A Fundamental Study of Char Oxidation Kinetics Using Model Materials

Citation

Levendis, Yiannis Angelo (1988) A Fundamental Study of Char Oxidation Kinetics Using Model Materials. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/FQBH-BT69. https://resolver.caltech.edu/CaltechETD:etd-11152007-091715

Abstract

A fundamental study concerning the reactivity of carbon to oxygen, under conditions pertinent to the combustion of pulverized fuel particles, was conducted. Model, man-made materials have been synthesized and produced to aid in understanding the events that occur during pyrolysis and oxidation of chars. The benefit of employing synthetic materials, along with natural fuels, was that they allowed control of the purity and composition of the chars, as well as enabled production of particles of specific physical properties relevant to modeling combustion processes.

Monodisperse, spherical, glassy carbon particles, of various sizes, were manufactured from spraying and thermally treating a carbon-yielding, highly crosslinked polymer. Various pore-forming agents were introduced and copolymerized, aiming to alter the pore structure, density and pore size distribution of the materials. Characterization of the chars, at various stages of pyrolysis and partial oxidation, employed widely varying techniques such as mercury intrusion, gas sorption, helium pycnometry, wide and small-angle scattering and nuclear magnetic resonance. Upon characterization, the influence of the physical factors on the combustion behavior was accounted for and the intrinsic reaction rates of the chars were correlated with their chemical nature. The mechanisms of pore coarsening, opening of pore restrictions and development of a large accessible pore surface area in the interior of the particles, in conjunction to the kinetics of structural ordering and graphitization, have been shown to influence critically the reactivity of chars. furthermore, experiments with calcium treated chars revealed that the catalytic effect of mineral matter on enhancing the combustion rate is very important.

Thesis Files