Title: Relating Darcy-Scale Chemical Reaction Order to Pore-Scale Spatial Heterogeneity
Authors: Huang, Po Wei
Flemisch, Bernd
Qin, Chao Zhong
Saar, Martin O.
Ebigbo, Anozie  
Language: eng
Keywords: Mineral dissolution;Reaction rate law;Reactive transport;Upscaling
Issue Date: 1-Sep-2022
Document Type: Article
Journal / Series / Working Paper (HSU): Transport in Porous Media
Volume: 144
Page Start: 507
Page End: 543
Abstract: 
Due to spatial scaling effects, there is a discrepancy in mineral dissolution rates measured at different spatial scales. Many reasons for this spatial scaling effect can be given. We investigate one such reason, i.e., how pore-scale spatial heterogeneity in porous media affects overall mineral dissolution rates. Using the bundle-of-tubes model as an analogy for porous media, we show that the Darcy-scale reaction order increases as the statistical similarity between the pore sizes and the effective-surface-area ratio of the porous sample decreases. The analytical results quantify mineral spatial heterogeneity using the Darcy-scale reaction order and give a mechanistic explanation to the usage of reaction order in Darcy-scale modeling. The relation is used as a constitutive relation of reactive transport at the Darcy scale. We test the constitutive relation by simulating flow-through experiments. The proposed constitutive relation is able to model the solute breakthrough curve of the simulations. Our results imply that we can infer mineral spatial heterogeneity of a porous media using measured solute concentration over time in a flow-through dissolution experiment.
Organization Units (connected with the publication): Hydromechanik 
ISSN: 01693913
Publisher DOI: 10.1007/s11242-022-01817-0
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