Patent Publication Number: US-2009223081-A1

Title: Methods and systems for solid waste processing

Description:
This application claims the benefit of U.S. Application No. 61/034,337, filed Mar. 6, 2008, which is hereby incorporated by reference in its entirety in the present application. 
    
    
     BACKGROUND 
     This patent is directed to methods and systems for solid waste processing, and, in particular, to methods and systems for solid waste processing utilizing vibratory equipment with mixed solid waste material. 
     SUMMARY 
     According to an aspect of the present disclosure, a vibratory system for processing solid waste material includes a storage conveyor including a trough with a deck and opposing side walls disposed to either side of the deck, a plurality of resilient members supporting the trough above a surface, and a vibration generator coupled to the trough to move solid waste material disposed in the trough along the deck to an outlet. The system also includes a heating unit including a container with an opening to receive solid waste material from the outlet of the storage conveyor, the opening being in communication with an interior chamber, a closure moveable relative to the opening to limit passage of solid waste material through the opening, and a source of steam coupled to the interior chamber to provide steam to the interior chamber to heat solid waste material disposed therein. 
     According to another aspect of the present disclosure, a method of processing solid waste material includes storing solid waste material in a storage conveyor, the conveyor including a trough with a deck and opposing side walls disposed to either side of the deck, a plurality of resilient members supporting the trough above a surface, and a vibration generator coupled to the trough to move solid waste material stored in the trough along the deck to an outlet. The method also includes activating the vibration generator to move the solid waste material along the deck to the outlet, receiving the solid waste material in a container, and supplying steam to the container to heat the solid waste material received therein to generate treated solid waste material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are a plan view of a system for solid waste processing according to the present disclosure; 
         FIG. 2A  is a side elevation view of a combination of a storage conveyor, a feed conveyor and a heating unit, with the feed conveyor in a first position; 
         FIG. 2B  is a side elevation view of the combination of storage conveyor, feed conveyor and heating unit of  FIG. 2A , with the feed conveyor in a second position; 
         FIG. 3  is a side elevation view of a combination of transfer conveyors and screening conveyors; 
         FIG. 4  is a side elevation view of a combination of transfer conveyors and presses; 
         FIG. 5A  is a side elevation view of a press for use in the sub-system of  FIG. 4 ; 
         FIG. 5B  is a cross-sectional view of the press of  FIG. 5A ; and 
         FIG. 6  is a side elevation view of a combination of the presses from  FIG. 4 , dryers and associated transfer conveyors; 
         FIG. 7  is a side elevation view of a first combination of transfer conveyors and picking stations associated with the screening conveyors of  FIG. 3 ; and 
         FIG. 8  is a side elevation view of a second combination of transfer conveyors and picking stations associated with the screening conveyors of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
     Although the following text sets forth a detailed description of different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the invention since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention. 
     It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. §112, sixth paragraph. 
     Referring first to  FIGS. 1A and 1B , a system  100  for processing solid waste material is illustrated. The waste material received by the system  100  may include a mix of materials, such as newspapers, boxes, bottles, cans, food wastes, etc., as may be found in solid municipal waste. Thus, the solid waste material may include a variety of material types, such as paper, cardstock, cardboard, glass, plastic, metal, biomaterials, etc. The solid waste material may be sorted before it is loaded into the system  100 , but the system  100  is designed to treat unsorted solid waste material as well. 
     Starting then at the left-hand side of  FIG. 1A , there is a space  102  in which a plurality of piles  104 ,  106 ,  108  may be disposed. These piles  104 ,  106 ,  108  are composed of solid waste materials, some piles being sorted before their arrival in the space  102  and other piles being unsorted. The space  102  is preferably an enclosed space, defined by a structure  110  so as to prevent the solid waste materials from being carried out of the space  102  by the action of wind and water, for example. An enclosed space  102  also limits the access that animals, in particular larger animals, have to the solid waste material. 
     A transport device (not shown) may be disposed in the space  102  to load the solid waste materials of the piles  104 ,  106 ,  108  into the system  100 . Such a transport device may take the form of a vehicle, such as a front loader, for example. Alternatively, the transport device may be in the form of an overhead crane fitted with a claw, a bucket or the like. Still further, the transport device may include a conveyor on which workers manually dispose the solid waste material for its transit along the conveyor into the system  100 . 
     The system  100  includes at least one storage conveyor  120 . Four storage conveyors  120  are illustrated in  FIG. 1A . The storage conveyors  120  are used to store the solid waste material  120  prior to its receipt in one of a plurality of heating units  130 . Each conveyor  120  may hold a sufficient amount of solid waste material to fill one of the heating units  130  according to the illustrated embodiment. However, it will be recognized that the conveyor  120  may be sized to store either more or less solid waste material than is required to fill one of the heating units  130 . 
     Referring now to  FIGS. 1A ,  2 A and  2 B, the storage conveyor  120  may include a trough  140 . The trough  140  has a deck  142  and opposing side walls  144  disposed to either side of the deck  142 . A plurality of resilient members  146  supports the trough  140  above a surface. As illustrated in  FIGS. 2A and 2B , the resilient members  146  (which may be coil springs) are attached at one end  148  to the trough  140  and at a second end  150  to a frame  152 . A vibration generator  154  is coupled to the trough  140  to move solid waste material disposed in the trough  140  along the deck  142  to an outlet  156 . 
     According to the illustrated embodiment, the frame  152  is required to provide a certain elevation for the solid waste material relative to other elements of the system  100 , such as the heating unit  130 . The size of the frame  152  is also dictated, in part, by the relative elevations of the surfaces on which the different elements of the system  100  are supported. It will be recognized that variations in elevation of the elements and surfaces will influence the construction of the system  100  in general, and of the frame  152  in particular. 
     It will also be recognized that considerable variation may occur relative to the suspension of the trough  140  relative to the surface on which it is supported, and in regard to the vibration generator  154 . That is, the resilient members  146  are typically paired with rigid linkages to support the trough  140 , as illustrated. The vibration generator  154  may be a two-mass system or may be a one-mass (or brute force) system. The vibration generator  154  may be coupled to the trough  140 , or may be mounted on a counterpoise which may be attached to the trough  140 . All of these elements may vary according the demands placed on the system  100 . 
     Importantly, the storage conveyor  120  provides the afore-mentioned trough  140  with continuous deck  142  flanked by opposing side walls  144 . The trough  140  may even include an end wall  160  at the end of the deck  142  opposite the outlet  156 . The deck  142 , side walls  144  and end wall  160  thus define a space  162  (see  FIG. 1A ) into which and from which passage is restricted. The solid waste material is disposed into the space  162  through the open top  164  (see  FIGS. 1A and 2A ), and exits the space  162  through the outlet  156 . 
     This is to be contrasted with a belt conveyor, wherein clearance typically exists between the belt and any side walls that may be provided to guide the solid waste material along the conveyor. Solid waste materials may pass through the clearance between the belt and the side walls, if any, and become disposed in a space that may be extremely difficult to clean regularly and/or completely. Where the solid waste material includes food and other biomaterials, the material trapped in this space may provide encourage an increase in the number of insects, rodents and the like. This may result in an extremely unhealthy environment in which to work. 
     Thus, it will be recognized that by providing a vibratory conveyor  120 , wherein the solid waste material is contained in the enclosed space  162  from which passage is restricted, the problems presented through the use of a belt or similar type of conveyor may be reduced or eliminated. Solid waste material does not end up being lost into the working gear of the conveyor  120 , as the deck  142  and side walls  144  are joined together to prevent materials from passing therebetween. Consequently, the solid waste material is contained in spaces, such as space  162 , that are relatively simple to clean regularly and completely. As a further consequence, insect and rodent contact with the solid waste material prior to heating may be limited. 
     As noted above, the system  100  also includes at least one heating unit  130 . In fact, as noted above, the system  100  includes four heating units  130 . It will be recognized that the number of heating units  130  illustrated is non-limiting; a greater number or a lesser number of heating units  130  may be included. 
     As seen in  FIGS. 1A and 2A , the heating unit  130  may include a container (or drum)  170  with an opening  172  to receive solid waste material from the outlet  156  of the storage conveyor  120 . The opening  172  may be in communication with an interior chamber  174 . The heating unit  130  may also include a closure or door  176  moveable relative to the opening  172  to limit passage of solid waste material through the opening  172 . According to the illustrated embodiment, the closure  176  may close the opening  172  so as to make the interior chamber  174  (and thus the container  170 ) airtight. 
     As seen in  FIG. 2A , the heating unit  130  may also include a source of steam  178  coupled to the interior chamber  174  to provide steam to the interior chamber  174  to heat treat solid waste material disposed therein. As illustrated, a single source of steam  178  is coupled to the plurality of heating units  130  through a system of conduits or pipes  180 . It will be recognized that the arrangement and number of sources of steam  178  relative to the arrangement and number of heating units  130  is a design choice influenced by a variety of factors. 
     The steam is released into the interior chamber  174  after first evacuating the air from the chamber  174 . Pressures within the container  170  may exceed 50 psi during the heat treatment in the chamber  174 . Furthermore, temperatures within the container  170  may exceed 500° Fahrenheit during this time. Consequently, the container  170  must be able to withstand such pressures and temperatures. 
     The container  170 , or a portion thereof, may rotate about an axis. For example, a drum may be disposed within the chamber  174  for rotation about its longitudinal axis, which axis may be aligned with the longitudinal axis of the container  170 . The interior surface of this drum may have angular or helical surfaces to provide proper agitation of the solid waste material in the chamber  174  during processing. For that matter, the rotation of the inner drum may facilitate movement of the solid waste materials into and out of the container  170  before and after processing. In this regard, the container  170  may have a structure and operation similar to the ROTOCLAVE® rotating autoclave system available from Tempico Inc. of Hammond, La. 
     To move the material from the storage conveyor  120  to the heating unit  130 , a feed conveyor  190  may be provided. The feed conveyor  190  may be disposed between the outlet  156  of the storage conveyor  120  and the opening  172  of the container  170  to bridge a space  192  between the outlet  156  and opening  172 . The space  192  may be provided, for example, to permit clearance for the door  174  to close over the opening  172 . The space  192  may also permit clearance for treated solid waste materials to be ejected from the container  170  on to a different conveyor or transport system for transport away from the heating units  130 . 
     The feed conveyor  190  may be similar in structure and operation to the storage conveyor  120 , with certain differences to provide mobility. The feed conveyor  190  may include a trough  194  with a deck  196  and opposing side walls  198  disposed to either side of the deck  196 . A moveable frame  200  is provided, the frame  200  having a first position ( FIG. 2A ) wherein the feed conveyor  190  bridges the space  192  between the outlet  156  and the opening  172  and a second position ( FIG. 2B ) wherein the feed conveyor  190  does not bridge the space  192  between the outlet  156  and the opening  172 . In particular, the frame  200  may include a carrier or carriage  202  having pairs of opposing wheels  204 , which wheels  204  may be mounted on rails  206  to guide the motion of the carrier  202 . A plurality of resilient members  208  mount the trough  194  to the frame  200 , and a vibration generator  210  is coupled to the trough  194  to move solid waste material disposed in the feed conveyor  190  between the outlet  156  of the storage conveyor  120  and the opening  174  of the heating unit  130 . 
     In operation, the feed conveyor  190  would be maintained in the position illustrated in  FIG. 2A  to move the solid waste material from the storage conveyor  120  into the heating unit  130 . Solid waste material may be moved from the storage conveyor  120  via feed conveyor  190  into the heating unit  130  at a rate such that 4500 cubic feet of solid waste material may be transferred from the conveyor  120  to the container  170  in six minutes. The feed conveyor  190  would then be moved (through the use of a hydraulic cylinder (not shown) arranged below the frame  200 , for example) from the position illustrated in  FIG. 2A  to that illustrated  FIG. 2B , and the door  176  may be closed to seal the container  170  of the heating unit  130 . The feed conveyor  190  would then remain in this position until after the container  170  has ejected the treated solid waste material into a discharge conveyor  220  (see  FIGS. 1A and 2B ). 
     The discharge conveyor  220  is the first in a series of conveyors that may define one or more transfer systems. In this regard, a transfer system may include a single conveyor, or a plurality of conveyors. A transfer system may couple various processing devices of the system  100  together through these conveyors alone, or in combination with other elements of the system  100 . In fact, the processing devices may themselves define, in whole or in part, a transfer system. For that matter, the conveyors  120 ,  190  and the heating unit  130  may define one or more transfer systems depending on the perspective of the element of the system  100  under discussion. 
     As illustrated in  FIG. 1A , one discharge conveyor  220  is provided for two of the heating units  130 . The number of discharge conveyors  220  may be determined according to the circumstances of a particular project. The discharge conveyors  220  may be vibratory conveyors, similar in structure and operation to the conveyors  120 ,  190  discussed above, or may be another type of conveyor. Given that the material being transported as this point is heat-treated (or simply “treated”) solid waste material, use of non-vibratory conveyors does not present as many drawbacks as is the case for their use prior to the treatment of the solid waste material. In fact, as illustrated in  FIG. 3 , each discharge conveyor  220  may have an outlet  222  that is coupled to an inclined belt conveyor  230 . 
