Nanoadditives to mitigate jamming in cohesive granular media

Handling and conveying cohesive granular media are common challenges for many industries, which demand smooth and uninterrupted granular flows. Cohesion settles at the cores of these problems, especially at high temperatures, when it rises sharply and flow patterns become intermittent; then, jamming, halts, and shutdowns. Here, we explore shielding limestone particles with nanoadditives to mitigate the adverse effect of cohesion, especially at high temperatures. The work focuses on concentrated solar plants assisted by the calcium looping cycle, a high-temperature environment plagued with jamming vulnerabilities. Experiments analyze the evolution of tensile strength as samples expand and fluidize freely, using three nanomaterials to coat fine limestone powders: silica, titania, and alumina. To investigate the efficacy of these coatings, samples were preconsolidated (up to 2 kPa) before fluidizing at high temperatures (up to 500 °C) — conditions that soften the contacts and cause cohesion to escalate. The results showed how discrete layers of nanoadditives shape stiffer surfaces, preventing particles from softening at high temperatures, and thereby limiting the contact area dilation that fuels cohesion. Coatings were prepared considering the optimal amount of nanoadditives to introduce minimal inert material. Concentrations below 1 wt % were enough to ensure uniform coatings and promote easy-flow regimes. Yet at 500 °C, only alumina coatings achieved easy-flow dynamics, offering a sintering shielding effect that reduces the rise in tensile strength up to 62 %. This is an outstanding conclusion to mitigate jamming in fine powders, which is paramount for a broad spectrum of granular processes that require transporting and storing cohesive granular media at high temperatures. • Handling and conveying cohesive granular media are challenging for many industries. • High temperatures widen particle contact area, strengthening attractive forces. • Cohesion skyrockets at high temperatures, leading to jamming and interruptions. • Alumina coatings significantly reduce limestone cohesion in thermochemical storage. • Limestone fine powders coated with alumina flow easily even at high temperatures.