NZ304348A - A separator for separating solids and liquids from a feed material comprises cone shaped tank with feed section having a widened discharge section - Google Patents

Description

New Zealand No. 304348 International No PCT/GB96/00688 TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates 22 03 1995, Complete Specification Filed 22 03 1996 Classification (6) BO 1D21/00,01,24 Publication date 28 October 1999 Journal No 1445 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention Liquid/solids separator Name, address and nationality of applicant(s) as in international application form ULTRASEP (PROPRIETARY) LIMITED, a South African company of Founders 1 Building, Bartlett Road, Boksburg North, 1461, South Africa LIQUID/SOLIDS SEPARATOR BACKGROUND TO THE INVENTION This invention relates to a clanfier/thickener or separator of the t\ pe adapted to be used to separate suspended solids from a liquid Clarifiers/thickeners of the above kind are used in man\ different applications and have particular relevance in the clarification of water and thickening of slimes produced in mining and mineral processing operations However, it is to be understood that the invention is not limited to use in any particular application Generally liquid and suspended solids are fed into the inlet of the separator at relatively low density Within the separator a large portion of the solids is separated out of the liquid and a clear liquid is then discharged usually at the top of the separator, and the solids which usually settle under the influence of gravity are withdrawn from the separator at the lower end thereof The clarified liquid is frequently referred to as "overflow" The high density solids, in the form of a sludge, is frequently drawn out of the bottom outlet from the separator This sludge matenal is frequenth termed "underflow" In operation the largest of the solid particles generally will separate under gravity to the lower region of the separator The smaller particles, known as colloidal solids will generally not settle within an acceptable time frame Clarifiers/thickeners therefore reiv on the addition of a coagulant or SUBSTITUTE SHEET (RULE 26) flocculant which provides an effective bridging mechanism between small particles This bridging mechanism results in larger particles being formed which will then settle under the influence of gravity In order to join together the particles need to "collide" with cach other, and for this reason energy must be applied to the liquid. Energy is generally provided by causing the liquid to flow through the separator With the correct energy input particles will remain together after collision Prior art clanflers/thickeners have often suffered from one or more disadvantages Generally what is required is that the separator will operate to an acceptable degree of efficiency, be relatively automatic and maintenance free, and will require acceptablc levels of flocculant.

SUMMARY OF THE INVENTION According to a first aspcct of the invention, a separator is provided for separating solids and liquids from a feed material containing a mix of solids and liquids, the separator comprising a tank having a top, generally vertical side walls, and a convergently tapered bottom, a clarified liquid outlet at or near the top of the tank; a sludge outlet from the tapered bottom of the tank; and a generally vertically aligned feed conduit located within the tank near the top thereof, the feed condint including a feed section and a discharge section, the feed section being adapted to receive feed material and the discharge section being adapted to discharge feed material into the tank below the top thereof, the discharge section being of wider diameter than the feed section The discharge section preferably tapers divergently in a downward direction The feed conduit may be centrally located and vertically aligned within the tank Preferably the feed section is cylindrical, and the discharge scction is of inverted conc shape, and the axis of the feed section and the discharge section are coincident with each other and with the vcrucal axis of the tank The discharge scction may terminate in a lower cadge which is substantially equidistantly spaced away from the vertical side walls of the tank around the entire periphery of the tank, thereby defining an annular throat between said lower edge and the vertical side walls The width of the throat may be between 5% and 15% of the diameter of the tank Preferably, the width of the throat is approximately 10% of the diameter of the tanK The upper surface of the cone shaped discharge section may define, together with the vertical side walls of the lank, an upwardly diverging settling bed The half cone angle of the discharge section may be between 20" and 45° Preferably, the half cone angle of the discharge scction is approximately 30° The separator may include a recycle conduit which extends upwardly within the tank from a region below the discharge section to the top or near the top of the tank The recycle conduit may be located within the feed conduit, preferably coaxiaHy therewith The recycle conduit may comprise an upper nght-circular cylindrical section, and a lower, downwardly diverging, conical section.

The discharge section may comprise a downwardly diverging conical section, with the lower conical section of the recycle conduit nesting within the discharge seen on The cone angles of the discharge scction and the lower conical scction are preferably substantially the same The separator may further include a plurality of downwardly converging truncated cones suspended, one below the other, within the tank, the lowermost truncated cone leading towards the tapered bottom of the tank Preferably, the separator has three truncated concs The truncated cones are preferably suspended from and he below the feed conduit The separator may include a launder at or near the top of the tank into which clarified liquid will flow in use The feed conduit may have an open upper end into which clarified liquid may flow in use Preferably, the levels of the launder and the upper end of the feed conduit can be adjusted relative to each other to thereby provide means for selectively varying the relative percentages of clarified liquid which flow into the feed conduit and the launder respectively The launder may be of annular shape and surround, but be spaced from, the upper end of the feed conduit The launder preferably incorporates a weir over which the clarified liquid will flow mto the launder, the weir comprising a plurality of V-shaped notches.

The V-shaped notches are preferably evenly spaced around the launder The launder may oe adjustable relative to the open upper end of the feed conduit.

The level of the open, end of the feed conduit may also be adjustable relative to the launder.

The open upper end of the feed conduit may include a weir over which clarified liquid will flow into the feed conduit, the weir comprising a plurality of V-shaped notches spaced around the upper end of the feed conduit The feed matenal may be fed into the feed conduit through a lateral supply conduit which joins into the feed conduit below the upper end of the feed conduit The lateral supply conduit may have an auxiliary conduit feeding into it, the auxiliary conduit being used to introduce flocculent into the feed matenal in use According to a second aspect of the invention, there is provided a feed conduit for a liquids/sohds separator, said feed conduit comprising a cylindrical feed scction, and a downwardly diverging discharge section which is fixed to and coaxially aligned with the feed section, the feed conduit being adapted to be mounted with its axis generally vertical within a liquids/solids separator.

The feed section may be right circular cylindrical, and the discharge section conical The feed conduit may further include a recycle conduit which extends through and is coaxially aligned with the feed scction and the discharge sccuon The rccycic conduit may have an upper, nght circular cylindrical section, and a lower, downwardly diverging, conical section According to a third aspcct of the invcnDon, there is provided a solids concentration apparatus for use within a liquids/solids separator, said solids concentration apparatus comprising a plurality of aligned, truncated, right angled cones, adapted to be mounted one below the other within a liquids/solids separator, each cone being oriented so as to be downwardly convergent The cone-angles of all of the truncated cones arc preferably substantially the same According to a fourth aspcct of the invention there is provided a method of separating a solids/liquids mixed feed matenal in a separation tank which has generally vertical side walls and a feed conduit including a downwardly diverging discharge section centrally located within the tank and spaced away from the walls of the tank thereby defining an annular throat between the tanW and the discharge section, the method including the steps of. introducing the feed matenal into the tank through the feed conduit, adding a flocculant to the feed materia] either before or after it has entered the tank allowing the feed matenal to pass through the discharge section, PCT/GB96i'00688 allowing heavier solid particles to settle under the influence of gravity towards the bottom of the tank, allowing lighter solid particles to pass upwardly through the throat, selecting and monitoring the flow of feed material into the tank so that a bed of solid particles forms within the tank above the throat, and withd; awing clarified liquid from the top of the tank above the bed, and sludge from the bottom of the tank The method may include the step of diverting a percentage of the clarified liquid into the feed conduit to mix with the feed material The method may include the step of varying the percentage of clarified liquid introduced into the feed conduit so as to vary the specific gravity of matenal passing into the feed conduit and thereby optimise the separation characteristics of the separator An embodiment of the invention is desenbed below by way of example with reference to the accompanying drawings The drawings, however, are merely illustrative of how the invention might be put into effect so that the specific form and arrangement of the various features shown is not to be understood as limiting on the invention BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a cross-sectional side view through a typical clarificr/thickcncr according to the invention, and Figure 2 shows a plan view of the claxificr/thickcncr shown in Figure 1 DETAILED DESCRIPTION OF AN EMBODIMENT As shown in the drawings, a separator 10 for separating solids from liquids in a feed, matenal includes a generally vertically extending tank 12 having vertical side walls 14, a substantially open top 16 and a downwardly tapering or cone shaped bottom 18 The tank 12 shown in the drawings is circular in cross-section, but the tank may be square or rectangular in cross-section and would operate m substantially the same manner as is described below The tank 12 has a clarified liquid outlet 20 located near the top 16, and a sludge outlet 22 through which sludge which has collected in the tapered bottom will be discharged.

