Effect of Localized Temperature Difference on Hydrogen Fermentation

초록

In a lab-scale bioreactor system, (20 L of effective volume in our study) controlling a constant temperature inside bioreactor with a total volume 25 L is a simple process, whereas it is a complicated process in the actual full-scale system. There might exist a localized temperature difference inside the reactor, affecting bioenergy yield. In the present work, the temperature at the middle layer of bioreactor was controlled at 35 & DEG;C, while the temperature at top and bottom of bioreactor was controlled at 35 & PLUSMN; 0.1, & PLUSMN;1.5, & PLUSMN;3.0, and & PLUSMN;5.0 & DEG;C. The H-2 yield of 1.50 mol H-2/mol hexose(added) was achieved at & PLUSMN;0.1 and & PLUSMN;1.5 & DEG;C, while it dropped to 1.27 and 0.98 mol H-2/mol hexose(added) at & PLUSMN;3.0 and & PLUSMN;5.0 & DEG;C, respectively, with an increased lactate production. Then, the reactor with automatic agitation speed control was operated. The agitation speed was 10 rpm (for 22 h) under small temperature difference (<& PLUSMN;1.5 & DEG;C), while it increased to 100 rpm (for 2 h) when the temperature difference between top and bottom of reactor became larger than & PLUSMN;1.5 & DEG;C. Such an operation strategy helped to save 28% of energy requirement for agitation while producing a similar amount of H-2. This work contributes to facilitating the upscaling of the dark fermentation process, where appropriate agitation speed can be controlled based on the temperature difference inside the reactor.</p>

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