Process for producing lithium sulfide through reaction of molten lithium hydroxide spray and hydrogen sulfide

Abstract

The invention relates to the field of lithium battery materials, and discloses a process for producing lithium sulfide through reaction of molten lithium hydroxide spray and hydrogen sulfide, and the process comprises the following steps: S1, in an inert atmosphere, heating a lithium hydroxide raw material to obtain molten lithium hydroxide; s2, spraying the molten lithium hydroxide in a reaction zone to form molten lithium hydroxide liquid drops; s3, introducing hydrogen sulfide gas into the reaction zone, and carrying out contact reaction on the hydrogen sulfide gas and the molten lithium hydroxide liquid drops to generate solid lithium sulfide and water vapor; s4, collecting and purifying the generated solid lithium sulfide, and discharging tail gas containing water vapor; and S5, performing heat energy recovery on the tail gas discharged from the upper part of the reaction area. The lithium hydroxide is used as the lithium source raw material and is heated in the preset temperature interval to obtain the molten lithium hydroxide, so that the problems of over-high reaction temperature and huge process energy consumption in the prior art are solved, and the technical effects of reducing energy consumption and lowering the requirement on high-temperature resistance of equipment are achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, specifically a process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide. Background Technology

[0002] Lithium sulfide, especially high-purity lithium sulfide, is one of the key cathode materials for developing next-generation energy storage technologies such as high-energy-density lithium-sulfur batteries. Currently, one common industrial approach to preparing lithium sulfide involves using lithium carbonate as the lithium source and reacting it with sulfur-containing gases (such as hydrogen sulfide) at high temperatures. This method typically requires temperatures exceeding the melting point of lithium carbonate (approximately 723°C) to promote contact and conversion between the solid or molten lithium carbonate and the gaseous reactants.

[0003] While the above methods can produce lithium sulfide, their inherent characteristics present room for further optimization in the pursuit of higher production efficiency and lower environmental impact. First, because the reaction needs to be carried out at a high temperature, the entire process maintains a high level of energy consumption, while also placing stringent requirements on the high-temperature resistance and long-term operational stability of the reaction equipment.

[0004] Furthermore, from the perspective of the reaction mechanism, using lithium carbonate as a raw material inevitably generates a large amount of carbon dioxide gas, which not only increases the complexity and cost of subsequent exhaust gas treatment, but also deviates to some extent from the current green and low-carbon development direction of the manufacturing industry.

[0005] Finally, the solid products obtained from high-temperature reactions are often non-uniform in morphology and may require multiple subsequent processing steps such as crushing, grinding and purification to obtain lithium sulfide powder that meets the specific application requirements. This prolongs the production cycle to some extent and affects the overall production efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide, which solves the problems of high reaction temperature, high energy consumption, generation of carbon dioxide byproducts, and complex process flow when preparing lithium sulfide using lithium carbonate as raw material.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide, comprising the following steps: S1. Nitrogen gas is introduced into a vacuum environment to purge lithium hydroxide to remove oxygen adsorbed on the surface of lithium hydroxide. Then, the lithium hydroxide raw material is heated to obtain molten lithium hydroxide. S2. The molten lithium hydroxide is sprayed within the reaction zone to form molten lithium hydroxide droplets; S3. Hydrogen sulfide gas is introduced into the reaction zone and reacts with the molten lithium hydroxide droplets to generate solid lithium sulfide and water vapor.

[0008] Preferably, in step S1, the temperature of the heated lithium hydroxide raw material is 400-600℃.

[0009] Preferably, in step S1, the inert atmosphere is nitrogen or argon with a purity of not less than 99.99%.

[0010] Preferably, in step S2, the average particle size of the molten lithium hydroxide droplets is 1-10 μm.

[0011] Preferably, in step S3, the hydrogen sulfide gas is introduced from the lower part of the reaction zone, and the molten lithium hydroxide droplets settle downwards from the upper part of the reaction zone, forming a countercurrent contact.

[0012] Preferably, the process further includes: S4. The generated solid lithium sulfide is collected at the bottom of the reaction zone, and the tail gas containing water vapor is discharged from the top of the reaction zone. The exhaust gas also contains unreacted hydrogen sulfide gas and nitrogen gas as an inert atmosphere.

