AU784807B2 - Improvements in or relating to methods and apparatus for the purification of particulate solids - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT r IMPROVEMENTS IN OR RELATING TO METHODS AND APPARATUS FOR THE PURIFICATION OF PARTICULATE SOLIDS The following statement is a full description of this invention, including the best method of performing it known to us: Mm M0110975006v1 000000 IMPROVEMENTS IN OR RELATING TO SYSTEMS AND METHODS FOR THE PURIFICATION OF PARTICULATE SOLIDS FIELD OF THE INVENTION The present invention is directed to improvements in or relating to systems and methods for the purification of particulate solids and, more particularly, to systems and methods for the purification of salt.

BACKGROUND OF THE INVENTION In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date: part of common general knowledge; or (ii) known to be relevant to an attempt to solve any problem with which this specification is concerned.

Whilst the following discussion is primarily directed to systems and methods for the purification of salt, it is to be understood that the same principles apply to the purification of other particulate solids such as sand and gypsum.

Salt (sodium chloride, or NaCI) is currently the largest mineral feedstock consumed by the chemical industry worldwide, and is typically produced in one of 20 three ways: S(a) solar evaporation; solution mining; or rock salt mining.

The salt produced by each of these methods will contain different impurities, which require different methods of purification to extract. The geographical region from which the salt was obtained also has a significant effect on the impurities present in the salt. For example, the main impurities generally present in solar salt are calcium sulphate (present as gypsum, CaS0 4 .2H 2 and ionic magnesium (typically present as magnesium sulphate (MgSO4), and magnesium chloride (MgC12)) whereas rock salt will often also contain impurities such as pyrite (FeS2), quartz (SiO 2 and dolomite (Ca(CO 3 2 Most of the impurities contained in salt deposits will typically occur on the surface of the salt crystals, rather than inside the cubic crystal structure itself. As a result, many of those impurities can be removed by washing the salt crystals with water, brine or chemical mixtures. Chemical mixtures are generally the most effective washing agents, but are also the most costly, and present a number of environmental problems. Water is generally the cheapest washing medium, but results in substantial salt loss due to dissolution of the salt in the water. Washing in brine is therefore the preferred solution. It is relatively cheap, effective, and because it is already saturated with sodium chloride, there is minimal loss of salt due to dissolution.

In the case of salt produced by solar evaporation, the salt is first "grown" by the action of sun and wind on seawater or natural brine in large crystallising ponds.

The water evaporates in successive ponds until the brine is fully concentrated and salt crystallises on the floor of the ponds. Seawater contains about 3 5 (by weight) dissolved minerals, of which sodium chloride constitutes about 77% (by weight).

Once the salt has crystallised, it is harvested and washed in brine before being added to a "wet stockpile," where it is drained thoroughly.

The washing process is an integral part of production as it removes many of the impurities which adhere to the surface of the salt crystals. The salt cannot be used for many applications, such as use as a food additive or chemical feedstock, unless it meets specific levels of purity. Other applications, such as the de-icing of roads in the Northern hemisphere, can safely employ low-cost crude salt that has not been purified this is one of the major uses of mined rock salt.

In order to be washed, the salt is typically mixed with a fluid to form a slurry in which the salt crystals and impurities remain suspended in solution. Ideally, the concentration of suspended particles in the slurry should be as high as possible to minimise production time and cost, but the limits of the washing apparatus will generally determine the maximum concentration that can be used.

A previously proposed technology for washing and purifying salt is embodied in the SALEX® system, which is described in Australian Patent Application No 33333/97 (WO 98/03241). The SALEX® system uses a vertical column comprising at least one conical section, and often two sections with the upper section being cylindrical and the lower section being conical. Each embodiment tapers down to a single discharge point at the base of the purification vessel. The slurry containing the salt to be purified is fed into the purification vessel through a fill aperture at the top, S while at least one feed line and downwardly widening nozzle are provided to feed purification brine into the vessel in counterflow to the flow direction of the solids to be purified.

This SALEX® system uses the simple and commonly known method of elutriation to separate particles based on their size and density. In this method, the particles to be separated are placed in a vertical column with a fluid flowing slowly upwards. This upwards flow is opposed by gravity, which causes the particles to fall through the column at speeds which vary according to their size and density. If the upwards flow rate is increased, the most slowly sinking particles will be swept upward with the fluid flow and removed from the top of the column. Intermediate particles will remain stationary, and the largest or densest particles will continue to move downward, where they can be removed from the base of the column. By careful control of the flow rate, particles can therefore be separated according to size and density.

Other existing devices, such as that described in US Patent No 5,068,092, also rely on elutriation but consist of two cylindrical vessels, with the upper vessel having a larger diameter than the lower vessel. These devices, however, still have inclined, conical bases which taper down to a single discharge point.

o °While the elutriation principle relies on the sedimentation of larger and denser particles at the base of the purification vessel, sedimentation can also serve to limit the efficiency of the vessel. One of the main problems that arises from the use •of particle-laden fluid in a purification vessel is the tendency of the particles to drop out of suspension and adhere to the walls of the vessel, building into solid deposits and disrupting or blocking the fluid flow in the vessel.

It is generally thought that when a fluid flows over a stationary surface, such as the wall of a tank, the fluid in contact with the surface is brought to rest by the shear stress at the wall. The velocity of the fluid flow increases with distance from the stationary surface, up to a maximum velocity in the main stream of the flow.

This region, in which there is a velocity profile from zero at the surface up to a maximum in the main stream of the flow, is called the boundary layer. The thickness of the boundary layer at any point is the distance from the wall to the point where the fluid velocity is 99% of the velocity of the main stream. As fluids pass over a greater length of solid surface, more fluid is slowed down by friction between the fluid layers close to the boundary layer. As a result, the thickness of the slower boundary layer increases over distance. This is an important problem when particleladen fluids such as slurries are involved, because in a flowing liquid, it is thought that particles tend to concentrate in areas of lower flow velocity, so solids are more likely to accumulate on the surface where there is a relatively thick boundary layer with laminar flow. In purification vessels such solid deposits can form zones of concentrated packing. These solid zones can extend by a bridging effect between deposits holding up the purified solid material while void spaces in between can form channels of preferential liquid flow, commonly known as "rat-holing".

Sedimentation rates are significantly increased when the process occurs on inclined surfaces, such as the sides of a traditional conical purification vessel.

Sedimentation in a conical vessel is generally faster than sedimentation in a vertical cylinder of the same height. In an attempt to minimise such sedimentation effects, the angle of the conical section at the base of such traditional vessels is kept as steep as possible, typically within the range of 100 to 300.

The difference in sedimentation rates between conical and cylindrical vessels is considered to be largely due to convection currents created as particles fall in accordance with the effects of gravity. These currents can be altered by introducing a counterflow via feed lines or spray bars within the vessel. Traditional salt purification systems, for example, feature feed lines to provide purification brine in counterflow to the flow direction of the solids to be purified, or flow that is tangential to the inclined walls of the vessel. In addition to facilitating the elutriation effect, this counterflow is often also intended to break up any deposits which are developing, disrupt the natural convection currents and minimise slow-moving boundary layer flows. By minimising slow-moving regions where particles are more likely to be deposited on the surface, and disrupting the natural convection currents that further facilitate such deposits, these systems are typically aiming to minimise the formation of solid obstructions and bridges within the purification vessel.

Due to the fluid mechanics within conical vessels, however, as the vessel is made larger, these countermeasures become less effective. The inability to place feed lines on the base of a conical vessel also creates a particular risk of obstructions and bridges forming in the lowest, narrowest region of the vessel, which can easily choke the discharge outlet or greatly reduce its efficiency. Lower slurry concentrations, typically in the order of 5 0% solids by mass, are also used to minimise these effects.

As a result, conical purification vessels suffer from an inherent lack of scalability once they exceed a certain physical size or slurry concentration, they cease to function in an optimal fashion and have an increased risk of blockages which can disrupt production.

Increasing the volume of a conical vessel also greatly increases the headroom required by that vessel within the plant.

The foregoing discussion does not constitute an admission as to the state of common general knowledge in Australia as it existed immediately prior to the filing date of this application.

To achieve efficiencies of scale when designing purification plants, there is therefore a need for an improved design that is not subject to the limitations of scale and efficiency inherent in traditional conical purification vessels.

