Abstract:
A portable extruding apparatus that is capable of densifying biomass to greater densities and higher caloric values than has been possible heretofore. This capability is possible through the use of a vented barrel on the end of the extruder that allows for the escape of any gasses that are built-up during the compression and densification process without loss of any of the densifying material through the vents of the barrel during the processing.

Description:
[0001]     This application claims priority from U.S. Provisional Patent Application No. 60/841,461 filed Aug. 30, 2006. 
     
    
       [0002]     The instant invention deals with a portable, vertical and horizontal extruding apparatus that is capable of densifying biomass to greater densities having higher British Thermal Unit (btu) potential than has been possible heretofore by using higher btu feed stock. This capability is possible through the use of a vented barrel that allows for the escape of any gasses that are built-up during the compression and densification process. The vents allow the compaction of high btu products by allowing the escape of gasses created by friction during the compression process  
       BACKGROUND OF THE INVENTION  
       [0003]     This invention deals with an extruding apparatus that is capable of densifying biomass to greater densities than has been possible heretofore. This invention allows the processing of material with heat content as high as 12,000 btu/lb., which is hotter than almost all coal used today, and, more importantly, much cleaner, that is, ultra low sulfur, low mercury and carbon dioxide neutral.  
         [0004]     Pelletizing biomass, especially wood products, has been used in the United States for a long time. A high degree of compaction, that is, densification, and pellet toughness, that is, a pellet&#39;s resistance to disintegration, are the desired properties of a commercial pellet product.  
         [0005]     Most prior art pelletizers and densification apparatii attempt to extrude particulate matter through a die of relative short barrel length. In such equipment, the particles are exposed to the compacting, shaping and densification forces in the barrel for only a short time.  
         [0006]     As early as 1892, in U.S. Pat. No. 474,412, continuous production of pellets to bricks that were used as fuel was disclosed. This disclosure dealt with particulate matter that was coal dust mixed with a binder, such a mixture being fed between converging belts and compacted into briquettes that were ultimately transported and burned.  
         [0007]     In 1940, U.S. Pat. No. 2,194,593 was issued to Graham and addressed a machine for compacting and densifying sawdust into briquettes for consumption in a heating apparatus. Very importantly, Graham recognized the now well-known principle that wood particulates contain sufficient natural resins, pitch and the like, that can be used for particle binding purposes, if enough heat and pressure are applied to activate them, that is, render the particulates “plastic”. Evenso, the briquettes derived by this method were not overly compacted owing to the fact that belts were used to do the compacting and had limited pressure on the particulate materials.  
         [0008]     One of the main reasons that extruders have not been extensively used for highly densified materials is the fact that the extruder is “contained”, that is, relatively little air or other gasses can escape from the barrel of the extruder and this results in high and dangerous pressure within the barrel. It was thought that the barrel could not be vented because of the fact that it was believed that the material being extruded would exit from any vents or openings that were placed in the barrel to relieve pressure.  
         [0009]     Contrary to this popular belief, it has been found that such openings can be placed in the extruder barrel to allow gasses to escape without the extruded material exiting through these openings. This results in highly densified materials without the dangers of high pressure.  
       SUMMARY OF THE INVENTION  
       [0010]     This invention deals with an extruding apparatus that is capable of densifying biomass to greater densities than has been possible heretofore. Such an apparatus is an extruder having a barrel that has vents or openings cut through it to allow for the escape of gasses that are built up during the heating and extrusion process.  
         [0011]     Thus, this invention deals with a densifying apparatus for densifying biomass. The apparatus comprises a support frame and mounted to the support frame is an extruder. The extruder has an extruder housing, a bearing housing having a front wall and a back wall, a feed hopper, and a vented barrel having a long axis. By “long axis” it is meant that the axis is centered in the barrel and runs the long length of the barrel. The extruder housing has mounted and supported therein, an extruder screw, the extruder screw comprising an extruder shaft, an auger segment mounted on the extruder shaft, a first end, a second end, and a middle zone.  
         [0012]     The extruder shaft has mounted on the first end, a means for connecting to a drive means, and the extruder shaft terminates near the second end. The auger segment is mounted near the middle zone. The bearing housing is located between the extruder housing and the first end of the extruder shaft and the extruder shaft is supported by a thrust bearing located near the bearing housing front wall and a roller bearing located near the bearing housing back wall.  
         [0013]     The vented barrel is mounted on a support wall and is centered such that it encloses the extruder shaft, the vent barrel being in linear alignment along the long axis with the extruder shaft.  
         [0014]     There is a pressure clamp encircling the vented barrel and a hopper mounted on the extruder housing such that the biomass can be delivered to the auger segment of the extruder screw. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a view in perspective of an apparatus of this invention shown mounted on a frame and the frame in turn mounted on a set of wheels.  
         [0016]      FIG. 2  is a cross sectional view of the apparatus of  FIG. 1  taken through line A-A.  
         [0017]      FIG. 3  is an enlarged side view of a portion B of the apparatus of  FIG. 2  with the wheel missing from the front side to ensure clarity and showing a motor and belt driven apparatus.  
         [0018]      FIG. 4  is an enlarged side view of a portion B of the apparatus of  FIG. 2  with the wheel missing from the front side to ensure clarity and showing a power take-off connection to the extruder screw.  
         [0019]      FIG. 5  is an enlarged side view of a portion B of the apparatus of  FIG. 2  with the wheels missing from the frame to ensure clarity and showing a gear box and gears.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     Turning now to  FIG. 1  and a detailed description of the invention, there is shown an apparatus  1  that is a biomass densifier. The  FIG. 1  apparatus is the preferred manner in which to make the apparatus  1  portable, although, it is not required to have wheels  2 .  
         [0021]     There is shown the frame  3 , on which the extruder  4  is mounted. Shown in this Figure are an electric motor  5  (this motor can also be a fuel driven motor, such as a gasoline or diesel driven motor), drive belts  6  configured to a drive pulley  7  for the electric motor  5 , a drive pulley  8  for the belts  6  on the shaft connector  9 , a hopper  10  for feeding biomass to the extruder  4 , a support plate  11  and support rods  12 , and attached to the front of the plate  11  is a barrel  13  that has elongated openings  14  in it, and an extension  15  that is attached to the barrel  13  to aid in the removal of the densified mass from the barrel.  
         [0022]     In more detail, and with reference to  FIG. 2 , there is shown the details of the extruder  4 . The extruder  4  comprises an extruder housing  16 , a bearing housing  17  adjacent the extruder housing  16 , and in alignment therewith, a front wall  18  for the bearing housing  17  and a back wall  19  for the bearing housing  17 .  
         [0023]     The Extruder  4  also comprises a feed hopper  10  for feeding biomass to the extruder  4 . The extruder housing  16  has mounted in it and supports an extruder shaft  20 . The extruder shaft  20  has a first end  22  and a second end  21 , the first end  22  being the lead end of the extruder shaft  20  and the second end  21  being the trailing or back end of the extruder shaft  20 . The extruder shaft  20  has at its middle zone  23 , an auger segment  24 .  
         [0024]     The first end  21  has mounted on it a means for connecting to a drive means. The drive means can be for example a motor, such as the electric motor  5  shown in  FIG. 1 , or it can be a motor that is gasoline or diesel driven. This connection is usually a belt  6  and pulley system  7  and  8  as described Supra. In addition, it is contemplated within the scope of this invention to use a power take-off drive means  25  shown in  FIG. 4  wherein the connector for the power take-off means is shown as  26 , or a gear box  34  with gears  35  and  37  as is shown in  FIG. 5 .  
         [0025]     The extruder shaft  20  is supported near the first end  21  by a set of bearings, namely, a thrust bearing  27  and a roller bearing  28 , all of which is housed in and supported by the bearing housing  17 . The thrust bearing  27  is located near the front wall  18  of the bearing housing and the roller bearing  28  is located near the back wall  19  of the bearing housing  17 .  
