US2931501A - Hydraulic flotation system - Google Patents

Description

April 1960 A. w. WAHLROOS ETAL 2,931,501

HYDRAULIC FLOTATION SYSTEM 2 Sheets-Sheet 1 l lll m f":

April 5, 1960 A. w. WAHLROOS ETAL 2,931,501

HYDRAULIC FLOTATION SYSTEM Filed Oct. 1. 1953 2 Sheds-Sheet 2 INVENTORJ ARI/l 14/. MHLRoos RUJSELL .[JTENBERG BY JhcK WMJ/eA/v United States. atent e HYDRAULIC sLorArioN SYSTEM Arvi W. Wahlroos, Minneapolis, Russell J. Stenberg, St. Paul, and Jack W. Sigan, Minueapoiis, Minn, assignors to Archer-Daniels-Midland Company, Minneapolis, Minn, a corporation of Delaware Application October 1, 195a, stair No. 383,650 15 Claims. or. 209- 160) This invention relates to an improved hydraulic system of separating particles of materials of different specific gravities by flotation and to a new and improved apparatus for carrying out that separation.

flotation system of cleaning grain by separating the lighter contaminating materials'from the grain and to an improved grain cleaning apparatus.

Depending upon a variety of circumstances, such as its source, method of harvesting, care in shipment, previous treatments and the like, grain may be contaminated by material which is lighter than the grain, such as chaff, bits'of husks and straw, weed seeds, insect fragments, rodent pellets and likelight weight foreign materials, or by material which is heavier than the grain, such as sand, pebbles, bits of rock, glass, cinders, metal and the like, or by both light and heavy foreign bodies. For convenience, hereinafter these'lighter contaminating materials will be referred to collectively as chaff and the heavier contaminants will be referred to as stones, al-

though it is to be understood that other materials are More particularly, the invention relates to an improved hydraulic included. Methods are known and apparatus is available for effecting separation of the very lightest and the very heaviest of these contaminating substances. These known means, however, do not'serve effectively to remove the contaminants which in their densities more.

nearly approach the specific gravity of the grain.

The term lighter as used in this specification and in the appended claims is meant to refer not only to the lesser weight or weight per unit volume of a contaminating body or particle as compared with the weight or weight per unit volume of the wanted material but also to the lesser velocity it would possess in free fall through a fluid. to include not only the greater weight or weight per unit volume of a contaminating body or particle as compared with that of the wanted material but also the greater velocity of that body or particle freely falling through a fluid. The terms thus encompass substances having approximately the same density as the grain. or

other wanted material but which have a shape which causes their hydraulic behavior to be different. practical matter, the substanceswhich are most difficultly removable from grain are those which, though a little lighter than the grain itself, have very nearly the same density and shapes, such as rodent pellets. It is to the separation and removal of such very slightly lighter foreign bodies that this invention is primarily directed.

While this invention will be described with particular reference to grain, and specifically to wheat, it is to be understood that the applications of the principals of this invention are by no means so limited. In addition As a.

Similarly, the term heavier is meant.

vention are likewise applicable to other grains such as barley, soybeans, rye, sorghums, oats, flax, peas, beans, peanuts and the like. I

The principal object of this invention is to provide an improved hydraulic flotation system of rapidly separating materials showing different hydraulic behaviors.

Another object of this invention is to provide an improved hydraulic flotation system of removing lighter contaminating materials from. other wanted material.

It is another object .of this invention to provide an improved hydraulic flotation system of cleaning grain by separating the lighter foreign substances, such as rodent pellets which are especiallydiflicult to remove.

Still another object of this inventionis to provide an improved hydraulic flotation system of cleaning wheat by separating the chaff, rodent pellets, insect fragments and the like therefrom, without causing an excessive gain in moisture content of the grain.

A further object of this invention is to provide novel and improved flotation apparatus for separating materials showing different hydraulic behaviors.

It is a further object of this invention to provide for hydraulically removing lighter contaminating material from other Wanted material by flotation.

A still further object of this invention is to provide an improved grain cleaning apparatus for hydraulically separating the lighter foreign substances, rapidly from the grain so as to prevent excessive moisture gain in the grain. v i I Another further object of this invention is to provide improved hydraulic separating apparatus comprising a vertical column having adjustable cone-shape means therein for varying the upward velocities of hydraulic liquids in said column.

Other objects of this invention will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various 'ways inwhich the principles of the invention may be employed.

This invention is further illustrated by reference to the drawings in which corresponding numerals refer to the same parts and in which:

Figure 1 is a vertical sectional elevational view of the hydraulic flotation separator and cleaner which form part of this invention; and

Figure Zis a diagrammatic and schematic representation of a cleaning or separating system of which the flotation unit of this invention may form a part.

Broadly stated, this invention comprises a hydraulic flotation system of separating particulate material having different hydraulic behaviorcharacteristics by first forming a slurry of the particulate material in the hydraulic to grains, the invention is also applicable to the hyliquid, introducing this slurry upwardly into a liquid column, the upper portion of which is upwardly moving and at least part of the lower portion of which is downwardly moving, adjusting the upward velocity of the upwardly moving portion of the liquid column until the desired critical separation of particulate materials is effected, the lighter chaff-like material floating out through an opening at the top of the liquid column and the heavier wanted material flowing downwardly against the upwardly moving liquid current and out through an opening at the bottom Patented Apr. 5, 1950 of-the column, and finally separating the liquid from the solid material. The system which comprises this invention embraces both a method of hydraulic separation and apparatus for carrying out that method. Depending upon the nature of the materials being separated or cleaned and the degree or nature of theforeign bodies, the system of this invention maybe used either alone, or in series, or in combination with other separating or cleaning means of a difierent nature. Thus, in Figure 2 of the drawings the system of this invention is shown in use in combination with an auxiliary and complementary hydraulic separating and cleaning unit of a different type which per se is the subjcct'rnatter of a copcnding' application Serial No. 383,533 of Arvi W. Wahlroos and Edwin T. Clocker filed of even "date herewith. Instead of an. auxiliary hydraulic separating unita dry mechanical separator could obviously also be used.

Referring now to the drawings and particularly 'to Figure 1 there is here illustrated the hydraulic separating or cleaning flotation apparatuswhich forms part stant invention.

.In the form here illustrated the apparatus comprises an elongated upright generally cylindrical standpipe it of the inmade up of' a plurality of flanged sections stacked one upon the other and held by bolts or clamping rings and means for carrying the discharged slurry of cleaned par ticulate material to dewatering and drying'means. The upper end of the outlet conduit 14 extends for some distance up into the standpipe TA and terminates in an inverted conical collar section in tapering outwardly to the Walls of the standpipe. This conical collaris provided with a plurality of radial longitudinal slits 17 around 1ts periphery. The lower end and bottom of; the standp'ipc, the upper end of outlet conduit and the conical slotted collar define an annular chamber 13 through which additional liquid is introduced through an opening 19 for movement upwardly through the slits for imparting some upward movement to theliquid column in the standpipcl A supply line 23 intersects the wall of the outlet conduit 14 and bends in an elbow 2i upwardly'as a supply inlet.

22 disposed concentrically within the outlet conduit and The lower end 15 of the outlet" extending above the top of the conical collar member.

Disposed concentrically within the standpipe It} and around the top of supply inlet 22' and held by brackets (not shown) is a cylindrical supply inlet extension 24 open at both ends and extending upwardly into the standpipe. The top 25 of the standpipe is intersected by an outlet pipe 26 closed at the top 27 but having a discharge pipe 23 in one side for carrying away the lighter particu 'late material separated Within the standpipe. 1h. Posi tioned within the upper portion of standpipe it} is a generally conical velocity regulating means 129*,the walls of which converge generally upwardly and terminate in an outlet 35 which extends through the top 25 of the standpipe and into outlet pipe 26. The conical velocity adusting mcmberis fr'eelyslidable within the standpipc and is provided with a float 31 slidably mounted on a rod 32 suspended from they-bottom of the center of the conical member by means of brackets. 34 and 35. Tue conical velocity-regulating member is adjustable up and down by means of a rod 36 welded to the outlet of the conical member and passing up through an opening in the top 27 of the outlet pipe 26 where it is held in position in tube 37 by a thumb screw 38.

As shown in Figure 2; the grain or other material to be cleaned or separated is fed by means of anyconventional conveying means into a feed box 40 from which it flows at a controlled rate'either through a spout 4. 41 into a preliminary hydraulic separator unit indicated generally at 4% or' through a preliminary conventional dry mechanical separator andzthence to a surge tube or it may be fed directly through line 44 into ,a surge tube 45 wherein water or other liquid is introduced through line umn is generally upwardv through the center of the sup ply. inlet and around the edges of the standpipe where the flow of liquid through the slits 17 enters the column.- The velocity of this upward flow of liquid is in the range of about 011 to 0.4 feed per second and is not ofv such magnitude as to carry the wheat upward and out through the top of the'standpipe to the discharge pipe but is so adjustedby movement of the velocity regulating means as to effect a sharp separation of wheat from chaff. The lighter chaff including rodent pellets,.insect fragments and the like is carried by the upward flow of liquid out through the outlet to the discharge pipe as shown by arrow 24-3. The velocity of the upwardly moving column of liquid is adjusted by-varying the distance between conical member '29 and supply inlet 24.- Reducing this distance results' in a greater upward velocity in this zone where the critical separation occurs. Increasing the distance reduces the velocity. The upward velocity of the liquid in this zone of separation is adjusted so as to be just insufiicient-to carry the wheat upward. V

The heavier grain passes'upwa'rdly through a zone of turbulence indicated by arrows 24A and then falls back downwardly as shown by arrows 24C againstthe relatively slowcountercurrentlyupwardly moving column of liquid from space 18 where it receives a final wash and passes out through the outlet conduit 14 to conventional dewatering unit 59 and thence on through ducts 51 and 54 when dryingis not required or through ducts 51 and 52 to a convention cyclonedryer 55 fed by air from inlet 56 heated at heater 57 and vented out through vent 58 by vent fan 59. The dried wheat is recovered at cyclone discharge 60. The floating chaif and other light contaminants'are carried through discharge pipe 28 toscreen 61' where the chafi joins that separated by unit 42 and is dewa'tered and discarded, the liquid being discharged to the sewer or recovered and carried through line 62 to recirculation. tank 64 from where it is recirculated through lines 65 and 66 to the preliminary separating unit 42. The liquid from the dewatering unit 50 may. also be recirculated through lines 67 and 68 to the recirculation unit or discharged to the sewer, as desired.

It is desired to emphasize that the hydraulic flotation unit which is the subject matter of this invention may be used alone or may be included as part of amore comprehensive hydraulic treating system such as isshown in Figure 2 of the drawings. The choice is dependent entirely upon the condition andrelative specific gravitics of the materials being treated. therein. Where the wanted materials. are either heavier or lighter than the contami natingsubstances, the fiotationunit of this invention may be used alone to effect theseparatiou. However, if the wanted material is contaminated with both heavier'ancl lighter foreignsubstances then some auxiliary means should be employed. The'hydi'aulic separator shownat 42 in Figure 2 o f'the-dra'wings inper se the subjectrn atter 'of the above identified copending applicationfiled of even date herewith. The combination system shown inFigure 2 is for purposes of illustration only. The construction and mode of operation of the hydraulic separating unit 42 aredisclosed in detail in the aforementioned copendtime into the disclosure of this application.

The separating section of complementary hydraulic cleaning unit 42 is briefly as follows: The grain containing contaminating foreign bodies which are both heavier and lighter than the grain itself is fed into the top of the unit 42' which comprises a generally vertical upright cylindrical standpipe 70 having an angularly upwardly extending conduit 71 branching therefrom. The standpipe 70 and its angularly projecting branch 71 are filled with a swirling upwardly moving column of water or other liquid inert to the material being treated. The swirling motion is imparted to the column by introducing .the

liquid tangentially at 72 into the lower portion of the standpipe at a rate sufiicient to provide the desired rotary movement and upward velocity. As thematerial from the feeder box falls onto the top of the liquid column thevery lightest chaif and like contaminating material is retained on the surface of the liquid and is floated off thru line 74 in the direction ofthe arrow to the screen 61 for dewatering. The material being treated then falls through a relatively quiescent zone of liquid in the top of the standpipe and the countercurrent flow of solid against liquid serves to separate more of the lighter foreign bodies and float them to the surface. The greater mass of the heaviest contaminants carries the pebbles and stones and the like down to the bottom of the standpipe and into a collectiug chamber 75. After falling through the relatively quiescent zone the material ,being treated enters into a Zone in which the liquid is moving upwardly in a swirling circular motion and is being diverted angu larly into conduit 71. The material being treated entering into this moving zone is carried off into the angularly disposed conduit. The centrifugal action of" the moving liquid serves to throw out the remaining heavier contaminating substances against the'walls of the conduit from where they fall to the bottom of the standpipe. Being already in the form of a slurry, the cleaned and separated grain or other material being carried out through the top of conduit 71 need not (unless desired) pass through surge tube 45, but may pass through lines 76 and '77 directly to supply line 20 and into the flotation unit.

Although it is to be understood that the scope of the invention is not limited thereto, the hydraulic flotation unit comprising this invention will now be further de-' scribed with reference to its use in cleaning grain and particularly wheat, with water being used asthe hydraulic fluid. A hydraulic flotation unit was designed'to have a capacity of about 5 to 40 bushels of wheat per hour and comprises generally an upright vertical standpipe approximately 8 inches in diameter and about 4 feet hi h made up of a stack of a plurality of flanged sections. A transparent section about one foot high is positioned about two feet from the top of the standpipe. The bottom outlet pipe has a diameter of about 6 inches and extends for about 4 inches into the bottom of the wheat while in the standpipe. Of this watenabout to percent is added in the surge tube and about 10 to 20 percent in the bottom of the standpipe. If the wheat is already in the form. of a slurry as it enters the surge tube only enough water need be added to establish the desired ratios. The make-up water and slurry of water and wheat are fed into the vertical standpipe and the conical section is so adjusted as to maintain an upward velocity of water through the intermediate zone between the top of the supply inlet and the bottom of the conical member of from about 0.1 to 0.4 feet per second and preferably'for cleaning of Wheat about 0.12 to 0.2 feet per second. As the upwardly moving slurry of wheat enters this relatively rapid moving portion of the column of water the critical separation of wheat from chaff occurs. The upward velocity is 'suflicient to transport the chaflf and like light foreign substances'upwardly and out through the discharge pipe but is just insufiicient to transport the wheat. The wheat then falls into the relatively slow moving column around the supply inlet extension, receiving a final separating action from the countercurrently-Irnoving stream of makeup water in which contaminants not theretofore removed, return and are directed into the lower open end of the inlet extension 24, as described, and the clean grain is discharged down through the bottom outlet pipe and passed to the dewatering and drying units.

As herein described, the feed extension 24 is in spaced relationship to the feed inlet 22 and the perforated collar 16, from which an upwardly directed flow of fluid is obtained as a relatively spaced separate moving column relative to the inlet feed .mixture moving upwardly through the inlet extension 24, from the. feed supply inlet '22. As indicated, the material to be separated flows upwardly through extension 24 in a velocity relative to the force of feed flow therethrough. Due to the enlarged column area immediately above the outlet of extension 24, the velocity of the feed flow is reduced and becomes more closely 'related to the upward flow velocity of the liquid column about the outer periphery of extension 24. As explained, the material desired to be separated then falls back in a counter flow relationship about the extension 24. In this fall back, there is retained contaminating material which has somewhat related properties as to size and specific gravity, but diiferent configuration or hydrau- These materials fall, adjacent to and into the fluid streams flowing upwardly from perforations 17. At this stage, materials of different configuration, lighter weight or specific gravity, and different hydraulic properties, are suspended or floated in the relatively independently spaced fluid column extending about the inlet column, as described. in conjunction with the separation effected by the action of the'fiuid streams flowing from perforations 17, a spaced relationship of extension 24, relative to feedinlet 22, causes an aspirating effect. This aspirating eifect serves to drag and pull into the inlet feed column materials having their hydraulic behavior standpipe. The supply inlet for the slurry of wheat has a diameter of about 2 inches and extends about 4 inches above the bottom outlet pipe and about 2 inches into the supply inlet extension which is about a foot high and 3 /2 inches in diameter. The conical'velocity regulating membet is about a foot and a half high and ranges from about an 8 inch diameter at its base to about 2 inches at its outlet. The maximum length ofthe zone between the wheat supply inlet 24 and the inlet to the conical section is thus about 16 to 18 inches and this may bereduced down to about 8 to 12 inches by adjusting the conical member.

The wheat is fed into the surge tube 45 at the rate of about 5 to 40 bushels per hour, preferably at about 20 to 30 bushels per hour. Suflicientwater'isintroduced into the surge tube and into the bottom of the standpipe to maintain a ratio of from about 7 to 10 parts by weight be construed as a limitation upon the scope of the invention.

Example I Wheat fed to a flotation unit constructed according to this invention was previously purposely contaminated with rodent pellets having a range in apparent specific gravity such that about 50 percent were lighter than water, about 35 percent had specific gravities between about 1.00 and 1.10 and about 15 percent had specific gravities between about-1.10 and 1.15. (The specific gravity of wheat rangesbetween about 1.2 to 1.35.) The rodent pellets used were identified by marking them with a spot of bright colored lacquer. One bushel of wheat was contaminated with: 20 marked pellets selectedas described above. This represents quite heavy con-- termination. This wheat containing the marked pellets Example II Another sample of wheat was contaminated with marked rodent pellets selected to have a range of specific gravities as described in Example I. One bushel of this: wheat containing 20 marked pellets was passed once through the flotation unit. The water to wheat ratio was 8.1 to 1. The upward velocity of the water through the separating zone was 0.14 feet per second. Fourteen marked and 3 unmarked pellets were removed in the flotation unit. However, the total amount of wheat which was removed with the pellets and other chafi was only 0.231 percent and this contained only an insignificant amount of good quality wheat.

. iect to normal contamination by rodents. Other tests made with relatively lighter rodent pellets obtained fromanimals fed a restricted diet resulted in separations of 100 percent with very little entrainment.

In the normal operation of this hydraulic fiotationunit, the actual contact time of the wheat with the water will be only fromabout 15 to 60 seconds. By making this contact time between wheat and water at a minimum very little water is absorbed and the wheat may be freed of that by dewatering and drying without damage to its physical or chemical properites. The wheat if dewatered immediately will retain only from about 2 to 3 percent water as surface moisture and that can be removed by drying resulting in an overall moisture gain in the wheat of only a few tenths of a percent. The use of a flash dryer employing high initial air temperatures (550 F.) is possible since drying occurs by free evaporation.

This case of drying illustrated by the following: Dururn wheat from the flotation unit was dewatered in a pilot scale commercial dewatering unitand discharged directly to a countercurrent cascade type of dryer. 7 The initial moisture content of the dry wheat before feeding to the flotation unit was 14.1 percent. As it left the dewatering unit the moisture content of the wheat was 17.1 percent and immediately after it left the dryer the moisture content was 15.0 percent. After being cooled in an air stream the final moisture content of the wheat was 14.2 percent, an-increase of 0.1 percent over the feed. The wheat was in the dryer for 15 seconds. Temperature of the air into the dryer was 198 F. and the temperature of the air out of the dryer was 84 F. The temperature of the wheat out of the dryer was 108 Tests showed no damage had occurred to the wheat. Durumwheat was selected for use in the experiment because it is considered to be the most sensitive of the wheats to damage be heat.

Spring wheat having a moisture content of 8.8 percent was wet to 12.5 percent moisture content after being exposed to contact with the water for 45 seconds discharged from the dryer was 80f F. The wheat showed no damage due. to treatment at these temperatures.

It" will be understood that" thedimensions and condh tions recited above are given fora particular material (wheat). and for operation at a particular capacity. Obviously, variations which will readily suggest themselves to persons skilled in this art may be made to adapt this invention to the treatment of different materials and at different rates.v v

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments herein.

What We claim is:

l. A hydraulic flotation unit comprising in combination an elongated vertical tube having a top and a bottom, a vertical outlet tube disposed within said elongated vertical tube at the bottom end thereof, a vertical feed inlet tube disposed. within said outlet tube and extending up into said. elongated vertical tube, liquid and feed flow guides adjacent the outlet of said inlet tube an outlet tube at the top of said elongated vertical tube and a movable conical member within said elongated vertical tube between the outlet at the top thereof and the feed inlet tube.

2. A hydraulic flotation unit comprising in combination an elongated vertical tube having a top and a bottom, a vertical outlet tube disposed within said elongated vertical tube at the bottom end thereof, means for introducing liquidiinto the bottom of said elongated vertical tube and around the outlet tube, a vertical feed inlet tube disposed 'within said outlet tube and extending up into said elongated vertical tube, a feed guide extending upwardly from said inlet tube, an outlet tube at the top of said elongated vertical tube and a movable conical member within said elongated vertical tube-between the outlet at the top thereof and the feed inlet tube.

3. A hydraulic flotation unit comprising in combination an elongated vertical tubular standpipe having a top and a bottom, a vertical outlet tube disposed within said standpipe at the bottom thereof and terminating in an outwardly and upwardly extending perforated conical collar section, means for introducing liquid into the bottom of the standpipe and around the outlet tube beneath said perforated .collar section, a vertical feed inlet tube disposed within said outlet tube and extending up into the standpipe, a collective fiowguide adjacent the outlet end of said feed inlet tube an outlet tube atthe top of the standpipe and a movable conical member within the standpipe between the outlet at the top thereof and the feed inlet tube.

4. A hydraulic flotation unit comprising a generally cylindrical vertical tubular standpipe having a top and a bottom, a vertical outlet tube of lesser diameter disposed within saidstandpipe at the bottom thereof and terminating in an outwardly and upwardly extending perforated conical collar section, means for introducing liquid into the bottom of the standpipe through the space around the outlet tube, a vertical feed inlet tube of lesser diameter disposed within said outlet tube'and extending up into the standpipe, a vertical feed inlet tube extension of greater diameter than the feed inlet tube, open at both ends,'disposed about and above the end of the feed inlet tube, an outlet tube at the top of the standpipe and a movable conical member within the standpipe between the outlet' at the top thereof and the feed inlet tube extension, the walls of said conical member COD. verging upwardly and terminating in'an outlet tube disposed within the outlet tube of said standpipe.

5. A hydraulic flotation .unit comprising a generally cylindrical vertical tubular standpipe having a top and a bottom, a vertical outlet tube of lesser diameter disposed axially within said standpipe at the bottom thereof and terminating in an outwardly and upwardly extending perforated conical collar section, means for introducing liquid into the bottom of the standpipe through the space Z'around the outlet tube and the perforations in the coniamen-cor.

ameter disposed axially within said outlet tube and extending up into the standpipe, a generally cylindrical vertical feed inlet tube extension of greater diameter than the feed inlet tube, open at both ends, disposed axially about and above the upper end of the feed inlet tube, an outlet tube at the top of the standpipe, a movable conical velocity regulating member within the standpipe between the outlet tube at the top thereof and the feed inlet extension, said conical member being open at both ends, the walls of said conical member converging upwardly and terminating in an outlet tube disposed within the outlet tube of the standpipe and means for adjusting the height of the conical member.

6. The hydraulic flotation unit of claim further characterized in that at least part of the walls of the standpipe in the zone between the top of the inlet tube extension and the bottom of the conical member is transparent.

7. A hydraulic flotation system for separating particles of materials of different specific gravities comprising an elongated substantially cylindrical tubular standpipe having a top and a bottom and adapted to contain a generally upwardly moving column of liquid, a vertical outlet tube of lesser diameter disposed axially within standpipe at thebottom thereof adapted to receive the downwardly moving portion of said generally upwardly moving column of liquid carrying the, heavier particulate material, said outlet tube terminating in an outwardly and upwardly extending perforated conical collar section, means for introducing liquid into the bottom of the standpipe through the space around the outlet tube and up through the perforations in the conical collar section, a vertical feed inlet tube of lesser diameter disposed axially within said outlet tube" and extending up into the standpipe for introducing a supply of a slurry ofsolid particulate material entrained in a liquid into said generally upwardly moving liquid column, a generally cylindrical vertical feed inlet tube extension of greater diameter than the feed inlet tube, open at both ends, disposed axially about and above the upper end of the feed inlet tube, an outlet tube at the top of the standpipe adapted to receive the lighter of the solid particulate material and deliver it to a discharge pipe, a movable conical liquid velocity regulating member within the standpipe between the outlet tube at the top thereof and the feed inlet extension, said conical member being open at both ends, the walls or" said conical member converging upwardly and terminating in an outlet disposed within the outlet tube of the standpipe, means for adjusting the height of the conical member whereby the velocity of the generally upwardly moving column may be regulated and the lighter and heavier solid particulate material separated thereby, and means for removing the liquid from said separated solid particulate materials.

8. In the process of hydraulically cleaning and separat-.

ing a selective material from contaminant material mixed therewith and having different hydraulic behavior in a liquid system, the steps comprising continuously mixing and introducing a feed stream of the mixture of materials into a liquid stream, maintaining a concurrently flowing liquid stream adjacent said first mixed flowing streams, joining all of said liquid streams at an outflow end ofsaid first mentioned mixed flowing streams, initially separating a portion of the contaminant material by its hydraulic behavior in the said juncture area of said liquid streams, discharging the liquid of said joined streams with said separated portion of contaminant material, returning the selective portion of the material and retained contaminant material therewith in countercurrent flow relationship in said adjacent concurrent flowing liquid stream, effecting a further separation of the selective material from retained contaminant material of different hydraulic behavior than said selective material, separating and recirculating retained contaminant material into and with said feed stream slurry, and continuouslyrwithdrawing a slurry of the countercurrent flowing; selective material from the cleaning process. 1

9. In the process of claim 8, the selective material being a grain material, contaminant material comprising rodent pellets and the liquid being water.

10. In a fluid unit for cleaning grain of contaminant material, the structure comprising a material feed means for a continuous flow of a mixtureof grain material and contaminant material, a fluid flow guide means for said mixture in spaced relationship to said material feed means and for recirculation therein of a portion of said contaminant material, a further fluid guide means about said feed means and said flow guide means and in spaced circumferential relationship thereto, a fluid inlet means for supplying concurrent fluid flows to each of said flow guide means, control means for aflecting the hydraulic behavior of said grain and contaminant materials, and discharge outlet means for continuously carrying cleaned grain from said unit.

11. A hydraulic flotation system of separatinglighter and heavier particles of materialsvof diflerent hydraulic behaviors which comprises forming a slurry of said pan I ticles, introducing said slurry upwardly into a generally upwardly relatively rapidly moving liquid column, maintaining a spaced upwardly moving liquid column in adjacent relationship to the said upwardly relatively rapidly moving liquid column, joining the said spaced upwardly moving liquid columns, effecting a primary separation of the lighter and heavior particles in said slurry at the juncture of saidcolumns, the upward velocity of said first column adjacent the point of introduction of the slurry being suflicient to transport and to create an aspiration cflect relative to said adjacent liquid column, the upward velocity of said adjacent liquid column being suflicient to transport the lighter of said particles upwardly but insufiicient to transport the heavier of said particles, eflecting a separation and recirculation of the entrapped lighter particles from the heavier particles by said aspiration effect, withdrawing lighter particles from the top of said liquid column, and withdrawing heavier particles from the bottom of said liquid column.

12. A hydraulic flotation system of cleaning grain of contaminant material which comprises forming a slurry of grain and its contaminant material, introducing said slurry upwardly into a generally upwardly moving liquid column, maintaining a second liquid column in adjacent concurrent flow relationship with said first slurry column, adjusting the upward flow velocity of said slurry column such that it is suficient to support said slurry of grain and create an aspiration efiect relative to said second liquid column and simultaneously produce separation and recirculatlon of foreign material from said second column back into said slurry column, adjusting the eifecting a juncture of saidv liquid columns and separation of grain into said second column, withdrawing contaminant material from the top of the said columns, withdrawing grain cleaned of contaminant material from the bottom of said columns, and removing the liquid from the grain.

13. The system of claim 12 further characterized in that the ratio of liquid to grain is in the range of about 7 to 10 parts by weight of liquid to each part of grain.

14. The system of claim 12 further characterized in that upward velocity of said generally upwardly moving liquid column adjacent the point of introduction of the slurry is in the range of about 0.1 to about 0.4 ft. per second.

'15. The system of claim 12 further characterized in that the liquid is water, the grain iswheat and the ratio of water to wheat by weight is from about 8.1 to about 8.7 to 1 and the upward velocity of the said generally upwardly moving liquid column of water adjacent to wax-max Middleton Nov. 16, 1,909

12 Y Whitney --:-v May- 22, 1923' Hatch Sept 20, 1932 Strohl Feb. 20, 1934 FOREIGN PATENTS Great Britain May 2, 1935' waxy

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