Method for smelting nickel-containing oxide ore

Abstract

Provided is a method for smelting a nickel-containing oxide ore with which the amount of CO2 generated is reduced and the nickel recovery rate is high. The present invention is a method for smelting a nickel-containing oxide ore, the method comprising: a step in which a tubular reaction vessel is used, a raw material containing a nickel-containing oxide ore is introduced into the reaction vessel so as to move from above to below, and a hydrogen-containing gas as a reducing agent is supplied to the raw material from below and side to perform a reduction treatment; a step for melting a reduced product obtained by the reduction treatment; and a step in which slag is separated from the melt obtained by the melting treatment and metal containing nickel is recovered. The gas supplied from below to the raw material is supplied at room temperature. The gas supplied from the side to the raw material has a temperature of 300 DEG C or more, and is supplied from the side above the position where the raw material after the reduction treatment has been stored.

Description

Technical Field

[0001] This invention relates to a smelting method for nickel oxide ores (nickel-containing oxide ores). Background Technology

[0002] To address climate change, the Paris Agreement was adopted at COP21 in 2015, prompting countries to make every effort to limit the increase in global average temperature to well below 2°C above pre-industrial levels. In 2021, the IPCC (International Panel on Climate Change) Sixth Assessment Report clearly stated that "there is no doubt that human impacts are causing warming of the atmosphere, oceans, and land," and subsequently, at COP26, a consensus was reached to "strive to limit the increase in global average temperature to well below 1.5°C above pre-industrial levels."

[0003] Amid these international trends, the Japanese government set a target in 2016 to reduce greenhouse gas emissions by 26% by 2030 and by 80% by 2050 compared to 1990 levels. In 2020, it proposed a new target of "virtually zero emissions by 2050," and in 2021, it proposed a new target of "46% reduction by 2030 compared to 2013 levels." The movement to reduce greenhouse gas emissions within Japan is also accelerating.

[0004] The non-ferrous metal smelting industry is also required to reduce emissions according to target values ​​and transition to carbon-neutral processes by 2050, and is developing new processes with low energy consumption and low fossil fuel usage.

[0005] For example, in the nickel-iron alloy smelting industry, the Elkem process is currently the mainstream. The Elkem process involves pre-drying sapropelic ore containing nickel oxide in a rotary kiln dryer, further dehydrating it by gradually increasing the temperature in the rotary kiln until the water of crystallization is removed, then reducing the trivalent iron in the ore to a divalent iron, and finally reducing almost all of the nickel and some of the iron to metal in an electric furnace to obtain the alloy. However, in the Elkem process, fossil fuels such as pulverized coal and heavy oil are used in the pre-drying process and the reduction process in the rotary kiln, and coal is used as both the reducing agent and heat source, resulting in the generation of a large amount of CO2. It should be noted that the CO2 generation is approximately 22.4 tCO2 / tNi.

[0006] As a countermeasure to reduce such CO2 production, reduction using hydrogen is considered. It is known that nickel oxides alone are easily reduced to metal by hydrogen. However, in the hydrogen reduction of nickel in nickel-containing oxide ores such as sapropel and limonite, the reduction rate is approximately 10%–70%, significantly lower than the over 95% achieved by the Elken process. This is because nickel is widely dispersed in the olivine phase ((Mg,Fe)₂SiO₄) and the mathematicianite phase ((Mg,Fe)O), and has low activity. Therefore, simple hydrogen reduction results in low nickel recovery, making it industrially impractical.

[0007] As a strategy to improve nickel recovery during hydrogen reduction, the addition of sodium compounds has been proposed. However, the amount of this compound required is enormous, and the high cost of the chemical reagents makes it impractical for industrial applications.

[0008] Patent Document 1 discloses a method for producing reduced iron, in which reduced iron is produced by reducing iron oxide charged into a shaft furnace. Specifically, the method is shown as follows: iron oxide is reduced by blowing a heated mixture of a reducing gas containing at least 90% hydrogen and nitrogen into the shaft furnace. However, as mentioned above, the degree of reduction in the hydrogen reduction of nickel is about 10% to 70%, which is significantly lower than the 95% or more achieved by the Elken process, an existing method. Applying the hydrogen reduction method to reduce CO2 production in the smelting of nickel-containing oxide ores presents difficulties, necessitating the development of a method that achieves high nickel recovery rates and is industrially feasible even when using the hydrogen reduction method.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent document 1: International Publication No. 2021 / 230307. Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] This invention is proposed in view of the following actual situation, and its purpose is to provide a smelting method for nickel-containing oxide ores that reduces CO2 production and has a high nickel recovery rate.

[0014] Methods for solving problems

[0015] To address the aforementioned issues, the inventors conducted in-depth research. The results showed that by using a tubular reaction vessel, loading a raw material containing nickel oxide ore into the vessel from top to bottom, and supplying the raw material with hydrogen-containing gas as a reducing agent from both below and the side at a predetermined temperature for reduction treatment, followed by melting the resulting reduced product, the reduction rate of nickel can be increased, and nickel can be recovered with a high recovery rate, thus completing this invention.

