Patent Application
20090100846
1. Field of the Invention
The present invention is directed to a cryogenic freeze chamber assembly. More specifically, the present invention is directed to a cryogenic freezing chamber assembly which more efficiently chills polymeric particles so that those particles can be effectively comminuted.
2. Background of the Prior Art
Cryogenic freeze chamber assemblies are extensively utilized in the processing of solid materials which have high impact resistance. That is, solids which resist fracture during comminution processes represent a major obstacle to reprocessing of solid materials. The reprocessing of solid materials is an ever more important commercial and environment undertaking. A prime example of such materials is vehicle tires. Tires, principally formed of rubber, are excellent examples of impact resistant solids whose comminution is difficult unless its temperature is reduced below the glass transition point. The removal of used tires is very important to good environmental practice and the comminution product, crumb and powder rubbers, represent valuable commercial products.
Although the utilization of cryogenic freeze chamber assemblies has become more common with the advent of solid comminution processing, present cryogenic freezing chamber assemblies have certain inefficiencies that call for improved design.
A major concern in the design of cryogenic freeze chamber assemblies is to effectively cool impact resistant particles with minimum use of cryogenic fluid. Indeed, the cost of the cryogenic fluid is probably the major variable cost in the process of comminuting solids. Thus, a design which results in significant reduction in the utilization of cryogenic fluid represents a major aim of artisans working in this art.
Another problem associated with cryogenic freeze chamber assemblies known in the art is meeting the requirement of providing adequate structural strength to withstand stress imposed on chamber assemblies due to the effect of thermal expansion and contraction. Obviously, the utilization of very cold temperatures makes this design aspect of prime importance in the successful and continuous operation of such an assembly.
Yet another problem associated with prior art chamber assemblies is the difficulty of identifying blockages in the continuous processing of solid materials. Oftentimes, plugging occurs during that processing. Quick removal of such blockages by rapid identification and elimination of the blockage is essential to successful operation of cryogenic freeze chamber assembles.
Still an additional problem associated with operation of a cryogenic freeze chamber assembly, common to the operation of major processing assembles, is easy assembly and disassembly to permit maintenance and repair. Thus, easier removal and reassembly of internal components of the subassemblies that constitute a cryogenic freeze chamber assembly is another concern in this art.
Cryogenic freeze chamber assembles designs of the prior art are used in association with redundant apparatus to remove foreign particles present in the feedstock stream. This is due not only to the difficulty of removing foreign particles from such assemblies but, also, to be able to remove such foreign particles from the chamber assembly once they are removed from the feedstock stream.
These and other structural advantages are highly desired in the art.
A new cryogenic freeze chamber assembly has now been developed which solves many structural and design problems associated with cryogenic freeze chamber assemblies of the prior art.
The newly developed cryogenic freeze chamber assembly addresses the issue of structural integrity effectuated by thermal expansion and contraction. The chamber assembly is fixed at its center to allow movement toward each end rather than the prior art design of concentrating total expansion and contraction at one end. This fixing of the chamber assembly at its center allows for movement toward each end thus minimizing the interfacial stress between stationery interconnecting flexible joints and the chamber assembly.
Another aspect of the cryogenic freeze chamber assembly of the present invention is improved utilization of cryogenic fluid. Cryogenic fluid is introduced into the freeze chamber assembly in two distinct patterns. The first is a continuous or pulsating spray directed upon the feedstock stream transmitted through the chamber assembly. This spray is controlled as a function of the chamber assembly operating temperature. The second spray is positioned and directed at the multiple and distinct rivulets of falling feedstock particles elevated by rotating agitators. As such, the second of the two cryogenic fluid introductions is limited to specific intervals of time when such introduction effectuates total contact with the total particle surface, maximizing the cooling effect of the cryogenic fluid.
Yet another major problem associated with cryogenic freeze chamber assemblies, overcome by the chamber assembly of the present invention, is the quick resolution of process downtime caused by blockages in the chamber. In order to remove or otherwise address blockages of solid particles moving through the freeze chamber assembly it is critical that the chamber be capable of inspection without interruption caused by disassembly of the Ofm.fal
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ports which permits viewing of the immediate area about the portion of the chamber within view of the port. Since these view-ports are strategically placed throughout the length of the chamber assembly, the total chamber assembly can be viewed during operation. To insure effectiveness, means to prevent fogging, caused by the cryogenic temperature, the view-ports are provided with heating means in communication with the glass viewing area of the view-port. This heating is automatically effectuated when the view-port cover is opened for viewing.
Still another issue associated with prior art cryogenic freeze chamber assemblies, addressed by the improved design of the chamber assembly of the present invention, is ease of assembly and disassembly of components of the overall chamber assembly. The chamber assembly of this invention is designed to permit vertical removal of interior components which simplifies repair and maintenance by vertical replacement of components compared to the horizontal removal of interior components required by freeze chamber assemblies of the prior art.
Yet another advance associated with the present chamber assembly is a self-contained means for removal of foreign materials present in the feedstock. In this advance means are provided for removal of foreign materials from the feedstock at the chamber assembly inlet prior to freezing. This advance is especially important when the feedstocks are obtained from processed tires or other material which contains fugitive ferrous metal. The removal of ferrous metal is important to the reliability and efficiency of not only the freeze chamber assembly but also for the protection of downstream equipment. This is accomplished by the inclusion of magnetic means at the feedstock inlet to attract and remove ferrous metal particles from the feedstock entering the chamber.
In accordance with the present invention cryogenic freezing chamber assembly is provided. The assembly includes an elongated chamber, an inlet means for introducing feedstock therein, an inlet means for introducing a cryogenic fluid into the chamber and fixed mounting means disposed midway between the ends of the elongated chamber assembly.
In accordance with the another embodiment of the present invention the chamber assembly includes an elongated chamber, a cryogenic fluid inlet means, a feedstock inlet means, an outlet means for removing feedstock from the chamber and a plurality of view-ports disposed on the chamber surface wherein the view-ports are provided with heating means to maximize clear viewing.
In yet accordance with another embodiment of the present invention a cryogenic freeze chamber assembly is provided which includes an elongated chamber, a rotating auger disposed in the chamber, an inlet means for introducing feedstock onto the auger, disposed in the chamber, wherein the auger contains, transports and agitates the feedstock particles, cryogenic fluid introductory means responsive to means provided on the rotating auger for introducing cryogenic fluid into the chamber and feedstock outlet means for removal of the feedstock from the chamber.
In still further accordance with the present invention a cryogenic freeze chamber assembly is drawn to an elongated chamber, a feedstock inlet means for introducing feedstock into the chamber, a cryogenic fluid inlet means for introducing cryogenic fluid into the chamber, a feedstock outlet means for removing feedstock below its glass transition temperature from the chamber and a rotating auger, supported by and rotating about end bearing assemblies for transmitting the feedstock from the feedstock inlet means to the feedstock outlet means.
The instant invention may be better understood by reference to the accompanying drawings of which:
a is a sectional view and
A cryogenic freeze chamber assembly 100 incorporates major sub-assemblies which represent embodiments of the present invention. These embodiments will be better understood by the description of their operation.
Feedstock 6 is introduced into the chamber assembly 100 from a feedstock storage silo 62 through an inlet means. The feedstock 6 may be any solid that is insufficiently brittle so that its temperature must be reduced to below its glass transition point in order to insure proper comminutability. Examples of feedstocks within the contemplation of the present invention includes rubbers, plants, soft polymers and the like. Of the feedstocks within the contemplation of the present invention, rubber, such as that provide by chopped vehicle tires, sterols and other plant material are particularly preferred.
The feedstock inlet means of chamber assembly 100 is provided with a slide gate 200 which is utilized when necessary to change feedstocks, make mechanical adjustments or to clear the chamber. Specifically, slide gate 200 is opened when feedstock 6 flow into chamber assembly 100 is desired and closed to stop feedstock 6 flow therein.
In view of the importance of chopped vehicle tires as a potential feedstock, a magnetic bar screen assembly 300 is provided to capture any tramp ferrous metal traveling with feedstock 6 when that feedstock is chopped tires or other feedstock containing fugitive ferrous metal.
A magnetic bar screen assembly 300 is provided with two stationery view-ports 4 which permit internal visual inspection of the presence, if any, of captured ferrous metal. Metal removal is accomplished by closing the slide gate 200, pulling out drawer 3, by means of draw pull handle 2, and manually removing the captured metal contaminates from at least one bar magnet 5 of assembly 300. After removal of the metal contaminates, the drawer 3 is repositioned by holding the drawer 3, by means of handle 2, and repositioning the bar magnet assembly 300 into its position in chamber assembly 100.
Once past the magnetic bar screen assembly 300, the feedstock 6 is introduced, in a controlled manner, into the cryogenic freeze chamber assembly 100 through a variable frequency driven (VFD) rotary valve 400. The feedstock 6 rate of introduction into chamber assembly 100 is a function of feedstock characteristics and downstream process requirements. These characteristics may be considered in the control of the VFD valve 400. VFD valve 400 controls the mass rate of feedstock into the assembly 100 by its rotary speed. It also acts as an air lock to prevent air from leaking into chamber assembly 100. The feedstock exiting VFD valve 400 flows through a flexible bellows 19 into the inner portion of the chamber 100.
It should be appreciated that bellows 19, as well as other bellows, discussed below, are preferably stainless steel. However, other flexible materials, such as those compatible with low temperature operation, may be used. Bellows are utilized in order to eliminate interfacial stress caused by chamber contraction and expansion due to changes in the temperature of the chamber assembly 100 due to the presence or absence of cryogenic fluid. On average, chamber assembly 100 contracts approximately 1 inch upon contact with cryogenic temperature. To minimize this size reduction, chamber assembly 100 is fixed at its center to reduce contraction length at each end to approximately ½ inch. This arrangement permits metered feedstock 6 to discharge through flexible bellows 19 directly into the freezing chamber assembly 100.
Conveyor means are provided in the interior portion of chamber assembly 100. The conveyor means may be in the form of an endless belt, a rotating auger or the like. In a preferred embodiment illustrated in the drawings, conveyor means is provided by a rotating auger 7. The rotating auger 7 is supported by and rotates about two end bearing assemblies. The first of these, the drive end bearing assembly 500, is mounted on the drive end assembly insert 11. The insert 11 also serves as the drive end cap of chamber assembly 100.
The drive end bearing assembly 500 also includes dual bearings 61, two insulator end caps 10 and a pressure plate 9. The end caps 10 are designed to accommodate “O” ring shaft seals 15 and “O” ring chamber seal 59. A VFD rotor (not shown) is coupled to a rotor drive shaft 14 and keyed with motor drive shear pin 13. The motor drive shaft 14 is tapered to assist in the installation alignment of a slotted male coupling 65 which is affixed to auger drive shaft 7. A tapered tip of motor drive shaft 14 is equipped with a drive key 18 which, when engaged with slotted male coupling 65, drives auger driver shaft 7. The male coupling slot accommodates expansion and contraction of the auger drive shaft 7. This arrangement allows for coupling in tight areas without the needs for bolts. A stationery feedstock barrier 8 prohibits feedstock 6 from infiltrating the coupling area 60.
The other end of the auger shaft 7 terminates in a front end bearing assembly 600. Specifically, shaft 7 is attached to a front end auger shaft connector 30 and a front end bearing shaft 28 supported by front end bearing 27 as part of a front end bearing block 26. The front end bearing assembly 600 includes a front end assembly insert 25 provided with two insulated “O” ring support seals 32 which are bolted together with insulator support assembly bolts 34. The entire insert 25 is connected to an insulated auger trough 24 by means of a multiplicity of front end assembly insert bolts 33. The front end bearing assembly 600 includes a front end rotating bearing shaft 28 which is sealed by means of “O” ring seals 29. The insulated chamber constituting the front end bearing assembly 600 is itself sealed by means of an “O” ring 59. The assembly 600 further includes a pull handle 31 to assist in the assembly or disassembly of the auger shaft 7 within the insulated trough 24. Front end leaving shaft 28 is extended a distance “G,” as shown in
The purpose of chamber assembly 100, to reduce temperature of the feedstock 6 to below the glass transition point, is accomplished by spraying the feedstock 6 with a cryogenic fluid. The cryogenic fluid, usually a cryogenic liquid, is chemically inert whose vaporization temperature is cryogenic at atmospheric pressure. Examples of cryogens within the contemplation of the present invention include argon, carbon dioxide, nitrogen and other inert gases. Of these, the most effective, in terms of cryogenic temperature, inertness and low cost, is liquid nitrogen.
Contact between the feedstock 6 and the cryogen is effectuated by means of a multiplicity of cryogen spray head assemblies 700. Each cryogen spray head assembly 700, which is preferably constructed of stainless steel or the like, includes a cryogen feed pipe 36 welded to a tapered plug 37, which fits into a matching tapered threaded plug receiver 39. The tapered plug receiver 39 is welded to a support pipe 40 which, in turn, is welded to the top of the cryogenic freezing chamber assembly 100. The top of the assembly 100 constitutes a plurality of flat trough covers 23.
It is common to encounter feedstock blockages during operation. Even in the absence of blockages and other operational problems, verification of feedstock movement and conditioning is vital in controlling operating parameters in chamber assembly 100. Thus, strategically located heated view-port assemblies 800 are included in chamber assembly 100. These view-port assemblies 800 are welded to the trough covers 23, specifically covers 23a and 23b. As such, they provide visual access, from the top of the assembly 100, to activities occurring in the interior of trough-shaped chamber 24. Each view-port assembly 800 includes a mounting frame 46, holding double-layered heated glass 44 cushioned between a gasket 45, which, in a preferred embodiment, is silicone rubber. Each view-port assembly 800 is protected by an insulated latch cover 43. When the latch cover 43 is opened for viewing, heat is supplied to insure the absence of clouding or frosting. This is accomplished by including a heating element (not shown) in the double glass 44 component of the view-ports assemblies 800. The heating element is activated by a switch turned on by the opening of latch cover 43. The heating element is switched off by the closing of latch cover 43. It is emphasized that the disposition of the view-port assemblies 800 in the figures is illustrative and actual disposition of those view-port assemblies are function of the design and operation of chamber 100.
As stated above, a preferred conveyor means for transporting feedstock 6 through the insulated trough 24 of chamber assembly 100 is a rotating auger. More specifically, an auger agitator assembly 900, preferably employed as the conveyor means in chamber assembly 100, includes an auger drive shaft 7 to which auger blades 47 are attached. The auger blades 47 are uniquely connected, preferably by welding, to serrated agitators 48. The serrated agitators 48, attached to auger blades 47, follow an orbital path as they first intersect and pass through feedstock 6 at the bottom of the trough 24 portion of the chamber assembly 100. Continued auger drive shaft 7 rotation elevates feedstock 6 from its safe angle of repose to a level where it begins to slide off serrated agitator 48. Because the feedstock 6 is discharged from a gear tooth-shaped edge, it flows in rivulets and feedstock 6 is thus easily and effectively sprayed with the cryogenic fluid as it falls free from serrated agitator 48. Spray is directed from the cryogenic spray head assembly 700, from nozzles 41 or 42. Specifically, directional nozzles 41 are employed in spraying feedstock 6 as it moves horizontally along the bottom of the trough 24 as illustrated in
It is emphasized that cryogenic spray is activated only when serrated agitator 48 embedded magnetic 49 triggers a stationery magnetic switch 50 mounted on the side of insulated auger trough 24. Timing between switch activation and cryogenic fluid spray initiation can be varied or turned off entirely depending upon feedstock requirements. It is emphasized that transported feedstock 6 is also subjected to cryogenic fluid contact from spray-head assemblies 700, by means of directional nozzles 41, as it traverses along the bottom of the insulated trough-shaped chamber 24. The directional nozzles 41 also serve to maintain set operational temperature.
To better explain the expansion features of chamber 100 it is again emphasized that a typical cryogenic freezing chamber assembly 100 will contract about 1 inch when exposed to cryogenic temperature, which approximates −346° F. To compensate for this contraction, and thus reduce undue stress on connecting equipment, flexible bellows are used at the inlets and outlets of feedstock flow. To further mitigate temperature-induced stress, chamber assembly 100 includes a fixed mounting at its center so that maximum thermal contraction is approximately ½ inch at each end. Because of differential temperatures, insulated auger trough 64 and auger drive shaft 7 expansions and contractions are not equal and must be compensated. Thus, the front end of auger drive shaft 7 is free to float with thermal expansions within the front end bearing assembly 600. This is illustrated by gap G. That is, rotating shaft 28 can move, due to thermal expansion, by a length G, as illustrated in
Externally, the insulated auger trough 24 is supported on multiple mounts. As illustrated in
Expansion and contraction capability of the chamber assembly 100 is provided by the chamber support assembly 1000 and expansion joint arrangement 1000a. Expansion joint subassembly 1000a is depicted in
The solid particles, entering the chamber assembly 100 through rotary valve feeder assembly 400, are removed as feedstock product 22, below its glass transition temperature, through product discharge 21. Discharge device 21 is again preferably provided by flexible bellows.
The above description and embodiments are given 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.
