PROCESSING POST CONSUMER FOOD PACKAGING

TECHNICAL FIELD

This invention relates to the recycling of post-consumer food packaging material, and more particularly to an improved method and apparatus for the automated cleaning and drying of such material so that it may be stored for an extended period of time before being recycled.

BACKGROUND

Efforts to recycle post-consumer food packaging have been growing in recent years as a result of environmental concerns, particularly with regard to a perceived shortage of suitable landfill sites. A significant impediment to these recycling efforts has been the absence of a satisfactory method to economically remove residual food from post-consumer materials. Unless residual food is removed, it becomes a breeding ground for mold, bacteria, and other micro-organisms. Depending on temperature and moisture levels, micro-organisms will also feed on the paperboard content of fiber-based cartons, degrading the value of the fibers for reuse in paper making. If the amount of contamination is extensive, the material also attracts insect and rodent pests. The problem is particularly acute with packages such as milk cartons, drink boxes, and the like which have intemal surfaces that remain relatively protected even after the contents are consumed.

Curbside collection programs have achieved some success in diverting post-consumer food packaging from the waste stream. This is largely due to the fact that the consumer typically rinses the material before placing it in a collection bin, thereby removing a good deal of the residual food. It is not generally feasible to hand-rinse materials that are generated by schools and

other institutions, however, and it is rarely feasible to collect, compact, and transport to a paper mill commercially viable quantities of milk cartons and drink boxes from school breakfast and lunch programs, for example, without some sort of processing to guarantee that the quality of the material will not be significantly compromised by biological activity. The large-scale recycling of institutional post-consumer food packaging requires an automated method of economically removing residual food.

Because residual food must be removed from the inside as well as the outside of post-consumer packaging, any method that hopes to clean this material must provide access to the interior surfaces. The most common method currently in use, and the method that effectively defines the current state-of-the-art, employs commercial "shred-rinsers" such as the model ST- 10SY available from Shred Tech Ltd. in Ontario, Canada. This system is comprised of a shredder which incorporates a pair of counter-rotating shafts fitted with cam-shaped teeth, and a cylindrical rinsing trommel. Packaging material introduced into the shredder is divided into pieces that range in size from a large fraction of a whole carton down to dime-sized and smaller. These pieces, which still carry residual food, are then transported into the rinsing trommel where the material is subjected to a spray of water which in some cases includes chlorine as an anti-biological agent. The material is carried through the rotating trommel by intemal spiral flighting, and typically exits the system by means of a conveyor which carries the rinsed pieces to a baler for compaction prior to storage and shipping.

The primary drawbacks of the commercial shred-rinser include: (1 ) the high capital cost of the equipment; (2) the significant proportion of small pieces produced by the shredding mechanism; (3) the relatively gentle rinsing action generated by the water spray; (4) the reliance on chlorine to discourage the subsequent growth of micro-organisms; and (5), the fact that the material is wet when it leaves the shred-rinser.

A workable shred-rinse system, including conveyors, can easily cost upwards of $60,000. Given the relatively low value of post-consumer packaging in the recycled materials market (in June, 1995 post-consumer polyethylene-coated paperboard was valued at between $120 and $160 per ton) the necessity to amortize such capital costs makes it difficult to operate a shred-rinse system on a profitable basis.

The fact that the shredding system generates a significant proportion of small pieces makes processed polyethylene-coated paperboard material somewhat unattractive to most paper mills since this material may be flushed away and lost during initial rinsing in the hydrapulper, or the small polyethylene pieces that remain after the paper fibers are removed may pass through the hydropulper's filter screen and must be removed by subsequent filtration steps. Additional filtration adds significant expense.

Because the rinsing action of the water spray in a shred-rinse system is relatively gentle, operating at the pressure of the water supply tap, food which has dried to the packaging material may not be adequately removed. The use of chlorine as an anti-biological agent adds expense and is environmentally questionable.

Finally, the fact that the processed material is baled in a wet condition usually means the baling equipment is subjected to a high rate of corrosion (a situation made worse by the presence of chlorine) and the likelihood that wet fiber-based material inside a bale will nevertheless deteriorate through a composting process even if a significant proportion of residual food has been removed. The fact that as much as a third of the weight of a bale may consist of water reduces the price that most mills are willing to pay for the material. It is, therefore, apparent that the need exists for a method and apparatus for processing post-consumer food packaging material which overcomes many of the disadvantages inherent in current systems and practice.

SUMMARY OF THE INVENTION

A method and apparatus for treating post-consumer packaging waste material wherein the material is caused to pass through one or more water jets which have sufficient force to pierce the sidewalls of the packaging. Water which thereby enters the package rinses a large proportion of residual food from the interior surfaces, while ambient spray rinses the exterior surfaces. The material is subsequently introduced into a drying chamber where mechanical action removes a proportion of the remaining liquid water and food residue, and heat is applied to evaporate a large proportion of the remaining moisture.

In an embodiment, an apparatus for processing waste material includes a hopper adapted and constructed to receive waste material. The hopper can include a bottom wall having a drain opening in proximity with the bottom wall.

A drying chamber is located in proximity with the hopper. The drying chamber can include a heated, insulated rotatable cylinder in connection with a high-velocity air source. A perforated wall can form an outer wall of the cylinder, with at least one motor-driven wheel in rotational driving contact with a surface of the rotatable cylinder.

A cutting and rinsing assembly is disposed between the hopper and the drying chamber. The cutting and rinsing assembly can include a highly- pressurized source of water in fluid connection with at least one nozzle having a relatively small-diameter exit opening.

A waste material conveyor assembly extends from the hopper to the drying chamber through the cutting and rinsing assembly. The waste material conveyor assembly can include a feed auger having a spiral auger flight with an outer edge. A generally cylindrical feed tube can be provided coaxially

surrounding the feed auger, and a longitudinal spline can be disposed on an inner surface of the feed tube in close proximity to the outer edge of the auger flight. The spline can be substantially coextensive with, and oriented parallel to a longitudinal axis of, the feed auger. The present invention provides a method and apparatus for processing post-consumer food packaging that requires capital equipment costs which are substantially Iower than the costs of current shred-rinse systems. The disclosed method and apparatus produces a very low proportion of pieces small enough to pass through a standard hydropulper's filter screens, while providing a more vigorous method of rinsing contaminated material than is available with water sprays working at standard water tap pressures. Thorough rinsing controls the subsequent growth of micro-organisms without the use of chlorine or other anti-biological additives. Material removed from the drying chamber is relatively dry and immune to composting processes after being baled, and will not significantly promote the corrosion of baling equipment.

Other objects and advantages of the present invention will become apparent upon reference to the accompanying description when taken in conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a schematic side cross-section view illustrating one embodiment of an apparatus embodying the principles of the present invention;

Fig. 2 illustrates a sectional view taken generally along lines II-II of Fig. 1 ; and Fig. 3 illustrates a schematic front cross-section view of the Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An apparatus 10 for processing post-consumer food packaging materials is illustrated in Fig. 1 . The apparatus 10 includes a hopper 12 adapted to receive waste material such as milk cartons, drink boxes, and the like. The hopper 12 includes a bottom wall 14 in which one or more drain openings 15 are formed.

A cutting and rinsing assembly 16 is located adjacent to the hopper 12. The cutting and rinsing assembly 16 includes one or more water jet nozzles 18 directed toward the interior of the cutting/rinsing chamber 20. Water is supplied to the nozzles 18 by a high-pressure source of water 22, which may be provided as a pump. The water source 22 is connected to the nozzles 18 via a suitable conduit 24. It is presently contemplated that the water source 22 would supply a pressure of at least 4,000, and preferably 6,000 pounds per square inch, with the water exiting the nozzles 18 through three nozzle exit orifices 26 of approximately 0.017 inches in diameter. At such a pressure and orifice diameter, the flow rate for three nozzles would be approximately one and a half gallons per minute. Of course, the cutting and rinsing assembly 16 would accomodate any suitable combination of water pressure and nozzle orifice diameter that would ensure adequate rinsing and cutting of the waste

material. For example, it may be desired to have 6,000 psi water supplied through a single exit orifice of approximately 0.24" in diameter.

