Mineralogical and thermal characterization of a volcanic ash: Implications for turbine interaction

Müller, Dirk; Kueppers, Ulrich; Hess, Kai-Uwe; Song, Wenjia und Dingwell, Donald B. (2019): Mineralogical and thermal characterization of a volcanic ash: Implications for turbine interaction. In: Journal of Volcanology and Geothermal Research, Bd. 377: S. 43-52

Abstract

Volcanic ash (grain size < 2 mm) is a ubiquitous product of explosive volcanic activity. Substantial input of volcanic ash into the atmosphere can lead to repetitive chronic global climate effects whose atmospheric impacts may have durations of up to years. In addition, several recent incidents document the acute hazard potential of volcanic ash interacting with infrastructure supporting technologies. One prominent example is the interaction of volcanic ash with operational jet engine turbines in commercial and/or military aviation. The physico-chemical and phase state of ash influences substantially the thermal behavior of volcanic ash and our ability to predict that behavior and therefore depends on reliable characterization of this state. Here, we have investigated the chemical composition and mineralogy (phase state) of fresh volcanic ash from Tungurahua volcano, Ecuador, as a function of grain size (below 180 mu m) in order to evaluate differences between ground-sampled ash and airborne ash, interacting with jet engines. For the sieved grain size fractions (down to <20 mu m) no significant grain size dependence of ash state is observable. At the <10 mu m (PM10) fraction, the influence of the separation and handling procedures requires special attention. A single-stage separation method, using a <20 mu m pre-sieved ash as source material, shows no grain size dependence of the phase state whereas the use of the unsieved original ash as source material results in an enrichment of plagioclase and a depletion of glass. In contrast, a multi stage gravitational separation procedure, using the unsieved original ash as source material, leads to an enrichment in the glassy phase and a depletion in all crystalline mineral phases. We thus infer that the phase state of the PM10 fraction strongly depends on the choice of starting material and the separation procedure. Using an optical dilatometer image analysis, we have characterized the thermal behavior of the volcanic ash upon heating, which we parameterize in terms of four characteristic temperatures. Using these data the determination of the flow temperature is refined to improve measurement accuracy for fine-grained (<63 mu m) volcanic ash. (C) 2019 Elsevier B.V. All rights reserved.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Geowissenschaften > Department für Geo- und Umweltwissenschaften
• Themengebiete: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
• ISSN: 0377-0273
• Sprache: Englisch