CN114492048A - Simulation method for predicting chemical silting of synthetic outer covering material - Google Patents

Simulation method for predicting chemical silting of synthetic outer covering material Download PDF

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CN114492048A
CN114492048A CN202210104615.3A CN202210104615A CN114492048A CN 114492048 A CN114492048 A CN 114492048A CN 202210104615 A CN202210104615 A CN 202210104615A CN 114492048 A CN114492048 A CN 114492048A
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郭宸耀
伍靖伟
赵强
李航
杨皓瑜
吴哲
朱焱
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Abstract

The invention discloses a simulation method for predicting chemical silting of a synthetic outsourcing material, which comprises the following steps: measuring basic physical parameters of the synthesized coating sample, and calculating its overlap factor b, external surface area A, and improved permeability coefficient Kg0(ii) a Carrying out precipitation crystallization test, measuring precipitation crystallization amount, and establishing chemical precipitation rate RgRelationship to flow rate V, SI; determining the critical crystallization precipitation amount Mgc(ii) a Judging whether the test is constant flow or constant water head treatment; judging whether the chemical clogging process is finished or not; according to MgtJudging a chemical clogging stage of the synthetic coating material; calculating the encryption effect of the synthetic outer wrapping material; calculating the plugging effect of the synthetic outer coating; and evaluating the model prediction value according to the test result.The simulation method for predicting the chemical clogging of the synthetic outer coating can prepare the cross-feed process of simulating the chemical clogging and the permeability coefficient of the synthetic outer coating, so that the actual chemical clogging condition can be displayed more truly, and a reliable prediction result can be obtained.

Description

Simulation method for predicting chemical silting of synthetic outer covering material
Technical Field
The invention belongs to the technical field of chemical silting of farmland closed conduit drainage, and particularly relates to a simulation method for predicting chemical silting of synthetic coating materials.
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 hidden pipe drainage technology is that the pipeline with small holes or narrow slits distributed on the pipe wall is buried underground, so that the water of the surrounding environment (soil, slag, solid garbage and the like) of the hidden pipe permeates into the buried pipeline and then is discharged to a leakage bearing area. The outer-wrapped filter material is a strong water permeable material which is arranged around the concealed pipe to ensure the water permeability of the concealed pipe and prevent the concealed pipe from being silted up.
The synthetic coating material has good filtering, water draining, isolating, reinforcing, seepage preventing and protecting functions, and is widely used in the field of water draining filter materials. Meanwhile, in the areas with shortage of sandstone materials, synthetic materials are selected as the outer-wrapping filter materials, so that the engineering cost can be greatly reduced. However, research has shown that the synthetic coating material inevitably encounters a certain degree of clogging during use, which not only reduces the drainage and salt discharge efficiency of the concealed pipe, but also increases the maintenance cost of the concealed pipe and reduces the service life.
Clogging can be classified into physical clogging, chemical clogging and biological clogging according to the kind of clogging substance and the mechanism of clogging occurrence. At present, physical clogging caused by soil particle loss is researched more, and a mature prevention and control technology is provided. The occurrence of biological fouling requires specific biochemical conditions and is not usually a major factor in farmland drainage. The existing research on chemical clogging focuses more on the clogging caused by iron-manganese precipitation driven by redox reaction, and the research on the clogging caused by chemical processes such as low-solubility salt crystallization precipitation is less, and the research is still in the experimental research and rule summarization stage. The existing research shows that the form of chemical precipitation in the porous medium has great influence on the permeability coefficient, and Ghezzehei (2012) adopts a simple model of cylindrical pores to evaluate that the difference between the permeability coefficients of a uniform precipitation model and a non-uniform precipitation model can reach 3 orders of magnitude at most. Liulifang (2002) establishes an expression of the permeability coefficient of the synthetic coating material, but the established equation is the permeability coefficient of the ideal coating material, the overlapping effect of the synthetic coating material is not considered, and the equation cannot be applied to the quantification of the permeability coefficient of the synthetic coating material after chemical clogging. Therefore, accurately evaluating the influence of clogging on the permeability coefficient of the outer coating of the drainage concealed pipe is the key for maintaining the performance of a drainage system, however, a mathematical model considering chemical clogging of the synthetic outer coating caused by crystallization and precipitation of low-solubility salt is not seen yet, so that the prediction of the permeability coefficient of the synthetic outer coating due to chemical clogging is difficult to predict, and thus an accurate and reliable prediction result is difficult to obtain.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a simulation method for predicting chemical clogging of a synthetic outsourcing material, which can prepare a mutual feed process for simulating chemical clogging and permeability coefficient of the synthetic outsourcing material, thereby more truly showing the actual chemical clogging condition and obtaining a reliable prediction result.
In order to solve the technical problems, the invention adopts the following technical scheme:
a simulation method for predicting chemical clogging of a synthetic outsourcing material comprises the following steps:
step 1, measuring to obtain basic physical parameters of a synthetic coating sample, and calculating the fiber surface area S of the synthetic coatinggOverlap factor b and simulated initial permeability coefficient Kg0；
Step 2, carrying out a precipitation crystallization test for synthesizing the coating material, introducing reaction solutions with different solution saturation degrees SI and flow rates V, and measuring corresponding crystallization precipitation rates RgFitting to obtain the chemical precipitation rate R of insoluble saltgAn empirical formula with solution saturation SI and flow rate V;
step 3, selecting a flowing solution with a certain saturation SI to carry out the precipitation crystallization test in the step 2, determining the permeability coefficient and the permeability quality when no crystallization occurs on the outer coating material and in the test process, and determining the critical crystallizationAmount of precipitate Mgc；
Step 4, calculating the change condition of the permeability coefficient of the synthesized outer coating material in the test process, firstly, judging whether the solution flow in the test is constant head treatment, and if the solution flow is constant head, calculating the flow velocity V which is equal to Kgt-1i，Kgt-1The permeability coefficient of the previous time step is set as i, the water head is set as i, and then the next step is carried out; if the flow is determined, directly entering the next step;
and 5, calculating the crystal precipitation amount delta M of the next unit time step delta T, wherein delta M is RgΔ T, calculating the cumulative deposition Mgt＝Mgt-1+ΔM，Mgt-1The accumulated precipitation amount of the previous time step is then judged whether the permeation process is finished or whether the permeation coefficient of the synthesized coating material is reduced to 0 at t, and if so, the final permeation coefficient K is outputgtAnd the cumulative amount of precipitate MgtEnding the calculation, and entering the step 8; if not, entering the step 6;
step 6, judging the accumulated precipitation amount Mgt≤MgcWhether or not: if yes, further calculating the encryption factor epsilon of the crystallized sediment substance in the current time step delta TgΔTAnd according to an encryption factor epsilongΔTCalculating the encryption factor epsilon of the chemical silting of the synthetic coating material at the current momentgtAnd then according to the encryption factor epsilongtCalculating the permeability coefficient of the synthesized outer coating material after the chemical clogging, and then returning to the step 4; if not, entering step 7;
step 7, if Mgt＞MgcThen according to MgcFurther calculating the blocking effect factor epsilon of the crystallized and precipitated substancessAnd according to the blocking effect factor epsilonsCalculating the permeability coefficient of the synthesized outer coating material after plugging, and then returning to the step 4;
and 8, evaluating the permeability coefficient and the variation of the synthetic coating obtained by simulation according to the steps until the test is finished so as to verify the effectiveness of the method.
Further, the thickness T of the synthetic capstock is measured in step 1gLinear density NdtAreal density μgDiameter of fiberdfCalculating the overlapping factor b and the fiber surface area S of the synthetic coating material by taking the cross section area of the coating material sample as A, the external surface area ratio a of the fabric fiber, the solution density rho and the dynamic viscosity mugAnd simulated initial permeability coefficient Kg0；
Wherein, the specific calculation formula is as follows:
overlap factor for synthetic overwrap sample fibers:
Figure BDA0003490386020000031
external surface area of synthetic overwrap sample fibers:
Figure BDA0003490386020000032
initial permeability coefficient simulated for the synthetic capstock sample:
Figure BDA0003490386020000033
further, in step 5, the method for judging whether the permeation process is finished at t includes: and judging whether T is greater than or equal to T, wherein T is the total time, if so, finishing the permeation process, and if not, finishing the permeation process.
Further, in step 6, the encryption factor ε of the crystallized precipitated material is calculatedgΔTWhen in use, the thickening effect of the fiber of the crystallization precipitation of the synthetic coating material is equivalent to the encryption factor of the fiber, the growth thickness of the crystallization precipitation substance on the surface of the fiber is delta d, and the molar volume of the calcium carbonate is vcalThe crystallization precipitation test unit time step is Δ T, and the fiber encryption factor can be expressed as follows:
Δd＝Rg×vcal×ΔT；
the encryption factor epsilon of the fiber in the unit volume of the outer coating material is synthesized after crystallization and precipitationgtCan be expressed as follows:
Figure BDA0003490386020000034
εgt＝εgt-1+εgΔT；
thus, the permeability coefficient of the synthetic coating after crystallization precipitation can be expressed as follows:
Figure BDA0003490386020000035
further, in step 7, the blocking effect factor epsilon of the crystallized and precipitated material is calculatedsThe method comprises the following steps:
when the crystallization and precipitation process of the fiber is finished, the crystallization and precipitation amount reaches a critical value MgcAt this time, the outer package encryption factor epsilon is synthesizedgtEqual to the critical encryption factor epsilongcThe permeability coefficient of the synthetic coating material reaches the critical value K of the fiber crystallization precipitationgcAs shown in the following formula:
Figure BDA0003490386020000036
the accumulation of crystalline precipitated material on the surface of the coating results in the formation of a filter cake, which forms a plug, on the basis of which it is assumed that the surface of the synthetic coating has a deposit thickness Δ dAAt this time, the surface accumulation plugging effect factor of the crystallized and precipitated outer coating is epsilonsExpressed as:
Figure BDA0003490386020000037
at this time, the permeability coefficient of the synthetic capstock can be expressed as:
Figure BDA0003490386020000041
in the formula, wherein RgThe precipitation rate of the chemical substance on the synthetic coating material; kgtThe permeability coefficient of the synthesized coating after deposition is obtained; epsilonS: the plugging effect of the surface accumulated sediment is dimensionless; epsilongcIs crystallized and precipitated for fiberCritical encryption factors in the process are dimensionless; kgcThe critical permeability coefficient of the outer coating material is synthesized after the fiber crystallization and precipitation process is finished; mgcThe mass of the precipitated substances after the fiber crystallization and precipitation process is finished; and A is the surface area of the synthesized coating sample.
Further, in step 8, R is used2And RMSE, specifically, comparing the permeability coefficient variation delta K of the synthetic coating material of each time step, which is calculated according to the method, with the actually measured permeability coefficient variation delta K of the synthetic coating material; in addition, the simulated value and the measured value of the permeability coefficient in the synthetic coating material test process are evaluated.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention establishes a mathematical model of chemical silting of the synthetic coating material, which can consider the fiber structure of the synthetic coating material and the crystallization and precipitation process of low-solubility salt, and can realize accurate evaluation of the performance of the synthetic coating material drainage concealed pipe under the condition of chemical silting of low-solubility salt;
(2) the method considers the mutual feedback effect of the hydrodynamic process and the chemical precipitation process, thereby more accurately quantifying the collaborative evolution process of chemical silting and permeability coefficient of the synthetic coating, and truly quantifying the change process of the drainage concealed pipe performance.
Drawings
FIG. 1 is a flow chart of a simulation method for predicting chemical fouling of a synthetic coating in accordance with an embodiment of the present invention;
FIG. 2 is a graph of the percentage of actual outer surface area of fibers in a sample of a synthetic capstock according to an embodiment of the invention;
FIG. 3 is a ratio of individual fibers of a synthetic overwrap to binder fibers in an example of the invention;
FIG. 4 is a diagram of a chemical clogging generator for synthetic coatings according to the present invention, wherein (a) is a flow solution tester for controlling the flow rate, and (b) is a flow solution tester for controlling the water head;
FIG. 5 is a graph of the crystallization precipitation rates for different saturations under flow conditions in an example of the invention;
FIG. 6 is a graph of the crystallization precipitation rates at different flow rates under conditions of equal saturation for an example of the present invention;
FIG. 7 is a microscopic image of the synthetic capstock after chemical fouling in an example of the invention;
FIG. 8 is a graph showing the relationship between the amount of crystal precipitation of the synthetic coating and the permeability coefficient in the example of the present invention;
FIG. 9 is a schematic view of the overlapping action of the fibers of the synthetic capstock according to the invention;
FIG. 10 is a schematic diagram of a model of the encryption effect of chemical fouling of synthetic coatings according to the present invention, (a) is an image of the crystals deposited on the fibers inside the fabric, (b) is a model diagram of the crystals deposited on the fibers, and (c) is a schematic diagram of the encryption effect;
FIG. 11 is a schematic diagram of a plugging effect model of chemical clogging of a synthetic coating designed by the invention, (a) is an image of accumulation of crystalline precipitates outside a fabric, (b) is a model diagram of filter cake plugging, and (c) is a schematic diagram of a plugging effect;
FIG. 12 is a comparison of the observed value and the simulated value of the variation of the permeability coefficient of the synthetic coating considering the overlap effect in the embodiment of the present invention;
FIG. 13 is a comparison of observed and simulated permeability coefficients for a synthetic capstock in a crystallization precipitation test for the capstock in accordance with an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention is further illustrated by the following examples, which are not to be construed as limiting the invention.
The invention provides a simulation method for predicting chemical silting of synthetic outsourcing materials, which comprises the following steps:
step 1, measuring to obtain basic physical parameters of a synthetic coating material sample, and calculating the fiber surface area Sg and the simulated initial permeability coefficient Kg of the synthetic coating material0And an overlap factor b;
in this step, the thickness T of the synthetic coating material is measuredgLinear density NdtAreal density μgDiameter d of the fiberfCalculating the overlapping factor b and the fiber surface area S of the synthetic coating material by taking the cross section area of the coating material sample as A, the external surface area ratio a of the fabric fiber, the solution density rho and the dynamic viscosity mugAnd simulated permeability coefficient Kg0；
Wherein, the specific calculation formula is as follows:
overlap factor of synthetic overwrap sample fibers:
Figure BDA0003490386020000051
external surface area of synthetic overwrap sample fibers:
Figure BDA0003490386020000052
initial permeability coefficient simulated for the synthetic capstock sample:
Figure BDA0003490386020000053
step 2, carrying out a precipitation crystallization test for synthesizing the coating material, introducing reaction solutions with different solution saturation degrees SI and flow rates V, and measuring corresponding crystallization precipitation rates RgFitting to obtain the chemical precipitation rate R of insoluble saltgAn empirical formula with solution saturation SI and flow rate V;
step 3, selecting a flowing solution with a certain saturation SI to carry out the precipitation crystallization test in the step 2, measuring the permeability coefficient and the permeability quality of the synthesized outer coating when no crystallization appears on the outer coating and after the test is finished, and determining the critical crystallization precipitation amount Mgc；
Step 4, calculating the change of the permeability coefficient of the coating material in the test processFirst, it is judged whether the solution flow in the test is constant head treatment, and if it is constant head, the flow velocity V is calculated as Kgt-1i，Kgt-1The permeability coefficient of the previous time step is set as i, the water head is set as i, and then the next step is carried out; if the flow is determined, directly entering the next step;
and 5, calculating the crystal precipitation amount delta M of the next unit time step delta T, wherein delta M is RgΔ T, calculating the cumulative deposition Mgt＝Mgt-1+ΔM，Mgt-1Judging whether the permeation process is finished or whether the permeation coefficient of the synthesized coating material is reduced to 0 or not for the accumulated precipitation amount of the previous time step, wherein the method for judging whether the permeation process is finished or not at the time of t comprises the following steps: judging whether i is more than or equal to T, wherein T is the total time, and if so, outputting the final permeability coefficient KgtAnd the cumulative amount of precipitate MgtEnding the calculation, and entering the step 8; if not, entering the step 6;
step 6, judging the accumulated precipitation amount Mgt≤MgcWhether or not: if yes, further calculating the encryption factor epsilon of the crystallized sediment substance in the current time step delta TgΔTAnd according to an encryption factor epsilongΔTCalculating the encryption factor epsilon of the chemical silting of the synthetic coating material at the current momentgtAnd then according to the encryption factor epsilongtCalculating the permeability coefficient of the synthesized outer coating material after the chemical clogging, and then returning to the step 4; if not, entering step 7;
in step 6, the encryption factor epsilon of the crystallized and precipitated substance is calculatedgΔTWhen in use, the thickening effect of the fiber of the crystallization precipitation of the synthetic coating material is equivalent to the encryption effect of the fiber, the growth thickness of the crystallization precipitation substance on the surface of the fiber is delta d, and the molar volume of the calcium carbonate is vcalThe crystallization precipitation test has a unit time step of Δ T, and the fiber encryption effect can be expressed as follows:
Δd＝Rg×vcal×ΔT；
the encryption factor epsilon of the fiber in the unit volume of the outer coating material is synthesized after crystallization and precipitationgtCan be expressed as follows:
Figure BDA0003490386020000061
εgt＝εgt-1+εgΔT；
thus, the permeability coefficient of the synthetic capstock after crystallization precipitation can be expressed as follows:
Figure BDA0003490386020000062
step 7, if Mgt＞MgcThen according to MgcFurther calculating the blocking effect factor epsilon of the crystallized and precipitated substancessAnd according to the blocking effect factor epsilonsCalculating the permeability coefficient of the synthesized coating material after plugging, and then returning to the step 4;
in step 7, calculating the blocking effect factor epsilon of the crystallized and precipitated substancessThe method comprises the following steps:
when the crystallization and precipitation process of the fiber is finished, the outside synthetic coating encryption factor epsilon is synthesized at the momentgtEqual to the critical encryption factor epsilongcThe amount of crystal precipitation reaches a critical value MgcAt this time, the outer package encryption factor epsilon is synthesizedgtEqual to the critical encryption factor epsilongcThe permeability coefficient of the synthetic coating material reaches the critical value K of the fiber crystallization precipitationgcAs shown in the following formula:
Figure BDA0003490386020000071
the accumulation of crystalline precipitated material on the surface of the coating results in the formation of a filter cake, which forms a plug, on the basis of which it is assumed that the surface of the synthetic coating has a deposit thickness Δ dAAt this time, the surface accumulation plugging effect factor of the crystallized and precipitated outer coating is epsilonsExpressed as:
Figure BDA0003490386020000072
at this time, the permeability coefficient of the synthetic capstock can be expressed as:
Figure BDA0003490386020000073
in the formula, RgThe precipitation rate of the chemical substance on the synthetic coating material; k isgtThe permeability coefficient of the synthesized coating after deposition is obtained; epsilonS: the plugging effect of the surface accumulated sediment is dimensionless; epsilongcIs a critical encryption factor in the fiber crystallization and precipitation process, and has no dimension; kgcThe critical permeability coefficient of the outer coating material is synthesized after the fiber crystallization and precipitation process is finished; mgcThe mass of the precipitated substances after the fiber crystallization and precipitation process is finished; a is the surface area of the synthetic capstock sample.
And 8, evaluating the permeability coefficient and the variable quantity of the synthesized coating obtained by simulation according to the steps until the test is finished so as to verify the effectiveness of the method.
In this step, R is used2And RMSE, specifically, comparing the permeability coefficient variation delta K of the synthetic coating material of each time step calculated according to the method with the actually measured permeability coefficient variation delta K of the synthetic coating material; in addition, the simulated value and the measured value of the permeability coefficient in the synthetic coating material test process are evaluated.
The chemical clogging process of the synthetic coating material mainly comprising calcium and magnesium precipitates in the outer coating material of the drainage concealed pipe in the arid region is exemplified, and the specific implementation steps are as follows:
as shown in fig. 1, step 1, measuring to obtain basic physical parameters of a synthetic coating sample; a fabric sample having a diameter of 3cm was cut using a compass shear, and the diameter of the flow cross section was 2.5cm, so that the sample participating in the reaction was calculated as a diameter of 2.5 cm. Measuring the thickness T of the synthetic capstockg＝2.52×10-4m, linear density Ndt17.87dtex, area density mug＝87g/m2Diameter of fiber df＝5.0×10-5m, the cross-sectional area of the coating sample is A ═ 4.91X 10-4m2Solution density rho is 998.2kg/m3Dynamic viscosity [ mu ] 1.004X 10-3m/S to calculate the overlap factor b of the synthetic coating, the fiber surface area SgEstablishing the permeability coefficient of the synthetic coating
Figure BDA0003490386020000081
The same meanings as those of the above symbols in the following formulae are also the same.
The specific calculation process is as follows:
the bonding compression between the fibers increases the contact surface area, the fiber external surface area in unit volume can be reduced when the fabric fiber single layers are overlapped, and the reduction ratios of the external surface areas in different overlapping modes are different. We assume that the bonding overlap between the individual fibers reduces the outer surface area of the fibers by 25%, and that the actual outer surface area is a different percentage of the theoretical outer surface area of the fibers for different bonding and overlapping combinations, as shown in fig. 2, the ratio of the distribution of the individual fibers and bonding fibers in the geotextile is 1: 1 (fig. 3), and the actual outer surface area of the fabric fibers is calculated to be 43.3% of the theoretical outer surface area of the fibers per unit volume, as shown in fig. 3.
External surface area of synthetic overwrap sample fibers:
Figure BDA0003490386020000082
initial permeability coefficient simulated for the synthetic capstock sample:
Figure BDA0003490386020000083
overlap factor b of synthetic overwrap sample fibers:
Figure BDA0003490386020000084
and substituting the overlapping factor b of 5.0 into the synthetic coating permeability coefficient calculation formula to obtain the theoretical simulation value of the synthetic coating.
And 2, carrying out a precipitation crystallization test of the chemical solution synthesized coating material. The test device is shown in fig. 4, and fig. 4(a) is a flow solution test device with controlled flow, which is composed of two constant flow peristaltic pumps, a reaction column (holding outer material), a tail gas bottle and an iron stand. Fig. 4(b) shows a test apparatus for controlling the flowing solution of the water head, which comprises two mahalanobis bottles, a reaction column (holding outer material), a tail gas bottle, an iron stand and a constant temperature and humidity box. The inner diameter of the experimental column is 3.0cm, the length of the experimental column is 10.0cm, the synthetic coating material is fixed in the middle of the experimental column through a fixing device, the diameter of a water passing section is 2.5cm, then reaction solution is introduced through two peristaltic pumps at equal flow, and the lengths of connecting conduits of the two peristaltic pumps are equal. Alternatively, the water supply device may be replaced with a majeldahl bottle for the equal head test, and the test protocol is shown in table 1. In the test process, a fluorescent lamp is adopted in the laboratory for uninterrupted illumination.
TABLE 1 synthetic coating fluid solution crystallization precipitation test design
Figure BDA0003490386020000085
Figure BDA0003490386020000091
In the test process, the crystallization precipitation rate R corresponding to the solutions with different solution saturations SI (C) and flow rates V (T) is determinedgFitting to obtain the chemical precipitation rate R of insoluble saltgAn empirical formula with solution saturation SI and flow rate V;
in this embodiment, according to the classical kinetic theory of crystallization precipitation, the relationship between the crystallization precipitation rate on the synthetic outer covering material under the flowing condition, the solution saturation SI and the flow rate V can be obtained, as shown in fig. 5 and 6;
Figure BDA0003490386020000092
in the formula, RgIndicating chemical depositionThe sedimentation rate, SI the solution saturation, V the real-time flow rate, V0Indicating the initial flow rate.
Step 3, selecting a flowing solution with a certain saturation SI to carry out the precipitation crystallization test in the step 2, measuring the permeability coefficient and the permeability quality of the synthesized outer coating when no crystallization occurs on the outer coating and in the test process, and determining the critical crystallization precipitation amount MgcAnd then proceeds to the next step.
As can be seen from the figure, the areal density of the amount of crystal precipitates on the synthetic coating was less than when the areal density of the amount of crystal precipitates was less than 42.5g/m2In time, the precipitated material grows mainly between the fibers of the synthetic capstock. When the crystal precipitation amount is from 42.5g/m2Rising to 110.62g/m2When the amount of the crystal precipitation is larger than 110.62g/m, the permeability coefficient of the synthesized coating material is not obviously increased2In time, the amount of change in permeability coefficient rapidly rises and then gradually remains stable. In this example, the critical crystal precipitation amount M was found by combining the super depth of field microscopic image of the synthetic coating (see FIG. 7)gc＝110.62g/m2See fig. 8.
Step 4, calculating the permeability coefficient change condition of the outer covering material in the test process, specifically, firstly, judging whether the solution flow in the test is constant head treatment? If the constant head i is adopted, the flow speed V is calculated to be Kgt-1i, calculating flow velocity V ═ Kgt-1i，Kgt-1The permeability coefficient of the previous time step is set as i, the water head is set as i, and then the next step is carried out; if the flow is the fixed flow, the flow velocity V is the fixed flow velocity, and the next step is directly carried out;
step 5, calculating the crystal precipitation amount Δ M ═ R per unit time step Δ Tg×ΔT，RgCalculating according to the flow rate in the step 4 and an empirical formula in the step 2; then, the cumulative deposition amount M is calculated from the Δ Mgt＝Mgt-+ Δ M, wherein Mgt-1The accumulated precipitation amount of the previous time step is used as the final time, and then whether the permeation process is finished or not (namely whether T is more than or equal to T and T is the total time) or the permeation coefficient (K) of the synthetic coating is judged according to the test timegtWhether or not ≦ 0 holds) whether or not to drop to 0: if so, outputting Kgt、MgtEnd of life meterCalculating, and entering the step 8; if not, entering the step 6;
step 6, judging the accumulated precipitation amount Mgt≤MgcWhether the result is true; if yes, further calculating the encryption factor epsilon of the crystallized sediment substance in the current time step delta TgΔTAnd according to an encryption factor epsilongΔTCalculating the encryption factor epsilon of the chemical silting of the synthetic coating material at the current momentgtAnd then according to the encryption factor epsilongtCalculating the permeability coefficient of the synthesized outer coating material after the chemical clogging, and then returning to the step 4; if not, step 7 is entered.
Specifically, in this step, as shown in fig. 9, the "fiber thickening effect" obtained by crystallizing and precipitating the synthetic coating is equivalent to the "fiber encryption effect", which increases the percolation resistance and decreases the permeability coefficient of the synthetic coating. Let the growth thickness of the crystalline precipitated substance on the fiber surface be Delta d and the molar volume of the calcium carbonate be vcalAnd the crystallization precipitation test duration is t, the fiber encryption effect can be expressed as follows, see fig. 10:
Δd＝Rg×vcal×ΔT；
then, the crystallization precipitation is followed by the synthesis of the packing factor (. epsilon.) of the fibers in the unit volume of the casinggt) Can be expressed as follows:
Figure BDA0003490386020000101
thus, the permeability coefficient of the synthetic capstock after crystallization precipitation can be expressed as follows:
Figure BDA0003490386020000102
step 7, if Mgt＞MgcThen according to MgtFurther calculating the blocking effect factor epsilon of the crystallized and precipitated substancessFurther calculating the permeability coefficient of the synthesized outer coating material after plugging, and then returning to the step 4;
in particular, the build-up of crystalline precipitated material on the surface of the encapsulate can lead to the formation of a filter cakeTo form a plugging effect. Based on this, assume that the surface stacking thickness of the synthetic coating material is Δ dAEquivalent to the plugging effect of the filter cake, as shown in fig. 11. Assuming that the surface accumulation blocking effect factor is epsilonsIt can be expressed as:
Figure BDA0003490386020000103
when the crystallization and precipitation process of the fiber is finished, the crystallization and precipitation amount reaches a critical value MgcAt this time, the outer package encryption factor epsilon is synthesizedgtEqual to the critical encryption factor epsilongcThe permeability coefficient of the coating material reaches the critical value K of the fiber crystallization and precipitationgcAs shown in the following formula:
Figure BDA0003490386020000111
at this time, the permeability coefficient of the synthetic capstock can be expressed as:
Figure BDA0003490386020000112
in the formula, RgTo synthesize the precipitation rate of the chemical on the coating, [ NL-2T-1]；Kgt(LT) permeability coefficient after deposition for the synthesis of coating material-1]；εS: the plugging effect of the surface accumulated sediment is dimensionless; epsilongcIs a critical encryption factor of the fiber crystallization and precipitation process and has no dimension; kgcThe critical permeability coefficient of the synthetic coating material after the fiber crystallization and precipitation process is finished, [ LT [ ]-1]；MgcThe mass of the precipitated material after the fiber crystallization precipitation process, [ M ]](ii) a A is the surface area of the sample of the synthetic capstock, [ L ]2]。
Step 8, repeating the steps until the test is finished (i.e. T is more than or equal to T) or the permeability coefficient of the synthetic coating material is reduced to 0 (i.e. K)gtLess than or equal to 0), and outputting the final Kgt、MgtIncorporating a penetrating system for the synthetic coatingEvaluating the analog value of the number and the variable quantity delta K thereof to verify the effectiveness of the method; specifically, the permeability coefficient variation Δ K of the synthetic coating material for each time step calculated according to the method is compared with the actually measured permeability coefficient variation Δ K of the synthetic coating material, in this embodiment, R is used2And rmse (root Mean Squared error) to evaluate the model:
Figure BDA0003490386020000113
Figure BDA0003490386020000114
wherein n is the total amount of the sample; y isiIs a test measurement; y isiIs an analog value;
Figure BDA0003490386020000115
is the average of the measurements;
Figure BDA0003490386020000116
is a measurement of an analog value.
In this embodiment, the amount of change in permeability coefficient (Δ K) of the coating material synthesized during the plugging test is selected from the crystals of the coating material in the flowing solutiongt＝Kgt-Kgt-1) The model is evaluated by the simulated and measured values of (1), where Δ KgtIs the amount of change of permeability coefficient, K, of the synthetic coating material in one time stepgtThe permeability coefficient of the synthetic coating material at t, Kgt-1The permeability coefficient of the resulting coating at t-1 is shown in FIG. 12, which is a simulation value and a measured value R2＝0.96，RMSE＝3.17×10-5m/s, as can be seen from fig. 12, the model can better describe the process of the synergistic evolution of the chemical fouling and permeability coefficient of the coating.
In addition, substituting the overlapping factor in step 1 into the estimated initial permeability coefficient K of the synthetic outer packageg0In the calculation formula, the simulated initial permeability coefficient K is obtained through calculationg0Permeability coefficient K calculated during the testgtPermeability coefficient K compared with actual measurementgtThe fitting was performed, and the results are shown in FIG. 13. from FIG. 13, it can be seen that the permeability coefficient model considering the overlapping effect can better predict the actual permeability coefficient, R, of the synthetic capstock2＝0.82，RMSE＝3.67×10-5m/s。
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (6)

1. A simulation method for predicting chemical clogging of a synthetic coating is characterized by comprising the following steps:
step 1, measuring to obtain basic physical parameters of a synthetic coating sample, and calculating the fiber surface area S of the synthetic coatinggOverlap factor b and simulated initial permeability coefficient Kg0；
Step 2, carrying out a precipitation crystallization test for synthesizing the coating material, introducing reaction solutions with different solution saturation degrees SI and flow rates V, and measuring corresponding crystallization precipitation rates RgFitting to obtain the chemical precipitation rate R of insoluble saltgAn empirical formula with solution saturation SI and flow rate V;
step 3, selecting a flowing solution with a certain saturation SI to carry out the precipitation crystallization test in the step 2, determining the permeability coefficient and the permeability quality when no crystallization occurs on the outer coating material and in the test process, and determining the critical crystallization precipitation amount Mgc；
Step 4, calculating the change condition of the permeability coefficient of the synthesized outer coating material in the test process, firstly, judging whether the solution flow in the test is constant head treatment, and if the solution flow is constant head, calculating the flow velocity V which is equal to Kgt-1i，Kgt-1The permeability coefficient of the previous time step is set as i, the water head is set as i, and then the next step is carried out; if the flow is determined, directly entering the next step;
step 5, countingCalculating the crystal precipitation amount DeltaM of the next unit time step DeltaT, wherein,
Figure FDA0003490386010000012
calculating the cumulative deposition amount Mgt＝Mgt-1+ΔM，Mgt-1The accumulated precipitation amount of the previous time step is then judged whether the permeation process is finished or whether the permeation coefficient of the synthesized coating material is reduced to 0 at t, and if so, the final permeation coefficient K is outputgtAnd the cumulative amount of precipitate MgtEnding the calculation, and entering the step 8; if not, entering the step 6;
step 6, judging the accumulated precipitation amount Mgt≤MgcWhether or not: if yes, further calculating the encryption factor epsilon of the crystallized sediment substance in the current time step delta TgΔTAnd according to an encryption factor epsilongΔTCalculating the encryption factor epsilon of the chemical silting of the synthetic coating material at the current momentgtAnd then according to the encryption factor epsilongtCalculating the permeability coefficient of the synthesized outer coating material after the chemical clogging, and then returning to the step 4; if not, entering step 7;
step 7, if Mgt＞MgcThen according to MgcFurther calculating the blocking effect factor epsilon of the crystallized and precipitated substancessAnd according to the blocking effect factor epsilonsCalculating the permeability coefficient of the synthesized outer coating material after plugging, and then returning to the step 4;
and 8, evaluating the permeability coefficient and the variation of the synthetic coating obtained by simulation according to the steps until the test is finished so as to verify the effectiveness of the method.
2. The simulation method for predicting chemical fouling of a synthetic coating according to claim 1, wherein the thickness T of the synthetic coating is measured in step 1gLinear density NdtAreal density μgDiameter d of the fiberfCalculating the overlapping factor b and the fiber surface area S of the synthetic coating material by taking the cross section area of the coating material sample as A, the external surface area ratio a of the fabric fiber, the solution density rho and the dynamic viscosity mugAnd the beginning of the simulationInitial permeability coefficient Kg0；
Wherein, the specific calculation formula is as follows:
overlap factor for synthetic overwrap sample fibers:
Figure FDA0003490386010000011
external surface area of synthetic overwrap sample fibers:
Figure FDA0003490386010000021
initial permeability coefficient simulated for the synthetic capstock sample:
Figure FDA0003490386010000022
3. the simulation method for predicting chemical fouling of a synthetic coating according to claim 1, wherein in the step 5, the method for judging whether the permeation process at t is finished or not comprises the following steps: and judging whether T is greater than or equal to T, wherein T is the total time, if so, finishing the permeation process, and if not, finishing the permeation process.
4. The method of claim 1, wherein in step 6, the encryption factor ε of the crystallized sediment material is calculatedgΔTWhen in use, the thickening effect of the fiber of the crystallization precipitation of the synthetic coating material is equivalent to the encryption factor of the fiber, the growth thickness of the crystallization precipitation substance on the surface of the fiber is delta d, and the molar volume of the calcium carbonate is vcalThe crystallization precipitation test unit time step is Δ T, and the fiber encryption factor can be expressed as follows:
Δd＝Rg×vcal×ΔT；
the encryption factor epsilon of the fiber in the unit volume of the outer coating material is synthesized after crystallization and precipitationgtCan be expressed as follows:
Figure FDA0003490386010000023
εgt＝εgt-1+εgΔT；
thus, the permeability coefficient of the synthetic capstock after crystallization precipitation can be expressed as follows:
Figure FDA0003490386010000024
5. the simulation method for predicting chemical fouling of synthetic coatings according to claim 1, wherein in step 7, the blocking effect factor epsilon of the crystalline precipitated material is calculatedsThe method comprises the following steps:
when the crystallization and precipitation process of the fiber is finished, the crystallization and precipitation amount reaches a critical value MgcAt this time, the outer package encryption factor epsilon is synthesizedgtEqual to the critical encryption factor epsilongcThe permeability coefficient of the synthetic coating material reaches the critical value K of the fiber crystallization precipitationgcAs shown in the following formula:
Figure FDA0003490386010000025
the accumulation of crystalline precipitated material on the surface of the coating results in the formation of a filter cake, which forms a plug, on the basis of which it is assumed that the surface of the synthetic coating has a deposit thickness Δ dAAt this time, the surface accumulation plugging effect factor of the crystallized and precipitated outer coating is epsilonsExpressed as:
Figure FDA0003490386010000026
at this time, the permeability coefficient of the synthetic capstock can be expressed as:
Figure FDA0003490386010000027
in the formula, wherein RgThe precipitation rate of the chemical substance on the synthetic coating material; kgtThe permeability coefficient of the synthesized coating after deposition is obtained; epsilons: the plugging effect of the surface accumulated sediment is dimensionless; epsilongcIs a critical encryption factor in the fiber crystallization and precipitation process, and has no dimension; k isgcThe critical permeability coefficient of the outer coating material is synthesized after the fiber crystallization and precipitation process is finished; mgcThe mass of the precipitated substances after the fiber crystallization and precipitation process is finished; a is the surface area of the synthetic capstock sample.
6. The simulation method for predicting chemical fouling of synthetic coatings of claim 4, wherein in step 8, R is used2And RMSE, specifically, comparing the permeability coefficient variation delta K of the synthetic coating material of each time step calculated according to the method with the actually measured permeability coefficient variation delta K of the synthetic coating material; in addition, the simulated value and the measured value of the permeability coefficient in the synthetic coating material test process are evaluated.
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Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018017316A (en) * 2016-07-28 2018-02-01 日立アプライアンス株式会社 Vacuum heat insulation material and refrigerator using the same
CN110856858A (en) * 2018-08-24 2020-03-03 北京中岩大地科技股份有限公司 In-situ decontamination method for polluted soil containing high-concentration pollutants
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