Method for removing ferrous iron from laterite-nickel ore by high-pressure acid leaching

Abstract

The present disclosure provides a method for removing ferrous iron from laterite-nickel ore by high-pressure acid leaching, comprising the following steps: S1, pulping laterite-nickel ore, preheating the slurry, and mixing the slurry with a sulfuric acid compound and a nitric acid compound for heating, pressurizing and acid leaching to obtain an acid-leached slurry; and S2, carrying out flash evaporation on the acid-leached slurry to obtain a slurry leachate, wherein steam generated by flash evaporation is used for the preheating process of the slurry in step S1.

Description

A method for removing ferrous iron from laterite nickel ore by high-pressure acid leaching Technical Field

[0001] The present invention belongs to the field of nonferrous metal smelting, and particularly relates to a method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore. Background Art

[0002] Nickel and cobalt, as strategic metals, are mainly used in the production of stainless steel, high-temperature alloy steel, high-performance special alloys and positive electrode materials for lithium batteries. However, the resources of nickel sulfide ore are decreasing, while laterite nickel ore is accompanied by cobalt. Efficient and economical extraction of nickel and cobalt from laterite nickel ore has become the main method.

[0003] The laterite nickel ore processing technology is mainly divided into pyrometallurgy and wet processing. The wet processing is suitable for processing minerals with low nickel content such as limonitic laterite nickel ore. The wet processing has the advantages of low energy consumption, low cost, low pollution and the ability to recover cobalt at the same time. At present, high pressure acid leaching (HPAL) is the mainstream process for wet processing of laterite nickel ore. The laterite nickel ore generally used in the HPAL process is limonite, which has a high iron content (>40%) and a chromium content of 1% to 3%. Therefore, the Fe content in the HAPL leaching solution is reduced. 2+ or Cr 6+ High impurity content. There is a high concentration of Fe in the leachate. 2+ This will result in a large amount of subsequent impurity removal auxiliary materials, a large amount of waste residue, a long production process, and a high impurity content in the product. 6+ It is a poison if swallowed / extremely toxic if inhaled. If the leachate contains high concentrations of Cr 6+ , which is more likely to cause genetic defects and cancer in organisms, and is also a lasting danger to the environment; if Cr 6+ Entering the product will affect product prices and sales.

[0004] Existing wet treatment processes for laterite nickel ore often have disadvantages such as long process flow, long reaction time, high acid consumption, high impurity content, and low iron removal rate. Some processes use reducing agents to reduce hexavalent chromium during high-pressure acid leaching, but this process produces a large amount of ferrous iron, which increases the difficulty of impurity removal and may also produce flammable and explosive gases, resulting in poor safety.

[0005] Summary of the Invention

[0006] The present disclosure aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present disclosure proposes a method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore, which is environmentally friendly, requires minimal modification of existing process equipment, and is suitable for large-scale promotion.

[0007] According to a first aspect of the present disclosure, a method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore is proposed, comprising the following steps:

[0008] S1: preparing a pulp of laterite nickel ore, preheating the pulp, mixing it with sulfuric acid and nitric acid compounds, and subjecting it to a temperature- and pressure-elevated acid leaching treatment to obtain an acid-leached pulp;

[0009] S2: flash evaporating the acid leached slurry to obtain a slurry leachate, and the steam generated by the flash evaporation is used for the preheating process of the slurry in step S1.

[0010] The slurry leachate obtained after flash evaporation has a sulfuric acid concentration of 10-60 g / L; an iron content of 0.05-1 g / L; and a ferrous ion content of Fe 2+ The content of hexavalent chromium ion Cr is about 0.00g / L; 6+ The content is about 0.00g / L.

