Adsorption by particles injected into a gas stream

A theoretical model for dry sorption injection is developed. The model uses a transient diffusion equation for particles with adsorption represented u sing a Freundlich isotherm, and a balance equation for the bulk gas phase. The case of injection of adsorbing particles having a log-normal distributi on of sizes is considered. It is found that for the conditions of practical interest just three parameters determine the adsorption behaviour. These a re the exponent, q, determining the non-linearity of the Freundlich equilib rium relation; the non-dimensional adsorbate capacity of the particles, K*p hi (T), where K* represents capacity per unit mass of particle and phi (T) the mass of particles injected; and the geometric standard deviation, ap, O f particle size in the particle population. Comparison is made between the model and existing experimental data for single particles under conditions of uniform external adsorbate concentration. The data span a range of parti cle geometries, sizes and adsorbate concentrations and the model is found t o reproduce the entire range of data to within about +/- 20%. The parameter s of the model are systematically varied in a series of computations that i llustrate and confirm the theoretical analyses. (C) 2001 Elsevier Science B .V. All rights reserved.