JP2016159214A - Contaminated soil purification simulation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contaminated soil remediation simulation method enabling an air supply condition to a contaminated soil to be recognized without performing an actual experiment.SOLUTION: The contaminated soil remediation simulation method is provided for optimizing, using a treating apparatus, supply amount of air to be supplied to aerobic microbes for decomposing contaminant in contaminated soil when a perforated pipe comprising a through-hole penetrating inside and outside of the pipe is inserted into a microbe-containing contaminated soil in which a contaminated soil and aerobic microbes for decomposing contaminant in the contaminated soil are mixed, then, air in the perforated pipe is sucked or air is supplied into the perforated pipe, thereby supplying air to the microbes in the microbe-containing contaminated soil for remediation of the contaminated soil. The method comprises: a model creation step of modeling the microbe-containing contaminated soil and the perforated pipe; an air flow calculation step of calculating an air flow in the perforated pipe and in the microbe-containing contaminated soil which are modeled by the model creation step; and an oxygen density calculation step of calculating oxygen density in the microbe-containing contaminated soil based on the air flow obtained in the air flow calculation step.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a contaminated soil purification simulation method, and more particularly to a contaminated soil purification simulation method for optimizing the amount of air supplied to a biopile when the contaminated soil is purified by a biopile.

  Conventionally, a microorganism-containing contaminated soil is prepared by mixing contaminated soil and aerobic microorganisms that decompose the pollutants in the contaminated soil, and the microorganism-containing contaminated soil is embanked. To activate the activity of microorganisms in the contaminated soil containing microorganisms by inserting a pipe into the pipe and supplying air to the pipe or sucking the air in the pipe with a pump attached to the pipe There is known a contaminated soil purification device for purifying contaminated soil.

JP 2006-255633 A JP, 2014-034028, A

However, in order to efficiently purify the contaminated soil, it is necessary to uniformly supply air to the microorganisms contained in the contaminated soil and activate the activities of the microorganisms. On the other hand, in order to uniformly supply air into the contaminated soil, there are many factors such as the embankment of the contaminated soil, the insertion position of the pipe, the position and diameter of the holes provided in the pipe, the number of holes, and the capacity of the pump. Therefore, there is a problem that it takes a lot of labor and time to grasp the optimum combination by an actual experiment.
Therefore, an object of the present invention is to provide a contaminated soil purification simulation apparatus that makes it possible to find the supply condition of air to the contaminated soil without performing an actual experiment.

As a contaminated soil purification simulation method to solve the above-mentioned problem, a through-hole penetrating inside and outside the pipe is formed in the contaminated soil containing microorganisms, which is a mixture of contaminated soil and aerobic microorganisms that decompose the contaminants in the contaminated soil. Supplied with microorganisms when purifying contaminated soil by supplying air to microorganisms in contaminated soil containing microorganisms by inserting the perforated pipe provided and sucking air in the perforated pipe or supplying air into the perforated pipe A simulation method for contaminated soil purification for optimizing the supply amount of air to be processed by a processing device, wherein a model generation step for modeling microorganism-containing contaminated soil and a perforated pipe, and a perforation modeled by the model generation step An air flow calculation step for calculating the air flow in the pipe and in the microorganism-containing contaminated soil, and in the microorganism-containing contaminated soil based on the air flow obtained in the air flow calculation step. The oxygen concentration calculation step is used to calculate the oxygen concentration to be obtained, so that the conditions such as the diameter of the perforated pipe, the size and position of the through hole, and the air in the perforated pipe are sucked in to supply the contaminated soil containing microorganisms. Or conditions, such as the supply amount of air when supplying air in a perforated pipe | tube, can be optimized based on the supply amount of oxygen.
As another form of the polluted soil purification simulation method, the pipe wall of the perforated pipe is modeled as one surface, so the air flow in the perforated pipe and in the microorganism-containing contaminated soil is calculated in the air flow calculation step. This makes it easier to set the boundary conditions.
Further, as another form of the contaminated soil purification simulation method, a region having a predetermined length is distributed along the axis of the perforated pipe, and the region having the predetermined length is modeled as a through hole of the perforated pipe. The through-hole provided in the pipe can be easily set.
As another form of the contaminated soil purification simulation method, a crushed stone layer is provided between the perforated pipe and the microorganism-containing contaminated soil, the crushed stone layer is modeled in the model generation step, and the crushed stone layer in the air flow calculation step. Since the air flow is calculated, it is possible to perform a simulation in a state in which the through hole of the perforated pipe is not affected by, for example, clogged soil containing microorganisms.

It is a block diagram which shows one Embodiment of a contaminated soil purification simulation apparatus. It is a block diagram which shows one Embodiment of a contaminated soil purification simulation apparatus. It is a figure which shows a contaminated soil purification apparatus. It is the figure which modeled the contaminated soil purification apparatus and biopile. It is a figure which shows the cut surface in alignment with the axis of a connection pipe in FIG. 3, and the cut surface in alignment with the axis of a perforated pipe. It is an enlarged view in the boundary part set as a suction part of a perforated pipe. It is a figure which shows transmission of the physical quantity in the boundary of a perforated pipe and a crushed stone layer. It is a figure which shows transmission of the physical quantity in the boundary of a crushed stone layer and a biopile. It is a flowchart which shows the process of a contaminated soil purification simulation apparatus. It is a figure which shows the result of having investigated the influence of the flow of the air in a biopile by the difference in the setting of an inhalation part. It is a figure which shows the time change of the oxygen concentration obtained by actual experiment. It is a figure which shows a simulation result when it sets to oxygen consumption rate coefficient (lambda) = 0.5 / day. It is a figure which shows the simulation result of the time change of the oxygen concentration in the center part of a biopile. It is a figure which shows the simulation result of oxygen concentration when the suction speed by a pump is changed.