[0011] Nitric acid compounds have strong oxidizing properties in acidic environments and can be used as oxidants to oxidize Fe 2+ The generated nitrogen oxide gas enters the preheater along with the steam and reacts with oxygen and water in a high temperature environment to form nitric acid. That is, the nitric acid oxidant is recycled in the preheater, autoclave, and flash tank. The reactions that occur in this process are as follows:

[0012] Fe 2+ Oxidized to Fe 3+ After that, it is hydrolyzed and precipitated under high temperature and high pressure environment and removed; at the same time, the original MnO2 in the ore will remove Cr 3+ Oxidized to Cr 6+ , and Cr 6+ Fe 2+ Reduction to Cr 3+ , then Cr 3+ After hydrolysis at high temperature and high pressure, Cr 6+ and Fe 2+ The reaction that occurs during this process is as follows: 3Fe 2+ +Cr 6+ →3Fe 3+ +Cr 3+ 2Fe 3+ +3H2O=Fe2O3+6H + 2Cr 3+ +3H2O=Cr2O3+6H +

[0013] In some embodiments, in step S1, after the laterite nickel ore is slurried, it is ground to a particle size of less than 0.075 mm. The slurry has a better leaching effect at this particle size.

[0014] In some embodiments, in step S1, the concentration of the sulfuric acid is 90% to 98%. When concentrated sulfuric acid is added to the autoclave, a large amount of heat is released, causing the slurry to be heated to the temperature required for leaching.

[0015] In some embodiments, in step S1, the mass ratio of the sulfuric acid to the dry mass of the laterite nickel ore is 0.2 to 0.4:1. If the amount of sulfuric acid is too low, the leaching effect is poor; if the amount of sulfuric acid is too high, the Fe content in the slurry leachate will increase.

[0016] In some embodiments, in step S1, the nitric acid compound is at least one of nitric acid, calcium nitrate, magnesium nitrate, sodium nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate or iron nitrate. Under acidic conditions, the nitric acid compound has strong oxidizing properties and can 2+ Oxidized to Fe 3+ , and will not Cr 3+ Oxidized to Cr 6+ .

[0017] In some embodiments, in step S1, the mass ratio of the nitric acid compound to the dry ore mass of the laterite nickel ore is 0.001 to 0.05:1. When the nitric acid compound is nitric acid or a hydrate of a nitric acid compound, the mass of the pure nitric acid compound is used for calculation. If the amount of the nitric acid compound is too low, the Fe 2+ Completely oxidized to Fe 3+ .

[0018] In some embodiments, in step S1, when the nitric acid compound is nitric acid, the concentration of the nitric acid is 40% to 98%. If the concentration of nitric acid is too low, Fe 2+ Completely oxidized to Fe 3+ .

[0019] In some embodiments, in step S1, the liquid-to-solid ratio of the acid leaching is 2 to 10:1 mL / g.

[0020] In some embodiments, in step S1, the acid leaching temperature is 240-260°C; and / or the acid leaching time is 30-90 minutes; and / or the acid leaching pressure is 3.5-5.0 MPa. The above leaching conditions better balance production efficiency and leaching effect.

[0021] In some embodiments, in step S1, the heat source for acid leaching is steam, and the temperature of the steam is 240-300° C. The high-temperature steam is used to heat the slurry, and the heat released when sulfuric acid is added is used to bring the slurry to the leaching temperature.

[0022] In some embodiments, in step S1, the preheating is divided into primary, secondary, and tertiary preheating. Gradually increasing the temperature of the slurry is beneficial for controlling the pressure in the kettle and reducing safety accidents. It also facilitates the gradual utilization of the steam after flash evaporation, thereby improving steam utilization efficiency.

[0023] In some embodiments, the temperature range of the first stage preheating is room temperature to 105° C., the temperature range of the second stage preheating is 105 to 150° C., and the temperature range of the third stage preheating is 150 to 240° C. Performing multi-stage preheating within this temperature range can improve steam utilization.

[0024] In some embodiments, in step S2, the flash evaporation is divided into a primary flash evaporation, a secondary flash evaporation, and a tertiary flash evaporation. Multi-stage flash evaporation can improve the utilization rate of steam.

[0025] In some embodiments, the slurry temperature after the primary flash evaporation is 200-240°C; the slurry temperature after the secondary flash evaporation is 160-180°C; and the slurry temperature after the tertiary flash evaporation is 100-120°C. Heat and energy balance calculations show that steam utilization is maximized within this temperature range. The flash tank's unique structure allows the high-temperature slurry to boil at low pressure, generating steam that removes heat, thereby controlling the slurry temperature.

