Title of Invention	PROCESS AND APPARATUS FOR MANUFACTURING CRUMB AND POWDER RUBBER
Abstract	A process of making crumb and powder rubber comprising: (a) granulating an initial charge of used rubber particles after removal of any tramp metal; (b) removing ferrous metal from said granulated rubber particles produced in step (a); (c) concurrently screening and removing fiber from said granulated rubber particles produced in step (b); (d) chilling said screened granulated rubber particles having a predetermined particle size range produced in step (c) with a stream of a cryogenic liquid spray and a stream of a cryogenic gas flowing concurrently with the screened granulated rubber particles wherein the final chilled temperature of the particles is controlled and the ferrous metal and fiber are removed from the screened granulated rubber particles subsequent to step (c) but prior to step (d); (e) grinding said stream of chilled rubber particles by varying impact speed wherein said particle size distribution of said ground rubber particles is controlled; and (f) screening said ground rubber particles into desired crumb and/or powder rubber particle size ranges.

Title of Invention

PROCESS AND APPARATUS FOR MANUFACTURING CRUMB AND POWDER RUBBER

Abstract

A process of making crumb and powder rubber comprising: (a) granulating an initial charge of used rubber particles after removal of any tramp metal; (b) removing ferrous metal from said granulated rubber particles produced in step (a); (c) concurrently screening and removing fiber from said granulated rubber particles produced in step (b); (d) chilling said screened granulated rubber particles having a predetermined particle size range produced in step (c) with a stream of a cryogenic liquid spray and a stream of a cryogenic gas flowing concurrently with the screened granulated rubber particles wherein the final chilled temperature of the particles is controlled and the ferrous metal and fiber are removed from the screened granulated rubber particles subsequent to step (c) but prior to step (d); (e) grinding said stream of chilled rubber particles by varying impact speed wherein said particle size distribution of said ground rubber particles is controlled; and (f) screening said ground rubber particles into desired crumb and/or powder rubber particle size ranges.

Full Text	PROCESS AND APPARATUS FOR MANUFACTURING CRUMB AND POWDER RUBBER BACKGROUND OF THE DISCLOSURE 1. Field of the Invention The present invention is directed to a process and apparatus for making crumb and powder rubber from recycled rubber sources. More specifically, the present invention is directed to a process and apparatus for making crumb and powder rubber from a preprocessed source of used rubber particles having a predetermined particle size range. 2. Background of Ike Prior Art It is long been known that the disposal of used tires and other rubber articles represents a major environmental problem insofar as used tires overwhelm waste disposal sites and indiscriminate discarding of tires and like rubber articles create major environmental problems. It is for this reason that processes have been developed to dispose of tires in a manner that not only eliminates them as an environmental problem but provides incentives for practice of those tire disposal processes. These processes originally focused upon tire comminution which recovered the inherent fuel value of the significant combustible content of the vehicle tires. More recently, processes wliich recover the rubber constituent of vehicle tires, for reuse in the manufacture of rubber-containing articles, have been developed. Although these processes encouraged environmental protection by providing processes for the utility of rubber in the further manufacturing of new rubber products. a major concern associated with these processes has been the inability to provide purchasers of the rubber products produced in these processes with a rubber material that can be readily incorporated into the purchaser's production feed. That is, randomness of comminution variables and the types and condition of the used vehicle tire feed have produced random rubber products. Probably the most vmdesirable result of this random production has been the unpredictable rubber product particle size distribution. That is, although a lively market exists for crumb and powder rubber this market has not yet been fully exploited due to the inability to produce crumb and powder rubber in the particle size ranges required by tire and other rubber product producers who are the target purchasers of crumb and powder rubber products. U.S. Patent No. 5,588,600 describes a process and apparatus for low temperature comminution of tires in which cryogenic fluids, employed in embrittling the tires so that comminution can effectively occur, is recycled. This process produces crumb rubber of a sufficiently small particle size desirable to tire and other rubber product manufacturers. However, even the process of the '600 patent provides no assurance that the product rubber particle size range is desired by the customer, the manufacturer of new tires and other rubber product goods. Otlier disclosures of process and apparatus for reducing rubber to fine particle size include U.S. Patent Nos. 5,368,240 and 4,863,106. Although both of these disclosures describe processes for producing fine-sized rubber utilizing cryogenic fluids, neither of these references disclose means for custom designing the particle size range of the product to enhance commercial viability of such processing. The above remarks establish the need in the art for a new apparatus and process which not only consumes used rubber goods, particularly tires, from the environment but, in addition, produces a crumb and powder rubber product that is highly marketable insofar as it is provided in predetermined particle size ranges and in increased quantities desired by manufactures of tires and other rubber products. BRIEF SUMMARY OF THE INVENTION A process and an apparatus has now been developed which provides crumb and powder rubber in a predictable and predeterminable particle size range in concentrations that permit tire and other rubber producers to utiUze such crumb and powder rubber in commercial production of tires and other rubber products. This process additionally provides substantially no foreign matter such as fiber, metals and the like which are pres«it in used tires and other used rubber products. In accordance with the present invention a process for producing crumb and powder rubber from used rubber products is provided. In this process rubber particles of predetermined particle size range are chilled by a cryogenic fluid under conditions permitting tight control of the output temperature of the particles. The chilled particles are thereupon ground under conditions permitting close control of the reduced particle size range of the ground product. The reduced ground rubber particles are screened into desired crumb and powder rubber particle size ranges. In further accordance with the present invention an apparatus for producing crumb and powder rubber having a predetermined particle size range is provided. The apparatus includes chilling means for chilling a preprocessed stream of used rubber particles of predetermined particle size range groxmd from tires and other rubber products. The apparatus includes grinding means or comminuting the chilled rubber particles to a predetermined particle size range. The apparatus also is provided with screening means for separating the ground rubber particles. BRIEF DESCRIPTION OF THJ^RAWINGS Tlie present invention will be better understood with reference to the accompanying drawings of which: Figure 1 is a schematic flow diagram of the process and apparatus of tlie present invention; Figure 2 is a schematic represotitation of the freezing chamber which provides controlled freezing of rubbCT particles; and Figure 3 is a schanatic elevational view of a grinding apparatus providing confroUed particle size product; DETAILED DESCRIPTION The process and apparatus of the present invention is initiated by the introduction of used rubber, particularly used tire. In one preferred embodiment rubber feedstock derived from commercial operators who randomly comminute used vehicle tires and other vised rubber products is utilized. Such material is introduced into the process and apparatus of the present invention by being charged into a feed metering hopper 1. This rubber is usually received in supersack quantities. In a preferred embodiment, the feed rubber particles are passed over a metal detector, preferably an electromagnetic field adjusted in strength to detect large ferrous metal particles, denoted as tramp metal. Tramp metal is distinguished from small ferrous particles resulting from the comminution of used steel belt-containing tires. This is illustrated in the drawings by metal detecting station 2. The metal detector station 2 is preferably an electromagnetic field adjusted to identify large metal objects. The strength of the electromagnetic field is adjusted so that small ferrous metal slivers are not identified and thus not removed. It is emphasized that tramp metal detection is employed to protect equipment from large metal objects that would damage equipment employed in the process and apparatus of the present invention if not removed prior to introduction into the apparatus. The removal of tramp metal is a manual operation wherein the large metal object or objects identified are physically removed from the feed material. The feed material, free of tramp metal, is then conveyed to a primary graiiulatine; means 3. Primary granulating means 3 effectuates granulation of the course particles by means of rotating and stationary blades between which the rubber particles are granulated. As a general rule the primary granulation means reduces the particles to a range roughly between about 0.1875 inch and particles passing through U.S. sieve size No. 30. It is emphasized that this granulation operation occurs under ambient thermodynamic conditions. The granulated particles exiting granulating means 3 is conveyed to a first ferrous metal removing means 4 wherein ferroxis metal slivers, usually liberated due to the granulation of rubber particles derived fi-om steel belted tires, are drawn off the granulated product stream by a magnetic belt preferably disposed in a perpendicular direction to the conveyor carrying the granulation product. Those skilled in the art appreciate that such an arrangement is denoted as a cross belt magnet. In an alternate embodiment the aforementioned processing steps are omitted in favor of the receipt fi-om vendors of off-specification rubber particles that have been granulated to approximately the same particle size range as that obtained in granulating means 3 and which has been subjected to a ferrous metal removal procedure similar to that occurring in first ferrous metal removing means 4. This is depicted in the drawings by off-specification supersack feeding hopper 5. Indeed, the present process and apparatus contemplates an embodiment where a combination of feed from hopper 5 and first ferrous metal removal means 4 is employed. This feed from removal means 4, hopper 5 or both is conveyed to a primary screening and fiber removal means 6. The primary screening and fiber removal means 6 includes a screen to remove oversized particles. In a preferred embodiment a primary screener removes particles having a size in excess of about 0.1875 inch. This screening device relies on vibrations to aid in separating oversized from in-specification size particles. The disturbances caused by these vibrations enable this processing step to include fiber removal. The granulation step produces a large concentration of fiber tlireads and fiber fuzz, hereinafter refened to as "fiber" especially when the rubber particles are derived from vehicle tires. The particles, disposed over a broad surface area, move from the upstream end of the screener to the downstream end. The disturbances caused by this vibration form a "fluidized bed" effect in which, due to density, the lifter fiber separates from the heaver rubber granules. At a predetermined distance toward the downstream end, the solid stream comprising rubber granules and fiber ©acounters a barrier wedge over which the stream must rise to pass. This barrio- fiirther agitates the solid particle stream and fiirther separates the lighter fiber from the heavier rubber particles. The primary screener fiber removal apparatus 6 includes a narrow adjustable width exhaust hood disposed upstream of the barrier wedge. The length of the exhaust hood is the same as the width of the fiber separator. This exhaust hood aspirates the lighter fiber from the top of the feedstock. The exhaust hood, whose height above the fluidized bed and aspiration is adjustable, controls fiber witrapment velocity. The primary screener and fiber removal means 6 includes a second barrier wedge. Although most of the fibo* is removed when the particle stream encounters the first barrier wedge, additional fiber aspiration occurs at the second barrier wedge. The extracted fiber, removed by aspiration in the primary screener and fiber removal apparatus 6, is delivered to a unit cyclone and baghouse 9. The unit cyclone and baghouse 9 permits optimvim fiber entrapment velocity and minimum product loss. Particles that pass through the screen of the primary screening and fiber removal means 6 are conveyed to a preprocessed rubber particle hopper 8. Particles that do not pass through the screen of the primary screening and fiber removal means 6 are conveyed to secondary granulation means 7. Secondary granulation means 7, in a preferred embodiment, is an apparatus substantially identical to the apparatus constituting the primary granulation means 3. Similarly, the processing of rubber particles in the secondary granulation means 7 emulates the processing conducted in the primary granulation means 3. Thus, granulation relies upon granulation of the particles between stationary and rotating blades conducted at atmospheric pressure and ambient temperature. The product exiting the secondaiy granulation means 7 is recycled back into the primary screening and fiber removal means 9 and the aforementioned procedure is repeated. In yet another preferred embodiment of the present invention rubber particle product eqmvalent to the rubber particle product present in the preprocessed rubber particle hopper 8 is utilized. This equivalent product, provided by vendors meeting specification requirements dictated by the operator of the process and ^paratus of the present invention, is shipped in supersacks and is loaded into preprocessed supersack feeding hopper 11, which is substantially identical to hopper 8. The product conveyed fi^om hopper 8, hopper 11 or both is conveyed to a second ferrous metal and fiber removal means 30. The second ferrovis metal and fiber removal means 30, in a preferred embodiment, is provided by disposing the rubber particle stream on a mesh surface that is agitated to separate the particles. A magnetic drum, preferably a rare earth magnetic drum, providing strong ferrous metal attraction, draws off ferrous metal particles. At the same time, agitation creates elevation of the non-metal particles above the mesh conveyer surface wherein the lower density fiber particles separate above the higher density rubber particles so that the higher elevation lower density fiber particles are easily separated and removed fi'om the lower elevation higher density rubber particles by aspiration. The aspirated fiber is conveyed to fiber cyclone and baghouse 9. The focus upon fiber removal of the rubber particle product is emphasized by the subsequent processing step that occurs at a third fiber removal means 32. Third fiber removal means 32 preferably employs a centrifugal separator. The particles, subsequent to ferrous metal and fiber removal in second fiber removal means 30, are introduced into a cylindrical shaped screen container provided with an impeller. When the impeller is rotated the centrifiigal force causes the desuable fine particles to pass through the screen and discharge at the bottom of the apparatus. Oversized particles and fiber, which balls up, cannot pass through the screen and are discharged tlirough a separate conduit. The thus processed rubber particles stream is conveyed to storage bin 10 provided with metering discharge to provide controlled flow therefrom. The metered rubber particle stream from storage bin 10 is fed into at least one chilling means 12. In a preferred embodiment, illustrated in the drawings, two parallel identical chilling means 12 and 12' are employed providing increased productivity. The chilling means 12 is diaracterized by being able to closely control the temperature of the rubber particles that are processed therein. This control is the result of control of the chillant, preferably a cryogenic fluid. The preferred cryogenic fluid is liquid nitrogen. This is not to say that Uquid inert gases, such as liquefied argon, neon or helixmi, cannot be used. However, liquid nitrogen, having a very low temperature at atmospheric pressure and readily available at relatively low cost, enjoys a tremendous cost advantage over liquefied inert gases. However, in the event that special circumstances warrant, liquefied inert gases may be employed. The cryogenic fluid, usually liquid nifrogen, is fed into a cylindrical shaped vessel 13, by means of a spray nozzle, ports, a manifold or the like, at a controlled volumetric rate. The liquid nitrogen is infroduced into cylindrical shaped vessel 13 at approximately the midpoint between the inlet and outlet ends. As those skilled in the heat transfer arts are aware, cooling efficiency is maximized by recycling cold vaporized nitrogen gas, which results from the heating of the nitrogen liquid during the chilling of the rubber particles, into the inlet end of vessel 13 concurrently with the metered introduction of the rubber particle stream from storage bin 10. This precooling makes more efficient the final chilling of the rubber particles stream primarily effectviated by the nitrogen liquid. The rubber particle stream from storage bin 10 is conveyed to a rotating auger 14, as illustrated by rubber particle stream 16, whose speed, and thus the duration of time the rubber particles remain in the chilling means 12, is controlled by variable speed rotor 15 controlling auger velocity. Thus, the combination of controlling rubber particle feed rate, the speed of the rotor turning the auger and the volumetric feed rate of the cryogenic fluid permit control of the tranperature of the chilled rubber particles exiting chilling means 12. As shown in the drawings, the cold vapored nitrogen gas 18 is recycled back into the inlet of cylindrical shaped vessel 13 so as to flow conciurently with rubb«- particle stream 16. The chilling means 12 is in communication with a grinding means 20 disposed downstream of the downstream end of the cylindrical shaped vessel 13. Chilling means 12 and grinding means 20 are coordinated so that the precise desired amoimt of chilled rubber particles 19 leaving cylindrical shaped vessel 13 is introduced into the grinding means 20. Grinding means 20 provides precise control of the particle size distribution of the rubber comminuted therein. Grinding means 20 includes an outer inverted cone 22. The inside surface 23 of the outer inverted cone 22 is serrated and acts as any reboimd surface does in a typical impact mill. The component corresponding to an impact surface in a typical impact mill is an inverted conical-shape surface 24 provided with a multiplicity of knife edges 25. The impact surface 24 is rotatable by a rotor 27 and rotates as indicated by arrow 26. Control of the rubber particle size distribution results from the adjustability of the outer inverted cone 22. The outer inverted cone 22 can be raised and lowered as depicted by arrows 29. The raising of the outer invented cone 22 increases the space between the rotating knives 25, and the serrated surface 23 of the outer inverted cone 22. Thus, depending on the desired particle size range product, the outer inverted cone 22 is moved down to obtain finer sized rubber particles. Obviously, tlie moving up of outer inverted cone 22 results in larger sized rubber particles. In operation, discharged frozen rubber particles 19 from the cliilling means 12 enter the top of grinding means 20 and fall between knives 25 of impact surface 24 and serrated surface 23 of outer inverted cone 22. The impact surface rotor 27 rotates the impact surface 24 at the desired rotational speed to grind the rubber particles between knives 25 and serrated edge 23. In a preferred embodiment discussed above and illustrated in the drawings, grinding means 20 is conically shaped. The material of construction of grinding means 20 is designed to operate under cryogenic temperature conditions. In a preferred embodiment, the outa: jacket is a cast metal alloy that can withstand cyrogenic operating temperatures. The outer inverted cone 22 is hydraulically removable for cleaning, normal maintenance and emergency repair. In a preferred embodiment the impact surface 24 rotates at a speed of approximately 1800 RPM. The knives 25, disposed on conical surface 24, are preferably "C" shaped and are complementary with the serrations on the inner surface 23 of the outer inverted cone 22. The knives 25 are removable for sharpening and replacement. The operation of grinding means 20 starts witli the introduction of a feedstock, e.g. chilled rubber particles, that is fed through the top of grinding means 20 and which immediately impacts a series of horizontal knives 25 atop impact surface 24. Particle size reduction of the rubber particles continue as the rubber particle stream flows downward in grinding means 20 insofar as the number of the knives 25 on the surface 24 in a horizontal row increases in number in the downward direction at higher I>eripheral speeds. The rubber particle stream is ultimately discharged at the bottom of grinding means 20. As stated above, in a preferred embodiment, in order to increase production, the process and apparatus of the present invention may include parallel identical cliilling means. In that preferred embodiment, depicted in the drawings, parallel grinding means 20', identical to parallel means 20, is provided. In this preferred embodiment, the rubber particles product of chilling means 12' are fed into grinding means 20', just as are the rubber particles product 19 of chiUing means 12 conveyed into grinding means 20. Whether one or two chilling means and grinding means is utilized, the nibber particle product of grinding means 20 or 20 and 20' are conveyed to a drying means 35. Drying means 35 is primarily provided to raise the temperature of the rubber particle product of the grinding operation in grinding means 20 to ambient. In a preferred embodiment, drying means 35 is provided by a rotary dryer provided with gas entraining means, preferably air, to "wash" the dried rubber particle product. This "wash" has the effect of agitating rubber particles and fiber, thus separating lighter density fiber from the rubber particle product by aspiration of the fiber. Again, this fiber is conveyed to fiber cyclone and baghouse 9. A final ferrous metal and fourth fiber removing means 50 for removing ferrous metal and fiber, downstream of drying means 35, is provided. Ferrous metal removal means 50, which receives the dried rubber particle product of drying means 35, is disposed immediately downstream of drying means 35. In a preferred embodiment, ferrous metal removal means 50 is in the form of a rare earth drum magnet. In this processing step the dried rubber particles are preferably separated from ferrous metal particles while on a vibratory screen whereat metal particles are drawn to the drum magnet and removed. At the same time, the vibrating action of the screen results in density separation of lightar density fiber from higher density particles. Tliis separated fiber is removed to the fiber cyclone and baghouse 9. Yet another fiber separation occurs immediately downstream of the above fiber removal step. This processing step is provided by fiftli fiber removal means 60. Fiber removal means 60, in a preferred embodiment, involves conveyance of the ferrous metal-free rubber particles to a centrifiigal separator wherein fiber, present in the rubber particle stream, is removed and fransferred to the fiber cyclone and baghouse 9. The centrifugal separator is of the same design and operates in like fashion to the centrifugal separator of the third fiber removal means 32. The above description emphasizes the many times that the process and apparatus of the present invention of making crumb and powder rubber includes fiber removal from the rubber particle product stream. Those skilled in the art appreciate that the present invention assigns criticality to fiber removal in the successfiil manufacture of rubber products, especially tires. Thus, consistent with this philosophy, the final steps in the process and apparatus of the present invention, which are screening processing steps, also involve fiber removal. The first final sca-eening operation is to transfer the rubber particles product exiting fiber separation means 60 to a two-deck screening means 65. Two-deck screening means 65 includes a screener to eliminate particles whose size is too large to meet the requirement of the crumb and/or powder rubber purchaser. Typically, particles that do not pass through a U.S. sieve size No. 40 screen are too large to be effective as crumb rubber. Thus, in a preferred embodiment, the screener is a U.S. sieve size No. 40. Particles that do not pass through this screen are recycled back into storage bin 10 for reprocessing. Rubber particles passing through the U.S. sieve size No. 40 screen are transferred to a final three-deck screening means 70. Indeed, in a preferred embodiment, two such screening means are provided. This is illustrated in the drawings by a second three-deck screening means 70'. The three-deck screening means 70 permits separation of particle sizes within the accepted size limits that define crumb and powder rubber. This is accomplished by disposing a courser screener atop a finer screener thus resulting in three different particle sized products, which are the products of the process and apparatus of the present invention. In a preferred embodiment, the top deck product, constituting rubber particles that do not pass through the top, courser screener is rubber particles of particle size smaller than U.S. sieve size No. 40 but larger than U.S. sieve size No. 80, which is the preferred courser size SCTeen employed in the three-deck screening means 70. This product is conveyed, by means of conduit 71 and, if present, 71', to storage bin 75. This conveyance to storage bin 75 is accomplished by pneumatic means as are the conveyance of the other two products discussed below. The second, intermediate cut of rubber particles produced in three-deck screening means 70 encompasses particles passing through the courser screener but too large to pass through the finer screener. In a preferred embodiment the finer screener is provided by a screen of U.S. sieve size No. 140. Thus, the particles held by the finer screener are conveyed to storage bin 78 through conduit means 72 and, if present, 72'. Storage bin 78 holds rubber particles having a particle size range of particles that pass through U.S. sieve size No. 80 but do not pass through U.S. sieve size No. 140. The third rubber particle size product, representative of powder rubber, encompass rubber particles passing through the finer screener, a U.S. sieve size No. 140 screen. That cut, denoted as "-140" is pneumatically conveyed, by conduit means 73 and, if present, 73' to storage bin 80. Turning again to fiber removal, fiber is aspirationally removed from each of the three decks of products and discharged into conduit means leading to the fiber cyclone and baghouse 40. It is emphasized that storage bins 75, 78 and 80 may be provided with bagging and weighing means (not shown) for conveyance to the purchaser or purchasers of these products. The embodiments given above are provided to illustrate the scope and spirit of the present invention. These embodiments will make apparent, to those skilled in the art, other embodiments and examples. These other embodiments and examples are within the contemplation of the present invention. Therefore, the present invention should be limited only by the appended claims. WE CLAIM; 1. A process of making crumb and powder rubber comprising; (a) granulating an initial charge of used rubber particles after removal of any tramp metal; (b) removing ferrous metal from said granulated rubber particles produced in step (a); (c) concurrently screening and removing fiber from said granulated rubber particles produced in step (b); (d) chilling said screened granulated rik>ber particles having a predetermined particle size range produced in step (c) with a stream of a cryogenic liquid spray and a stream of cryogenic gas flowing concurrently with the screened granulated rubber particles wherein the final chilled tempera- ture of the particles is controlled and the ferrous metal and fiber are removed from the screened granulated rubber particles subsequent to step (c) but prior to step (d); (e) grinding said stream of chilled rubber particles by varying impact speed wherein said particle size distribution of satd ground rubber particles is controlled; and (0 screening said ground rubber particles into desired crumb and/or powder rubber particle size ranges. 2. A process as ciaimed in ciaim 1 wherein said used rubber particles are particles of used vehicle tires. 3. A process as claimed in claim 1 wherein said fiber removing steps comprise agitating said rubber particle and aspirating lower density fiber from higher density rubber particles. 4. A process as claimed in claim 1 wherein said control of particle size temperature in step (e) irKludes control of duration of contact of said rubber particles with said cryogenic fluid. 5. A process as claimed in claim 4 wherein said control of rubber particle size temperature includes volumetric flow rate control of said cryogenic fluid contacting said rubber particles. 6. A process as claimed in claim X wherein said control of particle size distribution further comprises varying the space between said impact surface and a rebound surface. 7. A process as claimed in claim 5 wherein said cryogenic fluid is liquid nitrogen. 8. A process as claimed in claim 1 wherein said ground stream of cryogenically cooled rubber particles after said step (f) are dried to ambient temperature. 9. A process as claimed in claim 2 wherein said ground stream of cryogenicaiiy cooled rubber particles after said step (0 are dried and fibers present in said ground stream are removed. 10. A process as claimed in claim 9 wherein ferrous metal and fibers in said dried stream of rubber particles are removed. 11. A process as claimed in claim 10 wherein said rubber particle stream from which ferrous metal and fiber are removed is screened to remove rubber particles whose particle size exceeds the maximum particle size of crumb rubber and wherein more fiber is removed. 12. A process as claimed in claim 11 wherein said particles from which excess sized particles are removed is screened into three rubber particle sizes within the particle size rar^ge of crumb and powder rubber. 13. A process as claimed in claim 12 wherein said rubber particles include a first particle size range of particles passing tlwough 420 vm (U.S. sieve size No. 40) but not passing through 177 ^ (U.S. sieve size No. 80); a second particle size in the range of between particles passing through 177 ^ (U.S. sieve size No. 80) but not passing through 105 pm (U.S.sieve size No. 140); and a third particle size of particles passing through 105 mhi (U.S. sieve size No. 140). 14. An apparatus for making crumb and powder rubber comprising: granulating means (3) for granulating an initial charge of used rubber particles ; ferrous metal removing means (4) provided with means for fiber removal for removing ferrous metal and fiber fi-om said granulated rubber particles; primary screening means (6) provided with fiber removal means for screening said granulated rubber particles; chilling means (12) for cooling said screened rubber particles having a predetermined particle size range provided with means for introducing said used rubber particles^ a acryogenic liquid spray and a cryogenic gaseous stream whereby said rubber particles are cooled to a predetermined temperature, wherein said ferrous metal removing means (4) and said fiber removal means are disposed upstream of said chilling means (12); grinding means (20) for grinding said cooled rubber particles at said predetermined temperature to a predetermined particle size range; and screening means for separating said ground rubber particles into desired crumb and/or powder rubber particle size ranges. iS. An apparatus as ciaimed in claim 14 wherein said chilling means (12) is suitable for chilling used vehicle tire particles. 16. An apparatus as claimed in claim 14 comprising metal detection means (2) for removing tramp metal present in said initial chwge of used rubber particles. 17. An apparatus as claimed in claim 14 comprising secondary granulation means (7) for graruilation of rubber particles that do not pass through said primary screening means; and a preprocessed rubber particle hopper (8) for holding said rubber particles exiting said primary and secondary granulation means. 18. An apparatus as claimed in claim 17 comprising a second ferrous metai and fiber removal means (30) for removing ferrous metal and fiber from said preprocessed rubber particles exiting said preprocessed rubber particles hopper (8). 19. An apparatus as claimed in claim 18 comprising a third fiber removal means (32) for removing fiber from said rubber particles exiting said second ferrous metal and fiber removal means (30). 20. An apparatus as claimed in claim 19 comprising a fiber cyclone and baghouse (9) for storage of said removed fiber removed by ail said fiber removal means. 21. An apparatus as claimed in claim 14 comprising a praprocessed supersack feeding hopper (11) for introduction of used rubber particles preprocessed to screen out particles larger than sizes within the range of crumb and powder rubber and from which ferrous metal and fiber have been removed; a second ferrous metal and fiber removal means (30) for removal of ferrous metal and fiber from said preprocessed used rubber particles fed fi-om said supersack feeding hopper (11); and a third fiber removal means (32) for removal of fibers from said rubber particles exiting said second ferrous metal and fiber removal means. 22. An apparatus as claimed in claim 21 comprising a storage bin with metering discharge (10) for storage of said rubber particles exiting said third fiber removal means (32) suitable for feeding said preprocessed used rubber particles into said cooling means (12). 23. An apparatus as claimed in claim 14 wherein said cooling means (12) comprises a cylindrical shaped vessel (13) provided with means for controlled introduction of a cryogenic fluid and for time controlled contact of said preprocessed stream of used rubber particles with said cryogenic fluid. 24. An apparatus as claimed in claim 23 wherein said time controlled contact is provided by variable speed auger (15), disposed in said cylindrical shaped vessel (13) suitable for disposing said rubber particles thereon. 25. An apparatus as claimed in claim 14 wherein a grinding means (20) comprises means for introduction of said cooled preprocessed rubber particle sfream (19) between a controlled speed impact surface (24) and an outer inverted surface (22). 26. An apparatus as claimed in claim 25 wherein said conb-olled speed impact surface (24) Is an Impact surface provided with a plurality of replaceable knives (25) and said outer inverted cone surface (22) has an interior surface (23), suitable for being in contact with said preprocessed stream of rubber particles (19), comprising a serrated surface. 27. An apparatus as claimed in claim 26 wherein said outer inverted cone surface (22) is movable in a vertical direction wherein volume between said impact surface (24) and serrated surface of outer invented cone surface (23) is increased or decreased. 28 An apparatus as claimed in claim 14 including drying means (30) for drying said ground stream of cryogenically cooled rubber particles to ambient temperature. 29. An apparatus as claimed in claim 28 wherein said drying means (30) is a rotary dryer provided with a gas entraining stream to separate lower density fiber from higher density rubber particles. 30. An apparatus as claimed in claim 24 wherein a means for feeding liquid nitrogen suitable as cryogenic fluid is provided and said cooling means (12) is provided with conduit means for recycle pf vaporized nitrogen gas resulting from cooling of said rubber particles suitable fjsr flowing concurrently into said cooling means with said preprocessed rubber particle stream. 31. An apparatus as claimed in claim 27 comprising a final ferrous metal and fourth fiber removal means (50) disposed downstream of said drying means for removal of ferrous metal (35) and fiber fi'i\|>m said dried rubber particles. 32. An apparatus as claimed in claim 3DI wherein said final ferrous metal and fourth fiber removal means (50), disposjed downstream of said drying means, comprises a magnetic separator disposed under a vibratory pan screen suitable for removing said ferrous metal below s^id screen and for removing said fibers above said screen. 33. An apparatus as claimed in claim 32\| comprising a fifth fiber removal means (60), disposed downstream of said fmal ferrous metal and fourth fiber removal means (50), for removal of fiber from $aid rubber particles exiting said final ferrous metal and fiber removal means (5D). 34. An apparatus as claimed in claim 33!Wherein said fifth fiber removal means (60) comprises a centrifugal screener suitlable for removing light fiber to a fiber cyclone and baghouse (40). 35. An apparatus as claimed in claim 32 comprising a two-deck screening means (65) disposed downstream of said fifth fiber removal means (60) for removal of rubber particles having a ^ize in excess of the size range of crumb and powder rubber. 36. An apparatus as claimed in claim 35 wherein a means for recycling said oversized particles to a storage bin (10^ is provided with metering discharge, said storage bin (10) being in downstream communication with said cooling means (12); and a three-deck screening means (70) is provided to which said particles passing through said two-deck screenir^g means (65) are conveyed. 37. An apparatus as claimed in clai\|n 36 wherein said three-deck screening means (70) comprises a top 177 pm (U.S. sieve size No. 80) screen holding particles passing through a 420 ^ (UiS. sieve size No. 40) screen, said particles held on said top screen provided with means for transfer to a 420 to 177^ (U.S. sieve No. 40 to No. 80) rubber crumb rubber particles storage bin (75); and a bottom 105 yon (U.S. sieve size fjlo. 140) screen, said particles held on said bottom screen provided with means for b-ansfer to a 177 to 105 ^ (U.S. sieve size No. 80 to No. 140) storage bin (78);said particles passing through said bottom screen provided with means for transfer to a powder rubber storage bin (80) holding particles finer than 105 ^ (U.S. sieve size No. 140). 38. An apparatus as claimed in claim 37 wherein pneumatic means are provided suitable for conveyance into said storage bins (75; 78; 80). A process of making crumb and powder rubber comprising: (a) granulating an initial charge of used rubber particles after removal of any tramp metal; (b) removing ferrous metal from said granulated rubber particles produced in step (a); (c) concurrently screening and removing fiber from said granulated rubber particles produced in step (b); (d) chilling said screened granulated rubber particles having a predetermined particle size range produced in step (c) with a stream of a cryogenic liquid spray and a stream of a cryogenic gas flowing concurrently with the screened granulated rubber particles wherein the final chilled temperature of the particles is controlled and the ferrous metal and fiber are removed from the screened granulated rubber particles subsequent to step (c) but prior to step (d); (e) grinding said stream of chilled rubber particles by varying impact speed wherein said particle size distribution of said ground rubber particles is controlled; and (f) screening said ground rubber particles into desired crumb and/or powder rubber particle size ranges.

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PROCESS AND APPARATUS FOR MANUFACTURING
CRUMB AND POWDER RUBBER
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The present invention is directed to a process and apparatus for making crumb
and powder rubber from recycled rubber sources. More specifically, the present
invention is directed to a process and apparatus for making crumb and powder rubber
from a preprocessed source of used rubber particles having a predetermined particle
size range.
2. Background of Ike Prior Art
It is long been known that the disposal of used tires and other rubber articles
represents a major environmental problem insofar as used tires overwhelm waste
disposal sites and indiscriminate discarding of tires and like rubber articles create
major environmental problems. It is for this reason that processes have been
developed to dispose of tires in a manner that not only eliminates them as an
environmental problem but provides incentives for practice of those tire disposal
processes.
These processes originally focused upon tire comminution which recovered the
inherent fuel value of the significant combustible content of the vehicle tires. More
recently, processes wliich recover the rubber constituent of vehicle tires, for reuse in
the manufacture of rubber-containing articles, have been developed.
Although these processes encouraged environmental protection by providing
processes for the utility of rubber in the further manufacturing of new rubber products.
a major concern associated with these processes has been the inability to provide
purchasers of the rubber products produced in these processes with a rubber material
that can be readily incorporated into the purchaser's production feed. That is,
randomness of comminution variables and the types and condition of the used vehicle
tire feed have produced random rubber products. Probably the most vmdesirable result
of this random production has been the unpredictable rubber product particle size
distribution. That is, although a lively market exists for crumb and powder rubber this
market has not yet been fully exploited due to the inability to produce crumb and
powder rubber in the particle size ranges required by tire and other rubber product
producers who are the target purchasers of crumb and powder rubber products.
U.S. Patent No. 5,588,600 describes a process and apparatus for low
temperature comminution of tires in which cryogenic fluids, employed in embrittling
the tires so that comminution can effectively occur, is recycled. This process produces
crumb rubber of a sufficiently small particle size desirable to tire and other rubber
product manufacturers. However, even the process of the '600 patent provides no
assurance that the product rubber particle size range is desired by the customer, the
manufacturer of new tires and other rubber product goods.
Otlier disclosures of process and apparatus for reducing rubber to fine particle
size include U.S. Patent Nos. 5,368,240 and 4,863,106. Although both of these
disclosures describe processes for producing fine-sized rubber utilizing cryogenic
fluids, neither of these references disclose means for custom designing the particle size
range of the product to enhance commercial viability of such processing.
The above remarks establish the need in the art for a new apparatus and
process which not only consumes used rubber goods, particularly tires, from the
environment but, in addition, produces a crumb and powder rubber product that is
highly marketable insofar as it is provided in predetermined particle size ranges and in
increased quantities desired by manufactures of tires and other rubber products.
BRIEF SUMMARY OF THE INVENTION
A process and an apparatus has now been developed which provides crumb
and powder rubber in a predictable and predeterminable particle size range in
concentrations that permit tire and other rubber producers to utiUze such crumb and
powder rubber in commercial production of tires and other rubber products. This
process additionally provides substantially no foreign matter such as fiber, metals and
the like which are pres«it in used tires and other used rubber products.
In accordance with the present invention a process for producing crumb and
powder rubber from used rubber products is provided. In this process rubber particles
of predetermined particle size range are chilled by a cryogenic fluid under conditions
permitting tight control of the output temperature of the particles. The chilled
particles are thereupon ground under conditions permitting close control of the
reduced particle size range of the ground product. The reduced ground rubber
particles are screened into desired crumb and powder rubber particle size ranges.
In further accordance with the present invention an apparatus for producing
crumb and powder rubber having a predetermined particle size range is provided. The
apparatus includes chilling means for chilling a preprocessed stream of used rubber
particles of predetermined particle size range groxmd from tires and other rubber
products. The apparatus includes grinding means or comminuting the chilled rubber
particles to a predetermined particle size range. The apparatus also is provided with
screening means for separating the ground rubber particles.
BRIEF DESCRIPTION OF THJ^RAWINGS
Tlie present invention will be better understood with reference to the
accompanying drawings of which:
Figure 1 is a schematic flow diagram of the process and apparatus of tlie
present invention;
Figure 2 is a schematic represotitation of the freezing chamber which provides
controlled freezing of rubbCT particles; and
Figure 3 is a schanatic elevational view of a grinding apparatus providing
confroUed particle size product;
DETAILED DESCRIPTION
The process and apparatus of the present invention is initiated by the
introduction of used rubber, particularly used tire. In one preferred embodiment
rubber feedstock derived from commercial operators who randomly comminute used
vehicle tires and other vised rubber products is utilized. Such material is introduced
into the process and apparatus of the present invention by being charged into a feed
metering hopper 1. This rubber is usually received in supersack quantities.
In a preferred embodiment, the feed rubber particles are passed over a metal
detector, preferably an electromagnetic field adjusted in strength to detect large
ferrous metal particles, denoted as tramp metal. Tramp metal is distinguished from
small ferrous particles resulting from the comminution of used steel belt-containing
tires. This is illustrated in the drawings by metal detecting station 2. The metal
detector station 2 is preferably an electromagnetic field adjusted to identify large metal
objects. The strength of the electromagnetic field is adjusted so that small ferrous
metal slivers are not identified and thus not removed. It is emphasized that tramp
metal detection is employed to protect equipment from large metal objects that would
damage equipment employed in the process and apparatus of the present invention if
not removed prior to introduction into the apparatus. The removal of tramp metal is a
manual operation wherein the large metal object or objects identified are physically
removed from the feed material.
The feed material, free of tramp metal, is then conveyed to a primary
graiiulatine; means 3. Primary granulating means 3 effectuates granulation of the
course particles by means of rotating and stationary blades between which the rubber
particles are granulated. As a general rule the primary granulation means reduces the
particles to a range roughly between about 0.1875 inch and particles passing through
U.S. sieve size No. 30. It is emphasized that this granulation operation occurs under
ambient thermodynamic conditions.
The granulated particles exiting granulating means 3 is conveyed to a first
ferrous metal removing means 4 wherein ferroxis metal slivers, usually liberated due to
the granulation of rubber particles derived fi-om steel belted tires, are drawn off the
granulated product stream by a magnetic belt preferably disposed in a perpendicular
direction to the conveyor carrying the granulation product. Those skilled in the art
appreciate that such an arrangement is denoted as a cross belt magnet.
In an alternate embodiment the aforementioned processing steps are omitted in
favor of the receipt fi-om vendors of off-specification rubber particles that have been
granulated to approximately the same particle size range as that obtained in
granulating means 3 and which has been subjected to a ferrous metal removal
procedure similar to that occurring in first ferrous metal removing means 4. This is
depicted in the drawings by off-specification supersack feeding hopper 5. Indeed, the
present process and apparatus contemplates an embodiment where a combination of
feed from hopper 5 and first ferrous metal removal means 4 is employed.
This feed from removal means 4, hopper 5 or both is conveyed to a primary
screening and fiber removal means 6. The primary screening and fiber removal means
6 includes a screen to remove oversized particles. In a preferred embodiment a
primary screener removes particles having a size in excess of about 0.1875 inch.
This screening device relies on vibrations to aid in separating oversized from
in-specification size particles. The disturbances caused by these vibrations enable this
processing step to include fiber removal. The granulation step produces a large
concentration of fiber tlireads and fiber fuzz, hereinafter refened to as "fiber"
especially when the rubber particles are derived from vehicle tires. The particles,
disposed over a broad surface area, move from the upstream end of the screener to the
downstream end. The disturbances caused by this vibration form a "fluidized bed"
effect in which, due to density, the lifter fiber separates from the heaver rubber
granules. At a predetermined distance toward the downstream end, the solid stream
comprising rubber granules and fiber ©acounters a barrier wedge over which the
stream must rise to pass. This barrio- fiirther agitates the solid particle stream and
fiirther separates the lighter fiber from the heavier rubber particles. The primary
screener fiber removal apparatus 6 includes a narrow adjustable width exhaust hood
disposed upstream of the barrier wedge. The length of the exhaust hood is the same as
the width of the fiber separator. This exhaust hood aspirates the lighter fiber from the
top of the feedstock. The exhaust hood, whose height above the fluidized bed and
aspiration is adjustable, controls fiber witrapment velocity.
