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Evaporative NaCl salt crusts : formation, patterning, displacement and detachment mechanisms

Licsandru, Glad calin. Evaporative NaCl salt crusts : formation, patterning, displacement and detachment mechanisms. PhD, Dynamique des fluides, Institut National Polytechnique de Toulouse, 2020

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Abstract

Halite (NaCl(s)) is often found in nature as large efflorescence salt crust deposits (salt flats).Reports show that salt crusts can greatly affect the evaporation process and can lead to puzzlingphenomena, such as the formation of salt domes or crust detachment from the underlying poroushost. In this context, the present work has the objective to bring forth a better understanding ofsalt crust formation and its dynamics through original laboratory-based experiments put against asimple modelling approach. A series of experiments are conducted in well controlled laboratoryenvironment (temperature, humidity, salt concentration, water saturation, etc.), in 2D (Hele Shawcell) and 3D (PTFE cylindrical containers) packed with a glass bead porous medium. The imagingis done with time-lapse high definition photography, while accompanied by 3D laser surfacescanning and X-ray based visualization. These allow identifying and quantifying crust behaviorssuch as growth, size, speed of displacement or even pattern formation. Controlled changes incrust morphology, displacement and detachment are presented by varying certain environmental factors. In addition to detailed information on the displacement of compact crusts and the crust’sdetachment process, the experiments show that a uniform compact crust can be changed into abranched morphology and vice versa. Further more, there are presented two types of salt crustcellular patterns which can be obtained under well controlled laboratory conditions.Simple reactive transport modeling coupling solute transport, evaporation, dissolution andprecipitation was then developed in order to help analyze the experimental results and developpredictive models. In particular, the modelling indicates that all the phenomena evidenced in the experiments can be explained by the combination of coupled evaporation - dissolution-recrystallization processes

Item Type:PhD Thesis
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Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
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Research Director:
Prat, Marc and Noiriel, Catherine
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Deposited On:07 Oct 2021 11:12

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