[0016] (1) The first invention of the present invention is a method for smelting nickel oxide ore, comprising: using a tubular reaction vessel, loading a raw material containing the nickel oxide ore into the reaction vessel in a manner that moves from top to bottom, and supplying the raw material with a hydrogen-containing gas as a reducing agent from below and the side to perform a reduction treatment; a step of melting the reduced product obtained by the reduction treatment; and a step of separating slag from the melt obtained by the melting treatment and recovering the nickel-containing metal, wherein the gas supplied to the raw material from below is supplied at room temperature, the gas supplied to the raw material from the side is supplied at a temperature of 300°C or higher, and the gas is supplied from the side at a position above the position where the raw material after the reduction treatment is stored.

[0017] (2) The second invention of the present invention is a method for smelting nickel oxide ore, wherein, in the first invention, the iron content of the nickel oxide ore is 5% by mass or more and 30% by mass or less.

[0018] (3) The third invention of the present invention is a smelting method for nickel oxide ore, wherein, in the first invention or the second invention, there is a step of granulating the raw material containing the nickel oxide ore, and a step of supplying the granulated raw material for the reduction treatment.

[0019] (4) The fourth invention of the present invention is a method for smelting nickel oxide ore, wherein, in any one of the first to third inventions, there is a step of heat-treating the raw material containing the nickel oxide ore at a temperature of 300°C or higher and 1200°C or lower, and a step of supplying the nickel oxide ore, which is the heat-treated product obtained by the heat treatment, to the reduction treatment.

[0020] (5) The fifth invention of the present invention is a method for smelting nickel oxide ore, wherein, in any one of the first to fourth inventions, the MgO / SiO2 mass ratio in the melt containing the reducing agent in the melting process is 0.5 or more and 0.7 or less.

[0021] (6) The sixth invention of the present invention is a smelting method for nickel oxide ore, comprising: a step of supplying a hydrogen-containing gas as a reducing agent to a raw material containing the nickel oxide ore for reduction treatment in a ratio satisfying the relationship H2 / (H2+H2O+CO2+O2)≥0.9; a step of melting the reduced product obtained by the reduction treatment; and a step of separating slag from the melt obtained by the melting treatment and recovering the nickel-containing metal.

[0022] (7) The seventh invention of the present invention is a method for smelting nickel oxide ore, wherein, in the sixth invention, the temperature of the gas is above 600°C.

[0023] (8) The eighth invention of the present invention is a method for smelting nickel oxide ore, wherein, in the seventh invention, the gas is heated by electricity to adjust the temperature of the gas to above 600°C.

[0024] (9) The ninth invention of the present invention is a method for smelting nickel oxide ore, wherein, in any one of the sixth to eighth inventions, in the reduction process, the gas is supplied from below to the raw material containing the nickel oxide ore.

[0025] (10) The tenth invention is a method for smelting nickel oxide ore, wherein, in the ninth invention, in the reduction process, the raw material containing the nickel oxide ore is supplied from top to bottom.

[0026] (11) The ninth invention of the present invention is a method for smelting nickel oxide ore, wherein, in any one of the sixth to tenth inventions, the iron grade of the nickel oxide ore is 5% by mass or more and 30% by mass or less.

[0027] (12) The ninth invention of the present invention is a method for smelting nickel oxide ore, wherein, in any one of the sixth to eleventh inventions, there is a step of granulating the raw material containing the nickel oxide ore, and a step of supplying the granulated raw material to perform the reduction treatment.

[0028] (13) The thirteenth invention is a method for smelting nickel oxide ore, wherein, in any one of the sixth to twelfth inventions, a step is further comprising heat-treating the raw material containing the nickel oxide ore at a temperature of 300°C or higher and 1200°C or lower, and supplying the nickel oxide ore, which is the heat-treated product obtained by the heat treatment, to the step of performing the reduction treatment.

[0029] (14) The fourteenth invention is a method for smelting nickel oxide ore, wherein, in any one of the sixth to thirteenth inventions, the MgO / SiO2 mass ratio in the melt containing the reducing agent in the melting process is 0.5 or more and 0.7 or less.

[0030] The effects of the invention

[0031] According to the present invention, a method for smelting nickel-containing oxide ores with reduced CO2 production and high nickel recovery rate can be provided. Attached Figure Description

[0032] Figure 1 This is a process diagram illustrating an example of a smelting method for nickel-containing oxide ores.

[0033] Figure 2 This is a STEM image of the cross-section of the sample after hydrogen reduction treatment (before melting treatment).

[0034] Figure 3 This is a schematic diagram of a tubular reduction reaction vessel, used to illustrate the loading direction of raw materials containing nickel oxide ore and the method of supplying hydrogen-containing gas.

[0035] Figure 4 These are STEM images of the sample cross-section (including areas where no metal particles were observed) after hydrogen reduction treatment (before melting treatment).

[0036] Figure 5 This is a schematic diagram of the test apparatus used in the embodiments.

[0037] Figure 6 This is a photograph of the sample recovered in the examples. Detailed Implementation

[0038] The following describes in detail specific embodiments of the present invention (hereinafter also referred to as "this embodiment"). It should be noted that the present invention is not limited to the following embodiments at all, and can be implemented by appropriate modifications without changing the spirit of the present invention.

