JP7498991B2 - How to treat chlorine gas - Google Patents

Description

The present invention relates to a method for treating chlorine gas.

In recent years, with the widespread use of lithium-ion batteries, methods are being considered for recovering valuable metals such as lithium, manganese, nickel, and cobalt from used lithium-ion batteries and reusing them as positive electrode active materials for the lithium-ion batteries.

Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, the waste lithium-ion batteries are heated (roasted), or crushed and classified without being heated to obtain a powder containing the valuable metals (hereinafter referred to as battery powder), which is dissolved in hydrochloric acid, and the valuable metals are leached with hydrochloric acid, and the leachate obtained is subjected to solvent extraction (see, for example, Patent Documents 1 and 2).

Patent No. 4388091 Patent No. 4865745

However, when the battery powder is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid, there is a disadvantage that the chlorine gas generated by the leaching reaction can corrode the equipment and pollute the working environment.

The present invention aims to eliminate such inconveniences and provide a method for treating chlorine gas that can render harmless or effectively utilize the chlorine gas generated when the battery powder is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid.

The inventors of the present invention have conducted extensive research in light of the above-mentioned problems and have discovered that powder containing valuable metals obtained from waste lithium-ion batteries can be dissolved in hydrochloric acid, and the chlorine gas generated when the valuable metals are leached with hydrochloric acid can be made harmless or effectively utilized by reacting it with at least one selected from the group consisting of a reducing agent, an alkali metal hydroxide, and an alkaline earth metal hydroxide. The present invention has been completed based on these findings.

In order to achieve this object , the method for treating chlorine gas of the present invention comprises dissolving a powder containing valuable metals obtained from waste lithium ion batteries in hydrochloric acid, and reacting the chlorine gas generated when the valuable metals are leached with hydrochloric acid with at least one selected from the group consisting of a reducing agent, an alkali metal hydroxide, and an alkaline earth metal hydroxide, thereby rendering the chlorine gas harmless or making effective use of it.

The method for treating chlorine gas of the present invention comprises the steps of dissolving powder containing valuable metals obtained from waste lithium ion batteries in hydrochloric acid, and absorbing chlorine gas generated when the valuable metals are leached with hydrochloric acid into a first aqueous ferrous chloride solution, thereby producing a second aqueous ferrous chloride solution containing ferric chloride in which the ferric chloride concentration is increased relative to the first aqueous ferrous chloride solution.
The concentration of ferric chloride in the ferrous chloride aqueous solution means the ratio of ferric chloride to the total number of moles of ferrous chloride and ferric chloride contained in the ferrous chloride aqueous solution. Since the second ferrous chloride aqueous solution has an increased ferric chloride concentration compared to the first ferrous chloride aqueous solution, it may be referred to as an ferric chloride aqueous solution hereinafter for convenience.
By this process, the chlorine gas is immobilized as ferric chloride, and the chlorine gas can be rendered harmless.

The method for treating chlorine gas of the present invention preferably further comprises a step of contacting a second aqueous ferrous chloride solution containing ferric chloride, produced by absorbing the chlorine gas into a first aqueous ferrous chloride solution, with iron to reduce at least a portion of the ferric chloride contained in the second aqueous ferrous chloride solution, thereby producing a third aqueous ferrous chloride solution containing ferric chloride in which the ferric chloride concentration is reduced relative to the second aqueous ferrous chloride solution.
The second aqueous ferrous chloride solution containing ferric chloride can be brought into contact with iron, whereby at least a portion of the ferric chloride contained therein is reduced to ferrous chloride, thereby producing a third aqueous ferrous chloride solution containing ferric chloride in which the ferric chloride concentration is reduced relative to the second aqueous ferrous chloride solution.

At least a portion of the third ferrous chloride aqueous solution containing the ferric chloride can be used as the first ferrous chloride aqueous solution to absorb the chlorine gas, thereby making effective use of the chlorine gas.

The method for treating chlorine gas of the present invention includes the steps of dissolving powder containing valuable metals obtained from waste lithium-ion batteries in hydrochloric acid, reacting the chlorine gas generated when the valuable metals are leached with hydrochloric acid with hydrogen gas to generate hydrogen chloride, and absorbing the hydrogen chloride into water to generate a second hydrochloric acid. As a result, the chlorine gas can be effectively utilized by converting it into hydrochloric acid.

The method for treating chlorine gas of the present invention preferably further includes a step of purifying the chlorine gas and removing oxygen contained in the chlorine gas before the step of reacting the chlorine gas with the hydrogen gas to generate the hydrogen chloride. By removing oxygen contained in the chlorine gas before the step of generating hydrogen chloride, it is possible to prevent hydrogen from being consumed by oxygen when the chlorine gas is reacted with the hydrogen gas.

At least a portion of the second hydrochloric acid is used, preferably as the first hydrochloric acid, for leaching the valuable metals.

