Process for recovery of values from a fermentation mass obtained in producing ethanol and products thereof

1. A process for the recovery of values from a fermentation mass obtained in producing ethanol, the fermentation mass comprising ethanol and an aqueous medium having a solids component suspended therein, the process comprising:

hydrolyzing biomass feedstock to produce treated biomass comprising fermentable sugars,

fermenting the treated biomass to form the fermentation mass, and

classifying the solids component of the fermentation mass to recover a solids fraction enriched in carbohydrates relative to the carbohydrate content of the solids component of the fermentation mass and a crude aqueous lignin slurry fraction comprising a solids component enriched in lignin relative to the lignin content of the solids fraction enriched in carbohydrates.

2. The process as set forth in claim 1 wherein prior to said classifying, at least a portion of the fermentation mass is subjected to distillation for recovery of ethanol, the solids component of the fermentation mass being retained in stillage from the distillation.

3. The process as set forth in claim 1 wherein the fermentation mass is obtained from a process for the production of ethanol from a biomass feedstock selected from the group consisting of corn stover, cereal straw, switchgrass, and mixtures thereof.

4. The process as set forth in claim 1 wherein the solids component of the fermentation mass is classified in a screen separation system comprising at least one screen.

5. The process as set forth in claim 1 wherein the particle size of the solids fraction enriched in carbohydrates is such that the fraction is retained on a screen having a mesh size of about U.S. Sieve No. 100 (150 μm) to about U.S. Sieve No. 70 (210 μm).

6. The process as set forth in claim 1 wherein the particle size of the solids component enriched in lignin of the crude aqueous lignin slurry fraction is such that the crude aqueous lignin slurry fraction passes through a screen having a mesh size of about U.S. Sieve No. 100 (150 μm) to about U.S. Sieve No. 70 (210 μm).

7. The process as set forth in claim 1 , wherein the process further comprises:

subjecting the crude aqueous lignin slurry fraction comprising a solids component enriched in lignin to a solid-liquid separation, thereby separating the solids component enriched in lignin from a liquid fraction.

8. The process as set forth in claim 1 wherein the solids component enriched in lignin comprises from about 30 wt. % to about 50 wt. % lignin and no greater than about 15 wt. % carbohydrates.

9. The process as set forth in claim 8 wherein the solids component enriched in lignin comprises from about 30 wt. % to about 55 wt. % inorganics.

10. The process as set forth in claim 1 wherein the process further comprises:

contacting the solids component enriched in lignin with an alkali in an aqueous medium having a pH between about 11.5 and about 13 and dissolving lignin contained in the solids fraction in the aqueous medium, thereby producing an aqueous alkaline extract fraction comprising dissolved lignin.

11. The process as set forth in claim 10 , wherein the aqueous alkaline extract fraction comprises dissolved lignin and dissolved inorganics, the process further comprising:

reducing the pH of the aqueous alkaline extract fraction to between about 7 and about 11 and precipitating inorganic solids from the aqueous alkaline extract fraction, thereby producing a slurry comprising particulate inorganic solids and dissolved lignin.

12. The process as set forth in claim 11 wherein the process further comprises:

subjecting the slurry comprising particulate inorganic solids and dissolved lignin to a solid-liquid separation to separate the particulate inorganic solids from the slurry, thereby producing a mineral-rich particulate solids fraction comprising inorganic solids and a lignin-rich aqueous fraction comprising dissolved lignin.

13. The process as set forth in claim 12 wherein the process further comprises:

contacting the lignin-rich aqueous fraction comprising dissolved lignin with an acidifying agent in sufficient proportion to reduce the pH of the product fraction to a value at which the lignin precipitates, thereby producing a slurry comprising precipitated lignin.

14. The process as set forth in claim 13 wherein the process further comprises:

subjecting the slurry comprising precipitated lignin to a solid-liquid separation to separate the lignin from the slurry, thereby producing a lignin-rich solids product fraction and a residual liquids fraction comprising the acidifying agent.

15. The process as set forth in claim 14 wherein the lignin-rich solids product fraction comprises at least about 50% lignin on a dry weight basis, no greater than about 20% inorganics on a dry weight basis, and no greater than about 10% carbohydrates on a dry weight basis.

16. The process as set forth in claim 1 wherein the process further comprises:

contacting the crude aqueous lignin slurry fraction with a solvent, thereby producing an extract comprising dissolved lignin.

17. The process as set forth in claim 16 wherein the solvent comprises an organic solvent.

18. A process for extraction of lignin and inorganics from a lignin- and inorganics-containing mass, the process comprising:

contacting the mass with an alkali in an aqueous medium having a pH between about 11.5 and about 13 and dissolving lignin contained in the mass in the aqueous medium, thereby producing an aqueous alkaline extract fraction comprising dissolved lignin;

reducing the pH of the aqueous alkaline extract fraction comprising dissolved lignin to between about 7 and about 11 and precipitating inorganic solids from the aqueous alkaline extract fraction, thereby producing a slurry comprising particulate inorganic solids and dissolved lignin;

subjecting the slurry comprising particulate inorganic solids and dissolved lignin to a solid-liquid separation to separate the particulate inorganic solids, from the slurry, thereby producing a mineral-rich particulate solids fraction comprising inorganic solids and a lignin-rich aqueous fraction comprising dissolved lignin; and

contacting the lignin-rich aqueous fraction comprising dissolved lignin with an acidifying agent in sufficient proportion to reduce the pH of the aqueous fraction to a value at which the lignin precipitates, thereby producing a slurry comprising precipitated lignin.

19. The process as set forth in claim 18 wherein the lignin- and inorganics-containing mass is obtained from a process for the production of ethanol from a biomass feedstock selected from the group consisting of corn stover, cereal straw, and mixtures thereof.