The cohesive behavior of granular solids at high temperature in solar energy storage

Ebri

et al. 2022

KONA

Understanding the flowability of cohesive powders at high temperature is of great importance for many industrial applications where these materials are handled at harsh thermal conditions. For instance, the Calcium-Looping (CaL) process, involving the transport, storage and fluidization of limestone powders at high temperature, is being considered nowadays as a promising technology for thermochemical energy storage (TCES) in concentrated solar power plants (CSP). In this context, the High Temperature Seville Powder Tester (HTSPT) is presented in this work as a useful tool to analyze how the flow behavior of cohesive powders changes with temperature. The manuscript reviews the main results obtained so far using this novel apparatus. The change of powder cohesiveness and therefore of powder flowability as depending on temperature, particle size, material properties and nanosilica surface coating is illustrated.

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Section: Effect Of Nanosilica Additionmentioning

confidence: 76%

Section: Effect Of Particle Size On the Powder Tensile Strengthmentioning

confidence: 99%

Section: Effect Of Nanosilica Additionmentioning

confidence: 99%

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The Sevilla Powder Tester: A Tool for Measuring the Flow Properties of Cohesive Powders at High Temperatures

Ebri

et al. 2022

KONA

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“…Cohesion is one of the central issues in granular-based thermochemical storage (TCES) technology . It affects the flowability of the powder through the storage circuit, making TCES systems especially vulnerable to jammings, interruptions, and eventually shutdowns.…”

Section: Introductionmentioning

confidence: 99%

“…Primarily, two factors modulate the flowability of these powders: particle size and temperature. , As particle size decreases: (1) The ratio between the reactive surface and the particle weight increases; and (2), with smaller particle sizes, cohesive forces dominate over inertial ones, turning the granular flow from inertial to cohesive. Hence, although small particles improve reactivity, they also promote cohesion.…”

Section: Introductionmentioning

confidence: 99%

Efficacy of Nanosilica Coatings in Calcium Looping Reactors

Durán-Olivencia

et al. 2023

Ind. Eng. Chem. Res.

Nanosilica coatings are considered a simple physical treatment to alleviate the effect of cohesion on powder flowability. In limestone powders, these coatings buffer the rise in cohesion at high temperatures. Here, we investigate the role of particle size in the efficiency (and resilience) of these layers. To this end, this work examines a series of four limestone powders with very sharp particle size distributions: average particle size ranged from 15 to 60 μm. All the samples were treated with nanosilica at different concentrations from 0 to 0.82 wt %. Powders were subjected to short- and long-term storage conditions in calcium looping based systems: temperatures that vary from 25 to 500 °C and moderate consolidations (up to 2 kPa). Experiments monitored powder cohesion and its ability to flow by tracking the tensile strength of different samples while fluidized freely. Fluidization profiles were also used to infer variation in packings and the internal friction of the powder bed. Interestingly, for particle sizes below 50 μm, the nanosilica treatment mitigated cohesion significantlythe more nanosilica content, the better the flowability performance. However, at high temperatures, the efficiency of nanosilica coatings declined in 60 μm samples. Scanning electron microscopy images confirmed that only 60 μm samples presented surfaces barely coated after the experiments. In conclusion, nanosilica coatings on limestone are not stable beyond the 50 μm threshold. This is a critical finding for thermochemical systems based on the calcium looping process, since larger particles can still exhibit a significant degree of cohesion at high temperatures.

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

Ebri

Chemical Engineering Journal

et al. 2021