US2896744A - Materials separation apparatus and method of materials separation - Google Patents

Description

H. M. CHAPMAN MATERIALS SEPARATION APPARATUS AND METHOD OF MATERIALS SEPARATION Flled July 20 1956 July 28, 1959 INVENTOR CHAZMAN HAQRLOW M United States PatrhtDfiFice 2,896,744 Patented July' 28, 1959 MATERIALS SEPARATION APPARATUS AND METHOD OF MATERIALS SEPARATION Harlow M. Chapman, Bethlehem, Pa.

Application July'ZO, 1956, Serial No. 599,197

4 Claims. (Cl. '18383) This invention relates to apparatus for separating particles of different densities and is especially directed to a novel and improved collector primarily for separating and removing dust particles and the like from a stream of moving air or gas although like principles of operation may be utilized for effecting other separations if desired.

Numerous dust collectors have heretofore been proposed dependent for their operation upon centrifugal force and thus so constructed as to impart to a moving stream of dust-laden air or gas a rotary or spiral motion converting a rectilinear velocity into a centrifugal force which tends to cause the particles to congregate together in the radially outermost layer of the stream and thus deprive the innermost layers of most of their burden thereof so that after the air has traversed a number of convolutions of a spiral or helical path it is discharged axially of the confining chamber relatively free of contaminating particles, the latter, usually more or less coalesced into a relatively dense mass, falling to the bottom of the chamber for passage to a suitable receptacle Or for other disposition.

I have found that for dust collectors of this type to be effective they must be so proportioned that the spiral air stream initially winds its way downward for a number of revolutions and then upward on a smaller radius and in the same direction of rotation, thus producing a spiral of opposite lead, that is, when the outer spiral corresponds generally to a right hand thread the inner one corresponds to a left hand thread and vice versa. As a result there is a zone between the two inwardly of which the air is moving in a direction in conflict with the direction of the immediately adjacent air in the outer zone, creating an intermediate zone of counterflow friction in which the average linear velocity of particles of air, and dust, is less than the average of the velocities of the immediately inward and outward particles in the other zones. Since to escape radially from the inner zone any particle still carried by the air must pass through the said intermediate zone of lower linear Velocity, it is apparent that any increased linear velocity in the inner zone derived from decreased radius of the spiral path, which might normally be expected to improve effectiveness in separating out any remaining particles, is largely counteracted by the slow moving air in the intermediate zone.

Furthermore, due primarily, it is believed, to the said counter flow friction at the intermediate zone interfaces power requirements of collectors of the type just described are excessive considering their relatively low elficiency.

' It is' therefore an object of the invention to provide separating apparatus such as a dust collector in which, while centrifugal force is relied upon to carry outwardly the denser particles in a moving stream containing particles of different densities when the path of movement of the stream is curved about an axis, a relatively thin vlayer of the lighter particles, that is, dust free air or gas, is separated from the remainder of the stream before completing even one complete revolution about the collector axis, and on each succeeding revolution of the main stream a further inner and hence dust free layer is similarly separated therefrom until after traversing several spiral convolutions of the path virtually all dust particles have been forced to the outer limits of the confining chamber and carried or allowed to fall into a subjacent hopper or other receiver and the dust free air or gas separated from them has been discharged from the collector separating chamber.

A further object is to provide a method of separating dense particles from lighter ones in a moving stream of air or gas containing a mixture thereof by diverting the stream into an arcuate path and then after centrifugal force has removed the denser particles from the radially innermost portion of the stream separating said portion from the latter and thereafter during successive revolutions of the denser particles and the remaining lighter ones about an axis in a spiral or helical path similarly separating portions of the stream centrifugally freed of denser particles until substantially all the latter originally contained in the stream have been collected in a receptacle and a stream of less dense material substantially freed therefrom remains for discharge from the collector.

Other objects, purposes and advantages of the invention will hereafter more fully appear or will be understood from the following description of a preferred embodiment of it specifically adapted for service as a dust collector for separating dust from air or gas and illustrated in the accompanying drawing in which:

Fig. l is a side elevation of the collector partly broken away in section to show internal construction;-

Fig. 2 is a section on line 2-2 in Fig. 1; and

Fig. 3 is a section on line 33 in Fig. l, the latter two figures being taken looking respectively in the directions of the arrows on the section lines.

Referring now more particularly to the drawing, the dust collector therein illustrated comprises a main housing 1 defining a substantially cylindrical chamber having a flat cover plate 2 at its top through which an axial exhaust duct 3 extends for conducting the dust-free air from the cleaner. At its lower end the housing is in the form of an inverted frustum of a cone forming a dust collecting hopper 4 discharging into an axial discharge pipe 5, and an inlet duct 6 substantially tangential to the housing near its upper end and discharging thereinto provides a passage through which dust laden air is admitted into the housing chamber, duct 6 being preferably rectangular in cross section particularly at its inner end Where it is connected with the housing. i

The elements of the dust collector thus far described are not substantially different from corresponding elements in dust collectors heretofore well known in the art and detailed discussion of their form, construction and assembly therefore would be superfluous. Internally of the housing, however, this does not apply, since in prior dust collectors of this general character an axial exhaust duct, corresponding to duct 3, usually extends in the housing considerably beyond the transverse plane of the lower edge of the inlet duct. In accordance with the invention, however, duct 3 as a cylindrical duct terminates approximately in alignment with the transverse plane of the bottom face 7 of duct 6 and is provided with a downwardly projecting bafile 8 extending from its lower end in the housing chamber in a diverging semispiral whereby, while the baffle is generally in the form of a slotted frustum of a hollow cone, a narrow inverted V-shaped slot 9 lying substantially in a radial plane from the housing axis is formed, being positioned to intercept progressive increments of air introduced to the housing through duct 6 after traversing either a little less than one full circuit about the housing axis or that distanoe plus a whole number of additional full circuits thereabout in a counterclockwise direction in Fig. 2. To attain this result the plane of the opening of slot 9 may coincide with the plane of that diameter of the chamber, designated C in Fig. 3, which parallels the direction in whichthe air travels in the tangential inlet duct 6 just prior to its introduction into the housing, which direction may be deemed as being represented on the average as substantially coincident withthe center plane D of the duct; the plane of the slot opening may be more remote than the plane C from the plane D but it is inadvisable to position it appreciably closer than plane C to plane D as contamination of dust free air by dust laden air entering through duct 6 may result if the relationship described is not substantially observed. Slot 9 iin the baffle diverges toward the bottom of the housing and is thus Widest at the lower edge 10 of the baffle, this edge of the batfie conforming substantially to an are drawn about the housing axis for about a semicircle from the radially outermost lower corner 11 of slot 9 and there converges inwardly in a spiral segment to the innermost lower corner 12 of slot 9, the edge 10 providing throughout its length a clearance 13 from the housing wall of at least sufficient width to permit the largest particles and accumulations of dust collected in the superjacent portion of the collector to fall into the hopper below, the preferred conformation of the baffle edge being apparent from Fig. 3.

In operation this collector is supported in upright position with duct 6 connected to a source of dust laden air or the like and the exhaust duct 3 to a chamber (not IT 1 shown) into which dust-free'air is to be discharged, or if preferred left open to the atmosphere, while the dust discharge pipe 5 is preferably connected to a suitable receptacle (not shown) for the collected dust.

As the dust laden air is introduced to housing 1 through duct fiat relatively high linear speed, preferably of the order of 1500 or more per minute, the tangential arrangement of the duct with relationship to the housing causes the latter to divert the air stream and guide it into an arcuate path about the housing axis. On this diversion of the relatively low density air the inertia of the higher density dust particles causes them to congregate by centrifugal force toward the radially outward portions of the stream, and a thin radially innermost layer of the stream is almost immediately freed of dust so that by the time'the air particles in this layer have completed slightly less than one full circuit or revolution in the housing and attained the upper narrower end of slot 9 they are in condition for discharge into exhaust duct 3. The remaining air in the stream, containing all the dust in the original stream, is forced by the dust laden air following it to continue in its circular, or by now spiral or helical course about the housing axis for further successive revolutions at the end of each of which another inner layer has been freed of dust and is discharged or peeled off from the stream when slot 9 is progressively reached.

The downward divergence of bafile 8 affords a gradually decreasing cross sectional area for passage of the stream, preferably corresponding generally to the diminution of its volume resulting from discharge of its inner layer at slot 9 on each spiral revolution whereby linear velocity is maintained, or even perhaps slightly increased, insuring thorough cleaning of the air, so that when the dust-free air particles are reunited in a single stream in exhaust duct 3 there is relatively little turbulence in the stream which therefore passes out through duct 3 with minimum expenditure of power.

Moreover, it will be noted the spiral movement of the stream downwardly in the housing is not obstructed or retarded by counter flow friction against an inner upwardly spiraling stream, bafiie 8 separating air moving in these conflicting directions from each other, while in practice it may be shown that but a small proportion, if any, of the air introduced through duct 6 ever moves into duct 3 after passing around the lower edge 10 of the baflle, the stream of air spiraling about the axis as it approaches this edge being repeatedly attenuated on each convolution of the spiral as it passes slot 9 so but little, if any, rapidly moving air normally reaches the lower corners 11, 12 of the slot and that below edge 10 of the baffle is relatively still, being moved only by particles of dust falling through it, and such particles thus accumulate in the hopper portion of the collector and fall therefrom through discharge pipe 5 by gravity and with little or no chance of their recirculation into the superja'cent moving air stream.

By thus eliminating counter flow friction between adjacent moving streams of more or less dust laden air my collector avoids wasteful expenditure of energy in counteracting such friction and by delivering to the exhaust duct progressive increments of air substantially immediately after separation of the dust therefrom the energy otherwise required to force all air introduced into the cleaner to follow the same elongated path afiords further material savings in energy with the result that a collector of any given size constructed in accordance with the invention cleans with equal or better efficiency a substantially larger quantity of air per unit of time than others of comparable size, or as much as other collectors materially larger in size, and with materially less expenditure of power.

While I have herein described with considerable par ticularity one embodiment of the invention which has been found highly efficient and economical in power requirements and hence Well adapted for use as a dust collector in freeing air or gas of mineral dusts and the like, it will be understood the principles utilized in its construction and operation may have application in effecting separations of different character, and consequently that 'I do not desire hereby to preclude their use for such purposes or otherwise to limit or confine the invention in any way, and further, that such changes and modifications in the form, structure, mode of assembly, arrangement and relationship of the several components of the collector as may occur to those skilled in the art may be made if desired without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I claim and desire to protect by Letters Patent of the United States:

1. In a collector or the like, the combination with means forming a substantially cylindrical separating chamber, means for introducing tangentially thereinto a stream of fluid containing finely divided particles of greater density than the fluid, and means providing an axial exhaust passage from the chamber, of a baffle extending in the chamber from the lower end of said last mentioned means angularly outwardly and downwardly and providing a slot communicating with said exhaust passage lying substantially in a radial plane from. the chamber axis spaced from the plane of said introducing means at least as far as the plane of that diameter of the'chaniber which parallels said introducing means having side edges diverging outwardly and downwardly in said radial plane.

2. A collector as defined in claim 1 in which said radial plane lies substantially parallel to the tangential path of the fluid stream introduced into the chamber.

3. In a collector or the like, the combination with means forming a substantially cylindrical separating chamber, means for introducing tangentially thereinto a stream of fluid containing finely divided particles of greater densitythan the'fiuid, and means providing an axial exhaust passage from the chamber, of a baffie extending in the chamber fromthe lower 'end of said last mentioned means angularly outward and downward and providing a slot communicating with said exhaust passage andlying substantially in a radial plane from the chamber axis, said slot having side edges diverging outward and downward in said plane, every transverse section of the baflle comprising an approximately semi-circular segment extending from one edge of the slot and a spiral segment extending therefrom to the other edge of the slot, the radii of said segments increasing in length as the sections are progressively taken downwardly from the upper end of the baffle.

4. In a collector or the like, the combination with means forming a substantially cylindrical separating chamlber, means for introducing tangentially thereinto a stream of fiuid containing finely divided particles of greater density than the fluid, and means providing an axial exhaust passage from the chamber, of a bafile extending in the chamber from the lower end of said last mentioned means angularly outward and downward and providing a slot communicating with said exhaust passage lying substantially in a radial plane from the chamber axis having side edges diverging outward and downward in said plane, the bafile at its lower edge being substantially uniformly spaced from the adjacent inner wall of the separating chamber for approximately 180 from one end of said edge and thence substantially conforming to a contracting spiral to the other end of said edge.

References Cited in the file of this patent UNITED STATES PATENTS 678,451 Allington July 16, 1901 969,769 Brassert et a1. Sept. 13, 1910 1,444,585 Collins Feb. 6, 1923 2,349,831 Osgood May 30, 1944 2,719,631 Vicard Oct. 4, 1955 FOREIGN PATENTS 273,475 Great Britain July 7, 19 27

Images