US3411759A

US3411759A - Apparatus for splashing liquids

Info

Publication number: US3411759A
Application number: US389653A
Authority: US
Inventors: Rapson Bryan
Original assignee: Aluminium Laboratories Ltd
Current assignee: Alcan Research and Development Ltd
Priority date: 1964-08-14
Filing date: 1964-08-14
Publication date: 1968-11-19
Anticipated expiration: 1985-11-19
Also published as: CH434765A; GB1081313A; NL6510630A

Description

Nov. 19, 1968 B. RAPSON APPARATUS FOR SPLASHING LIQUIDS 3 Sheets-Sh 2 Filed Aug, 14 1964 INVENTOR. Y PARsa/v Afro/wa y Nov. 19, 1968 B. RAPSON 3,411,759

APPARATUS FOR SPLASHING LIQUIDS Filed Aug. 14, 1964 3 Sheets-Sheet 5 Arm/(way United States Patent 3,411,759 APPARATUS FOR SPLASHING LIQUIDS Bryan Rapson, Arvida, Quebec, Canada, assignor to Aluminium Laboratories Limited, Montreal, Quebec, Canada, a corporation of Canada Filed Aug. 14, 1964, Ser. No. 389,653 16 Claims. (Cl. 261-91) ABSTRACT OF THE DISCLOSURE In a treatment chamber for bringing a flow of gas into contact with a spray of liquid, a rotated impeller partially dipping into a body of the liquid for splashing such liquid into the gas-passage space above the body comprises a cluster of arcuate vanes on one side of a base plate that extends across the axis of rotation of the impeller, the vanes providing curved, radially-extending pockets inwardly closed by a hub portion and opening both peripherally and opposite the base plate.

This invention relates to an impeller for splashing liquid contained in a treatment chamber. The invention especially relates to an impeller for splashing molten metals to spray the metal into a gas or vapor space above the liquid metal. For instance, such spray may be used to condense metal from a vapor state into a molten body of it, as in the refining of zinc. The invention also particularly relates to such an impeller creating a spray of molten aluminum in a chamber containing the latter, the spray being directed into a flow of gaseous aluminum monochloride to decompose it and deposit metallic aluminum in the droplets.

Heretofore impellers of different forms have been used which have been disposed so as to dip into the liquid or the molten metal within the chamber and by rotation of the impeller on its axis the liquid or molten metal has been sprayed into the space above the liquid. Various dispositions of such an impeller have been suggested with a view to securing a more uniform distribution of the spray of liquid or metal, including dispositions in which the axis of rotation is inclined to the level of the liquid, the periphenal portion of the impeller dipping into the liquid. These impellers have been formed with vanes of various contours but the distribution of the spray secured has not been. uniform and, depending on the angular relation of the impeller to the liquid level and its position in relation to the chamber, the spray produced upon rotation of the impeller has varied in its density and uniformity between the portion of the spray which is thrown into the space above the liquid by the impeller as it leaves the liquid and the portion of the spray carried over and thrown into the space adjacent the point at which the periphery of the impeller enters the liquid.

The present invention is directed to the problem of securing a more uniform distribution of the spray in the space above the liquid as well as increasing the intensity of the spray produced by the rotating impeller so as to improve the contact between the liquid and the gas or vapor and making possible the use of splash chambers of greater width with .a given size impeller than heretofore has been possible.

It is an object of the invention to provide an impeller having impeller vanes of such form as to secure improved distribution and intensity of the spray and to secure a greater amount of spray thrown into the space above the liquid by the impeller than heretofore has been accomplished.

It is a further object of the invention to provide an impeller of this form and for this purpose which may be made of a material which is not reactive with the liquid or the gas contained within the spray chamber.

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It is another object of the invention to provide an impeller which will have the desired form to accomplish the purposes of the invention but which may be molded, cast or readily machined to secure the desired contours of the impeller surfaces.

It is an additional object of the invention to provide an impeller which will be strong while providing the charaoteristics which secure the advantages of the invention,

In one aspect of the invention it is found that the vanes of the impeller may be of arcuate or spiral form extending outwardly from a hub portion of the impeller, this impeller being provided with a circular base plate disposed transversely of the axis of rotation and integrally abutting the edges of the cluster of vanes at one side of the cluster, the sides or faces of the vanes being parallel to the axis so that their other edges lie in a plane remote from but parallel to the base plate. The vanes are each preferably defined by a concave arcuate surface at one side or face thereof, which surface thus defines one side of the space between the given vane and the convex side of the adjacent vane of similar form. As will be understood more clearly from the drawings, the radius from the axis of rotation to the point of intersection of the concave side of the given vane with the periphery of the impeller is disposed in a certain angular relation to the corresponding radius from the axis of rotation to the intersection with the periphery of the concave surface of the adjacent vane disposed at the opposite side of the space between the convex surface of the given vane and the oppositely disposed concave surfiace. The angle between these radii is determined by the number of vanes which are utilized in a given impeller.

In order, however, to secure the desired distribution of the spray and to spray into the gas space an adequate quantity of the liquid, it has been found that the length of the arcuate or spiral surfaces defining the vanes must be of substantial extent, the concave surface of one vane being also preferably connected to the convex surface of the adjacent vane defining the space between the two vanes by a smooth arcuate surface, which thus provides the bottom of the impeller pocket that is constituted, in effect, by the defined space. This arcuate surface is advantageously required to be disposed in a location adjacent the radius to the point of intersection (with the impeller periphery) of the concave surface of the vane which -is disposed across the next space and in opposed relation to the convex surface of the given vane, as mentioned. Thus, the concave surface of any given vane extends from the intersection thereof with the periphery of the impeller, spirally inward to a location that is adjacent the radius which extends to the intersection (with the impeller periphery) of the concave surface of the next adjacent vane, i.e. the vane that is disposed at the opposite side of and in opposed relation to the convex surface of the given vane. In this manner a relatively long space is provided for receiving the liquid therein to be thrown out by the impeller into the space above the liquid in the chamber and the liquid is retained in thereby increases the spray density on the side where the vanes enter the liquid, thus to secure a more uniform and balanced condition with respect to the spray density at the side where the vanes leave the surface of the liquid. As indicated above also, an adequate quantity of the liquid is carried in the space between vanes and is available for being sprayed into the space above the liquid level in the chamber.

In order to improve still further the spray thrown into the space above the liquid level, in accordance with another aspect of the invention the vanes may extend a substantial distance in the direction along the axis, so that more liquid can be scooped up in a revolution of the impeller than is possible with an impeller having a base plate and vanes of limited length along the axis in accordance with previous practice. To secure this greater length of the vanes in the axial direction in a strong impeller structure the edge surfaces of the vanes at the ends thereof remote from the base plate are modified so that instead of lying in a plane perpendicular to the axis as heretofore, they are disposed (in accordance with this aspect of the invention) on a surface of revolution extending about the axis of rotation and converging from the base plate toward the axis of rotation at a point more remote from the base plate. This surface of revolution preferably is an arcuate surface such as a hemispherical surface and the end and edge surfaces of the vanes are disposed in this hemispherical surface. Within the scope of the invention, however, other forms of surfaces of revolution may be utilized, for example a conical surface. It will be understood that thus a substantially increased length of the vanes in the direction along the axis is secured while obtaining a strong structure for the impeller and one which provides adequate volume of the spaces between the vanes for receiving therein the liquid into which the impeller dips and carrying it upwardly and into the space above the liquid and spraying it into this space.

In accordance with another feature of the invention it has been found that the spray distribution compared to that secured with impellers having the arcuate surface of each vane perpendicular to the base plate (so that each arcuate surface is as if generated by movement of a line that is kept parallel to the axis) may be improved by undercutting the outer portion of the vane at the side thereof defined by the concave surface, or by otherwise inclining one or both surfaces of the vanes to the base plate whereby a similar acute angle is formed between the concave surface and the base. This feature may be utilized in impellers which have the edge surfaces of the vanes in a plane perpendicular to the axis of rotation as well as in those which are defined by a surface of revolution, such as a hemisphere or a cone, including a truncated cone.

It is found in some cases that further improvement may be secured by providing blades at the side of the base plate which is opposite to the side thereof from which the principal vanes of the impeller extend. These blades may extend radially from the axis and may extend a relatively short distance parallel to the axis. The impeller provided with such blades and having the edge surfaces of the vanes defined by a spherical surface was found to secure an improved distribution of the spray on the side of the impeller where the impeller leaves the surface of the liquid without decreasing the amount of the spray at the opposite side where the vanes enter the liquid. Satisfactory splashing and spraying were secured at lower speed with this form of impeller.

It has been found desirable also to provide in each vane near the base plate a small hole through each vane to allow escape of gas which may be entrapped in the liquid.

Other aspects, objects and features of the invention will be understood from the description of the drawings to follow in which:

FIG. 1 is a plan view of an impeller having blades defined by arcuate surfaces in accordance with one aspect of the invention;

FIG. 2 is a vertical section on line 2-2 of FIG. 1;

FIG. 3 shows in perspective an impeller in which the edge surfaces of the vanes are defined by a hemispherical surface;

FIG. 4 shows an impeller having the arcuate vanes in accordance with the aspect of the invention shown in FIG. I, the vanes being also undercut at the concave arcuate surfaces thereof adjacent the periphery of the impeller;

FIG. 5 is an elevation showingan impeller in which the edge surfaces of the vanes are defined by a hemispherical surface and the vanes are inclined to the base plate in such manner that their concave surfaces form an acute angle therewith;

FIG. 6 is a plan View of the hemispherical impeller of FIG. 5;

FIG. 7 shows an impeller in which the edge surfaces of the vanes are defined by a hemispherical surface and are shaped as in FIG. 5 and in which blades are provided at the side of the base plate opposite to the vanes; and

FIG. 8 is a schematic illustration, as in vertical section, of a treatment chamber for subjecting a fiow of vapor to molten metal splashed by an impeller, e.g. of the type of FIG. 7.

