CN201921638U - Membrane element with two-way permeability - Google Patents

Abstract

The utility model relates to a membrane element with two-way permeability, which is characterized in that the separation layer medium has pore passages with different selective permeation effects, and the separation medium can be realized by using the difference in permeability of different materials in different pore passages. The selectivity of different materials on both sides passes through at the same time. In the case of the same shape of the membrane element, the membrane element can have selective permeation pore channels with different composition ratios, thereby improving the two-way permeability of the membrane element. The bidirectional permeable membrane element of the utility model is used in the selective bidirectional mass transfer process of the heterogeneous system, and has the characteristics of high mass transfer efficiency, controllable process, simple equipment manufacturing and low cost.

Description

A membrane element with bidirectional permeability

technical field

The utility model relates to a membrane element with different selective hole channels, in particular to a membrane element with two-way permeability, which can simultaneously undertake a plurality of membrane separation tasks with different separation selectivities for different materials, and its inhomogeneous The application of phase system selective two-way osmosis process.

Background technique

Membrane separation is achieved by the selective separation of membrane materials. Common pressure-driven membrane separation processes include microfiltration, ultrafiltration, nanofiltration, etc., which are used to separate fluids containing heterogeneous particles and macromolecules. Solvents and small molecule solutes in the medium pass through the membrane, and macromolecules or large-sized particles are retained by the membrane. Compared with conventional filtration, membrane filtration has the characteristics of high filtration precision and energy saving.

In order to improve the permeability of the membrane element and the membrane area filled per unit volume, the membrane element is designed as a hollow fiber type, capillary type, tubular type, flat type, pleated skirt type, spiral wound type and the patents given in US5873998 and US5853582 Irregular multi-channel type.

When there is a liquid phase in the system, due to the existence of surface tension, when the fluid flows through a small-pore channel, the membrane pressure will be affected by the channel size and the hydrophilic/hydrophobic factors of the manufacturing material. The difference is due to the difference of liquid phase composition and operating conditions.

In the process of membrane element preparation, avoiding the occurrence of large and small pores on the membrane separation medium as much as possible, maintaining a sufficiently narrow pore size distribution and uniformity of membrane materials are important guarantees for the selective permeation performance of membrane elements. Therefore, in addition to the membrane pore size that directly affects the shape-selective rejection performance, the membrane pore size and the uniformity of the membrane material have also become important indicators to measure the quality of the current membrane elements.

In the currently applied membrane elements, the separation membrane medium is designed as a selective separation barrier for the fluid. The two sides of the barrier are the raw material side and the permeate side respectively. Under the action of osmotic driving force, the target substance can only be transferred from the raw material side. To the permeate side, and is collected and removed from the permeate side, so that the original feed liquid is separated to achieve the purpose of recovery or removal. In the application process, due to the uniformity of membrane pore size and membrane material, under the action of unidirectional osmotic driving force, this type of membrane element can only realize the "unidirectional" permeation of materials from the fixed raw material side to the permeate side at the same time. At this time, the membrane element can only undertake the selective separation task for one material.

Contents of the invention

In order to effectively utilize the selective permeation effect of the membrane element and improve the utilization efficiency and performance of the membrane element, the utility model proposes a new type of membrane element with different osmosis channels, without changing the shape and total surface area of the membrane element. , by adjusting the pore size distribution, number ratio, microstructure of the pore channel and the material composition of the separation medium, and using the difference in the permeation pressure difference of different materials in different channels, the separation medium can be different from its two sides. The selective permeation of materials at the same time, a single membrane element can have two-way permeation, and can simultaneously undertake the membrane separation task of different separation selectivities for two or more materials.

Here, the selective permeation pore channel refers to the pore channel that has selective permeation effect on specific components or fluids in the application system under operating conditions.

According to the specific application system and operating conditions, by adjusting the average pore size, channel microstructure and constituent materials of different selective osmosis pore channels, the permeation bubble pressure and Osmotic resistance, the two-way permeability of the membrane element can be realized by using the difference in the permeation bubble pressure and osmotic resistance of the fluid on both sides of the separation layer of the membrane element in the pore channel of different selective osmosis; Adjusting the quantity ratio and pore size distribution between them can control the bidirectional permeation flux of the fluid on both sides of the separation layer of the membrane element, and then realize the balance and stability of the bidirectional permeation process of the fluid on both sides of the separation layer of the membrane element.

Therefore, without changing the shape and structure of the membrane element, designing pore channels with different permeation functions for different materials and adjusting their proportions appropriately will realize the multi-task bidirectional membrane permeation process on the basis of one membrane element. This is different from the previous design idea aimed at improving the membrane pore size and the uniformity of the membrane material among the permeable channels.

