OA20838A - Spiral separators and parts therefore - Google Patents

Abstract

A spiral separator for separating more-desired material from less-desired material has a feed arrangement (32) for feeding a slurry of mixed more-desired material and less-desired material, a spiral trough (100), and a splitting arrangement (34) for off-take of a concentrate band of more desired material, and the spiral trough is configured to provide an effective cross-trough floor slope of less than 8 degrees to horizontal in a turn (160) immediately upstream of the splitting arrangement. The separator may be a multi-stage separator and include a slurry preparation apparatus (800) between each pair of stages

Description

SPIRAL SEPARATORS AND PARTS THEREFORE

Fieid

The présent disclosure relates to spiral separators and especially, but not exclusively to spiral separators for wet gravity séparation of desired minerai materials from undesired minerai matcrials in cire uni stances where the desired and undesired materials hâve different spécifie gravities. The disclosure extends to parts or components of spiral separators, and to related method s.

Définition

In the spécification the terni “comprising” shall be understood to hâve a broad meaning similar to the terni “including” and will be understood to impi y the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This définition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

Background

Spiral separators are extensively used for the wet gravity séparation of particulate solids according to theîr spécifie gravity.

A known type of spiral separator comprises one or more helical sluices, often referred to as spirals or spiral troughs, inounted on a central column which is vertical in use. Spiral separators with two or more intertwined helical troughs are known as double- or multiple-start separators. A feed arrangement is provided for feeding a mineral/water slurry to the uppennost part of the, or each, spiral trough. The slurry is induced, by gravity, to flow down the spiral. The particulates in the slurry are subject to a number of different forces, including gravitational force, drag forces due to contact with the spiral, and centrifugal force due to movement along a generally helical path. Broadly speaking, particles with higher spécifie gravity move toward the radially inner part of the spiral, and particles with lower spécifie gravity (lower density) move towards the outer parts of the spiral. Suitably distributed off-take openings or channels collect streams of particulates which hâve undergone this séparation. However, further séparation Processing is often required.

Spiral separators hâve been used commercially since the early to mid-1900s. Early commercial spiral separators were quite unsophisticated, using substantially uniform spirals, that 1 is, spirals in which both the pitch and the profile were uniform and did not vary between different turns of a spiral trough.

Significant contributions to the effectiveness and efficiency of spiral separators were made by Douglas Charles Wright in the early 1980’s. One substantial contribution was invention of a spiral separator in which the (or each) spiral trough was not unifomi over ail the successive turns, but rather had a cross-sectional profile which was different in different turns.

US Patent 4324334 describes a spiral separator in which the profile of the spiral varies in a spécifie progression over successive turns, in a manner that was found to improve séparation performance compared to use of a uniform trough. This patent descrîbes a spiral separator in which each helical trough has a floor or trough bottom which is substantially straight in radial cross section, and îndined in radial cross section, being lower at its more inward part and higher at its more outward part. The change in profile of the trough, through different tums, is described by reference to a varying cross sectional angle ‘A’ of the spiral bottom to horizontal. The varying cross sectional angle of the spiral (trough) bottom is described as being about 21 degrees in the first 3.5 turns of the spiral, then reducing, below these upper turns, to about 15° in the fourth tum, then to about 12° in the fifth tum, and then being âirther reduced to about 9° for the sixth and final tum.

Another, related, US Patent to Douglas Wright, US Patent 4563279, describes a trough shape in which the sloping trough bottom, or floor, has a more inner straight région and a more outer straight région, the more outer straight région having a uniform cross sectional angle, to horizontal, of about 21 degrees, and the more inner straight région having a varying cross sectional angle described as being about 21 degrees in the first two complété tums of the spiral, then reducing, below these upper turns, to about 15° in the third tum, then to about 12° in the fourth tum, and then being further reduced to about 9° for the fifth and final tum.

The decrease from 21 degrees to 9 degrees was evidently considered particularly important by Wright, with this feature being recited in seven of the sixteen daims of US 4563279.

The varying cross sectional angle of the trough bottom is described in US 4324334 and US 4563279, as providing a braking effect on the flow of material, and particularly on the flow of material near to the inside of the spiral, resultîng in a spreading of the innermost stratum of pulp.

It is believed that substantially ail high-performance wet spiral concentrators recently made and sold commercially worldwide, at least for séparation of desired heavy minerais from undesired minerai with a lower spécifie gravity, such as silica sand, hâve incorporated the concepts taught by Wright in the early 1980s. It is also believed that substantially ail highperformance wet spiral concentrators recently made and sold commercially worldwide hâve used spiral s of about 5 to 7 turns, or in the case of multiple stage séparai ors, about 5 to 7 tums per stage.

The reference to prior art or other background in this spécification is not, and should not be taken as, an acknowledgment or any form of suggestion that the referenced prior art or other background forms part of the common general knowledge in Australia or in any other country

Summary

According to a first aspect of the présent disclosure there is provided a spiral separator for separating more-desîred material from less-desired material, the spiral separator comprising:

a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material;

a spiral trough; and a splitting arrangement for off-take of a concentrate band of more desired material;

wherein the spiral trough is configured to provide a trough floor région with an effective cross-trough floor slope which reduces by between 5 and 8 degrees in a tum immediately upstream of the splitting arrangement.

In an embodiment at least some of the tum immediately upstream of the splitting arrangement comprises a concentrate refîner région, in which a concentrate band of the slurry is refined by radially outward migration of less-desired material from the concentrate band.

In an embodiment the trough is configured to provide a trough floor région with an effective cross-trough floor slopc of between 4 and 8 degrees from horizontal in a tum immediately upstream of the splitting arrangement.

In an embodiment the trough is configured to provide a feed transition zone proximal to the feed arrangement.

In an embodiment the at least part of the feed transition zone provides a floor région with an effective cross-trough floor si ope of between 16 and 20 degrees from horizontal.

In an embodiment the floor région with an effective cross-trough floor slope of between 16 and 20 degrees from horizontal is provided within 1.5 tums of the feed arrangement.

In an embodiment the feed transition zone is provided within 1.5 tums ofthe feed arrangement.

In an embodiment the feed transition zone terminâtes within 1.5 tums of the feed arrangement.

In an embodiment the feed transition zone provides a région in which a cross sectional shape of the trough transitions gradually from providing a relatively narrow feed entry channel, adjacent a radial 1 y outer part of the trough, to providing a substantially full width floor profile with an effective cross-trough floor slope of between about 15 and about 20 degrees.

In an embodiment the relatively narrow feed entry channel has a floor part with crosstrough floor slope less than 12 degrees.

In an embodiment the relatively narrow feed entry channel has a floor part with crosstrough floor slope less than 5 degrees.

In an embodiment the trough is configured to provide an effective cross-trough floor slope which reduces at a mean rate of between 2 and 4 degrees per tum for at least one further tum downstream of the feed transition zone.

In an embodiment the trough is configured to provide an effective cross-trough floor slope which reduces at a mean rate of between 2 and 4 degrees per tum for at least two further tums downstream of the feed transition zone.

A région in which an effective cross-trough floor slope which reduces at a mean rate of between 2 and 4 degrees, and which is downstream of the feed transition zone and upstream of the concentrate refîner région may be considérée! an intermediate zone.

In an embodiment the effective cross-trough floor slope is the slope of a straight line which ex tends radially between radially inner and radially outer parts of a trough floor surface on which séparation occurs.

In an embodiment the effective cross-trough floor slope is the slope of a straight line which extends radially between radially inner and radially outer parts of a trough floor surface on which séparation occurs, wherein the radially inner part is a part where the floor surface meets a radially inner wall.

In an embodiment the effective cross-trough floor slope is the slope of a straight line which extends radially between radially inner and radially outer parts of a trough floor surface on which séparation occurs, wherein the radially outer part of the trough floor surface is a part where the floor surface meets a radially outer upstanding wall of the trough.

In an embodiment the line which extends radially between radially inner and radially outer parts of a trough floor surface on which séparation occurs is substantiaily coincident with the aciual trough floor surface. In other embodiments the actual trough floor surface deviates from the line, for example havîng a curved profile, or a profile comprising two or more straight segments which meet at a point which is not on the line.

In an embodiment the trough extends between about two tums and about five tums between a slurry feed point and a concentrate off-take point.

In an embodiment the trough extends between about 2.5 tums and about 4.5 tums between a slurry feed point and a concentrate off-take point.

In an embodiment the trough extends between about three tums and about four tums between a slurry feed point and a concentrate off-take point.

In an embodiment the trough extends about 3.5 tums between a slurry feed point and a concentrate off-take point.

In an embodiment the trough is in the form of a modulât trough unit, providing between about 2.5 tums and about 4.5 tums.

In an embodiment the trough provides an upstream coupling configuration at a more upstream part thereof for coupling to a more upstream part of a separator.

In an embodiment the upstream coupling configuration comprises a flange arrangement.

In an embodiment the trough provides a downstream coupling configuration at a more downstream part thereof for coupling to a more downstream part of a separator.

In an embodiment the downstream coupling configuration comprises a flange arrangement.

In an embodiment the trough provides a helical pitch of between 35 and 50cm.

In an embodiment the trough has a helical diameter of between 50 and 75 cm.

in an embodiment the trough has a helical diameter of between 60 and 65cm.

In an embodiment the spiral separator is a spiral separator for wet gravity séparation of minerais.

In an embodiment the spiral separator is a spiral separator for wet gravity séparation of heavy minerais from silica sand.

in an embodiment the spiral separator comprises at least two stages, at least two stages each comprising: a feed arrangement for feeding a slurry of mixed more-desired material and less-desîred material; a spiral trough; a splîtting arrangement for off-take of a concentrate band of more desired material; and wherein in at least two stages the spiral trough is configured as defined above in relation to the first aspect.

In an embodiment at least a second stage is provided substantially below a first stage.

In an embodiment the feed arrangement of at least one second or subséquent stage comprises a slurry préparation apparatus.

In an embodiment the slurry préparation apparatus comprises a mixing région for mixing material from a more fluid stream of a slurry flow exiting a more upstream stage with material from a less fluid stream of the slurry flow exiting the more upstream stage prior to feeding mixed prepared slurry into said second or subséquent stage.

In an embodiment the slurry préparation apparatus comprises an energy dissipation région to reduce kinetic energy of at least a substantial amount of material from a more fluid stream of a slurry flow exiting a more upstream stage, to thereby reduce the downstream velocity of said at least part of the more fluid stream.

In an embodiment the slurry préparation apparatus is in accordance with at least one of the aspects of the présent disclosure relating to a slurry préparation apparatus.

According to a second aspect of the présent disclosure there is provided a spiral separator for separating more-desîred material from less-desired material, the spiral separator comprising:

a feed arrangement for feeding a slurry of mixed more-desircd material and less-desired material;

a spiral trough; and a splitting arrangement for off-take of a concentrate band of more desired material;

wherein the spiral trough is configured to provide an effective cross-trough floor slope of less than 8 degrees to horizontal in a tum immédiately upstream of the splitting arrangement.

In an embodiment the spiral separator comprises at least two stages, at least two stages each comprising: a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material; a spiral trough; a splitting arrangement for off-take of a concentrate band of more desired material; and wherein in at least two stages the spiral trough is configured as defined above in relation to the second aspect.

In an embodiment at least a second stage is provided substantîally below a fïrst stage.

In an embodiment the feed arrangement of a second or subséquent stage comprises a slurry préparation arrangement.

