Abstract:
According to one aspect of the present disclosure, a mechanism and method is provided to clean and remove or separate cellulose fibers from the source fibrous material without stressing and/or damaging the cellulose fibers. The mechanism includes an agitator that directs the washing fluid in a vertical direction into engagement with the fibrous material to effect maximum cleaning of the cellulose from the remainder of the fibrous material without damaging or stressing the cellulose, thereby providing cellulose that can enhance the strength and other beneficial characteristics of a biocomposite material formed using the cellulose.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 61/955,429, filed on Mar. 19, 2014, the entirety of which is expressly incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The subject matter disclosed herein relates generally to biocomposite materials and, in particular, to a method and system for the preparation of cellulose fibers from raw cellulosic fibrous materials for use in the manufacture of biocomposite materials. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fibrous materials such as straw from flax, sisal, hemp, jute and coir, banana among others, consist of four main compounds: cellulose, hemicellulose, lignin, and impurities (e.g., dirt, dust). When these fibrous materials are used in the formation of biocomposite materials, it is the cellulose component of the fibrous material that contains and provides the strength and structural properties that are desired, while the hemicellulose, lignin, and the impurities have no real value for the biocomposite material in terms of properties or performance enhancements. As a result, these components of the fibrous material are removed prior to use in the formation of biocomposite materials. 
         [0004]    One method in which the cellulose is removed from the remainder of the fraction is by pretreatment and washing the fibrous material. Current washing practices are able to remove the maximum amount of hemicellulose and impurities from the fibrous materials. However, these washing techniques have problems removing the lignin from the fibers, which necessitates additional processing of the fibers in order to remove the lignin, which is undesirable for use in the formulation of biocomposite materials for various reasons. 
         [0005]    As a result, it is desirable to develop a mechanism and method that can overcome the deficiencies of prior art washing methods to remove the maximum amount of unwanted compounds from fibrous materials, e.g., the hemicellulose and lignin fractions along with the impurities that may be present, while leaving the cellulose undamaged to maximize the benefits provided to the biocomposite material including the cellulose. In particular, such a mechanism will maximize the strength characteristics of the fiber by leaving the cellulose fraction undamaged. The mechanism must additionally be formed of materials that are resistant to corrosion (i.e. plastic, stainless steel), as the washing agents utilized in the method can be corrosive. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one aspect of an exemplary embodiment of the present disclosure, a mechanism and method is provided to clean and separate cellulose fibers from the source fibrous material without stressing and/or damaging the cellulose fibers. The separation of the cellulose fibers from the hemicelluloses, lignin and impurities in the disclosed mechanism and method allows for the optimization/close control of the washing environment, and the recycling of the washing agents to reduce consumption of water and the chemical washing agents used therein, thereby reducing waste and cost for the preparation of the cellulose fibers. 
         [0007]    According to another aspect of an exemplary embodiment of the present disclosure, the washing of the fibrous material in the disclosed mechanism and method also maintains the desired cellulose material in an undamaged condition, thus maintaining the beneficial strength characteristics of the fibrous material/cellulose fibers for use in forming the biocomposites. 
         [0008]    According to another aspect of an exemplary embodiment of the present disclosure, the manual labor necessary for the washing of the fibrous material is also reduced significantly, and the mechanism is easily scalable to accommodate larger or smaller amounts of the fibrous material to be washed to obtain the cellulose fibers for use in forming biocomposites. 
         [0009]    These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The drawings furnished herewith illustrate a preferred construction of the present invention in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description of the illustrated embodiment. 
           [0011]    In the drawings: 
           [0012]      FIG. 1  is a schematic illustration of an exemplary embodiment of a washing tank constructed according to the present disclosure; 
           [0013]      FIG. 2  is a top perspective view of the exemplary embodiment of the tank of  FIG. 1 ; 
           [0014]      FIG. 3  is a partially broken away perspective view of one exemplary embodiment of the impeller of the tank of  FIG. 1 ; and 
           [0015]      FIG. 4  is a side perspective view of the exemplary embodiment of the tank of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, one exemplary illustrated embodiment of a system or mechanism provided for washing various types of fibrous materials in order to separate the cellulose fraction or component of the fibers from the remainder of the fibrous material, which can include hemicelluloses, lignin and impurities, such as dust and dirt, among others, is illustrated generally at  10  in  FIGS. 1 and 4 . In the illustrated embodiment, the system or mechanism  10  includes a tank  12  formed of any suitable type of corrosion-resistant material, such as a metal, e.g., a stainless steel, or plastic material. The tank  12  includes an inlet  14  and an outlet  16 , with the inlet  14  positioned in a side wall  17  near the upper end  18  of the tank  12  and the outlet  16  disposed in a bottom wall  20  of the tank  12 , though the inlet  14  and outlet  16  can be located in other positions on the tank  12 . 
         [0017]    The tank  12  can have any desired shape, and in the illustrated embodiment is generally cylindrical, with a lid  22  that can be displaced from over the upper end  18  either in whole or in part, or in the illustrated exemplary embodiment, can be pivotally secured to the tank  12  to be able to selectively cover the open upper end  18  an expose the interior of the tank  12 . The tank  12  can also be constructed to include a stand  24  engaged with and extending downwardly from the bottom wall  20  of the tank  12 . The stand  24  operates to support the tank  12  over a surface, such as a floor, depending upon the size of the tank  12 , which can vary in order to hold the desired amount of the fibrous material to be treated. 
         [0018]    The tank  12  also includes a measurement scale  25  disposed on the tank  12  that provides a ready indication of the level or volume of materials and washing agents present within the tank  12 . The scale  25  can be disposed on the interior or exterior of the tank  12  and in the exemplary embodiment is located on an interior surface of the side wall  17 , where the scale  25  can be viewed through the open upper end  18 . Alternatively, the scale  25  can be disposed on the exterior of the side all  17 , or can positioned at a location on the side wall  17  at a location where it can be viewed through a window or other suitable viewing port (not shown) formed in the side wall  17 . 
         [0019]    Referring now to  FIGS. 1-3 , in the illustrated exemplary embodiment the tank  12  includes a heating element  26  disposed within the tank  12  on the bottom wall  20 , though in other embodiments the location of the element  26  can be altered as desired such that the element  26  can be operated to control the temperature of the contents of the tank  12 . A screen  28  is also disposed within the tank  12  at a position between the inlet  14  and the outlet  16 . The screen  28  is secured in a suitable manner to the side wall  17  of the tank  12 , and can be removable for easier cleaning of the interior of the tank  12  when not in use. The screen  28  is formed to enable fluids to pass freely therethrough, such as by having apertures  30  formed in the screen  28 , but to retain solid matter over a certain size on top of the screen  28 . Thus, the screen  28  functions to enable the fibrous material (not shown) placed in the tank  12  to rest on the screen  28  above the bottom wall  20  to enable efficient washing of the material positioned on the screen  28 . 
         [0020]    Located in the tank  12  below the screen  28  but above the bottom wall  20  is an agitating device or propeller/impeller  32 . The impeller  32  includes a blade  34  disposed within the interior of the tank  10  on a rotating shaft  36 . The rotating shaft  36  extends through a suitable watertight but rotatable bearing/sealing member (not shown) disposed within the side wall  17  into operable connection with a motor  38  located adjacent the exterior of the tank  12 . The motor  38  operates to rotate the shaft  36  and the blade  34  to agitate the materials held within the tank  12 . In the illustrated exemplary embodiment of  FIGS. 1-3 , the blade  34  of the impeller  32  is oriented vertically in order to rotate in a vertical plane around a horizontal axis of the shaft  36 , thereby causing the fluid and washing agent(s) (not shown) present in the tank  12  to move upwardly and/or downwardly, i.e., vertically within the tank  12 , enhancing the contact of the fluids and/or washing agent(s) with the fibrous material (not shown) disposed on or above the screen  28 . 
         [0021]    Further, due to the positioning of the impeller  32  below the level of the screen  28 , the blade  34  can rotate freely to agitate the washing fluid/agents within the tank  12  in this manner as a result of the screen  28  limiting the size of any solid material within the tank  12  coming into contact with the blade  34 . The orientation of the blade  34  also limits contact of solid material with the blade  34  as a result of the direction of the force imparted to the material in the tank  12  by the impeller  32 . 
         [0022]    To rotate the blade  34 , the motor  38  is connected to a suitable power source  40  also disposed outside of the tank  12  for operation of the motor  38 , with the power source  40  and/or motor  38  able to be operated to control the speed of the impeller  32  i.e., rpm increase or decrease, according to the type of fiber positioned in the tank  12 . In addition, the power source  40  is also operably connected to the heating element  26  to operate the element  26  such that control of the power source  40  to operate the impeller  32  can also control the operation of the heating element  26 . 
         [0023]    Still referring to the exemplary embodiment of  FIGS. 1-3 , also located within the tank  12  beneath the screen  28  are sensors for sensing various operating parameters of the tank  12 , such as a pH meter  42  and a thermocouple  44 , though the location and type of these sensors can be varied as desired and/or necessary. Each are operably connected to the power source  40  for operation, if necessary, and to a suitable controller  46 , such as directly or wirelessly, as is known in the art. The controller  46  is capable of monitoring and/or controlling the operation of the pH meter  42  and the thermocouple  44  in order to determine the conditions present within the tank  12 . As a result of this data obtained from the pH meter  42  and the thermocouple  44 , the controller  46  can control the operation of the impeller  32  via the motor  38  and power source  40 , as well as the heating element  26 , as desired, to maintain or alter the conditions within the tank  12  as necessary. The pH meter  42  and thermocouple  44  provide measurements of the pH level and temperature of the materials within the tank  12 , such that the controller  46  can be operated to provide conditions within the tank  12  that are optimal for the washing of the fibrous materials placed within the tank  12 . 
         [0024]    In operation, in either order, the tank  12  is charged with an amount of the washing agents/fluids and the fibrous materials to be washed. Operating conditions within the tank  12  vary depending on various factors, including one or more of the quantity of the fiber positioned within the tank  12 , size of fiber positioned within the tank  12 , type of pretreatment to be performed within the tank  10 , type of washing agent/chemicals to be utilized, water activities temperature, the pH of the water, and/or the particular usage of biocomposite end products to be formed using the biocomposite material incorporating the fiber treated in the tank  12 , among others. Some exemplary embodiments of these types of treatments that can be performed within the tank  12  of this disclosure are found in co-owned and co-pending U.S. Non-Provisional patent application Ser. No. 14/087,326, filed on Nov. 22, 2013, the entirety of which is expressly incorporated by reference herein. 
         [0025]    In one exemplary embodiment of the method of operation of the tank  12 , the selected washing agents are introduced through the inlet  14 , while the fibrous material is placed within the tank  12  through the open upper end  18 . The lid  22  is subsequently closed over the tank  12  and the motor  38  connected to the impeller  32  is started, thereby causing the washing agent to move up and down within the tank  12  and through the screen  28 . This movement optimizes the contact of the washing agents/fluids with the fibrous materials disposed within the tank  12  and/or on the screen  28  to cause the maximum amount of hemicellulose, lignin, and impurities to be separated from the cellulose. Further, using the data obtained by the pH meter  42  and the thermocouple  44 , the conditions within the tank  12  can be optimized in a known manner during operation for separation of the cellulose using the heating element  26  and/or by adding, removing or altering the types and/or amounts of washing agents/fluids present within the tank  12 . 
         [0026]    The hemicellulose, lignin, and impurities that are separated from the cellulose and fall through the screen  28  to the bottom of the tank  12 , while the cellulose fibers remains on the screen  28 . Once the washing process is complete, the hemicellulose, lignin and impurities can be drained out of the tank  12  along with the washing agent through the outlet  16 . The cleaned and washed cellulose remaining on the screen  28  can then be taken out via the open end  18  once the lid  22  is removed and dried for later use in forming biocomposite materials. After being drained from the tank  12 , the washing agent removed through the outlet  16  can be separated and/filtered from the hemicelluloses, lignin and impurities for re-use in the tank  12 . By utilizing this system  10  to separate and clean the cellulose fibers from the remainder of the fibrous material fractions and impurities, the cellulose fibers are maintained in a highly undamaged state, maximizing the enhancements provided by the inclusion of the cellulose fibers in a biocomposite material, such as strength enhancements. 
         [0027]    In one example, Saskatchewan gown oil seed flax straw placed within the tank  12  as the fibrous material and treated in a manner disclosed in U.S. Non-Provisional patent application Ser. No. 14/087,326, the entirety of which is expressly incorporated by reference herein, has almost 50-68% w/w cellulose content with the remainder being hemicellulose and lignin. After suitable pretreatment of the fiber, in similar washing conditions (same water temperature, pH, same fiber, washing time etc.), it is possible to extract up to 60% w/w of clean cellulose in this developed system using the tank  12 , as compared to 30 to 40% w/w of cellulose along with a portion of lignin and hemicellulose in currently used, prior art normal washing practices. Further, this washing system  10  and method is developed not only for research and development, but also for industrial usage. The current developed system  10  also reduces the water usage 30-40% and can reduce by half the washing time compared to prior art currently used, normal washing practices and systems. This system  10  also allows the capture the black liquor, which is a mixture of hemicellulose, lignin, any residual chemicals/washing agent and other impurities in an effective manner to reprocess, dispose and/or extract these biopolymers for different applications. 
         [0028]    In alternative embodiments for the mechanism/system  10 , in addition to or as a replacement for the impeller  32 , the agitating device can be formed from jets of pressurized air (not shown) can be directed from suitable nozzles (not shown) disposed on the bottom wall  20  of the tank  12  upwardly towards the screen  28  to agitate the washing agent(s) and fibrous material. In another alternative embodiment, either in conjunction with or separately from the impeller  32 , the stand  24  for the tank  12  can operate as an agitating device, e.g., in the manner of a shaker table (not shown), to move the entire tank  12  in order to agitate the contents of the tank  12 . 
         [0029]    It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.