Patent Publication Number: US-2004045629-A1

Title: Wood chip flinger and method of densely packing wood chips

Description:
[0001] This application is a continuation-in-part application of U.S. patent application Ser. No. 10/241,725, filed Sep. 11, 2002, still pending, the disclosure of which is incorporated herein by reference. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates generally to the field of wood chip processing, and more particularly to a machine and associated method for dense packing of wood chips for storage, transport, or processing.  
       [0003] One major factor in the cost of wood chips for paper making is the cost of transporting the wood chips from the chip manufacturing site to the paper mill. The wood chips are typically transported in rail cars, but may also be transported in barges, trailers, or the like. Typically, the transportation costs are based primarily on the number of containers used to ship a given load of wood chips. As more densely packed containers means that fewer containers are required to ship a given amount of wood chips, it follows that more densely packed containers will generally supply more useable wood chips to the paper mill at a lower transportation cost.  
       [0004] Space considerations are also relevant in the storage and processing of wood chips. For instance, the storage of wood chips on site, such as at a pulp mill, consumes space. As such, it is advantageous to have the wood chips densely packed when “stacking” the wood chips for storage. Similarly, many methods of processing wood chips include batch processing steps that take place in pressure vessels, or other containers, that have fixed volumes. If additional wood chip materials can be packed into the containers, the batch process can likely be made more efficient.  
       [0005] Even with these considerations, many wood chip transporting, storing, and/or processing approaches rely on either conventional free-fall techniques or on techniques that result in packing densities of typically not more than 17% over free-fall techniques.  
       [0006] Accordingly, there remains a substantial need in the industry for alternate wood chip handling techniques that allow for higher packing densities.  
       SUMMARY OF THE INVENTION  
       [0007] A wood chip handling device of the present invention allows wood chips to be packed with a density greater than that achieved using conventional free-fall techniques. Preferably, the device packs the wood chips at a density that is at least 20% more than that achieved with the conventional free-fall techniques.  
       [0008] In one embodiment, the wood chip handling device includes a movable boom having a distal end. A redirecting device is supported by the distal end of the movable boom, the redirecting device comprising a drum having a plurality of outwardly extending blades and a motor, the motor coupled to the drum so as to rotate the drum. A stream of incoming wood chips fed to the redirection device while the drum is rotating about a generally horizontal axis at a rate of 50 rpm or more is redirected to form an output stream of wood chips flung by the drum that land with a preferential orientation. Preferably, while the boom moves in a first direction, the output stream is directed in the generally opposite direction. The boom may rotate or move linearly. Preferably, the output stream forms a pile on the ground, optionally in the shape of an arc or annular, having a packing density factor of at least 1.20.  
       [0009] In another embodiment, a method of processing wood chips comprises feeding a stream of incoming wood chips to a drum disposed so as to rotate about a generally horizontal axis and spinning under power at a rate of about 50 rpm or more, the drum including a plurality of outwardly extending blades; directing wood chips output from the drum into a wood chip digestion chamber; packing the wood chips in the wood chip digestion chamber to a density greater than a free-fall density; and digesting the wood chips in the digestion chamber for a period of time. The wood chips in the wood chip digestion chamber may be packed with a packing density factor of at least 1.20. The usual digesting chemicals may be added before, during, or after the wood chip loading, with the amounts thereof adjusted to accommodate the increased weight quantity of wood chips present in a batch. The digesting process may then continue as in the conventional digesting technique.  
       [0010] Some embodiments of the present invention a feed chute assembly may be used that allows for adjustment of the ratio of the input stream that is delivered to the middle and side portions of the spinning drum. In some of these embodiments, this adjustment may be made while the device is operating, thereby allowing for “on-the-fly” adjustments by the operator. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 shows one embodiment of the device of the present invention employed in a wood chip loading station for filling railcars.  
     [0012]FIG. 2 shows a perspective view of one embodiment of the device of the present invention.  
     [0013]FIG. 3A shows a side view of the embodiment of FIG. 2.  
