GB2540145A

GB2540145A - Pneumatic conveying system for particulate material

Info

Publication number: GB2540145A
Application number: GB1511801.1A
Authority: GB
Inventors: Shinn Daniel
Original assignee: Schenck Process UK Ltd
Current assignee: Schenck Process UK Ltd
Priority date: 2015-07-06
Filing date: 2015-07-06
Publication date: 2017-01-11
Also published as: GB201511801D0

Abstract

A pneumatic conveyor system features one or more flexible conduit sections 10 and one or more flexible mounting systems 24, such as slings 24. In use, the passage of particulate material may cause the conduit section 10 to flex, thus dislodging solid build ups of material within the conduit 10. Also disclosed is a corresponding method of making the conveyor system, in which more than one conduits 10 are joined together. The system may further feature coupling arrangements 16, 18, and air injectors 20. The system may have particular application for low velocity, dense phase, full bore conveying.

Description

PNEUMATIC CONVEYING SYSTEM FOR PARTICULATE MATERIAL FIELD OF THE INVENTION

The present invention relates to an improved pneumatic conveying system for granular or particulate material. In particular, but not exclusively, the present invention relates to a low velocity dense phase pneumatic conveying system configured to prevent build-up of particulate material within a conveying conduit without the need for physical intervention of the system.

BACKGROUND TO THE INVENTION

Pneumatic conveying is the use of a gas (typically air) to move particulate material, for example, powders, granular materials or dry bulk materials between locations. The conveying gas is moved through an enclosed pipework or conduit system, either by positive pressure or by vacuum (negative pressure). By controlling the pressure or vacuum and the airflow inside the conveying conduit system material can be successfully conveyed. The material is carried along with the gas and is moved between locations.

Pneumatic conveying can be categorised into three types (or phases) of conveying; namely, lean phase, medium phase and dense phase.

Lean phase pneumatic conveying employs a low pressure differential, relatively high velocity and the material is entrained in the airflow. Medium phase pneumatic conveying employs, as the name suggests, medium pressure differential, medium velocity and the conveyed material is fluidised and entrained. Dense phase pneumatic conveying, typically, employs a higher pressure differential and a lower velocity than lean and medium phase conveying. In dense phase pressure conveying material flow is typically full-bore flow.

Dense phase pressure conveying is used typically to convey fragile or abrasive particulate materials. The system conveys materials at a relatively low velocity to reduce material degradation, air consumption, and abrasion on the conduit system.

Low velocity dense phase conveying often results in high conveying pressures. The effect of these high pressures can be made less severe by using supplementary air injectors at regular intervals along the conveying conduit or pipeline. The injectors provide additional air to help maintain conveying velocity, to transfer materials over long distance, and to minimize plugging/blocking of the conduit or pipeline. They can also be used to gently restart flow when materials are left in the conduit or pipeline after a conveying cycle.

When the conveyed material is cohesive or pressure sensitive, a build up of material can form on the inside of the conveying conduit or pipeline, which can lead to a blockage in the conveying conduit or pipeline and where the supplementary air injectors can have little or no effect in dispersing the blockage. As a result the system generally needs to be dismantled to remove the blockage.

It is desirable to provide an improved pneumatic conveyor device which minimises the risk of blockages within the conduit.

It is desirable to provide an improved pneumatic conveyor device which can actively disperse blockages without the need for physical intervention.

It is desirable to provide an improved pneumatic conveyor system which reduces the ability of material within the conveying conduit to adhere to the inside of the conveying conduit or pipeline, thereby reducing the occurrence of a build-up of material within the conduit.

SUMMARY OF THE INVENTION A first aspect of the present invention provides a pneumatic conveying system operable to convey granular or particulate materials; the system comprises: at least one elongate flexible conduit; at least one flexible mounting system arranged to support the flexible conduit whilst allowing flexural multiple axis movement of the flexible conduit, wherein material passing through the conduit effects flexural movement of the flexible conduit assisting in transportation of material through the conduit thereby minimising occurrence of blockages; and at least one gas injection system arranged to inject air directly into the conduit.

The flexible conduit may comprise a corrugated outer surface.

The corrugated outer surface may be formed by winding metallic, non-metallic or composite material to form an outer sheath having a helical undulating outer surface and an inner hollow bore. The flexible conduit may comprise a composition of layered materials that form a pressure-containing conduit. The pressure containing conduit may comprise a composition of metallic layers, metallic and non-metallic layers or non-metallic layers. Each layer may comprise a helically wound tape element. A flexible conduit may comprise, at least a corrugated outer layer. It will be appreciated that a flexible conduit allows larger deflections without a significant increase in bending stresses compared with a rigid conveying pipe.

