Influence of pore structure and impregnation–drying conditions on the solid distribution in porous support materials

Abstract

Deposition of solids within porous materials from a drying solution is an important phenomenon in numerous natural and industrial processes. A profound knowledge about influences of different parameters on the solid distribution in the material is required for an effective targeted impregnation process. Experimental investigations and simulations are used to study the influence of pore structure, drying conditions and solute concentration on the solid distribution in porous support materials after impregnation and drying. It is found that low drying rates lead to strong solid accumulation at the material surface, whereas high drying rates reduce the solute transport to the surface and result in more uniform solid distributions. A small pore diameter and distribution width reduces solute migration during drying and leads to uniform solid distributions without being influenced by the drying conditions. A higher initial concentration of the impregnation solution causes pronounced surface accumulation while low initial solute concentrations result in more uniform distributions. Fundamental effects during drying are captured in an existing pore network model by adaption of experimental pore structures and impregnation-drying conditions resulting in good general agreement of experiments with simulations.

New insights into saline water evaporation from porous media: Complex interaction between evaporation rates, precipitation, and surface temperature

“…Evaporation of saline water from porous media is important in many environmental, engineering, and hydrological processes including vegetation and plant growth, soil salinization, land-atmosphere interaction, functioning of the ecosystem, and crop production [Rodriguez-Navarro and Doehne, 1999;Suweis et al, 2010;Ott et al, 2015;Bergstad and Shokri, 2016]. This has motivated many researchers to investigate various aspects of this process including the effects of grain size, wettability, heterogeneity, and external conditions [Huinink et al, 2002;Guglielmini et al, 2008;Nachshon et al, 2011aNachshon et al, , 2011bEloukabi et al, 2013;Norouzi Rad et al, 2015;Jambhekar et al, 2015;Börnhorst et al, 2016;Dai et al, 2016;Shokri-Kuehni et al, 2017].…”

Drying of thin porous disks from pore network simulations

“…These findings are instrumental in controlling the drying process of TPM and could be useful to better control the drying of salt solutions and dispersions, as the final particle distribution inside the solid matrix depends on the evolution of gas-liquid distributions during drying. [29,30]…”

“…9). Figure 10 compares the top view of the phase distributions at network saturation of S ∼ 0.1 for the varying disk heights with N k ¼ [4,10,20,30,40]. Fully saturated throats are shown in blue and empty throats are not plotted in Fig.…”

“…It must be highlighted that the direction of liquid migration is important in drying processes incorporating crystallization effects [29] or transport of dispersed particles, because the final distribution of particles inside the solid matrix depends on liquid pumping effects and the order of emptying of the pore space. [30] Imposing of thermal gradients might thus be instrumental to control the pore level transport in TPM. Moreover, temperature affected mass transfer plays a role in the example of the GDL during operation-here one would like to obtain optimum water and gas saturation to allow for continuous transportation of reactants and products.…”

Temperature gradient induced double stabilization of the evaporation front within a drying porous medium

“…Control of the final distribution of these species after drying can be essential. For instance, in the case of salts, the drying process leads to the formation of salt crystals either within the porous medium [8,9] or on its surface [10]. This in turn can greatly affect the drying process depending on the properties of the crystallized salt layers [10].…”