Martin F. Sunding

Reference data set of volcanic ash physicochemical and optical properties

Uncertainty in the physicochemical and optical properties of volcanic ash particles creates errors in the detection and modeling of volcanic ash clouds and in quantification of their potential impacts. In this study, we provide a dataset that describes the physicochemical and optical properties of a representative selection of volcanic ash samples from nine different volcanic eruptions covering a wide range of silica contents (50 - 80 wt. % SiO2). We measured and calculated parameters describing the physical (size distribution, complex shape, and dense-rock equivalent mass density), chemical (bulk and surface composition) and optical (complex refractive index from ultra-violet to near-infrared wavelengths) properties of the volcanic ash and classified the samples according to their SiO2 and total alkali contents into the common igneous rock types Basalt to Rhyolite. We found that the mass density ranges between ρ = 2.49 and 2.98 g/cm3 for rhyolitic to basaltic ash types, and that the particle shape varies with changing particle size (d < 100 μm). The complex refractive indices in the wavelength range between λ = 300 nm and 1500 nm depends systematically on the composition of the samples. The real part values vary from n = 1.38 to 1.66 depending on ash type and wavelength and the imaginary part values from k = 0.00027 to 0.00268. We place our results into the context of existing data, and thus provide a comprehensive dataset that can be used for future and historic eruptions, when only basic information about the magma type producing the ash is known.

Fe2O3–Al2O3 oxygen carrier materials for chemical looping combustion, a redox thermodynamic and thermogravimetric evaluation in the presence of H2S

Alumina-supported Fe2O3 oxygen carrier material (OCM) system is among the most promising OCM systems for solid and gaseous fuel CLC. This work utilizes a comprehensive thermogravimetric and thermodynamic equilibrium approach to redox and CLOU performance, oxygen transfer capacity, reduction rate and sulfur tolerance of the Fe2O3 impregnated on Al2O3 OCM. Thermodynamic evaluations reveal that the beneficial composition range lies in a wide range of 7.5–34% molar Fe2O3 ratios. This is the range at which aluminum-rich corundum phase, i.e., (Al, Fe)2O3, remains stable throughout the oxidizing to very reducing oxygen partial pressures in fuel reactor. The experimental system in this study contains 20xa0mass% Fe2O3, i.e., XFeu2009=u200913.8% molar which lies well within this interval. Deep redox cycle experiments confirm the thermodynamic modeling and during the long residence time of this experiment, the sample is almost fully reduced and exhibits its thermodynamic redox oxygen capacity of close to 1.5xa0mass%. Extension of the deep redox cycles to 15 cycles induces no performance deterioration in terms of capacity, rate of reduction or morphological failure. The redox experiment under sour reducing gas indicates no H2S poisoning for the 20xa0mass% Fe2O3 supported on Al2O3 OCM. The findings that this system is not affected with the H2S content of the gas, and the prediction of the SO2 release from the fuel reactor is in good agreement with our recent reactor testing findings available in the literature.