GB2128905A - Apparatus for separating mixtures of solids in particular mixtures of minerals into at least three products of different specific gravity - Google Patents

Abstract

This invention relates to an apparatus for separating mixtures of solids, in particular mixtures of minerals, into at least three products of different specific gravity by means of a single dense medium of substantially unvaried density, comprising a hollow body (1) divided into at least one pair of communicating consecutive chambers (3, 4), each provided with tangential (9, 10) and axial (5, 6, 8) conduits arranged to allow the introduction and discharge of the products concerned, characterised in that of said pair of chambers one is substantially conical (3) and the other is substantially cylindrical (4). <IMAGE>

Description

SPECIFICATION Apparatus for separating mixtures of solids, in particular mixtures of minerals, into at least three products of different specific gravity Italian PatentApplication No. 27291 A/77 in the name ofthe presentapplicantdescribes an apparatus for separating mixtures solids of different specific gravity, in particular minerals, comprising a pair of cylindrical chambers in series, into each ofwhich a different density aqueous suspension, defined as the dense separation medium, is fed in orderto produce a final separation ofthefed mixture into three different products.

The dense medium is known to be generally constituted by an aqueous suspension of a finely ground mineral, such as magnetite, oran alloy, such asferrosilicon,ableto produce the requiredsepara- tion in a centrifugal field.

Afirst object of the present invention is to produce the sharp separation of a mixture of the aforesaid type into at leastthree different products of different specific gravity by using an apparatus for separation in a centrifugal field which is able to operate with a single dense separation medium withoutthe need to vary the density ofthis latter. In other words, a single dense medium of unvaried density is to be used instead oftwo different densities as provided by the aforesaid patent application in order to obtain separation into three products.

The fact of operating with a single dense medium of unvaried density provides the obvious advantage of considerable plant simplification with corresponding reduced investment and operating costs, in comparison with the plant provided by the known art involving two dense feed media of different densities.

Afurther object of the invention is to reduce the total quantity of dense medium necessary for separation compared with the known art, so as to be able to attain afurtherreduction in operating costs,thus saving energy.

Afurther object of the invention is to attain a sharper and more precise separation ofthefinal products.

These objects are attained according to the invention by an apparatus for separating mixtures of solids, in particular mixtures of minerals, into at leastthree products of different specific gravity by means of a single dense medium of substantially unvaried density, comprising a hollow body divided into at least one pair of communicating consecutive chambers, each provided with tangential and axial conduits arranged to allowthe introduction and discharge of the products concerned, characterised in that of said pair of chambers one is substantially conical and the other substantially cylindrical.

Within the basic idea ofthe invention, i.e. of associating a conical chamber with a cylindrical chamber in series, it is possible in practice to provide variousembodimentsofthis apparatus, all with this basic characteristic.

The. characteristics and advantages of the invention and of its various embodiments will be more apparent from the description given hereinafter of these embodiments with reference to the figures of the accompanying drawings.

These embodiments are in no way to be considered as limitative ofthe invention and merely illustrate various possible constructional forms.

Figure 1 is an axial longitudinal section through the apparatus.

Figure 2 is a cross-section on the line ll-ll of Figure 1.

Figure 3 is a view analogous to that of Figure 2 but illustrating a modified embodiment.

Figures 4,5,6 and 7 are views analogous to that of Figure 1 but illustrating a further four embodiments.

With reference to Figure 1, an apparatus according to the invention is constituted by a hollow body 1 divided by a transverse wall 2 into a pair of consecutive chambers3 and 4, ofwhich the first is of substantially conical form with a cylindrical portion in proximityto the wall 2, and the second is entirely of cylindrical form. Thetwo chambers communicate by way of a tubular conduit 5 disposed in the wall 2 along the axis of the body 1.

The apex ofthe conical chamber3, positioned oppositethewall 2, is open at 6, whereas at the other end ofthe body ofthe apparatus the end ofthe cylindrical chamber4 is provided with a front wall 7 in which an axial conduit8 is disposed.

In proximity to the transverse wall 2, both chambers are provided with a tangentially mounted conduit, namely the chamber 3 with the conduit9 and the chamber4with the conduit 10. These conduits can be either cylindrical pipes which are tangentially inserted into the body 1 as shown in Figure 2, or pipes which are connected to the wall of the body 1 by means of a volute as shown in Figure 3. An analogous conduit 11 is mounted on the body 1 in proximity to thefrontwall 7.

The mixture of solids to be separated, together with the dense separation medium, is fed through the conduit9 into the chamber 3 ata suitable pressure, which is obtained for example by means of a charging vessel or a pump. High-density separation occurs in this chamber. For example if the dense medium has a density of 2.6 g/cm3, The separation which can be attained in the conical chamberwill be at a density of 2.9-3 g/cm3 according to the rates at which the output flows are regulated, and the type and particle size distribution ofthe dense medium used.Thus a higher density product leavesthe apex6 ofthe chamber 3, while a lower density product is also separated in said chamber and flows in the axial direction towards the chamber 4, into which it penetrates through the conduit S together with part of the dense medium.

Further dense medium is fed through the conduit 11 and into the chamber4, so asto inducetheseparation in this latter of a first product of higher densitythan that ofthe mixture fed through 5, said product being discharged through the conduit 10, and a second product of lower density, which is discharged through the conduit 8.

Thusthe apparatus of Figure 1 separates a mixture into three products, namely a product of higher density, a product of intermediate density and a product of lower density.

If separation into four products is required, according to the invention the apparatus shown in Figure 4 is suitable, this differing from that of Figure 1 by the presence of a third chamber 12, of cylindrical form, provided with a pair of tangential conduits 13 and 14 and an axial discharge conduit 15 mounted in a front wall 16. In this case, the product of lower density which emerges from the discharge conduits of the chamber4acts asthefeed tothe chamber 12 in which further separation takes place into a product of higher density which leaves through the discharge conduit 13, and a product of lower density which is discharged through the conduit 15. Thus four products are obtained from the discharge conduits 6, 10,13 and 15, and consist of fractions of the feed through 9, in decreasing order of density.

Theapparatusof Figure4can also beadvan- tageouslyusedfortheproduction of only three products by combining the discharged products from 10 and 13 into a single product. In this case, the separation carried out in 12 represents an improvement ofthat carried out in 4, i.e. able to recover those fractions of heavy mineral which, in an apparatus comprising only two chambers, would be entrained into the axial discharge stream and lost with any tailings.

The arrangement ofthe apparatus during operation can be as shown in Figures 1 and 2, i.e. with the longitudinal axis disposed horizontally, or alternativeliy with the axis inclined either with the apex ofthe conical chamber pointing upwards or with it pointing downwards, according to the specific separation requirements. A modification of the invention is shown in Figure 5, in which the hollow body 1 is of V configuration, with a conical chamber3 communicating with a cylindrical chamber 4 byway of a passage conduit 5 provided in an angular connection piece 17, of which the length and curvature are predetermined in orderto limit pressure drop of the vortexflow as it passes from one chamberto the otherthrough the conduit 5. This modification has the advantage of facilitating discharge ofthe separated products from 6 and 8.

Further modifications with respect to the apparatus of Figure 5 and to the apparatus of Figure 1 when of inclined longitudinal axis can be attained by reversing the positions ofthe conduit 11 forfeeding dense medium into the cylindrical chamber and the discharge conduit 10 for product of intermediate density with respecttothe positions shown in said figures, i.e.

by mounting the conduitforfeeding dense medium into the chamber 4 in proximity to the transverse wall 2 (or angular connection piece 17), and mounting the tangential product outlet conduit in proximity to the frontwall 7.

Afurther modificationof the invention is shown by way of example in Figure 6, in which the chamber4 slightlytapers towards the centre ofthe apparatus.

This slight conicity can facilitate the discharge of the product (in the case oftwo-chamber apparatus) or of the products (in the case ofthree-chamber apparatus) from the tangential outlets ofthe thus tapered cylindrical chamber, in that the tangential velocity inside the separators increases between the zones of greater diameter (where the dense medium is fed) and the zones of smaller diameter (wherethe tangential discharge is located), due to the law of momentum conservation in vortex motion fluids. Consequently, and in particularwhen a considerable quantity of product is to be discharged tangentially, this arrangement can result in improved operation of the apparatus. Afurther modification ofthe apparatus is shown diagrammatically in Figure 7.Briefly, the difference between the apparatus shown in Figures 1 and 7 is simplythatthe position of the conical and cylindrical chambers is reversed. In the version of Figure 7, the feed mixture is fed into the conical chamber 3together with the dense medium through the conduit 9. In chamber 3, by adjusting the density ofthe dense feed medium, its pressure and the type and particle size distribution ofthe solid used for producing the dense suspension, it is possible to obtain low-density separation. In this manner, a product of lower density is obtained atthe discharge conduit 18,whereasa heavy product is discharged from the apex 19 ofthe chamberto form the feed to the cylindrical chamber 4.

A dense medium having a density hig her than that ofthe dense medium fed through 9 is fed into the chamber4through a tangential conduit 20. The feed to the chamber4isthus separated into two products, namelyaproductwhich leaves through the discharge conduit21 and a product which leavesthroughthe discharge conduit 22 to constitute the product of intermediate density.

The apparatus of Figure 7 can be especially useful in coal treatment, especiallywhen the proportion of coal (i.e.the lightcomponent) inthefeed is high. In this case, the chamber3 separates most of the coal, which is discharged through 18. There is thus much less material to be treated in the chamber4, in which it is separated into mixed product (which is discharged through 22) and final tailings (which are discharged through 21). The separation can thus require a relatively small chamber4and a small volume of dense medium. Moreover, separation carried out on a small quantity by an overabundant apparatus can be more precise.

Again in the case ofthe apparatus of Figure 7, the conduits 9, 20 and 21 can be made either tangential to the inner surface of the body or be in the form of a volute as heretofore specified for the version shown in Figure1.Thechamber4canalsotapertowardsthe conduit 21 in orderto give a higher discharge rate through itforthe reasons explained heretofore.

As already seen forthe apparatus of Figure 1, the embodiment of Figure 7 can also have a third chamber added,fed by the conduit 22 of the chamber 4, so that the apparatus can give four products. The apparatus of Figure 7 can also have the positions of its conduits 20 and 21 reversed. In all the aforegoing examples, the discharge port provided atthe apex ofthe conical chambercan be of adjustable diameter. The tangential discharge conduitsforthe intermediate density products from the cylindrical chambers can be adjustable both in terms of diameter and in terms ofthe back-pressure applied to them forthe correct operation ofthe apparatus.

From the aforegoing description, it is apparentthat the invention effectively attains the stated objects.

Firstly, it is possible to use a single dense medium of substantially unvaried density. The main reason for this is thatthe density at which separation occurs in the conical chamber is higherthan that of the dense medium fed, whereas in the cylindrical chamber it is approximately equal to that ofthe dense medium.

Moreover, because the conical chamber requires a volume of dense medium which is less than that ofthe cylindrical chamber, the total quantity of dense medium necessary is less than in the known art.

Furthermore, the separation according to the invention can be more precise, especially when the cylincrical cyclone which normally constitutes the first stage gives a high proportion offinished product, so thatthe residual fraction to be separated in the second stage is reduced, with consequent separation improvement. The apparatus ofthe invention can also be usedwith dense media of different densities.

Claims (10)

CLAIMS:

1. An apparatusforseparating mixtures of solids, in particular mixtures of minerals, into at least three products ofdifferentspecific gravity by means of a single dense medium of substantially unvaried density, comprising a hollow body divided into at least one pair of communicating consecutive chambers, each provided with tangential and axial conduits arranged to allowthe introduction and dischargeofthe productsconcerned, characterised in that of said pair of chambers oneis substantiallyconical and the other is substantially cylindrical.

2. Anapparatusasclaimed in claim 1,characte- rised inthat said hollow body is divided into three consecutive chambers which mutually communicate in pairs.

3. Anapparatusasclaimed in claim 1,characte- risedinthatsaid hollow body isof rectilinear longitudinal axis.

4. An apparatus as claimed in claim 1, characterised in that said hollow body has an axial longitudinal section substantiallyofVform due to the presence of a central curvature in a position corresponding with the communication zone between said two chambers.

5. An apparatus as claimed in claim 1, characterised in that said substantially cylindrical chamber tapers with decreasing diameter towards the zone of tangential discharge of one of the separated products.

6. An apparatus as claimed in claim 1, characterised in that said tangential conduits are cylindrical pipes directly inserted into the body of the apparatus.

7. An apparatus as claimed in claim 1, characterised in that said tangential conduits are pipes which are connected to the body of the apparatus by means of a volute.

8. An apparatus as claimed in claim 1, characterised in thatthe arrangement of said chambers is such thatthe apex of the substantially conical chamber constitutes one end ofthe apparatus.

9. An apparatus as claimed in claim 1, characterised in that the arrangement of said chambers is such thatthe apex of the substantially conical chamber communicates with the substantially cylindrical chamber.

10. An apparatus for separating mixtures of solids, in particular mixtures of minerals, into at least three products of different specific gravity, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as shown in the drawings.