NaCl溶液运移过程的电容成像法室内监测研究

电容成像法是根据被测物质各相具有不同的介电常数,当各相组分分布或浓度发生变化时,将引起被测介质介电常数发生变化,从而使测量电极对间的电容值发生变化。以这些电容测量值作为投影数据,通过一定的图像重建算法,便可以获得介电常数分布,从而获得物质分布的图像。本研究运用电容成像法对NaCl溶液运移过程进行了实时监测,首先通过小砂盒进行了用不同浓度NaCl溶液饱和的多孔介质测定,得到了电容标定曲线,从而说明了电容成像法的有效性,然后通过砂槽进行了非饱和带中NaCl溶液的运移试验,并利用电容成像法进行了同步的动态监测,得到横纵向电容时间变化曲线,以及影像图,并通过三维电容相对值变化明显的看出NaCl溶液运移过程。这说明利用电容成像法对非饱和多孔介质中NaCl溶液的空间分布范围进行圈定并监测其迁移过程是完全可行的。

Laboratorial monitoring of NaCI solution migration process by using electrical capacitance tomography

Electrical capacitance tomography method is based on the theory that each phase of the tested material has different permittivity which will change when the component distribution or concentration of each phase varies, and thus they make the measuring electrode capacitance change. Considering the capacitance values measured as the projection data, the permittivity distribution can be got by certain set of image reconstruction algorithms and then the material distribution of images will also be obtained. In this study, the electrical capacitance imaging method is used to monitor NaCl solution real-time migration process. Firstly, the saturated porous medium tests for NaCl solution of different concentrations are carried out by using small sand box and thereby the capacitance calibration curves are got, proving that the capacitance tomography method is very effective. After that, the migration tests for NaCl solution in non- saturated zone is held by using a sand box and the process is dynamically monitored by the capacitance tomography method. As a result, both the cross and longitudinal capacitances time-changing curves are obtained including the image figures. The migration process of NaCl solution is clearly reflected from the changing values of three dimensional relative capacitances. The results of this study showe that the use of electrical capacitance tomography method is entirely feasible for NaCl solution spatial distribution outlining and its migration process monitoring in unsaturated porous medium.