[0039] The method described in this embodiment is a smelting method for separating and recovering nickel from nickel-containing oxide ores (nickel-containing oxide ores).

[0040] There are no particular limitations on the nickel-containing oxide ores that can be used as raw materials; examples include sapropel and limonite. Nickel-containing oxide ores contain nickel oxide (NiO) and iron oxide (Fe2O3) as constituent components.

[0041] Furthermore, the iron content of the nickel-containing oxide ore is preferably 5% by mass or more and 30% by mass or less. If the iron content is less than 5% by mass, the amount of iron reduced in the hydrogen reduction treatment of the reduction step S3 described later will decrease, and the amount of iron metal contributing as a reducing agent in the melting treatment of the melting step S4 will decrease, which may result in no improvement in the nickel reduction rate and a decrease in the nickel recovery rate. In addition, if the iron content exceeds 30% by mass, it may lead to a decrease in the nickel grade of the recovered nickel metal (alloy) or an increase in the amount of slag.

[0042] Specifically, Figure 1 This is a process diagram illustrating an example of the smelting method for nickel-containing oxide ore (hereinafter also simply referred to as the "smelting method") according to this embodiment. The method is characterized by comprising: a reduction step S3, in which a reduction treatment is performed while a gas containing hydrogen in a specific proportion is supplied as a reducing agent to a raw material containing nickel-containing oxide ore; a melting step S4, in which the reduced product obtained through the reduction treatment is melted; and a recovery step S5, in which slag is separated from the melt obtained through the melting treatment and nickel-containing metal is recovered.

[0043] In addition, a process (granulation process S1) can be further set up to granulate the raw material containing nickel oxide ore, and the granulated raw material is then supplied for reduction treatment.

[0044] In addition, a process for heat-treating raw materials containing nickel oxide ore under specific temperature conditions, or a process for heat-treating the granulated raw materials after granulation in the granulation process S1 (heat treatment process S2), can be further provided, and the nickel oxide ore, as the heat-treated product, is supplied for reduction treatment.

[0045] In this smelting method according to the present embodiment, a reduction treatment (hydrogen reduction treatment) is performed on a raw material containing nickel oxide ore using a hydrogen-containing gas as a reducing agent, and then the resulting reduced product is subjected to a melting treatment. This allows for the effective reduction of nickel contained in the nickel oxide ore and the recovery of nickel-containing metals with a high recovery rate.

[0046] Specifically, in the smelting method according to this embodiment, in the reduction step S3, a raw material containing nickel-containing oxide ore is loaded into a tubular reaction vessel (reduction reaction vessel) in a manner that moves from top to bottom, and hydrogen-containing gas is supplied to the raw material from below and the side to perform reduction treatment. Furthermore, the gas supplied to the raw material from below is supplied at room temperature, while the gas supplied to the raw material from the side is set to a temperature of 300°C or higher and supplied from a position above the location where the reduced raw material is stored.

[0047] By performing hydrogen reduction in this way, incomplete reduction can be suppressed and oxidation (re-oxidation) of the nickel and iron metals generated by reduction can be prevented, and nickel-containing metals can be recovered with a higher recovery rate.

[0048] [Granulation Process]

[0049] Although not strictly necessary, the smelting method described in this embodiment can include a step of granulating the raw material containing nickel oxide ore (granulation step S1). By granulating the raw material containing nickel oxide ore and supplying the granulated raw material (raw material particles) with hydrogen-containing gas to perform reduction treatment, the proportion of the raw material being carried over along with unreacted hydrogen or with the waste gas containing water vapor after the reaction can be suppressed.

[0050] There are no particular limitations on the method for granulating raw materials. For example, it can be obtained by: making nickel-containing oxide ore into powder, adding water required for granulation to the ore powder, and then forming it into granules of a specified size and shape using known granulation equipment such as a rolling granulator, compression molding machine, or extrusion molding machine. Alternatively, it can be granulated manually by an operator.

[0051] There are no particular limitations on the shape of the particles; for example, they can be made into spheres.

[0052] There is no particular limitation on the particle size. For example, considering the particle size (diameter in the case of spherical particles) of the reduction reaction vessel or the like loaded into the reduction step S3, it is preferably set to about 5 mm or more and about 50 mm or less. Furthermore, the particle size is more preferably 8 mm or more and 40 mm or less, and even more preferably 10 mm or more and 35 mm or less. If the particle size is less than 5 mm, due to the small diameter or breakage of small-diameter particles, when the reaction vessel for the reduction process is filled with these raw materials, the gaps between the particles become smaller, and the flowability of the hydrogen-containing gas, which serves as the reducing agent, may sometimes be impaired. In such cases, if the supplied gas pressure exceeds a certain value, it is easy for the raw materials to be pushed upwards all at once, and most of the gas is discharged in an unreacted state. On the other hand, if the particle size exceeds 50 mm, the contact area between the particles and the gas becomes smaller, the reduction reaction takes longer, and efficient processing may not be possible.

