Methods and systems for removing undissolved solids prior to extractive fermentation in the production of butanol

A method for producing a fermentation product and an animal feed co-product comprising:

• providing a feedstock, wherein the feedstock comprises sugar, oil, gluten, and fiber;
• milling the feedstock in a dry-grind liquefaction system comprising a hammer mill and liquefaction vessel and liquefying the feedstock to create a feedstock slurry, wherein the feedstock slurry comprises sugar, liquid oil, and undissolved solids, wherein said undissolved solids comprise gluten and fiber;
• separating said undissolved solids and the liquid oil from the feedstock slurry in a single vessel, to create:
• an aqueous solution comprising sugar (i), a wet cake comprising the undissolved solids (ii), and the liquid oil (iii);
• recovering the aqueous solution (i), the wet cake (ii), and the liquid oil (iii) as separate streams from the single vessel;
• contacting the recovered aqueous solution (i) with a fermentation broth in a fermentor;
• fermenting the sugar in the aqueous solution (i) in the fermentor to produce the fermentation product;
• and
• processing the wet cake (ii) to produce the animal feed co-product.