Preparation method of blended high-molecular polymer hollow fiber membrane spinning

Abstract

The invention discloses a preparation method of blended high-molecular polymer hollow fiber membrane spinning, which comprises the following steps: preparing a spinning solution: taking a membrane casting solution and a core solution, and uniformly mixing the membrane casting solution and the core solution respectively; the membrane casting solution comprises the following raw materials in percentage by mass: 25-30% of polysulfone particles, 0.5-10% of polyimide A powder, 0.5-10% of polyimide B powder, 35-40% of a weakly volatile organic solvent, 20% of a volatile organic solvent and 10% of a non-solvent; the core liquid comprises the following raw materials in percentage by mass: 20% of pure water and 80% of a weakly volatile organic solvent; spinning: spinning the mixed solution by adopting a dry-wet phase separation process to obtain membrane filaments; the membrane filaments are placed in a water tank for three days to remove residual solution, water stored in the water tank is replaced every day, the membrane filaments are taken out of the water tank and dried at room temperature, and a finished product is obtained. According to the invention, a plurality of polymers are blended according to different proportions to prepare the membrane casting solution, and meanwhile, the operation process is accurately adjusted, so that the balance of the gas separation effect is finally achieved.

Description

Technical Field

[0001] The present invention relates to the field of hollow fiber membranes, and in particular to a preparation method of spinning a blended high molecular polymer hollow fiber membrane. Background Art

[0002] Flue gas from thermal power plants is a major source of global carbon dioxide emissions. Its main components are carbon dioxide and nitrogen. Reducing carbon dioxide emissions from power plants is a key measure to curb global warming. Currently, mainstream decarbonization methods include chemical absorption, physical adsorption, and membrane separation. Chemical absorption is the most commercially mature and widely used technology. It uses amine solvents to react with carbon dioxide in flue gas in a spray tower, achieving decarbonization. However, this process is energy-intensive and requires significant equipment space. Furthermore, the solvents used are environmentally unfriendly and prone to corrosion. Membrane separation offers compact equipment, simple operation, and the separation process does not involve the use of chemical reagents, resulting in lower energy consumption. However, for power plant flue gas decarbonization, a carbon dioxide permeation flux exceeding 40 GPU and a carbon dioxide / nitrogen selectivity exceeding 30 are required to effectively and economically remove carbon dioxide from power plant flue gas, which has extremely high flow rates per unit time. Currently, the main raw materials used for mainstream hollow fiber gas separation membranes worldwide are polysulfone, polyethersulfone, and polyimide. Key membrane products include AIRPRODUCTS's PRISM membrane, made from polysulfone, GENERON's GENERON membrane, made from polyimide, and EVONIK's SEPURAN membrane, also made from polyimide. Some of these commercial membranes have low CO2 permeation fluxes, requiring a large membrane area to decarbonize power plant flue gas, which has extremely high flow rates per unit time. Others are expensive due to the high cost of synthesizing the polyimide raw material, making them uneconomical.

[0003] Hollow fiber membranes used for gas separation are fibrous in shape and hollow in interior. Asymmetric hollow fiber membranes have a separation function only on their outer surface, while the rest of the membrane serves only as a self-supporting element. Compared to other membrane types, asymmetric hollow fiber membrane modules offer superior separation performance, high efficiency, high packing density, and a compact footprint, making them ideal for treating power plant flue gases with extremely high flow rates per unit time.

[0004] The main raw materials of hollow fiber gas separation membranes are polymers, including polysulfone, polyethersulfone, and polyimide. Different polymers have different chemical structures, resulting in different carbon dioxide permeation flux and carbon dioxide / nitrogen selectivity. Taking polysulfone and polyimide as examples, the structural formula is The polysulfone carbon dioxide permeability coefficient is 4.6BARRER, the carbon dioxide / nitrogen selectivity is 24.2, and the structural formula is The carbon dioxide permeability coefficient of polyimide A is 8.7BARRER, the carbon dioxide / nitrogen selectivity is 37.8, and the structural formula is Polyimide B has a carbon dioxide permeability coefficient of 0.99 barrer and a carbon dioxide / nitrogen selectivity of 40.2. The above data show that polyimide A has the highest carbon dioxide permeation flux, and polyimide B has the highest carbon dioxide / nitrogen selectivity, making both suitable for decarbonization of power plant flue gas. However, the high cost of the synthetic monomers for polyimide A and polyimide B makes them economically disadvantageous. Although the synthesis cost of polysulfone is only about 1 / 20 of that of polyimide, its separation efficiency is lower than that of the above two polyimides. Treating the same volume of power plant flue gas requires a large membrane area, thus reducing its cost advantage.

[0005] It can be seen that it is extremely necessary to develop a hollow fiber gas separation membrane preparation process that has a high carbon dioxide permeation flux and carbon dioxide / nitrogen selectivity suitable for decarbonization of power plant flue gas and has cost advantages. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of blended high molecular polymer hollow fiber membrane spinning.

[0007] The innovation of the present invention lies in that it utilizes the gas separation parameters of different types of polymers to prepare the casting liquid by blending multiple polymers in different proportions, and at the same time accurately adjusts the operating process to ultimately achieve a balance in gas separation effects and have economic advantages.

[0008] To achieve the above-mentioned purpose, the technical solution of the present invention is: a preparation method of spinning a blended polymer hollow fiber membrane, comprising the following steps:

[0009] (1) Preparation of spinning solution: Take the casting solution and the core solution, and mix the casting solution and the core solution evenly;

[0010] The casting solution includes the following raw materials in percentage by mass: 25-30% polysulfone particles,

[0011] 0.5-10% polyimide A powder, 0.5-10% polyimide B powder, 35-40%

[0012] Weakly volatile organic solvent, 20% volatile organic solvent, 10% non-solvent;

[0013] The core liquid includes the following raw materials in percentage by mass: 20% pure water, 80% weak volatile organic solvent;

[0014] (2) Spinning: The mixed solution is spun using a dry-wet phase separation process to obtain membrane fibers;

[0015] (3) Post-processing: The membrane fibers were placed in a water tank for three days to remove the residual solution. The water in the water tank was changed every day. The membrane fibers were taken out of the water tank and dried at room temperature to obtain the finished product.

[0016] Furthermore, the weakly volatile organic solvent is N-methylpyrrolidone, and the volatile organic solvent is tetrahydrofuran.

[0017] Furthermore, the non-solvent is ethanol.

[0018] Furthermore, during the spinning process of the dry-wet phase separation, at a temperature of 70°C, an initial hollow fiber membrane is extruded from a spinneret by a gear pump at a flow rate of 50 ml / h of casting liquid and 25 ml / h of core liquid. The initial hollow fiber membrane enters a gel bath after passing through an air gap distance of 10 cm in the air. The gel bath medium is pure water. The initial hollow fiber membrane passes through a traction wheel, a tension control device and a swing device and is collected on a collecting wheel. The collecting wheel traction rate is 20 m / min.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention uses a blend of polysulfone, polyimide A and polyimide B with an optimized ratio as raw materials to prepare a hollow fiber membrane. The prepared hollow fiber membrane has excellent carbon dioxide permeation flux and carbon dioxide / nitrogen selectivity.

[0021] 2. The present invention ensures that the polymer concentration in the outer edge of the membrane filament reaches a reasonable level when entering the gel bath by adding a mixture of volatile and weakly volatile organic solvents in an optimized ratio to the casting liquid, thereby ensuring that the outer edge of the membrane filament forms a dense structure in the initial stage of thermodynamic phase separation.

[0022] 3. The present invention adds an optimized ratio of non-solvent to the casting solution, ensuring that the outer wall of the hollow fiber membrane enters a thermodynamic phase imbalance state at the optimal time point after entering the gel bath, thereby reducing the thickness of the dense layer while ensuring smooth formation of the dense layer;

[0023] 4. The present invention adds an optimized ratio of organic solvent to the core liquid, which effectively reduces the activity of the core liquid, thereby avoiding the rapid solidification of the inner side of the membrane wall and preventing the development and formation of finger-shaped and teardrop-shaped cavities in the support layer. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0025] Example 1: A method for preparing a blended polymer hollow fiber membrane by spinning, comprising the following steps:

[0026] (1) Preparation of spinning solution: Take the casting solution and the core solution, and mix the casting solution and the core solution evenly;

[0027] The casting solution includes the following raw materials in percentage by mass: 25% polysulfone particles, 9% polyimide A powder, 1% polyimide B powder, 35% weak volatile organic solvent, 20% volatile organic solvent, and 10% non-solvent, wherein the non-solvent is ethanol;

[0028] The core liquid comprises the following raw materials in percentage by mass: 20% pure water and 80% weak volatile organic solvent; the weak volatile organic solvent is N-methylpyrrolidone, and the volatile organic solvent is tetrahydrofuran;

[0029] (2) Spinning: The mixed solution is spun by a dry-wet phase separation process to obtain membrane fibers; when the dry-wet phase separation process is spun at a temperature of 70°C, 50 ml of the casting solution is pumped through a gear pump.

[0030] / hour, and a core liquid flow rate of 25 ml / hour are extruded from the spinneret to obtain an initial hollow fiber membrane. The initial hollow fiber membrane passes through an air gap of 10 cm in the air and then enters a gel bath. The gel bath medium is pure water. The initial hollow fiber membrane passes through a traction wheel, a tension control device, and an oscillating device, and is then collected on a collection wheel. The collection wheel traction rate is 20 m / min.

[0031] (3) Post-processing: The membrane fibers were placed in a water tank for three days to remove the residual solution. The water in the water tank was changed every day. The membrane fibers were taken out of the water tank and dried at room temperature to obtain the finished product.

[0032] Example 2: A method for preparing a blended polymer hollow fiber membrane by spinning, comprising the following steps:

[0033] (1) Preparation of spinning solution: Take the casting solution and the core solution, and mix the casting solution and the core solution evenly;

[0034] The casting solution includes the following raw materials in mass percentage: 29% polysulfone particles, 0.5% polyimide A powder, 0.5% polyimide B powder, 40% weak volatile organic solvent, 20%

[0035] Volatile organic solvent, 10% non-solvent, non-solvent is ethanol;

[0036] The core liquid comprises the following raw materials in percentage by mass: 20% pure water and 80% weak volatile organic solvent; the weak volatile organic solvent is N-methylpyrrolidone, and the volatile organic solvent is tetrahydrofuran;

[0037] (2) Spinning: The mixed solution is spun by a dry-wet phase separation process to obtain membrane fibers; during the dry-wet phase separation process, at a temperature of 70°C, 50 ml of the casting solution is pumped through a gear pump.

[0038] / hour, and a core liquid flow rate of 25 ml / hour are extruded from the spinneret to obtain an initial hollow fiber membrane. The initial hollow fiber membrane passes through an air gap of 10 cm in the air and then enters a gel bath. The gel bath medium is pure water. The initial hollow fiber membrane passes through a traction wheel, a tension control device, and an oscillating device, and is then collected on a collection wheel. The collection wheel traction rate is 20 m / min.

[0039] (3) Post-processing: The membrane fibers were placed in a water tank for three days to remove the residual solution. The water in the water tank was changed every day. The membrane fibers were taken out of the water tank and dried at room temperature to obtain the finished product.

[0040] Example 3: A method for preparing a blended polymer hollow fiber membrane by spinning, comprising the following steps:

[0041] (1) Preparation of spinning solution: Take the casting solution and the core solution, and mix the casting solution and the core solution evenly;

[0042] The casting solution includes the following raw materials in mass percentage: 30% polysulfone particles, 2% polyimide A powder, 2% polyimide B powder, 36% weak volatile organic solvent, 20%

[0043] Volatile organic solvent, 10% non-solvent, non-solvent is ethanol;

[0044] The core liquid comprises the following raw materials in percentage by mass: 20% pure water and 80% weak volatile organic solvent; the weak volatile organic solvent is N-methylpyrrolidone, and the volatile organic solvent is tetrahydrofuran;

[0045] (2) Spinning: The mixed solution is spun by a dry-wet phase separation process to obtain membrane fibers; during the dry-wet phase separation process, at a temperature of 70°C, 50 ml of the casting solution is pumped through a gear pump.

[0046] / hour, and a core liquid flow rate of 25 ml / hour are extruded from the spinneret to obtain an initial hollow fiber membrane. The initial hollow fiber membrane passes through an air gap of 10 cm in the air and then enters a gel bath. The gel bath medium is pure water. The initial hollow fiber membrane passes through a traction wheel, a tension control device, and an oscillating device, and is then collected on a collection wheel. The collection wheel traction rate is 20 m / min.

[0047] (3) Post-processing: The membrane fibers were placed in a water tank for three days to remove the residual solution. The water in the water tank was changed every day. The membrane fibers were taken out of the water tank and dried at room temperature to obtain the finished product.

[0048] Example 4: A method for preparing a blended polymer hollow fiber membrane by spinning, comprising the following steps:

[0049] (1) Preparation of spinning solution: Take the casting solution and the core solution, and mix the casting solution and the core solution evenly;

[0050] The casting solution includes the following raw materials in percentage by mass: 25% polysulfone particles, 1% polyimide A powder, 9% polyimide B powder, 35% weak volatile organic solvent, 20% volatile organic solvent, and 10% non-solvent, wherein the non-solvent is ethanol;

[0051] The core liquid comprises the following raw materials in percentage by mass: 20% pure water and 80% weak volatile organic solvent; the weak volatile organic solvent is N-methylpyrrolidone, and the volatile organic solvent is tetrahydrofuran;

[0052] (2) Spinning: The mixed solution is spun by a dry-wet phase separation process to obtain membrane fibers; during the dry-wet phase separation process, at a temperature of 70°C, 50 ml of the casting solution is pumped through a gear pump.

[0053] / hour, and a core liquid flow rate of 25 ml / hour are extruded from the spinneret to obtain an initial hollow fiber membrane. The initial hollow fiber membrane passes through an air gap of 10 cm in the air and then enters a gel bath. The gel bath medium is pure water. The initial hollow fiber membrane passes through a traction wheel, a tension control device, and an oscillating device, and is then collected on a collection wheel. The collection wheel traction rate is 20 m / min.

[0054] (3) Post-processing: The membrane fibers were placed in a water tank for three days to remove the residual solution. The water in the water tank was changed every day. The membrane fibers were taken out of the water tank and dried at room temperature to obtain the finished product.

[0055] Comparative Example 1: Referring to Example 1, the polyimide A powder was replaced with polysulfone particles.

[0056] Comparative Example 2: Referring to Example 1, the polyimide A powder and the polyimide B powder were all replaced with polysulfone particles.

[0057] Comparative Example 3: Referring to Example 1, the polyimide B powder was replaced with polysulfone particles.

[0058]

[0059] The embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a blended polymer hollow fiber membrane by spinning, characterized in that: The following steps are involved: (1) Preparation of spinning solution: Take the casting solution and the core solution, and mix them evenly; The casting solution includes the following raw materials in percentage by mass: 25-30% polysulfone particles, 0.5-10% polyimide A powder, 0.5-10% polyimide B powder, 35-40% weak volatile organic solvent, 20% volatile organic solvent, and 10% non-solvent; The core liquid includes the following raw materials in percentage by mass: 20% pure water, 80% weak volatile organic solvent; (2) Spinning: The mixed solution is spun using a dry-wet phase separation process to obtain membrane fibers; (3) Post-processing: The membrane filaments are placed in a water tank for three days to remove the residual solution. The water in the water tank is replaced every day. The membrane filaments are taken out of the water tank and dried at room temperature to obtain the finished product.

2. The method for preparing a blended polymer hollow fiber membrane by spinning according to claim 1, characterized in that: The weakly volatile organic solvent is N-methylpyrrolidone, and the volatile organic solvent is tetrahydrofuran.

3. The method for preparing a blended polymer hollow fiber membrane by spinning according to claim 1, characterized in that: The non-solvent is ethanol.

4. The preparation method of blended polymer hollow fiber membrane spinning according to claim 1, characterized in that: During spinning using the dry-wet phase separation process, at a temperature of 70°C, an initial hollow fiber membrane is extruded from a spinneret by a gear pump at a flow rate of 50 ml / h of casting liquid and 25 ml / h of core liquid. The initial hollow fiber membrane enters a gel bath after passing through an air gap of 10 cm in the air. The gel bath medium is pure water. The initial hollow fiber membrane passes through a traction wheel, a tension control device, and a swing device, and is collected on a collecting wheel. The collecting wheel traction rate is 20 m / min.

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