Lithium sulfide manufacturing equipment

Abstract

To provide a method for producing lithium sulfide that is industrially suitable for use, and to provide an apparatus for producing lithium sulfide that is industrially suitable for use. [Solution] The method includes a preparation step of placing lithium hydroxide powder into a reaction vessel equipped with a gas inlet and a gas exhaust port, and a reaction step of introducing hydrogen sulfide gas into the reaction vessel from the gas inlet to react with lithium hydroxide, and exhausting unreacted hydrogen sulfide gas from the gas exhaust port, wherein the concentration of hydrogen sulfide gas at the gas inlet C in A method for producing lithium sulfide, wherein the concentration is maintained within the range of 5-50%. Also, a lithium sulfide production apparatus comprising: a first reaction vessel having a first gas inlet and a first gas exhaust port and capable of containing lithium hydroxide powder; a second reaction vessel having a second gas inlet and a second gas exhaust port, the second gas inlet being connected to the first gas exhaust port by piping and capable of containing lithium hydroxide powder; and a hydrogen sulfide gas supply device that supplies hydrogen sulfide gas from the first gas inlet into the first reaction vessel.

Description

[Technical Field]

[0001] This invention relates to a method for producing lithium sulfide and an apparatus for producing lithium sulfide. [Background technology]

[0002] Lithium sulfide (Li2S) is attracting attention as a material for battery manufacturing, particularly for the manufacture of all-solid-state lithium secondary batteries. Therefore, various methods for producing lithium sulfide are being investigated. In the following patent documents 1 to 3, lithium sulfide is produced by reacting lithium hydroxide powder with hydrogen sulfide gas through the chemical reaction 2LiOH + H2S → Li2S + 2H2O.

[0003] Patent Document 1 describes a method for producing lithium sulfide by the reaction of lithium hydroxide and hydrogen sulfide. Specifically, it describes a method for producing lithium sulfide that includes the steps of (A) placing particulate lithium hydroxide inside a reaction vessel equipped with a gas inlet pipe and a gas outlet pipe, and (B) introducing a reaction gas containing hydrogen sulfide into the reaction vessel from the gas inlet pipe and bringing the reaction gas into contact with the particulate lithium hydroxide to react the particulate lithium hydroxide with hydrogen sulfide, thereby producing particulate lithium sulfide, wherein in step (B), the pressure inside the reaction vessel is less than 0.101 MPa in absolute pressure.

[0004] Patent Document 2 describes a lithium sulfide production apparatus comprising a reaction vessel for contacting lithium hydroxide powder with hydrogen sulfide gas, a stirring blade inside the reaction vessel, a first heating device for maintaining the temperature of the inner wall of the reaction vessel that is in contact with the powder, and a second heating device for maintaining the temperature of the lid of the reaction vessel. In this lithium sulfide production apparatus, the capacity of the reaction vessel is 0.1 liters or more and 100 kiloliters or less, the temperature of the inner wall in contact with the powder is maintained at 140 to 230°C, and the temperature of the lid is maintained at 100°C or higher.

[0005] Patent Document 3 describes a method for producing lithium sulfide, in which lithium raw material is continuously supplied into a heated reaction vessel, the lithium raw material is moved in a certain direction within the reaction vessel, and hydrogen sulfide gas is continuously supplied into the reaction vessel, causing the lithium raw material and hydrogen sulfide gas to react within the reaction vessel to continuously produce lithium sulfide, and the lithium sulfide is recovered. In this production method, hydrogen sulfide gas is flowed within the reaction vessel from upstream to downstream along the direction of movement of the lithium raw material. Furthermore, the peripheral wall of the intermediate region of the reaction vessel is directly heated in relation to the positional relationship in the direction of movement of the lithium raw material, making the intermediate region within the reaction vessel a directly heated region. In addition, a heating region with an inner wall surface of 100°C or higher is provided downstream of the intermediate region, and the gas in the reaction vessel is exhausted from the heating region. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6612145 [Patent Document 2] Patent No. 6697398 [Patent Document 3] Patent No. 6753753 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Based on general principles of chemical reactions, in dry methods for synthesizing lithium sulfide by reacting lithium hydroxide powder with hydrogen sulfide gas, as described in Patent Documents 1-3, the reaction time is related to the hydrogen sulfide concentration, and it is thought that the higher the hydrogen sulfide concentration, the shorter the reaction time.

[0008] However, preliminary studies by the inventors have shown that in the initial stages of the reaction, when lithium hydroxide powder is reacted with a high concentration of hydrogen sulfide gas, the rapidly generated by-product water vapor causes the lithium hydroxide powder particles to adhere to each other, forming clumps of lithium hydroxide powder. When these clumps form, the hydrogen sulfide gas flows through the powder parts other than the clumps, making it difficult for the clumped lithium hydroxide powder to come into contact with the hydrogen sulfide gas, resulting in a longer overall reaction time. Furthermore, if such flow paths are formed, the amount of unreacted hydrogen sulfide gas discharged increases, placing a greater burden on exhaust gas treatment. These issues can pose problems in the industrial production of lithium sulfide, such as production efficiency, and therefore require improvement.

[0009] Based on the above circumstances, one of the objectives of the present invention is to provide a method for producing lithium sulfide that is industrially suitable and usable. Another objective of the present invention is to provide an apparatus for producing lithium sulfide that is industrially suitable and usable. [Means for solving the problem]

[0010] The inventors have completed the invention described below and solved the above problems.

[0011] According to the present invention, A preparation step involves placing lithium hydroxide powder into a reaction vessel equipped with a gas inlet and a gas exhaust port. The reaction step includes introducing hydrogen sulfide gas into the reaction vessel from the gas inlet and reacting it with lithium hydroxide, and exhausting the unreacted hydrogen sulfide gas from the gas exhaust port, In the reaction step, the concentration C of hydrogen sulfide gas at the gas inlet in The lithium sulfide production method is maintained within the range of 5-50%. It will be provided.

[0012] Furthermore, according to the present invention, A first reaction vessel equipped with a first gas inlet and a first gas exhaust port, and capable of containing lithium hydroxide powder, It includes a second gas inlet and a second gas outlet, the second gas inlet is connected to the first gas outlet by a pipe, and a second reaction tank capable of accommodating lithium hydroxide powder. A hydrogen sulfide gas supply device for supplying hydrogen sulfide gas from the first gas inlet into the first reaction tank. It is provided with a lithium sulfide production device. is provided.

Advantages of the Invention

[0013] According to the present invention, a method / device for producing lithium sulfide that can be preferably used industrially is provided. By the method for producing lithium sulfide or the device for producing lithium sulfide of the present invention, for example, the production efficiency in the production of lithium sulfide can be increased.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram schematically showing an example of a reaction tank that can be used for the production of lithium sulfide. [Figure 2] It is a diagram schematically showing an example of a lithium sulfide production device. [Figure 3] It is a diagram schematically showing an example of a lithium sulfide production device. [Figure 4] It is a diagram schematically showing an example of a lithium sulfide production device. [Figure 5] It is a diagram schematically showing an example of a lithium sulfide production device. [Figure 6] It is a graph showing the change in the concentration of hydrogen sulfide gas in Example 1. [Figure 7] It is an image showing the state of lithium sulfide synthesized in reaction tank 1 in Example 1. [Figure 8] It is an image showing the state of lithium sulfide synthesized in reaction tank 2 in Example 1. [Figure 9] It is a graph showing the change in the concentration of hydrogen sulfide gas in Comparative Example 1. [Figure 10]This image shows the state of lithium sulfide synthesized in reaction vessel 1 in Comparative Example 1. Cracks are indicated by arrows for illustrative purposes. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and explanations are omitted where appropriate. To avoid complexity, (i) if there are multiple identical components in the same drawing, only one will be assigned a reference numeral, and none of them will be assigned a reference numeral; and (ii) especially in Figure 2 and later, components similar to those in Figure 1 may not be assigned a reference numeral again. All drawings are for illustrative purposes only. The shapes and dimensional ratios of the components shown in the drawings do not necessarily correspond to actual items.

[0016] In this specification, the unit "%" for gas concentration means volume percentage unless otherwise specified. For example, C, which is detailed below. out and C In The unit "%" means volume percentage. In this specification, the notation "X~Y" in descriptions of numerical ranges means "X or greater and Y or less" unless otherwise specified. For example, "1~5 mass%" means "1 mass% or greater and 5 mass% or less".

[0017] <Method for producing lithium sulfide> Figure 1 is a schematic diagram showing an example of a reaction vessel 100 that can be used in the lithium sulfide production method of this embodiment. The lithium sulfide production method of this embodiment is a method for producing lithium sulfide by the reaction of lithium hydroxide powder with hydrogen sulfide gas. More specifically, the lithium sulfide production method of this embodiment typically includes the following two steps. Preparation step: A step of placing lithium hydroxide powder 105 inside a reaction vessel 100 equipped with a gas inlet 101 and a gas exhaust port 103. · Reaction process: A step of introducing a reaction gas containing hydrogen sulfide gas from the gas inlet 101 into the reaction tank 100 and bringing the reaction gas into contact with the powder 105 of lithium hydroxide. In this step, at least a part of the powder 105 of lithium hydroxide reacts with at least a part of the hydrogen sulfide gas introduced into the reaction tank 100 to produce lithium sulfide. The unreacted hydrogen sulfide gas is exhausted from the gas outlet 103 to the outside of the reaction tank 100.

[0018] In the method for producing lithium sulfide according to the present embodiment, in the above reaction step, the concentration C of hydrogen sulfide gas in the reaction gas introduced from the gas inlet 101 into the reaction tank 100 in is maintained within the range of 5 to 50%, preferably 5 to 30%, more preferably within the range of 5 to 20%. By appropriately adjusting the flow rate of the reaction gas introduced from the gas inlet 101 into the reaction tank 100, the concentration of hydrogen sulfide in the reaction gas, etc., C in can be set to an appropriate value. Just to mention for the sake of caution, in the reaction step, that C In is "maintained" within the range of x to y% means that from the beginning to the end of the reaction step, C In does not become less than x%, and C In does not become greater than y. The same applies to C out below.

[0019] Also, preferably, in the method for producing lithium sulfide according to the present embodiment, in the above reaction step, the concentration C of hydrogen sulfide gas in the gas discharged from the gas outlet 103 out is preferably maintained within the range of 0 to 50%, more preferably 0 to 30%, and even more preferably within the range of 0 to 20%. By appropriately adjusting the amount of the powder 105 of lithium hydroxide, the flow rate of the reaction gas introduced into the reaction tank 100, the concentration of hydrogen sulfide in the reaction gas, etc., C out can be made to fall within the above range.

[0020] Incidentally, C out and C inThis can be determined, for example, by installing measuring devices capable of measuring the concentration of hydrogen sulfide gas at the gas inlet 101 and the gas exhaust port 103.

[0021] As described above in the inventors' preliminary studies, in the dry method for synthesizing lithium sulfide by reacting lithium hydroxide powder with hydrogen sulfide gas, when lithium hydroxide powder is reacted with a high concentration (e.g., 100%) of hydrogen sulfide gas in the initial stage of the reaction, the rapidly generated by-product water vapor causes the lithium hydroxide powder particles to adhere to each other, resulting in the formation of clumps in the lithium hydroxide powder.

[0022] Based on the results of preliminary studies, the inventors decided to intentionally keep the concentration of hydrogen sulfide gas in the reaction vessel low when synthesizing lithium sulfide by reacting lithium hydroxide powder with hydrogen sulfide gas. Specifically, when reacting lithium hydroxide powder with hydrogen sulfide gas in a reaction vessel 100 equipped with a gas inlet 101 and a gas exhaust port 103, the concentration of hydrogen sulfide gas at the gas inlet 101 is C in The concentration was set to be 5% or more, which is necessary for stable reaction progress, but not exceeding 50%, resulting in a relatively low concentration. In this way, crack formation due to shrinkage of lithium sulfide powder is suppressed during the dry synthesis of lithium sulfide, thereby increasing the production efficiency of lithium sulfide.

[0023] Incidentally, the concentration of hydrogen sulfide gas at the gas inlet 101 is C in You can set it to 5-50%, or C out By setting the concentration to 0-50%, hydrogen sulfide gas can flow more uniformly through the lithium hydroxide powder layer in the reaction vessel 100, further increasing the production efficiency of lithium sulfide.

[0024] The following provides a detailed explanation of each step.

[0025] (preparation process) First, lithium hydroxide powder 105 is placed inside a reaction vessel 100, which is equipped with a gas inlet 101 and a gas exhaust port 103.

