Processes and systems for dry-milled corn ethanol and corn oil production with improved carbon footprint

Abstract

The present invention improves corn dry milling in several ways. Integrated corn biorefinery processes are disclosed which can produce ethanol, edible corn oil, DDG or DDGS, solvent-extracted meal, power, and optionally crude corn oil, starting from corn. Some variations employ corn fractionation and edible corn oil recovery using liquid carbon dioxide, avoiding hazardous hydrocarbon-based solvents to produce edible corn oil. Some variations employ integration of gas-fired co-generation into the dry-milled corn ethanol plant to significantly reduce energy usage and carbon footprint associated with the overall process. Counter-current drying is preferably employed to produce a high-quality DDG or DDGS product with high protein content, low mycotoxin content, and low residual ethanol content.

What is claimed is: 
     
         1 . A process for drying a solids-rich still residue derived from corn, said process comprising:
 (a) introducing corn-derived glucose to an aqueous fermentor containing a microorganism to ferment glucose into a dilute fermentation product and carbon dioxide;   (b) introducing said dilute fermentation product to a distillation unit configured to generate a distillate (overhead) and a solids-rich still residue (still bottoms);   (c) drying said solids-rich still residue using a drying gas in a counter-current dryer disposed in a vertically stacked dryer, to generate a dried solids stream;   (d) cooling said dried solids stream using a cooling gas in a cooler disposed in communication with said vertically stacked dryer, to generate a cooled solids stream comprising distillers' dried grains with solubles (DDGS); and   (e) recovering said DDGS.   
     
     
         2 . The process of  claim 1 , said process further comprising recycling or recovering at least a portion of exhaust gases from said counter-current dryer. 
     
     
         3 . The process of  claim 2 , wherein said recycling or recovering includes recycling water back to step (a). 
     
     
         4 . The process of  claim 2 , wherein said recycling or recovering includes recycling said fermentation product back to step (b). 
     
     
         5 . The process of  claim 1 , wherein said counter-current dryer utilizes superheated air to dry said solids-rich still residue. 
     
     
         6 . The process of  claim 1 , said process further comprising removing some liquid from said solids-rich still residue, prior to step (c). 
     
     
         7 . The process of  claim 1 , wherein said fermentation product is selected from the group consisting of alcohols, organic acids, amino acids, enzymes, microorganisms, and combinations thereof. 
     
     
         8 . The process of  claim 1 , wherein said DDGS has higher nutritional value than DDGS produced by an otherwise-equivalent process that does not utilize said vertically stacked dryer. 
     
     
         9 . A process for drying a solids-rich still residue derived from corn, said process comprising:
 (a) introducing corn-derived glucose to an aqueous fermentor containing a microorganism to ferment glucose into a dilute fermentation product and carbon dioxide;   (b) introducing said dilute fermentation product to a distillation unit configured to generate a distillate (overhead) and a solids-rich still residue (still bottoms);   (c) drying said solids-rich still residue using a drying gas in a counter-current dryer disposed in a vertically stacked dryer, to generate a dried solids stream;   (d) cooling said dried solids stream using a cooling gas in a cooler disposed in communication with said vertically stacked dryer, to generate a cooled solids stream comprising distillers' dried grains; and   (e) recovering said distillers' dried grains.   
     
     
         10 . The process of  claim 9 , said process further comprising recycling or recovering at least a portion of exhaust gases from said counter-current dryer. 
     
     
         11 . The process of  claim 10 , wherein said recycling or recovering includes recycling water back to step (a). 
     
     
         12 . The process of  claim 10 , wherein said recycling or recovering includes recycling said fermentation product back to step (b). 
     
     
         13 . The process of  claim 1 , wherein said counter-current dryer utilizes superheated air to dry said solids-rich still residue. 
     
     
         14 . The process of  claim 1 , said process further comprising removing some liquid from said solids-rich still residue, prior to step (c). 
     
     
         15 . The process of  claim 1 , wherein said fermentation product is selected from the group consisting of alcohols, organic acids, amino acids, enzymes, microorganisms, and combinations thereof. 
     
     
         16 . The process of  claim 1 , wherein said distillers' dried grains has higher nutritional value than distillers' dried grains produced by an otherwise-equivalent process that does not utilize said vertically stacked dryer. 
     
     
         17 . A process for drying a solids-rich still residue derived from corn, said process comprising:
 (a) drying a corn-derived solids-rich still residue using a drying gas in a counter-current dryer disposed in a vertically stacked dryer, to generate a dried solids stream;   (b) cooling said dried solids stream using a cooling gas in a cooler disposed in communication with said vertically stacked dryer, to generate a cooled solids stream comprising distillers' dried grains with optional solubles; and   (e) recovering said distillers' dried grains with optional solubles,   wherein said distillers' dried grains with optional solubles has higher nutritional value than distillers' dried grains with optional solubles produced by an otherwise-equivalent process that does not utilize said vertically stacked dryer.   
     
     
         18 . The process of  claim 17 , said process further comprising removing some liquid from said solids-rich still residue, prior to step (c). 
     
     
         19 . The process of  claim 17 , wherein said counter-current dryer utilizes superheated air to dry said solids-rich still residue. 
     
     
         20 . The process of  claim 17 , said process further comprising recycling or recovering at least a portion of exhaust gases from said counter-current dryer.