Method of degumming cellulosic fibres
View Patent ↗A process for producing dissolving pulp includes a degumming step using a degumming liquor which includes hydrogen peroxide and ammonia.
1. A method of degumming cellulosic fibres comprising the step of treating the fibres with a degumming liquor comprising between about 5% to about 30% (v:v) aqueous ammonia and between about 0.5% to 3% (on OD fibre) hydrogen peroxide, at a temperature between about 50° to about 200° C., at a consistency of about 3:1 to about 20:1 liquor to solids (v/w).
2. The method of claim 1 wherein the degumming liquor further comprises potassium hydroxide.
3. The method of claim 1 or 2 wherein the degumming liquor further comprises anthraquinone.
4. The method of claim 1 wherein the degumming liquor is recovered following degumming, and is treated to separate it into an ammonia stream for reuse in the process and a solid fraction.
5. The method of claim 4 wherein the solid portion is recovered and treated to form a fertilizer.
6. The method of claim 1 further comprising the step of bleaching the degummed fibres to form dissolving pulp.
7. The method of claim 1 wherein the cellulosic fibres comprise bast fibre plant fibres.
8. The method of claim 7 wherein the bast fibre plant is one of hemp, flax, kenaf, linseed, jute, or ramie.
9. The method of claim 8 wherein the bast fibre plant is hemp.
10. The method of claim 8 wherein the bast fibre plant is flax.
11. The method of claim 8 wherein the bast fibre plant is kenaf.
12. The method of claim 1 wherein the cellulosic fibres comprise wood fibre, cereal straw fibre, perennial grass fibre, or legume fibre.
13. The method of claim 6 wherein the bleaching step comprises an elemental chlorine-free or total chlorine-free bleaching step.
14. A method of forming dissolving pulp from bast fibre plants, comprising the steps of:
(a) pulping the plant fibre with a degumming liquor comprising about 5% to about 30% (v:v) aqueous ammonia and between about 0.5% to 3% (on OD fibre) hydrogen peroxide;
(b) recovering and recycling an aqueous portion from step (a);
(c) recovering the pulped fibres and bleaching to produce dissolving pulp.
15. The method of claim 14 wherein the degumming step takes place at a temperature between about 50° to about 200° C., at a consistency of about 3:1 to about 20:1 liquor to solids (v/w).
16. The method of claim 13 wherein the final bleaching step comprises an elemental chlorine-free or total chlorine-free bleaching process.