Method for processing straw

• US 10,233,592 B2
• Filed: 10/02/2015
• Issued: 03/19/2019
• Est. Priority Date: 10/03/2014
• Status: Active Grant

• Current Assignee: Nafici Environmental Research Ltd.
• Original Assignee: Nafici Environmental Research Ltd.
• Inventors: Nafici, Shahriar
• Primary Examiner(s): Fortuna, Jose A
• Application Number:
  US15/516,294
• Publication Number:
  US 20170306556A1
• Time in Patent Office: 1,264 Days
• CPC Class Codes: D21C 1/06 with alkaline reacting compounds
• CPC Class Codes: D21C 11/0007 Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for volatile compounds obtained by decomposition of spent liquors in order to regenerate them D21C11/125; compounds obtained by fractionating the liquors in order to regenerate them D21C11/0042
• CPC Class Codes: D21C 11/04 of alkali lye
• CPC Class Codes: D21C 3/02 with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
• CPC Class Codes: D21C 7/06 Feeding devices
• CPC Class Codes: D21C 7/08 Discharge devices
• CPC Class Codes: D21C 7/10 Heating devices
• CPC Class Codes: D21H 11/12 Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse

Abstract

Described herein is a method for processing straw into an intermediate straw product. The method comprises: (a) treating straw with an alkaline solution having a p H of between about 10 and about 14, at a temperature of between about 20° C. and about 80° C., for a period of between about 6 hours and about 30 hours; (b) separating excess alkaline solution and the treated straw from each other; and (c) maintaining the treated straw in an anaerobic environment at a temperature of between about 30° C. and about 45° C., for a period of between about 6 hours and about 30 hours to produce an intermediate straw product. Also described is an intermediate product produced by the method; a method for extracting lignin from straw; lignin thereby produced; a method for extracting cellulose fibers from straw to produce paper pulp; cellulose fibers and paper pulp thereby produced; a method for producing a paper pulp product or a paper product; a product thereby produced; and a container and apparatus for processing straw according to the methods described.

Claims

1. A method for processing straw into an intermediate straw product, the method comprising:

(a) treating straw with an alkaline solution having a pH of between about 10 and about 14, at a temperature of between about 20°

C. and about 80°

C., for a period of between about 6 hours and about 30 hours;

(b) separating excess alkaline solution and the treated straw from each other; and

(c) maintaining the treated straw in an anaerobic environment at a temperature of between about 30°

C. and about 45°

C., for a period of between about 6 hours and about 30 hours to produce an intermediate straw product into which some of the solution has been absorbed.

2. A method according to claim 1, wherein the intermediate straw product is further processed and/or refined into cellulose fibres useful for paper production.

3. A method according to claim 1, wherein before step (c) the method comprises removing air to produce an anaerobic environment.

4. A method according to claim 1, which comprises

further processing the intermediate straw product into paper pulp.

5. A method according to claim 4, which comprises,

(d) mixing the intermediate straw product with water and pulping the straw and water mixture;

(e) processing the pulped straw to obtain cellulose fibres from the straw; and

(f) obtaining a straw fibres pulp.

6. A method according to claim 5, wherein step (e) comprises the following sub-steps:

(e1) filtering the pulped straw through a filter to extract cellulose fibres from the straw;

(e2) refining the filtered pulp straw in a refiner to extract further cellulose fibres from the straw;

(e3) screening the refined pulp to separate lignin and/or ash from the cellulose fibres;

(e4) washing the screened pulp with water to separate more lignin and/or ash; and

(e5) returning liquid from step (e2) for re-use in any preceding step.

7. A method according to claim 5, wherein step (e) comprises processing the pulped straw by de-flaking.

8. A method according to claim 4, which comprises recovering lignin that has been separated from the cellulose fibres.

9. A method according to claim 1, wherein the alkaline solution comprises caustic soda.

10. A method according to claim 1, wherein the alkaline solution comprises an alkali selected from the group consisting of sodium carbonate, potassium hydroxide and potassium carbonate.

11. A method according to claim 1, wherein the pH at step (a) is about 14.

12. A method according to claim 1, wherein the temperature at step (a) is about 80°

C.

13. A method according to claim 1, wherein the time period at step (a) is about 12 hours.

14. A method according to claim 1, wherein step (a) comprises the following sub-steps:

(a1) placing the straw in a first container;

(a2) mixing water and an alkali in a second container to produce an alkaline solution having a pH of between about 10 and about 14;

(a3) heating the solution in the second container to a temperature of between about 20°

C. and about 80°

C.;

(a4) transferring the heated solution from the second container to the first container;

(a5) leaving the solution in the first container with the straw for a time period of between about 6 and about 30 hours at a temperature of between about 20°

C. and about 80°

C. during which time period some of the solution is absorbed by the straw; and

(a6) transferring the remaining solution in the first container to the second container.

15. A method according to claim 1, wherein the temperature at step (c) is about 35°

C.

16. A method according to claim 1, wherein the time period at step (c) is about 12 hours.

17. A method according to claim 1, wherein the straw is placed in a holder prior to step (a).

18. A method according to claim 17, wherein the holder is arranged to be movable between a plurality of positions to allow for the straw to be immersed in the alkaline solution, and then transferred to a pulper tank.

19. A method for processing straw, the method comprising:

(a) treating straw with an alkaline solution having a pH of between about 10 and about 14, at a temperature of between about 20°

C. and about 80°

C., for a period of between about 6 hours and about 30 hours;

(b) separating excess alkaline solution and the treated straw from each other; and

(c) maintaining the treated straw in an anaerobic environment at a temperature of between about 30°

C. and about 45°

C., for a period of between about 6 hours and about 30 hours.

20. A method according to claim 19, the method further comprising:

(d) mixing the treated straw with water and pulping the treated straw and water mixture to produce pulped straw;

(e) processing the pulped straw to obtain cellulose fibres from the straw; and

(f) obtaining a straw fibres pulp.