Wood chip flinger and method of densely packing wood chips

Abstract

A handling device allows wood chips to be packed with a density greater than that achieved using conventional free-fall techniques by 20%-35% or more. The device includes a drum rotating about a generally horizontal axis that includes a plurality of outwardly extending blades that act to fling the wood chips so as to land with a substantially uniform orientation. The device may be attached to a movable boom and form a pile on the ground. The device may be used to pack a wood chip digestion chamber more densely. The device may also include a feed chute assembly 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.

Description

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. 7A-7B 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'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'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 & 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 210C, right side subsector 210R, and left side subsector 210L may be uneven and/or otherwise undesirable for some reason (e.g., output shifted left of center, leaving right side subsector 201R relatively unfilled). If the optional variably positioned dividers 46 are employed, then the ratio of output flow to the various subsectors 210C,210R,210L 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 ft3 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 ft3 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/ft3 to 29.3 pounds/ft3 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 & 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/ft3. 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. 7A-7B 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/ft3. 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.

Claims

1. A method of handling wood chips, comprising: supporting a redirecting device with a distal end of a movable boom, said redirecting device comprising a drum having a plurality of outwardly extending blades; rotating said drum under power about a generally horizontal axis at a rate of 50 rpm or more; feeding a stream of incoming wood chips to said redirection device and moving said boom in a first direction while rotating said drum; forming an output stream of wood chips flung by said drum, said output stream forming a pile on the ground having a packing density factor of at least 1.20.

2. The method of claim 1 wherein said feeding said stream of incoming wood chips to said redirection device comprises moving said wood chips upward towards said distal end of said boom.

3. The method of claim 1 wherein said forming said pile on the ground comprises forming a non-linear elongate pile on the ground.

4. The method of claim 1 wherein forming said output stream of wood chips comprises forming said output stream in a direction generally opposite said first direction.

5. The method of claim 1 wherein moving said boom comprises rotating said boom in said first direction, and wherein forming said output stream of wood chips comprises forming said output stream in a direction generally opposite said first direction.

6. An assembly for handling wood chips, comprising: a movable boom having a distal end; a redirecting device supported by said distal end of said movable boom, said redirecting device comprising a drum having a plurality of outwardly extending blades and a motor, said motor coupled to said drum so as to rotate said drum; wherein a stream of incoming wood chips fed to said redirection device while said 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 said drum that land with a preferential orientation.

7. The assembly of claim 6 wherein said boom moves in a first direction, and wherein said output stream is directed in a direction generally opposite said first direction.

8. The assembly of claim 7 wherein said boom rotates in said first direction.

9. The assembly of claim 6 wherein said output stream forms a pile on the ground having a packing density factor of at least 1.20.

10. The assembly of claim 9 wherein said output stream forms a pile on the ground having a packing density factor of at least 1.3.

11. A method of processing wood chips, comprising: 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, said drum including a plurality of outwardly extending blades; directing wood chips output from said drum into a wood chip digestion chamber; packing said wood chips in said wood chip digestion chamber to a density greater than a free-fall density; and digesting said wood chips in said digestion chamber for a period of time.

12. The method of claim 11 wherein said packing said wood chips in said wood chip digestion chamber comprises packing said wood chips in said wood chip digestion chamber with a packing density factor of at least 1.20.

13. The method of claim 11 further comprising adding chemicals to said chamber prior to said digesting.