Thermodynamic screening of candidate ceria and perovskite systems as potential oxygen carrier materials for chemical looping water gas shift.
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| Title: | Thermodynamic screening of candidate ceria and perovskite systems as potential oxygen carrier materials for chemical looping water gas shift. |
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| Authors: | Aljabr, Ahmed H.1,2 (AUTHOR), Scheffe, Jonathan R.1 (AUTHOR) jscheffe@ufl.edu |
| Source: | International Journal of Hydrogen Energy. Dec2023, Vol. 48 Issue 95, p37086-37096. 11p. |
| Subjects: | Oxygen carriers, Water-gas, Thermodynamics, Metallic oxides, Carbon dioxide, Biomass gasification, Water gas shift reactions, Steam reforming, Synthesis gas |
| Abstract: | Methane reforming and gasification processes are valuable pathways toward hydrogen production, and currently they represent nearly 79% of the worldwide hydrogen production market share. Chemical looping-water gas shift (CL-WGS) is a promising downstream process that can be integrated with reforming and gasification reactors and utilizes redox active metal oxides as oxygen exchange materials to produce separate streams of H 2 and CO 2. Thus, this technology can enable the production of high-purity hydrogen coupled with carbon capture without the need for an additional CO 2 separation system. Although a number of redox-active metal oxides have been proposed in the literature as viable candidates for CL-WGS, the majority are based on stoichiometric metal oxides. However, non-stoichiometric oxides, which have the benefit of stability, rapid kinetics, and thermodynamic tunability, have only been proposed a handful of times. And of the prior proposed non-stoichiometric materials, none of the so called "water splitting" redox materials of the solar thermochemical H 2 O splitting (STCH) fields have been discussed for CL-WGS applications, despite their potentially favorable thermodynamic properties. In this research, we have identified 13 potential oxygen carrier materials and screened these for CL-WGS viability based on a simplified closed-system thermodynamic analysis. Ceria (CeO 2-δ), CZO20 (Ce 0.8 Zr 0.2 O 2-δ), and LSMA4060 (La 0.6 Sr 0.4 Mn 0.4 Al 0.6 O 3-δ) are identified to have the most suitable properties in terms of operating temperatures, specific H 2 yields, and conversions of syngas, during reduction, and steam, during oxidation. Results show that CZO20 and LSMA4060 have especially excellent reduction and oxidation extents at relatively low operating temperatures. For example, CZO20 and LSMA4060 have 85% syngas and steam conversions when cycled between 485-912 and 100–635 °C, respectively. Results show that only CZO20 is viable for isothermal operation, but higher temperatures are required; at 1023 °C, syngas and steam conversions are 80 and 12%. • Screening of 13 candidate oxygen carriers for chemical looping water gas shift reactor. • A thermodynamic analysis is implemented to compare the candidate materials. • The comparison based on operating temperatures, H 2 yields, and conversions of syngas and steam. • La 0.6 Sr 0.4 Mn 0.4 Al 0.6 O 3-δ shows highest conversions (i.e., >85%) at low T (e.g., 100–635 °C). • Ce 0.8 Zr 0.2 O 2-δ shows highest conversions (i.e., >85%) at moderate T (e.g., 485–912 °C). [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
| Abstract: | Methane reforming and gasification processes are valuable pathways toward hydrogen production, and currently they represent nearly 79% of the worldwide hydrogen production market share. Chemical looping-water gas shift (CL-WGS) is a promising downstream process that can be integrated with reforming and gasification reactors and utilizes redox active metal oxides as oxygen exchange materials to produce separate streams of H 2 and CO 2. Thus, this technology can enable the production of high-purity hydrogen coupled with carbon capture without the need for an additional CO 2 separation system. Although a number of redox-active metal oxides have been proposed in the literature as viable candidates for CL-WGS, the majority are based on stoichiometric metal oxides. However, non-stoichiometric oxides, which have the benefit of stability, rapid kinetics, and thermodynamic tunability, have only been proposed a handful of times. And of the prior proposed non-stoichiometric materials, none of the so called "water splitting" redox materials of the solar thermochemical H 2 O splitting (STCH) fields have been discussed for CL-WGS applications, despite their potentially favorable thermodynamic properties. In this research, we have identified 13 potential oxygen carrier materials and screened these for CL-WGS viability based on a simplified closed-system thermodynamic analysis. Ceria (CeO 2-δ), CZO20 (Ce 0.8 Zr 0.2 O 2-δ), and LSMA4060 (La 0.6 Sr 0.4 Mn 0.4 Al 0.6 O 3-δ) are identified to have the most suitable properties in terms of operating temperatures, specific H 2 yields, and conversions of syngas, during reduction, and steam, during oxidation. Results show that CZO20 and LSMA4060 have especially excellent reduction and oxidation extents at relatively low operating temperatures. For example, CZO20 and LSMA4060 have 85% syngas and steam conversions when cycled between 485-912 and 100–635 °C, respectively. Results show that only CZO20 is viable for isothermal operation, but higher temperatures are required; at 1023 °C, syngas and steam conversions are 80 and 12%. • Screening of 13 candidate oxygen carriers for chemical looping water gas shift reactor. • A thermodynamic analysis is implemented to compare the candidate materials. • The comparison based on operating temperatures, H 2 yields, and conversions of syngas and steam. • La 0.6 Sr 0.4 Mn 0.4 Al 0.6 O 3-δ shows highest conversions (i.e., >85%) at low T (e.g., 100–635 °C). • Ce 0.8 Zr 0.2 O 2-δ shows highest conversions (i.e., >85%) at moderate T (e.g., 485–912 °C). [ABSTRACT FROM AUTHOR] |
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| ISSN: | 03603199 |
| DOI: | 10.1016/j.ijhydene.2023.06.043 |
