Inorganic salt recovery during processing of lignocellulosic feedstocks

• US 7,670,813 B2
• Filed: 10/25/2006
• Issued: 03/02/2010
• Est. Priority Date: 10/25/2006
• Status: Expired due to Fees

• Current Assignee: Iogen Energy Corporation (Iogen Corporation)
• Original Assignee: Iogen Energy Corporation (Iogen Corporation)
• Inventors: Anand, Vijay, Tolan, Jeffrey S., Foody, Brian, Rahme, Ziyad
• Primary Examiner(s): Lilling; Herbert J.
• Application Number:
  US11/586,135
• Publication Number:
  US 20080102502A1
• Time in Patent Office: 1,224 Days
• Field of Search: None
• US Class Current: 435/105
• CPC Class Codes: C08H 8/00 Macromolecular compounds derived from lignocellulosic materials pretreatment thereof B27N
• CPC Class Codes: C12P 19/02 Monosaccharides 2-ketogulonic acid C12P7/60
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

A method for recovering inorganic salt during processing of a lignocellulosic feedstock is provided. The method comprises pretreating the lignocellulosic feedstock by adding an acid or a base to the feedstock to produce a pretreated lignocellulosic feedstock. A soluble base or acid is then added to the pretreated lignocellulosic feedstock to adjust the pH and produce a neutralized feedstock. The neutralized feedstock is then hydrolyzed to produce an hydrolyzed feedstock and a sugar stream. Inorganic salt is recovered from a wash stream obtained from the pretreated lignocellulosic feedstock, a stream obtained from the neutralized feedstock, a stream obtained from the sugar stream, or a combination of these streams. The inorganic salt may be concentrated, clarified, recovered and purified by crystallization, electrodialysis, drying, or agglomeration and granulation, and then used as desired, for example, as a fertilizer.

Claims

1. A method for processing a lignocellulosic feedstock and obtaining an inorganic salt selected from the group consisting of ammonium sulfate, potassium sulfate, ammonium phosphate and potassium phosphate during said processing, said method comprising:

(a) pretreating the lignocellulosic feedstock by adding one or more than one soluble base selected from the group consisting of ammonia, ammonium hydroxide and potassium hydroxide to the lignocellulosic feedstock to produce a pretreated lignocellulosic feedstock;

(b) optionally separating an aqueous stream from the pretreated lignocellulosic feedstock;

(c) adding sulfuric acid or phosphoric acid to the pretreated lignocellulosic feedstock to adjust the pH of the pretreated lignocellulosic feedstock to produce a neutralized feedstock and inorganic salt selected from the group consisting of ammonium sulfate, potassium sulfate, ammonium phosphate and potassium phosphate;

(d) hydrolyzing the neutralized feedstock to produce a hydrolyzed feedstock; and

(e) recovering an inorganic salt comprising inorganic salt arising from step (c) from a salt-containing stream obtained during the processing of the lignocellulosic feedstock.

2. The method of claim 1, wherein the lignocellulosic feedstock is selected from the group consisting of corn stover, wheat straw, barley straw, canola straw, rice straw, oat straw, soybean stover, grass, switch grass, miscanthus, cord grass, reed canary grass, aspen wood, sawdust, bagasse and beet pulp.

3. The method of claim 1, wherein, in the step of recovering (step (e)), the inorganic salt is recovered by ion exclusion.

4. The method of claim 3, wherein the step of recovering (step (e)) is followed by crystallization of the inorganic salt, electrodialysis, drying, or agglomeration and granulation.

5. The method of claim 3, wherein the inorganic salt is concentrated by evaporation, membrane filtration, or a combination thereof, prior to recovery to produce a concentrated solution comprising the inorganic salt.

6. The method of claim 5, wherein the concentrated solution is clarified by microfiltration, plate and frame filtration, or centrifugation prior to recovery.

7. The method of claim 1, wherein the one or more than one soluble base is selected from the group consisting of ammonium hydroxide and ammonia.

8. The method of claim 7, wherein the step of pretreating (step (a)) is performed at a temperature from about 20°

C. to about 200°

C., at a pH from about pH 9.5 to about 12 and for a time period of from about 2 to about 20 minutes.

9. The method of claim 1, wherein the processing of the lignocellulosic feedstock further comprises:

(f) fermenting the sugar stream to produce a fermentation broth comprising ethanol; and

(g) distilling the fermentation broth to produce concentrated ethanol and a still bottoms stream.

10. The method of claim 9, wherein the salt-containing stream, from which the inorganic salt is recovered, is the still bottoms stream and wherein the inorganic salt so recovered is purified.

11. The method of claim 10, wherein, prior to the step of recovering the inorganic salt from the still bottoms, the concentration of the still bottoms is increased by evaporation, membrane filtration, or a combination thereof, to produce concentrated still bottoms, followed by a step of ion exclusion chromatography using a simulated moving bed (SMB) process.

12. The method of claim 11, wherein the concentrated still bottoms are clarified by microfiltration, plate and frame filtration or centrifugation, prior to the step of ion exclusion chromatography.

13. The method of claim 12, wherein the step of purifying the inorganic salt comprises crystallization of the inorganic salt, electrodialysis, drying, or agglomeration and granulation.

