Preparation method and system of lithium sulfide

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method and system of lithium sulfide, and the method comprises the following steps: raw material pretreatment: mixing lithium hydroxide powder with an organic solvent according to a certain mass ratio, and stirring in a dissolving kettle to form a suspension; supergravity reaction: feeding the suspension liquid into a rotating filler layer of a supergravity reactor in an axial liquid inlet manner, and introducing preheated hydrogen sulfide gas into the rotating filler layer in a tangential gas inlet manner at the same time for reaction; and product separation: carrying out filter pressing separation on the reaction liquid of the supergravity reactor to obtain a lithium sulfide wet material, washing the lithium sulfide wet material for a plurality of times, and drying the lithium sulfide wet material to obtain lithium sulfide powder. According to the method disclosed by the invention, the mass transfer resistance limitation in the gas-liquid-solid three-phase reaction can be broken through in the lithium sulfide preparation process, the volume mass transfer coefficient of H2S in the liquid phase is remarkably improved, and the purposes of increasing the gas-liquid contact area and shortening the reaction time are achieved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology and relates to a method and system for preparing lithium sulfide. Background Technology

[0002] Lithium sulfide (Li2S) is the core raw material for sulfide solid-state batteries, and its purity directly affects the battery's ionic conductivity and cycle life.

[0003] Traditional methods for preparing lithium sulfide employ a stirred tank process, but this process has the following drawbacks: low gas-liquid mass transfer efficiency: the volumetric mass transfer coefficient (kLa) of H₂S in the liquid phase is only 0.5-1.2 s⁻¹. -1 This results in a reaction time of 8-12 hours.

[0004] Therefore, the present invention aims to provide a method and system for preparing lithium sulfide to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for preparing lithium sulfide, which can overcome the limitation of mass transfer resistance in gas-liquid-solid three-phase reaction, significantly improve the volumetric mass transfer coefficient of H2S in the liquid phase, and achieve the purpose of increasing the gas-liquid contact area and shortening the reaction time.

[0006] According to a first aspect of the present invention, a method for preparing lithium sulfide is provided, comprising the following steps:

[0007] Raw material pretreatment: Lithium hydroxide powder and organic solvent are mixed at a certain mass ratio and stirred in a dissolving tank to form a suspension;

[0008] Hypergravity reaction: The suspension is fed into the rotating packing layer of the hypergravity reactor in an axial manner, and at the same time, preheated hydrogen sulfide gas is introduced into the rotating packing layer in a tangential manner to carry out the reaction.

[0009] Product separation: The reaction liquid of the supergravity reactor is separated by pressure filtration to obtain lithium sulfide wet material, and after washing several times, the lithium sulfide wet material is dried to obtain lithium sulfide powder.

[0010] A preferred embodiment also includes the following steps: gas circulation: unreacted hydrogen sulfide gas is purified sequentially by passing it through a cyclone separator, a condensation dehydration tower, and a molecular sieve adsorption tower, and then returned to the hypergravity reactor for recycling via a booster pump.

[0011] A preferred embodiment is that, in the raw material pretreatment, the lithium hydroxide powder and the organic solvent are mixed at a mass ratio of 4-6%; the conditions of the dissolving vessel are set as follows: stirring temperature of 125-135℃, stirring speed of 200-400 rpm, and stirring time of 30-60 min.

[0012] A preferred embodiment is that, in the raw material pretreatment, the organic solvent is an aprotic polar organic solvent, including one or more of amide organic solvents, lactam organic solvents, urea-based organic solvents, organic sulfur solvents, and cyclic phosphating organic solvents.

[0013] A preferred embodiment is that, in the hypergravity reaction, the conditions of the hypergravity reactor are set as follows: reaction temperature of 155-195℃, reaction pressure of 0.2-0.5MPa, and rotational speed of the rotating packing layer of 800-1500rpm.

[0014] A preferred embodiment is that, in the hypergravity reaction, the hydrogen sulfide gas is preheated to a temperature of 140-160°C and the gas flow rate is 0.5-1.2 m³ / s. 3 / h, liquid hourly space velocity is 0.8-1.5 / h.

[0015] A preferred embodiment is that, in the aforementioned hypergravity reaction, the rotating packing layer is made of stainless steel wire mesh with a wire diameter of 0.1-0.3 mm, a corrugation angle of 45-60°, and a specific surface area of ​​2000-3000 m². 2 / m 3 The surface is coated with a 10-50μm thick PTFE coating.

[0016] According to a second aspect of the present invention, the present invention also provides a lithium sulfide preparation system, comprising:

[0017] Raw material handling system, supergravity reactor system, and liquid delivery pipelines connecting the two;

[0018] The raw material processing system includes a dissolving tank, which is used to stir a mixture of lithium hydroxide and organic solvent to form a homogeneous suspension.

