Method and system for coupling sodium slag purification process to prepare calcium-based hydrogen storage material

Abstract

Disclosed is a method and system for coupling sodium slag purification process to prepare calcium-based hydrogen storage material, in which dry sodium slag is sent into a horizontal tube furnace reactor under inert atmosphere protection, the temperature is controlled at 850-950 DEG C, and the system pressure is controlled at 5-20 kPa, so that metallic sodium is volatilized to form a sodium vapor-inert gas mixed gas stream, and calcium and impurities remain in solid form, realizing separation of sodium and calcium; the mixed gas stream is sent into a first condenser and a second condenser in sequence, the condensing temperature difference is controlled at 100-200 DEG C, metallic sodium vapor is gradually condensed into liquid metallic sodium, which is collected into a sodium collection tank by gravity flow for recycling, and the solid-phase calcium and impurities remaining in the horizontal tube furnace reactor are used as calcium-based precursors; hydrogen is introduced into the horizontal tube furnace reactor, the temperature is controlled at 580-680 DEG C, the hydrogen pressure is controlled at 5-20 kPa, and the reaction is carried out for 2-4 hours, so that the solid-phase calcium is subjected to a hydrogenation reaction to obtain calcium-based hydrogen storage material containing CaH2.

Description

Technical Field

[0001] This invention relates to the field of sodium recovery and hydrogen storage material preparation technology, and in particular to a method and system for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process. Background Technology

[0002] Sodium slag generated during the production of metallic sodium is a typical hazardous solid waste. Its main components are metallic sodium (60%–85%), metallic calcium (10%–25%), and small amounts of sodium oxide and calcium oxide. Due to the active chemical properties of metallic sodium and metallic calcium, they readily form strong alkalis and release hydrogen gas when they come into contact with water (reaction equations: 2Na + 2H₂O = 2NaOH + H₂↑, Ca + 2H₂O = Ca(OH)₂ + H₂↑). They are also easily oxidized and exothermic or even spontaneously combustible when exposed to air. Traditional treatment methods have significant drawbacks: alcoholysis requires a large amount of ethanol, and the resulting sodium alkoxide solution has high treatment costs; landfilling requires passivation treatment first, and calcium resources are completely wasted.

[0003] Calcium, as a high-capacity hydrogen storage element, has a theoretical hydrogen storage density of 4.76 wt% for its hydrides (such as CaH2), making it a potential hydrogen storage material for applications such as vehicles and energy storage. However, current preparation processes rely on high-purity metallic calcium as a raw material. High-purity calcium needs to be prepared through electrolytic calcium chloride or aluminothermic reduction, which involves long processes and high energy consumption, resulting in high market prices for CaH2. In existing technologies, sodium slag treatment only focuses on recovering metallic sodium (such as the sodium slag sodium extraction process disclosed in CN202110867892.3), with the calcium component discarded as waste. The preparation of calcium-based hydrogen storage materials independently consumes high-purity calcium, forming a vicious cycle of "solid waste pollution - resource waste - high-cost production." Therefore, it is urgent to develop a coupled process to achieve synergy between the two.

[0004] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the shortcomings, this invention provides a method and system for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process. Through "gradient separation-in-situ conversion", the high-value utilization of all components of sodium slag is achieved, overcoming the defects of low calcium resource utilization rate and high cost of calcium-based hydrogen storage material preparation in traditional sodium slag treatment.

[0006] A method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process includes: Step a, sodium-calcium gradient separation: Under the protection of an inert atmosphere, the dried sodium slag is fed into a horizontal tubular furnace reactor, and the temperature is controlled at 850-950℃ and the system pressure at 5-20kPa. This causes the metallic sodium to volatilize and form a mixed gas flow of sodium vapor and inert gas, while calcium and impurities remain in solid form, thus achieving the separation of sodium and calcium. Step b, calcium-based precursor preparation: The mixed gas flow is sequentially fed into the first-stage condenser and the second-stage condenser, and the condensation temperature difference is controlled at 100-200℃. The metallic sodium vapor is gradually condensed into liquid metallic sodium, which is then collected by gravity into the sodium collection tank for recovery. The solid phase calcium and impurities retained in the horizontal tubular furnace reactor are used as calcium-based precursors. Step c, preparation of hydrogen storage material: Hydrogen gas is introduced into a horizontal tubular furnace reactor, the temperature is controlled at 580-680℃ and the hydrogen pressure is controlled at 5-20 kPa, and the reaction is carried out for 2-4 hours to make the solid-phase calcium undergo hydrogenation reaction to obtain a calcium-based hydrogen storage material including CaH2.

