PROCESS AND SYSTEM FOR TREATING VAPOURS RELEASED FROM LIGNOCELLULOSE BIOMASS DURING ACID TREATMENT

Abstract

The invention relates to a process for treating vapours released from lignocellulose biomass during acid treatment at elevated temperature of the lignocellulose biomass. The process comprises condensing (3) the vapours to produce a condensate, adjusting (4) the pH of the condensate to about 9, and decanting (5) the condensate to produce turpentine, and may further comprise distilling (6) the mixture remaining after decanting to produce furfuraland a reject comprising tall oil fatty acids. The invention also relates to a corresponding system for treating vapours released from lignocellulose biomass during acid treatment at elevated temperature of the lignocellulose biomass.

Claims

1. Process for treating vapours released from lignocellulose biomass during acid treatment at elevated temperature of said lignocellulose biomass, said process comprising: condensing said vapours to produce a condensate, adjusting the pH of the condensate to about 9, and decanting the condensate to produce turpentine.

2. The process according to claim 1, further comprising: distilling the mixture remaining after decanting to produce furfural and a reject comprising tall oil fatty acids.

3. The process according to claim 1, further comprising subjecting an uncondensed fraction of said vapours from said step of condensing to an additional step of condensing to produce a second condensate, wherein said step of decanting comprises decanting the second condensate to produce turpentine, and distilling the condensate from the step of condensing and the mixture remaining after decanting to produce furfural and a reject comprising tall oil fatty acids.

4. The process according to claim 2, further comprising: Subjecting said reject resulting from said distilling to a tall oil separation process.

5. The process according to claim 2, further comprising: Subjecting said reject to saponification to produce soap.

6. The process according to claim 1, wherein said adjusting comprises adding an alkali to adjust the pH.

7. The process according to claim 6, wherein said alkali is added to said condensate.

8. The process according to claim 6, wherein said alkali is sprayed into the vapours to mix therewith.

9. The process according to claim 6, wherein said alkali is mixed with the vapours and/or condensate by means of a separate mixing device.

10. The process according to claim 6, further comprising separating said vapours released from said lignocellulose biomass, wherein said separating is performed using at least one cyclone, and wherein said alkali is sprayed into the cyclone during separation.

11. The process according to claim 6, wherein said alkali is selected from a group comprising NaOH, Ca(OH)2, Mg(OH)2, white liquor and weak white liquor.

12. The process according to claim 1, further comprising: adjusting the temperature of the condensate to 55° C. or higher.

13. The process according to claim 3, wherein said step of condensing comprises adjusting the temperature of the condensate to about 80-90° C., and wherein said additional step of condensing comprises adjusting the temperature of the second condensate to about 55-70° C.

14. The process according to claim 1, wherein said acid treatment comprises a pretreatment or a main treatment process of wood chips, wood pulp, saw dust, or any other wood-based biomass.

15. The process according to claim 1, wherein said acid treatment comprises acid cooking of wood chips.

16. System for treating vapours released from lignocellulose biomass during acid treatment at elevated temperature of said lignocellulose biomass, said system comprising: at least one condenser arranged to condense said vapours to produce a condensate, at least one decanting device configured to decant the condensate to produce turpentine, and a pH adjusting arrangement for adjusting the pH of the condensate prior to decanting, said arrangement comprising addition means configured to add an alkali upstream the at least one condenser or between the condenser and the decanting device.

17. The system according to claim 16, further comprising: a distilling device configured to distill the mixture remaining after decanting to produce furfural and a reject comprising tall oil fatty acids.

18. The system according to claim 17, further comprising: At least one tall oil separation arrangement configured to subject said reject to tall oil separation.

19. The system according to claim 17, further comprising: At least one saponification arrangement configured to subject said reject to saponification.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Above discussed and other aspects of the present invention will now be described in more detail using the appended drawings, which show presently preferred embodiments of the invention, wherein:

[0023] FIG. 1 shows a flow chart illustrating an embodiment of the process according to the first or second aspect of the invention;

[0024] FIG. 2 shows a flow chart illustrating another embodiment of the process according to the first or second aspect of the invention;

[0025] FIG. 3 schematically illustrates an embodiment of a system according to the third or fourth aspect of the invention, and

[0026] FIG. 4 schematically illustrates another embodiment of a system according to the third or fourth aspect of the invention.

DETAILED DESCRIPTION

[0027] FIG. 1 shows a flow chart illustrating an embodiment of the process according to the first or second aspect of the invention, which process comprises acid treatment at elevated temperature 1 of the lignocellulose biomass (not part of the embodiment to the first aspect of the invention).

[0028] The process further comprises separation 2 of the acid/heat treated biomass into a solid portion and a vapour (blow steam), for example by means of a cyclone. Thereafter, the vapours are subjected to a condensation step 3. The condensation may include adjusting the temperature of the condensate to 55° C. or higher. The pH of the condensate is adjusted 4 for example by means of addition of an alkali. In this embodiment, the alkali is added to the condensate directly, for example by means of an external mixing device. In other embodiments, the alkali may be added to the vapour before condensing. The pH adjusted condensate is thereafter decanted 5 to produce turpentine. The reject from decanting is subjected to distillation 6 to produce furfural. The reject resulting from distillation, i.e. the water mixture remaining after distillation is subjected to a tall oil separation step 7 in which the tall oil fatty acids and any dissolved and undissolved extractives are used to produce tall oil. In other embodiments, the reject may be subjected to saponification to produce soap.

[0029] FIG. 2 shows a flow chart illustrating another embodiment of the process according to the first or second aspect of the invention. This embodiment is similar to the embodiment in FIG. 1, and comprises acid treatment at elevated temperature 11 of the lignocellulose biomass (not part of the embodiment to the first aspect of the invention), separation 12, pH adjustment 14 by means of addition of an alkali, and condensation 13a. In this embodiment, the alkali is added to the vapours prior to condensation, for example by means of an external mixing device, or by spraying into a cyclone used for separation. This embodiment however differs from the embodiment shown in FIG. 1 in that it comprises an additional condensation step 13b which condenses an uncondensed fraction from the first condensation step 13a. The condensate from the condensing 13b is subject to decanting 15 to produce turpentine. Distillation 16 is performed on the condensate from condensation step 13a and the reject from decanting 15 to produce furfural. The reject resulting from distillation is subjected to saponification 17 to produce soap. Alternatively, the reject may be subjected to a tall oil separation step as described above with reference to FIG. 1. The condensation step 13a comprises adjusting the temperature of the condensate to about 80-90° C., and the additional condensation step 13b comprises adjusting the temperature to about 55-70° C.

[0030] FIG. 3 schematically illustrates an embodiment of a system according to the third or fourth aspect of the invention. The system 20 comprises a reactor vessel 21 configured for acid treatment at elevated temperature of the lignocellulose biomass (not part of the embodiment to the third aspect of the invention), a cyclone 22 arranged to separate the vapours (blow steam) released from the lignocellulose biomass, a condenser 23 arranged to condense the vapours to produce a condensate, a pH adjusting arrangement comprising addition means 24 in the form of an external/separate mixer configured to add an alkali before the condenser 23, pH measurement means (not shown) and control means (not shown) configured to control the addition means in response to a control signal from the pH measurement means, a decanting device 25 configured to decant the condensate from the condenser 23 to produce turpentine, and a distilling device 26 configured to distill the mixture remaining after decanting to produce furfural and a reject comprising tall oil fatty acids. The condenser is configured to provide a condensate having a temperature of 55° C. or higher. A tall oil separation arrangement 27 is configured to subject the reject from the distilling device 26 to tall oil separation. In other embodiments, the separation arrangement is replaced with a saponification arrangement. In yet other embodiments, the tall oil separation or saponification arrangement is omitted altogether, and the reject is used as-is in for various purposes.

[0031] FIG. 4 schematically illustrates another embodiment of a system 30 according to the third or fourth aspect of the invention. This embodiment is similar to the embodiment in FIG. 3 in that it comprises a reactor vessel 31, a cyclone 32, a condenser 33a, a pH adjusting arrangement comprising addition means 34 in the form of an external/separate mixer configured to add an alkali before the condenser 33a, and a tall oil separation arrangement 37. This embodiment however differs from the embodiment shown in FIG. 3 in that it comprises an additional condenser 33b which condenses an uncondensed fraction from the first condenser 33a, where the condensate from the additional condenser is decanted by the decanter 35 to produce turpentine. The distilling device 36 is configured to distill the condensate from condenser 33a and the reject from the decanter 35 to produce furfural.

[0032] The description above and the appended drawings are to be considered as non-limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention. For example, more than two condensation steps may be used, and other methods for adjusting the pH may be used. The scope of protection is determined by the appended patent claims.