     [0014]FIG. 3B shows a top view of the embodiment of FIG. 2, with the optionally extended offset sections on the deadwall.  
     [0015]FIG. 4 shows a simplified top view of the drum and deadwall of FIG. 2, with the optionally extended offset sections on the deadwall.  
     [0016]FIG. 5 shows a side view of the drum of FIG. 4 with the near endcap removed.  
     [0017]FIG. 6 shows a front perspective view of the baseplate assembly of the embodiment of FIG. 2.  
     [0018] FIGS.  7 A- 7 B show a side view and top view respectively of a wood chip inventory station using a moving boom with a flinger attached thereto.  
     [0019]FIG. 8 shows a wood chip digestion station. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0020] In order to provide a better understanding of the present invention, one embodiment of the wood chip handling device according to the present invention is shown in FIG. 1 in the context of a wood chip loading station  10  for filling railcars  12 . The wood chip handling device, generally indicated at  20 , is shown installed in a tower structure  16  that extends above a rail line with a railcar  12  thereon. Wood chips  5  are fed to the handling device  20  in the tower  16  by any suitable means, such as by conventional conveyor system  14  (only the output funnel of which is shown for clarity), or alternatively via a pneumatic means into a cyclone, or by other like means known in the art. The handling device  20  takes the input stream of wood chips from the conveyor  14  and directs it into the railcar  12  so that the wood chips  5  are relatively densely packed in the railcar  12 . In most applications, the railcar  12  will be moved underneath the handling device  20  during the loading process so as to fill the entirety of the railcar&#39;s length, but the device  20  (with or without the tower  16 ) may alternatively be moved while the railcar  12  is held stationary, if desired.  
     [0021] One embodiment of the handling device  20 , sometimes referred to herein as the “flinger,” includes a frame  22 , a motor  24 , a feed chute assembly  30 , and a drum  80 . The frame  22  supports the motor  24 , feed chute assembly  30 , and drum  80 , and may take any suitable form known in the art, such as welded assembly of angle iron. The motor  24  supplies rotational power to the drum  80 , typically via a pulley and belt arrangement (not shown). The motor  24  may be of any type known in the art, but is typically an electric motor of approximately fifteen horsepower or more.  
     [0022] Disposed above the drum  80 , and between the drum  80  and the conveyor system  14 , is a feed chute assembly  30 . Referring to FIG. 6, the feed chute assembly  30  includes a sloped baseplate assembly  40  and an optional deadwall  60  towards the output end  50  thereof. The baseplate assembly  40  of a preferred embodiment includes a baseplate  42  and dividers  46 . The baseplate  42  is a sturdy, substantially rectangular plate with side flanges  44 . The baseplate  42  is disposed in a tilted orientation, so that the input end is higher than the output end  50 . Referring to FIG. 6, the output end  50  preferably has a stepped profile, with a center section  52  flanked by respective side sections  54 , and corresponding transition sections  56 . The center and side sections  52 , 54  are preferably straight and parallel to one another, with the center section  52  ending earlier than the side sections  54 . The transition sections  56  provide a transition between the center section  52  and the side sections  54 . In a preferred embodiment, the overall appearance of the output end  50  of the baseplate  42  is that of a trapezoid cutout as shown in FIG. 6, but this is not required.  
     [0023] Two dividers  46  may be moveably attached to the baseplate  42  so as to be selectively positioned by pivoting about corresponding pivot points  47  (e.g., shouldered bolts extending through the baseplate  42 ). The location of the upper ends of the dividers  46  may be adjusted with respect to the baseplate  42  using a suitable adjusting mechanism  48 . By way of non-limiting example, the adjusting mechanism  48  may take the form of a crank and threaded rod arrangement, with suitable pivoting connections between the tops of the dividers  46  and the threaded rods. Of course, other means known in the art may be used to control the position of the upper ends of the dividers  46 . Whatever means is selected, it will be advantageous to position the controls thereof (e.g., the crank) so as to allow easy access thereto by a user during operation of the handling device  20 . The purpose of the dividers  46  is to control the flow ratio of the wood chips flowing down the baseplate assembly  40  to the center  82  and side portions  84  of drum  80 .  
     [0024] The deadwall, or directing wall,  60  is a generally vertical wall that acts to focus the flow of the wood chips flowing down the baseplate assembly  40  generally vertically onto the drum  80 . As shown in FIG. 2 and FIG. 4, the deadwall  60  may include a center section  62 , flanking side sections  64 , and appropriate offset sections  66  therebetween. The center and side sections  62 , 64  are preferably straight and parallel to one another, and preferably are disposed a height from the center of drum  80 . The offset sections  66  are preferably generally perpendicular to the center and side sections  62 , 64  and are likewise disposed at the same height from drum  80 . Thus, the deadwall  60 , when viewed from above, preferably has the shape shown in FIG. 4. Further, the deadwall  60  should be located, and be of sufficient height, so that the wood chips from the baseplate  42  impact in the vertical middle of the deadwall  60 . It should be noted that the offset sections  66  may simply connect the center and side sections  62 , 64 ; or, alternatively, the offset sections  66  may be longer such that they extend to a point well beyond the intersection with the center section  62 , such as having approximately twice the length as shown in FIG. 4. This optional “extra” length for the offset sections  66  is believed to aid in achieving the desired side-to-side balance of wood chips being supplied to the drum  80 .  
     [0025] The deadwall  60  is located forward of the output end  50  of the baseplate assembly  40 , so that a substantial gap is formed therebetween to allow passage of the wood chips without jamming as the wood chips change flow direction. Further, while the deadwall  60  may be located prior to top dead center (behind the rotation axis  86  of the drum  80 ), the deadwall is advantageously located at a position that is beyond top dead center of the drum  80  (see FIGS. 3A and 3B). For the optimum gap to be formed, the center section  62  of the deadwall  60  should be narrower than the center section  52  of baseplate  42  by about an inch, with the transition sections  56  of the baseplate  42  extending laterally approximately another two inches. Of course, the gap size is at least partially governed by the spacing between the output end of the baseplate assembly  40  and the location of the deadwall  60 . The position of the deadwall  60  relative to the baseplate  42  and/or drum  80  may be permanently fixed; however, the position of the deadwall  60  may be adjustable (for instance, ±3 inches) in some embodiments of the present invention, such as by mounting the deadwall  60  using bolts, with multiple bolt holes provided in the frame  22 . It may be advantageous to vary the gap size, nominally eight inches, in proportion to the desired output rate of the device  20 .  
     [0026] While the space above the baseplate  42  of the feed chute assembly  30  may be open, the feed chute assembly  30  may optionally include a cover (not shown) spaced from the baseplate  42  to help contain any errant wood chips. The optional cover may extend above the top of the deadwall  60 , and be spaced therefrom, so as to provide an overflow route, if desired.  
     [0027] The drum  80  is mounted for rotation about a generally horizontal axis  86 , and supported by the frame  22 . The drum  80  may be mounted to an axle  106 , which may be a central shaft or a pair of stub shafts, which is in turn supported by suitable bearings mounted to the frame  22 . As indicated above, the axle  106  should have a pulley, gear, or like means for accepting non-gravitational rotational power to turn the drum  80 , such as from motor  24 . The drum  80  includes a main body core  90  with a plurality of outwardly extending blades  100 , and preferably a pair of lateral endcaps  94 . The main body  90  of the drum  80  may have a circular cross-section, but preferably has a faceted cross-section, such as an octagonal cross-section as shown in FIG. 5. The blades  100  are mounted to the core  90  so as to extend away from the surface thereof; for instance, the blades  100  may extend generally perpendicular from the corresponding facet  92  forming the perimeter of the drum  80 . The blades  100  should preferably extend from one lateral endcap  94  to the other. Each blade  100  may be a single straight piece, disposed parallel to the axis of rotation  86  or at an angle thereto, for instance alternating ±30°, or preferably ±10°. Alternatively, each blade  100  may advantageously include at least two sections  102  that angled with respect to one another at angle α. For instance, as shown in FIG. 4, each blade  100  may have left and right portions  102  that meet in the center of the core  90  and are angled with respect to one another 1°-30°, preferably about 3°-10°. When this arrangement is viewed from above, each facet  92  of the drum&#39;s core  90  appears to have a chevron shaped blade  100  thereon (see FIG. 4). Each blade  100  preferably has an approximately uniform height across its width, and the blades  100  are preferably substantially identical, but neither aspect is strictly required for all embodiments. A reinforcing gusset  104  may extend circumferentially from one blade  100  to the next blade  100 .  