[0026] In some embodiments, the steam generated by the first-stage flash evaporation is used to increase the temperature of the third-stage preheating; the steam generated by the second-stage flash evaporation is used to increase the temperature of the second-stage preheating; and the steam generated by the third-stage flash evaporation is used to increase the temperature of the first-stage preheating. The steam generated by the flash evaporation is utilized step by step to improve the utilization rate of the steam.

[0027] In some embodiments, in step S2, the steam generated by the flash evaporation directly heats the slurry in step S1. The steam generated by the flash evaporation contains Fe 2 O 2+ The nitrogen oxide gas produced after the reaction with oxygen and water to generate nitric acid, which can continue to oxidize the Fe in the slurry. 2+ .

[0028] According to a second aspect of the present disclosure, a method for removing impurities from an ore is proposed, comprising the steps of the method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore described in the first aspect of the present disclosure.

[0029] According to one embodiment of the present disclosure, there are at least the following beneficial effects:

[0030] (1) In industrial production, oxidants such as manganese dioxide and sodium persulfate are often used to oxidize Fe 2+ , and excess oxidant will convert Cr in the solution 3+ Oxidized to Cr 6+ The present invention adopts steam and gas circulation to oxidize Fe with nitric acid compounds.2+ The nitrogen oxides produced are recycled and no Cr is produced. 6+ , and will not cause secondary pollution to the environment;

[0031] (2) The oxidant added in the present disclosure does not introduce new impurities into the solution system and has no effect on product quality;

[0032] (3) During the acid leaching process, Fe 2+ Oxidized to Fe 3+ , Fe 3+ In a high temperature and high pressure environment, Cr 6+ Reduction to Cr 3+ , achieving simultaneous removal of Cr 6+ and Fe 2+ The effect of Fe in solution 2+ , Cr 6+ Comply with environmental protection requirements, and the leaching rate of valuable metals in laterite nickel ore is not affected;

[0033] (4) The ferrous oxide process uses nitric acid compounds as auxiliary oxidants, which requires little change to the traditional production process, requires little equipment modification, requires little investment, and is easy to industrialize;

[0034] (5) The Fe content in the solution is reduced, the amount of auxiliary materials used in the production and impurity removal process is reduced, the production cost is reduced, and the amount of waste residue discharged is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present disclosure is further described below with reference to the accompanying drawings and embodiments, wherein:

[0036] FIG1 is a flow chart of embodiment 1 of the present disclosure. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the concept and technical effects of the present disclosure in conjunction with embodiments to fully understand the purpose, features and effects of the present disclosure.

[0038] The element contents of the laterite nickel ores described in the following examples and comparative examples are as follows:

[0039] Example 1

[0040] A method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore, as shown in FIG1 , comprises the following steps:

[0041] (1) Slurry preparation: the laterite nickel ore is washed and slurried with water at a solid-liquid ratio of 1:3, sieved through 50 mesh, the undersize is ball milled for 15 minutes, sieved through 200 mesh, the undersize is ≥90%, and the undersize is concentrated to a solid content of 30%;

[0042] (2) Slurry preheating: 1 kg of concentrated slurry with a solid content of 30% is fed into the first-stage preheater, the second-stage preheater, and the third-stage preheater in sequence using a high-pressure feed pump. The slurry is directly heated by steam. The first-stage preheater is heated to 110°C, the second-stage preheater is heated to 160°C, and the third-stage preheater is heated to 200°C.

[0043] (3) High-pressure acid leaching: The slurry after three-stage preheating is pumped into the autoclave through a high-pressure pump. Sulfuric acid with a concentration of 98% is added according to the acid-ore ratio of 250kg / t-dry ore. Nitric acid with a concentration of 69% is added in different proportions. Steam at 240-300°C is added to the reaction temperature of 255°C, the pressure is 4.0MPa, and the reaction time is 60min.

[0044] (4) Slurry flash evaporation: The slurry after high-pressure acid leaching is sequentially fed into a first-stage flash evaporation tank, a second-stage flash evaporation tank, and a third-stage flash evaporation tank using a high-pressure pump. The slurry temperature after the first-stage flash evaporation is 200°C, the slurry temperature after the second-stage flash evaporation is 160°C, and the slurry temperature after the third-stage flash evaporation is 110°C to obtain a slurry leachate. The steam generated by the flash evaporation directly heats the slurry in step (2). The third-stage flash evaporation steam heats the first-stage preheater, the second-stage flash evaporation steam heats the second-stage preheater, and the first-stage flash evaporation steam heats the third-stage preheater.

[0045] In step (3), 0%, 0.1%, 0.5%, 1% and 5% nitric acid by weight of the dry laterite nickel ore were added respectively, and the test results of the slurry leachate finally obtained are shown in Table 1:

[0046] Table 1

[0047] It can be seen from Table 1 that after adding nitric acid during the acid leaching process, the slurry leachate basically does not contain Fe 2+ and Cr 6+ , the content of iron and chromium dropped significantly, while the leaching rate of nickel and cobalt was basically unaffected. When the addition amount of nitric acid reached 5%, the concentration of residual acid in the solution was too high, which led to an increase in the content of Fe.

[0048] Example 2

[0049] A method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore is different from that of Example 1 in that a nitric acid compound is mixed with the concentrated ore pulp in step (2) and preheated, and the nitric acid compound is ferric nitrate nonahydrate. The specific steps are as follows:

[0050] (1) Slurry preparation: the laterite nickel ore is washed and slurried with water at a solid-liquid ratio of 1:3, sieved through 50 mesh, the undersize is ball milled for 15 minutes, sieved through 200 mesh, the undersize is ≥90%, and the undersize is concentrated to a solid content of 30%;

[0051] (2) Slurry preheating: 1 kg of concentrated slurry with a solid content of 30% is mixed with ferric nitrate nonahydrate in different proportions and fed into the first-stage preheater, second-stage preheater, and third-stage preheater in sequence using a high-pressure feed pump. The slurry is directly heated by steam, with the first-stage preheater heated to 110°C, the second-stage preheater heated to 160°C, and the third-stage preheater heated to 200°C.

[0052] (3) High-pressure acid leaching: The slurry after three-stage preheating is pumped into the autoclave through a high-pressure pump. Sulfuric acid with a concentration of 98% is added according to the acid-ore ratio of 250kg / t-dry ore. Steam at 240-300°C is added to the reaction temperature of 255°C, the pressure is 4.0MPa, and the reaction time is 60min.

[0053] (4) Slurry flash evaporation: The slurry after high-pressure acid leaching is sequentially fed into a first-stage flash evaporation tank, a second-stage flash evaporation tank, and a third-stage flash evaporation tank using a high-pressure pump. The slurry temperature after the first-stage flash evaporation is 200°C, the slurry temperature after the second-stage flash evaporation is 160°C, and the slurry temperature after the third-stage flash evaporation is 110°C to obtain a slurry leachate. The steam generated by the flash evaporation directly heats the slurry in step (2). The third-stage flash evaporation steam heats the first-stage preheater, the second-stage flash evaporation steam heats the second-stage preheater, and the first-stage flash evaporation steam heats the third-stage preheater.

[0054] In step (2), 0%, 0.1%, 0.5%, 1% and 5% of the weight of the dry laterite nickel ore were added to the slurry leachate, and the test results of the slurry leachate finally obtained are shown in Table 2:

[0055] Table 2

[0056] It can be seen from Table 2 that after adding more than 0.5% of the weight of laterite nickel ore into the preheating process, the slurry leachate contains almost no Fe. 2+ and Cr 6+ , the iron content dropped significantly, the chromium content also decreased to a certain extent, while the leaching rates of nickel and cobalt were basically unaffected.

[0057] Example 3

[0058] A method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore is different from that of Example 1 in that a nitric acid compound is mixed with the concentrated ore pulp in step (2) and preheated, and the nitric acid compound is ferrous nitrate hexahydrate. The specific steps are as follows:

[0059] (1) Slurry preparation: the laterite nickel ore is washed and slurried with water at a solid-liquid ratio of 1:3, sieved through 50 mesh, the undersize is ball milled for 15 minutes, sieved through 200 mesh, the undersize is ≥90%, and the undersize is concentrated to a solid content of 30%;

[0060] (2) Slurry preheating: 1 kg of concentrated slurry with a solid content of 30% is mixed with ferrous nitrate hexahydrate in different proportions and fed into the first-stage preheater, second-stage preheater, and third-stage preheater in sequence using a high-pressure feed pump. The slurry is directly heated by steam, with the first-stage preheater heated to 110°C, the second-stage preheater heated to 160°C, and the third-stage preheater heated to 200°C.

