US2875823A - Apparatus for converting liquids, solutions, emulsions, suspensions, and the like int dry powders - Google Patents

Description

March 3, 1959 2,875,823

M. J. ST-AM APPARATUS FOR CONVERTING LIQUIDS, SOLUTIONS, EMULSIONS, SUSPENSIONS, AND THE LIKE INTO DRY POWDERS Filed Dec. 21, 1954 INVENTOR MART/NUS J, .5 TAM ATTORNEYS Un t St tes Pet-ea [0. 1

APPARATUS FOR CONVERTING LIQUIDS, SOLU- TIONS, EMULSIONS, SUSPENSIONS, AND THE LIKE INTO DRY POWDERS Martinus Joiinnes Stam, Rotterdam, Netherlands, assignor to Rubber-Latex-Poeder-Compagnie N. V., Amsterdam, Netherlands, a company of The Netherlands Application December 21, 1954, Serial No. 476,796

Claims priority, application Netherlands December 28, 1953 4 Claims. (Cl. 159-4) My invention relates to an apparatus for converting liquids, solutions, emulsions, suspensions and like media into dry powders. I It is an object of this invention to improve such apparatus so that an extremely fine dry powder with a great uniformity of particle size is obtained. It is a further object of this invention to attain the above object with a simple and reliable apparatus. It has been proposedto obtain dry powders from liquids or the like by introducing the liquids into a cupshaped atomizer, centrally disposed in a casing and-being rotated so as to project the liquid as a thin film outwards into a flow of gas, which atomizes the liquid in said film and entrains it while further drying it into a fine powder. My invention improves such known proposals. In this respect I propose according to the present invention to embody such an apparatus in combination with a casing, atomizer means centrally disposed therein, said atomizer means comprising a vertically disposed rotary cup having an open top, a sharp upper rim around saidopen top, a substantially concave closed bottom portion and a straight substantially conical side wall intermediate said open top and said bottom portion, said open top being of a diameter larger than said bottom portion and smaller than the depth of said cup, a shaft for rotating said cup about its central cone axis, a supply conduit for the, medium to be atomized, which supply conduit enters the cup through said open top, ends directly above the bottom and is disposed coaxially with said shaft, means defining a narrow annular slot formed along said upper rim of said cup between the latter and said casing,

, 2,875,823 Patented Mar. 3,1959

' A cup-shaped atomizer 1 is carried by a driving shaft. 2, which is connected to the atomizer by a square head 3 engaging in a square hole in the bottom of the atomizer. The atomizer 1 is rotatable by shaft 2about a vertical axis and is shaped as a body of revolution generated around said axis. It has an open top, a sharp upper rim 4 about said open top, a substantially hemispherical closed bottom portion 5 and conical part 6 widening upwardly and connecting the bottom portion-5 While, continuously changing into said portion to the upper rim 4. The depth of the atomizer 1 is larger than the diameter of the said rim 4.

A stationary vertical supply conduit 7 for medium to be atomized is positioned-with its axis in the axis 'of rotation of'the atomizercup 1. Said conduit 7 is' open at top and bottom ends has atits top an internal fairing 8 constituted by two cones with joined bases and sup ported in the upper conicalpart of the conduit by struts supporting the lower cone. l

The conduit 7 extends downwards into the atomizer cup 1 to a' short distance from the bottom thereof. In

the proximity of the top of the atomizer cup 1 the con-' duit 7 is provided with a guiding member 9 shaped as a body of revolution about the vertical axis of the con-. duit 7 and filling the space in the top surface of the atomizer cup so that a small annular space is left between the rim 4'and this guiding member. Said guiding member is secured 'to the conduit 7 and its shape in vertical cross-section is about a downwardly widening hyperboloid in the upper part and a spherical lower part, joined together at their largest diameter, as will be clear from the drawing. p

The atomizer cup 1 is provided on its outer surface in the proximity of the rim 4 but a short distance below g conduit 7 for the liquid medium. Its flanged end is bolted struts 16 in the lower part of said elbow 13 support the said slot opening from the cup into the interior of said casing and through which slot said medium is dischargeable from the cup into the casing, when said medium atomized, and a gas conduit formed around said open cup top, said narrow annular slot opening into said conduit also, and which conduit'is of a narrowest cross'sectional area in the vicinity of said open cup top and gradually increases in cross sectional area from said narrow annular slot to attain the cross sectional area of said discharge tube. The gas conduit will of course be made I to guide a suitable drying gas such as hot air.

With an apparatus according to the present invention it is, for example, possible to atomize a latex film with a thickness when leaving the atomizer cup of 0.3 to 101;. After drying, very fine rubber particles are obtained, viz,, of 0.1 to. 3u'. Such favorable results have never before been obtained with such simpleand small cost involving apparatus.

[Other objects and advantages of the invention will become apparent from the further description thereof in connection with the accompanying drawings, wherein ,Figure 1 shows a vertical cross-section of the apparatus according tothe invention.

Figure 2 is a horizontal cross -sectionof the above drier apparatus along the line IIII in Figure 1.

conduit 7 so that when mounting or removing the elbow 13 the conduit 7 with guiding member 9 is simultaneously mounted and removed respectively. Said vertical gas conduit 15 diverges downwardly in 7 its lower part 17 and so passes into a part 18 in the shape of the lower half of a torus with acircular crosssection and symmetrical about the vertical axis of conduit 7, conduit 15 and atomizer cup 1. The outer side of said toroidal part 18 changes into a vertical cylindrical wall 19, continuing in an outwardly extending wall 20, which latter at its outer periphery changes into a downwardly directed cylindrical wall 21 terminating in a flange 22. The wall part 20 is not situated in a plane perpendicular to the vertical axis. of the cup 1, etc., but

is positioned at a varying height, being the smallest at 23 in Figure 2 and gradually increasing in the sense of clockwise rotation as seen in Figure 2, so that it is much higher in the left part of Figure 1 than in the The parts 15, 17, 18,19, 20, 21 and 22 constitute the greater part of a volute casing with'a volute discharge passage 27 therein. 'Said' passage is .limited at 'symmetricalwith respect to the common verticalaxis of conduit 7 and cup 1. q I

In its centre, casing'lpar't'28 extends inwardly towards the cup 1 below theblades" 10 thereon and is bent downwardly' below said blades to change into a downwardly extending cylindrical duct 31 openat its lower end. Between said duct .31 and the cup 1 there is left a small annular gap 32. p I

y A g'uiding wall 33 is rovided between top and bottom of the'casing' in the narrowest part 23 thereof. Said wall 33 is secured, e. g by welding, to the lower casing art 28 with its lower edge; Its upper edge has a shape so that it almost contacts the upper ca's'ing part along the walls 21, 20, 19' and 18 thereof. The wall 33 is generated bystra'ight vertical lines and its shape" in a horizontal direction clearly appears from FigureiZ of the drawings.

As seen from the drawings the gas passage through conduit decreases downwardly in annular cross-sec tional area until it has reached its smallest area at the greatest diameter of guiding member 9, where a narrow annular slot 34, is formed. i

First this slot the gas passage again increases in area to" change continuously into the discharge casing with volute passage 27.

The operation of the above apparatus will now be des ribed.

Drying gas, e. g), hot air, is introduced through gas supply conduit 11 and flows through elbow 13 'down throughvertical gas conduit 15. The guidin member 9 guides the gas outwardly within the lower part 17 of gas conduit 15, so that the gas flows downwards and radially outwards as a small annulus through the narrow or rotation .of cup 1 is chosen so high'that an extremely thin him of said medium is formed in the cup' 1. Said flows upwards in the cup and leaves it at the sharp upper rim 4,-where it flows almost exactly radially outward's into the narrow, annular slot 34. The drying gas, which flows almost without rotation in inlet conduit 11, caused to rotate in Vertical gas conduit 15 by the action of the blades 10 on the cup 1 and by the fact thatithe' gas leaving'the apparatus flows through volute gages'the liquid film projected outwardly from rim 4' while substantially flowing in the-same direction as said him, said film flowing horizontally outwards and said gas flowing at an angle of about 40 to the horizontal.

It has appeared that in this way a very'fine powder isr'nade from the liquid-medium instantaneously and that thepowder obtained is not only extremely fine but also to a considerable extent uniform in dimension and.

perfectly dry.v Said powder is discharged with the gases through volutepassage 27 in the discharge casing and Outlettube 24. I n v The suction generatedby the blades 10 also causes the inflow of ambient air upwardly through the small annular gap 32 between duct 31 and atomizer cup 1. air cools the atomizer cup. Heating of this cup is further prevented by the fact that the cup 1 is largely located outside the casing and further parts of the apparatus.

The guidingm'ember 9 not only guides the drying 'ga s but also prevents it from flowing into the atomizer cup 1, so that premature drying of the liquid film in-said cup by said gas is prevented;

The guiding wall 33 prevents powder, which is not yet entirely dry, to escape to the outlet 24, 26. To this end said guiding wall 33 causes gas and liquid film, being transferred to powder, in that part of the periphery of the narrow annular slot-34' which is close to the outlet 24, 26, to pass through the entire volute passage 27 in the casing before leaving the apparatus through the outlet 24, 26.

As the liquid leaving the atomizer cup 1 is spread out radially outwards after leaving upper rim 4 and as the gas flows substantially in the same direction when engaging said liquid film, agglomeration of fine droplets, into which the film breaks in this area, is prevented so that there are no coarser particles formed in the powder.

If the liquid medium is a solution, suspension or the like, the liquid constituent which is not transferred into powder, such as the solvent or the water in a suspension or emulsion is vaporized and discharged together with the gas. n I

The gas flow not only prevents the liquid particles from sticking together, but also prevents said particles from reaching the wall of the lower part 17 of vertical conduit 15. The supply of gas, the action of blades 9 and the shape of the apparatus is such that the gas has a sufliciently high speed in the narrow annular slot 34 to prevent this. Preferably the gas speed isequal to or higherthan the speed of the liquid particles in their zone of first contact.

Iclaim: V ppm 1. In an apparatus for converting liquids, solutions, emulsions, suspensions and the like media into drypow: ders, the combination of an annular casing, a discha'rge tube on the perimeter of said casing, atomizer centrally disposed in said casing and comprising a v'er tically positioned rotatably mounted cup havingan open top and located in the center of said annular casing, the: said cup having a substantially concave closedbottorn portion, and substantially straight conical walls interme} diate the open top and the closed bottom portion, said open top having a diameter larger than said bottom portion and smaller than the depth of the cup, a' sha'ft for rotating said cup about its central axis, a' supply con; duit for the medium to be atomized coaxial with said shaft and entering the open top of said cup to terminate: short of said cup bottom portion, guiding means in the center'of said annular casing and spaced above said clip rim to form a first narrow annular slot with said cup" rim'which first slot opens into said casing, and'a gas con duit within the center of said annular casing and flaring" outwardly just outside of said cup rim and said guiding means to form a second narrow annular slot with said guiding means for the passage of gases from said conduit' into said casing whereby said first narrow annular slot opens into said gas conduit and said second slot,- so that atomized liquid thrown out'of said cup over theiriin thereof is discharged through said second narrowj slot into said casing, said gas conduit having a narrow'cross section in the vicinity of said open cup top and greaua'ny increasing in cross-sectional area to attain the cross-sectionala'rea of said discharge tube.

2. An atomizer as described in claim 1, further eehi prising blades for rotating the" drying gas, said blades being mounted on the outside of said side walls of said rotary cup adjacentsaid opening thereon 3. In an apparatus for converting liquids, solutions, emulsions, suspensions and the like media into dry powders, the combination of an annular casing, a discharge tube on the perimeter of said casing, atomizer means centrally disposed in said casing and comprising a vertically positioned rotatably mounted cup having an open top and located in the center of said annular casing, the said cup having a substantially concave closed bottom portion and substantially straight conical walls intermediate the open top and the closed bottom portion with said open top having a diameter larger than said bottom portion and smaller than the depth of the cup, a shaft for rotating said cup about its central axis, a supply conduit for the medium to be atomized coaxial with said shaft and entering the open top of said cup to terminate short of said cup bottom portion, guiding means in said annular casing above said rotatably mounted cup and terminating above said cup rim to form a first narrow annular slot with said top rim which first slot opens into said casing, and a gas conduit within the center of said annular casing and flaring outwardly just outside of said cup rim and said guiding means to form a second narrow annular slot with said guiding means for the passage of gases from said conduit into said casing whereby said first narrow annular slot opens into said gas conduit and said second slot so that atomized liquid thrown out of said cup over the rim thereof is discharged through said second narrow slot into said casing, said gas conduit having a narrow cross-section in the vicinity of said open cup top and gradually increasing in cross-sectional area to attain the cross-sectional area of said discharge tube.

4. In an apparatus for converting liquids, solutions, emulsions, suspensions and the like media into dry powders, the combination of an annular casing, a discharge tube on the perimeter of said casing, atomizer means centrally disposed in said casing and comprising a vertically positioned rotatably mounted cup having an open top and located in the center of said annular casing, the

said cup having a substantially concave closed bottom portion and substantially straight conical walls intermediate the open top and the closed bottom portion with said open top having a diameter larger than said bottom portion and smaller than the depth of the cup, a shaft for rotating said cup about its central axis, a supply conduit for the medium to be atomized coaxial with said shaft and entering the open top of said cup to terminate short of said cup bottom portion, a substantially conical guiding member having its apex above said cup and opening outwardly toward the direction of said cup to terminate short of said cup rim to form a first narrow annular slot therewith which slot opens into said casing, and a gas conduit within the center of said annular casing and flaring outwardly just outside of said cup rim and said guiding means to form a second narrow annular slot with said guiding means for the passage of gases from said conduit into said casing whereby said first narrow annular slot opens into said gas conduit and said second slot so that atomized liquid thrown out of said cup over the rim thereof is discharged through said second narrow slot into said casing, said gas conduit having a narrow cross-section in the vicinity of said open cup top and gradually increasing in cross-sectional area to attain the cross-sectional area of said discharge tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,330,218 Rieber Feb. 10, 1920 1,636,317 Nyrop July 19, 1927 1,796,982 Culter Mar. 17, 1931 1,853,682 Hechenbleikner Apr. 12, 1932 1,952,308 Bowen Mar. 27, 1934 2,002,252 Stam May 21, 1935 2,047,699 MacLachlan July 14, 1936 2,415,527 Peebles Feb. 11, 1947

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