US2167432A - Granulation of nongranular materials - Google Patents

Description

July 25, 1939.

G. E. cox Er Al. 2,167,432

GRANULATION OF NONGRANULAR MATERIVALS Filed May 14, 192.7 2 Sheets-Sheet 1 zNvENToR. /VAM riff 6;. Mc a/F/vfy,

BY v2-0,4265 Cox ATTORNEY.

Juh' 25, 1939. G. E CQX Er AL 2,167,432

GRANULATION OF NONGRANULAR MATERIALS Filed May 14, 1937 2 sheets-sheet? BY 650576 60x,

ATTORNEY.

Patented July 25, 1939 UNITED STATES PATENT OFFICE GRANULATI'ON 0F NONGRANULAR MATERIALS Application May-14, 1937, Serial No. 142,632v

, 1 Claim.

The present invention relates to a method of treating non-granular materials to produce therefrom substantially spherical or globular aggregates in the form of substantially stable hard 5 granules.

In many arts today, materials heretofore in the form of powders or powdery materials, the individual particles of which are either of uniform or of heterogeneous sizes, are more desirable for 10 many purposes in the form of granules. For in.-

stance, fertilizer materials such as calcium cyanamid, heretofore marketed as a powdery or nongranular product, becomes more desirable and acceptable to the trade in the form of granules with minimum quantities of fines and many thousands of tons of this material are now marketed an- Y nually. This is but one example of granular materials which are constantly finding a larger place in industry. l

The principal object of the invention is, therefore, to produce granules from 'non-granular materials by a simple and eicient method with Vminimum handling'difficulties so that as a result of these operations, a maximum number of optimum sized aggregates areproduced with minimum quantities of fines, and of a stable character.

To this end, the invention contemplates in its broadest aspect, passing the materialv to be granulated through or between closely approaching surfaces such as rolls or presses, so that the material will be compacted together in the form of a flake. It is intended that the thickness' of this iiake will, in large measure, determine the eventual v diameter of the produced granule. rI'he invention contemplates subsequently treating the ake so as to break it up into smaller pieces, which will be termed herein as rough granules. These broken pieces will, of course, have relatively sharp edges and will be of irregular shape. The sub- 40 sequent treatment includes tumbling these rough granules upon themselves to knock off the rough edges and bring them more nearly into a spherical or globularv shape. During the tumbling operation, the nes or iinal particles produced as a result will be in large measure pounded into the granules and become a part thereof. If the material treated is of such acharacter that more nes are produced than can normally be pounded into and become incorporated with the granules,

5 they may be subsequently separated.

`The invention likewise contemplates the heat treatmentof the thus roundedgranules to reduce their liquidcontent to a desiredv point,I such point being determined by the degree. of Y hardness desired dependent upon the use to which the granular material will be put.

The invention further consists in the further details hereinafter described. v

In the drawings: 5

Fig. 1 illustrates diagrammatically' the character of equipment used to carry out the process;`

Fig. 2 showing the remaining equipment;y Fig. 3 is a sectional View along the line 3-3 of Fig. 2. 10i

Referring now with particularity to the em. bodiment illustrated and taking crude calcium cyanamid as a representative material to bev treated, although it is to be understood that this is illustrative only, the fully hydrated powdery 1T!)I cyanamidy is introduced from a suitable source into hopper I from which it may be fed by screw device 2 into a suitable type of automatic Weighing scale 3 emptying into mixer 4. In some instances, the cyanamid entering the mixer will 20' contain sunicient moisture so that in the subsequent compacting or flake forming operation, sufficient adherence may be obtained between the particles. If, however, the cyanamid at the point of entering the mixer 4 does not contain sufficient 25 moisture, additional quantities may be added from tank 5 through metering device 6 until'the proper consistency has `been obtained. Where desired, the water in the tank 5 may contain ma terials dissolved therein, such, for instance, as 30 potash salts and/or phosphates where a complete fertilizer is desired. On the other hand, such liquid may contain binding materials such asv a solution of calcium nitrate or the like. Again, it may contain such substances as the sugars Where 35 it is desired to utilize the dicyandiamid inhibiting eiiect thereof during the process. These, or any combinations of the above, may be utilized in any manner desired and they may be introduced from a single tank or an additional tank 1 with 40 its metering device 8 may be utilized.

The requisite amount of liquid, vwhere necessary, and containing desired additional material, or none at all, having been introduced into the mixer 4 as at 9, the cyanamid and the added ma- 45 teri'alarewell mixed by means of the rotatingpaddles I0 inside of the mixer. From the mixer, the' moist cyanamid then passes to a compa'cting nucleus or flake forming device, which may conveniently take the form of a squeeze roll mechanism shown generally at il. 'Ihese rolls arevso arranged with relation to each other, that their proximity may be adjusted and the cyanamid in passing between' themis compacted and formed into flakes. The clearance between the rolls isi so adjusted that a flake of any desired thickness may be obtained, which thickness will in large measure determine the eventual diameter of the finished granule.

From the flakjng device Il, the flakes drop into a breaker mechanism I2 containing rotating knives I3 which, during the passage of the cyanamid through the breaker, cut or break the flakes into smaller fragments which may be termed partially formed or rough granules. The action of the knives in the breaker is not such as to again reduce the flakes to powder but should be only carried to the extent that fragments or rough granules are formed. From the breaker I2, the material is fed through line I4 to a granulating equipment I5 which may be in the form of a slightly inclined rotating cylinder. In this piece of apparatus, the rough granules are gently tumbled upon themselves so as to knock off the edges of the fragments and form substantially globular granules therefrom. The length, diam-- eter, inclination and speed of rotation of this equipment may be suitably chosen so as to produce the desired quantity of granules of the specified size with minimum fines. During this tumbling operation, all or most of the fines produced are pounded into the granules during their formation. This operation, therefore, has a tendency to reduce the total amount of iines discharged from the granulator while at the same time producing a more dense or compact granule. This has the effect of displacing the water or other liquid in the granule toward the surface thereof, which facilitates drying or liquid removal in a subsequent operation.

From the granulator, the granules drop upon screen I6, the oversize being caught in trough I'I andreturned through conveyor I8 to a supplemental flaking device I9 similar to the flaking device II for return to the breaker l2.

The mesh of the screen I6 is chosen so as to deliver into the drier the size granules desired.

The drier 2D may take the form of an inclined rotating cylinder within which is located a cylindrically arranged core 2| with radial vanes or division plates 22 therebetween (Fig. 3), inasmuch as the granules delivered to the drier 2B at this point are relatively weak, they will not stand a great deal of abuse and, hence, by constructing the drier as above set forth, the movement of such particles during tumbling Yis of a restricted extent, while at the same time giving the drier a large capacity without increasing its length or the time of drying. j

`The drier may be suitably heated, preferably interiorly, by means of the products of combustion of burner 23, which latter is fed by fuel through the line 24 and air through the line 25. The products of combustion are delivered through duct 26 to the drier 20 and pass concurrently therethrough with the granules. The temperature of the combustion gases entering the drier may be adjusted by admitting requisite quantities of cool air through duct 2l by proper use of the damper 28, Any dust'formed during the passage of the granules through the drier is pulled out by means of exhaust fan 29 and conducted to a dust separator Sil, from which the same is delivered to hopper 3| and returned through line 32 to a feed device 33 and from thence into a weighing scale 34 and into the mixer 4. Thus an absolute control may be obtained on the quantities of dry or'substantially dry materialV entering the drier in a cyclic manner.

The length, inclination, and speed of rotation of the drier 20 and the temperature, quantity and velocity of the heated gases delivered thereto are chosen with a View to producing granules having a desired moisture content. This moisture ligure will obviously vary over wide limits, depending upon the use to which the granules are to be put. In the case of granular cyanamid used for fertilizer purposes, the total moisture content should be reduced to the neighborhood of 5%, more or less. The thus dried granules are then delivered to conveyor 35 and passed over screen 36 to separate the oversize therefrom. These oversize particles are caught in trough 3l and through conveyor 38, passed to Crusher de- Vice 39, whereupon they are return-ed to the conveyor 35 and screen 36. The granules of the proper size pass through screen 36 and pass downwardly through one or more dust separators 40 into conveyor 4I, where they pass` out of the train of apparatus to the packaging machine or storage. Exhaust fan I2 draws air into the dust separators 4G through air inlets 43, countercurrent to the moving finished granules and this dust is returned through line 44, through separator 45, hopper 33 and into line 32 for return eventually to the mixer ll.

, Where desirable, some of the initially dry material from the feeder 2 may be by-passed through either or both of lines 46 or dl to the breaker i2. This insures the proper amount of fines in granulator I5 in the event that the material delivered to the granulator is too wet or an insuicient quantity of lines is produced during the granulating process. It may be added that the iines either knocked off of the rough granules or additionally supplied through the lines 46 and 47 assist materially in preventing a too fast building up of granules in the granulator and thus assist in the production of maximum quantities of granules of an optimum size.

Among the other materials which may be successfully granulated by this method are the mono and diammonium phosphates, the mono, di or tri calcium phosphates, calcined phosphates, basic slag, alkali chlorides and sulphates, bauxite fines or the like, or any combination thereof.

In addition, llers, either reactive with the materialrbeing granulated, or inert thereto, may be added such as gypsum, sand, clay, ground dolomite, limestone or the like.

Where the material treated is water or liquid soluble, the liquid added may contain `a solution of the material treated. For such insolubles, however, as basic slag, bauxite, or the like, a solution of some suitable binding agent will befound desirable, such as calcium chloride, calcium nitrate, cautic soda, sugar or the like.

While the invention has been shown and described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto, but is to be construed broadly and limited only by the scope of the claim.

We claim:

A method of granulating a non-granular material chosen from the group consisting of calcium cyanamid, ammonium phosphates, calcium phosphates, basic slag, calcined phosphates, alkali and ammonium sulfates and muriates and bauxite fines which includes the following steps: adjusting the liquid content thereof so that when thematerial is passed through squeeze rolls it will have sufcient adherence to formflakes, passing the moistened material through 'squeeze' ros to form Hakes, the thickness of the flake largely determining the eventual diameter of the granules, breaking up the akes into rough granules, tumbling the rough granules upon themselves to round up the same and compact the solid matter thereof While driving lthe liquid content thereof to the surface, separating the oversize masses from the desirably sized granules by passing the result of the granulating operation over a screen, and thereafter separately drying the rounded compacted granules freed from oversize.

GEORGE E. COX.

WALTER G. MCBRNEY.

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