A method to simplify the difficulty of hydraulic control of high-solid anaerobic digestion based on flow state dimensionality reduction

Abstract

The present invention belongs to the field of environmental engineering technology and relates to a method for simplifying the difficulty of hydraulic control of high-solid anaerobic digestion based on flow state dimensionality reduction, comprising: constructing a geometric model of the reactor and agitator according to the target reactor; using a relatively adaptable unstructured grid to mesh the entire fluid domain; using a rheometer to simulate the rheological properties of the anaerobic digestion matrix; using CFD software to numerically simulate the anaerobic digestion flow field, and deriving the results after the calculation converges; drawing a two-dimensional cumulative flow velocity distribution normalization curve and constructing a one-dimensional high-solid anaerobic digestion hydraulic characteristic model; and obtaining the relationship between hydraulic characteristic parameters and research variables through data analysis. The present invention can optimize hydraulic conditions and reduce energy consumption generated by stirring by controlling the geometric configuration and rotation speed in the reactor, providing new insights into mixing characterization in the reactor and better controlling the mixing effect in the reactor.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental engineering, relates to anaerobic digestion, and in particular to a method for simplifying the difficulty of hydraulic control of high-solid anaerobic digestion based on flow state dimension reduction. Background Art

[0002] Anaerobic digestion can not only effectively degrade organic waste, but also recover energy from waste by producing biogas. However, there are some defects in the anaerobic digestion of organic solid waste, such as low methane yield, high retention time requirements, and incomplete digestion of the substrate. Compared with low-solid anaerobic digestion, high-solid anaerobic digestion has the advantages of small reactor footprint, large processing capacity, and excellent hygienic properties of the digestate. However, its fluid flow characteristics are poor, and the matrix heat and mass transfer effect is poor, which easily leads to the accumulation of ammonia nitrogen and acid, inhibiting the reaction. Regulating the hydraulic conditions of high-solid anaerobic digestion can enhance heat and mass transfer in the system and promote the operational performance of high-solid anaerobic digestion.

[0003] High-solid anaerobic digestion systems contain vast amounts of three-dimensional hydraulic information, making it extremely difficult to control the system using this massive amount of complex hydraulic information. Computational fluid dynamics (CFD) can visualize the three-dimensional hydraulic characteristics of anaerobic digestion systems and obtain comprehensive flow field information. Grids are the computational units of CFD models. An anaerobic digestion reactor with an effective volume of 8L has 742,593 grids, while a 30L anaerobic digestion reactor has a grid count of 3,928,848. Therefore, using this massive amount of three-dimensional information to directly control the hydraulic conditions in high-solid anaerobic digestion reactors is extremely difficult. Summary of the Invention

[0004] In response to the necessity of hydraulic regulation of high-solid anaerobic digestion and the difficulty in regulating hydraulic conditions due to the massive flow field information in the reactor, the present invention discloses a method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimensionality reduction.

[0005] Technical Solution

[0006] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimensionality reduction comprises the following steps:

[0007] (1) Construct the geometric model of the reactor and agitator according to the target reactor, and set its working volume and three-dimensional structure;

[0008] (2) Perform grid division. Use relatively adaptable unstructured grid to divide the entire fluid domain into grids, and perform grid independence test to prove that the simulation results are independent of the number of grids. Select the number of grids based on the simulation time and simulation effect.

[0009] (3) Use a rheometer to simulate the rheological properties of the anaerobic digestion matrix and select a suitable rheological model to fit the matrix rheological properties;

[0010] (4) Use CFD software to perform numerical simulation of the anaerobic digestion flow field, export the results after the calculation converges, and perform post-processing through post-processing software to collect the velocity and dead zone distribution patterns of multiple surfaces;

[0011] (5) Divide the flow field of the reactor into dead zone, low speed zone, medium speed zone and high speed zone according to the flow velocity, draw the spatial distribution diagram of different speed intervals, further divide the flow velocity interval in the reactor into multiple intervals, and draw the two-dimensional cumulative flow velocity distribution normalization curve;

[0012] (6) Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model based on the two-dimensional cumulative velocity distribution normalized curve, fit the data of each working condition to the high-solid anaerobic digestion hydraulic characteristic model, and extract the hydraulic characteristic parameters for hydraulic control;

[0013] (7) The relationship between hydraulic characteristic parameters and research variables is obtained through data analysis, and steps (1)-(6) are repeated to further construct a high-solid anaerobic digestion hydraulic control model.

[0014] In a preferred embodiment of the present invention, the organic waste treated by the high-solid anaerobic digestion process includes pig manure, straw, kitchen waste or sludge.

[0015] Furthermore, in the high-solid anaerobic digestion process, the anaerobic digestion temperature is 35-55°C.

[0016] Furthermore, the anaerobic digestion includes direct anaerobic digestion, co-digestion, heat treatment enhanced anaerobic digestion, additive enhanced anaerobic digestion, alkali treatment enhanced anaerobic digestion or microwave pretreatment anaerobic digestion.

[0017] In a preferred embodiment of the present invention, the rheological model in step (3) is a Power-law model, a Carreau model or a Hershel-Bulkley model.

[0018] In a preferred embodiment of the present invention, the numerical simulation settings described in step (4) include but are not limited to: selecting a physical model according to the working conditions to be simulated, such as selecting an energy model when considering energy, and selecting a multiphase flow model when considering multiphase flow; determining the boundary type and physical quantities; setting solution parameters, including but not limited to monitoring physical quantity settings, convergence standard settings, solution accuracy settings, etc.; selecting a suitable initialization method according to the simulation working conditions and iterative calculations.

[0019] Furthermore, the multiphase flow model is a Eulerian model or a VOF (Volume of Fluid) model.

[0020] The present invention extracts and fits massive flow field information into a hydraulic characteristic parameter, simplifies the difficulty of hydraulic regulation in the reactor, can improve the operating effect of the anaerobic digestion reactor, and is expected to provide a reference for anaerobic digestion operation under actual working conditions.

[0021] Beneficial effects

[0022] Based on three-dimensional flow field information obtained from CFD simulations, the present invention constructs a two-dimensional normalized cumulative velocity distribution curve to analyze the velocity field pattern. This then constructs a one-dimensional mathematical model to extract hydraulic characteristic parameters to control hydraulic conditions. This reduces the difficulty of using massive amounts of information to control the hydraulic conditions of high-solids anaerobic digestion, providing a new perspective for strengthening high-solids anaerobic digestion strategies. By controlling the geometry and rotational speed within the reactor, hydraulic conditions can be optimized and the energy consumption associated with stirring can be reduced. This can provide new insights into the characterization of mixing within the reactor and better control the mixing effect within the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Example 1 (a) Flow field diagram of high-solid anaerobic digestion under different rotation speed conditions, (b) diagram of the reactor and stirring paddle;

[0024] Figure 2 . Spatial distribution diagram of different speed intervals of the cross section of Examples 1, 2, 3, 4, and 5x = 0mm;

[0025] Figure 3 Effect of rotation speed on dead zone volume fraction in Examples 1, 2, 3, 4, and 5;

[0026] Figure 4 . Examples 1, 2, 3, 4, and 5 flow rate interval volume fraction diagram at different speeds;

[0027] Figure 5 Example 1 normalized curve of cumulative flow rate distribution at different speeds;

[0028] Figure 6 Example 2 (a) Flow field diagram of high-solid anaerobic digestion under different rotation speed conditions, (b) diagram of the reactor and stirring paddle;

[0029] Figure 7 Example 2 normalized curve of cumulative flow rate distribution at different speeds;

[0030] Figure 8 Example 3 (a) Flow field diagram of high-solid anaerobic digestion under different rotation speed conditions, (b) diagram of the reactor and stirring paddle;

[0031] Figure 9 Example 3 normalized curve of cumulative flow rate distribution at different speeds;

[0032] Figure 10Example 4 (a) Flow field diagram of high-solid anaerobic digestion under different rotation speed conditions, (b) diagram of the reactor and stirring paddle;

[0033] Figure 11 Example 4 normalized curve of cumulative flow rate distribution at different speeds;

[0034] Figure 12 Example 5 (a) Flow field diagram of high-solid anaerobic digestion under different rotation speed conditions, (b) diagram of the reactor and stirring paddle;

[0035] Figure 13 .Example 5 Normalized curve of cumulative flow rate distribution at different rotation speeds. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the following examples so that those skilled in the art can better understand the present invention. However, the present invention is not limited to the following examples.

