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Analysis of configurational factors that influence the reversibility of nonstoichiometric countercurrent thermal reduction reactors.

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Bibliographic Details
Title:	Analysis of configurational factors that influence the reversibility of nonstoichiometric countercurrent thermal reduction reactors.
Authors:	Albukhari, Alaa M.^1,2 (AUTHOR), Scheffe, Jonathan R.^1,2 (AUTHOR) jscheffe@ufl.edu
Source:	International Journal of Hydrogen Energy. Apr2024, Vol. 63, p528-537. 10p.
Subjects:	Geothermal reactors, Gibbs' free energy, Factor analysis, Isothermal flows, Separation of gases
Abstract:	Recently, thermodynamic modeling has demonstrated that reduction of nonstoichiometric oxides in a counterflow gas current with a single inlet and exit must result in an equilibrium temperature gradient that deviates from the typically assumed isothermal operation at every single point but one, under assumed mass balance constraints. This necessity for a temperature gradient results in real processes that are near isothermal to deviate from the ideal reversible process, except for the single point where the Gibbs free energy change is zero. In this paper, new configurations with additional inlets and exits that can better approximate reversible and isothermal countercurrent flow reactors are considered and thermodynamically modeled. We show that it is possible to decrease irreversibilities while operating under the same maximum temperature, gas flowrates and initial nonstoichiometry simply by employing two or more exits and/or inlets. Under the most optimal conditions where the normalized irreversibilities are lowest, utilizing either an extra exit or extra inlet and exit show improved results in terms of minimizing the Gibbs free energy and lowering the needed separation work for the gases. Generally, as more irreversibilities are generated within the reactor, the more significant the usage of extra inlets/exits becomes. • Development of thermodynamic models for two new thermal reduction reactor configurations. • Gibbs free energy and separation work are examined to compare the different reactors. • Parametric study based on operating temperature, initial oxidized nonstoichiometry, and inlet sweep gas purity. • Both new reactor designs demonstrate a decrease in irreversibilities compared to the conventional design. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	Recently, thermodynamic modeling has demonstrated that reduction of nonstoichiometric oxides in a counterflow gas current with a single inlet and exit must result in an equilibrium temperature gradient that deviates from the typically assumed isothermal operation at every single point but one, under assumed mass balance constraints. This necessity for a temperature gradient results in real processes that are near isothermal to deviate from the ideal reversible process, except for the single point where the Gibbs free energy change is zero. In this paper, new configurations with additional inlets and exits that can better approximate reversible and isothermal countercurrent flow reactors are considered and thermodynamically modeled. We show that it is possible to decrease irreversibilities while operating under the same maximum temperature, gas flowrates and initial nonstoichiometry simply by employing two or more exits and/or inlets. Under the most optimal conditions where the normalized irreversibilities are lowest, utilizing either an extra exit or extra inlet and exit show improved results in terms of minimizing the Gibbs free energy and lowering the needed separation work for the gases. Generally, as more irreversibilities are generated within the reactor, the more significant the usage of extra inlets/exits becomes. • Development of thermodynamic models for two new thermal reduction reactor configurations. • Gibbs free energy and separation work are examined to compare the different reactors. • Parametric study based on operating temperature, initial oxidized nonstoichiometry, and inlet sweep gas purity. • Both new reactor designs demonstrate a decrease in irreversibilities compared to the conventional design. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:	03603199
DOI:	10.1016/j.ijhydene.2024.03.166