Flue gas CO2 capturing system and method based on ceramic membrane separation technology

Abstract

The invention relates to the technical field of industrial gas purification and carbon capture, in particular to a flue gas CO2 capture system and method based on a ceramic membrane separation technology. The flue gas CO2 trapping system comprises: a pretreatment unit; the fine purification and temperature regulation unit is used for carrying out deep desulfurization and denitrification on the flue gas and regulating and controlling the temperature; a tubular ceramic membrane is arranged in the ceramic membrane separation unit, and the ceramic membrane separation unit is used for separating the flue gas into CO2-enriched permeate flow and CO2-depleted retentate flow; the permeation side pressurizing and cooling unit is used for carrying out multi-stage compression and interstage cooling on the CO2 enriched gas on the permeation side so as to liquefy the CO2 enriched gas; the product CO2 storage unit is connected to a liquid phase outlet of the permeation side pressurizing and cooling unit and is used for collecting and storing high-purity liquid or supercritical CO2; wherein a retentate side outlet of the ceramic membrane separation unit returns to a pipeline on the upstream side of the ceramic membrane separation unit through a circulating pipeline. According to the invention, continuous capture and liquefaction output of CO2 in medium-high temperature flue gas are realized.

Description

Technical Field

[0001] This invention relates to the field of industrial gas purification and carbon capture technology, specifically to a system and method for capturing CO2 in flue gas based on ceramic membrane separation technology. Background Technology

[0002] Dry quenching is an important energy-saving and environmentally friendly process in the coking industry. During the cooling of red-hot coke, it generates a large amount of circulating gas. This gas contains a high concentration of CO2, as well as N2, CO, H2, and SO2. x NO x In addition to impurities such as dust. With the advancement of the "dual carbon" goals, capturing, storing or utilizing CO2 in dry quenching flue gas has become a key path for emission reduction in coking enterprises.

[0003] Currently, mainstream technologies for CO2 capture in flue gas include amine absorption, cryogenic distillation, pressure swing adsorption, and membrane separation. However, these technologies all have certain limitations when applied to dry quenching flue gas applications.

[0004] Amine liquid absorption method: technically mature, but energy consumption is high (regeneration process requires a large amount of steam), amine liquid is easily degraded, corrosive to equipment, and SO2 in the flue gas is also a problem. x Impurities such as O2 can cause amine poisoning, requiring a complex and sophisticated pretreatment system, resulting in huge investment and operating costs.

[0005] Low-temperature distillation: suitable for high-concentration CO2 gas sources, but it has extremely high energy consumption, and the water vapor in the dry quenching flue gas is prone to freezing and clogging the equipment, and the pretreatment requirements are stringent.

[0006] Pressure swing adsorption (PSA) has the following drawbacks: product purity fluctuates greatly, adsorbent life is limited, and multiple pressurization / depressurization cycles result in high energy consumption, making it uneconomical for large-scale applications.

[0007] Polymer membrane method: Although the process is simple, dry quenching flue gas usually has a high temperature (>100°C) and contains a variety of organic and inorganic impurities, which far exceed the thermal and chemical stability limits of polymer membranes. This can easily lead to membrane plasticization, aging and failure. Therefore, the flue gas must be deeply cooled and purified first, which increases the system complexity and energy consumption. Summary of the Invention

[0008] I. Technical problems to be solved The present invention aims to at least partially solve one of the above-mentioned technical problems.

[0009] II. Technical Solution The first aspect of this invention provides a flue gas CO2 capture system based on ceramic membrane separation technology. The flue gas CO2 capture system includes: The pretreatment unit is used for dust removal and preliminary desulfurization of flue gas; The fine purification and temperature control unit is connected downstream of the pretreatment unit and is used to perform deep desulfurization and denitrification of flue gas and control its temperature. The ceramic membrane separation unit is connected downstream of the fine purification and temperature control unit. It has a built-in tubular ceramic membrane for separating flue gas into CO2 enriched permeate flow and CO2 depleted permeate flow. The permeate-side pressurization and cooling unit is connected to the permeate-side outlet of the ceramic membrane separation unit. It is used to perform multi-stage compression and inter-stage cooling on the CO2-enriched gas on the permeate side to liquefy it. The product CO2 storage unit is connected to the liquid phase outlet of the permeation-side pressurization and cooling unit and is used to collect and store high-purity liquid or supercritical CO2. The permeate outlet of the ceramic membrane separation unit is returned to the pipeline upstream of the ceramic membrane separation unit through a circulation pipeline, so that the circulating flue gas is mixed with the original flue gas that originally entered and can be recycled.

[0010] In some embodiments of the present invention, the ceramic membrane separation unit includes: multiple tubular ceramic membranes arranged in an array; each tubular ceramic membrane includes, from the inside out: a support substrate, a transition layer and a separation layer formed on the outside of the support substrate, wherein: the support substrate is cylindrical, with through-holes of 1~10μm formed on its wall, and a permeation cavity is formed on the inner side of the support substrate; the separation layer is made of nanomaterials with the function of sieving or preferentially adsorbing CO2; wherein the outer side of the separation layer is connected to the flue gas inlet and the permeate side outlet of the ceramic membrane separation unit, and the permeation cavity is connected to the permeate side outlet of the ceramic membrane separation unit; the pressure on the permeate side of the ceramic membrane separation unit is lower than that on the permeate side.

[0011] In some embodiments of the present invention, at least one of the following is satisfied: the thickness of the support substrate is 1 to 3 mm, and it is sintered from one of the following materials: α-alumina, zirconium oxide, titanium oxide, and silicon carbide; the thickness of the transition layer is 10 to 50 micrometers, and it is formed by sintering γ-alumina and titanium dioxide; the thickness of the separation layer is 0.5 to 5 micrometers, which is a functional group molecule with a strong affinity for CO2 obtained by chemical grafting or physical adsorption, and the functional group molecule is an amine functional group; the surface of the separation layer is hydrophobically treated by one of the following methods: ① grafting hydrophobic functional groups on the transition layer; ② depositing a hydrophobically modified film on the transition layer, and forming the separation layer on the hydrophobically modified film.

[0012] In some embodiments of the present invention, the surface of the separation layer is hydrophobically treated using method ②; the hydrophobically modified film includes: a SiO2 roughening layer formed on the surface of the separation layer; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughening layer; and a polydimethylsiloxane curing layer formed on the polydopamine intermediate bridging layer; the hydrophobically modified film is formed by the following steps: step B, forming a SiO2 roughening layer on the surface of the separation layer; step C, forming a polydopamine intermediate bridging layer on the surface of the SiO2 roughening layer; and step D, forming a polydimethylsiloxane curing layer on the polydopamine intermediate bridging layer.

[0013] In some embodiments of the present invention, step C includes: sub-step C1, preparing a dopamine Tris-citric acid buffer solution; wherein the concentration of the dopamine Tris-citric acid buffer solution is 1~10 mg / mL, and the pH of the solution is adjusted to 8~9; sub-step C2, immersing the tubular ceramic membrane substrate treated in step B into the dopamine Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for more than 6 hours; sub-step C3, rinsing and drying the tubular ceramic membrane substrate obtained in sub-step C2, thereby forming a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0014] In some embodiments of the present invention, step D includes: sub-step D1, preparing a PDMS solution; wherein the PDMS solution is prepared by mixing Dow Corning Sylgard 184 elastic substrate, curing agent and n-hexane, the mass ratio of elastic substrate to curing agent is 5:1 to 15:1, and the mass concentration of PDMS in the solution is 2 to 10%; sub-step D2, immersing the tubular ceramic membrane substrate treated in step C into the PDMS solution and then taking it out, the immersion time is 4 to 6 hours; sub-step D3, subjecting the tubular ceramic membrane substrate treated in sub-step D2 to heat treatment, wherein the heat treatment temperature is 60 to 80°C and the time is 2 to 4 hours.

[0015] In some embodiments of the present invention, the fine purification and temperature control unit includes: a desulfurization and denitrification reactor, connected to the downstream side of the pretreatment unit, which is an activated carbon-based reactor or a catalytic oxidation reactor, for deep desulfurization and denitrification; and a heat exchanger, connected to the downstream side of the purification device, for stabilizing and controlling the flue gas temperature at a preset value between 100°C and 400°C.

[0016] In some embodiments of the present invention, the permeation-side pressurization and cooling unit includes: a vacuum pump and an N-stage compressor connected thereto, where N≥1; wherein the vacuum pump maintains the negative pressure at the permeation level of the ceramic membrane separation unit; and an interstage cooler and a gas-liquid separator are provided between adjacent compressor stages to achieve step-by-step pressurization and cooling condensation.

[0017] In some embodiments of the present invention, a first valve V1 is provided on the circulation pipe of the ceramic membrane separation unit; the permeate side outlet of the ceramic membrane separation unit is connected to the discharge side through a pipe; a second valve V2 is provided between the permeate side and the discharge side of the ceramic membrane separation unit; a first flow sensor F1 and a first CO2 concentration sensor A1 are provided on the downstream side of the pretreatment unit; a second flow sensor F2 and a second CO2 concentration sensor A2 are provided at the permeate side outlet of the ceramic membrane separation unit; and a control unit is also included, whose sensor interface is connected to the first and second flow sensors and the first and second CO2 concentration sensors, and whose control interface is connected to the first valve V1 and the second valve V2, for changing the circulation ratio by adjusting the opening degree of the first valve V1 and the second valve V2 according to the flow rate and CO2 concentration of the original flue gas and the circulating flue gas, so as to ensure a stable capture rate when the flue gas flow rate or concentration fluctuates.

[0018] In some embodiments of the present invention, temperature sensors—a first temperature sensor T1 and a second temperature sensor T2—are installed before and after the heat exchanger of the fine purification temperature control unit; pressure transmitters—a first pressure transmitter P1 and a second pressure transmitter P2—are installed on the feed side and the permeate side of the ceramic membrane separation unit, respectively; and a control unit is also included, whose sensor interface is connected to the first temperature sensor, the second temperature sensor, the first pressure transmitter P1, and the second pressure transmitter P2, and whose control interface is connected to the heat exchanger, the vacuum pump, and the compressor, for: ① using the temperature data sensed by the first and second temperature sensors to control the heat exchanger and ensure that the temperature of the flue gas entering the ceramic membrane separation unit is within the target range; ② using the first pressure transmitter P1 and the second pressure transmitter P2 to control the vacuum pump and the compressor and ensure a stable and adjustable transmembrane pressure difference between the feed side and the permeate side of the ceramic membrane separation unit.

[0019] In some embodiments of the present invention, the flue gas is: dry quenching flue gas.

[0020] In some embodiments of the present invention, the pretreatment unit includes: a desulfurization device, which is a dry or semi-dry desulfurization device; and a dust removal device, which is a bag filter dust removal device.

[0021] In some embodiments of the present invention, the system further includes an induced draft fan connected between the pretreatment unit and the fine purification and temperature control unit to provide power for conveying the raw flue gas.

[0022] In some embodiments of the present invention, a pressure sensor P, a temperature sensor T, and a CO2 concentration sensor A are deployed at the outlet of each stage compressor and after the interstage cooler in the permeation-side pressurization and cooling unit; these sensors monitor the state and purity of the gas in real time; and a control unit is also included, which is used to automatically adjust the load of each stage compressor and the cooling power of the cooler based on the monitoring data, so as to achieve step-by-step pressurization and precise cooling, so that non-condensable light component impurities are discharged from the top of each stage gas-liquid separator into the flue gas CO2 capture system.

[0023] A second aspect of this invention provides a method for capturing CO2 in flue gas based on ceramic membrane separation technology. This method utilizes the aforementioned flue gas CO2 capture system to capture CO2 in flue gas, including: Step A: Dust removal and preliminary desulfurization of the flue gas; Step B involves deep desulfurization and denitrification of the flue gas and temperature control. Step C: The flue gas after temperature adjustment is input into the ceramic membrane separation unit to separate the flue gas into CO2 enriched permeate flow and CO2 depleted permeate flow. The ceramic membrane separation unit incorporates a tubular ceramic membrane. Each tubular ceramic membrane comprises, from the inside out: a support substrate, a transition layer and a separation layer formed on the outer side of the support substrate. The support substrate is cylindrical with 1-10 μm through-holes formed on its wall, and a permeation cavity is formed on the inner side of the support substrate. The separation layer is made of nanomaterials with the function of sieving or preferentially adsorbing CO2. The outer side of the separation layer is connected to the flue gas inlet and the permeate side outlet of the ceramic membrane separation unit, and the permeation cavity is connected to the permeate side outlet of the ceramic membrane separation unit. Step D involves multi-stage compression and interstage cooling of the CO2-enriched gas on the permeate side of the tubular ceramic membrane to liquefy it; and collecting and storing high-purity liquid or supercritical CO2. Step E: The CO2-depleted residual flow from the permeate side of the tubular ceramic membrane is returned to the pipeline at the front end of the induced draft fan through a circulation pipe, where it is mixed with the original flue gas and recycled.

[0024] III. Beneficial Effects As can be seen from the above technical solution, the present invention has at least one of the following beneficial effects compared to the prior art: (1) Overall structure of the physical integrated link This invention forms a physical integrated chain with "ceramic membrane separation - pressurization and cooling liquefaction - CO2 storage" as the core; it eliminates the chemical absorption and solvent regeneration steps and uses a fully physical process to achieve high-temperature CO2 capture and liquefaction; the residual gas circulation loop maintains the capture rate and balances the flue gas concentration.

[0025] Through the above-mentioned technical means, the present invention realizes the continuous capture and liquefaction output of CO2 from medium and high temperature flue gas, significantly reducing energy consumption, with high system integration, stable operation, and products that can be directly used for storage or chemical utilization, thus avoiding the high energy consumption and pollution problems of amine absorption method.

[0026] (2) Systematic design improves overall economic efficiency Furthermore, the system of this invention integrates multiple units sequentially from front to back, including pretreatment, fine purification and temperature control, membrane separation, and product liquefaction. It also incorporates a percolator for circulating residual gas, which can return some of the CO2-depleted percolator gas to the front end of the system to improve the overall capture rate. Journal articles focus on improving the performance of individual membrane modules (such as reducing wetting resistance through hydrophobic modification), which pertains to unit-level technologies. This invention, however, is a systems engineering design specifically for dry quenching flue gas (high dust, SO2 content...). x / NO x The specific characteristics of the various units (high temperature, medium temperature, and high temperature) are organically coupled. In particular, the "fine purification and temperature control unit" ensures that the flue gas entering the membrane module is clean and at a suitable temperature, protecting the membrane and optimizing its separation performance; the "permeate gas circulation" design optimizes the membrane separation process and improves overall economic efficiency.

[0027] (3) Tubular ceramic membrane module with multi-layer composite structure In this invention, the tubular ceramic membrane module adopts a multi-layer composite structure with clearly defined layers of supporting substrate, transition layer, and separation layer; the separation layer is extremely thin and can withstand high pressure differentials and high temperature environments; the permeate chamber design forms a stable gas transmembrane pressure differential. Through the above technical means, this invention enhances mechanical strength and gas selectivity, achieves stable separation under high temperature and high pressure, avoids the thermal degradation problem of polymer membranes, and ensures high-flux and long-life operation.

