A multi-stage membrane separation purification device and method for biogas purification and upgrading.

Abstract

This invention relates to the field of environmental engineering technology, and discloses a multi-stage membrane separation purification device and method for biogas purification, comprising: a fixed end; a telescopic tube connected to the upper side of the fixed end; a movable end, including a lifting head connected to the upper end of the telescopic tube and a rotating head horizontally rotatably connected to the lifting head; and a plurality of hollow fiber membrane filaments connected between the fixed end and the rotating head and located inside the telescopic tube. This invention can adjust the hollow fiber membrane filaments into a spirally densely arranged state, significantly reducing the spacing between the membrane filaments, increasing the contact area between biogas and the membrane filaments, extending the gas-liquid contact time, ensuring sufficient separation of impurities such as carbon dioxide, hydrogen sulfide, and water vapor, and improving purity. The lifting and rotating linkage structure allows for flexible switching between the dense membrane filament working state and the stretched cleaning state: during cleaning, the membrane filaments are straightened and the spacing is expanded, eliminating dead angles between the dense membrane filaments and providing space for impurities to fall off.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, specifically to a multi-stage membrane separation purification device and method for biogas purification and upgrading. Background Technology

[0002] Biogas is a renewable and combustible gas produced by the fermentation of organic waste by microorganisms in a closed anaerobic environment. Its main component is methane, supplemented by carbon dioxide, and it also contains small amounts of toxic and odorous gases such as hydrogen sulfide and hydrogen. Straw, human and animal excrement, kitchen waste, and livestock and poultry manure can all be used as fermentation raw materials. Biogas has a wide range of uses. It can be used as fuel for cooking, heating, and lighting, as well as for power generation and driving machinery. After purification, it can also be used as biogas. It is clean, environmentally friendly, and recyclable. However, biogas is flammable and explosive and contains toxic gases, so leak prevention measures must be taken when using it.

[0003] The direct purpose of biogas purification is to reduce pollutant emissions, deodorize, remove harmful impurities such as hydrogen sulfide and carbon dioxide, and prevent sewage, odor, and toxic gases from polluting water bodies, the atmosphere, and soil. It is an environmental pollution control and waste resource utilization project.

[0004] Biogas purification mainly involves sequentially desulfurizing, dehydrating, removing impurities such as dust, ammonia, and siloxanes from raw biogas, and further removing carbon dioxide to increase the methane content to over 95%, making it meet the standards for biogas or vehicle fuel. Desulfurization primarily employs dry adsorption, wet absorption oxidation, and biological desulfurization to reduce the toxic and corrosive hydrogen sulfide content to a safe range. Dehydration removes water vapor through condensation and molecular sieve drying, preventing water accumulation in pipelines and equipment damage. Decarbonization is the core of purification, commonly using pressure swing adsorption (PSA), high-pressure water washing, and membrane separation. Biogas membrane separation purification relies on polymer membranes to separate gas components. Taking advantage of the fact that impurities such as carbon dioxide can more easily penetrate the membrane than methane, biogas flows through the membrane module, where carbon dioxide, water vapor, and other impurities are continuously separated and removed, while methane is retained and enriched, ultimately yielding high-purity biogas. For example, patent CN107653016B describes a method for separating and purifying biogas by combining membrane separation and pressure swing adsorption.

[0005] Multi-stage membrane separation and purification equipment for biogas is a complete set of equipment that connects two or more membrane modules in series to purify crude biogas to 95%–99% methane in stages. Its core principle is step-by-step separation and concentration. Examples include the multi-stage membrane separation biogas purification device with publication number CN206121466U and the multi-stage membrane separation biogas purification device for purifying biogas with publication number CN216223707U. To improve separation and purification efficiency and ensure sufficient contact between biogas and membrane fibers, the membrane fibers are densely distributed with small spacing. Although pretreatment is performed before biogas membrane separation and purification, residual solid dust, liquid water mist impurities, and precipitated elemental sulfur in the raw material cause dust and impurities to accumulate on the surface and between the membrane fibers, leading to increased inlet resistance, decreased gas flux, and poorer separation efficiency. Furthermore, the densely distributed membrane fibers are not conducive to the removal of impurities. Summary of the Invention

[0006] The purpose of this invention is to solve at least one of the problems in the prior art mentioned above, and to provide a multi-stage membrane separation purification device and method for biogas purification.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A multi-stage membrane separation purification device for biogas purification and upgrading includes: Fixed end; The telescopic tube is connected to the upper side of the fixed end; The movable end includes a lifting head connected to the upper end of the telescopic tube and a rotating head that is horizontally rotatably connected to the lifting head; Several hollow fiber membrane filaments are connected between the fixed end and the rotating head and located inside the telescopic tube.

[0008] Furthermore, the fixed end is provided with a groove-shaped lower end cap, and the lower end cap is provided with a bottom filling body. The lower end of the hollow fiber membrane extends into the interior of the bottom filling body. The upper part of the bottom filling body protrudes from the lower end cap and is conical. There is an annular gap between the lower end cap and the inner wall of the fixed end cap and they are connected by several radial plates. A sludge collection hopper is connected to the lower side of the fixed end cap.

[0009] Furthermore, the fixed end, telescopic pipe, movable end, and sludge collection hopper are arranged in multiple sets in a one-to-one correspondence; a closed screw conveyor is provided on the lower side of the sludge collection hopper, a sludge discharge port is provided on the lower side of the downstream end of the screw conveyor, and a backflushing air outlet is provided on the upper side of the upstream end of the screw conveyor.

[0010] Furthermore, the lower end cap is provided with a fixing plate, and several vertical tubes are evenly distributed on the upper circumference of the fixing plate. The inner hole of the vertical tube extends to the lower side of the fixing plate. The vertical tube passes through the bottom potting body. A vertically lifting top vibration block is provided inside the vertical tube. The top vibration block is connected to the movable end by a traction rope.

[0011] Furthermore, the bottom inner side of the lower end cap is provided with an inner support plate, and the top vibration blocks are all connected to the upper side of the inner support plate. The middle part of the fixing plate has an upwardly recessed receiving groove, and the receiving groove is provided with a spring whose lower end abuts against the inner support plate.

[0012] Furthermore, a rotational support is provided between the lifting head and the rotating head, and a top potting body is provided on the inner side of the middle part of the rotating head, through which the upper end of the hollow fiber membrane filament passes.

[0013] Furthermore, the fixed end is connected to a biogas inlet pipe, the lifting head is connected to a biogas exhaust pipe, and the upper side of the rotating head is connected to a permeate gas exhaust pipe.

[0014] Furthermore, the telescopic tube is provided with several vertical guide rods at intervals on its outer side, and the lifting head is connected to a lower lifting plate that moves vertically along the guide rods on its outer side. A bottom plate, a middle plate, and a top plate are provided sequentially from bottom to top along the guide rods.

[0015] Furthermore, an upper lifting plate is provided between the middle plate and the top plate, which moves up and down along the guide rod. An automatic telescopic rod for driving the upper lifting plate to move up and down is installed on the middle plate. A screw rod is rotatably connected to the middle of the upper lifting plate. A screw hole that meshes with the screw rod is provided in the middle of the middle plate. A rotating head is connected to the lower end of the screw rod.

[0016] This invention also provides the following technical solutions: A multi-stage membrane separation purification method for biogas purification: biogas enters from the fixed end and passes through the outer side of the hollow fiber membrane inside the telescopic tube, while impurities permeate through the hollow fiber membrane and are discharged from the rotating head. The lowering of the lifting head reduces the length of the telescopic tube, while the rotation of the rotating head causes the hollow fiber membrane filaments to be densely distributed in a spiral shape inside the telescopic tube to purify the biogas. The raising of the lifting head increases the length of the telescopic tube, while the rotation of the rotating head in the opposite direction lengthens the hollow fiber membrane filaments, increasing the spacing between them and allowing impurities to be discharged from between them.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention can adjust hollow fiber membrane filaments into a spirally densely arranged state, significantly reducing the spacing between membrane filaments, increasing the contact area between biogas and membrane filaments, extending the gas-liquid contact time, ensuring that impurities such as carbon dioxide, hydrogen sulfide, and water vapor are fully separated, improving methane purity, and stably increasing the methane content to over 95%, meeting the standards for biogas and vehicle fuel. The telescopic tube of this invention forms a deflection channel after compression, which effectively avoids short-circuiting biogas along the gap between the shell and the membrane module, and forces the airflow through the membrane fiber area, solving the problems of airflow short-circuiting and insufficient purification in traditional equipment; the multi-stage membrane module series design realizes step-by-step purification, adapts to raw biogas with different impurity contents, and has a wider range of applications. This invention innovatively adopts a lifting and rotating linkage structure, which can flexibly switch between the dense working state of membrane fibers and the stretching and cleaning state: during cleaning, the membrane fibers are straightened and the spacing is expanded, eliminating dead corners between dense membrane fibers and providing space for impurities to fall off. This invention features a top-mounted vibration block mechanism that, combined with a traction rope and spring, creates mechanical vibration. This promotes the collection of falling impurities into the sludge collection hopper, and utilizes a screw conveyor to centrally transport the impurities collected by the multi-stage membrane, ensuring comprehensive cleaning. The screw conveyor also serves as a channel for backflushing gas discharge. The bottom potting body adopts a conical surface structure with chamfered radial plates to reduce impurity retention, thereby reducing the probability of localized contamination at the source and enabling the equipment to operate continuously and stably for extended periods. The pipeline and slag discharge structure of this invention adopt a closed design, and the screw conveyor is sealed to prevent the leakage of flammable and explosive biogas and toxic hydrogen sulfide gas, thereby improving the safety of equipment operation and meeting the explosion-proof and leakage-proof requirements of biogas conditions. Key components such as the lower end cap, the bottom wall of the lower end cap, and the upper wall of the rotating head are all connected by detachable bolts. The internal membrane wires, top vibration blocks, springs and other vulnerable components are easy to inspect and replace, reducing the difficulty of later operation and maintenance. This invention integrates membrane separation, vibration impurity removal, pulse backflushing, and centralized slag discharge functions into one unit. The entire set of equipment has a compact structure and occupies a small area. The entire device relies on an automatic telescopic rod, a screw rod, and a screw hole drive transmission mechanism to achieve automated lifting, rotation, and working condition switching. It is suitable for industrial continuous gas production scenarios such as environmental biogas projects, livestock and poultry manure treatment, and kitchen waste fermentation, and has high value for large-scale application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] Figure 2 This is a schematic diagram of the connection structure between the single-stage membrane and the screw conveyor of the present invention.

[0020] Figure 3 This is a schematic diagram of the single-stage membrane structure of the present invention.

[0021] Figure 4 This is a schematic diagram of the support structure and drive structure of the present invention.

[0022] Figure 5 This is an external schematic diagram of the purification and refining structure of the present invention.

[0023] Figure 6 This is a schematic diagram of the internal structure of the purification and refining process of the present invention.

[0024] Figure 7 This is a schematic diagram of the lifting head and rotating head of the present invention in a separated state.

[0025] Figure 8 This is a schematic diagram of the dense distribution of hollow fiber membrane filaments according to the present invention.

[0026] Figure 9 This is a schematic diagram of the internal structure of the fixed end of the present invention.

[0027] Figure 10 This is a schematic diagram of the fixed end head structure from the upper side.

[0028] Figure 11 This is a schematic diagram of the fixed end of the present invention from the lower view.

[0029] Figure 12 This is a schematic diagram of the connection between the traction rope and the top vibration block of the present invention.

[0030] In the diagram: 1. Fixed end; 2. Telescopic pipe; 3. Lifting head; 4. Rotating head; 5. Hollow fiber membrane; 6. Lower end cap; 7. Bottom filling body; 8. Radial plate; 9. Sludge hopper; 10. Screw conveyor; 11. Sludge outlet; 12. Backflushing gas outlet; 13. Fixed plate; 14. Vertical pipe; 15. Top vibrating block; 16. Inner support plate; 17. Receiving trough; 18. Spring; 19. Main traction rope; 20. Support traction rope; 21. Biogas inlet pipe; 22. Biogas exhaust pipe; 23. Guide rod; 24. Lower lifting plate; 25. Rotary support; 26. Top frame; 27. Top filling body; 28. Bottom plate; 29. ​​Middle plate; 30. Top plate; 31. Upper lifting plate; 32. Automatic telescopic rod; 33. Screw rod; 34. Screw hole; 35. Permeate gas exhaust pipe; 36. Frame. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention; that is, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Specific embodiments of the multi-stage membrane separation purification device and method for biogas purification and upgrading provided by the present invention are as follows: Please refer to the attached document. Figures 1-12This multi-stage membrane separation purification device for biogas purification consists of multiple sets of identical single-stage membrane modules connected in series. Each set of single-stage membrane modules includes four core components: a fixed end 1, a telescopic tube 2, a movable end, and hollow fiber membrane filaments 5. The complete set of equipment is equipped with a frame 36, a screw conveyor 10, a drive mechanism, pipelines, valves, and other auxiliary structures, and is installed on the frame 36 to achieve integrated operation of biogas purification, membrane filament self-cleaning, and centralized collection and discharge of impurities.

[0033] The lower part of the fixed end 1 is a cylindrical shell, and the upper part gradually narrows into a conical shell and connects with the telescopic tube 2. The lower end 6 with a groove structure is embedded inside. An annular gap is left between the lower end 6 and the inner wall of the fixed end 1. The two are fixed by welding multiple radial plates 8 evenly around the circumference. The upper side of the radial plate 8 is chamfered to form a sharp point, which can reduce the retention of dust and impurities.

[0034] The lower end cap 6 is equipped with a bottom potting body 7. The lower end of the hollow fiber membrane filament 5 is integrally potted and fixed inside the bottom potting body 7, thereby achieving the lower part fixation and lower end port sealing of the hollow fiber membrane filament 5. The upper part of the bottom potting body 7 protrudes upward from the lower end cap 6, and its upper part is designed as a truncated cone structure, which facilitates the sliding of impurities to the surrounding area.

[0035] The bottom wall of the lower end cap 6 is detachably connected to the ring side wall with bolts, which facilitates the inspection and replacement of internal components. A circular fixing plate 13 is horizontally installed inside the lower end cap 6. The fixing plate 13 forms a lower limit on the bottom potting body 7. At the same time, multiple vertical tubes 14 are installed on the upper side of the fixing plate 13. The vertical tubes 14 extend vertically and are arranged radially along the fixing plate 13. The vertical tubes 14 penetrate the bottom potting body 7, and their inner holes extend to the lower side of the fixing plate 13.

[0036] Each vertical tube 14 is equipped with a vertically sliding top vibration block 15. All top vibration blocks 15 are uniformly fixed on the inner support plate 16 inside the lower head 6. The inner support plate 16 moves vertically up and down within the lower head 6. Rubber buffer pads are attached to the upper and lower surfaces of the middle part of the inner support plate 16 to prevent direct impact with the fixing plate 13 and the bottom wall of the lower head 6 during up and down movement, thereby reducing the vibration of the device body. The fixing plate 13 has an upwardly recessed receiving groove 17 at its center. A spring 18 is installed inside the receiving groove 17. The lower end of the spring 18 abuts against the inner support plate 16. Under normal conditions, the spring 18 is in a compressed state, providing a restoring elastic force for the reciprocating vibration of the top vibration block 15.

[0037] The lower side of the fixed end 1 is sealed and connected to the sludge collection hopper 9 by flange bolts. The sludge collection hopper 9 is a cone-shaped structure that is wider at the top and narrower at the bottom, used to collect falling solid impurities. The upper side wall of the fixed end 1 is connected to the biogas inlet pipe 21. A shut-off valve is installed at each pipe interface to control the biogas feed.

[0038] The telescopic pipe 2 adopts a telescopic corrugated pipe structure, with its lower end sealed and connected to the upper port of the fixed end 1, and its upper end sealed and connected to the lifting head 3 of the movable end. Multiple vertical guide rods 23 are evenly distributed around the outer circumference of the telescopic pipe 2. There is a horizontal gap between the guide rods 23 and the telescopic pipe 2. The guide rods 23 are provided with a bottom plate 28, a middle plate 29, and a top plate 30 from bottom to top. The three plates are all fastened to the frame 36, forming the vertical guide reference of the entire equipment.

[0039] The lower lifting plate 24 is fixedly connected to the outside of the lifting head 3. The lower lifting plate 24 has a sliding hole that matches the guide rod 23, allowing it to move vertically up and down along the guide rod 23, while restricting the lifting head 3 from circumferential rotation. The side wall of the lifting head 3 is connected to the biogas exhaust pipe 22, which is also equipped with a shut-off valve to discharge the main biogas after membrane separation.

[0040] The movable end consists of two parts: a lifting head 3 and a rotating head 4. A rotating support 25 is installed between the two to ensure that the rotating head 4 can rotate horizontally circumferentially relative to the lifting head 3, while a rotational seal is provided between them. In some embodiments, the upper outer side of the lifting head 3 has an annular flange, and the lower end of the rotating head 4 has an annular track with a U-shaped cross-section. The U-shaped opening faces radially toward the center, and the annular flange rotates within the annular track. A sealing ring is provided on the annular flange to ensure a rotational seal.

[0041] A top frame 26 is set at the center of the inner side of the rotating head 4. The top frame 26 is filled with a top potting body 27. The upper end of the hollow fiber membrane filament 5 passes through and is fixed inside the top potting body 27. The upper end of the hollow fiber membrane filament 5 is located between the top potting body 27 and the top wall of the rotating head 4 to discharge permeated impurities. A flow gap is reserved between the upper wall of the rotating head 4 and the top potting body 27. The top of the rotating head 4 is connected to a permeate gas exhaust pipe 35 to discharge permeate impurities such as carbon dioxide, hydrogen sulfide, and water vapor. The pipeline is equipped with a shut-off valve.

[0042] An upper lifting plate 31 is provided between the middle plate 29 and the top plate 30. The upper lifting plate 31 is also sleeved on the guide rod 23 and can slide vertically. Two automatic telescopic rods 32 are symmetrically provided on the lower side of the middle plate 29. The telescopic ends of the automatic telescopic rods 32 pass through the middle plate 29 and are connected to the bottom surface of the upper lifting plate 31, providing vertical lifting power for the upper lifting plate 31 and the rotating head 4.

[0043] A spiral rod 33 is rotatably mounted at the center of the upper lifting plate 31. The upper end of the spiral rod 33 is rotatably connected to the center of the upper lifting plate 31. Horizontal friction is reduced through a thrust bearing. The rotation direction is the same as the spiral rod 33's own rotation direction. The spiral rod 33 extends downwards, and a spiral hole 34 is opened at the center of the middle plate 29. The outer wall of the spiral rod 33 meshes with the inner wall of the spiral hole 34. The lower end of the spiral rod 33 passes through the spiral hole 34 and connects to the upper wall of the rotating head 4. When the automatic telescopic rod 32 drives the upper lifting plate 31 to move vertically, the spiral rod 33 rotates synchronously circumferentially under the action of the thread in the spiral hole 34, thereby driving the rotating head 4 to rotate and the lifting head 3 to rise and fall synchronously, realizing a lifting + rotation linkage action.

[0044] Multiple hollow fiber membrane filaments 5 are arranged in a bundle and housed inside the telescopic tube 2. The upper and lower ends are fixed between the top potting body 27 and the bottom potting body 7, respectively.

[0045] The telescopic tube 2 has a traction rope at its center, which includes a main traction rope 19 and multiple branch traction ropes 20. The upper end of the main traction rope 19 is connected to the movable end, which can be connected to the inner wall of the top frame 26 or the lifting head 3. The lower end branches into several branch traction ropes 20, and each branch traction rope 20 is connected to a top vibration block 15. Under normal conditions, the upper surface of the top vibration block 15 is smoothly connected to the conical surface of the bottom potting body 7 to receive falling impurities. When the movable end rises to the top and moves back and forth, the traction rope pulls the inner support plate 16 and the top vibration block 15 to vibrate back and forth along the vertical tube 14. The spring 18 cooperates to complete the reset, promoting the falling of impurities on the upper side of the top vibration block 15 through the radial plate 8 and into the sludge collection hopper 9. At this time, although the hollow fiber membrane filament 5 is stretched and straightened, it is not stretched to its straightest state to avoid overload damage to the hollow fiber membrane filament 5.

[0046] Each set of sludge collection hoppers 9 is uniformly connected to a sealed screw conveyor 10 at its lower side. The screw conveyor 10 is completely sealed to prevent biogas leakage. A backflushing gas outlet 12 is opened on the upper side of the upstream section of the screw conveyor 10. The backflushing gas outlet 12 has a built-in filter screen to prevent impurities from leaking out. This interface can be connected to an external waste gas collection device or biogas raw material storage device to collect gas during backflushing and prevent gas leakage. A sewage outlet 11 is opened on the lower side of the downstream section of the screw conveyor 10 for discharging collected solid impurities such as dust, elemental sulfur, and liquid sludge. Both the sewage outlet 11 and the backflushing gas outlet 12 are equipped with shut-off valves.

[0047] The entire device is equipped with three sets of the above-mentioned single-stage membrane modules to form a multi-stage series structure, which are connected in series by hoses and arranged with backflushing pipes and valves to achieve step-by-step purification of biogas.

[0048] This multi-stage membrane separation purification method is used for biogas purification and upgrading. The device operates in two modes: normal purification mode and membrane fiber cleaning + pulse backflushing cleaning mode, which alternate in a cyclical manner. The specific steps are as follows: Normal purification operation (membrane filaments are densely separated); Pipeline valve switching: Open biogas inlet pipe 21, biogas exhaust pipe 22, and permeate gas exhaust pipe 35 valves, and close sludge collection hopper 9, sludge outlet 11, and backflushing gas outlet 12 valves.

[0049] When the automatic telescopic rod 32 is activated, it drives the upper lifting plate 31 and the screw rod 33 to move downward. The screw rod 33 is driven by the thread of the screw hole 34 to rotate circumferentially, which synchronously drives the rotating head 4 to rotate horizontally. At the same time, the lifting head 3 moves downward, compressing the telescopic tube 2 to shorten its overall length.

[0050] Changes in membrane filament morphology: As the two ends of the large number of hollow fiber membrane filaments 5 approach and rotate relative to each other, the spacing between them decreases, and the whole structure twists into a dense spiral arrangement, with the gap between the membrane filaments decreasing significantly.

[0051] Biogas separation process: Raw crude biogas enters the fixed end 1 through the biogas inlet pipe 21, then enters the telescopic pipe 2, and flows along the outside of the hollow fiber membrane filaments 5. Utilizing the selective permeability of the hollow fiber membrane, impurities such as carbon dioxide, hydrogen sulfide, and water vapor penetrate the inner cavity of the membrane filaments, enter the upper part of the rotating head 4 through the upper port of the hollow fiber membrane filaments 5, and are discharged from the permeate exhaust pipe 35; combustible components such as methane are trapped by the membrane filaments and flow out from the biogas exhaust pipe 22, entering the next stage membrane module for further purification.

[0052] Airflow optimization: After compression, the telescopic pipe 2 forms a bent annular groove, changing the direction of biogas flow and increasing the airflow resistance through the inner wall of the telescopic pipe 2. This prevents biogas from short-circuiting along the pipe wall and forces the biogas to fully contact the hollow fiber membrane filaments 5, improving separation efficiency. Multi-stage membrane modules work in series, progressively removing impurities from the crude biogas, ultimately increasing the methane content to over 95%, meeting the standards for biogas use.

[0053] Cleaning and pulse backwashing operations (membrane filament stretching and cleaning state). When dust, elemental sulfur, and other impurities accumulate on the surface and gaps of the membrane fibers, causing increased air intake resistance and decreased flow rate, the cleaning mode is activated. Mechanism reset and stretching: The automatic telescopic rod 32 extends, driving the upper lifting plate 31 and the spiral rod 33 to move upward. The spiral rod 33 rotates in the opposite direction, and the rotating head 4 rotates in the opposite direction synchronously. The lifting head 3 moves upward to stretch the telescopic tube 2, and the telescopic tube 2 reaches its maximum length. At this time, the hollow fiber membrane filaments 5 change their spiral density and are stretched to a near-straight state. The distance between the membrane filaments increases significantly, leaving space for impurities to fall off.

[0054] Vibration impurity removal: The movable end is controlled to perform short-distance, high-frequency reciprocating lifting and lowering. The main traction rope 19 and the branch traction rope 20 pull the top vibrating block 15 and the inner support plate 16 to vibrate up and down at high frequency along the vertical tube 14. The vibration directly shakes off the adhering impurities on the surface of the membrane fibers and between the gaps. On the other hand, the vibration waveform is transmitted to the hollow fiber membrane fibers 5, further promoting the removal of stubborn impurities. The removed impurities slide down the conical surface of the bottom potting body 7 and fall into the sludge collection hopper 9 through the annular gap between the lower end cap 6 and the fixed end 1.

[0055] Pulse backflushing cleaning: Close the biogas inlet pipe valve 21, and sequentially open the reverse inlet valves of the biogas exhaust pipe 22 and the permeate exhaust pipe 35 to introduce purified clean biogas for pulse-type reverse purging: Reverse air intake from biogas exhaust pipe 22: The airflow impacts the outer side of hollow fiber membrane filament 5 from top to bottom, forcefully flushing away attached impurities. The impurity-containing airflow carries the impurities into the sludge collection hopper 9, then flows into the screw conveyor 10, and finally is discharged from the backwash gas outlet 12 for recycling.

[0056] Reverse air intake from permeate exhaust pipe 35: The airflow backflushes from the inner cavity of the membrane fibers, and in conjunction with pressure holding or pulse mode, causes the membrane fibers to vibrate slightly, promoting the shedding of impurities from the outer side of the membrane fibers. Pulse backflush and vibration impurity removal can be performed simultaneously.

[0057] After cleaning, close the backflushing valve and the lower valve of the sludge collection hopper 9, and switch back to normal purification mode. Centralized discharge of impurities: The screw conveyor 10 continues to operate, transporting the solid impurities falling from the sludge collection hopper 9 downstream, and opening the drain valve 11 to discharge the impurities outwards.

[0058] The device operates in a cyclical pattern of purification operation, timed or differential pressure triggered backflushing, and purification operation, achieving continuous biogas purification and membrane module cleaning, and ensuring efficient production of biogas separation and purification.

[0059] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-stage membrane separation purification device for biogas purification, characterized in that, include: Fixed end (1); Telescopic tube (2) is connected to the upper side of the fixed end (1); The movable end includes a lifting head (3) connected to the upper end of the telescopic tube (2) and a rotating head (4) connected to the lifting head (3) in a horizontal rotation. Several hollow fiber membrane filaments (5) are connected between the fixed end (1) and the rotating head (4) and located inside the telescopic tube (2).

2. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 1, characterized in that, The fixed end (1) is provided with a groove-shaped lower end cap (6), and the lower end cap (6) is provided with a bottom filling body (7). The lower end of the hollow fiber membrane filament (5) extends into the bottom filling body (7). The upper part of the bottom filling body (7) protrudes from the lower end cap (6) and is conical. There is an annular gap between the lower end cap (6) and the inner wall of the fixed end (1) and they are connected by several radial plates (8). The lower side of the fixed end (1) is connected to a sludge collection hopper (9).

3. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 2, characterized in that, The fixed end (1), telescopic pipe (2), movable end and sludge collection hopper (9) are arranged in a one-to-one correspondence and multiple sets are provided; a closed screw conveyor (10) is provided on the lower side of the sludge collection hopper (9), a sludge discharge port (11) is provided on the lower side of the downstream end of the screw conveyor (10), and a backflushing air outlet (12) is provided on the upper side of the upstream end of the screw conveyor (10).

4. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 2, characterized in that, The lower end cap (6) is provided with a fixing plate (13). Several vertical tubes (14) are evenly distributed on the upper circumference of the fixing plate (13). The inner hole of the vertical tube (14) extends to the lower side of the fixing plate (13). The vertical tube (14) passes through the bottom potting body (7). The vertical tube (14) is provided with a vertically lifting top vibration block (15). The top vibration block (15) is connected to the movable end through a traction rope.

5. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 4, characterized in that, The bottom inner side of the lower end cap (6) is provided with an inner support plate (16), and the top vibration block (15) is connected to the upper side of the inner support plate (16). The middle part of the fixing plate (13) has an upwardly recessed receiving groove (17), and the receiving groove (17) is provided with a spring (18) whose lower end abuts against the inner support plate (16).

6. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 1, characterized in that, A rotating support (25) is provided between the lifting head (3) and the rotating head (4). A top potting body (27) is provided on the inner side of the middle part of the rotating head (4). The upper end of the hollow fiber membrane filament (5) passes through the top potting body (27).

7. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 6, characterized in that, The fixed end (1) is connected to a biogas inlet pipe (21), the lifting head (3) is connected to a biogas exhaust pipe (22), and the upper side of the rotating head (4) is connected to a permeate gas exhaust pipe (35).

8. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 1, characterized in that, The telescopic tube (2) is provided with several vertical guide rods (23) at intervals on the outside. The lifting head (3) is connected to a lower lifting plate (24) that moves vertically along the guide rods (23). A bottom plate (28), a middle plate (29) and a top plate (30) are provided sequentially from bottom to top along the guide rods (23).

9. The multi-stage membrane separation purification device for biogas purification and upgrading according to claim 8, characterized in that, An upper lifting plate (31) is provided between the middle plate (29) and the top plate (30) and moves up and down along the guide rod (23). An automatic telescopic rod (32) for driving the upper lifting plate (31) to move up and down is installed on the middle plate (29). A screw rod (33) is rotatably connected to the middle part of the upper lifting plate (31). A screw hole (34) that meshes with the screw rod (33) is provided in the middle part of the middle plate (29). A rotating head (4) is connected to the lower end of the screw rod (33).

10. The multi-stage membrane separation purification method for biogas purification according to any one of claims 1-9, characterized in that, Biogas enters from the fixed end (1), passes through the hollow fiber membrane (5) inside the telescopic tube (2), and impurities permeate through the hollow fiber membrane (5) and are discharged from the rotating head (4). The lifting head (3) descends, reducing the length of the telescopic tube (2), while the rotating head (4) rotates, causing the hollow fiber membrane filaments (5) to be densely distributed in a spiral shape inside the telescopic tube (2) to purify biogas; the lifting head (3) rises, increasing the length of the telescopic tube (2), while the rotating head (4) rotates in the opposite direction, causing the hollow fiber membrane filaments (5) to lengthen, increasing the spacing between the hollow fiber membrane filaments (5), and allowing impurities between the hollow fiber membrane filaments (5) to be discharged.

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