Medium-high temperature anaerobic methane production system and working method thereof

Abstract

The invention discloses a medium-high temperature anaerobic methane production system and a working method thereof, and relates to the field of organic solid waste anaerobic digestion system equipment. The iron composite material adding unit is communicated with the reactor and is used for continuously or intermittently adding the magnetic iron-biomass charcoal composite carrier into the reactor; the effluent magnetic recovery unit is communicated with a water outlet of the reactor and is used for capturing a magnetic iron-biomass charcoal composite carrier flowing out along with effluent on line under the action of a magnetic field; the reflux unit is used for refluxing the carrier-microorganism enriched sludge subjected to magnetic recovery to the reactor; the on-line monitoring and control unit is used for monitoring operation parameters of the reactor in real time and controlling the working states of the iron composite material adding unit, the effluent magnetic recovery unit and the reflux unit in a linkage manner according to a monitoring result. According to the medium-high temperature anaerobic methane production system and the working method thereof, the loss of microorganisms and functional materials can be reduced, and the operation cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of equipment technology for anaerobic digestion systems for organic solid waste, and in particular to a medium-high temperature anaerobic biogas production system and its working method. Background Technology

[0002] In the field of organic solid waste resource utilization, medium- and high-temperature anaerobic digestion technology has become one of the core technologies for large-scale treatment of high-concentration organic waste (such as livestock and poultry manure, kitchen waste, and industrial organic wastewater) and energy recovery due to its ability to significantly improve the degradation rate of organic substrates, shorten the treatment cycle, and have higher methane yield potential. The core principle of this technology is to rely on the synergistic metabolism of anaerobic microbial communities (especially key functional microorganisms such as symbiotic acetic acid oxidizing bacteria and methanogenic archaea) to convert organic pollutants into clean energy such as methane.

[0003] To further enhance the efficiency of high-temperature anaerobic digestion, existing technologies have proposed adding functional materials such as zero-valent iron, activated carbon, and biochar to the reaction system. The core objective is to improve the activity and metabolic efficiency of key microorganisms by promoting direct interspecies electron transfer (DIET) and regulating the physicochemical properties of the system (such as redox potential and pH buffering capacity). However, existing technologies still face numerous unresolved technical bottlenecks in practical engineering applications, severely restricting the stability and economics of high-temperature anaerobic biogas production systems. Specifically, traditional functional materials such as zero-valent iron and activated carbon are largely lost with the effluent or residual sludge, increasing operating costs and potentially causing blockages or secondary pollution risks in subsequent treatment units. The surface of functional materials gradually adsorbs and enriches key functional microorganisms such as symbiotic acetic acid oxidizing bacteria and methanogenic archaea, which are crucial for maintaining efficient anaerobic digestion. However, because functional materials cannot be effectively recovered, the key microorganisms attached to their surfaces are lost along with the materials, leading to a continuous decrease in the concentration of functional microorganisms in the reaction system. This results in a gradual decline in the enhancement effect over long-term operation and a weak system resistance to shock loads.

[0004] Therefore, there is an urgent need to design a technical solution that can reduce the loss of microorganisms and functional materials and lower operating costs. Summary of the Invention

[0005] The purpose of this invention is to provide a medium-high temperature anaerobic biogas production system and its working method to solve the problems existing in the prior art, thereby reducing the loss of microorganisms and functional materials and lowering operating costs.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a medium-high temperature anaerobic biogas production system, comprising: A reactor used for anaerobic digestion reactions within a set temperature range; An iron composite material dosing unit, connected to the reactor, is used to continuously or intermittently add a magnetic iron-biochar composite carrier to the reactor to attach microorganisms within the reactor. The effluent magnetic recovery unit is connected to the effluent outlet of the reactor and is used to capture the magnetic iron-biochar composite carrier flowing out with the effluent online under the action of a magnetic field. A reflux unit, whose inlet is connected to the collection end of the effluent magnetic recovery unit and whose outlet is connected to the feed inlet or reaction zone of the reactor, is used to reflux the magnetically recovered carrier-microbial enriched sludge back to the reactor; and The online monitoring and control unit is used to monitor the reactor's operating parameters in real time and, based on the monitoring results, to control the working status of the iron composite material dosing unit, the effluent magnetic recovery unit, and the reflux unit.

[0007] In one embodiment, the effluent magnetic recovery unit includes a magnetic separation tank, and a magnetic attraction part is provided on the outside of the magnetic separation tank. The magnetic attraction part can apply a magnetic field to the magnetic separation tank to capture the magnetic iron-biochar composite carrier in the effluent flowing into the effluent magnetic recovery unit.

[0008] In one embodiment, the effluent magnetic recovery unit is provided with a non-magnetic stripping component, which is used to strip the adsorbed magnetic iron-biochar composite carrier and introduce it into the collection end of the effluent magnetic recovery unit after the magnetic field is weakened or removed; the inner bottom of the effluent magnetic recovery unit is formed as the collection end.

[0009] In one embodiment, the iron composite material dosing unit includes a storage bin for storing a magnetic iron-biochar composite carrier. The dosing pipeline has one end connected to the outlet of the storage silo and the other end connected to the reactor; and A quantitative feeder is connected in series to the feeding pipeline and is used to quantitatively transport the magnetic iron-biochar composite carrier in the storage silo to the reactor through the feeding pipeline.

[0010] In one embodiment, the reflux unit includes a sludge pump and a reflux pipeline. The inlet of the sludge pump is connected to the collection end of the effluent magnetic recovery unit, and the outlet of the sludge pump is connected to the feed inlet or reaction zone of the reactor via the reflux pipeline.

[0011] In one embodiment, the online monitoring and control unit includes a detection component and a controller. The detection component is located on the reactor and is used to monitor the temperature, pH value, redox potential and methane volume fraction in the reactor in real time, and transmit the detection data to the controller. The controller can control the iron composite material dosing unit, the effluent magnetic recovery unit and the reflux unit in conjunction with the received data to maintain stable system operation.

[0012] In one embodiment, the reactor is a fully mixed medium-high temperature anaerobic biogas-producing reactor.

[0013] In one embodiment, the temperature range for the anaerobic digestion reaction in the reactor is 41–49 °C.

[0014] In one embodiment, the outer wall of the reactor is provided with a temperature control component, which is capable of heating the interior of the reactor and maintaining it within a set temperature range.

[0015] The present invention also provides a method for operating the medium-high temperature anaerobic biogas production system as described above, comprising the following steps: A set amount of inoculum sludge and substrate is added to the reactor, and a set amount of magnetic iron-biochar composite carrier is added to the reactor through an iron composite material addition unit. The effluent from the reactor is discharged continuously or intermittently through the outlet and enters the effluent magnetic recovery unit. Under the magnetic attraction of the magnetic suction unit, the magnetic iron-biochar composite carrier, along with the attached enriched microorganisms, is adsorbed in the effluent magnetic recovery unit, achieving separation from the effluent. The separated effluent is discharged through the liquid outlet. The controller controls the magnetic suction part to weaken or turn off the magnetic field, and then drives the non-magnetic peeling part to scrape the adsorbed magnetic iron-biochar composite carrier along with the attached enriched microorganisms to the collection end. Start the reflux unit to return the magnetic iron-biochar composite carrier and the attached enriched microorganisms in the collection end to the reactor.

[0016] The present invention achieves the following technical effects compared to the prior art: This invention introduces a predetermined dose of magnetic iron-biochar composite carrier into a reactor via an iron composite material dosing unit. Microorganisms attached to the carrier flow out through the effluent outlet and are then captured by magnetic attraction in the effluent magnetic recovery unit. The captured magnetic iron-biochar composite carrier and its attached microorganisms can then return to the reactor via a reflux unit to participate in the reaction, achieving efficient retention of medium- and high-temperature anaerobic microorganisms and forming a microorganism-carrier-reactor cycle. This increases the system's biomass concentration and activity, significantly reduces the loss of functional materials such as the magnetic iron-biochar composite carrier, saves operating costs, and ensures the long-term reusability of the magnetic iron-biochar composite carrier composite material. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the 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.

[0018] Figure 1 This is a schematic diagram of the overall structure of a medium-high temperature anaerobic biogas production system in one or more embodiments of the present invention. Figure 2 for Figure 1 A cross-sectional schematic diagram of the magnetic recovery unit for water output.

[0019] Figure labeling: 1-Reactor; 11-Insulation coil; 12-Inlet; 13-Outlet; 14-Agitator; 15-Biogas outlet; 2-Iron composite material dosing unit; 21-Storage silo; 22-Quantitative feeder; 23-Dosing pipeline; 3-Effluent magnetic recovery unit; 31-Magnetic separator; 32-Electromagnet; 33-Non-magnetic stripping component; 4-Recirculation unit; 41-Sludge pump; 42-Recirculation pipeline; 5-Online monitoring and control unit; 51-pH, ORP, and temperature composite sensor; 52-Biogas analysis probe; 53-Controller. Detailed Implementation

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

[0021] The purpose of this invention is to provide a medium-high temperature anaerobic biogas production system and its working method to solve the problems existing in the prior art, thereby reducing the loss of microorganisms and functional materials and lowering operating costs.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] In existing medium- and high-temperature anaerobic biogas production systems, functional materials such as zero-valent iron, activated carbon, and biochar are added. The surfaces of these materials gradually adsorb and enrich key functional microorganisms such as symbiotic acetic acid oxidizing bacteria and methanogenic archaea. However, because these functional materials cannot be effectively recycled, the key microorganisms attached to their surfaces are lost along with the materials, leading to a continuous decrease in the concentration of functional microorganisms in the reaction system. This results in a gradual decline in the enhancement effect over long-term operation, and the system's weak resistance to shock loads. To address this problem, this invention provides a medium- and high-temperature anaerobic biogas production system, such as... Figure 1 and Figure 2As shown, the system includes a reactor 1, an iron composite material addition unit 2, an effluent magnetic recovery unit 3, a reflux unit 4, and an online monitoring and control unit 5. In one embodiment, the reactor 1 can be a completely mixed medium-high temperature anaerobic digester (CSTR) or other reactor forms suitable for medium-high temperature anaerobic digestion. Those skilled in the art can select different reactor 1 structures according to the treatment scale and waste properties, without affecting the essence of the technical solution of this invention. The reactor 1 is equipped with an inlet 12, an outlet 13, and a biogas outlet 15 for anaerobic digestion within a set temperature range. The iron composite material addition unit 2 is connected to the reactor 1 and is used to continuously or intermittently add a magnetic iron-biochar composite carrier to the reactor 1. The magnetic iron-biochar composite carrier is a functional material that adheres to the microorganisms in the reactor 1 and promotes the direct interspecies electron transfer (DIET) process and the enrichment and enhancement of key microorganisms. In this embodiment, the microorganisms are anaerobic microbial communities, including symbiotic acetic acid oxidizing bacteria and methanogenic archaea, among other key functional microorganisms. The system includes: an effluent magnetic recovery unit 3 connected to the effluent outlet 13 of reactor 1, used to capture the magnetic iron-biochar composite carrier flowing out with the effluent online under the action of a magnetic field; a reflux unit 4 connected to the collection end of the effluent magnetic recovery unit 3 at its inlet and to the feed inlet or reaction zone of reactor 1 at its outlet, used to return the magnetically recovered carrier-microbial enriched sludge to reactor 1; and an online monitoring and control unit 5 used to monitor the operating parameters of reactor 1 in real time and to control the working status of the iron composite material addition unit 2, the effluent magnetic recovery unit 3, and the reflux unit 4 in conjunction with the monitoring results. This invention introduces a predetermined dose of magnetic iron-biochar composite carrier into reactor 1 via an iron composite material dosing unit 2. Microorganisms attached to the carrier flow out through outlet 13 and are then captured by magnetic attraction in the effluent magnetic recovery unit 3. The captured magnetic iron-biochar composite carrier and its attached microorganisms can then return to reactor 1 via reflux unit 4 to participate in the reaction, achieving efficient retention of medium- and high-temperature anaerobic microorganisms and forming a microorganism-carrier-reactor 1 cycle. This increases the system's biomass concentration and activity, significantly reduces the loss of functional materials such as the magnetic iron-biochar composite carrier, saves operating costs, and ensures the long-term reusability of the magnetic iron-biochar composite carrier composite material.

[0024] In one embodiment, the effluent magnetic recovery unit 3 includes a magnetic separation tank 31, a magnetic attraction part, and a non-magnetic stripping component 33. The effluent magnetic recovery unit 3 is located downstream of the outlet 13 of the reactor 1 and is used to recover the magnetic iron-biochar composite carrier adsorbed with key anaerobic microorganisms from the effluent. In this embodiment, the magnetic attraction part includes an electromagnet 32 ​​disposed outside the magnetic separation tank 31. A collection hopper for collecting magnetically enriched sludge is disposed at the lower part of the magnetic separation tank 31, and the collection hopper forms a collection end. A rotating shaft is disposed inside the magnetic separation tank 31, and scrapers made of plastic or other non-magnetic materials are disposed on the side wall of the rotating shaft. A drive motor is driven to the top of the rotating shaft. The effluent from the reactor 1 enters the inlet of the magnetic separation tank 31 through a pipeline. When the electromagnet 32 ​​is energized to generate a magnetic field, the magnetic iron-biochar composite carrier in the effluent is adsorbed on the inner wall of the magnetic separation tank 31 or in a designated magnetic field concentration area. After adsorption for a period of time, the current of the electromagnet 32 ​​can be weakened or cut off, while simultaneously driving the scraper to move along the pipe wall, scraping off the magnetic carrier and its attached sludge adsorbed on the pipe wall, allowing them to fall into the collection hopper below under gravity, thus achieving effective separation of the carrier and the effluent. To increase the scraping range of the scraper, the magnetic separation tank 31 in this embodiment can be a horizontally arranged tubular separation tank or a vertically arranged cylindrical separation tank; the electromagnet 32 ​​can also be replaced with an external permanent magnet drum structure, forming a magnetic field on the surface of the drum. The magnetic composite carrier is adsorbed to the surface under the drive of the drum and is peeled off by the scraper after leaving the magnetic field area. Those skilled in the art can select different forms of magnetic separation devices according to the effluent flow rate and operation and maintenance requirements, all of which fall within the protection scope of this invention.

[0025] In one embodiment, the rotating shaft is a threaded shaft structure, and a slider is threadedly connected to the rotating shaft. The scraper is fixedly connected to the slider. During the rotation of the rotating shaft, the slider spirals up or down along the thread of the rotating shaft, and the scraper moves synchronously with the slider to achieve a large-scale scraping operation inside the magnetic separation tank 31. By changing the rotation direction, the rotating shaft can control the slider and scraper to spiral up or down, realizing a reciprocating scraping process.

[0026] In one embodiment, the iron composite material addition unit 2 is used to quantitatively replenish the magnetic iron-biochar composite carrier into the reactor 1 during system startup and operation. The iron composite material addition unit 2 includes a storage silo 21, a quantitative feeder 22, and a addition pipeline 23. The storage silo 21 stores the pre-prepared magnetic iron-biochar composite material and can be a sealed structure to prevent the material from becoming damp and oxidized. The quantitative feeder 22 is located below or to the side of the storage silo 21 and can be a screw conveyor, a rotary metering feeder, or other device capable of quantitatively conveying solid materials. The outlet of the quantitative feeder 22 is connected to the feed pipe of the reactor 1 through the addition pipeline 23, allowing the magnetic iron-biochar composite material to mix with fresh substrate before entering the reactor 1; alternatively, the addition pipeline 23 can be directly connected to the upper or middle part of the reactor 1, allowing the composite material to directly enter the reaction zone.

[0027] In one embodiment, the reflux unit 4 is used to return the magnetically enriched sludge collected by the effluent magnetic recovery unit 3 to the reactor 1. The reflux unit 4 includes a sludge pump 41 and a reflux pipeline 42. The inlet of the sludge pump 41 is connected to the collection hopper at the bottom of the magnetic separation tank 31, and the outlet of the sludge pump 41 is connected to the reactor 1 through the reflux pipeline 42. The reflux pipeline 42 can be connected to the feed pipeline of the reactor 1, so that the enriched sludge is mixed with fresh substrate and enters the reactor 1 together; it can also be connected to the reaction zone at the bottom or middle of the reactor 1, so as to quickly replenish the enriched microorganisms and magnetic carriers to the highly reactive area. Through the continuous or intermittent operation of the reflux unit 4, the magnetically enriched sludge is continuously sent back to the reactor 1, thereby constructing a closed-loop cycle of carriers and microorganisms within the system. In one embodiment, the reflux pipeline 42 can be equipped with a flow regulating valve or a frequency-controlled sludge pump 41 to adjust the reflux ratio. The reflux ratio can be optimized based on operating parameters such as the concentration of volatile solids, ORP, or methane yield in reactor 1, and can generally be controlled within the range of 5% to 50% of the effluent flow rate.

[0028] In one embodiment, the online monitoring and control unit 5 includes a detection component and a controller 53. The detection component is located on the reactor 1 and is used to monitor the temperature, pH value, redox potential, and methane volume fraction inside the reactor 1 in real time. In this embodiment, the detection component includes a pH, ORP, and temperature composite sensor 51 arranged inside the reactor 1, and a biogas analysis probe 52 installed at the biogas outlet 15. The pH, ORP, and temperature composite sensor 51 is used to monitor changes in the acidity and alkalinity of the digestate, the degree of anaerobic digestion, and the internal temperature of the reactor 1. The biogas analysis probe 52 is connected to an online biogas flow meter or component analyzer and is used to detect the content of components such as methane and carbon dioxide, and the gas production rate. The signals from the above sensors are all transmitted to the controller 53. The controller 53 can be a PLC, an industrial computer, or other devices with data acquisition and control functions. According to preset control logic and operating parameters, the controller 53 starts, stops, and adjusts the intensity of actuators such as the quantitative feeder 22, electromagnet 32, and sludge pump 41, thereby achieving automated and coordinated control of the feeding, magnetic recovery, and reflux processes. In this embodiment, the controller 53 can preset different operating modes, such as a startup mode, a normal steady-state operating mode, and a high-load impact mode. In the startup mode, the controller 53 can increase the amount of magnetic carrier added and appropriately increase the reflux frequency to accelerate the enrichment of functional microorganisms; in the high-load impact mode, the controller 53 can automatically increase the magnetic field strength and reflux ratio according to the monitoring results to enhance the system's impact resistance.

[0029] In one embodiment, the temperature range for anaerobic digestion within reactor 1 is 41–49 °C. A temperature control component is installed on the outer wall of reactor 1, capable of heating the interior of reactor 1 and maintaining it within the set temperature range. Reactor 1 provides a reaction site for the medium-to-high temperature anaerobic fermentation process. In this embodiment, the temperature control component is an insulated coil 11 surrounding the outer wall of reactor 1. Hot water, steam, or an electric heating device can be introduced into the insulated coil 11 to maintain the internal temperature of reactor 1 within the medium-to-high temperature range of 41–49 °C. A mechanical stirrer 14, which can be a paddle stirrer 14, is installed inside reactor 1 to ensure thorough mixing of the substrate, sludge, and magnetic iron-biochar composite carrier within reactor 1, preventing the formation of dead zones. A biogas outlet 15 is installed at the top of reactor 1 to collect the generated biogas; a sludge discharge port is installed at the bottom of reactor 1 for periodically discharging excess sludge; and a water outlet 13 is installed on the side wall of reactor 1 to discharge the digestate after anaerobic fermentation, i.e., effluent.

[0030] The present invention also provides a method for operating the above-mentioned medium-high temperature anaerobic biogas production system, comprising the following steps: During the system startup phase, an appropriate amount of inoculum sludge and substrate is first added to reactor 1, and a certain dose of magnetic iron-biochar composite carrier is added to reactor 1 through iron composite material addition unit 2. As the system operates, the composite carrier comes into full contact with anaerobic microorganisms in reactor 1, and key meso- and thermo-aerobic microorganisms gradually attach to and enrich its surface. The biogas produced in reactor 1 is discharged from the top and can be used as a clean energy source after desulfurization and dehydration.

[0031] The digestate in reactor 1 is discharged continuously or intermittently through outlet 13 and enters the effluent magnetic recovery unit 3. When electromagnet 32 ​​is energized, a magnetic field is formed inside magnetic separator 31. As the digestate carrying the magnetic composite carrier passes through magnetic separator 31, the magnetic composite carrier, along with the attached enriched microorganisms, is adsorbed onto the inner wall of magnetic separator 31 or a specific area where the magnetic field is concentrated, achieving separation from the effluent. The separated digestate is discharged through outlet and enters a subsequent treatment or discharge unit.

[0032] When the carrier accumulates to a certain thickness on the inner wall of the magnetic separation tank 31, the controller 53 issues a control command based on indicators such as running time or ORP. First, it weakens or shuts off the magnetic field of the electromagnet 32, then drives the scraper to scrape the adsorbed magnetic carrier and sludge into the collection hopper. The magnetically enriched sludge in the collection hopper is pumped by the sludge pump 41 and returned to the reactor 1 through the return pipe 42, allowing the carrier and its attached highly active microorganisms to re-enter the reaction zone, forming a cycle of addition-reaction-magnetic separation-stripping-return. In this cycle, the magnetic iron-biochar composite carrier can be reused multiple times, and the key microorganisms attached to the carrier surface can remain continuously in the system, effectively increasing the biomass concentration and reactivity within the reactor 1.

[0033] With the online monitoring and control unit 5, this system can adaptively adjust according to the reaction status. For example, when the pH sensor detects that the pH in reactor 1 drops to the preset lower limit, the controller 53 can reduce the added organic load or appropriately increase the reflux flow to prevent acidification instability. When the biogas component analysis results show that the methane volume fraction decreases and the ORP increases, the controller 53 can increase the supplementary addition of the iron-biochar composite carrier or increase the current of the electromagnet 32 ​​to improve the carrier recovery rate, while increasing the operating frequency of the sludge pump 41 and shortening the circulation cycle of the carrier in the system, thereby restoring and enhancing the system's methane production capacity.

[0034] Therefore, this embodiment achieves efficient enrichment and recycling of the magnetic iron-biochar composite carrier and key anaerobic microorganisms within the system through the coordinated operation of the medium-high temperature anaerobic biochar reactor 1, the iron composite material addition unit 2, the effluent magnetic recovery unit 3, the reflux unit 4, and the online monitoring and control unit 5. This not only significantly improves methane yield and system stability but also reduces the amount of functional materials needed and operating costs. This invention, through device-based coupling and integration, achieves efficient retention and enhanced enrichment of key anaerobic microorganisms under medium-high temperature conditions, significantly improving methane yield, system stability, and functional material utilization efficiency, making it suitable for the efficient energy utilization of high organic load waste.

[0035] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A medium-to-high temperature anaerobic biogas production system, characterized in that: include: A reactor used for anaerobic digestion reactions within a set temperature range; An iron composite material dosing unit, connected to the reactor, is used to continuously or intermittently add a magnetic iron-biochar composite carrier into the reactor. The effluent magnetic recovery unit is connected to the effluent outlet of the reactor and is used to capture the magnetic iron-biochar composite carrier flowing out with the effluent online under the action of a magnetic field. The reflux unit has its inlet connected to the collection end of the effluent magnetic recovery unit and its outlet connected to the feed inlet or reaction zone of the reactor. It is used to reflux the magnetically recovered carrier-microbial enriched sludge back to the reactor. as well as The online monitoring and control unit is used to monitor the reactor's operating parameters in real time and, based on the monitoring results, to control the working status of the iron composite material dosing unit, the effluent magnetic recovery unit, and the reflux unit.

2. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The effluent magnetic recovery unit includes a magnetic separation tank, and a magnetic attraction part is provided on the outside of the magnetic separation tank. The magnetic attraction part can apply a magnetic field to the magnetic separation tank to capture the magnetic iron-biochar composite carrier in the effluent flowing into the effluent magnetic recovery unit.

3. The medium-high temperature anaerobic biogas production system according to claim 2, characterized in that: The effluent magnetic recovery unit is equipped with a non-magnetic stripping component, which is used to strip the adsorbed magnetic iron-biochar composite carrier and introduce it into the collection end of the effluent magnetic recovery unit after the magnetic field is weakened or removed; the inner bottom of the effluent magnetic recovery unit forms the collection end.

4. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The iron composite material feeding unit includes a storage bin, which is used to store magnetic iron-biochar composite carriers. The dosing pipeline has one end connected to the outlet of the storage silo and the other end connected to the reactor; and A quantitative feeder is connected in series to the feeding pipeline and is used to quantitatively transport the magnetic iron-biochar composite carrier in the storage silo to the reactor through the feeding pipeline.

5. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The reflux unit includes a sludge pump and a reflux pipeline. The inlet of the sludge pump is connected to the collection end of the effluent magnetic recovery unit, and the outlet of the sludge pump is connected to the feed inlet or reaction zone of the reactor via the reflux pipeline.

6. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The online monitoring and control unit includes a detection component and a controller. The detection component is installed on the reactor and is used to monitor the temperature, pH value, redox potential and methane volume fraction in the reactor in real time, and transmit the detection data to the controller. The controller can control the iron composite material dosing unit, the effluent magnetic recovery unit and the reflux unit in conjunction with the received data to maintain the stable operation of the system.

7. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The reactor is a fully mixed, medium-high temperature anaerobic biogas-producing reactor.

8. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The temperature range for anaerobic digestion in the reactor is 41–49 °C.

9. The medium-high temperature anaerobic biogas production system according to claim 1, characterized in that: The outer wall of the reactor is equipped with a temperature control component, which can heat the inside of the reactor and maintain it within a set temperature range.

10. A method for operating a medium-high temperature anaerobic biogas production system as described in any one of claims 1 to 9, characterized in that: Includes the following steps: A set amount of inoculum sludge and substrate is added to the reactor, and a set amount of magnetic iron-biochar composite carrier is added to the reactor through an iron composite material addition unit. The effluent from the reactor is discharged continuously or intermittently through the outlet and enters the effluent magnetic recovery unit. Under the magnetic attraction of the magnetic suction unit, the magnetic iron-biochar composite carrier, along with the attached enriched microorganisms, is adsorbed in the effluent magnetic recovery unit, achieving separation from the effluent. The separated effluent is discharged through the liquid outlet. The controller controls the magnetic suction part to weaken or turn off the magnetic field, and then drives the non-magnetic peeling part to scrape the adsorbed magnetic iron-biochar composite carrier along with the attached enriched microorganisms to the collection end. Start the reflux unit to return the magnetic iron-biochar composite carrier and the attached enriched microorganisms in the collection end to the reactor.

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