US2829771A - Process and apparatus for classifying solid materials in a hydrocyclone - Google Patents

Description

April 8, 1958 v D. A. DAHLSTROM 2,829,77E

PROCESS AND APPARATUS FOR CLASSIFYTNG SOLID MATERIALS m A HYDROCYCLONE Filed Jan.f6, 195 3 I s Sheets-Sheet 1 Fig. i. I1. .131 Slime Rich o" 1 q I Fine Solids #27 Fraction Slime-bearing 2/ Feed Slurry 1'1 1. 5 (Coarse, Fine a o Slime Particles in Liquid Suspension) Auxiliary Treatment Liquid 0 Coarse Solids Washed INVENTOR a Fine Solids Deslimed Dohald A s Slime Coarse $ollds BY Fracllon 2Q ATTORN April 1958 u. A. DAHLSTROM 2,829,771

- PROCESS AND APPARATUS FOR CLASSIFYING SOLID 7 MATERIALS IN A HYDROCYCLONE Filed Jan. 6 1953 5 Sheets-Sheet 2 Slime Rich Fine Solids Fraction Fl 2. g t 27 Slime-bearing Feed Slurry J I.

- 42 Auxiliary Treatment Liquid Supplementary Auxiliary Treatment Liquid Donald A. Dahlstrom T" Ma ATTORNEY A r il s, 1958 D. A. DAHLSTRO M 2,829,771 PROCESS AND APPARATUS FOR CLASSIFYTNG SOLID MATERIALS IN A HYDROCYCLONE Filed Jan. 6. 1953 5 Sheets-Sheet 3 Fig. 3'.

INVENTOR Donald A. Dchlstrom ATTORNEY Aprll 8, 1958 D. A. DAHLSTROM 2,829,771

PROCESS AND APPARATUS FOR CLASSIFYTNG SOLID MATERIALS IN A HYDROCYCLONE Filed Jan. 6, 1953 5 Sheets-Sheet 5 INVENTOR Donald A. Doh lstrom l I BY ATTORNEY United "States PatentO PROCESS AND APPARATUS FOR CLASSIFYING SOLID MATERIALS IN A HYDROCYCLONE Donald A. Dahlstrom, Deerfield, Ill., assignor to Dorr- Oliver Incorporated, a corporation of Delaware Application January 6, 1953, Serial No. 329,838

28 Claims. (Cl. 209-211) This invention relates to the treatment in hydrocyclones of slime-bearing solids suspended in a liquid, whereby slime is removed from the coarser solids.

In general, a hydrocyclone is an enclosed machine having a stationary, smooth, and continuous surface of revolution about a longitudinal axis of radial symmetry and usually comprising a short cylindrical chamber merging without obstruction into a coaxially aligned conical chamber. Feed is supplied under predetermined pressure tangentially to the cylindrical chamber so as to create therein a swirling stream of liquid, which stream follows a path of gradually decreasing radius toward the point of smallest radius of the cone, commonly known as the apex. The feed is under such a pressure or hydrostatic head that spiralizing first in the cylinder and then in the cone it develops centrifugal forces considerably in excess of gravitational forces so that the elfect of gravity is effectively eliminated. The hydrocyclone accordingly can be operated either in an upright position, upside-down or lying on its side.

As the spiralling stream approaches the apex of the hydrocyclone, a portion of it turns and begins to flow toward the opposite or base end of the machine. This flow is in a spiral path of radius smaller than the radius of the first spiral, which rotates in the same direction. Two concentric vortices are thus formed in the very center of which will normally be found an uprising column or core of air passing completely through the machine. Particles in the feed suspension, which are more rapidly settleable in still Water, are thrown towards the wall of the hydrocyclone and travel in the outer vortex to discharge through a coaxially aligned outlet at the apex, while particles in the feed suspension, which settle less rapidly in still water, generally are dragged into the inner vortex to discharge through a coaxially aligned outlet through the base of the coned machine. In such a manner particles are separated into two fractions on the basis of specific gravity differences, and if there are substantially no specific gravity differences, on the basis of particle size differences. The base comprising a substantially flat end-closure member usually has mounted therein a short pipe or tube of definite size extending down into the cylindrical chamber a distance sufficient to prevent short circuiting of the feed material through this opening. This pipe is known as a vortex finder and the discharge therethrough is known either as the vortex discharge or as the hydrocyclone overflow. The discharge from the opposite end of the machine is known either as the apex discharge or the underflow.

Thus, hydrocyclones are useful for the classification or segregation of coarse solids from fine solids suspended in a liquid. However, the efficiency of this operation, that is, the capability to remove the ultra fine or slime particles, from the coarse particles is too limited for most such operations. Slime as-used herein is defined in general as any approximately minus 200 mesh particles and more particularly refers to clay particles, colloids or particles below 2 to 10 microns in size. An object of this invention is therefore to develop a hydrocyclone classifier which will more efiiciently and effectively deslime liquid suspensions than has been heretofore possible.

This and other objects will be developed as this specification proceeds.

In summary, this invention proposes to attain these objects by controllably and'forcibly introducing an auxiliary treatment liquid through inlet ports into the conical section of a hydrocyclone, preferably in a region adjacent the apex outlet.

I have discovered that the slime recovery in the overflow of the hydrocyclone can be increased by forcibly and controllably introducing an auxiliary treatment liquid into the conical chamber adjacent the apex, without causing thereby a loss of solids above the top size classification point to the overflow.

The means of introduction of the auxiliary treatment liquid may be one or more inlet ports disposed in the interior periphery of the conical chamber, and preferably so disposed in a tangential manner. The plurality of ports may be located equidistant from each other all in one plane normal to the longitudinal axis of thehydrocyclone, or each may be in a separate plane with each plane normal to the longitudinal axis to permit a stagewise introduction of auxiliary treatment liquid.

Slime removal from the coarse solids may be further increased by operating the hydrocyclone so that the apex discharge is at as high a consistency as may be discharged therethrough and then controllably injecting the auxiliary treatment liquid according to the disclosures herein. The high consistency of the apex discharge may be accomplished by having an apex valve of sufiiciently small size so as to materially reduce the diameter of the apex aperture. As a matter of fact, with this invention, the apex valve may be reduced to a diameter smaller than that through which the coarse solids fractionwill normally discharge so that operating in a conventional manner this apex would be quickly clogged by the high consistency of discharge. Operating in this manner a large portion of the slimes are initially displaced and discharged through the overflow. The injection of the auxiliary treatment liquid maximizes the slime recovery in the overflow.

However, the apex discharge may still be at such a high consistency that plugging or clogging conditions may prevail. lably introducing small amounts of the auxiliary treatment liquid tangentially into the conical chamber sufiiciently close to the apex outlet, not only is the slime removed, but the coarse solids easily discharge without plugging or clogging the apex outlet.

Thus, the forcible and controllable injection of auxiliary treatment liquid into the conical chamber adjacent the apex outlet may function to remove residual slime from the coarse solids fraction as well as to facilitate discharge of the coarse solids from the chamber.

The cause of the limited capability of conventional hydrocyclones to deslime can be summarized as follows:

In operation, the hydrocyclone will create forces up to 2000 times that of gravity, under which conditions the suspended particles act in a manner not entirely predictable. Slirne particles if present tend to act as if they were dissolved'in the liquid in which they are suspended and are thus no longer entirely responsive to the centrifugal forces being exerted on them. The radial-friction forces tending to sweep the particles into the inner vortex have thus become large on these small but high specific surface particles in comparison to the centrifugal forces. Thus, the smaller the particle, the greater the tendency to act as a dissolved solid. Since slime tends to act like the suspending liquid, the percentage of slime reporting I have also found that by forcibly and control-.

high consistency a large portion of the slime-bearing 'feed liquid reports to the overflow. However, the'apex discharge still contains a substantial concentration of slime bearing feed liquid sufficient in many cases to warrant further slime removal. I believe that the workability of my invention hinges on the fact that the slime bearing feed liquid'in the outer vortex is replaccd by the auxiliary treatment liquid and forced into the inner vortex under the critical conditions herein disclosed.

It is therefore one feature of this invention that the coarse solids fraction may also be washed free of the feed suspension liquid by the introduction of an auxiliary treatment liquid differing in substance from the suspension liquid.

It is another feature of this invention that it may be utilized to wash a valuable feed suspension liquid, or carrier liquid, free from coarse solids and to recover such liquid in the overflow substantially undiluted by the auxiliary treatment liquid.

Thus, not only may a feed slurry carrying fine solids and coarse solids suspended in a valuable liquid be classified,'but the valuable liquid may be completely recovered in the fine solids fraction, or overflow, substantially undiluted by the auxiliary treatment liquid (which here might be called a washing liquid) and free of coarse particles above the top size classification point.

Hydrocyclones are also known to be useful in separating solids on the basis of specific gravity differences when such solids are suspended in a liquid medium of an intermediate specific gravity. -Such a liquid medium may comprise only a liquid of specific gravity greater than water, or it may comprise a liquid suspension of extremely fine particles which, in effect, yields a liquid media of intermediate specific gravity. This invention may also be used to advantage in such specific gravity separations to deslime the heavy solids fraction, to remove the liquid media of intermediate specific gravity from the heavy solids fraction or underfiow, and to recover the suspension media in the light solids fraction or overflow substantially undiluted by the auxiliary-treatment liquid and substantially free of heavy solids from the underflow.

The invention may be embodied in several specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, as the scope of the invention is to be determined by the appended claims, and all changes that fall within the meaning and range of equivalents of the claims are therefore intended to be embraced thereby.

Reference is now made to the accompanying drawings.

s Figure l is an idealized functional drawing showing a sectional view of a hydrocyclone of this invention.

Figure 2 is an idealized sectional view of a hydrocyclone showing another embodiment of the invention whereby auxiliary treatment liquid is introduced in a stagewise manner.

Figure 3 is a perspective view of the lower portion of the conical chamber of the hydrocyclone showing a plurality of ports all in one plane adjacent the apex outlet for the inlet of auxiliary treatment liquid tangentially of the hydrocyclone.

Figure 4 is a more detailed perspective view of the hydrocyclone with stagewise washing liquid inlet means.

Figure '5 is a cross-section through section 55 of Figure 6 showing the tangential feed entry.

Figure 6 is a partially cut-away view showing the lower half of the hydrocyclone in sections.

Figure 7 is a cross-section through section 77 of Figure 6 showing an auxiliary treatment liquid inlet-port.

More particularly, in Figures'l and 2 the hydrocyclone 20 havinga longitudinal axis of radial symmetry comprises an upper'cylindrical chamber 21 merging without obstruction into a conical chamber 22. The upper cylindrical chamber 21 is enclosed on its upper edge by a substantially flat endwall 23 through which passes the tubular vortex finder 24 extending inwardly into the body of the hydrocyclone so that its lower end 25 terminates below the place of entry of the tangential feed pipe 26. The upper or discharge end 27 of the vortex finder 24 is shown terminating in'an overflow chamber 28 from which the fines and feed liquid are withdrawn through pipe 29. The lowermost end of the cone and the point of minimum radius is apex 34, where the thickened coarse solids discharge into the apex discharge container 35. The coarse solids fraction is removed from container 35 through conduit 36.

In operation, when a slime-bearing feed slurry is forcibly and tangentially introduced into the cylindrical chamber 21 via feed pipe 26, the interior of the hydrocyclone will contain two axially-aligned concentric liquid vortices rotating at such radial velocities that enormous centrifugal forces substantially in excess of gravity are developed. The outer vortex 30 spirals towards the apex of the conical chamber 22 in a path of ever decreasing radius, whereas the inner vortex 39, having an apex proximate terminus in the lower portion of the hydrocyclone, spirals upwardly and passes from the hydrocyclone through vortex finder 24. If the hydrocyclone is open to the atmosphere, at the apex discharge, then there will be created in the hydrocyclone an uprising air core 50 which will be located at the center of the inner vortex and which will be constantly drawing air into'and through the hydrocyclone. Under operative conditions the coarse suspended solids 32 of the feed suspension are thrown against the peripheral wall of the conical chamber 22 whereas the fine solids 33 are swept into the inner vortex 39. The outer vertex 3% of coarse solids in suspension discharges at the apex outlet 34 while the inner vortex 39 of fine solids in suspension discharges through the vortex finder 24.

As pointed out before, however, under operative conditions slime particles 31 act as though dissolved in the feed liquid (sometimes referred to herein as carrier liquid) and therefore appear in the fractions discharged at each outlet in direct proportion to the amount of feed liquid in each fraction. Thus, while some of the slime particles 31 will be swept into the inner vortex 39 as indicated at 37, the remainder of the slime particles in the conventional hydrocyclone will remain in the outer vortex 30 to be discharged with the coarse solids fraction at apex outlet 34. However, if an auxiliary treatment liquid is forcibly and controllably injected into the conical chamber 22, as by inlet means 40, slime particles in the'outer vortex 30 will be forced into the inner vortex 39 as shown by the arrow 38, thus desliming the coarse solids fraction discharged at 34. v

' Upon further investigation of this phenomena I have found that the maximum. amount of desliming for each volume per unit of time of auxiliary treatment liquid introduced, or maximum desliming efficiency will occur when the auxiliary treatment liquid is forcibly and controllably injected into the conical chamber 22 close to the plane perpendicular to the longitudinal axis of the hydrocyclone at which the inner vortex 39 is believed to commence. The distance H of this plane of maximum desliming efficiency from the apex 34 depends on many variables one of which is the amount of auxiliary treatment liquid introduced but it can be approximately determined by the formula:

wherein T is the underflow volume per unit of time, Q is the feed slurry volume per unit of time, Q is the auxiliary treatment liquid volume per unit of time, and

D is the distance between the vortex finder and the apex.

In Figure 2 auxiliary treatment liquid is introduced into conical chamber 22 by inlet. means 42-which is located above this plane of maximum desliming efliciency having distance H. Desliming will also occur, but it will not be as efficient;in other words, a greater quantity of auxiliary treatment liquid must be .introduced per unit of time to achieve the same amount of desliming. Also in Figure 2 auxiliary treatment liquid may be controllably and forciblyintroduced into conical chamber 22 below this plane of maximumdeslirhing ctliciency and above the apex 34 by way of inlet means 41. Again, the desliming is not as elficient, but it is important to, note that a portion of this treatment liquid tends'to dilute the coarse solids fraction discharged in the underfiow. At any point of introduction of auxiliary treatmentliquid, however, if the'introduction is controlled'within the limitations hereinafter more fullydeveloped, there .will be no loss of coarse solids tothe overflow c ausedby'such introduction nor will there by dilution of the overflow.

The operation of my desliming hydrocyclone, therefore appears to be as follows, referring-again to Figure 1. As the coarse solids 32 proceed along the peripheral wall of the conical chamber 22in the outer vortex 30 of ever decreasing radius, they being to concentrate or pack together forcing fine particles33 and a portion of the carrier or feed liquid with slime particles 31 to be swept into inner vortex 39. 'However, an appreciable quantity of carrier liquid with entrained slime particles 31, is trapped within the interstices of the coarse solids 32. When the soarse solids spiral past the inlet conduit 40 which is continuously introducing auxiliary treatment liquid under pressure into conical chamber 22, the carrier liquid so trapped is replaced by' the treatment liquid and the carrier liquid with its slime content is forced into the inner vortex 39. The exact mechanism of this replacement action has not been exactly determined; in other words, it may be a displacement action, or a dilution and reconcentration action, or a combination of both actions.

In Figure 2, at outlet of conduit 42 the coarse solids are not so greatly concentrated along the peripheral wall of the conical chamber 22 wherefore thec'oarse solids fraction at that point contains a greater volume of carrier liquid and thus a greater quantity of entrained slime. Consequently, more auxiliary treatment liquid mustbe introduced through the inlet conduit 42, than through the inlet conduit 41, to achieve the same result. At the point of outlet of the inletconduit 41 the coarse solids are at their maximum concentration. However, this is below the commencement of .the inner vortex 39 and it becomes diflicult to force the carrier liquid with its contained slimes to flow against the oncomingcoarse solids fraction into the inner vortex 39. As a result there is a dilution of the underfiow. Therefore, below the plane of maximum desliming efiiciency, while there is some desliming, the desliming efiiciency becomes increasingly reduced while the tendency to dilute the underflow becomes greater as the point of introduction of auxiliary treatment liquid approaches the apex outlet 34. This dilution eiiect becomes important when there is a tendency for the coarse solids fraction to clog or plug the apex outlet 34. Thus, as in Figure 2, it may be of advantage to introduce auxiliary treatment liquid'into conical chamber by way of inlet means 42 above the plane of maximum washing efiiciency primarily for desliming purposes, and to introduce a supplementary auixiliary treatment liquid via inlet means 41 below the plane of maxi mum desliming efiiciency not only to deslime but to facilitate discharge.

Auxiliary treatment liquid may be introduced into the conical chamber 22 by way of one inlet means, as illustrated in Figure 1 or more preferably by a plurality of inlet means disposed to the conical chamber 22 so that all of the coarser solids in the outer vortex 30 are exposed to the action of the auxiliary treatment liquid.

Figure 3 showing in idealized perspective the lower portion of the conical chamber 22, illustrates one em bodiment of this invention whereby a plurality of inlet means are used for the introduction of auxiliary liquid. Here inlet pipes 43 are disposed tangentially to the conical chamber 22 so that their outlets 44 are spaced equidistant from each other about the periphery of conical chamber 22 and in the same plane that is normal to the longitudinal axis of the hydrocyclone. This plane is preferably located slightly above the plane of maximum desliming efficiency to permit suflicient time for the auxiliary treatment liquid to enter the interstices of the mass of coarse particles in the outer vortex and to replace tlie slime bearing carrier or feed liquid at the plane of maximum desliming efliciency.

Figures 2, 4 and 6 illustrate another embodiment of this invention whereby a plurality of inlet means for the forcible and controllable introduction of auxiliary treatment liquid are disposed in a stagewise manner to the conical chamber.

Figure 4 is a perspective of the hydrocyclone particularly showing the manner of construction of the stagewise inlet pipes. In Figure 4 hydrocyclone 20- comprises conical section 122, upper cylindrical section 121 enclosed by upper plate 170. Feed to the hydrocyclone enters through pipe 126 and overflow discharge from the vortex finder (not shown) is removed through dis charge pipe 129. The apex 134 of the hydrocyclone is connected to tail pipe 172 from whence is removed the deslimed coarse solids. Washing liquid under pressure is fed to the hydrocyclone through main-header 173 comprising a 1" section of pipe from which there is taken off a plurality of A pipes to serve as means for introducing the washing liquid to the hydrocyclone. These pipes 140 through 146 are suitably valved to control the flow through each pipe and enter the hydrocyclone through ports 180 to 186 (inclusive) respectively.

Figure 5 shows a sectional view of the feed-entry port with the feed pipe 126 entering the conical section 121 tangentially at point 200 so as to create a swirling motion therein. Also shown in this section is vortex finder 124 from which the overflow discharge is removed.

Figure 6. shows the hydrocyclone in section, particularly showing the detail of the controllable apex valve. The lower end of conical section 122 is attached to apex valve assembly 190. This assembly comprises housing 191, constriction rings 192 and 192', and rubber valve 193. The adjustable tailpiece 194 is threaded through the housing so as to be movable thereupon. In the adjustable tailpiece there are provided inserts for attaching turning rods 195 and 196. If it is desired to decrease is threaded further up the housing 191, thereby compressing rubber valve 193 causing it to extend further into the discharge passage 197 causing a further constric tion. In operating the hydrocyclone it is preferred that the diameter of this valve be decreased until incipient clogging is reached and then the auxiliary treatment liquid is turned on so as to begin the desliming operation.

Figure 7 shows a view through section 7-7 of Figure 6. Feed entry pipe 143 enters conical section 122 tangentially at point 198 and in the same general direction as the rotation of the outer vortex at that point.

It is mandatory that the auxiliary treatment liquid 'be introduced into the conical chamber of the hydrocyclone under certain critical conditions. For instance, the pressure or hydrostatic head under which the auxiliary treatment liquid to be introduced is critical. It should be as that of the outer vortex flow' at thepoint of introduction, which, in any case, would be towards the apex. Another condition, I believe, for maximum desliming efl'iciency is that the entrance velocity of the auxiliary treatment liquid should be approximately equal to that of the outer vortex at the point of introduction. If the entrance velocity be too great the overflow will become diluted with the auxiliary treatment liquid. If the entrance velocity be too low more slime will appear in the underflow. Another condition of maximum efficiency is that the volume of auxiliary treatment liquid introduced per unit of time should be at a maximum which is just short of that conducive to unstable operation. This volume per unit of time is dependent on many variables but it can be approximately determined; Thus, the maximum volume per unit of time (V) of auxiliary treatment liquid to be introduced at any given plane normal to the longitudinal axis to the hydrocyclone can be determined from the formula:

wherein a' is the distance of the plane from the apex, D is the distance between the apex and the vortex finder, Q is the feed slurry volume per unit of time, Q, is the auxiliary treatment liquid volume per unit of time, S is the volume of underflow solids per unit of time and V is the volume per unit of time of auxiliary treatment liquid, supplementary or otherwise, being introduced elsewhere into the conical chamber.

The auxiliary treatment liquid may comprise the same liquid as the carrier liquid, or it may comprise a liquid differing in substance from the carrier liquid. When the liquids are the same, the overflow from the desliming hydrocyclone of the invention after treatment by gravity settling or other methods to remove the fine and slime particles, may be reintroduced into the hydrocyclone as auxiliary treatment liquid, or as a supplementary auxiliary treatment liquid.

As noted before, this invention can be utilized to wash coarse solids free of the carrier liquid in which they have been suspended by introducing an auxiliary treatment liquid dilfering in substance from the suspension liquid. Similarly, this invention may be utilized to wash a valuable suspension liquid or carrier liquid free from coarse solids and to recover such liquid in the overflow substan ially undiluted by the auxiliary treatment liquid. Under such circumstances the same critical conditions for the introduction of the auxiliary treatment liquid will prevail and the same conditions that exist for maximum desliming etficiency should be observed in order to have maximum washing efficiency.

Example I A commercial installation has been made to deslime a high quality chemical sand, wherein purity requirements made necessary a final product with less than 0.5% slime. This installation comprised two stages of hydrocyclones, a primary stage of two hydrocyclones operating in parallel on the feed slurry, and 'a secondary stage of two hydrocyclones for treating the overflows from the first units. The secondary stage was necessary to recover fine sand from the overflows of the primary hydrocyclones. The feed stream to the primary stage had such a high concentration that a heavy media effect occurred 8 within the primary hydrocyclones, without the introduction' of desliming water, so that finesand was discharged in the primary overflows. In the hydrocyclones used in this installation the following measurements were noted:

Primary Secondary Diameter of Cylindrical Section...-. 36 30". Length of Cylindrical Section 18..- l6". Included Angle of Conical Section... 30 20. Feed Nozzle 8" Std. Pipe 6" Std. Pipe. Overflow Nozzle 10 Std. Pipe 6 Std. Pipe. Diameter of Underflow Nozz 3 2%.

Means of Desliming Water Introduc: None.

ion. Dilgmeter of Desliming Water Inlet ipes. Distance of Desllming Water Inlet Piiile from Apex:

It was observed that practically all sand was recovered in this installation but, without the introduction of desliming water to the primary stage, at an unsatisfactory slime content of 0.6%; Consequently, in accordance with the disclosures herein, desliming water was introduced into the primary hydrocyclones. Slime content in the primary underflow was reduced from 0.6% to 0.03% resulting in an increase in slime removal from 82.6% to 99.1%. When combined with the product from the secondary hydrocyclones, the resultant slime content was only 0.12%. A comparison of the results in the primary stage with and without the introduction of desliming water is striking as shown by the following table:

Without With Deslilning Desliming Water per Water per 36 1537- 36 Hydrodrocyclone cyclone Feet}; 1

ressure, p. s. g 3 3 Percent Solids 45% 45% Percent 200 Mesh Slimes 3.0 3.0 G. P. M. Slurry 962 962 Tons/Hour Solids 151. 2 151. 2 G. P. M. Desliming Water 0 200 Overflow:

Percent Solids 10.83 10.50 Percent 200 Mesh Slimes 20. 8 23. 8 Tons/Hour Solids 18.2 18. 9 Underfiow:

Percent Solids 79. 2 77. 9 Percent 200 Mesh Slimes 0.6 0.03 Tons/Hour Solids 133. 0 132. 3 Percent Removal of Slimes To Overflow 82. 6 99.1 Percent; Dcsliming Water of Total Water Fed to Cyclone 0 20.2

From these results it can be seen that in applying the teachings of this invention to the primary hydrocyclones the amount of slime is reduced to a minimum in the underflow. Furthermore as indicated by the solids concentration figures there was no substantial dilution of the overflow by the desliming water.

The results also form a striking comparison with the previous gravitational classifying operation employed. Approximately 2000 G. P. M. of fresh water were required in the gravitational classification operation to achieve a washed sand that would pass specifications but not equal the desliming water results. Furthermore, appreciable quantities of high value fine sand were lost in the process. However, in the desliming water hydrocyclones, only a total of 400500 G. P. M. of desliming water were required to obtain the much reduced slime content, and with the primary hydrocyclones 95.6% of the sand was recovered, in the underflows. In combining the underflows of the primary and secondary hydrocyclones 99.9% of the sand was recovered, thus yielding further economies. y,

9 Example ll As another typical application of this invention a slime bearing coal slurry was treated in accordance with the disclosures herein:

A conventional 9" diameter hydrocyclone of galvanized sheet metal was constructed with a 2 standard pipe feed entry and 3.2 /2" 1. D. copperftubing overflow. The cone had a length of 23 inches and an included angle of 20. Four standard 1''' pipes were brazed to the conical section at 90 around a circle normal to the longitudinal axis of the hydrocyclone, at a distance along this axis from the apex corresponding to 20.6% of the total distance between the apex outlet and the vortex finder, below the plane of maximum desliming efliciency. Through flexible connections from regulation valves on a 2" manifold to the tangential inlets, desliming water under pressure was admitted to the hydrocyclone. Water rate was measured by a calibrated orifice on the 2" line. In performing tests, rate and analysis samples were taken of both overflow and underflow streams as well as feed pressures and desliming water rates. From this data it was possible to calculate the feed conditions. Tests were made with and without the introduction of desliming water.

Without With Desliming Desliming Water Water Overfiow Rate, G. P. M 9.0 57.1

Underflow Rate, G. P. M 44. 0 59.0

Feed Solids Rate, Tons/Hour 5. 80 7. 57

Feed Solid Concentration, Wt. Percent 23.0 28. 18

Overflow Solids Concentration, Wt. Percent..- 8. 71 9. 53

Underfiow Solid Concentration, Wt. Percent- 38.0 37. 96

Percent of Total volume to Underflow 47. 4 50. 9

Percent of Total water to Underflow 39. 4 42. 7

Percent of Total Solids to underflow- 80. 7 S1. 3

Percent -200 Mesh Slimes in Feed"-.- 31.3 22. 9

Percent 200 Mesh Slimes in Overflow 92. 8 86. 2

Percent --200 Mesh Slimes in Underfiow 16. 6 8. 4 Percent Solid Recovery in Underflow:

+20 Mesh- 100.0 100.0

lim 7 42.9 29. 8

Percent Desliming Water of Total Feed Volume 0. 0 14. 5

Percent Desliming Water of Total Feed Water. 0 18.0

From these results it can be seen that the amount of slime is reduced to a minimum in the underflow without any loss of solids of top size to the overflow even though the desliming 'water was introduced below the plane of maximum desliming efficiency. Noteworthy too, as indicated by the solids concentration figures, there was no substantial dilution of the overflow by the desliming liquid.

This application is a continuation-in-part of my application Serial No. 231,512 filed June 14, 1951, and titled Process and Apparatus for Classifying Solid Material in a Hydrocyclone.

Weclaim:

1. A hydrocyclone comprising a chamber defined by a substantially conical wall and a base end closure plate, with means for inducing inner and outer vortices about the longitudinal axis of the cone, said inner vortex being coextensive with a portion of said axis, feed inlet means disposed at the base end of said chamber, open discharge means for an eflluent fraction bearing readilysettleable solids disposed at the apex end of said chamher to provide for the continuous discharge of said fraction from the hydrocyclone during operation, discharge meansfor an efiluent fraction bearing less-readily-settleable solids coaxial with said chamber and discharging through said closure means; said hydrocyclone being ing substantially into a significant plane which is normal to the longitudinal axis and being the plane in which the apex-proximate terminus of the inner vortex lies.

1 2. A hydrocyclone according to claim 1 wherein the said feed inlet means is tangentially disposed and thereby constitutes said vortex inducing means by reason of the fact that the energy of the influent feed is utilized to supply all the energy required to bring about the vortical movement of the hydrocyclone contents.

3.' A hydrocyclone according to claim 1 wherein the said auxiliary liquid injection means comprises a conduit adapted to discharge said auxiliary liquid into said chamber in a direction substantially tangential to the circle of intersection of said significant plane with the said conical chamber wall.

'4. A hydrocyclone according to claim 1 wherein the auxiliary liquid injection means comprises a conduit adapted to discharge'said auxiliary liquid into said chamber in a direction such that the directional vector of said auxiliary liquid which lies in said significant plane is substantially tangential to the circle of intersection of said plane with said conical chamber wall, while that directional vector' which is parallel to the axis of the hydrocyclone is directed toward the apex thereof.

5. A hydrocyclone according to claim 1 wherein the auxiliary liquid injection means comprises a plurality of conduits spacedly disposed from each other in the said significant plane.

6. A hydrocyclone according to claim 1 wherein the said auxiliary treatment liquid injection means is spaced from the discharge means for the fraction bearing readilysettleable solids by a distance measured along the axis of said hydrocyclone to be slightly greater than the distance H found in applying the formula wherein T is the volume of readilysettleable solids fraction per unit of time, Q is the feed suspension volume per unit of time, Q is the auxiliary treatment liquid volume per unit oftime, and D is the distance along said axis between the readily-settleable solids discharge means and the less-readily-settleable solids discharge means.

7. A hydrocycloneaccording to claim 1 wherein supplemental auxiliary liquid injection means are provided, said supplemental auxiliary liquid'injection means being adapted to discharge into a second plane spacedly disposed along the hydrocyclone axis from said significant plane, and parallel thereto.

8. A hydrocyclone according to claim 7 wherein said second plane is spacedly disposed from the said significant plane along the hydrocyclone axis in the direction of the said hydrocyclone base.

9. A hydrocyclone according to claim 7 wherein said second plane is spacedly disposed from the said significant plane along the hydrocyclone axis in the direction of the hydrocyclone apex.

10. A hydrocyclone according to claim 1 wherein supplemental auxiliary liquid injection means are provided, said supplemental auxiliary liquid injection means discharging into a plurality of additional planes spacedly disposed along the hydrocyclone axis from said significant plane and parallel thereto; at least one of said additional planes being disposed away from the significant plane in the direction of the hydrocyclone base, and at least one of said additional planes being disposed away from the significant plane in the direction of the hydrocyclone apex.

11. A hydrocyclone comprising a chamber defined by a substantially conical wall and a base end closure plate, with means for inducing inner and outer vortices about thelongitudinal axis of the cone, said inner vortex being coextensive with a portion of said axis, feed inlet means disposed at the base end of said chamber, open discharge means for an'efiluent fraction bearing readily-settleable solids disposed at the apex endrof said chamber to pro vide forthe continuous discharge of said fraction from the hydrocyclone during operation, discharge means for an effiuent fraction bearing less-readily-settleable solids coaxial with said chamber and discharging through said closure means; said hydrocyclone being characterized by auxiliary liquid injection means adapted to discharge into a plane which is parallel to and spacedly disposed from a significant plane, said significant plane being disposed normal to the longitudinal axis of the hydrocyclone, and being the plane in Which the apex-proximate terminus of the inner vortex lies.

12. A hydrocyclone according to claim 11 wherein said plane of disposition of said auxiliary liquid injection means is at a fixed distance from said significant plane in the direction of the hydrocyclone base.

1 3. A hydrocyclone according to claim 11 wherein said plane of disposition of said auxiliary liquid injection means is at a fixed distance from said significant plane in the direction of the hydrocyclone apex.

14. A hydrocyclone comprising a chamber defined by a substantially conical wall and a base end closure plate, with means for inducing inner and outer vortices about the longitudinal axis of the cone, said inner vortex being coextensive with a portion of said axis, feed inlet means disposed at the base end of said chamber, open discharge means for an efiiuent fraction bearing readily-settleable solids disposed at the apex end of said chamber to provide for the continuous discharge of said fraction from the hydrocyclone during operation, discharge means for an effluent fraction bearing less-readily-settleable solids coaxial with said chamber and discharging through said closure means; said hydrocyclone being characterized by auxiliary liquid injection means adapted to discharge into a plurality of planes parallel to and spacedly disposed from a significant plane, said significant plane being the axisnormal plane in which the apex-proximate terminus of the inner vortex lies; at least one of said plurality of planes being disposed at a fixed distance from the said significant plane in the direction of the hydrocyclone base, and atleast another of the said plurality of planes being disposed at a fixed distance from the said significant plane in the direction of the hydrocyclone apex.

15. The continuous method for separating from a liquid suspension bearing both readily-settleable solids and lessreadily-settleable solids a fraction bearing said readilysettleable solids and a fraction bearing said less-readilysettleable solids which comprises establishing and maintaining an enclosed generally conical body of the suspension, inducing a dual-vortical movement of said body whereby the outer portion thereof moves helically about and along the axis of rotation toward the apex of said conical body while the inner portion moves helically about and along the axis of rotation toward the base of the said conical body, removing said readily-settleable solids fraction at the apex of said conical body, removing said less-readily-settleable fraction near the base of said body; said continuous method being characterized by the introduction of auxiliary treatment liquid into said vortically moving body in that portion of the outer vortex which is proximate the significant axis-normal plane which passes through the apex-proximate terminus of the inner vortex.

16. The continuous method according to claim 15, wherein the vortical movement is induced by a substantially tangential introduction of the feed suspension.

17. The continuous method according to claim 15 wherein the said introduction of auxiliary treatment liquid into said vortically moving body is substantially tangential thereto.

18. The continuous method according to claim 15, wherein the said auxiliary treatment liquid is introduced in a direction such that the directional vector of said auxiliary liquid which lies in said significant plane is substantially tangential to the outer extremity of said body at its circle of intersection with. saids'ignificant plane,

i2 while the directional vector which is parallel to the rotational axis is directed toward'the apex of said body.

19.. The continuous method according to claim 15 wherein the said introduction of auxiliary treatment liquid is eflfected at a plurality of points in said significant plane.

20. The continuous method according to claim 15 Wherein'said auxiliary treatment liquid introduction is eifected at a distance measured along the said axis of rotation slightly greater than the distance H found by applying the formula wherein T is the volume of the readily-settleable solids fraction per unit of time, Q is the feed suspension volume per unit of time, Q is the auxiliary treatment liquid volume per unit of time, and D is the distance along said axis of rotation between the zone of removal of said readily-settleable solids fraction and said less-readilysettleable solids fraction;

2l. The continuous method according to claim 15 wherein supplemental auxiliary treatment liquid is introduced at a second plane within said body, said second plane being spacedly disposed along the axis of rotation from said significant plane and parallel thereto.

22.--The continuous method accord ng to claim 21, wherein saidsecond plane is spacedly disposed from the said significant plane along the axis of rotation in the direction of the apex of the conical body.

23. The continuous method according to claim 21,

wherein said second plane is spacedly disposed from the said significant plane along the axis of rotation in the direction of the base of the'conical body.

24. The continuous method according to claim 15, wherein supplemental auxiliary'liquid is introduced to the conical body at a plurality of additional planes spacedly disposed along the axis of rotation of said body from the said significant plane and parallel thereto; at least one of the said additional planes being disposed away from the significant plane in the direction of the base of the conical body, and at least one of the said additional planes being disposed away from the significant plane in the direction. of the apex of the conical body.

25. The continuous method for separating from a liquid suspension bearing both readily-settleable solids and less-readily-settleable solids a fraction bearing said readily-settleable solids and a fraction bearing less-readilysettleable solids which comprises the steps of establishing and maintaining an enclosed, generally conical body of the suspension, inducing a dual-vertical movement of said body whereby the outer portion thereof moves helically about and along the axis of rotation toward the apex of said conical body while the inner portion moves helically about and along a portion of the axis of rotation toward the base of said conical body; said continuous methodbeing characterized by the introduction of auxiliary treatment liquid into said vortically moving body in a plane which is parallel to and spacedly disposed from a significant plane, said significant plane being the axisnormal plane which passes through the apex-proximate terminus of the inner vortex.

26. The continuous method according to claim 25, wherein said plane of disposition of auxiliary treatment liquid introduction is at a fixed distance from said significant plane in the direction of the base of the conical body.

27. The continuous method according to claim 25, wherein said plane of disposition of said auxiliary treatment liquid introduction is at a fixed distance from said significant plane in the direction of the apex of the conical body.

28. The continuous method for separating from a liquid suspension bearing both readily-settleable solids and less-readilysettleable solids a fraction bearing said less-readily-settleable solids which comprises establishing and maintaining an enclosed, generally conical body of the suspension, inducing a dual-vortical movement of said body whereby the outer portion thereof moves helically about and along the axis of rotation toward the apex of said conical body while the inner portion moves helically about and along the axis of rotation toward the base of said conical body; said continuous method being characterized by the introduction of auxiliary treatment liquid into said vortically moving body in a plurality of planes parallel to and spacedly disposed from a significant plane, said significant plane being the plane which is normal to the axis of rotation of the body and in which the apex-proximate terminus of the inner vortex lies; at least one of said plurality of planes being disposed at a fixed distance from the said significant plane in the direction of the base of the conical body, and at least another of the said plurality of planes being disposed at a fixed distance from the said significant plane in the direction of the apex of the conical body.

References Cited in the file of this patent UNITED STATES PATENTS

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