Ethanol production process
An improved ethanol production process providing novel stillage treatment is disclosed wherein the stillage is separated into four value added product streams that are subjected to drying conditions reducing or eliminating volatization of any VOC's in the product streams.
1. An ethanol production process wherein a corn feedstock is hydrolyzed to produce ethanol and whole stillage, the improvement to which comprises:
a. reducing production of a volatile organic compounds stream by separating the whole stillage to produce a wet distillers grain containing protein-containing solids and a thin stillage containing a solubles stream containing vitamins, minerals, proteins and yeast;
b. filtering at least a portion of the thin stillage through a microfilter to form a carotenoid-containing retentate and a water soluble permeate comprising vitamin, mineral, protein and yeast; and
c. filtering at least a portion of the water soluble permeate through an ultrafilter to produce a protein and yeast- containing retentate and a vitamin and mineral-containing permeate;
d. drying at least one from the group consisting of: wet distillers grain, the carotenoid-containing retentate, the protein and yeast containing retentate and the vitamin and mineral-containing permeate in a spray dryer operating at an inlet hot air temperature of less than about 450° F. and an exhaust temperature of between about 140° F. and about 170° F. for a period of time to produce at least one product having a water content of less than about 15% by weight and a reduced stream of volatile organic compounds.
2. The ethanol production process according to claim 1 further comprising drying the water-soluble permeate under operating conditions to produce a vitamin, mineral, protein and yeast-rich product having a water content of less than about 15% by weight.
3. The process according to claim 1 wherein filtering the at least a portion of the water soluble permeate comprises an ultrafilter having a pore size of less than about 100,000 molecular weight and drying the protein and yeast-containing retentate.
4. The process according to claim 1 wherein the wet distillers grain, the retentate, the protein and yeast containing retentate, and the vitamin and mineral-containing permeate are each dried separately to produce four products.
5. The process according to claim 1 wherein said drying produces at least one vapor stream comprising volatile organic compounds.
6. The process according to claim 1 wherein said volatile organic compounds are retained by a cold trap.
7. An ethanol production process wherein a starch-containing feedstock is hydrolyzed to produce ethanol and whole stillage, the improvement to which consists essentially of:
a. reduction of capital expense and production of a volatile organic compound stream by separating the whole stillage to produce a wet distillers grain containing a protein-containing solids stream and a thin stillage containing a solubles stream containing vitamins, minerals, proteins and yeast;
b. filtering the thin stillage solubles stream through a microfilter having a pore size of about 0.1-1.0 microns to form a carotenoid-containing retentate and a permeate stream;
c. filtering the permeate stream through an ultrafilter having a filter size of less than about 100,000 molecular weight to obtain a protein and yeast-containing retentate and a vitamin and mineral containing permeate; and
d. employing conditions for drying said wet distillers grain, said carotenoid-containing retentate, said protein and yeast-containing retentate and said vitamin and mineral containing permeate to a water content of less than about 15% by weight including operating a spray dryer to achieve hot air exhaust temperature between about 140° F. and about 170° F. for a period of time equal to about three minutes but not more than three minutes.
8. The ethanol production process according to claim 7 further comprising drying said wet distillers grain to produce a first water-containing vapor stream and drying said protein and yeast-containing retentate to produce a second water-containing vapor stream.
9. The ethanol production process according to claim 8 wherein drying said carotenoid containing retentate produces a third water-containing vapor stream.
10. An improvement to an ethanol production process wherein a starch-containing feedstock is hydrolyzed to produce ethanol and whole stillage, the whole stillage including protein containing solids, the improvement to which consists essentially of:
a. separating the whole stillage to produce a wet distillers grain comprising most of the protein containing solids and a thin stillage comprising vitamins, minerals, proteins and yeast;
b. filtering the thin stillage solubles to form a first retentate and a first permeate;
c. filtering the first permeate stream to obtain a second retentate and a second permeate; and
d. selecting at least one from the group consisting of the first retentate, the second retentate, the second permeate, and wet distillers grain and drying to a water content of less than about 15% by weight by operating a spray dryer at an inlet temperature of less than about 450° F. and an outlet temperature between about 140° F. and about 170° F. for a period of time adequate to produce at least one product comprising non-denatured proteins and a reduced stream of volatile organic compounds.