A drying chamber 28 is provided adjacent to the cutting and rinsing assembly 16. The drying chamber 28 includes an insulated housing 30 having an exit opening 31. A cylinder 32 is mounted for rotational movement within the housing 30. The cylinder 32 can be provided with a perforated outer wall 34, and is supported for rotation by a plurality of wheels 36, one of which is driven by a motor M1 which in turn causes the cylinder 32 to rotate.

As seen in Figs. 1 and 3, a source of heated air 38 can be provided with the drying chamber 28. The source 38 can include a blower 40 that directs air over a heater 42, through a duct 44, and into the housing 30. A second blower 46 draws heated air from the interior of the drying chamber 28, through a duct 48, and redirects the heated air at high velocity back into the chamber 28 via a nozzle 49 along a path that crosses the cylinder 32 transversely.

Turning to Figs. 1 and 2, a waste material conveyor 50 extends from the hopper 12 to the drying chamber 28, through the cutting and rinsing assembly 16. The conveyor includes a rotatable feed auger 52 that is actuable by a motor M2. The feed auger 52 is disposed within a feed tube 54, and includes a spiral flight 56 having an outer edge 58. A longitudinal spline 60 is disposed on an inner surface of the feed tube 54 in close proximity to the outer edge 58 of the auger flight 56. The spline 60 is substantially coextensive with, and oriented parallel to a longitudinal axis of, the feed auger 52. In operation, waste material is placed into the hopper 12. The motor

M2 then actuates the feed auger 52. Material which drops into the spaces between the auger's flight 56 is fed into a cutting/rinsing chamber 20. Material which becomes caught on the edge of the auger flight 56 is prevented from continuing to rotate around the axis of the auger 52 by the spline 60, which

causes the caught material to be fed by a continuous wiping action into the cutting/rinsing chamber 20.

As the material passes through the cutting and rinsing assembly 16, water from the nozzles 18 simultaneously cuts through the waste material while removing residual contaminants from the material's various surfaces. Excess water, along with the removed residual contaminants, drains from the bottom of the hopper 12 through the drain openings 15.

After the material passes through the cutting and rinsing assembly 18, the auger 52 transports the wet, cut material through and out of the feed tube 54, from which the material drops onto the rotating perforated cylinder 32 in the drying chamber 28. As the stream of high-velocity air is directed across the rotating perforated cylinder 32 by the nozzle 49, material is blown across the interior of the rotating perforated cylinder 32 with considerable force. Any remaining residual contaminants or water is thrown off when the material hits the opposite wail of the rotating perforated cylinder 32. As the material continues to tumble within the perforated rotating cylinder 1 1 through the heated air inside the housing 38, additional moisture is removed by evaporation.

The material tumbling within the rotating perforated cylinder 32 distributes itself through mutual collisions along the length of the cylinder 32, and eventually tumbles out through opening 31 . At this point the rinsed, cut, and dried material can be collected and baled by external conveying and/or baling equipment (not shown).

The present invention overcomes many drawbacks inherent in current systems. The capital cost of the equipment is approximately one-third the cost of off-the-shelf shred-rinse systems. The present invention cleans both the interior and exterior surfaces of the packaging, but creates very few pieces of material small enough to pass through the filter screens of a hydrapulper. Indeed, the vast majority of material consists of whole cartons

which contain a small number of narrow slits created by the action of the high- pressure water jets. The vigorous action of the high-pressure jets scours residual food from the packaging more thoroughly than sprays operating at water tap pressure, and because the processed material is substantially clean and dry before it is baled, there is no need to introduce chlorine or other anti- biological additives to prevent the growth of micro-organisms. The material is sufficiently dry to allow storage of paperboard-based material for several months without suffering significant degradation from composting or other biological action. Because the material is substantially dry when it leaves the apparatus, it also is much less likely than current systems to promote corrosion of down-stream equipment such as a baler.

In addition to these improvements, the amount of energy used to dry the material is relatively modest due to both the insulated nature of the drying chamber and the physical de-watering that is accomplished by the stream of high-velocity air which is directed across the rotating perforated cylinder. The heat source may include, but is not limited to, natural gas, propane, and fuel oil burners, and electric and infrared heaters. An additional advantage of the present invention is the fact that the jets of water that cut the packaging material cannot be broken or dulled by the introduction of foreign objects such as bottles or flatware.

Although the present invention has been described with reference to a specific embodiment, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.