Using a flexible conduit may reduce the ability of the conveying material to adhere to the inside wall of the conduit, as is typically experienced in a rigid conveying pipe. Natural flexural movement of the flexible conduit may be caused by material passing through the conduit and as such acts to detach any material adhered to the wall. Therefore, transportation of the material through the pneumatic conveying system is improved and the incidence of blockages is reduced.

The flexible mounting system may comprise a mechanical sling arrangement, where the flexible conduit is cradled within a flexible sling in a basket hitch or a choker hitch, such that the flexible conduit is supported against excessive sagging, whilst allowing flexural multiple axis movement of the flexible conduit. The support of the flexible conduit may be by suspension.

As material passes through the conduit, in particular plugs of material, it will be appreciated that internal forces created by the movement of the material will encourage flexural movement of the flexible conduit. A flexible mounting system allows substantially unrestricted flexural movement of the flexible conduit such that material is encouraged to pass through the conduit and the occurrence of blockages may be minimised. Accordingly, maintenance downtime to remove blockages may also be reduced and preferably eliminated.

The flexible mounting system may comprise an actuating mechanism, which is operable to actuate flexural multiple axis movement of the flexible conduit. It will be appreciated that physical actuation of the flexible conduit to flex or move in multiple directions provides the advantage that if a blockage does occur within the conduit the actuation mechanism can cause the flexible mounting system to move the flexible conduit such that the material contained inside is agitated to release the blockage. The actuating mechanism may be mounted between the conduit and a solid mounting. The actuating mechanism may operate with varying frequency, force and distance to create additional deflection on the conduit. The actuator may also force the conduit to strike a fixed surface and shock the conduit for an additional effect to detach more stubborn build-ups.

The gas injection system may comprise a coupling, which is mounted directly about the outer surface of the flexible conduit, wherein the coupling may comprise a sleeve and an injector coupled to the sleeve and arranged to inject gas through the wall of the flexible conduit via an orifice provided through each of the sleeve and the wall of the flexible conduit. The sleeve may comprise an internal profile that complements an external profile of the flexible conduit such that the coupling is physically engaged with the outer surface of the conduit.

The gas may be air. A coupling may be arranged at each end of the, or each, flexible conduit. The coupling may comprise a flange attached to the sleeve, wherein the flange is configured to attach one flexible conduit to another flexible conduit, wherein each flexible conduit comprises a coupling at each end.

It will be appreciated that the complementary profile of the sleeve and the flexible conduit provides grip between the coupling and the flexible conduit, alignment of the injector and the orifice provided through the wall of the flexible conduit and improved structural integrity of the flexible conduit. A sealing member, such as a deformable seal may be provided between the mating surfaces of the sleeve and the flexible conduit. The couplings / sleeves may not just be used at the end of each section of conduit. The couplings / sleeves may be located at, for example, 0.5 - 2m intervals along the conduit. The flanges may be attached to the sleeve but may also be manufactured without the flange. Couplings may be located at each end of the conduits and at intervals along the conduits such as 0.5 - 5 m which are solely used for air injection.

Silicone sealant may also be used to mate the sleeve and conduit. The sleeve may also compress the conduit by, for example, about 0.5 - 10 mm which also helps with the seal.

The inclusion of a coupling member at each end of the flexible conduit allows continuity of the form of the flexible conduit when two or more lengths are joined together. A pressure tight seal may also be provided by attaching the coupling to the conduit.

The pneumatic conveying system may comprise a plurality of flexible conduits joined together end to end, wherein at least one flexible mounting system is arranged between each end of each flexible conduit and wherein at least one gas injection system may be provided on each flexible conduit.

The gas injection system may be provided towards one end of each flexible conduit. Alternatively, the gas injection system may be provided towards each end of each flexible conduit.

The pneumatic conveying system comprises a low velocity dense phase conveying system. A further aspect of the present invention provides a method of constructing a low velocity dense phase conveying system, comprising the steps of providing lengths of flexible conduit; positioning each length of flexible conduit on at least one flexible mounting system; coupling the lengths of flexible conduit together with a coupling to provide a continuous conduit for transporting granular or particulate material, and providing a gas injection system to one coupling per length of flexible conduit such that gas can be injected into the flexible conduit at spaced intervals.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of a perspective view of a section of a pneumatic conveying system according to an embodiment of the present invention;

Figure 2 is a diagrammatic representation of a gas injection system employed with the pneumatic conveying system as illustrated in figure 1;

Figure 3a to 3c are representations of a rigid conveying pipe of a prior art system illustrating build up of material inside the conduit and the resulting blockage; and

Figure 4 is a representation of a flexible conveying pipe according to an embodiment of the present invention illustrating reduced build up of material compared with figures 3a to 3c.

BRIEF DESCRIPTION

Figure 1 illustrates a conduit section 10 of a low velocity dense phase pneumatic conveying system according to an embodiment of the present invention. A low velocity dense phase conveying system is used particularly in conveying friable products.

In the illustrated example the conduit section 10 comprises a length of flexible conduit 12. The flexible conduit 12 is configured to be coupled to further lengths of flexible conduit via couplings 14, which are mounted on each end of the flexible conduit 12.

In the illustrated example, each coupling 14 includes an annular sleeve section 16, which is mounted onto the flexible conduit 12, and a flange section 18, which facilitates joining conduit sections 12 together.

An air injector 20 is illustrated as part of each coupling 14. Coincident orifices or holes (not visible in figure 1) are provided through the wall of the sleeve 16 and the wall of the flexible conduit 12 such that the air injector 20 can, when attached to the system, inject air into the bore 22 of the conduit 12.

In the illustrated example, a flexible mounting system 24 supports the conduit 12 at points along the length of the conduit 12. In the illustrated example, two sling elements are shown. However, it will be appreciated that one or more flexible mounting systems 24 may be employed along each length of flexible conduit 12. Each flexible mounting system 24 is represented, for illustrative purposes only, as a sling configured as a vertical basket hitch. Alternative slinging arrangements could be used, for example wide or narrow angled basket hitch or choking hitch. It will be appreciated that the end or ends 26 of the slings 24 will be anchored from above such that the conduit 12 is supported by suspension. Means of anchoring the flexible mounting system 24 is not illustrated. The flexible mounting system or slings 24 are provided to prevent excessive downward flexing of the conduit 12, whilst allowing otherwise unrestricted flexural movement.

Figure 2 illustrates a representation of an end section of the conduit 12, which includes an example of a suitable coupling 14. The coupling 14 includes a retaining sleeve 16 and an air injector 20, which is operable to inject air into the bore 22 of the conduit 12. Air is injected into the bore 22 of the conduit 12 to mitigate high conveying pressures associated with the low velocity system.

In the illustrated example (see figure 1 and 2) the conduit 12 comprises an outer surface in the form of a helix, which provides an undulating/corrugated surface finish on the outside wall of the conduit 12. The sleeve 16 includes a complementary profile on the inside surface such that the complementary profiles mate and the sleeve 16 physically engages the outer surface of the conduit 12. As such, the coupling 14 is retained on the section of the conduit 12. Pressure in the conduit may also act to ensure physical engagement of the conduit 12 and the sleeve 16.

The air injector 20 is mounted on the sleeve 16 such that the injector 26 is located adjacent a hole 28, 30 through both the sleeve 16 and the wall of the conduit 12. This arrangement reduces leakage from the system because the arrangement of sleeve 16 and conduit 12 provides a dynamic, pressure tight seal. As such air is injected efficiently into the bore 22 of the conduit 12.

Figures 3a to 3c illustrate examples of prior art systems that utilise a rigid conveying pipe 32 as the conveying medium. Figures 3a to 3c each illustrate a build up of material 34 within a rigid conveying pipe 32. Figure 3c shows the scale of the build up after it is partially removed from the pipe 32. In the examples illustrated the material 34 being conveyed is cohesive therefore has a tendency to adhere to the walls of the conveying pipe 32 and progressively builds until the pipe 32 becomes completely blocked. Due to the rigid construction of the pipe 32, it will be appreciated that the system needs to be dismantled such that the build up of material 34 causing a blockage can be removed.

In contrast to figures 3a to 3c, figure 4 illustrates a flexible conduit 12 as described above with reference to figure 1, where the flexural behaviour of the flexibly mounted conduit reduces the ability of material 36 to adhere to the inside wall of the conveying conduit 12. As such, a build up of material 36 and therefore complete blockage as illustrated in figures 3a to 3c is highly unlikely to occur.

In the embodiment illustrated in figures 1, 2 and 4 a flexible system is presented which utilises a flexible conduit 12 and a flexible mounting system 24. The flexible mounting system 24 allows unrestricted flexural movement of the flexible conduit 12 such that the conduit is free to move as material, in particular plugs of material pass through the conduit 12. The movement of material through the system stimulates flexural movement of the conduit and the flexible mounting allows unrestricted flexural movement to occur.

The flexural movement of the conduit 12 results in the conduit 12 bending and flexing such that any material having a tendency to adhere to the internal walls of the conduit 12 is dislodged from the internal wall and is conveyed with passing material. This is particularly relevant to a low velocity dense phase conveyor, which involves full bore flow.

The flexible mounting system 24 as described with reference to figures 1, 2 and 4 may include a supplementary actuating mechanism (not illustrated) that is operable, on demand, to manipulate the mounting system 24 such that the mounting system is physically displaced and in turn causes flexing and bending of the conduit 12 such that blockages are dispersed or avoided.

The low velocity dense phase conveying system as described above with reference to figures 1, 2 and 4 includes airtight mounting of an air injector 20 and injection nozzle to the conduit 12 such that effectively all of the air injected through the nozzle into the bore is received in the bore 22 to assist with the transportation of granular or particulate material through the conduit.

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.

Claims

1. A pneumatic conveying system operable to convey granular or particulate materials; the system comprises: at least one elongate flexible conduit; at least one flexible mounting system arranged to support the flexible conduit, whilst allowing flexural multiple axis movement of the flexible conduit, wherein material passing through the conduit effects flexural movement of the flexible conduit assisting in transportation of material through the conduit thereby minimising occurrence of blockages; and at least one gas injection system arranged to inject gas directly into the conduit.

2. A pneumatic conveying system as claimed in claim 1, wherein the flexible conduit comprises a corrugated outer surface.

3. A pneumatic conveying system as claimed in claim 2, wherein the corrugated outer surface is formed by winding metallic, non-metallic or composite material to form an outer sheath having a helical undulating outer surface and an inner hollow bore.

4. A pneumatic conveying system as claimed in any preceding claim, wherein the flexible conduit comprises a composition of layered materials that form a pressure-containing conduit.

5. A pneumatic conveying system as claimed in claim 4, wherein the pressure containing conduit comprises a composite structure composed of metallic layers, metallic and non-metallic layers or non-metallic layers.

6. A pneumatic conveying system as claimed in claim 5, wherein each layer comprises helically wound tape.

7. A pneumatic conveying system as claimed in any preceding claim, wherein the flexible mounting system comprises a mechanical sling arrangement, where the flexible conduit is cradled within a sling in a basket hitch or a choker hitch, such that the flexible conduit is supported against excessive sagging, whilst allowing flexural multiple axis movement of the flexible conduit.

8. A pneumatic conveying system as claimed in any preceding claim, wherein the flexible mounting system comprises an actuating mechanism, which is operable to actuate flexural multiple axis movement of the flexible conduit.

9. A pneumatic conveying system as claimed in any preceding claim, wherein the gas injection system comprises a coupling, which is mountable directly about the outer surface of the flexible conduit.

10. A pneumatic conveying system as claimed in claim 9, wherein the coupling comprises a sleeve comprising an internal profile that complements an external profile of the flexible conduit, wherein an injector is coupled to the sleeve and is arranged to inject gas through the coupling and the wall of the flexible conduit via an orifice provided in each of the coupling and the wall of the flexible conduit.

11. A pneumatic conveying system as claimed in claim 9 or 10, wherein a coupling is arranged at each end of the flexible conduit.

12. A pneumatic conveying system as claimed in claim 9, 10 or 11, wherein the coupling comprises a flange attached to the sleeve, wherein the flange is configured to attach one flexible conduit to another flexible conduit, wherein each flexible conduit comprises a coupling at each end.

13. A pneumatic conveying system as claimed in any of claims 9 to 12, wherein a sealing member, such as a deformable seal is provided between the mating surfaces of the sleeve and the flexible conduit.

14. A pneumatic conveying system as claimed in any preceding claim comprising a plurality of flexible conduits joined together end to end, wherein at least one flexible mounting system is arranged between each end of each flexible conduit and wherein at least one gas injection system is provided on each flexible conduit.

15. A pneumatic conveying system as claimed in claim 14, wherein the gas injection system may be provided towards one end of each flexible conduit.

16. A pneumatic conveying system as claimed in claim 14, wherein the gas injection system is provided towards each end of each flexible conduit.

17. A pneumatic conveying system as claimed in any preceding claim comprising a low velocity dense phase conveying system.

18. A method of constructing a low speed dense phase conveying system, comprising the steps of: providing lengths of flexible conduit; mounting each length of flexible conduit on at least one flexible mounting system; coupling the lengths of flexible conduit together with a coupling thereby providing a continuous conduit for transporting granular or particulate material; and providing a gas injection system at each coupling such that gas can be injected into the flexible conduit.

19. A pneumatic conveying system as described herein and with reference to the accompanying drawings.

20. A method as described herein and with reference to the accompanying drawings.