title: Activated carbon load equalization of gas-phase toluene: effect of cycle length and fraction of time in loading.
abstract: Fluctuating pollutant concentrations pose challenges in the design and operation of air pollution control devices such as biofilters. Effective load equalization could decrease or eliminate many of these difficulties. In research described here, experiments were conducted to evaluate effects of cycle length and fraction of time contaminants are supplied on the degree of load equalization achieved by passively operated granular activated carbon (GAC) beds. Columns packed with Calgon BPL 4 x 6 mesh GAC were subjected to a variety of cyclic loading conditions in which toluene was supplied at concentrations of 1000 or 250 ppm, during loading intervals, and uncontaminated air flowed through the columns during no-loading intervals. The fraction of time when toluene was supplied ranged from 1/2 to 1/6, and cycle lengths ranged from 6 to 48 h. Results demonstrate that passively operated GAC columns can temporarily accumulate contaminants during intervals of high influent concentration and desorb contaminants during intervals of no loading, resulting in appreciable load equalization without need for external regeneration by heating or other means. Greater load equalization was achieved as the fraction of time toluene was loaded decreased and as the cycle length decreased. A pore and surface diffusion model, able to predict the level of contaminant concentration attenuation in GAC columns with reasonable accuracy, was used to further explore the range of load equalization performance expected from columns of various packed bed depths.
authors.affiliation: Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, Louisiana 70803-6405, USA. moemwil@lsu.edu
authors.forename: William M
authors.initials: WM
authors.lastname: Moe
authors.forename: Kodi L
authors.initials: KL
authors.lastname: Collins
authors.forename: John D
authors.initials: JD
authors.lastname: Rhodes
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D003198:Computer Simulation; D005740:Gases / Q000737:chemistry*; D013997:Time Factors; D014050:Toluene / Q000737:chemistry*