The invention relates to an improved mixing apparatus. Particularly, but not exclusively, the invention relates to an improved mixing apparatus for mixing a fluid flow. The invention further relates to a method of mixing a fluid flow,

"F!uidic technology" is a term commonly used to describe the utilisation of fluids to provide control for, and power to, other fluids. Fiuidic mixers are apparatus which operate to use a pressurised fluid to generate a motive force to move and mix a fluid flow; the fluid flow often containing soiids material, Fiuidic mixers are desirable because installation and maintenance costs are minimal, and such mixers are suited for use in a variety of applications and environments. For example, fiuidic mixers can be used for mixing bio-so!ids, sludge, or slurries, and in chemical process, food process, water effluent treatment industries, oil related industries, nuclear industries and deep sea mining,

Examples of fiuidic mixers are shown in GB2242370 and GB2313410 which describe fiuidic mixers comprising a pressurised fluid flow feed, a central zone and a series of perforations which extend into the centra! zone. Such mixers operate to transfer the pressurised fluid through the perforations and into the central zone. The arrangement of the perforations directs said fluid in a manner so as to cause the fluidisation and mixing of a fluid flow passing through the central zone, However, disadvantageous^, said arrangement suffers from the inherent problem of seepage of materia! in the fluid flow into the perforations and externa! chamber. The material solidifies and causes blockages in the pressurised fluid flow path. Over a period, due to blockage, the fiuidic mixer ceases to be operational and must be replaced. A further example of a fiuidic mixer is shown in WO 00/71235. Similarly, the fiuidic mixer of WO 00/71235 also suffer from internal blockages due to material seepage into the chamber, A further disadvantage of known fiuidic mixers is thai external surface of the mixers comprise sharp edges, such as bolts, which protrude from the surface and readily trap debris in the material flow, for example, rags, plastic bags. Over time, the debris builds on and around the mixer, to cause the eventual blockage of the inlet of the mixer, it is an object of the invention to provide a mixing apparatus for mixing a fluid, particularly a fluid flow, which aims to overcome the aforementioned problems, it is a further object of the invention to provide a method of mixing a fluid flow, According to an aspect of the present invention there is provided a mixing apparatus for mixing a fluid, the mixing apparatus comprising a body having an axis, a core through which the fluid passes, a chamber for receiving a feed flow, and at least one jet member, wherein a valve member is located on the mixing apparatus, the valve member being operable to move to a first position in which the fluid is substantially prevented from entering the chamber.

Advantageously, ir¾ the first position, the vaive member operates to close, so as to prevent fluid from entering the chamber. In so doing, material in the fluid cannot pass Into the chamber and so the likelihood of the chamber becoming blocked is minimised. Therefore, the apparatus has an enhanced lifespan in comparison to known mixing apparatus.

Preferably, the mixing apparatus is for mixing a fluid flow. Preferably, the valve member is operable to move to a second position in which the vaive member is substantially open, preferably to allow the feed flow to pass therethrough.

Preferably, the valve member is a non return valve. Preferably, the valve member is a tapered lid-type valve. Preferably, the valve member comprises an assembly body, the assembly body preferably having a nozzle, and/or a spring and/or a fixing.

Preferably, a cap is located on the at least one vaive member, preferably being located at an end thereof. Preferably, at least one orifice is provided on the cap. Preferably, said orifice is substantially between 1 to 10mm diameter, most preferably substantially between 3 to 6mm in diameter.

Preferably, the valve member is located on the at ieast one jet member. Preferably, a plurality of jet members are provided on the mixing apparatus, Most preferably, each jet member comprises a valve member most preferably having a cap comprising an orifice. Preferably, the body comprises an outer casing and an inner casing. Preferably, the chamber is located between said casings. Preferably, the inner casing forms the core. Preferably, the inner and/or the outer casing comprise a smoothed surface. Preferably, both the inner and outer casings comprise a smoothed surface. Advantageously, provision of smoothed surfaces minimises the risk of material being inadvertently caught on the mixing apparatus. In so doing, the risk of blockage of the apparatus is reduced.

