KR20210079708A - Method for preparing nickel matt from ferronickel having low nickel content - Google Patents

Abstract

The present invention relates to a method for preparing nickel matte from low-grade ferronickel, comprising the steps of: melting ferronickel to obtain a melt; increasing the nickel concentration of the melt by injecting oxygen into the melt to remove carbon and silicon and oxidizing and removing at least a portion of iron; adding sulfur to the melt having an increased nickel concentration to sulfide iron and nickel to form sulfide; and oxidizing and removing iron sulfide by introducing oxygen to the melt in which the sulfide is formed. According to the present invention, nickel matte can be prepared by effectively removing iron from nickel pig iron (NPI) that is produced at lower costs than FeNi.

Description

METHOD FOR PREPARING NICKEL MATT FROM FERRONICKEL HAVING LOW NICKEL CONTENT

The present invention relates to a method for manufacturing a nickel mat using a low-grade nickel iron alloy.

The use of high-purity nickel as a battery material is increasing. However, due to the lack of supply of high-purity nickel, a wet smelting method using limonite, a low-grade nickel oxide mineral, as a raw material is being developed (Korean Patent No. 10-1353721, Korean Patent No. 10-1359179, Korean Patent No. 10-1657810, etc.), the investment cost is high and the development period is long, which is insufficient to solve the supply shortage. Accordingly, nickel-iron alloys, which traditionally account for more than half of nickel demand, are attracting attention as a source of high-purity nickel for battery materials.

The nickel iron alloy has a nickel content of 10 to 30% by weight, and most of the remainder is made of iron, so a nickel iron alloy having such an iron content is a good raw material in the stainless steel process, and therefore is mainly used for stainless steel. However, high-purity nickel is required as a battery material, so iron contained in a nickel-iron alloy is recognized as an impurity. Therefore, in order to use it as a battery material, it is necessary to convert the nickel-iron alloy to high-purity nickel as described above.

In the process of manufacturing high-purity nickel from the nickel-iron alloy as described above, economically removing iron, which is an impurity, is the most important process. In this regard, a process for manufacturing a nickel mat containing about 75 wt% of nickel by removing iron from FeNi containing about 25 wt% of nickel as a raw material through a sulfiding process and oxygen blowing was developed and commercialized, but nickel used as a raw material 25% by weight of FeNi is expensive, so the production cost increases, and the factory operation is currently suspended due to economic problems.

Accordingly, the present invention is to provide a method for manufacturing a nickel mat by effectively removing iron using NPI (Nickel Pig Iron), which is an alloy of about 10% nickel produced at a lower manufacturing cost than FeNi, as a raw material.

The present invention relates to a method for manufacturing a nickel mat by using a low-grade nickel iron alloy, comprising the steps of: melting iron and a nickel alloy to obtain a melt; increasing the nickel concentration of the melt by injecting oxygen into the melt to remove carbon and silicon and oxidizing and removing at least a portion of iron; adding sulfur to the molten material having a high nickel concentration to sulfide iron and nickel to form sulfide; And it provides a method of manufacturing a nickel mat from a low-grade nickel-iron alloy comprising the step of oxidizing and removing iron sulfide by introducing oxygen to the sulfide-generated melt.

According to the present invention, a nickel mat can be manufactured at a low manufacturing cost by using a low-grade ferroalloy of Ni.

1 is a diagram schematically illustrating a concept in which iron is selectively oxidized and removed by oxygen injection.
FIG. 2 is a NiO capacity phase diagram _{in CaO—SiO 2} —Fe _{t O slag at 1450° C. FIG.}
3 is a CaO—SiO ₂ —FeO-based slag phase diagram.
4 is a graph showing the Fe-Ni phase diagram (Fe-Ni binary phase diagram) (a) and the equilibrium phase (b) of iron and nickel according to temperature and sulfur partial pressure.
5 is a graph showing the stable phases of nickel and iron according to the oxygen/sulfur partial pressure at 1550°C.
6 is a graph showing the change in the selective oxidation removal reaction rate of iron according to the oxygen blowing time in Example 1.
7 is a view showing the XRD analysis results of the Fe-Ni mat before the oxygen blow and the nickel mat after the oxygen blow in Example 1;

EMBODIMENT OF THE INVENTION Hereinafter, this invention is given embodiment and demonstrated concretely. However, the present invention is not limited to the following embodiments, and may be modified in various embodiments.

The present invention provides a step of melting a nickel-iron alloy as a raw material, increasing the concentration of nickel by removing impurities and some iron by oxygen blowing, sulfiding iron and nickel in the melt, and slag and oxygen and oxidizing the sulfide by adding

The present invention relates to a method for manufacturing a nickel mat from a low-grade nickel-containing ferroalloy having a low nickel content. The low-grade nickel-containing ferroalloy is not limited thereto, but may be NPI (Nickel Pig Iron) having a nickel content of about 10% by weight, such as about 5 to 15% by weight, as a raw material. The NPI has, for example, a composition as shown in Table 1 below.

