Patent Application
20060243645
The invention relates to apparatus and processes for separating solid materials of different density with air flow.
Recycling of waste material is an application of a process where materials can be separated on the basis of density. The materials are subjected to a powerful air stream that can separate and/or carry off the less dense materials from the more dense materials. A specific example of an application in which air separation processes are used such as is in the recycling of automobiles and the like, which begins by shredding them in a hammer mill or other apparatus. The shredding process generates a mixture primarily of metal and “fluff”, the latter being typically formed of upholstery, carpeting, soundproofing, hoses, ducts, and similar materials. It is important to separate the fluff from the metal components to obtain a higher purity and, therefore, more valuable recycled metal product. It is known to separate mixed shredded material such as produced from shredding automobiles in a chamber where the material is arranged to cascade or tumble such as in a Z box or transfer chute with air flowing in counter-flow relation to the gravity induced movement of the materials through the chamber. Typically, such systems are “open” in that at least a portion of the air circulating through the separation system is continuously released to the atmosphere.
The invention provides an air separator process with improved effectiveness and which can be operated as a “closed” system. The invention uses an air knife disperser to direct a high velocity air jet over the material being separated in a zone being swept, at the same time, by a more conventional air flow of greater volume and lower velocity. In the disclosed embodiment, flow from the air knife operates in a cascade separation chamber in the form of a Z box. The air knife, in addition to improving the ability of the system to separate materials, enables the system to operate as a closed air circuit, thereby avoiding potential air pollution and/or the need for supplemental air cleaning devices.
In the disclosed embodiment, the separator includes an air circuit having a cyclone separator for removing low density material from the air stream picked up at the cascade separation chamber. A blower or fan of the air circuit forcibly circulates air through the cascade separation chamber and the cyclone separator. A branch line taps a pressure side of the air circuit and conducts air under pressure to the air knife assembly. The outlet of the air knife is advantageously directed to the flow stream of the solid material being separated where it is in a free fall condition and, therefore, fully exposed to the air jet produced by the air knife. The velocity of the air from the air knife is increased over that of the main air flow so that it is particularly effective in separating low density material from high density material even where these materials are physically intertwined or moderately adhering.
An air separator system 10 includes a cyclone separator 11, fan 12 in the form of a centrifugal blower, and a cascade separation chamber 13. Material to be separated is delivered to the cascade separation chamber 13 by a belt conveyor 14. High density material is carried away from the cascade separation chamber 13 by another or second belt conveyor 16.
The disclosed system 10 is useful in recycling plant operations such as scrap automobiles which are passed through a hammer mill or like apparatus and are shredded or otherwise reduced to relatively small sized chunks or fragments of material, for example, into pieces that can pass through a screen or grid/grate typically having openings of between 4″ and 8″ but not limited to the same. Such fragmented material exiting the hammer mill and small enough to pass through the associated screen or screens or grids/grate, can be separated to remove non-ferrous metals by suitable methods known in the industry. In the disclosed system, fragmented automobile materials, comprising ferrous material and loosely associated fluff material, are carried by the conveyor 14 into the cascade separation chamber 13. The belt conveyor 14 is driven by a motor reducer set in a conventional manner. It will be understood, that other forms of conveyors such as a vibratory conveyors can be used to transport material into the separation chamber 13. An entrance 17 to the cascade separation chamber 13 receives the discharge end of the conveyor 14 and is provided with an air lock seal of resilient flaps 18 of rubber or other suitable material to substantially prevent air flow through the entrance 17. Where conditions are severe, the flaps 18 can be replaced or supplemented with a rotary seal 20 described below in connection with a conveyor at the cascade separation chamber 13.
The chamber 13, in a generally conventional manner, is fabricated of flat steel plates such that it has a rectangular cross-section in planes perpendicular to the plane of the drawing in
A covered discharge chute 31 at a lower side of the Z box shaped separation chamber 13 directs material to the material takeaway conveyor 16 operating below the chamber 13 and chute 31. The chute 31 is lined with wear plates indicated by the broken lines 32. A cover 33 extends over a substantial portion of the conveyor 16 and includes an air lock seal 39; an opening 34 in the cover 33 allows the chute 31 to discharge to the conveyor 16. A dust residue takeoff hood 36, with a corresponding opening 37 in the cover 33, is located downstream of the chute 31 with reference to the conveying direction of the conveyor 16. The hood 36 is connected to a vacuum duct 38 that branches into the main return duct 28. A rotary seal 39 can be employed at the downstream end of the hood 36 where excessive dust may discourage the use of simple hanging flaps. The rotary seal 39 has resilient flaps extending radially from a rotary shaft that is power driven at a speed where the flap tips are synchronized with the conveyor speed.
An air knife nozzle assembly 41 is disposed to supply a relatively high velocity air flow stream into the path of solid material passing through the separation chamber or cascade box 13. The air knife nozzle assembly 41 is supplied with pressurized air by a branch line 42 connected to a main supply line 43.
In operation of the installation 10, mixed high and low density material, in the described automotive scrap recycling process, being primarily in the form of ferrous metal fragments and fluff comprising mostly organic material such as fragmented pieces of carpeting, upholstery, soundproofing, plastic panels, ducts, tubing, and the like, is delivered into the cascade or separation chamber 13 by the conveyor 14. The initial trajectory or path taken by the material being separated, particularly the high density material, is indicated by the broken lines 46 in
Air flowing through the chamber 13 and laden with low density material, is delivered into the cyclone separator 11 through the line or duct 28 where, in a known manner, solid materials are caused to drop out of the airstream. Air cleaned in the cyclone separator 11 returns to the inlet of the fan 12 through a duct 57. A rotary valve 56 is energized periodically to discharge collected solids from the lower end of the cyclone separator.
It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.
