Anaerobic digestion stirring system based on vertical partition of rheological characteristics and control method

Abstract

The application provides an anaerobic digestion stirring system based on vertical partition of rheological characteristics and a control method, relates to the technical field of biomass energy utilization and environmental protection equipment, and aims at the problems that the prior art has the problems of upper layer crust slipping and idling, low middle layer mass transfer efficiency, serious lower layer dead zone deposition and lack of effective viscosity online monitoring means. The reactor is divided into three virtual functional areas of upper layer crust breaking, middle layer mass transfer and lower layer deposition prevention along the vertical direction according to the flow field action range, an independent coaxial transmission mechanism is adopted, a multi-phase coupling soft measurement model is constructed in the control unit, the fluid intrinsic viscosity is accurately inversed by introducing the gas content and temperature compensation of produced gas, and dynamic partition control is respectively performed on the upper layer crust breaking area, the middle layer mass transfer area and the lower layer deposition prevention area based on the accurate rheological state. The application solves the problems of the prior art and effectively meets the differentiated rheological characteristic requirements of each area in the vertical direction.

Description

Technical Field

[0001] This invention belongs to the field of anaerobic digestion treatment technology for organic waste, and particularly relates to an anaerobic digestion stirring system and control method based on rheological characteristics and vertical partitioning. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] High-concentration anaerobic digestion processes (such as total mixed anaerobic digestion, CSTR) are widely used in the treatment of organic wastes such as livestock and poultry manure and kitchen waste. In actual operation, the materials inside the reactor exhibit significant differences in rheological properties along the vertical direction, resulting in differentiated rheological requirements: the upper layer is prone to crusting and slippage, the middle layer requires sufficient mass transfer, and the lower layer is prone to sedimentation dead zones.

[0004] However, existing technologies typically employ a single stirring shaft and a uniform stirring paddle type (such as a full-paddle or full-frame type), setting a single rotation speed. This "one-size-fits-all" approach has the following drawbacks: if the rotation speed is too low, it cannot break up the upper layer of scum and prevent the lower layer from settling; if the rotation speed is too high, it will damage the floc structure of the middle layer of activated sludge and consume a huge amount of energy; and it cannot cope with the sudden changes in rheological properties caused by fluctuations in feed concentration.

[0005] Furthermore, existing anaerobic digestion systems lack effective means of monitoring material viscosity. Traditional online viscometers (physical probes) are prone to entanglement, scaling, and wear when processing materials with high solids content and complex fibrous composition (such as straw and livestock manure), leading to measurement failure and making maintenance extremely difficult. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides an anaerobic digestion stirring system and control method based on rheological characteristics and vertical partitioning. Through partitioned differentiated blade design and intelligent control strategy of independent drive and coordinated linkage, three virtual rheological functions are formed in the reactor, solving the problems of high energy consumption, low mass transfer efficiency and dead zone deposition.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: A first aspect of the present invention provides an anaerobic digestion stirring system based on rheological properties and vertical partitioning, comprising: Reactor body, stirring shaft assembly, drive motor and control unit; A drive motor unit is installed at the top center of the reactor body along the axis; the drive motor unit is connected to the stirring shaft assembly through an independent transmission mechanism; the control unit is electrically connected to the drive motor unit. The reactor body is divided into an upper shell-breaking zone, a middle mass transfer zone, and a lower anti-settling zone from top to bottom. The stirring shaft assembly is nested from the inside out in the divided zones: an inner shaft, a middle hollow shaft, and an outer hollow shaft. The outer hollow shaft is equipped with a slanted blade turbine propeller corresponding to the upper shell-breaking zone. The middle hollow shaft is equipped with a propeller propeller corresponding to the middle mass transfer zone. The inner shaft is equipped with an anchor scraper propeller corresponding to the lower anti-sinking zone.

[0008] In one implementation, the inner shaft, middle hollow shaft, and outer hollow shaft of the stirring shaft assembly are connected by a thin-walled deep groove ball bearing nested with a self-lubricating special bushing; the gap between the shafts is filled with food-grade grease, and multiple mechanical seal components are provided.

[0009] In one implementation, the inner shaft is connected to the anchor-type scraper propeller, the middle hollow shaft to the propeller propeller, and the outer hollow shaft to the inclined blade turbine propeller via expansion sleeves; the inclined blade turbine propeller, propeller propeller, and anchor-type scraper propeller are respectively connected to the drive motor unit via corresponding independent transmission mechanisms.

[0010] In one implementation, the blades of the inclined blade turbine are rigidly connected to the hub via a flange, and the blade surface is covered with a PTFE anti-stick coating; the blade edge of the propeller is provided with several triangular or trapezoidal stainless steel shear teeth; the geometric contour of the anchor scraper blade is closely fitted with the bottom shape of the reactor body, and the blade end is provided with a wear-resistant scraper.

[0011] As one implementation, it also includes several online viscometers, temperature sensors and biogas flow meters, which are electrically connected to the control unit to collect rheological correlation parameters and transmit them to the control unit.

[0012] A second aspect of the present invention provides a control method for an anaerobic digestion stirring system based on rheological properties and vertical partitioning, comprising: Acquire multi-source data, including at least instantaneous gas production rate, temperature of each layer, and operating electrical parameters and speed of motors in each layer; Based on multi-source data, a power characteristic curve relationship model of each layer of impeller was established, and the rheological threshold of each layer of material was set. Based on the power characteristic curve relationship model, a multiphase coupled dynamic compensation algorithm is used to perform soft measurement calculations to obtain normalized apparent viscosity and shear stress. Based on the normalized apparent viscosity, shear stress, and low-frequency basic viscous drag torque, dynamic control strategies for each layer are generated, and dynamic zoning control is implemented for the upper shell-breaking zone, the middle mass transfer zone, and the lower anti-settlement zone, respectively.

[0013] As one implementation method, based on the power characteristic curve relationship model, a multiphase coupled dynamic compensation algorithm is used for soft measurement calculation to obtain the normalized apparent viscosity and shear stress. The specific process is as follows: Based on the operating electrical parameters of each motor, the total output shaft torque is calculated and frequency domain decoupled to obtain the equivalent net output shaft power. Based on the instantaneous gas production rate, the apparent density of the fluid is dynamically compensated to obtain the corrected apparent density of the fluid. Based on the corrected fluid apparent density and equivalent net output shaft power, the apparent viscosity of the current state is calculated by inverting the power characteristic curve relationship model. Using the Arrhenius-type viscosity-temperature equation, the apparent viscosity of the current state is calibrated by temperature normalization to obtain the normalized apparent viscosity.

[0014] As one implementation method, the total output shaft torque is calculated based on the operating electrical parameters of each layer of motors, and then frequency-domain decoupling is performed to obtain the equivalent net output shaft power. The specific process is as follows: The total output shaft torque is decoupled in the frequency domain using fast Fourier transform to filter out high-frequency pulsation components and extract low-frequency basic viscous drag torque. The equivalent net output shaft power is calculated using the low-frequency foundation viscous resistance torque.

[0015] As one implementation method, the apparent density of the fluid is dynamically compensated based on the instantaneous gas production rate to obtain a corrected apparent density. The specific process is as follows: Calculate the dynamic gas content based on the instantaneous gas production rate; The apparent density of the fluid is corrected in real time based on the dynamic gas content, resulting in the corrected apparent density of the fluid.

[0016] As one implementation method, dynamic zoning control is performed on the upper crust-breaking zone, the middle mass transfer zone, and the lower anti-settling zone based on the normalized apparent viscosity. The specific process is as follows: If the normalized apparent viscosity is greater than the set crusting threshold, an anti-cavitation adaptive collapse perturbation strategy is implemented in the upper crust-breaking zone. This involves sequentially performing trial acceleration and cavity detection, shutdown retreat collapse, and asymmetric second-burst tearing, and repeating this process until the normalized apparent viscosity reaches the set crusting threshold. When the shear stress is less than the preset mass transfer threshold, an intermittent cell disruption and interlayer synergistic support strategy is implemented in the middle mass transfer zone. When the bottom resistance torque is greater than the set torque threshold, a pendulum swing escape and pulse sand blowing strategy is implemented for the lower anti-sinking zone.

[0017] The above one or more technical solutions have the following beneficial effects: This embodiment breaks through the traditional single-axis, single-stirring mode. Based on the significant differences in the rheological properties of the materials in the reactor along the vertical direction, the reactor body is divided into three virtual functional zones: an upper crust-breaking zone, a middle mass transfer zone, and a lower anti-settling zone. Differentiated stirring impellers are configured for the material characteristics of each zone. The upper zone uses a PTFE anti-sticking coated inclined blade turbine impeller to generate concentrated axial downward pressure flow; the middle zone uses a propeller with shear teeth to construct a radial main circulation flow and break up large organic particles; and the lower zone uses an anchor-type wall scraper to eliminate dead zones adhering to the bottom wall. The three-zone stirring impellers achieve independent drive and coordinated linkage through a coaxial multi-channel sleeve-type transmission mechanism, which can apply high-intensity stirring in the energy-intensive crust-forming and sedimentation zones, while maintaining low-speed and gentle stirring in the more fluid middle zone. CFD simulations have verified that applying high-intensity stirring only in the high-viscosity region (upper layer) or the deposition region (lower layer), while maintaining low-speed and gentle stirring in the middle layer, can reduce the dead zone volume at the bottom of the reactor from 32% to 4% with conventional stirring, increase the effective volume utilization rate to over 95%, and reduce overall energy consumption by more than 20% compared to existing technologies, thus solving the defects of the one-size-fits-all approach in existing technologies.

[0018] In this embodiment, the robustness and adaptability of the system are enhanced through layered independent response and inter-layer dynamic collaboration. A dual-mode control architecture with independent lower-level response and collaborative upper-level response is adopted. At the software logic level, it can achieve independent response to single-layer anomalies, such as only the lower layer performing pulsed sand-lifting while the middle and upper layers maintain low-speed cruising. It can also achieve cross-layer flow field coupling and linkage. When the apparent viscosity of the upper-layer crust-breaking zone remains persistently high, the control of the middle-layer motor is forced to switch to reverse mode. The upward surge generated by the reverse propeller pushes the upper-layer scum crust upwards, coordinating with the downward shearing of the upper-layer turbine propeller to form a three-dimensional collaborative cutting action of downward pushing and upward chopping. This architecture enables the system to adapt to fluctuations in feed concentration, gas production rate, and temperature, dynamically adjusting the zoned stirring strategy without manual intervention. It is particularly suitable for high-concentration anaerobic digestion scenarios with complex compositions and large fluctuations, such as livestock and poultry manure and kitchen waste.

[0019] In this embodiment, the upper turbine propeller, combined with a PTFE coating, effectively solves the crusting problem. Based on this, an adaptive collapse perturbation crust-breaking strategy was designed, incorporating trial acceleration, void detection, shutdown retreat, and asymmetric pulse tearing. When a sharp drop in torque is detected, the system actively shuts down, allowing the scum layer to collapse and backfill under gravity. Then, the inertial water hammer effect generated by the rapid start and stop forcefully tears the crust layer, completely avoiding voiding and idling. This strategy improves the crust-breaking efficiency by more than 40% compared to the traditional acceleration method, significantly reduces the total energy consumption of a single crust-breaking operation, solves the voiding slippage problem, and achieves efficient crust-breaking of high-viscosity fluids.

[0020] In this embodiment, the lower-layer scraper blade, in conjunction with pulse action, effectively prevents bottom caking. A biomimetic safety escape strategy is designed for the lower-layer anchor-type scraper blade: a pendulum-like oscillation to loosen the soil, followed by pulse-driven sand lifting and suspension. When the detected bottom resistance torque exceeds 1.5 times the set threshold, the system automatically intercepts the full-speed start command and controls the lower-layer motor to perform alternating forward and reverse rotations with progressively increasing operating times. This reciprocating oscillation gradually breaks down the caking layer. Once the real-time torque returns to within the safe threshold, a rapid acceleration and sudden stop pulse sequence utilizes the inertial water hammer effect of the sudden fluid stop to lift the bottom sediment and entrain it into the middle-layer circulating flow. This strategy completely avoids the risk of mechanical jamming, eliminates dead zones, effectively protects the transmission mechanism and motor, extends the overall service life of the equipment, and increases the reactor's effective volume utilization rate to over 95%.

[0021] In this embodiment, the limitations of traditional single-variable soft measurement are overcome. In response to the technical bias of traditional torque viscosity measurement algorithms in the case of cavitation drag reduction effect and apparent density decay that easily occur in high-concentration anaerobic fermentation broth during peak gas production, which leads to false low viscosity misjudgment, the coupling compensation of gas phase flow rate and temperature is introduced to eliminate the interference of bubble pseudo-lubrication and thermal shock on mechanical load. The intrinsic rheological structure characteristics of the solid and liquid phases are accurately reflected, fundamentally eliminating control failure and false triggering under harsh working conditions.

[0022] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 This is a schematic diagram of the anaerobic digestion stirring system based on rheological properties and vertical partitioning according to Embodiment 1 of the present invention. The reactor consists of the following components: 1. Reactor body; Ⅰ. Upper shell-breaking zone; Ⅱ. Middle mass transfer zone; Ⅲ. Lower anti-settling zone; 2. Feed inlet; 3. Discharge / slag discharge outlet; 4. Drive motor assembly; 5. Independent transmission mechanism; 6. Stirring shaft assembly; 7. Inclined blade turbine propeller; 71. PTFE anti-stick coating; 8. Propeller propeller; 81. Stainless steel shear teeth; 9. Anchor scraper; 10. Control unit; 111. Online viscometer; 112. Temperature sensor; 113. Biogas flow meter. Figure 2 The figures show a top view and a partial enlarged view of the propeller structure according to Embodiment 1 of the present invention; Figure 3 This is the control method flow of the anaerobic digestion stirring system based on rheological characteristics and vertical partitioning according to Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the control method framework for the anaerobic digestion stirring system based on rheological characteristics and vertical partitioning, according to Embodiment 2 of the present invention. Figure 5 This is a flowchart of the dynamic partition control method according to Embodiment 2 of the present invention. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0027] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0028] Example 1 The purpose of this embodiment is to provide an anaerobic digestion stirring system based on rheological characteristics and vertical partitioning, including: a reactor body, a stirring shaft assembly, a drive motor unit, and a control unit; the drive motor unit is installed at the top center of the reactor body; the drive motor unit is connected to the stirring shaft assembly through an independent transmission mechanism; the control unit is electrically connected to the drive motor unit; the reactor body is divided into an upper shell-breaking zone, a middle mass transfer zone, and a lower anti-settling zone from top to bottom; the stirring shaft assembly is nested in the following order from the inside to the outside according to the partitioned zones: an inner shaft, a middle hollow shaft, and an outer hollow shaft; the outer hollow shaft is equipped with a slanted blade turbine propeller corresponding to the position of the upper shell-breaking zone; the middle hollow shaft is equipped with a propeller propeller corresponding to the position of the middle mass transfer zone; and the inner shaft is equipped with an anchor scraper propeller corresponding to the position of the lower anti-settling zone.

