Method for producing oxidized lignin in kraft pulp mill

Patent metadata

Field	Value
Publication number	US-12054886-B2
Application number	US-202017427700-A
Country	US
Kind code	B2
Filing date	Jan 31, 2020
Priority date	Feb 1, 2019
Publication date	Aug 6, 2024
Grant date	Aug 6, 2024

Abstract

According to an example aspect of the present invention, there is provided a method for producing an oxidised lignin based high performance surface active agent in techno-economically feasible manner within kraft pulp mill without interfering the main process.

First claim

The invention claimed is:

1. A method for producing oxidized lignin in a kraft pulp mill comprising at least the steps of:
isolating unwashed kraft lignin from the kraft pulp mill,
dissolving the unwashed kraft lignin in oxidized or un-oxidized white liquor to obtain an alkaline lignin solution,
oxidizing the alkaline lignin solution at alkaline conditions to produce an oxidized lignin with:
a) O 2 gas over pressure, and
b) added NaOH and/or oxidized white liquor,

treating the oxidized lignin with membrane filtration and recovering a concentrated lignin product, and
recovering at least some side products from the membrane filtration as such and recycling the at least some side products and chemicals back to the kraft pulp mill.

2. The method according to claim 1 , further comprising introducing hydrogen peroxide as an oxidative agent during the oxidizing of the lignin solution in combination with a) or a) and b) for oxidizing the lignin solution.

3. The method according to claim 1 , wherein the O 2 gas atmospheric pressure is maintained below 30 bars.

4. The method according to claim 1 , wherein the oxidized lignin is acid precipitated prior to the membrane filtration.

5. The method according to claim 1 , wherein the filtration increases the lignin content at least to 10 wt-% in the concentrated lignin product.

6. The method according to claim 1 , wherein the unwashed kraft lignin is dissolved in oxidized white liquor (OWL) having an unwashed kraft lignin content of 0.5-40 wt-%.

7. The method according to claim 1 , further comprising producing kraft lignin based surface active agents from the concentrated lignin product.

8. The method according to claim 1 , wherein the O 2 gas atmospheric pressure is maintained below 20 bars during the oxidizing step.

9. The method according to claim 1 , wherein the O 2 gas atmospheric pressure is maintained below or at about 18 bars during the oxidizing step.

10. The method according to claim 1 , wherein the filtration increases the lignin content to 10-40 wt-% in the concentrated lignin product.

11. The method according to claim 1 , wherein the filtration increases the lignin content to 10-75 wt-% in the concentrated lignin product.

12. The method according to claim 1 , wherein the unwashed kraft lignin is dissolved in oxidized white liquor (OWL) having an unwashed kraft lignin content of 5-25 wt-%.

13. The method according to claim 1 , wherein the membrane filtration is ultrafiltration or nanofiltration.

14. The method according to claim 1 , wherein the membrane filtration comprises a plurality of filtration steps, and wherein the plurality of filtration steps are repeated multiple times.

15. The method according to claim 1 , wherein the side products from the membrane filtration comprise sodium, sulphur, and small organic acids.

Assignees

• Andritz Oy
• Metsae Fibre Oy
• Teknologian Tutkimuskeskus Vtt Oy

Inventors

• Pehu-Lehtonen Lauri
• Sjögård Pauliina
• Poukka Outi
• Kemppainen Katariina
• Kalliola Anna
• Liitiä Tiina
• Vehmas Tapio

Classifications

• D21C11/0042

  Fractionating or concentration of spent liquors by special methods (concentration by evaporation D21C11/10) · CPC title

• D21H11/04

  Kraft or sulfate pulp · CPC title

• D21C11/0057

  Oxidation of liquors, e.g. in order to reduce the losses of sulfur compounds, followed by evaporation or combustion if the liquor in question is a black liquor (deodorisation of gases D21C11/08; combustion D21C11/12, D21C11/14) · CPC title

• C08H6/00 Primary

  Macromolecular compounds derived from lignin, e.g. tannins, humic acids · CPC title

• D21C11/04

  of alkali lye · CPC title