System and method for hydrogen production from waste aluminum and resource utilization of by-products

Abstract

This invention discloses a system and method for hydrogen production from waste aluminum and resource utilization of byproducts, belonging to the field of solid waste treatment and resource utilization technology. This invention innovatively integrates four technologies—hydrogen production from waste aluminum alkaline solution, calcification for silicon removal, seed decomposition for aluminum extraction, and intelligent alkaline solution recycling—into a continuous system. While producing hydrogen from waste aluminum, it simultaneously recovers aluminum hydroxide and calcium silicate resources, improving resource utilization. A staged impurity removal strategy is adopted to ensure the purity of byproducts while simultaneously achieving the recycling of alkaline solution, thereby reducing process costs and improving environmental benefits. An energy recovery and utilization unit is set up to use the heat released from the tail gas and hydrogen production reaction to heat the internal heating devices, significantly reducing external energy demand. An inert gas recovery device is also equipped in the hydrogen storage unit to reduce external material consumption, thus improving the economics and engineering feasibility of the process.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and resource utilization technology, and in particular relates to a system and method for producing hydrogen from waste aluminum and utilizing by-products. Background Technology

[0002] Aluminum, an abundant metallic element in the Earth's crust, is widely used in various industrial sectors, including food packaging, building materials, and machinery. Consequently, when consumed aluminum products reach their end-of-life, a considerable amount of scrap aluminum is generated. Currently, the main method of utilizing scrap aluminum in my country is re-electrolysis. Re-electrolysis involves feeding scrap aluminum into an electrolytic cell and extracting pure aluminum through high-temperature electrolysis. While this method can yield high-purity aluminum, it is extremely energy-intensive and has poor economic and environmental performance.

[0003] To address the aforementioned issues with waste aluminum utilization, research has shown that waste aluminum can be used to produce hydrogen through an aluminum-water reaction, providing a new pathway for the resource-based treatment and high-value utilization of waste aluminum. Hydrogen, due to its cleanliness and high energy efficiency, is considered an important carrier of future energy systems; therefore, this solution has attracted widespread attention from academia and industry, and is of great significance for achieving aluminum resource recycling and energy structure transformation. Currently, aluminum-water reaction hydrogen production technology based on an alkaline environment is becoming increasingly mature and has the potential to replace traditional fossil fuel hydrogen production technologies.

[0004] However, existing waste aluminum hydrogen production technologies still face pressing problems in practical applications. Due to the complex composition of waste aluminum, direct use in aluminum-water reactions can affect hydrogen production efficiency. Furthermore, the large amount of waste liquid containing aluminum and other impurities generated during the reaction process cannot be effectively recovered and utilized at high value, resulting in resource waste and hindering the overall economic and environmental benefits of the technology. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for hydrogen production from waste aluminum and resource utilization of byproducts, solving the problems of high energy consumption, poor economic efficiency, and poor environmental performance in existing waste aluminum recycling technologies. Specifically, this invention simultaneously achieves hydrogen production from waste aluminum and recovers aluminum hydroxide and calcium silicate resources, improving resource utilization; through a graded removal mechanism for waste aluminum impurities, it ensures the quality of byproducts and enables internal recycling of alkali solution; furthermore, through multi-stage energy utilization and material recycling design, it significantly reduces the consumption of external energy and materials, thereby improving the economic efficiency and engineering feasibility of the process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A system for producing hydrogen from waste aluminum and utilizing by-products includes: The pretreatment unit is used to crush mixed waste aluminum raw materials into particles, sort and remove combustible impurities, ferrous impurities, non-magnetic metal and non-metal impurities; A hydrogen production reaction unit, connected to the pretreatment unit, is used to react waste aluminum particles and sodium hydroxide solution to produce hydrogen gas. A hydrogen storage unit, connected to the hydrogen production reaction unit, is used to separate hydrogen from an inert protective gas, store the produced hydrogen, and recover the inert protective gas. A solution purification and separation unit, connected to the hydrogen production reaction unit, is used to remove impurities from the solution and produce and separate calcium silicate by-products. An aluminum recovery unit, connected to the solution purification and separation unit, is used to crystallize aluminum hydroxide from the purified solution using a seed decomposition method and to separate aluminum hydroxide byproducts. An alkaline solution recycling unit, connected to the aluminum recovery unit, is used to selectively evaporate and concentrate the remaining solution for reuse in the hydrogen production reaction unit. An energy recovery and utilization unit is connected to the pretreatment unit, hydrogen production reaction unit, aluminum recovery unit and alkaline solution circulation unit, and is used to recover the heat generated in the system and provide heat to the heat-using units. The online monitoring unit is connected to the hydrogen production reaction unit, solution purification and separation unit, aluminum recovery unit and alkali circulation unit, and is used to monitor container pressure, solution temperature, solution pH and concentration of various ions in the solution.

[0007] A further improvement of the present invention is that the pretreatment unit includes a coarse crushing device, a pyrolysis device, a fine crushing device, a sorting device, and a raw material bin; the coarse crushing device is used to crush large pieces of waste aluminum into coarse particles / fragments with a particle size <200 mm; the pyrolysis device operates under a nitrogen protective atmosphere; the fine crushing device is used to crush the brittle aluminum material after pyrolysis into small particles with a particle size <10 mm; and the sorting device is used to separate non-metallic impurities. The hydrogen production reaction unit includes a solution preparation system and a hydrogen production reactor. The solution preparation system is equipped with a dissolving tank with heating and stirring devices, which is used to mix and dissolve deionized water from the process water tank with fresh sodium hydroxide solid, prepare a sodium hydroxide solution of a specified concentration, preheat it, and then transport it to the hydrogen production reactor. The hydrogen storage unit includes a condenser, a gas-liquid separator, a pressure swing adsorption system, a hydrogen storage tank, and an inert gas recovery device. The condenser uses circulating cooling water to cool the wet hydrogen gas exiting the reactor to below 50 °C. The gas-liquid separator is a cyclone separator used to remove condensate droplets and trace amounts of alkaline mist that may be carried in the hydrogen gas. The pressure swing adsorption system is used for deep purification and drying of the hydrogen gas. The solution purification and separation unit includes a first solid-liquid separation device, a silicon removal device, a second solid-liquid separation device, a zinc removal device, and a third solid-liquid separation device; the slurry sequentially passes through the first solid-liquid separation device, the silicon removal device, the second solid-liquid separation device, the zinc removal device, and the third solid-liquid separation device to remove solution impurities and produce and recover calcium silicate by-products. The aluminum recovery unit includes a seed decomposition tank and a fourth solid-liquid separation device. The seed decomposition tank consists of multiple decomposition tanks connected in series. Each decomposition tank is equipped with a stirring device and a temperature control jacket. The purified solution flows in from the first tank and flows through the subsequent tanks in sequence. The slurry discharged from the last tank enters the fourth solid-liquid separation device to achieve efficient separation of aluminum hydroxide and the remaining solution. The alkaline solution circulation unit includes a buffer tank, a diversion control device, and a high-efficiency evaporator. The buffer tank is equipped with a fourth online monitoring device for sampling and analyzing the concentration of each ion in the remaining solution. The diversion control device is implemented by an electric three-way valve controlled by a PLC, and a threshold for impurity ion concentration is set. The high-efficiency evaporator uses saturated steam provided by the energy recovery unit as a first-effect heat source to concentrate the remaining solution and send it back to the hydrogen production reaction unit. The energy recovery and utilization unit includes a secondary combustion chamber, a steam generator, a high-temperature heat exchanger, a low-temperature heat exchanger, a flue gas purification device, and a reaction chamber heat exchanger. The secondary combustion chamber uses a swirl burner and is equipped with an auxiliary burner for ignition and combustion stabilization. The high-temperature flue gas discharged from the secondary combustion chamber first enters the steam generator to produce saturated steam. The flue gas from the steam generator then enters the high-temperature heat exchanger and the low-temperature heat exchanger in sequence. After the flue gas undergoes staged heat exchange, it enters the flue gas purification device. The reaction chamber heat exchanger recovers the heat released during the reaction process, which, while suppressing overheating in the reaction chamber, can be used to heat other process media, thus achieving heat reuse. The online monitoring unit includes a first online monitoring device to a fourth online monitoring device, which are respectively configured in the hydrogen production reactor, the silicon removal device, the zinc removal device, and the buffer tank.

[0008] A further improvement of the present invention is that the sorting device includes a magnetic separator and an eddy current separator, which are connected to a fine crushing device to remove ferrous impurities and non-metallic impurities.

[0009] A further improvement of the present invention is that the solution preparation system includes a water tank, a sodium hydroxide storage tank, and a solution preparation chamber; wherein, the water tank is used to store reaction water; the sodium hydroxide storage tank is used to store solid sodium hydroxide; and the solution preparation chamber is equipped with a stirring device, a heating device, and a temperature sensor for dissolving and preparing the sodium hydroxide solution required for the reaction and heating it to a specified temperature.

[0010] A further improvement of the present invention is that the flue gas purification device includes a denitrification device, a dust removal device, and a desulfurization and deacidification device connected in series; wherein, the denitrification device is used to remove nitrogen oxides from the flue gas, the dust removal device is used to remove particulate matter from the flue gas, and the desulfurization and deacidification device is used to remove sulfur dioxide and acidic gases from the flue gas, so that the flue gas meets the emission standards.

[0011] A further improvement of the present invention is that the sensors of the online monitoring device include a pressure sensor, a temperature sensor, a solution pH sensor, and an ion concentration sensor.

[0012] A further improvement of this invention is that the coarse crushing device is a twin-shaft shear crusher.

[0013] A further improvement of the present invention is that the pyrolysis device adopts an externally heated rotary kiln.

[0014] A further improvement of this invention is that a hammer crusher is selected as the fine crushing device.

[0015] A method for producing hydrogen from waste aluminum and utilizing by-products, the method being based on the aforementioned system for producing hydrogen from waste aluminum and utilizing by-products, comprising: The mixed waste aluminum raw materials are crushed into granules, and combustible impurities, iron impurities, non-magnetic metals and non-metals are removed. Hydrogen gas is prepared by reacting the waste aluminum particles with sodium hydroxide solution and then stored. Calcium silicate and aluminum hydroxide byproducts were prepared from the remaining solution; Remove impurities from the solution to achieve mother liquor recycling.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: This invention innovatively integrates four technologies—hydrogen production from waste aluminum alkali solution, silicon removal through calcification, aluminum extraction through seed decomposition of sodium aluminate solution, and intelligent recycling of alkali solution—into a continuous system. This system enables the joint production of hydrogen, aluminum hydroxide, and calcium silicate, and allows for the internal recycling of the alkali solution, significantly improving the comprehensive utilization rate of resources.

[0017] This invention employs a graded removal strategy targeting different impurity characteristics: thermal decomposition of combustible impurities, magnetic separation for iron removal, calcification for silicon removal, and precise pH control for zinc precipitation removal. Among these, zinc removal is key to further improving the purity of aluminum hydroxide products.

[0018] For trace soluble impurities that are difficult to remove, an innovative strategy of "limited enrichment within the system + intelligent online monitoring and discharge" is adopted. By evaporating, concentrating and regenerating the seed mother liquor and intelligently discharging and replenishing the new liquor, the recycling of alkali liquor is realized, reducing process costs and improving the economic efficiency and environmental friendliness of the process.

[0019] This invention combines the pyrolysis treatment of organic matter on the surface of waste aluminum with secondary combustion. While decomposing the organic matter, it recovers chemical energy and converts it into heat energy. This heat energy, along with the reaction heat released by the aluminum-alkali hydrogen production reaction itself, is transported to devices such as water tanks, hydrolysis tanks, and high-efficiency evaporators for heating, which significantly reduces the energy demand from outside the system and reduces the overall process energy consumption. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a waste aluminum hydrogen production and by-product resource utilization system provided by the present invention.

[0022] Figure 2 This is a flowchart illustrating the specific process of the energy recovery and utilization unit and the pretreatment unit of the present invention.

[0023] Figure 3 This is a flowchart illustrating the specific process of the hydrogen storage unit, hydrogen production reaction unit, and solution purification and separation unit of the present invention.

[0024] Figure 4 This is a flowchart illustrating the specific process of the aluminum recovery unit and the alkali circulation unit of the present invention. Detailed Implementation

[0025] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0030] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0031] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0032] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0033] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0034] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0035] Example 1 like Figures 1 to 4 As shown, the present invention provides a system for hydrogen production from waste aluminum and resource utilization of by-products. The system includes a pretreatment unit, a hydrogen production reaction unit, a hydrogen storage unit, a solution purification and separation unit, an aluminum recovery unit, an alkali circulation unit, an energy recovery and utilization unit, and an online monitoring unit.

[0036] The pretreatment unit is used to crush the mixed waste aluminum raw materials into particles, sort and remove combustible impurities, ferrous impurities, non-magnetic metals (such as copper) and non-metallic impurities, including: A coarse crushing device is used to crush waste aluminum raw materials into coarse particles with a particle size of <200 mm; The pyrolysis unit, connected to the coarse crushing unit, heats the coarse particles to 300°C under an inert atmosphere. 500 ℃, used to remove organic matter from the surface of waste aluminum particles and generate pyrolysis gas; A fine crushing device, connected to a pyrolysis device, is used to further crush waste aluminum particles into small particles with a particle size of <10 mm suitable for the reaction. The sorting device uses a magnetic separator and an eddy current separator, which are connected to a fine crushing device to remove ferrous and non-metallic impurities.