[0061] (3) High-pressure acid leaching: The slurry after three-stage preheating is pumped into the autoclave through a high-pressure pump. Sulfuric acid with a concentration of 98% is added according to the acid-ore ratio of 250kg / t-dry ore. Steam at 240-300°C is added to the reaction temperature of 255°C, the pressure is 4.0MPa, and the reaction time is 90min.

[0062] (4) Slurry flash evaporation: The slurry after high-pressure acid leaching is sequentially fed into a first-stage flash evaporation tank, a second-stage flash evaporation tank, and a third-stage flash evaporation tank using a high-pressure pump. The slurry temperature after the first-stage flash evaporation is 200°C, the slurry temperature after the second-stage flash evaporation is 160°C, and the slurry temperature after the third-stage flash evaporation is 110°C to obtain a slurry leachate. The steam generated by the flash evaporation directly heats the slurry in step (2). The third-stage flash evaporation steam heats the first-stage preheater, the second-stage flash evaporation steam heats the second-stage preheater, and the first-stage flash evaporation steam heats the third-stage preheater.

[0063] In step (2), 0%, 0.1%, 0.5%, 1% and 5% of the weight of the dry laterite nickel ore were added to the ferrous nitrate hexahydrate, and the test results of the slurry leachate finally obtained are shown in Table 3:

[0064] Table 3

[0065] It can be seen from Table 3 that after adding 0.5% or more of ferrous nitrate based on the weight of laterite nickel ore during the preheating process, the slurry leachate contains almost no Fe. 2+ and Cr 6+ , the iron content dropped significantly, the chromium content also decreased to a certain extent, while the leaching rates of nickel and cobalt were basically unaffected.

[0066] Example 4

[0067] A method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore is different from that of Example 1 in that a nitric acid compound is mixed with the concentrated ore pulp in step (2) and preheated, and the nitric acid compound is sodium nitrate. The specific steps are as follows:

[0068] (1) Slurry preparation: the laterite nickel ore is washed and slurried with water at a solid-liquid ratio of 1:3, sieved through 50 mesh, the undersize is ball milled for 15 minutes, sieved through 200 mesh, the undersize is ≥90%, and the undersize is concentrated to a solid content of 30%;

[0069] (2) Slurry preheating: 1 kg of concentrated slurry with a solid content of 30% is mixed with sodium nitrate in different proportions and fed into the first-stage preheater, second-stage preheater, and third-stage preheater in sequence using a high-pressure feed pump. The slurry is directly heated by steam. The first-stage preheater is heated to 110°C, the second-stage preheater is heated to 160°C, and the third-stage preheater is heated to 200°C.

[0070] (3) High-pressure acid leaching: The slurry after three-stage preheating is pumped into the autoclave through a high-pressure pump. Sulfuric acid with a concentration of 98% is added according to the acid-ore ratio of 250kg / t-dry ore. Steam at 240-300°C is added to the reaction temperature of 255°C, the pressure is 4.0MPa, and the reaction time is 60min.

[0071] (4) Slurry flash evaporation: The slurry after high-pressure acid leaching is sequentially fed into a first-stage flash evaporation tank, a second-stage flash evaporation tank, and a third-stage flash evaporation tank using a high-pressure pump. The slurry temperature after the first-stage flash evaporation is 200°C, the slurry temperature after the second-stage flash evaporation is 160°C, and the slurry temperature after the third-stage flash evaporation is 110°C to obtain a slurry leachate. The steam generated by the flash evaporation directly heats the slurry in step (2). The third-stage flash evaporation steam heats the first-stage preheater, the second-stage flash evaporation steam heats the second-stage preheater, and the first-stage flash evaporation steam heats the third-stage preheater.

[0072] In step (2), sodium nitrate was added at 0%, 0.1%, 0.5%, 1% and 5% of the weight of the dry laterite nickel ore, respectively. The test results of the slurry leachate finally obtained are shown in Table 4:

[0073] Table 4

[0074] As can be seen from Table 4, after adding more than 0.5% of sodium nitrate by weight of laterite nickel ore during the preheating process, the slurry leachate contains almost no Fe. 2+ and Cr 6+ , the iron content dropped significantly, the chromium content also decreased to a certain extent, while the leaching rates of nickel and cobalt were basically unaffected.

[0075] Example 5

[0076] A method for removing ferrous iron by high-pressure acid leaching of laterite nickel ore is different from that of Example 1 in that a nitric acid compound is mixed with the concentrated ore pulp in step (2) and preheated, and the nitric acid compound is calcium nitrate tetrahydrate. The specific steps are as follows:

[0077] (1) Slurry preparation: the laterite nickel ore is washed and slurried with water at a solid-liquid ratio of 1:3, sieved through 50 mesh, the undersize is ball milled for 15 minutes, sieved through 200 mesh, the undersize is ≥90%, and the undersize is concentrated to a solid content of 30%;

[0078] (2) Slurry preheating: 1 kg of concentrated slurry with a solid content of 30% is mixed with calcium nitrate tetrahydrate in different proportions and fed into the first-stage preheater, second-stage preheater, and third-stage preheater in sequence using a high-pressure feed pump. The slurry is directly heated by steam. The first-stage preheater is heated to 110°C, the second-stage preheater is heated to 160°C, and the third-stage preheater is heated to 200°C.

[0079] (3) High-pressure acid leaching: The slurry after three-stage preheating is pumped into the autoclave through a high-pressure pump. Sulfuric acid with a concentration of 98% is added according to the acid-ore ratio of 250kg / t-dry ore. Steam at 240-300°C is added to the reaction temperature of 255°C, the pressure is 4.0MPa, and the reaction time is 60min.

[0080] (4) Slurry flash evaporation: The slurry after high-pressure acid leaching is sequentially fed into a first-stage flash evaporation tank, a second-stage flash evaporation tank, and a third-stage flash evaporation tank using a high-pressure pump. The slurry temperature after the first-stage flash evaporation is 200°C, the slurry temperature after the second-stage flash evaporation is 160°C, and the slurry temperature after the third-stage flash evaporation is 110°C to obtain a slurry leachate. The steam generated by the flash evaporation directly heats the slurry in step (2). The third-stage flash evaporation steam heats the first-stage preheater, the second-stage flash evaporation steam heats the second-stage preheater, and the first-stage flash evaporation steam heats the third-stage preheater.

[0081] In step (2), 0%, 0.1%, 0.5%, 1% and 5% of calcium nitrate tetrahydrate by weight of the dry laterite nickel ore were added, and the test results of the slurry leachate finally obtained are shown in Table 5:

[0082] Table 5

[0083] It can be seen from Table 5 that after adding more than 0.5% of calcium nitrate by weight of laterite nickel ore during the preheating process, the slurry leachate contains almost no Fe. 2+ and Cr 6+ , the iron content dropped significantly, the chromium content also decreased to a certain extent, while the leaching rates of nickel and cobalt were basically unaffected.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that nitric acid is directly used as the acid solution to carry out high-pressure acid leaching on the laterite nickel ore, and the specific steps are as follows:

[0086] (1) Slurry preparation: the laterite nickel ore is washed and slurried with water at a solid-liquid ratio of 1:3, sieved through 50 mesh, the undersize is ball milled for 15 minutes, sieved through 200 mesh, the undersize is ≥90%, and the undersize is concentrated to a solid content of 30%;

[0087] (2) Slurry preheating: 1 kg of concentrated slurry with a solid content of 30% is fed into the first-stage preheater, the second-stage preheater, and the third-stage preheater in sequence using a high-pressure feed pump. The slurry is directly heated by steam. The first-stage preheater is heated to 110°C, the second-stage preheater is heated to 160°C, and the third-stage preheater is heated to 200°C.

[0088] (3) High-pressure acid leaching: The slurry after three-stage preheating is pumped into the autoclave through a high-pressure pump. Nitric acid with a concentration of 69% is added according to the acid-ore ratio of 250kg / t-dry ore. Steam at 240-300°C is added to the reaction temperature of 255°C, the pressure is 4.0MPa, and the reaction time is 60min.

[0089] (4) Slurry flash evaporation: The slurry after high-pressure acid leaching is sequentially fed into a first-stage flash evaporation tank, a second-stage flash evaporation tank, and a third-stage flash evaporation tank using a high-pressure pump. The slurry temperature after the first-stage flash evaporation is 200°C, the slurry temperature after the second-stage flash evaporation is 160°C, and the slurry temperature after the third-stage flash evaporation is 110°C to obtain a slurry leachate. The steam generated by the flash evaporation directly heats the slurry in step (2). The third-stage flash evaporation steam heats the first-stage preheater, the second-stage flash evaporation steam heats the second-stage preheater, and the first-stage flash evaporation steam heats the third-stage preheater.

[0090] The test results of the slurry leachate after flash evaporation are shown in Table 6:

[0091] Table 6

[0092] From the data of Comparative Example 1 and Examples 1 to 5, it can be seen that the leaching rates of valuable metals nickel and cobalt are higher when laterite nickel ore is leached under high-pressure acid leaching conditions using sulfuric acid and nitric acid compounds.

[0093] In addition, for nitric acid compounds, NO3 - The ions account for a small proportion per unit mass, so nitric acid compounds with a specific gravity of 0.1% or less cannot completely oxidize Fe within the reaction time (60 minutes). 2+ Due to Cr 6+ Will oxidize Fe 2+ , there is Fe in the solution 2+ In the case of Cr 6+ Excessive nitric acid or nitric acid compounds will not cause Cr to 3+ Oxidized to Cr 6+ .

Claims

1. A method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching, characterized in that, it includes the following steps: S1: Pulverize the laterite nickel ore, preheat the slurry, and then mix it with sulfuric acid and nitrate compounds, and carry out temperature-raising and pressure-raising acid leaching treatment to obtain an acid leaching pulp; S2: Carry out flash evaporation on the acid leaching pulp to obtain a slurry leaching solution, and the steam generated by the flash evaporation is used for the preheating process of the slurry described in step S1.

2. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, after the laterite nickel ore is pulped, it is ground to a particle size less than 0.075 mm.

3. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the concentration of the sulfuric acid is 90% - 98%.

4. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the mass ratio of the sulfuric acid to the dry ore mass of the laterite nickel ore is 0.2 - 0.4:

1.

5. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the nitrate compound is at least one of nitric acid, calcium nitrate, magnesium nitrate, sodium nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate or iron nitrate.

6. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the mass ratio of the nitrate compound to the dry ore mass of the laterite nickel ore is 0.001 - 0.05:

1.

7. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 5 or 6, characterized in that, in step S1, when the nitrate compound is nitric acid, the concentration of the nitric acid is 40% - 98%.

8. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the liquid-solid ratio of the acid leaching is 2 - 10:1 mL / g.

9. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the temperature of the acid leaching is 240 - 260 °C; and / or, the time of the acid leaching is 30 - 90 min; and / or, the pressure of the acid leaching is 3.5 - 5.0 MPa.

10. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the heat source of the acid leaching is steam, and the temperature of the steam is 240 - 300 °C.

11. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1, characterized in that, in step S1, the preheating is divided into primary preheating, secondary preheating and tertiary preheating.

12. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 11, characterized in that, in step S2, the flash evaporation is divided into primary flash evaporation, secondary flash evaporation and tertiary flash evaporation.

13. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 12, characterized in that, the steam generated by the primary flash evaporation is used for the temperature increase of the tertiary preheating; the steam generated by the secondary flash evaporation is used for the temperature increase of the secondary preheating; the steam of the tertiary flash evaporation is used for the temperature increase of the primary preheating.

14. The method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to claim 1 or 13, characterized in that, in step S2, the steam generated by flash evaporation directly heats the slurry described in step S1.

15. A method for extracting nickel and cobalt, characterized in that, it includes the steps of the method for removing ferrous ions from laterite nickel ore by high-pressure acid leaching according to any one of claims 1-14.

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