Method for producing nickel sulfate solution for secondary batteries from nickel cathode

Abstract

The present invention provides a method for producing a nickel sulfate solution, comprising: a leaching step of leaching a nickel cathode in sulfuric acid at high temperature and pressure; a neutralizing step of neutralizing the leachate from the leaching step; and a filtration step of filtering the neutralized solution from the neutralizing step to produce a filtrate.

Description

[Technical field]

[0001] The present invention relates to a method for producing a nickel sulfate solution for a secondary battery from a nickel cathode. [Background technology]

[0002] Demand for secondary batteries is increasing with the development of the IT industry, electric vehicles, and energy storage system (ESS) markets, which is also driving demand for nickel sulfate, which is used as a raw material for the positive electrodes of secondary batteries.

[0003] Conventionally, nickel sulfate solution was produced by leaching and impurity purification processes using raw materials such as nickel concentrate and nickel-containing mixed hydroxide precipitates (MHP) cake. However, when nickel sulfate solution was produced by leaching raw materials containing nickel using a method in which oxygen gas or ozone was added as an oxidizing agent under normal pressure conditions, there was a problem that the leaching efficiency was reduced. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for producing a nickel sulfate solution with high leaching efficiency while inputting only sulfuric acid and oxygen gas and / or nitrogen gas. [Means for solving the problem]

[0005] According to one embodiment of the present invention, At a temperature of 170°C to 200°C and a pressure of 8.5bar to 16bar, Nickel Cathode Sulfurization A leaching step of leaching in acid, , add nickel powder The present invention provides a method for producing a nickel sulfate solution, comprising: a neutralization step of neutralizing a nickel sulfate solution; and a filtration step of filtering the neutralized solution obtained in the neutralization step to produce a filtrate.

[0006] According to one embodiment of the present invention, the leaching step is characterized by introducing oxygen gas.

[0007] According to one embodiment of the present invention, the leaching process is characterized by introducing nitrogen gas.

[0010] According to one embodiment of the present invention, the nickel concentration in the neutralized solution after the neutralization process is 120 to 140 g / L. Effect of the Invention

[0011] According to the present invention, there is provided a method for producing a nickel sulfate solution exhibiting high leaching efficiency by simply introducing oxygen gas and / or nitrogen gas under high temperature and pressure.

[0012] According to the present invention, it is possible to provide a method for producing a nickel sulfate solution that is safer and more efficient by introducing nitrogen gas under high temperature and pressure. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a process diagram showing a process for producing nickel sulfate for a secondary battery from a nickel cathode. [Diagram 2] 1 is a graph showing Ni dissolution rates after the leaching process in each of the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The embodiments of the present disclosure are illustrated for the purpose of explaining the technical idea of ​​the present disclosure, and the scope of the rights of the present disclosure is not limited to the embodiments presented below or the specific description of these embodiments.

[0015] The method for producing nickel sulfate for secondary batteries from the nickel cathode of the present invention is to dissolve the nickel cathode in water, sulfuric acid (H 2 SO 4 ) and oxygen gas (O 2 ) and / or nitrogen gas (N 2 ) in the presence of leaching.

[0016] The method for producing nickel sulfate for secondary batteries from the nickel cathode of the present invention includes a neutralization step of adding nickel powder (Ni Powder) to the leachate.

[0017] The method for producing nickel sulfate for secondary batteries from the nickel cathode of the present invention includes a filtration step of filtering the neutralized liquid to separate it into a filtrate and a cake.

[0018] The manufacturing process of the present invention will now be described in detail with reference to FIG.

[0019] [Leaching process (S100)] The leaching step (S100) is a step in which nickel cathode cut to a size suitable for leaching is introduced into an autoclave in an amount of about 2 equivalents relative to the target nickel concentration, and then reacted for 5 to 24 hours at a temperature of 170°C to 200°C and a pressure of 8.5 bar to 16 bar under conditions of introducing about 1 equivalent of sulfuric acid, oxygen gas and / or nitrogen gas. The nickel cathode can be cut to a size of, for example, 2 to 10 cm and introduced. Here, the target nickel concentration may be the nickel concentration in the neutralized solution after the neutralization step (S200) described later. Such a target nickel concentration can be set to an appropriate target concentration in consideration of the solubility of nickel and crystallization due to temperature. If the nickel concentration after neutralization is less than 120 g / L, the efficiency of the subsequent crystallization process will decrease, and if it is more than 140 g / L, nickel may crystallize during the neutralization process if the solution temperature drops, which will result in a loss during filtration. Therefore, the target nickel concentration is preferably 120 to 140 g / L. When the leaching step (S100) is carried out at a temperature below 170°C, the solubility of nickel is low and the efficiency is low, and when the temperature exceeds 200°C, the dissolution rate does not increase significantly. Therefore, the leaching step (S100) is preferably carried out at a temperature of 170°C to 200°C.

[0020] In one embodiment of the present invention, when the target nickel concentration is 120 g / L, the nickel cathode can be cut into a size of 2 to 10 cm and 2 equivalents (240 g / L) can be added, and 1 equivalent of sulfuric acid (200 g / L) can be added. Then, the leaching process (S100) can be performed by adding oxygen gas at a temperature of 170°C to 180°C or nitrogen gas at a temperature of 180°C to 200°C.

[0021] When oxygen gas is introduced, the introduced nickel reacts with sulfuric acid to form nickel sulfate, and hydrogen ions react with oxygen gas to produce water. gas The reaction that generates the following reaction may also occur at the same time. If oxygen gas is added, the oxygen gas acts as an oxidizing agent, and the efficiency of nickel leaching may be higher than when nitrogen gas is added. The reaction formulas when oxygen gas is added are as shown in the following formulas (1) and (2).

[0022] Ni+H 2 SO 4 +1 / 2 O 2 →NiSO 4 +H 2 O...Equation (1) Ni+H 2 SO 4 →NiSO 4 +H 2 ...Equation (2)

[0023] When nitrogen gas is injected, the injected nickel reacts with sulfuric acid to become nickel sulfate, which may result in a reaction that generates hydrogen gas. However, in this case, since nitrogen gas is an inert gas with very low reactivity, the hydrogen gas can be removed by discharging both the nitrogen gas and hydrogen gas. Therefore, injecting nitrogen gas is safer than injecting oxygen gas. The reaction formula when nitrogen gas is injected is shown above in formula (2).

[0024] In the leaching step (S100), oxygen gas and nitrogen gas can be introduced together. Nitrogen gas reduces the partial pressure of hydrogen gas that is generated when oxygen gas is introduced, thereby enabling safer operation.

[0025] In order to promote the leaching of nickel, a stirrer may be placed inside the autoclave and the nickel may be dissolved while stirring.

[0026] [Neutralization process (S200)] The neutralization step (S200) is a step in which nickel powder (Ni Powder) is added to the leachate after the leaching reaction has progressed in the autoclave to neutralize it to a target pH range.

[0027] In order to subsequently evaporate and concentrate the nickel sulfate solution, it is necessary to lower the acidity. If the pH range is 6 to 7 or more, no more nickel will be leached into the solution, so the target pH range may be pH 5.0 to 7.0. It is preferable to neutralize the solution to pH 6 through the neutralization step (S200). The neutralization reaction formula is as shown in the above formula (2).

[0028] In the neutralization step (S200), since the purpose is to neutralize the acid of sulfuric acid present in the leachate, an appropriate amount of nickel powder can be added to efficiently reach the target pH range. In the neutralization step (S200), the nickel powder can be added, for example, in an amount of 1.5 to 3 equivalents, and preferably in an amount of 2 equivalents (for example, if the final acidity of the leachate is 10 g / L, nickel powder can be added in an amount of 12 g / L). When powdered nickel powder is used, it is preferable to use nickel powder because it has high reactivity and the neutralization reaction occurs frequently, but it is not limited thereto as long as the neutralization purpose can be achieved.

[0029] When oxygen gas is used at 180°C, the final acidity of the leachate may be about 8g / L, and when nitrogen gas is used at 180°C, the final acidity may be about 50g / L. When nitrogen gas is used at 200°C, the final acidity may be about 38g / L. When nitrogen gas is used, the final acidity is higher than when oxygen gas is used, so more nickel powder may be required to neutralize it. However, in terms of the risk of hydrogen gas explosion, the introduction of nitrogen gas may be a safer method than the introduction of oxygen gas.

[0030] [Filtration process (S300)] Metallic nickel that did not dissolve in the leaching step (S100) and neutralization step (S200) remains in the neutralization solution as a solid component, so the neutralization solution is transferred to a filtration device and filtered, and the filtrate, which is a nickel sulfate solution, is sent to the refining step, and the cake is fed back into the neutralization step. The nickel sulfate in the filtrate is crystallized through the refining step.

[0031] [Example 1] In this example, nickel sulfate solution was produced by leaching nickel cathode in sulfuric acid. For a target nickel (Ni) concentration of 120 g / L, 2 equivalents of nickel cathode, 1 equivalent of sulfuric acid, and oxygen gas were added. The reaction was carried out at 170°C (8.5 bar) and 180°C (10.5 bar) for 24 hours. The dissolution rate for each reaction time is shown in Table 1.

[0032] In the neutralization step (S200), 2 equivalents of Ni powder are added to prepare a Ni 120g / L solution at 90°C and pH 6.0.

[0033] The neutralized solution is filtered, and the filtered nickel sulfate solution is sent to the purification process, and the cake is again fed into the neutralization process (S200).

[0034] [Table 1]

[0035] [Example 2] Two equivalents of nickel cathode, one equivalent of sulfuric acid, and nitrogen gas instead of oxygen gas were added. The reaction was carried out at 180°C (10.5 bar) and 200°C (16 bar) for 24 hours. The dissolution rate for each reaction time is shown in Table 2.

[0036] The neutralization step (S200) and the filtration step (S300) are the same as those in Example 1.

[0037] [Table 2]

[0038] [Comparative Example 1] Two equivalents of nickel cathode, one equivalent of sulfuric acid, and oxygen gas were added. The reaction was allowed to proceed at 95°C (atmospheric pressure) for 24 hours. The dissolution rate for each reaction time is shown in Table 3.

[0039] The neutralization and filtration steps are the same as in Example 1.

[0040] [Comparative Example 2] Two equivalents of nickel cathode, one equivalent of sulfuric acid and ozone were charged.

[0041] The reaction was allowed to proceed at 95°C (atmospheric pressure) for 24 hours. The dissolution rates for each reaction time are shown in Table 3.

[0042] The neutralization and filtration steps are the same as in Example 1.

[0043] [Table 3]

[0044] It can be seen that the Ni dissolution rate is very low in Comparative Example 1 in which oxygen gas was introduced at normal pressure and Comparative Example 2 in which ozone was introduced at normal pressure, whereas Examples 1 and 2 show a much better dissolution rate than the respective Comparative Examples.

[0045] 2 is a graph showing the Ni dissolution rate after the leaching process for each Example and Comparative Example, allowing the dissolution rates of each Example and Comparative Example to be compared.

[0046] That is, in Examples 1 and 2, a nickel sulfate solution can be efficiently produced by introducing oxygen gas or nitrogen gas under high temperature and pressure.

[0047] It should be understood that the above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above detailed description, and all modifications and alterations derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. A leaching step in which a nickel cathode is leached in sulfuric acid at a temperature of 170°C to 200°C and a pressure of 8.5 bar to 16 bar; a neutralization step of neutralizing the leaching solution from the leaching step by adding nickel powder; The method for producing a nickel sulfate solution includes a filtration step of filtering the neutralized solution from the neutralization step to produce a filtrate.

2. 2. The method for producing a nickel sulfate solution according to claim 1, wherein the leaching step is performed by introducing oxygen gas.

3. 3. The method for producing a nickel sulfate solution according to claim 1, wherein the leaching step is performed by introducing nitrogen gas.

4. 3. The method for producing a nickel sulfate solution according to claim 1, wherein the nickel concentration in the neutralized solution after the neutralization step is 120 to 140 g / L.

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