Modeling and Simulation of Trickle Bed Air Biofilter for Removal of VOCs

In this study, a mathematical model is proposed which incorporates mass transfer process and biofilm reactions in trickle bed air biofilter (TBAB). The model consists of a set of mass balance equations for isopropyl alcohol (IPA), acetone (ACE) and oxygen within the bulk gas phase and within the biofilm. These set of ordinary differential equations are converted into non-dimensionalised form and then are reduced to a set of non-linear algebraic equations by using orthogonal collocation technique. The model described above is used to obtain the VOCs concentration along the biofilm thickness and gas phase concentrations at different heights of TBAB. The model is validated with the data supporting the theoretical phenomena occurring within the biofilm as reported in the previous literature. Based on the results obtained, the simulations are carried out for different parameters such as specific growth rate, empty bed residence time, and specific surface area of biofilm per unit of packing material. INTRODUCTION Biofiltration is a technology, which is used for the treatment of gas streams contaminated with biologically degradable compounds (Babu and Raghuvanshi,2004). Biofilters contain packing materials such as compost, soil, peat, granular activated carbon or other porous media capable of adsorbing gaseous compounds and support biological growth. Contaminants pass into a wet biofilm layer surrounding the support particles and are aerobically degraded to carbon dioxide and water. At first glance, its principles are simple but when the process is examined in more detail it appears quite complex as Ottengraf and Van den Oever (1983) indicated in their pioneering work. The biofiltration using trickle bed air biofilter (TBAB) is a relatively new technology, which has been proven very efficient for treatment of many kinds of volatile organic compounds (VOCs) from waste gases by number of researchers. The process involves mass transfer of VOCs from the gas phase to the biofilm, and subsequent bio-oxidation takes place within the biofilm. To obtain its deeper understanding and to find suitable parameters for scaling up and design of the biofilters, number of models of different complexity have been proposed (Zarook et al., 1997; Den and Pirbazari, 2002). In the present model, air stream containing VOCs such as isopropyl alcohol (IPA) and acetone (ACE) moving through a trickle bed column filled with coal Session: Multiphase Reactors Modeling and Simulation of Trickle Bed Air Biofilter for Removal of VOCs Smita Raghuvanshi, and B.V. Babu a Department of Chemical Engineering, Birla Institute of Technology & Science, Pilani, Pilani – 333031, India, Email: [email protected] b Department of Chemical Engineering, Birla Institute of Technology & Science, Pilani, Pilani333031, India, Email: [email protected]