Characterization of sand and sand–binder systems from the foundry industry with electrical impedance spectroscopy
<p>The global economy consumes an estimated <span class="inline-formula">4×10<sup>10</sup></span> t of sand per year, with only <span class="inline-formula">2×10<sup>10</sup></span> t of sand being reproduced by natural sedime...
Main Authors: | , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2021-02-01
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Series: | Journal of Sensors and Sensor Systems |
Online Access: | https://jsss.copernicus.org/articles/10/43/2021/jsss-10-43-2021.pdf |
Summary: | <p>The global economy consumes an estimated <span class="inline-formula">4×10<sup>10</sup></span> t of sand
per year, with only <span class="inline-formula">2×10<sup>10</sup></span> t of sand being reproduced by natural
sedimentation (Götze and Göbbels, 2017; Peduzzi, 2014). Among other things, sand
is also used as a basic material for the production of molds and cores in
the foundry industry. The consumption and the economic as well as ecological
savings' potential in this area of application can be appreciated by way of
an example: the environmental certificate of a single, albeit big German
foundry (5160 employees) can be consulted, which states that 39 820 t of
sand for casting molds had to be purchased in 2017 (Denes, 2018). In order
to avoid having to dispose of the used sand in landfills and to reduce the use of new sand,
it is therefore advantageous to renew the used sand in a so-called
regeneration process and reuse it as a substitute for new sand in the
production of molds and cores. It would be very advantageous if the
condition of molding materials (sand–binder systems) in regenerator units
could be monitored in real time because of the economic and ecological
advantages of a monitored and optimized regeneration process. This work
presents the results of investigations in this direction. The objects of
investigation in this work are typical molding materials in the foundry
industry, e.g., quartz sand, chromite sand, and bentonite as a binder, which
are measured impedimetrically with the help of a plate capacitor measuring
cell which is connected to an LCR meter (Agilent E4980A). The impedance of
the filled capacitor is measured in a frequency range from 1.2 kHz to 1 MHz,
containing 123 frequency points. The aim of this research is to work out if
the mentioned substances can be measured with the presented measuring method
and classified on the basis of impedance characteristics and thus whether impedance
spectroscopy can be considered for process monitoring in the molding
industry. It is shown that the condition monitoring can possibly be based on
impedance spectroscopy because the resulting curves are characteristic of
the material used. New and used sands as well as two-component mixtures of
sands and binders showed a systematic behavior, which allows the sand or the
composition of the mixture to be identified (classified) in the future. The
examination of the scatter of the measurement results shows that the
impedance data obtained with this method can be measured reproducibly. A
descriptive model for multi-component systems is developed in order to be
able to interpret the impedance scatter results and their representation in
Nyquist plots. From this model, the filling density of the measurement cell
and the density of conduction paths can be extracted as essential influence
quantities.</p> |
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ISSN: | 2194-8771 2194-878X |