| Résumé | The conversion of carbon monoxide (CO) into hydrogen (H2) by a Carboxydothermus hydrogenoformans pure culture was investigated and optimized in a 35 L gas-lift reactor. The reactor was operated with a continuous supply of gas for 3 months. Reactor performance was evaluated under various operational conditions, such as gas recirculation rates (0.3 and 1.5 L min-1), CO feeding rates (from 0.05 to 0.46 mol L-1 reactor day-1) and bacto-peptone addition to the medium. Overall, the H2 yields were constant at 95 ± 1% and 82 ± 1% (molH2 {dot operator} molCO - 1) with growth supported by peptone and unsupported respectively, regardless of the operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.17 molCO L-1 reactor day-1 or 3.79 LCO L-1 reactor day-1 was achieved. The ratio of gas recirculation over CO feed flow rates (QR:Qin) was the major parameter that impacted both biological activity and volumetric gas-liquid mass transfer. The CO conversion performance of the gas-lift reactor was kinetically limited over a QR:Qin ratio of 40, and mass transfer limited below that ratio, resulting in a maximum conversion efficiency of 90.4 ± 0.3% and a biological activity of 2.7 ± 0.4 molCO g-1 VSS day-1. Overall, the CO conversion performance in the gas-lift reactor was limited by a low cell density, typical of C. hydrogenoformans planktonic growth. This limitation was found to be the most restrictive factor for higher CO loading rates. Crown Copyright © 2013. |
|---|
