Capture and conversion of CO2 by biological methanization process in h2 based membrane biyofilm reactor (MBfR)

This thesis aims to optimize the biomethane process in a batch anaerobic membrane biofilm reactor (AnMBfR) and this study consists of two different stages. In the first stage of the study, anaerobic batch reactors were operated at different H2:CO2 (v:v) ratios (4:1-3:1-2:1-1:1) and different temperatures (37 and 55 °C). At this stage, the optimum H2:CO2 ratio and temperature were found to be 4:1 and 55 °C, respectively. At the same time, the highest methane (CH4) concentration in the outlet gas under optimum conditions was found to be 81%, and the hydrogen (H2) utilization efficiency and carbon dioxide (CO2) conversion efficiency were found to be 96% and 98%, respectively. In the second stage of the study, the effects of changing the H2:CO2 (v:v) ratio (4:1-5:1), temperature (37-55 °C), and gas feeding times (60-90-120-150 min.) on the AnMBfR performance were investigated. Study findings showed that varying H2:CO2 ratio, temperature, and gas feeding times played an important role in biomethane production in the intermittently operated AnMBfR, and the optimum gas feeding time, H2:CO2 ratio, and temperature were determined as 120 min, 4:1, and 55 °C, respectively. In addition, the highest CH4 concentration in the outlet gas under optimum conditions was 83% and H2, which has a very low solubility in the liquid phase, was not detected in the outlet gas (100% H2 usage efficiency). Under optimum conditions, the CO2 conversion efficiency was obtained as 86%. As a result, the use of a membrane in the system caused the complete dissolution of H2 in the liquid phase and an increase in the CH4 concentration. Keywords: Biological biogas upgrade, Anaerobic membrane biofilm reactor, Biomethane.