In an embodiment the slurry préparation arrangement comprises a slurry préparation apparatus comprising a mixing région for mixing material from a more fluid stream of a slurry flow exiting a more upstream stage with material from a less fluid stream of the slurry flow exiting the more upstream stage prier to feeding mixed prepared slurry into said second or subséquent stage. In an embodiment the slurry préparation arrangement comprises a slurry préparation apparatus in accordance with an aspect of the présent disclosure.

According to a third aspect of the présent disclosure there is provided a spiral separator for providing ai least partial séparation of a fïrst species and a second species, comprising:

a feed arrangement;

a spiral trough comprising a more upstream région and a more downstream région;

a splitting arrangement;

wherein the feed arrangement is, in use, arranged to feed a feed slurry comprising a mix of said first species and said second species into the more upstream région of the spiral trough at a feed entry région;

wherein the more upstream région of the spiral trough has a trough floor région, and provides an effective cross-trough floor slope relative to the horizontal, which reduces from between 15 and 20 degrees to a cross-trough floor angle of between 10 degrees and 14 degrees;

wherein the more downstream région of the spiral trough has a trough floor région having an effective cross-trough floor angle which reduces to between 4 degrees and 8 degrees, relative to the horizontal; and wherein the splitting arrangement is provided ai or immedîately adjacent the more downstream région, to split a concentrated band of the first species from the rest of the flow in the spiral trough.

In an embodiment a downstream end of the more upstream région is connected to an upstream end of the more downstream région.

In an embodiment a downstream end of the more upstream région is contiguous with an upstream end of the more downstream région.

In an embodiment a downstream end of the more upstream région is continuons with an upstream end of the more downstream région.

In an embodiment in the more upstream région of the spiral trough at least part of a région which has said effective cross-trough floor angle relative to the horizontal, of between 15 and 20 degrees is provided at a position within 1.5 tums from the feed entry région.

In an embodiment, in the more upstream région of the spiral trough said réduction in effective cross-trough floor angle occurs at rate of between 2 degrees réduction in angle and 4 degrees réduction in angle, over at least one tums of the more upstream région of the spiral trough.

In an embodiment, in the more upstream région of the spiral trough said réduction in effective cross-trough floor angle occurs at rate of between 2 degrees réduction in angle and 4 degrees réduction in angle, over each of at least two tums of the more upstream région of the spiral trough.

In an embodiment the spiral separator comprises at least two stages, at least two stages each comprising: a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material; a spiral trough; a splitting arrangement for off-take of a concentrate band of more desired material; and wherein in at least two stages the spiral trough is configured as defmcd above in relation to the third aspect.

In an embodiment at least a second stage is provided substantially below a first stage.

In an embodiment the feed arrangement of a second or subséquent stage comprises a slurry préparation arrangement. In an embodiment the slurry préparation arrangement comprises a slurry préparation apparatus comprising a mixing région for mixing material from a more fluid stream of a slurry flow exiting a more upstream stage with material from a less fluid stream of the slurry flow exiting the more upstream stage prior to feeding mixed prepared slurry into said second or subséquent stage. In an embodiment the slurry préparation arrangement comprises a slurry préparation apparatus in accordance with an aspect of the présent disclosure.

According to a fourth aspect of the présent disclosure there is provided a spiral separator for separating more-desired material from less-desired material, the spiral separator comprising;

a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material;

a spiral trough;

a splitting arrangement for off-take of a concentrate band of more desired material; and wherein the spiral trough is configured to provide a trough floor with an effective crosstrough floor slope which reduces between an upstream région thereof and a downstream région thereof, and wherein the réduction in effective cross-trough floor slope in a tum immediately upstream of the splitting arrangement is provided by the pîtch of a more radially outer région of the spiral trough and the pîtch of a more radially inner région of the trough being different over said tum of the spiral trough, and wherein the différence in pîtch over saîd tum is between 0.08 and 0.18 times the radial distance between said more radially outer région and said more radially inner région.

In an embodiment, the différence in pitch over said tum is between 0.9 and 0.14 times the radial distance between said more radially outer région and said more radially inner région.

In an embodiment, the différence in pîtch over said turn is between 0.95 and 0.12 times the radial distance between said more radially outer région and said more radially inner région.

In an embodiment the turn immediately upstream of the splitting arrangement provides a refîner région of the trough, and the trough provides least one turn upstream of the refîner région over which the pîtch of a more radially outer région and the pîtch of a more radially inner région are different, and wherein the différence in pitch over said tum is less than 0.08 times the radial distance between said more radially outer région and said more radially inner région.

In an embodiment the turn immediately upstream of the splitting arrangement provides a refîner région of the trough, and the trough provides least one tum upstream of the refîner région over which the pîtch of a more radially outer région and the pitch of a more radially inner région are different, and wherein the différence in pitch over said tum, expressed as a multiple of radial distance between more radially outer and more radially inner régions, is less than that in the refîner région.

In an embodiment the spiral separator comprises at least two stages, at least two stages each comprising: a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material; a spiral trough; a splitting arrangement for off-take of a concentrate band of more desîred material; and wherein in at least two stages the spiral trough is configured as defîned above in relation to the fourth aspect.

According to a fîfth aspect of the présent disclosure there is provided a spiral separator for separating a more-desired material from a less-desired minerai of a feed slurry containing said more-desired and less-desired inaterials, wherein the less-desired material has a spécifie gravity less than that of the more-desired material, the spiral separator comprising:

a feed arrangement;

a spiral trough comprising a more upstream région and a more downstream région;

a splitting arrangement;

wherein the feed arrangement is, in use, arranged to feed a feed slurry of the moredesired and less-desired materials into the more upstream région of the spiral trough;

wherein the more upstream région of the spiral trough has a trough floor région, and provides one or more effective cross-trough floor angles relative to the horizontal, to thereby provide a preliminary concentrate band in which some of the less-desired minerai is mixed with concentrated more-desired material;

wherein the more downstream région of the spiral trough has at least one floor région, having a cross-trough floor angle configured to provide a refîner région where a balance of centrifugal and gravitational forces on the concentrate band is such that both the more-desired and less-desired materials would, if the balance of forces were maintained, migrate outwardly;

wherein the apparatus provides a refinement part of the refîner région at which least some of the less-desired material has migrated outwardly from a radial position corresponding to that of the preliminary concentrate band, and at which no substantial amount of the more-desired material has migrated substantially outwardly due to the balance of centrifugal and gravitational forces, so that a retîned concentrate band is provided at the refinement part; and wherein the splitting arrangement is provided at or immédiately downstream of the refinement part to split the refmed concentrate band from the rest of the slurry in the spiral trough.

In an embodiment said cross-trough floor angle which is configured to provide said refîner part région is smaller than a cross-trough floor angle of a radially corresponding région of the more upstream part of the trough.

In an embodiment the trough is configured to provide an effective cross-trough floor angle in the refîner part which is substantially smaller than the smallest effective cross-trough floor angle in the more upstream région.

In an embodiment the spiral separator is for séparation of more desired parti cul ate minerai from a less-desired particulate minerai.

In an embodiment the spiral separator is for séparation of more desired heavy minerai from a less-desired silica sand.

In an embodiment the trough is configured to provide an effective cross-trough floor angle in the refîner région which is at least 5 degrees smaller than the smallest effective crosstrough floor angle in the more upstream région.

In an embodiment the trough is configured to provide an effective cross-trough floor angle in the refîner région which is at least 5 degrees smaller than the effective cross-trough floor angle one turn upstream of the refîner région.

In an embodiment the feed arrangement is connected to the more upstream part of the spiral trough.

In an embodiment the spiral separator comprises at least two stages, at least two stages each comprising: a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material; a spiral trough; a splitting arrangement for off-take of a concentrate band of more desired material; and wherein in at least two stages the spiral trough is configured as defïned above in relation to the fifth aspect.

In an embodiment at least a second stage is provided substantîally below a first stage.

In an embodiment the feed arrangement of a second or subséquent stage comprises a slurry préparation apparatus.

According to a sixth aspect of the présent disclosure there is provided a method for séparaiing a first species from a second species of a feed slurry containing said first and second species, wherein the second species has a spécifie gravity less than that of the first species, the method comprising:

feeding a feed slurry of the first and second species down a trough of a spiral separator, wherein an effective cross-trough floor slope of the trough, relative to horizontal, reduces relatively gradually over at least one more-upstream tum of the trough, and wherein the effective cross-trough floor slope of the trough reduces relatively rapidly over a more downstream tum of the trough, and providîng a take-off opening at or adjacent said more downstream tum of the trough.

In an embodiment, the method comprises:

providing the trough such that during movement of the slurry along said at least one more upstream tum of the trough a higher proportion of said first species than of said second species migrâtes to a radially inward région of the trough to form a preliminary concentrate band containing both said first and second species, wherein the proportion of the first species to second species is substantîally higher than in the feed slurry; and wherein the relatively rapid réduction in effective cross-trough floor slope in said more downstream tum results in a more rapid migration of said second species than of said first species, outwardly from said preliminary concentrate stream, to leave an improved concentrate stream, wherein the proportion of the first species to second species is higher than in the prelimmary concentrate stream, at a radially inward région of the more downstream tum.

In an embodîment, the method comprises splitting ail or part of the improved concentrate band from the rcst of the slurry.

In an embodîment, the method comprises segregating ail or part of the improved concentrate band from the rest of the slurry via the take-off opening.

In an embodîment the take-off opening is at least partially defined by a splitter member.

In an embodîment the splitter member is moveable to allow adjustment of the size of the take-off opening.

In an embodîment, in at least some of the more downstream part, the effective crosstrough floor slope, relative to the horizontal, is less than 8 degrees.

In an embodîment the method comprises use of a spiral separator in accordance with at least one of the first to fifth aspects.

In an embodîment the method comprises use of a spiral separator havîng at least two séparation stages.

In an embodîment the method comprises providing a slurry préparation apparatus between two successive stages.

In an embodîment the slurry préparation apparatus comprises a mixing région for mixing material from a more fluid stream of a slurry flow exiting a more upstream stage with material from a less fluid stream of the slurry flow exiting the more upstream stage prier to feeding mîxed prepared slurry into said second or subséquent stage. In an embodîment the slurry préparation apparatus comprises a slurry préparation apparatus in accordance with an aspect of the présent disclosure.

According to a seventh aspect of the présent disclosure there is provided a slurry préparation apparatus for preparing a slurry from an upstream spiral trough région of a spiral separator, in which the slurry comprises a more fluid stream and a less fluid stream, for entry to a downstream spiral trough région as a prepared mîxed slurry, the slurry préparation apparatus comprising:

an inlet région for ingress of received slurry from an upstream trough région;

an outlet région for providing prepared mixed slurry to a downstream spiral trough région;

an energy dissipation région to reduce kinetic energy of at least a substantial amount of material from the more fluid stream, to thereby reducc the downstream velocîty of said at least part of the more fluid stream before the prepared mixed slurry exits the outlet région; and a mixing région for mixing material from the more fluid stream with material from the less fluid stream.

In an embodiment, the slurry préparation apparatus, by virtue of reducing the kinetic energy of material from the more fluid stream and mixing material from the more fluid and less fluid streams, is adapted to provide a prepared slurry from the outlet région, in which said prepared slurry is substantîally the same in its characteristics of fluid/particulate distribution and downstream velocîty as a typical slurry fed from a feedbox onto an upstream part of a trough of a spiral separator.

In an embodiment, the slurry préparation apparatus, by virtue of reducing the kinetic energy of material from the more fluid stream and mixing material from the more fluid and less fluid streams, îs adapted to provide a prepared slurry from the outlet région, in which the more fluid stream and less fluid stream are thoroughly mixed and in which the prepared slurry has low outlet velocîty.

In an embodiment the apparatus is configured such that the down trough progress of the less fluid stream is continues substantîally unimpeded throughout by reflux of water or pulp upstream, dewatering or direction changes on the trough floor that may initiate sanding.

In an embodiment the apparatus is configured such that the down trough progress of the material from the less fluid stream is, at least until the mixing of said material from the less fluid stream with material from the more fluid stream in the mixing région, unimpeded by reflux of water or pulp upstream, dewatering within the slurry préparation apparatus, or direction changes on the trough floor that may initiate sanding.

In an embodiment the slurry préparation apparatus comprises a trough floor part to receive and convey material from the less fluid stream, from the inlet région.

In an embodiment, the slurry préparation apparatus comprises a passageway for passage of at least part of the received slurry along at least part of a route between the inlet région and the outlet région, wherein the passageway provides a floor région which has a downstream si ope and wherein said floor région of the passageway is configured ίο provide the apparatus with a drop région providing a vertically downward accélération of at least some material from the more fluid stream to facilitate mixing of the more fluid stream with the less fluid stream in the mixing région.

In an embodiment, the floor région has a downstream slope which is different to the downstream slope of the upstream spiral trough région.

In an embodimenÎ, the floor région has a downstream slope which is different to the downstream slope of the upstream spiral trough région at a corresponding radial position.

In an embodiment, the floor région has a downstream slope which is different to the downstream slope of the upstream spiral trough région at a part of the upstream spiral trough région proximal to the slurry préparation apparatus.

In an embodiment the floor région comprises a ramp région which extends at a greater angle of élévation, in a downstream direction, than does a trough floor part of the slurry préparation apparatus.

In an embodiment the floor région of the passageway comprises a ramp région to elevate said at least some material from the more fluid stream relative to material from the less fluid stream.

In an embodiment the passageway provides a drop région by tennination of said floor région of the passageway.

In an embodiment the drop région provides a région at which at least some of the material from the more fluid stream falls onto at least some of the material from the less fluid stream.

In an embodiment the drop région provides a région at which a stream of material from the more fluid stream falls onto at a stream of material from the less fluid stream.

In an embodiment the energy dissipation région is provided before or substantially at the drop région.

In an embodiment the slurry préparation apparatus is configured to act upon material from the more fluid stream to reduce the kinetic energy, in the energy dissipation région, before said material from the more fluid stream mixes with the material from the less fluid stream in the mixing région.

In an embodiment tire slurry préparation apparatus is configured to provide the energy dissipation région at, or upstream relative to, the mixing région.

In an embodiment the apparatus provides a first route between the inlet région and the mixing région, solely or primarily for material from the more fluid stream, and a second route between the inlet région and the mixing région, solely or primarily for material from the less fluid stream.

In an embodiment the first route is elevated relative to the second route.

In an embodiment the first route is provided at least partially by a ramp arrangement.

In an embodiment the second route is provided by a trough floor part of the apparatus.

in an embodiment the first route is provided at least partially by a compartment of the apparatus which is elevated relative to the second route.

In an embodiment the energy dissipation région comprises at least one impeding element to impede downstream flow of at least a substantial amount of material from the more fluid stream.

In an embodiment at least one impeding element comprises a baffle part.

In an embodiment at least one baffle part is provided at or substantially above a drop région of the apparatus which, in use, provides a vertically downward accélération of at least some material from the more fluid stream to facîlitate mixing.

In an embodiment material from the more fluid stream drops onto material from the less fluid stream at said drop région.

In an embodiment at least one baffle part comprises a barrier part having an upper edge and a lower edge.

In an embodiment at least one baffle part comprises a barrier part having a lower edge which is substantially free.

In an embodiment at least one baffle part comprises a barrier part having a lower edge which is substantially free and below which material may flow.

In an embodiment at least one baffle part comprises a barrier part having an upper edge by which the barrier part is supported.

In an embodiment at least one baffle part comprises ai least part of a downstream wall of the apparatus.

In an embodiment at least one impeding element comprises at least part of a downstream wall of the apparatus.

In an embodiment at least one impeding element comprises a wall of said passageway.

In an embodiment the energy dissipation région comprises a convoluted or serpentine passageway région.

In an embodiment the energy dissipation région is provided downstream of the mixing région.

In an embodiment the apparatus is configured so the energy dissipation région, in use, acts on the material from the more fluid stream after it is mixed with material from the less fluid stream.

In an embodiment the mixing région comprises a converging channel région.

In an embodiment the mixing région comprises a converging channel région in which a radially outer wall of the channel région guides material from the more fluid stream inwardly towards the more fluid stream.

In an embodiment the converging channel région guides material from the more fluid stream and material from the more fluid stream into a descending conduit.

In an embodiment at least one of the converging channel and descending conduit provides a drop région which, in use, provides a vertically downward accélération of at least some material from the more fluid stream, to facilitate mixing.

In an embodiment the drop région may also provide a vertically downward accélération of material from the less fluid stream.

In an embodiment the energy dissipation région comprises an energy dissipation box.

In an embodiment the energy dissipation box comprises a radially outer wall portion, a radially inner wall portion, an upper wall portion providing at least part of a cover part of the energy dissipation box.

In an embodiment the energy dissipation box comprises at least one impeding élément.

In an embodiment the mixing région is provided within the energy dissipation box.

According to an eighth aspect of the présent disclosure there is provided a slurry préparation apparatus for preparing a slurry from an upstream spiral trough région of a spiral separator, in which the slurry comprises a more fluid stream and a less fluid stream, for entry to a downstream spiral trough région as a prepared mixed slurry, the slurry préparation apparatus comprising:

an inlet région for ingress of received slurry from an upstream trough région;

an outlet région for providing prepared mixed slurry to a downstream spiral trough région;

a passageway for passage of at least part of the received slurry along at least part of a route between the inlet région and the outlet région, wherein the passageway provides a floor région which has a downstream slope, and wherein said floor région of the passageway is configured to provide the apparatus with a drop région providing a vertically downward accélération of at least some material from the more fluid stream to facilitate mixing of the more fluid stream with the less fluid stream between said inlet région and said outlet région; and at least one impeding element to impede downstream flow of at least some material from the more fluid stream, to thereby reduce the downstream velocîty of said at least part of the more fluid stream before the prepared mixed slurry exits the outlet région.

In an embodiment, the floor région has a downstream slope which is different to the downstream slope ofthe upstream spiral trough région.

In an embodiment, the floor région has a downstream slope which is different to the downstream slope of the upstream spiral trough région at a, or any, radial position on the upstream spiral trough région corresponding to the radial position of the floor région.

In an embodiment, the floor région has a downstream slope which is different to the downstream slope of the upstream spiral trough région at a part of the upstream spiral trough région proximal to the slurry préparation apparatus.

In an embodiment the floor région of the passageway comprises a ramp région to elevate said at least some material from the more fluid stream relative to material from the less fluid stream.

In an embodiment the apparatus provides a trough floor région for passage of at least some material from the less fluid stream along at least part of a route between the inlet région and the outlet région.

According to a ninth aspect of the présent disclosure there is provided a slurry préparation apparatus for preparing a slurry from an upstream spiral trough région of a spiral separator, in which the slurry comprises a more fluid stream and a less fluid stream, for entry to a downstream spiral trough région as a prepared mixed slurry, the slurry préparation apparatus comprising:

an inlet région for ingress of received slurry from an upstream trough région;

an outlet région for providîng prepared mixed slurry to a downstream spiral trough région;

an energy dissipation box comprising a radially outer wall portion, a radially inner wall portion, an upper wall portion providîng at least part of a covering part of the energy dissipation box and at least one impeding élément for impeding downstream flow of at least a substantial amount of material from the more fluid stream, to reduce kinetic energy thereof and to thereby reduce the downstream velocity of said at least part of the more fluid stream before the prepared mixed slurry exits the outlet région; and a mixing région for mixing material from the more fluid stream with material from the less fluid stream.

In an embodiment the mixing région is provided within the energy dissipation box.

In an embodiment at least one impeding element comprises a baffle part.

In an embodiment the energy dissipation box comprises at least one downstream wall portion extending at least part of the way between the radially outer wall portion and the radially inner wall portion.

In an embodiment the downstream wall portion provides an opening therein for allowing prepared mixed slurry to exit the energy dissipation box.

In an embodiment the openïng is provided at a of the energy dissipation box which is located at a radially outward part, with respect to an axis of the upstream spiral trough.

In an embodiment at least one baffle part is provided by at least part ofthe downstream wall portion.

In an embodiment the inlet région is configured to be connected to a downstream end région of the upstream spiral trough.

In an embodiment the inlet région comprises a floor région correspondîng generally in shape to a floor région of a trough of a spiral separator.

In an embodiment the inlet région comprises a floor région correspondîng generally in shape to a floor région of a downstream end région of the upstream spiral trough.

According to a tenth aspect of the présent disclosure there is provided a slurry préparation apparatus for preparing a slurry from an upstream spiral trough région of a spiral separator, in which the slurry comprises a more fluid stream and a less fluid stream, for entry to a downstream spiral trough région as a prepared mixed slurry, the slurry préparation apparatus comprising:

an inlet région for ingress of received slurry from an upstream trough région;

an outlet région for provîding prepared mixed slurry to a downstream spiral trough région;

an energy dissipation région to reduce kinetic energy of at least a substantial amount of material from the more fluid stream, to thereby reduce the downstream velocity of said at least part of the more fluid stream before the prepared mixed slurry exits the outlet région;

a mixing région for mixing material from the more fluid stream with material from the less fluid stream; and wherein the apparatus îs configured such that the down trough progress of the less fluid stream is continues substantially unimpeded throughout b y reflux of water or pulp upstream, dewaterîng or direction changes on the trough floor that may înitiate sanding.

According to an eleventh aspect of the présent disclosure there is provided a slurry préparation apparatus for preparing a slurry from an upstream spiral trough région of a spiral separator, in which the slurry comprises a more fluid stream and a less fluid stream, for entry to a downstream spiral trough région as a prepared mixed slurry, the slurry préparation apparatus comprising:

an inlet région for ingress of received slurry from an upstream trough région;

an outiet région for providing prepared mixed slurry to a downstream spiral trough région;

an energy dissipation région to reduce kînetic energy of at least a substantial amount of material from the more fluid stream, to thereby reduce the downstream velocity of said at least part of the more fluid stream before the prepared mixed slurry exits the outiet région;

a mixing région for mixing material from the more fluid stream with material from the less fluid stream; and wherein the apparatus is configured such that the down trough progress of the material from the less fluid stream is, at least until the mixing of said material from the less fluid stream with material from the more fluid stream in the mixing région, unimpeded by reflux of water or pulp upstream, dewaterîng within the slurry préparation apparatus, or direction changes on the trough floor that may initiate sanding.

According to a twelfth aspect of the présent disclosure there is provided a spiral trough for use in a spiral separator in accordance with any one or more of the fïrst to fifth aspects.

According to a thîrteenth aspect of the présent disclosure there îs provided a spiral trough for use in a spiral separator, the spiral trough comprising an upstream région and a downstream région, wherein the spiral trough is configured to provide a trough floor région with an effective cross-trough floor slope which reduces b y between 5 and 8 degrees in a tum at said downstream région.

In an embodiment the upstream région is adapted, in use, to receive a slurry of mixed more-desired material and less-desired material from a feed arrangement of said spiral separator.

The feed arrangement may comprise a feedbox of a spiral separator. In one alternative the feed arrangement may comprise an arrangement between two stages of a spiral separator which feeds slurry to a downstream stage.

In an embodiment the upstream région comprises an upstream end région of the trough.

