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Numerical analysis of the hydration of calcium oxide in a fixed bed reactor based on lab-scale experiments

Risthaus, Kai and Bürger, Inga and Linder, Marc Philipp and Schmidt, Matthias (2020) Numerical analysis of the hydration of calcium oxide in a fixed bed reactor based on lab-scale experiments. Applied Energy (261). Elsevier. DOI: 10.1016/j.apenergy.2019.114351 ISSN 0306-2619

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Abstract

Thermochemical energy storage is gaining popularity as one possibility to integrate renewable energies into existing energy systems by providing large energy storage capacities at low costs. Systems based on the reversible reaction of calcium oxide and steam forming calcium hydroxide, are especially promising as the storage material is cheap, abundantly available, and non-toxic. Potential applications are the storage of industrial process heat, concentrated solar power, or novel power to heat concepts. Reactor design is increasingly accompanied by simulations. However, for indirectly heated fixed bed reactors, there currently exist only simulation models that are validated at 200 kPa. Therefore, a model coupling heat and mass transfer as well as the chemical reaction is set up and validated with recently published experimental data for an indirectly heated fixed bed with an operating range between 8.7 and 470 kPa. The simulation reveals that in this design with a thin reactive layer mass transfer is not limiting, while thermal losses have a significant influence and thus have to be accounted for in the model. Furthermore, at steam pressures above 200 kPa the reaction kinetics is not limiting and simplified kinetic models describe the reactor reasonably well. Whereas for lower pressures (below 50 kPa), the reaction kinetics becomes limiting and none of the analyzed kinetic models predict the reaction rate exactly. We conclude that the reaction kinetics at low steam pressures (8.7-50 kPa) is very sensitive towards pressure and temperature. The results can assist the design and upscaling of reactors for technical applications and show the necessity for further studies at low pressures.

Item URL in elib:https://elib.dlr.de/133302/
Document Type:Article
Title:Numerical analysis of the hydration of calcium oxide in a fixed bed reactor based on lab-scale experiments
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Risthaus, KaiKai.Risthaus (at) dlr.dehttps://orcid.org/0000-0002-8435-4513
Bürger, Ingainga.buerger (at) dlr.deUNSPECIFIED
Linder, Marc PhilippMarc.Linder (at) dlr.deUNSPECIFIED
Schmidt, Matthiasmatthias.schmidt (at) dlr.dehttps://orcid.org/0000-0002-8795-4370
Date:1 March 2020
Journal or Publication Title:Applied Energy
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1016/j.apenergy.2019.114351
Publisher:Elsevier
ISSN:0306-2619
Status:Published
Keywords:Thermochemical energy storage, Reaction kinetics, Calcium oxide/hydroxide, Fixed bed reactor, 2D simulation
HGF - Research field:Energy
HGF - Program:Storage and Cross-linked Infrastructures
HGF - Program Themes:Thermal Energy Storage
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Thermochemical Processes (Storage)
Location: Köln-Porz , Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Thermal Process Technology
Deposited By: Risthaus, Kai
Deposited On:09 Jan 2020 15:45
Last Modified:09 Jan 2020 15:45

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