Showing papers by "M. Douglas LeVan published in 2003"

Frequency Response Method for Measuring Mass Transfer Rates in Adsorbents via Pressure Perturbation

Abstract: A new apparatus for the measurement of equilibria and dynamics for gas-phase adsorption systems is utilized to examine the adsorption of carbon dioxide on BPL activated carbon. The apparatus has a flow-through configuration. For dynamics, with constant inlet flow, pressure within the adsorbent-containing section is varied sinusoidally, and the time-dependent outlet flow rate is measured to determine an amplitude ratio and phase lag. Studies are made of temperature effects and particle size effects. Results are compared with several mathematical models. Frequency response data show that the BPL system follows surface (or micropore) diffusion kinetics. The rate of adsorption for the activated carbon is found to be only weakly dependent on the bulk particle size.

New Frequency Response Method for Measuring Adsorption Rates via Pressure Modulation: Application to Oxygen and Nitrogen in a Carbon Molecular Sieve

Abstract: A new frequency response method based on a sinusoidal modulation of pressure is developed to measure gas adsorption equilibria and kinetics simultaneously. The transfer phenomena of pure N2 and O2 gases on carbon molecular sieve are investigated for different pressures and particle sizes by this method. The mass-transfer mechanism for N2 can be explained by a surface barrier using a linear driving force model, but that for O2 requires a combination of a surface barrier and micropore diffusion using a combined resistance model. Alternatively, a distribution of surface barrier resistances is introduced to take into account heterogeneity of the surface and describes the experimental data well. The linear driving force mass-transfer coefficients increase with increasing pressure but depend on the particle size only slightly. The effects of pressure on the transfer coefficients for N2 are less pronounced than those for O2. The apparatus is shown to be useful in providing accurate and rapid transfer coefficient...

Consistency of Energy and Material Balances for Bidisperse Particles in Fixed-Bed Adsorption and Related Applications

Abstract: This paper develops material and energy balances for fixed-bed adsorption of a multicomponent nonideal gas in bidisperse particles by defining enthalpies from thermodynamic paths chosen such that t...

Regenerable Incinerator Exhaust Purification and Trace Contaminant Control System

Abstract: In this novel approach to air purification, contaminants removed from a process air stream by a high-capacity adsorbent are displaced periodically by a warm, high-humidity, reverse-flow air stream. Displaced contaminants flow into a closed regeneration loop, in which organic compounds are oxidized catalytically and acid gases are removed by a gas- water contactor (which also serves as the source of the water vapor). These features are expected to result in a design that has few expendables and lower energy consumption than alternative regenerable techniques. The joint project between NASA Ames Research Center and Vanderbilt University has completed its third year. Breadboard development continues at NASA Ames, while Vanderbilt has completed most of its adsorption equilibria development. Vanderbilt has completed its fixed-bed apparatus for investigation of dynamic adsorption and desorption processes for trace organic compounds and water vapor, and is continuing its development of the mathematical model describing the column dynamics.