The method for treating chlorine gas of the present invention includes a hypochlorite generation step of contacting chlorine gas with an alkaline absorption liquid containing at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to generate hypochlorite , and a first hypochlorite reduction step of reacting hypochlorite with carbon .
The method for treating chlorine gas of the present invention comprises a hypochlorite generation step of contacting chlorine gas with an alkaline absorbing liquid containing at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to generate hypochlorite, and a second hypochlorite reduction step of reacting hypochlorite with aluminum.

The chlorine gas treatment method of the present invention includes a carbon dioxide production process in which chlorine gas is reacted with carbon and water to produce carbon dioxide.

The chlorine gas treatment method of the present invention includes an aluminum chloride production step in which chlorine gas is reacted with aluminum to produce aluminum chloride.

1 is a flow chart showing a method for treating chlorine gas according to one embodiment of the present invention. FIG. 1 is a system configuration diagram showing an example of an apparatus configuration used in a chlorine gas treatment method according to one embodiment of the present invention. 1 is a flow chart showing a method for treating chlorine gas according to one embodiment of the present invention. FIG. 1 is a system configuration diagram showing an example of an apparatus configuration used in a chlorine gas treatment method according to one embodiment of the present invention.

The invention will now be described in more detail with reference to the accompanying drawings.
The method for treating chlorine gas of the present invention can be used to treat chlorine gas generated when a powder containing valuable metals (battery powder) obtained from waste lithium ion batteries is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid.

In the chlorine gas treatment method of the present invention, the waste lithium ion batteries refer to used lithium ion batteries that have reached the end of their life as battery products, lithium ion batteries that have been discarded as defective products during the manufacturing process, residual positive electrode materials used in the manufacture of products during the manufacturing process, etc.

The powder containing the valuable metals can be obtained, for example, as follows. First, the positive electrode foil (a positive electrode mixture containing a positive electrode active material is applied to an aluminum foil current collector) that is the residual positive electrode material used in the manufacturing process of lithium-ion batteries is heat-treated (roasted) in an electric furnace at a temperature in the range of, for example, 100 to 450°C, or is crushed with a crusher such as a hammer mill or jaw crusher without being heat-treated, and the casing, current collector, etc. that constitute the waste lithium-ion battery are removed (classified) by sieving to obtain a battery powder containing valuable metals.

Alternatively, used lithium ion batteries that have not been discharged or heated may be crushed in the crusher, the casing, current collectors, etc. may be removed by sieving, and then the battery powder may be obtained by heat treatment at a temperature within the above range.

In the chlorine gas treatment method of the present invention, the battery powder is leached with hydrochloric acid. As a result, a leachate containing the various valuable metals is obtained.

The method for treating chlorine gas of the present invention includes a step of reacting the chlorine gas with a reducing agent. The reaction between chlorine gas and the reducing agent is described in more detail below.

In a first embodiment of the chlorine gas treatment method of the present invention, as shown in FIG. 1, the waste lithium ion batteries are pretreated in STEP 1, and battery powder is obtained in STEP 2.

Next, in STEP 3, the battery powder is dissolved in hydrochloric acid, and the valuable metals are leached with the hydrochloric acid. As a result, in STEP 4, a leachate that is a hydrochloric acid solution of the valuable metals can be obtained.
The leachate is neutralized in the solvent extraction in STEP 5, and then manganese, cobalt, and nickel are successively extracted from the valuable metals by solvent extraction in STEP 6. Then, an aqueous lithium salt solution can be obtained as an extraction residue in STEP 6. The aqueous lithium salt solution can be reacted with carbon dioxide gas or a carbonate compound to obtain lithium carbonate.

On the other hand, when the battery powder is dissolved in hydrochloric acid in STEP 3, a leaching reaction occurs when the valuable metal is leached into the hydrochloric acid, and chlorine gas is generated in STEP 7. The chlorine gas treatment method of the first embodiment is a method for treating the chlorine gas generated in STEP 7, and can be carried out, for example, by the chlorine gas treatment device 1 shown in FIG.

The chlorine gas treatment device 1 comprises a hydrochloric acid leaching tank 2 in which battery powder obtained from waste lithium ion batteries is dissolved in hydrochloric acid and valuable metals contained in the battery powder are leached with hydrochloric acid, a reaction tower 3 in which the chlorine gas produced in the hydrochloric acid leaching tank 2 is absorbed into a first aqueous ferrous chloride solution (hereinafter, for convenience, may be referred to as an aqueous ferrous chloride solution) to produce a second aqueous ferrous chloride solution containing ferric chloride, and a reduction reaction tank 4 in which the second aqueous ferrous chloride solution containing ferric chloride produced in the reaction tower 3 is brought into contact with iron to reduce at least a portion of the ferric chloride contained in the second aqueous ferrous chloride solution to ferrous chloride.

