Aluminum recycling method for metallic aluminum energy storage and hydrogen production

Abstract

Disclosed herein is an aluminum recycling method for metallic aluminum energy storage and hydrogen production, comprising: electrolyzing aluminum oxide to obtain molten metallic aluminum; processing the molten metallic aluminum to obtain an aluminum-based hydrogen production material; under the action of a catalyst, chemically reacting the aluminum-based hydrogen production material with water to obtain hydrogen gas and an aluminum oxide hydrate slurry; subjecting the aluminum oxide hydrate slurry to solid-liquid separation to obtain an aluminum oxide hydrate and an aqueous solution containing the catalyst; calcining the aluminum oxide hydrate to obtain aluminum oxide; and recycling the aluminum oxide to the step of electrolyzing the aluminum oxide, and recycling the aqueous solution containing the catalyst to the step of chemically reacting the aluminum-based hydrogen production material with water, thereby forming a closed-loop cycle.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Chinese Patent Application No. 202411798932.5, filed on December. 09, 2024. The disclosure of the aforementioned application is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to the field of new energy application technologies, and in particular, to an aluminum cycling method for metallic aluminum based energy storage and hydrogen production. BACKGROUND

[0003] In 2020, based on intrinsic requirements for promoting sustainable development and sense of responsibility for building a community with a shared future for mankind, China announced goals of carbon peak and carbon neutrality. Developing new energy technologies such as wind power and photovoltaic power generation, as well as high-efficiency energy storage technologies, is the main technical paths to achieve the goals of carbon peak and carbon neutrality. Currently, there are two main new energy technologies based on metallic aluminum based energy storage : aluminum-air batteries and hydrogen production via aluminum-based hydrogen-producing material-water reaction. Although the aluminum-air batteries have outstanding advantages such as a high specific energy density and environmental friendliness, they also have defects such as a low specific power density, which affect their large-scale commercial use. The technique of hydrogen production via aluminum-based hydrogen-producing material-water reaction makes full use of the unique advantages of metal aluminum, such as a high energy density, a high power conversion efficiency of hydrogen fuel cells, strong power adjustability, environmental friendliness, and a short hydrogenation time, and thus has good development prospects.

[0004] However, at present, related research on the technique of hydrogen production via aluminum-based hydrogen-producing material-water reaction only proposes a technical concept of recycling aluminum elements after the hydrogen production via aluminum-based hydrogen- producing material-water reaction, and no practically feasible technical route has yet been established. SUMMARY

[0005] According to one or more embodiments of the present disclosure, an aluminum cycling method for metallic aluminum based energy storage and hydrogen production is provided to solve the technical problem of how to achieve a complete cycle for metallic aluminum based energy storage and hydrogen production.

[0006] In a first aspect, an aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure includes: electrolyzing alumina to obtain molten metallic aluminum; processing the molten metallic aluminum to obtain an aluminum-based hydrogen-producing material having a large specific surface area; chemically reacting, under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material with water, to obtain hydrogen gas and an alumina hydrate slurry; subjecting the alumina hydrate slurry to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst; calcining the alumina hydrate to obtain a high-activity metallurgical-grade alumina; and recycling the high-activity metallurgical-grade alumina to the step of electrolyzing the alumina, and recycling the aqueous solution containing the catalyst to participate in the step of chemically reacting the aluminum-based hydrogen-producing material with water, to form a closed-loop cycle. BRIEF DESCRIPTION OF DRAWINGS

[0007] The accompanying drawings, which are incorporated into and form a portion of this specification, illustrate embodiments consistent with the present disclosure, and together with the specification, serve to explain the principles of the present disclosure.

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or in the related art, the drawings required to be used in the description of the embodiments or the related art will be briefly introduced below. Obviously, for those with ordinary skill in the art, other drawings may be obtained based on these drawings without creative efforts.

[0009] FIG. 1 shows a schematic flow diagram of an aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure.

[0010] FIG. 2 shows a simplified schematic flow diagram of an aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0011] In order to make objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those with ordinary skill in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.

[0012] Various embodiments of the present disclosure may be presented in a range format. It should be understood that the description in a range format is merely for convenience and brevity, and should not be construed as an inflexible limitation on the scope of the present disclosure. Therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and individual numerical values within that range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. This applies regardless of the range. In addition, whenever a numerical range is indicated in the specification, it is meant to include any referenced number (fractional or integer) within the indicated range.

[0013] In the present disclosure, unless otherwise specified to the contrary, directional terms such as "upper" and "lower" used in the specification specifically refer to the orientation in the drawings. In addition, in the description of the present specification, the terms "comprising," "including," etc., mean "including but not limited to." In this specification, relational terms such as "first" and "second" are used merely for distinguishing one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this specification, "and / or" describes an association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may indicate: A exists alone, A and B exist together, and B exists alone. Where A and B may be singular or plural. In this specification, "at least one" means one or more, and "multiple" means two or more. "At least one of," "one or more of," or similar expressions mean any combination of these items, including any combination of a single item or plural items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," may indicate: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, c may each be single element or multiple elements. For the proportional relationships described in the specification, parameters that need to be described by a ratio shall be understood as the antecedent in the ratio according to the order of description, and the ratio numbers shall be understood as the consequent in the ratio. For example, if a mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C shall correspond one-to-one with the ratio numbers in the ratio according to the order of description, i.e., mass of substance A: mass of substance B: mass of substance C = 1:2:3.

[0014] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc., used in the present disclosure are commercially available or may be prepared by existing methods.

[0015] In a first aspect, the present disclosure provides an aluminum cycling method for metallic aluminum based energy storage and hydrogen production. FIG. 1 shows a schematic flow diagram of an aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure. Referring to FIG. 1, the aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure includes:

[0016] step S1: electrolyzing alumina to obtain molten metallic aluminum;

[0017] step S2: processing the molten metallic aluminum to obtain an aluminum-based hydrogen-producing material having a large specific surface area;

[0018] step S3: chemically reacting, under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material with water, to obtain hydrogen gas and an alumina hydrate slurry;

[0019] step S4: subjecting the alumina hydrate slurry to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0020] step S5: calcining the alumina hydrate to obtain a high-activity metallurgical-grade alumina; and

[0021] step S6: recycling the high-activity metallurgical-grade alumina to the step of electrolyzing the alumina, and recycling the aqueous solution containing the catalyst to participate in the step of chemically reacting the aluminum-based hydrogen-producing material with water, to form a closed-loop cycle.

[0022] From the above, it may be seen that according to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, the alumina is electrolyzed to obtain the molten metallic aluminum. During the electrolyzing, an electrical energy is converted into chemical energy stored in the molten metallic aluminum, thereby achieving energy storage of the metal aluminum (which is liquid). The molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area, thereby increasing a contact area between the aluminum-based hydrogen-producing material and the water. The aqueous solution containing the catalyst which is nitrogen-containing and strong alkaline organic is capable of rapidly dissolving and removing an oxide film on a surface of the aluminum-based hydrogen-producing material, thereby accelerating a chemical reaction rate between the aluminum-based hydrogen-producing material and the water, and thus improving an efficiency of hydrogen production. Meanwhile, during the chemical reaction of the aluminum-based hydrogen-producing material with the water, the chemical energy stored in the aluminum-based hydrogen-producing material (metal aluminum) is transferred and stored in the produced hydrogen, and the chemical energy stored in the hydrogen is more convenient for application. For example, the chemical energy stored in the hydrogen may be applied through hydrogen fuel cells, etc. In addition, the catalyst which is nitrogen-containing and strong alkaline organic has a high solubility in the water and has a good dispersing effect on the alumina hydrate produced by hydrolysis, thereby exerting the catalytic effect more effectively. A high-activity metallurgical-grade alumina can be obtained by calcining the alumina hydrate obtained by subjecting the alumina hydrate slurry to the solid-liquid separation. The high-activity metallurgical-grade alumina is recycled to the process of electrolyzing the alumina. By utilizing a high dissolution rate of the high-activity metallurgical-grade alumina in a molten electrolyte, a current efficiency of the process of electrolyzing the alumina may be effectively improved. By recycling the high-activity metallurgical-grade alumina to the above-mentioned process of electrolyzing the alumina, and recycling the aqueous solution containing the catalyst to participate in the above-mentioned chemical reaction of the aluminum-based hydrogen-producing material with the water, a closed-loop cycle of the metallic aluminum based energy storage and hydrogen production is formed, i.e., a full cycle of the metallic aluminum based energy storage and hydrogen production is achieved.

[0023] In addition, according to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, in the closed-loop cycle of the metallic aluminum based energy storage and hydrogen production, an efficient utilization of the aluminum, a zero solid waste discharge, and a near-zero carbon emission are also achieved.

[0024] In some embodiments, in step S1, an electrical energy for the electrolyzing is derived from a green electrical energy.

[0025] In some embodiments, in step S1, an inert anode for the electrolyzing includes any one of: a SnO2 ceramic anode and a Cu-Ni-Fe metal anode.

[0026] In some embodiments of the present disclosure, first, the alumina may be used as a raw material for the electrolyzing to obtain the molten metallic aluminum, thereby converting the electrical energy into the chemical energy stored in the aluminum, and thus the purpose of storing the electrical energy can be achieved by using the metal aluminum. During the electrolyzing, the alumina is dissolved in a molten salt electrolyte such as cryolite (NasAlFe or KsAlFe), and under an action of a direct current, the alumina is reduced at a cathode to form the molten metallic aluminum, and the electrical energy is converted into the chemical energy stored in the molten metallic aluminum. The electrical energy for the electrolyzing may be derived from the green electrical energy, thereby reducing emissions of greenhouse gases such as carbon dioxide from the source, and thus making an aluminum electrolysis production process more environmentally friendly. A green electricity may be one of wind power, solar power, and photovoltaic power. The green electricity (e.g., wind power) is supplied to an aluminum electrolysis plant that applies an inert anode technology. The process of electrolyzing the alumina uses the inert anode technology, an thus the problem of perfluorocarbon (PFC) emissions and CO2 emissions from anode consumption is fundamentally solved. The inert anode for the electrolyzing may be a SnO2 ceramic anode or a Cu-Ni-Fe metal anode. During the alumina electrolysis production process using this inert anode, a small amount of metal elements such as Sn and Fe in the inert anode may enter the molten metallic aluminum to form an aluminum alloy with the molten metallic aluminum, to be advantageous for improving a reaction activity of the aluminum-based hydrogen-producing material, and thus accelerating a subsequent reaction rate of the hydrogen production via aluminum-based hydrogen-producing material-water reaction.

