Pilot Thermopervaporation Membrane Bioreactor for the Low-Cost Biobutanol Production

摘要

Biobutanol is second generation alcohol fuel with a higher energy density and lower volatility vs. ethanol. However, butanol toxicity to the fermenting microorganisms limits its concentration in the fermentation broth, resulting in low butanol yields and a high cost for butanol recovery from the dilute solutions. For this reason biobutanol production is successful only when this process is coupled to the technology of effective product recovery for the removal of inhibitory products. Here in TIPS we have been developing thermopervaporation (TPV) approach for the removal of biobutanol from fermentation broths since 2009. Pervaporation is known to be the membrane technique which provides selective separation of organics from water by evaporation through the dense hydrophobic membranes, and this approach is considered to be the most promising separation technology for the recovery and partial concentration of butanol from the ABE fermentation broth. The TPV is the variant of pervaporation in which permeate is condensed on the cold surface just in the membrane module at the atmospheric pressure. Thermopervaporation pilot setup was designed. The corresponding membrane surface area for the pilot-scale TPV module is 336 cm~2, and easily can be scale up to 1 m2. TPV separation of the multicomponent model fermentation mixture makes it possible to increase the concentration: (i) butanol from 1 to 20 wt. %, (ii) ethanol from 0.15 to 0.74 wt. % and (iii) acetone from 0.45 to 1.7 wt.%. In this case, acetic and butyric acids are partially rejected by the membrane. In the TPV mode of butanol recovery from model fermentation mixtures, the permeate flux exceeds 1 kg/(m~2 h) (comparable with industrial pervaporation processes) at the atmospheric pressure and at a condensation temperature of 10° C .