US2092307A - Pulverizer - Google Patents

Description

Sept. 7, 1937. J. B. GAFFNEY PULVERIZER Filed June 20, 1955 num Plon

X' QVENTO Patented Sept. 7, 1931 PATENT oFFlcE PULVEBIZER Joseph B. Gaffney, New York, N. Y., signor to Peabody Engineering Corporation, New York, N. Y., acorporation of New York Application June zo, 1935, serial No. 2":,501 i 2 claims. (ol. sami-11)` My invention relates to a method of and apparatus for reducing materials to a powdered condition.

It is;well known that impact may be used in pulverizers, to reduce the sizing of materials being treated, with relatively little power consumption. It is also well known that the product produced due to impact alone is not sufficiently fine for many purposes, and, that to produce a product that is sufficiently fine, it is necessary to supplement the effect of impact with attrition.

To further reduce the relatively ne particles produced by impact, which are too `large for delivery from the mill as `finished product, the following means of providing attrition are generally employed. The particles are kept in ciri `culation within the mill, are acted upon by the hammers or arms at high rotative speed, and/or the hammers or arms rub and drag through an accumulation of the relatively fine material which collects in the mill.

Because of the small mass of these particles, thereaction offered by them to the hammers or arms is insufficient for their further economical reduction. Due to the high rotative speed of the hammers or arms, air currents are `set up within the mill and along the faces of the hammers or arms that are sufficient to materially reduce thechance of contact betweenthe rotating hammers or arms and the particles. Because of the small mass of the relatively ne particles and their inability to offer sufficient reaction unless `effectively confined, the action of the hammers or` arms in passing through or dragging over `the relatively une material that has accumulated in the mill, is an ineiiicientmeans of effecting further reduction in size. v Due to windage losses, high rotative speeds, dragging of the hammers or arms making contact with the material being treated at a` maximum distance from the rotating shaft, the lack of confinement of the relativcly fine material being treated to provide re` action by the particles to make the'eiect of the forces being exerted upon them efficient, and unnecessary continued circulation of these particles to be further reduced within the mill, at-

trition by such means is very uneconomical in power consumption, and inefficient in its ability to produce the quantity offines so necessary for many purposes.`

One object of my invention is to provide a method by which impact and attrition areused in a single pulverizer, independent of each other. A further object is to provide a pulverizer that makes efficient use of the effect of impact' and does not require that the impact elements be I used for providing attrition.

A further object is `to provide a pulverizer, that discharges finished product as soon as it is received or produced, that delivers material too small for emcient reduction by impact and yet too large to be finished product to an eiiicient means'for further reduction by attrition as soon as it is received or produced, and delivers all other material to an efficient means for initial reduction byimpact.

, A further object is to provide a pulverizer in which the impact means will not drag in the material being treated.

A further object is to provide a pulverizer in which the relatively fine material ready for attrition will be confined in order that the means provided for attrition will be employed efciently.

The invention will be understood from the following description taken in connection with the accompanying drawing, in which Fig. 1 is a view in elevation, Fig. 2a transverse section on the plane of the lines 2 2, of Fig. 1, and a part View in elevation, Fig. 3, showing an alternate arrangement of impact means and air admission.

Referring to the drawing, the method of operation, and the apparatus illustrated which is enclosed in a suitable housing, may for the convenience of description, be considered as divided into eight parts, designated generally by the letters A, B, C, D, ELF, G and H. The material to bepulverized enters at A, the rate of delivery being controlled orregulated by a suitable feeder, driven from the mill shaft by a suitable means, or independently driven. That part of the mill where the material is reduced by impact, for convenience called the impact zone, is designated as B. Mill air entering the mill below the center of the rotating impact means is admitted at C. One of the purposes served by this method of admitting mill air is to remove nes from the impact `zone B, as they are produced. This prevents a possible wasteful use of power that "would result from the dragging of the impact lmeans through material accumulating in the the separating or classifying zone the finished product is separated from that which requires further treatment by attrition, the finished product leaving the mill at the mill outlet E, and the product requiring further reduction being delivered to that portion of the mill, for convenience called the attrition zone, and designated as F. Auxiliary air for conveying may or may not be used depending upon the materia] being pulverized, or the purpose for which the pulverizer is being used. When auxiliary air is used, it will enter at the auxiliary air inlet designated as G. Mill air, the finished pulverized product, and auxiliary air, if auxiliary air is used, will be discharged into a duct or suitable delivery means at H.

'I'he apparatus as illustrated is particularly adapted for pulverizing coal. It will be understood, however, that for this purpose and when used for pulverizing other materials the arrangement of apparatus may be varied. For example, auxiliary air may be omitted, the fan may be a separate unit driven from the pulverizer mill shaft, or separately driven, the discharge of the mill may enter the suction side of a separately mounted fan or the discharge of a separately mounted fan may be connected to the mill air inlet designated as C, or the fan may be omitted and the necessary air provided by the fan blades I6 attached to the disc II. The power to drive the rotating parts of the apparatus may be sup` plied by a motor or any other suitable means, and may be applied either above or below the pulverizer.

In the apparatus illustrated I, is a suitable housing preferably provided with flanged and bolted connections not shown. The housing I, is provided with an opening A to admit coal, an opening for air to enter at C, and a discharge outlet at E. superimposed on housing I, and either an integral part thereof, or flanged and bolted thereto, is a chamber enclosed in the supplementary housing 3, provided with an inlet for mill discharge at E, an inlet for supplementary air at G, and an outlet at H.

The motor 4, supported on the housing 3, drives the vertical shaft 5, through a flexible coupling 6. The shaft 5 is supported by suitable bearings 1 and 6. Rigidly attached to the shaft 5 and suitably supported thereby, there is a fan rotor 9 provided with fan blades, and an adjustably mounted classifying bar III, clamped to the shaft by means of the bolts I lla. At thc lower part of the shaft 5. also rigidly attached thereto, there is a rotating disc II carrying flexibly mounted hammers or arms I3 and, if desired, fitted with the fan-like blades I6. The rotating attrition element I9, and its wearing surface 20, is supported by. is rigidly secured to, and rotates with the disc I I. The rotating parts I9 and 20 may if preferred, be independently supported by the shaft 5. The stationary wearing surface surrounding the impact zone B is lined with the replaceable wearing parts I4 and I5.

The stationary part of the attrition means 22, with its wearing face 23, is supported by brackets 24 securely attached to the stationary cone I1. The stationary cone I 1 is rigidly attached to the housing I by means of the brackets 38. The adjustment of the space between the wearing surfaces 20 and 23 is provided for, if a space is desired, by the adjusting means 25. A suitable number of springs 26 with means 21 for adjusting their pressures, exert pressure on the stationary part of the attrition device 22, through the brackets 23 rigidly attached to, or a part of 22.

The protective covering 2i, is provided as a means of protecting the shaft 5 from wear due to material collecting in the attrition zone, if such protection is found necessary. The stationary cone il rigidly secured to the housing I, forms an enclosure for the classifying element I0, and an outlet 39, from the mill.

Attached to the casing I by suitable flanges `and bolts not shown is a feeder housing 29. Ma-

terial is delivered to the conveyor 30 through the hopper 3i. The sprocket or pulley 32 is driven by any suitable means and causes the conveyor 39 to deliver material over the idling sprocket or pulley 33 to the discharge opening in the feeder housing 29 at 34. Material to be pulverized is delivered to the mill through the opening 35 in the mill housing I. 'Ihe adjustable gate 36 serves as a means of admitting a smalll amount of air to the mill and as a means of access to the pocket 31.

One or more means of access to the interior of the mill are provided through the opening or openings 46 in the housing I. A cover or covers 4I are provided to close the opening or openings 40 when not in use.

For clearness the direction of flow of mill air entering the mill at 42 and leaving at 39, is shown by the solid arrows I2. The path of thc supplementary air when used is shown by the dotted arrows 29. A removable portion 43 of the cone I1 is provided for access to the adjustable classifying bar I0.

The illustration shows one impact element assembly II and I3, and one attrition device I9 and 22. In any mill one or more of either or both assemblies may be used.

In the alternate arrangement of the impact zone, B1, shown as a part view in elevation, Fig. 3, the brackets 44 supporting the flexibly mounted hammers 45, are rigidly mounted on the revolving disc I la. The fan-like blades I6 are rigidly attached to the under side of the revolving disc II a. A relatively small circumferential opening 46 is provided between the outer circumference of the revolving disc IIa and the stationary re-v placeable liner 41. A plurality of pegs or bars 48, spaced along the circumferences formed by the intersection of horizontal planes and the replaceable liner 41, form the stationary impact means. The pegs or bars 48 project inward from 41, and are located in horizontal planes spaced so that the hammers will not contact the pegs or bars 48 when the mill is in operation. It will be understood that the impact means may take other forms and if preferred that the stationary impact means I4 and I5 shown in Fig. l may be used with the revolving impact means shown in Fig. 3, or that the stationary impact means shown in Fig. 3 may be used with the revolving impact means shown in Fig. 1. Air inlet openings 49, in the mill casing I, admit air induced by the fan blades on the fan rotor 9. Fig. 1, to the air chamber 50, and into the mill through the relatively small circumferential opening 5I A tube 52 connects the air space under the revolving disc IIa, with the U tube or manometer 53 containingv a suitable liquid 54, responsive in its movement within the U tube or manometer 53 to air pressure variation in the air space below the revolving disc IIa.

Numbered parts in Fig. 3 also appearing in Fig. 1 are identical parts and that portion of the view in elevation not shown in Fig. 3 is identical with Fig. 1.

The operation is as follows: Assume that codis the material to be treated,

that it is received-in thecondition it comesv from the mine, that it has been crushed or screened to a suitable size to. be delivered to the pulverizer/ in this condition, the coal may be dry, or contain various percentages of moisture.

the description.

Heated mill air' improves the emciency of puiverizing whenwet coal is being treated. To provide heated mill air, the air entering at C may be" heated by any suitable means, such as passing the air through an air heater or. other sui/table means of heat transfer, taking hot yair from air cooled furnace walls, diluting the mill air with hot air from any source, or diluting the mill air with hot ilue gases.

Coal is delivered by the mill feeder at the rate desired. As the coal falls from the feeder it is carried into the mill at A by a current of air admittedthrough and regulated as to amount by thecleanout pocket gate I6. Tramp iron and other foreign materials, heavier than coal, which may causev damage if allowed. to enter the mill with Kthe coal, are ltooheavy to be carried into the mill by the air referred to, and instead are deposited in the pocket 31.

The direction of flow of the mill air is indicated by the solid arrows I2. That coal which is sufiiciently fine for delivery to the attrition 4 zone F and for delivery to the mill outlet E `is carried by the mill air to these points. 4,The coal too coarseto be carried oif as it is delivered to the pulverizer at A by. the mill air flow I2, falls tothe impact z one B. It is acted upon by the hammers I3, supported by the rapidly rotating disc II. The hammersare/ supported in a manner that they will extend outward as shown when the mill is in operation, and revolve on their own axes, to prevent damage when contact is made by them with foreign material such as metal that may enter with the coal. 'Ihe eiect of impact upon the coarse coal by the hammers i3, and the impact of the coal due to the motion imparted to it bythe impact hammers I3 on they/replaceable wearing parts I4 and I5 reduces its size. As the reduction in sizing of thecoal progresses that partwhich has been reduced sufficiently is carried by the mill air I2 and delivered to either the mill outlet E or the attrition zone F, depending upon whether it is suiiiciently fine enough for delivery from the mill as finished product, or requres further reduction by attrition. The harnmers I3 and the removable wearing surfaces I4 and I5, may be of other forms. such as paddles in place of hammers I3, and pegs in place of wear ing surfaces Il and i5.

As the coal enters the mill at A, and is reduced by impact at B, the lines ready for delivery from the pulverizer and those ready for further reduction by attrition yare delivered to the stationary cone Il. The cone I'I, serves to form part of a separating or classifying chamv ber and also a means of delivering that portion of the coal ready for further reduction by attrition, to the attrition zone F.. The coarse particles entering the stationary cone l1 will fall out of thev mill air currents I2, due to the air expanding in the separating chamber and losing velocity, due to gravity, and due to the change of direction of the air currents. Thbalance of the product as it passes upward carried by the mill air encounters the rapidly rotating classifying device I0, operating within the stationary cone I8. The classifying device I is adjustable vertically along the shaft 5 as a part of the means of fixing the neness of the mill output. Due to the high rotative speed of the separating or classifying device II), the air currents with the in the stationary cone I8, and because of the centrifugal force imparted to the heavier particles due to their greater mass, they are returned to the stationary cone I 'I for delivery to the attrition zone F. 'I'he finished product passing the separating or classifying device lil, is delivered `to the mill outlet E by the mill air currents I2.

The coal particles rejected by the separating` or classifying device I0, and those falling out` of the faces and 23 on the material, and the effect of the rubbing of the'material` upon itself, l

will produce a product that has been treated effectively by attrition as to its nneness, and eiliciently with reference to the power requirements. 'I'he fines leaving the attrition zone will not clog or impede the action of the impact pulverlzlng devices, since they are picked up by the mill air currents I2 as they are produced.

'I'he blade I8 on the under side of the rotating disck II servesto assist the fan 9 in causing the mill air currents I2 to flow through the pulverizer,` and keep the impact zone B lclear of ma-f terial that the hammers I3 and disc II,might otherwise drag on. For some purposes it will be d fines carried by them are caused to rotate with-s advantageous to omit fan 9 and use only fan blades I6 to furnish mill air.

Auxiliary air discharging at H with mill air and finished product, when used, enters at G, and its flow is indicated by the dotted arrows 29.

Suitable dempers not shown may be used in one or more of the following ducts, the mill air duct delivering air to C, the auxiliary air duct delivering air to G. and the duct taking the mill discharge at H, for the proper regulation of air flow.

For'some materials it will be found advantageous to use the alternate arrangement of the impact zone B1 as illustrated in the' part view in elevation Fig; 3. This arrangement will be particularly advantageous when treating materials with a relatively high specific gravity, or in cases where it is necessary to limit the air used in the impact zone to the minimum that will prevent the dragging of. the rotating impact elements in accumulation of the material being treated.

Air for use in the impact zone enters at C, induced by the fan like blades I6 attached to. the

CII

under side of the revolving disc ila. The air is delivered to the impact none B through the circumferential opening Il. Additional air is admitted to the mill above the impact zone B1, induced by the fan blades on the fan motor l, Fig. 1, through openings Il in the mill housing I. This air enters the circumferential chamber Bil, and is delivered from. it into the mill through the circumferential opening Il.

If desired, the air entering at C may be controlled by suitable dampers, not shown, ln the duct leading to C. The air entering through the openings I9 may be controlled by suitable dampers, not shown, in the duct leading from the discharge of the fan in the fan housing 3, at H, Fig. 1, or if preferred suitable dampen! or control gates may be provided in the openings Il, or in a duct with manifold connections to the openings I9. If the material being pulverized is of such a nature that a gas would serve the purpose better than air, for example, a gas that will not support combustion when grinding highly combustible materials, or a gas for combining with the material being treated duringthe process of pulverization, then gas or gases, gas and air, or gases and air, may be used as described for air in the foregoing. It is understood that the air or gas, or air and gas may be heated if desired to whatever temperature is found to give the best results.

The material to be pulverized is delivered to the mill by the same means as has beendescribed in the foregoing. It then drops to the impact zone B. 'Ihe material as it is leaves the rotating disc ila by centrifugal force, impinges against the stationary wearing face 41. It is further acted upon by the hammers Il supported above the revolving disc Ila. The material as it is impacted by the hammers II is driven with considerable force against the pegs or bars 4l. 'I'he result of these various impact actions will be to reduce the size of the material being treated by impact to a suiciently small size for removal from the impact zone by the air or gas entering through the opening 4|. T'he air or gas passing through the circumferential opening II will effectively prevent any accumulation of material being treated at the outer edge of the rotating disc lla. The material being treated on leaving the impact zone meets additional air entering the mill through the circumferential opening 5I. The further action of classification, attrition, and discharge from the pulverizer, of the material being treated, is identical with that previously described in this specification.

The pressure of the air or gas flow developed by the action of the fan-like blades I8 on the underside of the revolving disc Ha will be indicated by the suitable liquid Il in the U tube or manometer 53. As the density of the mixture of air or gas and material in the impact zone increases, the resistance to the air or gas flow will increase and be indicated. This pressure indication will be useful as a guide to an operator in the regulation of the supply of material delivered to the pulverizer for treatment. The variation in pressure may if desired be made use of to automatically control the rate at which the feeder delivers material to be treated to the pulverizer. It will be understood that while the use of the tubing 52, and the U tube or manometer i3, will be helpful to an operator for control purposes, that its use is optional, and that its omission will not in any way interfere with the mill functioning as a pulverizer.

What I claim is:

l. A pulverizing mill, comprising a vertically extending housing, a vertically iournalled shaft operating therein, an impact pulverizer in the lower portion of said housing and operated by said shaft, said housing having an air inlet below said impact pulverizer and air passages extending upwardly about said impact pulverizer, means for delivering material to be pulverized to said impact pulverizer, an attrition pulverizer above said impact pulverizer and operated by said shaft, a conical wall about the shaft above said attrition pulverizer and forming with the surround` ing wall of the housing an air passage for conveyance of the materials reduced by the impact pulverizer and attrition pulverizer, an inverted conical wall above said conical wall for deflecting material carrying air currents downwardly in the conical wall toward said attrition pulverizer, a rotating classifier on the shaft at said inverted conical wall for assisting in classification of iine and coarse particles and for aiding in deflecting the coarse particles into the conical wall, the housing having a discharge passage in the top of the same extending from said inverted conical wall and means for creating upwardly flowing mill air currents through the housing from said inlet at the bottom through said outlet at the top.

2. A pulverizing mill, comprising a vertically extending housing having an air inlet at the bottom and a discharge outlet at the top, an upright shaft rotating in said housing, impact pulverizer elements mounted on the-lower portion of the shaft above said air inlet, an attrition pulverizer element on said shaft above said impact pulverizer elements, a conical hopper about said shaft and having its lower end discharging to said attrition element on the shaft, attrition element means supported by the lower end of said hopper in cooperative relation with said attrition element on the shaft, material classifying means above said conical hopper and in communication with the discharge outlet of the housing, said conical hopper and the surrounding wall of the housing forming passages extending upwardly from said impact and attrition pulverizers and downwardly into the upper end of the conical hopper and means for creating a flow of mill air currents from said inlet to said discharge outlet.

JOSEPH B. GAFFNEY.

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