Study of suspension condition of yeast flocs in air lift bioreactor for ethanol fermentation

摘要

In this paper, the design principles and characteristics of biroreactor using yeast flocs was introduced, and the minimum air input for the suspension of yeast flocs was studied. The research showed that the air input calculated according to the formula established on a 12L bioreactor in reference (1) can not match the experiment result in the scale up of biroeactors(2.35L, 500L, 10000L) for ethanol production usign yeast flocs, but after the influence of the difference of solid fraction on the both sides of the draft tube was taken into account in the momentum balance equation, the air input required to suspend the yeast flocs and maintain the circulation of the media in the bioreactor can be well predicted by the formula in the scale up the bioreactors, thus it can be well concluded that the resistance force caused by solid fraction difference on both sides of the draft tube can not be neglected, further calculation showed that it is the main resistance to be overcome by the air input. at critical liquid circulation speed in bioreactors large than 12L, although the friction force may becoem strogner at high circulation speed.