Method for utilizing lignin separated from black liquor as lime-kiln fuel

Patent metadata

Field	Value
Publication number	US-10179972-B2
Application number	US-201515316668-A
Country	US
Kind code	B2
Filing date	May 26, 2015
Priority date	Jun 6, 2014
Publication date	Jan 15, 2019
Grant date	Jan 15, 2019

Abstract

A method of utilizing lignin-containing material separated from spent kraft pulping liquor including: acidifying the liquor to a pH not less than seven thereby precipitating solid particles, separating precipitated solid particles from the accompanying liquid, and subjecting the separated precipitated solid particles to a washing process in which: the separated precipitated solid particles are washed with an aqueous medium or aqueous media in one or more washing steps, in each one of the washing steps, the aqueous washing medium contains, in a dissolved form, significant amounts of one or more added sodium salts, and a combined concentration of the added sodium salts in the washing medium in each of the washing step exceeds three percent by weight; and utilizing as fuel in a lime kiln at least part of the washed lignin-containing material is utilized as fuel in a lime kiln of a pulp mill.

First claim

The invention claimed is:

1. A method of utilizing lignin-containing material separated from spent kraft pulping liquor comprising:
acidifying the liquor, or fraction thereof, to a pH not less than 7 thereby precipitating solid particles,
separating the precipitated solid particles from the liquor or a fraction thereof, and
subjecting the separated precipitated solid particles to a washing process in which:
i. the separated precipitated solid particles are washed with an aqueous medium or aqueous media in at least two washing steps,
ii. in each of the at least two washing steps, the aqueous washing medium or media contains, in a dissolved form, significant amounts of one or more added sodium salts, and
iii. a combined concentration of the one or more added sodium salts in the aqueous washing medium or media in each of the washing step exceeds three percent (3%) by weight;
iv. utilizing as fuel in a lime kiln at least part of the washed, separated precipitated solid particles.

2. The method according to claim 1 , wherein the combined concentration of the one or more added sodium salts in the aqueous washing medium or media in each washing step exceeds 5% by weight.

3. The method according to claim 1 , wherein acid is not added to any of the at least two washing steps.

4. The method according to claim 1 , wherein sodium sulphate is included in the one or more added sodium salts.

5. The method according to claim 1 , wherein a source of the one or more added sodium salts dissolved in the aqueous washing medium or media is fly ash from a chemical recovery boiler of a pulp mill.

6. The method according to claim 1 , wherein a source of the one or more added sodium salts dissolved in the aqueous washing medium or media is an internal aqueous stream in a pulp mill.

7. The method according to claim 1 , wherein a part of the washed, separated precipitated solid particles is further washed in one or more steps, with at least one of the steps being undertaken under acidic conditions, in order to reduce the sodium content of the washed, separated solid precipitated solid particles used as the fuel.

8. The method according to claim 1 , wherein at least a part of the dust separated from the flue gas exhausted by the lime kiln is not recycled directly to the lime kiln.

9. The method as in claim 8 , wherein the at least part of dust that is not recycled directly to the lime kiln is recycled to a calcium cycle of a pulp mill at a location upstream of the lime kiln.

10. A method comprising:
acidifying spent kraft pulping liquor or fraction of the liquor to a pH of not less than 7 to precipitate solid lignin-containing particles;
separating the precipitated solid lignin-containing particles from the liquor or the fraction;
in each of at least two washing steps, washing the separated precipitated solid lignin-containing particles with an aqueous liquid that includes at least one sodium salt, wherein a concentration of all of the at least one sodium salt is at least three percent (3%) by weight, and
fueling a lime kiln with the washed precipitated solid lignin-containing particles.

11. The method of claim 10 , wherein in each of the at least two washing steps, the washing of the precipitated solid lignin-containing particles is performed without addition of an acid.

12. The method of claim 10 , wherein the concentration exceeds five percent.

13. The method of claim 10 , wherein the at least one sodium salt includes sodium sulphate.

14. The method of claim 10 , further comprising obtaining the at least one sodium salt from fly ash from a chemical recovery boiler of a pulp mill.

15. The method of claim 10 , further comprising obtaining the at least one sodium salt from an aqueous stream in a pulp mill.

16. The method of claim 10 , further comprising washing a portion of the washed precipitated solid lignin-containing material under an acidic condition and thereby reducing a sodium content of the portion of the washed precipitated solid lignin-containing material.

17. A method comprising:
precipitating lignin-containing material from spent kraft pulping liquor or a fraction of the liquor by acidifying the liquor or the fraction to a pH of not less than seven (7);
separating the precipitated lignin-containing material particles from the liquor or the fraction;
in each of at least two washing steps, washing the separated precipitated lignin-containing material using an aqueous liquid having a sodium salt concentration of at least three percent (3%) by weight, and
fueling a lime kiln with the washed precipitated lignin-containing material.

18. The method of claim 17 wherein the washing of the precipitated solid lignin-containing material is performed without addition of an acid.

19. The method of claim 17 further comprising adding fly ash from a chemical recovery boiler of a pulp mill to the aqueous liquid to increase the sodium concentration to the at least three percent.

20. The method of claim 17 further comprising adding sodium salt to the aqueous liquid to raise the sodium concentration to the at least three percent.

Assignees

• Andritz Oy

Inventors

• Mckeough Paterson

Classifications

• D21C11/0035

  Introduction of compounds, e.g. sodium sulfate, into the cycle in order to compensate for the losses of pulping agents · CPC title

• D21C11/00 Primary

  Regeneration of pulp liquors {or effluent waste waters} · CPC title

• D21C11/0007 Primary

  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 title

• D21C11/0021

  Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle) · CPC title

• D21C11/0042

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