US2368961A - Pulverizer - Google Patents

Description

6, 1945. R L I 2,368,961

PULVERIZER Filed April 2, 1942 2 Sheets-Sheet l Fig 1 INV ENT OR.

Thomas H Arnold ATTORNEY Feb. 6, 1945. T. ARNOLD 2,368,961

PULVERIZER Filed April 2, 1942 '2 Sheets-Sheet 2 Fig.3

IIIIIIIIIIIIIIIIIIIIIIIIII INVENTOR BY 7770 Q5 HAZUOZd I ATTORNEY Patented Feb. 6, 1945 2,368,961 PULVERIZER Thomas H. Arnold, Cherubsco, Mexico, assignor to-The Babcock & Wilcox Company, Newark, .N. J., a corporation of New Jersey i Application April 2, 1942, Serial No. 437,330

s Claims. (01. 241 61 I The present invention relates to the construction and operation of pulverizers of the type designed for pulverizing coal, cement materials and the like and in which the pulverizedmaterial is removed from the grinding zone of the pulverizer in suspension in a gaseous carrier mediiun;

The general object of my invention is the provision of a pulverizer' of the type described which is characterized by the high degree of fineness of -m the" pulverized material discharged and the relatively low power consumption of the 'pulverizer. A further and more specific object is the provision of an improved rotary classifier construction and arrangement for a pulverizer of the type described which greatly contributes to the fineness of the output.

--The various features of novelty which characterize my "invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, itsoperating advantages and specific objects attained by its use, reference should be had to theaccompanying drawings and descriptive matter in whichI have 111115:- trated and. described a preferred embodiment of my invention.

Of'the drawings:

Fig. 1 is a sectional elevation of a pulverizer constructed in accordance with my invention;

Fig. 2 is an enlarged view of the classifier section of Fig. 1; and

Fig. 3 is a fragmentary plan view of the rotary classifier.

The pulverizer illustrated is of the general type disclosed and claimed in U. S. Patent 2,275,595, granted March 10, 1942, andas shown in Fig. 1 comprises a substantially cylindrical housing it, the base of which includes the drive assembly for a vertical drive shaft II. The shaft II has a conical yoke I2 keyed on its upper end. The grinding parts of the pulverizer comprise a lower rotary grinding ring l3 carried on the lower outer pension into the portion of segmental relief gate 23 in one part thereof. The pulverized material'leaving the outer edge of the lower grinding ring is swept up by the high velocity air stream and carried upwardly in susthe housing above the grinding zone.

The housing top is formed by the annular plate I! and a raised cylindrical center section or turret 25 forming a cylindrical chamber 26 as a continuation of the central opening in the plate I].

Ancpening 21 is formed in the top of the turret for the discharge of material-laden air. 1 During the passage of the material-laden air upwardly along the side walls of the housing some of the oversize particles separate from the air stream and drop back into the grinding zone. Before the material-laden air can enter the turret section it is subjected to the action of a rotary classifier symmetrically arranged relative to the outlet 21;. The rotary classifier is formed by upper and lower horizontally arranged annular plates 3! 'a'nd"32 respectively. The plate 3| extends'beyondthe circumference of the plate 32 andQat' itsinner periphery has an uprising circular flange 33 which extends into-the opening in the top plate [1. "A circular serie of fan or impact blades 35 is symmetrically arranged in an inverted frusto-conical formation between the plates 3! and 32. The classifier blades are preferably of angular cross -section, as shown in Fig. 3, and welded at theirends to the plates 3| and 32. The angular blades have an angle of approximately 90 betweenitheir 'rangement oversize particles in the air streamtend to collect in the blade'pockets and slide downwardly along the pocket to the plate 32 and 0 thus out of the path of the stream of materialend of the yoke, a circular row of grinding balls l4 arranged in a track on the ring l3, and a spring pressed non-rotary uppercring l5 carried on theball row. The .material to be pulverized is delivered through a feed spout l6 opening through the top wall ll of thehousing adjacent laden air passing through the classifier.

The classifier is detachably mounted on a supporting structure carried .by the drive yoke [2. The classifier support 31 forms a downwardly tapering continuation of the opening in the plate 32 to receive oversize material dropping outof the classifier. The material deposits on the top of the drive shaft and on a support base plate 38 and is discharged from that area through slots between rectangular plates 39 as in .said Paten't No. 2,275,595. The discharged-oversize particles are returned to the grinding zone for further pulverization.

In operation the classifier blades give the material-laden' air stream a swirl as it passes into the turret chamber 26; This swirling action throws the coarse material towards the sides of the turret chamber and tends to produce eddy currents in the upper circumferential corner of the chamber which cause the coarse material to move downwardly in a relatively dense stream along the side wall of the chamber. In order to reduce the static pressure drop through the turret outlet 2?, a cone member 46 is positioned in the opening 2! so as to form an upwardly tapering entrance to the outlet 21. The cone 40 is vertically adjustable relative to the turret section by means of supporting hangers 4| extending through the top Wall of the turret and externally adjustable. This arrangement of the cone aids in confining the eddy currents to the upper corner of the turret chamber.

