US2570423A - Apparatus for pelleting solids - Google Patents

Description

1951 cs. w. BATCHELDER ETAL 2,570,423

APPARATUS FOR PELLETING SOLIDS 2 Sheets-Sheet 1 Filed March 20, 1948 1N VEN TOR-5 65a? W Ban/4a 0E2 B0rVE J- EEa/wv Arrme/vEv 1951 G. w. BATCHELDER EIAL APPARATUS FOR PELLETING SOLIDS 2 Sheets-Sheet? Filed March 20, 1948 INVENTORS GEORGE 14 .BHTCHEL as: 041M512 Patented Oct. 9, 1951 George W. Batchelder and Oliver J. Bronn, Milwaukee County, Wis., assignors' to The F. G. Findley 00., Milwaukee, Wis., a corporation of Wisconsin Application March 20, 1943, Serial No. 16,036

8 Claims. (01. 18 2.7)

This invention relates to apparatus for pelleting or tableting materials which are solid at anrbient temperatures and particularly relates to a method and an apparatus for forming pellets or tablets of a liquefiable material, such as certain adhesives.

Forming solids, such as adhesives, into pellets or' tablets has heretofore required grinding of the solid followed by pressing the ground material into masses of the desired size; the shape being immaterial for most uses and being determined only by the pressing device. 'The grinding of adhesiveshad to be done in a refrigerated room and wa's accompanied by the formation of considerable quantities of fines which were not recoverable, made equipment maintenance difiicult and produced undesirable working conditions. Both the grinding and pressing operations require considerable quantities of power which, together with the handling of the materials required in the grinding and pressing methods of pelleting, are important factors in cost of production. Further, the danger of contamination, with some compositions at least, is such as to make the usual pelleting methods difficult to carry out satisfactorily. JAfurther object of the invention is to provide apparatus for pelleting a greater variety of adhesive compositions than is possible by the pressing methods now in use.

And a further object of the invention is to provide apparatus for continuously shaping liquefiable solids into pellets or tablets of a given size by formation of spheroids thereof in a liquid and causing solidification of the spheroids in the liquid. 7 v

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the ac companying drawing in which:

Fig. 1 diagrammatically represents one embodiment of apparatus for performing the method of the present invention.

Fig. 2 is a full scale sectional view of a portion of one nozzle of the structure shownin Fig. 1, showing the relative size of the nozzle and of a spheroid forming thereon,

Fig. 3 is a diagram representing the liquid 7 column of a modified form of apparatus employed when the pelleted solid is lighter than the liquid in which the pellets are formed, and

Fig. 4 is a diagrammatic representation of one element of a modified form of. liquid column in which a physical condition along the column is .2. controlled in a manner differing from that shown in Figs. 1 and 2.

Generally, the method of the present invention includes liquefaction of the solid to be pelleted by the use of heat or otherwise and depositing of the liquefied solid as distinct and well spaced globules or spheroids in a column of' liquid immiscible with the liquefied solid. The liquid column about the globulizing means is maintained at a temperature only slightly lower than the liquefaction temperature of the solid, to assist in forming and in limiting the spheroid size. The globules are freed from the edges of the globulizing apertures or nozzles at a given size and move through the liquid column in a direction and at a rate dependent in part on the relative densities of the solid and liquid. Such rate of movement is also affected by the progressive reduction of temperature of the liquid column from the globulizing zone to the opposite end of the column, the rate of movement preferably being such that the globu les crystallize throughout rather than forming a crystalline shell with a liquefied center under pressure. The degree or extent of cooling is such as to bring the pellets substantially to room temperature at which, in the case of certain adhesives, the pellets will not adhere to each other. A continuous flow of liquid is maintained into the column to produce a flow parallel to the path of movement of the pellets for at least a portion of such path and the liquid flow is continuously discharged from the column in such manner as to maintain a given liquid level therein and to carry the solid and cooled pellets out of the column. The pellets are discharged into suitable means for 'pair'ating the pellets from the liquid and for dr ing the pellets by removal of liquid adhering to the surfaces thereof.

