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Title:
OIL/WATER SEPARATION PROCESS AND APPARATUS
Document Type and Number:
WIPO Patent Application WO/2011/000044
Kind Code:
A1
Abstract:
The present invention relates to an improved method of oil clarification in particular for refining palm oil, a separator plate used in the improved oil clarification process, and an oil/water separator which incorporates a plurality of such separator plates in a novel formation.

Inventors:
ERSKINE, Gilbert (Lot 691 Bains Road, Onkaparinga Hills, South Australia 5162, AU)
ERSKINE, Craig (Lot 691 Bains Road, Onkaparinga Hills, Queensland 5162, AU)
NORTON, Jeff (16 Lennard Drive, Moana, South Australia 5169, AU)
Application Number:
AU2010/000834
Publication Date:
January 06, 2011
Filing Date:
June 30, 2010
Export Citation:
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Assignee:
STERI-FLOW FILTRATION SYSTEMS (AUST) PTY LTD (32 Heath Street, Lonsdale, South Australia 5160, AU)
ERSKINE, Gilbert (Lot 691 Bains Road, Onkaparinga Hills, South Australia 5162, AU)
ERSKINE, Craig (Lot 691 Bains Road, Onkaparinga Hills, Queensland 5162, AU)
NORTON, Jeff (16 Lennard Drive, Moana, South Australia 5169, AU)
International Classes:
B01D17/028; C02F1/40; C11B13/00
Attorney, Agent or Firm:
LESICAR PERRIN (58 Rundle Street, Kent Town, South Australia 5067, AU)
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Claims:
CLAIMS

1. A separator plate for use in an oil/water mixture separation environment, said separator plate characterised by:

a rigid body including a generally planar surface which encourages coalescing of said oil; one or more baffles extending at least partially across said planar surface and generally outwardly therefrom, said baffles providing an additional coalescing surface.

2. A separator plate as characterised in claim 1, wherein said separator plate further includes a means of interconnecting with a further separator plate such that when said separator plates are interconnected they extend perpendicularly to one another in a zig zag formation.

3. A separator plate as characterised in claim 2 wherein the interconnection means takes the form of interconnecting lugs that mate with corresponding sockets on adjacent separator plates.

4. A separator plate as characterised in any one of claims 1-3, wherein said separator plate further includes a means of stacking one or more separator plates to form an array of separator plates.

5. A separator plate as characterised in claim 4 wherein said rigid body further includes two upstanding outermost walls between which said planar surface extends to thereby form an elongated I- shaped structure. 6. A separator plate as characterised in claim 5 wherein said means of stacking plates is in the form of locating pins adapted to interconnect with a corresponding locating hole that can be found in each wall.

7. A separator plate as characterised in claim 6 wherein the locating pins are positioned parallel to the separator plate wall midway between upper and lower edges of the walls and each locating pin connecting with one of a pair of locating holes therein positioned parallel to a separator plate wall midway between upper and lower edges of the walls and each locating pin connecting with one of a pair of locating holes therein positioned either side of a midway point between the upper and lower edges of the wall in an offset fashion to thereby facilitates the stacking of a series of plates.

8. A separator plate as characterised in any one of claims 5-7 wherein said baffles extend sequentially from opposed outermost walls, each baffle extending across said planar surface to a location short of the opposed wall. 9. A separating apparatus for use in the separation of oil/water mixtures, said apparatus characterised by one or more separator plates each consisting of a wide central web and outermost upstanding side walls forming a generally shallow open channel and a series of generally transverse baffle members located within the channel formed by the web for encouraging coalescing of oil as the oil/water mixture moves across said plate.

10. A separating apparatus as characterised in claim 9 wherein a plurality of separator plates are connected in series, to create an extended coalescing surface, and wherein the series of connected separator plates are arranged in a zigzag fashion. 11. A separating apparatus as characterised in claim 10 wherein said apparatus includes a plurality of horizontally stacked separator plates connected in series and arranged in a zig zag formation, forming a separator array.

12. A separating apparatus as characterised in claim 11 wherein said separating apparatus includes two vertically disposed arrays.

13. A separating apparatus as characterised in claim 12 wherein the upper of said arrays is eight plates deep, and the lower of said arrays is six plates deep, each of said plates being arranged in a zig zag formation.

14. A separating apparatus as characterised in any one of claims 9-14 wherein the baffles extend sequentially from opposing side walls of the central web, and each baffle projects approximately two thirds of the distance across the web between the walls. 15. An oil/water mixture separation plant characterised by:

a coalescing separation tank adapted to receive raw product, said tank including at least one set of laminar plates through which said mixture rises, said laminar plates configured to encourage coalescing of oil present in said mixture. 16. An oil/water mixture separation plant as characterised in claim 15 wherein said plant further includes a means of retrieving oil from the top of the separation tank.

17. An oil/water mixture separation plant as characterised in claim 15 or claim 16 wherein said plant further includes one or more filters through which water from the bottom of the separation tank is processed to produce substantially oil and particulate free water.

18. An oil/water mixture separation plant as characterised in claim 17 wherein plant further includes a means of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture.

19. An oil/water mixture separation plant as characterised in claim 15 or claim 16 wherein said plant further includes a settling tank into which solids and water which settle at the bottom of the separation tank are fed. 20. An oil/water mixture separation plant as characterised in claim 19 wherein said plant further includes one or more filters through which water from the bottom of the settling tank is processed to produce substantially oil and particulate free water.

21. An oil/water mixture separation plant as characterised in claim 20 wherein said plant further includes a means of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture.

22. An oil/water mixture separation plant as characterised in any one claims 17-21 wherein said one or more filters includes a de-watering filter and a cross flow micro filter.

23. A process for the separation of oil from process water, said process characterised by the steps of:

introducing an oil/water mixture into a separation tank such that said mixture rises through at least one set of laminar plates configured to encourage coalescing of oil present in the mixture.

24. A process as characterised in claim 23 wherein said process includes the further step of retrieving oil from the top of the separation tank.

25. A process as characterised in claim 23 or claim 24 wherein said process includes the further step of filtering water from the bottom of the separation tank to produce substantially oil and particulate free water. 26. A process as characterised in claim 25 wherein said process includes the further step of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture. 27. A process as characterised in claim 23 or claim 24 wherein said process includes the further step of feeding solids and water which settle at the bottom of the separation tank into a settling tank.

28. A process as characterised in claim 27 wherein said process includes the further step of filtering water from the bottom of the settling tank to produce substantially oil and particulate free water.

29. A process as characterised in claim 28 wherein said process includes the further step of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture.

30. A process for the separation of oil from process water, said process characterised by the steps of:

a) introducing a mixture to be separated into an array of separator plates, each separator plate consisting of a generally shallow three sided open channel having a wide central web, outermost upstanding side walls, a series of generally transverse baffle members located within the channel formed by the web, whereby a plurality of separator plates may be connected in series as to create an extended separation surface, and wherein the series of connected separator plates are arranged in a zigzag fashion to form the array; b) allowing the mixture to rises up the underside of the separator plates and washing the mixture with water flowing in the opposite direction in counter current fashion; and c) collecting a separated oil product from the top of the array. 31. A method of refining palm oil comprising the steps of: a) treating (sterilizing) the FFB with steam at 60° to 100° for about 60 mins to deactivate the enzymes responsible for the formation f free fatty acids in the fruit bunches;

b) stripping or separating the fruit from other plant material;

c) digesting the released fruit, usually by pressurization and rapid pressure release at 6O0C to 100°C;

d) pressing the digested frit mass to yield a crude oil extract from which the palm oil is purified; and

e) subjecting the crude oil extract to a separation process comprisisng

f) introducing a mixture to be separated into an array of separator plates, each separator plate consisting of a generally shallow three sided open channel having a wide central web, and outermost upstanding side walls, a series of generally transverse baffle members located within the channel formed by the web, whereby a plurality of separator plates may be connected in series as to create an extended separation surface, and wherein the series of connected separator plates arranged in a zigzag fashion to form the array;

g) allowing the mixture to rises up the underside of the separator plates and washing the mixture with water flowing in the opposite direction in counter current fashion; and h) collecting a separated oil product from the top of the array.

Description:
Oil/Water Separation Process and Apparatus

FIELD OF THE INVENTION The present invention relates to a method and apparatus for the separation of oil from water. The method and apparatus of the invention is of particular relevance in the separation and refining of palm oil from water. However, it is to be understood that the method and apparatus of the invention have a wide applicability in the use of separating oil/water mixtures. BACKGROUND OF THE INVENTION

Oil Palm, which originated in Africa, exists in wild, semi- wild and cultivated land areas of the equatorial tropics of Africa, South East Asia and South America. At the present time, the oil palm is cultivated over a wide range of tropical climatic conditions and soil types. The palm oil milling process has not changes significantly over the last 80 years, although over the last 15 years there has been significant investment by the Malaysian government, private investors and commercial businesses to overcome inherent process problems and increase processing efficiencies without a noticeable success. The palm oil milling process, known in the art, comprises the major steps of: preparing fresh fruit bunches (FFB), digestion, oil extraction, oil clarification, sludge separation and kernel separation. The typical processing steps for extraction of palm oil from harvested fruit is described in some detail in US patent number 5039455. Whilst the precise operating details of different extraction and refining plants vary, there are in general a number of processing steps that are common to all oil processing and extraction operations. One of these is the use of water/steam in the extraction of the oil and the consequent need to separate the extracted oil from the water and process waste.

To this end, known mill designs include very large waste water lagoons with long retention times. This has meant that unless the dam sizes are significantly increased there is no opportunity for them to expand their production throughput. Furthermore, dams require frequent maintenance to sustain their performance thereby adding to the overall refining cost. The existing technology is known to be generally inefficient and wasteful of resources.

To date this has been accepted, together with the consequential oil losses and large volumes of waste produced. Thus, the oil clarification process is a key process where technology can be applied with the greatest impact to potentially increase oil quality, increase oil yields, increase plant throughput and reduce water effluent-palm oil mill effluent (POME).

Traditionally oil clarification has been achieved through the use of settling and clarification tanks along with centrifuge and/or decanter technology.

Theoretically this process splits the three phases present - oil, water and solids. The reality and main issue is the presence of a fourth layer, sometimes referred to as the "X-layer". The fourth layer is formed by the fine fibres, and light solids and particulate matter which does not readily separate and settle to the bottom of the clarifying tank. The buoyancy of this layer is added to by the rising oil which becomes "captured" below and within the mat of small and lightweight fibres. The oil within this layer will take extended lengths of time to be separated, if it is separated from the solids, thus its quality is greatly reduced by extensive oxidation.

Many mills have installed centrifuge and/or decanter technology to aid in the separation of oil from the fourth layer. This works only to a limited extent, due to the similar densities of the components. However, this technology is maintenance and power consumption intensive. Many mills using this technology have installed a second train of equipment to ensure equipment up-time/availability meets production demands.

In most processes, dilution water (usually hot) is added to aid in the separation of the oil and solids. It is documented that up to 0.65 cubic metres of water per tonne of FFB (free fruit bunches) processed is used. For an average 40 tonne FFB/hr mill operation, water consumption can be in excess of 400 tonnes per day. Thus this water, contaminated with various solids etc adds significantly to the water effluent/POME stream and requires large biological processing lagoons, which in turn occupy otherwise usable land. It is an object of the present invention to provide an alternative to existing oil clarification processes.

SUMMARY OF THE INVENTION

Therefore according to the first aspect of the present invention there is provided a separator plate for use in an oil/water mixture separation environment, said separator plate characterised by:

a rigid body including a generally planar surface which encourages coalescing of said oil;

one or more baffles extending at least partially across said planar surface and generally outwardly therefrom, said baffles providing an additional coalescing surface.

Preferably said separator plate further includes a means of interconnecting with a further separator plate such that when said separator plates are interconnected they extend

perpendicularly to one another in a zig zag formation.

In preference the interconnection means takes the form of interconnecting lugs that mate with corresponding sockets on adjacent separator plates. Preferably said separator plate further includes a means of stacking one or more separator plates to form an array of separator plates.

In preference said rigid body further includes two upstanding outermost walls between which said planar surface extends to thereby form an elongated I-shaped structure.

Preferably said means of stacking plates is in the form of locating pins adapted to interconnect with a corresponding locating hole that can be found in each wall.

In preference the locating pins are positioned parallel to the separator plate wall midway between upper and lower edges of the walls and each locating pin connecting with one of a pair of locating holes therein positioned parallel to a separator plate wall midway between upper and lower edges of the walls and each locating pin connecting with one of a pair of locating holes therein positioned either side of a midway point between the upper and lower edges of the wall in an offset fashion to thereby facilitates the stacking of a series of plates. Preferably said baffles extend sequentially from opposed outermost walls, each baffle extending across said planar surface to a location short of the opposed wall.

In a further form of the invention there is provided a separating apparatus for use in the separation of oil/water mixtures, said apparatus characterised by one or more separator plates each consisting of a wide central web and outermost upstanding side walls forming a generally shallow open channel and a series of generally transverse baffle members located within the channel formed by the web for encouraging coalescing of oil as the oil/water mixture moves across said plate.

Preferably the one or more separator plates are connected in series, to create an extended coalescing surface, and wherein the series of connected separator plates are arranged in a zigzag fashion. In preference said apparatus includes a plurality of horizontally stacked separator plates connected in series and arranged in a zig zag formation, forming a separator array.

Preferably said separating apparatus includes two vertically disposed arrays.

Advantageously the upper of said arrays is eight plates deep, and the lower of said arrays is six plates deep, each of said plates being arranged in a zig zag formation.

In preference the baffles extend sequentially from opposing side walls of the central web, and each baffle projects approximately two thirds of the distance across the web between the walls.

In a still further form of the invention there is proposed an oil/water mixture separation plant characterised by:

a coalescing separation tank adapted to receive raw product, said tank including at least one set of laminar plates through which said mixture rises, said laminar plates configured to encourage coalescing of oil present in said mixture.

Preferably said plant further includes a means of retrieving oil from the top of the separation tank. In preference said plant further includes one or more filters through which water from the bottom of the separation tank is processed to produce substantially oil and particulate free water.

In preference the plant further includes a means of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture.

In a further aspect, said plant further includes a settling tank into which solids and water which settle at the bottom of the separation tank are fed.

Alternatively said plant further includes one or more filters through which water from the bottom of the settling tank is processed to produce substantially oil and particulate free water.

In preference said plant further includes a means of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture.

Preferably said one or more filters includes a de-watering filter and a cross flow micro filter.

In a yet further form of the invention there is proposed a process for the separation of oil from process water, said process characterised by the steps of:

introducing an oil/water mixture into a separation tank such that said mixture rises through at least one set of laminar plates configured to encourage coalescing of oil present in the mixture.

Preferably said process includes the further step of retrieving oil from the top of the separation tank.

In preference said process includes the further step of filtering water from the bottom of the separation tank to produce substantially oil and particulate free water.

In preference said process includes the further step of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture. In a further aspect, said process includes the further step of feeding solids and water which settle at the bottom of the separation tank into a settling tank. Alternatively said process includes the further step of filtering water from the bottom of the settling tank to produce substantially oil and particulate free water.

Preferably said process includes the further step of washing the rising oil/water mixture in the separation tank using said filtered water by introducing said water to the separation tank in an opposite direction to the rising mixture.

In a further form of the invention there is proposed a process for the separation of oil from process water, said process characterised by the steps of:

a) introducing a mixture to be separated into an array of separator plates, each separator plate consisting of a generally shallow three sided open channel having a wide central web, outermost upstanding side walls, a series of generally transverse baffle members located within the channel formed by the web, whereby a plurality of separator plates may be connected in series as to create an extended separation surface, and wherein the series of connected separator plates are arranged in a zigzag fashion to form the array; b) allowing the mixture to rises up the underside of the separator plates and washing the mixture with water flowing in the opposite direction in counter current fashion; and c) collecting a separated oil product from the top of the array.

In a still further form of the invention there is provided a method of refining palm oil comprising the steps of:

a) treating (sterilizing) the FFB with steam at 60° to 100° for about 60 mins to deactivate the enzymes responsible for the formation f free fatty acids in the fruit bunches;

b) stripping or separating the fruit from other plant material;

c) digesting the released fruit, usually by pressurization and rapid pressure release at 6O 0 C to 100°C;

d) pressing the digested frit mass to yield a crude oil extract from which the palm oil is purified; and

e) subjecting the crude oil extract to a separation process comprisisng f) introducing a mixture to be separated into an array of separator plates, each separator plate consisting of a generally shallow three sided open channel having a wide central web, and outermost upstanding side walls, a series of generally transverse baffle members located within the channel formed by the web, whereby a plurality of separator plates may be connected in series as to create an extended separation surface, and wherein the series of connected separator plates arranged in a zigzag fashion to form the array; and

g) allowing the mixture to rises up the underside of the separator plates and washing the mixture with water flowing in the opposite direction in counter current fashion; and collecting a separated oil product from the top of the array.

DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment on conjunction with the accompanying drawings. In the drawings:

Figure 1 illustrates in front and rear perspective views a separator plate forming a part of an oil/water separator in accordance with the present invention;

Figure 2 illustrates schematically in cross-section an arrangement of a plurality of

separator plates in a chevron formation as might be used in an oil/water separator;

Figure 3a illustrates a front view an oil/water separator including the plates of figure 1;

Figure 3b illustrates a right hand side view of the oil/water separator of Figure 3a; and

Figure 4 illustrates in block schematic form a palm oil processing arrangement

incorporating the oil/water separator of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts. The present invention relates to an improved method of oil clarification, a separator plate

10 used in the improved oil clarification process, and an oil/water separator (also referred to herein as a coalescing three phase separation tank) 11 which incorporates a plurality of separator plates 10 in a novel formation. Each of these aspects of the present invention is described in detail below.

Shown in figure 1 is a separator plate 10 in accordance with the present invention, the purpose for which will become apparent. The plate 10 consists of a generally three surfaces, a wide central web 12 and two outermost upstanding walls 14 forming a stretched I-shaped structure. The space between the walls defines a shallow, open channel and located within the channel on one side (the underside when arranged according to the present invention) of web 12 are a series of generally transverse baffle members 16. The baffles 16 extend sequentially from opposing side walls 14, each baffle 16 extending to a location short of the opposing wall.

It is to be understood that, in the context of the present invention, the spacing of the baffle members 16 may vary subject to the nature of any liquids being separated. In particular, the distance between adjacent baffle members may be varied, as may the length of any baffle member, and the gap between a baffle member and the opposing wall 14, all such variations being comprehended within the scope of the invention. In the embodiment under consideration there are four baffle members 16 on each separator plate 10. Increasing the number of baffles present in a separator plate 10 effectively increases the surface area of the separator plate and therefore increases the reactive area available for separation.

The separator plates 10 also include connection means to allow individual plates 10 to be connected to one another to form a separation array. In the form of the invention shown, the connection means takes the form of interconnecting lugs that mate with corresponding sockets. In particular, there is a pair of opposed projecting connection lugs 20 at one end of the plate 10, each lug 20 fitting snugly into a retrospective socket 22 located at the lower end of a second separator plate 10 in an array. The upper and lower edge of each upstanding wall 14 is cut by 45 degrees. The skilled addressee would realise that if say the plate 10 in the upper drawing of figure 1 was tilted such that the top of the plate was rotated out of the page by 45 degrees, and the top of the plate 10 in the lower drawing of figure 1 was tilted into the page by 45 degrees, the lower edge of walls 14 of the upper plate 10 would extend parallel with the upper edge of walls 14 of the lower plate 10, which would enable engagement between the associated lugs and sockets. Once engaged, the baffles 16 of the upper plate extend generally downwardly, the baffles 16 of the lower plate also extend generally downwardly, and the two plates would extend perpendicularly to one another in a vertical zigzag formation. This is shown clearly in figure 2. Preferably, two separator plates, when connected end to end in series fashion are able to pivot relative to one another.

The separator plates 10 also contain stabilising connector means 24 to permit stacking of an array of plates. In the case of the present embodiment the stabilising connector means 24 takes the form of locating pins depending downwardly from walls 14 of the plate 10 (when in the zigzag formation described above) that interconnect with a locating hole 26 that can be found in each wall 14. The locating pins 24 are generally positioned parallel to the wall 14 midway between upper and lower edges of the wall 14. Thus, the locating pins 24 of the separator plate

10 are adapted to be attached to one pair of opposed holes 26 in a second separator plate 10 in an offset fashion. Figure 2 illustrates how both pairs of holes 26 are utilised when the plates 10 are arranged in the zigzag formation of the present invention. This offset connection facilitates the stacking of a series of plates in the zigzag array shown in the oil/water separator 11 of figures 3a, 3b and figure 4.

The arrangement of plates 10 shown in the drawings can thus be used in a way that ensures that liquid encountering the separator is presented with a large surface area over which oil/liquid separation can take place. As will be described in more detail below, the design allows for oil to gather on the underside of the plates 10 and grow in size until such time as it moves along and up the baffles 16 to the top of the separator 11. The baffles extend on a slight angle to promote the rise of oil in this manner.

Figure 4 illustrates schematically a palm oil processing facility 28 including a separator

11 having an array of separator plates 10 and incorporating the improved oil clarification method of the present invention. Only a portion of the total palm oil processing steps have been included in the schematic. However, a person skilled in the art would be familiar with the basic steps including: a) treating (sterilizing) the FFB with steam at 60° to 100° for about 60 mins to deactivate the enzymes responsible for the formation of free fatty acids in the fruit bunches; b) stripping or separating the fruit from other plant material; c) digesting the released fruit, usually by pressurization and rapid pressure release at 6O 0 C to 100°C; and d) pressing the digested fruit mass to yield a crude oil extract from which the palm oil is purified. The material entering the raw product tank 30 shown in the lower left hand side of figure 4 should be understood as having undergone such typical processing steps as are known in the art to produce a raw product.

The raw product from the screw press (not shown) is measured for water content, adjusted and fed into the coalescing three phase separation tank 11. In the example,

approximately 12000 Kg/hr of raw product is mixed with 24000 Kg/hr process water and fed to the separator tank 11. The tank, 11, includes an array of separator plates 10 formed in accordance with the invention. The tank 11 has two sets of separator plates 10 with the product being fed between both sets.

In a preferred form of the invention, the plates are spaced at 22mm and set at an angle of 45 0 C, and are 300mm wide and 250mm high, they are set out in a zigzag formation.

As the oil rises up the underside of the plates 10 in the separation tank 11, it is washed by 85 0 C to 95°C water flowing in the opposite direction as shown by 32. The oil water mixture in the separation tank 11 encounters a hydrophobic surface in the form of the plates 10. The extent of the surface encountered by the oil water mixture encourages the oil to coalesce and separate from the mixture. Furthermore as the oil rises up the separator tank 11 along the underside of the baffles 16 the oil is continually presented with cleaner water thereby promoting the separation in a counter current fashion.

Any solids present in the mixture are induced to settle to the bottom of the tank 11 where they are carried to the exit end of the tank by a screw 34. Thus, in the example under

consideration of the 12000 Kg/hr of raw product enter the separator tank, approximately

4000Kg/hr solids are removed and are subsequently fed to a settling tank 36 and 4000 Kg/hr of cleaned oil is removed. The oil removed from the top of the separator 11 is subject to an oil filtration through a 5 micron oil filter 38 and is subsequently vacuum-dried in a dryer 40 to produce the final product which is a finished high grade oil.

Of the solids removed in the screw 34 it is at this point considered that there would be somewhere in the vicinity of 0.5 to 1.0 percent oil in the solids. Recovery of this oil presents the opportunity to increase the overall yield and efficiency of the process and also the opportunity to reduce the environmental damage that might be caused by discharge of polluted waste. There are further advantages to be gained at this stage. By removal of the oil from the solid waste a useable and saleable product is also produced. The solids produced are spadeable and suitable for anaerobic digestion, they can be converted to a high quality fertilizer. As an additional byproduct the harvesting of methane is also possible. Thus, the processing plant 28 has either an additional product to sell and/or means of reducing the overall fuel cost thereby improving profitability.

Extraction of the solids takes place in the settling tank 36 where a small amount of oil separates from the solids and rise to the top of the tank. Oil that is harvested is fed into the oil filter 38 and undergoes the same process described above to product high quality product.

Water from the bottom of the settling tank 36 is fed into a 60 micron dewatering filter 42, and, in turn, water from the dewatering filter 42 is fed to a further water or cross flow filter 44 (including 0.3 micron metallic membrane), and also returned to the suction side of the raw product feed pump where it is used to dilute the raw product. Solids discharged from the retentate side of the cross flow filter 44 are fed back to the dewatering filter. Filtrate from the cross flow filter 44 is oil and particulate free. This water is fed back to three phase separation tank 11 and forms the counter current wash water to form a three phase split between water, oil and solids. Excess water goes to the waste water storage lagoons. This oil clarification process is thus a closed circuit system providing a number of distinct advantages over traditional oil room operations, including but not limited to:

• increase in oil quality;

• increase in oil recovery / yield (1.5%);

• increase in plant throughput capacity;

• reduced water usage;

• reduced water effluent / POME;

• reduced water effluent retention / processing time;

• reduced land requirements for the milling process;

• reduced/minimised power requirements;

• reduced/minimised/removed the need for chemical and additive usage;

• reduced/minimised specialty knowledge required locally for operations and maintenance;

• reduced/minimised maintenance requirements and costs; and

• reduced the requirement for investment in a standby plants or complex equipment.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirits of the invention, which is not limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.