|Publication number||US3817458 A|
|Publication date||Jun 18, 1974|
|Filing date||Jun 19, 1972|
|Priority date||Jun 19, 1972|
|Publication number||US 3817458 A, US 3817458A, US-A-3817458, US3817458 A, US3817458A|
|Original Assignee||Chicago Hydraulics Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (41), Classifications (14)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1191 GLASS Gilberto June 18, 1974 RECYCLING METHOD AND APPARATUS Primary ExaminerGranville Y. Custer, Jr.  Inventor: Matthew J. Gilberto, Glendale Attorney Agent or Plyer Dom &
Heights, lll. McEachran  Assignee: Chicago Hydraulics lnc., Addison,
 ABSTRACT Filedi J 1972 A recycling system for solid municipal waste, in which 21 A No; 263,943 the garbage is milled to given maximum size, then fed 1 pp to a three-level flotation separation vessel; in the flotaton separation vessel, paper is raked from the surface,  US. Cl 241/20, 241/24, 241/791' tal, glass and like heavy solids are removed from lilt- Cl. the essel bottom a deep drum eparator and Field of 46-17, organic materials are extracted from an intermediate 241/79, level by a dewatering screw. The paper materials are dried and compressed; the organic materials are References Cited treated separately but similarly. The heavy solids are UNITED STATES PATENTS passed through a magnetic separator to recover fer- 3,159,353 12/1964 Atwater 241/39 mus metals, which are washed in Vibratory Cleaner- 3,595,488 7/1971 Blakley 241/21 The residual av O idS f ai v t 3,650,396 3/1972 Gillespie et a1. 241/24 tion separation vessel to segregate metal from glass on 3,680,796 8/1972 Galeano 241/21 a surface-differential basis; the two outputs of this sec- 3,716,197 2/1973 C g et l- 241/4617 0nd vessel are washed in vibratory cleaners. 3,720,380 3/1973 Marsh 241/20 1 14 Claims, 9 Drawing Figures 11 19 21 23 v to f f f 1 Ma e" e-nc \/1 euros? WASTE HAMMER WATER, FERROUS MATERIAL (amuse) M' semen-on CLEANER FOR RE-CYCLING NON-MAO.
1 We 1s 22 I HYDRAULlC DE-WATERER PAPER PULP DEHSI FlER 26 27 [IT 3 r WATER WBRATNG GLASS 'Ro'TARY ozue Dl- S '1 crumea PAPER MATERIAL WArsmHm- 2 Mau summon scnaw ES E l I 29 L v i METAL .SEPARATmN' l WATER- VIBRATN METAL ves sm. No 4 MR CLEANER v l l I lMR avomuuc V DE-WATERER LAND Fl LL 35 36 uewsunea cause sukme SB Wm. We
SEPARATOR S9 L I I FlLTER -PUMP VES SEL PATENTEU I 13 B7 sum 1 or 5 4 3 LTI PATENTEDJuu 18 m4 sum 2 or 5 50 PP LY Pmmmmmmu 3.817;,458
. SHEEI 3 OF 5 PIC-3.4
FLUID PRESSURE APPARATU'S O L c. e
III/I Ill/III III/II IIIIIIIII/IIIIIIIIIIIIlIIlIlIIIII/III/II I PATENTEDJUIHBIBH 381K445 sum 5 [1F 5 WATER III] I 111 11/ AIR SUPPLY RECYCLING METHOD AND APPARATUS BACKGROUND OF THE INVENTION There is a substantial current interest in the recycling of various materials that, cumulatively and collectively, may be termed solid municipal waste, including cans, bottles, paper, food scraps, and a wide variety of other waste matter. The objectives of recycling are two-fold: first, to reduce the rate of depletion of natural resources, both mineral and agricultural, and second, to solve increasingly difficult problems of disposing of ever-greater quantitiesof waste. Indeed, it has been contended that recycling may prove necessary to preclude the possibility that urbanization may result in burial of the race under its own waste materials.
As regards solid municipal waste, the most prevalent recycling approach has been on a piecemeal basis. For many years, particular kinds of paper have been collected by a variety of community organizations for reprocessing and reuse. Typically, newspapers may be accumulated and collected at periodic intervals, usually by charitable organizations, for recycling purposes. Substantially similar techniques have been adopted for glass containers, especially non-returnable bottles. The piecemeal approach has also applied to aluminum cans; the price of aluminum scrap affords a marginal economic basis for redemption and recycling in the same manner as news print and glass bottles. Even in a community in which all of these approaches are combined, however, there is no reutilization or effective recycling of many of the components of solid municipal waste, including much scrap glassware, wood, many varieties of paper, steel cans, and food scraps. Furthermore, what recycling is accomplished is on a voluntary basis, and far from comprehensive in nature. Consequently, the approach can ameliorate the waste problem to only I a limited extent.
One governmental agency has attempted a more unified approach; the Bureau of Mines has conducted some investigations of comprehensive solid waste disposal. Publications relating to this program include a Bureau of Mines Report of investigations No. 7204 entitled Composition and Characteristics of Municipal Incinerator Residues, published in December, 1968, and a technical progress report TPR 33 entitled Economics of Recycling Metals and Minerals from Urban Refuse, published in Apr. 1971. However, these Bureau of Mines investigations have been concerned with municipal waste that hasbeen passed through an incinerator, so that the only recycling entailed applies to metals, glass, and the limited quantity of ash remaining from the burning of paper and other organic materials. Thus, a substantial quantity and almost certainly the majority of the materials are not recycled in this type of program.
There have been some indications of a more basic ap proach to the recycling problem. For example, Dalberg et al US. Pat. No. 3,477,649 issued Nov. 11, 1969 describes a solidwaste reclamationsystem for recycling solid waste material without primary resort to incineration. The Dalberg system utilizes air blast separation techniques'that appear to be rather limited in efficiency and practicality with respect to large quantities of waste materials, such as those generated by a city of moderate size. Another similar system, again using air balance or air blast separation as a basic part of the system, is set forth in Anderson et al., US. Pat. No. 3,524,594, issued Aug. 18, 1970. A somewhat different approach is incorporated in Baxter US. Pat. No. 3,549,092, issued Dec. 22, 1970. The Baxter patent pertains to a liquid treatment system in which many of the materials, particularly paper and other organic materials, end up mixed together in a fonn from which they cannot be effectively separated.
SUMMARY OF THE INVENTION It is a primary object of the present invention therefore, to provide a new and improved system for classifying and reclaiming usable materials from solid municipal waste, other than sewage, that can be effectively and efficiently applied to large quantities of waste produced by an urban community of substantial size.
A particular object of the invention is to provide a new and improved recycling system for solid municipal waste that employs efficient liquid separation techniques but with only relatively limited water requirements, so that the system does not place an undue burden on available water supplies.
A specific object of the invention is to provide a new and improved system for classifying and reclaiming usable materials from solid municipal waste that effectively segregates, in its outputs, paper, solid organic material other than paper, ferrous metals, light metals such as aluminum, and glass and other ceramic materials.
A distinct object of the invention is to provide a new and improved method and apparatus for classifying and reclaiming usable materials from solid municipal waste that is efficient and effective in operation, entails a minimum of cost for the processing plant, and that can be operated at minimum expense.
Accordingly, the invention is directed to a method of classifying and reclaiming usable materials from solid municipal waste; the method comprises first milling the solid waste to particulate form, of predetermined maximum size, and then supplying the milled waste to an inlet point at the surface of the fluid flotation medium in a first fluid medium flotation separation vessel. Floating flake'material is raked from the surface of the 'fluid medium adjacent the inlet of the first vessel; this flake material is primarily paper. Dense material, comprising primarily metal and glass heavier than the fluid medium, is removed from the bottom of the first flotation vessel, preferably by a rotary drum separator. Additional solid material, comprising primarily solid or organic material that is lighter than the fluid medium, is removed from the upper part of the first flotation vessel at a location displaced from the inlet to that vessel. The various components in the dense material removed from the first vessel are segregated by magnetic separation. Subsequently, the remainder of the dense material is separated into glass and lightmetals, on the area of surface area differentials, in a second flotation separation vessel. Thus, the method of the invention affords outputs comprising primarily paper, solid organic material other than paper, ferrous metals, light metals, and glass.
In another aspect, the invention relates to a system for classifying and reclaiming usable materials from solid municipal waste. The system comprises milling means for milling raw solid waste to particulate form, of predetermined maximum size. The system further comprises a first flotation separation vessel, filled with a liquid flotation medium which is preferably water, and equipped with a surface rake for raking off floating flake material from the surface of the liquid medium, the flake material primarily comprising paper. The first separation vessel also includes a dense material separator for removing dense material, primarily metal and glass, from the bottom of the vessel, and a dewatering elevator for removing lighter solid material, primarily comprising solid organic material other than paper, from the upper part of the vessel. Conveyor means are provided for conveying the output of the milling means to the first flotation separation vessel and for depositing that output onto the surface of the liquid in the vessel at a point closely adjacent the surface rake. The system includes a magnetic separator for separating ferrous metals from the dense material that constitutes the output of the dense material separator in the first vessel. The system further includes a glass-metal separator for segregating the remainder of the dense material into glass material and light metal material, on the basis of surface area differentials, the glass-metal separator comprising a second liquid medium flotation separation vessel.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a system for classifying and reclaiming usable materials from solid municipal waste, constructed in accordance with the present invention;
FIG. 2 is a sectional elevation view of a first liquid flotation separation vessel incorporated in the system of FIG. 1;
FIG. 3 is a sectional elevation view taken approximately along line 3-3 in FIG. 2;
FIG. 4 is a partially schematic elevation view of a hydraulic dewatering and densifying apparatus incorporated in the system of FIG. 1;
FIG. 5 is a plan view taken approximately as indicated by line 5-5 in FIG. 4;
FIG. 6 is a simplified elevation view of one form of magnetic separator that may be used in the system of FIG. 1;
FIG. 7 is a sectional elevation view, similar to FIG. 2, of a second liquid medium flotation separation vessel incorporated in the system of FIG. 1;
FIG. 8 is a simplified sectional elevation view of a vibratory cleaner that may be utilized in the system of FIG. 1; and
FIG. 9 is a sectional elevation view taken approximately along line 9-9 in FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a system 10, constructed in accordance with the present invention, for classifying and reclaiming usable materials from solid municipal waste. FIG. 1 is utilized in explaining the overall organization and operation of system 10, and also affords a basis for explanation of the method of the invention.
The equipment generally illustrated in FIG. 1, and comprising the waste classification and reclamation system 10, includes a hammermill 11 preferably equipped with an input conveyor for charging the hammermill from dump trucks or other vehicles utilized to collect solid municipal waste. I-Iammermill ll discharges to a conveyor 12 that introduces the output of the hammermill to a first flotation separation'vessel 13. Vessel 13 is filled with a liquid flotation medium; the practical and economical flotation medium is water.
There are three output devices associated with the first liquid flotation separation vessel 13. The first of these output devices is a rotary paper rake 14 that discharges to a conveyor 15. Material from conveyor 15 is supplied to a hydraulic dewatering densifying device 16 which is one of the output devices of system 10. The output of device 16, a principal output of system 10, is a relatively dense and dry product consisting primarily of paper.
The second output device for the first flotation vessel 13 is a dense material separator 17 which, as described herinafter, preferably comprises a large drum extending to the bottom of vessel 13 and projecting above the liquid level in the vessel. The dense material dredged from vessel 13 by separator 17 is supplied to a conveyor 18 that feeds a magnetic separator 19. Magnetic separator 19 has two outputs, a conveyor 21 and a conveyor 22. Magnetic materials are deposited on conveyor 21 and fed by that conveyor to a vibratory cleaner 23. Cleaner 23 is one of the end output devices of system 10, producing a relatively clean supply of iron, steel, and other ferrous metals suitable for recycling.
Conveyor 22 deposits the non-magnetic output of separator 19 into a second liquid medium flotation separation vessel 24. Vessel 24 comprises a glass-metal separator that separates the remainder of the dense material into primarily glass material and primarily light metal material. The glass is removed from vessel 24 by a densematerial separator 25 and supplied to a conveyor 26 that deposits the material in a vibratory cleaner 27. The output of cleaner 27 is a relatively clean material consisting primarily of glass suitable for reuse. The light metal materials from vessel 24 are deposited on a conveyor 28 that feeds another vibratory cleaner 29. The output of cleaner 29 consists primarily of aluminum and other light metals, cleaned and essentially ready for reuse.
The third output from the first fluid flotation separation vessel 13 is a dewatering elevator 31 that projects a short distance below the surface level of the liquid in vessel 13, and removes from the vessel solid organic materials that are of lower specific gravity than the liquid in the vessel. The output of elevator 31, which is almost entirely organic material, is discharged to a conveyor 32 which supplies this material to a second hydraulic dewatering and densifying apparatus 33 essentially similar to the device 16. The output of densifier 33 is a milled mixture of organic materials, relatively dense and dry, suitable for use as a raw material for land fill purposes.
The vibratory cleaners 23, 27 and 29 each have an excess water drain; these drains are all returned to a third flotation separation vessel 34. Similarly, the dewatering and densifying devices 16 and 23 have drains that are connected back to vessel 34. Heavy solids are removed from the bottom of vessel 34 by a separator drum 35 to a conveyor 36 that conveys these materials to the land fill outlet of system 10. A surface rake 59 removes floating solids to the same conveyor 36 for disposition as land fill material. The liquid in vessel 34 is removed by a pump 58 that supplies process fluid to vessels l3 and 24, through a filter 58A. Solids from filter 58 may be combined with the output of densifier 33.
Additional water supplies may be required for the vibratory cleaners 23, 27 and 29. Compressed air supplies may be utilized in the vibratory cleaners and in the separation vessels 13 and 24, as described more fully hereinafter.