[0053] It should be noted that it is preferable to dry the granules after granulating the raw material containing nickel oxide ore. If moisture necessary for granulation is added during the granulation process, the material will become viscous due to the added moisture. Therefore, from the viewpoint of facilitating subsequent operations, drying the granules can remove the moisture adhering to them. The drying method is not particularly limited; for example, it can be performed by blowing hot air at 300°C to 400°C onto the granules.

[0054] [Heat treatment process]

[0055] In addition, although not a necessary method, in the smelting method involved in this embodiment, a heat treatment step S2 can be provided, in which the raw material containing nickel oxide ore or the granulated raw material (raw material particles) after being provided in the case of a granulation step S1 is heat treated under specific temperature conditions.

[0056] Specifically, in heat treatment step S2, the raw material particles containing nickel oxide ore are heated to a temperature of 300°C or higher and 1200°C for heat treatment. This heat treatment is a pretreatment performed before the subsequent hydrogen reduction treatment step (reduction step S3) and the further melting of the reduced product step (melting step S4). By performing heat treatment on the nickel oxide ore in this way, the water of crystallization contained in the nickel oxide ore can be removed.

[0057] The heat treatment is carried out at a temperature of 300°C or higher and 1200°C or lower, as described above. If the heat treatment temperature exceeds 1200°C, fir olivine slag may be generated before the iron metal contained in the nickel oxide ore is generated during the hydrogen reduction treatment in the subsequent reduction step S3. If fir olivine slag is generated, the amount of iron metal contributing as a reducing agent in the melting step S4 will decrease, and the reduction rate of nickel may not increase. On the other hand, if the heat treatment temperature is lower than 300°C, the reduction reaction in the reduction step S3 or the removal of crystal water contained in the nickel oxide ore may be hindered, and the reduction rate of nickel may decrease.

[0058] Furthermore, the heat treatment temperature is preferably set in the range of 400°C or higher and 1000°C or lower. It is preferable that by performing heat treatment within this temperature range, most of the water of crystallization contained in nickel-containing oxide ores can be effectively removed, and the increase in energy costs can be suppressed.

[0059] [Restoration Process]

[0060] The smelting method according to this embodiment has a reduction step S3, wherein a reduction treatment (hydrogen reduction treatment) is performed while a gas containing hydrogen in a specific proportion is supplied as a reducing agent to a raw material containing nickel oxide ore.

[0061] It should be noted that when the nickel-containing oxide ore used as raw material is heat-treated by the aforementioned heat treatment step S2, the resulting heat-treated product is subjected to hydrogen reduction treatment. Furthermore, "raw material containing nickel-containing oxide ore" refers to raw material particles when the granulation step S1 is included.

[0062] In this way, by performing hydrogen reduction treatment on raw materials containing nickel oxide ores, nickel in nickel oxide ores is reduced to metal, and most or all of the iron existing in the valence of 3 is reduced to valence of 2 oxide, thereby reducing a portion of the iron to metal.

[0063] The reduction process using hydrogen-containing gas as a reducing agent (hydrogen reduction process) becomes a process utilizing a carbon-neutralizing reducing agent, which can effectively reduce CO2 production compared to existing technologies. It should be noted that "carbon-neutralizing reducing agent" refers to a reducing agent that contains almost no carbon, meaning it is a reducing agent that helps reduce greenhouse gas emissions. Specifically, for example, a hydrogen-containing gas in a ratio shown as H2 / (H2+H2O+CO2+O2) < 0.9 is a carbon-neutralizing reducing agent.

[0064] Here, as mentioned above, the reduction rate to nickel metal by hydrogen reduction treatment of nickel-containing oxide ores is lower compared to the Elkem process. However, as... Figure 2 STEM images of the sample cross-section after hydrogen reduction treatment (before the melting treatment described later) show that although the hydrogen reduction treatment produces fine and few particles, it is still possible to confirm the formation of nickel and iron metal particles. Details are described later. By melting the reduced product obtained through hydrogen reduction treatment, the resulting fine metal particles (metal microparticles) will settle and agglomerate for recovery. However, it is desirable to effectively utilize the nickel and iron metal particles generated by hydrogen reduction treatment for melting treatment at this point.

[0065] Therefore, the method according to this embodiment is characterized in that, in the reduction step S3, a raw material containing nickel-containing oxide ore is loaded into a tubular reaction vessel (reduction reaction vessel) in a manner that moves from top to bottom, and hydrogen-containing gas as a reducing agent is supplied to the raw material from below and the side to perform reduction treatment. Furthermore, the gas supplied to the raw material from below is supplied at room temperature, and the gas supplied to the raw material from the side is set to a gas temperature of 300°C or higher and supplied from a position above the location where the raw material after reduction treatment is stored.

[0066] Figure 3 This is a schematic diagram of a tubular reduction reaction vessel, used to illustrate the loading direction of raw materials containing nickel oxide ore and the method of supplying hydrogen-containing gas.

[0067] In the reduction process, the raw material containing nickel oxide ore (hereinafter also referred to as "raw material M", mainly referring to the raw material that has not undergone the reduction reaction) is introduced from the top of container 1 ( Figure 3 The raw material M is loaded into the tubular reduction reaction vessel 1 at a location near the symbol 11 shown in the figure, and the reduction reaction proceeds gradually as the raw material M moves from top to bottom. Then, the raw material after the reduction treatment (hereinafter, the raw material after the reduction treatment will also be referred to as "raw material M'") is stored at the lower position of the reduction reaction vessel 1. Figure 3 (The location near the symbol 12 in the diagram).