Unit: % by weight Ni Fe Si C NPI about 10% 80-85% 1.5 2.5

When a nickel mat is manufactured by simply applying a sulfiding process using such low-grade NPI, about three times more sulfur is consumed compared to the sulfiding process for removing iron from FeNi containing 25 wt% of nickel. There are disadvantages such as an increase in process cost due to the use of such a large amount of sulfur, and an increase in environmental treatment cost due to additional generation of a large amount of SOx during the process. Accordingly, the present invention confirmed that the quality of nickel can be improved before the sulfiding process by selectively oxidizing and removing iron by simultaneously utilizing slag and oxygen blow before sulfiding, and completed the present invention.

First, according to an embodiment of the present invention, it includes the step of melting an iron and nickel alloy to obtain a melt. The raw material containing nickel in the present invention is not limited thereto, but a nickel-iron alloy containing nickel and iron as main components may be used. More preferably, a nickel-iron alloy having a nickel content of 5 to 15% by weight, for example, about 10% by weight may be used.

It can be melted in a temperature range of 1,500 to 1,550 °C in consideration of the melting point of the nickel-iron alloy of 1,450 °C. It is more preferable to melt a low-grade nickel-iron alloy through an induction heating method in consideration of the blow tempering process, etc., which is a post-process.

Next, it includes the step of concentrating the nickel by removing iron and impurities. The low-grade nickel-iron alloy contains iron, silicon, and carbon, which are major impurities, and it is desirable to remove them.

Oxygen is injected at high pressure to remove these impurities. If oxygen is injected into the melt after melting the nickel-iron alloy, iron, silicon, and carbon can be removed through the reactions of Equations (1) to (7) below.

2C(l) + O ₂ (g) = 2CO(g) (1)

C(l) + O ₂ (g) = CO ₂ (g) (2)

2CO(g) + O ₂ (g) = 2CO ₂ (g) (3)

Si(l) + O ₂ (g) = SiO ₂ (l in slag) (4)

3Fe(l) + 2O ₂ (g) = Fe ₃ O ₄ (l in slag) (5)

Fe(l) + O ₂ (g) = FeO(l in slag) (6)

6FeO(l) + O ₂ (g) = 2Fe ₃ O ₄ (l in slag) (7)

In particular, iron can be selectively oxidized by the oxygen blow to produce slag, and the produced iron oxide is separated by moving to the upper part of the melt, whereby the iron oxide can be easily removed.

More specifically, when oxygen is injected into the lower portion of the melt and blown, carbon and silicon contained in the FeNi alloy as a raw material are oxidized and removed before iron, and then iron is oxidized and removed as slag.

On the other hand, since nickel has a smaller content in the alloy than iron, and also has a smaller standard free energy change than iron thermodynamically, iron is oxidized first and floats on the surface as slag. Due to this, it is possible to remove a large amount of iron as well as carbon and silicon as impurities.

However, since some nickel may also be oxidized, it is preferable to prevent oxidation of nickel by introducing slag into the melt of iron and nickel. _{Since acid slag such as SiO 2} and iron oxide (Fe _x O) is generated by oxygen blowing, loss of nickel can be reduced by adding basic slag.

The basic slag may include slag containing at least one of CaO, Na ₂ O, BaO, and MgO. Among them, it is more preferable to use CaO and/or MgO in terms of economy and reactivity.

As shown in FIG. 2, the basic slag can reduce the content of nickel that can be contained in the slag by continuously injecting the slag into an area that minimizes the capacity and distribution ratio of nickel in the slag, and, thereby, nickel through oxidation. loss can be suppressed. At this time, the capacity of nickel in the slag indicates the amount of nickel that the slag can contain, and the content ratio of nickel between the slag and the metal at this time is called a distribution ratio.

2 shows the capacity of nickel in the slag at 1723K (1450° C.), and the smaller the number, the less nickel is contained in the slag. _{As seen from FIG. 2, it is preferable to adjust the composition of the region in which the Fe t} O composition is large and the number in the graph, that is, the nickel capacity, is small in consideration of the oxidation and removal of iron.

Therefore, the content of the basic slag to be added is not particularly limited as it can be controlled through the NiO capacity phase diagram in _{CaO—SiO 2} —Fe _{t O slag as shown in FIG. 2 .}

For example, Figure 3 shows _{the equilibrium composition at a specific temperature of CaO, SiO 2} , FeO, the inside of the thick solid line is a region that exists in the liquid phase at 1500 ° C. When _{the concentrations of SiO 2} and CaO are determined, the concentration of FeO is can be decided. _{Therefore, when the amount of CaO and SiO 2} is determined in the direction in which the FeO content is high, that is, in the direction of the arrow, FeO must be present in the slag, so that iron in the metal combines with oxygen to promote formation of FeO.

