Patent Document

This application is a divisional of U.S. application Ser. No. 09/525,621, filed Mar. 14, 2000, now U.S. Pat. No. 6,588,690, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to systems and methods for treating process material and, more particularly, to systems and methods for treating municipal solid waste material, medical waste material, reclaimed paper and the like. 
     As a result of increasing scarcity of landfills and more stringent environmental regulations, efforts have been made to reduce the volume of process material, such as municipal solid waste (“MSW”) and paper material, such as newsprint and other reclaimed and recycled paper products as a step in the process of disposing of the material, either by depositing it in landfills, incinerating it or recycling it. Processes have been developed to break down such material for disposal, or in the case of paper products, use as insulation. An example of such a process and device is Holloway U.S. Pat. No. 5,190,226. That patent discloses an apparatus and method for separation, recovery and recycling of MSW. The apparatus includes a rotating drum which is fed at an upstream end by a reciprocating ram, a steam source which is connected to introduce high temperature steam into the drum, and a spiral rib or flight mounted within the drum to transport material deposited in an upstream end of the drum along the length of the drum. 
     The drum is maintained in a pressurized state during a sterilization process by inlet and exit air locks which are connected to and enclose the inlet and outlet of the rotating drum. The outlet air lock is connected to a rotating trommel which receives sterilized waste from the drum and rotates it over screens to provide a sizing function. 
     In view of heightened concerns over the spread of infectious diseases, many of which are fatal to humans, governmental agencies have imposed strict requirements on the disposal of waste, and more particularly, medical waste. Such medical waste may include relatively soft items such as hospital linen, garments worn by patients and health care providers, bandages, gauze and other fabric material which comes in contact with a patient, as well as harder materials such as disposable plastic surgical instruments and hypodermic needles. In order to treat such materials to render them safe and at the same time comply with federal, state and local standards, it is often necessary to grind, shred, or otherwise comminute such medical waste, and in addition, to sterilize the waste by heating it, contacting it with a disinfectant, or a combination of both. Furthermore, as in most sterilization processes, it is necessary that the actual sterilization steps be conducted in a closed and controlled atmosphere. 
     An example of such a device and method is shown in Lewis et al. U.S. Pat. No. 5,941,468. That patent discloses a medical waste sterilization system in which medical waste is shredded and placed in a rotating autoclave cylinder where it is first tumbled and contacted by steam to heat it, then is heated further in a downstream section of the autoclave cylinder which is surrounded by a steam jacket. The waste is then cooled and dehydrated in a third section of the cylinder and deposited in a compactor. The object of the device and method is to heat the medical waste thoroughly to a sterilizing temperature (typically above 212° for at least 30 minutes), then dehydrate the material to reduce its volume and weight. 
     A disadvantage with such systems is that, while they may be effective in treating MSW or process material, or sterilizing medical waste, they either operate on a batch process, that is, as in the device of aforementioned U.S. Pat. No. 5,190,226 the heating vessel is first loaded with solid waste, rotated to expose the waste to steam at elevated temperature and pressure, then the waste is evacuated from the rotating drum or pressure vessel completely before new waste is introduced for sterilization; or, as in the device of U.S. Pat. No. 5,941,468, the vessel is maintained below ambient pressure since no air-tight seal is effected in the waste material inlet and outlet openings of the vessel. 
     A second disadvantage with such systems is that the heating of material is performed entirely within a rotating drum or other vessel which typically has a volume much larger than that of the waste material to be sterilized. As a result, the entire interior volume of the drum must be heated to the desired temperature, and the waste tumbled to expose it to steam so that it is heated evenly. Consequently, a larger amount of steam, and therefore heat energy, is required to heat the entire interior of the vessel, in comparison to the amount of steam and heat energy to required to heat simply the waste material itself. 
     Accordingly, there is a need for a material treatment system and method which can utilize a pressurized vessel operated on a continuous basis, as opposed to being operated on a batch basis, the latter process having the disadvantage of providing a reduced through put rate, and further, requires successive heating and cooling cycles which require relatively large amounts of energy. There is also a need for a system and method for treating material, including medical waste, in which the energy needed to heat the material is concentrated on the material itself, as opposed to a process in which material is heated simply by placing it in a large volume, the entirety of which must be heated to the necessary temperature. 
     SUMMARY OF THE INVENTION 
     The present invention is a system and method for treating material under pressure in which the material is compacted into a plug within an inlet extrusion tube and preheated, then heated to the desired temperature within a rotating autoclave vessel fed by the extrusion tube. In a preferred embodiment of the present invention, the system includes inlet and outlet extrusion tubes through which material to be treated enters and exits a pressurized treatment zone which includes the autoclave vessel. Inlet and outlet injector screws feed material into the inlet and outlet extrusion tubes, respectively, to create continuously moving or “dynamic,” air-tight plugs of material within the tubes to seal the treatment zone. 
     Since it is the material itself that forms the seals of the pressurized treatment zone inlet and outlet, the system of the present invention can perform a treating function on a continuous basis, even though the vessel is pressurized above ambient. This design represents an improvement over prior art devices in which material treatment is performed in autoclaves which are sealed with a conventional gate or door, such that the treatment process must be performed in a batch mode. As a result, the system and process of the present invention provides a greater throughput rate than prior art designs and processes, and a concomitant greater energy efficiency, since the pressurized treatment zone does not need to be successively heated to treat material, then cooled to allow the material to be removed at a safe handling temperature. 
     The system and method of the present invention is effective in treating medical waste, in which case the material is heated and retained within the pressurized treatment zone sufficiently to sterilize it, preferably being heated to at, least 212° F., as well as MSW and paper, such as newsprint, in which case the material is heated and retained within the pressurized treatment zone sufficiently to “cook” it and break it down, especially the paper fibers. Medical waste, MSW and paper shall be referred to herein collectively as “material.” 
     In a preferred embodiment of the invention, the system has an input component which includes a conveyor which conveys material through an air lock to a hopper, a shear shredder which receives material from the hopper and shreds it to reduce its size, and an injector screw which receives the shredded material and feeds it to the inlet extrusion tube of the pressurized treatment zone. In alternate embodiments, the input component includes a hopper having a reciprocating ram which forces material into the shear shredder, and an air lock, located between the shear shredder and the injector screw, which eliminates the need for an air lock associated with the conveyor. 
     The central component of the present invention is the pressurized treatment zone, which includes a rotating autoclave vessel. Essential to the operation of the rotating autoclave vessel is the heated inlet extrusion tube which connects the inlet feed screw with the interior of the autoclave vessel. The inlet extrusion tube preferably comprises a cylindrical tube having a slightly diverging interior wall, a chamber for receiving pressurized, heated steam, and an inner face with orifices shaped and oriented to direct steam from the interior of the extrusion tube into the interior of the autoclave. It is within this extrusion tube that material received by the inlet injector screw and compacted to form an air-tight plug, heated and largely sterilized (if desired) prior to its entering the autoclave vessel. Since the material is compacted and in intimate contact with the heated extrusion tube, the heating is more efficient than in prior art vessels which are largely empty during operation. 
     The autoclave vessel is a horizontally oriented cylinder which is mounted for rotation. The interior of the vessel includes a continuous, helical rib so that rotation of the vessel about its central, longitudinal axis causes material deposited within it to progress along the length of the vessel. The interior of the vessel is heated exclusively by the steam which exits the orifices formed in the extrusion tube. The purpose of the vessel is to fluff the material and expose it thoroughly to the heat from the steam, which will sterilize medical waste and cook and break down MSW and paper pulp. The helical rib located within the vessel includes a plurality of longitudinally extending ribs which extend between flights and act to lift the hazardous material and tumble it as it progresses along the vessel. This further ensures the even heating and sterilization of the material. 
     In the preferred embodiment, the vessel includes an open exit end which empties into a stationary, vertically-oriented pressure vessel or hopper. That pressurized hopper directs the now-treated material downwardly into a second or exit injector screw which feeds it into a second or exit extrusion tube, forming a plug of material. This downstream or exit plug of material also acts as a seal so that the atmosphere within the pressure vessel, pressurized hopper, and exit injector screw is sealed from the environment. The exit extrusion tube preferably is connected to, and therefore deposits treated material into, a tumbler, where the material is dehydrated and cooks. The tumbler preferably includes an exhaust blower which maintains the interior of the tumbler at a slightly-below-atmospheric pressure. The tumbler also includes a helical rib which causes the material to break apart as it progresses along the tumbler, and the tumbler is open at its exit end so that the material may be deposited upon a conveyor for removal. 
     In an alternate embodiment, the exit injector screw and exit extrusion tube are replaced by an air lock which acts to seal the interior of the vessel and stationary exit vessel from the ambient. Also in alternate embodiments, the exit air lock is replaced with a sealable door so that the sterilization process may be conducted, if desired, on a batch basis. With that embodiment, the pressure vessel processes material along its length, then after the material has been adequately heated, the exit door is opened and the treated material is forced outwardly through it by the helical ribs within the vessel unto a conveyor for removal. However, the inlet injector screw and inlet extrusion tube of that embodiment allow continuous feeding into the pressurized autoclave vessel during treatment. 
     With all of the embodiments summarized above, the input component, which includes an injector screw, creates a plug within an inlet extrusion tube which acts as a dynamic seal, since the material progressing through the extrusion tube into the vessel seals the interior of the autoclave vessel from the ambient and from the shredding and input segments of that component. 
     The method of the present invention includes the steps of receiving material within an enclosed environment, shredding the material within that environment, forming a dynamic plug of shredded material while simultaneously heating the material to a predetermined temperature (preferably greater than 212° F.), depositing the heated material into a rotating vessel where it is broken up and maintained at a temperature above 212° F., then cooling and dehydrating the material. Also in the preferred method, the treated material is formed into a dynamic plug which seals the pressurized treatment zone of the apparatus. 
     Accordingly, it is an object of the present invention to provide a system and apparatus for treating material in which the material can be heated under pressure on a continuous basis if desired; a system and method for treating waste in which the waste itself is formed into dynamic plugs which form seals to isolate the heating regions of the apparatus from the input and exit regions; and a system and method for heating material which is rugged and can be modified easily to perform treatment of material on a batch basis, if desired. 
     Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat schematic, perspective view of a system embodying a preferred embodiment of the system and method of the present invention; 
     FIG. 2 is a somewhat schematic, perspective detail of the system of FIG. 1 showing the vessel, inlet injector screw and outlet injector screw; 
     FIG. 3 is a schematic, perspective view of the detail of FIG. 2, partially broken away to reveal the inlet and outlet injector screws, input and exit extrusion tubes and sterilization vessel; 
     FIG. 4 is a detail showing a schematic, perspective view of the inlet extrusion tube of the device of FIG. 3; 
     FIG. 5 is a schematic, perspective view of the input component of the system of FIG. 1; 
     FIG. 6 is a schematic, perspective view of an alternate embodiment of the input component of the preferred embodiment of the present invention; 
     FIG. 7 is a schematic, perspective view of the input component of FIG. 6, partially broken away to reveal the interior of the air locks and feed hopper; 
     FIG. 8 is a schematic perspective view of an alternate embodiment of the invention in which the pressure vessel is sealed with a door; 
     FIG. 9 is embodiment of FIG. 8 showing the door in an open position; 
     FIG. 10 is a schematic, perspective view of a detail of the system of FIG. 1 in which the outlet injector screw, exit extrusion tube and tumbler are shown broken away; and 
     FIG. 11 is a detail of an alternate embodiment of the present invention showing an air lock at the exit end of the vessel. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, the system of the present invention includes an input or feeding component  12 , a pressurized treatment component  14 , and a cooling and drying or output component  16 . The input component  12  includes an input conveyor system  18 , an air lock  20 , an input hopper  22 , a shredder  24  and a feed or compression screw  26 . 
