A METHOD OF PURIFYING LIGNIN BY SUBJECTING A SLURRY COMPRISING LIGNIN TO AN ELECTRIC FIELD

Abstract

The present invention relates to a process for purifying, such as salt/ion depletion, and/or ash reduction,and/or sulphur removal, and/or free sugar depletion,and/or VOC depletion or fractionating,preferably by using dewatering, of a slurry comprising a lignin or lignin derivative or a combination thereof. A lignin or lignin derivative obtainable from said process and uses thereof are also disclosed.

Claims

1. A process for purifying, comprising at least one of salt/ion depletion, ash reduction, sulphur removal, free sugar depletion and VOC depletion, or fractionating, by using dewatering, of a slurry comprising a lignin or lignin derivative or a combination thereof, wherein the process comprises the following steps: a) providing a slurry comprising a lignin or lignin derivative or a combination thereof, b) subjecting the slurry to an electric field inducing the liquid and polar, molecules, species or components thereof such as ions, of the slurry to flow, and c) separating the liquid from the lignin or lignin derivative or a fraction emanating from both said lignin species, thus obtaining a liquid depleted purified or fractionated lignin or lignin derivative or intermediate lignin product, optionally in slurry form.

2. The process according to claim 1 also comprising the following steps: d) adding a washing liquid, comprising an organic solvent or water or a combination thereof, and/or a pH controlling agent, comprising CO.sub.2, to the liquid depleted slurry or during dewatering, e) subjecting the slurry of step d) to an electric field inducing the washing liquid of the slurry to flow, preferably involving a relatively fast increase of the current, and f) separating the washing liquid from the slurry, thus obtaining a purified lignin or lignin derivative or a fraction emanating from both said purified lignin or lignin derivative or intermediate lignin product, and g)

3. The process according to claim 1 wherein the dewatering is done by electro-osmosis.

4. The process according to claim 1 wherein an electric field with a voltage of 10-200 V is used, whereby said voltage may be AC or DC or a combination of both.

5. The process according to claim 1 wherein pressure and/or suction and/or ultrasound and/or magnetic induced separation also is applied in order to dewater the slurry.

6. The process according to claim 5 wherein the pressure is applied after the electric field has been applied and the dewatering has started.

7. The process according to claim 5 wherein the pressure is a mechanical pressure.

8. The process according to claim 1 wherein the dry content of the slurry comprising a lignin or lignin derivative or a combination, before dewatering, and/or salt/ion depletion and/or free sugar depletion, is about 1-50% by weight.

9. The process according to claim 1 wherein the temperature of the slurry during the dewatering is above 30° C. and below 140° C.

10. The process according to claim 1 wherein the slurry comprises nanoparticles, absorbents, salt, free sugars and/or surfactants which are stimulated by the electric field.

11. The process according to claim 1 wherein the washing liquid is water and/or an organic solvent, or a combination thereof.

12. The process according to claim 1 followed by, or preceded by, a counter-ion change and/or one or more washing steps, such as acid or alkaline washing steps, and/or a filtration step, such as ultrafiltration step, and/or a fractionation step.

13. A lignin or lignin derivative or an intermediate lignin product, dewatered according to the process of claim 1.

14. A lignin or lignin derivative or an intermediate lignin product, obtainable by the process according claim 1.

15. (canceled)

16. The process according to claim 1 wherein step b) is performed in combination with a pressure force and/or a suction force.

17. The process according to claim 2 wherein steps d)-f) are repeated at least 3 times.

18. The process according to claim 1 wherein an electric field with a voltage of 10-100 V is used, whereby said voltage may be AC or DC or a combination of both.

19. The process according to claim 1 wherein the temperature of the slurry during the dewatering is above 30° C. and below 100° C.

Description

FIGURES

[0060] FIG. 1 discloses the results of the experiment 1.

[0061] FIG. 2 discloses the anode filter (left) and the cakes anode side (right) in the experiment 1.

[0062] FIG. 3 discloses the cathode filter (left) and the cakes cathode side (right) in the experiment 1.

[0063] FIG. 4 discloses the results of the experiment 2.

[0064] FIG. 5 discloses the anode filter (left) and the cakes anode side (right) in the experiment 2.

[0065] FIG. 6 discloses the cathode side of the cake in the experiment 2.

[0066] FIG. 7 discloses the results of the experiment 3.

[0067] FIG. 8 discloses the anode filter (left) and the cakes anode side (right) in the experiment 3.

[0068] FIG. 9 discloses the cathode filter (left) and the cakes cathode side (right) in the experiment 3.

[0069] FIG. 10 discloses the cell of example 1.

[0070] FIG. 11 discloses a setup scheme (left) and cathode plate with holes. Instead of a MFC dispersion a lignin dispersion was used in example 1.

EXAMPLES

[0071] The lignin was obtained from a LignoBoost™ type of process and contained about 1.04% ash when determined at 550° C.

Experiment 1.

[0072] Dry lignin powder was ground in a mortar and 30 g of the powder was mixed with 30 ml of distilled water. After light shaking it was a liquid substance. 20 g of this mixture was placed into the dewatering cell, and the pressure was 650 Pa. Filter paper was used in the bottom. For the first 5 min. there was free dewatering monitored, no water emerged. At 5 min. moment 97 V voltage was applied, only very slow water outflow was present. The current was strong at the beginning, but it fell sharply after about 3 min. At 12.5 min. 20 ml of water was added over the anode, this was followed by the sharp increase of the electric current and very quick water outflow. Later water was added three times more, the outflow was very quick after each addition. The results are in FIG. 1. At 20 min. water vapor was emerging through the cathode. The experiment was ended after 22.5 min.; the sample of the water collected was taken. The mass of the cake was 16.2 g, the cake was with big cracks (FIG. 2, 3) and it was hard on the cathode side. The presence of the cracks in the cake was the cause of very quick water outflow after addition.

Experiment 2

[0073] The 3:5 mixture of the Lignin powder and water was prepared similarly as in experiment 1. To avoid crack formation the experiment was ended shortly after the current fell to low value. Water was not added. Only small amount of water was collected. The cake was soft on the anode side but hard and with cracks on the cathode side. The mass of the cake was about 19 g.

Experiment 3

[0074] The same mixture as in experiment 2 was used. The experiment was similar to the previous experiment, but the voltage was applied earlier and the experiment lasted longer. FIG. 7 shows that the water outflow ended after about 6 min.; again the content of the collected water was low. The waters collected in this experiment and in experiment 2 were mixed together to make one sample. The mass of the cake was about 17 g. The anode side of the cake was liquid, but a solid crust formed on the cathode side. The cake was without cracks and it is not clear why, while in experiment 3 it was with cracks.

TABLE-US-00001 TABLE 1 The setup of FIG. 11 was used. Dry solids Ash content Ash content content, DS at 550° C. (% at 925° C. (% Sample (%) in DS) in DS) Reference 63.0 1.04 0.96 lignin Exp. 1 66.2 0.15 0.12 Exp. 2 55.8 0.30 0.29 Exp. 3 59.3 0.20 0.19

Example 1

[0075] A cell was designed to be used in the process according to the first aspect of the invention and is explained in FIG. 10 (c.f. literature [1, 2]).

[0076] Before an experiment the chamber (camera) 1 was to be filled with the material to be investigated, and the chambers (cameras) and 5 filled with water. During the experiment water was to flow into one of the chamber (cameras) 4 or 5 and was to be collected for analysis. Lost water could be refilled adding it into either of cameras, according to the plan and the results of the experiment.

[0077] During an experiment free ions were to be extracted by the electric field into the cathode or the anode cameras and would be carried away by flowing water. The possible reactions at the electrodes products would also be also carried out by water and would not contaminate the material investigated.

[0078] The crust formation as in the case of Lignin powder may be avoided by maintaining temperature low enough by a sufficient water flow in the electrode cameras.

Tests were done whereby the cell disclosed in FIG. 10 was compared with the setup given in FIG. 11. [0079] The cell of FIG. 10 gave the following results: [0080] a. monovalent, divalent, multivalent cations, and anions removed [0081] b. major change in s-content [0082] The setup of FIG. 11 gave the following results: [0083] c. one sided dewatering (normally monovalent, divalent and/or multivalent cations removed) [0084] d. no major change in S-content [0085] An estimate done regarding sulphur (S) reduction is summarized below: [0086] reference lignin—about 0.24% S [0087] washed lignin—about 0.012% S [0088] a reduction of about 95% (with the method of FIG. 11 the reduction was close to 0%) [0089] In table 2 and 3 results are given from the FIG. 10 device and FIG. 11 device respectively.

TABLE-US-00002 TABLE 2 FIG. 10 device. Removal of ash. Dry solids Ash content Ash content content, DS at 550° C. (% at 925° C. (% Sample (%) in DS) in DS) Lignin 83.3 1.11 No data Powder original Lignin 67.3 0.11 No data powder Exp. LP14

TABLE-US-00003 TABLE 3 FIG. 11 device. Removal of ash. The figures also appears in table 1. Dry solids Ash content Ash content content, DS at 550° C. (% at 925° C. (% Sample (%) in DS) in DS) Reference 63.0 1.04 0.96 lignin Exp. 1 66.2 0.15 0.12 Exp. 2 55.8 0.30 0.29 Exp. 3 59.3 0.20 0.19 [0090] In table 4 specific elements are given:

TABLE-US-00004 TABLE 4 Elements. Washing Elements** FIG. with mg/kg, on dry 11. FIG. 10 basis for ash setup setup Limit of Theoretical, mg/kg in DS 56 6 quantification based on the (LOQ) 0.5% Na Calculated, EDXA of the mg/kg in DS 2480 130 TGA residue Mg Calculated, EDXA of the mg/kg in DS 20* 0* TGA residue Al Calculated, EDXA of the mg/kg in DS 170 50 TGA residue Si Calculated, EDXA of the mg/kg in DS 260 170 TGA residue P Calculated, EDXA of the mg/kg in DS 10* 0* TGA residue S Calculated, EDXA of the mg/kg in DS 2380 120 TGA residue K Calculated, EDXA of the mg/kg in DS 1110 70 TGA residue Ca Calculated, EDXA of the mg/kg in DS 80 10 TGA residue Ti Calculated, EDXA of the mg/kg in DS  0* 0* TGA residue Mn Calculated, EDXA of the mg/kg in DS 30* 10 TGA residue Fe Calculated, EDXA of the mg/kg in DS 70 40 TGA residue **The values correspond only to elements (or elemental fraction) that are not volatilized during the combustion at 550° C.. The values below the LOQ are marked with* [0091] 1. R. Hofmann, T. Käppler, C. Posten. Electrofiltration of Biomaterials. Biomaterials, DOI: 10.1007/978-0-387-79374-0_6. [0092] 2. G. Gözke, C. Posten. Electrofiltration of Biopolymers. Food Eng Rev (2010) 2:131-146. DOI 10.1007/s12393-010-9016-2.

[0093] In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.