A multi-stage treatment system for papermaking wastewater

Abstract

The present application relates to wastewater treatment technical field, disclose a kind of multistage processing system for papermaking wastewater, including air suspension pond, at least one switchable filtration unit is provided in air suspension pond;Rotary assembly is provided with at least one filtration channel and at least one flushing channel isolated from each other, the water inlet end of filtration channel or flushing channel can be selectively aligned and communicated with the water inlet hole on water distribution column during the rotation of rotary assembly;Through the automatic switching of rotary assembly between filtration and flushing channel, the junction of filtration and online cleaning is realized, and the system can continuously output clean water without shutdown. Flushing channel uses unique strong negative pressure suction mechanism, can strongly strip filter cake on filter cloth surface, cleaning is thorough and water consumption is extremely low, especially suitable for easily adhered papermaking wastewater suspended solids, ensure the long-term stability of filtration performance.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically to a multi-stage wastewater treatment system suitable for the papermaking industry. Background Technology

[0002] The pulp and paper industry is a typical water-intensive industry, generating large amounts of wastewater with complex compositions and high pollution loads during its production processes. Direct discharge without effective treatment will cause serious harm to the aquatic environment. To address this challenge, the industry has developed and applied various wastewater treatment technologies, mainly including physicochemical methods, biological treatment methods, and combinations of both. Physicochemical methods (such as coagulation, sedimentation, filtration, and advanced oxidation) react rapidly, but often suffer from high treatment costs, potential chemical sludge production, or the need for high energy input. In multi-stage treatment systems, solid-liquid separation is a key component. For example, Chinese patent CN101792225A discloses a high-efficiency purification system for papermaking wastewater. This system integrates major components such as a processor, sludge thickener, separator, and pre-filter to achieve rapid separation and purification of wastewater. However, it essentially still relies on the traditional static separation and series connection of external filtration units. When treating papermaking wastewater containing large amounts of fine suspended solids and colloidal substances, such systems still face problems such as easy clogging of filter media and the need for frequent shutdowns for backwashing or replacement. Summary of the Invention

[0003] The main objective of this invention is to provide a multi-stage treatment system for papermaking wastewater, which addresses the problems of filter media clogging and the need for frequent shutdowns for backwashing or replacement in existing high-efficiency papermaking wastewater purification systems that contain large amounts of fine suspended solids and colloidal substances.

[0004] To achieve the above objectives, the present invention provides a multi-stage treatment system for papermaking wastewater, including an air suspension tank, wherein at least one switchable filtration unit is provided in the air suspension tank. The filtration unit includes a fixed water distribution column and a rotating component that can rotate relative to the water distribution column. The water distribution column has multiple water inlet holes on its circumferential sidewalls; The rotating assembly is provided with at least one filter channel and at least one flushing channel that are isolated from each other. During the rotation of the rotating assembly, the water inlet end of the filter channel or the flushing channel can be selectively aligned with and connected to the water inlet hole on the water distribution column. The filter channel is equipped with filter cloth, and its outlet end is connected to a first pump body for suction. The outlet of the flushing channel is connected to a second pump body for suction.

[0005] Preferably, the multi-stage treatment system for papermaking wastewater also includes a collection tank located on one side of the air suspension tank; The air suspension tank is equipped with at least one scraper driven by a drive mechanism, which is used to push the scum on the surface of the air suspension tank into the collection tank.

[0006] Preferably, the drive mechanism includes two parallel drive shafts, a drive motor, and a chain that is arranged around the two drive shafts; Two sprockets are fixedly mounted on each drive shaft; Each chain is mounted on two drive shafts via two sprockets; Two drive shafts are rotatably supported on the air suspension tank, and the output shaft of the drive motor drives one of the drive shafts; The scraper is fixed to two chains.

[0007] Preferably, the rotating component includes: A rotating shaft, which is rotatably supported within the air suspension tank; A cylindrical shell is fixedly fitted onto a rotating shaft and is coaxially arranged with the water distribution column. The filtration and flushing channels are formed within the wall structure of the cylindrical shell.

[0008] Preferably, the cylindrical shell comprises: The inner cylinder is fixed to the rotating shaft; A disc-shaped support component is fixed to one axial end of the inner cylinder via multiple connecting pipes; A sealing gasket is connected to a disc-shaped support by fasteners, and clamps and fixes the filter cloth between the two; Among them, the sealing gasket, the disc-shaped support and the inner cylinder are respectively provided with multiple interconnected first channels and second channels at corresponding positions. The sealing gasket is sealed and abuts against the end face of the water distribution column in the assembled state. The first channel, the connecting pipe, and the corresponding passage inside the inner cylinder form a filtration channel; The second channel, the connecting pipe, and the corresponding passage inside the inner cylinder form a flushing channel.

[0009] Preferably, it also includes a switching mechanism for driving the rotating component to rotate; The switching mechanism includes a toggle arm fixed to the rotating shaft, an elastic element that provides a reset force to the toggle arm, and a trigger rod that is linked to the drive mechanism. The trigger lever is positioned on the motion path and is used to intermittently push the lever arm, causing the rotating component to rotate at a certain angle.

[0010] Preferably, the switching mechanism further includes a mounting plate fixedly installed in the air suspension tank, and the elastic element is a spring, with both ends of the spring fixedly connected to the actuating arm and the mounting plate, respectively. The trigger lever is fixedly connected to a link of a chain.

[0011] Preferably, the locking device consists of multiple bolts; The sealing gasket has multiple countersunk holes on the side facing the disc-shaped support. The bolt passes through the sealing gasket, filter cloth and disc-shaped support in sequence and is then locked with the nut. The head of the bolt is accommodated in the countersunk hole.

[0012] Preferably, the multi-stage treatment system for papermaking wastewater also includes a pH adjustment tank, a flocculation tank, and a reaction tank arranged sequentially along the wastewater flow path, with the outlet of the reaction tank connected to the inlet of the air suspension tank.

[0013] The beneficial effects of the above scheme are: Papermaking wastewater, after preliminary treatment by preceding processes (such as coagulation and flotation), is introduced into an air suspension tank and then enters a fixed water distribution column. A rotating assembly aligns the inlet of its filter channel precisely with the inlet holes on the peripheral wall of the water distribution column. The first pump, connected to the outlet of the filter channel, is activated, creating suction within the channel. Driven by the pressure difference, the wastewater flows from the inlet into the filter channel and penetrates the filter cloth installed within it. Suspended solids in the water (such as fine fibers and packing particles) are trapped by the filter cloth, and the filtered water is pumped out by the first pump, ready for the next stage of processing or reuse. As filtration continues, the trapped contaminants gradually accumulate on the surface of the filter cloth, forming a filter cake. This filter cake itself also provides precision filtration, but it also slowly increases the filtration resistance. After the set filtration time is reached, the automatic cleaning and regeneration process begins. The rotating assembly begins to rotate, moving the filter channel away, while the inlet of the isolated rinsing channel rotates to align and connect with the same set of inlet holes. At this point, the second pump connected to the outlet of the flushing channel starts. The second pump generates a stronger suction force. This strong suction force acts on the filter cake that was originally covering the filter cloth area corresponding to the inlet holes through the flushing channel, effectively "peeling off" the tightly attached filter cake layer and sucking it into the flushing channel. The peeled-off high-concentration sludge impurities, along with a small amount of wastewater, are sucked out by the second pump and discharged back to the downstream sludge treatment process, thus completing the efficient online cleaning of the filter cloth in this area. After the flushing process continues for a preset short cycle, the rotating component rotates again, aligning the filter channel corresponding to the cleaned filter cloth area back with the inlet holes, and the filtration state described above begins the next working cycle.

[0014] The rotating assembly automatically switches between the filtration and rinsing channels, enabling seamless integration of filtration and online cleaning. The system can continuously produce clean water without shutdown. The rinsing channel employs a unique strong negative pressure suction mechanism, which powerfully peels the filter cake from the filter cloth surface, ensuring thorough cleaning with extremely low water consumption. It is particularly suitable for easily adhering suspended solids in papermaking wastewater, guaranteeing long-term stability of filtration performance. Attached Figure Description

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 This is a three-dimensional structural schematic diagram of the present invention; Figure 2 This is a top view of the structure of the present invention; Figure 3 This is a three-dimensional structural diagram of the filter unit of the present invention; Figure 4 This is a three-dimensional structural diagram of the filter unit of the present invention from another perspective; Figure 5 This is a cross-sectional structural diagram of the filter unit of the present invention; Figure 6 This is a partial three-dimensional structural diagram of the filter unit of the present invention.

[0017] Explanation of reference numerals in the attached figures 1. Air suspension tank; 11. Scraper; 12. Drive mechanism; 121. Drive shaft; 122. Drive motor; 123. Chain; 124. Sprocket; 2. Filtration unit; 21. Water distribution column; 211. Water inlet; 22. Rotating assembly; 221. Rotating shaft; 222. Cylindrical shell; 2221. Inner cylinder; 2222. Disc support; 2223. Connecting pipe; 2224. Sealing gasket; 2225. Locking fastener; 2226. Nut; 2227. Countersunk hole; 2228. First channel; 2229. Second channel; 23. Filtration channel; 231. Filter cloth; 24. Washing channel; 22251. Bolt; 3. Collection tank; 4. Switching mechanism; 41. Actuating arm; 42. Elastic component; 43. Trigger rod; 44. Mounting plate; 5. pH adjustment tank; 6. Flocculation tank; 7. Reaction tank. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Example

[0019] Please see Figures 1 to 6 This embodiment provides a multi-stage treatment system for papermaking wastewater, aiming to solve the problems of easy clogging of filter units and the need for frequent shutdowns for cleaning in the prior art, and to achieve continuous and efficient solid-liquid separation. Figure 1 and Figure 2As shown, the multi-stage treatment system, following the wastewater treatment process, includes a pH adjustment tank 5, a flocculation tank 6, a reaction tank 7, an air suspension tank 1, and a collection tank 3. The pH adjustment tank 5, flocculation tank 6, reaction tank 7, air suspension tank 1, and collection tank 3 all utilize existing technology and will not be described in detail. The papermaking wastewater to be treated first enters the pH adjustment tank 5, where the pH value is adjusted to a suitable range for subsequent coagulation treatment by adding acid or alkali. Subsequently, the wastewater enters the flocculation tank 6, where coagulants (such as PAC) and flocculants (such as PAM) are added, causing the fine suspended solids and colloidal substances in the water to destabilize and aggregate into larger flocs. Next, the wastewater flows into the reaction tank 7, where the flocs further grow through stirring or settling. The outlet of the reaction tank 7 is connected to the inlet of the air suspension tank 1 via a pipe, introducing the wastewater containing flocs into the air suspension tank 1 for crucial solid-liquid separation. A collection tank 3 is located on one side of the air suspension tank 1. A scum scraping device is installed above the air suspension tank 1. This device includes at least one scraper 11 and a drive mechanism 12 that drives its movement. Specifically, the drive mechanism 12 includes two parallel drive shafts 121, a drive motor 122, four sprockets 124, and two chains 123. Each drive shaft 121 has two sprockets 124 fixedly mounted at both ends. The two chains 123 are respectively wrapped around the sprockets 124 on both sides, forming a closed-loop transmission. The two drive shafts 121 are rotatably supported on the tank wall of the air suspension tank 1 by bearing seats. The output shaft of the drive motor 122 drives one of the drive shafts 121 to rotate through a coupling. The two ends of the scraper 11 are fixed to the two chains 123 by connectors. When the drive motor 122 starts, the scraper 11 is driven along the tank surface through the chain 123, smoothly pushing the scum (mainly light flocs, grease, etc.) that floats to the surface during the air flotation process into the collection tank 3, realizing continuous removal of scum.

[0020] The filtration unit 2 mainly includes a fixed water distribution column 21 and a rotating assembly 22 rotatable relative to the water distribution column 21. The water distribution column 21 is fixedly connected to the air suspension tank via a bracket (not shown). The water distribution column 21 is typically horizontally and detachably mounted on the side wall of the air suspension tank 1, and has multiple inlet holes 211 on its circumferential side wall. Wastewater from the reaction tank 7 enters the air suspension tank 1 and, under hydraulic pressure, flows through these inlet holes 211 into the water distribution column 21. The rotating assembly 22 includes a rotating shaft 221 and a cylindrical shell 222. The rotating shaft 221 is rotatably supported on the tank structure of the air suspension tank 1 via bearings. The cylindrical shell 222 is fixedly fitted onto the rotating shaft 221 and is coaxially aligned with the internal water distribution column 21. Within the wall structure of the cylindrical shell 222, at least one filtration channel 23 and at least one rinsing channel 24 are formed, which are fluid-isolated from each other.

[0021] More specifically, such as Figure 5 and Figure 6 As shown, the cylindrical shell 222 is assembled from the following components: an inner cylinder 2221 is fixed to a rotating shaft 221; a disc-shaped support 2222 is fixedly connected to one axial end of the inner cylinder 2221 via multiple circumferentially distributed connecting pipes 2223; a sealing gasket 2224 is fastened to the disc-shaped support 2222 via multiple locking fasteners 2225 (bolts in this embodiment); and a ring-shaped or disc-shaped filter cloth 231 is clamped and fixed between the sealing gasket 2224 and the disc-shaped support 2222. Preferably, the locking fasteners 2225 are multiple bolts 22251, and the sealing gasket 2224 has multiple countersunk holes 2227 on its side facing the disc-shaped support 2222. After the bolts 22251 pass through the countersunk holes 2227 of the sealing gasket 2224, the filter cloth 231, and the through holes on the disc-shaped support 2222, they are locked with nuts 2226. The bolt head is accommodated in the countersunk hole 2227, ensuring the flatness of the sealing gasket 2224 when it is in contact with the end face of the water distribution column 21, thus avoiding interference. In the assembled state, the sealing gasket 2224 and the fixed end face of the water distribution column 21 maintain a sealed contact, forming a dynamic sealing surface with relative rotation.

[0022] To achieve the channel function, multiple interconnected first channels 2228 and multiple second channels 2229 are respectively provided at corresponding positions on the sealing gasket 2224, the disc-shaped support 2222, and the inner cylinder 2221. These channels connect with the connecting pipe 2223 and the corresponding passage inside the inner cylinder 2221, thereby forming two independent fluid paths. The filter channel 23, formed by the first channel 2228, the corresponding connecting pipe 2223, and the passage inside the inner cylinder 2221 in series, has its final outlet connected to a first pump body (such as a clean water pump) for suction via a sealing conversion component such as a rotary joint (not shown in the figure). The flushing channel 24, formed by the second channel 2229, the corresponding connecting pipe 2223, and the passage inside the inner cylinder 2221 in series, has its final outlet connected to a second pump body (such as a sludge pump) for suction via a rotary joint. The second pump body (not shown in the figure) is usually designed to generate a stronger suction force than the first pump body (not shown in the figure). The filter channel 23 is connected to the first pump body via a first hose (not shown in the figure), and the flushing channel 24 is connected to the second pump body via a second hose (not shown in the figure).

[0023] The rotation of the rotating component 22 is driven by a switching mechanism 4. The switching mechanism 4 includes a toggle arm 41 fixedly mounted on the rotating shaft 221, an elastic element 42 (such as a spring) providing a restoring force to the toggle arm 41, and a trigger rod 43 linked to the scraping drive mechanism 12. In this embodiment, the switching mechanism 4 also includes a mounting plate 44 fixed within the air suspension tank 1, with one end of the spring connected to the toggle arm 41 and the other end connected to the mounting plate 44. The trigger rod 43 is fixedly mounted on a specific link of a chain 123 and moves with the chain 123. The movement path of the trigger rod 43 passes through the swing range of the toggle arm 41.

[0024] The system works as follows: Filtration Stage: In the initial state, the rotating component 22 is in a fixed position under the action of the elastic element 42. At this time, the water inlet end of the filter channel 23 (i.e., the first hole 2228 on the sealing gasket 2224) is aligned and connected with a set of water inlets 211 on the side wall of the water distribution column 21. The first pump starts, generating suction force in the filter channel 23. Wastewater in the air suspension tank 1 enters the filter channel 23 through the water inlet 211 and the first hole 2228, and penetrates the filter cloth 231. Suspended solids (fine flocs, fibers, etc.) in the water are intercepted by the filter cloth 231 to form a filter cake, while the filtered clean water is pumped away by the first pump and enters the subsequent treatment unit or is reused.

[0025] Trigger Switching: The scraper drive mechanism 12 operates continuously, and the scraper 11 moves cyclically. When the chain 123, to which the trigger rod 43 is fixed, moves to a specific position, the trigger rod 43 contacts and pushes the actuating arm 41, overcoming the elastic force of the elastic element 42, and causing the rotating shaft 221 and the entire rotating assembly 22 to rotate by a preset angle. This angle is just enough to move the filter channel 23 away, and the water inlet end of the flushing channel 24 (i.e., the second hole 2229 on the sealing gasket 2224) rotates to align and connect with the same set of water inlets 211 used for filtration. At the same time, the scraper 11 completes one scraping stroke.

[0026] Washing and regeneration stage: Once the washing channel 24 is aligned, the second pump starts (the first pump can be stopped simultaneously or continue operating at low flow). The strong suction force generated by the second pump acts directly on the filter cake formed on the surface of the filter cloth 231 outside the inlet holes 211 during the filtration stage through the washing channel 24. The powerful negative pressure quickly "tears" and peels off the tightly attached filter cake, which is then sucked out through the second channel 2229 and the washing channel 24 and sent to the sludge treatment system. This process consumes very little water and only removes sludge.

[0027] Reset and Cycle: The trigger rod 43 continues to move with the chain 123, disengaging from the actuating arm 41. Under the reset action of the elastic element 42, the actuating arm 41 and the rotating assembly 22 rotate in the opposite direction, returning to their initial positions. At this time, the filter channel 23 corresponding to the filter cloth area that was just cleaned is re-aligned with the water inlet 211, and the system returns to the filtration stage, starting the next working cycle. Multiple filter units 2 can operate alternately to ensure a continuous and stable total output water from the system.

[0028] In summary, this invention integrates filtration and online high-pressure negative pressure cleaning into one unit through a clever rotary switching design. By using the system's own power (scraping drive) to trigger the switching, it achieves efficient and low-consumption automatic cleaning of the filter media without interrupting the wastewater treatment process. This completely solves the problem of easy clogging of filter media in papermaking wastewater treatment and ensures the long-term, stable and efficient operation of the multi-stage treatment system.

[0029] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A multi-stage treatment system for papermaking wastewater, comprising an air suspension tank (1), characterized in that, The air suspension tank (1) is equipped with at least one switchable filter unit (2). The filter unit (2) includes a fixed water distribution column (21) and a rotating component (22) that is rotatable relative to the water distribution column (21). The water distribution column (21) has multiple water inlet holes (211) on its circumferential sidewall. The rotating assembly (22) is provided with at least one filter channel (23) and at least one flushing channel (24) that are isolated from each other. During the rotation of the rotating assembly (22), the water inlet end of the filter channel (23) or the flushing channel (24) can be selectively aligned with and connected to the water inlet hole (211) on the water distribution column (21). The filter channel (23) is provided with a filter cloth (231), and its outlet end is connected to a first pump body for suction. The outlet of the flushing channel (24) is connected to a second pump body for suction.

2. The multi-stage treatment system for papermaking wastewater according to claim 1, characterized in that, It also includes a collection tank (3) located on one side of the air suspension tank (1); The air suspension tank (1) is provided with at least one scraper (11) driven by a drive mechanism (12), the scraper (11) being used to push the scum on the surface of the air suspension tank (1) into the collection tank (3).

3. The multi-stage treatment system for papermaking wastewater according to claim 2, characterized in that, The drive mechanism (12) includes two parallel drive shafts (121), a drive motor (122), and two chains (123) arranged around the two drive shafts (121). Two sprockets (124) are fixedly mounted on each of the drive shafts (121). Each of the chains (123) is mounted on two drive shafts (121) via two sprockets (124); The two drive shafts (121) are rotatably supported on the air suspension tank (1), and the output shaft of the drive motor (122) drives one of the drive shafts (121). The scraper (11) is fixed to the two chains (123).

4. The multi-stage treatment system for papermaking wastewater according to claim 1, characterized in that, The rotating assembly (22) includes: A rotating shaft (221) is rotatably supported within the air suspension tank (1); A cylindrical shell (222) is fixedly fitted onto the rotating shaft (221) and coaxially arranged with the water distribution column (21); The filter channel (23) and the flushing channel (24) are formed within the wall structure of the cylindrical shell (222).

5. The multi-stage treatment system for papermaking wastewater according to claim 4, characterized in that, The cylindrical shell (222) includes: An inner cylinder (2221) is fixed to the rotating shaft (221); A disc-shaped support (2222) is fixed to one axial end of the inner cylinder (2221) by a plurality of connecting pipes (2223); A sealing gasket (2224) is connected to the disc-shaped support (2222) by a plurality of fasteners (2225) and clamps and fixes the filter cloth (231) between the two; The sealing gasket (2224), the disc-shaped support (2222), and the inner cylinder (2221) are respectively provided with a plurality of interconnected first channels (2228) and a plurality of second channels (2229). The sealing gasket (2224) is sealed and abutted against the end face of the water distribution column (21) in the assembled state. The first channel (2228), the connecting pipe (2223) and the corresponding passage in the inner cylinder (2221) form the filter channel (23); The second channel (2229), the connecting pipe (2223), and the corresponding passage in the inner cylinder (2221) form the flushing channel (24).

6. The multi-stage treatment system for papermaking wastewater according to claim 4, characterized in that, It also includes a switching mechanism (4) for driving the rotation of the rotating component (22); The switching mechanism (4) includes a toggle arm (41) fixed to the rotating shaft (221), an elastic element (42) that provides a reset force to the toggle arm (41), and a trigger rod (43) that is linked to the driving mechanism (12). The trigger rod (43) is set on the movement path and is used to intermittently push the toggle arm (41) to drive the rotating component (22) to rotate a certain angle.

7. The multi-stage treatment system for papermaking wastewater according to claim 6, characterized in that, The switching mechanism (4) also includes a mounting plate (44) fixedly installed in the air suspension tank (1). The elastic element (42) is a spring, and the two ends of the spring are fixedly connected to the toggle arm (41) and the mounting plate (44) respectively. The trigger rod (43) is fixedly connected to a link of one of the chains (123).

8. The multi-stage treatment system for papermaking wastewater according to claim 5, characterized in that, The locking fastener (2225) consists of multiple bolts (22251); The sealing gasket (2224) has multiple countersunk holes (2227) on its side facing the disc-shaped support (2222). The bolt (22251) passes through the sealing gasket (2224), the filter cloth (231) and the disc-shaped support (2222) in sequence and is then locked with a nut (2226). The head of the bolt (22251) is accommodated in the countersunk hole (2227).

9. The multi-stage treatment system for papermaking wastewater according to claim 1, characterized in that, It also includes a pH adjustment tank (5), a flocculation tank (6) and a reaction tank (7) arranged sequentially along the wastewater flow path, wherein the outlet of the reaction tank (7) is connected to the inlet of the air suspension tank (1).

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