Ethanol process using pre-fermentation solids removal
View Patent ↗A process for preparing a starch-containing biomass particle stream having a significant percentage of fiber for processing into ethanol comprises the first step of: mixing the particle stream with a liquid solvent to dissolve at least a portion of the starch in the carbohydrate particle stream to form a carbohydrate slurry stream containing starch dissolved in the liquid solvent. This first step removes a portion of the fiber from the carbohydrate slurry stream. In a second step, the carbohydrate slurry stream is held in a settling tank to remove a further portion of the fiber. An enhancement to the process is suitable for use with shell corn or other biomass having an oil-containing germ portion and a non-germ portion comprising mainly carbohydrates and fiber. This enhancement includes the step of grinding the corn to particles of a size suitable for separating the germ particles from the non-germ particles. The germ particles are processed first to remove the oil and then to remove the carbohydrates.
1. A process for treating a stream of dry corn kernels having therein a significant percentage of fiber, comprising the steps of:
a) milling the corn kernels to form particles, some particles being germ particles that predominantly comprise germ material from the kernels and other particles being starch-containing particles that predominantly comprise starch material from the kernels;
b) mechanically separating at least some of the germ particles from the starch-containing particles to form a germ particle stream with the remainder of the particles forming a starch-containing particle stream;
c) mixing the starch-containing particle stream with a liquid solvent comprising a mixture of ethanol and water to dissolve at least a portion of the starch in the starch-containing particle stream to form a carbohydrate slurry stream containing (i) fiber and (ii) starch dissolved in the liquid solvent;
d) transferring the carbohydrate slurry stream to a settling tank;
e) holding the carbohydrate slurry stream in the settling tank for a time sufficient to allow settling of a portion of the fibers;
f) removing the upper volume of the dissolved carbohydrate stream to form a reduced fiber liquid carbohydrate stream containing a smaller fraction of the fiber than did the original starch-containing particle stream; and
g) thereafter, mixing an enzyme with the reduced fiber liquid carbohydrate stream to convert at least a portion of the starch in the reduced fiber liquid carbohydrate stream to sugars.
2. The process of claim 1 , wherein the mechanical separation step comprises:
a) transporting the milled kernel particles to a separator tank; and
b) forcing air upwards through the milled kernel particles in the separator tank.
3. The process of claim 1 , wherein the starch-containing particle stream-solvent mixing step includes the step of mixing the starch-containing particle stream with a liquid comprising a mixture of approximately 60-80% ethanol by weight.
4. The process of claim 1 , including an evaporating step for removing a substantial percentage of the ethanol from the carbohydrate slurry stream.
5. The process of claim 1 , including the steps of:
a) fermenting the sugars in the reduced fiber liquid carbohydrate slurry stream produced by the enzyme-mixing step to produce ethanol; and
b) mixing at least a portion of the ethanol formed by the fermentation step with the starch-containing biomass particle stream.
6. The process of claim 1 , including the step of holding the carbohydrate slurry stream in the settling tank for at approximately 30 minutes to approximately 60 minutes.
7. The process of claim 1 , wherein the step of mixing the starch-containing biomass carbohydrate particle stream with a liquid solvent occurs at a pressure substantially above atmospheric.
8. The process of claim 3 , including evaporating at least a portion of any solvent in the carbohydrate slurry stream.
9. The process of claim 8 , wherein the evaporating step includes removing a substantial percentage of the ethanol from the liquid carbohydrate stream, and further including the steps of:
a) fermenting the liquid carbohydrate slurry stream to produce ethanol; and
b) mixing at least a portion of the ethanol formed by the fermentation step with the starch-containing particle stream.
10. The process of claim 4 , further including the steps of:
a) fermenting the sugars in the reduced fiber liquid carbohydrate stream to produce ethanol and CO 2 gas;
b) capturing the CO 2 gas and forming liquid CO 2 therefrom;
c) mixing the liquid CO 2 with the germ particle stream to dissolve the germ particle stream's corn oil in the liquid CO 2 to form a dissolved corn oil stream;
d) evaporating the liquid CO 2 from the dissolved corn oil stream to create a corn oil stream; and
e) separating the corn oil stream to produce a germ particle carbohydrate stream with reduced corn oil.
11. The process of claim 10 , including the steps of:
a) mixing a carbohydrate solvent with the germ particle carbohydrate stream with reduced corn oil to form a germ particle carbohydrate slurry stream;
b) mixing an enzyme with the germ particle carbohydrate slurry stream to convert at least a portion of the carbohydrate in the germ particle carbohydrate slurry stream to sugars; and
c) fermenting the sugars in the germ particle carbohydrate stream to produce ethanol and CO 2 gas.
12. The process of claim 11 , wherein the steps of mixing the liquid CO 2 with the germ particle stream and mixing a carbohydrate solvent with the germ particle stream occur in the same chamber.