Method for purifying hydrogen sulfide and method for producing lithium sulfide

Abstract

A method for purifying hydrogen sulfide uses a cyclone separator to remove a lithium raw material from a mixed gas (101) containing unreacted hydrogen sulfide and the lithium raw material, said mixed gas being generated in a process for producing lithium sulfide by reacting hydrogen sulfide with the lithium raw material.

Description

Technical Field

[0001] The present invention relates to a method for purifying hydrogen sulfide, a method for producing lithium sulfide, a hydrogen sulfide purification device and a lithium sulfide production device. Background Art

[0002] Lithium sulfide (Li2S) is used as a solid electrolyte for lithium secondary batteries, etc. As a method for producing lithium sulfide, for example, a method of reacting lithium hydroxide or the like as a lithium raw material with hydrogen sulfide in a tray dryer is known (for example, see Patent Document 1).

[0003] The sulfidation reaction between the lithium raw material and the hydrogen sulfide gas can be represented by the following formulas (1) to (3), for example.

[0004] 2LiOH+H2S→Li2S+2H2O (1)

[0005] Li2CO3+H2S→Li2S+H2O+CO2 (2)

[0006] Li2O+H2S→Li2S+H2O (3)

[0007] On the other hand, the Claus process is well known for recovering sulfur by recovering hydrogen sulfide in the form of elemental sulfur. In the Claus process, hydrogen sulfide is partially combusted by air in a reactor to generate a mixed gas containing one volume of sulfur dioxide to two volumes of hydrogen sulfide, and the mixed gas is passed through a catalyst bed filled with a catalyst such as natural bauxite, activated alumina, titanium dioxide, etc. to generate vaporous elemental sulfur, and the vaporous sulfur is recovered as molten sulfur by further cooling.

[0008] The reactions in the above-mentioned reactor and catalyst bed can be represented by the following formulas (i) and (ii).

[0009] Reactor: 3H2S+3 / 2O2→2H2S+SO2+H2O (i)

[0010] Catalyst bed: 2H2S+SO2→3S+2H2O (ii)

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2017-222567 Summary of the invention

[0014] However, in the sulfidation reactions represented by the above formulas (1) to (3), if one attempts to recover sulfur by the Claus process from the unreacted H2S that does not participate in the sulfidation reaction and remains, there is a problem of poisoning the Claus catalyst that contributes to the reaction represented by the above formula (ii).

[0015] The inventors of the present invention have studied the poisoning of the Claus catalyst and found that it is caused by the lithium raw material contained in the unreacted H2S. For example, in the technology disclosed in the above-mentioned Patent Document 1, although the particle size of the lithium raw material is adjusted to 0.1 mm to 1.5 mm from the viewpoint of reaction efficiency, such fine powder particles are easily diffused into the unreacted H2S in the tray dryer, resulting in the mixing of the fine powder lithium raw material into the unreacted H2S.

[0016] Furthermore, if the fine powder lithium raw material coexists with water, there is another problem of corrosion of metal pipes.

[0017] Therefore, an object of the present invention is to provide a method for purifying hydrogen sulfide which can suppress poisoning of the Claus catalyst and prevent corrosion of metal pipes when recovering sulfur using unreacted hydrogen sulfide generated in a process of producing lithium sulfide by reaction of hydrogen sulfide with a lithium raw material.

[0018] The present invention is as follows.

[0019] (1) A method for purifying hydrogen sulfide, comprising removing the lithium raw material from a mixed gas containing unreacted hydrogen sulfide and a lithium raw material generated in a process of producing lithium sulfide by a reaction of hydrogen sulfide and a lithium raw material using a cyclone separator.

[0020] Another embodiment of the present invention provides a method for purifying hydrogen sulfide and a method for producing lithium sulfide as described in the following (2) to (4).

[0021] (2) The method for purifying hydrogen sulfide according to (1) above, wherein the water content in the mixed gas from which the lithium raw material has been removed is 10% by mass or less.

[0022] (3) A method for producing lithium sulfide, comprising reacting hydrogen sulfide with a lithium raw material to produce lithium sulfide, wherein the hydrogen sulfide includes hydrogen sulfide obtained by the method for purifying hydrogen sulfide according to (1) or (2) above.

[0023] (4) A method for producing lithium sulfide, comprising reacting a lithium raw material with hydrogen sulfide to produce lithium sulfide, wherein the lithium raw material comprises a lithium raw material purified by the method for purifying hydrogen sulfide according to (1) or (2) above.

[0024] According to one embodiment of the present invention, when sulfur is recovered using unreacted hydrogen sulfide generated in a process of producing lithium sulfide by reacting hydrogen sulfide with a lithium raw material, the lithium raw material is removed from a mixed gas containing unreacted hydrogen sulfide and the lithium raw material. Therefore, a method for purifying hydrogen sulfide that suppresses poisoning of a Claus catalyst and prevents corrosion of metal pipes can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of a reaction tank for explaining the production process of lithium sulfide and a lithium sulfide generating unit.

[0026] Figure 2 This is a schematic diagram for explaining the process and apparatus for recovering a mixed gas containing unreacted hydrogen sulfide and a lithium raw material and removing the lithium raw material to purify hydrogen sulfide.

[0027] Figure 3 This is a schematic diagram for explaining a cyclone separator section as a raw material separator. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described in further detail.

[0029] A method for purifying hydrogen sulfide according to one embodiment of the present invention is characterized in that a cyclone separator is used to remove the lithium raw material from a mixed gas containing unreacted hydrogen sulfide and a lithium raw material generated in a process of producing lithium sulfide by a reaction of hydrogen sulfide and a lithium raw material.

[0030] In addition, a hydrogen sulfide purification apparatus for implementing a method for purifying hydrogen sulfide according to one embodiment of the present invention is characterized in that it includes: a lithium sulfide generating section that reacts hydrogen sulfide with a lithium raw material to generate lithium sulfide, a mixed gas recovery section that recovers a mixed gas containing unreacted hydrogen sulfide and the lithium raw material in the above-mentioned lithium sulfide generating section, and a hydrogen sulfide purification section that removes the lithium raw material from the above-mentioned mixed gas using a cyclone separator to purify hydrogen sulfide.

[0031] As described above, lithium sulfide is produced by a sulfidation reaction between a lithium raw material and hydrogen sulfide gas, which can be represented by the following formulas (1) to (3). In the following formula (1), LiOH is described as the lithium raw material, but the present invention is not limited to this embodiment.

[0032] 2LiOH+H2S→Li2S+2H2O (1)

[0033] Li2CO3+H2S→Li2S+H2O+CO2 (2)

[0034] Li2O+H2S→Li2S+H2O (3)

[0035] Here, in the mixed gas containing unreacted hydrogen sulfide and lithium raw material in the present invention, unreacted hydrogen sulfide refers to unreacted hydrogen sulfide that does not participate in the sulfidation reaction represented by the above formulas (1) to (3) and remains. In addition, the lithium raw material also includes lithium sulfide (Li2S) produced in the process of producing lithium sulfide and other lithium compounds.

[0036] Next, a process of producing lithium sulfide by reacting hydrogen sulfide with a lithium raw material (lithium sulfide production process) and a lithium sulfide production unit that produces lithium sulfide by reacting hydrogen sulfide with a lithium raw material are described. Such lithium sulfide production process and lithium sulfide production unit are well known, and examples thereof include those disclosed in Japanese Patent Application Laid-Open No. 2017-222567 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2016-150859.

[0037] Specifically, in the lithium sulfide production process and the lithium sulfide production unit, the lithium raw material is continuously or discontinuously supplied to a heated reaction tank, and the lithium raw material is moved in a certain direction in the reaction tank. In addition, in the lithium sulfide production process and the lithium sulfide production unit, hydrogen sulfide gas is continuously or discontinuously supplied to the reaction tank, and the lithium raw material reacts with the hydrogen sulfide gas to produce lithium sulfide continuously or discontinuously.