[0027] Exemplarily, the step S1 includes: in an aluminum electrolysis plant using the wind power and applying the SnO2 or Cu-Ni-Fe ceramic anode technology, first, dissolving the alumina in a cryolite molten salt, and then obtaining the molten metallic aluminum by electrolyzing.

[0028] In some embodiments, in step S2, a purpose of processing the molten metallic aluminum is to increase the specific surface area of the aluminum-based hydrogen-producing material, so that the aluminum-based hydrogen-producing material has a larger specific surface area compared to aluminum ingots in the related art, thereby enhancing a surface activity of the aluminum-based hydrogen-producing material. The specific surface area refers to a surface area per unit mass or unit volume of a material, and is an important parameter for measuring the surface activity of the material. A purpose of increasing the specific surface area is to improve a reaction rate of the material, enhance an adsorption capacity, improve an electrochemical performance, etc., thereby enhancing a performance of material in specific applications. A processing methods for increasing the specific surface area include: physical methods, chemical methods, and biological methods. Compared with unprocessed materials, materials with an increased specific surface area after processed have significant advantages in the reaction rate and an adsorption efficiency.

[0029] In some embodiments, a form of the aluminum-based hydrogen-producing material includes any one of: aluminum particles and aluminum chips.

[0030] In some embodiments, the D90 particle size of the aluminum particles (i.e., the particle size of 90% of the aluminum particles is not greater than a value of the D90) ranges from 30 pm to 1000 pm.; and / or a maximum thickness of the aluminum chips is < 1 mm.

[0031] In some embodiments of the present disclosure, in step S2, the processing method for processing the molten metallic aluminum may be an atomization method or a mechanical processing method. The obtained aluminum-based hydrogen-producing material may be in the form of the aluminum particles and / or the aluminum chips. The aluminum particles may have a D90 (i.e., the particle size of 90% of the aluminum particles is not greater than a value of the D90) ranging from 30 pm to 1000 pm. The aluminum chips may have a maximum thickness of < 1 mm, thereby ensuring that the aluminum-based hydrogen-producing material has a large specific surface area, so that the chemical reaction rate of the aluminum-based hydrogen-producing material with the water is accelerated, and thus ensuring that the aluminum-based hydrogen-producing material is capable of completely reacting with the water.

[0032] Exemplarily, when the aluminum particles have the D90 (i.e., the particle size of 90% of the aluminum particles is not greater than a value of the D90) ranging from 30 pm to 1000 pm, the specific surface area of the aluminum-based hydrogen-producing material in the form of the aluminum particles is about 11.11 cm2 / g to 370.37 cm2 / g.

[0033] Exemplarily, the D90 (i.e., the particle size of 90% of the aluminum particles is not greater than a value of the D90) of the aluminum particles may be 30 pm, 40 pm, 50 pm, 60 pm, 100 pm, 200 pm, 300 pm, 400 pm, 500 pm, 600 pm, 700 pm, 800 pm, 900 pm, 1000 pm, etc.

[0034] In some embodiments of the present disclosure, the catalyst which is nitrogen-containing and strong alkaline organic in step S3 includes at least one of the following: diethylenetriamine, triethylenetetramine, and dimethylbiguanide hydroxide.

[0035] In some embodiments of the present disclosure, the aqueous solution of the catalyst which is nitrogen-containing and strong alkaline organic can remove an oxide film on a surface of the aluminum-based hydrogen-producing material, thereby accelerating the chemical reaction rate of the aluminum-based hydrogen-producing material with the water, and thus improving the efficiency of hydrogen production. The catalyst which is nitrogen-containing and strong alkaline organic has a high solubility in the water, allowing the catalyst which is nitrogen-containing and strong alkaline organic to be uniformly dispersed in the water, and thus the dispersibility and fluidity of the produced alumina hydrate slurry can be increased, thereby exerting the catalytic effect more effectively. Moreover, under a catalysis of the catalyst which is nitrogen-containing and strong alkaline organic, and with relatively mild process parameters of the chemical reaction, an efficient hydrogen production may be achieved, and the obtained alumina hydrate contains no sodium element.

[0036] In some embodiments of the present disclosure, the catalyst which is nitrogen-containing and strong alkaline organic may be one or a combination of two or more of diethylenetriamine, triethylenetetramine, and dimethylbiguanide hydroxide.

[0037] In some embodiments, process parameters of the chemical reaction include: a reaction temperature ranging from 20°C to 95°C, and a reaction time ranging from 60 min to 720 min.

