Effects of Residence Time Distribution and Packing on Methanol Oxidation in Biotrickling Filter

Abstract

The effects of residence time distribution (RTD) on biotrickling filter systems and the comparison of the maximum elimination capacity (EC) and poisoning limits as functions of loadings of two packing media, Celite Bio-catalyst Carrier R-635 and a subituminous coal, were studied. To alter the RTD patterns in the two reactor columns, two baffle designs were chosen. The RTD tests were done under dry conditions, over a range of airflow rates, with zero baffle, one baffle, and two baffles added into each column. Mixed culture from compost was used to acclimate the bed for the methanol removal efficiency study. No nutrients were added in the coal column. To study the poisoning limit, the inlet methanol concentration was randomly increased until a severe drop in removal efficiency occurred. From the RTD tests and the removal efficiency runs, which did not result in 100% conversion, number of tank-in-series (N) values, maximum EC values, and rate constants of each column with different baffle configurations could be obtained. Results from duplicate runs showed that addition of baffles decreased the N values of the columns and increased the back mixing in both systems. Maximum EC values, critical loadings, and poisoning limits also increased with increasing back mixing. Coal was superior to Celite Biocatalyst Carrier R-635 because it gave good conversions without additional nutrients. In all runs, the rate of methanol removal was controlled by a zero order process.