WO2018075877A1

WO2018075877A1 - A method for creation of cellulose nanofibrils with a refining plate

Info

Publication number: WO2018075877A1
Application number: PCT/US2017/057567
Authority: WO
Inventors: Michell CAHILL; Jonathan Nelson
Original assignee: Cahill Michell; Jonathan Nelson
Priority date: 2016-10-22
Filing date: 2017-10-20
Publication date: 2018-04-26

Abstract

A cellulose nanofibrils production method comprising the step of: refining pulp to produce cellulose nanofibrils with a refining plate including an aperture at least partial through one of a dam or bar on the surface of the refining plate.

Description

APPLICATION FOR UNITED STATES PATENT

A METHOD FOR CREATION OF CELLULOSE NANOFIBRILS WITH A

REFINING PLATE

SPECIFICATION

FIELD OF THE INVENTION

[0010] This disclosure relates to refiner plates used to treat wood and non- wood fibers for the generation of cellulose nanofibrils (CNF) or other highly refined fiber applications.

BACKGROUND OF THE INVENTION

[0011] The functional elements of a refiner are opposing wearable refiner plates whereby at least one of the plates is rotating. The fibers are captured between the bar edge crossing where energy is applied to them. The energy absorbed by the fibers results in a physical modification to the physical properties of the fibers.

[0012] There are some applications of CNF that require greater purity or less long fiber than others. Conventional production of this purer product requires longer refining times to reach thai condition, CNF, also commonly referred to as Microfibrillated Cellulose (MFC), Micro-Nano Fibrillafed Cellulose (MNFC), Cellulose Nanomaferials, etc., are small cellulose fibers on the order of about .25 to .05 mm in length and 10-500 nm in width,

[0013] A conventional process for producing CNF pulp uses refiners equipped with various differing refiner plates. The process involves the expending of significant amounts of refining energy applied to bleached or unbleached, softwood, hardwood, virgin or recycled fiber, or other plant fiber. This refining process is usually a recirculation .system whereby the refiner discharge m directed back into an agitated feed tank and then back through the refiner numerous limes. As energy is applied to shorten the fiber and increase the CMF content of the pulp, the refiner plate gaps are reduced, to obtain the desired energy. This constant application of energy and shortening of the fiber results in a decreasing ability of the refiner plates to capture the fiber on the bar edges resulting in reduced refining efficiency. This results in potentially significant plate wear along with the additional power applied over time,

[0014] The current refiner plate design has bars and grooves. The refiner plates can also include a groove obstruction or dam. The dam's function is to force the fiber bundles up on the surface of the plate where the energy is applied. Traditional dams occupy the full width of the groove, although some may occupy only a portion of the full width of the groove. The dams may fully block the flow If they are surface (full height of the bars on either side) or partially block the flow if they are sub-surface or mini dams (stopping below the top surface of the bars). As dams are an .obstruction,, they force more fibers up on the surface of the bars.

[0015] The conventional method of producing CNF is through a multistage refining or grinding process which starts with any number of various pulp types, like, but not limited to, bleached softwood draft: pulp, The pulp supply can be bleached or unbleached, softwood, hardwood, virgin or recycled fiber, or other plant fiber. The refining process is carried out in a way that recirculates all or a portion of the pulp supply through the refiner while applying energy to the fiber to result in an ever increasing fines level in the pulp. The process can be either continuous or batch. As the refining energy is applied the CNF level increases but at a. decreasing rate as the fiber Is shortened and CNF increases, This process can be carried out in several stages; possibly each stage using a different refiner plate pattern than the previous. As the refining process continues, the efficiency of energy transfer to the fiber decreases as the decreasing fiber length and increasing CNF level takes place. Thus, more and more energy is expended to further increase the CNF content to a desired target,

[0016] Short weak fibers are difficult to refine as they cannot support the motor load to apply energy to them, ft is difficult to capture the fibers on the refiner plate surfaces to apply the lead as the short weak: fibers do not floe together.

[0017] The conventional process, when run to the point of very high fines concentration, such as but not limited to 70% and higher, uses increasingly greater energy as the CNF level increases,

[0018] Conventional refiner plate designs with bar and groove designs do not effectively capture the fibers on the bar surfaces to apply energy, Conventional bar and groove designs have a higher rate of fibers channeling up through the grooves and thus pass the plates in an un-refined condition,

SUMMARY OF THE INVENTION

[0019] Disclosed is a cellulose nanefibriSs production method comprising the step of: refining pulp to produce cellulose nanofibhls with a refining plate including an aperture at least partial through one of a dam or bar on the surface of the refining plate.

BRIEF DESCRIPTION OF THE DRAWINGS [002 0 ] F IG. 1 is a single stage conventional CNF system.

[0021] FIG, 2 is a multistage conventional CNF system. [0022] FIG. 36 is a top view of a refiner plate according to this disclosure. FIG. 3A is an enlarged view of a portion of the top of the plate. FIG. 3C is a cross section through the plate. FIG, 3D is a cross section of the plate showing: slots in the tops of bars,

[0023] FIG. 4A is a top view of another refiner plate according to this disclosure. FIG. 4C is an enlarged view of a portion of the top of the plate, FI6, 4B is a cross section through the plate. FIG, 4D is a cross section of the plate shewing slots in dams,

[0024] FIG. 5 is a cross section of another refiner plate according to this disclosure, showing slots in the sides of bars.

[0025| FIG, BA is: a top view of another refiner plate according to this disclosure. FIG. 6B is a side cross sectional view of a portion of the plate. FIG. 80 is a front cross sectional view of the plate showing holes in dams in the plate.

[0026] FIG. 7 illustrates test data where pulp was passed several times or passes through a refiner, with total energy used on the X axis and percent fines level achieved on the Y axis. The fines concentration in the test data is based on a Moffi optical analyzer. Other optical analyzers may measure the fines differently.

[0027] Before one embodiment of the disclosure is explained in detail, It is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, if is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Use of "including" and: "comprising" and: variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of "consisting of and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Further, it is to be understood that such terms as "forward", "rearward , "left", "right", "upward", ''downward", "side", "top" and "bottom", etc., are words of convenience and are not to be construed as limiting terms.

DETAILED DESCRIPTION

[0028] The critical component parts for a 21 conventional refining system to generate CNF includes a source of raw material 23; slushed: pulp 25 which is discharged into an agitated refiner feed tank 28 with a refiner system feed pump 32 with its suction connection attached to the tanks (FIS, 1), A two-stage refiner system 33 comprises one or more refiners 38 connected in series or parallel or some combination of both with the refining system discharge connected back to the refiner feed tank 28 or forward to an CNF storage tank 40, as shown in FIG 2.

[0028] The functional elements of a refiner 36 are opposing wearable refiner plates 42 whereby at least one of the plates is rotating and one is stationary. In some embodiments, both refiner plates are rotating, The refiner 36 may be a disk, conical or cylindrical configu ration. The refiner 38 will operate in pumping (pressure rise) or hold back (pressure neutral or loss) mode.

[0030] Disclosed herein is a cellulose nanofibrits production method comprising the step of refining pulp to produce cellulose nanofihrils in such a refiner 38 with a refining plate 42, as shown in FIG. 3 including an aperture 48 at least partial through one of a dam 14 or bar 20 on the surface 24 of the refining plate 42, The aperture 48 acts to extrude the fibers (not shown), thereby adding energy to the fibers, resulting in shorter length fibers.

[0031] More particularly, the disclosed refiner plate design has bars 20 and grooves 82 extending from the inner and outer locations on the plate, as shown in FIGS- 3 ~ 4. Surface or sub-surface- 'dams 14 may be present in all or some of the grooves 62. The dams 14 may he located at any point along the length of the groove 62. For ally given groove 62, there may be one or multiple dams 14 present,

[0032] Some or all of the dams 14 will have the aperture 48 in the form of a hole(s) 64 (FIB. 6) or a narrow slot(s) 10' (FIG, 4) that is the entire length of the dam 1-4 from the center of the plate 42 to the outside diameter of the plates 42. The slot(s) 10' may be positioned at any point on the surface 63 of the dam 14. The slot 10' will be an area that will cause turbulence and force the fibers up onto or through the bars 20, where energy is applied. A portion of the flow will be forced through the slot(s) 10' in the plate 42 as an additional area where a shear force Is generated and applied to the fibers. An example of a plate 42' of this configuration with slots 10' is shown in FIG. 4. An example of a plate 42"' of this configuration with holes 64 in a dam 14' is shown in FIG, 6. The slots ID (FIB. 3) on the top of the bars 20 can also be at any angle relative to the sides of the bars 20. In other words, across the top of the bar 20 or along the length of the bar 20,

[0033] It has thus been determined that the addition of slots 10 to the top of the refiner bars is effective in applying additional refining energy to the fibers. An example of a plate 42 of this oonfigu ration is shown in FIG, 3. The means by which this effect is achieved is similar to the effect of slot 10' on the dams 14,

[0034] Although shown with the slots 10 on the top of the darns 14 in FIG.4, in other embodiments, such as in the refiner plate 42" shown in FIG. 5, the slot or slots 10" may be in either the inside diameter side or the outside diameter side of the bars or dams, or any combination thereof, These embodiments can be effected alone or in combination together to increase the load applied to fibers in a refiner.

[0035] A slotted dam will he an area that will cause turbuience and more efficiently foree the fibers up on the bars where energy is applied, with less flow disruption, Additionally, a portion of the flow will be forced through the slot in the plate where a shear force is applied to the fibers:. Slotted surfaces on the; refiner bars will Similarly- cause turbulence and more efficiently force the fibers to more effectively absorb energy load.

[0036] The disclosed design will incorporate a narrow slof(s) through the middle of a: surface or sub-surface dam {mini dam) and/or slots or grooves on the: top of the refiner bars. It will be an area that will cause turbulence and force the fibers up on the bars where energy Is applied. Additionally_* a portion of the flow will be forcod through the slot creating an added feature in the plate where energy can be applied to the fibers,

[0037] In the embodiment disclosed in FIG, 3A -3D, the dimensions of the plate are as follows. The plate bars are spaced apart by 1.;6mm, with the groove depth between bars is 1.6mm. The plate bars are each about 8,35mm in width, and the width between slots is ,99nim. The slot depth is ,79mm, and the width of the slots in the bars is .79mm. The volume of all of the grooves is about 1 1.43 cubic inches, and the average bar angle is about 28.25 degrees off from straight lines through the piate center, in other embodiments,, other dimensions can be used,

[0038] In the embodiment disclosed in FIG. 4A -4D, the dimensions of the plate are as follows. The bars are 3,96mrn in width, and the; grooves between bars are 3,96mm in width. The grooves between bars are 7.14mm deep, and the overall plate groove volume is 59,21 cubic inches. The average bar angle is about 21.25 degrees off from straight lines through the plate center. The slots in the dams between bars_: are .78mm deep, and the width of the slots is 1.59mm,. In other embodiments, other dimensions can be used,

[0039] Any or all of the embodiments may be of a cast, machined or fabricated design. In one preferred embodiment, slots are cut in the bars and dams using wire electrical discharge machining.

[0040] As herein applied to the creation of CNF, the very unexpected discovery is the ability of the refining plates of this disclosure to maintain a significantly higher refiner loading at high fines level (above 90%), This had not been possible previously with more conventional plates. I n other words, the practice of this disclosure gives the abiiity to retain a load on the refiner to a much higher fines level than has previously been possible with the prior art.

[0041] FIG. 7 illustrates two attempts to refine pulp into CNF. In the Run U28 example, a convention non-aperture refiner plate was used, And in the Run 31 example, a conventional non-aperture refiner plate was used for several passes through the refiner, and then the refiner plate of this disclosure was used. More particularly, in Run 31 , a first Stage with with a non-aperture refiner plate ran for about 160 minutes at an average flow of 180 GPM using 1100 gallons of pulp, or 23 passes; and then a second Stage with another non-aperture refiner plate ran for about 130 minutes at an average flow _..of 140 GPM using 1 100 gallons of pulp, or about 16.5 passes; and then a third Stage with the aperture refiner plate of this disclosure ran for about 1.150 minutes at an average flow of 110 GPM again with 1 100 gallons of pulp, or about 1 15 passes.

[0042] FiG; 7 shows that not only do the_: aperture plates of this disclosure allow an over-ail higher power loading at high pulp fines levels, but the aperture plates of this disclosure also allow thai load to be sustained without refiner plate clash and extreme plate wear, as is seen when using conventional refiner plates when refining at high fines levels.

[0043] FIG, 7 also illustrates how,_, with the convention non-aperture refiner plate (Run U28), one can reach about 97% fines after expending about 8300 Gross kWh/t of energy. But note how, with the refiner plate of this disclosure, even greater fine levels can be achieved with more passes. Achieving such fine levels with the non- aperture refiner plate is not possible.

[0044] And, quite unexpectedly, it was discovered that, if one combines an initial number of passes of the pulp with the refiner plate without apertures, with subsequent passes with the refiner plate with apertures, then significantly higher fine levels can be achieved with less energy (Run 31). And, for those instances of where fine levels of about 98% are all that are required, then this approach results in substantial energy savings over the conventional approach (some 2000 Gross kWh/t savings). And where fine levels of 100% are required, then this result can be achieved with, about 6000 Gross kWh/t (Bun 31), where it can never be reached with the conventional approach (Run U28).

[0045] Various oiher features of this: disclosure are set forth in following claims.

Claims

1 A cellulose nanofibriis production method comprising the step of: refining pulp to- produce cellulose nanofibriis with a refining plate including an aperture at least partial through one of a dam or bar on a surface of the refining, plate.

2. The cellulose nanofibriis production method according to claim 1 wherein the aperture is a hole through a clam or bar,

3. The cellulose nanofibriis production method according to claim 1 wherein the aperture is a slot in a dam.

4. The cellulose nanofibriis procluciion method according to claim 1 wherein the aperture is a slot in the top of a dam.

5. The cellulose nanofibriis production method according to claim 1 wherein there are at least two bars, and the aperture is a slot In the side of a mini .dam halfway across the width of the groove from bar to bar.

6. The cellulose nanofibriis production method according to claim 1 wherein the aperture is a slot in the top of a bar.

7. The cellulose nanofibriis production method according to claim 1 wherein the aperture is a slot in the side of a bar.

B. A cellulose nanofibriis production method comprising the step of: refining pulp to produce cellulose nanofibriis with a refining plate by extruding fibers in an aperture in a. surface of the refining plate.

9. A cellulose nanofibrils production method . comprising: the step of: refining pulp to produce cellulose nanofibril with a refining plate including without an aperture at least partial through one of a dam or bar on a surface of the refining plate, and then

refining pulp to produce cellulose nanofibrils with a refining plate with a refining plate including an aperture at least partial through one of a dam or bar on the surface of the refining plate.