AU596592B2 - Hydraulic classifying procedure and means - Google Patents

Description

Au-_Al 5 6 648 8 6 PCTWORLD INTLLECTUA POERT ORGANI~ZATION 3 M_''_ERNATIONAL APPLICATION PUBLISH 5 U ER E P EPIZ ATION TET PT (21) International Application Number: PCT/F186/00045 (81) Designated States: AT (European patent), AU, DE (European patent), DK, FR (European patent), GB (Eu- (22) International Filing Date: 5 May 1986 (05.05.86) ropean patent), HU, JP, SE I.European patent), SU, Us.

(31) Priority Application Number; 851763 Pul~ished (32) Priority Date: 3 May 1985 (03.05.85) With internatonal search report.

In English translation (filed in Finnish).

(33) Priority Country: FL (71) Applicant (for all designated States except US): LAROX QY [Fl/Fl]; Pallonkatu 10, SF-53900 Lappeenranta (F71).

(72) Inventor; and Inventor/Applicant (or US only) OVASKAINEN, Pertti [Fl/Fl]; SF-54250 Rapattila (171). P. 15 J/AN 1987 (74) Agent: PAT' NTTITOIMISTO QY HEINANEN AB; Annankatu 3 1-33 C, SF-00100 Helsinki 10 (FL1). 7 ASTRAI IAN -4 DEC N86 PATIENT OFFICE (54)Titig. HYDRAULIC CLASSIFYING PROCEDURE AN1,D MEANS l'ht6 LJ.UWuent woiain-S the klnjendment a made ujadex section 49, (57) Abstract Hydraulic classifying proce-4 dure and apparatus wherein particulate material transported by a Fzand is correct for p-rbntDB.

l iquid is c4ivided in. a centrifugal field estaiblished in a cylindrical, substl itially vertical classifying sparte into a fines product con- h.

sistin~g of lighter particles, this product becoming separated in the centre of the centrifugal field, C4 and a coarse product consisting of

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heavier particles, which is separat-U ed o *n the outer margin of the centrifugal field and descends in a I spiralling flow conforming to margin of the field, to the lower 8-al end of the classifying space, As 1 taught by the invention, the coarse 3 S 6 b 7 product is removed from the centrifugal field through an annular gap formed on the lower end of the classifying space using in aid a separate liquid flow conducted tangentially in relation to 1 the centrifugal field and running4 tangentially to said gap. The coarse peocluct may be removed together with the liquid flow to a hydrocyclone (10) which separates the coarse product, whereafter the liquid can be returned x. the classifying process to serve as fluid medium in the classification takkig place in the centrifugal field.

WO 86/06653 PCT/FI86/00045 HYDRAULIC CLASSIFYING PROCEDURE AND MEANS The present invention concerns a hydraulic classifying procedure wherein particulate material transported by a liquid is divided, in a centrifugal field established in a cylindrical, substantially vrtical classifying space, into a fines product consisting of lighter particles, this product becoming separated in the centre of the centrifugal field, and into a coarse product consisting of heavier particles, this iltter pvoduct being separated on the outer margin of the centrifugal field and descending in a siralling f lIw following the margin of the field, to the lower end of the classifying space.

The commonest means employed towards hydraulic classification of particulate material is the hydrocyclone, usually consisting of a cylindrical upper part and-a conical lower part. The hydrocyclone divides the material to be classified into a fines product, which is removed through the top end of the cyclone, and a coarse product, which is removed from the lower end of the cyclone, i.e., through an aperture at the tip of the coical lower part. In addition to the partly conical hydrocyclones mentioned, cyclones with level bottom have been used, in which separation of the fines and coarse products and their dep rture take place in substantially like manner. Moreover, such classifying means are knwon in which the coarse product is removed tangentially with the aid of a passage commencing on the periphery or at the bottom of the means.

The classifying carried out with said means of prior art is encumbered by the drawback that the coarse product is removed by a liquid classifying fluid among which there is also finely dividd matter contained in the material that is being classified and which, ideally, should end up among the fines product. Finely divided matter is removed al(9g with the coarse product in at least equal proprotion as classifying fluid is removed, in other words, the more such matter is removed the higd.r is thus the ratio of coarse and fine product quantities, When the classification constir -2 tutes part of a wet grinding process, where optimally said ratio is about 100 to 300%, the separation sharpness of classification carried out with means of prior art, that is the proportion of particles smaller than a give!i limit size contained in the material being classified which are successfully separated to form the fines product, is typically only about 50%, and occasionally it is even less than The most commonly employed hydrocyclones have the further drawback that regulation of said limit size during operation is nearly impossible. Hardly any ways of regulation are known other than regulating the size of the coarse product removal aperture on the lower end of the cyclone; even this is rarely applied, owing to practical 15 difficulties.

The present invention provides a hydraulic a classifying procedure comprising transporting particulate a 9 material by a liquid into a centrifugal field established in a cylindrical, substantially vertical classifying space wherein said material is divided into a fines product consisting of lighter particles which is separated in the center of the centrifugal field, and a coarse product consisting of heavier particles which is separated on the outer margin of the centrifugal field and descends in a 0.0 0: 25 spiralling flow, conforming to the margin of the field, to the lower end of the classifying space, providing an S annular aperture, which forms an unbroken annular gap surrounding a substantially round closing memiber placed at the lower end of the classifying space and separating the S 30 .a into upper and lower cylindrical portions, providing a separate liquid from a separate supply passage adjacent to said aperture, the liquid flowing tangentially in relation to the centrifugal field and running tangentially to said aperture, and removing the coarse product from the centrifugal field through said annular 2a aperture utilizing said separate liquid, the coarse product as passed through

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*5 S S. S S S S S *5 -3said annular aperture being removed by said separate liquid.

By using a pure liquid flow conducted tangentially in relation to the centrifugal field, one gains the effect that with the coarse product are entrained fewer, if any, finely divided particles having a size below the fines limit size, than before. The amount of liquid flow can be adjusted to be such that the liquid fluid supplied into the classifying process together with the material to be 10 classified does not participate at all in the removal of coarse product and, instead, in its entirety departs together with the fines. It is also possible to increase said liquid flow even further, whereby it can be applied 15 in adjusting the limit size between the fines and coarse 15 products. When necessary, the centrifugal field can be boosted with said liquid flow so that the coarse product is caused to separate at a sufficient rate even in those instances in which the limiting size between the fines and 6*a* coarse products is small.

By the design of the invention, a secondary classification step has been created in the region of the annular gap, its operation being based on the fact that the velocity and direction, in the gap, of the separate liquid flow supplied tangentially in relation to the 25 centrifugal field determine that particles size of which the removal as coarse product, enforced by the centrifugal field, is possible. Since the coarse product has not yet, at this stage, finally departed from the first classifying step taking place in the classifying space proper, said secondary classification influences the separation limit in such way that particles finer than the limit size which have been entrained will return to the classifying space, and by this route further to join the fines product. If the coarse product were brought into contact with the separate liquid flow removing it, only after it has I r- 3a departed from the classifying space proper, the result would merely be dilution of the coarse product flow.

An embodiment of the invention is characterized in that the coarse product is separated from said separate liquid flow in a hydrocyclone, whereafter the liquid is returned to the classifying process to serve as fluid medium in the classification taking place in the centrifugal field. The advantage gained is then that the liquid balance in the classification is not changed, compared with classical hydrocyclone separation. This is of particular significance in solid material wet grinding processes, in which the solid matter content of the sludges which they produce is usually stronger limited owing to further processing steps.

15 The present invention further provides an apparatus for classifying particulate material, comprising a cylindrical, substantially vertical classifying chamber constituting a space for a centrifugal field, a feed passage for conducting material to be classified and a liquid serving as a fluid medium into the classifying chamber, a removal aperture in said chamber for removing a fines product consisting of lighter particles which become separated at the center of the classifying chamber, a substantially round closing member disposed at the lower end of the cylindrical classifying chamber to separate the chamber into upper and lower cylindrical portions and to form an annular aperture, forming an unbroken annular gap between said closing member and a w-l of the chamber, g 30 said annular aperture constituting a removal aperture for 30 a coarse product consisting of heavier particles which separates on the outer margin of the classifying chamber and descends in the form of a spiralling flow to the lower end of the classifying chamber, and a tangential passage to the centrifugal field and connected to the chamber adjacent to said annular aperture for the removal of the -r I 3b coarse product utilizing a separate liquid supplied from a separate supply passage and conducted through said tangential passage, said tangential passage also running tangentially in relation to said aperture, said separate supply passage being adjacent to said aperture and said separate liquid flowing tangentially in relation to the centrifugal field and running tangentially to said aperture.

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.o *e o• 00 e 0 e0 o WO 86/06653 PCT/FI86/00045 4 -Cemsikoting o5 llchter particles, which utpara-4ri the conrpi the classifying space, and the coarse product consisting-f heavier particles, which separates on the outer margin oft classifying space and further separates in the form of piralling, descending flow in the lower part of the classif g space. The means is characterized in that the coarse prd ct removal aperture consists of an annular gap on the lof- end of the classifying space, and that with the means, a aid gap, connects a passage which is tangential to the cen ugal field, so that in removing the coarse prodlr," one arfutilize a liquid flow conducted through this separate paaget i u Pn in -ta ngent i yt t -it t gapn The invention is described ii *rtail in the following with the aid of examples, referring to th, *iachad drawing, wherein:- Fig. I presents a hydraulic classifying apparatus aicording to the invention, Fig. 2 shbws the lower part of the cylindrical classifying space belonging to the apparatus of Fig. 1, in section II-II as indicated in Fig. 1, Fig. 3 presentc par- of the classifying space of the apparatus in accordance with another embodiment of the invention, and Fig. 4 shows the classifying apparatus of the invention, installed as a component in a grinding circuit.

In Figs I and 2 is depicted a hydraulic classifying apparatus which divides particulate material composed of various-sized particles and transported by a liquid, such as water for instance, into a fines priduct consisting of lighter particles and a coarse product consisting of heavier particles. This classification takes place in a vertical, cylindrical classifying space I in a centrifugal field created by the tangential supply of material to be classified and of liquid serving as fluid medium, this centrifugal field separating the fines product to reside in the centre of the classifying space and the coarse product to its outer margin. The WO 86/06653 PCT/F186/00045 Imtoral to be classified and the fluid are in spiralling rotary motion in the classifying space 1, this motion lifting Ln the centre of the space the fines product to the removal aperture 2 located calse to the upper end of said space, and on the outer margin of the space by gravity action urging the coarse product to the coarse product removal aperture 3 in the lower part of said space.

The apparatus of Figs I and 2 comprises on the side of the cylindrical classifying space 1, as essential components, a feed passage 4 for material to be classified and for fluid medium, tangentially connecting with the upper end of the classifyir n space; a passage for removing fines product and fluid conducting same, commencing at the removal aperture 2; a r~rnd closing plate 6 in the lower part of the classifying space, this plate confning the coarse product removal aperture to be an annular gap 3 between this plate and the cylindrical wall of the classifying spa.e; and horizontal passages 7a,7b connecting tangentially with the lower end of the classifying space for removal of the coarse product that has passed through the gap, with the aid of a separate liquid flow which runs tangentially to said gap. The liquid flow coming through the passage 7a is supplied through the aperture 9a into the lower end of the classifying space, immediately under the annular gap 3, where ,t is set in spiralling motion conforming to the outer margin of said space and which is a direct continuation of the spiralli.ng motion present htgh6 up, in the classifying space I proper, and it departs by the aperture 9b into the passage 7b. The passage 7a has been provided with a control valve, indicated in Fig. i with reference numeral 8.

The liquid flow departing by the passage 7b transports the coarse product to a hydrocyclone 10, wher, the coarse product is separated to go to the removal aperture 11 at the conical end of the cyclone and the liquid, to the vertical removal passage 12 commencing in the upper part of the cyclone.

In Fig. 3 is depicted an embodiment of the classifying apparatus which differs from that of Fig. I in the respect that the lower part 13 of the cylindrical classifying space i has been enlarged and on the boundary 15 between the wider lower part of the space WO 86/06653 6 PCT/FI86/00045 and the narrower part 14 thereabove has been disposed a conical, vertically movable closing member 16. The size of the annular coarse product removal aperture 3 between the closing member 16 kAod the classifying space 3 can be regulated in this embodiment with the aid of the positioning oa said closing member.

It is essential in the preented classifying apparatus of the invention that the removal of the coarse product through the passage 7 with the aid of a liquid flow conducted tangentially in relation to the classifying space I and not participating in the classifying process prevents any finely divided material, which belongs to the fines product, from being ntrained with the coarse product. The liquid flow can be regulated by mens of the control valve 8 in said passage, and the flow can be arranged to be such, for instance, that it takes care alone by itself of the coarse product removal, whereby the fluid coming into the classifying space I together with the material to be classified will in its entirety depart along with the fines product and there will be no fluid medium flow in one direction nor in the other at the coarse product removal aperture 3. It is also possible to adjust the flow coming through the passage 7 into the classifying space I to be greater than the flow departing along with the coarse product, in which case part of said liquid will go along with the fines product. It is possible by such regulation to enlarge or diminish the limit size of the fines and coarse product particles.

In Fig. 4 is presented a solid material grinding circuit comprising a classifying space I and a separator cyclone 10, which may both be as illustrated in Fig. 1. The material, consisting in part of not previously processed material (reference numeral 17) and in part of Scoarse product separated by the hydrocyclone 10 (reference numeral 11) is ground in the mill 18, and after grinding, the material is mixed together with water obtained from the cyclone 10 and it is fed by the aid of the pump 19, tangentially, into the centrifugal field in the classifying space 1. The fines product separated by the classification departs fro' the process, while the water departing at the same time is replaced with a water flow Introduced through the passage 7, this flow carrying the coarse product to the

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WO 86/06653 PCT/F186/00045 separator cyclIone 10 and, as has been stated, thereaf ter return ing to serve as f luid rnedi.~m in the classif fcation taking place in the classifying -space 1. The solid matter content of e-ach particular flow has been entered in Fig. 4) as a percentage figure.

It is obvious to a person sIkit'led in the art that different embodimnents of the invention are not confined to th'e exmples presented in the foregoinTj and that they m'ay, rather, vary within the scope of the claims following below.

Claims (1)

1. 7- li.ll 8 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A hydraulic classifying procedure comprising transporting particulate material by a liquid into a centrifugal field established in a cylindrical, substantially vertical classifying space wherein said material is divided into a fines product consisting of lighter particles which is separated in thp center of the centrifugal field, and a coarse product consisting of heavier particles which Is separated on the outer margin of the centrifugal field and descends in a spiralling flow, conforming to the margin of the field, to the lower end of the classifying space, providing an annular aperture, which forms an unbroken annular gap surrounding o* a substantially round closing member placed at the lower end of the classifying space and separating the into upper and lower cylindrical portions, providing a separate liquid from a separate supply passage adjacent to said aperture, the liquid flowing tangentially in relation to the centrifugal field and running tangentially to said aperture, and removing the coarse product from the centrifugal field through said annular aperture utilizing said separate liquid, the coarse product as passed through said annular aperture being removed by said separate liquid. 2. A hydraulic classifying procedure according to claim S1 i, further comprising separating said coarse product from said liquid in a hydrocyclone, and thereafter returning the liquid to the classifying procedue to serve as fluid medium in the classificatia taking place in the centrifugal field. 3. An apparatus for classifying particulate material, comprising a cylindrical, substantially vertical classifying thamber constituting a space for a centrifugal field, a feed passage for conducting material to be classified and a liquid serving as a fluid medium into the 9 classifying chamber, a removal aperture in said chamber for removing a fines product consisting of lighter particles which become separated at the center of the classifying chamber, a substantially round closing member disposed at the lower end of the cylindrical classifying chamber to separate the chamber into upper and lower cylindrical portions and to form an annular aperture, forming an unbroken annular gap between said closing member and a wall of the chamber, said annular aperture constituting a removal aperture for a coarse product consisting of heavier particles which separates on the outer margin of the classifying chamber and descends in the form of a spiralling flow to the lower end of the classifying chamber, and a tangential passage to the centrifugal field and connected to the chamber adjacent to said annular aperture for the removal of the coarse product utilizing a separate liquid supplied from a goo 0 separate supply passage and conducted through said tangential passage, said tangential passage allso running tangentially in relation to said aperture, said separate supply passage being adjacent to said aperture and said 5 separate liquid flowing tangentially in relation to the centrifugal field and running tangentially to said aperture. 4. An apparatus according to claim 3, wherein said classifying chamber widens at its lower end, and said closing member is vertically movable for regulating the size of said annular aperture. PFI An apparatus according to claim 3, wherein said tangential passage is connected to a hydrocyclone for separating the coarse product from the liquid, and there is provided a connecting passage and pump for connecting said hydrocyclone to said feed passage of the classifying chamber, whereby the U.quid is ret.urned to the classifying chamber to serve as -Q-uid mediuini in the classification which takes place in the cent, fugal field. DATED this 22nd day of January 1990 LAROX QY Patent Attorneys for the Applicant: @055 F.B. RICE CO. A-S 5 I 0