A bypass type anaerobic digestion liquid phase index full online monitoring system and a monitoring method

Abstract

This invention relates to the field of anaerobic digestion process monitoring and intelligent early warning technology, specifically to a bypass-type online monitoring system and method for anaerobic digestion liquid phase indicators. The specific technical solution is as follows: A bypass-type online monitoring system for anaerobic digestion liquid phase indicators includes a homogenization tank, a feed pump, and an anaerobic digestion reactor connected in sequence. A bypass circulation pipeline is provided at the discharge end of the anaerobic digestion reactor. A bypass circulation pump, a first flow tank, a solid-liquid separation unit, and a second flow tank are sequentially arranged on the bypass circulation pipeline. A sensor for detecting the liquid phase is installed on the first flow tank, and a near-infrared online monitoring sensor is installed on the second flow tank. This invention overcomes the shortcomings of existing technologies, such as insufficient online monitoring methods for key anaerobic digestion liquid phase indicators and the dependence of existing monitoring devices on the tank body, making flexible installation and modification difficult.

Description

Technical Field

[0001] This invention relates to the field of anaerobic digestion process monitoring and intelligent early warning technology, specifically to a bypass-type anaerobic digestion liquid phase index fully online monitoring system and monitoring method. Background Technology

[0002] Anaerobic digestion is a crucial technological approach for reducing, rendering harmless, and recycling organic waste, widely applied in the treatment of livestock and poultry manure, kitchen waste, fruit and vegetable waste, crop straw, and industrial organic wastewater. Anaerobic digestion converts various organic wastes into biogas, not only achieving resource utilization but also contributing to the realization of carbon neutrality ("dual carbon") goals. Currently, domestic biogas projects are typically designed with low organic load rates during design and operation to ensure stability. During actual operation, the organic load rate is further reduced to maintain stability. Consequently, existing biogas projects often suffer from low gas production efficiency and insufficient waste treatment capacity. Therefore, improving the organic load rate of biogas projects is crucial to increasing the gas production rate per unit volume and the unit treatment capacity of various organic wastes.

[0003] Under high organic loading rates, anaerobic digestion systems are more prone to problems such as volatile acid accumulation and ammonia nitrogen suppression, making them more susceptible to instability. Acidification, ammonia suppression, or buffer imbalance can easily lead to decreased gas production and reduced methane content, resulting in additional maintenance and tank cleaning costs for biogas projects. Therefore, real-time online monitoring of key indicators in anaerobic digestion systems is necessary to continuously monitor their operational status.

[0004] Current anaerobic digestion monitoring methods mainly rely on manual intermittent sampling and offline detection. These methods suffer from problems such as low sampling frequency, delayed results, easy secondary changes in samples, and difficulty in reflecting the real-time dynamics of the reactor. Especially for continuously operating or high-solids systems, there is often a significant deviation between offline detection results and the real-time state of the reactor, which is not conducive to timely identification of instability signs and implementation of process control.

[0005] Among existing online monitoring technologies, conventional indicators such as pH, temperature, and redox potential are relatively easy to continuously detect. However, key liquid phase indicators such as ammonia nitrogen, volatile fatty acids, and alkalinity usually still rely on chemical analysis or laboratory instrument testing, resulting in a low degree of online availability. Near-infrared spectroscopy has advantages such as fast response speed, no reagents required, and easy integration with data models, making it a promising technology for online monitoring of complex liquid systems. However, anaerobic digestion mixed biogas slurry typically contains high concentrations of suspended solids and particulate matter, which can cause significant scattering interference in near-infrared spectral acquisition, affecting the stability of quantitative models and monitoring accuracy. Therefore, how to construct a bypass-type online monitoring system that can continuously acquire fresh dynamic liquid phase information, meet the requirements of near-infrared online detection, and minimize disturbance to the main anaerobic digestion process has become an urgent technical problem to be solved in this field.

[0006] Furthermore, in existing biogas projects, online monitoring devices are mostly fixedly installed on the anaerobic digester during the construction or equipment installation phase. The monitoring points, indicators, and interface types are usually determined during the design phase, leaving limited room for later modifications. Some existing biogas projects even lack comprehensive online monitoring systems, relying solely on manual sampling and offline testing. For these existing projects, adding online monitoring functions for comprehensive liquid-phase indicators such as ammonia nitrogen, volatile fatty acids, alkalinity, and near-infrared spectroscopy often faces challenges such as difficulty in opening holes in the tank, increased sealing and safety risks, high construction and modification costs, and operational disruptions due to downtime. Meanwhile, even for newly built biogas projects, if the method of directly installing a small number of fixed detectors on the tank is still used, it is difficult to flexibly expand or dynamically adjust the monitoring indicators, sensor types, and monitoring units according to different raw material types, operating conditions, and instability early warning requirements. Therefore, it is difficult to meet the multi-indicator, fully online, and upgradeable instability early warning monitoring needs of the anaerobic digestion process. Therefore, developing a bypass-type anaerobic digestion online monitoring system suitable for both new and existing biogas projects, capable of achieving full online monitoring of multiple liquid-phase indicators without significant alterations to the main reactor structure, and possessing good scalability and adaptability, has significant engineering application value. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a bypass-type anaerobic digestion liquid phase index online monitoring system and method. It overcomes the deficiencies of existing technologies, such as insufficient online monitoring methods for key indicators of anaerobic digestion liquid phase and the fact that existing monitoring devices are attached to the tank body and are difficult to flexibly install and modify. It achieves continuous online monitoring of multiple dynamic indicators of the liquid phase without damaging the original structure and operating status of the main reactor, and provides basic data for instability early warning and intelligent control.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention discloses a bypass-type anaerobic digestion liquid phase index fully online monitoring system, comprising a homogenization tank, a feed pump, and an anaerobic digestion reactor connected in sequence. The discharge end of the anaerobic digestion reactor is provided with a bypass circulation pipeline. The bypass circulation pipeline is provided with a bypass circulation pump, a first flow tank, a solid-liquid separation unit, and a second flow tank in sequence. The first flow tank is equipped with a sensor for detecting the liquid phase, and the second flow tank is equipped with a near-infrared online monitoring sensor. The solid residue separated by the solid-liquid separation unit is mixed with the clear liquid flowing out of the second flow tank and then returned to the anaerobic digestion reactor.

