US2927693A - Cleaning of paper pulp suspensions - Google Patents

Description

March 8, 1960 Filed March 10, 1955 H. FREEMAN ET AL 2,927,693

CLEANING OF PAPER PULP SUSPENSIONS 5 Sheets-Sheet l INVENTORY. Hoe/acEFeEEMA/v MLM,M

ATTORNEYS.

March 8, 1960 H. FREEMAN ET L CLEANING OF PAPER PULP SUSPENSIONS' 5 Sheets-Sheet. 2-

Filed March 10, 1955 IN V EN TORS.

HORACE Hera-MAN JOHN D. BOADW/H.

March 8, 1960 Filed March 10, 1955 H. FREEMAN ET AL CLEANING OF PAPER PULP 'SUSPENSIONS 5 Sheets-Sheet 3 y JOHNQBOADWAY.

Z MMOWI ATTORNEYS.

March 8, 1960 5 Sheets-Sheet 4 Filed March 10, I955 v III IN s E uw MM N m -5 m M w m V Hm W N m h v a a z 4 mm M M HJ w MMMQM March 8, 1960 Filed March 10, 1955 H. FREEMAN ET AL CLEANING OF PAPER PULP SUSPENSIONS 5 Sheds-Sheet a CLEANING EA 770 NUMBER or OVEESIZED PARTICLES l/V FEED STOCK NUMBER OF OVEES/ZED PARTlCfl-EJ IN ACCEPTED STOCK I I L/vo 5 10 AEJECT/ON ar- 501.105

IN V EN TORS. Ho EA c5: Fe'ssMA/v.

BY JOHN D. 50A 0 wA K MAM/Mahdi ATTORNEY-51 CLEANING OF PAPER PULP SUSPENSIONS Horace Freeman, Cap de la Madeleine, Quebec, and Eohn D. Boadway, Three Rivers, Quebec, Canada, assignors, by mesne assignments, to Nichols Engineering and Research Corporation, New York, N.Y., a corporation of Delaware Application March 10, 1955, Serial No. 493,352

6 Claims. (Cl. 209--211) This invention relates to apparatus for separating oversized or heavy particles from liquids, liquid mixtures or suspensions and is particularly adapted among other uses for the separation of undesired particles from paper pulp stock.

The apparatus of the invention involves the use of chambers in which the mixture to be treated is introduced and caused to maintain high velocity vortices from which the treated liquid or stock is conducted from one end of the apparatus, while the particles to be separated, along with a small amount of the stock therewith, are conducted out of the other end of the apparatus.

While apparatus of this general character has been widely used in the cleaning of paper pulp stock, the efiiciency thereof in removing undesired particles has either been. unsatisfactory, or inv cases where better efiiciency has been obtained in dirt removal, this has been accomplished at the expense of removing an excessively large percentage of the desired solids of the pulp mixture along with the dirt. These shortcomings have only to an undesirably limited extent been relieved by passing the rejected dirty stock through so-called secondary or even tertiary cleaners or by using various expensive multiplicities of small vortex devices, each of low capacity.

The cleaning efficiency of such apparatus may properly be expressed in terms of its cleaning ratio, that is, the ratio between the number of oversized or undesired particles in the feed stock as compared with the number of such particles in the accepted treated stock. But although this ratio may be high for a given apparatus arrangement, that does not necessarily mean that the apparatus would be of a desirable type in practice, unless such high ratio is secured with only a small percentage of rejection of the total solids in the mixture.

The overall object of the present invention is to provide a method and apparatus which will give a high cleaning ratio but with only a very small percentage rejection of the total solids or desired pulp particles from the suspension. With the present invention, cleaning ratios of from about to or more may be readily attained with a percentage rejection of total solids varying from about 1% to 3%, or 4%. That is, the stock to be treated may contain from 5 to 10 times more of the oversized or undesired particles than does the treated accepted stock, and this may be accomplished without rejecting with the undesired particles more than about 1-4% of the desired pulp particles, these figures varying within these limitsdepending upon the particular embodiment of the invention used under different conditions and the adjustment thereof. So far as is known, no comparable cleaning ratio for such apparatus has heretofore been obtained with any comparable low- United States Patent 0 percentage rejection of total solids from pulp suspensions.

