US3739485A - Apparatus for drying rubber crumb and the like - Google Patents

Abstract

A polyolefin or rubber crumb is fed into the first of plural serially arranged drying compartments having separating partitions and having restricted flow communication beneath the partitions so that gradual downstream compartment-to-compartment product flow will exist. The compartments have opposing inclined side walls for the formation of downwardly tapering product beds in the several compartments and each has a perforated bottom wall through which upwardly flowing drying gas is directed and diffused into the beds to fluidize the beds and sweep over the total surfaces of the rubber crumbs to effectively dry the product increasingly in the downstream direction. Gas and fines are continuously drawn off at the tops of the compartments and the dried product is discharged from the final downstream compartment for weighing and baling. The system contains a builtin fire extinguishing system. An automatic control system is provided.

Description

United States Patent 1 [111 3,739,485 Tailor June 19, 1973 APPARATUS FOR DRYING RUBBER CRUMB AND THE LIKE [76] Inventor: John P. Tailor, Box 587, Davenport,

Iowa 52805 [22] Filed: Dec. 3, 1968 [21] Appl. No.: 780,734

[52] US. Cl 34/57 A [51] Int. Cl. F26b 3/08 [58] Field of Search 34/10, 57 A, 57 T,

[56] References Cited UNITED STATES PATENTS 3,525,162 8/1970 Brewer et al. 34/10 2,085,842 7/1937 Wentworth 34/10 2,513,369 7/1950 Shaw 34/10 2,529,366 11/1950 Bauer 263/21 A 2,824,723 2/1958 Turney et a1... 34/57 T X 2,837,467 6/1958 McClure 34/10 X 3,241,246 3/1966 Pollock 34/10 3,349,499 10/1967 Katano 34/10 3,360,867 1/1968 Sanderson... 34/10 3,391,913 7/1968 Jones 263/21 A Primary Examiner-William F. OlDea Assistant Examiner-William C. Anderson Att0rneyWynne and Finken [57] ABSTRACT A polyolefin or rubber crumb is fed into the first of plural serially arranged drying compartments having separating partitions and having restricted flow communication beneath the partitions so that gradual down stream compartment-to-compartment product flow will exist. The compartments have opposing inclined side walls for the formation of downwardly tapering product beds in the several compartments and each has a perforated bottom wall through which upwardly flowing drying gas is directed and diffused into the beds to fluidize the beds and sweep over the total surfaces of the rubber crumbs to effectively dry the product increasingly in the downstream direction. Gas and fines are continuously drawn off at the tops of the compartments and the dried product is discharged from the final downstream compartment for weighing and baling. The system contains a built-in fire extinguishing system. An automatic control system is provided.

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sum u or 6 INVENTOR JOHN P. TAILOR ATTORNEY! PATENIEB JUR! 1 91m SHEH 5 BF 6 FIGS INVENTOR JOHN P. TAILOR WW 4 "Klgwk FIG? ATTORNEYS PATENIE JUN 1 9 I975 SHEETBUFG glomerates and the material also tends to stick and accumulate on metal surfaces. The rubber crumb has a moisture content of about 30 percent by weight as it enters the drier. Other products and even rubber crumb may have higher moisture contents of to about 60 percent. Preferably the rubber crumb enters the drier at 400 F. and beds are maintained at depths varying from 2 to 8 feet; this facilitates surging through the compartments.

One known prior art system for drying rubber crumb involves the use of trays which are conveyed back and forth through a long drying building. Frequent conveyor break-down is experienced and equipment down time for maintenance is very significant.

Some of the problems of drying wet rubber crumb are set forth in U.S. Pat. No. 3,241,246 to Pollock, among others, and this patent is incorporated herein by reference. The prior art difficulties and deficiencies are overcome by the present invention method and apparatus through a drying process which, for example, eliminates the need for dusting additives in the rubber crumb as discussed in the Pollock patent. The tendency for the rubber crumb to adhere to surfaces and to clump or agglomerate is also successfully dealt with without any mechanical moving parts in the critical heating zone (the rubber crumb flow path) where equipment is most likely to fail and require frequent and expensive maintenance. In the invention, moving parts are located remote from the heating or drying zone in the auxiliary delivery and discharge systems.

The instant four bed drying system is capable of receiving rubber crumb having a moisture content of 30 percent by weight and discharging the dried crumbs from the downstream compartment and bed at 0.5 percent or less of moisture by weight. The invention system is capable of discharging rubber crumb with 0.2 percent moisture by weight in commercial operations.

A feature of the invention resides in the formation in each of the drying compartments of distinct rubber crumb beds having opposing uniformly tapered sides above the perforated plate which defines the bottoms of the beds. The tapered sides converge downwardly at an angle from the vertical of about 12 degrees and preferably in the range of about 5-30 degrees in accordance with the product characteristics. The perforations of the bottom plate are preferably graduated in a predetermined manner so that a single hot gas drying and fluidizing system may be employed with a minimum of valving to satisfy flow requirements.

Other features and advantages will be understood more fully as the specification proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system flow and instrumentation diagram; FIG. 2 is a fragmentary side elevational view,

partly in section of main apparatus components in- FIG. 2;

FIG. 4 is an end elevational view of the same apparatus, partly in section;

FIG. 5 is an enlarged transverse vertical section through the drying chamber means;

FIG. 6 is a horizontal section taken on line 6-6 of FIG. 5;

FIG. 7 and FIG. 8 are views of the product inlet means showing the development of a gas blanket within the inlet preventing the product from adhering to side walls; and

FIGS. 9, l0 and 11 are views of the dried product outlet gate means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail, wherein like numerals designate like parts, and referring first to FIG. 1 which illustrates diagrammatically the entire system, the rubber crumb product before processing may enter the system from a shaker screen 20, delivering it to a washer tank 21 having a filter 22, the washed product then being delivered to a centrifuge 23 having an outlet feeder 24 generally of the type shown in U.S. Pat. No. 3,151,784 to Tailor. The product is then delivered to the main drier unit or chamber 25 through a suitable hose 26. The delivery capacity of the system may average 20,000 pounds per hour of crumb with 8,570 pounds per hour of water.

The product enters the first or upstream drying compartment 27 of chamber 25 which contains three addi tional serially downstream drying compartments 28, 29 and 30, each having a perforated horizontal bottom wall or grid 31 whose perforations may he graduated in each compartment in a predetermined pattern to allow the desired drying air flow gradient and diffusion with a minimum of valving. A divided hot air plenum 32 is formed below the perforated plate 31, including an imperforate bottom wall 33, closed side and end walls and divider plates 34, as shown more fully in FIGS. 2, 4, 5 and 6.

As shown in these figures, the heating or drier chamber 25 is rectangular in horizontal cross section and the two side walls 35 and 36 thereof are inclined to the vertical and converge downwardly to the horizontal perforated plate 31, which establishes: the bottom of each drying compartment 27 through 30. Vertical imperfo rate partition walls 37 or dividers separate the four drying compartments between the upstream and downstream end walls of the chamber 25 and the lower edges 38 of these partition walls are spaced approximately 2 inches above the perforated plate 31 to allow continuous but restricted and gradual downstream feeding of the rubber crumb from compartment 27 through compartments 28 and 29 to compartment 30 under the pressure of the product fluid heads which are developed in the several compartments. The side walls 35 and 36 are preferably angled at about 12 degrees to the vertical or within the range of 5-30 degrees approximately. With this arrangement, the rubber crumb bed developed in each drying compartment will be fully tapered between the walls 35 and 36 for several feet 5 feet for rubber crumb above the perforated plate 31 and the other sides of each bed will be defined by the partition walls 37 and/or the chamber end walls which are vertical or untapered. The tapering of the beds of rubber crumb during drying is a critical aspect of the invention and is essential to the required fluidizing action within the drying compartments under influence of the forced drying gas (air or the like) passing upwardly through the perforated plate 31. In effect, during drying, the rubber crumbs boil and become fluidized, substantially in suspension in the hot drying gas stream and clumping, adhering 01' agglomerating is successfully eliminated while uniform and complete drying is accomplished. The total surface areas of the crumbs are swept by the hot gas.

The drying chamber 25 has its lower plenum 32 sup plied with drying air in the following manner. A suitable direct combustion heater 39 receives natural gas from a convenient source through a conventional flow regulated line 40 and also receives regulated combustion air through another line 41 and quench air through a line 42. Hot air produced by the combustion heater 39 passes through a duct 43 which is shown physically in FIGS. 2, 3 and 4 leading from the combustion heater 39. A filter house 44 and blower 45 deliver the aforementioned combustion and quench air to the heater 39 and a cool air duct 46 is also fed air by the blower means 45 and is adapted, when required, to feed into the four lateral branches 47 of the hot air duct 43, which connect directly into the plenum chamber 32 beneath the perforated plate 31. Short connecting branches 48 are provided between the coil air duct 46 and the upper sides of hot air branch ducts 47, as best shownin FIG. 4. Suitable valving 49, FIG. 1, controls the admission of cooling air from the duct 46 into the hot air branch ducts 47, as required to maintain the desired temperature in the drying chamber 25. Conventional temperature recorder control means are utilized in the system to maintain the correct air temperature entering the plenum 32.

The drying chamber 25 is provided at its top with a hood 50 having explosion blow-out doors 51 for safety. Viewing ports 52 are provided for an observer on the elevated walkway 53 for inspection of the drying operation in the compartments.

A transition duct 54 leads from the top of hood 50 to an elbow 55 and duct 56 connecting with a cyclone apparatus 57 having a center flow fan 58 and exhaust stack 59 and a lower cone 60. Air and fines are constantly drawn upwardly through the compartments 27 through 30 and pass through the elements 54, 55 and 56 to the cyclone apparatus and ultimately, as will be described, these fines are delivered back into the dried rubber crumb product at the downstream outlet end of the system. The bottom outlet of the cyclone apparatus 57 shown at 61, FIG. 1, may also be of the rotary feed type shown in U.S. Pat. No. 3,151,784, to Tailor, previously noted.

When the rubber crumb has passed through the successive drying compartments 27, 28, 29 and 30, it will have been effectively dried. without clumping or agglomeration to a moisture content of 0.5 percent or less by weight. The movement of the constantly agitated or boiling tapered beds of crumb rubber in the several compartments to the next downstream compartment is regulated or throttled by the partition walls 37 and the restricted passages between their lower edges 38 and the perforated plate 31. A sufficient pressure head exists in each tapered compartment 27, 28 and 29 to gradually feed the crumb rubber through the 2 inch high passages beneath the lower edges of the partition walls 37 to the next downstream drying compartment, as additional product is continuously introduced in a controlled manner into the upstream compartment 27.

The dried rubber crumb discharges from the last downstream compartment 30 through preferably three discharge gate mechanisms 62 as shown diagrammatically in FIG. 1. With other products, a different number of gate mechanisms may be employed, such as two, or more than three; even with rubber crumb they may vary.

The details of each discharge gate mechanism are shown in FIGS. 9, 10 and 11, showing one typical gate mechanism. The mechanism comprises a power cylinder-piston unit 63 having a depending piston rod 64 connected at 65 with a gusset plate carriage 66 having slots 67 and being backed up by wavy springs 68 within grooves 68' whose force is resisted by pins 69 within the slots 67. Slide plates 70 are disposed on opposite sides of the carriage 66, FIG. 10, and slidably engage an outlet valve plate 71 against which the springs 68 bear so as to be resiliently urged against the two slide plates. The bottom edge of valve plate 71 has a flow discharge notch 72 therein whose profile may be varied to cause the required dry product discharge flow rate. One preferred notch configuration is shown in FIG. 10. The vertically shiftable valve plate 71 cooperates with a fixed gate or blade 73 which constitutes a weir over which the outflowing product passes from the final drying compartment 30. The product discharge flow rate is rendered variable by raising and lowering the valve plate 71 by means of cylinder-piston unit 63. The plural discharge gate mechanisms 62 of the system indicated in FIG. 1 are all constructed and all operate in accordance with the device shown an described in FIGS. 9 through 11.

When the dried rubber crumb discharges through the gate or valve mechanisms 62, it enters hoppers or receptacles 74 after passing through suitable conduits 75. The aforementioned fines from the cyclone apparatus 57 also enter the hoppers 74 by way of conduits 76 and the dry product in the hoppers will consist of rubber crumbs and fines. The hoppers 74 are equipped with the same rotary type outlet control devices 77 previously indicated at 61 and 24. The dry product leaving the hoppers 74 is finally forced through lines 78 by blowers 79 and passes into cyclones 80 and finally into scale hoppers 81 from which the product moves to vbaler means 82 and from such means at the rate of about 10,000 pounds per hour. Temperature recorder,

flow recorder and level recorder controls throughout the system are conventional and conventional instrumentation including pressure measuring devices and valving may be utilized as needed.

The drying system is further equipped with fire protection means including radiant energy means to detect fire in the drying chamber and coacting means to suppress or extinguish such a fire.

The fire protection means comprises infrared fire detecting elements 83, FIG. 1, adjacent to the drying compartments 27, 28, 29 and 30 and having under their control a fire quench line 84 having nozzles 85 located within the portions of the plenum 32 beneath the perforated plate 31 at each compartment 27 through 30. A second perforated plate 86 or grid is mounted in the plenum 32 below the plate 31, the nozzles 85 discharge water between the two perforated plates below the rubber crumb beds on the upper plate. Preferably, the top perforated plate 31 has 4 to 6 percent open air apertured surface while the lower plate 86 has 20 to 40 percent of its area open. The drying air slowly passes up through the lower plate 86 from the ducts 47 and then passes at increased velocity through the plate 31 which has less total aperture area. If fire breaks out, it is detected by the elements 83, and nozzles 85 are activated by conventional controls and water is sprayed into the plenum between the two plates or grids 31 and 86 and is swiftly carried upwardly into the compartments 27 through 30 to form a froth for smothering the fire. Preferably simultaneously water from overhead nozzles 85 is flowed down the inclined walls 35 and 36 of compartments 27 through 30 and the moving rubber crumb scrubs this flowing water into itself thereby preventing explosion and extinguishing the fire. Falling water produced by operation of the fire protection system will settle to the lower grid 86 and will ultimately travel upwardly with the hot drying gas. The water flowing over the walls not only helps to quench the fire but also prevents buckling or distortion of the walls.

FIG. 1 shows the hose 26 blowing the rubber crumb into the top of compartment 27 and this is satisfactory in some operations. Optionally, as detailed in FIGS. 7 and 8, where it is desired to overcome the tendency of the wet rubber crumb from sticking to and building up on the product inlet walls above the drying compartment 27, such inlet walls are louvered or formed as an air directing screen 87 so that a gas blanket coming from air duct 88 will surround and envelope the inflowing product mass 89 and, in effect, keep this mass centered in the inlet passage and out of physical contact substantially with walls to which it would normally ad here. As indicated, this is an optional refinement which will not be employed in all cases.

SUMMARY OF OPERATION The rubber crumb is constantly fed in a controlled manner into the first drying compartment 27 of the four tapered serially arranged compartments 27, 28, 29 and 30. Hot drying gas is continuously fed upwardly from the ducts 47 through the plenum 32 and apertured grids 86 and 31, the latter forming the support for the downwardly tapering beds of rubber crumb in the several drying compartments. The drying air causes the product to move and boil in suspension while drying as previously described to overcome clumping or agglomeration and adherance to compartment walls. The partition walls 37, whose lower edges 3% are spaced from the grid 31, throttle the gradual flow of the increasingly dried product from the bottom of one compartment into the downstream compartment as the drying process continues and as the wet product enters the upstream end of the chamber 25 and discharges continuously from the downstream end through the gate mechanisms 62. The plural gate mechanisms 62 are arranged side by side immediately above the perforated plate 31 or grid.

Continuously and simultaneously, fines, moisture and residue are withdrawn through the hood 50 and overhead ducting to cyclone 57 and the dry fines are then fed back into he dried rubber crumb entering the hoppers 74, as described.

The fire extinguishing system monitors the drying cycle at all times and comes into action as described in detail previously when necessary.

The finally baled product is essentially dry and ready for use or further processing when it leaves the invention system. This system requires much less maintenance and has its moving parts located outside of the high temperature drying zone, which zone is essentially free of all moving mechanisms and this constitutes a major advantage of the invention. The net result is that expensive down time for the system is substantially completely eliminated. During the drying process, the boiling and moving rubber crumbs. in the tapering beds in the compartments 27 through 30 are subjected continuously to the moving stream of hot gas in the interstitial spaces between particles and therefore each particle is swept over its whole surface by hot gas and thoroughly dried.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts and steps may be resorted to, without departing from the spirit of the invention or scope of the subjoined claims.