[0029] In high-concentration anaerobic digestion (such as Total Mixed Anaerobic Digestion, CSTR), when treating livestock and poultry manure and kitchen waste, a crust of scum easily forms on the upper layer. This crust has an extremely high solids content and exhibits primarily non-Newtonian fluid characteristics, with high viscosity, hindering biogas escape. Current technologies typically address this crusting problem by blindly increasing the impeller speed. However, high-viscosity fluids are prone to pseudoplastic yielding, and high-speed impeller rotation easily creates a "fluid void effect" around the crust, causing slippage and idling. This not only fails to break up the scum at the far end but also results in significant energy waste due to prolonged high-load idling of the motor. The middle layer is the main reaction zone, where material flow is relatively good. Sufficient mass transfer mixing is required to ensure contact between microorganisms and the substrate, maintaining stable anaerobic digestion operation. In the lower layer, inorganic sand and heavy sediments tend to accumulate, leading to an increase in the "dead zone" volume. In current technologies, the dead zone often exceeds 30%, and it easily causes equipment wear.

[0030] Based on the above, this embodiment specifically designs an anaerobic digestion stirring system based on rheological characteristics and vertical partitioning for materials with high viscosity, non-Newtonian fluid characteristics and easy crusting and sedimentation (such as high-concentration anaerobic fermentation broth).

[0031] like Figure 1 As shown, the system mainly includes a reactor body 1, a stirring shaft assembly 6, a drive motor assembly 4, and a control unit 10. The drive motor assembly 4 is installed at the top center of the reactor body; the drive motor assembly 4 is connected to the stirring shaft assembly 6 via an independent transmission mechanism 5; the control unit 10 is electrically connected to the drive motor assembly 4.

[0032] like Figure 1 As shown, the reactor body 1 is divided into three virtual stirring functional zones vertically from top to bottom according to the range of the flow field: the upper shell-breaking zone I, the middle mass transfer zone II, and the lower anti-settling zone III.

[0033] Furthermore, the effective height ratio of the upper shell-breaking zone I, the middle mass transfer zone II, and the lower anti-settlement zone III is controlled to be 1:(2.5-4):1, preferably 1:3:1.

[0034] like Figure 1 As shown, the stirring shaft assembly 6 adopts a coaxial multi-channel sleeve structure, including an inner shaft, a middle hollow shaft and an outer hollow shaft, which are respectively connected to the stirring paddles of the lower, middle and upper layers. The stirring paddles are designed differently according to the rheological characteristics of each layer.

[0035] Specifically, the stirring shaft assembly 6 is nested in three layers from the inside out, with an inner shaft, a middle hollow shaft, and an outer hollow shaft nested within the divided zones. Employing a compact triaxial sleeve-type coaxial drive structure, it achieves independent flow field control in the upper, middle, and lower regions of the reactor without increasing the number of openings.

[0036] Furthermore, the inner shaft, middle hollow shaft, and outer hollow shaft of the stirring shaft assembly 6 are connected by a thin-walled deep groove ball bearing nested with a self-lubricating special bushing; the gap between the shafts is filled with food-grade grease, and multiple mechanical seal components are provided. This structure ensures that the three shafts do not interfere with each other when running at different speeds and in different directions, and there is no risk of material leakage.

[0037] An inclined blade turbine propeller 7 is installed on the outer hollow shaft corresponding to the upper shell-breaking zone I; a propeller-type propeller 8 is installed on the middle hollow shaft corresponding to the middle mass transfer zone II; and an anchor-type wall-scraping propeller 9 is installed on the inner shaft corresponding to the lower anti-sinking zone III. The shaft diameters of the drive shafts increase sequentially from the inside out, with the inner diameter of the middle hollow shaft being larger than the outer diameter of the inner shaft, and the inner diameter of the outer hollow shaft being larger than the outer diameter of the middle hollow shaft, to meet the coaxial nesting requirement.

[0038] Furthermore, in the upper breaking-out zone I, the inclined blade turbine propeller 7 is connected to the outermost hollow drive shaft (outer hollow shaft). The inclined blade turbine propeller 7 forms a local axial downward pressure flow on the liquid surface, specifically targeting the scum layer for pulling and shearing. The blades of the inclined blade turbine propeller 7 are rigidly connected to the hub via flanges, and the blade surface is covered with a PTFE anti-stick coating 71 to effectively prevent the adhesion of high-viscosity scum. The blade inclination angle is 30°-45°, and its installation depth is located 0.5-1.0 meters below the fermentation material, ensuring that the flow field mainly acts on the scum layer without interfering with the middle layer.

[0039] In the intermediate mass transfer zone II, a propeller 8 connects to the hollow drive shaft (intermediate hollow shaft) of the intermediate layer. The propeller 8, equipped with shearing teeth, is used to construct the radial main circulation flow and for shearing and breaking up. For example... Figure 2 As shown in the top view, the propeller 8 has three blades. Figure 2 As can be seen from the enlarged partial view A, each blade edge is provided with several triangular or trapezoidal stainless steel shearing teeth 81, which are arranged in a serrated pattern along the outer edge of the blade.

[0040] Each stainless steel shear tooth has a root width of 10-15mm, a tooth height of 8-12mm, and sharpened tips. The shear teeth are used to break up large suspended organic particles. The propulsion design promotes radial circulation in the middle of the reactor and enhances microbial mass transfer.

[0041] As the blades rotate, these serrations act as micro-cutting knives, forcibly cutting long fibrous impurities while propelling the fluid, and breaking down pseudoplastic aggregates of non-Newtonian fluids, thus enhancing micro-mixing.

[0042] In the lower anti-settling zone III, the anchor-type wall scraper 9 is connected to the central solid drive shaft (inner shaft) for physical scraping and suspension of bottom materials. Its low-speed operation eliminates dead angles adhering to the wall, and when sediment is detected, it breaks up the crust through a special mechanical pulse action. The geometric contour of the anchor-type wall scraper 9 closely matches the bottom shape of the reactor body 1, such as a conical bottom. The blade ends are equipped with wear-resistant scrapers, which are flexible Teflon scrapers for physical scraping.

[0043] By precisely controlling the rotational speed and installation position of each blade layer, and utilizing the high viscosity of non-Newtonian fluids as natural damping, excessive interference between the upper and lower flow fields is limited, thereby achieving functional stratification of the upper layer for shell breaking, the middle layer for mass transfer, and the lower layer for anti-sinking.

[0044] Furthermore, considering the significant resistance of high-viscosity materials and the frequent acceleration and deceleration impacts in the control strategy, the traditional single-key connection between the impeller hub and the agitator shaft was abandoned. A high-load, impact-resistant connection was designed instead. The inner shaft is connected to the anchor-type scraper impeller, the middle hollow shaft to the propeller, and the outer hollow shaft to the inclined blade turbine impeller via expansion sleeves. This connection method distributes the alternating torque evenly through 360° mechanical clamping force, effectively preventing the expansion of mechanical clearances under pulse oscillation mode.

[0045] Furthermore, the upper, middle, and lower stirring paddles are connected to the drive motor unit 4 through independent transmission mechanisms 5, that is, the inclined blade turbine paddle 7, the propeller 8, and the anchor scraper paddle 9 are respectively connected to the drive motor unit 4 through their respective independent transmission mechanisms 5.

[0046] The independent transmission mechanism 5 includes three sets of independent reducers and frequency converters. The inclined blade turbine propeller 7, the propeller propeller 8, and the anchor scraper propeller 9 are connected to the upper, middle, and lower motors of the drive motor unit through a set of independent reducers and frequency converters, which can realize independent control of the speed and direction of each layer of stirring paddle.

[0047] like Figure 1 As shown, it also includes a multi-dimensional data monitoring unit, which includes several online viscometers 111, temperature sensors 112 and biogas flow meters 113, which are electrically connected to the control unit 10 and are used to collect rheological correlation parameters and transmit them to the control unit 10.

[0048] Specifically, each layer is equipped with a multi-dimensional data monitoring unit to acquire multiphase rheological correlation parameters inside and outside the reactor and transmit the data to the control unit 10. The multi-dimensional data monitoring unit is equipped with physical hardware sensing components, including an online viscometer 111 for directly measuring the apparent viscosity of the fluid, a temperature sensor 112 installed inside the reactor, and a biogas flow meter 113 installed on the exhaust pipe at the top of the reactor.

[0049] In the upper shell-breaking zone I, the middle mass transfer zone II, and the lower anti-settling zone III, holes are made at corresponding positions on the side wall of the reactor body, and a temperature sensor 112 and an online viscometer 111 are installed respectively.

[0050] The biogas flow meter 113 and the online viscometers 111 and online temperature sensors 112 of each layer are all electrically connected to the control unit 10.

[0051] The control unit 10 internally includes a soft measurement calculation module and a logic judgment module. The soft measurement calculation module contains a rheological state sensing soft measurement component. Based on the real-time operating electrical parameters of the drive motor assembly 4 and in conjunction with data from the physical hardware sensing components, the calculation module uses a multiphase coupling dynamic compensation algorithm to invert and calculate the normalized viscosity of the material.

[0052] like Figure 1 As shown, the system also includes a feed inlet 2 and a discharge / slag outlet 3. The feed inlet 2 is used for top feeding, and the discharge / slag outlet 3 is used for bottom discharge.

[0053] In this embodiment, the operation mode of feeding waste through the feed inlet 2 and discharging waste through the discharge outlet / slag outlet 3 utilizes the flow field characteristics of different blades to construct three fluid dynamic functional zones within the connected space. Through three layers of differentiated blades driven independently on the same axis, the zoned coordination of shell breaking, mass transfer, and anti-settling is achieved. Combined with multiphase coupling soft measurement and adaptive control, the pain points of traditional anaerobic digestion stirring, such as shelling, sedimentation, high energy consumption, and dead zones in the flow field, are solved, achieving efficient, low-consumption, and stable intelligent stirring.

[0054] Specifically, after feeding through inlet 2, the multi-dimensional data monitoring unit collects rheological correlation parameters and transmits them to the control unit 10; the control unit 10 performs multi-phase coupled soft measurement calculation (frequency domain decoupling, gas content compensation, temperature normalization, elimination of cavitation and temperature interference, to obtain the true rheological state, i.e., normalized apparent viscosity); based on the calculation results, the control unit 10 sends a command to the drive motor group 4, and the drive motor group 4 drives the three-layer coaxial sleeve shaft of the stirring shaft assembly 6 through the independent transmission mechanism 5, adjusting the speed, direction and operating mode of each layer of blades, to achieve closed-loop feedback of viscosity-torque-flow field-control.

[0055] In the upper shell-breaking zone I, the high-speed rotation of the outer hollow shaft inclined blade turbine propeller 7 creates a radial and axial composite flow field, which shears and tears the surface shell. The PTFE coating prevents the adhesion of highly viscous materials and avoids blade patina failure. The control unit judges the degree of shelling through viscosity / torque signals and triggers anti-cavitation collapse and pulse tearing strategies. Through trial acceleration, shutdown retreat, and asymmetric pulses, the hard shell is efficiently broken up while avoiding the formation of cavitation idling.

[0056] In the middle mass transfer zone II, the propeller 8 of the middle hollow shaft forms an axial mainstream field, driving the material to circulate up and down; the stainless steel shearing teeth 81 on the outer edge break up the gas-containing flocs, releasing the trapped biogas, reducing the apparent viscosity, and enhancing the mass transfer efficiency. When the upper layer is under high load and breaking down, the middle layer propeller can reverse to form an upward surge, working in conjunction with the upper layer propeller to support the material, accelerating the collapse of the hard shell, and achieving interlayer synergy.

[0057] In the lower anti-settlement zone III, the anchor-type wall scraper 9 on the inner shaft rotates at the bottom of the reactor body 1 to prevent material from settling and caking; when the bottom resistance torque exceeds the standard, the control unit triggers a pendulum-type swing escape and pulse sand lifting strategy.

[0058] After completion, discharge the material through the discharge port / slag discharge port three times.

[0059] Example 2 This embodiment discloses a control method for an anaerobic digestion stirring system based on rheological properties and vertical partitioning.

[0060] To more clearly illustrate this embodiment, the control implementation process of the anaerobic digestion stirring system based on rheological characteristics and vertical partitioning can be specifically described as follows: like Figure 3 As shown, the control method for an anaerobic digestion stirring system based on rheological characteristics and vertical partitioning includes: S1. Acquire multi-source data, including at least the instantaneous gas production rate, temperature of each layer, and operating electrical parameters and speed of the motors in each layer; S2. Based on multi-source data, establish a power characteristic curve relationship model for each layer of agitator and set the rheological threshold for each layer of material. S3. Based on the power characteristic curve relationship model, a multiphase coupled dynamic compensation algorithm is used to perform soft measurement calculations to obtain the normalized apparent viscosity and shear stress. S4. Based on the normalized apparent viscosity, shear stress, and low-frequency basic viscous resistance torque, generate dynamic control strategies for each layer, and implement dynamic zoning control for the upper shell-breaking zone, the middle mass transfer zone, and the lower anti-settlement zone respectively.

[0061] Existing methods for calculating viscosity based on single motor power have serious technical biases and risks of misjudgment under harsh anaerobic fermentation conditions: First, during the peak gas production period of high-concentration materials, "cavitation" is easily formed behind the impeller. A large number of tiny biogas bubbles act as lubricants, causing a sharp drop in motor resistance, which can easily lead to a false judgment of "low viscosity". Second, when encountering cold feed thermal shock or spatial temperature gradient, local cooling can cause a physical spike in viscosity, which can easily trigger a false "crust formation".

[0062] like Figure 4 As shown, based on this, this embodiment constructs a control method framework for an anaerobic digestion stirring system with vertical zoning based on rheological characteristics, and implements a control method for an anaerobic digestion stirring system with vertical zoning based on rheological characteristics. The entire process from data acquisition and intelligent decision-making to drive execution is designed, divided into two main functional areas, A and B. Area A is the data processing and decision-making center (brain), responsible for data acquisition, calculation and analysis, and control command generation; Area B is the independent drive execution system (hands and feet), responsible for receiving commands, driving the three-layer stirring paddles to operate independently, and providing status feedback. The two form a closed-loop control through command issuance and status feedback.

[0063] like Figure 3 As shown, in step S1, multi-source data is acquired, including at least the instantaneous gas production rate, the temperature of each layer, and the operating electrical parameters and speed of the motors in each layer.

[0064] like Figure 4As shown, in the data processing and decision-making center of area A, the instantaneous gas production rate was measured using a biogas flow meter. Temperature data for each layer were measured using temperature sensors on each layer. The viscosity of each layer was measured using an online viscometer; the root mean square current of each layer's motor was collected in real time. Operating voltage U, power factor PF, and rotational speed N.

[0065] After the above steps, the instantaneous gas production rate, temperature of each layer, and electrical parameters and speed of the motors in each layer are obtained, enabling accurate perception of the rheological state and providing a data foundation for reliable support for subsequent control decisions and adaptive optimization of stirring operation.

[0066] like Figure 3 As shown, in step S2, a power characteristic curve relationship model of each layer of stirring blades is established based on multi-source data, and the rheological threshold of each layer of material is set.

[0067] (1) such as Figure 4 As shown, in the data processing and decision-making center of area A, all the multi-source data obtained in step S1 is sent to the control unit. In the control unit, based on the multi-source data, flow field models of materials with different concentrations and rheological properties are established through computational fluid dynamics (CFD) numerical simulation. The stirring power, Reynolds number, and power coefficient of the upper inclined blade turbine, the middle propeller, and the lower anchor scraper are simulated and calculated under different speeds and viscosities. The power characteristic curves Np–Re relationship models of each layer of impeller are fitted and used as the benchmark for the control unit's preset parameters and rheological state judgment.

[0068] (2) Set the rheological threshold of each layer of material.

[0069] The crust formation threshold is set to 5000 cP, the mass transfer threshold to 200 Pa, and the drag torque threshold to a preset reference torque. For example, 500 N·m, or obtained from the system's no-load cruise calibration.

[0070] After the above steps, a power characteristic curve relationship model of each layer of impeller is established based on multi-source data, providing a precise benchmark and quantitative basis for rheological parameter inversion, intelligent control and energy consumption optimization.

[0071] like Figure 3 As shown, in step S3, based on the power characteristic curve relationship model, a multiphase coupling dynamic compensation algorithm is used to perform soft measurement calculations to obtain the normalized apparent viscosity and shear stress.

[0072] like Figure 4As shown, in the data processing and decision-making center of area A, to eliminate the interference of gas-liquid-solid three-phase fermentation conditions on viscosity measurement, the soft measurement and calculation module of the control unit integrates viscosity, temperature, gas production rate, etc., and uses a multi-phase coupled dynamic compensation algorithm for compensation and calculation to obtain the true normalized apparent viscosity, solve the problem of false viscosity (bubble, temperature interference), and restore the true rheological state of the material. The specific process is as follows: (1) Calculate the total output shaft torque based on the operating electrical parameters and speed of each motor and decouple it in the frequency domain to obtain the equivalent net output shaft power.

[0073] In this example, the specific process is as follows: 1) Calculate the total output shaft torque based on the operating electrical parameters and speed of each motor.

[0074] First, calculate the input power of each motor based on its operating electrical parameters and speed.

[0075] Based on real-time acquisition of the root mean square current of each layer's motors Given the operating voltage U, power factor PF, and speed N, calculate the motor input power using the following formula: .

[0076] The input electrical power of each motor can be obtained using the above formula.

[0077] Secondly, based on the input electrical power of each layer of motors, the output mechanical power of the motors is calculated. .

[0078] The formula is: ; in, Input electrical power to the motors on each floor; It is the product of the motor efficiency and the transmission mechanism efficiency, which can be determined in advance through calibration experiments.

[0079] The input electrical power of each motor can be obtained using the above formula.

[0080] Next, the angular velocity of the stirring shaft in each layer is calculated. .

[0081] The formula is: ; Where N is the rotational speed of each layer of agitator.

[0082] Finally, the total output shaft torque is calculated based on the input electrical power of each layer's motor and the angular velocity of each layer's stirring shaft.

[0083] Total output torque The calculation formula is: .

[0084] 2) Use Fast Fourier Transform to decouple the total output shaft torque in the frequency domain, filter out high-frequency pulsation components, and extract the low-frequency basic viscous resistance torque as the current resistance torque.

[0085] The total output shaft torque signal calculated based on electrical parameters is subjected to Fast Fourier Transform (FFT) or wavelet decoupling to filter out high-frequency pulsating components generated by large particle solid-phase collisions and bubble collapses, thereby extracting the low-frequency fundamental viscous drag torque that reflects the true rheological properties of the fluid. .

[0086] Low-frequency foundation viscous resistance torque The formula is: ; in, This is the transfer function of the low-pass filter.

[0087] 3) Calculate the equivalent net output shaft power using the low-frequency basic viscous resistance torque.

[0088] Multiply the extracted low-frequency basic viscous drag torque by the stirring shaft angular velocity to calculate the equivalent actual stirring power. The formula is: .

[0089] After the above steps, the total output shaft torque is calculated based on the operating electrical parameters of each motor and decoupled in the frequency domain. This effectively filters out high-frequency interference from solid-phase collisions and bubble disturbances, accurately reflects the intrinsic viscous resistance of the material, and provides a stable and reliable power basis for rheological soft measurement.

[0090] (2) Based on the instantaneous gas production rate, the apparent density of the fluid is dynamically compensated to obtain the corrected apparent density of the fluid.

[0091] In this example, the specific process is as follows: 1) Calculate the dynamic gas content based on the instantaneous gas production rate.

[0092] To eliminate resistance loss caused by gas lubrication, the dynamic gas content is calculated based on the gas production rate.

[0093] Dynamic gas content The calculation formula is: ; in, The bubble retention coefficient for non-Newtonian fluids; This refers to the instantaneous gas production rate; For effective volume.

[0094] The dynamic gas content of the corresponding material level can be obtained using the above formulas.

[0095] 2) Based on the dynamic gas content, the apparent density of the fluid is corrected in real time to obtain the corrected apparent density of the fluid.

[0096] The apparent density of the fluid is corrected in real time using the following formula: ; in, The corrected apparent density of the fluid; For dynamic gas content; The reference material density is bubble-free to eliminate the false low drag interference caused by the cavitation effect of non-Newtonian fluids.

[0097] Using the above formula, the apparent density of the material is corrected in real time to obtain the corrected apparent density of the fluid in each layer, thus restoring the true density boundary conditions of the high-viscosity fluid containing bubbles.

[0098] (3) Based on the corrected fluid apparent density and equivalent net output shaft power, the apparent viscosity of the current state is calculated by inversion using the power characteristic curve relationship model.

[0099] In this embodiment, the specific process is as follows: 1) Based on the extracted equivalent net output shaft power and the corrected fluid apparent density Calculate the corrected power number.

[0100] Corrected power level The calculation formula is: ; in, This is the equivalent net output shaft power; The corrected apparent density of the fluid; The rotational speed of the stirring paddles in each layer; The diameter of each layer of the agitator is denoted as .

[0101] The corrected power numbers for each layer are obtained using the above formula.

[0102] 2) Obtain the Reynolds number by inverse solving the power characteristic curve relationship model. .

[0103] Using pre-stored propeller patterns Inverse solution of the characteristic curve to obtain the Reynolds number .

[0104] 3) Calculate the apparent viscosity of the current state based on the Reynolds number and the corrected fluid apparent density.

[0105] Apparent viscosity in the current state The calculation formula is: ; in, The corrected apparent density of the fluid; The rotational speed of the stirring paddles in each layer; The diameter of the stirring paddle in each layer; It is the Reynolds number.

[0106] (4) Using the Arrhenius viscosity-temperature relationship equation, the apparent viscosity of the current state is normalized by temperature to obtain the normalized apparent viscosity.

[0107] To prevent control malfunctions caused by feed temperature differences, the apparent viscosity at the current state is used as a reference. Combined with real-time online temperature Using the Arrhenius-type viscosity-temperature equation, the measured viscosity is converted to a preset reference temperature in real time. Normalized apparent viscosity at (e.g., 35°C).

[0108] Normalized apparent viscosity (Arrhenius-type viscosity-temperature relationship equation), the calculation formula is: ; in, The apparent viscosity at the current state; Preset reference temperature; is the real-time online temperature; E is the activation energy; R is the gas constant.

[0109] The corrected power numbers for each layer are obtained using the above formula, and this... This serves as the threshold for determining whether to trigger dynamic zoning control.

[0110] (5) Calculate the shear stress based on the normalized apparent viscosity.

[0111] Shear stress The calculation formula is: ; in, Shear rate, , The shear constants of each blade layer; This is the normalized apparent viscosity.

[0112] After the above steps, the interference of biogas production rate fluctuations and cold feed temperature fluctuations is completely eliminated, and only the true physical state of the solid-liquid phase rheological structure inside the reactor (such as whether crusting or caking) is reflected. This greatly improves the accuracy of adaptive stirring control and avoids ineffective high-speed stirring energy consumption and mechanical damage to anaerobic bacterial flocs.

[0113] like Figure 3 , Figure 5 As shown, in step S4, dynamic control strategies for each layer are generated based on normalized apparent viscosity, shear stress, and low-frequency basic viscous drag torque, and dynamic zoning control is performed on the upper shell-breaking zone, the middle mass transfer zone, and the lower anti-settling zone respectively.

[0114] like Figure 4 As shown, in the data processing and decision-making center of area A, the logic judgment module of the control unit determines the current state of crusting, deposition, and mass transfer resistance based on the calculated actual viscosity, generates multi-dimensional control commands (including speed setting, forward / reverse switching, pulse sequence control, etc.), and sends them to the drive system of area B.

[0115] The specific process is as follows: (1) For the upper shell-breaking zone, determine whether the normalized apparent viscosity is greater than the shell-forming threshold. If yes, then execute the anti-cavitation adaptive collapse perturbation shell-breaking strategy. If no, then maintain low-speed cruising.

[0116] If the normalized apparent viscosity is greater than the set crusting threshold, an anti-cavitation adaptive collapse perturbation crusting strategy is implemented in the upper crusting zone. This involves sequentially performing trial acceleration and cavity detection, shutdown retreat collapse, and asymmetric second-burst tearing, and repeating this process until the normalized apparent viscosity reaches the set crusting threshold.

[0117] Existing constant-speed or stepped-acceleration shell-breaking strategies often lead to localized pseudo-plastic yielding of the fluid when dealing with highly viscous non-Newtonian fluid scum. The blades displace material around the scum, creating a "fluid cavity," causing a sudden drop in motor load and resulting in ineffective "slippage and idling," failing to break down the distant crust layer and consuming excessive energy.

[0118] like Figure 5 As shown, in order to solve the above problems, an air-raid shelter adaptive collapse perturbation shell-breaking strategy is implemented for the upper shell-breaking zone I, namely the air-raid shelter collapse and pulse heavy impact shell-breaking mode.

[0119] The upper-level motor defaults to low-energy surface renewal flow circulation at a constant speed of 20 rpm. When the normalized apparent viscosity value calculated by multiphase coupling soft measurement exceeds the set crusting threshold of 5000 cP, the system determines that severe crusting has formed. The control unit stops continuous acceleration and instead initiates an adaptive crust breaking program, which specifically includes: 1) Acceleration and Void Detection: Control the upper motor to increase its speed with a set acceleration, while simultaneously monitoring the motor torque change rate in real time. If the engine speed increases but a sharp drop in torque is detected (i.e., (Set a negative threshold) to determine that the fluid around the blades undergoes pseudoplastic yielding, forming "void slippage".

[0120] Specifically, the control unit first instructs the drive motor to accelerate tentatively at a slope of 5 rpm / s, and then differentiates the torque within a very short period (e.g., 100 ms). If it detects an increase in speed but a sharp drop in resistance torque, the system keenly detects this as a "voiding illusion" and immediately terminates the acceleration behavior.

[0121] 2) Stop and retreat collapse (air raid shelter collapse). After the cavity is determined, immediately cut off the acceleration command, control the upper motor to perform a rapid deceleration or forced stop and maintain it for a set time (such as 3-5 seconds), use the gravity of the scum layer to destroy its supporting structure, and make it collapse towards the center area of ​​the blade to fill the fluid cavity.

[0122] Specifically, the motor immediately decelerates to 0 rpm at the fastest possible rate and is forcibly locked in place for 3-5 seconds. After losing the centrifugal thrust of the blades, the heavy scum layer that was originally pushed away becomes structurally unstable under the action of gravity, "collapses" back towards the center, and re-encapsulates the PTFE anti-stick coating on the blades.

[0123] 3) Asymmetric Pulse Tear (Pulse Impact). After the collapse action is completed, the control motor executes asymmetric pulse drive, that is, it instantly increases to the target speed for breaking the shell (e.g., 50 rpm) with extremely high acceleration and holds it briefly, followed by a sudden stop without slope. Utilizing the violent fluid inertial shear force and water hammer effect caused by the sudden start and stop, the scum layer is torn apart from the inside out.

[0124] Specifically, after the material re-encapsulates the blades, the motor outputs its maximum starting torque, which surges from 0 rpm to 50 rpm within 1 second, is maintained for 2 seconds, and then reverse braking is applied to bring it back to zero at high speed. This "asymmetric pulse" does not rely on a high-speed steady-state flow field, but rather purely utilizes the "water hammer impact force" and "huge inertial shear force" generated by the instantaneous acceleration and sudden stop of the fluid to forcibly tear apart the external scum agglomerates like a heavy punch.

[0125] 4) Logical loop, repeatedly alternate between executing the above 2) retreat collapse and 3) pulse tear until the normalized apparent viscosity of the upper layer falls below the safe threshold and the low-speed cruise state is restored.

[0126] Specifically, the "collapse-impact" cycle is repeated 5 to 10 times, and the normalized viscosity is evaluated again using soft measurement. If the viscosity drops below 3000 cP, it indicates that the hard crust has been broken down into a more fluid slurry, and the system automatically resumes cruising at 20 rpm. This strategy completely eliminates idling due to voids, improves the crust-breaking efficiency by more than 40% compared to traditional acceleration methods, and significantly reduces the total energy consumption of a single crust-breaking operation.

[0127] (2) For the middle layer mass transfer zone, determine whether the shear stress is less than the preset mass transfer threshold. If so, implement the intermittent cell disruption and interlayer synergistic support strategy. If not, maintain normal stirring.

[0128] When the shear stress is less than the preset mass transfer threshold, an intermittent cell disruption and interlayer synergistic support strategy is implemented in the middle mass transfer zone.

[0129] Because long-term unidirectional rotation easily forms a "fluid-driven isolation layer" rotating at the same speed as the blades in the middle layer, the substrate mass transfer efficiency decreases significantly. At the same time, as the flow field hub connecting the upper and lower layers, the middle layer flow field needs to dynamically respond according to the overall system operating conditions.

[0130] like Figure 5 As shown, an intermittent wall-breaking and interlayer synergistic support strategy is implemented for the middle mass transfer zone, namely, the intermittent wall-breaking and synergistic support mode. When the calculated shear stress is less than the preset mass transfer threshold (e.g., 200 Pa), the intermittent wall-breaking cycle is activated, the middle layer motor is controlled to decelerate to zero and be forced to stand still for a set time, and after shearing collision with the stationary blades using the inertia of the following fluid, it is restarted in reverse to the rated speed to tear the laminar boundary layer; when the upper shell-breaking zone is detected to be in a state of high load and continuous shell-breaking, the interlayer flow field synergy is triggered, the middle layer motor is controlled to perform high-speed reverse rotation, and the propeller is used to stimulate the upward flow from the center, which pushes and impacts the upper scum shell from bottom to top, and forms a combined force to break the shell with the upper blades.

[0131] Specifically, 1) Intermittent wall disruption. When the shear stress calculated by the soft sensor is less than 200 Pa, the control unit triggers the "wall disruption cycle." The middle layer motor is decelerated to zero in forward rotation and forced to remain stationary for 5 seconds. At this time, the huge servo water flow continues to rotate due to inertia, and violently shears against the stationary propeller. Subsequently, the motor suddenly reverses and starts up to the rated speed, completely tearing apart the laminar boundary layer of the pseudoplastic fluid, maintaining this for 1 minute before resuming forward rotation.

[0132] 2) Interlayer Coordinated Support (Core Linkage). When the system detects that the apparent viscosity of the upper shell-breaking zone I remains persistently high, and the upper motor is in a high-load adaptive shell-breaking state, it automatically triggers the interlayer flow field coupling linkage. The middle layer motor is forced to switch to the reverse high-speed propulsion mode (e.g., -30 rpm). Utilizing the strong upward surge generated by the reverse rotation of the propeller, the hard upper scum crust is "lifted, thinned, and dispersed" from the bottom. Combined with the downward shearing action of the upper turbine propeller, a three-dimensional flow field collaborative cutting of "bottom-up and top-cutting" is formed, effectively solving the problem of limited shell-breaking capacity of a single blade.

[0133] (3) For the lower anti-sinking zone, determine whether the resistance torque is greater than the torque threshold. If so, execute the pendulum swing escape and pulse sand blowing strategy. If not, maintain low speed scraping.

[0134] When the bottom resistance torque is greater than the set torque threshold, a pendulum swing escape and pulse sand blowing strategy is implemented for the lower anti-sinking zone.

[0135] Because the inorganic sand and heavy sludge at the bottom of the reactor body easily form a rigid, concrete-like slab layer after long-term deposition, current technology that directly uses high torque to forcibly start the scraper wall is prone to mechanical jamming, leading to motor burnout or drive shaft breakage.

[0136] like Figure 5 As shown, a pendulum-style swinging escape and pulse sand-throwing strategy is implemented for the lower anti-settlement zone, namely, a swinging escape and pulse sand-throwing mode. A biomimetic safety escape strategy is designed for the bottom anchor-type scraper, which first swings to loosen the soil and then pulses to throw sand.

[0137] When the bottom resistance torque is detected to exceed 1.5 times the set threshold (torque threshold), it is determined that severe sedimentation and compaction have occurred at the bottom. The system intercepts the motor's full-speed start command and controls the lower-level motor to prioritize the execution of alternating forward and reverse rotation actions with progressively increasing running time. Through pendulum-like reciprocating oscillation, the rigid compaction layer is gradually broken down. After the real-time torque drops back to within the safe threshold, the lower-level motor is controlled to execute a pulse sequence of rapid acceleration and emergency stop. The inertial water hammer effect of the sudden fluid stop is used to lift the bottom sediment and entrain it into the middle layer of circulation flow.

[0138] Specifically, during normal operation, the anchor-type scraper paddle cruises at a low speed of 5 rpm close to the wall. When the starting torque or running resistance torque of the bottom motor exceeds 1.5 times the set dynamic threshold, it is determined that severe caking has occurred at the bottom. The system automatically intercepts the full-speed start command and triggers the following timing actions: 1) Pendulum-type loosening and detachment (swinging detachment). The lower motor is controlled to perform alternating forward and reverse rotation movements with small angles and gradually increasing increments. For example, 1 second forward rotation - 1 second reverse rotation - 2 seconds forward rotation - 2 seconds reverse rotation - 3 seconds forward rotation - 3 seconds reverse rotation. Utilizing the anchor-type propeller, it swings back and forth like a pendulum in the hard sediment layer, gradually widening the loosening gap between the propeller blades and the sediment, safely and non-destructively breaking down the rigid, compacted layer.

[0139] 2) Pulse-driven sand lifting suspension (pulse-driven sand lifting). After the "pendulum loosening" sequence is completed and the resistance torque is monitored in real time to fall back to the safe allowable range (indicating that the sediment has been broken up and loosened), the motor immediately performs a large-stroke pulse-driven sand lifting action, rapidly accelerating to 30 rpm - abruptly stopping for 0.5 seconds - and then rapidly accelerating in the opposite direction to -30 rpm. Purely utilizing the strong inertial water hammer effect and local eddies generated when the fluid stops abruptly, the loose sediment at the bottom is instantly lifted up and drawn into the main circulating flow field of the middle mass transfer zone, and then returns to the 5 rpm cruising state.

[0140] like Figure 4 As shown, the control strategy is distributed to three independent frequency converters, which drive three layers of drive motors (drive motor groups) respectively. The speed setting, forward / reverse switching, and pulse sequence control of the control strategy are transmitted to the drive motors via the frequency converters.

[0141] In the upper shell-breaking zone, the upper motor (M1) of the drive motor unit is driven by the frequency converter (VFD-1) to drive the inclined blade turbine propeller to perform shell-breaking, anti-cavitation, and pulse tearing strategies.

[0142] In the middle mass transfer zone, the middle motor (M2) of the drive motor unit is driven by the frequency converter (VFD-2) to drive the propeller and execute the mass transfer enhancement and cooperative support strategy.

[0143] In the lower anti-settling zone, the lower motor (M3) of the drive motor unit is driven by the frequency converter (VFD-3) to drive the anchor scraper paddle to implement anti-settling, pendulum swaying, and pulse sand blowing strategies.

[0144] The three motors are controlled by independent frequency converters, achieving complete decoupling of speed, direction, and operating mode. They can run different stirring strategies simultaneously, solving the problem of "one-size-fits-all" in traditional single-shaft stirring.

[0145] like Figure 4 As shown, in addition to issuing control strategies, a closed loop is formed through two feedback links: 1) Real-time current / torque feedback. The current and torque of the motor during operation are transmitted back to the control unit in real time, serving as an auxiliary basis for judging whether the blades are stuck or the material is caking.

[0146] 2) Speed / Power Soft Measurement Feedback. The actual speed and power of the motor are transmitted back to the control unit to verify the stirring effect, dynamically adjust the control parameters, and achieve closed-loop optimization of measurement-decision-execution-feedback-readjustment.

[0147] The control unit calculates the actual rheological state and generates zone control commands, independently drives the execution of differentiated stirring strategies, and then achieves closed-loop optimization through state feedback, ultimately solving the problems of crusting, sedimentation and high energy consumption in anaerobic digestion.

[0148] Experimental and simulation verification were conducted using CFD simulation software (such as ANSYS Fluent) with the material model set to the Herschel-Bulkley non-Newtonian fluid. Simulation results showed that even without baffles, the differentiated impeller combination and coaxial allochthonous velocity control of this invention created three relatively independent flow field structures within the reactor. The upper high-shear zone did not excessively interfere with the main circulating flow in the middle layer, and the bottom dead zone volume (region with velocity <0.01 m / s) decreased from 32% in conventional stirring to 4%. Tracer experiments confirmed that the overall mixing time of this system was reduced by 45% compared to traditional single-shaft stirring, and the mixing efficiency of the system was significantly improved.

[0149] After the above steps, based on the normalized apparent viscosity, shear stress, and low-frequency basic viscous drag torque, the upper shell-breaking zone is subjected to anti-cavitation collapse perturbation and pulsed heavy impact, the middle mass transfer zone is subjected to intermittent wall breaking and synergistic support, and the lower anti-settlement zone is subjected to pendulum-type swinging detachment and pulsed sand blowing. This achieves precise control of each zone as needed, significantly reduces energy consumption, eliminates dead zone deposition, and improves mass transfer efficiency.

[0150] The methods described in the above embodiments are based on the system implementation of Embodiment 1.

[0151] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0152] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An anaerobic digestion stirring system based on vertical partitioning of rheological properties, characterized in that, include: Reactor body, stirring shaft assembly, drive motor and control unit; A drive motor unit is installed at the top center of the reactor body along the axis; the drive motor unit is connected to the stirring shaft assembly through an independent transmission mechanism; the control unit is electrically connected to the drive motor unit. The reactor body is divided into an upper shell-breaking zone, a middle mass transfer zone, and a lower anti-settling zone from top to bottom. The stirring shaft assembly is nested from the inside out in the divided zones: an inner shaft, a middle hollow shaft, and an outer hollow shaft. The outer hollow shaft is equipped with a slanted blade turbine propeller corresponding to the upper shell-breaking zone. The middle hollow shaft is equipped with a propeller propeller corresponding to the middle mass transfer zone. The inner shaft is equipped with an anchor scraper propeller corresponding to the lower anti-sinking zone.

2. The anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 1, characterized in that, The stirring shaft assembly consists of three shafts: the inner shaft, the middle hollow shaft, and the outer hollow shaft. These three shafts are connected by a thin-walled deep groove ball bearing nested with a self-lubricating special bushing. The gaps between the shafts are filled with food-grade grease, and multiple mechanical seal components are provided.

3. The anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 1, characterized in that, The inner shaft is connected to the anchor-type scraper propeller, the middle hollow shaft to the propeller propeller, and the outer hollow shaft to the inclined blade turbine propeller through expansion sleeves; the inclined blade turbine propeller, propeller propeller, and anchor-type scraper propeller are respectively connected to the drive motor unit through corresponding independent transmission mechanisms.

4. The anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 1, characterized in that, The blades of the inclined blade turbine are rigidly connected to the hub via a flange, and the blade surface is covered with a PTFE anti-stick coating; the blade edge of the propeller is provided with several triangular or trapezoidal stainless steel shear teeth; the geometric contour of the anchor scraper blade is closely fitted with the bottom shape of the reactor body, and the blade end is provided with a wear-resistant scraper.

5. The anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 1, characterized in that, It also includes several online viscometers, temperature sensors and biogas flow meters, which are electrically connected to the control unit to collect rheological parameters and transmit them to the control unit.

6. A control method for an anaerobic digestion stirring system based on rheological characteristics and vertical partitioning, characterized in that, Acquire multi-source data, including at least instantaneous gas production rate, temperature of each layer, and operating electrical parameters and speed of motors in each layer; Based on multi-source data, a power characteristic curve relationship model of each layer of impeller was established, and the rheological threshold of each layer of material was set. Based on the power characteristic curve relationship model, a multiphase coupled dynamic compensation algorithm is used to perform soft measurement calculations to obtain normalized apparent viscosity and shear stress. Based on the normalized apparent viscosity, shear stress, and low-frequency basic viscous drag torque, dynamic control strategies for each layer are generated, and dynamic zoning control is implemented for the upper shell-breaking zone, the middle mass transfer zone, and the lower anti-settlement zone, respectively.

7. The control method for an anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 6, characterized in that, Based on the power characteristic curve relationship model, a multiphase coupled dynamic compensation algorithm is used for soft measurement calculation to obtain the normalized apparent viscosity and shear stress. The specific process is as follows: Based on the operating electrical parameters and speed of each motor, the total output shaft torque is calculated and frequency domain decoupled to obtain the equivalent net output shaft power. Based on the instantaneous gas production rate, the apparent density of the fluid is dynamically compensated to obtain the corrected apparent density of the fluid. Based on the corrected fluid apparent density and equivalent net output shaft power, the apparent viscosity of the current state is calculated by inverting the power characteristic curve relationship model. Using the Arrhenius-type viscosity-temperature relationship equation, the apparent viscosity of the current state is calibrated by temperature normalization to obtain the normalized apparent viscosity. Shear stress is calculated based on normalized apparent viscosity.

8. The control method for the anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 7, characterized in that, Based on the operating electrical parameters and speeds of the motors on each floor, the total output shaft torque is calculated and frequency domain decoupled to obtain the equivalent net output shaft power. The specific process is as follows: Calculate the input electrical power of each motor based on its operating electrical parameters and speed. Calculate the motor output mechanical power based on the input electrical power of each layer of motors; Calculate the total output shaft torque based on the input electrical power of each motor and the angular velocity of each stirring shaft. The total output shaft torque is decoupled in the frequency domain using fast Fourier transform to filter out high-frequency pulsation components and extract the low-frequency basic viscous drag torque as the current drag torque. The equivalent net output shaft power is calculated using the low-frequency foundation viscous resistance torque.

9. The control method for the anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 7, characterized in that, Based on the corrected fluid apparent density and equivalent net output shaft power, the apparent viscosity of the current state is calculated using a power characteristic curve relationship model. The specific process is as follows: The corrected power number is calculated based on the extracted equivalent net output shaft power and the corrected fluid apparent density. The Reynolds number is obtained by inverse solving a model of the power characteristic curve relationship; Calculate the apparent viscosity of the current state based on the Reynolds number and the corrected fluid apparent density.

10. The control method for the anaerobic digestion stirring system based on rheological characteristics and vertical partitioning as described in claim 6, characterized in that, Based on the normalized apparent viscosity, shear stress, and low-frequency foundation viscous drag torque, dynamic control strategies for each layer are generated, and dynamic zonal regulation is implemented for the upper shell-breaking zone, the middle mass transfer zone, and the lower anti-settlement zone, respectively. The specific process is as follows: If the normalized apparent viscosity is greater than the set crusting threshold, an anti-cavitation adaptive collapse perturbation strategy is implemented in the upper crust-breaking zone. This involves sequentially performing trial acceleration and cavity detection, shutdown retreat collapse, and asymmetric second-burst tearing, and repeating this process until the normalized apparent viscosity reaches the set crusting threshold. When the shear stress is less than the preset mass transfer threshold, an intermittent cell disruption and interlayer synergistic support strategy is implemented in the middle mass transfer zone. When the bottom resistance torque is greater than the set torque threshold, a pendulum swing escape and pulse sand blowing strategy is implemented for the lower anti-sinking zone.

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