[0010] Preferably, the solid-liquid separation unit includes a pre-filtration module and a membrane separation module. The membrane separation module includes a separation chamber, a positioning column is coaxially arranged at the center of the separation chamber, and multiple filter membrane components are evenly arranged around the positioning column to divide the separation chamber into multiple filtration zones. A partition is vertically arranged between the filter membrane components and on the positioning column. The two sides of the partition are divided into an inlet zone and an outlet zone. The pre-filtration module communicates with the inlet zone.

[0011] Preferably, the pre-filtration module includes a filter box disposed outside the separation box, the filter box and the separation box being connected by a through hole, a filter screen being inclinedly disposed inside the filter box, the filter screen having a pore size of 0.5-1.0mm, and an inlet pipe being disposed at the top of the filter box, the through hole being connected to the inlet area.

[0012] Preferably, a slag discharge pipe is provided at the bottom of the filter box, and a flow guide platform is provided at the inner bottom of the filter box. The thickness of the flow guide platform gradually decreases from the edge of the filter box toward the slag discharge pipe, and the slag discharge pipe is located close to the through hole.

[0013] Preferably, a slag cleaning trough is provided on the outside of the filter box, the slag cleaning trough is connected to the filter box through a slag cleaning hole, and a slag cleaning pipe is provided at the bottom of the slag cleaning trough.

[0014] Preferably, a security filter assembly is provided between the pre-filtration module and the membrane separation module. The security filter assembly includes a mesh plate disposed within the through holes, and the mesh plate has a pore size of 60-350 μm.

[0015] Preferably, a motor is provided on the top of the separation box, and the output end of the motor passes through the top of the separation box and is connected to the top of the positioning column by a spline. A connecting sleeve is provided at the center of the outer bottom of the separation box, and an adjusting sleeve is threaded onto the connecting sleeve. A support platform is coaxially provided on the inner bottom of the adjusting sleeve, and the positioning column passes through the bottom of the separation box and extends into the connecting sleeve to abut against the support platform.

[0016] Preferably, the filter membrane assembly includes a limiting frame detachably connected to the positioning column, two limiting frames forming a group, a filter membrane inserted between the two limiting frames, and a plurality of ball bearings embedded in the side of the limiting frame facing the inner wall of the separation chamber, the ball bearings contacting the inner wall of the separation chamber, and the filter membrane being a microfiltration membrane with a pore size of 0.14-0.45μm or an ultrafiltration membrane with a molecular weight cutoff of 5-150kDa.

[0017] Preferably, the positioning post has an L-shaped groove along its axial direction in the circumferential direction, and the limiting frame has a limiting plate on the side facing the positioning post. The limiting plate is perpendicular to the limiting frame, the limiting plate is inserted into the L-shaped groove, and the bottom surface of the limiting frame is in contact with the inner bottom surface of the separation box.

[0018] The top of the positioning column is provided with a fixing sleeve, and the inner top of the fixing sleeve is provided with a fixing block corresponding to the L-shaped groove. A circular hole is opened at the center of the fixing sleeve for the motor output end to pass through.

[0019] Accordingly, a method for online monitoring of anaerobic digestion liquid phase indicators using the bypass-type anaerobic digestion liquid phase indicator online monitoring system includes the following steps:

[0020] (1) The material to be digested in the homogenizing tank is transported to the anaerobic digestion reactor by a feed pump for anaerobic digestion;

[0021] (2) A portion of the mixed biogas slurry is led out from the effluent end of the anaerobic digester to the bypass circulation pipeline and transported to the first flow tank through the bypass circulation pump. pH, redox potential, temperature and conductivity parameters are collected.

[0022] (3) The mixed biogas slurry from the first flow tank is sent to the solid-liquid separation unit for solid-liquid separation to obtain clean biogas slurry and solid residue;

[0023] (4) The biogas slurry is transported to the second flow tank, and near-infrared spectral information is collected;

[0024] (5) The data processing center performs quantitative or qualitative analysis on pH, redox potential, temperature, conductivity, ammonia nitrogen, volatile fatty acids and alkalinity;

[0025] (6) The sludge and solid residue flowing out of the second flow tank are remixed and returned to the anaerobic digester to continuously form a fresh and dynamic bypass closed-loop circulation monitoring.

[0026] The present invention has the following beneficial effects:

[0027] (1) By constructing a bypass closed-loop circulation at the discharge end of the anaerobic digester, continuous online monitoring of fresh, dynamically mixed biogas slurry can be achieved, which can more accurately reflect the real-time status of the reactor than offline detection.

[0028] (2) By organically integrating conventional liquid phase sensors with near-infrared online spectral sensors, the online acquisition of basic parameters and key liquid phase indicators can be taken into account, thereby improving the monitoring dimensions and information integrity.

[0029] (3) By integrating and analyzing multi-source online data through the data processing center, online monitoring of key indicators such as ammonia nitrogen, volatile fatty acids, and alkalinity can be achieved, providing an online data foundation for intelligent operation of anaerobic digestion.

[0030] (4) The present invention has a simple structure and strong adaptability. It can be applied to the rapid modification of existing biogas projects and the installation and deployment of new projects, which facilitates the expansion and upgrading of monitoring units. It is also applicable to anaerobic digestion systems and continuous or semi-continuous reactors under different raw material types and different solid content conditions.

[0031] (5) The solid-liquid separation unit of the present invention adopts a three-stage integrated structure of pre-filtration module, security filtration component and membrane separation module. The three work together in terms of flow path, function and structure to form a gradient clarification system adapted to the characteristics of anaerobic digestion slurry. The pre-filtration module first intercepts large particulate suspended matter and fibrous impurities, reducing the pollution load for subsequent security filtration and membrane separation. The security filtration component further removes fine particles to protect the membrane element. The membrane separation module finally treats the slurry to meet the clarification requirements for near-infrared online monitoring. The three-stage structure is connected and compactly arranged in sequence inside the integrated shell of the separation box and the filter box. It forms a continuous monitoring channel with the bypass circulation flow path, the first flow pool, the second flow pool and the return system. While realizing solid-liquid separation, it does not destroy the material balance and dynamic characteristics of the bypass closed-loop circulation, ensuring the real-time and accuracy of online monitoring data. The solid-liquid separation structure is highly integrated and inseparable from the overall monitoring system. Attached Figure Description

[0032] Figure 1 Schematic diagram of a bypass-type anaerobic digestion liquid phase index fully online monitoring system;

[0033] Figure 2 This is a schematic diagram of the solid-liquid separation unit;

[0034] Figure 3 for Figure 2 Enlarged view of part A in the middle;

[0035] Figure 4 A top view of the separation chamber and filter chamber after removing the top cover and the filter screen.

[0036] Figure 5 This is a structural diagram of the positioning post and the limiting frame;

[0037] Figure 6Another implementation of the limiting frame and positioning post (top view);

[0038] Figure 7 for Figure 6 Enlarged view of part B in the middle;

[0039] Figure 8 This is a connection diagram of the limiting frame and the limiting plate;

[0040] Figure 9 A schematic diagram of the fixed sleeve (viewed from below);

[0041] Figure 10 This is a schematic diagram of the filter membrane assembly after it has been adjusted upwards;

[0042] In the diagram: A-homogenizing tank, B-feed pump, C-anaerobic digester, D-bypass circulation pump, E-first flow tank, F-solid-liquid separation unit, G-data processing center, H-second flow tank, 1-separation box, 2-positioning column, 3-partition plate, 4-filter box, 5-filter screen, 6-inlet pipe, 7-slag discharge pipe, 8-guide platform, 9-slag cleaning trough, 10-slag cleaning hole, 11-slag cleaning pipe, 12-mesh plate, 13-motor, 14-connecting sleeve, 15-adjusting sleeve, 16-support platform, 17-limiting frame, 18-filter membrane, 19-ball bearing, 20-L-shaped groove, 21-limiting plate, 22-fixing sleeve, 23-fixing block, 24-round hole, 25-drainage hopper, 26-drainage pipe, 27-guide rod, 28-drainage pipe. Detailed Implementation

[0043] 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.

[0044] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0045] like Figure 1As shown, the bypass-type anaerobic digestion liquid phase index online monitoring system of the present invention includes a homogenization tank A, a feed pump B, and an anaerobic digestion reactor C connected in sequence. A bypass circulation pipeline is provided at the discharge end of the anaerobic digestion reactor C. A bypass circulation pump D, a first flow tank E, a solid-liquid separation unit F, and a second flow tank H are sequentially arranged on the bypass circulation pipeline. A sensor for detecting the liquid phase is installed on the first flow tank E, and a near-infrared online monitoring sensor is installed on the second flow tank H to collect the near-infrared spectral information of the clarified liquid. The solid residue separated by the solid-liquid separation unit F mixes with the clarified liquid flowing out of the second flow tank H and returns to the inlet side of the feed pump B via the return pipeline, and then enters the anaerobic digestion reactor C body to form a closed-loop circulation, reducing the impact of bypass monitoring on the material residence time, total solids concentration, and material balance of the anaerobic digestion reactor C. It should be noted that the bypass circulation pipeline is equipped with one or more of the following: valves, flow regulating devices, sampling ports, backwash interfaces, and / or bypass interfaces, to achieve online monitoring, maintenance cleaning, and flow control. The solid-liquid separation unit F is used to reduce the suspended solids content in the bypass mixed biogas slurry to meet the requirements of subsequent near-infrared online detection for liquid phase clarity.

[0046] Furthermore, the sensors and near-infrared online monitoring sensors are connected to the data processing center G via communication lines. The sensors include a pH sensor, a redox potential sensor, a temperature sensor, and a conductivity sensor. The data processing center G establishes a calibration model and / or an early warning model based on the collected near-infrared spectra and reference detection data, and performs state identification, trend judgment, and anomaly alarms for the anaerobic digestion process according to preset thresholds. Simultaneously, the data processing center G is configured to collect, store, preprocess, model, invert, display trends, identify anomalies, and provide instability early warnings for the online sensor signals and near-infrared spectral information, in order to obtain one, multiple, or coupled indices of pH, redox potential, temperature, electrolytes, ammonia nitrogen, volatile fatty acids, and alkalinity of the anaerobic digester liquid.

[0047] The specific process of the above-mentioned online monitoring system is as follows:

[0048] (1) The material to be digested in the homogenizing tank A is transported to the anaerobic digestion reactor C by the feed pump B for anaerobic digestion; a bypass circulation pipeline is set next to the outlet of the anaerobic digestion reactor C, and part of the mixed biogas slurry is pumped out by the bypass circulation pump D and transported to the first flow tank E.

[0049] (2) The first flow cell E is used to install conventional online sensors for liquid phase parameters, preferably including a pH sensor, a redox potential sensor, a temperature sensor, and a conductivity sensor. To improve the convenience of sensor maintenance, it is preferable to install the above sensors in the same flow cell to reduce installation space, reduce the number of interfaces, and facilitate unified cleaning and maintenance.

[0050] (3) The mixed biogas slurry flowing out of the first flow tank E enters the solid-liquid separation unit F. Preferably, the solid-liquid separation unit F includes a pre-filtration module and a membrane separation module. The pre-filtration module is used to remove larger fiber particles and suspended solids, and the membrane separation module is used to further reduce turbidity and fine particulate interference, thereby obtaining a clear liquid more suitable for near-infrared spectroscopy online detection. The specific filtration accuracy, membrane material, membrane pore size, operating pressure, and cleaning method of the solid-liquid separation unit F can be adjusted according to the raw material type, total solids content, and target indicators.

[0051] In a preferred embodiment, the pore size of the pre-filtration module can be set to 0.5-1.0 mm. To further reduce the risk of membrane fouling and improve the stability of subsequent spectral detection, a security filter assembly can optionally be installed between the pre-filtration module and the membrane separation module. The filtration accuracy of the security filter assembly is preferably 60-350 μm. The membrane separation module can be a microfiltration membrane with a pore size of 0.14-0.45 μm or an ultrafiltration membrane with a molecular weight cutoff of 5-150 kDa. Ceramic membranes, hollow fiber membranes, etc., can also be selected. For high-fiber or high-viscosity materials, pressure gauges, bypass valves, and backwash ports are preferably installed before and after the solid-liquid separation unit F to reduce the risk of clogging.

[0052] (4) The clarified liquid obtained from the solid-liquid separation unit F enters the second flow cell H. A near-infrared online monitoring sensor, preferably a single-probe or multi-probe contact or non-contact near-infrared spectral acquisition device, is installed in the second flow cell H to acquire spectral data of the clarified liquid. This data is then combined with reference analysis to establish quantitative models for indicators such as ammonia nitrogen, volatile fatty acids, and alkalinity. The near-infrared online monitoring probe is connected to the pH sensor, redox potential sensor, temperature sensor, and conductivity sensor in the first flow cell E via a communication line to the data processing center G. The data processing center G is used to display sensor data results, store data, and provide alarms for abnormalities. By modeling the near-infrared spectrum with laboratory reference data, key liquid phase indicators such as ammonia nitrogen, volatile fatty acids, and alkalinity can be monitored online in real time.

[0053] In the preferred implementation, the near-infrared spectral acquisition wavelength range can be 780-2526nm, and the sampling time interval can be set to 30 times / s; in the data processing center G, the model used for the near-infrared spectral unit can be partial least squares regression, support vector machine, random forest, neural network or a combination thereof, and the specific model form and the number of calibration set samples need to be further determined in combination with the actual detection object.

[0054] (5) The slurry flowing out of the second flow tank H and the solid residue separated by the solid-liquid separation unit F are recombined through the return pipeline to form a mixed slurry, which is then returned to the anaerobic digester C through the return pipeline. With the above structure, continuous bypass sampling and online monitoring can be achieved without significantly changing the material composition and solid residence characteristics of the main reactor.

[0055] In the preferred embodiment, the effective volume of each of the first flow cell E and the second flow cell H is 300-1000 mL. The bypass circulation flow rate is preferably controlled at 30-100 mL / min. Preferably, the bypass liquid is completely replaced within 10-30 min to balance online monitoring response speed, particle deposition control, and system operational stability. For high-fiber, high-viscosity, or easily settling materials, the bypass circulation flow rate can be increased to 100-150 mL / min.

[0056] Furthermore, such as Figure 2-10 As shown, to adjust the filtration accuracy through the solid-liquid separation unit F, the membrane separation module includes a separation box 1, preferably cylindrical. A positioning column 2 is coaxially positioned at the center of the separation box 1. Multiple filter membrane assemblies are evenly arranged around the positioning column 2, dividing the separation box 1 into multiple filtration zones. A partition 3 is vertically positioned between the filter membrane assemblies and on the positioning column 2. The two sides of the partition 3 are divided into an inlet zone and an outlet zone. A funnel-shaped drain hopper 25 is positioned at the bottom of the outlet zone, and a drain pipe 26 is installed at the bottom of the drain hopper. This facilitates not only the discharge of the biogas slurry but also the subsequent removal of particles adhering to the inner wall of the separation box. The pre-filtration module is connected to the inlet zone. It should be noted that different filtration accuracies are achieved by selecting the pore size of the filter membranes and the number of filter membrane assemblies. The partitions are for inlet and outlet filtration. Figure 4 As shown, avoid mixing the incoming liquid and the filtered liquid.

[0057] Furthermore, the pre-filtration module includes a filter box 4 located outside the separation box 1. The filter box 4 is connected to the separation box 1 through a through hole. A filter screen 5 is inclinedly arranged inside the filter box 4. The filter screen 5 has a pore size of 0.5-1.0 mm and is used to intercept larger particles and suspended solids. An inlet pipe 6 is located at the top of the filter box 4, with a through hole communicating with the inlet area. The mixed biogas slurry flowing out of the first flow tank E enters the filter box 4 through the inlet pipe and then enters the inlet area through the through hole. It then undergoes step-by-step filtration through the filter membrane assembly before finally entering the outlet area and being discharged to the second flow tank H. This further reduces interference from suspended solids, colloidal particles, fine particulate matter, and turbidity, thereby obtaining a clear biogas slurry more suitable for near-infrared online detection, while improving the stability and repeatability of the detection. It should be noted that the mixed biogas slurry enters the filter box through the inlet pipe and passes through the filter screen to filter out larger impurities. Figure 2 , Figure 4 As shown, the shape of the filter screen is adapted to the shape of the filter box, with its bottom abutting against the side away from the through hole and its top abutting against the outer wall of the separation box.

[0058] Furthermore, a security filter assembly is provided between the pre-filtration module and the membrane separation module. The security filter assembly includes a mesh plate 12, which is disposed within the through hole. The mesh plate 12 has a pore size of 60-350μm, thereby further filtering the mixed biogas slurry after the initial filtration by the filter screen.

[0059] Furthermore, a slag discharge pipe 7 is provided at the bottom of the filter box 4, and a flow guide platform 8 is provided at the inner bottom of the filter box 4. The thickness of the flow guide platform 8 gradually decreases from the edge of the filter box 4 towards the slag discharge pipe 7, and the slag discharge pipe 7 is located close to the through hole. It should be noted that the slag discharge pipe is designed to discharge the particles filtered through the filter screen and blocked by the screen plate inside the filter box. The flow guide platform, on the other hand, helps to prevent excessive particle accumulation inside the filter box, thus avoiding difficulties in cleaning.

[0060] Furthermore, to facilitate the mixing of larger particles and suspended solids filtered through the filter screen with the particles (totaling as solids) retained after filtration in the separation tank and the slurry in the second flow tank H, and to transport them to the anaerobic digester C, a sludge cleaning trough 9 is provided on the outside of the filter box 4. The sludge cleaning trough 9 is connected to the filter box 4 through a sludge cleaning hole 10. The bottom surfaces of the sludge cleaning trough and the filter box are flush with the bottom surfaces of the sludge cleaning hole, so that the solids such as particles left after the mixed slurry passes through the filter screen are directly flushed into the sludge cleaning trough through the sludge cleaning hole and discharged through the sludge cleaning pipe. A sludge cleaning pipe 11 is provided at the bottom of the sludge cleaning trough 9, and the sludge cleaning pipe is connected to the mixing tank (not shown in the figure). Similarly, the second flow tank H is also connected to the mixing tank. A return pipe is connected between the mixing tank and the feed pump B to mix the solids and slurry and return them to the anaerobic digester C through the feed pump.

[0061] Furthermore, to facilitate the cleaning of particulate matter adhering to the inner wall of the separation chamber, a motor 13 is installed on the top of the separation chamber 1. The top cover of the separation chamber is separate from the chamber body and is locked to the separation chamber by fasteners, similar to the buckles or snaps on a storage box, allowing the top cover to be fixed or detached from the separation chamber. The motor is fixed to the top cover, and the output end of the motor 13 passes through the top of the separation chamber 1 and is connected to the top of the positioning post 2 via a spline. That is, a spline groove is axially provided at the center of the top of the positioning post, and the output end of the motor is a spline shaft adapted to the spline groove, and the two are compatible. After filtration is complete, a positioning column is rotated by a motor. The filter membrane assembly scrapes away particles adhering to the inner wall of the separation chamber and particles deposited at the bottom. As the positioning column rotates, the particles scraped away by the filter membrane assembly gradually enter the drain hopper. During the rotation of the positioning column, the adhering particles flow down along the contact point between the filter membrane assembly and the inner wall of the separation chamber. Furthermore, due to the contact between the bottom of the filter membrane assembly and the bottom surface of the separation chamber, the scraped particles, containing water, are scraped into the drain hopper area and discharged. The funnel-shaped drain hopper also facilitates the filter membrane assembly scraping particles into and discharging them. Of course, filtration stops when cleaning the inner wall of the separation chamber; filtration resumes after cleaning. It's easy to understand that a three-way valve is installed on the drain pipe at the bottom of the drain hopper, connecting not only to the second flow tank H but also to the mixing tank. The valve on the corresponding pipeline needs to be opened as needed. The motor and the positioning column are detachably connected via a spline, which is to facilitate the removal of the positioning column or the filter screen for replacement or cleaning.

[0062] Furthermore, since the filter membrane assembly and positioning column are fixed inside the separation chamber by the motor, during cleaning, when the motor rotates and drives the filter membrane assembly to rotate, the friction between the bottom of the filter membrane assembly and the bottom of the separation chamber is relatively large, making the filter membrane assembly prone to deformation. Therefore, a connecting sleeve 14 is provided at the center of the outer bottom of the separation chamber 1. The connecting sleeve has open ends, and the bottom of the separation chamber communicates with the connecting sleeve. At the same time, in order to adjust the lifting and lowering of the positioning column, an adjusting sleeve 15 is externally threaded onto the connecting sleeve 14. That is, the adjusting sleeve has a closed bottom end and an open top end, and is fitted onto the connecting sleeve by a threaded connection. A support platform 16 is coaxially provided at the inner bottom of the adjusting sleeve 15. The positioning column 2 passes through the bottom of the separation chamber 1 and extends into the connecting sleeve 14 to abut against the support platform 16. The cross-section of the support platform is preferably T-shaped to increase the contact surface between the support platform and the bottom of the positioning column. A drain pipe 28 is provided at the bottom of the adjusting sleeve. When liquid enters the adjusting sleeve through the gap between the positioning column and the separation chamber, when the separation chamber needs to be cleaned, the liquid in the adjusting sleeve is first discharged through the drain pipe. Then, release the top cover and screw on the adjusting sleeve to raise the positioning column a certain distance. The distance can be set as needed. Since the particulate matter deposited at the bottom of the separation chamber needs to be scraped by the filter membrane assembly, only a small adjustment to the upward height of the positioning column is required. The operation can be performed according to the actual situation and is not limited.

[0063] Meanwhile, to prevent radial displacement of the top cover, multiple guide grooves are provided on the top surface of the side wall of the separation box, and multiple guide rods 27 are provided on the bottom surface of the top cover. The guide rods extend into the guide grooves, and when the positioning column moves upward, the guide rods also move upward synchronously along the guide grooves. Figure 10 As shown.

[0064] Furthermore, the filter membrane assembly includes a limiting frame 17 detachably connected to the positioning post 2. Two limiting frames 17 form a group, and a filter membrane 18 is inserted between the two limiting frames 17. The two limiting frames are used to fix the filter membrane. Depending on its type, the filter membrane can be fixed with pressure strips around its perimeter to secure it and increase its strength. The bottom surface of the filter membrane is flush with the bottom surface of the limiting frame. Several ball bearings 19 are embedded in the side of the limiting frame 17 facing the inner wall of the separation chamber 1. The ball bearings 19 contact the inner wall of the separation chamber 1 to reduce friction between the limiting frame and the inner wall of the separation chamber when the positioning post rotates, leaving only the filter membrane in contact with the inner wall of the separation chamber. The filter membrane 18 is a microfiltration membrane with a pore size of 0.14-0.45μm or an ultrafiltration membrane with a molecular weight cutoff of 5-150kDa.

[0065] Furthermore, to adjust the number of filter membrane assemblies, the positioning post 2 is provided with an L-shaped groove 20 along its axial direction in the circumferential direction. Two L-shaped grooves form a group, corresponding to the filter membrane assembly. The limiting frame 17 is provided with a limiting plate 21 on the side facing the positioning post 2. The limiting plate 21 is set perpendicular to the limiting frame 17. The limiting plate and the limiting frame form an L-shape, which is adapted to the L-shaped groove, so that the limiting plate is inserted into the L-shaped groove. The limiting plate 21 is inserted into the L-shaped groove 20, and the bottom surface of the limiting frame 17 is in contact with the inner bottom surface of the separation box 1. It should be noted that the L-shaped groove does not penetrate through the positioning post. However, when the bottom end of the positioning post is inserted into the connecting sleeve, the L-shaped groove also extends into the connecting sleeve. Thus, when adjusting the height of the positioning post, the limiting frame and the filter membrane are always in contact with the inner bottom of the separation box. The force borne by the inner bottom of the separation box is only the weight of the filter membrane assembly itself, which does not affect the rotation of the filter assembly. Since the adjusting sleeve only makes minor adjustments to the height of the positioning column, when the limiting plate and the limiting frame are fully inserted into the L-shaped groove, the bottom of the limiting plate and the limiting frame are in contact with the inner bottom surface of the separation box. The force borne by the separation box is the weight of the limiting frame and the filter membrane itself, while the area above the limiting plate is empty. During the process of the mixed biogas slurry flowing through the filter membrane, there may be slight floating of the filter membrane, causing some of the mixed biogas slurry to enter the next area without being filtered. Therefore, a fixing sleeve is set at the top of the positioning column to limit the limiting frame.

[0066] Specifically: A fixing sleeve 22 is provided on the top of the positioning post 2. A fixing block 23 corresponding to the L-shaped groove 20 is provided on the inner top of the fixing sleeve 22. The number of fixing blocks is the same as the number of L-shaped grooves. A circular hole 24 is provided at the center of the fixing sleeve 22 for the output end of the motor 13 to pass through. It should be noted that the fixing sleeve is directly fastened to the top of the positioning post, and the fixing blocks are inserted into the L-shaped groove, abutting against the top of the limiting plate inside the L-shaped groove, thus preventing the filter screen from floating. The edge thickness of the fixing sleeve gradually increases from the open end towards the top of the fixing sleeve, i.e., the cross-section is wedge-shaped, facilitating direct insertion into the positioning post for fixation. The circular hole is provided to expose the spline groove, facilitating the insertion of the motor's output end.