     The conveyor system  18  includes an input conveyor  28  and, as best shown in FIG. 5, an air lock conveyor  30  which is aligned with the input conveyor  28 . The air lock  20  includes an enclosure  32  having an input opening  34  and an outlet opening  36 , which are alternately opened and closed by inlet and outlet gates  38 ,  40 , respectively. The input conveyor  28  is enclosed on four sides by a hood  42 . An exhaust system, generally designated  44 , includes conduit  46 , which communicates with the hood  42 , and conduit  48 , which communicates with the air lock enclosure  32 . The exhaust system  44  includes a blower  50  and a HEPA (high efficiency particulate air) filter  51 . 
     The feed hopper  22  includes an enclosure  52  having a front wall  54  which is common with the air lock  32  and in communication with the exit opening  36 , and a converging rear Wall  56 . A reciprocating ram  58  is positioned within the hopper  22  and is operated by a double-acting cylinder (not shown). The hopper  22  includes a bottom opening  60  which is in communication with the shredder  24 . Shredder  24  preferably is a shear shredder, such as Komar Industries, Inc. Model QR3030-50. 
     As best shown in FIGS. 2 and 3, the feeding component  12  includes a feed screw hopper  62  which interconnects the hopper enclosure  52  (FIG. 5) with the feed screw  26 . The feed screw  26  includes a screw  27  having a tapered shaft  29  and a helical flight  31  which is oriented horizontally within an enclosure  63  which conforms generally to the tapered, conical shape of the screw. The screw  27  is powered by a bi-directional, variable speed hydraulic motor  64 . 
     The operation of the feed component  12  is as follows. As shown in FIG. 5, material (not shown), such as containerized medical waste, is placed on input conveyor  28 . The atmosphere within the hood  42  is slightly below atmospheric as a result of the operation of the blower  50 , so that fumes are drawn through the HEPA filter  51 . The air lock door  38  is opened and the conveyor  28  conveys the containerized waste onto the air lock conveyor  30 . The door  38  then closes, and subsequently, air lock outlet door  40  opens, conveyor  30  is actuated, and the material is conveyed into the feed hopper  52 , where it falls downwardly into the shear shredder  24 . If the material “hangs up” or bridges the rotating shredder components of shear shredder  24 , the reciprocating ram  58  is cycled to force the material downwardly to be shredded by the shredder  24 . The shredded material enters the feed screw enclosure  63  where it is transported horizontally and, simultaneously, compressed by the screw  27 . 
     As shown in FIGS. 3 and 4, the pressurized treatment component  14  of the present invention includes an inlet extrusion tube, generally designated  66 , a rotating autoclave vessel  68 , an evacuation hopper  70 , and an outlet injector screw assembly  72 . The inlet extrusion tube  66  extends into the interior of the vessel  68  and includes a generally cylindrical, horizontally extending body  74  having an inner wall  76  which tapers outwardly along its length (preferably about ½″ of diameter for 3′ of length), an outer, generally cylindrical wall  78 , and a squared end face  80 . The inner and outer walls  76 ,  78  form a steam jacket or chamber  82  which is generally cylindrical in shape and communicates with a steam supply conduit  84 . The conduit  84  is connected to a source of steam  85  (FIG.  5 ). The upstream end of the tube  74  includes a flange  86  which mates with a corresponding flange  88  which is part of an extension  90  connected to the downstream wall  92  of the feed screw enclosure  63 . 