Preferably, at least a part of the or each jet member is located in the chamber. Preferably, a portion of the or each jet member is in communication with the core. Preferably, the core comprises the inner casing,

Preferably, a feed flow conduit is provided on the apparatus. Preferably, the feed flow conduit is operable to supply a feed flow to the body, preferably to the chamber. Preferably, the feed flow conduit is located substantially perpendicular to the axis of the apparatus, preferably to a longitudinal axis of the body.

Most preferably, the feed flow is supplied to the or each jet member. Preferably, the jet member is operable to direct the feed flow towards the fluid, preferably the fluid flow. Preferably, the fluid, most preferably the fluid flow is caused to be entrained by the feed flow and to move, preferably along the core, preferably in a direction towards an outlet end of the mixing apparatus.

Preferably, the feed flow comprises a liquid or gas. Most preferably, the feed fbw is a gas, preferably a compressed gas. Most preferably, the feed flow is compressed air. Preferably, the feed flow is a steady flow. Preferably, the feed flow rate is substantially between 40 to 80cfm, most preferably substantially 80cfm,

Preferably, the valve member is operable to move to the first position when the feed flow conduit is In a closed position, in the closed position, the feed flow is prevented from entering the chamber. Preferably. In the first position, the orifice is substantially closed to the fluid, preferably the fluid fiow, and is preferably closed to the feed flow.

Preferably, a first row of jet members Is located on the mixing apparatus. Preferably, the first row comprises a plurality of jet members, preferably three jet members. Preferably, said first row is located substantially between 10 and 50mm from an inlet end of the mixing apparatus, most preferably substantially 20mm from the inlet end of the apparatus. Preferably, one jet member is located coaxial with an axis of the apparatus, Preferably, the or each or ail said jet members are orientated so as to be directed downwardly, towards the longitudinal axis of the apparatus, by an angle of substantially between 25° and 50°, most preferably 35°.

Preferably, a second row of jet members is located on the mixing apparatus. Preferably, the second row comprises a plurality of jet members, preferably six jet members. Preferably, said second row is located substantially between 20 and 80mm from an Inlet end of the mixing apparatus, most preferably substantially 80mm from the inlet end. Preferably, the or each or ail said jet members are located in a position which is offset from the axis, preferably the longitudinal axis of the apparatus, by substantially between 1° and 5°. most preferably 3°,

Preferably, the or each or all jets In the said second row is orientated so as to be directed downwardly, towards the longitudinal axis of the apparatus, by an angle of substantially between 20° and 50°, most preferably 30*. The fluid, preferably the fluid flow may contain a mixture of fluid material and solid material. The mixture may be waste water or sewage, drill cuttings (in oil industries) or nuclear waste products {in nuclear industries),

The arrangement of the first row and second row of jet members creates a dual flow regime in the mixing apparatus, A first flow is created along the longitudinal axis of the apparatus, along the core. This first fiow is preferably a highly turbulent flow which is operable to entrain the fluid fiow to move said flow through the apparatus. A second flow is created adjacent the wails of the inner casing. Preferably, the second flow is a non turbulent flow. In so doing, a high volume of fluid, preferably fluid fiow, can be passed through the core in a reduced period of time. Preferably, the core is substantia!iy 15 to 250mm in diameter, most preferably substantially 100mm in dlairteter.

Preferably, the mixing apparatus is located In a holding tank, A plurality of mixing apparatus may be provided. The or each mixing apparatus may be located towards the base of the holding tank, preferably adjacent the base thereof. The or each mixing apparatus may be spaced from an edge of the holding tank.

According to a further aspect there is provided a method of mixing a fluid comprising the steps of,

1. Supplying a feed flow to a mixing apparatus comprising a body, a chamber for receiving the feed flow, a core through which the fluid passes, and at least one jet member, a valve member being located on the body;

2. Ejecting the feed flow from the at least one jet member to cause entratnment of the fluid:

3. Moving the valve member to a first position in which the fluid is substantially prevented from entering the chamber.

Preferably, the fluid is a fluid flow.

Preferably, the valve member is located on the at least one jet member.

Preferably, the mixing apparatus is operable to turn over a volume of substantially between 500m ³ and 1500m ³ of sludge in 45 minutes. Most preferably, the apparatus is operable to turn over substantially 836m ³ in 45 minutes, most preferably at 60cfm and 2bar.

All of the features described herein may be combined with any of the above aspects, in any combination.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 shows a schematic side view of a mixing apparatus according to the present invention; Figure 2 shows a schematic rear view taken along sine B of Figure 1. of a mixing apparatus according to the present invention;

Figure 3 shows a schematic front view taken aiong fine C of Figure 1 , of a mixing apparatus according to the present invention;

Figure 4 shows a schematic front view of a mixing apparatus according to the present invention; Figure 5 shows a schematic side sectionai view of a mixing apparatus according to the present invention;

Figure 8 shows a schematic sectional view of a part of a mixing apparatus, taken aiong line G of Figure 5, according to the present invention;

Figure 7 shows a schematic sectionai view of a part of a mixing apparatus, taken along !ine F of Figure 5, according to the present invention;

Figure 8 shows a schematic side view of a member of a mixing apparatus according to the present invention;

Figure 9 shows an exploded schematic side view of the member of the mixing apparatus of Figure 8; Figure 10 shows a schematic sectional side view of a part of the member of Figures 8 and 9;

Figure 11 shows a schematic sectional side view of a further part of the member of Figures 8 and 9;

Figures 11a and l i b show a schematic sectional side view and cross sectional view respectively of a mixing apparatus according to the present invention; and

Figure 12 shows a schematic view of a theoretical fluid flow in a mixing system incorporating a mixing apparatus according to the present invention. Figure 1 shows a mixing apparatus 2 according to the present invention, The mixing apparatus 2 comprises a body 4 having a first portion 8, a second portion 8, and a third potion 10. Said portions may comprise individual parts, joined together, or may be an integral one piece section. A feed flow inlet 12 communicates with the body 4, being adapted to supply a feed flow to the apparatus 2 as will be described in further detail below. Fluid flow enters the apparatus 2 through the third portion 10 and out of an outlet 15 in the first portion 8, along a centra! axis 18,

References to feed flow will be understood to mean the introduction of a fluid, a gas or a liquid, into the apparatus to promote entrainment of the fluid flow through the apparatus 2, References to fluid flow will be understood to mean the stream of flow passing through the apparatus which will be effected by the action of the feed flow.

The mixing apparatus 2 comprises an outer casing 18 and inner casing or centra! tube 20 as shown in Figure 2. Said casings are preferably welded together to form a transfer chamber 24. The casings 18,20 are circular in cross section. The outer casing 18 has an internal diameter of 200mm and an outer diameter of 208mm. The inner casing 20 has an interna! diameter of 100mm and an outer diameter of 06mm. Said casings comprise smoothed surfaces to prevent unwanted disturbance of fluid flow and to minimise the likelihood of trapping of unwanted debris on the apparatus 2. It can be seen from Figure 3 and 4 that the mixing apparatus 2 comprises an outer surface 22 having no obvious obstructions thereon. The arrangement of the present invention minimises the effect of rag build u , on or around the apparatus, thus enhancing the lifespan of the apparatus.

Figure 5 shows a cross section of the mixing apparatus 2. in particular, said Figure shows the centra! tube 20 and the transfer chamber 24. The feed flow inlet 12 is in communication with the transfer chamber 24 to provide a supply of the- feed flow to the transfer chamber 24.

A plurality of jets 26 are arranged in the transfer chamber 24. Specifically, and as shown in Figures 6 and 7, a first row of jets 28 is provided towards the inlet 29 of the third portion 10, and a second row of jets 30 is provided downstream of said first row 28. The first row of jets 28 are positioned 20mm from the inlet 29, The second row of jets 30 is 60mm from the inlet 29, AN said jets are arranged generally circumferentially about the centra! tube 20. The first row of jets 28 comprises three jet members 32 as shown in Figure 7. The first said row 28 is located 20mm from the inlet 29 of the apparatus. Said jet members 32 are orientated in a forwards direction towards the axis 16, to a position upstream of the inlet, at a distance half the diameter of the central tube 20 or bore. Figure 7 shows the position of each jet member 32 with respect to the central longitudinal axis 16, an axis X~X and an axis Y'-Y ^! of the apparatus 2.

The positioning of the second row of jets 30 is shown in Figure 6. The second row of jets comprises six jet members 34 which are fixed at an angle (a) of 30 degrees towards the central tube 20 or bore. The jet members 34 are further offset at 3° from the longitudinal axis 18 of the apparatus 2.

Figures 8 to 10 show the arrangement of a non return valve 38 incorporated into the apparatus 2. The valve 36 comprises an assembly body 38, a nozzle barrel 40, a spring 42 and a fixing 44. As shown in Figure 9, a valve stem 48 and O ring 48 are provided between the nozzle barrel 40 and assembly body 38. Further, the fixing 44 comprises a Nylon locating washer 50 and an assembly nut 52. A sectional view taken along line A-A of Figure 9 shows the internal configuration of the nozzle barrel 40. Figure 10b shows a sectional view taken along line B-B of Figure 9 of the assembly body 38. A non return valve 36 is fitted to each said jet member 32,34.

Figures 11a and l i b show a schematic of the mode of operation of the apparatus 2. In use, a feed flow, preferably compressed air, is passed through the jet members 32, 34 via the transfer chamber 24. The first row of jets 28 creates a vacuum, entraining the fluid flow and any solids contained within, into the inlet of the apparatus 2, A forward thrust of the jet forces the fluid flow through the central tube 20. The second row of jets 30 forms an air cushion 56 between the fluid flow and an inner side wall 58 of the central tube 20 reducing friction and creating a rifling effect along the inside wall 58 of the apparatus 2. in so doing, solids and any materials that could, potentially, block the apparatus 2, pass through the apparatus 2, and at a greater velocity, approximately being increased by a margin of 4. The vacuum created at inlet 10 is also increased by the same margin. Additionally, it is considered that the orientation and the number of the second jet members 34 causes particulate material in the fluid flow to be directed at high velocity towards the air cushion 56 and the wail 58. The air cushion 56 itseif is fikeiy to comprise highly turbulent flow and, as a result, particulate matter is likely to be caused to de-agglomerate in this turbulent flow. Further, impaction of particulates on the wall 58 is likely due to the turbulent flow regime, The overall effect on the particulate material will be a reduction in particulate materia! size.

It Is considered that the particulate materia! of reduced size may either be readily moved along the air cushion 56 and/or returned to the fluid flow adjacent the outlet end of the apparatus 2. Due to the reduction in particulate size, residency time of particulates in the fluid flow is increased; the particulates being less Sikeiy to fall out of the flow due to gravitational forces. Fiuid flowing out of the apparatus 2 is directed into a fluid holding tank 60, where the particulates of reduced size provide a greater surface area for mixing to occur. As such, mixing of material predominately occurs outside of the apparatus 2, Further, such mixing is likely to be highly efficient.

Figure 12 shows a schematic of the likely directional mixing occurring outside of the apparatus, within the holding tank 60. Arrows 62 indicate the flow of fluid 61 throughout the tank 60. Crucially, the present invention incorporates non return valves 36 which are operable to close against the fluid flow when the feed flow is stopped. Each non return valve 36 prevents fluid flow entering the transfer chamber 24. This is achieved by the provision of a cap end, having an orifice machined on the top face, to each jet member 32,34. The orifice is of suitable size to allow the required amount of feed flow to pass through the bore and through each jet member 32,34. The orifice size varies between 3mm and 6mm depending on mixing requirements. The feed flow is a steady flow of 80cfm. A valve seat is machined on the Internal top face of the cap, A screwed valve stem, complete with a spring retaining nut and washer are all fitted and fixed through the orifice on the outer face of the cap end, with the valve closing against the interna! machined surface. The valve stern, spring, retaining nut and washer are all contained within the transfer chamber 24 and protected from contamination by the fluid flow.

Provision of a non return valve having an interna! spring/valve seat and lid. guide jets and valve housing, ail fabricated In stainless steel, ensures that material seepage from the fluid flow is minimised. The position and angles of the jets design, comprising two rows of jet holders complete with non return valves, creates an increased vacuum at the inlet end of the mixing apparatus, together with an increase in the throughput of materia! flow through the apparatus.

Advantageously, the present invention provides for an increased throughput of material flow through the apparatus. Although some mixing is likely to occur in the core of the apparatus 2, it is considered that the majority of mixing of the material flow within a given tank is generated in the upward movement of the materia! directly above the position of the mixing apparatus.

Advantageously, the fabrication of the apparatus 2 is streamlined to avoid accumulating of rags etc. Three long jets including non return valves 36 are positioned as close to the inlet side of the unit as practical, these inlet jets point upstream to the centre of the internal casing, by approx half the diameter of the inner casing. A further row of six Song jet members complete with non return valves 36 are positioned upstream of the inlet jets, these are set at a shaliow angle and are offset a few degrees, preferably between 1° and 10°, preferably between 2° and 5°, most preferably 3°, from the flow line. This row of jets forms an air cushion 56 between the fluid flow and the internal bore of the inner casing.

The air cushion 58 allows material to pass through the inner casing at a higher velocity; the external flow over the apparatus also increases. The air supply or feed flow (motive air) can be reduced to 45cfm at 45psi for each mixing apparatus 2 without any effect on the efficiency of the system.

As minimal mixing takes place within the core of the mixing apparatus 2, the apparatus 2 can now be considered to be a catalyst that promotes mixing within its zone of influence within a given area, The apparatus 2 does not have any mixing properties as such, In its present form.

Advantageously, the apparatus of the present invention is efficient and economical to operate, and provides the end user with a product having a long operational !ife span. Advantageously, the arrangement of the present invention is more efficient in creating an environment of aggressive agitation than known fiuidic mixers. The present apparatus is operabie to use 50% 3ess feed flow (compressed air) to power a single apparatus than known fiuidic mixers. The present apparatus is operabie to promote a mixing action in a vessel which will turn over a volume of 836 ^J of sludge in 45 minutes with a gas flow of 6Qcfm at 2bar pressure, ail within a sfudge storage tank. Given the low power and iniet pressure, it is not possible to pass 836 M ³ of material through the 100mm nominal bore of the apparatus in 45 minutes. One possible theory for the desirable effect is that the apparatus acts as a catalyst within a storage tank, generating violent upward movement, and creating a vertical mixing column, exterior to the apparatus.

The introduction of nan return valves within the mixing apparatus gives said apparatus a new and practical advantage over previous fiuidic type mixers.

The introduction of precision machined jet members, retains the shape of the air jet further into the product within the centra! tube of the apparatus to create a more powerful vacuum, in so doing, the apparatus is efficient at preventing the apparatus from blockage. Furthermore, the second row of jets 30 creates an air cushion 56 within the apparatus 2 to allow more products to pass safely through the apparatus at a higher velocity; the effect is to reduce the power input by a factor in excess of 50%. The apparatus creates a vertical mixing column within its area of influence in any given storage tank. The movement within the vertical column is enough to break up any solid material (macerate) that may have formed within the tank.

In comparison to other types of mixing apparatus, the apparatus of the present invention is economical to operate due to reduced power input needed and whole life running costs. The reader's attention is directed to a\\ papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or ail of the steps of any method or process so disclosed, may be combined in any combination , except combinations where at ieast some of such features and/or steps are mutually exclusive.

Each feature disciosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiments). The invention extends to any novei one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed,