Process and apparatus for classifying solid materials in a hydrocyclone

Αρη! 8, 1958 d. a. dahlstrom 2,829,771

PROCESS AND APPARATUS FOR CLASSIFYING SOLID

MATERIALS IN A HYDROCYCLONE

Filed Jan. 6. 1953 5 Sheets-Sheet 1

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Slime Rich Fine Solids Fraction

Feed Slurry (Coarse, Fine 8 Slime Particles in Liquid Suspension)

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Auxiliary Treatment Liquid

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a q Coarse Solids o Fine Solids

Slime

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A^20 '36

Washed Deslimed Coarse Solids Fraction

INVENTOR

Donald A. Dahlstrom

ATTORNI

Apnl 8, 1958 d. a. dahlstrom 2,829,771

PROCESS AND APPARATUS FOR CLASSIFYING SOLID MATERIALS IN A HYDROCYCLONE

Sheets-Sheet 2

Filed Jan. 6., 1953

Slime Rich Fine Solids

<img file="US2829771A_D0004.tif" />

Washed Deslimed Coarse Solids Fraction

INVENTOR

Donald A. Dahlstrom

BY

<img file="US2829771A_D0005.tif" />

ATTORNEY

Filed Jan. 6, 1953

April 8, 1958. d. a. dahlstrom 2,829,771

PROCESS AND APPARATUS FOR CLASSIFYING SOLID ’ ’

MATERIALS IN A HYDROCYCLONE

Sheets-Sheet 3

Fig. 3.

<img file="US2829771A_D0006.tif" />

INVENTOR

BY

Donald A. Dahlstrom

<img file="US2829771A_D0007.tif" />

ATTORNEY

April 8, 1958 d. a. dahlstrom 2,829,771

PROCESS AND APPARATUS FOR CLASSIFYING SOLID ’ ’ , , „ MATERIALS IN A HYDROCYCLONE

Filed Jan. 6. 1953

Sheets-Sheet 4

Fig. 4.

<img file="US2829771A_D0008.tif" />

INVENTOR Donald A. Dahlstrom by ca-zIuaai nuufet*.

ATTORNEY

April 8, 1958 d. a. dahlstrom 2,829,771

PROCESS AND APPARATUS FOR CLASSIFYING SOLID

MATERIALS IN A HYDROCYCLONE

Filed Jan. 6, 1953 5 Sheets-Sheet 5

<img file="US2829771A_D0009.tif" />

ATTORNEY

2,829,771

Patented Apr. 8, 1958

United States Patent Office tides below 2 to 10 microns in size. An object of this invention is therefore to develop a hydrocyclone classifier which will more efficiently and effectively deslime liquid suspensions than has been heretofore possible.

δ 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 10 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 15 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 20 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 the hydrocyclone, or each may be in a separate plane with each 25 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 30 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 sufficiently small size so as to materially reduce the diameter of the apex aper35 ture. 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 fraction will normally discharge so that operating in a conventional manner this apex would be quickly clogged by the high consistency ⁴⁰ 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. I have also found that by forcibly and control-, lably introducing small amounts of the auxiliary treatment liquid tangentially into the conical chamber sufficiently 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 _rK. 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: _n 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. Slime 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, γθ 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

2,829,771

PROCESS AND APPARATUS FOR GLASSIFYING SOLID MATERIALS IN A HYDROCYCLONE

Donald A. Dahlstrom, Deerfield, Π1., assignor to DorrOliver Incorporated, a corporation of Delaware

Application January 6,1953, Serial No. 329,838

Claims. (CI. 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 effect 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 par2,829,771 to the apex and being discharged therethrough with the coarser materials will be a function of the quantity of feed liquid being discharged through this same opening. By constricting the apex outlet to obtain a discharge of 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 replaced 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 underflow, 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.

Figure 1 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 5—5 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 7—7 of Figure 6 showing an auxiliary treatment liquid inlet-port.

More particularly, in Figures 1 and 2 the hydrocyclone having a 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 apexproximate 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 vortex 30 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.

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:

<img file="US2829771A_D0010.tif" />

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

3,829,771

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 efficiency 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 forcibly introduced into conical chamber 22 below this plane of maximum desliming efficiency and above the apex 34 by way of inlet means 41. Again, the desliming is not as efficient, but it is important to note that a portion of this treatment liquid tends to dilute the coarse solids fraction discharged in the underflow. At any point of introduction of auxiliary treatment liquid, however, if the introduction is controlled within the limitations hereinafter more fully developed, there will be no loss of coarse solids to the overflow caused by such introduction nor will there by dilution of the overflow. 20 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 22 in the outer vortex 30 of ever decreasing radius, they being to concentrate or 25 pack together forcing fine particles 33 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 ³⁰32. 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 ³⁵inner 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 ⁴⁰are not so greatly concentrated along the peripheral wall of the conical chamber 22 wherefore the coarse 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 must be 45 introduced through the inlet conduit 42, than through the inlet conduit 41, to achieve the same result. At the point of outlet of the inlet conduit 41 the coarse solids are at their maximum concentration. However, this is below the commencement of the inner vortex 39 and it 50 becomes difficult to force the carrier liquid with its contained slimes to flow against the oncoming coarse solids fraction into the inner vortex 39. As a result there is a dilution of the underflow. Therefore, below the plane of maximum desliming efficiency, while there is some 55 desliming, the desliming efficiency 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 effect becomes important when there is a tend- 60 ency 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 efficiency primarily for desliming pur- 65 poses, and to introduce a supplementary auixiliary treatment liquid via inlet means 41 below the plane of maximum desliming efficiency not only to deslime but to facilitate discharge.

Auxiliary treatment liquid may be introduced into the 70 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. 75

Figure 3 showing in idealized perspective the lower portion of the conical chamber 22, illustrates one embodiment of this invention whereby a plurality of inlet means are used for the introduction of auxiliary liquid. 5 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 pref10 erably located slightly above the plane of maximum desliming efficiency to permit sufficient time for the auxiliary treatment liquid to enter the interstices of the mass of coarse particles in the outer vortex and to replace the slime bearing carrier or feed liquid at the 15 plane of maximum desliming efficiency.

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 discharge 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 W 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 •the size of the apex opening, then the adjustable tailpiece 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 constriction. 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 is introduced should at least be sufficient to force the liquid into the outer vortex, but insufficient to disrupt the flow patterns within the conical chamber so that coarser particles are discharged in the overflow and the auxiliary treatment liquid short-circuits to the underflow, as well as possibly diluting the overflow. Likewise the volume per unit of time of auxiliary treatment liquid to be introduced is critical. It should be

2,820,771 at least sufficient to effectively deslime, but insufficient to cause coarse particles to be discharged in the overflow and to. substantially dilute the overflow with auxiliarytreatmentliquid.

For maximum desliming efficiency there are many 5 critical conditions, some of which already have been noted, the remainder being noted as follows. For example, the auxiliary treatment liquid should be introduced tangentially and furthermore I am inclined to believe that such introduction should be at the same angle 10 as that of the outer vortex flow at the point of introduction, which, in any case, would be towards the apex. Another condition, I believe, for maximum desliming efficiency is that the entrance velocity of the auxiliary treatment liquid should be approximately equal to that 15 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 wiil appear in the underflow. Another condition of maximum efficiency 20 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, 25 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:

, ³⁰ wherein d is the distance of the plane from the apex, D is the distance between the apex and the vortex finder, Q_P is the feed slurry volume per unit of time, Q_A is the 35 auxiliary treatment liquid volume per unit of time, S_uis 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. 40

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 45 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 50 coarse solids free of the carrier liquid in which they have been suspended by introducing an auxiliary treatment liquid differing in substance from the suspension ’ liquid. Similarly, this invention may be utilized to wash a valuable suspension liquid or carrier liquid free from 55 coarse solids and to recover such liquid in the overflow substantially 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 60 desliming efficiency should be observed in order to have maximum washing efficiency.

Example I

A commercial installation has been made to deslime a 65 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 70 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 75 within the primary hydrocyclones, without the introduction of desliming water, so that fine sand was discharged in the primary overflows. In the hydrocyclones used in this installation the following measurements were noted:

Diameter of Cylindrical Section_____

Length of Cylindrical Section_______

Included Angle of Conical Section___

Feed Nozzle_________________________

Overflow Nozzle.___________________

Diameter of Underflow Nozzle______

Means of Desliming Water Introduction.

Diameter of Desliming Water Inlet Pipes.

Distance of Desliming Water Inlet Pige from Apex:

# 3_______________________________ # 4_______________________________ # 5_______________________________ # 6_______________________________ # 7_______________________________

Primary

Secondary

36..............

18..............

30°._____________

Std. Pipe....

Std. Pipe...

3_______________

Stagewise_______

1_______________

30.

16.

20°.

Std. Pipe.

Std. Pipe.

2K.

None.

10..____________

14______________

18______________

23______________

28______________

33______________

38______________

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 Desliming Water per 36 Hydrocyclone

With Desliming Water per 36 Hydrocyclone

Feed: Pressure, p. s. i. g.........................

Percent Solids_____________________________

Percent —200 Mesh Slimes_________________

G. P. M. Slurry___________________________

Tons/Hour Solids_________________________

G. P. M. Desliming Water.................

Overflow: Percent Solids.............................

Percent —200Mesh Slimes.._______________

Tons/Hour Solids_________________________

Underflow:

Percent Solids_____________________________

Percent —200 Mesh Slimes_________________

Tons/Hour Solids.........................

Percent Removal of Slimes To Overflow______

Percent Desliming Water of Total Water Fed to Cyclone..______________________________

3¾

45.0

3.0

962

151.2

200

10.50 23.8 18.9

77.9

0.03 132.3

99.1

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 tire 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 400-500 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.

2,829,771

Example II

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 a 2Ά I. D. copper tubing 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 efficiency. 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

Feed Pressure, p. s. i________________________

Feed Slurry Rate, G. P. M____________________

Desliming Water Rate, G. P. M._.____________

Overflow Rate, G. P. M_______________________

Underflow Rate, G. P. M_-._.________________

Feed Solids Rate, Tons/Hour_________________

Feed Solid Concentration, Wt. Percent________

Overflow Solids Concentration, Wt. PercentUnderflow Solid Concentration, Wt. PercentPercent of Total volume to Underflow-_ ______

Percent of Total water to Underflow--——.. Percent of Total Solids to underflow.__________

Percent —200 Mesh Slimes in Feed..—________

Percent —200 Mesh Slimes in Overflow____

Percent —200 Mesh Slimes in Underflow. _____ Percent Solid Recovery in Underflow:

-1-20 Mesh————___________

20x40_____________________________________

40x60__________________________...

60x100—_______________________________

100x140___________________________________

140x200 _..._ —200 Coarse Solids.——________....

—200 Slimes.....

Percent Desliming Water of Total Feed Volume. Percent Desliming Water of Total Feed Water.

4¼ 93.0

49.0 44.0 5.80 23.0 8.71 38.0 47.4 39.4 80.7 31.3 92.8 16.6

100.0

99.8

98.4

95.4

87.8

77.5 . 78.3

42.9

0.0 0

99.2 16.9 57.1 59.0 7.57

28.18 9.53

37.96 50.9 42.7

81.3

22.9 86.2

8.4

100.0 99.9 98.4 88.6 74.3 68.4

71.3

29.8

14.5

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 lune 14, 1951, and titled Process and Apparatus for Classifying Solid Material in a Hydrocyclone.