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Microwave drying of wet clay with intermittent heating

Vorhauer, Nicole and Tretau, Anne and Bück, Andreas and Prat, Marc Microwave drying of wet clay with intermittent heating. (2019) Drying Technology, 37 (5). 664-678. ISSN 0737-3937

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Official URL: https://doi.org/10.1080/07373937.2018.1547740

Abstract

In this article, we study an alternative process for the conservative drying of wet clay based on combined microwave heating and convective drying. The study is founded on an experimental analysis of the processes that control drying of porous matter in presence of temperature gradients. We show and discuss that process control cannot be reliably based on temperature alone because mass transfer phenomena associated with microwave heating dictate drying kinetics. Essentially, the occurrence of pressure build up and liquid expulsion, dominating mass transfer if microwave heating is uncontrolled or with high power, vitally depend on the moisture content of the clay. As a consequence, the deterioration of clay is problematic if internal evaporation rates are high, thus at the start of drying when also the moisture content is high. Following this, we propose intermittent microwave heating in combination with convective drying periods with the aim to reduce overall drying time (compared to conventional convective drying) and to improve product quality by reduced material shrinkage. Drying experiments indicate that the overall drying time reduction and product quality depend on the frequency and duration of the two subsequent periods of intermittent heating and convective drying. The observations can be explained with the evolution of the pore-scale distribution of liquid and vapor during drying.

Item Type:Article
HAL Id:hal-02361159
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Friedrich-Alexander-Universität Erlangen-Nürnberg - FAU (GERMANY)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Other partners > Institut für Ziegelforschung Essen e.V. - IZF (GERMANY)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Otto Von Guericke Universität Magdeburg - OVGU (GERMANY)
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Deposited On:13 Nov 2019 10:31

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