[0037] Example 1

[0038] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimension reduction includes the following steps:

[0039] Step 1: Construct the geometric model of the reactor. The reactor is a cylinder with a diameter of 170 mm, a height of 300 mm, and a working liquid level of 270 mm. The reactor uses a ribbon agitator with a diameter of 51 mm, installed 80 mm from the bottom of the reactor, and a pitch of 42.5 mm.

[0040] Step 2: Use ANSYS Fluent to perform meshing. Use a relatively adaptable unstructured grid to mesh the entire fluid domain. Then divide the grid into four groups for mesh independence testing. Considering the simulation time and simulation effect, the number of grids for subsequent numerical simulation is selected.

[0041] Step 3: Use a rheometer to simulate the rheological properties of the matrix in the anaerobic digestion system of food waste, and select the Power-law model to fit the matrix rheological properties;

[0042] Step 4: The rotational speeds were set to 2.5 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, and 80 rpm, respectively. ANSYS Fluent was used to numerically simulate the anaerobic digestion flow field for all 10 working conditions. After the calculations converged, the results were exported and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns on multiple surfaces.

[0043] The numerical simulation settings include:

[0044] Viscosity model: Select the Laminar model based on the Reynolds number;

[0045] Multiphase flow model: VOF model is used to simulate the hydraulic conditions of gas-liquid two phases in the reactor, and the liquid phase is set

[0046] The main phase is the gas phase, and the secondary phase is the gas phase; the gas phase height is 30mm, and the rest is set as the liquid phase;

[0047] Boundary conditions: The rotating domain and the stationary domain are coupled through the interface, where the rotating domain sets the rotation

[0048] direction and speed to simulate the flow field inside the reactor, while the rest of the surfaces are set to static;

[0049] Convergence criteria: two conditions must be met: the torque on the monitoring impeller is stable, and the parameter residual is

[0050] The setting accuracy is less than 1×10 -3 ;

[0051] Step 5: Divide the reactor flow field into a dead zone, a low-speed zone, a medium-speed zone, and a high-speed zone according to the flow velocity, and draw spatial distribution diagrams of different velocity intervals; further divide the flow velocity interval in the reactor into 32 intervals, and draw a two-dimensional cumulative flow velocity distribution normalization curve;

[0052] Step 6: Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model Y based on the two-dimensional cumulative velocity distribution normalized curve (v) =100(1-e - k v ), and the data of each working condition were fitted with the high-solid anaerobic digestion hydraulic characteristic model through Origin, and the hydraulic characteristic parameter k was extracted for hydraulic control, where Y (v) is the cumulative flow volume fraction (%) when vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

[0053] Step 7: Obtain the relationship between k, propeller diameter ratio and rotation speed through data analysis, and further construct the high-solid anaerobic digestion hydraulic control model Where N is the rotation speed (rpm).

[0054] The flow field of high solid anaerobic digestion under different rotation speed conditions Figure 1 As shown in (a), the reactor and stirring blade are as follows Figure 1 As shown in (b), the spatial distribution of different velocity intervals on the cross section x = 0 mm is as follows Figure 2 Example 1, the effect of rotation speed on the dead zone volume fraction is as follows Figure 3 Example 1, the volume fraction of flow rate interval at different speeds is as follows Figure 4Example 1, Example 1 cumulative flow rate distribution normalized curve is as follows Figure 5 .

[0055] Example 2

[0056] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimensionality reduction comprises the following steps:

[0057] Step 1: Construct the geometric model of the reactor. The reactor is a cylinder with a diameter of 170 mm, a height of 300 mm, and a working liquid level of 270 mm. The reactor uses a ribbon agitator with a diameter of 68 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon agitator is 42.5 mm.

[0058] Step 2: Use ANSYS Fluent to perform meshing. Use a relatively adaptable unstructured grid to mesh the entire fluid domain. Then divide the grid into four groups for mesh independence testing. Considering the simulation time and simulation effect, the number of grids for subsequent numerical simulation is selected.

[0059] Step 3: Use a rheometer to simulate the rheological properties of the matrix in the anaerobic digestion system of food waste, and select the Power-law model to fit the matrix rheological properties;

[0060] Step 4: The rotational speeds were set to 2.5 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, and 80 rpm, respectively. ANSYS Fluent was used to numerically simulate the anaerobic digestion flow field for all 10 working conditions. After the calculations converged, the results were exported and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns on multiple surfaces.

[0061] The numerical simulation settings include:

[0062] Viscosity model: Select the Laminar model based on the Reynolds number;

[0063] Multiphase flow model: VOF model is used to simulate the hydraulic conditions of gas-liquid two phases in the reactor, and the liquid phase is set

[0064] The main phase is the gas phase, and the secondary phase is the gas phase; the gas phase height is 30mm, and the rest is set as the liquid phase;

[0065] Boundary conditions: The rotating domain and the stationary domain are coupled through the interface, where the rotating domain sets the rotation

[0066] direction and speed to simulate the flow field inside the reactor, while the rest of the surfaces are set to static;

[0067] Convergence criteria: two conditions must be met: the torque on the monitoring impeller is stable, and the parameter residual is

[0068] The setting accuracy is less than 1×10 -3 ;

[0069] Step 5: Divide the reactor flow field into a dead zone, a low-speed zone, a medium-speed zone, and a high-speed zone according to the flow velocity, and draw spatial distribution diagrams of different velocity intervals; further divide the flow velocity interval in the reactor into 32 intervals, and draw a two-dimensional cumulative flow velocity distribution normalization curve;

[0070] Step 6: Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model Y based on the two-dimensional cumulative velocity distribution normalized curve (v) =100(1-e - k v ), and the data of each working condition were fitted with the high-solid anaerobic digestion hydraulic characteristic model through Origin, and the hydraulic characteristic parameter k was extracted for hydraulic control, where Y (v) is the cumulative flow volume fraction (%) when vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

[0071] Step 7: Obtain the relationship between k, propeller diameter ratio and rotation speed through data analysis, and further construct the high-solid anaerobic digestion hydraulic control model Where N is the speed (rpm);

[0072] The flow field of high solid anaerobic digestion under different rotation speed conditions Figure 6 As shown in (a), the reactor and stirring blade are as follows Figure 6 As shown in (b), the spatial distribution of different velocity intervals on the cross section x = 0 mm is as follows Figure 2 Example 2, the effect of rotation speed on the dead zone volume fraction is as follows Figure 3 Example 2, the volume fraction of the flow rate interval at different speeds is as follows Figure 4 Example 2, Example 2 cumulative flow rate distribution normalized curve is as follows Figure 7 .

[0073] Example 3

[0074] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimensionality reduction comprises the following steps:

[0075] Step 1: Construct the geometric model of the reactor. The reactor is a cylinder with a diameter of 170 mm, a height of 300 mm, and a working liquid level of 270 mm. The reactor uses a ribbon agitator with a diameter of 85 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon agitator is 42.5 mm.

[0076] Step 2: Use ANSYS Fluent to perform meshing. Use a relatively adaptable unstructured grid to mesh the entire fluid domain. Then divide the grid into four groups for mesh independence testing. Considering the simulation time and simulation effect, the number of grids for subsequent numerical simulation is selected.

[0077] Step 3: Use a rheometer to simulate the rheological properties of the matrix in the anaerobic digestion system of food waste, and select the Power-law model to fit the matrix rheological properties;

[0078] Step 4: The rotational speeds were set to 2.5 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, and 80 rpm, respectively. ANSYS Fluent was used to numerically simulate the anaerobic digestion flow field for all 10 working conditions. After the calculations converged, the results were exported and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns on multiple surfaces.

[0079] The numerical simulation settings include:

[0080] Viscosity model: Select the Laminar model based on the Reynolds number;

[0081] Multiphase flow model: VOF model is used to simulate the hydraulic conditions of gas-liquid two phases in the reactor, and the liquid phase is set

[0082] The main phase is the gas phase, and the secondary phase is the gas phase; the gas phase height is 30mm, and the rest is set as the liquid phase;

[0083] Boundary conditions: The rotating domain and the stationary domain are coupled through the interface, where the rotating domain sets the rotation

[0084] direction and speed to simulate the flow field inside the reactor, while the rest of the surfaces are set to static;

[0085] Convergence criteria: two conditions must be met: the torque on the monitoring impeller is stable, and the parameter residual is

[0086] The setting accuracy is less than 1×10 -3 ;

[0087] Step 5: Divide the reactor flow field into a dead zone, a low-speed zone, a medium-speed zone, and a high-speed zone according to the flow velocity, and draw spatial distribution diagrams of different velocity intervals; further divide the flow velocity interval in the reactor into 32 intervals, and draw a normalized curve of the cumulative flow velocity distribution;

[0088] Step 6: Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model Y based on the two-dimensional cumulative velocity distribution normalized curve (v) =100(1-e - kv ), and the data of each working condition were fitted with the high-solid anaerobic digestion hydraulic characteristic model through Origin, and the hydraulic characteristic parameter k was extracted for hydraulic control, where Y (v) is the cumulative flow volume fraction (%) when vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

[0089] Step 7: Obtain the relationship between k, propeller diameter ratio and rotation speed through data analysis, and further construct the high-solid anaerobic digestion hydraulic control model Where N is the rotation speed (rpm).

[0090] The flow field of high solid anaerobic digestion under different rotation speed conditions Figure 8 As shown in (a), the reactor and stirring blade are as follows Figure 8 As shown in (b), the spatial distribution of different velocity intervals on the cross section x = 0 mm is as follows Figure 2 Example 3, the effect of rotation speed on the dead zone volume fraction is as follows Figure 3 Example 3, the volume fraction of the flow rate interval at different speeds is as follows Figure 4 Example 3, Example 3 cumulative flow rate distribution normalized curve is as follows Figure 9 .

[0091] Example 4

[0092] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimensionality reduction comprises the following steps:

[0093] Step 1: Draw the geometric model of the reactor. The reactor is a cylinder with a diameter of 170 mm, a height of 300 mm, and a working liquid level of 270 mm. The reactor uses a ribbon agitator with a diameter of 119 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon agitator is 42.5 mm.

[0094] Step 2: Use ANSYS Fluent to perform meshing. Use a relatively adaptable unstructured grid to mesh the entire fluid domain. Then divide the grid into four groups for mesh independence testing. Considering the simulation time and simulation effect, the number of grids for subsequent numerical simulation is selected.

[0095] Step 3: Use a rheometer to simulate the rheological properties of the matrix in the anaerobic digestion system of food waste, and select the Power-law model to fit the matrix rheological properties;

[0096] Step 4: The rotational speeds were set to 2.5 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, and 80 rpm, respectively. ANSYS Fluent was used to numerically simulate the anaerobic digestion flow field for all 10 working conditions. After the calculations converged, the results were exported and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns on multiple surfaces.

[0097] The numerical simulation settings include:

[0098] Viscosity model: Select the Laminar model based on the Reynolds number;

[0099] Multiphase flow model: VOF model is used to simulate the hydraulic conditions of gas-liquid two phases in the reactor, and the liquid phase is set

[0100] The main phase is the gas phase, the secondary phase is the gas phase. The gas phase height is 30mm, and the rest is set as the liquid phase;

[0101] Boundary conditions: The rotating domain and the stationary domain are coupled through the interface, where the rotating domain sets the rotation

[0102] direction and speed to simulate the flow field inside the reactor, while the rest of the surfaces are set to static;

[0103] Convergence criteria: two conditions must be met: the torque on the monitoring impeller is stable, and the parameter residual is

[0104] The setting accuracy is less than 1×10 -3 ;

[0105] Step 5: Divide the reactor flow field into a dead zone, a low-speed zone, a medium-speed zone, and a high-speed zone according to the flow velocity, and draw spatial distribution diagrams of different velocity intervals; further divide the flow velocity interval in the reactor into 32 intervals, and draw a two-dimensional cumulative flow velocity distribution normalization curve;

[0106] Step 6: Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model Y based on the two-dimensional cumulative velocity distribution normalized curve (v) =100(1-e - k v ), and the data of each working condition were fitted with the high-solid anaerobic digestion hydraulic characteristic model through Origin, and the hydraulic characteristic parameter k was extracted for hydraulic control, where Y (v) is the cumulative flow volume fraction (%) when vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

[0107] Step 7: Obtain the relationship between k, propeller diameter ratio and rotation speed through data analysis, and further construct the high-solid anaerobic digestion hydraulic control model Where N is the rotation speed (rpm).

[0108] Flow field of high solid anaerobic digestion under different rotation speed conditions Figure 10 As shown in (a), the reactor and stirring blade are as follows Figure 10 As shown in (b), the spatial distribution of different velocity intervals on the cross section x = 0 mm is as follows Figure 2 Example 4, the effect of rotation speed on the dead zone volume fraction is as follows Figure 3 Example 4, the volume fraction of the flow rate interval at different speeds is as follows Figure 4 Example 4, Example 4 cumulative flow rate distribution normalized curve is as follows Figure 11 .

[0109] Example 5

[0110] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimension reduction includes the following steps:

[0111] Step 1: Construct the geometric model of the reactor. The reactor is a cylinder with a diameter of 170 mm, a height of 300 mm, and a working liquid level of 270 mm. The reactor uses a ribbon agitator with a diameter of 153 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon agitator is 42.5 mm.

[0112] Step 2: Use ANSYS Fluent to perform meshing. Use a relatively adaptable unstructured grid to mesh the entire fluid domain. Then divide the grid into four groups for mesh independence testing. Considering the simulation time and simulation effect, the number of grids for subsequent numerical simulation is selected.

[0113] Step 3: Use a rheometer to simulate the rheological properties of the matrix in the anaerobic digestion system of food waste, and select the Power-law model to fit the matrix rheological properties;

[0114] Step 4: The rotational speeds were set to 2.5 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, and 80 rpm, respectively. ANSYS Fluent was used to numerically simulate the anaerobic digestion flow field for all 10 working conditions. After the calculations converged, the results were exported and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns on multiple surfaces.

[0115] The numerical simulation settings include:

[0116] Viscosity model: Select the Laminar model based on the Reynolds number;

[0117] Multiphase flow model: The VOF model is used to simulate the hydraulic conditions of the gas-liquid two-phase in the reactor, with the liquid phase set as the primary phase and the gas phase as the secondary phase. The gas phase height is 30 mm, and the rest is set as the liquid phase.

[0118] Boundary conditions: The rotating domain and the stationary domain are coupled through an interface, where the rotating domain is set with a rotation direction and speed to simulate the flow field inside the reactor, while the remaining surfaces are set to a stationary state;

[0119] Convergence criteria: two conditions must be met: the torque on the monitoring impeller is stable, and the parameter residual setting accuracy is less than 1×10 -3 ;

[0120] Step 5: Divide the reactor flow field into a dead zone, a low-speed zone, a medium-speed zone, and a high-speed zone according to the flow velocity, and draw spatial distribution diagrams of different velocity intervals; further divide the flow velocity interval in the reactor into 32 intervals, and draw a two-dimensional cumulative flow velocity distribution normalization curve;

[0121] Step 6: Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model Y based on the two-dimensional cumulative velocity distribution normalized curve (v) =100(1-e -kv ), and the data of each working condition were fitted with the high-solid anaerobic digestion hydraulic characteristic model through Origin, and the hydraulic characteristic parameter k was extracted for hydraulic control, where Y (v) is the cumulative flow volume fraction (%) when vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

[0122] Step 7: Obtain the relationship between k, propeller diameter ratio and rotation speed through data analysis, and further construct the high-solid anaerobic digestion hydraulic control model Where N is the rotation speed (rpm).

