Patent Description:
Hydrocyclones are used for separating suspended matter carried in a flowing liquid such as a mineral slurry into two discharge streams by creating centrifugal forces within the hydrocyclone as the liquid passes through a conical shaped chamber. Basically, hydrocyclones include a conical separating chamber, a feed inlet which is usually generally tangential to the axis of the separating chamber and is disposed at the end of the chamber of greatest cross-sectional dimension, an underflow outlet at the smaller end of the chamber, and an overflow outlet at the larger end of the chamber.

The feed inlet is adapted to deliver the liquid containing suspended matter into the hydrocyclone separating chamber, and the arrangement is such that the heavy (for example, denser and coarser) matter tends to migrate towards the outer wall of the chamber and towards and out through the centrally located underflow outlet. The lighter (less dense or finer particle sized) material migrates towards the central axis of the chamber and out through the overflow outlet. Hydrocyclones can be used for separation by size of the suspended solid particles or by particle density. Typical examples include solids classification duties in mining and industrial applications.

For enabling efficient operation of hydrocyclones the internal geometric configuration of the larger end of the chamber where the feed material enters, and of the conical separating chamber are important. In normal operation such hydrocyclones develop a central air column, which is typical of most industrially-applied hydrocyclone designs. The air column is established as soon as the fluid at the hydrocyclone axis reaches a pressure below the atmospheric pressure. This air column extends from the underflow outlet to the overflow outlet and simply connects the air immediately below the hydrocyclone with the air at the top. The stability and cross sectional area of the air core is an important factor in influencing the underflow and overflow discharge condition, to maintain normal hydrocyclone operation.

During normal "stable" operation, the slurry enters through an upper inlet of a hydrocyclone separation chamber in the form of the inverted conical chamber to become separated cleanly. However, the stability of a hydrocyclone during such an operation can be readily disrupted, for example by collapse of the air core due to overfeeding of the hydrocyclone, resulting in an ineffective separation process, whereby either an excess of fine particulates exit through the lower outlet or coarser particulates exit through the upper outlet.

Another form of unstable operation is known as "roping", whereby the rate of solids being discharged through the lower outlet increases to a point where the flow is impaired. If corrective measures are not timely adopted, the accumulation of solids through the outlet will build up in the separation chamber, the internal air core will collapse and the lower outlet will discharge a rope-shaped flow of coarse solids.

Unstable operating conditions can have serious impacts on downstream processes, often requiring additional treatment (which, as will be appreciated, can greatly impact on profits) and also result in accelerated equipment wear. Hydrocyclone design optimisation is desirable for a hydrocyclone to be able to cope with changes to the composition and viscosity of input slurry, changes in the flowrate of fluid entering the hydrocyclone, and other operational instabilities.

<CIT> describes stationary centrifugal separators including a centrifugation chamber into which the mixture to be separated, such as a suspension, dispersion or emulsion, is fed.

In a first aspect, embodiments are disclosed of an overflow outlet control device for a hydrocyclone, the device including:.

The use of an improved configuration of overflow outlet control device has been found to produce some metallurgically beneficial outcomes during its operation, as measured by various standard classification parameters. These beneficial outcomes include a reduction both in the amount of water, and in the amount of fine particles, which bypass the classification step and which are improperly carried away in the cyclone coarse particle underflow discharge stream, rather than reporting to the fine particle overflow stream as should be the case during optimal cyclone operation. Also observed was a reduction in the average particle cut size (d50%) in the overflow stream from the classification step, as a consequence of more fine particles now reporting to the fine particle overflow stream.

The inventors surmise that the use of an overflow outlet control device to assist in the separation of fine particles from coarser particles can also enable operational advantages in related processes, for example an improvement in the recovery performance in a downstream flotation process. An increase in the amount of fine particles in the flotation feed can lead to better liberation and flotation separation of valuable materials in a subsequent process step. Also, reducing the amount of recirculating load of particle material in the milling and cyclone separation circuit can avoid overgrinding of particles which are already sufficiently finely ground, as well as increasing the capacity of the grinding circuit because unnecessary regrinding wastes energy in the milling circuit. Overall the inventors expect that the use of an overflow outlet control device in conjunction with the hydrocyclone separation step will maximise throughput of product in terms of, for example, tonnage per hour, and maintain the physical separation process parameters at a stable level.

