This thesis investigates membrane gas separation and its application to post-combustion carbon capture from coal-fired power plants as alternative to the conventional amine absorption technology. The attention is initially focused on membrane module modelling, with the aim of obtaining more detailed predictions of the behaviour of the separation though spiral-wound and hollow-fibre modules. Both one- and bi-dimensional models are implemented, compared and tested for different separations. Module geometry is investigated as well as the effect on the performances due to possible fabrication defects. A key part of the work involves the integration of the customised models into UniSim® Design, the Honeywell process simulator. Thanks to the developed interface, multi-stage process designs are developed, compared with the available literature and linked to a rigorous economic analysis. In particular, a long-term indicator such as the Levelised Cost Of Electricity (LCOE) is evaluated and parametric analyses are conducted with respect to both material and process parameters.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 92-93.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 158-164). Available also in a digital version from Dissertation Abstracts.

This dissertation discusses the effect of synthesis route and ortho-position group on the thermal and transport properties of thermally rearranged polymers. Thermally rearranged polymers are polybenzoxazoles formed via the solid state rearrangement of ortho-functional polyimides. In this study, polymers were derived from 3,3'-dihydroxy-4,4'-diamino-biphenyl and 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (HAB-6FDA). These HAB-6FDA polymers were synthesized using chemical and thermal imidization, and hydroxyl, acetate, propanoate, or pivalate ortho-position groups were considered. In these polymers, gas permeability increases as a function of conversion for all samples. The polyimide synthesis route does not affect the thermal or transport properties. However, the precursor ortho-position group strongly influences the thermal and transport properties of TR polymers. Additionally, it was determined that an increase in gas diffusivity was the primary cause of increased permeability as a function of thermal rearrangement. / text

Thermally rearranged polymers are formed from the solid-state thermal reaction of polyimides and polyamides that contain reactive groups ortho position to their diamine. These polymers have shown outstanding transport properties for gas separation applications. The thrust of this work is to critically examine the chemical and morphological structure of these polymers and to identify the fundamental contributions of gas sorption to permeability. To accomplish this goal, a series of TR polymers and TR polymer precursors have been synthesized and investigated for transport properties. As a function of conversion, diffusivity increases more dramatically than sorption, which explains the outstanding permeabilities observed for these samples. Modifications to the polymer backbone structure, which can be achieved by adding rigid functional groups such as hexafluoroisopropylidene-functional linking groups, can further be used to improve permeabilities. The precursor used to form TR polymers has dramatic effects on the final polymer transport properties. Despite having nearly identical polymer structure, TR polymers formed from polyamide precursors have lower combinations of permeability and selectivity than TR polymers formed from polyimide precursors. In addition to structure-property studies with TR polymers, this thesis also present comparisons of permeability, diffusivity, and sorption of sparingly soluble gases (i.e., hydrogen and helium) for hydrocarbon-based polymer, highly fluorinated polymers, perfluoropolymers, and a silicon-based polymer. An explanation for the unique transport properties of perfluoropolymers is presented from the standpoint of the solution-diffusion model, whereby perfluoropolymers have uniquely different solubility selectivities than hydrocarbon-based polymers. Additionally, a large database of sorption, diffusion, and permeability coefficients is used to determine the contributions of free volume on solubility selectivity in polymers. / text

This research effort investigated the influence of confinement on the physical aging behavior of thin and ultrathin glassy polymer membranes. Membrane permeability changes with time due to physical aging, and for reasons not completely understood, the rate of permeability change can become orders of magnitude faster in films thinner than one micron. Special experimental techniques were developed to enable the study of free standing, ultrathin glassy polymer films using gas permeability measurements. The gas transport properties and physical aging behavior of free-standing glassy polysulfone (PSF) and Matrimid® films from 18-550 nm thick are presented. Physical aging persists in glassy films approaching the length scale of individual polymer coils. The membranes exhibited significant reductions in gas permeability and increases in selectivity with aging time. Additionally, the influence of physical aging on the free volume profile in thin PSF films was investigated using variable energy positron annihilation lifetimespectroscopy (PALS). The films exhibited decreasing o-Ps lifetime during physical aging, while o-Ps intensity remained constant. The o-Ps lifetime was reduced at lower implantation energies, indicating smaller free volume elements near the film surface. Thin films aged dramatically faster than bulk PSF and the PALS results agree favorably to behavior tracked by gas permeability measurements. The physical aging behavior of ultrathin films with different previous histories was also studied. The state of these materials was modulated by various conditioning treatments. Regardless of the previous history, the nature of the aging response was consistent with the aging behavior of an untreated film that was freshly quenched from above Tg, i.e., permeability decreased and pure gas selectivity increased with aging time. However, the extent of aging-induced changes in transport properties of these materials depended strongly on previous history. The properties of these ultrathin films deviate dramatically from bulk behavior, and the nature of these deviations is consistent with enhanced mobility and reduced Tg in ultrathin films, which allows them to reach a lower free volume state more quickly than bulk material. The Struik physical aging model was extended to account for the influence of film thickness on aging, and was shown to accurately describe the experimental data. / text

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 186-197). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 221-227). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Gary T. Rochelle and William J. Koros. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: William J. Koros and Donald R. Paul. Vita. Includes bibliographical references.