[0068] On the other hand, inside the tubular reduction reaction vessel 1, from below ( Figure 3 The hydrogen-containing gas is supplied to the raw material at a location near the symbol 13 shown in the figure. The hydrogen-containing gas supplied from below (hereinafter also referred to as "gas D") is at room temperature. Therefore, gas D supplied to the raw material from below is introduced at room temperature from below the reduction reaction vessel 1, and then reacts with the raw material M' (in the figure) immediately after the reduction treatment. Figure 3 The raw material (stored at position 12) comes into contact with and rises while being cooled. Furthermore, the gas D supplied from below reaches a temperature of approximately 300°C or higher immediately after the reduction treatment of the raw material M'. As it rises further upwards, it gradually reduces the raw material M (new raw material before the reduction treatment is complete), and then it is discharged as waste gas from the top of the reduction reaction vessel 1. In this way, by supplying the raw material with room-temperature gas D from below, the raw material M' after the reduction treatment can be kept in a reducing environment and cooled, and oxidation (re-oxidation) of the raw material M' after the reduction treatment can be suppressed.

[0069] In addition, within the tubular reduction reaction vessel 1, the raw material M' after the reduction process is stored at a position ( Figure 3 The position of the symbol 12) is on the upper side ( Figure 3 The hydrogen-containing gas supplied from this side (referred to as "gas S") has a gas temperature of 300°C or higher. This gas S is used for the reduction treatment of unreacted raw material M. Since the reduction reaction using hydrogen is an endothermic reaction, by using the hydrogen-containing gas (gas S) set at a temperature of 300°C or higher, the raw material M can be heated, and the reduction reaction can be carried out efficiently. Therefore, in order to prevent the generation of insufficiently reduced raw material, it is preferable to supply hydrogen-containing gas from the position below the tubular reduction reaction vessel 1 after the reduction treatment is completed (referred to as gas S). Figure 3 The position of the symbol 12) is higher and as close as possible to its side ( Figure 3(At position 14) a hydrogen-containing gas S, set to a temperature above 300°C, is introduced. Additionally, because it is introduced from a position higher than the location where the raw material M' after reduction treatment is stored (…),… Figure 3 The gas S is supplied at position 14 (symbol 14), so it hardly comes into contact with the raw material M' after the reduction process is completed, and therefore does not hinder cooling.

[0070] Regarding the proportion of hydrogen in the gas, when the gas contains hydrogen in a proportion where H2 / (H2+H2O+CO2+O2) < 0.9, components such as H2O, CO2, and O2 contribute as oxidants, potentially leading to insufficient reduction and possible oxidation (re-oxidation) of the nickel and iron metal particles generated by hydrogen reduction as described above. Therefore, regarding the hydrogen-containing gas as a reducing agent, it is preferable to use a hydrogen-containing gas in a proportion that satisfies the relationship H2 / (H2+H2O+CO2+O2) ≥ 0.9 for hydrogen reduction treatment.

[0071] The temperature of the gas S supplied from the side is preferably a predetermined temperature or higher. Specifically, the gas temperature is preferably 600°C or higher, more preferably 700°C or higher, and even more preferably 800°C or higher. It is preferable that by supplying the hydrogen-containing gas S at such a gas temperature, the reduction reaction of the raw materials can proceed more smoothly.

[0072] It should be noted that an electric heater or similar device can be used as the heating device for the supplied gas. By electrically heating the gas, the gas temperature can be adjusted to, for example, a temperature of 300°C or higher. Alternatively, a heat exchanger, such as a heat exchange heater, can be used to heat the gas. It should be noted that if a burner is used to burn the gas as a heat source, the H₂O and CO₂ contained in the combustion gas act as oxidants in the furnace, potentially re-oxidizing the generated nickel and iron metal particles, thereby reducing the nickel recovery rate.

[0073] In this way, for raw materials containing nickel oxide ores, hydrogen reduction treatment is performed by supplying hydrogen-containing gas as a reducing agent from below at room temperature (gas D) and from the side at a gas temperature of 300°C or higher (gas S). This suppresses incomplete reduction and prevents the oxidation (re-oxidation) of the nickel and iron metals generated by reduction. That is, it prevents the re-oxidation of nickel and iron metal particles in the reduced products generated by hydrogen reduction treatment. Nickel metal particles are substances that settle and agglomerate in the next melting process, forming what are called nuclei. By preventing the re-oxidation of these nickel metal particles, nickel metal can be recovered with a high recovery rate through melting treatment. In addition, iron metal particles are substances that contribute as a reducing agent in the next melting process (details will be described later). By preventing the re-oxidation of these iron metal particles, the reduction of nickel during melting treatment is promoted, resulting in an increased nickel metal recovery rate.

[0074] Furthermore, by supplying hydrogen-containing gas to the raw material containing nickel oxide ore from below and the side for reduction treatment, the generated waste gas can be guided upwards. This allows for the introduction of a supply gas with a high hydrogen concentration at locations where the nickel oxide concentration is low, and conversely, the introduction of a supply gas with a low hydrogen concentration at locations where the nickel oxide concentration is high, thus efficiently advancing the reduction reaction.

