|Publication number||US3254881 A|
|Publication date||Jun 7, 1966|
|Filing date||May 25, 1965|
|Priority date||May 25, 1965|
|Also published as||DE1501421A1|
|Publication number||US 3254881 A, US 3254881A, US-A-3254881, US3254881 A, US3254881A|
|Inventors||Glenn O Rusk|
|Original Assignee||Glenn O Rusk|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (12), Classifications (22)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 7, 1966 G. o. RUSK HELICAL RAMP H E A .T EXCHANGER 3 Sheets-Sheet 1 Original Filed Dec. 24, 1963 FIG. I.
June 7, 1966 G. o. RUSK HELIGAL RAMP HEAT EXGHANGER 5 Sheets-Sheet 2 Original Filed Dec. 24, 1963 FIGS.
INVENTOR. GLEN/V a. RUSK United States Patent 3 254 881 HELICAL RAMI HFZAT EXCHANGER Glenn 0. Rusk, 396 Bleecker St., New York, N.Y. 10014 Continuation of application Ser. No. 333,220, Dec. 24, 1963. This application May 25, 1965, Ser. No. 463,457 14 Claims. (Cl. 263-6) This is a continuation of Serial No. 333,220, filed December 24, 1963.
This invention relates to improvements in heat exchanging apparatus and in particular to a hearth furnace of the type used for burning a continuous flow of solid and liquid materials such as sewage sludge and for processing by the application of heat as in ore reduction, calcining, re-activating charcoal, and the like. This invention also contemplates the provision of improved elevators of the pneumatic type used for raising material to be fed for processing in a hearth furnace as well as in other systems.
Conventional furnaces used for the burning or heating of a continuous flow of material, are frequently of the multiple-hearth type or of the horizontal rotary type. The multiple-hearth type furnace is provided with multi-stay annular hearths traversed by slowly moving, toothed rabble arms which sweep the solid material from one hearth surface to the hearth surface immediately below. Heated gases are introduced at the bottom of the furnace and travel upward in a tortuous path from one hearth to another, heating or burning the solid material being processed. High velocity of the hot gases can only be attained at the cascade openings in each hearth, with the result that the major areas of the hearth are covered with stagnate solid material, remote from intimate mixture with the hot gases which are flowing at comparatively low velocity in a deep path across them. Consequently, multiple-hearth furnaces have been found to be inefficient with relation to the amount of material processed by a large installation. Moreover, the need for maintenance of large moving parts, in very high temperature atmos-' phere and in contact with the solid material being proc essed, has proven a problem in some applications of this design.
The horizontal rotary type furnace, a predecessor of the multiple-hearth furnace, has survived for many applications where moving parts would not tolerate the high temperature atmosphere within the furnace or contact therein with the solid material being processed. In that design, material progresses from one end of a, horizontal, or nearly-horizontal, rotating cylindrical furnace to the other, continuously falling as a long, rolling windrow from the rising side of the cylindrical interior, and continuously exposing new surfaces to the sweep of hot gases. In the horizontal rotary furnace the -material is again largely stagnate, being buried and remote from the hot gases;
the investment in hearth is poorly used, as it is operative with material upon it in one quadrant only at all times, and the straight horizontal travel, in one plane of limited width, by the material requires an installation of broad space requirement which is poorly accommodated in a modern industrial or municipal plant.
It is an object of the present invention to provide a hearth furnace capable of performing the functions of a multiple-hearth furnace or of a horizontal rotary furnace, but incorporating greatly improved heat distribution along the entire hearth surface, requiring considerably less power for its operation, and having no close-fitting or externally-driven or stressed mechanical parts operating in the furnace atmosphere or in contact with the material being processed.
Another object of the invention is the provision of a furnace having a long and continuous hearth surface for the burning ofcontinuously fed material, and incorporating gravity-actuated parts for rabbling thematerial along ICC the continuous hearth to an outlet at the bottom of the furnace.
Another object of the invention is to provide novel and improved means for elevating the gravity-actuated parts of the furnace and/ or the material to be treated, the elevating means utilizing the parts as free pistons and operating continuously and rapidly with a minimum of mechanical working parts or without mechanical working parts, and with or without external power input.
Another object of the invention is the provision of a.
furnace having a long and continuous path for the hot gases in intimate contact at high velocity with the material being processed on a long and continuous hearth, such path being unobstructed by enlargements, contractions or sudden changes of direction, and therefore allowing efof the gases tend to scavenge and cast out any solid particles which become gas borne. v
In accordance with the present invention there is provided a furnace having a continuous hearth in the form of a helical ramp extending from the upper end to the bottom thereof, means for feeding material to be processed onto the surface of the ramp at the upper end thereof, and a plurality of heavy balls or other generally spherical objects introduced into the furnace at the upper end of the ramp in such a manner that the balls will roll down the ramp, rabbling the material thereon and gradually carrying the material to the bottom end of the ramp where it is removed in reduced or oxidized form. The furnace also includes elevator means for transporting the balls from the bottom of the furnace back to the upper end of the ramp for continuous and successive travels down the ramp.
Additional objects and advantages of the invention will become apparent during the course of the following specification when taken in connection with the accompanying drawings, in which:
FIG. 1 is a side elevational view, with portions broken away and shown in section, of a helical hearth furnace made in accordance with the present invention, the furnaceincorporating ball recovery, programming and valving mechanism of the mechanical type;
FIG. 2 is a section taken along line 22 of FIG. 1;
FIG. 3 is a section taken along line 3-3 of FIG. 1;
FIG. 4 is a sectional view of the ball-feeding assembly incorporated in the elevator section of the furnace with the mechanism thereof shown partially schematically;
FIG. 5 is a sectional view similar to FIG. 4, but showing a succeeding step in the operation of the ball-feeding assembly;
FIG. 6 is an enlarged sectional view of a portion of the ball-feeding assembly;
FIG. 7 is a side elevational view with portions broken away and shown in section, of a modified form of helical hearth furnace made in accordance with the present in- 'vention, the furnace incorporating an elevator system in which ball recovery, programming, valving and elevating are performed without any internal mechanical working parts.
FIG. 8 is a section taken along line 88 of FIG. 7;
FIG. 9 is an elevational view of one form of ball which may be used in the furnace; and
FIG. 10 is a section taken along line 1010 of FIG. 9.
a circular wall 12 forming a cylindrical shell for the helical ramp 14. The furnace is supported by an open framework 16 formed of angle irons or the like.
The helical ramp 14 is vertically disposed, and extends continuously from the upper end of the furnace 10 to the lower end thereof, winding at its center about a verticallyupstanding pipe 18. The side edges of the ramp 14 extend closely adjacent to the inner surface of the furnace wall 12 or are fixed to it, for instance by anchoring an extension of the ramp periphery between brick in the wall.
At its upper end, the furnace 10 terminates in a flue gas scrubber 20 including a truncated conical section 21, and the ramp 14 has an upper extension portion 14a having a radial slope in the reverse direction. This ramp extension portion 14a decreases in diameter as it approaches the top of section 20, to conform to the conical wall shape of said section.
A plurality of large, heavy balls 22, preferably made of metal or other heat-retaining material, are provided to successively traverse the ramp 14 from top to bottom. These balls may be made in unbroken spherical shape, as shown, or may be made in other desired shapes and forms, as will be presently explained in greater detail.
When the balls are fed through a ball inlet opening 24 at the upper end of the ramp 14, they roll downwardly the entire length of the ramp 14, rabbling the material fed thereon and carrying the material progressively down the ramp. The bottom end of the ramp terminates in a ball collection pipe 26, leading to a ball feeding arrangement 28, which in turn communicates with a pneumatic elevator 30 for lifting the balls up to the inlet opening 24.
Toward the lower end of the ramp 14, the furnace wall 12 has a plurality of inlet openings 32 connected by conduits 34 to the combustion chamber of an external burner (not shown). The burner may provide direct fire to the interior of the furnace, or may provide heated air for indirect firing, depending upon the type of material being treated.
The pneumatic elevator 30 terminates in an energy absorber device consisting of a housing 36 of particular shape, as will be presently described. The energy absorber housing 36 communicates with the interior of the furnace through the wall opening 24 at the upper portion of ramp 14. The opposite end of the housing 36 communicates with a hopper 40 through a short pipe section 42. Material to be processed, for example sewage sludge, may be fed into hopper 40 and enters the furnace interior through the ball inlet opening 24 of the energy absorber housing or through alternate openings described hereinafter. This sewage sludge, having a high liquid content,
flows slowly down the ramp 14 until it is dried by the heated gas travelling up the ramp.
The heated gas introduced from the combustion chamber through the gas inlet openings 32, travels upwardly in an uninterrupted path along the ramp 14 and ramp extension 14a leaving through the open upper end of a chimney 44 leading from the truncated section 21 of flue gas scrubber 20. In the construction shown in FIG. 1, the upper turns of the helical ramp 14 constitute a drying zone while the intermediate turns constitute a heating zone and the lower turns constitute a maximum temperature zone. The sewage sludge fed into the furnace quickly dries as it seeps down along the drying zone of ramp 14, and thus hardens and begins to burn on said ramp. The balls 22 are employed to push and carry the drying or burning material downward along the ramp 14 until it finally reaches an outlet passage 48 at the bottom of the furnace.
As the balls 22 are successively fed to the upper portion of ramp 14 through opening 24, they roll down the ramp and over the material accumulated thereon, stirring, rabbling, separating, pulverizing and breaking up the materials accumulated on the ramp, in the course of their downward travel. At the same time, the balls spread the material, push it downwardly along the ramp 14, through the succeeding drying, heating and maximum temperature zones. Thus, the material is progressively advanced along the ramp 14, first being thoroughly dried, then heated and burned, or brought to an optimum process temperature, or finally subjected to maximum temperature for complete oxidation and decomposition. To insure that the balls 22 follow a varied and random path down the ramp 14, in order to progressively cover the entire surface thereof, the furnace wall 12 is provided with a series of projecting baffles 50 which are engaged by the balls to deflect the downward path of the latter along the helical ramp.
Each baffie 50 presents a vertical concave plane to the up-wind side to act as a fly ash arrester, as will be presently described, and it presents a convex vertical plane to the descending balls 22, with a'sligh t spring reaction to impact. This latter function is as follows. A purpose of this invention is to provide a highly active hearth, with all surfaces stirred by a heavy trafiic of scouring edges, such as the edges of angularly arrayed discs which may constitute each ball 22. The peripheral bafiles 50 work to this end, not only by returning the balls 22 across the hearth at random angles from the periphery, but by diverting rotational velocity of each ball as well as its translatory velocity toward a rotation quite unsympathetic with the new direction of travel and therefore erosive to the path. This repeated diversion of rotational energy of the ball serves also to keep the possibly destructive downward velocity of the ball 22 within acceptable limit-s, and the number of active balls on the first turn of the helical hearth is not greatly different from the number on the bottom turn, considering the gravitytime force which has elapsed in the vertical distance.
The outlet opening 48 for the decomposed material or ash is set within a downwardly concave bottom wall 52 of furnace 10. The bottom end of ramp 14 is formed as an open-screenterminal portion 54 at the area in which the ramp merges with the ball collection pipe 26. This screened or mesh portion 54 is located directly above the concave furnace bottom wall 52. As each ball 22 reaches the lower end of ramp 14, the material which it is pushing or carrying on its surface falls through the open screen 54 to the bottom wall 52 and passes through the outlet opening 48 into a suitable receptacle placed therebeneath. At the bottom end of the ramp 14, at the screened portion 54 thereof, the edge of the ramp is bordered by an auxiliary wall 56 which accelerates the balls 22 by reducing their radius of gyration and which ends at the mouth of the ball collection pipe 26 and guides the balls 22 accurately into said ball collection pipe. This method of recovering the balls 22 from random travel assures their alignment in proper succession and avoids crowding at the ball collection pipe entry. As the material is dried or burned on the hearth surface of the ramp 14, the gases traveling upwardly along the surface of the ramp lift ash, soot and other fine particles. Aided by an induced draft in the chimney 44 these gasborne but comparatively heavy solids are thrown by centrifugal action toward the outer periphery of the gas stream, where some of the solids deposit as a growing coating on the inner surface of the circular wall 12.
' Other of the gas-borne solids are propelled by the combination of wind and gravity forces angularly downward along the circular wall 12 to the intersection of the ramp 14 and the circular wall 12; or they are swept by the gases along the circular wall 12 to the next bafile 50. All of these solids are thus arrested in their travel and subjected to further heat treatment, until the soot is reduced to ash and the ash or other fine particles is returned to the stream of material travelling down the ramp 14.
That material which accumulates as a small deposit along the obtuse angle formed by the intersection of the circular wall 12 and the ramp 14, bounded inwardly by the path of a scouring ball 22 of circumference tangent to the wall 12 and the ramp 14, is usually tolerable; otherwise this form may be made a permanent structural fillet. That material which accumulates in continuous deposits in the concave up-wind side of each baffle is jarred and loosened regularly by the impact of balls 22, after the gas-deposited solids have attained sufficent mass to react to impact and therefore at a time when the solids will tend to fall rather than to rejoin the air stream. Referring to FIG. 1, it may be noted that most materials being treated are in liquid form for at least two turns of the ramp 14, so that ash, soot and scribed require a flue gas scrubber in most cases to meet the requirements of local ordinances, and these are provided as a separate installation, separately supported with respect to the furnace, with breeching inlet and outlet connections in the path of the gases to the induced draft fan. The breeching friction and the inlet and outlet velocity changes are a source of high power requirement on the fan. In this furnace 10, on the other hand, because no internal mechanical working parts such as upper central shaft bearings are required, it is suitable to mount the flue gas scrubber directly upon the circular wall 12 and as an extension thereof.
The central pipe 18 is provided with a plurality of small perforations or nozzles 57 in the vicinity of the ramp extension 14a. Water is fed under pressure to the bottom of pipe 18 and is emitted in the form of a fine spray from the perforations or nozzles 57. This spray collects the particles of material ascending the ramp 14, and flows down the ramp-extension 14a to the point where it merges with a water outlet pipe 58. The water thus drains through the outlet pipe 58 and does not travel down the ramp 14. The ball feeding arrangement 28 includes a ball escapement chamber 60 containing an escapement 62 for individual and successive feeding of the balls 22 stored in the'ball collection pipe 26. The escapement 62 is an inverted cradle, formed by joining two U-shaped bars angularly at the extreme ends of their legs, ball-retaining rods 64 and 66 being the bases of the two U -shapes. The escapement 62 is mounted at its center on two pins 68 which each extend rotatably through the Wall of the escapement chamber 60, and one is affixed to the end of a link 70 located outside of said chamber 60. The link 70 constitutes a portion of a spring loaded operating linkage consisting of link 72 connected at one end to link 70 and at its other end to links 74 and 76. A spring 77 normally urges the linkage in a counterclockwise direction to the position shown in FIG. 1, wherein the escapement rod 64 is in engagement with the first ball 22a of the series of balls in the collection pipe 26, holding said ball against movement through the escapement chamber 60.
The outlet end of the escapement chamber 60 is closed by a check valve in the form of a plate 78 swivelly mounted at its upper end by a hinge 80 at the mouth of escapement chamber 60. A weighted arm 82 connected to said plate 78 at hinge 80 normally biases said plate in a counter-clockwise direction to a closed position in which its lower end engages a flanged shoulder 84 at the outlet end or mouth of escapement chamber 60. The plate 78 thus may turn in a clockwise direction to an open position against the weight of the arm 82, but may not turn further in the opposite direction because of the stop provided by shoulder 84.
The escapement chamber 60 is downwardly inclined and leads into a connecting chamber 86 which is vertically disposed. The upper end of the chamber 86 is closed by the check valve or plate 78, as previously described, and the lower end thereof is normally closed bya triggering check valve in the form of plate 88. The triggering check valve or plate 88 is mounted by a hinge 90 within an enlarged chamber 92. The plate 88 is secured at its hinge 90 to the link 74, and is therefore normally urged by spring 77 in a counterclockwise direction to the closed position shown in FIG. 1, in which its end engages a shoulder 94 at the mouth of chamber 92.
The plate 88 is connected by a spring 96 to an air relief valve in the nature of a cap 98 which is sized to overlie an air outlet opening 100 in the upper wall of chamber 92. The cap 98 is normally held by spring 96 in' an open position spaced above air outlet opening 100, but when the plate 88 is swung downwardly, as shown in FIG. 4, the cap 98 is drawn downwardly over opening 100 and seals said opening against the passage of air therethrough.
The pneumatic elevator 30' comprises a vertical elevator pipe 102 which extends along the outside of furnace 10 and terminates in a bottom section 104 of inverted U- shape. The section 104 communicates with the bottom end of chamber 92. At its central portion, the bottom section 104 is fed by an air Y connection 106 to an air accumulator tank 108 through an air supply valve 110. The accumulator tank 108 is supplied with air under pressure by a motor driven air pump 112, the flow of the air released from the tank 108 being set by a manually adjustable valve 114.
The air supply valve 110 is controlled by a pilot valve 116 to which it is connected by pipe 118. The pilot valve 116 has an operating handle 120 which is connected to the end of link 76, and is normally held by link 76, under tension of spring 77, in the lowered, valve-closure position shown in FIG. 1.
FIG. 1 shows the ball feeding arrangement 28 at a temporary moment of inactivity. The leading ball22a of the line of balls 22 in the ball collection pipe 26 is retained by the escapement 62, while the preceding ball 22b, previously released by the escapement 62, is seated momentarily upon the triggering check valve plate 88, and is about to open said plate 88 and fall into the chamber 92 under the force of its own weight. The next preceding ball 22c is located in the elevator pipe bottom section 104 in alignment with the air Y 106.
FIG. 4 shows the next step in the sequence of operation. The weight of ball 22b has caused said ball to turn plate 88 to its open position against the tension of spring 77, and the ball 22b is about to drop past said plate 88 into the elevator pipe section 104. Downward turning movement of plate 88 has turned link 74 to an upward position, moving the entire linkage upwardly, and simultaneously causing both link 70 and pilot valve handle 120 to turn in a clockwise direction, as indicated by the arrows in FIG. 4. The handle 120 opens pilot valve 116 at the moment the plate 88 reaches its fully open position of FIG. 4, and the pilot valve 116 opens the air supply valve 110, releasing a blast of air from air accumulator tank 108 into the elevator pipe section 104. This blast of air propels the ball 22c at high velocity up through the elevator pipe 102 to the energy absorber housing 36.
Simultaneously, the turning movement of link 70 turns the escapement 62 in a clockwise direction, raising the rod 64 out of engagement with ball 22a to release the latter, and moving rod 66 downwardly into engagement with the next ball 22d of the line of balls to hold the latter against movement. The released ball 22a thus begins to roll through escapement chamber 60 toward check valve plate 78. i
FIG. 5 shows the next step in the sequence which occurs a fraction of a second later. Ball 220 is now well advanced through the elevator pipe 102. Ball 22b has dropped past plate 88 and entered elevator pipe section 104, having almost reached the air Y 106. The downward movement of the ball 22b has not been prevented by back pressure of air emitted from said air Y 106, because in the open position of the plate 88 (shown in FIG. 4), the spring 96 has been tensioned as shown, drawing the cap 98 into a tightly closed air-sealing position over opening 100, and the check-valve plate 78 is in closed position. This forms a closed air pocket in the connected chambers 86 and 92, in which the air pressure is substantially equal to that in the elevator pipe section 104, so that the ball 22a can drop freely. The closed check valve plate 78 also prevents the release of this high air pressure into the escapement chamber 60.
In FIG. 5, the check-valve plate 88, having been released by ball 22b, has turned back upwardly toward its closed position, in turn rotating link 74 in a counterclockwise direction and permitting spring 77 to bias the linkage back toward its position of FIG. 1. This causes the handle 120 to snap shut pilot valve 116, in turn snapping shut air control valve 110. At the same time, link 70 is also turned in a counter-clockwise direction, turning escapement 62 so that its rod 66 moves upwardly out of engagement with ball 22d and rod 64 moves downwardly into the path of the ball 22d in order to engage and hold said ball 2 2d, which has now become the first in the line of balls being fed.
The plate 88 moves to its closed position just before the ball 22a engages and opens the check valve plate 78. In closing, the plate 88 acts as a check valve, preventing back air pressure from entering the connecting chamber 86. At the same time, as the plate 88 closes, the cap 98 is lifted from air outlet opening 100, permiting air to escape through said opening 100' and equalizing the pressure between connecting chamber 86 and escapement chamber 60, so that the ball 22a may open plate 78 and pass therethrough.
Time of moving the plate 88 to its closed position may be controlled in various ways, by counter-weighting, by a dashpot restraining attachment, by an air-driven piston accelerating attachment, or by adjusting the strength of the spring 77. The closing time of the triggering check valve plate 88 is therefore used as a programming source for timing the frequency of arrival of balls 22 at the top of the ramp 14. Manual or automatic adjustment of this rate of feeding the balls 22 is desired in some installations, to vary the rate with varying quantity or quality of the material being processed, for instance. Where the closing time of the plate 88 is rapid, deceleration without destructive impact is brought about by the presence of a volume of air which must escapefrom the diminishing space above the plate 88, and which cushions the impact velocity of the plate 88 while it is escaping by leaking past the edges of the same. Final and complete escape occurs as the plate 88 has become seated and has uncovered the air outlet opening 100.
It may thus be seen that the balls 22 are fed individually and in rapid succession to the pipe section 104 from where they are shot pneumatically up the elevator pipe to the top of ramp 14.
The energy absorber housing-36 comprises a truncated conical shell having an axis inclined downwardly from its outer end of larger diameter to its inner end of smaller diameter. At its inner end, the housing 36 has an end wall 126 arranged angularly to the axis of housing 36, as an inward flange bordering the inner edge of the housing 36 excepting the lower edge, and containing the inverted U-shaped opening 24. The elevator pipe 102 has a bent terminal extension 128 which communicates tangentially with the outer end of the housing 36 through an opening 130. The extension 128 is so arranged that the balls 22 are propelled into the interior of housing 36 in a path normal to the axis of said housing, such that the balls spin rapidly about the inner circumference of housing 36, initially at the outer end of larger diameter and gradually working toward the inner end of smaller diameter. As the balls spin within the housing 36, the reduction in the diameter of the housing tends to constrain the balls to gyrate in orbits remote from the smaller, inner end as long as the balls have substantial momentum velocity, but, on the other hand, the inclined axis of the shell tends to urge the balls toward the lower inner end. Thus, the balls soon lose their initial momentum and in gyrating, work their Way to the inner end of housing 36. Thereafter, so long as the balls have any velocity, the centrifugal force of their revolving movement and the constraint of the end wall 126 cause them to gyrate in small orbits at the inner end of the housing 36 until they have lost their momentum. At such time, the balls roll through the opening 24 onto the ramp 14, rather than dropping thereupon.
Instead of utilizing compressed air as a source of energy for the pneumatic elevator, it may be more efficient to employ steam, or the gaseous products of combustion from a furnace operating under the low pressure needed for the elevator. The latter would have the added ad vantage of maintaining the balls 22 at high temperature, since the balls themselves serve as heat-exchange agents in contacting the material being processed.
A check-valve plate 134 is pivotally mounted between the material inlet pipe 42 and the feed hopper.40, this plate 134 being kept in closed position by a Weighted arm 136 unless the weight of material flowing out-balances the weighted arm. The closed plate prevents the material fed into the hopper 40 and pipe 42 from being blown back out of the hopper by a surge of air passing through the pneumatic elevator, and it seals against the flow of air from the hopper 40 into the furnace 10. Some of the material arriving with the balls 22 through the ball inlet opening 24 tends to build up in inert banks on both sides of the initial path of the balls 22. This condition is tolerable with some processes, as for instance in the burning of sewage sludge where the fire at the end of a days run is allowed to burn upward over the areas and to consume all remnants which have not been properly rabbled. Where stagnation of the material is not tolerable, an alternate material inlet pipe 132 is provided, with a hopper 138 and a check valve plate 144, at a location lower on the ramp 14. Here the 'balls 22 are properly distributed across the ramp 14 in the manner previously described, and no inert material remains. The elevator pipe 102 may also be provided with an alternate material inlet pipe 140 and feed pipe 142, also incorporating a counter-balanced check-valve plate (not shown).
Instead of having unbroken spherical surfaces, as shown, the ball-s 22 may be provided with broken or pocketed outer surfaces, or may be made in open framework form, for example, in the form shown in FIGS. 9 and 10 in which a plurality of discs 38 are angularly arranged relative to each other, with their centers passing through a common axis. Such forms of balls have the advantage of providing more effective rabbling of the material on the ramp, and the balls are able to carry along a large amount of material.
FIG. 7 illustrates an alternate embodiment of a pneumatic ball-elevator system which has the advantage of eliminating the mechanical working parts of the system shown in the previous embodiment. The balls are fed successively by a combination of pneumatic and gravitational forces, which provide comparatively trouble-free operation in lifting very hot balls and balls carrying an accumulation of material to be processed, which balls are incompatible with parts which are subject to rotational, sliding or other mechanical movement.
In FIG. 7, like reference numerals are used for identical parts. The helical ramp 14 terminates at its lower end in a ball collection pipe 162 which continues downwardly on a helical curve, the extent of which is determined by the number of balls required to be stacked in train to counteract the upward force of the source of loW pressure air in the collection pipe, as will be presently described in greater detail.
A ball arrester 160 is mounted near the lower end of the ball collection pipe 162 and comprises a cover plate -164 secured to and forming a portion of the wall of pipe 162, and a. dog 158 movably mounted on said cover plate 164. The dog 158 is flexible and is formed of a plate fixed at its upstream end to the cover plate 164 and curved concavely at its downstream end to match the circumference of the balls 22. The cover plate "164 also mounts a fixed nut 170 through which a manual crank 156 extends threadedly. The end of crank 156 engages an intermediate portion of the dog 158 and is adapted to depress the latter when required.
The ball collection pipe 162 terminates in an ejector 150, which connects pipe 162 to an elevating pipe 170. Said ejector 150 is atthe lowest level of the elevator system and is fed by a source of air or other gas under low pressure through an air distribution pipe manifold 145 and a manually operated air feed shut-off valve 172. The air or gas passes into an annular distribution chamber 146 from which pressure is converted to high velocity along the. path of the balls 22 in the elevating pipe 170 by an annular array of nozzles 148.
The nozzles 148 are thus directed to propel each ball 22 upwardly through the elevating pipe 170 as the ball reaches the mouths of the nozzles 148 at the bottom of the elevator system. At the same time, provision is made to prevent the balls from being propelled backwardly through the system, as will be understood from the subsequent description of operation.
Each of the balls 22 is of a diameter slightly less than the internal diameter of the ball collection pipe 162, so that it forms with said pipe an annular orifice for the passage of air. During operation, a series of balls 22 are normally maintained in stacked condition in the ball collection pipe 162, representing a series of such annular orifice in succession, each of which provide resistance to the passage of air. The sum of such orifice resistances is utilized in maintaining the balls in stacked condition as will be presently described.
FIG. 7 illustrates the furnace in a normal operating condition, with balls 22 falling in random. paths down the ramp 14, then guided with increased velocity by the auxiliary wall- 56 to the entry of the ball collection pipe 162, thence entrained in the ball collection pipe 162 to the air ejector 150 with velocity maintained or increased, and finally lifted by further accelerating influence to the top of the ramp 14. In FIG. 7, the mid-furnace balls are omitted for clarity of illustration.
The falling train of balls 22 in the ball collection pipe 162, following the lead ball 22], are in a close rank because of the air pressure on the leading face of the hall 22 This air pressure is leaking back to the atmosphere at the foot of the ramp 14 through the series of annular orifices existing as clearances between the balls 22 and the interior of the pipe 162. Said air pressure is attenuated by a series of pressure differentials across each ball 22 in the train, the sum of which pressure differentials equals the pressure differential between atmospheric pressure at the foot of the ramp 14 and the pressure on the forward face of the lead ball 22 The pressure differentials thus become progressively smaller from that across the ball 22 through the last ball in the train, and therefore the decelerating effect of said pressure differentials is lesser on each succeeding ball in the train so that each succeeding ball tends to overtake its predecessor.
-This tendency to close the rank until each following ball is in contact with, and slightly accelerating, its predecessor, gradually corrects any irregular flow of balls brought about by normal accidents in their random travel down the ramp 14.
The air or gas pressure in the ball collection pipe 162 tends to drive the balls therein in an upward direction, that is, back toward the ramp 14. This tendency is counteracted by the weight of the stacked balls 22, which ten-d to fall by gravity toward the ejector 150. To insure effective and continued operation, there is constantly maintained in the collection pipe 162 a sufficient number of balls 22 in the stack to insure that their combined weight overcomes the force of air pressure to the extent of causing the constantly-replenished stack to move continually toward the ejector 150. As each lead ball reaches the ejector it is propelled upwardly by the air or gas jet through the elevator pipe to the energy absorber housing 36.
The regular and constantar-rivals of the balls 22 in the position of the ball 22 for acceleration, ensures a regular and substantially unvarying time of rise ofthe balls to the energy absorber, prevents the rise of two or more balls in contact with each other, and delivers balls regularly to the top of the ramp 14 so that coverage of all areas rabbled on the ramp 14 by the balls is substantially constant and therefore most efficient. As the eifect of the constant source of air pressure on the approaching train of balls 22 brings about regularity of performance throughout the furnace system, and since the effect may be adjusted and the rate of operation changed by a change of air pressure at its source, the air shut-off valve 172 which is used for regulating air pressure, is referred to as the programming valve 172. Dependable programming allows selection of minimum requirements for components for the entire system, such as the size of the air pump, the number of balls required, the height and area of the ramp 14, and the size and maximum duty required of the energy absorber 36.
The desired propulsion of the balls 22, by air or any gas introduced to the ball train by the ejector 150 through the nozzles 148, occurs as a result of four distinct effects. First, there is the jet action which imparts to each ball a momentary accelerating impact which increases its velocity, and this impulse is in the downstream direction only. Second, air pressure increases between balls because additional volume of air is added in the chamber shown on FIG. 7 as bounded by the balls 22 and 22g and this volume pressure works to decelerate the upstream balls 22 as leaking air flows to the atmosphere at the foot of the ramp .14 through the series of orifices formed by clearances of the balls 22 within the ball collection pipe 162 as previously described. This volume pressure works to rapidly accelerate the first downstream ball, 22g in FIG. 7, and, by a series of leakages of progressively diminishing flow past each ball 22 downstream, this volume pressure works to support the velocity of each preceding ball with a progressively weaker force over each of the series to the top of the elevating pipe 170. The third effect brought about by introducing air through the nozzles 148 to the chamber between balls 22f and 22g results from the conversion of velocity head to pressure head or velocity pressure of the air as its flow is arrested abruptly by ball 22g, and this velocity pressure is mostly operative downstream only and it is additive to the second propulsion eifect in the matter of sharply accelerating the ball 22g and supporting the velocities of each preceding ball 22 with progressively weaker force over each of the procession to the top of the elevating pipe 170.
The fourth effect of introducing air between balls 22 results from expansion pressure, and occurs since the air is cooler than the very hot balls. The effect occurs after the small amount of very hot gas, swept to the air entry location by the travelling chamber formed by the ball collection pipe 162 and two balls therein moving in mutual contact, is mixed with a comparatively large amount of cool air, and after the direct supply of cool air is cut off from the now greatly enlarged chamber as the .lead ball 22 moves into the position occupied by ball 22g. The turbulent and comparatively cool air, confined by the hot walls of the elevating pipe 170 and the very hot halls 22g and 22h, absorbs heat, expands and increases in pressure rapidly. This expansion continues with little diminution 1 1 throughout the rise of the pair of balls to the top of the elevating pipe 170.
The heat storage capacity of the balls 22 is vastly in excess of that needed for the flow of balls 22 to keep hot the insulated elevating pipe 17 0, and'the mass ratio of the stream of balls 22 to the stream of cool air is so great that only a few degrees of temperature are removed from the balls before they are returned to be re-heated in the furnace 10, so that the temperature gradient for heat transfer from the balls 22 to the air is very high. By this fourth effect of introducing air between balls 22, in which comparatively cool air is heated and expands in each travelling chamber which exists between each pair of balls 22 in the series rising to the top of elevating pipe 170, a large accelerating force is sustained on the leading ball 22 of each such travelling chamber; an equal decelerating force is sustained on the following ball 22 of each such travelling chamber.
The extent of the curve formed by the ball collection pipe 162 is determined by the number of balls 22 required in train at ,all times to establish a sufiicient series of annular orifices, between the balls and the interior Wall of the ball collection pipe 162, to attenuate satisfactorily the leakage of air from a constant source of low pressure air at the bottom of the ball collection pipe 162 to atmospheric pressure at the foot of the ramp 14. The height of said curve is determined by the number of balls required to outweigh the upward force of said constant source of low pressure air at the bottom of the ball collection pipe 162. The ball arrester 160 is normally inoperative, withdrawn from the stream of balls 22 by its normal spring fiexure. It is used to gradually arrest the flow of balls 22 by depressing the dog 158 to interfere with passage of said flow, turns of the crank 156 shaft in the fixed nut 178 effecting this braking action. It is used tohold the train of balls 22 in elevated position to facilitate starting operation after a shut-down of the system. In the depressed position it prevents blow-back of balls during certain nonnormal manipulations of the system.
In summary, the effect of introducing cool air under low pressure to the stream of hot balls 22 through the nozzles 148 is to sharply accelerate each ball in succession by the application of impulse, volume and velocity pressures, said acceleration also providing a succession of chambers for repository of cool air which expands as it is heated by said hot balls 22 and by the hot elevating pipe 170, and as the succession of chambers rises the continued expansion of air in each, minus the leakage flow to the furnace past the downstream balls 22, tends to support each ball in its initial velocity despite the force of gravity. The balls 22 rise, with rather steady but decreasing velocity and with rather even but decreasing vertical separations as measured at different levels, to the top of the elevating pipe 170 where their residual velocity is wasted in the energy absorber 36.
In FIG, 7 there is shown two low pressure air Y connections 152 and 154 which are simple air ejectors, normally inoperative, but upon demand capable of supplying to the train of balls 22 the accelerating forces of air impulse, air volume and air velocity pressures previously described as the function of the more efiicient air ejector 150. In the event of voluntary shut-down of the elevating system, the ball arrester 160 previously described, is used to bring to a halt the train of balls 22 by turning the handle of the crank 156 so that its threaded shaft enters the ball collection pipe 162 through the threaded nut 178 and depresses the dog 158 until it imparts a braking action on the passing train of balls 22. The air ejector 150 continues to operate so that all balls which pass the dog 158 are returned to the top of the ramp 14 and flow down to positions in the top of the train which is being decelerated. This is continued until the train is halted and all balls are in the train, with the lead ball 22 securely held by the dog 158 at an elevated position and all other balls 22 in secure positions behind and above it, ready for normal gravity flow to the air ejector 150 whenever the system is to be started again. If the shutdown is of short duration, the balls 22 remain sufficiently hot to cause the expansion of heated air which supports the normal lifting effects of the ejector 150. If the shutdown is long enough to allow the balls to cool, about twice the quantity of air normally used by the air ejector 150 is required for normal ball circulation velocities. Such increased air volume is supplied by starting a second, standby air pump to deliver air through the air distribution manifold to the air ejector and to the air Ys 152 and 154, and by opening the shut-off valves 174 and 176 to said air Ys. If said stand-by compressor is not available, flow of balls 22 past the ball arrester may be controlled by slightly depressing the dog 158 so that velocity of the train of balls 22 is slowed to below normal velocity and the air ejector 150 is then competent to handle the reduced flow of cold balls, using a normal supply of low pressure air, until all of the balls have been heated by repeated passes down through the hot gases of the furnace 10.
In any vertically disposed hearth furnace such as the furnace of this invention it is necessary to elevate the material to be processed to the top of the furnace, and inclined belt elevators are commonly used, requiring Wide spaces for approach so that the pitch of the elevating belt will support the material. The ball elevating system of this invention may be used for elevating such bulk materials, requiring a minimum of horizontal area, using hot balls 22 which are re-heated and are used for rabbling as in the furnace 1%) of the invention, or using hot balls which are re-heated in a simpler ball-heating furnace similarly disposed for providing them a heated descent, or using cold balls which are recirculated by a downward duct to the elevating system of this invention after they have served as carriers of such bulk material on the elevating side of the cycle.
The material feed inlet Y 130 shown in FIG. 7 is an alternate to feed connections 42, 132 and 140 of FIG. 1, and constitutes a branch on a horizontal run of the ball elevating pipe 170, the branch approaching obliquely to favor the downstream movement of the balls 22 and to provide an oblong connection in the wall of the ball elevating pipe for good distribution of the entering face of material to the maximum number of balls 22 simultaneously. Pressure at the junction is maintained somewhat greater in the feed inlet Y 184) than it is in the ball elevating pipe 170 by the head of the material approaching in the supply pipe 182.
If the material entering the elevator system through feed inlet Y 180 is dry, it is caught and lifted in the pockets or in the ventilated cores of balls 22 variously designed for the purpose, and is lifted in the leakage flow past each ball 22 serving at the same time as a resistance to the leakage, with some saving of air pumping power resulting. Some classes of dry bulk material adheres on contact with the very hot balls 22, forming an exterior layer, whether or not the balls are pocketed. The very hot coated balls descend the ramp 14 as an active fire-ball, with maximum exposure to combustion air and to heat. This constitutes a particular advantage of the hot-ball elevator invention over the commonly used pneumatic type employing no balls. Another advantage is that the heating of the cool gases in contact with the hot elevating pipe 170 on the way to the top of the elevating pipe 170 provides an expansion pressure greatly reducing the amount of air or other gases which must be otherwise supplied to a pneumatic elevating system. A further advantage is that air leakage upward through the material being lifted in a pneumatic elevating duct without balls is much greater than air leakage upward through elevating pipe 170, where the balls 22 rise as pistons with the bulk material tending to seal the clearances between the balls and the interior wall of the ele- 13 vating pipe 170, and consequently the size of air pump required is greatly reduced.
Where wet bulk material is handled by the pneumatic elevator of this invention, the advantages enumerated above are the same but of improved effectiveness in most cases. As an additional unique advantage, the wet bulk material tends to adhere to the very hot balls, and a proper proportioning of the quantity of balls 22 flowing to the amount of wet material flowing yields a drying action completed in the elevating pipe 170, with each ball 22 arriving at the top of the ramp 14 with a major portion of the fed material already heated to its ignition temperature, or higher, and bursting into flame upon contact with the hot combustion air travelling up the ramp 14. The high rate of steam production within the elevating pipe 170 precludes any ignition or combustion of material while the material is being elevated, but on arrival at the top of the ramp 14 the steam vapor is swept upward by the induced draft and the dried material is borne downward on the ball in adhering layers or in pockets, design of the ball 22 being arranged to allow complete combustion of the burden of each ball before said ball completes its random travel down the ramp 14.
Loose material carried up between balls in the ball elevating pipe 170 or released from balls on the ramp 14 travels more slowly, being rabbled down rather than carried down the ramp 14, but the burning of it too benefits fr'om the prior drying and separation of the vapors before starting down the ramp in that the drying and heating zones of said ramp are eliminated and combustion begins at once.
The high temperature attained by the material in the confinement of the elevating pipe 170 in the absence of air yields chemical changes to the material being processed, such as a reducing action which is beneficial in certain industrial processes. Such a treatment in the burning of sewage sludge, prior to exposure in hearth furnaces, overcomes an. objectionable odor problem brought about by volatile gases being released and escaping with water vapor in the drying levels of these furnaces, where heat is not sufiicient to either burn or convert said volatile and objectionable gases.
As in the case of handling dry bulk material, the wet bulk material tends to seal the clearances between the balls 22 and theinterior wall of the ball elevating pipe tery material in contact with very hot balls 22 and in contact with the hot walls of ball elevating pipe 170. This escape of steam is also the only propellant required for lifting the balls 22 after the pneumatic equipment has operated at start-up of the 'furnace system and a proper balance of material flow and the flow of the balls 22 has been established,'so that the costs of air pump operating may be eliminated excepting for start-up service.
Once the train of balls 22 is heated, any water evaporated between any pair of balls in the series rising in the ball elevating pipe 170 will impart an accelerating force to the lead ball 22 of the chamber formed between them, and it will impart a decelerating force to the following ball 22. But the following ball 22 is supported in its velocity by a succession of chambers of expanding gas and by a long train of balls 22 of great mass, and continuous to a height sufficient to over-weigh any expansion pressure exerted'by the steam. The leading ball of the expanding chamber on the other hand, is loaded by only a few balls rising above it, each supported by a chamber which is attempting to expand due to the formation of steam from wet material within it, so that the weight of these few balls plus the weight of the wet bulk material and the steam being elevated is all that opposes the steam expansion in the bottom chamber between balls 22, where wet material is being introduced by the feed inlet Y 180, and the leading ball of that chamber is accelerated and lifts vthe entire load above it.
The elevator system of this invention operates by the action of a system of free pistons which are in themselves useful as gravity operated parts when placed in an elevated position. These free pistons may be used to elevate bulk material, and these free pistons when repeatedly heated contribute in that heat to the source of power needed to elevate themselves and certain wet bulk material.
While preferred embodimentsof the invention have been shown and described herein, it is obvious that numerous omissions, changes and additions can be made therein without departing from the spirit and scope of the invention.
What I claim is:
'1. A material distributing system comprising a vertically-disposed helical ramp, a plurality of balls capable of traversing said ramp, a ball collection conduit at the bottom of said ramp, elevator means for raising said balls vertically to an elevated position from which they are fed to the top of said ramp, means for feeding flow-type material to the lower end of said elevator means, whereby said balls collect said material and carry it to said elevated position, the balls then descending said ramp to collect further of said material.
2. A heat exchange assembly comprising a housing having an interior surface of circular cross-section, a helical ramp disposed within the housing and extending vertically and continuously'from the upper end thereof to the lower end thereof, means for feeding material to be treated continuously to said ramp, a plurality of balls capable of rolling down said ramp, means for feeding said balls continuously to the upper end of said ramp, a ball collecting conduit communicating with the bottom end of said ramp, and elevator means connected to said ball collecting conduit for lifting said balls continuously and successively to said ball feeding means, whereby said balls are caused repeatedly to traverse the ramp, rabbling the material thereon, and carrying said material toward the bottom of the ramp.
3. A hearth furnace comprising a housing, having an interior surface of circular cross-section, a helical ramp disposed within the housing and extending vertically and continuously from the upper end thereof to the lower end thereof, an inlet for material to be treated communicating with the upper end of said ramp for feeding said material onto the upperportion of said ramp, 'a plurality of balls capable of rolling down said ramp, means for feeding said balls continuously to the upper end of said ramp, a ball collecting conduit communicating with the bottom end of said ramp, and elevator means connected to said ball collecting conduit for lifting said balls continuously and successively to said ball feeding means, whereby said balls are caused repeatedly to traverse the ramp, rabbling the 1 material thereon, and carrying said material toward the a the bottom of the ramp.
4. A hearth furnace comprising a housing, having an interior surface of circular cross-section, a helical ramp disposed within the housing and extending vertically and continuously from the upper end thereof to the lower end thereof, an inlet for material to be treated communicating with the upper end of said ramp for feeding said material onto the upper portion of said ramp, a plurality of balls capable of rolling down said ramp, means for feeding said balls continuously to the upper end of said ramp, a ball collecting conduit communicating with the bottom end of said ramp, elevator means connected to said ball collecting conduit for lifting said balls continuously and successively to said ball feeding means, whereby said balls are caused repeatedly to traverse the ramp, rabbling the material thereon, said balls being sized and shaped to pick up and carry said material progressively from the upper end of the ramp to the lower end thereof, and heat supply 1 means communicating with the lower end of said furnace housing for supplying suificient heat flowing upwardly along said ramp to burn the material thereon as said material is progressively carried to the bottom of said ramp under action of said balls.
5. A hearth furnace according to claim 4 in which said balls have non-continuous outer surfaces forming pockets for receiving and carrying said material.
6. A hearth furnace according to claim 5 in which said balls are formed by a plurality of discs intersecting at their centers.
7. A hearth furnace comprising a cylindrical housing, a helical ramp disposed within said housing and extending vertically and continuously from the upper end thereof to the lower end thereof, the diameter of said ramp being substantially equal to the inner diameter of said housing, a plurality of balls each having a diameter less than half the diameter of said ramp, means for feeding said balls successively and repeatedly to the top of said ramp, said ball feeding means comprising a ball collection conduit communicating with the bottom of said ramp and a pneumatic elevator communicating with the ball collection conduit and extending to the top of said ramp, and means for feeding material to be treated to the top of said ramp for collection thereon.
8. A hearth furnace comprising a cylindrical housing, a helical ramp disposed within said housing and extending vertically and continuously from the upper end thereof to the lower end thereof, the diameter of said ramp being substantially equal to the inner diameter of said housing, a plurality of'balls each having a diameter less than half the diameter of said ramp, means for feeding said balls successively and repeatedly to the top of said ramp, said ball feeding means comprising a ball collection conduit communicating with the bottom of said ramp, a pneumatic elevator communicating with the ball collection conduit and including an elevator pipe extending vertically along the exterior of the furnace housing, and a ball inlet opening at the upper end of said ramp communicating with the top of said elevator pipe, and means for feeding material to be treated to the top of said ramp for collection thereon, said balls rolling from the upper end of said helical ramp to the lower end thereof whereby to rabble the collected material thereon and carry said material progressively to the bottom end of the ramp.
9. A hearth furnace comprising a cylindrical housing, a helical ramp disposed within said housing and extending vertically and continuously from the upper end thereof to the lower end thereof, the diameter of said ramp being substantially equal to the inner diameter of said housing, a plurality of balls each having a diameter less than half the radius of said ramp, means for feeding said balls successively and repeatedly to the top of said ramp, said ball feeding means comprising a ball collection conduit communicating with the bottom of said ramp, a pneumatic elevator communicating with the ball collection conduit and including an elevator pipe extending vertically along the exterior of the furnace housing, and a ball inlet opening at the upper end of said ramp communicating with the top of said elevator pipe, and means for feeding material to be treated to the top of said ramp for collection thereon, said balls rolling from the upper end of said helical ramp to the lower end thereof whereby to rabble the collected material thereon and carry said material progressively to the bottom end of the ramp, and burner means at the lower end portion of the ramp for supplying heat thereto, whereby the material on said ramp is burned as it progresses down said ramp under action of said balls.
10. A hearth furnace comprising a cylindrical housing, a helical ramp disposed within said housing and extending vertically and continuously from the upper end thereof to the lower end thereof, the diameter of said ramp being substantially equal to the inner diameter of said housing, a plurality of balls each having a diameter less than half the radius of said ramp, means for feeding said balls successively and repeatedly to the top of said ramp, said ball feeding means comprising a ball collection conduit communicating with the bottom of said ramp and extending downwardly therefrom, a pneumatic elevator communicating with the ball collection conduit and including an elevator pipe extending vertically along the exterior of the furnace housing and a gas inlet conduit opening into the lower end of said elevator pipe for supplying gas under pressure thereto, and a ball inlet opening at the upper end of said ramp communicating with the top of said elevator .pipe, and means for feeding material to be treated to the top of said ramp for collection thereon, said balls rolling from the upper end of said helical ramp to the lower end thereof whereby to rabble the collected material thereon and carry said material progressively to the bottom end of the ramp, said balls then entering said ball collection conduit and passing to the gas inlet conduit, whereby the gas under pressure supplied by said conduit li-fts said balls to the top of said elevator pipe.
11. A hearth furnace according to claim 10 in which escapement means are interposed between said ball collection conduit and said pneumatic elevator, said escapement means normally holding a plurality of balls in a train in said ball collection conduit and being operable by movement of a ball into the pneumatic elevator to release the next succeeding ball in said train.
12. A hearth furnace according to claim 10 in which said ball collection conduit is of sufficient length to maintain a plurality of balls in a train therein, said balls being slightly smaller than the cross-sectional area of said ball collection pipe and said elevator pipe whereby to olfer resistance to pressure of gas within said elevator system and to cause the force of said gas pressure to be exerted in a direction to carry said balls upwardly through the elevator pipe.
13. A hearth furnace according to claim 10 in which the furnace housing terminates at its upper end in a stack, and a flue gas scrubber interposed between the upper end of said ramp and said stack, said flue gas scrubber comprising a helical upper extension of said ramp, means for feeding liquid in spray form over said extension, and means for draining said liquid from said extension.
14. A hearth furnace according to claim 10 in which a ball energy absorber is interposed between the top of said elevator pipe and said ramp, said energy absorber comprising a housing having a circular cross-section and a decreasing cross-sectional area, said balls upon leaving said elevator pipe revolving within said energy absorber until their momentum is sufficiently diminished to permit them to roll upon the upper end of said ramp.
References Cited by the Examiner UNITED STATES PATENTS 1,259,241 3/1918 Joachim 263-19 1,614,387 1/1927 Pereda 263-49 2,805,841 9/1957 Kyle 34164X 2,983,051 5/1961 Zimmerman et a1. 34-164 FREDERICK L. MATTESON, In, Primary Examiner.
JOHN J. CAMBY, Assistant Examiner.
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|U.S. Classification||432/51, 34/165, 432/215, 432/98, 432/67, 432/197, 193/12, 165/104.18, 432/139|
|International Classification||F27B3/26, F28D19/04, B65G11/06, B65G11/00, F28D19/00, F27B3/10|
|Cooperative Classification||F28D19/04, F27B3/26, B65G11/066, B65G2812/087|
|European Classification||B65G11/06B, F28D19/04, F27B3/26|