The second ferrous chloride aqueous solution is produced by absorbing chlorine gas from the first ferrous chloride aqueous solution in the reaction tower 3, and as a result, the concentration of ferric chloride is increased relative to the first ferrous chloride aqueous solution, and therefore, for convenience, may be referred to as ferric chloride aqueous solution hereinafter. In addition, in the reduction reaction tank 4, at least a portion of the ferric chloride contained in the second ferrous chloride aqueous solution is reduced to ferrous chloride, and a third ferrous chloride aqueous solution (hereinafter, for convenience, may be referred to as ferrous chloride aqueous solution) containing ferric chloride is produced, in which the concentration of ferric chloride is reduced relative to the second ferrous chloride aqueous solution.

The hydrochloric acid leaching tank 2 is provided at its upper part with a hydrochloric acid supply pipe 21 for supplying hydrochloric acid, a battery powder supply means 22 for supplying battery powder, and a dilution air supply pipe 23 for supplying dilution air, while at its bottom part is provided with a leaching solution extraction pipe 25 for extracting leaching solution 24 obtained by leaching valuable metals contained in the battery powder with hydrochloric acid. The hydrochloric acid leaching tank 2 is also provided at its upper part with a chlorine gas extraction pipe 26 for extracting chlorine gas generated by the leaching reaction when the valuable metals are leached with hydrochloric acid, and the chlorine gas extraction pipe 26 is connected to the reaction tower 3.

The reaction tower 3 has an aqueous ferrous chloride solution 31 (first aqueous ferrous chloride solution) stored at the bottom, and a filler layer 32 filled with filler formed above the aqueous ferrous chloride solution 31. The reaction tower 3 also has a circulation conduit 33 that takes out the aqueous ferrous chloride solution 31 stored at the bottom and supplies it from above the filler layer 32. The circulation conduit 33 has a first pump 34 in the middle, and a first switching valve 35 downstream of the first pump 34. A ferric chloride aqueous solution supply conduit 36 that supplies the aqueous ferric chloride solution (second aqueous ferrous chloride solution containing ferric chloride) generated in the reaction tower 3 to the reduction reaction tank 4 branches off from the first switching valve 35, and the ferric chloride aqueous solution supply conduit 36 is connected to the upper part of the reduction reaction tank 4. Furthermore, the reaction tower 3 is provided with an air release conduit 37 for releasing air to the atmosphere at the top of the tower above the packing layer 32, and the air release conduit 37 is provided with a blower 38 for sucking air from inside the reaction tower 3 in the middle.

The reduction reaction tank 4 is provided with a water supply conduit 41 for supplying concentration-adjusted water and an iron supply means 42 for supplying iron such as iron chips at the top, and a ferrous chloride solution extraction conduit 44 at the bottom for extracting a third ferrous chloride solution 43 containing ferric chloride, which is generated by reducing at least a portion of the ferric chloride contained in the ferric chloride solution (second ferrous chloride solution containing ferric chloride) supplied by the ferric chloride solution supply conduit 36 by reaction with iron. The ferrous chloride solution extraction conduit 44 is connected to the bottom of the reaction tower 3 via a second pump 45 provided midway, and is provided with a second switching valve 46 downstream of the second pump 45. An increment extraction conduit 47 for extracting an increment of the ferrous chloride solution 43 branches off from the second switching valve 46.

Next, a method for treating chlorine gas using the chlorine gas treatment apparatus 1 according to this embodiment will be described.
In the chlorine gas treatment device 1, first, the battery powder obtained in STEP 2 is supplied to the hydrochloric acid leaching tank 2 from the battery powder supply means 22, while hydrochloric acid is supplied to the hydrochloric acid leaching tank 2 from the hydrochloric acid supply conduit 21. The hydrochloric acid has a concentration of, for example, 3 to 12 mol/L, and is supplied in an amount of, for example, 3 to 15 L per kg of the battery powder. As a result, the battery powder is dissolved in the hydrochloric acid in the hydrochloric acid leaching tank 2, and the valuable metals are leached by the hydrochloric acid (STEP 3), and a leachate 24, which is a hydrochloric acid solution of the valuable metals, can be obtained (STEP 4). The leachate 24 is taken out through the leachate withdrawal conduit 25 and is used for solvent extraction in STEP 5.

In addition, in the hydrochloric acid leaching tank 2, chlorine gas is generated by the leaching reaction when the valuable metals are leached with hydrochloric acid (STEP 7). The chlorine gas is extracted from the hydrochloric acid leaching tank 2 by being sucked through the chlorine gas extraction conduit 26 by a blower 38 provided in the air release conduit 37 of the reaction tower 3, and is introduced into the reaction tower 3.

The chlorine gas introduced into the reaction tower 3 through the chlorine gas extraction conduit 26 is sucked into the blower 38 and moves from bottom to top within the reaction tower 3 together with the air flowing in from the dilution air supply conduit 23. Meanwhile, the aqueous ferrous chloride solution 31 stored at the bottom of the reaction tower 3 is sucked into the first pump 34 through the circulation conduit 33, and is taken out of the reaction tower 3 and supplied into the reaction tower 3 from above the packing layer 32.

The concentration of ferric chloride in the ferrous chloride aqueous solution 31, i.e., the ratio of ferric chloride to the total number of moles of ferrous chloride and ferric chloride contained in the ferrous chloride aqueous solution 31, is, in the initial state, for example, in the range of 0.1 to 30 mol %.

The chlorine gas is absorbed into the ferrous chloride aqueous solution 31 while moving from the bottom to the top in the reaction tower 3 (STEP 8), and a part of the ferrous chloride contained in the ferrous chloride aqueous solution 31 is oxidized to ferric chloride to generate an aqueous ferric chloride solution (a second aqueous ferrous chloride solution containing ferric chloride) (STEP 9). The reaction in which the chlorine gas is absorbed into the ferrous chloride aqueous solution 31 is a gas-liquid reaction, and proceeds efficiently when the two come into contact on the surface of the filler that forms the filler layer 32. As the filler, a mesh-shaped ring made of glass or synthetic resin (for example, Raschig Super Ring (registered trademark) manufactured by Raschig) or the like can be used.

In addition, the air supplied to the reaction tower 3 together with the chlorine gas is not absorbed by the aqueous ferrous chloride solution 31, so it is sucked into the blower 38 and released into the atmosphere through the air release conduit 37.

When the ferrous chloride is oxidized to generate the ferric chloride, the concentration of ferric chloride contained in the ferrous chloride aqueous solution 31 stored at the bottom of the reaction tower 3 gradually increases, and the absorption efficiency of the chlorine gas gradually decreases accordingly. Therefore, in the chlorine gas treatment device 1, in order to prevent the concentration of ferric chloride contained in the ferrous chloride aqueous solution 31 from increasing to such an extent that the absorption efficiency of the chlorine gas decreases, a first switching valve 35 provided in the middle of the circulation conduit 33 is operated to supply a part of the ferric chloride aqueous solution (a second ferrous chloride aqueous solution containing ferric chloride) to the reduction reaction tank 4 via a ferric chloride aqueous solution supply conduit 36. The supply of the ferric chloride aqueous solution (a second ferrous chloride aqueous solution containing ferric chloride) may be performed continuously by adjusting the flow rate of the ferric chloride aqueous solution supply conduit 36 with the switching valve 35, or may be performed by intermittently operating the switching valve 35.

In the reduction reaction tank 4, iron such as iron pieces is supplied from the iron supply means 42 to the ferric chloride aqueous solution (second ferrous chloride aqueous solution containing ferric chloride) supplied from the ferric chloride aqueous solution supply conduit 36, and at least a portion of the ferric chloride contained in the ferric chloride aqueous solution is reduced by reaction with the iron to form ferrous chloride (STEP 10), thereby producing a ferrous chloride aqueous solution (third ferrous chloride aqueous solution containing ferric chloride) 43 (STEP 11).

At this time, in the reduction reaction tank 4, the concentration of ferric chloride contained in the ferrous chloride aqueous solution 43 produced can be adjusted to the range of 0.1 to 30 mol %, which is equivalent to the initial state of the ferrous chloride aqueous solution 31 stored at the bottom of the reaction tower 3, by using concentration-adjusted water supplied from the water supply conduit 41.

At least a portion of the third aqueous ferrous chloride solution 43 is removed from the reduction reaction tank 4 and returned to the reaction tower 3 by being sucked into the second pump 45 via the aqueous ferrous chloride solution extraction conduit 44, and is used as the first aqueous ferrous chloride solution 31 to absorb the chlorine gas in STEP 8.

In the reduction reaction tank 4, the amount of the ferrous chloride aqueous solution 43 produced is increased by the concentration-adjusted water supplied from the water supply conduit 41 in accordance with the amount of chlorine gas absorbed by the ferric chloride aqueous solution (the second ferrous chloride aqueous solution containing ferric chloride) compared to the amount of the ferric chloride aqueous solution supplied. Therefore, by operating the switching valve 46 provided in the ferrous chloride aqueous solution extraction conduit 44, the increase in the ferrous chloride aqueous solution 43 produced may be taken out from the increase extraction conduit 47. The increase in the ferrous chloride aqueous solution 43 taken out from the increase extraction conduit 47 can be made into an ferric chloride aqueous solution that does not substantially contain ferrous chloride by separately oxidizing the ferrous chloride contained therein with chlorine to form ferric chloride, and the ferric chloride aqueous solution can be used, for example, as an etching solution for copper in printed circuit boards.

In this embodiment, the increase in the ferrous chloride aqueous solution 43 is extracted from the increase extraction conduit 47 by operating the switching valve 46, but the reduction reaction tank 4 may be an overflow type, and the increase may be allowed to overflow and stored in a storage tank (not shown) and then extracted from the storage tank.

In a second embodiment of the chlorine gas treatment method of the present invention, as shown in Figure 3, the waste lithium ion batteries are pretreated in STEP 1, and battery powder is obtained in STEP 2.

Next, in STEP 3, the battery powder is dissolved in a first hydrochloric acid, and the valuable metal is leached by the first hydrochloric acid. As a result, in STEP 4, a leachate that is a hydrochloric acid solution of the valuable metal can be obtained.

The leachate is neutralized in the solvent extraction in STEP 5, and then manganese, cobalt, and nickel are successively extracted from the valuable metals with a solvent. Then, in STEP 6, an aqueous lithium salt solution can be obtained as the extraction residue. The aqueous lithium salt solution can be reacted with carbon dioxide gas or a carbonate compound to obtain lithium carbonate.

On the other hand, when the battery powder is dissolved in the first hydrochloric acid in STEP 3, a leaching reaction occurs when the valuable metal is leached into the first hydrochloric acid, and chlorine gas is generated in STEP 7. The method for treating chlorine gas in this embodiment is a method for treating chlorine gas generated in STEP 7, and can be carried out, for example, by a chlorine gas treatment device 1a shown in FIG.

The chlorine gas treatment device 1a includes a hydrochloric acid leaching tank 2 in which battery powder obtained from waste lithium-ion batteries is dissolved in a first hydrochloric acid and valuable metals contained in the battery powder are leached with the first hydrochloric acid, a chlorine refining tower 3a in which oxygen-containing air and dust are separated and removed from the chlorine gas produced in the hydrochloric acid leaching tank 2 to produce chlorine gas, a hydrogen supply facility 4a in which hydrogen gas is refined, a combustion tower 5 in which the refined chlorine gas and hydrogen gas are reacted at high temperature to produce hydrogen chloride, a hydrochloric acid absorption tower 6 in which the hydrogen chloride produced in the combustion tower 5 is absorbed into water to produce a second hydrochloric acid, and an absorption liquid supply tank 7 in which an absorption liquid is supplied to the hydrochloric acid absorption tower 6.

The hydrochloric acid leaching tank 2 is provided at its top with a hydrochloric acid supply pipe 21 for supplying the first hydrochloric acid and a battery powder supply means 22 for supplying the battery powder, while at its bottom with a leaching solution extraction pipe 24a for extracting the leaching solution 23a obtained by leaching the valuable metals contained in the battery powder with the first hydrochloric acid. The hydrochloric acid leaching tank 2 is also provided at its top with a chlorine gas extraction pipe 25a for extracting the chlorine gas produced by the leaching reaction when the valuable metals are leached with the first hydrochloric acid, and the chlorine gas extraction pipe 25a is connected to the chlorine purification tower 3a.

The chlorine purification tower 3a is equipped with a purified chlorine gas extraction conduit 31a at the top for extracting purified chlorine gas, and the purified chlorine gas extraction conduit 31a is connected to a chlorine burner 51 in the combustion tower 5.

The hydrogen supply equipment 4a has a hydrogen gas extraction pipe 41a at the top, which is connected to a chlorine burner 51 in the combustion tower 5.

The combustion tower 5 is equipped with a chlorine burner 51 at the bottom that burns chlorine gas supplied from the purified chlorine gas extraction conduit 31a and hydrogen gas supplied from the hydrogen gas extraction conduit 41a to generate hydrogen chloride, and a combustion tower cooling water jacket 52 at the outer periphery that cools the generated hydrogen chloride. The combustion tower 5 is also equipped with a hydrogen chloride supply conduit 53 at the top that supplies the generated hydrogen chloride to the hydrochloric acid absorption tower 6. The combustion tower cooling water jacket 52 is equipped with a combustion tower cooling water supply conduit 54 at the bottom that supplies cooling water, and a combustion tower cooling water extraction conduit 55 at the top that extracts cooling water.

Above the hydrogen chloride supply conduit 53, there is provided a spray tank 56 that sprays cooling water to cool the hydrogen chloride, and below, there is provided a water receiving tank 57 that stores the cooling water sprayed from the spray tank 56. The spray tank 56 is provided with a spray tank cooling water supply conduit 58 that supplies the cooling water, and the water receiving tank 57 is provided with a water receiving tank cooling water extraction conduit 59 that extracts the cooling water.

The hydrochloric acid absorption tower 6 is provided with a hydrochloric acid extraction conduit 61 at the bottom for extracting the generated second hydrochloric acid, and a hydrogen chloride extraction conduit 62 at the bottom for extracting unreacted hydrogen chloride. The hydrochloric acid absorption tower 6 is also provided with a first storage tank 63 directly below the top of the tower, to which the absorption liquid is supplied from the absorption liquid supply tank 7, and an inner cylinder 64 below the first storage tank 63. The inner cylinder 64 is provided with a second storage tank 65 on the outer periphery of the upper edge. The hydrochloric acid absorption tower 6 is also provided with a hydrochloric acid absorption tower cooling water jacket 66 on the outer periphery for cooling the hydrogen chloride and the generated second hydrochloric acid.

The hydrochloric acid extraction conduit 61 is connected to the hydrochloric acid leaching tank 2 via a hydrochloric acid pump 61a installed midway. The hydrogen chloride extraction conduit 62 is connected to the bottom of the absorption liquid supply tank 7 via a blower 62a installed midway. The hydrochloric acid absorption tower cooling water jacket 66 is provided with a hydrochloric acid absorption tower cooling water supply conduit 67 that supplies cooling water to the lower part, and a hydrochloric acid absorption tower cooling water extraction conduit 68 that extracts cooling water from the upper part.

The absorption liquid supply tank 7 is provided with a water supply conduit 71 for supplying water and a gas release conduit 72 for releasing gas at its upper part, and an absorption liquid supply conduit 73 at its lower part for supplying the absorption liquid that has absorbed hydrogen chloride and become dilute hydrochloric acid to the upper part of the hydrochloric acid absorption tower 6. The gas release conduit 72 is provided with a check valve 74 that opens when the internal pressure of the absorption liquid supply tank 7 reaches or exceeds a certain level.

The chlorine gas treatment device 1a may also be configured so that the cooling water taken out from the hydrochloric acid absorption tower cooling water jacket 66 by the hydrochloric acid absorption tower cooling water take-out conduit 68 is circulated to the hydrochloric acid absorption tower cooling water take-out conduit 68 via the sprinkler tank 56, the water receiving tank 57 and the combustion tower cooling water jacket 52. In this case, for example, the hydrochloric acid absorption tower cooling water take-out conduit 68 is connected to the sprinkler tank cooling water supply conduit 58 that supplies cooling water to the sprinkler tank 56, the water receiving tank cooling water take-out conduit 59 that takes out cooling water from the water receiving tank 57 is connected to the combustion tower cooling water supply conduit 54 that supplies cooling water to the combustion tower cooling water jacket 52, and the combustion tower cooling water take-out conduit 55 that takes out cooling water from the combustion tower cooling water jacket 52 is connected to the hydrochloric acid absorption tower cooling water supply conduit 67 that supplies cooling water to the hydrochloric acid absorption tower cooling water jacket 66. Further, a heat exchanger 81 and a cooling water pump 82 may be provided midway between the combustion tower cooling water outlet pipe 55 and the hydrochloric acid absorption tower cooling water supply pipe 67 .

Next, a method for treating chlorine gas using the chlorine gas treatment apparatus 1a according to the second embodiment of the present invention will be described.
In the chlorine gas treatment device 1a, first, the battery powder obtained in STEP 2 is supplied to the hydrochloric acid leaching tank 2 from the battery powder supply means 22, while the first hydrochloric acid is supplied to the hydrochloric acid leaching tank 2 from the hydrochloric acid supply pipe 21. The first hydrochloric acid has a concentration of, for example, 3 to 12 mol/L, and is supplied in an amount of, for example, 3 to 15 L per kg of the battery powder. As a result, the battery powder is dissolved in the first hydrochloric acid in the hydrochloric acid leaching tank 2, and the valuable metals are leached by the first hydrochloric acid (STEP 3), and a leachate 23a, which is a hydrochloric acid solution of the valuable metals, can be obtained (STEP 4). The leachate 23a is taken out through the leachate withdrawal pipe 24a and is used for solvent extraction in STEP 5.

In addition, in the hydrochloric acid leaching tank 2, chlorine gas is generated by the leaching reaction when the valuable metals are leached by the first hydrochloric acid (STEP 7). The chlorine gas is extracted from the hydrochloric acid leaching tank 2 through the chlorine gas extraction conduit 25a by a chlorine gas supply means (not shown) provided in the chlorine purification tower 3a, and is supplied to the chlorine purification tower 3a.

The chlorine gas introduced into the chlorine purification tower 3a through the chlorine gas extraction conduit 25a is purified by separating and removing oxygen-containing air and dust by a wet scrubber filled with water, a membrane separation method, liquefying chlorine by pressurized cooling, etc. (STEP 8). The purified chlorine gas is extracted from the chlorine purification tower 3a by the chlorine gas supply means and supplied to the combustion tower 5 through the purified chlorine gas extraction conduit 31a.

The chlorine gas supplied to the combustion tower 5 is combusted by the chlorine burner 51 together with the hydrogen gas supplied by the hydrogen supply equipment 4a (STEP 9), and reacts at high temperature to produce hydrogen chloride (STEP 10). The produced hydrogen chloride is cooled by the combustion tower cooling water jacket 52, introduced into the hydrogen chloride supply conduit 53, and further cooled by cooling water sprayed from the water spray tank 56 into the water receiving tank 57, and introduced into the hydrochloric acid absorption tower 6.

