METHOD FOR PRODUCING FERRONICKEL AND REMOVING CHROMIUM FROM NICKEL LATERITE ORE

Abstract

Method for producing ferronickel and removing chromium from nickel laterite ore. This disclosure discloses a method for producing ferronickel and removing chromium from nickel laterite ore, comprising the following steps: (1) washing and separating the nickel laterite ore to obtain an ore slurry and mineral aggregate, adding an alkaline liquid and a bromate, and introducing oxygen into the ore slurry to enable oxidation leaching, and then carrying out solid-liquid separation to obtain a chromium-containing solid and filtrate; (2) washing and separating the solid obtained in step (1) to obtain a solid phase and wash water, and mixing the solid phase with quicklime and a reducing agent to obtain a mixture; and (3) roasting and smelting the mixture obtained in step (2) successively to obtain a finished ferronickel product.The method can achieve chromium enrichment and produce ferronickel by smelting nickel laterite ore while removing chromium impurities, which can protect the safety of a furnace.

Description

METHOD FOR PRODUCING FERRONICKEL AND REMOVING CHROMIUM FROM THE NICKEL LATERITE ORE TECHNICAL FIELD This disclosure pertains to the technical field of metallurgy and, in particular, relates to a method for producing ferronickel and removing chromium from nickel laterite ore. BACKGROUND With the widespread application of stainless and specialty steels worldwide, nickel, the most important element for smelting these steels, is becoming increasingly scarce and expensive. Traditionally, nickel is primarily extracted from nickel sulfide ores, which account for 30% of the world's nickel resources, and the corresponding production process is well-established. However, after nearly a century of continuous mining, nickel reserves are now insufficient, leading to a nickel resource crisis. Consequently, nickel laterite ores (nickel oxide ores), which represent 70% of the world's nickel resources, have attracted attention, and attempts have been made to extract nickel from this mineral. Nickel laterite ore is a loose, clay-like aggregate containing oxides of nickel, iron, magnesium, cobalt, silicon, aluminum, and similar elements. It forms due to the prolonged geological weathering of a nickel-bearing olivine bedrock. The iron in nickel laterite is in a +3 valence state due to intense oxidation, which explains its generally reddish-brown color, hence its name. Currently, nickel laterite ore is primarily produced through a calcination process (mainly a ferronickel production process in a rotary kiln-electric furnace (RKEF)) and a wet process (primarily a high-pressure acid leaching process). Because nickel laterite ore often contains carbon (C₂O₃) and chromium has a very high melting point, the nickel-chromium molten iron produced during pyrometallurgical processes has high viscosity and therefore cannot flow easily, resulting in serious consequences such as furnace condensation and furnace destruction. Many companies and research institutions have conducted extensive research on a process to produce ferronickel in a single-stage blast furnace from nickel laterite ore, but so far the process has not been successfully developed. The wet process, especially high-pressure acid leaching, will cause corrosion in the equipment, and the spinel-like chromite in nickel laterite ore also has a strong abrasive effect on the equipment.Therefore, when nickel laterite ore is subjected to the wet process, expensive corrosion-resistant equipment is required, which increases equipment costs and carries unpredictable safety risks. Therefore, whether in the wet process or the pyrometallurgical process, nickel laterite ore needs to undergo chromium removal; that is, chromite must be removed from the nickel laterite ore through a chromium removal process. However, in an actual smelting process, chromium, as an important metallic element, is mostly discarded. Therefore, full utilization of resources cannot be achieved. In particular, during the pyrometallurgical process, ferronickel smelting has High chromium content requirements in nickel laterite ore (the chromium content must not exceed 0.1%). Therefore, there is an urgent need for a process that can remove chromium during the smelting of nickel laterite ore and obtain a concentrate of qualified chromium while removing chromium, which achieves utilization comprehensive resource management and facilitate the full use of chromium resources. SUMMARY This disclosure aims to solve at least one of the existing technical problems in the prior art. In view of this, this disclosure provides a method for producing ferronickel and removing The method can achieve chromium enrichment and produce ferronickel by smelting the nickel laterite ore. of nickel laterite while removing chromium impurities, which can protect furnace safety and facilitate the full use of resources chrome. The above technical objective of this disclosure is achieved by the following technical solutions. A method for producing ferronickel and removing chromium is provided. of nickel laterite ore, which includes the following stages: (1) subject the nickel laterite ore to washing and mineral separation to obtain an ore slurry and an ore aggregate, add a alkaline liquid and a bromate and introduce oxygen into the mineral slurry to allow oxidation leaching and then carry out solid-liquid separation to obtain a solid and a filtrate containing chromium; (2) subjecting the solid obtained in step (1) to washing and solid-liquid separation to obtain a solid phase and wash water, and mixing the solid phase with quicklime and a reducing agent to obtain a mixture; and (3) subject the mixture obtained in step (2) to roasting and melting successively to obtain a finished ferronickel product. Preferably, in stage (1), the mineral slurry has a solid content of 10% to 25%. More preferably, in stage (1), the mineral slurry has a solid content of 15% to 20%. Preferably, the method also includes: subjecting the mineral aggregate obtained in stage (1) to crushing and re-separation in an agitator to obtain chrome concentrate and tailings, and returning the tailings for mineral washing. Preferably, the chromium-containing filtrate and the chromium concentrate can be sent to a chromium processing plant for further treatment. Preferably, in stage (1), the mineral aggregate is crushed to a particle size of less than 2 mm and then further separated in the agitator. More preferably, in step (1), the mineral aggregate is crushed to a particle size of less than 1.5 mm and then further separated in the agitator. Preferably, in stage (1), during reseparation in the agitator, the agitator has a water flow rate of 1 l / min to 5 l / min. More preferably, in stage (1), during reseparation in the agitator, the agitator has a water flow rate of 3 l / min to 4 l / min. Preferably, in stage (1), the nickel laterite ore is subjected to washing and ore separation in a cylindrical ore washer, a channel ore washer and a hydrocyclone successively, wherein the ore washing is done with water and the hydrocyclone yields nickel laterite ore with a particle size of 0.05 mm. Preferably, in stage (1) , for oxidation leaching, a mass ratio between alkaline liquid and bromate and ore slurry is (0.5-1) 1 (1-2) 1100. More preferably, in step (1) , for oxidation leaching, a mass ratio between alkaline liquid and bromate and ore slurry is (0.8-1) : (1-1.5) :100. Preferably, in stage (1), oxidation leaching is carried out in a closed state, and the oxygen pressure is from 1.5 MPa to 4 MPa. More preferably, in step (1), oxidation leaching is carried out under closed conditions, and the oxygen pressure is 2 MPa to 3 MPa. Preferably, in step (1), oxidation leaching is carried out at a temperature of 100 °C to 150 °C for 1 h 5 h. More preferably, in step (1), oxidation leaching is carried out at a temperature of 110 °C to 130 °C for 2 to 4 h. Preferably, in stage (1), oxidation leaching is carried out with stirring at a rotation speed of 100 r / min to 500 r / min. More preferably, in step (1), oxidation leaching is carried out with stirring at a rotation speed of 200 r / min to 300 r / min. Preferably, in step (1), the alkaline liquid is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide. Preferably, in step (1), the bromate is at least one selected from the group consisting of potassium bromate and sodium bromate. Preferably, the wash water obtained in stage (2) is returned to stage (1) for washing the ore. Preferably, in step (2), a mass ratio between quicklime and reducing agent and solid phase is (2-10) : (3-8) :100. More preferably, in step (2), a mass ratio between quicklime and reducing agent and solid phase is (4-10) : (4-8) :100. Preferably, in step (2), the reducing agent is at least one selected from the group consisting of anthracite and semi-coke. Preferably, in step (3), the mixture is further granulated to a particle size of 10 mm to 30 mm before toasting. More preferably, in step (3), the mixture is further granulated to a particle size of 15 mm to 20 mm before toasting. Preferably, in step (3), toasting is carried out at a temperature of 600 °C to 1000 °C for 10 min to 50 min. More preferably, in step (3), the roasting is carried out at a temperature of 800 °C to 900 °C for 20 min to 30 min. Preferably, in step (3), the melting is carried out at a temperature greater than or equal to 1,500 °C. More preferably, in step (3), the melting is carried out at a temperature greater than or equal to 1,600 °C. Preferably, a method is provided for producing ferronickel and removing chromium from nickel laterite ore, which includes the following steps: (1) subjecting the nickel laterite ore as raw ore to washing and mineral separation in a cylindrical ore washer, a channel ore washer and a hydrocyclone successively to obtain an ore slurry and an ore aggregate, wherein the ore washing is carried out with water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled between 15% and 20%; subjecting the ore slurry to oxidation leaching, subjecting the ore aggregate to crushing to a particle size of 1.5 mm or less and further separating it in an agitator with a water flow rate of 3 l / min to 4 l / min to obtain chrome concentrate and tailings, and returning the tailings to the ore washing process; (2) adding sodium hydroxide and a bromate (potassium / sodium