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EP-4735532-A1 - METHOD FOR PRODUCING A LIGNIN PRODUCT

EP4735532A1EP 4735532 A1EP4735532 A1EP 4735532A1EP-4735532-A1

Abstract

It is disclosed a method for producing a lignin product, comprising the steps of: providing a soluble lignin-containing organic solution; providing an aqueous precipitant solution; adding the precipitant solution to the soluble lignin-containing organic solution to provide a mixture comprising precipitated lignin, mixing the mixture in a dynamic mixer at a speed of about 500 rpm to about 2000 rpm; separating and recovering the precipitated lignin product from the mixture.

Inventors

  • Kupiainen, Laura
  • ROUHIAINEN, MAIJA

Assignees

  • Chempolis Oy

Dates

Publication Date
20260506
Application Date
20240628

Claims (14)

  1. 1. A method for producing a lignin product, comprising the steps of: - providing a soluble lignin-containing organic solution, - providing an aqueous precipitant solution comprising acid(s) in amount of 0 wt.% to about 40 wt.%, - adding the aqueous precipitant solution to the soluble lignin-containing organic solution to provide a mixture comprising precipitated lignin, - mixing the mixture in a dynamic mixer at a rotation speed of about 500 rpm to about 2000 rpm, - separating and recovering the precipitated lignin product from the mixture.
  2. 2. The method of claim 1, wherein the soluble lignin -containing organic solution is a spent cooking liquor from an organosolv pulping process of a lignocellulosic material.
  3. 3. The method of claim 1 or 2, wherein the soluble lignin -containing organic solution comprises formic acid, acetic acid, and water, and optionally furfural.
  4. 4. The method of any one of the preceding claims, wherein the dry matter of the soluble lignin-containing organic solution is in the range of about 50% to about 90%, specifically about 60% to about 85%, more specifically about 70% to about 80%.
  5. 5. The method of any one of the preceding claims, wherein the aqueous precipitant solution is water.
  6. 6. The method of any one of claims 1-4, wherein the aqueous precipitant solution contains the acid(s).
  7. 7. The method of claim 6, wherein the acid(s) is organic acid(s).
  8. 8. The method of claim 6 or 7, wherein the aqueous precipitant solution comprises an acidic process side stream from organosolv pulping process of the lignocellulosic material.
  9. 9. The method of any one of claims 6-8, wherein the acid(s) is at least one of formic acid and acetic acid.
  10. 10. The method of any one of claims 6-9, wherein the aqueous precipitant solution contains acid(s) in amount of about 5 wt.% to about 30 wt.%, specifically about 10 wt.% to about 20 wt.%.
  11. 11. The method of any one of the preceding claims, wherein the aqueous precipitant solution is added to the soluble lignin -containing organic solution in a weight ratio of about 0.7:1 to about 2.5:1, specifically about 1:1 to about 2:1.
  12. 12. The method of any one of the preceding claims, wherein the mixture comprising precipitated lignin has a temperature of below 90°C.
  13. 13. The method of any one of the preceding claims, wherein the mixture is mixed in the dynamic mixer for about less than 45 sec, specifically about 2 sec.
  14. 14. The method of any one of the preceding claims, wherein the separation is carried out by filtration.

Description

METHOD FOR PRODUCING A LIGNIN PRODUCT FIELD OF THE INVENTION The present invention relates to a method for producing a lignin product. More particularly, the invention relates to an improved method for producing a precipitated lignin product with enhanced solids yield and good filterability in an efficient and controlled way. BACKGROUND OF THE INVENTION Precipitation of lignin from a lignocellulosic material with water is known. WO 2011/154293 Al discloses a process for separation of lignins and sugars from an extraction liquor involving concentrating the extraction liquor, mixing the concentrated liquor with water in equal parts, stirring the resultant mixture to obtain a stable suspending of the lignins in the solution, filtering the solution comprising the suspended lignins. WO 2021/198555 Al discloses a method for the separation of lignin from an organic solvent, comprising multiple two-step cycles involving a first step of adding an aqueous solution to a lignin-containing organic solvent to precipitate lignin, and a second step of subjecting the resultant lignin-reduced solution to the first step of addition of an aqueous solution. Precipitated lignin is separated and recovered in each step. The multi-step addition of an aqueous solution to a lignincontaining solution provides lignin precipitates with a different molecular weight distribution. Current methods for precipitation of lignin from an organic spent cooking liquor obtained from organosolv pulping of a lignocellulosic material do not provide means to affect solids yield, particle size distribution or filterability of solid-liquid mixture. It is challenging to produce a homogeneous mixture containing precipitated lignin at industrial scale, e.g., at high total solids content, without blockages or operational challenges in the system and without unpredictable properties of precipitated mixture. Current batch-wise and continuous methods cause several problems. Batch-wise operation produces various mixture properties, such as unfavorable and unpredictable particle size distribution and challenging separation of solids and liquid. Continuous operation with a static mixer suffers from reduced production capacity and operational challenges due to slow blockage possibilities. BRIEF DESCRIPTION OF THE INVENTION We have now found an improved method for efficient and controlled production of a precipitated lignin product having targeted properties. The method is based on an organosolv pulping of a lignocellulosic material in which cellulose, lignin and hemicellulose present in the lignocellulosic material are separated in two main streams, i.e., cellulosic pulp and a solution of soluble lignin and hemicellulosic sugars, by using an aqueous organic solvent as a cooking liquor. The cooking liquor is acidic and includes formic acid and acetic acid, water and furfural. During cooking, hemicellulosic sugars and a portion of lignin are dissolved in the cooking liquor. In context of the invention, a soluble lignin -containing organic solution obtained from cooking of a lignocellulosic material with an aqueous organic solvent is described here as "a spent cooking liquor". The spent cooking liquor thus contains, e.g.., soluble lignin, hemicellulosic sugars, inorganics, proteins and extractives, and also components of original cooking liquor. In the method of the invention, soluble lignin is precipitated from the spent cooking liquor using water as a precipitant solution. It was surprisingly found that using a dynamic mixer for combining an aqueous precipitant solution and a soluble lignin-containing organic solution in a controlled way results in enhanced yield of total solids and good filterability of a mixture containing precipitated lignin. The yield and properties of the mixture, such as particle size of lignin precipitate, can be adjusted by changing the rotation speed of the dynamic mixer, and an acid concentration of the aqueous precipitant solution. The present invention provides an efficient and economic method for producing and recovering a precipitated lignin in a controlled way. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows an apparatus used for precipitation of lignin in the method of the invention. Figures 2, 3a-3c, and 4a-4c relate to lignin precipitates precipitated with water. Figures 5a-5b relate to lignin precipitates precipitated with an acidic aqueous solution. Figure 2 shows a yield of precipitated lignin in wt.% based on total solids of a mixture containing precipitated lignin vs. rotation speed [rpm] of a dynamic mixer. Figures 3a-3c show particle size distribution of a lignin precipitate in volume (%) vs. mean particle size (gm). Figure 4a and figure 5a show mean particle size d(0.5) (gm) vs. rotation speed (rpm) of a dynamic mixer. Figure 4b and figure 5b show filterability (kg D.S./m2h) of a lignin precipitate vs. rotation speed (rpm) of a dynamic mixer. Figure 4c and figure 5c show filterability (kg D.S./m2h) of a lignin precipi