     [0028] The handling device  20  may be used to load wood chips, and particularly uniformly-sized paper making wood chips, into a suitable container. The device  20  is mounted to the tower  16  of the loading station  10 . A container, such as a railcar  12 , is positioned below and forward of the handling device  20 , and motor  24  is started to start the drum  80  rotating. Before feeding wood chips to the device  20 , the drum  80  should be rotating at a rate of at least approximately 50 rpm, more particularly at least about 200 rpm, and more particularly at approximately 350 rpm. When the drum  80  is spinning properly, wood chips are supplied to the feed chute assembly  30  by the conveyor system  14 . The wood chips slide down the baseplate  42 , between the dividers  46 , hit against the deadwall  60 , and then fall as an input stream  200  to the drum  80 . The output end  50  of the baseplate  42 , the deadwall  60 , and the dividers  46  collectively control the relative proportions wood chips being fed to the center  82  and side portions  84  of the drum  80 . The wood chips fall to the drum  80  and are then flung forward by the blades  100  of the spinning drum  80 . The wood chips flung from the drum  80  are captured by the container  12 . Due to the interaction of the feed chute assembly  30  and the drum  80  spinning on a generally horizontal axis  86 , the output pattern  210  of the wood chips leaving the drum  80  is such that the vast majority of the wood chips would (if unconstrained by the container) land forward of the device  20  and within in an area that angularly sweeps less than 180°. This output pattern  210  may be conceptually described as a truncated sector that sweeps angle β, where β is less than 180°. Indeed, β, is preferably less than 45°, and more preferably less than about 20°. Further it should be noted that while the term “sector” has been used, the strict geometrical definition is not meant, as the boundaries of the pattern  210  do not need to be arc shaped. Indeed, when β is very small, such as about 10°, the output pattern may be described as substantially rectangular. Thus, defining the output pattern  210  as a truncated sector means that the output pattern where substantially all of the wood chips leaving the device  20  would fall, if not deflected by intervening surfaces (such as walls of the container  12 ), forms any shape that does not fall outside a 180° angular sweep from the middle of the drum  80 . Thus, the truncated sector output pattern  210  is intended to include, without limitation, the pattern shown in FIGS. 3A &amp; 3B, and similar substantially rectangular patterns.  
     [0029] Even with a truncated sector output pattern  210 , there may be an undesirable side-to-side distribution of the wood chips within the output pattern  210 . For instance, the distribution of wood chips in the output pattern  210  to the middle subsector  210 C, right side subsector  210 R, and left side subsector  210 L may be uneven and/or otherwise undesirable for some reason (e.g., output shifted left of center, leaving right side subsector  201 R relatively unfilled). If the optional variably positioned dividers  46  are employed, then the ratio of output flow to the various subsectors  210 C, 210 R, 210 L may be adjusted by the operator during operation (via adjusting mechanism  48 ) to reach the desired ratios. Of course, adjustments can also be made to the drum  80  rotational speed and to the wood chip supply rate from the conveyor system  14 .  
     [0030] While the exact principles are not fully understood, the handling device  20  of the present invention is able to pack wood chips within the containers  12  at density substantially higher than so-called free-fall loading. In free-fall loading, the wood chips from the conveyor system  14  are directed to the container via a simple chute system. Examination of free-fall loaded wood chips “packed” in a container show that they land with widely varying orientations, sometime referred to as “jack strawed” (like unstacked firewood), resulting in non-optimum density. In contrast, the wood chips loaded via the present device  20  land with a substantially consistent orientation, resulting in increased density.  
     [0031] The actual packed density achieved is expected to vary depending on variations in size and moisture content of the wood chips. However, a simple ratio, referred to herein as the packing density factor, can be used to quantify the improvement provided by the present invention. The packing density factor is simply the ratio of the weight of wood chips in a given volume when packed with the test device  20  divided by to the weight of the same volume of the same type wood chips (i.e., same size and moisture content), packed using the free-fall method. For instance, it is expected that a common 7100 ft 3  railcar  12  loaded with wood chips using the free fall method will have approximately seventy-seven tons of wood chips. It is expected that if the same type wood chips are loaded using the device  20  of the present invention, the 7100 ft 3  railcar  12  would hold approximately one hundred tons of wood chips. Using these values, the packing density factor for the present invention would be 100/77=1.30. Clearly, substantial improvements in packing may be achieved using the present device  20 , with resulting packing density factors in the range of 1.20 to 1.35 or higher. Just for reference, these type of packing density factors typically correspond to densities of 26.0 pounds/ft 3  to 29.3 pounds/ft 3  or more.  
     [0032] One example of the handling device  20  of the present invention may be made using a drum  80  with a diameter of approximately 18 inches, approximately 48 inches in width, and an octagonal cross-section of approximately 7 inch wide facets  92 . The blades  100  may be approximately 6 inches in height, with two sections of approximately 24-⅛ inches meeting at an angle α of approximately 8°, and spaced at intervals of approximately 7 inches. The gussets  104  may be approximately 3 inches in height. The baseplate  42  of the feed chute assembly  30  may be at a 45° angle, with the 24-30 inch high deadwall  60  positioned such that the center section  62  is approximately 5 inches after top dead center and the side sections  64  are approximately 10 inches after top dead center, for a gap of approximately 8 inches. The pivoting divider walls  46  may be made adjustable, with a target distribution of 25%-50%-25% for feeding to the left  84 , center  82 , and right  84  portions of the drum  80  respectively. All portions of the device  20  contacting the wood chips may advantageously be made from ¼ inch abrasion resistant (AR) steel. The output pattern  210  of such a device should correspond to that shown in FIGS. 3A &amp; 3B with β approximately equal to 8°-10°.  
     [0033] It should be noted that in order to minimize the escape of errant wood chips during loading, the frame  22  may advantageously include additional scatter shields at appropriate locations. The shield locations generally include on either side of the feed chute assembly  30 , and slightly downstream from the drum  80 , but these locations may vary depending on the details of a particular installation site.  
     [0034] The resulting truncated sector output pattern  210  when using preferred embodiments of the present invention is particularly suited to the filling of rectangular containers, such as railcars  12 . Prior art devices which rely on a distribution device that spins about a generally vertical axis tend to create round output patterns covering substantially a full 360°, which are ill suited to filling rectangular containers. As the majority of wood chips shipped between domestic locations are shipped by rail, using rectangular railcars  12 , the preferred embodiments of the present invention are more suited to the needs of the industry.  
     [0035] The discussion above has shown the device  20  having an output that is forward and downward, which is believed to be advantageous for most applications. However, by moving the input stream of wood chips relative to the drum  80 , from after top dead center to before top dead center, it is believed that the output may be changed to forward and upward, with the wood chips leaving such at device  20  having a slightly “lofted” trajectory. However, the resulting output pattern  210  should still remain a truncated sector (e.g., generally rectangular), not circular.  
     [0036] The discussion above has described a device  20  using a single rotating drum  80 . In most applications, this will be sufficient. However, the present invention is not limited thereto, and devices  20  employing a plurality of drums  80  rotating about one or more generally horizontal axes  86  are intended to be encompassed by the present invention. The most likely arrangement for such a multiple drum  80  arrangement would be to have the drums  80  located coaxially, in a manner easily understood by one of ordinary skill in the art based on the teachings of the present application.  
     [0037] The densely packed output from the flinger  20  is useful in densely packing wood chips in a variety of containers, and even for stacking wood chips on the ground. For example, many wood pulp mills receive wood chips generated at other locations and then store the wood chips as inventory for subsequently making wood pulp. It is common for this “inventory” of wood chips to be stored in a pile on the ground  132 , such as on rough cleared land or on a concrete pad. This pile is typically formed by the wood chips falling off the distal moving end  122  of an inclined boom  120 , with the wood chips routed thereto by a conveyor  114  that runs along the boom  120 . The booms  120  may be track-guided linear motion booms, or may be rotating type booms. In the former case, the resulting pile of wood chips is typically an elongated mound; in the later case, the resulting pile of wood chips has an arc or annular shape when viewed from above, as dictated by the rotating boom  120 . In both cases, the resulting pile is rather loosely packed, as it is formed by a free-fall process, with densities generally in the range of 1923 pounds/ft 3 . The flinger  20  of the present invention may be used in such situations to allow more chips to be stored in the same space. FIGS.  7 A- 7 B show a simplified representation of the flinger  20  suspended from the distal end  122  of the boom  120 , just below the output of the conveyor  114  on the boom  120 . Thus, as the boom  120  moves in a given direction  124 , such as clockwise, the flinger  20  travels with the moving end  122  of the boom  120 . The flinger  20  may advantageously be oriented such that its output  210  is directed generally opposite the direction of movement of the boom, as indicated by arrow  126 . As the boom moves, the resulting pile  130  is formed behind the boom  120 , but with significantly higher density compared to the conventional free-fall technique, typically on the order of 25-30 pounds/ft 3 . Thus, the pile  130  may be said to have a packing density factor of 1.20 or more, and preferably a packing density factor of 1.3 or more.  
     [0038] The dense packing advantage of the flinger  20  may also be used to improve the efficiency of various processes that use wood chips. For instance, the “digesting” process well known in the wood pulp industry uses wood chips loaded into a digestion chamber  140  with various chemicals to generate wood pulp with the general consistency of mashed potatoes. The digestion chamber  140  is operated in a batch mode, with the wood chips and chemicals added, the digestion chamber (container) closed, and heat, high pressure steam, or the like, added for a specified period of time, and then the digestion chamber is unloaded and the process repeated on a new batch. The conventional technique for loading wood chips into the digestion chamber is to have the wood chips free-fall from a conveyor into an opening  142  in the top of the container. Instead, according to the present invention, the flinger  20  may be interposed between a conveyor system  14  and the opening  142 . The input stream  200  of wood chips is fed to the rotating drum  80  of the flinger  20  so that the wood chips are redirected and flung into the digestion chamber  140  with a preferential orientation so as to be packed therein more densely. FIG. 8 shows a simplified representation of the flinger  20  disposed between the conveyor  14  and the digestion chamber  140 , with the output wood chips being flung downward through the opening  142  of the digestion chamber so as to arrange themselves therein with a preferential orientation with respect to one another, thereby allowing for tighter packing. The wood chips packed in the digestion chamber  140  using the present technique may have a packing density factor of 1.20 or more, and preferably a packing density factor of 1.3 or more. The usual digesting chemicals may be added before, during, or after the wood chip loading, with the amounts thereof adjusted to accommodate the increased weight quantity of wood chips present in a batch. The process may then continue as in the conventional digesting technique. By using the flinger  20  to aid in densely packing the wood chips in the digestion chamber  140 , more wood chips may be processed by a given piece of equipment in a given time period, resulting in a more cost effective process.  
     [0039] The increase in packing density readily achieved by the present invention has clear benefits to the industry. In the simplest terms, more wood chips can be packed into a smaller space, thereby lowering transportation, storage, and processing costs. Further, given the substantial increase in packing density achieved, the cost savings can be considerable.  
     [0040] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only some embodiments have been shown and described and that all changes and modifications that come within the meaning and equivalency range of the appended claims are intended to be embraced therein.