System and method for recycling aluminum resources through cooperative utilization of aluminum casting by-products and carbon dioxide

Abstract

The invention provides an aluminum resource recovery system and method for synergistically utilizing aluminum casting byproducts and carbon dioxide, and belongs to the technical field of resource utilization. The system provided by the invention comprises an aluminum casting by-product treatment module and a combustion flue gas treatment module, wherein the aluminum casting by-product treatment module comprises an aluminum dissolution precipitation tank, an ultrafiltration unit, a first reverse osmosis device, a second reverse osmosis device, a concentrated water storage tank, an evaporator, and a low-pressure pump and a high-pressure pump between pipelines; the combustion flue gas treatment module comprises a gas cooling device, a carbon dioxide trapping device, a heat exchanger, a carbon dioxide degassing device and a carbon dioxide storage device, can synchronously realize standard treatment of high-concentration aluminum wastewater and storage and cyclic utilization of carbon dioxide, and realizes efficient precipitation and recovery of aluminum ions; the dual effects of environmental governance and resource utilization are achieved.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology, specifically to a system and method for aluminum resource recovery through the synergistic utilization of aluminum casting by-products and carbon dioxide. Background Technology

[0002] As a significant source of lightweight metal materials, the aluminum industry is experiencing continuous expansion in production scale due to increasing global demand. Aluminum casting is a crucial process for producing complex-shaped aluminum castings. However, during the aluminum casting process, by-products often remain and accumulate inside the mold. If these by-products are not cleaned promptly, they will accumulate, reducing process efficiency and severely limiting production capacity. Therefore, the removal and reuse of aluminum casting by-products has become a critical issue that urgently needs to be addressed in the aluminum industry.

[0003] In industrial practice, alkaline leaching is often used to remove byproducts from aluminum casting. However, this process generates wastewater with high concentrations of aluminum ions and strong alkalinity, posing a challenge for high-salinity wastewater treatment. Direct discharge of this wastewater without treatment will severely pollute water bodies, thus requiring corresponding high-efficiency treatment technologies. Meanwhile, during aluminum casting, maintaining the molten metal requires a continuous high temperature of 700-900°C. This process often uses fossil fuels such as natural gas and coke as energy sources, and their combustion produces large amounts of carbon dioxide. As a typical greenhouse gas, its emissions will further exacerbate global climate change. Conventional CO2 capture systems are energy-intensive and suffer from difficulties in recovering the captured liquid.

[0004] Current resource recovery systems lack integrated devices for achieving "aluminum-CO2 dual resource recycling." How to simultaneously address the two major environmental challenges of high-concentration aluminum wastewater and carbon dioxide emissions in aluminum casting processes has become a critical technological challenge that urgently needs to be overcome. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a structurally integrated system that can simultaneously treat aluminum by-products and CO2 combustion waste gas, achieving aluminum resource recovery and CO2 immobilization through the linkage of chemical reaction and membrane separation. This invention can simultaneously achieve compliant treatment of high-concentration aluminum wastewater and the storage and recycling of carbon dioxide, as well as the efficient precipitation and recovery of aluminum ions, achieving the dual effects of environmental remediation and resource utilization.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an aluminum resource recycling system for the synergistic utilization of aluminum casting by-products and carbon dioxide, including an aluminum casting by-product processing module and a combustion flue gas processing module. The aluminum casting by-product processing module includes an aluminum dissolution and precipitation tank. An ultrafiltration unit is connected to the outlet of the aluminum dissolution and precipitation tank; the ultrafiltration unit is provided with a permeate phase outlet and a retrieval phase outlet; a first low-pressure pump is provided between the ultrafiltration unit and the aluminum dissolution and precipitation tank; A second low-pressure pump with its inlet permeable to the ultrafiltration unit has an outlet that is divided into a first branch and a second branch. The first high-pressure pump whose inlet is connected to the first branch; The first reverse osmosis device is divided into a first high-salt side and a first low-salt side by a first reverse osmosis membrane, and the inlet of the first high-salt side is connected to the outlet of the first high-pressure pump. A second high-pressure pump whose inlet is connected to the outlet of the first high-salt side; The second reverse osmosis unit is divided into a second high-salt side and a second low-salt side by a second reverse osmosis membrane. The inlet of the second high-salt side is connected to the outlet of the second high-pressure pump. The second branch is connected to the inlet of the second low-salt side. The outlet of the second low-salt side is connected to the inlet of the first low-salt side. The outlet of the first low-salt side is connected to the inlet of the aluminum dissolution precipitation tank. A concentrated water storage tank whose inlet is connected to the outlet of the second high-salt side and the outlet of the ultrafiltration unit's filtration phase. An evaporator whose inlet is connected to the outlet of the concentrated water storage tank; the evaporator includes an aqueous phase outlet and a solid phase outlet, the aqueous phase outlet being connected to the inlet of an aluminum dissolution and precipitation tank; The combustion flue gas treatment module includes a gas cooling device, a carbon dioxide capture device, a heat exchanger, a carbon dioxide degassing device, and a carbon dioxide storage device connected in sequence. The carbon dioxide capture device contains a monoethanolamine solution, and the outlet of the carbon dioxide storage device is connected to the inlet of the aluminum dissolution and precipitation tank.

[0007] Preferably, the ultrafiltration membrane in the ultrafiltration unit is a polyvinylidene fluoride hollow fiber membrane with a pore size of 0.01~0.05 μm; The first reverse osmosis membrane and the second reverse osmosis membrane are independently polyamide hollow fiber membranes or polyamide flat spiral wound membranes.

[0008] Preferably, an energy recovery device is provided between the outlet of the second high-salt side of the second reverse osmosis unit and the inlet of the concentrated water storage tank.

[0009] Preferably, the mass concentration of the monoethanolamine solution is 20-30 wt%. The carbon dioxide degassing device is provided with a liquid phase outlet, which is connected to the liquid phase inlet of the carbon dioxide capture device via a heat exchanger.

[0010] This invention provides a method for aluminum resource recovery by synergistically utilizing aluminum casting by-products and carbon dioxide. The aluminum resource recovery system employing the aforementioned synergistic utilization of aluminum casting by-products and carbon dioxide includes the following steps: Aluminum casting byproducts enter an aluminum dissolving and precipitation tank, are mixed with water and an alkaline regulator, and undergo alkaline leaching. CO2 is then introduced to carry out a precipitation reaction, yielding a leachate. The leachate is pressurized by a first low-pressure pump and enters an ultrafiltration unit for ultrafiltration to obtain a permeate phase and a retentate phase. The retentate phase enters a concentrated water storage tank. The permeate phase is pressurized by a second low-pressure pump and divided into two streams. One stream is pressurized by a first high-pressure pump and enters the first high-salt side of the first reverse osmosis unit for first reverse osmosis treatment. The effluent from the first high-salt side is pressurized by the second high-pressure pump and enters the second high-salt side of the second reverse osmosis unit for second reverse osmosis treatment. The other stream enters the second low-salt side of the second reverse osmosis unit to participate in the second reverse osmosis treatment. The effluent from the second low-salt side enters the first low-salt side of the first reverse osmosis unit to participate in the first reverse osmosis treatment. The effluent from the first low-salt side enters the aluminum dissolution precipitation tank to participate in the precipitation reaction. The second high-salt side effluent enters the concentrated water storage tank, and then enters the evaporator for evaporation treatment to obtain solid aluminum compounds and distilled water; the distilled water enters the aluminum dissolution precipitation tank to participate in alkaline leaching; The exhaust gas from aluminum casting combustion enters a gas cooling device for cooling, and then enters a carbon dioxide capture device for carbon dioxide capture reaction, resulting in exhaust gas with CO2 removed and a solution that absorbs CO2. The CO2-absorbing solution sequentially enters a heat exchanger for heating, then enters a carbon dioxide degassing device for carbon dioxide desorption reaction, and the resulting CO2 enters a carbon dioxide storage device, subsequently entering an aluminum dissolution precipitation tank to participate in a precipitation reaction.

[0011] Preferably, the pH value of the alkaline leaching is ≥13, the alkaline leaching time is 45~60 min, and the conductivity of the liquid obtained after alkaline leaching is 150000~250000 μS / cm; The pH value of the leachate obtained after the precipitation reaction is 6-7.

[0012] Preferably, the transmembrane pressure difference of the ultrafiltration is 2 bar; the conductivity of the permeate phase is 150,000~250,000 μS / cm, and the turbidity is ≤1 NTU; The volume ratio of the permeate phase entering the first high-salt side to the permeate phase entering the second low-salt side is 1:0.2~0.5.

[0013] Preferably, after the first reverse osmosis treatment, the flow ratio on the first high-salt side decreases from 1.00 to 0.91; and the flow ratio on the first low-salt side increases from 0.58 to 0.67. After the second reverse osmosis treatment, the flow ratio on the second high-salt side decreased from 0.91 to 0.83; the flow ratio on the second low-salt side increased from 0.50 to 0.58.

[0014] Preferably, the evaporation process is vacuum evaporation, wherein the temperature of vacuum evaporation is 80~90℃ and the pressure is 25~35kPa.

[0015] Preferably, the temperature of the carbon dioxide capture reaction is 35~40℃, and the temperature of the carbon dioxide desorption reaction is 100~140℃; After the carbon dioxide desorption reaction, the resulting monoethanolamine solution is cooled by a heat exchanger and then recycled into a carbon dioxide capture device.

[0016] This invention provides an aluminum resource recovery system for the synergistic utilization of aluminum casting by-products and carbon dioxide. The system includes an aluminum casting by-product treatment module and a combustion flue gas treatment module. The aluminum casting by-product treatment module includes an aluminum dissolution and precipitation tank, an ultrafiltration unit, a first reverse osmosis device, a second reverse osmosis device, a concentrated water storage tank, an evaporator, and low-pressure and high-pressure pumps in the pipelines. The combustion flue gas treatment module includes a gas cooling device, a carbon dioxide capture device, a heat exchanger, a carbon dioxide degassing device, and a carbon dioxide storage device. Aluminum casting by-products mainly exist in the form of alumina (Al2O3), metallic aluminum, and other alloy residues. These substances adhere to the molds, rendering them unusable. This invention addresses this issue by using alkaline leaching in the aluminum dissolution and precipitation tank, where metallic aluminum reacts with hydroxide ions (OH-). - The reaction occurs, producing [Al(OH)4]. - The aluminum ions enter the solution through a complex anion. By introducing carbon dioxide gas into the solution, the aluminum ions undergo a chemical reaction and precipitate as Al(OH)3 or Al2(CO3)3·xH2O. Ultrafiltration separates the precipitate, suspended solids (SS), and fine aluminum hydroxide flocs, thus preventing contamination and clogging in the subsequent reverse osmosis (RO) process. The retained phase (concentrate), which does not permeate the ultrafiltration membrane, enters the concentrate storage tank. This retained phase still contains aluminum precipitate, which, after evaporation, can be used as a raw material for subsequent resource recovery, further regenerating and enhancing the value of byproducts. Furthermore, the distilled water produced during evaporation can be returned to the aluminum dissolution and precipitation tank as alkaline leaching water for resource reuse.

[0017] In this invention, the permeate phase treated by the ultrafiltration unit still contains a large amount of aluminum ions, with a conductivity as high as 150,000~250,000 μS / cm, classifying it as high-salinity wastewater. If treated using conventional reverse osmosis, extremely high operating pressures would be required, potentially exceeding the limiting operating pressure of the reverse osmosis membrane. Therefore, to reduce the reverse osmosis operating pressure, this invention employs a special reverse osmosis operation method. By setting up two interconnected reverse osmosis units, with relatively high-salinity and low-salinity solutions respectively configured in the first and second reverse osmosis units, the osmotic pressure difference between the two sides is effectively reduced. This not only reduces concentration polarization during the reverse osmosis process but also significantly lowers the operating pressure required for system operation. The two reverse osmosis units share the same volume of water to be treated, reducing the operating load on individual units and contributing to improved overall system stability and recovery rate. The second high-salinity effluent from the second reverse osmosis unit has a higher salinity and enters the concentrate storage tank. The resulting solid aluminum compounds can be collected again and extracted into metallic aluminum through a remelting process, thus achieving the recycling and reuse of aluminum resources. The first low-salinity effluent from the first reverse osmosis unit is reintroduced into the aluminum dissolution precipitation tank. This effluent has a lower ionic strength compared to the original permeate phase treated by the ultrafiltration unit. When it re-participates in the precipitation reaction, it can reduce the ionic strength of the solution, thereby increasing the driving force of the precipitation reaction.

[0018] The waste gas generated during aluminum casting and melting typically reaches temperatures above 150-300°C. This high temperature environment makes it difficult for monoethanolamine solution to function effectively. This invention utilizes a gas cooling device to lower the temperature of the waste gas, creating suitable conditions for the carbon dioxide capture device to stably absorb carbon dioxide. Subsequently, the cooled waste gas enters the carbon dioxide capture device, where the monoethanolamine solution captures and adsorbs the carbon dioxide. The remaining gas, with carbon dioxide levels meeting standards, is either discharged or enters subsequent tail gas treatment processes. The monoethanolamine solution containing adsorbed carbon dioxide is heated by a heat exchanger and then enters a carbon dioxide degassing device for carbon dioxide desorption reaction. The resulting CO2 enters a carbon dioxide storage device and subsequently enters an aluminum dissolution precipitation tank to participate in a precipitation reaction. Furthermore, after the carbon dioxide desorption reaction, the resulting monoethanolamine solution is cooled by a heat exchanger and then recycled back into the carbon dioxide capture device. Therefore, this invention can effectively recover and reuse the heat generated during the capture and regeneration process of the monoethanolamine solution, thereby significantly reducing system energy consumption.

[0019] Therefore, this invention can simultaneously achieve the treatment of high-concentration aluminum wastewater to meet standards, the storage and recycling of carbon dioxide, and the efficient precipitation and recovery of aluminum ions, thus achieving the dual effects of environmental governance and resource utilization. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the aluminum resource recycling system for the synergistic utilization of aluminum casting by-products and carbon dioxide according to the present invention. Figure 1 In the diagram, 101-Aluminum plant, 201-Aluminum dissolution and precipitation tank, 202-First low-pressure pump, 203-Ultrafiltration unit, 204-Second low-pressure pump, 205-First high-pressure pump, 206-First reverse osmosis unit, 207-Second high-pressure pump, 208-Second reverse osmosis unit, 209-Energy recovery unit, 210-Concentrated water storage tank, 211-Evaporator, 301-Gas cooling unit, 302-Carbon dioxide capture unit, 303-Heat exchanger, 304-Carbon dioxide degassing unit, 305-Compressor, 306-Carbon dioxide storage unit. Detailed Implementation

[0021] This invention provides an aluminum resource recycling system for the synergistic utilization of aluminum casting by-products and carbon dioxide, including an aluminum casting by-product processing module and a combustion flue gas processing module. The aluminum casting by-product processing module includes an aluminum dissolution and precipitation tank. An ultrafiltration unit is connected to the outlet of the aluminum dissolution and precipitation tank; the ultrafiltration unit is provided with a permeate phase outlet and a retrieval phase outlet; a first low-pressure pump is provided between the ultrafiltration unit and the aluminum dissolution and precipitation tank; A second low-pressure pump with its inlet permeable to the ultrafiltration unit has an outlet that is divided into a first branch and a second branch. The first high-pressure pump whose inlet is connected to the first branch; The first reverse osmosis device is divided into a first high-salt side and a first low-salt side by a first reverse osmosis membrane, and the inlet of the first high-salt side is connected to the outlet of the first high-pressure pump. A second high-pressure pump whose inlet is connected to the outlet of the first high-salt side; The second reverse osmosis unit is divided into a second high-salt side and a second low-salt side by a second reverse osmosis membrane. The inlet of the second high-salt side is connected to the outlet of the second high-pressure pump. The second branch is connected to the inlet of the second low-salt side. The outlet of the second low-salt side is connected to the inlet of the first low-salt side. The outlet of the first low-salt side is connected to the inlet of the aluminum dissolution precipitation tank. A concentrated water storage tank whose inlet is connected to the outlet of the second high-salt side and the outlet of the ultrafiltration unit's filtration phase. An evaporator whose inlet is connected to the outlet of the concentrated water storage tank; the evaporator includes an aqueous phase outlet and a solid phase outlet, the aqueous phase outlet being connected to the inlet of an aluminum dissolution and precipitation tank; The combustion flue gas treatment module includes a gas cooling device, a carbon dioxide capture device, a heat exchanger, a carbon dioxide degassing device, and a carbon dioxide storage device connected in sequence. The carbon dioxide capture device contains a monoethanolamine solution, and the outlet of the carbon dioxide storage device is connected to the inlet of the aluminum dissolution and precipitation tank.

[0022] This invention provides a system for the synergistic utilization of aluminum casting by-products and carbon dioxide in aluminum resource recovery, comprising an aluminum casting by-product processing module. In this invention, the aluminum casting by-product processing module includes an aluminum dissolution and precipitation tank. Preferably, the aluminum dissolution and precipitation tank is equipped with a liquid phase inlet and a gas phase inlet. The liquid phase inlet is preferably purged with water or a sodium hydroxide solution, wherein the water is tap water or distilled water from an evaporator. This invention does not impose special requirements on the specific material or specifications of the aluminum dissolution and precipitation tank; it can be designed according to actual usage. In this invention, the aluminum casting by-products undergo alkaline leaching and CO2 precipitation reactions in the aluminum dissolution and precipitation tank to obtain a leachate.

[0023] The aluminum casting by-product treatment module of this invention includes an ultrafiltration unit whose inlet is connected to the outlet of the aluminum dissolution and precipitation tank. In this invention, the ultrafiltration membrane in the ultrafiltration unit is preferably a polyvinylidene fluoride hollow fiber membrane, with a pore size preferably of 0.01~0.05 μm, more preferably 0.02~0.04 μm, and the membrane area is determined according to actual working conditions, specifically 1.2~30 m². 2 In this invention, the ultrafiltration unit effectively retains precipitates, suspended solids (SS), and fine aluminum hydroxide flocs in the leachate, while ensuring the permeation of dissolved ions in the solution. The membrane material maintains chemical stability even at high pH levels, making it suitable for use in conjunction with a subsequent reverse osmosis unit.

[0024] The aluminum casting by-product processing module of the present invention includes a first low-pressure pump, which is disposed between the ultrafiltration unit and the aluminum dissolution and precipitation tank, and is used to increase the pressure of the leachate by 2 bar.

[0025] The aluminum casting by-product treatment module of this invention includes a second low-pressure pump whose inlet is connected to the ultrafiltration unit via permeation. The outlet of the second low-pressure pump is divided into a first branch and a second branch. In this invention, the second low-pressure pump is used to increase the pressure of the permeate water from the ultrafiltration unit by 1-2 bar.

[0026] The aluminum casting by-product processing module of this invention includes a first high-pressure pump whose inlet is connected to the first branch. In this invention, the first high-pressure pump is used to pressurize the permeate phase of the ultrafiltration unit of the first branch by 25-35 bar.

[0027] The aluminum casting by-product treatment module of this invention includes a first reverse osmosis unit, which is divided into a first high-salt side and a first low-salt side by a first reverse osmosis membrane. The inlet of the first high-salt side is connected to the outlet of a first high-pressure pump. In this invention, the first reverse osmosis membrane is preferably a polyamide hollow fiber membrane or a polyamide flat-sheet spiral wound membrane. This material has a high desalination rate and good durability, making it suitable for high-salinity water treatment processes. In this invention, the first reverse osmosis membrane is preferably a seawater-type reverse osmosis membrane.

[0028] The aluminum casting by-product treatment module of this invention includes a second high-pressure pump whose inlet is connected to the outlet of the first high-salt side. In this invention, the second high-pressure pump is used to apply a differential pressure of 10-15 bar to the effluent from the first high-salt side of the first reverse osmosis membrane.

[0029] The aluminum casting by-product treatment module of this invention includes a second reverse osmosis unit, which is divided into a second high-salt side and a second low-salt side by a second reverse osmosis membrane. The inlet of the second high-salt side is connected to the outlet of a second high-pressure pump. In this invention, the second reverse osmosis membrane is preferably a polyamide hollow fiber membrane or a polyamide flat-sheet spiral wound membrane. In this invention, the second reverse osmosis membrane is preferably a seawater-type reverse osmosis membrane.

[0030] In this invention, the second reverse osmosis unit and the first reverse osmosis unit are interconnected. Specifically, the high-salt side of the first reverse osmosis unit and the low-salt side of the second reverse osmosis unit are connected in the forward direction, and the reverse side is connected in the reverse direction. In this invention, the second branch is connected to the inlet of the second low-salt side. By setting up two interconnected reverse osmosis units, and configuring relatively high-salinity solutions and low-salinity solutions in the first and second reverse osmosis units respectively, this invention effectively reduces the osmotic pressure difference between the two sides. This not only reduces concentration polarization during the reverse osmosis process but also significantly reduces the operating pressure required for system operation. The two reverse osmosis units share the treatment capacity of the same water, which not only reduces the operating load of individual units but also helps improve the overall stability and recovery rate of the system.

[0031] The aluminum casting by-product treatment module of this invention includes a concentrated water storage tank whose inlet is connected to the outlet of the second high-salt side and the outlet of the ultrafiltration unit's retained phase. In this invention, the concentrated water storage tank is used to store the retained phase liquid of the ultrafiltration unit and the effluent from the second high-salt side of the second reverse osmosis unit, and to transport it to the evaporator.

[0032] In this invention, an energy recovery device is preferably provided between the outlet of the second high-salinity side of the second reverse osmosis unit and the inlet of the concentrate storage tank. In this invention, the effluent from the second high-salinity side also has relatively high water pressure; therefore, the residual pressure can be recovered by the turbine-type energy recovery device before entering the concentrate storage tank. In this invention, the residual pressure carried by the effluent from the second high-salinity side is preferably recovered in the form of shaft work. In this invention, the energy recovery device is preferably a turbine-type energy recovery device, and the recovered energy can be reused in different stages within the system.

[0033] The aluminum casting by-product processing module of this invention includes an evaporator whose inlet is connected to the outlet of the concentrated water storage tank; the evaporator includes an aqueous phase outlet and a solid phase outlet, and the aqueous phase outlet is connected to the inlet of the aluminum dissolution and precipitation tank. In this invention, the evaporator is preferably a vacuum evaporator.

[0034] The aluminum resource recovery system for the synergistic utilization of aluminum casting by-products and carbon dioxide provided by this invention includes a combustion flue gas treatment module, which includes a gas cooling device. This invention does not impose any special requirements on the gas cooling device; any cooling device well-known in the art can be used.

[0035] The combustion flue gas treatment module of the present invention includes a carbon dioxide capture device, wherein the carbon dioxide capture device contains a monoethanolamine solution. In the present invention, the carbon dioxide capture device preferably includes a gas inlet, a monoethanolamine solution inlet, a gas outlet, and a CO2 absorption solution outlet. In the present invention, the mass concentration of the monoethanolamine solution is preferably 20-30 wt%, more preferably 25 wt%.

[0036] The combustion flue gas treatment module of this invention includes a heat exchanger, preferably a plate heat exchanger or a shell-and-tube heat exchanger. In this invention, the heat exchanger is used to raise the temperature of the CO2-absorbing solution discharged from the carbon dioxide capture device and to lower the temperature of the regenerated monoethanolamine solution discharged from the carbon dioxide degassing device.

[0037] The combustion flue gas treatment module of this invention includes a carbon dioxide degassing device, which is used to absorb the thermal decomposition reaction of a monoethanolamine solution containing CO2, thereby releasing carbon dioxide and regenerating the monoethanolamine solution. In this invention, the carbon dioxide degassing device also has a liquid phase outlet, which is connected to the liquid phase inlet of a carbon dioxide capture device via a heat exchanger.

[0038] The combustion flue gas treatment module of this invention includes a carbon dioxide storage device, the outlet of which is connected to the inlet of the aluminum dissolution and precipitation tank. By connecting the carbon dioxide storage device to the inlet of the aluminum dissolution and precipitation tank, this invention can simultaneously achieve the treatment of high-concentration aluminum wastewater to meet standards and the storage and recycling of carbon dioxide.

[0039] In this invention, a compressor is preferably provided between the carbon dioxide degassing device and the carbon dioxide storage device.

[0040] In this invention, a schematic diagram of the aluminum resource recycling system for the synergistic utilization of aluminum casting by-products and carbon dioxide is shown below. Figure 1 As shown.

[0041] This invention provides a method for aluminum resource recovery by synergistically utilizing aluminum casting byproducts and carbon dioxide, comprising the following steps: Aluminum casting byproducts enter an aluminum dissolving and precipitation tank, are mixed with water and an alkaline regulator, and undergo alkaline leaching. CO2 is then introduced to carry out a precipitation reaction, yielding a leachate. The leachate is pressurized by a first low-pressure pump and enters an ultrafiltration unit for ultrafiltration to obtain a permeate phase and a retentate phase. The retentate phase enters a concentrated water storage tank. The permeate phase is pressurized by a second low-pressure pump and divided into two streams. One stream is pressurized by a first high-pressure pump and enters the first high-salt side of the first reverse osmosis unit for first reverse osmosis treatment. The effluent from the first high-salt side is pressurized by the second high-pressure pump and enters the second high-salt side of the second reverse osmosis unit for second reverse osmosis treatment. The other stream enters the second low-salt side of the second reverse osmosis unit to participate in the second reverse osmosis treatment. The effluent from the second low-salt side enters the first low-salt side of the first reverse osmosis unit to participate in the first reverse osmosis treatment. The effluent from the first low-salt side enters the aluminum dissolution precipitation tank to participate in the precipitation reaction. The second high-salt side effluent enters the concentrated water storage tank, and then enters the evaporator for evaporation treatment to obtain solid aluminum compounds and distilled water; the distilled water enters the aluminum dissolution precipitation tank to participate in alkaline leaching; The exhaust gas from aluminum casting combustion enters a gas cooling device for cooling, and then enters a carbon dioxide capture device for carbon dioxide capture reaction, resulting in exhaust gas with CO2 removed and a solution that absorbs CO2. The CO2-absorbing solution sequentially enters a heat exchanger for heating, then enters a carbon dioxide degassing device for carbon dioxide desorption reaction, and the resulting CO2 enters a carbon dioxide storage device, subsequently entering an aluminum dissolution precipitation tank to participate in a precipitation reaction.

[0042] In this invention, the aluminum casting byproducts are introduced into an aluminum dissolution and precipitation tank, mixed with water and an alkaline regulator, and subjected to alkaline leaching. CO2 is then introduced to induce a precipitation reaction, yielding a leachate. In this invention, the aluminum casting byproducts refer to aluminum-containing solids generated during the aluminum casting process or aluminum-containing solids remaining in the mold. When the aluminum casting byproducts are aluminum-containing solids remaining in the mold, this invention preferably places the mold containing the aluminum casting byproducts in an aluminum dissolution and precipitation tank, and removes it after alkaline leaching.

[0043] In this invention, the alkaline regulator is preferably NaOH or NaOH solution. In this invention, the pH value of the alkaline leaching is preferably ≥13, the leaching time is preferably 45-60 min, more preferably 50-55 min; the conductivity of the liquid obtained after alkaline leaching is preferably 150000-250000 μS / cm, more preferably 200000 μS / cm. In this invention, during the alkaline leaching process, metallic aluminum reacts with hydroxide ions (OH-). - The reaction occurs, producing [Al(OH)4]. - The complex anion enters the solution, and the reaction process is shown in Equation 1: Formula 1.

[0044] This process effectively removes aluminum adhering to the mold, enabling the reuse of the aluminum mold. However, the solution in the aluminum dissolution and precipitation tank maintains a pH above 13 and an aluminum ion concentration exceeding 200,000 μS / cm, making it extremely alkaline. Direct discharge of such a solution without treatment would not only cause serious environmental pollution but also lead to the loss of aluminum resources; therefore, further recycling measures are necessary.

[0045] After the aluminum by-products are leached alkaline, carbon dioxide gas is introduced into the solution in this invention. This causes aluminum ions to undergo a chemical reaction and precipitate as Al(OH)3 precipitate or Al2(CO3)3·xH2O. The pH value of the leachate obtained after the precipitation reaction is preferably 6-7. This invention does not have special requirements for the flow rate and time of the carbon dioxide gas introduction, as long as the pH value of the leachate reaches 6-7. As a specific embodiment of this invention, the flow rate of the carbon dioxide gas is preferably 0.5-0.8 Nm. 3 / h, more preferably 0.6 Nm 3 / h, the infusion time is preferably 60~80min, more preferably 70min.

[0046] In the process of introducing CO2, the present invention preferably includes adding acid to the solution to adjust the pH value of the precipitation reaction to 6-7, thereby promoting the precipitation reaction.

[0047] In this invention, the process of introducing carbon dioxide gas achieves several benefits. First, the addition of carbon dioxide lowers the pH value of the solution, allowing some of the aluminum in high-concentration aluminum-containing wastewater to precipitate and be removed, thereby effectively suppressing unnecessary osmotic pressure increases in the subsequent reverse osmosis (RO) process. Second, the decrease in pH helps maintain the chemical stability of the membrane material during the operation of subsequent ultrafiltration (UF) and RO membrane separation units, preventing membrane damage from alkaline environments. Finally, introducing carbon dioxide emitted from the aluminum foundry into the wastewater treatment stage achieves carbon dioxide fixation and reuse, thus contributing to the reduction of greenhouse gas emissions.

[0048] In this invention, the reaction process of the precipitation reaction is shown in Formula 2: Equation 2.

[0049] Under strongly alkaline conditions, aluminum ions typically exist as [Al(OH)4]. - It exists stably in its original form; however, as the pH decreases, it gradually transforms into Al. 3+ The aluminum reacts with Al(OH)3(s) to form an insoluble precipitate. This process increases the supersaturation of the solution, accelerating the precipitation reaction. Therefore, this invention enables the continuous recovery of aluminum, while the resulting precipitate is continuously removed by an ultrafiltration device.

[0050] After obtaining the leachate, the present invention pressurizes the leachate through a first low-pressure pump and sends it into an ultrafiltration unit for ultrafiltration to obtain a permeate phase and a retentate phase. The retentate phase enters a concentrated water storage tank. In the present invention, the pressurization pressure of the first pressurizing pump is preferably 2 bar.

[0051] In this invention, ultrafiltration effectively removes precipitates, suspended solids (SS), and fine aluminum hydroxide flocs, thereby preventing contamination and clogging in subsequent RO membrane separation processes. The recovery rate of the ultrafiltration treatment is preferably ≥90%. To achieve a high recovery rate of over 90%, the system typically operates at a pressure of 2 bar. After ultrafiltration, the permeate phase enters a second low-pressure pump and continues to be transported to the subsequent reverse osmosis stage, while the retained phase that does not permeate the ultrafiltration membrane enters the concentrate storage tank. The retained phase still contains aluminum precipitates, which can be used as raw materials for subsequent resource recovery, further realizing the regeneration and value enhancement of by-products. In this invention, the conductivity of the permeate phase is preferably 150,000~250,000 μS / cm, more preferably 200,000 μS / cm, and the turbidity is preferably ≤1 NTU.

[0052] In this invention, the permeate phase is pressurized by a second low-pressure pump and divided into two streams. One stream is pressurized by a first high-pressure pump and enters the first high-salt side of the first reverse osmosis unit for first reverse osmosis treatment. The effluent from the first high-salt side is pressurized by the second high-pressure pump and enters the second high-salt side of the second reverse osmosis unit for second reverse osmosis treatment. The other stream enters the second low-salt side of the second reverse osmosis unit to participate in the second reverse osmosis treatment. The effluent from the second low-salt side enters the first low-salt side of the first reverse osmosis unit to participate in the first reverse osmosis treatment. The effluent from the first low-salt side enters the aluminum dissolution precipitation tank to participate in the precipitation reaction. In this invention, the pressure applied by the second low-pressure pump is preferably 1~2 bar. In this invention, the volume ratio of the permeate phase entering the first high-salt side to the permeate phase entering the second low-salt side is preferably 1:0.2~0.5, more preferably 1:0.3~0.4.

[0053] In this invention, the second high-pressure pump preferably applies a differential pressure of 10 to 15 bar to the first high-salt side outlet water of the first reverse osmosis membrane.

[0054] In one embodiment of the present invention, after the first reverse osmosis treatment, with the influent flow rate on the first high-salt side being 1.00, the flow rate ratio on the first high-salt side decreases from 1.00 to 0.91, and the conductivity increases from 200,000 μS / cm to 220,000 μS / cm; the flow rate ratio on the first low-salt side increases from 0.58 to 0.67, and the conductivity decreases from 171,631 μS / cm to 148,466 μS / cm.

[0055] After the second reverse osmosis treatment, the flow ratio on the second high-salt side preferably decreases from 0.91 to 0.83, and the conductivity increases from 220,000 μS / cm to 242,000 μS / cm; the flow ratio on the second low-salt side increases from 0.50 to 0.58, and the conductivity decreases from 200,000 μS / cm to 171,631 μS / cm.

[0056] In this invention, the effluent from the first low-salt side of the first reverse osmosis unit is reintroduced into the aluminum dissolution and precipitation tank to participate in the precipitation reaction, thereby achieving secondary precipitation. In high-concentration aluminum solutions, the excessively high ionic strength results in a significant charge shielding effect, which inhibits the formation of metal ion hydroxides, making the precipitation reaction difficult to proceed smoothly. Therefore, returning the relatively diluted water after reverse osmosis treatment to the reaction tank can reduce the ionic strength of the solution, thereby increasing the driving force of the precipitation reaction.

[0057] In this invention, the second high-salinity side effluent enters a concentrated water storage tank, and then enters an evaporator for evaporation treatment to obtain solid aluminum compounds and distilled water; the distilled water then enters an aluminum dissolution and precipitation tank to participate in alkaline leaching. Before entering the concentrated water storage tank, since the second high-salinity side effluent also has high water pressure, this invention preferably uses an energy recovery device to recover the energy from the second high-salinity side effluent. The recovered energy can be reused in different stages within the system.

[0058] In this invention, the evaporation process is preferably vacuum evaporation, wherein the temperature of vacuum evaporation is preferably 80-90°C, more preferably 85°C, and the pressure is preferably 25-35 kPa, more preferably 30 kPa. The distilled water produced during the evaporation process can be returned to the aluminum dissolution and precipitation tank for diluting the influent and for reuse.

[0059] In this invention, the exhaust gas from aluminum casting combustion is cooled by a gas cooling device, and then enters a carbon dioxide capture device for a carbon dioxide capture reaction, yielding exhaust gas with removed CO2 and a solution that absorbs CO2. In this invention, the temperature of the exhaust gas from aluminum casting combustion is preferably 150-300°C. This high-temperature environment would hinder the effective functioning of the carbon dioxide capture absorbent. Therefore, the exhaust gas must first enter the gas cooling device to lower the temperature to below 40°C, thereby creating suitable conditions for the monoethanolamine solution to stably absorb carbon dioxide. In this invention, the temperature of the carbon dioxide capture reaction is preferably 35-40°C, and the time is preferably 20-30 minutes. During the carbon dioxide capture reaction, monoethanolamine (MEA) reacts with carbon dioxide to generate a solution that absorbs CO2, the main component of which is ethanolamine bicarbonate salt.

[0060] In this invention, the CO2-absorbing solution sequentially enters a heat exchanger for heating, then enters a carbon dioxide degassing device for a carbon dioxide desorption reaction. The resulting CO2 enters a carbon dioxide storage device, and subsequently enters an aluminum dissolution precipitation tank to participate in a precipitation reaction. In this invention, the preferred temperature for the carbon dioxide desorption reaction is 100-140°C, more preferably 120-130°C, and the preferred time is 40-60 min, more preferably 50 min. During the carbon dioxide desorption reaction, a thermal decomposition reaction occurs, releasing carbon dioxide and regenerating the monoethanolamine solution. In this invention, the regenerated monoethanolamine solution is cooled to a suitable temperature via a heat exchanger and then recycled back to the carbon dioxide capture device. This design effectively recovers and reuses the heat generated during the capture and regeneration processes, thereby significantly reducing system energy consumption.

[0061] In this invention, the carbon dioxide separated in the carbon dioxide desorption reaction is preferably 90-99% pure. After being compressed by a compressor, it is transported to a carbon dioxide storage device for storage. The stored carbon dioxide can be reintroduced into an aluminum dissolution and precipitation tank to adjust the pH value of highly alkaline wastewater and promote the precipitation reaction of aluminum ions. Therefore, this invention achieves both aluminum removal and carbon dioxide immobilization in wastewater, achieving the dual effects of environmental remediation and resource utilization.

[0062] The following detailed description, in conjunction with embodiments, of the system and method for aluminum resource recovery through the synergistic utilization of aluminum casting by-products and carbon dioxide provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0063] The following examples use Figure 1 The system shown represents the recovery of aluminum resources through the co-utilization of aluminum casting byproducts and carbon dioxide. Example 1: Pilot-scale continuous operation (daily processing capacity 3 m³) 3 ) In the aluminum casting by-product treatment module, the aluminum casting by-products are added to an aluminum dissolution and precipitation tank. The pH of the solution is adjusted to 13.3 using NaOH, and the liquid volume is set to 2.5 m³. 3 The stirring and dissolving time should be set to 45-60 minutes to facilitate the formation of [Al(OH)4]. - The stable liquid phase baseline was established; the initial conductivity of the solution after dissolution was 200,000 μS / cm, the soluble aluminum content was 4.8 g / L, the suspended solids content was 0.6 g / L, and the temperature was 30 ℃. After confirming complete aluminum dissolution, the solution was subjected to a concentration of 0.6 Nm... 3 CO2 is introduced at a rate of / h and contacted for 70 min to reduce the pH value to 6.9; the Al(OH)3 flocs are allowed to stand for 20 min to stabilize, and then pressurized to 2 bar by the first low-pressure pump before entering the ultrafiltration unit for processing.

[0064] The ultrafiltration unit uses a PVDF hollow fiber membrane with an average pore size of 0.02 μm and a membrane area of ​​1.2 m². 2 The transmembrane pressure difference is 2 bar, the recovery rate is 90%, and the target is to remove flocs and suspended solids. The conductivity of the resulting permeate remains unchanged before and after ultrafiltration, and the turbidity of the permeate is controlled below 1 NTU and used as feed water for reverse osmosis. The resulting retentate enters the concentrate storage tank.

[0065] The reverse osmosis section employs an interconnected configuration of a first reverse osmosis unit and a second reverse osmosis unit. A second low-pressure pump pressurizes the permeate by 1.5 bar, splitting it into two streams. The first stream enters the low-salt side of the second reverse osmosis unit, while the second stream, pressurized by a first high-pressure pump, enters the high-salt side of the first reverse osmosis unit. The volume ratio of the first to second streams is 0.2–0.5:1. The outlet pressure of the first high-pressure pump is set within the range of 25–35 bar based on the effective drive pressure and membrane flux, and fine-tuned according to online parameters, with a 10% concentration rate as the operating target for this section. The second high-pressure pump applies a differential pressure of 10–15 bar to the effluent from the first high-salt side of the first reverse osmosis membrane. During stable operation, the following representative values ​​were observed: The high-salt side flow ratio of the first reverse osmosis unit decreased from 1.00 to 0.91, and the conductivity increased from 200,000 μS / cm to 220,000 μS / cm; the low-salt side flow ratio of the first reverse osmosis unit increased from 0.58 to 0.67, and the conductivity decreased from 171,631 μS / cm to 148,466 μS / cm; the high-salt side flow ratio of the second reverse osmosis unit decreased from 0.91 to 0.83, and the conductivity increased from 220,000 μS / cm to 242,000 μS / cm; the low-salt side flow ratio of the second reverse osmosis unit increased from 0.50 to 0.58, and the conductivity decreased from 200,000 μS / cm to 171,631 μS / cm. The high-salt side effluent (high-salt concentrate) from the second reverse osmosis unit, after recovering residual pressure through a turbine-type energy recovery device, enters the concentrate storage tank, while the low-salt side effluent from the first reverse osmosis unit is returned to the aluminum dissolution sedimentation tank.

[0066] The energy recovery and evaporation sections adhere to hydraulic consistency. The discharge pressure on the high-salt side of the second reverse osmosis unit is 2 bar lower than the RO feed main pressure at the outlet of the first high-pressure pump. The residual pressure carried is recovered in the energy recovery unit as shaft work and fed back to the drive end, with a recovery rate controlled at 30%. The high-salt concentrated water enters the energy recovery unit, with a typical aluminum content of 9.2 g / L and a sludge content of 1.1 g / L. It then enters the evaporator and operates under reduced pressure evaporation conditions of 85 ℃ in the jacket, 30 kPa absolute pressure, and a residence time of 4 h. The resulting distilled water has a conductivity of 120 μS / cm and is returned to the aluminum dissolution precipitation tank to regulate ionic strength. The solid product is aluminum hydroxide mainly composed of gibbsite.

[0067] In the combustion flue gas treatment module, the CO2 content of the aluminum casting combustion exhaust gas is 12 vol%, and the temperature is 180 ℃. After being cooled to 35 ℃ by a gas cooling device, it enters the carbon dioxide capture device. The absorbent is a 25 wt% monoethanolamine solution. After contacting for 30 minutes, the amine-rich loading is 0.45 (mol CO2 / mol MEA). After heat exchange, it enters the carbon dioxide degassing device for desorption at 120~125 ℃. After desorption, the regenerated solution is passed through a heat exchanger, cooled to 40~60 ℃, and returned to the carbon dioxide capture device for reuse. The CO2 generated after desorption in the carbon dioxide degassing device is compressed by a compressor to a concentration of 0.6 Nm³. 3 The material is continuously fed back to the aluminum dissolution and precipitation tank at a rate of / h.

[0068] Example 2: Scale-up Operation (Daily Processing 20 m³) 3 ) In the aluminum casting by-product treatment module, an alkaline solution with a pH of 13.5 is prepared using NaOH in an aluminum dissolution and precipitation tank, and the aluminum casting by-products are added and stirred for 60 min to dissolve. After confirming complete dissolution, the by-products are then treated with 3.0 Nm³ of NaOH solution. 3 CO2 is introduced at a rate of / h and contacted for 60-80 minutes to lower the pH to 6.8, while maintaining the temperature at 32 ℃. After standing for 20 minutes to stabilize the generated Al(OH)3 flocs, the mixture is pressurized to 2 bar by the first low-pressure pump and then enters the ultrafiltration unit for processing.

[0069] The ultrafiltration unit uses a PVDF hollow fiber membrane with a pore size of 0.02~0.04 μm and a membrane area of ​​8 m². 2 The transmembrane pressure difference was 2 bar, the recovery rate was 92%, and the conductivity remained unchanged before and after ultrafiltration, with the permeate conductivity ranging from 175,000 to 185,000 μS / cm. The reverse osmosis section employed a configuration where a first and second reverse osmosis unit were interconnected. A second low-pressure pump divided the permeate into two streams. The first stream entered the low-salt side of the second reverse osmosis unit at 1.5 bar, while the second stream, pressurized to 25-35 bar by a first high-pressure pump, entered the high-salt side of the first reverse osmosis unit. The volume ratio of the first to second streams was 0.2-0.5:1. The second high-pressure pump applied a differential pressure of 10-15 bar to the effluent from the first high-salt side of the first reverse osmosis membrane. Within the steady-state range, the flow ratio and conductivity of the high-salt and low-salt sides of the first and second reverse osmosis units were similar to those in Example 1. The high-salt side effluent from the second reverse osmosis unit, after recovering residual pressure through a turbine-type energy recovery device, enters the concentrate storage tank, while the low-salt side effluent from the first reverse osmosis unit is returned to the aluminum dissolution sedimentation tank.

[0070] The energy recovery section uses the pump outlet side as a reference to stabilize the hydraulic relationship. The discharge pressure on the high-salt side of the second reverse osmosis unit is 2 bar lower than the RO feed main pressure on the outlet side of the first high-pressure pump, and is recovered in the form of shaft work in the energy recovery unit, with a recovery rate controlled at a target of 30%. After the high-salt concentrate enters the concentrate storage tank, it is subjected to reduced pressure evaporation in the evaporator under conditions of shell side 88 ℃, absolute pressure 28 kPa, and residence time of 5 h. The resulting distilled water is returned to the aluminum dissolution precipitation tank, and the solid product is mainly Al(OH)3.

[0071] In the combustion flue gas treatment module, the CO2 content of the aluminum casting combustion exhaust gas is 12 vol%, and the temperature is 180 ℃. After being cooled to 33~37℃ by the gas cooling device, it enters the carbon dioxide capture device. The carbon dioxide capture device uses a 30 wt% monoethanolamine solution and operates with a contact time of 25~35 min. The carbon dioxide degassing device is regenerated at 120~130 ℃ to reduce the rich amine load from 0.47 (mol CO2 / mol MEA) to 0.20 (mol CO2 / mol MEA). The CO2 at the top of the tower is compressed by 305 and continuously fed back to the aluminum dissolution precipitation tank at a rate of 2.5~3.0 Nm³ / h.

[0072] Example 3: Integrated Engineering Operation (Daily Processing Capacity of 50 m³) 3 ) In the aluminum casting by-product treatment module, a 40 m³ aluminum melting and precipitation tank is established. 3 The alkaline solution was prepared and the pH value stabilized at 13.2. After complete dissolution of aluminum by mechanical stirring for 45-60 min, it was then discharged at 6.0 Nm³. 3 CO2 is introduced at a rate of / h and contacted for 60 min to lower the pH to 6.7, while maintaining the bath temperature at 30~32 ℃. After stable Al(OH)3 flocs are formed, the resulting leachate is pressurized to 2 bar by the first low-pressure pump and then enters the ultrafiltration unit for treatment.

[0073] The ultrafiltration unit uses four parallel PVDF modules with a total membrane area of ​​30 m². 2 The transmembrane pressure difference was 2 bar, the recovery rate was 93%, and the transmembrane flux was 45–55 L·m. -2 ·h -1 The conductivity remains unchanged before and after ultrafiltration. The reverse osmosis section adopts a configuration where the first and second reverse osmosis units are interconnected. After being pressurized by the second low-pressure pump, the permeate phase is divided into two streams. The first stream is driven at 0.7 m at 1.5~3 bar. 3 The second stream enters the low-salt side of the second reverse osmosis unit at a rate of / h. After being pressurized to 25~35 bar by the first high-pressure pump, it flows for 1.4 m. 3The first stream flows into the high-salt side of the reverse osmosis unit at a rate of 0.2-0.5:1. A second high-pressure pump applies a differential pressure of 10-15 bar to the high-salt side effluent of the first reverse osmosis membrane. During stable operation, the flow ratio and conductivity of the high-salt and low-salt sides of the first and second reverse osmosis units are similar to those in Example 1. The overall system recovery rate is 50%, with the low-salt side portion of the first reverse osmosis unit being recirculated to the aluminum dissolution precipitation tank to reduce ionic strength and promote redeposition.

[0074] The energy recovery and evaporation unit employs hydraulic control with the pump outlet side as a reference. The discharge pressure on the high-salt side of the second reverse osmosis unit is 2 bar lower than the RO feed main pressure on the outlet side of the first high-pressure pump. The residual pressure carried is supplied to the drive end after shaft power recovery in the energy recovery unit. The typical aluminum content of the high-salt mixed flow in the concentrate storage tank is 9~11 g / L, and the sludge content is 1~2 g / L. It enters the evaporator and completes reduced pressure evaporation under the conditions of absolute pressure 25~30 kPa, shell side 90 ℃, and residence time of 5~6 h. The resulting distilled water has a conductivity of 100~180 μS / cm and is returned to the aluminum dissolution precipitation tank. The final solid product is an aluminum compound mainly composed of gibbsite.

[0075] In the combustion flue gas treatment module, the CO2 content of the aluminum casting combustion exhaust gas is 10-13 vol%, and the temperature is 160-220℃. After being cooled to 35-40℃ by the gas cooling device, it enters the carbon dioxide capture device. It operates with a 25-30 wt% monoethanolamine solution, a reflux ratio of 1.2-1.5, and a residence time of 20-30 min. After heat exchange in the heat exchanger, it is regenerated in the carbon dioxide degassing device at 120-130℃, and the lean amine is stabilized in the range of 0.18-0.22 (mol CO2 / mol MEA). The CO2 at the top of the tower is compressed by 305 and released at a concentration of 5-6 Nm³. 3 / h continuous return aluminum dissolution and precipitation tank.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An aluminum resource recycling system for the synergistic utilization of aluminum casting by-products and carbon dioxide, characterized in that, Includes an aluminum casting by-product processing module and a combustion flue gas processing module; The aluminum casting by-product processing module includes an aluminum dissolution and precipitation tank. An ultrafiltration unit is connected to the outlet of the aluminum dissolution and precipitation tank; the ultrafiltration unit is provided with a permeate phase outlet and a retrieval phase outlet; a first low-pressure pump is provided between the ultrafiltration unit and the aluminum dissolution and precipitation tank; A second low-pressure pump with its inlet permeable to the ultrafiltration unit has an outlet that is divided into a first branch and a second branch. The first high-pressure pump whose inlet is connected to the first branch; The first reverse osmosis device is divided into a first high-salt side and a first low-salt side by a first reverse osmosis membrane, and the inlet of the first high-salt side is connected to the outlet of the first high-pressure pump. A second high-pressure pump whose inlet is connected to the outlet of the first high-salt side; The second reverse osmosis unit is divided into a second high-salt side and a second low-salt side by a second reverse osmosis membrane. The inlet of the second high-salt side is connected to the outlet of the second high-pressure pump. The second branch is connected to the inlet of the second low-salt side. The outlet of the second low-salt side is connected to the inlet of the first low-salt side. The outlet of the first low-salt side is connected to the inlet of the aluminum dissolution precipitation tank. A concentrated water storage tank whose inlet is connected to the outlet of the second high-salt side and the outlet of the ultrafiltration unit's filtration phase. An evaporator whose inlet is connected to the outlet of the concentrated water storage tank; the evaporator includes an aqueous phase outlet and a solid phase outlet, the aqueous phase outlet being connected to the inlet of an aluminum dissolution and precipitation tank; The combustion flue gas treatment module includes a gas cooling device, a carbon dioxide capture device, a heat exchanger, a carbon dioxide degassing device, and a carbon dioxide storage device connected in sequence. The carbon dioxide capture device contains a monoethanolamine solution, and the outlet of the carbon dioxide storage device is connected to the inlet of the aluminum dissolution and precipitation tank.

2. The system according to claim 1, characterized in that, The ultrafiltration membrane in the ultrafiltration unit is a polyvinylidene fluoride hollow fiber membrane with a pore size of 0.01~0.05 μm; The first reverse osmosis membrane and the second reverse osmosis membrane are independently polyamide hollow fiber membranes or polyamide flat spiral wound membranes.

3. The system according to claim 1, characterized in that, An energy recovery device is installed between the outlet of the second high-salt side of the second reverse osmosis unit and the inlet of the concentrated water storage tank.

4. The system according to claim 1, characterized in that, The mass concentration of the monoethanolamine solution is 20-30 wt%. The carbon dioxide degassing device is provided with a liquid phase outlet, which is connected to the liquid phase inlet of the carbon dioxide capture device via a heat exchanger.

5. A method for aluminum resource recovery by synergistically utilizing aluminum casting by-products and carbon dioxide, characterized in that, The aluminum resource recovery system employing the co-utilization of aluminum casting by-products and carbon dioxide as described in any one of claims 1 to 4 includes the following steps: Aluminum casting byproducts enter an aluminum dissolving and precipitation tank, are mixed with water and an alkaline regulator, and undergo alkaline leaching. CO2 is then introduced to carry out a precipitation reaction, yielding a leachate. The leachate is pressurized by a first low-pressure pump and enters an ultrafiltration unit for ultrafiltration to obtain a permeate phase and a retentate phase. The retentate phase enters a concentrated water storage tank. The permeate phase is pressurized by a second low-pressure pump and divided into two streams. One stream is pressurized by a first high-pressure pump and enters the first high-salt side of the first reverse osmosis unit for first reverse osmosis treatment. The effluent from the first high-salt side is pressurized by the second high-pressure pump and enters the second high-salt side of the second reverse osmosis unit for second reverse osmosis treatment. The other stream enters the second low-salt side of the second reverse osmosis unit to participate in the second reverse osmosis treatment. The effluent from the second low-salt side enters the first low-salt side of the first reverse osmosis unit to participate in the first reverse osmosis treatment. The effluent from the first low-salt side enters the aluminum dissolution precipitation tank to participate in the precipitation reaction. The second high-salt side effluent enters the concentrated water storage tank, and then enters the evaporator for evaporation treatment to obtain solid aluminum compounds and distilled water; the distilled water enters the aluminum dissolution precipitation tank to participate in alkaline leaching; The exhaust gas from aluminum casting combustion enters a gas cooling device for cooling, and then enters a carbon dioxide capture device for carbon dioxide capture reaction, resulting in exhaust gas with CO2 removed and a solution that absorbs CO2. The CO2-absorbing solution sequentially enters a heat exchanger for heating, then enters a carbon dioxide degassing device for carbon dioxide desorption reaction, and the resulting CO2 enters a carbon dioxide storage device, subsequently entering an aluminum dissolution precipitation tank to participate in a precipitation reaction.

6. The method according to claim 5, characterized in that, The pH value of the alkaline leaching is ≥13, the alkaline leaching time is 45~60min, and the conductivity of the liquid obtained after alkaline leaching is 150000~250000 μS / cm. The pH value of the leachate obtained after the precipitation reaction is 6-7.

7. The method according to claim 5, characterized in that, The transmembrane pressure difference of the ultrafiltration is 2 bar; the conductivity of the permeate phase is 150,000~250,000 μS / cm, and the turbidity is ≤1 NTU. The volume ratio of the permeate phase entering the first high-salt side to the permeate phase entering the second low-salt side is 1:0.2~0.

5.

8. The method according to claim 5, characterized in that, After the first reverse osmosis treatment, the flow ratio on the first high-salt side decreased from 1.00 to 0.91; the flow ratio on the first low-salt side increased from 0.58 to 0.

67. After the second reverse osmosis treatment, the flow ratio on the second high-salt side decreased from 0.91 to 0.83; The flow ratio on the second low-salt side increased from 0.50 to 0.

58.

9. The method according to claim 5, characterized in that, The evaporation process is vacuum evaporation, and the vacuum evaporation temperature is 80~90℃ and the pressure is 25~35 kPa.

10. The method according to claim 5, characterized in that, The temperature of the carbon dioxide capture reaction is 35~40℃, and the temperature of the carbon dioxide desorption reaction is 100~140℃; After the carbon dioxide desorption reaction, the resulting monoethanolamine solution is cooled by a heat exchanger and then recycled into a carbon dioxide capture device.

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