Magnetic material and reactor system for intensifying anaerobic fermentation using the same

Abstract

The application discloses a kind of magnetic materials and utilize the material to strengthen anaerobic fermentation reactor system, belong to wastewater anaerobic biological treatment technical field.Reactor system includes: reactor main body, three-phase separator, magnetic recovery mechanism and biogas injection redispersion mechanism, magnetic recovery mechanism is integrated in the outside of center reflux pipe, and under the action of driving mechanism along the axial lifting movement of center reflux pipe;Biogas injection redispersion mechanism is used to inject biogas to liftable magnetic roller unit, so that the magnetic material on it is redispersed.The application is designed by magnetic roller unit and biogas injection redispersion mechanism, solves the problems such as magnetic material settlement in anaerobic reactor and long-term operation failure, achieves to significantly reduce magnetic material settlement, reduces material corrosion, and optimizes reaction zone distribution uniformity, realizes material efficient recycling while avoiding blockage, substantially reduces supplement cost.

Description

Technical Field

[0001] This invention relates to a magnetic material and a reactor system for enhancing anaerobic fermentation using the same material, belonging to the field of anaerobic biological wastewater treatment technology. Background Technology

[0002] Upflow anaerobic sludge blanket (UASB) reactors and their derivative processes (such as EGSB and IC reactors) play an important role in the treatment of high-concentration organic wastewater. However, their long-term operation has been hampered by several technical bottlenecks, such as severe sludge loss, poor shock resistance, and low biogas production, which seriously restrict their economic efficiency. In recent years, iron-based magnetic materials have been introduced into anaerobic systems as conductive mediators. By establishing a direct interspecies electron transport (DIET) pathway, they can improve methane production efficiency. Simultaneously, their iron components act as cofactors for key enzymes such as hydrogenase and ferricredoxin, enhancing microbial metabolic activity and growth. Furthermore, magnetic particles can act as "nuclei" for microbial aggregation, accelerating the formation of granular sludge and thus optimizing reactor performance. For example, Chinese invention patent CN105036320A proposes a method for improving the efficiency of anaerobic biogas production from organic waste and wastewater by strengthening iron powder with a magnetic field. A magnetic field is applied to the outside of the anaerobic digester, while zero-valent iron is added inside. The magnetic field inhibits the formation of a passivation film on the iron powder, promotes the release of electrons from the iron powder, improves electron transport efficiency, and significantly increases methane production. For example, Chinese invention patent CN104529116A proposes a method for improving the activity and methanogenic efficiency of anaerobic digestion methanogens using nano-ferric oxide. This method utilizes nano-ferric oxide as an iron donor in the anaerobic treatment system, fully leveraging the ability of nano-ferric oxide to accommodate and slowly release Fe. 3+ and Fe 2+ This causes Fe in the reaction system 3+ and Fe 2+ The concentration of iron can be maintained within a stable range for a relatively long period of time to meet the iron requirements of anaerobic methanogens.

[0003] However, despite the significant advantages of iron-based magnetic materials in enhancing anaerobic fermentation, they still face the following technical problems due to their physicochemical properties during long-term application: (1) The density of iron-based magnetic materials (such as the density of iron(III) oxide is about 5.2 g / cm³) is much higher than that of bioflocs (about 1.05 g / cm³). In the upflow system, they are rapidly deposited to the bottom of the reactor due to gravity settling, which exacerbates the risk of blockage of the water distributor and leads to a shortage of materials in the middle and upper reaction zones; (2) Iron-based magnetic materials spontaneously agglomerate under the action of a magnetic field, forming aggregates. After agglomeration, the specific surface area decreases, the microbial attachment sites are sharply reduced, and the electron transfer efficiency is reduced; (3) After long-term operation, iron-based magnetic materials (such as iron(III) oxide) are easily corroded by sulfides in the anaerobic environment, and sometimes they are dissolved by sudden acidic environment impacts, so the long-term enhancement effect will weaken. The above defects make it difficult to utilize iron-based magnetic materials, forcing the continuous replenishment of new magnetic seeds during operation, and the long-term enhancement effect decays significantly with the operating time. Summary of the Invention

