Method and system for treating biomass

Abstract

The invention relates to a method for treating biomass (2). In a step (S10), biomass (2) and an impregnation liquid are fed into a first reactor unit (10) such that the biomass (2) is impregnated with the impregnation liquid while the biomass (2) is transferred through the first reactor unit (10) by a conveyor means (11). In another step (S20), the impregnated biomass (2a) is transferred from the first reactor unit (10) to a separation unit (25), wherein at least a part of the impregnation liquid is separated from the impregnated biomass (2a) within the separation unit. In a step (S30), the separated impregnation liquid is discharged from the separation unit (25), such that a first part (26a) of the impregnation liquid is recirculated back to the first reactor unit (10). The invention further relates to a system for treating biomass (2).

Claims

1. A method for treating biomass, the method comprising: feeding biomass (2) and an impregnation liquid into a first reactor unit (10) such that the biomass (2) is impregnated with the impregnation liquid while the biomass (2) is transferred through the first reactor unit (10) by a conveyor means (11, S10); wherein the first reactor unit (10) is filled with impregnation liquid up to a predetermined fill level (13), the biomass (2) is transferred in an upward direction within the first reactor unit (10) and the entire biomass (2) is transferred through the impregnation liquid; transferring the impregnated biomass (2a) from the first reactor unit (10) to a separation unit (25), wherein at least a part of the impregnation liquid is separated from the impregnated biomass (2a) within the separation unit (25, S20); discharging the separated impregnation liquid from the separation unit (25), such that a first part (26a) of the separated impregnation liquid is recirculated back to the first reactor unit (10, S30); and injecting the recirculated first part of impregnation liquid (26a) from the separation unit (25) into the first reactor unit (10) such that the recirculated first part of impregnation liquid (26a) is used for impregnating the fed biomass (2) within the first reactor unit (10, S33).

2. The method of claim 1, wherein the separation of the impregnation liquid within the separation unit (25) comprises a compression stage (26) in which the impregnation liquid is released from the impregnated biomass (2a) by compressing the impregnated biomass (2a).

3. The method of claim 2, wherein a second part (27a) of the impregnation liquid released from the impregnated biomass (2a) in the compression stage (26) is transferred to a treatment step (S50) downstream the separation unit (25).

4. The method of claim 1, wherein the separation of the impregnation liquid within the separation unit (25) comprises a drainage stage (27) in which free impregnation liquid (27a) is drained from the impregnated biomass (2a) without compression.

5. The method of claim 4, wherein the free impregnation liquid (27a) drained from the impregnated biomass (2a) in the drainage stage (27) is transferred to a treatment step (S50) downstream the separation unit (25).

6. The method of claim 1 further comprising fractionating the separated first part of impregnation liquid (26a) in a fractionation unit (29) until a predetermined purity degree of the recirculated impregnation liquid is reached (S31).

7. The method of claim 1 further comprising mixing the recirculated first part of impregnation liquid (26a) from the separation unit (25) with impregnation liquid (12b) from a reservoir (40) before injecting the mixed impregnation liquid to the first reactor unit (10, S32).

8. The method of claim 1 further comprising feeding the impregnated biomass (2a) from the first reactor (10) unit into a second reactor unit (20) before transferring the impregnated biomass (2a) to the separation unit (25), wherein a hydrolysis of the impregnated biomass (2a) takes place within the second reactor unit (20, S11).

9. The method of claim 1 further comprising transferring the impregnated biomass (2a) from the separation unit (25) to a third reactor unit (30), wherein a steam impact of the impregnated biomass (2a) takes place within the third reactor unit (30, S40).

10. The method of claim 1, wherein the impregnation liquid is fed into the first reactor unit (10) up to a predetermined fill level (13) such that at least a part of the biomass (2) which is fed into the first reactor unit (10) is in permanent contact with the impregnation liquid.

11. The method of claim 1, wherein the conveyor means (11) of the first reactor unit (10) is a screw conveyor arranged with a vertical component, such that the biomass (2) is conveyed in an upward direction (3) during the impregnation.

12. The method of claim 1 further comprising compressing the biomass (2) in a compression unit (5) before feeding the biomass (2) into the first reactor unit (10), wherein the compression unit (5) comprises a plug screw for compressing the biomass (2, S2).

13. The method of claim 1 further comprising pre-compressing the biomass (2) in a pre-compression unit (6) before compressing the biomass (2) within the compression unit (5), wherein the pre-compression unit (6) in particular comprises a force feed screw for pre-compressing the biomass (2, S1).

14. The method of claim 2, wherein the compressing the impregnated biomass (2a) is conducted with a screw press (28).

15. The method of claim 4, wherein the free impregnation liquid (27a) is drained from the impregnated biomass (2a) without compression and by gravity draining.

16. The method of claim 9, wherein the steam impact is a steam explosion.

17. The method of claim 11, wherein the vertical component is vertically within the first reactor unit (10).

18. The method of claim 1, wherein the conveyor means (11, S10) is a mechanical conveyor means.

19. The method of claim 1, wherein the conveyor means (11, S10) is a screw conveyor.

20. The method of claim 1, wherein the first reactor unit is a longitudinal vessel arranged vertically with respect to an earth's surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a system for treating biomass according to an embodiment of the invention.

(2) FIG. 2A shows a separation unit according to an embodiment of the invention.

(3) FIG. 2B shows a separation unit according to another embodiment of the invention.

(4) FIG. 3 shows a flow diagram for a method for treating biomass according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 shows a system 1 for treating biomass 2. The system 1 comprises a first reactor unit 10 for impregnating biomass 2 with an impregnation liquid while the biomass 2 is transferred through the first reactor unit 10 by a conveyor means 11 which for instance is a screw conveyor. The biomass 2 is impregnated with impregnation liquid in the first reactor unit 10 such that impregnated biomass 2a is obtained. The separation unit 25 is adapted for separating at least a part of the impregnation liquid from the impregnated biomass 2a. The separated impregnation liquid 26a, 27a is discharged from the separation unit 25 such that only a part of the impregnation liquid 26a is recirculated back to the first reactor unit 10.

(6) The biomass 2 is fed by means of a compression unit 5 into the first reactor unit 10. A pre-compression unit 6 may be arranged before the compression unit 5 such that the biomass 2 is pre-compressed in the pre-compression unit 6 before it is further compressed in the compression unit 5. After compressing the biomass 2, it is introduced into the first reactor unit 10. The reactor unit 10 is filled with impregnation liquid up to a predetermined fill level 13. The reactor unit 10 may be a longitudinal vessel vertically arranged with respect to the earth's surface. The vertical direction is indicated by arrow 3 and the horizontal direction which is substantially parallel to the earth's surface is indicated by arrow 4. The biomass 2 is introduced into the reactor unit 10 and is conveyed by the conveyor means 11 in the vertical direction 3 wherein during the conveyance of the biomass 2 through the first reactor unit 10, the biomass 2 is impregnated by the impregnation liquid filled into the first reactor unit 10. The impregnation liquid may be provided by a reservoir 40 and/or by a recirculation circuit which is connected to the separation unit 25.

(7) The impregnated biomass 2a is then fed into a buffer tank 15 which is arranged between the first reactor unit 10 and a second reactor unit 20 in which a hydrolysis of the impregnated biomass 2a takes place.

(8) The impregnated biomass 2a is then transferred to the separation unit 25 after the hydrolysis of the impregnated biomass 2a within the second reactor unit 20. In the separation unit 25, the impregnated biomass 2a and the impregnation liquid solved in the impregnated biomass 2a are at least partly separated. In particular, the impregnation liquid is separated from the impregnated biomass 2a within the separation unit 25. The impregnation liquid separated from the impregnated biomass 2a is then discharged wherein only a part of the impregnation liquid 26a is recirculated back to the first reactor unit 10, for example via recirculation line 12a. Another part 27a of the separated impregnation liquid may be discharged and fed to a further treatment step S50 downstream the separation unit 25. Before the first part of the separated impregnation liquid 26a is fed back into the reactor unit 10, a filtration of this impregnation liquid 26a may be carried out in a filtration unit 29. For example, before the first part of the separated impregnation liquid 26a is fed back into the reactor unit 10, a fractionation of this impregnation liquid 26a may be carried out in a fractionation unit 29. The second part of the impregnation liquid 27a which is fed to a further treatment step S50 downstream the separation unit 25 may also be filtered in the fractionation unit 29. Within the fractionation unit or filtration unit 29, a separation of solid particles within the impregnation liquid may be carried out such that a predetermined purity degree of the recirculated impregnation liquid 26a as well as for the second part of the impregnation liquid 27a which is fed to the treatment step S50 may be adjusted. Evaporation and concentration of compounds present in the separated impregnation liquid 26a may also be carried out in the fractionation unit 29.

(9) The impregnated biomass 2a is transferred to a third reactor unit 30 after the separation of the excess impregnation liquid within the separation unit 25. In the third reactor unit 30, a steam explosion reaction of the impregnated biomass 2a is carried out.

(10) Before feeding the impregnation liquid into the first reactor unit 10 via the recirculation line 12a, a mixing of fresh impregnation liquid 12b from the reservoir 40 and the recirculated impregnation liquid 26a from the separation unit 25 may be carried out. In this manner, it is possible to adjust chemical characteristics of the impregnation liquid fed into the first reactor unit 10. Therefore, the line 12a for feeding the recirculated impregnation liquid 26a from the separation unit 25 as well as a line 12c from the reservoir 40 are connected in order to feed the mixed impregnation liquid via line 12 into the first reactor unit 10.

(11) FIG. 2A shows an embodiment of the separation unit 25 in detail. In particular, FIG. 2A shows a two-staged separation unit 25 in which a drainage stage 27 and a compression stage 26 are provided. The impregnated biomass 2a is fed into the drainage stage 27 in which free impregnation liquid 27a is drained from the impregnated biomass 2a. This free impregnation liquid 27a which may also be called the second part of the impregnation liquid 27a is then transferred to a treatment step S50 downstream the separation unit 25. However, it is also possible that this drained, second part of the impregnation liquid 27a is recirculated back to the first reactor unit 10.

(12) The impregnated biomass 2a is then fed into the compression stage 26 in which the first part of the impregnation liquid 26a is released from the impregnated biomass 2a by compression. The compression may be provided by a screw press 28 in the compression stage 26. The first part of the impregnation liquid 26a released from the impregnated biomass 2a in the compression stage 26 is also recirculated back to the first reactor unit 10. The separation unit 25 may comprise other stages in which impregnation liquid can be released from the impregnated biomass 2a. The characteristics, e. g. the composition of the impregnation liquid separated in the drainage stage 27 and in the compression stage 26 of the separation unit 25 may be different. In particular, the characteristics of the separated impregnation liquid 26a, 27a may determine the target location of the separated parts of impregnation liquid 26a, 27a, for example whether these parts of impregnation liquid 26a, 27a are transferred to the first reactor unit 10 or to the treatment step S50 downstream the separation unit 25.

(13) As shown in FIG. 2A the compression stage 26 is arranged before the drainage stage 27 within the separation unit 25. However, it is also possible that the drainage stage 27 is arranged before the compression stage 26.

