Session: 07-01: Experimental Characterization of Particle Flows

Paper Number: 156809

156809 - Attrition Cycling of Thermally Aged Generation 3 Particle CSP Media 

Abstract: 

Generation three (Gen 3) concentrating solar power (CSP) utilizes solid particle heat transfer media with unique degradation characteristics, which must be considered for the design and lifetime evaluation of Gen 3 CSP plants. Sandia National Laboratories (SNL) has conducted experimental testing to characterize the degradation, or attrition, of CarboBEAD HSP 16/30 sintered bauxite particles for use as heat transfer and energy storage media. While our prior work on ambient-temperature attrition revealed minimal changes to particle size distribution (PSD) over time, high-temperature impacts on particle wear are critically relevant to the design, operations, and maintenance of Gen 3 CSP facilities to ensure particle flowability and adequate management of dust and fine particles.

In this study, a modified Los Angeles (LA) attrition machine was utilized to evaluate particle attrition resulting from particle-particle and particle-wall contact at elevated temperatures. Particles were installed in the machine, which rotates at 30 revolutions per minute for a programmable number of rotations to simulate particle attrition and the formation of dust and fines. The LA machine was modified by installing an insulated stainless-steel insert to minimize thermal losses from preheated particles and to enable chamber preheating via high-temperature strip heaters in the future.

Elevated-temperature testing was performed by heating HSP particles within a high-temperature box furnace to 775 °C, installing the particles into the LA machine, and performing revolutions until the particles cooled to a defined lower temperature bound. Particle temperatures were measured using thermocouple probes inserted into the particle bed before and after testing, and the cooling profile of the particles was validated through multiple intermittent measurements during initial tests. A total of 55,000 revolutions were performed with intermittent reheating of the particles between testing increments. Samples were taken at specified increments for later particle surface analysis. Attrition was characterized by sieving and recording mass measurements to examine quantitative changes to the PSD.

In cold flow testing, statistically significant changes in the PSD of the attrited particles were only observed within the first 55,000 revolutions. Therefore, the results of heated testing will be compared to cold flow results after 55,000 revolutions have been performed. Optical microscopy and image processing will be performed to detect qualitative changes in surface characteristics as particles are worn. Electric guard preheaters will also be installed to preheat the insert, reducing thermal losses from the particles via conduction through the insert and drum walls and extending test durations.

Presenting Author: Jawad Khalaf Sandia National Laboratories

Presenting Author Biography: I have my Bachelor's of Science in Mechanical Engineering and Master's of Science in Biomedical Engineering, both from the University of New Mexico. I have been with Sandia Labs for over 3 years in the Concentrated Solar Power department, where much of my work has focused on heat transfer and energy storage media.