US2504378A - Rotary drier - Google Patents

Description

J. W ROTARY DRIER April 18, 19

Filed Aug. 20, 1946 WVENTOR B) hn W Be// ATTORNEY Patented Apr. 18, 1950 UNITED STATES PATENT OFFICE ROTARY DRIER John W. Bell, St. Catherines, Ontario, Canada Application August 20, 1946, Serial No. 691,802

i My invention relates to drying apparatus and more particularly to improvements} in rotary driers for drying comminuted material and the like.

- A typical form of drier for the drying of comminuted or powdered material consists of an elongated rotating cylinder into which the material to be dried is fed and in which it is subject to a current of warm air blown through the cy1inder. Commonly the cylinder is mounted with its axis slightly inclined and the material is continuously fed through an opening at the high end and is continuously expelled at the other end." To expose the material to the drying eflect ofthe-current of air, it is customary to provide scoops on the inner cylindrical wall whereby as the cylinder rotates the material is picked up by the scoops from the mass of material at the bottom and is later spilled from the scoops at a, further period of their rotation.

The object of my invention is to provide a drier having an improved construction and arrangement of scoops whereby an improved exposure of the material to the current of air is obtained, with consequent increase in the drying capacity of the apparatus.

A further object of my inventionls to provide a drier having material distributing scoops which are self-cleaning.

Other objects and advantages of my invention will become apparent from a consideration of the following detailed description :of a specific embodiment thereof in which Fig; 1 is a sectional view transversely of a drier cylinder taken along the line AA of Fig. 2; Fig. z fis a longitudinal view of a drier cylinder, shown-broken for convenience of illustration and with the left hand end in section; and Fig. 3 is' 'a view on an enlarged scale of a detail.

Referring to the drawi gs.- in represents a drying cylinder which is of considerable length, but in Fig. 2 is shown broken away for convenience of illustration. The cylinder will be mounted for rotation by anyyssuitable means of known type which has not been illustrated as the particular means forms no part of my invention. The cylinder is mounted at elf-slight incline and a feed inlet l I is shown at the axis of the upper end. A suitable outlet for dried material is indicated at l2 at the lower end of the cylinder. The direction of rotation of the".'cylinder is indicated by the arrow shown above the cylinder in Fig. 1. During operation, materialfto be dried is fed in the inlet II and graduallyfworks its way to the outlet H where it is discharged. During its 2Claims. (01.34-186) p 2 passage through the cylinder, it is picked from the accumulation l3 of material in the bottom" of the cylinder by scoops M which spill it into a current of warm air which may be passed through the cylinders either with the flow or in counterflow thereto. A series of rows of flights or scoops M are symmetrically spaced circumferentially on the inner wall of the cylinder, twelve rows being shown. As can be best seen in Fig. 2, each row of scoops consists of a plurality of individual scoops IQ of relatively short length compared to the length of the drier. The spaces l'l separating the individual scoops I 4 of a row are of sufiicient width to permit the passage of the particular type of material being operated on. The scoops M are made of spring metal of a composition adapted to resist corrosion by the moist material being dried and of a gauge thin enough so that the scoop when loaded will tend to oscillate and have a configuration as shown in Fig. 1. They are mounted with one end anchored to the cylindrical wall l0 and with the other end I5 free. As the drum rotates the scoops I4 enter the accumulated material l3 in the bottom of the drum at the left-hand side and pick up a full charge of material. As the scoops emerge from the material I 3 and progress in their travel, they continuously spill the material over their ends l5. Due to the scoops being of thin gauge spring material anchored only at their wall end and are otherwise unsupported they tend to vibrate or oscillate through a narrow range about the clamped end as an axis and the period of vibration varies with the degree of loading. As the scoops are supported separately they vibrate" independently of one another. The scoops are bent in a smooth curve so that the material hearing surface is free from sharp bends, the free ends thereof are reverted towards the cylinder wall whereby some material is retained therein for the greater part of the upper half of their travel. The material in the scoops is also spilled through the slots l'l between the scoops I 4 and this spilling will continue as long as there is material in the scoop due to the continuous readjustment of the position of the material in the scoop in its travel. As stated the slots between the adjacent scoops are wide enough to permit the passage of a particular size of particles of material to be dried. They are, however, as shown'in Fig. 2 relatively narrow compared to the width of the scoop whereby the flow of material there-j through from the sides of thepiles oi materialin the scoop is regulated. The regular flow of material through the slots between the scoops is of falling material, indicated at l t in Fig. 1,. ex

tending lengthwise of the cylinder, and the material spilling through the slots l1 form a plurality of curtains of falling material indicated at l8 Fig. 1 and extending transversely of the cylinder and the air current. It will be apparent that for a given size of drier that the-addition of "the" large number of curtains of falling material-.10? cated across the path of the drying medium, in-

contour of the scoops tends to prevent particles of material sticking thereto and gradually clogging them.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a rotary drier for drying granular material, a cylindrical shell with a feed opening at one end, a discharge opening at the other end, means for circulating a drying gas lengthwise therethrough,. and means for elevating and releasing the material to fall in a series of Iongitudinal curtains and a series of transverse curtains through the drying gas comprising rows of creases to a great extent the surface: area" of adrierof given-drying capacity to be constructed of: shorter length with theconsequent saving: in initial cost and with theadvantage of requiring less-floor space and less driving power.

Inzthe'preferred manner of use. the drying gas passes through the drier flowing counter to the material; In conventional rotary'driers for granular: material; such for example as those illus trated: and discussed in an article published in the: Transactions of the American Institute of Ghemical Engineers vol. 38: at page 124 et seq. and at page 841' et seq., entitled Factorsinfiuerrcingi rotary drier performance the material to be: dried cascades from the flights in a seriesofcurtains-of falling: material longitudinally of the drier and the war-m2 air flows through the cylinder between and parallel tothese curtains. A. certain amount of fine dry material is carried from the drier with-theair current.

material lying instheair passage'between' the longitudinal curtains serve todntercept the dry fines as they are carried towards the moister material at'the input end to a greater extent thanwould be: the case if? the transverse curtains were not present.

Asuitable-means for attaching-the-ends of. thescoops: It to the, cylinder wall: is indicated in- Fig; 3; The? attachment endof the: scoop I 4 is bent tosemi-cylindrical form to correspondin curvature: to the surface" of a: haltround: bar" I 9..

A single-bar: 1 9 may engage a plurality of the scoops in a" row and bolts 20 detachably secure them to the shell l0 with the curved surface clamped. thereagainst. The extreme ends- 21 ofthe scoops are bent to engage the-fiat side of the bar l 9. The mounting-above" described supportsthe'iclamped end of the spring: in a manner such that the tendency of. the springs to weaken and break atthe clampingpoint. under vibration is minimized. As-statedthe scoops. M are ,of'springmaterial-anchored-at one: end only andin operation are free to vibrate individually. This construction. makes for a self-cleaning apparatus. The relative movement of adjacent scoops l4 dueto the vibrationprevents the slots ll between themfrom. clogging with material.

In the drier of-;myinvention the transverse curtains of falling.

In addition. the continuous vibrationtogetherwith thesmooth flights circumferentially spaced about the inner surface of the cylinder wall, each row lying parallel totheaxis of thecylindrical shell and comprising,ag lurality of: aligned individual scoops spaced from one another a distance sufficient to permit the'granular material to pass therebetween but close enough together to control the flow of the material therethr'ough as the drier rotates, clamping means securing the individualscoops-t at one end. to'the wall of the drier, said"scoops'= being otherwise unsupported and unobstructed? and made of spring metal of sufiiciently light gauge'so that they wil1=oscillatethrough a'-narf-" row-range about their clamped end as a. pivot when loaded 'withmaterial, said scoops having; a continuously curved material bearing-surface shaped to retain some of the material throughout the greater portion'offeachrevolution of thedriern 2: In a rotary drier for drying granular mate-- rial, acylindrical shell with a feed opening at one end, a discharge opening at the other end; means for circulating a drying gas lengthwise? therethrough,.and means for elevating and're:-' leasing the material to fall in a series of lon gitudinal curtains and a-series of transverse-cur tains through'the drying gas comprising rows of? curved flights circumferentially spacedaboutthe inner surface of the cylinder wall and shapedito pickup material and gradually spill it throughout. thegreater: part of eachrevolution of the drier; each row of flights comprising a plurality: of?

' alignedindividual'sections spaced-'from one arr-- other a distance sufficient to permit the granular material to passtherebetween but closev enough together to control theflow of material there'-- through as the drier rotates, each section having; its wall'engagi'n'g end' formed in a curve reverse to' the curve of-the body of the section,zmeans forclamping the sectionsto the wall of the drier? comprisingaa' bar with a transversely curved sur face-co-operatively, engaging the said curved end of the-section, said sections made of'springimetali of'sufiiciently'light gauge'so that they will oscil-- late-through a narrow range-about their clamped: ends when: loaded with. material.

' JOI-INW.

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

UNITED STATES PATENTS Number Name Date 1,196,376 Meyer Aug. 29,1916 1,595,659 HOW Aug. 10; l9'26 2,096,049 Lissauer .Oct. 19,1937 2,275,600. Arnold Mar. 10;-l9'42- FOREIGN PATENTS Number Country Date 394,574 Germany Oct. 20", 1922

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