US2076288A

US2076288A - Pulverizing mill

Info

Publication number: US2076288A
Application number: US575453A
Authority: US
Inventors: Ervin G Bailey; Perry R Cassidy; Ralph M Hardgrove
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1931-11-16
Filing date: 1931-11-16
Publication date: 1937-04-06
Anticipated expiration: 1954-04-06

Description

April 6, 1937. E. BAILEY ET AL 2,076,288

PULVERIZ ING MILL Filed Nov. 16, 1931 4 Sheets-Shgaet l INVENTORS from G.Baz/Le err .Cass Rab fia/rdgrove BY TH E iR ORNEY April 6, 1937. E. G. BAILEY ET AL 2,076,288

PULVERIZING MILL Filed Nov. 16, 1931 4 Sheets-Sheet 2 g I g a '1 y 19 l 1.9 2 l E 186"- g m 3 IR ZTORNEY 4 April 6, 1937.

E. cs. BAILEY ET AL 88 PULVERIZING MILL Filed Nov. 16, 1931 4 Sheets-Sheet 3 INVENTORS GB Perr 13.62253 W E l T ORN Y j zzw.

April 6, 1937. E. e. BAILEY ET AL PULVERIZING MILL Filed Nov. 16, 1931 4 Sheets-Sheet 4 VENTORS Ervon My Ral nh I 1 718 j HE TO Patented Apr. 6, 1937 UNITED STATES PATENT OFFICE PULVERIZING MILL Application November 16, 1931, Serial No. 575,453 11 Claims. (01. 83-45) The invention relates to pulverizing mills, more particularly such mills wherein grinding balls are used. The invention is especially useful in connection with such mills wherein there is no air separation resulting from a continuous flow of air through the mill.

One object of the invention is the provision of a pulverizing mill wherein the material to be pulverized is given a greater number of successive pulverizations than has heretofore been possible. Another object is the construction of such a mill wherein the displacement of one or more grinding balls in the upper part of the mill will not affect other grinding balls in the same part of the mill, or the pulverizing operation carried out by grinding balls at a different level. A further object is the provision of a pulverizing mill having greater capacity per unit of floor space and per unit of head room than has heretofore been possible. Other objects will appear upon consideration of the following specification.

The invention is shown by way of illustration in the accompanying drawings, wherein- Figure l is a plan view of a mill constructed in accordance With the invention,

Fig. 2 is a vertical section on the line I1'II of Fig. 1,

Fig. 3 is a horizontal section on the line TIL-III of Fig. 2,

Fig. 4 is a horizontal section on the line IVIV of Fig. 2, and

Fig. 5 is a diagrammatic lay-out of a pulverizing plant in which the invention is employed.

Fig. 6 is a detail of Fig. 2.

In the drawings there is shown a puiverizing mill in comprising a casing i l and grinding rings cooperating with grinding balls therein. One of the grinding rings is a rotatable grinding ring 12 having two concentric ball races therein, these races comprising an inner b-all race l3 and an outer ball race l4. Separate sets of grinding balls [5 and 16 respectively operate in the ball races l3 and M. A separate grinding ring is disposed opposite each set of balls, a grinding ring l'l cooperating with the inner row of balls l5 and a grinding ring i8 cooperating with the outer set of balls I6.

The separate grinding rings l1 and I8 each cooperating with the balls I5 and I6 are stationary and do not rotate, being held against rotation in any convenient manner. As here illustrated, the grinding ring i8 is held against rotation by contact between a lug [8a. thereon and a lug Ila. on the casing H; and the grinding ring I1 is held against rotation by contact between lugs Ila thereon, and lugs I811 on the grinding ring I8. However, the grinding rings may be moved slightly in a vertical direction, each ring being held down upon the grinding balls with which it coacts by resilient compression means. The resilient compression means are here shown as a set of compression springs l9 acting upon the inner grinding ring I1 and a set of compression springs 20 acting upon the outer grinding ring i8. Provision is made for independently adjusting the compression of each of the springs l9 and 20, such adjusting means is here indicated by the boltslSf and 20 respectively. By providing separate sets of springs for each of two independent grinding rings, it is possible for a piece of hard material to pass beneath one or more balls in one row without disturbing the operation of the other row of grinding balls.

Beneath the rotatable grinding ring [2 there is provided another row or ring of grinding balls 20 2|; which are carried in a lower grinding ring 22 disposed in stationary relationship to the mill. Thus pressure is transmitted from: the springs l9 and 20 to the upper grinding rings l1 and I8, thence to the upper grinding balls 15 and I6, 2 and from them to the intermediate rotatable grinding ring l2, whence it is carried to a lower row of grinding balls 2i and to a lower grinding ring 22. By means of the arrangement just described provision is made for varying the grind- 0 ing pressure throughout the mill in accordance with the hardness of the material to be pulverized. The intermediate rotatable grinding ring I2 is rotated by a vertical shaft 23, carried by a thrust bearing 23'. The vertical shaft 23 is keyed to a frame 37 which rotates therewith, and a lug 3111 on the frame 31 coacts with a lug l2a on the intermediate grinding ring l2 as rotated. By means of this arrangement it is possible for the intermediate grinding ring to float vertically, 40 theoretically transmitting no pressure to the vertical shaft 23. As a practical matter there will be friction between the faces of the lugs lZa and 31a, which will result in some vertical thrust being transmitted to the shaft 23. A spur gear 4 it, provided upon the vertical shaft 23, meshes with a spur gear 25 on a vertical stub shaft 26, on which there is also a bevel gear 21. The bevel gear 21 on the stub shaft 26 meshes with another bevel gear 28 on a drive shaft 29. The 50 apparatus is driven from the drive shaft 29 by interposing the stub shaft 25 between the vertical shaft 23 and the drive shaft 29, and by operating the vertical shaft 23 from the stub shaft 26 by means of the

spur gears

24 and 25 provision is 55 to the top of the mill casing H, where it enters the mill. Upon entering the mill the material to be ground falls upon the top of an upwardly inclined conical member 32 which is carriedby the rotatable intermediate grinding ring l2, and

thence passes by centrifugal force and gravity beneath the inner row of upper grinding ballsd 5; An upwardly extending fin 33 on the conical member 32 assists in moving the material to be pulverized beneath the inner row of upper grind ingballs l5. The firststage of pulverization is carried on between the inner row of upper grinding balls l5'and. the inner grinding race IE! on the intermediate grinding ring 92, the material passing outwardlyby means of centrifugal force to a position between the outer row-of upper grinding balls !6 and the outergrinding race M; In this latter position,.the-material undergoesa second stage of pulverization and passes outwardly of the mill, the fine material descendingthrough an annular opening 34 and the outer edge of the intermediate grinding ring. The annular opening 34 is adjustable, an annular ring 35 being provided which may belrnoved nearer to or further. from the intermediate .grindingring by means ofa bolt 35a. Material which is too coarse to pass throughthe annular opening S ipiles up outside of the outer row of grinding'balls l6 and eventually; slides back-into the; grindingrace M by gravity.

Material passing through the annular opening 34- falls to a position outside of the lower row of grinding balls 2!, whence it passes by gravity between this lower. rowof grinding balls and the lower grinding ring 22. Here the material under goes the third stage of its pulverization, working inwardly andfalling through an annular opening 36 between the lower grinding ring 22eand a member'3'l rotatably carried by the vertical shaft 23;

From theforegoing it will be apparent thatthe materialsare moved in a generally radial directionof theemillduring. the successive stages of pulverization; beneath the two upper rows of grinding balls, and are there subjected to successive. stages of pulverizationat substantially the same elevation; The materials are then dropped to'a lower plane, that is to say, to the level of the lower'row of grinding balls 2!, and are there passedin an opposite radial direction while being subjected to further pulverization.

Flalling through the annular opening 36, the material, which has now been pulverized, enters a chamber 33 which is swept by aplurality of sweeps 39 carried by the member 3'1; The plurality of sweeps wimp-art a rotary action to the pulverized material which is carried by centrifugal force -to-a chute Q0 which carries it out of the mill.

As illustratedin Fig. 5, the chute 49 may pass the pulverized material to a bucket conveyor 4!, which in turn elevates the material to a second chute 42, which delivers the material to a mechanical separator 43 having a hopper bottom 44a. The fine material is separated from the coarse and conveyed to the hopper bottom Ma whence it may be withdrawn through a chute 45 to a suitable conveying apparatus 46, here illustrated as a Fuller-Kinyon pump. The coarse material is deposited in an inner hopper 44 and returned to the pulverizer through a return pipe 4'! for further pulverization.

By subjecting the material to a greater number of pulverizing operations than has been possible in previously constructed apparatus, and by separating the fine material so pulverized from the coarse externally of the mill, more rapid travel of the material through the mill is effected and a greater capacity per unit of floor space and head room isrealized.

The embodiment of the invention illustrated in the drawings and specifically described in this specification, is presented merely by way of example, and is not to be considered as limiting "the invention. With this understanding therefore, we claim- 1. A pulverizer comprising a casing. enclosing an upper circular row of rolling grinding elements constituting. an upper pulverizing stage having an outward. flow of material therethrough, anintermediate grinding ring supporting said upper row of elements, an upper grinding ring supportedpn said upper row of elements, means for exerting a grinding pressure on said upper row of elements, a material feed opening in the upper portion of said casing arranged to deliver material to the inner side of said upper row of elements, a lower grinding ring arranged below said upper row of elements, alower row of rolling grinding elements positioned between. said intermediate and lower grinding rings and constituting a lower pulverizinglstage receivingmaterial by gravity fromlsaid upper pulverizingv stage andhaving inward flow of material therethrough, means at the. outer side of andout of contact with said upper row of elements and arranged to cooperate with said intermediate grinding ring in partly damming the outward flow of material from said upper pulverizing stage, and rotary means receiving and ejecting from saidcasing the material leaving theinner side of saidllower row of elements.

2. A pulverizer comprising a casing enclosing amupper circular row of rolling grinding elements constituting an upper pulverizing stage having an outward flow of material therethrough, an intermediate rotary grinding ring supporting said, upper row of elements, an upper grinding ring supported on said upper row of elements, means for exerting a grinding pressure onisaid upper row of elements, a material feed opening in the upper portion of said casing, means on said intermediate ring arranged to receive material from said feed opening and to direct the material to the inner side of said upper row of elements, a lower grinding ring arranged below said upper row of elements, a lower row of rolling grinding elements positioned between said intermediate and lower grinding rings and constituting a lower pulverizing stage receiving materialby gravity from said upper pulverizing stage and having an inward flow of material therethrough, adjustable means forming a ledge gap of variable flow area between said rotary intermediate ring and said casing in the path of material flow between said upper and lower pulverizing stages, and rotary means receiving and ejecting from said casing the material leaving the inner side of said lower row of elements.

3. A pulverizer comprising a casing enclosing upper inner and outer concentric rows of rolling grinding elements constituting first and. second pulverizing stages having an outward flow of material therethrough, a rotary intermediate grinding ring supporting said inner and outer rows of elements, a plurality of concentric stationary upper grinding rings respectively supported on said inner and outer rows of elements, means for exerting independently adjustable grinding pressures on said inner and outer rows of elements, a material feed opening in the upper portion of said casing arranged to deliver material to the inner side of said upper inner row of elements, a lower stationary grinding ring, a

' lower row of rolling grinding elements positioned between said intermediate and lower grinding rings and constituting a third pulverizing stage receiving material by gravity from said second pulverizing stage and having an inward fiow of material therethrough, means at the outer side of and out of contact with said upper outer row of elements and arranged to cooperate with said intermediate grinding ring in partly damming F the outward fiow of material from said second pulverizing stage, and rotary means receiving and ejecting from said casing the material leaving the inner side of said lower row of elements.

4. A pulverizer comprising a casing enclosing upper inner and outer concentric rows of rolling grinding elements constituting first and second pulverizing stages having an outward fiow of material therethrough, a rotary intermediate grinding ring having inner and outer grinding tracks supporting said inner and outer rows of elements respectively, said outer track being arranged at a higher elevation than said inner track to retard the fiow of material between said first and second pulverizing stages, .a plurality of concentric stationary upper grinding rings respectively supported on said inner and outer rows of elements, means for exerting independently adjustable grinding pressures on said inner and outer rows of elements, a material feed opening in the upper portion of said casing arranged to deliver material to the inner side of said upper inner row of elements, a lower stationary grinding ring, a lower row of rolling grinding elements positioned between said intermediate and lower grinding rings and constituting a third pulverizing stage receiving material by gravity from said second pulverizing stage and having an inward flow of material therethrough, means at the outer side of and out of contact with said upper outer row of elements and arranged to cooperate with said intermediate grinding ring in partly damming the outward flow of material from said second pulverizing stage, and rotary means receiving and ejecting from said casing the material leaving the inner side of said lower row of elements.

5. A pulverizer comprising a casing enclosing inner and outer concentric rows of rolling grinding elements, a rotary grinding ring supporting said inner and outer rows of elements, inner and outer concentric non-rotary grinding rings respectively supported on said inner and outer rows of elements, means for exerting independent grinding pressures on said inner and outer rows of elements comprising a circular series of compression springs adjacent the side wall of said casing and arranged to act on said outer grind ing ring, and a second series of compression springs arranged to act on said inner grinding ing elements, a rotary grinding ring supporting said inner and outer rows of elements, inner and outer concentric non-rotary grinding rings respectively supported on said inner and outer rows of elements, means for exerting independent grinding pressures on said inner and outer rows of elements comprising a circular series of compression springs adjacent the side wall of said casing and acting solely on said outer grinding ring and extending through the top of said casing, and a second series of compression springs acting solely on said inner grinding ring and extending through the top of said casing and arranged in the same circular row as said first named series of compression springs.

'7. A pulverizer comprising a casing enclosing inner and outer concentric rows of rolling grinding elements, a rotary grinding ring supporting said inner and outer rows of elements, inner and outer concentric non-rotary grinding rings respectively supported on said inner and outer rows of elements, means for exerting independent grinding pressures on said inner and outer rows of elements comprising a circular series of compression springs held between said outer grinding ring and the top of said casing adjacent the side wall of said casing, bracket arms extending outwardly from said inner grinding ring, and a second series of compression springs held between said inner grinding ring bracket arms and the top of said casing and arranged in the same circular row as said first named series of compression springs.

8. A pulverizer comprising a casing enclosing inner and outer concentric rows of rolling grinding elements, a rotary grinding ring supporting said inner and outer rows of elements at different elevations, inner and outer concentric non-rotary grinding rings respectively supported on said inner and outer rows of elements, means for exerting independent grinding pressures on said inner and outer rows of elements comprising a circular series of compression springs held between said outer grinding ring and top of said casing adjacent the side wall of said casing, a second series of compression springs held between said inner grinding ring and the top of said casing and arranged in the same circular row as said first named series of compression springs, and externally operable means for separately adjusting the compression of each of said compression springs.

9. A pulverizer comprising a casing enclosing upper inner and outer concentric rows of rolling grinding elements constituting first and second pulverizing stages having an outward fiow of material therethrough, a rotary intermediate grinding ring having inner and outer grinding tracks supporting said inner and outer rows of elements respectively, said outer track being arranged at a higher elevation than said inner track to retard the flow of material between said first and second pulverizing stages, a plurality of concentric non-rotary upper grinding rings respectively supported on said inner and outer rows of elements, means for exerting independently adjustable grinding pressures on said inner and outer rows of elements, a material feed opening in the upper portion of said casing arranged to deliver material to the inner side of said upper inner row of elements, a lower non-rotary grinding ring, a lower row of rolling grinding elements positioned between said intermediate and lower grinding rings and constituting a third pulverizing stage receiving material from said second pulverizing stage and having an inward flow of material therethrough, and rotary means receiving and ejecting from said casing the pulverized material leaving the inner side of said lower row of elements.

10. A-pulverizer comprising a casing enclosing a lower rotary grinding ring, inner and outer concentric rows of rolling grinding elements supported on said lower grinding ring, vertically movable inner and outer concentric non-rotary grinding rings mounted on said inner and outer rows of elements respectively, means extending between said outer grinding ring and said casing for preventing rotation and permitting tilting of said outer grinding ring, and means extending between said inner and outer grinding rings for preventing rotation and permitting tilting of said inner grinding ring.

11. A pulverizer comprising a casing enclosing a lower rotary grinding ring, inner and outer concentric rows of rolling grinding elements supported on said lower grinding ring, vertically movable inner and outer concentric non-rotary grinding rings mounted on said inner and outer rows of elements respectively, means for exerting independent grinding pressures on said inner and outer grinding rings, means extending between said outer grinding ring and said casing for preventing rotation and permitting tilting of said outer grinding ring, and means extending between said inner and outer grinding rings for preventing rotation and permitting tilting of said inner grinding ring.

ERVIN G. BAILEY.

PERRY R. CASSIDY.

RALPH M. HARDGROVE.