[0026] The reaction vessel 100 is made of a heat-resistant material such as carbon, stainless steel, glass, alumina, aluminum, Inconel, or Hastelloy. From the viewpoint of reducing the amount of lithium carbonate, which is an impurity, in the resulting lithium sulfide, and from the viewpoint of increasing the strength of the reaction vessel 100 and preventing the inclusion of metallic impurities, the reaction vessel 100 is preferably made of one or more materials selected from stainless steel and glass, more preferably made of glass, and particularly preferably made of hard glass or quartz glass. Furthermore, the reaction vessel 100 may be a container with a stirring function. Examples of stirring functions include a rotary kiln type stirring function.

[0027] The configuration for arranging lithium hydroxide 105 inside the reaction vessel 100 is not particularly limited, but for example, as shown in Figure 1, one configuration is to arrange lithium hydroxide powder 105 on a porous sheet 111 placed inside the reaction vessel 100. This increases the contact area between the reaction gas flowing to the lithium hydroxide 105 and the lithium hydroxide 105, thereby allowing the reaction between the reaction gas and lithium hydroxide 105 to proceed more effectively. Examples of porous sheets 111 include metal mesh such as stainless steel mesh; perforated metal such as stainless steel punching; and expanded metal such as stainless steel expanded.

[0028] It is preferable to dehydrate the crystal water and dry any adhering water of lithium hydroxide 105 beforehand. This suppresses the clumping of lithium hydroxide 105 and inhibits the formation of water sulfides, thereby allowing the reaction between the reaction gas and lithium hydroxide 105 to proceed more effectively. Dehydration and drying of lithium hydroxide-105 can be carried out by methods such as heating in the atmosphere, heating while flowing a gas such as hydrogen gas, nitrogen gas, or argon gas, or heating under reduced pressure.

[0029] (Reaction process) In the reaction process, a reaction gas containing hydrogen sulfide is introduced into the reaction vessel 100 from the gas inlet 101, and the reaction gas is brought into contact with the lithium hydroxide powder 105. In this way, the lithium hydroxide powder 105 reacts with hydrogen sulfide to produce particulate lithium sulfide. The reaction equation for this chemical reaction can be expressed as 2LiOH + H2S → Li2S + 2H2O, as described above.

[0030] Incidentally, once the reaction between lithium hydroxide 105 and hydrogen sulfide proceeds and the lithium hydroxide 105, the starting material, disappears from the reaction system, the generation of water from the reaction stops. Therefore, by monitoring the amount of water generated using some means of detecting water (not shown in Figure 1), the progress of the reaction can be determined.

[0031] In the reaction process, the reaction between lithium hydroxide powder 105 and hydrogen sulfide is preferably carried out under reduced pressure (specifically, under a pressure of 0.100 to 0.010 MPa). In the reaction process, it is preferable to control the pressure inside the reaction vessel 100 by adjusting the amount of reaction gas introduced into the reaction vessel 100. Furthermore, in the lithium sulfide production method of this embodiment, when hydrogen sulfide is consumed, the pressure inside the reaction vessel 100 decreases. Therefore, it is preferable to detect this pressure drop using a pressure detection means such as a pressure sensor, and replenish the hydrogen sulfide equivalent to the pressure drop from a container storing hydrogen sulfide. These operations can be performed by automatic control. In this case, since the amount of hydrogen sulfide used is only the amount necessary for the reaction with lithium hydroxide 105 and the amount remaining in the hydrogen sulfide circulation system, the utilization rate of hydrogen sulfide is greatly improved, and the treatment of exhaust gas can also be reduced.

[0032] As mentioned above, the concentration C of hydrogen sulfide gas in the reaction gas introduced into the reaction vessel 100 from the gas inlet 101 is in This is 5-50%, preferably 5-30%, and more preferably 5-20%. in This can be controlled by adjusting the amount of dilution gases such as nitrogen gas, argon gas, and hydrogen gas introduced into the reaction vessel 100.

[0033] The average particle size d in the weight-based particle size distribution of lithium hydroxide powder 105, measured by laser diffraction scattering particle size distribution analysis. 50 The average particle size d is preferably 1.5 mm or less, and more preferably 1.0 mm or less. 50 If the value is below the above upper limit, the contact area between lithium hydroxide 105 and the reaction gas increases, promoting the reaction and thus reducing the amount of unreacted raw materials in the resulting lithium sulfide. As a result, higher purity lithium sulfide can be obtained. Furthermore, the average particle size d in the weight-based particle size distribution of lithium hydroxide-105 measured by laser diffraction scattering particle size distribution analysis. 50 The average particle size d is preferably 0.1 mm or larger, more preferably 0.2 mm or larger. 50 If the value is above the lower limit mentioned above, the water generated in the reaction system can adhere to the lithium sulfide particles, effectively preventing the particles from sticking. Furthermore, it can suppress the emission of lithium hydroxide and the resulting lithium sulfide along with the reaction gas, thus simplifying exhaust gas treatment. Additionally, it can suppress the scattering of lithium hydroxide and the resulting lithium sulfide by the reaction gas, thereby improving the yield of lithium sulfide.

[0034] In the reaction process, for example, the reaction gas is heated while in contact with lithium hydroxide 105 to cause a reaction between the reaction gas and lithium hydroxide 105. This allows lithium sulfide to be produced. The temperature at which the reaction gas and lithium hydroxide 105 are heated is preferably 445°C or lower, and more preferably 420°C or lower. When the heating temperature is below the above upper limit, the melting of lithium hydroxide 105 can be suppressed, thereby preventing fusion between lithium hydroxide particles and the formation of lumps. This allows the reaction between the reaction gas and lithium hydroxide 105 to proceed more effectively. Furthermore, the temperature at which the reaction gas and lithium hydroxide 105 are heated is preferably 130°C or higher, and more preferably 200°C or higher. If the heating temperature is above the lower limit mentioned above, the reaction rate between the reaction gas and lithium hydroxide 105 can be further improved.

[0035] Incidentally, the hydrogen sulfide gas used in the reaction can be commercially available or manufactured on-site. One method for producing hydrogen sulfide gas is to heat hydrogen gas and sulfur gas at 400-450°C. Sulfur gas can be obtained, for example, by heating solid sulfur.

[0036] The heating apparatus for heating lithium hydroxide 105 is not particularly limited. For example, it can consist of a heating means capable of heating the inside of the reaction vessel 100 and a temperature controller that can adjust the output of the heating means to maintain a constant temperature inside the reaction vessel 100. The heating means is not particularly limited, but any known heating means such as heating wires or lamp heating can be used as long as it can heat the inside of the reaction vessel 100.

[0037] In the reaction process, the flow rate of the reaction gas introduced into the reaction vessel 100 may be increased so that the lithium hydroxide powder 105 is suspended in the reaction gas, and the lithium hydroxide powder 105 may be reacted with hydrogen sulfide. In other words, the reaction between lithium hydroxide powder 105 and hydrogen sulfide may be carried out in a fluidized bed. This can further increase the reaction efficiency between the reaction gas and lithium hydroxide 105.

[0038] The reaction time depends on various conditions, but to balance manufacturing efficiency and sufficient reaction progress, it is, for example, 0.24 to 3.6 min / g, specifically 0.48 to 1.02 min / g. Here, for example, 1.0 min / g means that it is preferable to have a reaction time of 1 minute per gram of lithium hydroxide 105 placed in the reaction vessel 100 during the preparation step.

[0039] (Water vapor collection process) In the reaction process, water vapor is generated by the aforementioned chemical reaction. Therefore, the lithium sulfide production method of this embodiment preferably includes a water vapor collection step for collecting the water vapor generated in the reaction process. The water vapor capture process is usually carried out during the reaction process. One specific method for collecting water vapor is to install a water collection device (cooling device) at the gas exhaust port 103 to collect water (water vapor) generated when lithium sulfide is produced. Once the reaction between the reaction gas and lithium hydroxide 105 is complete, the water generated when lithium sulfide is produced will no longer accumulate in the water collection device. Therefore, by continuing the reaction process until the water generated when lithium sulfide is produced no longer accumulates in the water collection device, the amount of exhaust gas can be minimized. For water vapor collection, one example is the use of a glass water collection device. In this case, the amount of water collected can be visually confirmed. When using a metal water collection device, the amount of water collected can be confirmed by using a water level gauge. Alternatively, the increase in water content can be confirmed by weight measurement.

[0040] (Inert gas introduction process) The lithium sulfide production method of this embodiment may include an inert gas introduction step in which an inert gas is introduced into the reaction vessel 100. For example, it is conceivable to predict in advance the amount of gas consumed by the reaction and the amount of water recovered by condensation, and then introduce an inert gas corresponding to those amounts into the reaction vessel 100. By doing so, it is thought that the overall gas inflow / outflow rate in the reaction process can be stabilized, and the chemical reaction can proceed stably. out and / or C in This can sometimes make it easier to control the situation properly. Examples of inert gases include noble gases and nitrogen gas. Any other gas can be used as long as it does not react with lithium hydroxide, hydrogen sulfide gas, lithium sulfide, etc. The inert gas may be introduced into the reaction vessel 100 from the gas inlet 101, or it may be introduced into the reaction vessel 100 from a different inlet (not shown in Figure 1).

[0041] <Lithium sulfide manufacturing equipment> As can be understood from the explanation above in <Method for Manufacturing Lithium Sulfide>, in the production of lithium sulfide by the dry method, even if the concentration of hydrogen sulfide gas is relatively low (C in The reaction with lithium hydroxide proceeds sufficiently even if the concentration is not 100% but 5-50%. In fact, by keeping the concentration of hydrogen sulfide gas relatively low, the formation of clumps in the lithium hydroxide powder layer can be suppressed. The inventor focused on this point and conceived of a manufacturing apparatus for producing lithium sulfide by the dry process, in which a first reaction vessel and a second reaction vessel are connected in series, and the relatively low-concentration hydrogen sulfide gas discharged from the first reaction vessel is "reused" in the second reaction vessel. The inventor then considered that by producing lithium sulfide using such a manufacturing apparatus, it would be possible to reduce the waste of hydrogen sulfide gas and lessen the effort required to recover it. The lithium sulfide production apparatus described below is based on this idea.

[0042] (Figure 2) Figure 2 is a schematic diagram showing an example of a lithium sulfide production apparatus according to this embodiment. The manufacturing apparatus shown in Figure 2. A first reaction vessel 100A is provided, which has a first gas inlet 101A and a first gas exhaust port 103A and is capable of containing lithium hydroxide powder. The second reaction vessel 100B is equipped with a second gas inlet 101B and a second gas exhaust port 103B, the second gas inlet 101B being connected to the first gas exhaust port 103A by piping 200, and capable of containing lithium hydroxide powder. A hydrogen sulfide gas supply device 120 supplies hydrogen sulfide gas from the first gas inlet 101A into the first reaction vessel 100A, It is equipped with.

[0043] The specific configurations of the first reaction vessel 100A and the second reaction vessel 100B can be the same as those of the reaction vessel 100 described in Figure 1.

[0044] Using the manufacturing apparatus shown in Figure 2, lithium hydroxide powder is placed in both the first reaction vessel 100A and the second reaction vessel 100B, and a reactive gas containing hydrogen sulfide gas is introduced through the first gas inlet. In this way, lithium hydroxide powder reacts with hydrogen sulfide gas in the first reaction vessel 100A to produce lithium sulfide. Furthermore, the unreacted hydrogen sulfide gas exhausted from the first gas exhaust port 103A passes through the piping 200 and is introduced into the second reaction vessel 100B through the second gas inlet 101B. As a result, lithium sulfide is obtained in the second reaction vessel 100B as well, through a reaction between the lithium hydroxide powder and the hydrogen sulfide gas. In other words, when producing lithium sulfide using a manufacturing apparatus as shown in Figure 2, the hydrogen sulfide gas that would conventionally be exhausted can be effectively utilized.

[0045] When producing lithium sulfide using the manufacturing apparatus shown in Figure 2, it is preferable to maintain the concentration of hydrogen sulfide gas in the first reaction vessel 100A (for example, the concentration of hydrogen sulfide gas at the gas exhaust port 103A) within the range of 5 to 50%. Furthermore, it is preferable to maintain the concentration of hydrogen sulfide gas in the second reaction vessel 100B (for example, the concentration of hydrogen sulfide gas at the gas exhaust port 103B) within the range of 0 to 50%. The reasons for this are as described above. The first reaction vessel 100A and the second reaction vessel 100B are connected in series. Therefore, if the concentration of hydrogen sulfide gas in the first reaction vessel 100A is kept below 50%, the concentration of hydrogen sulfide gas in the second reaction vessel 100B will "naturally" also be kept below 50%. In other words, when lithium sulfide is produced using the manufacturing apparatus shown in Figure 2, the formation of clumps in the lithium sulfide powder layer is "essentially" suppressed.