The coarse particles descending along the sides of the turret would ordinarily accumulate on the classifier top plate 3| and spill over into the air stream leaving the inner side of the classifier and recirculate in the turret chamber or be carried out through the discharge outlet 21. accordance with myinvention the upper portion of the classifier is constructed and arranged to receive any coarse material separated in the turret section and return the same to the grinding zone. As shown in Fig. 2, the classifier upper plate 3| is'arranged slightly below and inwardly of the central opening inthe housingtop plate IT. A circular series of angularly spaced symmetrically arranged bars 4 5 are mounted on the upper surface of the classifier plate 3! and welded thereon in a position in which the inner end of each bar is the leading end and the bar is tangentially arranged relative to a circle of slightly smaller diameter 1 than a the plate flange 33. A fiat annular seal plate 46 is mounted on the outer section'of the bars 45 in a position in which the circumferential outer edge of the plate 46 has a slight clearance relative to the top plate I! and the inner circumferential edge is spaced from the classifier top platefiange 33 leaving an annular opening 4'! therebetween through which coarse materialfrom the turret chamber can drop onto the top'plate 3! and be forced outwardly therefrom when the classifier is in operation by the bladeaction of the obliquely arranged bars 45. A centrifugal effect is thus imposed on the coarse particles sufiicient to overcome the pressure differentialjthrough the classifier. The circumferentially discharged material is, directed downwardly by a frusto-conical plate 48 on the underside of the housing top plate l1.

The 'coarse particles, separated in the turret chamber are, thus directed towards the grinding zone of the I pulverizer, therebyincreasing the fineness of the output through the discharge cone 40. The increased fineness of the output is demonstrated by test results on a coal 'pulverizer of I the character described used in a cement ,kiln direct firing pulverized coal system, before and after'the installation of a classifier construe tion and arrangement in accordance with my in-- vention: 1 o

Original Present Fmeness installation arrangement Per cent Per cent Through'50 mesh 99. 95 100 Through 100 mesh.. 99. 52 99.94 Through 150 mesh. 96. 44 99. 48 Through 200 mesh.. 85.14 95. 55 Through 325 mesh 74. 88. 38

In the operation" of my invention the coarse material in efiect'is stripped from the circumference of the whirling stream of air and material in the turret chamber. 'This separating action can bevaried by altering the width of the bars 45 to thus alter the quantity of airand this condition. A substantial increase in fineness of the pulverizer output is thus obtainable with the described construction and arrangement,

while at the same time the wear on the classifier top plate due to coarse material accumulating and riding around thereon is substantially elimi- "hated.

changes may be made in the form of the apparatus and character of the carrier medium disclosed without departing from the spirit of the invention covered by the claims, and that certain features of the invention may sometimes be used without a. corresponding use 'of other features. In the claims, the word air is intended to generically cover anygaseous carrier medium suitable for removing pulverized material in themanner described. I

I claim: I

1. In a pulverizer comprising a housing enclosing grinding parts forming a grinding zone, means for delivering material to be pulverized to said grinding zone, means for. directing an air stream upwardly through said grinding zone to .sweepup pulverized material discharging therefrom, and anopening in'the top of said housing, the combination of a turret forming an upward continuation of said opening and having a discharge outlet, a rotary member symmetrically arranged at the lower end of said housing opening and having an annular plate Within the periphery of said housing opening, and means .onsaid plate for circumferentially discharging coarse particles separated in said plate.

2. In a pulverizer comprising a substantially cylindrical housing enclosing grinding parts forming a 'grindingzone, means for delivering material to be pulverized to said grinding zone, means for directing an air stream upwardly through said grinding zone tosweep up pulverized 'material discharging therefrom, and an opening in the top of said housing, the combination of a cylindrical turret forming an upward continuation of said opening and having a discharge outlet in the top thereof, a rotary classifier symmetrically arranged at the lower end and Within the periphery of said housing opening and having upper and lower annular plates, a circular series of impact'blades extending between said plates, and means on the upper side of said upper classifier plate for defiecting coarse particles depositing on'said upper plate towards saidgrinding zone. 7

3. Ina pulverizer comprising a housing 'enclosing grinding parts forming agrinding zone, means for'delivering material tobe pul erized to said grinding zone, means for directingan air stream upwardly through said grinding zone to sweep up pulverized materialdischarging therefrom, and an opening in the top of said housing, thecombination of a turret formingan upward continuationof said opening and having an air discharge outlet, a rotary classifier arranged within the periphery of said housing opening "and turret and depositing on said o f said housing opening.

ticles separated in said turret towardssaid grin mg zone, said upper plat and'said material directing means thereon having at least'a stilostantial part thereof extending within the periphery a. In a 'pulverizer comprising a closing grinding parts iorniing a grinding zone, means for delivering materi-al to be pulverized to said grinding none, means for directing an air stream upwardly through said grinding zone to sweep up pulverized material discharging therefrom, and'an opening in the top of said housing, the combination of a cylindrical turret forming an upward continuation of said opening and having a fiat top plate with a central discharge outlet therein, a rotary classifier symmetrically arranged at the lower end of said housing opening and having upper and lower annular plates, a circular series of impact blades extending between said plates, a conical member forming-a downwardly flaring extension of said turret outlet, and means on the upper plate of said classifier "for deflecting coarseparticles separated in said turret and depositing on said upper plate towards said grinding zone.

5. In a pulverizer comprising a housing enclosing grinding parts forming a grinding zone, means for delivering material to be pulverized to said grinding zone, means for directing an air stream upwardly through said grinding zone to sweep up pulverized material discharging therefrom, and a central opening in the top of said housing, the combination of a cylindrical turret forming an upward continuation of said opening and having a central discharge outlet in the top thereof, a rotary classifier symmetrically arranged at the lower end and within the periphery of said housing opening and having upper and lower annular plates, a circular series of angular impact blades extending between said plates, a conical member forming a downwardly flaring extension of said turret outlet, and means on the upper plate of said classifier for deflecting coarse particles separated in said turret towards said grinding zone including an upwardly extending flange on the inner periphery of said upper plate and a series of obliquely extending bars on the upper side of said upper plate.

6. In a pulverizer comprising a substantially cylindrical housing enclosing grinding parts including a vertical drive shaft, a lower grinding ring operatively connected to said drive shaft, a non-rotary upper grinding ring, and a circular row of rolling grinding elements between said grinding rings, means for delivering material to be pulverized to the inner side of said row, means for directing an annular air stream upwardly past the outer side of said grinding parts to sweep up pulverized material discharging therefrom, and a central discharge opening in the top of said housing, the combination of a cylindrical turret surrounding said opening and having an outlet in its top, a rotary classifier below said housing opening and operatively connected to said drive shaft, said classifier having upper and lower annular plates arranged within the periphery of said housing opening, a circular series of angularly spaced blades extending between said plates, and means on the upper plate of said classifier for directing coarse separated in said turret towardsrsaid housing grinding :zone.

1'7. In a pulverizer icompri'sing'a substantially cylindrica'i lipusing enclosing vgrinding parts inousing en- @5110 eluding :a *vre tic'al drive shaft, a lower grinding ring'sop'erati ly connected to said drive shaft, warren-rota upper grinding ring, and a circular of rolling grinding elements between said grinding rings, means for delivering material to ice-pulverized to the inner side of said row, means for directing an annular air stream upwardly past the outer side of said grinding parts to sweep up pulverized material discharging therefrom, panda central discharge opening in the top of said housing, the combination or a cylindrical turret surrounding and forming a continuation of said opening and having an outlet in its top, a rotary classifier below said housing opening and operatively connected to said drive shaft, said classifier having upper and lower annular plates, a circular series of blades extending,

between said plates, a conical member forming a downwardly flaring extension of said turret outlet, and means on the upper plate of said classifier for directing coarse particles separated in said turret and depositing on said upper plate towards said housing grinding zone.

8. A rotary classifier adapted to rotate about a vertical axis and comprising horizontally arranged upper and lower concentric annular plates, a circular series of angularly spaced blades extending between said plates, and bars on the upper side of said upper plate arranged substantially tangential to the inner circumference of said upper plate with their inner ends leading in the direction of rotation of said upper plate for outwardly deflecting separated material depositing on said upper plate.

9. A rotary classified adapted to rotate about a vertical axis and comprising horizontally arranged upper and lower concentric annular plates of different diameters, a circular series of angularly spaced blades extending between said plates in an inverted frusto-conical formation, and bars on the upper side of said upper plate, arranged substantially tangential to the inner circumference of said upper plate with their inner ends leading in the direction of rotation of said upper plate for outwardly deflecting separated material depositing on said upper plate.

10. A rotary classifier adapted to rotate about a Vertical axis and comprising horizontally arranged upper and lower concentric annular plates of different diameters, a circular series of angularly spaced blades extending between said plates in an inverted frusto-conical formation, and means on the upper side of said upper plate for outwardly deflecting material depositing on said upper plate including an upwardly extending flange on the inner periphery of said upper plate and obliquely arranged bars secured to the upper side of said upper plate at the outer side of said flange. I

11. A rotary classifier adapted to rotate about a'vertical axis and comprising horizontally ar ranged upper and lower concentric annular plates of different diameters, and a circular series of angularly spaced impact blades extending between said plates in an inverted frusto-conical formation, said blades having a V-shaped transcharge opening-in its upper'end fora gas carand means on the upper side of said classifieri 10 plate for directing coarse particles separatedin said turret and depositing on said plate into said housing; I

13. In combination, a housing having a circular discharge opening in its upper end for a;-l5

gas carrying vparticles of finely divided material in suspension, a' cylindrical turret forming an upward continuation of said housing opening and having a' gas discharge outlet .in the top thereof; a rotary classifier symmetrically arranged relative to saidhousing opening and having an upper annular plate arranged within the periphery of said housing opening, a lower plate, a circular series of spaced blades extending between said plates, and means on the upper side of said upper classifier plate for directing coarse particles separated in said turret and depositing on said upper plate into said housing.

THOMAS H. ARNOLD.

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