Lignin Dewatering Process

• US 20090038212A1
• Filed: 08/08/2008
• Published: 02/12/2009
• Est. Priority Date: 08/08/2007
• Status: Active Grant

• Current Assignee: Harrison R. Cooper
• Original Assignee: Harrison R. Cooper
• Inventors: Cooper, Harrison R.
• Granted Patent: US 8,613,781 B2
• Time in Patent Office: Days
• US Class Current: 44/550
• CPC Class Codes: C08H 6/00 Macromolecular compounds derived from lignin, e.g. tannins, humic acids
• CPC Class Codes: C08L 97/005 Lignin
• CPC Class Codes: D21C 11/0007 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 Class Codes: D21C 9/002 by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
• CPC Class Codes: D21C 9/18 De-watering de-watering in general F26B; Elimination of cooking or pulp-treating liquors from the pulpD21C9/002, D21C9/02 take precedence; paper-making machines D21F; strainers in digesters D21C7/00; presses in general B30B

Abstract

A lignin plastics solids mass containing lignin solids and liquids with up to 85% liquids can be partially dewatered by heating the lignin plastics solids mass to above a critical temperature at which time the lignin plastics solids agglomerate into lower moisture granular solids with between about 45% to 55% liquids releasing excess liquid which can be easily removed from the solids. The process is particularly useful for lignin plastics solids removed from black liquor from paper mills, or for similar lignin plastics solids masses, which can contain up to 85% liquids and which need to be dried to form useful lignin solids, which can be used for example for fuel. The dewatering process can be combined with the process for separating the lignin from the black liquor to separate the dewatered lignin directly from the black liquor.

Claims

1. A method of at least partially dewatering lignin plastic solids in the form of a lignin plastic mass having a moisture content of more than about 60%, comprising:

heating the lignin plastic mass to a temperature above a critical temperature;

cooling the heated lignin plastic mass to a temperature below the critical temperature thus causing lignin plastic solids to agglomerate into lower moisture solids and a residual liquid, said lower moisture solids having a moisture content of less than about 60%; and

separating at least a portion of the residual liquid from the lower moisture solids to obtain dewatered lignin plastic solids.

2. The method of claim 1, wherein the lower moisture solids have a moisture content of less than about 50%.

3. The method of claim 1, wherein the lower moisture solids have a moisture content of from about 45% to about 55%.

4. The method of claim 1, wherein the critical temperature is greater than about 170°

F.

5. The method of claim 1, wherein the critical temperature is greater than about 180°

F.

6. The method of claim 1, wherein the critical temperature is from about 170°

F. to about 200°

F.

7. A process for treating a substantially spent, alkaline and non-sulphite digestion liquor obtained from digestion of a cellulosic biomass, said digestion liquor containing lignin as a potential precipitant upon acidification of said digestion liquor, leaving substantially clarified residual liquid, said process comprising:

mixing into said spent digestion liquor a water soluble, surface active, polymeric, coagulant agent;

acidifying the so mixed liquor to a pH below 7 to separate the lignin and other organic compounds and to coagulate them as solids which tend to float to the surface of the residual liquid to form a lignin plastic mass having a moisture content above about 60%;

heating the lignin plastic mass to a temperature above a critical temperature;

cooling the heated lignin plastic mass to a temperature below the critical temperature thus causing the lignin plastic solids to agglomerate into lower moisture solids and a residual liquid, said lower moisture solids having a moisture content of less than about 60%; and

separating at least a portion of the residual liquid from the lower moisture solids to obtain dewatered lignin solids.

8. The process of claim 7, wherein a surface active agent coactive with the polymeric, coagulant agent is added to the spent digestion liquor prior to the acidification thereof so as to coact with the polymeric coagulant agent and thereby facilitate lignin separation.

9. The process of claim 7, wherein the step of acidifying the so mixed liquor to a pH below 7 is the step of acidifying the so mixed liquor to a pH below 3.5.

10. The process of claim 7, wherein the spent digestion liquor is taken from a pulping plant of the paper making industry.

11. The process of claim 7, wherein the spent digestion liquor is diluted prior to treatment.

12. The method of claim 7, wherein the dewatered lignin solids have a moisture content of less than about 50%.

13. The method of claim 7, wherein the dewatered lignin solids have a moisture content of from about 45% to about 55%.

14. The method of claim 7, wherein the critical temperature is greater than about 170°

F.

15. The method of claim 7, wherein the critical temperature is greater than about 180°

F.

16. The method of claim 7, wherein the critical temperature is from about 170°

F. to about 200°

F.

17. The process of claim 7, wherein the solids and the residual liquors are used as valuable products.

18. The solids product resulting from the process of claim 7.

19. The clarified liquid product resulting from the process of claim 7.

20. A process for treating a substantially spent, alkaline and non-sulphite digestion liquor obtained from digestion of a cellulosic biomass, said digestion liquor containing lignin as a potential precipitant upon acidification of said digestion liquor, leaving substantially clarified residual liquid, said process comprising:

mixing into said spent digestion liquor a water soluble, surface active, polymeric, coagulant agent;

making a heated acidified dilution liquid;

mixing the heated acidified dilution liquid and the spent digestion liquid to produce a mixture having a pH below 7 and a temperature above a critical temperature;

cooling the mixture to a temperature below the critical temperature thus causing the lignin to agglomerate into lignin solids and to separate from a residual liquid, said lignin solids having a moisture content of less than about 60%; and

separating at least a portion of the residual liquid from the lignin solids to obtain dewatered lignin solids.

21. The method of claim 20, wherein the temperature of the heated acidified dilution liquid is at a temperature above about 180°

F.

22. The method of claim 20, wherein the temperature of the digestion liquor is between about 200°

F. and 300°

F.

23. The method of claim 20, wherein the step of cooling the mixture includes the step of placing the mixture in a tank.

24. The method of claim 23, wherein the lignin solids collect in the bottom of the tank, and the step of separating at least a portion of the residual liquid from the lignin solids includes removing lignin solids collected in the bottom of the tank from the tank.

25. The method of claim 20, wherein the critical temperature is from about 170°

F. to about 200°

F.

26. The process of claim 20, wherein the step of mixing the heated acidified dilution liquid and the spent digestion liquid to produce a mixture having a pH below 7 is the step of mixing the heated acidified dilution liquid and the spent digestion liquid to produce a mixture having a pH below 3.5.

27. A combustible fuel source comprising the precipitated lignin of claim 20.