     The inclined belt conveyor  230  transports the treated solid waste material to the inlet end  240  of a first of a pair of screening conveyors  242 ,  244  (see  FIGS. 1B and 3 ). Although two screening conveyors  242 ,  244  are illustrated, the number of screen conveyors according to other embodiments may be smaller or larger. The screening conveyors  242 ,  244  are coupled to the heating units  130  (via the transfer system including the conveyors  220 ,  230 ) to receive treated solid waste material from the heating units  130 . 
     Each of the screening conveyors  242 ,  244  has a similar structure and operation. For example, referring to the screening conveyor  242 , the conveyor  242  includes a screening conveyor trough  246  with a foraminous deck  248  and opposing side walls  250  disposed to either side of the deck  248 . In fact, the sides  250  are coupled to the bottom  252  of the trough  246  so that material that passes through the deck  248  collects on the bottom  252  of the trough  242 . The deck  248  may be defined by one or more conventional finger screens  254 . A plurality of resilient members  256  supporting the trough  246  above a surface. 
     A vibration generator  258  is coupled to the trough  246  to move materials along the deck  248  and the bottom  252  of the trough  246 . In particular, larger treated solid waste materials move along the deck  248  to an outlet  260 . On the other hand, smaller treated solid waste materials pass through the deck  248 , along the bottom  252  and to an outlet  262 . In this fashion, the treated solid waste material is sorted according to physical size. 
     The materials passing through the outlet  260  are directed onto a deck  270  of the screening conveyor  244 , which deck may be defined by one or more finger screens  272 . Similar to the structure and operation of the conveyor  244 , the larger treated solid waste materials move along the deck  270  while the smaller treated solid waste materials pass through the deck  270  and are collected on a bottom  274  of a trough  276 . The materials moving along the deck  270  are directed to an outlet  278 , while the materials moving along the bottom  272  are directed to an outlet  280 . 
     It will be recognized that by selecting the size of the finger screens  254 ,  272  that define the foraminous decks  248 ,  270 , three differently sized streams of treated solid waste material may be generated at outlets  262 ,  278 ,  280 . Each of these streams is carried by a separate transfer system to a different part of the system  100  for further processing. Each of the transfer systems includes at least one belt conveyor  282 ,  284 ,  286 , which conveyors are shown in part in  FIGS. 1B and 3 , and separately in  FIGS. 4 ,  7 , and  8 . 
     The treated solid waste stream with the smallest relative physical size passes through outlet  262  and along conveyor  282  to a press  300 ; as illustrated, the treated solid waste material may pass to one of two presses  300  that are arranged to processes the material in parallel. The press  300  is the first of two different processing devices in the system  100  that may be used to remove moisture from the treated solid waste material to generate dried, treated solid waste material. As seen in  FIG. 4 , the conveyor  282  has an inlet  302  coupled to the outlet  262  of the screening conveyor  242  and an outlet  304  coupled to the inlet  306  of the press  300 . 
     The press  300  may be a screw press, such as is illustrated in  FIGS. 5A and 5B . In addition to the inlet  306 , the press  300  may have a first outlet  308  for passing the dried, treated solid waste material and a second outlet  310  for passing the filtrate that is removed from the treated solid waste material during handling. The inlet  306  and outlets  308 ,  310  may be defined by or attached to a housing  312  that receives the pressure cone  314  therein (see  FIG. 5B ). The moisture content of the treated solid waste material may be reduced from 70% to 45% in the press  300 . 
     The inner structure of the screw press is shown in greater detail in  FIG. 5B . Solid waste material enters the housing  312  via the inlet  306 . The solid waste material may enter with certain degree of moisture, shown to an exaggerated state in  FIG. 5B . The housing  312  may include a screened section  316  that extends between the inlet  306  and the outlet  308 , the screened section  316  having a first end  320  adjacent the inlet  306  and a second end  322  adjacent the outlet  308 . The diameter of the screened section  316  between the first end  320  and the second end  322  is substantially constant. By contrast, the pressure cone  314  has an increasing diameter between a first end  324  and a second end  326 , such that the clearance space between an inner surface  328  of the screened section  316  and an outer surface  330  of the pressure cone  314  decreases between the spaced ends. As a consequence, the moisture content of the material passing through the press  300  is ejected through the screened section  316 , and passes out of the housing  312  via outlet  310 . A vane or blade  332  may be attached to the pressure cone  314  to advance the solid waste material through the press  300  and eject the dried, treated solid waste material from the press  300 . 
