Nanosilica to improve the flowability of fine limestone powders in thermochemical storage units

Abstract

Fine powders are the cornerstone of new energy storage solutions to assist concentrated solar power plants. Though, their ability to behave like fluid can be seriously affected at high temperatures. This work investigates the use of nanosilica in fine limestone (calcium carbonate, CaCO3) powders to mitigate the promotion of cohesion forces at high temperatures. Experiments were conducted over limestone powder samples with particle sizes around 45 µm. The analysis was performed monitoring the tensile yield strength as the samples were subjected to different temperatures and consolidation stresses while varying the nanosilica content up until 0.82 wt%. Temperatures reached a maximum of 500 .C (close to the Tamman temperature in limestone), whereas consolidation stresses were increased up to 2 kPa. Results show that nanosilica coating is an efficient solution to inhibit the enhancement of powder cohesiveness at high temperatures and consolidations. A solution that offers better control to smooth the granular flow regimes in production environments.