US3905546A - Centrifugal extractor - Google Patents

Abstract

There is provided within the rotor of an extractor, mounted on a hollow shaft, a centrifugal chamber into which the initial product is fed and distributed with the help of distributing means provided in the hollow shaft, with the shaft additionally carrying perforated plates providing for additional separation of the products obtained, the products being subsequently directed into delivery devices arranged coaxially about said shaft intermediate of the respective end walls of said rotor and said centrifugal chamber.

Description

United States Patent 1191 Vlasov et al.

14 1 Sept. 16, 1975 {54] CENTRIFUGAL EXTRACTOR 2,593,278 4 1952 Edwards 233/7 x 2, ,372 6 I952 Mill'k tal. 233 7 [76] Inventors: Pavel Semenovich Vlmov, ulitsa 25 2 325 233/28; Oktyabrya, 6; Alexandr 2,847,l58 8/l958 Thylefors... 233/29 Karlovich lvanov, 2 Kr n n ky 3,211,530 10/1965 Harvey 233/23 x pereulok 2, kv. 38', Erik Nikolaevicl'l 3,4l9,2l0 12/1968 Schneider et al. 233/7 Svechnikov, ulitsa 25 let Oktyabrya, 3,623,656 I l/l97l Lavanchy 233/39 X 28, kv. 13; Ivan Nikolaevich Sidorov, ulitsa Bogdana FOREIGN PATENTS OR APPLICATIONS Khmemmkg 50; l,036,976 4 1953 France 233/39 Kuzmich Tjurin, l Krasnodonsky pereulok, l4, kv. 3|; Valentin lvano i h Boldov. ulitsa Alexandra Primary ExaminerGeorge H. Krizmanich N Q all Of Attorney, Agent, or Firm-Holman & Stern Novosibirsk; Vladimir Vasilievich Kolosltov, I Peschany pereulok, 20, kv. 48, Moscow, all of USSR.

ABSTRACT [22] Filed: July 10, 1973 (2 AppL 377910 There is provided within the rotor of an extractor. mounted on a hollow shaft, a centrifugal chamber into m II W m i led ltd W m I! U8. 0. 2am. 2331M; 233129; u u of m m b m 233/32 shaft, with the shaft additionally carrying perforated [51] Int. Cl. B04!) 11/06 Fumes providing f additionm separation f the [58] Field of Search 233/3, 7, 10, 2|, 27, 28, m bmi d th products being subsequently di- 233/29 32 rected into delivery devices arranged coaxially about said shaft intermediate of the respective end walls of Rehrfllm Cited said rotor and said centrifugal chamber.

UNITED STATES PATENTS 1,257,235 2/l9l8 Howell 233/28 5 Claims, 3 Drawing Figures I I "J' F 2 l x 2 Z l a 4 My em I I In 1- f i. 2 E v 6 a 5 6 5 I! Q It A 5 H I \\\\\\\\\X CENTRIFUGAL EXTRACTOR BACKGROUND OF THE INVENTION The invention relates to apparatus for performing extraction processes in hydrometallurgy, and, more particularly for the extraction of metals directly from pulp containing a considerable amount of solid particles and suspended matter, for the extraction of metals from filtered pulps (pure solutions), as well as for separating immiscible liquids having different specific gravity, for extract washing, etc.

More particularly, the invention relates to the structure of centrifugal extractors.

PRIOR ART At present, known in the art are various centrifugal extractors for hydrometallurgical processes. particularly for the extraction of metals from a liquid-liquid system, i.e. a system of two liquid phases, containing relatively small amount of suspended matter.

Recently, a considerable effort has been dedicated to research and production of centrifugal extractors for handling a system having a liquid containing suspended solid matter and a liquid (the solvent), with an intermittent discharge of the sediment. The initial product to be treated by such extractors may be in the form of a mixture of pulps and a solvent.

A pulp is, in most cases, a chemical concentrate or an ore dissolved in a mineral acid, i.e. it is a solution of the valuable component, a metal in a mineral acid, with an amount of a solid matter also being present.

The solvent is usually an organic composition capable of absorbing therein selectively the valuable component and having a specific gravity lower than that of the solution.

There is known a centrifugal extractor including a centrifugal chamber shaped as a cylinder and devices delivering the final products. arranged within a rotor fixedly mounted on a hollow shaft, with the shaft receiving therein a device for feeding the initial product and a device distributing this product along the centrifugal chamber.

The devices delivering the final products are in the form of tubular members arranged within the hollow shaft and ending with outlets within the centrifugal chamber, while the distributing device of this known extractor is in the form of passages made Within the hollow shaft.

In addition, the known extractor includes an attachment within the centrifugal chamber in the form of a series of perforated cylinders arranged concentrically with respect to the rotor axis.

The perforated attachment is intended to enhance a mass exchangc between the solvent and the suspension of the initial product, and thus to intensify the process of extraction.

However, when the known extractor is employed for processing initial products containing a relatively great amount of solid matter, this initial product is to be filtered prior to the extraction process.

As a result of the filtering of the initial product. the yield ofthc valuable component. i.e. of the metal. is reduced because part of this metal is turned together with the solid matter to waste.

On the other hand, when the initial pr duct subjected to extraction contains but a small percentage of solid matter. the abo\cdescribcd attachment ofthc extractor becomes clogged, and the extractor has to be stopped at time intervals for cleaning and flushing this attachment.

With the final products being delivered through out' lets and tubes arranged adjacent to the axis of rotation of the rotor, it is imperative, when the initial product to be processed contains components having consider ably different values of the specific gravity, to feed this product into the rotor under a considerable gauge pressure. This necessity of providing the extraction plant with high-pressure pumps increases the cost of this plant and complicates its operation (see, N. l. Angelo US. Pat. No. 2,652,975 and W. Podbclniak U.S. Pat. No. 2,67(),l32).

Furthermore, a centrifugal extractor is known which comprises a rotor accommodating therein a centrifugal chamber and a sedimentation chamber, a perforated attachment and a feeding passage, as well as a delivery device in the form of a scooping tube.

However, this last-mentioned extractor is likewise incapable of continuous processing of an initial product containing a considerable amount of solid matter, on account of the necessity of stopping the extractor periodically for cleaning and flushingv OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to eliminate these disadvantages.

it is also an object of the present invention to provide a structure for a centrifugal extractor, which is capable of continuous extraction of metals directly from pulp, even with a high volume concentration of solid matter.

it is another object of the present invention to provide a structure for a centrifugal extractor. which sim plifies the process of extraction of metals.

it is still another object of the present invention to provide a centrifugal extractor, which offers extraction of an increased amount of a metal from an initial prod uct.

It is further an object of the present invention to provide a structure for a centrifugal extractor, which provides for the extraction of a metal from an initial product, containing minimal amount of impurities,

These and other objects are attained in a centrifugal extractor comprising a centrifugal chamber and a device delivcring the final product, arranged within a rotor rigidly fixed on a horizontal hollow shaft receiving thereinsidc a product feeding device and a device distributing the initial product along the centrifugal chamber, in which extractor, in accordance with the present invention, said rotor includes said centrifugal chamber defined by a conical vessel mounted coaxially about said shaft, along the same portion of said shaft, where there is arranged said device distributing the ini tial product, said device delivering the final product in cluding annular spaces arranged coaxial]: about said shaft between the respective end walls of said rotor and said centrifugal chamber and an additionally annular space arranged coaxially about said shaft adjacent to the greater-diameter end wall of said centrifugal chamber. within said chamber. said additional space communicating with said centrifugal chamber and receiving therein a stationary mixing means.

Due to the herein disclosed structure of an extractor, it has become possible to process an initial product continuously, the product containing a considerable amount of solid matter. i.e. with a solid to liquid phase ratio within a range of 1:3 and even greater. the solid particles being of a relatively great size. The use of an initial product with a considerable content of solid matter has enabled, in its turn, to simplify the technology of extraction of the valuable component, since a filtrating operation has been eliminated and it has become possible, following an operation of dissolving either chemical concentrates or an ore in a non-organic acid, to feed the thus prepared product directly for extraction of the valuable component.

Furthermore, due to the filtration of the initial product having been eliminated, the loss of the extracted metal is reduced, and the yield of the metal is increased.

According to an embodiment of the present invention, said stationary mixing means mounted within said additional space has, in longitudinal section, the shape of a flat spiral and in cross-section, a symmetrical profile.

Due to the abovespecified shape of the mixing means, it has become possible to prevent splashing of the liquid from the additional space.

Furthermore, according to an embodiment of the present invention, there is fixedly mounted within said centrifugal chamber on said shaft, coaxially with said shaft, a series of conical perforated plates and a discshaped partition dividing said series of said plates into two parts, one part of this series of said plates being mounted on that portion of said shaft, where said device distributing the initial product is arranged, said plates of said one part having their greater diameters facing the smaller-diameter end wall of said centrifugal chamber, whereas the other part of said series of said plates is mounted on said shaft behind said disc-shaped partition, said plates of said other part facing the direetion opposite to that faced by said plates of said first portion.

Due to these perforated conical plates and the discshaped partition being mounted on the rotor shaft within the centrifugal chamber, it has become possible to divide the initial product distinctly into phases, to prevent intermixing ofthese phases, and, consequently, to enhance the purity of the product being extracted.

It is expedient that the device distributing the initial product should be in the form of a perforated cylinder of a diameter greater than the diameter of said shaft.

Due to the employment of the above specified distributing device it has become possible to accelerate a mass exchange between the phases of the liquid by feeding into the centrifugal chamber of the extractor the initial product subdivided into small droplets.

It is further advisable that the free end of said mixing means should carry thereon agitating means in the form of pins,

The employment of the agitating means enhances the discharge of the sediment from the centrifugal chamber by creating additional turbulence adjacent to the wall of the extractor.

Other objects and advantages of the present invention will become apparent from the following detailed description and from the appended drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectional view of an extractor in accordance with the present invention;

FIG. 2 is a view along line IIII in FIG. l, the vicv. looking in the direction of the arrows; and

FIG, 3 is a sectional view along line IIIIII in FIG. I the view looking in the direction of the arrows.

DETAILED DESCRIPTION OF THE INVENTION Referring now in particular to the appended drawings, the extractor has for its major work-performing member a rotor I mounted for rotation in bearings 2. The rotor I has end walls la and accommodates a frusto-conical centrifugal chamber 3 fixed on a shaft 4, e.g. by welding, the shaft 4 having one end thereof provided with an internal bore, i.e. hollow. Extending through this internal bore of the shaft 4 is a stationary tube 5 intended for feeding an initial product into a distributing device 6 carried by the shaft 4 and serving for distributing this initial product along the centrifugal chamber 3.

According to the present invention the distributing device 6 should be in the form of a vessel, eg of a per forated cylinder of which the internal diameter is greater than the external diameter of the shaft 4.

We have found that with the internal diameter of the cylinder of the distributing device 6 being greater than the diameter of the shaft 4, there is no return flow of the initial product into the space intermediate of the feeding tube 5 and the internal wall of the hollow shaft 4. We arrange the perforations in the cylinder of the distributing device 6 in uniformly spaced rows, with these perforations promoting breaking of the initial product fed into the centrifugal chamber 3 into droplets. It is commonly known that increasing of the sur face area of the phases of the initial product (by break ing it into droplets) accelerates a mass exchange and intensifies the process of extraction.

It is also known that the initial product, upon having been introduced into the centrifugal chamber, is divided by the centrifugal process into a lighter phase and into a heavier phase. which are subsequently delivered from the chamber; however, experience in operation of centrifugal extractors has proved that when the lighter phase of the initial product, obtained by extraction, is delivered from the centrifugal chamber, it takes therealong a certain amount of the heavier phase.

To eliminate this phenomenon, we suggest that there should be arranged on the shaft 4, intermediate of the distributing device 6 and the smallerdiameter end wall of the centrifugal chamber, a series of perforated conical plates or cups 7, of which the generatrix of the cone is inclined at 70 to the axis of the shaft 4. The value of the greater diameter of the conical plates 7 is above the level of the delivery of the lighter phase, but is short of the level of the separation of the lighter and heavier phases, The plates 7 have their greater diameter facing the smaller-diameter end wall of the chamber 3, i.e. they should flare toward the smaller-diameter end wall.

Furthermore, we suggest that perforated conical plates 8 should be arranged about the cylinder of the distributing device 6, so that each one of these lastmentioncd plates 8 should be positioned between two adjacent rows of the perforations in this cylinder of the distributing device 6.

The generatrix of the cone of the plates 8 should be inclined at approximately relative to the axis of the shaft 4.

The perforated conical plates 8 are disposed on the distributing device 6 so that they have the greater diamctcr facing the butt end of the centrifugal chamber having the smaller diameter.

The provision of the series of perforated conical plates 8 on the distributing device 6 has ensured a distinct division of the initial product into the lighter and heavier phases, due to the additional thin-layer separation of the initial product.

In addition to the above described conical perforated plates 7 and 8, we suggest that a disc-shaped imperforate partition 9 should be mounted on the shaft 4. The partition 9 is mounted on the shaft 4 so as to separate the conical plates 7 from the conical plates 8.

The disc-shaped partition 9 enhances the purity of the obtained phases of the product being extracted.

It should be noted that the perforated conical plates 7 and 8 and the disc-shaped partition 9 are rigidly fixed on the shaft 4, eg, by spot welding, coaxially therewith.

The centrifugal chamber 3 which is rigidly fixed on the shaft 4 is a vessel in the form of a truncated cone, narrowing in the direction of the feed of the initial product into this chamber 3, which prevents settling on the wall of the chamber 3 of the component of the heavier phase, i.e. of the sediment of the product being extracted, and also creates a directed axial motion of the sediment toward an additional annular space 10 and therefrom into a device 11 for discharge of the heavier phase.

The additional annular space 10 is arranged coaxially about the shaft 4, adjacent to the greater-diameter end wall of the centrifugal chamber 3, within this chamber. The provision of the space 10 enables to maintain within the centrifugal chamber 3 a permanent level of separation of the lighter and heavier phases of the liquid subjected to extraction, because the additional space 10 and the centrifugal chamber 3 are communicating vessels.

lt should be noted that a partition 12 separating this additional space 10 from the chamber 3 is in the form of a disc fixed to the shaft 4 and to the conical wall of the centrifugal chamber. There are recesses 13 (FIGS. 1 and 3) cut in the periphery of this disc. so that only the heavier phase with the sediment of the initial product should overflow into this additional space 10.

We further suggest that a mixing means 14 (F105. 1 and 3) should be accommodated within the additional space 10, with this mixing means 14 being stationary in respect of the rotor 1.

In the presently described embodiment, the geometric shape ofthe mixing means 14 is such that in longitudinal or axial section it presents a flat spiral, while in cross-section it has a symmetrical profile. To render the mixing means 14 even more effective, we suggest that the free end thereof, adjacent to the wall of the centrifugal chamber 3 should carry thereon agitating members l5, eg in the form of pins.

Arranged on the shaft 4, coaxially therewith, are product delivery devices 11 and 16, each in the form of an annular space defined by the respective end walls of the rotor 1 and those of the centrifugal chamber 3. in these delivery devices I] and 16 there are rigidly fixed stationary scooping tubes [7 and 18 respectively bent to face the direction of rotation of the products to be delivered The end wall ofthe delivery device 11, which is at the same time the respective end wall of the centrifugal chamber 3, is an annular disc 19 of which the internal diameter defines the level of separation of the lighter and heavier phases of the product subjected to extraction, supplied into the centrifugal chamber 3.

The end wall of the delivery device 16, which is at the same time end wall 30 of the centrifugal chamber 3, has provided therein overflow openings 20, for the lighter phase, obtained by extraction, to overflow through these openings from the centrifugal chamber 3 into the delivery device 16.

It is possible to provide similar openings in the annular disc [9, with the area of these opening varying step wise about the disc.

The centrifugal extractor, constructed in accordance with the present invention, operates, as follows:

The initial product, Le. a mixture of pulp and a solvent is supplied via the feed tube 5 into the perforated cylinder of the product distributing device 6, wherein the action of the centrifugal forces effects final mixing of the pulp and solvent and distributes this initial product about the internal wall of the perforated cylinder. With the perforations having been provided in the cylinder of the distributing device 6., the centrifugal forces break the initial product into droplets which enter the centrifugal chamber 3, in which the centrifugal forces impinge them against the perforated conical plates 8 along which the product is spread in a thin layer. The initial product, subjected to extraction, is distributed over the surfaces of the conical plates 8 and flows thercalong under the action of the centrifugal forces, with this flow having both radial and axial components. The distribution of the product subjected to extraction over the surfaces of the plates 8 in a thin layer, in combination with the relative axial and radial motion of the product yields a distinct division of the initial product into phases.

It is generally known that in the course ofextraction the valuable component is transferred from the solution into the organic solvent. Let us hereinafter refer to the solvent saturated with the valuable component as the extract", and to the solution relatively free from the valuable component as the rafinate.

Under the action of the centrifugal forces brought about by rotation of the rotor l, the initial mixture of the pulp and solvent is divided within the centrifugal chamber 3 into the rafinate with a sediment and the extract. The rafinate with the sediment being the heavier phase, it is driven against the conical wall of the centrifugal chamber 3 and flows thercalong toward the greater-diameter end of the chamber, finding its way into the additional annular space 10 through the recesses [3 in the partition 12.

Due to the incorporation of this additional annular space 10, there is permanently maintained within the centrifugal chamber 3 a predetermined level of division of the heavier and lighter phases of the initial product, independently of the volume of the product, fed to be subjected to extraction.

There is mounted within the additional annular space 10 the mixing means [4. which is stationary with respect to the rotor l. with the mixing means having in longitudinal section the shape of a Hat spiral and in cross-section a regular symmetrical profile.

There are mounted on the free end of the mixing means 14 the agitating means 15. eg in the form of pins.

The mixing means 14 effect turbulization of the flow of the rafinatc with the sediment within the additional space 10.

As a result of thus created turbulence. the solid mattcr of the sediment is transformed into a suspended state. The flow of the rafinatc carries the solid particles suspended therein through the opening in the annular disc 19 toward the delivery device 1]. Under the head resulting from the angular speed of the flow (the raftnate and the sediment rotate together with the rotor while the scooping tube I7 is bent to face this rotation and is stationary). the rafinate with the sediment is delivered under pressure from the centrifugal extractor.

The extract, which is the lighter phase, is brought under the action of the centrifugal forces nearer to the axis of the rotor. than the above-mentioned heavier phase, and acquires a minimal level defined by the position of the overflow openings 20.

The extract moves along the axis of the rotor l toward the smaller-diameter end of the frusto-conical centrifugal chamber 3.

Under the action of the centrifugal forces, the extract overcomes the resistance of the disc-shaped partition 9 and is subjected to separation in a thin layer on the surfaces of the conical plates 7. Furthermore, the extract overcomes the resistance of the plates '7, rids itself of the dispersed droplets of the rafmate and overflows through the perforations successively from one plate to the next one, toward the overflow openings 20. The extract, now devoid of the rafinatc, flows through these overflow openings into the delivery device 16 from which it is discharged with the help of the scooping tube 18. in the manner described hereinabovc in connection with the delivery of the rafinate from the extractor.

A centrifugal extractor constructed in accordance with the present invention may be employed in technological processes involving the use of a single extractor, as well as in those requiring several extractors connected in series.

When a single extractor is employed, the process of extraction is carried out with pre-mixed initial products.

When stepwise extraction is effected in several extractors connected in a serial fashion, each centrifugal extractor should be provided, in order to effect mixing of the initial products, i.e. of the solution and the solvent. with a feed-in device, eg in the form of a tube bent in a direction coinciding with that of rotation of the rotor and also in a direction of the delivery device. this feed-in device being connected via a corresponding conduit with the extract-scooping tube of the previous stage of the stepwise extraction battery.

It should be clearly understood that those competent in the art of extraction are able to introduce various modifications and changes into the abovedcscribed structure of the centrifugal extractor. which has been described exclusively for the sake of illustration of the major features ofthe present invention and is in no way meant to limit the scope of the invention.

What we claim is:

l. A centrifugal extractor, comprising a horizontal hollow shaft; a rotor fixedly mounted on said horizontal hollow shaft; said rotor having end walls; a centrifugal chamber defined by a frusto-conical vessel mounted on said shaft coaxially therewith within said rotor; said vessel having end walls; a device feeding an initial prod uct into said chamber. said feeding device being arranged within said hollow shaft; a device for distributing the initial product longitudinally of said chamber, said distributing device being provided on said hollow shaft within said centrifugal chamber; means for deliv ering the product obtained, including annular spaces arranged coaxially about said shaft intermediate of the respective end walls of said rotor and said centrifugal chamber; an additional annular space arranged coaxially about said shaft adjacent to the greater-diameter one of said end walls of said centrifugal chamber, within said chamber, said additional annular space presenting a vessel communicating with said centrifugal chamber; and stationary mixing means received inside said additional space.

2. The centrifugal extractor as claimed in claim I, wherein said stationary mixing means has in longitudinal section a shape in accordance with the equation of a flat spiral and in cross-section a symmetrical profile.

3. The centrifugal extractor as claimed in claim 1, wherein there are rigidly fixed on said shaft within said centrifugal chamber coaxially with said shaft, a series of conical perforated plates and a disc-shaped partition dividing said series into two parts, one part of said series of said plates being mounted on that portion of said shaft. where said initial product distributing device is positioned, said plates of said one part having their greater diameters facing the smaller-diameter end wall of said centrifugal chamber. the other part of said series of said plates being mounted on said shaft behind said discshaped partition, so that said plates of said other part of said series are facing in a direction opposite to that in which said plates of said one part of said series are facing.

4. The centrifugal extractor as claimed in claim 3, wherein said initial product distributing device includes a perforated cylinder of which the internal diameter is greater than the diameter of said shaft.

5. The centrifugal extractor according to claim 2. wherein the free end of said mixing means carries thereon agitating means in the form of pins.

Claims (5)

1. A centrifugal extractor, comprising a horizontal hollow shaft; a rotor fixedly mounted on said horizontal hollow shaft; said rotor having end walls; a centrifugal chamber defined by a frusto-conical vessel mounted on said shaft coaxially therewith within said rotor; said vessel having end walls; a device feeding an initial product into said chamber, said feeding device being arranged within said hollow shaft; a device for distributing the initial product longitudinally of said chamber, said distributing device being provided on said hollow shaft within said centrifugal chamber; means for delivering the product obtained, including annular spaces arranged coaxially about said shaft intermediate of the respective end walls of said rotor and said centrifugal chamber; an additional annular space arranged coaxially about said shaft adjacent to the greater-diameter one of said end walls of said centrifugal chamber, within said chamber, said additional annular space presenting a vessel communicating with said centrifugal chamber; and stationary mixing means received inside said additional space.

2. The centrifugal extractor as claimed in claim 1, wherein said stationary mixing means has in longitudinal section a shape in accordance with the equation of a flat spiral and in cross-section a symmetrical profile.

3. The centrifugal extractor as claimed in claim 1, wherein there are rigidly fixed on said shaft within said centrifugal chamber, coaxially with said shaft, a series of conical perforated plates and a disc-shaped partition dividing said series into two parts, one part of said series of said plates being mounted on that portion of said shaft, where said initial product distributing device is positioned, said plates of said one part having their greater diameters facing the smaller-diameter end wall of said centrifugal chamber, the other part of said series of said plates being mounted on said shaft behind said disc-shaped partition, so that said plates of said other part of said series are facing in a direction opposite to that in which said plates of said one part of said series are facing.

4. The centrifugal extractor as claimed in claim 3, wherein said initial product distributing device includes a perforated cylinder of which the internal diameter is greater than the diameter of said shaft.

5. The centrifugal extractor according to claim 2, wherein the free end of said mixing means carries thereon agitating means in the form of pins.

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