Method for simplifying high-solid anaerobic digestion hydraulic regulation and control difficulty based on flow state dimension reduction

Abstract

The invention belongs to the technical field of environmental engineering, and relates to a method for simplifying high-solid anaerobic digestion hydraulic regulation difficulty based on flow state dimensionality reduction, which comprises the following steps: constructing geometric models of a reactor and a stirring paddle according to a target reactor; performing grid division on the whole fluid domain by using an unstructured grid with relatively high adaptability; adopting a rheometer to simulate the rheological property of the anaerobic digestion substrate; carrying out numerical simulation on the anaerobic digestion flow field by using CFD software, and calculating a result after convergence; drawing a two-dimensional cumulative flow velocity distribution normalization curve and constructing a one-dimensional high-solid anaerobic digestion hydraulic characteristic model; and the relationship between the hydraulic characteristic parameters and the research variables is obtained through data analysis. By controlling the geometric configuration and the rotating speed in the reactor, the hydraulic condition can be optimized, the energy consumption generated by stirring can be reduced, a new insight is provided for mixing characterization in the reactor, and the mixing effect in the reactor can be better controlled.

Description

Technical Field

[0001] The 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 regulation 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 anaerobic digestion of organic solid waste, such as low methane yield, high retention time requirements, and incomplete digestion of substrates. 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 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 operating performance of high-solid anaerobic digestion.

[0003] The high-solid anaerobic digestion system contains a large amount of three-dimensional hydraulic information, and it is extremely difficult to control the system with massive and complex hydraulic information. Computational Fluid Dynamics (CFD) can visualize the three-dimensional hydraulic characteristics of the anaerobic digestion system and obtain comprehensive flow field information. Among them, the grid is the calculation unit of the CFD model. The number of grids in the anaerobic digestion reactor with an effective volume of 8L is 742593, and the number of grids in the anaerobic digestion reactor with an effective volume of 30L is as high as 3928848. Therefore, it is extremely difficult to use three-dimensional massive information to directly control the hydraulic conditions of the high-solid anaerobic digestion reactor. Summary of the invention

[0004] In view of the necessity of hydraulic regulation of high-solid anaerobic digestion and the difficulty in regulating hydraulic conditions with 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 dimension reduction comprises the following steps:

[0007] (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;

[0008] (2) Perform grid division. Use relatively adaptable unstructured grids to divide the entire fluid domain into grids, and perform grid independence tests 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 rheological properties of the matrix;

[0010] (4) Use CFD software to perform numerical simulation on 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 reactor flow field 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 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, thermal 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 disclosed example 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 conditions and iterating the calculation.

[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 operation 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] The present invention is based on the three-dimensional flow field information obtained by CFD simulation, and constructs a two-dimensional cumulative velocity distribution normalized curve to analyze the velocity field law, and then constructs a one-dimensional mathematical model to extract hydraulic characteristic parameters to regulate hydraulic conditions. This reduces the difficulty of regulating the hydraulic conditions of high-solid anaerobic digestion with massive information, and provides a new perspective for strengthening the high-solid anaerobic digestion strategy. By controlling the geometric configuration and rotation speed in the reactor, the hydraulic conditions can be optimized and the energy consumption generated by stirring can be reduced. It can provide new insights for the mixing characterization in the reactor and better control the mixing effect in 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 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 . Volume fraction diagram of flow rate intervals at different speeds in Examples 1, 2, 3, 4, and 5;

[0027] Figure 5 Example 1 Normalized curve diagram 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 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 reactor and stirring paddle;

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

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

[0033] Fig.11 Example 4 Normalized curve diagram of cumulative flow rate distribution at different speeds;

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

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

[0036] The present invention is described in detail below in conjunction with the embodiments so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0037] Example 1

[0038] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimension reduction comprises 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 stirring paddle with a diameter of 51 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon stirring paddle is 42.5 mm.

[0040] Step 2: ANSYS Fluent is used for meshing. The relatively adaptable unstructured grid is used to mesh the entire fluid domain. Four groups of grids are divided for mesh independence test. The number of grids for subsequent numerical simulation is selected based on the simulation time and simulation effect.

[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 rheological properties of the matrix;

[0042] Step 4: The 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 perform numerical simulations on the anaerobic digestion flow field for all 10 working conditions. The results were exported after the calculations converged and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns of multiple surfaces.

[0043] The numerical simulation setup includes:

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

[0045] Multiphase flow model: The VOF model is used to simulate the hydraulic conditions of the gas-liquid two-phase 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 height of the gas phase is 30 mm, 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 remaining surfaces were set to static;

[0049] Convergence criteria: two conditions must be met: the torque on the impeller must be stable and the parameter residuals must be

[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 speed 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 v is vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

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

[0054] 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 the 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 dimension 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 impeller with a diameter of 68 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon impeller is 42.5 mm.

[0058] Step 2: ANSYS Fluent is used for meshing. The relatively adaptable unstructured grid is used to mesh the entire fluid domain. Four groups of grids are divided for mesh independence test. The number of grids for subsequent numerical simulation is selected based on the simulation time and simulation effect.

[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 rheological properties of the matrix;

[0060] Step 4: The 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 perform numerical simulations on the anaerobic digestion flow field for all 10 working conditions. The results were exported after the calculations converged and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns of multiple surfaces.

[0061] The numerical simulation setup includes:

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

[0063] Multiphase flow model: The VOF model is used to simulate the hydraulic conditions of the gas-liquid two-phase 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 height of the gas phase is 30 mm, 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 remaining surfaces were set to static;

[0067] Convergence criteria: two conditions must be met: the torque on the impeller must be stable and the parameter residuals must be

[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 speed 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 according to 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 v is vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

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

[0072] 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, the normalized curve of cumulative flow rate distribution in Example 2 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 dimension 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 impeller with a diameter of 85 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon impeller is 42.5 mm.

[0076] Step 2: ANSYS Fluent is used for meshing. The relatively adaptable unstructured grid is used to mesh the entire fluid domain. Four groups of grids are divided for mesh independence test. The number of grids for subsequent numerical simulation is selected based on the simulation time and simulation effect.

[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 rheological properties of the matrix;

[0078] Step 4: The 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 perform numerical simulations on the anaerobic digestion flow field for all 10 working conditions. The results were exported after the calculations converged and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns of multiple surfaces.

[0079] The numerical simulation setup includes:

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

[0081] Multiphase flow model: The VOF model is used to simulate the hydraulic conditions of the gas-liquid two-phase 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 height of the gas phase is 30 mm, 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 remaining surfaces were set to static;

[0085] Convergence criteria: two conditions must be met: the torque on the impeller must be stable and the parameter residuals must be

[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 speed intervals; further divide the flow velocity interval in the reactor into 32 intervals, and draw a normalized curve of cumulative flow velocity distribution;

[0088] Step 6: Construct a one-dimensional high-solid anaerobic digestion hydraulic characteristic model Y according to 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 v is vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

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

[0090] 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, the normalized curve of cumulative flow rate distribution in Example 3 is as follows Fig. 9 .

[0091] Example 4

[0092] A method for simplifying the difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimension 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 impeller with a diameter of 119 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon impeller is 42.5 mm.

[0094] Step 2: ANSYS Fluent is used for meshing. The relatively adaptable unstructured grid is used to mesh the entire fluid domain. Four groups of grids are divided for mesh independence test. The number of grids for subsequent numerical simulation is selected based on the simulation time and simulation effect.

[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 rheological properties of the matrix;

[0096] Step 4: The 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 perform numerical simulations on the anaerobic digestion flow field for all 10 working conditions. The results were exported after the calculations converged and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns of multiple surfaces.

[0097] The numerical simulation setup includes:

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

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

[0100] The main phase is the gas phase, and the secondary phase is the gas phase. The height of the gas phase is 30 mm, 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 remaining surfaces were set to static;

[0103] Convergence criteria: two conditions must be met: the torque on the impeller must be stable and the parameter residuals must be

[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 speed 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 according to 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 v is vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

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

[0108] Flow field of high solid anaerobic digestion under different rotation speed conditions Fig.10 As shown in (a), the reactor and stirring blade are as follows Fig.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, the normalized curve of cumulative flow rate distribution in Example 4 is as follows Fig.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 comprises 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 impeller with a diameter of 153 mm and is installed 80 mm from the bottom of the reactor. The pitch of the ribbon impeller is 42.5 mm.

[0112] Step 2: ANSYS Fluent is used for meshing. The relatively adaptable unstructured grid is used to mesh the entire fluid domain. Four groups of grids are divided for mesh independence test. The number of grids for subsequent numerical simulation is selected based on the simulation time and simulation effect.

[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 rheological properties of the matrix;

[0114] Step 4: The 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 perform numerical simulations on the anaerobic digestion flow field for all 10 working conditions. The results were exported after the calculations converged and post-processed using CFD-Post to collect the velocity and dead zone distribution patterns of multiple surfaces.

[0115] The numerical simulation setup includes:

[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 main 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 in the reactor, while the remaining surfaces are set to a stationary state;

[0119] Convergence criteria: two conditions must be met: the torque on the impeller must be stable and the parameter residual setting accuracy must be 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 speed 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 according to 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 v is vm / s, v is the flow velocity (m / s), and k is the hydraulic characteristic parameter;

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

[0123] Flow field of high solid anaerobic digestion under different rotation speed conditions Fig.12 As shown in (a), the reactor and stirring blade are as follows Fig.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 Fig.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 specification 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 regulation of high-solid anaerobic digestion based on flow state 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. Select the number of grids 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 rheological properties of the matrix; (4) Use CFD software to perform numerical simulation on 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) Divide the reactor flow field 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, and further divide the flow velocity interval in the reactor into multiple intervals, and draw the two-dimensional cumulative flow velocity distribution normalization curve; (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 hydraulic characteristic parameters 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 difficulty of hydraulic regulation of high-solid anaerobic digestion based on flow state dimension reduction according to claim 1, characterized in that: The organic waste treated by the high-solid anaerobic digestion process includes pig manure, straw, kitchen waste or sludge.

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

4. The method for simplifying the difficulty of hydraulic regulation 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, thermal treatment-enhanced anaerobic digestion, additive-enhanced anaerobic digestion, alkali treatment-enhanced anaerobic digestion or microwave pretreatment anaerobic digestion.

5. The method for simplifying the difficulty of hydraulic regulation 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 difficulty of hydraulic regulation 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 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, and solution accuracy settings; selecting a suitable initialization method according to the simulation conditions and iterating the calculation.

7. The method for simplifying the difficulty of hydraulic regulation 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.

Images