Process to improve protein recovery in stillage processing streams

A method of recovering protein from stillage produced in an ethanol production process, the method comprising:

• treating stillage comprising oil, protein, and water upstream of a separation, concentration or evaporation step with about 50 ppm to about 500 ppm of a coagulant comprising poly(diallyldimethylammonium chloride) (polyDADMAC), epichlorohydrin-diethylamine, or a combination thereof, and about 50 ppm to about 500 ppm of a polymer comprising a monomer unit derived from a monomer selected from 2-acrylamido-2-methylpropane sulfonic acid (“AMPS”), 2-acrylamido-2-methylbutane sulfonic acid (“AMBS”), [2-methyl-2-[(1-oxo-2-propenyl)amino |propyl]-phosphonic acid, methacrylic acid, acrylic acid, salts thereof, and combinations thereof, to produce a treated stillage comprising solids which include at least a portion of the oil and protein;
• and subjecting the treated stillage to a solid/liquid separation process, to produce a clarified stillage comprising a clarified aqueous phase and a separated solids phase, wherein the separated solids phase comprises at least a portion of the protein from the stillage,
• wherein the stillage is whole stillage or thin stillage and the separated solids phase is in the form of a float layer and
• the method further comprising separating at least a portion of the oil from the float layer to produce a de-oiled float layer by treating the float layer with an oil recovery agent, comprising a blend of 75-95% castor oil ethoxylate, 5-15% hydrophobic precipitated silica, 10-30% vegetable oil, and <10% propylene glycol.