US2315084A - Attrition mill - Google Patents

Description

March 30, 1943. 1. cHEsLl-:R

` ATTRITION MILL Filed Sept. 13, 1940 'ugg'n'n' 1...... r1.1'.

A INVENToR lsv'dor CeJer BY @@mwf ATTORNEYS l Patented Mar. 30, 1943 2,315,084 A'rrmrroN Mm.

Isidor Chesiei",

Oceanport, N. J., assigner to Eagler Pencil Company, New York, N. Y., a corporation oi `Delaware Application September 13, 1940, Serial No. 356,611

6 Claims.

My present invention relates to the art of pulverizing granular material such as graphite, clay, coal, sandstone, cinder, cement, ore and the like.

It is an object of the invention to provide a simple method and correspondingly simple apparatus for expeditiously and reliably pulverizing material of the above character to substantially any selected degree of flneness, even to the utmost i'lneness required in the industrial arts.

Another object is to provide a pulverizing mill which shall be highly eillcient for its intended purpose and yet be simple and compact in construction with the elimination of swinging hammers, blades, paddles. rotors or other impacting elements, and which shall operate without waste or dust.

Another object is to provide a mill of the above type. in which the material is comminuted by attrition without adulteration thereof by particles gougedr out of the attrition mill and with substantial elimination of wear on the llatter and the avoidance of the need for periodical replacement of worn parts.

Another object vis to provide a `mill of the above type which may be operated without the need for expert care or attention and in which, as long as a sufllcient supply of raw material is maintained, feed to the machine at the required rate occurs inherently throughout operation and in which, the material to be comminuted is inherently retained in the attrition chamber of the mill without resort to valves, restrictions or baiiles to impede its escape, during the period 'of time required to eilect comminution to the degree desired under the high propulsive force of the comminuting agency.

According to the invention expansive fluid under high pressure is preferably admitted at various parts of the length of a column of the raw material confined against lateral spreading and so tightly packed that it can advance but slowly under the propulsive force'and that must give way by attrition for escape of the uid. The bulking of the material resulting in such attrition affords increased opposition to the advance of the pressure fluid for progressively increased attrition and comminution from the inlet to the discharge end of the column. The mill is preferably used for pulverizing dry material of granular form and the comminuting agency is a gas or vapor, usually introduced at high temperature and high pressure. In a preferred construction of mill the attrition is effected in an elongated strong-Welled metal pipe, preferably disposed in a number of convolutions for compactness of installation.

While any desired method or means may be used for packing the raw material into the attrition pipe or other confined column and replenishing such column as comminuted end product is discharged therefrom. it is preferred to' maintain the column packed by means of an injector connected in the path of high pressure gas ilow and communicating with the source of ,raw material, preferably with the bottom of the' 4thereof which alone is suflciently light to be y levitated by the gas through the ultimate delivery oi' the separator.

The supply chamber for the raw material is in communication with the separator, being preferably disposed directly'therebelow. with pervious container of any coarser comminuted particlesv `connection through which gas pressure may be relieved, thereby to minimize the opposition to gravity return from the separator to the supply discharged from the attrition chamber.

In the accompanying drawing in which are shown one or more of various possible embodiments of the several features of the invention,

Fig. l is a diagrammatic sectional view of the attrition mill, taken on line I--I of Fig. 2,

Fig. 2 is a plan viewof the attrition coil,

. Fig. 3 is a diagrammatic view on a larger scale illustrating vthe mode of operation in the attrition chamber and Fig. 4 is a fragmentary sectional view illustrating an arrangement for determining a coarser degree of comminution.

Referring now to the drawing, the mill comprises a supply container I0 for the rawmaterial, which feeds downward from the inclined floor II thereof through an outlet I2 delivering to pipe I3 plugged at its end I4 and provided with an- 'gular projection I5 into which is fitted an injector jet I6 through which high pressure fluid, preferably air or steam, is admitted by way of pipe Il.

'I'he pipe I3 may extend vertically upward at I8 is preferably madeof extra heavy steel tube and has a substantial length thereof coiled as a multiplicity of convolutions I9 constituting the attrition chamber, which may encircle the separator 20 shown directly above the supply container I0. The supply container I and separator have aligned necks 2l and 22 respectively, connected by a sleeve 23 of canvas to permit venting of gas pressure for the purpose hereinafter set forth.

The delivery end 24 of the attrition coil I9 opens into the outer shell 25 of the separator which preferably is built with a plurality of spaced concentric cylindrical walls 26, 21, and 28, wall 26 being rigidly connected to the top wall 29 of the separator and wall 21 being supported by means of an oblique downwardly extending spout 30 protruding through the neck 22 While the inner wall 28 protrudes through the top 29 of the separator to which it is connected and extends as a conduit 3| to the settling chambers (not shown).

The supply container i0 derives the raw material from a hopper 32 delivering thereto by means of a ight conveyor 33 turned by a pulley drive 34. To prevent the raw material from becoming clogged in the supply container, a vertical flight conveyor 35 may be slowly turned by pulley drive 36 at the upper end of a shaft 31 extending the height of the mill. Alternatively an appropriate pneumatically or electrically operated vibrator of conventional construction (not shown) may be employed to act by percussion against floor il of the container I0 for the purpose set forth.

The attrition coil is preferably provided with a multiplicity of jets 38 spaced along the length thereof, for delivering pressure fluid thereto. Illustratively these nozzles are uniformly distributed as shown, are welded to the coil and deliver tangentially, four such jets ninety degrees apart being shown for each convolution. A manifold comprising a plurality of vertical inlet pipes 39 supplied from a common inlet 40 connected by cross pipes 4| may be used to supply said various jets 38 with air or steam at high pressure from the same source as supplies jet i6.

The raw material 43 should preferably be dry and in granular form not larger than four mesh.

It should be lodged in the supply chamber to a depth suficient to be taken up by the .injector i6 as rapidly as the injector will take it. In practice this could be to a level indicated at 42, approximately midway between the injector I6 and the conveyor 33, the container I0 being about one-third full. Pressure fluid, usually a gas or a vapor, desirably superheated steam but preferably air at a temperature of about 650 F. and at pressure in excess of 75 pounds per square inch is employed. I

In operation, hot air or steam is preferably rst passed throughthe empty mill to heat all parts uniformly. When the supply container lil is now charged to the desired level 42 the further supply of the hot expansive fluid through jet I6 into empty attrition coil i9, causes the injector I6 to entrain the raw material 43 at a fast rate, so that it becomes crowded and to some degree crushed in the attrition coil i9, and as it becomes thus packed in a column filling and blocking said coil, the aspirating action at the injector I6 is correspondingly diminished and the high pressure iluid from jets I6 and 38,` as it forces its way through the packed column causes the particles to be broken up by mutual friction or attrition. As the material becomes a progressively reduced in size in the movement and expansion of the gas through the elongated attrition coil its bulking value increases within the confines of the coil length and more frictional resistance is engendered with correspondingly further attrition. The series of jets 38 of compressed air or steam distributed along the length of attrition coil I9 assure the supply of -steam or air of adequate pressure, even through the most closely packed material near the delivery end of the attrition pipe. `As illustrated in Fig. 3. the particles become progressively finer from the inlet to the delivery end of the attrition coil in the forceful propulsion of the compressed air or steam therethrough.

Despite the fact that the attrition pipe is ol uniform diameter throughout its length, without restrictions or obstruction, and the applied air or steam pressure is of high magnitude, the material is yet greatly retarded in its advance through the attrition chamber, thereby to be subjected to the attrition action for a period of time sufficiently long to reduce it to the desired degree of neness under the expansive andPropulsive force of the gas, much of the energy of which becomes dissipated in the attrition chamber, andA the action occurs automatically without the need for adjustment.

In the operation set forth the gas forces its way for attrition and slow advance of the particles packed in the coil I9 and the major attrition action occurs between said particles and little friction under the outward expansive action of the steam or air is incurred at the smooth innerwall-of the coil, little or no movement occurring therealong, so that the pipe wall shows l little or no evidence of wear even after prolonged service.

As comminuted product is delivered to the separator 20 the aspirating action at injector i6 will be sufficient to entrain more raw material to the inlet `of the attrition pipe, thereby automatically to maintain the same charged or packed so that the comminution proceeds without the need for attention as long as the supply chamber is adequately charged with raw material from the hopper 32. The jet I6 serves thus, automatically to pack the stock into the attrition coil and to keep the same at al1 times packed with stock, whiler jets 38 serve as the pulverizing agency, assisted to some extent by the residual efeciiveness of the air or steam pressure from jet I While the mill described and diagrammatically shown in the drawing is a desirable practical embodiment, it is understood that Wide departures are possible within ,the scope of the invention. Manifestly the attrition chamber shown in the form of a coiled pipe might be arranged in any of a variety of other ways, although it is preferred so to dispose the conduit as to afford a mill of small bulk. The conduit for instance might extend rectilinearly along the walls of the chamber or its convolutions might extend about the neck or about the supply container I0, or about the entire height of the apparatus. Where extra iine material is required it may be obtained by making the pipe of correspondingly greater length or lby introducing the pulverized material in one or more further passes through the mill.

Those skilled in the art may design mill structures other than that illustratively shown herein by which the method claimedv may becarried out and by which the raw material, closely confined in acolumn is caused to. be comminuted by attrition under high pressure expansive duid forced therethrough.

In Fig. 4 is shown a modification in which the 2,315,084;- pipe is provided with a plurality of removable As the ne particles are driven out of the at-.a trition pipe through the outer shell of the separator, the coarser elements thereof will separate, dropping by gravity as indicated by arrows d6,

upon the raw material 63 in the supply containeri0, the venting of air or steam through canvas sleeve 23 precluding any back pressure that might impede such gravity return. The ner particles are levitated with the steam or air upward between walls 26 and 2l and thence directed downward between walls 2l and 28 where separation again takes place, the heavier particles dropping by gravity for collection in an appropriate bin (not shown) under spout 30, the linest particles being levitated through pipe 28 to settling chambers (not shown).

Pulley 3i is driven at such rate as to cause the hopper 32 to maintain the supply container it charged substantially to the desired level d2, in other words to supply fresh raw material at substantially the combined rate-at which it discharges through spout 3d and outlet duct 3i.

As many changes could be made in the above construction and method and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above descriptionv or shown in the accompanying drawing shall be interpreted as illustrative and notin a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patentis:

l. An attrition mill unit comprising a supply container for granular material, a separator thereabove, an attrition pipe connected at its j lower end to the bottom of said supply container and coiled near its upper end in a plurality of convolutions about said separator and delivering thereinto, means for injecting gas under high pressure both through the lower end of said pipe and through one or more points along the coiled part of said pipe,' the inlet part of said separator communicating directly with said supply container, the outlet of said separator discharging the finely pulverlzed material. l

2. An attrition mill comprising a supply container for granular material, a separator thereabove, an attrition pipe connected'at'its lower end to the bottom of said supply container and coiled near its upper end in a plurality of convolutions about said separator and delivering thereinto, means for supplying gas under high pressure to the lower end of said pipe and an injecwr in communication with the lower end of said supply container and discharging into said pipe. the inlet part of said separator communieating directly with said supply container, the outlet of said separator discharging nely pulverized material, an intermediate portion of the separator having aj discharge spout associated therewith for delivering an intermediate grade of pulverlzed material.

3. An attrition .mill comprising a 4source of granular stock, a helical pipe ofY substantially uniform diameter, and of a length at least one hundred times its diameter, having an inlet communicating with said source and having an outlet, an injector near said inlet and .directed lengthwise of the pipe to entrain granular stock thereinto, a plurality of jets distributed along the length of said pipe and directed tangentially 'thereof and toward said outlet, a. source of gas` under high pressure, delivering to said injector and to said plurality of jets. the length and dlameter of pipe, and the means for feeding from lthe source being so proportioned and arranged as to provide for packing granular stock into the pipe and maintaining the same packed as comminuted material is ejected therefrom.

4. An attrition mill comprising a strong walled helical metal conduit substantially uniform in diameter, small relative to its length, a supply container for granular material to be pulverized,

said conduit having an inlet communicating with said container and having an outlet, means for applying high pressure gas to said conduit, means for introducing high pressure gas into said conduit at various points along the length thereof and directed toward said outlet and including an injector connection to said container, to feed granular material into V,said conduit, a separator about which the outer part of said conduit is coiled and into which the outlet of said conduit delivers and in which residual gas pressure is dissipated, the length and diameter of pipe and the means for feeding material to be comminuted being so proportioned and arranged as to provide for packing such material intothe pipe and automatically to determine the subsequent rate of injection in accordance with the rate of discharge of comminuted material under the attrition effeet resulting from the iiow and expansion of the .gas in the column of granular material packed its length, a container below said separator, charged with the granular material to be pulverized and communicating with said separator for return thereto by gravity of heavier particles de-4 livered therefrom, means for feeding the granular material from said container to said pipe, a source of high pressure gas having a plurality of jets distributed along the length of said pipe and directed toward the discharge end thereof, the length and diameter of pipe and the feeding means being so proportioned and arranged as to provide for packing the granular material in the pipe and to maintain the pipe packed as comminuted material passes therefrom into`the.separator.

6. An attrition mill comprising a supply container for granular material, a separator thereabove, an attrition pipe connected at its lower end to the bottom of saidl supply container and delivering into said separator at its upper end, means for supplying gas under high pressure to' fthe lower end of said pipe and an injector in communication with the lower end Yoi' said supply container and discharging into said pipe, the inlet 'part of said separator communicating directly with said supply container, the outlet of saidseparator discharging nely pulverized material, anv intermediate portion of the separator having a discharge spout associated therewith for delverizlig an intermediate grade ,of pulverized ma e a :sinonarrastran. y

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