In FIGS. 1 and 2 the impeller is provided with a base plate 1 of disc-like shape extending to the periphery 3. At one side of the base plate 1 vanes 5 extend from a hub portion 7 generally outwardly to the periphery 3 of the base plate. The vanes generally designated 5 are each defined by a concave surface 9, such as the surface 9a (of a selected vane 5a) extending from the point of intersection of a radius 10 and of this surface 9a with the periphery 3 of the impeller inwardly toward the radius 12; the radius 12 is a radius which extends from the axis of rotation to a corresponding point of intersection of the concave surface 9b of the adjacent vane 5b which is disposed across the space 11b from the convex side 13a of the given vane 5a. Thus the vanes 5 are separated by spaces generally designated 11, e.g. the spaces 11a and 111) as shown in FIG. 1. Space 11a is bounded on one side by the concave surface 9a (of the above-selected vane 5a) and on the opposite side by the convex surface 13c (of another adjacent vane 5c); similarly space 11]) is bounded on one side by the concave surface 9]) (of the first-mentioned adjacent vane 5b) and on the opposite side by the convex surface 13a (of the vane 5a). The convex surface of the vane 50, forming a side of the space 11a, is connected to the concave surface 9a of the first-selected vane 511 (on the other side of the space 11a) by a smooth arcuate surface 15, which thus forms the inner end of the space 11a and which is disposed closely adjacent the radius 12; as indicated, the radius 12 extends to the point where the concave surface 9b of the first-mentioned adjacent vane 51) intersects the periphery 3 of the impeller.

By utilizing arcuate surfaces of this character and disposition to form the vanes 5 it has been found that a longer space 11, such as the spaces 11a and 11b, is provided and that the liquid is retained in the impeller a longer time during rotation and the spray density is increased on the side of the impeller where the vanes enter the liquid. It will be noted in the impeller as exemplified in FIGS. 1 and 2 that seven vanes 5 are utilized and therefore the angle between two adjacent radii, such as the two radii 10 and 12, which extend to the points of intersection of the concave surfaces 9 of adjacent blades with the periphery, is 51.4". The thickness of the blades in this embodiment may be substantially uniform and in an impeller, for example, having an outside diameter of 14 inches may be equal to about 1 inch. In such case the radius 15x of the connecting arcuate surface 15 may be of about inch. The radii 15y from the axis of rotation (the center of the impeller) to the center 15' of the radius 15x of the arcuate surface 15 (as between vanes 5a and 5c) may be generally at an angle of 16 with respect to the radius 12 to the point of intersection of the concave surface 9b of the next following vane 51), it being understood that the configurations and dimensions of all pockets and vanes are conveniently the same. In this embodiment in which the diameter of the impeller and its base plate is about 14 inches the radius 15y from the axis of rotation to the center 15 of the arcuate surface 15 may be about 3%, inches.

Bearing in mind that for some purposes the arrangements of vanes and pockets such as shown in FIGS. 1 and 2, and also as disclosed below in connection with other figures, may involve pocket-defining surfaces which are other than spiral or circular curves, as for instance being composed of one or more planes appropriately arranged for equivalent effect, the impeller and its pockets may be described in a generic but nevertheless similar manner. Thus significant features of improvement are believed to reside in an impeller having a cluster of vanes distributed around a central hub region and arranged to define a corresponding plurality of pockets opening outward at the periphery of the impeller. Each pocket extends inward from the periphery to a region adjacent the hub and is defined by a vane on either side which extends from the hub to the periphery, each vane serving to partition successive pockets from each other. Each vane thus has two pocket-defining surfaces which respectively intersect the periphery at localities spaced by the thickness of the vane.

In a more particular sense, the innermost extremity of each pocket is disposed, approximately, at a locality on a radius running from the center of the impeller to the periphery at the point of intersection with such periphery of the further face of the next adjoining pocket, which is, of course, the nearer face of the next vane, such last-mentioned vane forming a boundary for the stated next pocket, such next pocket being bounded on its nearer side by the vane that lies between it and the given pocket. Thus in FIG.

1, the pocket 11a extends approximately to the radius 12 which is drawn from the center to the intersection with the periphery 3 of the face 9b that defines the opposite side of the adjoining pocket 11b.

Moreover, the locality where the end of the given pocket approximately adjoins the stated radius is disposed at about the mid-point of such radius, or at least at a distance from the center of the impeller of not less than about one-third of the radius. Thereby and with the number of vanes selected within the preferred range of about 5 to about as explained below and with each vane having a preferred thickness between successive pockets that is relatively substantial, for purposes of strength and reliability, especially where the impeller is made of refractory material such as graphite (e.g. preferably .at'least about" one-third the crosswise dimension of the pocket), an unusually effective impeller is provided.

Defined in this way, the pockets each extend along a course inward from the periphery which departs outwardly from a simple radial direction, e.g. .a course which lies very generally along a path at a considerable angle to a radius between the center of the impeller and the intersection, with the periphery, of the bounding surface of that vane which separates the pocket from the next adjacent pocket mentioned above, such angle being preferably an acute angle (e.g. 63) in a range from about 55 to 75. So arranged in spiral or other skew relation to radii of the impeller, the pockets function effectively to lift the successive quantities of the liquid, and to develop spray therefrom which is released substantially throughout the travel of a :given pocket from its leaving the liquid at one side and to its return at the other.

FIG. 3 shows in perspective an impeller which has a hemispherical periphery and in which the vanes 17 extend from the base plate 1 at one side thereof and are defined by arcuate surfaces which are generally parallel to each other and generally parallel to the axis of rotation of the impeller. While this embodiment, by way of example, does not have arcuate or other vane-defining surfaces, particularly disposed and extending as described in connection with the vanes 5 of FIG. 1, the length of the vanes in the direction parallel to the axis is considerably greater than those of the vanes 5 of FIGS. 1 and 2, the cluster of vanes being here in the shape of a hemisphere. Thus, a large volume of the spaces 19 between the vanes 17 is secured. With the impeller having vanes 5 of uniform and relatively shallow axial length along their arcuate extent most of the liquid is thrown off in a relatively thin sheet of relatively uniform velocity. It has been found that, with the greater axial length of the vanes 17 of the impeller shown in FIG. 3, the thickness of the sheet of spray was increased. In addition by reason of the hemispherical (or other sloping) nature of the peripheral surface the points from which the liquid is thrown off vary in distance from the axis of the impeller. Since the peripheral velocity is proportional to the radius of rotation, the liquid thrown off by this hemispherical impeller has a wide velocity range. The liquid leaving the impeller from a point close to the axis travels a shorter distance than the liquid leaving the periphery of the impeller adjacent the base plate 1. The result is that a larger amount of the liquid fills a larger volume of the gas space within the chamber than is possible with the impeller of the type shown in FIGS. 1 and 2.

It was further found with the impeller of FIG. 3 that within limits the amount of liquid thrown off by the impeller increased with the depth to which the periphery of the impeller was dipped into the liquid in the chamber, e.g. with the nose 20 of the device extending downwardly into the liquid, with the axis at an angle of about 45 to the surface of the liquid, and with a drive shaft (not shown) extending upward (at such angle) from the side of the base plate 1 opposite to the vanes 17. This depth with an impeller 14 inches in diameter at the base plate 1 may be within the preferred range of 3 to 5 inches, i.e. asmeasured vertically between the center 20a of the impeller nose 20 and the normal liquid surface. The greater the depth the greater the load on the driving motor. With too great a depth of immersion, however, the liquid tends to be thrown off as large slugs having a relatively low ratio of surface area to weight. Since it is more efficient to provide :a maximum possible surface area of the liquid droplets for the weight being splashed, the depth of the dipping of the periphery of the impeller into the liquid in the chamber (measured as above) preferably should not exceed the maximum stated above. The optimum conditions of operation found with a 14 inch diameter impeller of about 6 /2 inches .axial length, as shown in FIG. 3, are given in Table 1 forming part of this specification.

FIG. 4- shows an impeller similar to that of FIGS. 1 and 2 with respect to form and disposition of the concave and convex arcuate surfaces of the vanes and the elongated spaces between the vanes 21. The vanes 21, however, adjacent their outer ends are undercut so that the outer portion 25 of the concave surface of each vane 21 is disposed at .an acute angle to the face of the base plate 1. The convex arcuate surface 27 at the opposite side of the vane 21 is generally perpendicular to the face of the base plate 1 in the direction parallel to the axis of rotation. The angle between the surface 25 .and the base plate preferably may be of the value of 60 or thereabouts. It is found that the spray distribution is improved over the spray produced by the impeller as shown in FIGS. 1 and 2, although the :average intensity of the spray was not as great as that of the impeller shown in FIG. 3 in which the vanes have a greater axial extent, this extent from the base plate 1 increasing in the direction inwardly toward the axis.

FIG. 5 shows in elevation and FIG. 6 shows in plan an impeller having concave surfaces 31 and convex surfaces 33 defining vanes 35 of the general form as shown in FIG. 4 including the undercut or sloping portion 36 at the outer end of the vane in which the concave surface 31 becomes disposed at an acute angle to the base plate 1. Indeed the inclined relation to the base plate here characterizes the concave side of the vane all the way inward. This angle preferably may be 60 at the outer end of the vane as in the embodiment of FIG. 4, and may become gradually larger (i.e. of less inclination) inward toward the center, being about 82 near the inner end of the pocket. Indeed, in this embodiment the concave surfaces 31 and the convex surfaces 33 of the vanes are not perpendicular to the base plate 1 but are both inclined thereto, the inclination of the concave surfaces 31 being for a purpose similar to that of the undercutting in FIG. 4, and the inclination of the convex surfaces 33 being for the sake of strength, e.g. to maintain the same nominal vane thickness throughout, such as a thickness of one inch. In the embodiment of FIGS. and 6, however, the edge surfaces 37 of the vanes 35 are disposed on a hemispherical surface similar to that of FIG. 3. In this embodiment the center of this peripheral hemispherical surface is disposed In Table I are shown for the different impellers which have been described the optimum conditions of speed of rotation and of depth to which the impeller is dipped into the liquid in the chamber, together with the motor load in kilowatts. In the last column of the table are given comsubstantially at the upper face 39- of the base plate 1 in ments on the condition of the spray produced by the sev- FIG. 5 and at the axis of rotation which is the center line eral impellers. of the base plate 1. As in the other embodiments described The effectiveness of the sprays produced by the different the radius of the sphere may be 7 inches and equal to the impellers was compared by directing a shower of incanradius of the base plate 1 measured from the axis of descent iron particles from an oxyacetylene torch into the rotation. spray which was produced by the impeller dipping into With the impeller as shown in FIGS. 5 and 6 the spray water contained in the spray chamber. At the same time a was dense and well distributed about the periphery of the 300 cubic feet per minute flow of air was drawn through impeller. It was denser, however, in front of the impeller. the space above the liquid in the splash tank and through This spray created by an impeller of 14 inches diameter the spray. The percentage of sparks passing through the extended for a distance of 27 inches from the impeller spray without being quenched was estimated as shown in rotating at 400 r.p.m. on the sides where the vanes left the the fifth column of the table. The impeller was disposed surface of the liquid to a distance of 43 inches on the side with its axis at an angle of 45 to the horizontal.

TABLE I Optimum Conditions Motor Percent Impeller type load, sparks Comments Speed, Depth, kw. in outlet r.p.m. inches 1 Figs. 1 and 2 400 l 0. 85 3 Good spray on side where vanes enter water but deficient on sides where vanes leave water.

Fig. 3 300 4 0.9 1 Spray very thick particularly in front of impeller and on side where vanes leave water.

Fig. 4 400 2 0. 95 1 Spray relatively thin, but effectively covering both sides of impeller. Little or no spray in front of impeller.

Figs. 5 and 6 400 4 1. 1 Very dense spray at center with good coverage on side where vanes enter liquid. Spray relatively thin where vanes leave liquid.

Fig. 7 300 4 0. 87 1 Very dense spray at center with good covering extending 2.5 feet on side where vanes leave water and 3.5 feet on side where vanes enter the water.

Immersion depth measured vertically from normal liquid surface to center of lower face of impeller.

where the vanes entered the liquid. At high rotational speeds some air was observed to be trapped between the vanes.

In order to gain a more even distribution and to overcome the entrapping of air, the impeller as shown in FIG. 7 was provided which is substantially the same as the impeller shown in FIGS. 5 and 6, with the hemispherical periphery 37 but with the addition of four straight blades 41 carried by the base plate at the side thereof opposite to the arcuate vanes 35, as may be seen in FIG. 7. These blades 41 extend straight outward radially from the vicinity of the drive shaft (or a hub around it), not shown, and may have a height of about 2 inches in the axial direction of a 14-inch diameter impeller.

In addition, in this embodiment holes 43 of %ths inch diameter were drilled through each vane near the base plate 1 to provide for the escape of entrapped gas. The spray distribution was found to be further improved on the side where the vanes leave the surface without decreasing the amount of spray at the opposite side. The impeller, also of 14 inches diameter, rotating at 300 r.p.m., effectively sprayed an area 6 feet wide measured at the surface of the liquid. Splashing at lower speeds also was improved over the impeller as shown in FIGS. 5 and 6. The impeller of FIG. 7 included the inclined relation of the vanes 35 to dispose the concave surface 31 at an acute angle (as at with respect to the upper surface of the base plate 1. Thus the concave surfaces 31 and the convex surfaces 33 of the vanes were disposed not perpendicular to but at an inclination to the base plate 1, as shown in FIGS. 5 and 6. In the embodiment of FIG. 7 the reference numerals are generally the same as in FIGS. 5 and 6. As stated, the straight blades 41 are of relatively short length in the axial direction and extend generally radially from the axis of rotation in the embodiment of FIG. 7.

Within the scope of the invention variations may be made in the form and curvature of the arcuate surfaces defining the vanes and also of the surface of revolution defining the edge surfaces of these vanes while providing a surface converging from the periphery of the base plate toward and along the axis of rotation. The axial length of the vanes may be varied to suit different conditions and the number of vanes used in the impeller also may be varied but for practical purposes it is preferable to use not less than five vanes nor more than ten in order that the strength of the vanes and the provision of adequate space therebetween for scooping up the liquid may be secured. The impellers may be made of different refractory materials, for example, graphite, where they are utilized for spraying molten metals. As shown in FIGS. 2 and 5, provision may be made for receiving internally of the hub 7 a suitable shaft which may be threaded into a. hole 47 in this hub. By suitable design and choice of materials for the shaft and the impeller the requisite strength, rigidity, ability to transmit the torque and other mechanical factors may be provided for.

As has been indicated above, the impellers of the invention are intended to be disposed in a partly submerged relation to the molten metal or other liquid, so that upon rotation, e.g. in the directions indicated by the arrows in the several figures, an intense and well distributed spray is thrown in the area above the liquid. One example of a device wherein impellers of the invention may be utillized is the splash-type decomposer for subhalide aluminum refining, shown and described in US. Patent No. 2,914,398 of A. H. Johnston et al., issued Nov. 24, 1959 for Recovery of Aluminum in Subhalide Distillation. As will also be appreciated, the impeller is thus mounted at the end of a drive shaft, so that its nose or outer face is partly submerged, the shaft and thus the axis of the im- 1 1 ness of said vanes defined by said arcuate surfaces is substantially uniform along the arcuate extent thereof.

8. Apparatus as defined in claim 6, in which the concave surface of each vane is disposed at an acute angle to the base plate at least along a substantial portion of the arcuate extent of said concave surface which extends to the periphery of the impeller.

9. Apparatus as defined in claim 8, in which said vanes are further defined by edge surfaces thereof which are disposed substantially upon a surface of revolution about said axis that constitutes a peripheral surface of the impeller and that converges from said base plate a substantial distance along and toward said axis of rotation, said impeller being further provided with a plurality of generally radially extending blades disposed at the opposite side of said base plate from said vanes and defined between surfaces extending generally along the axis of rotation of said impeller.

10. In apparatus for contactof gas flowing above thesurface of a mass of liquid, with spray of said liquid, in combination with a chamber arranged to contain said liquid mass partly filling said chamber and having gas inlet means and gas outlet means at mutually spaced localities for traversal of said gas flow through the chamber above the liquid surface, an impeller arranged in the chamber and supported for rotation on an axis so disposed that parts of the impeller on opposite sides of the axis are respectively above and below the surface of said liquid, whereby on rotation the peripheral portions of said impeller successively dip into the liquid for spraying liquid into the space above said mass, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller comprising a cluster of vanes distributed around a central hub region and extending transversely of and from said base plate generally along said axis of rotation and arranged to define, between successive vanes, a plurality of liquid-receiving pockets each of which opens outward at the periphery of the impeller, said vanes being disposed so that each side of each pocket extends inwardly from the periphery of the impeller toward the hub region substantially at an acute angle to a radius which extends from the axis to the point of intersection of such side with the periphery, said vanes being further defined by edge surfaces thereof which are disposed substantially upon a surface of revolution about said axis that constitutes a peripheral surface of the impeller and that converges from said base plate a substantial distance along and toward said axis of rotation, said vanes extending inwardly of the impeller along the base plate to the hub region and each of the pockets having an inner end wall, closing the inner extremity of the pocket, which extends substantially axially of the impeller along the hub region from the base plate to a locality, of said surface of revolution, that is remote from the base plate.

11. Apparatus as defined in claim 10, in which said surface of revolution that defines the edge surfaces of the vanes is a surface of a hemisphere which has its center disposed on said axis and adjacent said base plate.

12. An impeller adapted to be supported within a chamber containing a mass of liquid and for rotation on an axis inclined to the surface of the liquid and with the peripheral portion of said impeller dipping into the liquid for spraying liquid into the space above the mass of liquid within the chamber, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller providing a plurality of vanes defined between arcuate surfaces extending outwardly with respect to said axis from a hub portion of the impeller to the periphery thereof and extending transversely of and from said base plate generally along said axis of rotation, said vanes being further defined by edge surfaces thereof which are disposed substantially upon a surface of revolution about said axis that constitutes a peripheral surface of the impeller and that converges from said base plate a substantial distance along and toward said axis of rotation, said vanes extending inwardly of the impeller along the base plate to the hub portion and each of the pockets having an inner end Wall, closing the inner extremity of the pocket, which extends substantially axially of the impeller along the hub portion from the base plate to a locality, of said surface of revolution, that is remote from the base plate.

13. An impeller adapted to be supported within a chamber containing a mass of liquid and for rotation on an axis inclined to the surface of the liquid and with the peripheral portion of said impeller dipping into the liquid for spraying liquid into the space above the mass of liquid within the chamber, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller providing a plurality of vanes defined between arcuate surfaces extending outwardly with respect to said axis from a hub portion of the impeller to the periphery thereof and extending transversely of and from said base plate generally along said axis of rotation, said vanes being further defined by edge surfaces thereof which are disposed substantially upon a hemisphere the center of which is disposed on the axis of rotation and adjacent said base plate, said vanes extending along said base plate to provide outwardly opening pockets between the vanes, each pocket being closed at one side by the base plate and at its innermost extremity by the hub portion.

14. An impeller as defined in claim 13, in which the concave surface of each vane is disposed at an acute angle to the base plate at least along a substantial portion of the arcuate extent of said concave surface which extends to the periphery of the impeller.

15. In apparatus for contact of gas flowing above the surface of a mass of liquid, with spray of said liquid, in combination with a chamber arranged to contain said liquid mass partly filling said chamber and having gas inlet means and gas outlet means at mutually spaced localities for traversal of said gas flow through the chamber above the liquid surface, an impeller arranged in the chamber and supported for rotation on an axis inclined to the surface of the liquid and with the peripheral portion of said impeller dipping into the liquid for spraying liquid into the space above the mass of liquid within the chamber, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller providing a plurality of vanes defined between arcuate surfaces extending outwardly with respect to said axis from a hub portion of the impeller to the periphery thereof and extending transversely of and from said base plate generally along said axis, the concave surface of each vane being disposed at an acute angle to the base plate at least along a substantial portion of the arcuate extent of said concave surface which extends to the periphery of said impeller, said vanes extending along said base plate to provide outwardly opening pockets between the vanes, each pocket being closed at one side by the base 'plate and at its innermost extremity by the hub portion.

16. An impeller adapted to be supported within a chamber containing a mass of liquid and for rotation on an axis inclined to the surface of the liquid and with the peripheral portion of said impeller dipping into the liquid for spraying liquid into the space above the mass of liquid within the chamber, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller providing a plurality of vanes defined between arcuate surfaces extending outwardly with respect to said axis from a hub portion of the impeller to the periphery thereof and extending transversely of and from said base plate generally along said axis of rotation, said impeller being further provided with a plurality of generally radially extending blades disposed at the opposite side of said base plate from said vanes and defined between surfaces extending generally along the axis of rotation of said impeller, said vanes extending along said base plate to provide outwardly opening pockets between peller being inclined at an acute angle to the surface of the liquid, preferably between about 20 and 70, and most preferably at about 45 FIG. 8 is a highly simplified schematic illustration of such disposition of an impeller 50 dipping into liquid metal 51 in a refractory lined chamber 52, and mounted and driven by a shaft 53, which extends toward the liquid at an angle of 45 through a sloping upper wall 54 of the chamber. Thus the impeller 50 may, for example, be of the type shown in FIG. 7 including the rear straight vanes 41, although it will be understood that the impellers of other figures may be substituted in similar dispositon. Assuming that the liquid 51 is molten metal and that the apparatus is employed for condensing metal into the spray from a vapor, as in the case of refining zinc, or for decomposing aluminum monohalide gas into metallic aluminum in the spray, as in the subhalide refining process, the vessel includes a gas inlet 56 at a remote end and an outlet 57 near the impeller so that the vapor passes into and through the spray. Suitable cooling means for removing heat from the liquid metal, and means for tapping metal from time to time, may be provided as is conventional for devices of this sort, and are here merely indicated by the side well 58.

The center 60 of the nose or front surface of the impeller is advantageously disposed below the surface 61 of the liquid 51, the vertical distance between these points indicated at 60a and 61a being the immersion depth specified in Table I above. The shaft 53 is driven at the selected speed, 'by suitable means not shown, and in the indicated direction, for the desired splashing action and production of spray. As stated, FIG. 8 is merely schematic, with the chamber 52 greatly reduced in size and modified in shape for brevity of illustration, it being appreciated that proportions, and other features and details may be as conventional for such devices, and that the chamber may be arranged, if desired, to include a plurality of impellers, for traversal successively or otherwise by the passing gas.

It is to be understood that the invention is not limited to the specific devices herein shown and described but may 'be embodied with variations and modifications as mentioned above or otherwise, without departure from its spirit as defined in the appended claims.

I claim:

1. In apparatus for contact of gas flowing above the surface of a mass of liquid, with spray of said liquid, in combination with a chamber arranged to contain said liquid mass partly filling said chamber and having gas inlet means and gas outlet means at mutually spaced localities for traversal of said gas flow through the chamber above the liquid surface, an impeller arranged in the chamber and supported for rotation on an axis so disposed that parts of the impeller on opposite sides of the axis are respectively above and below the surface of said liquid, whereby on rotation the peripheral portions of said impeller successively dip into the liquid for spraying liquid into the space above said mass, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller comprising a cluster of vanes distributed around a central hub region and extending transversely of and from said base plate generally along said axis of rotation and arranged to define, between successive vanes, a plurality of liquid-receiving pockets each of which opens outward at the periphery of the impeller and extends inward to a region adjacent the hub, where the pocket is closed at its innermost extremity,

each vane extending in a generally spiral relation to said axis and having first and second surfaces which intersect the impeller periphery and respectively constitute faces of adjacent pockets, and said vanes being disposed so that as considered in a plane near the base plate, each given pocket, which is defined by the first surface of a given vane and the second surface of a second vane that is next in one circumferential direction, has its innermost extremity disposed: (1) adjacent a first radius from the axis to the point of intersection, with the impeller periphery, of the first surface of a third vane that is next to the given vane in the opposite circumferential direction, and (2) between the second surface of the given vane and a second radius from the axis to the point of intersection, with the impeller periphery, of the first surface of the given vane.

2. Apparatus as defined in claim 1, in which said vanes are further defined by edge surfaces thereof which are disposed substantially upon a surface of revolution about said axis that constitutes a peripheral surface of the impeller and that converges from said base plate a substantial distance along and toward said axis of rotation.

3. Apparatus as defined in claim 2, in which the spiral relation of the vanes is such that with respect to each pocket, at localities near its innermost extremity, the first surface of the given vane is closer to the impeller periphery, in a radial direction from the axis, than the second surface of the first-mentioned next vane, and wherein each said first surface of each vane is disposed at an acute angle to the base plate at least along a substantial portion of the extent of said last-mentioned first vane surface which extends to the periphery of the impeller.

4. Apparatus as defined in claim 3, said impeller being further provided with a plurality of generally radially extending blades disposed at the opposite side of said base plate from said vanes and defined between surfaces extending generally along the axis of rotation of said impeller.

5. Apparatus as defined in claim 4, in which the surface of revolution that defines the edge surfaces of the vanes is a hemisphere which has its center disposed on the axis and adjacent said base plate.

6. In apparatus for contact of gas flowing above the surface of a mass of liquid, with spray of said liquid, in combination with a chamber arranged to contain said liquid mass partly filling said chamber and having gas inlet means and gas outlet means at mutually spaced localities for traversal of said gas flow through the chamber above the liquid Surface, an impeller arranged in the chamber and supported for rotation on an axis inclined to the surface of the liquid and with the peripheral portion of said impeller dipping into the liquid for spraying liquid into the space above the mass of liquid within the chamber, said impeller being provided with a base plate disposed in a plane transverse to the axis of rotation, said impeller providing a plurality of vanes each defined between two arcuate respectively convex and concave surfaces extending outwardly with respect to said axis from a hub portion of the impeller to the periphery of the impeller and extending transversely of and from said base plate generally along said axis of rotation, said vanes defining pocket spaces between said vanes for receiving liquid therein, each pocket space being defined by concave and convex surfaces of the respective adjoining vanes and being disposed, as considered near the base plate, as follows: the arcuate surface which defines the concave side of a given vane extending from the periphery of said impeller to a location adjacent a radius which extends from the axis to the intersection, With said impeller periphery, of the concave surface of the next adjacent vane that defines another pocket space with the convex side of said given vane, said concave arcuate surface of said given vane and the arcuate surface defining the convex side of the other vane which coacts with the given vane in defining the first-defined pocket space being connected by a surface which forms the inner end of said first-defined pocket space and is disposed between the convex side of the given vane and a radius which extends from the axis to the intersection, with said impeller periphery, of the aforesaid arcuate convex side surface of the said other vane.

7. Apparatus as defined in claim 6, in which the thickness.

References Cited UNITED STATES PATENTS Akins et a1 26192 Nelson 68-134 X Ducart 230-13445 X Ingalls et al. 26184 X 10/1950 l/1952 10/1953 11/1953 11/1953 l/l959 14 Lhota 261-9l Robson Q 261-84 X Olsen 103115 Seinfeld 103-115 Wahle 103115 X Mahler 26191 X FOREIGN PATENTS Belgium. Great Britain.

HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner.