Carbon dioxide capture methods and systems

Abstract

The present invention provides a carbon dioxide capture method and system thereof. The method includes: (1) passing the gas to be treated through a membrane module and then entering an aqueous absorbent solution for carbon dioxide absorption treatment to obtain an absorbent liquid; (2) electrolyzing the absorbent liquid to obtain carbon dioxide. This method can not only achieve effective capture of carbon dioxide and reduce secondary pollution, but also greatly reduce energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture technology, specifically relating to a carbon dioxide capture method and system. Background Technology

[0002] Low-carbon emission reduction technologies are a focus of attention in industry and academia. Direct CO2 capture (DAC) technology refers to the capture of carbon dioxide (CO2) from ambient air. This technology can effectively reduce the concentration of CO2 in the atmosphere and is an important technological path to achieve carbon neutrality.

[0003] Currently, DAC (Clean Air Depletion) technology includes solvent absorption and adsorption methods. Solvent absorption involves using an alkaline solution to absorb CO2 from the air, producing carbonate precipitates, which are then calcined and regenerated. Solvent absorption often consumes large amounts of water, and the calcination and regeneration temperatures are often as high as 900℃, resulting in high energy consumption. Adsorption methods involve using adsorbents to absorb CO2 from the air. On the one hand, common adsorbents have relatively small adsorption capacities. To increase adsorption capacity, the amount of adsorbent used is often increased, but excessive adsorbent leads to overly large adsorption equipment. While organic amine-modified adsorbents have relatively superior adsorption capacities compared to other adsorbents, the tendency of organic amines to leach out often leads to secondary environmental pollution. On the other hand, the solid nature of adsorbents results in poor fluidity, which in turn creates difficulties for their recycling and regeneration. Summary of the Invention

[0004] This invention provides a carbon dioxide capture method and system. The method uses membrane absorption to capture carbon dioxide in the gas to be treated, and then uses an electrochemical method to regenerate the carbon dioxide. This method can not only achieve effective capture of carbon dioxide and reduce secondary pollution, but also greatly reduce energy consumption.

[0005] In one aspect, the present invention provides a carbon dioxide capture method, comprising the following steps: (1) passing the gas to be treated through a membrane module and then into an absorbent aqueous solution for carbon dioxide absorption treatment to obtain an absorbent liquid; (2) electrolyzing the absorbent liquid to obtain carbon dioxide.

[0006] According to one embodiment of the present invention, the absorbent aqueous solution is an alkaline aqueous solution.

[0007] According to one embodiment of the present invention, the absorbent includes at least one of alkaline inorganic substances and nitrogen-containing organic substances; the nitrogen-containing organic substances include at least one of amino acid salts and organic alcohol amines.

[0008] According to one embodiment of the present invention, the mass concentration of the absorbent in the absorbent aqueous solution is 10wt%-60wt%.

[0009] According to one embodiment of the present invention, the gas-liquid ratio of the gas to be treated to the aqueous absorbent solution is (20m). 3 -1000m 3 ): 1L.

[0010] According to one embodiment of the present invention, the membrane has a pore size of less than 0.2 μm and a porosity of 30%-50%.

[0011] According to one embodiment of the present invention, the raw material composition of the membrane includes at least one of polypropylene, polytetrafluoroethylene, and polyvinylidene fluoride.

[0012] According to one embodiment of the present invention, the electrolysis conditions for electrolysis are: a current density of 2 mA / cm². 2 -3mA / cm 2 The temperature is 50℃-80℃.

[0013] In another aspect, the present invention provides a carbon dioxide capture system for implementing the above-described carbon dioxide capture method, comprising: an absorption unit for absorbing carbon dioxide from a gas to be treated, the absorption unit having at least one membrane module, a gas phase inlet for introducing the gas to be treated, and a liquid phase inlet for introducing an absorbent aqueous solution; and a regeneration unit having an electrolysis device for electrolyzing the absorbent, the inlet of the regeneration unit being connected to the liquid phase outlet of the absorption unit.

