Reactor Cycling of Granulated Ca(OH)2 Encapsulated with Chemically Modified Semipermeable Shell Materials

Klaus Afflerbach1,*, Sandra Afflerbach1, Reinhard Trettin2, Wolfgang Krumm1

1Department of Mechanical Engineering, Chair For Environmental and Process Engineering, University of Siegen,
Paul-Bonatz-Strasse 9-11, Siegen, 57076, Germany

2Department of Chemistry and Biology, Institute For Building and Materials Chemistry, University of Siegen,
Paul-Bonatz-Strasse 9-11, Siegen, 57076, Germany

Adv. Mater. Lett., 2020, 11 (12), 20121582

DOI: 10.5185/amlett.2020.121582

Publication Date (Web): Nov 09, 2020



One major scientific challenge is a shift of the energy generation and utilization towards sustainability and efficiency. Therefore, thermochemical heat storage concepts offer a promising contribution as for example by integration in Concentrated Solar Power (CSP) applications. The reaction system Ca(OH)2/CaO is seen as a superior candidate but its poor powder properties yet hinder a technical implementation. The authors have recently proven, that these obstacles can be overcome by a persistent particle size stabilization of the pre-granulated storage material. Within the present study, the mechanical capsule material properties are improved by admixing of additives to the powdery precursor. By thermochemical conversion in a laboratory reactor, the cyclability and the suitability for moved reaction beds of the storage material is proven. The investigations are complemented by attrition tests on the most promising sample material and an encapsulated reference material. It is shown that the chemically enhanced encapsulation is a suitable approach to retain good flow properties and reduce attrition significantly. An encapsulated sample with an enhanced shell material composition containing 5%(w/w) of diatomaceous earth and 1%(w/w) of flux agent is found to be of superior stability over ten thermochemical cycles. A comparative macroscopic evaluation of the sample material after tenfold thermochemical cycling emphasizes the potential of this approach.


Thermochemical energy storage, calcium hydroxide, core-shell particles, powder flowability, concentrated solar power, semipermeable encapsulation, porous ceramics

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