FIELD OF THE INVENTION

The present invention relates to an adjustable multi-hole orifice plate in a pneumatic conveying apparatus. More particularly, the present invention relates to an adjustable multi-hole orifice plate which can be used in a pneumatic conveying apparatus to assist in the discharge of material.

BACKGROUND OF THE INVENTION

To assist the discharge of material from pneumatic conveying vessels and to the final delivery point gas is fed into various points on a vessel through a distribution manifold. From test data and knowledge the gas split through the manifold can be calculated.

Orifice plates are used to control the flow of gas through the gas distribution manifold. The number and size of holes required in the orifice plate can be calculated using real life data and using the following mathematical calculation: the gas flow (volume / time); the area of the orifice (area) and the velocity of the gas (distance/time).

The calculation gives the theoretical area and therefore the size and number of holes necessary to convey the material. Often, during commissioning, adjustments have to be made to the air distribution through the manifold to get the material to convey. This is achieved by altering the number of holes in the orifice plate.

Changing the number of holes in the orifice plate is usually done by drilling additional holes in a steel plate or welding over the existing holes to reduce the number of holes. As the pneumatic conveying vessels are situated in process plants any work on the system has to be carried out under a permit to work and any modifications carried out in a workshop that could be on the other side of the plant to the vessel. To modify the prior art devices is therefore time consuming and requires specialist tools.

Prior art devices which use adjustable flow control methods often use a single hole with a restrictor of some kind e.g. needle or moveable plug. Again such devices have disadvantages. It is an object of at least one aspect of the present invention to obviate or mitigate at least one or more of the aforementioned problems.

It is a further object of at least one aspect of the present invention to provide an improved orifice plate for assisting the discharge of material from a pneumatic conveying apparatus.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a pneumatic conveying apparatus comprising:

an adjustable multi-hole orifice plate which has a front and back plate;

the front plate has a series of radial apertures or slots and the back plate has a series of holes; and

wherein the front and/or back plate is capable of being rotated to close and expose the holes and thereby control the flow of air through a manifold and hence the discharge of material.

The present invention therefore resides in the provision of an adjustable multi-hole orifice plate which can be used in a pneumatic conveying apparatus to assist in the discharge of material.

The adjustable multi-hole orifice may be mounted in pipework with a flow of gas moving through the hoes in the multi-hole orifice. The holes may have a size of about 1 - 20 mm or preferably about 2 - 8 mm.

The adjustable multi-hole orifice may therefore comprise two circular plates: a front (i.e. top) plate and a back (i.e. bottom) plate.

The front plate may comprise a series of radial apertures or slots extending around the front plate. The radial slots extend partially around the circumference of the front plate.

The back plate may comprise holes located at the same radius as the apertures or slots in the front plate and these can therefore be exposed (i.e. opened) or closed by rotating the front and/or back plates. The rotation of the front and back plates may be adjusted using simple hand tools such as a spanner to undo a locking nut.

The front and back plates may be mounted on a common axis with a locking screw and nut holding them in place.

During use the required number of holes may be exposed by rotating the front plate with radial slots over the bottom plate with radially drilled holes. Once the desired number of holes are uncovered the two plates may be locked in position by tightening the screw and nut that are located on the axis of the plates.

The adjustable multi-hole orifice may be used as part of conveying apparatus for dry solids. Often such solids contaminate other kinds of adjustable flow control reducing their performance.

• The pneumatic conveying apparatus may be any suitable type of apparatus such as a twin vessel pneumatic injection apparatus and a pneumatic conveying apparatus known in the field as a densphase pneumatic conveying apparatus which can be used on any of the following:Gypsum industry for the transfer of pre-calcined materials, additives, plaster and the re-cycling of scrap material

• Iron and Steel industry for the transfer of sinter fines, dust conveying, lump, granular and pulverised coal and furnace slag

• Non-ferrous industries for the transfer of reverts, metallurgical dusts, lime, granulated wire, zinc, lump, granular and pulverised coal and dusts

• Aluminium industry for the transfer of fresh alumina, fluorite, fine dusts, chips, packing lump carbon, machined carbon dust and recycled materials

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is representation of a sectional view through an adjustable multi-hole orifice mounted in pipework according to an embodiment of the present invention; Figure 2 is a representation of an adjustable multi-hole orifice in a minimum hole position according to an embodiment of the present invention;

Figure 3 is a representation of the adjustable multi-hole orifice shown in Figure 2 in a mid-position; and

Figure 4 is a representation of the adjustable multi-hole orifice shown in Figures 2 and 3 in a maximum hole position;

Figure 5 is a representation of a dispensing vessel containing adjustable multi-hole orifices according to a further embodiment of the present invention;

Figure 6 is a representation of a twin vessel pneumatic injection apparatus containing a dispensing vessel and adjustable multi-hole orifices according to a further embodiment of the present invention; and

Figure 7 is a representation of densphase pneumatic conveying apparatus containing adjustable multi-hole orifices according to a further embodiment of the present invention. BRIEF DESCRIPTION

Generally speaking, the present invention resides in the provision of an adjustable multi- hole orifice plate which can be used in a pneumatic conveying apparatus to assist in the discharge of material.

Figure 1 is a representation of an adjustable multi-hole orifice 10 mounted in pipework 12. There is also shown a locking screw and nut 14. There is shown a gas flow moving from the left to the right through the multi-hole orifice 10.

The adjustable multi-hole orifice 10 is, for example, made from any of the following suitable materials: stainless steel; plastics; ABS and nylon.

Figures 2 to 4 show the operation of the adjustable multi-hole orifice 10. The adjustable multi-hole orifice 10 comprises two circular plates: a front (i.e. top) plate 18 and a back (i.e. bottom) plate 16. The front plate 18 has a series of radial slots: a large slot 22 extending around toward the outer periphery of the front plate 18; and three smaller slots 24, 26, 28 closer to the centre of the front plate 18. The back plate 16 has holes located at the same radius as the slots 24, 26, 28 and these can therefore be exposed (i.e. opened) or closed by rotating the front and back plates 16, 18.

The rotation of the front and back plates 16, 18 can be adjusted using simple hand tools. Therefore, as opposed to prior art devices no drilling or welding is required. Moreover, the rotation of the front and back plates 16, 18 can be altered adjacent to the conveying vessel meaning that the alteration can be done very simply and quickly.

The front and back plates 16, 18 are mounted on a common axis with the locking screw and nut 14 holding them in place.

During use the required number of holes 20 is achieved by rotating the front plate 18, with radial slots 22, 24, 26, 28 over the bottom plate 16 with radially drilled holes 20. Once the desired number of holes 20 are uncovered the two plates 16, 18 can be locked in position by tightening the screw and nut 14 that are located on the axis of the plates 16, 18. The maximum number and size of holes 20 are dependent on the size of the plates 16, 18.

The adjustable multi-hole orifice 10 would be used as part of conveying apparatus for dry solids. Often such solids contaminate other kinds of adjustable flow control reducing their performance.

It has been found that the choice of large holes in robust metal sheet will make the device more tolerant of dirt and wear, providing more reliable operation. Wear on one hole in multiple holes also has a lower effect on change in flow than a single hole. This is a further advantage of the present invention.

Other methods for flow control usually involve a single hole. Tests show that multiple holes for the adjustable multi-hole orifice 10 of the present invention will reduce noise when attached to tanks. Therefore, the idea of using a multi hole orifice plate in conjunction with an adjustable device is advantageous.

During commissioning, it is often required to make changes to the orifice plate quickly in order to optimise the conveying performance of the machine. The current method of drilling or welding is time consuming and also subject to poor quality assurance. Pre-drilled holes with predefined characteristics as shown in the adjustable multi-hole orifice 10 of the present invention allow far quicker adjustment with improved ability to record the expected gas flow through the plate.

Figure 2 shows the adjustable multi-hole orifice 10 in the minimum hole position where only one hole 20 is present. The stop pin 30 is shown abutting against the end of the slot 22 and preventing further movement to one side. In Figure 3 the front plate 18 has been rotated to expose six holes 20. In Figure 4 the front plate 18 has been further rotated to expose twelve holes 20 and is in the maximum hole position. In the configuration shown in Figure 4 the maximum amount of flow will be allowed through the orifice 10.

Figure 5 is a representation of a dispensing vessel 100 according to the present invention. Figure 5 shows that the dispensing vessel 100 comprises an inlet dome valve 1 10, a vessel shell 1 12, a pressure regulator 114, a main blow valve 1 16 and an outlet blend 1 18. In this particular embodiment there are three multi-hole orifice plates 120, 122, 124 according to the present invention. The multi-hole orifice plates 120, 122, 124 are similar to those shown in Figures 2 to 4. Therefore, the multi-hole orifice plates 120, 122, 124 can be adjusted as previously described by rotating a front and/or back plate to expose or cover a series of holes which allow the flow of material through the dispensing vessel 100 to be controlled.

Figure 6 is a representation of a twin vessel pneumatic injection apparatus 200 according to a further embodiment of the present invention. There is shown a dispensing vessel 210 and a lock vessel 212. This embodiment of the invention has two multi-hole orifice plates 214, 216. The multi-hole orifice plates 214, 216 are as previously described and operate in a similar manner.

Figure 7 is a representation of pneumatic conveying apparatus 300 known in the field as a densphase pneumatic conveying apparatus which can be used on any of the following:

• Gypsum industry for the transfer of pre-calcined materials, additives, plaster and the re- cycling of scrap material

• Iron and Steel industry for the transfer of sinter fines, dust conveying, lump, granular and pulverised coal and furnace slag • Non-ferrous industries for the transfer of reverts, metallurgical dusts, lime, granulated wire, zinc, lump, granular and pulverised coal and dusts

• Aluminium industry for the transfer of fresh alumina, fluorite, fine dusts, chips, packing lump carbon, machined carbon dust and recycled materials

The pneumatic conveying apparatus 300 comprises a dispense vessel 310 and a lock vessel 312. This embodiment of the invention has three multi-hole orifice plates 314, 316, 318. The multi-hole orifice plates 314, 316, 318 are as previously described and operate in a similar manner.

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 and shape of front and back plate may be used. The device may also comprise any suitable number and arrangement of holes which can be opened and closed by rotating the front and/or back plate.