US2578166A - Rotary drier - Google Patents

Description

Dec. 11, 1951 c. E. BILL ROTARY DRIER Filed March 21, 1950 INVENTOR: CLIFFORD E. BILL.

ATT'YS Patented Dec. 11, 1951 ROTARY DRIER Clifford E. Bill, Louisville, Ky., assignor to General American Transportation Corporation, Chicago, 111., a corporation of New York Application March 21, 1950, Serial No. 150,909

3 Claims.

ing, particularly in the case of direct fire dryerswhere the hot air and gases employed for drying purposes contact the materials directly.

The principal object of the present invention is to provide an improved dryer of a simple, compact and inexpensive form which may be operated more eificiently than those heretofore known and without damage to the materials being dried. The present invention is preferably embodied in a rotary dryer of the direct fire parallel flow type wherein the hot gases and the materials to be dried move in the same direction through the drying chamber and in direct contact with each other. By means of a novel form and. arrangement of lifting vanes, intercepting disks and baffles in the chamber, the materials to be dried are caused to have a maximum intimate contact of the materials with the gases. The contact or retention time between the particles and the gases is decreased as compared with former practice because a substantially higher velocity of flow of the gases is employed. An important feature is that this tremendous increase in the velocity of the hot gases in relation to the material flow gives a proportionately higher increase in dryer capacity. By reason of the more effective use of the hotgases, a more complete rem'ovalj'of the water or other liquid from the materials is effected. These advantages lead to a further one in that it is possible to employ a smaller dryer for a particular task, thereb ef fecting a saving in cost and operation.

Because of the lowretention time for the materials in the dryer,.in the practice of the present invention, the temperature of the dried product is comparatively low so that the requirements for cooling the product are less than formerly. These and other objects and advantages of the invention will appear more fully hereinafter.

The nature of the invention will be understood from the following specification taken with the accompanying drawings in which one embodiment is illustrated. In the drawings,

Figure 1 shows a side elevation of the improved rotary dryer and associated parts with the upper part of the dryer shown in longitudinal section and with some of the longitudinal lifting vanes removed;

Fig. 2 shows a vertical section taken on'the line 2-2 of Fig. 1;

Fig. 3 shows a sectional view taken on the line 33 of Fig. 1;

Fig. 4 shows a sectional view taken on the line 4-4 of Fig. 1;

Fig. 5 shows a sectional view taken on the line" 55 of Fig. 1; y 7 v Fig. 6 shows a sectional view taken on the line 6-6 of Fig. 1; and

Fig. 7 shows a sectional view taken on the line" 1-1 of Fig. 1. I V

As illustrated in the drawing theinvention comprises a rotary cylindrical drumlfl formed of sheet metal and provided at the inlet end thereof with a transverse end wall Illa and, at the outlet end thereof, with a cone-shaped wall lob. This cylindrical drum is provided ,on its outer side with two relatively fixed annular tires or bearing members. II which areadapted to be engaged by supporting rollers l2 mountedon bearing blocks l3 fixed uponthe fiooror other. support M. The blocks l3 have rollers |3 a which. extend on opposite sidesof the associated tire. II to hold the rotary drum against endwise movement. The drum is preferably mounted to rotate about a horizontal axis, as illustrated in, the drawings, and its rotation is effected through power applied to a ring gear 15 which extends around and is secured to the wall of thedrum adjacent one of the tires II. This ring gear is attached to the wall of the drum through brackets l6 and an annular plate H, as shown particularlyin Fig. 7, and the gear is actuated toretate the drum byanendless chain l9 which e x= tendsdownwardly beneath the drumand meshes with a driving pinion 20 fixed upon a shaft This. shaft is journaled in a bearing Zi 'and is driven an electriclmotor 23. The bearing 2?" and the motor are mounted upon a supporting block 24 which is secured to the base 14. With this arrangement, the drum I0 is adaptedto be rotated at a suitable speed for agitating the materials in the dryer and bringing them into con-- tact with the hot gases of combustion which are employed for drying purposes. j

The hot gases are supplied from a gas furnace 25 provided with a burner 26 through which the liquid or gaseous fuel is introduced into the cornbustion chamber. This furnace is supported upon saddle members 21 carried by the supporting blocks 28 which rest upon the base [4. The hot gases of combustion pass from the furnace chamber through the outlet fiue 30 which has a relatively close fit with the walls of a central opening formed in the end wall 1a of the rotary drum.

The materials to be dried are introduced into the drum. ID through the central opening in its end wall |a by means of a feed chute 32 which has an upwardly directed inlet opening 32a and which has its lower part inclined downwardly and forwardly through the flue 38 to discharge at a point located centrally of the rotary drum l8 9. short distance inwardly from the plane of the end wall Illa.

The hot air and gases and the dried materials are withdrawn at the discharge end of the drying drum l0 through the tapered portion 10b thereof and through a power driven centrifugal exhaust fanv 33-. which. is adapted to discharge the mixture. into asuitable settling chamber from: which the air and gases escape and from which the solid dried materials settle by gravity to a discharge opening at the bottom.

As apart of the means for agitating the materials to be dried and maintaining. a sufficient turbulence thereof to bring them into intimate contact with the hot drying gases, the cylindrical drum I8 is provided on its inner side with a plurality of spaced lifting vanes 35 which extend radially and. which have their outer edges welded or otherwise secured to the wall 1.. For a considerable distance, preferably about one-half of the length of the drum III, the vanes 35 are of equal radial. depth, as shown. in Figs. 1 and 4, and all parts of each vane lie in one plane. From. apoint adjacent the middle of the drum l0 to the discharge end thereof,. the. vanes H] are increased in. radial depth as shown. at. 35a in Figs. 1 and 6.. some of the vanes 35 which have the shorter radial dimension have their inner edges bent at angles to the radial body portions thereof as sho n at 351) in Fig.. 5. Beyond the middle point of the dryer where the radial vanes have an increased depth, an increased number of the vanes have their inner margins bent at angles to the body portions thereof as shown at 350 in Fig- 6. The purpose of angularity of the inner edges of some of the vanes is to enable these vanes more readily to pick up the materials being dried and to convey these materials around in the paths of. travel of the vanes so they are dropped when the vanes reach or approach the upper parts of their paths. As the materials become dryer and perhaps more finely divided, it is usually desira-ble to have an increased number of vanes provided with. inclined inner edges as the dischar eend' of the dr ing drum is approached.

The lifting vanes 35 are adapted to cooperate with a plurality of radially extending sheetmetal.

rings 31 and a plurality of radially extending metal disks 38 which are arranged in pairs and spaced. apart. The rings 31 are slotted at their outer margins. to receive the vanes 35 and their outer edges are welded to the drum l0. Each ring 31 is provided with a central opening 31a and. these openings are preferably of the s me size throughout the length of the drum. Each ring 31 cooperates with an adjacent disk 38 which is circular in form and. preferably of slightly larger diameter than the aperture 31a, in. the ring which is located on the: inlet side thereof so: that the gases and materials to be dried are compelled to follow a tortuous path in moving Toward the middle of the drum Ill from the inlet side of the ring 3'! to the outlet side of the associated disk 38. These disks may be mounted as shown in Fig. 4 by a series of radially extending rods 39 which are securely attached to the outer part of the disk 38 and which have their outer threaded extremities extending through holes in the drum [0 where they are secured by nuts 40.

A considerable number of baflle rings 3'! and disks or targets 38 are embodied in the construction and distributed preferably in a uniform manner throughout the length of the drying drum. Each ring 31 is associated with one of the disks 38 and these members constitute a pair which are spaced substantially from another similar pair so that each disk is closer to the ring 3'! preceding it than it is to the next ring on the discharge side thereof. The distance between each disk 38 and the preceding ring 31': may preferably be about one-third of the distance between two adjacent rings 3! measured longitudinally of the dryer. For illustration, with a drumi'lfl which is. sixty feet long, the first ring 31 is located six feet from the inlet end of the drum, is spaced two feet from the disk 38 which is associated therewith on its discharge side and is spaced six feet from the next following ring. In this particular embodiment, the drying drum EU has an internal diameter of eight feet, the rings 31 have central openings which are four feet five inches in diameter and the disks 38 are five feet in diameter. These dimensions are given by way of illustration and not by way of limitation and are intended to indicate relative proportions which have been found to give very satisfactory results in practice.

With the foregoing construction and arrangement of apparatus, the materials to be dried are introduced more or less continuously through the feed chute 32 and they are drawn with the hot gases of combustion passing through the flue 30 and then through the chamber of the drying drum l8 by the action of the centrifugal blower 33 which has its suction inlet connected to the discharge end of the drying chamber. As the gases and materials are drawn through the chamber, the drum is rotated at a relatively low speed, for example, 8 revolutions per minute, and, as this rotation continues, the materials are carried around by the vanes 35 and continually dropped as the vanes reach their uppermost position while, at the same time, the current of hot air and gases causes the materials to impinge upon the rings 31 and upon the disks 38. The gases and materials must pass around disks 38 through the tortuous path which is provided by the spaced rings and disks and the gases and materials then have an opportunity to lose momentum on the discharge side of. each disk 38 before they are accelerated again to contact with the next following ring 3i and disk 38. In this way the gases and materials are thoroughly intermingled with each other and are caused to move in tortuous paths and with constantly changing velocities so that the materials as well as the gases move both longitudinally and radially and in other directions in a manner adapted to bring about a thorough mingling of the gases and particles to be dried even though the gases and materials pass through the chamber of the drum H1 at. relatively high speeds. As a consequence, very surprising results are obtained with respect to the thoroughness of the drying of the materials and the rapidity with which they are dried during the short time interval of their passage through the drying chamber.

To obtain the desired results, a relatively large number of the fiat rings 31 and the circular disks 38 should be employed, so that the materials to be dried will be caused to follow a tortuous path along with the hot gases, thereby bringing about intimate and repeated contacts of all surfaces of each particle with the hot drying medium. The number of baflle rings and cooperating disks will depend upon the length of the drying drum but desirable results may be obtained if the spacing of two successive rings is not greater than the diameter of the drum. The results are improved by arranging the rings in pairs, that is, with each disk closer to the next preceding ring than it is to the next following ring. This spacing is preferably followed throughout the length of the drum. It is believed that this spacing arrangement results in alternate increases and decreases in the velocity of the gases with a consequent tendency for the materials to drop from the gas current during the periods of decreased velocity, thereby further increasing the general turbulence and the intimate contact of the gases with the particles. The closely spaced vanes, rings and disks have the further advantage that they become heated by the passing hot gases and radiate their heat to the moving materials, thereby supplementing the direct action of the gases.

Although one form of the invention has been shown and described by Way of illustration, it will be understood that it may be constructed in various other embodiments which come within the scope of the appended claims.

I claim:

1. A rotary dryer comprising a rotatable cylindrical drum having inlet and outlet openings, means for rotating said drum, means for introducing hot gases and materials to be dried through said inlet opening, means communicating with said outlet opening for drawing said gases and said materials through said drum, a series of longitudinally extending lifting vanes attached to the inner surface of said drum and extending inwardly therefrom, a plurality of flat radial rings attached to said drum and distributed throughout its length, and a plurality of disks each located opposite the opening of one of said rings on the discharge side thereof, said vanes increasing in radial depth toward the discharge end of said drum.

2. A rotary dryer comprising a rotatable cylindrical drum having inlet and outlet openings, means for rotating said drum, means for introducing hot gases and materials to be dried through said inlet opening, means communicating with said outlet opening for drawing said gases and said materials through said drum, a series of longitudinally extending lifting vanes attached to the inner surface of said drum and extending inwardly therefrom, a plurality of flat radial rings attached to said drum and distributed throughout its length, and a plurality of disks each located opposite the opening of one of said rings on the discharge side thereof, some of said vanes having their inner edges bent to form flanges directed at angles to radial planes, said flanges increasing in number toward the discharge end of said drum.

3. A rotary dryer comprising a rotatable cylindrical drum having inlet and outlet openings, means for rotating said drum, means for introducing hot gases and materials to be dried through said inlet opening, means communicating with said outlet opening for drawing said gases and said materials through said drum, a series of longitudinally extending lifting vanes attached to the inner surface of said drum and extending inwardly therefrom, a plurality of flat radial rings attached to said drum and distributed throughout its length, and a plurality of disks each located opposite the opening of one of said rings on the discharge side thereof, some of said vanes having their inner edges bent to form flanges directed at angles to radial planes, said flanges increasing in number and said vanes increasing in radial depth toward the discharge end of said drum.

CLIFFORD E. BILL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,299,492 Mangelsdorf Apr. 8, 1919 1,898,480 Corkill Feb. 21, 1933 2,096,049 Lissauer Oct. 19, 1937 2,341,101 Howard Feb. 8, 1944 FOREIGN PATENTS Number Country Date 605,221 Great Britain July 19, 1948

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