AU2019350100A1

AU2019350100A1 - Method for treating low-magnesium limonite type laterite nickel ore

Info

Publication number: AU2019350100A1
Application number: AU2019350100A
Authority: AU
Inventors: Yong DAN; Wei Liu; Lin Zhao; Peng Zhao
Original assignee: Sichuan Shunying Power Battery Mat Co Ltd
Current assignee: Sichuan Shunying Power Battery Material Co Ltd
Priority date: 2018-09-25
Filing date: 2019-06-24
Publication date: 2020-08-13
Anticipated expiration: 2039-06-24
Also published as: CU20200060A7; PH12020551380A1; AU2019350100B2; WO2020062964A1; CN109252056A; CU24629B1

Abstract

Disclosed in the present invention is a method for treating low-magnesium limonite type laterite nickel ore. The method specifically comprises the following seven steps: ore grinding pretreatment, nitric acid pressure leaching, neutralization for removing iron and aluminum, neutralization for precipitating nickel and cobalt, recovery of nickel and cobalt by resin column, ratio adjustment for solution, and evaporating concentration and drying. The selective use of a leaching agent and a pH regulator in a synergistic cooperation treatment process enables all steps in the whole process synergistically cooperate with each other so as to implement efficient and sufficient leaching and recovery of cobalt and nickel in the laterite nickel ore, and enables chemical agents added in the treatment process to cooperate with calcium and magnesium metals in the laterite nickel ore so as to all convert into a directly recyclable calcium magnesium nitrate mixed fertilizer, thereby implementing completely full utilization and treatment of resources, and solving the difficult problem in the past of comprehensive utilization of the low-magnesium limonite type laterite nickel ore. Moreover, substances discharged in the entire treatment process are all directly recyclable products, and no waste water/waste residue/waste gas is discharged. The method has simple and easily-controlled treatment steps, low energy consumption, low costs, and high industrial practical values.

Description

Specification

Method for treating a low-magnesium limonitic laterite-nickel ore

Technical Field The present invention relates to the technical fields of hydrometallurgy and chemical technology, and particularly to a treatment method for recycling a laterite-nickel ore resource. In particular, the present invention relates a comprehensive resourceful treatment method for leaching and recovering valuable metals such as cobalt, nickel and aluminum from a low-magnesium limonitic laterite-nickel ore having features of low magnesium and high iron, while recovering a calcium magnesium nitrate mixture which can be used as a fertilizer.

Background Art Nickel is a very important strategic material, and is mainly used in producing stainless steel, alloy, new energy batteries, and the like. Nickel products are widely used in aviation, aerospace, petrochemical industry, machine manufacturing, energy material, and the like. China lacks of nickel materials seriously, especially after 2016. With development of new energy automobiles, ternary lithium batteries are in great demand, and shortage of nickel metal becomes very severe. For the view of China's nickel refining production, the production of refined nickel in China can hardly meet domestic demand, and it is necessary to import refined nickel from abroad. The statistical data from General Administration of Customs show that: in 2007-2016, the import amounts of refined nickel and alloys thereof in China generally maintained a rapid growth, increasing from 105,300 tons to 370,700 tons, with a compound growth rate of 15.01%; in 2007-2016, the export amounts of refined nickel and alloys thereof in China are less than the import amounts, with an export amount of only 16,700 tons in 2016; and in 2007-2016, all the net import amounts of refined nickel and alloys thereof in China are positive values, and the difference between import amount and export amount is gradually increased in last two years, so China is always a net import country. In 2016, foreign dependence of refined nickel in China reached 42.48%, and thus the demand for refined nickel was dependent on import. The data issued from the United States Geological Survey in 2017 show that global proved nickel (calculated as nickel content in nickel ores) basic reserve is about 78 million tons, and the total amount of the resource is 0.13 billion tons, wherein about 60% of the basic reserve is laterite-nickel ore, while about 40% is nickel sulfide ore. Therefore, it is an urgent problem how to economically and efficiently extract nickel from a laterite-nickel ore. Existed technologies for extracting nickel from a laterite-nickel ore include a pyrometallurgy treatment process and a hydrometallurgy treatment process. (1) The pyrometallurgy treatment process is suitable for a mainly high-magnesium and high-silicon laterite-nickel ore, which contains more cobalt and nickel metals than a limonitic ore, and the ore produces a nickel-iron matte after the pyrometallurgy treatment. The pyrometallurgy treatment process has disadvantages of large energy consumption, strong dependence on electrical power, and low recovery of metals. (2) The hydrometallurgy treatment process can be divided into reduction roasting-atmospheric pressure ammonia leaching process or acid leaching process, and high pressure acid leaching process. Here, (a) the reduction roasting-ammonia leaching process is suitable for a limonitic ore. In the process, the former procedures of drying, roasting and reduction have a high energy consumption. Although the latter ammonia leaching process does not leach iron, it has disadvantages of large ammonia consumption, harsh work environment, difficult subsequent waste water treatment, and low recovery of metals of nickel and cobalt. (b) In the atmospheric pressure acid leaching process, although leaching rates of cobalt and nickel are increased, the process has disadvantages of high impurity leaching, especially in the case of high iron content, difficult iron treatment, large residue amount, large pressure imposed on environment, and great consumption of auxiliary materials, during the whole hydrometallurgy treatment. (c) The high pressure acid leaching process is suitable for treating a laterite-nickel ore with a low magnesium content (< 5%). The leaching process will consume a large amount of acid, but the leaching solution has a low iron content. Iron is mainly enriched in the leaching residue. In the case that the raw material has a high iron content, the iron content in the leaching residue can reach % or more. However, due to high sulfur content in the residue, it is difficult for this iron residue to be used as a steelmaking raw material, leading to great waste. In addition, since conventional high pressure leaching process is performed under a high leaching temperature and a large pressure, and results in high impurity leaching, the process has disadvantages of complex process, long flow, high requirements for autoclave and matched pressurizing device, and high equipment investment. Further, since the process uses a sulfuric acid system, it easily causes calcium and magnesium scaling in the high pressure device, leading to low use efficiency of the device. Therefore, the effect of using the high pressure sulfuric acid leaching process in the industry is not desirable. The low-magnesium limonitic laterite-nickel ore has features of low magnesium and high iron. Since the ore has a high iron content, the recovery of nickel and cobalt is low when using a conventional pyrometallurgy treatment. If a conventional hydrometallurgy treatment is used, the high pressure sulfuric acid leaching not only consumes a large amount of auxiliary materials, but also it is difficult to utilize the high iron leaching residue, resulting in great pollution on environment. Therefore, all conventional treatment processes cannot treat a low-magnesium limonitic laterite-nickel ore well. CN Patent No. CN106591579A discloses a method for performing an atmospheric leaching on a laterite-nickel ore. The method comprises: crushing the laterite-nickel ore, then adding sodium fluoride and water thereto, and fully mixing them to obtain a mixture; spraying concentrated sulfuric acid into the mixture, and performing an activation treatment under a self-heating condition to produce an activated material; performing an atmospheric pressure water leaching on the activated material to produce a leaching ore slurry; performing a thickening separation on the leaching ore slurry to obtain a leaching solution and a leaching residue; washing the leaching residue to obtain an iron residue; neutralizing the leaching solution with magnesium oxide to precipitate cobalt, so as to obtain a post-neutralization separated solution and a nickel cobalt hydroxide; and sequentially performing precipitation defluorination and evaporation crystallization on the post-neutralization separated solution to recover magnesium sulfate. In this patent, the final product of magnesium is magnesium sulfate hexahydrate. Since application demand for magnesium sulfate hexahydrate is low, the method has a disadvantage of poor practical applicability. CN Patent No. CN1718787 discloses a method for extracting nickel and cobalt from a low grade laterite-nickel ore by dump leaching. The method comprises: crushing the ore, directly transferring ore particles of 100 mesh-1.5 cm into a dump, while uniformly mixing ore particles with a particle diameter of less 100 mesh and ore particles with a particle diameter of larger than 1.5 cm in a mass ratio of 0.5-0.8:1 and transferring the mixture into the dump; spraying and dripping a spray solution with an acidity of 5-18% at a spray intensity of 15-30 L/m 2.h; collecting a leaching solution after spraying and dripping and adjusting the leaching solution, such that the leaching solution has a nickel iron concentration of 2-4 g/L, obtaining a leaching solution containing nickel and cobalt. In this method, the leaching rate of nickel is around 70%, and there is a great waste of resource. CN Patent No. CN106673071A discloses a method for treating a laterite-nickel ore acid leaching solution by removing iron while producing a black iron oxide pigment. The method comprises: performing an atmospheric pressure leaching with sulfuric acid, then converting iron in the leaching solution into a black iron oxide pigment product, then precipitating nickel and cobalt, and finally evaporation crystallizing a solution containing magnesium sulfate to produce magnesium sulfate hexahydrate. Although this method solves the problem of a large number of iron residue produced in sulfuric acid leaching, the requirement for parameter control node in the process is high, which is not beneficial for industrialized application. Sometimes, magnesium sulfate hexahydrate has a disadvantage of poor practical applicability. In summary, all treatments on a laterite-nickel ore in the existed technologies have problems such as large energy consumption, severe equipment corrosion, low recovery of metals of nickel and cobalt, difficult treatment of residue or waste water produced in the process, and low application demand for the final product.

Summary The present invention provides a method for treating a low-magnesium limonitic laterite-nickel ore. In views of the features of high iron and low magnesium of the low-magnesium limonitic laterite-nickel ore, this method specially uses nitric acid pressurized leaching, in combination with resin adsorption, as well as using compounds such as calcium oxide and magnesium oxide as an acid-base modifier. After recovering cobalt and nickel metals by acid leaching and adsorption, the solution is subjected to evaporation concentration and drying treatment to obtain a calcium magnesium nitrate mixture, which can be directly recycled as a fertilizer. The whole treatment method can achieve efficient leaching recover of cobalt, nickel and iron in the laterite-nickel ore, and enable all chemical agents added in the treatment process to cooperate with calcium and magnesium metals in the laterite-nickel ore to fully convert them into a calcium magnesium nitrate mixed fertilizer which can be directly recycled. Nickel, cobalt, iron, calcium and magnesium in the raw material are respectively made into products, achieving complete and sufficient utilization of the resource. The method has features such as high leaching rates, easy liquid-solid separation after leaching, simple process, convenient operation, low energy consumption, low auxiliary agent consumption, and no environmentpollution. In order to achieve the above object, the present invention provides the following technical solutions. A method for treating a low-magnesium limonitic laterite-nickel ore, comprising steps of: (1) pretreatment: crushing the low-magnesium limonitic laterite-nickel ore, wherein the treated ore particles with a particle size of 120-160 tm accounts for 80-90% or more of the total ore particles; (2) pressurized leaching: mixing the pretreated ore with a nitric acid solution in a ratio, with nitric acid as a leaching agent, then heating the mixture in an autoclave to increase temperature, stirring the mixture, and performing a pressurized leaching on the mixture, wherein an amount of nitric acid used is 0.4-1.2 g HNO 3/gore, a mass ratio of the nitric acid solution to the ore is 3-8:1, a pressurized leaching temperature is 150-250°C, a stirring speed is 300-600 rpm, a leaching time is 50-150 min, and a pressure is 0.8-1.4 MPa;

