Abstract
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/ltoluene in air and biofilm thickness and bed porosity of the biofilter at the start of operations, were 10-6 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.