[0038] (Hydrogen Sulfide)

[0039] Hydrogen sulfide usually reacts with the lithium raw material in the form of hydrogen sulfide gas to generate lithium sulfide. The hydrogen sulfide gas may be a gas consisting of hydrogen sulfide alone, or a gas having hydrogen sulfide as a main component and containing other gas components. Here, the main component refers to the component with the largest content in the gas, for example, 50 vol% or more. In one embodiment of the present invention, in order to suppress the rapid occurrence of sulfidation reaction, for example, an inert gas may be mixed in the hydrogen sulfide gas to reduce the hydrogen sulfide partial pressure.

[0040] From the above viewpoints, the concentration of hydrogen sulfide gas is preferably 10 to 100 vol%. It should be noted that a concentration of hydrogen sulfide gas of 100 vol% means a gas consisting of only hydrogen sulfide gas, that is, a pure gas. In addition, a concentration of hydrogen sulfide gas of less than 100 vol% means a mixed gas of hydrogen sulfide gas, an inert gas such as Ar and nitrogen, and a reducing gas such as hydrogen.

[0041] From the viewpoint of maintaining reactivity with the lithium raw material and appropriately keeping the gas flow rate in the reaction tank, the concentration of hydrogen sulfide gas is preferably 10 vol% to 100 vol%, more preferably 20 vol% or more or 90 vol% or less, and particularly preferably 30 vol% or more or 80 vol% or less.

[0042] (Lithium raw materials)

[0043] The lithium raw material is a raw material that becomes a lithium source of lithium sulfide, and examples thereof include lithium hydroxide, lithium carbonate, lithium oxide, etc. Among them, lithium hydroxide is preferred because it undergoes a sulfidation reaction at a low temperature and has excellent stability.

[0044] (Sulfurization reaction)

[0045] When the lithium raw material supplied to the reaction tank contacts the hydrogen sulfide gas, the sulfidation reaction of the above formulas (1) to (3) occurs, generating lithium sulfide (Li2S) as a main product and water (H2O) as a by-product.

[0046] If the lithium raw material is brought into contact with hydrogen sulfide gas in a sufficiently heated state, the above reaction will further proceed.

[0047] At this time, the lithium raw material is preferably heated to a temperature range where the lithium raw material does not melt.

[0048] (Reaction tank)

[0049] The reaction tank is a device that provides a space for the lithium raw material and hydrogen sulfide gas to react, and its shape and size are arbitrary. The outer shape of the reaction tank is any shape such as a rectangular parallelepiped, a cylindrical shape, a polygonal prism shape, etc. The reaction tank can be equipped with a stirrer that promotes the reaction of the lithium raw material and the hydrogen sulfide gas.

[0050] (Heating of reaction tank)

[0051] In the lithium sulfide production process, it is preferred to heat the reaction tank, especially the part in contact with the moving lithium sulfide, and heat the lithium raw material moving in the reaction tank. The sufficiently heated lithium raw material can be brought into contact with hydrogen sulfide gas to promote the sulfidation reaction.

[0052] Figure 1 It is a schematic diagram of the reaction tank 11 for explaining the production process of the above-mentioned lithium sulfide and the lithium sulfide generating unit.

[0053] Regarding the heating of the reaction tank 11, Figure 1 As shown, from the direction in which the lithium raw material 12 moves, it is preferred that the middle area 13 of the reaction tank 11 is heated by the heating device 14 .

[0054] By heating in this way, Figure 1 As shown, from the positional relationship of the moving direction of the lithium raw material 12, the middle area 13 in the reaction tank 11 can be used as the area for directly heating the reaction tank 11, and as the heating area for heating the temperature of the inner wall surface of the reaction tank 11 in the upstream area and the downstream area on both sides of the middle area 13, specifically, to 100° C. or more. It should be noted that Figure 1 The left side in the figure is the upstream side, and the right side is the downstream side.

[0055] At this time, from the viewpoint of promoting the sulfurization reaction, the temperature of the inner wall surface of the reaction tank 11 in the intermediate region 13 is preferably 200° C. to 450° C., and particularly preferably 300° C. or higher and 450° C. or lower.

[0056] The inner wall temperature of the reaction tank 11 in the middle region 13 is considered to be substantially the same as the product temperature of the lithium raw material 12 . Therefore, if the inner wall temperature of the reaction tank 11 in the middle region 13 is 200° C. to 450° C., the sulfidation reaction can be sufficiently promoted.

[0057] (Supply and movement of lithium raw material into reaction tank)

[0058] In the above-mentioned lithium sulfide manufacturing process and lithium sulfide generating unit, if Figure 1 As shown, the lithium raw material 12 can be continuously supplied to the reaction tank 11, and the lithium raw material 12 can be moved in a certain direction in the reaction tank 11.

[0059] In addition, the direction in which the lithium raw material 12 is moved in the reaction tank 11 is any direction such as the horizontal direction, the vertical direction, the rotation direction, the rotation axis direction, and the longitudinal direction of the reaction tank 11. Figure 1 As shown, the lithium raw material 12 can be moved in the length direction of the reaction tank 11.

[0060] (Supply and movement of hydrogen sulfide gas into the reaction tank)

[0061] exist Figure 1 In the lithium sulfide production step and the lithium sulfide production unit of the embodiment shown, the hydrogen sulfide 15 is continuously supplied into the reaction tank 11 .

[0062] In the above-mentioned lithium sulfide manufacturing process and lithium sulfide generating unit, if Figure 1 As shown, the hydrogen sulfide 15 can be made to flow in the reaction tank 11 from the downstream side to the upstream side in a direction opposite to the moving direction of the lithium raw material 12 .

[0063] In addition, in the lithium sulfide production step and the lithium sulfide generating unit, the moving direction of the hydrogen sulfide 15 may be the same as the moving direction of the lithium raw material 12 .

[0064] At this time, the speed at which the hydrogen sulfide 15 is made to flow in the reaction tank 11 is arbitrary.

[0065] Furthermore, in the above-mentioned lithium sulfide production process and lithium sulfide production unit, if Figure 1 As shown, in the positional relationship of the moving direction of the lithium raw material 12 , it is preferred that the hydrogen sulfide 15 is supplied into the reaction tank 11 from the downstream side of the position where the lithium raw material 12 is supplied into the reaction tank 11 .

[0066] In addition, in the positional relationship in the moving direction of the lithium raw material 12 , the supply position of the hydrogen sulfide 15 may be set in the heating region (upstream side) or in the intermediate region 13 .

[0067] (exhaust)

[0068] In the above-mentioned lithium sulfide manufacturing process and lithium sulfide generating unit, if Figure 1 As shown, water vapor (H 2 O) and carbon dioxide (CO 2 ) generated as by-products by the above-mentioned sulfidation reaction, as well as unreacted hydrogen sulfide gas, are exhausted 17 to the outside of the reaction tank 11 .

[0069] The unreacted hydrogen sulfide gas exhausted can be recovered as elemental sulfur by the Claus process. However, as described above, the unreacted hydrogen sulfide gas exhausted contains a fine powder lithium raw material, which may poison the Claus catalyst or corrode metal pipes due to the presence of water.

[0070] Therefore, one embodiment of the present invention is characterized by comprising a step and an apparatus for recovering a mixed gas containing unreacted hydrogen sulfide and a lithium raw material, removing the lithium raw material, and purifying hydrogen sulfide. Specific methods and apparatus are described below.

[0071] (Recovery of lithium sulfide)

[0072] The lithium sulfide (Li2S) produced as the main product by the above-mentioned sulfidation reaction is preferably as follows Figure 1 As shown, it moves to the downstream side and is recovered into the lithium sulfide recovery tank 18.

[0073] When lithium sulfide (Li 2 S) is recovered and stored in the lithium sulfide recovery tank 18 , it is preferred that the inner wall surface temperature of the lithium sulfide recovery tank 18 be heated to 100° C. or higher.

[0074] Sometimes, water as a reaction byproduct condenses in the lithium sulfide recovery tank 18, and the lithium sulfide as a reaction product reacts with the condensed water to generate lithium hydroxide, and the purity of the lithium sulfide is reduced. In contrast, if the inner wall surface of the lithium sulfide recovery tank 18 is heated as described above, the water in the lithium sulfide recovery tank 18 can be gasified and can be prevented from existing in the form of water (liquid). Furthermore, the water in the lithium sulfide recovery tank 18 can be volatilized, and the recovered lithium sulfide can be suppressed from condensing or adhering to the inner wall surface of the lithium sulfide recovery tank 18.

[0075] Furthermore, an inert gas may be supplied into the lithium sulfide recovery tank 18. Thus, water can be discharged to the outside of the lithium sulfide recovery tank 18 together with the inert gas.

[0076] Next, a process and an apparatus for recovering a mixed gas containing unreacted hydrogen sulfide and a lithium raw material and removing the lithium raw material to purify hydrogen sulfide according to one embodiment of the present invention will be described.

[0077] Figure 2This is a schematic diagram for explaining a process and an apparatus for recovering a mixed gas containing unreacted hydrogen sulfide and a lithium raw material and removing the lithium raw material to purify hydrogen sulfide.

[0078] exist Figure 2 In, from Figure 1 The above-mentioned lithium sulfide production process described in the above and the mixed gas containing unreacted hydrogen sulfide gas and lithium raw material exhausted in the lithium sulfide generation unit are recovered to the raw material separator 10, and the lithium raw material is removed from the above-mentioned mixed gas by the hydrogen sulfide purification unit provided in the raw material separator 10 to purify the hydrogen sulfide.

[0079] Figure 3 This is a schematic diagram for explaining the hydrogen sulfide purification section provided in the raw material separator 10 .

[0080] exist Figure 3 In the embodiment, the cyclone separator 104 as the raw material separator 10 mainly includes a mixed gas inlet 102 and a gas outlet 116 for discharging the purified hydrogen sulfide gas. In addition, the recovered lithium raw material 108 is discharged through a storage tank (not shown). The gas outlet 116 may have a demister.

[0081] Next, the operation will be described.

[0082] from Figure 1 The mixed gas 101 containing unreacted hydrogen sulfide gas and lithium raw material exhausted from the lithium sulfide production unit described above is introduced into the raw material separator 10 from the mixed gas inlet 102 .

[0083] Since the mixed gas 101 contains water, the mixed gas temperature is preferably adjusted to 100 to 220° C., and more preferably adjusted to 140 to 180° C. By setting the mixed gas temperature to 100° C. or higher, condensation of water in the raw material separator 10 can be suppressed, and by setting the mixed gas temperature to 220° C. or lower, the cost of components of the raw material separator 10 can be suppressed.

[0084] In the cyclone separator section 104, gravity and centrifugal force are used to separate the recovered lithium raw material 108 from the hydrogen sulfide gas 118. The diameter of the mixed gas inlet 102 is preferably smaller than the diameter of the gas outlet 116. That is, the linear velocity of the mixed gas 101 inlet 102 is preferably greater than the linear velocity of the gas outlet 116 of the hydrogen sulfide gas 118.

[0085] As a demister, a known demister can be used without particular limitation, and examples thereof include a component made of a three-dimensional network structure of metal wires, resins, glass fibers, etc. stacked in multiple layers to form a felt-like component, so as to increase the contact surface with the fluid while reducing pressure loss.

[0086] Purified hydrogen sulfide gas 118 is stored in a purified hydrogen sulfide gas storage unit (not shown) provided outside raw material separator 10 through gas discharge port 116. The water concentration of purified hydrogen sulfide gas 118 is preferably 10% by mass or less, more preferably 8% by mass or less.

[0087] It should be noted that the purified hydrogen sulfide gas and the recovered lithium raw material can be used as follows: Figure 2 The purified hydrogen sulfide gas and the recovered lithium raw material may be used alone in the lithium sulfide production process, or hydrogen sulfide gas and lithium raw material may be mixed and used again.

[0088] Therefore, according to another aspect of the present invention, there is provided a lithium sulfide production apparatus comprising: a lithium sulfide generating section for reacting hydrogen sulfide with a lithium raw material to generate lithium sulfide, a mixed gas recovery section for recovering a mixed gas containing unreacted hydrogen sulfide and the lithium raw material in the above-mentioned lithium sulfide generating section, a hydrogen sulfide purification section for removing the lithium raw material from the above-mentioned mixed gas to purify the hydrogen sulfide, and a hydrogen sulfide supply section for supplying the hydrogen sulfide obtained in the above-mentioned hydrogen sulfide purification section to the above-mentioned lithium sulfide generating section.

[0089] Alternatively, a lithium sulfide production apparatus is provided, comprising: a lithium sulfide generating section for reacting hydrogen sulfide with a lithium raw material to generate lithium sulfide, a mixed gas recovery section for recovering a mixed gas containing unreacted hydrogen sulfide and the lithium raw material in the above-mentioned lithium sulfide generating section, a hydrogen sulfide purification section for removing the lithium raw material from the above-mentioned mixed gas to purify the hydrogen sulfide, and a lithium raw material supply section for supplying the lithium raw material recovered by the above-mentioned hydrogen sulfide purification section to the above-mentioned lithium sulfide generating section.

[0090] Above, various embodiments have been described with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to the above examples. As long as one is skilled in the art, various variations or modifications can be thought of within the scope of the scope of the patent claim, and it should be understood that these also belong to the technical scope of the present invention. In addition, the various constituent elements in the above embodiments can be arbitrarily combined without departing from the scope of the invention.

[0091] It should be noted that the present application is based on the Japanese patent application (Japanese Patent Application No. 2022-128251) filed on August 10, 2022, and the contents thereof are incorporated herein by reference.

[0092] Explanation of symbols

[0093] 10Raw material separator

[0094] 11Reaction tank

[0095] 12 Lithium Raw Materials

[0096] 13 Middle Area

[0097] 14Heating device

[0098] 15 Hydrogen sulfide

[0099] 17 Exhaust

[0100] 18 Lithium sulfide recovery tank

[0101] 101 Mixed Gas

[0102] 102 Mixed gas inlet

[0103] 104 Cyclone separator

[0104] 108 Recycling of lithium raw materials

[0105] 116 Gas outlet

[0106] 118 Hydrogen sulfide gas

Claims

1. A method for purifying hydrogen sulfide, comprising removing a lithium raw material from a mixed gas containing unreacted hydrogen sulfide and a lithium raw material generated in a process of producing lithium sulfide by reacting hydrogen sulfide with a lithium raw material, using a cyclone separator.

2. The method for purifying hydrogen sulfide according to claim 1, wherein: The water content in the mixed gas from which the lithium raw material is removed is 10 mass % or less.

3. A method for producing lithium sulfide, comprising reacting hydrogen sulfide with a lithium raw material to produce lithium sulfide, wherein the hydrogen sulfide comprises hydrogen sulfide obtained by the method for purifying hydrogen sulfide according to claim 1 or 2.

4. A method for producing lithium sulfide, comprising reacting a lithium raw material with hydrogen sulfide to produce lithium sulfide, wherein the lithium raw material comprises a lithium raw material purified by the method for purifying hydrogen sulfide according to claim 1 or 2.

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