Influence of trickling liquid velocity and flow pattern in the improvement of oxygen transport in aerobic biotrickling filters for biogas desulfurization

Abstract

AbstractBACKGROUNDBiological oxidation in biotrickling filters of high H2S loads contained in biogas streams still requires further study to reduce elemental sulfur accumulation due to limited gas–liquid oxygen mass transfer inside biotrickling filter beds. Reduction of elemental sulfur accumulation may be improved by regulating the main manipulated variables related to oxygen mass transfer efficiency during biological hydrogen sulfide removal in biotrickling filters.RESULTSTrickling liquid velocity and co‐current flow were selected as the most appropriate manipulated variable and flow pattern configuration compared with manipulating the air supply flow rate and a counter‐current flow pattern in order to improve gas–liquid oxygen mass transfer in abiotic conditions. The influence of trickling liquid velocity on the performance of a lab‐scale biotrickling filter treating high loads of H2S in a biogas mimic and operating in co‐current flow at neutral pH and packed with plastic pall rings was investigated.CONCLUSIONSThe effect of trickling liquid velocity modulation between 4.4 and 18.9 m h−1 in biotrickling filter performance was compared with operation without trickling liquid velocity regulation. Velocity regulation resulted in an improvement of 10% in the elimination capacity and, most importantly, a 9% increase in product selectivity to sulfate at a loading rate of 283.8 g S‐H2S m−3 h−1. Concentration profiles along the biotrickling filter height evidenced that trickling liquid velocity regulation progressively led to better dissolved oxygen distribution and, thus, enhanced overall biotrickling filter performance. © 2015 Society of Chemical Industry