The apparatus of the invention involves an elongated chamber of circular cross-section which may be either cylindrical or somewhat tapered, if desired, and into one end of which a suspension to be treated is introduced under pressure through a restricted tangential inlet such that a substantial part of the pressure energy will beconverted to velocity energy, causing a high velocity vortex to be maintained and to extend from the inlet end of the chamber to the other end, and then back as an inner vortex to an accepted stock outlet, the vortices being usually of such velocity as to maintain an axial gas core therein. The end of the chamber opposite from the inlet is provided with a cone, the elements oi which cone are preferably inwardly curved as hereinafter explained, and the apex of which cone discharges into an enclosure so shaped that the portions of the vortices which extend through such apex, as well as the gas core therein, will be retained in a stabilized centered. position, while the separated particles containing a small amount of liquid stock pass through an annular slot and are then withdrawn tangentially and so as not to disturb such stabilized conditions.

Various further and more specific objects, features and advantages of the invention will appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by way of example, preferred forms of apparatus for the practice'of thein vention. The invention consists of such novel features; arrangements and combinations of parts and method steps as may be shown and described herein.

In the drawings:

Fig. l is a vertical sectional view of one of the preferred embodiments of the invention;

Fig. 2 is a vertical sectional view of the upper portion 1 of Fig. 1, but taken at a different angle; 1

Fig. 3 is a horizontal sectional view taken substantially along line 3-3 of Fig. 1;

Fig. 4 is an enlarged vertical sectional view of the lower portion of Fig. l and indicating in further detail the paths of the vortices and of the separated particles and gas core; a

Figs. 5 and 6 are horizontal sectional views taken substantially alonglines 55 and 6-6 of Fig. 4 respectively;

Fig. 7 is a view similar to Fig. 4 but on a smaller scale and showing an alternative embodiment of the invention;

Fig. 8 is a horizontal sectional view taken substantiallyalong line 88 of Fig. 7;

Fig. 9 is a diagram showing the manner in which one of the devices of the invention may be used as asecondary cleaner for cleaning the stock rejected from a plurality of primary devices designed to remove gas and dirt from paper pulp in the manner disclosed in our copending application, Serial No. 425,942, filed April 27, 1954, now Patent No. 2,757,582;

Fig. 10 is a similar diagram but illustrating the manner in which one form of the invention may be arranged for use to provide for primary separation of solidparticles from paper pulp stock, while another embodiment of the invention is used for secondary cleaning purposes, and

Fig. 11 comprises certain curves indicating the chiciency of the operation of the devices in accordanc j with the invention under various conditions.

The form of the-invention as shown-in Figs; 1-3

Patented Mar. 8, 1960 particularly adapted for use as a secondary cleaner or classifier, although same may under certain conditions also be desirably used as a primary classifier. The other embodiment of the invention (having a different lower portion, as shown in Figs. 7 and 8) is particularly desirable for use as a primary cleaner or classifier, although this also, under certain conditions, may be efficiently used as a secondary classifier.

Referring to Fig. 1 in further detail, the device as here shown comprises a headpiece 12, a barrel portion 13, a cone piece 14 and a rejects control enclosure 15. The headpiece has a trumpet-shaped stock inlet portion 16 designed to so restrict the fluid entering under'pressure as to convert a considerable part of the pressure energy (for example 45%) into velocity energy, thereby causing a high velocity vortex as at 17 to occur in the barrel 13 and to travel down to the cone piece 14. The headpiece further includes a passage as at 18 which may be of rectangular cross-section and in which the liquid spirals around and downwardly at the start of the formation of the vortex 17. inwardly of this passage there is a cylindrical partition portion 19 terminating at its lower end at an annular plate portion 20 containing a central outlet aperture 21 for the discharge of the cleaned accepted stock. An inner cylindrical portion 22 extends up from such outlet 21 and has a portion 23 of expanding diameter and adapted to be connected to the treated stock outlet conduit 24.

