Method of processing ethanol byproducts and related subsystems
In one aspect of the invention, a method recovers oil from a concentrated byproduct, such as evaporated thin stillage formed during a dry milling process used for producing ethanol. The method includes forming a concentrate from the byproduct and recovering oil from the concentrate. The step of forming the concentrate may comprise evaporating the byproduct. Further, the step of separating the oil from the concentrate may comprise using a centrifuge and, in particular, a disk stack centrifuge. Other aspects of the invention include related methods and subsystems for recovering oil from thin stillage.
1. A method of recovering oil in a dry milling corn-to ethanol plant, the method comprising:
dry milling corn at the ethanol manufacturing facility by converting starch in the corn to sugar;
fermenting the sugar to produce ethanol and whole stillage;
separating the whole stillage in a separator to produce a distillers wet grains and a thin stillage, wherein each of the distillers wet grains and the thin stillage contain corn oil;
evaporating the thin stillage in an evaporator in the ethanol manufacturing facility to remove water and form a concentrated byproduct, wherein the concentrated byproduct contains corn oil;.
centrifuging the concentrated byproduct in a centrifuge located downstream from the evaporator in the ethanol manufacturing facility to separate at least a portion of the corn oil from the concentrated byproduct, wherein the concentrated byproduct has a moisture content of greater than 60% and less than 85% by weight; and recovering the separated oil from the centrifuge.
2. The method of claim 1 , further comprising mixing the concentrated byproduct remaining after centrifuging with distillers wet grains to form a mixture; and drying the mixture in a dryer downstream from the evaporator and centrifuge to make distillers dried grains with solubles.
3. The method of claim 1 , wherein evaporating the thin stillage in the evaporator to remove water and form the concentrated byproduct comprises processing the thin stillage to a temperature of between about 150 and about 212° F., and a pH of between about 3 and about 6.
4. The method of claim 1 , wherein the centrifuge is a disc stack centrifuge.
5. The method of claim 2 , wherein drying the concentrated byproduct in the dryer is to a moisture content of less than 10% by weight.
6. The method of claim 1 , wherein evaporating the thin stillage in the evaporator in the ethanol manufacturing facility to form the concentrated byproduct and centrifuging the concentrated byproduct to separate at least the portion of the oil from the concentrated byproduct is continuous.
7. The method of claim 1 , wherein the separator is selected from a group consisting of a press, an extruder, a decanter centrifuge, and a screen centrifuge.