[0028] (4) High-temperature ceramic membrane separation technology is used as the core collection unit to directly treat medium and high temperature flue gas. The core of this invention is a ceramic membrane separation unit. This unit uses a high-temperature resistant (40℃-600℃) and chemically corrosion-resistant inorganic ceramic membrane (such as alumina or zirconia-based membranes). It can directly receive and process medium-to-high-temperature flue gas from the fine purification and temperature control unit without deeply cooling the flue gas to room temperature. This approach is fundamentally different from the "gas-liquid membrane contactor" technology described in journal articles. The hydrophobic ceramic membranes in journal articles act as a physical barrier for amine absorbents, preventing flooding and maintaining the gas-liquid interface. The separation relies entirely on the chemical absorption of the amine, and the operating temperature needs to be close to room temperature. In contrast, the ceramic membrane in this invention is a selective separation medium. Its separation mechanism is based on the difference in dissolution-diffusion rates between CO2 and other gas molecules (such as N2) within the membrane, achieving physical separation driven by the transmembrane pressure difference.

[0029] Through the aforementioned technical means, this invention avoids the significant sensible heat loss caused by cooling high-temperature flue gas to room temperature to protect the polymer film or accommodate amine absorption, and also completely eliminates the large amount of steam energy required for amine regeneration. It eliminates a series of complex unit operations such as amine circulation, regeneration, and cooling, resulting in a more compact system structure. It can flexibly respond to fluctuations in dry quenching flue gas conditions, exhibiting higher system stability and resilience.

[0030] (5) In this invention, a robust gaseous SiO2 layer is first constructed, then the strong adhesion of PDA is used as an intermediate layer, and finally a hydrophobic PDMS layer is introduced, forming a multilayer hydrophobic modified membrane with hydrophobic stability far superior to that of traditional coating methods. This multilayer hydrophobic modified membrane can effectively resist the chemical erosion and physical scouring of alkaline absorbents, enabling the superhydrophobic ceramic membrane to exhibit excellent durability during CO2 capture, significantly delaying membrane wetting, and ensuring the long-term, efficient, and stable operation of the membrane contactor. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the flue gas CO2 capture system based on ceramic membrane separation technology according to an embodiment of the present invention.

[0032] Figure 2 for Figure 1 The diagram shows the structure of the tubular ceramic membrane module in the ceramic membrane separation unit of the flue gas CO2 capture system. Detailed Implementation

[0033] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system and method for capturing CO2 in dry quenching flue gas based on ceramic membrane separation technology, which has a reasonable process, low energy consumption, high capture efficiency, and stable operation.

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0035] The first aspect of the present invention provides a system for capturing CO2 in flue gas based on ceramic membrane separation technology. Figure 1This is a schematic diagram of the flue gas CO2 capture system based on ceramic membrane separation technology according to an embodiment of the present invention. As shown in the figure, the flue gas CO2 capture system based on ceramic membrane separation technology in this embodiment includes, in sequence along the flue gas treatment process: a pretreatment unit 1, an induced draft fan 2, a fine purification and temperature control unit 3, a ceramic membrane separation unit 4, a permeate-side pressurization and cooling unit 5, a product CO2 storage unit 6, and a control unit. The pretreatment unit 1, induced draft fan 2, fine purification and temperature control unit 3, and ceramic membrane separation unit 4 are connected sequentially by pipelines; the permeate-side outlet of the ceramic membrane separation unit 4 is connected to the inlet of the permeate-side pressurization and cooling unit 5; the outlet of the permeate-side pressurization and cooling unit is connected to the product CO2 storage unit 6. The control unit is connected to the control terminals of the induced draft fan 2, the fine purification and temperature control unit 3, and the permeate-side pressurization and cooling unit 5, respectively.

[0036] This embodiment establishes a physically integrated process centered on "ceramic membrane separation—pressurization, cooling, liquefaction—CO2 storage." It eliminates the chemical absorption and solvent regeneration steps, employing a fully physical process to achieve high-temperature CO2 capture and liquefaction. A permeate gas circulation loop maintains the capture rate and balances the flue gas concentration. Through these technical means, this embodiment achieves continuous capture and liquefaction output of medium- and high-temperature flue gas CO2, significantly reducing energy consumption. The system boasts high integration, stable operation, and the products can be directly used for storage or chemical applications, avoiding the high energy consumption and pollution problems of amine absorption methods.

[0037] The various components of this embodiment will be described in detail below.

[0038] This embodiment uses dry quenching flue gas treatment as an example for illustration. However, this invention does not use this as an example. In other embodiments of the invention, the CO2 capture system can also be used to treat other types of flue gas, achieving the same result and falling within the scope of protection of the invention.

[0039] In this embodiment, the inlet of the pretreatment unit 1 is connected to the dry quenching flue gas source, and its outlet is connected to the inlet of the fine purification and temperature control unit 3 via the induced draft fan 2; the induced draft fan 2 is used to provide the power for the flue gas to flow throughout the system. The medium-high temperature raw flue gas generated by the dry quenching device first enters the pretreatment unit 1, where most of the dust and SO2 are removed through dry or semi-dry desulfurization combined with bag filter dust collection and other means. x Subsequently, the purified flue gas is transported by the induced draft fan 2 to the fine purification and temperature control unit 3.

[0040] In this embodiment, the outlet of the fine purification and temperature control unit 3 is connected to the feed-side inlet of the ceramic membrane separation unit 4, and includes: at least one stage of desulfurization and denitrification reactor (such as an activated carbon-based adsorption bed or a catalytic oxidation reactor) for deep removal of residual trace amounts of SO2. x NO xOther harmful impurities; and a precisely temperature-controlled heat exchanger that can stably control the flue gas temperature between 100°C and 400°C as designed for the ceramic membrane module.

[0041] In this embodiment, the permeate-side outlet of the ceramic membrane separation unit 4 is connected to the inlet of the permeate-side pressurization and cooling unit 5. This ceramic membrane separation unit incorporates a tubular ceramic membrane for selectively separating CO2, used to separate the flue gas into a CO2-enriched permeate stream and a CO2-depleted residual stream. The liquid phase outlet of the permeate-side pressurization and cooling unit 5 is connected to the product CO2 storage unit 6, used for multi-stage compression and interstage cooling of the CO2-enriched gas on the permeate side, liquefying it. The residual gas outlet of the ceramic membrane separation unit returns to the pipeline at the front end of the induced draft fan via a circulation pipe, allowing some of the residual gas to be returned to the pipeline at the front end of the induced draft fan 2 and mixed with the original flue gas.

[0042] It should be noted that the exhaust gas discharged from the permeate side outlet of the ceramic membrane separation unit is purified flue gas with a significantly reduced CO2 concentration. Part of it can be returned to the front end of the induced draft fan through the circulation pipeline, mixed with the original flue gas, and then separated again to improve the overall CO2 capture rate; the other part can be discharged in compliance with emission standards after waste heat recovery.

[0043] The ceramic membrane separation unit 4 consists of multiple tubular ceramic membrane modules arranged in an array, each filled with a CO2-selective ceramic membrane. Driven by the pressure difference across the tubular ceramic membrane (formed by the positive pressure on the feed side provided by the induced draft fan 2 and / or the negative pressure provided by the vacuum pump connected to the permeate side), CO2 molecules in the flue gas preferentially and selectively permeate through the ceramic membrane. The permeate side receives CO2-rich permeate gas, with a significantly increased CO2 concentration. The retrieval side receives retrieval gas, which is predominantly N2.

