Date of Award
Master of Science in Chemical Engineering
Washkewicz College of Engineering
Air separation using zeolite based adsorption processes is a widely-studied topic. Proper process modeling is a key requirement to simulate the process. Conventional process modeling for air separation is designed for large scale adsorption processes using a long cycle time. However, advanced technology now permits to use of a short cycle time using small particles, which significantly reduces the size of the process.
Traditional process models were mostly developed for large particles (dp > 1.5 mm). Typically, it is safely assumed that intra particle diffusion controls the rate of the process while axial dispersion has a much smaller effect. This is a safe assumption since a long diffusional path exists inside the large particles. The diffusional path inside the small particles (dp> 0.5 mm) is reduced significantly. In addition, smaller particle size increases specific particle surface area which reduces the effect of film resistance. Hence, effect of axial dispersion is more significant for process modeling with small particles.
The primary objective of this thesis is to determine the impact of external diffusion to the particles in the process. In this study, breakthrough experiments are utilized to understand the behavior of mass transfer in small particles. Mass transfer zone length is measured from breakthrough experiments at different velocities and pressures to identify the effect of axial dispersion in small particles.
This thesis demonstrates two important parameters that utilized in determining extent of axial dispersion. depends on the level of adsorbent-adsorbate interaction and represents the level of eddy diffusion in the process. Typical value of 0.7 and 0.5 are assumed for and respectively for large particles. In this study, and are evaluated experimentally using mass transfer zone curve for small particles are 13 and 9 respectively. Comparison between parameter values for large and small particles is varies significantly, which ultimately make difference in magnitude of the axial dispersion coefficient. Hence, it is essential to account for proper values of while designing process model for small particles.
Patel, Mihikumar S., "Evaluation of Mass Transfer Rate in Column of Small Lilsx Particles" (2017). ETD Archive. 996.