Hollow fiber gas dehumidification membrane module with self-sweeping structure and preparation method thereof

Abstract

The present application relates to a kind of hollow fiber gas dehumidification membrane module with self-blowing structure and its preparation method, the module includes membrane shell and several hollow fiber membrane filaments packaged in it, each membrane filament is made of polysulfone hollow fiber base membrane and the polydimethylsiloxane coating layer coated in outer wall partition, coating area accounts for 85%~90% of total area of membrane filament, 10%~15% of uncoated area.Production, first polysulfone base membrane is prepared by dry jet wet spinning method and is packaged, then sodium alginate gel liquid is injected through the side opening of membrane shell to form mask layer, then PDMS coating is coated and crosslinked and solidified, finally, EDTA disodium aqueous solution is used to dissolve mask layer, and form partition structure.Coating area is responsible for the selective permeation of water vapor dehydration, and uncoated area forms self-blowing air flow by high permeation flux, without external blowing gas source;It has the advantages of high selectivity, high flux and system simplification, and is suitable for industrial compressed air drying and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane material technology, and particularly relates to a hollow fiber gas dehumidification membrane module with a self-blowing structure and its preparation method. Background Technology

[0002] In the field of industrial gas dehumidification such as compressed air drying, according to the requirements of the national standard GB / T 10893-2025 "Specifications and Tests for Compressed Air Dryers", the pressure dew point level of the dried compressed air must reach below -40 ℃, and the industry standard requires that the membrane module's unit membrane area processing capacity at an operating pressure of 0.8 MPa should not be less than 60 Nm³ / m²·h, in order to meet the needs of high-throughput and low-energy-consumption industrial applications.

[0003] However, existing commercially available gas dehumidification membrane modules cannot simultaneously meet the aforementioned industrial standards in terms of selectivity and permeability. Insufficient selectivity leads to excessive moisture content in the product gas, which in turn causes corrosion of subsequent equipment; low permeate flux forces the equipment to increase membrane area, significantly increasing investment costs. In addition, existing membrane dehumidification systems mostly use external purge gas sources or permeate gas recovery systems, which are complex processes and have high equipment costs.

[0004] Current gas dehumidification membrane technologies primarily rely on homogeneous polymer membrane systems. For example, US Patent 5259869A discloses a membrane-based gas drying process using hollow fiber membrane materials such as polysulfone and polyethersulfone. Under standard testing conditions, the water vapor permeability is approximately 30–40 SCF / ft²·h·100psi, and the water vapor selectivity for nitrogen is approximately 30–60. According to its example data, under conditions of an inlet pressure of 0.7 MPa, an ambient temperature of 25 °C, and an inlet relative humidity of 60%–80%, the product gas pressure dew point can only reach the range of -10 °C to -30 °C. To achieve a lower dew point, the membrane area needs to be increased or multiple stages need to be connected in series, leading to a significant increase in equipment costs. Although this patent mentions that a permeate gas recovery system can increase the gas recovery rate to over 95%, it requires additional auxiliary equipment such as compressors, condensers, and gas-liquid separators, significantly increasing the system complexity.

[0005] Chinese utility model patent CN223931052U discloses an externally connected uniform backflushing membrane drying structure. It improves the uniformity of purge gas distribution by creating air chambers through grooves on the outer surface of the inlet and outlet end caps. The patent points out that existing external backflushing structures only have threaded holes on the membrane dryer shell surface to connect the purge gas, resulting in a linear gas flow that cannot evenly cover all membrane core rods, leading to drying performance failure in unpurged areas. This patent achieves uniform backflushing through structural improvements, effectively removing permeate water from the membrane surface and reducing pressure on the membrane core rods, thereby increasing service life. However, this patent still relies on an external purge gas source and does not fundamentally simplify the system structure; furthermore, its improvements mainly focus on component structure optimization, without addressing the performance enhancement of the membrane material itself, and core performance indicators such as water vapor selectivity and permeate flux are not disclosed with specific data. In addition, the spiral-wound woven membrane core rod structure used in its manufacturing process is complex and costly.

[0006] In summary, existing technologies mainly employ either a fully coated membrane combined with an external recovery system, or an optimized component structure coupled with an external gas source. For example, US Patent US5259869A relies on an external permeate gas recovery system, and Chinese Patent CN223931052U relies on an external purge gas source. Both require complex external auxiliary equipment and fail to simplify the system structure or reduce costs.

[0007] The fundamental limitation of existing technologies lies in the lack of functional integration thinking: either selectivity is improved by full coating but at the expense of flux and dependence on external systems, or the uniformity of purging is improved by structural improvements but still requires an external air source. It is difficult to meet the industrial requirements of high selectivity and high flux simultaneously without the need for external auxiliary equipment. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hollow fiber gas dehumidification membrane module with a self-blowing structure and its preparation method.

[0009] This hollow fiber gas dehumidification membrane module with a self-purge structure includes a membrane shell with side openings, and several hollow fiber membrane filaments. The top and bottom of the hollow fiber membrane filaments are respectively encapsulated with adhesive on the top and bottom inner walls of the membrane shell. Each hollow fiber membrane filament includes a polydimethylsiloxane coated area and an uncoated area.

[0010] The polydimethylsiloxane coated region includes a polysulfone hollow fiber base membrane and a polydimethylsiloxane coating located on the outer wall of the polysulfone hollow fiber base membrane; the uncoated region includes only the polysulfone hollow fiber base membrane.

[0011] The polydimethylsiloxane coated area accounts for 85% to 90% of the total area of ​​the corresponding hollow fiber membrane (the coating area ratio is a key parameter affecting the overall performance of the module), while the uncoated area accounts for 10% to 15% of the total area of ​​the corresponding hollow fiber membrane.

[0012] Preferably, the water vapor permeation flux of the hollow fiber gas dehumidification membrane module with a self-blowing structure is 750–1050 GPU.

[0013] Preferably, under the conditions of inlet pressure 0.8 MPa, temperature 25 ℃, and relative humidity 80%, the hollow fiber gas dehumidification membrane module with self-blowing structure has a pressure dew point below -45 ℃, a gas recovery rate of ≥90%, and a unit membrane area processing capacity of ≥80 Nm³. 3 / m 2 ·h.

[0014] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure includes the following steps:

[0015] Step 1: Prepare casting solution, and use dry-jet wet spinning method to spin the casting solution into filaments to prepare polysulfone hollow fiber base membrane. Then, encapsulate the top and bottom of several polysulfone hollow fiber base membranes onto the top and bottom inner walls of the membrane shell, respectively.

[0016] Step 2: Prepare the gel solution and inject it into the membrane shell through the opening on the side of the membrane shell. The gel solution solidifies on part of the surface of the polysulfone hollow fiber base membrane to form a mask layer, which covers part of the outer surface of the polysulfone hollow fiber base membrane.

[0017] Step 3: Prepare the polydimethylsiloxane coating solution, circulate and inject the polydimethylsiloxane coating solution into the membrane shell through the opening on the side of the membrane shell, drain the polydimethylsiloxane coating solution, and dry it to coat the outer surface of the polysulfone hollow fiber base membrane that is not covered by the mask layer with a polydimethylsiloxane coating. Then crosslink and cure to form a polydimethylsiloxane coating area (PDMS forms a three-dimensional network polydimethylsiloxane structure (-Si-O-Si-) after full crosslinking and curing, which has excellent chemical inertness. PDMS has good resistance to water, weak acid and weak alkali solutions and can be used stably for a long time in the pH range of 4 to 10).

[0018] Step 4: Inject disodium ethylenediaminetetraacetate (EDTA) aqueous solution into the membrane shell through the side opening. After dissolving the mask layer covering the outer surface of the polysulfone hollow fiber base membrane, drain and rinse to obtain a hollow fiber gas dehumidification membrane module with a self-blowing structure containing several hollow fiber membrane filaments. After the PDMS coating is completed and cross-linked and cured, injecting EDTA aqueous solution can chelate calcium ions to completely dissolve the gel. The membrane filament area covered by the gel returns to an uncoated state, while the membrane filament area not covered by the gel forms a highly selective PDMS coating. The target of the disodium ethylenediaminetetraacetate aqueous solution is calcium ions. Through chelation, it disintegrates the sodium alginate-calcium ion cross-linking network. This reaction is highly selective, targeting only calcium ions and not reacting chemically with the PDMS coating. The PDMS coating and the polysulfone base membrane are bound by physical adsorption and van der Waals forces, without involving calcium ion cross-linking, and therefore are not affected by EDTA treatment.

[0019] As a preferred option, such as Figures 1 to 7 As shown, steps 1 and 4 are as follows:

[0020] Step 1: Take the components by mass percentage according to the ratio of 15%–22% polysulfone, 1%–5% polyvinylpyrrolidone, 1%–5% lithium chloride, and 70%–83% N-methylpyrrolidone. Stir and dissolve the components at 50–80°C for 12–24 hours, and degas under vacuum to obtain the casting solution. Use a dry-jet wet spinning method to spin the casting solution at 50–80°C to prepare filamentous polysulfone hollow fiber base membranes with an outer diameter of 400–420 μm, an inner diameter of 250–260 μm, and a porosity of 65%–70%. Seal the top and bottom of several polysulfone hollow fiber base membranes onto the top and bottom inner walls of the membrane shell, respectively.

[0021] Step 2: (Through extensive experimental verification, the inventors discovered that sodium alginate calcium ion crosslinking gel has excellent resistance to n-hexane and controllable water solubility, making it an ideal mask material); Prepare a gel solution by mass percentage according to the following ratio: 2.5–5% sodium alginate, 1–1.5% calcium chloride, 0.5–1% glycerol, and 92.5–96% deionized water (sodium alginate calcium ion crosslinking gel can uniformly wet the surface of the membrane fibers in liquid state, and forms a gel layer with a certain hardness after calcium ion crosslinking); Inject the gel solution into the membrane shell through the side opening, and allow it to solidify at room temperature. The gel solution solidifies on part of the surface of the polysulfone hollow fiber base membrane to form a mask layer, which covers part of the outer surface of the polysulfone hollow fiber base membrane;

[0022] Step 3: Prepare a polydimethylsiloxane coating solution by weight percentage, using 3-8% polydimethylsiloxane (PDMS) prepolymer, 0.3-0.8% polydimethylsiloxane curing agent, 0.05-0.12% dibutyltin dilaurate catalyst, and 91.8-96.65% n-hexane. Circulate the polydimethylsiloxane coating solution into the membrane shell through an opening on the membrane shell side for 5-30 minutes. Then, drain the polydimethylsiloxane coating solution and dry it. This coats the outer surface of the polysulfone hollow fiber membrane not covered by the masking layer with a polydimethylsiloxane coating. Then, apply the coating at 100-110... Crosslinking and curing at ℃ for 2 hours forms a polydimethylsiloxane coating area (experiments have verified that the gel layer does not swell significantly after immersion in hexane solvent for 24 hours, which can protect the covered membrane fiber area from PDMS coating liquid penetration; polysulfone-based membrane combined with polydimethylsiloxane ultrathin coating can achieve a significant improvement in water vapor selectivity).

[0023] Step 4: Inject a 0.5-2% sodium ethylenediaminetetraacetate aqueous solution into the membrane shell through the side opening and soak for 30 minutes. Dissolve the mask layer covering the outer surface of the polysulfone hollow fiber base membrane at 25-30 ℃ and then discharge it (the temperature conditions are mild, far below the thermal decomposition temperature of PDMS (>200℃), and will not cause thermal degradation of the coating). Rinse three times with deionized water to obtain a hollow fiber gas dehumidification membrane module with a self-blowing structure containing several hollow fiber membrane filaments.

[0024] The PDMS coating solution uses n-hexane as a solvent, while gel dissolution uses an aqueous EDTA solution. PDMS is soluble in n-hexane but insoluble in aqueous solution. Fully cross-linked and cured PDMS may only experience slight swelling (<5%) in aqueous solution, without dissolution or peeling.

[0025] As a preferred option:

[0026] In step 1, the coagulation bath temperature of the dry-jet wet spinning method is 25–35 ℃ and the drafting speed is 10–50 m / min;

[0027] In step 2, the amount of gel liquid injected into the membrane shell through the opening on the side of the membrane shell is 5 to 20% of the empty volume of the membrane shell assembled with several polysulfone hollow fiber base membranes, and it is cured at room temperature for 2 hours.

[0028] Preferably, the pH value of the disodium ethylenediaminetetraacetate aqueous solution in step 4 is 8-9, which is in the weakly alkaline range and does not damage the siloxane backbone structure of PDMS.

[0029] Preferably, steps 1 and 4 are as follows:

[0030] Step 1: Take the components by mass percentage according to the ratio of 15%–20% polysulfone, 1%–5% polyvinylpyrrolidone, 1%–5% lithium chloride, and 70%–83% N-methylpyrrolidone. Stir and dissolve the components at 50–80°C for 12–24 hours, and degas under vacuum for 2 hours to obtain the casting solution. Use the dry-jet wet spinning method to spin the casting solution at 50–80°C to prepare filamentous polysulfone hollow fiber base membranes with an outer diameter of 400–420 μm, an inner diameter of 250–260 μm, and a porosity of 65%–70%. Seal the top and bottom of several polysulfone hollow fiber base membranes onto the top and bottom inner walls of the membrane shell, respectively.

[0031] Step 2: Prepare a gel solution by mass percentage of 3-5% sodium alginate, 1-1.5% calcium chloride, 0.5-1% glycerol, and 92.5-95.5% deionized water; inject the gel solution into the membrane shell through the side opening, and allow it to solidify at room temperature. The gel solution solidifies on part of the surface of the polysulfone hollow fiber base membrane to form a mask layer, which covers part of the outer surface of the polysulfone hollow fiber base membrane.

[0032] Step 3: Prepare a polydimethylsiloxane coating solution by weight percentage, using 3-5% polydimethylsiloxane (PDMS) prepolymer, 0.3-0.5% polydimethylsiloxane curing agent, 0.05-0.1% dibutyltin dilaurate catalyst, and 94.4-96.65% n-hexane. Circulate the polydimethylsiloxane coating solution into the membrane shell through an opening on the membrane shell side for 5-30 minutes. Then, drain the polydimethylsiloxane coating solution and dry it to coat the outer surface of the polysulfone hollow fiber base membrane not covered by the mask layer with a polydimethylsiloxane coating. Finally, crosslink and cure at 100-110 °C for 2 hours to form the polydimethylsiloxane coating area.

[0033] Step 4: Inject a 0.5-2% sodium ethylenediaminetetraacetate aqueous solution into the membrane shell through the side opening and soak for 30 minutes. After dissolving the mask layer covering the outer surface of the polysulfone hollow fiber base membrane, drain it and rinse it three times with deionized water to obtain a hollow fiber gas dehumidification membrane module with a self-blowing structure containing several hollow fiber membrane filaments.

[0034] Preferably, in step 2, the amount of gel liquid injected into the membrane shell through the opening on the side of the membrane shell is 15-20% of the empty volume of the membrane shell into which several polysulfone hollow fiber base membranes are assembled, and it is cured at room temperature for 2 hours.

[0035] The beneficial effects of this invention are:

[0036] Polysulfone hollow fiber membranes have high gas permeation flux but generally low water vapor selectivity. After being coated with PDMS according to this invention, the water vapor selectivity can be improved by three to five times. By controlling the gel injection amount and viscosity, the ratio of coated to uncoated areas can be precisely controlled. Preferably, the coated area accounts for 85%–90% of the total membrane fiber area, and the uncoated area accounts for 10%–15%. The coated area is responsible for the main dehydration function, selectively permeating water vapor from the feed gas to the permeate side. The uncoated area has a high permeation flux, allowing some of the feed gas to quickly permeate to the permeate side, forming a self-purge airflow that carries water vapor from the permeate side out of the assembly, eliminating the need for an external purge air source.

[0037] This invention not only solves the bottleneck of drying performance, but also eliminates the need for a permeate gas recovery system due to its self-purge design, thus meeting the industrial demands for system simplification and cost reduction. Furthermore, sodium alginate gel is inexpensive and non-toxic, the PDMS coating solution is recyclable, and optimized drying and crosslinking processes can reduce energy consumption and production costs.

[0038] The membrane module prepared by this invention can achieve a gas pressure dew point below -45 ℃ under the conditions of inlet pressure of 0.8 MPa, temperature of 25 ℃ and relative humidity of 80%, with a gas recovery rate of not less than 90% and a unit membrane area processing capacity of not less than 80 Nm³ / m²·h. Its comprehensive performance is more than 20% better than that of the prior art.

[0039] This invention utilizes an innovative gel mask partitioning coating process to achieve precise functional partitioning of highly selective dehydration and self-blowing regions within the same membrane module. This achieves excellent drying performance without the need for external auxiliary equipment, providing a technically feasible and economically reasonable solution for the industrial application of gas dehumidification membrane modules. The hollow fiber gas dehumidification membrane module with a self-blowing structure prepared by this invention is suitable for industrial applications such as compressed air drying, industrial gas dehydration, and instrument air purification. Attached Figure Description

[0040] Figure 1 A schematic diagram of a cross-section of a polysulfone hollow fiber membrane filament coated with a polydimethylsiloxane coating on its outer surface;

[0041] Figure 2 This is a side view of the gas dehumidification membrane assembly after encapsulation with potting compound.

[0042] Figure 3 This is a top view of the gas dehumidification membrane assembly after encapsulation with potting compound.

[0043] Figure 4 A side view of the gas dehumidification membrane assembly after gel injection and curing;

[0044] Figure 5A top view of the polydimethylsiloxane (PDMS) coating liquid being applied in a circulating flow within a gas dehumidification membrane assembly;

[0045] Figure 6 A schematic diagram of dissolving gel in a gas dehumidification membrane component by injecting an aqueous solution of disodium ethylenediaminetetraacetic acid (EDTA-2Na).

[0046] Figure 7 This is a side view of a hollow fiber gas dehumidification membrane assembly with a self-purge structure.

[0047] Explanation of reference numerals in the attached figures: 1. Membrane shell; 2. Hollow fiber membrane filament; 3. Polydimethylsiloxane coated area; 4. Uncoated area; 5. Polysulfone hollow fiber base membrane; 6. Polydimethylsiloxane coating; 7. Side opening of membrane shell; 8. Adhesive encapsulation area. Detailed Implementation

[0048] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0049] Example 1

[0050] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure includes the following steps:

[0051] Preparation of polysulfone hollow fiber membrane. Casting solution formulation: 20% polysulfone (molecular weight 60,000), 4% polyvinylpyrrolidone, 1.5% lithium chloride, and 74.5% N-methylpyrrolidone. The above components were stirred and dissolved at 70 °C for 12 hours, followed by vacuum degassing for 2 hours to obtain the casting solution. Dry-jet wet spinning was used, with a spinning temperature of 70 °C. The coagulation bath was a mixture of water and N-methylpyrrolidone at a mass ratio of 75:25, a coagulation bath temperature of 30 °C, a drawing speed of 40 m / min, and a drying temperature of 90 °C, yielding a hollow fiber membrane with an outer diameter of 420 μm, an inner diameter of 260 μm, and a porosity of 70%.

[0052] Sodium alginate gel preparation and injection. Gel solution formulation: sodium alginate 3%, calcium chloride 1.2%, glycerol 0.8%, deionized water 95%. Inject the gel solution into the membrane module shell side, the injection volume is 15% of the module's empty volume, and cure at room temperature for 2 hours.

[0053] PDMS coating solution preparation and application. Coating solution formulation: 5% PDMS prepolymer, 0.5% PDMS curing agent, 0.08% dibutyltin dilaurate catalyst, 94.42% n-hexane. The coating solution was circulated for 5 minutes at a flow rate of 1 L / min. After draining the coating solution, it was dried at 70 °C for 4 hours and then crosslinked at 110 °C for 2 hours.

[0054] Gel dissolution and component drying: A 0.8% sodium EDTA aqueous solution was injected into the component and immersed for 30 minutes. After the gel was completely dissolved, it was drained, rinsed three times with deionized water, and vacuum dried at 80 °C for 24 hours to obtain the finished component.

[0055] Example 2

[0056] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure:

[0057] The polysulfone-based film preparation process is the same as in Example 1; the sodium alginate gel formulation is adjusted to: sodium alginate 2.5%, calcium chloride 1.0%, glycerol 0.5%, deionized water 96%; other conditions are the same as in Example 1; the PDMS coating process is the same as in Example 1.

[0058] Example 3

[0059] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure:

[0060] The polysulfone-based membrane preparation process was the same as in Example 1; the sodium alginate gel preparation was the same as in Example 1; the PDMS coating liquid formulation was adjusted to: 8% PDMS prepolymer, 0.8% PDMS curing agent, 0.12% dibutyltin dilaurate catalyst, and 91.08% n-hexane; the cycle time was extended to 30 minutes, and other conditions were the same as in Example 1; the increased coating thickness led to improved selectivity but decreased permeation flux.

[0061] Example 4

[0062] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure:

[0063] The polysulfone-based film preparation process is the same as in Example 1; the sodium alginate gel preparation is the same as in Example 1; the gel injection amount is adjusted to 5% of the component's empty volume, and other conditions are the same as in Example 1; the reduction in injection amount leads to a decrease in the proportion of the coating area and an increase in the proportion of the purging area.

[0064] Example 5

[0065] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure:

[0066] The polysulfone-based film preparation process was the same as in Example 1; the sodium alginate gel preparation was the same as in Example 1; the PDMS coating solution formulation was the same as in Example 1; the crosslinking temperature was adjusted to 120 °C, the crosslinking time was 2 hours, and other conditions were the same as in Example 1.

[0067] Example 6

[0068] A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure:

[0069] The casting solution formulation was adjusted to: 22% polysulfone (molecular weight 60000), 3% polyvinylpyrrolidone, 1% lithium chloride, and 74% N-methylpyrrolidone; other spinning conditions were the same as in Example 1, resulting in a hollow fiber membrane with an outer diameter of 400 μm, an inner diameter of 250 μm, and a porosity of 65%; the gel preparation, PDMS coating, and gel dissolution processes were the same as in Example 1.

[0070] Example 7

[0071] like Figures 1 to 7 As shown, a hollow fiber gas dehumidification membrane module with a self-purge structure includes a membrane shell 1, with a membrane shell side opening 7 on the membrane shell 1, and a plurality of hollow fiber membrane filaments 2. The top and bottom of the plurality of hollow fiber membrane filaments 2 are respectively encapsulated with adhesive in the encapsulation areas 8 on the top inner wall and bottom inner wall of the membrane shell 1; each hollow fiber membrane filament 2 includes a polydimethylsiloxane coated area 3 and an uncoated area 4; wherein:

[0072] The polydimethylsiloxane coated region 3 includes a polysulfone hollow fiber base membrane 5 and a polydimethylsiloxane coating 6 located on the outer wall of the polysulfone hollow fiber base membrane 5; the uncoated region 4 includes only the polysulfone hollow fiber base membrane 5.

[0073] The polydimethylsiloxane coated area 3 accounts for 85% to 90% of the total area of ​​the corresponding hollow fiber membrane filament 2 (the coating area ratio is a key parameter affecting the overall performance of the module), while the uncoated area 4 accounts for 10% to 15% of the total area of ​​the corresponding hollow fiber membrane filament 2.

[0074] Comparative Example 1

[0075] The polysulfone-based membrane preparation process is the same as in Example 1; the gel injection and dissolution steps are omitted, all membrane fibers are coated with PDMS, and other conditions are the same as in Example 1; although this scheme has higher selectivity and recovery rate, it requires an external purging gas source, which increases the system complexity.

[0076] Comparative Example 2

[0077] The polysulfone-based membrane preparation process is the same as in Example 1; the PDMS coating step is omitted, and only the polysulfone-based membrane is used, with other conditions the same as in Example 1; this scheme has high throughput but poor selectivity, and the drying effect cannot meet industrial requirements.

[0078] Comparative Example 3

[0079] The polysulfone-based membrane preparation process was the same as in Example 1; the EDTA soaking time during gel dissolution was extended to 120 minutes, and other conditions were the same as in Example 1; the results showed that the coating adhesion decreased slightly and the gas recovery rate decreased to 89%, indicating that the soaking time should be controlled within a reasonable range.

[0080] Comparative Example 4

[0081] The polysulfone-based membrane preparation process was the same as in Example 1; the crosslinking temperature of the PDMS coating was reduced to 80°C and the crosslinking time was shortened to 30 minutes, while other conditions were the same as in Example 1; after EDTA treatment, local peeling of the coating occurred and the gas recovery rate decreased to 82%, proving that sufficient crosslinking is the key to ensuring the coating's resistance to EDTA treatment.

[0082] Comparative Example 5

[0083] The polysulfone-based film preparation process is the same as in Example 1; the sodium alginate gel formulation is adjusted to: sodium alginate 1%, calcium chloride 0.4%, glycerol 0.2%, and deionized water 98.4%; other conditions are the same as in Example 1; the low gel concentration leads to poor masking effect, and the coating area ratio cannot be accurately controlled, with fluctuations of ±12%.

[0084] Comparative Example 6

[0085] The polysulfone-based membrane preparation process was the same as in Example 1; the concentration of disodium EDTA aqueous solution was adjusted to 0.2%, the soaking time was 30 minutes, and other conditions were the same as in Example 1; the low concentration of EDTA resulted in incomplete gel dissolution, and the residual gel blocked the membrane pores, causing a 18% decrease in permeation flux.

[0086] Comparative Example 7

[0087] The polysulfone-based membrane preparation process is the same as in Example 1; the gel injection amount is adjusted to 40% of the module's empty volume, and other conditions are the same as in Example 1; the coating area ratio is reduced to 70%, the high-selectivity dehydration area is insufficient, and although the self-purge area is increased to 30%, the dehydration capacity is limited, the product gas dew point rises to -35℃, and the gas recovery rate drops to 85%.

[0088] Comparative Example 8

[0089] The polysulfone-based membrane preparation process is the same as in Example 1; the gel injection amount is adjusted to 5% of the module's empty volume, and other conditions are the same as in Example 1; the coating area ratio is increased to 95%, the self-purge airflow is insufficient, water vapor accumulates on the permeation side, and the dew point rises to -38°C.

[0090] The hollow fiber gas dehumidification membrane modules with self-blowing structures prepared in Examples 1 to 6, and the membranes prepared in Comparative Examples 1 to 8, were subjected to performance tests. The performance test results are shown in Table 1 below:

[0091] Table 1. Membrane performance test results of Examples 1 to 6 and Comparative Examples 1 to 8

[0092]

[0093] As shown in Table 1 above, Example 1 (the optimal solution) achieved excellent comprehensive performance with a water vapor permeation flux of 920 GPU, a water vapor / nitrogen selectivity of 210±8, a product gas pressure dew point of -48 ℃, a gas recovery rate of 94%, and a unit membrane area throughput of 68 Nm³ / m²·h under the condition of a coating area ratio of 88±2%, which meets the requirements of industrial compressed air drying (pressure dew point below -40 ℃, recovery rate ≥90%).

[0094] The balance of the coating area ratio in the hollow fiber gas dehumidification membrane module with self-blowing structure prepared in this invention was fully verified by Comparative Examples 7 and 8: When the coating ratio decreased to 70% (Comparative Example 7), the highly selective dehydration area was insufficient, and although the self-blowing area increased to 30%, the product gas dew point still rose to -35°C, and the gas recovery rate dropped to 85%; when the coating ratio increased to 95% (Comparative Example 8), insufficient self-blowing airflow led to water vapor accumulation on the permeate side, and the dew point rose to -38°C. This proves that a coating ratio of 85%–90% is the optimal balance point between dehydration capacity and self-blowing effect.

[0095] Examples 2-6 and Comparative Examples 3-6 systematically investigated the effects of key process parameters such as gel concentration, PDMS coating thickness, crosslinking temperature, base film porosity, and EDTA treatment conditions, verifying the process stability of the hollow fiber gas dehumidification membrane module with self-blowing structure prepared by this invention. The results show that the module coating prepared under the preferred process conditions has good integrity and controllable performance fluctuations (selectivity fluctuation <10%, flux fluctuation <15%), and the PDMS coating is not significantly damaged after EDTA gel dissolution treatment, proving that the gel masking process and the PDMS coating have good compatibility.

[0096] Compared with Comparative Example 1 (fully coated and requiring external purging), this invention completely eliminates the need for an external purging gas source and a permeate gas recovery system while reducing the gas recovery rate by only 4 percentage points, greatly simplifying the equipment structure and reducing system costs. Compared with Comparative Example 2 (uncoated base film), the selectivity is improved by 6.5 times and the dew point is reduced by 30°C, meeting the requirements for industrial drying.

[0097] In summary, this invention, through an innovative gel mask partitioning coating process, achieves precise functional partitioning of highly selective dehydration areas and self-blowing areas within the same membrane module, achieving excellent drying performance without the need for external auxiliary equipment. This provides a technically feasible and economically reasonable solution for the industrial application of gas dehumidification membrane modules.

[0098] The inventors believe that breakthroughs in gas drying performance must stem from synergistic innovation in component structure design and coating process. Specifically, this involves using a gel mask to achieve zoned coating, allowing the highly selective coated areas to handle the primary dehydration function, while the uncoated areas handle the self-purging function. Therefore, the design concept of the hollow fiber gas dehumidification membrane component with a self-purging structure in this invention is not self-evident; it originates from a deep understanding of the mass transfer mechanism in the membrane separation process, rather than a simple combination of existing technologies.

Claims

1. A hollow fiber gas dehumidification membrane assembly with a self-blowing structure, comprising a membrane shell, wherein the membrane shell has a membrane shell side opening, characterized in that, It also includes a plurality of hollow fiber membrane filaments, the top and bottom of which are respectively encapsulated with adhesive on the top inner wall and bottom inner wall of the membrane shell; each of the hollow fiber membrane filaments includes a polydimethylsiloxane coated area and an uncoated area; wherein: The polydimethylsiloxane coated region includes a polysulfone hollow fiber base membrane and a polydimethylsiloxane coating located on the outer wall of the polysulfone hollow fiber base membrane; the uncoated region includes only a polysulfone hollow fiber base membrane; The polydimethylsiloxane coated area accounts for 85% to 90% of the total area of ​​the corresponding hollow fiber membrane filament, and the uncoated area accounts for 10% to 15% of the total area of ​​the corresponding hollow fiber membrane filament.

2. The hollow fiber gas dehumidification membrane module with self-blowing structure according to claim 1, characterized in that: The water vapor permeation flux of the hollow fiber gas dehumidification membrane module with self-blowing structure is 750–1050 GPUs.

3. The hollow fiber gas dehumidification membrane module with self-blowing structure according to claim 1, characterized in that: Under conditions of inlet pressure of 0.8 MPa, temperature of 25 ℃, and relative humidity of 80%, the gas pressure dew point of the hollow fiber gas dehumidification membrane module with self-blowing structure is below -45 ℃, the gas recovery rate is greater than or equal to 90%, and the treatment capacity per unit membrane area is greater than or equal to 80 Nm³. 3 / m 2 ·h.

4. A method for preparing a hollow fiber gas dehumidification membrane module with a self-blowing structure as described in claim 1, characterized in that, Includes the following steps: Step 1: Prepare casting solution, and use dry-jet wet spinning method to spin the casting solution into filaments to prepare polysulfone hollow fiber base membrane. Then, encapsulate the top and bottom of several polysulfone hollow fiber base membranes onto the top and bottom inner walls of the membrane shell, respectively. Step 2: Prepare the gel solution and inject it into the membrane shell through the opening on the side of the membrane shell. The gel solution is cured on a portion of the surface of the polysulfone hollow fiber base membrane to form a mask layer, which covers a portion of the outer surface of the polysulfone hollow fiber base membrane. Step 3: Prepare polydimethylsiloxane coating liquid, circulate the polydimethylsiloxane coating liquid into the membrane shell through the opening on the membrane shell side, discharge the polydimethylsiloxane coating liquid, and dry it so that the outer surface of the polysulfone hollow fiber base membrane not covered by the mask layer is coated with polydimethylsiloxane coating, and then crosslink and cure to form polydimethylsiloxane coating area. Step 4: Inject disodium ethylenediaminetetraacetate aqueous solution into the membrane shell through the opening on the membrane shell side, dissolve the mask layer covering the outer surface of the polysulfone hollow fiber base membrane, and then discharge and rinse to obtain a hollow fiber gas dehumidification membrane assembly with a self-blowing structure having a number of hollow fiber membrane filaments.

5. The preparation method according to claim 4, characterized in that, Steps 1 and 4 are specifically as follows: Step 1: Take the components by mass percentage according to the ratio of 15%–22% polysulfone, 1%–5% polyvinylpyrrolidone, 1%–5% lithium chloride, and 70%–83% N-methylpyrrolidone. Stir and dissolve the components at 50–80°C for 12–24 hours, and degas under vacuum to obtain a casting solution. Use a dry-jet wet spinning method to spin the casting solution at 50–80°C to prepare filamentous polysulfone hollow fiber base membranes with an outer diameter of 400–420 μm, an inner diameter of 250–260 μm, and a porosity of 65%–70%. Seal the top and bottom of several of the polysulfone hollow fiber base membranes onto the top and bottom inner walls of the membrane shell, respectively. Step 2: Prepare a gel solution by weight percentage according to the following ratio: 2.5-5% sodium alginate, 1-1.5% calcium chloride, 0.5-1% glycerol, and 92.5-96% deionized water; inject the gel solution into the membrane shell through an opening on the membrane shell side, and cure it at room temperature. The gel solution cures on a portion of the surface of the polysulfone hollow fiber base membrane to form a mask layer, and the mask layer covers a portion of the outer surface of the polysulfone hollow fiber base membrane. Step 3: Prepare a polydimethylsiloxane coating solution by weight percentage according to the following ratio: 3-8% polydimethylsiloxane, 0.3-0.8% polydimethylsiloxane curing agent, 0.05-0.12% dibutyltin dilaurate catalyst, and 91.8-96.65% n-hexane. Circulate the polydimethylsiloxane coating solution into the membrane shell through an opening on the membrane shell side for 5-30 minutes. Then, drain the polydimethylsiloxane coating solution and dry it to coat the outer surface of the polysulfone hollow fiber base membrane, which is not covered by the mask layer, with a polydimethylsiloxane coating. Then, crosslink and cure at 100-110 °C for 2 hours to form a polydimethylsiloxane coating area. Step 4: Inject a 0.5-2% sodium ethylenediaminetetraacetate aqueous solution into the membrane shell through the opening on the membrane shell side and soak for 30 minutes. After dissolving the mask layer covering the outer surface of the polysulfone hollow fiber base membrane at 25-30 °C, drain the membrane and rinse it three times with deionized water to obtain a hollow fiber gas dehumidification membrane module with a self-blowing structure containing several hollow fiber membrane filaments.

6. The preparation method according to claim 5, characterized in that: In step 1, the coagulation bath temperature of the dry-jet wet spinning method is 25-35 ℃ and the drafting speed is 10-50 m / min. In step 2, the amount of gel liquid injected into the membrane shell through the opening on the side of the membrane shell is 5 to 20% of the empty volume of the membrane shell in which several polysulfone hollow fiber base membranes are assembled, and it is cured at room temperature for 2 hours.

7. The preparation method according to claim 5, characterized in that: In step 4, the pH value of the disodium ethylenediaminetetraacetate aqueous solution is 8-9.

8. The preparation method according to claim 4, characterized in that, Steps 1 and 4 are specifically as follows: Step 1: Take the components by mass percentage according to the ratio of 15%–20% polysulfone, 1–5% polyvinylpyrrolidone, 1–5% lithium chloride, and 70%–83% N-methylpyrrolidone. Stir and dissolve the components at 50–80°C for 12–24 hours, and degas under vacuum for 2 hours to obtain a casting solution. Use a dry-jet wet spinning method to spin the casting solution at 50–80°C to prepare filamentous polysulfone hollow fiber base membranes with an outer diameter of 400–420 μm, an inner diameter of 250–260 μm, and a porosity of 65%–70%. Seal the top and bottom of several of the polysulfone hollow fiber base membranes onto the top and bottom inner walls of the membrane shell, respectively. Step 2: Prepare a gel solution by weight percentage according to the following ratio: 3-5% sodium alginate, 1-1.5% calcium chloride, 0.5-1% glycerol, and 92.5-95.5% deionized water; inject the gel solution into the membrane shell through an opening on the membrane shell side, and cure it at room temperature. The gel solution cures on a portion of the surface of the polysulfone hollow fiber base membrane to form a mask layer, and the mask layer covers a portion of the outer surface of the polysulfone hollow fiber base membrane. Step 3: Prepare a polydimethylsiloxane coating solution by weight percentage according to the following ratio: 3-5% polydimethylsiloxane, 0.3-0.5% polydimethylsiloxane curing agent, 0.05-0.1% dibutyltin dilaurate catalyst, and 94.4-96.65% n-hexane. Circulate the polydimethylsiloxane coating solution into the membrane shell through an opening on the membrane shell side for 5-30 minutes. Then, drain the polydimethylsiloxane coating solution and dry it to coat the outer surface of the polysulfone hollow fiber base membrane not covered by the mask layer with a polydimethylsiloxane coating. Finally, crosslink and cure at 100-110 °C for 2 hours to form a polydimethylsiloxane coating area. Step 4: Inject a 0.5-2% sodium ethylenediaminetetraacetate aqueous solution into the membrane shell through the opening on the membrane shell side and soak for 30 minutes. After dissolving the mask layer covering the outer surface of the polysulfone hollow fiber base membrane, drain it and rinse it three times with deionized water to obtain a hollow fiber gas dehumidification membrane module with a self-blowing structure containing a number of hollow fiber membrane filaments.

9. The preparation method according to claim 8, characterized in that: In step 2, the amount of gel liquid injected into the membrane shell through the opening on the side of the membrane shell is 15-20% of the empty volume of the membrane shell in which several polysulfone hollow fiber base membranes are assembled, and it is cured at room temperature for 2 hours.

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