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Thermochemical production of hydrogen and sulfur: Development and modeling of a solar reactor for decomposition of sulfuric acid

Thomey, Dennis and Henke, Felix and Breuer, Stefan and de Oliveira, Lamark and Säck, Jan-Peter and Roeb, Martin and Sattler, Christian (2012) Thermochemical production of hydrogen and sulfur: Development and modeling of a solar reactor for decomposition of sulfuric acid. 6th International Conference on Energy Sustainability, 23.-26. Jul. 2012, San Diego, USA.

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Abstract

Solar energy underlies significant diurnal and seasonal fluctuations and hence requires qualified storage in order to fully replace fossil sources. While thermal storage systems (e.g. molten salt tanks) can bridge short periods of discontinuity or intermittence of insolation during cloud passage or over night, chemical storage is needed to compensate for longer periods without solar radiation or to transport solar energy into regions without sufficient sunlight. Hydrogen produced by solar thermal water splitting is a clean energy carrier free of greenhouse gases and a promising candidate to substitute fossil fuels in combustion engines. Sulfur generated from sulfuric acid in a reversible solar driven process allows baseload operation of solar power plants. Thermochemical cycles are introduced to efficiently produce hydrogen and sulfur by concentrated solar radiation: the Hybrid Sulfur Cycle is a two step process to thermally split water at a manageable temperature level below 1000°C. In a variant of this cycle, sulfur can be generated form sulfuric acid by introducing a disproportionation reaction. Both cycles haven in common the decomposition of sulfuric acid by concentrated solar radiation. To technically realize this reaction, a two-chamber solar reactor has been developed and operated in extended experimental campaigns in the solar furnace of DLR in Cologne. In this receiver-reactor porous absorbers of siliconized silicon carbide (SiSiC) are heated by concentrated solar radiation while the reaction proceeds inside their open volume. Liquid sulfuric acid is injected into the SiSiC foam structure of the first chamber forming SO3 at 400°C. In the second chamber the SO3 is reduced in a catalytically activated SiSiC honeycomb structure to produce SO2 at 850°C. With different catalysts (i.e. Fe2O3, CuFe2O4, FeCr2O4) conversion of up to 80% was reached at a thermal efficiency of more than 25%. Both chambers have been modeled to gain an in-depth understanding of the process and optimize the operation of the reactor. Here the model of the second chamber for decomposition of SO3 will be presented. It consists of a set of sub-models of the solar radiation, the heat transfer and chemical reaction inside the absorber as well as the radiative and convective heat loss of the system. The model was implemented in Dymola using the Modelica Standard Library and validated by experimental results of steady-state and transient operation.

Item URL in elib:https://elib.dlr.de/79147/
Document Type:Conference or Workshop Item (Speech)
Title:Thermochemical production of hydrogen and sulfur: Development and modeling of a solar reactor for decomposition of sulfuric acid
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Thomey, DennisUNSPECIFIEDUNSPECIFIED
Henke, FelixUNSPECIFIEDUNSPECIFIED
Breuer, StefanUNSPECIFIEDUNSPECIFIED
de Oliveira, LamarkUNSPECIFIEDUNSPECIFIED
Säck, Jan-PeterUNSPECIFIEDUNSPECIFIED
Roeb, MartinUNSPECIFIEDUNSPECIFIED
Sattler, ChristianUNSPECIFIEDUNSPECIFIED
Date:2012
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Keywords:solar thermochemical hydrogen sulfur sulfuric acid
Event Title:6th International Conference on Energy Sustainability
Event Location:San Diego, USA
Event Type:international Conference
Event Dates:23.-26. Jul. 2012
Organizer:ASME
HGF - Research field:Energy
HGF - Program:Renewable Energies
HGF - Program Themes:Concentrating Solar Systems (old)
DLR - Research area:Energy
DLR - Program:E SF - Solar research
DLR - Research theme (Project):E - Solare Verfahrenstechnik (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Solar Research > Solare Verfahrenstechnik
Deposited By: Thomey, Dennis
Deposited On:06 Dec 2012 15:03
Last Modified:06 Dec 2012 15:03

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