[0007] In the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step a, before the sodium slag is fed, it is cut into blocks with a particle size of 5-10 cm under the protection of an inert atmosphere, and after feeding, the air in the horizontal tubular furnace reactor is removed by inert gas replacement.

[0008] In the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, step a, the preparation of dried sodium slag includes: crushing the sodium slag to a particle size of 5-10 cm, and vacuum drying it at 100-150℃ for 2-4 h in an inert gas atmosphere with a purity of ≥99.99%.

[0009] In the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step a, the inert gas is argon, and the flow rate is 0.5~2L / min.

[0010] In the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step b, both the primary condenser and the secondary condenser adopt a shell-and-tube structure, and the cooling medium is heat transfer oil.

[0011] In the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step b, the temperature of the primary condenser is 400-450℃ and the temperature of the secondary condenser is 200-280℃.

[0012] In the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step c, after the hydrogenation reaction is completed, heating is stopped and the temperature is allowed to drop naturally to below 60°C. Then, inert gas is introduced into the horizontal tubular furnace reactor for protection, and the calcium-based hydrogen storage material is then taken out, packaged, and stored.

[0013] A system for performing the method includes: Horizontal tubular furnace reactor, comprising, The feeding tray holds the sodium slag. The heating furnace heats the horizontal tubular reactor by controllably adjusting the temperature, causing metallic sodium to volatilize and form a sodium vapor-inert gas mixture. A sealing cover for sealing a horizontal tubular furnace reactor; A vacuum system connected to the horizontal tubular furnace reactor to regulate system pressure; A gas control system is connected to the horizontal tubular furnace reactor to regulate the gas state of the system. The gas control system introduces hydrogen into the horizontal tubular furnace reactor, controls the temperature at 580-680°C and the hydrogen pressure at 5-20 kPa, and reacts for 2-4 hours to cause the solid-phase calcium to undergo a hydrogenation reaction, thereby obtaining a calcium-based hydrogen storage material including CaH2. Gradient condensation unit, comprising, A primary condenser, connected to the horizontal tubular furnace reactor, cools the mixed gas stream. A secondary condenser, connected to the horizontal tubular furnace reactor, is used to cool the water and form liquid sodium metal, while simultaneously separating impurities through static sedimentation. Sodium collection tank, which is connected to a secondary condenser to collect liquid metallic sodium. The sodium recovery module is connected to a sodium collection tank to recover liquid metallic sodium. A gas buffer tank, connected to the secondary condenser via a drain pipe, contains sealing white oil. The outlet is connected to the gas buffer tank to discharge exhaust gas.

[0014] The system uses a stainless steel pipe sealing structure with a leakage rate of ≤1×10-7Pa•m³ / s and is equipped with a hydrogen detection alarm device.

[0015] In the system described, the calcium-based hydrogen storage material has a hydrogen storage density of ≥2wt% and a calcium utilization rate of ≥99%.

[0016] Compared with existing technologies, this invention has the following advantages: the sodium recovery rate is ≥95% and the calcium utilization rate is ≥99%, completely solving the problem of calcium resource waste in traditional processes; using sodium slag as raw material, the synthesis cost of calcium-based hydrogen storage materials is lower than that of traditional high-purity calcium routes, and the process is simple; a fully sealed inert atmosphere system is adopted to avoid contact between sodium and calcium and air / water, eliminating the risk of combustion and explosion; the process has no wastewater or exhaust gas emissions (after the tail gas is confirmed to have no leakage by a hydrogen detector, it is treated by flare combustion), which complies with GB18597-2023 "Standard for Pollution Control of Hazardous Waste Storage"; the prepared CaH2 type hydrogen storage material has a purity of ≥40% and a hydrogen storage density of ≥2wt%. Attached Figure Description

[0017] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0018] In the attached diagram: Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a system structure diagram of the present invention; Figure 3 The results of testing the calcium hydride mass fraction and hydrogen storage density of the products from Examples 1, 2, and 3 are as follows; Figure 4 The images show the XRD patterns of the hydrogen storage material products from Examples 1, 2, and 3.

[0019] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0020] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0021] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0022] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0023] like Figures 1 to 4 As shown, the method for preparing calcium-based hydrogen storage materials by coupling the sodium slag purification process includes the following steps: Step a, sodium-calcium gradient separation: Under the protection of an inert atmosphere, the dried sodium slag is fed into a horizontal tubular furnace reactor, and the temperature is controlled at 850-950℃ and the system pressure at 5-20kPa. This causes the metallic sodium to volatilize and form a mixed gas flow of sodium vapor and inert gas, while calcium and impurities remain in solid form, thus achieving the separation of sodium and calcium. Step b, calcium-based precursor preparation: The mixed gas flow is sequentially fed into the first-stage condenser and the second-stage condenser, and the condensation temperature difference is controlled at 100-200℃. The metallic sodium vapor is gradually condensed into liquid metallic sodium, which is then collected by gravity into the sodium collection tank for recovery. The solid phase calcium and impurities retained in the horizontal tubular furnace reactor are used as calcium-based precursors. Step c, preparation of hydrogen storage material: Hydrogen gas is introduced into a horizontal tubular furnace reactor, the temperature is controlled at 580-680℃ and the hydrogen pressure is controlled at 5-20 kPa, and the reaction is carried out for 2-4 hours to make the solid-phase calcium undergo hydrogenation reaction to obtain a calcium-based hydrogen storage material including CaH2.

[0024] In a preferred embodiment of the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step a, before the sodium slag is fed, it is cut into blocks with a particle size of 5-10 cm under the protection of an inert atmosphere, and after feeding, the air in the horizontal tubular furnace reactor is removed by inert gas replacement.

[0025] In a preferred embodiment of the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, step a, the preparation of dried sodium slag includes: crushing the sodium slag to a particle size of 5-10 cm, and vacuum drying it at 100-150°C for 2-4 hours in an inert gas atmosphere with a purity of ≥99.99%.

[0026] In a preferred embodiment of the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step a, the inert gas is argon, and the flow rate is 0.5~2L / min.

[0027] In a preferred embodiment of the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step b, both the primary condenser and the secondary condenser adopt a shell-and-tube structure, and the cooling medium is heat transfer oil.

[0028] In a preferred embodiment of the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step b, the temperature of the primary condenser is 400-450℃ and the temperature of the secondary condenser is 200-280℃.

[0029] In a preferred embodiment of the method for preparing calcium-based hydrogen storage materials by coupling sodium slag purification process, in step c, after the hydrogenation reaction is completed, heating is stopped and the temperature is allowed to drop naturally to below 60°C. Then, inert gas is introduced into the horizontal tubular furnace reactor for protection, and the calcium-based hydrogen storage material is then taken out, packaged, and stored.

[0030] A system for performing the method as described above includes: Horizontal tubular furnace reactor 1, comprising, Feeding tray 12, which carries sodium slag, The heating furnace heats the horizontal tubular reactor 1 by controllably adjusting its temperature, causing metallic sodium to volatilize and form a sodium vapor-inert gas mixture. The sealing cover 3 seals the horizontal tubular furnace reactor 1. Vacuum system 9, which is connected to the horizontal tubular furnace reactor 1 to regulate system pressure; A gas control system 11 is connected to the horizontal tubular furnace reactor 1 to regulate the gas state of the system. The gas control system 11 introduces hydrogen into the horizontal tubular furnace reactor, controls the temperature to 580-680℃ and the hydrogen pressure to 5-20kPa, and reacts for 2-4 hours to cause the solid-phase calcium to undergo a hydrogenation reaction to obtain a calcium-based hydrogen storage material including CaH2. Gradient condensation unit, comprising, The primary condenser 10 is connected to the horizontal tubular furnace reactor 1, and the mixed gas flow is cooled in the primary condenser 10. The secondary condenser 5 is connected to the horizontal tubular furnace reactor 1 to cool and form liquid metallic sodium, while simultaneously separating impurities through static sedimentation. Sodium collection tank 4 is connected to a secondary condenser 5 to collect liquid metallic sodium. Sodium recovery module 6, which is connected to sodium collection tank 4 to recover liquid metallic sodium, Gas buffer tank 7, which is connected to the secondary condenser 5 via a drain pipe 14, contains sealing white oil 8. The outlet 13 is connected to the gas buffer tank 7 to discharge exhaust gas.

[0031] In a preferred embodiment of the system, the system employs a stainless steel pipe sealing structure with a leakage rate ≤1×10⁻⁶. -7 It has a pressure of Pa•m³ / s and is equipped with a hydrogen detection alarm device.

[0032] In a preferred embodiment of the system, the calcium-based hydrogen storage material has a hydrogen storage density ≥2wt% and a calcium utilization rate ≥99%.

[0033] In one embodiment, the horizontal tubular furnace reactor 1 is provided with a protective sleeve 2.

[0034] In one embodiment, the method for preparing calcium-based hydrogen storage materials by coupling the sodium slag purification process achieves high-value utilization of all components of sodium slag through "gradient separation-in-situ conversion". The specific technical solution is as follows: Process principle: Utilizing the boiling point difference between metallic sodium (boiling point 883℃) and metallic calcium (boiling point 1484℃), sodium volatilization and separation are achieved through precise temperature control; the residual metallic calcium is hydrogenated in situ to generate CaH2 under a hydrogen atmosphere, avoiding the loss caused by secondary transfer of calcium components. Step details: (1) Sodium-calcium gradient separation: The lumpy sodium slag (particle size 5-10cm) is loaded into a special feeding tray (material 316L stainless steel) under argon protection, and then transferred into a horizontal tube furnace. After closing the sealing cover, the vacuum system (vacuum degree ≤5Pa) is started to remove the air, and then argon (purity ≥99.99%) is introduced to replace it 3 times to maintain the pressure inside the furnace at 5-20kPa. The heating furnace is started and the temperature is raised to 850-950℃ at a rate of 5-10℃ / min. The temperature is held for 1-2 hours, and the metallic sodium evaporates into vapor and enters the condenser with the argon flow. (2) Preparation of calcium-based precursor: The first-stage condenser (temperature 400-450℃) condenses most of the sodium vapor into liquid, and the second-stage condenser (temperature 200-280℃) captures the residual sodium vapor to prevent sodium vapor from being discharged with the tail gas; the liquid sodium obtained by condensation flows by gravity through the pipeline to the sodium collection tank (with built-in sealed white oil to prevent sodium from contacting air), and the solid phase remaining in the reactor (mainly metallic calcium and a small amount of oxides) is the calcium-based precursor; (3) Preparation of hydrogen storage material: Close the argon gas passage, switch the hydrogen gas system (hydrogen purity ≥ 99.999%), introduce hydrogen gas into the reactor and maintain the pressure at 5-20 kPa; raise the temperature to 580-680℃ at a rate of 3-5℃ / min, keep it at the temperature for 2-4 hours, and the metallic calcium reacts with the hydrogen gas; after the reaction is completed, stop heating and let it cool naturally to below 60℃, introduce argon gas to replace the hydrogen gas, and then take out the product and seal it (to prevent moisture absorption).

[0035] The method uses sodium slag (containing 60%–85% metallic sodium, 10%–25% metallic calcium, and small amounts of sodium oxide, calcium oxide, and other impurities) generated during the production of metallic sodium as raw material. It achieves full utilization of all components through a three-step coupled process: sodium-calcium gradient separation, calcium-based precursor preparation, and hydrogen storage material preparation. The first step involves separating metallic sodium by volatilizing it in a horizontal tubular furnace at 850–950℃ and 5–20 kPa under an inert atmosphere (argon purity ≥99.99%). The liquid metallic sodium is then condensed and recovered via a two-stage condenser (first stage 400–450℃, second stage 200–280℃). The second step retains the solid-phase calcium and impurities in the reactor as calcium-based precursors. The third step involves reacting the solid-phase calcium for 2–4 hours at 580–680℃ and 5–20 kPa in a hydrogen atmosphere to convert the solid-phase calcium into a CaH2-type calcium-based hydrogen storage material. This invention solves the problems of waste of calcium resources and high cost of calcium-based hydrogen storage material preparation in traditional sodium slag treatment. The process has no secondary pollution and has both environmental and economic benefits.

[0036] Example 1

[0037] (1) Raw material preparation: Take 50g of block sodium slag (composition: 80% metallic sodium, 10% metallic calcium, 5% sodium oxide, 5% calcium oxide) and cut it into 5cm×5cm×5cm blocks in an argon glove box; (2) Sodium-calcium separation: Sodium slag is loaded into a 316L stainless steel feeding tray and transferred into a horizontal tube furnace (model GSL-1700X). The sealing cover is closed. The vacuum system is started to evacuate to a vacuum degree of 0.5Pa. Argon gas (purity 99.999%) is introduced to replace the vacuum three times to maintain the furnace pressure at 20kPa. The temperature is increased to 950℃ at 5℃ / min and held for 2 hours. (3) Sodium recovery: The temperature of the first-stage condenser was 450℃, and the temperature of the second-stage condenser was 250℃. 38.2g of liquid sodium was obtained by condensation, and the sodium recovery rate was 95.5%. (4) Hydrogenation reaction: Switch the hydrogen system, introduce hydrogen (purity 99.999%) to maintain the pressure at 20 kPa, raise the temperature to 680°C at 5°C / min, and keep it at that temperature for 3 hours; (5) Product testing: After cooling, the product was taken out and tested by X-ray diffraction (XRD) and by the hydrolysis hydrogen method. The purity of CaH2 was 46.2% and the hydrogen storage density was 2.20wt%.

[0038] Example 2

[0039] (1) Raw material preparation: Take 60g of block sodium slag (composition: 65% metallic sodium, 25% metallic calcium, 5% sodium oxide, 5% calcium oxide) and cut it into 8cm×8cm×8cm blocks in an argon glove box; (2) Sodium-calcium separation: The sample was transferred into a horizontal tube furnace, evacuated to 0.5 Pa, and replaced with argon gas 3 times to maintain the furnace pressure at 10 kPa. The temperature was increased to 950 °C at 5 °C / min and held for 1.5 hours. (3) Sodium recovery: The temperature of the first-stage condenser was 450℃, and the temperature of the second-stage condenser was 200℃. 36.7g of liquid sodium was obtained from the condensation, and the sodium recovery rate was 94.0%. (4) Hydrogenation reaction: Hydrogen gas is introduced to maintain a pressure of 10 kPa, and the temperature is increased to 650°C at 4°C / min and kept at the temperature for 2 hours; (5) Product testing: The purity of CaH2 was 60.1% and the hydrogen storage density was 2.86wt% as determined by XRD and hydrolysis hydrogenation method.

[0040] Example 3

[0041] (1) Raw material preparation: Take 5000g of block sodium slag (composition: 65% metallic sodium, 25% metallic calcium, 5% sodium oxide, 5% calcium oxide) and cut it into 5cm×5cm×5cm blocks in an argon glove box; (2) Sodium-calcium separation: The sample was transferred into a horizontal tube furnace, evacuated to 0.5 Pa, and replaced with argon gas 3 times to maintain the furnace pressure at 10 kPa. The temperature was increased to 950 °C at 5 °C / min and held for 2 hours. (3) Sodium recovery: The temperature of the first-stage condenser was 450℃, and the temperature of the second-stage condenser was 200℃. 3244g of liquid sodium was obtained by condensation, and the sodium recovery rate was 99.8%. (4) Hydrogenation reaction: Hydrogen gas is introduced to maintain a pressure of 10 kPa, and the temperature is increased to 680°C at 5°C / min and kept at the temperature for 4 hours; (5) Product testing: The purity of CaH2 was 72.2% and the hydrogen storage density was 3.44wt% as determined by XRD and hydrolysis hydrogenation method.

[0042] See Figures 3 to 4 It can be seen that the CaH2-type hydrogen storage material prepared by the present invention has a purity of ≥40% and a hydrogen storage density of ≥2wt%.

[0043] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process, characterized in that, Includes the following steps: Step a, sodium-calcium gradient separation: Under the protection of an inert atmosphere, the dried sodium slag is fed into a horizontal tubular furnace reactor, and the temperature is controlled at 850-950℃ and the system pressure at 5-20kPa. This causes the metallic sodium to volatilize and form a mixed gas flow of sodium vapor and inert gas, while calcium and impurities remain in solid form, thus achieving the separation of sodium and calcium. Step b, calcium-based precursor preparation: The mixed gas flow is sequentially fed into the first-stage condenser and the second-stage condenser, and the condensation temperature difference is controlled at 100-200℃. The metallic sodium vapor is gradually condensed into liquid metallic sodium, which is then collected by gravity into the sodium collection tank for recovery. The solid phase calcium and impurities retained in the horizontal tubular furnace reactor are used as calcium-based precursors. Step c, preparation of hydrogen storage material: Hydrogen gas is introduced into a horizontal tubular furnace reactor, the temperature is controlled at 580-680℃ and the hydrogen pressure is controlled at 5-20 kPa, and the reaction is carried out for 2-4 hours to make the solid-phase calcium undergo hydrogenation reaction to obtain a calcium-based hydrogen storage material including CaH2.

2. The method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process according to claim 1, characterized in that, Preferably, in step a, the sodium slag is cut into blocks with a particle size of 5-10 cm under an inert atmosphere before being fed, and the air in the horizontal tubular furnace reactor is removed by inert gas replacement after feeding.

3. The method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process according to claim 1, characterized in that, In step a, the preparation of dried sodium slag includes: crushing the sodium slag to a particle size of 5-10 cm, and vacuum drying it at 100-150℃ for 2-4 h in an inert gas atmosphere with a purity of ≥99.99%.

4. The method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process according to claim 1, characterized in that, In step a, the inert gas is argon, and the flow rate is 0.5~2L / min.

5. The method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process according to claim 1, characterized in that, In step b, both the primary and secondary condensers adopt a shell-and-tube structure, and the cooling medium is heat transfer oil.

6. The method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process according to claim 1, characterized in that, In step b, the temperature of the first-stage condenser is 400–450°C and the temperature of the second-stage condenser is 200–280°C.

7. The method for preparing calcium-based hydrogen storage materials by coupling a sodium slag purification process according to claim 1, characterized in that, In step c, after the hydrogenation reaction is completed, heating is stopped and the temperature is allowed to drop naturally to below 60°C. Then, inert gas is introduced into the horizontal tubular furnace reactor for protection. Finally, the calcium-based hydrogen storage material is removed, packaged, and stored.

8. A system for performing the method as described in any one of claims 1 to 7, characterized in that, It includes: Horizontal tubular furnace reactor (1), which includes, Feeding tray (12), which carries sodium slag, A heating furnace, whose heating is achieved by controllably adjusting the temperature of the horizontal tubular furnace reactor (1), causes metallic sodium to volatilize and form a sodium vapor-inert gas mixture. The sealing cover (3) seals the horizontal tubular furnace reactor (1). A vacuum system (9) is connected to the horizontal tubular furnace reactor (1) to regulate the system pressure; A gas control system (11) is connected to the horizontal tubular furnace reactor (1) to regulate the gas state of the system. The gas control system (11) introduces hydrogen into the horizontal tubular furnace reactor, controls the temperature to 580-680℃ and the hydrogen pressure to 5-20kPa, and reacts for 2-4 hours to make solid calcium undergo hydrogenation reaction to obtain calcium-based hydrogen storage material including CaH2. Gradient condensation unit, comprising, A primary condenser (10) is connected to the horizontal tubular furnace reactor (1), and the mixed gas flow is cooled in the primary condenser (10). A secondary condenser (5) is connected to the horizontal tubular furnace reactor (1) to cool and form liquid metallic sodium, while simultaneously separating impurities through static sedimentation. Sodium collection tank (4), which is connected to a secondary condenser (5) to collect liquid metallic sodium, Sodium recovery module (6), which is connected to sodium collection tank (4) to recover liquid metallic sodium, A gas buffer tank (7) is connected to the secondary condenser (5) via a drain pipe (14), and the gas buffer tank (7) contains sealing white oil (8). The outlet (13) is connected to the gas buffer tank (7) to discharge exhaust gas.

9. The system according to claim 8, characterized in that, The system adopts a stainless steel pipe sealing structure with a leakage rate of ≤1×10-7Pa•m³ / s, and is equipped with a hydrogen detection alarm device.

10. The system according to claim 8, characterized in that, The calcium-based hydrogen storage material has a hydrogen storage density of ≥2wt% and a calcium utilization rate of ≥99%.

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