WO2015085168A1

WO2015085168A1 - Finely ground biomass

Info

Publication number: WO2015085168A1
Application number: PCT/US2014/068784
Authority: WO
Inventors: Earnest Stuart
Original assignee: Earnest Stuart
Priority date: 2013-12-05
Filing date: 2014-12-05
Publication date: 2015-06-11

Abstract

The invention is a finely ground biomass material made from biomass material, where at least 98% of the biomass particles have a particle size of 20 microns or less. The invention also provides a method for producing finely ground biomass material from biomass material. The biomass material is first ground using a hammermill equipped with a screen having a screen with a 0.5 millimeter or smaller hole pattern until all the ground biomass particles have passed through the screen. The hammermilled biomass particles are then ground with a dry grinding attritor until less than 2% of the particles have a particle size greater than 20 microns. The method may also include forming a slurry by adding water to the ground material. The slurry may then be processed using a high shear and cavitation device, dried, and processed with an attrition mill to disagglomerate agglomerated material in the dried material.

Description

FINELY GROUND BIOMASS

CROSS-REFERENCE TO RELATED APPLICATIONS

[01] This application claims priority to U.S. Provisional Patent Application No. 61/912,233, filed December 5, 2013 the entire contents of which are incorporated herein by reference in its entirely.

FIELD OF THE INVENTION

[02] The present invention relates generally to finely ground plant matter, and more particularly to finely ground seed hulls or husks such as oat hulls, ground to a maximum particle size of 10 microns or less.

BACKGROUND OF THE INVENTION

[03] Hard hulls, or husks, of seeds such as oat hulls, are waste products that are typically discarded or sold very cheaply, where producers of those hulls generally have to pay to discard the hulls.

[04] The outermost layer of the oat grain is the oat hull fiber which contains high amounts of cellulose, insoluble non-cellulosic polysaccharides, and lignin. The most common varieties of oats grown today have approximately 20 - 35% of their weight from the hulls. In the unprocessed state, these hulls contain approximately 85% insoluble dietary fiber and, with further processing to bleached oat fiber, the insoluble dietary content can be more than 90%.

[05] Oat hulls contain cellulose, hemicellulose and lignin in a framework comprising the cell walls. Hemicellulose is a polysaccharide containing a number of simple sugars in addition to glucose. Others have reported the presence of mannose and ribose in addition to sugars.

[06] By-products from an agricultural milling process include hulls or mill feeds, which are very inexpensive.

[07] Oat hulls are typically managed by oat processors as a waste stream, or as a very low value stream. Values to the processor can be from a negative value up to its value as an energy source for boiler steam. Uses by downstream parties include animal bedding, burning as a fuel source, and emergency low digestibility winter cattle feed filler. No broad use of oat hulls with a value comparable to other types of biomass, such as alfalfa, is enjoyed by bulk purchasers of oat hulls. Oat hulls and rice hulls are known for their abrasiveness and difficulty to grind, although oat hulls are known to be less abrasive than rice hulls.

[08] While the potential utility of such finely ground seed hulls is clear, nobody has produced a finely ground material, suitable for high value, small dimension plastics manufacturing. Ground agricultural by-products having particle sizes of about 25 to 50 microns have been reported, such as ground corn hominy as fine as 40 microns. The use of such material to form containers has been disclosed, although generally the finer materials are formed from by-products other than oat hulls, largely starch with minimal cellulose. Oat hulls may be more difficult to grid very finely to reach a marketable value in direct plastic compounding.

[09] Presently, "green" bio-based plastics are produced by fermenting biochemicals from sugar sources such as grain and cellulose. From the core biochemicals, bioresins are produced. A lower-cost additive/filling is desired by industry to produce foam used in auto interiors, bio-strings which can be woven into ultra thin, yet strong fabrics, or extruded as thin film used in a wide range of food and other packaging, as examples. Opportunity exists to employ biomass based resins in 3D printers.

[10] The cost for foam resins is about 70 cents per pound, and thin film plastics resins cost between 90 cents and $1.00 per pound. Manufacturing biomass fillers which can create small dimension particles or films at a cost below those described above holds market potential in the billions of dollars per annum

SUMMARY OF THE INVENTION

[11] The invention provides a finely ground biomass material made from biomass material, which is hard or dried biomass, where at least 98% of the dried biomass particles have a particle size of 20 microns or less.

[12] Preferably, at least 98% of the particles have a particle size of 15 microns or less. [13] Preferably, at least 99% of the particles have a particle size of 20 microns or less.

[14] Preferably, at least 99% of the particles have a particle size of 15 microns or less.

[15] Preferably, at least 98% of the particles have a particle size of 10 microns or less.

[16] Preferably, at least 75% of the particles have a particle size of 7 microns or less, and at least 25% of the particles have a particle size of 4.2 microns or less.

[17] Preferably, at least 99% of the particles have a particle size of 10 microns or less.

[18] In some embodiments, least 85% of the particles have a particle size of 7 microns or less, and at least 50% of the particles have a particle size of 4.2 microns or less.

[19] The finely ground biomass material may be seed hulls. The finely ground biomass material may oat hulls or wheat hulls.

[20] The invention also provides a method for producing finely ground biomass material from biomass material. The biomass material is first ground using a hammermill equipped with a screen having a screen with a 0.5 millimeter or smaller hole pattern until all the ground biomass particles have passed through the screen. The hammermilled biomass particles are then ground with a dry grinding attritor until less than 2% of the particles have a particle size greater than 20 microns.

[21] Preferably, the hammermilled biomass particles are ground with a dry grinding attritor until less than 2% of the particles have a particle size greater than 15 microns.

[22] Preferably, the hammermilled biomass particles are ground with a dry grinding attritor until less than 2% of the particles have a particle size greater than 10 microns.

[23] The method may also include forming a slurry by adding water to the ground material after the step of grinding the hammermilled biomass particles with a dry grinding ball mill. The slurry may then be processed using a high shear and cavitation device. The slurry may then be dried, and the dried material processed with an attrition mill to disagglomerate agglomerated material in the dried material.

[24] In these methods, the biomass material may be seed hulls, which may be oat hulls or wheat hulls or rice hulls, or any other type of hull biomass.

[25] These methods may further include the step of compounding the ground biomass particles with plastic resin to form a plastic film.

[26] The invention also provides the use of the finely ground biomass material described above to form a plastic film by compounding the finely ground biomass material with resin.

[27] The invention also provides a plastic film formed by compounding a plastic resin with the finely ground biomass material described above. The plastic resin may be, for example, polylactic acid or polybutylene succinate, A filler, such as lime may also be included. At least 10% of the material forming the plastic film may be the finely ground biomass material. Preferably at least 25% or 50% of the material forming the plastic film is the finely ground biomass material

DETAILED DESCRD?TION OF THE INVENTION

[28] This invention provides powdered seed hull material with very small particle sizes, such as 99% or more of the material being less than 10 microns, or less than 1 micron, and a process for creating the powdered seed hulls. The process creates unique fine fibers by ball milling particles in combinations of dry milling, wet milling in water- followed by drying, both followed by compounding with bio-based plastic resins such as PL A (polylactic acid or polylactide) or PBS (polybutylene succinate) to compound the resin and particles while dis-agglomerating the final fiber products to achieve a controlled upper target particle size mostly no greater than individual particle sizes created before agglomeration. Additional particle size reduction, or major particle size reduction to ultimate target upper particle size in combination with disagglomeration is employed to achieve resins which can be converted into thin film with small particles, or thin string surfaces with smooth appearance and/or function. [29] The powdered material may be used in thin dimension products such as plastic films, or particles, in the presence of plastic resins and optional fillers, above 10% of biomass-to-plastic-resin ratios, including percentages up to 80%, such as 25%, 50% or 60%. In one embodiment, extremely thin films of resins containing or not containing processed fibers as described herein can be used in single or multiple layers to create the outer layers of a thin sheet in which fine fibers, or fine fibers in a compound of resins and optional fillers such as calcium carbonate is filled in between the outer layers described above, to produce a smooth surface, effectively sandwiching powdered oat hull fibers with veneers on each side of the final film to minimize or virtually eliminate, or completely eliminate measurable surface irregularities.

[30] In a preferred embodiment of the method, the first step is to grind lignocellulosic biomass, specifically oat hulls, using a mechanical mill such as a Prater Mega Mill.™ A Fitzmill,™ which combines hammers and sharp cutting blades, may alternatively be used. Both types of machines may be configured with screens as small as 120 mesh. Other types of mechanical grinding mills can alternately be used.

[31] Hammermilling with a Prater Mega Mill was performed with the following configuration.

[32] Oat hulls acquired from an oat processing operation were hammermilled through a 0.3 millimeter screen with delta shaped holes. The Prater Mega Mill grinds oat hulls by contact with a set of steel hammers which swing on a central shaft driven by an electric motor. The hammers shatter, cut and grind and crush oat hulls into ever smaller particles until they can pass through the chosen size screen.

[33] This resulted in the following distribution of particle sizes. The powder was passed through meshes of varying sizes to assess the particle size distribution.

[34] Thus, 66% of the powdered oat hull material had a particle size of 150 microns or less and 17% had a particle size of 45 microns or less.

[35] Alternatives to the Prater Mega Mill include burr mills, double disk attrition mills, a new custom, and a large impact mill such as Prater's Classifier Mills (CLM). The CLM is a grinder/classifier mill with a screen hammermill function which recycles oversize particles back through the machine until target particle size is reached. However, testing has shown that, while the CLM is capable of producing a substantial number of particles below 10 micron, it was not feasible to get everything below 10 micron and available equipment is more suitable for very small volume processing, but not volumes which can practically address the market potential. A newly designed CLM type of grinder could be used within the present process with utility. Other systems referenced above are not designed for high percentage biomass grinding below 10 micron, but could potentially be redesigned for the process described herein.

[36] A Prater Mega Mill hammermill may be equipped with a screen having a 0.5 millimeter or smaller hole pattern, such as 0.3 mm as in the above described run, although screens with a 0.2 millimeter or smaller may also be employed. Larger screen hole sizes may be optionally employed to shift work to downstream processing, such as ball mills. The oat hulls are ground in the hammermill until all material has passed the through the screen.

[37] In a second step, hammermilled oat hulls with a moisture content of about 7.3%, may be processed with a dry grinding attritor, such as a Union Process™ SD- 50 attritor for a period such as about 150 minutes. The attritor is a vertical shaft ball mill with a 75 hp engine and a ball mill tank that can hold 81 gallons. In one run, the ball mill grinding tank was filled with stainless steel grinding media balls weighing 1520 pounds representing about 38/81 of the volume of the stainless steel tank. Horizontal arms attached to a vertical shaft move the stainless steel balls around the shaft at about 150 RPM. 34.2 pounds of oat hulls were added to the steel media balls in the process tank. The final processed powdered oat hull yield was about 33.1 pounds due to system losses. The temperature of powder during processing was about 150-175°F .The powdered oat hulls were processed in the attritor for about 2.5 hours and the processed oat hulls were separated by opening an exit valve while the mixing arms continued rotating, causing the fine powders to fall off the balls through the exit port. Upon completion of grinding, the attritor was operated with an open port on the bottom to allow powder to systematically exit the tank, and to separate from the media balls. The powder is recovered and tested. Upon completion of grinding, 99.35% of the particles were recorded by Microtrakto be less than 10 micron mesh, while 90% were recorded by Microtrakto be less than 7.02 micron mesh and 50% were recorded by Microtrakto be less than 4.16 micron mesh.

[38] In one embodiment, the generally <10 micron particles are blended with a choice of plastic resins, such as polylactic acid (PLA) or polybutylene succinate (PBS) resins, both biomass derived "bioplastic resins", at a temperature suitable for pumping with a progressive cavity pump, such as a Moyno or other similar brand. The resin based slurry which can consist of 10% particles to 90% resin, up to 80% biomass and 20% resin, or 60% biomass, 20% lime filler, or other combinations of the above, is flowed into an attritor or other type of ball mill such as a Netsch horizontal ball mill to blend the fiber, resin and optional lime filler to

disagglomerate the mainly <10 micron particles from each other until the target maximum particle size is achieved before the final plastic is cooled and formed into pellets, thin sheets, strings or small individual plastic compound particles.

Optionally, the above described ball mill based disagglomeration is combined in sequence, repeated as necessary, with traditional compounding systems. [39] While the embodiments described above generally refer to oat hulls by way of example, the invention is not limited to finely ground oat hull material. As will be appreciated by skilled persons, the above-described methods can be used to produce finely ground versions of various dried or relatively hard biomass materials, such as hulls of wheat, corn, wheat, rice, beans and various seeds. A "hull" (or husk) in general is the outer shell or coating of a seed.

[40] As used herein "particle size" of a particle means the length of the largest dimension of the particle. For example, if a particle is generally spherical, then the particle size is the diameter of the particle. Although it is preferred that, for example, 99% or more of the material has a particle size of less than 10 microns,

embodiments where, for example, 98% or 99% of the material has a particle size of less than 20 microns are also within the scope of the invention, as are embodiments where 98% or 99% of the material has a particle size of less than 15 microns.

[41] It should be understood that the above-described embodiments of the present invention, particularly, any "preferred" embodiments, are only examples of implementations; merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments) of the invention as will be evident to those skilled in the art.

[42] Where, in this document, a list of one or more items is prefaced by the expression "such as" or "including", is followed by the abbreviation "etc.", or is prefaced or followed by the expression "for example", or "e.g.", this is done to expressly convey and emphasize that the list is not exhaustive, irrespective of the length of the list. The absence of such an expression, or another similar expression, is in no way intended to imply that a list is exhaustive. Unless otherwise expressly stated or clearly implied, such lists shall be read to include all comparable or equivalent variations of the listed item(s), and alternatives to the item(s), in the list that a skilled person would understand would be suitable for the purpose that the one or more items are listed.

