WO2008053276A1

WO2008053276A1 - Transition piece for the transfer of powder or granular material from a discharge opening to a conveying line and method of transferring powder or granular material

Info

Publication number: WO2008053276A1
Application number: PCT/IB2006/054004
Authority: WO
Inventors: Michel Simon Waldron
Original assignee: Collette Nv
Priority date: 2006-10-30
Filing date: 2006-10-30
Publication date: 2008-05-08

Abstract

A transition piece (1) for the transfer of powder or granular material from a larger diameter discharge opening to a smaller diameter conveying line comprises a housing (2) having an inlet end (3) mating the discharge opening and an outlet end (4) mating the conveying line. The housing (2) is provided with a flexible liner (10) having a first end and a second end that has a substantially smaller cross-sectional dimension than the first end. The circumference of the flexible liner is connected in a fluid tight manner with the housing (2) at each end of the flexible liner (10), so that an annular enclosure (19) is formed between the flexible liner (10) and the housing (2). The annular enclosure (19) communicates with a control fluid connection (20).

Description

Transition piece for the transfer of powder or granular material from a discharge opening to a conveying line and method of transferring powder or granular material

The present invention relates to a transition piece for the transfer of powder or granular material from a discharge opening to a conveying line, the discharge opening having a substantially larger cross- sectional dimension than the conveying line, the transition piece comprising a housing having an inlet end mating the discharge opening and an outlet end mating the conveying line.

JP 2001151346 discloses a screw pump for transfer of powder, having a transfer pipe connected to its discharge port. In order to prevent clogging in the transfer pipe, a flexible wire extending throughout the length of the pipe is locked to an end of the rotor of the pump, so that the wire rotates with the rotor. However, this arrangement is not suitable, for instance, for the transport of wet granules by means of transport gas, from a large diameter discharge to a smaller diameter pipe. In this case, the problem is to avoid that the wet granule builds up on the walls of the transition from the large to the small diameter. GB 698,374 discloses an apparatus for feeding powder in a continuous system. The apparatus comprises a flexible funnel that may be made of woven fabric and that is supported at its upper edge by means of a support frame. The support frame may be oscillated mechanically in order to prevent build-up of powder in the funnel. The upper opening of the funnel is free accessible in order to load powder material manually. The oscillating upper edge of the funnel is not suitable for connection with a fixed discharge opening.

JP 2001026320 discloses an occlusion preventing method for a powder transport pipe. The pipe is designed with double walls, and the inside pipe wall is porous so that it has air permeability. An intermittent air pressure is applied to the space between the outer and the inner wall of the pipe, whereby powder adhering to the inner wall is blown off.

JP 11091950 discloses a method for elimination of the blocking up of a powder transport pipeline. An expansible pipeline is utilized, and, at intervals, a valve is closed at the downstream end of the pipeline, whereby the pipeline expands and powder adhering to its walls is loosened. However, in this way, the flow through the pipeline is disturbed each time the valve is closed. The object of the present invention is to provide a transition piece suitable for the transfer of powder or granular material from a large diameter discharge to a small diameter pipe, whereby the build-up of material on the walls of the transition piece is avoided.

In view of this object, the housing is provided with a flexible liner having a first end and a second end that has a substantially smaller cross-sectional dimension than the first end, the circumference of the flexible liner being connected in a fluid tight manner with the housing at each end of the flexible liner, so that an annular enclosure is formed between the flexible liner and the housing, and the annular enclosure communicates with a control fluid connection.

In this way, the form of the flexible liner may be repeatedly changed by changing the fluid pressure in the annular enclosure, whereby powder or granular material building up on the walls of the flexible liner will loosen. The fluid pressure in the annular enclosure may be varied by means of the control fluid connection. Because the second end of the flexible liner has a substantially smaller cross-sectional dimension than the first end, the flexible liner narrows the stream of powder or granular material substantially without causing the material to clog up. In an embodiment, the annular enclosure, in the relaxed state of the flexible liner, constitutes an annular chamber having a volume greater than zero. Thereby, the diameter of the flexible liner may be increased from the relaxed state of the liner by applying an underpressure to the control fluid connection. Thereby, the loosening of powder or granular material adhering to the flexible liner may be facilitated.

In an embodiment, the flexible liner, in its relaxed state, has an inner diameter that is decreasing or constant from the first end of the liner to the second end of the liner. Thereby, the stream of powder or granular material may be gradually narrowed. In an embodiment, the wall thickness of the flexible liner is less than 1/5, and preferably less than 1/7, of the inner diameter of the liner at the outlet end of the transition piece. Thereby, a suitable flexibility of the flexible liner may be achieved. In an embodiment, the wall thickness of the flexible liner is decreasing from the first end of the liner to the second end of the liner. Thereby, when overpressure is applied in the annular cavity, a desired controlled collapse of the flexible liner may be obtained, whereby the passage through the liner may even be closed. In an embodiment, the wall thickness of the flexible liner is substantially constant. Thereby, the manufacturing of the liner may be facilitated.

In an advantageous embodiment, the flexible liner, in its relaxed state, is composed by a conical section extending from the inlet end of the housing and a cylindrical section extending from the outlet end of the transition piece.

In an embodiment, the largest inner cross-sectional dimension of the inlet end of the transition piece is at least two times the largest inner cross-sectional dimension of the outlet end of the transition piece. In an embodiment, the largest inner cross-sectional dimension of the inlet end of the transition piece is at least three times the largest inner cross-sectional dimension of the outlet end of the transition piece.

In an embodiment, the flexible liner is made of silicone rubber.

In an embodiment, the control fluid connection communicates with a suction device through a control valve governed by means of a computer.

In an embodiment, the computer is programmed to activate the control valve at regular intervals.

In an embodiment, the inlet end of the transition piece is con- nected to a granulator, and the outlet end of the transition piece is connected to a first end of a conveying line, and a second end of the conveying line is connected to a dryer.

In an embodiment, the granulator is a screw granulator, and the dryer is a fluid bed dryer. The invention furthermore relates to a method of transferring powder or granular material from a discharge opening to a conveying line, the discharge opening having a substantially larger cross-sectional dimension than the conveying line, whereby a stream of the powder or granular material is guided through a transition piece.

The method is characterized by that the powder or granular material is guided through a flexible liner of a housing of the transition piece, the flexible liner thereby narrowing the stream of powder or granular material substantially, whereby the form of the flexible liner is varied repeatedly by providing underpressure or overpressure in an enclosure formed between the flexible liner and the housing, so that powder or granular material sticking to the flexible liner is loosened. Thereby, the above-mentioned advantages may be achieved.

In an embodiment, the powder or granular material is trans- ferred by means of suction.

In an embodiment, the form of the flexible liner is varied by alternately providing an underpressure in the enclosure formed between the flexible liner and the housing, whereby the diameter of the flexible liner is increased at least along a part of the liners length, and relieving said underpressure. Thereby, the above-mentioned advantages may be achieved.

In an embodiment, the flexible liner, in its relaxed state, maintains an inner diameter that is decreasing or constant from the inlet end to the outlet end of the transition piece. In an embodiment, the flexible liner, in its relaxed state, maintains a form composed by a conical section extending from the inlet end of the housing and a cylindrical section extending from the outlet end of the transition piece.

In an embodiment, the control fluid connection communicates with a control valve that alternately connects the control fluid connection with two different fluid connections having different pressure, and a computer governs the control valve.

In an embodiment, the computer activates the control valve at regular intervals. In an embodiment, granular material is supplied to the inlet end of the transition piece by means of a granulator, and the granular material is conveyed from the outlet end of the transition piece to a dryer through a conveying line. In an embodiment, the granulator is working by means of at least one screw, and the dryer is maintaining a fluid bed.

The invention will now be explained in more detail below by means of examples of embodiments with reference to the very schematic drawing, in which Fig. 1 is an axial cross-section through a transition piece according to the invention,

Fig. 2 shows in diagrammatic form an installation comprising a screw granulator, a transition piece according to the invention, a conveying line and a fluid bed dryer. Fig. 1 shows an axial cross-section through a transition piece 1 for the transfer of powder or granular material according to the invention. The transition piece comprises a substantially tubular housing 2 made of a rigid material, such as plastic or metal and having an inlet end 3 and an outlet end 4. The inlet end 3 has an inlet flange connection 5, and the outlet end 4 has an outlet flange connection 6, whereby the diameter of the inlet flange connection 5 is substantially larger than the diameter of the outlet flange connection 6. A passage 7 through the housing 2 from the inlet flange connection 5 to the outlet flange connection 6 is formed by means of a first conical section 8 and a second coni- cal section 9, whereby the internal diameter of the housing 2 is decreased substantially from the inlet end 3 to the outlet end 4.

The passage 7 through the housing 2 is provided with a liner 10 made of a flexible material, such as silicone rubber, thereby forming a flexible passage 22 through the transition piece 1. The flexible liner 10 is composed by a substantially conical section 11 and a substantially cylindrical section 12, so that a smaller end 13 of the conical section 11 is forming a smooth transition with the cylindrical section 12. A larger end 14 of the conical section 11 is provided with a flange 15 abutting a flange surface 16 of the inlet flange connection 5 of the housing 2. When the inlet flange connection 5 is connected with a not shown flange connection of a discharge opening, the flange 15 of the liner 10 will be sandwiched tightly between said not shown flange connection and the inlet flange connection 5. Opposite the transition with the conical section 11, the cylindrical section 12 is provided with a flange 17 abutting a flange surface 18 of the outlet flange connection 6 of the housing 2. When the outlet flange connection 6 is connected with a not shown flange connection of a conveying line, the flange 17 of the liner 10 will be sandwiched tightly between said not shown flange connection and the outlet flange connection 6. In this way, the circumference of the flexible liner 10 is connected in a fluid tight manner with the housing 2 at each end of the flexible liner 10.

Between the housing 2 and the flexible liner 10, an annular enclosure 19 is formed in the passage 7. In the embodiment shown in Fig. 1, the flexible liner 10 is shown in its relaxed state, whereby the annular enclosure 19 forms a chamber having a volume greater than zero. The annular enclosure 19 is by means of a control fluid connection 20 through a wall 21 of the housing 2 connected with a suction device and/or a pressurized fluid source. The control fluid may be any suitable kind of gas or liquid or a combination thereof. By changing the fluid pressure inside the annular enclosure 19 relative to the fluid pressure inside the flexible passage 22, the form of the flexible liner 10 may be changed, whereby material, such as possibly wet granules or powder, built up on the inside of the flexible liner 10 in the flexible passage 22 may be loosened. Furthermore, by regularly varying said fluid pressure, building-up of material on the flexible liner 10 may be substantially avoided.

The fluid pressure inside the annular enclosure 19 may be controlled by means of a control valve 23 governed by means of a computer 24; see Fig. 2. The control valve may 23, for instance, be a solenoid valve having three positions for either closing the control fluid connection 20, connecting it with a suction device 25 or connecting it with the surroundings. Thereby, for instance, it is possible to evacuate fluid from inside the annular enclosure 19 in order to deform the flexible liner 10 relative to its form shown in Fig. 1, maintain the obtained form during a period of time by closing the control fluid connection 20 and subsequently allowing fluid to enter the annular enclosure 19 from the surroundings in order for the flexible liner 10 to obtain its form shown in Fig. 1 again or obtain an even more constricted form, if the fluid pressure inside the flexible passage 22 is lower than the fluid pressure at the surroundings. If necessary, the flexible liner 10 may even be constricted to close the flexible passage 22.

Alternatively, the control valve 23 may be adapted to connect the control fluid connection 20 with a not shown pressurized fluid source. The control valve 23 may also be arranged to alternately connect the control fluid connection 20 to the suction device 25 and a not shown pressurized fluid source. In any case, the computer 24 may be adapted to activate the control valve 23 periodically, at regular or irregular inter- vals, or substantially continuously.

In another, not shown embodiment, the flexible liner 10 may, in its relaxed state, fit the form of the passage 7, so that the annular enclosure 19 forms a chamber having a volume equal zero. In that case, the control fluid connection 20 may be connected to a not shown pres- surized fluid source in order to change the form of the flexible liner 10, whereby material built up on the inside of the flexible liner 10 in the flexible passage 22 may be loosened.

Alternatively to the control valve 23, the annular enclosure 19 can be connected to a source of variable fluid pressure capable of apply- ing suction or pressure and holding or varying that suction or pressure with time. Thereby, the annular chamber can also be vented to atmosphere. Alternatively to using a computer, also a very simple control system may be used, even a pneumatic system.

Fig. 2 shows an installation comprising a screw granulator 26 having a discharge opening 27 connected with the inlet flange connection 5 of the transition piece 1 according to the invention, a conveying line 28 having a first end 29 connected with the outlet flange connection 6 of the transition piece 1 and a second end 30 connected with an inlet 31 of a fluid bed dryer 32. By means of an exhaust fan 33, suction fluid is drawn from the fluid bed dryer 32 through filters 34. The resulting underpressure in the fluid bed dryer 32 causes granular material produced by the screw granulator 26 to be drawn through the conveying line 28 from the screw granulator 26. If more suction is required an inlet valve 35 of the fluid bed dryer 32 can be partially closed.

Because the granular material flows through the transition piece 1 from the larger diameter discharge opening 27 to the smaller diameter conveying line 28, the flow velocity is increased substantially, whereby the granular material is easily transported through the conveying line 28. In the shown installation, the transition piece 1 is arranged vertically, which facilitates the transport of material from the discharge opening 27 of the granulator 26 into the transition piece. However, as the material is drawn through the transition piece 1 by means of suction, it could also be arranged differently, for instance horizontally. Alterna- tively, in other arrangements, if the transition piece 1 is arranged vertically, as shown, the transport of material may be performed by means of gravity instead of suction.

As an example, in the installation shown in Fig. 2, fluid may be evacuated from inside the annular enclosure 19 in order to deform the flexible liner 10 three times in rapid succession, for instance one time per second, each time a filter is blown back, which may typically be every three minutes. However, the necessary frequency may be much more or less than this. As another example, it would be possible to provide a constant "flutter" or cyclic expansion of the flexible liner 10. The transition piece 1 according to the invention may be applied in many other set-ups than that shown in Fig. 2. The granulator 26 may be any kind of suitable granulator, such as a single or twin screw granulator. The conveying line 28 may, for instance, be 2.5 to 3 metres long, and it may, for instance, be made of a PTFE lined, antistatic, braided hose. Preferably, the diameter of the conveying line 28 is relatively small in order to minimise the conveying fluid volume flow rate, make removal and re-fitting fast and easy and simplify cleaning. As an example, the discharge opening 27 of the screw granulator 26 may have a diameter or cross-sectional dimension of 50 mm and the conveying line 28 may have a diameter of 16 mm. However, the discharge opening 27 of the screw granulator 26 may have a diameter or cross-sectional dimension from approximately 40 to 100 mm and the conveying line 28 may have a diameter from approximately 12.5 to 25 mm. It is noted that the dis- charge opening 27 of the screw granulator 26 does not necessarily have a circular cross-section; it may as well have an oval, a square or a rectangular cross-section. The fluid bed dryer 32 shown is a segmented fluid bed dryer for continuous processing of separate batches, but it may be a basic continuous fluid bed dryer or a microwave dryer or any other suitable dryer.

Claims

P A T E N T C L A I M S

1. A transition piece for the transfer of powder or granular material from a discharge opening to a conveying line, the discharge opening having a substantially larger cross-sectional dimension than the con- veying line, the transition piece comprising a housing having an inlet end mating the discharge opening and an outlet end mating the conveying line, c h a r a c t e r i z e d in that the housing is provided with a flexible liner having a first end and a second end that has a substantially smaller cross-sectional dimension than the first end, the circumference of the flexible liner being connected in a fluid tight manner with the housing at each end of the flexible liner, so that an annular enclosure is formed between the flexible liner and the housing, and in that the annular enclosure communicates with a control fluid connection.

2. A transition piece according to claim 1, wherein the annular enclosure, in the relaxed state of the flexible liner, constitutes an annular chamber having a volume greater than zero.

3. A transition piece according to claim 1 or 2, wherein the flexible liner, in its relaxed state, has an inner diameter that is decreasing or constant from the first end of the liner to the second end of the liner.

4. A transition piece according to any one of the preceding claims, wherein the wall thickness of the flexible liner is less than 1/5, and preferably less than 1/7, of the inner diameter of the liner at the outlet end of the transition piece.

5. A transition piece according to any one of the preceding claims, wherein the wall thickness of the flexible liner is decreasing from the first end of the liner to the second end of the liner.

6. A transition piece according to any one of the claims 1 to 4, wherein the wall thickness of the flexible liner is substantially constant.

7. A transition piece according to any one of the preceding claims, wherein the flexible liner, in its relaxed state, is composed by a conical section extending from the inlet end of the housing and a cylindrical section extending from the outlet end of the transition piece.

8. A transition piece according to any one of the preceding claims, wherein the largest inner cross-sectional dimension of the inlet end of the transition piece is at least two times the largest inner cross- sectional dimension of the outlet end of the transition piece.

9. A transition piece according to any one of the preceding claims, wherein the largest inner cross-sectional dimension of the inlet end of the transition piece is at least three times the largest inner cross- sectional dimension of the outlet end of the transition piece.

10. A transition piece according to any one of the preceding claims, wherein the flexible liner is made of silicone rubber.

11. A transition piece according to any one of the preceding claims, wherein the control fluid connection communicates with a suction device through a control valve governed by means of a computer.

12. A transition piece according to any one of the preceding claims, wherein the computer is programmed to activate the control valve at regular intervals.

13. A transition piece according to any one of the preceding claims, wherein the inlet end of the transition piece is connected to a granulator, and the outlet end of the transition piece is connected to a first end of a conveying line, and wherein a second end of the conveying line is connected to a dryer.

14. A transition piece according to any one of the preceding claims, wherein the granulator is a screw granulator, and the dryer is a fluid bed dryer.

15. A method of transferring powder or granular material from a discharge opening to a conveying line, the discharge opening having a substantially larger cross-sectional dimension than the conveying line, whereby a stream of the powder or granular material is guided through a transition piece, c h a r a c t e r i z e d by that the powder or granular material is guided through a flexible liner of a housing of the transi- tion piece, the flexible liner thereby narrowing the stream of powder or granular material substantially, whereby the form of the flexible liner is varied repeatedly by providing underpressure or overpressure in an enclosure formed between the flexible liner and the housing, so that powder or granular material sticking to the flexible liner is loosened.

16. A method according to claim 15, whereby the powder or granular material is transferred by means of suction.

17. A method according to claim 15 or 16, whereby the form of the flexible liner is varied by alternately providing an underpressure in the enclosure formed between the flexible liner and the housing, whereby the diameter of the flexible liner is increased at least along a part of the liners length, and relieving said underpressure.

18. A method according to any one of the claims 15 to 17, whereby the flexible liner, in its relaxed state, maintains an inner diame- ter that is decreasing or constant from the inlet end to the outlet end of the transition piece.

19. A method according to any one of the claims 15 to 18, whereby the flexible liner, in its relaxed state, maintains a form composed by a conical section extending from the inlet end of the housing and a cylindrical section extending from the outlet end of the transition piece.

20. A method according to any one of the claims 15 to 19, whereby the control fluid connection communicates with a control valve that alternately connects the control fluid connection with two different fluid connections having different pressure, and whereby a computer governs the control valve.

21. A method according to claim 20, whereby the computer activates the control valve at regular intervals.

22. A method according to any one of the claims 15 to 21, whereby granular material is supplied to the inlet end of the transition piece by means of a granulator, and the granular material is conveyed from the outlet end of the transition piece to a dryer through a conveying line.

23. A method according to any one of the claims 15 to 22, whereby the granulator is working by means of at least one screw, and the dryer is maintaining a fluid bed.