Removal of hydrogen sulfide from biogas using red rock materials

Abstract

In this study, the potential of red rock materials for the removal of hydrogen sulfide from biogas was studied. The rock samples were collected, sieved and organized in various particle size ranges such as 0.32 - 250 µm, 250 - 500 µm, 500 - 750 µm, 750 µm – 1.0 mm and 1.0 - 1.5 mm. These samples were calcined at temperatures of, 500 °C, 750 °C and 1000 °C and then characterized for phase composition by Energy Dispersive X-ray Fluorescent, for surface area by the Brunauer-Emmett-Teller method and surface morphology by Zeiss Ultra Plus Field Emission Scanning Electron Microscopy. The calcined red rock was filled in the bed reactor, and biogas was allowed to pass through the adsorbent while recording the inlet and exit concentration of hydrogen sulfide. The results show that particle size, calcination temperature, adsorbent mass and biogas flow rate influence the removal efficiency and adsorption capacity of red rock. The sample sieved at 0.32 - 250 µm, and calcined at temperature 1000 °C showed high removal efficiency 95% and adsorption capacity of 0.37 g/100 g of the sorbent. Regeneration of spent materials when exposed to air, followed by reuse in the column, appeared to have nearly similar removal efficiency as the original calcined sample. Thus, the overall performance of the materials is promising, which is due to the presence of metals like iron. Therefore, proving the red rock is available material it can be considered as a suitable adsorbent for biogas purification. Keywords: Red rock, Nadosoito, H2S removal, calcination, flowrate and particle size