Full-quantitative treatment system and process for landfill leachate

Abstract

The invention relates to a landfill leachate full-quantitative treatment system and a process thereof, and relates to the technical field of environment-friendly water treatment.The MVR evaporative crystallization unit of the landfill leachate full-quantitative treatment system comprises a heating chamber and a plurality of heat exchange pipes located in the heating chamber; the plurality of magnetic composite cleaning balls are dispersed between the outer wall of the heat exchange tube and the inner wall of the heating chamber and flow along with the feed liquid; the cleaning ball interception mechanism is used for limiting all the magnetic composite cleaning balls in a self-cleaning area in the heating chamber; the external magnetic field generating device is arranged on the outer side of the heating chamber and used for generating a rotating magnetic field for driving the magnetic composite cleaning balls to move and generating a high-frequency alternating magnetic field for exciting high-frequency oscillation of the magnetic composite cleaning balls in the self-cleaning area. In the conventional evaporation stage, the magnetic composite cleaning ball is driven to roll and rotate along with liquid flow, soft scale deposition is prevented, turbulence is enhanced, and the heat transfer efficiency is improved; and the magnetic composite cleaning ball can be excited to oscillate at high frequency in the self-cleaning area for self-cleaning, and shutdown is not needed.

Description

Technical Field

[0001] This application relates to the technical field of environmental water treatment, and in particular to a comprehensive treatment system and process for landfill leachate. Background Technology

[0002] Landfill leachate is a high-concentration organic wastewater generated during the transfer, landfilling, or incineration of waste. It is characterized by complex pollutant composition, large fluctuations in water quality and quantity, high content of ammonia nitrogen and heavy metals, and significant changes in the main components of leachate with the years of landfilling. It is widely recognized as one of the most difficult high-concentration industrial wastewaters to treat.

[0003] Currently, the mainstream landfill leachate treatment process in China typically employs a combination of "pretreatment + biological treatment (MBR) + membrane deep treatment (NF / RO)". Its working principle mainly relies on biochemical reactions to remove most organic matter and ammonia nitrogen, followed by the use of nanofiltration (NF) and reverse osmosis (RO) membranes to retain recalcitrant organic matter and dissolved salts, thereby ensuring the permeate meets discharge standards.

[0004] For example, Chinese patent application CN201910166431.8 in the related technology proposes a full-volume treatment process for landfill leachate, including the following steps: pretreatment; membrane permeation treatment, in which the pretreated landfill leachate is permeated through a reverse osmosis membrane under a first preset pressure to obtain a retained concentrate and a first clear liquid; softening and hardening treatment, in which a hardening agent is added to the concentrate to reduce its hardness; binary wet catalytic oxidation treatment, in which the organic matter in the concentrate undergoes ring-opening and chain breaking at a second preset pressure and a first preset temperature; evaporation treatment, in which the concentrate treated by binary wet catalytic oxidation is evaporated to obtain crystalline salt and a second clear liquid; and subsequent treatment.

[0005] However, at the end of the full-volume treatment, the MVR evaporation crystallization unit is usually used to evaporate the concentrate. The leachate membrane concentrate contains extremely high concentrations of calcium, magnesium, silicon and humic acid. During the evaporation process in the MVR evaporation crystallization unit, a hard "inorganic-organic composite scale" will form on the heat exchange tube wall within a few hours, causing the heat transfer coefficient to drop sharply. Moreover, it is difficult to remove by chemical cleaning, and often requires shutdown for maintenance, which affects the efficiency of full-volume treatment of landfill leachate. Summary of the Invention

[0006] To address the problem that scaling easily occurs in MVR evaporation and crystallization units when treating landfill leachate, thus affecting the efficiency of full-volume leachate treatment, this application provides a landfill leachate full-volume treatment system and its process.

[0007] The landfill leachate full-volume treatment system and process provided in this application adopt the following technical solution: The first aspect of this application provides a landfill leachate full-volume treatment system using the following technical solution: A landfill leachate full-volume treatment system includes a pretreatment unit, a biochemical treatment unit, a membrane deep treatment unit, and an MVR evaporation and crystallization unit connected in sequence; the MVR evaporation and crystallization unit includes a heating chamber and several heat exchange tubes located inside it, and also includes; Magnetic composite cleaning balls are provided in multiples and dispersed between the outer wall of the heat exchange tube and the inner wall of the heating chamber, and flow with the liquid. A cleaning ball trapping mechanism is used to confine all the magnetic composite cleaning balls within the self-cleaning zone of the heating chamber; and An external magnetic field generating device is located outside the heating chamber and is used to generate a rotating magnetic field that drives the magnetic composite cleaning ball to move, and to generate a high-frequency alternating magnetic field that excites the magnetic composite cleaning ball located in the self-cleaning zone to oscillate at high frequency.

[0008] Furthermore, the magnetic composite cleaning ball comprises: The spherical core is made of magnetostrictive metal; A spherical shell, with a gap fitted around the outer periphery of the spherical core, is made of heat-resistant and corrosion-resistant material; and A buffer medium layer is filled in the gap cavity between the spherical core and the spherical shell.

[0009] Furthermore, the buffer medium layer is filled with a non-Newtonian fluid; When the magnetic composite cleaning ball is subjected to a low-frequency rotating magnetic field by the external magnetic field generator, the buffer medium layer becomes liquid, and the ball core floats and rotates within the ball shell. When a high-frequency alternating magnetic field is applied to the magnetic composite cleaning ball by an external magnetic field generator, the buffer medium layer transforms into a near-solid state and rigidly transmits the high-frequency vibration of the ball core to the ball shell.

[0010] Furthermore, the outer wall of the spherical shell is provided with a plurality of cleaning protrusions arranged in rows, the cleaning protrusions being made of flexible rubber.

[0011] Furthermore, a flexible positioning rope is connected between the spherical core and the spherical shell; When the flexible positioning rope is taut, the center of the ball core does not coincide with the center of the ball shell.

[0012] Furthermore, the center of gravity of the sphere is offset from its geometric center.

[0013] Furthermore, the external magnetic field generating device includes: A high-frequency excitation coil is wound around the outer wall of the heating chamber and is positioned corresponding to the self-cleaning zone; Multiple sets of three-phase winding coil arrays are distributed at intervals along the axial direction of the heating chamber, and multiple sets of three-phase winding coil arrays are electrically connected to a vector frequency converter controller. The vector frequency converter is configured to generate a superimposed rotating magnetic field and an axial traveling wave magnetic field inside the heating chamber by adjusting the phase sequence and frequency of the three-phase current, thereby driving the magnetic composite cleaning ball to move along a spiral trajectory in the opposite or forward direction to the liquid flow in the heating chamber.

[0014] Furthermore, the vector frequency converter is also configured to control the three-phase winding coil array to alternately output drive current in reverse current ramp-up mode and in-current fall-down mode; In the counter-current climbing mode, the thrust direction of the traveling wave magnetic field is opposite to the liquid flow direction and the thrust is greater than the sum of the liquid flow resistance and the gravity of the magnetic composite cleaning ball; In the downstream flow mode, the thrust direction of the traveling wave magnetic field is the same as or zero, causing the magnetic composite cleaning ball to reset to the bottom of the heating chamber under the impact of the liquid flow.

[0015] Furthermore, the cleaning ball interception mechanism includes a funnel-shaped intercepting plate fixed to the inner wall of the bottom of the heating chamber, the aperture of the intercepting plate being smaller than the diameter of the magnetic composite cleaning ball, and the high-frequency excitation coil corresponding to the axial center of the intercepting plate.

[0016] The second aspect of this application provides a comprehensive landfill leachate treatment process using the following technical solution: A process for the full-volume treatment of landfill leachate, based on the aforementioned full-volume treatment system for landfill leachate, includes the following steps: S1. The landfill leachate is subjected to oil and slag removal treatment in the pretreatment unit; S2. The pretreated landfill leachate is then subjected to biochemical treatment unit for degradation of organic matter and denitrification; S3. Deep filtration is performed through the membrane deep treatment unit to produce a concentrate; S4. The concentrate is fed into the MVR evaporation and crystallization unit for evaporation and crystallization to obtain condensate and evaporation residue. During the evaporation process, the magnetic composite cleaning balls are driven by the external magnetic field generator to move in the flowing concentrate to improve the turbulence and heat transfer efficiency and clean the soft scale. Alternatively, the magnetic composite cleaning balls gathered in the self-cleaning zone are driven to oscillate at high frequency to clean the scale on them. S5. The evaporation residue and the scale removed from the magnetic composite cleaning ball are sent to the subsequent process to obtain the stabilized product.

[0017] In summary, the beneficial technical effects of this application are as follows: 1. By applying a specific magnetic field pattern through an external magnetic field generator, the movement of the magnetic composite cleaning balls can be precisely controlled: During the normal evaporation stage, the magnetic composite cleaning balls are driven to roll and rotate with the liquid flow, scraping and disturbing the wall surface to prevent soft scale deposition and enhance turbulence and improve heat transfer efficiency; when deep cleaning is detected or periodically required, the magnetic composite cleaning balls are gathered in the self-cleaning zone, and a high-frequency alternating magnetic field is applied to excite the magnetic composite cleaning balls to oscillate at high frequency, using vibration energy to break up and peel off the harder scale layer attached to its surface and the nearby wall surface; the entire cleaning process is carried out online without stopping the machine. 2. By combining the rheological properties of the non-Newtonian fluid in the buffer medium layer with magnetic field control, the same magnetic composite cleaning ball can intelligently switch between two physical states and cleaning modes, namely "liquid buffering-soft cleaning" and "solid transfer-rigid rapping", depending on the frequency of the external magnetic field. It can not only continuously remove soft dirt for a long time, but also perform self-cleaning and extend its service life. Moreover, the switching method is extremely simple, which has significant technical advantages. 3. By offsetting the center of gravity of the ball core and the shell, or by directly offsetting the center of gravity of the ball core, the center of gravity of the high magnetic composite cleaning ball changes continuously during rotation, resulting in irregular centrifugal oscillation. This makes the trajectory of the high magnetic composite cleaning ball unpredictable and chaotic, thereby greatly increasing the probability of random collisions in complex flow channels, eliminating cleaning dead zones, improving descaling and turbulence effects, and improving heat transfer efficiency. 4. By using a three-phase winding coil array to generate a controllable "rotation + traveling wave" superimposed magnetic field, and by cyclically executing the control logic of the counter-current climbing mode and the counter-current climbing mode, the magnetic composite cleaning ball is forced to perform a spiral motion against the liquid flow. This not only completely eliminates the cleaning dead corners and ball accumulation in the heating chamber, but also uses the violent disturbance generated by the reverse motion to destroy the laminar boundary layer on the surface of the heat exchange tube, significantly improving the overall heat transfer efficiency of the MVR evaporation crystallization unit. 5. The external magnetic field generator used for driving in this application is located outside the heating chamber. The magnetic field penetrates the pipe wall and acts on the corrosion-resistant magnetic composite cleaning ball inside, avoiding the need to install mechanical shaft seals or motors in the highly corrosive leachate concentrate. This not only eliminates the risk of leakage under high pressure, but also significantly reduces the maintenance cost and failure rate of the equipment. It is particularly suitable for the high temperature, high salt, and high corrosion conditions at the end of the full-volume treatment of landfill leachate. Attached Figure Description

[0018] Figure 1 This is a simplified structural diagram of the processing system according to an embodiment of this application; Figure 2 This is a partial cross-sectional view of the MVR evaporation and crystallization unit according to an embodiment of this application; Figure 3 yes Figure 2A magnified view of part A in the middle; Figure 4 This is a schematic diagram of the structure of the magnetic composite cleaning ball according to an embodiment of this application; Figure 5 This is a cross-sectional view of a magnetic composite cleaning ball with a flexible positioning rope inside, according to an embodiment of this application. Figure 6 This is a cross-sectional view of the magnetic composite cleaning ball in the embodiment of this application when the center of gravity of the ball core is eccentric; Figure 7 This is a flowchart of the processing technology in the embodiments of this application.

[0019] Explanation of reference numerals in the attached figures: 11. Pretreatment unit; 12. Biochemical treatment unit; 13. Membrane deep treatment unit; 14. MVR evaporation and crystallization unit; 2. Heating chamber; 21. Heat exchange tubes; 3. Magnetic composite cleaning ball; 31. Ball core; 32. Ball shell; 33. Buffer medium layer; 34. Cleaning spikes; 35. Flexible positioning rope; 41. High-frequency excitation coil; 42. Three-phase winding coil array; 5. Interception plate. Detailed Implementation

[0020] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] This application discloses a comprehensive landfill leachate treatment system. (Refer to...) Figure 1 , Figure 2 and Figure 3 It includes a pretreatment unit 11 (such as an equalization tank and an oil-water-sludge separation device), a biochemical treatment unit 12 (such as a two-stage A / O biochemical tank), a membrane deep treatment unit 13 (such as a tubular ultrafiltration + nanofiltration / reverse osmosis membrane module), and an MVR evaporation and crystallization unit 14 connected in sequence. The MVR evaporation and crystallization unit 14 includes a heating chamber 2 and several heat exchange tubes 21 located inside it. The specific structure and connection method of the above modules are all existing technologies, which can be fully implemented by those skilled in the art and need not be elaborated.

[0022] Most importantly, the MVR evaporation crystallization unit 14 also includes; Magnetic composite cleaning balls 3 are provided in multiples and dispersed between the outer wall of the heat exchange tube 21 and the inner wall of the heating chamber 2 and flow with the liquid. A cleaning ball trapping mechanism is used to confine all magnetic composite cleaning balls 3 within the self-cleaning zone of the heating chamber 2; and An external magnetic field generating device is located outside the heating chamber 2 and is used to generate a rotating magnetic field that drives the magnetic composite cleaning ball 3 to move, and to generate a high-frequency alternating magnetic field that excites the magnetic composite cleaning ball 3 located in the self-cleaning zone to oscillate at high frequency.

[0023] Specifically, refer to Figure 4 , Figure 5 and Figure 6 The magnetic composite cleaning ball 3 includes: The ball core 31 is made of a magnetotropic metal, such as an iron-nickel alloy, which can be attracted by an external magnetic field and move; and the diameter of the ball core 31 is preferably 15 to 25 mm, and the surface can be treated with zinc or nickel-phosphorus plating to prevent corrosion.

[0024] The spherical shell 32, spaced around the outer periphery of the spherical core 31, is made of a heat-resistant and corrosion-resistant material, such as polytetrafluoroethylene (PTFE) or PEEK. Furthermore, the outer wall of the spherical shell 32 is provided with a plurality of cleaning protrusions 34 arranged in rows. These cleaning protrusions 34 are made of flexible rubber, specifically fluororubber or perfluoroether rubber. Preferably, the wall thickness of the spherical shell 32 is 2–4 mm, and the outer diameter is 25–35 mm.

[0025] The buffer medium layer 33 fills the gap cavity between the spherical core 31 and the spherical shell 32, and its average thickness is 3 to 10 mm.

[0026] The buffer medium layer 33 is filled with a non-Newtonian fluid, such as a nano-silica dispersion. When the magnetic composite cleaning ball 3 is subjected to a low-frequency rotating magnetic field by an external magnetic field generator, the buffer medium layer 33 is in a liquid state, and the ball core 31 floats and rotates inside the ball shell 32. When the magnetic composite cleaning ball 3 is subjected to a high-frequency alternating magnetic field by an external magnetic field generator, the buffer medium layer 33 transforms into a near-solid state and rigidly transmits the high-frequency vibration of the ball core 31 to the ball shell 32.

[0027] Therefore, during the full-scale treatment of landfill leachate, the concentrate produced by the membrane deep treatment unit 13 enters the heating chamber 2 of the MVR evaporation and crystallization unit 14. Specifically, the concentrate is introduced from the lower part of the heating chamber 2 into the cavity between the inner wall of the heating chamber 2 and the outer wall of the heat exchange tube 21, i.e., the shell side, for boiling, circulating, and performing online cleaning of the landfill leachate concentrate to be evaporated. Meanwhile, steam is introduced from the upper part of the heating chamber 2 and then distributed to multiple heat exchange tubes 21, i.e., the tube side. As the steam flows downward through the heat exchange tubes 21, it exchanges heat with the concentrate outside the tubes, releasing latent heat and gradually condensing. The specific evaporation and crystallization process is existing technology and can be fully implemented by those skilled in the art, so it will not be elaborated further.

[0028] Inside heating chamber 2, a large number of magnetic composite cleaning balls 3 are dispersed with the liquid. A specific magnetic field pattern is applied by an external magnetic field generator, allowing for precise control of the movement of the magnetic composite cleaning balls 3. For example, during the normal evaporation stage, the magnetic composite cleaning balls 3 are driven to roll and rotate with the liquid flow, scraping and agitating the wall surface to prevent soft scale deposition and enhance turbulence and heat transfer efficiency. When deep cleaning is detected or periodically required, the magnetic composite cleaning balls 3 are gathered in a specific area (self-cleaning zone), and a high-frequency alternating magnetic field is applied to excite high-frequency oscillation of the magnetic composite cleaning balls 3. This vibration energy breaks up and peels off the harder scale layer adhering to their surface and the surrounding wall. The entire cleaning process is performed online without requiring machine shutdown.

[0029] In this case, since the core 31 and shell 32 of the magnetic composite cleaning ball 3 are filled with a buffer medium layer 33 made of non-Newtonian fluid, when a low-frequency rotating magnetic field is applied by an external magnetic field generator, the core 31 is driven to rotate by magnetic force. Since the buffer medium layer 33 is in a "liquid state", the rotation of the core 31 is transmitted to the shell 32 through fluid friction in a non-rigid manner, causing the shell 32 and the cleaning protrusions 34 on the outer wall to rotate and roll relatively gently. In this way, firstly, the flexible protrusions on the spherical shell 32 can conform to the curve of the wall and continuously scrape, preventing the adhesion and accumulation of soft scale such as colloids and organic sludge; secondly, the random movement of a large number of magnetic composite cleaning balls 3 greatly disturbs the flow of liquid in the heating chamber 2, destroys the stagnant layer near the wall (the main source of thermal resistance), and strongly mixes the fluid in the core high-temperature zone with the fluid near the wall, which significantly improves the heat transfer coefficient, thereby increasing the evaporation efficiency under the same steam consumption, or reducing energy consumption under the same evaporation amount; thirdly, with the buffering effect of the buffer medium layer 33, when the movement of the magnetic composite cleaning balls 3 is obstructed or stuck, the ball core 31 can slide and roll relative to the spherical shell 32, avoiding the ball breakage or scratches on the heat exchange tube 21 that may be caused by the rigid mechanical structure, thus improving the reliability of the system.

[0030] When it is necessary to remove harder scale, the external magnetic field generator switches to a high-frequency alternating magnetic field. At this time, the core 31 vibrates at high frequency, causing the buffer medium layer 33 to experience an extremely high shear rate and instantly undergo a phase transition to become a near-solid (rigid). At this moment, the magnetic composite cleaning ball 3 instantly becomes a "solid hard ball," and the high-frequency vibration energy of the core 31 is rigidly and 100% losslessly transferred to the shell 32 and the flexible protrusions. The impact energy generated by this high-frequency oscillation can effectively break and peel off the hard scale that has already formed and clean its own shell 32. This is a function that traditional cleaning balls that rely on fluid kinetic energy collision cannot achieve, solving the problem of existing technologies being ineffective against hard scale. Moreover, the high-frequency oscillation helps the magnetic composite cleaning ball 3 shake off the scale adhering to its surface, preventing it from being "encased" by the scale and becoming ineffective.

[0031] Therefore, this application combines the rheological properties of the non-Newtonian fluid in the buffer medium layer 33 with magnetic field control, enabling the same magnetic composite cleaning ball 3 to intelligently switch between two physical states and cleaning modes—"liquid buffering-soft cleaning" and "solid transfer-rigid rapping"—depending on the frequency of the external magnetic field. This "integrated dual-mode" design solves the problems of "preventing soft scale" (requiring continuous action) and "removing hard scale" (requiring high-intensity impact) simultaneously with a simple structure, and the switching method is extremely simple (only changing the magnetic field frequency), demonstrating significant technical advantages.

[0032] In order to further improve the disordered movement effect of the magnetic composite cleaning ball 3 in the concentrate of the heating chamber 2 after being subjected to a rotating magnetic field.

[0033] In one feasible embodiment, a flexible positioning rope 35 is connected between the spherical core 31 and the spherical shell 32, as shown in FIG5; When the flexible positioning rope 35 is in a taut or slack state, the center of the ball core 31 and the center of the ball shell 32 do not coincide, so that the high magnetic composite cleaning ball 3 is in a state of eccentricity in any state.

[0034] In another feasible embodiment, the center of gravity of the ball core 31 is offset from its geometric center, for example, by machining an eccentric cavity or embedding a high-density metal block in the ball core 31, as shown in Figure 6.

[0035] Of course, in other feasible embodiments, both of the above schemes can be used simultaneously. By arranging the ball core 31 and the ball shell 32 with their centers of gravity offset, or by directly offsetting the center of gravity of the ball core 31, the center of gravity of the high magnetic composite cleaning ball 3 can be made to change continuously during rotation, thereby generating irregular centrifugal oscillations. This makes the motion trajectory of the high magnetic composite cleaning ball 3 present an unpredictable "chaotic" state, which greatly increases the probability of random collisions in complex flow channels, eliminates cleaning dead zones, improves descaling and intensifies turbulence, and improves heat transfer efficiency.

[0036] In addition, refer to Figure 2 and Figure 3 The aforementioned external magnetic field generating device includes: A high-frequency excitation coil 41 is wrapped around the outer wall of the heating chamber 2 and is positioned corresponding to the self-cleaning zone; Three-phase winding coil array 42 is distributed in multiple sets along the axial direction of heating chamber 2, and multiple three-phase winding coil arrays 42 are electrically connected to a vector frequency converter controller. The vector frequency converter is configured to generate a superimposed rotating magnetic field and an axial traveling wave magnetic field inside the heating chamber 2 by adjusting the phase sequence and frequency of the three-phase current, thereby driving the magnetic composite cleaning ball 3 to move along a spiral trajectory in the opposite or forward direction to the liquid flow in the heating chamber 2.

[0037] Therefore, the vector frequency converter, through programming, controls the phase, frequency, and amplitude of the current flowing into each group of three-phase winding coil arrays 42. By adjusting the phase sequence of the three-phase current, a horizontal rotating magnetic field can be generated; by controlling the phase of multiple coil currents to lag or lead sequentially along the axial direction, a traveling wave magnetic field advancing along the axial direction can be generated. The vector superposition of the two magnetic fields drives the magnetic composite cleaning ball 3 with magnetism to move along a spiral trajectory, ensuring that the entire wall surface of the heat exchange tube 21 can be cleaned regularly, eliminating cleaning blind spots.

[0038] Furthermore, in another feasible embodiment, the vector frequency converter controller is also configured to control the three-phase winding coil array 42 to alternately output drive current in reverse current ramp-up mode and forward current fall-down mode, and its specific control strategy is as follows: In the counter-current climbing mode, the thrust direction of the traveling wave magnetic field is opposite to the liquid flow direction and the thrust is greater than the sum of the liquid flow resistance and the gravity of the magnetic composite cleaning ball 3. In the downstream reflux mode, the thrust direction of the traveling wave magnetic field is the same as the liquid flow direction or the thrust is zero, so that the magnetic composite cleaning ball 3 is reset to the bottom of the heating chamber 2 under the impact of the liquid flow.

[0039] Specifically, in a specific instance, for different operating modes: The counter-current climbing mode is used for daily scale prevention and soft scale cleaning. Specifically, the vector frequency converter adjusts the three-phase current frequency to 1-3Hz and sets a phase difference to make the traveling wave magnetic field direction upward, which is opposite to the direction of gravity settling of the liquid in the heating chamber 2, i.e., opposite to the normal liquid flow direction. At this time, the axial thrust of the traveling wave magnetic field is greater than the sum of the liquid flow resistance and the gravity of the magnetic composite cleaning ball 3, driving the magnetic composite cleaning ball 3 to spiral upward along the outer wall of the heat exchange tube 21. At the same time, the rotating magnetic field causes the cleaning ball to rotate, and the cleaning protrusions 34 scrub the tube wall. Because the applied thrust is greater than the gravity, the magnetic composite cleaning ball 3 can overcome the resistance and move actively in the high viscosity liquid, covering the entire bundle height of the heat exchange tube 21, achieving uniform scale prevention.

[0040] The downstream fall mode is used for reset and self-cleaning. Specifically, the vector frequency converter switches the three-phase current phase sequence or reduces the frequency to close to 0Hz, so that the direction of the traveling wave magnetic field thrust is downward or the same as the direction of liquid flow, or completely shuts off the axial magnetic field and retains only a weak rotating magnetic field. At this time, the magnetic composite cleaning ball 3 falls back to the self-cleaning area at the bottom of the heating chamber 2 along the spiral trajectory under its own gravity and the impact of the downward flow of the liquid.

[0041] The aforementioned control strategy of periodic "climb-fall" cyclical motion forces the magnetic composite cleaning balls 3 to perform periodic spiral scanning motion covering the entire height of the heating chamber 2, ensuring that the entire wall surface of the heat exchange tube 21 can be cleaned regularly, eliminating cleaning blind spots; moreover, compared to filling the entire heating chamber 2, this control strategy only requires a smaller number of magnetic composite cleaning balls 3, which can achieve the cleaning effect of a large number of static balls by making them cyclical.

[0042] Furthermore, refer to Figure 2 The cleaning ball interception mechanism includes a funnel-shaped interception plate 5 fixed to the inner wall of the bottom of the heating chamber 2. The interception plate 5 is porous and its pore diameter is smaller than the diameter of the magnetic composite cleaning ball 3 and larger than the diameter of the scale. The high-frequency excitation coil 41 corresponds to the middle of the axial direction of the interception plate 5.

[0043] Therefore, when the system detects a decrease in heat transfer efficiency or reaches the set cycle, it enters the self-cleaning mode: the vector frequency converter controls the traveling wave magnetic field downward, driving all the magnetic composite cleaning balls 3 into the funnel-shaped interceptor plate 5 at the bottom to clump together, and then the external high-frequency excitation coil 41 is activated. At this time, the magnetic composite cleaning balls 3 collide with each other and vibrate at high frequency in this area, and the flexible cleaning protrusions 34 on their surface peel off the scale adhering to them through mechanical collision and vibration; the peeled scale is discharged with the liquid to the subsequent crystallization separator. After completing the self-cleaning, the vector frequency converter switches to the counter-current climbing mode, and the magnetic composite cleaning balls 3 re-enter the working area to perform anti-scaling work. Thus, without changing the cleaning medium or disassembling the equipment, the magnetic composite cleaning balls 3 realize the function switch from daily anti-scaling to deep descaling, significantly extending the continuous operation cycle of the MVR evaporation crystallization unit 14.

[0044] This application discloses a process for the full-volume treatment of landfill leachate, based on the aforementioned full-volume treatment system for landfill leachate, with reference to... Figure 1 , Figure 2 and Figure 7 It includes the following steps: S1. The landfill leachate is treated in the pretreatment unit 11 to remove oil and slag; S2. The pretreated landfill leachate is degraded for organic matter and denitrified in the biochemical treatment unit 12; S3. Deep filtration is performed through the membrane deep treatment unit 13 to produce a concentrate; S4. The concentrate is fed into the MVR evaporation and crystallization unit 14 for evaporation and crystallization to obtain condensate and evaporation residue. During the evaporation process, the magnetic composite cleaning ball 3 is driven by the external magnetic field generator to move in the flowing concentrate to improve the turbulence and heat transfer efficiency and clean the soft scale; or, the magnetic composite cleaning ball 3 gathered in the self-cleaning zone is driven to oscillate at high frequency to clean the scale on it. S5. The evaporation residue and the scale removed from the magnetic composite cleaning ball 3 are sent to the subsequent process to obtain the stabilized product.

[0045] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "a" or "an," and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising," "including," and similar terms mean that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including," and their equivalents, but do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0046] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A comprehensive landfill leachate treatment system, comprising a pretreatment unit, a biochemical treatment unit, a membrane deep treatment unit, and an MVR evaporation and crystallization unit connected in sequence; the MVR evaporation and crystallization unit includes a heating chamber and a plurality of heat exchange tubes located therein, characterized in that, Also includes; Magnetic composite cleaning balls are provided in multiples and dispersed between the outer wall of the heat exchange tube and the inner wall of the heating chamber, and flow with the liquid. A cleaning ball trapping mechanism is used to confine all the magnetic composite cleaning balls within the self-cleaning zone of the heating chamber; and An external magnetic field generating device is located outside the heating chamber and is used to generate a rotating magnetic field that drives the magnetic composite cleaning ball to move, and to generate a high-frequency alternating magnetic field that excites the magnetic composite cleaning ball located in the self-cleaning zone to oscillate at high frequency.

2. The landfill leachate full-volume treatment system according to claim 1, characterized in that, The magnetic composite cleaning ball comprises: The spherical core is made of magnetostrictive metal; A spherical shell, with a gap fitted around the outer periphery of the spherical core, is made of heat-resistant and corrosion-resistant material; and A buffer medium layer is filled in the gap cavity between the spherical core and the spherical shell.

3. The landfill leachate full-volume treatment system according to claim 2, characterized in that, The buffer medium layer is filled with a non-Newtonian fluid; When the magnetic composite cleaning ball is subjected to a low-frequency rotating magnetic field by the external magnetic field generator, the buffer medium layer becomes liquid, and the ball core floats and rotates within the ball shell. When a high-frequency alternating magnetic field is applied to the magnetic composite cleaning ball by an external magnetic field generator, the buffer medium layer transforms into a near-solid state and rigidly transmits the high-frequency vibration of the ball core to the ball shell.

4. The landfill leachate full-volume treatment system according to claim 2, characterized in that, The outer wall of the spherical shell is provided with a plurality of cleaning protrusions arranged in a row, and the cleaning protrusions are made of flexible rubber.

5. The landfill leachate full-volume treatment system according to claim 2, characterized in that, A flexible positioning rope is connected between the spherical core and the spherical shell; When the flexible positioning rope is taut, the center of the ball core does not coincide with the center of the ball shell.

6. The landfill leachate full-volume treatment system according to claim 2, characterized in that, The center of gravity of the sphere is offset from its geometric center.

7. A landfill leachate full-volume treatment system according to any one of claims 1-6, characterized in that, The external magnetic field generating device includes: A high-frequency excitation coil is wound around the outer wall of the heating chamber and is positioned corresponding to the self-cleaning zone; Multiple sets of three-phase winding coil arrays are distributed at intervals along the axial direction of the heating chamber, and multiple sets of three-phase winding coil arrays are electrically connected to a vector frequency converter controller. The vector frequency converter is configured to generate a superimposed rotating magnetic field and an axial traveling wave magnetic field inside the heating chamber by adjusting the phase sequence and frequency of the three-phase current, thereby driving the magnetic composite cleaning ball to move along a spiral trajectory in the opposite or forward direction to the liquid flow in the heating chamber.

8. The landfill leachate full-volume treatment system according to claim 7, characterized in that, The vector frequency converter is also configured to control the three-phase winding coil array to alternately output drive current in reverse current ramp-up mode and in-current fall-down mode; In the counter-current climbing mode, the thrust direction of the traveling wave magnetic field is opposite to the liquid flow direction and the thrust is greater than the sum of the liquid flow resistance and the gravity of the magnetic composite cleaning ball; In the downstream flow mode, the thrust direction of the traveling wave magnetic field is the same as or zero, causing the magnetic composite cleaning ball to reset to the bottom of the heating chamber under the impact of the liquid flow.

9. A landfill leachate full-volume treatment system according to claim 7, characterized in that, The cleaning ball interception mechanism includes a funnel-shaped intercepting plate fixed to the inner wall of the bottom of the heating chamber. The aperture of the intercepting plate is smaller than the diameter of the magnetic composite cleaning ball, and the high-frequency excitation coil corresponds to the axial center of the intercepting plate.

10. A process for the full-volume treatment of landfill leachate, based on the full-volume treatment system for landfill leachate as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. The landfill leachate is subjected to oil and slag removal treatment in the pretreatment unit; S2. The pretreated landfill leachate is then subjected to biochemical treatment unit for degradation of organic matter and denitrification; S3. Deep filtration is performed through the membrane deep treatment unit to produce a concentrate; S4. The concentrate is fed into the MVR evaporation and crystallization unit for evaporation and crystallization to obtain condensate and evaporation residue. During the evaporation process, the magnetic composite cleaning balls are driven by the external magnetic field generator to move in the flowing concentrate to improve the turbulence and heat transfer efficiency and clean the soft scale. Alternatively, the magnetic composite cleaning balls gathered in the self-cleaning zone are driven to oscillate at high frequency to clean the scale on them. S5. The evaporation residue and the scale removed from the magnetic composite cleaning ball are sent to the subsequent process to obtain the stabilized product.

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