     Coupled to the outlet  308  of the press  300  is a further transfer system, in this case including a belt conveyor  340  as shown in  FIG. 6 . In particular, the outlet  308  of the press  300  is coupled to an inlet  342  of the belt conveyor  340 , and the outlet  344  of the belt conveyor  340  is coupled to an inlet  350  of a dryer  352 . 
     The dryer  352  may be a conventional fluid bed dryer. The dryer  352  illustrated has the advantage of drying the treated solid waste material entering via the inlet  350  and moving the solid waste material from the inlet  350  to the outlet  354 . In this regard, the dryer  352  may have a structure similar to the screening conveyors  342 ,  344 , in that the dryer  352  may include a trough  360  with a deck  362  and opposing side walls  364  disposed on either side of the deck  362 . An air plenum  366  is defined beneath the deck  362  to receive heated air therein from a source of heated air  368 . The deck  362  has a plurality of openings therein to permit heated air from the plenum  366  to pass through the deck  362  and the material disposed above the deck  362 . A plurality of resilient members  370  supports the trough  360  above a surface. A vibration generator  372  is coupled to the trough  360  to move materials along the deck  362 . 
     The dried, treated solid waste material exiting dryers  352  via the respective outlets  354  is carried by a transfer system to a densifying and pelletizing apparatus  380 . The transfer system may include several different devices for further sorting the dried treated solid waste material prior to its delivery to the densifying and pelletizing apparatus  380 . The input of the transfer system is coupled to the outlet of the dryer  352  and the outlet of the transfer system is coupled to the inlet of the densifying and pelletizing apparatus  380 . 
     The transfer system includes a first belt conveyor  390  is coupled to the outlets  354  of the dryers  352 . An overhead belt magnet  392  is disposed at the output end of the belt conveyor  390  to attract and remove any metallic solid waste materials that may have been conveyed to this section of the system  100 . The materials not removed by the belt magnet  392  are passed from the output end of the belt conveyor  390  to an input end of a second belt conveyor  394  with its output end coupled to the input end of a high-stroke feeder  396 . The output end of the high-stroke feeder  396  may be coupled to the input end of a separation apparatus  398 , such as a gear sorter. The output end of the separation apparatus  398  may be coupled in turn to further belt conveyor  400 , which passes the dried, treated solid waste materials to dryer and cyclone separator  402 , the output of which is coupled to the densifier and pelletizing apparatus  380 . The pelletized, dried, treated solid waste material may then be transported to be used as fuel, for example. 
     Referring next to  FIGS. 1B ,  7  and  8 , the movement of the treated solid waste materials that exit the screening apparatuses  244  via the outlets  278 ,  280  is now discussed. Material exiting both outlets  278 ,  280  is transported via transfer systems to picking stations  420 ,  422 . According to the illustrated embodiments, the transfer system from the outlet  278  to the picking station  420  includes belt conveyors  286 ,  424 , while the transfer system from the outlet  280  to the picking station  422  includes belt conveyors  284 ,  426 . 
     As illustrated in  FIGS. 1B and 7 , an overhead belt magnet  430  may be arranged at an output end  432  of the belt conveyor  286  to separate any metallic materials that may remain in with the solid waste materials transferred along the belt conveyor  286 . The non-metallic materials are passed along a series of individual stations via the conveyor  424 , wherein various material are removed from the treated solid waste materials for separate processing, such as recycling. The materials that are not removed from the non-metallic materials at the picking stations  420  may be disposed of in a landfill, for example. 
     As illustrated in  FIGS. 1B and 8 , an output end  434  of the belt conveyor  284  discharges at an input end of the conveyor  426 . While no magnet is arranged at the output end  434  of the conveyor  284 , a similar approach is followed at the picking station  422  as was followed at the picking station  420 . Certain materials are removed from the treated solid waste materials for separate processing, while the remaining materials may be compacted in one of two compactors  436 ,  438  prior to transport to a landfill, for example. 
     It is believed that the present disclosure may have several benefits, one or more of which may be present in a particular embodiment according to the present disclosure.