[0004] To address the problems of existing iron-based magnetic materials in enhancing anaerobic fermentation processes, such as reactor clogging, spontaneous aggregation leading to a sharp reduction in microbial attachment points and low electron transfer efficiency, and easy corrosion and dissolution resulting in a significant decline in long-term enhancement effects during actual operation, this invention provides a magnetic material and a reactor system for enhancing anaerobic fermentation using this material. The technical solution is as follows: The first objective of this invention is to provide a magnetic material, which is a polyaniline-encapsulated iron oxide nanocomposite material, and the preparation method of this magnetic material includes the following steps: S1. Take 1 part by weight of Fe3O4 nanoparticles and add them to 50 to 200 parts by weight of a dilute hydrochloric acid solution with a concentration of 40 to 200 mM. Disperse the solution under ultrasonic conditions for 10 to 60 minutes to form a uniform magnetic fluid dispersion. S2. Add 0.2 to 0.8 parts by weight of aniline monomer to the dispersion obtained in step S1, and continue the reaction in an ice-water bath at 0 to 10°C for 30 to 120 minutes under mechanical stirring or ultrasonic conditions, so that the aniline monomer is fully adsorbed on the surface of the nano Fe3O4 magnetic core. S3. Add 0.2 to 1 part by weight of ammonium persulfate to 20 to 50 parts by weight of dilute hydrochloric acid solution with a concentration of 40 to 200 mM. After mechanically stirring in an ice-water bath at 0 to 10°C for 10 to 30 minutes, slowly and dropwise add it to the nano Fe3O4 / aniline mixture obtained in step S2 with continuous stirring and ice-water bath cooling, controlling the dropwise addition time to 10 to 30 minutes. S4. After the addition is complete, continue the reaction at 0~5℃ for 4~24 hours to complete the in-situ oxidative polymerization of aniline; S5. After the reaction is complete, let the reaction mixture stand, and place a permanent magnet with a strength of not less than 0.3 T on the outer wall of the container for magnetic adsorption. After the solid product is completely adsorbed to the container wall, carefully pour off the supernatant, remove the permanent magnet, add sufficient deionized water, and redisperse the product by stirring or sonication. Use the magnet to adsorb again and pour off the supernatant. Repeat this washing process 3 to 5 times until the supernatant is colorless to obtain the initial material. S6. Add the initial material obtained in step S4 to 50 to 100 parts by weight of dilute hydrochloric acid with a concentration of 40 to 200 mM containing 0.1 to 0.4 parts by weight of aniline monomer, and stir at 0 to 5°C for 60 minutes to allow the monomer to be adsorbed onto the surface of the initial material. S7. Secondary polymerization: Add 0.1 to 0.4 parts by weight of ammonium persulfate to 20 to 50 parts by weight of dilute hydrochloric acid solution with a concentration of 40 to 200 mM. After mechanically stirring in an ice-water bath at 0 to 10°C for 10 to 30 minutes, add the solution dropwise to the system at a very slow rate for ≥ 60 minutes. Continue the reaction at 0 to 5°C for 4 to 24 hours. S8. After the reaction is complete, let the reaction mixture stand and place a permanent magnet with a strength of not less than 0.3 T on the outer wall of the container for magnetic adsorption. After the solid product has completely aggregated, carefully pour off the supernatant. Remove the permanent magnet and use acetone and deionized water as washing solvents in sequence. Redisperse the product by stirring or sonication, and then use the magnet for adsorption and pour off the supernatant. Repeat this washing operation 3 to 5 times for each solvent until the supernatant is colorless. S9. Freeze-dry the product for 24-72 hours to obtain nano Fe3O4@PANI core-shell composite material powder.

[0005] Furthermore, after step S8 is completed, steps S6 to S8 are repeated for a third round of repeated coating and polymerization, wherein the amount of aniline monomer used is 0.05 to 0.2 parts by weight.

[0006] A second object of the present invention is to provide a reactor system based on enhanced anaerobic fermentation using the aforementioned magnetic materials, comprising: The reactor body is divided into a sludge bed zone, a suspension zone and a three-phase separation zone from bottom to top. Anaerobic sludge containing magnetic materials is added to the reactor body. A three-phase separator is located at the top of the reactor body. It includes a central reflux pipe, which is vertically arranged. The upper end of the central reflux pipe is connected to the gas-liquid separator, and its lower end extends to the bottom of the sludge bed zone. The magnetic recovery mechanism is integrated outside the central return pipe. It includes a liftable magnetic roller unit and a drive mechanism. The magnetic roller unit is located outside the central return pipe and is poweredly connected to the drive mechanism. Under the action of the drive mechanism, it moves up and down along the axial direction of the central return pipe. A biogas injection and redispersion mechanism is provided near the upper end of the central return pipe. The biogas injection and redispersion mechanism is used to inject biogas into the liftable magnetic roller unit, so that the magnetic material magnetically attracted on it is redispersed.

[0007] Furthermore, the three-phase separator also includes a gas collecting hood and sedimentation inclined plates. The gas collecting hood is installed at the upper end of the central reflux pipe, and the sedimentation inclined plates are evenly distributed at the lower end of the gas collecting hood.

[0008] Furthermore, when the magnetic roller unit moves down to the lower limit point at the bottom of the central return pipe, it is in the recovery position, the magnetic roller unit is energized, and it adsorbs the magnetic material in the sludge bed area; when the magnetic roller unit moves up to the upper limit point at the top of the central return pipe, it is in the dispersion position, the magnetic roller unit is de-energized, and at the same time the biogas injection and redispersion mechanism is activated to inject biogas into the magnetic roller unit.

[0009] Furthermore, the biogas injection and redispersion mechanism includes an annular injection pipe and a biogas branch pipe. The annular injection pipe includes two pipes, spaced apart at the upper and lower ends of the central return pipe. Each annular injection pipe is provided with a set of nozzles inclined towards the magnetic roller unit. The two annular injection pipes are connected to the biogas collection main pipe through the biogas branch pipe.

[0010] Furthermore, the nozzles are evenly distributed in a ring at an angle of 30° to 45°, and the injection pressure range is 0.2 to 0.5 MPa.

[0011] Furthermore, it also includes a PLC control system, which is electrically connected to the magnetic roller unit and the drive mechanism. The biogas branch pipe is equipped with a biogas injection solenoid valve and a booster pump. The PLC control system is also electrically connected to the start / stop module of the biogas injection solenoid valve and the booster pump.

[0012] Furthermore, the PLC control system includes a start-up magnetic recovery stage and a switching redistribution stage.

[0013] Furthermore, the magnetic recovery startup stage involves the PLC control system controlling the magnetic roller unit to descend to a set position in the sludge bed area, generating a magnetic field strength of 0.15~0.5 T for 5-30 minutes. The switching and redispersing stage is as follows: the PLC control system controls the magnetic roller unit to rise, triggers the displacement sensor, controls the magnetic roller unit to be powered off, and controls the biogas injection and redispersing mechanism to perform 3 to 5 pulse injections, with a single injection duration of 1 to 10 seconds, an interval of 5 to 30 seconds, and a pressure of 0.2 to 0.5 MPa.

[0014] The beneficial effects of this invention are: By integrating a liftable magnetic roller unit on the outside of the central return pipe, the magnetic roller unit sinks into the sludge bed area to actively adsorb the settled magnetic materials. After working for a period of time, it is raised to the top and combined with the biogas injection mechanism to redisperse the magnetic materials. This solves the problems of magnetic materials settling in the anaerobic reactor and long-term failure. It significantly reduces magnetic material settling, reduces material corrosion, and optimizes the uniformity of the reaction zone distribution. It also achieves efficient recycling of materials while avoiding blockage and greatly reduces replenishment costs.

[0015] Meanwhile, the magnetic material is a polyaniline-coated iron oxide nanocomposite material. The multiple coatings can better isolate sulfur corrosion, further reduce material corrosion, and ensure improved impact load resistance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an overall structure according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the magnetic recycling mechanism according to Embodiment 1 of the present invention; Figure 3 This is a control principle diagram of the PLC control system of Embodiment 1 of the present invention; Figure 4 This is the logic diagram of the PLC control system of Embodiment 1 of the present invention; Explanation of reference numerals in the attached figures 1. Reactor body; 2. Three-phase separator; 201. Gas collection hood; 202. Sedimentation inclined plate; 203. Central reflux pipe; 3. Magnetic recovery mechanism; 301. Magnetic roller unit; 302. Drive mechanism; 302a. Stepper motor; 302b. Vertical guide rail; 4. Biogas injection and redisperization mechanism; 401. Annular injection pipe; 402. Biogas branch pipe; 403. Nozzle; 5. Gas-water separator; 6. Inlet pump; 7. Differential pressure sensor; 8. pH sensor; 9. Conductivity sensor; 10. Biogas injection solenoid valve; 11. Booster pump; 12. Biogas flow meter; 13. Biogas collection tank; 14. Biogas collection main pipe. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0019] Example 1, such as Figure 1 As shown, a reactor system for enhancing anaerobic fermentation using magnetic materials includes a reactor body 1, a three-phase separator 2, a magnetic recovery mechanism 3, a biogas injection and redispersion mechanism 4, and a PLC control system.

[0020] Specifically, reactor body 1, which can be an EGSB reactor body, is divided into a sludge bed zone, a suspension zone, and a three-phase separation zone from bottom to top. During the system startup phase, anaerobic sludge containing polyaniline-coated iron oxide composite material (PANI-Fe3O4) is added to EGSB reactor body 1. The concentration of anaerobic inoculated sludge in the anaerobic reaction system is 10-30 g / L, and the amount of magnetic material added is 0.5-10 g / L. Wastewater to be treated is introduced to 80% of the effective volume, and the pH is controlled at 6.8-7.5, the temperature at 35±1℃, the upward flow velocity at 2.5-8 m / h, and the organic loading at 1-30 kg COD / (m³·d).

[0021] The three-phase separator 2 is located at the top of the reactor body 1, and the top of the three-phase separator 2 is connected to the gas-liquid separator 5. Specifically, it includes a gas collection hood 201, sedimentation inclined plates 202, and a central reflux pipe 203. The central reflux pipe 203 is vertically arranged, with its upper end connected to the gas-liquid separator 5. The output end of the gas-liquid separator 5 is connected to the biogas collection main pipe 14, which is connected to the biogas collection tank 13. The lower end of the central reflux pipe 203 extends to the bottom of the sludge bed zone. The gas collection hood 201 is located at the top of the central reflux pipe 203, and the lower end of the gas collection hood 201 is provided with uniformly distributed sedimentation inclined plates 202.

[0022] Specifically, the magnetic recovery mechanism 3 is integrated outside the central return pipe 203, such as... Figure 2As shown, it includes a liftable magnetic roller unit 301 and a drive mechanism 302. The magnetic roller unit 301 is composed of an electromagnetic coil surrounding a metal roller core and is connected to an external power source through a slip ring brush. The drive mechanism 302 includes a drive motor 302a and a telescopic rod 302b. The output shaft of the drive motor 302a is connected to a drive gear. The telescopic rod 302b includes three sections from top to bottom: the first section is an internal threaded gear, the second section is a telescopic rod composed of an external threaded screw and internal and external threaded nuts, and the third section is an external threaded rod. The lower end of the external threaded rod of the third section is fixedly connected to the magnetic roller unit 301. During operation, when the drive motor 302a drives the drive gear to rotate clockwise, the internal thread gear and the internal and external thread nuts of the telescopic rod 302b rotate counterclockwise simultaneously, and the external thread rod extends downward, driving the magnetic roller unit 301 to move downward along the axial direction of the central return pipe 203; conversely, when the drive motor 302a drives the drive gear to rotate counterclockwise, the external thread rod drives the magnetic roller unit 301 to move upward along the axial direction of the central return pipe 203.

[0023] Furthermore, the magnetic recovery mechanism 3 has two working positions during operation: a recovery position and a dispersion position. In the recovery position, when the magnetic roller unit 301 moves down to the lower limit point at the bottom of the central return pipe 203, it is located in the middle of the sludge bed. At this time, the magnetic roller unit 301 is energized and adsorbs the magnetic material in the sludge bed area. In the dispersion position, when the magnetic roller unit 301 moves up to the upper limit point at the top of the central return pipe 203, the magnetic roller unit 301 is de-energized, and simultaneously, the biogas injection and redispersion mechanism 4 is activated to inject biogas into the magnetic roller unit 301.

[0024] Specifically, the biogas injection and redispersing mechanism 4 includes annular injection pipes 401 and biogas branch pipes 402. Two annular injection pipes 401 are spaced apart outside the central return pipe 203. The two annular injection pipes 401 are connected to the biogas collection main pipe 14 via the biogas branch pipes 402. Each of the two annular injection pipes 401 has upward / downward-sloping nozzles 403, evenly distributed in a ring at an angle of 30°~45°, with an injection pressure range of 0.2~0.5MPa. When the magnetic roller unit 301 moves upward to the upper end of the central return pipe 203, the nozzles 402 of the two annular injection pipes 401 correspond to the upper and lower surfaces of the magnetic roller unit 301.

[0025] Specifically, such as Figure 3 As shown, the PLC control system is electrically connected to the magnetic roller unit 301 and the drive mechanism 301. The biogas branch pipe 402 is equipped with a biogas injection solenoid valve 10 and a booster pump 11. The PLC control system is also electrically connected to the start / stop module of the biogas injection solenoid valve 10 and the booster pump 11.

[0026] The PLC control system can dynamically adjust the operation cycle of the magnetic roller unit 301 according to the settlement data, or manually set the operation cycle according to the actual operation. The operation cycle is 2 to 24 hours, and the lifting or lowering speed of the magnetic roller unit 301 is 5 to 30 cm / min.

[0027] The PLC control system includes a magnetic recovery initiation stage and a redispersion switching stage. In the magnetic recovery initiation stage, the PLC control system lowers the magnetic roller unit 301 to the center of the sludge bed, generating a magnetic field strength of 0.15~0.5 T for 5-30 minutes to complete magnetic recovery. In the redispersion switching stage, the PLC control system raises the magnetic roller unit 301, triggering its displacement sensor. At this time, the magnetic roller unit 301 is de-energized, and simultaneously the biogas injection redispersion mechanism 4 performs 3-5 pulse injections on the magnetic roller unit 301, with each injection lasting 1-10 seconds, an interval of 5-30 seconds, and a pressure of 0.3-0.5 MPa, to complete magnetic distribution.

[0028] Specifically, the PLC control system (5) is also connected to a bed pressure differential sensor 7, a multi-point conductivity sensor group (multiple conductivity sensors 9), a pH sensor 8, and a biogas flow meter 12 arranged along the height of the reactor, for monitoring the operating conditions of the reactor system of this invention. In the magnetic recovery stage, the system adopts a three-layer intelligent control logic, as follows: (1) Main trigger signal (magnetic material distribution signal) Differential pressure monitoring of the sludge bed: Differential pressure sensors 7 are installed at the top and bottom of the sludge bed. When the differential pressure of the sludge bed increases beyond a set threshold (based on the differential pressure when the sludge bed is uniformly and stably distributed, the threshold can be set to 10% to 20% according to actual operating conditions), it indicates that the magnetic material and sludge are excessively accumulated at the bottom, immediately triggering the magnetic recovery program and entering the magnetic recovery stage. This is the most direct and reliable trigger signal.

[0029] Conductivity gradient monitoring: Conductivity probes (conductivity sensor groups) are installed in the sludge bed (bottom), suspended layer (middle), and effluent outlet (top) of the reactor. When the conductivity ratio between the bottom and the middle exceeds a set threshold (the threshold can be set from 1.5 to 3.0 depending on the actual situation), it indicates that the magnetic material is severely unevenly distributed and enriched at the bottom, triggering the magnetic recovery program and entering the magnetic recovery stage.

[0030] (2) Auxiliary trigger signal (system performance signal): Gas production rate / methane content decrease: When the biogas flow meter 12 detects that the rate of methane production decreases by more than the set threshold per hour for 2 consecutive hours (the threshold can be set to 5% to 20% according to the actual situation), the DIET efficiency may be reduced due to the agglomeration of magnetic materials, triggering the recovery-redispersion process to activate the materials.

[0031] pH anomaly: When the hourly drop in bottom pH exceeds the set threshold (the threshold can be set from 0.1 to 0.3 depending on the actual situation) for two consecutive hours, acidification may occur due to uneven local mass transfer, triggering the recovery process to redistribute the material evenly and enhance mass transfer.

[0032] (3) Emergency trigger signal: Fixed-period safety margin: Even if there are no abnormalities in the above signals, a maximum safety period (such as 24 hours) is still set to perform magnetic recovery once to prevent sensor failure or unknown situations.

[0033] For the initiation of the magnetic recovery phase, such as Figure 4 As shown, the PLC control system executes the following intelligent control logic: (a) Settling and Accumulation Judgment and Triggering (Main Triggering Condition): Real-time calculation of the pressure difference change rate at the bottom of the sludge bed and the ratio of the conductivity at the bottom to the middle. When any value exceeds its set threshold, the magnetic recovery process is immediately triggered. (b) Activity decay judgment and triggering (auxiliary triggering conditions): Real-time monitoring of methanogenesis rate and bottom pH changes in reactor. When the rate of methanogenesis decreases by more than its set threshold every hour for two consecutive hours or the bottom pH decreases by more than its set threshold every hour for two consecutive hours, the magnetic recovery process is triggered. (c) Adaptive execution: Dynamically adjust the recycling parameters based on the trigger signal type. If triggered by condition (a) (trigger type set to 1), the magnetic roller unit is controlled to descend to the bottom of the bed, and a magnetic field strength of 0.3~0.5 T is used for adsorption for 30~40 minutes; If triggered by condition (b) (trigger type set to 2), the magnetic roller unit is controlled to descend to the bottom of the bed, and a magnetic field strength of 0.15~0.25 T is used for adsorption for 20~30 minutes; (d) Guaranteed operation: If the above conditions are not triggered for 24 consecutive hours, a standard magnetic recovery process will be executed automatically. (e) Feedback optimization: Record whether the pressure difference / conductivity ratio or methanogenesis rate / reactor bottom pH returns to the effective range of the baseline value (baseline value ±5%) within 2 hours after each recovery operation. If not, automatically increase the magnetic field strength and adsorption time by 5%~10% under the next similar triggering conditions, but the cumulative increase shall not exceed 50% of the original set value.

[0034] Example 2: The magnetic material of this invention is a polyaniline-coated iron(III) oxide nanocomposite material. The preparation method of this magnetic material includes the following steps: S1. Take 1 part by weight of Fe3O4 nanoparticles and add them to 50 to 200 parts by weight of a dilute hydrochloric acid solution with a concentration of 40 to 200 mM. Disperse the solution under ultrasonic conditions for 10 to 60 minutes to form a uniform magnetic fluid dispersion. S2. Add 0.2 to 0.8 parts by weight of aniline monomer to the dispersion obtained in step S1, and continue the reaction in an ice-water bath at 0 to 10°C for 30 to 120 minutes under mechanical stirring or ultrasonic conditions, so that the aniline monomer is fully adsorbed on the surface of the nano Fe3O4 magnetic core. S3. Add 0.2 to 1 part by weight of ammonium persulfate to 20 to 50 parts by weight of dilute hydrochloric acid solution with a concentration of 40 to 200 mM. After mechanically stirring in an ice-water bath at 0 to 10°C for 10 to 30 minutes, slowly and dropwise add it to the nano Fe3O4 / aniline mixture obtained in step S2 with continuous stirring and ice-water bath cooling, controlling the dropwise addition time to 10 to 30 minutes. S4. After the addition is complete, continue the reaction at 0~5℃ for 4~24 hours to complete the in-situ oxidative polymerization of aniline; S5. After the reaction is complete, let the reaction mixture stand, and place a permanent magnet with a strength of not less than 0.3 T on the outer wall of the container for magnetic adsorption. After the solid product is completely adsorbed to the container wall, carefully pour off the supernatant, remove the permanent magnet, add sufficient deionized water, and redisperse the product by stirring or sonication. Use the magnet to adsorb again and pour off the supernatant. Repeat this washing process 3 to 5 times until the supernatant is colorless to obtain the initial material. S6. Add the initial material obtained in step S4 to 50-100 parts by weight of dilute hydrochloric acid with a concentration of 40-200 mM, containing 0.1-0.4 parts by weight of aniline monomer (the amount is reduced to 40%-50% of the first round), and stir at 0-5°C for 60 minutes to allow the monomer to be adsorbed onto the surface of the initial material. S7. Secondary polymerization: Add 0.1 to 0.4 parts by weight of ammonium persulfate to 20 to 50 parts by weight of dilute hydrochloric acid solution with a concentration of 40 to 200 mM. After mechanically stirring in an ice-water bath at 0 to 10°C for 10 to 30 minutes, add the solution dropwise to the system at a very slow rate for ≥ 60 minutes. Continue the reaction at 0 to 5°C for 4 to 24 hours. S8. After the reaction is complete, allow the reaction mixture to stand. Place a permanent magnet with a strength of not less than 0.3 T on the outer wall of the container for magnetic adsorption. After the solid product has completely aggregated, carefully decant the supernatant and remove the permanent magnet. Use acetone and deionized water as washing solvents in sequence, and redisperse the product by stirring or sonication. Then use the magnet for adsorption again and decant the supernatant. Repeat this washing operation 3 to 5 times for each solvent until the supernatant is colorless. S9. Freeze-dry the product for 24-72 hours to obtain nano Fe3O4@PANI core-shell composite material powder.