[0123] Flow field of high solid anaerobic digestion under different rotation speed conditions Figure 12 As shown in (a), the reactor and stirring blade are as follows Figure 12 As shown in (b), the spatial distribution of different velocity intervals on the cross section x = 0 mm is as follows Figure 2 Example 5, the effect of rotation speed on the dead zone volume fraction is as follows Figure 3 Example 5, the volume fraction of the flow rate interval at different speeds is as follows Figure 4 Example 5, Example 5 cumulative flow rate distribution normalized curve is as follows Figure 13 .

[0124] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for simplifying the difficulty of hydraulic control of high-solid anaerobic digestion based on flow dimensionality reduction, characterized in that: The steps include: (1) Construct the geometric model of the reactor and the impeller according to the target reactor, and set its working volume and three-dimensional structure; (2) Use relatively adaptable unstructured grids to mesh the entire fluid domain, and perform grid independence tests to prove that the simulation results are independent of the number of grids. The number of grids is selected based on the simulation time and simulation effect. (3) Use a rheometer to simulate the rheological properties of the anaerobic digestion matrix and select a suitable rheological model to fit the matrix rheological properties; (4) Use CFD software to perform numerical simulation of the anaerobic digestion flow field, export the results after the calculation converges, and perform post-processing through post-processing software to collect the velocity and dead zone distribution patterns of multiple surfaces; (5) The flow field of the reactor is divided into dead zone, low speed zone, medium speed zone and high speed zone according to the flow velocity, and the spatial distribution diagram of different speed intervals is drawn. The flow velocity interval in the reactor is further divided into multiple intervals, and the two-dimensional cumulative flow velocity distribution normalization curve is drawn; (6) A one-dimensional high-solid anaerobic digestion hydraulic characteristic model is constructed based on the two-dimensional cumulative velocity distribution normalized curve, and the data of each working condition are fitted to the high-solid anaerobic digestion hydraulic characteristic model, and the hydraulic characteristic parameters are extracted for hydraulic control; (7) The relationship between hydraulic characteristic parameters and research variables is obtained through data analysis, and steps (1)-(6) are repeated to further construct a high-solid anaerobic digestion hydraulic control model.

2. The method for simplifying the hydraulic control difficulty of high-solid anaerobic digestion based on flow state dimension reduction according to claim 1, characterized in that: The organic waste processed by the high-solid anaerobic digestion includes pig manure, straw, restaurant kitchen waste or sludge.

3. The method for simplifying the hydraulic control difficulty of high-solid anaerobic digestion based on flow state dimension reduction according to claim 1, characterized in that: The high-solid anaerobic digestion has an anaerobic digestion temperature of 35-55°C.

4. The method for simplifying the hydraulic control difficulty of high-solid anaerobic digestion based on flow state dimension reduction according to claim 1, characterized in that: The anaerobic digestion includes direct anaerobic digestion, co-digestion, heat treatment enhanced anaerobic digestion, additive enhanced anaerobic digestion, alkali treatment enhanced anaerobic digestion or microwave pretreatment anaerobic digestion.

5. The method for simplifying the hydraulic control difficulty of high-solid anaerobic digestion based on flow state dimension reduction according to claim 1, characterized in that: The rheological model described in step (3) is a Power-law model, a Carreau model or a Hershel-Bulkley model.

6. The method for simplifying the hydraulic control difficulty of high-solid anaerobic digestion based on flow state dimension reduction according to claim 1, characterized in that: The numerical simulation settings described in step (4) include: selecting a physical model according to the working conditions to be simulated, selecting an energy model considering energy, and selecting a multiphase flow model considering multiphase flow; determining the boundary type and physical quantities; setting solution parameters, including monitoring physical quantity settings, convergence standard settings, and solution accuracy settings; selecting a suitable initialization method according to the simulation working conditions and performing iterative calculations.

7. The method for simplifying the hydraulic control difficulty of high-solid anaerobic digestion based on flow state dimension reduction according to claim 6, characterized in that: The multiphase flow model is a Eulerian model or a VOF model.

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