Biomass conversion systems having a fluid circulation loop containing backflushable filters for control of cellulosic fines and methods for use thereof

1. A method comprising:

providing a biomass conversion system that comprises a fluid circulation loop comprising:

a hydrothermal digestion unit;

a solids separation unit that is in fluid communication with an outlet of the hydrothermal digestion unit;

wherein the solids separation unit comprises a plurality of filters; and

a catalytic reduction reactor unit that is in fluid communication with an outlet of the solids separation unit and an inlet of the hydrothermal digestion unit;

providing a cellulosic biomass in the hydrothermal digestion unit;

at least partially digesting the cellulosic biomass in the hydrothermal digestion unit to form a hydrolysate comprising soluble carbohydrates and cellulosic fines within a liquor phase;

flowing the liquor phase through at least one of the filters to sequester the cellulosic fines; and

backflushing at least a portion of the cellulosic fines to the hydrothermal digestion unit while the liquor phase continues to flow through one or more of the filters to the catalytic reduction reactor unit; and

converting the hydrolysate into higher hydrocarbons.

2. The method of claim 1 , further comprising:

forming a reaction product in the catalytic reduction reactor unit.

3. The method of claim 2 , wherein the reaction product is used to backflush the cellulosic fines.

4. The method of claim 1 , wherein the fluid circulation loop is configured such that countercurrent flow is established in the hydrothermal digestion unit.

5. The method of claim 1 , wherein at least one of the plurality of filters comprises a catalytic filter comprising a solid support and a catalyst that is capable of activating molecular hydrogen.

6. The method of claim 5 , further comprising:

at least partially converting the soluble carbohydrates into a reaction product on the catalytic filter.

7. The method of claim 6 , further comprising:

further converting the soluble carbohydrates into the reaction product in the catalytic reduction reactor unit.

8. The method of claim 1 , wherein the plurality of filters are connected in parallel to one another.

9. The method of claim 1 , wherein the plurality of filters are arranged on a rotatable filter array.

10. The method of claim 1 , further comprising:

reversing a direction of fluid flow in the filters being backflushed; and

reversing a direction of fluid flow in one or more of the other filters so as to backflush cellulosic fines therefrom.

11. The method of claim 1 , wherein at least about 60% of the cellulosic biomass, on a dry basis, is digested to produce hydrolysate.

12. The method of claim 1 , wherein at least about 90% of the cellulosic biomass, on a dry basis, is digested to produce hydrolysate.

13. The method of claim 1 , further comprising:

converting the hydrolysate into a biofuel.

14. A method comprising:

providing a biomass conversion system that comprises a fluid circulation loop comprising:

a hydrothermal digestion unit;

a solids separation unit that is in fluid communication with an outlet of the hydrothermal digestion unit;

wherein the solids separation unit comprises a plurality of filters; and

a catalytic reduction reactor unit that is in fluid communication with an outlet of the solids separation unit and an inlet of the hydrothermal digestion unit;

providing a cellulosic biomass in the hydrothermal digestion unit;

at least partially digesting the cellulosic biomass in the hydrothermal digestion unit to form a hydrolysate comprising soluble carbohydrates and cellulosic fines within a liquor phase;

flowing the liquor phase through at least one of the filters to sequester the cellulosic fines;

at least partially converting the soluble carbohydrates into a reaction product in the catalytic reduction reactor unit; and

backflushing at least a portion of the cellulosic fines to the hydrothermal digestion unit using at least a portion of the reaction product; and

converting the hydrolysate into higher hydrocarbons.

15. The method of claim 14 , wherein backflushing takes place while the liquor phase continues to flow through one or more of the filters to the catalytic reduction reactor unit.

16. The method of claim 14 , wherein the fluid circulation loop is configured such that countercurrent flow is established in the hydrothermal digestion unit.

17. The method of claim 14 , wherein at least one of the plurality of filters comprises a catalytic filter comprising a solid support and a catalyst that is capable of activating molecular hydrogen.

18. The method of claim 17 , further comprising:

at least partially converting the soluble carbohydrates into the reaction product on the catalytic filter.

19. The method of claim 14 , wherein the plurality of filters are connected in parallel to one another.

20. The method of claim 14 , wherein the plurality of filters are arranged on a rotatable filter array.

21. The method of claim 14 , further comprising:

reversing a direction of fluid flow in the filters being backflushed; and

reversing a direction of fluid flow in one or more of the other filters so as to backflush cellulosic fines therefrom.

22. The method of claim 14 , wherein at least about 60% of the cellulosic biomass, on a dry basis, is digested to produce hydrolysate.

23. The method of claim 14 , wherein at least about 90% of the cellulosic biomass, on a dry basis, is digested to produce hydrolysate.

24. The method of claim 14 , further comprising:

converting the hydrolysate into a biofuel.