The membrane element described therein includes two or more kinds of selectively permeable pore channels, which may be fixed tubular channels; when the membrane element includes a dynamic layer formed by particle accumulation, the pore channels with permeability also have There may be "dynamic" channels formed by dynamic membrane layers. "Dynamic" here refers to the limited changeable state of the internal pore channel microstructure of the membrane layer during the application of the membrane element due to the compressibility or mobility of the constituent particles. The degree of this change It can be controlled by adjusting the influencing conditions such as the bulk density, particle size distribution, and rigidity of the constituent materials of the film layer particles.

Wherein the membrane elements mentioned above are aimed at the same material system, the reason for the difference in permeability of different membrane pore channels may be microstructures such as pore size and channel path; It can also be the difference in application conditions such as temperature, pressure, field action (electric field, magnetic field, inertial force field, etc.), the inhomogeneity of the distribution of matter systems, etc. In practical applications, the above multiple factors are allowed to work together (such as adjusting the constituent materials and pore size distribution of a certain type of selective permeable pore channel at the same time) to better realize and strengthen the flow of fluid in the selective permeable pore channel. two-way permeability.

The specific technical solution of the utility model is: a membrane element with two-way permeability, characterized in that the separation layer of the membrane element has pore passages with different selective permeation effects, and a single membrane element passes through the pore passages with different selective permeation effects. The two-way selective permeation effect of the fluid on both sides of the membrane can be realized.

Wherein the membrane element has a support layer, an intermediate layer, and one or more layers of the membrane layer that can be refined, wherein the membrane layer with the main separation function can be located on the surface of the membrane element, constitute the intermediate layer or independently constitute the membrane element subject.

The membrane elements described therein can be in the form of flat plate, tube (including multi-channel tube), spiral wound, hollow fiber, or in the form of ring, curved, polyhedral, or irregular membrane elements. It can be in the form of spherical, fibrous, and irregular free membranes.

The pore channels with different permeation selectivities described therein are distributed uniformly, or locally concentratedly, or randomly distributed,

The support structure layer of the membrane element described therein can be formed by extrusion, casting, coating, and sintering, and the separation layer can be formed by deposition, dipping, pyrolysis, emulsion polymerization, hot pressing, particle sintering, particle accumulation, sol -Preparation by methods of gel, phase separation, synthesis, coating, casting.

The membrane element mentioned therein can have a one-layer or multi-layer structure, and the constituent materials of the same layer can be the same or different (that is, the constituent materials of different parts of the same layer can be different); the constituent materials of different layers can be be the same, or they can be different.

The constituent materials of the membrane element mentioned therein can be stainless steel, copper and copper alloy, titanium and titanium alloy, aluminum oxide, zirconium oxide, titanium oxide, silicon oxide and cordierite, mullite, graphite, carbon fiber, polytetrafluoroethylene , polysulfone, polyimide, PVA, perfluorinated resin, epoxy resin, styrene resin, acrylic resin, any one or a compound of several. When the membrane element is prepared by sintering, one or more of magnesium oxide, potassium oxide, sodium oxide, lithium oxide, bentonite, and kaolin can be used as additives.

A membrane element with bidirectional permeability according to claim 1, characterized in that the following (1), (2), (3) or (4) can be used in the preparation process of the membrane element. One or more methods in ), to control the proportion of the number of membrane pores whose bubble pressure value is 0.01Mpa lower than the bubble pressure value corresponding to the average pore diameter of the membrane layer to be greater than 0.01%. The above (1) is to limit the particle size distribution of the constituent particles of the membrane layer, so as to realize the difference in the average pore diameter of different permeable channels. 1% of the particles and the total average particle size of the constituent particles, the average difference between the two ranges from 10 to 10,000 times; where (2) is to limit the local packing density of the constituent particles of the membrane layer to produce permeable channels of different pore sizes, The local packing density of the limiting material particles can be realized by forming a dynamic film, applying uneven pressure, dissolution, and ablation; the (3) is the use of PVA, polyvinyl alcohol, silica gel, fluorine rubber, etc. Water-based materials or polytetrafluoroethylene, vinylidene fluoride, and paraffin-based hydrophobic materials modify and dope the surface of pore channel materials to strengthen the differences in physical and chemical properties of materials with different permeable pore channel structures; (4) by adjusting the membrane Layer thickness (0.01um ~ 100mm), membrane porosity (1% ~ 80%) form, in order to control the penetration resistance of fluid in different pore channels.

In particular, a plurality of the same or different membrane elements can be combined to form a complete and relatively independent functional unit, and the relationship between the functional unit and its constituent membrane elements is a whole-part relationship. When the functional unit exhibits selective bi-directional permeability as a whole, the functional unit can be considered as a single membrane element in a broad sense.

The bidirectional permeable membrane element of the utility model is mainly used in the separation process of selective bidirectional permeation of heterogeneous matter systems.

The selective separation process of the gas-liquid two-phase system in the above separation process can be simply described as follows: the two sides of the separation membrane are respectively the liquid phase component and the gas phase component to be permeated. It is advisable to record the liquid phase as A and the gas phase as B. And it may be said that the permeation from the A fluid side to the B fluid side is forward, and vice versa; the separation membrane material can be infiltrated by A, and the membrane pore channels on the separation membrane are mainly divided into two types, which are called large pores and small pores here. After being infiltrated by A, the penetrating "bubble pressure" values of fluid B corresponding to the large pores and small pores are ΔP ₁ and ΔP ₂ , and ΔP ₁ <ΔP ₂ ; the pressure difference between the B fluid side and the A fluid side is controlled to be ΔP ₃ ( ΔP ₁ <ΔP ₃ <ΔP ₂ ), at this time, under the action of capillary force, fluid A can permeate forward to the side of fluid B through the small hole, and fluid B can also overcome the "bubble pressure" and reverse to the side of fluid A through the large hole penetration. Under specific operating conditions, a single membrane pore channel exhibits unidirectional permeability, but the membrane element as a whole exhibits bidirectional permeability. Therefore, on the basis of a single membrane element, the selective two-way permeation of different fluids by the membrane element can be realized by utilizing the permeability difference of different membrane pore channels.

In particular, when the cavity wall on one side of the separation layer is tightly attached to the surface of the membrane element, there are two situations: when the separation layer is located inside the membrane element, the gap between the separation layer and the cavity wall constitutes the part of the membrane element The fluid micro-pitch cavity on this side; when the separation layer is located on the surface of the membrane element attached to the wall of the cavity, the fluid on the corresponding side can be located on the interface between the separation layer and the cavity wall, that is, a zero-pitch cavity appears. At this time, a heterogeneous fluid may appear on the micro-pitch cavity or zero-pitch cavity due to reaction, phase change, etc., and the fluid directly permeates and diffuses to the other side of the separation layer corresponding to the cavity wall.

The beneficial effects of the utility model:

1. In the case of the same external size, the new microstructured membrane elements can have pore channels with different osmotic effects, and can simultaneously undertake the membrane separation of different separation selectivities for two or more materials under the condition of stable osmotic driving force task, so that a single membrane element has two-way permeation.

2. For a specific material system, without changing the total surface area of the membrane element, by adjusting the pore size distribution, quantity ratio, microstructure of the pore channel and the material composition of the separation medium for different permeation channels, the separation layer on both sides of the separation layer can be realized. The balanced and controllable penetration rate of heterogeneous materials can effectively meet the requirements of mass transfer, heat transfer and reaction of different processes, and improve the utilization efficiency and performance of membrane elements.

3. Compared with ordinary membrane element tubes, the new microstructure membrane element of the utility model does not have much change in appearance and structure, but because of the two-way permeation effect, it can undertake multiple membrane separation tasks for different materials at the same time, reducing the production cost and operating cost of the device.

4. The two-way permeation of heterogeneous fluid will form a large number of heterogeneous suspended particles, such as small bubbles in the liquid phase. When these particles escape from the surface of the membrane element, they will alleviate the pollution of the membrane element due to impact and adsorption. Phenomenon, to avoid a large amount of accumulation of pollutants, so that the membrane elements have a long operating cycle, life and high operating flux.

Description of drawings

Among them, Figure 1 is a schematic diagram of two-way permeability; 1-1 in the figure is liquid phase fluid, 1-2 is gas phase fluid,

Figure 2 The positional relationship of the membrane layer that plays the main role of separation in the membrane element; Figure 2-1 is the positional relationship when the separation layer is on the surface of the membrane element, and 2-2 is the positional relationship when the separation layer is inside the membrane element.

Figure 3 Example of micro-pitch and zero-pitch cavities; 3-1 in the figure is the separation layer, 3-2 is the cavity wall, 3-3 is the micro-pitch cavity, and 3-4 is the zero-pitch cavity.

Figure 4 An example diagram of the "bottleneck" part that controls the direction of penetration; Figure 4-1 is the "bottleneck" part that controls the direction of penetration.

Figure 5 Example diagram of the relationship between membrane material components and membrane elements; 5-1 in the figure is a membrane element component, and 5-2 is a membrane element composed of multiple membrane element components.

Figure 6 Example diagram of the distribution of different functional pore channels in the membrane separation medium; 6-1 in the figure is evenly distributed, 6-2 is locally concentrated arrangement, and 6-3 is irregularly arranged.

Detailed ways

Implementation example 1

Rectangular sheet-shaped flat membrane element, the support body is made of 316L stainless steel metal powder material extruded and sintered, with a thickness of 3mm, a diameter of 100mm, an average pore diameter of 10um, and a porosity of 40%. One side of the support is covered with a film layer of 316L stainless steel metal powder material, the thickness of the film layer is 25um, the porosity of the film layer is 25%, the average pore size is 0.2um, and the pore channels with a pore size of 0.95-1.5um (accounting for the total 1% of the amount). Put the membrane element into the plate-and-frame filter equipment, one side of the separation layer of the membrane element is pure water material liquid 1-1, and the other side is air 1-2. The principle of bidirectional permeability is shown in Figure 1; the local structure of the membrane element is shown in Figure 2, 2-1, and the filled part in the figure is the membrane layer. Maintain the pressure difference between the air side and the pure water side at 0.2Mpa, and the room temperature is 25°C. At this time, pure water 1-1 permeates to the air side through small holes with a pore size of 0.2um, and the average permeation flux is 8Lm ^-2 h ^-1 ; air 1 -2 permeates to the pure water side through small holes with a diameter greater than 0.95um, with an average permeation flux of 500L m ^-2 h ^-1 .

Implementation example 2

The support body of the circular tubular membrane element is formed by extrusion and sintering of alumina powder material, the tube wall thickness is 1mm, the inner diameter is 6mm, the average pore diameter is 5um, and the porosity is 40%. The inner surface of the tube is covered with a film layer of zirconia powder material, the thickness of the film layer is 15um, the porosity of the film layer is 35%, the average pore diameter is 0.35um, and the pore channels with a pore diameter of 1.8-2.2um are irregularly distributed (accounting for 10% of the total) 2%). A 304 stainless steel tube with an outer diameter of 5.5mm is inserted into the support tube, and 304 stainless steel metal powder material is evenly filled between the support tube and the stainless steel tube. The average particle size of the powder is 15um, the average pore diameter is 2um, and the porosity of the filling layer is 25%. .

The filling layer together with the support layer and the zirconia layer constitute the membrane element. The structure of the membrane element is shown as 2-2 in Figure 2. The zirconia separation layer is located between the support layer and the filling layer of the membrane element. The filling layer also provides a micro-pitch cavity (3-3 in Figure 3) between the zirconia film layer (3-1 in Figure 3) and the stainless steel pipe wall (3-2 in Figure 3). If there is no filling layer and the zirconia film layer is closely attached to the stainless steel pipe wall (3-1 in Figure 3) (3-2 in Figure 3), a "zero-spacing" cavity can be formed between the two (Figure 3 Middle 3-4). Water vapor at 160°C is passed into the stainless steel tube, and isothermally condensed. The support body is pure water at normal pressure boiling point temperature. At this time, the pure water penetrates into the stainless steel powder filling layer through the small holes of the zirconia layer, and is heated in this layer to become hot steam. Afterwards, the dynamic pore channels of the filled layer penetrate through the macropores of the zirconia layer. At this time, the interstitial pressure and evaporation rate of the filling layer are self-balanced, and the evaporation rate of pure water can be stabilized at 50Kg m ^-2 h ^-1 .

At this time, forward osmosis and reverse osmosis occur in the same membrane element at the same time, but the membrane pore channels they pass through are different. It should be noted that for the permeable membrane layer formed by particle accumulation, the membrane pore channel is a non-uniform section and a single tubular channel, and the part that controls the permeation direction is the "bottleneck" part (4-1 in Figure 4), and the other Part of it can be temporarily used as a channel for forward osmosis or reverse osmosis, and a "dynamic" two-way osmosis occurs. Of course, the "dynamic" permeation channel here also includes a situation, such as the permeation channel formed by the accumulation of particles similar to the packing layer that can move within a certain range. change.

Implementation example 3

Tubular membrane elements, coated with a layer of zirconia powder material on the surface of carbon steel pipes with a diameter of 6mm and a wall thickness of 1mm, the thickness of the film layer is 10um, the porosity of the film layer is 25%, the average pore size is 0.5um, and the pore diameters are uniformly distributed 3 ~ 5um hole channels (accounting for 2% of the total). A layer of silica powder is evenly sintered outside the membrane layer, the thickness of the silica powder layer is 1mm, the average pore diameter is 25um, and the porosity is 40%.

At this time, a "zero gap" cavity (3-4 in Figure 3) is formed between the zirconia film layer (3-1 in Figure 3) and the carbon steel pipe wall (3-2 in Figure 3). Water vapor at 160°C is introduced into the stainless steel tube and isothermally condensed. The support body is pure water at normal pressure boiling point temperature. At this time, the pure water penetrates into the surface of the carbon steel tube through the small holes of the zirconia layer and turns into hot steam on the heat exchange surface. It penetrates through the large pore channels of the zirconia layer. At this time, the interstitial pressure and evaporation rate of the filling layer are self-balanced, and the evaporation rate of pure water can be stabilized at 60Kg m ^-2 h ^-1 .

Implementation example 4

The regular hexagonal membrane element component (5-1 in Figure 5), the support body is made of 316 stainless steel metal powder material extruded and sintered, with a thickness of 3mm, an average pore diameter of 6um, and a porosity of 40%. One side surface of the 6 supports is covered with a film layer of titanium oxide powder material, the thickness of the film layer is 20um, the porosity of the film layer is 32%, and the average pore size is 0.25um. Weld or assemble the 6 coated polygonal components and one non-coated polygonal component (the structure is shown as 5-2 in Figure 5) to form a membrane element. The membrane element is packaged in the middle of the tubular pressure vessel. The cavity on the side of the support body is filled with pure water, and the cavity on the membrane side is filled with benzene. The fluids on both sides flow cross-flow on the surface of the membrane element to maintain the pressure difference between the benzene side and the pure water side. 0.1Mpa, room temperature 25°C. At this time, the average permeation flux of pure water to the benzene side is 5Lm ^-2 h ^-1 , and the average permeation flux of benzene to the pure water side is 20L m ^-2 h ^-1 . .

Example 5

Three square flat membrane elements, the support body is made of titanium metal powder material extruded and sintered, with a thickness of 3mm, a side length of 60mm, an average pore diameter of 2um, and a porosity of 21%. Cover the surface of the support body with a layer of mixed material of manganese dioxide powder and polytetrafluoroethylene (mass ratio 5:1). Distribute pore channels with a pore diameter of 1-2um (accounting for the total 0.8% of the amount). Press the diaphragm with an average pore diameter of 0.05um on the membrane side surface of the membrane element to make the two closely adhere. The titanium metal membrane element is encapsulated in a pressure-bearing cavity, the cavity on the side of the support body is filled with hydrogen peroxide solution and pressurized at 0.1MPa, and the other side is pure water at normal pressure. Under the catalysis of manganese dioxide, hydrogen peroxide decomposes in the manganese dioxide-containing membrane layer, and the hydrogen peroxide is decomposed to generate water and oxygen. The um membrane seeps out, and the hydrogen peroxide solution penetrates through the small holes of the membrane element to the manganese dioxide layer to replenish the hydrogen peroxide lost after decomposition. At 25°C, the gas and liquid permeation rates of the corresponding decomposition reactions can be kept balanced and stable. Among them, the membrane elements whose membrane layer is evenly distributed, locally concentrated, and randomly arranged to distribute macropore channels, the proportions of the gas generated by the reaction passing through the macropores to the side of the support body are 99%, 95%, and 98.5%, respectively.

Claims (5)

1. A membrane element with bidirectional permeability, characterized in that the separation layer of the membrane element has pore passages with different selective permeation effects, and a single membrane element can realize the flow of fluid on both sides of the membrane through the pore passages of different selective permeation effects Two-way selective osmosis. 2. A membrane element with bidirectional permeability according to claim 1, wherein said membrane element has one or more layers of support layer, intermediate layer and membrane layer, wherein there is a main separation The active membrane layer can be located on the surface of the membrane element, constitute an intermediate layer or independently constitute the main body of the membrane element. 3. A membrane element with bi-directional permeability according to claim 1, characterized in that the pore channels with different permeation selectivities are distributed uniformly or locally , or randomly distributed. 4. A membrane element with bidirectional permeability according to claim 1, characterized in that said membrane element can have a one-layer or multi-layer structure, and the constituent materials of the same layer can be the same, or can be are different; the constituent materials of different layers may be the same or different. 5. A membrane element with bidirectional permeability according to claim 1, characterized in that the membrane element is in the form of a flat plate, a tube, a spiral wound, a hollow fiber, or a ring or a curved surface Shaped, polyhedral, and irregular membrane elements, or spherical, fibrous, and irregular free membranes.

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