Kinetic Evaluation of H2S and Ammonia Biofiltration for Air Emissions Control

摘要

Traditionally the control of H2S emissions includes direct air stripping, precipitation and chemical oxidation. In this study, low cost biofiltration using a natural media of wood chips and compost and a commercial biofiltration media were evaluated for the removal of moderate concentrations of H2S (up to 50 ppmv) at different Empty Bed Contact Times (EBCT) in the range of 10-80 seconds. A natural media blend of 50/50 compost/wood chips was selected for the evaluation based on results that compared different proportions of compost and wood chips for H2S removal. A synthesized gas stream of hydrogen sulfide mixed with humidified air was passed through the two media columns and effluent readings for H2S at different bed heights were measured. The overall removal efficiency of commercial media column was 95% at 50 ppmv inlet H2S concentration. The overall removal efficiency of natural media column was similar at 96% at 50 ppmv inlet H2S concentration. Pressure drop across the natural media was almost twice that of the commercial media under these conditions. Most of the H2S removal was achieved in the first section (lowermost section) of the biofilter for both the media. Added NH3 did not significantly affect the H2S removal process efficiency and calculated kinetic rate constants. The natural media exhibited very high removal efficiency from the start, which may result from the high surface area available for contaminant sorption, however the pressure drops experienced and future compaction may limit its utility in some high velocity applications.