CN-115544829-B - Numerical simulation method for enhanced vapor phase extraction of geothermal conduction in organic contaminated site

CN115544829BCN 115544829 BCN115544829 BCN 115544829BCN-115544829-B

Abstract

The invention provides a simulation method for heat conduction strengthening gas phase extraction of an organic pollution site, which comprises the steps of S1, establishing a heat conduction strengthening gas phase extraction finite element model, S2, conducting mesh division on the heat conduction strengthening gas phase extraction finite element model, S3, configuring corresponding parameters according to an actual site repair process, S4, conducting control calculation parameter setting on the heat conduction strengthening gas phase extraction finite element model, S5, conducting natural condition initialization on the heat conduction strengthening gas phase extraction finite element model, S6, conducting initial concentration assignment of pollutants on the heat conduction strengthening gas phase extraction finite element model, and S7, executing a heat conduction strengthening gas phase extraction numerical simulation program to realize repair process simulation. The invention solves the problem that the existing method can not realize the simulation of the heat conduction and vapor extraction coupling repair process, can simulate the time-space distribution rule of the temperature field and pollutants in the repair process, and provides reference and scientific basis for the heat conduction reinforced vapor extraction repair of the organic pollution field.

Inventors

GU QINGBAO
SUN CHAO
MA FUJUN
Shen Jialun
SUN ZONGQUAN

Assignees

中国环境科学研究院

Dates

Publication Date: 20260512
Application Date: 20220922

Claims (7)

1. The numerical simulation method for the heat conduction enhanced vapor extraction of the organic contaminated site is characterized by comprising the following steps of: S1, establishing a heat conduction reinforced vapor extraction finite element model, namely obtaining geometric parameters of an actual field research area to perform model construction, and setting layout modes of a heating well, an extraction well and a temperature measurement well in the research area; s2, meshing the heat conduction reinforced vapor extraction finite element model; s3, configuring corresponding parameters according to an actual site repair process; S4, performing control calculation parameter setting on the heat conduction reinforced vapor extraction finite element model; s5, initializing natural conditions of the heat conduction reinforced vapor extraction finite element model; s6, carrying out initial concentration assignment on the heat conduction enhanced vapor extraction finite element model, and S7, executing a heat conduction reinforced vapor extraction numerical simulation program to realize the simulation of the repair process, wherein the heat conduction mode is realized by designing a heating grid, setting heating materials and injecting heating power, the vapor extraction mode is realized by a TMVOC model built-in module, Wherein in step S1, the geometrical parameters of the actual field research area comprise inflection point coordinates of the research area, various soil layer thicknesses and heat preservation thicknesses of the research area, and model sizes are set according to the actual size 1:1 of the field, wherein in the research area, the heating wells are distributed in a regular triangle, the extraction wells are distributed at the centroid position of the regular triangle, the temperature measurement wells are positioned on a line formed by connecting two heating wells, In step S2, mesh division in the vertical direction is set according to specific pollution layering by adopting a self-defining method, the mesh type in the horizontal direction is polygonal mesh, the maximum mesh area is set to be 0.5 m 2 , and the minimum improvement angle is set to be 15 degrees.
2. The numerical simulation method for heat conduction enhanced vapor extraction of the organic contaminated site according to claim 1, further comprising fitting verification of the heat conduction enhanced vapor extraction finite element model, wherein a fitting goodness evaluation mode is represented by a linear regression equation R 2 , the closer R 2 is to 1, the higher the simulation precision is, and fitting indexes are temperature rise data and chlorobenzene concentration data after repair.
3. The numerical simulation method for enhanced vapor phase extraction of organic contaminated sites by thermal conduction according to claim 1, wherein in step S3, the parameters include contaminant parameters including diffusion coefficients of water, air and contaminants in three phases of gas, liquid and non-aqueous liquid, respectively, soil parameters including soil density, porosity, horizontal permeability, vertical permeability, thermal conductivity, specific heat capacity, relative permeability, capillary pressure, organic carbon content, and process parameters including heating power, extraction rate, extraction pressure.
4. The numerical simulation method of enhanced vapor phase extraction of organic contaminated site heat conduction according to claim 1, wherein in step S4, the control calculation parameters include a running time, a step size, a maximum number of steps, a maximum number of iterations per step, a conjugate gradient solver, a maximum number of iterations, a convergence criterion, a relative error, an absolute error, a derivative increment factor, and an iteration maximum residual.
5. The numerical simulation method for enhanced vapor phase extraction of heat conduction in an organic contaminated site according to claim 1, wherein in step S5, the natural conditions include phase state, pressure, temperature, and water content, the top layer mesh is set as an atmospheric boundary, the bottom layer mesh is set as a fixed boundary, and the periphery is set as a fluxless boundary.
6. The numerical simulation method for enhanced vapor phase extraction of heat conduction in an organic contaminated site according to claim 1, wherein in step S6, the method for assigning the initial concentration of the contaminant is to set a source-sink term near the designed leakage point to perform leakage of the contaminant at a rate of 1.0 x 10 -10 ~1.6×10 -7 kg/S, thereby completing assignment of the initial concentration of the site, and includes: 1) Taking the result of the natural condition initialization as the initial condition of execution; 2) Selecting chlorobenzene as a pollutant, and setting relevant parameters of the chlorobenzene; 3) Designing distribution of leakage points of pollutants, setting source and sink items and continuous leakage rate, performing independent assignment on grids of each layer of a polluted area, disabling other layers when performing concentration assignment on a single-layer grid, taking the last operation result as the initial condition of the next time, increasing the diffusion rate of chlorobenzene in air to 3X 10 -5 m 2 /s when assigning, removing the leakage points after the pollutant leaks for 1 year, changing the diffusion rate to a normal value of 7.6X10 -6 m 2 /s, and freely migrating and diffusing for 1 year to enable the diffusion rate to be close to the initial pollution state; 4) And enabling all the pollution layers after all the assignment of the pollution layers is completed.
7. The numerical simulation method for enhanced vapor phase extraction of geothermal conduction in an organic contaminated site according to claim 1, wherein step S7 comprises: 1) Taking the result of the completion of the assignment of the initial concentration of the pollutant as an initial condition for execution; 2) Arranging the heating well, the extraction well and the temperature measuring well according to actual field data, and setting related parameters, wherein the volume weight of the heating material is 7930g/cm 3 , the heat conductivity coefficient is 16.8W/m.K, the heating grid source and sink are injected with 520W/m of heat power, and the extraction well is directly inserted by the TMVOC model; 3) The operation period t=56 days, which is divided into 8 output time points, and the simulation program is operated; 4) Carrying out visual treatment on an output result after the model operation is finished to obtain a simulated repair effect cloud picture of field heat conduction reinforced vapor extraction; 5) And (3) carrying out data analysis on an output result after the model operation is finished to obtain a simulated heating law curve of the field and a change trend curve of the total mass of pollutants.

Description

Numerical simulation method for enhanced vapor phase extraction of geothermal conduction in organic contaminated site Technical Field The invention relates to the technical field of environmental protection, in particular to a numerical simulation method for heat conduction reinforced vapor extraction of an organic pollution field. Background As a common soil in-situ restoration technology, the soil vapor extraction technology (Soil Vapor Extraction, SVE) has the advantages of low cost, simple operation, high efficiency, small influence on the surrounding environment and the like, and can efficiently remove volatile organic compounds in soil. However, under the condition of normal temperature, the SVE technology is easy to be limited by factors such as physical and chemical properties of soil, pollutant characteristics and the like, and the application range of the SVE technology can be enlarged and the repair efficiency can be improved by coupling with an in-situ thermal repair technology. Among other things, in situ heat transfer (Thermal Conduction Heating, TCH) techniques are based on heating elements that heat up soil through soil particles and pore fluids to accelerate removal of organic contaminants. The heat conduction enhanced vapor extraction technology is widely regarded as a promising organic pollution site restoration technology because of the short restoration period, controllable secondary pollution, strong applicability to soil texture and pollutant properties and high restoration efficiency. At present, the design and operation of the polluted site geothermal conduction enhanced vapor extraction process mostly refer to an empirical formula and limited site practical experience. However, the effectiveness of process remediation is commonly affected by a variety of factors such as soil texture, hydrogeologic properties, well placement, and aeration rate. Therefore, the energy waste is reduced, the pollution site repair process is predicted to realize accurate repair, and the method is a trend of the future pollution site repair industry. Numerical simulation technology is widely applied to various engineering practices as an important means of scientific research and engineering planning. Currently, the predictive model for the environmental behavior of organic pollutants in soil groundwater mainly includes TOUGH, stmp and NAPL simulator. The STOMP and NAPL simulator numerical models can only simulate the migration process of organic pollutants in the soil and underground water, and the technical requirement of the organic pollution site gas phase extraction technology restoration effect prediction is difficult to meet. TMVOC module in TOUGH software (a module in commercial visualization software PERTRASIM of TOUGH software) can simulate the removal process of target pollutants in the vapor extraction repair process of an organic pollution site and predict the repair effect of vapor extraction technology on the organic pollution site. However, TMVOC has not been provided with the function of simulating the heat conduction heating process, which results in nearly blank research on the numerical simulation method of heat conduction enhanced vapor extraction of the organic contaminated site. Disclosure of Invention The invention provides a numerical simulation method for heat conduction strengthening vapor extraction of an organic pollution field, which solves the problem that the simulation of the heat conduction and vapor extraction coupling repair process cannot be realized by the existing method, can simulate the time-space distribution rule of a temperature field and pollutants in the repair process, and can provide powerful reference and scientific basis for heat conduction strengthening vapor extraction repair of the organic pollution field. In order to solve the technical problems, the technical scheme of the invention is as follows: The numerical simulation method for the heat conduction strengthening vapor extraction of the organic pollution field comprises the following steps of S1, obtaining geometric parameters of an actual field research area to carry out model construction, setting layout modes of heating wells, extraction wells and temperature measurement wells in the modeling area, S2, carrying out grid subdivision on the heat conduction strengthening vapor extraction finite element model, S3, configuring corresponding parameters according to an actual field restoration process, S4, carrying out control calculation parameter setting on the heat conduction strengthening vapor extraction finite element model, S5, carrying out natural condition initialization on the heat conduction strengthening vapor extraction finite element model, S6, carrying out pollutant initial concentration assignment on the heat conduction strengthening vapor extraction finite element model, and S7, executing a heat conduction strengthening vapor extraction numerical simulation program to realize restorati