Assessment and improvement of optical properties of particles for solid particle receiver

Abstract

Particle receiver technology is an increasing research field. Researchers are investigating various different types of receivers, such as falling particle receivers, obstructed flow particle receivers, beam down fluidized bed systems, dense particle receivers, or the centrifugal receiver (Ho, 2016). This paper describes the assessment of three samples of commercial available particles (“proppants”) by microscopy and by X-ray diffraction phase analysis: Sintered Bauxite from Saint Gobain (mean diameter 1.2 mm and 0.45 mm), and Carboprop HD from Carbo Ceramics. Analyzed proppants consist of alpha-Al2O3, a glassy phase, and minor amounts of FeAlTiO5 and mullite. Particle samples have been prepared, to measure the reflectivity by a Lambda 950 spectrometer and evaluate the solar absorptance. As-received Bauxite proppants of a reference batch (Saint Gobain) showed a solar absorptance of 87%. To enhance solar absorptance, the particles were coated by inorganic pigments using sol-gel methods, diffusion of coloring ions. Furthermore, a modification of the proppant́s raw material was investigated, such as bauxite power mixed with commercial inorganic pigments and a natural mixture of mainly quartz and clay.