Attrition and dust formation of pure and core-shell SiC powders

Abstract : A recent innovation in concentrating solar systems makes use of a new heat transfer fluid (htf) that operates in such a way that a dense suspension of SiC particles acts as a heat transfer fluid with a heat capacity similar to the molten salts traditionally used as a HTF in concentrated solar energy. In this kind of system the wall absorbs solar radiation and transfers the heat to a flowing heat transfer medium. This innovation is currently developed in the frame of a European project FP7 EC project CSP2 (http://www.csp2-project.eu/). During powder handling operations inherent to this process a number of sources of powder attrition are present and this important phenomena is key in industrial environments not only because of its impact on the containing equipment but also because of dust formation; this has serious implications with regards to health and safety so there is a clear need for research on these operations and it appears as one of the premises of HANHAZ2015. Some causes of powder attrition are “Mechanical stress” in screw feeders or rotary valves, "Kinetic stress" caused by the impact of particles due to high velocity jets, bubbling action, collisions in tubes, baffles, cyclones; "Thermal stress" due to the thermal shock produced when cold particles get in touch with hot beds or "Chemical stress" due to evolving gases or water vapour. The sources of equipment erosion are mostly a result of mechanical action of particle impacts. The hydrodynamics of the fluidised particle suspension are a key parameter in the efficiency of the energy harvesting system. We use Positron Emission Particle Tracking (PEPT) to study the circulation and mobility of the particles in the tubes. The tracer particle is prepared by an indirect labelling technique using 18F as radio-isotope. However, SiC particles have shown low affinity and low activation efficiency for this isotope surely due to the inert chemical properties of this material. Consequently, a new tracer has to be found. In this work we aim at modifying the surface of the SiC particles so they can be used as tracers, thus providing more reliable measurements. In this work a thin layer of alumina (approximately 500nm) is deposited on the surface of the SiC using gas-phase deposition technique with a layer-by-layer growth mechanism. The ratio of the film thickness compared to the particle size is very small, therefore the properties such as size, shape and density will not be influenced by the alumina coating. In this study two novel setups for particle aerosol measurement and wear are used in order to quantify the aerosol mass concentration and aerosolized wear particles. We wanted to determine whether the alumina shell would produce energy dissipation during the collisions, when compared with the collision of two uncoated SiC particles. The release of coating is found to increase with the wear energy applied on the surface of the particles.
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Submitted on : Tuesday, August 7, 2018 - 2:46:15 PM
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P. Garcia-Trinanes, Somik Chakravarty, Martin Morgeneyer, Olivier Le Bihan, D. Valdesueiro, et al.. Attrition and dust formation of pure and core-shell SiC powders. 10. European Congress of Chemical Engineering (ECCE 10), Sep 2015, Nice, France. pp.611-612. ⟨ineris-01855210⟩

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