Double-layer hollow black crystal fiber membrane filter assembly and filtering method

Abstract

This invention relates to the field of hollow fiber membrane technology, specifically to a double-layer hollow black crystal fiber membrane filtration structure and filtration method, comprising: a filtration container with a drain pipe and a water inlet; a fiber membrane assembly disposed within the filtration container, the fiber membrane assembly comprising multiple double-layer hollow fiber membranes, the first and second ends of the multiple double-layer hollow fiber membranes being connected to a water distribution tray; and a water inlet pipe, the first end of which is connected to a water pump, and the second end of which is connected to the input end of a switching valve. This invention, through the double-layer membrane design of the double-layer hollow fiber membrane, creates two filtration paths. When one filtration path becomes clogged, the other filtration path can be switched. Simultaneously, backwashing can be performed on the membrane structure, causing the adhering contaminants to detach, achieving a cleaning effect. When the first filtration path becomes clogged again, the system switches back to the previous filtration path, improving filtration efficiency and reducing the need for repeated and frequent disassembly and cleaning of the membrane structure.

Description

Technical Field

[0001] This invention relates to the field of hollow fiber filtration membrane technology, and more specifically to a double-layer hollow black crystal fiber membrane filtration assembly and filtration method. Background Technology

[0002] Hollow fiber membranes are widely used in coal chemical wastewater treatment projects due to their superior separation performance. They are commonly used in the pretreatment of reverse osmosis (RO) membranes, and are also widely used in the chemical, electronics, pharmaceutical, drinking water, wastewater discharge, and food industries.

[0003] Hollow fiber membranes filter macromolecules in solutes through their microporous structure. As filtration time increases, dirt adhering to the membrane surface forms a membrane layer. As solute molecules continue to be adsorbed and accumulated on the membrane surface, the filtration performance deteriorates, leading to an increase in pressure differential and making it impossible to effectively filter wastewater. Frequent replacement and cleaning of the filter membrane module are required. Summary of the Invention

[0004] According to a first aspect of the present invention, a double-layer hollow black crystal fiber membrane filtration assembly is provided, comprising:

[0005] The filter container is equipped with a drain pipe and a water inlet.

[0006] A fiber membrane module is disposed inside the filter container. The fiber membrane module includes multiple double-layer hollow fiber membranes, and the first and second ends of the multiple double-layer hollow fiber membranes are connected to a water distribution tray.

[0007] The water inlet pipe has a first end connected to a water pump and a second end connected to the input end of a switching valve. The first output end of the switching valve is connected to a first water supply pipe, and the second end of the switching valve is connected to a second water supply pipe.

[0008] Drainage pipes;

[0009] The double-layer hollow fiber membrane includes a hollow inner membrane and a hollow outer membrane, wherein the hollow outer membrane is located outside the hollow inner membrane, and an annular channel is formed between the hollow inner membrane and the hollow outer membrane;

[0010] The outer wall of the hollow outer membrane and the inner wall of the filter container form a first cavity, and the interior of the hollow inner membrane forms a second cavity. The annular channel and the first cavity are separated by the hollow outer membrane, and the annular channel and the second cavity are separated by the hollow inner membrane.

[0011] The first water supply pipe is connected to the water inlet, so that the first cavity is connected to the first water supply pipe; the second water supply pipe is connected to the water distribution plate, so that the second water supply pipe is connected to the second cavity.

[0012] The hollow outer membrane is configured such that the pore density gradually decreases from the first cavity toward the annular channel;

[0013] The hollow inner membrane is configured such that the pore density gradually decreases from the second cavity toward the annular channel;

[0014] The first end of the drainage pipe is connected to the water distribution plate, so that the drainage pipe is connected to the annular channel.

[0015] Preferably, the system also includes a controller. The first water supply pipe is equipped with a first pressure sensor, the second water supply pipe is equipped with a second pressure sensor, and the sewage pipe is equipped with a first solenoid valve. The controller is configured to control the switching valve to switch the output port when the pressure detected by the first or second pressure sensor exceeds a threshold, and within a time T after the switching valve switches, the first solenoid valve is controlled to open according to a preset state.

[0016] Preferably, the first solenoid valve is controlled to open in a pulsed state.

