AU755909B2 - Feed arrangement for a treatment vessel - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

b* Name of Applicant: Actual Inventor: Address of Service: Invention Title: M.I.M. HOLDINGS LIMITED, A.C.N. 009 814 019 Emmanuel Salvador Viana MANLAPIG BALDWIN SHELSTON WATERS MARGARET STREET SYDNEY NSW 2000 "FEED ARRANGEMENT FOR A TREATMENT VESSEL" Details of Associated Provisional Application No's. PO 7492 dated 23rd June 1997 and PO 9503 dated 29th September 1997 The following statement is a full description of this invention, including the best method of performing it known to us:- -2- BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for feeding and removing multi-phase fluids from a fluid treatment apparatus. It is particularly useful, but not limited to, methods for feeding and removing dual phase liquids such as slurries or suspensions to flotation apparatus such as Jameson cells.

BACKGROUND ART When feeding non-lhomogeneous fluids to a treatment apparatus eg feeding slurries i..

S* or suspensions to settlers, mixers, flotation apparatus etc, the treatment apparatus is usually !preceded by a vessel or pump box into which the fluid is fed. Most fluid treatment vessels i! 10i operate best when they have a constant feed rate. The fluid dynamics and separation efficiency of flotation cells in particular can be disturbed even by small variations in the feed rate. Generally therefore a fixed speed pump is connected to this pump box for maintaining a consistent flow rate to the fluid treatment apparatus.

There are several difficulties with this system, however. It is vital that the level of 15 fluid in the pump box does not exceed certain minimum or maximum levels. Since the flow rate provided by the fixed speed pump is constant, the level in the pump box will rise and fall according to the feed rate into the pump box. If the feed flow rate is higher than the flow rate of the fixed speed pump, the pump box will overfill and some of the feed may be lost or will short circuit the treatment vessel. Equally if the feed of the flow rate is below the fixed speed pump, the level in the pump box will drop. If the pump box level is very low or indeed the pump box runs dry, the fixed speed pump may be damaged.

Some of these difficulties can be overcome by partial recycle mechanisms. This however requires additional pumping equipment with associated additional expense.

-3- Alternatively, this may be achieved by the use of a tailing recycle chamber attached to the pump box.

Another disadvantage of conventional systems is the expense associated with the separate construction. Take for example a flotation cell as defined by Australian patent application number 45592/96 (hereinafter referred to as the "Jameson cell"). To separate particulate matter from a slurry or suspension as shown in Figure 1, cells 100 are placed above pump box 200 and pump 300 transfers the slurry from pump box 200 on the ground upwardly to the bank of Jameson cells. The tailings then fall downwardly under force of gravity, rather than a separate recycle pumping circuit, for partial recycle back to the pump box. Situating a bank of Jameson cells above the pump box, however, is expensive both in terms of capital construction costs and operational cost since pump 300 must force the slurry upwards for between 5 and 10 metres to reach the Jameson cells.

*°o o It is an object of the present invention to overcome or ameliorate at least one of oo 15 the disadvantages of the prior art, or to provide a useful alternative.

DISCLOSURE OF THE INVENTION g Accordingly in a first aspect, the present invention provides a feed arrangement for ooooo •a vessel for treating non-homogeneous fluids comprising a pump box to receive the fluid oooo from a fluid feed and provide the fluid to an inlet side of the treatment vessel via a pumping means wherein a fluid transfer port extends between the pump box and treatment vessel for two way fluid communication therebetween to equalise the respective hydrostatic pressures in the treatment vessel and pump box.

21004-00.DOC -4- In another aspect, the present invention provides a treatment vessel for treating non-homogeneous fluids, said vessel being divided into a treatment chamber, a pump chamber and one or more outlet chambers for one or more components of the nionhomogeneous fluid, and a pumping means transferring fluid from said pump chamber to said treatment chamber, wherein a transfer port extends between an outlet side of the treatent chamber to the pump chamber to permit two-way fluid communication therebetween for equalising the respective hydrostatic pressures in the treatment chamrb er and pump box.

In a first embodiment, the pump box and treatment vessel are side by side.

0:10 By positioning the pump chamber box next to thle treatment vessel there is a substantial saving both in capital construction costs but also in operating costs as it is now unnecessary for the pump which transfers fluid from the pump chamber into the treatment chamber to overcome the substantial head of liquid in conventional apparatus (see figure I).

In aniother preferred embodiment, the transfer port comprises a recycle chamber.

The fluid leaving the treatment vessel enters the recycle chamber. One or more control means such as valves then allows this fluid to leave the recycle chamber and pass to the outlets. The recycle chamber is separated from the pump chamber preferably by means of a wail. The recycle means comprises an orifice through the wall separating the recycle chamber from the pump chamber. Preferably, this orifice comprises one or more slits extending along the floor of the recycle and pump chambers. This orifice allows fluid to flow in both directions. The arrangement provides that the pump chamber is in fluid communication with the treatment chamber via the recycle chamber. In this way US465Ds .WrjCMW t7od 82,9'ON 666LEBE920 TL2VTV2G Z T9 60:9T ZO/OT/TZ 4a the levels of fluid between the treatment chamber and pump chamber may equalise by flow through the orifice.

0. 0 BL9 *ON ON ~66 z9E0 TL2TVtE6 E T9 609 60:9T EO/OT/TE In a particularly preferred embodiment, the recycle means is arranged to agitate the fluid entering the pump chamber via the transfer port. In this way the fluid is thoroughly mixed prior to being pumped from the pump chamber into the treatment chamber or vessel.

In a particularly preferred embodiment, the treatment chamber comprises one or more Jameson cells.

In another embodiment, the transfer port is configured to provide fluid to the pump box which is essentially representative of the bulk content of the fluid in the recycle 2~ i- chamber. To explain, as will be appreciated by persons skilled in the art, when dealing with solid/liquid or sold/gas fluids if the fluid is not continually mixed, the solid particles 10 tend to settle out. If one then removes or recycles some of the fluid at an upper portion of the vessel eg by an overflow, the fluid has little or no solids content. It is important to recycle fluid back to the pump box which is representative of the fluid entering the recycle chamber. For this reason, it is preferred that any orifice between the recycle chamber and the pump box is positioned at a maximum height that the fluid entering the pump box is 15 substantially representative of the bulk content of the fluid in the recycle chamber. In another embodiment, the transfer orifice and/or port may be positioned at a lowermost portion of the pump box. This ensures that a substantial portion of the solids as well as the liquid is recycled back to, the pump box.

In a ffirther aspect, the present invention provides a method of feeding a fluid to a treatment vessel comprising feeding a fluid to a pump box upstream of the treatment vessel, pumping the fluid from the pump box to the treatment vessel and providing a transfer port between'the pump box and treatment vessel for equalising their respective hydrostatic pressures.

-6- In still a further aspect, the present invention provides a method of controlling the head of fluid in the pump box and/or a treatment vessel in which fluid is transferred from said pump box to the treatment vessel by a pump, said method comprising providing a transfer port between the pump box and treatment vessel to maintain direct two-way fluid communication between the treatment vessel and the pump box for equalising their respective hydrostatic pressures.

It is preferred that the hydrostatic head in the treatment vessel and recycle chamber is ee S.I :greater than the pump box. This provides continuous recycling of fluid from the recycle chamber to the pump box. This continuous partial recycle of fluids can be obtained by 10 appropriate sizing of the treatment chamber, recycle chamber, pump chamber and transfer .**port.

Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Non-homogeneous fluids can include, but are not limited to, slurries.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described by way of example only with reference to the naccompanvin drawings in which: Figure 1 is a conventional Jameson cell flotation plant, Figure 2 is an external perspective view of an.apparatus according to a first embodiment of the present invention, Figure 3 is a perspective view of the interior of the apparatus of figure 1, -7- Figures 4 and 5 are perspective and interior views of an apparatus according to a second embodiment of the present invention, Figures 6 and 7 are perspective and internal views of an apparatus according to a third embodiment of the present invention, and Figures 8 and 9 are perspective and plan views of an apparatus according to a fourth embodiment of the present invention.

Figure 10 is a perspective view of an apparatus according to a fifth embodiment of the present invention.

MODE(S) FOR CARRYING OUT THE INVENTION 10 Referring firstly to figures 2 and 3, the present invention comprises a structure which houses a pump box or chamber 20, an outlet chamber 40 and treatment chamber or vessel 60. Each of these chambers 20, 40 and vessel 60 are in fluid communication with each other. The pump box chamber 20 comprises feed inlet 21 and pump outlet 22. The pump is not shown in the drawings but will be discussed below. As shown more clearly in 15 figure 3, the outlet chamber 40 comprises outlet 41. The outlet flow rate is controlled by valves 42 as will be discussed further below.

A transfer port which comprises recycle chamber 55 extends from treatment vessel to pump box 20. This recycle chamber 55 is in fluid communication with the pump box via orifice 70. This orifice may he of any particular shape but for reasons that will be discussed below a slit on the lowermost edge of wall 45 dividing the pump box 20 from recycle chamber 55 is preferred.

As discussed above, the treatment vessel 60 may be of any desired construction. For the sake of illustration in the following description, treatment vessel 60 is a flotation cell, however, it could equally be a settler, a mixer etc.

-8- The inventive apparatus operates as follows. A slurry or suspension comprising a liquid and particulate material is fed into pump box 20 via inlet 21. A pump (not shown) is connected to outlet 22 positioned at a lower portion of the pump box 20. This pump transfers the slurry from pump box 20 into treatment vessel 60 via external piping. Once the treatment or separation occurs in vessel 60, the valuable floated material is separated as a froth in a known manner and exits through outlet 61. The tailings or gangue material flows downwardly along the sloping tank floor 62 towards transfer port 50 and into recycle **ee chamber 55. If valves 42 are open, once recycle chamber 55 is full the tailings/gangue will flow upwardly through valves 42 and exit through outlet 41. Valves 42 may for example o 10 be dart valves.

will be clear to persons skilled in the art, pump box 20 remains in fluid communication with the treatment vessel 60 via transfer port 50, the recycle chamber and orifice 70. This in turn will ensure that the level in pump box 20 remains fairly constant since the relative heads of liquid in the pump box 20 and treatment vessel 60 will 15 alter the quantity oftailings recycled back to pump box 20 through transfer port 50 and orifice 70. In the embodiments shown, the orifice 70 is adjacent the lowermost portion of the pump box. As will be explained later, however, transfer port 50 and orifice 70 are configured to provide liquid to the pump box which is representative of the bulk content of the fluid in the recycle chamber To explain, there are several modes of operation of the present application. In a first or constant flow mode of operation, the feed rate through inlet 21 should be equal to the flow rate of the fixed speed pump transferring the slurry from pump box 20 to treatment vessel 60. In this instance, the level in the pump box 20 will remain constant as will the -9flow rate into the flotation cell(s) 60. This is an ideal situation which only rarely occurs in practice.

If, however, the feed rate through inlet 21 is lower than the capacity of the fixed speed pump, the level in pump box 20 will drop below the level of liquid in the treatment vessel 60. Then the inventive arrangement operates in recycle mode. In this instance, due to the higher head of liquid in treatment vessel 60, the tailings/gangue will flow through transfer port 50 and recycle chamber 55 and a portion will be recycled through orifice back into pump box 20 until the levels of fluid in the treatment vessel 60 and pump box equalise. This ensures that the level of fluid in the pump box 20 will not fall below the 10 level of the liquid in the treatment vessel thereby guaranteeing constant flow rate to the treatment vessel which as discussed above is particularly important for flotation or similar separation operations.

The third or overflow mode of operation is where the incoming feed rate 21 is higher than the capacity of the fixed speed pump. In this instance, the level in pump box 20 will 15 slowly rise until it is above the level of liquid in the treatment vessel. Since the head of liquid in the pump box 20 is greater than the head of liquid of treatment vessel 60, some of the incoming slurry will be forced through the orifice 70 from the pump box 20 into recycle chamber 55 until the level of the fluid in the pump box 20 equalises with the level in trpeatment vessel 60. Even if ,ome of the valuable particulate material enters recycle chamber 55 this material is not lost. Once the feed rate drops below the capacity of fixed speed pump, the apparatus will revert to its "recycle" mode of operation where the fluid level in treatment vessel 60 is higher than in pump box 20 and fluid will be forced from recycle chamber 55 through the orifice 70 back into the pump box 20 from where it is transferred to the treatment apparatus 60. Accordingly, any particulate material remaining in recycle chamber 55 will be transferred back to pump box 20 from where it is forwarded to the treatment vessel 60. This ensures that none of the slurry "short circuits" the treatment vessel and escapes through outlet 41.

The wall 45 separating pump box 20 from outlet chamber 40 preferably has an overflow weir 46 at its uppermost portion. This overflow weir 46 is set at a distance slightly below the upper point of treatment vessel 60 such that if the level in pump box continues to rise due to an increased feed rate, some of the slurry will overflow to outlet chamber 40 and escape through outlet 41. This is the only instance where some of the o•* incoming slurry will short circuit the treatment apparatus.

Accordingly it can be seen that the inventive apparatus may be dimensioned such that the pump box 20 is essentially self-regulating. The fluid communication between the pump box 20 and vessel 60 via orifice 70, recycle chamber 5 5 and outlet chamber •ensures that the fluid in the pump box is maintained between appropriate minimum and maximum levels without the need for expensive and complicated recycling componentry.

I. In the embodiment shown in figures 2 and 3, orifice 70 is positioned adjacent the lowermost portion of the pump box 20. This ensures that the solids in the slurry entering recycle chamber 55 are recycled back to pump box 20. The orifice may be positioned at any point on the pump box 20 provided that the fluid entering the pump box from the reccle chnmbpr is represPntivn of nfth hulk content of fluids in the recycle chamber. In the prior art, fluid is generally recycled from the upper portion of the recycle chamber.

Unless the fluid in the recycle chamber is continuously mixed, such a configuration will recycle mainly liquid and the solids in the slurry will settle out to the bottom of the recycle chamber and not be returned to the pump box.

-11- Figures 4 and 5 show the inventive apparatus when used in conjunction with the Jameson cell and its downcomers. As mentioned above, in the prior art these Jameson cells are positioned directly above the pump box (see figure 1) to allow for recycling of the tailing by gravity back to the pump box. Of course, this not only requires a larger pump to transfer the fluid from the pump box vertically upwards by 5-10 metres to the Jameson cells but requires substantial supporting structures to be constructed for the Jameson cells.

With the inventive apparatus, a much smaller pump may be used to transfer the incoming slurry in pump box 20 to the inlet of the Jameson cell 110.

It will therefore be clear to persons skilled in the art that by providing the pump box 10 20 at the same level as the treatment apparatus 60, and preferably the same level as the outlet chamber 40, there is a substantial saving in terms of construction cost. It is not necessary to provide separate supporting structures for each of the process components nor is it necessary to provide extensive piping to transfer the various fluids from the pump box to the treatment apparatus to the outlet apparatus. It is also clear to persons skilled in the art that by providing the pump box 20 next to and at the same level as the treatment apparatus 60 the pump to transfer the fluid from the pump box to the treatment apparatus may be much smaller than conventional apparatus. The operating costs for such a pump will also be reduced it is estimated by about 20% as compared to a conventional arrangement since the pump is not renuired to overcome the substantial head of liquid from the pump box to the treatment vessel above.

The applicant has also found that the inventive arrangement has significant advantages in terms of the quality of the fluid entering the treatment vessel. To explain, in the circumstances where the head of liquid in the treatment vessel is higher than that in the pump box 20, liquid will be forced through recycle chamber 55 and orifice 70 into the -12pump box 20. The velocity of this recycled tailings portion can be quite high and serves to agitate the liquid in the pump box 20. In this regard it is preferred that orifice 70 is provided by a slit extending substantially across the entire width of recycle chamber 55 and pump box 20. With this configuration the fluid travelling from recycle chamber 55 to pump box 20 serves to sweep any particulate material resting on the floor of pump box for subsequent removal by the pump through outlet 22. Other configurations of orifice have also been envisaged and in fact there may be several orifices between pump box O 3and recycle chamber This agitation of the fluid in pump box 20 is a distinct advantage over conventional i-°o 10 recycle mechanisms which may, in some instances, require additional agitation apparatus S" for example an impeller.

S"A further embodiment of the inventive apparatus is shown in figures 6 and 7. In this embodiment a section of the floor 25 of the pump box 20 between the outlet 22 and inlet 21 is sloped. This provides that any particulate material settling on this portion of the o* o 15 pump box floor 20 will slide downwardly toward the outlet 22 and be taken up by the oo pump and fed to settlement vessel A still further advantage of the present application is that it provides a complete package to an end user without the necessity for building a separate pump box. Generally the construction and installation of fluid treatment vessels is a specialised business. A plant operator will order a treatment vessel which will be installed by a contractor. The pump box is then generally built by the plant owner/operator and connected to the treatment vessel. This causes some difficulties as the pump box is not always tailored to suit the particular liquid treatment vessels. Generally a plant owner/operator will have a standard pump box which they will use for virtually every treatment vessel. As mentioned 13above, the maintenance of consistent flow to treatment vessels such as flotation cells is vital to efficient operation. A poorly constructed pump box may cause the treatment vessel to operate at less than optimum level. This is not because of any inherent problem in the treatment vessel but rather that the pump box is not tailored to maintain the required flow rate to the treatment vessel.

With the inventive apparatus, there is no need to build a separate pump box as it is already included in the apparatus and tailored specifically to match the treatment vessel This is a significant advantage over the prior art. Not only is the capital cost less, the plant owner/operator will not have to delay operation of the treatment vessel until the pump box 10 can be constructed since the pump box/treatment vessel comes as a single unit. It will also help manufacturers of specialised treatment vessels since they can ensure that the pump box 20 is of the correct dimensions to maintain optimal operation of the treatment vessel A still further embodiment of the inventive apparatus is shown in figures 8 and 9. In 15 this embodiment, the treatment vessel is provided by a circular or conical tank 160. The pump box 120, outlet chamber 140, control valves 242, exit 241 and recycle chamber 150 are provided on one side of the treatment tank 160. The fluid communication between treatment vessel 160 and the pump box 120 is via orifice 170. This modification of the treatment vessel reduces the costs of material and manufacture. The modification allows for the use of thinner steel plates and less structural side and bottom supports.

It also allows for an innovative multiple treatment tank layout as shown in figure 9.

As it will be seen in this embodiment, the outlet chamber 140 of one treatment apparatus 100 may be easily connected to the pump box 120 of an adjacent vessel and so on and so on by pipeline 200. Indeed, it may be possible to place the feed box of an adjacent vessel -14at a slightly lower level such that the tailings from a first outlet chamber 140 are gravity fed to the pump box 120 of the next treatment apparatus.

A further embodiment of the inventive apparatus is shown in figure 10. Similar to figure 8, the treatment vessel 260 comprises a circular tank with a conical bottom. Again this embodiment has the advantage of reduced cost of construction material and manufacture. The figure shows an alternative location arrangement of the pump box 220, the recycle chamber 255 and the outlet chamber 240 with respect to the treatment vessel :260. Compared to the embodiment shown in figure 8 only the outlet chamber shares a wall "*."o246 with the treatment vessel. The unfloated portion of the fluid in the treatment chamber o°oo 10 260 enters the recycle chamber. A part of the fluid in the recycle chamber recycles back to the pump box 220 through the orifice 270 and the remaining exits through control valves 0 242 to the exit 241 via the outlet chamber 240.

These configurations also provides a very small footprint for the plant layout as compared to conventional structures.

It will be clear to persons skilled in the art that the present invention may be embodied in forms other than those shown in the preferred embodiments without departing from the spirit or scope of the invention as described.

Claims (21)

1. A feed arrangement for a vessel for treating non-homogeneous fluids comprising a pump box to receive the fluid from a fluid feed and provide the fluid to an inlet side of the treatment vessel via a pumping means wherein a fluid transfer port extends between the pump box and treatment vessel for two way fluid communication therebetween to equalise the respective hydrostatic pressures in the treatment vessel and pump box.

2. A feed arrangement as claimed in claim 1 wherein the pump box and treatment vessel are placed side by side. .g

3. A feed arrangement as claimed in claim 1 wherein the transfer port extends from an o 10 outlet side of the treatment vessel to the pump box.

4. A feed arrangement as claimed in any one of the preceding claims wherein the transfer port includes a recycle chamber for receiving fluid from the treatment vessel and .partially recycling it to the pump box. A feed arrangement as claimed in any one of the preceding claims wherein the 15 transfer port is configured to provide fluid to the pump box that is substantially representative of the bulk content of the fluid in the recycle chamber.

6. A feed arrangement as claimed in any one of the preceding claims wherein the transfer port includes an orifice between the recycle chamber and the pump box, the orifice being position: at a maximum height such that the fluid entering the pump box is substantially representative of the bulk content of the fluid in the recycle chamber.

7. A feed arrangement as claimed in any one of the preceding claims wherein the transfer port opens into the pump box at a point adjacent the lowermost portion of the pump box. -16-

8. A treatment vessel for treating non-homogeneous fluids, said vessel being divided into a treatnent chamber, a pump chamber and one or more outlet chambers for one or more components of the non-homogeneous fluid, and a pumping means transferring fluid from said pump chamber to said treatment chamber, wherein a transfer port extends between an outlet side of the treatment chamber to the pump chamber to permit two-way fluid communication therebetween for equalising the respective hydrostatic pressures in the treatment chamber and pump box.

9. A treatment vessel as claimed in claim 8 wherein the transfer port of the treatment chamber includes a recycle chamber in constant fluid communication with the pump chamber. V A treatment vessel as claimed in claimS8 or 9 wherein the transfer port is configured to provide fluid to the pump chamber that is representative of the bulk content of the fluid in the recycle chamber.

11- A treatment vessel as claimed in claims 8 to 10 wherein the tansferp~ort includes an orifice between the recycle chamber and the pump box, the orifice being positioned at a maximum height such that the fluid entering the pump box is substantially representative of the bulk content of the fluid in the recycle chamber.

12. A treatment vessel as claimed in any one of claims 8 to 11 wherein the transfer port opens into the lowermost portion of the pump box.

13. A treatment vessel as claimed in any one of claims 8 to 12 further including means to agitate the fluid in the pump chamber.

14. A treatment vessel according to claim 13 wherein the means to agitate the fluid in the pump chamber is fluid entering the pump chamber via the transfer port. eL9'ON BtS ON ~6Bt 28E9E0 e_ TtLt'TPE6 E 19 6:1 E/11 60:91 EO/OT/TE -17- A treatment vessel as claimed in any one of claims 8 to 13 wherein the treatment chamber includes one or more Jameson cells.

16. A treatment vessel according to any one of claims 8 to 15 wherein the treatment chamber, the outlet chamber and the pump chamber are attached in sequence.

17. A method of feeding a fluid to a treatment vessel comprising feeding a fluid to a pump box upstream of the treatment vessel, pumping the fluid from the pump box to the treatment vessel and providing a transfer port between the pump box and treatment vessel i! for equalising their respective hydrostatic pressures. to. 18. A method of controlling the head of fluid in a pump box and/or a treatment vessel in which fluid is transferred from said pump box to the treatment vessel by a pump, said method comprising providing a transfer port between the pump box and treatment vessel to maintain direct two-way fluid communication between the treatment vessel and the pump box for equalising their respective hydrostatic pressures. C

19. A method as claimed in claim 17 or 18 wherein the transfer port includes a recycle 15 chamber. 0 A method as claimed in any one of claims 17 to 19 wherein the treatment chamber, recycle chamber, pump chamber and transfer port are sized to ensure that the hydrostatic pressure in the treatment vessel is maintained at a level greater than the hydrostatic pressure in the pump chamber andu thereby continus,,ly recyl. fluid from the recycle chamber to the pump box.

21. A multiple vessel arrangement wherein a transfer port of a first treatment vessel according to any one of claims 8 to 16 is in fluid connection to a pump box of a second treatment vessel according to any one of claims 8 to 16. -18-

22. A multiple vessel arrangement wherein a transfer port of a first treatment vessel according to any one of claims 8 to 16 is in fluid connection to both the first treatment vessels own pump box and a pump box of a second treatment vessel according to any one of claims 8 to 16.

23. A multiple vessel arrangement according to claims 21 or 22 wherein the second vessel is downstream of the first vessel.

24. A multiple vessel arrangement according to any one of claims 21 to 23 wherein the fluid is fed from the first vessel to the second vessel by gravity. S. 25. A feed arrangement substantially as hereinbefore described with reference to any one 10 of the accompanying drawings.

26. A treatment vessel substantially as hereinbefore described with reference to any one of the accompanying drawings.

27. A method of feeding a fluid to a treatment vessel substantially as herein described with reference to any one of the accompanying drawings. S: 15 28. A method of controlling the head of fluid in a pump box and/or a treatment vessel 0.: substantially as hereinbefore described with reference to any one of the accompanying drawings. DATED this 23rd Day of June, 1998 M.I.M. HOLDINGS LIMITED Attorney: IAN T ERNST Fellow Institute of Patent Attorneys of Australia of BALDWIN SHELSTON WATERS