[0067] It should be noted that when the limiting frame and the positioning post are detachably connected, the function of the fixing sleeve is essentially the same as the adjusting sleeve. The force exerted when the fixing sleeve abuts against the limiting plate can be controlled by the depth to which it is inserted into the top of the positioning post. This adjustment requires removing the top cover. Alternatively, when cleaning is required, adjusting the adjusting sleeve will allow the filter assembly to fall naturally, releasing the pressure on the filter assembly. Regardless of the method used, it does not affect the implementation of this invention; flexible operation is possible as needed. For this invention, the adjustment is very flexible, whether using the adjusting sleeve or the fixing sleeve, and can be adjusted according to the actual situation. The adjustment method described in this invention is not unique, but rather an example.

[0068] This invention also provides a method for online monitoring of anaerobic digestion liquid phase parameters using the above system, specifically including the following steps:

[0069] (1) The raw materials to be digested are mixed and homogenized in homogenizing tank A, and then transported to anaerobic digester C by feed pump B;

[0070] (2) During the operation of the anaerobic digester C, a portion of the mixed biogas slurry is drawn out from its discharge end in real time into the bypass circulation pipeline and transported to the first flow tank E through the bypass circulation pump D;

[0071] (3) Continuously acquire basic parameters such as pH, redox potential, temperature and conductivity using the online sensor in the first flow cell E;

[0072] (4) The mixed biogas slurry passing through the first flow tank E is transported to the solid-liquid separation unit F to separate the biogas slurry and solid residue;

[0073] (5) The biogas slurry is transported to the second flow tank H, and spectral information is collected using a near-infrared online monitoring sensor;

[0074] (6) Data processing center G records, stores, and analyzes indicators such as pH, redox potential, temperature, conductivity, ammonia nitrogen, volatile fatty acids, and alkalinity online.

[0075] (7) The slurry flowing out of the second flow tank H is mixed with the solid residue separated from the first flow tank E and returned to the anaerobic digester C to continue to participate in the anaerobic digestion process, thus continuously forming a fresh and dynamic bypass closed-loop circulation monitoring.

[0076] (8) When the data processing center G identifies that the liquid phase index exceeds the set threshold, the rate of change is abnormal, or the overall status is abnormal, it outputs an early warning message and can link the operator to adjust the feed load, reflux ratio, stirring intensity, temperature, or reagent addition.

[0077] The warning thresholds can be set according to different raw material systems, temperature conditions and operating loads, such as ammonia nitrogen warning threshold, volatile fatty acid warning threshold and volatile fatty acid / alkalinity ratio warning threshold.

[0078] Furthermore, the flow rate, pre-filtration accuracy, membrane separation degree, near-infrared sampling interval, spectral wavelength range, and early warning threshold of the bypass circulation pipeline are set according to the type of anaerobic digestion feedstock, total solids content, reactor load, and target monitoring indicators.

[0079] In one optional embodiment, the anaerobic digester C is one of a continuous stirred tank anaerobic digester, a plug flow anaerobic digester, a solid anaerobic digester, an upflow anaerobic sludge bed reactor, or an anaerobic membrane reactor, or may be other anaerobic reactors suitable for treating high-solids organic waste. This invention does not limit the specific type of the main reactor.

[0080] The present invention will be further described below with reference to specific embodiments.

[0081] Example 1

[0082] Chicken manure was used as the anaerobic digestion feedstock. The reactor had an effective volume of 55 L, an operating temperature of 55 °C, an organic loading rate of 1-5 g VS / (L·d), and a hydraulic retention time of 20 days. The bypass circulation flow rate was set to 50 mL / min. A pH sensor, a redox potential sensor, a temperature sensor, and a conductivity sensor were installed in the first flow tank E. The solid-liquid separation unit F used a pre-filtration module with a pore size of 1.0 mm (i.e., the pore size of the filter screen), and the security filter assembly had a filtration accuracy of 350 μm (i.e., the pore size of the mesh plate). The membrane separation module had a pore size of 0.45 μm (i.e., the pore size of the filter membrane). A contact-type near-infrared online sensor was installed in the second flow tank H. Ammonia nitrogen, volatile fatty acids, and alkalinity were measured using a laboratory reference method, and a calibration model was established based on the near-infrared spectral data. After 150 days of continuous operation, the system's online monitoring accuracy, stability, and early warning effect were evaluated.

[0083] Example 2

[0084] Based on Example 1, the organic loading rate was increased to 6-7 g VS / (L·d) to enable the anaerobic digestion system to operate above the organic loading rate, creating an unstable disturbance condition. This was continuously operated for 30-60 days, and the changing trends of pH, redox potential, temperature, conductivity, ammonia nitrogen corresponding to near-infrared spectroscopy, volatile fatty acids corresponding to near-infrared spectroscopy, alkalinity corresponding to near-infrared spectroscopy, and gas production parameters were recorded. This verified the system's ability to identify anaerobic digestion instability in advance. The system's early warning lead time was 20 days.

[0085] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0086] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A bypass-type anaerobic digestion liquid phase index fully online monitoring system, characterized in that: The apparatus includes a homogenizing tank (A), a feed pump (B), and an anaerobic digester (C) connected in sequence. The anaerobic digester (C) has a bypass circulation pipeline at its discharge end. The bypass circulation pipeline is equipped with a bypass circulation pump (D), a first flow tank (E), a solid-liquid separation unit (F), and a second flow tank (H). The first flow tank (E) is equipped with a sensor for detecting the liquid phase, and the second flow tank (H) is equipped with a near-infrared online monitoring sensor. The solid residue separated by the solid-liquid separation unit (F) is mixed with the clear liquid flowing out of the second flow tank (H) and then returned to the anaerobic digester (C).

2. The bypass-type anaerobic digestion liquid phase index fully online monitoring system according to claim 1, characterized in that: The solid-liquid separation unit (F) includes a pre-filtration module and a membrane separation module. The membrane separation module includes a separation box (1). A positioning column (2) is coaxially arranged at the center of the separation box (1). Multiple filter membrane components are evenly arranged on the circumference of the positioning column (2), dividing the separation box (1) into multiple filtration zones. A partition (3) is vertically arranged between the filter membrane components and on the positioning column (2). The two sides of the partition (3) are divided into an inlet zone and an outlet zone. The pre-filtration module is connected to the inlet zone.

3. The bypass anaerobic digestion liquid-phase index full online monitoring system according to claim 2, characterized in that: The pre-filtration module includes a filter box (4) located outside the separation box (1). The filter box (4) is connected to the separation box (1) through a through hole. A filter screen (5) is inclinedly arranged inside the filter box (4). The pore size of the filter screen (5) is 0.5-1.0 mm. An inlet pipe (6) is provided on the top of the filter box (4). The through hole is connected to the inlet area.

4. The bypass anaerobic digestion liquid-phase index full online monitoring system according to claim 3, characterized in that: The bottom of the filter box (4) is provided with a slag discharge pipe (7), and the bottom of the filter box (4) is provided with a flow guide platform (8). The thickness of the flow guide platform (8) gradually decreases from the edge of the filter box (4) toward the slag discharge pipe (7). The slag discharge pipe (7) is located close to the through hole.

5. A bypass-type anaerobic digestion liquid phase index fully online monitoring system according to claim 3 or 4, characterized in that: The filter box (4) is provided with a slag cleaning trough (9) on the outside. The slag cleaning trough (9) is connected to the filter box (4) through a slag cleaning hole (10). A slag cleaning pipe (11) is provided at the bottom of the slag cleaning trough (9).

6. The bypass-type anaerobic digestion liquid phase index fully online monitoring system according to claim 3, characterized in that: A security filter assembly is provided between the pre-filtration module and the membrane separation module. The security filter assembly includes a mesh plate (12), which is disposed in the through hole. The pore size of the mesh plate (12) is 60-350μm.

7. The bypass-type anaerobic digestion liquid phase index fully online monitoring system according to claim 2, characterized in that: A motor (13) is provided on the top of the separation box (1). The output end of the motor (13) passes through the top of the separation box (1) and is connected to the top of the positioning column (2) by a spline. A connecting sleeve (14) is provided at the center of the outer bottom of the separation box (1). An adjusting sleeve (15) is connected to the external thread of the connecting sleeve (14). A support platform (16) is coaxially provided on the inner bottom of the adjusting sleeve (15). The positioning column (2) passes through the bottom of the separation box (1) and extends into the connecting sleeve (14) to abut against the support platform (16).

8. The bypass anaerobic digestion liquid-phase index full online monitoring system according to claim 2, characterized in that: The filter membrane assembly includes a limiting frame (17) detachably connected to the positioning column (2). Two limiting frames (17) form a group, and a filter membrane (18) is inserted between the two limiting frames (17). Several balls (19) are embedded in the side of the limiting frame (17) facing the inner wall of the separation box (1). The balls (19) are in contact with the inner wall of the separation box (1). The filter membrane (18) is a microfiltration membrane with a pore size of 0.14-0.45μm or an ultrafiltration membrane with a molecular weight cutoff of 5-150kDa.

9. The bypass anaerobic digestion liquid-phase index full online monitoring system according to claim 8, characterized in that: The positioning column (2) has an L-shaped groove (20) arranged along its axial direction in the circumferential direction. The limiting frame (17) has a limiting plate (21) on the side facing the positioning column (2). The limiting plate (21) is arranged perpendicular to the limiting frame (17). The limiting plate (21) is inserted into the L-shaped groove (20) and the bottom surface of the limiting frame (17) is in contact with the inner bottom surface of the separation box (1). The top of the positioning column (2) is provided with a fixing sleeve (22), and the inner top of the fixing sleeve (22) is provided with a fixing block (23) corresponding to the L-shaped groove (20). A circular hole (24) through which the output end of the power supply (13) passes is opened at the center of the fixing sleeve (22).

10. A method for full online monitoring of anaerobic digestion liquid phase indicators using the full online monitoring system for anaerobic digestion liquid phase indicators according to any one of claims 1 to 9, characterized in that, Includes the following steps: (1) The material to be digested in the homogenizing tank (A) is transported to the anaerobic digestion reactor (C) by the feed pump (B) for anaerobic digestion; (2) A portion of the mixed biogas slurry is drawn from the discharge end of the anaerobic digester (C) to the bypass circulation pipeline and transported to the first flow tank (E) through the bypass circulation pump (D). The pH, redox potential, temperature and conductivity parameters are collected. (3) The mixed biogas slurry from the first flow tank (E) is sent to the solid-liquid separation unit (F) for solid-liquid separation to obtain clean biogas slurry and solid residue; (4) The biogas slurry is transported to the second flow tank (H) and near-infrared spectral information is collected; (5) The data processing center (G) performs quantitative or qualitative analysis on pH, redox potential, temperature, conductivity, ammonia nitrogen, volatile fatty acids and alkalinity; (6) The sludge and solid residue flowing out of the second flow tank (H) are remixed and returned to the anaerobic digester (C) to continuously form a fresh and dynamic bypass closed-loop circulation monitoring.

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