[0017] Preferably, the pressure threshold of the first pressure sensor and the second pressure sensor is 1.5-2.0 MPa.

[0018] Preferably, the water distribution plate located above the double-layer hollow fiber membrane is provided with a water distribution pipe. The first end of the water distribution pipe is connected to the second water supply pipe, and the second end of the water distribution pipe is connected to the second cavity. The water distribution plate located below the double-layer hollow fiber membrane is provided with a manifold box. The first end of the manifold box is connected to the annular channel, and the second end of the manifold box is connected to the drain pipe. The hollow inner membrane passes through the manifold box and extends into the first cavity.

[0019] Preferably, the lower end of the hollow inner membrane is provided with a second solenoid valve, so that the second cavity is connected to the first cavity through the second solenoid valve. The second solenoid valve is configured to close when the switching valve is switched to the second output end, and to open or close simultaneously with the first solenoid valve when the switching valve is switched to the first output end.

[0020] Preferably, the hollow outer membrane and the hollow inner membrane each have a three-layer structure, with the first layer having a pore size of 150-250 μm, the second layer having a pore size of 100-150 μm, and the third layer having a pore size of 20-50 μm.

[0021] Preferably, the pore size density of the first membrane structure includes dense pore regions and sparse pore regions, with the length ratio of the dense pore regions to the sparse pore regions being 1:4-5, and the dense pore regions and sparse pore regions being alternately distributed in the longitudinal direction.

[0022] According to a second aspect of the present invention, a filtering method is provided, comprising the following steps:

[0023] Step 1: Input raw water with stable pressure into the inlet pipe, so that the raw water is filtered through a double-layer hollow fiber membrane in the first or second chamber. The filtration path includes the first filtration path and the second filtration path.

[0024] Step 2: Continuously monitor the pressure data detected by the first pressure sensor and the second pressure sensor. When the pressure data detected by either one exceeds the threshold, switch the original filtration path of the raw water and open the drain pipe at the same time to backwash the membrane structure. The raw water is discharged through the drain pipe after being filtered by the double-layer hollow fiber membrane.

[0025] The first filtration path is a first cavity - hollow outer membrane - annular channel, and the second filtration path is a second cavity - hollow inner membrane - annular channel.

[0026] Preferably, when the raw water is filtered through the first filtration path, the second cavity is connected to the first cavity when the sewage pipe drains water; when the raw water is filtered through the second filtration path, the second cavity is not connected to the first cavity.

[0027] Compared with the prior art, the hollow black crystal fiber membrane filtration structure proposed in this invention, through the double-layer membrane design of the double-layer hollow fiber membrane, forms two filtration paths. When one filtration path is blocked, the other filtration path can be switched. At the same time as filtration, the membrane structure can be backwashed to remove the dirt attached to the membrane structure, forming a cleaning effect. When the first filtration path is blocked, it can be switched back to the previous filtration path, improving the efficiency of filtration and reducing the need for repeated and frequent disassembly and cleaning of the membrane structure. Attached Figure Description

[0028] The accompanying drawings are not intended to be drawn to scale. In the drawings, every identical or nearly identical component shown in each figure may be indicated by the same reference numeral. For clarity, not every component is labeled in each figure.

[0029] Figure 1 This is a schematic diagram of the double-layer hollow black crystal fiber membrane filtration assembly shown in this invention, wherein the raw water is backwashed through the first filtration path.

[0030] Figure 2 This is a schematic diagram of the double-layer hollow black crystal fiber membrane filtration assembly shown in this invention, wherein the raw water is filtered through the first filtration path.

[0031] Figure 3 This is a schematic diagram of the double-layer hollow black crystal fiber membrane filtration assembly shown in this invention, wherein the raw water is backwashed through the second filtration path.

[0032] Figure 4This is a schematic diagram of the double-layer hollow black crystal fiber membrane filtration assembly shown in this invention, illustrating the filtration of raw water through a second filtration path.

[0033] Figure 5 This is an exemplary structural schematic diagram of the fiber membrane assembly shown in this invention.

[0034] Figure 6 This is a schematic diagram of the membrane structure of the double-layer hollow fiber membrane shown in this invention. Detailed Implementation

[0035] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0036] Currently, hollow fiber membranes are typically either externally supported or internally supported. In externally supported membranes, raw water passes through the hollow fiber membrane from the outside into the membrane interior, and contaminants are filtered to the outside of the membrane. As contaminants gradually adhere and accumulate on the outside of the membrane structure, they form a colloidal membrane that covers the surface of the fiber membrane. At this point, the filtration pressure of the filtration device increases, the filtration capacity decreases, and the membrane structure needs to be disassembled and cleaned.

[0037] The present invention aims to reduce the need for repeated and frequent disassembly and cleaning of the membrane structure by setting a novel double-layer hollow fiber membrane structure, which switches the filtration path when the filtration pressure reaches a threshold and backwashes the original filtration path.

[0038] Double-layer hollow black crystal fiber membrane filter module

[0039] Combination Figure 1-4 as well as Figure 5 The double-layer hollow black crystal fiber membrane filter assembly of the embodiment shown includes a filter container 10, a fiber membrane assembly 20, an inlet pipe and an outlet pipe 12.

[0040] As shown in the figure, the water inlet pipe includes a main pipe and two branch pipes. The main pipe is connected to a water pump for pumping raw water. The first water delivery pipe 32 and the second water delivery pipe 31 are respectively connected to two filtration paths. The main pipe and the first water delivery pipe 32 and the second water delivery pipe 31 are connected by a switching valve 30.

[0041] Referring to the diagram, the filter container 10 is equipped with a drain pipe 11 and a water inlet 322, and the fiber membrane module 20 is disposed inside the filter container 10. The fiber membrane module 20 includes multiple double-layer hollow fiber membranes, especially black crystal hollow fiber membranes, which are hollow fiber membranes made of casting solution incorporating graphene, thereby enhancing the strength of the hollow fiber membrane and improving the efficiency of treating N and P organic matter in raw wastewater.

[0042] The fiber membrane module 20 serves as a raw water separation and filtration element, used to filter the raw water entering the filter container 10, so that the dirt is trapped in the filter container 10.

[0043] As an optional embodiment, in order to improve the filtration efficiency of the double-layer hollow fiber membrane, multiple double-layer hollow fiber membranes are arranged in a manner that... Figure 5 The distribution shown forms a set of fiber membrane modules 20, and more than one set of fiber membrane modules 20 is set in the filter container 10 according to the actual raw water filtration flow rate.

[0044] Furthermore, in combination Figure 5 As shown, the first and second ends of multiple double-layer hollow fiber membranes are connected to the water distribution plate 23.

[0045] As an optional example, the upper water distribution plate 23 is connected to the top of the filter container 10, and the lower water distribution plate 23 is located at the bottom of the filter container 10.

[0046] Combination Figure 1-5 As shown, specifically, the double-layer hollow fiber membrane includes a hollow inner membrane 221 and a hollow outer membrane 222.

[0047] The hollow outer membrane 222 is located outside the hollow inner membrane 221, forming an annular channel 223 between the hollow inner membrane 221 and the hollow outer membrane 222.

[0048] Thus, raw water can pass through the outer wall of the hollow outer membrane 222 and enter the annular channel 223, or raw water can pass through the inner wall of the hollow inner membrane 221 and enter the annular channel 223. It can be seen that raw water can be filtered by the double-layer hollow fiber membrane through two paths.

[0049] In an optional embodiment, the outer wall of the hollow outer membrane 222 and the inner wall of the filter container 10 form a first cavity 101, and the interior of the hollow inner membrane 221 forms a second cavity 201. The annular channel 223 and the first cavity 101 are separated by the hollow outer membrane 222, and the annular channel 223 and the second cavity 201 are separated by the hollow inner membrane 221.

[0050] Furthermore, the first water supply pipe 32 is connected to the water inlet 322, so that the first cavity 101 is connected to the first water supply pipe, and the second water supply pipe 31 is connected to the water distribution plate 23, so that the second water supply pipe 31 is connected to the second cavity 201.

[0051] Thus, the first water supply pipe 32 enters the first cavity 101 through the water inlet 322, and then enters the annular channel 223 through the filtration of the hollow outer membrane 222 to form the first filtration path. The second water supply pipe 32 enters the second cavity 201 through the water distribution pipe 21, and then enters the annular channel 223 through the filtration of the hollow inner membrane 221 to form the second filtration path.

[0052] As an optional example, when raw water passes through the hollow outer membrane 222 from the outside of the hollow outer membrane 222, it has a flushing effect on the hollow inner membrane 221. When raw water passes through the hollow inner membrane 221 from the inside of the hollow inner membrane 221, it has a flushing effect on the hollow outer membrane 222. Thus, the dirt attached to the membrane structure can be backwashed, so that the dirt is flushed and discharged.

[0053] Combination Figure 6 In the example shown, in order to facilitate the removal of contaminants adhering to the membrane structure during backwashing, the hollow outer membrane 222 is configured such that the porosity gradually decreases from the first cavity 101 toward the annular channel 223; the hollow inner membrane 221 is configured such that the porosity gradually decreases from the second cavity 201 toward the annular channel 223.

[0054] Because the pore density on the outer side of the membrane structure is high and its binding ability with the attached material is weak, it is easy for the raw water to detach from the inner side of the membrane structure.

[0055] Combination Figure 1 and Figure 5 As shown, the water distribution plate 23 located above the double-layer hollow fiber membrane is provided with a water distribution pipe 21. The first end of the water distribution pipe 21 is connected to the second water supply pipe 31, and the second end of the water distribution pipe 21 is connected to the second cavity 201. The water distribution plate 23 blocks the annular channel 223.

[0056] As an optional example, the water distribution tray 23 located below the double-layer hollow fiber membrane is provided with a manifold 231.

[0057] Referring to the attached drawings, the first end of the manifold 231 is connected to the annular channel 223, the second end of the manifold 231 is connected to the drainage pipe 12, and the hollow inner membrane 221 passes through the manifold 231 and extends into the first cavity 101.

[0058] Thus, after the raw water enters the first cavity 101 through the inlet hole 322, it can only pass through the hollow outer membrane 222 into the annular channel, and then enter the manifold 231 through the annular channel 223 and be discharged from the drain pipe 12. Therefore, the first filtration path and the second filtration path are relatively independent and will not cross-flow.

[0059] In a further embodiment, the first water supply pipe 32 is equipped with a first pressure sensor 321, the second water supply pipe 31 is equipped with a second pressure sensor 311, and the sewage pipe 11 is equipped with a first solenoid valve 111, which can be switched and controlled by a controller based on the detected pressure. For example, when the pressure detected by the first pressure sensor 321 or the second pressure sensor 311 exceeds a threshold, the switching valve 30 is controlled to switch the output port. Furthermore, within a preset time T after the switching valve 30 switches, the first solenoid valve 111 is controlled to open according to a preset state.

[0060] Furthermore, a second solenoid valve 233 is provided at the lower end of the hollow inner membrane 221, so that the second cavity 201 and the first cavity 101 are connected through the second solenoid valve 233. The second solenoid valve 233 is configured to close when the switching valve 30 is switched to the second output end, and to open or close simultaneously with the first solenoid valve 111 when the switching valve 30 is switched to the first output end.

[0061] It should be understood that in the embodiments of the present invention, pressure sensors and other detection devices, as well as pumps, solenoid valves and other actuators, are all connected to the controller in an advantageous manner to realize data and signal communication, and to complete the transmission and reception of sensor data and the transmission of control commands. As an optional implementation, the controller may be an industrial-grade PLC controller, configured with a control box or control cabinet, on which a display for representing information such as pressure values ​​and raw water flow rate to the operator, and a control panel for controlling the pumps, solenoid valves and other actuators, are configured.

[0062] Combination Figure 1 As shown, assuming the raw water previously flowed through the second filtration path, when the second pressure sensor 311 detects that the pressure exceeds the threshold, indicating that the deposits on the inner surface of the hollow inner membrane 221 are attached, the switching valve 30 switches the output port, causing the raw water to switch from the second water supply pipe 31 to the first water supply pipe 32, i.e., the raw water flows through the first filtration path. At this time, the second solenoid valve 233 opens, and the first solenoid valve 111 opens. The pressure inside the hollow inner membrane 221 is low, and the water flowing through the hollow outer membrane 222 flows through the annular channel 223 to the hollow inner membrane 221, scouring the inner surface of the hollow inner membrane 221, causing the deposits to fall off and forming sewage, which is discharged from the drain pipe 11.

[0063] Combination Figure 2 As shown, after the sewage has been discharged for a certain period of time, the first solenoid valve 111 and the second solenoid valve 233 are closed. At this time, the channel inside the hollow inner membrane 221 is blocked. Therefore, the raw water can only be discharged from the drain pipe 12 along the annular channel 223 after being filtered by the hollow outer membrane 222.

[0064] Combination Figure 3 As shown, as the filtration time of the hollow outer membrane 222 increases, dirt adheres to its surface, and the filtration pressure increases. When the first pressure increases to a preset value, the switching valve 30 switches the output port, causing the raw water to switch from the first water supply pipe 32 to the second water supply pipe 31. That is, the raw water flows through the second filtration path. The raw water enters the second cavity 223 inside each hollow inner membrane 221 from the water distribution pipe 21. At the same time, the first solenoid valve 111 opens, and the water flowing through the hollow inner membrane 221 flows through the annular channel 223 to the hollow outer membrane 222, and washes the outer surface of the hollow outer membrane 222, causing the adhering substances to fall off and forming sewage. The sewage is discharged from the drain pipe 11.

[0065] Combination Figure 4 As shown, after the sewage has been discharged for a certain period of time, the first solenoid valve 111 is closed. At this time, the first cavity 101 is closed. Therefore, the raw water can only be discharged from the drain pipe 12 along the annular channel 223 after being filtered by the hollow inner membrane 221.

[0066] In the above embodiment, the first solenoid valve 111 is controlled to open in a pulsed state, so that the resulting pulsed water flow can better remove dirt from the surface of the membrane structure.

[0067] In a preferred embodiment, the pressure thresholds of the first pressure sensor 321 and the second pressure sensor 311 can be preset to 1.5-2.0 MPa. In another embodiment, the thresholds can be adjusted according to the designed raw water filtration environment.

[0068] In a specific embodiment, the membrane structures of both the hollow outer membrane 222 and the hollow inner membrane 221 include three layers: the first layer has a pore size of 150-250 μm, the second layer has a pore size of 100-150 μm, and the third layer has a pore size of 20-50 μm.

[0069] Preferably, the pore size density of the first membrane structure includes dense pore regions and sparse pore regions, with the length ratio of the dense pore regions to the sparse pore regions being 1:4-5, and the dense pore regions and sparse pore regions being alternately distributed in the longitudinal direction.

[0070] In this way, the separation between the dense and sparse pore areas makes the thickness of the dirt adhesion uneven, which makes it easier to fall off in chunks during backwashing, thus improving the backwashing effect.

[0071]

Filtering Method

[0072] The process of using the double-layer hollow black crystal fiber membrane filter assembly described in the above embodiments for raw water filtration includes the following steps:

[0073] Step 1: Input raw water with stable pressure into the water inlet pipe, so that the raw water is filtered through the first chamber 101 or the second chamber 201 through the double-layer hollow fiber membrane. The filtration path includes the first filtration path and the second filtration path.

[0074] Step 2: Continuously monitor the pressure data detected by the first pressure sensor 321 and the second pressure sensor 311. When the pressure data detected by either one exceeds the threshold, switch the original filtration path of the raw water and open the drain pipe 12 at the same time to backwash the membrane structure. The raw water is discharged through the drain pipe 12 after being filtered by the double-layer hollow fiber membrane.

[0075] The first filtration path is the first cavity 101 - hollow outer membrane 222 - annular channel 223, and the second filtration path is the second cavity 201 - hollow inner membrane 221 - annular channel 223. Example

[0076] Combination Figure 1 As shown, assuming the raw water previously flowed through the second filtration path, when the second pressure sensor 311 detects that the pressure exceeds the threshold, indicating that the inner surface of the hollow inner membrane 221 is covered with deposits, the switching valve 30 switches the output port, causing the raw water to switch from the second water supply pipe 31 to the first water supply pipe 32, that is, the raw water flows through the first filtration path. At this time, the second solenoid valve 233 opens, the first solenoid valve 111 opens, the pressure inside the hollow inner membrane 221 is low, and the water flowing through the hollow outer membrane 222 flows through the annular channel 223 to the hollow inner membrane 221, and washes the inner surface of the hollow inner membrane 221, causing the deposits to fall off and forming sewage, which is discharged from the drain pipe 11.

[0077] Combination Figure 2 As shown, after the sewage has been discharged for a certain period of time, the first solenoid valve 111 and the second solenoid valve 233 are closed. At this time, the channel inside the hollow inner membrane 221 is blocked. Therefore, the raw water can only be discharged from the drain pipe 12 along the annular channel 223 after being filtered by the hollow outer membrane 222.

[0078] Combination Figure 3 As shown, as the filtration time of the hollow outer membrane 222 increases, dirt adheres to its surface, and the filtration pressure increases. When the first pressure increases to a preset value, the switching valve 30 switches the output port, causing the raw water to switch from the first water supply pipe 32 to the second water supply pipe 31. That is, the raw water flows through the second filtration path. The raw water enters the second cavity 223 inside each hollow inner membrane 221 from the water distribution pipe 21. At the same time, the first solenoid valve 111 opens, and the water flowing through the hollow inner membrane 221 flows through the annular channel 223 to the hollow outer membrane 222, and washes the outer surface of the hollow outer membrane 222, causing the adhering substances to fall off and forming sewage. The sewage is discharged from the drain pipe 11.

[0079] Combination Figure 4 As shown, after the sewage has been discharged for a certain period of time, the first solenoid valve 111 is closed. At this time, the first cavity 101 is closed. Therefore, the raw water can only be discharged from the drain pipe 12 along the annular channel 223 after being filtered by the hollow inner membrane 221.

[0080] Preferably, when the raw water is filtered through the first filtration path, the second chamber 201 is connected to the first chamber 101 when the sewage pipe 11 drains water; when the raw water is filtered through the second filtration path, the second chamber 201 is not connected to the first chamber 101.

[0081] Specifically, the lower end of the hollow inner membrane 221 is provided with a second solenoid valve 233, so that the second cavity 201 and the first cavity 101 are connected through the second solenoid valve 233. The second solenoid valve 233 is configured to close when the switching valve 30 is switched to the second output end, and to open or close simultaneously with the first solenoid valve 111 when the switching valve 30 is switched to the first output end.

[0082] When the raw water is filtered through the first filtration path, the second solenoid valve 233 and the first solenoid valve 111 open simultaneously, connecting the second chamber 201, the first chamber 101, and the drain pipe 11; when the raw water is filtered through the second filtration path, the second solenoid valve 233 closes and the first solenoid valve 111 opens, connecting the first chamber 101 and the drain pipe 11.

[0083] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A double-layer hollow black crystal fiber membrane filtration module, wherein the hollow black crystal fiber membrane is a hollow fiber membrane made of a casting solution incorporating graphene, characterized in that, include: The filter container (10) is equipped with a drain pipe (11) and a water inlet (322). A fiber membrane module (20) is disposed inside the filter container (10). The fiber membrane module (20) includes multiple double-layer hollow fiber membranes, and the first and second ends of the multiple double-layer hollow fiber membranes are connected to a water distribution tray (23). The water inlet pipe is connected to a water pump at one end and to the input end of a switching valve (30) at the other end. The first output end of the switching valve (30) is connected to a first water supply pipe (32), and the second end of the switching valve (30) is connected to a second water supply pipe (31). Drainage pipe (12); The double-layer hollow fiber membrane includes a hollow inner membrane (221) and a hollow outer membrane (222). The hollow outer membrane (222) is located outside the hollow inner membrane (221), forming an annular channel (223) between the hollow inner membrane (221) and the hollow outer membrane (222). The outer wall of the hollow outer membrane (222) and the inner wall of the filter container (10) form a first cavity (101). The interior of the hollow inner membrane (221) forms a second cavity (201). The annular channel (223) and the first cavity (101) are separated by the hollow outer membrane (222), and the annular channel (223) and the second cavity (201) are separated by the hollow inner membrane (221). The first water supply pipe (32) is connected to the water inlet (322), so that the first cavity (101) is connected to the first water supply pipe, and the second water supply pipe (31) is connected to the water distribution plate (23), so that the second water supply pipe (31) is connected to the second cavity (201); The hollow outer membrane (222) is configured such that the void density gradually decreases from the first cavity (101) toward the annular channel (223); The hollow inner membrane (221) is configured such that the void density gradually decreases from the second cavity (201) toward the annular channel (223); The first end of the drainage pipe (12) is connected to the water distribution plate (23), so that the drainage pipe (12) is connected to the annular channel (223); The first water supply pipe (32) is equipped with a first pressure sensor (321), the second water supply pipe (31) is equipped with a second pressure sensor (311), and the sewage pipe (11) is equipped with a first solenoid valve (111). The water distribution tray (23) located below the double-layer hollow fiber membrane is provided with a manifold (231), and the hollow inner membrane (221) passes through the manifold (231) and extends into the first cavity (101).