[0044] Figure 2 for Figure 1 The diagram shows the structure of the tubular ceramic membrane module in the ceramic membrane separation unit of the flue gas CO2 capture system. Figure 2 The left image shows a perspective view of the tubular ceramic membrane assembly; the right image shows a cross-sectional view of the tubular ceramic membrane assembly. As shown, each tubular ceramic membrane, from the inside out, includes: a support substrate, a transition layer formed on the outside of the support substrate, and a separation layer. The outer side of the separation layer is connected to the flue gas inlet and the permeate-side outlet of the ceramic membrane separation unit, and the permeate cavity is connected to the permeate-side outlet of the ceramic membrane separation unit.

[0045] In this embodiment, the support substrate is tubular, providing mechanical strength for the entire tubular ceramic membrane assembly to withstand high pressure differentials and high temperature environments during operation. A permeation cavity is formed on the inner side of the support substrate; the thickness of the support substrate is 1-3 mm. The support substrate is sintered from coarse-grained α-alumina or other inexpensive ceramic materials, such as zirconium oxide, titanium oxide, silicon carbide, etc., and has through-holes with relatively large pore sizes (typically 1-10 μm).

[0046] The transition layer, located between the support substrate and the separation layer, typically consists of one or more layers with a total thickness of approximately 10-50 micrometers. Its main purpose is to smooth and bridge the gap. Due to the rough surface and large pore size of the support substrate, ultrathin separation layers cannot be directly fabricated. The transition layer is prepared from finer ceramic particles (such as γ-alumina and titanium dioxide), with the pore size decreasing progressively.

[0047] The separation layer, the core technology layer of the entire ceramic membrane, directly determines the CO2 separation selectivity and permeation flux. This layer is extremely thin, typically only 0.5-5 micrometers, and is composed of nanomaterials with precise sieving or preferential adsorption capabilities for CO2. Within the separation layer, at the interface between the transition layer and the separation layer, a layer of functional group molecules (such as amine functional groups) with a strong affinity for CO2 can be chemically grafted or physically adsorbed. The amine functional groups can chemically react with CO2 molecules, acting like a ferry, capturing CO2 on one side of the ceramic membrane and transferring it to the permeate side before releasing it. Inert gases such as N2 cannot undergo this reaction, resulting in extremely slow transfer rates.

[0048] In addition, hydrophobic functional groups can be grafted onto the surface of the separation layer according to the water vapor content in the flue gas to reduce the adverse effects of condensable gases on the CO2 capture process.

[0049] In this tubular ceramic membrane module, driven by the transmembrane pressure difference, CO2 molecules preferentially permeate through the membrane pores, forming a CO2-enriched permeate flow on the permeate side, while gases such as N2, CO, and H2 are retained by the membrane, forming a CO2-depleted residual flow. Part of the residual flow is returned to the front end of the system through the circulation pipe 7 to improve the overall CO2 recovery rate; the remaining part, after waste heat recovery, is discharged into the atmosphere through the emission chimney 8 in compliance with standards.

[0050] It should be noted that the core of the system of the present invention is the ceramic membrane separation unit. This unit uses an inorganic ceramic membrane (such as alumina or zirconia-based membrane) that is resistant to high temperature (40℃-600℃) and chemical corrosion. It can directly receive and process medium- and high-temperature flue gas from the fine purification and temperature control unit without having to deeply cool the flue gas to room temperature. This reduces the stringent requirements on the depth of front-end pretreatment and makes the system structure more compact.

[0051] This embodiment differs fundamentally from the existing "gas-liquid membrane contactor" technology. In existing "gas-liquid membrane contactors," the hydrophobic ceramic membrane acts as a physical barrier for the amine absorbent, preventing flooding and maintaining the gas-liquid interface. Separation relies entirely on the chemical absorption of the amine, and the operating temperature must be close to room temperature. In contrast, the ceramic membrane in this invention is a selective separation medium. Its separation mechanism is based on the difference in dissolution-diffusion rates between CO2 and other gas molecules (such as N2) within the membrane, achieving physical separation driven by the transmembrane pressure difference.

[0052] This invention, through a specific ceramic membrane separation unit, avoids the significant sensible heat loss caused by cooling high-temperature flue gas to room temperature to protect the polymer membrane or accommodate amine absorption, and completely eliminates the large amount of steam energy required for amine regeneration. It eliminates a series of complex unit operations such as amine circulation, regeneration, and cooling, resulting in a more compact system structure. It can flexibly respond to fluctuations in dry quenching flue gas conditions, exhibiting higher system stability and resilience.

[0053] Furthermore, in this invention, the tubular ceramic membrane module adopts a multi-layer composite structure with clearly defined layers of supporting substrate, transition layer, and separation layer; the separation layer is extremely thin and can withstand high pressure differentials and high temperature environments; the permeate chamber design forms a stable gas transmembrane pressure differential. Through the above technical means, this invention enhances mechanical strength and gas selectivity, achieves stable separation under high temperature and high pressure, avoids the thermal degradation problem of polymer membranes, and ensures high-flux and long-life operation.

[0054] In this embodiment, the permeation-side pressurization and cooling unit 5 includes one or more vacuum pumps / compressors connected in series, as well as an interstage cooler and a gas-liquid separator. Through staged pressurization and cooling, CO2 gas is liquefied to obtain a high-purity liquid CO2 product. The product CO2 storage unit 6 is connected to the liquid phase outlet of the permeation-side pressurization and cooling unit for collecting and storing high-purity liquid or supercritical CO2.

[0055] It is important to note that this invention constructs an integrated physical capture process of "membrane separation-compression cooling-liquefaction," eliminating the need for chemical absorbents. Following the membrane separation unit, the system of this invention connects a permeate-side pressurization and cooling unit (including a multi-stage compressor, cooler, and gas-liquid separator). By progressively pressurizing and cooling the CO2-enriched permeate gas, it directly liquefies it to obtain a high-purity (>99.5%) liquid CO2 product, which is then transported to the product storage unit. The entire process completely avoids the use of chemical absorbents such as amine solutions. Existing gas-liquid membrane contactor technology produces a CO2-rich amine solution, which must be transported to a desorption tower for thermal regeneration to release pure CO2 gas. Subsequent compression and liquefaction steps are still required, resulting in a long process and concentrated energy consumption. This invention tightly integrates membrane separation with downstream product purification processes. The gaseous CO2 produced by the membrane unit directly enters the compression and liquefaction process, forming a complete, chemical-reactive physical capture path.

[0056] This invention utilizes an integrated physical capture process of "membrane separation-compression cooling-liquefaction," completely avoiding problems such as degradation, volatilization, and oxidation associated with the use of amine liquids. It produces no waste liquid discharge and no secondary pollution. The product boasts high purity and an easily usable form: high-purity liquid CO2 is directly obtained, facilitating transportation, storage, or direct use for resource recovery (such as chemical synthesis and oil displacement). It eliminates the entire lifecycle costs of amine liquid procurement, replenishment, purification, and waste liquid treatment.

[0057] Please refer to the attached diagram. The exhaust gas discharged from the permeate side outlet of ceramic membrane separation unit 4 is purified flue gas with a significantly reduced CO2 concentration. Part of it can be returned to the front end of the induced draft fan through the circulation pipeline, mixed with the original flue gas, and then separated again to improve the overall CO2 capture rate; the other part can be discharged in compliance with emission standards after waste heat recovery.

[0058] It is worth noting that the system of this invention integrates multiple units from front to back, including pretreatment, fine purification and temperature control, membrane separation, and product liquefaction. It also incorporates a percolator for circulating residual gas, which can return some of the CO2-depleted percolator gas to the front end of the system to improve the overall capture rate. Existing research focuses on improving the performance of individual membrane modules, representing a unit-level technology. This invention, however, is a systems engineering design specifically for dry quenching flue gas (high dust, SO2 content)... x / NO x The specific characteristics of the various units (high temperature, medium temperature, and high temperature) are organically coupled. In particular, the "fine purification and temperature control unit" ensures that the flue gas entering the membrane module is clean and at a suitable temperature, protecting the membrane and optimizing its separation performance; the "permeate gas circulation" design optimizes the membrane separation process and improves overall economic efficiency.

[0059] In this embodiment, the system can flexibly respond to fluctuations in flue gas load and composition by adjusting the operating pressure, temperature, and circulation ratio. Combined with the pressurized liquefaction process on the permeation side, high-purity liquid CO2 products can be directly obtained, facilitating transportation and subsequent utilization or storage. The system offers high operational flexibility and high product purity.

[0060] 1. Stable capture rate Flow sensors and CO2 concentration sensors are installed at the pretreatment unit outlet, induced draft fan inlet, and the permeate side circulation pipe of the ceramic membrane separation unit to monitor the flow rate and composition of the raw flue gas and the circulating flue gas in real time.

[0061] Specifically, a first flow sensor and a first CO2 concentration sensor are installed downstream of the pretreatment unit; a second flow sensor and a second CO2 concentration sensor are installed at the permeate outlet of the ceramic membrane separation unit. A first valve V1 is installed on the circulation pipeline of the ceramic membrane separation unit; the permeate outlet of the ceramic membrane separation unit is connected to the discharge side via a pipeline; a second valve V2 is installed between the permeate side and the discharge side of the ceramic membrane separation unit. Based on this data, the system's control unit adjusts the circulation ratio by regulating two valves—V1 and V2—on the circulation pipeline, thereby flexibly adjusting the CO2 load at the system inlet to ensure a stable capture rate even when flue gas flow or concentration fluctuates. The circulation ratio is defined as the ratio of the flow rate of the recirculated flue gas re-entering the ceramic membrane separation unit from the permeate side through the circulation pipeline to the original flue gas entering the ceramic membrane separation unit through the fine purification and temperature control unit.

[0062] 2. Precise temperature control and transmembrane pressure differential enable efficient operation of the ceramic membrane separation unit. Temperature sensors—first temperature sensor T1 and second temperature sensor T2—are installed before and after the heat exchanger of the fine purification temperature control unit. The control terminal of the control unit is connected to the heat exchanger of the fine purification temperature control unit, thus forming a closed-loop temperature control. The control unit adjusts the heat medium flow rate of the heat exchanger in real time according to the set optimal temperature range for ceramic membrane separation (100°C–400°C), precisely controlling the flue gas temperature at the target value to optimize the separation selectivity and flux of the ceramic membrane separation unit.

[0063] Pressure transmitters—P1 (first pressure transmitter) and P2 (second pressure transmitter)—are installed on the feed and permeate sides of the ceramic membrane separation unit, respectively. The control unit maintains a stable and adjustable transmembrane pressure differential by adjusting the speed of the induced draft fan and the power of the permeate-side vacuum pump / compressor. When the sensor detects a pressure differential deviation from the set value, the system automatically adjusts these power devices to adapt to changes in operating conditions and ensure separation efficiency.

[0064] 3. Obtaining high-purity CO2 products To achieve high-purity products, pressure sensors P, temperature sensors T, and CO2 concentration sensors A are deployed at the outlet of each compressor stage and after the interstage cooler in the permeate-side pressurization and cooling unit. These measuring points monitor the state and purity of the gas in real time. Based on this monitoring data, the control unit automatically adjusts the load of each stage compressor and the cooling power of the cooler to achieve step-by-step pressurization and precise cooling. Non-condensable light component impurities (such as N2 and O2) are discharged from the system at the top of each stage gas-liquid separator, thus obtaining liquid CO2 with a purity higher than 99.5% in the final stage, which is then transported to the product CO2 storage unit.

[0065] Through the above methods, the flue gas CO2 capture system in this embodiment forms a multi-parameter, multi-measuring-point intelligent closed-loop control network, ultimately achieving strong adaptability to flue gas operating condition fluctuations (high operational flexibility) and stable output of high-purity liquid CO2 products.

[0066] In this invention, the various units are seamlessly integrated, and the pretreatment depth is matched to the membrane's antifouling and corrosion resistance characteristics, ensuring long-term stable operation of the membrane without excessively increasing pretreatment requirements. By adjusting the circulation ratio, the final CO2 capture rate of the system can be flexibly controlled within a certain range to adapt to different emission reduction needs. This integrated system design is more suitable for the continuous and stable industrial production environment of dry quenching equipment, with a high degree of automation, and is easy to implement and promote.

[0067] Based on the above-described flue gas CO2 capture system, a second aspect of the present invention also provides a flue gas CO2 capture method. In an exemplary embodiment of the present invention, the flue gas CO2 capture method includes: Step A: Dust removal and preliminary desulfurization of the flue gas; Specifically, the medium-to-high temperature raw flue gas generated by the dry quenching unit first enters the pretreatment unit 1, where most of the dust and SO₂ are removed through dry or semi-dry desulfurization combined with bag filter dust collection and other methods. x Subsequently, the purified flue gas is transported by the induced draft fan 2 to the fine purification and temperature control unit 3.

[0068] Step B involves deep desulfurization and denitrification of the flue gas and temperature control. Specifically, in the fine purification and temperature control unit 3, the flue gas undergoes deep removal of residual trace amounts of SO2 through an activated carbon adsorption bed or a catalytic oxidation reactor. x NO x It removes other harmful impurities and precisely adjusts the flue gas temperature to the optimal temperature designed for the ceramic membrane module through a precisely controlled heat exchanger.

[0069] Step C: The flue gas after temperature adjustment is input into the ceramic membrane separation unit to separate the flue gas into CO2 enriched permeate flow and CO2 depleted permeate flow. The ceramic membrane separation unit includes: multiple arrayed tubular ceramic membranes; each tubular ceramic membrane includes, from the inside out: a support substrate, a transition layer and a separation layer formed on the outside of the support substrate, wherein: the support substrate is cylindrical, with 1~10μm through-holes formed on its wall, and a permeation cavity is formed on the inside of the support substrate; the separation layer is made of nanomaterials with the function of sieving or preferentially adsorbing CO2; wherein, the outside of the separation layer is connected to the flue gas inlet and the permeate side outlet of the ceramic membrane separation unit, and the permeation cavity is connected to the permeate side outlet of the ceramic membrane separation unit.

[0070] Specifically, the conditioned clean high-temperature flue gas enters the ceramic membrane separation unit 4. This unit consists of multiple membrane modules filled with CO2 selective ceramic membranes. Driven by the transmembrane pressure difference, CO2 molecules preferentially permeate through the membrane pores, forming a CO2-enriched permeate flow on the permeate side, while gases such as N2, CO, and H2 are retained by the membrane, forming a CO2-depleted permeate flow.

[0071] Step D involves multi-stage compression and interstage cooling of the CO2-enriched gas on the permeate side of the tubular ceramic membrane to liquefy it; and collecting and storing high-purity liquid or supercritical CO2. Specifically, the CO2-enriched gas from the permeate side enters the permeate-side pressurization and cooling unit 5. This unit first maintains negative pressure on the membrane permeate side using one or more vacuum pumps, then employs a multi-stage compressor to progressively pressurize the CO2 gas. After each stage of compression, the gas is cooled by an interstage cooler to separate condensate. Finally, the high-pressure, low-temperature CO2 gas is liquefied to obtain liquid CO2 with a purity >99.5%, which is then transported to the product CO2 storage unit 6 (storage tank) for external use in chemical synthesis, oil displacement, or geological sequestration.

[0072] In step E, the CO2-depleted residual flow from the permeate side of the tubular ceramic membrane is returned to the pipeline at the front end of the induced draft fan through a circulation pipe, where it is mixed with the original flue gas and recycled to improve the overall CO2 capture rate; the other part can be discharged in compliance with emission standards after waste heat recovery.

[0073] This concludes the description of this embodiment.

[0074] In the above embodiments, hydrophobic functional groups are grafted onto the surface of the ceramic membrane to reduce the adverse effects of condensable gases on the CO2 capture process. In another embodiment of the present invention, a hydrophobically modified membrane can also be formed on the outside of the separation layer. In other words, the only difference between this embodiment and the previous embodiment is that: in this embodiment, a hydrophobically modified membrane is deposited on the transition layer, and a separation layer is formed on the hydrophobically modified membrane.

[0075] In this embodiment, the hydrophobic modified film includes: a SiO2 roughening layer formed on the surface of the separation layer; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughening layer; and a polydimethylsiloxane curing layer formed on the polydopamine intermediate bridging layer.

[0076] The method for forming the hydrophobic modified film in this embodiment includes: Step A, pre-cleaning of the tubular ceramic membrane substrate (the tubular ceramic membrane after the separation layer is formed); Step B: A SiO2 roughening layer is formed on the surface of the separation layer; Step C: A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; Step D: A polydimethylsiloxane cured layer is formed on the polydopamine intermediate bridging layer.

[0077] This invention constructs a stable and reliable multilayer hydrophobic modified film on the surface of a ceramic membrane using a three-step method. First, smaller fumed SiO2 nanoparticles are used, and a uniform nanoscale rough structure is formed on the substrate surface by precisely controlling the impregnation-pulling speed and sintering temperature. Then, utilizing the spontaneous polymerization property of polydopamine in a weakly alkaline buffer solution, a highly adhesive intermediate bridging layer is constructed. Finally, by adjusting the ratio of PDMS to the curing agent and the curing conditions, a low surface energy hydrophobic coating layer is formed. This multilayer structure design ensures a strong bond between the functional layers, significantly improving the stability of the superhydrophobic coating.

[0078] The following provides a detailed description of each step in this embodiment.

[0079] In this embodiment, the tubular ceramic membrane substrate is a tubular single channel after the separation layer is formed. The outer diameter of the membrane tube is 12~16mm, the inner diameter is 8~12mm, and the length is 100~600mm. The main components of the membrane material are aluminum oxide and silicon dioxide, and the pore size is 0.03~1μm.

[0080] In step A of this embodiment, the tubular ceramic membrane substrate is ultrasonically cleaned in deionized water, ethanol, and acetone in sequence, and then dried for later use. During ultrasonic cleaning, the ultrasonic power is 540~750W and the cleaning time is 20~30min. During drying, the drying temperature is 60~80℃ and the drying time is 6~8h.

[0081] Those skilled in the art will understand that pre-cleaning ensures a clean surface and unobstructed pores on the tubular ceramic membrane substrate, resulting in more uniform silica deposition, PDA film formation, and PDMS curing, thus preventing localized delamination. However, this invention is not limited thereto. In other embodiments of this invention, if the surface of the tubular ceramic membrane substrate is sufficiently clean, this step can be omitted, and the invention can still be achieved.

[0082] In step B of this embodiment, a SiO2 roughening layer is formed on the surface of the tubular ceramic film substrate. Step B further includes: Sub-step B1, preparing the suspension slurry, specifically includes: Silica particles are dispersed in a mixed solvent of anhydrous ethanol and ethylene glycol to form a mixed solution; wherein the volume ratio of anhydrous ethanol to ethylene glycol in the mixed solvent is 9:1; and the mass ratio of silica particles to the mixed solvent is 1:10. Adjust the pH of the mixed solution to between 8 and 9 by adding ammonia dropwise. The pH-adjusted mixed solution was ultrasonically mixed for 1-2 hours using an ultrasonic power of 450-600W to obtain a suspension slurry. The suspension slurry is formed by dispersing SiO2 nanoparticles in a mixed solvent of ethanol and ethylene glycol. The SiO2 nanoparticles are gaseous SiO2 particles with a particle size of 5-20 nm and a pH value between 8 and 9. Sub-step B2 involves depositing a SiO2 precursor on the surface of a tubular ceramic film substrate; Specifically, this includes repeating the immersion and lifting process several times. Each immersion and lifting process includes: vertically immersing the ceramic membrane into the slurry, lifting it at a speed of 5-10 mm / s after 20-30 seconds, and letting it stand at room temperature for 10-20 minutes.

[0083] Sub-step B3 involves sintering and solidification to form a coarsened SiO2 layer. Specifically, the process involves: first, pre-drying in an oven at 60-80℃ for 1-2 hours, then placing it in a muffle furnace and heating it to 400℃ at a rate of 3-6℃ / min, holding it at that temperature for 2-4 hours, and then cooling it to room temperature with the furnace to form a stable SiO2 layer.

[0084] In this embodiment, it is not simply a matter of "creating a layer of SiO2 on the surface of a ceramic film," but rather constructing a surface morphology with micro- and nano-scale roughness using nanoscale silica particles, and then permanently fixing this morphology to the ceramic substrate surface by high-temperature sintering. This rough layer provides the micro- and nano-structural basis required for superhydrophobicity, resulting in a typical composite gas-solid interface on the final surface. On the other hand, this rough layer provides a high specific surface area and a large number of adsorption / complexation sites for subsequent PDA attachment, improving the spreading uniformity of the bridging layer.

[0085] It is important to note that, because this layer and the ceramic matrix form a "quasi-inorganic" bond after sintering, rather than relying solely on physical adsorption, its mechanical strength and chemical corrosion resistance are far superior to the fragile monolayers in existing technologies that rely on the self-assembly of fluorinated silanes. Therefore, this roughened layer is not merely decorative roughness, but a stable "long-life skeleton layer" that can withstand high-alkali environments and high-shear erosion. This is precisely what is lacking in existing CO2 membrane contactors using polypropylene membranes, PTFE membranes, or fluorinated silane-treated ceramic membranes.

[0086] Furthermore, a suspension slurry is obtained through ultrasonic dispersion, and SiO2 precursors are formed through multiple impregnation and pulling processes. These controlled processes avoid nanoparticle aggregation, cracking, or local detachment, ensuring the continuity and stability of the roughened layer; at the same time, they provide high reproducibility, enabling the same method to stably replicate similar roughened morphologies on different batches of membrane tubes with different geometries.

[0087] In step C of this embodiment, a polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer. Step C further includes: Sub-step C1: Prepare a dopamine Tris-citric acid buffer solution with a concentration of 1~10 mg / mL and adjust the pH of the solution to 8~9. Specifically, 4.8456 g of tris(hydroxymethyl)aminomethane was weighed and dissolved in distilled water, 2 mL of citric acid solution was added, and the volume was adjusted to 1 L to obtain a Tris-CA buffer solution with pH=8.5; 500 mL of the Tris-CA buffer solution was taken and 2.5 g of dopamine hydrochloride was added to prepare a 5 mg / mL dopamine Tris-citric acid buffer solution.

[0088] Sub-step C2 involves immersing the tubular ceramic membrane substrate treated in step B into a dopamine Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for more than 6 hours. Specifically, the tubular ceramic membrane substrate treated in sub-step C1 was immersed in Tris-citric acid buffer solution and subjected to ultrasonic oscillation at room temperature for 8 hours.

[0089] In sub-step C3, the tubular ceramic film substrate obtained in sub-step C2 is rinsed and dried to form a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0090] Specifically, the tubular ceramic film substrate treated in sub-step C2 is rinsed with deionized water and dried to form a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0091] In this embodiment, the polydopamine interlayer significantly enhances the bonding strength and durability of the superhydrophobic coating. The abundant catechol groups in the polydopamine molecule can form strong hydrogen bonds with the SiO2 layer and covalently crosslink with the PDMS layer, effectively solving the problem of weak bonding between the functional layer and the substrate in traditional superhydrophobic coatings. Experimental verification shows that the prepared superhydrophobic coating maintains its complete hydrophobic properties and a contact angle of over 150° even after undergoing rigorous testing under conditions such as water rinsing and mechanical friction, demonstrating excellent mechanical stability and service life.

[0092] It is important to note that in this embodiment, it is not simply about "having a layer of PDA," but rather about controlling the PDA layer to form a continuous network within a nanometer-thickness (typically between 10 and 50 nm) through specific pH and reaction time, rather than forming a non-uniform, blocky deposition. This controlled thickness ensures that the intermediate bridging layer neither forms an excessively thick, brittle interface leading to cracking and peeling, nor is it so thin that it cannot provide sufficient binding sites for PDMS. In the subsequently cured polydimethylsiloxane layer, PDMS is no longer "applied as a whole sheet," but rather undergoes interfacial coupling with this PDA network, resulting in higher erosion resistance and durability.

[0093] In step D of this embodiment, a polydimethylsiloxane cured layer is formed on the polydopamine intermediate bridging layer. Step D further includes: Sub-step D1: Prepare the PDMS solution; The PDMS solution is prepared by mixing Dow Corning Sylgard 184 elastic substrate, curing agent and n-hexane. The mass ratio of elastic substrate to curing agent is 5:1 to 15:1, and the mass concentration of PDMS in the solution is 2% to 10%. Sub-step D2: Immerse the tubular ceramic membrane substrate treated in step C into PDMS solution and then remove it. The immersion time is 4-6 hours. Sub-step D3 involves heat-treating the tubular ceramic film substrate after sub-step D2, wherein the heat treatment temperature is 60~80℃ and the time is 2~4h.

[0094] In this embodiment, instead of the conventional method of "directly brushing a layer of PDMS onto a ceramic film," PDMS is dip-coated and cured onto a surface with PDA activity to obtain a continuous, dense, elastic, low surface energy layer. The technical advantages are reflected in three aspects: ① The cured layer has extremely low surface energy, which makes the membrane surface exhibit typical superhydrophobic behavior (high contact angle, low roll-off angle), reducing the residence of liquid in the pores; ② After being bridged by PDA, the PDMS layer exhibits significantly improved adhesion and peel resistance. It is not easy to swell and peel off in alkaline amine absorbents and high-temperature environments, thus avoiding the problem of "peeling after a period of operation" of traditional PDMS coated films. ③PDMS provides a more flexible buffer against thermal stress and water flow erosion stress than existing rigid and brittle fluorinated silane self-assembled layers. As a result, the membrane maintains a stable and effective separation interface under long-term carbon dioxide absorption conditions.

[0095] In summary, this embodiment first constructs a robust vapor-phase SiO2 layer, then utilizes the strong adhesion of PDA as an intermediate layer, and finally introduces a hydrophobic PDMS layer, forming a multilayer hydrophobic modified membrane with hydrophobic stability far superior to traditional coating methods. This structure effectively resists the chemical erosion and physical scouring of alkaline absorbents, enabling the superhydrophobic ceramic membrane to exhibit excellent durability during CO2 capture, significantly delaying membrane wetting, and ensuring the long-term, efficient, and stable operation of the membrane contactor.

[0096] Furthermore, test results show that its static water contact angle can reach over 150° and its roll-off angle is less than 10°, fully meeting the superhydrophobic standard. This is mainly due to the combined effect of the uniform micro-nano structure constructed by SiO2 nanoparticles and the low surface energy characteristics of PDMS, which causes water droplets to exhibit a typical Cassie-Baxter state on the membrane surface, greatly reducing surface adhesion. In practical applications, this characteristic makes it difficult for contaminants to adhere to the membrane surface, and even if contaminants are deposited, they are easily carried away by the rolling water droplets, demonstrating excellent self-cleaning effect.

[0097] Furthermore, the preparation process of this invention has outstanding advantages such as mild conditions, controllable parameters, and wide applicability. The entire process is carried out under relatively mild conditions, with the highest processing temperature not exceeding 400°C, and avoids the investment in complex equipment. In addition, the selected raw materials are all commercially available, and the solvents can be recycled, demonstrating good prospects for industrial application and economic benefits.

[0098] This concludes the description of this embodiment.

[0099] This concludes the description of the various embodiments of the present invention. Based on the above description, those skilled in the art should have a clear understanding of the present invention.

[0100] It should be noted that for certain implementation methods, if they are not the key content of this invention and are well known to those skilled in the art, they are not described in detail in the accompanying drawings or text due to space limitations. In such cases, they can be understood by referring to the relevant prior art.

[0101] Unless explicitly stated otherwise, the numerical values ​​and ranges mentioned in this invention are approximate and can be changed according to the content of this invention. Specifically, all figures in the specification and claims indicating the content of composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases, meaning that they include variations of ±10% in certain embodiments.

[0102] Those skilled in the art will understand that in the claims and specification of this invention, the word "comprising" does not exclude the presence of elements (or steps) not listed in the claims. The word "a" or "an" preceding an element (or step) does not exclude the presence of a plurality of such elements (or steps).

[0103] Furthermore, the above embodiments are provided only to enable the invention to meet legal requirements, and the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein.

[0104] Similarly, it should be understood that, for the sake of brevity, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of invention should not be construed as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, the various inventive aspects consist of fewer than all the features of the preceding single embodiment. Furthermore, embodiments may be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0105] The above specific embodiments have provided a detailed description of the purpose, technical means, and beneficial effects of the present invention. It should be understood that the purpose of the detailed description is to enable those skilled in the art to better understand the present invention, and it is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flue gas CO2 capture system based on ceramic membrane separation technology, characterized in that, include: The pretreatment unit is used for dust removal and preliminary desulfurization of flue gas; The fine purification and temperature control unit is connected downstream of the pretreatment unit and is used to perform deep desulfurization and denitrification of flue gas and control its temperature. The ceramic membrane separation unit is connected downstream of the fine purification and temperature control unit. It has a built-in tubular ceramic membrane for separating flue gas into CO2 enriched permeate flow and CO2 depleted permeate flow. The permeate-side pressurization and cooling unit is connected to the permeate-side outlet of the ceramic membrane separation unit. It is used to perform multi-stage compression and inter-stage cooling on the CO2-enriched gas on the permeate side to liquefy it. The product CO2 storage unit is connected to the liquid phase outlet of the permeation-side pressurization and cooling unit and is used to collect and store high-purity liquid or supercritical CO2. The permeate outlet of the ceramic membrane separation unit is returned to the pipeline upstream of the ceramic membrane separation unit through a circulation pipeline, so that the circulating flue gas is mixed with the original flue gas that originally entered and can be recycled.

2. The flue gas CO2 capture system according to claim 1, characterized in that, The ceramic membrane separation unit includes: multiple tubular ceramic membranes arranged in an array; Each tubular ceramic membrane, from the inside out, comprises: a supporting substrate, a transition layer and a separation layer formed on the outer side of the supporting substrate, wherein: The supporting matrix is ​​in the shape of a cylindrical tube, with through-holes of 1~10μm formed on its tube wall, and a permeable cavity is formed on the inner side of the supporting matrix; The separation layer is made of nanomaterials with the function of sieving or preferentially adsorbing CO2. The outer side of the separation layer is connected to the flue gas inlet and the permeate side outlet of the ceramic membrane separation unit, and the permeation chamber is connected to the permeate side outlet of the ceramic membrane separation unit; the pressure on the permeate side of the ceramic membrane separation unit is lower than that on the permeate side.

3. The flue gas CO2 capture system according to claim 2, characterized in that, Meet at least one of the following: The support substrate has a thickness of 1 to 3 mm and is sintered from one of the following materials: α-alumina, zirconium oxide, titanium oxide, and silicon carbide; The transition layer has a thickness of 10 to 50 micrometers and is formed by sintering γ-alumina and titanium dioxide. The separation layer has a thickness of 0.5 to 5 micrometers and consists of functional group molecules with a strong affinity for CO2, which are obtained by chemical grafting or physical adsorption. The functional group molecules are amine functional groups. The surface of the separation layer is hydrophobically treated using one of the following methods: ① grafting hydrophobic functional groups onto the transition layer; ② depositing a hydrophobically modified film onto the transition layer, and forming a separation layer on the hydrophobically modified film.

4. The flue gas CO2 capture system according to claim 3, characterized in that, The surface of the separation layer is hydrophobically treated using the second method; The hydrophobic modified membrane comprises: a SiO2 roughened layer formed on the surface of the separation layer; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughened layer; and a polydimethylsiloxane cured layer formed on the polydopamine intermediate bridging layer. The hydrophobic modified membrane is formed in the following manner: Step B: A SiO2 roughening layer is formed on the surface of the separation layer; Step C: A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; Step D: A polydimethylsiloxane cured layer is formed on the polydopamine intermediate bridging layer; Step C includes: sub-step C1, preparing a dopamine Tris-citric acid buffer solution; wherein the concentration of the dopamine Tris-citric acid buffer solution is 1~10 mg / mL, and the pH of the solution is adjusted to 8~9; sub-step C2, immersing the tubular ceramic membrane substrate treated in step B into the dopamine Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for more than 6 hours; sub-step C3, rinsing and drying the tubular ceramic membrane substrate obtained in sub-step C2, thereby forming a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer; Step D includes: sub-step D1, preparing a PDMS solution; wherein the PDMS solution is prepared by mixing Dow Corning Sylgard 184 elastic substrate, curing agent and n-hexane, the mass ratio of elastic substrate to curing agent is 5:1 to 15:1, and the mass concentration of PDMS in the solution is 2 to 10%; sub-step D2, immersing the tubular ceramic membrane substrate treated in step C into the PDMS solution and then taking it out, the immersion time is 4 to 6 hours; sub-step D3, subjecting the tubular ceramic membrane substrate treated in sub-step D2 to heat treatment, wherein the heat treatment temperature is 60 to 80°C and the time is 2 to 4 hours.

5. The flue gas CO2 capture system of claim 1, wherein, The precision purification and temperature control unit includes: The desulfurization and denitrification reactor, connected downstream of the pretreatment unit, is an activated carbon-based reactor or a catalytic oxidation reactor, used for deep desulfurization and denitrification. A heat exchanger, connected downstream of the purification device, is used to stably control the flue gas temperature between a preset value of 100°C and 400°C.

6. The flue gas CO2 capture system according to claim 5, characterized in that, The permeation-side pressurization and cooling unit includes: a vacuum pump and an N-stage compressor connected thereto, where N≥1; The vacuum pump maintains the negative pressure of the ceramic membrane separation unit's permeation measurement; an interstage cooler and a gas-liquid separator are installed between adjacent compressor stages to achieve step-by-step pressurization and cooling / condensation.

7. The flue gas CO2 capture system according to claim 6, characterized in that, A first valve V1 is installed on the circulation pipeline of the ceramic membrane separation unit; The permeate side outlet of the ceramic membrane separation unit is connected to the discharge side via a pipeline; a second valve V2 is provided between the permeate side and the discharge side of the ceramic membrane separation unit. A first flow sensor F1 and a first CO2 concentration sensor A1 are installed on the downstream side of the pretreatment unit; a second flow sensor F2 and a second CO2 concentration sensor A2 are installed at the permeate side outlet of the ceramic membrane separation unit. It also includes a control unit, whose sensor interface is connected to the first and second flow sensors and the first and second CO2 concentration sensors, and whose control interface is connected to the first valve V1 and the second valve V2, for adjusting the circulation ratio by adjusting the opening of the first valve V1 and the second valve V2 according to the flow rate and CO2 concentration of the raw flue gas and the circulating flue gas, so as to ensure a stable capture rate when the flue gas flow rate or concentration fluctuates.

8. The flue gas CO2 capture system according to claim 7, characterized in that, Temperature sensors—first temperature sensor T1 and second temperature sensor T2—are installed before and after the heat exchanger of the fine purification temperature control unit. Pressure transmitters—first pressure transmitter P1 and second pressure transmitter P2—are installed on the feed side and permeation side of the ceramic membrane separation unit, respectively. It also includes: a control unit, whose sensor interface is connected to the first temperature sensor, the second temperature sensor, the first pressure transmitter P1, and the second pressure transmitter P2, and whose control interface is connected to the heat exchanger, the vacuum pump, and the compressor, for: ①Using the temperature data sensed by the first and second temperature sensors, the temperature of the flue gas entering the ceramic membrane separation unit is ensured to be within the target range by controlling the heat exchanger. ② By using the first pressure transmitter P1 and the second pressure transmitter P2, and controlling the vacuum pump and compressor, a stable and adjustable transmembrane pressure difference between the feed side and the permeate side of the ceramic membrane separation unit is ensured.

9. The flue gas CO2 capture system according to any one of claims 1 to 6, characterized in that, The flue gas is: dry quenched coke flue gas; and / or... The pretreatment unit includes: desulfurization equipment, which is a dry or semi-dry desulfurization equipment; dust removal equipment, which is a bag filter dust collector; and / or, It also includes: an induced draft fan, connected between the pretreatment unit and the fine purification temperature control unit, for providing power for conveying the raw flue gas; and / or, Pressure sensor P, temperature sensor T, and CO2 concentration sensor A are deployed at the outlet of each compressor stage and after the interstage cooler in the permeation-side pressurization and cooling unit. These sensors monitor the state and purity of the gas in real time. The unit also includes a control unit, which automatically adjusts the load of each stage compressor and the cooling power of the cooler based on the monitoring data to achieve step-by-step pressurization and precise cooling, so that non-condensable light component impurities are discharged from the flue gas CO2 capture system at the top of each gas-liquid separator.

10. A flue gas CO2 capture method based on ceramic membrane separation technology, characterized by, The flue gas CO2 capture system according to any one of claims 1 to 9 includes: Step A: Dust removal and preliminary desulfurization of the flue gas; Step B involves deep desulfurization and denitrification of the flue gas and temperature control. Step C: The flue gas after temperature adjustment is input into the ceramic membrane separation unit to separate the flue gas into CO2 enriched permeate flow and CO2 depleted permeate flow. The ceramic membrane separation unit incorporates a tubular ceramic membrane. Each tubular ceramic membrane comprises, from the inside out: a support substrate, a transition layer and a separation layer formed on the outer side of the support substrate, wherein: the support substrate is cylindrical with 1-10 μm through-holes formed on its wall, and a permeation cavity is formed on the inner side of the support substrate; the separation layer is made of nanomaterials with the function of sieving or preferentially adsorbing CO2; wherein the outer side of the separation layer is connected to the flue gas inlet and the permeate side outlet of the ceramic membrane separation unit, and the permeation cavity is connected to the permeate side outlet of the ceramic membrane separation unit; Step D involves multi-stage compression and interstage cooling of the CO2-enriched gas on the permeate side of the tubular ceramic membrane to liquefy it; and collecting and storing high-purity liquid or supercritical CO2. Step E: The CO2-depleted residual flow from the permeate side of the tubular ceramic membrane is returned to the pipeline at the front end of the induced draft fan through a circulation pipe, where it is mixed with the original flue gas and recycled.

Images