure leaching is 230-250°C.