| abstract |
Ethanol and other liquid products produced by the contacting CO and/or a mixture of CO 2 and H 2 with a microorganism in a bioreactor are separated using a combination of distillation and vapor permeation membranes. The bioreactor passes an effluent with an ethanol concentration of 1 to 6 wt % to a distillation column that produces an overhead vapor stream enriched in ethanol. A series of vapor permeation membranes retain ethanol as retentate and produce a 99 wt % or higher ethanol product. Ethanol depleted permeate streams flow back to the column and the bioreactor. Coupling a bioreactor with distillation and pervaporation efficiently and economically separates ethanol when present at low concentration in an aqueous fermentation broth. The separation arrangement may also include a flash zone ahead of the distillation column to raise the concentration of the ethanol in the input stream to the distillation column. |