[0075] Furthermore, by setting the temperature of the gas S supplied from the side to the raw material containing nickel oxide ore to 300°C or higher, preferably, for example, 600°C or higher, an upward airflow is effectively generated, thus creating a smoother airflow. As a result, the supply gas or exhaust gas can flow efficiently, and the hydrogen reduction reaction can proceed more efficiently.

[0076] Furthermore, as described above, the raw material M containing nickel oxide ore is loaded into the tubular reduction reaction vessel 1 in a manner that moves from top to bottom, i.e., in a direction opposite to the supply direction of the hydrogen-containing gas. This allows for convective contact between the raw material and the hydrogen-containing gas, resulting in a more efficient reduction reaction. In other words, by supplying hydrogen-containing gas to the raw material supplied from top to bottom from below and guiding the waste gas upwards, a supply gas with a high hydrogen concentration can be introduced at locations where the nickel oxide concentration is low, and a supply gas with a low hydrogen concentration can be introduced at locations where the nickel oxide concentration is high.

[0077] In hydrogen reduction processing, the amount of hydrogen supplied is preferably set to at least 1.2 times the equivalent of the hydrogen required to reduce the iron and nickel in nickel-containing oxide ores. If the supplied amount of hydrogen is less than 1.2 times the required amount, the reduction may become incomplete. It should be noted that there is no particular upper limit to the amount of hydrogen to be supplied; it can be appropriately set by considering factors such as the cost of hydrogen supply and the form of contact between the raw materials and hydrogen in the reduction reaction vessel (i.e., reaction efficiency).

[0078] As mentioned above, there are no particular limitations on the type of tubular container used for hydrogen reduction reactions. For example, a vertical shaft furnace can be used.

[0079] However, as mentioned above, the reduction rate to nickel metal from nickel-containing oxide ores via hydrogen reduction treatment is generally low compared to the existing Elken process. Regarding this, as explained below, in the method of this embodiment, after hydrogen reduction treatment of the raw material containing nickel-containing oxide ores, the resulting reduced product is subjected to a melting process (melting step S4). This improves the reduction rate of nickel.

[0080] [Melting Process]

[0081] In the melting process S4, the reduced product obtained through hydrogen reduction is charged into a furnace, such as an electric furnace, for melting. By melting the obtained reduced product (hydrogen reduced product), the nickel recovery rate can be improved. Furthermore, the nickel reduction rate can be increased.

[0082] Nickel is more easily reduced than iron. Therefore, it is speculated that by melting the hydrogen reducer, the nickel oxide remaining in an unreacted state after hydrogen reduction comes into contact with the reduced iron metal and ferrous oxide, and an oxygen displacement reaction occurs as shown in equations [1] and [2], thereby reducing nickel oxide to nickel metal. That is, iron metal and ferrous oxide, as iron reducers, can act effectively as reducing agents to reduce nickel oxide.

[0083] Fe + NiO → Ni + FeO Formula [1]

[0084] 2FeO + NiO → Ni + Fe2O3 Equation [2]

[0085] That is, it is believed that since the sample after hydrogen reduction is in a solid state, the reactions of the above formulas [1] and [2] are very difficult to carry out. However, by melting the hydrogen reducing agent, the metal in the slag can move easily, thereby promoting the reaction of formulas [1] and [2]. As a result, the metallization rate of nickel is increased, and the recovery rate of nickel recovered through the melting process S4 can be improved.

[0086] In addition, by melting the hydrogen reducing agent, the sedimentation and agglomeration of nickel metal particles that are too fine to be recovered by physical separation such as magnetic separation can be promoted, thereby improving the nickel recovery rate.

[0087] It should be noted that, Figure 4This is a STEM image of the cross-section of the sample after hydrogen reduction treatment (before melt treatment), including areas where no metal particles were observed (elemental analysis (EDX analysis) results are also included in the image). Figure 4 As shown, approximately 1-2% nickel was also detected in areas where no metal particles were observed (areas in (2) and (3) of the figure). From this result, it can be seen that a high nickel recovery rate cannot be obtained by simply relying on the precipitation of the metal components generated by hydrogen reduction treatment. It is speculated that some of the nickel in the raw material is reduced by iron metal and divalent iron oxide based on the reactions of the above formulas [1] and [2].

[0088] In the melting process, the temperature conditions are not particularly limited as long as the hydrogen reducing agent can be melted, but it is preferable to be, for example, 1400°C or higher and 1600°C or lower. By setting the melting temperature to 1400°C or higher, slag with good properties can be obtained, and the slag and metal can be separated efficiently. In addition, by setting the melting temperature to 1600°C or lower, the loss of refractory materials constituting the melting furnace and energy costs can be suppressed.

[0089] Here, as described above, the nickel-containing oxide ore used as raw material in the method according to this embodiment preferably has an iron content of 5% by mass or more and 30% by mass or less. If the iron content is less than 5% by mass, the amount of iron reduced during reduction in reduction step S3 is reduced, and the amount of iron metal contributing as a reducing agent during melting in melting step S4 is reduced. As a result, the nickel recovery rate may decrease.

[0090] Furthermore, during the melting process, the MgO / SiO2 mass ratio in the molten material containing the reducing agent to be melted is preferably 0.5 or more and 0.7 or less. A MgO / SiO2 mass ratio less than 0.5 or greater than 0.7 may lead to an increase in the slag melting point.

[0091] The raw material for processing is preferably prepared and prepared in a manner in which the MgO / SiO2 mass ratio is within the aforementioned range during the smelting process. Furthermore, during the smelting process, fluxes such as SiO2 may be added. In this case, the amount of flux added is considered to ensure that the MgO / SiO2 mass ratio in the smelted product is within the aforementioned range. It should be noted that fluxes can lower the melting temperature of the slag and promote the settling of metals (nickel metal) in the slag.

[0092] [Recycling Process]

[0093] In the recycling process S5, slag is separated from the molten material obtained through melting treatment, and nickel-containing metals (alloys) are recovered. For example, in a furnace where a reducing agent is melted, the slag is separated to the upper layer (gravity separation) and the metal is separated to the lower layer according to its specific gravity. The nickel-containing metal separated from the slag can be efficiently recovered through operations such as tapping from metal holes provided in the furnace sidewall.

[0094] It should be noted that a single furnace can be used to perform all or multiple of the aforementioned heat treatment process S2, reduction process S3, melting process S4, and recycling process S5 in different areas within the furnace. Alternatively, it can be carried out in batches. For example, a vertical shaft furnace or blast furnace can be used, dividing the furnace into sections starting from the top for heat treatment process S2, reduction process S3, melting process S4, and recycling process S5, and finally separating the slag from the metal in the molten metal at the bottom of the furnace by gravity.

[0095] Example

[0096] The following describes embodiments of the present invention in more detail, but the present invention is not limited to the following embodiments at all.

[0097] [Example 1]

[0098] Using nickel-containing oxide ore (saprophytic ore) with the composition shown in Table 1 below as raw material, water is added to the raw material powder and shaped into spherical particles with a diameter of 10 mm.

[0099] [Table 1]

[0100] use Figure 5 The experimental apparatus shown in the schematic diagram was used to perform hydrogen reduction treatment on the obtained particles (raw material particles). Specifically, the raw material particles were loaded into a wire mesh cage, heated to 800°C in nitrogen, and then a 100% concentration of hydrogen gas (satisfying the relationship H2 / (H2+H2O+CO2+O2)=1.0, gas temperature: 800°C) was passed through the raw material particles in the wire mesh cage from below, and the reduction treatment was carried out for 120 minutes. After the hydrogen reduction treatment, the power supply to the furnace was cut off, and the obtained reduced sample was cooled to below 300°C while supplying the furnace with 100% concentration of hydrogen (gas temperature: room temperature), and then recovered. It should be noted that the amount of hydrogen supplied was set to be more than 10 times the amount required to reduce nickel and iron in nickel-containing oxide ores.

[0101] The recovered reduced sample, along with a small amount of flux (SiO2), was placed in an alumina crucible and heated to 1600°C in nitrogen to melt it. After maintaining the melting process for 60 minutes, it was cooled, and the resulting slag and button-shaped metal were recovered. It should be noted that SiO2 was added as a flux to lower the slag melting temperature and promote the sedimentation of the metal (nickel) in the slag. Furthermore, the amount of flux added was set such that the MgO / SiO2 mass ratio in the melted sample containing the reduced sample was 0.6.

[0102] Figure 6 These are photographs showing the state of the recovered samples after melt treatment. For example... Figure 6 As shown in the photograph, the slag has melted, and no metal can be visually identified within it. It is clear that the metal was obtained in button-like blocks.

[0103] Furthermore, Table 2 below shows the results of metallization calculated based on the weight of the obtained metal and chemical analysis using ICP. As shown in Table 2, the obtained nickel metallization is a value of over 95%. It should be noted that the metallization rate is expressed as a percentage of the mass of recovered nickel metal (or iron metal) relative to the mass of nickel (or iron) contained in the nickel-containing oxide ore of the raw material.

[0104] [Table 2]

[0105] Additionally, Table 3 below shows the metallization rates calculated using chemical analysis of the reduced sample after hydrogen reduction treatment (before melt treatment) via the bromomethanol method. As shown in Table 2 above, the metallization rates of nickel and iron are significantly increased compared to the results shown in Table 3 below.

[0106] It should be noted that the reason for the increased metallization rate despite the absence of a reducing agent during melt treatment is that fine nickel and iron metal components are introduced into the silicate during chemical analysis, potentially preventing the bromine-methanol solution from contacting the metal and thus failing to dissolve it. When observing the sample cross-section after hydrogen reduction treatment (before melt treatment) using STEM, as shown... Figure 2 The photographs confirm the introduction of fine nickel and iron particles into the silicate. It is therefore believed that the metal particles generated by hydrogen reduction can be recovered through melting after hydrogen reduction treatment, causing them to settle and agglomerate. It should be noted that... Figure 2 The sample matrix shown in the photograph is MgO-SiO2-FeO slag.

