CN114937479B - Simulation method for predicting collaborative evolution of chemical clogging and permeability coefficient of outer-wrapped filter material - Google Patents
Simulation method for predicting collaborative evolution of chemical clogging and permeability coefficient of outer-wrapped filter material Download PDFInfo
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- 239000000126 substance Substances 0.000 title claims abstract description 128
- 239000000463 material Substances 0.000 title claims abstract description 127
- 230000035699 permeability Effects 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000004088 simulation Methods 0.000 title claims abstract description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000012856 packing Methods 0.000 claims abstract description 16
- 238000012360 testing method Methods 0.000 claims abstract description 16
- 230000000903 blocking effect Effects 0.000 claims abstract description 6
- 239000010410 layer Substances 0.000 claims description 57
- 238000001914 filtration Methods 0.000 claims description 18
- 238000009388 chemical precipitation Methods 0.000 claims description 14
- 230000003204 osmotic effect Effects 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 8
- 239000002356 single layer Substances 0.000 claims description 8
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 239000011148 porous material Substances 0.000 claims description 7
- 230000000149 penetrating effect Effects 0.000 claims description 6
- 238000011049 filling Methods 0.000 claims description 5
- 238000012946 outsourcing Methods 0.000 claims description 4
- 238000010603 microCT Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 41
- 239000006004 Quartz sand Substances 0.000 description 33
- 238000001556 precipitation Methods 0.000 description 18
- 238000002425 crystallisation Methods 0.000 description 11
- 230000008025 crystallization Effects 0.000 description 11
- 150000003839 salts Chemical class 0.000 description 7
- 239000004576 sand Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 230000035515 penetration Effects 0.000 description 5
- 238000011160 research Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 3
- 239000002689 soil Substances 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000013178 mathematical model Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000013517 stratification Methods 0.000 description 1
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- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
- G16C60/00—Computational materials science, i.e. ICT specially adapted for investigating the physical or chemical properties of materials or phenomena associated with their design, synthesis, processing, characterisation or utilisation
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2113/00—Details relating to the application field
- G06F2113/14—Pipes
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- General Engineering & Computer Science (AREA)
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- Filtering Materials (AREA)
Abstract
The invention provides a simulation method for predicting the collaborative evolution of chemical clogging and permeability coefficient of an outer-coated filter material, which comprises the following steps: measuring physical parameters of the outer filter material to calculate an initial permeability coefficient thereof; developing a test, establishing a relation between the specific surface area and the porosity of the outer-packing filter material, and determining the porosity of the outer-packing filter material when chemical clogging substances are contacted with each other and the porosity of the outer-packing filter material when the chemical clogging substances enter an external clogging stage; measuring the relation among the chemical clogging quantity, the chemical clogging speed and flow rate, the solution saturation index and the distance between the chemical clogging position and the water inlet surface of the outer wrapping filter material; dividing the filter material into n layers, and traversing to calculate the blocking amount, the porosity, the specific surface area and the permeability coefficient of each layer after chemical blocking in unit time step; judging whether the chemical clogging process is finished; and calculating the integral permeability coefficient and chemical clogging quantity of the outer-packed filter material. The invention can accurately quantify the co-evolution process of the chemical clogging and the permeability coefficient of the outer-packing filter material, thereby more truly describing the actual condition of the chemical clogging.
Description
Technical Field
The invention belongs to the technical field of chemical clogging of farmland concealed pipe drainage, and particularly relates to a simulation method for predicting the collaborative evolution of chemical clogging and permeability coefficient of an outer-wrapped filter material.
Background
The concealed pipe drainage is widely applied to a plurality of fields such as engineering geology, sponge cities, environmental protection, farmland drainage and the like. The drainage technology of the concealed pipe is to embed the pipeline with small holes or narrow slits distributed on the pipe wall into the ground, so that the water in the surrounding environment (soil, slag, solid garbage and the like) of the concealed pipe is permeated into the embedded pipeline and then is discharged to the bearing and discharging area. The outer packing filter material is a strong permeable material which is arranged around the concealed pipe to ensure the permeability of the concealed pipe and prevent the concealed pipe from being blocked. In the traditional drainage engineering, the sand gravel meeting the design specification grading is an ideal buried pipe drainage outer-coating material, can well exert the hydraulic performance of the material, and has excellent water and soil permeability resistance. However, the outer-packed filter material inevitably encounters a certain degree of clogging problem in the use process, which reduces the drainage and salt drainage efficiency of the concealed pipe, increases the maintenance cost of the concealed pipe and reduces the service life.
The clogging can be classified into physical clogging, chemical clogging and biological clogging according to the kind of clogging substances and the mechanism of occurrence of clogging. At present, many physical clogging researches are carried out on soil particle loss, and a mature prevention and control technology is provided. The occurrence of biological plugs requires specific biochemical conditions and is generally not a major factor in farmland drainage. The existing research on chemical clogging is focused on clogging caused by iron and manganese precipitation driven by oxidation-reduction reaction, and the research on clogging caused by chemical processes such as low-solubility salt crystallization precipitation and the like is less, and the research is still in the experimental research and rule summarizing stage. Studies have shown that the form of chemical precipitation in porous media has a large influence on the permeability coefficient, and studies have shown that the difference between the permeability coefficient of a homogeneous precipitation and a heterogeneous precipitation model can reach up to 3 orders of magnitude.
The influence of the clogging on the permeability coefficient of the outer-covered filter material of the drainage concealed pipe is accurately estimated, but a mathematical model for quantifying the chemical clogging of the outer-covered filter material by considering the form of low-solubility salt crystallization precipitation is not yet seen at present.
Disclosure of Invention
The invention aims to provide a simulation method for predicting the co-evolution of the chemical clogging and the permeability coefficient of an outer filter material, aiming at the defects of the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
a simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer-coated filter material comprises the following steps:
step 1, filling an outer packing filter material column, and measuring physical parameters of the filter material column to calculate an initial permeability coefficient K of the outer packing filter material 0 ；
Step 2, carrying out a test of penetrating a filter column by a chemical solution, establishing a relation between the specific surface area S of the outer filter material and the porosity phi, and determining the porosity phi when chemical clogging substances in the pores of the outer filter material are contacted with each other 1 Porosity phi of chemical plugging when entering external plugging stage 2 The method comprises the steps of carrying out a first treatment on the surface of the Then establishing a functional relation between a chemical clogging rate Rs and a flow velocity V, a solution saturation index SI and a chemical clogging position and a filter material column inlet distance x according to a test;
step 3: dividing a filter column into n layers from a water inlet surface to a water outlet surface, wherein the 1 st layer consists of a single-layer filter material at the water inlet surface of the filter column, dividing the rest filter columns into n-1 layers uniformly, and establishing the porosity phi and the chemical clogging rate R of the outer-packed filter material on the assumption that the chemical clogging rate of each layer is equal to the chemical reaction rate at the center of each layer s Relationship of time t;
step 4: calculating chemical clogging rate R of ith layer of filter material column at t time si And calculating the specific surface area S of the layer at t according to the formulas in the steps 2 and 3 it And a porosity phi it ；
Step 5: when the porosity phi calculated in step 4 it ≥φ 1 In accordance with the porosity phi at that time it And specific surface area S it Calculating the permeability coefficient of the filtering material column at the moment, if not, calculating phi it ＝φ 1 Critical chemical clogging quantity M sc1 Then, the next step is carried out;
step 6: when the porosity phi calculated in step 4 2 ≤φ it ＜φ 1 When the method is used, the external clogging factor b is measured according to the chemical clogging quantity of the filter column, and then the porosity phi at the moment is measured according to the external clogging factor b it And specific surface area S it Calculating the permeability coefficient of the filtering column at the moment; if not, calculate phi it ＝φ 2 Critical permeability coefficient K of (2) sc2 The chemical clogging amount is M sc2 Then, the next step is carried out;
step 7: when the porosity phi calculated in step 4 it ＜φ 2 When the method is used, the chemical plugging rate is directly used for calculating the chemical plugging amount to obtain an external plugging factor b, and then the permeability coefficient of the filter column is calculated according to the external plugging factor b, and then the next step is carried out;
step 8: calculating the chemical clogging quantity M under the osmotic coefficient sit Judging whether each layer of the filtering column is calculated, if not, returning to the step 4 to calculate the next layer; if yes, entering the next step;
step 9: calculating the integral permeability coefficient and chemical clogging quantity of the filtering material column at the moment, and if the filtering material column is permeable by an equal water head, calculating the current speed at the moment, wherein V=K st l, judging whether the running time is over, if so, outputting the integral permeability coefficient K s And chemical clogging amount M s The method comprises the steps of carrying out a first treatment on the surface of the If not, returning to the step 3 to calculate the next time step.
Further, the step 1 specifically includes:
filling and outsourcing filter material column with equal pressure solidity, column length L equal to thickness of outsourcing filter material layer, dividing the filter material column into n layers, measuring average particle diameter d of filter material s Initial porosity phi 0 And specific surface area S 0 To calculate the initial permeability coefficient K of the filter column 0 Wherein, the equation of the calculation of the permeability coefficient is:
in step 2, the Micro-CT is used for scanning and reconstructing the filter material column, and the relation between the specific surface area S of the outer-packed filter material and the porosity phi is established.
Further, in step 3, the relation between the porosity and the chemical plugging rate is:
φ it ＝φ 0 -R si S m0 tv cal /(V sm ×(1-φ 0 ))；
in phi it The porosity of the filter material column of the ith layer at t, phi 0 For the initial porosity of the filter column, R si At a center distance x from the inlet end i Chemical precipitation rate, S m0 V for the initial mass specific surface area of the filter column cal To density of chemical plugging material, V sm Is the volume occupied by the filter material with unit mass phi 0 Initial porosity for the filter material column;
in this step, the specific surface area S of the ith layer at the time of the filter column t is calculated from the relation between the porosity phi and the specific surface area S obtained in step 2 it 。
Further, in step 3, the distance between the center of the first layer and the water inlet surface isWherein d s The ith layer is formed by the column of the filter material which is the average grain diameter of the filter material>The thickness of the part is->And L is the total length of the filter material column.
Further, in step 6, the calculation formula of the external clogging factor b is:
wherein Δd sA The thickness increment of the chemical siltation outside the outer-packed filter material is increased; d, d s Is the average particle size of the filter material; m is M sc1 Is outside toCritical chemical blocking amount when blocking substances in the pores of the filter material are contacted with each other; v (v) cal Is the density of the chemical plugging material; c is when phi 2 ＜φ it ＜φ 1 When the chemical clogging substance distribution coefficient is obtained by the ratio of the cross section area of the penetrating filter material column to the specific surface area of the single-layer outer-packed filter material at the inlet end, and the distribution coefficient is dimensionless; a represents the water cross-section area of the filter column;
then, the specific surface area S at this time is calculated it And a porosity phi it The method comprises the steps of carrying out a first treatment on the surface of the Then according to the specific surface area S it And a porosity phi it Calculating the permeability coefficient K at this time sit The osmotic coefficient is calculated as follows:
further, in step 7, the calculation formula of the external clogging factor b is:
wherein M is sc2 For critical chemical clogging quantity delta d at the end of chemical clogging stage in the outer filter material sA The thickness increment of the chemical siltation outside the outer-packed filter material is increased; d, d s R is the average particle diameter of the filter material si At a center distance x from the inlet end i Chemical precipitation rate is set, t is time; v cal Is the density of the chemical plugging material;
then, the specific surface area S at this time is calculated it And a porosity phi it The method comprises the steps of carrying out a first treatment on the surface of the Then according to the specific surface area S it And a porosity phi it Calculating the permeability coefficient K at this time sit The osmotic coefficient is calculated as follows:
wherein K is sc2 Indicating the end of the internal chemical plugging phase it ＝φ 2 The critical permeability coefficient at that time is determined in step 6.