     The face  80  is perforated with a plurality of orifices  94  which communicate with the chamber  82  so that steam entering the chamber will exit through the orifices  94  and into the vessel  68 . It is within the scope of the invention to provide additional orifices (not shown) in the outer wall  78  of the inlet extrusion tube  66  located at the inner end portion (that is, the portion of the inlet extrusion tube within the interior of the vessel  68 ), or to provide orifices only in the outer wall of the inner end portion of the inlet extrusion tube, and/or to provide such orifices (not shown) in the inner wall  76  of the tube at that location. 
     The vessel  68  includes a horizontally-extending cylindrical body  96  having an inlet opening  98  at an upstream end shaped to receive the inlet extrusion tube  66  there through. The outer wall  78  of the extrusion tube  66  includes a radially-extending flange  100  which forms a labyrinth seal with a correspondingly-arranged annular flange  102 , and an annular gasket  104 , both retained with an end extension  106 . Consequently, the flanges  100 ,  102  and gasket  104  form a rotating seal between the stationary tube  66  and rotating body  96 . The body  96  is supported on bearings  108 ,  110  which engage annular external ribs  112 ,  114 , respectively, which extend about the exterior surface of the body. The body  96  is rotated by a gear drive  116  which includes an electric drive motor  118 , which preferably is a variable-speed, bi-directional drive motor. 
     As shown in FIG. 3, the interior  120  of the body  96  includes a continuous, helical, raised rib  122  which extends along the length of the interior. The flights of the rib  122  are separated by a plurality of flat spacer plates  124  which extend radially and axially relative to the body  96 . The size and spacing of the rib  122  promotes the transport of hazardous material along the length of the body  96 . 
     The downstream end of the cylinder  96  includes an outlet extension  126  which defines an outlet opening  128  and includes a radially-inwardly extending flange  130 . The pressurized hopper  70  includes a cylindrical body  132  and a flange  134  which includes a radially extending flange  136  which forms a labyrinth seal with the flange  130 . The labyrinth seal created by flanges  130 ,  136  is of similar construction to the labyrinth seal formed between the injection tube  66  and cylinder extension  106 . An annular gasket (not shown) is also included in the labyrinth seal. 
     The pressurized hopper  70  includes a mating flange  138  which is connected to the flange  140  of the inlet hopper  142  for the exit injector screw assembly  72 . The hopper  142  is of a tapered, conical shape and communicates with a conical housing  144  of the exit injector screw assembly  72 . The exit injector screw assembly  72  includes a tapered screw  146  which is driven by a variable-speed, bi-directional hydraulic motor  148 . The screw  146  includes a tapered shaft  150  and a helical flight  152 . The tip of the screw  146  extends into an exit extrusion tube  154  which tapers outwardly in a downstream direction. Thus, during operation of the system of the present invention, a pressurized treatment zone, which includes the cylinder  96 , pressurized hopper  70 , inlet hopper  142  and exit injector screw assembly  72  is created between the inlet extrusion tube  66  and the outlet extrusion tube  154 , both of which are sealed by air-tight, dynamic plugs of material. 
     As shown in FIGS. 3 and 10, an evacuation system, generally designated  156 , includes a condenser  158 , blower  160  and conduit  162  which communicates with the interior of the drum  164  which is a part of the cooling and drying component  16 . The conduit  162  is connected to annular chamber  166  which includes a plate  168  having a plurality of orifices  170  formed in it. The orifices  170  open into the interior  172  of the drum  164 . The drum  164  includes a cylindrical body  174  having a plurality of raised ribs  176  which extend inwardly from the inner wall  178  of the drum in a spiral pattern. The drum  164  includes raised external ribs  180 ,  182  which engage bearings  184 ,  186 , respectively. The drum  16  is rotated about its central longitudinal axis by a reversible electric motor (not shown). The downstream end of the drum  164  is defined by an opening  188  which communicates with an open hopper  190 . The end  188  includes a radially-extending flange  192  which is received within an arcuate opening  194  of the open hopper  190 . The open hopper  190  includes converging walls  196 ,  198  which are shaped to direct material onto a conveyor  200  for removal from the site. 
     The operation of the system shown in FIG. 1 is as follows. Material which has been shredded by shredder  24  and dumped into inlet feed screw enclosure  63  (see FIG. 3) is compressed and displaced sidewardly into the inlet extrusion tube  66 , where friction between the material and the inner wall of the tube causes the material to form a compacted plug (not shown) within the tube. The material within the tube  66  is heated by steam which is injected into the chamber  82  through conduit  84 . The steam entering the chamber preferably is between 250° F. and 280° F., but in any event is above 212° F. As additional material is driven into the tube  66  by the screw  27 , material is forced from the end of the tube adjacent to the perforated face  80  and is deposited into the cylinder  96 . Additional size reduction of the material is accomplished by the abrasion of tip of the shaft and tip of the flight  30  of the screw  27  against the adjacent material of the non-rotating plug within the tube  66 . 
     The material within the inlet extrusion tube  66  is sufficiently compacted to provide an airtight plug which seals the inlet to the vessel cylinder  96 . However, this airtight plug is dynamic in that it is composed of a progression of comminuted waste material which is being fed continuously into the cylinder  96  by screw  27 . Consequently, as material leaves the tube  66  and is deposited within the cylinder  96 , it is replaced at the upstream end of the tube by material which has fallen downwardly into the feed screw enclosure  63  and is “pumped” sidewardly by the tapered screw  27 . This tapered screw  27  not only abrades the material falling within the chamber  32  against the non-rotating plug of material within the tube  66 , thereby further reducing its size, the tapering shaft  29  of the screw  27 , in combination with the helical flight of that screw, compresses the material into the tube  66 . Consequently, the material within the tube  66  is heated to the desired temperature by steam in the steam jacket  82  of the chamber. 
     The material exiting the tube  66  is deposited within the rotating body  96 , where it is transported downwardly along the cylinder by the helical cylinder flight  122 . This material is fluffed and tumbled by contact with the plates  124  as the cylinder  96  is rotated by drive motor  118 . The steam within the tube  66  exits through the orifices  94  into the cylinder  96  where it continues to heat and sterilize the waste material. Residence time within the body  96  of the vessel  82  can be varied by adjusting the rotational speed of the body, and/or by periodically reversing the rotation of the body. Similarly, the feed rate of material through the extrusion tubes  66 ,  154  can be varied to effect a desired throughput rate by adjusting the rotational speed of the inlet and outlet screws  27 ,  146 , and/or by periodically reversing rotation of one or both of those screws. In the case of medical waste, the material is preheated within the inlet tube  66  and retained within the cylinder  96  sufficiently to heat it to a sterilization temperature, and the rotation of the cylinder is sufficient to retain the material therein sufficiently to effect the necessary retention time to sterilize the material. In the case of MSW and paper material, including paper pulp, the temperature and retention times are adjusted such that they are sufficient to “cook” or break down such material. 
     When the material has been transported to the downstream end  128  of the body  96 , it has been treated sufficiently either to sterilize it or to break it down, as required. The material is then emptied from the cylinder  96  and deposited into the pressurized hopper  70 , where it falls downwardly into the exit screw 1   146 . That screw  146  acts in a fashion similar to screw  27  in that it displaces the now-treated material sidewardly into the exit extrusion tube  154  where it is again compressed into a plug. As before, the plug within tube  154  is sufficiently compacted to form an airtight seal. Consequently, with the embodiment of FIGS. 1 and 3, the sterilization environment of the invention, which is accomplished by tube  66  and cylinder  96 , is sealed by plugs formed within the tube  66  and the exit extrusion tube  154 . Again, the seal between the rotating cylinder  96  and stationary tube  66  and stationary pressurized hopper  70  is accomplished by the rotating seals which have been described earlier and are located between those components. 
     As shown in FIG. 10, the compacted material is compressed into the outlet extrusion tube  154  and ultimately is deposited into the rotating drum  164  where it is tumbled and separated when it contacts the spiral ribs  176  of that drum. Moisture which is given off by the cooling material is removed through conduit  162  (and conduit  166 ) through a condenser  158  and is, if desired, recycled. The now-treated (sterilized, if desired), dried and broken-apart material then leaves the drum  164  where it is guided by open hopper  190  onto conveyor  200  for loading into a container and removal from the site. 
     As will be described below, variations can be made to the system described thus far without departing from the scope of the invention. For example, the input component  12  can be modified as shown in FIGS. 6 and 7 as  12 ′. The input component  12 ′ includes an input conveyor  18 ′ which is enclosed in a hood  42  and opens into a hopper  22  which includes a reciprocating ram  58  (see FIG.  1 ). That hopper  22  empties into a shredder  24  which is positioned directly above an air lock, generally designated  202 . Air lock  202  includes inlet and outlet doors  204 ,  206  respectively, and an air lock enclosure  208 . The air lock is in communication with the input injector screw  26 , which is identical in construction to that shown in FIG.  3 . 
     The operation of the input component  12 ′ of the embodiments of FIGS. 6 and 7 is as follows. Material is placed on conveyor  18 ′ and conveyed through hood  42  to hopper  22  where it falls downwardly into shredder  42 . Feeding of the material into the shredder  42  is expedited by the reciprocating ram  58 . The shredded material is permitted to exit the shredder when the inlet door  204  of air lock  202  is opened, so that shredded material collects within enclosure  208 . When enclosure  208  is at or near capacity, door  204  closes and door  206  opens to allow material to fall downwardly into the feed screw enclosure  26 . From there, the material is displaced sidewardly into the inlet extrusion tube  66  (see FIG. 3) and processed as described above. In another embodiment of invention shown in FIGS. 8 and 9, the treatment component  14 ′ is modified such that the cylinder  96 ′ terminates in a stationary door  210  which is supported on a pivotal hinge  212 . The door is sealed with respect to the exit extension  126 ′ of the body  96 ′ by a rotatable seal. With this embodiment, the system operates on a batch mode, such that a plug of material is formed in the injection tube  66  (see FIG.  4 ), the material is deposited into the body  96 ′, where it is treated and transported in a downstream direction by flight  122 , and upon the completion of the sterilization process, the door  210  is opened so that the treated material can exit the body  96 ′, where it is guided by an open hopper  214  to a removal conveyor  200 . 
     In another embodiment, shown in FIG. 11, the cylinder  68  includes an extension  216  which is supported by bearings  218 ,  220  that engage raised external ribs  222 ,  224 , respectively. The extension  216  communicates with a pressurized hopper  226  by a rotating seal  228 . The hopper  226  communicates with an exit air lock  230 , having an inlet door  232  and exit  234  and an air lock chamber  236 . The air lock  230  deposits material onto an open hopper  240  which guides the material to the conveyor  200  for removal. Material entering the pressurized hopper  226  is allowed to fall downwardly into the air lock chamber  236  when door  232  is opened. Door  232  is then closed when the chamber  236  is at or near capacity, and door  234  is opened, to allow material to fall downwardly into the hopper  240 . 
     Again, the embodiment shown in FIG. 11 can be used with the present invention to operate in a batch mode, at least insofar as the flow of material into pressurized hopper  226  is concerned. If the cycling of the air lock  230  is timed properly, the overall system can operate substantially continuously. 
     With all of the foregoing embodiments, the advantage of the system of the present invention is that a “dynamic” plug of ground material is created at at least the inlet end of a treatment chamber which, in the case of the preferred embodiment, consists of the injection tube and rotating cylinder body. 
     While the methods and forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms, and that variations therein may be made without departing from the scope of the invention.

Technology Category: 4