bromate) to the ore slurry in a mass ratio of sodium hydroxide to bromate (potassium / sodium bromate) to the ore slurry of (0.8-1) : (1-1.5) : 100, introducing oxygen under an oxygen pressure of 2 MPa to 3 MPa, and under closed conditions, heating a resulting system from 110 °C to 130 °C to allow oxidation leaching for 2 to 4 h with stirring at a rotation speed of 200 rpm to 300 rpm; (3) after the oxidation leaching is completed in stage (2), carry out solid-liquid separation by means of a pressure filter to obtain a chromium-containing filtrate and a filter cake, and send the chromium-containing filtrate and the chromium concentrate to a chromium processing plant; (4) subject the filter cake to further washing with clean water and pressure filtration to obtain a liquid and a solid, and send the liquid for mineral washing and use the solid in the next stage; (5) mixing with quicklime, a reducing agent, and the solid obtained in step (4) in a mass ratio of (4-10) : (4-8) :100 and manufacturing from a resulting mixture granules with a particle size of 15 mm to 20 mm, wherein the reducing agent is at least one selected from the group consisting of anthracite and semi-coke; (6) subject the granules to roasting in a rotary calciner oven at a temperature of 800 °C to 900 °C for 20 to 30 min; and (7) subject the roasted granules to melting in an electric furnace at a temperature greater than or equal to 1,600 °C to obtain a finished ferronickel product. This disclosure has the following beneficial effects: (1) In the method for producing ferronickel and removing chromium from nickel laterite ore described herein, the nickel laterite ore is washed and separated to obtain an ore slurry and an ore aggregate. The ore slurry is then subjected to oxidation leaching. Due to the strong oxidizability of bromate under alkaline conditions and the use of oxygen for oxidation leaching, the chromium oxide is oxidized and dissolves in an alkaline solution to produce sodium chromate, thereby separating the chromium element. The method described herein further reduces the chromium content in a ferronickel smelter feedstock, protects a furnace, and reduces the chromium impurity content in the ferronickel. One reaction principle is as follows: Oxidation Leaching: 5Cr2O3+14NaOH+6NaBrO3^10Na2CrO4+3Br2+7H2O 6NaOH+3Br2^5NaBr+NaBrO3+3H2O 4NaBr+O2+2H2O=4NaOH+2Br2 2Cr2O3+8NaOH+3O2^4Na2CrO4+4H2O (2) In the method for producing ferronickel and removing chromium from nickel laterite ore of the present disclosure, after the ore slurry and mineral aggregate are obtained by washing and separating the ore, since the ore slurry has a low chromium content, oxidation leaching is used to extract the chromium element in the ore slurry in a leaching solution, and then the resulting mixture is subjected to solid-liquid separation; in addition to that, the mineral aggregate with a high chromium content is re-crushed and re-separated to obtain a chromium concentrate with a high density and tailings with a low chromium content, and the tailings can be returned to the ore washing procedure, thus avoiding a waste of resources. (3) In the method for producing ferronickel and removing chromium from nickel laterite ore described herein, the separation of the nickel laterite ore yields ferronickel while simultaneously extracting the element chromium, thereby reducing the chromium content in the finished ferronickel product. Additionally, the liquid resulting from washing the solid obtained after oxidation leaching is returned for ore washing, further reducing water consumption, achieving full resource utilization, and enhancing the mining value of the nickel laterite ore. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram illustrating a process flow of a method from Example 1 of this disclosure. DETAILED DESCRIPTION This disclosure is further described below along with specific examples. The particle size and composition of the nickel laterite ore used in Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1, where the term yield refers to the percentage of the relevant particle size in the total. Example 1: As shown in Figure 1, a method for producing ferronickel and removing chromium from nickel laterite ore was provided, which includes the following steps: (1) the nickel laterite ore as raw ore was subjected to a mineral washing in a cylindrical mineral washer, a mineral washer of channel, and a hydrocyclone successively and separation to obtain a mineral slurry and a mineral aggregate, wherein the washing of the mineral is carried out with Using water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled at 20%; the mineral slurry was subjected to oxidation leaching, the mineral aggregate was subjected to crushing to a particle size of 1.5 mm or less and was separated again in an agitator with a water flow rate of 4 l / min to obtain chrome concentrate and tailings, and the tailings were returned to the ore washing process; (2) Sodium hydroxide and sodium bromate were added to the ore slurry in a mass ratio between sodium hydroxide and sodium bromate and the 1:1, 5:100 mineral slurry, oxygen was introduced under an oxygen pressure of 3 MPa, and under closed conditions, the resulting system was heated to 130 °C to allow oxidation leaching for 2 h with stirring at a rotation speed of 200 r / min; (3) After the oxidation leaching was completed in stage (2), solid-liquid separation was carried out using a pressure filter to obtain a chromium-containing filtrate and a filter cake, and the chromium-containing filtrate and chromium concentrate were sent to a chromium processing plant; (4) The filter cake was subjected to further washing with clean water and pressure filtration to obtain a liquid and a solid, and the liquid was sent for ore washing and the solid was used in the next stage; (5) quicklime, semi-lime and the solid obtained in step (4) were mixed in a mass ratio of 10:8:100 and the resulting mixture was converted into granules with a particle size of 20 mm; (6) the granules were roasted in a rotary calciner oven at a temperature of 900 °C for 20 min; and (7) The roasted granules were melted in an electric furnace at a temperature of 1,600 °C to obtain a finished ferronickel product. Example 2: A method was provided for producing ferronickel and removing chromium from nickel laterite ore, which includes the following steps: (1) The nickel laterite ore as raw ore was subjected to ore washing in a cylindrical ore washer, a channel ore washer, and a hydrocyclone successively and separation to obtain an ore slurry and an ore aggregate, wherein the ore washing is carried out with water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled to 18%; the ore slurry was subjected to oxidation leaching, the ore aggregate was subjected to crushing to a particle size of 1.5 mm or less and was further separated in an agitator with a water flow rate of 3.5 l / min to obtain chrome concentrate and tailings, and the tailings were returned to the ore washing procedure; (2) Sodium hydroxide and sodium bromate were added to the ore slurry in a mass ratio of sodium hydroxide and sodium bromate to ore slurry of 0.9:1.3:100, oxygen was introduced under an oxygen pressure of 2.5 MPa, and under closed conditions, the resulting system was heated to 120 °C to allow oxidation leaching for 3 h with stirring at a rotation speed of 250 rpm; (3) After the oxidation leaching was completed in stage (2), solid-liquid separation was carried out using a pressure filter to obtain a chromium-containing filtrate and a filter cake, and the chromium-containing filtrate and chromium concentrate were sent to a chromium processing plant; (4) The filter cake was subjected to further washing with clean water and pressure filtration to obtain a liquid and a solid, and the liquid was sent for ore washing and the solid was used in the next stage; (5) quicklime, semi-lime and the solid obtained in step (4) were mixed in a mass ratio of 7:6:100 and the resulting mixture was converted into granules with a particle size of 17 mm; (6) the granules were roasted in a rotary calciner oven at a temperature of 850 °C for 25 min; and (7) The roasted granules were melted in an electric furnace at a temperature of 1,700 °C to obtain a finished ferronickel product. Example 3: A method was provided for producing ferronickel and removing chromium from nickel laterite ore, which includes the following steps: (1) The nickel laterite ore as raw ore was subjected to ore washing in a cylindrical ore washer, a channel ore washer, and a hydrocyclone successively and separation to obtain an ore slurry and an ore aggregate, wherein the ore washing is carried out with water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled to 15%; the ore slurry was subjected to oxidation leaching, the ore aggregate was subjected to crushing to a particle size of 1.5 mm or less and was further separated in an agitator with a water flow rate of 3 l / min to obtain chrome concentrate and tailings, and the tailings were returned to the ore washing procedure; (2) Sodium hydroxide and potassium bromate were added to the ore slurry in a mass ratio of sodium hydroxide to sodium bromate to ore slurry of 0.8:1:100, oxygen was introduced under an oxygen pressure of 2 MPa, and under closed conditions, the resulting system was heated to 110 °C to allow oxidation leaching for 4 h with stirring at a rotation speed of 300 r / min; (3) After the oxidation leaching in stage (2) was completed, solid-liquid separation was carried out using a pressure filter to obtain a filtrate containing chromium and a filter cake, and the filtrate containing chromium and the chromium concentrate were sent to a processing plant chrome; (4) The filter cake was subjected to additional washing with clean water and pressure filtration to obtain a liquid and a solid, and the liquid was sent for The washing of the mineral and the solid was used in the next stage; (5) quicklime, anthracite, and the solid obtained in step (4) were mixed into a mass ratio of 4:4:100 and the resulting mixture was turned into granules with a particle size of 15 mm; (6) the granules were subjected to roasting in a rotary calciner kiln at a temperature of 800 °C for 30 min; and (7) The roasted granules were melted in an electric furnace at a temperature of 1,800 °C to obtain a finished ferronickel product. Comparative Example 1 (which was different from Example 1 only in that oxygen High pressure was not introduced during the oxidation leaching of the slurry of mineral) A method was provided for producing ferronickel and removing chromium. of nickel laterite ore, which includes the following stages: (1) The nickel laterite ore as raw ore was subjected to ore washing in a cylindrical ore washer, an ore washer of channel, and a hydrocyclone successively and separation to obtain a mineral slurry and a mineral aggregate, wherein the washing of the mineral is carried out with Using water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled at 20%; the mineral slurry was subjected to oxidation leaching, the aggregate The ore was crushed to a particle size of 1.5 mm or less and further separated in an agitator with a water flow rate of 4 l / min to obtain chrome concentrate and tailings, and the tailings were returned to the ore washing process; (2) Sodium hydroxide and sodium bromate were added to the ore slurry in a mass ratio of sodium hydroxide and sodium bromate to ore slurry of 1:1, 5:100, and under closed conditions, the resulting system was heated to 130 °C to allow a reaction for 2 h with stirring at a rotation speed of 200 r / min; (3) After the oxidation leaching was completed in stage (2), solid-liquid separation was carried out using a pressure filter to obtain a chromium-containing filtrate and a filter cake, and the chromium-containing filtrate and chromium concentrate were sent to a chromium processing plant; (4) The filter cake was subjected to further washing with clean water and pressure filtration to obtain a liquid and a solid, and the liquid was sent for ore washing and the solid was used in the next stage; (5) quicklime, semi-lime and the solid obtained in step (4) were mixed in a mass ratio of 10:8:100 and the resulting mixture was converted into granules with a particle size of 20 mm; (6) the granules were roasted in a rotary calciner oven at a temperature of 900 °C for 20 min; and (7) The roasted granules were melted in an electric furnace at a temperature of 1,600 °C to obtain a finished ferronickel product. Comparative Example 2 (which differed from Example 2 only in that high-pressure oxygen was not introduced during the oxidative leaching of the ore slurry) A method was provided for producing ferronickel and removing chromium from nickel laterite ore, which includes the following steps: (1) The nickel laterite ore as raw ore was subjected to ore washing in a cylindrical ore washer, a channel ore washer, and a hydrocyclone successively and separation to obtain an ore slurry and an ore aggregate, wherein the ore washing is carried out with water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled to 18%; the ore slurry was subjected to oxidation leaching, the ore aggregate was subjected to crushing to a particle size of 1.5 mm or less and was further separated in an agitator with a water flow rate of 3.5 l / min to obtain chrome concentrate and tailings, and the tailings were returned to the ore washing procedure; (2) Sodium hydroxide and sodium bromate were added to the ore slurry in a mass ratio of sodium hydroxide and sodium bromate to ore slurry of 0.9:1.3:100, and under closed conditions, the resulting system was heated to 120 °C to allow oxidation leaching for 3 h with stirring at a rotation speed of 250 r / min; (3) After the oxidation leaching was completed in stage (2), solid-liquid separation was carried out using a pressure filter to obtain a chromium-containing filtrate and a filter cake, and the chromium-containing filtrate and chromium concentrate were sent to a rum processing plant; (4) The filter cake was subjected to further washing with clean water and pressure filtration to obtain a liquid and a solid, and the liquid was sent for The washing of the mineral and the solid was used in the next stage; (5) quicklime, semi-lime and the solid obtained in step (4) were mixed in a mass ratio of 7:6:100 and the resulting mixture was converted into granules with a particle size of 17 mm; (6) the granules were subjected to roasting in a rotary calciner kiln at a temperature of 850 °C for 25 min; and (7) The roasted granules were melted in an electric furnace at a temperature of 1,700 °C to obtain a finished ferronickel product. Comparative Example 3 (which was different from Example 3 only in that the oxygen High pressure was not introduced during the oxidation leaching of the slurry of mineral) A method was provided for producing ferronickel and removing chromium. of nickel laterite ore, which includes the following stages: (1) The nickel laterite ore as raw ore was subjected to ore washing in a cylindrical ore washer, an ore washer of channel, and a hydrocyclone successively and separation to obtain a mineral slurry and a mineral aggregate, wherein the washing of the mineral is carried out with Using water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled at 15%; the mineral slurry was subjected to oxidation leaching, the mineral aggregate was subjected to crushing to a particle size of 1.5 mm or less and was separated again in an agitator with a water flow rate of 3 l / min to obtain chrome concentrate and tailings, and the tailings were returned to the ore washing process; (2) Sodium hydroxide and sodium bromate were added to the ore slurry in a mass ratio of sodium hydroxide and sodium bromate to ore slurry of 0.8:1:100, and under closed conditions, the resulting system was heated to 110 °C to allow oxidative leaching for 4 h with stirring at a rotation speed of 300 rpm; (3) After the oxidation leaching was completed in stage (2), solid-liquid separation was carried out using a pressure filter to obtain a chromium-containing filtrate and a filter cake, and the chromium-containing filtrate and chromium concentrate were sent to a chromium processing plant; (4) The filter cake was subjected to further washing with clean water and pressure filtration to obtain a liquid and a solid, and the liquid was sent for ore washing and the solid was used in the next stage; (5) Quicklime, anthracite, and the solid obtained in step (4) were mixed in a mass ratio of 4:4:100 and the resulting mixture was converted into granules with a particle size of 15 mm; (6) the granules were roasted in a rotary calciner oven at a temperature of 800 °C for 30 min; and (7) The roasted granules were melted in an electric furnace at a temperature of 1,800 °C to obtain a finished ferronickel product. Comparative example 4: A method for producing ferronickel by smelting was provided. of nickel laterite ore, which includes the following stages: (1) The nickel laterite ore as raw ore was subjected to ore washing in a cylindrical ore washer, an ore washer of channel, and a hydrocyclone successively and separation to obtain a mineral slurry and a mineral aggregate, wherein the washing of the mineral is carried out with Using water, the hydrocyclone produces nickel laterite ore with a particle size of 0.05 mm, and the solid content of the ore slurry is controlled at 15%; (2) quicklime and semi-lime were added to the mineral slurry obtained in stage (1) in a mass ratio between the mineral slurry and the quicklime and the 100:10:8 semi-cooking mixture, and the resulting mixture was converted into granules with a particle size of 20 mm; (3) the granules were roasted in a rotary calciner kiln at a temperature of 850 °C for 25 min; and (4) The roasted granules were subjected to melting in an electric furnace at a temperature of 1,800 °C to obtain a finished ferronickel product. Test example 1. The chemical compositions of the chromium concentrates obtained in Examples 1 to 3 and the mineral aggregate in the Comparative Example were tested 4, and the test results are shown in Table 2. Table 2: Results of the chemical composition test (%) It can be seen in Table 2 that a percentage of C2O3 in the chromium concentrate obtained by the method for producing ferronickel and removing chromium from the nickel laterite ore of the present disclosure is 36, 37% or higher, which achieves chromium enrichment and reduces the chromium content in the tailings. 2. The chromium-containing filtrates obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were each analyzed to determine the chromium concentration, and the test results are shown in Table 3. Table 3: Chromium concentrations in the filtrate containing chromium Table 3 shows that the Cr concentration in the chromium-containing filtrate obtained by the method for producing ferronickel and removing chromium from nickel laterite ore described herein reaches 1.13 g / kg or more, and the chromium leaching rate reaches 93.4% or more. This indicates that the chromium element is effectively separated from the ore slurry to reduce the chromium content in the feedstock for ferronickel production, which protects the furnace and reduces the chromium impurity content in the ferronickel. Furthermore, a comparison between Example 1 and Comparative Example 1, between Example 2 and Comparative Example 2, and between Example 3 and Comparative Example 3 shows that when high-pressure oxygen is not introduced during the oxidative leaching of the ore slurry, the chromium leaching from the ore slurry is significantly reduced. The finished ferronickel products obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were each tested for chromium content, and the test results are shown in Table 4. Table 4: Content drmnlrf rr ní l erminado Table 4 shows that the Cr concentration in the finished ferronickel product obtained using the method for producing ferronickel and removing chromium from nickel laterite ore described in this disclosure is less than 0.053%. Furthermore, a comparison between Example 1 and Comparative Example 1, between Example 2 and Comparative Example 2, and between Example 3 and Comparative Example 3 shows that when high-pressure oxygen is not introduced during the oxidative leaching of the ore slurry, the chromium content in the final ferronickel product increases. The preceding examples are preferred implementations of this disclosure. However, implementations of this disclosure are not limited by the preceding examples. Any changes, modifications, substitutions, combinations, and simplifications made without departing from the spiritual essence and principle of this disclosure must be an equivalent form of replacement and are all included within the scope of protection of this disclosure.

Claims

1. A method for producing ferronickel and removing chromium from nickel laterite ore, comprising the following steps: (1) washing and separating the nickel laterite ore to obtain an ore slurry and mineral aggregate, adding an alkaline liquid and a bromate, and introducing oxygen into the ore slurry to enable oxidation leaching, and then carrying out solid-liquid separation to obtain a chromium-containing solid and filtrate; (2) washing and separating the solid obtained in step (1) to obtain a solid phase and wash water, and mixing the solid phase with quicklime and a reducing agent to obtain a mixture; and (3) roasting and smelting the mixture obtained in step (2) successively to obtain a finished ferronickel product. 2.The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (1), the ore slurry has a solid content of 10% to 25%.

3. The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, further comprising: subjecting the mineral aggregate obtained in step (1) to crushing and re-separating in an agitator to obtain chromium concentrate and tailings, and returning the tailings for ore washing.

4. The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (1), for oxidation leaching, a mass ratio between the alkaline liquid and bromate and the ore slurry is (0.5-1) : (1-2) :

100. 5.The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (1), oxidation leaching is carried out under closed conditions, and the oxygen pressure is from 1.5 MPa to 4 MPa.

6. The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (1), oxidation leaching is carried out at a temperature of 100 °C to 150 °C for 1 to 5 h.

7. The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein the wash water obtained in step (2) is returned to step (1) for washing the ore. 8.The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (2), the mass ratio between quicklime and reducing agent and solid phase is (2-10) : (3-8) :

100.

9. The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (3), roasting is carried out at a temperature of 600 °C to 1000 °C for 10 min to 50 min.

10. The method for producing ferronickel and removing chromium from nickel laterite ore according to claim 1, wherein in step (3), smelting is carried out at a temperature greater than or equal to 1500 °C.

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