Bleaching and shive reduction process for non-wood fibers

1. A method for scouring and increasing the brightness of non-wood fibers, the method comprising:

forming a mixture of non-wood fibers having a mean length of at least 7 millimeters (mm) into a fiber mat within a perforated basket arranged within a kier;

exposing the mixture to a scouring liquor and a scouring agent comprising oxygen gas to form a scouring mixture; and

scouring the scouring mixture in the perforated basket by radially circulating the scouring liquor, by a circulation pump, throughout the mixture to provide scoured fibers.

2. The method of claim 1 , wherein scouring is performed at a temperature between about 95 and about 150° C.

3. The method of claim 1 , wherein scouring is performed at a temperature less than 110° C.

4. The method of claim 3 , wherein the scouring liquor comprises magnesium sulfate.

5. The method of claim 1 , further comprising dissolving the oxygen gas in the scouring liquor under a pressure in a range between about 1 and about 10 Bar.

6. The method of claim 1 , further comprising cooling the scoured fibers to a temperature below 100° C.

7. The method of claim 1 , further comprising draining the scouring liquor from scoured fibers.

8. The method of claim 7 , further comprising rinsing the scoured fibers with water and then centrifuging the scoured fibers to remove excess water.

9. The method of claim 1 , further comprising introducing a gas into the chamber after scouring to displace residual scouring liquor from the scoured fibers.

10. The method of claim 1 , further comprising drying the scoured fibers.

11. The method of claim 1 , further comprising internally recirculating the scouring liquor within the kier.

12. The method of claim 11 , further comprising externally recirculating the scouring liquor outside the kier.

13. The method of claim 1 , wherein the scouring liquor comprises magnesium sulfate.

14. The method of claim 1 , wherein the scouring liquor comprises sodium hydroxide.

15. The method of claim 1 , further comprising exposing the non-wood fibers to an organic acid.

16. The method of claim 15 , wherein the organic acid is acetic acid, citric acid, formic acid, lactic acid, oxalic acid, uric acid, or any salt thereof.

17. The method of claim 16 , where in the salt of citric acid is trisodium citrate, calcium citrate, or both trisodium citrate and calcium citrate.

18. The method of claim 1 , wherein the non-wood fibers are bast fibers.

19. The method of claim 1 , wherein the non-wood fibers are flax fibers, hemp fibers, jute fibers, ramie fibers, nettle fibers, Spanish broom fibers, kenaf plant fibers, or any combination thereof.

20. The method of claim 1 , wherein the non-wood fibers are cotton fibers.

21. The method of claim 1 , wherein the scouring liquor has a pH in a range between about 6 and about 8.

22. The method of claim 1 , wherein the scouring liquor has a pH in a range between about 7 and about 12.

23. The method of claim 1 , further comprising carding the scoured fibers.

24. The method of claim 1 , further comprising hydroentangling the scoured fibers.

25. A method for increasing the brightness of non-wood fibers, the method comprising:

forming a mixture of non-wood fibers having a mean length of at least 7 millimeters (mm) into a fiber mat within a perforated basket arranged within a kier; and

scouring the mixture in the perforated basket with a scouring liquor comprising oxygen gas to provide scoured and brightened fibers, the scouring comprising radially circulating and recirculating the scouring liquor through the mixture using a circulation pump;

wherein the scoured and brightened fibers have a brightness in a range between about 30 and about 60 as measured by Technical Association of the Pulp and Paper Industry (TAPPI) 525 standard test method.

26. The method of claim 25 , wherein scouring is performed at a temperature less than 110° C.

27. The method of claim 25 , wherein the scouring liquor comprises magnesium sulfate.

28. The method of claim 25 , further comprising draining the scouring liquor from scoured fibers.

29. The method of claim 28 , further comprising rinsing the scoured fibers with water and then centrifuging the scoured fibers to remove excess water.

30. The method of claim 29 , further comprising introducing a gas after scouring to displace residual scouring liquor from the scoured fibers.

31. The method of claim 25 , further comprising drying the scoured fibers.

32. The method of claim 25 , wherein the scouring liquor comprises magnesium sulfate.

33. The method of claim 25 , further comprising exposing the non-wood fibers to an organic acid.

34. The method of claim 33 , wherein the organic acid is acetic acid, citric acid, formic acid, lactic acid, oxalic acid, uric acid, or any salt thereof.

35. The method of claim 34 , where in the salt of citric acid is trisodium citrate, calcium citrate, or both trisodium citrate and calcium citrate.

36. The method of claim 25 , wherein the non-wood fibers are bast fibers.

37. The method of claim 25 , wherein the non-wood fibers are flax fibers, hemp fibers, jute fibers, ramie fibers, nettle fibers, Spanish broom fibers, kenaf plant fibers, or any combination thereof.

38. The method of claim 25 , wherein the non-wood fibers are cotton fibers.

39. The method of claim 25 , further comprising bleaching the scoured and brightened fibers to provide bleached fibers.

40. The method of claim 39 , wherein bleaching comprises exposing the scoured and brightened fibers to a peroxide compound, oxygen gas, a reducing agent, or a combination thereof.

41. The method of claim 39 , further comprising exposing the bleached fibers to a second bleaching stage.

42. The method of claim 41 , wherein the second bleaching stage comprises exposing the bleached fibers to a peroxide compound, oxygen gas, a reducing agent, or a combination thereof.

43. A method of reducing the amount of residual shive in non-wood fibers, the method comprising:

forming a mixture of non-wood fibers having a mean length of at least 7 millimeters (mm) into a fiber mat within a perforated basket within a kier; and

scouring the mixture in the perforated basket with a scouring liquor comprising oxygen gas to provide scoured and low-shive fibers, the scouring comprising radially circulating the scouring liquor through the mixture using a circulation pump;

wherein the scoured and low-shive fibers have less visible shive content than the fibers of the mixture before exposure.

44. The method of claim 43 , wherein the structural integrity of the residual shive is reduced during scouring.

45. The method of claim 43 , wherein scouring is performed at a temperature between about 95 and about 150° C.

46. The method of claim 43 , wherein scouring is performed at a temperature less than 110° C.

47. The method of claim 46 , wherein the scouring liquor comprises magnesium sulfate.

48. The method of claim 43 , further comprising dissolving the oxygen gas in the scouring liquor under a pressure in a range between about 1 and about 10 Bar.

49. The method of claim 43 , further comprising cooling the scoured fibers to a temperature below 100° C.

50. The method of claim 43 , further comprising draining the scouring liquor from scoured fibers.

51. The method of claim 50 , further comprising rinsing the scoured fibers with water and then centrifuging the scoured fibers to remove excess water.

52. The method of claim 43 , further comprising introducing a gas into the chamber after scouring to displace residual scouring liquor from the scoured fibers.

53. The method of claim 43 , further comprising drying the scoured fibers.

54. The method of claim 43 , wherein the scouring liquor comprises magnesium sulfate.

55. The method of claim 43 , wherein the scouring liquor comprises sodium hydroxide.

56. The method of claim 43 , further comprising exposing the non-wood fibers to an organic acid.

57. The method of claim 56 , wherein the organic acid is acetic acid, citric acid, formic acid, lactic acid, oxalic acid, uric acid, or any salt thereof.

58. The method of claim 43 , wherein the non-wood fibers are bast fibers.

59. The method of claim 43 , wherein the non-wood fibers are flax fibers, hemp fibers, jute fibers, ramie fibers, nettle fibers, Spanish broom fibers, kenaf plant fibers, or any combination thereof.

60. The method of claim 43 , wherein the non-wood fibers are cotton fibers.