CA1100481A

CA1100481A - Eductor-mixer system

Info

Publication number: CA1100481A
Application number: CA301,754A
Authority: CA
Inventors: Avrom R. Handleman
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-05-31
Filing date: 1978-08-24
Publication date: 1981-05-05
Also published as: DE2857923A1; NL7805843A; FR2392712B1; DE2823604A1; AU521769B2; FR2392712A1; GB1604326A; SE7805697L; NL188931B; BE867513A; JPS53148765A; DE2857922A1; SE438272B; DE2823604C2; JPS5731443B2; NL188931C; AU3644178A; US4186772A

Abstract

Abstract of the Disclosure An eductor-mixer system in which pressur-ized working fluid is discharged through a nozzle as a concentric, high speed jet flowing past the end of an inlet tube into a mixing chamber for generating a vacuum thereby to positively draw a pressure trans-portable material through the inlet tube and into the mixing chamber and for mixing with the working fluid to form a dispersion with the walls of the g chamber being spaced from the projected path of the jet. A bypass is disclosed for the flow of pressurized working fluid around the nozzle thereby to control the amount of material drawn into the eductor-mixer. A recycle system is also disclosed which withdraws a portion of the mixed dispersion and recirculates it through the nozzle for shearing as it passes through the nozzle. Additional material and/or working fluid may be added so as to vary the concentration level or quality of the resulting dispersion.

Description

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E~UCTOR FOP~ THE PRE~ARATIO~ OF SLURRIF.S ~ND SOLIJTI~NS
~ackground of the Inven-tio_ This invention relates to an eductor-rnixer system particularly adapted for the preparation of dis-persions, solutions and slurries. More particularly, the eductor-mixer system of this invention is an improve-ment over the eductor-mixer system disclosed in the U.S. atent 3,777,775 to Avrom R. Ilandleman, issuecl December 11, 1973.
An eductor--mixer system is well suited to continuously mix a solute (e.g., a powder, particu-late, or other pressure transportable or fluidizab]e material, a liquid or a gas) an~l a solvent or ~orking Eluid (e.g., a liquid or in some instances a gas) to form a dispersion, slurry or solution. The eductor-mixer system of the present invention is particularLy well suited for use with readily transportable con-tainers, such as is shown in the above-noted ~atent and ln the co-assigned U.S. patent 4,007,694 to Timothy J. Fowler et al., issued February 15, 1977, in which a "semi-bulk'l quantity (e.g., 500-4,000 pounds or more) of powder or other solute material is stored and trans-ported and in which the load may be fluidized for .. ~ ~
..... ~ 1 ready discharge to the eductor-mixer system.
These containers are commercially available under the registered trademark AIR PALLET from Semi-Bulk : Systems, Inc, oE St. Louis, Missouri, the assignee of the present invention. The solute inlet of the above-mentioned eductor-mixer system is convention-ally connected to the discharge outlet of the fluidized container so -that the vacuum generated within the eductor-mixer by the flow of solvent : ~-(~water3 therethrough cooperates with the fluidized : discharge of the powder from the container to positively draw the fluidized powder into the eductor-mixer.
In certain applications, such as in the use~ of fire retardants for fightin~ forest fires, it is often necessary to rapidly unload thousands of pounds of powdered fire retardant solute material and to mix it in proper proportion with water to form a slurry or solution for application to the fire. In many known prior art eductor-mixer systems, the powder supply, even if it were a fluidized container, was requi.xed to be located above the le.ve~l of the eductor-mlxe~ Sy~tOr becau~e the latt_~ wa, de~endent ~n =he , ~ 2 gravity feed of the powdex. In the sys-tem shown ;n the above-mentioned U.S. patent 3,777,77~, the eductor-mixer system was not dependent upon gravity feed because the vacuum withi:n the educ-tor-mixer positively drew the powder from the container into the eductor-mixer system and thus the system shown in the above-mentioned patent was not depen-dent on the relative location of the powder con-tainer and the eductor-mixer system. However, the eductor-mixer system shown in the above-mentioned patent was thought to be somewhat complex in tha-t it utilized two stages or noz~les and i.t was not as efficient as was theoretically poss;~le in generating the vacuum which positively drew the solute thereinto~ .
When eductor-mixers are utilized to mix abrasive powders, they are subject to destructive in-ternal wear caused by the flow of the abrasive powder and resulting slurry within the eductor. It has been difficult to make ad~ustments wi.thin the eductor to compensate for wear and to accommodate different flow .rates of solute an~ soLvent rhrough the eductor.

. 3 In many prior eductor-mixers which are used to mix a powdered solute ~ith a li~uid 501--vent, it has been heretofore difficult to control the flow of the powdered solute into the eductor.
This was usually accomplished by a -throttling valve in the solute inlet line or at the bottom of the hopper feeding the eductor-mixer with powder. This throttling valve, however, was often unsatisfactor~ for controllin~ ths flow of solu-te in continuous operations As shown in the co-assigned U.S. patent 3,777,775 to Avrom R. Ilanclleman, issued December 11, 1973, solute flow control has been achieved by providing an air bleed valve in t~e solute inlet line thus allowing air to enter thc line and to regulate the vacuum generate~ within the eductor-mixer. In some instances, however, this air bleed control was not an altogether satisfactory way to control the -flow of solute to the eductor-mixer.
In mixing certain solutions and so]vents, - it has heretofore been a problem to break up ag-glomerates (i.e., glo~ules or lumps) of powder or to reduce the size of powder particles ancl to disperse the powder in a solvent. For example, in mixing paint pigment with a solvent, it was heretofore necessar~ to mechanically mix batches of the pigment and solvent ;n a Cowles-t~pe blender or the li~e for ~ .

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'' several hours or even several days to hreak up anf3 ~et agglomerates of the pigment with the solvent and to ~mi-formly disperse the pigment in the solvent.
In cer-tain prior eductor-mixer systems, it was not possible -to mix certain solute and solvent mix-tures in sufficient proportion to form slurries or solutions of desired concentration levels.
Reference may be made to U.S. patent 1,806,287 to John H. Forrest issued May 19, 1931, U.S. patent

2,100,185 to Gunnar G. Engstrand issued ~lovember 23, 1937, U.S. patent 2,310,255 to Robert P. S~eeney issued -February 9, 1943, U.S. patent 2,695,265 to ~lilliam J.
Degnen issued November 23, 1954, U.S. patent 2,722,372 to Howard C. E-1wards issued November 1, 1955, U.S.
patent 3,156,020 to Ernest F.. Cook issued January 16, 1965, U.S. patent 3,186,769 to Thomas W. Howlett, Jr.
issued June 1, 1965, and Canadian patent 78~,113 to Melvln K. Katzer et al. issued March 12, 1968 ~hich disclose various eductor-mixer mixing systems, and air conveying apparatus in the same general -Eield as the present invention.
Summary of the Invention Among the several objects and features of this invention may he noted the provision of an improved eductor-mixer system particularly well suited for either continuous or hatch preparation of dispersions, solutions, or slurries :Erom a fine granular, particulate, or powdered solute or other pressure transportable or fluidizable material and a working fluicl or solvent; and the provision of such an improved eductor-mixer system which is also ca~able of mixing gas or vapor solutes with li~uid or gaseous working fluids.
In general, an eductor-mixer system of -this invention comprises an eductor body having a curved passage extending -therethrough for flow of a pressurized ~orking fluid from one encl of the passaye, constituting an inlet end, to the other end of the passage, consti-tuting a discharge end, the passage being generallv of uniform circu:Lar cross-sect;.on throughout its length.
rrhe body has an opening therein o~posite the discharge end of the passage, said opening heing coaxial with said discharge end and of substantially smaller diameter than the diameter of said passage. A no~zle memher comprising a ring separate from -the body having inside and outside faces and a central opening therethrough from its inside to its outside face is removably mounted in place at the cdischarge end of sa.id passage coaxial with said discharge end, said central opening in the ring being of substantially smaller diameter than the diameter of said passage. A cylindrical tube of suh-stantially smaller diameter than the diameter of said passage extends from outside said body through said opening in the body opposite the discharge end of the :~ .
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passage an~ extends forward in said passage from the inner end of said opening in the body into the central opening in the ring, said tube being open at its end.
in said central opening in the ring, said open end of the tube constituting a discharge end~ The tube is axially adjustable in and removable -from said oPening, and ls adapted for connection of its end outside the body to a source of fluen-t material to be educted and mixed with said working fluid for flow of said material through said tube and out of the discharge end of the tube. The discharge end o:E the tube is substantially flush with the outside face o:E said ring, and the tube is exteriorly tapered a-t its said dischar~e end and thereby has an exterior conical surface convergent in the direction toward its said discharge end with the angle of taper with respect to the axis of the tube less than about 30. The inner periphery of the rlng bounding the central opening in the ring is formed as a conical nozzle surface extending from the inside face to the outside face of the ring and convergen-t in downstream direction from the i.nside to the outside face of the ring, said conical nozzle surface of the ring surrounding and being spaced from said exterior conical surface of the tube a distance which is small relative to diameter of the outer end of said conical nozzle surface, thereb~ providing an annular conical orifice between the ex-terior conical surface of the ~ube and said conical nozzle surface of the ring for delivery of the pressurized workin~ fluid from said passage ..... ~ , .

- . . --through said orifice in -the form of a hollow conical jet converging in downstream direction from -the out-side face of the ring. ~he gap between the exterior conical surface of the -tube and the conical nozzle surface of the ring is relatively smal:l and the length of said orifice is relatively short for rapid acceler-ation of working fluid flowing through the orifice to a relatively high lineal velocity with low flow lossesO
~eans separate from the ring providing a passage down-stream from said ring at the discharge end of -the passage in said body in which the ma-terial issuing from the clischarge end of the tube and the working fluid conically jetted through said orifice may mix is removably secured to said body at the discharge end of the passage in the body extending outwardly from said ring a.nd haviny an external diameter at its end at the outside face of said ring larger than the di.ameter of said conical nozzle surface of the ring at the outside face of the ring and the internal surface of said passage means lylng outward of and wholly clear of the projection of said conical jet throughout the length of the jet.
0ther objects and features of this invention will be in part apparent and in part pointed out here-inafter.

Brief Description of the Drawings Fi.g. 1 is an ex loded perspective view of an eductor-mixer of this invention;
Fig. 2 is a longi-tudinal cross-sectional view of the eductor-mixer;

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: .,c Fig. 3 ls an enlarged cross-sectional view of a portion of the eductor-mixer illustrating certain details of the eductor nozzle;
Fig. 4 is a semi-diagrammatic illustration of a method of and system for bypassing a por-tion of the working fluid supplied to the eductor-mixer so as to regula-te the flow of solute into the eductor-mixer;
Fig. 5 is a semi-diagrammatic illustration of a method of and apparatus for recycling a portlon of the mixed dispersion through the eductor-mixer thereby to shear the dispersion;
Fig. 6 is a semi-diagrammatic illustration of a modification of the apparatus shown in Fig. 5;
and Fig. 7 is a cross-sectional view taken on line 7--7 of Fig. 4/ Fig. 7 being on the first sheet of drawings adjacent Fig. 1.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Description of Preferred ~mbodiments Referring now to the drawings, an eductor-mixer of thi.s invention, indicated in its entirety at 1 J iS shown to comprise an eductor body or housing 3 having a curved passage therethrough for a working fluid or solvent from an inlet 5 at one end of the ', . .
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passage (also reEerred to as a Eirst inlet) adapted to be connected to a source of pressurized worklng fluid or solvent (e~g., to a li~uid line or a pump) to the other end of the passaqe, constitutinq a dis-charge end, and a second inlet 7 adapted to be connected to a supply of pressure transportable or Eluidizable material (also reEerred to herein as a solute or fluent material). The passage is generally of uniform circular cross-section throu~hout its length.
The eductor-mixer system is an improvement over -the eductor-mixer system shown in said U.S. patent 3,777,775 to Avrom R. Handleman, issued December 11, 1973. As ~ -mentioned above/ the solvent inlet ma~ be connected to the discharye side of a li~uid pump (see Fig. 5) or other source oE pressurized workiny fluid. Inlet 7 ma~ be con-nected via an appropriate hose to the discharge opening of a fluidized container, such as is shown in the above-mentioned U.S. patents 3,777,775 and 4,007,694. These Eluidized containers are commerciallv available from Semi-Bulk S~stemsl Inc. o:E St. Louis, Missouri under their re~istered trademark AIR PALLET. These AIR P~LLET
containers are used in transporting and storing "semi~
bulk" ~uantities (e.g., more than a kagful and less than a truck or railroad car full) oE powdered, fine granular, particulate, or other fluent or Eluidizable mater1al, such as powdered Eire retardant materials, paint pigments, cement, oil well drilling muds, diatomaceous earth, talc, lime, etc. It is often necessary to mix the powdered solute with a solvent upon unloading of the solute to form a dlspersion, slurry or solution. While the eductor-mixer system of this invention described and claimed hereinafter will be referred to primarily in con~unction with the above-mentioned AIR PALLET fluidized containers for mixing powdered solutes with liquid solvents, it will be understood that the eductor mi~er system of this invention need not be used in conjunction with an AIR
PALL~T container and it may be used to mix all types of solutes and solvents. It will be particularly under-s-tood that the eductor-mixer system of this invention may be used to mix both li~uid and gaseous solvents and solukes.
~ eferring now to FicJs. 1 and 2, the body or housing 3 of the eductor-mixer system of -this invention is preferably cast or fabricated of a suitable metal, such as stainless steel, and has the passage of plenum chamber 9 formed therewithin in communication with solvent inlet 5. A sleeve 11 extends from the housing coaxial with the discharge end of the passage. It will be understood, however, that sleeve 11 could extend internally into housing 3. While housing 3 is shown to be generally in the shape of a 90 pipe elbow, it will be understood that the housing may assume other shapes and still be in the scope of the invention.
Solute inlet 7 is shown to comprise a cylindrical tube 13 of somewhat smaller diameter than -the bore of sleeve ll. Tube 13 is insertable into the sleeve so as to . .
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extend through plenum chamber or passage 9 with the pressurized working fluid or solvent filling the plenum chamber or passage and surrounding the solute inlet tube. A receiving me~ber or passage means, genera].ly indicated at 15, is removahly secured to housing 3. The interior of this receiving member or passage means constitutes a mixing chamber 17 in which the solute is dispersed in the solvent and in which the solute and solvent are mixed. A nozzle member 19 is disposed within housing 3 at the dis-charge end of the passage or chamber ~ between chamber 9 and mixing chamber 17. This nozæle member is shown to be a flat ri.ny having a cen-tral or nozzle opening ; 21 therein which receives the inner or discharge end of solute tube 13. The nozzla opening 21 is somewhat larger than the outer diameter of the discharge end : of the solute tube and the latter is substantially centered within the opening 21 thereby to define an annular nozzle opening or orifice N through which working fluid under pressure in plenum chamher or passaye 9 is discharged at high velocity into the receiving member 15. The solvent is discharged as a concentric, converging hollow jet J and it generates ; a vacuum within the mixing chamber. The vacuum is in communication with the- discharge encl of solute tube 13 and thus positively draws or sucks the solute into mixing chamber 17.

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~ 12 As best shown in Fig. 3, solute tube 13 is of substantially smaller diameter than passage 9 and is exteriorly tapered at its discharge end, thereby having an exterior conical surface ?3 at its discharge end with the taper angle ~ of this surface relative -to the longitudinal center line of the tube ranging between about 1 and 30 and preferably ranging between about 5 and 15. Nozzle member 19 has an inner conical nozzle surface 25 which defines its central opening 21.
The diameter of opening 21 and the length of nozzle surface 25 in the direction of flow through the nozzle de~encl on the desired Elow conditions through the nozzle.
It will be ap~reciated that the flow rate through the nozzle is similarly a function of the pressllre within plenum chamber or passage 9 and mixing chamber 17 and the flow area of nozzle N. The latter is the cross-sectional area of the gap G between conical surface 23 of the solute tube and the conical nozzle surface 25.
The vacuum generated by the jet discharged from the nozzle into the mixing chamber is dependent in part upon the veloci-ty of the jet.
The eductor-mixer 1 of this invention is particularly well suited to efficiently accelerate the working fluid from plenum chamber or passage 9 into the mixing chamber 17 in at least two important ways. First, the cross-sectional area of the plenum chamber or passage is quite larye in relation to the cross~sectional area of nozzle N. This allows working fluid to flow through the passage at a speed much slower than it flows through the nozzle so that there is little or no energy lost by the flow of the working fluid through the passage. The length L of the nozæle in the direction of the flow therethrough is relatively quite short. This permits the solvent to be almost instantaneously accelerated to its discharge veloci-ty in a short distance thus minimizing the flow losses while flowing through and discharging from the noææle at high lineal ~elocity. At one extreme, nozæle surEace 25 may be a sharp kniEe edge having an extremely short eEfective length L (e.g., a few thousandths of an inch) in the direction of flow throuyh the nozzle. In other instances, the noæzle surface ma~ preferably have longer length L for purposes that will appear. It will be understood that as the nozæle length L increases, shear (and related energy loss) in the nozæle is increased. Shear, of course, is greater with narrower nozæle gaps. Under most operating conditions, it has been found that the diameter Dl of the outlet end of the solute tube 13 should approach the diameter of the solute feed conduit 37 as will be hereinafter discussed~
For example, in eductors through which pass about 500 gallons per minute of solvent (e.g., water) diameter ~1 is about 2.~ inches (6.1 cm.) and the diameter oE

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the solute Eeed conduit is ahout 2.5 inches (6.0 cm.).
Gap G is sized to permit desired or available working fluid flow rates at pressure drops across the gap (e.g., 30~200 psig) to sufflclently accelerate the worklng fluid to produce a deslred working vacuum.
It has also been found that the ratio of the nozzle Length ~ to the gap thickness G (i.e., ~/G) preferably should range between about 0.001 Eor a knife edge surface 23 and up to about 10 for a conical nozzle surface 25 which ls generally parallel to the exterior conical surface 23 on tube 13. It will be understood that while surfaces 23 and 25 are shown to be parallel and while in some instances this may be preEerred so as to insure that solven-t jet J is well defined and is directed into the mixing chamber in a converglng cone generally parallel to tapered surface 23, it ls not essential to this invention that these surfaces be parallel.
As shown in Figs. 2 and 3, receivin~ member 15 comprises a constant-diameter discharge conduit 26 with a transitlon section 27 positioned between nozzle member 19 and conduit 26. The diameter D3 of the inner end or bore of the transition section is ap-preciably larger than the diameter D2 of nozzle opening 21.
The third way in which the educ-tor-mlxer system of this invention minimizes energy losses is that the internal surface of transition section 27 .,

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between nozzle N and the conduit 26 lies outward of and is wholly clear of the projected pa-th oE the con- -verging jet J ~as indica-ted by the dotted lines in Fig. 3) as the jet is discharged Erom the nozzle and as the jet converges on itself in the mixing chamber.
This insures that frictional wall losses along the mixing chamber walls are minimized as it flows at high speeds into the mixing chamher. Further, the diameter of the transition section at any point therealong is larger than the diameter of the projected path of the converging jet so as -to insure that the walls of the transition section are clear of the je-t. In accordance with this invention, the cross-sectional area o~ dis-charge conduit 26 downstream from mixing chamher 17 is about 3 to 7 times the cross-sectional area of nozzle gap G.
It wlll be understood that in operation jet J of working fluid converges on the stream of fluidiz-able material discharged from inlet tube 13 into mixing [?48~1L
chamber 17 thereby initiating mixing of the working fluid and the material. The working Eluid and the material move at high velocity through the mixing chamber (i~e., through the interior of transition S section 27 and conduit 26) thus maintaining a rela-tivel~ high vacuum. As the working fluid and mate-rial enter conduit 26, mixing is even further enhanced and mixing continues substantially along the length of the conduit.
As an example of the efficiency of the eductor-mixer 1 of the present invention in transfer-ring momentum oE the working Eluid jet to the disper-sion within the mixing chamber, an eductor-mixer in accordance with this invention so sized as to have a pressure drop o~ 40 psi across the nozzle generates a partial vacuum within mixing chamber 17 and within solute tube 13 which has been measured to exceed 28 inches ~710 millibars) of mercury when solute tube 13 is closed, and more than 2a inches (610 millibars) of ~nercur~ when solute is flowing. This high vacuum positively sucks airborne (fluidized) powdered solute out of one of the above-described fluidized containers at high flow rates. For example, an eductor-mixer system o~ this invention sized to have 500 gallons (1892 1.) per minute of water pumped therethrough at 30 psig will draw about lOOO lbs. (450 kg.) of a pow-dered solute, such as barlte, through an eductor-mi~er ' : , , ~, .

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system in about 1 minute. The vacuum genexated b~
the eductor-mixer system 1 of this invention is even more efficient than the prlor art edu~or-mixer system shown in the above U.S. patent 3,777,775 in positively drawing the solute into the eductor-mixer system. Thus, the eductor-mixer system oE this invention is able ~o.be vertically displaced from the level of the powdered solute in the solute fluidized container a greater dis~
tance than had been heretofore possible there~y making the relative location o~ the eductor-mixer system and the solute supply even less critical.
It will be understood that the surfaces 23 and 25 on the solute tube and nozzle member, respec-tively, may be hardened (e.g., carburized or nitrided) lS to provide a hard wear-resistant surface for resisting flow wear abrasion by the solvent and solute flowing therethrough at high speeds. It will also be understood that, alternatively, these surfaces may be hardened by making them of a special materi.al which resists flow wear abrasion.
As heretofore described, solute tube 13 extends into housing 3 through sleeve 11 with the sleeve having an inside diameter slightly greatex than the outside di-ameter of the solute tube. The latter has one or more circumferential grooves 28 for receiving an Q~ring seal 29 which in turr seals the solute tube relative to the .:

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bore o:E the sleeve when -the former is axially inser-ted in-to the lat-ter. ~his seal permi-ts the solu-te t~e -to be moved axially in and out o:E the sleeve while remain-ing sealed relative -thereto. As is best shown in Fig. 2, the sleeve ll is subs-tantially coaxia] with nozzle open-ing 21 in nozzle memher l9 and with mixing tube 15.
Preferably, solute tube 13 is inserted into housing 3 via sleeve 11 and through plenum 9 so that the discharge end of the tube is general]y coplanar with the downs-tream end of nozzle surEace 25 and is coaxial with nozzle open-ing 21 so that the nozzle gap G is of uniform thickness all around -the tube and so -tha-t the solvent in the plenum surrounds the solute t~be. ~ plurality te.g., three) of threaded fasteners 31 is threadably carried by sleeve 11 for engagement with the outer surface of solute tube 13.
With all of the fasteners 31 engaging the outer surface of tube 13, the tube is firmly secured in place relative to the sleeve at any desired axial position within the sleeve. By adjusting the various fasteners 31 in and out, the end of the tube may be readily adjusted relative to nozzle surface 25 and secured in position when the tube is properly centered within the nozzle openiny with gap G being oE substantially uniform thickness around the outlet end of the solute tube. It will also be noted that in the event the tapered surface 23 of the solute tube becomes worn so as to affect the flow geometry through the eductor-mixer, fasteners 31 may be loosened and solute tube 13 may he readily removed thereby to enable resurfacing of tapered surface 23 on ~.

the tube, or the solute tube may be moved arther into the housing thereby to accommodate the wear of the sol-ute tube and/or the wear of nozzle surface 25. With fasteners 31 located in sleeve 11 clear of the nozzle member 19 and plenum 9, solven-t flows through the plenum and the nozzle openiny wi-thout encoun-tering any resis-tance from the fasteners. It will also be no-ted that in its preferred embodiment, the nozzle opening or orifice through the eductor-mlxer of the present invention is a continuous annular yap around the solute tube with no supports, ~low dividers or other restructions in the nozzle which would block or otherwise impede the flow of fluid therethrough. In this manner, the concentric solvent jet is a continuous annular jet as it is dis-charged from the nozzle. It will be understood, however, that flow dividers could be placed between the outer surface of the solute tube and the inner sur-face of the nozzle for supporting ox centering the outer end of the solute tube in the noæzle openin~. If this is done, the solvent jet discharged from the nozzle wilL
not necessarily be a continuous annular jet, but rather would be a series of separate jets converyiny within the mi~iny chamber. These separate converying jets are considered to be within the scope of the present invention.
~ orking fluid inlet 5 is shown to have a coup-ler connection 33 thereon which enables a water hose or the like to be readily connected to the eductor. Sol-ute inlet tube 13 has a tee 35 threaded thereon and the latter is adapted to have a hose 37 from the solute ..

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supply, such as from the discharge outlet of a flu-idized container, readily connected thereto~ Tee 35 has a so-called vacuum break valve 39 connected there-to.
This vacuum break valve when closed blocks communication S between the vacuum generated within mixing chamber 17 and within solute tube 13 and the atmosphere and when in its open positions opens communication between the vacuum and the atmosphere. When the vacuum break valve is open ~it need not be fully open), air will flow into the mixing chamber through the vacuum break valve and the solute tube thereby to break or reduce the ~acuum withln the eductor which sucks the solute into the eductor-mixer from the solute supply and to thus decrease or terminate solute from being drawn into the eductor.
lS Thus, by adjusting the vacuum break valve, the amount of solute drawn into the eductor-mixer via the solute tube may be readily controlled. A bleed valve (not shown) may be located else~here ln solute feed line 37 for con-trolling solute feed (i.e., adjacent the solute supply), but a break valve should be located at the hi~h point of solute feed ~or convenient starting and stopping of solute feed.
As heretofore mentioned, no~zle member l9 is a ring-like member and~ as best shown in Fig. 3, has a ~-shoulder 41 in its front face toward chamber 9 and an outwardly projectlng flange 43. Shoulder 41 has a diam-eter substantially the same as the circular innex bore o housing 3 and thus the step is readily recelved within the open end o~ the housing so as to center the nozzle opening relative to the longitudinal center line of sleeve 11 and solute tube 13 inserted therein. Housing 3 and receiving tube 15 each have respective flanges 45 and 47 adapted to be sealingly secured together in face-to-face xelation. With the receiving tube flange 47 in sealing enga~ement with nozzle flange 43, ring 19 is held captive in a desired position relative to the hous-ing and the receiving membern A circumerential groove 49 is provided on the outer face of flange 47 for receiving an O-ring 51 which seals the receiving member to the hous-ing. ~langes 45 and 47 each have sloped outer faces and are adapted to be drawn together by a sealing hoop clamp 53, such as is commercially available from the Ae~oquip Company of Los Angeles, California. Upon tightening clamp 53 on flanges 45 and 47, these flanges are drawn into face to-face sealing engagement with the O-ring 51.
It will be understood, however, that means other than clamp 53 may be used for releasably and sealably securing the mixing tube 15 to housing 3~ It will thus be appre-clated that eductor 1 of this invention may readily be converted from one flow rate capacity to another mexely ~y exchanging one nozzle ring 19 for another having dif-erent nozzle opening dimensions and exchanging receiving member 15 to main~ain a desired ratio between nozzle area and mixing chamber cross sectional area. -In accordance ~ith this invention, the length L' of the cond~it 26 is preferably about~5 to 50 times longer than its diameter D4, and even more pre~erably, is about - :

15 to 25 times lon~er than its diameter so as to e~hance the mixing (i.e , dispersion~ of he solute and the work-ing fluid within the conduit. Expressed in another manner, the ratio L'/D4 prefer~bly should range between about 5 and 50 and even more preferably between about 15 and 30.
It will be understood, however, that this ratio could be variea considerably and even be outside the above-stated prelerred ranges and still be within the scope o thls invention. This ratio depends upon many factors, such as the physical characteristics of the solute and solvent being mixed, the flow rates and pressures, and temperatures o~ the solute and solvent, and many other actors. Thus, this xatio could vary considexably and satisfactory mixing of the solute and solvent could still be attained within t~
eductor-mixer system of this invention. The above-stated - preferrea ranges indicate ranges which for many materials have been readily and satisEactorily mixed by the apparatus of this invention.
In mixing powdered solutes with a liquid working ; 20 1uid in an eductor-mixer system/ it has been heretofore dif~lcult to control the flow of airborne or ~luidized po~dersolute to the eductor-mixer. In many prior applica-tions, the flow of powdered solute was regulate~ by valves in the powder supply line. As heretofore mentioned, the vacu~m break valve 39 ~or a controllahly throttled side stream from the at sphere) serves to regulate the flot~
of powder to the eductor-mixer by controllably red~cing or limit1ng the vacuum generated within the housing.

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~urthe.r in accordance with this invention, rneans, as generally indicated at 57 (see F.i~. 4~, is provided for bypassing a portion of the ~orking fluid supplied under pressure to the educ~or-mixer via inlet 5 around nozzle N thereby to decrease the vacuum generated with-in the eductor-mixer housing. This bypass means is shown to comprise a line 59 interconnected between the inlet 5 of housing 3 and receiving tube 15 downstream from noæzle N. A throttle valve 61 is provided in by-pass line ~9 to control the flow of pressurized working ~ -fluid there~hrough. Bypass line 59 is connected to mix-ing tube 15 in such manner that the pressuri.zed working fluid discharged therefrom into the receiving tube does not act as a second nozzle jet creating a second stage !.
lS for the eductor and thus genexating additional vacuum, but rather enters the receiving tube in such direction, preferably at an angle of about 45 with respect to the centerline of discharge conduit 26 so as not to generate any appreciable vacuum within conduit 26 thereby to de-crease the overall ~acuum pumping of the solute at theups-tream portion of mixin~ chamber 17 upstream from the outlet of bypass tube 59 into discharge conduit 2G. As shown in Fig. 7, a manifold M surrounds discharge conduit 26. This manifold is in communication with l.ine 59 and distributes the solvent to openings 60 in condui-t.26 for generally ~5 for~ard discharge into the condu.~t. By i.ncreasing the flow through bypass line 59 around the nozzle, the overall vacuum generated within the eductor-:

mixer is decreased by reducing work;ng fluid fl.owthrough the nozzle, and -the amount of solute drawn into the eductor-mixer svstem is there~y decreased.
Further, in accordance with this invention, educ-tor-mixer l, as heretofore described, func-tions well '~ to repeatedly shear -the dispersion mixed therehy and to add additional solute ~o as to increase the concentration . level o the solute in the dispersion over t~at which can '' be attained by a single pass -through the educt~r-mixer system. As shown in Fig. 5, an eductor-mixer s~stem 1 of this invent.ion is shown in a recycling mixing systeml as is generally indicated at 63. Receiving tube 15 discharges into a reservoir 65 for holding the dispersion mixed by the eductor. The inlet of a pump 67 is connected to reservoir 65 by a line 6g and the outlet or discharge side of the . pump is connected to inlet 5 of eductor-mixer system 1 by a line 71. A suppl~ of solvent 73 is also connected to the inlet side of the pump, and a valve 75 is provided bet~een inlet 5 and the source of working Eluid to control the amount of solvent dra~n from the solvent supplv and `' supplied to the pump inlet and to inlet 5. Thus, pump 67 withdraws a portion oE the disperslon from reservoir 65 and pu~ps it along with any desired amount of addi.tional working fluid unde.r pressure into plenum 9 of the eductor-mixer. The dispersion is-then discharged through nozzle .~l into mixing chamber 17. Reservoir 65 has an outlet 78 through which the mixed slurry solution may be discharged via a valve 7g. It is therefore seen that the recycling ..
~`~. ' mixing system 63 of this invention constltutes means for withdrawing the dispersion discharged from receiv-ing memher 15, for returning the clispersion to plenum 9 under pressure, and for discharging the dispersion through nozzle N.
As heretofore mentioned, the fluid (i.e., working fluid and/or the recycled dispersion) is subject to shear as it flows through nozzle ~. This fluid shear-ing action breaks up agglomerates and reduces the size of all dispersed solute particles flowing through the nozzle in a highly expeditious and efficient manner.
As heretofore mentioned, the shear losses in thi~s nozzle are minimized when nozzle surface 25 is a knife edged opening. If, however, it is desired that the fluid being circulated through the nozzle be subjected to shearing, the length of nozzle surface 25 in the direction of flow through the nozæle preferably should be made longer or the thickness of nozzle gap G should be made narrower. Thus, it is preferred that the ratio of the nozzle len~th L to the gap thickness G (i.e., L/G) be less than about 20 and preferably range between about 0.001 (for a knife edge nozzle surface) to about 10. Of course, by repeatedly recirculating slurry from the reservoir through the eductor-mixer nozzle, the slurry can be re~eatedl~y sheared until the desired state is attained.
As heretofore mentioned, the eductor-mixer system 1 of this invention incorporated in recirculation or recy-cling system 63, in addition to functioning as an efficient . .

one or multi-pass mi~er, may be utilized to mix disper-sions, slurries, or solutions having higher solute con-centration levels than can normally be attained by one pass of the solvent and solute through the eductor-mixer system. The solvent is pumped under pressure through t~e eductor to positively draw the solu~e into the eductor-mixer via solute tube 13. The resulting mixture of sol-vent and solute, which is lower than desired concentration level, is discharged into holding reservoir 6S. This low concentration mixture is withdrawn from reservoir 65 and is then pumped through the eductor-mixer so as to posi-tively draw additional solute into the eductor-mixer system and to mix the solute with the mixture discharged from nozzle N into mixing chamber 15 to increase the solute concentration. The mixture from the reservoir may be repeatedly circulated through ~he eductor-mixer system so as to have additional solute mixed therewith until a desired concentration level is attained from the reservoir via line 78 and valve 79. Additional solvent from solvent suppl~ 73 may be added to the mixture to maintain the de-sired concentration level and to maintain a desired quan-tity in the reservoir. O~ course, the slurry may be con-~ tinuously circulated through the eductor-mixer to repeatedly ; shear the slurry until it attains a desired state.
2S It will be understood, however, that in accordance with this invention, the mixing system may also be operated as a continuous ~ixing system. As shown in Fig. 6 recycling m xing system 63 may be provi~ed wi~h a valve 81, such as a float control valve or the like, responsive to the with-drawal of dispersion from reservoir 65 which pennits p~p 67 to draw additional solvent from the solvent supply and to pump it along with previously mixed dispersion through the eductor-mixer system 1 thereby to automatically dra additional solute into the eductor-r~xer via solute tube 13. Product is withdrawn from reservoir 65 via a with-drawal valve 79, which may open and close in response to a signal from a concentration ~easuring device 80 (such as a density sensor~ so as to deliver finished product at or above a desired concentration~ All other hydraulic or other feedback controls (e.g., float valve 81) xespond to this rate o withdrawal. Valve 81 is shown between the supply of working fluid or solvent and the inlet to pump 67 and is operable in response to a predetermined range of levels o the dispersion in the reservoir 50 as to supply additional working 1uid to the pump inlet and to maintain the dispersion on the reservoir within its predetermined range of levels.
It will be appreciated that the system i:Llus~
trated in Fig. 6 may be made ~ully automated by install-; ing well-known instr~entation and controls in reservoir 65 and line 78 to monitor the quality (i.e., the density concentration level, or state of mixin~ or subdivision) of the product and to control operation of product with-drawal valve 79 in response to the quality o~ the product in reservoir 65. Product will be withdrawn so lon~ as the product meets the desired specificatiQns. Withdra~al . .

8~

of product from reservoir 65 causes the level of the product to drop thereby actuating float control valve 81 so as to supply additional working fluid to eductor 1. The additional working fluid will decrease the con-centration level of solute in the dispersion~ If theconcentration level or other reused properties of the produc~, as sensed by sensor 80, fall below preestab-lished levels, valve 79 will be automatically closed or proportionately throttled to maintain the properties of the dispersion at the desired levels.
In Figs. 4-6, eductor-mixer 1 is shown with its receiving member 15 horizontal, but it is to be understood that in operation the outlet end of the mixing tube may be pre~erably pointed at a downward angle of 15-~0 so as to prevent solvent from entering the solute tube when the eductor-mixer is not in operation.
~ s the dispersion is recirculated through nozzle N, fluid shear subdivides the solute particles, agglomerates or masses. Upon the working fluid along with any dispersion in plenum 9 being ejected from the nozzle at high velocity, the wor~ing fluid (including any recycled dispersion) cavi-tates in the vacuum within mi~ing chamber 17 to form a multiplicity of droplets thus ~astly increasing the surface for contact with solid liquid or gaseous solute. These droplets are wldely dispersed in the mixing chamber and violently collide with solute drawn into the mixing chamber and with other droplets so as to enhance mixing. It is to be understood that in aGcordance with this lnvention :
, the shear and impact dispersion may be substantially inde~endently varied so as to more readily attain a.
desired state o:E -the resulting slurry. More specif-ically by holding the flow area of nozæle ~ constant, but by varying the thic]~ness of the nozzle gap G with appropriate adjustments in pl.enum pressure, shear may be controlled. Impact dispersion, on the other hand, may be varied by varylng the 10w velocity through the nozzle as by varying the pressure within plenu~ 9 with appropriate reduction o:E gap thickness to deemphasize them.
Since the liquid jet J flowlng throu~h noz-zle N cavitates upon entering mixing chamber 17 thus producing a multiplicity oE liquid dxoplets having a large surace area when comparecl to the volume of the liquid, a stream of gaseous solute, such as air or oxygen supplied via solute tube 13, may be readily drawn into the mixing cham~er whereby the gaseous solute is brought into intimate contact with the 1iquid parti-cles -for being readily dissolved therein to ~orm a liquid solution approaching saturation. In this manner, appa-ratus 1 of this invention may be used to carry out a ~as dissolving process, such as oxygenation or aeration ~rocesses, in a highly efficient manner. By recirculating the liquid solution through the eductor-mixer and by adding more gaseous solute on each pass relatively high concen~
trations o a gaseous solute in the manner heretoore described may be readily dissolved in a liquid solvent.

"~ ",.~

~ ~LU~

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
~s various changes could be made in the above 5 constructions without depar-ting from the scope of the invention, it is intended that all matter contained in the abovè description or shown in the accompanying draw-ings shall be interpreted as illustrative and not in a ~imitinS s_nse.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An eductor-mixer system comprising:

an eductor body having a curved passage extending there-through for flow of a pressurized working fluid from one end of the passage, constituting an inlet end, to the other end of the passage, constituting a discharge end, said passage being generally of uniform circular cross-section throughout its length;

said body having an opening therein opposite said dis-charge end of the passage, said opening being coaxial with said discharge end and of substantially smaller diameter than the diameter of said passage;

a nozzle member comprising a ring separate from the body having inside and outside faces and a central opening therethrough from its inside to its outside face, said ring being removably mounted in place at the discharge end of said passage coaxial with said discharge end, said central opening in the ring being of substantially smaller diameter than the diameter of said passage;

a cylindrical tube of substantially smaller diameter than the diameter of said passage extending from outside said body through said opening in the body opposite the discharge end of the passage and extending forward in said passage from the inner end of said opening in the body into the central opening in the ring, said tube being open at its end in said central opening in the ring, said open end of the tube constituting a discharge end;

(Continuation of claim 1) said tube being axially adjustable in and removable from said opening;

said tube being adapted for connection of its end out-side the body to a source of fluent material to be educted and mixed with said working fluid for flow of said material through said tube and out of the dis-charge end of the tube;

the discharge end of the tube being substantially flush with the outside face of said ring;

the tube being exteriorly tapered at its said discharge end and thereby having an exterior conical surface convergent in the direction toward its said discharge end with the angle of taper with respect to the axis of the tube less than about 30°;

the inner periphery of the ring bounding the central opening in the ring being formed as a conical nozzle surface extending from the inside face to the outside face of the ring and convergent in downstream direction from the inside to the outside face of the ring;

said conical nozzle surface of the ring surrounding and being spaced from said exterior conical surface of the tube a distance which is small relative to the diameter of the outer end of said conical nozzle surface, thereby providing an annular conical orifice between the exterior (Continuation of claim 1) conical surface of the tube and said conical surface of the ring for delivery of the pressurized working fluid from said passage through said orifice in the form of a hollow conical jet converging in downstream direction from the outside face of the ring;

the gap between the exterior conical surface of the tube and the conical nozzle surface of the ring being rela-tively small and the length of said orifice being relatively short for rapid acceleration of working fluid flowing through the orifice to a relatively high lineal velocity with low flow losses;

and means separate from the ring providing a passage downstream from said ring at the discharge end of the passage in said body in which the material issuing from the discharge end of the tube and the working fluid conically jetted through said orifice may mix;

said passage means being removably secured to said body at the discharge end of the passage in the body extending outwardly from said ring and having an internal diameter at its end at the outside face of said ring larger than the diameter of said conical nozzle surface of the ring at the outside face of the ring and the internal surface of said passage means lying outward of and wholly clear of the projection of said conical jet throughout the length of the jet.

2. An eductor-mixer system as set forth in claim 1 wherein said ring has a flange engaging the end of said body at the discharge end of said passage, and said passage means comprises a discharge conduit and a transition section between the ring and said conduit, said transition section engaging said ring and holding it in place in the discharge end of said passage, and where-in means is provided removably securing said transition section to said body, said transition section having a tapered bore convergent in downstream direction away from the ring, the diameter of the bore at the outside face of the ring being larger than the diameter of said conical nozzle surface of the ring at the outside face of the ring.

3. An eductor-mixer system as set forth in claim 1 further comprising a valve in communication with said tube and with a source of gas, such as the atmosphere, said valve being operable between a closed position in which it blocks communication between said tube and said gas source and an open position in which it opens communication therebetween.

4. An eductor-mixer system as set forth in claim 1 wherein said eductor body is in the form of an elbow and has an integral elongate sleeve extending out from the bend of the elbow coaxial with the dis-charge end of the passage in the body, the sleeve defining said opening for the tube, the tube extending axially through the sleeve, and wherein there is provided means (Continuation of claim 4) releasably securing said tube in the sleeve and adjustable for centering the tube in the sleeve, said securing means being releasable for axial adjustment of the tube, and a seal between the tube and the sleeve.

5. An eductor-mixer system as set forth in claim 4 wherein:

said ring has a peripheral flange engaging the end of the elbow at the discharge end of the passage;

said passage means comprises a discharge conduit and a transition section between the ring and said conduit, said transition section engaging said ring and holding it in place in the discharge end of said passage;

means is provided removably securing said transition section to the elbow; and said transition section has a tapered bore convergent in downstream direction away from the ring, the diameter of the bore at the outside face of the ring being larger than the diameter of said conical nozzle surface of the ring at the outer face of the ring.

6. An eductor-mixer system as set forth in claim 5 further comprising a valve in communication with said tube and with a source of gas, such as the atmosphere, said valve being operable between a closed position in which it blocks communication between said tube and said gas source and an open position in which it opens communi-cation therebetween.