A feed conduit 24 is located withm the tank 12 near the upper end thereof The feed conduit is generally vertically aligned and includes a feed section 26 and a discharge section 28 which is located below the feed section 26 The feed section 26 is preferably of cylmdncal form The discharge section 28 is of larger diameter from the feed section 26 and is preferably of downwardly diverging form as shown The cross-sectional shape of the discharge section should match that of the tank so ihnt the lower edge 30 of the a. schiirge section is equally spaced from the walls 14 of the tank around the entire lower periphery of the discharge section 28 Feed matenal is supplied to the feed conduit 24 through a feed pipe 32 which passes through the side will 14 of the tank and extends into the feed conduit 24 The discharge end 34 of the feed pipe 32 may be downwardly directed as shown in the drawings to direct incoming feed matenal downwardly The feed pipe has a flocculant supply pipe 36 connected thereto by means cf which flocculant is added to the feed material as it travels ui the feed pip-: 32 The discharge section 28 is, as mentioned above, preferably comcally shaped The half-cone angle of the discharge section may be between about 20° and 45° and is preferably about 30° The axes of the feed section and the discharge section are preferably coincident with the axis 38 of the tank A throat 40 is defined between the lower edge 30 of the discharge scction 28 and the side walls 14 As mentioned above, the throat 40 is preferably f constant width around the entire penphery of the discharge section The width of the throat may be between 5% and 15% of the total width of the tank 12 In the preferred arrangement the width of the throat 40 is about 10% of the diameter of the tank 12 A rccycle conduit 42 is located within the tank, co-axialiy with the feed conduit 24 The recycle conduit includes an upper cylindrical section 44, and a lower truncated conical section 46 The conical section 46 is downwardly diverging as shown and is nested within the discharge section 28 An annular gap 48 is thus defined between the discharge scction 28 and - II - the conical section 46 Located below the recycle conduit 42 is a solids concentration apparatus SO. The solids concentration apparatus comprises a plurality of downwardly converging truncated codes 52 The cones 52 lead one into the other and serve to direct solids settling within the tank-12 towards the sludge outlet 22 The cones 52 are suspended from the recycle conduit 42 by a plurality of suspense rods 54 The clarified liquid outlet 20 is supplied with clarified liquid from the separator via a launder 56 The launder is of annular shape and is supported in position from a gantry 58 located at the top of the tank 12 The launder receives liquid which has been clarified m the tank 12 The liquid flows into the launder over a weir which is defined by both the radially inner edge 60 and the radially outer edge 62 of the launder 56 The weir is defined by a series of V-shaped notches In the embodiment shown in the drawings the elevation of the launder 56, relative to the tank, is variable The upper end 64 of the feed conduit also serves as a weir for clarified liquid. As shown the upper end 64 of the feed conduit is also provided with a senes of V-shaped notches By varying the elevation of the launder 56 relative to the upper end 64 of the feed conduit the relative percentages of clarified liquid which flows into the launder and into the feed conduit can be varied This feature is discusscd in more detail below In use, feed material which contains a mix of solids and hquids will be introduced through the feed pipe 32. A controlled volume of flocculant will be added to the feed material via the flocculant supply pipe 36 The feed matenal, as it enters the feed conduit 24, will move downwardly towards the discharge section 28 As the feed maieria] enters the discharge section and moves radially outwards through the gap 48 its flow velocity will slow and, m so doing, the heavier and larger solid particles in the flow will begin to settle towards the lower regions of the tank. The flocculant will assist particles to join together Lighter and smaller solid particles will tend to move around the lower edge 30 of the discharge secuon 28 The liquid and similar particles will then move upwardly through the throat 40 into a settling bed or "floe bed", indicated by the shaded area 66 located above the throat 40 It will be noted that the floe bed 66 is upwardly diverging and therefore as the liquids and smaller solids flow upwardly there will be a tendency for the flow velocity to decrease Thus, at the underside of the floe bed 66 the relatively rapidly upwardly moving solid particles will tend to collide with the underside of the floe bed 66 Solid particles will collide with each other thereby increasing the collective size of the particles As the solid particles increase in size they will tend to begin settling downwardly, back through the throat, towards the bottom of the tank The floe bed 66 thus acts somewhat like a sieve to trap upwardly flowing solid particles Liquid will pass up through the floe bed towards the launder but even small solids will be trapped m the floe bed The floe bed 66 will form naturally as a consequence of the upwardly diverging configurauon of the flow path above the discharge section 28 Thus, the cone-shaped form of the discharge secnon serves firstly to slow the velocity of flow to allow larger particles to settle, and then secondly, as after flow has passed through, the throat, to again slow the flow velocity above the throat to allow the floe bed 66 to form It is important that the density of the feed matenal is optimised for proper efficiency of the settler For this reason rt is preferred that at least some of the clarified liquid which is available for discharge from the settler is fed back into the feed conduit 24 for mixing -with fresh feed matenal For this reason the relative elevations of the launder 56 and the upper end of the feed conduit should be adjustable This can be achieved by either raising or lowering the launder, or by raiding or lowering the feed conduit. In the embodiment shown the elevation of the launder 56 is adjustable and for this reason a flexible connecting pipe 67 is fitted between the launder 56 and the clarified liquid outlet 20. The V-shaped notches which define the respective weirs ensure relatively precise control of flow into the feed conduit and launder. DiluUon of the fed matenal results in less flocculant consumption and higher settling rates As solid pamclcs settle they will pass towards the tapered bottom 18 The lower part of the tank is referred to as the consolidation zone The cones 52 serve to de-water solid matenal passing downwardly mto the consolidation zone so that material drawn out of the sludge outlet 22 is sludge-like m nature As solid matenal deposits on the upper surface of the cones 52 it will begin to slide down the inner surfaces of those cones through the respective throats of the cones until it deposits as sludge in the cone shaped bottom 18 Liquid, depicted by arrows 68, will move m an upward direction and will move upward into the conc shaped lower scction of the recycle conduit It is envisaged that the liquid 68 will be moving upwardly at a relatively low upward flow rate so as not to carry wuh it many solid particles moving downward in this consolidation zone One distinct advantage of the configuration of the cones 52 is that the cones serve to guide solid particles moving down in this consolidation zone towards the centre of the conc shaped bottom 18 It will be noted that a solid particle build up as indicated at numeral 70 occurs below the lower most cone 52 The advantage of this is that discharge which takes place through the outlet 22 will tend to draw sludge from this central region and thus the problem of open sludge free passages (known as "rat holes") being formed in the sludge will, to a large extent, be eliminated Instead, discharge which does take place through the outlet 22 will tend to consolidate the solid sludge material and this sludge material will generally be guided towards the centre of the bottom 18 thereby plugging any such "rat holes" that may tend to occur It is envisaged that a separator of the type desenbed will have a number of advantages The separator will, it is envisaged, remove suspended solids over a wide range of flow rates and solids levels It will also remove particles of varying densities and provide a relatively clear overflow Controllable underflow densities over a wide range of densities is also possible The separator can also be used to achieve classification of solid particles by monitonng the feed flow rate, flocculant addition levels and optimising or adjusting the annular opening to suit the required classification Clearly there may be multiple inlets and a separator shown in the drawings a relatively simple example of the manner in which the invention may be used A5 previously mentioned, the separator does not need to be circular in cross-section A square or rectangular separator may be used Thus, where the term "cone" is used in this specification it is not intended to only refer to circular cones The term should be taken to include within its scope pyramid or other shaped cones There are many advanlagcs to be obtained by using a clanficr/thickcncr of the type described herein. Firstly, dilution of the feed may be automatically controlled over a full range of operational conditions and could be changed to cope with changes in feed flow rates and feed matenal liquid/solids ratios The change in area of the annular passage leads to a very high rate of mixing due to the change in feed velocities This is particularly advantageous when multiple units are employed in counter current decantation (washing) when high mixing efficicncics are required The change in cross-section of the clanficr/thickcner upward of the annular throat 40 quickly stabilises the depth of the floe bed and also increases the efficiency of the floe bed since the upward velocity imparted on the floe particles rapidly decreases. This will lead to more collisions between particles and larger floes will quickly occur thus allowing the larger floe particles to fall under gravity through the throat 40 thereby constantly depleting the floe bed of solids The discharge from the consolidation cone is essentially above the underflow discharge The bulk of the high density sludge is thus allowed to build from the centre outwards thereby ensuring minimising the effect of "rat holes" and blockages or compaction which often results from "rat holes" forming It is envisaged that corrosion/erosion rates will be low due to the slow movement of solids in a downward direction It will also be appreciated that there are no moving parts of the apparatus The apparatus will be self-cleaning and it is envisaged that it will have a low flocculant consumption due to the larger particles tending to settle under gravity so they will not be earned up into the floe bed The floe bed above the annular throat 40 is self-balancing It should be noted that the form of the throat 40 can be vaned For example, a downwardly depending skirt could be attached to the lower edge of the discharge section 28 Such a skirt will than define an annular cykndncally shaped throat which will have the effect of lowering the top of the floe bed but would possibly improve the efficiency of the floe bed 17 -x-

Claims (4)

1 A separator for separating solids and liquids from a feed matenal containing a mix of solids and liquids, the separator comprising a tank ha\ing a top, generally vertical side walls, and a convergently tapered bottom, a clarified liquid outlet at or near the top of the tank; a sludge outlet from the tapered bottom of the tank, a generally vertically aligned feed conduit located within the tank near the top thereof, the feed conduit including a feed section and a discharge section, the feed section being adapted to receive feed matenal and the discharge section being adapted to discharge feed matenal into the tank below the top thereof, the discharge section being of wider diameter than the feed section, a zone for upwardly flowing liquid between the side walls of the tank and the feed conduit, wherem at least part of the zone increases in cross-sectional area so that the velocity of liquid flowing upwardly within the zone will decrease, and a recycle conduit within the feed conduit 'intellectual rurrRTTo orwz 14 APR 1999 RE C EI V E D 3 0 4 Af W - f 3 4 8

2 The separator of claim 1 wherein the discharge section of the feed conduit tapers divergently m a downward direction

3 The separator of claim 1 or claim 2 wherein the recycle conduit includes a downwardly diverging section

4. The separator of claim 3 wherein the downwardly diverging section of the recycle conduit is conical 5 The separator of claim 3 or claim 4 wherein the downwardly diverging section of the recycle conduit nests within the discharge section of the feed conduit 6 The separator of any of claims 3 to 5 wherein the recycle conduit includes a right circular cylindrical section located above the downwardly diverging section. 7 The separator of any of the above claims including a downwardly depending skirt extending from the loweT edge of the discharge section of the feed conduit, between which downwardly depending skirt and the side walls of the tank a lower section of the zone for upwardly flowing liquid is defined 8 The separator of any of the above claims including a supply conduit for feeding the feed material into the feed conduit below the upper end of the feed conduit iwt LlLLo i Ori1— i wl _nT i Un ) ji OFilZ 14 APR 1999 RECEIVED 26 - ^ ^ ^ .) /, o tt 9 The separator of any of the above claims including a solids concentration apparatus 10 The separator of claim 9 wherein the solids concentration apparatus consists of truncated cones 11 The separator of any of the above claims including a launder into which clarified liquid can flow, 12 The separator of any of the above claims including means for varying the percentage of clarified liquid introduced into the feed conduit to vary the specific gravity of the feed matenal in the feed conduit 13 A separator substantially as herein described and illustrated with reference to the accompanying drawings 14 A method of separating a solids/liquids mi\ed feed material in a separation tank which has generally vertical side walls and a feed conduit including a downwardly diverging discharge section centrally located within the tank and spaced away from the walls of the tank thereby defining an annular throat between the tank and the discharge section, the method lnclndmg the steps of introducing the feed matenal into the tank through the feed conduit, adding a flocculent to the feed matenal either before or after it has entered the tank, INTELLECTUrtuP ^,\RTY 0i i :C~" OF M I 14 APR 1999 RECEIVED 3 0 4 0 4 ffl- s Q allowing the feed matenal to pass through the discharge section whilst the velocity of the feed matenal decreases, allowing heavier solid particles to settle under the influence of gravity towards the bottom of the tank, allowing lighter solid particles to pass upwardly through the annular throat to a zone which increases in cross-sectional area so that the velocity of liquid flowing upwardly within the zone will decrease, selecting and monitonng the flow of feed matenal into the tank so that a bed of solid particles forms within the tank above the throat in the zone winch increases m cross-sectional area, and withdrawing clarified liquid from the top of the tank above the bed, and sludge from the bottom of the tank 15 A method according to claim 14 which includes the step of diverting a percentage of the clanfied liquid into the feed conduit to mix with the feed matenal 16 A method according to claim 15 which includes the step of varying the percentage of clanfied liquid introduced into the feed conduit so as to vary the specific gravity of the feed matenal in the feed conduit »LtCT.J,;f~V~Lf,T/ Or! OF 14 APR 1999 RECEIVED 3 0 4 5 4 8 V 17 A. method of separating a solids/liquids nu\ substantia]!} as hereinbefore descnbed with reference to the drawings END OF CLAIMS Ii\j lEi-itCTucvL r „i lRTY Ori ,Ci. OF i\l I 14 APR 1999 RECEIVED