As described above, the basic slag may be added to the molten material of the nickel-iron alloy, and may be added in advance in the step of melting the nickel-iron alloy to melt the nickel-iron alloy.

When CaO, which is basic slag, and SiO ₂ , which is acidic slag, is added in advance, iron is continuously oxidized to form a stable Fe _t O composition. In addition, if the Fe _t O concentration is increased by the oxidation reaction, the reaction driving force may be slightly decreased. In this case, CaO and SiO ₂ may be additionally added to increase the oxidation reactivity of iron into FeO. Therefore, the basic slag may be added before melting, may be added after melting, and may be continuously added during the oxidation reaction after melting.

By removing the generated slag, it is possible to obtain a metal including nickel and iron having a reduced content.

By such oxygen blowing, carbon can be vaporized or impurities such as silicon and iron can be produced as slag. The slag produced thereby moves upward due to the difference in specific gravity, and thus, by removing the upper slag, it is possible to obtain a melt of the lower metal having a reduced iron content. Accordingly, a low-grade nickel-iron alloy containing about 10% by weight of nickel can be concentrated to a level of about 25% by weight of nickel concentration. A method of removing the generated slag is not particularly limited, and for example, the slag may be removed using a means such as a tap hole in the upper portion of the furnace.

The present invention includes the step of sulfiding by adding sulfur to the molten iron and nickel after removing the slag. The sulfiding is for further removal of iron components from the melt containing concentrated nickel and iron.

When sulfur is added to the molten material of the nickel-iron alloy, as shown in FIG. 4(b) , iron and nickel react with sulfur to form a stable sulfide of _{FeS and Ni 3} S _{2 .}

When the sulfur is based on the equivalent required to sulfide the metal melt containing 25 wt% of nickel and 75 wt% of iron with FeS and Ni ₃ S ₂ , 1.0 to 1.4 of the standard equivalent for the generation of the stable phase as described above It is preferable to put it into a boat. If the amount of sulfur input is less than 1.0 times the standard equivalent, there is a problem that sulfation _{of iron and nickel into FeS and Ni 3} S _{2 does not occur.} there is

In the case of adding the sulfur, it is preferable that the temperature of the melt is 1,500 to 1,550° C. for the generation of the stable phase as described above. As can be seen from the figure shown in FIG. 4 (a), the nickel ferroalloy may have a difference depending on the composition, but has a melting point in the range of 1432 to 1538 ° C. If the temperature of the melt is less than 1500 ° C, the solution phase is It may not be generated, and when it exceeds 1550° C., an excessive temperature is required, and there is a problem in that energy consumption increases.

The present invention includes the step of removing sulfides of iron after generating sulfides of iron and nickel by the addition of sulfur. The removal of the sulfide of iron can be performed by selectively oxidizing FeS by blowing oxygen by injecting oxygen into the sulfide produced by the input of sulfur _{to produce iron oxide of Fe t} O, and the produced iron oxide is slag by specific gravity difference move to the top Therefore, iron oxide can be separated and removed by the slag removal method as described above.

At this time, the oxygen input amount is changed according to the composition and process conditions of the melt, and cannot be uniformly defined, but it may be input so that _{FeS can be oxidized to Fe t O in consideration of the partial pressure with sulfur. That is, the oxidation of FeS and Ni 3} S ₂ according to the oxygen injection is determined by the partial pressure of sulfur and oxygen, and as shown in FIG. 5 , only iron among the stable phases _{of FeS and Ni 3} S _{2 is converted to FeO at 1550° C.} It is preferable to input oxygen under the condition of partial pressure of sulfur and oxygen in which the oxidation reaction (direction of the arrow) occurs.

In the oxygen blowing, it is preferable to add slag. The slag is to help oxidative removal of iron and to minimize the loss of nickel _{, and basic slag including at least one of CaO, Na 2} O, BaO and MgO, more preferably at least one of CaO and MgO A basic oxide or an acid oxide containing _{SiO 2 may be added.} By additionally adding the slag as described above, the oxidation and removal of iron can be helped, and iron can be oxidized before nickel. Since nickel is thermodynamically more stable, iron is oxidized first. By adding slag, only iron can be continuously oxidized. More preferably, the basic slag and acidic slag may be mixed and added.

The sulfide of iron as described above becomes iron oxide by oxygen blowing, moves to the top of the melt, and exists as slag, and by removing the slag as described above, sulfide of nickel with a higher nickel content can be obtained, from this A nickel mat can be obtained by removing the sulfur and cooling. The method for removing sulfur from the sulfide of nickel can be applied to a conventionally known technique, and is not specifically limited in the present invention.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are examples of carrying out the present invention, and are not intended to limit the present invention thereby.

Example 1 and comparative example One

As a raw material, an NPI alloy having a composition as shown in Table 2 below was used.

Ni Fe Si C Unit: % by weight 13% 83% 1.5 2.5

After 400 g of the NPI alloy was completely melted by raising it to 1550 ° C in an induction furnace, slag was added at a rate of 58.2% CaO and 41.8% MgO, and oxygen was injected from the bottom at an amount of 300 ml/min to oxidize impurities and iron. slag was produced. The change in the oxidation removal reaction rate of impurities according to the oxygen blowing time was observed, and the results are shown in FIG. 6 . As can be seen from FIG. 6 , the oxidation reaction of carbon and silicon was first removed by oxygen blowing for about 50 minutes, and then it was found that the iron removal rate increased as the blowing time increased.

After removing the slag present on top of the molten NPI, the molten NPI and components of the slag were analyzed, and the results are shown in Tables 3 and 4, respectively.

Molten NPI Unit: % by weight Ni Fe C Si After selection is removed 20.8 79.2 - -

slag Unit: % by weight CaO SiO ₂ Fe ₃ O ₄ Al ₂ O ₃ After selection is removed 41.75 2.21 41.95 12.49

As can be seen from Tables 3 and 4, there was no carbon and Si remaining in the molten NPI, and it was confirmed that both were removed, and the iron removal rate was 41.7%, while the nickel loss was only 0.35%. Sulfur was added in an amount of 1.42 kg to 3 kg of the NPI melt (1550 ° C.), and oxygen was injected at 10 L/min to perform oxygen blowing. After removing the top slag thus produced, the slag and the melt were cooled.

The components of the nickel mat obtained by this and the produced slag were analyzed, and the results are shown in Table 5 below. In addition, XRD analysis was performed on the iron nickel mat obtained from the melt before oxygen blowing and the nickel mat obtained from the melt after oxygen blowing, and the results are shown in FIG. 7 . In Table 5, oxygen efficiency represents the amount of oxygen used to generate FeO compared to the total amount of oxygen required to remove all iron oxygen.

division Fe Ni S Fe/Ni weight ratio Composition after blowing Ni mat (wt%) 38.6 28.7 32.7 1.34 Slag composition after blowing (wt%) FeO SiO ₂ Al ₂ O ₃ 40.1 24.9 35.0 Iron Removal Rate (%) 61.5 Oxygen Efficiency (%) 73.5

As can be seen from Table 5, iron is removed as slag by oxygen blowing, and it can be seen that the nickel content of the finally obtained nickel mat is significantly increased. In addition, it can be seen from FIG. 7 that the content of iron sulfide is significantly reduced and the concentration of nickel sulfide is significantly increased by oxygen blowing.

Claims (9)

melting an iron and nickel alloy to obtain a molten product;
injecting oxygen into the melt to remove carbon and silicon and to oxidize and remove at least a portion of iron to increase the nickel concentration of the melt;
A step of sulfiding iron and nickel by adding sulfur to the melt with a high nickel concentration to produce sulfide
The step of oxidizing and removing iron sulfide by adding oxygen to the melt in which the sulfide is produced.
A method for producing a nickel mat from a low-grade nickel iron alloy comprising a. The method of claim 1, wherein the melting is performed at 1500 to 1550°C. The method of claim 2, wherein the melting is performed by induction heating. The method for producing a nickel mat from a low-grade nickel iron alloy according to claim 1, wherein the slag is added to the step of obtaining a melt or increasing the nickel concentration of the melt. 5. The method of claim 4, wherein the slag is a basic slag containing at least one _{of CaO, MgO, Na 2 O, and BaO.} The method according to claim 1, wherein the sulfur is 1.0 to 1.4 times the reference equivalent, based on the equivalent required to sulfide the metal melt containing 25 wt% of nickel and 75 wt% of iron with FeS and Ni ₃ S ₂ A method for producing a nickel mat from a low-grade nickel-iron alloy that is added in the equivalent of The method of claim 1, wherein the sulfiding is performed at a temperature of 1500 to 1550°C. The method of claim 1, wherein the step of oxidizing the sulfide is to add slag together. The low-grade nickel iron according to claim 8, wherein the slag input to the step of oxidizing the sulfide is basic slag containing at least one of CaO and MgO, _{acidic slag containing SiO 2} , or mixed slag of the basic slag and acidic slag. A method of making a nickel mat from an alloy.

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