I claim:

1. Apparatus for treating particulate solids, compris ing in combination:

1. An elongated chamber having a. a horizontal perforate bottom plate for diffusing a fluid medium,

b. side walls slanting outwardly from said bottom plate and wherein said sides walls are at an angle from the vertical within the range of 5 to 30 degrees,

c. substantially vertical upstream and downstream end walls,

d. at least one baffle extending between said side walls for defining discrete compartments for beds of solids, the lowermost portion of said battle being provided with an opening above said bottom plate to throttle downstream flow,

2. means for delivering particulate solids to the top of the upstream compartment; and

3. means for removing particulate solids from the downstream compartment; and

4. including a quench means for cooling each compartment to inhibit or extinguish fires therein including first means for producing a liquid froth at the bottom plate and a second means for producing a flowing liquid barrier wall on the walls of each compartment.

2. Apparatus for drying particulate solids comprising a drying enclosure having serially arranged separate drying compartments, each of said compartments having a perforated bottom plate, said compartments having restricted communication near and above the perforated bottom plates so that fluidized solids can flow gradually downstream from one drying compartment to the next, said compartments each having a pair of opposing downwardly converging inclined side walls whereby fluidized solid beds are built up in the compartments, said beds tapering downwardly from their tops to the perforated bottom plates, means to continuously introduce solids into the top of the first upstream drying compartment, means to continuously discharge dried solids from the final downstream compartment, and means to continuously force hot drying gas upwardly through the perforated bottom plates of the compartments and thereby diffuse said gas as it flows upwardly through said beds and automatic fire protection means within said drying enclosure including fire detectors adjacent said compartments and quenching water discharge means operable to extinguish fire in response to the operation of the detectors, and including 8 3. The apparatus of claim 1, wherein said bottom plates have 4 to 6 percent open area and said bottom grid below said bottom plates have 20 to 40 percent open area.

Claims (7)

1. An elongated chamber having a. a horizontal perforate bottom plate for diffusing a fluid medium, b. side walls slanting outwardly from said bottom plate and wherein said sides walls are at an angle from the vertical within the range of 5 to 30 degrees, c. substantially vertical upstream and downstream end walls, d. at least one baffle extending between said side Walls for defining discrete compartments for beds of solids, the lowermost portion of said baffle being provided with an opening above said bottom plate to throttle downstream flow, 2. means for delivering particulate solids to the top of the upstream compartment; and 3. means for removing particulate solids from the downstream compartment; and 4. including a quench means for cooling each compartment to inhibit or extinguish fires therein including first means for producing a liquid froth at the bottom plate and a second means for producing a flowing liquid barrier wall on the walls of each compartment.

1. Apparatus for treating particulate solids, comprising in combination:

2. means for delivering particulate solids to the top of the upstream compartment; and

2. Apparatus for drying particulate solids comprising a drying enclosure having serially arranged separate drying compartments, each of said compartments having a perforated bottom plate, said compartments having restricted communication near and above the perforated bottom plates so that fluidized solids can flow gradually downstream from one drying compartment to the next, said compartments each having a pair of opposing downwardly converging inclined side walls whereby fluidized solid beds are built up in the compartments, said beds tapering downwardly from their tops to the perforated bottom plates, means to continuously introduce solids into the top of the first upstream drying compartment, means to continuously discharge dried solids from the final downstream compartment, and means to continuously force hot drying gas upwardly through the perforated bottom plates of the compartments and thereby diffuse said gas as it flows upwardly through said beds and automatic fire protection means within said drying enclosure including fire detectors adjacent said compartments and quenching water discharge means operable to extinguish fire in response to the operation of the detectors, and including a bottom grid below said bottom plates and wherein said water discharge means comprises nozzle means between said perforated bottom plates and said grid, and additional nozzle means substantially above said bottom plates to cause water to flow downwardly over said inclined side walls.

3. The apparatus of claim 1, wherein said bottom plates have 4 to 6 percent open area and said bottom grid below said bottom plates have 20 to 40 percent open area.

3. means for removing particulate solids from the downstream compartment; and

4. including a quench means for cooling each compartment to inhibit or extinguish fires therein including first means for producing a liquid froth at the bottom plate and a second means for producing a flowing liquid barrier wall on the walls of each compartment.

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