Process for producing ethanol by continuous fermentation of

Abstract

This invention relates to a process for producing ethanol by continuous fermentation of polysaccharide-containing raw materials. The fermentation is carried out in one or several fermentors, a stream of fermentation liquor being separated into a yeast concentrate stream and a yeast-free stream, and possibly one sludge stream, of which the yeast concentrate stream is recirculated to the fermentor, at least part of the yeast-free stream being fed to a simple evaporator unit, corresponding to one or a few distilling stages, wherein it is separated, partly into a first vapor stream, enriched in ethanol, which is fed to a plant for production of the desired ethanol grade, and partly into a first liquid bottom stream, which is at least in part recirculated to the fermentor. Especially characterizing for the new process is, that a raw material stream is fed to a circulation circuit, comprising said fermentor and said evaporator unit, and that the raw material stream is hydrolyzed, in the evaporator unit, to a fermentable state. It is especially advantageous to carry out this hydrolysis by enzymes, preferably by a gluco-amylase at a temperature within the range 35.degree. C. to 75.degree. C.