[43] Where, in this document, including the claims, the conjunction "or" is used in a list, such as in "w is done by performing x, performing y or by performing z", unless otherwise clearly implied, the "or" is non-exclusive. In this example, w may therefore be done by performing all of x, y and z, performing any two of x, y and z, or performing any one of x, y and z, unless the simultaneous performance is not possible or does not make sense.

[44] The words "comprises" and "comprising", when used in this specification and the claims, are to used to specify the presence of stated features, elements, integers, steps or components, and do not preclude, nor imply the necessity for, the presence or addition of one or more other features, elements, integers, steps, components or groups thereof.

[45] The scope of the claims that follow is not limited by the embodiments set forth in the description. The claims should be given the broadest purposive construction consistent with the description as a whole.

Claims

What is claimed is:

1. A finely ground biomass material comprising biomass material comprising particles where at least 98% of the particles have a particle size of 20 microns or less.

2. The finely ground biomass material of claim 1, wherein at least 98% of the particles have a particle size of 15 microns or less.

3. The finely ground biomass material of claim 1, wherein at least 99% of the particles have a particle size of 20 microns or less.

4. The finely ground biomass material of claim 1, wherein at least 99% of the particles have a particle size of 15 microns or less.

5. The finely ground biomass material of claim 1, wherein at least 98% of the particles have a particle size of 10 microns or less.

6. The finely ground biomass material of claim 5, wherein at least 75% of the particles have a particle size of 7 microns or less, and at least 25% of the particles have a particle size of 4.2 microns or less.

7. The finely ground biomass material of claim 1, wherein at least 99% of the particles have a particle size of 10 microns or less.

8. The finely ground biomass material of claim 7, wherein at least 85% of the particles have a particle size of 7 microns or less, and at least 50% of the particles have a particle size of 4.2 microns or less.

9. The finely ground biomass material of any one of claims 1 to 8, wherein the biomass material is seed hulls.

10. The finely ground biomass material of claim 9, wherein the biomass material is oat hulls.

11. The finely ground biomass material of claim 9, wherein the biomass material is wheat hulls. plastic film by compounding the finely ground biomass material with resin.

13. A method for producing finely ground biomass material, the method comprising the steps of:

(a) providing biomass material;

(b) grinding the biomass material using a hammermill equipped with a

screen having a screen with a 0.5 millimeter or smaller hole pattern until all the ground biomass particles have passed through the screen; and

(c) grinding the hammermilled biomass particles with a dry grinding attritor until less than 2% of the particles have a particle size greater than 20 microns.

14. The method of claim 13, wherein the hammermilled biomass particles are

ground with a dry grinding attritor until less than 2% of the particles have a particle size greater than 15 microns.

15. The method of claim 14, wherein the hammermilled biomass particles are

ground with a dry grinding attritor until less than 2% of the particles have a particle size greater than 10 microns.

16. The method of claim 13, further comprising the step of compounding the ground biomass particles with plastic resin to form a plastic film.

17. The method of claim 13, further comprising the steps of:

(d) after the step of grinding the hammermilled biomass particles with a dry grinding attritor, forming a slurry by adding water to the ground material;

(e) processing the slurry using a high shear and cavitation device;

(f) drying the slurry after processing the slurry using a high shear and

cavitation device; and

(g) processing the dried material with an attrition mill to disagglomerate agglomerated material in the dried material.

18. The method of claim 17, further comprising the step of compounding the dried material with plastic resin to form a plastic film.

19. The method of and one of claims 13 to 18, wherein the biomass material is seed hulls.

20. The method of and one of claims 13 to 18, wherein the biomass material is oat hulls.

21. The method of and one of claims 13 to 18, wherein the biomass material is wheat hulls.

22. A plastic film formed by compounding a plastic resin with the finely ground biomass material of any one of claims 1 to 8.

23. The plastic film of claim 22, wherein the plastic resin is polylactic acid.

24. The plastic film of claim 22, wherein the plastic resin is polybutylene succinate.

25. The plastic film of claim 22 further comprising a filler.

26. The plastic film of claim 22, wherein the filler is lime.

27. The plastic film of claim 22, wherein at least 10% of the material forming the plastic film is the finely ground biomass material.

28. The plastic film of claim 27, wherein at least 25% of the material forming the plastic film is the finely ground biomass material.

29. The plastic film of claim 28, wherein at least 50% of the material forming the plastic film is the finely ground biomass material.