[0046] In the manufacturing apparatus shown in Figure 2, preferably, the second gas exhaust port 103B is connected by piping 200 to a water vapor collection device 130B that can collect water vapor contained in the gas discharged therefrom and discharge gas with a reduced water vapor content. Furthermore, the water vapor collection device 130B is preferably connected by piping 200 to a gas cleaning device 131 capable of cleaning hydrogen sulfide gas contained in the gas from which the amount of water vapor discharged has been reduced. These devices make it possible to suppress the release of hydrogen sulfide gas into the atmosphere that was not consumed in the second reaction vessel 100B.

[0047] Incidentally, it is preferable to have a vapor collection device 130A in the middle of the piping 200 connecting the first gas exhaust port 103A and the second gas inlet port 101B. The presence of the vapor collection device 130A suppresses the inflow of water vapor into the second reaction vessel 100B. Considering the chemical reaction equation 2LiOH + H2S → Li2S + 2H2O, it is thought that water vapor does not contribute to improving the rate or yield of the lithium sulfide synthesis reaction. Therefore, by suppressing the inflow of water vapor into the second reaction vessel 100B, it is thought that the clumping of lithium sulfide in the second reaction vessel 100B is suppressed, and the synthesis reaction proceeds more smoothly and uniformly.

[0048] The first reaction vessel 100A preferably comprises the following: • Piping 210A that allows direct introduction of hydrogen sulfide gas from the hydrogen sulfide gas supply device 120 into the first reaction vessel 100A, equipped with an openable / closable valve 201A. • Piping 211A equipped with an openable / closable valve 201A, which allows exhaust gas to be discharged directly to the gas cleaning device 131. • Piping 212A for introducing inert gas, equipped with a valve 201A that can be opened and closed.

[0049] Furthermore, the second reaction vessel 100B preferably includes the following: • Piping 210B, equipped with an openable / closable valve 201B, allows direct introduction of hydrogen sulfide gas from the hydrogen sulfide gas supply device 120 into the second reaction vessel 100B. • Piping 211B equipped with an openable / closable valve 201B, which allows exhaust gas to be discharged directly to the gas cleaning device 131. • Piping 212B for introducing inert gas, equipped with a valve 201B that can be opened and closed.

[0050] As described above, one of the features of the lithium sulfide production apparatus of this embodiment is that the first reaction vessel 100A and the second reaction vessel 100B are connected in series. As a result, if the concentration of hydrogen sulfide gas in the first reaction vessel 100A is kept below 50%, the concentration of hydrogen sulfide gas in the second reaction vessel 100B will "naturally" also be kept below 50%. In addition, by equipping each of the first reaction vessel 100A and the second reaction vessel 100B with the various types of piping (and appropriate devices connected to the piping) described above, it becomes easier to precisely and accurately control the concentration of hydrogen sulfide gas in each reaction vessel, as well as other parameters related to the progress of the chemical reaction.

[0051] Incidentally, by (i) the first reaction vessel 100A being equipped with a piping 210A that allows hydrogen sulfide gas to be directly introduced into the first reaction vessel 100A from a hydrogen sulfide gas supply device 120 equipped with an openable and closable valve 201A, and (ii) the second reaction vessel 100B being equipped with a piping 210B that allows hydrogen sulfide gas to be directly introduced into the second reaction vessel 100B from a hydrogen sulfide gas supply device 120 equipped with an openable and closable valve 201B, the production efficiency of lithium sulfide can be further increased, as will be explained below. Specifically, when the lithium hydroxide in the first reaction vessel 100A has been sufficiently converted to lithium sulfide, valve 201A is closed and valve 201B is opened instead. In this way, the chemical reaction in the first reaction vessel 100A is substantially stopped, while in the second reaction vessel 100B, lithium hydroxide continues to be converted to lithium sulfide by hydrogen sulfide gas supplied from the hydrogen sulfide gas supply device 120. At this time, in order to completely stop the chemical reaction in the first reaction vessel 100A, it is preferable to introduce inert gas into the first reaction vessel 100A from the inert gas introduction pipe 212A (purging). It is also preferable to discharge the gas from the first reaction vessel 100A from the pipe 211A, which can directly discharge the exhaust gas to the gas cleaning device 131. Then, while the chemical reaction is progressing in the second reaction vessel, the lithium sulfide produced is removed from the first reaction vessel 100A, where the chemical reaction has completely stopped. Furthermore, lithium hydroxide is added to the first reaction vessel 100A, which has become "empty" after the lithium sulfide has been removed, and (after the chemical reaction in the second reaction vessel 100B has progressed sufficiently) valve 201B is closed and valve 201A is opened instead, thereby producing lithium sulfide again in the first reaction vessel 100A. Alternatively, as explained in the apparatus in Figure 3 described later, the "entire" first reaction vessel 100A may be removed and another reaction vessel filled with lithium hydroxide connected to the piping. In this way, by producing lithium sulfide using an apparatus in which two reaction vessels, the first reaction vessel 100A and the second reaction vessel 100B, are appropriately connected by various piping, continuous operation of the apparatus becomes possible, and lithium sulfide can be produced industrially and efficiently. While this explanation describes the production of lithium sulfide by switching between two reaction vessels, it is also possible to industrially and efficiently produce lithium sulfide using a system with three or more reaction vessels appropriately connected.

[0052] The lithium sulfide production apparatus of this embodiment preferably includes various gas concentration detection means and a device for detecting the amount of water generated by the chemical reaction, from the viewpoint of more precise control of the chemical reaction, understanding the progress of the chemical reaction, and more efficient production. As an example, it is preferable that the first gas inlet 101A and / or the first gas exhaust port 103A in the first reaction vessel 100A be equipped with a hydrogen sulfide gas concentration detection device. The same applies to the second reaction vessel 100B. As another example, information regarding the progress of a chemical reaction can be obtained from the amount of water collected by the water vapor collection device 130.

[0053] Incidentally, in the dry method for synthesizing lithium sulfide by reacting solid lithium hydroxide with hydrogen sulfide gas, it is preferable to quickly discharge the water generated by the reaction from the reaction vessel in order to improve the quality of the product. For this reason, it is preferable to maintain the gas flow rate necessary for the discharge of water. The apparatus in Figure 2 is designed with reaction vessels arranged in series, allowing exhaust gas from the upstream reaction vessel to flow into the downstream vessel, thereby effectively utilizing unreacted hydrogen sulfide gas that was not used in the upstream reaction vessel for the downstream reaction. Therefore, as the reaction in the upstream vessel progresses, the amount of gas flowing into the downstream vessel decreases by the amount of water generated. For this reason, it is preferable to estimate the volume of water vapor generated per unit time in the upstream reaction and inject approximately the same amount of inert gas to maintain a constant gas flow rate in the downstream reaction vessel. Specifically, it is preferable to inject an appropriate amount of inert gas into the second reaction vessel 100B from the inert gas introduction piping 212B. This method makes it possible to proceed with the synthesis of lithium sulfide in the downstream reaction vessel under favorable conditions without being affected by the reaction status of the upstream reaction vessel.

[0054] The following describes the production of lithium sulfide based on more specific equipment examples.

[0055] (Figure 3) Figure 3 is a schematic diagram showing an example of a lithium sulfide production apparatus, different from that shown in Figure 2. The main components of the lithium sulfide production apparatus shown in Figure 3 are H2S supply device 1, H2S supply device 2, Li2S reaction vessel 1, cooler 1, H2O collector 1, Li2S reaction vessel 2, cooler 2, H2O collector 2, Li2S reaction vessel 3, cooler 3, H2O collector 3, and a gas scrubbing tower.

[0056] Li2S reaction vessels 1, 2, and 3 are heated and controlled to, for example, 300-400°C by external heaters. The gas inlet of one reaction vessel is connected to the gas outlet of the other reaction vessel by piping. Each reaction vessel is connected by gas piping, and lithium sulfide can be synthesized in the downstream reaction vessel using unreacted hydrogen sulfide gas from the upstream reaction vessel.

[0057] Furthermore, each reactor is equipped with a piping route for directly introducing hydrogen sulfide gas from a hydrogen sulfide gas supply source. By properly opening and closing valves, all reactors can be configured to be at the upstream end of the gas flow within the route. In addition, each reactor is equipped with an individual inert gas introduction route. Specifically, by properly opening and closing the valves, the flow of gas (reactive gases including hydrogen sulfide gas) can be changed as follows. H2S supply unit 1 or 2 → Li2S reaction tank 1 → Li2S reaction tank 2 → Li2S reaction tank 3 → Gas scrubbing tower H2S supply unit 1 or 2 → Li2S reaction tank 2 → Li2S reaction tank 3 → Li2S reaction tank 1 → Gas scrubbing tower H2S supply unit 1 or 2 → Li2S reaction tank 3 → Li2S reaction tank 1 → Li2S reaction tank 2 → Gas scrubbing tower

[0058] In the initial state before the reaction starts, for example, the gas piping routes between Li2S reaction vessel 1 and Li2S reaction vessel 2, Li2S reaction vessel 2 and Li2S reaction vessel 3, and Li2S reaction vessel 3 and Li2S reaction vessel 1 are blocked off. Also, Li2S reaction vessels 1, 2, and 3 are each loaded with the lithium hydroxide raw material. The valve status of the gas piping route is as follows: valve 1: open, valve 2: closed, valve 3: closed, valve 4: open, valve 5: open, valve 6: closed, valve 7: open, valve 8: open, valve 9: closed, valve 10: open, valve 11: closed, valve 12: open. Inert gas (e.g., nitrogen gas) is injected into Li2S reaction vessel 1 through valve 4, into Li2S reaction vessel 2 through valve 7, and into Li2S reaction vessel 3 through valve 12.

[0059] Subsequently, heating of Li2S reaction vessel 1, Li2S reaction vessel 2, and Li2S reaction vessel 3 is started. The set temperature of the reaction vessels can be, for example, 200 to 400°C, preferably 300 to 350°C. Incidentally, lithium sulfide synthesis proceeds sufficiently once the temperature is raised to 200°C or higher, so even if the set temperature is not reached, hydrogen sulfide gas can be introduced once the temperature reaches 200°C or higher. When introducing hydrogen sulfide gas from the upstream to the downstream reaction vessels and flowing the hydrogen sulfide gas into Li2S reaction vessel 1 and Li2S reaction vessel 2, the piping route is changed by closing valve 6 and opening valve 5, and by opening valve 5 and closing valve 6, so that the exhaust gas from Li2S reaction vessel 1, which passes through H2O collector 1, flows into Li2S reaction vessel 2. At the same time, valve 7 is opened and closed to stop the injection of nitrogen gas (inert gas). Similarly, to introduce gas from Li2S reaction vessel 2 to Li2S reaction vessel 3, valve 8 is opened and closed, and valve 9 is closed and opened. At the same time, valve 12 is opened and closed to stop the injection of nitrogen gas (inert gas). As the reaction proceeds in Li2S reaction vessel 1, water vapor is gradually mixed into the exhaust gas. The water vapor is cooled, condensed, and collected in collector 1. Unreacted hydrogen sulfide gas from Li2S reaction vessel 1 exits H2O collector 1, passes through valve 6, and flows into Li2S reaction vessel 2. Similarly, unreacted hydrogen sulfide gas from Li2S reaction vessel 2 exits H2O collector 2, passes through valve 9, and flows into Li2S reaction vessel 3. Once the completion of synthesis in Li2S reaction vessel 1 is confirmed by measuring the hydrogen sulfide gas concentration before and after Li2S reaction vessel 1, valve 2 is closed and then opened, and valve 1 is opened and then closed to allow hydrogen sulfide gas to be supplied directly to Li2S reaction vessel 2 (without passing through Li2S reaction vessel 1). At the same time, valve 4 is closed and then opened to replace the inside of Li2S reaction vessel 1 with an inert gas such as nitrogen gas. Once the synthesis is complete and the temperature has dropped sufficiently, the lithium sulfide generated in Li2S reaction vessel 1 is recovered.

[0060] After recovering the lithium sulfide generated in Li2S reaction vessel 1, Li2S reaction vessel 1 is removed, and in its place, Li2S reaction vessel 4, which has been pre-filled with lithium hydroxide, is installed. After connecting the gas piping to Li2S reaction vessel 4, valve 11 is opened, valve 9 is closed, and valve 5 is opened so that the exhaust gas from Li2S reaction vessel 3 flows into Li2S reaction vessel 4. In this state, Li2S reaction vessel 2 is at the upstream end and Li2S reaction vessel 4 is at the downstream end. Once the reaction has progressed and lithium hydroxide has been sufficiently converted to lithium sulfide in Li2S reaction vessel 2, the gas flow path is changed by opening and closing the valves in the same manner to recover the lithium sulfide generated in Li2S reaction vessel 2. A new Li2S reaction vessel can also be installed using the same process, allowing operation with three reaction vessels to continue.

[0061] In the series of procedures described above, the progress of the lithium sulfide synthesis reaction in each Li2S reaction vessel can be determined by the amount of water collected in the H2O water collector installed immediately after each Li2S reaction vessel. Furthermore, the hydrogen sulfide gas concentration in each Li2S reaction vessel can be measured, for example, at the inlet and outlet of each vessel. Gas concentration measurements may be performed by periodic sampling, or the gas concentration may be continuously monitored. By calculating the amount of hydrogen sulfide gas used in the reaction from the hydrogen sulfide gas concentrations before and after the lithium sulfide synthesis reaction, the progress of the reaction can be determined. The amount of hydrogen sulfide gas entering each Li2S reaction vessel can be determined by the product of the inflow gas volume and the measured hydrogen sulfide gas concentration. On the other hand, the amount of gas discharged from the reaction vessel decreases by the amount of condensed water vapor, so it is necessary to correct for this water vapor content in the inflow gas volume. Specifically, the volume of water vapor generated per unit time can be estimated from the increase in the amount of collected water vapor, and the amount of discharged gas can be calculated from the difference between this and the volume of inflow gas.

[0062] This concludes the explanation of the manufacturing apparatus shown in Figure 3. It should be noted that the various points explained regarding the lithium sulfide manufacturing apparatus in Figure 2 are also applicable to the lithium sulfide manufacturing apparatus shown in Figure 3.

[0063] (Figure 4) Figure 4 is a schematic diagram showing an example of a lithium sulfide production apparatus, which differs from those shown in Figures 2 and 3. The apparatus shown in Figure 4 has essentially the same configuration as the apparatus shown in Figure 3, except that it contains two Li2S reactors instead of three. Therefore, a detailed explanation is omitted. The apparatus shown in Figure 4 can also be suitably used for the industrial production of lithium sulfide.

[0064] (Figure 5) Figure 5 is a schematic diagram showing an example of a lithium sulfide production apparatus, which differs from Figures 2, 3, and 4. The apparatus shown in Figure 5 has essentially the same configuration as the apparatus shown in Figure 3, except that a dew point meter (e.g., a lithium chloride dew point meter) is installed downstream of each Li2S reaction vessel to detect the endpoint of the lithium sulfide synthesis reaction. Therefore, a detailed explanation is omitted. By producing lithium sulfide using an apparatus with this configuration, it becomes possible to more accurately detect the completion of the lithium sulfide synthesis reaction, and thus the apparatus can be operated more efficiently. The apparatus shown in Figure 5 can also be suitably used for the industrial production of lithium sulfide.

[0065] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0066] Embodiments of the present invention will be described in detail based on examples and comparative examples. It should be noted that the present invention is not limited to these examples.

[0067] <Example 1> Lithium sulfide was produced using the apparatus shown in Figure 4. Li2S reaction vessel 1 and Li2S reaction vessel 2 were each filled with 530g of lithium hydroxide dehydrate. Initially, only the outlet valve, valve 1, valve 6, and valve 8 of H2S supply device 1 were open, while all other valves were closed. Also, in the initial state, 1 L / min of nitrogen gas was flowed into the gas path from H2S supply device 1 to the gas scrubbing tower. H2S supply device 1 had a sulfur heating section at the bottom and an activated alumina layer in the middle section. The sulfur heating section was temperature-controlled to a range of 250-300°C, and the activated alumina layer to 430°C. 1.2 kg of sulfur was added to the sulfur heating section. Li2S reaction vessel 1 and Li2S reaction vessel 2 were also temperature-controlled, with both set to a temperature of 350°C.

[0068] All heating devices were powered on and the heating process began. Once the temperature of the activated alumina layer reached the set temperature, valve 3 was opened and valve 1 was closed to switch the gas supplied to H2S supply device 1 from nitrogen gas to hydrogen gas. The flow rate of hydrogen gas was set to 1 liter per minute, the same as for nitrogen gas. The concentration of hydrogen sulfide gas was measured periodically, and after confirming that the concentration was 20% or higher, valve 1 was opened and valve 3 was closed to introduce hydrogen sulfide into Li2S reaction vessel 1. This point marked the start of operation. During the operation of the apparatus, the hydrogen sulfide gas concentration was measured using a Gastec GV-100 gas sampler and gas detection tubes (4HH and 4HT used as appropriate). Hydrogen sulfide gas concentration was measured at appropriate intervals before Li2S reaction vessel 1 (raw material gas concentration), after Li2S reaction vessel 1, and after Li2S reaction vessel 2. A graph of the measurement results is shown in Figure 6. As shown in Figure 6, the hydrogen sulfide gas concentration was kept relatively low at each measurement point (in other words, the amount of hydrogen sulfide gas supplied was adjusted as appropriate to keep the hydrogen sulfide gas concentration at each measurement point low). Furthermore, in accordance with the rate of sulfur consumption of the raw material in H2S supply device 1, H2S supply device 2 was operated as needed, and valves were opened and closed appropriately to ensure that an appropriate amount of hydrogen sulfide was supplied.

[0069] After 14 hours from the start of operation, no water generation was detected from Li2S reaction vessel 1, so it was determined that Li2S synthesis in Li2S reaction vessel 1 was complete after another hour. The total Li2S synthesis time in Li2S reaction vessel 1 was 15 hours. Subsequently, valves were switched to open valve 5, closed valve 6, open valve 2, and closed valve 1 to directly introduce hydrogen sulfide from H2S supply device 1 or 2 into reaction vessel 2. Next, valve 4 was opened to introduce nitrogen gas into reaction vessel 1 and purge the inside of Li2S reaction vessel 1. The Li2S in Li2S reaction vessel 1 was recovered when it was determined that the temperature had sufficiently decreased and the inside had been sufficiently purged with nitrogen gas. Meanwhile, after 20 hours from the start of operation of Li2S reaction vessel 2, no water generation was detected, so it was determined that Li2S synthesis in reaction vessel 2 was complete after another hour. The total Li2S synthesis time in Li2S reaction vessel 2 was 22 hours.

[0070] The Li2S synthesized in both Li2S reaction vessels was in good condition, and no clump formation was observed (see Figure 7: Li2S reaction vessel 1 and Figure 8: Li2S reaction vessel 2). In other words, in the synthesis of lithium sulfide by the chemical reaction 2LiOH + H2S → Li2S + 2H2O, the formation of clumps of lithium hydroxide powder was suppressed by maintaining a relatively low concentration of hydrogen sulfide gas, as shown in Figure 6. From this, it can be said that the method in this example is a method for producing lithium sulfide that is industrially preferable and usable. Incidentally, the total amount of Li2S recovered from Li2S reaction vessel 1 and Li2S reaction vessel 2 was 1010g, and the synthesis rate per hour was 45.9g.

[0071] <Comparative Example 1> Similar to Example 1, lithium sulfide was produced using the apparatus shown in Figure 4. However, Li2S synthesis was performed only in Li2S reaction vessel 1, and the exhaust gas from H2O collector 1 was discharged directly to the gas scrubbing tower. The sulfur heating section was controlled to a temperature range of 250-300°C, and the activated alumina layer was controlled to 450°C, 20°C higher than in the example. Approximately 0.7 kg of sulfur was added to the sulfur heating section of H2S supply device 1 or 2. The set temperature of Li2S reaction vessel 1 was 350°C.

[0072] All heating devices were switched on and the heating process began. When the temperature of the activated alumina layer reached 400°C, valve 3 was opened and valve 1 was closed to switch the gas supplied to H2S supply device 1 from nitrogen gas to hydrogen gas. The flow rate of hydrogen gas was set to 1 liter per minute, the same as for nitrogen gas. After about 5 minutes, the hydrogen sulfide concentration was measured and was found to be low at 14%, but operation was started anyway, and hydrogen sulfide was introduced into reaction vessel 1 by opening valve 1 and closing valve 3.

[0073] Figure 9 shows the changes in hydrogen sulfide gas concentration before and after Li2S Reactor 1. One hour after the start of operation, the hydrogen sulfide gas concentration (raw material gas concentration) before Li2S Reactor 1 was measured at 52%, exceeding 50%. At this time, the hydrogen sulfide gas concentration after Li2S Reactor 1 was already 14%. Measurements were continued at 2 hours, 4 hours, and 5 hours, and at 5 hours the concentration fell below 40%. At 8 hours the hydrogen sulfide gas concentration was 26%. After that, the hydrogen sulfide gas concentration did not rise sharply and remained between 20% and 25%.

[0074] Approximately 17 hours after the start of operation, no water generation was detected from Li2S reaction vessel 1, so it was determined that Li2S synthesis was complete after another hour. The total Li2S synthesis time in this operation was 18 hours. The synthesized Li2S was in the form of large, cracked lumps (see Figure 10). In other words, in the synthesis of lithium sulfide by the chemical reaction 2LiOH + H2S → Li2S + 2H2O, it is understood that, as shown in Figure 9, even a temporary increase in the concentration of hydrogen sulfide gas (raw material gas concentration) in front of Li2S reaction vessel 1 is industrially undesirable. Incidentally, the total amount of Li2S recovered from Li2S reaction vessel 1 was 505g, and the synthesis rate per hour was 28.1g. [Explanation of symbols]

[0075] 100 reaction vessels 101 Gas inlet 103 Gas exhaust port 105 Lithium hydroxide powder 111 Porous Sheet 100A First reaction vessel 100B Second reaction vessel 101A First gas inlet 101B Second gas inlet 103A First gas exhaust port 103B Second gas exhaust port 120 Hydrogen sulfide gas supply device 130 Water vapor collection device 131 Gas cleaning device 200 piping 201A Valve 201B Valve 210A piping 210B Piping 211A Piping 212A Piping 212B Piping

Claims

1. A preparation step involves placing lithium hydroxide powder into a reaction vessel equipped with a gas inlet and a gas exhaust port. The reaction step includes introducing hydrogen sulfide gas into the reaction vessel from the gas inlet and reacting it with lithium hydroxide, and exhausting the unreacted hydrogen sulfide gas from the gas exhaust port, In the reaction step, the concentration C of hydrogen sulfide gas at the gas inlet ｉｎ A method for producing lithium sulfide, in which the concentration is maintained within the range of 5-50%.

2. A method for producing lithium sulfide according to claim 1, In the reaction step, the concentration C of hydrogen sulfide gas at the gas exhaust port ｏｕｔ A method for producing lithium sulfide, in which the concentration is maintained within the range of 0-50%.

3. A method for producing lithium sulfide according to claim 1 or 2, A method for producing lithium sulfide, comprising a water vapor collection step for collecting water vapor generated in the reaction step.

4. A method for producing lithium sulfide according to any one of claims 1 to 3, A method for producing lithium sulfide, comprising an inert gas introduction step of introducing an inert gas into the reaction vessel.

5. A first reaction vessel equipped with a first gas inlet and a first gas exhaust port, and capable of containing lithium hydroxide powder, A second reaction vessel is provided with a second gas inlet and a second gas exhaust port, the second gas inlet being connected to the first gas exhaust port by piping, and capable of containing lithium hydroxide powder. A hydrogen sulfide gas supply device that supplies hydrogen sulfide gas into the first reaction vessel from the first gas inlet, A lithium sulfide production apparatus equipped with the following features.

6. A lithium sulfide production apparatus according to claim 5, The lithium sulfide production apparatus is connected by piping to a water vapor collection device capable of collecting water vapor contained in the gas discharged from the gas exhaust port and discharging gas with a reduced water vapor content.

7. A lithium sulfide production apparatus according to claim 6, The aforementioned water vapor collection device is connected by piping to a lithium sulfide production apparatus, which includes a gas cleaning device capable of cleaning hydrogen sulfide gas contained in the gas from which the amount of water vapor discharged from the water vapor collection device has been reduced.

8. A lithium sulfide production apparatus according to any one of claims 5 to 7, The first reaction vessel and the second reaction vessel are, A piping system equipped with an openable and closable valve, which allows direct introduction of hydrogen sulfide gas from the hydrogen sulfide gas supply device, A piping system equipped with an openable and closable valve that can directly discharge exhaust gas to the gas cleaning device, A piping system for introducing inert gas, equipped with a valve that can be opened and closed, A lithium sulfide production apparatus having the following features.

9. A lithium sulfide production apparatus according to claim 8, A lithium sulfide production apparatus, wherein the hydrogen sulfide gas supply device and the first gas inlet are connected by piping equipped with an openable and closable valve.

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