US2268661A - Tube mill - Google Patents

Description

A4.Iem- 6, 1942i. J. E. KENNEDY y 2,268,661

' TUBE MILL I Filed July 7, 1959 ATTORNEY l Patented Jan. 6, 1942 TUBE MILL l Joseph E. Kennedy, New York, N. Y., assignor to Kennedy-Van Salm Mfg.

& Eng. Corporation,

New York, N. Y., a corporation of Delaware Application July 7, 1939, Serial No. 283,159-

3 Claims. (Cl. 839) 'Ihis invention relates to tube mills for reducing and pulverizing material, and particularly to tube mills wherein the pulverized material is delivered from the mill in suspension in an air stream drawn from the mill, and including a rotatable drum having therein freely moving material reducing elements, such as balls or pebbles, cascaded with the material in the drum by the rotation thereof and reducing the material by impact of the balls thereon. To facilitate cascading the balls and material by the rotation ofthe drum and thereby effect separation and delivery of the pulverized material by the air drawn from the drum, the inner surface of the drum, or the surface of a liner of wear resisting material for the drum, is arranged of sinuous form disposed circumferentially about and extending longitudinally of the drum for the entire length thereof. The output capacity or tonnage of the tube mill depends upon the diameter and length of the' drum and the volume of air required to deliver the `pulverizecl material from the drum.

Tube mills of this character `are utilized to pulverize coal in pulverized coal firing systems for furnaces of steam generators and of billet heating furnaces, the pulverized coal being delivered from the mill directly to the furnace in suspension inv an air stream and constituting with the aira fuel. In utilizing a tube mill in a pulverized coal firing system for furnaces the capacity output of the J mill may not be required for firing the furnace. However, in .a mill wherein the drum has or is provided with a liner having such a sinuous form of surface should the speed of rotation of the drum be reduced with the object of reducing the output of the mill the reduction in the output of the mill will be so much greater in proportion to the reduction in the speed of rotation of the mill that it is not possible to control the output of the mill. It is, therefore, required that the drum be rotated at the high speed required to produce the output capacity or tonnage of the mill and a consequent large amount of power is required lto rotate the drum at all times.

It is the primary object of the invention to provide an improved arrangement of the inner surface of the drum, or drum liner, in tube mills to increase the cascading movement of thematerial and balls in the mill and :an increase in the. output capacity or tonnage of the mill without any increase required in the volume of air to deliver the material from the drum, and that will cause the mill to lfunction as eiciently with 1a reduction in the speed of rotation of the drum as at full speed and produce a reduction in the output of the mill corresponding to the reduction in the speed of rotation of the drum, and a reduction in the power required to rotate the drum proportional to any reduction in the speed of rotation of the drum, as well as a reduction in the volume of air required to deliver the material from the drum.

- A further object of the invention is the arranging of the inner surface of the drum of atube mill with sections of different forms of irregular surfaces disposed about the drum, one section of said surface at the outlet end of the drum being arranged to cause the material and material reducing elements to be lifted to a higher level and eiect a greater cascading of the reducing elements and material in said portion of the drum by the rotation thereof.

It is another object of the invention to arrange the ,inner surface of the drum of a tube mill with circumferential sections disposed longitudinally of the drum with different forms of surfaces, the surface of one section at the inlet end of the drum being arranged of sinuous or sinusoid form disposed circumferentially about the drum, and the surface of a section at the outlet end of the drum arranged with pockets of arcuate form equidistantly spaced about and extending longitudinallyfof the drum andvbeing of increased depth relative to the inwardly curved sinuous surface.

It is a further object of the invention` to provide an improved construction and arrangement of a liner for the drums of tube mills, comprising segments of equal length and Width and curved tofconform to the inner surface of the drum and said segments disposed in sectionscircumferentially Vof and spaced longitudinally of the drum, the concave surface of the segments of certain ofthesections being arranged of sinuous form circumferentially of the drum having uniform inwardly and outwardly curved portions, and the concave surface of the segments of another section arranged with pockets spaced circumferentially of the drum having arcuate portions of increased depth and width relative to the inwardly curved portions of the sinuous surface of the other sections. v

In the drawing accompanying and forming a part of this application, Figure 1 is a longitudinfal sectional view of the drum of a tube mill showing an embodiment of my improved liner applied thereto. A

Figure 2 is a cross sectional view taken substantially on the line 2 2 of Figure 1.

Figure 3 is a cross sectional view taken substantially on the line 3-3 of Figure 1.

Figure 4 is a sectional view, on an enlarged scale, taken onA the line 4-4 of Figure 2 and showing the means for securing the liner to the cylindrical wall of the drum'. v l

Figure 5 is an elevational view looking at the rear of a .portion of the assembled liners. f

Figure 6 is a diagrammatic Aview to show .lthe movement of the material Aand reducingelements by the rotation of the drum from below theaxis portions of ythe of the drum and imparting cascading movement thereto by the form of surface shown in Figure 2; and

Figure 7 is a diagrammatic view to show the movement of the material and reducing elements by the rotation of the drum from below the axis of the drum and imparting cascading movement thereto by the form of surface shown in Figure 3'.

An embodiment of the invention is shown in the drawing in connection with the drum of a tube mill having a cylindrical body 8 of uniform internal diameter secured at the ends by annular members 9 of angle form in cross section to heads I0, II and securing said heads to the body, the heads having axial hollow trunnions I2, I3 constituting inlet and outlet openings for the drum and whereby the drum is supported to rotate on a horizontal axis. The drum contains material to be reduced and pulverized and material reducing elements, such as balls or pebbles, adapted by fthe rotation of the drum to reduce and pulveriyzethe material. The pulverized material is delivered from the drum in suspension in an air stream caused to flow into the drum through one trunnion and from the drum through the other trunnion by a fan, not shown. The drum is rotated from a suitable source of power through a gear I4 disposed about and secured to the drum andshown as ksecured to the peripheral por-tion ofthe head lI`I by the annular member 9 securing the head I I to the body S. A sleeve I5 is mounted inI the trunnion I2 constituting the charging opening of the drum and the sleeve is provided with an internal spiral rib operative to convey material through the sleeve into the drum. A sleeve I6 is secured in the trunnion I3 having an internal'rspiral rib arranged to reenter into the drum rnaterial and reducing elements passing therein from the drum. The inner surfaces of the heads are provided with liners of Wear resisting material IEl' and II.

The inner Asurface of the body 8l is provided with la liner of wear resisting material, such as manganese steel, and which as shown, comprises a series of annular sections of successively abutting segments of equal length and width and conforming to the curvature of the inner surface of the drum, and the sections being arranged- Aedgewise longitudinally of the drum, the liner ybeing shownin the present instance as comprising rive sections of substantially equal length, a, 1:,V c, d and e, and each section including eightsegments, as shown in Figure 2. To mountand secure the segments of the annular sections upon the inner surface of the body 8, the segments of each section have a tongue and groove connection, as at I'I, with the exception of two of the segments, the adjacent edges of which are arranged to diverge from the outer to the inner surface of said segments, as at I8, and adapted for the engagement of a wedge shaped key I9 drawn between the ends of` said segments by nuts threaded onto the ends of bolts 2I extended through countersunk openings in the keys and openings inthe body 8, said bolts being adapted to secure sheathing of noise deadeningmaterial 22 to the exterior Of the body by laterally flanged cup members 23, the bolts being extended through openings in, said members 23 and spacing` sleeves, 24. interposed between the body 8 and said cup members 2.3 with a flange at one end. of the sleeves. abutting the body of thedrum, asshownin Figures Zand 4.

The securingkeys lI9-for certain of thesections.

arecircumferentially. spaced. from. suchy securing.

means for segments of adjacent sections, as shown in Figure 5.

rIfhe concave or front surface of the segments Vof certain of the sections exposed to the interior at -25 in Figure 2, and the ridges and the dales of said surface of the segments of the respective sections a, b and d being circumferentially spaced about and extending in alinement longitudinally of the drum, as shown inFigure 1 the dales or inwardly curved portions and the ridges or out- Wardly curved portions of said surfaces of the segments being in arcs of a circle struck from radii of equal length. The rear or convex face of the segments of said sections a, b and d is in an arc concentric with the inner surface of the drum and recessed, as at 26, for the engagement of a noise deadeningand cushioning material, such as cork, interposed and clamped between the segments and the wall of the body 8. The concave orfront surface of the segments of the other sections c and e are arranged with pockets in the form of equidistantly spaced arcuate recesses 21 extending transversely of the segments, as shown in Fig-ure 3, and said recesses of the sections c and e extending in alinement longitudinally of the drum, as shown in Figure 1. The pockets or recesses 2? are of greater depth and area than the inwardly curved portions of the sinuous surface 25 of the sections a, b and d. The rear or convex face of the segments of the sectionsc and e is also in an arc concentric with the inner surface ofthe drum and recessed, as at 28,l andarranged with inwardly curved recesses 29 opposed to the wall portions between the recesses 21 in the concave face and said recesses being adapted forthe engagement of a noise deadening and cushioning material, such as cork, interposed between said segments and the body 8 of the drum.

In Figure 6= there is shown in a diagrammatic mannerthemovement of the material from'belowA the axis of the drum and the cascadingv ci the material by the rotation ofthe drum in the portions of the drum arranged with the sections a, bI andd having the sinuous surface 25'. In such movement and cascading of the material and the reducing elements the air drawn through the drum to serve as the conveying vehicle. for the pulverized material from the mill is caused to pass above the material inthe drum and reduced material ispickedup only by `such air as comes in conta-ct with Vthel material'.

In- Figure '7 there is shown in a diagrammatic manner the movement ofthe material from below the axis of the drum and the cascading of the material and reducing elements by the rota-A tion of the drum in the portions'of the drum arrangedwitirthesections\c and e having the arcuate pockets 21". It will be notedthat the material andvreducing elements are moved from below the axisof the drum andl lifteclto a higher'plane tha-nrthe material liftedbyl the sections with the sinuous surfacel 25 andl causing a greater cascadingy of the material andthe-reducing elements in the drum, andas the material as it is reduced and pulverized has. a. tendency.l to move toward the outlet end of: theedrum, the cascadingv material has a greater quantity offnes .than the remaining portion. of the drum. anda the airjustprior to. itsv passage. from. the. outlet; of the drurrr` is `causedi to pass through the cascading material and thereby separating and picking up an increased quantity of the fines or pulverized material and conveying the same from the drum.

In practice it has been found that by arranging the surface with the circumferentially spaced packets 21 substantially equal to one section, such as section c or e, of one-fifth the length of the drum, that the output capacity or tonnage of material delivered in suspension in the air stream is increased 16% Without any increase in the volume of the air required to deliver the material from the mill over a type of mill wherein the entire interior surface of drum is provided with a surface such as the sinuous surface 25. Also that by reducing the speed of rotation of the drum 25% there is a corresponding reduction of 25% in the output capacity or tonnage of the mill and a decrease in the Volume of air required to deliver the material from the drum and a corresponding reduction in the power 'required to rotate the drum, and there is a proportional reduction in the output of the mill when the drum is rotated at one-half or onequarter speed and a proportional reduction in the air required to deliver the pulverized material from the drum as well as in the power required to rotate the drum. This is a great advantage where two, three or more mills are utilized in connection with the firing of the furnace or furnaces of a battery of boilers, since the mills may be normally operated to re the furnace or furnaces, say at 75% of the capacity of the mills and a corresponding reduction in power required to operate the mills, and in case it may be neci essary to shut down one mill the other mills may be operated at full capacity and serve to re the furnace or furnaces, resulting in a great saving in the cost of power as Well as in the maintenance of the mills.

Having described my invention, I claim.

1. In a tube mill, a drum including a cylindrical body of uniform internal diameter having closures arranged with axial hollow trunnions at the opposite ends to rotatably support the drum and through which trunnions material to be reduced is delivered into the drum and reduced material delivered from the drum in suspension in an air stream, and a liner for the cylindrical body of the drum, comprising arcuate segments curved to conform to the curvature of the drum, assembled edgewise and secured to the Ainner surface of the body in annular sections disposed longitudinally of the drum, the concave surface of the segments of the first two sections at one end of the drum and of the successive alternate section being arranged of sinusoid form disposed circumferentially about and extending parallelly of the axis of the drum and adapted by the rotation of the drum to move the material to be reduced and the material reducing elements in the drum from below the axis up the side of the drum and impart cascading movement thereto, and the concave surface of the segments of the section at the opposite end of the drum and of the successive alternate section being arranged with pockets of arcuate form in cross section circumferentially spaced about and extending parallelly of the axis of the drum, said pockets being of greater depth than and arranged in staggered relation to the inwardly curved portions of the sinusoid surface of the segments of to move the material to the other sections and the portions between the rpockets being in arcs of a circle whose center lies in the axis of the drum adapt dto move the material and material reducing elements from below the axis up the side of the drum to a higher level in the drum and impart greater cascading movement thereto than the surface of the segments of the sections with theA sinusoid surface, and the convex surface of the segments of the respective sections arranged with recesses, and a noise deadening and cushioning material disposed in said recesses in interposed relation between the segments and cylindrical body of the drum.

2. In a tube mill, a horizontal axis drum including a cylindrical body of uniform diameter having closures with axial openings at the opposite ends, said body having an annular section of the inner surface at one end arranged of sinusoid form circumferentially of the body and adapted by the rotation of the drum to move material to be reduced and reducing elements in the drum from below the axis up the side of the drum and impart cascading movement thereto, and an annular section of the inner surface of the body at the opposite end arranged with pockets of arcuate form in cross section circumferentially spaced about and extending parallelly of the axis of the body, said pockets being of greater depth and of less width than the dales of the sinusoid surface of the i'lrst mentioned section and adapted by the rotation of the drum be reduced and the reducing elements in said section of the body from below the axis up the side of the body to a higher level and effect greater cascading movement thereof than the material and rreducing elements moved up the side of the body by the section of the drum .having the sinusoid surface.

3. In a tube mill, a rotatable horizontal axis drum including a cylindrical body having closures with axial openings at the opposite ends adapted .to contain the material to be reduced and freely moving reducing elements, and a liner for the cylindrical body comprising arcuate segments conforming to the curvature of the body arranged in annular sections disposed in endwise relation longitudinally of the body, the inner surface of the segments of the sections at one end and a section within the opposite end of the body being arranged of sinusoid form'disposed circumferentially about and extending parallelly of the axis of the drum, and the inner surface of the segments of the annular sections at the opposite end and midway of the ends of the body arranged with pockets of arcuate form in cross section uniformly spaced circumferentially about the body and extending parallelly of the axis of the body, and said pockets being of greater depth than and arranged in staggered relation to the inwardly curved portions of the sinusoid surface of the other sections, and said sinusoid surfaces and pockets by the rotation of the drum adapted to move the material and reducing elements from below the axis up the side of the body and effect cascading movement thereof, and the sections with the pockets adapted to move the material and reducing elements to a higher level and effect greater cascading movement thereof than the sections with the sinusoid surface.

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