During the travel of the liquid of the vortex 17 downwardly, the larger and heavier particles therein which are of a nature which would settle faster than the remainder of the mixture, are thrown outwardly by centrifugal force to the wall of the barrel and then travel downwardly to the cone 14. At the cone, the more central portions of the vortex, that is the cleaner portions thereof, are reversed in direction, that is, same are turned upwardly to form an upward inner vortex as indicated by the arrows 25, this inner vortex being of a diameter at least suflicient to fill the outlet opening 21, and as indicated, the velocity of the vortices will generally be such that a low pressure gas core 26 will be formed axially of the device. The liquid immediately surrounding such gas core spirals upwardly as indicated by the arrows 27. Such gas core will ordinarily extend upwardly at least into the expanding outlet portion 23, where, due to the increasing diameter of the outlet, the core will soon become extinguished. At its lower end the gas core will ordinarily extend down to the bottom of the rejects control enclosure as hereinafter explained.

The heavier or larger particles which are thrown onto the wall of the barrel will slide down over the internal surface of the cone 14 and into the rejects control chamber 15.

The optimum length of the barrel is dependent upon a balance between two extreme conditions. If the barrel is unduly long, the downward vortex becomes unstable and tends to turn back within itself before it reaches the conical reversing zone, thus tending to sweep the dirt particles back up with it, giving a low cleaning efiiciency. If on the other hand the barrel is unduly short, much of the possible residence time during which the dirt can move to the walls of the barrel will be lost. If the barrel walls are made extremely smooth, the barrel may be made longer without encountering vortex instability. The barrel and'other parts are shown drawn to scale in Fig. 1 with appropriate proportions for a typical installation, assuming the barrel is of a diameter of about and with a length of about 50".

As above indicated, the cone piece is preferably so made that vertical elements thereof curve inwardly as shown. That is, toward the lower portions of the cone, thewalls slant more and more directly downwardly than at the upper portions, the preferred curvature being derived in accordance with formulae hereinafter stated and explained.

With any such cone, it may he theoretically predicted that as the liquid on the wall thereof progresses over its internal surface to a smaller and smaller diametcr, there will be an increase in rotational speed of the liquid due to the conversion of pressure into velocity energy, and this increase in speed with the rotation at a smaller radius, will lead to an increase in the centrifugal forces on the particles in the liquid. With large round particles, however, this may result in their being supported on the slope of the cone near the outlet and thus prevented from proceeding any further toward rejection from the cone apex due to a component of centrifugal force against the sloping wall. Thus if a cone with straight-sided elements is used, there is a tendency for certain types of particles to have an orbiting effect more or less permanently at a certain level and this effect will be considerably more for large low density undesired particles than for small high density particles. The latter can be accommodated in a very thin liquid layer next to the surface of the cone in which friction loss by shear is sufiicient so as to minimize the possibility of such continued orbiting. The larger diameter particles such as wood slivers, on the other hand, may extend into the layers of liquid which are not so close to the cone wall, and hence will be kept moving at a very high velocity because of the high velocity of the liquid continuously washing over their inner edges. Such larger particles will thus, in a straight-sided cone, be kept from moving down and prevented from leaving with the rejected stock. Some of such particles may be of such a nature that with continuing orbiting, they will tend rapidly to abrade away the metal of the cone, and if they are large, they may from time to time be dislodged and pass up with the accepted stock in the inner vortex.

While various different efifects may be obtained by using either an elongated or a relatively blunt straightsided cone, yet for various reasons, both of these expedients are relatively unsatisfactory. It has been found, however, that the troublesome orbiting above referred to may best be eliminated by using a cone, the elements of which are inwardly curved, that is, slanted more and more directly downwardly at the lower end of the cone, the preferred curvature being determined in accordance with the following mathematical formula. But first it should be noted that the tangential velocity at any point in a vortex may be predicted by the following equation:

:Kf where V is the tangential velocity at a point in the vortex liquid;

K is a constant;

1' is the radius to said point;

it is a function which will have a value depending on the friction encountered by the vortex, and somewhere between 1 for a theoretical frictionfree vortex and +1 for a theoretical friction vortex in which all energy is lost by friction. For a typical practical example, this function n will be an intermediate value, say of 0.75.

Thus the value of the constant K which is used in the formula given below may be determined or estimated by the above equation transposed as follows:

Now if we consider that the liquid according to the above equation is moving to smaller radii and that it is following a cone, the slope of which must be adjusted so that a balance may be obtained at any point between the component of centrifugal force tending to move a particle upwardly, as against gravity tending to games move it downwardly, then the following integrat'ed equation can be obtained for such a curve:

where H is the distance from the top of the cone down to a point on the curve;

K- is the constant derived from the previous equation above;

n is determined or estimated as above explained;

g=32 feet per second;

r isthe radius to said point on the curved cone;

R is the radius of the cone at the top.

" :In order to insure that solid particles on the wall of the cone will pass down for rejection, it will be understood that the curvature of the cone element should be at lcast slightly less than determined by the above formula, but preferably not very substantially less, lest the cone be unable 'efiiciently to cause reversal of the greater part of the vortex flow upwardly.

: It will be noted that the lower or outlet end of the cone 14 provides an exit of fairly large diameter and for that reason, if such outlet were left unobstructed,

the quantity of the rejected liquid and desired fiber would be excessive and would be a critical function of the out let pressure of the accepted stock at the top of the device.

For these reasons a further part, namely the reject control enclosure 15, is added below the cone apex and is.

adapted for controlling quite accurately the amount of material rejected, and permits removal of the undesired dirt and heavy material without carrying away any excessive amounts of the desired acceptable stock.

As mostclearly shown in Fig. 4, the outlet end of the cone is preferably connected to a cylindrical extension 30 which protrudes somewhat down into the enclosure 15 and is integrally formed with a tangential water inlet connection 31 adapted to receive a supply of water or white water from a paper machine for elutriating the material within the enclosure 15. As shown in the sectional view' of Fig. 5, the tangential inlet 31 is somewhat restricted so as to convert a part of the energy of the incoming water to velocity energy, thereby to maintain a vortex in the enclosure 15 as indicated by the arrows '32. The main body portion of the enclosure 15 may comprise a cylinder 33 of transparent material retained as. by bolts 34, sealed in position between the upper head portion and a lower base portion 35. The lower or base portion 35 isformed with an annular chamber 36 closed by a bottom piece 37 held in place as by screws 38. It will be noted that the greater part of the area of the bottom piece 37 against which the liquid impinges is shaped in the form of a blunt upstanding cone 39, but with a small inverted conical portion 40 at the middle of this area. The Space within the enclosure 15 communicates with the annular cavity '36 by. way of an annular slot 41. The annular space 36 is formed with a tangential rejects outlet 42.

As will be noted from the vortex indicating arrows in Fig. 4, the relatively thin annular outer part of the down- Ward vortex 17, 17 continues as at 45 down into the enclosure 15, carrying with it the undesired particles infiicated as passing down along the inside wall surfaces of the cylinder portion 30. As this downward vortex portion mixes with the elutriation water coming in through inlet 31, the downward vortex portion becomes substantially diluted and expands to fill the peripheral port-ions of the enclosure 15, causing the undesired par- -ticles to be thrown against the walls thereof andto pass down without any substantially irregular turbulence, to the annular outlet slit 41.

However, due to the impingement of the downward vortex against the bottom conical area 39, taken together iwithj the restriction at the annular slit 41; a 'small portionnfz-such vortex will be caused to reverse and flow 6 back upwardly as indicated by the arrows 46 to join and form a part of the upward vortex 25, 25. The central gas core at 26, 26' will continue down and be stopped by the inverted conical area 40. This inverted conical area is made of a diameter slightly greater than the estimated diameter of the gas core, so that the gas core will be received within the circumference of this. inverted cone, which acts to stabilize the position of the gas core at the axis of the vortices, thereby avoiding irregular turbulence which might cause some of the undesired particles to be reversed in direction of travel and be taken back up with the inner vortex.

Since the annular chamber 36 is spaced outwardly of the annular slit 41, the construction insures that the undesired particles which escape out through the slit,

cannot come back and be swept up in the inner vortexa Furthermore, since the outlet 42 from the cavity 36 is located at a relatively widely spaced position from the inner vortex and gas core and is separated from same by the slit 41, there is no danger that the withdrawn stream passing out through exit 42 will cause any displacement or turbulence about the central upward vortex'and gas core. And the gas core being in effect trapped by the inverted conical area 40, there is no danger that bubbles of gas will escape therefrom to the outlet 42'. The oversized and heavy material in the enclosure 15 is capable of falling through the vortex.32, whereas the fine acceptable material is not, but is swept back by the slight amount of elutriation water flowing back upwardly in the inner vortex 25'. The oversized and high density material having been washed free of fine acceptable material, is thus discharged without difiiculty through the annular slit 41. The rate of discharge of the rejected material through outlet 42 may be controlled by valves or orifices hereinafter described. The withdrawal of the clean accepted stock through this outlet is minimized by the nature of the inverted conical surface 40 which tends to hold the clean acceptable stock in the middle, rather than allowingit to follow the conical surface 39 toward theslit 41. The inverted cone further prevents the draw-. ing of the undesired material into the middle where it would be swept back upwardly with the accepted stock. By adjusting the in-flow of elutriation water at inlet I 31, one may regulate the proportion of fine material and fibers which will be rejected. That is, with more water flowing in through inlet 31, there is a tendency for some of the slower settling types of material to be reversed in direction into the inner upward vortex, whereas with less water coming in through inlet 31, more of the fine particles and fiber will go out withthe rejected material.

In case it is not desired to subject the material in the enclosure 15 to elutriation, then the construction shown in Figs. 7 and 8 may be used, parts corresponding to thoseof Fig. '1 being identified in these figures by like reference numerals accompanied by prime marks. This embodiment has the advantage of simplicity'and also it does not dilute the rejected stock, but discharges same as a more thickened material, well suited for cases where it is desirable to have the rejected material relatively concentrated as compared with the untreated stock.

On the other hand, where rejects outlet plugging difficulties might arise with the construction of Fig. 7, then the elutriation method of reject control as of Fig. 4 is desirable and makes possible the virtual elimination of plugging difficulties.

Referring now to Fig. 9, there is here shown a plurality of separators at A of a type adapted to separate both gas and heavier particles from pulp suspensions. For example, these devices may be as per the construction shown in our co-pending application Serial No. 425,942, filed April 27, 1954, now Patent No. 2,757,582, reference to which is hereby made. The incoming stock to be treated is pumped from a conduit 50 by pump 51 and pipe line 52 into the inlets 53 of the devices A. The accepted cleaned stock from these devices 'is" conducted,

out through outlets 54 and pipe line 55 to a suction pump 56. The undesired gases, and heavier particles pass from the devices A down through outlets 57 into a tank 58. The gases are withdrawn as by a vacuum pump 59 from above the liquid in tank 58 whereas liquid containing the rejected material is withdrawn through a pipe 60 by a pump 61 which pumps the rejected material into one of the devices at B of the construction hereinabove described in connection with Figs. 1 and 4.

Arrangements are also preferably provided to introduce water or white water from the paper mill into the rejected stock in pipe 60 through an automatically oper ated valve at 62. This may be an air pressure diaphragm operated valve, for example, automatically controlled by a flow-type level controller as schematically indicated at 63 at the tank 58. That is, in the. event that the liquid level in tank 58 falls below a predetermined height, then the level controller acts automatically to operate the air-operated valve 62 to introduce more water into the pipe 60 whereby the pump 61 may receive a relatively constant head or supply of liquid tov be pumped into the device B.

It will be apparent that the device B in the arrangement of Fig. 9 acts as a so-called secondary cleaner which will ordinarily receive rejected stock containing considerable quantities of dirt and undesired particles and accordingly the reject control enclosure 15 at the bottom of the device B is preferably made of a form providing for the reception of elutriation water through inlet 31 to insure against plugging of the outlet connection. As indicated, the flow through the outlet connection 42 may be controlled by an orifice 64. The connection to waste from this orifice preferably is formed with a T-shaped coupling 65, containing a removable plug 66 so that upon removal of such plug a pin may be introduced to clean out the orifice 64 in case same becomes obstructed. Accepted stock from the device B may be conducted through a'pipe 67 back to the main stock inlet 50,.

Referring now to Fig. 10, there is here shown at C a plurality of classifying devices of the type shown in Fig. 1, except having reject control enclosures as per the embodiment of Fig. 7. Since these are so-called primary classifiers or cleaners from which the rejected stock may be relatively dilute, the reject outlet means is preferably not equipped for elutriation. They are each provided with orifice and outlet fittings 64, 65 and 66 as above described. These connections also may include sight glasses 68 connected to the tank 58. There is indicated at D a secondary cleaner which is constructed as per Fig. 1 with provision for elutriation. of the various other parts of the system of Fig. will be readily understood, same being identified by the same numerals as corresponding parts in Fig. 9.

The performance in a typical case of the reject control with elutriation as per Fig. 1, as compared with the embodiment of Fig. 7, is shown by the curves 70 and 71 respectively of Fig. 11. That is, on this diagram the vertical distances represent the cleaning ratio above referred to, whereas the horizontal distances represent the percentage of rejection of the total solids of the suspension being treated. Thus, assuming the primary cleaners C of Fig. 10, for example, are so adjusted and provided with reject orifices that about 3 /2 of the total solids of a suspension are being rejected, then as indicated by the point 72 on curve 71, the cleaning ratio will be about 10. That is, there will be ten times as many oversized or undesired particles in the feed stock as in the treated accepted stock.

It will be noted that if the rejection of solids exceeds about 4%, then the two types of rejects controls (as of Figs. 4 and 7) will approach each other in performance. With the rejects control without elutriation (as per Fig. 7, curve 71) there will be a tendency for the outlet of the device to plug, if less than about 2% of the solids are rejected (see poin 73 on curve 1),, 0:-

The construction responding to a cleaning ratio of about 9. Such plugging,

however, will not ordinarily interfere with the use of the device as of Fig. 7 as a primary cleaner. With elutriation as indicated by curve 70, however, the percentage of rejection of solids may be carried down to less than 1% without a tendency of plugging, this corresponding to a cleaning ratio of about 5, as indicated by the point 74 on curve 70. Thus the device of Fig. l with elutriation is well adapted for use as a secondary cleaner since same may be operated without plugging with a very low wastage of desired solids, but yet with a cleaning ratio as high as 5, which is ample considering the small amount of material passing through the secondary device.

The curves 70 and 71 represent the results of tests made with apparatus of the size and proportions hereina above disclosed and with the stock to be treated intro-v duced to the device at a pressure of about 41 lbs. per sq.

in., the cleaned or accepted stock being withdrawn at a pressure of about one lb. per sq. in. The rejects outlet pressure will then be about 2%. lbs. Such devices thus operated will have a hydraulic capacity of up to about 440 US. gallons per minute.

From curve 71, it will be apparent that with reject control means as per Fig. 7, the percentage of rejection of solids from the initial stock during primary" cleaning may be kept down to below 3%. Then when such rejected stock is put through a secondary device with elutriation rejects control, the percentage of rejection can be kept down in the neighborhood of one percent. Thus by the use of the system of Fig. 10, the percentage of useful solids in the initial stock which is finally wasted at the secondary reject outlet, amounts overall to no more than a quite insignificant fraction of one percent of the desired solids in the original stock, and yetthe cleaning ratio is maintained exceptionally high. So far as known, the best results heretofore obtained with vortex type classifiers for paper pulp stock have been far in ferior to these results, particularly as to the waste of desired fiber stock. The system of Fig. 10 is also especially elfective in removing wood shives or slivers as well as dirt. If the barrel is made of smaller sizes, such as from 3 to 6 inches diameter, although the capacity will of course be less, the removal of the finer wood shives is made possible, even those having a surface area as small as 0.06 square millimeters.

It should be noted that these highly advantageous results are achieved as the result of the combined use of the curved cone and reject control enclosures above described. For example, if instead of the curved cone, a cone having straight elements is used, but otherwise of comparable proportions, but with rejects controls above described, then the cleaning ratio will suffer very substantially. On the other hand, even if a curved cone is used, but with an open outlet instead of with the above-described rejects control enclosure means, then the percentage of rejection of useful fiber will greatly tncrease.

While the cleaning devices are shown in the drawings in upright or vertical positions and the parts thereof are described by terms such as upper or lower" portions, it will be understood that such terms are used only for convenience, since the devices may be installed in positions other than vertical.

Although certain particular embodiments of the invention are herein disclosed for purposes of explanation, various further modifications thereof, after study of this specification, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope of the invention.

What is claimed is:

1. Apparatus for separating undesired particles from iqu ds, n iqu s p nsions. c mprising an. e ngated chamber of circular cross-secti n n whi h vortex f m 9 tions are adapted to be maintained, a headpiece at'the upper end of said chamber shaped to provide a tangential restricting inlet for the liquid to be treated, whereby a vortex will be maintained around within the walls of said chamber and extending down to its lower end, said headpiece also being formed with a central outlet for 7 treated liquid, an extension at the lower end of said chamber shaped internally to provide a general conical cavity but the walls of which are curved inwardly and more and more downwardly at its lower portions, a rejects control enclosure concentric with and into which the restricted lower end of said cavity opens, a tangential inlet for introducing elutriation liquid into said enclosure, the lower portion of said enclosure being formed around its walls with an annular slit-like passage for discharge of rejected material, said slit in turn being surrounded by an annular enclosure having a tangential outlet the internal bottom surface of said enclosure being formed with a relatively blunt upright conical surface but with an inverted conical area at the mid-portion thereof.

2. Apparatus for separating undesired particles from liquids and liquid suspensions comprising an elongated chamber of circular cross-section in which vortex formations are adapted to be maintained, a headpiece at the upper end of said chamber shaped to provide a tangential inlet for the liquid to be treated, such inlet being restricted so as to provide for converting a substantial part of the pressure energy of the incoming fluid into velocity energy whereby a high velocity vortex will be maintained around within the walls of said chamber and extending down to its lower end, said headpiece also being formed with a central outlet for the treated liquid, an extension at the lower end of said chamber shaped internally to provide a general conical cavity but the walls of which are curved inwardly and more and more downwardly at its lower portions, a rejects control enclosure concentric with and into which the restricted lower end of said cavity opens, a tangential liquid inlet for said enclosure, the lower portion of said enclosure being formed around its walls with an annular slit-like passage for discharge of rejected material, said slit in turn being surrounded by an annular enclosure having a tangential outlet, the internal bottom surface of said enclosure being formed with a relatively blunt upright conical surface but with an inverted conical area at the mid-portion thereof, the parts being so constructed and arranged that the inner portions of the downward vortex are reversed within said cavity to form an inner vortex of treated liquid flowing up and out the headpiece outlet and surrounding a gas core whereas the outer portions of the downward vortex containing the undesired particles continue down into said enclosure to form with the liquid introduced therein a further downwardly spiralling vortex from which the undesired material escapes through said slit while the inner portions of the latter vortex are reversed to flow upwardly from adjacent the periphery of said inverted conical area which area also stops and stabilizes the downward extension of the gas core.

3. Apparatus for separating undesired particles from liquids and liquid suspensions comprising an elongated chamber of circular cross-section having means at its upper end for introducing the liquid to be treated as a downwardly spiralling outer vortex and also having at its upper end central outlet means for discharging an upwardly spiralling central vortex of the treated liquid, an extension at the lower end of said chamber shaped internally to provide a generally conical cavity with walls which are curved inwardly and more and more downwardly at its lower portions where an axial 'discharge passage is provided and through which lower portions of said vortices may extend in restricted form, a member coaxial with and below such passage formed with a relatively blunt conical upright surface but with an inverted conical area at the mid-portion thereof, an annular restricted discharge opening being provided above and coaxial with said surface, an' 'd enc'losiire' mean? surrounding said opening and having a -discharge connection for rejected material.

4. Apparatusvfor separating undesired particles from liquids and liquid suspensions comprising an elongated chamber of circular cross-section having means at its upper end for introducing the liquid to be treated as a downwardly spiralling outer vortex and also having at its upper end central outlet means for discharging an upwardly spiralling central vortex of the treated liquid, an extension at the lower end of said chamber shaped internally to provide a generally conical cavity having an axial discharge passage at its lower end through which lower portions of said vortices may extend in restricted form, a member coaxial with and below such passage formed with a relatively blunt conical upright surface but with an inverted conical area at the mid-portion thereof, an annular restricted discharge opening being provided above and coaxial with said surface, and enclosure means surrounding said opening and having a discharge connection for rejected material.

5. Apparatus for separating undesired particles from liquids and liquid suspensions comprising an elongated cylindrical chamber having means at its upper end for introducing the liquid to be treated as a downwardly spiralling outer vortex and also having at its upper end central outlet means for discharging an upwardly spiralling central vortex of the treated liquid, an extension at the lower end of said chamber and remote from the means for introducing the liquid and shaped internally to provide a generally conical cavity with walls which are curved abruptly inwardly at the upper portion of the cavity and more and more downwardly at its lower portions where an axial discharge passage is provided and through which lower portions of said vortices may extend in restricted form, a member extending across the path of said vortices adjacent the outlet of said lastnamed discharge passage for preventing further downward flow of said vortices, said member being formed with a central depression coaxial'with said discharge passage and with an annular raised area surrounding said depression, said raised area extending substantially inwardly of the periphery of said discharge passage and forming the lower boundary of an annular restricted discharge opening provided about and coaxial with said raised annular area and enclosing means surrounding said annular opening and having a discharge connection for rejected material.

6. Apparatus for separating undesired particles from liquids and liquid suspensions comprising an elongated cylindrical chamber in which vortex formations are adapted to be maintained, a headpiece at the upper end of said chamber shaped ot provide a tangential inlet for the liquid to be treated, such inlet being restricted so as to provide for converting a substantial part of the pressure energy of the incoming fluid into velocity energy whereby a high velocity vortex will be maintained around within the walls of said chamber and extending down to its lower end and there largely reversing to return as an upwardly flowing vortex surrounding a central gas core, said headpiece also being formed with a central outlet for said upwardly flowing vortex, an extension at the lower end of said chamber and remote from the means for introducing the liquid and shaped internally to provide an inverted and generally conical cavity having an axial discharge passage at its lower end for containing downward extensions of such vortices and core, a member extending across the path of said vortices adjacent the outlet of said last-named discharge passage for preventing further downward flow of said vortices and terminating said core, said member being formed with 1 1 12 said raised annular area and-enclosing means surround 2,377,524 Samson June 5, 1945 ing said annular opening and having a discharge connec- 2,521,103 Vickery Sept. 5, 1950 tion for rejected material. 2,532,885 Berges Dec. 5, 1950 I I 2,757,582 Freeman ...-.5 Aug. 7, 1956 References Cited in the file of this patent 5 UNITED STATES PATENTS FOREIGN PATENTS 2,346,005 Bryson Apr. -4, 194-4 607,787 Great Britain Sept. 6, 1948

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