(3) removal of iron and aluminum by neutralization: adding calcium oxide or magnesium oxide as a neutralizer into the solution obtained after the leaching to control a solution pH between 3.0-4.0, so as to remove iron and aluminum by precipitation, wherein the treated solution has an iron content of less than 0.05 g/L and an aluminum content of less than 0.05 g/L; (4) precipitation of nickel and cobalt by neutralization: adding calcium oxide or magnesium oxide into the solution with iron and aluminum removed to adjust a pH between 5-7, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, wherein nickel and cobalt contents in the solution are 0.005 g/L or less after precipitation of nickel and cobalt, then dissolving and extracting the nickel hydroxide and the cobalt hydroxide to obtain a nickel-cobalt product; (5) Recovery of nickel and cobalt metals with a resin: adsorbing and recovering nickel and cobalt remained in the solution obtained after precipitation of nickel and cobalt with a resin column, such that leaching amounts of both nickel and cobalt in the solution obtained after adsorption and recovery with the resin column are less than 0.0002 g/L. (6) solution proportion adjustment: performing magnesium-calcium proportion and solution pH adjustments on the solution obtained after recovery of nickel and cobalt with a resin, such that the solution pH after adjustment is 7-8, and contents of calcium, magnesium and nitrogen elements in the solution after the adjustment are as follows: magnesium: 4.0-8.0%, calcium: 13.0-17.0%, and nitrogen: 11-15%; and (7) evaporation concentration and drying: subjecting the solution adjusted in Step (6) to evaporation concentration and spray drying treatments to obtain a calcium magnesium nitrate mixture. Here, the calcium magnesium nitrate mixutre refers to a mixture of calcium nitrate and magnesium nitrate. Further, the mixture can be directly used as a calcium magnesium nitrate mixed fertilizer product, and directly recycled. According to the above technical solution, the present invention can achieve high leaching rates of nickel and cobalt metals by using nitric acid as a leaching agent. The solution is purified and neutralized to precipitate nickel and cobalt, which can result in a high content nickel cobalt hydroxide product. The solution obtained after precipitation of nickel and cobalt has a low impurity content. The solution obtained after recovery of elements such as nickel and cobalt with a resin column is subjected to evaporation concentration and drying to obtain a calcium magnesium nitrate mixture. The method can efficiently treat the low-magnesium limonitic laterite-nickel ore. As a result, the leaching rates of nickel and cobalt metals are more than 95%, and the iron content of the leaching solution is less than 0.5 g/L. Iron is precipitated into the residue in a hematite form, and the washed residue has an iron content of -50% and a nitrogen content of less than 0.02%. The residue can be sold as an iron ore raw material. Calcium and magnesium in the solution are subjected to evaporation concentration and drying to obtain a calcium magnesium nitrate mixture, which can be directly sold as a fertilizer product. The whole treatment process can achieve sufficient leaching recovery of iron, aluminum, cobalt and nickel in the laterite-nickel ore, and has advantages of simple process and low energy consumption. The method also enables all chemical agents added in the treatment process to cooperate with calcium and magnesium metals in the laterite-nickel ore to fully convert them into a calcium magnesium nitrate mixture which can be directly recycled, so as to achieve complete and sufficient utilization and treatment of a resource, without any waste water/waste residue/waste gas discharged. The method is green and environment-friendly, and effectively solves the difficulty in comprehensive utilization of the low-magnesium limonitic laterite-nickel ore before.

Further, the low-magnesium limonitic laterite-nickel ore comprises: 0.02-0.15% of cobalt, 0.5-1.5% of nickel, 35-45% of iron, 0.1-1% of calcium, 0.54% of magnesium, 0.5-2% of aluminum, and 0.1-1% of silicon. Further preferably, in Step (1), the treated ore particles with a particle size of 150 tm accounts for 90% or more of the total ore particles. Preferably, the low magnesium limonitic ore is pretreated by crushing such that 90% or more of ore particles are powders with a particle size of 150 tm, which is more beneficial for combining with process parameter control in subsequent treating steps, achieving effective recycling of elements in the ore. Further preferably, in Step (2), the amount of nitric acid used is 0.8-1.0 g HNO3 /g ore, and the ratio of the nitric acid solution to the ore is 4-6:1. Further preferably, in Step (2), the pressurized leaching temperature is 200-250°C, and the pressurized leaching pressure is 0.8-1.0 MPa. Further preferably, a leaching residue obtained after the pressurized leaching in Step (2) is washed with water and filtered to obtain a filter residue with an iron content of 40-50% and a nitrogen content of less than 0.02%, wherein the filter residue can be recycled as an iron ore raw material. More preferably, a filtrate obtained after the leaching can be cycled to Step (1) for reuse. The method achieves the effect of no waste water discharge during the whole treatment method, while enabling sufficient and reasonable utilization of the resource. Further preferably, in Step (3) and Step (4), the solution obtained after the leaching and the solution with iron and aluminum removed respectively can be first heated to 60-80°C, and then subjected to a neutralization adjustment treatment. This is more beneficial for increasing the efficiency of adjustment by neutralization.

Further preferably, in Step (6), the pH of the solution and the contents of calcium, magnesium and nitrogen elements in the solution are adjusted by using magnesium oxide, calcium oxide, calcium nitrate and/or magnesium nitrate. Preferably, the pH of the solution is adjusted to 7-8 with alkaline compounds of magnesium oxide and calcium oxide and compounds of calcium nitrate and/or magnesium nitrate as a modifier, while the contents of calcium, magnesium and nitrogen elements in the solution are adjusted in the following range: magnesium: 4.0-8.0%, calcium: 13.0-17.0%, and nitrogen: 11-15%, and more preferably, magnesium: 5.0-7.0%, calcium: 14.0-16.0%, and nitrogen: 12-14%. The solution with pH and element contents adjusted is then subjected to evaporation concentration and drying treatment to produce a calcium magnesium nitrate mixture, which can be directly recycled as a calcium magnesium nitrate mixture product. Further preferably, in Step (3) and Step (4), the solution obtained after the leaching and the solution with iron and aluminum removed are preferably subjected to a neutralization adjustment treatment with calcium oxide as a neutralizer. Accordingly, in Step (6), the contents of calcium, magnesium and nitrogen elements in the solution and the solution pH are preferably adjusted with magnesium oxide, magnesium nitrate and/or calcium nitrate as a modifier. Further preferably, in Step (6), iron nitrate and iron oxide can be particularly used as a microelement modifier, in combination with remained trace amount of iron metal element in the solution in the treatment process of the present invention, such that the adjusted solution has an iron element content of 0.01-0.05%, so as to produce a calcium magnesium nitrate mixed fertilizer containing an amount of iron microelement, thereby further improving the efficacy value of the calcium magnesium nitrate mixed fertilizer.

Here, the calcium magnesium nitrate mixed fertilizer is a novel, completely water soluble, sustained release multipurpose fertilizer, suitable for use in mixing with most of agricultural chemicals. About 6% of water soluble magnesium contained therein can rapidly supplement magnesium to a crop, and increase the chlorophyll content in the crop body, facilitating the photosynthesis and improving the nucleic acid translation and protein synthesis. Calcium ions can adjust the pH of soil, and facilitate increase in crop's absorption of nitrogen, phosphorus and potassium in the soil, increasing the resistance of the crop, and thus are used a lot in agricultural production. As compared to the existed technologies, the present invention has the following advantageous effects. 1. According to the treatment method of the present invention, the method can achieve comprehensive and efficient recover and treatment of metal elements in the low-magnesium limonitic laterite-nickel ore, wherein the leaching rates of nickel and cobalt are more than 95%, and the iron content in the leaching solution is less than 0.5 g/L; iron is precipitated into the residue in a hematite form, and the washed residue has an iron content of 40-50% and a nitrogen content of less than 0.02%; the residue can be sold as an iron ore raw material; calcium and magnesium elements in the ore cooperate with salts of calcium nitrate and magnesium nitrate and chemical agents of calcium oxide and magnesium oxide added in the treatment method of the present invention, and are fully converted into a calcium magnesium nitrate mixture, which can be directly sold as a fertilizer product, through treatment; this completely enables a resourceful treatment, solving the difficulty in comprehensive utilization of a low-magnesium limonitic laterite-nickel ore before. 2. According to the treatment method of the present invention, the method can fully convert all chemical substances added in the treatment process into a calcium magnesium nitrate mixed fertilizer product which can be directly recycled; this effectively avoids the problem of secondary pollution due to the use of chemical agents in the treatment process, and indeed enables changing waste into valuables, thereby improving the economic and applicable value and environmental-friendliness of the ore treatment process. 3. According to the treatment method of the present invention, all substances discharged during the whole treating steps are byproducts which can be directly sold and used, and have high economical and applicable value; and the whole treatment process can achieve no waste water/waste residue/waste gas discharge and is very environmental-friendly. 4. According to the treatment method of the present invention, the whole method also has advantages of good leaching effect, simple process, low energy consumption, low production cost, and good industrial applicability.

Brief Description of Drawings Fig. 1 is a schematic process flow diagram of a method for treating a low-magnesium limonitic laterite-nickel ore according to an embodiment of the present invention.

Detailed Description The present invention will be further described in detail below with reference to experimental examples and particular embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is only limited to the following examples, but all technologies achieved based on the present disclosure fall within the scope of the present invention.

As shown in Fig. 1, the present invention provides a method for treating a low-magnesium limonitic laterite ore, comprising the following steps. (1) (Ore grinding) pretreatment: crushing the low-magnesium limonitic laterite-nickel ore, wherein the treated ore particles with a particle size of 100-150 tm accounts for 80-90% or more of the total ore particles. (2) Pressurized leaching (with nitric acid): mixing the pretreated ore with a nitric acid solution in a ratio, with nitric acid as a leaching agent, then heating the mixture in an autoclave to increase temperature, stirring the mixture, and performing a pressurized leaching on the mixture, wherein an amount of nitric acid used is 0.4-1.2 g HNO 3 /g ore, a ratio of the nitric acid solution to the ore is 3-8:1, a pressurized leaching temperature is 150-250°C, a stirring speed is 300-600 rpm, a leaching time is 50-150 min, and a pressure is 0.8-1.4 MPa. Here, an ore residue obtained after the pressurized leaching is washed with water and filtered to obtain a filter residue with an iron content of 40-50% and a nitrogen content of less than 0.02%, wherein the filter residue can be recycled as an iron ore raw material. A filtrate obtained after the washing can be directly returned to Step (2) for reuse. This enables sufficient and reasonable utilization of a resource, while achieving an effect of no waste water discharge during the whole treatment method. (3) Removal of iron and aluminum by neutralization: heating the solution obtained after the leaching to 60-80°C, and adding calcium oxide as a neutralizer thereto to control a solution pH between 3.0-4.0, so as to remove iron and aluminum by precipitation, wherein the treated solution has an iron content of less than 0.05 g/L and an aluminum content of less than 0.05 g/L.

(4) Precipitation of nickel and cobalt by neutralization: heating the solution with iron and aluminum removed to 60-80°C, and adding calcium oxide thereto to adjust a pH between 5-7, so as to obtain a nickel hydroxide-cobalt hydroxide product through precipitation, wherein nickel and cobalt contents in the solution are 0.005 g/L or less after precipitation of nickel and cobalt. Here, the nickel hydroxide-cobalt hydroxide product obtained in this step is then dissolved and extracted to further obtain a nickel-cobalt product. (5) Recovery of nickel and cobalt metals with a resin: adsorbing and recovering nickel and cobalt remained in the solution obtained after precipitation of nickel and cobalt with a resin column, such that leaching amounts of both nickel and cobalt in the solution obtained after adsorption and recovery with the resin column are less than 0.002 g/L. (6) Solution proportion adjustment: performing magnesium-calcium proportion and solution pH adjustments on the solution obtained after recovery of nickel and cobalt with a resin, such that the solution pH after adjustment is 7-8, and contents of elements in the solution after the adjustment are as follows: magnesium: 4.0-8.0%, calcium: 13.0-17.0%, nitrogen: 11-15%, and iron: 0.01-0.05%. Further preferably, in this step, magnesium oxide is preferably used as the neutralizer for adjusting the pH of the solution, and calcium nitrate, magnesium nitrate and/or iron nitrate are then used for adjusting the contents of elements in the solution. The solution pH is first adjusted in a range of 7-8, and then depending on the contents of calcium, magnesium, iron and nitrogen in the pH-adjusted solution, the contents of elements in the solution are adjusted in the following range by particularly using a neutral compound such as calcium nitrate, magnesium nitrate, and/or iron nitrate as a modifier: magnesium: 4.0-8.0%, calcium: 13.0-17.0%, nitrogen: 11-15%, and iron: 0.01-0.05%, and more preferably, magnesium: 5.0-7.0%, calcium: 14.0-16.0%, nitrogen: 12-14%, and iron: 0.01-0.05%. (7) Evaporation concentration and drying: then subjecting the solution adjusted in Step (6) to evaporation concentration and spray drying treatments to obtain a mixture of calcium nitrate and magnesium nitrate (abbreviated as calcium magnesium nitrate mixture). The mixture product can be directly sold and used as a calcium magnesium nitrate mixed chemical product. As seen from Fig. 1, in the whole treatment process of the treatment method of the present invention, all substances discharged are products which can be directly recycled. The method can really achieve no discharge of waste water, waste residue or waste gas, is economical and environmental-friendly, and has advantages of simple and easy to control treating steps, low energy consumption, low cost, and high industrial practical value. The above embodiments of the present invention will be described below with reference to the following practical treatment examples.

Example 1 This example provides a method for treating a low-magnesium limonitic laterite-nickel ore, particularly comprising that the metal element contents of the laterite ore used were as follows: cobalt: 0.055%, nickel: 0.96%, iron: 37.94%, calcium: 0.16%, magnesium: 1.87%, aluminum: 0.66%, and silicon: 0.35%. The treating steps were as follows. (1) The laterite ore was crushed and ball milled, and in the treated ore, particles with a particle size of 150 tm accounted for 91% of the total ore particles. (2) A leaching was performed on 0.5 kg of treated ore in a 10 L autoclave, wherein an amount of nitric acid used was 0.5 g HNO 3/gore, a liquid-to-solid ratio was 4:1, a leaching time was 60 min, a leaching temperature was 150°C, a stirring speed was 300 rpm, and a pressure was 0.88 MPa. Here, leaching rates were 96.27% for cobalt and 96.34% for nickel; a leaching solution contained 0.27 g/L of iron; and a leaching residue contained 44.63% of iron and 0.0088% of nitrogen after washing. (3) The solution obtained after the leaching was heated to 60-80°C, and calcium oxide was added thereto as a neutralizer to control a solution pH between 3.0-4.0, so as to remove iron and aluminum by precipitation, wherein the solution with iron and aluminum removed had an iron content of 0.014 g/L and an aluminum content of 0.023 g/L. (4) The solution with iron and aluminum removed was heated to -80°C, and calcium oxide was added to adjust a pH between 5-7, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, in which nickel and cobalt was precipitated to obtain nickel hydroxide and cobalt hydroxide precipitates; the solution obtained after precipitation of nickel and cobalt had a nickel content of 0.0038 g/L and a cobalt content of 0.002 g/L, and a nickel hydroxide-cobalt hydroxide residue (also known as nickel cobalt hydroxide residue) had a cobalt content of 0.86% and a nickel content of 31.26%. (5) Cobalt and nickel in the solution obtained after precipitation of nickel and cobalt were adsorbed with a resin, and then contents of both cobalt and nickel in the solution were 0.002 g/L or less. (6) A pH of the solution obtained after the recovery of nickel and cobalt with a resin was adjusted to 7-8 with magnesium oxide, and then the solution was subjected to evaporation concentration and spray drying to obtain a calcium magnesium nitrate mixture, wherein the calcium magnesium nitrate mixture contained 16.78% of calcium oxide, 6.59% of magnesium oxide, and 13.78% of nitrogen, and could be directly recycled as a calcium magnesium nitrate mixed fertilizer.

Example 2

This example provides a method for treating a low-magnesium limonitic laterite-nickel ore, particularly comprising that the metal element contents of the laterite ore used were as follows: cobalt: 0.063%, nickel: 1.12%, iron: 41.34%, calcium: 0.36%, magnesium: 2.67%, aluminum: 0.54%, and silicon: 0.51%. The treating steps were as follows. (1) The laterite ore was crushed and ball milled, and in the treated ore, particles with a particle size of 150 tm accounted for 93% of the total ore particles. (2) A leaching was performed on 0.5 kg of treated ore in a 10 L autoclave, wherein an amount of nitric acid used was 0.8 g HNO 3 /g ore, a liquid-to-solid ratio was 6:1, a leaching time was 90 min, a leaching temperature was 180°C, a stirring speed was 400 rpm, and a pressure was 0.96 MPa. Here, leaching rates were 97.16% for cobalt and 95.83% for nickel; a leaching solution contained 0.31 g/L of iron; and a leaching residue contained 45.63% of iron and 0.0062% of nitrogen after washing. After the removal of iron and aluminum, the solution had an iron content of 0.016 g/L and an aluminum content of 0.017 g/L. (3) The solution obtained after the leaching was heated to 60-80°C, and calcium oxide was added thereto as a neutralizer to control a solution pH between 3.0-4.0, so as to remove iron and aluminum by precipitation, wherein the solution with iron and aluminum removed had an iron content of 0.016 g/L and an aluminum content of 0.017 g/L. (4) The solution with iron and aluminum removed was heated to -80°C, and calcium oxide was added to adjust a pH between 5-7, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, in which nickel and cobalt was precipitated to obtain nickel hydroxide and cobalt hydroxide precipitates; the solution obtained after precipitation of nickel and cobalt had a nickel content of 0.0016 g/L and a cobalt content of 0.0011 g/L, and a nickel hydroxide-cobalt hydroxide residue (also known as nickel cobalt hydroxide residue) had a cobalt content of 0.92% and a nickel content of 32.14%. (5) Cobalt and nickel in the solution obtained after precipitation of nickel and cobalt were adsorbed with a resin, and then contents of both cobalt and nickel in the solution were 0.002 g/L or less. (6) A pH of the solution obtained after the recovery of nickel and cobalt with a resin was adjusted to 7-8 with magnesium oxide, and then the solution was subjected to evaporation concentration and spray drying to obtain a calcium magnesium nitrate mixture, wherein the calcium magnesium nitrate mixture contained 16.35% of calcium oxide, 6.23% of magnesium oxide, and 13.88% of nitrogen, and could be directly recycled as a calcium magnesium nitrate mixed fertilizer.

Example 3 This example provides a method for treating a low-magnesium limonitic laterite-nickel ore, particularly comprising that the metal element contents of the laterite ore used were as follows: cobalt: 0.071%, nickel: 1.24%, iron: 43.25%, calcium: 0.41%, magnesium: 3.64%, aluminum: 0.61%, and silicon: 0.72%. The treating steps were as follows. (1) The laterite ore was crushed and ball milled, and in the treated ore, particles with a particle size of 150 tm accounted for 96% of the total ore particles. (2) A leaching was performed on 0.5 kg of treated ore in a 10 L autoclave, wherein an amount of nitric acid used was 1.1 g HNO 3/gore, a liquid-to-solid ratio was 8:1, a leaching time was 120 min, a leaching temperature was 230°C, a stirring speed was 500 rpm, and a pressure was 1.12 MPa. Here, leaching rates were 95.32% for cobalt and 96.23% for nickel; a leaching solution contained 0.43 g/L of iron; and a leaching residue contained 46.87% of iron and 0.0031% of nitrogen after washing.

After the removal of iron and aluminum, the solution had an iron content of 0.031 g/L and an aluminum content of 0.0086 g/L. (3) The solution obtained after the leaching was heated to 60-80°C, and calcium oxide was added thereto as a neutralizer to control a solution pH between 3.0-4.0, so as to remove iron and aluminum by precipitation, wherein the solution with iron and aluminum removed had an iron content of 0.031 g/L and an aluminum content of 0.0086 g/L. (4) The solution with iron and aluminum removed was heated to -80°C, and calcium oxide was added to adjust a pH between 5-7, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, in which nickel and cobalt was precipitated to obtain nickel hydroxide and cobalt hydroxide precipitates; the solution obtained after precipitation of nickel and cobalt had a nickel content of 0.0013 g/L and a cobalt content of 0.0012 g/L, and a nickel cobalt hydroxide residue had a cobalt content of 1.012% and a nickel content of 33.35%. (5) Cobalt and nickel in the solution obtained after precipitation of nickel and cobalt were adsorbed with a resin, and then contents of both cobalt and nickel in the solution were 0.002 g/L or less. (6) A pH of the solution obtained after the recovery of nickel and cobalt with a resin was adjusted to 7-8 with magnesium oxide, and then the solution was subjected to evaporation concentration and spray drying to obtain a calcium magnesium nitrate mixture, wherein the calcium magnesium nitrate mixture contained 16.51% of calcium oxide, 6.18% of magnesium oxide, and 13.69% of nitrogen, and could be directly recycled as a calcium magnesium nitrate mixed fertilizer.

Example 4 This example provides a method for treating a low-magnesium limonitic laterite-nickel ore, particularly comprising that the metal element contents of the laterite ore used were as follows: cobalt: 0.15%, nickel: 1.24%, iron: 40.25%, calcium: 0.92%, magnesium: 3.64%, aluminum: 1.8%, and silicon: 0.5%. (1) The above laterite-nickel ore was crushed and ball milled, and in the treated ore, particles with a particle size of 160 tm accounted for 93% of the total ore particles. (2) A leaching was performed on 0.5 kg of treated ore in a 10 L autoclave, wherein an amount of nitric acid used was 0.9 g HNO 3 /g ore, a liquid-to-solid ratio was 7:1, a leaching time was 120 min, a leaching temperature was 250°C, a stirring speed was 300 rpm, and a pressure was 0.95 MPa. Here, leaching rates were 96.02% for cobalt and 96.58% for nickel; a leaching solution contained 0.38 g/L of iron; and a leaching residue contained 48.23% of iron and 0.0027% of nitrogen after washing. (3) The solution obtained after the leaching was heated to 60°C, and magnesium oxide was added thereto as a neutralizer to control a solution pH = 3.0, so as to remove iron and aluminum by precipitation, wherein the solution with iron and aluminum removed had an iron content of 0.040 g/L and an aluminum content of 0.0075 g/L. (4) The solution with iron and aluminum removed was heated to °C, and calcium oxide was added to adjust a pH = 6, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, in which nickel and cobalt was precipitated to obtain nickel hydroxide and cobalt hydroxide precipitates; the solution obtained after precipitation of nickel and cobalt had a nickel content of 0.0011 g/L and a cobalt content of 0.0015 g/L, and a nickel hydroxide-cobalt hydroxide residue had a cobalt content of 1.25% and a nickel content of 35.42%. (5) Cobalt and nickel in the solution obtained after precipitation of nickel and cobalt were adsorbed with a resin, and then contents of both cobalt and nickel in the solution were 0.002 g/L or less. (6) A pH of the solution obtained after the recovery of nickel and cobalt with a resin was adjusted to pH = 7 with magnesium oxide, calcium oxide, magnesium nitrate, calcium nitrate and iron nitrate, and at the same time, the contents of elements in the solution were adjusted as follows: magnesium: 8.0%, calcium: 13.0%, nitrogen: 12%, and iron: 0.02%. (7) Finally, the adjusted solution was subjected to evaporation concentration and spray drying to obtain a calcium magnesium nitrate mixture, wherein the calcium magnesium nitrate mixture contained 13.0% of calcium oxide, 8.0% of magnesium oxide, 12% of nitrogen, and 0.02% of iron, and could be directly recycled as a calcium magnesium nitrate mixed fertilizer.

Example 5 This example provides a method for treating a low-magnesium limonitic laterite-nickel ore, particularly comprising that the metal element contents of the laterite ore used were as follows: cobalt: 0.071%, nickel: 1.24%, iron: 43.25%, calcium: 0.41%, magnesium: 3.64%, aluminum: 0.61%, and silicon: 0.72%. The treating steps were as follows. (1) The laterite ore was crushed and ball milled, and in the treated ore, particles with a particle size of 120 tm accounted for 94% of the total ore particles. (2) A leaching was performed on 0.5 kg of treated ore in a 10 L autoclave, wherein an amount of nitric acid used was 1.0 g HNO 3 /g ore, a liquid-to-solid ratio was 6:1, a leaching time was 120 min, a leaching temperature was 200°C, a stirring speed was 400 rpm, and a pressure was 1.0 MPa. Here, leaching rates were 95.32% for cobalt and 96.23% for nickel; a leaching solution contained 0.43 g/L of iron; and a leaching residue contained 46.87% of iron and 0.0031% of nitrogen after washing. (3) The solution obtained after the leaching was heated to 75°C, and magnesium oxide was added thereto as a neutralizer to control a solution pH = 4.0, so as to remove iron and aluminum by precipitation, wherein the solution with iron and aluminum removed had an iron content of 0.031 g/L and an aluminum content of 0.0086 g/L. (4) The solution with iron and aluminum removed was heated to °C, and magnesium oxide was added to adjust a pH = 6, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, in which nickel and cobalt was precipitated to obtain nickel hydroxide and cobalt hydroxide precipitates; the solution obtained after precipitation of nickel and cobalt had a nickel content of 0.0013 g/L and a cobalt content of 0.0012 g/L, and a nickel cobalt hydroxide residue had a cobalt content of 1.012% and a nickel content of 33.35%. (5) Cobalt and nickel in the solution obtained after precipitation of nickel and cobalt were adsorbed with a resin, and then contents of both cobalt and nickel in the solution were 0.002 g/L or less. (6) A pH of the solution obtained after the recovery of nickel and cobalt with a resin was adjusted to pH = 7.5 with calcium oxide, calcium nitrate and iron nitrate, and at the same time, the contents of elements in the solution were adjusted as follows: magnesium: 6.57%, calcium: 15.21%, nitrogen: 13.7%, and iron: 0.05%. (7) Finally, the adjusted solution was subjected to evaporation concentration and spray drying to obtain a calcium magnesium nitrate mixture, wherein the calcium magnesium nitrate mixture contained 15.20% of calcium oxide, 6.57% of magnesium oxide, 13.69% of nitrogen, and 0.048% of iron, and could be directly recycled as a calcium magnesium nitrate mixed fertilizer.

Example 6 This example provides a method for treating a low-magnesium limonitic laterite-nickel ore, particularly comprising that the metal element contents of the laterite ore used were as follows: cobalt: 0.071%, nickel: 1.24%, iron: 43.25%, calcium: 0.41%, magnesium: 3.64%, aluminum: 0.61%, and silicon: 0.72%. The treating steps were as follows. (1) The laterite ore was crushed and ball milled, and in the treated ore, particles with a particle size of 140 tm accounted for 97% of the total ore particles. (2) A leaching was performed on 0.5 kg of treated ore in a 10 L autoclave, wherein an amount of nitric acid used was 1.0 g HNO 3 /g ore, a liquid-to-solid ratio was 3:1, a leaching time was 120 min, a leaching temperature was 160°C, a stirring speed was 600 rpm, and a pressure was 1.4 MPa. Here, leaching rates were 95.32% for cobalt and 96.23% for nickel; a leaching solution contained 0.43 g/L of iron; and a leaching residue contained 46.87% of iron and 0.0031% of nitrogen after washing. (3) The solution obtained after the leaching was heated to 80°C, and calcium oxide was added thereto as a neutralizer to control a solution pH = 3.5, so as to remove iron and aluminum by precipitation, wherein the solution with iron and aluminum removed had an iron content of 0.031 g/L and an aluminum content of 0.0086 g/L. (4) The solution with iron and aluminum removed was heated to 76°C, and calcium oxide was added to adjust a pH = 5, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, in which nickel and cobalt was precipitated to obtain nickel hydroxide and cobalt hydroxide precipitates; the solution obtained after precipitation of nickel and cobalt had a nickel content of 0.0013 g/L and a cobalt content of 0.0012 g/L, and a nickel cobalt hydroxide residue had a cobalt content of 1.012% and a nickel content of 33.35%. (5) Cobalt and nickel in the solution obtained after precipitation of nickel and cobalt were adsorbed with a resin, and then contents of both cobalt and nickel in the solution were 0.002 g/L or less. (6) A pH of the solution obtained after the recovery of nickel and cobalt with a resin was adjusted to pH = 8 with magnesium oxide, magnesium nitrate and iron nitrate, and at the same time, the contents of elements in the solution were adjusted as follows: magnesium: 5.82%, calcium: 16.24%, nitrogen: 15.0%, and iron: 0.03%. (7) Finally, the adjusted solution was subjected to evaporation concentration and spray drying to obtain a calcium magnesium nitrate mixture, wherein the calcium magnesium nitrate mixture contained 16.05% of calcium oxide, 5.81% of magnesium oxide, 14.98% of nitrogen, and 0.028% of iron, and could be directly recycled as a calcium magnesium nitrate mixed fertilizer. As seen from the experimental results of Examples 1-6, the treatment method of the present invention can efficiently treat the low-magnesium limonitic laterite-nickel ore. As a result, the leaching rates of nickel and cobalt metals are more than 95%, and the iron content of the leaching solution is less than 0.5 g/L. Iron is precipitated into the residue in a hematite form, and the washed residue has an iron content of 4 0 - 5 0 %. Calcium and magnesium in the solution are subjected to evaporation concentration and drying to obtain a calcium magnesium nitrate mixture, which can be directly sold as a fertilizer product. The method has advantages of good leaching effect, simple process, and low energy consumption. Nickel, cobalt, iron, calcium and magnesium in the raw material are respectively made into products. This completely enables a resourceful treatment, solving the difficulty in comprehensive utilization of a low-magnesium limonitic laterite-nickel ore before.

Claims

1. A method for treating a low-magnesium limonitic laterite-nickel ore, characterized in that, the method comprises steps of: (1) pretreatment: crushing the low-magnesium limonitic laterite-nickel ore, wherein the treated ore particles with a particle size of 120-160 tm accounts for 80-90% or more of the total ore particles; (2) pressurized leaching: mixing the pretreated ore with a nitric acid solution in a ratio, with nitric acid as a leaching agent, then heating the mixture in an autoclave to increase temperature, stirring the mixture, and performing a pressurized leaching on the mixture, wherein an amount of nitric acid used is 0.4-1.2 g HNO 3/gore, a mass ratio of the nitric acid solution to the ore is 3-8:1, a pressurized leaching temperature is 150250°C, a stirring speed is 300600 rpm, a leaching time is 50~150 min, and a pressure is 0.8~1.4 MPa; (3) removal of iron and aluminum by neutralization: adding calcium oxide or magnesium oxide as a neutralizer into the solution obtained after the leaching to control a solution pH between 3.0~4.0, so as to remove iron and aluminum by precipitation, wherein the treated solution has an iron content of less than 0.05 g/L and an aluminum content of less than 0.05 g/L; (4) precipitation of nickel and cobalt by neutralization: adding calcium oxide or magnesium oxide into the solution with iron and aluminum removed to adjust a pH between 5~7, so as to obtain nickel hydroxide and cobalt hydroxide through precipitation, wherein nickel and cobalt contents in the solution are 0.005 g/L or less after precipitation of nickel and cobalt, then dissolving and extracting the nickel hydroxide and the cobalt hydroxide to obtain a nickel-cobalt product;

(5) Recovery of nickel and cobalt metals with a resin: adsorbing and recovering nickel and cobalt remained in the solution obtained after precipitation of nickel and cobalt with a resin column, such that leaching amounts of both nickel and cobalt in the solution obtained after adsorption and recovery with the resin column are less than 0.0002 g/L. (6) solution proportion adjustment: performing magnesium-calcium proportion and solution pH adjustments on the solution obtained after recovery of nickel and cobalt with a resin, such that the solution pH after adjustment is 7-8, and contents of calcium, magnesium and nitrogen elements in the solution after the adjustment are as follows: magnesium: 4.0~8.0%, calcium: 13.0~17.0%, and nitrogen: 11~15%; and (7) evaporation concentration and drying: subjecting the solution adjusted in Step (6) to evaporation concentration and spray drying treatments to obtain a calcium magnesium nitrate mixture.

2. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, the low-magnesium limonitic laterite-nickel ore comprises: 0.02-0.15% of cobalt, 0.5-1.5% of nickel, 35-45% of iron, 0.1-1% of calcium, 0.5-4% of magnesium, 0.5-2% of aluminum, and 0.1-1% of silicon.

3. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (1), the treated ore particles with a particle size of 150 tm accounts for 90% or more of the total ore particles.

4. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (2), the amount of nitric acid used is 0.8~1.0 g HNO3 /g ore, and the mass ratio of the nitric acid solution to the ore is 4-6:1.

5. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (2), the pressurized leaching temperature is 200-25 0 °C, and the pressurized leaching pressure is 0.8~1.0 MPa.

6. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (2), a leaching residue obtained after the pressurized leaching treatment is washed with water and filtered to obtain a filter residue with an iron content of 40-50% and a nitrogen content of less than 0.02%, wherein the filter residue can be recycled as an iron ore raw material.

7. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 6, characterized in that, a filtrate obtained after the washing and filtering can be cycled to Step (1) for reuse.

8. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (3) and Step (4), the solution obtained after the leaching and the solution with iron and aluminum removed respectively can be first heated to 60~80°C, and then subjected to a neutralization adjustment treatment.

9. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (6), the solution pH and the contents of calcium, magnesium and nitrogen elements in the solution are adjusted with magnesium oxide, calcium oxide, calcium nitrate and/or magnesium nitrate.

10. The method for treating a low-magnesium limonitic laterite-nickel ore according to claim 1, characterized in that, in Step (6), the contents of calcium, magnesium and nitrogen elements in the solution after the adjustment are as follows: magnesium: 5.0~7.0%, calcium: 14.0~16.0%, and nitrogen: 12~14%.