US2693280A - Separating apparatus - Google Patents

Description

H. R. BRAMEI. SEPARATING APPARATUS Nov. 2, 1954 2 Sheets-Sheet l Filed Nov. 8, 1949 mmmmmmm" Nov. 2, 1954 H. R. B RAMEI. 2,693,280

y SEPARATING APPARATUS Filed Nov. 8, 1949 2 Sheets-Sheet 2 9a /00E 99 U /O/ Fig. 6

Had/ey Bra/nel Attorneys United States Patent "Ofiice SEPARATING APPARATUS Hadley yIl. Bramel, Los Angeles, Calif.

Application November 8, 1949, Serial No. 126,188

2 Claims. (Cl. 210-51) My invention s related to the processing of materials, and is particularly suited to the continuous separation of the physical components of fiuid suspensions as, for example, slurries, slips, pulps, juices, milks, emulsions, sludges, mists, dust bearing gases, the control of waste products and the like.

The separatory operations to which this invention may be adapted include the classification of suspended solids according to size, sorting according to shape, sorting according to densities, the thickening or concentration of suspended material, the clarification of fiuids, and various combinations of these operations as, for example, thickening, together with clarification.

These operations are now commonly performed by machines such as hydraulic, rake and spiral classifiers, elutriators, settling tanks of various forms in which settling may occur quiescently or with stream motion, Dorr type thickeners, batch and continuous centrifuges, cyclones, screens of stationary and dynamic type filters of continuous or discontinuous kind. and various types gravity concentrators and sedimentation devices.

To this broad and intricate technological field my invention is related as an improvement and by contribution of distinctive and unprecedented separatory operations.

With reference to basic physical mechanism the majority-of well-known machines for the separation of suspended material primarily belong either to the sedimentation family, including in general the classifiers, elutriators, settlers, tank thickeners, centrifuges, cyclones and gravity sedimentation devices; or to the screen membrane family including the various screening and filtering devices. J

A general characteristic and limitation especially of gravity sedimentation devices lies in the fixed pace at which sedimentation takes place with a given product. The achievementof a desired result requires that a certain volume of process fluid be in process for a certain length of time. Since. centrifugal equipment is generally operated at or near top speed, similar conditions prevail.

This infiexibility of operation results in several practical disadvantages. Not only must the original selection of equipment be made with great care and with attendant risk of error in choice, but also costly provision must be made to insure steadiness of operation. Furthermore, changes in the scale of operation by addition or subtraction of such equ'pment must proceed by gross jumps rather than by graduation. n

A further limiting characteristic of sedimentation equipment, especially in the commonplace function of classification, lies in the rapid decrease of capacity for a given installation with decrease in the particle size of separation. As a rough rule, an installation which would yield a ton of product at a particle size of unity would yield only a quarter ton at a particle size of half unity. As a result of this limitation the continuous classification by gravity settling of such important products as the majority of mineral raw materials is generally regarded as economically marginal at 5d to 70 micron particle size.

Similarly where the nature and value of the product are such as to allow accommodation to the pecularities and high costs of continuous centrifugation, separations may be practical to a particle size of about 5 microns and only rarely to finer sizes.

The large space requirements of gravity` sedimentation equipment is often disadvantageous, especially When 2,693,280 Patented Nov. 2, 1954 scale of operation must be increased in a crowded, industrial area. A corollary disadvantage may be the large volume of material tied up in process-a condition particularly objectionable in the case of material subject to bacterial deterioration or evaporation.

Effective performance of gravity sedimentation devices in the function of classication often requires a comparatively high dilution of the suspension in process. Such dilution may, in turn, require correction by costly thickening operations.

Screens may be distinguished from filters by both purpose and mechanism. Whereas screens are generally intended to effect separations between particles according' to size, or size and shape, filters are generally used to make a more or less complete separation of solids and liquids. In point of mechanism, the screen membrane itself is the effective barrier in a screen, whereas in a filter the screen membrane serves mainly as a foundation for the effective barrier formed autogenously of material in suspension.

The cost of screening operations, as a general rule, like that of gravity classification, increases rapidly with decreasing particle size. The aperture of the finest available screen cloth is 37 microns, although few commercial products in quantity can be economically screened below 100 to 200 micron size.

A further characteristic and limitation of screening operations is determined by the comparative abundance of so-called difficult particles, or those which approximate the size of the screen aperture. Where such particles are abundant screening is greatly impeded.

Filtration devices used for the purpose of thickening a suspension have the occasional disadvantage of concentrating the suspended material beyond the point desired. This is particularly objectionable where particles subsequently to be dispersed adhere to one another to form indestructible aggregates.

Certain materials as, for example, solids of flaky shape may be impractical to filter by formation of impervious filter cake.

Both gravity thickening and the filtration of fine-sized materials frequently depend on the mechanism of fioc formation. Although a few materials, such as certain clays, flocculate naturally, the fiocculation of most process materials must be caused artificially by the use of reagents. The large quantity of pasted starch used for this purpose in thickening and filtering the red mud residues from the caustic leaching of aluminum ores furnishes a practical example of reagent costs approaching prohibitive levels.

The following example from practice illustrates several of the foregoing points.

In the blending and firing operations of the Wet process for cement manufacture a finely ground cement rock slurry of high solids concentration is required. Although the grinding of the rock in ball mills is accomplished at approximately the solids concentration desired for blending, considerable dilution of the ball mill product is essential to the efficiency of the subsequent hydraulic classification. Dewatering the classified fine product then requires two further operations: first, thickening in Dorr type thickeners, and nally filtration by continuous filters. Since the resulting filter cake is too dry for direct blending it must be suitably diluted.

This brief review of the prior art brings out the considerable need and long unsatisfied demand for a generally fiexible, compact and inexpensive separatory method, particularly suited to the accomplishment of the Various separatory functions in the range of finer particle size for example in approximately micron size and finer.

A series of problems of long standing concerns the separation of suspended particles of non-granular shape. Such problems include the classification of flexible fibers according to length, the sorting of fibrous and flaky materials and the separation of these irregular bodies from associated compact particles. Furthermore, the degree of difficulty in separations of this kind is often Vincreased by the association of particles into aggregates. Separation must therefore be accompanied by mild disintegrating action.

Certain problems in the paper manufacturing industry may be cited as examples. The control of fiber length isessential in paper making. Since no machine has heretofore been available which can satisfactorily classify fibers in pulp slurries, fiber length must be controlled by the type of wood used and more particularly bycontrolling the thickness of chips cut from the solid wood. v

Furthermore, for lack of adequate classifying means, the beating or mechanical disintegration stepA inpaper making remains a batch process which must be continued lfor each batch for a sufficient duration to-assure-the complete disintegration of the most refractory materials present. The slotted screens which are used yfollowing beating in an attempt yto eliminate non-fibrous solids, such as knot fragments are only partially effective.

j Industries using reclaimed paper fiber arev `similarly handicapped. In order to provide fibers of desired length the used paper, at considerable cost, must be hand-sorted yinto various grades. An additional problem is that of removing from the beaten pulp the numerous akes ofi-unf disintegrated paper which inevitably escape the beating process and are deleterious to the quality of finished paper land fiber products. As in the manufacture of 'virgin paper, slotted screens having high maintenance costs and requiring much manual effort are used with indifferent success to reject undesirable particles. Y

Similar unsolved problems of fiber classification and speck removal exist in the fruit juice industries. A

The separation of clay and clay-like product such `as weighted and unweighted rotary drilling mudfrom sandy impurities and the separation of the weighting materials such as barytes and iron oxides, afford examples of separation and classification requirements in which processing at high solids consistency would be desirable. -Clays are often of extremely occulent nature so that even cornparatively dilute suspensions form a rigid flee-structure which entraps sand grains and prevents satisfactory separation bv relatively inexpensive gravitationalmethods.

A further general problem of long standing is that-of fractionating a fine-sized product comprising a wide range of particle sizes into groups of closely similar size, The preparation of abrasive powders, isa practical `example of this kind and a similar example is the close sizingreouirements of certain radioactive solids. Heretofore the slow and expensive laboratory elutriation method Ainwair or liquid media has been the principal means of effecting such separations.` A method capable of conducting such operations at hivh production rates is very desirable.

Tn certain dredging operations silt ispumn into-barges and towed for dumping into deep water. Tfit wereeconomically practicable to classify the dredgings -into'slow settling andfast settling fractions it would be possible to dump the Vslow settling fraction at the site to bev dispersed by tidal or river currents and thereby effect enormous savings in disposal transportation. A- method of sufficient compactness and overall economyforthis purpose would so alter the practice as to be regarded as a far reaching economic development. Y

f In general -my invention solves the foregoing'problerris by-application of-my discoveryvthat solid particles entrained with a confined fluid stream, as between plates or ina tube tend to migrate in course of passage from regions adjacent the boundaries towardthe center of the stream. In applying my discovery in the preferred embodiments of my invention I provide apparatus of various types to move fluid suspensions of the materials to be separated in confined streams while transforming'po# tential energy to kinetic energy, and continuing the movement of certain components of the stream in the-saine direction, while removing other components inangular directions, and then convert the kinetic energy of the separated components substantially to potential energy by reducing their speeds. y

Among the advantages of my inventiony are-(l) lits ability to disperse aggregates of fibrous or other material in suspension and to classify such materials according to size orto sort them accordingto shape; (2) itsability to separate oversize materials from thixotropicocculent fine materials such as clay. A. similar advantage is its ability to classify materials without need for lexcessive dilution; (3) its adaptability to separations of materials in-the sub-size range of particle sizes. A related but specialized advantage is its ability to classify sub-sieve materials into fractions of closely identical size; (4) the thickening and clarification of fine material may be accomplished without the use of flocculating or other reagents; (5) performance characteristics such as se- `tions without additional pumping equipment. y y advantages willube apparent to those skilled in the art 4 lectivity and intensity of effect in separatoryoperations may be varied over a Wide :range simply by the variation ow rate; (6) wide range of through-put capacities which may be accommodated by a given installation without appreciable change in quality of performance; (7) relative compactness of the equipment for a given capacity range; (8) relatively small quantities of material are in process at onetime; (9`) entire separatory operations may be conducted herxnetically sealed and, if desired, under lowered or elevated ,pressures and temperatures, advantages of considerable importance in the treatment of foamingor volatile uids, iiuids'sensitive to oxidation, or materials of sensitive thermodynamic equilibria; (l0) most of the parts of the separator are subject only to small mechanical stresses and may therefore be fabricated from a wide variety of corrosion-resistant or abrasion-resistant materials; (l1) ease with which the separatory units may beopened for inspection, cleaning, or for the substitution of parts; (l2) the fluid undergoingseparation is kept c'ontinuously` inrnotionwith little opportunity Vfor the .accumulation or stagnation of material in process; (13) and by. appropriate choice of the pump which provides the fiow through the separatory systemthe productsof the separation maybe|elevated or piped toy remote destina- Additional fromthefollowing ,.f. v l

, :Accordingly .a primaryl object of my invention is to employ, asia means: of separation of materials iniuid suspension, novel hydrodynamic 'effects, which have proved adaptable to systematioutilization for-'thatpurposeI Another-objectniis--tto provide a pressure-actuated separatory mechanismfof compact. unitary character arid which;y functions continuously according to novel hydrodynamicprinciples requiring the use of no moving mechanicalparts.l f5- -1 Y v. `Still anotheinobject is tot provide, for operation `of the separatory mechanismdescribed, a choice of l practicable circuit arrangementstadaptedto -theperformance 'of a wide range and 'combination of separatory operationsincluding sorting, classification,- thickening, and clarification of diversefluid suspensions.v t l .Afurther object is to provide'novel separatory'mechanism andicircuit systemsV for its practical application to fluid lsuspensions `whose separation in a desired manner by machines heretofore available has proved partiallyor wholly unsatisfactory. f

Another objectV is to provide separatoryunits whose through-put capacity can be materially increased or decreased, as desired,'by 'simplified manipulations'involving the addition 4or subtraction of standardr interchangeable parts. A I- Still another object is to provide separatoryunit's whose performance characteristics, particularly as these lconcern accommodation to differences in the nature of materials to bev separated,` may be adjusted over a wide range by simplified procedures involving the substitution of standardized parts.

l Other objects will become apparent las the description proceeds-in connection Withthe accompanying drawings, andrfrorn the appendedclaim's.

-As shown inthe drawings:

Figure l isa-section in a plane parallel to the principal `direction` of fluid motion and illustrates an aspect of one embodiment of apparatus for carrying out my in- Ventron; y

Figure 2 is a cross-section'on the line 2-2 of Figure l, and supplements Figure l to define one form;

Figure 43 is also a cross-sectionon the line 2 2 of Figure l and supplements Figure 1 to define another orm;

t Figure 4 is a view partially'in elevation and partially in section along line 4--4 of Figure 5, and illustrates another form;

Y Figure Sis a partial section along the line 5 5 of Figure 4 and supplements Figure 4 to illustrate the duct system and other features of Figure 4;

Figurel 6 is a circuit diagram illustrating one system in which my invention is utilized. y

Figure 7 is a more conventionalized representation of Figure 6;

Figure 8 isa circuit diagram illustrating yanother systern utilizing'm'y invention; l

Figure 9 is a circuit diagram illustrating another system;

. Figure is a circuit diagram illustrating still another system;

, Figure 11 is a circuit diagram illustrating another system.

Referring to Figures 1y to 3 which illustrate perhaps the most simplified embodiment of my invention, a casing 13 may be assembled of two similar parts 14 and 15 having mating flanges 16 and 17 by which the parts may be held together by screws or bolts, etc., not shown. Opposing facing cavities in the parts 14 and 15 form a fore-chamber 18, to which an inlet 21 is connected, to admit the uid suspension to the fore-chamber. Spaced from the fore-chamber 18 in the parts 14 and 15 is a first afterchamber 22 also formed by oppositely facing cavities in the parts 14 and 15. Between the fore-chamber 18 and the first after-chamber 22 is a second after-chamber 23, similarly formed by oppositely facing cavities in the parts 14 and 15. An outlet pipe 24 for the thickened fraction T is connected to the first after-chamber 22, the flow through the p'pe being controlled by a suitable valve 25. A pair of outlet pipes y26 are connected to the oppositely facing cavities forming the second after-chamber 23, to carry of the clarified fraction C of the separation, in a manner to be explained.

Clamped between the parts 14 and 15, and extending from the fore-chamber 18 almost to the first afterchamber 22 is a converging nozzle or passageway which forms a separatory duct 27 (Figures l and 2). This converging separatory duct 27 may be formed in a cylindrical member 28 as shown in Figure 2, the member being clamped between the parts 14 and 15. In this case the converging separatory duct is in the form of a long tapered cone. Alternately, the converging separatory duct may be formed within a rectangular member 31 clamped between the parts 14 and 15 as shown in Figure 3, in which case the separatory duct, here identified by the reference number 32 has converging facing spaced walls 33 and 34 to define the separatory duct, the side walls 35 and 36 being either parallel, or slightly converging in the direction of fluid ow.

In either case, whether the separatory duct is conical as in Figure 2 or merely converging as in Figure 3 it terminates in what may aptly be termed a splitting chamber 37, shown in Figure l. This splitting chamber 37 is formed by the junction of diverging discharge duct 41 and 43. The discharge duct 41 is coaxial with the separatory duct 27, whether it be of the form of Figures 2 or 3, and it discharges into the first after-chamber 22 for the thickened fraction T. If thesdevice be in the form of Figure 2 the discharge duct 41 is of diverging conical shape within a cylindrical member 44. Also, in this form, the diverging discharge duct 43 may be formed between the conical end of cylindrical member 28 and a conical recess 45 in the inlet end of the cylindrical member 44, the angles of the cones being dissimilar so that the clarified fraction discharge duct 43 is of expanding cross-section with its outlet at the second after-chamber 23, and in the formof an annulus surrounding the cylindrical member 28. ln the form of Figure 3 the cylindrical member 44 of Figure l is replaced by a rectangular member similar to the member 31 of Figure 3 except that it is shorter. and the thickened fraction expanding nozzle corresponding to duct 41 of Figure l is of rectangular cross-section throughout its length, and the clarified fraction discharge duct. corresponding to duct 41 of Figure l, instead of being in the form of an annulus, may be in the form of two divergent discharge passageways, extending on opposite sides of the outlet end of the rectangular member 3l and toward the second after-chamber 23 in the manner shown in Figure l. In either form, whether the separatory duct is circular in cross section as shown at 27 in Figure 2 or rectangular as shown at 32 in Figure 3, the entrance to the separatory duct is rounded or streamlined as best shown by the rounded corners 46 of Figure l.

'Ihe rectilinear longitudinal contours of separatory duct 27 and similarly 32 may be modified by curved forms or by tangents connected by curves without essential deviation from the general forms illustrated and described. Likewise the clarified fraction duct 41 shown in Figure l as rearwardly directed may be at any angle to the axis of separatory duct 27 or 32. Also when utilized with gaseous carriers it will be understood that the contours of the passages 27 and 32 may be modified to take full advantage of the thermodynamic factors involved, as for example by making the separatory ducts of converging-diverging form in a manner lthat will be apparent to those skilled in the art.

In operation, the embodiments shown in Figures 2 and 3 in conjunction with Figure 1 operate in the same manner and in accordance with principles which will be explained later. In either case the mixture enters the fore-chamber 18 and passes through the separatory duct 27, emerging into the splitting chamber 37. From there the thickened fraction passes through the discharge duct 41 to the first after-chamber 22 and the clarified fraction passes through the discharge duct or ducts 43 to the second after-chamber 23. The separated fractions pass thence to the outlet pipes 24 and 26 as is obvious.

Figures 4 and 5 illustrate an embodiment wherein the capacity and separatory characteristics, although operating under the same principles as those of Figures l and 2, may be widely varied by the addition, subtraction, or substitution of interchangeable parts.

Referring to these Figures 4 and 5, the converging separatory ducts corresponding to the ducts 27 and 32 of Figures l to 3 are formed between facing annular surfaces 47 and 4S of a pair of ring elements 51 and 52, the aforesaid annular surfaces being spaced to provide an annular convergent separatory duct 53 through which the mixture passes to be separated. The ring elements of each pair have aligned central openings or holes 54, and the axial distance between two facing ring elements 51 and 52 that define a pair is adjusted by varying the number or thickness of shims 55 therebetween. Thus the number and thickness of shims 55 determine the effective spacing of the oppositely facing annular surfaces 47 and 48 that define the converging separatory ducts 53. Each pair of ring elements 51 and 52 is held in coaxial alignment by means of coupling rings 56 which are of insufficient thickness axially to affect the axial spacing of the ring elements.

The aforesaid ring elements each have annular channels 57 surrounding the coupling rings 56, the channels in the ring elements facing each other to provide circular fore-chambers 58 communicating directly with the rounded or streamlined entrance ends of the annular separatory ducts 53. A series of substantially equiangularly spaced holes 61 arranged around and parallel to the axes of the pair of ring elements 5l. and 52 provide passages for the entrance of the separable mixture to the annular fore-chamber 58.

Referring to Figure 4, it will be seen that an outer ring element 62 surrounds the ring element 52 and has a series of short radial spokes 63 (Figure 5) that rest upon an annular shoulder 64 on the upper ring element 52. A similar outer ring element 65 has short radial spokes resting against a similar annular shoulder on the underside of the lower ring element 51. The two outer ring elements 62 and 65 define between them an annular divergent passageway 67 communicating at its outlet end in a first annular after-chamber 66 for the thickened fraction. The same outer ring elements 62 and 65, in conjunction with the ring elements 51 and 52, define an annular splitting chamber 68 similar in principle to the splitting chamber 37 of Figure l. From the splitting chamber 68 lead divergent annular passageways 71 and 72 which conduct the clarified fraction of the liquid to the lower surface of ring element 51 and the upper surface of ring element 52 respectively. lt should be appreciated at this point that since the outer ring elements 62 and 65 rest against shoulders on the ring elements 51 and 52, that the size of the thickened fraction divergent passageway 67 is adjusted in accordance with and at the same time as the separatory duct 53 when the number or size of the shims 55 are changed.

A clarified fraction passageway 73 is provided by aligned central openings 74 in the ring elements 51 and 52. The ring elements 51 and 52 are provided on their outer surfaces with raised bosses 75 surrounding the equiangularly spaced holes 61 therethrough. These raised bosses provide supports for adjacent identical ring elements. which form between them and the ring elements 51 and 52 a series of radial passageways for the passage of the clarified fraction from the divergent passageways 71 and 72 to the central openings 74. These central openings 74 form the discharge passageway 73 for lthe claried fraction.

stacked in the above manner to provide a separator having the desired capacity and characteristics.` The top and bottom of the stack is completed by closure elements 76 and 77 respectively (Figure il7 which mateg'with the upper and lower of the ring'elements forming the stack to form the uppermost and lowermost thickened fraction divergent passageways 78 and '79 respectively, it being seen that these closure elements 76 and 77 include outer peripheral portions 82 and 83 that have parts corresponding to the outer ' ring elements 62 and 65.' yThe closure elements 76' and 77 are similar except that the -upper -element 76 lacks the series of equiangularly spaced holes that lead to the fore-chambers 58. l l The entire described assembly is assembled -and'compressed between an upper closure'84` and a-lower closure 85, thelatte'r having an inlet pipe 86 leading to an annular inlet channel or manifold 87 that'places itin communication simultaneously with tothe forecharnbers 55.5. Also,-the lower closure SIV has an' outlet pipe 88 which discharges the thickened fraction from the first -after-chamber'ee.' A control Valve (not shown) similiar to the valve of Figure l is incorporated in ythis outlet pipe. The clariied fra'ctiondischarges fromthe central clariiied fraction passageway 73 downwardly into a fitting 9 threaded` into `the lower closure 85 and then passes through a suitable vdischarge pipe '90 that is threaded into thefitting 89. "This fitting 89 `is closed at its lower end'by a threaded plug v91` and a central bolt 9E is threaded into the plug tti, passing up lthrough the clariiiedfraction passage- 'Band through the upper closure 841. A nut 93 securely clampsthe assembled ring elements between the upper and lower closures" 84- and 85.` The enclosure of 'the assembled ring elements is completed by an annular casing 94 that maybe positively located by a flange 95 seated upony the'upper closure 4842-.' Sealing between the casing 94 *and the closures 84 and 85 may be by any suitable device such as the packings 96. -As illustrated-the end ysurfaces of housing 94 are hydrostatically balanced; However `the tensile strength of housing 94 may if desired be utilized by use of retaining ring 97 seated against the Arim of closure 85 by suitable cap screws. i

The principle of'operation of the embodiment of Figures 4 and 5 is the same as those of Figures 'l` to 3, in that the converging separating ducts, splitting chambers, thedivergentpassageways for the thickened 'fraction T and the rearwardly directed divergent passageways for the clarified fraction C are similar. These passageways may bemodifiedas herein before set forth to takey advantage of'thermodynamic factors when utilizingI gaseous carriers. Figures 6 to ll` illustrate in schematic form several systems 'or liow circuits in `which the separators illustrated in Figures l to 5 may be usedto obtain'a desired separatory effect. In each of the Figures 6 to- 1l the rectangular shaped elements 98 represent'aseparator'constructed in accordance with my invention, of which `three embodiments are illustrated in Figures ll` to 5'. Conduits o'rpip'es carrying thickenedfractions are identifiedrbythe reference characterT. Those carrying Vclarified fractions are identified by the reference character C. ln each case the pipeline carrying the fluid lto be separated is identified by Athe `reference character99, and includes a pump 100 for delivering the fluid atpthe desired pressure to the separator 98. Control valves having the purpose of the valve y25 ofFigure l are identied 'by reference character 1'01. f f Figures 6 and 7 illustrateva simple owfcircuit cornprising `an inlet pipe 99 having a pump `10Q-delivering the mixture to theseparator 98. The thickened fraction issues through pipe T and isfcontrolled by valve 1M, while the clarified fraction issues through the pipe'C. Figure 7 is a liow circuit identical to Figure 6 buthaving the pipes or conduits indicated by single lines. 1t t In thecircuit shown in `Figure 8 yatliuid suspension passes through pipe 99 and pump lili) to separator 98. The C outlet from the separator is discharged from the circuit.r The T product line from the unit has `two branches, each containing flow regulating means or valves 101. One branch is` dischargedffrorn the circuit; 'the other branch returns to join the incoming fluid in pipe 99 at a= point upstream from the pump 100. l. j `Figure 9 representsthe useof three separatory `units 98 in what might be termed a T series circuiti or thickall of the'y holes 6l 'that` lead ened fractioncircuitf Any number of units beyond two could be so-employed. A pressure elevating means 100 delivers fluid through pipe 99.1to lthe inletof the iirst separator 98. The T outlet of the iirst unit communicates with the inlet `of a second.separator 98,v andsimilarly the T outletof the'secondwithfthe inlet of a third separator 98. Thef'fl` outlet line ofthe'tinal separator containsV ow lregulatingtmeans 101 which discharges from the circuit. Similarly the Coutlet linesof all but the rstseparator contain fiow1 regulating: means v101 following which the lines may;l if desired,` bev joined as shown for single discharge from the circuit. v

Figure l0 `represents the vuseof three separators in whaty might becalledt a` tC series circuit or 'a clarified fraction circuit. VTwo or, .more separators 98 are so employed. A pump vdeliversiluidtvia pipe 99 `to :themlet of the iirs'tseparator 98.4 `The lC outlet` of ltheflrst unit communicates", with 'the' inlet ofa second separator 98 and similarly the Cl outletf'of the second `with the inlet of athird separator 98.:The `Coutlet line of the'ftnal separatoris discharged :from the circuit.. TheT outlets of each separatorncontain valvesl 101, 'following :which thelines may be joined as .shown to a' common iline discharging from the circuit. t. i f

Figure ll represents a `combination-of `ithe circuit principles of` Figures 9,and 10, andmightlbe icalledga ffcompound circuit. AlthoughY asymmetrical arrangement of live separatory units ,is shown .in Figure-l l, Vany number above ytwo could be so employed. Fluid is =de-, liveredto the inlet of 'the uppermosty separator-98 ,via pipe 99 andpump 100. v .f The T outlet of the uppermost separator-.communicates with the inlet of a second separator; the 'I zoutlet of the'second with -the yinletof `a third. separator andv the T outlet line from .the iinal T .leg.,separator.containspa valveltll `which discharges from `theqcircuit.y Similarly the C outlet of the uppermostseparator98 communicates with the inlet of a fourthseparator; thevC outlet lof the fourth with the inletofza fthfseparator; and the final yC outlet from the fC legfis discharged from the circuit. The C lines from the T 'leg.- as wellas theT Vlines from me Cf v1egeeach containfow regulating or .valve'means lltllffollowing,whichv alljoin alcommonreturn'line 102 leading totheinletlpipe 99.at.a-po`int .upstream from `the pump 100. :j l, l 'v vAs hereinbefore ,pointed tout,l .my .invention operates Iin part by virtue of my discovery .that-solidvpar-ticles er1- trainedwith a fluid `stream confined, asy between plates yor in' a tube tend to migrate in course of vpassage vfrom regions adjacent ,to the lboundaries toward the center n of thestream.` Y

With reference `to fFigurey 1 the `essence/of the-'inven tion is applied: dirst, bytheusecf separatory duct.27 Vof appropriate characteristics Atobringaboutran accumulation of avprescribedfraction `of the process .materialdn the central regionof'the .stream Yapproaching?,the splitting chamber .37, and, .second by`appropriate.characteristics of this splitting'chamber andfdivergingducts 41, 43 and 45, vandby suitable .control ,of ow. through. regulating means, such as'` valve 25, of 'effecting .a symmetrical three-way division ofthe segregated streaml andzdiversion of `itsparts intact as oftheinstant4 preceding `thesplitting event. Suitable vpassages and .dischargel vopenings -provided for' ,the productsl complete` rthe .desired ,physical separation. ,v g y Although thepeculiar hydrodynamiceffect on ywhich my separatory `method `is `in lpart `based has Lnot .to my knowledge heretofore beenf .isolated `oranalyticallydescribed, Lcertainaspects offtheflow congurations used in,l the methody have ,beenrationalized .in yengineering terms and their-brief Vdiscussion is therefore-vin order.

The sectional configuration of separatory duct .27.in combination with discharge duct 41, resembles the-familiar venturi tube rwhich is used 'for metering fluids and which vis notable for yits 'e'iciency .in the energy transformation cycle of'potentialto kineticto potential energy. As in the venturi tube a substantial portion-'of the potential energy available in theluid at fore-chamber 11.8 reappears-as 'potential energy at 4the'iirs't afterl chamber 22, and if the outlet'tothis chamberis stopped byvalvey 25 a somewhat reducedzquantityfofrpotential energy becomes, available in fthe tsecond *after-'chamber 23.y Similarly the iiowv maybel'divided,feach stream of the division containing laproportionate-share of -the available` energy. 4 This characteristic of the separatory units makes it practicable to use various flow circuits employing the interconnection of several units with flow maintained by a single pressure generating means.

Part of the energy inflow between boundaries, as in duet 27 is transformed by the mechanism of viscous fric- -tion into heat. One of the primary factors determining the scale of this transformation is the degree to which the flow follows a systematic pattern. Flow at low velocities between relatively stationary boundaries is characterized by a uniformly laminar pattern in which adjacent layers of fluid parallel with the boundaries, slip frictionally over one another and with velocities increasing uniformly toward the center of the stream. The frictional energy transformed in such flow is propor- -tional to the average velocity of the stream, and with velocity held constant, is inversely proportional to the dimensions between boundaries. This form of flow may be described as having a uniform shearing gradient.

At lcertain higher fluid velocities the flow pattern tends to become unstable and to pass more or less abruptly into transient complex configurations in the aggregate known as turbulence. The frictional energy transformation in turbulent flow, depending on the degree of turbulence, is proportional to some power of velocity between one and two. The shearing pattern which in extreme turbulence can only be regarded as a composition of averages is of a general form not unlike that of laminar flow. The shearing gradient and its energy relations in flow between boundaries have been particularly mentioned because it is reasonable to associate with them the observed segregation phenomena. Tentatively it may be assumed that the segregation action in the separatory ducts is in some wise proportional to the prevailing systematic shearing intensity.

Since fluid turbulence is by nature a mixing action, an objective in the design of the separatory duct would be to employ means not only for retarding the onset of turbulence but also of suppressing so far as possible the magnitudes of such irregularities of motion as must inevitably'arise at extreme flow velocities. The rounded entrances 46 of Figure l and 103 of Figure 4 and converging walls of separatory ducts 27 and 53 are consistent with this objective.

n the assumption, as suggested, that the segregative action is associated with the energy systematically transformed in fluid friction the following may be predicted as to certain operating characteristics of my separatory unit. l

With ow velocities held constant more intensesegregative action would be expected with decrease in the clearance of the separatory ducts:

Since at all velocities within the regime of laminar flow the frictional energy expended per unit of fluid passing would be constant, the net segregative effect over this velocity range will be constant also.

Some change in the separatory characteristics would be expected as velocities increased beyond the incipience of streamline turbulence;

Since the frictional energy per unit of fluid passing increases with velocity in the turbulent regime within this regime some-increase in segregative intensity should accompany an increase in' velocity.

Such reasonable expectations have been substantially verified by observation. I have found, for example, that uids containing very fine suspended material can be more effectively thickened at flow rates within the laminar regime, although thickening action with such material can be produced over an unrestricted range of velocities. The laminar regime of operation is entirely consistent With economic rates of throughput and coincides in the cases of many separation problems with convenient and economical pumping pressures. The choice of operation abovev or below critical flow rates affords for certain separations a usefully selective operating control.

It should be particularly noted that thisy segregative mechanism whose operation has been visually observed in transparent apparatus is unique in that the forces effectively utilized, ias distinct from inertial or gravitational effects are of fluid origin and `mode of action. It is also noteworthy that these forces take effect on the external surfaces of suspended materials in a new and peculiarly selective fashion. The effect might aptly be termed the shearing effect to distinguish it from other effects with which the inertial separation is apparently properties or body forces of matter are more closely associated. l

Suspended matter whose density is closely similar to that of the suspending medium, a condition sometimes approached withv process materials such as certain synthetic as Well as animal and vegetable substances, reacts to gravitation or acceleration as if it were part of the suspending fluid. Thus a suspended particle in precise hydrostatic equilibrium would have no tendency to move with respect to the neighboring fluid whether the system were at rest or subject to accelerated motion as in a centrifuge. The successful application of my invention to materials in approximate hydrostatic equilibrium, by Way of isolating the shearing eect from possible inertial effects has further demonstrated its existence and intensity.

` The densities of most process materials, however, differ perceptibly from and are usually greater than those of the suspending media. Also, since both rectilinear acceleration and curvilinear motion take place in the duct systems of my invention, inertial effects both assisting and opposing the action of the shearing effect are known to exist. Two of the more important inertial effects Will be discussed.

In the splitting chamber of my invention, side fractions of a stream, often moving at high velocity, are turned aside into lateral ducts while the central portion, usually simultaneously checked and expanded continues in generally forward motion. Since the arc of curvature followed by the diverted lamina is of small radius, the inertial forces developed, although covering a duration of say only a few microseconds may be sufficient to transfer dense particles from streamlines entering the lateral ducts to those continuing forward. Since the more common separations involve suspended substances of densities above those of the suspending media the intertial action accompanying the splitting event more often assists than hinders the separatory purpose. When the density differential is extreme, as in the case of a dust-laden gas, this inertial action may predominate to effect separation.

It should be noted that analysis of the character of confined flow around bends shows the elements of uid near the inside of a bendl to be accelerated while those travelling longer arcs are decelerated. Therefore, the inertial forces tending to shift those particles entrained with lamina close to the separatory duct boundary may, during the splitting event, reach considerably greater intensities than approach velocities would indicate. In general and in the light of familiar principles, the hydrodynamic action in the splitting chamber nicely supplements the preparatory action of the shearing effect.

Another inertial effect and one generally capable of acting with some degree of hindrance to the purposes of present under certain circumstances. The shearing effect may be identified with fluid forces tending to move suspended particles from regions of higher to regions of lower shearing intensity; that is in the case of flow through the separatory duct from boundary lamina toward central lamina. Such crossstream motion traverses lamina of increasing axial velocity and a particle which makes this traverse is therefore subject to considerable axial acceleration. When the density difference between particle and medium is small inertial resistance to such a lateral shift is also small, but when the density difference is large the inertial resistance to lateral shift may approach the magnitude of the shearing effort and eectively cancel it in the simpler types of converging separatory duct. Even with such ducts the inertial effects opposing segregation toward the axis of the stream can be minimized by appropriate choice of duct length and convergence angle. Modifications in the entrance section of the separatory duct may be so employed as to bring all elements of the stream to high velocity and the shearing and inertial effects thereafter employed in concert.

1t should be pointed out that the several hydrodynamic effects discussed and their interaction are subject to a wide range of control by comparatively minor mechanical adjustments in the embodiments of my invention, as illustrated and described. Furthermore, the existence' of controllable inertial effects increases the range of possible application of the separatory system to include separation of materials into classes according to density.

The separatory mechanisms. shown in Fig. 1 in conjunction with Fig. 3 and in Figs. 4 and 5 are alike in having symmetrically opposed parts including clarified fraction ducts. The objective of this symmetry is partly to make an elicient fractionation of the dissimilar parts of a stream Whose components are symmetrically disposed. It is` noteworthy that separatory actionstill takes place When the symmetry `is absent as forsome special purpose. Thus where one `of the opposing boundaries comprising a separatory duct and splitting chamber system is formed as a flat unbroken surface,` separatory action suitable for certain purposes is st ill secured. The principal means by which control may be exercised over selectivity and intensity of separatory action include: the form and angle of convergence `of the separatory ducts, the clearance dimensions 'of the `separatory ducts, the relative magnitudes of the product ,fractions as set by the ow regulating means, 25; the velocity of the streams as mainly determined by the pressure drop between fore-chamber 18 and splitting chambery/for 6 8, the nature and concentration ofthe suspension in process; and the circuit by which the units are operated.`

ln atypical case using a substance such asa potato starch suspended in a liquid carrier,I in order to assure the capture of a particle of given size inthe thickened product of separation, the clearancey of the'separatory,

duct near the splitting chamber should be not in excess of say or l5 times the effective diameter `of the particle, and separatory duct length of one tok three inches with a converging angle of about 1/2 gives excellent results. In a pneumaticdustcollectingsystem the relative sizes of particles and duct clearances may be much smaller. Since therange of particle sizes encountered in separatory problems is extremely wide, provision of means forthe adjustment of d uct 'clearance is desir,- able and, although duct systems having fixed convergence angles can be effectively used over a comparatively wide range of clearances, special formsy may be employed vto suit extreme cases. `Adjus'tr'rieiit of clearance'betvveen the ring elements 5 1 arid 52 frmiiigseparatory di`1c't" 51 i in Figure 4 is obtained byir'iterchanging'shims 55.I Major adjustments of duct form involve substitutions of the ring elements themselves. It is noteworthy that Vthe units are made accessible to changes simply by Vremoval of mit 93. Alterations in the numberof separatory chambers require substitutions also ofparts 92 'and 94.I Once an appropriate selection of units, working pressures and internal dimensions has been made to suit f'a particular problem one 'of the chief operating controls is inflow regulatingmeans 25. By `itsuse the'segregated stream in the separatory j'ducts 'may be 'symmetrically fractionated as desired through 'variation ofthe amount of thickened `fraction drawn otf. Normally fthe draw-off of thickened fraction will range from ten to ninety pei',- centof thegtotal ow. In general, to increase the degree of'selectivity toward coarser particles of thickeningfthe thickened fraction is reduced by increased throttling` at 25. Conversely to increase thedegiee of selek'ztivityl toward finer particlesthe clarified fraction is decreased.y

r`Althoughrthethroughput volume of algivenfunit witha given product lmay be 'varied over a V wide range with littlefchan'ge `i'n separatory results, l certain'separations maybe more etfectivelyfrnadeby operating-withiiijcertain regimes of flow Aas dened by such hydrodynamic criteria a`s vReynolds number. With given dimensional l'settings the `volumeofithroug'hiput, as determinedby'thepressure drop vbetween chambers :1 8 and 3,7V (Figure 1 is'the chief means"ofcontrolling this-condition. When the uidadrnitted to 'the separatory ducts contains a high concentration fof suspended material the effect is similarto a decreasein duct clearance andthe separatory intensityis'increased. This fact may be used advantageously to expedite certain separations. vIntroduction of appropriateneutral materials preliminary to and as an aidtofseparation may be used, removingthe neutral materials followingthe primary separation; The elementary'flow circuit shown 1n Figure 6 or Figure 7 is 'adequate fornumerous separatoryfunctions including thickening, clarification, classification `and'sorting. Sinceall the processuid delivered by the pump is discharged fromthe circuitdirectly following separation this circuit is the most economicalk one with respect to installation andoperating costs.

The circuit shown'in Figure 8 embodies the principle ofv recirculation of 'a portion of the T or thickenedv product of separation whose function is to increase the`thickeningfeect or `the selectivity of sorting'or classification.

For `a given through-put this circuit requires a larger pump and may require a separatory unit of larger capacity than thatof Figure 7.v

Y' As shown, vthe circuit of Figure 9, like that of Figure 8` is especially suitedtofthickening, sorting and classification.- `Theoperation of this circuit in certainapplicationsmight be improvedy by drawing off the nal clariied fraction product C lfrom.`the first unity and recir culating the .C products of remaining units. i

iThe circuitvinfFigure 10 istY especially suited to the purpose. of, delivering a` highly k'clariied C product. In the circuits 'of Figures 7-', 8 and.9 the minimum clearances offtheseparatory ducts are largely determined by the size of the coarse particles. in ,the `process fluid. In Figure l0, howeven; each successive unit of the series may be` setto a smaller clearance. Extremely tine sus'- pendedmaterial may thereforebe removed from the inal C product." L

Figure .ll represents aco'mbiiiation. ofA the specialized Vthickening circuit. ofy Figure `9 and the specialized `clarifying circuitlofrFigure .10. The combination circuit i's therefore adapted toi-effective :thickening and yclarification offprocess vuids whosesuspended ."material. comprises a Zwide range ,of sizes. Thel separatorynductsin the T leg arejset toapass thecoarser suspended materials whereasfthe `ducts. intheC leg.A are -set successively, closer to remove the finer suspended materials. i

The complete, fractionation of ai productl of 'wide par.- ticle size range into` groups of, relatively .uniform size may be accomplished as a semi-batch voperation -utilizing the circuit 'of Figure 38, `modified by 'addition lof a storage tankinthe return line ahead of the pump., During operation thevalVeinthe T discharge Iline is kept closed and make-up liquid comprisinggclear suspending medium isadded to the tank, in place of fresh suspension.

l. The procedureof thefractionation operation isY that successivelydeeper cuts of 'the peripheralzones of the segregated-stream are .taken by` progressive closurevof the valve in the Treturn line. Each adjustment -ismaintained `until jthe` supply of suspended ,materialrcpresented ina particular zoneof `the segregated stream is exhausted by discharge as aCproduct. The process may be-carried out rapidly by virtue of the large throughput/capacity offthe separatory unit. t. 1 K i v Flow regulationviii .circuits comprisingthe interconnection of two or more units derives from 'the-principles described in discussing the analogy between the.flow -in separatory units and in venturi tubes. In general, each unit H exertsy a` characteristic back pressure, ldepending mainly on llow rates and internal clearances., rThe yhy.-

draulic resistance of thel T and Cdischarge ducts lcan in fact be so selected-aste 'yield automatically Tand 'C `frz/. ictioris Tof, lany relative magnitudes. Partial closure of the, T ,dischargeopenings in. anyy case f results yin in'- creased oyv from the AC discharge openings but doe's not ,substantially alter Ithe fpressure at theinlet 'toxthe unit. To elevate 'this pre'ssurefandthere'by control vow inl upstream `units,both lout'ltsfto the'l downstream unit mustbezregulated. f,. 'A t' Iii-cases where theseparatory ducts are liable to stoppage vbyoccasionaloversize material vin the 1-process `fluid a separatory unit.witlifiwide-clearancesand/in v--closed circuit, `as fin Figure I8, .may be -added las ialip'rotective device 4at the head of the rvariousicircuitsshown. Rotation fof voneoffthe vopposing 'duct :surfaces fmay also be utilized for thislpurpose. w i f The invention may be embodied inf' othervspeciiic forms without departing `from. the "spirit for `v`essential characteristics thereof; The. 'presenty embodiments-fare therefore to -be considered in all vrespe'cts:'as illustrative kand not restrictive, the scope vvofNthe -finventionsbeing indicated by lthe appendedy claims arather: than 'by :the foregoing description an'd-allichangesiwhicli come'within the meaning andrange of equivalency 4of :fthe claims are therefore intendedto' be embraced therein. Ther .phrase laminar pattern ot flow4 as lused .hereinggincludes ltrue yviscous ow as well as stream-line.llow,\and;is.-iiot limited to laminar hows. "as fdesignated technicallyby Reynolds number.

What is claimed and desired to be secured by United States Letters Patent is:

1. A lluid separating device, comprising means forming a converging passageway having an inlet at its larger end and a splitting chamber at its smaller end; a rst after-chamber; a second after-chamber; a rst divergng passageway having an inlet smaller than the outlet of said converging passageway and centrally aligned therewith, said lirst divergng passageway extending between said splitting chamber and said rst after-chamber, and in alignment with said converging passageway; means adopted to effect varying of the size of said converging passageway and said rst divergng passageway simultaneously; a second passageway between said splitting chamber and said second after-chamber; and outlets from said rst and second after-chambers.

2. A uid separating device, comprising converging passageway forming a separatory duct and having an inlet at its larger end and a splitting chamber at its smaller end; a rst after-chamber; a second after-chamber; a rst divergng passageway having an inlet smaller than the outlet of said converging pasageway and centrally aligned therewith, said rst divergng passageway extending between said splitting chamber and said rst after-chamber and in alignment with said converging of said converging passageway and said rst divergng passageway simultaneously; a second passageway between said splitting chamber and said second afterchamber; outlets from said first and second after-chambers; and How control means in one of said outlets.

References Cited in the lile of this patent UNITED STATES PATENTS Number Name Date 382,614 Knickerbocker May 8, 1888 485,915 Duckham Nov. 8, 1892 1,544,712 Zwicky July 7, 1925 1,614,135 Lasche et al Jan. 11, 1927 1,684,025 1,922,920 Aug. 15, 1933 2,006,587 Eckstein July 2, 1935 2,289,474 Anderson July 14, 1942 2,422,464 Bartholomew June 17, 1947 FOREIGN PATENTS Number Country Date 4,836 Great Britain 1908

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