Abstract
A dewatering apparatus for cellulosic materials includes a chamber for an aqueous solution of a cellulosic material, an inner electrode in the chamber, an outer electrode in the chamber about the inner electrode, and a power supply connected to the inner electrode and the outer electrode applying a voltage potential across the electrodes to remove water associated with the aqueous solution and to dewater the cellulosic materials.
Claims
1. A dewatering method for cellulosic materials comprising: placing an aqueous solution of a cellulosic material in a chamber with an inner electrode and outer electrode about the inner electrode; applying a pulse and/or pulse reverse waveform across the inner and outer electrodes; rotating at least one electrode to apply a shear stress to the cellulosic material to decrease its viscosity; urging liquid material to migrate through the outer electrode; and urging solid material to migrate towards the inner electrode.
2. The method of claim 1 in which the outer electrode is a mesh electrode.
3. The method of claim 1 including rotating the inner electrode.
4. The method of claim 1 which the inner electrode includes protrusions.
5. The method of claim 4 in which the inner electrode includes fins, paddles, dimples, and/or one or more blades.
6. The method of claim 5 in which the paddles include edge wipers.
7. The method of claim 5 in which the inner electrode is in the form of an auger with a helical screw blade.
8. The method of claim 1 further including feeding the aqueous cellulosic material into the chamber from a hopper.
9. The method of claim 5 in which the paddles include mesh.
10. The method of claim 5 in which the paddles include one or more orifices therethough.
11. The method of claim 1 further including an intermediate electrode between the inner electrode and the outer electrode.
12. The method of claim 1 further including a separator about the outer electrode.
13. The method of claim 1 including rotating the outer electrode.
14. The method of claim 1 in which the dewatered cellulosic materials are 12-30 wt % solids.
15. A dewatering method for cellulosic material comprising: applying an electric field to the cellulosic material in a chamber to dewater the cellulosic material; and simultaneously stressing the cellulosic material to lower its viscosity to further dewater the cellulosic material.
16. The method of claim 15 in which the chamber includes an inner electrode and an outer electrode and applying an electric field to the cellulosic material includes providing a power supply connected to the inner and outer electrodes.
17. The method of claim 15 in which stressing the cellulosic material includes rotating the inner electrode and/or the outer electrode.
18. The method of claim 12 in which the inner electrode includes spaced protrusions extending therefrom.
19. The method of claim 18 in which the inner electrode includes fins, paddles, dimples, and/or one or more blades.
20. The method of claim 15 in which the dewatered cellulosic materials are 12-30 wt % solids.
21. The method of claim 15 including urging the liquid material to migrate through the outer electrode while urging solid material to migrate towards the inner electrode.
22. The method of claim 16 in which applying an electric field includes applying a pulse and/or pulse reverse waveform across the inner and outer electrodes.
23. A dewatering method for cellulosic materials, the method comprising: placing an aqueous solution of a cellulosic material in a chamber with an inner electrode and outer electrode about the inner electrode; applying a pulse/pulse reverse waveform across the inner and outer electrodes to apply an electric field to the cellulosic metal to dewater the cellulosic material; and while applying the pulse and/or pulse reverse waveform across the inner and outer electrodes, stressing the cellulosic material to decrease its viscosity and to further dewater the cellulosic material to between 12-30 wt % solids.
24. The method of claim 23 in which stressing the cellulosic material includes rotating at least one electrode.
25. The method of claim 23 in which the outer electrode is a mesh electrode.
26. The method of claim 23 including rotating the inner electrode.
27. The method of claim 23 which the inner electrode includes protrusions.
28. The method of claim 23 in which the inner electrode includes fins, mesh paddles, dimples, and/or one or more blades.
29. The method of claim 28 in which the paddles include edge wipers.
30. The method of claim 23 in which the inner electrode is in the form of an auger with a helical screw blade.
31. The method of claim 23 including urging the liquid material to migrate through the outer electrode while urging solid material to migrate through towards the inner electrode.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0022] Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:
[0023] FIG. 1 is a schematic representation of a generalized pulse reverse waveform;
[0024] FIG. 2 is a schematic representation of a generalized chopped AC waveform;
[0025] FIGS. 3A and 3B schematically illustrate suspensions of CNCs with (a) low and (b) high solids content;
[0026] FIGS. 4A and 4B schematically illustrate suspensions of CNFs with (a) low and (b) high solids content;
[0027] FIG. 5 schematically illustrates the change in viscosity of a non-Newtonian pseudoplastic fluid as a function of shear rate;
[0028] FIG. 6 schematically illustrates wall slip resulting in regions of higher and lower concentrations of nanocellulosic materials subjected to a rotating cylinder;
[0029] FIG. 7 schematically illustrates shear banding resulting in regions of higher and lower concentrations of nanocellulosic materials subjected to a rotating cylinder;
[0030] FIGS. 8A and 8B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode and a concentric mesh electrode;
[0031] FIGS. 9A and 9B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with protruding spines and a concentric mesh electrode;
[0032] FIGS. 10A and 10B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with dimples and a concentric mesh electrode;
[0033] FIGS. 11A and 11B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with mesh paddles and a concentric solid electrode;
[0034] FIGS. 12A and 12B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with mesh paddles with insulating wipers and a concentric solid electrode;
[0035] FIGS. 13A and 13B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with slotted paddles with insulating wipers and a concentric solid electrode;
[0036] FIGS. 14A and 14B schematically illustrate a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with holed paddles with insulating wipers and a concentric solid electrode;
[0037] FIG. 15 schematically illustrates a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode in electrical contact with an outer concentric mesh electrode and another concentric mesh electrode interspersed between the solid rod electrode and the outer concentric mesh electrode;
[0038] FIG. 16 schematically illustrates a cylindrical electrochemical cell with a nanocellulosic suspension with a solid rod electrode with holed paddles with insulating wipers and a concentric mesh electrode with a concentric microporous separator in a liquid catch basin;
[0039] FIG. 17 schematically illustrates a cylindrical tilted electrochemical cell with a nanocellulosic suspension with an inner auger electrode and a tilted outer concentric mesh electrode with an outer concentric microporous separator with a liquid catch basin and a concentrated nanoellulosic suspension catch basin;
[0040] FIGS. 18A and 18B show representative nanocellulosic samples before and after the dewatering trials for (A) CNC and (B) CNF;
[0041] FIGS. 19A and 19B show dewatered CNC and CNF samples (A) before re-dispersion in water and (B) after re-dispersion in water;
[0042] FIG. 20 is optical microscopy of CNCs before and after dewatering/redispersion; and
[0043] FIG. 21 is optical microscopy of CNFs before and after dewatering/redispersion.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.
[0045] In one preferred embodiment, electrochemical dewatering a suspension includes removing water from the suspension and thus the solids content of the suspension is increased to a range of approximately 15 to 70 wt %. Drying the suspension includes removing water from the suspension and thus the dry content of the suspension is preferably increased to a range of approximately >90 wt % solids content. By cellulose nanocrystals (CNCs), we mean cellulose particles, regions, or crystals that contain nanometer-sized domains, or both micron-sized and nanometer-sized domains. Larger domains, including long fibers may be present in cellulose nanocrystals. By cellulose nanofibers (CNFs), we mean cellulose fibers or regions that contain nanometer-sized particles or fibers, or both micron-sized and nanometer-sized particles or fibers. Larger domains, including long fibers may be present in cellulose nanofibers. By micron-sized, we mean dimensions of 1 μm to 100 μm. By nanometer-sized, we mean dimensions of 0.01 nm to 1000 nm or 1 μm. By nanocellulosic suspension we mean nanocellulose particles including cellulosic nanocrystals (CNCs), cellulosic nanofibers (CNFs), microfibrilated cellulose (MFC), nanofibrilated cellulose (NFC), bacterial cellulose (BC), bacterial nanocellulose (BNC) and the like or mixtures thereof in an aqueous solution.
[0046] ElectroDewatering is an electrochemical technology that utilizes direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage electric waveforms in conjunction with a cylindrical electrochemical cell for removal of water from an aqueous suspension of particulates such as cellulosic nanomaterials consisting of cellulosic nanocrystals (CNCs) of cellulosic nanofibers (CNFs) or mixtures thereof. While the instant invention is not bound by theory, this low-energy ElectroDewatering process may remove water by one or more mechanisms comprising Joule heating removal as water vapor, electrolysis removal as hydrogen and oxygen gas, electroosmotic transport of water to the cathode and electrophoretic transport of nanocellulosic material to the anode with subsequent removal of the liquid water from the cathode region, and/or creating regions of high nanocellulosic material content and low nanocellulosic material content due to the relative rotation of the anode and cathode with subsequent removal of liquid water from the low concentration nanocellulosic material region.
[0047] Joule heating, ohmic or resistive heating occurs when a high current is passed through a resistor, which creates interactions between charge carriers (usually electrons) and the body of the conductor and leads to an increase in temperature. More specifically, heating is generated rapidly and uniformly when applying a voltage across the nanocellulosic suspension due to the low conductivity of the nanocellulosic suspension. In some examples provide herein, the temperature of the cellulosic nanomaterials rapidly increases to ˜80-90° C. (lower than the boiling point of water thus preventing structural damage of the nanocellulose). At these temperatures, the water is drawn from the cellulosic nanomaterials into as a water vapor thereby concentrating the nanocellulosic suspension.
[0048] The nanocellulosic suspension may also be concentrated by the electrolysis of water via the following well know half-cell electrochemical reactions with positively charged protons, [0049] Anode (proton)—2H.sub.2O.fwdarw.O.sub.2+4H.sup.++4e.sup.− [0050] Cathode (proton)—4H.sup.++4e.sup.−.fwdarw.2H.sub.2 [0051] Net (proton)—2H.sub.2O.fwdarw.O.sub.2+2H.sub.2
And with negatively charged hydroxyl ions, [0052] Anode (hydroxyl)—4OH.sup.−.fwdarw.O.sub.2+2H.sub.2O+4e.sup.− [0053] Cathode (hydroxyl)—4H.sub.2O+4e.sup.−.fwdarw.2H.sub.2+40H.sup.− [0054] Net (hydroxyl)—2H.sub.2O.fwdarw.O.sub.2+2H.sub.2
With either the proton or hydroxyl ion the net reaction is the consumption of water and generation of hydrogen and oxygen gas.
[0055] Electroosmotic transport of water under the influence of an electric field towards the cathode is well known in the art and has been discussed in the context of dewatering of cellulose nanocrystals (J. Wetterling, K. Sahlin, T. Mattsson, G. Westman, H. Theliander “Electroosmotic dewatering of cellulose nanocrystals Cellulose (2018) 25:2321 to 2329).
[0056] Nanocellulosic materials in a water suspension are reported to exhibit a negative surface charge (T. Navab-Daneshmand, R. Beton, R. Hill, D. Frigon “Impact of Joule Heating and pH on Biosolids Electro-dewatering” Environ. Sci. Technol. 15 Dec. 2014). Electrophoretic transport of nanocellulosic materials under the influence of an electric field towards the positively charged anode is a possible mechanism for creating regions of high and low concentrations of nanocellulosic suspensions.
[0057] Due to the pseudoplastic behavior of the nanocellulosic suspensions, the relative rotation of the electrodes in the rotating cylindrical electrode apparatus may induce changes in the viscosity of the nanocellulosic suspensions to generate region of low and high concentration of nanocellulosic material.
[0058] Any or all of the above mechanisms of water removal and transport may be combined into an electrochemical dewatering method and apparatus for low energy concentration of particle suspensions in water such as nanocellulosic suspensions.
[0059] Direct current or constant voltage electric fields may be used for effective electrodewatering of nanocellulsoic suspensions at low energy consumption. Furthermore, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage may be used for effective electrodewatering of nanocellulsoic suspensions at low energy consumption. Pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage waveforms are interrupted, asymmetric waveforms characterized by an anodic or cathodic period and optionally followed by an off time and optionally followed by a cathodic or anodic period and optionally followed by an off time as shown in FIG. 1. These waveforms may be continued during the electrolytic process. The preferred waveform parameters are: (1) the anodic pulse current density, i.sub.anodic, (2) the anodic on-time, t.sub.anodic, (3) the anodic off-time, t.sub.off, anodic (4) the cathodic pulse current density, i.sub.cathodic, (5) the cathodic on-time, t.sub.cathodic, and (6) the cathodic off-time, t.sub.off, cathodic. In some embodiments all of these parameters are used to generate the appropriate electrodewatering waveform. In other embodiments, one or more of the off-time parameters may be absent. In still other embodiments the waveform parameters may consist of only anodic or cathodic pulses. One of skill in the art realizes that applying a pulse waveform to one electrode in an electrochemical cell automatically applies a waveform of opposite polarity to the other electrode in the electrochemical cell. By convention, the electrode which experiences the net anodic waveform is designated the anode and the electrode which experiences the net cathodic waveform is designated the cathode. The sum of the cathodic and anodic on-times and the off times is the period, T, of the waveform. The inverse of the period is the frequency, f, of the waveform. The cathodic, λ.sub.c, and anodic, λ.sub.α, duty cycles are the ratios of their respective on-times to the waveform period. The average current density (i.sub.avg) is given by:
i.sub.avg=i.sub.cλ.sub.c−i.sub.αλ.sub.α (1)
[0060] In pulse/pulse reverse process there are numerous combinations of peak current densities, duty cycles, and frequencies to obtain a given average current. These parameters provide the potential for much greater process control compared to direct current (DC).
[0061] With improvements in the output, control and accuracy of available pulse/pulse reverse power supplies, pulse/pulse reverse electrolytic processes have become more prevalent. In an ultimate production-scale device, a “chopped AC” waveform, schematically shown in FIG. 2, could be obtained by passing AC current through a properly tuned passive circuit comprising diodes, transformers, resistors, and other circuitry. In FIG. 2, the “active” region represents the voltage output delivered to the electrochemical cell while the “inactive” region represents the chopped part of the AC waveform which is not delivered to the cell. These chopped AC waveforms are potentially suitable for the proposed technology and afford superior power efficiency and highly favorable capital cost as compared to a fully functional, programmable pulse power supply.
[0062] Suspensions of cellulosic nanomaterials are non-Newtonian fluids including CNCs or CNFs, free water, and immobilized water bound to the CNCs or CNFs by hydrogen bonds. (see generally Li et. Al. “Cellulose Nanoparticles: Structure-Rheology Relationships” ACS Sustainable Chem. Eng. 3, 821-832 (2015)) In FIG. 3 we schematically illustrate low (FIG. 3A) and high (FIG. 3B) concentration suspensions of CNCs 10. The suspensions include CNCs 10 as well as immobilized water 20 bound to the CNCs 10 and free water 24 not bound to the CNCs 10. In FIG. 4, we schematically illustrate low (FIG. 4A) and high (FIG. 4B) concentration suspensions of CNFs 12. The suspensions include CNFs 12 as well as immobilized water 20 bound to the CNCs 10 and free water 24 not bound to the CNCs 10. In addition, due to the high aspect ratio of CNFs 12, these suspensions include regions of CNFs 12 entangled with other CNFs 12. The unique structure of aqueous suspensions results in a non-Newtonian pseudoplastic behavior.
[0063] As illustrated in FIG. 5, the application of force such as a shear stress from a rotating spindle causes a change in the viscosity of the suspension wherein the viscosity is inversely related to the applied force. The nanocellulosic suspensions are non-Newtonian fluids and exhibit pseudo plastic behavior as depicted in FIG. 5. Consequently, when exposed to a shear stress, such as a turning cylinder (with or without paddles) their viscosity decreases. The applied force could be a shear rate caused by the relative rotation of the electrodes in a rotating cylindrical electrode apparatus. The addition of protrusions or paddles attached to one or more of the electrodes creates additional force resulting in additional shear rate motion.
[0064] FIG. 6 schematically illustrates the wall slip effect during laminar shear flow generated by the relative rotation of smooth walled cylinders. (see generally Hubbe et. al. “Nanocellulose rheology” BioResources 12(4) 9556-9661 (2017)) In FIG. 6 an inner cylinder 2 is rotating within an outer cylinder 6. Contained within the inner cylinder 2 and outer cylinder 6 is a suspension of nanocellulosic materials. While FIG. 6 illustrates rotation of inner cylinder 2 while the outer cylinder 6 is stationary, one skilled in the art recognizes that the outer cylinder 6 could be rotating while the inner cylinder 2 is stationary or both the inner cylinder 2 and the outer cylinder 6 could be rotating. One feature of the illustration in FIG. 6 is the relative rotation of the inner cylinder 2 and the outer cylinder 6. This relative rotation of the inner cylinder 2 and the outer cylinder 6 leads to wall slip resulting in regions of low nanocellulosic material concentration 10a and regions of high nanocellulosic material concentration 10b. This non-Newtonian characteristic of nanocellulosic suspensions may be used to enhance the separation of water from nanocellulosic suspensions.
[0065] FIG. 7 schematically illustrates the shear banding effect generated by high relative rotation of smooth walled cylinders. At high relative rotation the laminar flow is disrupted. In FIG. 7 an inner cylinder 2 is rotating within an outer cylinder 6. Contained within the inner cylinder 2 and outer cylinder 6 is a suspension of nanocellulosic materials. While FIG. 7 illustrates rotation of inner cylinder 2 while the outer cylinder 6 is stationary, one skilled in the art recognizes that the outer cylinder 6 could be rotating while the inner cylinder 2 is stationary or both the inner cylinder 2 and the outer cylinder 6 could be rotating. One feature of the illustration in FIG. 7 is the high relative rotation of the inner cylinder 2 and the outer cylinder 6. This high relative rotation of the inner cylinder 2 and the outer cylinder 6 leads to Taylor vortices 4. These Taylor vortices 4 disrupt the laminar flow which occurs at low relative rotation resulting in bands of regions of low nanocellulosic material concentration 10a and regions of high nanocellulosic material concentration 10b. This non-Newtonian characteristic of nanocellulosic suspensions may be used to enhance the separation of water from nanocellulosic suspensions.
[0066] FIG. 8A schematically illustrates a cylindrical electrochemical cell 30 with a cylindrical solid rod inner electrode 32 and a concentric mesh outer electrode 34 within container 36. Power supply 37 is connected to inner electrode 32 and outer electrode 34 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. By rotating electrode 32 (and/or electrode 34), the viscosity of the material near the rotating electrode(s) decreases and the resulting mater migrates (e.g., by electromigration) through electrode 34 and into chamber 36. FIG. 8B depicts the solid inner rod electrode 32.
[0067] FIG. 9A schematically illustrates a cylindrical electrochemical cell 30 with a cylindrical solid rod inner electrode 32 with mixing protusions 38 to apply additional shear forces to the nanocellulosic suspension 31 and a concentric mesh outer electrode 34 within container 36. Power supply 37 is connected to inner electrode 32 and mesh outer electrode 34 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 preferably is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. FIG. 9B depicts inner electrode 32 with mixing protrusions 38.
[0068] In FIG. 10A, schematically illustrates a cylindrical electrochemical cell 30 with a cylindrical solid rod inner electrode 32 with dimples 39 to minimize wall slip forces to the nanocellulosic suspension 31 and a concentric mesh outer electrode 34 within container 36. Power supply 37 is connected to inner electrode 32 and mesh outer electrode 34 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. FIG. 10B depicts inner electrode 32 with dimples 39. Of course, one skilled in the art would recognize that equivalent features other than dimples 39 may be employed to eliminate the will slip effect at the inner electrode 32.
[0069] FIG. 11A schematically illustrates a cylindrical electrochemical cell 30 with a solid rod inner electrode 32 with mesh paddles 40 and a concentric solid outer electrode 35 within container 36. The addition of mesh paddles 40 to the rotating inner electrode 32 results in additional shear forces to the nanocellulosic material resulting in a higher water content near the surface of the mesh paddles 40 which may facilitate water removal from the nanocellulosic suspension 31. Power supply 37 is connected to inner electrode 32 and solid outer electrode 35 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. FIG. 11B depicts inner electrode 32 with mesh paddles 40.
[0070] FIG. 12A schematically illustrates a cylindrical electrochemical cell 30 with a solid rod innerelectrode 32 with mesh paddles 40 with insulating wipers 42 and a concentric solid outer electrode 35. The insulating wipers 42 provide a mechanical means for removing nanocellulosic suspension from the outer electrode 35 to prevent obstruction of the water movement. Power supply 37 is connected to inner electrode 32 and solid outer electrode 35 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. FIG. 12B depicts inner electrode 32 with mesh paddles 40 with insulating wipers 42.
[0071] FIG. 13A schematically illustrates a cylindrical electrochemical cell 30 with a solid rod inner electrode 32 with slotted paddles 44 with insulating wipers 42 and a concentric solid outer electrode 35. Power supply 37 is connected to inner electrode 32 and solid outer electrode 35 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. FIG. 13B depicts inner electrode 32 with slotted paddles 44 with insulating wipers 42.
[0072] FIG. 14A schematically illustrates a cylindrical electrochemical cell 30 with a solid rod inner electrode 32 with holed paddles 46 with insulating wipers 42 and a concentric solid outer electrode 35. Power supply 37 is connected to inner electrode 32 and solid outer electrode 35 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. FIG. 14B depicts inner electrode 32 with holed paddles 46 with insulating wipers 42.
[0073] FIG. 15 schematically illustrates a cylindrical electrochemical cell 30 with a solid inner electrode 32 in electrical contact with a concentric mesh outer electrode 34 and another mesh interspersed electrode 33 between the inner electrode 32 and mesh outer electrode 34. Power supply 37 is connected to inner electrode 32 in electrical contact with outer electrode 34 and interspersed electrode 35 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b.
[0074] FIG. 16 schematically illustrates a cylindrical electrochemical cell 30 containing a nanocellulosic suspension 31 with a solid rod inner electrode 32 with holed paddles 46 with insulating wipers 42 and a concentric mesh outer electrode 34 with an outer concentric porous separator 58. The porous separator 58 has pores which primarily permits water or low concentration nanocellulosic suspension 56 to pass through. The cylindrical electrochemical cell 30 has a bottom cap 50 and is sitting in liquid catch basin 54. During electrochemical dewatering liquid moves towards the mesh outer electrode 34 by one or more of the various mechanisms discussed herein or another mechanism and passes through the mesh outer electrode 34 and then through porous separator 58 and is collected in liquid catch basin 54 as water or low concentration nanocellulosic suspension 56. The contained liquid 56 consists of water or contains nanocelluslosic material of lower concentration than nanocellulosic suspension 31. Power supply 37 is connected to inner electrode 32 and outer electrode 34 to provide electric current or voltage across the electrochemical cell 30 containing the nanocellulosic suspension 31. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b.
[0075] In one embodiment, the mesh outer electrode 34 has larger pore sizes than separator 58 and thus separator 58 prevents cellulosic material from escaping from cell 30.
[0076] FIG. 17 schematically illustrates a cylindrical tilted electrochemical cell 70 with an inner auger electrode 72 and a tilted concentric mesh outer electrode 74 with an outer concentric porous separator 78 within container 76. Auger 72 includes a helical screw blade as shown. The porous separator 58 has pores which primarily permits water or low concentration nanocellulosic suspension to pass through. Nanocellulosic suspension 31 is feed to tilted electrochemical cell 70 from hopper 60. Power supply 37 is connected to inner electrode 72 and mesh outer electrode 74 to provide electric current or voltage across the electrochemical cell 70 containing the nanocellulosic suspension 31. The electrochemical cell 70 is equipped with a rotating mechanism to apply rotation to inner electrode 72. The inner electrode 72 may be rotated at a fixed or variable rotation rate by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The tilted electrochemical cell 70 may be operated at a titled angle, a ranging from 45-degree to the horizon, 90-degree to the horizon or horizontally. The cylindrical tilted electrochemical cell 70 may be operated in a continuous manner such that water or low concentration nanocellulosic suspension 82 passes through mesh outer electrode 74 and then through porous separator 78 and into liquid catch basin 84 and concentrated nanocellulosic suspension 86 passes into nanocellulosic catch basin 88.
[0077] One skilled in the art would readily recognize that in all of the illustrations, the anode may be the inner electrode and the cathode the outer electrode or the anode may be the outer electrode and the anode outer electrode. In addition, the outer electrode may be a solid electrode or a mesh electrode. The relative rotation may be varied during processing in order to maintain a constant viscosity as the solids concentration is increasing.
[0078] In the various rotating electrochemical apparatus described herein, the water vapor resulting from Joule heating and/or electrolysis escapes in a gaseous state to the surrounding atmosphere or may be recovered as liquid water in a condenser. In addition, water may be concentrated at the outer mesh cylinder by either or all of 1) the wall slip mechanism resulting from laminar shear flow, or 2) the shear banding mechanism resulting from disrupted laminar flow, or 3) electroosmotic water transport to the outer cathode, or 4) electrophoretic transport of nanocellulosic materials away from an outer cathode and towards an inner anode. The concentrated CNCs or CNFs remain in the electrodewatering apparatus as a batch processed material or the CNCs or CNFs are continuously collected from the extrusion apparatus.
[0079] The following examples illustrate various embodiments of the instant invention. All suspensions of CNCs and CNFs were obtained from American Process Inc. The beginning solids contents for the CNCs and CNFs were 3 wt % solids and 7 wt % solids, respectively.
Example I
[0080] In this example illustrated in FIG. 8 we used a cylindrical electrochemical cell 30 containing a nanocellulosic suspension 31 in container 36 with a mesh mixed metal oxide cylinder as the outer electrode 34 and a solid mixed metal oxide rod as the inner electrode 32 in a concentric arrangement. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The outer electrode 34 was polarized as the cathode and the inner electrode 32 was polarized as the anode. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 45 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. The data in Table I shows that the electrodewatering process increased the solid content of CNF from 3% to ˜18 wt % and CNC from 7% to ˜15 wt %. Representative picture of CNC from Trial #10 before and after dewatering are shown in FIG. 18A and of CNF before and after dewatering are shown in FIG. 18B. The dewatered samples of CNC (Trial #10) and CNF (Trial #11) were further characterized in terms of their ability to be re-dispersed and via optical analysis. As shown in FIG. 19, the dewatered samples (FIG. 19A) of CNC (Trial #10) and CNF (Trial #11) were easily re-dispersed in water (FIG. 19B) by mixing in water under vortex for two minutes. The dewatered samples of CNC (Trial #10) and CNF (Trial #11) were observed optically at 400X before dewatering of the CNCs (FIG. 20) and CNFs (FIG. 21). As demonstrated in the optical micrographs, the CNCs and CNFs look the same before and after dewatering and re-dispersion in water.
TABLE-US-00001 TABLE I Data acquired using a cylindrical mixed metal oxide mesh outer cathode 32 and a solid mixed metal oxide rod inner anode 34 in a concentric arrangement. Final Applied Polarization solid Potential time I.sub.max I.sub.end T.sub.max N.sub.2 content Trial Nanocellulose (V) (min) (A) (A) (° C.) Stirring purge (wt. %) 4 CNF 50 60 2.00 0.12 80 Yes Yes 18.50 5 CNF 50 60 2.30 0.20 90 Yes No 14.80 6 CNF 50 60 3.30 0.12 90 No Yes 13.60 7 CNF 50 30 2.65 0.12 90 No Yes 13.86 8 CNF 50 60 2.50 0.20 92 No Yes 16.90 9 CNF 60 15 3.50 0.09 90 No Yes 12.26 10 CNC 90 60 0.95 0.13 70 No Yes 15.10 11 CNF 50 60 3.00 0.15 90 No Yes 12.00
Example II
[0081] In this example illustrated in FIG. 11 we used an electrochemical cell 30 containing a nanocellulosic suspension 31 in container 36 with solid mixed metal oxide cylinder as the outer electrode 35 and solid mixed metal oxide rod as the inner electrode 32 with mesh mixed metal oxide mesh paddles 40. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The outer electrode 35 was polarized as the cathode and the inner electrode 32 was polarized as the anode. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 90 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 150 mL and was loaded with approximately 45 g of either CNF or CNC nanocellulosic suspension 31 for each trial. As shown in Table II, this design concept caused the nanocellulose to agglomerate on the inner surface of the solid mixed metal oxide rod inner electrode 32 which led to a decrease in the electrodewatering performance/final solid content as compared to setup without the impellers.
TABLE-US-00002 TABLE II Data acquired using a solid mixed metal oxide cylinder as the outer cathode 35 and solid mixed metal oxide rod inner anode 32 with mesh mixed metal oxide paddles 40. Final Applied Polarization solid Potential time I.sub.max I.sub.end N.sub.2 content Trial Nanocellulose (V) (min) (A) (A) Stirring purge (wt. %) 12 CNF 30 90 1.50 0.92 Yes No 8.55 13 CNF 30 120 2.00 0.50 Yes No 7.31 14 CNC 50 60 1.00 0.50 Yes No 12.67 15 CNC 50 60 0.90 0.65 Yes Yes 13.38 16 CNC 50 120 1.00 0.50 Yes No 10
Example III
[0082] In this example illustrated in FIG. 12 we used an electrochemical cell 30 containing a nanocellulosic suspension 31 (not shown) in container 36 with a solid mixed metal oxide cylinder as the outer electrode 35 and a solid mixed metal oxide rod as the inner electrode 32 with mixed metal oxide mesh paddles 40 with insulating wipers 42. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The outer electrode 35 was polarized as the cathode and the inner electrode 32 was polarized as the anode. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 35 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. Nitrogen at 1 psi was also used to sparge the nanocellulose suspension during the electrodewatering process. The data in Table III shows that the electrodewatering process increased the solid content of CNF from 3% to ˜15% and CNC from 7% to ˜20%.
TABLE-US-00003 TABLE III Data acquired using a solid mixed metal oxide cylinder as the outer cathode 34 and mixed metal oxide rod inner anode 32 with mixed metal oxide mesh paddles 40 with insulating wipers 42. Final Applied Polarization solid Potential time I.sub.max I.sub.end N.sub.2 content Trial Nanocellulose (V) (min) (A) (A) Stirring purge (wt. %) 17 CNF 50 60 4.00 0.10 Yes No 15.00 18 CNF 70 30 4.00 0.05 Yes No 9.00 19 CNC 100 30 0.50 0.05 Yes No 20.00 20 CNC 100 30 0.50 0.00 No No 14.54 21 CNC 100 30 2.00 0.03 Yes No 16.08 22 CNF 50 30 4.00 0.10 Yes No 13.00 23 CNF 50 30 4.00 0.10 Yes Yes 15.00
Example IV
[0083] In this example illustrated in FIG. 12, we used an electrochemical cell 30 containing a nanocellulosic suspension 31 in container 36 with a solid mixed metal oxide cylinder as the outer electrode 35 and a solid mixed metal oxide rod as the inner electrode 32 with a mesh mixed metal oxide mesh paddles 40 with insulating wipers 42. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 40 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In some trials the outer electrode 35 was polarized as the cathode and the inner electrode 32 was polarized as the anode and in other trials the outer electrode 35 was polarized as the anode and the inner electrode 32 was polarized as the cathode. The data in IV shows that the electrodewatering process increased the solid content of CNF from 3% to ˜17% and CNC from 7% to ˜14%.
TABLE-US-00004 TABLE IV Data acquired using a solid mixed metal oxide cylinder as the outer electrode 34 and mixed metal oxide rod inner electrode 32 with mixed metal oxide mesh paddles 40 with insulating wipers 42 Final Applied Polarization Energy Solid Nano- Potential I.sub.avg Time (kW Content Trial cellulose Anode Cathode (V) (A) (min) h/kg) (wt. %) 24 CNF Outer cylinder Inner rod 20 1.04 15 5 5 25 CNF Outer cylinder Inner rod 40 1.78 15 18 10 26 CNF Outer cylinder Inner rod 60 1.46 15 23 12 27 CNF Outer cylinder Inner rod 80 1.11 15 23 12 28 CNF Outer cylinder Inner rod 100 0.93 15 24 13 29 CNF Outer cylinder Inner rod 60 0.90 30 14 13 30 CNF Outer cylinder Inner rod 80 0.86 30 18 15 31 CNF Outer cylinder Inner rod 100 0.52 30 14 17 32 CNF Inner rod Outer cylinder 20 1.09 15 6 4 33 CNF Inner rod Outer cylinder 40 1.74 15 18 8 34 CNF Inner rod Outer cylinder 60 1.40 15 22 10 35 CNF Inner rod Outer cylinder 80 1.17 15 24 12 36 CNF Inner rod Outer cylinder 100 0.80 15 21 12 37 CNF Inner rod Outer cylinder 60 0.83 30 13 12 38 CNF Inner rod Outer cylinder 80 0.44 30 9 9 39 CNF Inner rod Outer cylinder 100 0.37 30 10 11 40 CNC Outer cylinder Inner rod 60 0.45 15 3 8 41 CNC Outer cylinder Inner rod 80 0.56 15 5 11 42 CNC Outer cylinder Inner rod 100 0.58 15 7 11 43 CNC Outer cylinder Inner rod 60 0.32 30 2 11 44 CNC Outer cylinder Inner rod 80 0.35 30 3 12 45 CNC Outer cylinder Inner rod 100 0.32 30 4 12 46 CNC Inner rod Outer cylinder 60 0.31 15 2 9 47 CNC Inner rod Outer cylinder 80 0.42 15 4 13 48 CNC Inner rod Outer cylinder 100 0.58 15 7 13 49 CNC Inner rod Outer cylinder 60 0.27 30 2 10 50 CNC Inner rod Outer cylinder 80 0.31 30 3 10 51 CNC Inner rod Outer cylinder 100 0.34 30 4 14 The observed power density for CNF under constant voltage operating conditions are 24 kW h per kg at ~14 wt. % solids. The observed power density for CNC under constant voltage operating conditions are 7 kW h per kg at ~12 wt. % solids.
Example V
[0084] In this example illustrated in FIG. 13 we used an electrochemical cell 30 containing a nanocellulosic suspension 31 in container 36 with solid mixed metal oxide cylinder as the outer electrode 35 and a platinized titanium rod as the inner electrode 32 with platinized titanium slotted paddles 44 with insulating wipers 42. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 40 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In some trials the outer electrode 35 was polarized as the cathode and the inner electrode 32 was polarized as the anode and in other trials the outer electrode 35 was polarized as the anode and the inner electrode 32 was polarized as the cathode. The data in V shows that the electrodewatering process increased the solid content of CNF from 3% to ˜17% and CNC from 7% to ˜16%.
TABLE-US-00005 TABLE V Data acquired using a solid mixed metal oxide cylinder as the outer electrode 34 and platinized titanium rod inner electrode 32 with platinized titanium slotted paddles 40 with insulating wipers 42 Final Applied Polarization Energy Solid Nano- Potential I.sub.avg Time (kW Content Trial cellulose Anode Cathode (V) (A) (min) h/kg) (wt. %) 52 CNF Outer Inner rod 20 1.56 15 8 4 cylinder 53 CNF Outer Inner rod 40 2.29 15 24 11 cylinder 54 CNF Outer Inner rod 60 1.42 15 22 11 cylinder 55 CNF Outer Inner rod 80 1.14 15 24 11 cylinder 56 CNF Outer Inner rod 100 0.99 15 26 17 cylinder 57 CNF Outer Inner rod 60 0.90 30 14 11 cylinder 58 CNF Outer Inner rod 80 0.69 30 14 13 cylinder 59 CNF Outer Inner rod 100 0.55 30 14 16 cylinder 60 CNF Inner rod Outer 20 0.78 15 4 5 cylinder 61 CNF Inner rod Outer 40 1.65 15 17 7 cylinder 62 CNF Inner rod Outer 60 1.20 15 19 8 cylinder 63 CNF Inner rod Outer 80 0.94 15 19 8 cylinder 64 CNF Inner rod Outer 100 0.62 15 16 9 cylinder 65 CNF Inner rod Outer 60 0.63 30 10 9 cylinder 66 CNF Inner rod Outer 80 0.34 30 7 9 cylinder 67 CNF Inner rod Outer 100 0.34 30 9 8 cylinder 68 CNC Outer Inner rod 60 0.43 15 3 7 cylinder 69 CNC Outer Inner rod 80 0.57 15 5 10 cylinder 70 CNC Outer Inner rod 100 0.59 15 7 13 cylinder 71 CNC Outer Inner rod 60 0.53 30 4 10 cylinder 72 CNC Outer Inner rod 80 0.51 30 5 15 cylinder 73 CNC Outer Inner rod 100 0.39 30 4 15 cylinder 74 CNC Inner rod Outer 60 0.33 15 2 9 cylinder 75 CNC Inner rod Outer 80 0.45 15 4 11 cylinder 76 CNC Inner rod Outer 100 0.58 15 7 10 cylinder 77 CNC Inner rod Outer 60 0.38 30 3 8 cylinder 78 CNC Inner rod Outer 80 0.38 30 3 9 cylinder 79 CNC Inner rod Outer 100 0.36 30 4 16 cylinder
Example VI
[0085] In this example illustrated in FIG. 13 we used an electrochemical cell 30 containing a nanocellulosic suspension 31 in container 36 with a solid platinized titanium cylinder as the outer electrode 35 and a solid platinized titanium rod as the inner electrode 32 with platinized titanium slotted paddles 44 with insulating wipers 42. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 40 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In some trials the outer electrode 35 was polarized as the cathode and the inner electrode 32 was polarized as the anode and in other trials the outer electrode 35 was polarized as the anode and the inner electrode 32 was polarized as the cathode. The data in VI shows that the electrodewatering process increased the solid content of CNF from 3% to ˜18% and CNC from 7% to ˜14%. Operating the system in different polarity did not show any significant correlation for CNC. However, eletrodewatering process while using Pt beaker as anode demonstrated higher final solid content in comparison to using Pt impeller as anode for CNF.
TABLE-US-00006 TABLE VI Data acquired using a solid platinized titanium cylinder as the outer electrode 35 and platinized titanium rod inner electrode 32 with platinized titanium slotted paddles 40 with insulating wipers 42 Final Applied Polarization Energy Solid Nano- Potential I.sub.avg Time (kW Content Trial cellulose Anode Cathode (V) (A) (min) h/kg) (wt. %) 80 CNF Inner rod Outer 20 1.06 15 5 4 cylinder 81 CNF Inner rod Outer 40 1.96 15 20 7 cylinder 82 CNF Inner rod Outer 60 1.23 15 19 7 cylinder 83 CNF Inner rod Outer 80 0.81 15 17 10 cylinder 84 CNF Inner rod Outer 100 1.22 15 32 8 cylinder 85 CNF Outer Inner rod 20 1.43 15 7 5 cylinder 86 CNF Outer Inner rod 40 2.11 15 21 9 cylinder 87 CNF Outer Inner rod 60 1.67 15 26 11 cylinder 88 CNF Outer Inner rod 80 1.25 15 26 11 cylinder 89 CNF Outer Inner rod 100 1.07 15 28 14 cylinder 90 CNF Outer Inner rod 60 0.91 30 14 11 cylinder 91 CNF Outer Inner rod 80 0.70 30 15 16 cylinder 92 CNF Outer Inner rod 100 0.60 30 15 18 cylinder 93 CNC Outer Inner rod 60 0.26 15 2 9 cylinder 94 CNC Outer Inner rod 80 0.61 15 6 11 cylinder 95 CNC Outer Inner rod 100 0.64 15 7 14 cylinder 96 CNC Outer Inner rod 60 0.47 30 3 11 cylinder 97 CNC Outer Inner rod 80 0.41 30 4 13 cylinder 98 CNC Outer Inner rod 100 0.37 30 4 13 cylinder
Example VII
[0086] In this example illustrated in FIG. 14 we used an electrochemical cell 30 with a nanocellulosic suspension 31 in a container 36 with solid platinized titanium cylinder as the outer electrode 35 and a mixed metal oxide rod as the inner electrode 32 with mixed metal oxide holed paddles 46 with insulating wipers 42. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 40 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In some trials the outer electrode 35 was polarized as the cathode and the inner electrode 32 was polarized as the anode and in other trials the outer electrode 35 was polarized as the anode and the inner electrode 32 was polarized as the cathode. The data in VII shows that the electrodewatering process increased the final solid content of CNF from 3% to ˜18% and CNC from 7% to ˜14%.
TABLE-US-00007 TABLE VII Data acquired using a solid platinized titanium cylinder as the outer electrode 35 and mixed metal oxide rod inner electrode 32 with mixed metal oxide holed paddles 46 with insulating wipers 42 Final Applied Polarization Energy Solid Nano- Potential I.sub.avg Time (kW Content Trial cellulose Anode Cathode (V) (A) (min) h/kg) (wt. %) 99 CNF Inner rod Outer cylinder 20 1.01 15 5 5 100 CNF Inner rod Outer cylinder 40 1.98 15 21 8 101 CNF Inner rod Outer cylinder 60 1.25 15 19 8 102 CNF Inner rod Outer cylinder 80 0.89 15 18 11 103 CNF Inner rod Outer cylinder 100 0.62 15 16 11 104 CNF Inner rod Outer cylinder 60 0.59 30 9 10 105 CNF Inner rod Outer cylinder 80 0.38 30 8 8 106 CNF Inner rod Outer cylinder 100 0.29 30 7 10 107 CNF Outer cylinder Inner rod 20 1.72 15 9 5 108 CNF Outer cylinder Inner rod 40 2.06 15 21 10 109 CNF Outer cylinder Inner rod 60 1.48 15 23 13 110 CNF Outer cylinder Inner rod 80 1.04 15 22 11 111 CNF Outer cylinder Inner rod 100 0.98 15 25 15 112 CNF Outer cylinder Inner rod 60 0.85 30 13 13 113 CNF Outer cylinder Inner rod 80 0.67 30 14 13 114 CNF Outer cylinder Inner rod 100 0.57 30 15 14 115 CNC Inner rod Outer cylinder 60 0.37 15 3 11 116 CNC Inner rod Outer cylinder 80 0.54 15 5 12 117 CNC Inner rod Outer cylinder 100 0.66 15 8 12 118 CNC Inner rod Outer cylinder 60 0.42 30 3 10 119 CNC Inner rod Outer cylinder 80 0.32 30 3 13 120 CNC Inner rod Outer cylinder 100 0.44 30 5 14 121 CNC Outer cylinder Inner rod 60 0.19 15 1 9 122 CNC Outer cylinder Inner rod 80 0.56 15 5 10 123 CNC Outer cylinder Inner rod 100 0.56 15 6 12 124 CNC Outer cylinder Inner rod 60 0.13 30 1 7 125 CNC Outer cylinder Inner rod 80 0.27 30 3 11 126 CNC Outer cylinder Inner rod 100 0.34 30 4 14
Example VIII
[0087] In this example illustrated in FIG. 15 we used an electrochemical cell 30 with a nanocellulosic suspension 31 in container 36 with a mesh mixed metal oxide cylinder as the outer electrode 34 in electrical contact with a solid mixed metal oxide rod as the inner electrode 32 and a mesh mixed metal oxide cylinder interspersed electrode 33 positioned between outer electrode 34 and inner electrode 32. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. Relative rotation of the assembly was not employed in these tests. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In some trials the outer electrode 34 in electrical contact with inner electrode 32 was polarized as the cathode and the interspersed electrode 33 was polarized as the anode and in other trials the outer electrode 34 in electrical contact with the inner electrode 32 was polarized as the anode and the interspersed electrode 33 was polarized as the cathode. The data in VIII shows that the electrodewatering process increased the final solid content of CNF from 3% to ˜21% and CNC from 7% to ˜28%.
TABLE-US-00008 TABLE VIII Data acquired using a mesh mixed meal oxide cylinder as the outer electrode 34 in electrical contact with a mixed metal oxide rod inner electrode 32 and a mixed metal oxide cylinder interspersed electrode 33 positioned between outer electrode 34 and inner electrode 32. Final Applied Polarization Energy Solid Nano- Potential I.sub.avg Time (kW Content Trial cellulose Anode Cathode (V) (A) (min) h/kg) (wt. %) 127 CNF Inner-Outer Interspersed 20 1.07 15 6 4 electrode electrode 128 CNF Inner-Outer Interspersed 40 2.17 15 23 10 electrode electrode 129 CNF Inner-Outer Interspersed 60 1.65 15 26 18 electrode electrode 130 CNF Inner-Outer Interspersed 80 1.32 15 27 19 electrode electrode 131 CNF Inner-Outer Interspersed 100 1.09 15 28 19 electrode electrode 132 CNF Inner-Outer Interspersed 60 1.07 30 17 14 electrode electrode 133 CNF Inner-Outer Interspersed 80 0.74 30 15 17 electrode electrode 134 CNF Inner-Outer Interspersed 100 0.61 30 16 21 electrode electrode 135 CNF Interspersed Inner-Outer 20 2.93 15 15 5 electrode electrode 136 CNF Interspersed Inner-Outer 40 2.24 15 23 8 electrode electrode 137 CNF Interspersed Inner-Outer 60 1.71 15 27 12 electrode electrode 138 CNF Interspersed Inner-Outer 80 1.40 15 29 12 electrode electrode 139 CNF Interspersed Inner-Outer 100 1.05 15 27 15 electrode electrode 140 CNF Interspersed Inner-Outer 60 1.12 30 17 11 electrode electrode 141 CNF Interspersed Inner-Outer 80 0.88 30 18 14 electrode electrode 142 CNF Interspersed Inner-Outer 100 0.65 30 17 16 electrode electrode 143 CNC Inner-Outer Interspersed 60 1.06 15 7 14 electrode electrode 144 CNC Inner-Outer Interspersed 80 1.10 15 10 17 electrode electrode 145 CNC Inner-Outer Interspersed 100 0.90 15 10 17 electrode electrode 146 CNC Inner-Outer Interspersed 60 0.89 30 6 14 electrode electrode 147 CNC Inner-Outer Interspersed 80 0.65 30 6 16 electrode electrode 148 CNC Inner-Outer Interspersed 100 0.55 30 6 28 electrode electrode 149 CNC Interspersed Inner-Outer 60 1.29 15 9 12 electrode electrode 150 CNC Interspersed Inner-Outer 80 1.15 15 11 20 electrode electrode 151 CNC Interspersed Inner-Outer 100 0.96 15 11 19 electrode electrode 152 CNC Interspersed Inner-Outer 60 0.83 30 6 14 electrode electrode 153 CNC Interspersed Inner-Outer 80 0.54 30 5 14 electrode electrode 154 CNC Interspersed Inner-Outer 100 0.55 30 6 17 electrode electrode
Example IX
[0088] In this example illustrated in FIG. 12 we used an electrochemical cell 30 with a nanocellulosic suspension 31 in container 36 with a solid mixed metal oxide cylinder as the outer electrode 35 and a solid mixed metal oxide rod as the inner electrode 32 with a mesh mixed metal oxide mesh paddles 40 with insulating wipers 42. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 40 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 50 mL and was loaded with approximately 25 g of either CNF or CNC nanocellulosic suspension 31 for each trial. The inner electrode 32 was polarized as an anode and the outer electrode 35 was polarized as a cathode. The results for the CNF trials are detailed in IX and the results for the CNC trials are detailed in X. For the CNF experiments under DC polarization, the solids content increased from 3% to 15% and consumed 24 kW-hr/kg. Under various pulsing conditions, the CNF solids content increased from 3% to 10-14% and consumed from 7 to 15 kW-hr/kg. For the CNC experiments under DC polarization, the solids content increased from 7% to 11% and consumed 7 kW-hr/kg. Under the best pulsing conditions, the CNC solids content increased from 7% to 13% and consumed 1 kW-hr/kg.
TABLE-US-00009 TABLE IX Trials conducted on CNF using a solid mixed metal oxide cylinder as the outer electrode 32 and a solid mixed metal oxide rod as the inner electrode 32 with a mesh mixed metal oxide mesh paddles 40 with insulating wipers 42. Final Applied Average Average Energy Solid DC/Pulse Potential Potential Frequency Duty Current Time (kW Content Trial process (V) (V) (Hz) Cycle (A) (min) h/kg) (wt. %) 28 DC 100 100 N/A 100 0.93 15 24 13 (DC) 155 Pulse 100 25 10 25 1.81 15 12 12 156 Pulse 100 50 10 50 0.57 15 7 14 157 Pulse 100 25 1 25 3.04 15 15 12 158 Pulse 100 50 1 50 1.65 15 13 14 159 Pulse 200 100 10 50 0.39 15 10 10 160 Pulse 200 100 1 50 0.45 15 12 12
TABLE-US-00010 TABLE X Trials conducted on CNC using solid mixed metal oxide cylinder as the outer electrode 32 and a solid mixed metal oxide rod as the inner electrode 32 with a mesh mixed metal oxide mesh paddles 40 with insulating wipers 42. Final Applied Average Average Energy Solid DC/Pulse Potential Potential Frequency Duty Current Time (kW Content Trial process (V) (V) (Hz) Cycle (A) (min) h/kg) (wt. %) 42 DC 100 100 N/A 100 0.58 15 7 11 (DC) 161 Pulse 100 25 10 25 0.37 15 1 7 162 Pulse 100 50 10 50 0.22 15 1 13 163 Pulse 100 75 10 75 0.32 15 3 11 164 Pulse 100 25 1 25 0.25 15 1 8 165 Pulse 100 50 1 50 0.45 15 2 7 166 Pulse 200 100 1 50 0.20 15 2 12
Example X
[0089] In this example illustrated in FIG. 16 we used an electrochemical cell 30 with a nanocellulosic suspension 31 with a solid mixed metal oxide inner electrode 32 with mixed metal oxide holed paddles 46 with insulating wipers 42 and a concentric mixed metal oxide mesh outer electrode 34 with an outer concentric porous separator 58. The cylindrical electrochemical cell 30 has a non-conducting bottom cap 50 and is sitting in liquid catch basin 54. The porous separator 58 is non-conducting and primarily permits water or low concentration nanocellulosic suspension 31 to pass through and be captured as contained liquid 56 in liquid catch basin 54. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 75 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 185 mL and was loaded with approximately 45 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In some trials the outer electrode 34 was polarized as the cathode and the inner electrode 32 was polarized as the anode and in other trials the outer electrode 34 was polarized as the anode and the inner electrode 32 was polarized as the cathode. The data in XI shows that when the cathode was the mixed metal oxide inner electrode 32 the electrodewatering process with a run time of 15 minutes increased the solid content of CNF from 3% to 13.21% with an energy consumption of 17.88 kW-hr/kg. When the cathode was the concentric mixed metal oxide mesh outer electrode 34 the electrodewatering process with a run time of 15 minutes increased the solid content of CNF from 3% to 19.66% with an energy consumption of 11.49 kW-hr/kg. When the cathode was the concentric mixed metal oxide mesh outer electrode 34 the electrodewatering process with a run time of 30 minutes increased the solid content of CNF from 3% to 26.35 to 28.04% with an energy consumption of 17.80 to 22.59 kW-hr/kg. When the cathode was the mixed metal oxide inner electrode 32 the electrodewatering process with a run time of 15 minutes increased the solid content of CNC from 7% to 9.93% with an energy consumption of 5.54 kW-hr/kg. When the cathode was the concentric mixed metal oxide mesh outer electrode 34 the electrodewatering process with a run time of 15 minutes increased the solid content of CNC from 7% to 18.2% with an energy consumption of 2.31 kW-hr/kg. When the cathode was the concentric mixed metal oxide mesh outer electrode 34 the electrodewatering process with a run time of 30 minutes increased the solid content of CNC from 7% to 21.78 to 22.07% with an energy consumption of 2.92 to 2.96 kW-hr/kg.
TABLE-US-00011 TABLE XI Data acquired using a cylinder mixed metal oxide mesh outer electrode 34 with a concentric porous separator 58 and mixed metal oxide rod inner electrode 32 with mixed metal oxide holed paddles 46 with insulating wipers 42. Applied Final solid Nano- Potential Time content Energy Energy Trial cellulose Anode Cathode (V) (min) (wt. %) (Wh) (kWh/kg) 32-II CNF Inner rod Outer 100 15 19.66 15.51 11.49 cylinder 25-II CNF Inner rod Outer 100 30 26.35 25.57 18.94 cylinder 26-II CNF Inner rod Outer 100 30 28.04 30.50 22.59 cylinder 27-II CNF Inner rod Outer 90 30 17.54 10.56 7.82 cylinder 42-II CNF Inner rod Outer 100 30 26.51 24.03 17.8 cylinder 40-II CNF Outer Inner rod 100 15 13.21 24.14 17.88 cylinder 38-II CNC Inner rod Outer 100 15 18.2 7.29 2.31 cylinder 39-II CNC Inner rod Outer 100 60 29.01 12.99 4.12 cylinder 34-II CNC Inner rod Outer 100 30 21.78 9.31 2.96 cylinder 44-II CNC Inner rod Outer 100 30 22.07 9.20 2.92 cylinder 41-II CNC Outer Inner rod 100 15 9.93 17.45 5.54 cylinder
Example XI
[0090] In this example illustrated in FIG. 16 we used an electrochemical cell 30 with a nanocellulosic suspension 31 with a solid mixed metal oxide inner electrode 32 with mixed metal oxide holed paddles 46 with insulating wipers 42 and a concentric mixed metal oxide mesh outer electrode 34 with an outer concentric porous separator 58. The cylindrical electrochemical cell 30 has a non-conducting bottom cap 50 and is sitting in liquid catch basin 54. The porous separator 58 is non-conducting and primarily permits water or low concentration nanocellulosic suspension 31 to pass through and be captured as contained liquid 56 in liquid catch basin 54. A power supply 37 capable of delivering direct current or constant voltage, pulse current or pulse voltage, or pulse reverse current or pulse reverse voltage is in electrical contact with the electrochemical cell 30. The electrochemical cell 30 is equipped with a rotating mechanism to apply rotation to inner electrode 32. The inner electrode 32 was rotated at a fixed 75 rpm by drive motor 90 and rotating shaft 96 via belt 92 and pulley 94a and pulley 94b. The electrochemical cell 30 had a volume of approximately 185 mL and was loaded with approximately 45 g of either CNF or CNC nanocellulosic suspension 31 for each trial. In these trials the outer electrode 34 was polarized as the cathode and the inner electrode 32 was polarized as the anode. The data in XII shows that the electrodewatering process with a run time of 15 minutes with pulse current (voltage) of 100 V at 75% duty cycle and 100 Hz frequency, the solid content of CNF increased from 3% to 20.6% with an energy consumption of 11.7 kW-hr/kg. With a run time of 15 minutes with pulse current (voltage) of 150 V at 75% duty cycle and 100 Hz frequency, the solid content of CNF increased from 3% to 22.5% with an energy consumption of 12.21 kW-hr/kg. With a run time of 30 minutes with pulse current (voltage) of 100 V at 75% duty cycle and frequencies in the range to 1 to 1000 Hz, the solid content of CNF increased from 3% to 21.1 to 34.1% with an energy consumption of 14.01 to 17.35 kW-hr/kg. The electrodewatering process with a run time of 15 minutes with a pulse current (voltage) of 100 V at a 75% duty cycle and 100 Hz frequency, the solid content of CNC from 7% to 19.3% with an energy consumption of 3.67 kW-hr/kg. With a run time of 15 minutes with a pulse current (voltage) of 180 V at a 75% duty cycle and 100 Hz frequency, the solid content of CNC from 7% to 26.9% with an energy consumption of 2.38 kW-hr/kg. With a run time of 30 minutes with a pulse current (voltage) of 100 V at 75% duty cycle and 100 Hz frequency, the solid content of CNC increased from 7% to 24.8% with an energy consumption of 7.69 kW-hr/kg. With a run time of 30 minutes with a pulse current (voltage) of 180 V at 50% duty cycle and 100 Hz frequency, the solid content of CNC increased from 7% to 25.1% with an energy consumption of 2.23 kW-hr/kg.
