Development of Regenerative and Low Pressure Drop Adsorbent Structure for Biogas Upgrading

This paper presents the development of energy efficient 13X zeolite adsorbent monoliths for the removal of contaminants such as carbon dioxide (CO2), hydrogen sulfide (H2) and water (H2O) vapor from the biogas stream. 13X zeolite adsorbent monoliths of novel chemical formulations have been manufactured and characterized in comparison with commercial 13X zeolite adsorbent beads. It has been found that the prepared 13X zeolite monoliths have larger total pore volume, larger mean pore diameter to improve adsorption kinetics, higher porosity and mechanically stronger on compression than the commercial 13X zeolite beads. The adsorption performance of 75% wt. 13X zeolite monoliths were tested under varying feed gas pressures and flow rates as well as dry and humid conditions. Results have demonstrated that 13X zeolite adsorbent monoliths have excellent adsorption performance for CO2, H2S and water vapor and they could upgrade the biogas to a high quality with about 98% vol. CH4 in the effluent stream. Results revealed that the equilibrium adsorption capacity for 13X zeolite monolith was increased from 0.11 mmol/g to 0.13 mmol/g for H2 S, from 1.95 mmol/g to 2.72 mmol/g for CO2 and from 0.11 mmol/g to 0.20 mmolg for CH4 when the (total) feed gas pressure was raised from 1 bar to 3 bar. The study found that the selectivity of CO2 over CH4 was increased by about 13 times when the feed gas stream was humidified with 93% RH.