Considering age and size distributions of activated-carbon particles in a completely-mixed adsorber at steady state

A steady-state model, based on the concept of homogeneous surface diffusion, was developed to describe an activated-carbon adsorber with continuous carbon replacement. Both age and size distributions of carbon particles were incorporated into the model. Using the resulting closed-form solution, a series of simulations was made to investigate the effects of adsorption characteristics, the average age of carbon particles, surface diffusion coefficient, particle size and carbon concentration on the effluent adsorbate concentration. Although there is no single, equivalent particle size that can exactly represent a particle-size distribution, the use of a carefully chosen equivalent particle size could lead to errors in adsorber performance predictions of less than 10%. Unfortunately, there is no formal protocol for selection of the equivalent particle size and trial and error iterations are necessary.