Method and system for reducing the unfermentable solids content in a protein portion at the back end of a corn dry milling process

A system for reducing an unfermentable solids content in a protein portion at a back end of a starch-containing grain dry milling process for making biofuel or biochemical, the system comprising:

• a first apparatus that receives a whole stillage byproduct produced via the starch-containing grain dry milling process, wherein the first apparatus separates the whole stillage byproduct into an insoluble solids portion, which includes fiber, and a stillage portion, which includes protein;
• a second apparatus that is situated after the first apparatus and prior to any evaporator, the second apparatus is configured to receive the stillage portion from the first apparatus and counter current wash water directly from a later apparatus in the system and to separate the stillage portion into a water soluble solids portion and a protein portion, wherein the addition of the counter current wash water facilitates separation of a larger concentration of unfermentable solids into the water soluble solids portion;
• and a centrifuge that is situated after the second apparatus and that is the later apparatus and configured to receive the separated protein portion from the second apparatus and a first wash water, the centrifuge further configured to dewater the protein portion to provide a dewatered protein portion and a centrate portion including the first wash water, wherein at least a portion of the centrate portion including the first wash water is provided to the second apparatus and defines at least a portion of the counter current wash water, and wherein the dewatered protein portion defines a high protein grain meal that includes at least 40 wt % protein on a dry basis.