TABLE-US-00012 TABLE XII Data acquired using a cylinder mixed metal oxide mesh outer electrode 34 with a concentric porous separator 58 and mixed metal oxide rod inner electrode 32 with mixed metal oxide holed paddles 46 with insulating wipers 42. Applied Average Duty Final solid Energy Nano- Potential Potential Time T.sub.ON T.sub.OFF Frequency Cycle content Energy (kWh/ Trial cellulose (V) (V) (min) (ms) (ms) (Hz) (%) (wt. %) (Wh) kg) 45-II CNF 100 75 30 750 250 1 75 21.1 18.91 14.01 46-II CNF 100 75 30 75 25 10 75 25.7 21.75 16.11 47-II CNF 100 75 30 7.5 2.5 100 75 33.0 23.39 17.33 48-II CNF 100 75 30 0.75 0.25 1000 75 34.1 22.56 16.71 49-II CNF 100 50 30 500 500 1 50 20.9 12.04 8.92 50-II CNF 100 50 30 50 50 10 50 22.2 13.20 9.78 51-II CNF 100 50 30 5 5 100 50 26.4 13.06 9.67 52-II CNF 100 50 30 0.5 0.5 1000 50 25.1 12.00 8.89 53-II CNF 100 25 30 250 750 1 25 7.4 4.07 3.01 54-II CNF 100 25 30 25 75 10 25 10.7 4.42 3.28 55-II CNF 100 25 30 2.5 7.5 100 25 10.4 3.68 2.73 56-II CNF 100 25 30 0.25 0.75 1000 25 11.3 4.04 2.99 57-II CNF 100 75 40 7.5 2.5 100 75 43.3 27.82 20.60 58-II CNF 100 50 60 0.5 0.5 100 50 29.3 18.84 11.73 59-II CNF 100 25 120 25 75 100 25 15.2 3.77 2.79 60-II CNF 100 75 40 7.5 2.5 100 75 40.5 26.77 19.83 61-II CNF 100 75 15 7.5 2.5 100 75 20.6 15.8 11.7 62-II CNF 100 75 60 7.5 2.5 100 75 44.9 32.53 24.1 63-II CNC 100 75 30 7.5 2.5 100 75 24.8 24.23 7.69 64-II CNC 100 75 40 7.5 2.5 100 75 30.1 31.29 9.93 65-II CNC 100 75 60 7.5 2.5 100 75 41.5 42.58 13.52 66-II CNC 100 75 90 7.5 2.5 100 75 61.3 58.65 18.62 67-II CNC 100 50 60 0.5 0.5 100 50 22.1 23.79 7.56 68-II CNC 100 25 120 2.5 7.5 100 25 16.8 10.24 3.25 69-II CNC 100 75 15 7.5 2.5 100 75 19.3 11.57 3.67 70-II CNC 133 99.75 30 7.5 2.5 100 75 26.7 12.44 3.95 71-II CNC 150 112.5 30 7.5 2.5 100 75 32.5 10.33 3.28 72-II CNC 180 135 30 7.5 2.5 100 75 40.8 11.30 3.59 73-II CNC 180 135 15 7.5 2.5 100 75 26.9 7.49 2.38 74-II CNC 180 135 5 7.5 2.5 100 75 19.7 4.33 1.37 75-II CNC 100 50 30 5 5 100 50 21.0 10.14 3.22 76-II CNC 180 135 30 5 5 100 50 25.1 7.02 2.23 77-II CNC 180 135 30 7.5 2.5 100 75 — — — 78-II CNC 100 100 30 — — — — — — — 79-II CNC 180 135 60 7.5 2.5 100 75 53.9 14.7 4.67 80-II CNC 180 135 90 7.5 2.5 100 75 68.3 16.17 5.13 81-II CNC 180 135 120 7.5 2.5 100 75 70.0 17.43 5.53 82-II CNF 180 135 5 7.5 2.5 100 75 19.2 11.49 8.52 83-II CNF 180 135 15 7.5 2.5 100 75 Charring* 84-II CNF 150 112.5 15 7.5 2.5 100 75 22.5 16.48 12.21 85-II CNF 150 112.5 30 7.5 2.5 100 75 Charring* 86-II CNF 133 99.75 40 7.5 2.5 100 75 Charring*
Example XII
[0091] Selected samples were selected from the previous studies to access the ability of the electrodewatered samples to be re-dispersed. The re-dispersion was conducted using a vortex mixer with a 0.2 wt % sample of electrodewatered nanocellulosic material in water for 10 minutes. The results are presented in Table XIII For CNC suspensions of approximately 26 to 30 wt %, the samples were able to be dispersed. For CNF suspensions of approximately 18 to 23 wt %, the samples were able to be dispersed. These are approximately the same limits reported for more energy intensive dewatering techniques.
TABLE-US-00013 TABLE XIII Re-dispersion results. Solids Redispersable content within 10 min Hornification Nanocellulose Trial (wt. %) under vortex observed CNC 38-II 18.3 Yes No CNC 67-II 21.7 Yes No CNC 70-II 26.0 Yes No CNC 39-II 29.0 Not quite Some small agglomerates CNC 66-II 61.3 No Yes CNC 144 17.0 Yes No CNF 27-II 18.4 Yes No CNF 84-II 23.3 Not quite Some small agglomerates CNF 46-II 26.0 No Yes CNF 58-II 29.0 No Yes CNF 62-II 44.9 No Yes CNF 130 19.0 Yes No
[0092] Although the figures illustrate that the central inner electrode 32 is rotating, the instant invention is not bound by which electrode is in rotation as either the inner electrode 32 or outer electrode 34 may be rotating or both inner electrode 32 and outer electrode 34 may be rotating. Furthermore, the figures illustrate the inner electrode 32 as the anode (positive polarity) and the outer electrode 34 as the cathode (negative polarity), however in some embodiments the inner electrode 32 may be the cathode (negative polarity) and the outer electrode 34 may be the anode (positive polarity). By the relative rotation of inner electrode 32 and outer electrode 34 the concentration of the nanocellulosic material near the rotating electrode surfaces decreases and the water may pass a mesh outer electrode 34 into container 36. This transport of water to the mesh outer 34 is further enhanced by electroosmosis transport of water to the mesh outer cathode 34. In addition, this transport of water to the mesh outer 34 is further enhanced by centrifugal forces due to the relative rotation of the inner electrode 32 and outer electrode 34 causing the nanocellulosic material suspension to rotate. In addition, the nanocellulosic material is concentrated at the inner electrode 32 surface by electrophoretic movement. Additionally, as an electric current is applied to cylindrical electrochemical cell 30 though the nanonocellulosic material suspension resulting in Joule heating, water is removed from the nanocellulosic suspension by evaporation. In addition, due to the application of an electric current to the cylindrical electrochemical cell 30 water is removed by the electrolysis reactions at the mesh outer cathode 34 and inner anode 32.
[0093] One aspect of a preferred embodiment is to provide a process and apparatus for dewatering aqueous suspensions of nanocellulosic materials, such as cellulosic nanocrystals (CNCs), cellulosic nanofibers (CNFs) and mixtures thereof in an improved manner with a reduced cost.
[0094] Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. Other embodiments will occur to those skilled in the art and are within the following claims.
[0095] In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for any claim element amended.