1 and 2 are block diagrams showing the configuration of the contaminated soil purification simulation apparatus 1. FIG. 3 is a diagram showing an outline of the contaminated soil purification apparatus 50 to be analyzed by the contaminated soil purification simulation apparatus 1.
The contaminated soil purification simulation apparatus 1 supplies air to a microorganism-containing contaminated soil (hereinafter referred to as biopile) 51 to which the contaminated soil purification apparatus 50 used for purifying the contaminated soil as shown in FIG. 3 is applied. In order to purify the contaminated soil most efficiently, the configuration of the contaminated soil purification device 50, for example, the capacity of the pump 53 with respect to the embankment amount of the biopile 51, the diameter of the perforated pipe 55, and the peripheral wall of the perforated pipe 55 are formed. It is intended to easily obtain the optimum conditions for the through holes 58 to be formed and the quantity and position of the through holes 58.

  The contaminated soil purification simulation device 1 is a processing device constituted by a so-called computer, and includes a CPU as arithmetic means provided as hardware resources, ROM and RAM as storage means, an input / output interface as communication means, and the like. Prepare. The CPU executes processing to be described later according to the simulation program stored in the storage means. The contaminated soil purification simulation apparatus 1 is connected to an input means 2 such as a keyboard, a mouse, or a magnetic or optical drive, and an output means 3 such as a monitor. Further, the simulation program causes the contaminated soil purification simulation device 1 configured as a computer to operate as each unit described later.

  Here, the contaminated soil purification apparatus 50 to be analyzed by the contaminated soil purification simulation apparatus 1 will be described. As shown in FIG. 3, the contaminated soil purification apparatus 50 is inserted into the biopile 51, a sheet 52 that prevents outflow of contaminants to the ground when the biopile 51 is embanked, a pump 53 as an intake means, and the like. A perforated pipe 55 having a through-hole penetrating the inside and outside of the pipe, a deodorizing device 56 for deodorizing the air sucked by the pump 53 and discharging it to the outside, and rainwater entering the embanked biopile 51 A waterproof sheet (not shown) for prevention is provided.

  The biopile 51 is configured by embedding a contaminated soil containing microorganisms in a predetermined shape, in which contaminated soil and aerobic microorganisms that decompose the contaminants in the contaminated soil are mixed. The biopile 51 is composed of, for example, contaminated soil contaminated with fuel oil (jet fuel, gasoline, light oil, heavy oil, etc.) or machine oil (lubricant oil, etc.), and degrading bacteria (for example, petroleum degrading bacteria) that decompose these oils. And a microorganism-containing contaminated soil in which a nutrient salt, compost, and the like are kneaded by a soil kneading apparatus (not shown).

As shown in FIG. 3, the perforated pipe 55 is formed in an annular shape by combining a straight pipe 61 and a curved pipe 62. The straight pipe 61 is formed with a plurality of through holes 58 penetrating from the inner circumference side to the outer circumference side in the entire pipe wall, and constitutes an inhalation section 60 for inhaling air contained in the biopile 51. One end of the connecting pipe 54 is connected to one of the straight pipes 61 so as to penetrate therethrough. A pump 53 is connected to the other end side of the connecting pipe 54. Then, by driving the pump 53, the air in the connecting pipe 54 and the perforated pipe 55 can be sucked. That is, the through hole 58 provided in the perforated tube 55 functions as an inlet for sucking air from the biopile 51.
A crushed stone layer 59 is provided around the perforated tube 55 so that the biopile 51 does not block the through hole 58. Note that the crushed stone layer 59 is not essential, but if the crushed stone layer 59 is not provided, the through hole 58 may be blocked by the biopile 51, and the intake efficiency of the pump 53 may be reduced. Therefore, by providing the crushed stone layer 59 around the perforated tube 55, not only can the clogging of the through-hole 58 be prevented, but also air from the inside of the biopile 51 can be evenly sucked. The pump 53 is configured to supply air from the biopile surface 51 a into the biopile 51 by connecting the suction port side to the connecting pipe 54 and sucking air in the perforated pipe 55.

Returning to FIG. 1, the configuration of the contaminated soil purification simulation apparatus 1 will be described. In the present embodiment, the contaminated soil purification apparatus 50 is treated as three-dimensional, but for convenience of explanation, each dimension for the flow velocity Ug, pressure Pg, and oxygen concentration Co2 in each of the formulas (1) to (5) in the following explanation. Display and description using are omitted.
The contaminated soil purification simulation apparatus 1 includes a preprocessing unit 10, an arithmetic processing unit 20, and a postprocessing unit 30. The pretreatment means 10 sets various data used for the calculation for simulating the air flow and the oxygen supply state in the biopile 51. As shown in FIG. 2A, the preprocessing unit 10 includes a data reading unit 11, a model generation unit 12, a lattice generation unit 13, and a boundary condition setting unit 14, and the shape to be analyzed and the mesh division Generate data such as (element division), material definition, boundary condition definition.

The data reading unit 11 reads various calculation data input via the input unit 2.
The calculation data includes, for example, property value data, element division data, initial condition data, and boundary condition data. The physical property value data includes an air permeability coefficient ratio Krg and an intrinsic permeability K indicating the physical property values of the biopile 51 and the crushed stone layer 59 to be analyzed, an air density ρg, a viscosity coefficient μg, a gas saturation Sg, and a soil porosity. This is data in which information on physical property values such as φ, substrate concentration S, volumetric gas phase rate θg, effective diffusion coefficient De, oxygen consumption rate coefficient λ, and gravitational acceleration g is collectively recorded. The element division data is data in which information for defining a division method for dividing the shape modeled by the model generation unit 12 into a plurality of small elements by the lattice generation unit 13 is recorded. The initial condition data is data in which information for setting a flow velocity and pressure as initial conditions in the biopile 51 and the perforated pipe 55 is recorded. Specifically, the initial state of the air in the perforated pipe 55, the biopile 51 and the crushed stone layer 59, the data for setting the flow velocity Ug and the pressure Pg, and the distribution of the oxygen concentration Co2 of the air in the biopile 51 are shown. Data to be set. The boundary condition data is data in which information for setting the internal boundary condition and the external boundary condition in the boundary condition setting unit 14 is recorded. Details will be described later.

The model generation unit 12 models the analysis target based on the shape data of the analysis target created on the computer by drawing software such as CAD. The shape data of the contaminated soil purification apparatus 50 is created in three dimensions, and is modeled on a predetermined three-dimensional coordinate system by the model generation unit 12.
FIG. 4 is a diagram in which the contaminated soil purification device 50 and the biopile 51 shown in FIG. 3 are modeled by the model generation unit 12. As shown in the figure, in the contaminated soil purification apparatus 50 and the biopile 51, the shape of the perforated pipe 55 including the biopile 51, the crushed stone layer 59, and the connecting pipe 54 is individually modeled as model data. In the modeling of the present embodiment, the sheet 52 and the deodorizing device 56 are omitted. In addition, the tube wall 55A serving as a boundary between the biopile 51 and the perforated tube 55 is represented as one surface that does not distinguish between the inner peripheral surface and the outer peripheral surface. Therefore, as shown in FIGS. 5A and 5B, the tube wall 55A of the perforated tube 55 is approximated to a straight line in a sectional view. The actual perforated tube 55 is provided with a plurality of through-holes 58, but the plurality of through-holes 58 are not directly modeled, and the diameter and the hole diameter of the through-holes 58 are determined according to boundary conditions described later. Express quantity and hole location.

  The lattice generation unit 13 reads all model data modeled by the model generation unit 12 and generates a lattice for dividing the model data into a plurality of small elements having a predetermined shape. In the present embodiment, in order to treat the analysis target as three-dimensional, each model data in the perforated pipe 55 including the biopile 51, the crushed stone layer 59, and the connecting pipe 54 is divided into, for example, tetrahedral small elements. The shape of the small element is not limited to a tetrahedron, but may be another three-dimensional shape such as a hexahedron.

Specifically, the boundary condition setting unit 14 includes an external boundary condition setting unit 15 and an internal boundary condition setting unit 16, and external boundary conditions and internal boundaries are added to the lattice points of the model data generated by the lattice generation unit 13. Set conditions.
The external boundary condition setting unit 15 includes an open end surface 54A to which the sheet 52 of the biopile installation surface, the biopile surface 51a, the connection pipe 54 exposed from the biopile 51 and the pump 53 of the connection pipe 54 shown in FIGS. Set the boundary condition to. Note that the open end surface 54A means an entrance to the inner circumferential side space in the actual connecting pipe 54.
No flow (zero flow rate) is set for the sheet 52. An atmospheric pressure is set on the biopile surface 51a. A driving force of the pump 53 is set on the open end surface 54 </ b> A of the connecting pipe 54. 4 and 5A, a part of the connecting pipe 54 is exposed to the outside from the biopile 51 and the rest is inside the biopile 51, so that the connecting pipe 54 is inside the biopile 51. For the remaining part, boundary conditions are set by the internal boundary condition setting unit 16.

5A shows a cut surface A along the axis of the connecting tube 54 in FIG. 4, and FIG. 5B shows a cut surface B along the axis of the perforated tube 55 in FIG.
The internal boundary condition setting unit 16 includes boundary conditions for the boundary surface 550 between the perforated pipe 55 and the crushed stone layer 59, the boundary surface 551 between the crushed stone layer 59 and the biopile 51, and the connecting pipe 54 located in the biopile 51. Set. As shown in FIGS. 5A and 5B, the wall 55A of the perforated pipe 55 serving as the boundary between the perforated pipe 55 and the crushed stone layer 59 is ignored by the model generation unit 12 in the thickness of the pipe wall 55A. It is modeled as one boundary surface 550, and the influence of negative pressure generated in the perforated pipe 55 by driving the pump 53 is transmitted to the crushed stone layer 59 through this boundary surface 550. The boundary surface 550 is a common part between the space for calculating the air flow in the perforated pipe 55 and the space for calculating the air flow in the crushed stone layer 59. A plurality of through holes 58 are formed in the actual perforated pipe 55, and air in the crushed stone layer 59 is sucked into the perforated pipe 55 through the through holes 58. In the boundary surface 550 that models 55, information on the size, position, and quantity of the through hole 58 provided in the tube wall 55A of the perforated tube 55 is not expressed. Therefore, in order to express the influence of the size, position, and quantity of the through hole 58 of the perforated tube 55, boundary conditions are set as described below.

For example, when a plurality of through-holes 58 are provided in the perforated tube 55, a method of distributing them at equal intervals in the axial direction of the perforated tube 55 and the circumferential direction of the tube wall 55A with a predetermined hole diameter as a reference is conceivable. However, in this embodiment, the distribution state of the through-holes 58 in the circumferential direction is not taken into consideration, and it is approximated as being distributed only in the axial direction of the perforated pipe 55, and the presence or absence of the through-holes 58 is set as a boundary condition. To do. Specifically, as shown in FIG. 5 (b), the straight pipe 61 of the perforated pipe 55 is divided into a plurality of annular regions of a predetermined length along the axis, for example, as shown by a cross hatch in the figure. A plurality of annular regions are selected and distributed as the suction part 60. That is, the entire suction part 60 is modeled as a through hole 58. Therefore, the lattice points located on the suction portion 60 among the lattice points generated by the lattice generation unit 13 are handled as the through holes 58.
That is, as shown in FIGS. 5B and 6, a range of a predetermined length is distributed as the suction portion 60 provided with the through-hole 58 along the axial direction of the straight pipe 61 of the perforated pipe 55, and the rest This portion is distributed as the wall portion 64 without the through hole 58. Thereby, the suction force by the pump 53 in the perforated tube 55 is transmitted to the crushed stone layer 59 side through the suction part 60. The wall 64 is set as a wall where no suction force from the pump 53 is transmitted to the crushed stone layer 59, and a boundary condition of no flow (zero flow velocity) is set.
Therefore, by changing the distribution and range of the suction portion 60 described above, it is possible to express the influence of the size, position, and quantity of the through holes 58 in the perforated tube 55.

FIG. 6 is an enlarged view of the boundary portion set as the suction portion 60 of the perforated pipe 55. In the figure, the broken line indicates the boundary surface 550, the grid points where the black circles A1 and A2 and the black circles A5 and A6 are set as the wall portion 64, and the white circles A3 and A4 and the white circles A7 to A9 are set as the suction portion 60. Shows the point.
Since the white circles A3 and A4 and the white circles A7 to A9 are lattice points set as the suction portion 60, they are lattice points calculated in the calculation of the flow in the perforated pipe 55 and the flow in the crushed stone layer 59. It is also a grid point calculated in the calculation. Therefore, at the lattice points of the white circles A3 and A4 and the white circles A7 to A9, the flow velocity Ug and the pressure Pg obtained by calculating the flow in the perforated tube 55 and the flow velocity obtained by calculating the flow in the crushed stone layer 59 are obtained. Both Ug and pressure Pg are set.

  FIG. 7 is a diagram illustrating transmission of physical quantities at the boundary between the perforated pipe 55 and the crushed stone layer 59. The triangular points in the figure indicate lattice points where physical quantities such as the flow velocity Ug and pressure Pg when calculating the flow in the perforated pipe 55 are set, and the square points indicate when calculating the flow in the crushed stone layer 59. The lattice points where physical quantities such as the flow velocity Ug and the pressure Pg are set are shown. Then, in the internal boundary condition setting means, when calculating the flow in the perforated pipe 55 by the arithmetic processing means 20 described later, the white circles A3 and A3 shown in FIG. At the positions of A4 and white circles A7 to A9, the flow velocity Ug and the pressure Pg obtained by calculation of the flow in the crushed stone layer 59 are set as shown in FIG. Further, when calculating the flow in the crushed stone layer 59, the positions of the white circles A3 and A4 and the white circles A7 to A9 shown in FIG. The boundary conditions are set so as to use the flow velocity Ug and the pressure Pg obtained by the calculation of the flow. Thus, by giving the flow interface at the boundary between the perforated tube 55 and the crushed stone layer 59 as an internal boundary condition, the flow in the perforated tube 55 and the flow in the crushed stone layer 59 are caused by the arithmetic processing means 20 described later. Can be calculated directly at the same time.

  Further, by distributing the plurality of through holes 58 provided in the perforated pipe 55 as the suction portion 60 and setting boundary conditions, the hole diameter of the through hole 58 is optimized when the supply of oxygen to the biopile 51 is optimized. And a change in the distribution in the axial direction can be simulated without re-modeling by the model generation unit 12, so various types of settings relating to the setting of the contaminated soil purification device 50 when optimizing the supply of oxygen to the biopile 51 are performed. The time required to obtain the conditions can be shortened.

FIGS. 8A and 8B are diagrams illustrating transmission of physical quantities at the boundary between the crushed stone layer 59 and the biopile 51. Square points in the figure indicate lattice points at which physical quantities such as flow velocity Ug and pressure Pg when calculating the flow in the crushed stone layer 59 are set, and inverted triangle points indicate when the flow in the biopile 51 is calculated. The lattice points where physical quantities such as the flow velocity Ug and the pressure Pg are set are shown. In addition, lattice points B1 to B9 in the figure indicate lattice points on the boundary surface 551 between the crushed stone layer 59 and the biopile 51. As shown in the figure, in the internal boundary condition setting unit 16, the internal boundary between the crushed stone layer 59 and the biopile 51 is set in the same manner as the setting of the internal boundary condition between the perforated pipe 55 and the crushed stone layer 59. Set conditions. That is, at the lattice points B1 to B9 on the boundary surface 551 between the crushed stone layer 59 and the biopile 51, the flow velocity Ug and pressure Pg obtained by calculating the flow in the crushed stone layer 59 and the flow in the biopile 51 are calculated. Both the obtained pressure Pg and the flow velocity Ug calculated based on the pressure Pg are set. When the flow in the crushed stone layer 59 is calculated by the calcified bed flow calculating section 22 of the arithmetic processing means 20 described later, the flow in the biopile 51 is calculated as shown by the broken line in FIG. When the flow in the biopile 51 is calculated using the pressure Pg on the boundary surface 551 obtained by the above, it is obtained by calculating the flow in the crushed stone layer 59 as shown by the broken line in FIG. The flow velocity Ug and the pressure Pg on the boundary surface 551 are set to be used.
The flow velocity Ug calculated based on the pressure Pg obtained by the calculation of the flow in the biopile 51 described above is the pressure Pg set at the lattice points B1 to B9, and the lattice points B1 to B9 and the lattice points. It is obtained by differentiating B1 to B9 by the distance from the adjacent lattice point on the biopile 51 side and multiplying by the air permeability coefficient in the biopile 51. Thus, by giving the flow at the boundary between the crushed stone layer 59 and the biopile 51 as an internal boundary condition, the flow in the crushed stone layer 59 and the flow in the biopile 51 can be directly correlated and calculated at a time.

  As described above, by setting internal boundary conditions between the perforated pipe 55 and the crushed stone layer 59, and between the crushed stone layer 59 and the biopile 51, an experiment is actually performed as in the past for the purpose of use in the simulation. To eliminate the necessity of obtaining specific numerical values for setting the boundary conditions between the perforated tube 55 and the crushed stone layer 59 and between the crushed stone layer 59 and the biopile 51.

As shown in FIG. 2B, the arithmetic processing means 20 includes a perforated pipe flow calculation unit 21, a crushed stone flow calculation unit 22, a biopile flow calculation unit 23, and an oxygen concentration calculation unit 24. And the flow of air in the biopile 51, the crushed stone layer 59, the perforated pipe 55, and the oxygen concentration Co2 in the biopile 51 based on the data processed by the pretreatment means 10. Calculate the change.
Hereinafter, calculation of the air flow by the arithmetic processing means 20 and calculation of the oxygen concentration Co2 in the biopile 51 will be described.

The perforated pipe flow calculation unit 21 calculates the air flow in the perforated pipe 55 based on the Naviestokes equation shown in the following formula (1).

The crushed stone layer flow calculation unit 22 calculates the flow of air in the crushed stone layer 59 based on the Brinkman equation shown in the following equation (2).
The body force F in the above formulas (1) and (2) is a force acting only in the vertical direction and is represented by the following formula (A).

The biopile flow calculation unit 23 calculates the air flow in the biopile 51 based on Darcy's equation shown in the following equation (3). The Darcy equation shown below is called Darcy's law.

The above formulas (1) and (2) are calculated together with the continuous formula shown in the following formula (4).

In the calculation of the air flow in the perforated pipe 55 according to the above equation (1), the suction portion obtained by the Brinkman equation of the equation (2) by setting the above internal boundary condition at the boundary with the crushed stone layer 59. The air flow rate Ug at 60 is set as the air flow rate Ug of the suction part 60 in the equation (1).
Further, in the calculation of the air flow in the crushed stone layer 59 by the above equation (2), the suction portion obtained by the Navier-Stokes equation of the equation (1) by setting the internal boundary condition at the boundary on the perforated tube 55 side. The air flow rate Ug of 60 is set as the air flow rate Ug of the suction part 60 in the equation (2).
Furthermore, the air flow velocity Ug at the boundary surface 551 determined by the Darcy equation of the equation (3) is set to the boundary with the biopile 51 in the equation (2) by setting the internal boundary condition at the boundary on the biopile 51 side. It is set as the air flow velocity Ug on the surface 551.
Further, in the calculation of the air flow in the biopile 51 according to the above equation (3), the flow velocity Ug of the air at the boundary surface 551 determined by the Brinkman equation of the equation (2) by the setting of the above internal boundary condition is It is set as the air flow velocity Ug at the boundary surface 551 with the biopile 51 in the equation (3).

The oxygen concentration calculation unit 24 is based on the air flow distribution calculated by the perforated pipe flow calculation unit 21, the crushed stone flow calculation unit 22, and the biopile flow calculation unit 23 according to the following equation (5). The change of the oxygen concentration Co2 in the biopile 51 is calculated in time series by solving the advection diffusion equation shown.
In the formula (5), the left side shows the change in the oxygen concentration Co2 with the air flow, and the right side shows the oxygen consumption by the microorganisms contained in the biopile 51.

Note that the fluid density and the fluid viscosity coefficient in the equations (1) to (5) are not changed, and the values of the physical property value data read by the data reading unit 11 are input. Air permeability coefficient ratio Krg and intrinsic permeability K, air density ρg, viscosity coefficient μg, gas saturation Sg, soil porosity φ, substrate concentration S, volumetric gas phase rate in the above formulas (1) to (5) Specific values are set for θg, effective diffusion coefficient De, oxygen consumption rate coefficient λ, and gravitational acceleration g. Specifically, 1.0 kg / m ³ is input to the air density ρg, and 1 × 10 ⁻⁵ Pa · s or the like is input to the air viscosity coefficient μg. Also, the air permeability coefficient ratio Krg, intrinsic permeability K, air density ρg, viscosity coefficient μg, gas saturation Sg, soil porosity φ, substrate concentration S, volumetric gas phase rate θg, effective diffusion coefficient De, oxygen consumption Similarly, a specific numerical value is set for the speed coefficient λ.

  The post-processing unit 30 outputs the flow state in the perforated pipe 55, the crushed stone layer 59 and the biopile 51, and the distribution state of the oxygen concentration Co2 in the biopile 51 obtained by the calculation of the arithmetic processing unit 20. Data displayed on the monitor as means 3 is processed. For example, on the modeled shape data of the perforated pipe 55, the crushed stone layer 59, and the biopile 51, as shown in FIG. 10, streamlines indicating the flow of air, as shown in FIG. 12, and oxygen concentration Co2 as shown in FIG. FIG. 13 and FIG. 14 are processed so that they can be displayed on the monitor, and the processing results are output to the monitor.

FIGS. 9A and 9B are flowcharts showing processing by the contaminated soil purification simulation apparatus 1. The simulation processing operation will be described below with reference to FIG.
S101: Reading calculation data is executed. Specifically, the embankment shape data of the biopile 51, the shape data of the contaminated soil purification device 50, and boundary conditions are read and set.
S102: Setting calculation conditions. The process in S102 is executed as shown in S201 to S203.
S201: Model data is generated based on the shape data of the biopile 51 and the contaminated soil purification apparatus 50.
S202: Divide the generated model data into a plurality of small elements to generate a calculation grid.
S203: An internal boundary condition and an external boundary condition are set based on the input calculation data.
S103: The flow velocity Ug and pressure Pg of the air in the biopile 51, the crushed stone layer 59, and the perforated pipe 55 are calculated by the equations (1) to (4).
S104: The flow velocity Ug distribution and pressure Pg distribution of the air in the biopile 51, the crushed stone layer 59, and the perforated pipe 55 are output.
S105: Oxygen concentration calculation conditions are set. Specifically, the flow velocity Ug distribution, the pressure Pg distribution, the oxygen consumption amount, and the concentration boundary conditions of the air in the biopile 51, the crushed stone layer 59, and the perforated pipe 55 output in S104 are set.
S106: The oxygen concentration Co2 in the biopile 51, the crushed stone layer 59, and the perforated pipe 55 is calculated at a predetermined time step, and the oxygen concentration Co2 in the biopile 51, the crushed stone layer 59, and the perforated pipe 55 is calculated. Calculate the time change of.
S107: The calculation result of the oxygen concentration Co2 is output.
S108: The distribution state of the oxygen concentration Co2 is determined. Specifically, it is determined whether the supply of the oxygen concentration Co2 in the biopile 51 is sufficient or excessive. For example, in the determination method, the distribution of oxygen concentration Co2 displayed on the monitor by the processing of the post-processing means 30 and the change over time are determined by visual recognition of the operator. If it is determined that the optimum condition is obtained, the process proceeds to S109 and the simulation is terminated. If the optimum condition is not obtained, the process proceeds to S110.
S110: Input a change in calculation conditions for simulation. Specifically, the internal boundary condition setting definition by the internal boundary condition setting unit 16 is changed, or the external boundary condition setting definition by the external boundary condition setting unit 15 is changed. For example, the scale of the biopile 51, the suction capacity of the pump 53, the diameters of the perforated pipe 55 and the connecting pipe 54, and the distribution of the suction portion 60 in the perforated pipe 55 are changed. By the input in S110, the same data set in S102 is overwritten. Then, a new simulation is executed according to the conditions input in S110. After inputting the simulation conditions, S102 to S108 are repeated, and when the optimum condition is obtained, the process proceeds to S109 and the simulation is terminated.

[Example]
In the physical property value data, actual measured values shown in Table 1 and Table 2 in FIG. 11 were set as the physical property values of the soil in the biopile 51. Note that the intake speed of the pump 53 obtained by actual experiments and the physical property values of the biopile 51 shown in Tables 1 and 2 in FIG. 11 are the values obtained in the experiments conducted for the purpose of obtaining boundary conditions used in the simulation. Rather, the values are used for simulation under the same conditions as in actual experiments. In the initial condition data, the air pressure in the biopile 51, the crushed stone layer 59, and the perforated pipe 55 was set to atmospheric pressure, no flow (no flow rate), and the oxygen concentration Co2 was set to 21%. As boundary condition data, the air pressure on the biopile surface 51a was set to atmospheric pressure and the oxygen concentration was 21% as the external boundary condition. The intake speed of the pump 53 used in the actual experiment was set on the open end face 54A of the connecting pipe 54 at the position where the pump 53 is installed. Specifically, 220 L / min was set as the external boundary condition as the suction force of the pump 53.
As an internal boundary condition, the flow velocity Ug and the pressure Pg when the air flow of the perforated tube 55 is calculated are calculated at the boundary between the perforated tube 55 and the crushed stone layer 59 when the air flow of the crushed stone layer 59 is calculated. The flow rate Ug and the pressure Pg are set. Further, the flow velocity Ug and the pressure Pg when calculating the air flow of the crushed stone layer 59 are set to be the flow velocity Ug and the pressure Pg when calculating the air flow of the perforated tube 55.
Further, at the boundary between the crushed stone layer 59 and the biopile 51, the flow velocity Ug and pressure Pg when the air flow of the crushed stone layer 59 is calculated are the flow velocity Ug and pressure when the air flow of the biopile 51 is calculated. Set to be Pg. Further, the flow velocity Ug and the pressure Pg when calculating the air flow of the biopile 51 are set to be the flow velocity Ug and the pressure Pg when calculating the air flow of the crushed stone layer 59.
Then, the validity of the simulation method according to the present embodiment was evaluated by comparing the result obtained in the actual experiment with the result obtained by the simulation by the above-described method.

First, in order to investigate the influence of the setting of the suction part 60, the air into the biopile 51 when the suction part 60 is set to the connecting pipe 54 and the perforated pipe 55 and when only the perforated pipe 55 is set. The flow was simulated. The results are shown in FIGS. 10 (a) and 10 (b). 10A and 10B, since the perforated pipe 55 has a symmetrical shape with the connecting pipe 54 in between, the result is shown by a single cross section along the axis of the connecting pipe 54. Moreover, the broken line shown in the figure has shown the streamline, respectively. When the suction part 60 is set in the connecting pipe 54 and the perforated pipe 55, the flow of air is short-circuited at the boundary between the biopile surface 51a and the connecting pipe 54, as indicated by the flow line in FIG. It can be seen that the negative pressure generated in the connection pipe 54 by 53 is dissipated and does not propagate in the depth direction of the perforated pipe 55 extending into the biopile 51, and air is not taken in from a position far from the connection pipe 54 side.
On the other hand, when the suction part 60 is set only in the perforated pipe 55, the air that has entered from the biopile surface 51a moves through the biopile 51 as shown by the streamline in FIG. It is guided to the open end face 54 </ b> A of the connecting pipe 54 through the perforated pipe 55 embedded therein. Thus, it has been found that the flow of air to be ventilated in the biopile 51 can be controlled only by changing the setting of the suction part 60. Therefore, according to the method according to the present embodiment, various air flows can be simulated only by changing the boundary condition for the perforated pipe 55.

  Next, the influence of the oxygen consumption rate on the biopile 51 on the optimum suction amount was examined. Purification of oil-contaminated soil by microorganisms contained in the biopile 51 can be regarded as an oxidation reaction. In order to maintain the decomposition rate of oil by microorganisms, it is necessary to supply appropriate oxygen into the biopile 51. FIG. 11A is a diagram showing the time change of the oxygen concentration Co2 obtained by actual experiments. As shown in the figure, from the start of the experiment to the 40th day, oxygen consumption in the biopile 51 is recognized as the oil is microbially decomposed. From the 40th day onward, it is considered that the oxygen concentration was increased and the oxygen concentration was increased due to the fact that the amount of substrate oil for microorganisms was decreased and the number of highly active microorganisms was decreased.

  In view of this, the oxygen consumption rate λ was inversely analyzed from the oxygen concentration profile from the start of the actual experiment to the 40th, and the optimum atmospheric suction speed exceeding the oxygen consumption rate in the biopile 51 was evaluated. Specifically, with the oxygen consumption rate coefficient λ calculated from the oxygen concentration profile shown in FIG. 11 (a) as an unknown, the oxygen concentration calculated from the numerical simulation matches the experimental value of FIG. 11 (a). The oxygen consumption rate coefficient λ was identified. Specifically, in order to obtain the oxygen consumption rate from the oxygen concentration profile of the experimental result (FIG. 11A), the oxygen concentration Co2 calculated by simulation with the oxygen consumption rate coefficient λ in Equation (4) as an unknown number. However, the oxygen consumption coefficient λ was identified so as to agree with the experimental result shown in FIG. At this time, as the substrate concentration S in the formula (4), the oil concentration in the biopile 51 shown in Table 1 of FIG. 11B was used.

FIG. 12 shows the simulation results when the oxygen consumption rate coefficient λ = 0.5 / day (day). 12A shows the change in the oxygen concentration Co2 immediately after the start of the experiment, FIG. 12B shows the change in the oxygen concentration Co2 on the third day, and FIG. 12C shows the change in the oxygen concentration Co2 on the 14th day.
As shown in FIG. 12 (a), immediately after the start of the experiment, the oxygen concentration Co2 in the biopile 51 is 21%, which is the same as that in the atmosphere. As the process proceeds, oxygen in the biopile 51 is consumed, and as shown in FIG. 12B, the oxygen concentration Co2 at the center of the biopile 51 is reduced to about 5%. Thereafter, as the decomposition of the oil proceeds, the activity of decomposing the oil by the microorganisms decreases as the substrate concentration S (oil concentration) decreases. As a result, the amount of oxygen consumed is reduced. As a result, the amount of oxygen supplied into the biopile 51 is increased by the air supplied from the biopile surface 51a, and as shown in FIG. The oxygen concentration Co2 is increased.

  FIG. 13 shows the time change of the oxygen concentration Co2 at the center of the biopile 51 in the simulation. The broken line shown in the figure is the monitoring result of the oxygen concentration Co2 in the actual experimental result. The solid line is the result of simulation. As shown in FIG. 13, the time change of the oxygen concentration Co2 by simulation can be predicted and calculated in accordance with the change of the oxygen concentration Co2 obtained by an actual experiment. When equation (4) is used as a model of oxygen consumption accompanying the decomposition of microbial oil, the calculation result closest to the experimental result when the oxygen consumption rate coefficient λ = 0.5 / day as the model parameter is became.

  FIG. 14 shows the simulation results when the oxygen consumption coefficient λ = 0.5 / day is set and the suction speed by the pump 53 is changed to four types of 110 L / min, 220 L / min, 440 L / min, and 880 L / min. Show. As shown in the figure, it was confirmed that the oxygen concentration Co2 in the biopile 51 is different by changing the suction speed of the pump 53, that is, the operation capability of the pump 53. That is, although the oxygen concentration Co2 in the biopile 51 depends on the amount of air sucked from the biopile surface 51a, the oxygen concentration Co2 is associated with the decomposition of microbial oil in the biopile 51 rather than simply setting a high suction amount. In order to save energy, such as suction devices such as the pump 53, power, and their electricity charges, it is preferable to design the suction amount to be the minimum necessary so as to compensate for the oxygen consumption. It has been confirmed that the simulation method according to the present embodiment is effective as one method for solving the problem.

  In the above-described embodiment, the Brinkman equation expressed by the equation (2) is applied to the calculation of the flow in the crushed stone layer 59. However, the Brinkman equation expressed by the equation (2) is expressed by the equation (3). An equation applied to a flow field intermediate between a flow field to which Darcy's equation is applied and a flow field to which the Navier-Stokes equation represented by Equation (1) is applied, but Darcy's equation represented by Equation (3) May be used. That is, since the air flow in the crushed stone layer 59 can also be regarded as the air flow in the porous layer, the Darcy equation expressed by the equation (3) can also be applied in the same manner as the flow in the biopile 51. In this case, as a matter of course, a value obtained by changing the values of the air permeability coefficient ratio k and the intrinsic permeability K set when calculating the flow in the biopile 51 so as to match the physical property values in the crushed stone layer 59. Should be set.

  In the above embodiment, the perforated pipe 55 of the contaminated soil purification apparatus 50 has been described as being annular. However, the present invention is not limited to this, and shape data corresponding to the shape is read from the data reading unit 11 even if the shape is other. Simulation can be executed. Further, when modeling the perforated pipe 55, the model is made as a boundary surface 550 having no thickness on the pipe wall 55A of the perforated pipe 55, but the shape data of the read pipe wall 55A of the perforated pipe 55 is used as it is. It may be used.

  In the above embodiment, the contaminated soil purification apparatus 50 has been described as sucking the air in the biopile 51 by the pump 53. However, instead of the suction pump 53, a discharge pump is connected to the connecting pipe 54. The present invention can also be applied to a simulation of a contaminated soil purification apparatus that supplies connected and pressurized air to the biopile 51. In this case, in the definition for setting the external boundary condition of the calculation data input to the contaminated soil purification simulation apparatus 1, it is only necessary to set the flow so as to flow toward the inside of the connecting pipe 54 on the open end surface 54A of the connecting pipe 54. In this case, the through hole 58 of the perforated tube 55 functions as a discharge port for discharging the air supplied from the pump toward the biopile 51.

  In the present embodiment, the contaminated soil purification apparatus 50 has been described in a form in which the crushed stone layer 59 is provided so as to cover the perforated pipe 55 and the biopile 51 is formed so as to cover them. When the biopile 51 is formed so as to directly cover the perforated tube 55 without being provided, the flow velocity when calculating the air flow of the perforated tube 55 at the boundary between the perforated tube 55 and the biopile 51. The internal boundary conditions are set so that the Ug and pressure Pg and the flow velocity Ug and the pressure Pg when calculating the air flow of the biopile 51 are the same as each other. If the air flow in the perforated tube 55 and the biopile 51 is calculated by the equations (1) and (3), and the oxygen concentration in the biopile 51 is calculated based on the obtained air flow, There.

  In the present embodiment, the finite element method is adopted. However, the present invention is not limited to this, and other numerical analysis methods such as a difference method and a finite volume method may be used.

1 Contaminated soil purification simulation device,
10 preprocessing means, 11 data reading unit, 12 model generating unit, 13 grid generating unit,
14 boundary condition setting unit, 15 external boundary condition setting unit, 16 internal boundary condition setting unit,
20 arithmetic processing means, 21 perforated pipe flow calculation section, 22 crushed stone flow calculation section,
23 Flow calculation section in biopile, 24 oxygen concentration calculation section, 30 post-processing means,
50 contaminated soil purification equipment, 51 biopile, 52 sheets, 53 pump,
54 connecting pipe, 55 perforated pipe, 58 through hole, 59 crushed stone layer, 60 suction part,
550: 551 interface.

Claims (4)

Insert a perforated pipe with through-holes that penetrates the inside and outside of the pipe into the contaminated soil containing microorganisms, which is a mixture of contaminated soil and aerobic microorganisms that decompose the pollutants in the soil. The amount of air supplied to the microorganism when the contaminated soil is purified by supplying air to the microorganism in the microorganism-containing contaminated soil by suctioning or supplying air into the perforated pipe is optimized by the processing device. A pollution soil purification simulation method for
A model generation step for modeling the microorganism-containing contaminated soil and the perforated pipe;
An air flow calculating step for calculating an air flow in the perforated pipe and in the microorganism-containing contaminated soil modeled by the model generating step;
A contaminated soil purification simulation method, comprising: an oxygen concentration calculating step of calculating an oxygen concentration in the microorganism-containing contaminated soil based on the air flow obtained in the air flow calculating step.   The contaminated soil purification simulation method according to claim 1, wherein the model generation step models the perforated pipe wall as one surface.   The area of a predetermined length is distributed along the axis of the perforated pipe, and the area of the predetermined length is modeled as the through hole of the perforated pipe. Simulation method. Providing a crushed stone layer between the perforated pipe and the microorganism-containing contaminated soil;
The contamination according to any one of claims 1 to 3, wherein the crushed stone layer is modeled in the model generating step, and the air flow of the crushed stone layer is calculated in the air flow calculating step. Soil purification simulation method.