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The thermodynamic analysis of two-step conversions of CO2/H2O for syngas production by ceria
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.ORCID iD: 0000-0002-2992-6814
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
2014 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, no 23, 12353-12360 p.Article in journal (Refereed) Published
Abstract [en]

Due to the challenges of demands on alternative fuels and CO2 emission, the conversion of CO2 has become a hot spot. Among various methods, two-step conversion of CO2 with catalyst ceria (cerium oxide, CeO2) appears to be a promising way. Solar energy is commonly employed to drive the conversion systems. This article proposes a solar-driven system with fluidized bed reactors (PER) for CO2/H2O conversions. N-2 is used as the gas of the heat carrier. The products of CO/H-2 could be further used for syngas. To evaluate the capability of the system for exporting work, the system was analysed on the basis of the Second Law of Thermodynamics and the reaction mechanism of ceria. Heat transfer barriers in practical situations were considered. The lowest solar to chemical efficiency is 4.86% for CO2 conversion, and can be enhanced to 43.2% by recuperating waste heat, raising the N-2 temperature, and increasing the concentration ratio. The analysis shows that the method is a promising approach for CO2/H2O conversion to produce syngas as an alternative fuel.

Place, publisher, year, edition, pages
2014. Vol. 39, no 23, 12353-12360 p.
Keyword [en]
Thermodynamic analysis, CO2 conversion, CeO2, Solar energy, Syngas
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-150930DOI: 10.1016/j.ijhydene.2014.03.250ISI: 000340328800059Scopus ID: 2-s2.0-84904727862OAI: oai:DiVA.org:kth-150930DiVA: diva2:746233
Note

QC 20140912

Available from: 2014-09-12 Created: 2014-09-11 Last updated: 2017-12-05Bibliographically approved
In thesis
1. A novel solar-driven system for two-step conversion of CO2 with ceria-based catalysts
Open this publication in new window or tab >>A novel solar-driven system for two-step conversion of CO2 with ceria-based catalysts
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Global warming is an unequivocal fact proved by the persistent rise of the average temperature of the earth. IPCC reported that scientists were more than 90 % certain that most of the global warming was caused by increasing concentrations of greenhouse gases (GHG) produced by human activities. One alternative to combat the GHG is to explore technologies for utilizing CO2 already generated by current energy systems and develop methods to convert CO2 into useful combustible gases.

Two-step conversion of CO2 with catalysts is one of the most promising methods. Ceria (CeO2) is chosen as the main catalyst for this conversion in the thesis. It releases O2 when it is reduced in a heating process, and then absorbs O2 from CO2 to produce CO when it is re-oxidized in a cooling process.

To make the conversion economic, solar power is employed to drive the conversion system. In this thesis, a flexible system with fluidized bed reactors (FBRs) is introduced.

The thermogravimetric analysis (TGA) was carried out to examine the performance of ceria during its reduction and oxidation. Subsequently, the exergy analysis was used to evaluate the system’s capability on exporting work. The theoretical fuel to chemical efficiency varied from 4.85 % to 43.2 % for CO2 conversions.

To investigate the operation mechanism of the system, a mathematical model was built up for the dynamic simulation of the system. Variables such as temperatures and efficiencies were calculated and recorded for different cases. The optimum working condition was found out to be at 1300 ⁰C for the commercial type of ceria.

Finally, an experimental system was set up. The hydrodynamics and heat transfer in the fluidized bed reactor were studied. A CFD model was built up and validated with the experimental trials around 120 ⁰C. The model was then used as a reliable tool for the optimization of the reactor.

The entire work in the thesis follows the procedure of developing an engineering system. It forms a solid basis for further improvements of the system to recycle CO2.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xxv, 159 p.
Series
TRITA-KRV, ISSN 1100-7990 ; 14:05
Keyword
CO2 conversion, solar, ceria, thermogravimetric test, exergy analysis, simulink, fluidized bed, gas-solid flow, simulation
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-152899 (URN)978-91-7595-285-7 (ISBN)
Public defence
2014-10-24, Sal M235 (Learning Theatre), Brinellvägen 68, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141006

Available from: 2014-10-06 Created: 2014-10-02 Last updated: 2014-10-06Bibliographically approved

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Fakhrai, Reza

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