[0035] Furthermore, after step S8 is completed, steps S6 to S8 are repeated for a third round of repeated coating and polymerization, wherein the amount of aniline monomer used is 0.05 to 0.2 parts by weight.

[0036] Furthermore, the Fe3O4 nanoparticles in the magnetic material have a particle size of 20 nm to 100 nm.

[0037] Example 3: A Case Study on the Efficient and Stable Operation of Treating Leachate from Food Waste The initial COD of a certain food waste leachate was 35,000 ± 500 mg / L. To compare with a conventional UASB system, the reactor system described in Example 1 was used, with an effective volume of 1 m³. At startup, the PANI@Fe3O4 composite material prepared in Example 2 was injected at a dosage of 4 g / L. The temperature was controlled at 35 ± 1℃, and the upflow velocity was 4 m / h. By gradually increasing the influent concentration and flow rate, the organic loading rate was gradually increased from 5 kg COD / (m³·d) to 20 kg COD / (m³·d).

[0038] Throughout the 180-day long-term operation, thanks to the periodic magnetic recovery and redispersion operations triggered by the PLC control system, the concentration of magnetic material in the reactor's suspended zone remained within the effective range of 3.5 ± 0.5 g / L. When the OLR stabilized at 20 kg COD / (m³·d), the system's COD removal rate remained stable at 93%–95%, and the average biogas yield reached 0.64 ± 0.03 m³ / kg COD, with methane content consistently remaining at a high level of 65%–68%. This is attributed to the persistent DIET effect provided by the PANI coating layer, which significantly improved the conversion efficiency of acetic acid and H₂ / CO₂. In contrast, the COD removal rate of the control system (traditional UASB system, without magnetic material addition) fluctuated significantly under the same load, gradually decreasing to around 82%, and the average biogas yield of the control system was only 0.5 ± 0.02 m³ / kg COD.

[0039] Example 4: Long-term performance comparison case with traditional Fe3O4 materials The leachate from a landfill had an initial COD of 22,000 ± 400 mg / L. A reactor system as described in Example 1, with an effective volume of 1 m³, was used. At startup, the PANI@Fe3O4 composite material prepared in Example 2 was injected at a dosage of 4 g / L, and the PLC control system of Example 1 was employed. A comparative example was a reactor using only conventional Fe3O4 material, without a magnetic recovery system. By gradually increasing the influent concentration and flow rate, the organic loading rate was gradually increased from 5 kg COD / (m³·d) to 20 kg COD / (m³·d).

[0040] By day 60, the COD removal rate of the comparative system had decreased from 90% to 83%. This indicates that traditional Fe3O4 materials in upflow anaerobic systems suffer from corrosion, dissolution, and sedimentation issues, leading to a significant decline in conductivity and anaerobic digestion enhancement. However, throughout the entire 200-day operation, the COD removal rate of the system in Example 4 remained stable above 92%, and the biogas yield increased from 0.45 ± 0.03 m³ / kg COD in the comparative system to 0.56 ± 0.02 m³ / kg COD. The polyaniline coating effectively isolated the magnetic material from the corrosive effects of harmful substances such as H2S, and, combined with the magnetic recovery system, enabled the magnetic material-enhanced anaerobic fermentation system to achieve long-term operational stability.

[0041] Example 5: Case Study on Coping with Shock Loads and Low-Carbon Source Wastewater Treatment A mixed wastewater from a food industry and landfill leachate, with COD fluctuating between 12,000 and 27,000 mg / L, was treated using the reactor system described in Example 1, with an effective volume of 1 m³. At startup, the PANI@Fe3O4 composite material prepared in Example 2 was injected at a dosage of 3 g / L, and the PLC control system of Example 1 was employed. Two high-load shocks were intentionally introduced during operation (instantaneous OLR increased from 15 kg COD / (m³·d) to 30 kg COD / (m³·d), lasting 12 hours), and the system's recovery capacity was observed. Under the shock load, the pH sensor at the bottom of the system detected a significant drop in pH (from 7.2 to 6.8). The PLC control system responded rapidly (within 1 hour), triggering a magnetic recovery-redispersion procedure based on the "pH anomaly" signal. By redistributing the magnetic material uniformly, microbial metabolism and mass transfer efficiency were rapidly enhanced. Simultaneously, this redistribution process prevented localized acid accumulation, and the system recovered to a normal pH level (above 7.1) within 6 hours without acidification collapse.

[0042] Beneficial effects: 1. This invention solves the problems of magnetic material aggregation, sedimentation, and uneven distribution, improving the utilization rate of the reaction zone: Compared to conventional iron oxide powder, nano-iron oxide possesses superparamagnetic properties and no remanence, enabling rapid response and reducing material adhesion. Furthermore, a liftable magnetic roller integrated into the central return pipe actively adsorbs and disperses the settled magnetic material in the sludge bed, combined with a biogas injection system. This system, through the cyclic adsorption and redispersion of the magnetic roller, significantly reduces magnetic material sedimentation and optimizes the uniformity of the reaction zone distribution, achieving efficient material recycling while avoiding clogging and greatly reducing replenishment costs.

[0043] 2. Simultaneous realization of anti-corrosion regeneration of magnetic materials and system stability: The magnetic material used in this invention application is a polyaniline-coated Fe3O4 nanocomposite material, which isolates sulfur corrosion. The PLC system monitors in real time and triggers emergency recovery, reducing the Fe3O4 corrosion rate and improving the system's resistance to impact loads.

[0044] 3. Intelligent collaborative control reduces energy consumption and improves engineering economy: PLC multi-parameter linkage control optimizes the magnetic recovery cycle, combined with biogas internal circulation to drive injection. Based on feedback adjustment of pressure difference / conductivity ratio or methanogenesis rate / reactor bottom pH, the energy consumption of magnetic roller operation is reduced, and biogas pressurization injection utilizes the system's own energy, requiring no external power. 4. Significantly improves COD removal rate, biogas production rate, and long-term stability: By maintaining a high concentration of activated sludge in the reaction zone and enhancing interspecies direct electron transfer (DIET), methane production rate is increased by more than 20%, and COD removal rate is increased by more than 10%. No significant performance degradation was observed during continuous operation, and the system has the ability to quickly recover from shock loads and can quickly return to a stable operating state.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A reactor system for enhancing anaerobic fermentation using magnetic materials, characterized in that, include: The reactor body is divided into a sludge bed zone, a suspension zone and a three-phase separation zone from bottom to top. Anaerobic sludge containing magnetic materials is added to the reactor body. A three-phase separator is located at the top of the reactor body. It includes a central reflux pipe, which is vertically arranged. The upper end of the central reflux pipe is connected to the gas-liquid separator, and its lower end extends to the bottom of the sludge bed zone. The magnetic recovery mechanism is integrated outside the central return pipe. It includes a liftable magnetic roller unit and a drive mechanism. The magnetic roller unit is located outside the central return pipe and is poweredly connected to the drive mechanism. Under the action of the drive mechanism, it moves up and down along the axial direction of the central return pipe. A biogas injection and redispersion mechanism is provided near the upper end of the central return pipe. The biogas injection and redispersion mechanism is used to inject biogas into the magnetic roller unit, so that the magnetic material magnetically attracted on it is redispersed. The magnetic material is a polyaniline-coated iron oxide nanocomposite material, and the preparation method of the magnetic material includes the following steps: S1. Take 1 part by weight of Fe3O4 nanoparticles and add them to 50 to 200 parts by weight of a dilute hydrochloric acid solution with a concentration of 40 to 200 mM. Disperse the solution under ultrasonic conditions for 10 to 60 minutes to form a uniform magnetic fluid dispersion. S2. Add 0.2 to 0.8 parts by weight of aniline monomer to the dispersion obtained in step S1, and continue the reaction in an ice-water bath at 0 to 10°C for 30 to 120 minutes under mechanical stirring or ultrasonic conditions, so that the aniline monomer is fully adsorbed on the surface of the nano Fe3O4 magnetic core. S3. Add 0.2 to 1 part by weight of ammonium persulfate to 20 to 50 parts by weight of dilute hydrochloric acid solution with a concentration of 40 to 200 mM. After mechanically stirring in an ice-water bath at 0 to 10°C for 10 to 30 minutes, slowly and dropwise add it to the nano Fe3O4 / aniline mixture obtained in step S2 with continuous stirring and ice-water bath cooling, controlling the dropwise addition time to 10 to 30 minutes. S4. After the addition is complete, continue the reaction at 0~5℃ for 4~24 hours to complete the in-situ oxidative polymerization of aniline; S5. After the reaction is complete, let the reaction mixture stand, and place a permanent magnet with a strength of not less than 0.3 T on the outer wall of the container for magnetic adsorption. After the solid product is completely adsorbed to the container wall, carefully pour off the supernatant, remove the permanent magnet, add sufficient deionized water, and redisperse the product by stirring or sonication. Use the magnet to adsorb again and pour off the supernatant. Repeat this washing process 3 to 5 times until the supernatant is colorless to obtain the initial material. S6. Add the initial material obtained in step S5 to 50 to 100 parts by weight of dilute hydrochloric acid with a concentration of 40 to 200 mM containing 0.1 to 0.4 parts by weight of aniline monomer, and stir at 0 to 5°C for 60 minutes to allow the monomer to be adsorbed onto the surface of the initial material. S7. Secondary polymerization: Add 0.1 to 0.4 parts by weight of ammonium persulfate to 20 to 50 parts by weight of dilute hydrochloric acid solution with a concentration of 40 to 200 mM. After mechanically stirring in an ice-water bath at 0 to 10°C for 10 to 30 minutes, add the solution dropwise to the system at a very slow rate for ≥ 60 minutes. Continue the reaction at 0 to 5°C for 4 to 24 hours. S8. After the reaction is complete, let the reaction mixture stand, and place a permanent magnet with a strength of not less than 0.3 T on the outer wall of the container for magnetic field adsorption. After the solid product has completely aggregated, carefully pour off the supernatant; remove the permanent magnet, and use acetone and deionized water as washing solvents in sequence. Redisperse the product by stirring or sonication, and then use the magnet to adsorb it and pour off the supernatant. Repeat this washing operation 3 to 5 times for each solvent until the supernatant is colorless. S9. Freeze-dry the product for 24-72 hours to obtain nano Fe3O4@PANI core-shell composite material powder; After step S8 is completed, steps S6 to S8 are repeated for a third round of repeated coating and polymerization, wherein the amount of aniline monomer used is 0.05 to 0.2 parts by weight.

2. The reactor system for enhanced anaerobic fermentation according to claim 1, characterized in that, The three-phase separator also includes a gas collecting hood and sedimentation inclined plates. The gas collecting hood is installed at the upper end of the central reflux pipe, and the sedimentation inclined plates are evenly distributed at the lower end of the gas collecting hood.

3. The reactor system for enhanced anaerobic fermentation according to claim 1, characterized in that, When the magnetic roller unit moves down to the lower limit point at the bottom of the central return pipe, it is in the recovery position. The magnetic roller unit is energized and adsorbs the magnetic material in the sludge bed area. When the magnetic roller unit moves up to the upper limit point at the top of the central return pipe, it is in the dispersion position. The magnetic roller unit is de-energized, and at the same time, the biogas injection and redispersion mechanism is activated to inject biogas into the magnetic roller unit.

4. The reactor system for enhanced anaerobic fermentation according to claim 1, characterized in that, The biogas injection and redispersion mechanism includes annular injection pipes and biogas branch pipes. The annular injection pipes include two pipes, which are spaced apart at the upper and lower ends of the central return pipe. Each annular injection pipe is provided with a set of nozzles that are inclined toward the magnetic roller unit. The two annular injection pipes are connected to the biogas collection main pipe through the biogas branch pipes.

5. The reactor system for enhanced anaerobic fermentation according to claim 4, characterized in that, The nozzles are evenly distributed in a ring at an angle of 30° to 45°, and the injection pressure range is 0.2 to 0.5 MPa.

6. The reactor system for enhanced anaerobic fermentation according to claim 5, characterized in that, It also includes a PLC control system, which is electrically connected to the magnetic roller unit and the drive mechanism. The biogas branch pipe is equipped with a biogas injection solenoid valve and a booster pump. The PLC control system is also electrically connected to the start / stop module of the biogas injection solenoid valve and the booster pump.

7. The reactor system for enhanced anaerobic fermentation according to claim 6, characterized in that, The PLC control system includes a start-up magnetic recovery stage and a switching redistribution stage.

8. The reactor system for enhanced anaerobic fermentation according to claim 7, characterized in that, The magnetic recovery startup phase involves the PLC control system controlling the magnetic roller unit to descend to a set position in the sludge bed area, generating a magnetic field strength of 0.15~0.5 T for 5-30 minutes. The switching and redispersing stage is as follows: the PLC control system controls the magnetic roller unit to rise, triggers the displacement sensor, controls the magnetic roller unit to be powered off, and controls the biogas injection and redispersing mechanism to perform 3-5 pulse injections, with a single injection duration of 1-10 seconds, an interval of 5-30 seconds, and a pressure of 0.2-0.5 MPa.

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