[0038] In some embodiments of the present disclosure, the reaction temperature of the above chemical reaction may range from 20°C to 95°C, thereby regulating the reaction rate of the chemical reaction, and controlling an appropriate reaction time for hydrogen production according to the reaction temperature. The reaction time may range from 60 min to 720 min, to be capable of fully improving a utilization rate of the aluminum-based hydrogen-producing material.

[0039] Exemplarily, the reaction temperature of the chemical reaction may be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 95°C, etc. The reaction time of the chemical reaction may be 60 min, 70 min, 80 min, 90 min, 100 min, 200 min, 300 min, 400 min, 500 min, 600 min, 720 min, etc.

[0040] In some embodiments, a mass ratio of the catalyst to the water ranges from 1:4 to 1:40.

[0041] In some embodiments of the present disclosure, the mass ratio of the catalyst to the water may be 1:(4 to 40), so that a concentration of the catalyst in the chemical reaction system is moderate. Therefore, the reaction may be quickly activated at an initial stage, and contact opportunities among molecules of the catalyst and the aluminum-based hydrogen-producing material and the water are increased. The catalyst may provide sufficient active sites to accelerate an electron transfer process between the aluminum-based hydrogen-producing material and the water, and thus accelerating the chemical reaction rate between the aluminum-based hydrogen-producing material and the water.

[0042] Exemplarily, the mass ratio of the catalyst to water may be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, etc.

[0043] In some embodiments, a mass ratio of the aluminum-based hydrogen-producing material to the water ranges from 1:4 to 1:60.

[0044] In some embodiments of the present disclosure, the mass ratio of the aluminum-based hydrogen-producing material to the water may range from 1:4 to 1:60, so that a concentration of the aluminum-based hydrogen-producing material in the chemical reaction system is moderate, thereby ensuring the hydrogen production reaction rate while providing a good fluidity of the alumina hydrate slurry after the chemical reaction.

[0045] Exemplarily, the mass ratio of the aluminum-based hydrogen-producing material to the water may be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, etc.

[0046] In some embodiments of the present disclosure, in step S5, process parameters of the calcination treatment include: a calcination temperature ranging from 750°C to 1020°C, and a calcination time ranging from 3 s to 20 min.

[0047] In some embodiments of the present disclosure, the alumina hydrate slurry is subjected to the solid-liquid separation to obtain the alumina hydrate and the aqueous solution containing the catalyst. Generally, the alumina hydrate obtained from the above chemical reaction of the aluminum-based hydrogen-producing material with the water also needs to be washed and dried. The alumina hydrate is calcined to obtain the high-activity metallurgical-grade alumina. The process parameters of the calcination treatment include: the calcination temperature ranging from 750°C to 1020°C, and the calcination time ranging from 3 s to 20 min, to be capable of ensuring that a qualified high-activity metallurgical-grade alumina is obtained. The high-activity metallurgical-grade alumina has an excellent dissolution performance in a molten electrolyte.

[0048] Exemplarily, the calcination temperature may be 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1020°C, etc. The calcination time may be 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 20 s, 30 s, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 12 min, 14 min, 15 min, 17 min, 19 min, 20 min, etc.

[0049] In some embodiments of the present disclosure, in step S6, the high-activity metallurgical-grade alumina has a large specific surface area and a high reaction activity, and may improve an efficiency of the electrolysis process. The high-activity metallurgical-grade alumina is recycled to participate in the electrolyzing, and has a high dissolution rate in the molten electrolyte, to be capable of improving a current efficiency of the electrolysis process. Compared with typical industrial alumina, the dissolution rate of the high-activity metallurgical-grade alumina in cryolite or potassium-containing cryolite molten salt may be increased by more than 50%, and the current efficiency of the electrolysis process may be increased by more than 2% (a dissolution rate of typical industrial alumina ranges from 100 s to 200 s, the current efficiency of a conventional electrolysis process ranges from 92% to 95%, and the current efficiency is less than 90% when the inert anode technology is applied). The high-activity metallurgical-grade alumina contains no sodium element, to be capable of reducing a consumption of fluoride salts in the process of electrolyzing the alumina. The high-activity metallurgical-grade alumina may be recycled for the electrolyzing to produce the molten metallic aluminum. The above aqueous solution containing the catalyst may be recycled for the above chemical reaction of the aluminum-based hydrogen-producing material with the water for the hydrogen production. Therefore, the efficient utilization of the aluminum, the zero solid waste discharge, and the near-zero carbon emission are achieved. In addition, a system for implementing the aluminum cycling method for metallic aluminum based energy storage and hydrogen production may include a hydrogen production system, an aluminum material recycling plant, a green electricity generation facility such as wind power, and a plant for electrolysis of aluminum applying the inert anode technology.

[0050] The aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure has the following advantages:

[0051] 1. The alumina is electrolyzed to obtain the molten metallic aluminum (energy storage stage)

[0052] Principle and significance: during the electrolysis process to produce the molten metallic aluminum, the electrical energy is converted into the chemical energy stored in the molten metallic aluminum, thereby making the molten metallic aluminum have a potential for subsequent energy release (hydrogen production or other applications). From a perspective of energy utilization, this energy storage method, combined with the green electricity (such as electricity generated from renewable sources like wind power and solar power), may effectively solve a problem of instability in renewable energy generation processes such as wind power, and thus improving a stability and flexibility of energy utilization.

[0053] 2. The molten metallic aluminum is processed into the aluminum-based hydrogen-producing material

[0054] Importance of the specific surface area: the aluminum-based hydrogen-producing material having a large specific surface area is obtained after the molten metal aluminum is processed. The large specific surface area indicates that more aluminum atoms are capable of coming into contact with the water, thereby increasing reaction sites, and thus accelerating the reaction rate.

[0055] 3. Role of the nitrogen-containing strong alkaline organic catalyst in the hydrogen production reaction

[0056] Catalytic mechanism: when the nitrogen-containing strong alkaline organic catalyst participates in the chemical reaction of the aluminum-based hydrogen-producing material with the water, the nitrogen-containing strong alkaline organic catalyst exists in the form of the aqueous solution containing the catalyst. The nitrogen-containing strong alkaline organic catalyst may rapidly dissolve and remove the oxide film on the surface of the aluminum-based hydrogen-producing material, thereby accelerating the chemical reaction rate of the hydrogen production. In addition, alkaline groups of the nitrogen-containing strong alkaline organic catalyst are capable of promoting a dissociation of the water, thereby generating more active hydroxide ions, and thus accelerating the chemical reaction process of the hydrogen production.

[0057] Advantage of solubility: a high solubility of the nitrogen-containing strong alkaline organic catalyst in the water ensures that it is uniformly dispersed, which may improve the dispersibility and fluidity of the produced alumina hydrate slurry, thereby promoting the chemical reaction.

[0058] 4. Calcination of the alumina hydrate

[0059] The alumina hydrate is calcined to obtain the high-activity metallurgical-grade alumina. Since the alumina hydrate has a higher surface activity compared to ordinary industrial aluminum hydroxide, the high-activity metallurgical-grade alumina may be obtained after the calcination.

[0060] 5. Recycling stage

[0061] Recycling of the high-activity metallurgical-grade alumina: the high-activity metallurgical-grade alumina, when being recycled to participate in the electrolyzing, has a high dissolution rate in the molten electrolyte. This is advantageous for improving an electrolysis efficiency. The high activity of the high-activity metallurgical-grade alumina also results in a higher current efficiency during the electrolyzing, thereby reducing energy loss, and thus lowering energy consumption.

[0062] Recycling of the aqueous solution containing the catalyst: the aqueous solution containing the catalyst is recycled to participate in the chemical reaction of the aluminum-based hydrogen-producing material with the water, thereby reducing a consumption of the catalyst, and thus lowering costs. Meanwhile, environmental pollution problems that may be caused by a discharge of the catalyst are avoided.

[0063] The present disclosure is further described below with reference to specific embodiments. It should be understood that these embodiments are only for illustrating the present disclosure, and are not intended to limit the scope of the present disclosure. In the following examples, experimental methods without specified conditions are generally carried out in accordance with national standards in China. If there is no corresponding national standard in China, they are carried out in accordance with general international standards, conventional conditions, or conditions recommended by a manufacturer.

[0064] Example 1

[0065] An aluminum cycling method for metallic aluminum based energy storage and hydrogen production is provided. FIG. 1 shows a schematic flow diagram of an aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure. FIG. 2 shows a simplified schematic flow diagram of an aluminum cycling method for metallic aluminum based energy storage and hydrogen production according to some embodiments of the present disclosure. Referring to FIG. 1 and FIG. 2, the aluminum cycling method for metallic aluminum based energy storage and hydrogen production includes that :

[0066] step S1: alumina is electrolyzed to obtain molten metallic aluminum;

[0067] Specifically, in an aluminum electrolysis plant using wind power and applying a SnO? ceramic anode technology, first, the alumina is dissolved in a cryolite molten salt at 945°C, and then the molten metallic aluminum is obtained by the electrolyzing;

[0068] step S2: the molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area; where the aluminum-based hydrogen-producing material is aluminum particles having a D90 of 30 pm (90% of the particles have a particle size less than 30 pm);

[0069] step S3: under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material is chemically reacted with water, to obtain hydrogen and an alumina hydrate slurry;

[0070] Specifically, the aluminum particles, a catalyst which is nitrogen-containing and strong alkaline organic, and distilled water are added in proportions to an aluminum-water hydrogen production system. The catalyst which is nitrogen-containing and strong alkaline organic is diethylenetriamine. A mass ratio of the catalyst which is nitrogen-containing and strong alkaline organic to the distilled water is 1:4. A mass ratio of the aluminum particles to the distilled water is 1:60. A chemical reaction temperature is 95°C. A reaction time is 60 min. A reaction rate of the aluminum particles is 98.1%;

[0071] step S4: the alumina hydrate slurry is subjected to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0072] step S5: the alumina hydrate is calcined to obtain a high-activity metallurgical-grade alumina; where a calcination temperature is 750°C, and a calcination time is 20 min;

[0073] step S6: the high-activity metallurgical-grade alumina is recycled to the electrolysis process of step S1, and the aqueous solution containing the catalyst after adding fresh water and the catalyst is recycled to participate in the chemical reaction of step S3, to form a closed-loop cycle.

[0074] Compared with ordinary industrial alumina, a dissolution rate of the high-activity alumina of Example 1 in the cryolite molten salt is increased by 56%, and the current efficiency of the electrolysis process is increased by 2.5%.

[0075] Example 2

[0076] An aluminum cycling method for metallic aluminum based energy storage and hydrogen production, includes:

[0077] step S1: alumina is electrolyzed to obtain molten metallic aluminum;

[0078] Specifically, in an aluminum electrolysis plant using wind power and applying a SnO? ceramic anode technology, first, the alumina is dissolved in a cryolite molten salt at 960°C, and then the molten metallic aluminum is obtained by the electrolyzing;

[0079] step S2: the molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area; where the aluminum-based hydrogen-producing material is aluminum particles having a D90 of 1000 pm (90% of the particles have a particle size less than 1000 pm);

[0080] step S3: under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material is chemically react edwith water, to obtain hydrogen and an alumina hydrate slurry;

[0081] Specifically, the aluminum particles, a catalyst which is nitrogen-containing and strong alkaline organic, and distilled water are added in proportions to an aluminum-water hydrogen production system. The catalyst which is nitrogen-containing and strong alkaline organic is triethylenetetramine. A mass ratio of the catalyst which is nitrogen-containing and strong alkaline organic to the distilled water is 1:10. A mass ratio of the aluminum particles to the distilled water is 1:20. A chemical reaction temperature is 20°C. A reaction time is 720 min. A reaction rate of the aluminum particles is 99.6%;

[0082] step S4: the alumina hydrate slurry is subjected to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0083] step S5: the alumina hydrate is calcined to obtain a high-activity metallurgical-grade alumina; where a calcination temperature is 1020°C, and a calcination time is 3 s;

[0084] step S6: the high-activity metallurgical-grade alumina is recycled to the electrolysis process of step S1, and the aqueous solution containing the catalyst after adding fresh water and the catalyst is recycled to participate in the chemical reaction of step S3, to form a closed-loop cycle.

[0085] Compared with ordinary industrial alumina, a dissolution rate of the high-activity alumina of Example 2 in the cryolite molten salt is increased by 70%, and the current efficiency of the electrolysis process is increased by 3.0%.

[0086] Example 3

[0087] An aluminum cycling method for metallic aluminum based energy storage and hydrogen production, includes:

[0088] step S1: alumina is electrolyzed to obtain molten metallic aluminum;

[0089] Specifically, in an aluminum electrolysis plant using wind power and applying a SnO2 ceramic anode technology, first, the alumina is dissolved in a cryolite molten salt at 950°C, and then the molten metallic aluminum is obtained by the electrolyzing ;

[0090] step S2: the molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area; where the aluminum-based hydrogen-producing material is aluminum chips with a maximum thickness of 1 mm;

[0091] step S3: under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material is chemically reacted with water, to obtain hydrogen and an alumina hydrate slurry;

[0092] Specifically, the aluminum chips, a catalyst which is nitrogen-containing and strong alkaline organic, and distilled water are added in proportions to an aluminum-water hydrogen production system. The catalyst which is nitrogen-containing and strong alkaline organic is dimethylbiguanide hydroxide. A mass ratio of the catalyst which is nitrogen-containing and strong alkaline organic to the distilled water is 1:4. A mass ratio of the aluminum chips to the distilled water is 1:6. A chemical reaction temperature is 65°C. A reaction time is 480 min. A reaction rate of the aluminum chips is 99.8%;

[0093] step S4: the alumina hydrate slurry is subjected to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0094] step S5: the alumina hydrate is calcined to obtain a high-activity metallurgical-grade alumina; where a calcination temperature is 1000°C, and a calcination time is 10 s;

[0095] step S6: the high-activity metallurgical-grade alumina is recycled to the electrolysis process of step S1, and the aqueous solution containing the catalyst after adding fresh water and the catalyst is recycled to participate in the chemical reaction of step S3, to form a closed-loop cycle.

[0096] Compared with ordinary industrial alumina, a dissolution rate of the high-activity alumina of Example 3 in the cryolite molten salt is increased by 51%, and the current efficiency of the electrolysis process is increased by 3.2%.

[0097] Example 4

[0098] An aluminum cycling method for metallic aluminum based energy storage and hydrogen production, includes:

[0099] step S1: alumina is electrolyzed to obtain molten metallic aluminum;

[0100] Specifically, in an aluminum electrolysis plant using wind power and applying a Cu-Ni-Fe metal anode technology, first, the alumina is dissolved in a cryolite molten salt at 750°C, and then the molten metallic aluminum is obtained by the electrolyzing ;

[0101] step S2: the molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area; where the aluminum-based hydrogen-producing material is aluminum particles having a D90 of 80 gm (90% of the particles have a particle size less than 80 gm);

[0102] step S3: under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material is chemically reacted with water, to obtain hydrogen and an alumina hydrate slurry;

[0103] Specifically, the aluminum particles, a catalyst which is nitrogen-containing and strong alkaline organic, and distilled water are added in proportions to an aluminum-water hydrogen production system. The catalyst which is nitrogen-containing and strong alkaline organic is a mixture of dimethylbiguanide hydroxide, diethylenetriamine, and triethylenetetramine in a mass ratio of 1:1:1. A mass ratio of the catalyst which is nitrogen-containing and strong alkaline organic to the distilled water is 1:10. A mass ratio of the aluminum particles to the distilled water is 1:4. A chemical reaction temperature is 55°C. A reaction time is 540 min. A reaction rate of the aluminum particles is 99.3%;

[0104] step S4: the alumina hydrate slurry is subjected to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0105] step S5: the alumina hydrate is calcined to obtain a high-activity metallurgical-grade alumina; where a calcination temperature is 750°C, and a calcination time is 20 min;

[0106] step S6: the high-activity metallurgical-grade alumina is recycled to the electrolysis process of step S1, and the aqueous solution containing the catalyst after adding fresh water and the catalyst is recycled to participate in the chemical reaction of step S3, to form a closed-loop cycle.

[0107] Compared with ordinary industrial alumina, a dissolution rate of the high-activity alumina of Example 4 in the cryolite molten salt is increased by 80%, and the current efficiency of the electrolysis process is increased by 4.2%.

[0108] Example 5

[0109] An aluminum cycling method for metallic aluminum based energy storage and hydrogen production, includes:

[0110] step S1: alumina is electrolyzed to obtain molten metallic aluminum;

[0111] Specifically, in an aluminum electrolysis plant using wind power and applying a Cu-Ni-Fe metal anode technology, first, the alumina is dissolved in a cryolite molten salt at 740°C, and then the molten metallic aluminum is obtained by the electrolyzing ;

[0112] step S2: the molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area; where the aluminum-based hydrogen-producing material is aluminum particles having a D90 of 40 pm (90% of the particles have a particle size less than 40 pm);

[0113] step S3: under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material is chemically reacted with water, to obtain hydrogen and an alumina hydrate slurry;

[0114] Specifically, the aluminum particles, a catalyst which is nitrogen-containing and strong alkaline organic, and distilled water are added in proportions to an aluminum-water hydrogen production system. The catalyst which is nitrogen-containing and strong alkaline organic is a mixture of diethylenetriamine and triethylenetetramine in a mass ratio of 2:1. A mass ratio of the catalyst which is nitrogen-containing and strong alkaline organic to the distilled water is 1:20. A mass ratio of the aluminum particles to the distilled water is 1:20. A chemical reaction temperature is 85°C. A reaction time is 120 min. A reaction rate of the aluminum particles is 99.6%;

[0115] step S4: the alumina hydrate slurry is subjected to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0116] step S5: the alumina hydrate is calcined to obtain a high-activity metallurgical-grade alumina; where a calcination temperature is 1000°C, and a calcination time is 3 s;

[0117] step S6: the high-activity metallurgical-grade alumina is recycled to the electrolysis process of step S1, and the aqueous solution containing the catalyst after adding fresh water and the catalyst is recycled to participate in the chemical reaction of step S3, to form a closed-loop cycle.

[0118] Compared with ordinary industrial alumina, a dissolution rate of the high-activity alumina of Example 5 in the cryolite molten salt is increased by 60%, and the current efficiency of the electrolysis process is increased by 5.3%.

[0119] Example 6

[0120] An aluminum cycling method for metallic aluminum based energy storage and hydrogen production, includes:

[0121] step S1: alumina is electrolyzed to obtain molten metallic aluminum;

[0122] Specifically, in an aluminum electrolysis plant using wind power and applying a Cu-Ni-Fe metal anode technology, first, the alumina is dissolved in a cryolite molten salt at 760°C, and then the molten metallic aluminum is obtained by the electrolyzing ;

[0123] step S2: the molten metallic aluminum is processed to obtain an aluminum-based hydrogen-producing material having a large specific surface area; where the aluminum-based hydrogen-producing material is aluminum particles having a D90 of 800 gm (90% of the particles have a particle size less than 800 gm);

[0124] step S3: under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material is chemically reacted with water, to obtain hydrogen and an alumina hydrate slurry;

[0125] Specifically, the aluminum particles, a catalyst which is nitrogen-containing and strong alkaline organic, and distilled water are added in proportions to an aluminum-water hydrogen production system. The catalyst which is nitrogen-containing and strong alkaline organic is a mixture of dimethylbiguanide hydroxide and triethylenetetramine in a mass ratio of 1:4. A mass ratio of the catalyst which is nitrogen-containing and strong alkaline organic to the distilled water is 1:40. A mass ratio of the aluminum particles to the distilled water is 1:12. A chemical reaction temperature is 95°C. A reaction time is 180 min. A reaction rate of the aluminum particles is 99.3%;

[0126] step S4: the alumina hydrate slurry is subjected to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;

[0127] step S5: the alumina hydrate is calcined to obtain a high-activity metallurgical-grade alumina; where a calcination temperature is 750°C, and a calcination time is 20 min;

[0128] step S6: the high-activity metallurgical-grade alumina is recycled to the electrolysis process of step S1, and the aqueous solution containing the catalyst after adding fresh water and the catalyst is recycled to participate in the chemical reaction of step S3, to form a closed-loop cycle.

[0129] Compared with ordinary industrial alumina, a dissolution rate of the high-activity alumina of Example 6 in the cryolite molten salt is increased by 75%, and the current efficiency of the electrolysis process is increased by 6.1%.

[0130] One or more technical solutions in the embodiments of the present disclosure have at least the following technical effects or advantages:

[0131] (1) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, compared with typical industrial alumina, a dissolution rate of the obtained high-activity metallurgical-grade alumina in cryolite or potassium-containing cryolite molten salt is increased by more than 50%, and a current efficiency of the electrolysis process is increased by more than 2%;

[0132] (2) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, the process of hydrogen production via aluminum-based hydrogen-producing material-water reaction uses a nitrogen-containing strong alkaline organic compound as a catalyst, which has the advantages of a fast reaction speed and that the obtained alumina hydrate contains no sodium element;

[0133] (3) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, during the process of electrolyzing the alumina using a SnO2 ceramic anode or a Cu-Ni-Fe metal anode as an inert anode, a small amount of metal elements such as Sn and Fe in the inert anode may enter the molten metallic aluminum to form an aluminum alloy, which is more beneficial for improving the reaction activity of the aluminum-based hydrogen-producing material, and thus accelerating the reaction rate of the hydrogen production via aluminum-based hydrogen-producing material-water reaction;

[0134] (4) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, a raw material used for the process of electrolyzing the alumina is the high-activity metallurgical-grade alumina, which contains no sodium element, thereby reducing a consumption of fluoride salts in the production process of the metal aluminum;

[0135] (5) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, the process of electrolyzing the alumina uses the inert anode technology, which fundamentally solves the problem of perfluorocarbon compound (PFC) emissions;

[0136] (6) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, the process of electrolyzing the alumina uses the high-activity metallurgical-grade alumina as a raw material to produce the molten metallic aluminum, and the high-activity metallurgical-grade alumina has the advantages of a high dissolution rate and a high current efficiency;

[0137] (7) According to the aluminum cycling method for metallic aluminum based energy storage and hydrogen production of some embodiments of the present disclosure, the efficient utilization of the aluminum, the zero solid waste discharge, and the near-zero carbon emission are achieved. The above descriptions are only specific implementations of the present disclosure, enabling those skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art. The generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments shown herein, but shall conform to a widest scope consistent with the principles and novel features disclosed in the specification.

Claims

1. An aluminum cycling method for metallic aluminum based energy storage and hydrogen production, comprising:electrolyzing alumina to obtain molten metallic aluminum;processing the molten metallic aluminum to obtain an  aluminum-basedhydrogen-producing material having a large specific surface area;chemically reacting, under action of a catalyst which is nitrogen-containing and strong alkaline organic, the aluminum-based hydrogen-producing material with water, to obtain hydrogen gas and an alumina hydrate slurry;subjecting the alumina hydrate slurry to a solid-liquid separation to obtain an alumina hydrate and an aqueous solution containing the catalyst;calcining the alumina hydrate to obtain a high-activity metallurgical-grade alumina; andrecycling the high-activity metallurgical-grade alumina to the step of electrolyzing the alumina, and recycling the aqueous solution containing the catalyst to participate in the step of chemically reacting the aluminum-based hydrogen-producing material with water, to form a closed-loop cycle.

2. The method according to claim 1, wherein the catalyst which is nitrogen-containing and strong alkaline organic comprises at least one of the following: diethylenetriamine, triethylenetetramine, and dimethylbiguanide hydroxide.

3. The method according to claim 1, wherein process parameters of the calcining comprise: a calcination temperature ranging from 750°C to 1020°C, and a calcination time ranging from 3 s to 20 min.

4. The method according to claim 1, wherein process parameters of the chemically reacting comprise: a reaction temperature ranging from 20°C to 95°C, and a reaction time ranging from 60 min to 720 min.

5. The method according to claim 1, wherein a mass ratio of the catalyst to the water ranges from 1:4 to 1:40.

6. The method according to claim 1, wherein a mass ratio of the aluminum-based hydrogen-producing material to the water ranges from 1:4 to 1:60.

7. The method according to claim 1, wherein a form of the aluminum-based hydrogen-producing material comprises any one of: aluminum particles and aluminum chips.

8. The method according to claim 7, wherein the aluminum particles have a D90 ranging from 30 gm to 1000 gm, ; and / ora maximum thickness of the aluminum chips is < 1 mm.

9. The method according to claim 1, wherein an electrical energy for the electrolyzing is derived from a green electrical energy.

10. The method according to claim 1 or claim 9, wherein an inert anode for the electrolyzing comprises any one of: a SnO2 ceramic anode and a Cu-Ni-Fe metal anode.

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