caa a22 4500 463163737 CHVBK 20180406164755.0 cr unu---uuuuu 170326e20070701xx s 000 0 eng 10.1007/s11242-006-9048-5 doi (NATIONALLICENCE)springer-10.1007/s11242-006-9048-5 Permeability anisotropy due to consolidation of compressible porous media [Elektronische Daten] [O. Scholes, S. Clayton, A. Hoadley, C. Tiu] The characterisation of flow through porous media is important for all solid-liquid separation and fluid transport realms. The permeability of porous media can be anisotropic and furthermore, the extent of anisotropy can be increased as a result of an applied compressive force. However, the understanding of how anisotropy develops is incomplete. An overview of research on permeability anisotropy is given and an expression for predicting anisotropy as a function of void ratio is offered. The two underlying assumptions of the proposed model are: flow in different directions occurs within the same network of pores and deformation is primarily due to the compression of the particles in the direction of the applied force rather than due to particle rearrangement. The assumption of network connectivity allows permeability anisotropy to be described as a function of flow path tortuosity only. Results are presented for hydraulic anisotropy measured in lignite that has been upgraded by a compression dewatering method known as mechanical thermal expression. The lignite permeability is shown to be up to eight times greater in the direction perpendicular to compression, suggesting that the rate of dewatering could be significantly increased by choosing the drainage to also be perpendicular to the direction of the applied compressive force. It is illustrated that the proposed anisotropy model can be used to accurately predict the experimentally determined permeability anisotropy ratios for lignite, as well as for other materials including sand, clay and kaolin. Springer Science+Business Media B.V., 2006 MTE nationallicence Tortuosity nationallicence Kozeny-Carman nationallicence Internally porous nationallicence Lignite nationallicence Coal nationallicence Dewatering nationallicence Filtration nationallicence a : Length of the major axis of a particle (m) nationallicence a 0 : Initial length of the major axis of a particle (m) nationallicence A : Anisotropy due to particle shape and orientation (-) nationallicence b : Length of the minor axis of a particle (m) nationallicence b 0 : Initial length of the minor axis of a particle (m) nationallicence C K : Kozeny shape factor (-) nationallicence c : Empirical constant (-) nationallicence d : Empirical constant (-) nationallicence e : Void ratio, which equals [volume of voids]/[volume of solids] (m3/m3) nationallicence e 0 : Maximum void ratio where permeability isotropy exists (m3/m3) nationallicence e 1 : First measured void ratio (m3/m3) nationallicence e max : Maximum void ratio (m3/m3) nationallicence e opt : Void ratio at optimum density of the modified proctor test (m3/m3) nationallicence F : Formation resistivity factor (-) nationallicence I e : Density index (-) nationallicence k : Coefficient of permeability (m/s) nationallicence k 1 (2, 3) : Principal permeability in the 1 (2, 3) direction (m2) nationallicence k 1 o (2 o , 3 o ) : Initial principal permeability in the 1 (2, 3) direction (m2) nationallicence k ax : Coefficient of permeability in the axial direction (m/s) nationallicence k p : Permeability proportionality constant (-) nationallicence k rad : Coefficient of permeability in the radial direction (m/s) nationallicence $$k_{\updownarrow}$$ : Coefficient of permeability in the vertical direction (m/s) nationallicence k ↔ : Coefficient of permeability in the horizontal direction (m/s) nationallicence K : Absolute permeability (m2) nationallicence K θ : Permeability at angle theta (m2) nationallicence K 0 : Permeability at zero degrees, i.e. horizontal orientation (m2) nationallicence K 90 : Permeability at ninety degrees, i.e. vertical orientation (m2) nationallicence L : Sample thickness or apparent path length (m) nationallicence L eff : Actual (effective) path length (m) nationallicence m : Fitting constant (-) nationallicence n : Porosity (%) nationallicence r k : Permeability anisotropy=ratio of horizontal to vertical or radial to axial permeability (-) nationallicence r τ : Ratio of vertical to horizontal or axial to radial tortuosity (-) nationallicence r 0 : Initial permeability ratio or initial tortuosity ratio (-) nationallicence r 1 : permeability ratio at e 1 (-) nationallicence S : Specific surface area (m2/m3) nationallicence T : Tortuosity due to material heterogeneity and particle arrangement (-) nationallicence x : Fitting factor that relates to the ratio of vertical to horizontal or axial to radial tortuosity in Eq. 18 (-) nationallicence x * : Fitting factor that relates to the ratio of vertical to horizontal or axial to radial tortuosity in Eq. 19 (-) nationallicence $$\overline{XY}$$ : Length of a shape's perimeter between points X and Y (m) nationallicence Greek Symbols nationallicence $$\varepsilon$$ : Strain (m/m) nationallicence $$\varepsilon_{1 (2, 3)}$$ : Principal strain, in the 1 (2, 3) direction (m/m) nationallicence γf : Fluid unit weight (kN/m3) nationallicence μf : Fluid viscosity (Pas) nationallicence θaverage : Average angle between the direction of macroscopic flow and the direction normal to an element of surface exposed to the flow (°) nationallicence τ : Tortuosity (m/m) nationallicence Ω : Resistance (e.g., diffusional) through a porous medium (cm2/s) nationallicence Ω0 : Resistance (e.g., diffusional) in the absence of a porous medium (cm2/s) nationallicence Subscripts nationallicence $$\updownarrow$$ : In the vertical or axial direction nationallicence ↔ : In the horizontal or radial direction nationallicence Scholes O. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut Clayton S. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut Hoadley A. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut Tiu C. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut Transport in Porous Media Kluwer Academic Publishers 68/3(2007-07-01), 365-387 0169-3913 68:3<365 2007 68 11242 https://doi.org/10.1007/s11242-006-9048-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11242-006-9048-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Scholes O. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut NATIONALLICENCE 700 1- Clayton S. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut NATIONALLICENCE 700 1- Hoadley A. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut NATIONALLICENCE 700 1- Tiu C. Department of Chemical Engineering, Cooperative Research Centre for Clean Power from Lignite, Monash University, 3800, Clayton, Victoria, Australia aut NATIONALLICENCE 773 0- Transport in Porous Media Kluwer Academic Publishers 68/3(2007-07-01), 365-387 0169-3913 68:3<365 2007 68 11242 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer