US3574558A - Jet-mixed liquid-liquid extraction column - Google Patents

Abstract

A JET-MIXED EXTRACTION COLUMN WHICH INCORPORATES THE ADVANTAGES OF EXISTING COLUMN-TYPE EXTRACTORS, WHILE ELIMINATING THE NEED FOR INTERNAL MOVING PARTS. THE COLUMN PROVIDES HIGH RATES OF MASS TRANSFER, WITH ONLY NORMAL OR EVEN DECREASED EXTENTS OF UNWANTED LONGITUDINAL DISPERSION COMPARED TO VARIOUS PRIOR COLUMN-TYPE EXTRACTORS. THE COLUMN UTILIZES UNIFORMLY SPACED, HORIZONTAL, TUBULAR JETTINGS AND INTAKE RINGS AT THE INNER AND OUTER BOUNDARIES OF AN ANNULAR CROSS-SECTION. AT EACH LEVEL, BOTH RINGS ARE PERFORATED SO AS TO PROMOTE NEARLY STRAIGHTLINE RADIAL FLOW BETWEEN THE JETTING AND INTAKE RINGS. EXTERNALLY THESE RINGS ARE CONNECTED BY WAY OF A CENTRIFUGAL CIRCULATING PUMP OR A DOUBLE-ACTION RECIPROCATING PUMP.

Description

Filed Mg}! 6, 1969 T; 'VERMEULEN/ ET L- JET-MIXED LIQUID-LIQUIDEXTRAC TiON COLUMN Fldllll ll.

.mm m NM NM INVENTORS THEODORE VERMEULEI DANIEL R. KAHI.

BY 7 I Y L/ 1 i ft /MZL4 L/ ATTORNEY April 1 3, 1971 United States Patent O 3,574,558 JET-MIXED LIQUID-LIQUID EXTRACTION COLUMN Theodore Vermeulen and Daniel R. Kalin, Berkeley, 'Calif., assignors to the United States of America as represented by the United States Atomic Energy Commission Filed May 6, 1969, Ser. No. 822,212 Int. Cl. B01d 11/04; B01f 5/02 U.S. Cl. 2327t).5 7 Claims ABSTRACT OF THE DISCLOSURE a centrifugal circulating pump or a double-action reciproeating pump.

RELATED APPLICATIONS This invention is an improvement over the extraction column disclosed and claimed in U.S. patent application Ser. No. 822,216, filed concurrently with this application, now U.S. Pat. 3,488,159 issued Jan. 6, 1970, entitled Jet Pulsed Liquid-Liquid Extraction Column, by I. S. Moon and T. Vermeulen, and assigned to the same assignee.

BACKGROUND OF THE INVENTION The invention described herein was made in the course of, or under, Contract No. W-7405-ENG-48, with the United States Atomic Energy Commission.

The present invention relates to solvent extraction columns and more particularly to an improved type of internal agitation for such column.

Various column-type extractors have been developed heretofore in an attempt to combine efiicient contacting between phases with such attributes as high capacity, low residence time, and the ability to handle systems with wide ranges of flow rates. In such column-type equipment, both phases are in continual contact; the dispersed phase remains in the form of uncoalesced small droplets, while the continuous phase follows a flow path that is relatively uninterrupted through the entire column. It is possible to suddivide column-type contactors into two main groups, depending on whether external power has been added to promote interphase dispersion. Those columns involving no external power are generally of the spray, packed and perforated-plate type. Those involving external power are further classified according to the force field used to transport and separate the two phases: these being (1) gravity transport, and (2) centrifugal transport. Where gravity transport is utilized, interphase dispersion is generally accomplished by (1) pulsation and (2) mechanical agitation. Pulsation is normally carried out in pulsed-packed or pulsed sieve-plate columns; while mechanical agitation normally involves the use of a central rotating shaft, such as is employed in the Scheibel, rotating-disc, or Oldshue-Rushton columns. Centrifugal transport is exemplified by the Podbielniak or Westfalia extractors.

