Rheological and morphological characterization of alternative solid particle materials for CSP applications

Abstract

This study is focused on four residual materials, volcanic ashes (VA), flotation sterile (FS), ladle furnace slag (LFS) and black slags (BS) and their potential application as solid particles’ media in fluidized beds for thermal radiation processes. Although all materials fall within the Geldart B classification—indicating favorable fluidization behaviour—only two, FS and LFS, exhibited stable and complete fluidization. Detailed rheological and morphological analyses were conducted before and after exposure to radiation and fluidization, revealing no significant structural degradation. Minimum fluidization velocities were determined to assess flowability, leading to the exclusion of BS and VA materials despite their adequate physical and thermal properties. Between the two suitable candidates, LFS demonstrated a yield stress approximately 50% lower than that of FS, suggesting superior flowability and reduced mechanical resistance under non-confined conditions. However, LFS required a slightly higher minimum fluidization velocity (1.1 L/min more) due to its heterogeneous particle morphology. These findings highlight the potential of LFS as a cost-effective and flow-efficient medium for use in particle-based thermal energy storage systems.