Ignition-Extinction Analysis of Coupled Homogeneous-Heterogeneous Reactions in Monolith Reactors

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dc.contributor.advisorBalakotaiah, Vemuri
dc.contributor.committeeMemberHarold, Michael P.
dc.contributor.committeeMemberBollini, Praveen
dc.contributor.committeeMemberAuchmuty, Giles
dc.contributor.committeeMemberDindoruk, Birol
dc.creatorSarkar, Bhaskar
dc.creator.orcid0000-0003-4686-8510
dc.date.accessioned2022-06-18T23:18:51Z
dc.date.createdAugust 2021
dc.date.issued2021-08
dc.date.submittedAugust 2021
dc.date.updated2022-06-18T23:18:52Z
dc.description.abstractWe use a multi-scale multi-mode reduced order model for coupled homogeneous-catalytic reaction systems to present a comprehensive ignition-extinction analysis of catalytically assisted propane and hydrogen combustion and oxidative coupling of methane (OCM) in monolith, gauze, or wire-mesh type reactors. The reduced order models are expressed in terms of phase averaged multiple concentration (temperature) modes and interfacial fluxes which are related through various transfer coefficients that are local scale, flow, and property dependent. Accurate expressions are provided for estimating the local transfer coefficient matrices in multi-component systems. Using these reduced order models, the space of design and operating variables are explored to determine the different types of ignition-extinction behaviors occurring in the catalytically assisted combustion processes. Bifurcation theory is used to construct phase diagrams in the plane of equivalence ratio versus feed temperature and equivalence ratio versus space time to classify the behaviors occurring and the extent of coupling between the homogeneous and catalytic conversion of the fuel. We also examine the impact of channel hydraulic diameter, precious metal (Pt) loading/dispersion, Lewis number, heat loss effects, reactor length, and substrate thermal conductivity on the ignition-extinction behavior. The results of the comprehensive analysis are used to present guidelines on the design and scale-up of monolith reactors for carrying out the catalytically assisted combustion processes. In OCM, we determine the impact of methane to oxygen ratio in the feed, space time, channel hydraulic radius, washcoat properties, operating pressure, and substrate thermal conductivity on the ignition-extinction behavior of the system as a function of the feed temperature. The computations show that for typical operating conditions, the methane conversion and C₂ product selectivity are non-monotonic on the ignited branch and there exists an optimum point of operation away from the extinction point. We also present the various species and temperature profiles along the length of the reactor and examine how these profiles are impacted by the substrate conductivity, space time, and heat loss. The results obtained for monolith, gauze, or wire-mesh reactors are compared to those in packed-beds, and suggestions are provided for scale-up and optimization of these reactors for carrying out OCM.
dc.description.departmentChemical and Biomolecular Engineering, William A. Brookshire Department of
dc.format.digitalOriginborn digital
dc.format.mimetypeapplication/pdf
dc.identifier.citationPortions of this document appear in: B. Sarkar, R. R. Ratnakar, V. Balakotaiah, "Multi-scale coarse-grained continuum model for bifurcation and transient analysis of coupled homogeneous-catalytic reactions in monoliths," Chem. Eng. J. 407 (2021) 126500; and in: B. Sarkar, R. R. Ratnakar, V. Balakotaiah, "Bifurcation analysis of catalytically assisted hydrogen combustion in monolith reactors," Chem. Eng. J. 2021 doi: https://doi.org/10.1016/j.cej.2021.130318; and in: B. Sarkar, D. H. West, V. Balakotaiah, "Bifurcation analysis of oxidative coupling of methane in monolith, gauze or wire-mesh reactors," Catal. Today 2021 doi: https://doi.org/10.1016/j.cattod.2020.12.040
dc.identifier.urihttps://hdl.handle.net/10657/9377
dc.language.isoeng
dc.rightsThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).
dc.subjectCatalytically assisted hydrogen combustion, Oxidative coupling of methane
dc.titleIgnition-Extinction Analysis of Coupled Homogeneous-Heterogeneous Reactions in Monolith Reactors
dc.type.dcmiText
dc.type.genreThesis
dcterms.accessRightsThe full text of this item is not available at this time because the student has placed this item under an embargo for a period of time. The Libraries are not authorized to provide a copy of this work during the embargo period.
local.embargo.lift2023-08-01
local.embargo.terms2023-08-01
thesis.degree.collegeCullen College of Engineering
thesis.degree.departmentChemical and Biomolecular Engineering, William A. Brookshire Department of
thesis.degree.disciplineChemical Engineering
thesis.degree.grantorUniversity of Houston
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy

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