[0107] Additionally, regarding samples after hydrogen reduction treatment (before melt treatment), when no metal particles were observed in the areas ( Figure 4 When analyzing the parts in (2) and (3), such as Figure 4 As shown in the photograph, approximately 1-2% nickel was detected. Therefore, it is believed that the Ni metallization rate shown in Table 2 cannot be obtained solely through the precipitation of the aforementioned metal components. It is thus believed that a portion of the nickel is reduced by iron metal or divalent iron oxide through reactions such as those described in formulas [1] and [2].

[0108] [Table 3]

[0109] The results shown in Tables 2 and 3 confirm that, in the process of recovering nickel from nickel-containing oxide ores, by granulating the raw material containing nickel-containing oxide ores and subjecting the raw material particles to hydrogen reduction treatment followed by melting treatment, high nickel recovery rates, such as over 95%, can be achieved by utilizing this hydrogen reduction treatment, i.e., reduction using a carbon-neutralizing reducing agent.

[0110] [Comparative Example 1]

[0111] In Comparative Example 1, the raw material containing nickel-containing oxide ore was granulated in the same manner as in Example 1, and the raw material granules were subjected to hydrogen reduction at a temperature of 800°C. Subsequently, the reduced sample obtained by pulverizing using a vibratory mill was analyzed for its metallic composition using the bromomethanol method. That is, in Comparative Example 1, no melting treatment was performed after hydrogen reduction.

[0112] The results are shown in Table 3 above, with a nickel metallization rate of approximately 3%. It should be noted that even if all these metals were recycled, it would not be feasible industrially.

Claims

1. A method for smelting nickel oxide ore, wherein, have: The process involves using a tubular reaction vessel to load a raw material containing the nickel-containing oxide ore into the reaction vessel in a manner that moves from top to bottom, and supplying the raw material with hydrogen-containing gas as a reducing agent from below and the side to perform a reduction treatment. The process of melting the reduced product obtained through the reduction treatment; as well as The process of separating slag from the molten material obtained through the melting process and recovering nickel-containing metals. The gas supplied from below to the raw material is supplied at room temperature. The gas supplied to the raw material from the side is at a temperature of 300°C or higher, and is supplied from a position above the location where the raw material after reduction treatment is stored.

2. The smelting method for nickel-containing oxide ore according to claim 1, wherein, The nickel-containing oxide ore has an iron content of 5% by mass or more and 30% by mass or less.

3. The smelting method for nickel-containing oxide ore according to claim 1 or 2, wherein, It also includes a process for granulating the raw material containing the nickel-containing oxide ore. The granulated raw materials are then fed into the reduction process.

4. The smelting method for nickel-containing oxide ores according to any one of claims 1 to 3, wherein, It also includes a step of heat-treating the raw material containing the nickel-containing oxide ore at a temperature of 300°C or higher and 1200°C or lower. The nickel-containing oxide ore, which is the heat-treated product obtained by the heat treatment, is supplied to the process of the reduction treatment.

5. The smelting method for nickel-containing oxide ores according to any one of claims 1 to 4, wherein, The MgO / SiO2 mass ratio in the melt containing the reducing agent during the melting process is 0.5 or more and 0.7 or less.

6. A method for smelting nickel oxide ore, wherein, have: A process of reducing a raw material containing nickel oxide ore by supplying a hydrogen-containing gas as a reducing agent in a ratio satisfying the relationship H2 / (H2+H2O+CO2+O2)≥0.

9. The process of melting the reduced product obtained through the reduction treatment; and The process of separating slag from the melt obtained through the melting process and recovering nickel-containing metals.

7. The smelting method for nickel-containing oxide ore according to claim 6, wherein, The temperature of the gas is above 600°C.

8. The smelting method for nickel-bearing ore according to claim 7, wherein, The gas is heated electrically to adjust its temperature to above 600°C.

9. The smelting method for nickel-containing oxide ore according to any one of claims 6 to 8, wherein, In the reduction process, the gas is supplied from below to the raw material containing the nickel-containing oxide ore.

10. The smelting method for nickel-containing oxide ore according to claim 9, wherein, In the reduction process, a raw material containing the nickel-containing oxide ore is supplied from top to bottom.

11. The smelting method for nickel-containing oxide ore according to any one of claims 6 to 10, wherein, The nickel-containing oxide ore has an iron content of 5% by mass or more and 30% by mass or less.

12. The smelting method for nickel-containing oxide ore according to any one of claims 6 to 11, wherein, It also includes a process for granulating the raw material containing the nickel-containing oxide ore. The granulated raw materials are then fed into the reduction process.

13. The smelting method for nickel-containing oxide ore according to any one of claims 6 to 12, wherein, It also includes a step of heat-treating the raw material containing the nickel-containing oxide ore at a temperature of 300°C or higher and 1200°C or lower. The nickel-containing oxide ore, which is the heat-treated product obtained by the heat treatment, is supplied to the process of the reduction treatment.

14. The smelting method for nickel-containing oxide ore according to any one of claims 6 to 13, wherein, The MgO / SiO2 mass ratio in the melt containing the reducing agent during the melting process is 0.5 or more and 0.7 or less.

Images