Cryptogamic packed biofilter as potential adsorbent for co2, h2s and nh3 impurities from biogas

Abstract

The presence of elevated concentrations of carbon dioxide, hydrogen sulfide, ammonia and trace impurities in biogas affect its caloric value as well as causes corrosion and are extremely toxic. There are various methods for removal of these impurities, but most are chemically based, expensive and limited in use. In this work, cryptogams (moss) integrated with soil and biochar packed in a filter have been employed for simultaneous removal of CO2, H2S and NH3, from biogas. Different soil types rich in metallic oxides at a different mass of (100 g, 150 g and 200 g) with a fixed mass of moss and biochar were tested in an on-site experiment to determine the removal efficiency (RE) and sorption capacity (SC). The adsorption dynamics of the filters were investigated at two flow rates, 80 ml/min and 100 ml/min, by determining removal efficiency. For the contribution of each substrate, sorption capacity and breakthrough time were determined by considering 5 g of each substrate that made up the filter. The soils with a high content of extractable cations showed excellent adsorption capacity for H2S by about 20 gS/100 g, which was higher than other adsorbents tested. It was found that integrated biofilter made up of bed arrangement of the soil, biochar and moss plant improved the quality of biogas with SC of 11 g-S and RE of 93% for H2S, 72% for NH3 and 68% for CO2. Keywords: Cryptogams, Biofiltration, Biochar, Removal efficiency, Sorption Capacity.