[0013] Preferably, step S4 further includes: The collected solid lithium sulfide is transported to a fluidized bed reactor and subjected to a secondary reaction and drying at 200-400°C in an atmosphere containing hydrogen sulfide and inert gas to obtain the final solid lithium sulfide product.

[0014] Preferably, the process further includes the following steps: S5. Perform heat recovery on the exhaust gas discharged from the upper part of the reaction zone.

[0015] Preferably, both the heated lithium hydroxide raw material and the molten lithium hydroxide are sprayed within the reaction zone under the inert atmosphere.

[0016] Preferably, the process is carried out in a device with an inner wall made of high-nickel stainless steel.

[0017] This invention provides a process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide. It has the following beneficial effects: 1. This invention solves the technical problems of excessively high reaction temperature and huge process energy consumption caused by using lithium hydroxide as a lithium source material and heating it within a preset temperature range to obtain molten lithium hydroxide. This invention achieves the technical effect of reducing energy consumption and reducing the requirements for high temperature resistance of equipment.

[0018] 2. This invention uses molten lithium hydroxide to react with hydrogen sulfide, so that the chemical reaction products are only solid lithium sulfide and water vapor. This solves the technical problem in the prior art that the reaction of lithium carbonate produces carbon dioxide byproducts, which leads to environmental pollution and increases the burden of subsequent treatment. This invention achieves the technical effect of avoiding carbon dioxide generation from the source and realizing clean production.

[0019] 3. This invention solves the technical problems of long overall process and low production efficiency caused by the need for complex post-processing steps such as drying and purification of products in traditional processes by using a method of spraying molten lithium hydroxide and reacting it with hydrogen sulfide gas to achieve one-step conversion of liquid raw materials into solid products and direct sedimentation collection. This achieves the technical effect of simplifying the overall process and improving production efficiency. Attached Figure Description

[0020] Figure 1 This is a flowchart of the process steps of the present invention. Detailed Implementation Example

[0021] See attached document Figure 1 This invention provides a process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide, the process comprising the following steps: S1, Nitrogen gas is introduced into a vacuum environment to purge lithium hydroxide to remove oxygen adsorbed on the surface of lithium hydroxide, and then the lithium hydroxide raw material is heated to obtain molten lithium hydroxide. S2, molten lithium hydroxide is sprayed into the reaction zone to form molten lithium hydroxide droplets; S3, hydrogen sulfide gas is introduced into the reaction zone and reacts with molten lithium hydroxide droplets to generate solid lithium sulfide and water vapor; S4, the generated solid lithium sulfide is collected and purified in the lower part of the reaction zone, and then the tail gas containing water vapor is discharged from the upper part of the reaction zone. S5 recovers heat energy from the exhaust gas containing water vapor discharged from the top of the reaction zone. Example

[0022] Step S1 involves introducing nitrogen gas to purge the lithium hydroxide under vacuum to remove adsorbed oxygen from its surface. The lithium hydroxide raw material is then heated to obtain molten lithium hydroxide. This step is performed in a sealed melting apparatus designed to create a vacuum environment. The melting apparatus is made of high-nickel stainless steel and can be further divided into the following sub-steps: S101, add the predetermined mass of anhydrous lithium hydroxide raw material into a clean and dry melting device. The water content of the lithium hydroxide raw material is controlled, and anhydrous lithium hydroxide is used to avoid side reactions between water and other substances at subsequent high temperatures.

[0023] S102, the melting device is sealed, and inert gas is introduced into it through a gas pipeline to replace the air inside the device. An inert atmosphere refers to a gaseous environment that does not chemically react with molten lithium hydroxide at the operating temperature; specifically, it can be nitrogen with a purity of not less than 99.99%, or argon. This replacement process can be repeated multiple times, for example, by using a cycle of three vacuuming and then filling with inert gas to ensure that the oxygen and carbon dioxide content inside the device meets the process requirements.

[0024] The process requirement is that, through atmosphere replacement, the volume fraction of oxygen inside the melting device is reduced to below 100 ppm, preferably below 10 ppm; and the volume fraction of carbon dioxide is reduced to below 50 ppm, preferably below 5 ppm.

[0025] During the introduction of the inert atmosphere, the oxygen adsorbed on the surface of lithium hydroxide can be removed by purging it with nitrogen, and then discharged in the cycle of three vacuuming and refilling with inert gas.

[0026] Throughout the heating and melting process, a slightly positive pressure inert atmosphere is continuously introduced into the melting device to prevent outside air from entering.

[0027] S103, the external heating unit of the melting device is activated to heat the lithium hydroxide raw material at a preset heating rate. The heating temperature is set within the range of 400-600℃. This temperature range is higher than the melting point of lithium hydroxide (common test value is approximately 471℃), ensuring that the lithium hydroxide is completely converted into a liquid phase and maintains good fluidity, facilitating subsequent transportation and spraying. The melting temperature is precisely controlled by a temperature sensor installed inside the melting device and an external temperature control system.

[0028] S104: Once the temperature reaches the set value (400-600℃), maintain the temperature for 30-90 minutes, depending on the amount of material fed, until the lithium hydroxide raw material is completely melted. This process is completed by visually confirming through the observation window of the melting device that the material in the vessel has completely transformed into a liquid phase, with no solid suspended matter, and presents a uniform and clear state. At this point, the molten lithium hydroxide is obtained for use in the subsequent step S2.

[0029] In step S2, molten lithium hydroxide is sprayed within the reaction zone to form molten lithium hydroxide droplets. This step aims to disperse the liquid reactants into tiny droplets with a large specific surface area, providing a sufficient contact interface for subsequent gas-liquid phase chemical reactions. The reaction zone is located inside a vertical spray reaction tower, the main body of which is made of high-nickel stainless steel.

[0030] Specifically, step S2 can be further broken down into the following sub-steps: In step S201, the molten lithium hydroxide prepared in step S1 is transported from the melting vessel to the atomizing nozzle located at the top of the spray reaction tower via a high-temperature conveying system. The high-temperature conveying system includes insulated pipelines and a high-temperature metering pump to ensure that the molten lithium hydroxide is maintained at a temperature of 400-600°C during the conveying process and to preserve its fluidity. The entire conveying process is carried out under an inert atmosphere to prevent the material from contacting the outside air.

[0031] S202, start the high-temperature metering pump to stably supply molten lithium hydroxide to the atomizing nozzle at a preset mass flow rate. The atomizing nozzle is designed to atomize high-viscosity molten salt at high temperatures.

[0032] In S203, molten lithium hydroxide is atomized into fine droplets at the top of the spray reaction tower through an atomizing nozzle. Process parameters such as nozzle type and operating pressure are controlled to ensure that the average particle size of the formed molten lithium hydroxide droplets is within the range of 1-10 μm.

[0033] These micrometer-sized droplets greatly increase the specific surface area of ​​the reactants, and the initial specific surface area (Asp) of a single droplet can be characterized by the following formula: ; In the formula, The specific surface area of ​​a single droplet, expressed in square meters per kilogram (m²). 2 / kg); The average diameter of the droplet is expressed in meters (m). This is the density of molten lithium hydroxide at the reaction temperature, expressed in kilograms per cubic meter (kg / m³). 3 ).

[0034] S204, after atomization, forms a group of molten lithium hydroxide droplets that settle from top to bottom in the spray reaction tower under the action of gravity, and react with the subsequently introduced hydrogen sulfide gas during this process.

[0035] In step S3, hydrogen sulfide gas is introduced into the reaction zone to react with molten lithium hydroxide droplets, generating solid lithium sulfide and water vapor. This step is the core chemical reaction process that transforms the liquid-phase raw material into a solid-phase product.

[0036] Specifically, step S3 can be further broken down into the following sub-steps: S301, through a gas supply and control system, hydrogen sulfide gas is mixed with an inert gas (e.g., nitrogen) as a carrier gas at a preset ratio. In this process, the volume fraction of hydrogen sulfide (H2S) in the mixed reaction gas is typically set within the range of 20-50%. For example, if set to 30%, the volumetric flow rate of the carrier gas will be set to 7 / 3 times the volumetric flow rate of hydrogen sulfide. The set value of the carrier gas flow rate is calculated and set based on this ratio and the flow rate of hydrogen sulfide. This concentration ensures sufficient reactant concentration for efficient reaction while effectively carrying the water vapor generated in the reaction away from the reaction zone using the carrier gas. A mass flow controller is used to precisely control the mass flow rate of hydrogen sulfide gas and the flow rate of the carrier gas to adjust the molar ratio (Rm) of the reactants. The molar ratio is defined as the ratio of the molar amount of hydrogen sulfide to the molar amount of lithium hydroxide introduced per unit time, and its calculation formula is: ; In the formula, The molar ratio of reactants to feed is dimensionless. This represents the molar amount of hydrogen sulfide introduced per unit time, expressed in moles (mol). This represents the molar amount of lithium hydroxide introduced per unit time, expressed in moles (mol). The mass flow rate of hydrogen sulfide is expressed in grams per second (g / s). The mass flow rate of molten lithium hydroxide is expressed in grams per second (g / s). The molar mass of hydrogen sulfide is expressed in grams per mole (g / mol). The value represents the molar mass of lithium hydroxide, expressed in grams per mole (g / mol). Before being introduced into the reaction zone, the mixed gas passes through a gas preheater to bring its temperature close to the operating temperature of the reaction zone, thus preventing the droplets from condensing due to cold gas.

[0037] In step S302, the preheated mixed gas is introduced from the bottom of the spray reaction tower, causing it to flow upwards within the reaction zone. Simultaneously, the molten lithium hydroxide droplets formed in step S2 settle downwards. This gas-liquid two-phase flow pattern creates countercurrent contact, increasing the relative velocity between the two phases and prolonging the effective contact time, thereby improving the mass and heat transfer efficiency of the reaction.

[0038] In reaction zone S303, molten lithium hydroxide droplets react chemically with hydrogen sulfide gas. The chemical equation for this reaction is as follows: ; As the reaction proceeds, the liquid lithium hydroxide is converted into the solid lithium sulfide, and water vapor is generated in the gaseous phase. Ultimately, each droplet is transformed into a solid lithium sulfide particle.

[0039] In step S4, the generated solid lithium sulfide is collected at the bottom of the reaction zone, and a tail gas containing water vapor is discharged from the top of the reaction zone. This step achieves effective separation of the solid and gas phases in the reaction products.

[0040] Specifically, step S4 can be further broken down into the following sub-steps: S401, during the reaction, solid lithium sulfide particles transformed from molten lithium hydroxide droplets, due to their higher density than the surrounding gaseous medium, continuously settle towards the bottom of the spray reaction tower under gravity. An intermediate product collector is installed at the bottom of the spray reaction tower to temporarily receive and buffer these settled solid lithium sulfide powders. The collector is a sealed container maintained under an inert atmosphere.

[0041] S402, to further remove any remaining trace amounts of unreacted matter and achieve deep drying, a secondary purification process begins. The solid lithium sulfide powder collected in step S401 is continuously fed into a fluidized bed reactor via a closed solid conveying device (e.g., a star-shaped feed valve or a screw conveyor). Inside the fluidized bed reactor, a mixed gas consisting of hydrogen sulfide and an inert gas (e.g., nitrogen) is introduced through a gas distribution plate at the bottom, with a gas flow rate sufficient to fluidize the solid particles within the bed. Simultaneously, the bed temperature is controlled within the range of 200-400°C. Under these conditions, the excess hydrogen sulfide atmosphere completely reacts with any residual lithium hydroxide in the solid lithium sulfide powder, while the high-temperature gas flow completely vaporizes and removes any adsorbed trace amounts of moisture from the product.

[0042] S403, after fluidized bed purification, yields a high-purity, dry final lithium sulfide product. This product is continuously discharged through an overflow port located below the fluidized bed and enters a final solid product collector. This collector is a sealed container maintained under an inert atmosphere to prevent oxidation or moisture absorption of the collected high-purity lithium sulfide product. Based on the total mass of the input lithium hydroxide feedstock, the theoretically generated mass of solid lithium sulfide can be calculated using the following formula: ; In the formula, The theoretical mass of lithium sulfide produced is expressed in kilograms (kg). The total mass of lithium hydroxide participating in the reaction is expressed in kilograms (kg). The value represents the molar mass of lithium hydroxide, expressed in kilograms per mole (kg / mol). The value represents the molar mass of lithium sulfide, expressed in kilograms per mole (kg / mol).

[0043] In step S404, simultaneously, the water vapor, unreacted hydrogen sulfide gas, and inert gas generated by the reaction constitute the primary tail gas. Since this tail gas is in the gas phase, it moves upwards within the spray reaction tower with the airflow and eventually reaches the top of the tower. During the fluidized bed treatment in step S402, the secondary tail gas, carrying a small amount of water vapor and unreacted hydrogen sulfide, is also discharged from its top. These two tail gases can be combined and then uniformly led out of the reaction zone through a main tail gas pipe for subsequent step S5.

[0044] In step S5, heat energy is recovered from the exhaust gas discharged from the top of the reaction zone. This step aims to utilize the sensible heat carried by the high-temperature exhaust gas leaving the reaction zone to improve the energy efficiency of the entire process.

[0045] Specifically, step S5 can be further broken down into the following sub-steps: S501, the high-temperature exhaust gas discharged from the top of the spray reaction tower in step S404 is introduced into a heat recovery device. The heat recovery device is a gas-to-gas heat exchanger. The high-temperature exhaust gas passes through one side channel of the heat exchanger.

[0046] S502, the mixed reaction gas of hydrogen sulfide and nitrogen, which was prepared to be introduced into the reaction zone at room temperature in step S301, is introduced into the other flow channel of the gas-to-gas heat exchanger. Through the wall of the heat exchanger, the high-temperature exhaust gas transfers some of the heat it carries to the low-temperature mixed reaction gas, thereby preheating the mixed reaction gas.

[0047] In S503, after heat recovery (i.e., preheating the mixed reactant gas), the cooled exhaust gas exits from the heat exchanger and enters the subsequent exhaust gas treatment unit for water vapor condensation and separation, as well as the absorption or recovery of unreacted hydrogen sulfide. The preheated mixed reactant gas then enters a gas preheater for further heating to the set reaction temperature, or is directly fed into the reaction tower. This step reuses energy that would otherwise be emitted, reducing dependence on external energy sources.

[0048] Comparative Example 1: Compared to Example 1, the difference lies in that the lithium hydroxide raw material in step S1 is replaced with an equimolar amount of lithium carbonate raw material, and the heating temperature in step S1 is set to 750°C to ensure that the lithium carbonate is completely melted. The remaining process parameters and steps are the same as in Example 1.

[0049] Comparative Example 2: The difference from Example 1 is that the heating temperature in step S1 is set to 400°C. All other process parameters and steps are the same as in Example 1.

[0050] Comparative Example 3: Compared with Example 1, the difference is that steps S1, S2, and S3 are all carried out in an unpurified air atmosphere, without the introduction of inert gas for protection. The remaining process parameters and steps are the same as in Example 1.

[0051] Comparative Example 4: Compared to Example 1, the difference is that the spraying operation in step S2 is omitted, and instead, in step S3, hydrogen sulfide gas is directly introduced into the molten lithium hydroxide-containing vessel through a gas distribution pipe to carry out a bubbling reaction. All other process parameters and steps are the same as in Example 1.

[0052] Test Example 1: Experimental description: This test case aims to compare the differences between Example 1 of the present invention (using lithium hydroxide as raw material) and Comparative Example 1 (using lithium carbonate as raw material) in terms of process energy consumption, reaction products and exhaust gas composition.

[0053] Lithium sulfide products were prepared according to the process conditions defined in Example 1 and Comparative Example 1, respectively. During both experiments, a high-precision power meter was used to monitor and record the total electrical energy consumption of the melting and heating unit and the heat preservation unit in real time. After the reaction was completed, the solid product and the gaseous tail gas were collected, respectively.

[0054] The collected solid products were subjected to phase analysis using X-ray diffraction (XRD) to determine their main crystalline phase composition. The lithium sulfide content was determined by chemical titration, and the yield was calculated accordingly.

[0055] The exhaust gas was analyzed by an online gas analyzer (integrating a non-dispersive infrared sensor and a thermal conductivity detector), with a focus on detecting and quantifying the volume fraction of carbon dioxide (CO2) (see Table 1 for data details).

[0056] Experimental data: Table 1 Experimental group lithium source raw materials Set the melting temperature (°C) Total energy consumption (kWh) Lithium sulfide yield (%) Main phase of product (XRD analysis) <![CDATA[CO2 concentration in tail gas (ppm)]]> Example 1 Anhydrous lithium hydroxide 465 15.7 98.6 <![CDATA[Li2S]]> 3 Comparative Example 1 Anhydrous lithium carbonate 750 28.2 96.1 <![CDATA[Li2S, trace Li2CO3]]> 215800 In summary, firstly, looking at the energy consumption data, the total energy consumption of Example 1 (15.7 kWh) is lower than that of Comparative Example 1 (28.2 kWh). This is due to the core mechanism of this invention, which is to use lithium hydroxide with a melting point of only 471°C instead of lithium carbonate with a melting point as high as 723°C as the lithium source, fundamentally reducing the process operating temperature, thereby achieving a significant reduction in energy consumption.

[0057] Secondly, analysis of the exhaust gas composition showed that no carbon dioxide produced by the chemical reaction was detected in the exhaust gas of Example 1 (the detection value of 3 ppm is the background level), while the exhaust gas of Comparative Example 1 contained a high concentration of carbon dioxide (21.58%). This data is completely consistent with the reaction principle: The reaction of the present invention: ; Its product is water, while the reaction in Comparative Example 1 is as follows: ; This is accompanied by the generation of carbon dioxide. This confirms the effectiveness of the present invention in eliminating carbon emissions from the process.

[0058] Finally, product analysis data showed that Example 1 achieved higher yield and purity. This indicates that the reaction was more complete and had fewer side reactions at lower reaction temperatures.

[0059] In summary, the test data shows that the present invention, by using lithium hydroxide as a raw material, successfully achieves the beneficial effects of reducing reaction temperature, significantly reducing energy consumption, and preventing carbon dioxide generation at the source.

[0060] Test Example 2: Experimental description: This test case aims to compare the differences in reaction efficiency and physical morphology of the final product between Example 1 of the present invention (using molten lithium hydroxide spray reaction) and Comparative Example 4 (using hydrogen sulfide bubbling reaction).

[0061] The reactions were carried out using equal masses of anhydrous lithium hydroxide feedstock, according to the process conditions defined in Example 1 and Comparative Example 4, respectively. For Example 1, the time from the start of spraying to the completion of all molten liquid delivery was recorded. For Comparative Example 4, the time required from the start of hydrogen sulfide introduction to the point where the hydrogen sulfide concentration at the tail gas outlet reached a stable level (indicating that the reaction in the reactor was essentially complete) was recorded; this time was denoted as the reaction time.

[0062] After the reaction was completed, the solid products were collected separately. The residual amount of unreacted lithium hydroxide in the products was determined by chemical titration, and the conversion rate of lithium hydroxide was calculated accordingly. The particle size distribution of the solid product powder was tested using a laser particle size analyzer, and the median particle size (D50) and particle size distribution width were recorded (see Table 2 for data details).

[0063] Experimental data: Table 2 Experimental group Reaction method Reaction time (min) Lithium hydroxide conversion rate (%) Median particle size of the product (D50, μm) Particle size distribution width (Span) Example 1 Molten liquid spray 28 99.1 2.8 0.8 Comparative Example 4 Molten liquid bubbling 155 87.3 45.6 2.5 In summary, firstly, regarding reaction efficiency, Example 1 achieved a significantly shorter conversion time (28 minutes) compared to Comparative Example 4 (155 minutes), and also achieved a higher lithium hydroxide conversion rate (99.1% vs. 87.3%). This directly stems from the core mechanism of this invention: atomizing molten lithium hydroxide into droplets with an average particle size of 1-10 μm greatly increases the contact surface area between the gas and liquid phases. This large reaction interface eliminates mass transfer as a limiting step in the reaction, resulting in extremely fast reaction kinetics and a highly complete reaction. In contrast, the bubbling method in Comparative Example 4 only provides a limited gas-liquid contact area, and the reaction is limited by mass transfer efficiency, leading to a slow and incomplete reaction.

[0064] Secondly, regarding the physical morphology of the product, the product obtained in Example 1 has a small particle size (median particle size of 2.8 μm) and a narrow distribution (particle size distribution width of 0.8), exhibiting a uniform micron-sized powder morphology. This is because the spray reaction process is similar to spray drying, where each droplet reacts independently and transforms into a solid particle, thus ensuring the uniformity of the product. In contrast, in Comparative Example 4, solid lithium sulfide is generated in a blocky molten liquid, and its nucleation and growth process is difficult to control, leading to severe agglomeration of the product, ultimately forming irregular particles with large particle size and wide distribution.

[0065] In summary, the test data confirms that the molten lithium hydroxide spray reaction method used in this invention is not only far superior to the traditional bubbling contact method in terms of chemical reaction efficiency, but also has a decisive advantage in controlling the physical morphology of solid products, and can prepare micron-sized lithium sulfide powder with uniform particle size.

[0066] Test Example 3: Experimental description: This test case aims to verify the effect of the reaction atmosphere on the chemical composition and purity of the final product in Example 1 (reaction carried out in an inert atmosphere) and Comparative Example 3 (reaction carried out in an air atmosphere).

[0067] Solid products were prepared according to the process conditions defined in Example 1 and Comparative Example 3, respectively. After the reaction was completed, samples of the solid products obtained from the two sets of experiments were taken in a glove box under an inert atmosphere.

[0068] The phase composition of the samples was qualitatively analyzed using X-ray diffraction (XRD). Ion chromatography (IC) was used to analyze the carbonate (CO3) content in the samples. 2- ) and sulfate (SO4) 2- Anionic impurities such as lithium sulfide (Li₂S) were quantitatively determined, and the corresponding mass fraction of lithium salts was calculated. The mass fraction of lithium sulfide (Li₂S) in the samples was determined by chemical titration (data details are shown in Table 3).

[0069] Experimental data: Table 3 Experimental group Reaction Atmosphere Main phase of product (XRD analysis) <![CDATA[Li2S content (wt%)]]> <![CDATA[Impurity content of Li2CO3 (wt%)]]> <![CDATA[Li2SO4 impurity content (wt%)]]> Example 1 <![CDATA[Inert atmosphere (N2)]]> <![CDATA[Li2S]]> 98.6 0.28 0.15 Comparative Example 3 Air <![CDATA[Li2S (main), Li2CO3 (secondary), Li2SO4 (trace)]]> 85.7 9.8 2.3 In summary, the phase and content analysis results of the products show that in Example 1, conducted under an inert atmosphere, the main phase of the product is pure lithium sulfide, with a lithium sulfide content as high as 98.6%, containing only trace amounts of impurities. In contrast, in Comparative Example 3, conducted under an air atmosphere, the lithium sulfide content in the product was significantly reduced to 85.7%, and a large amount of lithium carbonate (9.8%) and lithium sulfate (2.3%) impurities were also generated.

[0070] The underlying mechanism of this result is that, under the high-temperature reaction conditions of Comparative Example 3, the molten lithium hydroxide, as a raw material, undergoes a chemical reaction with carbon dioxide in the air: ; This can lead to some of the raw materials being converted into lithium carbonate impurities. More importantly, the target product, lithium sulfide, is chemically reactive at high temperatures and readily undergoes oxidation with oxygen in the air to form lithium sulfate.

[0071] This invention effectively isolates the reaction system from carbon dioxide and oxygen in the air by maintaining an inert atmosphere throughout the entire process. This technique fundamentally suppresses the aforementioned side reactions, ensuring that lithium hydroxide raw materials can be efficiently converted into lithium sulfide and protecting the generated high-temperature lithium sulfide product from oxidation, thereby obtaining a high-purity final product.

[0072] In summary, the test results show that using an inert atmosphere for protection is a necessary condition for the preparation of high-purity lithium sulfide and is the technical guarantee for obtaining high-quality products in this invention.

[0073] Test Example 4: Experimental description: This test case aims to verify the necessity of the heating temperature range defined in Example 1 of the present invention. By comparing it with Comparative Example 2 (which uses a heating temperature lower than the melting point of lithium hydroxide), the decisive influence of temperature parameters on whether the process can be successfully implemented is examined.

[0074] The process conditions for Example 1 and Comparative Example 2 were set separately. In Example 1, the heating temperature of the melting vessel was set to 475°C; in Comparative Example 2, the heating temperature of the melting vessel was set to 400°C. Equal masses of anhydrous lithium hydroxide raw material were used in both experiments.

[0075] After the set holding time is reached, the high-temperature conveying system is started to attempt to transport the material in the melting vessel to the atomizing nozzle via the high-temperature metering pump. During this process, the pressure data at the inlet and outlet of the high-temperature metering pump are closely monitored and recorded, and the working status of the atomizing nozzle is directly observed. After the set running time is completed, the mass of the solid product collected at the bottom of the reaction tower is collected and weighed (data details are shown in Table 4).

[0076] Experimental data: Table 4 Experimental group Set the melting temperature (°C) Macroscopic state of materials inside the reactor Metering pump outlet pressure (MPa) atomizing nozzle status Final collected product mass (kg) Example 1 465 homogeneous transparent liquid phase 1.18 Forming a stable and uniform fog cone 4.12 Comparative Example 2 400 White loose solid powder 4.8 (Pressure Overload) No material was ejected. 0.01 In summary, the experimental phenomena and data show that at a heating temperature of 400℃ (Comparative Example 2), the lithium hydroxide raw material did not melt and remained as a solid powder. When the conveying system was started, the solid powder could not be effectively conveyed by the high-temperature metering pump, causing the pump's outlet pressure to rise rapidly and triggering overload protection. No material was ejected from the atomizing nozzle. Therefore, the entire spray reaction process was interrupted at its source and could not proceed, ultimately failing to collect the target product.

[0077] Conversely, at a heating temperature of 475°C (Example 1), the lithium hydroxide feedstock was completely transformed into a molten liquid phase with good flowability. This liquid phase material could be stably delivered by a high-temperature metering pump and successfully atomized at an atomizing nozzle, thereby enabling the subsequent gas-liquid reaction to proceed smoothly and ultimately obtaining the desired lithium sulfide product.

[0078] The underlying mechanism of this result lies in the fact that the core process of this invention is based on atomizing liquid raw materials to provide a large reaction interface. The physical prerequisite for achieving this process is converting solid lithium hydroxide into a liquid state. The temperature range of 400-600°C proposed in this invention is precisely near the melting point of lithium hydroxide (approximately 471°C) and ensures its complete melting, which is fundamental to ensuring the success of all subsequent steps. The failure of Comparative Example 2 directly proves that if the temperature is below this critical range, the technical solution itself will not be valid.

[0079] In summary, the test results show that the limitation on heating temperature in this invention is not a simple parameter optimization, but a key control point to ensure the success of the entire technical route.

Claims

1. A process for producing lithium sulfide by spraying molten lithium hydroxide with hydrogen sulfide, characterized in that, Includes the following steps: S1. Nitrogen gas is introduced into a vacuum environment to purge lithium hydroxide to remove oxygen adsorbed on the surface of lithium hydroxide. Then, the lithium hydroxide raw material is heated to obtain molten lithium hydroxide. S2. The molten lithium hydroxide is sprayed within the reaction zone to form molten lithium hydroxide droplets; S3. Hydrogen sulfide gas is introduced into the reaction zone and reacts with the molten lithium hydroxide droplets to generate solid lithium sulfide and water vapor.

2. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, In step S1, the temperature of the heated lithium hydroxide raw material is 400-600℃.

3. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, In step S1, the inert atmosphere is nitrogen or argon with a purity of not less than 99.99%.

4. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, In step S2, the average particle size of the molten lithium hydroxide droplets is 1-10 μm.

5. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, In step S3, the hydrogen sulfide gas is introduced from the lower part of the reaction zone, and the molten lithium hydroxide droplets settle downwards from the upper part of the reaction zone, forming a countercurrent contact.

6. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, The process also includes: S4. The generated solid lithium sulfide is collected at the bottom of the reaction zone, and the tail gas containing water vapor is discharged from the top of the reaction zone. The exhaust gas also contains unreacted hydrogen sulfide gas and nitrogen gas as an inert atmosphere.

7. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 6, characterized in that, Step S4 further includes: The collected solid lithium sulfide is transported to a fluidized bed reactor and subjected to a secondary reaction and drying at 200-400°C in an atmosphere containing hydrogen sulfide and inert gas to obtain the final solid lithium sulfide product.

8. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, The process also includes the following steps: S5. Perform heat recovery on the exhaust gas discharged from the upper part of the reaction zone.

9. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, The heating of the lithium hydroxide raw material and the spraying of the molten lithium hydroxide within the reaction zone are both carried out under the inert atmosphere.

10. The process for producing lithium sulfide by reacting molten lithium hydroxide spray with hydrogen sulfide according to claim 1, characterized in that, The process is carried out in a device with an inner wall made of high-nickel stainless steel.

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