SUMMARY OF THE INVENTION ;20 The present invention accordingly provides in one embodiment a treatment vessel for treating a component of a feed stream, the vessel comprising a body portion having a substantially flat base, first inlet means for a feed stream having a component to be treated, second inlet means for a fluid stream to facilitate countercurrent contact with the feed stream, and outlet means comprising a plurality 25 of discharge points in the base for removal of at least some of the treated component.

It has been observed that by using a substantially flat base, the present invention allows the diffusion of purification fluid upwards from the bottom of the vessel which, combined with the use of a plurality of discharge points in the base of 30 the vessel, minimises the formation of channels, rat-holes or other obstructions.

.4 The feed stream is typically a flowable solids stream including a loose particle or conveyable solids stream. The feed stream may also be a slurry, or other stream carrying entrained paruticles or solids. One example of a feed stream suitable for treatment in a vessel according to the invention is salt.

A treatment according to the present invention is typically washing of the component. It may include a purification of the component. The treatment may include both washing and a purification of the component.

The fluid stream is typically a purification fluid capable of washing and/or purifying a component in the feed stream. It may comprise recirculated fluid. Other fluids are envisaged within the scope of the invention.

The body portion may take any suitable form. The body portion may be substantially cylindrical. In one embodiment, the body portion comprises a plurality of cylindrical sections. The cylindrical sections may be of different diameter.

Preferably the cylindrical sections are disposed one above the other. In one particularly preferred embodiment, the body portion comprises a pair of cylindrical sections disposed one on top of the other, the upper cylindrical section being of larger diameter than the lower cylindrical section. Other body portion arrangements are envisaged within the scope of the invention.

The first inlet means is typically disposed in an upper region of the vessel body. It may comprise one or more inlet ports. An inlet port may be in the form of a pipe. The pipe will typically provide an open pipe discharge of the feed stream into an upper region of the vessel body.

The second inlet means may be disposed in any suitable region of the vessel body. Preferably the second inlet means is disposed so as to facilitate sufficient countercurrent contact between the component of the feed stream to be treated and the fluid stream. In one embodiment the second inlet means is disposed in an 25 intermediate region of the vessel body. The second inlet means may comprise one o or more inlet ports. The inlet ports may be in the form of nozzles providing a spray of the fluid stream. Other second inlet means are envisaged within the scope of the invention.

The substantially flat base may take any suitable form. The base may •30 comprise a grid. The grid may be a diffusion grid. At least some of the interstices of 2 the grid may provide discharge points for the treated component. At least some of the interstices of the grid may provide inlet points for further fluid for treatment of the component. The base may be perforated. At least some of the perforations may provide a plurality of discharge points for the treated component. At least some of the perforations may provide inlet points for further fluid for treatment of the component.

A third inlet means may accordingly be provided in the region of the base of the vessel to allow for a further source of fluid for contact with a component of the feed stream to be treated. The third inlet means may be disposed so as to provide the further source of fluid to the vessel through the base.

The discharge points may comprise valves. The valves may be opened on a random, semi-random or controlled basis to permit discharge of fluid on a random, semi-random or controlled basis.

The present invention provides in a separate embodiment a washing and/or purification vessel for washing and/or purifying a component of a feed stream, the vessel comprising: at least two cylindrical sections placed one above the other, with the upper section having a larger diameter than the lower section; a distribution manifold and an array of spray bars at the region of fluid interface between the sections; a flat perforated diffusion grid at the base of the lower section; a plurality of discharge points in the flat base of the lower section for discharge of the washed and/or purified component.

In one typical example of this embodiment of the invention, purified product is extracted from the lower section of the purification vessel by opening the discharge valves in a series of semi-random pulses. Alternatively, purified product is extracted from the lower section of the purification vessel by opening the discharge valves in a series of controlled pulses. This has been observed to substantially prevent the formation of fixed flow patterns and further reduces the formation of S. channels, blockages and other obstructions.

Due to the reduced risk of obstructions forming, the present invention can allow the use of a higher operating density of solids in the slurry, in the order of 30 60-70% solids by mass, as opposed to a typical slurry mix of 50% solids by mass for traditional conical classifier vessels. The flat-bottom design and plurality of discharge points also allows systems consistent with the present invention to be scaled up to much larger sizes without losing efficiency, and without requiring the same amount of head-room as a conical vessel of equivalent volume.

Rather than having a purification vessel of the prior art with a conical base which tapers down to a single discharge point, a flat-based purification vessel according to the present invention is used with a plurality of discharge points set into the base. The flat base allows purification fluid to be sprayed upwards from the actual base of the vessel through a plurality of spray nozzles set into the base plate, which facilitates the separation of impurities by elutriation and prevents the formation of channels, rat holes and other solid obstructions on the base and walls of the vessel. A semi-random series of pulse discharges from the plurality of discharge points also serves to prevent the formation of channels, rat holes or other obstructions by preventing fixed flow patterns from developing within the vessel.

The increased reliability and scalability permitted by these advances allows the creation of purification vessels larger than those permitted by the existing technology. The decreased risk of channels, rat holes or other obstructions also allows the use of particle-laden slurries with higher concentrations of solids by mass.

As a result, systems consistent with the present invention are more efficient, reliable, and result in a higher rate of particle recovery than existing systems.

Further efficiency may be achieved by using recirculated purification fluid in the upper section of the vessel, and pure fluid in the lower section of the vessel.

Because pure fluid is being sprayed upwards from the base of the vessel, a "hydraulic lock" is established between the two sections which prevents the recirculated fluid in the upper section passing into the lower section and contaminating the purified fluid and solids, yet still allows purified solids to pass down into the lower section.

The present invention provides in another separate embodiment a method for treating a component of a feed stream, the method comprising the steps of introducing the feed stream into a vessel according to the invention, contacting the *feed stream with a countercurrent stream of treatment fluid, and removing at least some of the treated component from the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the present invention will now be described with reference to particular non-limiting examples and the accompanying drawings. In the drawings, in which like integers are given like numerals: Figure 1 is a schematic representation of a flat-bottom purification vessel according to one embodiment of the present invention.

Figure 2 is a top elevation of an array of spray bars for use at the region of interface between the upper section and lower section of the purification vessel according to one embodiment of the present invention.

Figure 3 is a cross-sectional view of a distribution manifold and array of spray bars according to Figure 2.

Figure 4 is a diagram illustrating the operation of the perforated diffusion grid 165 at the base of the lower section 120 of the purification vessel according to one embodiment of the present invention.

Figure 5 is a top elevation illustrating an arrangement of discharge valves and spray nozzles on the base of the lower section of the vessel according to one embodiment of the present invention.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENT Turning to the drawings, Figure 1 shows an apparatus consistent with the present invention for the purification of particulate solids. A cylindrical purification vessel 100 consists of at least two vertically standing cylindrical sections 110 and 120, with the upper section 110 having a larger diameter than the lower section 120. The internal areas of sections 110 and 120 are in fluid contact with one another.

In a preferred embodiment, the top of the uppermost section 110 has a feed inlet 130 to allow the introduction of the feed stream to be treated. The top of the uppermost section 110 also features an overflow catchment 140, with a tailings discharge outlet 145 which allows the overflowing material and fluid to be removed for further processing or recirculation.

Due to the force of gravity, the particles of the feed stream move towards the bottom of the purification vessel at different rates, because their relative sizes and S•buoyancy levels will affect the rate at which they descend.

However, at the interface between the upper section 110 and lower section S•120 there is at least one feed line 150 leading into a horizontal array of spray bars 155 30 which spray a fluid stream into the upper section 110, establishing a steady counterflow to the downward flow of the feed stream due to gravity.

This upward flow from the spray bars 155 has an elutriation effect, in that it carries with it particles smaller than a certain critical size, which overflow the top of the upper section 110 and are collected in the overflow catchment 140. For the larger particles, the force of gravity remains stronger than the upward flow of the fluid stream, so they continue falling into the lower section 120 of the vessel. By controlling the flow of the fluid stream from the spray bars 155, the effective density of the particles retained in the vessel can therefore be controlled.

In one embodiment, the feed stream is salt, and the fluid stream being sprayed into the upper section 110 via feed line 150 and spray bars 155 is recirculated brine. Solid impurities such as gypsum (CaSO 4 .2H 2 0) and ionic magnesium (present as MgSO4 and MgC2) are removed by elutriation and are washed into the overflow catchment 140 as particles suspended in the recirculated brine solution. An additional purification effect also occurs due to displacement crystallisation, whereby salt crystals suspended in the brine solution act as seeds for crystallisation and grow as additional salt crystallises out of the brine solution. The principle of displacement crystallisation is based on the physico-chemical equilibrium of Na in the solution saturated with both Mg 2 and Na Addition of more Mg 2 ions to the system with injection of recirculated brine causes equilibrium to shift towards additional displacement of Na from the system to establish a new physico-chemical equilibrium corresponding to additional amount of Mg 2 in the mix. The source of additional Na* in the system derives from the stream coming from the lower section of the vessel where very little Mg2+ is present due to rinsing effect of clean brine so that when gradual increase of Mg 2 concentration occurs in the slow rising flow of clean brine then Na* concentration responds to new conditions progressively 25 precipitating from liquid to solid state on the surface of the existing crystals of NaCl.

This effect is not though to provide a means of purification to existing crystals of NaCI (that is, it does not displace impurities) but provides means of a increasing the crystal's size and so its ability to sink the crystal becomes large enough to counter the effects of the hindered zone conditions.

The lower section 120 may be of a smaller diameter but not necessarily than the upper section 110, and is both joined to, and in fluid contact with, the upper section 110.

At the base of the lower section 120 is a flat, horizontal diffusion grid 165, from which a fluid stream is directed upwards through a series of openings, such as spray nozzles. The fluid stream is fed into the diffusion grid 165 via at least one feed line 160.

In one embodiment, where the material to be purified is salt, the fluid stream fed into the lower section 120 via the feed line 160 and diffusion grid 165 is purified brine (an aqueous solution of NaC1). The upward flow of fluid from the lower section 120 prevents impure fluid in the upper section 110 from entering the lower section 120 and contaminating the purified product, but still allows purified particulate matter to cross from the upper section 110 to the lower section 120.

The upward flow of liquid from the diffusion grid 165 also improves the efficiency with which the vessel may be operated and cleaned, particularly when breaking up solidified deposits such as the packed beds which can accumulate if the vessel is inactive for any period of time. Such solidified deposits are typically only accessible to fluid streams directed from feed inlets located below or within the deposit.

Fluid streams directed from above the deposit will simply be redirected upwards due to the density difference between the packed solids in the lower section of the vessel and the fluid in the upper portion of the vessel. The substantially flat base of the present invention allows a fluid stream to be introduced from the bottom of the vessel, thus making all of the packed solids in the vessel subject to that fluid stream.

Set within the diffusion grid 165 on the base of the lower section 120 are a plurality of discharge valves 170 which allow the extraction of purified product from the vessel.

•The formation of channels, rat-holes or other solid obstructions in the lower section 120 is prevented by opening the discharge valves 170 in a series of orderly or semi-random pulses. In a preferred embodiment, the order of discharge pulses depends on the product concentration in different regions of the lower section 120 at any given time. This semi-random discharge prevents the establishment of fixed flow patterns and substantially reduces the likelihood of solid deposits such as packed beds and bridges forming. This also prevents the formation of preferential channels of uncontrolled liquid flow(s), rat-holing. The brief disruption to the settled product caused by each discharge pulse also serves to break up any bonds forming 1° ~between settled crystals, further preventing rat-holing and bridging effects.

S"Figure 2 is a cross-sectional view looking down upon an array of spray bars 155 consistent with one embodiment of the present invention. The array is positioned at the interface between the upper section 110 and lower section 120, and comprises a distribution manifold 200 extending around the inner circumference of the upper section 110, and a series of parallel spray bars 210 which are connected to the distribution manifold 200. Fluid is fed into the distribution manifold 200 and spray bars 210 by at least one feed line 150. The fluid is sprayed upwards from distribution manifold 200 and spray bars 210 through a plurality of spray nozzles.

Figure 3 is a cross-sectional view, along axis 300, of the distribution manifold 200 and parallel spray bars 210 according to Figure 2. Spray nozzles on the distribution manifold 200 spray fluid both vertically upwards and diagonally upwards.

The vertical flow is directed up the walls of the upper section 110, and in addition to facilitating the elutriation effect, it also helps disrupt the slow-moving boundary layer reducing the build-up of solid deposits on the walls of the vessel. Spray nozzles set into the spray bars 210 also discharge purification fluid in an upward direction into the upper section 110.

Figure 4 is a diagram illustrating the operation of the diffusion grid 165 at the base of the lower section 120 of the purification vessel according to one embodiment of the present invention.

Feed line 160 feeds purification fluid into diffusion grid 165, which is then discharged upward into the lower section 120 through spray nozzles 410. This upward flow 420 facilitates the elutriation effect by establishing a counterflow to the S• downward movement of the slurry due to gravity. For those spray nozzles which are close or adjacent to discharge valves 170 part of the flow 430 helps facilitate the movement of purified solids into the discharge valves 170.

0 °0 The flow from spray nozzles 410 also improves the efficiency with which solidified deposits on the base of the vessel may be removed following any periods .ooo.i of inactivity.

The pulsed fashion in which discharge valves 170 are opened also helps break •any bonds which may be forming between crystals which have settled in the lower section 120 of the vessel, thus preventing the process which leads to the formation 30 of channels, rat-holes and solid obstructions.

o0o Figure 5 illustrates an arrangement of discharge valves 170 and spray nozzles on the base of the lower section of the vessel, as seen from above, according to one 13 embodiment of the present invention. The section of detail 500 shows a plurality of spray nozzles arranged around a discharge valve 170.

The greater efficiency achieved by the present invention has been observed to lead to higher levels of salt recovery, which minimises the tailings discharge and S results in a cleaner wash overall.

Systems consistent with the present invention have also been observed to be easier to clean, and suffer from substantially less down-time following periods of inactivity, as the ability to spray fluid upwards from the base of the vessel makes it much easier to break up sediment and solid deposits which have accumulated.

The word "comprising" or forms of the word "comprising" as used in this description does not limit the invention claimed to exclude any variants or additions.

Whilst it has been convenient to describe the invention herein in relation to particularly preferred embodiments, it is to be appreciated that other constructions and arrangements are considered as falling within the scope of the invention.

Various modifications, alterations, variations and/or additions to the constructions and arrangements described herein are also considered as falling within the scope and ambit of the present invention.

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Claims (39)

1. A treatment vessel for treating a component of a feed stream comprising: a body portion having a substantially flat base; first inlet means for a feed stream having a component to be treated; second inlet means for a fluid stream to facilitate countercurrent contact with the feed stream; and outlet means comprising a plurality of discharge points in the base for removal of at least some of the treated component.

2. The treatment vessel according to claim 1 wherein the body portion is substantially cylindrical.

3. The treatment vessel according to claim 1 or 2 wherein the body portion comprises a plurality of cylindrical sections.

4. The treatment vessel according to claim 3 wherein the cylindrical sections are of different diameter.

5. The treatment vessel according to claim 3 or 4 wherein the cylindrical sections are disposed one above the other.

6. The treatment vessel according to any one of claims 1 to 5 wherein the body portion comprises a pair of cylindrical sections disposed one on top of the other, the upper cylindrical section being of larger diameter than the lower cylindrical section.

7. The treatment vessel according to claim 1 wherein the first inlet means is disposed in an upper region of the body portion.

8. The treatment vessel according to any one of the preceding claims wherein •the first inlet means comprise one or more inlet ports.

9. The treatment vessel according to claim 8 wherein said inlet port is in the form of a pipe providing an open pipe discharge of the feed stream to said vessel.

The treatment vessel according to claim 1 wherein the second inlet means is located so as to facilitate sufficient countercurrent contact between the component of the feed stream to be treated and the fluid stream.

11. The treatment vessel according to any one of the preceding claims wherein the second inlet means is disposed in an intermediate region of the vessel body.

12. The treatment vessel according to any one of the preceding claims wherein the second inlet means comprises one or more inlet ports.

13. The treatment vessel according to claim 12 wherein said inlet port(s) of the second inlet means are in the form of nozzles providing a spray of the fluid stream.

14. The treatment vessel according to any one of claims 1 to 13 wherein the substantially flat base comprise a grid.

The treatment vessel according to claim 14 wherein the grid is a diffusion grid.

16. The treatment vessel according to claim 14 or 15 wherein at least some of the interstices of the grid provide discharge points for the treated component.

17. The treatment vessel according to any one of claim 14 to 16 wherein at least some of the interstices of the grid provide inlet points for further fluid for treatment of the component.

18. The treatment vessel according to any one of claims 1 to 13 wherein the base ~is perforated. 20

19. The treatment vessel according to claim 18 wherein at least some of the *perforations provide a plurality of discharge points for the treated component.

20. The treatment vessel according to claim 18 or 19 wherein at least some of the perforations provide inlet points for further fluid for treatment of the 25 component.

21. The treatment vessel according to any one of the preceding claims and further comprising a third inlet means to allow for a further source of fluid for contact with a component of the feed stream to be treated.

22. The treatment vessel according to claim 21 wherein the third inlet means is provided in the region of the base of the vessel.

23. The treatment vessel according to claim 21 or 22 wherein the third inlet means is specifically disposed so as to provide the further source of fluid to the vessel through the base.

24. The treatment vessel according to claim 1 wherein the discharge points comprise valves.

The treatment vessel according to any one of the preceding claims wheremin the treatment vessel is used with a feed stream comprising a flowable solids stream, a slurry, or other stream carrying entrained particles or solids.

26. The treatment vessel according to any one of the preceding claims wherein the treatment vessel is used with a feed stream being a salt or a brine.

27 The treatment vessel according to any one of the proceeding claims wherein the treatment vessel is used with a feed stream comprising a quantity of salt.

28. A treatment vessel for treating a component of a feed stream, substantially as hereinbefore described and with reference to any one of the accompanying drawings.

29. The treatment vessel according to claim 28 wherein the discharge points in use are capable of being opened in a series of semi-random pulses to permit too ~the extraction of purified product from the lower section of the vessel.

30. The treatment vessel according to claim 28 wherein the discharge points in 20 use are capable of being opened in a series of controlled pulses to permit the ooo ~extraction of purified product from the lower section of the vessel.

31. A method for treating a component of a feed stream comprising the steps of: introducing the feed stream into a treatment vessel according to any preceding claim; contacting the feed stream with a countercurrent stream of treatment S. fluid; and fluid; and removing at least some of the treated component from the vessel.

32. A washing and/or purification vessel for washing and/or purifying a component of a feed stream, the vessel comprising: at least two cylindrical sections placed one above the other, with the upper section having a larger diameter than the lower section; a distribution manifold and an array of spray bars at the region of fluid interface between the sections; a flat perforated diffusion grid at the base of the lower section; and a plurality of discharge points in the flat base of the lower section for discharge of the washed and/or purified component.

33. The washing and/or purification vessel according to claim 32 wherein the discharge points, in use are capable of being opened in a series of semi- random pulses to permit the extraction of purified product from the lower section of the vessel.

34. The washing and/or purification vessel according to claim 33 wherein the discharge points in use are capable of being opened in a series of controlled pulses to permit the extraction of purified product from the lower section of the vessel.

The washing and/or purification vessel according to any one of claim 32 to 34 wherein the washing and/or purification vessel is used with a feed stream comprising a flowable solids stream, a slurry, or other stream carrying S entrained particles or solids.

36. The washing and/or purification vessel according to any one of claims 32 to wherein the washing and/or purification vessel is used with a feed stream being a salt or a brine.

37. The washing and/or purification vessel according to any one of claims 32 to wherein the treatment vessel is used with a feed stream comprising a quantity of salt.

38. A washing and/or purification vessel for washing and/or purifying a component of a feed stream, substantially as herein before described and with reference to any one of the accompanied drawings.

39. A method for treating a component of a feed stream comprising the steps of: introducing the feed stream into a washing and/or purification vessel according to any one of claims 33 to 38; contacting the feed stream with a countercurrent stream of treatment fluid; and removing at least some of the treated component from the vessel. Dampier Salt Limited 24 August 2001 S oo *o