Generally, one apparatus which may be employed includes a kettle in which. the solid is liquefied by heating and from which the liquefied solid is pumped to globulizing means. The pump dischargehas a discharge line to the kettle and the, globulizing means has a return line to the kettle and an overflow line for maintaining a con- 'stant hydraulic head on the discharge nozzles. The globulizing means has a heating coil to keep the material liquefied and has nozzles discharging into a column filled with liquid immiscible with the liquefied solid. The column has means for maintaining a liquid temperature progressively varying fromapproximately the. temperature of the liquefied solid in the zone adjacent the nozzles to ambient temperature at the end of the cglumn remote from the nozzles. As shown in Fig. 1, liquid column temperature control is obtained by partially interwound heating and cooling coils while Figs. 3 and 4 respectively show the use of jets and of rings in controlling the temperature of the column. A continuous flow of cool liquid is supplied adjacent one end of the column (see Fig.1) to aid in controlling the temperature therein and to provide a current for removal of solidified pellets by way of a discharge conduit coacting with the column to form a U-tube controlling the level of the liquid in the column. The discharge conduit leads to a screen for separating the discharged liquid and pellets and the pellets are discharged from such screen after surface drying thereof by a flow of air about the pellets.

Referring particularly to the drawing by characters of references, the numeral 5 generally designates a melting kettle which is double walled to provide a space 6 receiving a heating medium by way of an inlet 1 and discharging such heating medium from an outlet 8. The bottom of the kettle is connected by a conduit [2 with a control valve 13, to the inlet of a pump I4 shown as being of the centrifugal type and discharging into a line l5 under the control of a valve 16. A line H from the discharge line is under the control "of a valve [8 for returning the pump discharge to the kettle whenever desired. It will be understood that the various conduits' and discharge and return lines herein mentioned are preferably jacketed to receive a heating medium, or are otherwise heated.

A liquefied solids globulizing means generally designated 23 comprises a chamber 24 with a plurality of nozzles '25 in one wall thereof and with a heating coil 26 in such chamber. Chamber 24 may be emptied into kettle 5 by a pipe 21 controlled by a valve 28 and the level of liquid in chamber 24 is controlled by a pipe 29 and a valve 30 connected with return line -21. The nozzles 25 extend into a liquid column comprising a container 3| for a body of liquid 32 having a heating coil 33 and a cooling coil 34 located adjacent the inner surface of the container and partially interwound so that the temperature in the liquid may be progressively or substantially uniformly varied from thezone of liquid about the ends of the nozzles at one end of the column toward the other end of the column. A frusto-conical hopper 36 with openings 31 is fixed in the bottom of the column to receive the solidified pellets, the solidified pellets being subjected to the action of a jet of liquid delivered tangentially into the column by a pipe 38 and to a flow of cool liquid delivered into the space between the side of the hopper 36 and the side of the column by a pipe 39 to flow counter to the path of movement of the pellets for at least a portion of their movement.

The smaller end, of the hopper 36 is connected with a discharge conduit 43 of relatively large size which is so arranged that a portion 44 thereof coacts with the column in forming a U -tube for maintaining a given level of liquid in the column. The end portion 45 of the discharge conduit is flexible to permit swinging the discharge conduit 5 about the axis of the rising leg thereof by use of a swivel joint 46. A vent pipe-41 is connected with the conduit and extends above the level of liquid in the column to prevent any siphon action in the discharge conduit.

The discharge conduit delivers a flow of liquid and the pellets carried therein, into a liquidpellets separator-drier comprising a chamber 5| having a screen partition 52 extending at an angle acrosssuch chamber, the partition being preferably so shaped as to guide pellets falling thereon to an opening in the wall of the chamber closable by a flap 53 and through which the pellets may be discharged into a chute 54. The level of liquid in the separator is controlled by an overflow 54 with a valve 55. A drain 56 and a valve 51 are provided to empty all liquid from the separator when desired. The portion of the chamber 5| below the partition 52 is connected by a conduit 60 with a blower 6| by which a current of air may be passed through the partition 52 and the pellets thereon, after drainage of liquid from chamber 5 I, for the purpose of removing residual surface water on such pellets. The air current may be heated, if desired. During drying of the pellets in one separator, the discharge conduit is swung to bring section 45 thereof into another separator similar to that described. And the same blower 6! may supply air to the second separator by way of a branch conduit 62.

In operation, a solid is liquefied in the kettle and the liquefied solid is delivered to the nozzles which are of an internal diameter smaller than the size of the pellets to be produced. The liquefied material flows into the liquid column as globules or spheroids of which the size is determined in part by the internal diameter of the nozzles and in part by the temperature of the liquid in the area about the nozzles. Such temperature in the zone about the globulizing nozzles is preferably not more than 10-50 F. below the temperature of liquefaction of the solid. As soon as a globule has attained a size determined as above indicated, the globule leaves the end of the nozzle while still in very liquid condition. The surface tension of the liquefied solids now causes the globule to assume a substantially spherical shape.

By proper relationship of the relative densities of the liquid column and of the relatively soft globules, a movement of the globules is now obtained from the area adjacent the ends of the nozzles to the opposite end ofthe column. The rate of movement of such globules through the liquid column is partially controlled by reducing the temperature of the column progressively and preferably at a substantially constant rate, from a zone adjacent the ends of the nozzles to the opposite end of the column and the column is preferably of such height for a given rate of cooling, that the globules are crystallized in their movement through the column and reach the end of the column at substantially ambient temperature. The rate of cooling (i. e., the rate of heat transfer) and the height of the column are, of course, related to the composition and the size of the globules.

Although the nozzles are spaced from each other more than the diameter of a globule, it is possible for the globules or spheroids to move into contact with each other while still sufficiently soft to be adherent and thus produce agglomerations. Such agglomerations are broken up by a jet of liquid delivered by pipe 38 to a point adjacent the periphery of column 3| to produce a swirling action in the lower portion of the column which, in combination with contact on the column hopper of such agglomerations, causes discharge of thepellets as separate globules.

The tangential jet 38 and liquid supply line 39 continuously produce a flow of liquid into the the solidified pellets out of the column into the liquid-pellets separator-drier. If a blockage occurs in'th'e discharge conduit, it is necessary only to close the end of the vent pipe 4'! for a short time thus creating a siphon acting in the discharge conduit 43, 44, 45, which rapidly removes the blockage.

If the solid material is of relatively low density, it may be necessary to place the liquefied solids distributing means at the bottom of the column and allow the globules or spheroids to rise upwardly through the liquid for discharge from the top of the column. Such structure is shown in Fig. 3 in which the column 65 is preferably made as a closed tank, with a. discharge conduit 66 adjacent the upper end thereof. Liquefied material is supplied from the pump [4 by way of a pipe 51 to a header 68 with nozzles 59. The liquefied solid being lighter than the liquid 12in the column, the header 68 is a closed chamber adjacent the bottom of the column and the nozzles 69 are directed upwardly therefrom. Coils Band 14 are arranged respectively closely adjacent to the header 5% and spaced at'a slight distance from the ends of the nozzles 69 for receiving a heating medium by which solidification of the material in the header can be prevented and by which the size of the masses of material separating at the nozzles, can be regulated. A liquid supply line 15 extends into the column and terminates in a plurality of upwardly directed nozzles 16. Such supply of liquid is preferably at a lower temperature than the materials being pelleted and is discharged in a series of jets which provide a rising conical flow of liquid in the column. The solidified masses rise upwardly through the column and are carried out of the column by overflow of the liquid through the offtake 66.

For some materials, it may be desirable to control the temperature gradient in the column by admitting liquid in jets distributed vertically along the column and preferably also distributed circumferentially thereof. The openings or nozzles for so supplying liquid are preferably so placed that thejets may produce both movement and sufiicient agitation of the pellets to prevent agglomeration thereof. Such structure is shown in Fig. l in which a heating coil 86 extends into the column 3| adjacent the ends of the nozzles 25 for the purpose of maintaining a temperature, in the zone adjacent the ends of the nozzles, only slightly lower than the temperature of liquefaction of the solid material itself. Hence, the size of the spheroids may be readily controlled, and such spheroids may be therein as indicated at 83, for discharge of the .liquid as jets around the circumference of the entire column. A second supply pipe 85 is shown as supplying liquid to a second header 86 for supplying an additional flow of liquid tov carry the pellets into the receiving hopper 35. It will, v

of course, be understood that the number of rin headers may be multiplied as desired dependent upon the composition of the material being pelleted and upon the relative densities of the pellets and the liquid and "upon the rapidity with which the pellets are to be cooled. The jets may be located to: give either asmooth flow of liquid or to give a itation (as-desired. I

It will thus be seen that the present method eliminates the waste and nuisances inherent. in the usual pelleting or tableting methods involving grinding the solid and pressing the ground material into shape and requires much less power than such prior method. No handling of the compound is required between the step of liquefaction thereof and the step of removal of the solidified pellets from the drier-thus avoiding danger of contamination, reducing the time and labor required and avoiding the limitations heretofore placed on the locations at which such pelleting methods could be performed. The liquefying step of the method aids in securing homogeneity of the composition; and the solidification step of the method. produces a solid air-free crystalline structure, at least in some compositions, as compared to the usual opaque aircontaining masses obtained with the pressing process.

The present process may be applied to any material which can be liquefied by heat or pressure or other means and to such materials as may be solidified by physical or chemical action in a liquid immiscible with the material to be pelleted. It will be understood, however, that-the pellets are always substantially spherical as a result of the surface tension of the surface thereof in contact with the immiscible liquid which shapes the masses while the material is still liquefied. v

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that variouschanges and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

We claim:

1. In a device'for forming a liquefied'solid into masses of given size, means for liquefying the solid, a column for receiving a. liquid immiscible with the liquefied solid, means for introducing separate massesof the solid into the liquid in the column and adjacent one end thereof, jets for continuously producing a fiow of liquid through a portion of the column and parallel with the path of movement of the masses therethrough, means for progressively controlling the temperature of the liquid in the. column from the solids receiving end thereof and along the path .of movement of the masses .therethrough, and a conduit connected with the column for discharging the flow of the liquid and the solidified masses therefrom, a chamber for receiving the masses and the liquid, means for separating the liquid and the masses, and means for drying the masses in the chamber by a current of ambient air.

2. In a device for forming a liquefied solid into masses of given size, means for liquefying the solid, a column for receiving a liquid immiscible with the liquefied solid, means for introducing temperature of the liquid in the column from the solids receiving end thereof and along the path of movement of the masses therethrough, and a conduit connected with the column for discharging the flow of the liquid and the solidified masses therefrom, a chamber for receiving the masses and the liquid, a foraminous partition dividing the chamber into two parts at different levels, and a blower discharging into the lower part of the chamber for drying the masses of solids resting on the partition.

3. In a system for forming a liquefied solid into masses of many sizes, means for liquefying the solid by melting, a column for receiving a liquid immiscible with the melted solid, means for introducing separate masses of the solid into the liquid in the column and adjacent one end thereof, means for progressively reducing the temperature of the liquid in the column from the solids receiving end thereof and along the path of movement of the masses therethrough, a false bottom in the column and having apertures therethrough, the column bottom and the false bottom defining a ringlike space, a conduit connected with said space for supplying liquid thereto for flow through the said apertures, and a conduit connected with the false bottom for discharging the flow of liquid and the solidified masses therefrom, the liquid supply being at a temperature for chilling the masses and preventing adhesions therebetween and thereof in movement through the discharge conduit.

4. In a system for forming a liquefied solid into masses of many sizes, means for liquefying the solid by melting, a column for receiving a liquid immiscible with the melted solid, means for introducing separate masses of the solid into the liquid in the column and adjacent one end thereof, means for progressively reducing the temperature of the liquid in the column from the solids receiving end thereof and along the path of movement of the masses therethrough, a conical false bottom in the column and having apertures spaced substantially uniformly about the larger end thereof, the column bottom and the false bottom defining a ringlike space, a conduit connected with said space for supplying liquid thereto for flow through the said apertures, and a conduit connected with the smaller end of the false bottom for discharging the flow of the liquid and the solidified masses therefrom, the liquid supply being at a temperature less than that of the lowest solidification temperature of the solid for chilling the masses and preventing adhesions therebetween and thereof in movement through the discharge conduit.

5. In a device for forming a liquefied solid into masses of given size, means for liquefying the solid, a column for receiving a liquid immiscible with the liquefied solid, means for introducing separate masses of the solid into the liquid in the column and adjacent one end thereof, downward- 1y directed jets at a plurality of vertically spaced locations in the column for supplying liquid to and continuously producing a flow of the liquid and the masses through a vertical portion of the column and parallel with the path of movement of the masses downwardly through the column, said jets progressively reducing the temperature of the liquid in the column along the path of movement of the masses therethrough, and a conduit connected with the column for discharging the flow of liquid and the solidified masses therefrom.

6. In a device for forming a liquefied solid into masses of given size, means for liquefying the solid, a column for receiving a liquid immiscible with the liquefied solid, means for introducing separate masses of the solid into the liquid in the column and adjacent one end thereof, a plurality of ring headers positioned at vertically spaced points in the column, each header having openings in its under side forming downwardly directed jets of the liquid for'continuously producing a flow of the liquid and the masses through a vertical portion of the column and parallel with the path of movement of the masses downwardly through the column, said headers progressively reducing the temperature of the liquid in the column along the path of movement of the masses therethrough, and a conduit connected with the column for discharging the flow of liquid and the solidified masses therefrom.

'7. In a device for forming a liquefied solid into masses of given size, means for liquefying the solid, a column for receiving a liquid immiscible with the liquefied solid, means for introducing separate masses of the solid into the liquid in the column and adjacent one end thereof, a ring header positioned adjacent and below said last mentioned means, a plurality of additional ring headers positioned at vertically spaced points in the column below the first mentioned ring header, each header having openings in its under side forming downwardly directed jets for continuously producing a flow of the liquid and the masses through a vertical portion of the column and parallel with the path of movement of the masses downwardly through the column, said headers progressively controlling the temperature of the' liquid in the column along the path of movement of the masses therethrough, and a conduit connected with the column for discharging the flow of liquid and the solidified masses therefrom. I

8. In a device for forming a liquefied solid into masses of given size, means for liquefying the solid, a column for receiving a liquid immiscible with the liquefied solid, means for introducing separate masses of the solid into the liquid in the column and adjacent one end thereof, means within the column for progressively reducing the temperature of the liquid in a portion of the column, downwardly directed jets at a plurality of vertically spaced locations in the column for supplying liquid to and continuously producing a fiow of the liquid and the masses through a vertical portion of the column and parallel with the path of movement of the masses downwardly through the column, said jets aiding in progressively reducing the temperature of the liquid in the column along the path of movement of the masses therethrough, and a conduit connected with the column for discharging the flow of liquid and the solidified masses therefrom.

GEORGE W. BATCHELDER. OLIVER J. BRONN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Mabbs July 3, 1945

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