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As widely recognized and pointed out in the above referenced concurrently filed patent application, longitudinal dispersion or axial mixing may substantially reduce the performance of continuous countercurrent solvent-extraction columns. Longitudinal dispersion is particularly evident in mechanically aided contactors, where large-scale flow effects can limit column operation even though interphase dispersion and mass-transfer rates are high. Longitudinal dispersion is the result of several effects, among these being (1) continuous-phase backmixing, (2) dispersed-phase backmixing, and (3) channeling flow due to the particular column internals. The above effects, whether acting separately or in combination, reduce the concentration driving force for mass transfer; thereby a longer column (for any given masstransfer coefficient) is required to achieve the same overall separation.

Hight rates of mass transfer usually require mixing patterns of sufiicient intensity to subdivide and circulate the dispersed-phase droplets without forming a stable emulsion. Certain column-type extractors, such as pulsedplate and rotating-shaft columns, meet these criteria wrile providing many transfer units (or many theoretical stages). Longitudinal dispersion is reduced in these types of columns by compartmentalizing the flow.

SUMMARY OF THE INVENTION The present invention is directed to a countercurrent solvent-extraction column which (1) provides for a high degree of mass transfer; (2) minimizes the efifect of longitudinal dispersion; and (3) has no internal moving parts. Also, the invention is applicable to any liquid extraction column wherein it is possible to increase efficiency by the pulsing method described in the above referenced patent application; i.e., by cyclically withdrawing and reinjecting a portion of the liquid in various spaced locations along the column without intermixing of the liquid at adjacent (or more distant) spaced locations. Additionally, the present invention utilizes no internal packing thereby allowing greatly increased flow rates in an extraction column of a given size.

In addition to high capacity and eflicient mass transfer, the inventive column is simple in construction, and reasonable in construction and operating costs. The primary diflerence in the present invention over the column disclosed in the above referenced patent application lies in the novel features of utilizing jetting and intake rings operative with either reciprocating or continuous-type pumps for pulsing or flowing the liquid through the rings, thereby improving the operation and the efiiciency of the extraction process over the column disclosed in said concurrently filed application, while substantially simplifying the construction thereof, this being accomplished particularly by the novel concept of utilizing continuous circulating pumps.

Therefore, it is an object of this invention to provide a liquid-liquid extraction column with an improved means of utilizing an injected fluid stream as the agitation agent.

A further object of the invention is to provide a solvent-extraction column which provides for a high degree of mass transfer, minimizes the effect of logitudinal dispersion, has no internal moving parts, and eliminates internal packing.

Another object of the invention is to provide a liquidliquid extraction column which utilizes the withdrawal and reinjection of liquid through spaced apart coaxial perforated ring assemblies having horizontally located ports either uniformly or non-uniformly spaced therein, the ring assemblies each being connected to either a reciprocating or continuous fluid-flow mechanism.

Other objects of the invention will become readily apparent from the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partially in crosssection, of an embodiment of the invention;

FIG. 2 is a partial enlarged view of the ring assembly and shield therefor usable in the FIG. 1 embodiment;

FIG. 3 is a view, partially in cross-section, of another embodiment of the invention;

FIG. 4 is a partial enlarged view similar to FIG. 2 except for the shield arrangement adapted for the FIG. 3 embodiment; and

FIG. 5 is a schematic view of the localized mixing patterns of the jet-mixed column obtainable in one operative mode of the FIG. 3 embodiment.

DESCRIPTION OF THE INVENTION The inventive jet-mixed extraction column illustrated in the FIG. 1 embodiment generally indicated at is encased in a vessel 11 of the typical design used in liquid extraction, having a long cylindrical construction with elliptical end closures and mounted in a vertical position An inlet feed line or pipe 12 for introducing the heavy liquid flow indicated at 13 extends into the upper portion of vessel 11 and terminates in a perforated distributor or outlet nozzle 14 located on the longitudinal axis of vessel 11. A second inlet feed line or pipe 15 introduces the light liquid flow indicated at 16 into the lower portion of the vessel 11 through a second similarly located perforated distributor or outlet nozzle 17. Both distributors 14 and -17 distribute the respective liquids 13 and 16 evenly throughout the cross-section of vessel 11. The liquids 13 and 16 are immiscible in each other, as is understood within the art, the column 10 being typically employed to transfer a soluble substance from one liquid to the other, the lighter liquid 16 moving upwardly in the vessel 11 while the heavier liquid 13 moves downwardly therein as described in greater detail hereinafter.

Positioned in the vessel 11, intermediate distributors 14 and 17, at various stages or levels in the vessel are a plurality of sets of coaxial tubular rings or similar distributing members comprising an inner or small ring 18 and an outer or large ring 19. A central cylindrical stub shaft or pin 20 is snugly inserted through each of the inner rings 18 which serves to eliminate downdrafting or updrafting inside the inner rings 18, thus reducing longitudinal dispersion.' The inner and outer rings 18 and 19 of each set or stage are connected to a double action reciprocating type pump unit 21 via lines or conduits 22 and 23, respectively, a sequentially controlled or actuated valve assembly 24, and lines or conduits 25 and 26. It is thus seen that either ring 18 or 19 can be the intake ring connected to the suction stroke of pump unit 21, while the opposite ring functions as the jetting ring connected to the discharge stroke of pump unit 21 by proper selection through. the valve assembly 2 1. Control valves which can be sequentially controlled to cooperate with the movement of a reciprocating pump are widely known in the art and thus need not be described in detail. If desired, however, the valve assembly 24 can be eliminated, whereby each of rings '18 and 19 Would operate in alternation for intake and jetting. Small diameter horizontal ports or apertures 27 of either uniform or nonuniform distance apart are drilled aound the outside of the inner rings 18 and apertures or ports 28 are drilled around the inside of the outer rings 19, to permit flow into or out of each ring on a horizontal plane .bisecting the rings. As shown in FIG. 2 and omitted from FIG. 1 for clarity, each intake ring (either rings 18 or 19) is provided with a shield or disc assembly 29 to shield the intake of rising (or falling) dispersed-phase droplets which when mixed intensively with continuous phase will produce a permanent emulsion.

The primary purpose of the jetting rings (either rings 18 or 19) is to intercept the dispersed-phase droplets, en-

train them into the local circulation patterns, intermix them by coalescence with other droplets if possible, and subdivide them by the local turbulence if they grow too large. In order to provide the interception of dispersedphase droplets, the inner and outer jetting ring-port designs are such as to provide a strong jetting action with reasonably uniform flow. These designs may be modified by increasing or decreasing the port or aperture diameter, increasing or decreasing the number of ports, and modifying the relative spacing between ports.

In operation of the FIG. 1 embodiment, with the liquids 13 and 16 dispersed via distributors 14 and 17 into vessel 11, reciprocating type pulsing units 21 via valve assemblies 24 withdraw liquid through the apertures 27 in rings 19 (intake rings) and reinject or readmit it through the apertures 28 in rings 18 (jetting rings) into the vessel 11 or vice versa. It is proposed in this embodiment that all of the rings 19 will function as intake rings and all of rings 18 as jetting rings or vice versa. The cross flow at each level or stage produced by the set of rings 18 and 19 is thus directed inward or outward depending on the desired type of operation. superimposing the radial flows at each stage of the countercurrent fiow of the continuous and dispersed phases produces in each compartment area (area intermediate two sets of rings) a pair of resultant vortex patterns of a generally toroidal circular configuration, the upper vortex lying beneath the plane of the upper ring set and the lower vortex lying on top of the plane of the lower ring set, such compartmented areas being described in greater detail with respect to FIG. 5. The radial withdrawal and reinjection of the liquid by the reciprocating pulsing units 21 through rings 19 and 18, or vice versa, maintains the dispersion of one liquid within the other in the form of droplets as is desired in solvent extraction process. The lighter liquid phase 16', after passing upwardly through vessel 11, leaves through a line or pipe 30 at the top of vessel 11. Conversely the heavier liquid phase 13" leaves the vessel 11 through a pipe or line 31 at the base of the vessel after having passed downwardly through vessel 11.

Pulsation, due to the rings 18 and 19 and the reciprocating pulsing units 21, promotes and maintains finer dispersion of the droplet phase and increases the masstransfer rate of the material to be extracted between the droplets and the continuous phase.

The absence of internal packing such as rings, saddles, or sieve plates provides a greater cross-sectional area for two-phase countercurrent fluid flow which substantially increases the capacity of a solvent extraction column embodying the present invention.

As pointed out above, if it is desired to alternate the pattern of withdrawal and reinjection of liquid cyclically, first withdrawing at ring 18 and injecting at ring 19 simultaneously, and then withdrawing at ring 19 and injecting at ring 18 simultaneously, in the ring set at any one spaced 'location the valve assembly 24 could be removed or inactivated such that movement of the doubleaction reciprocating piston of the pulsing unit 21 in one direction would function to circulate the liquid through the two rings in one direction, While movement thereof in the opposite direction would function to circulate the liquid in the opposite direction. Also, it is within the scope of this invention to utilize a sequential actuated valve assembly having reversing capabilities, or valve assembly 24 connected through as separate reversing valve, such that the function of rings 18 and 19 as either intake or jetting rings could be selectively controlled by actuation of the reversing feature of the valve assembly. In addition, due to the separate stages or levels at which the sets of rings 18 and 19 are located, and because each ring set is provided with its individual reciprocating pulsing unit 21, the timing of each of the pulsing units may be randomly diiferent; however, the best operation is obtained if the timing is synchronized such that all of rings 18 or all of rings 19 simultaneously function in turn as intake rings or jetting rings. Good operation is also ob tained if, at adjacent ring levels at the same instant, the jetting occurs in opposite directions.

Referring now to the embodiment of the invention illustrated in FIGS. 3-5, the novel jet-mixed extraction collumn is similar in construction to the FIG. 1 embodiment except in the novel utilization of a continuous circulating type unit and the configuration of the shields for the rings. Therefore, similar elements will be given like reference numerals. The column consists of a vessel 11, perforated distributors 14 and 17 for liquids 13 and 16 supplied thereto through pipes or lines 12 and 15, respectively, and outlets 30 and 31 for the discharge of liquid phases 16' and 13' as described above in the FIG. 1 embodiment. A plurality of sets of coaxial tubular inner and outer rings 18 and 19 are positioned at various levels 15 or stages in the vessel 11. A central shaft or rod 32 is snugly inserted through each of the inner rings 18 and serves to reduce longitudinal dispersion or axial mixing. The inner rings 18 and outer rings 19 of each ring set are connected respectively through conduits or lines 22 and 23 with a value assembly 24 which is connected to a continuous circulating type pump unit 21' via lines or conduits 25 and 26. The valve assembly 24' may if desired be provided with reversing capabilities. The rings 18 and 19 are provided respectively with small diameter 25 horizontal ports or apertures 27 and 28 to permit flow into or out of each ring on a horizontal plane. "If desired, the central shaft 32 can be replaced by disks atttached to each of the inner ring 18, so as to close completely the hole inside each ring.

As shown in FIGS. 3 and 4, one of the rings 18 and 19 of each set is provided with a curved shield or bonnet 29' to shield the intake ports from the dispersed phase, as previously discussed. While FIG. 3 shows the bonnets 29 alternately located on rings 18 and 19, this pattern applies specifically to the case where oppositely directed jetting action is used at the alternate spaced locations. For a uniform jetting direction, the bonnets would be placed on all of the inner rings 18 or on all of the outer rings 19, whichever are functioning as intake rings. Bonnets 29' are attached to the under side of the rings if the dispersed phase is the lighter, rising phase, or to the upper side of the rings if the dispersed phase is the heavier, descending phase. The continuous pumping units 21 may, for example, be small centrifugal pumps having the low pressure or intake side thereof connected to line 25 and the high pressure or discharge side connected to line 26. By the utilization of the valve assembly 24 either inner ring 18 or outer ring 19 can be connected via lines 22 or 23, respectively, to either the intake or discharge side of the pulsing unit 21'. Valves of this type are widely known in the art and need not be described in any greater detail. Also, if the valve assembly 24 is provided with reversing capabilities, either of rings 18 or 19 can be connected to the output of the pumps units 21' by simply actuating the valve assembly as well known in the art.

In operation of the FIG. 3 embodiment with the liquids 13 and 16 flowing countercurrently through vessel 11 as described above in the operation of the FIG. 1 embodiment, at each stage or level in which the coaxial ring sets are located, liquid is continually withdrawn from the column through the ports in the rings (intake rings 19 for example) connected to the lowpressure side of the pumps 21', via, for example, lines 23, valve assemblies 24 and lines 25; and re-emitted into the column through the ports of the opposite rings (jetting rings 18 for example) connected to the high pressure side of the pumps 21', via, for example, lines 26, valve assemblies 24' and lines 22. The cross flow at each ring-level may be directed inward or outward depending on the position of the valve assemblies 21' if such assemblies are provided with reversing capabilities. Since the liquid withdrawn from the column is subjected to high shearing forces when passing through a centrifugal pump utilized as a motive unit 21', it is important to recirculate only the continuous phase to avoid forming stable colloidal dispersions. It is not intended to limit the continuous circulating motive unit 21 to a centrifugal type pump since other types of continuous pumps can function to agitate the column.

superimposing the radial flows by the use of the novel rings 18 and 19 and continuous motive units 21' at each stage or level on the countercurrent flow of the continuous and dispersed phases (liquids 13 and 16 or vice versa), the resultant vortex patterns (indicated by the dual pair of counter rotating arrows) produced in each compartmented area 33 intermediate to the sets of rings 18 and 19, and with all the inner ring 18 functioning as the jetting rings, are schematically shown in FIG. 5. The localizing patterns are enhanced by the utilization of the shaft or rod 32 snugly inserted through the inner rings 18, which serves as indicated by the patterns to effectively eliminate downdrafting or updrafting and thus reduce the overall longitudinal dispersion in the column. While the patterns illustrated in FIG. 5 were determined by tests utilizing the inner rings 18 as the jetting rings at each level or stage, test results also show that with the outer rings 19 functioning as the jetting rings at alternate stage levels or at every level, longitudinal dispersion is substantially reduced although not to as great an extent as indicated by the patterns of FIG. 5. Tests also show that as the stage or level spacing (compartmented areas 33) was increased the vortices produced between the set of coaxial rings 18 and 19 also become progressively larger, thus increasing the longitudinal dispersion. Thus, depending on the size of the column utilized, there is apparently an optimum in the amount of spacing between the successive stages or levels in which the ring sets are located. For example, in tests conducted using a 5.5 inch diameter column of 24 inch length, and the inner rings 18 as the jetting rings, compartmented area 33 height of 3 inches gave the best result, producing an effective vortex structure in each stage or level while avoiding overlap or vortices between adjacent compartments. This column had an annular width of 2.2 inches. In general, therefore, it can be said that the ring spacing should be about 1.5 times the annular width when all ring levels are in parallel flow and about 0.75 times the annular width when alternating levels are in opposed flow.

In tests conducted on the FIG. 3 embodiment of the inventive jet-mixed column, and with the vessel 11 having an inside diameter of 5.5 inches and a height of 24 inches, each pair of rings 18 and 19 was formed from inch O.D. tubing with 0.049 inch wall thickness. The outside diameters of the inner and outer rings were 1.875 inches and 5.25 inches, respectively. The tubes or lines 22 and 23 were /2 inch diameter. Radial circulation at each ring set stage or level was provided by a centrifugal pump delivering up to 1.5 gal/min. It was found that maintaining equal radial flow rates at each stage was important, and thus variable transformers connected to the pumps provided flow control at circulation rates between 0.2 and 1.5 gal/min.

As pointed out above, the primary purpose of the jetting rings is to intercept the dispersed-phase droplets, entrain them into the local circulation patterns, intermix them by coalescence with other droplets if possible, and subdivide them by the local turbulence if they grow too large. In order to improve the interception of dispersedphase droplets, the inner and outer jetting ring port designs may need be modified by increasing or decreasing the port diameter and increasing or decreasing the number of ports, to provide the desired strong jetting action with reasonably uniform flow. For example, with the inner ring functioning as the jetting ring, tests have been conducted using from 8 to 29 ports of a diameter of X to inch, and with a continuous slit having a & inch thickness, while the outer rings when used as jetting rings used 16 to 31 ports of a diameter from to A inch.

While not shown, longitudinal dispersion in the FIG. 3 embodiment may be further reduced in the end portions of the column by inserting a calming grid or wire-mesh screen approximately one-half to one stage or compartmented area height above the first stage (upper end) and below the last stage (lower end) in the column.

During two-phase flow tests, it was found that a milky emulsion Was formed throughout the column at moderate radial flows (0.4 to 0.7 gal/min.) without evidence of sufficient droplet breakup. The emulsion was attributed to the capture of rising droplets by the intake rings, the droplets becoming finely dispersed as they passed through the radial centrifugal pumps. The utilization of the curved shield or bonnet 29' secured to the bottom of each intake ring, be it ring 18 or 19, as shown in FIG. 4, and which extended upward to the level of the top of the ring, thus shielding the intake ports from the dispersed-phase droplets proved to be a solution to the emulsion problem. The addition of bonnets 29' permitted radial jetting flows to be increased as high as 0.9 gaL/min. before the contents of the column became cloudy.

It is thus seen that the inventive jet-mixing extraction column provides for nearly uniform, controllably fine dispersion of the discontinuous phase. The effect of longitudinal dispersion is reduced by both the position and the action of the rings; the ring tends to compartmentalize the flow, while the radial jetting gives a nearly uniform concentration across any one cross-section of the column. The internal design of the inventive column contributes several other important advantages. Because packing is eliminated and the void volume is high, relatively large throughputs can be attained. Also, since there are no moving parts within the column, maintenance costs are kept low. If a pump (pulsing unit) fails it can be externally disconnected and quickly replaced, thereby minimizing shut-down time. Therefore, this type of extraction column appears to be well suited for shielded nuclear installations or other application where access thereto is restricted due to the materials involved.

Although particular embodiments of the invention have been illustrated and described, modifications and changes will become apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications and changes as come within the spirit and scope of the invention.

We claim: 4

1. A jet-mixed extraction column for intimately contacting and subsequently separating substantially immiscible liquids of different specific gravities comprising: a hollow column, an inlet for heavy liquid and an outlet for light liquid at one end portion of the column, an inlet for light liquid and an outlet for heavy liquid at the other end portion of the column, a plurality of spaced sets of coaxial hollow ring members positioned in spaced relation within the column, each set of coaxial hollow ring members having an outer ring member thereof located adjacent the column internal surface and an inner ring member thereof centrally located in the column, the inner and outer ring members of each set being concentrically positioned with respect to a central longitudinal axis of the column, each of said inner ring members being provided with a plurality of apertures on the outer surface thereof located in a horizontal plane bisecting the inner ring members and substantially perpendicular to the longitudinal axis of said hollow column, each of said outer ring members being provided with a plurality of apertures on the inner surface thereof located in a horizontal plane bisecting the outer ring members and substantially perpendicular to the longitudinal axis of said hollow column, and means operatively connected to each set of ring members for continuously withdrawing liquid from said column through the apertures in one of said ring members of each set and readmitting such liquid into the column through the apertures in the other of said ring members of that set.

2. The jet-mixed extraction column defined in claim 1, additionally including means mounted within the area defined by the inner surface of each of said inner ring members for blocking flow therethrough and for further reducing longitudinal dispersion of liquids flowing through said column.

3. The jet-mixed extraction column defined in claim 1,

wherein said means for continuously withdrawing and readmitting liquid includes a continuous-flow type pumping means having the inlet side thereof operatively connected to said one of said ring members through which liquid is withdrawn and the outlet side thereof operatively connected to said other of said ring members through which liquid is readmitted.

4. The jet-mixed extraction column defined in claim 3, wherein said continuous-flow type pumping means is of the centrifugal type.

5. The jet-mixed extraction column defined in claim 3, additionally including a reversing type valve assembly operatively connected intermediate said inner and outer ring members of each set and the continuous-flow type pumping means for each set of ring members.

6. The jet-mixed extraction column defined in claim 1, additionally including shield-like means operatively connected to at least a similar ring member of each of said sets of ring members.

7. The jet-mixed extraction column defined in claim 1, wherein said means for continuously withdrawing and readmitting liquid includes a double-action reciprocating type pump assembly operatively connected through a sequentially actuated valve assembly such that said one of said ring members is continuously connected to suction strokes of said double-action pump assembly and said other of said ring members is continuously connected to a discharge stroke of said double-action pump assembly.

References Cited UNITED STATES PATENTS 2,629,654 2/ 1953 Olney 233 10 2,729,550 1/1956 Maycock 23267X 2,765,913 10/1956 Weiss 23270X 2,927,006 3/ 1960 Brooks 23267X 3,204,934 9/1965 Graham 259-4 3,279,890 10/1966 Szasz 23--270 3,294,672 12/ 1966 Torobin 23273X 3,307,914 3/1967 Heiss 23271X 3,376,976 4/1968 Wallen 23267X 3,488,159 1/1970 Moon 23270.5 3,499,752 3 1970 Vermijs 23267 3,519,401 7/1970 Hellman 23--3 10 NORMAN YUDKOFF', Primary Examiner S. I. EMERY, Assistant Examiner US. Cl. X.R.

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