Further, in step 9, it is determined whether the running time is over, i.e., T is greater than or equal to T s Whether or not to do so, where T S Indicating the set running time, if so, calculating the permeability coefficient of the whole filter material column
And calculating the integral chemical clogging quantity of the filter column: m is M st ＝M s1 +M si +…+M sn ；
Wherein L is the total length of the filter material column, L i Represents the thickness, K, of the ith layer of filter column si Represents the permeability coefficient of the i-th layer; m is M si Indicating the amount of chemical plugging of the i-th layer. Compared with the prior art, the invention has the beneficial effects that:
(1) The simulation method for predicting the chemical clogging of the outer-packing filter material can accurately predict the co-evolution process of crystallization precipitation and permeability coefficient in the chemical clogging process, can accurately describe the accumulation of chemical clogging substances and the distribution situation of a flow field at different positions of the outer-packing filter material, and can provide theoretical basis and technical support for reasonable design and performance maintenance of an outer-packing filter material concealed pipe drainage system;
(2) The invention establishes a mathematical model of the chemical clogging of the outer filter material, which can consider the crystallization and precipitation of low-solubility salt, and can realize the accurate evaluation of the drainage hidden pipe performance of the outer filter material under the condition of the chemical clogging of the low-solubility salt; in addition, the mutual feedback effect of the hydrodynamic process and the chemical precipitation process can be considered, so that the co-evolution process of the chemical clogging and the permeability coefficient of the outer packing filter material can be more accurately quantized, and the change process of the drainage hidden pipe performance can be truly quantized.
Drawings
FIG. 1 is a flow chart of a method for predicting the co-evolution of chemical clogging and permeability coefficient of an overwrap filter material in an embodiment of the invention;
FIG. 2 is a schematic diagram of a series model of quartz sand column plugging and permeability coefficient stratification in an embodiment of the invention;
FIG. 3 is a diagram of a generator for a test of penetration of a chemical solution through a quartz sand column in accordance with an embodiment of the present invention;
FIG. 4 is a graph showing the variation of the specific surface area S of the silica sand column with respect to the porosity phi in the embodiment of the present invention;
FIG. 5 is a graph showing the amount of crystal precipitation and the equation of simulation in a quartz sand column for different flow rate and different concentration penetration tests in accordance with the present invention; wherein (a) is the chemical precipitation rate R at a fixed flow rate s Relationship with different concentrations and reaction sites x; (b) Is the relationship between the rate of chemical precipitation Rs and different flow rates and reaction positions x at a fixed concentration;
FIG. 6 is a graph showing the simulation of the process and model of the permeability coefficient of the quartz sand column under the action of different flow rates calculated in the embodiment of the present invention; wherein, (a) is the correlation between the simulation value (dotted line) and the actual measurement value (solid line) of the test model, and (b) is the correlation between the simulation value and the actual measurement value of the model;
FIG. 7 is a graph showing the simulation of the process and model of the permeability coefficient of the quartz sand column under the action of different concentrations calculated in the embodiment of the present invention; wherein (a) is the correlation between the simulation value (dotted line) and the actual measurement value (solid line) of the test model, and (b) is the correlation between the simulation value and the actual measurement value of the model.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention will be further illustrated, but is not limited, by the following examples.
As shown in FIG. 1, the invention provides a simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer-wrapped filter material, which comprises the following steps:
step 1, filling an outer-packed filter column, and measuring physical parameters of a filter material to calculate an initial permeability coefficient K of the filter material;
in this embodiment, quartz sand is used as the outer filter material, however, in other embodiments, other outer filter materials (such as sand gravel, zeolite, etc.) may be selected, and the acid-washed, washed and air-dried quartz sand (with a diameter of 0.50-1.00 cm) is packed into an organic glass column with an inner diameter of 3.0cm, the length of the packed quartz sand column is about l=10.2 cm, and the weight of the packed quartz sand is about 280.0 g. As shown in FIG. 2, the average particle diameter d of the quartz sand was measured s =0.56 mm, porosity and specific surface area S 0 To calculate the initial permeability coefficient K of the quartz sand 0 The permeability coefficient was calculated based on the classical Kozeny-Carman equation:
wherein K is 0 : initial permeability coefficient [ LT ] -1 ]；S 0 : initial quartz sand column volume specific surface area, [ L ] -1 ]；φ 0 : initial porosity, dimensionless.
Step 2: developing a test of penetrating a filtering material column by a chemical solution, establishing a relation between the specific surface area S of the outer filtering material and the porosity phi, and determining the porosity phi when chemical clogging substances in pores of the outer filtering material are contacted with each other 1 Porosity phi of chemical plugging when entering external plugging stage 2 The method comprises the steps of carrying out a first treatment on the surface of the Then according to the test, establishing a chemical clogging rate R s The functional relation between the flow velocity V, the solution saturation index SI and the chemical clogging position and the filter material column inlet distance x;
in this example, a test of penetration of the chemical solution through a quartz sand column was conducted, 3 flow rate gradients were set, the single pump flow rates were set to 0.3, 0.9 and 1.5ml/min, and the flow rates were 1.40X10, respectively -3 ，4.24×10 -3 And 7.07×10 -3 At cm/s, the concentration of the solution was 0.01mol/L CaCl 2 And 0.01mol/L NaHCO 3 Equal volume mixing of solutionsThe method comprises the steps of carrying out a first treatment on the surface of the 3 concentration gradients were set, the single pump flow was set at 0.3ml/min, and the cross-sectional flow rate was 1.41×10 -3 cm/s, caCl with solution concentrations of 0.005, 0.010 and 0.020mol/L, respectively 2 And NaHCO 3 The solutions were mixed in equal volumes. The solution temperature was set at 20.+ -. 2 ℃ and crystallization precipitation penetration experiments were performed with the test apparatus shown in FIG. 3.
After the test is finished, the Micro-CT is utilized to scan and reconstruct the quartz sand column, and the relation between the specific surface area S of the quartz sand column and the porosity phi is established, as shown in fig. 4.
S＝-0.2055φ 2 +0.1094φ，R 2 ＝0.95；
As can be seen from FIG. 4, the porosity phi of the pores of the quartz sand when the chemically precipitated substances are in contact with each other 1 =26.5%, the porosity at the inlet end of the quartz sand column is 14.2%, assuming the porosity Φ when the chemical precipitation enters the external plugging stage 2 =14.2%. Then the quartz sand column is taken out and dissolved in hydrochloric acid solution with the ratio of 1:1 in a layering way, the content of insoluble salt in the solution is measured by a titration method, and the chemical precipitation rate R of the insoluble salt is established s As a function of flow velocity V, SI (T, C) and distance x from the quartz sand column inlet position (as shown in fig. 5), the function is as follows:
R s ＝(6.52×10 -6 ×V×SI 3.25 +8.72×10 -9 )×x (-0.355SI-17.93×SI×V-0.7775) ；
wherein R is s : crystal precipitation rate of quartz sand surface, [ NL ] -2 T -1 ]The method comprises the steps of carrying out a first treatment on the surface of the V: average flow velocity of penetration section [ LT ] -1 ]The method comprises the steps of carrying out a first treatment on the surface of the SI: the saturation index, dimensionless, is calculated by using Phreexc 3.4, and is related to the temperature, concentration, ion composition and the like of the solution; x: distance from the inlet end [ L ]]。
Step 3: dividing a filter column into n layers from a water inlet surface to a water outlet surface, wherein the 1 st layer consists of a single-layer filter material at the water inlet surface of the filter column, dividing the rest filter columns into n-1 layers uniformly, and establishing the porosity phi and the chemical clogging rate R of the outer-packed filter material on the assumption that the chemical clogging rate of each layer is equal to the chemical reaction rate at the center of each layer s Relationship of time t;
in the present embodiment, it willThe quartz sand column is divided into 50 layers from an inlet end to an outlet, the 1 st layer is composed of a single layer of sand (with equivalent radius d at the water inlet surface of the sand filter material s ) The composition of the sand filter material is divided into 49 layers, the chemical reaction rate of each layer is equal to the chemical reaction rate of the center of each layer, and the center distance x of the first layer 1 ，x 1 ＝d s 2; the center distance of the ith layer isAnd then proceeds to the next step.
Step 4: calculating chemical clogging rate R of ith layer of filter material column at t time si And calculating the specific surface area S of the layer at t according to the formulas in the steps 2 and 3 it And a porosity phi it ；
According to the chemical precipitation rate calculated in step 2, R s Calculating the porosity phi of the ith layer at t it ：
φ it ＝φ 0 -R si S m 0tv cal /(V sm ×(1-φ 0 ))；
In phi 0 Is the initial porosity of the quartz sand column phi it For the porosity of the ith layer, R si At a center distance x from the inlet end i Chemical clogging Rate at site S m0 Is the initial mass specific surface area, v of the quartz sand column cal Is the density of calcium carbonate, V sm The volume occupied by the quartz sand in unit mass is shown; meanwhile, based on the relation between the specific surface area S and the porosity phi obtained in the step 2, calculating the specific surface area S of the ith layer when the quartz sand column t it 。
Step 5: when the porosity phi calculated in step 4 it ≥φ 1 In accordance with the porosity phi at that time it And specific surface area S it Thereby calculating the permeability coefficient of the filtering material column at the moment, if not, calculating phi it ＝φ 1 Critical crystallization precipitation M of (2) sc1 Then, the next step is carried out;
i.e. in the present embodiment, when the porosity phi it When the permeability is more than or equal to 26.5%, calculating the permeability coefficient at the moment, if not, calculating phi it When=26.5%Critical crystalline precipitation amount M of (2) sc1 Entering the next step; in this step, the osmotic coefficient is calculated as follows:
step 6: when the porosity phi calculated in step 4 2 ≤φ it ＜φ 1 When the method is used, the external clogging factor b is measured according to the chemical clogging quantity of the filter column, and then the porosity phi at the moment is measured according to the external clogging factor b it And specific surface area S it Calculating the permeability coefficient of the filtering column at the moment; if not, calculate phi it ＝φ 2 Critical permeability coefficient K of (2) sc2 The chemical clogging amount is M sc2 Then, the next step is carried out;
that is, in this example, when the porosity is 16.4% to phi it At < 26.5%, the pores and the crystal precipitation amount of the surface are distributed according to the ratio of the surface area to the cross-sectional area of the quartz sand, and the external clogging factor b is measured from the surface chemical precipitation amount, specifically,
wherein Δd sA : thickness increment of quartz sand outside [ L ]]；d s : penetrate the thickness of the single layer of quartz sand in the column, [ L ]]The method comprises the steps of carrying out a first treatment on the surface of the c: when the phi is more than or equal to 14.3 percent and less than 26.5 percent, the distribution coefficient of the crystallization precipitation substances is dimensionless, because the cross section area of the penetrating column accounts for 12.26 to 15.59 percent of the specific surface area of the single-layer quartz sand at the inlet end, and because the average value of 13.92 percent is taken as the proportion of the crystallization precipitation substances distributed to the external crystallization precipitation layer, namely, in the embodiment, c=13.92 percent, A represents the water cross section area of the filter column and is calculated according to the water cross section radius of the filter column; then calculating the specific surface area S according to the formula in the step 2 it ；
Step 7: when the porosity phi calculated in step 4 it ＜φ 2 When the method is used, the chemical clogging quantity is directly calculated from the chemical clogging rate to obtain an external clogging factor b, and then roots are grownCalculating the permeability coefficient of the filter column according to the external clogging factor b, and then entering the next step;
i.e. in the present example, when the porosity phi it When the concentration is less than 16.4%, the external clogging factor is obtained by directly calculating the surface crystallization precipitation amount according to the chemical precipitation rateThe symbols are the same, so that the permeability coefficient at the moment is calculated, and then the next step is carried out; in this step, the osmotic coefficient calculation formula is as follows:
step 8: calculating the chemical clogging quantity M under the osmotic coefficient sit Judging whether each layer of the filtering column is calculated, if not, returning to the step 4 to calculate the next layer; if yes, entering the next step;
calculating chemical precipitation amount M under the osmotic coefficient according to the test sit ＝R si t, i= (i-1) +1, judging whether each layer of the quartz sand column is calculated (i.e. whether i is equal to or greater than 50 is met), if so, entering the next step; if not, returning to the step 4 to enter the calculation of the next layer;
step 9: calculating the integral permeability coefficient and chemical clogging quantity of the filtering material column at the moment, and if the filtering material column is permeable by an equal water head, calculating the current speed at the moment, wherein V=K st l, judging whether the running time is over, if so, outputting the integral permeability coefficient K s And chemical clogging amount M s The method comprises the steps of carrying out a first treatment on the surface of the If not, returning to the step 3 to calculate the next time step.
If the water is equal head (l) permeated, the current speed at the moment is calculated, and V=K st l, t= (T-1) +Δt, and determining whether the run time is over, i.e., determining that T is not less than T s Whether or not to establish (T) s For a set total running time), if so, output the result K s 、M s The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the permeability coefficient of the whole quartz sand column at the momentIntegral clogging quantity M st ＝M s1 +M si +…+M sn The method comprises the steps of carrying out a first treatment on the surface of the If not, returning to the step 3 to calculate the next time step. Fig. 6 (a) and 7 (a) are respectively simulation values (dotted lines) and actual measurement values (solid lines) of a quartz sand filter column model in an equal flow rate and equal concentration test, and as can be seen from the figures, the established model can well predict the change trend of the permeability coefficient in the quartz sand crystallization and precipitation process; FIGS. 6 (b) and 7 (b) show the correlation between the model simulation value and the measured value, from which R can be seen 2 The model is more than or equal to 0.92, the RMSE is less than or equal to 0.020cm/s, and the model has better prediction precision.
The foregoing is merely illustrative of the preferred embodiments of the present invention and is not intended to limit the embodiments and scope of the present invention, and it should be appreciated by those skilled in the art that equivalent substitutions and obvious variations may be made using the teachings of the present invention, which are intended to be included within the scope of the present invention.
Claims (8)
1. A simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer-coated filter material is characterized by comprising the following steps:
step 1, filling an outer packing filter material column, and measuring physical parameters of the filter material column to calculate an initial permeability coefficient K of the outer packing filter material 0 ；
Step 2, carrying out a test of penetrating a filter column by a chemical solution, establishing a relation between the specific surface area S of the outer filter material and the porosity phi, and determining the porosity phi when chemical clogging substances in the pores of the outer filter material are contacted with each other 1 Porosity phi of chemical plugging when entering external plugging stage 2 The method comprises the steps of carrying out a first treatment on the surface of the Then according to the test, establishing a chemical clogging rate R s The functional relation between the flow velocity V, the solution saturation index SI and the chemical clogging position and the filter material column inlet distance x;
step 3: dividing a filter column into n layers from a water inlet surface to a water outlet surface, wherein the 1 st layer consists of a single-layer filter material at the water inlet surface of the filter column, dividing the rest filter columns into n-1 layers uniformly, and establishing the chemical plugging rate of each layer is assumed to be equal to the chemical reaction rate at the center of each layerPorosity phi and chemical clogging rate R of outer-packed filter material s Relationship of time t;
step 4: calculating chemical clogging rate R of ith layer of filter material column at t time si And calculating the specific surface area S of the layer at t according to the formulas in the steps 2 and 3 it And a porosity phi it ；
Step 5: when the porosity phi calculated in step 4 it ≥φ 1 In accordance with the porosity phi at that time it And specific surface area S it Calculating the permeability coefficient of the filtering material column at the moment, if not, calculating phi it ＝φ 1 Critical chemical clogging quantity M sc1 Then, the next step is carried out;
step 6: when the porosity phi calculated in step 4 2 ≤φ it ＜φ 1 When the method is used, the external clogging factor b is measured according to the chemical clogging quantity of the filter column, and then the porosity phi at the moment is measured according to the external clogging factor b it And specific surface area S it Calculating the permeability coefficient of the filtering column at the moment; if not, calculate phi it ＝φ 2 Critical permeability coefficient K of (2) sc2 The chemical clogging amount is M sc2 Then, the next step is carried out;
step 7: when the porosity phi calculated in step 4 it ＜φ 2 When the method is used, the chemical plugging rate is directly used for calculating the chemical plugging amount to obtain an external plugging factor b, and then the permeability coefficient of the filter column is calculated according to the external plugging factor b, and then the next step is carried out;
step 8: calculating the chemical clogging quantity M under the osmotic coefficient sit Judging whether each layer of the filtering column is calculated, if not, returning to the step 4 to calculate the next layer; if yes, entering the next step;
step 9: calculating the integral permeability coefficient and chemical clogging quantity of the filtering material column at the moment, and if the filtering material column is permeable by an equal water head, calculating the current speed at the moment, wherein V=K st l, judging whether the running time is over, if so, outputting the integral permeability coefficient K s And chemical clogging amount M s The method comprises the steps of carrying out a first treatment on the surface of the If not, returning to the step 3 to calculate the next time step.
2. The simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer packing filter material according to claim 1, wherein the step 1 specifically comprises:
filling and outsourcing filter material column with equal pressure solidity, column length L equal to thickness of outsourcing filter material layer, dividing the filter material column into n layers, measuring average particle diameter d of filter material s Initial porosity phi 0 And specific surface area S 0 To calculate the initial permeability coefficient K of the filter column 0 Wherein, the equation of the calculation of the permeability coefficient is:
3. the simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer filter material according to claim 1, wherein in the step 2, the filter material column is scanned and reconstructed by utilizing Micro-CT, and the relation between the specific surface area S of the outer filter material and the porosity phi is established.
4. The simulation method for predicting the co-evolution of chemical plugging and permeability coefficient of an outer filter material according to claim 1, wherein in the step 3, the relation between the porosity and the chemical plugging rate is:
φ it ＝φ 0 -R si S m0 tv cal /(V sm ×(1-φ 0 ))；
in phi it The porosity of the filter material column of the ith layer at t, phi 0 For the initial porosity of the filter column, R si At a center distance x from the inlet end i Chemical precipitation rate, S m0 V is the initial mass specific surface area of the filter column cal To density of chemical plugging material, V sm Is the volume occupied by the filter material with unit mass phi 0 Initial porosity for the filter material column;
in this step, the specific surface area of the ith layer at the time of the filter column t is calculated from the relation between the porosity phi and the specific surface area S obtained in step 2Product S it 。
5. The simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer packing filter material according to claim 1, wherein in step 3, the distance between the center of the first layer and the water inflow surface isWherein d s The ith layer is formed by the column of the filter material which is the average grain diameter of the filter material>The thickness of the part is->And L is the total length of the filter material column.
6. The simulation method for predicting the co-evolution of chemical plugging and permeability coefficient of an outer filter material according to claim 1, wherein in step 6, the calculation formula of the outer plugging factor b is:
wherein Δd sA The thickness increment of the chemical siltation outside the filter material column is increased; d, d s Is the average particle size of the filter material; m is M sc1 Critical chemical blocking amount when blocking substances in the pores of the outer filter material are contacted with each other; v cal Is the density of the chemical plugging material; c is when phi 2 ＜φ it ＜φ 1 When the chemical clogging substances are distributed, the distribution coefficient of the chemical clogging substances is obtained by the ratio of the cross-sectional area of the penetrating filter material column to the specific surface area of the single-layer outer-packed filter material at the inlet end; a represents the water cross-section area of the filter column;
then, the specific surface area S at this time is calculated it And a porosity phi it The method comprises the steps of carrying out a first treatment on the surface of the Then according to the specific surface area S it And a porosity phi it Calculating the permeability coefficient K at this time sit The osmotic coefficient is calculated as follows:
7. the simulation method for predicting the co-evolution of chemical plugging and permeability coefficient of an outer filter material according to claim 1, wherein in step 7, the calculation formula of the outer plugging factor b is:
wherein M is sc2 Is critical chemical clogging quantity delta d at the end of the chemical clogging stage in the outer filter material sA The thickness increment of the chemical siltation outside the filter material column is increased; d, d s R is the average particle diameter of the filter material si At a center distance x from the inlet end i Chemical precipitation rate is set, t is time; v cal Is the density of the chemical plugging material;
then, the specific surface area S at this time is calculated it And a porosity phi it The method comprises the steps of carrying out a first treatment on the surface of the Then according to the specific surface area S it And a porosity phi it Calculating the permeability coefficient K at this time sit The osmotic coefficient is calculated as follows:
wherein K is sc2 Indicating the end of the internal chemical plugging phase it ＝φ 2 The critical permeability coefficient at that time is determined in step 6.
8. The simulation method for predicting the co-evolution of chemical clogging and permeability coefficient of an outer packing filter material according to claim 1, wherein in step 9, it is judged whether the operation time is ended, i.e. T is equal to or greater than T s Whether it is true or not,wherein T is S Indicating the set running time, if so, calculating the permeability coefficient of the whole filter material column
And calculating the integral chemical clogging quantity of the filter column: m is M st ＝M s1 +M si +…+M sn ；
Wherein L is the total length of the filter material column, L i Represents the thickness, K, of the ith layer of filter column si Represents the permeability coefficient of the i-th layer; m is M si Indicating the amount of chemical plugging of the i-th layer.
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