In an embodiment the downstream région is adapted to receive or comprise a splitting arrangement of said spiral separator, and to provide said trough floor région such that the effective cross-trough floor si ope reduces by between 5 and 8 degrees in a tum immediately upstream of the splitting arrangement.

In an embodiment the downstream région comprises a downstream end région of the trough.

It will be appreciated that a spiral trough in accordance with the thirteenth aspect may be for use in a spiral separator in accordance with the first aspect.

According to a fourteenth aspect of the présent disclosure there is provided a spiral trough for use in a spiral separator, the spiral trough comprising an upstream région and a downstream région, wherein the spiral trough is confîgured to provide an effective cross-trough floor slope of less than 8 degrees to horizontal in a tum at said downstream région.

In an embodiment the upstream région is adapted, in use, to receive a slurry of mixed more-desîred material and less-desired material from a feed arrangement of said spiral separator.

In an embodiment the upstream région comprises an upstream end région of the trough.

In an embodiment the downstream région is adapted to receive or comprise a splitting arrangement of said spiral separator, and to provide said effective cross-trough floor slope of less than 8 degrees to horizontal in a tum immediately upstream of the splitting arrangement.

In an embodiment the downstream région comprises a downstream end région of the trough.

It will be appreciated that a spiral trough in accordance with the fourteenth aspect may be for use in a spiral separator in accordance with the second aspect.

According to a fïfteenth aspect of the présent disclosure there is provided a spiral trough for use in a spiral separator for providing at least partial séparation of a first species and a second species, the spiral trough comprising:

a more upstream région, the more upstream région comprising a sluiTy feed région adapted, in use, to receive a feed slurry comprising a mix of said first species and said second species from a feed arrangement of said spiral separator;

a more downstream région, adapted to be provided in said spiral separator with a splitting arrangement provided at or immediately adjacent the more downstream région, to split a concentrated band of the first species from the rest of the flow in the spiral trough;

wherein the more upstream région of the spiral trough has a trough floor région, and provides an effective cross-trough floor slope relative to the horizontal, which reduces from between 15 and 20 degrees to a cross-trough floor angle of between 10 degrees and 14 degrees; and wherein the more downstream région of the spiral trough has a trough floor région having an effective cross-trough floor angle which reduces to between 4 degrees and 8 degrees, relative to the horizontal,

It will be appreciated that a spiral trough in accordance with the fïfteenth aspect may be for use in a spiral separator in accordance with the third aspect,

According to a sixteenth aspect of the présent disclosure there is provided a spiral trough for use in a spiral separator wherein the spiral trough is configured to provide a trough floor with an effective cross-trough floor slope which reduces between an upstream région thereof and a downstream région thereof, and wherein the réduction in effective cross-trough floor slope in a turn at a downstream région of the spiral trough is provided by the pitch of a more radially outer région of the spiral trough and the pitch of a more radially inner région of the trough being different over said tum of the spiral trough, and wherein the différence in pitch over said tum is between 0,08 and 0,18 times the radial distance between said more radially outer région and said more radially inner région.

In an embodiment the downstream région is adapted to receive or comprise a splitting arrangement of said spiral separator, and to provide said tum of the spiral trough in a turn immediately upstream of the splitting arrangement.

In an embodiment the downstream région comprises a downstream end région of the trough.

It will be appreciated that a spiral trough in accordance with the sixteenth aspect may be for use in a spiral separator in accordance with the fourth aspect.

According to a sevcnteenth aspect of the présent disclosure there is provided a spiral trough for use in a spiral separator for separating a more-desired material from a less-desired minerai of a feed slurry containing said more-desired and less-desired materials, wherein the less-desired material has a spécifie gravity less than that of the more-desired material, and wherein the spiral trough comprises:

a more upstream région adapted, in use, to receive the slurry from a feed arrangement of said spiral separator;

a more downstream région;

wherein the feed arrangement is, in use, arranged to feed a feed slurry of the moredesired and less-desired materials into the more upstream région of the spiral trough;

wherein the more upstream région of the spiral trough has a trough floor région, and provides one or more effective cross-trough floor angles relative to the horizontal, to thereby provide a preliminary concentrate band in which some of the îess-desired minerai is mixed with concentrated more-desired material;

wherein the more downstream région of the spiral trough has at least one floor région, having a cross-trough floor angle configured to provide a refîner région where a balance of centrifugal and gravitational forces on the preliminary concentrate band is such that both the more-desired and less-desired materials would, if the balance of forces were maintained, migrate outwardly;

wherein spiral trough provides a refinement part of the refîner région at which, in use, least some of the less-desired material has migrated outwardly from a radial position corresponding to that of the preliminary concentrate band, and at which no substantial amount of the more-desired material has migrated substantially outwardly due to the balance of centrifugal and gravitational forces, so that a refïned concentrate band is provided at the refinement part.

In an embodiment the more downstream région is adapted to receive or comprise a splitting arrangement of said spiral separator, and to provide said refinement part immediately upstream ofthe splitting arrangement.

In an embodiment the refinement part is provided substantially at a downstream end part of said trough.

It will be appreciated that a spiral trough in accordance with the seventeenth aspect may be for use in a spiral separator in accordance with the flfth aspect.

will be appreciated that features or characteristîcs of any of the above aspects or embodiments thereof may be incorporated into any of the other aspects. Further, features and characteristîcs described in relation to any embodiment of a particular given aspect may be considered to be disclosed as being independently applicable to other aspects wîthout requiring importation of other limitations of the said particular given aspect.

Brief description of the drawings

Embodiments will be described below, in detail, with reference to accompanying drawings. The primary purpose of this detaîled description is to instruct persons having an interest in the subject matter of the invention how to carry the invention into practical effect. However, it is to be clearly understood that the spécifie nature of this detailed description does not supersede the generality of the preceding broad description. In the accompanying diagrammatic drawings:

Figure l(a) is a schematic side elevational view of an embodiment of a spiral separator in accordance with the présent disclosure, being a three start separator with three spirals;

Figure l(b) is a schematic side élévation of the spiral separator of Figure IA, but showing only one of the three spirals;

Figures 2 to 6 are schematic radial cross sectional views, to larger scale, of parts of the spiral shown in Figure l(a);

Figure 7 is a schematic side élévation of a modular spiral trough used in the embodiment of Figures l(a) and l(b);

Figure 8 is a schematic perspective view of a first embodiment of a slurry préparation apparatus in accordance with the présent disclosure;

Figure 9 is a schematic perspective view of a lid part of the embodîment of Figure 8;

Figure 10 is a top plan view of the embodîment of Figure 8, in use, with the lid omitted so that internai detail is visible;

Figure 11 is a perspective view of the embodîment of Figure 8, in use, with the lid omitted so that internai detail is visible;

Figure 12 is a further perspective view of the embodîment of Figure 8, with the lid omitted;

Figure 13 is a cross sectîonal view on B-B of Figure 12;

Figure 14 is a further perspective view of the embodîment of Figure 8, with the lid omitted;

Figure 15 is a cross sectional view on XV-XV of Figure 14;

Figures 1 6 to 19 illustrate a second embodîment of a slurry préparation apparatus, with Figure 19 being a cross sectional view on A-A of Figure 18;

Figures 2 0 to 22 illustrate a thîrd embodîment of a slurry préparation apparatus, with Figure 22 beîng a cross sectional view on C-C of Figure 21 ;

Figure 23 illustrâtes use of the embodîment of Figures 20 to 22 in a multiple-start spiral separator; and

Figures 2 4 to 26 are comparative séparation performance curves comparing séparation including the teachîng of the présent disclosure with other approaches.

Detailcd description of embodiments

With reference to the accompanying drawings, an embodîment of a spiral separator, generally designated b y the reference numéral 1, will now be described. The spiral separator 1 is an embodîment for use in wet gravity séparation of desired (or more-desired) higher-densîty material, which in a particular embodîment is a heavy minerai, from an undesired (or lessdesired) material with a lower spécifie gravity, for example silica sand.

The spiral separator 1, as illustrated in Figure l(a), comprises an upright central column 3 supporting three spirals 5, 5A and 5B.

Figure l(b) shows for clarity, only a first of the three spirals, designated by the reference numéral 5. The second and third spirals 5A and 5B, shown in Figure 1, are substantîally identical to spiral 5, As will be appreciated by those skilled in the field of spiral scparators for wet gravity séparation, the spiral separator 1, having three spirals, may be regarded as a “three start” separator.

In the embodiment illustrated in Figure i(a), the second and third spirals 5A, 5B are arranged so that each respective tum of each of the second and third spirals is substantîally below the correspond!ng tum of the first spiral 5. As the three spirals of the separator 1 are substantîally identical, for simplicity and clarity only the first spiral 5 will be described in detail, and it should be appreciated that where only one spiral is explicitly described or illustrated, the other spirals correspond. However, it should also be appreciated that the présent disclosure is not limited to a spiral separator having three spirals, but is also applicable to spiral séparai ors having a single spiral, two spirals, or four or more spirals, that is, generally, to single-start and to multiple-start spiral separators.

A conventional arrangement (not shown), for example including a powered pump, is provided for admitting a slurry or pulp to each spiral via a feedbox, for example feedbox 7, at a predetermined rate, at or adjacent the top of the spiral. The feedbox 7 may be a conventional type of feedbox having stilling baffles (not shown) installed înternally to slow and “still” the feed allowing low velocîty entry of the slurry or pulp onto the first tum of the corresponding spiral. The ternis slurry and pulp, as used herein, should be considered to be used interchangeably. Similarly the ternis hélix and spiral should be considered to be used interchangeably, unless context dictâtes otherwise

A splittîng arrangement 9, which may be a conventional splitting arrangement, is provided at the bottom of each spiral 5, 5A, 5B for splitting the descending slurry stream into fractions (for example corresponding to radîally distributed streams or bands) and recovering certain desired fractions. In the illustrated embodiment the splitting arrangement 9 comprises spli tiers (not shown) and off-take channels 9A, 9B, 9C provided to split and off-take the descending slurry flow into a concentrâtes fraction, a middlings fraction and a tails fraction, respectively.

The spiral separator 1 may be regarded as a two-stage separator, comprising a first stage 30 and a second stage 50.

The first stage 30 comprises a first helical trough part of each spiral, for example a first helical trough 100 ofthe first spiral 5. The first helical trough 100 is 3.5 tums from a pulp feed point 32, where pulp is fed onto the first helical trough 100 by the feedbox 7 to a concentrate offtake point 34 provided at or adjacent the downstream end of the first helical trough 100, that is, substantially at the end of the first stage 30.

Directly downstream of the first stage 30 there is provided a mixing région 40 for remixing components of the slurry which exit the first stage 30, other than a concentrâtes stream which is removed at the take-off point 34. The second stage 50 is directly downstream of the mixing région 40, and comprises a second helical trough 100A which is 3.5 tums from a pulp feed point 52, where pulp exits the mixing région 40 and is fed onto the second helical trough 100A, to an off-take point 54 at the splitting arrangement 9. The first and second helical troughs 100, 100A of the first spiral 5 may be substantially identical, each providing a substantially sîmilar trough shape and variation of floor angle over corresponding turns, as will be described in due course. If desired, further similar stages may be provided, with each stage being separated by a mixing région. The mixing région 40, in the ilîustrated embodiment, provides a slurry préparation apparatus, for ex ample slurry préparation apparatus 800, which will be described in due course with reference to Figures 8 to 15, for preparing the slurry for entry onto the second stage 50. In the described embodiment the slurry préparation apparatus includes a concentrate take-off, at take-off point 34, but is will be appreciated that the concentrate take-off at take-off point 34 may, in a variation, be provided on, or as part of, the trough 100.

The shape of the first trough 1Ü0 will now be described in more detail, bearing in mind that the shape ofthe second trough 100A is substantially similar in the ilîustrated embodiment.

Figures 2, 3, 4, 5 and 6 are somewhat schematic radial cross sectional views at progressively lower, or more downstream, parts of the trough 10Û, illustrating the variation of the profile of the first trough 100, in the spiral separator 1 of Figure 1, in successively downstream parts of the first trough 100. The particular embodiment ilîustrated by Figures 2 to 6 is provided by way of example only, and other embodiments and variations are of course possible.

It should be appreciated that reference to a radial cross section at a given point is intended to mean a cross section in a plane which includes that point, which extends in a radial direction of the trough, and which is parallel to and intersects the hélix axis (which is also, in this embodiment, the axis of the central column 3). Reference to cross-trough floor slope or cross trough floor angle is intended to mean the slope or angle of the floor of the trough when viewed in radial cross section.

Figure 2 illustrâtes the radial cross sectional shape, or profile, of the first trough 100, at an uppennost or most upstream part, that is, at or adjacent the slurry feed point 32. This position îs marked as TURN 0 in Figure 1 (b), indicating that this position corresponds to approximately zéro turns after the feed point. At this part the trough 100 has a floor profile providing a relatively narrow feed entry channel 120 allowing feed to enter the trough 100, from the feedbox 7, at a radially outer part of the trough 100. The feed entry channel 120 has a floor part 122 which is substantially horizontal in radial cross section. The feed entry channel 120 is bounded on the radially outer side of the channel 120 by an upstanding outer wall 125 of the trough 100, and bounded on the radially inner side of the channel 120 by a raised profile part 127 of the trough 100.

In the illustrated embodiment the trough profile changes with successive turns of the trough 100, as illustrated by Figures 2 to 6 when considered together.

As can be seen by comparison of Figures 2 and 3, the raised profile part 127 is rapidly flattened, over the first half tum.

In the illustrated embodiment, from tum 0.5 down, the trough 100 provides a trough floor 130, with a profile which is substantially straight and which extends across most of the radius of the trough 100, as can be seen generally from Figures 3 to 6.

The trough floor 130 is provided between, and bounded by, the upstanding outer wall 125 of the trough 100 on the radially outer side of the trough floor 130, and an upstanding inner wall part 132 of the trough 100 on the radially inner side of the trough floor section 130.

In the illustrated embodiment the upstanding inner wall part 132 of the trough 100, provides a barrier between the trough floor 130, and a radially inner concentrate gutter 134, which may be used (particularly in second or subséquent stages of the spiral separator) to convey concentrate which has been separated from the rest of the slurry, quarantined away from the slurry which is still subject to the séparation process in the spiral.

The trough floor 130, in the illustrated embodiment, may be regarded as the région which is substantially straight in profile and the profile of which extends outwardly and upwardly from a radially inner part 136, where the inner wall part 132 transitions into the trough floor 130, to a radially outer part 138, where the trough floor 130 transitions into the upstanding outer wall 125. It should, however, hc appreciated that the trough floor 130 is not required to be straight in profile in ail embodiments,

The trough floor 130 may be regarded as a working surface of the trough 100 on which séparation occurs, and on which components of the slurry are desirably radially mobile to allow séparation of different materials.

The variation in profile of the trough, and in particular the change in cross-trough angle of the trough floor, relative to horizontal, over successive tums will now be described in relation to the illustrated embodiment. The different angles of the trough floor are indicated by angles marked on Figures 3 to 6. It should be appreciated that the numerical values provided in the Figures for the trough floor angles and the positions indicated by number of hélix tums from the feed point 32, are for a particular embodiment and by way of example only.

As illustrated in Figure 3, at tum 0.5 the trough floor 130 may hâve a cross-trough floor slope angle of about 18 degrees (or, more broadly speaking, of between about 15 and about 20 degrees). The transition from the profile shown in Figure 2 to the profile shown in Figure 3 may be regarded as a feed transition zone, designated 140 in Figure l(b), within which the slurry increases in velocity in a steady and controlled manner.

In this feed transition zone, the cross sectional shape of the trough transitions gradually from providing relatively narrow feed entry channel 120, adjacent the outer wall 125 of the trough 100, having a floor part 122 with substantially zéro cross-trough floor slope (at Tum 0, as illustrated in Figure 2) to providing a substantially full wîdth floor profile (at Tum 0.5, illustrated in Fig 3) with a cross trough slope of between about 15 and about 20 degrees.

The increase in velocity of the slurry will of course be somewhat dépendent on the slope of the trough floor 130 in the down-trough direction, in addition to the slope in the crosstrough direction, which is represented by the profile or cross sectional slope, as illustrated in Figures 2 to 6. As will be understood by those familiar with spiral separators for wet gravity séparation, the slope in the down-trough direction varies across the width of the trough, as the radially outward part of a helical trough, being further from the hélix axis, describes a much longer path over each turn than does the more inward part of the helical trough, while undergoing approximately the same vertical descent. The down-trough slope at any gîven radial point (ignoring cross-trough slope) is broadly speaking determîned by the pitch of the spiral trough. The described embodiment has substantially similar pitch to that used in known and widely used spiral separators, utilising a pitch of 42cm. In variations the pitch could be different, for example in the range of 35 to 50cm for spirals of 60 to 65cm diameter, although it will be appreciated that modified rates of change of cross-trough floor profile, compared to the examples provided, may be necessary or désirable in such variations. The described embodiment has substantially similar spiral width to that used in known and widely used spiral separators, for example a maximum distance from the spiral axis of about 32.5 cm.

In alternative embodiments the feed transition zone may be between about a quarter tum and about 1.5 tums, and the transition in the trough profile over this zone may be to a profile which provides a cross-trough floor angle of between about 15 and about 20 degrees. A crosstrough floor angle within this range may be regarded as a relatively shallow cross-trough floor angle for such an early (or upstream) part of a spiral separator for wet séparation of heavy minerai from silica sand.

As illustrated by Figure 4, in the illustrated embodiment the cross-trough floor angle is reduced by 3 degrees from about 18 degrees to about 15 degrees between tum 0.5 and turn 1.5. More generally, the trough profile transitions, immediately or soon after the feed transition zone 140, to provide the trough floor 130 with a cross-trough floor angle which is reduced by about 2 to 4 degrees over about a tum, to provide a cross-trough floor angle of about 14 to 16 degrees.

As illustrated by Figure 5, in the illustrated embodiment the cross-trough floor angle is reduced by 3 degrees from about 15 degrees to about 12 degrees between tum 1.5 and tum 2,5. More generally, the trough profile may continue to transition, downstream of the feed transition zone, to provide the trough floor 130 with a cross floor trough angle which is reduced by about 2 to 4 degrees over about a tum, to provide a cross-trough floor angle of about or about 10 to 14 degrees.

These values described in the two paragraphs above may be considered to represent a graduai réduction of the cross-trough si ope, for this part of the spiral, compared to most or ail spiral separators commercially used, at least for wet gravity séparation of heavy minerais from silica sand. The région over which this graduai réduction in cross-trough slope is provided, downstream of the feed transition zone, but not extending town as far as the concentrate off-take point 34, may be regarded as an intermediate région of the trough, schematically desîgnated by the reference numéral 150 in Figure l(b). In the illustrated embodiment this région extends approximately two tums of the spiral trough, but it will be appreciated that in variations it may ex tend fewer than or more than two tums. However, it is considered désirable that the trough extends between about two turns and about five tums between feed point 32 and a concentrate off-take point 34.

As illustrated by Figure 6, in the illustrated embodiment the trough profile transitions in the final turn before a concentrate split is taken off, at an increased rate of réduction of the crosstrough floor angle, of about 6 degrees per tum, to provide a cross-trough floor angle of about 6 degrees in the final tum before a concentrate split is taken off, at concentrate off-take point 34, which in the illustrated embodiment is at about turn 3.5. More generally, m accordance with the présent disclosure, the trough profile transitions in the final tum before a concentrate split is taken off, at an increased rate of réduction of the cross-trough floor angle of about 5 to 8 degrees, to provîde a trough floor 130 with a cross-trough floor angle of about 4 to 8 degrees in the final turn before a concentrate split is taken off.

This may be regarded as a rapid change in the rate of réduction of floor angle just upstream of the concentrate split, and also a réduction to a very small or shallow cross-trough floor angle.

This progression of profile changes has been found to provide a trough which provides good séparation efficiency compared to at least some known trough configurations.

Without wishing to be bound by theory, the mechanisms by which the good séparation efficiency are believed to be achieved will be outlined below.

Before the tum of the trough immédiately upstream of the concentrate off-take, the slurry has undergone a substantial amount of séparation to provide a concentrate stream at a radially inner part of the trough, a middlings stream at a radîally more outer région of the trough and a tailings stream at and adjacent the most radially outer région of the trough.

The concentrate stream contains a substantîally higher concentration of the desîred higher-density material from the slurry, for example a heavy minerai, than the initially fed slurry, but also contains some of the lower densîty, undesired material, for example silica sand, which it îs désirable to remove from the concentrate stream before splitting the concentrate band from the rest of the slurry flow.

The rapid change in the rate of réduction of floor angle just upstream of the concentrate split, and also the very small or shallow cross-trough floor angle in this région, resuit in a région just upstream of the concentrate split in which the balance of gravitaiional and centrifrigal forces is different to that in the more upstream parts to the spiral trough. That is, the gravitaiional force 32 on the slurry in the inwardly radial direction is reduced due to the reduced cross-trough slope. This results in a tendency for the slurry components to move outwardly. The lower-density, less-desîred, material in the concentrate stream is more mobile than the higher-density, moredesîred material, at least in part becausc the higher-density, more-desired material expériences greater drag on the trough floor. Water in the concentrate stream, is even more mobile than the lower-density material.

A substantiel amount of lower-density material (and water) in the concentrate stream therefore migrâtes outwardly before a substantîal amount of the higher-density material migrâtes outwardly. This may be regarded as providing a “tippîng” or “panning” effect, somewhat related to séparation using a gokl pan in a swirling manner with variable tilt to the pan to wash or tip off lower density material from hîgher density material.

Thus the concentrate stream entering the région immediately upstream of the concentrate off-take may be regarded as a preliminary concentrate stream. The région immediately upstream of the concentrate off-take may be regarded as a refîner région, schematically designated 160 in Figure I(b), which refînes the preliminary concentrate stream by causing outward migration of a substantîal amount of the lower-density material from the preliminary concentrate stream, to leave a refîned concentrate stream with a greater concentration of higher-density material than is présent in the preliminary concentrate stream. The refîner région may therefore be regarded as having a refinement part at which the preliminary concentrate stream has substantially become a refîned concentrate stream.

The concentrate off-take is positioned to splît off the refîned concentrate stream from the rest of the flow before a substantîal amount of the higher-density material migrâtes outwardly out of the refîned concentrate stream.

Use of a trough which provides a reiatively shallow cross-trough floor angle at an early (or upstream) part of a the spiral trough, and which then decreases in cross-trough floor angle reiatively slowly is believed to assist in preventing or reducing uncontrolled and un-damped water flow down the spiral which can occur due to low slurry viscosity at and near the slurry feed in point. Such uncontrolled and un-damped water flow is believed to be characteristic of steep cross-trough profiles.

The reiatively low initial cross-trough slope is thus believed to assist in allowing the slurry fed into the trough to settle into a steady and low turbulence régime conducîve to good séparation.

Once the flow pattern on the trough surface starts to develop, water begins to move outward under the influence of centrifugal force and low surface drag and the higher-density material, being constrained b y high surface drag, inward, so that the concentrate stream, middlings stream and tailings stream (referred to above) develop.

The dcveloping concentrate and middlings slurry streams on the radially central and inner parts of the trough, hâve far greater viscosity than the slurry immediately exiting the feedbox 7. This is believed to damp the flow of slurry so that a graduai réduction in the crosstrough floor slope (of about 2 to 4 degrees per turn) in the part of the trough between the feed transition zone and the refîner région is sufficient to allow effective séparation. This is in contrast to the rapid réduction in cross-trough floor slope (of about 6 degrees over one tum, from 21 deg to 15) at this part of the trough taught by Wright, and widely used in commercial wet gravity spiral separators.

This relatively graduai réduction in cross-trough floor slope in the intermediate part of the trough is believed to be conducive to maintaining more water in the pulp at ail downstream points once the flow settles, allowing good mobility and freedom for the more dense material to move along the bottom of the slurry and migrate inwards to form, or joîn, a concentrate stream.

The relatively high level of water in the radially central and inner parts of the trough is believed to assist the refmement of the concentrate in the refîner région, as water migrating outwardly from the preliminary concentrate stream will tend to carry with it lower density material, thereby facilitating or improving the refinement.

Thus, the configuration of the trough of preferred embodiments in the régions upstream of the refîner région is considered to assist the refmement of the preliminary concentrate band in the refîner région.

It will be appréciât ed that in the illustrated embodiment the profile of the trough floor, that is, the shape of the trough floor when viewed in radial cross section of the spiral, in a plane which includes the spiral or hélix axis, describes an inclined, substantially straight line. The angle of this line to the horizontal equates to the cross-trough floor slope in a straîghtforward manner.

However other trough floor shapes are possible, and with such other trough floor shapes the trough floor slope is less straîghtforward to define. For example, US Patent 4,476,980 describes a trough of a spiral separator in which the floor profile comprises a radially inner région with a straîght profile of smaller slope which meets a radially outer région of greater slope, at a point referred to as the point of maximum displacement, The slope of each région remains uniform over successive turns of the trough, but the overall slope of the trough floor between its most radially inner and outer parts is varied over successive tums by changing the position of the point of maximum displacement. That is, near the top of the trough the point of maximum displacement is posîtioned more radially inwardly, so the radially inner région is small and the radially outer région is large, so that the overall slope ofthe trough floor is doser to that of the radially outer région (ie relative!y great). Nearer the bottom of the trough, the point of maximum displacement is posîtioned more radially outwardly, so the radially inner région is large and the radially outer région is small, so that the overall slope of the trough floor is doser to that of the radially inner région (ie relatively small). In other spiral separators the trough floor profile is convex, between a radially inner trough wall and a radially outer trough wall.

In troughs which hâve a non-straight trough floor profile, and therefore might not be regarded as having a single well defmed cross-trough floor slope, the overall slope of the working surface ofthe trough floor, on which séparation occurs, may be regarded as the effective cross-trough floor slope. For clarity, in order that statements regarding cross-trough floor slope may be applicable to troughs with floors that do not hâve a straîght profile, the tenus “effective cross-trough floor slope” and “effective cross-trough floor angle” are used herein to mean the overall angle or slope of the working surface of a trough floor a given point, as viewed in cross section in a plane which includes that point and which is parallel to and intersects the hélix axis. The overall working surface is typically a surface extendîng between a transition between the trough floor and a radially inner wall of the trough, and a transition point between the trough floor and a radially outer wall of the trough.

Figure 7 illustrâtes a trough correspondîng to the trough 100 (or the trough Ι00Α) in isolation. It will be appreciated that in this embodiment the trough 100 is provided as a unit manufactured separately from the feedbox 7, slurry préparation apparatus 800, and (substantially identical) trough 100A, although în a variation the troughs 100, 100A and at least a floor part of the slurry préparation apparatus 800 may be manufactured as a single intégral unit.

As shown în Figure 7, the upper end of the trough 100 is provided with an upstreamend flange part 170 for attachment to the feedbox 7, with an upper part of the upstream-end flange part 170 having a profile reflectîng the trough profile at the top of the trough (tum 0), as illustrated in Figure 2, such as the channel 120 and raised profile part 127. The correspondîng part (not shown) of the trough 100A provides these parts for attachment to the slurry préparation apparatus 800,

A lower end of the of the trough 100 is provided with a downstream-end flange part 180 for attachment to the slurry préparation apparatus 800, with an upper part of the downstream-end flange part 170 having a profile reflecting the trough profile at the bottom of the trough (turn 3.5), as illustrated in Figure 6. The corresponding part of the trough 100A (or, more broadly, the trough used in the final stage of a multistage separator) provides these parts for attachment to the splitting arrangement 9 at the end of the second or final stage.

Changes in cross-trough slope (or effective cross-trough slope) are related to différences in pitch between inner and outer parts of the trough, and in particular between an outer région of the trough floor and an inner région of the trough floor. As illustrated somewhat schematically in Figure 7, the pitch of an outer région of the trough floor, designated 701, is constant, with a pitch PO. The pitch of an inner région of the trough floor designated 702 varies, having a pitch Pi in a penultimate tum of the trough, and a pitch Pi’ in the final tum of the trough. The pitch Pi of the inner région 702 in the penultimate tum of the trough is slightly smaller than the pitch PO of the outer région 701, corresponding to a relatively small or graduai réduction in cross-trough floor slope over the penultimate tum. The pitch Pi’ of the inner région 702 in the final tum of the trough is substantially smaller than the pitch PO of the outer région 701, corresponding to a relatively large réduction in cross-trough floor slope over the final tum.

In embodiments in accordance with the présent disclosure the refinement région may be provided by a différence in pitch between the pitch Pi’ (of the inner région in the final tum) and the pitch PO of the outer région over the final tum being between 0.08 and 0.18 times the radial distance between the inner région 701 and the outer région 702. The différence in pitch may be between 0.9 and 0.14 times the radial distance between the inner région 701 and the outer région 702. The différence in pitch may be between 0.95 and 0.12 times the radial distance between the inner région 701 and the outer région 702.

The smaller réductions in slope in the intermediate région 150 may be provided by smaller différences in pitch.

As stated above, the separator 1 is a two stage spiral separator, and variations may provide additional stages.

In the separator 1 the fïrst and second stages 30, 50 of the fïrst spiral 5 are connected in line as a continuons spiral 5 via a slurry préparation apparatus 800, which préparés the slurry exiting the fïrst stage 30 (other than the taken-off concentrate) for entry to the second stage 50. The slurry préparation apparatus 800 may also be regarded as being part of the continuons spiral 5. If additional stages are provided then, in an embodiment, the splitting arrangement 9 at the downstream end of the second stage 50, may be replaced by a further slurry préparation apparatus 800, and a thîrd trough may be coupled to that further slurry préparation apparatus. If desired, one or more subséquent further slurry préparation apparatuses and troughs may be provided to provide one or subséquent stages.

Providing a mechanism in the part of the spiral between the fïrst and second stages to préparé the slurry for entry to the second stage can greatly enhance séparation in the second stage. In the fïrst stage it îs nonnal for the slurry flow to develop a higli velocity water component flowing in the radially outer part of the trough which contains very low solids content and, in parallel, a high solids slurry flow spread out over the trough floor which has been dewatered due to centrifugal forces over a number of tums, and which has a solids content of around 60% to 80% by weight. Séparation in the high solids slurry flow is poor due to the low mobility of heavy materials in this high solids flow, and the high solids flow tends to travel down the spiral trough without substantial radial movement of the solids, preventing efficient séparation. It is therefore désirable to rewater the high solids slurry flow leaving the fïrst stage before entry of the slurry to the second stage, in order to allow effective séparation in the second stage. One function of the slurry préparation apparatus 800 is to mîx water from the high velocity water component flowing in the radially outer part of the trough 100 with the high solids slurry flow flowing along the floor 130 of the fïrst trough 100.

It has also been observed that if the slurry flow onto the second stage has substantially the same kinetic energy and momentum as it has when exiting the fïrst stage, an undesirably high level of turbulence may occur in the trough of the second stage, which may not be conducive to rapid or effective settling of finer minerais or efficient séparation in the second stage. Accordingly, it may be désirable to remove kinetic energy from, and dissipate the downstream momentum of, the slurry before entry to the second stage. A function of the slurry préparation apparatus 800 îs to remove kinetic energy from the slurry prior to introduction of the prepared mixed slurry to the second stage.

It should be appreciated that the removal of kinetic energy and downstream momentum from the slurry flow exiting the fïrst stage has been found to be problematic, especially for s lûmes with overall solids content of about or above 40% b y weight, which is considered conducive to good séparation efficiency for heavy minerais séparation. In particular, removal of energy and momentum from the dewatered hîgh solids slurry flow can cause the high solids slurry flow to stall altogether, causing sanding of the trough and effectively stoppîng operation of the spiral separator until the stalled solids are removed, for example by being hosed down the second stage trough. Of course it will be appreciated that hosing a portion of the slurry into the second stage trough will tend to créâte, at least for that portion of the slurry, a high levcl of turbulence which is not conducive to efficient séparation.

In the embodiment of Figures 8 to 15, the slurry préparation apparatus 800 acts to remove kinetic energy and downstream momentum from the high velocity water stream prior to re-introducing the water of the high velocity water stream into the high solids slurry flow. Up until the water is reîntroduced, the high solids slurry flow is substantially uninterrupted, and continues to flow substantially as it was flowing at the end of the first stage. The water from the high velocity water stream is re-introduced into the high solids slurry flow by allowîng the water to drop onto, and into, the dewatered high solids slurry flow, so that mixing occurs despite the water having little or no momentum in the forwards or downstream direction of the spiral. The well mixed slurry, which has much lower viscosîty than the dewatered high solids slurry flow, is then fed onto the second stage, into feed entry channel 120, adjacent to the outside wall 125, of the second stage trough 100A, in a low velocity condition and manner similar to new feed exiting the feedbox 7 on the uppermost stage.

With reference to Figures 8 to 15 an embodiment of a slurry préparation apparatus 800, will now be described in more spécifie detail.

The slurry préparation apparatus 800 provides a slurry entry région 802 at an upstream part thereof for entry of slurry exiting the trough 100 of the first stage 30. The slurry entry région 8Ü2 pro vides a trough floor part 804 configured to be continuous with the trough floor 130 of the first trough 100 at the most downstream end of the first trough 100, so that slurry can flow substantially uniinpeded from the first trough 100 onto the slurry préparation apparatus 800. The slurry préparation apparatus 800 provides an upstanding radially outer wall 806, which in use is generally continuous with the upstanding outer wall 125 of the trough 100, and an upstanding inner wall part 808, which in use is generally continuous with the upstanding inner wall part 132 of the trough 100, and provides a radially inner concentrate gutter 810 which in use is generally continuous with the radially inner concentrate gutter 134 of the trough 100. It will be appreciated that in the illustrated embodîment a radially inner wall of the concentrate gutter S10 will be provided by the central column 3.

A radially intermediate région S12 of the trough floor 804, which is inclined downwardly in the downstream direction receives a high solid content, or middlings, part of the slurry flow from the first stage 30.

A radially outer région 814 of the trough floor 804 receives the high velocity water stream from the first stage 30. It will be appreciated that the high velocity water stream will also extend some way up the radially outer wall 806. The radially outer région 814 of the trough floor 804 transitions into a guide or ramp arrangement 816, which in use directs the high velocity water stream into an upper compartment 818 of a box-like arrangement 820 via an upper opening 822.

The radially intermediate région 812 of the trough floor 804 conveys the high solid content part of the slurry flow from the first stage 30 in the downstream direction into a lower compartment 824 of the box-like arrangement 820, configuration via a lower opening 826.

The box-like arrangement 820 has a radially outer wall, provided by the radially outer wall 806, and a radially inner wall 828. The box-like arrangement 820 further comprises an upstream end wall 830 and a downstream end wall 832. A lower edge 834 of the upstream end wall 832 is vertically spaced apart from the intermediate région 812 of the trough floor part 804, to thereby provide the lower opening 826 therebetween. The downstream end wall provides a lower, radially outer, outlet opening 833 for egress of prepared mixed slurry onto a downstream spiral trough.

The box-like arrangement 820 further comprises a lower floor, provided by the trough floor part 804 and an upper cover 836. In the illustrated embodîment the upper cover 836 is in the form of a removabie close-fitting lid, which is provided with fixing apertures 838, which in use align with complementary fixîng apertures 840, provided in the upstream end wall 830 and downstream end wall 832, to allow the lid to be securely attached using fixings such as screws (not shown).

The box-like arrangement 820 further comprises an intermediate floor part 842, which séparâtes the upper compartment 818 and lower compartment 824. The intermediate floor part 842 provides an opening 844 through which the high water content part of the slurry flow drops οnto, and into the high solids content slurry which is progressing through the lower compartment 824, beneath the opening 844.

The upper compartment 818 provides a dividing wall 846 to define a convoluted, serpentine passageway 848 through the upper compartment 818, for passage of the high water content part of the slurry flow. In the illustrated embodiment the dividing wall 846 provides a first dividing wall part 846A substantially parallel to and spaced apart from the radially outer wall 806, a second dividing wall part 846B substantially parallel to and spaced apart from the downstream end wall 832, and a short retum dividing wall part 846C directed away from the second dividing wall part 846B in the upstream direction. The passageway 848 is thus configured to provide a first passageway part 848A between the first dividing wall part 846A and the radially outer wall 806, a second passageway part 848B between the second dividing wall part 846B and the downstream end wall 832, and a third passageway part 848C directed substantially upstream parallel to the radially inner wall 828, with pronounced directional changes between the passageway parts.

It will be appreciated that the high water content part of the slurry flow must flow through the passageway 846, before it reaches the opening 844. The flow through the passageway 846, with substantial directional changes and at least one reversai in direction, substantially reduces the kinetîc energy and downstream momentum of the high water content part of the slurry flow, due to the baffle effect of impacts with the walls of the passageway and the création of turbulence in the water. The high water content part of the slurry flow may impact and be further baffled by impacts with further wall parts, such as the downstream-side surface of the upstream end wall 830, the radially inner surface of the first dividing wall part 846A, and the upstream-side surface of the second dividing wall part 846B, as can be seen, for example in Figure 10, in which the route of the high water content part of the slurry flow is schematically illustrated by broken-line arrow 850. Thus by the time the water from the high water content part of the slurry flow falls through the opening 844, its kinetic energy and downstream momentum hâve been effectively dissipated.

The faiiing of the water onto the high solids content slurry below provides effective mixing without împarting substantial downstream velocity to the slurry as a whoie. This provides a mîxed, low velocity, low viscosity slurry, which is then directed by a suitable guide arrangement in the lower compartment to the outlet opening 833, to provide a slurry feed onto a second (or subséquent) stage and spiral trough. It is desired that the prepared mixed slurry flows into the second or subséquent stage in much the same well mixed and low velocity condition as the slurry exiting the fcedbox 7 onto the first stage.

It is believcd that the illustrated embodiment facilitâtes the low energy water percolating down through opening 844 in a low velocity spiral, which enhances mixing with the high solid content slurry in the lower compartment.

The upper compartment 818 of the box-like annngement 820 may be regarded as an ex ample of an energy dissipation région, and the box-like arrangement 820 may be regarded as an example of an energy-dissipation box. The vicinity of the opening 844, may be regarded as an ex ample of a drop région, which pro vides a vertically downward accélération of material (water) from a more fluid stream to facilitate mixing of the water with a less fluid stream, which in this example is the high solid content middling stream from the first stage. The walls of the passageway 848 may be regarded as baffles, which at least contribute to dissipation of the kinetic energy of the more fluid, high water content part of the slurry.

It will be appreciated that the configuration of the ramp and passage, to provide a floor part which diverges upwardly relative to the trough floor, and therefore allows the high water content component to be elevated relative to the high solid content slurry flow is, at least in this embodiment, important to thereby provide the drop région

It should be appreciated that in the illustrated embodiment the area under the guide or ramp arrangement 816 is solid material or biocked off by a blocking wall 817 to prevent water from the high solid content flow migrating outwardly into this area, as such further dewatering of the already dewatered high solid content flow could further increase its viscosity sufficiently to undesîrably impede flow, for example causing sanding as discussed above.

It should be appreciated that the préparation of slurry for feeding onto a second or subséquent stage occurs after (or downstream of where) a concentrate stream has been split from the rest of the slurry. Thus a concentrate off-take is provided upstream of, or at an upstream part of, the slurry préparation apparatus 80Û.

In the illustrated embodiment the slurry préparation apparatus 800 provides a concentrate splitter 852, at an upstream part thereof and adjacent to the inner concentrate gutter 810, to take a concentrate split (which may be of the refmed concentrate stream, discussed above) from the slurry flow, directing it into the concentrate gutter 810. In the illustrated embodiment the concentrate splitter S52, comprises a splitter vane 854 which can be pivoted about a vane support 856 such as a suitable post, in order to vary the size of the off-take opening. The splitter vane 854 has a sharp vertically orientated leading edge 858 to facilitate taking a clean split. The splitter vane 854 is set down in a slightly recessed région 860 of the trough floor part 804 as a slîght drop in the slurry as it contacts the leading edge 858 of the splitter vane 854 has been found advantageous. (It should be appreciatcd that the splitter vane 854 and vane support 856 are omitted from Figures 12, 14 and 15.)

As foreshadowed above, in a variation, at least a floor part of the slurry préparation apparatus 800 may be manufactured as a single intégral unit with at least one of the upstream and downstream spiral troughs. However, in the illustrated embodiment the slurry préparation apparatus 800 and each of the upstream and downstream spiral troughs 100, 100A is manufactured as a separate modular unit.

The slurry préparation apparatus 800 therefore provides arrangements for facilitating connection to the upstream and downstream spiral troughs 100, 100A. The slurry préparation apparatus 800 pro vides upstream and downstream fl anges, with the upstream flange 862 adapted to allow coupling to a downstream flange (not shown) of a trough located upstream of the slurry préparation apparatus 800, and the downstream flange 864 adapted to allow coupling to an upstream flange of a trough located downstream of the slurry préparation apparatus 800. The flanges 862, 864 may be provided with fixing holes 866 to facilitate connection using fasteners such as screws or bolts. In the illustrated embodiment, the configuration of the downstream flange 864, as well as the positioning of the outlet opening 833, to the functionally similar parts of the feedbox 7, so that the configuration of flange plate 170 suitable for attachment to the feedbox 7 is also suitable for attachment to the downstream flange 864 of the slurry préparation apparatus 800.

It should be appreciated that the broken line arrows in Figures 10, 11 and 15 are intended to schematically illustrate flow of the slurry through the slurry préparation apparatus 800 in use. Broadly: broken line arrows designated 870 indicate flow of the concentrate stream (into concentrate gutter 810); broken line arrows 872 indicate flow of the more fluid stream from the more upstream trough; broken line arrows 874 indicate flow of the of less fluid stream, which in this example is the high solid content middling stream from the more upstream trough; and broken line arrows 876 indicate flow of the prepared, mixed and low energy slurry for entry onto the next-stage trough. The broken line designated 878 in Figure 13 illustrâtes schematically an example of a slurry profile of slurry leaving amore upstream trough.

With reference to Figures 16 to 20 an alternative embodiment of a slurry préparation apparatus 1600 will now be described. The slurry préparation apparatus 1600 is similar in many respects to the slurry préparation apparatus 800, and the following description will focus on the différences.

The main différence is that the slurry préparation apparatus 1600 does not include a circuitous passageway for dissipating energy from the high-velocity water stream, but rather provides a relatively short open channel or passageway 1602, which substantially follows the path of an upstanding radially outer wall 1606 (corresponding to upstanding radially outer wall 806 of the slurry préparation apparatus 800). The short open channel or passageway 1602 provides a ramp région 1608 having a floor configuration 1610 which elevates the fluid, high velocity, water stream relative to the high solids middlings stream, which moves along a trough floor 1612. The floor configuration 1610 terminâtes in an uptumed floor part 1613, which directs the fluid, high velocity, water stream upwardly and înto a baffle plate 1614, which is spaced above the trough floor 1612, which conveys the high solids content stream from the first (or other upstream) stage. Impact of the fluid, high velocity, water stream with the baffle plate 1614 dissipâtes the kînetîc energy and downstream momcntum of the fluid, high velocity, water stream, and the water drops, at low downstream velocity (in what may be regarded as a drop zone) onto the high solids content stream, thereby providing a low energy mixed slurry stream, similar to that previously described.

With reference to Figures 21 to 24, a further alternative embodiment of a slurry préparation apparatus 2100 will now be described. The slurry préparation apparatus 2100 does not elevate the fluid, high velocity, water stream relative to the high solids content stream, but rather provides a converging or funnel arrangement 2102 in which the fluid, high velocity, water stream and the high solids content stream are brought together and directed, with a rapid increase in down-spiral slope, into a conduit 2104 which is steeply inclined compared to the down trough slope of radially équivalent parts of the spiral troughs. The steep slope, as well as the early convergence of the fluid, high velocity, water stream with the high solids content stream prevents sanding, or stalling of the high solids content stream. The steep incline of the conduit 2104 (and therefore a floor région of the conduit - not shown) and, desirably of at least part of the converging or funnel arrangement 2102, may be regarded as a drop zone which facilitâtes mixing of the fluid, high velocity, water stream with the high solids content stream.

The conduit 2104 channels the combined slurry into an energy dissipation box 2106.

The energy dissipation box 2106, comprises a radially inner wall 2108, a radially outer wall 2110, an upstream wall 2112, a downstream wall 2114, a floor 2116 and a top or upper cover wall part 2118. The upstream wall 2112 provides a radially inner inlet 2120 of the energy dissipation box 2106 which is in fluid connection with a lower end of the conduit 2104, for feeding of the mixed, but still relativcly high energy slurry into the energy dissipation box 2106. The downstream wall 2114 provides a radially outer, outlet opening 2122 for egress of prepared mîxed slurry onto a downstream spiral trough.

The energy dissipation box 2106 also provides a plurality of internai baffles 2124, 2126 therein, and provides a circuitous path 2128 therethrough, between the inlet 2120 and the outlet opening 2122. The circuitous path 2128 is defined by the defined by the internai baffles 2124, 2126, the walls 2108, 2110, 2112, 2114, and the floor 2116 and a top or upper cover wall part 2118. Impacts of the slurry flow with these parts and turbulence in the slurry flow effectively dissipate kinetic energy and downstream momentum of the combined slurry.

The energy dissipation box 2106 thus dissipâtes kinetic energy and downstream momentum of the combined slurry (and therefore, also of the water from the fluid, high velocity, water stream) allowing egress of a low-energy, mixed, slurry stream, similar to that previously described. It should be appreciated that an energy dissipation box similar or identical to the energy dissipation box 2106, may be used as a feedbox at the very top of the spiral.

Figure 23 illustrâtes how a slurry préparation apparatus 2100 can be provided in each of multiple spirals wîthout the slurry préparation apparatus 2100 of any spiral înterfering with the slurry préparation apparatus 2100 of any spiral.

Indicative testing of embodiments substantially as described above has been performed and suggests that substantial improvements in séparation efficiency can be achieved compared to at least some known configurations of spiral separator, in wet gravity séparation of heavy minerais.

Figures 24 to 26 show comparative séparation performance curves for spiral separators incorporating at least some of the présent disclosure in comparison with spiral separators not incorporating teachings of the présent disclosure.

Figure 24 shows comparative séparation performance curves for the spiral trough configuration substantially as illustrated in, and described in relation to, Figures l(b) to 6, that is with for a spiral comprising two troughs each of 3.5 tums, and each substantially corresponding to the trough 100, with and without slurry préparation apparatus. The higher curve represents séparation performance with a slurry préparation apparatus substantially corresponding to the slurry préparation apparatus S00 provided between the two troughs. The lower curve represents same trough configuration, but without the slurry préparation apparatus 800 between the troughs. Rather, a corresponding quarter turn trough, without provision for mixing and energy/momentum dissipation was used to connect the two troughs.

in each of Figures 25 and 26, the higher curve is a séparation performance curve for the 3.5 turn spiral trough configuration substantially as illustrated in, and described in relation to, Figures l(b) to 6. The lower curve in each of Figures 25 and 26 is for a 3.5 tum trough of reducing angle of cross-trough floor slope from top to bottom (generally following the teachings of Wright), that is, not having the more graduai réductions in cross-trough slope in the higher tums and the more rapid réduction in cross trough slope in the final tum before concentrate offtake. Figures 25 and 26 differ because they show séparation performance curves for two different minerais, one easy to separate and one hard to separate.

It can be seen that the teachings of the présent disclosure appear to provide commercially significant benefits in séparation performance.

The variation in cross sectional angle of the trough floor in the described embodiments, départs markedly from the teachings of US 43 243 34 and US4563279. Indeed, the progressive relative!y gentle réduction in the floor angle, followed by a relative!y rapid and sudden réduction in floor angle in the final tum before the split, as described above in relation to the preferred embodiments, is consîdered to be in direct opposition to the teaching in US4324334 and US4563279. These patents teach that the initial variation in floor angle should relatively large a réduction in cross sectional angle first from 21 degrees to 15 degrees after two or more tums of the spiral with a 21 degree angle - and that subséquent réductions in floor angle should be relatively gentle - from 15 degrees to 12 degrees for one later tum, and then from 12 degrees to 9 degrees for one subséquent later tum, immediately before the different streams (concentrate, millîngs and taîlings) are split.

This îs more than a mere numerical différence. US4324334 and US4563279 are consîdered to teach an initial, relatively rapid braking of the pulp flow, and then continued but significantly more gentle braking. In contrast, the principle adopted in at least described embodiments of the présent disclosure îs to provide a relatively gentle réduction in cross sectional slope ofthe trough floor in upstream tums followed by a substantîally larger réduction în floor angle at the final tum îmmediately before splitting of the concentrate band,

Further the substantîally larger réduction in floor angle reduces the floor angle îtself to an angle smallcr than the smallest floor angle disclosed in either ofUS4324334 and US4563279. The disclosed configuration is believed to resuit in a ‘tipping off of the non-dcsired minerai, Further the disclosed configuration is believed (compared to the teachîng of Wright) to reduce uncontrolled and un-damped water flow down the spiral which is characteristic of steep crosstrough profiles, by starting relatively flatter but not flattening as quickly.

The shallow cross-trough floor angle in the final tum of described embodiments is believed to resuit in a bénéficiai panning or tipping off effect as described herein.

Thus instead of looking to optimise the brakîng effect taught by Wright, embodiments disclosed herein instead aim to achieve or maximise a tipping off or ‘panning’ effect to împrove séparation performance. In so doing, the rate of réduction in cross-trough floor slope angle increases markedly towards the end of the spiral trough, in contrast to the initial rapid réduction and subséquent more graduai réduction taught by Wright,

Further - and iinportantly - US4324334 describes at col 5 lines 7 to 15, that a variation for difficult séparations is to not reduce the cross trough floor slope over the bottom two tums at all. This is in stark contrast to embodiments disclosed herein, în which a relatively large réduction in cross trough floor slope over the bottom turn is important.

The described embodiments can resuit în an effective spiral separator, for example for métal minerai sands, in which a reduced number of tums (about 3,5 tums in the described embodiments) can resuit in commercîally useful séparation performance, This is in contrast to the standard îndustry practice of using spiral separators of five to seven tums (or five to seven tums per ‘stage’ în multiple stage separators).

Embodiments of the slurry préparation apparatus disclosed herein are believed to provide a refreshed or ‘restarted’ slurry which can signîficantly împrove séparation performance in a second or subséquent stage of a spiral separator. Further, embodiments are believed to desirably dissîpate energy in a slurry, prior to further treatment of the slurry, without undue risk of causing stalling ofthe flow or sanding in the spiral trough. However, it should be noted that some testing has indicated that use of other, previously known, types of slurry préparation apparatus, between stages of spiral separator with trough configurations in accordance with the présent disclosure. can provide results which are. at least in some cases, better than those provided by, for example, the slurry préparation apparatus 800. For example, using a conventional repulper provided on the trough outer wall to deflect water (and small amounts of entrained particulatcs) from the région of the trough outer wall into the dcnser slower moving 5 particulate stream in the intermediate région of the trough, has been found to provide good results in the immediately following stage. Accordingly, it is envisaged that the trough configurations in accordance with the présent disclosure, may be used effectively with such conventional slurry préparation apparatus.

Of course, the above features or functionalities described in relation to the 10 embodiments are provided b y way of example only. Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims (10)

1. A spiral separator for separating more-desired material from less-desired material, the spiral separator comprising:

a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material;

5 a spiral trough; and a splîttîng arrangement for off-take of a concentrate band of more desired material;

wherein the spiral trough is configured to provide a trough floor région with an effective crosstrough floor slope which reduces by between 5 and 8 degrees in a turn immediately upstream of the splitting arrangement.

2. A spiral separator in accordance with claim 1, wherein at least some of the turn immediately upstream of the splitting arrangement comprises a concentrate refîner région, in which a concentrate band of the slurry is refmed by radially outward migration of less-desired material from the concentrate band;

wherein the refîner région provides a cross-trough floor angle such that a balance of centrifugal «IP and gravîtational forces on the concentrate band is such that both the more-desired and lessdesired materials WOuld, if the balance of forces were maintained, migrate outwardly;

wherein the apparatus provides a refinement part of the refîner région at which least some of the less-desired material has migrated outwardly from a radial position corresponding to that of a preliminary concentrate band, and at which no substantial amount of the more-desired material 2é has migrated substantîally outwardly due to the balance of centrifugal and gravîtational forces, so that a refmed concentrate band is provided at the refinement part; and wherein the splitting arrangement is provided at or immediately downstream of the refinement pari to split the refmed concentrate band from the rest of the slurry in the spiral trough.

3. A spiral separator in accordance with claim 2, wherein the trough is configured to 2^ provide a trough floor région with an effective cross-trough floor slope of between 4 and 8 degrees from horizontal in a tum immediately upstream of the splîttîng arrangement.

4. A spiral separator in accordance with claim 2:

wherein the trough is confîgured to provide a feed transition zone proximal to the feed arrangement, wherein at least part of the feed transition zone provides a floor région with an effective cross-trough floor slope of between 16 and 20 degrees from horizontal;

wherein the floor région with an effective cross-trough floor slope Of between 16 and 20 degrees 5 from horizontal is provided within 1.5 turns of the feed arrangement;

wherein the feed transition zone provides a région in which a cross sectional shape of the trough transitions gradually from providing a relatively narrow feed entry channel, adjacent a radially outer part of the trough, to providing a substantially full width floor profile with an effective cross-trough floor slope of between about 15 and about 20 degrees; and wherein the relatively lé narrow feed entry channel has a floor part with cross-trough floor slope less than 12 degrees; and.

wherein the trough is confîgured to provide an effective cross-trough floor slope which reduces at a mean rate of between 2 and 4 degrees per turn for at least one further turn in an intermediate zone downstream of the feed transition zone and upstream of the concentrate refîner région.

15

5. A spiral separator in accordance with claim 1, wherein the spiral separator is a spiral separator for wet gravity séparation of minerais, and wherein the trough provides a helîcal pitch of between 35 and 50cm and has a helical diameter of between 50 and 75 cm, and wherein the trough extends between about 2.5 turns and about 4.5 tums between a slurry feed point and a concentrate off-iake point, and comprises a modular trough unit, providing between about 2.5 tums and about 4.5 tums.

6. A spiral separator for providing at least partial séparation of a first species and a second species, comprising:

a feed arrangement;

a spiral trough comprising a more upstream région and a more downstream région;

a splitting arrangement;

wherein the feed arrangement is, in use, arranged to feed a feed slurry comprising a mix of said first species and said second species into the more upstream région of the spiral trough at a feed entry région;

wherein the more upstream région of the spiral trough has a trough floor région, and provides an effective cross-trough floor slope relative to the horizontal, which reduces from between 15 and 20 degrees to a cross-trough floor angle of between 10 degrees and 14 degrees;

wherein the more downstream région of the spiral trough has a trough floor région having 5 an effective cross-trough floor angle which reduces to between 4 degrees and 8 degrees, relative to the horizontal; and wherein the splitting arrangement is provided at or immediately adjacent the said trough floor région having an effective cross-trough floor angle which reduces to between 4 degrees and 8 degrees , to split a concentrated band of the first species from the rest of the flow in the spiral trough,

7. A spiral separator in accordance with claim 6, wherein a downstream end of the more upstream région is connected to an upstream end of the more downstream région; and wherein in the more upstream région of the spiral trough at least part of a région which has said effective cross-trough floor angle relative to the horizontal, of between 15 and 20 degrees is provided at a position within 1.5 turns from the feed entry région.

8. A spiral separator in accordance with claim 6, wherein, in the more upstream région of the spiral trough, said réduction in effective cross-trough floor angle occurs at rate of between 2 degrees réduction in angle and 4 degrees réduction in angle, over each of at least two turns of the more upstream région of the spiral trough.

9. A spiral separator in accordance with 6, wherein the spiral separator comprises at least two stages, at least two stages each comprising: a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material; a spiral trough; a splitting arrangement for offtake of a concentrate band of more desired material; and wherein in at least two stages the spiral trough îs configured as set out in claim 6, and wherein the feed arrangement of a second or 25 subséquent stage comprises a slurry préparation apparatus, comprising a mixing région for mixing material from a more fluid stream of a slurry flow exiting a more upstream stage with material from a less fluid stream of the slurry flow exiting the more upstream stage prior to feeding mixed prepared slurry into said second or subséquent stage.

10. A slurry préparation apparatus for preparing a slurry from an upstream spiral trough 5^ région of a spiral separator, in which the slurry comprises a more fluid stream and a less fluid stream, for entry to a downstream spiral trough région as a prepared mixed slurry, the slurry préparation apparatus comprising:

an inlet région for ingress of received slurry from an upstream trough région;

an outlet région for providing prepared mixed slurry to a downstream spiral trough région;

an energy dissipation région to reduce kinetic energy of at least a substantial amount of material from the more fluid stream, to thereby reduce the downstream velocity of said at least part of the more fluid stream before the prepared mixed slurry exits the outlet région; and a mixing région for mixing material from the more fluid stream with material from the less fluid stream.