System and method for producing a sugar stream using membrane filtration

Abstract

An improved dry grind system and method for producing a sugar stream from grains or similar carbohydrate sources and/or residues, such as for biofuel production, using membrane filtration. In particular, a sugar/carbohydrate stream, which includes a desired Dextrose Equivalent (DE) where DE describes the degree of conversion of starch to dextrose (aka glucose) and/or has had removed therefrom an undesirable amount of unfermentable components, can be produced after saccharification and prior to fermentation (or other sugar conversion process) using membrane filtration, with such sugar stream being available for biofuel production, e.g., alcohol production, or other processes. In addition, the systems and methods also can involve the removal of certain grain components, e.g., corn kernel components, including protein, oil and/or fiber, prior to fermentation or other conversion systems. In other words, sugar stream production and/or grain component separation occurs on the front end of the system and method.

What is claimed is: 
     
         1 . A method for producing an oligosaccharide stream comprising:
 milling grain and/or grain components into grain particles;   mixing the grain particles with a liquid to produce a slurry;   subjecting the slurry to liquefaction to convert starch in the slurry to oligosaccharides to produce a stream including the oligosaccharides;   separating the stream into a first solids portion and a first liquid portion including the oligosaccharides; and   separating the first liquid portion, via membrane filtration, into a second solids portion and a second liquid portion including the oligosaccharides to produce an oligosaccharide stream.   
     
     
         2 . The method of  claim 1  wherein, after subjecting the slurry to liquefaction, directly separating the stream into a first solids portion and a first liquid portion including the oligosaccharides. 
     
     
         3 . The method of  claim 1  wherein, after separating the stream, directly separating the first liquid portion, via membrane filtration, into a second solids portion and a second liquid portion including the oligosaccharides. 
     
     
         4 . The method of  claim 1  wherein, after separating the first liquid portion via membrane filtration, directly subjecting the second liquid portion to saccharification to convert the oligosaccharides to simple sugars and produce a sugar stream including the simple sugars having a dextrose equivalent of at least 20 D.E. 
     
     
         5 . The method of  claim 1  wherein, after subjecting the slurry to liquefaction, separating the stream, via particle sizes, into a first solids portion and a first liquid portion including the oligosaccharides. 
     
     
         6 . The method of  claim 5  wherein separating the stream, via particle sizes, comprises separating the stream, via a paddle screen, into a first solids portion and a first liquid portion including the oligosaccharides. 
     
     
         7 . The method of  claim 1  wherein separating the first liquid portion, via membrane filtration, comprises separating the first liquid portion, via microfiltration, into a second solids portion and a second liquid portion including the oligosaccharides. 
     
     
         8 . The method of  claim 1  further comprising combining the second solids portion with the first solids portion to form a combined solids portion. 
     
     
         9 . The method of  claim 1  further comprising subjecting the second liquid portion to saccharification to convert the oligosaccharides to simple sugars and produce a sugar stream including the simple sugars having a dextrose equivalent of at least 20 D.E. 
     
     
         10 . The method of  claim 9  further comprising subjecting the sugar stream to a sugar conversion process to produce a biofuel and/or a biochemical. 
     
     
         11 . The method of  claim 9  further comprising subjecting the sugar stream to fermentation to produce a biofuel and/or a biochemical. 
     
     
         12 . The method of  claim 10  wherein the biofuel is ethanol. 
     
     
         13 . The method of  claim 9  further comprising subjecting the sugar stream to a sugar conversion process to produce a biofuel and/or a biochemical other than ethanol. 
     
     
         14 . A method for producing an oligosaccharide stream comprising:
 milling grain and/or grain components into grain particles;   mixing the grain particles with a liquid to produce a slurry;   subjecting the slurry to liquefaction to convert starch in the slurry to oligosaccharides to produce a stream including the oligosaccharides;   separating the stream, via a paddle screen, into a first solids portion and a first liquid portion including the oligosaccharides; and   after separating the stream via the paddle screen, directly separating the first liquid portion, via microfiltration, into a second solids portion and a second liquid portion including the oligosaccharides to produce an oligosaccharide stream.   
     
     
         15 . The method of  claim 14  further comprising combining the second solids portion with the first solids portion to form a combined solids portion. 
     
     
         16 . The method of  claim 14  further comprising, after separating the first liquid portion via microfiltration, directly subjecting the second liquid portion to saccharification to convert the oligosaccharides to simple sugars and produce a sugar stream including the simple sugars having a dextrose equivalent of at least 20 D.E. 
     
     
         17 . The method of  claim 16  further comprising subjecting the sugar stream to a sugar conversion process to produce a biofuel and/or a biochemical. 
     
     
         18 . The method of  claim 16  further comprising subjecting the sugar stream to fermentation to produce a biofuel and/or a biochemical. 
     
     
         19 . The method of  claim 18  wherein the biofuel is ethanol. 
     
     
         20 . The method of  claim 16  further comprising subjecting the sugar stream to a sugar conversion process to produce a biofuel and/or a biochemical other than ethanol.