US1721594A - Classification system for pulverized materials - Google Patents

Description

H. HARDINGE July 23, 1929.

CLASSIFICATION SYSTEM FOR PULVERIZED MATERIALS Origizial Filed Aug. 28, 1925 g-wwemtoz w W b'tom Patented July 23, 1929.

' UNITED STATES PATENT OFFICE.

HARLOWE HARDINGE, OF YORK, PENNSYLVANIA, ASSIGNOR 'IO HARDINGE COMPANY, INCORPORATED, OF YORK, PENNSYLVANIA, A CORPORATION OF NEW YORK.

CLASSIFICATION SYSTEM FOR PULVERIZEI) MATERIALS.

Original application filed August 28, 1925, Serial No. 53,174. Divided and this application filed December This invention relates to systems whereby dusts are separated or classified by the agency of moving currents of air or of other buoyant or elastic fluid capable of carrying particles in suspension. The subject matter of this application is fully disclosed in my co-pending application Serial No. 53,17 l, filed August 28, 1925, of which this application is a division. In that application I disclosed and claimed a dust classifier or separator having two main compartments in which the compartments are relatively adjustable and/or the deflector blades are adjustable whereby products covering a large number of different grades of fineness may be efficiently classified under different settings. This application is concerned with a system or assembly of units which may or may not include a dust classifier capable of the adjustments referred to, yet is such a system in which such a dust classifier is admirably adapted to be used.

The system differs fundamentally from systems previously devised in that nearly every part of the system operates under pressure below atmospheric pressure. Such a condition of operation is accomplished by positioning the exhauster beyond the classifier and the collector and just before the disintegrating mill thereby producing a system of complete circulation with only a short portion of conduit comprising the connection between the last dust collecting unit and the disintegrating mill under pressure. In systems of the general class heretofore used the exhausters have been placed just after the disintegrating mill or just after the dust classifier in either of which cases the dust classifiers and collectors after the exhauster are operated, together with long sections of piping, under pressures greater than atmospheric pressure. Such systems do not lend themselves to the flexibility of adjustments of pressures obtained by my system nor are they operable at as high an e ficiency.

In addition to providing a general assembly operable under a partial vacuum, I provide dampers and Valves so designed and positioned as to aid in the properdistribution and necessary regulation of the pressure of the moving mass of dust carrying fluid throughout the assembly, The section of piping connecting the pressure side of the exhauster and the disintegrating mill serves Serial No. 243,824.

as a fluid feed conduit and also as an oversize return conduit and it is caused to serve ef ficiently in the latter capacity by the utilization of an adjustable damper or bafiie disposed therein and adjacent to a duct or pocket conducting oversize material rejected by the classifier. This arrangement is such as to be able to effectuate an increase in the rate of flow of the fluid past the pocket and an attendant drop in pressure at the mouth of the pocket whereby the discharge of oversize material from the classifier and the return of the oversize material to the disintegrating mill is facilitated and efiiciently accomplished.

. Other and more detailed objects will be pointed out hereinafter in the accompanying specification and claims, and shown in the drawings which, by way of illustration, show one and a preferred embodiment of the invention.

The figure illustrated comprises an elevation of a general assembly in which 10 designates a disintegrating mill of the well-known conical type from which pulverized material is carried through trunnion 11 by a current of air which is introduced to the mill through a section of pipe, 12. In this type of mill, material to be disintegrated or ground is supplied thereto through the inlet trunnion (not shown) and is disintegrated upon rotation of the mill in a manner well known to those skilledin the art. While I prefer todisclose my invention in conjunction with this type of mill, it is to be understood that it may be utilized with other types of disintegrating mills. Air is blown into thesection of pipe, 12, from conduit 13 and it leaves the mill by following a path along the outside of pipe 12 and through a barrel 14 into a conduit 15 leading to the classifier 16. In the mill, the pulverized material is continually being agitated by the rotation of the mill and the moving air becomes laden with material and is then drawn through the barrel where some of the coarse particles may drop out. Some of the pulverized material may overflow at the discharge end of the mill and fall into barrel 14. The rotation of the barrel causes the material that has dropped into it to be raised, with the result that material is continually being dropped into the break between pipe 12 and conduit 13, and the current of air flowing from conduit 13 and through pipe 12 returns it to the mill. The current of air going to the classifier and passing along the outside of pipe 12 and of a portion of conduit 13, passes through the screen of falling material and dust and collects therefrom the finer material. Conduit 13 is directly connected with the pressure side of an exhauster or blower 17, and, accordingly, this conduit may be designated the fluid feed conduit for the disintegrating mill as well as the oversize return conduit, to which capacity reference will be included hereinafter.

The classifier 16 has an inner casing 18 along the outside of which flows the current of material laden air entering through condu-it 15. Between the inner casing 18 and the outer wall of the classifier there are disposed a plurality of deflector blades 19 which 20 create a vortex or whirling action of the air passing therethrough.

The exact arrangement of the deflector blades is not particularly concerned with the present subject matter of invention and a detailed description'of the same will be refrained from in view of the fact that several arrangements have been fully disclosed in my said copending application Serial No. 53,174. The vortex created within the classifier causes the heavier particles to be cast out of the stream of flowing air. These heavy or large particles leave the inner casing at its lower end 20 and are collected in an over-size discharge pocket or conduit 21. This latter pocket opens directly into the fluid feed or over-size return conduit 13 into which it discharges whatever material is collected.

The material laden air leaving the classifier is conducted through a conduit 22 to a dust collector 23 which may be of any desirable construction. This dust collector serves the purpose of removing the particles of material from the air and collects the same so that the dust may be withdrawn when desired through .a duct 24. The clear air, which is thusly relieved of its burden, is withdrawn from the dust collector 23 by means of a conduit 25 which has communicatli pn with the low pressure side of exhauster The separation or classification of certain grades of material might make it desirable to have a series of dust collectors similar to dust collector 23, and,-in that event, the low pressure side of the exhauster 17 would have connections with the last one of the series of dust collectors.

A complete cycle of the air has been.de-

grinding unit is absolutely dustless and that the exhauster handles returned air only. This last feature contributes to the efliciency of the entire system in that the exhauster is not called upon to drive air which is laden with material. It also-is readily understood that the saving on the wear of exhauster blades is considerable because of this fact.

Within the oversize return conduit 13 there is disposed, close to the pocketor discharge opening 21, an adjustable baffle 26. This adjustable baflie may be used for the purpose of restricting the cross-sectional area of the over-size return conduit at this point in order thatthe velocity. of the flow of air be increased so as to cause'an increased exhausting effect through opening 21, and from the interior ofthe classifier. It will be found that the position of the battle will have to be varied for differentmaterials and under different operating conditions. In general, a slight depression or restriction of the cross-sectional area of the over-size return conduit 13 usual- 1 gives the best results and the Venturi effiict produced will sufficiently aid the withdrawal ofthe oversize material through the pocket opening 21. Once within theoversize return conduit 13, the over-size material will be returned to the disintegrating mill 10 where it will again be subjected to pulverizing action. 1

Tapped into the fluid feed conduit 13 there is a vent-pipe 27 which is open at its upper end. This vent pipe serves the purpose of expelling moisture from the system and it also exhausts whatever extra air that is drawn into the system as a result ofinfiltration. A valve 28 may be adjusted to any desired position so as to properly control the amount of air exhausted through the ventpipe and also control the back pressure in the fluid feed conduit 13. It will be found that where the moisture content is low, satisfactory results may be had by venting only a relatively small amount of air.

Under certain conditions it is referable to drive air directly into the classi er insead of v forcing all of the air through the mill and this expedient may be accomplished by the interpositioning of a by-pass conduit 29 between the high pressure side of exhauster 17 and conduit 15 leading to the classifier. A valve 30 within this'by-pass conduit may be so positioned as to entirely shut off any passage of air or positioned to permit so much air to pass as Will accomplish the purpose desired. It is obvious that the system disclosed lends itself particularly well to the disintegrating mill. This close adjustment is assisted materially by having the high pressure side of the exhauster connected directly with the disintegrating mill. By such direct connection all of the adjustments desired may be made within a small area and the results of different ad ustments may be observed duringthe process of obtaining the balance in pressures desired. All of the pressures throughout the entire system are easily controlled within this small area. I wish it to be understood, however, that these desirable conditions are incidental or follow from the arrangement of the several units in the entire system. Iii this respect I attribute the successful results which I attain to the placing of the exhauster in position beyond the dust classifiers or collectors in order that the greater part of the system may be operating under a partial vacuum.

My invention is capable of a wide variation in relationship of parts without departure from the nature and principle thereof, and I do not restrict myself unessentially in the foregoing or other particulars, but contemplate such alterations and modifications within the scope of the appended claims as may be found to be advisable.

I claim:

1. In an apparatus of the class described, the combination comprising, a disintegrating mill, a classifier, a dust collector, an exhauster, the suction end of said exhauster having connections with said collector so as to draw material-laden fluid from said disintegratin mill and through said classifier, collector an connections, the pressure end of said exhauster being connected with said disintegrating mill and means between said exhauster and said mill for removing a portion of the fluid current from the apparatus.

2. In an apparatus of the class described, the combination comprising, a disinte ating mill, means for separating material rom material-laden fluid, connections between said disintegrating mill and said first named means, exhauster means having connections with the fluid discharge end of said firstnamed means, connections independent of said first named connections for directly connecting said exhauster means with said disintegrating mill and means associated with said last named connections for controlling the pressures in the apparatus.

3. In an apparatus of the class described, the combination comprising, a disintegrating mill, a classifier having a fluid exhaust duct and inlet duct leading to said classifier, a fluid feed conduit leading into said disintegrating mill, connections between said fluid feed conduit and said classifier and exclusive of said inlet duct, and means for preventing fluid current from said fluid feed conduit entering said classifier and permitting the extraction of material from said classifier.

4. In an apparatus of the class described, the combination comprisin a material classifier, a disintegrating mil connections between said classifier and said disintegrating mill for the passage of fluid currents, said connections including a fluid feed duct to said mill and a conduit for delivering a flow of material-laden fluid from said mill said classifier, and a pocket for collecting oversize material, said pocket opening into said fluid feed duct outside of said conduit.

5. In an apparatus of the class described, the combination comprising, a disintegrating mill, a classifier, a dust collector, an exhauster having connections with said collector whereby fluid is successively drawn from said mill, classifier and collector, connecting means intermediate the pressure end of said exhauster and said disintegrating, mill, and means for controlling the pressure in said connecting means whereby the pressure within said disintegrating mill may be maintained at substantially atmospheric pressure.

6. In an apparatus of the class described, the combination comprising, a disintegrating mill communicating with the atmosphere, a dust collector, connections intermediate said mill and said collector, an exhauster intermediate said collector and said mill and connected therewith, and means intermediate said exhauster and said mill for controlling the pressure in said mill.

7 In an apparatus of the class described, the combination comprising, a disintegrating mill communicating with the atmosphere, a dust collector, connections intermediate said mill and said collector, an exhauster having its suction end connected to said collector and its pressure end connected to said mill, and an adjustable vent intermediate said exhauster and said mill for permitting the escape of fluid whereby pressures may be controlled.

8. In an apparatus of the class described, the combination comprising, a material classifier and a disintegrating mill having connections therebetween for the passage of fluid currents, said connections including a conduit for receiving a flow of material-laden fluid from said mill and a pocket opening into a fluid feed duct to the mill for collecting oversize material extracted by the classifier, and a bafile for creating a change in fluid flow in the vicinity of said pocket.

9. In an apparatus of the class described, the combination comprising, a material "classifier and a. disintegrating mill having connections therebetween for the passage of fluid currents, said connections comprising a con duit for conveying material-laden fluid from said mill to said classifier and an opening connecting said classifier with a fluid feed duct leading to the discharge end of said mill, and a bafile for controlling the pressure in said fluid feed duct and in said mill.

10. In an apparatus of the class described, the combination comprising, a material classifier and disintegrating mill having connections therebetween for the assage of fluid currents, said connections in'c uding a conduit for receiving a flow of material-laden fluid size material extracted by the classifiergand means adjacent said pocket for creating a suction to aid the discharge of oversize material into said feed duct.

hauster connected with said collector, a conduit between said exhauster and said mill, and means disposed between said exhauster and said connections for bypassing a portion of fluid current without having said portion of fluid current enter said mill.

12. In an apparatus of the class described, the combination comprising, a disintegrating mill'communicating with the atmosphere, a dust collector, connections intermediate said mill and said collector, an exhauster having its suction end connected to said collector and its pressure end connectedto said mill, means intermediate said exhauster and said mill for controlling the pressure in said mill, and a vent intermediate the exhauster and said mill for permitting the escape of excess fluid and expelling moisture from the system.

13. A pneumatic system for conveying and collecting pulverized material comprising a disintegrating mill, exhauster means and dust collecting means for separating the pulver ized material which is conveyed from the mill to the dust collecting means by' fluid currents created by the exhauster means, said exhauster means being so connected in the system as to discharge into the mill, and vent means communicating the discharge side of the exhauster means with the atmosphere.

14. A pneumatic system for collecting pulverized material in a dust collector under sub-atmospheric pressure conditions comprising a disintegrating mill and means connecting the same with the dust collector, an exhauster having its suction end connected with the dust collector and its discharge-end connected with said mill whereby fluid currents may be conveyed through the system, and means between the discharge end of the exhauster and the mill for removing a portion of the fluid currents from the system.

In testimony whereof I hereto aflix my sig- 7 nature.

HARLOWE' HARDINGE.

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