US2361278A

US2361278A - Pulverizing mill

Info

Publication number: US2361278A
Application number: US483087A
Authority: US
Inventors: Evans Richard Henry
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-04-08
Filing date: 1943-04-15
Publication date: 1944-10-24
Anticipated expiration: 1961-10-24

Description

Oct. 24, 1944. R. H. EvANs PULVERISING MILLl Filed April 15, 1943 4 Sheets-Sheet l Oct. 24, 1944. R. H. EvANs 2,361,278

PULVERISING MILL Filed April 15, 1943 4 Sheets-Sheet 2 Ric/mrd HenryEz/ans Inventor Attorney OC. 24, 1944. R H, EVANS 2,361,278

PULVERISING MILL Filed April 15, 194s 4 sheets-sheet 5 Inventor Oct. 24, 1944. R, EVANS i 2,361,278

PULVERISING MILL Filed April 15, 1945 4 Sheets-Sheet 4 .Eje/70rd Henry Evans Iyn ventor Patented Oct. 24, 1944 UNITED STATES PATENT OFFICE Application April 15, 1943, Serial No. 483,087 In Great Britain April 8, 1942 (Cl. 83-l1) 4 Claims.

This invention relates to pulverizing mills of the beater type. an object being the provision of simple but highly effective mills.

The present invention includes a pulverzing mill comprising a rotary beater, including a circle of beater elements, disposed within a chamber arranged to be swept by gaseous fluid and means for introducing material to be pulverized into the chamber, together with directing means adapted to effect removal of oversize particles from a region within the chamber radially outward of the beater elements and to effect movement of the particles to a region sidewardly of the beater elements and radially inwards of the outer edges thereof and to direct the particles towards the zone of action of the beater elements.

'I'he invention also includes a pulverizing mill comprising a rotary beater, including a circle of beater elements extending sidewardly from their supporting means, disposed within a chamber arranged to be swept by gaseous uid and means for introducing material to be pulverized into the chamber, together with guiding means which includes a scroll-like surface or scroll-like surfaces extending radially inwards at one side of the beater and which is adapted to direct oversize particles from a region of the chamber radially outwards of the beater elements and to guide the particles radially inwards and to deliver them to the space within the circle of beater elements.

The invention also includes a4 pulverizing mill comprising a rotary beater, including a circle of beater elements extending sidewardly from their supporting means, disposed within a chamber arranged to be swept by gaseousuid and means for introducing material to be pulverized into the chamber. together with an impact member and a chute arranged in a space at one side of the beater and in communication with the region of the chamber radially outwards of the beater elements and with the space within the circle of beater elements, the impact member being disposed in the path of movement of oversize particles which enter the space at one side of the beater from the said region and the chute being disposed below the impact member and arranged to receive particles falling from the impact member and direct them into the space within the circle 0f beater elements. 1

The invention further includes a pulverizing mill comprising a chamber arranged to be swept by gaseous fluid and containing a rotary beater, means for introducing material to be pulverized into the chamber,an outlet for gaseous 'fluid and entrained pulverized material at one side of the beater, which outlet is screened by bathing means or by rejector vanes mounted on the beater and an impact surface surrounding the beater and flaring away from the outlet.

The invention will'now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a sectional end view of one form of mill for pulverizing fuel taken on the line I-I of Figure 2;

Figure 2 is a side view of the mill, in section on the line II-II of Figure 1 with the exception of the bedplate, bearing brackets and bearings;

Figure 3 is an end view of another form of fuel pulverizing mill a portion of which is in section on the broken line III-III of Figure 4 and certain hidden parts of which are indicated by dotted lines;

Figure 4 is a side view of the mill, in section on the broken line IV-IV of Figure 3 with the exception of the bedplate, bearing brackets and bearings.

In the drawings a bedplate I supports by means of brackets 2 and bearings 3 a rotary shaft 4 adapted to be driven by any suitable means. On the shaft 4 are mounted for rotation therewith a beater including a hub' and a disc 6, from which project sidewardly towards the adjacent end of the casing a circle of beater elements 'I equiangularly spaced around the disc and set sidewardly, and a fan including a hub 8, disc 9 and principal and auxiliary vanes I0 and II arranged in two circles respectively on opposite sides of the disc 9. The shaft 4 extends through apertures in the ends of a casing I2 in which the beater and fan are disposed and is provided with sleeves I3 and I4 which are suitably secured to the shaft and serve to protect the shaft from abrasion and help to space and position the

hubs

5 and 8.

The casing I2 is divided by a diaphragm I5 into a beater compartment I6 and a fan compartment I1 in communication with one another through a central aperture I8 in the diaphragm. The aperture is iltted with a ring I9 formed with a iiange 20 and a circle of radially extending rejector vanes 2|, mounted on the beater disc 6 and extending across the aperture I8, rotate with their outer ends in proximity with the flange 20.

Surrounding the beater is an impact plate 22 which ares towards the material inlet side of the beater and which is suitably of frusta-conical form as shown. The radially outer edges of the beater elements 'I are inclined outwardly at an angle equal to the outward inclination of the impact plate. 'Ihe impact plate is provided with a wear resistant removable lining 23 and is formed below with an aperture 24 leading to a tramp metal chamber 25 tted with doors 25 through which the contents of the chamber may be withdrawn.

Fuel to be pulverized may be fed by a suitable feeder to a fuel inlet 21 and the flanged air inlet 28 may be connected with a duct for supplying primary air. l

The radially outer wall of the fan compartment I1 is of involute form and is lined with a removable wear plate 28. The compartment is formed with an outlet 38 for air and entrained pulverized fuel and the side wall 3| of the compartment is provided with an inlet 32 for additional air, such air being drawn in by the auxiliary vanes II and being under the control of a sliding damper 33 by means of which the inlet 32 may be closed to desired extent.

Turning now to Figures 1 and 2 of the drawings, the fuel inlet 21 extends through the end plate 34 of the casing and is adapted to deliver the fuel to be pulverized to the space within the circle of overhanging beater elements 1 and in front of the outlet from the air inlet 28 which includes an annular projection 35 on the inner surface of the end plate 34 and concentric with the shaft 4.

Provided within the beater compartment I3 are four scroll-like members 36 formed from metal strips mounted on the end plate 34 so as to be readily replaceable. Each scroll-like member extends from the impact plate 22 to the annular projection 35. Over the greater part of the length of each scroll-like member the member extends normally from the plate 34, but the inner end 31 of the member is directed radially inwards and is so inclined to the plate 34 that particles travelling along the member will be directed by the end 31 away from the plate 34 into the space within the circle of overhanging beater elements 1.

In operation, the shaft 4 is driven in a clockwise direction as seen in Figure 1 and material to be pulverized, such as coal in lumps, and air are respectively delivered through the fuel inlet 21 and the air inlet 28 to the space within the circle of overhangingV beater elements 1 and pass outwardly into the zone of action of the beater elements. The beater elements strike the lumps of material to be pulverized and throw them outwardly and cause a whirling of the air and material within the beater compartment I6. 'I'he impacts between the lumps and the beater elements 1, the impact plate 22 and other stationary surfaces within the beater compartment and between the lumps themselves tend to reduce the material to a powder which is entrained by the air and carried thereby through the aperture I8 into the fan compartment I1 whence the air and entrained pulverized material pass through the outlet 38 to the place of use or storage.

On account of the flaring of the impact plate 22, particles striking the surface thereof are deflected away from the outlet from the beater compartment constituted by the aperture I8. Moreover, should any oversize particle bounce into the space between thebeater disc 6 and the diaphragm I it is struck and thrown outwardly by a deilector vane 2|.

The beater elements 1 produce a local circulation of air radially outwards through the beater elements and radially inwards in the region of the scroll-like members 35.

Since the particles thrown against the impact plate 22 are deflected towards the end plate 34 of the casing. they are directed onto the outer ends of lthe scroll-like members 35. The Parrticles are also carriedtowards those members by the local circulation of air. On account of the residual momentum of the particles and the local inward flow of air over the surfaces of the scroll-like members, the movement of theparticles is continued and the scroll-like members guide the particles inwards until the particles reach the inner ends 31 of the said members and are thereby directed axially into the space within the circle of the beater elements 1 to impact with substantial velocity upon the side of the beater disc 3. or upon the fresh material passing to the zone of action of the beater elements. Thus oversize particles are recirculated through the zone of action of the beater elements.

The recirculation causes material rapidly to pass repeatedly through the beater elements 1 so that the beater operates quickly to reduce the material to the desired degree of fineness. Moreover, the direction of the oversize material from the impact plate 22 away from the outlet from the beater chamber I8 and the action of the rejector vanes 2I screening the said outlet, reduce or eliminate the danger of oversize particles passing through the aperture I8 so that good classification of the pulverized material by the entraining stream of air is ensured. As a result, the mill consisting of a single stage is capable of giving a high output with satisfactory uniformity of fineness of the pulverized material.

Lumps of iron or other relatively heavy foreign bodies are removed from the beater compartment, since they are flung through the aperture 24 and become embedded in the body of fuel particles which collects in the chamber 25.

In Figures 3 and 4 of the drawings, the beater elements 1l include foundation members 38 extending between beater disc 8 and a shroud ring 38 and renewable facing members 40 bolted to the foundation members 38. The ring 38 shrouds the sides of the members 40 remote from the beater disc.

Immediately adjacent the outer end of the impact plate 22 is a plate 4I formed immediately adjacent to but inwardly of the impact plate with an arcuate slot or aperture 42 extending over an upper sector of the plate and with a central aperture 43 concentric with the shaft 4.

An extension 44 of the casing is formed with the vertical fuel inlet 21 and` to one side of the fuel inlet with the horizontal air inlet duct 28 which may be provided with an air control valve having a pivot 45.

One side of the fuel inlet 21 is continued only to a position a short distance below the upper end of the aperture 42 and is faced by an impact block 46. Below the fuel inlet and impact block is a. chute for directing material falling from the fuel inlet and impact block through the control aperture 43 into the space within the circle of overhanging beater elements 1. The chute is formed by

side walls

41 and 48 extending normally from the end plate 48 of the extension 44 of the casing and converging in a downward direction and a bottom 50 sloping downwardly from the end plate 48. A wall 5I extending normally from the end plate 48 curves upwardly from a point adjacent the lower end of the aperture 42 and away from the aperture to join the side wall 41 at the top thereof. l

Secured to the plate 4I and in register with the aperture 43 is a ring 52 which supports an annulus 53, slightly spaced from the beater disc 'I'he extension 44 of the casing helps vte formA a wind box for leading air from the air inlet 28 to the aperture 4l.

In operation, the shaft 4 is driven in a clockwise direction as seen in Figure 3 and air flows from the inlet 28 through the wind box B8, the

aperture 43, the spaces on opposite sides of the 4 lugs 56 and between the beater elements 1. From the beater compartment Il the air with entrained pulverized material ilows through the aperture I8 to the fan compartment l1 and thence through the outlet Il to the place of use or storage.

There is also a local circulation of air from the space within the extension 44 of the casing with which the aperture 42 communicates through the aperture 43, the spaces on opposite sides of the lugs 56, between the beater elements 1 and through the aperture 42 back to the said space.

Lumps of material fed through the fuel inlet 21 are direcetd by the sloping bottom SII of the chute through the aperture 44 onto the slideway 54 and are discharged therefrom, in a sense opposed to the direction of movement of the beater elements past the point of discharge, through the space between the lower end of the slideway and the adjacent lug I8 into the zone of action of the beater elements 1. strike the lumps of material to be pulverized and throw them outwardly and cause a whirling of the air and material within the beater compartment I 6. The impacts between the lmps and the beater' elements, the impact plate 22 and other stationary parts and'between the lumps themselves tend to reduce the material to a powder which is entrained by the air and carried thereby from the beater compartment through the aperture I8.

As explained in connection with Figures 1 and 2, the flaring impact plate 22 and the reiector vanes 2l lessen or inhibit the passage of oversize particles through the aperture I 8.

'Ihe local circulation of air tends to carry par- -ticles through the aperture 42 and particles which make impact with the plate 22 are deflected towards the plate 4i and the oversize particles are thus directed through the aperture 42v towards the block 46 upon which at least most of them impact, whereby the reduction of the material to the powder is assisted. 'I'he lmaterial which passes through the aperture 42 either falls into the chute and is directed by the sloping bottom within the extension 44 of the casing in communication with the aperture 42 in to the zone of action of the beater elements.

'I'he invention may be applied to mills for verizing material other than fuel.

I claim:

1. In a pulverizing mill having a beater arranged for rotation'about a horizontal axis, said beater comprising an imperforate disc-like support together with a circular row of circumferentially spaced radially extending beater elements mounted peripherally of said support and projecting from one side thereof, each of said elements having its effective beater surface mainly disposed radially inward of the circumferential boundary of said support, a stationary casing surrounding said beater having a circumferential impact surface spaced from said beater to provide an annular clearance region therebetween. said casing being extended at opposite sides of said beater to provide a casing space at pul- . each of said sides, said casing having an inlet The beater elements 50 thereof, together with fresh material from the fuel inlet 21, through the aperture 43 or is entrained by the recirculating air and thereby carried by the air through the aperture 43. The

`material from the aperture 42 is thus returned r to the zone of action of the beater element 1.

The recirculation causes material rapidly to pass repeatedly through the zone of action of the beater elements so that the beater operates quick: ly to reduce the material to thedesired degree of neness. Both gravity and the recirculating air assist the passage of' material from the space for air and a, separate inlet for material to be pulverized, each connected to said casing at the side of said beater from which said beater elements project, means for directing air from said air inlet to the space inside of said circular row of beater elements, means for separately directlng material from said material inlet to said inside space including a chute for delivering said material by gravity into said space, said casing having a common outlet for said air and entrained pulverized material at the side of said beater remote from said air and material inlets, an exhauster fan connected to said casing outlet and effecting a primary iiow of said inlet air from said inside space radially outward through said circular row of beater elements to said annular clearance region and from said region laterally toward the side of said beater adjacent said outlet, said casing space at the side of said beater adjacent said inlets being continuously open to said annular clearance region and to said inside space whereby as a result of beater rotation said beater elements produce a local circulation of a portion of said air radially outward between said beater elements and radially inward within said inlet side casing space, said local circulation of air including return of said portion to said inside space, said directing means for said inlet air being arranged to prevent said returned air becoming mingled with said inlet air before both said streams of air are delivered to said inside space, said circumferential impact surface being formed and arranged relative to said beater to cause coarse particles of material thrown thereagainst by said beater elements to be deflected axially from said clearance region into said inlet side casing space parallel to the direction of ow of said local circulation of air, and stationary material directing surface means ln said inlet side casing space for returning said coarse particles to said inside space within said circular row of beater elements.

2. In a pulverizing mill having a beater arranged for rotation about a horizontal axis, said beater comprising an imperforate disc-like support together with a circular row of circumfers entially spaced radially extending beater elements mounted peripherally of said support and projecting from one side thereof, each of said elements having its effective beater surface mainly disposed radially inward of the circumferential boundary of said support, a stationary casing surrounding said beater having a circumferential impact surface spaced from said beater to provide an annular clearance region therebetween, said casing having transversely arranged end walls spaced from said beater at opposite sides for defining a casing space at each of said sides, said casing having an inlet for air and a separate inlet for material to be pulverized, each connected to said casing at the side of said beater from which said beater elements project,

means for directing air and material from said inlets to the space inside'of said circular row of beater elements, said means for directing said material includingA achute for delivering said material by gravity into said inside space, said casing having a common outlet for said air and entrained pulverized material in said end wall at the side of said beater remote from said air and material inlets, an exhauster fan connected to said casing outlet and effecting a primary flow of said inlet air from said inside space ra-f dially outward through said circular row of beater elements to said annular clearance region and from said region laterally toward the side of said beater adjacent said outlet said casing space at the side of said beater adjacent said inlets being continuously open to said annular clearance region and to said inside space whereby as a result of beater rotation said beater elements produce a local circulation of a portion of said air radially outward between said beater elements and radially inward within said inlet side casing space, said local circulation of air including return of said portion to said inside space, said directing means for said inlet air being arranged to prevent said returned air becoming mingled with said inlet air before both said streams of air are delivered to said inside space, said circumferential impact surface being formed and arranged relative to said beater to cause coarse particles of material thrown thereagainst by said beater elements to be deflected axially from said clearance region into said inlet side casing space parallel to the direction of flow of said local circulation of air, and stationary material directing surface means in said inlet side casing space for returning said coarse particles to said inside space within said circular row of beater elements, said surface means including a surface normal to said end wall at said inlet side arranged in the path of coarse particles defiected from said clearance region for guiding said particles toward an inner portion of said casing space opposite said inside beater circle inlet for material to be pulverized, each opening into said casing through said end wall at the side of said beater having said projecting beater elements, a cylindrical outlet member connected to said air inlet and extending axially across said inlet side casing space for discharging air into the space inside of said circular row of beater elements, means for separately directing material from said material inlet to said inside space adjacent the introduction of said inletv air including chute means -for delivering said material by gravity into said inside space, said casing having a common outlet for said air and entrained pulverized material in said vend wall at the side of said beater remote from said air and material inlets, an exhauster fan connected to said casing outlet and effecting a primary flow of said inlet air from said inside space radially outward through said circular row of beater elements to said annular clearance region and from said region laterally toward the side of said beater adjacent said outlet, said casing space at the side of said beater adi acent said inlets being open to said .annular clearance region and to said central space to provide a continuous flow path for local circulation of a portion of said inlet air produced by said beater elements upon rotation of said beater radially outward between said beater elements and radially inward within said inlet side casing space, said circumferential impact surface being of conical formation flaring toward said inlet side casing space to cause oversize particles of material thrown thereagainst by said beater elements to be deflected axially from said clearance region into said inlet side casing space parallel to the direction of flow oi said local circulation of air, and stationary material directing surface means in said inlet side casing space comflared end of said conical impact surface to a dispace, said surface means includinga surface opposite said inside space arranged at an abrupt inclination to said normal surface for directing Y particles discharged from( said normal surface into said inside space.

3. In 'a pulverizing mill having a beater arranged for rotation about a horizontal axis, said beater comprising an imperforate disc-like support together with a circular row of circumferen- I tially spaced radially extending beater elements spaced from said beater at opposite sides forv defining a casing space at each of said sides, said ameter adjacent said cylindrical air outlet member, each said scroll-like member presenting a material directing surface normal to said adjacent end wall throughout the greater portion of its length with the inner end of each member having an abrupt change in direction to provide a substantially radially extending redirecting surface inclined to said wall for directing said oversize particles away from said wall into said inside space within said circular row of beater elements.

4. In a pulverizing mill having a beater arranged for rotation about a horizontal axis, said beater comprising an imperforate disc-like support together with a circular row of circumfertially spaced radially extending beater elements mounted peripherally of said support and projecting from one side thereof, each of said elements having its effective beater surface mainly disposed radially inward of the circumferential boundary of said support, a stationary casing surrounding said beater, having a circumferential impact surface spaced from said beater to provide an annular clearance region therebetween, said casing being extended. at opposite sides of said beater-to provide a casing space at each of said sides, said casing having an inlet for air and a separate inlet for material to be pulverized, each connected to said casing at the side of said beater having said projecting beater elements, means for directing air and material from said inlets to the space inside of said circular row of casing having an inlet for air and a separate u beater elements, said means for directingsaid said region laterally toward the side of said beater adjacent said outlet. said casing being formed with a transversely arranged plate member partially separating said inlet side casing space from the path of rotation of said beater, said plate member having an arcuate aperture in an upper sector thereof opposite said clearance region and a central aperture opposite said inside space to provide a continuous now path for local circulation of a portion oi said inlet air produced by said beater elements upon rotation of said beater radially'outward between said beater elements 20 ments.

and radially inward within said inlet side casing space, said circumferential impact surface being oiconical formation ilaring toward said inlet side casing space to cause oversize particles of material thrown thereagainst by said beater elements to be directed from said clearance region toward said plate member and through said arcuate aperture into said inlet side casing space parallel to the direction of ilow of said local circulation of air, a stationary member within' said inlet side casing space presenting an impact surface arranged upright adjacent the upper end of said arcuate aperture in normal relation to said plate member and in the path oi said oversize particles, and chute means below said upright' impact surface arranged to receive oversize particles discharged i'rom said surface and to direct said particles through said central aperture into said inside space within said circular row of beater ele- RICHARD HENRY EVANS.