[0037] The hydrogen production reaction unit, connected to the pretreatment unit, is used to react waste aluminum particles and sodium hydroxide solution to produce hydrogen gas and sodium aluminate solution, including: The solution preparation system is equipped with stirring and heating functions for preparing and preheating sodium hydroxide solution; The hydrogen production reactor is equipped with a stirring device and a first online monitoring device. The stirring device can promote the mixing of reactants and reduce particle aggregation, while the online monitoring device can monitor the reaction status and ensure the safety of the reaction.

[0038] Furthermore, the solution preparation system includes a water tank, a sodium hydroxide storage tank, and a solution preparation chamber. The water tank stores the reaction water; the sodium hydroxide storage tank stores solid sodium hydroxide; and the solution preparation chamber is equipped with a stirring device, a heating device, and a temperature sensor for dissolving and preparing the sodium hydroxide solution required for the reaction and heating it to a specified temperature.

[0039] The hydrogen storage unit, connected to the hydrogen production unit, is used to store the hydrogen produced by the system and recover the inert protective gas, including: A condenser, connected to the hydrogen production reactor, is used to cool the high-temperature humid hydrogen gas output from the hydrogen production reactor to room temperature and condense the water vapor it carries. A gas-liquid separator, connected to a condenser, is used to remove alkaline mist and condensate entrained in hydrogen gas. Pressure swing adsorption (PSA) system, with an adsorption tower inside, is used to remove trace impurity gases from hydrogen to obtain high-purity hydrogen; Hydrogen storage tanks are used to store purified product hydrogen. An inert gas recovery unit is used to recover desorbed inert gases in the PSA process.

[0040] The solution purification and separation unit, connected to the hydrogen production unit, is used to remove impurities from the solution and produce and recover calcium silicate byproducts, including: The first solid-liquid separation device is connected to the hydrogen production reactor and is used to separate insoluble residues in the solution after the reactor is completed. The silicon removal device is connected to the first solid-liquid separation device and is used to add calcium salt to the separated solution to generate calcium silicate precipitate. The second solid-liquid separation device, connected to the silicon removal device, is used to separate calcium silicate precipitate; The zinc removal device is connected to the second solid-liquid separation device. By adjusting the pH of the solution to 10-11, zinc impurities are selectively precipitated. The third solid-liquid separation device is connected to the zinc removal device and is used to separate zinc-containing precipitates.

[0041] The aluminum recovery unit, connected to the solution purification and separation unit, is used to recover aluminum from the purified solution, including: The seed decomposition tank, consisting of multiple decomposition tanks connected in series, is used to crystallize and precipitate aluminum hydroxide under the condition of adding seed crystals. The fourth solid-liquid separation unit is used to separate the obtained aluminum hydroxide product and produce the remaining solution.

[0042] The alkali solution circulation unit, connected to the aluminum recovery unit, is used to treat the remaining solution and realize alkali solution circulation, including: A buffer tank, equipped with a built-in online monitoring device, is used to temporarily store the remaining solution after separation; The diversion control device diverts the mother liquor to the regeneration pipeline or the sewage pipeline based on the monitoring results. A high-efficiency evaporator is used to concentrate the diverted mother liquor, regenerate it into a concentrated sodium hydroxide solution, and return it to the hydrogen production reactor; The energy recovery and utilization unit is connected to the pretreatment unit, hydrogen production reaction unit, aluminum recovery unit, and alkali circulation unit, and is used to recover the heat energy generated in the system and supply heat to the heat-using units, including: A secondary combustion chamber, connected to the pyrolysis device, is used to burn the pyrolysis gas produced by the pyrolysis device; Steam generator is used to produce steam from high-temperature flue gas; Heat exchangers are used to recover heat from flue gas and reactors to heat water tanks, seed decomposition tanks and high-efficiency evaporators within the system. Flue gas purification devices are used for terminal flue gas treatment to ensure that emissions meet standards.

[0043] Furthermore, the flue gas purification device includes a denitrification device, a dust removal device, and a desulfurization and deacidification device arranged in sequence.

[0044] The online monitoring unit is deployed in various key devices, including: According to the measurement requirements, the system includes various types of sensors such as temperature sensors, ion concentration sensors, pressure sensors, and pH sensors, and has four online monitoring devices.

[0045] Furthermore, the first online monitoring device is arranged in the hydrogen production reaction chamber to monitor the temperature, pressure, solution temperature, solution pH, and concentration of various ions in the hydrogen production reactor, thereby monitoring the reaction status and ensuring reaction safety. The second online monitoring device is arranged in the silicon removal device to monitor the concentration of various ions in the solution after treatment by the first solid-liquid separation device, and the data is used to calculate the amount of calcium salt to be added. The third online monitoring device is arranged in the zinc removal device to monitor the pH and temperature of the solution in the zinc removal device, and the data is used to calculate the required amount of dilution water and control the solution pH. The fourth online monitoring device is arranged in the buffer tank to monitor the concentration of various ions in the solution after treatment by the third solid-liquid separation device, and the data is used to determine the mother liquor diversion situation.

[0046] Example 2 Figure 1 An exemplary structure of a waste aluminum hydrogen production and by-product resource utilization system is shown, including a pretreatment unit, a hydrogen production reaction unit, a hydrogen storage unit, a solution purification and separation unit, an aluminum recovery unit, an alkali circulation unit, an energy recovery and utilization unit, and an online monitoring unit.

[0047] The mixed waste aluminum raw material has a disordered composition, with aluminum accounting for approximately 90% to 95%, and the remainder consisting of various impurities such as silicon, iron, copper, magnesium, zinc, and manganese. Furthermore, its irregular shape makes it unsuitable for direct use in hydrogen production reactions. Therefore, pretreatment is required before the reaction, which involves sequentially passing it through a coarse crushing unit, a pyrolysis unit, a fine crushing unit, and a sorting unit. The specific implementation of the pretreatment unit is as follows: The coarse crushing device uses a twin-shaft shear crusher to crush large pieces of waste aluminum into coarse particles / fragments with a particle size of <200 mm. The pyrolysis unit uses an externally heated rotary kiln and operates under a nitrogen protective atmosphere; The fine crushing device uses a hammer crusher to crush the brittle aluminum material after pyrolysis into small particles with a particle size of <10 mm, which are suitable for the reaction. The sorting device first uses a permanent magnet drum separator to remove ferrous impurities, and then uses an eddy current separator to effectively separate non-metallic impurities.

[0048] After pretreatment, the waste aluminum particles are temporarily stored in a raw material silo, and then precisely metered and transported to the hydrogen production reaction unit. This hydrogen production reaction unit includes a solution preparation system and a hydrogen production reactor. The specific implementation of the hydrogen production reaction unit is as follows: The solution preparation system is equipped with a dissolving tank with heating and stirring devices, which is used to mix and dissolve deionized water from the process water tank with fresh sodium hydroxide solids to prepare a sodium hydroxide solution of a specified concentration and preheat it, and then deliver it to the hydrogen production reactor by a metering pump. The hydrogen production reactor is a jacketed reactor with heat exchange pipes inside the jacket. The main reaction in the hydrogen production reactor is: 2Al + 2NaOH + 6H2O → 2Na[Al(OH)4] + 3H2↑. Furthermore, the hydrogen production reactor is equipped with a stirrer, which can promote the mixing of reactants and reduce particle aggregation.

[0049] Furthermore, the reactor integrates a first online monitoring device for process monitoring, including a temperature sensor, a pH sensor resistant to strong alkalis, and a pressure sensor; the signal output terminals of the sensors are all connected to a distributed control system to realize real-time monitoring of the reaction status and safety interlock control.

[0050] Furthermore, the reaction is carried out under normal pressure. Before the reaction is started, an inert atmosphere is established by purging and replacing the reaction chamber with an inert gas (such as nitrogen).

[0051] Furthermore, after the reaction starts, the system temperature is mainly maintained by the intense heat of reaction released by the aluminum-alkali reaction itself. The heat exchange loop connected to the reactor jacket can remove some of the excess heat of reaction and use it as a heat source to supply the subsequent seed decomposition tank.

[0052] Furthermore, when the system detects that the hydrogen yield is continuously below the set threshold, it determines that the main reaction has ended.

[0053] Hydrogen gas in the hydrogen production reaction chamber is collected by the hydrogen storage unit and sequentially passes through a condenser, a gas-liquid separator, and a pressure swing adsorption system before being stored in a hydrogen storage tank. The specific implementation of the hydrogen storage unit is as follows: The condenser uses circulating cooling water to cool the wet hydrogen gas exiting the reactor to below 50°C; The gas-liquid separator uses a cyclone separator to remove condensate droplets and trace amounts of alkaline mist that may be carried in the hydrogen gas. Pressure swing adsorption (PSA) systems are used for the deep purification and drying of hydrogen. Furthermore, the PSA system is preferably configured with a four-adsorption tower process, which uses programmable valves to cyclically execute steps such as adsorption, pressure equalization, reverse release, purging, rinsing and pressurization in a predetermined sequence to achieve continuous production.

[0054] Furthermore, the adsorption tower is filled with a composite adsorbent, with the bottom layer being activated alumina, mainly used to remove residual moisture; and the upper layer being zeolite molecular sieve, used to adsorb and remove inert gases.

[0055] Hydrogen storage tanks are used to store high-purity hydrogen produced by the PSA system.

[0056] The inert gas recovery unit is connected to the PSA system. This unit is mainly used to desorb the inert gas adsorbed by the PSA, purify and dry it, and collect it. The collected inert gas is then used as a purge gas before the subsequent hydrogen production reaction, which significantly reduces the external replenishment consumption of inert gas.

[0057] After the aluminum-alkali reaction is completed, the slurry in the reactor (mainly containing sodium aluminate solution and a small amount of unreacted solid residue) is discharged and transported to the solution purification and separation unit. It then sequentially passes through a first solid-liquid separation device, a silicon removal device, a second solid-liquid separation device, a zinc removal device, and a third solid-liquid separation device to remove impurities from the solution and produce and recover calcium silicate as a byproduct. The specific implementation method of the solution purification and separation unit is as follows: The solid-liquid separation devices all use chamber filter presses, and the filter cloth material is alkali-resistant polypropylene. The silicon removal device is a sedimentation tank with stirring. Based on the silicon ion concentration fed back by the second online monitoring device, slaked lime is added at a Ca / Si molar ratio of 1:1, and stirring continues until precipitation no longer increases. The main reaction in this step is: +Ca(OH)₂→CaSiO₃↓+2OH⁻ - ; The zinc removal unit is a pH-controlled precipitation tank. Based on pH feedback from a third online monitoring device, water is added via a metering pump to dilute the solution, precisely controlling the pH to 10-11, causing Zn(OH)₂ to precipitate. The main reaction in this process is: [Zn(OH)₄]₄. 2+ →Zn(OH)2↓+2OH - .

[0058] The purified sodium aluminate solution, after the removal of silicon and zinc impurities, enters the aluminum recovery unit. In this unit, the aluminum in the solution is crystallized and recovered as aluminum hydroxide using a seed decomposition method. The specific implementation method of the aluminum recovery unit is as follows: The seed decomposition tank consists of multiple decomposition tanks connected in series. Each decomposition tank is equipped with a stirring device and a temperature control jacket. The purification solution flows in from the first tank and flows through the subsequent tanks in sequence. Furthermore, a predetermined amount of seed mother liquor and fine aluminum hydroxide seed crystals are continuously added to the first tank of the system.

[0059] Furthermore, a temperature control curve for gradient cooling is established to maintain a suitable supersaturation, promote the directional growth of crystals on the seed surface, and inhibit the secondary nucleation of fine particles.

[0060] The slurry discharged from the last tank enters the fourth solid-liquid separation unit, which uses a horizontal screw discharge centrifuge to achieve efficient separation of aluminum hydroxide and the remaining solution.

[0061] The remaining solution after separation enters the alkali circulation unit, which includes a buffer tank, a flow control device, and a high-efficiency evaporator to treat the remaining solution and realize alkali circulation. The specific implementation of the alkali circulation unit is as follows: The buffer tank is equipped with a fourth online component monitoring device, which can sample and analyze the concentration of each ion in the remaining solution. The diversion control device is implemented by an electric three-way valve controlled by a PLC. The system sets a threshold for the concentration of impurity ions. When the monitored concentration is lower than this value, all the remaining solution enters the evaporator. When the concentration exceeds this value, 50% of the volume of the remaining solution is diverted to the wastewater treatment station, and the fresh alkali replenishment program is started. The high-efficiency evaporator uses saturated steam provided by the energy recovery unit as a primary heat source to concentrate the remaining solution and send it back to the hydrogen production reaction unit.

[0062] The energy recovery and utilization unit is connected to the pretreatment unit, hydrogen production reaction unit, aluminum recovery unit, and alkali circulation unit, and is used to recover the heat energy generated within the system and supply heat to the heat-using units. The specific implementation of the alkali circulation unit is as follows: The secondary combustion chamber employs a swirl burner and is equipped with an auxiliary burner for ignition and combustion stabilization. Excess air / O2 is supplied via a blower to ensure stable combustion and complete decomposition of organic matter. The high-temperature flue gas discharged from the secondary combustion chamber first enters the steam generator to produce saturated steam. This steam is preferentially used to drive the steam turbine generator set to generate electricity for the system's own use. Secondly, it can be used as a heat source for the high-efficiency evaporator. The flue gas from the steam generator enters the high-temperature heat exchanger and the low-temperature heat exchanger in sequence, transferring heat to other heat-using devices such as the seed decomposition tank and the water tank. Furthermore, the low-temperature reaction heat recovered from the hydrogen production reactor is also transferred to the seed decomposition tank via a heat exchanger. After passing through a series of heat exchangers, the flue gas enters a flue gas purification device, which includes a selective catalytic reduction denitrification system, a bag filter, and an alkaline spray scrubbing tower, which are used to remove pollutants such as nitrogen oxides, particulate matter, and sulfur dioxide, so that the flue gas can be discharged in compliance with standards.

[0063] The online monitoring unit, consisting of sensors and actuators deployed at key nodes, is implemented as follows: The first online monitoring device is located in the hydrogen production reaction chamber to monitor the temperature, pressure, solution temperature, solution pH, and concentration of various ions in the solution within the hydrogen production reaction chamber, thereby monitoring the reaction status and ensuring reaction safety. The second online monitoring device is located in the silicon removal device and is used to monitor the concentration of each ion in the solution after being treated by the first solid-liquid separation device. The data is used to calculate the amount of calcium salt added. The third online monitoring device is installed in the zinc removal unit to monitor the pH and temperature of the solution inside the zinc removal unit. The data is used to calculate the required amount of dilution water and control the pH of the solution. The fourth online monitoring device, located in the buffer tank, is used to monitor the concentration of each ion in the solution after it has been treated by the third solid-liquid separation device. The data is used to determine the mother liquor circulation status.

[0064] In summary, the system and method for hydrogen production from waste aluminum and resource utilization of byproducts provided by this invention have the following advantages: (1) The four technologies of hydrogen production from waste aluminum alkali solution, silicon removal by calcification, aluminum extraction by seed decomposition, and intelligent recycling of alkali solution are innovatively integrated into a continuous system, which can realize the joint production of hydrogen, aluminum hydroxide and calcium silicate, and improve resource utilization. (2) The heat released from the tail flue gas and hydrogen production reaction is recovered and utilized by the heat exchange device to provide heat for the water tank, seed decomposition tank and high-efficiency evaporator in the system, thereby reducing dependence on external energy. (3) Setting up an inert gas recovery device to realize the recycling of inert gas can reduce process costs; (4) A graded impurity removal strategy is adopted, including magnetic separation to remove iron, filtration to remove copper, calcification to remove silicon, and precise pH control to precipitate zinc-containing impurities. The impurity treatment is economical and effective and can improve the purity of by-products. Among them, zinc removal is the key to further improving the purity of aluminum hydroxide products. (5) By evaporating, concentrating and regenerating the remaining solution and intelligently discharging and replenishing it, the alkaline solution can be recycled, thereby reducing process costs and improving environmental benefits.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A system for producing hydrogen from waste aluminum and utilizing by-products, characterized in that, include: The pretreatment unit is used to crush mixed waste aluminum raw materials into particles, sort and remove combustible impurities, ferrous impurities, non-magnetic metal and non-metal impurities; A hydrogen production reaction unit, connected to the pretreatment unit, is used to react waste aluminum particles and sodium hydroxide solution to produce hydrogen gas. A hydrogen storage unit, connected to the hydrogen production reaction unit, is used to separate hydrogen from an inert protective gas, store the produced hydrogen, and recover the inert protective gas. A solution purification and separation unit, connected to the hydrogen production reaction unit, is used to remove impurities from the solution and produce and separate calcium silicate by-products. An aluminum recovery unit, connected to the solution purification and separation unit, is used to crystallize aluminum hydroxide from the purified solution using a seed decomposition method and to separate aluminum hydroxide byproducts. An alkaline solution recycling unit, connected to the aluminum recovery unit, is used to selectively evaporate and concentrate the remaining solution for reuse in the hydrogen production reaction unit. An energy recovery and utilization unit is connected to the pretreatment unit, hydrogen production reaction unit, aluminum recovery unit and alkaline solution circulation unit, and is used to recover the heat generated in the system and provide heat to the heat-using units. The online monitoring unit is connected to the hydrogen production reaction unit, solution purification and separation unit, aluminum recovery unit and alkali circulation unit, and is used to monitor container pressure, solution temperature, solution pH and concentration of various ions in the solution.

2. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 1, characterized in that, The pretreatment unit includes a coarse crushing device, a pyrolysis device, a fine crushing device, a sorting device, and a raw material silo; the coarse crushing device is used to crush large pieces of waste aluminum into coarse particles / fragments with a particle size of <200 mm; the pyrolysis device operates under a nitrogen protective atmosphere; the fine crushing device is used to crush the brittle aluminum material after pyrolysis into small particles with a particle size of <10 mm; the sorting device is used to separate non-metallic impurities. The hydrogen production reaction unit includes a solution preparation system and a hydrogen production reactor. The solution preparation system is equipped with a dissolving tank with heating and stirring devices, which is used to mix and dissolve deionized water from the process water tank with fresh sodium hydroxide solid, prepare a sodium hydroxide solution of a specified concentration, preheat it, and then transport it to the hydrogen production reactor. The hydrogen storage unit includes a condenser, a gas-liquid separator, a pressure swing adsorption system, a hydrogen storage tank, and an inert gas recovery device. The condenser uses circulating cooling water to cool the wet hydrogen gas exiting the reactor to below 50 °C. The gas-liquid separator is a cyclone separator used to remove condensate droplets and trace amounts of alkaline mist that may be carried in the hydrogen gas. The pressure swing adsorption system is used for deep purification and drying of the hydrogen gas. The solution purification and separation unit includes a first solid-liquid separation device, a silicon removal device, a second solid-liquid separation device, a zinc removal device, and a third solid-liquid separation device; the slurry sequentially passes through the first solid-liquid separation device, the silicon removal device, the second solid-liquid separation device, the zinc removal device, and the third solid-liquid separation device to remove solution impurities and produce and recover calcium silicate by-products. The aluminum recycling unit includes a seed decomposition tank and a fourth solid-liquid separation device. The seed decomposition tank consists of multiple decomposition tanks connected in series. Each decomposition tank is equipped with a stirring device and a temperature control jacket. The purified solution flows in from the first tank and flows through the subsequent tanks in sequence. The slurry discharged from the last tank enters the fourth solid-liquid separation unit to achieve efficient separation of aluminum hydroxide and the remaining solution; The alkaline solution circulation unit includes a buffer tank, a diversion control device, and a high-efficiency evaporator; The buffer tank is equipped with a fourth online monitoring device for sampling and analyzing the concentration of each ion in the remaining solution; the diversion control device is implemented by an electric three-way valve controlled by a PLC, and the impurity ion concentration threshold is set. The high-efficiency evaporator uses saturated steam provided by the energy recovery unit as a primary heat source to concentrate the remaining solution and send it back to the hydrogen production reaction unit. The energy recovery and utilization unit includes a secondary combustion chamber, a steam generator, a high-temperature heat exchanger, a low-temperature heat exchanger, a flue gas purification device, and a reaction chamber heat exchanger. The secondary combustion chamber uses a swirl burner and is equipped with an auxiliary burner for ignition and combustion stabilization. The high-temperature flue gas discharged from the secondary combustion chamber first enters the steam generator to produce saturated steam. The flue gas from the steam generator then enters the high-temperature heat exchanger and the low-temperature heat exchanger in sequence. After the flue gas undergoes staged heat exchange, it enters the flue gas purification device. The reaction chamber heat exchanger recovers the heat released during the reaction process, which, while suppressing overheating in the reaction chamber, can be used to heat other process media, thus achieving heat reuse. The online monitoring unit includes a first online monitoring device to a fourth online monitoring device, which are respectively configured in the hydrogen production reactor, the silicon removal device, the zinc removal device, and the buffer tank.

3. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, The sorting device includes a magnetic separator and an eddy current separator, which are connected to a fine crushing device to remove ferrous and non-metallic impurities.

4. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, The solution preparation system includes a water tank, a sodium hydroxide storage tank, and a solution preparation chamber; wherein, the water tank is used to store reaction water; the sodium hydroxide storage tank is used to store solid sodium hydroxide; the solution preparation chamber is equipped with a stirring device, a heating device, and a temperature sensor, used to dissolve and prepare the sodium hydroxide solution required for the reaction and heat it to a specified temperature.

5. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, The flue gas purification device includes a denitrification device, a dust removal device, and a desulfurization and deacidification device connected in series. The denitrification device is used to remove nitrogen oxides from the flue gas, the dust removal device is used to remove particulate matter from the flue gas, and the desulfurization and deacidification device is used to remove sulfur dioxide and acidic gases from the flue gas, so that the flue gas meets emission standards.

6. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, The sensors in the online monitoring device include pressure sensors, temperature sensors, solution pH sensors, and ion concentration sensors.

7. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, The coarse crushing unit uses a twin-shaft shear crusher.

8. The system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, The pyrolysis unit uses an externally heated rotary kiln.

9. A system for producing hydrogen from waste aluminum and utilizing by-products according to claim 2, characterized in that, Hammer crushers are selected for fine crushing.

10. A method for producing hydrogen from waste aluminum and utilizing by-products, characterized in that, This method is based on a waste aluminum hydrogen production and by-product resource utilization system according to any one of claims 1 to 9, comprising: The mixed waste aluminum raw materials are crushed into granules, and combustible impurities, iron impurities, non-magnetic metals and non-metals are removed. Hydrogen gas is prepared by reacting the waste aluminum particles with sodium hydroxide solution and then stored. Calcium silicate and aluminum hydroxide byproducts were prepared from the remaining solution; Remove impurities from the solution to achieve mother liquor recycling.

Images