Thursday, March 19, 2009

Ethanol removal from reaction–separation integration

The reaction–separation integration is an attractive alternative for the intensification of ethanol fermentation processes. When ethanol is removed in-situ, the product inhibition will be reduced.The methods to remove ethanol from fermented broth are listed as follows:

· Vacuum extraction, which can be conducted by coupling of fermentor vessel with a vacuum chamber extracting the more volatile ethanol from fermentation broth which allows the partial product removal and the increase of overall process productivity.
· Gas stripping to increase the concentration of sugars in the stream feeding the fermentor and improvement of improves liquid circulation and mass transfer.
· Membrane separation. For example, ceramic membranes can be used to filter cell biomass and remove ethanol during the fermentation.The removed ethanol is then distilled and the resulted bottoms are recycled to the culture broth resulting in a drastic reduction of generated wastewater. The coupling of fermentation with the pervaporation is another case to remove produced ethanol and reduce the natural inhibition of the cell growth caused by high concentrations of ethanol product.
In membrane distillation, aqueous solution is heated for vapor formation, which go through a hydrophobic porous membrane favoring the pass of vapors of ethanol (that is more volatile) related to the vapors of water. The process driving force is the gradient of partial pressures mainly caused by the difference of temperatures across the membrane.
Liquid extraction is to use an extractive biocompatible agent (solvent) that favors the migration of ethanol to solvent phase, a process known as extractive fermentation.
Hopefully,we will have lab or trial date rather than just modeling for the evaluation, right?

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