PNEUMATIC CONVEYING SYSTEM FOR SEPARATING BULK PRODUCT

Abstract

There as herein defined a pneumatic conveying system comprising a cyclonic feed apparatus. In particular, there is described a pneumatic conveying system comprising a vessel (e.g. a cyclonic separator) in combination with a sifting device (e.g. a centrifugal device) which is capable of separating pneumatically conveyed material into oversize powder discharge (e.g. waste material) and fine powder discharge (e.g. valuable product material).

Claims

1-28. (canceled)

29. An apparatus (500) for pneumatically conveying and separating bulk material comprising: a vessel (526) for receiving and separating gas and bulk material; at least one material inlet (512) located on the vessel (526) for inputting gas and bulk material into the vessel (526) and forming a cyclone which separates the gas and bulk material within the vessel (526); and a sifting device (534) for receiving the bulk material from the vessel (526), wherein bulk material is separated via centrifugal forces into at least two or more different powder discharges.

30. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the vessel (526) is a cyclonic separator and the sifting device (534) is a centrifugal sifting device which is capable of separating pneumatically conveyed material into oversize powder discharge from a first sifter outlet and fine powder discharge (544) from a second sifter outlet.

31. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the vessel (526) is substantially cylindrical in shape with a conically shaped bottom section (532) which is used to funnel material to the sifting device (534).

32. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the vessel (526) is located substantially vertically during use and has a substantially longitudinal axis extending vertically through the vessel (526) thereby allowing the separated bulk material to be gravity fed to the sifting device (534).

33. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the vessel (526) comprises two or a plurality of material vessel inlets for the inputting of air and bulk material into the vessel (526).

34. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the at least one, two or plurality of material vessel inlets are located on the vessel (526) substantially tangential to the longitudinal axis of the vessel (526) thereby facilitating the formation of a cyclone of air and bulk material within the vessel (526).

35. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the vessel (526) comprises at least one or more air and/or material outlets which feed separated air and material to the sifting device (534).

36. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein in use a positive pressure gradient is maintained from the at least one vessel inlet (512) to a pneumatic conveying outlet located on the sifter device (534).

37. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the vessel (526) comprises at least one more gas and/or material outlets which are substantially aligned with the longitudinal axis of the vessel (526).

38. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the sifting device (534) comprises a material inlet for receiving air, material from the vessel (526), or a combination thereof.

39. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the sifting device (534) is in the form of a cylindrical chamber which is positioned substantially horizontally.

40. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the sifting device (534) is lined with a series of perforations such as in the form of a perforated sheet, and wherein the sifting device (534) comprises a shaft with outlying and/or protruding members located on the shaft which on rotation are used to stir and/or rotate the material within the sifting device whereupon under centrifugal forces, the stirred and/or rotated material is forced against the perforated sheet or substantially cylindrical sieve in the form of a perforated drum or mesh-like structure which allows separation of the bulk material to occur into larger and smaller particulate material.

41. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the sifting device (534) is in the form of a cylindrical sieve comprising a mesh-like structure with a series of small apertures, the small apertures having a cross-section diameter of 100-1,000 mm, and wherein larger particulate material is retained within the cylindrical sieve and exits through an outlet as an oversize powder discharge and fine particulate material passes through the cylindrical sieve as a fine powder discharge and exits through an outlet as a fine powder discharge.

42. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein by rotating the material in the sifting device (534) causes at least part of the bulk material to pass through perforations and/or apertures in the sifting device (534), and wherein material which passes through perforations of the sifting device (534) exits the sifting device (534) via a first material outlet as fine powder discharge and is valuable product material and larger sized particulate material which is unable to pass through the perforations in the sifting device (534) exits the sifting device (534) via a second material outlet as oversize powder discharge and is waste material.

43. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein a conduit (570) connects the cyclonic separator (526) and an outlet (546) located below the sifting device (534) which allows a flow of air to travel from the cyclonic separator (526) along the conduit (570) to the outlet (546) which assists in the collection and transfer of fine powder discharge (544).

44. An apparatus (500) for pneumatically conveying and separating bulk material according to claim 29, wherein the apparatus also comprises a hopper (402) to feed bulk material from a transport silo or any other storage system into the apparatus, and wherein the sifting device (534) comprises a drive to rotate the cylindrical sieve located in the sifting device (534).

45. A method of conveying and separating bulk material comprising: providing a vessel (526) for receiving and separating gas and bulk material; providing at least one material inlet (512) located on the vessel (526) for inputting air and bulk material into the vessel (526) and forming a cyclone which separates the gas and bulk material within the vessel (526); and providing a sifting device (534) for receiving bulk material from the vessel (524) wherein the sifting device (534) separates the bulk material via centrifugal forces into at least two or more different powder discharges.

46. A method of conveying and separating bulk material according to claim 45, wherein in use a positive pressure gradient is maintained from the at least one vessel inlet (512) to one or a plurality of pneumatic conveying outlets located on the sifting device (534).

47. A method of conveying and separating bulk material according to claim 45, wherein, in use, the material is fed into the at least one vessel inlet (512) at a speed such that the material within the vessel (526) adopts a cyclonic tubular configuration, and wherein the material passes from at least one vessel material outlet whilst maintaining its cyclonic tubular configuration to the sifting device (534) which facilitates the separation of the air and bulk material.

48. A method of conveying and separating bulk material according to claim 45, wherein bulk material is caused to rotate in a cyclonic vortex due to the rotation of air within the vessel (526) and during the cyclonic motion of the particulate material, the particulate material is forced to the outer surfaces of the vessel (526) in a vortex-like manner; and wherein during use, particulate material is thrown against the sidewalls of an upper section of the vessel (526) and then funneled down along into a lower section (532) of the vessel (526) wherein the cyclone of air therefore builds a rotating mass of material against the sidewalls of the vessel (526) which has the ability to absorb sudden increases and/or decreases in material feed by adjusting the thickness dimension ‘T’ and density of the particulate material being forced against the inner surfaces of the vessel (526).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Embodiments of the present invention will now be described, by way of example only, with reference to the following Figures:

[0074] FIG. 1 is a representation of a cyclonic feed apparatus according to an embodiment of at least one aspect of the present invention wherein the cyclonic feed apparatus is receiving material from an unloading vehicle and feeding material to a storage silo;

[0075] FIG. 2 is a representation of a cyclonic feed apparatus according to a further embodiment of at least one aspect of the present invention;

[0076] FIG. 3 is a side view of the cyclonic feed apparatus shown in FIG. 2;

[0077] FIG. 4 is a front view of the cyclonic feed apparatus shown in FIGS. 2 and 3;

[0078] FIG. 5 is a representation of a sectional side view of a further cyclonic feed apparatus according to an embodiment of at least one aspect of the present invention wherein the cyclonic feed apparatus is attached to a centrifugal sifter;

[0079] FIG. 6 is a representation of the cyclonic feed apparatus and centrifugal sifter shown in FIG. 5 with an additional filter and an additional bypass fitted;

[0080] FIG. 7 is a representation of a partial sectional view of a further cyclonic feed apparatus according to an embodiment of at least one aspect of the present invention showing the separation of oversize powder discharge (e.g. waste material) and fine powder discharge (e.g. valuable product material);

[0081] FIG. 8 is a representation of a further cyclonic feed apparatus according to an embodiment of at least one aspect of the present invention illustrating the flow of material and air through a cyclone separator and a centrifugal sifter during use; and

[0082] FIG. 9 is an expanded cross-sectional view of the cyclone separator shown in FIG. 8 illustrating the flow of material and air through the apparatus during use.

DETAILED DESCRIPTION

[0083] Generally speaking, the present invention therefore relates to a pneumatic conveying system comprising a cyclonic separator in combination with a cyclonic sifting apparatus which is capable of separating pneumatically conveyed material into oversize powder discharge (e.g. waste material) and fine powder discharge (e.g. valuable product material). This is discussed below in detail.

[0084] FIG. 1 is a representation of a cyclonic feed apparatus 10 according to the present invention. As shown in FIG. 1, the cyclonic feed apparatus 10 is capable of receiving material from a vehicle 12. The vehicle 12 contains a transport silo 14 which feeds material to a vibration sifter 16. The vibration sifter 16, which is an optional feature, shakes the material to be conveyed and helps to prepare the material to be pneumatically conveyed by breaking down any large clumps of condensed material. This material is then fed to the cyclonic feed apparatus 10. Material then passes through the cyclonic feed apparatus 10 which is described in more detail below. The pneumatically conveyed material is then fed into a storage silo 18 via, for example, any suitable means such as a static sifter (e.g. a grid) 20.

[0085] FIGS. 2 to 4 are representations of a further cyclonic feed apparatus 100 according to the present invention.

[0086] FIGS. 2 and 3 show material entering via the direction identified by arrow ‘A’ into the inlet feed 120. FIG. 3 also shows the material exiting the cyclonic feed apparatus 100 via outlet feed 150 along the direction identified by arrow ‘B’.

[0087] FIGS. 2 to 4 show that the cyclonic feed apparatus 100 comprises an inlet feed 120. Through the inlet feed 120 material may be received from the transport silo 104 and optionally the vibration sifter 16. Pneumatically conveyed material is then fed up through a substantially vertically located passageway 122, for example, in the form of a pipe. Located along the substantially vertical passageway 122 there is a coarse sieve 124.

[0088] The conveyed material is then passed through inlet 125 into an upper section of a cyclone separator 126. The cyclone separator 126 may have a large volume such as over 50, 100 or 200 litres. The cyclone separator 126 is located substantially vertically along a substantially vertical axis 128 of the cyclonic feed apparatus 100. The cyclone separator 126 comprises two main sections. The first upper section 130 is substantially cylindrical in shape. The lower main section 132 is in a funnel form to feed material into the sifting device 134. It should be noted that the size and proportions of the cylindrical and funnel shapes may vary significantly from what is shown in the figures.

[0089] Material is fed through the lower main section 132 of the cyclone separator 126 via an outlet 136 into the sifting device 134 through an opening 146. The sifting device 134 is a centrifugal sifting device. This is described in more detail below.

[0090] Material once passed through the cyclonic separator 126 and the sifting device 134, then exits the cyclonic feed apparatus 100 via an outlet 150.

[0091] FIGS. 2 to 4 also show that the cyclonic feed apparatus 100 comprises a control panel 138 which is used to control the apparatus 100 and monitor the feed rate and operation of the apparatus 100.

[0092] The cyclonic feed apparatus 100 also comprises elongate sections 140, 142 in the form of skids which allows a fork lift truck to easily lift and manoeuvre the cyclonic feed apparatus 100.

[0093] There is also shown a pneumatic control device 144 which is used to control the pneumatic feed.

[0094] FIGS. 2 to 4 also show that there is a conduit generally designated 160 which extends from below the sifting device to above the cyclone separator 126. In particular, the conduit 160 is in the form of a pipe extending from below a chute 162 located below the device 134. The conduit 160 comprises a substantially vertical section which may comprise a sieve 164. The conduit 160 then extends to above the cyclone separator 126 and is then connected to an upper section of the cyclone separator 126 via a section of pipe 168 and an upper located inlet 166.

[0095] The function of the conduit 160 is to take the separated air from the cyclone separator 126 and reintroduce the air into the pneumatic conveying pipeline, via the outlet 150. This novel process of using the separated air to continue to convey the material after the sifting device 134 has many benefits. One such benefits is that there only needs to be one propulsive air source to convey material through the whole system. The air which is used to introduce the material into the cyclonic feed apparatus 100, is the same as the air used to convey the material out of the apparatus 100. This removes any need for additional energy sources within the apparatus to convey the air, thereby making the process more energy efficient.

[0096] FIG. 5 represents part of a further cyclonic feed apparatus 200 according to the present invention. The cyclonic feed apparatus 200 comprises a cyclone separator 226 which comprises an upper section 228 and a lower section 232. There is also shown an inlet 225 into an upper section of the cyclone separator 226.

[0097] Of particular relevance, FIG. 5 shows a sifting device 234. The sifting device 234 is generally a substantially hollow cylindrical member which is located substantially horizontally. The sifting device 234 comprises a centrally and substantially horizontally mounted shaft 227 which is rotated during use resulting in material being forced to the outside surfaces 270, 272 of the sifting device 234 via centrifugal forces. Although not shown, outlying and/or protruding members such as paddles maybe located on the shaft 227 which assist in the material being stirred and/or rotated. There is also shown a chute 262. Sifted material exits through outlet 250.

[0098] FIG. 6 represents a further cyclonic feed apparatus 300 according to the present invention. The cyclonic apparatus 300 shown in FIG. 6 is very similar to the cyclonic apparatus 200 shown in FIG. 5.

[0099] The cyclonic apparatus 300 comprises a cyclone separator 326 which comprises an upper section 328 and a lower section 332. There is also shown an inlet 325 into the upper section 328 of the cyclone separator 326. Of particular relevance, FIG. 5 shows a sifting device 334.

[0100] The sifting device 334 is generally a substantially hollow cylindrical member which is located substantially horizontally. A shaft 327 optionally comprising outlying and/or protruding members such as paddles is rotated during use resulting in material being forced to the outside surfaces 370, 372 of the sifting device 334 via centrifugal forces. There is also shown a chute 362. Sifted material exits through outlet 350.

[0101] The cyclonic feed apparatus 300 also comprises a coarse screen 380 which is used to filter material prior to entering the cyclone separator 326. The coarse screen 380 may have a screen range size of about 10-30 mm or about 15 mm. There is also shown a fine screen 382 which secures an air bypass. The fine screen 382 may have a screen range size of about 0.5-5 mm or about 2 mm.

[0102] The air bypass with a cyclone provides that the pneumatically conveyed product has a possibility to be sieved because the airspeed and/or volume fluctuates due to a range of factors such as any one of or combination of the following: pneumatic conveying settings set by a truck driver; air supply; amount of product and a tanker silo on a vehicle; a variety of piping which may be used in different apparatus; and pressure drops anywhere in the systems.

[0103] The cyclonic apparatus 200, 300 shown in FIGS. 5 and 6 may be used in the embodiments shown in FIGS. 1 to 4.

[0104] FIG. 7 is a representation of a partial sectional view of a further cyclonic feed apparatus 400 according to the present invention. The cyclonic feed apparatus 400 is shown in a partial sectional view which illustrates the travel of pneumatically conveyed material through the apparatus 400. This will now be discussed.

[0105] As shown in FIG. 7, powder feed material 401 is fed into a hopper 402. The powder feed material 401 may be fed from a transport silo 14 as shown in FIG. 1. However, it should be noted that the powder feed material 401 may be fed from any location or storage system.

[0106] The powder feed material 401 is therefore gravity fed via the hopper 402 into a cyclone separator 404. The cyclone separator 404 will be similar to that shown in FIGS. 2 to 5. As shown in FIG. 7, the cyclone separator 404 is located substantially vertically. The cyclone separator 404 comprises an upper section through which material 401 is fed into from the hopper 402 and a lower section. Inside the cyclone separator 404 a vortex of air and particulate material is formed where separation of the material 401 may occur. This is discussed in more detail below.

[0107] As shown in FIG. 7, the material exits the cyclone separator 404 along a substantially horizontal path into the sifting device generally designated 415. The material may be fed into the sifting device 415 via any suitable means such as a screw shaft.

[0108] The sifting device 415 has an outer casing 410 which may contain an opening in the form of a door which may allow inspection and maintenance of the sifting device 415.

[0109] FIG. 7 also shows that there is a substantially centrally mounted shaft 412 which extends substantially horizontally through the sifting device 415. Although not shown, the substantially centrally mounted shaft 412 may comprise outlying and/or protruding members such as paddles which may assist in the stirring and/or rotation of the material within the sifting device.

[0110] FIG. 7 also shows that the sifting device 415 comprises a substantially horizontally mounted substantially cylindrical sieve 414 within which the powder feed material 401 is rotated and circulated at a speed of: about 100-1,000 rpm; about 200-750 rpm or about 500 rpm. The speed varies for different sizes of machines and the diameters of rotation involved.

[0111] The cylindrical sieve 414 comprises a mesh-like structure with a series of small apertures. The apertures in the mesh-like structure may have a cross-sectional diameter of any of the following: about 50 mm; about 100 mm; about 200 mm; about 300 mm; about 380 mm; about 400 mm; about 500 mm; about 600 mm; about 700 mm; about 800 mm; about 900 mm; about 1,000 mm; or about 2,000 mm. Alternatively, the apertures may have a cross-sectional diameter of any of the following: about 100-1,000 mm; about 200-750 mm; about 300-500 mm; or about 300-400 mm.

[0112] The mesh-like structure allows fine particulate material 422 to pass through the cylindrical sieve 414 and exit as shown as a fine powder discharge 422 through an outlet 430 located below the sifting device 415.

[0113] The cross-sectional size of the fine powder discharge 422 particles is selected from any of the following: about 50 microns to about 50 mm; about 100 microns to 10 mm; or about 200 microns to 10 mm.

[0114] The fine powder discharge 422 is valuable product material. It has been found that the present invention allows the capture of a much greater percentage of fine powder discharge material 422 in comparison to prior art systems. This is because fewer ‘clumps’ of material enter into the sifting device 415, due to the presence of the cyclone separator 404. The cyclone separator 404 maintains an almost constant material mass flow rate at its outlet, before being fed into the sifting device 415. The constant mass flow rate received by the sifting device 415 prevents the sifting device 415 becoming clogged up, and becoming less efficient.

[0115] Larger particulate material (e.g. waste material) is retained within the cylindrical sieve 414 and exits through an outlet 440 as an oversize powder discharge 420. The size of the oversize powder discharge 420 particles is larger than the apertures or holes in the cylindrical sieve 414.

[0116] FIG. 7 also shows that the cyclonic feed apparatus 400 comprises a release assembly 416 which may in some embodiments be a quick release basket assembly. There is also a motor 408 which is used to provide rotation to the shaft 412 located in the sifting device 415.

[0117] Furthermore, there is shown an inspection door 418 which may be hinged and quick release to allow easy and quick access. There is also a chute 440 which collects the fine powder material which exits as a fine powder discharge 422.

[0118] FIG. 8 is a further cyclonic feed apparatus according to the present invention generally designated 500. The cyclonic feed apparatus 500 is similar to the apparatus previously described in FIGS. 1 to 7.

[0119] The cyclonic feed apparatus 500 comprises a cyclone separator 526 which is located substantially vertically. The cyclone separator 526 comprises an upper section 528 which is substantially cylindrical and a lower section 532 which funnels material down into a sifting device 534.

[0120] As shown in FIG. 8, particulate material enters via an inlet 512 into the upper section 528 of the cyclone separator 526. Although not shown there may be more than one, two, three or a plurality of inlets feeding particulate material into the cyclone separator 526.

[0121] A preferred embodiment is shown in FIG. 8 where the inlet 512 passes the particulate material in a substantially tangential direction into the cyclone separator 526 which is substantially cylindrical in shape. The tangential direction is tangential to a central axis extending through the centre of the cyclone separator 526. The tangential direction of the particulate material has been found to be preferred but other directions of input for the material may be used.

[0122] The material may be fed at a velocity ‘V’ into the cyclone separator 526 at a range of: about 5 m/s to 100 m/s; about 20 m/s to about 60 m/s or about 8 m/s to 50 m/s. Alternatively, the material may be fed at a velocity ‘V’ into the cyclone separator 526 at a range of: about 5 m/s; about 10 m/s; about 20 m/s; about 30 m/s; about 40 m/s; about 50 m/s; about 60 m/s; about 60 m/s; about 70 m/s; about 80 m/s; about 90 m/s or about 100 m/s.

[0123] As shown in FIG. 8, the particulate material 528 is then caused to rotate in a cyclonic vortex due to the rotation of air within the cyclonic separator 526. They pneumatically conveyed air and particulate material fed into the inlet 512 causes the cyclonic vortex rotation of the air and particulate material within the cyclone separator 526. During the cyclonic motion of the particulate material the particulate material is forced to the outer surfaces of the cyclone separator 526 in a vortex-like manner.

[0124] The particulate material then passes through an outlet 536 of the cyclone separator 526 and into a substantially horizontally located channel 538. Via the channel 538 material is then fed via, for example, a screw shaft, and pneumatically conveyed into the sifter device 534. The screw shaft may be driven by a motor.

[0125] As shown in the cross-sectional view in FIG. 8, the sifter device 534 comprises a substantially longitudinally oriented cylindrical hollow sieve 540. For example, the cylindrical sieve 540 may be in the form of a drum. The cylindrical sieve 540 comprises a mesh-like structure with a series of small apertures with the cross-sectional diameter. Alternatively, the cylindrical sieve 540 may comprise and be lined with a series of screens which are perforated with holes.

[0126] The apertures in the mesh-like structure have a cross-sectional diameter of any of the following: about 50 mm; about 100 mm; about 200 mm; about 300 mm; about 380 mm; about 400 mm; about 500 mm; about 600 mm; about 700 mm; about 800 mm; about 900 mm; about 1,000 mm; or about 2,000 mm. Alternatively, the apertures have a cross-sectional diameter of any of the following: about 100-1,000 mm; about 200-750 mm; about 300-500 mm; or about 300-400 mm.

[0127] A screw conveyor 537 is shown transferring the material from the outlet 536 of the cyclone separator 526 along and into the sifter device 534. However, any suitable type of device may be used to assist the transfer of the material into the sifter device 534.

[0128] There is also shown a shaft 535 which contains a series of outlying and/or protruding members (e.g. paddles) 539 which are used to assist in the stirring and/or rotation of the material. The shaft 535 is therefore rotated and driven by the motor M whereupon the outlying and/or protruding members (e.g. paddles) 539 force the material outwards to the cylindrical sieve 540. This allows the separation of the material to occur under centrifugal forces into smaller and larger particulate material.

[0129] There is also shown a chute 562. Sifted material exits through outlet 544.

[0130] The mesh-like structure allows fine particulate material 542 to pass through the cylindrical sieve 534 and exit as shown as a fine powder discharge 544 out through an outlet 546 from the bottom of the cyclonic feed apparatus 500. The size of the fine powder discharge 544 particles is smaller than the size of the apertures in the mesh-like structure.

[0131] Larger sized particulate material is retained within the cylindrical sieve 540 and exits through an outlet 550 as an oversize powder discharge. The size of the oversize powder discharge particles is larger than the size of the apertures in the mesh-like structure in the cylindrical sieve 540. The flowrate of the oversized power discharge particles may depend upon the efficiency of the sieving process, i.e. a higher rate of sieving efficiency=a lower flow rate of oversized particles.

[0132] FIG. 8 also shows that there is a conduit (or passageway) 570 connecting the upper section 528 of the cyclonic separator 526 and the outlet 546 from the bottom of the cyclonic feed apparatus 500. There is therefore a flow of air from an opening 572 located on an upper surface of the cyclone separator 526 along the conduit (or passageway) 570 to the outlet 546 located below the sifting device 534. This has been found to be pneumatically efficient in conveying the material and air. The additionally conveyed pneumatic air along the conduit (or passageway) 570 may therefore collect and assist in transfer of the fine powder discharge 544. This is a specific advantage of the present invention in that there is a highly efficient use of the pneumatically conveyed air in the whole system.

[0133] Material exiting from the outlet 546 at the bottom of the cyclonic feed apparatus 500 may then be collected and continued to be conveyed.

[0134] FIG. 9 is an expanded cross-sectional view of the cyclone separator 526 shown in FIG. 8. The particulate material 580 is shown to be thrown against the sidewalls of the upper section 528 of the cyclone separator 526 and then funneled down along into the lower section 532 of the cyclone separator 526. Pneumatically fed air and material is tangentially fed via inlet 512 into the cyclone separator 526 at a sufficient rate to cause a vortex within the cyclone separator 526 to allow separation of material to start to occur.

[0135] FIG. 9 clearly shows that the cyclone (i.e. vortex) of air builds a rotating mass of material 580 against the sidewalls of the cyclonic separator 526. The material being formed against the sidewalls of the cyclonic separator 526 therefore forms, for example, a tubular shape.

[0136] A specific advantage of the rotating mass of material 580 in the cyclone separator 526 is that the rotating mass of particulate material 580 has the ability to absorb sudden increases in material feed by adjusting the thickness dimension ‘T’ and density of the particulate material 580 being forced against the inner surfaces of the cyclone separator 526. The dimension ‘T’ showing the thickness of the tubular shape of particulate material circulating in a cyclone form is shown in FIG. 9.

[0137] The velocity ‘V’ of the air and particulate material being fed into the cyclone separator 526 has to be sufficiently high to cause the particulate material to spin and form, for example, a substantially tubular shape. The required velocity ‘V’ of the air and particulate material being fed into the cyclone separator 526 changes with different materials but is typically in the range of: 5 m/s to 100 m/s; or 8 m/s to 50 m/s. As described in reference to FIG. 8, after the air has created a cyclone, it exits up through the centre of the cyclone separator 526 via the outlet 572.

[0138] The apparatus described in the present invention have a number of technical advantages and benefits. The centrifugal sifters described in the present invention use a fine aperture screen to separate material into oversize powder discharge (e.g. waste product) and fine powder discharge (e.g. desired product). A “large” aperture screen can tolerate variations in instantaneous mass flow rate and airflow which occurs inherently in pneumatic conveying systems. The market trend is to use “finer” apertures two separate waste and product. The finer the aperture the less tolerant the screen is of the air and variations of air entering the feeding by pneumatic conveying. The present inventors have found that it is highly advantageous in such situations to use a cyclonic separator (i.e. a cyclonic centrifuge) to smooth out the mass flow by damping the fluctuations in the cyclone body and also by separating the air from the material using the cyclone. It has been found that the combination of these two aspects (i.e. the cyclonic separator and the centrifugal sifter) provides a more stable system with reduced mass flow fluctuations. The flow of separated material and air is then presented to the fine aperture screen of the cyclonic sifter. This allows the centrifugal sifter to pass a larger amount of material than would otherwise be the case in the short residence time the material has in the centrifugal sifter. This results in less waste material (i.e. oversize powder discharge) and more product (i.e. fine powder discharge) being separated even if a finer aperture screen is used in the centrifugal sifter. This is a significant advantage over prior art systems.

[0139] The present inventors have therefore found it to be technically advantageous to take a cyclone which is usually used to separate air and material at atmospheric pressure and use it at positive pressure (i.e. above atmospheric pressure) in order to store material in order to dampen the constant variation in mass flow inherent to pneumatic conveying. It has also been found that by using the cyclone at positive pressure provides the further advantage in that positively pressurised air can be reused to pneumatically convey the “product” from the centrifugal sifter to the downstream process. This is shown in FIG. 8 using the conduit 570. This provides the additional benefit of avoiding the need for a second pneumatic conveying power source that would otherwise be required. There are clear environmental and commercial benefits in only having the requirement for one pneumatic conveying power source.

EXAMPLE

[0140] As a specific example we now compare using a prior art vibration sifter to separate material such as wheat flour in comparison to the apparatus according to the present invention using the combination of a cyclonic separator and centrifugal sifter as shown in FIGS. 8 and 9.

[0141] It has been found that using the combination of cyclonic separator and centrifugal sifter allows smaller mesh widths to be used in the centrifugal sifter, greater throughput is achieved, there is significantly reduced de-agglomeration of the particulate material being conveyed, and a much finer sieving is achievable.

[0142] Using a prior art vibration sifter with a mesh size of 50/70 μm it was compared with the apparatus 500 according to the present invention of using a combination of a cyclonic separator 526 and cyclonic sifter device 534 with a mesh size of 50/70 μm.

[0143] Using the prior art system with a vibration sifter the following was achievable.

[0144] Capacity Wheat Flour: [0145] D50=50/70 micron [0146] MW 2 mm≈30-35 T/hr. [0147] MW 5 mm≈40-45 T/hr.

[0148] In comparison, using the present invention combination of the cyclonic separator and a cyclonic sifter the following was achievable:

[0149] Capacity Wheat Flour: [0150] D50=50/70 micron [0151] MW 2 mm≈5-6 T/hr. [0152] MW 5 mm≈15-20 T/hr.

[0153] Using the present invention it was therefore possible to achieve a much higher tonnage rate per hour (i.e. T/hr.) for the pneumatically conveyed particulate material.

[0154] Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention. For example, any suitable type of cyclonic separator and cyclonic sifter may be used. Moreover, any suitable type of pipework may be used to connect the different parts of the apparatus. The apparatus of the present invention may also be used to convey any suitable type of particulate, granular and/or powder bulk material.