FIELD OF THE INVENTION This invention relates to a fluid removal apparatus, and in particular, but not exclusively to a fluid removal apparatus for removing water from pulp and sludge type products.

BACKGROUND

There are many situations where it is necessary to remove large quantities of water from a product. The products are often waste products, slurries or sludges, and come from a wide range of activities, for example from sewage treatment plants, manufacturing processes, power plants, and quarries.

These wet products can often be difficult to manage, and often end up in holding tanks or settling ponds. Care must be taken with the management of these wet products to ensure.. that waste does not enter natural waterways and cause environmental pollution.

A number of devices have been developed and used for the removal of water from wet products, for example centrifugal separators and belt presses. However these devices have a limited ability to remove water or other fluids and the de-watered end products still have relatively large percentages of water. Such devices may be suitable in situations where it is only necessary to remove enough water to allow a de-watered product to be transported to a dump site. However, such devices can have limitations where the dewatered product needs to have a relatively low moisture level, for example where the de-watered product is to be used as a fuel in a furnace. In this specification unless the contrary is expressly stated, 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, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

OBJECT

It is therefore an object of the present invention to provide a fluid removal apparatus which will at least go some way towards overcoming one or more of the above mentioned problems, or at least provide the public with a useful choice.

STATEMENTS OF THE INVENTION

Accordingly, in a first aspect, the invention may broadly be said to consist in a fluid removal apparatus having a chamber with an inlet through which material containing solids and fluids enter the chamber, a first outlet through which the material minus some of the fluids exits the chamber and a second outlet comprising a plurality of apertures through which at least a portion of the fluid exits the chamber, the apparatus having a valve which is configured to control the flow of material out of the first outlet, and the apparatus having a plunger and a plunger actuation means, the plunger and plunger actuation means being configured to compress the material while the valve is in a closed configuration and the valve is preventing the material exiting the chamber. Preferably the chamber is a cylindrical chamber.

Preferably the inlet is situated at a first end of the chamber.

Preferably the first outlet is situated at a second end of the chamber which is situated opposite to the first end.

Preferably the plunger comprises a piston. Preferably the piston includes a skirt, and the piston and skirt are configured to close the inlet while the piston is operating within the chamber. Preferably the plunger actuation means includes a hydraulic actuator.

Preferably the sidewalls of the chamber include a plurality of layers or walls.

Preferably an inner layer or wall of the chamber includes the apertures.

Preferably one or more of the layers are configured to provide structural integrity for the chamber to allow the material to be compressed at relatively high pressures while the material is within the chamber.

Preferably the chamber includes an inner layer or wall having primary apertures and a second layer or wall which surrounds the inner layer or wall and which has secondary apertures that are larger in size when compared to the primary apertures. Preferably the primary apertures communicate with the secondary apertures.

Preferably the apertures are in the form of slots.

Preferably the slots are aligned with the direction of motion of the plunger.

Preferably the slots in the inner layer or wall of the chamber are narrower than the slots in the second layer. Preferably the chamber includes fluid collection passages configured to collect any fluid that is extracted from the material and which passes through the apertures.

Preferably the fluid collection passages include a plurality of circumferential passages which each communicate with a series of slots of the chamber.

Preferably the chamber comprises a plurality of sections, and is openable to allow the interior of the chamber to be cleaned.

Preferably the chamber comprises two halves, each being pivotally connected to the other along a length of the chamber.

Preferably the chamber includes fastening means configured to hold the sections of the chamber together while the apparatus is in use. In a second aspect, the invention may broadly be said to consist in a material processing plant incorporating at least one fluid removal apparatus substantially as specified herein.

Preferably the plant includes a material delivery means configured to supply material to the inlet. Preferably the material delivery means includes one or more controllable air inlet vents adapted to assist with movement of the material through the material delivery means and into the chamber of the fluid removal apparatus.

Optionally the material delivery means includes one or more controllable vibration creating means adapted to assist with movement of the material through the material delivery means and into the chamber of the fluid removal apparatus.

Optionally the vibration creating means is associated with the controllable air inlet vents.

Preferably the material processing plant includes a furnace configured to use material from the fluid removal apparatus as a fuel.

Preferably the material processing plant is configured such that material can be passed directly into the furnace as the material exits the first outlet of the chamber of the fluid removal apparatus.

The invention may also broadly be said to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of the parts, elements or features, and where specific integers are mentioned herein which have known equivalents, such equivalents are incorporated herein as if they were individually set forth.

DESCRIPTION

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: FIGURE 1 is a cross sectional side elevation view of a fluid removal apparatus according to the present invention, and

FIGURE 2 is a cut-away perspective view of a section of screen which forms a part of the fluid removal apparatus.

With reference to Figures 1 and 2, a fluid removal apparatus (11) according to the present invention will now be described. The fluid removal apparatus (11) has been developed primarily to remove water from material such as wood fibre pulp and bio-sludge. The apparatus (11) is configured to remove enough moisture from this material that the de- watered material is able to be used directly as a fuel. And since the apparatus (11) can be used in a process that requires no additional energy input to carry out further drying of the material it is possible to achieve a useful net energy output from the process that de- waters and burns the material.

It can be seen that the fluid removal apparatus (11) includes a chamber (13), and the chamber (13) has an inlet (15) through which the material containing solids and fluids can enter the chamber (13). The chamber (13) also has a first outlet (17) through which the material minus some of the fluids can exit the chamber (13). The apparatus (11) has a valve (19) which is configured to control the flow of material out of the first outlet (17).

The chamber (13) also has a second outlet (21) which comprises a plurality of apertures through which at least a portion of the fluid can exit the chamber (13).

The apparatus (11) includes a plunger (25) and a plunger actuation means (27). The plunger (25) and the plunger actuation means (27) are configured to compress the material while it is within the chamber (13) while the valve (19) is in a closed configuration. When the valve (19) is closed the valve (19) prevents the material from exiting the chamber, and when the valve (19) is opened the material can be pushed out of the chamber (13) by the plunger (25). In this example the chamber (13) is a cylindrical chamber having the inlet (15) at a first end (29) of the chamber (13), and the first outlet (17) is situated at a second end (31) of the chamber (13), which is situated opposite to the first end (29).

The plunger (25) comprises a piston (33) having a number of circumferential grooves similar to piston ring grooves., The piston (33) can include piston rings, however trials have shown that the grooves can fill up with de-watered wood pulp which act in a similar fashion to piston rings to help close the clearance between the piston (33) and the inner diameter of the chamber (13).

It can be seen that the piston (33) includes a long skirt (37). The piston (33) and the skirt (37) close the inlet (15) while the piston (33) is operating within the chamber (13) to compress the material. The skirt (37) has a half round profile that has a radius of curvature similar to that of the piston (33). The piston (33) is withdrawn out of the chamber (13) and past the inlet (15) when new material is being introduced into the chamber (13). In this example the plunger actuation means (27) includes a hydraulic actuator (39). The hydraulic actuator (39) has sufficient stroke to withdraw the piston (33) past the inlet (15), and to push the piston substantially along the length of the chamber (13). The actuation means (27) can exert sufficient force to squeeze a significant proportion of the water (and/or other fluids) from the material while it is within the chamber (13) and the valve (19) is closed.

The piston is also used to push the dewatered material out through the first outlet (17) after the valve (19) has been opened.

Figure 2 shows a partially cutaway section of a part of the chamber (13). It can be seen that the sidewalls (41) of the chamber (13) include a number of layers or walls, in this case there are three layers. An inner layer or wall (43) includes the apertures (23).

An outer layer or wall (45) is configured to provide the primary structural integrity for the chamber (13), to allow the material to be compressed to relatively high pressures while the material is within the chamber (13), for example pressures in the region of twenty to two hundred and thirty Bar. In this example the chamber (13) also has an intermediate layer or wall (47). The inner layer or wall (43) has primary apertures (23a) and the second layer or wall (47), which surrounds the inner layer or wall (43), has secondary apertures (23b). The secondary apertures (23b) are larger in size when compared to the primary apertures (23a). The primary apertures (23a) communicate with the secondary apertures (23b) to allow fluid to exit the chamber (13). It can be seen that the apertures (23a) and (23b) are in the form of slots, and they are aligned with the direction of motion of the plunger (25). The slots (23) in the inner layer or wall (43) are narrower than the slots (23) in the intermediate layer (47). An apparatus (11) has been constructed from steel using the following approximate dimensions and has been shown to work well. The chamber (13) has an internal diameter of three hundred millimetres (mm) and a length of one metre. The inner wall (43) is four mm thick, the intermediate wall is six mm thick, and the outer wall is seventeen mm thick. The primary slots (23a) are seventy millimetres long and are 0.2 mm wide, and the secondary apertures (23b) are the same length and are five millimetres wide. The slots (23) are arranged in circumferential rows and within each row they are spaced forty millimetres apart. The rows are spaced forty millimetres from adjacent rows, and the slots (23) of each row are staggered with respect to the slots (23) of an adjacent row. The chamber (13) includes fluid collection passages that are configured to collect any fluid that is extracted from the material and which passes through the apertures (23). The fluid collection passages (49) include a number of circumferential passages (49) which each communicate with a row of slots (23). The circumferential passages (49) in the test apparatus (11) are triangular passages that are about eight mm wide. The number of slots (23) and the size of the slots (23) and the passages (49) has been selected to ensure that the flow velocities within them are relatively high so that they can be kept relatively clear when the apparatus (11) is in use.

The chamber (13) is made up of two halves, and is openable to allow the interior of the chamber to be cleaned. Each half of the chamber (13) is pivotally connected to the other along a length of the chamber (13). The chamber (13) includes fastening means configured to hold the two halves of the chamber (13) together while the apparatus (11) is in use.

The fluid removal apparatus (11) can form a part of a material processing plant. The plant can include a material delivery means (51) configured to supply material to the inlet. The material delivery means includes one or more controllable compressed air inlet vents (53) adapted to assist with movement of the material through the material delivery means (51) and into the chamber (13) via the inlet (15).

The controllable compressed air inlet vents (53) can be operated in sequence with the operation of the piston (33). When the skirt (37) and the piston (33) have been fully withdrawn past the inlet (15), so that the inlet (15) is unobstructed, the air inlet vents (53) can be operated to allow a downward blast of air to assist the movement of a fresh charge of material into the chamber (15).

In figure 1 it can be seen that the material delivery means (51) includes a substantially vertical chute which connects with the inlet (15). The chamber (13) is below the inlet (15) and is at an angle of about 20 to 70 degrees (preferably between 40 to 50 degrees) to the vertical, so that material will flow readily into the chamber (13). In the configuration shown in figure 1, where the chamber is aligned at about forty five degrees to the vertical, it can be seen that the material only has to turn through about forty five degrees as it enters the chamber (13) from the vertical chute (51). The combination of the substantially vertical delivery chute (51), the relatively low angle through which the material must turn, the downward sloping chamber (13), and the blast or air, has been found to be very effective in consistently causing a full charge of material to enter the chamber (13) during each fill cycle. The moist material naturally sticks to the side of the delivery chute, and has a strong tendency to bridge and to stop flowing. However, this tendency to stick and block has been overcome by a clever system that combines the force of gravity with an air blast.

Also, vibration in the delivery chute (51) is caused by the operation of the air valve (55) that controls the flow of the compressed air to the inlet vents (53). This vibration further assists by shaking material off the sides of the delivery chute (51) and helps the material to settle and compact within the chamber ( 13). Preferably the delivery chute (51) has a slight negative taper, that is the chute (51) is has a slightly larger cross section near the bottom than it does at the top, to further assist in the free movement of the material down the chute (51) and into the chamber (13).

The material processing plant can include a furnace that is configured to use material from the fluid removal apparatus (11) as a fuel, for example by configuring the plant such that material can be passed directly into the furnace as the material exits the first outlet (17) of the chamber (13).

Testing has shown that it is often preferable to compress two loads of material within the chamber (13) before opening the valve (19) and pushing the 'biscuit' of dewatered material from the chamber (13). That is, a first charge of material is compressed within the chamber (13), and then a fresh charge of material is added and is compressed against the first compressed mass. Once the two charges have been compressed, the valve (19) is opened and the resulting biscuit of dewatered material is pushed out of the chamber (13).

VARIATIONS In the example described above the inner layer (43) of the chamber (13) comprised a four mm thick tube having slots cut in it. In an alternative configuration the inner wall of the chamber (13) could comprise a wedge wire screen. However, it is considered preferable to use the inner layer (43) described above because the width of the slots do not increase at the inside diameter wears. This compares to wedge wire screen in which the width of the slots increase as the inside diameter wears.

In the above example the primary slots (23a) were noted as being 0.2 mm wide. It is anticipated that slots in the range of 0.08 to 0.4 mm wide will be suitable, depending on the type of material being dewatered.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof. DEFINITIONS

Throughout this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps. ADVANTAGES

Thus it can be seen that at least the preferred form of the invention provides a fluid removal apparatus which has the following combination of advantages;

• The apparatus is able to able to remove a high percentage of water or other fluids from wet materials, slurries and sludge, · The apparatus is relatively simple and is robust providing a high level of reliability,

• The apparatus can remove water from difficult products with minimal requirements for the use of flocculants,

• The inner wall can be constructed at relatively low cost and can be replaced easily as it becomes worn.

While many dewatering machines can only produce de-watered material that is about 10 to 20% dry solids, the apparatus (11) of the present invention has been shown to produce de-watered material that is between 35 and 50% dry solids. It is this significant increase in the dry solids content that makes the apparatus (11) useful in producing fuel from waste products for a furnace. The 'biscuits' of fuel produced are relatively dense and compacted, and can fall directly into the bed of a furnace to produce useful heat.

Testing has also shown that the apparatus can produce these water removal rates with a mixture of 1/3 wood fibre pulp and 2/3 bio-sludge. In this way the apparatus is able to produce useful fuel from a common waste product that in the past has been very difficult to de-water.