Earth Sciences Division and ‡Computational Research Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States.
Environ Sci Technol. 2014 Jul 1;48(13):7453-60. doi: 10.1021/es5013438. Epub 2014 Jun 10.
A combination of experimental, imaging, and modeling techniques were applied to investigate the pore-scale transport and surface reaction controls on calcite dissolution under elevated pCO2 conditions. The laboratory experiment consisted of the injection of a solution at 4 bar pCO2 into a capillary tube packed with crushed calcite. A high resolution pore-scale numerical model was used to simulate the experiment based on a computational domain consisting of reactive calcite, pore space, and the capillary wall constructed from volumetric X-ray microtomography images. Simulated pore-scale effluent concentrations were higher than those measured by a factor of 1.8, with the largest component of the discrepancy related to uncertainties in the reaction rate model and its parameters. However, part of the discrepancy was apparently due to mass transport limitations to reactive surfaces, which were most pronounced near the inlet where larger diffusive boundary layers formed around grains and in slow-flowing pore spaces that exchanged mass by diffusion with fast flow paths. Although minor, the difference between pore- and continuum-scale results due to transport controls was discernible with the highly accurate methods employed and is expected to be more significant where heterogeneity is greater, as in natural subsurface materials.
采用实验、成像和建模技术相结合的方法，研究了在高 pCO2 条件下碳酸钙溶解的孔隙尺度输运和表面反应控制。实验室实验包括将在 4 巴 pCO2 下的溶液注入到用碎碳酸钙填充的毛细管中。基于由反应性碳酸钙、孔隙空间和从体积 X 射线微断层扫描图像构建的毛细管壁组成的计算域，使用高分辨率孔隙尺度数值模型来模拟实验。模拟的孔隙尺度流出浓度比测量值高 1.8 倍，差异的最大组成部分与反应速率模型及其参数的不确定性有关。然而，差异的一部分显然是由于反应表面的传质限制，在入口附近最为明显，在那里较大的扩散边界层围绕颗粒形成，并且在通过扩散与快速流路交换质量的缓慢流动孔隙空间中形成。尽管很小，但由于传输控制导致的孔隙和连续体尺度结果之间的差异在采用的高精度方法下是明显的，并且在异质性更大的情况下（例如在天然地下材料中），这种差异预计会更加显著。