The primary screener and fiber removal means 6 includes a second barrier
wedge. Although most of the fibo* is removed when the particle stream encounters the
first barrier wedge, additional fiber aspiration occurs at the second barrier wedge. The
extracted fiber, removed by aspiration in the primary screener and fiber removal
apparatus 6, is delivered to a unit cyclone and baghouse 9. The unit cyclone and
baghouse 9 permits optimvim fiber entrapment velocity and minimum product loss.
Particles that pass through the screen of the primary screening and fiber
removal means 6 are conveyed to a preprocessed rubber particle hopper 8. Particles
that do not pass through the screen of the primary screening and fiber removal means
6 are conveyed to secondary granulation means 7. Secondary granulation means 7, in
a preferred embodiment, is an apparatus substantially identical to the apparatus
constituting the primary granulation means 3. Similarly, the processing of rubber
particles in the secondary granulation means 7 emulates the processing conducted in
the primary granulation means 3. Thus, granulation relies upon granulation of the
particles between stationary and rotating blades conducted at atmospheric pressure and
ambient temperature. The product exiting the secondaiy granulation means 7 is
recycled back into the primary screening and fiber removal means 9 and the
aforementioned procedure is repeated.
In yet another preferred embodiment of the present invention rubber particle
product eqmvalent to the rubber particle product present in the preprocessed rubber
particle hopper 8 is utilized. This equivalent product, provided by vendors meeting
specification requirements dictated by the operator of the process and ^paratus of the
present invention, is shipped in supersacks and is loaded into preprocessed supersack
feeding hopper 11, which is substantially identical to hopper 8.
The product conveyed fi^om hopper 8, hopper 11 or both is conveyed to a
second ferrous metal and fiber removal means 30. The second ferrovis metal and fiber
removal means 30, in a preferred embodiment, is provided by disposing the rubber
particle stream on a mesh surface that is agitated to separate the particles. A magnetic
drum, preferably a rare earth magnetic drum, providing strong ferrous metal attraction,
draws off ferrous metal particles. At the same time, agitation creates elevation of the
non-metal particles above the mesh conveyer surface wherein the lower density fiber
particles separate above the higher density rubber particles so that the higher elevation
lower density fiber particles are easily separated and removed fi'om the lower
elevation higher density rubber particles by aspiration. The aspirated fiber is
conveyed to fiber cyclone and baghouse 9.
The focus upon fiber removal of the rubber particle product is emphasized by
the subsequent processing step that occurs at a third fiber removal means 32. Third
fiber removal means 32 preferably employs a centrifugal separator. The particles,
subsequent to ferrous metal and fiber removal in second fiber removal means 30, are
introduced into a cylindrical shaped screen container provided with an impeller.
When the impeller is rotated the centrifiigal force causes the desuable fine particles to
pass through the screen and discharge at the bottom of the apparatus. Oversized
particles and fiber, which balls up, cannot pass through the screen and are discharged
tlirough a separate conduit.
The thus processed rubber particles stream is conveyed to storage bin 10
provided with metering discharge to provide controlled flow therefrom. The metered
rubber particle stream from storage bin 10 is fed into at least one chilling means 12.
In a preferred embodiment, illustrated in the drawings, two parallel identical chilling
means 12 and 12' are employed providing increased productivity.
The chilling means 12 is diaracterized by being able to closely control the
temperature of the rubber particles that are processed therein. This control is the result
of control of the chillant, preferably a cryogenic fluid. The preferred cryogenic fluid
is liquid nitrogen. This is not to say that Uquid inert gases, such as liquefied argon,
neon or helixmi, cannot be used. However, liquid nitrogen, having a very low
temperature at atmospheric pressure and readily available at relatively low cost, enjoys
a tremendous cost advantage over liquefied inert gases. However, in the event that
special circumstances warrant, liquefied inert gases may be employed.
The cryogenic fluid, usually liquid nifrogen, is fed into a cylindrical shaped
vessel 13, by means of a spray nozzle, ports, a manifold or the like, at a controlled
volumetric rate. The liquid nitrogen is infroduced into cylindrical shaped vessel 13 at
approximately the midpoint between the inlet and outlet ends. As those skilled in the
heat transfer arts are aware, cooling efficiency is maximized by recycling cold
vaporized nitrogen gas, which results from the heating of the nitrogen liquid during
the chilling of the rubber particles, into the inlet end of vessel 13 concurrently with the
metered introduction of the rubber particle stream from storage bin 10. This
precooling makes more efficient the final chilling of the rubber particles stream
primarily effectviated by the nitrogen liquid.
The rubber particle stream from storage bin 10 is conveyed to a rotating auger
14, as illustrated by rubber particle stream 16, whose speed, and thus the duration of
time the rubber particles remain in the chilling means 12, is controlled by variable
speed rotor 15 controlling auger velocity. Thus, the combination of controlling rubber
particle feed rate, the speed of the rotor turning the auger and the volumetric feed rate
of the cryogenic fluid permit control of the tranperature of the chilled rubber particles
exiting chilling means 12. As shown in the drawings, the cold vapored nitrogen gas
18 is recycled back into the inlet of cylindrical shaped vessel 13 so as to flow
conciurently with rubb«- particle stream 16.
The chilling means 12 is in communication with a grinding means 20 disposed
downstream of the downstream end of the cylindrical shaped vessel 13. Chilling
means 12 and grinding means 20 are coordinated so that the precise desired amoimt of
chilled rubber particles 19 leaving cylindrical shaped vessel 13 is introduced into the
grinding means 20.
Grinding means 20 provides precise control of the particle size distribution of
the rubber comminuted therein. Grinding means 20 includes an outer inverted cone
22. The inside surface 23 of the outer inverted cone 22 is serrated and acts as any
reboimd surface does in a typical impact mill. The component corresponding to an
impact surface in a typical impact mill is an inverted conical-shape surface 24
provided with a multiplicity of knife edges 25. The impact surface 24 is rotatable by a
rotor 27 and rotates as indicated by arrow 26. Control of the rubber particle size
distribution results from the adjustability of the outer inverted cone 22. The outer
inverted cone 22 can be raised and lowered as depicted by arrows 29. The raising of
the outer invented cone 22 increases the space between the rotating knives 25, and the
serrated surface 23 of the outer inverted cone 22. Thus, depending on the desired
particle size range product, the outer inverted cone 22 is moved down to obtain finer
sized rubber particles. Obviously, tlie moving up of outer inverted cone 22 results in
larger sized rubber particles.
In operation, discharged frozen rubber particles 19 from the cliilling means 12
enter the top of grinding means 20 and fall between knives 25 of impact surface 24
and serrated surface 23 of outer inverted cone 22. The impact surface rotor 27 rotates
the impact surface 24 at the desired rotational speed to grind the rubber particles
between knives 25 and serrated edge 23.
In a preferred embodiment discussed above and illustrated in the drawings,
grinding means 20 is conically shaped. The material of construction of grinding
means 20 is designed to operate under cryogenic temperature conditions. In a
preferred embodiment, the outa: jacket is a cast metal alloy that can withstand
cyrogenic operating temperatures. The outer inverted cone 22 is hydraulically
removable for cleaning, normal maintenance and emergency repair. In a preferred
embodiment the impact surface 24 rotates at a speed of approximately 1800 RPM.
The knives 25, disposed on conical surface 24, are preferably "C" shaped and are
complementary with the serrations on the inner surface 23 of the outer inverted cone
22. The knives 25 are removable for sharpening and replacement.
The operation of grinding means 20 starts witli the introduction of a feedstock,
e.g. chilled rubber particles, that is fed through the top of grinding means 20 and
which immediately impacts a series of horizontal knives 25 atop impact surface 24.
Particle size reduction of the rubber particles continue as the rubber particle stream
flows downward in grinding means 20 insofar as the number of the knives 25 on the
surface 24 in a horizontal row increases in number in the downward direction at higher
I>eripheral speeds. The rubber particle stream is ultimately discharged at the bottom of
grinding means 20.
As stated above, in a preferred embodiment, in order to increase production,
the process and apparatus of the present invention may include parallel identical
cliilling means. In that preferred embodiment, depicted in the drawings, parallel
grinding means 20', identical to parallel means 20, is provided. In this preferred
embodiment, the rubber particles product of chilling means 12' are fed into grinding
means 20', just as are the rubber particles product 19 of chiUing means 12 conveyed
into grinding means 20. Whether one or two chilling means and grinding means is
utilized, the nibber particle product of grinding means 20 or 20 and 20' are conveyed
to a drying means 35.
Drying means 35 is primarily provided to raise the temperature of the rubber
particle product of the grinding operation in grinding means 20 to ambient. In a
preferred embodiment, drying means 35 is provided by a rotary dryer provided with
gas entraining means, preferably air, to "wash" the dried rubber particle product. This
"wash" has the effect of agitating rubber particles and fiber, thus separating lighter
density fiber from the rubber particle product by aspiration of the fiber. Again, this
fiber is conveyed to fiber cyclone and baghouse 9.
A final ferrous metal and fourth fiber removing means 50 for removing ferrous
metal and fiber, downstream of drying means 35, is provided. Ferrous metal removal
means 50, which receives the dried rubber particle product of drying means 35, is
disposed immediately downstream of drying means 35. In a preferred embodiment,
ferrous metal removal means 50 is in the form of a rare earth drum magnet.
In this processing step the dried rubber particles are preferably separated from
ferrous metal particles while on a vibratory screen whereat metal particles are drawn
to the drum magnet and removed. At the same time, the vibrating action of the screen
results in density separation of lightar density fiber from higher density particles. Tliis
separated fiber is removed to the fiber cyclone and baghouse 9.
Yet another fiber separation occurs immediately downstream of the above fiber
removal step. This processing step is provided by fiftli fiber removal means 60. Fiber
removal means 60, in a preferred embodiment, involves conveyance of the ferrous
metal-free rubber particles to a centrifiigal separator wherein fiber, present in the
rubber particle stream, is removed and fransferred to the fiber cyclone and baghouse 9.
The centrifugal separator is of the same design and operates in like fashion to the
centrifugal separator of the third fiber removal means 32.
The above description emphasizes the many times that the process and
apparatus of the present invention of making crumb and powder rubber includes fiber
removal from the rubber particle product stream. Those skilled in the art appreciate
that the present invention assigns criticality to fiber removal in the successfiil
manufacture of rubber products, especially tires. Thus, consistent with this
philosophy, the final steps in the process and apparatus of the present invention, which
are screening processing steps, also involve fiber removal.
The first final sca-eening operation is to transfer the rubber particles product
exiting fiber separation means 60 to a two-deck screening means 65. Two-deck
screening means 65 includes a screener to eliminate particles whose size is too large to
meet the requirement of the crumb and/or powder rubber purchaser. Typically,
particles that do not pass through a U.S. sieve size No. 40 screen are too large to be
effective as crumb rubber. Thus, in a preferred embodiment, the screener is a U.S.
sieve size No. 40. Particles that do not pass through this screen are recycled back into
storage bin 10 for reprocessing.
Rubber particles passing through the U.S. sieve size No. 40 screen are
transferred to a final three-deck screening means 70. Indeed, in a preferred
embodiment, two such screening means are provided. This is illustrated in the
drawings by a second three-deck screening means 70'.
The three-deck screening means 70 permits separation of particle sizes within
the accepted size limits that define crumb and powder rubber. This is accomplished
by disposing a courser screener atop a finer screener thus resulting in three different
particle sized products, which are the products of the process and apparatus of the
present invention.
In a preferred embodiment, the top deck product, constituting rubber particles
that do not pass through the top, courser screener is rubber particles of particle size
smaller than U.S. sieve size No. 40 but larger than U.S. sieve size No. 80, which is the
preferred courser size SCTeen employed in the three-deck screening means 70. This
product is conveyed, by means of conduit 71 and, if present, 71', to storage bin 75.
This conveyance to storage bin 75 is accomplished by pneumatic means as are the
conveyance of the other two products discussed below.
The second, intermediate cut of rubber particles produced in three-deck
screening means 70 encompasses particles passing through the courser screener but
too large to pass through the finer screener. In a preferred embodiment the finer
screener is provided by a screen of U.S. sieve size No. 140. Thus, the particles held
by the finer screener are conveyed to storage bin 78 through conduit means 72 and, if
present, 72'. Storage bin 78 holds rubber particles having a particle size range of
particles that pass through U.S. sieve size No. 80 but do not pass through U.S. sieve
size No. 140.
The third rubber particle size product, representative of powder rubber,
encompass rubber particles passing through the finer screener, a U.S. sieve size No.
140 screen. That cut, denoted as "-140" is pneumatically conveyed, by conduit means
73 and, if present, 73' to storage bin 80.
Turning again to fiber removal, fiber is aspirationally removed from each of
the three decks of products and discharged into conduit means leading to the fiber
cyclone and baghouse 40.
It is emphasized that storage bins 75, 78 and 80 may be provided with bagging
and weighing means (not shown) for conveyance to the purchaser or purchasers of
these products.
The embodiments given above are provided to illustrate the scope and spirit of
the present invention. These embodiments will make apparent, to those skilled in the
art, other embodiments and examples. These other embodiments and examples are
within the contemplation of the present invention. Therefore, the present invention
should be limited only by the appended claims.
WE CLAIM;
1. A process of making crumb and powder rubber comprising;
(a) granulating an initial charge of used rubber particles after removal of any
tramp metal;
(b) removing ferrous metal from said granulated rubber particles produced in
step (a);
(c) concurrently screening and removing fiber from said granulated rubber
particles produced in step (b);
(d) chilling said screened granulated rik>ber particles having a predetermined
particle size range produced in step (c) with a stream of a cryogenic
liquid spray and a stream of cryogenic gas flowing concurrently with the
screened granulated rubber particles wherein the final chilled tempera-
ture of the particles is controlled and the ferrous metal and fiber are
removed from the screened granulated rubber particles subsequent to
step (c) but prior to step (d);
(e) grinding said stream of chilled rubber particles by varying impact speed
wherein said particle size distribution of satd ground rubber particles is
controlled; and
(0 screening said ground rubber particles into desired crumb and/or
powder rubber particle size ranges.
2. A process as ciaimed in ciaim 1 wherein said used rubber particles are
particles of used vehicle tires.
3. A process as claimed in claim 1 wherein said fiber removing steps comprise
agitating said rubber particle and aspirating lower density fiber from higher
density rubber particles.
4. A process as claimed in claim 1 wherein said control of particle size
temperature in step (e) irKludes control of duration of contact of said rubber
particles with said cryogenic fluid.
5. A process as claimed in claim 4 wherein said control of rubber particle size
temperature includes volumetric flow rate control of said cryogenic fluid
contacting said rubber particles.
6. A process as claimed in claim X wherein said control of particle size
distribution further comprises varying the space between said impact surface and
a rebound surface.
7. A process as claimed in claim 5 wherein said cryogenic fluid is liquid
nitrogen.
8. A process as claimed in claim 1 wherein said ground stream of cryogenically
cooled rubber particles after said step (f) are dried to ambient temperature.
9. A process as claimed in claim 2 wherein said ground stream of cryogenicaiiy
cooled rubber particles after said step (0 are dried and fibers present in said
ground stream are removed.
10. A process as claimed in claim 9 wherein ferrous metal and fibers in said
dried stream of rubber particles are removed.
11. A process as claimed in claim 10 wherein said rubber particle stream from
which ferrous metal and fiber are removed is screened to remove rubber
particles whose particle size exceeds the maximum particle size of crumb rubber
and wherein more fiber is removed.
12. A process as claimed in claim 11 wherein said particles from which excess
sized particles are removed is screened into three rubber particle sizes within the
particle size rar^ge of crumb and powder rubber.
13. A process as claimed in claim 12 wherein said rubber particles include a
first particle size range of particles passing tlwough 420 vm (U.S. sieve size No.
40) but not passing through 177 ^ (U.S. sieve size No. 80); a second particle
size in the range of between particles passing through 177 ^ (U.S. sieve size
No. 80) but not passing through 105 pm (U.S.sieve size No. 140); and a third
particle size of particles passing through 105 mhi (U.S. sieve size No. 140).
14. An apparatus for making crumb and powder rubber comprising:
granulating means (3) for granulating an initial charge of used rubber
particles ;
ferrous metal removing means (4) provided with means for fiber removal
for removing ferrous metal and fiber fi-om said granulated rubber particles;
primary screening means (6) provided with fiber removal means for
screening said granulated rubber particles;
chilling means (12) for cooling said screened rubber particles having a
predetermined particle size range provided with means for introducing said used
rubber particles^ a acryogenic liquid spray and a cryogenic gaseous stream
whereby said rubber particles are cooled to a predetermined temperature,
wherein said ferrous metal removing means (4) and said fiber removal means
are disposed upstream of said chilling means (12);
grinding means (20) for grinding said cooled rubber particles at said
predetermined temperature to a predetermined particle size range; and
screening means for separating said ground rubber particles into desired crumb
and/or powder rubber particle size ranges.
iS. An apparatus as ciaimed in claim 14 wherein said chilling means (12) is
suitable for chilling used vehicle tire particles.
16. An apparatus as claimed in claim 14 comprising metal detection means (2)
for removing tramp metal present in said initial chwge of used rubber particles.
17. An apparatus as claimed in claim 14 comprising secondary granulation
means (7) for graruilation of rubber particles that do not pass through said
primary screening means; and a preprocessed rubber particle hopper (8) for
holding said rubber particles exiting said primary and secondary granulation
means.
18. An apparatus as claimed in claim 17 comprising a second ferrous metai and
fiber removal means (30) for removing ferrous metal and fiber from said
preprocessed rubber particles exiting said preprocessed rubber particles hopper
(8).
19. An apparatus as claimed in claim 18 comprising a third fiber removal means
(32) for removing fiber from said rubber particles exiting said second ferrous
metal and fiber removal means (30).
20. An apparatus as claimed in claim 19 comprising a fiber cyclone and
baghouse (9) for storage of said removed fiber removed by ail said fiber removal
means.
21. An apparatus as claimed in claim 14 comprising a praprocessed supersack
feeding hopper (11) for introduction of used rubber particles preprocessed to
screen out particles larger than sizes within the range of crumb and powder
rubber and from which ferrous metal and fiber have been removed; a second
ferrous metal and fiber removal means (30) for removal of ferrous metal and
fiber from said preprocessed used rubber particles fed fi-om said supersack
feeding hopper (11); and a third fiber removal means (32) for removal of fibers
from said rubber particles exiting said second ferrous metal and fiber removal
means.
22. An apparatus as claimed in claim 21 comprising a storage bin with
metering discharge (10) for storage of said rubber particles exiting said third
fiber removal means (32) suitable for feeding said preprocessed used rubber
particles into said cooling means (12).
23. An apparatus as claimed in claim 14 wherein said cooling means (12)
comprises a cylindrical shaped vessel (13) provided with means for controlled
introduction of a cryogenic fluid and for time controlled contact of said
preprocessed stream of used rubber particles with said cryogenic fluid.
24. An apparatus as claimed in claim 23 wherein said time controlled contact is
provided by variable speed auger (15), disposed in said cylindrical shaped vessel
(13) suitable for disposing said rubber particles thereon.
25. An apparatus as claimed in claim 14 wherein a grinding means (20)
comprises means for introduction of said cooled preprocessed rubber particle
sfream (19) between a controlled speed impact surface (24) and an outer
inverted surface (22).
26. An apparatus as claimed in claim 25 wherein said conb-olled speed impact
surface (24) Is an Impact surface provided with a plurality of replaceable knives
(25) and said outer inverted cone surface (22) has an interior surface (23),
suitable for being in contact with said preprocessed stream of rubber particles
(19), comprising a serrated surface.
27. An apparatus as claimed in claim 26 wherein said outer inverted cone surface
(22) is movable in a vertical direction wherein volume between said impact
surface (24) and serrated surface of outer invented cone surface (23) is
increased or decreased.
28 An apparatus as claimed in claim 14 including drying means (30) for drying
said ground stream of cryogenically cooled rubber particles to ambient
temperature.
29. An apparatus as claimed in claim 28 wherein said drying means (30) is a
rotary dryer provided with a gas entraining stream to separate lower density
fiber from higher density rubber particles.
30. An apparatus as claimed in claim 24 wherein a means for feeding liquid
nitrogen suitable as cryogenic fluid is provided and said cooling means (12) is
provided with conduit means for recycle pf vaporized nitrogen gas resulting from
cooling of said rubber particles suitable fjsr flowing concurrently into said cooling
means with said preprocessed rubber particle stream.
31. An apparatus as claimed in claim 27 comprising a final ferrous metal and
fourth fiber removal means (50) disposed downstream of said drying means for
removal of ferrous metal (35) and fiber fi'i|>m said dried rubber particles.
32. An apparatus as claimed in claim 3DI wherein said final ferrous metal and
fourth fiber removal means (50), disposjed downstream of said drying means,
comprises a magnetic separator disposed under a vibratory pan screen suitable
for removing said ferrous metal below s^id screen and for removing said fibers
above said screen.
33. An apparatus as claimed in claim 32| comprising a fifth fiber removal means
(60), disposed downstream of said fmal ferrous metal and fourth fiber removal
means (50), for removal of fiber from $aid rubber particles exiting said final
ferrous metal and fiber removal means (5D).
34. An apparatus as claimed in claim 33!Wherein said fifth fiber removal means
(60) comprises a centrifugal screener suitlable for removing light fiber to a fiber
cyclone and baghouse (40).
35. An apparatus as claimed in claim 32 comprising a two-deck screening
means (65) disposed downstream of said fifth fiber removal means (60) for
removal of rubber particles having a ^ize in excess of the size range of crumb
and powder rubber.
36. An apparatus as claimed in claim 35 wherein a means for recycling said
oversized particles to a storage bin (10^ is provided with metering discharge, said
storage bin (10) being in downstream communication with said cooling means
(12); and a three-deck screening means (70) is provided to which said particles
passing through said two-deck screenir^g means (65) are conveyed.
37. An apparatus as claimed in clai|n 36 wherein said three-deck screening
means (70) comprises a top 177 pm (U.S. sieve size No. 80) screen holding
particles passing through a 420 ^ (UiS. sieve size No. 40) screen, said particles
held on said top screen provided with means for transfer to a 420 to 177^
(U.S. sieve No. 40 to No. 80) rubber crumb rubber particles storage bin (75);
and a bottom 105 yon (U.S. sieve size fjlo. 140) screen, said particles held on said
bottom screen provided with means for b-ansfer to a 177 to 105 ^ (U.S. sieve
size No. 80 to No. 140) storage bin (78);said particles passing through said
bottom screen provided with means for transfer to a powder rubber storage bin
(80) holding particles finer than 105 ^ (U.S. sieve size No. 140).
38. An apparatus as claimed in claim 37 wherein pneumatic means are
provided suitable for conveyance into said storage bins (75; 78; 80).

A process of making crumb and powder rubber comprising: (a) granulating
an initial charge of used rubber particles after removal of any tramp metal; (b)
removing ferrous metal from said granulated rubber particles produced in step
(a); (c) concurrently screening and removing fiber from said granulated rubber
particles produced in step (b); (d) chilling said screened granulated rubber
particles having a predetermined particle size range produced in step (c) with a
stream of a cryogenic liquid spray and a stream of a cryogenic gas flowing
concurrently with the screened granulated rubber particles wherein the final
chilled temperature of the particles is controlled and the ferrous metal and fiber
are removed from the screened granulated rubber particles subsequent to step
(c) but prior to step (d); (e) grinding said stream of chilled rubber particles by
varying impact speed wherein said particle size distribution of said ground rubber
particles is controlled; and (f) screening said ground rubber particles into desired
crumb and/or powder rubber particle size ranges.

PROCESS AND APPARATUS FOR MANUFACTURING CRUMB AND POWDER RUBBER

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PCT Conventions: