PURIFICATION AND UPGRADING OF BIOGAS WITH NATURAL ZEOLITES FROM TUFFS

In this study, the possibility of using natural zeolites for the purification and the upgrading of biogas to biomethane is proposed. Several kinds of tuff waste from construction industry are available at low price and contain a high fraction of natural zeolites and in this study these materials were tested for the purification and the upgrading of biogas. Results obtained show that, even for small streams, it is possible to reach the specifications required for the distribution grid of natural gas. The adsorption of carbon dioxide was tested at two different flow rates, and at different grain sizes. Results showed a very high upgrading efficiency, even at atmospheric pressure. Reducing the flow rate and the grain size leaded to a very low enhancement of this saturation level, while the efficiency remained the same. Hydrogen sulphide also was efficiently adsorbed on the zeolites. After the saturation, tuffs were regenerated by heating and by vacuum.