In certain embodiments, the flow control formation is radially symmetrical.

In certain embodiments, the enlarged end portion of the flow control formation includes a convex region which faces towards the inlet.

In certain embodiments, the flow control formation progressively narrows in a direction from the top wall to the narrowed portion and progressively widens in a direction from the narrowed portion to the enlarged end portion. In one form of this, the narrowed portion is a concave region of the flow control formation.

In certain embodiments, the end portion of the flow control formation terminates at a position closer to the inlet than to the interior surface of the chamber located at the top wall.

In certain embodiments, the chamber is generally volute-shaped in cross-section when viewed in a plane in which the axis of the outlet is located.

The accompanying drawings facilitate an understanding of the various embodiments which will be described:.

This disclosure relates to the design features of a hydrocyclone of the type that facilitates separation of a liquid or semi-liquid material mixture into two phases of interest. The hydrocyclone has a design which enables a stable operation, with maximised throughput and good physical separation process parameters.

A hydrocyclone, when in use, is normally orientated with its central axis X-X being disposed upright, or close to being upright. Referring to the drawings, there is shown a hydrocyclone generally indicated at <NUM> which includes a main body <NUM> having a chamber <NUM> therein, the chamber <NUM> including an inlet (or feed) section <NUM>, and a conical separating section <NUM>. The hydrocyclone <NUM> further includes a cylindrical feed inlet port <NUM> of circular cross-section, in use for feeding a material mixture, typically a particle-bearing slurry mixture, into the inlet section <NUM> of the chamber <NUM>.

An overflow outlet or vortex finder <NUM>, typically in the form of a cylindrical, short length of pipe, is provided at one end of the chamber <NUM> adjacent the inlet section <NUM> thereof, and an underflow outlet <NUM> at the other end of the chamber, remote from the inlet section <NUM> of the chamber <NUM>.

The hydrocyclone <NUM> further includes a control unit <NUM> having an overflow outlet control device <NUM> located adjacent to the inlet section <NUM> of the chamber <NUM> of the hydrocyclone <NUM> and in communication therewith via the overflow outlet <NUM>. The overflow outlet control device <NUM> includes a central chamber <NUM>, and a tangentially located, circular cross-sectional discharge outlet <NUM> leading out from the central chamber <NUM>, and a centrally located air core stabilising orifice <NUM> which is remote from the overflow outlet <NUM>, across the other side of the central chamber <NUM>. The stabilising orifice <NUM>, overflow outlet <NUM> and underflow outlet <NUM> are generally axially aligned along the axis X-X of the hydrocyclone <NUM>.

The central chamber <NUM> of the overflow outlet control device <NUM> has an inner surface which when viewed in cross-sectional plan view is generally in the shape of a volute, for directing material entering the chamber <NUM> of the overflow outlet control device <NUM> outward towards the discharge outlet <NUM>. Preferably, the volute shape of the inner surface subtends an angle of up to <NUM>°.

The inlet section <NUM> of the chamber <NUM> of the hydrocyclone <NUM> has an inner surface, which is generally in the shape of a volute and preferably the volute is ramped axially toward the converging end of the separation chamber and extends around the inner surface for up to <NUM>°.

The stabilising orifice <NUM> comprises tapering side walls which extend a short distance into the central chamber <NUM>, which as shown in <FIG> forms a generally conical shaped inlet section. The control unit <NUM> may be integral with the hydrocyclone <NUM> or separate therefrom so that it enables it to be retrofitted to existing hydrocyclones.

The underflow outlet (hereafter "lower outlet") <NUM> is centrally located at the other end of the chamber <NUM> (that is, at the apex of the conical separating section <NUM>) being remote from the inlet section <NUM>, in use for discharge of a second one of the phases. The underflow outlet <NUM> shown in the drawings is the open end of the conical separating section <NUM>. In the hydrocyclone <NUM> in use, material passing via the underflow outlet <NUM> flows into a further section in the form of a cylindrical length of pipe known as a spigot <NUM>.

The hydrocyclone <NUM> is arranged in use to generate an internal air core around which the slurry circulates. During stable operation, the hydrocyclone <NUM> operates such that a lighter solid phase of the slurry is discharged through the uppermost overflow outlet <NUM> and a heavier solid phase is discharged through the lower underflow outlet <NUM>, and then via the spigot <NUM>. The internally-generated air core runs the length of the main body <NUM>.

Referring now to the features of the overflow outlet control device of the present disclosure, reference will be made to <FIG>. In this embodiment of the device, if a part performs a similar function to a part which has already been described in relation to prior art hydrocyclones or to prior art overflow outlet control devices, then it has been given the same part number designation followed by the letter "A".

The hydrocyclone overflow outlet control device 21A includes a central chamber 29A, which has interior wall surfaces which are rounded in shape, and located within (or as part of) an exterior housing <NUM> which is generally octagonal when viewed in plan (as can be seen in <FIG>). As presented in <FIG> and <FIG>, the shape of the interior wall surface of the chamber 29A is in the mathematical shape of a torus - that is, the shape of the chamber cavity 29A is defined by rotation of a circle around a central axis to product a circular section ring (a surface of revolution with a hole in the middle like a doughnut).

Rather than being of a specific mathematical form, in other embodiments, the shape of the interior wall surface of the chamber 29A, when the device is viewed in vertical cross-section, can simply be configured firstly to curve outwardly and then subsequently to curve inwardly again, when moving in a direction from the base portion to the top wall, and thus to provide a smooth flow path for the liquid and solid materials moving through the chamber 29A, as will shortly be described.

In the chamber 29A, there is a circular inlet <NUM> located in the base portion <NUM> and which is connected to the overflow outlet <NUM> of the adjacent cyclone (not shown), the inlet <NUM> being arranged to receive a flow of material from the overflow outlet <NUM> which, in use, passes in and through the chamber 29A, exiting via the circular cross-sectional discharge outlet 22A located in a side wall <NUM>. The chamber 29A of the overflow outlet control device 21A has an inner circumferential surface which, when viewed in cross-sectional plan view (as can be seen in <FIG>), is generally in the shape of a volute, for directing material entering the chamber 29A via the circular inlet <NUM> at the base portion <NUM> tangentially outward towards the discharge outlet 22A located in the side wall <NUM>.

The top wall region <NUM> of the interior wall of the chamber 29A has an area which is located opposite to the base portion <NUM> of the device 21A, which itself includes the circular inlet <NUM>. The top wall region <NUM>, a side wall portion <NUM> and base portion <NUM> together seamlessly form the chamber 29A which is shaped internally as a torus in the embodiment shown in <FIG> and <FIG>. When material flows in use between the inlet <NUM> and the discharge outlet 22A, and passes through the central chamber 29A, it encounters no sharp corners or edges, but just smoothly curved or rounded interior wall surfaces.

The top wall region <NUM> of the chamber 29A also features a protruding flow control formation <NUM> which is joined or formed therewith, and which is arranged to extend into the chamber 29A, being directed face towards the inlet <NUM> such that in use the flow of material into the chamber 29A via the inlet <NUM> directly encounters the formation <NUM>. As a result of its shape, the formation <NUM> functions to smoothly deflect and direct the material flow therearound, and to circulate it into the chamber 29A.

As shown in <FIG> and <FIG>, the flow control formation <NUM> is generally in the shape of a symmetrical, narrow elongate neck or stem <NUM>, and having an enlarged end head <NUM>, which is joined to the top wall region <NUM> by the narrow neck <NUM>. The enlarged end head <NUM> has a convex face <NUM> which is directed to face downwardly towards the inlet <NUM>. In the embodiment shown, the narrow neck portion <NUM> is radially symmetrical about the axis X-X and has a generally tapering, and then widening shape with concave sides <NUM> therearound, when moving in a direction downward from the top wall region <NUM>.

The convex face <NUM> at the end of the enlarged head <NUM> is located at a distance into the chamber 29A which is closer to the inlet <NUM> than it is to the interior surface of the top wall region <NUM> - in other words, the convex face <NUM> extends below a horizontal midpoint of the control chamber 29A which is indicated by line C-C in <FIG> and <FIG>. This means that the convex face <NUM> is placed in a direct flow path of the material entering into the chamber 29A when in use, and the centre of the convex face is the first portion of the flow control device 21A to encounter the material flow, which then serves to redirect that flow towards the rounded interior walls of the chamber 29A.

Along the X-X axis of the hydrocyclone therefore also lies the inlet <NUM>, as well as the principal axis of the narrow neck <NUM> and of the enlarged head <NUM> located within the chamber 29A of the overflow outlet control device 21A. When material flow exits the central chamber 29A via the discharge outlet 22A, the axis D-D of the discharge outlet 22A is generally perpendicular to the axis X-X. The material flow in the chamber 29A therefore experiences a perpendicular change in direction between entry and exit, but the rounded internal walls of the chamber 29A, as well as the rounded surfaces of the convex face <NUM> of the enlarged head <NUM> and of the concave side wall <NUM> of the narrow neck <NUM>, all serve in conjunction to reduce the turbulence of the flow as much as possible, leading to more stable operating conditions in the adjacent hydrocyclone.

The convex face <NUM> of the enlarged head <NUM> creates a narrow opening area, and thus a higher velocity for the slurry as it moves into the central chamber 29A. As well as that, the shape of the convex face <NUM> maintains the slurry in the chamber 29A and prevents it from returning into the hydrocyclone below, as well as providing smooth passage of that slurry without generation of turbulence. In turn, this improves the metallurgical performance of the hydrocyclone.

Referring to <FIG>, the enlarged head <NUM> is attached through the narrow neck <NUM> to the top wall region <NUM> by means of an elongate fixing bolt <NUM> and nut <NUM> arrangement. In other embodiments, the enlarged head can be directly formed with the narrow neck, and the neck is then attached at its uppermost in use end to the top wall region <NUM>.

Referring to <FIG>, the upper <NUM> and lower <NUM> half portions of the overflow outlet control device 21A are joined together by a plurality of circumferentially spaced nut <NUM> and bolt <NUM> fastening arrangements located around the perimeter of the device 21A, which is also shown in <FIG>. The device 21A may therefore be cast or molded in two portions which are subsequently joined together, and the enlarged head and narrow neck parts of the flow control formation can be fitted to the upper portion <NUM> prior to the two portions <NUM>, <NUM> being connected.

In the embodiment shown, the neck <NUM> and head <NUM> formation is radially symmetrical about the central axis X-X of the hydrocyclone, however in further embodiments, the flow control formation can be of other shapes and configurations which serve to smoothly deflect the flow of inlet material into the overflow outlet control device.

The shape and configuration of the walls of the internal chamber 29A and of the flow control formation <NUM> serve to allow the free flow of material through the overflow outlet control device 21A, reducing turbulence because of all the rounded surfaces which are presented to the material flow.

In certain other embodiments, it is possible to operate a cyclone overflow outlet control device of this type without all of the aforementioned surfaces being curved in each embodiment. For example, the flow control formation can still have the convex face <NUM> placed in a direct flow path of the material entering into the chamber 29A when in use, so that the centre of the convex face is the first portion of the flow control device 21A to encounter the material flow, and to redirect it as described. However, in that same example, the feature of the enlarged head and narrow neck parts of the flow control formation may not be curved - the narrow neck could simply be cylindrical and the enlarged head arranged to extend out from that neck in a tapered manner (rather than being curved). Whilst all surfaces are still smooth, and without sharp edges or disjointed portions, they are not all curved in the manner shown in <FIG> and <FIG>.

In certain other embodiments, the flow control formation may have some different features of shape at the enlarged head region, but this time the concave side wall <NUM> of the narrow neck <NUM> could be in place, to serve to reduce the turbulence of the flow as much as possible in the chamber, leading to more stable operating conditions in the adjacent hydrocyclone.

Experimental results have been produced by the inventors using the new equipment configuration disclosed herein, to assess whether there are any metallurgically beneficial outcomes during the operation of the hydrocyclone, in comparison with the baseline case (without the new configuration).

Table <NUM>-<NUM> shows the results of various experiments in which an overflow outlet control device 21A is located at the uppermost position atop a hydrocyclone <NUM>, that is connected to the cyclone overflow outlet via the vortex finder <NUM>, compared to a situation without.

The parameters which were calculated included: the percentage (%) change in the amount of water bypass (WBp); and the percentage (%) change in the amount of fine particles (Bpf) which bypass the classification step. In a poorly-operating hydrocyclone, some water and fine particles are improperly carried away in the cyclone coarse particle underflow (oversize) discharge stream, rather than reporting to the fine particle overflow stream, as should be the case during optimal cyclone operation. The parameters WBp and Bpf provide a measure of this.

Also observed was the percentage (%) change in the average particle cut size (d50) in the overflow stream from the classification step, as a measure of whether more or less fine particles reported to the fine particle overflow stream. Particles of this particular size d50, when fed to the equipment, have the same probability of reporting to either the underflow or to the overflow.

Also observed was a quantification of the efficiency factor of classification of the hydrocyclone, in comparison with a calculated 'ideal classification'. This parameter alpha (α) represents the acuity of the classification. It is a calculated value, which was originally developed by <NPL>). The size distribution of particulates in a feed flow stream is quantified in various size bands, and the percentage in each band which reports to the underflow (oversize) discharge stream is measured. A graph is then drawn of the percentage in each band which reports to underflow (as ordinate, or Y-axis) versus the particle size range from the smallest to the largest (as abscissa, or X-axis). The smallest particles have the lowest percentage reporting to oversize. At the d50 point of the Y-axis, the slope of the resultant curve gives the alpha (α) parameter. It is a comparative number which can be used to compare classifiers. The higher the value of the alpha parameter, the better the separation efficiency will be.

When comparing the use of the overflow outlet control device having an internal chamber in accordance with the present disclosure with a hydrocyclone which does not have any overflow outlet control chamber, the data in Table <NUM>-<NUM> demonstrates:.

In summary, overall the best results were observed in the improvements to the water bypass (WBp), and to the average particle cut size (d50) of the solid-liquid mixture flowing through a hydrocyclone using an overflow outlet control device of the present disclosure - that is, there was both a reduction in the amount of water bypassing (WBp) the hydrocyclone and ending up in the underflow stream, and also a reduction in the average particle cut size (d50) in the overflow stream.

The inventors surmise that the overflow outlet control device disclosed herein can be most useful in those situations where a narrower classification of a product by size is the predominant requirement.

The inventors have discovered that the use of the a hydrocyclone separation apparatus fitted with the overflow outlet control device of the present disclosure can realise optimum (and stable) operating conditions therein, and this physical configuration has been found to:.

In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "upper" and "lower", "above" and "below" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

The preceding description is provided in relation to several embodiments which may share common characteristics and features. It is to be understood that one or more features of any one embodiment may be combinable with one or more features of the other embodiments. In addition, any single feature or combination of features in any of the embodiments may constitute additional embodiments.

Claim 1:
An overflow outlet control device (<NUM>) for a hydrocyclone (<NUM>), the device (<NUM>) including:
a base portion (<NUM>) including an inlet (<NUM>);
a top wall (<NUM>); and
a side wall (<NUM>) extending between the base portion (<NUM>) and the top wall (<NUM>), the side wall (<NUM>) including an outlet (22A);
the side wall (<NUM>), base portion (<NUM>) and top wall (<NUM>) together defining an outlet flow control chamber (29A);
the inlet (<NUM>) being arranged to receive a flow of material from an overflow outlet (<NUM>) of an adjacent hydrocyclone, such that in use the flow of material passes through the chamber (29A) and leaves by way of the outlet (22A), and wherein an axis of the outlet (22A) from the chamber (29A) is arranged to be generally perpendicular to an axis of the inlet (<NUM>) of the chamber (29A) so that the material flow in the chamber (29A) experiences a perpendicular change in direction between the inlet (<NUM>) and the outlet (22A);
wherein an interior surface of the chamber (29A) located at the top wall (<NUM>) includes a flow control formation (<NUM>) which extends into the chamber (29A) towards the inlet (<NUM>), the flow control formation (<NUM>) including an enlarged end portion and a narrowed portion disposed between the end portion and the top wall (<NUM>);
wherein the enlarged end portion of the flow control formation (<NUM>) includes a curved convex region (<NUM>) which faces towards the inlet (<NUM>);
wherein the interior surface of the side wall (<NUM>) of the flow control chamber (29A) is rounded in shape; and
characterised in that the rounded interior surface of the side wall (<NUM>) of the chamber (29A) is in the shape of a torus.