The method of the present invention, in classifying and reclaiming usablematerials from solid municipal waste, can best be understood by consideration of the operation of system as generally illustrated in FIG. 1. The municipal waste or garbage, as received at the processing plant, is initially discharged into hammermill 11. Mill 11 may be of conventional construction and should have a relatively high capacity so that it can handle the needs of an urban community of substantial size. Typically, mill 11 may be equipped with a large input conveyor to permit direct discharge from trucks into the mill. Mill 11 beats the solid waste to particulate form of predetermined maximum size. The output of mill 11, as supplied to conveyor 12, preferably comprises particles having a maximum dimension of the order of three inches or less.
The milled waste from mill 11 is discharged, by conveyor 12, onto the surface of the liquid medium in the first fluid flotation separation vessel 13. The discharge onto the surface of the flotation fluid, which is preferably water, should be at a relatively low angle so that flaked paper incorporated in the waste material will float for a limited period of time. The inlet point to vessel 13 is located closely adjacent to the rotary paper rake 14. Rake l4 rakes off the floating flake material from the surface of vessel 13 and discharges that floating material to conveyor 15. The flaked material consists almost entirely of paper. This paper is supplied to the dewatering and densifying device 16, which compresses the paper waste and squeezes thewater out of it. This produces a relatively dense and relatively dry paper pulp, suitable for reuse, as one of the outputs of system 10.
The heavier particles in the output from mill l1 sink to the bottom of the flotation separation vessel 13. These heavy particles, in municipal waste, consist primarily of metal and glass. The heavy material is removed from the bottom of vessel 13 by the dense material separator 17 and supplied to the conveyor 18. Conveyor l8 discharges to the magnetic separator 19, which segregates the magnetic elements (iron, steel, and other ferrous materials) for discharge to conveyor 21. This material is washed in the vibratory cleaner 23 and produces an output consisting of ferrous material suitable for recycling.
The non-magnetic output of separator 19 is supplied to conveyor 22 and discharged into the second fluid medium flotation separation vessel 24. The materials entering vessel 24 consist primarily of aluminum and glass. The glass has considerably less surface area in relation to its weight, although the specific gravities of both materials are greater than the specific gravity of the flotation medium. Consequently, the aluminum can be captured at a higher level in the fluid medium in vessel 24, particularly through use of an airstream or similar means, and thus can be segregated out before it reaches the bottom of the vessel. Thus, the light metal components can be supplied to conveyor 28 and 'washed in the vibrating cleaner 29 toafford a light metal output suitable for recycling. The glass, with its smaller surface area, sinks to the bottom of vessel 24 and is removed by the dense material separator 25 for application to vibratory cleaner 27, the output of which is a relatively clean and consistent glass suitable for reuse.
' In the first flotation separation vessel 13, the dewatering elevator 31 preferably projects a short distance below the surface of the flotation medium and is located at the opposite side of the vessel from rake l4. Elevator 31 removes from the vessel solid organic materials that have a specific gravity equal to or lighter than the aqueous flotation medium. This material is virtually all organic material. It is supplied to the dewatering and densifying device 13, where it is compressed and squeezed relatively dry. The output of device 33 constitutes a substantially consistent milled organic material that is suitable for landfill use. In a typical system, it may be desirable to add nitrogen, phosphorus, or potassium,or combinations thereof, to the output of densifier 33 to afford a high grade fertile landfill product.
System 10 can be constructed for effective and efficient operation with large quantities of waste, such as those produced by an urban community of substantial size. Virtually all of the original waste material is reclaimed for further use, although some may be lost in solution in the flotation separation vessels. Some water replacement may be necessary, if the quantity of material in solution in the output of filter 58A, which is preferably a vacuum filter, becomes excessive. On the other hand, the system water is recycled, being returned to the first flotation vessel 13 through vessel 34, pump58 (connected to the central portion of vessel 34), and filter 58A. Almost inevitably, some solid materials of various kinds will be transferred to vessel 34 from the other stages of the system; this solid material is conveyed to the landfill outlet separator 35, rake 59, and conveyor 36. Because an essentially closed water system is employed, makeup water requirements are quite limited and system 10 does not place a substantial burden on local water supplies.
FIGS. 2' and 3 afford a more detailed illustration of one construction that may be used for the first fluid medium separation vessel 13 of system 10. As shown therein, vessel 13 comprises a tank 37 filled with a flotation separation medium 38, preferably water, to a surface level 39. The milled waste from hammermill 11 is discharged, at a relatively low angle of incidence, onto the liquid surface 39 at the left-hand side of the tank as seen in FIG. 2. The inlet point 41 is located immediately adjacent the rotary paper rake 14. In the illustrated construction, rake 14 comprises a drum 42 having a multiplicity of rake tines 43 projecting outwardly thereof. The rake tines extend just below the surface 39 of the fluid separation medium 38. Drum 42 is continuously rotated by appropriate drive means connected to a shaft 44; the drive means has not been illustrated. A comb 40 can be employed to remove flake material from the rake tines 43 for deposit on conveyor 15.
Preferably, vessel 13 is equipped with air nozzles 45 and 46 that extend into tank 37 at locations closely adjacent the rotary paper rake 14. Nozzles 45 and 46 are connected to a conventional compressed air supply 47. A baffle 48 may be interposed between the nozzles. It should be understood that each of the air nozzles 45 and 46 may represent a plurality of nozzles, depending medium 37 by nozzles 45 and 46 aids in keeping paper afloat on the liquid surface 39, adjacent inlet 41, long enough to be efficiently and consistently picked up by rotary rake 14.
The dense material separator 17, as illustrated in FIGS. 2 and 3, comprises a large cylinder or drum 51 mounted upon a central shaft 52 by suitable means such as the braces 53 (FIG. 2). Preferably, drum 51 has an external configuration corresponding closely to the configuration of the bottom of tank 37, in the central portion of the tank, as shown in FIG. 3. Thus, there is little opportunity for waste material to collect in the bottom of the tank below the separator drum.
The interior of drum 51 is equipped with a multiplicity of inwardly projecting baffles or vanes 55. The output conveyor 18 for the dense material separator 17 extends into drum 51 above the liquid surface level 39 and immediately below the vanes 55 at the top of the drum. Shaft 52 of drum 51 is connected to a drive means (not shown) that rotates the drum continuously. Thus, as glass and metal particles collect at the bottom of tank 37, within drum 51, they are carried upwardly by vanes 55 and are deposited on the upper surface of conveyor 18. In this manner, separator 17 functions to remove the dense material that would otherwise accumulate on the bottom of vessel 13.
In the form shown in FIG. 2, the dewatering elevator 31 comprises an elongated cylindrical conduit 56 that projects into vessel 13 at an angle and extends a limited distance below the surface level 39 of the liquid flotation medium 38 in tank 37. A helical screw 57 extends axially of conduit 56 and substantially fills the conduit.
- Drive means (not shown) are providedfor screw 57 to rotate the screw continuously in a direction tending to lift particulate material upwardly through conduit 56 to a point at which it can be discharged to conveyor 32 (FIG. 1). As shown in FIG. 2, the dewatering screw or elevator 31 is located a substantial distance from paper rake 14. Thus, the dewatering screw 31 is able to remove light organic material from the flotation medium 39 without collecting a substantial quantity of paper, most of the paper being removed in advance by rake l4.
FIGS. 4 and illustrate one construction that may be used for the dewatering and densifying apparatus 16; the illustrated construction is equally applicable to the second dewatering and densifying device 33 (FIG. 1). As shown in FIGS. 4 and 5, device 16 comprises an elongated, relatively wide conveyor 61 extending around a tail-end pulley 62 and a head-end or drive pulley 63. Conveyor 61 is of open mesh construction and may comprise a conveyor of the type commonly referred to as a chain conveyor. The input end of conveyor 61 is located immediately below the discharge end of conveyor (FIG. 1).
As shown in FIGS. 4 and 5, the dewatering and densifying device 16 includes three pairs of pressure rolls located at spaced points along the conveyor between the idler pulley 62 and the drive pulley 63. The first pressure roll pair comprises the rolls 64 and 65, located on opposite sides of the chain conveyor 61 a short distance from the input end of the conveyor. The second pair comprises the rolls 66 and 67, located near the middle of conveyor 61. The third pair of pressure rolls 68 and 69 is located near the discharge end of conveyor 61, adjacent drive pulley 63. The pressure rolls 64-69 are all driven in synchronism with pulley 63 at rotational speeds which afford equalized surface speeds for the pressure rolls and the conveyor at the points where the pressure rolls engage the conveyor, the drive means being generally illustrated at 71.
Device 16 further comprises a fluid pressure apparatus 72 for continuously applying relatively high pressure to each pair of the pressure rolls 64-69. A scraper blade 73 contacts conveyor 61 as the chain conveyor proceeds around drive pulley 63, scraping material from the chain conveyor for discharge to an output conveyor 74. A tank 75 is positioned below conveyor 61 to collect entrained liquid released during operation of device 16, as described hereinafter. A pan 76 may be located below conveyor 61 near the input point, be tween conveyor 15 and the first pair of pressure rolls 64,65.
In operation, the paper waste collected by rake 14 (FIG. 1) is discharged from conveyor 15 onto the input end of the chain mesh conveyor 61 (FIGS. 4 and 5). As deposited on conveyor 61, the paper waste is a relatively narrow stream 81. The initial stream of paper waste 81 is compressed by rolls 64 and 65, losing a part of its water and spreading to the wider stream 82 (FIG. 5 The same material is further compressed and spread to the stream 83 by the pressure rolls 66 and 67. The stream 83 is further compressed by the pressure rolls 68 and 69, so that the output stream 84 is thin and wide, spreading across virtually the full width of conveyor 61. Additional water is squeezed out of the paper pulp stream by each of the pairs of pressure rolls 66,67, and 68,69; all of the water is collected in tank 75 (FIG. 4) so that it can be returned to vessel 34 for subsequent re-use. The output material 84, as supplied to conveyor 74, is a relatively dry and dense paper pulp suitable for reuse.
FIG. 6 illustrates a simple form of magnetic separator that may be utilized as the magnetic separator 19. As shown therein, the last section 18A of the conveyor 18 from the dense material separator 17 in vessel 13 (FIG. 1) extends around an idler pulley 91 and a drive pulley 92. Drive pulley 92 is of magnetic construction, incorporating a relatively large permanent magnet or a plurality of permanent magnets with appropriate external pole pieces completing the pulley, or an equivalent electromagnetic structure. In addition, a magnetic plate 93 may be incorporated in conveyor 18A, within the lower reach of the conveyor immediately beyond the magnetic drive pulley 92. The intake end of the conveyor 22 for non-magnetic material is located directly below the drive pulley 92. The intake end of the conveyor 21 for magnetic material is positioned below the portion of conveyor 18A that extends just beyond the magnetic plate 93.
In operation, the dense material moving along conveyor section 18A proceeds to the end of the conveyor adjacent magnetic pulley 92. The non-magnetic portions of this material drop off of conveyor 18A onto conveyor 22. The magnetic components of the material remain with the conveyor around drive pulley 92 and through'the portion of the conveyor engaged by magnetic plate 93, being held to the conveyor by magnetic attraction. These magnetic components drop from the conveyor onto conveyor 21, after clearing plate 93. In this manner, the ferrous materials are separated and discharged onto conveyor 21, whereas glass and nonmagnetic metals flow to conveyor 22.
FIG. 7 illustrates one construction for the second flotation separation vessel 24 that may be utilized in the system of FIG. 1. As shown in FIG. 7, vessel 24 includes a tank 95 filled to a level 96 with a liquid flotation medium 97, preferably water. At one side of the tank, the non-magnetic mixture of light metals and glass is discharged into tank 95, near the water surface, by conveyor 22.
Vessel 24 incorporates a first drum separator 98, located near the inlet point at which conveyor 22 dis charges material into tank 95. Drum separator 98 is similar in construction to drum 51 (FIGS. 2 and 3), but extends only a relatively limited distance below the liquid surface level 96 instead of projecting down to the bottom of the tank. Drum 98 is equipped with internal vanes, like drum 51, and is rotated continuously by drive means (not shown) connected to a drum shaft 99. Conveyor 28 extends into drum 98 to recover material collected on the internal vanes of the drum.
A deflection baffle 101 is supported within tank 95 at a position closely adjacent the lower edge of drum 98. Another segment 102 of the baffle projects inwardly from tank 95 toward drum 98, there being a relatively narrow gap 103 between the two baffle segments 101 and 102. Two air nozzles 104 and 105 extend into tank 95 on opposite sides of baffle segment 102; nozzle 105 is aimed toward the gap 103 between baffle segments 101 and 102. The two nozzles 104 and 105 are connected to the plant air supply 47.
Vessel 24 further comprises a dense material separator 25, comprising a drum 107 mounted upon a shaft 108, that is essentially similar in construction to drum 51 as described hereinabove-in connection with FIGS. 2 and 3. Thus, drum 107 extends to the bottom of tank 95. It is provided with internal vanes for collecting solid material from the bottom of the tank and depositing that material on the conveyor 26, which extends into the drum above the liquid level surface 96 and below the internal drum vanes.
In operation, the dense non-magnetic material carried by conveyor 22 from magnetic separator 19 is deposited on the surface 96 of the flotation liquid 97 adjacent the first separator drum 98. The particles in this waste material that have the least surface area, primarily glass particles, have little or no tendency to float. They move downwardly through gap 103 to the bottom of tank 95 and into the interior of drum 107. Drum 107 rotates continuously; it dredges up glass particles and deposits them on conveyor 26 for transport to vibrating cleaner 27 (FIG. 1).
The particles of aluminum and other light metals, on the other hand, almost uniformly have much greater surface area and move downwardly through the liquid medium 97 at a lesser rate. These particles may move toward gap 103 but are deflected toward drum 98 by the air discharged from nozzle 104 and 105. The greater surface area of the metal scraps renders them much more susceptible to movement of this sort than the smaller and more compact glass particles, depsite the fact that both have a specific gravity in excess of that of the flotation medium 97. Consequently, the metal particles are collected in drum 98 and deposited upon conveyor 28 for transportto the metal vibrating cleaner 29 (FIG. 1). Thus, the first separator drum 98 collects the light metal components and the second separator drum 107 collects theglass and other ceramic materals discharged into vessel 24 from conveyor 22.
The aluminum-glass separation vessel 24 is capable of relatively highly efiicient operation. Indeed, virtually one hundred percent separation can be achieved for one of its two outputs, but with limited contamination of the other product, of the order of four percent. To attain optimum purity in both outputs, two vessels such as vessel 24 may be used in series, adjusting one for maximum purity of one product (such as the glass) and the other for maximum purity of the other. This will provide two valuable outputs and a minimal amount of waste, about four or five percent. Adjustment is effected by adjusting the angle of vane I01 and the air blast from nozzles 104 and 105.
FIGS. 8 and 9 illustrate a construction that may be employed for the vibratory cleaner 23 and that is equally applicable to the vibrating cleaners 27 and 29 (FIG. 1). As shown in FIGS. 8 and 9, the vibration cleaner 23 includes an elongated tank-like frame 111. The rear wall 114 of the tank-frame 111 includes an inwardly projecting overflow pan 114A that is slightly lower than the other tank walls, affording a weir for overflow water, as indicated by arrows 115.
A support frame 116 is rigidly mounted within the tank-frame 111, near the bottom of the tank, and extends longitudinally of the tank at a slight angle to the horizontal. An elongated trough 117, similar in length to frame 116, is supported upon frame 116 by a plurality of resilient support members 118. The rear wall 117A of trough 117 is located above the overflow pan 1 14A. Water is supplied to trough 117, through an inlet 125, filling the trough with water 112 to a level 113 determined by the height of the rear wall 117A of the trough. The opposite end 1173 of trough 117 is clear of the water in tank 111. An output conveyor 119 is located below the upper end 117B of trough 117.
The input conveyor 21 that feeds vibratory cleaner 23 discharges the ferrous material that it carries into the lower end 117A of trough 117. An air supply connection 121 is located within trough 117 near the point at which conveyor 21 deposits its material into the trough, the air supply connection 121 being connected to the plant air supply 47. Trough 117 is connected to an external drive means, not shown, for continuously moving the trough backward and forward, at an angle, as indicated by the arrows 122. t
The material discharged into trough 117 is immersed in the water 112 in trough 117. This water is aerated to a degree by the air connection 121 to aid in cleaning the material deposited in the trough. The washed and agitated material is slowly elevated in trough 117, due to the reciprocating motion of the trough, and is discharged from the trough end 117B onto conveyor 1 19. The angle of inclination of trough 117 is maintained constant by themultiple parallel supports 118, which flex during operation of the vibrating conveyor as indicated by the dash lines 118A and 118B in FIG. 8. The same cleaning arrangement may be used for glass and non-magnetic metals in the cleaning devices 27 and 29 (FIG. 1).'
It will be recognized that any of the outputs from system 10 may incorporate additional process equipment for further refinement of the system products. On any of the outputs, for example, if a finer particle size is desired,-further pulverizing or like equipment can be employed.
1. A method of classifying and reclaiming usable materials from solid municipal waste comprising:
1. milling the solid waste to particulate form, of predetermined maximum size;
ll. supplying the milled waste to an inlet point at the surface of the fluid flotation medium in a first fluid medium flotation separation vessel;
a. raking off floating flake material from the surface of the fluid flotation medium adjacent the inlet of the first flotation separation vessel, the flake material primarily comprising paper;
b. removing dense material, comprising primarily metal and glass heavier than the fluid flotation medium, from the bottom of the first floation vessel; and
c. removing solid material, comprising primarily solid organic material lighter than the fluid medium, from the upper part of the first flotation vessel, at a location displaced both from the raking location and from the inlet to that vessel;
lll. magnetically separating ferrous materials from the dense material removed in step II (b); and thereafter IV. separating the remainder of the dense material into glass material of little surface area and lightmetal material of larger surface area, on the basis of the differential in surface area, in a second flotation separation vessel, thereby affording separate outputs comprising primarily A. paper B. solid organic material C. ferrous material D. light metal material E. glass.
2. A method of classifying and reclaiming usable materials from municipal waste, according to claim 1, including the additional step of compressing the flake material raked off from the fluid flotation medium in step ll(a) by passing that material along an open mesh conveyor between a plurality of successive pairs of pressure rollers to remove entrained fluid therefrom and produce a relatively dry, dense paper material.
3. A method of classifying and reclaiming usable materials from municipal waste, according to claim 1, in which the solid material removed from the first fluid medium flotation separation vessel, is taken from below the surface of the fluid medium, with the solid material being elevated as it is withdrawn from the first vessel and the fluid medium permitted to drain back into the vessel during removal.
4. A method of classifying and reclaiming usable materials from municipal waste, according to claim 3, including the additional step of compressing the solid organic material removed from the fluid flotation medium in Step by passing that material along an open mesh conveyor between a plurality of successive pairs of pressure rollers to remove entrained fluid therefrom and produce a relatively dry, dense organic material suitable for use as a landfill material.
5. A method of classifying and reclaiming usable materials from municipal waste, according to claim 1, in which each of the outputs W B, C and D is passed through a cleaning fluid and simultaneously vibrated to clean the output product.
6. A system for classifying and reclaiming usable materials from solid municipal waste comprising:
milling means for milling raw solid waste toparticulate form, of predetermined maximum size;
a first flotation separation vessel, filled with a liquid flotation medium, and including a surface rake for raking off floating flake material from the surface of the liquid medium, the flake material primarily comprising paper, a dense material separator for removing dense material, comprising primarily metal and glass heavier than the liquid medium, from the bottom of the first flotation vessel, and a dewatering elevator for removing solid material, comprising primarily solid organic material lighter than the fluid medium, from the upper part of the first flotation vessel; said elevator being displaced from both said rake and said dense material separator;
conveyor means for conveying the output of the milling means to the first flotation separation vessel and for depositing that output onto the surface of the liquid in the first flotation vessel at a point closely adjacent the surface rake;
a magnetic separator for magnetically separating ferrous materials from the dense material constituting the output of the dense material separator in the first flotation separation vessel;
and a glass-metal separator for separating the remainder of the dense material into glass material of little surface area and light-metal material of larger surface area on the basis of surface area differentials, the glass-metal separator comprising a second liquid medium flotation separation vessel.
7. A system for classifying and reclaiming usable materials from municipal waste, according to claim 6, in which the liquid flotation medium utilized in both the first and the second flotation separation vessels is water.
8. A system for classifying and reclaiming usable materials from municipal waste, according to claim 7, in which the dense material separator in the first flotation separation vessel comprises a rotary drum extending to the bottom of the vessel and projecting above the liquid surface in the vessel, the drum having a multiplicity of radially directed interior vanes, and a conveyor extending into the interior of the drum between the vanes and the surface of the flotation liquid for carrying away dense material removed from the bottom of the vessel on the vanes of the drum and released when the vanes have rotated to the top of the drum.
9. A system for classifying and reclaiming usable materials from municipal waste, according to claim 6, in which the dewatering elevator for the first flotation separation vessel comprises an elongated conduit projecting into the vessel at an angle to the horizontal and extending below the surface level of the liquid flotation medium, a helical screw extending axially of the conduit and substantially filling the conduit, and means for continuously rotating the screw, and in which the dewatering elevator is located at a substantial distance from the surface rake in the first flotation separation vessel.
10. A system for classifying and reclaiming usable materials from municipal waste, according to claim 6, and further comprising first dewatering and densifying means for the paper flake material comprising the output of the surface rake in the first flotation separation vessel and second dewatering and densifying means for the solid organic material removed from the first flotation separation vessel by the dewatering elevator.
11. A system for classifying and reclaiming usable materials from solid municipal waste, according to claim 10, in which at least one of the dewatering and densifying means comprises an elongated, open mesh conveyor of substantial width, means for depositing material to be densified on one end of the conveyor in a narrow stream, and a plurality of pairs of pressure rolls located on opposite sides of the conveyor at spaced points along the conveyor for successively pressing the material into thinner and wider configuration across the conveyor and for squeezing entrained liquid from the material.
12. A system for classifying and reclaiming usable materials from municipal waste, according to claim 11, in which each pair of pressure rolls is continuously driven so that the surface of each roll engaging the conveyor is moving in the same direction and at approximately the same speed-as the conveyor.
13. A system for classifying and reclaiming usable materials from municipal waste, according to claim 6,
in which the glass-metal separator further comprises a first separator drum extending only partly below the surface of the liquid flotation medium in the second separation vessel, a deflection baffle located adjacent the bottom of the first separator drum, means for introducing the remainder of the dense material into the second separation vessel immediately above the baffle, and a second separator drum extending to the bottom of the second separation vessel, the first separator drum serving to collect light metal and the second separator drum serving to collect glass and other ceramic materials.
14. A system for classifying and reclaiming usable materials from municipal waste, according to claim 13, in which the baffle includes a relatively narrow gap spaced from the first separator drum, and further comprising means for directing an air stream upwardly through that gap to deflect light metal particles toward the first separator drum without materially interferring with movement of heavier particles to the bottom of the second separation vessel.
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