[0014] According to one embodiment of the present invention, the device further includes a separation unit for separating carbon dioxide, the inlet of which is connected to the gas phase outlet of the regeneration unit; and / or, a power source for providing DC power to the cathode and anode of the electrolysis apparatus.

[0015] The implementation of this invention has at least the following beneficial effects:

[0016] The carbon dioxide capture method provided by this invention employs membrane absorption to capture carbon dioxide from the gas to be treated, followed by electrochemical regeneration of the carbon dioxide. In the membrane absorption method, the gas to be treated passes through a membrane module and then enters an absorbent aqueous solution. The absorbent aqueous solution captures the carbon dioxide from the gas. Furthermore, the membrane module acts as a separation interface between the gas and liquid phases, reducing the loss of the absorbent aqueous solution and avoiding increased water consumption and secondary pollution due to its loss. Using an electrochemical method to treat the absorbent not only enables carbon dioxide regeneration under mild conditions but also allows for the electrolysis of water to produce hydrogen, achieving co-production of carbon dioxide and hydrogen, reducing energy consumption, and increasing product added value.

[0017] Furthermore, the carbon dioxide capture method provided by this invention is simple, easy to operate, requires no harsh conditions such as high temperature, is low in cost, environmentally friendly, and conducive to practical industrial production and application. Attached Figure Description

[0018] Figure 1 This is a flowchart of the carbon dioxide capture method in Example 1. Detailed Implementation

[0019] The specific embodiments listed below are merely descriptions of the principles and features of the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set up," "connected," "linked," etc., should be interpreted broadly. For example, connection can be direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meanings of the above terms within the context of this invention based on the specific circumstances.

[0021] The present invention provides a carbon dioxide capture method, comprising the following steps: (1) passing the gas to be treated through a membrane module and then into an absorbent aqueous solution for carbon dioxide absorption treatment to obtain an absorbent liquid; (2) electrolyzing the absorbent liquid to obtain carbon dioxide.

[0022] The carbon dioxide capture method provided by this invention uses membrane absorption to capture carbon dioxide in the gas to be treated, and then uses an electrochemical method to regenerate the carbon dioxide. The membrane absorption method combines membrane and absorption methods, allowing carbon dioxide in the gas to pass through a membrane module and then react in an absorbent aqueous solution to be removed. The carbon dioxide reacts in the absorbent aqueous solution to form a carbon dioxide absorbent liquid, which can be electrolyzed to recover carbon dioxide under mild conditions.

[0023] The carbon dioxide capture method provided by this invention is applicable to the capture of carbon dioxide from gases containing carbon dioxide, especially for the capture of low-concentration carbon dioxide. For example, it can be used to capture carbon dioxide from the air, enabling large-scale carbon emission reduction. Air diffuses through the pores of the membrane from the gas phase to the membrane-liquid interface. The carbon dioxide in the air reacts chemically with the absorbent aqueous solution, causing the concentration of carbon dioxide at the membrane-liquid interface to be almost zero. Driven by the concentration gradient, the carbon dioxide further diffuses towards the absorbent aqueous solution side, reacts chemically with the absorbent aqueous solution, and is removed. Other components in the air (e.g., nitrogen, oxygen) have very low solubility in the absorbent aqueous solution and hardly react with it. Therefore, without the driving force of the concentration gradient, other components in the air cannot pass through the membrane module.

[0024] The inventors, through research and analysis, believe that membrane modules can also serve as a separation interface between gas and liquid phases, preventing liquid phase leakage and reducing energy consumption and secondary pollution. The electrochemical method used to electrolyze the absorbent aqueous solution recovers carbon dioxide while simultaneously generating hydrogen. Hydrogen, as a clean and safe energy source, effectively increases added value and facilitates large-scale application.

[0025] Typically, before the gas to be treated passes through the membrane module, it undergoes pretreatment. This pretreatment primarily removes moisture and particulate matter from the gas, effectively protecting the normal operation of the subsequent membrane module and preventing it from affecting the carbon dioxide capture efficiency. Pretreatment methods can include filtration and drying.

[0026] In this invention, carbon dioxide in the gas to be treated passes through a membrane module and enters an aqueous absorbent solution to undergo a chemical reaction. The carbon dioxide content in the gas after the reaction is significantly reduced, and an absorbent liquid is generated. The membrane has a pore size of less than 0.2 μm, preferably 0.01 μm-0.1 μm, and a porosity of 30-50%.

[0027] This invention does not limit the specific type of absorbent aqueous solution. Exemplarily, in some embodiments, since carbon dioxide is an acidic gas, alkaline or alkaline salt solutions can be preferentially selected as the absorbent aqueous solution for absorption. To ensure that the absorbent aqueous solution has strong reactivity with carbon dioxide and can selectively absorb carbon dioxide, in some embodiments, the absorbent aqueous solution is an alkaline aqueous solution.

[0028] In the above embodiments, carbon dioxide reacts chemically with the absorbent aqueous solution to obtain an absorbent liquid containing carbon anions, such as carbonate ions or bicarbonate ions.

[0029] The absorbent described above can be a conventional carbon dioxide absorbent in the art. To further enhance the absorption capacity of the absorbent aqueous solution for carbon dioxide and to facilitate subsequent electrolytic recovery of carbon dioxide, a water-soluble absorbent is usually selected. In the specific implementation of this invention, the absorbent can be dissolved in water to prepare an absorbent aqueous solution. The mass concentration of the absorbent is 10wt%-60wt%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any combination thereof.

[0030] In the above embodiments, the absorbent includes at least one of alkaline inorganic substances and nitrogen-containing organic substances, preferably a mixture of alkaline inorganic substances and nitrogen-containing organic substances, wherein the alkaline inorganic substances include at least one of potassium hydroxide and sodium hydroxide, and the nitrogen-containing organic substances include at least one of amino acid salts and organic alcohol amines, such as potassium glycinate, 2-amino-2-methyl-1-propanol (AMP), etc.

[0031] In this invention, by adjusting the flow rate of the gas to be treated and the flow rate of the absorbent solution, a stable reaction between the gas and liquid can be maintained, achieving stable and effective capture of carbon dioxide from the gas. In some embodiments, the gas-liquid ratio of the gas to be treated to the absorbent aqueous solution is (20m). 3 -1000m 3 ): 1L. In the specific implementation of this invention, the liquid flow rate of the absorbent aqueous solution can be controlled to 1L / h, and the gas flow rate of the gas to be treated can be controlled to 20m. 3 / h-1000m 3 / h.

[0032] In this invention, the membrane module can be a component consisting of multiple membranes and a housing. Conventional microporous membranes can be used as the components of the membrane module. The micropores allow carbon dioxide to pass through the membrane, and the gas can diffuse through the micropores of the membrane and react with the absorbent aqueous solution that meets the above requirements. This process greatly reduces the concentration of carbon dioxide in the gas. In some embodiments, the pore size of the membrane is less than 0.2 μm and the porosity is 30%-50%.

[0033] The membrane of the membrane module of the present invention can be commercially available or obtained by conventional methods. The present invention does not limit the membrane raw materials of the membrane module and can be made from conventional polymer raw materials in the art. In order to prevent water in the absorbent aqueous solution from permeating through the membrane into the environment, hydrophobic membrane materials can usually be used.

[0034] Generally, the choice of membrane material has a certain impact on the stability and service life of membrane modules. Sufficient mechanical strength, good thermal stability and chemical stability are factors to be considered when selecting membrane materials. Based on considerations such as membrane cost and hydrophobicity, in some embodiments, the raw materials of the membrane include at least one of polypropylene, polytetrafluoroethylene and polyvinylidene fluoride.

[0035] In the specific implementation of this invention, the gas to be treated is usually introduced into the gas phase side of the membrane module, and the absorbent aqueous solution is introduced into the liquid phase side. The fluids on both sides of the membrane are independent of each other and do not come into contact with each other. Carbon dioxide can diffuse from the gas phase side of the membrane module through the micropores, diffuse from the gas phase to the membrane-liquid interface, and react chemically with the absorbent aqueous solution on the liquid phase side of the membrane module to be removed.

[0036] In this invention, the directions of gas and liquid flow can be the same or different. The flow direction of the gas to be treated and the flow direction of the absorbent aqueous solution can be in the same direction along the membrane, or the flow direction of the gas to be treated and the flow direction of the absorbent aqueous solution can be in the opposite direction along the membrane.

[0037] Normally, carbon dioxide regeneration is an endothermic reaction. The absorbent liquid formed after absorbing carbon dioxide can regenerate carbon dioxide through subsequent regeneration processes, and the absorbent aqueous solution can also be regenerated and reused.

[0038] This invention electrolyzes the absorbent to regenerate carbon dioxide using an electrochemical method. By electrolyzing the absorbent using electrochemical principles, hydrogen, oxygen, and carbon dioxide gas products can be co-produced, combining carbon dioxide regeneration with hydrogen production and reducing the energy consumption of carbon dioxide regeneration.

[0039] The electrolytic treatment process of the present invention can be carried out in an electrolytic device, which includes at least an electrolytic cell, a cathode region, and an anode region. The cathode region and the anode region are both located in the electrolytic cell. The present invention does not limit the electrode materials of the cathode region and the anode region, and they can be selected according to the actual situation. For example, they can be transition metal oxides and their compounds, metal alloy materials, or carbon-based composite materials.

[0040] In the above electrolytic treatment, the absorbent is introduced into an electrolytic cell and electrolyzed. The voltage and current of the electrolysis process are controlled. During electrolysis, carbon-containing anions such as carbonate and bicarbonate ions, as well as hydroxide ions, in the absorbent lose electrons, generating a mixture of carbon dioxide and oxygen in the anode region. Hydrogen ions in the absorbent gain electrons, generating hydrogen gas in the cathode region. After electrolysis, the remaining solution in the electrolytic cell is the electrolytic residue, which can be recycled as an absorbent aqueous solution.

[0041] To further improve the purity of the regenerated carbon dioxide product gas, the mixture of carbon dioxide and oxygen generated in the anode zone can be subjected to low-temperature distillation to separate the carbon dioxide and oxygen, thereby obtaining high-purity carbon dioxide product gas.

[0042] In this invention, a stable voltage is typically used to electrolyze the absorbent to avoid voltage fluctuations and reduce current variations. This invention does not limit the electrolysis voltage; in some embodiments, the electrolysis conditions are: a voltage of 1V-8V, for example, a range of 1V, 2V, 3V, 4V, 5V, 6V, 7V, 8V, or any combination thereof. Lower voltages result in slower electrolysis rates and slower carbon dioxide regeneration; higher voltages result in faster electrolysis rates and faster carbon dioxide regeneration, making collection more difficult. Therefore, a suitable voltage for electrolysis should be selected based on the specific circumstances.

[0043] In some embodiments, the absorbent is typically electrolyzed using a stable current at a current density of 2 mA / cm². 2 -3mA / cm 2 For example, 2.5mA / cm 2 2.6mA / cm 2 2.7mA / cm 2 2.8mA / cm 2 2.9mA / cm 2 3mA / cm 2 Or a range consisting of any two of these. If the current during electrolysis is too low, the electron flow rate is low, the probability of electron transfer decreases, which is not conducive to the regeneration of carbon dioxide; if the current is too high, the plates are prone to overheating, affecting the normal operation of the electrolysis device.

[0044] To ensure the normal operation of the electrolysis process, the temperature needs to be maintained constant between 50℃ and 80℃. For example, a range of 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any combination thereof. Lower temperatures will result in a slower electrolysis rate, increasing energy consumption and affecting electrolysis efficiency; higher temperatures will lead to increased evaporation of the absorbent solution, negatively impacting the electrolysis effect.

[0045] In the specific implementation of this invention, the electrolytic cell and the absorbent can be preheated first. The preheated absorbent is then introduced into the electrolytic cell, causing the absorbent to flow between the anode and cathode regions. When the space between the anode and cathode regions in the electrolytic cell is filled with absorbent, electricity is applied to set the voltage between the anode and cathode regions, and the absorbent is electrolyzed. This facilitates uniform electrolysis of the absorbent, improves the carbon dioxide recovery rate, and allows for large-scale processing of the absorbent.

[0046] In this invention, the combined application of the above-mentioned membrane absorption method and electrochemical method can achieve large-scale capture of carbon dioxide, and is also beneficial to improve the carbon dioxide recovery rate and reduce energy consumption.

[0047] This invention provides a carbon dioxide capture system for implementing the above-described carbon dioxide capture method, comprising:

[0048] An absorption unit is provided, which is equipped with at least one membrane module for absorbing carbon dioxide from the gas to be treated. The gas phase inlet of the absorption unit is used to introduce the gas to be treated, and the liquid phase inlet of the absorption unit is used to introduce an aqueous solution of absorbent.

[0049] The regeneration unit is equipped with an electrolysis device for electrolyzing the absorbent. The inlet of the regeneration unit is connected to the liquid phase outlet of the absorption unit.

[0050] In this invention, the gas to be treated enters the gas phase side of the membrane module through the gas phase inlet of the absorption unit, and the absorbent aqueous solution enters the liquid phase side of the membrane module through the liquid phase inlet of the absorption unit. When implementing the carbon dioxide capture method, the membrane in the membrane module can separate the gas to be treated and the absorbent aqueous solution.

[0051] The carbon dioxide capture system described above also includes a collection tank for the gas to be treated, which is used to collect the gas to be treated. The collection tank is connected to the gas phase inlet of the absorption unit.

[0052] The carbon dioxide capture system described above also includes a pretreatment device for pretreating the gas to be treated. The inlet of the pretreatment device is connected to the outlet of the gas collection tank, and the outlet of the pretreatment device is connected to the gas phase inlet of the absorption unit.

[0053] In this invention, when there are multiple membrane modules within the absorption unit, these modules are connected in series. Specifically, the gas phase outlet of the first membrane module is connected to the gas phase inlet of the second membrane module, the gas phase outlet of the second membrane module is connected to the gas phase inlet of the third membrane module, and so on. By connecting multiple membrane modules, the gas to be treated is sequentially absorbed through the absorption unit composed of these modules, achieving multi-stage membrane absorption treatment of the gas.

[0054] In the above embodiments, the gas after absorption treatment is discharged through the gas phase outlet of the absorption unit, and the absorbent obtained after absorption treatment is discharged through the liquid phase outlet of the absorption unit.

[0055] In this invention, the regeneration unit includes at least an electrolysis device for electrolyzing the absorbent obtained after membrane absorption treatment. The inlet of the electrolysis device is connected to the liquid phase outlet of the absorption unit. The absorbent can be introduced into the electrolysis tank of the electrolysis device through the inlet of the electrolysis device.

[0056] In this invention, the electrolysis apparatus includes a power source, an electrolytic cell, a cathode region, and an anode region. Both the cathode and anode regions are located within the electrolytic cell. The cathode and anode regions are respectively equipped with a cathode plate and an anode plate. The apparatus also includes a power source that provides DC power to the cathode and anode of the electrolysis apparatus. The anode plate is connected to the positive terminal of the power source, and the cathode plate is connected to the negative terminal of the power source.

[0057] In the electrolysis process of the above-mentioned electrolysis device, carbon-containing anions such as carbonate ions and bicarbonate ions and hydroxide ions in the absorbent lose electrons and generate a mixture of carbon dioxide and oxygen in the anode region, while hydrogen ions in the absorbent gain electrons and generate hydrogen gas in the cathode region.

[0058] In this invention, to improve the purity of carbon dioxide regeneration, a separation unit can be provided. This separation unit is connected to the gas phase outlet of the anode region of the regeneration unit and is used to separate carbon dioxide from the mixed gas. In the separation unit, low-temperature distillation can be used to separate carbon dioxide from oxygen.

[0059] In the above embodiments, a liquid storage device is also included. The liquid storage device is used to temporarily contain the absorbent liquid. When the amount of absorbent liquid in the liquid storage device meets a certain volume, the absorbent liquid flows to the electrolysis device.

[0060] In the above embodiments, a gas storage tank is also included, which is used to temporarily contain the gas generated by electrolysis, including a hydrogen storage tank and a mixed gas storage tank. The mixed gas storage tank is connected to the anode region of the electrolysis device, and the hydrogen storage tank is connected to the cathode region of the electrolysis device.

[0061] In a specific implementation of the present invention, a lean solution tank may also be included. The residual electrolyte is discharged from the liquid phase outlet of the electrolysis device and can flow to the lean solution tank. The lean solution tank may be connected to the liquid inlet of the membrane module so that the residual electrolyte can be returned to the absorption unit for recycling.

[0062] It should be noted that the connection or linking in this invention can be a pipe connection.

[0063] To achieve control over the gas and liquid flow rates, the carbon dioxide capture system of the present invention may further include a flow control device, which includes a gas flow control device and a liquid flow control device, wherein the gas flow control device is located at the rear end of the pretreatment device and the rear end of the gas flow control device is connected to the gas phase inlet of the absorption unit.

[0064] In the above embodiments, the valve can be configured to adjust and control the flow control device in real time based on the data obtained from monitoring.

[0065] The carbon dioxide capture system of the present invention may further include a gas composition analysis device, which is installed in the gas phase outlet section of the absorption unit for performing composition analysis on the exhaust gas at the gas phase outlet.

[0066] In this invention, the carbon dioxide capture system described above is used to implement the carbon dioxide capture method, and the specific process steps are as follows:

[0067] Step 1: The gas to be treated is pretreated by a pretreatment device;

[0068] Step 2: The pretreated gas obtained in Step 1 is regulated by a gas flow control device and then fed into the gas phase side of the membrane module through the gas phase inlet of the absorption unit. The absorbent aqueous solution is fed into the liquid phase side of the membrane module through the liquid phase inlet of the absorption unit. The two phases absorb carbon dioxide in a parallel countercurrent manner. After absorption, absorbent liquid and absorbed gas are obtained.

[0069] Step 3: The absorbent obtained after the reaction flows out from the liquid phase outlet of the absorption unit, and the exhaust gas after absorption treatment flows out from the gas phase outlet of the absorption unit. The exhaust gas is analyzed for composition, and after the exhaust gas meets the standards, it is discharged into the atmosphere.

[0070] Step 4: The absorbent is fed into the electrolysis unit of the regeneration unit for electrolysis. Gas is collected in the cathode and anode areas of the electrolysis unit using a gas collection tank. A mixture of carbon dioxide and oxygen is collected in the anode area using a gas storage tank, and hydrogen is collected in the cathode area. The residual electrolyte after electrolysis is collected using a lean liquid tank.

[0071] In the above embodiments, the gas to be treated and the absorbent aqueous solution can be introduced into the absorption unit by pumping.

[0072] In this invention, to further improve the purity of carbon dioxide, the mixed gas collected in step four is subjected to low-temperature distillation. This utilizes the different boiling points of carbon dioxide and oxygen to achieve their separation. Through low-temperature distillation, a carbon dioxide product with a purity of over 99% can be obtained.

[0073] The carbon dioxide capture system provided by this invention has a simple structure and is convenient and quick to use. It can capture carbon dioxide from the gas to be treated, and is especially suitable for capturing carbon dioxide from the air, further reducing the carbon dioxide content in the air and achieving large-scale carbon emission reduction. In addition, the system also includes a regeneration unit, which can be used in conjunction with an electrolytic hydrogen production process. This can significantly reduce the energy consumption for carbon dioxide regeneration and also reduce the operating cost of the carbon dioxide capture system, facilitating its large-scale application.

