US2389844A - Pulverizer - Google Patents

Description

Nov. 27, 1945. 3,3, so 2,389,844

PULVERI'ZER Filed Sept. 19, 1942 2 Sheets-Sheet 1 I 62 y) 79 u 20 q) INVEN] OR.

BY Gear 8 B Eberso/e I ATTORNEY Nov. 27, 1945. e. B. EBERSOLE 2,389,844

PULVERI ZER Filed Sept. 19, 1942 2 Sheets-Sheet 2 III ' INVENTOR.

By 995. Ebersole ATTORNEY Patented Nov. 27, 1945 mvmuzan George B. Ebersole, Akron, Ohio, asslgnor to The Babcock & Wilcox Company, Jersey City, N. J., a corporation of New Jersey Application September 19, 1942, Serial No. 458,935

13 Claims.

The present invention relates to'the construction and operation of pulverizers of the type having rolling grinding elements located between operating relatively movable grinding rings and particularly to pulverizers of the type described designed for pulverizing coal, cement materials and the like at moderate capacities and in which the pulverized material is removed from the pulverizer in suspension in a gaseous carrier medium, such as the pulverizer shownv in the Schwartz U. S. Patent No. 2,275,595.

The general object of my invention is the provision of a pulverizer of the type described which is characterized by an improved construction and arrangement of the parts in the air entranc area of the pulverizer. A further and more specific object is the provision of an improved pulverizer construction for disposing of ungrindable portion of the material undergoing pulverization, such as the pyrites constituents of coal, with a minimum wear on the pulverizer parts. A further specific object is the provision of an improved pulverizer construction for preventing material from working inwardly between certain rotary and stationary parts of the pulverizer, and thereby increasing the load on the drive mechanism of the pulverizer.

The various features of novelty which characterize my invention are pointed out with particularity in the claim annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of my invention.

Of the drawings:

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

Fig. 2 is an enlarged sectional View of some of the parts shown in Fig. 1 at a different location;

Fig. 2 is a horizontal section taken on the line 33 of Fig. 2;

Fig. 4 is a fragmentary sectional elevation illustratin a modified construction; and

Figs. 5 and 6 are views similar to Fig. 4 illustrating further modifications.

The pulverizer illustrated has a substantially cylindrical sectional housing i0 having a base section II with a slightly conical bottom plate mounted on a foundation H. The base section contains the pulverizer drive assembly including a horizontal pinion shaft l3 arranged to drive a vertical drive shaft l4 axially arranged in the housing. The drive shaft I4 extends upwardly through bearings arranged in a base plate l5 forming the top of the base section i I. The upper section l6 of the housing is of substantially cylindrical form and detachably secured in the base section plate IS. The upper housing section encloses the grinding part of the pulverizer, which comprises a drive yoke ll of generally conical form keyed on the upper part of the drive shaft M. An annular lower grinding ring I9 is supported on and keyed to the lower outer portions of the drive yoke. The upper face of the grinding ring 19 is shaped to form a track for a circular row of rolling grinding elements 20, preferably ball of wear resistant alloy steel. The balls 20 support an upper grinding ring 2| having a ball track formed in its lower face. An annular spider 22 mounted on the upper ring is provided with lugs 23 arranged in guides on the inner wall of the housing section It for preventing rotation, but permitting vertical movement, of the spider and upper grinding ring. A esilient grinding pressure is exerted downwardly on the grinding parts by coil springs 24 engaging the spider,

The material to be pulverized i supplied through a feed spout 25 to the inner side of the upper grinding rin and ball row and deposits on the inclined upper surface of the drive yoke H, being distributed throughout the grinding area by the rotation of the drive yoke and associated parts. The material fiows outwardly over the upper surface of the yoke and lower grinding ring, is pulverized between the relatively moving balls and grinding rings, and discharge at the outer edge of the lower grinding ring I9.

