CHEMICAL ENGINEERING TRANSACTIONS VOL. 29, 2012 A publication of The Italian Association of Chemical Engineering Online at: www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Hon Loong Lam, Jiří Jaromír Klemeš Copyright © 2012, AIDIC Servizi S.r.l., ISBN 978-88-95608-20-4; ISSN 1974-9791 DOI: 10.3303/CET1229174 Please cite this article as: Vafajoo L., Naserranjbar A. and Khorasheh F., (2012), A mathematical model for removal of VOC’S from polluted air utilizing a biofilter, Chemical Engineering Transactions, 29, 1039-1044 1039 A Mathematical Model for Removal of VOC’s From Polluted air Utilizing a Biofilter Leila Vafajoo*, Ali Naserranjbar, Farhad Khorasheh Department of Chemical and Environmental Engineering, Islamic Azad University, Tehran South Branch, Tehran, Iran vafajoo@azad.ac.ir Recently, for the elimination or reduction of volatile organic compounds (VOC’s) biofilters are being utilized more often. Degradation of the VOC’s is made possible upon different packing of immobilized microbes. When removing such compounds as toluene in waste gases through a biofilter, clogging phenomenon will occur over time due to the formation of excessive biomass accumulation on the packing hence increasing of biofilm thickness. This phenomenon causes changes in the bed porosity and a subsequent increase in pressure drop and flow channelling which will eventually reduce the efficiency of the biofilter. In This study, differential equations related to the concentration distribution of toluene in the gas phase, Mass balance in the biofilm and the growth of microorganisms in a biofilter packed with spherical particles made of silica walls (R-635 Celite) with an equivalent diameter of 6mm were developed while simultaneously and dynamically solved with the MATLAB software. Consequently, the dynamic behavior of biofilter was predicted. Inlet gas stream contained 0.5 mg/l toluene in air and biofilm thickness and bed porosity of the biofilter at the start of operations, were10 -6 m and 34 %; respectively. These parameters changed to 350*10 -6 m and 6 %; respectively after 92 hours. The toluene conversion also reached 82 % at this time. In order to ensure accurate modeling, the results of the mathematical model were compared with the existing experimental data of a biofilter and 14 % error was calculated. It seems that the error is due to physical properties of fluid assumed to be constant during the operation. However, the mathematical modeling in this area is very scarce and most researches on biofilter were experimental. 1. Introduction Since the enactment of the 1990 Amendments to the Clean Air Act (CAA), technologies including adsorption, absorption, condensation, incineration, flaring, and biological control methods have been developed for the removal of VOCs and odors from waste gases (Yang et al., 2010). Many volatile organic compounds (VOCs) are classified as hazardous air pollutants (HAPs), and have been emitted from various industrial complexes (Qi and Moe, 2006). Although, gas biofiltration is considered to be a cost effective and reliable technology for control of low-concentration waste gases contaminated by VOCs and other odors (Devinny et al., 1999). Since pollutant degradation occurs at normal temperature and pressure, biofiltration represents a potentially energy-efficient and low-capital technology when compared to more energy demanding or capital intensive physical and chemical abatement processes, such as catalytic wet oxidation, incineration, scrubbing or regenerative adsorption. It is particularly cheap and reliable for treating off- gas streams having large flow rates at minute contaminant levels (Iliuta and Larachi, 2004b). It has also become known as an environmental friendly technology due to environmentally benign end-products of