The hydrogen chloride introduced into the hydrochloric acid absorption tower 6 is absorbed by the absorbing liquid supplied from the absorbing liquid supply tank 7 and flowing down (STEP 11), producing a second hydrochloric acid (STEP 12). Here, the absorbing liquid supplied from the absorbing liquid supply tank 7 is temporarily stored in the first storage tank 63, the absorbing liquid overflowing from the first storage tank 63 is stored in the second storage tank 65, and the absorbing liquid overflowing from the second storage tank 65 flows down along the outer and inner surfaces of the inner cylinder 64. The absorbing liquid flowing down along the outer surface of the inner cylinder 64 absorbs hydrogen chloride to produce a second hydrochloric acid, and the absorbing liquid flowing down along the inner surface of the inner cylinder 64 works in cooperation with the hydrochloric acid absorption tower cooling water jacket 66 to cool the produced second hydrochloric acid. The concentration of the generated second hydrochloric acid is in the range of, for example, 1 to 37 mass %. The second hydrochloric acid is supplied to the hydrochloric acid leaching tank 2 via the hydrochloric acid extraction conduit 61 by the hydrochloric acid pump 61a and can be reused as the first hydrochloric acid for leaching of the valuable metals.

The unreacted hydrogen chloride in the hydrochloric acid absorption tower 6 is sucked into the blower 62a and introduced into the absorption liquid supply tank 7 through the hydrogen chloride extraction conduit 62. The hydrogen chloride introduced into the absorption liquid supply tank 7 is absorbed into the water supplied from the water supply conduit 71 to produce dilute hydrochloric acid. The dilute hydrochloric acid produced is supplied to the hydrochloric acid absorption tower 6 as an absorption liquid through the absorption liquid supply conduit 73. The remaining gas after the hydrogen chloride is absorbed in the absorption liquid supply tank 7 is discharged to the outside of the chlorine gas treatment device 1a through the gas release conduit 72.

In the second embodiment of the present invention, the hydrochloric acid absorption tower 6 is provided with a hydrochloric acid extraction conduit 61 at the bottom, and the hydrochloric acid extraction conduit 61 is connected to the hydrochloric acid leaching tank 2, so that the second hydrochloric acid produced in the hydrochloric acid absorption tower 6 is reused as the first hydrochloric acid used for leaching valuable metals. However, the hydrochloric acid extraction conduit 61 may be connected to a storage tank (not shown) so that the second hydrochloric acid is stored in the storage tank and then extracted.

A third embodiment of the chlorine gas treatment method of the present invention includes a hypochlorite generation step in which chlorine gas is contacted with an alkaline absorption liquid containing at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to generate hypochlorite.

The alkali metal constituting the alkali metal hydroxide preferably includes at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and francium, more preferably includes at least one selected from the group consisting of lithium, sodium, and potassium, and even more preferably includes at least one selected from the group consisting of sodium and potassium. The alkaline earth metal constituting the alkaline earth metal hydroxide preferably includes at least one selected from the group consisting of beryllium, magnesium, calcium, strontium, and barium, more preferably includes at least one selected from the group consisting of magnesium, calcium, and barium, and even more preferably includes at least one selected from the group consisting of magnesium and calcium.

The alkaline absorption liquid is preferably an aqueous solution or suspension containing at least one selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide.

For example, when the alkaline absorbing liquid contains sodium hydroxide, a reaction represented by the following formula (1) occurs in the hypochlorite production step.
2NaOH+ _Cl2 →NaClO+NaCl+ _H2O (1)

The third embodiment of the chlorine gas treatment method of the present invention preferably further comprises a first hypochlorite reduction step of reacting hypochlorite with carbon. The alkaline absorption solution containing hypochlorite is contacted with carbon as a reducing agent to generate chloride salt and carbon dioxide. For example, when the alkaline absorption solution contains sodium hydroxide, the reaction shown in the following formula (2) occurs in the first hypochlorite reduction step.
2NaClO+C→2NaCl+ _CO2 (2)

The third embodiment of the chlorine gas treatment method of the present invention preferably further comprises a second hypochlorite reduction step of reacting hypochlorite with aluminum. The alkaline absorption solution containing hypochlorite is contacted with aluminum as a reducing agent to generate aluminum oxide and chloride salt. For example, when the alkaline absorption solution contains sodium hydroxide, the reaction shown in the following formula (3) occurs in the second hypochlorite reduction step.
3NaClO+2Al→ _2Al2O3 + _3NaCl (3)

The fourth embodiment of the method for treating chlorine gas of the present invention includes a carbon dioxide production step in which chlorine gas is reacted with carbon and water to produce carbon dioxide. For example, chlorine gas is directly passed through a carbon-packed column, and water showering or steam introduction is performed. In the carbon dioxide production step, the reaction shown in the following formula (4) occurs.
_2Cl2 + C + _2H2O → _CO2 + 4HCl (4)

A fifth embodiment of the method for treating chlorine gas of the present invention includes an aluminum chloride production step in which chlorine gas is reacted with aluminum to produce aluminum chloride. Chlorine gas can be directly passed through an aluminum packed tower to directly cause a reduction reaction. In the aluminum chloride production step, a reaction represented by the following formula (5) occurs. Water may be showered into the aluminum packed tower to elute the produced aluminum chloride.
2Al+ _3Cl2 → _2AlCl3 (5)

1...Chlorine gas treatment device, 2...Hydrogen leaching tank, 3...Reaction tower, 4...Reduction reaction tank, 21...Hydrogen acid supply conduit, 22...Battery powder supply means, 23...Dilution air supply conduit, 24...Leachate, 25...Leachate extraction conduit, 26...Chlorine gas extraction conduit, 31...Aqueous ferrous chloride solution, 32...Packaging layer, 33...Circulation conduit, 34...First pump, 35...First switching valve, 36...Aqueous ferric chloride solution supply conduit, 37...Air release conduit, 38...Blower, 41...Water supply conduit, 42...Iron supply means, 43...Aqueous ferrous chloride solution, 44...Aqueous ferrous chloride solution extraction conduit, 45...Second pump, 46...Second switching valve, 47...Increased amount extraction conduit, 1a...Chlorine gas treatment device, 3a...Chlorine purification tower, 4a...hydrogen supply device, 5...combustion tower, 51...chlorine burner, 6...hydrochloric acid absorption tower, 7...absorption liquid supply tank.

Claims (10)

A method for treating chlorine gas generated when a powder containing valuable metals obtained from waste lithium ion batteries is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid, comprising the steps of:
The method for treating chlorine gas comprises the step of: absorbing the chlorine gas into a first aqueous solution of ferrous chloride to produce a second aqueous solution of ferrous chloride containing ferric chloride, the second aqueous solution of ferrous chloride having an increased ferric chloride concentration relative to the first aqueous solution of ferrous chloride. 2. The method for treating chlorine gas according to claim 1 , further comprising the step of contacting the second aqueous ferrous chloride solution containing ferric chloride with iron to reduce at least a portion of the ferric chloride contained in the second aqueous ferrous chloride solution, thereby producing a third aqueous ferrous chloride solution containing ferric chloride in which the concentration of ferric chloride is reduced relative to that of the second aqueous ferrous chloride solution. 3. The method for treating chlorine gas according to claim 2 , wherein at least a part of the third aqueous solution of ferrous chloride is used as the first aqueous solution of ferrous chloride for absorbing the chlorine gas. A method for treating chlorine gas generated when a powder containing valuable metals obtained from waste lithium ion batteries is dissolved in a first hydrochloric acid and the valuable metals are leached with the first hydrochloric acid, comprising the steps of:
reacting the chlorine gas with hydrogen gas to produce hydrogen chloride;
A method for treating chlorine gas, comprising the step of absorbing the hydrogen chloride into water to produce a second hydrochloric acid. 5. The method for treating chlorine gas according to claim 4 , further comprising the step of purifying the chlorine gas and removing oxygen contained in the chlorine gas prior to the step of reacting the chlorine gas with the hydrogen gas to produce the hydrogen chloride. 6. The method for treating chlorine gas according to claim 4 or 5 , wherein at least a part of the second hydrochloric acid is used as the first hydrochloric acid for leaching the valuable metals. A method for treating chlorine gas generated when a powder containing valuable metals obtained from waste lithium ion batteries is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid, comprising the steps of:
A hypochlorite generation step of contacting the chlorine gas with an alkaline absorption liquid containing at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to generate hypochlorite ;
A method for treating chlorine gas, comprising a first hypochlorite reduction step of reacting hypochlorite with carbon . A method for treating chlorine gas generated when a powder containing valuable metals obtained from waste lithium ion batteries is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid, comprising the steps of:
A hypochlorite generation step of contacting the chlorine gas with an alkaline absorption liquid containing at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to generate hypochlorite;
A method for treating chlorine gas, comprising a second hypochlorite reduction step of reacting hypochlorite with aluminum. A method for treating chlorine gas generated when a powder containing valuable metals obtained from waste lithium ion batteries is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid, comprising the steps of:
The method for treating chlorine gas comprises a carbon dioxide production step of reacting the chlorine gas with carbon and water to produce carbon dioxide. A method for treating chlorine gas generated when a powder containing valuable metals obtained from waste lithium ion batteries is dissolved in hydrochloric acid and the valuable metals are leached with hydrochloric acid, comprising the steps of:
The method for treating chlorine gas comprises a step of reacting the chlorine gas with aluminum to produce aluminum chloride.

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