CA1215942A

CA1215942A - Hydraulic separating method and apparatus

Info

Publication number: CA1215942A
Application number: CA000456111A
Authority: CA
Inventors: Clinton A. Hollingsworth
Original assignee: CH Development and Sales Inc
Current assignee: CH Development and Sales Inc
Priority date: 1984-01-27
Filing date: 1984-06-07
Publication date: 1986-12-30
Also published as: GB2160445B; GB2153261B; AU2919884A; ZA844362B; GB2160445A; AU567347B2; GB8415902D0; GB8415895D0; GB2153261A

Abstract

ABSTRACT OF THE INVENTION

Apparatus and method for the separation of hydrous slurries having particles of different settling velocities, such as slurries containing minerals including ore solids, coal and sands. The slurry solids are introduced into the upper portion of a tank that has a perforated annular barrier between its upper and lower portions. Separating conditions are maintained in the upper portion of the tank. Means is provided for removing a separated overflow fraction from the upper tank portion and separate means surrounded by the annular barrier serves to remove an underflow fraction.
Preferably the slurry is continuously introduced tangentially into the upper portion of the tank to cause swirling movement of the body of material.

Description

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HYDRAULIC SEPARATING METHOD AND APPARATUS

This invention relates generally to methods and apparatus for separating solid particles of hydrous slurries or pulps into fractions containing particles of different settling velocities. The invention is applicable to various slurries, such as those containing minerals like ore solids, coal and sands.
Many types of apparatus and methods are used commercially for the hydraulic separation of solid particles of slurries or pulps which have solid particles of different settling velocities.
Generally such apparatus consists of a tank having means for introducing the slurry, means at the upper end of the tank for removing an overflow, and means for removing an underflow from a lower portion of the tank. One g2~594~

-2-particular type of apparatus makes use of a so-called con-striction plate, or perforat d barrier, which separates the upper portion of the tank into which the feed slurry is introduced, from the lower portion of the tank. In opera-5 tion, water is continuously introduced into the lower portionof the tank and flows upwardly through the perforations or openings in the barrier~ whereby separation is carried out in the upper portion of the tank, in accordance with the set-tling velocities of the solid particles. The means for 10 withdrawing the underflow is arranged to rem~ve the solid particles of greater settling velocity from a region adjacent and above the constriction plate, and may consist of one or more pipes communicating through the side walls of the tank.
Equipment and methods of this type have not provided a 15 separating action which is as precise or sharp as is as desired, and in addition the apparatus is relatively large for a given capacity.

In general it is an object of the present invention to provide an improved hydraulic separating method and apparatus 20 which produces improved separation between solid particles of different settling velocities, and is relatively compact in size cn~pared to conventional prior art separating apparatus of oomparable capacity.

Another object is to provide a hydraulic separating method 25 and apparatus which has improved means and method for re-moving the separated underflow fraction.

Another object is to provide a method and apparatus which is not critical with respect to variations in the solids of the feed slurry, such as variations in the oGmposition of the 30 solid particles, the relative proportions between particles of greater and lower settling velocities.

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In general, the present invention comprises an upright tank having overflcw discharge means at the upper end of the tank for removing an overflow fraction, and a perforated barrier, or constriction plate disposed between upper and lower 5 portions of the tank. Means is provided for introducing feed slurry into the upper tank portion, and means for introducing water into the lower tank portion whereby water flows up-wardly through the perforations of the barrier into the upper tank portion. Separating conditions are maintained in the 10 upper ~ank portion to cause particles of greater settling velocity to prcgress dcwnwardly and particles of lower settling velocity to progress upwardly for discharge in the overflow. Means is further provided for removing an under-flow from a region immediately above the barrier, which 15 provides outlet openings adjacent the upper side of the barrier and radially spaced from the adjacent side walls of the tank. Preferably the means for introducing the feed slurry connects tangentially with the upper tank portion, thereby causing swirling movement of the body of material in 20 the upper tank portion. The means for removing an underflow fraction preferably consists of a conical member in the upper tank portion that is aligned with the axis of the tank and positioned with its annular base coincident with the barrier, the outlet openings being in the base portion. Also the last 25 named means includes means below the barrier for collecting and removing the underflow. The method comprises continu-ously supplying feed slurry to the upper tank portion, continuously supplying water to the lower tank portion belaw the barrier to cause water to flow continuously through ~he 30 barrier and into the upper tank portion. The introduction of the feed slurry and water is such that separation of solid particles takes place within the upper tank portion whereby particles of greater settling velocity progress downwardly ~2~42 into a region adjacent the barrier and solid particles of lesser settling velocity progress upwardly and discharge from the upper end of the tank in an overflcw. m e solid par-ticles of greater settling rate are removed from an annular 5 region adjacent the upper side of the barrier, the removal being a direction toward the axis of the tank. me rem~ved solids of greater settling velocity are collected below the barrier and delivered to the exterior of the tank as an underflow fraction. Preferably the solid particles of 10 greater settling velocity are directed toward the annular region of the barrier as they progress downwardly. Also the feed slurry is preferably introduced tangentially into the upper tank portion to cause swirling movement about the axis of the tank.

15 Additional objects and features of the invention will appear from the following description in which the preferred embodi-ments are set forth in detail in conjunction with the acccm-panying drawing.

Referring to the drawin~:

20 Figure 1 is a side elevational view of apparatus in accordance with the present invention.

Figure 2 is a detail in section of a portion of the barrier 14.

Figure 3 is a plane view of Figure 1.

25 Figure 4 is a detail in section illustrating another embcdiment of perforated barrier.

Figure 5 is a schematic view illustrating the apparatus as in a commercial installation.

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Figure 6 is a detail in section showing a gate for control-ling discharge of feed miaterial into the apparatus.

m e apparatus as shown in Figures 1 and 2 consist of an upright tank lO which is annular in horizontal section. The 5 upper end of the tank is provided with overflow discharge means consisting of a weir 11, which may be of the saw-tcoth type as illustrated, together with the collection launder 12.
The collected overflow is discharged through conduit or pipe 130 The upper and lcwer portions lOa and lOb of the tank are 10 separati~d by the annular barrier 14. This barrier is of ~he constriction plate type, being provided with perforations or openings through which water may pass. Pipe 15 serves as means for introducing feed slurry into the upper tank por-tion, and preferably connects tangentially through one side 15 of the tank, as illustrated in Fii~ures 1 and 2. Pipe 16 serves as means for introducing water into the lower tank portion lOb, and may likewise be connected tangentially through one side wall of the tank.

m e means for re ving underflow material is indicated 20 generally at 17. In the form illustrated it includes a conical shaped member 18 which has its axis coincident with the vertical axis of the tank, and its base coincident with the barrier 14. m e lower base portion 19 is provided with a plurality of evenly and circumferentially spaced outlet 25 openings 21, which serve to receive solids from a region immediately above the barrier 14. Extending below the barrier there is a collecting n~n~er 22 which in this in-stance is an inverted cone, and which serves to collect ~aterial flowing through the openings 21. m e upper end of 30 member 22 has a diameter substantially the same as the diameter of the base of cone 18, and it is disposed coinci-~z~ss4æ

dent with the barrier 14. A pipe 23 connects with the lc~Jerend of the collecting memker 22, and extends through the lower end of the ta~nk. It is shown provided wi~h a valve 24, which may be of the pinch tube type, and which may be ar-5 ranged for manual or automatic operation. An additional pipeand valve 26 and 27 are shown connected to the lower portion of the tank, and may be used for clean-out operations.

Figure 2 shows a portion of the barrier plate 14. The holes 14a are evenly distributed about the circumferential area of 10 the annular plate 14 and preferably are sloped whereby discharging water tends to imFart swirling move~ent to material immediately above the plate, the direction of such swirling movement being the same as that produced by tangen-tial introduction of feed slurry through pipe 15. The axes 15 of holes 14a are normal to radii extending from the central ~ axis of the tank.

Operation of the apparatus described above, and the method of the invention, are as follows. A hydrous feed slurry ~e.g.
one containing a natural sand~ is continuously introduced 20 into the upper tank portion through pipe 14, at a relatively constant rate. Water is continuously introduced into the lower tank portion below the barrier 14, through pipe 16.
The water pressure maintained in the tank below the barrier 14 is sufficient to maintain flow of water upwardly through 25 the openings 14a in the barrier, and into the material in the upper tank portion. It has been found that by maintaining the body of material in the upper tank portion swirling about the central tank axis, some solid particles of greater settling velocity ~e.g. the coarser particles of sand) tend 30 to progress outwardly toward the sides of the tank, and downwardly toward the barrier 14. Solid particles of lower -- ~LZ~S94~

settling velocity progress upwardly and are discharged over the weir 11 as an overflow. me solid particles of greater settling velocities accumulate in the region immediately above the annular barrier 14 and surrounding the base of the 5 conical member 18. In this region the material is in con-tinual swirling movement and also movement inwardly toward the base of the cone 18 and outlet openings 21. Such solid particles progress through the outlet openings 21 and from thence into the collecting member 22, for discharge through 10 the underflow pipe 23. Movement of material adjacent the upper surface of the barrier prevents accumulation of solids in localized regions of the barrier such as would interfere with proper flow through the openings 21. Although the body material in the upper tank portion lOa is caused to swirl 15 about the central axis of the tank, it is sufficiently quiesoe nt as not to interfere with effective separating action. m e water pressure in the tank portion lOb is such as to ~aintain upward flow of water throu~h the barrier opening, that is of sufficient rate to prevent solids from 20Passing dcwnwardly through the openings.

Commercial operations of the apparatus and method have demonstrated that it provides improved separation between the overflow and underflow fractions, and that the apparatus has relatively high capacity for its size. Another feature of 2sthe apparatus and method is that it is not unduly sensitive to changes in the ccmposition of the slurry solids, or in the rate with which the solids are introduced into the tank. For example, when the apparatus and method are used to sep~rate the coarse and fine particles of a slurry consisting of sand, 30the relative amount of coarse and fine sand particles may vary considerably without interfering with the desired sharpness of separation. The same applies to the rate of ~Z~LS9~Z

intrcduction of slurry solids into the tank. The separating action does not depend upon maintenance of a condition of teter, which is dee~.ed to be due to the continual swirling of material in the upper tank p~rtion.

5 Another embodiment of the invention is shown in Figure 4.
The constriction plate 29 in this instance is dished dcwn-wardly, or in other words it conforms generally to the surface of a truncated cone. Such a sloped constriction plate tends to aid movement of the solid particles of greater 10 settling velocity toward the openings 21. Preferably the holes 29a are likewise sloped as shown in Figure 2.

Figure 5 shows a commercial installation of the apparatus.
The tank 10 is carried by the uprights 30, and pipe 15 is connected to a feed hopper 31. The feed hopper has a screen 15 33 through which feed slurry is introduced, and the lower end of the hopper is connected through valve 32 with pipe 16.

Figure 1 and 6 show an adjustable flow control gate 36 for controlling discharge of feed slurry into the tank from pipe 15. It is adjustably carried by bolts 37 which are accom-20~odated in slots 38 in the gate. Adjusting the position ofthis gate serves to control the rate of swirling movement of material in the upper tank portion lOa for optimum separation under given operating conditions (e.g., character of fe~d slurry~.

25 An example of the invention is as follows:

Example 1 The apparatus was constructed substantially as shown in Figures 1 and 2, and was installed as shown in Figure 4. me ~L2~S942 portion lOa o the tank was cylindrical and 4.5 feet in diameter. The top of the tank ~as about 5 feet above the constriction plate 14. The cone 18 was 1.5 ~eet in height, with a base diameter of 2.25 feet. The slope of the cone 18 5 was about 45. The base of the cone was provided with six openings 21, each having a circumferential length of about 6 inches, and a height of about 3 inches. A natural sand was used to prepare the feed slurry. The coarse particles of the sand were plus 48 mesh (Tylor Standard Screen). The re-lO mainder of the solids were relatively finer particles. The slurry was prepared to have an optimum solids content of about 17%, although in practice this varied scmewhat during an operating run. The slurry was ~ed from the hopper 31 through pipe 15 into the tank at a hydrostatic head of about 15 18 inches. me feed rate was about lO0 tons per hour of solid particles contained in the slurry. A screen analysis made o the solid particles in the underflow was as follows.

PRODUCT SCREEN ANALYSIS (% CUMULATIVE, TYLER) +14 +28 +48 +lO0 Coarse 2.9 49.4 94.3 99.3 Fines -- 0.3 15.2 60.1 -It will be evident from the above that the apparatus and method makes possible relatively sharp separation between the coarse and fine solid particles. Over an operating period of 250ne hour, during which the feed slurry delivered 100 tons of sand as provided by a sand dredging operation, typical sampling showed that 94.3% of the coarse solids of the underflow were plus 48 mesh, and only 15.2% of the fines were contained in the underflow.

~2~sg~2 When the invention is used for the processing of sand and similar mineral slurries, it may be referred to as a sizer, since the larger coarse sand particles are separated from the smaller fine particles. However, the invention is applicable 5 to other mineral containing slurries where the objective is to effect separation according to differences in settling velocities, rather than sizing. While the sharpness of separation obtained in a single stage operation is generally sufficient for most ccmmercial purposes, a fraction (e.g.
10 underflow) can be subjected to a second stage separating operation using the same apparatus, or using conventional equipment such as hydrocyclones.

Claims

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

1. Apparatus for separating the solid particles of a hydrous feed slurry into overflow and underflow fractions having solid particles differing in their settling velocities, comprising an upright tank, the upper end of the tank having overflow discharge means for removing an overflow fraction, an annular constriction barrier having holes there-through disposed in the tank to divide the interior of the tank into upper and lower regions, the barrier having outer and inner radially spaced peripheral margins, the upper tank portion having a side wall that is circular in horizontal section, means for introducing the hydrous feed slurry tangentially into the upper tank portion interme-diate the top of the tank and the barrier to thereby cause material in the upper region to swirl about the central vertical axis of the tank, means for introducing water into the lower tank region of the tank so that water flows upwardly through the holes in the barrier and into the upper region to establish separating conditions in the upper region whereby particles of greater settling velocity are permitted to pro-gress downwardly into a region adjacent the upper side of the barrier and particles of lower settling velocity are caused to progress up-wardly to the overflow discharge means for removal in an overflow fraction, means for removing and collecting the particles of greater settling velocity in an overflow fraction from the region adjacent the upper side of the barrier, said removing and collecting means including circumferentially spaced outlet openings adjacent the inner peripheral margin of the annular barrier for removing the underflow from said last named region, and means comprising walls sloped downwardly toward the barrier and extending over the area surrounded by the inner peripheral margin of the barrier for directing settling particles of greater settling velocity into said last named region adjacent the upper side of the barrier, said collecting means also including means disposed below said area for receiving and for separately deliverying the underflow fraction from the tank.

2. Apparatus as in Claim 1 in which said outlet openings are circum-ferentially spaced about the central axis of the tank.

3. Apparatus as in Claim 1 in which said deflecting means for direct-ing settling particles comprises a conical member in the upper tank portion aligned with the axis of the tank and positioned with its circular base portion coincident with the inner margin of the barrier, the circumferencially spaced outlet openings being in said base portion.

4. Apparatus as in Claim 3 in which the collecting means below the barrier for collecting the underflow fraction passing through the outlet openings is an inverted cone having an upper end of a diameter substantially the same as the lower end of the conical member in the upper tank portion.

5. Apparatus as in Claim 3 in which the collecting means comprises an inverted conical shaped member in the lower tank portion and aligned with the central axis of the tank, said member having its upper open end disposed adjacent the barrier and below said outlet openings.

6. Apparatus as in Claim 1 in which the holes in the barrier are sloped to discharge water flowing therethrough in the direction of the swirling movement of material in the upper tank portion.

7. Apparatus as in Claim 1 in which the barrier is sloped downwardly toward the outlet openings.

8. Apparatus as in Claim 1 in which the means for introducing feed slurry comprises a pipe communicating tangentially through an opening in a side wall portion of the tank, and a gate for controlling the flow

Claim 8 continued of feed slurry through said opening into the upper tank portion thereby controlling the rate of swirling movement of material of the feed slurry therein, said gate being adjustably carried by the wall of the tank adjacent said opening in said tank wall portion.

9. The method of separating a feed slurry of solid particles having different settling velocities into an underflow fraction containing solid particles of greater settling velocity and an overflow fraction containing solid particles of lower settling velocity, the method making use of an upright tank having means for removing an overflow fraction from its upper end, an annular constriction barrier having inner and outer radially spaced peripheral margins disposed in the tank to form upper and lower regions in the tank, the barrier having open-ings therein establishing communication between upper and lower re-gions, the upper portion of the tank being circular in horizontal section, and the tank also having means for introducing a hydrous feed slurry into the upper tank portion; the method comprising continuously supplying hydrous feed slurry tangentially into the upper tank portion and into the upper region intermediate the upper end of the tank and the barrier to cause the material in the upper region to swirl about the central vertical axis of the tank, supplying water to the lower tank portion so that water flows continuously through the openings in the barrier and into the swirling material in the upper region, whereby hydraulic separation of solid particles in the slurry takes place during swirling movement of the slurry in the upper region, in that solid particles of greater settling velocity move downwardly, in that solid particles of lower settling velocity are permitted to progress upwardly and be discharged from the upper end of the tank in an over-flow, and in that solid particles of greater settling velocity are permitted to progress downwardly into an annular region adjacent the upper side of the annular barrier, and removing and separately collecting the solid particles of greater settling velocity from an annular region adjacent the upper side of the annular barrier, said removal being through circumferentially spaced outlet openings adjacent the inner peripheral margin of the annular barrier, separately discharging the collected solid underflow particles from the tank, and deflecting solid under flow particles moving downwardly toward the area surrounded by the annular constriction barrier, outwardly from the central axis of the tank and into the region adjacent the upper side of the barrier.

10. A method as in Claim 9 in which the water flowing through the openings of the barrier is discharged therefrom in the direction of swirling movement of material of the feed slurry in the upper tank region.

11. A method as in Claim 9 in which introduction of the feed slurry is adjusted to control the rate of swirling movement.