[0019] The hypergravity reactor system includes a hypergravity reactor, a rotating packing layer, an axial liquid inlet pipe, a tangential air inlet pipe, and a liquid outlet pipe;

[0020] The infusion pipeline connects the dissolving vessel and the hypergravity reactor, and is used to transport the suspension into the hypergravity reactor;

[0021] The rotating packing layer is rotatably disposed within the hypergravity reactor;

[0022] The axial inlet pipe connects the rotating packing layer and the supergravity reactor, and is also connected to the conveying pipe, for feeding the suspension into the rotating packing layer in an axial manner;

[0023] The tangential air inlet pipe is connected to the supergravity reactor and is used to introduce preheated hydrogen sulfide gas into the rotating packing layer in a tangential manner.

[0024] The liquid outlet pipe is connected to the supergravity reactor and is used to output the reaction liquid.

[0025] A preferred embodiment is that the supergravity reactor system further includes a circulation pipeline connected to the outlet pipeline and the delivery pipeline, for returning unreacted reaction liquid to the rotating packing layer.

[0026] A preferred embodiment is that the surface of the corrugated wire mesh filler of the rotating filler layer is coated with a polytetrafluoroethylene coating.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In this application, lithium hydroxide is dissolved in an organic solvent to form a suspension. The suspension is then transported to the rotating packing layer of a hypergravity reactor via axial infeed. The high-speed rotating packing layer shears the suspension into fine liquid films. The suspension is then thrown outward by centrifugal force through the packing material, where it is fully cut and dispersed, resulting in a significant expansion of the surface area. Preheated hydrogen sulfide gas is then introduced into the outside of the rotating packing layer via tangential infeed. This significantly increases the gas-liquid contact area between the suspension and the hydrogen sulfide gas, accelerating the gas-liquid mass transfer process. Thus, through the synergistic design of tangential infeed and axial infeed, the mass transfer resistance limitation in the gas-liquid-solid three-phase reaction can be overcome, significantly improving the volumetric mass transfer coefficient of H2S in the liquid phase, increasing the gas-liquid contact area by 5-8 times, and shortening the reaction time to 1 / 4 of the traditional process. Attached Figure Description

[0029] Figure 1 This is a schematic flowchart of a method for preparing lithium sulfide in this embodiment;

[0030] Figure 2 This is a schematic diagram of the raw material processing system in this embodiment;

[0031] Figure 3 This is a schematic diagram of the supergravity reactor system in this embodiment.

[0032] Figure Labels

[0033] 10. Raw material processing system; 11. Dissolving vessel; 12. Temporary storage vessel; 13. Liquid inlet pipe; 14. Liquid inlet pump; 15. Solution tank; 20. Hypergravity reactor system; 21. Hypergravity reactor; 22. Rotating packing layer; 23. Axial liquid inlet pipe; 24. Tangential air inlet pipe; 25. Liquid outlet pipe; 251. Liquid outlet valve; 26. Circulation pipe; 261. Circulation valve; 27. Exhaust pipe; 28. Liquid outlet pump; 29. ​​Rotary motor; 291. Rotating shaft; 30. Liquid delivery pipe; 31. Liquid delivery pump. Detailed Implementation

[0034] The following specific embodiments further illustrate the technical solution of the present invention. These specific embodiments do not represent a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention.

[0035] The "range" disclosed herein is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0037] Unless otherwise specified in this disclosure, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0038] In this disclosure, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] The existing technology for preparing lithium sulfide using the traditional stirred tank process has the following drawbacks: low gas-liquid mass transfer efficiency, with the volumetric mass transfer coefficient (kLa) of H2S in the liquid phase being only 0.5-1.2 s⁻¹. -1 This results in a reaction time of 8-12 hours.

[0040] Based on the above problems, this application provides a method and system for preparing lithium sulfide. It uses a rotating packed bed type ultragravity device to enhance the micro-mixing efficiency. Through the synergistic design of tangential gas inlet and axial liquid inlet, the gas-liquid contact area is increased by 5-8 times and the reaction time is shortened to 1 / 4 of the traditional process.

[0041] The following is a detailed description of a method for preparing lithium sulfide provided in this embodiment. Please refer to [link / reference]. Figure 1 As shown, the preparation method of lithium sulfide includes the following steps:

[0042] S1. Raw material pretreatment: Lithium hydroxide powder and organic solvent are mixed in a certain mass ratio and stirred in a dissolving tank to form a suspension;

[0043] S2, Hypergravity reaction: The suspension is fed into the rotating packing layer of the hypergravity reactor in an axial manner, and at the same time, preheated hydrogen sulfide gas is introduced into the rotating packing layer in a tangential manner to carry out the reaction.

[0044] S3. Product separation: The reaction liquid of the supergravity reactor is separated by pressure filtration to obtain lithium sulfide wet material, and after washing several times, the lithium sulfide wet material is dried to obtain lithium sulfide powder.

[0045] In this embodiment, lithium hydroxide powder is dissolved in an organic solvent to form a mixture. This mixture is then transferred to a dissolving vessel and stirred to form a homogeneous suspension. The suspension is then fed axially into a rotating packing layer of a hypergravity reactor. The rotating packing layer rotates 360° horizontally within the reactor. During this rotation, the suspension is propelled outwards by centrifugal force through the packing material, forming a micron-sized liquid film with a thickness reduced to 10-100 μm. This significantly increases the kLa value. For the same mass of water, atomized water has a much larger specific surface area than liquid water, thereby increasing the gas-liquid contact area by 5-8 times. Simultaneously, the rotating packing layer... Preheated hydrogen sulfide gas is introduced into the rotating packing layer at the tangential position of the outer periphery to carry out the reaction, which can increase the gas-liquid contact area. The reaction liquid after the reaction is separated by pressure filtration to obtain lithium sulfide wet material. After washing several times, the lithium sulfide wet material is dried to obtain lithium sulfide powder. In this embodiment, the tangential air inlet allows the gas mist, i.e. liquid film, formed on the outside of the rotating packing layer to fully contact with hydrogen sulfide gas, thereby carrying out a gas-liquid-solid three-phase reaction. Through the synergistic design of tangential air inlet and axial liquid inlet, the mass transfer resistance limitation in the gas-liquid-solid three-phase reaction can be overcome, significantly improving the volume mass transfer coefficient of H2S in the liquid phase, shortening the reaction time from more than 8 hours in the prior art to less than 3 hours, and reducing the reaction time to 1 / 4 of the traditional process.

[0046] Each step is explained in detail below.

[0047] S1. Raw material pretreatment: Lithium hydroxide powder and organic solvent are mixed in a certain mass ratio and stirred in a dissolving tank to form a suspension;

[0048] In this embodiment, it should be noted that lithium hydroxide powder and organic solvent are mixed at a mass ratio of 4-6% and stirred in a dissolving vessel to form a homogeneous suspension. The mass ratio of lithium hydroxide powder to organic solvent can be 4%, 4.5%, 5%, 6%, etc.

[0049] In one example, the conditions for the dissolving vessel are set as follows: stirring temperature 125-135℃, stirring speed 200-400 rpm, and stirring time 30-60 min. The stirring temperature can be 125℃, 128℃, 130℃, 135℃, etc.; the stirring speed can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, etc.; and the stirring time can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc. Setting the dissolving vessel to the above conditions results in a more uniform mixture of lithium hydroxide powder and organic solvent, leading to a better formation of a homogeneous suspension.

[0050] In one example, the organic solvent is a non-protic polar organic solvent, including one or more of the following: amide organic solvents (e.g., dimethylformamide), lactam organic solvents (e.g., N-methylpyrrolidone), ureated organic solvents, organosulfur solvents such as dimethyl sulfoxide, and cyclic phosphating organic solvents. These organic solvents can be used well as individual solvents or mixed solvents. Preferably, in this embodiment, N-methylpyrrolidone (boiling point 202°C, flash point 95°C) is used. Its high dielectric constant (ε = 32.2) favors the dissociation of LiOH, and its Henry's law coefficient with H₂S (H = 12.3 MPa·m) is favorable. 3 ( / mol) matching.

[0051] S2, Hypergravity reaction: The suspension is fed into the rotating packing layer of the hypergravity reactor in an axial manner, and at the same time, preheated hydrogen sulfide gas is introduced into the rotating packing layer in a tangential manner to carry out the reaction.

[0052] In this embodiment, it should be noted that the suspension obtained in S1 is pumped into the rotating packing layer of the hypergravity reactor, and the suspension is fed into the rotating packing layer axially, while preheated hydrogen sulfide gas is introduced into the rotating packing layer tangentially for reaction. It should be noted that axial feeding means the direction of the feeding is parallel to the rotation axis of the rotating packing layer; tangential feeding means the direction of the gas intake is along the tangential direction of the outer side of the rotating packing layer.

[0053] In one example, the conditions of the hypergravity reactor are set as follows: reaction temperature 155-195℃, reaction pressure 0.2-0.5MPa, and rotational speed of the rotating packing layer 800-1500rpm. Specifically, the reaction temperature can be 155℃, 160℃, 165℃, 170℃, 180℃, 185℃, 195℃, etc.; the reaction pressure can be 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, etc.; and the rotational speed of the packing layer can be 800rpm, 1000rpm, 1200rpm, 1350rpm, 1400rpm, 1500rpm, etc. It should be noted that the reaction temperature, reaction pressure, and rotational speed range in this embodiment achieve the best reaction effect. If the reaction temperature is lower than that in this embodiment, the reaction effect will be poor, and if it is lower than 100℃, the generated water cannot be converted into gas and discharged in time; if the rotational speed is lower than that in this embodiment, the atomization effect of water droplets will be poor.

[0054] In one example, the hydrogen sulfide gas was preheated to 140-160℃ and the gas flow rate was 0.5-1.2 m³ / s. 3The liquid hourly space velocity (LHSV) is 0.8-1.5 m³ / h. The preheating temperature of the hydrogen sulfide gas can be 140℃, 145℃, 150℃, 155℃, 160℃, etc., and the gas flow rate can be 0.5 m³ / h. 3 / h, 0.8m 3 / h, 0.95m 3 / h, 1.2m 3 The liquid hourly space velocity (LHSV) can be 0.8 / h, 1.0 / h, 1.2 / h, 1.4 / h, 1.5 / h, etc. It should be noted that preheating the hydrogen sulfide gas to 140-160°C increases the molecular activation energy of the gas, and keeping it as close to the reaction temperature as possible can increase reaction efficiency. The gas flow rate and LHSV range specified in this embodiment achieve the best reaction results. Too low a gas flow rate will reduce the reaction efficiency, while too high a flow rate may lead to the formation of lithium polysulfides.

[0055] In one example, the conditions for the rotating packing layer were set as follows: stainless steel wire mesh with a wire diameter of 0.1-0.3 mm, a corrugation angle of 45-60°, and a specific surface area of ​​2000-3000 m². 2 / m 3 The surface is coated with a 10-50μm thick PTFE (polytetrafluoroethylene) coating. The wire diameter can be 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, etc., the corrugation angle can be 45°, 48°, 50°, 55°, 60°, etc., and the specific surface area can be 2000m². 2 / m 3 2500m 2 / m 3 2850m 2 / m 3 2950m 2 / m 3 3000m 2 / m 3 The thickness of the PTFE coating can be 10μm, 15μm, 20μm, 30μm, 35μm, 45μm, 50μm, etc. It should be noted that setting the wire diameter to the range in this embodiment, considering cost, can increase the atomization effect; setting the corrugation angle in this embodiment can increase the atomization area; setting the specific surface area in this embodiment can increase the contact degree with hydrogen sulfide gas; considering the trade-off between cost and protective tolerance, the thickness of the PTFE coating is set to 10-50μm. The use of the PTFE coating can inhibit the scaling and deposition of Li2S on the inner wall of the reactor, ensuring long-term stable operation of the device, and extending the continuous operation cycle to more than 500 hours.

[0056] S3. Product separation: The reaction liquid of the supergravity reactor is separated by pressure filtration to obtain lithium sulfide wet material, and after washing several times, the lithium sulfide wet material is dried to obtain lithium sulfide powder.

[0057] In this embodiment, it should also be noted that the reaction liquid from the centrifugal reactor is separated by plate and frame filter press to obtain wet lithium sulfide material. After washing three times with n-hexane, it is transferred to a vacuum drying oven for drying until the moisture content is <0.1%, thereby obtaining lithium sulfide powder with a purity ≥99.5%, and the product particle size D50 = 0.5-2μm, Span <1.0, meeting the requirements for direct application in solid-state batteries. It should be noted that the conditions of the vacuum drying oven are set as follows: drying temperature 80-100℃, vacuum degree -0.09MPa.

[0058] In this embodiment, the method for preparing lithium sulfide further includes the following steps:

[0059] S4. Gas Circulation: Unreacted hydrogen sulfide gas is purified sequentially by passing through a cyclone separator, a condenser dehydration tower, and a molecular sieve adsorption tower, and then returned to the hypergravity reactor for recycling via a booster pump.

[0060] In this embodiment, it should also be noted that unreacted hydrogen sulfide gas is purified sequentially through a cyclone separator, a condensation dehydration tower, and a molecular sieve adsorption tower, and then returned to the hypergravity reactor for recycling via a booster pump. The condensation dehydration tower is set to operate at a temperature of -10°C to 5°C to better remove moisture entrained in the hydrogen sulfide gas. It should be noted that recycling unreacted hydrogen sulfide gas after purification through a cyclone separator, condensation dehydration tower, and molecular sieve adsorption tower achieves highly efficient H2S recycling (≥98%), reducing raw material consumption and tail gas treatment costs.

[0061] This application also provides a lithium sulfide preparation system, please refer to... Figure 2 and Figure 3Therefore, it includes: a raw material processing system 10, a hypergravity reactor system 20, and a liquid delivery pipeline 30 connecting the two. The raw material processing system 10 includes a dissolving vessel 11, used to stir a mixture of lithium hydroxide and an organic solvent to form a homogeneous suspension. The hypergravity reactor system 20 includes a hypergravity reactor 21, a rotating packing layer 22, an axial liquid inlet pipe 23, a tangential air inlet pipe 24, and a liquid outlet pipe 25. The liquid delivery pipeline 30 connects the dissolving vessel 11 and the hypergravity reactor 21, used to transfer the suspension... The liquid is transported into the hypergravity reactor 21; the rotating packing layer 22 is rotatably arranged inside the hypergravity reactor 21; the axial liquid inlet pipe 23 connects the rotating packing layer 22 and the hypergravity reactor 21, and is connected to the liquid delivery pipe 30, for inputting the suspension into the rotating packing layer 22 in an axial liquid inlet manner; the tangential air inlet pipe 24 is connected to the hypergravity reactor 21, for introducing preheated hydrogen sulfide gas into the rotating packing layer 22 in a tangential air inlet manner; the liquid outlet pipe 25 is connected to the hypergravity reactor 21, for outputting the reaction liquid.

[0062] In this embodiment, the dissolving vessel 11 has a volume of 5-20m³. 3 The jacketed stirring vessel is equipped with an anchor-type stirring paddle (50-100 rpm) and a built-in coil heater. The mixture of lithium hydroxide and organic solvent is stirred in the dissolving vessel 11 to form a homogeneous suspension. The suspension is then transported through the delivery pipe 30 to the axial inlet pipe 23 of the hypergravity reactor 21. The suspension is axially fed into the rotating packing layer 22 relative to the position of the axial inlet pipe 23. The rotating packing layer 22 rotates horizontally at 360° high speed within the hypergravity reactor 21. During this high-speed rotation, the suspension is propelled outwards by centrifugal force through the packing material, atomizing the liquid to form a micron-sized film. Simultaneously, during the high-speed rotation, the tangential air inlet pipe 24 runs along the outer side of the rotating packing layer 22. Preheated hydrogen sulfide gas is introduced tangentially to initiate a gas-liquid-solid three-phase reaction. Through the coordinated design of tangential gas inlet and axial liquid inlet, the mass transfer resistance limitation in the gas-liquid-solid three-phase reaction can be overcome, significantly improving the volumetric mass transfer coefficient of H2S in the liquid phase and shortening the reaction time to 1 / 4 of the traditional process. Subsequently, the liquid outlet pipe 25 transports the reacted liquid to a plate and frame filter press for filtration to obtain wet lithium sulfide material. After several washings, it is transferred to a vacuum drying oven for drying until the moisture content is <0.1%, thus obtaining lithium sulfide powder with a purity ≥99.5%. Preferably, the hypergravity reactor 21 is equipped with a rotary motor 29, which is connected to a rotating packing layer 22 via a rotating shaft 291, causing the rotating packing layer 22 to rotate at high speed. The centrifugal acceleration (50-200g) generated by the high-speed rotation enables the liquid to atomize into a micron-sized thin film.

[0063] Please refer to Figure 2As shown, in one possible implementation, the raw material processing system 10 further includes a temporary storage tank 12 for storing a mixture of lithium hydroxide and an organic solvent. An inlet pipe 13 connects the temporary storage tank 12 and the dissolving tank 11. An inlet pump 14 is installed on the inlet pipe 13 to pump the mixture from the temporary storage tank 12 into the dissolving tank 11. In other embodiments, the temporary storage tank 12 may be omitted, and a spare inlet can be directly provided at the top of the dissolving tank 11. A solution chamber 15 is located at the spare inlet, and the solution chamber 15 is controlled by a valve to add the mixture of lithium hydroxide and an organic solvent into the dissolving tank 11. The specific configuration is not limited in this embodiment.

[0064] Please refer to Figure 2 and Figure 3 As shown, in one feasible embodiment, a delivery pump 31 is installed on the delivery pipeline 30. The delivery pump 31 facilitates the pumping of the suspension in the dissolving vessel 11 into the hypergravity reactor 21 through the delivery pipeline 30. A discharge pump 28 is installed on the discharge pipeline 25. A discharge valve 251 is installed on the pipeline between the discharge pump 28 and the plate and frame filter press. By opening the discharge valve 251, the discharge pump 28 facilitates the pumping of the reaction liquid in the hypergravity reactor 21 into the subsequent plate and frame filter press for processing.

[0065] Please refer to Figure 3 As shown in this embodiment, it should also be noted that the hypergravity reactor system 20 further includes a circulation pipe 26 and an exhaust pipe 27. One end of the circulation pipe 26 is connected to the liquid delivery pipe 30, and the other end is connected to the liquid outlet pipe 25 between the liquid outlet pump 28 and the liquid outlet valve 251. A circulation valve 261 is installed on the circulation pipe 26. When the reaction liquid is not fully reacted, the liquid outlet valve 251 is closed, and the circulation valve 261 is opened. The liquid outlet pump 28 pumps the reaction liquid in the hypergravity reactor 21 through the circulation pipe 26 into the hypergravity reactor 21 for circulation processing. When the reaction liquid is fully reacted, the liquid outlet valve 251 is opened, and the circulation valve 261 is closed. The liquid outlet pump 28 pumps the reaction liquid in the hypergravity reactor 21 through the liquid outlet pipe 25 into the subsequent plate and frame filter press for processing. It should be noted that the hypergravity reactor 21 is equipped with a pH sensor to dynamically detect the acidity or alkalinity of the reaction solution inside the hypergravity reactor 21. When the pH value reaches 10.5-11.0, it indicates that the reaction solution has reacted sufficiently, and the product can be discharged. If the pH value is between 10.5 and 11.0, it means that too much alkali solution has been neutralized by excess hydrogen sulfide gas, and the alkali solution should be replaced in time to prevent excess hydrogen sulfide from being discharged.

[0066] Exhaust pipe 27 is connected to the hypergravity reactor 21 to discharge exhaust gas. The exhaust gas sequentially passes through a cyclone separator to remove entrained droplets, a condenser dehydration tower to remove moisture, and a molecular sieve adsorption tower for purification. Unreacted hydrogen sulfide gas is then returned to the hypergravity reactor 21 for recycling via a booster pump. It should be noted that the concentration of hydrogen sulfide in the exhaust gas can be monitored in real time using an infrared spectrometer. The circulation flow rate of the booster pump can be adjusted based on this concentration feedback. A low concentration of hydrogen sulfide in the exhaust gas may indicate insufficient hydrogen sulfide, while a high concentration may indicate an excessive amount, potentially leading to the formation of lithium polysulfides.

[0067] In one feasible approach, a polytetrafluoroethylene (PTFE) coating is sprayed onto the surface of the corrugated wire mesh packing of the rotating packing layer 22. In traditional stirred tank processes, Li2S forms a hard deposit layer on the surface of the agitator, requiring frequent shutdowns for cleaning. However, in this application, by spraying a PTFE coating onto the surface of the corrugated wire mesh packing of the rotating packing layer 22, the scaling and deposition of Li2S on the inner wall of the reactor can be inhibited, ensuring long-term stable operation of the device.

[0068] The effects of the present invention will be illustrated below through Examples 1-4 and Comparative Examples 1-2.

[0069] Example 1:

[0070] Raw materials: 50 kg LiOH·H₂O (99.9% purity), 950 kg N-methylpyrrolidone; add the raw materials to 5m 3 The dissolving vessel was heated to 130°C with jacketed steam, and the anchor-type agitator was run at 80 rpm for 40 minutes. The viscosity of the suspension was measured to be 48.7 mPa·s (meeting the requirement of ≤50 mPa·s). The centrifugal reactor was started at 1200 rpm, and H2S gas was introduced (initial flow rate 0.8 m³ / s). 3 / h); maintain temperature 160℃, pressure 0.3MPa, liquid hourly space velocity 1.0 / h; real-time monitoring data: pH value decreased from 13.2 to 10.8 (reaction endpoint), H2S recycling rate 98.3%. The wet material obtained by pressure filtration had a moisture content of 32.7%, was washed with n-hexane and then dried to obtain the finished product; quality testing: LiOH conversion rate over 96%, Li2S purity 99.6%, D50 = 1.2μm, tap density 1.85g / cm³. 3 .

[0071] Example 2:

[0072] Raw materials: 50 kg LiOH·H₂O (99.9% purity), 950 kg N-methylpyrrolidone; add the raw materials to 5m 3The dissolving vessel was heated to 140°C with jacketed steam, and the anchor-type agitator was run at 80 rpm for 40 minutes. The viscosity of the suspension was measured to be 48.7 mPa·s (meeting the requirement of ≤50 mPa·s). The centrifugal reactor was then started at 1200 rpm, and H2S gas was introduced (initial flow rate 0.8 m³ / s). 3 / h); maintain temperature 180℃, pressure 0.3MPa, liquid hourly space velocity 1.0 / h; real-time monitoring data: pH value decreased from 13.2 to 10.8 (reaction endpoint), H2S recycling rate 98.3%. The wet material obtained by pressure filtration had a moisture content of 32.7%, was washed with n-hexane and then dried to obtain the finished product; quality testing: LiOH conversion rate over 96%, Li2S purity 99.6%, D50 = 1.16μm, tap density 1.84g / cm³. 3 .

[0073] Example 3:

[0074] Raw materials: 50 kg LiOH·H₂O (99.9% purity), 1000 kg N-methylpyrrolidone; add the raw materials to 5m 3 The dissolving vessel was heated to 130°C with jacketed steam, and the anchor-type agitator was run at 90 rpm for 2 hours. The viscosity of the suspension was measured to be 48.7 mPa·s (meeting the requirement of ≤50 mPa·s). The centrifugal reactor was started at 1200 rpm, and H2S gas was introduced (initial flow rate 1 m³ / s). 3 / h); maintain temperature 170℃, pressure 0.3MPa, liquid hourly space velocity 1.0 / h; real-time monitoring data: pH value decreased from 13.2 to 10.8 (reaction endpoint), H2S recycling rate 98.3%. The wet material obtained by pressure filtration had a moisture content of 32.7%, was washed with n-hexane and then dried to obtain the finished product; quality testing: LiOH conversion rate over 96%, Li2S purity 99.6%, D50 = 1.1μm, tap density 1.83g / cm³. 3 .

[0075] Example 4:

[0076] Raw materials: 50 kg LiOH·H₂O (99.9% purity), 950 kg N-methylpyrrolidone; add the raw materials to 5m 3 The dissolving vessel was heated to 130°C with jacketed steam, and the anchor-type agitator was run at 78 rpm for 40 minutes. The viscosity of the suspension was measured to be 48.7 mPa·s (meeting the requirement of ≤50 mPa·s). The centrifugal reactor was then started at 1200 rpm, and H2S gas was introduced (initial flow rate 0.7 m³ / s). 3 / h); maintain temperature 160℃, pressure 0.3MPa, liquid hourly space velocity 1.0 / h; real-time monitoring data: pH value decreased from 13.2 to 10.8 (reaction endpoint), H2S recycling rate 98.3%. The wet material obtained by pressure filtration had a moisture content of 32.7%, was washed with n-hexane and then dried to obtain the finished product; quality testing: LiOH conversion rate over 96%, Li2S purity 99.6%, D50 = 1.5μm, tap density 1.8g / cm³. 3 .

[0077] Comparative Example 1

[0078] Raw materials: 50 kg LiOH·H₂O (99.9% purity), 950 kg dimethylformamide; add the raw materials to 5m 3 The dissolving vessel was heated to 130°C with jacketed steam, and the anchor-type agitator was run at 78 rpm for 40 minutes. The viscosity of the suspension was measured to be 48.7 mPa·s (meeting the requirement of ≤50 mPa·s). The centrifugal reactor was then started at 1200 rpm, and H2S gas was introduced (initial flow rate 0.8 m³ / s). 3 / h); maintained temperature 160℃, pressure 0.3MPa, liquid hourly space velocity 1.0 / h; real-time monitoring data: pH value decreased from 13.2 to 10.8 (reaction endpoint), H2S recycling rate 98.3%. The wet material obtained by pressure filtration had a moisture content of 32.7%, was washed with n-hexane and then dried to obtain the finished product; quality testing: LiOH conversion rate 90%, Li2S purity 99.5%.

[0079] Comparative Example 2

[0080] Raw materials: 50 kg LiOH·H₂O (99.9% purity), 950 kg N-methylpyrrolidone; add the raw materials to 5m 3 The dissolving vessel was heated to 130°C with jacketed steam, and the anchor-type agitator was run at 78 rpm for 40 minutes. The viscosity of the suspension was measured to be 48.7 mPa·s (meeting the requirement of ≤50 mPa·s). The stirred reactor was operated at 300 rpm, and H2S gas was introduced (initial flow rate 0.8 m³ / min). 3 The reaction was carried out at 160℃ and 0.3MPa for 8 hours. The conversion rate of LiOH was 68% and the purity of Li2S was 95%.

[0081] A comparison of Examples 1-4 and Comparative Example 1 shows that, under the process described in Examples 1-4, N-methylpyrrolidone is preferred over dimethylformamide in Comparative Example 1, resulting in higher LiOH conversion. This is because N-methylpyrrolidone (boiling point 202℃, flash point 95℃) has a high dielectric constant (ε = 32.2), which favors the dissociation of LiOH. Furthermore, the Henry's coefficient (H = 12.3 MPa·m) of N-methylpyrrolidone is relatively low. 3( / mol) matching.

[0082] By comparing the above Examples 1-4 and Comparative Example 2, it can be seen that the process method in Examples 1-4 of this application has a higher conversion rate of LiOH and an improved purity of Li2S compared with the traditional process.

[0083] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A method for preparing lithium sulfide, characterized in that, Includes the following steps: Raw material pretreatment: Lithium hydroxide powder and organic solvent are mixed at a certain mass ratio and stirred in a dissolving tank to form a suspension; Hypergravity reaction: The suspension is fed into the rotating packing layer of the hypergravity reactor in an axial manner, and at the same time, preheated hydrogen sulfide gas is introduced into the rotating packing layer in a tangential manner to carry out the reaction. Product separation: The reaction liquid of the supergravity reactor is separated by pressure filtration to obtain lithium sulfide wet material, and after washing several times, the lithium sulfide wet material is dried to obtain lithium sulfide powder.

2. The method for preparing lithium sulfide according to claim 1, characterized in that, It also includes the following steps: Gas circulation: Unreacted hydrogen sulfide gas is purified by passing it sequentially through a cyclone separator, a condensation dehydration tower, and a molecular sieve adsorption tower, and then returned to the hypergravity reactor for recycling via a booster pump.

3. The method for preparing lithium sulfide according to claim 1, characterized in that, In the raw material pretreatment, the lithium hydroxide powder and the organic solvent are mixed at a mass ratio of 4-6%. The conditions for the dissolving vessel are set as follows: stirring temperature of 125-135℃, stirring speed of 200-400rpm, and stirring time of 30-60min.

4. The method for preparing lithium sulfide according to claim 1, characterized in that, In the raw material pretreatment, the organic solvent is an aprotic polar organic solvent, including one or more of amide organic solvents, lactam organic solvents, urea organic solvents, organic sulfur solvents, and cyclic phosphating organic solvents.

5. The method for preparing lithium sulfide according to claim 1, characterized in that, In the hypergravity reaction, the conditions of the hypergravity reactor are set as follows: reaction temperature is 155-195℃, reaction pressure is 0.2-0.5MPa, and rotation speed of the rotating packing layer is 800-1500rpm.

6. The method for preparing lithium sulfide according to claim 1, characterized in that, In the aforementioned hypergravity reaction, the hydrogen sulfide gas is preheated to 140-160°C and its flow rate is 0.5-1.2 m³ / s. 3 / h, liquid hourly space velocity is 0.8-1.5 / h.

7. The method for preparing lithium sulfide according to claim 1, characterized in that, In the aforementioned hypergravity reaction, the rotating packing layer is made of stainless steel wire mesh with a wire diameter of 0.1-0.3 mm, a corrugation angle of 45-60°, and a specific surface area of ​​2000-3000 m². 2 / m 3 The surface is coated with a 10-50μm thick PTFE coating.

8. A lithium sulfide preparation system, characterized in that, include; Raw material handling system (10), supergravity reactor system (20), and liquid delivery pipeline (30) connecting the two; The raw material processing system (10) includes a dissolving tank (11), which is used to stir a mixture of lithium hydroxide and organic solvent to form a homogeneous suspension; The hypergravity reactor system (20) includes a hypergravity reactor (21), a rotating packing layer (22), an axial liquid inlet pipe (23), a tangential air inlet pipe (24), and a liquid outlet pipe (25); The infusion pipeline (30) connects the dissolving vessel (11) and the hypergravity reactor (21) and is used to transport the suspension into the hypergravity reactor (21); The rotating packing layer (22) is rotatably disposed inside the hypergravity reactor (21); The axial inlet pipe (23) connects the rotating packing layer (22) and the supergravity reactor (21), and is also connected to the conveying pipe (30) for feeding the suspension into the rotating packing layer (22) in an axial manner. The tangential air inlet pipe (24) is connected to the supergravity reactor (21) and is used to introduce preheated hydrogen sulfide gas into the rotating packing layer (22) in a tangential manner. The liquid outlet pipe (25) is connected to the supergravity reactor (21) and is used to output the reaction liquid.

9. The lithium sulfide preparation system according to claim 8, characterized in that, The supergravity reactor system (20) also includes a circulation pipe (26) that connects the liquid outlet pipe (25) and the liquid delivery pipe (30) to return unreacted reaction liquid to the rotating packing layer (22).

10. The lithium sulfide preparation system according to claim 8, characterized in that, The surface of the corrugated wire mesh filler of the rotating filler layer (22) is coated with polytetrafluoroethylene.

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