14. The method of claim 1, wherein, in the step of hydrolyzing (step (d)), one or more than one cellulase enzyme is added to the neutralized feedstock so that at least a portion of cellulose in the neutralized feedstock is hydrolyzed to produce glucose.

15. The method of claim 1, wherein, after the step of hydrolyzing (step (d)), the sugar stream is separated from the hydrolyzed feedstock to form a solid residue and a sugar hydrolyzate stream.

16. The method of claim 15, wherein the inorganic salt is concentrated by evaporation, membrane filtration, or a combination thereof.

17. The method of claim 1, wherein, in the step of hydrolyzing (step (d)), the neutralized feedstock is treated with one or more than one acid so that at least a portion of cellulose and hemicellulose in the neutralized feedstock is hydrolyzed to produce a sugar stream comprising glucose, xylose, arabinose, mannose and galactose.

18. The method of claim 1, wherein the inorganic salt is soluble.

19. The method of claim 1, wherein the inorganic salt is for use as a fertilizer.

20. The method of claim 1, wherein the salt-containing stream from which the inorganic salt is recovered, is the neutralized feedstock, the sugar stream, a still bottoms stream or a combination thereof.

21. The method of claim 20, wherein

in the step of pretreating (step (a)), the one or more than one soluble base is ammonia, ammonium hydroxide, or a combination thereof;

in the step of adding (step (c)), the one or more than one acid is sulfuric acid; and

the inorganic salt that is recovered from the salt-containing stream is ammonium sulfate.

22. The method of claim 21, wherein, in the step of recovering (step (e)), the inorganic salt is recovered by ion exclusion.

23. The method of claim 22, wherein the step of recovering (step (e)) is followed by crystallization of the inorganic salt, electrodialysis, drying, or agglomeration and granulation.

24. The method of claim 21, wherein the step of pretreating (step (a)) is performed at a temperature from about 20°

C. to about 200°

C., at a pH from about pH 9.5 to about 12 and for a time period of from about 2 to about 20 minutes.

25. The method of claim 24, wherein the ammonium sulfate is for use as a fertilizer.

26. The method of claim 1, wherein the sugar stream is processed by

fermenting the sugar stream to produce a fermentation broth comprising ethanol or butanol;

and

separating the ethanol or butanol from the fermentation broth to produce a stream comprising concentrated ethanol or butanol and an aqueous stream comprising the inorganic salt,

wherein the salt-containing stream, from which the inorganic salt is recovered, is the aqueous stream comprising the inorganic salt produced during the step of separating the ethanol or butanol.

27. The method of claim 26, further comprising the steps of purifying the recovered inorganic salt to obtain a purified inorganic salt and producing a product comprising the purified inorganic salt.

28. The method of claim 27, wherein the step of purifying comprises performing ion exclusion chromatography, followed by electrodialysis, crystallization, drying, or agglomeration and granulation.

29. A method for processing a lignocellulosic feedstock and obtaining an inorganic salt selected from the group consisting of ammonium sulfate, potassium sulfate, ammonium phosphate and potassium phosphate, said method comprising:

(a) pretreating the lignocellulosic feedstock by adding one or more than one soluble base selected from the group consisting of ammonia, ammonium hydroxide and potassium hydroxide to the lignocellulosic feedstock to produce a pretreated lignocellulosic feedstock;

(b) separating an aqueous sugar-base mixture from solids contained in the pretreated lignocellulosic feedstock;

(c) neutralizing the sugar-acid mixture with sulfuric acid or phosphoric acid, thereby producing a neutralized aqueous stream comprising sugar and inorganic salt selected from the group consisting of ammonium sulfate, potassium sulfate, ammonium phosphate and potassium phosphate; and

(d) recovering the inorganic salt from the neutralized aqueous stream.

30. The method of claim 29, wherein the lignocellulosic feedstock is selected from the group consisting of corn stover, wheat straw, barley straw, canola straw, rice straw, oat straw, soybean stover, grass, switch grass, miscanthus, cord grass, reed canary grass, aspen wood, sawdust, bagasse and beet pulp.

31. The method of claim 29, wherein, in the step of recovering (step (d)), the inorganic salt is recovered by ion exclusion.

32. The method of claim 31, wherein the step of recovering (step (d)) is followed by crystallization of the inorganic salt, electrodialysis, drying, or agglomeration and granulation.

33. The method of claim 31, wherein the inorganic salt is concentrated by evaporation, membrane filtration, or a combination thereof, prior to recovery to produce a concentrated solution comprising the inorganic salt.

34. The method of claim 33, wherein the concentrated solution is clarified by microfiltration, plate and frame filtration, or centrifugation prior to recovery.

35. The method of claim 29, wherein the one or more than one acid is sulfuric acid.

36. The method of claim 35, wherein the one or more than one alkali is selected from the group consisting of ammonium hydroxide and ammonia.

37. The method of claim 36, wherein the step of pretreating (step (a)) is performed at a temperature from about 20°

C. to about 200°

C., at a pH from about pH 9.5 to about 12 and for a time period of from about 2 to about 20 minutes.