Process for treating biomass

1. A process comprising:

contacting biomass with a biomass swelling agent within a vessel under conditions sufficient to swell or rupture at least a portion of the biomass, thereby providing a treated biomass;

removing at least a portion of the swelling agent from a first end of the vessel, while leaving at least a majority of the treated biomass within the vessel;

introducing steam into a second end of the vessel different from the first end; and

contacting the treated biomass left within the vessel with the steam to further remove swelling agent from the first end of the vessel.

2. The process of claim 1 , wherein the biomass is contained within the vessel at a bed porosity of at least 85 vol %.

3. The process of claim 1 , wherein the swelling agent is ammonia.

4. The process of claim 1 , wherein swelling agent is added to the vessel to provide a weight ratio of swelling agent to biomass in a contacting zone of the vessel of at least 0.1:1.

5. The process of claim 1 , wherein the contact of the steam and the treated biomass in the vessel is carried out to provide an Archimedes number of at least 4.5.

6. The process of claim 1 , wherein the swelling agent that is removed from the vessel by contact with the steam is recovered directly from the treatment vessel during the steam contacting step, and the directly recovered swelling agent has a water content of not greater than 15 wt %, based on total content of swelling agent recovered during the steam contacting step.

7. The process of claim 6 , wherein the swelling agent that is removed from the vessel is removed as a vapor.

8. The process of claim 1 , wherein the biomass is contained within a contact zone of the vessel, with the contact zone having a length to diameter ratio of greater than four.

9. The process of claim 1 , wherein the steam is supplied to the vessel as saturated or superheated steam.

10. The process of claim 1 , wherein the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel.

11. The process of claim 1 , wherein during the contact of the steam and the treated biomass in the vessel, the vessel is at a bed angle of not greater than 25 degrees from vertical.

12. The process of claim 1 , wherein the swelling agent comprises a water-soluble amine having the structure NRR 1 R 2 where R, R 1 and R 2 are the same or different and are selected from the group consisting of H and hydrocarbons containing 1-20 carbons, optionally substituted with oxygen, nitrogen, sulfur or phosphorous, and optionally where two or more of the R groups are attached to form a cyclic group.

13. The process of claim 12 , wherein the water-soluble amine is selected from the group consisting of ammonia, methylamine, dimethylamine, ethylamine, tripropylamine, morpholine, and mixtures thereof.

14. The process of claim 1 , wherein the swelling agent comprises water-soluble ammonium ions having the structure + NRR 1 R 2 R 3 where R, R 1 , R 2 , and R 3 are the same or different and are selected from the group consisting of H and hydrocarbons containing 1-20 carbons, optionally substituted with oxygen, nitrogen, sulfur or phosphorous, and optionally where two or more of the R groups are attached to form a cyclic group.

15. The process of claim 1 , wherein the swelling agent comprises a hydroxide, carbonate, or bicarbonate of lithium, sodium, potassium, magnesium, or calcium.

16. The process of claim 1 , wherein the swelling agent comprises a water soluble mono- or poly-carboxylic acid.

17. The process of claim 1 , wherein the swelling agent comprises an inorganic acid.

18. The process of claim 1 , wherein the vessel includes a plurality of containers within the vessel and positioned vertically relative to each other, each container comprising a perforated end plate and containing a portion of the biomass therein.

19. The process of claim 18 , wherein the biomass in each container is compressed therein.

20. The process of claim 18 , wherein the biomass is contained within the vessel at a bed porosity of at least 85 vol %.

21. The process of claim 1 , further comprising:

recycling the swelling agent removed from the vessel to a second vessel containing biomass therein; and

contacting the biomass in the second vessel with the recycled swelling agent to swell or rupture at least a portion of the biomass.

22. The process of claim 21 , wherein recycling the swelling agent comprises feeding the removed swelling agent to the second vessel with no processing to remove water when the removed swelling agent has a moisture content at or below a desired moisture content.

23. The process of claim 22 , wherein the desired moisture content is 15 wt. %.

24. The process of claim 1 , wherein removing at least a portion of the swelling agent from a first end of the vessel comprises, prior to introducing steam into the second end of the vessel, reducing pressure in the vessel to a value less than 50% of the pressure in the vessel during contacting the biomass with the swelling agent.

25. The process of claim 1 , wherein:

the swelling agent is ammonia, and

swelling agent is added to the vessel to provide a weight ratio of swelling agent to biomass in a contacting zone of the vessel of at least 0.1:1.

26. The process of claim 1 , wherein:

the swelling agent is ammonia, and

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel.

27. The process of claim 1 , wherein:

the swelling agent that is removed from the vessel by contact with the steam is recovered directly from the treatment vessel during the steam contacting step, and the directly recovered swelling agent has a water content of not greater than 15 wt %, based on total content of swelling agent recovered during the steam contacting step,

the swelling agent that is removed from the vessel is removed as a vapor, and

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel.

28. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

the swelling agent comprises a water-soluble amine having the structure NRR 1 R 2 where R, R 1 and R 2 are the same or different and are selected from the group consisting of H and hydrocarbons containing 1-20 carbons, optionally substituted with oxygen, nitrogen, sulfur or phosphorous, and optionally where two or more of the R groups are attached to form a cyclic group.

29. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

the water-soluble amine is selected from the group consisting of ammonia, methylamine, dimethylamine, ethylamine, tripropylamine, morpholine, and mixtures thereof.

30. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

the swelling agent comprises water-soluble ammonium ions having the structure + NRR 1 R 2 R 3 where R, R 1 , R 2 , and R 3 are the same or different and are selected from the group consisting of H and hydrocarbons containing 1-20 carbons, optionally substituted with oxygen, nitrogen, sulfur or phosphorous, and optionally where two or more of the R groups are attached to form a cyclic group.

31. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

the swelling agent comprises a hydroxide, carbonate, or bicarbonate of lithium, sodium, potassium, magnesium, or calcium.

32. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

the swelling agent comprises a water soluble mono- or poly-carboxylic acid.

33. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

the swelling agent comprises an inorganic acid.

34. The process of claim 1 , wherein:

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

removing at least a portion of the swelling agent from a first end of the vessel comprises, prior to introducing steam into the second end of the vessel, reducing pressure in the vessel to a value less than 50% of the pressure in the vessel during contacting the biomass with the swelling agent.

35. The process of claim 1 , wherein:

the contact of the steam and the treated biomass in the vessel is carried out to provide an Archimedes number of at least 4.5, and

the vessel includes a plurality of containers within the vessel and positioned vertically relative to each other, each container comprising a perforated end plate and containing a portion of the biomass therein.

36. The process of claim 1 , wherein:

during the contact of the steam and the treated biomass in the vessel, the vessel is at a bed angle of not greater than 25 degrees from vertical, and

the vessel includes a plurality of containers within the vessel and positioned vertically relative to each other, each container comprising a perforated end plate and containing a portion of the biomass therein.

37. The process of claim 1 , wherein:

the swelling agent is ammonia,

swelling agent is added to the vessel to provide a weight ratio of swelling agent to biomass in a contacting zone of the vessel of at least 0.1:1,

the swelling agent that is removed from the vessel by contact with the steam is recovered directly from the treatment vessel during the steam contacting step, and the directly recovered swelling agent has a water content of not greater than 15 wt %, based on total content of swelling agent recovered during the steam contacting step,

the steam is supplied to the vessel as saturated or superheated steam,

the biomass is treated with the swelling agent to increase enzyme digestibility by at least 10% relative to that initially supplied to the vessel, and

during the contact of the steam and the treated biomass in the vessel, the vessel is at a bed angle of not greater than 25 degrees from vertical.