The pulverizer disclosed is of the air swept type having an annular stream of carrier air passing upwardly through the pulverizer grinding zone and through a material classifier 30 to the pulverizer outlet 3|. The carrier air is normally preheated and supplied under pressure by a. suitable forced draft fan to an annular wind box 32 surrounding the lower part of the housing section It. The annular stream of carrier air passes into the pulverizer housing through passages hereinafter described, and upwardly through a Venturi-shaped throat passage 33 formed between the outer side of the lower grinding ring I 9 and an annular throat plate 35 secured to the inside of the housing and shaped to provide a high velocity stream of air sweeping past the discharge side of the lower grinding ring, the flow areas and air velocities being proportioned to prevent any pulverized material within the designed density range from dropping through the throat and cloasins the entering air passages. The air stream does not prevent the downward discharge of relatively unpulverizable mall size particles or high density, such as is present in the pulverizetion of coal having a high pyrites or sulphur con tent. In such cases the heavy particles tend to drop through the throat against the rising air stream and into the subjacent portion or the pulverizer. A portion of the throat ring is also provided with a segmental spring-pressed relief gate 86 for the passage of any pieces oi unpulverizable foreign material, such as tramp iron, and allowing the same to drop into' the lower portion or the housing. At a point opposite the location of the relief gate 35", the base section of the housing is provided with a compartment 40 for the collection of such unpulverizable material. The compartment 40 communicates with the grinding zone through a small opening 4| in the housing base plate below which a slidable gate 42 is mounted and manually operated through a rack and pinion system 43 to open and close the opening 4|,

In accordance with my invention the pulverizer parts are constructed to facilitate the elimination oi unpulverizable material without excessive wear on the material contacted parts, such as tends to occur when sweeps or plows are mounted on the lower grinding ring for moving the unpulverizable material to the discharge opening 4|. Such material would ordinarily drop through the air throat onto the upper surface of the base plate, and unless removed would tend to work its way into the space between the base plate and rotating lower grinding ring or yoke, increasing the frictional wear on those parts. Sulphur balls in this area are also highly objectionable as they tend to freeze the rotating parts to the base plate when the pulverizer is shut down and thereby increase the load on the drive mechanism when again starting up. This freezing of the parts is accentuated by the thermal contraction of these parts when no longer subject to the preheated air I or the heat developed during the grinding operation.

In the construction illustrated in Figs. 1-3 the rotating drive parts and base plate are so constructed that any such action is minimized. For

.this purpose the drive yoke I1 is terminated radially short of the outer side of the lower grinding ringl9, and the latter provided with a depending annular skirt 50 extending downwardly beyond the outer edge of the yoke to a point having a slight clearance from the base plate I5. The lower end of the skirt projects outwardly in the form of a lip 5| to provide a surface on which material dropping into that area can be supported and carried around towards the discharge opening 4|. The supporting. action of the lip is facilitated by the relative arrangement of a circular series or segmental filler plates 55 located on the inclined bottom of the wind box and extending downwardly towards the skirt lip 5| to form a narrow annular slot or gap 56 therebetween. The plates 55 tend to direct any material depositing thereon downwardly onto the rotating lip. The gap 56 is enlarged immediately above the discharge opening 4| by shortening the corresponding plate 55, as shown in Fig. 1.

The depending annular skirt on the lower grinding ring has its inner side arranged at an angle to and spaced from the outer side of the drive yoke II. This construction provides an upwardly tapering space 51 which is occupied by an upwardly tapering annular bafiie ring 58 on the base plate l5 proportioned to form a narrow annular inverted V -shaped space between the stationary and rotating parts. 'This baille construction obstructs'the movement 01 any material into the space between the bottom of the drive yoke and base plate.

The angular rotation of th lower grinding ring is indicated by the direction of the arrow in Fig. 3. Consequently the pulverized coal leaving the upper'suriace of the grinding ring tends to flow over the outer edge thereof at an angle to but in the same general direction as the rotation of the lower ring. The pressure drop through the throat section of the pulverizer can beappreciably reduced when the air from the wind box enters the pulverizing zone in approximately the same direction as the flow of fuel. For this purpose adjoining segmental iiller plates 55 are provided with curved vertical blade sections 6|] and 6| relatively arranged thereon to form a circular series of outwardly-tapering composite curved blades or vanes 62 forming passages 63 therebetween curving inwardly in the direction of rotation of the lower grinding ring. The vanes 62 terminate at their inner ends opposite posts 64, between the plates 55 and forming spaced continuations of the pulverizer casing and the discharge ends of the air passages. With this vane arrangement the enterin air is distributed about the circumference of the throat section and directed obliquely to the normal direction of pulverized material leaving the grinding zone, i. e. at an angle of approximately 45 thereto. Confining the entering air to the curving passages 63 facilitates the movement of the unpulverizable material down the plates 55 and onto the tip 5|, and thus to the discharge opening 4|.

While in Figs. l-3 the plates 55 formin the stationary seal ring for the grinding ring skirt lip 5| are formed integrally with the vanes 60 and 6|, the seal ring can be separately formed,

- above the discharge opening 4| to permit the material carried by the lip 5| to discharge thereto. In this modification the baflle ring 58 is separately formed and secured to the base plate I5 to provide a steeply inclined annular space between the baille ring and grinding ring skirt.

In .the modified constructions illustrated in Figs. 5 and 6, the annular supporting lip 5| is formed on a peripheral portion of the drive yoke which extends beyond the outer side of the grinding ring I9. The projecting portion can be integrally formed as shown in Fig. 5 or by a circumferential band 15 welded to the periphery of the drive yoke, as shown in Fig. 6. Ahorizontally arranged seal ring Hi is secured to the pulverizer casing opposite the lip 5| in Fig. 5

' lower grinding ring at an oblique angle thereto due to the rotation of the ring. The pulverized material is swept up by the annular air stream entering through the passages 63 and swirling upwardly through the air throat, the materialladen air then passing upwardly to the classifier and pulverizer outlet. The particles of material not swept up by the air stream due to their size or density fall through the air throat into the air entrance area at the outer side of the lower grinding ring. These particles collect on the bottom of this section and are carried around by the lip formed on the lower grinding ring skirt or drive yoke until the recessed portion of the seal ring is reached and the particles permitted to fall into the discharge opening II. The air stream swirling in the direction of rotation of the lower. grinding ring aids the movement of these particles towards the discharge opening. The arrangement of the supporting lip on the lower grinding ring is especially advantageous as this member is normally mad with a harder wearing surface than the Yoke, with corresponding longer life, and because replacement of the ring'due to excessive wear in the track area also restores the original lip outside diameter. With the described lip and seal ring constructions, the bottom of the pulverizer is kept comparatively clean of foreign material.

While in accordance with the provisions of the statutes I have illustrated and described herein the best forms of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features. In the claims, the word "air is intended to generically cover any gaseous carrier medium suitable for removing pulverized material in the manner described.

I claim:

1. A pulverizer comprising a casing having an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, means for efiecting relative movement of said grinding elements and ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber Opening to said casing at the outer side of said grinding ring and below the level of said grinding elements a discharge opening for unpulverized material at the outer side of said grinding ring and adjacent said air entrance opening, and an outwardly projecting annular lip member at the outer side of and rotating with said grinding ring, said lip member having an upper surface portion horizontally arranged and in position to receive unpulverized material discharged from" said grinding ring and carry said unpulverized material towards said discharge opening.

2. A pulverizer comprising a casing having an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, means for efiecting relative move-' ment of said grinding elements and ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer outer side of said grinding ring and below the level of said grinding elements, a'discharge opening for unpulverized material at the outer side of said grinding ring and adjacent said air entrance opening, an outwardly projecting annular lip at the outer side of and rotating with said grinding ring shaped and arranged for carrying unpulverized material to said discharge opening, and means forming a stationary sea1 ring in the space between said lip and casing and cooperating with said lip to form a narrow annular slot therebetween.

3. A pulverizer comprising a casing having an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, means for effecting relative movement of said grinding elements and ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side of said grinding ing and below the level of said grinding elements, a discharge opening for unpulverized material at the outer side of said grinding ring and adjacent said air entrance opening, and a depending skirt on the outer side of said grinding ring having an outwardly projecting lip with an upper surface portion horizontally arranged and in position to receive unpulverized material discharged from said grinding ring and carry said unpulverized material to said discharge opening.

4. A pulverizer comprising a casing having an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, means for efiecting relative movement of said grinding elements and ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing an annular stream of air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side of said grinding ring and below the level of said grinding elements, a discharge opening for-unpulverized material at the outer side of said grinding ring and adjacent said air entrance opening, 3, depending skirt on the outer side of said grinding ring having an outwardly projecting lip with an upper surface portion horizontally arranged and in p0 sition to receive unpulverized material discharged from said grinding ring and carry said unpulverized material to said discharge opening, and means forming a stationary seal ring in the space between said skirt and casing.

5. A pulverizer comprising a casing having a base plate and an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, an annular drive yoke superjacent said base plate and supporting said grinding ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side of said grinding ring and below the level of said grinding elements, a discharge opening for unpulverised material in said base plate at the outer side or said drive yoke and adjacent said air entrance opening, and an outwardlymrojecting lip on the outer side or said drive yoke, said lip having an upper surface portion horizontally arranged and in position to receive unpulverized material discharged from said grinding ring and carry said unpulverized material toward said dis charge opening.

6. A pulverizer comprising 'a casing having a base plate and an outlet for material-laden air at its upper end and enclosing a horizintally arranged rotary grinding ring, rotary grinding elements on said grinding ring. an annular drive yoke superiacent said base plate and supporting said grinding ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer side of said grind: ing ring to sweep up pulverized material discharging thereirom including an air supply chamber opening to said casing at the outer side of said grinding" ring and below the level of said grinding elements, a discharge opening idr unpulverized material in said base plate at the outer side of said grinding ring and adjacent said air entrance opening, a depending skirt on the outer side of said grinding ring beyond said drive yoke, and a baille ring on said base plate projecting upwardly into the space between said skirt and drive yoke to obstruct the inward flow of unpulverized material.

7. A pulverizer comprising a casing having a base plate and an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring,-an annular drive yoke superjacent' said base plate and supporting said grinding ring, means for delivering material to be pulverized to the inner side or said grinding elements, means for directing an annular stream of air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side of said grinding ring and below the level of said grinding elements, a discharge opening for unpulverized material in said base plate at the outer side of said grinding ringand adjacent said air entrance opening, a depending skirt on the outer side of said grinding ring beyond said drive yoke and having means for carrying unpulverized material to said discharge opening, means forming a stationary seal ring in the space between said skirt and casing, and a baiiie ring on said base plate projecting upwardly into the space between said skirt and drive yoke to obstruct the inward flow of unpulverized material between said base plate and drive yoke.

8. A pulverizer comprising a casing having an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, means for eflecting relative movement of said grinding elements and ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing an annular stream oi air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including,an air supply chamber and an air entrance opening from said chamber to said casing at the outer side or said grinding ring and below the level of said grinding elements, and

assaass a circular series or curved vanes in said air entrance opening defining air passagescurving inwardly in the normal direction 01' rotation of said grinding ring.

9. A pulverizer comprising a casing having an outlet for material-laden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding rin means for eflecting relative movement of said grinding elements and ring, means for delivering material to bepulverized to the inner side of said grinding elements, means for directing an annular stream or air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side. of said grinding rin and below the level 01' said grinding elements, a discharge opening for unpulverized material at the outer side of said grinding ring and adiacent said air entrance opening, a depending skirt on the outer side of said grinding ring having means for carrying unpulverized material to said discharge opening, and a circular series of curved vanes in said air entrance opening defining air passages curving inwardly in the normal direction of rotation 0! said grinding ring.

10. A pulverizer comprising a casing having an outlet for material-Jaden air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, means for eflecting relative movement of said grinding elements and ring. means ior delivering material to be pulverized to the inner side or saidgrinding elements, means for directing an annular stream 01' ai upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side of said grinding ring and below the level or said grinding elements, a discharge opening for unpulverized material at the outer side oi said grinding ring and adjacent said air entrance opening, a depending skirt on the outer side 01' said grinding ring havin means for carrying pulverized material to said discharge opening, a circular series of plates in said air entrance opening forming a stationary seal ring surrounding said skirt, and'a circular series of curved vanes on said plates defining air passages curving inwardly in the normal direction of rotation of said grinding ring.

11. A pulverizer comprising a casing having a stationary base plate and an outlet for materialladen air at its upper end and enclosing a horizontally arranged rotary grinding ring, rotary grinding elements on said grinding ring, an annular drive yoke superjacent said base plate and supporting said grinding ring, means for deliv- -ering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer side of said grinding ring to sweep up pulverized ma- ,tween said drive yoke and base plate.

- 12. A pulverizer comprising a casing having a stationary base plate and an outlet for materialladen air at its upper end and enclosing a horizontally arranged rotary grinding ring, rotary grinding elements on said grinding ring, an annular drive yoke superjacent said base plate and supporting said grinding ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of ai upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber opening to said casing at the outer side of said grinding ring and below the level of said grinding elements, a discharge opening fo unpulverized material in said base plate at the outer side of said grinding ring and adjacent said air entrance opening, and a balile ring on said base plate projecting upwardly into the space below said grinding ring and arranged to obstruct the inward fiow of unpulverized material between said drive yoke and base plate.

13. A pulverizer comprising a casing having a stationary base plate and an outlet for materialladen air at its upper end and enclosing a horizontally arranged rotary grinding ring, rolling grinding elements on said grinding ring, a circular drive yoke superjacent said base plate and supporting said grinding ring, means for delivering material to be pulverized to the inner side of said grinding elements, means for directing a stream of air upwardly past the outer side of said grinding ring to sweep up pulverized material discharging therefrom including an air supply chamber and an air entrance opening from said chamber to said casing at the outer side of said grinding ring and below the level of said grinding elements, a discharge opening for unpulverized material in said base plate ad jacent to the outer side of said grinding ring and said air entrance opening, a depending skirt on the outer side of said grinding ring beyond said drive yoke and having means for carrying material depositing thereon tosaid discharge opening, and said base plate having an upper inclined surface arranged to obstruct the inward flow of material through the space below said skirt.

GEORGE B. EBERSOLE.

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