[0074] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0075] Example 1

[0076] The carbon dioxide capture system in this embodiment includes:

[0077] An absorption unit is used to absorb carbon dioxide from a gas to be treated. The absorption unit includes at least one membrane module. The gas phase inlet of the absorption unit is used to introduce the gas to be treated, and the liquid phase inlet of the absorption unit is used to introduce an aqueous solution of absorbent. The membrane in the membrane module is made of polypropylene, has a pore size of 0.1 μm, and a porosity of 30%.

[0078] The regeneration unit is equipped with an electrolysis device for electrolyzing the absorbent. The inlet of the regeneration unit is connected to the liquid phase outlet of the absorbent unit.

[0079] The separation unit is used to separate carbon dioxide, and the inlet of the separation unit is connected to the gas phase outlet of the regeneration unit.

[0080] The power source provides DC power to the cathode and anode of the electrolysis unit.

[0081] The carbon dioxide capture method in this embodiment is performed in the above-described processing system, such as... Figure 1 The flowchart shown includes:

[0082] Make the air at 1000m 3 A flow rate of 1 L / h is introduced into the gas phase side of the membrane module through the gas phase inlet of the absorption unit, while a 60 wt% KOH solution is introduced into the liquid phase side of the membrane module through the liquid phase inlet of the absorption unit at a flow rate of 1 L / h to absorb carbon dioxide and obtain an absorbent.

[0083] The absorbent is introduced into the electrolysis unit of the regeneration unit through pipe b, with the temperature controlled at 50°C and the current density at 2 mA / cm². 2 Electrolysis is performed, and a mixture of carbon dioxide and oxygen is collected in the anode region of the electrolysis device, while pure hydrogen is collected in the cathode region. Analysis shows that the molar content of carbon dioxide in the mixture is 66.7%. The residual liquid after electrolysis can be returned to the absorption unit of the membrane module for recycling through pipeline a.

[0084] The mixed gas is introduced into the separation unit, pressurized to 2MPa, and then cooled to -15℃ before entering the low-temperature distillation column for low-temperature distillation to obtain carbon dioxide product gas with a concentration of over 99%.

[0085] Example 2

[0086] The carbon dioxide capture system in this embodiment includes:

[0087] An absorption unit is used to absorb carbon dioxide from a gas to be treated. The absorption unit includes at least one membrane module. The gas phase inlet of the absorption unit is used to introduce the gas to be treated, and the liquid phase inlet of the absorption unit is used to introduce an aqueous solution of absorbent. The membrane in the membrane module is made of polytetrafluoroethylene, and the membrane has a pore size of 0.05 μm and a porosity of 40%.

[0088] The regeneration unit is equipped with an electrolysis device for electrolyzing the absorbent. The inlet of the regeneration unit is connected to the liquid phase outlet of the absorbent unit.

[0089] The separation unit is used to separate carbon dioxide, and the inlet of the separation unit is connected to the gas phase outlet of the regeneration unit.

[0090] The power source provides DC power to the cathode and anode of the electrolysis unit.

[0091] The carbon dioxide capture method in this embodiment is performed in the above-described processing system, such as... Figure 1 The flowchart shown includes:

[0092] Make the air at 100m 3 A flow rate of 1 L / h is introduced into the gas phase side of the membrane module through the gas phase inlet of the absorption unit. At the same time, a 35% 2-amino-2-methyl-1-propanol (AMP) solution is introduced into the liquid phase side of the membrane module through the liquid phase inlet of the absorption unit at a flow rate of 1 L / h to absorb carbon dioxide and obtain an absorbent.

[0093] The absorbent is introduced into the electrolysis unit of the regeneration unit through pipeline b, with the temperature controlled at 60℃ and the current density at 2.5 mA / cm². 2 Electrolysis is performed, and a mixture of carbon dioxide and oxygen is collected in the anode region of the electrolysis device, while pure hydrogen is collected in the cathode region. Analysis shows that the molar content of carbon dioxide in the mixture is 66.7%. The residual liquid after electrolysis can be returned to the absorption unit of the membrane module for recycling through pipeline a.

[0094] The mixed gas is introduced into the separation unit, pressurized to 2MPa, and then cooled to -15℃ before entering the low-temperature distillation column for low-temperature distillation to obtain carbon dioxide product gas with a concentration of over 99%.

[0095] Example 3

[0096] The carbon dioxide capture system in this embodiment includes:

[0097] An absorption unit is used to absorb carbon dioxide from a gas to be treated. The absorption unit includes at least one membrane module. The gas phase inlet of the absorption unit is used to introduce the gas to be treated, and the liquid phase inlet of the absorption unit is used to introduce an aqueous solution of absorbent. The raw material of the membrane in the membrane module is polyvinylidene fluoride, the pore size of the membrane is 0.01 μm, and the porosity is 50%.

[0098] The regeneration unit is equipped with an electrolysis device for electrolyzing the absorbent. The inlet of the regeneration unit is connected to the liquid phase outlet of the absorbent unit.

[0099] The separation unit is used to separate carbon dioxide, and the inlet of the separation unit is connected to the gas phase outlet of the regeneration unit.

[0100] The power source provides DC power to the cathode and anode of the electrolysis unit.

[0101] The carbon dioxide capture method in this embodiment is performed in the above-described processing system, such as... Figure 1 The flowchart shown includes:

[0102] Make the air at 20m 3 A flow rate of 1 L / h is introduced into the gas phase side of the membrane module through the gas phase inlet of the absorption unit. At the same time, a 10 wt% potassium glycinate solution is introduced into the liquid phase side of the membrane module through the liquid phase inlet of the absorption unit at a flow rate of 1 L / h to absorb carbon dioxide and obtain an absorbent.

[0103] The absorbent is introduced into the electrolysis unit of the regeneration unit through pipe b, with the temperature controlled at 80℃ and the current density at 3mA / cm². 2 Electrolysis is performed, and a mixture of carbon dioxide and oxygen is collected in the anode region of the electrolysis device, while pure hydrogen is collected in the cathode region. Analysis shows that the molar content of carbon dioxide in the mixture is 66.7%. The residual liquid after electrolysis can be returned to the absorption unit of the membrane module for recycling through pipeline a.

[0104] The mixed gas is introduced into the separation unit, pressurized to 2MPa, and then cooled to -15℃ before entering the low-temperature distillation column for low-temperature distillation to obtain carbon dioxide product gas with a concentration of over 99%.

[0105] The carbon dioxide capture method and system provided by this invention can effectively capture and recover carbon dioxide from the gas to be treated. It can be used in conjunction with the electrolysis hydrogen production process, which can significantly reduce energy consumption and operating costs, and is conducive to large-scale promotion and application.

[0106] The preferred embodiments and experimental verifications of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for capturing carbon dioxide, characterized in that, Includes the following steps: (1) passing air through a membrane module and into an absorbent aqueous solution to absorb carbon dioxide to obtain an absorption solution; the gas-liquid ratio of the air to the absorbent aqueous solution is (20m 3 -1000m 3 ): 1L; the pore size of the membrane is 0.2 μm or less, and the porosity is 30%-50%; (2) The absorbent is electrolyzed to obtain carbon dioxide; during the electrolysis of the absorbent, a mixture of carbon dioxide and oxygen is generated in the anode region and hydrogen is generated in the cathode region; the absorbent includes alkaline inorganic substances. The electrolysis conditions for the electrolysis treatment are: current density of 2 mA / cm². 2 -3mA / cm 2 The temperature is 50℃-80℃.

2. The carbon dioxide capture method according to claim 1, characterized in that, The absorbent aqueous solution is an alkaline aqueous solution.

3. The carbon dioxide capture method according to claim 1 or 2, characterized in that, The mass concentration of the absorbent in the aqueous solution is 10wt%-60wt%.

4. The carbon dioxide capture method according to claim 1 or 2, characterized in that, The raw material for the membrane includes at least one of polypropylene, polytetrafluoroethylene, and polyvinylidene fluoride.

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