2. The double-layer hollow black crystal fiber membrane filter module according to claim 1, characterized in that, It also includes a controller, which is configured to control the switching valve (30) to switch the output port when the pressure detected by the first pressure sensor (321) or the second pressure sensor (311) exceeds the threshold, and the first solenoid valve (111) is controlled to open according to a preset state within a time T after the switching valve (30) is switched.

3. The double-layer hollow black crystal fiber membrane filter module according to claim 2, characterized in that, The first solenoid valve (111) is controlled to open in a pulse state.

4. The double-layer hollow black crystal fiber membrane filter module according to claim 1, characterized in that, The pressure threshold of the first pressure sensor (321) and the second pressure sensor (311) is 1.5-2.0 MPa.

5. The double-layer hollow black crystal fiber membrane filter assembly according to claim 1, characterized in that, The water distribution plate (23) located above the double-layer hollow fiber membrane is provided with a water distribution pipe (21). The first end of the water distribution pipe (21) is connected to the second water supply pipe (31), and the second end of the water distribution pipe (21) is connected to the second cavity (201). The first end of the manifold (231) is connected to the annular channel (223), and the second end of the manifold (231) is connected to the drain pipe (12).

6. The double-layer hollow black crystal fiber membrane filter module according to claim 1, characterized in that, The lower end of the hollow inner membrane (221) is provided with a second solenoid valve (233), so that the second cavity (201) and the first cavity (101) are connected through the second solenoid valve (233). The second solenoid valve (233) is configured to close when the switching valve (30) is switched to the second output end, and to open or close simultaneously with the first solenoid valve (111) when the switching valve (30) is switched to the first output end.

7. The double-layer hollow black crystal fiber membrane filter assembly according to any one of claims 1-6, characterized in that, The hollow outer membrane (222) and the hollow inner membrane (221) both have three layers: the first layer has a pore size of 150-250 μm, the second layer has a pore size of 100-150 μm, and the third layer has a pore size of 20-50 μm.

8. The double-layer hollow black crystal fiber membrane filter assembly according to claim 7, characterized in that, The pore size density of the first membrane structure includes dense pore regions and sparse pore regions, with a length ratio of 1:4-5 between the dense and sparse pore regions, and the dense and sparse pore regions are alternately distributed in the longitudinal direction.

9. A filtration method based on the double-layer hollow black crystal fiber membrane filtration module according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Input raw water with stable pressure into the water inlet pipe, so that the raw water is filtered through the first chamber (101) or the second chamber (201) through the double-layer hollow fiber membrane. The filtration path includes the first filtration path and the second filtration path. Step 2: Continuously monitor the pressure data detected by the first pressure sensor (321) and the second pressure sensor (311). When the pressure data detected by either of them exceeds the threshold, switch the original filtration path of the raw water and open the drain pipe (12) at the same time to backwash the membrane structure. The raw water is discharged through the drain pipe (12) after being filtered by the double-layer hollow fiber membrane. The first filtration path is a first cavity (101) - hollow outer membrane (222) - annular channel (223), and the second filtration path is a second cavity (201) - hollow inner membrane (221) - annular channel (223).

10. The filtration method according to claim 9, characterized in that, When the raw water is filtered through the first filtration path, the second cavity (201) is connected to the first cavity (101) when the sewage pipe (11) drains water. When the raw water is filtered through the second filtration path, the second cavity (201) is not connected to the first cavity (101).

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