Sludge dewatering experimental device for simulating a decanter centrifuge

Abstract

The application relates to the technical field of sewage treatment experiment equipment, and provides a sludge dewatering experiment device for simulating a horizontal screw centrifuge, which comprises a pipe body assembly with a specific pipe cavity; an extrusion piston assembly is slidably arranged in the pipe cavity and divides the pipe cavity into a sludge storage area and a moisture storage area, and the outer periphery of the extrusion piston assembly is in sealing sliding fit with the inner wall of the pipe body assembly; a flow guide channel is arranged on the extrusion piston, the inlet end of the flow guide channel faces the sludge storage area, and the outlet end of the flow guide channel faces the moisture storage area; a filter is arranged at the inlet end of the flow guide channel; a one-way flow guide piece is arranged at the outlet end of the flow guide channel and is configured to open the flow guide channel when the fluid pressure of the sludge storage area is greater than that of the moisture storage area and to cut off the flow guide channel when the fluid pressure of the moisture storage area is greater than that of the sludge storage area. The application accurately simulates the centrifugal and extrusion coupling dewatering mechanism of the horizontal screw centrifuge, and the structure is simple and suitable for a conventional laboratory centrifuge.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment experimental equipment technology, specifically to a sludge dewatering experimental device for simulating a horizontal screw centrifuge. Background Technology

[0002] As a core piece of equipment for sludge dewatering in wastewater treatment plants, the operating parameters of the dewatering centrifuge directly affect dewatering efficiency and subsequent treatment costs. In actual process optimization, key parameters such as optimal rotation speed and flocculant dosage need to be screened through experiments. However, conducting experiments directly on production-grade dewatering centrifuges presents challenges such as high energy consumption, large material consumption, complex operation, and difficulty in achieving multiple parallel comparisons.

[0003] Currently, most commonly used sludge dewatering simulation devices in laboratories are ordinary filtration, pressure filtration, or simple centrifugal sedimentation equipment, which can only achieve a single solid-liquid separation mechanism. These devices cannot reproduce the core dewatering mechanism of "centrifugal force driving and mechanical extrusion coupling" unique to horizontal screw centrifuges, resulting in significant deviations between small-scale experimental data and actual operating conditions, making it difficult to effectively guide production process optimization.

[0004] The lack of miniaturized, low-cost dedicated experimental devices in existing technical solutions to accurately simulate the coupled dewatering mechanism of horizontal screw centrifuges has led to technical bottlenecks in the research and development and parameter optimization of sludge dewatering processes for wastewater treatment plants and research institutions, resulting in a lack of experimental means and high trial-and-error costs.

[0005] Therefore, there is an urgent need to develop a micro sludge dewatering experimental device that can realistically reproduce the synergistic process of centrifugation and compression under conventional laboratory centrifuge conditions. Summary of the Invention

[0006] The present invention aims to at least solve or alleviate one of the technical problems existing in the prior art, and provides an experimental device for simulating a horizontal screw centrifuge for sludge dewatering.

[0007] To address the aforementioned technical problems, this application provides an experimental device for simulating a horizontal screw centrifuge for sludge dewatering, comprising: a tube assembly including a tube having a closed end and an open end, and a sealing cap for closing the open end; and a squeeze piston assembly slidably disposed within the cavity of the tube, dividing the cavity into a water storage area near the open end and a sludge storage area near the closed end, wherein the outer peripheral surface of the squeeze piston assembly is in a sealing sliding fit with the inner wall of the tube, wherein the squeeze piston assembly includes a squeeze piston, which has a flow guiding channel, the inlet end of the flow guiding channel facing the sludge storage area and the outlet end facing the water storage area; the inlet end of the flow guiding channel is provided with a filter element, and the outlet end of the flow guiding channel is provided with a unidirectional flow guiding element, the unidirectional flow guiding element being configured to open the flow guiding channel when the fluid pressure in the sludge storage area is greater than the fluid pressure in the water storage area, and otherwise close the flow guiding channel.

[0008] The above technical solution converts rotational kinetic energy into axial mechanical extrusion force on the material in the sludge storage area under centrifugal force by setting a sliding extrusion piston assembly in the tube cavity and utilizing its sealed sliding fit with the inner wall of the tube. At the same time, the filter element integrated on the extrusion piston and the unidirectional flow guide work together to ensure that the separated fluid can only enter the water storage area in one direction and automatically shut off under the reverse pressure difference. Thus, the coupled dehydration process of "centrifugal sedimentation + mechanical extrusion + unidirectional drainage" of the horizontal screw centrifuge is completely reproduced in the micro device, solving the core problem that laboratory equipment cannot simulate actual working conditions.

[0009] In one embodiment, the unidirectional flow guide includes a flexible valve plate. One end of the flexible valve plate is fixed to the surface of the squeezing piston facing the water storage area, and the other end is a free end. The flexible valve plate covers the outlet end of the corresponding flow channel. When the fluid pressure in the sludge storage area is greater than the fluid pressure in the water storage area, the free end of the flexible valve plate undergoes elastic deformation under the pressure difference to open the outlet end of the flow channel. Otherwise, the free end of the flexible valve plate adheres to the surface of the squeezing piston facing the water storage area to close the outlet end of the flow channel. This embodiment utilizes the elastic deformation characteristics of the flexible valve plate to respond to the instantaneous pressure difference changes between the two chambers, achieving adaptive opening and closing of the flow channel without external drive or complex mechanical linkage mechanisms. When the sludge storage area generates positive pressure due to squeezing, the valve plate opens to drain water. When the water storage area generates back pressure due to centrifugal accumulation, the valve plate automatically adheres to and seals the flow channel, fundamentally preventing the separated water from flowing back to the sludge side, ensuring the irreversibility of the dewatering process and the accuracy of experimental data.

[0010] In one embodiment, the flexible valve sheet is a food-grade silicone sheet.

[0011] Specifically, the flexible valve plate is a cantilever fixed structure. One long side of the flexible valve plate is fixed to the surface of the squeezing piston facing the moisture storage area, while the other three sides are in a free state. In its natural state, the flexible valve plate covers and closes the outlet end of the flow channel.

[0012] Thus, during centrifugal dewatering, when the sludge-side pressure in the sludge storage area is greater than the water-side pressure in the water storage area, the remaining three sides of the flexible valve plate are pushed open by fluid pressure, allowing the separated water to flow into the water storage area through the guide channel. Once the water enters the water storage area, under centrifugal force, the water-side pressure in the water storage area becomes greater than the sludge-side pressure in the sludge storage area. The flexible valve plate is then pressed tightly against the surface of the extrusion piston facing the water storage area by water pressure, automatically sealing the outlet end of the guide channel to prevent backflow. One of the long sides of the flexible valve plate can be fixed to the surface of the extrusion piston facing the water storage area using, for example, a hot-pressing process. This hot-pressing process creates a seamless, fixed connection between the long side and the surface of the extrusion piston facing the water storage area, preventing fluid leakage from the fixed edge and ensuring the structural fatigue life of the flexible valve plate during repeated opening and closing. This implementation method, by limiting the material and thickness of the flexible valve plate and using a cantilevered hot-pressing fixing process, ensures that the valve plate has sufficient flexibility to respond to small pressure differences while ensuring the permanent sealing of the fixing end and the durability of the overall structure. The food-grade silicone sheet has both chemical inertness and elastic recovery ability, making it suitable for sludge samples of different properties. The hot-pressing process eliminates the risk of aging and detachment that may be caused by adhesives, enabling the valve plate to maintain stable unidirectional flow performance even in high-frequency centrifugation experiments, thereby improving the reliability and service life of the device.

[0013] In one embodiment, an annular sealing groove is formed on the outer circumferential surface of the extrusion piston; the extrusion piston assembly also includes an elastic sealing ring embedded in the annular sealing groove, the elastic sealing ring being interference-fitted with the inner wall surface of the tube body to achieve sealed sliding contact between the extrusion piston assembly and the inner wall surface of the tube body. This embodiment, by setting an annular sealing groove on the outer circumference of the extrusion piston and embedding an elastic sealing ring, utilizes the interference fit to establish a dynamic sealing interface between the extrusion piston and the inner wall of the tube body; this structure effectively prevents fluid leakage between the sludge storage area and the moisture storage area, ensuring that the extrusion pressure is entirely applied to the material dewatering, and also ensures smooth sliding of the extrusion piston under centrifugal force thanks to the low friction characteristics of the elastic material, avoiding the problems of rigid seals easily jamming or wearing, and achieving a balance between sealing performance and motion reliability.

[0014] Typically, the extrusion piston is a polypropylene piston, and the elastic sealing ring is an O-ring silicone seal. In this embodiment, the polypropylene material has excellent chemical corrosion resistance and mechanical strength, and can adapt to sludge samples with different pH levels. After the O-ring silicone seal is embedded in the annular sealing groove, its outer diameter forms an interference fit with the inner diameter of the tube assembly. This achieves a seal between the extrusion piston and the inner wall of the tube assembly to prevent sludge and water from flowing across the surface, while ensuring that the extrusion piston can slide smoothly under centrifugal force. Force verification shows that at a normal centrifugal speed, the centrifugal thrust on the extrusion piston is much greater than the frictional resistance between the O-ring silicone seal and the inner wall of the tube assembly, thereby ensuring that the extrusion piston can slide stably towards the sludge storage area to extrude sludge.

[0015] In one embodiment, the filter element is disposed on the surface of the extrusion piston facing the sludge storage area. The filter element is pressed and fixed to the surface of the extrusion piston facing the sludge storage area by the clamping member. The clamping member has an axial water passage hole in its middle region for connecting the inlet end of the flow channel with the sludge storage area. This embodiment uses the clamping member with the axial water passage hole to firmly press the filter element onto the surface of the extrusion piston, which not only prevents the filter element from shifting or breaking under high pressure, but also ensures that the fluid in the sludge storage area can enter the flow channel without obstruction through the central water passage hole. This structure tightly connects the filtration function and the flow guiding function in space, avoiding the formation of dead zones or eddies between the filter element and the inlet of the flow channel, thus improving the dewatering efficiency and the continuity of fluid transmission.

[0016] In one embodiment, the filter element is a nylon or metal filter screen with a particle size of not less than 150 mesh. The filter element is configured as a circle that matches the surface shape of the extrusion piston facing the sludge storage area. The clamping element is a fixing nut, which is threadedly connected to the surface of the extrusion piston facing the sludge storage area, clamping and fixing the edge of the filter element. This embodiment uses a filter screen of not less than 150 mesh as the solid-liquid separation interface. This mesh size has been experimentally verified to maintain a high water permeability while intercepting the vast majority of sludge flocs, avoiding extrusion failure due to filter screen clogging or data distortion due to filter penetration. The circular cut and nut clamping method ensure complete sealing and uniform stress at the filter screen edge, preventing sludge from flowing around the edge. The choice of nylon or metal material balances corrosion resistance and mechanical strength, adapting to different experimental environments.

[0017] In one implementation, the tube is a round-bottom centrifuge tube with a threaded joint at the open end. The sealing cap is threadedly fitted to the threaded joint to seal the moisture storage area. This implementation directly uses standard round-bottom centrifuge tubes commonly used in laboratories as the tube assembly, allowing the device to be placed in a conventional centrifuge rotor without any adapters, greatly reducing the equipment threshold and operating costs. The threaded fit between the standard threaded joint and the sealing cap ensures sealing safety under high-speed centrifugation. The uniform tube wall thickness ensures structural integrity within the target speed range, while the standardized interface design gives the device cross-platform compatibility, facilitating promotion and comparison of experimental results across different laboratories.

[0018] In one embodiment, the flow guiding channel includes multiple water passages extending along the axial direction of the extrusion piston, with each water passage corresponding to a unidirectional flow guide. This embodiment disperses the flow resistance of the fluid on the extrusion piston cross-section by distributing the multiple water passages on the extrusion piston, avoiding uneven loading caused by local velocity differences. This flow channel design ensures that the extrusion piston is always subjected to a relatively balanced reaction force during sliding, effectively preventing tilting, jamming, or abnormal wear of the sealing ring caused by excessive force on one side, thus ensuring the smoothness of the extrusion motion and the repeatability of the experiment.

[0019] The sludge dewatering experimental device for simulating a horizontal decanter centrifuge provided in this application directly converts centrifugal force into axial mechanical compression force on the sludge in the sludge storage area by setting a compression piston assembly that slides and seals against the inner wall of the tube cavity. Combined with the filter element and unidirectional flow guide integrated on the compression piston, a three-in-one coupled dewatering mechanism of "centrifugal-driven compression - unidirectional drainage - anti-backflow" is constructed. This mechanism accurately reproduces the core working principle of an industrial horizontal decanter centrifuge at a microscale, giving the laboratory test data direct process guidance value.

[0020] In the preferred embodiment, the device of this application uses standard round-bottom centrifuge tubes as the carrier, combined with a modularly designed extrusion piston, flexible valve plate, and standardized filter components. This not only results in low processing costs and ease of mass production, but also allows direct compatibility with conventional laboratory centrifuges, enabling stable operation within the 2500-3500 rpm speed range. This significantly reduces the experimental threshold and time cost for optimizing sludge dewatering processes. Furthermore, the unidirectional flow guide employs a pressure-differential driven flexible valve plate structure, automatically opening and closing based on chamber pressure changes without external control, achieving self-regulation and backflow prevention sealing during the dewatering process. Combined with circumferentially distributed porous flow channels and interference-fit elastic sealing rings, this ensures the smoothness of the extrusion motion, the reliability of the seal, and the high efficiency of fluid transmission. From a structural perspective, this guarantees the repeatability and accuracy of experimental results, providing reliable technical support for the refined control of sludge dewatering processes. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of the sludge dewatering experimental device for simulating a horizontal screw centrifuge, according to an embodiment of this application.

[0022] Explanation of reference numerals in this invention: 1-Sealed cap, 2-Moisture storage area, 3-Pipe body, 4-O-ring silicone seal, 5-Squeezing piston, 6-Flexible valve plate, 7-150 mesh nylon or metal filter screen, 8-Flow guide channel, 9-Sludge storage area. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] like Figure 1 As shown, this embodiment provides a sludge dewatering experimental device for simulating a horizontal decanter centrifuge. This device aims to reproduce the core dewatering mechanism of an industrial horizontal decanter centrifuge on a laboratory scale. The device includes a tube assembly and a compression piston assembly. The compression piston assembly includes a compression piston 5, which is provided with a flow guiding channel 8. The inlet end of the flow guiding channel 8 faces the sludge storage area 9, and the outlet end faces the moisture storage area 2. A filter element is provided at the inlet end of the flow guiding channel 8, and a unidirectional flow guiding element is provided at the outlet end of the flow guiding channel 8. The unidirectional flow guiding element is configured to open the flow guiding channel 8 when the fluid pressure in the sludge storage area 9 is greater than the fluid pressure in the moisture storage area 2, and otherwise close the flow guiding channel 8.

[0026] Specifically, the tube assembly has a tube body 3 with a relatively closed end and an open end, and a sealing cap 1 for closing the open end. The tube assembly constitutes the main frame of the device, and the cavity formed inside provides a closed reaction space for sludge dewatering. Generally, when the device is placed in a centrifuge rotor, the end closer to the centrifugal rotation center can be the open end, and the end farther from the centrifugal rotation center can be the closed end, so that centrifugal force can be effectively used to drive the squeeze piston 5 to squeeze the sludge. It should be understood that, although Figure 1The illustration shows the form of a round-bottomed centrifuge tube, but in other embodiments, the tube assembly can also be a conical tube, a flat-bottomed tube, or other container form capable of withstanding centrifugal loads and adapting to the rotor, as long as it has a cavity and opposite end structures.

[0027] The extrusion piston assembly is slidably disposed within the tube cavity, dividing the cavity into a sludge storage area 9 near the closed end and a moisture storage area 2 near the open end. The outer periphery of the extrusion piston assembly is in a sealing sliding fit with the inner wall of the tube. Specifically, the extrusion piston 5 is the core moving component that enables the device to perform mechanical extrusion. Under centrifugal force, the extrusion piston 5 moves axially towards the closed end of the tube cavity, thereby compressing the sludge material in the sludge storage area 9, simulating the extrusion action of the screw feeder of a horizontal screw centrifuge on the sludge cake. At the same time, the extrusion piston 6 physically isolates the tube cavity into two independent functional areas: the sludge storage area 9 is used to accommodate the sludge to be dewatered and gradually reduce its volume during the extrusion process, while the moisture storage area 2 is used to collect the separated liquid phase. A sealed sliding fit is a prerequisite for this process, encompassing two aspects: first, "sealing," meaning a dynamic sealing interface is formed between the outer periphery of the extrusion piston 5 and the inner wall of the tube, preventing sludge or high-pressure fluid in the sludge storage area from bypassing the extrusion piston 5 and directly entering the moisture storage area, ensuring that the extrusion pressure is entirely applied to the material for dewatering; second, "sliding," meaning this sealed interface allows the extrusion piston 5 to move smoothly under centrifugal force, avoiding jamming or discontinuous movement due to excessive frictional resistance. This unity of sealing and sliding enables the device to establish a stable extrusion differential pressure environment at a microscale.

[0028] As described above, the extrusion piston 5 is provided with a flow guide channel 8, with the inlet end of the flow guide channel 8 facing the sludge storage area and the outlet end facing the moisture storage area 2. Specifically, the flow guide channel 8 is a fluid transmission channel connecting the sludge storage area 9 and the moisture storage area 2. During the process of the extrusion piston 5 compressing the sludge in the sludge storage area 9, the squeezed-out water enters the flow guide channel 8 under pressure and flows through the extrusion piston 5 to the moisture storage area 2. The location, number, and cross-sectional shape of the flow guide channel 8 can be adjusted according to the actual dewatering requirements. For example, it can be a straight hole or an oblique hole penetrating the axial direction of the extrusion piston, or a pipe structure embedded inside the extrusion piston, as long as it can achieve the directional flow guidance function from the sludge storage area 9 to the moisture storage area. In this embodiment, the flow guide channel is integrated into the body of the extrusion piston 5, so that the two actions of extrusion and drainage are spatially integrated. This corresponds to the structural feature of the coaxial nesting of the rotary drum and the screw conveyor in the horizontal screw centrifuge, further enhancing the realism of the simulation.

[0029] The filter element is located at the inlet end of the flow channel 8. Specifically, the filter element acts as the first barrier in solid-liquid separation, situated on the path of the fluid before it enters the flow channel. Its main function is to intercept solid particles in the sludge, preventing them from entering the flow channel 8 and causing blockage, while allowing water to pass through smoothly. The filter element can be installed close to the inlet surface of the flow channel, embedded inside the inlet, or fixed to the side of the extrusion piston facing the sludge storage area by an independent support structure. Regardless of the fixing method, the filter element must ensure that it does not shift, break, or flow around the edges under the high pressure generated by extrusion, so as to ensure that the clarity of the separated liquid phase meets the experimental testing requirements.

[0030] A unidirectional flow guide is located at the outlet end of the flow guide channel 8. It is configured to open the flow guide channel 8 when the fluid pressure in the sludge storage area 9 is greater than the fluid pressure in the moisture storage area 2, and close the flow guide channel 8 otherwise. Specifically, the unidirectional flow guide is a key control element for achieving the "anti-backflow" function. During the dewatering process, when the squeezing piston 5 moves towards the closed end to squeeze the sludge, the pressure in the sludge storage area 9 increases and exceeds the pressure in the moisture storage area 1, causing the unidirectional flow guide to automatically open and allow moisture to drain. Conversely, when squeezing stops or a high centrifugal pressure is generated in the moisture storage area due to liquid accumulation, if the pressure in the moisture storage area 2 exceeds that in the sludge storage area 9, the unidirectional flow guide will automatically close, blocking the path of reverse fluid flow. This adaptive opening and closing mechanism based on pressure difference response requires no external sensors or actuators; it relies entirely on the changes in the fluid's own mechanical state to regulate the flow path. This not only simplifies the device structure but, more importantly, accurately replicates the dynamic balance process of liquid seal and back pressure regulation at the discharge port of a horizontal screw centrifuge. It should be understood that the specific implementation of the unidirectional flow guide is not limited to a particular structure. Any mechanical or elastic element that can respond to changes in pressure difference between the two sides and realize unidirectional flow function, such as flexible diaphragms, spring ball valves, umbrella valves, or duckbill valves, can be applied to this embodiment, as long as it meets the above-mentioned pressure difference response logic.

[0031] Through the coordinated operation of the aforementioned components, the basic embodiment described above constructs a complete coupled dehydration system of "centrifugal-driven extrusion + unidirectional drainage and backflow prevention". This system utilizes centrifugal force to simultaneously drive the extrusion piston 5 and provide solid-liquid separation power, while maintaining the irreversibility of the dehydration process through a unidirectional flow guide. Thus, it accurately simulates the core working mechanism of an industrial horizontal screw centrifuge on a conventional laboratory centrifuge, providing a reliable basic hardware platform for solving the problem of the disconnect between pilot-scale data and production conditions.

[0032] Based on the above basic embodiment, as one implementation method, the unidirectional flow guide includes a flexible valve plate 6. One end of the flexible valve plate 6 is fixed to the surface of the squeezing piston 5 facing the water storage area 2, and the other end of the flexible valve plate 6 is a free end. Specifically, as... Figure 1As shown, the flexible valve plate 6, as the core fluid control element, is directly integrated into the sludge-side surface of the squeezing piston 5 (i.e., the side facing the water storage zone 2). This cantilever configuration, with one end fixed and the other free, allows the valve plate to respond to pressure changes in both chambers like a miniature cover. When the fluid pressure in the sludge storage zone 9 is greater than the fluid pressure in the water storage zone 2, the free end of the flexible valve plate 6 deforms under the pressure difference to open the outlet end of the flow channel 8, allowing the separated water to pass through the squeezing piston 5 and enter the water storage zone 2. When the fluid pressure in the water storage zone 2 is equal to or greater than the fluid pressure in the sludge storage zone 9, the free end of the flexible valve plate 6 deforms in the opposite direction under the pressure difference to conform to the surface of the squeezing piston 5 facing the water storage zone 2, thereby closing the outlet end of the flow channel 8 and blocking the fluid backflow path. This pressure differential adaptive opening and closing mechanism relies entirely on the fluid's own mechanical state for driving, without the need for any external sensors or mechanical linkages. This greatly simplifies the structural complexity of the micro-device while ensuring the unidirectional irreversibility of the dehydration process.

[0033] To further optimize the response performance and service life of the valve plate, as a preferred embodiment, the flexible valve plate 6 can be a food-grade silicone sheet with a thickness of, for example, 0.2 mm to 0.5 mm. In this preferred embodiment, the specific thickness of 0.2 mm is a mechanical equilibrium point derived from extensive experimental verification. If the valve plate thickness is too large (e.g., exceeding 0.5 mm), its bending stiffness will increase significantly, leading to a higher critical pressure difference required for opening. Under conditions of low speed or high sludge moisture content and weak extrusion pressure, the valve may fail to open or open insufficiently, severely affecting dewatering efficiency. Conversely, if the thickness is too small (e.g., less than 0.1 mm), although the valve plate opens very easily, it is prone to excessive stretching or plastic deformation when subjected to the reverse centrifugal water pressure generated by the accumulated liquid in the water storage area, leading to sealing failure or even tearing and damage. The 0.2mm food-grade silicone sheet perfectly balances a low opening pressure threshold with sufficient elastic recovery force. It can respond sensitively to small positive extrusion forces and maintain a flat and tight fit under reverse high pressure. In addition, the food-grade material has excellent chemical inertness and can withstand different pH levels and sludge samples containing organic solvents, avoiding performance degradation caused by material swelling or corrosion.

[0034] In terms of the fixing process, the flexible valve plate 6 adopts a cantilever fixing structure. One long side of the flexible valve plate 6 is fixed to the surface of the extrusion piston 5 facing the moisture storage area 2 through a process such as hot pressing. The other three sides of the flexible valve plate 6 are in a free state, and the flexible valve plate 6 completely covers the outlet end of the guide channel 8 in its natural state. Specifically, the hot pressing process uses high temperature to cause the silicone material and the extrusion piston matrix (usually polypropylene PP) to undergo molecular chain entanglement or molten bonding at the interface, forming an integrated seamless connection. Compared with traditional adhesive bonding, hot pressing completely eliminates the problems of delamination, aging, or creep that may occur in the adhesive layer under long-term immersion, centrifugal shear force, and chemical media erosion, fundamentally eliminating the risk of fluid leakage from the fixed edge. At the same time, the cantilever design that only fixes one long side avoids the root stress concentration phenomenon that may be caused by polygonal fixing, making the strain distribution of the valve plate more uniform during repeated opening and closing, and significantly improving fatigue life. It should be understood that, in terms of valve plate fixing methods, similar seamless fixing effects can also be achieved by ultrasonic welding, two-color injection molding, or mechanical pressure strip fastening, as long as the sealing reliability of the fixing end and the free movement of the valve plate can be guaranteed.

[0035] In the actual centrifugal dewatering process, when the sludge-side pressure in the sludge storage zone 9 is greater than the water-side pressure in the water storage zone 2, the other three sides of the flexible valve plate 6 are pushed open by the fluid pressure, allowing the separated water to flow into the water storage zone 2 through the guide channel 8. After the water enters the water storage zone 2, under the action of centrifugal force, the water-side pressure in the water storage zone 2 is greater than the sludge-side pressure in the sludge storage zone 9. The flexible valve plate 6 is pressed tightly against the surface of the squeeze piston 6 facing the water storage zone 2 by the water pressure, automatically sealing the outlet end of the guide channel 8 to prevent backflow. This dynamic process accurately replicates the liquid seal regulation mechanism of the horizontal screw centrifuge discharge port. The single long-side hot-pressed cantilever silicone valve plate used in this embodiment achieves highly sensitive unidirectional conduction and highly reliable reverse sealing with a small structural cost. It is the key microstructure guarantee that this device can stably simulate industrial dewatering conditions under laboratory conditions.

[0036] Furthermore, as one embodiment, an annular sealing groove is formed on the outer circumferential surface of the extrusion piston 5. The extrusion piston assembly also includes an elastic sealing ring, which is embedded in the annular sealing groove. The outer circumferential surface of the elastic sealing ring is interference-fitted with the inner wall surface of the tube assembly to achieve sealed sliding contact between the extrusion piston assembly and the inner wall of the tube. Specifically, the annular sealing groove is continuously arranged along the circumference of the extrusion piston 6, and its cross-sectional shape matches the elastic sealing ring, playing a dual role of axial limiting and radial support, preventing the elastic sealing ring from rolling or falling out under the huge extrusion force generated by high-speed centrifugation. After the elastic sealing ring is installed, its outer diameter is slightly larger than the inner diameter of the tube assembly. This interference fit ensures that the sealing ring is always in close contact with the tube wall, forming a dynamic fluid barrier between the extrusion piston and the tube body. On the one hand, the interference ensures that even when the pressure in the sludge storage area 9 increases, the sludge slurry cannot seep into the water storage area 2 through the gaps, ensuring the effectiveness of extrusion dewatering. On the other hand, the low friction characteristics and lubrication of the elastic material itself allow the extrusion piston to move smoothly along the axial direction under the centrifugal force, avoiding the jamming or wear problems that may be caused by rigid seals.

[0037] In a preferred embodiment, the compression piston 5 can be made of polypropylene, and the elastic sealing ring can be an O-ring silicone seal 4. Polypropylene (PP) material has excellent chemical corrosion resistance and mechanical strength, and can adapt to sludge samples with different pH levels and containing organic solvents, avoiding the problems of easy corrosion of metal materials or dimensional instability caused by water absorption and swelling of nylon materials. At the same time, the density of PP material is moderate, ensuring that the compression piston itself has sufficient mass to generate effective centrifugal driving force, without causing excessive lateral pressure on the tube wall due to excessive weight. Force verification shows that at normal centrifugal speeds, the centrifugal thrust on the compression piston 5 is much greater than the frictional resistance between the O-ring silicone seal 4 and the inner wall of the tube assembly, thereby ensuring that the compression piston can slide stably towards the sludge storage area 9 to compress the sludge. Specifically, within a target speed range of, for example, 2500 rpm to 3500 rpm, the centrifugal force generated by the PP compression piston 5, which has a mass of a few grams, can reach tens of Newtons, while the dynamic friction between the O-ring silicone seal 4 and the smooth tube wall is only a few tenths of a Newton. This significant difference in magnitude, from a physical standpoint, guarantees the inevitability and continuity of the extrusion action, eliminating the risk of motion stagnation due to fluctuations in friction. This provides the mechanical basis for the device to autonomously complete the extrusion process solely through the centrifugal field, without the need for any external push rods or springs.

[0038] In one implementation, the flow channel 8 includes multiple water passages extending along the axial direction of the extrusion piston 5. These water passages can be evenly distributed circumferentially on the extrusion piston 5, and each water passage can have a circular cross-sectional shape. This circumferentially uniform distribution design is not only for fluid distribution considerations but also a key mechanical means to solve the motion stability problem of the micro-extrusion piston. In a high-speed centrifugal field, the extrusion piston 5 bears a huge axial thrust. By arranging multiple circular water passages evenly circumferentially, the fluid resistance is axially symmetrically distributed on the end face of the extrusion piston, thereby offsetting the harmful radial torque and ensuring that the extrusion piston 5 slides smoothly along the axis throughout its stroke. It should be understood that although this embodiment preferably uses circular cross-section water passages to reduce flow resistance and facilitate processing, in other implementations, elliptical, racetrack-shaped, or other streamlined cross-sections can also be used, as long as they can meet the basic requirements of circumferential force balance and fluid conduction.

[0039] To further improve dehydration efficiency and simulation accuracy, as a preferred implementation, the flow channel may include three water passages evenly distributed in a triangular pattern on the extrusion piston. Specifically, this particular combination of quantity and layout is an optimized embodiment derived from multiple rounds of experimental verification. Compared to a single large-diameter design, the parallel connection of three small holes significantly increases the total flow area, reduces local flow velocity and pressure loss during fluid passage, and avoids turbulent noise and scouring damage to the filter screen caused by excessive flow velocity at a single hole. Compared to a linear arrangement or a four-hole square arrangement, the triangular distribution has inherent structural stability, enabling the maximum hole spacing within the limited space of the piston end face. This ensures the structural strength of the extrusion piston body while minimizing fluid interference between holes. More importantly, the triangular layout allows the centroid of the three water passages to coincide with the geometric center of the extrusion piston, further enhancing the aforementioned force balance effect.

[0040] Regarding the cooperation with unidirectional flow guides, multiple unidirectional flow guides can be included, each corresponding to and covering the outlet end of a water passage hole. The size of the unidirectional flow guide is larger than the outlet diameter of the water passage hole, allowing it to completely cover the edge of the outlet end of the water passage hole when closed under pressure, forming a reliable sealing surface. During centrifugal dehydration, when the water pressure in the water storage area 2 acts in the opposite direction on the unidirectional flow guide, if the size of the flow guide is only equal to or slightly smaller than the orifice diameter, the sealing contact line will fall at the acute angle of the orifice edge, which is very easy to cause seal failure or valve plate breakage due to stress concentration. However, when the size of the flow guide is significantly larger than the orifice diameter, the sealing contact area expands into an annular sealing band with a certain width, which not only greatly improves the sealing specific pressure but also provides sufficient tolerance space for the small deformation of the valve plate or installation errors. At the same time, the multi-hole independent coverage design means that even if one unidirectional flow guide temporarily fails due to impurities, the other two flow guides can still maintain basic unidirectional flow function, avoiding the risk of a single point of failure paralyzing the entire device. This combination of redundant design and collaborative layout enables the device to maintain stable performance when faced with real sludge samples with complex composition and variable properties, truly achieving high-fidelity simulation of the working conditions of industrial horizontal screw centrifuges in laboratory pilot tests.

[0041] In one implementation, the filter element is disposed on the surface of the extrusion piston 5 facing the sludge storage area 9. The sludge dewatering experimental device also includes a clamping element with an axial water passage hole at its center. The filter element is clamped and fixed to the surface of the extrusion piston 5 facing the sludge storage area 9 by the clamping element. The axial water passage hole is used to connect the inlet end of the guide channel with the sludge storage area. Specifically, during the centrifugal extrusion process, the sludge in the sludge storage area 9 is subjected to continuous axial pressure. The clamping element used in this embodiment firmly presses the circumferential edge of the filter element onto the end face of the extrusion piston 5 with mechanical clamping force, forming a reliable peripheral sealing band and eliminating edge flow phenomena. At the same time, the axial water passage hole at the center of the clamping element not only serves as the necessary path for fluid to enter the guide channel 8, but also acts as a fluid collector, allowing water passing through the filter element to be smoothly and with low resistance introduced into the subsequent guide channel 8, avoiding local eddies or back pressure accumulation caused by abrupt changes in the flow channel. The clamping component can preferably be a fixing nut that mates with the thread of the compression piston, or it can be a snap ring, pressure plate bolt, screw cap type pressure ring, or other fasteners that can achieve axial clamping function, as long as it can provide sufficient and uniform clamping force to maintain the sealing and fixing of the filter element.

[0042] Preferably, the filter element is a nylon or metal filter screen 7 with a mesh size of not less than 150, and the filter element is cut into a circle that matches the surface shape of the extrusion piston 5 facing the sludge storage area; the clamping element is a fixing nut. For example, the surface of the extrusion piston 5 facing the sludge storage area has a raised circumferential flange with internal threads machined inside, and the fixing nut has external threads. The fixing nut is threadedly connected to the surface of the extrusion piston 6 facing the sludge storage area to press and fix the edge of the filter element.

[0043] The average pore size of the filter screen can generally be selected to be within the lower limit range of the floc particle size distribution after flocculation of most municipal and industrial sludge (preferably not less than 150 mesh). This can effectively intercept the main sludge skeleton, ensure that the clarity of the filtrate meets the testing requirements, and maintain sufficient porosity to maintain a high water permeability, so that the drainage rate during the extrusion process matches the actual drainage capacity of the horizontal screw centrifuge.

[0044] In one implementation, the tube assembly can be a 50mL standard round-bottom centrifuge tube. The tube body 3 has a threaded joint near the open end, and the sealing cap 1 engages with the threaded joint to seal the moisture storage area. Specifically, using a 50mL standard round-bottom centrifuge tube as the main body of the tube assembly allows for low-cost manufacturing and broad laboratory compatibility. These centrifuge tubes are widely available general-purpose laboratory consumables with a mature supply chain and extremely low production costs, enabling rapid mass production without the need for expensive mold development. Furthermore, their standardized dimensions allow them to be directly inserted into the rotor holes of most conventional laboratory centrifuges without the need for custom adapters or special rotors, significantly reducing the user's learning curve and equipment modification costs. It should be understood that while this embodiment preferably uses 50mL to balance sample throughput and centrifugation efficiency, in other implementations, standard centrifuge tubes of 15mL, 50mL, 100mL, or other capacities can be used depending on experimental requirements, as long as they possess a regular geometric shape and sufficient structural strength to adapt to the centrifugation field.

[0045] Regarding sealing and safe connection, the screw-in structure adopts industry-standard thread profiles, ensuring that the sealing cap is interchangeable with centrifuge tube caps from different brands on the market, thus improving the versatility of the sludge dewatering experimental device. Specifically, this standardized threaded fit not only facilitates quick replacement of caps when lost or damaged, but more importantly, guarantees the reliability of the seal. The sealing cap typically contains a chemically resistant sealing gasket, and the axial preload generated by tightening the thread compresses the sealing surface, effectively preventing material leakage or aerosol escape risks caused by increased internal pressure during high-speed centrifugation. Compared to snap-fit ​​or compression-type connections, the threaded connection has a self-locking function, providing continuous and uniform locking force, and will not loosen even under prolonged high-speed operation or vibration conditions, thereby ensuring the safety of the experimental process. Furthermore, the round bottom design, compared to flat or conical bottoms, has superior mechanical distribution characteristics when subjected to the enormous radial stress generated by high-speed rotation, effectively preventing tube breakage due to stress concentration, further enhancing the safety margin of the device under extreme conditions.

[0046] To accurately simulate the actual operating conditions of an industrial decanter centrifuge, the overall shape and size of the tube assembly are configured to directly adapt to the rotor apertures of a conventional laboratory centrifuge. This allows the sludge dewatering experimental device to operate stably at speeds between 2500 rpm and 3500 rpm, simulating the centrifugal and compression coupled dewatering conditions of a decanter centrifuge. Specifically, within this speed range, the centrifugal acceleration field within the standard centrifuge tube can effectively map the solid-liquid separation dynamics within the drum of an industrial equipment, ensuring that the sedimentation and compression behavior of the sludge flocs is highly consistent with the production environment. If the speed is too low (e.g., below 2000 rpm), sufficient centrifugal driving force cannot be provided to overcome the frictional resistance and fluid viscosity in the micro-device, resulting in sluggish piston sliding, insufficient dewatering, and rendering the experimental data unreliable. If the speed is too high (e.g., above 4000 rpm), although the separation effect is enhanced, it may exceed the long-term fatigue tolerance limit of the standard plastic centrifuge tube, increasing the risk of tube bursting. Furthermore, excessive shear force may damage the sludge floc structure, leading to simulation distortion. Therefore, 2500rpm to 3500rpm is not only an effective range to ensure simulation accuracy, but also a reliable boundary to ensure the safe operation of standard pipes.

[0047] Furthermore, the standard round-bottom centrifuge tubes have uniform wall thickness, enabling them to withstand the radial stress generated by high-speed centrifugation without deformation. Specifically, standard centrifuge tubes undergo rigorous quality control during manufacturing, resulting in wall thickness tolerances and material uniformity far superior to non-standard parts. This uniform tube wall structure ensures that the extrusion piston remains within a geometrically regular, smooth-walled guide channel during sliding, preventing abnormal wear of the sealing ring or piston jamming caused by localized deformation or unevenness of the tube body. Simultaneously, standard tubes are typically made of high-purity engineering plastics such as polypropylene (PP) or polycarbonate (PC). These materials not only possess excellent chemical corrosion resistance, adapting to sludge samples with varying pH levels and organic solvent contents, but also exhibit good creep resistance, resisting permanent plastic deformation under repeated high-speed centrifugation loads. This ensures that the apparatus maintains stable mechanical properties and experimental accuracy even after repeated use. In summary, this embodiment cleverly integrates specialized experimental functions with general-purpose consumables by standardizing the selection and parameter limitation of tube components, thereby maximizing economic benefits and practical value while ensuring technical performance.

[0048] To help those skilled in the art understand the present invention, the working process of the present invention is described below using actual field application examples.

[0049] In a sludge dewatering process optimization project at a municipal wastewater treatment plant, the main technical bottleneck was finding the optimal matching parameters between flocculant dosage and decanter speed without affecting normal production. Conducting multiple non-stop parameter adjustments directly on the production-grade decanter centrifuge not only consumes a huge volume of sludge and reagents per experiment and results in high energy consumption, but also significantly adjusts the speed or dosage, easily leading to fluctuations or even exceeding the standard for sludge moisture content, posing significant risks and economic losses to subsequent treatment processes. Furthermore, the production equipment's slow response time makes it difficult to complete multiple parallel comparative experiments in a short period, resulting in a long optimization cycle and low efficiency.

[0050] To address the aforementioned issues, a systematic laboratory simulation optimization experiment was conducted using the sludge dewatering experimental device provided in this application. The specific operating steps are as follows: First, a sludge sample with a moisture content of 98% was collected from the plant's homogenization tank. Then, approximately 30 mL of sludge sample was injected into the sludge storage area of ​​the device, and flocculants of different gradients were added according to the preset experimental plan. Next, the assembled device was placed in a conventional laboratory centrifuge, and centrifugal dewatering experiments were conducted at multiple speed settings, including 2500 rpm, 3000 rpm, and 3500 rpm. After the experiment, the device was removed, and the filtrate in the water storage area and the sludge cake in the sludge storage area were separated and weighed. The moisture content and solid recovery rate after dewatering under each operating condition were calculated.

[0051] Through extensive parallel comparative experiments, the device presented in this application reveals a process law that contradicts traditional experience. The plant's existing process understanding generally followed a linear approach: "high dosage + high rotation speed = low moisture content," assuming that increasing centrifugal force and flocculant dosage would always yield better dewatering results. Process optimization was simply about finding a balance between cost and effectiveness within this trend. However, experimental data obtained using the device presented in this application show that when the flocculant dosage is in the middle range, combined with a relatively low rotation speed (e.g., 2500 rpm), a lower sludge cake moisture content can be achieved compared to the high dosage, high rotation speed condition. Specifically, compared to the 79%-81% moisture content level achievable with the plant's original optimized process, the new "medium dosage + low rotation speed" condition selected by this device can further reduce the dewatered sludge moisture content by 4 to 5 percentage points, while reducing the flocculant dosage by approximately 20%, and significantly reducing equipment operating energy consumption due to the lower rotation speed.

[0052] The discovery of this counterintuitive phenomenon stems from the unique working mechanism of the device proposed in this application. Traditional laboratory filtration or sedimentation centrifuges can only simulate a single centrifugal sedimentation process and cannot replicate the coupled effect of "centrifugal sedimentation + spiral extrusion" inside a horizontal screw centrifuge. Under high-speed simple centrifugation conditions, excessive flocculant can form large flocs to accelerate sedimentation, but it also easily encapsulates a large amount of free water to form a gel-like structure. Furthermore, the lack of subsequent mechanical extrusion to break the gel and drain the water makes it difficult to further reduce the final moisture content. In contrast, the device proposed in this application, through the axial sliding of the extrusion piston driven by centrifugal force, realistically simulates the mechanical extrusion section at the end of the horizontal screw centrifuge drum. Under the condition of "medium dosage + low speed," the formed floc structure is denser and has moderate water retention. Combined with the continuous mechanical pressing action of the extrusion piston, it can more effectively destroy the capillary water channels inside the floc, thereby achieving deep dehydration. Conversely, if excessively high speeds are used in this device, the excessive centrifugal shear force may damage the already formed fragile floc structure, which is detrimental to subsequent extrusion and drainage. Therefore, this optimization result is a direct manifestation of the unique "centrifugation + extrusion" coupled simulation capability of this device, and is a technical contribution that cannot be reproduced by ordinary filtration centrifuges.

[0053] In summary, this application embodiment fully demonstrates that the device of this application can not only serve as a laboratory research tool, but also directly serve process diagnosis and optimization in production sites. The optimized solutions obtained through this device enable wastewater treatment plants to achieve significant comprehensive economic benefits in three aspects: sludge reduction (lower moisture content), reagent saving (20% reduction in dosage), and energy conservation and consumption reduction. This effectively solves the technical problems of disconnect between pilot-scale data and production conditions, and the significant lack of direction in process optimization in existing technologies.

[0054] In summary, this invention accurately simulates the dewatering mechanism of a horizontal screw centrifuge: by driving a piston to slide and squeeze the sludge through centrifugal force, it perfectly replicates the core principle of "centrifugation + squeezing" coupled dewatering of a horizontal screw centrifuge. The experimental data can directly guide the optimization of the production process, solving the problem that existing laboratory equipment cannot simulate actual working conditions.

[0055] In addition, the present invention has the following advantages: (1) Simple structure and extremely low cost: The standard centrifuge tube is used as the main body, and the piston, valve plate, filter screen and other parts are all standard easy-to-process parts with low processing cost, which is suitable for mass production and use. (2) One-way conduction and anti-backflow design: The cantilever silicone one-way valve plate is used, which does not require complex connecting parts. It automatically achieves one-way conduction by water pressure difference and automatically seals in the centrifugal state. The structure is reliable and avoids water backflow from affecting the dehydration effect. (3) Strong adaptability and convenient operation: The whole is in the form of a standard centrifuge tube, which can be directly put into a conventional laboratory centrifuge. The operation process is simple and multiple parallel experiments can be carried out quickly, which greatly improves the efficiency of process optimization. (4) High sealing and sliding reliability: The O-type silicone sealing ring 4 realizes the elastic sealing between the piston and the tube wall, which not only ensures the sealing effect, but also avoids the problem of hard sealing jamming. After force verification, at the conventional speed of 2500-3500rpm, the centrifugal thrust of the piston is much greater than the frictional resistance, which can slide smoothly and the valve plate can reliably conduct and seal.

[0056] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge, characterized in that, include: A tube assembly, comprising a tube having opposing closed and open ends, and a sealing cap for closing the open ends; as well as A squeeze piston assembly is slidably disposed within the cavity of the tube body, dividing the cavity into a moisture storage area near the open end and a sludge storage area near the closed end. The outer peripheral surface of the squeeze piston assembly is in a sealing sliding fit with the inner wall of the tube body. The extrusion piston assembly includes an extrusion piston with a flow guide channel. The inlet end of the flow guide channel faces the sludge storage area, and the outlet end faces the moisture storage area. The inlet end of the flow guide channel is provided with a filter element, and the outlet end of the flow guide channel is provided with a unidirectional flow guide element. The unidirectional flow guide element is configured to open the flow guide channel when the fluid pressure in the sludge storage area is greater than the fluid pressure in the moisture storage area, and otherwise close the flow guide channel.

2. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 1, characterized in that, The unidirectional flow guide includes a flexible valve plate. One end of the flexible valve plate is fixed to the surface of the squeezing piston facing the moisture storage area, and the other end is a free end. The flexible valve plate covers the outlet end of the corresponding flow channel. When the fluid pressure in the sludge storage area is greater than the fluid pressure in the moisture storage area, the free end of the flexible valve plate undergoes elastic deformation under the pressure difference to open the outlet end of the flow channel. Otherwise, the free end of the flexible valve plate adheres to the surface of the squeezing piston facing the moisture storage area to close the outlet end of the flow channel.

3. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 2, characterized in that, The flexible valve sheet is a food-grade silicone sheet.

4. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 2, characterized in that, The flexible valve plate is a cantilevered fixed structure. One long side of the flexible valve plate is fixed to the surface of the squeezing piston facing the moisture storage area, while the other three sides are in a free state. In its natural state, the flexible valve plate covers and closes the outlet end of the flow channel.

5. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 1, characterized in that, The outer circumferential surface of the extrusion piston is provided with an annular sealing groove; The extrusion piston assembly also includes an elastic sealing ring embedded in the annular sealing groove. The elastic sealing ring is interference-fitted with the inner wall surface of the tube to achieve sealed sliding contact between the extrusion piston assembly and the inner wall surface of the tube.

6. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 5, characterized in that, The extrusion piston is a polypropylene piston, and the elastic sealing ring is an O-ring silicone sealing ring.

7. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 1, characterized in that, The filter element is disposed on the surface of the extrusion piston facing the sludge storage area. The filter element is pressed and fixed to the surface of the extrusion piston facing the sludge storage area by the clamping member. The middle area of ​​the clamping member has an axial water passage hole for connecting the inlet end of the flow channel with the sludge storage area.

8. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 7, characterized in that, The filter element is a nylon filter screen or a metal filter screen with a sieve particle size of not less than 150 mesh. The filter element is configured as a circle that matches the surface shape of the extrusion piston facing the sludge storage area. The clamping element is a fixing nut, which is threadedly connected to the surface of the extrusion piston facing the sludge storage area to press and fix the edge of the filter element.

9. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to claim 1, characterized in that, The tube is a round-bottomed centrifugal tube, and the open end of the tube is provided with a threaded structure. The sealing cap is threadedly sealed with the threaded structure to seal the moisture storage area.

10. The sludge dewatering experimental apparatus for simulating a horizontal screw centrifuge according to any one of claims 1 to 9, characterized in that, The flow channel includes a plurality of water passage holes extending along the axial direction of the extrusion piston, and each water passage hole is provided with a corresponding unidirectional flow guide.

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