US2041287A

US2041287A - Ball mill pulverizer

Info

Publication number: US2041287A
Application number: US589919A
Authority: US
Inventors: Frisch Martin
Original assignee: Foster Wheeler Inc
Current assignee: Foster Wheeler Inc
Priority date: 1931-10-20
Filing date: 1931-10-20
Publication date: 1936-05-19
Anticipated expiration: 1953-05-19

Description

May19,1936. y M me@ 2,041,287

I l BALL MILL PULVERIZER Filed oct. 2o, 1951 2 sheets-s116611 3%wwil f f i9 May 19, 1936.

' M. FRISCH BALL MILL PULVERIZER Filed Oct. 20, 1931 .2 Sheets-Sheet 2 K INVENTOR M@ www 'L ATTORNEY atente lMay 19, i936 v 8 Claims.

My invention relates to pulverlzing apparatus and more particularlyto pulverizlng apparatus employing a plurality of metal grinding balls loosely arranged in the grinding chamber;y that is, balls which have considerable latitude of free movement relative to each other, as distinguished from balls which operate in. a groove, race or other defined path of movement.

In particular, my invention relates to pulverizers'oi the vertical axis type as distinguished from horizontal axis pulverizers.

The primary object of the present invention is to provide a pulverizer of the type set forth in which the balls not only Contact the stationary and rotatable parts of the structure enclosing the balls, but also roll against each other, thus producing grinding by both crushing and attrition. Another object ofthe invention is to reduce liner wear by providing slow movement between the liner elements and balls immediately adjacent the liner relative to the movement of the more active balls. A still further object of the invention is to provide an emcient distribution of air in a pulverizer of the type referred to.

Other objects and the advantages of my invention will be made clear upon consideration of the following description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, which form a part of this specification and of which:

Fig. l isa vertical cross-sectional view of a pulverizer embodying the invention and is taken on the line I--I of Fig. 2;

Fig. 2 is a horizontal cross-sectional view taken on the line 2--2 of Fig. l;

Fig. 3 is a horizontal cross-sectional view taken on'the line 3-3 of Fig.' 1;

Fig. 4 is a. horizontal cross-sectional view, looking upward, taken on the line 4-4 of Fig. l;

Fig. 51s a plan view of an element of the pulverirer shown in Fig. l;y

Fig. 6 is a cross-sectional view taken on line tof Fig. and

Fig. .7 is a bottom view of the member shown in Fig. 5.

The pulverizer is mounted on a suitable foundation it. Immediately resting on the .foundation is a base plate II. Mounted on the base plate is acylindrical casing or housing member I2 which,

the

together with the base plate lll encloses the grind- BALL MILL PULVEI l These liners are made Price'- f y Martin Frisch, New York, N. Y., gnor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York application october zo, 1931, sel-ni No. 569,919

in a number of separate piebes so that they may be removed and replaced'when worn. As shown in the drawings, the liners'cover the base plate Il within chamber I3 and line the sides upwardly. to a point above the part of the chamber containing the balls. The liner portion may be considered -as a stationary bowl constituting a grinding or crushing zone.

A plurality of balls l5 are loosely contained within chamberi3. A charging door I li is provided for 4admitting the balls to the chamber.

rThe balls are of dierent sizes, as shown. In

through the chamber I3. Depending from the baseV plate Il is a housing or support i8 enclosing or carryingarollerbearing I9 and an adjustable step bearing 2t. The-shaft is supported on the step bearing and is journalled in the roller bearing. Mounted on shaft I'I between roller bearing I9 and step bearing 20 is a bevel gear 2l. This gear 2l meshes with a bevel gear 22 mounted on a horizontal shaft 23, which may be driven from any suitable source. A stuiling box 9 is provided where the shaft I1 passes through base plate I I.

The housing I2 has a cover 24 on which is mounted a hollow supply member 25. A roller guide bearing 26 is mounted in member 25 and serves to journal the upper end of shaft Il.

Mounted on shaft Il is a tubular feeding member 28 suitably secured thereto by webs 29. The tubular" member is concentrically mounted with respect to the shaft Il and constitutes a substantially large air inlet duct. It rotates with the'shaft I'II.V Attached to the lower end of tubular member 28 is an impeller 30. Impeller 30 is formed with a plurality of outwardly extending arms or blades 3l. These arms or blades 3l extend into the grinding zone and contact the balls I5. The arms or blades 3| are hollow and are open at the bottom, but closed at the top, permitting air and coal or other material to be ground to flow downwardly therethrough and out at the bottom thereof. Each armor blade 3| is covered by a suitable liner element which may be removably bolted or riveted thereto. Mounted on shaft I1 within the impeller'3ll is a hub 33 from which webs 34 extend to the outer portion of the impeller. l

Also mounted on shaft I1 at the lower part of the chamber I3 is what may be termed a slinger or expeller 35, shown in detail in Figs. 5, 6, and 7. The slinger is rotatable with the shaft I1. On its upper side it has outwardly extending ribs\or vanes 36. On its lower side it has curved air vanes 31 for drawing air upwardly through stuffing box 9 and preventing coal from entering the stuiilng box.

Member 25 is connectedto a source of air supply, as a fan 39, and connected to a source ofv fuel, as feeder 40. The cover 24 is provided with a tangential outlet 4I for the final product which may be a mixture of pulverized coal and air to be burned.

Separator or

classifier plates

42 and 43 are provided within the apparatus, plate 42 being secured to member 23, and plate 43 being secured to the casing. A plurality of spaced projections 44 of curved configuration preferably may be provided on either of these members in juxtaposition to the passage between them. They are preferably provided on the plate 42 so as to serve to throw entrained coal particles away from the path of thereby and in part falls onto the slinger 35 and is thrown outwardly into the grinding zone. Theair passes` downwardly and through the insides of the impeller arms or `blades 3l and internally into the mass of coal or other material being ground.

Shaft 23y is rotated and in turn rotates shaft I1,

' which in turn rotates the tubular member 28 and the impeller 30. The impeller contacts and moves the balls around in the chamber I3, the number of balls being sufficient for this action. The space between the lower end of impeller 3l) and the liner on the base plate II or bottom of the casing is of greater height than the diameter of the largest ball and the maximum external diameter of the impeller is less than the inside diameter of chamber I3 by an amount more than equal to twice the diameter of the largest ball so that the clearance between the lowermost and outermost portions of the impeller and the bottom and side walls respectively of the casing is but slightly greater than the diameter of the largest balls used in the casing. The balls, in normal operation, dispose themselves, as shown in Fig. 1, outside the impeller 30 and below the same over the entire bottom of the grinding zone outwardly of the slinger 35. The coal is ground by the balls both by attrition and crushing.

The balls I5 are made of metal and are heavy. The larger balls will seek the lower locations due` to gravity. The more active grinding takes place outside the impeller 30 above the position of the lowermost balls. It will be seen that the impeller `30 moves any balls which it contacts at a rate equal to the of the impeller. -The balls below the impellerj30'A-.can move at a slower speed. Consequently, the higher balls are moved, over entering the stuiiing box. 1

and in contact with the lowermost layer of balls. The lowermost layer of balls, however, will have movement and will do considerable grinding. But the movement oi.' the lowermost layer of balls is relatively slow. This is important because it 5 saves wear on the liner members. i

The curved fan vanes 31 on the under side o member tend to cause air to pass upwardly through stufiing box 9 thus preventing c oal from The air blows in a steady stream through the pulverizer and carries the ground coalaway from the grinding zone and upwardly within chamber I3. The mixture of air and pulverized coal passes between the classifying

plates

42 and 43 which cause a change in direction of iiow of the pulverized material. Any relatively large particles cannot pass through the space between plates 42 and 43Hon account of the projections 44 which throw such particles outwardly by centrifugal force, allowing them to fall back into the grinding zone. The mixture of air and powdered coal passes through the tangential outlet 4I to the point of use. The tangential outlet provides further classification to that provided by the classl- 25 fying plates 42l and 43. It will be seen that there is an expansion above the

plates

42 and 43 as a result of which heavier particles will settle out of the air-fuel mixture.

My invention has various advantages. Prob- 30 ably the most important are the efficient grinding action and the minimum wear on the liners. It will be obvious that my improved pulverizer has some'of the characteristics of a horizontal loose ball mill pulverizer while having the advantage 35 that it requires less floor space and that more efficient grinding can be obtained because of the relative movement of the balls and the rubbing action of the balls against each other. The maintenance cost is low because wear is concentrated in the balls rather than the liners and because new .balls may be charged into the pulverizing chamber without dismantling or even stopping the pulverizer. As above pointed out, moreover, a new ball of a diameter slightly less than the clearance space between the bottom of the pulverizing chamber and the impeller 30 may be introduced and may be worn down completely. The eiiiciency of the herein disclosed ball pulverizer will be high as compared with the ordinary type of ball mill because higher speeds may be used and because of the high grinding pressures and the relative speeds of the balls with respect to each other and with respect to the non-rotating parts.

While I have shown but one embodiment of 55 my. invention in accordance with therequirements of the patent laws, it will be understood that this is not by way of limitation andthat the invention may be embodied in a great vao riety of structures.

What I claim is: 4

1. A ball mill pulverizer comprising a stationary, substantially cylindrical, casing having a grinding zone in the lower portion thereof, a plurality of balls in the casing, an impeller mounted in thecasing for rotation about a substantially vertical axis, means for rotating said im peller, said impeller 'having a plurality of blades disposed in said grinding zone, said blades beingy arranged and disposed in the casing so that the clearance between the lowermost and the outermost portions of the blades and the bottom and side walls respectively of the casing is slightlygreater than the diameter of the largest balls in the casing, said impeller blades being hollow and having an outlet opening adjacent the bottom of the casing, a tubular member connected to the impeller blades, meansfor supplying air and material to be pulverized to said tubular member for introduction into the grinding zone of the casing through the hollow impeller blades, an outlet for the casing and a plurality of spaced plates disposed in the casing between the grinding zone and the outlet for classifying the pulverized material. Y

2. A bailmiil pulverizer comprising a stationary, substantially cylindrical, casing having a grinding zone in the lower portion thereof, a plurality of balls in the casing, an impeller mounted in the casing for rotation about a sub` stantially vertical axis, means for rotating said impeller, said impeller l having a plurality of blades disposed in said grinding zone. said blades being arranged and disposed in the casing so that the clearance between the lowermost and outermost portions of the blades and the bottom and side walls respectively of the casing is slightly greater than the diameter of the largest balls in the casing, said impeller blades being hollow and having an outlet opening adjacent the bottom of the casing, a tubular member connected tothe impeller blades, and means for supplying air and material to be pulverized to said tubular member for introduction into the grinding zone of the casing through the `hollow impeller blades.

3. A ball mill pulverizer comprising a casing, a plurality of balls in the casing, means for introducing material to be pulverized into the casing, an impeller having blades in the casing mounted for rotation about a substantially vertical axis and so as to contact the balls in the casing, the blades of the impeller being hollow, and means for introducing air into the casing through said hollow impeller blades.

4. A bali mill pulverizer comprising a casing, a plurality ot balls in the casing, means forintroducing material to be pulverized into the casing. an impellerbaving blades in the casing mounted for rotation about a substantially vertical axis and so as to contact the balls in the casing, the blades of the impeller being hollow. and means for introducing the material to be y 3 pulverized into the casing through said hollow impeller blades. l

5. A ball mill pulverizer comprising a stationary casing, a plurality of balls in the casing, means for introducing material to be pulverized into the casing, an impeller having blades in the casing mounted for rotation about a substantially vertical axis and so as to contact the balls in the casing, the blades of the impeller being hollow and having outlet openings in the lower portions oi the impeller blades, and means for introducing air into the hollow impeller blades and through said outlet openings into the bot- 'tom of the casing.

6. A ball mill pulverizer comprising a stationary casing, a plurality of balls in the casing, means for introducing material to be pulverized into the casing, an rimpeller having blades in the casing mounted for rotation about a substantially vertical axis and so as to contact the balls in the casing, the blades of the impeller 4being hollow and having outlet openings in the a tubular member connected with the impellerA 4 blades, and means for supplying air to said tubular member for introduction through the impeller blades.

8. A ball mill pulverizer comprising a casing,

into the casing a'plurality of ballsin the casing, an impeller having blades in the casing mounted for rotation about a substantially vertical axis and so as to contact the balls in the casing, the blades of the impeller being hollow, a tubular member connected with the impeller blades, and means for supplying material to be pulverized to said tubular member for 'introduction -into the casing through the impeller blades. MARTIN FRISCH.