(14) FIG. 2B shows an embodiment of the separation unit 25 with only one stage, in particular with a compression stage 26. It is possible that, in the compression stage 26, a part of impregnation liquid 27a is drained from the impregnated biomass 2a and that another part of the impregnation liquid 26a is released from the impregnated biomass 2a by the compression. The compression stage 26 may thus result in a first part of impregnation liquid 26a released from the impregnated biomass 2a by compression and a second part of impregnation liquid 27a drained from the impregnated biomass 2a wherein the first part of impregnation liquid 26a and the second part of impregnation liquid 27a are fed or transferred to different target locations.

(15) The separation unit 25 may also be referred to as a dewatering or washing stage. The separation unit 25 comprises a drainage stage integrated into the compression stage 26. The drainage stage may comprise a drain screw for conveying the impregnated biomass 2a during the drainage in which free water is released from the impregnated biomass 2a. The compression stage 26 may comprise one of a screw press, a plug screw, twin rolls or simply a press such that the first part of the impregnation liquid 26a can be released from the impregnated biomass 2a.

(16) In case the separation unit 25 comprises a one-stage configuration, e. g. the separation unit 25 only comprises the compression stage 26, then the compression stage 26 may comprise one of a screw press, a plug screw, twin rolls or simply a press. Furthermore, several areas within the compression unit 26 may be provided in which different parts of the liquid are released from the impregnated biomass 2a. In this manner, it is possible that the first part of impregnation liquid 26a is released separately from the second part of impregnation liquid 27a.

(17) FIG. 3 shows a flow diagram for a method for treating biomass 2. In step S1 of the method, a pre-compression of the biomass 2 in a pre-compression unit 6 is carried out before compressing the biomass 2 within a compression unit 5. The pre-compression unit 6 may comprise a force feed screw for pre-compressing the biomass 2. In a step S2 of the method, a compression of the biomass 2 in a compression unit 5 is carried out before feeding the biomass 2 to a first reactor unit 10, wherein the compression unit 5 comprises a plug screw for compressing the biomass 2. In a step S10 of the method, the biomass 2 and an impregnation liquid are fed into the first reactor unit 10 such that the biomass 2 is impregnated with the impregnation liquid while the biomass 2 is transferred through the first reactor unit 10 by a conveyor means 11. In a step S11, impregnated biomass 2a is fed from the first reactor unit 10 into a second reactor unit 20 before transferring the impregnated biomass 2a to the separation unit 25, wherein a hydrolysis of the impregnated biomass 2a takes place within the second reactor unit 20. In a step 20 of the method, the impregnated biomass 2a is transferred from the first reactor unit 10 to the separation unit 25 wherein at least a part of the impregnation liquid 26a, 27a is separated from the impregnated biomass 2a within the separation unit 25. In a further step S30 of the method, the separated impregnation liquid 26a, 27a is discharged from the separation unit 25 such that only a part of the impregnation liquid 26a is recirculated back to the first reactor unit 10. In another step S31, a fractionation or a filtration of the separated impregnation liquid 26a, 27a is carried out in a fractionation unit 29 or filtration unit 29 such that a predetermined purity degree of the recirculated impregnation liquid 26a can be adjusted. In another step S32, a mixing of the recirculated impregnation liquid 26a from the separation unit 25 with fresh impregnation liquid 12b from the reservoir 40 is carried out before injecting the mixed impregnation liquid into the first reactor unit 10. In another step S33, an injection of the recirculated impregnation liquid 26a from the separation unit 25 into the first reactor unit 10 is carried out such that the recirculated impregnation liquid 26a is reused for impregnating the fed biomass 2 within the first reactor unit 10. In another step S40, the impregnated biomass 2a is transferred from the separation unit 25 to a third reactor unit 30 wherein a steam explosion on the impregnated biomass 2a takes place within the third reactor unit 30. In yet another step S50 of the method, a second part of the impregnation liquid 27a separated in the separation unit 25, e. g. the part of the separated impregnation liquid which is not recirculated back to the first reactor unit 10 is transferred to a treatment step downstream the separation unit 25.

(18) While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative and exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claim. In the claims the term “comprising” does not exclude other elements, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of protection.