         [0026]     Turning now to  FIG. 4  and the vented barrel  13 , which is the essence of this invention, there is shown the vented barrel  13 , the elongated openings  14  and there is also shown a gap  29 . The gap  29  is formed by placing two halves of the barrel together and leaving a small gap  29  to aid in the venting of the barrel  13 . The barrel  13  can be made of more than two pieces of material, and in each case, the barrel  13  should have a gap where the pieces join together. It should be noted that the elongated openings  14  can be elongated or round or any other configuration as long as they allow the gasses to exit the barrel  13  conveniently. The vent openings can be spaced 1 to 1½ inches apart around the circumference of the barrel openings should be approximately about 1½ inches from the beginning of the barrel and extend to about 3 inches. It should also be noted that it is more efficient to place the openings  14  more in the forward end of the barrel  13 .  
         [0027]     As shown in  FIG. 4 , there is also a clamp  30  that surrounds the outside of the barrel  13  and holds the barrel  13  in the gapped configuration. As can be observed, the barrel  13  is held in place on the support wall  11  and the support wall  11  is supported by support rods  12  that are connected securely to the extruder housing  16 /bearing housing  17  common wall (front wall  18  of the bearing housing  17 ) and the opposite end of the support rods  12  are held in place in the support wall  11  by fasteners, in this case as shown, threaded nuts  33 . Both the bearing housing  17  and the extruder housing  16  are securely fastened to the frame  3 .  
         [0028]     It should be noted that the clamp  30  is configured such that the pressure exerted by the auger segment  24  of the extruder screw can be balanced such that there is some back pressure on the forming material, without the barrel  13  exploding and such that the pressure is sufficient to form the densified material according to the invention.  
         [0029]     At the first end  22  of the extruder shaft  20  is a connector  31  that connects the connector for the drive means  26  to the extruder shaft  20 . The connector  31  surrounds the ends of the extruder shaft  20  and the connector for the drive means  26  and is pinned in place by a shear pin  32 . In the event that the extruder gets bogged down because of overload of material, the shear pin  32  will shear rather than twisting the shaft  20 . The power take-off is conventional state of the art in power equipment and is not shown.  
         [0030]     Turning now to  FIG. 5 , wherein like numbers indicate like components, there is shown a gear box  34  that contains within it, a drive gear  35  driven by a gear drive shaft  36 . Also shown is a gear  37  that is used for driving the shaft  21 , it being noted that gears  35  and  37  complement each other. The energy means for the drive shaft  36  is not shown and can be any conventional means for driving such shafts.  
         [0031]     Comminuted, chipped, or otherwise small-sized biomass is fed into the hopper  10  with the extruder screw  20  operating, and the extruder screw  20  conveys the biomass towards the barrel  13  and slowly compresses the material. As the biomass material feeds into the barrel  13 , it is further compacted such that it is densified and because of the vent holes in the barrel  13 , the material is highly compressed. The apparatus of this invention can yield densities on the order of about 100 pounds/cubic foot, while prior art devices can produce materials having densities only in the range of about 70 pounds/cubic foot. As the biomass compresses, there is heat generated and this heat is sufficient under the pressures of the extruder to furnish the high density material while venting the gasses generated from such heating. Such temperatures can be as high as 160° C. No additional heating means is required.  
         [0032]     It should be noted that even though the apparatus  1  of  FIG. 1  is shown as essentially mounted in a horizontal position, it is contemplated within the scope of this invention to mount the apparatus at any angle convenient to use the apparatus, including a totally vertical mounting. Positioning the extruder in a vertical position allows for additional venting as the gasses can escape the apparatus upwardly from the auger face.  
         [0033]     Biomass that is conventionally used in prior art devices can easily be used in the apparatus of the instant invention. Such materials as waste wood products, such as slashing, sawdust, bark, and the like, grasses, weeds, tree branches and twigs, leaves, grain stalks, grains, starch containing grain products, pine needles, pine cones, nut shells, and lumber scraps to mention a few.  
         [0034]     The apparatus of this invention is lightweight and is portable to the extent that it can be moved from site to site and can accommodate clean up proceedings. The portability of the unit is such that it is economically maintainable. The portable nature of the device allows finished product to be manufactured in forest or field thus greatly reducing transportation costs. It reduces the cost of using wood chips by a factor of eight if the densification can be done on site where the chips are produced. The high wear components can easily be replaced in the field for efficient maintenance.